Domino Heck/Lactonization-Catalyzed Synthesis of3-C-Linked Mannopyranosyl Coumarins

摘要

Selective syntheses of methyl a- (8) and, fi-C-mannopyra-nosyl acrylates (9) were obtained from a-C-allyl mannopyr-anoside (3) by ozonolysis to 4 followed by a-methylenationto provide intermediate aldehydes 5 and 6. The β-anomer 6was obtained by in situ anomeric epimerization. The acry-lates and the homologous a-anomer 16, obtained by oxida-tive hydroboration, oxidation, and α-methylenation, wereconverted into 3-C-linked mannopyranosyl coumarins 11,12, and 19 in good yields under one-pot Heck/lactonizationconditions.