SYNTHESIS OF CYCLOCHOLATES AND DERIVATIVES, III - CYCLOCHOLATES WITH 12-OXO AND 7,12-OXO GROUPS

Syntheses of bile acid cyclooligomers with 12- and 7,12-oxo groups (6a -d, 7a-c, 8a-b) by the Yamaguchi method are described. Cyclotrimerizat ion is the principal reaction route for these cholic acid systems. Con version of 7- and 12-hydroxy groups in cholic acid (1a-b) to oxo group s (4a-c, 5a-c), followed by macrocyclization (6a-d, 7a-c, 8a-b) and se lective reduction of the oxo groups back to hydroxy ones without cleav ing the 24-carboxylic ester Linkages (11) constitutes a new strategy i n the synthesis of cyclocholates having unprotected hydroxy groups.