Determination of the configuration of epimeric diols of vitamin D3 series by mass spectrometry.

The mass spectral elimination of water in epimeric 1,3-diols of vitamin D3 (colecalciferol) series has been investigated. It was found that the mass spectra of these steroisomers differ sharply in the relative intensities of the ions M-H2O (m/e 382) and a-H2O (m/e +/- 34), where ion a (formed via formal cleavage of the 7, 8-double bond) is characteristic of vitamin D3 and its derivatives. So while epimeric 1, 3-diols of vitamin D3 series have very close UV and NMR characteristics, the comparison of the ratios of the peaks M-H2O and M.+, a-H2O and a, respectively, makes it possible to distinguish between stereoisomeric 1 alpha, 3 beta-, 1 beta, 3 beta-, 1 alpha, 3 alpha- and 1 beta, 3 alpha-diols using their mass spectra.