| Abstract
| - The well established one-carbon homologation method ofprotected monosaccharides employing2-(trimethylsilyl)thiazole (2-TST) as a formyl anion equivalent hasbeen used for high yield andmultigram scale synthesis of the title rare hexoses froml-xylose. Thus, l-gulose has beenobtainedby stereoselective anti-addition of 2-TST toaldehydo-l-xylose diacetonide followed bythiazole toformyl conversion of the resulting alcohol. The inversion ofconfiguration at C-1 of this alcohol byan oxidation−reduction sequence prior to the aldehyde releasing fromthiazole led to l-idose. Thesame alcohol was readily elaborated into1,3,4,6-tetra-O-acetyl-l-gulopyranose whosehighlystereoselective glycosidation coupling with3-O-carbamoyl-2,4,6-tri-O-acetyl-α-d-mannosyldiethylphosphate afforded the same peracetylated disaccharide subunit employedby Boger and Honda inthe total synthesis of the antibiotic bleomycinA2.
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