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The 4,6-O-[alpha-(2-(2- iodophenyl)ethylthiocarbonyl)benzylidene] protecting group: stereoselective glycosylation, reductive radical fragmentation, and synthesis of beta-D-rhamnopyranosides and other deoxy sugars



The 4,6-O-[alpha-(2-(2- iodophenyl)ethylthiocarbonyl)benzylidene] protecting group: stereoselective glycosylation, reductive radical fragmentation, and synthesis of beta-D-rhamnopyranosides and other deoxy sugars



Organic Letters 5(12): 2189-2191



[reaction: see text] In the thioglycoside/BSP/Tf(2)O glycosylation method, the 4,6-O-[alpha-(2-(2-iodophenyl)ethylthiocarbonyl)benzylidene] group enforces beta-selectivity in mannopyranosylations. Following glycosylation, treatment with Bu(3)SnH in toluene at reflux affords regioselective, reductive fragmentation to the 6-deoxy-beta-mannosides (beta-rhamnosides). Applied to glucosides, the radical fragmentation provides 6-deoxyglucosides, whereas 4-deoxygalactosides are the preferred products in the galactose series. The radical fragmentation is fully compatible with the presence of benzyl and p-methoxybenzyl ethers and with acetate esters

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Accession: 050520344

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PMID: 12790561

DOI: 10.1021/ol034741r


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