Studies directed toward synthesis of quassinoids. VI—mass spectral fragmentation of D‐ring seco esters and δ‐lactone derivatives of cholic acid

Abstract

AbstractAnalogy and deuterium labeling demonstrate that considerable remote group interaction occurs between functional groups at positions 7 and 16 in 16, 17‐secosteroids. It is proposed that ion‐dipole interact̂ions separations of distances of 10 to 2 Å will involve energies of 1–30 kcal mol−1 and can play a significant role in fragmentation processes. Successive loss of one, two and three HOAc molecules from a milecular or daughter ion increase progressively in relative intensity; irregularity in this pattern indicates the operation of special factors or multiple genesis of daughter ions having the same m/e. Evidence is presented which suggests that facile ketene ejection from the acetate functional group only occurs from a radical ion and must be preceded by transfer of a hydrogen radical from the acetate group to the site of charge localization.