Steroids Part 22. Photochemistry of 5,6-epoxy-4,4-dimethylcholestan-3-ones and 5,6-epoxy-17-hydroxy-4,4-dimethylestran-3-ones

Abstract

The P,y-epoxy ketones (5), (6), (7), and (8) photolyse essentially as the equivalent ketones, e.g. (9), in methanol in that little evidence of epoxide cleavage is detected and the major products are the methyl 5-isopropyl-4-nor-3,5-secoesters. In ether, the 3-keto SP,GP-epoxide ( 8 ) photodecarbonylates via a double hydrogen shift (C-2 --+ C-4 and C-1 --+ C-2) and it is suggested that epoxide photocleavage in P,y-epoxy ketones may be subject t o stereoelectronic control.

Photochemistry of 3ζ,5ζ-epoxycholestan-6-ones

“…167-172 "C; v,,,. Photoljjsis uf 3a,S-Epaxy-5a-cholestan-6-one (4).-A solution of the 3a,5sr-epoxy 6-ketone (4) (50 mg) in dry benzene (130 ml) was irradiated for 2 h. Removal of the solvent gave the crude unsaturated 0x0 aldehyde (14); v, , , .…”

“…Photoljjsis uf 3a,S-Epaxy-5a-cholestan-6-one(4).-A solution of the 3a,5sr-epoxy 6-ketone (4) (50 mg) in dry benzene (130 ml) was irradiated for 2 h. Removal of the solvent gave the crude unsaturated 0x0 aldehyde (14); v, , , .2 725 (CHO), 1726 (CHO), 1 694 (x,P-unsaturated C=O), and 1604 cm-' (C=C); 6 9.71 (m, W+ 3 Hz, CHO), 5.81 (m, W, 3 Hz, H,C=C-C=O, H cis to C=O), and 5.04 (m, W, 3 Hz, H,C=C-C=O, H trans to C=O) which was dissolved in dry THF (2 ml) and treated with a solution of NaBH, ( 5 mg) in ethanol (0.5 ml). After 45 min the solution was diluted with water and acidified with dilute acetic acid to pH 5.…”