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Beckmann rearrangement of (Z)-cholest-4-en-6-one oxime (4) (prepared in 4 steps starting from cholest-5-en-3β-ol ο1)) with thionyl chloride in dioxane solution afforded an enamide-type lactam, i.e. 7-aza-B-homocholest-4-en-6-one (6) as a single product. Photoreaction of the same compound in methanol or benzene-acetic acid solution gave a mixture of products, with the formation of the parent ketone 3 and the occurrence of Z/E isomerization, while the lactam 6 was obtained only when the reaction was performed in methanol and then in very low yield (7%).

In the present paper, the preparation of 3β-hydroxy-17β-dimethyl-tert-butylsilyloxy- 5-azaandrostane (15) in fourteen steps is described. B-nor-17-oxoandrost- 5-en-3β-yl acetate (1)1,2 was used as the starting material, which was transformed to the key intermediate of the synthesis, B-nor-17β-dimethyl-tert-butylsilyloxyandrost- 4-en-3β-yl acetate (7).

The acid-catalyzed reaction of (Z)- and (E)-B-nor-5,10-seco-ketones 2 and 3 resulted in an intramolecular cyclization to give the 5-hydroxy-A-nor-1β,5β-10(19)-methylidene derivative 8, the 5β-hydroxy-A-nor-1(10)-unsaturated compound 9 and the 5β,10β-dihydroxy A-nor-product 10, from the (Z)-isomer and the 5-hydroxy-A-nor-1β,5β-10(19)-methylidene product 11, from the (E)-isomer. Upon UV-irradiation, the (Z)- and (E)-seco-ketones 2 and 3 underwent a reversible (Z)/(E) and (E)/(Z)-isomerization and in addition to a transannular photocyclization to afford the 10(19)-methylidene derivatives 8 and 11, respectively, while photolysis of the 10(19)-methylidene-B-nor-5,10-seco-ketone 4 gave the oxetane derivative 12.

Expoxidation of cholesta-5,8-dien-3β-yl acetate (1) with peracids takes place preferentially at the more highly substituted Δ8-olefinic double bond to give: (a) with monoperphthalic acid, 8α,9α-epoxycholest-5-en-3β-yl acetate (2) (in 39 % yield) and 9α-hydroxy-5α,6α-epoxycholest-8(14)-en-3β-yl acetate (3) (in 30 % yield); and (b) with m-chloroperbenzoic acid, the 8α,9α-epoxide 2 (64 %) and 5α,6α-epoxy derivative 3 (20%). Some chemical transformations of the obtained epoxides are described.