Rotational isomerism about the 17(20)-bond of steroids and euphoids as shown by the crystal structures of euphol and tirucallol.

W. D. Nes, R. Y. Wong, M. Benson, J. R. Landrey, W. R. Nes

Research output: Contribution to journalArticle

32 Scopus citations

Abstract

The influence of configuration at C-20 on rotation about the 17(20)-bond in steroids and euphoids was examined by x-ray crystallographic studies of the C-20 epimers euphol and tirucallol. The H atom on C-20 was in back next to C-18 in the crystal structures of both of the compounds, and C-22 was found to be cis-oriented ("left-handed") to C-13 in euphol and trans-oriented to it ("right-handed") in tirucallol. The results, which are consistent with the known left-handed crystal structure of 24(25)-dihydroeuphol and right-handed crystal structure of cholesterol and other natural sterols, lend further credence to the earlier suggestion that rotational isomerism at the 17(20)-bond can arise in C-20 epimers and that there is preference for an arrangement with the 20-H atom adjacent to C-18.

Original languageEnglish
Pages (from-to)5896-5900
Number of pages5
JournalProceedings of the National Academy of Sciences of the United States of America
Volume81
Issue number18
DOIs
StatePublished - Sep 1984

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