Synthesis and photolysis of some lanostanes unsaturated in rings B and C. Characterisation of the stable dithiet tautomer of a dithio-o-quinone

Abstract

The preparation of 3β-acetoxy-7,7-ethylenedithio-5α-lanosta-8,11-diene (1) and its novel conversion by phos-phoryl chloride in pyridine into 3α-acetoxy-5′,6′-dihydro-19-norlanosta-5,7,9,11 -tetraeno[6,1-b][1,4]dithin (4) are described. Photolysis of the latter affords quantitatively the stable, crystalline lanostatetraeno[6,7-c][1,2]-dithiet (6). The structure of this new class of product was confirmed by X-ray analysis. Irradiation of the diene (1) converts rings c and D into a tricyclo[4,3,0,0^2,9]nonene system (3; R = Ac).