N-pentenyl Glycosides Research Articles

N-pentenyl glycosides in the efficient assembly of the blood group substance B tetrasaccharide

The fact that n-pentenyl glycosides (nPGs) are stable to a wide variety of reaction conditions but yet can be chemospecifically activated is advantageous for the efficient, convergent assembly of oligosaccharides. The nPGs are prepared directly from the aldose or by normal glycoside-forming reactions, and by using N-iodosuccinimide/triethylsilyl triflate as the iodonium source, even “disarmed” glycosyl donors react within minutes. The four monosaccharide components of the human blood-group determinant B are prepared with full or partial protection as required. Assembly of the tetrasaccharide then requires only five steps, three to give, in sequence, the disaccharide (68%), trisaccharide (82%), and tetrasaccharide (91%), the other two steps being required to deprotect hydroxyl groups at the di- and tri-saccharide levels for the ensuing coupling reactions.

N-Pentenyl Glycosides in Organic Chemistry: A Contemporary Example of Serendipity

Recent work in our laboratory has shown that n-pentenyl glycosides (NPGs) are excellent substrates for a wide variety of reactions occurring at the anomeric center. They are prepared readily by standard glycoside forming procedures, including Fischer's direct method, and although they are stable to a wide range of reagents, they are readily activated by treatment with a halonium ion. Because of their stability and the neutral conditions for their activation, NPGs are promising substrates for a wide variety of mechanistic and synthetic studies. The effect of some of the commonly used protecting groups upon glycoside reactivity has been probed with these substrates, and the "armed/disarmed" strategy for oligosaccharide assembly emanated directly from these investigations. Thus esters disarm electronically, while benzylidene and isopropylidene rings disarm by torsional strain. However further investigations have shown that the use of N-iodosuccinimide-trifluoromethanesulfonates as the iodinating agent induces smooth reactions of the disarmed substrates. As a result, coupling procedures can be regulated either by the strategic deployment of appropriate groups, or by changing the inorganic promoter. A further level of finesse emanates from the development of procedures to convert the pentenyl group into its vicinal dibromide. These derivatives represent "blocked" NPGs since the reverse reaction is readily carried out via reductive elimination. Thus NPG activity can be sidetracked temporarily by conversion to the dibromide. Under appropriate conditions, the reaction of NPGs in acetonitrile generates acetonitrilium ions which can be trapped in situ with carboxylic acid. This has paved the way for a simple entry to glycoproteins. 1. Prologue 2. Introduction 3. Discovery 4. 4-Pentenyloxymethyl Based Protecting Groups 5. n-Pentenyl Glycosides 5.1. Synthetic Routes 6. Oxidative Hydrolysis of NPGs 7. Acetal Exchange of NPGs 8. Armed/Disarmed Coupling 9. Promoters 10. Typical Procedures for Saccharide Couplings 11. Mechanistic Questions Concerning Armed/Disarmed Effects 11.1. Rationalization 11.2. Dependence on Promoters 11.3. Sidetracking 12. NPGs as Synthons for Glycoproteins 13. Promotor-Mediated Assembly of Oligosaccharides 14. Torsion-Mediated Coupling of Saccharides 15. Epilogue

Synthetic glycoconjugates. 2. n-Pentenyl glycosides as convenient mediators for the syntheses of new types of glycoprotein models

Synthetic glycoconjugates. 2. n-Pentenyl glycosides as convenient mediators for the syntheses of new types of glycoprotein models

N-Pentenyl esters versus n-pentenyl glycosides. Synthesis and reactivity in glycosidation reactions

n-Pentenyl esters, which are readily obtained by mild esterification of the anomeric hydroxy group of sugars, can be efficiently used in glycosidation reactions, and they appear to be less prone to armed–disarmed phenomena than their n-pentenyl glycoside counterparts.

N-Pentenyl glycosides as efficient synthons for promoter-mediated assembly of n-.alpha.-linked glycoproteins

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTn-Pentenyl glycosides as efficient synthons for promoter-mediated assembly of n-.alpha.-linked glycoproteinsA. J. Ratcliffe, P. Konradsson, and Bert Fraser-ReidCite this: J. Am. Chem. Soc. 1990, 112, 14, 5665–5667Publication Date (Print):July 1, 1990Publication History Published online1 May 2002Published inissue 1 July 1990https://doi.org/10.1021/ja00170a055RIGHTS & PERMISSIONSArticle Views362Altmetric-Citations57LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (389 KB) Get e-AlertsSupporting Info (1)»Supporting Information Supporting Information Get e-Alerts

N-Pentenyl glycosides as mediators in the asymmetric synthesis of monosubstituted chiral nonracemic tetrahydrofurans and .gamma.-lactones

n-Pentenyl glycosides can be oxidatively hydrolyzed by treatment with N-bromosuccinimide, previous work having been focused on the usefulness of the resulting glycosyl moiety. In this paper, attention is focused on asymmetric induction in the 2-(bromomethyl) furan that is liberated. The enantiomeric excess depends strongly on the orientations at the anomeric centers and at C2, as well as on the protecting group on the C2 oxygen. α-Anomers display higher asymmetric induction, and rationalization of this observation is based on the assumption that the molecule reacts from the favored ground-state orientation, wherein the exo anomeric effect is displayed

Iodonium promoted reactions of disarmed thioglycosides

N-Iodosuccinimide/trifluoromethanesulfonic acid, which had been shown to promote the solvolysis of disarmed n-pentenyl glycosides, has been found to induce the same reactivity with disarmed thioglycosides as substrates.

N-Pentenyl glycosides facilitate a stereoselective synthesis of the pentasaccharide core of the protein membrane anchor found in Trypanosoma brucei

n-Pentenyl glycosides facilitate a stereoselective synthesis of the pentasaccharide core of the protein membrane anchor found in Trypanosoma brucei

Armed and disarmed n-pentenyl glycosides in saccharide couplings leading to oligosaccharides

Armed and disarmed n-pentenyl glycosides in saccharide couplings leading to oligosaccharides