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Paper | Regular issue | Vol 53, No. 8, 2000, pp.1745-1764
Published online, 1st January, 1970
DOI: 10.3987/COM-00-8937
Cyanoglycosylation Accompanied by Ring-Opening of Spirostanols

Akihiko Tobari, Hiroshi Miyamae, Akira Nagasawa, Junich Koyanagi, Masami Kawase, and Setsuo Saito*

*Faculty of Pharmaceutical Sciences, Josai University, Keyakidai 1-1, Sakado, Saitama 350-0295, Japan

Abstract

The reaction of 3-O-acetylsarsasapogenin (7), which has no hydroxyl group susceptible to glycosylation, with 2,3,4,6-tetra-O-acetyl-α-D-glucopyranosyl bromide (5) in the presence of a mixed catalyst, Hg(CN)2 and HgBr2, caused by cleavage the F-ring to give a 22-α-cyano-3,26-di-O-acetyl-5β-furostan derivative (8) and five monoglycosides (9-13) which were also products resulted from the cleavage of the F-ring of 7 accompanied by glycosylation. The trigger of the cleavage of the F-ring was speculated that a cyano anion generated from Hg(CN)2 used as catalyst attacked at C-22 of 7 from α-site to open the F-ring, then the six products were produced. The orientation of the attacking CN- group to C-22 of 7 was determinated on the basis of the X-Ray structure of 17.