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Contents list for Organic & Biomolecular Chemistry, issue 18, 2008
Front cover
Org. Biomol. Chem., 2008, 6, 3213
DOI: 10.1039/b814087c
Contents and Chemical Science
Org. Biomol. Chem., 2008, 6, 3215
DOI: 10.1039/b814088j
Perspective
Brønsted-acid and Brønsted-base catalyzed Diels–Alder reactions
Juan Shen and Choon-Hong Tan,
Org. Biomol. Chem., 2008, 6, 3229
DOI: 10.1039/b809505c
The enantioselective Diels–Alder reaction is one of the most important reactions for the synthesis of complex molecules. It provides access to chiral six-membered carbocyclic compounds containing up to four stereogenic centers in a single step. In this perspective, we describe several cases of chiral Brønsted-acid and Brønsted-base catalyzed Diels–Alder reactions, providing an overview of this rapidly growing field.
Communications
Regio- and chemoselective magnesiation of protected uracils and thiouracils using TMPMgCl·LiCl and TMP2Mg·2LiCl
Marc Mosrin, Nadège Boudet and Paul Knochel,
Org. Biomol. Chem., 2008, 6, 3237
DOI: 10.1039/b812528g
Two successive regio- and chemoselective magnesiations using TMPMgCl·LiCl and TMP2Mg·2LiCl enable the full functionalization of protected uracils and thiouracils in good to excellent yields.
Synthesis of (2S)-2-amino-7,8-epoxyoctanoic acid and structure of its metal-bridging complex with human arginase I
Tatiana Y. Zakharian, Luigi Di Costanzo and David W. Christianson,
Org. Biomol. Chem., 2008, 6, 3240
DOI: 10.1039/b811797g
The synthesis of (2S)-2-amino-7,8-epoxyoctanoic acid is reported along with the X-ray crystal structure of its complex with human arginase I, revealing unique coordination interactions with two manganese ions in the enzyme active site.
Papers
Cyclic tetraureas with variable flexibility – synthesis, crystal structures and properties
Denys Meshcheryakov, Françoise Arnaud-Neu, Volker Böhmer, Michael Bolte, Julien Cavaleri, Véronique Hubscher-Bruder, Iris Thondorf and Sabine Werner,
Org. Biomol. Chem., 2008, 6, 3244
DOI: 10.1039/b808773c
As potential anion receptors, cyclic tetraurea compounds comprising all six combinations of rigid xanthene and flexible diphenyl ether units have been synthesized and characterized by 1H NMR, single-crystal X-ray diffraction, UV spectrophotometry and molecular modeling.
Computational design, synthesis and biological evaluation of para-quinone-based inhibitors for redox regulation of the dual-specificity phosphatase Cdc25B
Shahar Keinan, William D. Paquette, John J. Skoko, David N. Beratan, Weitao Yang, Sunita Shinde, Paul A. Johnston, John S. Lazo and Peter Wipf,
Org. Biomol. Chem., 2008, 6, 3256
DOI: 10.1039/b806712k
Quinoid inhibitors of Cdc25B were designed based on the linear combination of atomic potentials (LCAP) methodology. In contrast to a published hypothesis, the biological activities and hydrogen peroxide generation did not correlate with the quinone half-wave potential, E1/2.
Amine and ammonium functionalization of chloromethylsilane-ended dendrimers. Antimicrobial activity studies
Paula Ortega, Jose Luis Copa-Patiño, Ma Angeles Muñoz-Fernandez, Juan Soliveri, Rafael Gomez and F. Javier de la Mata,
Org. Biomol. Chem., 2008, 6, 3264
DOI: 10.1039/b809569h
Carbosilane dendrimers with peripheral ammonium groups present antimicrobial activity against both Gram+ and Gram- bacteria. The studies carried out showed that the multivalency of dendrimers plays a major role in the antibacterial activity of these compounds.
