Diastereoselective Additions of Allylmetal Reagents to Free and Protectedsyn-?,?-Dihydroxyketones Enable Efficient Synthetic Routes to Methyl Trioxacarcinoside A

Abstract

Two routes to the 2,6-dideoxysugar methyl trioxacarcinoside A are described. Each was enabled by an apparent α-chelation-controlled addition of an allylmetal reagent to a ketone substrate containing a free α-hydroxyl group and a β-hydroxyl substituent, either free or protected as the corresponding di-tert-butylmethyl silyl ether. Both routes provide practical access to gram-quantities of trioxacarcinose A in a form suitable for glycosidic coupling reactions.