Recent Journal Articles: Organic Chemistry -- Neurotransmitter.net

Recent Articles in Natural Product Reports

Liu Y, Wang L, Jung JH, Zhang S
Sesterterpenoids.
Nat Prod Rep. 2007 Dec;24(6):1401-1429.
Covering: 1996 to 2006. [Abstract]

St�ckigt J, Panjikar S
Structural biology in plant natural product biosynthesis-architecture of enzymes from monoterpenoid indole and tropane alkaloid biosynthesis.
Nat Prod Rep. 2007 Dec;24(6):1382-1400.
Covering: 1997 to 2007. [Abstract]

Fraga BM
Natural sesquiterpenoids.
Nat Prod Rep. 2007 Dec;24(6):1350-1381.
Covering: January 2006 to December 2006. [Abstract]

Hanson JR
Steroids: partial synthesis in medicinal chemistry.
Nat Prod Rep. 2007 Dec;24(6):1342-1349.
Covering: January-December 2006. [Abstract]

Hanson JR
Diterpenoids.
Nat Prod Rep. 2007 Dec;24(6):1332-1341.
Covering: January-December 2006. [Abstract]

Abe I
Enzymatic synthesis of cyclic triterpenes.
Nat Prod Rep. 2007 Dec;24(6):1311-1331.
Covering: 2002 to 2006. [Abstract]

Dixon N, Wong LS, Geerlings TH, Micklefield J
Cellular targets of natural products.
Nat Prod Rep. 2007 Dec;24(6):1288-1310.
Covering: 2001 to 2006 inclusive. [Abstract]

Rokem JS, Lantz AE, Nielsen J
Systems biology of antibiotic production by microorganisms.
Nat Prod Rep. 2007 Dec;24(6):1262-1287.
Covering: 1995 to 2006. [Abstract]

Nett M, K�nig GM
The chemistry of gliding bacteria.
Nat Prod Rep. 2007 Dec;24(6):1245-1261.
Covering: up to November 2006. [Abstract]

Baker DD, Chu M, Oza U, Rajgarhia V
The value of natural products to future pharmaceutical discovery.
Nat Prod Rep. 2007 Dec;24(6):1225-1244.
Covering: 2004 to 2006. [Abstract]

Wenzel SC, M�ller R
Myxobacterial natural product assembly lines: fascinating examples of curious biochemistry.
Nat Prod Rep. 2007 Dec;24(6):1211-1224.
Covering: up to April 2007. [Abstract]

Hill RA, Sutherland A
Hot off the press.
Nat Prod Rep. 2007 Dec;24(6):1207-10.
A personal selection of 31 recent papers is presented covering various aspects of current developments in bioorganic chemistry and novel natural products such as trigoxazonane from Trigonella foenum-graecum, which inhibits the germination of seeds of Orobanche crenata. [Abstract]

Gao JM, Wu WJ, Zhang JW, Konishi Y
The dihydro-beta-agarofuran sesquiterpenoids.
Nat Prod Rep. 2007 Oct;24(5):1153-89.
Dihydro-Beta-agarofuran sesquiterpenoids are a structurally diverse class of natural products based on tricyclic 5,11-epoxy-5Beta,10alpha-eudesman-4-(14)-ene skeleton. Between January 1990 and June 2006, 462 new dihydro-Beta-agarofuran sesquiterpenoids of 74 structural types have been isolated from about 64 species of Celastraceae, 3 species of Hippocrateaceae and one species of Lamiaceae. The present review covers the chemical and biological activity research of dihydro-Beta-agarofuran sesquiterpenoids in the past 16 years. The chemical research includes structural classification into sesquiterpene polyesters and macrolide sesquiterpene pyridine alkaloids, synthesis of dihydro-Beta-agarofuran as well as extraction, isolation and purification methods. The biological activity research includes activities such as multidrug resistance (MDR) reversal activity, HIV inhibition, cytotoxicity, antitumor activity, antifeedant activity and insecticidal activity with some insights to their modes of actions. [Abstract]

Saleem M, Ali MS, Hussain S, Jabbar A, Ashraf M, Lee YS
Marine natural products of fungal origin.
Nat Prod Rep. 2007 Oct;24(5):1142-52.
In the search for novel and bioactive molecules for drug discovery, marine-derived natural resources are becoming an important research area. Over 15 marine-derived secondary metabolites are currently in human clinical trials. Terrestrial fungi have produced many therapeutically significant molecules. However, the potential of marine fungi has only been investigated to a limited extent. This review article contains 103 marine-derived fungal metabolites and 77 references. [Abstract]

Daniel JF, Filho ER
Peptaibols of trichoderma.
Nat Prod Rep. 2007 Oct;24(5):1128-41.
The fungal genus Trichoderma has various applications in industry and in medicine, and several species have economic importance as sources of enzymes, antibiotics, plant growth promoters, decomposers of xenobiotics, and as commercial biofungicides. Peptaibiotics and peptaibols are a class of linear peptides synthesized by such fungi, and more than 300 have been described to date. Of this class, those compounds exhibiting antimicrobial activity are referred to as antibiotic peptides. In this review, the biosynthesis, fermentation, structure elucidation (by MS and NMR techniques in particular) and biological activity of antibiotic peptides from Trichoderma species are described. [Abstract]

Buist PH
Exotic biomodification of fatty acids.
Nat Prod Rep. 2007 Oct;24(5):1110-27.
Many biotransformations of mid- to long chain fatty acyl derivatives are intrinsically interesting because of their high selectivity and novel mechanisms. These include one carbon transfer, hydration, isomerization, hydrogenation, ladderane and hydrocarbon formation, thiolation and various oxidative transformations such as epoxidation, hydroxylation and desaturation. In addition, hydroperoxidation of polyunsaturated fatty acids leads to a diverse array of bioactive compounds. The bioorganic aspects of selected reactions will be highlighted in this review; 210 references are cited. [Abstract]

Donadio S, Monciardini P, Sosio M
Polyketide synthases and nonribosomal peptide synthetases: the emerging view from bacterial genomics.
Nat Prod Rep. 2007 Oct;24(5):1073-109.
A total of 223 complete bacterial genomes are analyzed, with 281 citations, for the presence of genes encoding modular polyketide synthases (PKS) and nonribosomal peptide synthetases (NRPS). We report on the distribution of these systems in different bacterial taxa and, whenever known, the metabolites they synthesize. We also highlight, in the different bacterial lineages, the PKS and NRPS genes and, whenever known, the corresponding products. [Abstract]

Smith S, Tsai SC
The type I fatty acid and polyketide synthases: a tale of two megasynthases.
Nat Prod Rep. 2007 Oct;24(5):1041-72.
This review chronicles the synergistic growth of the fields of fatty acid and polyketide synthesis over the last century. In both animal fatty acid synthases and modular polyketide synthases, similar catalytic elements are covalently linked in the same order in megasynthases. Whereas in fatty acid synthases the basic elements of the design remain immutable, guaranteeing the faithful production of saturated fatty acids, in the modular polyketide synthases, the potential of the basic design has been exploited to the full for the elaboration of a wide range of secondary metabolites of extraordinary structural diversity. [Abstract]

