Cyclocholates with 12-Oxo and 7,12-Oxo Groups

Abstract

Syntheses of bile acid cyclooligomers with 12- and 7,12-oxo groups (6a−d, 7a−c, 8a−b) by the Yamaguchi method are described. Cyclotrimerization is the principal reaction route for these cholic acid systems. Conversion of 7- and 12-hydroxy groups in cholic acid (1a−b) to oxo groups (4a−c, 5a−c), followed by macrocyclization (6a−d, 7a−c, 8a−b) and selective reduction of the oxo groups back to hydroxy ones without cleaving the 24-carboxylic ester linkages (11) constitutes a new strategy in the synthesis of cyclocholates having unprotected hydroxy groups.