The mechanism of the phosphoramidite synthesis of polynucleotides
Mark A. Russell, Andrew P. Laws, John H. Atherton and Michael I. Page,
Org. Biomol. Chem., 2008, 6, 3270
DOI: 10.1039/b808999j
The coupling of phosphoramidite in polynucleotide synthesis involves O-saccharin nucleophilic catalysis, with a change in rate limiting step with increasing alcohol concentration from breakdown to formation of the intermediate.
Direct formation of 
-glycosides of N-acetyl glycosamines mediated by rare earth metal triflates
Helle Christensen, Mira Steinicke Christiansen, Jette Petersen and Henrik Helligsø Jensen,
Org. Biomol. Chem., 2008, 6, 3276
DOI: 10.1039/b807064d
A direct, mild and efficient protocol for the preparation of -glycosides of N-acetyl glucosamine (GlcNAc) and N-acetyl galactosamine (GalNAc) has been developed using peracetylated -GlcNAc and -GalNAc as donors.
Substituted 2-nitrobenzyltrichloroacetate esters for photodirected oligonucleotide detritylation in solid films
Pawel J. Serafinowski and Peter B. Garland,
Org. Biomol. Chem., 2008, 6, 3284
DOI: 10.1039/b806902f
Synthesis of film-forming photogenerators of trichloroacetic acid, including some with high quantum yields (0.3–0.8) and absorption in the 365–405 nm range, for polymer-less photolithographic fabrication of oligonucleotide arrays.
Modeling the reactive properties of tandemly activated tRNAs
Maria Duca, Shengxi Chen and Sidney M. Hecht,
Org. Biomol. Chem., 2008, 6, 3292
DOI: 10.1039/b806790b
Activated tRNAs bearing amino acids at the 2
- and 3-positions of the 3-terminal adenosine participate efficiently in protein synthesis, although the mechanism by which they function is not well understood. It is shown that both amino moieties of the aminoacyl groups are important to function. The results suggest a model for participation of bisaminoacylated tRNAs in protein synthesis.
Formation of cross-linked adducts between guanine and thymine mediated by hydroxyl radical and one-electron oxidation: a theoretical study
Vanessa Labet, Christophe Morell, André Grand, Jean Cadet, Paola Cimino and Vincenzo Barone,
Org. Biomol. Chem., 2008, 6, 3300
DOI: 10.1039/b805589k
A theoretical study (DFT) on the mechanism of formation of G
T and TG intrastrand adducts to continue previous work on AT and TA intrastrand cross-links.
The neomycin biosynthetic gene cluster of Streptomyces fradiae NCIMB 8233: genetic and biochemical evidence for the roles of two glycosyltransferases and a deacetylase
Qingzhi Fan, Fanglu Huang, Peter F. Leadlay and Jonathan B. Spencer,
Org. Biomol. Chem., 2008, 6, 3306
DOI: 10.1039/b808734b
Specific gene knockouts in neomycin biosynthesis have highlighted the in vivo roles of the glycosyltransferases Neo8 and Neo15, and of the dual-specificity deacetylase Neo16.
Engineered biosynthesis of hybrid macrolide polyketides containing D-angolosamine and D-mycaminose moieties
Ursula Schell, Stephen F. Haydock, Andrew L. Kaja, Isabelle Carletti, Rachel E. Lill, Eliot Read, Lesley S. Sheehan, Lindsey Low, Maria-Jose Fernandez, Friederike Grolle, Hamish A. I. McArthur, Rose M. Sheridan, Peter F. Leadlay, Barrie Wilkinson and Sabine Gaisser,
Org. Biomol. Chem., 2008, 6, 3315
DOI: 10.1039/b807914e
Novel glycosylated macrolides were produced through biosynthetic engineering.
Stereoselective cyclopropanation of serine- and threonine-derived oxazines to access new morpholine-based scaffolds
Filippo Sladojevich, Andrea Trabocchi and Antonio Guarna,
Org. Biomol. Chem., 2008, 6, 3328
DOI: 10.1039/b808895k
The stereoselective cyclopropanation of dihydroxazines, readily obtained from serine and threonine, allows the generation of a unique bicyclic scaffold possessing high conformational constraint and up to five stereocenters.