Marquet A, Bui BT, Smith AG, Warren MJ
Iron-sulfur proteins as initiators of radical chemistry.
Nat Prod Rep. 2007 Oct;24(5):1027-40.
Iron-sulfur proteins are very versatile biological entities for which many new functions are continuously being unravelled. This review focus on their role in the initiation of radical chemistry, with special emphasis on radical-SAM enzymes, since several members of the family catalyse key steps in the biosynthetic pathways of cofactors such as biotin, lipoate, thiamine, heme and the molybdenum cofactor. It will also include other examples to show the chemical logic which is emerging from the presently available data on this family of enzymes. The common step in all the (quite different) reactions described here is the monoelectronic reductive cleavage of SAM by a reduced [4Fe-4S](1+) cluster, producing methionine and a highly oxidising deoxyadenosyl radical, which can initiate chemically difficult reactions. This set of enzymes, which represent a means to perform oxidation under reductive conditions, are often present in anaerobic organisms. Some other, non-SAM-dependent, radical reactions obeying the same chemical logic are also covered. [Abstract]

Scott DE, Ciulli A, Abell C
Coenzyme biosynthesis: enzyme mechanism, structure and inhibition.
Nat Prod Rep. 2007 Oct;24(5):1009-26.
This review highlights five key reactions in vitamin biosynthesis and in particular focuses on their mechanisms and inhibition and insights from structural studies. Each of the enzymes has the potential to be a target for novel antimicrobial agents. [Abstract]

Webb ME, Marquet A, Mendel RR, R�beill� F, Smith AG
Elucidating biosynthetic pathways for vitamins and cofactors.
Nat Prod Rep. 2007 Oct;24(5):988-1008.
The elucidation of the pathways to the water-soluble vitamins and cofactors has provided many biochemical and chemical challenges. This is a reflection both of their complex chemical nature, and the fact that they are often made in small amounts, making detection of the enzyme activities and intermediates difficult. Here we present an orthogonal review of how these challenges have been overcome using a combination of methods, which are often ingenious. We make particular reference to some recent developments in the study of biotin, pantothenate, folate, pyridoxol, cobalamin, thiamine, riboflavin and molybdopterin biosynthesis. [Abstract]

Holliday GL, Thornton JM, Marquet A, Smith AG, R�beill� F, Mendel R, Schubert HL, Lawrence AD, Warren MJ
Evolution of enzymes and pathways for the biosynthesis of cofactors.
Nat Prod Rep. 2007 Oct;24(5):972-87.
The evolution of metabolic pathways is discussed with reference to the biosynthesis of a number of vitamins and cofactors. Retrograde and patchwork models are highlighted and their relevance to our knowledge of pathway processes and enzymes is examined. Pathway complexity is explained in terms of the acquisition of broad specificity enzymes. [Abstract]

Mendel RR, Smith AG, Marquet A, Warren MJ
Metal and cofactor insertion.
Nat Prod Rep. 2007 Oct;24(5):963-71.
Cells require metal ions as cofactors for the assembly of metalloproteins. Principally one has to distinguish between metal ions that are directly incorporated into their cognate sites on proteins and those metal ions that have to become part of prosthetic groups, cofactors or complexes prior to insertion of theses moieties into target proteins. Molybdenum is only active as part of the molybdenum cofactor, iron can be part of diverse Fe-S clusters or of the heme group, while copper ions are directly delivered to their targets. We will focus in greater detail on molybdenum metabolism because molybdenum metabolism is a good example for demonstrating the role and the network of metals in metabolism: each of the three steps in the pathway of molybdenum cofactor formation depends on a different metal (iron, copper, molybdenum) and also the enzymes finally harbouring the molybdenum cofactor need additional metal-containing groups to function (iron sulfur-clusters, heme-iron). [Abstract]

R�beill� F, Ravanel S, Marquet A, Mendel RR, Smith AG, Warren MJ
Roles of vitamins B5, B8, B9, B12 and molybdenum cofactor at cellular and organismal levels.
Nat Prod Rep. 2007 Oct;24(5):949-62.
Many efforts have been made in recent decades to understand how coenzymes, including vitamins, are synthesised in organisms. In the present review, we describe the most recent findings about the biological roles of five coenzymes: folate (vitamin B9), pantothenate (vitamin B5), cobalamin (vitamin B12), biotin (vitamin B8) and molybdenum cofactor (Moco). In the first part, we will emphasise their biological functions, including the specific roles found in some organisms. In the second part we will present some nutritional aspects and potential strategies to enhance the cofactor contents in organisms of interest. [Abstract]

Weinreb SM
Some recent advances in the synthesis of polycyclic imidazole-containing marine natural products.
Nat Prod Rep. 2007 Oct;24(5):931-48.
This Highlight describes some of the recent synthetic work on imidazole-containing alkaloids isolated from marine sponges. Target molecules have been chosen which demonstrate synthetic strategies leading towards metabolites containing intact imidazole moieties as well as systems bearing modified imidazole rings. [Abstract]

Leeper FJ, Smith AG
Editorial: vitamins and cofactors - chemistry, biochemistry and biology.
Nat Prod Rep. 2007 Oct;24(5):923-6. [Abstract]

Jin Z
Amaryllidaceae and Sceletium alkaloids.
Nat Prod Rep. 2007 Aug;24(4):886-905.
A great number of natural products, especially alkaloids, which exhibit a range of biological activities including acetylcholinesterase inhibition and antineoplastic, cardiovascular and immunostimulatory activities, have been isolated from the plants of the Amaryllidaceae family. this review summarizes isolation, biological activity, and synthetic studies of these alkaloids. The primary biosynthetic pathways of each type of alkaloids are also proposed. [Abstract]

O'Connor PD, Brimble MA
Synthesis of macrocyclic shellfish toxins containing spiroimine moieties.
Nat Prod Rep. 2007 Aug;24(4):869-85.
An overview of the structure and biological activity of macrocyclic polyketides derived from dinoflagellates that contain unusual cyclic imine units is provided. The total and partial syntheses of these molecules are discussed with an emphasis on the construction of the spiroimine functionality thought to be the key pharmacophore of these fact-acting shellfish toxins. [Abstract]

Higuchi K, Kawasaki T
Simple indole alkaloids and those with a nonrearranged monoterpenoid unit.
Nat Prod Rep. 2007 Aug;24(4):843-68.
This review covers the literature on simple indole alkaloids and those with a nonrearranged monoterpenoid unit. Newly isolated alkaloids, structure determinations, total syntheses and biological activities are included. [Abstract]

Schulz S, Dickschat JS
Bacterial volatiles: the smell of small organisms.
Nat Prod Rep. 2007 Aug;24(4):814-42.
This review describes volatiles released into the air by bacteria growing on defined media. Their occurrence, function, and biosynthesis are discussed, and a total of 308 references are cited. An effort has been made to organize the compounds according to their biosynthetic origin. [Abstract]

Recent Articles in Organic Letters

Pathak AK, Yerneni CK, Young Z, Pathak V
Oligomannan Synthesis Using Ionic Liquid Supported Glycosylation.
Org Lett. 2007 Dec 11; .
The synthesis of complex oligosaccharides has been a challenge for researchers. Herein, we describe a strategy for the synthesis of an activated oligomannan 1 that employs ionic liquid (IL) support glycosylation methodology on an IL-tagged mannosyl fluoride donor. This method is capable of rapidly producing linear alpha(1-->6) oligomannan thioglycosides in a convenient and cost-effective manner without the need of column purification after each glycosylation step. [Abstract]

