Phosphonates 0-glycosylation

Salicylic acid was used for phosphite protection in the synthesis of glycosyl phosphites and phosphates. This derivative is very reactive and readily forms a phosphite upon treatment with an alcohol or a phosphonic acid upon aqueous hydrolysis. ... 

Similarly, starting from 2,3 5,6-di-0-isopropylidene-D-mannofuranose 72, a one-pot procedure that implies the synthesis of glycosyl sulfones by Horner-Wadsworth-Emmons olefination with phosphonate 73, followed by subsequent Michael addition and Ramberg-Backlund reaction92 gives compound 74 in 78% yield93 (Scheme 24). 

Application of H-phosphonate approach in the preparation of glycosyl 1-phosphates... 

D-Ribonolactone is a convenient source of chiral cyclopentenones, acyclic structures, and oxacyclic systems, useful intermediates for the synthesis of biologically important molecules. Cyclopentenones derived from ribono-lactone have been employed for the synthesis of prostanoids and carbocyclic nucleosides. The cyclopentenone 280 was synthesized (265) from 2,3-0-cyclohexylidene-D-ribono-1,4-lactone (16b) by a threestep synthesis that involves successive periodate oxidation, glycosylation of the lactol with 2-propanol to give 279, and treatment of 279 with lithium dimethyl methyl-phosphonate. The enantiomer of 280 was prepared from D-mannose by converting it to the corresponding lactone, which was selectively protected at HO-2, HO-3 by acetalization. Likewise, the isopropylidene derivative 282 was obtained (266) via the intermediate unsaturated lactone 281, prepared from 16a. Reduction of 281 with di-tert-butoxy lithium aluminum hydride, followed by mesylation, gave 282. 

Stereoelectronic effects can be invoked for the radical reaction at anomeric centre of carbohydrates. The high stereoselective preparation of a-substituted C-glycosyl phosphonates in a a p ratio of 98 2 was achieved by reductive addition of bromide 2 to a-phosphonoacrylate (Reaction 7.5) [10]. Yields (in parentheses) depend on the sugar configuration D-galacto (80%), D-manno (47 %), D-gluco (30 %) and L-fuco (62 %). 

The correct anomeric configuration of the a-D-glucopyranosyl pyrophosphate ester is essential (the /3-D-glucopyranosyl ester does not react),342 but the exact distance between the nucleoside moiety and the glycosyl group seems to be a less critical factor. Thus, the phosphonate analog 67 can serve as a substrate.210... 

C-glycosyl phosphonates are important inhibitors of enzymes [87]. An interesting approach to such derivatives was proposed recently [88],... 

Behr, J.-B., Evina. C.M.. Phung, N., and Guillerm, G., Synthesis of (difluoromethyl)phosphonate azasugars designed as inhibitors for glycosyl transferases, J. Chem. Soc., Perkin Trans. 1, 1597. 1997. 

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