Abstract:
A new transformation of the spiroketal side chain of diosgenin is reported: treatment of 23-hydroxyiminodiosgenin acetate with phosphorous oxychloride in pyridine produced an abnormal Beckmann rearrangement directing to the cleavage of the spiroketal side chain and generating 23,24-bisnorchol-5-enic skeletons: (2'R)-3'-cyano-2'-methylpropyl 3beta-acetoxy-16alpha-chLoro-23,24-bisnorchol-5-en-22-oate as the main product, and small amounts of (2'R)-3'-cyano-2'-methylpropyl 3beta-acetoxy-16alpha-hydroxy-23,24-bisnorchol-5-en-22-oate and vespertilin acetate. (C) 2004 Elsevier Ltd. All rights reserved.