According to the materials of geochemical study in the core of the ultradeep hole SV-27 of aromatic fractions of bitumoids of the Vilyui syneclise (East Siberia) by the method of chromatography-mass spectrometry, starting from the depth of > 5000 m, four diastereomers of previously unknown hydrocarbons, which become predominant in the fraction at a depth of similar to 6500 m, were distinguished. Similar hydrocarbons were found in organic matter of Upper Paleozoic rocks of the Kharaulakh anticlinorium in the Verkhoyansk folded area. According to the intense molecular ion m/z 366 and the character of the basic fragmental ions (m/z 238, 309, and 323), the major structure of the compounds studied was determined as 17-desmethyl-23-methylmonoaromatic steroid C-27. The absence of such steroids in oil of the Vilyui syneclise shows that deep micro-oils did not participate in the formation of oil fringes of gas condensate deposits of the region.