Coldham I, Patel JJ, Raimbault S, Whittaker DT, Adams H, Fang GY, Aggarwal VK
Asymmetric Lithiation-Substitution of Amines Involving Rearrangement of Borates.
Org Lett. 2007 Dec 11;
Asymmetric lithiation of substituted benzylamines, N-Boc-pyrrolidine, or N-Boc-indoline using Beak's methodology was followed by electrophilic quench with trialkylboranes. The resulting borate intermediates rearrange with concomitant C-N bond breakage to give, after oxidation, chiral secondary alcohols with high enantioselectivity. [Abstract]

L�pez CS, P�rez-Balado C, Rodr�guez-Gra�a P, Lera AR
Mechanistic Insights into the Stereocontrolled Synthesis of Hexahydropyrrolo[2,3-b]indoles by Electrophilic Activation of Tryptophan Derivatives.
Org Lett. 2007 Dec 11;
A three-step mechanism involving the formation and rearrangement of an intermediate with indoline-azetidine spirocyclic core structure was shown by DFT computations to account for the electrophilic cyclization of tryptophan derivatives to hexahydropyrrolo[2,3-b]indoles. The corresponding 3a-bromo derivatives have been obtained in high yields and synthetically useful exo/endo ratios. [Abstract]

Matsuda Y, Kitajima M, Takayama H
First Total Synthesis of Trimeric Indole Alkaloid, Psychotrimine.
Org Lett. 2007 Dec 11;
The first total synthesis of (+/-)-psychotrimine, a novel trimeric indole alkaloid isolated from Psychotria rostrata, was achieved. In the total synthesis, the copper-mediated intramolecular and intermolecular aminations of halobenzenes, which respectively contributed to the construction of a pyrrolidinoindoline core and the installation of a third tryptamine unit, were used as key steps. [Abstract]

Esteban J, Costa AM, G�mez A, Vilarrasa J
Michael Addition-Elimination Reactions of Chiral Enolates with Ethyl 3-Halopropenoates.
Org Lett. 2007 Dec 11;
Key dienoic or dienal substructures of cytotoxic macrolides amphidinolide E and dictyostatin have been prepared via a Michael addition (followed by elimination of X-) of chiral enolates on beta-halo derivatives of ethyl acrylate, with full retention of the initial E or Z configuration. Evans oxazolidin-2-ones and our related thiazolidin-2-ones, as well as a fine-tuning of the reaction conditions, have been essential. Many chiral building blocks are accessible from these adducts. [Abstract]

Stoll AH, Knochel P
Preparation of Fully Substituted Anilines for the Synthesis of Functionalized Indoles.
Org Lett. 2007 Dec 11;
A wide range of highly functionalized indoles were prepared by the successive magnesiation of readily available o-alkynyl protected anilines using TMPMgCl.LiCl or LDA, followed by a KH-mediated cyclization reaction. [Abstract]

Zhang X, Xiao Y, Qian X
Highly Efficient Energy Transfer in the Light Harvesting System Composed of Three Kinds of Boron-Dipyrromethene Derivatives.
Org Lett. 2007 Dec 11;
A light-harvesting system containing three kinds of BODIPY fluorophores was synthesized. It exhibited very strong absorption in the region from 300 to 700 nm, and the energy transfer within it was highly efficient. [Abstract]

Tremblay MS, Lee M, Sames D
A Luminescent Sensor for Tyrosine Phosphorylation.
Org Lett. 2007 Dec 11;
We have developed a luminogenic probe for tyrosine phosphorylation based on a short peptide sequence containing an iminodiacetate moiety near the site of phosphorylation. In response to kinase activity, the probe provides a strong luminescence enhancement, resulting from the increased ability of the probe to bind and sensitize Tb3+ and Eu3+ ions upon phosphorylation. [Abstract]

Jung ME, Zhang TH
Anti Aldol Selectivity in a Synthetic Approach to the C(1)-C(12) Fragment of the Tedanolides.
Org Lett. 2007 Dec 8;
In a synthetic approach to the completely protected C1-C12 fragment of the macrocyclic cytotoxic agent tedanolide 1, we carried out the tin-catalyzed Mukaiyama aldol reaction between the 2,3-dialkoxypropanal 5 and the silyl enol ether 6 derived from the ketone 7, which gave, unexpectedly, the anti aldol isomer, rather than the expected syn isomer 4, as the major diastereomer formed. [Abstract]

Hu HY, Xiang JF, Yang Y, Chen CF
A Helix-Turn-Helix Supersecondary Structure Based on Oligo(phenanthroline dicarboxamide)s.
Org Lett. 2007 Dec 8;
An artificial helix-turn-helix (HTH) supersecondary structure based on the oligo(phenanthroline dicarboxamide)s, in which the 2,2'-dimethoxy-1,1'-binaphthyl-6,6'-diamine subunit was utilized as the turn to impart a bias in the twist sense of the supersecondary structure, was reported. The HTH structure has been demonstrated by UV/vis, NMR, CD spectra, and X-ray crystal analysis. [Abstract]

Dunet G, Mayer P, Knochel P
Highly Diastereoselective Addition of Cinnamylzinc Derivatives to alpha-Chiral Carbonyl Compounds.
Org Lett. 2007 Dec 8;
Cinnamylzinc reagents react with cyclic and acyclic alpha-chiral ketones under very mild conditions (-78 degrees C, 1 h), yielding the corresponding homoallylic alcohols bearing three adjacent stereocenters with high diastereoselectivity. An extension of this reaction to enantioenriched alpha-chiral ketones is also described. [Abstract]

Schmidt B, Biernat A
Tandem RCM-Isomerization Approach to Glycals of Desoxyheptoses from a Common Precursor.
Org Lett. 2007 Dec 8;
Ring closing metathesis and tandem RCM-isomerization have been applied to the synthesis of six- to eight-membered oxacycles, starting from a common precursor. The products of the tandem RCM-isomerization sequence are glycals of 3-deoxyheptoses of varying ring size. [Abstract]

Marois JS, Cantin K, Desmarais A, Morin JF
[3]Rotaxane-Porphyrin Conjugate as a Novel Supramolecular Host for Fullerenes.
Org Lett. 2007 Dec 8;
A new supramolecular host with good affinity toward fullerenes has been developed. This host having a tweezer-like shape is built on a [3]rotaxane scaffold and contains two free-base porphyrin moieties as recognition units for fullerenes. The ability of this tweezer to bind fullerenes strongly depends on the solvent system used and the size of fullerene. [Abstract]

Waetzig JD, Hanson PR
A Multifaceted Phosphate Tether: Application to the C1-C14 Subunit of Dolabelides A-D.
Org Lett. 2007 Dec 7;
A phosphate tether approach to the C1-14 subunit of dolabelide is described. The phosphate tether serves a multifaceted role mediating several processes, including (i) diastereotopic differentiation via RCM, (ii) selective CM by imparting Type III behavior to the exocyclic olefin, (iii) regioselective hydrogenation, and (iv) regioselective Pd(0)-catalyzed reductive opening of the bicyclic phosphate. Overall, this strategy uses orthogonal protecting- and leaving-group properties innate to phosphate esters to rapidly assembly the titled subunit. [Abstract]

