Contributions to the Study of Marine Products. Xx. Remarks Concerning the Structure of Sterols From Marine Invertebrates

Abstract

In 1941, Fernholz and Ruigh (1) convincingly demonstrated that campesterol and campestanol differ from 22,23-dihydrobrassicasterol and ergostanol solely in the optical configuration at C-24. Since then it has been shown that this C-24 epimerism is not infrequently encountered among naturally occurring sterols, and that the C2s-sterols from marine invertebrates such as the stellasterols and stellastenols (2), neospongosterol (3) and chalinasterol (4) predominantly belong to the campestanol series. In conformity with the customary designation of steroid epimers, it is here proposed to refer to the ergostanol and campestanol series as the 24-(a)-and 24-(0)-methylcholestanol series, and following a suggestion by Ruigh (5), to write the 24-methyl group above the side chain in the «-series (I) and below the side chain in the 0-series (II).

Determination of the absolute configuration at C‐20 and C‐24 of ergosterol in ascomycetes and basidiomycetes by proton magnetic resonance spectroscopy

“…The configurations at C-20 and C-24 were examined early in the history of steroids (2) and the one at C-24 was studied still more recently by Tsuda et al (3). The latter authors were able to show conclusively that in stigmasterol the 24-ethyl group is a-oriented reversing the assignment made by Bergmann and Low (4). Bergmann and Low (4) also reported stigmasterol and ergosterol to have the same configuration, so Tsuda et al (3) proceeded to define the configuration in ergosterol.…”

The Chemical Constituents Of Tobacco And Tobacco Smoke

“…The C 24 epimer of stigmasterol is poriferasterol (24a-ethylcholesterol) and that of ß-sitosterol is clionasterol. It is not certain whether 7-sitosterol is identical with the C 24 epimer of /3-sitosterol (clionasterol) or whether it possesses, in addition, the opposite configuration at C 20 (15). The point remains to be settled when larger quantities of pure 7-sitosterol become available.…”

Relations between the Optical Rotatory Power and Structure of Polynuclear Natural Products. I. Steroid Hydrocarbons

“…Replacement of hydrogen at C-24 by a methyl or an ethyl group creates a nqw center of asymmetry. Several pairs of C-24 epimers, formally derived from cholesterol, are known (17). Table I shows the rotations2 of one pair of such isomers, in which the contribution of the 24-methyl group is represented by B, and the optical activity associated with the nuclear centers and C-20 by A. van't Hoff's rule applies here because A and B are separated by two methylene groups.…”