Stereoselective synthesis of 2,4,5-trisubstituted piperidines by carbonyl ene and Prins cyclisations
Claire A. M. Cariou, Benson M. Kariuki and John S. Snaith,
Org. Biomol. Chem., 2008, 6, 3337
DOI: 10.1039/b808644c
Cyclisation of aldehydes 1a–f catalysed by concentrated hydrochloric acid affords the all cis 2,4,5-trisubstituted piperidines 7a–f with diastereomeric ratios of up to 94 : 6 when the 2-substituent is small, while catalysis by MeAlCl2 gives the trans piperidines 8a–f with diastereomeric ratios of up to 99 : 1.
Intramolecular kinetic isotope effect in hydride transfer from dihydroacridine to a quinolinium ion. Rejection of a proposed two-step mechanism with a kinetically significant intermediate
Charles L. Perrin and Chen Zhao,
Org. Biomol. Chem., 2008, 6, 3349
DOI: 10.1039/b806869k
The KIE for hydride transfer for the reaction illustrated has been found to be 5–6; this is inconsistent with the high intermolecular KIEs derived by fitting to a two-step mechanism with a kinetically significant intermediate complex. Therefore, a two-step mechanism for this reaction is rejected.
A radical-anion chain mechanism following dissociative electron transfer reduction of the model prostaglandin endoperoxide, 1,4-diphenyl-2,3-dioxabicyclo[2.2.1]heptane
David C. Magri and Mark S. Workentin,
Org. Biomol. Chem., 2008, 6, 3354
DOI: 10.1039/b809356c
-Scission fragmentation of the distonic radical-anion 3a, resulting from dissociative electron transfer reduction of the endoperoxide O–O bond at a glassy carbon electrode, participates in a homogeneous radical-anion catalytic cycle.
Probing osmotic effects on invertase with L-(-)-sucrose
Seung-kee Seo and Alexander Wei,
Org. Biomol. Chem., 2008, 6, 3362
DOI: 10.1039/b810158b
The sugar-processing enzyme invertase, which is susceptible to substrate inhibition at high concentrations of (+)-sucrose, is also affected by the biochemically inert L-(-)-sucrose. This reveals that invertase is sensitive to osmotic pressure, a factor which can be deconvoluted from true substrate inhibition by the application of mirror-image substrates.
Regioselective synthesis of functionalized 3,5-diketoesters and 2,4-diketosulfones by uncatalyzed condensation of 1-methoxy-1,3-bis(trimethylsilyloxy)-1,3-butadienes with 
,-unsaturated acid chlorides and sulfonyl chlorides
Thomas Rahn, T. H. Tam Dang, Anke Spannenberg, Christine Fischer and Peter Langer,
Org. Biomol. Chem., 2008, 6, 3366
DOI: 10.1039/b810151e
Functionalized 3,5-diketoesters and 2,4-diketosulfones were regioselectively prepared by reaction of 1,3-bis(trimethylsilyloxy)-1,3-butadienes with ,-unsaturated acid chlorides and sulfonyl chlorides.
Synthetic tetra-acylated derivatives of lipid A from Porphyromonas gingivalis are antagonists of human TLR4
Yanghui Zhang, Jidnyasa Gaekwad, Margreet A. Wolfert and Geert-Jan Boons,
Org. Biomol. Chem., 2008, 6, 3371
DOI: 10.1039/b809090d
Two chemically synthesized lipid As derived from P. gingivalis LPS were unable to activate human and mouse TLR2 and TLR4 to produce cytokines, but were found to be potent antagonists of cytokine secretion induced by enteric LPS.
Dendritic effects in catalysis by Pd complexes of bidentate phosphines on a dendronized support: Heck vs. carbonylation reactions
Amal Mansour, Tzofit Kehat and Moshe Portnoy,
Org. Biomol. Chem., 2008, 6, 3382
DOI: 10.1039/b809715a
Pd catalysts derived from bidentate phosphines immobilized on a dendronized support exhibited a negative dendritic effect in the Heck reaction, but mostly a positive one in amidocarbonylation catalysis.