Bouffard J, Kim Y, Swager TM, Weissleder R, Hilderbrand SA
A Highly Selective Fluorescent Probe for Thiol Bioimaging.
Org Lett. 2007 Dec 7;
A new fluorescent turn-on probe (3) for the selective sensing and bioimaging of thiols is reported. In aqueous buffer solutions at physiological pH, thiols cleave the 2,4-dinitrobenzenesulfonyl group to release the red-emissive donor-acceptor fluorophore (4). The probe displays excellent immunity to interference from nitrogen and oxygen nucleophiles and the imaging of thiols in living cells is demonstrated. [Abstract]

Nelson HM, Stoltz BM
Progress toward the Synthesis of the Basiliolides and Transtaganolides: An Intramolecular Pyrone Diels-Alder Entry into a Novel Class of Natural Products.
Org Lett. 2007 Dec 7;
Efforts directed toward the synthesis of a basiliolide/transtaganolide model system are disclosed. A highly endo-selective intramolecular pyrone Diels-Alder (IMPDA) cycloaddition rapidly constructs the tricyclic core of the basiliolides and transtaganolides. [Abstract]

Burns AC, Forsyth CJ
Intramolecular Diels-Alder/Tsuji Allylation Assembly of the Functionalized trans-Decalin of Salvinorin A.
Org Lett. 2007 Dec 7;
An enantioselective synthesis of the highly functionalized trans-decalin core (2) of salvinorin A is described. The tetraene 4 was synthesized in six steps from a known l-(+)-tartaric acid derivative. Three contiguous stereocenters, two of them quaternary, on the trans-decalin were established asymmetrically by an intramolecular Diels-Alder/Tsuji allylation sequence. [Abstract]

Cui SL, Wang J, Wang YG
Facile Access to Pyrazolines via Domino Reaction of the Huisgen Zwitterions with Aziridines.
Org Lett. 2007 Dec 7;
A novel, efficient, and general domino reaction of 2-acylaziridines with the Huisgen zwitterions to furnish 2-pyrazoline rings is described. A possible mechanism for the domino sequence is proposed. [Abstract]

Lee SS, Kim HS, Hwang TK, Oh YH, Park SW, Lee S, Lee BS, Chi DY
Efficiency of Bulky Protic Solvent for S(N)2 Reaction.
Org Lett. 2007 Dec 6;
We calculate and compare the effects of aprotic vs protic solvent on the rate of SN2 reaction [F- + C3H7OMs--> C3H7F + OMs-]. We find that aprotic solvent acetonitrile is more efficient than a small protic solvent such as methanol. Bulky protic solvent (tert-butyl alcohol) is predicted to be quite efficient, giving the rate constant that is similar to that in CH3CN. Our calculated relative activation barriers of the SN2 reaction in methanol, tert-butyl alcohol, and CH3CN are in good agreement with experimental observations. [Abstract]

Wang JL, Tang ZM, Xiao Q, Zhou QF, Ma Y, Pei J
Molecular Wires Based on Thienylethynylene: Synthesis, Photophysical Properties, and Excited-State Lifetime.
Org Lett. 2007 Dec 6;
A series of pi-conjugated molecular wires based on thienylethynylene units have been developed to understand the effect of the molecular structures on their photophysical properties. The investigation of their photophysical properties indicates that the formation of aggregates at the ground state is effectively suppressed by the incorporation of truxene units. The excited-state lifetimes are observed to be biexponential for these molecular wires. [Abstract]

Sessler JL, Cho DG
The Benzil Rearrangement Reaction: Trapping of a Hitherto Minor Product and Its Application to the Development of a Selective Cyanide Anion Indicator.
Org Lett. 2007 Dec 5;
The isolation and characterization of an intermediate from the benzil-cyanide reaction is reported. The use of this trapping chemistry to produce a chemical indicator for the cyanide anion is described. It relies on the synthesis and reaction of a pi-extended analogue of benzil. Addition of tetrabutylammonium cyanide to organic solutions of this species, referred to as compound 3 in the text, gives rise to a dramatic change in both color and fluorescence properties. [Abstract]

Lee KS, Kim HJ, Kim GH, Shin I, Hong JI
Fluorescent Chemodosimeter for Selective Detection of Cyanide in Water.
Org Lett. 2007 Dec 5;
A coumarin-based fluorescent chemodosimeter with a salicylaldehyde functionality as a binding site has been developed for selective detection of cyanide anions over other anions in water at biological pH. [Abstract]

Zapata F, Caballero A, Espinosa A, Tarraga A, Molina P
Triple Channel Sensing of Pb(II) Ions by a Simple Multiresponsive Ferrocene Receptor Having a 1-Deazapurine Backbone.
Org Lett. 2007 Dec 5;
A new redox, chromogenic, and fluorescent chemosensor molecule based on a deazapurine ring selectively senses aqueous Pb2+ in acetonitrile over other metal ions examined: redox shift (DeltaE1/2 = 0.15 V of the Fe(II)/Fe(III) redox couple), the colorless to orange color change, and an emission change of 620-fold, with an unprecedented detection limit of 2.7 mug L-1. The signal transduction occurs via a reversible CHEF with this inherent quenching metal ion. [Abstract]

Marshall JA, Eidam PM
A Formal Synthesis of the Callipeltoside Aglycone.
Org Lett. 2007 Dec 5;
A synthesis of the macrocyclic core structure of callipeltoside A and a C9 epimer has been achieved by applications of chiral vinylzinc or Kishi-Nozaki-Hiyama (K-N-H) additions, Roskamp homologations, and acylketene or intramolecular K-N-H macrolactonizations as key bond-forming steps. [Abstract]

Simsek S, Horzella M, Kalesse M
Oxazaborolidinone-Promoted Vinylogous Mukaiyama Aldol Reactions.
Org Lett. 2007 Dec 4;
delta-Hydroxy-alpha,beta-unsaturated carbonyl compounds were prepared in one step via the vinylogous Mukaiyama aldol reactions with O,O-silyl ketene acetals. Isopropyl alcohol as additive and tryptophane-based B-phenyloxazaborolidinone were required for obtaining the gamma-alkylated product in high enantioselectivities. [Abstract]

Chou HH, Wu HM, Wu JD, Ly TW, Jan NW, Shia KS, Liu HJ
Polyene Cyclization Promoted by the Cross-Conjugated alpha-Carbalkoxy Enone System. Observation on a Putative 1,5-Hydride/1,3-Alkyl Shift under Lewis Acid Catalysis.
Org Lett. 2007 Dec 4;
Polyene cyclization of compounds 3 and 4 under catalysis with AlCl3 and/or SnCl4 gave rise to complex bicyclic products 8 and 9, structures of which were highly unexpected, and X-ray analyses were invoked for unambiguously structural identification. Mechanistically, a tandem sigma-bond rearrangement process, including an unusual through-space 1,5-hydride or 1,3-alkyl shift as a key operation, is proposed. [Abstract]

