Synthesis 1996; 1996(9): 1135-1138
DOI: 10.1055/s-1996-4343
paper
© Georg Thieme Verlag, Rüdigerstr. 14, 70469 Stuttgart, Germany. All rights reserved. This journal, including all individual contributions and illustrations published therein, is legally protected by copyright for the duration of the copyright period. Any use, exploitation or commercialization outside the narrow limits set by copyright legislation, without the publisher's consent, is illegal and liable to criminal prosecution. This applies in particular to photostat reproduction, copying, cyclostyling, mimeographing or duplication of any kind, translating, preparation of microfilms, and electronic data processing and storage.

First Steroidal Carbamoyloxa-Bridged Cyclophanes: Regioselective Macrocyclization of Methyl Cholate by Double Transesterification

Shin Irie, Makoto Yamamoto* , Keiki Kishikawa, Shigeo Kohmoto, Kazutoshi Yamada
  • *Department of Materials Science, Faculty of Engineering, Chiba University, 263, Japan, Fax +81(43)2903039
Further Information

Publication History

Publication Date:
31 December 2000 (online)

Facile regioselective macrocyclization of methyl cholate (1) using dimethyl α,α,α’,α’-tetramethyl-m-xylylenedicarbamate (2) by transesterification was achieved, in refluxing toluene (0.004 M), using 3% of SnCl2 and 1% of glycoluril as an additive. After a reaction time of 2 hours, the kinetically favorable 3 was obtained selectively in excellent yield (94%). Conversion of the 16-membered 3 to the 18-membered cyclophane 4 was achieved by establishing an equilibrium (7 days), to give the thermodynamically stable 4 in practical yield (68%). This mild conversion of the regiochemistry of the steroidal macrocycles is remarkable as a characteristic of the carbamoyloxa-bridged cyclophanes. The new steroidal carbamoyloxa-bridged cyclophanes is the first example of a pair of the regioisomeric steroidal cyclophanes.