Bridged-ring steroids. III. The synthesis of bridged steroids with a bicyclo[2.2.1]heptane ring B system

Abstract

Reaction of cholesta-5,7-dien-3β-yl 2-tetrahydropyranyl ether with bromoform and potassium tert-butoxide gave 3′,3′-dibromo-3′,6β-dihydrocyclopropa[5,6]-5a-cholest-7-en-3β-yl 2-tetrahydropyranyl ether (1c), which on treatment with lithium aluminum hydride and water gave 5,8α-methano-5α-cholest-6-en-3β-yl 2-tetrahydropyranyl ether (2c). This has been converted to 3β-acetoxy-5,8α-methano-5α-cholestan-6-one (16c) and 3β-acetoxy-5,8α-methano-5α-cholestan-7-one (17c). A preliminary investigation of the photochemistry of 16c and 17c has shown that the incorporation of the bicyclo[2.2.1]heptan-2-one system in the B ring of a steroid results in photoreactions of this system that are different from those observed in the case of simple bicyclo[2.2.1]heptan-2-ones.