BICYCLO(3.4.0)NON-1-ENE DERIVATIVES - SYNTHESIS OF DES-A-PREGN-9-ENE-3,20-DIONE

Cyclization of the allylic alcohols 12,17 and 22 easily obtainable from Hagemann's ester (2 or 1) via the cyclohexenone derivatives 7 and 10 was investigated with regard to steroid syntheses of the pregnane series. The 6,7-cis-tetrahydroindane derivatives 16a and 23 are formed stereoselectively by acid catalyzed cyclization of 12 or 22; ring closure of 22 occurs largely regioselectively. Cyclization of 17 yields selectively the 6,7-cis (18a) or 6,7-trans compound (18b). Des-A-pregn-9-en-3,20-dion (28a) was obtained by allylic oxidation of 23, subsequent hydrogenation and aldol condensation. © 1979.