摘要:
A steroid containing a multi-linked glycoside, analogous to the bufadienolide orbicuside A, has been prepared. The key steps were (i) the preparation of a 2alpha-allyloxycarbonyloxy-3beta-hydroxy steroid, (ii) a Ferrier reaction between the steroid and a rhamnal derivative, (iii) removal of protecting group and oxidation of the 2-hydroxy group, (iv) dihydroxylation of the pseudoglycal from the sterically more hindered side and finally (v) ring closure by acetal formation under acidic conditions. (C) 2004 Elsevier Ltd. All rights reserved.