Siebert MR, Yudin AK, Tantillo DJ
Cycloaddition/Ring Opening Reaction Sequences of N-Alkenyl Aziridines: Influence of the Aziridine Nitrogen on Stereoselectivity.
Org Lett. 2007 Dec 4;
The cycloaddition of (Z)-7-(prop-1-enyl)-7-azabicyclo[4.1.0]heptane with dimethyl acetylene dicarboxylate (DMAD) was reported previously to proceed with complete stereoselectivity. Quantum chemical calculations (B3LYP) were used to evaluate the mechanism of the cyclization process, and it was discovered that a stepwise pathway is preferred. The subsequent electrocyclic ring opening reaction of the cyclobutene was also studied, and it was found that ring opening to the "methyl-in" dienamine is preferred to the "methyl-out" product by some 4-5 kcal/mol. [Abstract]

Magens S, Ertelt M, Jatsch A, Plietker B
A Nucleophilic Fe Catalyst for Transesterifications under Neutral Conditions.
Org Lett. 2007 Dec 4;
Carboxylic esters belong to the most important functional groups in organic chemistry. Strong efforts have been made in developing mild catalytic procedures for their preparation. Among the various methods developed to date, transesterifications have occupied an important space. In the present paper, a new catalytic method for this process based on the use of nucleophilic Fe(-II) complexes is presented. Evidence for the formation of an intermediate acyl Fe complex will be presented as well as investigations on scope and limitations. [Abstract]

Toueg J, Prunet J
Dramatic Solvent Effect on the Diastereoselectivity of Michael Addition: Study toward the Synthesis of the ABC Ring System of Hexacyclinic Acid.
Org Lett. 2007 Dec 4;
During our studies toward the synthesis of the ABC ring system of hexacyclinic acid, we have observed a dramatic influence of the solvent on both our key steps. The diastereoselectivity of the intermolecular Michael addition could be totally reversed by changing the polarity of the solvent, and trifluoroethanol was found to be the optimal solvent for the following Mn(III)-promoted radical cyclization. [Abstract]

Yamashita F, Kuniyasu H, Terao J, Kambe N
Platinum-Catalyzed Regio- and Stereoselective Arylthiolation of Internal Alkynes.
Org Lett. 2007 Dec 4;
Unsymmetrical internal alkynes such as ethyl phenylpropiolate (2b) successfully underwent Pt-catalyzed decarbonylative arylthiolation by thioesters. The regio- and stereoselective insertion of 2b into an S-Pt bond was confirmed by reaction with a platinum complex with an S-Pt-Cl framework. [Abstract]

Recent Articles in The Journal of Organic Chemistry

Cornel VM
Number 87.
J Org Chem. 2007 Dec 11; .
Reviews are listed in order of appearance in the sources indicated. In multidisciplinary review journals, only those reviews which fall within the scope of this Journal are included. Sources are listed alphabetically in three categories: regularly issued review journals and series volumes, contributed volumes, and other monographs. Titles are numbered serially, and these numbers are used for reference in the index. Major English-language sources of critical reviews are covered. Encyclopedic treatises, annual surveys such as Specialist Periodical Reports, and compilations of symposia proceedings are omitted. This installment of Recent Reviews covers principally the middle part of the 2007 literature. Previous installment: J. Org. Chem. 2007, 72(20), 7809-16. [Abstract]

Avirah RR, Jyothish K, Ramaiah D
Infrared Absorbing Croconaine Dyes: Synthesis and Metal Ion Binding Properties.
J Org Chem. 2007 Dec 11;
Quinaldine-based croconaine dyes synthesized by the condensation reaction between croconic acid and the respective quinaldinium salts are described. These dyes exhibit absorption maximum in the infrared region (840-870 nm) with high molar extinction coefficients (1-5 x 105 M-1 cm-1) and have very low fluorescence quantum yields. Upon binding to divalent metal ions, these dyes were found to form complexes with a 2:1 stoichiometry having high association constants of the order of 1011-1014 M-2, while the monovalent metal ions showed negligible affinity. The binding of the croconaine dye 3d with divalent metal ions especially Zn2+, Pb2+, and Cd2+ led to significant chelation-enhanced fluorescence emission. The broadening of the aromatic signals, vinylic and N-methyl protons and the negligible changes at the aliphatic region of the dye 3d in the 1H NMR spectrum in the presence of Zn2+, indicate that the binding occurs at the carbonyl groups of the croconyl ring. The shift in the croconyl carbonyl stretching frequency in the [3d-Zn2+] complex analyzed through FT-IR analysis further confirms the involvement of two electron-rich carbonyl groups of the croconyl moiety in the complexation. These results demonstrate that the binding of the divalent metal ions at the carbonyl oxygens of these infrared absorbing dyes can be favorably utilized for the development of potential sensors for the detection of metal ions and further can be exploited as sensitizers for photodynamic therapeutic applications. [Abstract]

Fenster E, Smith BT, Gracias V, Milligan GL, Aub� J
Nucleophilic Addition to Iminium Ethers in the Preparation of Functionalized N-Alkyl Heterocycles.
J Org Chem. 2007 Dec 11;
Bicyclic iminium ethers can be synthesized by the reactions of ketones with hydroxyalkyl azides. These cationic species react with a variety of nucleophiles via two possible pathways. The initially formed, kinetic product arises from direct addition to the iminium carbon in the substrate. In some cases, the initial adduct reverts to the starting iminium ether and the ultimate product arises from nucleophilic displacement at the O-alkyl group to afford the terminally functionalized N-substituted amide. The behavior of a range of nucleophiles was studied by using several iminium ethers. In general, the relevant pathway could be identified by characterization of the product formed. For hydroxide addition, which can afford only one product regardless of mechanism, the reaction was shown to arise by the kinetic pathway, using 18O-labeled hydroxide. A one-pot synthesis of functionalized lactams entailing treatment of ketones first with hydroxyalkyl azides followed by nucleophilic addition was also developed. [Abstract]

Chen P, Wang J, Liu K, Li C
Synthesis and Structural Revision of (+/-)-Laurentristich-4-ol.
J Org Chem. 2007 Dec 11;
The structure of tetracyclic natural sesquiterpene laurentristich-4-ol was revised based on its synthetic studies. The proposed and the revised structures of laurentristich-4-ol were both synthesized with SmI2-mediated ketyl radical cyclization as the key step to construct the spirocyclic ether skeleton. [Abstract]

Valiulin RA, Kutateladze AG
2,6,7-Trithiabicyclo[2.2.2]octanes as Promising Photolabile Tags for Combinatorial Encoding.
J Org Chem. 2007 Dec 11;
The adducts of trithiabicyclo[2.2.2]octane (TTBO) and carbonyl compounds undergo efficient photoinduced fragmentation with quantum yields comparable to that of dithiane adducts. The effect of the third sulfur on the stability of the respective radical cations and radicals is examined computationally and experimentally in a laser flash photolysis study. A straightforward synthetic approach to a variety of 4-substituted trithiabicyclo[2.2.2]octanes from 3-bromo-2,2-bis(bromomethyl)propanol is developed, making a diverse set of mass-differentiated photolabile tags readily available for combinatorial encoding. [Abstract]

