Cholestane skeletons

Steroid alkaloids have been isolated from four famihes of terrestrial plant sources (Soianaceae l iliaceae pOijnaceae and Buxaceae) two animal sources (Saiamandra and Phjllobates) and several marine sources. Steroid alkaloids can be classified based on stmcture and fall into a variety of categories. The spirosolanes contain a cholestane skeleton with a C20 spiroaminoketal moiety, as exemplified by the most abundant members of this class, veramine... 

The cholestane molecule may have hydroxyl groups substituted at 25 of its 27 carbon atoms (C-10 and C-13 excepted). Each of these carbon atoms is so situated that it renders its hydroxyl substituent(s) sterically and, more subtly, electronically unique with respect to each of the others. If the cholestane skeleton is maintained, each of the possible secondaiy hydroxyls may assume... 

A half-boat conformation of the cyclobutanone ring (in an octant projection) of 74 correctly explains the observed positive CD near 300 nm. A pseudo-axial chlorine substituent in 75 substantially enhances the positive Cotton effect. The cyclobutanone ring in 76 is nearly planar, thus the effect of exo and endo chloro substituents is effectively cancelled while the remainder of cholestane skeleton resides in a negative octant175. 

From the viewpoint of the steroid structure, SAAF (30) has several unique features. The hydroxylation pattern at the 3, 4, 7, and 26 positions of a cholestane skeleton has not been reported in any other natural products.73 The positions of the C-3 and C-26 sulfate esters are also unique among sulfated polyhydroxysterols of marine origin. In general, steroid hormones act on nuclear receptors and activate gene expression. However, the chemotactic behavior of sperm occurs within a few seconds, and the sperm nucleus is condensed, indicating that genes could not be expressed in the sperm. Furthermore, since SAAF has a hydrophilic nature due to the presence of two hydroxyl and two sulfated esters, it may bind to receptors located on the sperm plasma membrane. 

The 4,5-cyclopropanocholestan-3-ols are expected to be inhibitors of cholesterol oxidase. There are two isomers, shown in part as A and B. (Protons pointing up are labeled 3 and protons pointing down are a.) The remainder of the structure is the cholestane skeleton and is not relevant to this problem. The DFQ-COSY and NOESY spectra for both isomers are... 

The behavior of rings A and B is well known nevertheless, it is useful to have a method for analyzing the structure of the side chain on various cholestane skeletons under El conditions. 

Veralkamine and veralinine are regarded as derivatives of the rearranged steroid hydrocarbon cholestane (5). However, there are also alkaloids possessing a normal cholestane skeleton (the 22,26-epiminocholestanes cf. Vol. X, p. 60). 

Verazine (verasine), baikeine, veralozine, veralozinine, veralozidine, and etioline represent the Veratrum alkaloids with the 22,26-epimino-cholestane skeleton. 

In the early 1970 s, it was proposed that spina bifida and anencephaly in humans resulted from a teratogen present in blighted potatoes (Renwick, 1972). This suggestion raised suspicion that potato alkaloids such as solanidine, which contains a C-27 cholestane skeleton with a tertiary amino group shared by rings E... 

This structural type is characterized by the integration of the side-chain (C-20-C-27) of the original cholestane skeleton (including the amino-iVby conjugation at C-16) into a terminally anellated indolizidine moiety. Thus, a unique hexacyclic system is formed. 

Al-lihaibi, S.S., Ayyad, S.-E.N., Al-Wessaby, E., and Alarif W.M. (2010) 3p,7P-Dihydroxy-5aoxidation pattern of cholestane skeleton from Laurencia papillosa. Biochem. Syst. Ecol., 38, 861-863. 

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