| Abstrakt: |
The mass spectra of twenty-seven C-19 modified cholestane derivatives have been determined, and have been compared with the mass spectra of similar compounds reported1 in the cholesteryl series. In the spectra of 2α,19-dihydroxy-5α-cholestane (la), initial loss of the 10β-hydroxymethyl group was observed followed by loss of water, whereas with the 2α-methoxy and 2α-acetoxy derivatives (Ib, Ic), loss of the 2α-substituent as methanol and acetic acid respectively, preceded the elimination of the 10β-hydroxymethyl group. Loss of the 10β-hydroxymethyl group was also observed in Δ1-, Δ2- and 2-oxo derivatives (VI, Va and VII), whilst loss of both the 1 substituent and the 10β-hydroxymethyl group from the molecular ion was observed with the 1α-ol (IIa) and the 1β-yl-chloride (III). In a series of 19-acetoxy derivatives loss of acetic acid [M - 60] from the 19-acetoxy group, involving abstraction of a sterically favourable hydrogen, always occurred, although this was usually accompanied by loss of the 10β-acetoxymethyl residue [M - 73]. The mass spectra of a series of 10β-carboxylic acids and their methyl esters were more complex with three or more fragmentation patterns being observed. 1,3-Diaxial interactions, similar to those observed in chemical reactions, were observed in the mass spectra of three 2β-oxygenated-19-substituted compounds. [ABSTRACT FROM AUTHOR] |
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