Studies directed toward synthesis of quassinoids. 2. D-ring cleavage of cholic acid derivatives

Mass spectral fragmentation of 24,24-diphenyl-23-ene derivatives of cholic acid

After electron impact in the mass spectrometer, 24,24-diphenyl-23-ene derivatives of cholic acid ejected the 17-sidechain as an ionized 1,1-diphenyl-butadiene derivative, and the 12 alpha-acetoxy group activated this loss. This contrasts markedly with the mass spectrometric fragmentation of typical sterols having unsaturated 17-sidechains that are also devoid of functionality on the C-ring.