Diastereoselective functionalizations of enecarbamates derived from pipecolic acid towards 5-guanidinopipecolates as arginine mimetics
Laurent Le Corre, Jean-Claude Kizirian, Camille Levraud, Jean-Luc Boucher, Véronique Bonnet and Hamid Dhimane,
Org. Biomol. Chem., 2008, 6, 3388
DOI: 10.1039/b805811c
Both cis and trans isomers of pipecolate-based arginine mimetics, with four restricted torsion angles (
1, 2, 3 and 
), were synthesized from rac-pipecolate derived enecarbamates via the corresponding ornithine mimetics.
Bioisosteric replacement of the pyrazole 3-carboxamide moiety of rimonabant. A novel series of oxadiazoles as CB1 cannabinoid receptor antagonists
Cheng-Ming Chu, Ming-Shiu Hung, Min-Tsang Hsieh, Chun-Wei Kuo, Suja T. D., Jen-Shin Song, Hua-Hao Chiu, Yu-Sheng Chao and Kak-Shan Shia,
Org. Biomol. Chem., 2008, 6, 3399
DOI: 10.1039/b807648k
Based on the strategy of bioisosterism, a novel class of CB1 antagonists with potent binding affinity and good CB2/1 selectivity was discovered.
Effect of (5S)-5,8-cyclo-2-deoxyadenosine on the conformation of di and trinucleotides. A NMR and DFT study
Boleslaw T. Karwowski, Jacques Gaillard, André Grand and Jean Cadet,
Org. Biomol. Chem., 2008, 6, 3408
DOI: 10.1039/b807046f
It was shown that the C5–C8 bond in the investigated purine cyclonucleoside induces an unusual West conformation of the furanose ring. Thus it can be postulated that 1 would perturb the geometry of DNA.
Inner reorganization during the radical–biradical transition in a nor--lapachone derivative possessing two redox centers
Dulce María Hernández, Maria Aline B. F. de Moura, Drochss Pettry Valencia, Felipe J. González, Ignacio González, Fabiane C. de Abreu, Eufrânio N. da Silva Júnior, Vitor F. Ferreira, Antônio Ventura Pinto, Marilia O. F. Goulart and Carlos Frontana,
Org. Biomol. Chem., 2008, 6, 3414
DOI: 10.1039/b806271d
The electrochemical and spectroelectrochemical-ESR study of an antitumoral derivative obtained from 3-bromo-nor--lapachone revealed that both quinone and nitro functions are reduced independently, successively forming a radical anion and a biradical dianion. Differences in the reorganization energy for both processes indicate changes in the molecular structure during the radical–biradical transition.
Total synthesis of cucurbitaxanthin A, cycloviolaxanthin and capsanthin 3,6-epoxide by applying a regioselective ring opening of tetrasubstituted epoxides
Yumiko Yamano, Masayoshi Ito and Akimori Wada,
Org. Biomol. Chem., 2008, 6, 3421
DOI: 10.1039/b807482h
The synthesis of 3,6-epoxy carotenoids cucurbitaxanthin A 1, cycloviolaxanthin 2 and capsanthin 3,6-epoxide 3, was accomplished via the C15-3,6-epoxides 20e and 20f, prepared by the regioselective ring opening of the 3-hydroxy-5,6-epoxides 10e and 10f.
A new synthetic approach to (+)-lactacystin based on radical cyclisation of enantiopure -ethynyl substituted serine derivatives to 4-methylenepyrrolidinones
Gerald Pattenden and Gwenaëlla Rescourio,
Org. Biomol. Chem., 2008, 6, 3428
DOI: 10.1039/b806681g
A new, formal synthesis of (+)-lactacystin, based on elaboration of the pyrrolidinone ring system, via a 5-exo dig radical cyclisation of an acetylenic bromo amide, is described.
Back cover
Org. Biomol. Chem., 2008, 6, 3439
DOI: 10.1039/b814089h
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