The synthesis of gracillin and dioscin: two typical representatives of spirostanol glycosides

Two representative spirostanol saponins that have the typical structure for the sugar moiety, diosgenyl alpha-L-rhamnopyranosyl-(1 --> 2)-[beta-D-glucopyranosyl-(1 --> 3)]-beta-D-glucopyranoside (gracillin) and diosgenyl alpha-L-rhamnopyranosyl-(1 --> 2)-[alpha-L-rhamnopyranosyl-(1 --> 4)]-beta-D-glucopyranoside (dioscin), were easily synthesized by a general approach. A procedure using guanidine for the selective deblocking of acetyl while retaining benzoyl protecting groups is described. (C) 2003 Elsevier Science Ltd. All rights reserved.