Ollevier T, Bouchard JE, Desyroy V
Diastereoselective Mukaiyama Aldol Reaction of 2-(Trimethylsilyloxy)furan Catalyzed by Bismuth Triflate.
J Org Chem. 2007 Dec 11;
We have developed an efficient vinylogous Mukaiyama aldol reaction of 2-(trimethylsilyloxy)furan with various aromatic aldehydes mediated by bismuth triflate in low catalyst loading (1 mol %). The reaction proceeds rapidly and affords the corresponding 5-(hydroxy(aryl)methyl)furan-2(5H)-ones in high yields with good to very good diastereoselectivities (dr up to >98:2). Such selectivities, albeit previously reported with other Lewis acids, could this time be achieved with a much lower catalyst loading. 5-(Hydroxy(alkyl)methyl)furan-2(5H)-ones derived from ketones could also be obtained with good diastereoselectivities. [Abstract]

Punidha S, Sinha J, Kumar A, Ravikanth M
First Triazole-Bridged Unsymmetrical Porphyrin Dyad via Click Chemistry.
J Org Chem. 2007 Dec 11;
Click chemistry has been successfully applied in the synthesis of the first example of a triazole-bridged porphyrin dyad containing N2S2 porphyrin and N4 or ZnN4 porphyrin subunits, and fluorescence study indicated a possibility of singlet-singlet energy transfer from the N4 or ZnN4 porphyrin subunit to the N2S2 porphyrin subunit. [Abstract]

Goh YW, Pool BR, White JM
Structural Studies on Cycloadducts of Furan, 2-Methoxyfuran, and 5-Trimethylsilylcyclopentadiene with Maleic Anhydride and N-Methylmaleimide.
J Org Chem. 2007 Dec 11;
The early stages of the retro-Diels-Alder reaction are clearly apparent in the structures of the cycloadducts formed between furan or 5-trimethylsilylcyclopentadiene with maleic anhydride and N-methylmaleimide. The degree of lengthening of the C-C bonds that break in this reaction is clearly related to the known reactivity of these cycloadducts toward this reaction. In the structures of the cycloadducts 21 and 22 derived from 2-methoxyfuran, the early stages of an alternative fragmentation reaction are apparent, consistent with the reactivity of these compounds in solution. [Abstract]

Bronstein HE, Scott LT
Fullerene-like Chemistry at the Interior Carbon Atoms of an Alkene-Centered C(26)H(12) Geodesic Polyarene(1).
J Org Chem. 2007 Dec 11;
The title compound (1) undergoes 1,2-addition reactions of both electrophilic and nucleophilic reagents preferentially at the "interior" carbon atoms of the central 6:6-bond to give fullerene-type adducts 2, 3, 4, and 5. Such fullerene-like chemistry is unprecedented for a topologically 2-dimensional polycyclic aromatic hydrocarbon and qualifies this geodesic polyarene as a "bridge" between the old flat world of polycyclic aromatic hydrocarbons (PAHs) and the new round world of fullerenes. The relief of pyramidalization strain, as in the addition reactions of fullerenes, presumably contributes to the atypical mode of reactivity seen in 1. Molecular orbital calculations, however, reveal features of the nonalternant pi system in 1 that may also play an important role. Thus, the fullerene-like chemistry of 1 may be driven by two or more factors, the relative importances of which are difficult to discern. [Abstract]

Tsuchiya T, Okada Y, Shimizu T, Hirabayashi K, Kamigata N
Molecular Transformations of Unsaturated Thiacrown Ethers.
J Org Chem. 2007 Dec 11;
Unsaturated thiacrown ethers with 15, 18, and 21 members were oxidized to sulfoxides by the reaction with m-CPBA. The reaction with t-BuOCl at -20 degrees C also afforded sulfoxides, whereas the reaction at room temperature yielded cis-trans isomerized compounds. The cis-trans isomerized compound was also obtained by the photochemical reaction or by the reaction with NCS and NCP. Meanwhile, the reaction with NBS and NBP provided an acetal via 1,2-bridged bromonium intermediate. [Abstract]

Hao W, Parker VD
Rapid Formation and Slow Collapse of a Carbocation-Anion Pair to a Neutral Molecule.
J Org Chem. 2007 Dec 8;
The 4,4',4' '-trimethoxytrityl cation (TMT+) was observed to react with acetate ion in acetic acid reversibly to give the corresponding ester (TMT-OAc). The rate of the reaction was found to be independent of [NaOAc] over a 25000-fold range. Similar results were observed in the presence of Bu4N+ in acetic acid as well as in HOAc/AN (1/1). It was concluded that {TMT+ (HOAc/AcO-)} is an ion pair that forms essentially completely from free TMT+ and HOAc/AcO- during the time of mixing under stopped-flow conditions. The process which was studied kinetically is the intramolecular collapse of the ion pair to TMT-OAc which takes place in two steps involving a kinetically significant intermediate. The remarkably close resemblance of this reaction to the Winstein scheme for solvolysis reactions is noted. In analogy to the Winstein scheme, it was proposed that the intermediate could be an intimate ion pair formed upon extrusion of solvent from the solvent separated ion pair. The product-forming step could then correspond to the intimate ion pair reacting further to form a covalent bond between the two moieties within the complex. The values of the thermodynamic and the activation parameters as well as the apparent rate constants for the reaction in the presence of either sodium or tetrabutylammonium ions suggest that these counterions play insignificant roles in the reactions. However, the equilibrium constant for the intramolecular step (K4) was observed to be two times greater in the presence of Bu4N+ than in the presence of Na+. The rate of the reaction in HOAc was observed to be about four times as great as that in HOAc/AN (1/1). [Abstract]

Lietard J, Meyer A, Vasseur JJ, Morvan F
New Strategies for Cyclization and Bicyclization of Oligonucleotides by Click Chemistry Assisted by Microwaves.
J Org Chem. 2007 Dec 8;
The synthesis of cyclic, branched, and bicyclic oligonucleotides was performed by copper-catalyzed azide-alkyne cycloaddition assisted by microwaves in solution and on solid support. For that purpose, new phosphoramidite building blocks and new solid supports were designed to introduce alkyne and bromo functions into the same oligonucleotide by solid-phase synthesis on a DNA synthesizer. The bromine atom was then substituted by sodium azide to yield azide oligonucleotides. Cyclizations were found to be more efficient in solution than on solid support. This method allowed the efficient preparation of cyclic (6- to 20-mers), branched (with one or two dangling sequences), and bicyclic (2 x 10-mers) oligonucleotides. [Abstract]

Liu Z, Shi F, Martinez PD, Raminelli C, Larock RC
Synthesis of Indazoles by the [3+2] Cycloaddition of Diazo Compounds with Arynes and Subsequent Acyl Migration.
J Org Chem. 2007 Dec 8;
The [3+2] cycloaddition of a variety of diazo compounds with o-(trimethylsilyl)aryl triflates in the presence of CsF or TBAF at room temperature provides a very direct, efficient approach to a wide range of potentially biologically and pharmaceutically interesting substituted indazoles in good to excellent yields under mild reaction conditions. Simple diazomethane derivatives afford N-unsubstituted indazoles or 1-arylated indazoles, depending upon the stoichiometry of the reagents and the reaction conditions, while dicarbonyl-containing diazo compounds undergo carbonyl migration to afford 1-acyl or 1-alkoxycarbonyl indazoles selectively. [Abstract]

