Abstract
The formation of a C20-carbonium cation during the hot acid hydrolysis of pregnanediol disulfate (1b) and the role of this cation in the rearrangement reactions were examined. Hydrolysis of 1b in boiling 3N hydrochloric acid in oxygen-18 water gave 17α-ethyl-17β-methyl-18-nor-5β-androst-13-en-3α-ol (2) as the main product, together with pregnanediol (1a), 17α-methyl-D-homo-5β-androstane-3α, 17aβ-diol (3), 17α-methyl-17aβ-chloro-D-homo-5β-androstan-3α-ol (4), 5β-pregn-20-en-3α-ol (5a), 5β-pregnane-3α, 20β-diol (10), and other minor degradation products. The isotope content of these products was determined by gas chromatography-mass spectrometry. Among then, 3 and 10 were quantitatively labeled with 18O at 17aβ- and 20β-ol, respectively, and 1a was 74% labeled at 20α-ol. No uptake of 18O into 3α-ol of the products was observed. These results confirm the formation of the C20-carbonium cation from 1b. Hydrolysis of 5β-pregn-20-en-3α-ol sulfate (5b), which is considered to be the conjugated base of the C20-cation, gave 2 as the main product accompanied with 1a, 3, 4, 5a, and 10. This result suggests that the C20-carbonium cation plays an important role as an intermediate to D-homosteroids as well as to the Δ15-olefin 2.
