1-O-Vinyl Glycosides via Tebbe Olefination, Their Use as Chiral Auxiliaries and Monomers

Abstract

A series of anomerically pure 1-O-formyl glycosides 1 was prepared and converted into the corresponding 1-O-vinyl glycosides 2 by Tebbe olefination. The unsubstituted vinyl glycosides were obtained as anomerically pure compounds in good yields, and the method of preparation was compatible with the presence of a variety of functional groups. Remarkably, the anomeric formate group was regioselectively converted into the corresponding olefin in the presence of acetate and benzoate protecting groups. With the perspective to use the 1-O-vinyl glycosides as monomers for the preparation of glycosylated poly(vinyl alcohol) derivatives with controlled tacticity, their scope as chiral auxiliaries for a stereodifferentiation in addition reactions to the olefin function was investigated by using the [2+2] cycloaddition to dichloroketene as a model reaction. In particular, vinyl 2,3,4,6-tetra-O-benzoyl-alpha-d-mannopyranoside (2i) exhibited excellent diastereoselectivity. Finally, the 1-O-vinyl glycosides were successfully subjected to radical homopolymerization in bulk or used as electron-rich comonomers in radical copolymerizations with maleic anhydride, yielding alternating, glycosylated poly(vinyl alcohol-alt-maleic anhydride).

Glycosylation of a Ketone with an O-Glycosyl Trichloroacetimidate Provides an Enol Glycoside

“…However, in certain special cases, such as enol O -glycosidic linkages, their formation often requires special synthetic approaches. For example, some acyclic enol glycosides, as represented by the O -isopropenyl and O -butenyl glycosides, are usually derived from corresponding allyl-type glycosides through isomerization, and these have been used extensively as glycosyl donors in oligosaccharide synthesis. − Other methods for their formation include conversion of the 1- O -formyl glycosides into the corresponding 1- O -vinyl glycosides by Tebbe olefination, or adding the C(1)–OH of a glycosyl hemiacetal to ethyl phenyl propiolate in the presence of a strong base, or palladium-catalyzed vinylation of a protected monosaccharide bearing a free C(1)–OH, etc. ,, The current methods for acyclic enol glycosylation require a careful selection of techniques, their modification, or the design of conceptually new approaches . Moreover, most of the reported methods only provide acyclic enol glycosides, with the synthesis of cyclic enol glycosides not being well studied.…”

Glycosylated vinyl ethers by the Julia–Lythgoe–Kocienski olefination: application to the synthesis of 2′,5′-dideoxydisaccharides and carbohydrated β-lactams

“…[16][17][18] It is the latter applications that we considered of most immediate interest to us, given the propensity and popularity of hetero-Diels-Alder methodology to prepare structurally complex frameworks. In order to establish some preliminary indications on the synthetic utility of these bsubstituted enol ether glycosides, we explored their reactivity as dienophiles in hetero-Diels-Alder reactions as illustrated in Scheme 4.…”

Synthesis and 13C NMR Spectroscopy of Model Compounds for the Microstructure Analysis of Poly(Vinyl Glycoside)s

“…[1][2][3][4][5][6] While most of these investigations have dealt with carbohydrate-functionalized standard monomers such as styrenes, acrylates, methacrylates, or acrylamides, we have recently reported the preparation of glycosylated poly-(vinyl alcohol) via free radical polymerization of 1-O-vinyl glycosides (Scheme 1). [7,8] The obtained poly(vinyl glycoside)s represent the structurally simplest glycosylated polymers with an all-carbon backbone; they may exhibit a defined tacticity and secondary structure formation; and they may be regarded as interesting candidates for both biocompatible and biodegradable materials.…”

“…While the free radical polymerization of the 1-O-vinyl mannopyranosides has worked acceptably well, [7,8] some details of the reaction mechanism remained inscrutable because the vinyl glycosides represent an entirely new class of radically polymerizable monomers (Scheme 2). Other examples of simple vinyl acetals had been reported to be nonpolymerizable, [9] and divinyl acetals had been found to produce complex mixtures of microstructures.…”

“…Synthesis of poly(vinyl glycoside)s via free radical polymerization of 1-O-vinyl glycosides; R = OAc, OBz. [7,8] tail-tail connectivity) would be present in the polymer, (iii) which kinds of termination or transfer reactions were encountered, (iv) and to which extent the polymerization proceeded in a stereoselective fashion, furnishing polymers with a controlled tacticity (relative stereochemistry of the repeating units). Moreover, the analysis of the microstructure by means of 1 H and 13 C NMR spectroscopy turned out to be less straightforward than in the case of poly(vinyl ether)s and poly(vinyl acetate), [11][12][13][14][15][16] probably due to the inherent rigidity of the obtained poly(vinyl glycoside)s and the presence of the chiral carbohydrate substituents.…”