Keith JM
One Step Conversion of Heteroaromatic-N-Oxides to Imidazolo-Heteroarenes.
J Org Chem. 2007 Dec 8;
Various pyridine-, quinoline-, isoquinoline-, and pyrimidine-N-oxides were converted to their corresponding alpha-imidazoloheteroarenes in good yield by treatment with sulfuryl diimidazole in nonpolar solvents at elevated temperatures. [Abstract]

Hubbard A, Okazaki T, Laali KK
Halo- and Azidodediazoniation of Arenediazonium Tetrafluoroborates with Trimethylsilyl Halides and Trimethylsilyl Azide and Sandmeyer-Type Bromodediazoniation with Cu(I)Br in [BMIM][PF(6)] Ionic Liquid.
J Org Chem. 2007 Dec 8;
Reaction of [ArN2][BF4] salts immobilized in [BMIM][PF6] ionic liquid (IL) with TMSX (X = I, Br) and TMSN3 represents an efficient method for the preparation of iodo-, bromo-, and azido-derivatives via dediazoniation. The reactions can also be effected starting with ArNH2 by in situ diazotization with [NO][BF4] followed by reaction with TMSX or TMSN3. Depending on the substituents on the benzenediazonium cation, competing fluorodediazoniation (ArF formation) and hydrodediazoniation (ArH formation) were observed. Dediazoniation with TMSN3 and with TMSI generally gave the highest chemoselectivity toward ArN3 and ArI formation. The IL was recycled and reused up to 5 times with no appreciable decrease in the conversions. Multinuclear NMR monitoring of the interaction of [ArN2][BF4]/TMSX, [BMIM][PF6]/TMSX, and [BMIM][PF6]/TMSX/[ArN2][BF4] indicated that TMSF is formed primarily via [ArN2][BF4]/TMSX, generating [ArN2][X] in situ, which gives ArX on dediazoniation. Competing formation of ArF in Sandmeyer-type bromodediazoniation of [ArN2][BF4] with Cu(I)Br immobilized in the IL points to significant involvement of heterolytic dediazoniation. [Abstract]

Xue J, Liu P, Pan Y, Guo Z
A Total Synthesis of OSW-1.
J Org Chem. 2007 Dec 8;
A new and practical method was developed to synthesize OSW-1, a natural saponin with potent antitumor activities, from (+)-dehydroisoandrosterone, l-arabinose, and d-xylose on gram scale. The synthesis was achieved in 10 linear steps with an overall yield of 6.4% starting from (+)-dehydroisoandrosterone. [Abstract]

Cernak TA, Gleason JL
Density Functional Theory Guided Design of Exo-Selective Dehydroalanine Dienophiles for Application Toward the Synthesis of Palau'amine.
J Org Chem. 2007 Dec 8;
Diels-Alder cycloadditions of dehydroalanine derivatives with cyclopentadiene, applicable to the synthesis of palau'amine, were investigated experimentally and using DFT computations at the B3LYP/6-31G* level of theory. Oxazolone and thiohydantoin dienophiles were found to be significantly more reactive than hydantoins or dehydroalanine methyl esters. The increased reactivity of the thiohydantoins relative to hydantoins is attributed to increased conjugation of nitrogen lone pairs into the thiocarbonyl group. beta-Substitution greatly decelerates the cycloadditions due to steric interactions in the transition states outweighing any electronic activation by chlorine. Hydantoins and thiohydantoins were found to be exo-selective, while the corresponding oxazolones and dehydroalanines were unselective. [Abstract]

Phan L, Andreatta JR, Horvey LK, Edie CF, Luco AL, Mirchandani A, Darensbourg DJ, Jessop PG
Switchable-Polarity Solvents Prepared with a Single Liquid Component.
J Org Chem. 2007 Dec 8;
Known liquids that can reversibly switch their polarity at atmospheric pressure are all prepared as mixtures of two liquid components; we now report a series of switchable-polarity solvents that consist, in their low-polarity form, of only a single liquid component, a secondary amine. These solvents operate in a polarity range that is significantly lower than those of previously reported switchable solvents. Application to the separation and purification of a polymer and recovery of a catalyst is described. [Abstract]

Herrero MA, Kremsner JM, Kappe CO
Nonthermal Microwave Effects Revisited: On the Importance of Internal Temperature Monitoring and Agitation in Microwave Chemistry.
J Org Chem. 2007 Dec 7;
The concept of nonthermal microwave effects has received considerable attention in recent years and is the subject of intense debate in the scientific community. Nonthermal microwave effects have been postulated to result from a direct stabilizing interaction of the electric field with specific (polar) molecules in the reaction medium that is not related to a macroscopic temperature effect. In order to probe the existence of nonthermal microwave effects, four synthetic transformations (Diels-Alder cycloaddition, alkylation of triphenylphosphine and 1,2,4-triazole, direct amide bond formation) were reevaluated under both microwave dielectric heating and conventional thermal heating. In all four cases, previous studies have claimed the existence of nonthermal microwave effects in these reactions. Experimentally, significant differences in conversion and/or product distribution comparing the conventionally and microwave-heated experiments performed at the same measured reaction temperature were found. The current reevaluation of these reactions was performed in a dedicated reactor setup that allowed accurate internal reaction temperature measurements using a multiple fiber-optic probe system. Using this technology, the importance of efficient stirring and internal temperature measurement in microwave-heated reactions was made evident. Inefficient agitation leads to temperature gradients within the reaction mixture due to field inhomogeneities in the microwave cavity. Using external infrared temperature sensors in some cases results in significant inaccuracies in the temperature measurement. Applying the fiber-optic probe temperature monitoring device, a critical reevaluation of all four reactions has provided no evidence for the existence of nonthermal microwave effects. Ensuring efficient agitation of the reaction mixture via magnetic stirring, no significant differences in terms of conversion and selectivity between experiments performed under microwave or oil bath conditions at the same internally measured reaction temperatures were experienced. The observed effects were purely thermal and not related to the microwave field. [Abstract]

Yusubov MS, Funk TV, Chi KW, Cha EH, Kim GH, Kirschning A, Zhdankin VV
Preparation and X-ray Structures of 3-[Bis(trifluoroacetoxy)iodo]benzoic Acid and 3-[Hydroxy(tosyloxy)iodo]benzoic Acid: New Recyclable Hypervalent Iodine Reagents.
J Org Chem. 2007 Dec 7;
Preparation, structural characterization, and reactivity of 3-[bis(trifluoroacetoxy)iodo]benzoic acid and 3-[hydroxy(tosyloxy)iodo]benzoic acid, new recyclable iodine(III) reagents derived from 3-iodosylbenzoic acid, are described. The reduced form of these reagents, 3-iodobenzoic acid, can be easily recovered from the reaction mixtures using ion-exchange resin or basic aqueous workup followed by acidification with HCl. [Abstract]

