SYNTHESIS OF CARDENOLIDE GLYCOSIDES AND PUTATIVE BIOSYNTHETIC PRECURSORS OF CARDENOLIDE GLYCOSIDES

A rapid and efficient procedure for glycosylation of steroids was esta blished using a modified Koenigs-Knorr procedure. Peracetylated beta-g lycosides were synthesized by reaction of cardenolides, various pregna nes and 23-nor-5,20(22)E-choldienic acid at room temperature with the peracetylated 1-bromo derivatives of D-glucose, D-galactose, D-fucose and cellobiose. Subsequent deprotection was performed by alkaline hydr olysis with sodium methoxide. Structures of the respective glycosides were established by NMR techniques. The complete protocol was shown to be non-destructive at all stages to the sugar moiety and the steroida l nucleus. The gamma-unsaturated lactone ring of the cardenolides was shown to remain intact and no formation of C-14 unsaturated compounds was observed. (C) 1998 by Elsevier Science Inc.