Usui K, Aso M, Fukuda M, Suemune H
Photochemical Generation of Oligodeoxynucleotide Containing a C4'-Oxidized Abasic Site and Its Efficient Amine Modification: Dependence on Structure and Microenvironment.
J Org Chem. 2007 Dec 7;
Bleomycin-induced oxidative DNA damage under limited oxygen conditions results in the formation of the C4'-oxidized abasic site (1). We synthesized the oligodeoxynucleotides (ODN) 5, which contains 4'-o-nitrobenzyloxythymidine (3), and 6, which contains 2-nitrobenzyloxy-4'-methoxy-2'-deoxy-d-ribofuranoside (4), as the caged precursors of 7, an ODN containing 1, to study its reactivity with amines. Photoirradiation of the single- and double-stranded 5 led to the formation of 7. Uncaging of the duplex was faster and the yield of 7 was higher with the double-stranded than with the single-stranded ODN. It was suggested that a low dielectric environment of the o-nitrobenzyloxy group in the minor groove of the duplex might accelerate the uncaging rate. Similarly, 6 and its duplex yielded 7 by photoirradiation. However, the yields of 7 were lower than those of 5, and duplex formation slowed the uncaging rate. Reaction of the obtained 7 with an amine resulted in the formation of the lactam 2b in good yield in both single- and double-stranded forms, showing that amine modification of biomolecules by an ODN containing 1 is possible under physiologic conditions. [Abstract]

Wang MC, Zhang QJ, Zhao WX, Wang XD, Ding X, Jing TT, Song MP
Evaluation of Enantiopure N-(Ferrocenylmethyl)azetidin-2-yl(diphenyl)methanol for Catalytic Asymmetric Addition of Organozinc Reagents to Aldehydes.
J Org Chem. 2007 Dec 7;
A facile and practical approach to preparation of enantiopure N-(ferrocenylmethyl)azetidin-2-yl(diphenyl)methanol was developed from cheap and easily available l-(+)-methionine. Synthetic highlights include the three-step, one-pot construction of the chiral azetidine ring and the development of an improved one-step procedure for the synthesis of the key intermediate l-2-amino-4-bromobutanoic acid. Enantiopure N-(ferrocenylmethyl)azetidin-2-yl(diphenyl)methanol was evaluated for catalytic asymmetric addition of organozinc reagents to aldehydes. The asymmetric ethylation, methylation, arylation, and alkynylation of aldehydes achieved enantioselectivity of up to 98.4%, 94.1%, 99.0%, and 84.6% ee, respectively, in the presence of a catalytic amount of chiral N-(ferrocenylmethyl)azetidin-2-yl(diphenyl)methanol. Our results demonstrated further that the four-membered heterocycle-based backbone was a good potential chiral unit for the catalytic asymmetric induction reaction, and the hindrance of the bulky ferrocenyl group, compared to a phenyl group, played an important role in the enantioselectivities. A possible transition for the catalytic asymmetric addition has been proposed on the basis of the crystal structure of the chiral ligand 3b including two HOAc molecules and previous studies. [Abstract]

Ligthart GB, Guo D, Spek AL, Kooijman H, Zuilhof H, Sijbesma RP
Ureidobenzotriazine Multiple H-Bonding Arrays: The Importance of Geometrical Details on the Stability of H-Bonds.
J Org Chem. 2007 Dec 7;
A 3-ureidobenzo-1,2,4-triazine 1-N-oxide (1) was synthesized successfully. The derivative displays an acceptor-donor-acceptor-acceptor (ADAA) hydrogen-bonding motif in CDCl3 and DMSO-d6 solution as well as in the solid state. Although moderately strong association of 1 was observed with DAD motifs, nonspecific binding is observed with ureidopyridines featuring a complementary DADD array. Density functional calculations of conformations 1a and 1b together with two complexes revealed the clearly nonplanar geometry of the multiply hydrogen-bonded complex, in which some bonds are significantly longer (3.2 A) than is optimal for H-bonds. As a result, only very small free energies of association were calculated, in line with the experimentally observed absence of specific assembly of the components. [Abstract]

Ryoda A, Yajima N, Haga T, Kumamoto T, Nakanishi W, Kawahata M, Yamaguchi K, Ishikawa T
Optical Resolution of (+/-)-1,2-Bis(2-methylphenyl)ethylene-1,2-diamine as a Chiral Framework for 2-Iminoimidazolidine with 2-Methylphenyl Pendant and the Guanidine-Catalyzed Asymmetric Michael Reaction of tert-Butyl Diphenyliminoacetate and Ethyl Acrylate.
J Org Chem. 2007 Dec 7;
(+/-)-1,2-Bis(2-methylphenyl)ethylene-1,2-diamine, prepared from benzil and ammonium acetate, was optically resolved as a chiral framework for 2-(1-benzyl-2-hydroxyethyl)imino-1,3-dimethylimidazolidine with 2-methylphenyl pendants at the 4,5-positions. Catalysis ability of the 1,3-dimethyl-4,5-bis(2-methylphenyl)imidazolidine and the related 1,3-dibenzyl-4,5-diphenylimidazolidine was examined in the asymmetric Michael reaction of t-butyl diphenyliminoacetate and ethyl acrylate. [Abstract]

Greer EM, Aebisher D, Greer A, Bentley R
Computational Studies of the Tropone Natural Products, Thiotropocin, Tropodithietic Acid, and Troposulfenin. Significance of Thiocarbonyl-Enol Tautomerism.
J Org Chem. 2007 Dec 7;
Computations provide insight to the stability and isomeric possibilities of thiotropocin, tropodithietic acid, and troposulfenin. Thiotropocin and tropodithietic acid contain a flat 7-membered ring and delocalized pi-bonds similar to those of tropylium ion (C7H7+). Troposulfenin is far less stable; it contains a puckered tropone ring and localized bonds similar to 1,3,5-cycloheptatriene. A facile 1,5-hydrogen shift suggests that thiotropocin and tropodithietic acid exist as a pair of interconverting tautomers. Loss of an acidic proton from these three tautomers produces the same conjugate base structure. [Abstract]

Hanessian S, Vinci V, Fettis K, Maris T, Viet MT
Self-Assembly of Noncyclic Bis-d- and l-tripeptides into Higher Order Tubular Constructs: Design, Synthesis, and X-ray Crystal Superstructure.
J Org Chem. 2007 Dec 7;
Trans (1R,2R)-diaminocyclohexane was used as a semirigid vicinal diamine to anchor two N-protected tripeptides consisting of l-d-l amino acids as carboxy terminal amides. The bis-tripeptide consisting of l-Ser (OBn)-d-Ser (OBn)-l-Ser (O-p-bromobenzyl) Boc afforded X-ray quality crystals containing benzene and chloroform solvent molecules. Analysis of the solid-state structure revealed a highly H-bonded helical open-ended tubular superstructure. The tripeptide strands intertwine like a pair of self-embracing arms, held together by a gamma-turn and a 14-membered antiparallel H-bonded macroring spanning the first and third amino acid residues within each strand. Whereas the tripeptide from the R,R anchor gave beautiful crystals from benzene and chloroform, the analogous construct from the S,S-anchored diamine gave a gel. Related bis-tripeptides with different amino acids showed extensive intramolecular H-bonding based on NMR titration and dilution experiments. [Abstract]

Kim YK, Lee HN, Singh NJ, Choi HJ, Xue JY, Kim KS, Yoon J, Hyun MH
Anthracene Derivatives Bearing Thiourea and Glucopyranosyl Groups for the Highly Selective Chiral Recognition of Amino Acids: Opposite Chiral Selectivities from Similar Binding Units.
J Org Chem. 2007 Dec 6;
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