Synthesis of 7-oxo- and 7-hydroxy- derivatives of stigmasterol

Abstract

The phytosteroids 313-hydroxy-(24S)-stigmast-5,22E-dien-7-one and (24S)-stigmasta-5,22E-diene-3{3, 713-diol have been synthesized from stigmasterol. Stigmasterol (la) is one of the main steroids of plants. Together with/3-sitosterol and campesterol, this substance ensures the functioning of plant cell membranes. Moreover, the biosynthesis of various biologically active steroids necessary for the normal vital activity of plants starts from phytosterols, including stigmasterol. Compounds of this type include, for example, the hydroxysteroids (3a-4a) detected in plants [1, 2], the structures of which are characterized by the same carbon skeleton as in the stigmasterol molecule. It has been established by numerous investigations [4][5][6][7][8][9] that phytosterol derivatives with oxygen-containing functions at C-7, including steroids (2a-4a), possess a pronounced antitumoral activity. This circumstance has induced us to undertake the synthesis of these substances from the commercially available stigmasterol, which is used as a raw material in drug manufacture. In the present paper we give the results of this investigation, which is a continuation of syntheses of 6-oxophytosteroids from/3-sitosterol [ 10] and stigmasterol [ 11] that we have performed previously. In the stigmasterol molecule, the H-7 atom is in an allyl position in relation to the 5(6) double bond, and, for this reason, it is activated_ Although precisely the same situation exists for the H-4 atom, the selective oxidation of 5(6)-unsaturated steroids at C-7 is possible, for example, with the complex of chromium trioxide and pyridine, which has the structure of pyridinium dichromate [12]. Since, under these conditions, the 3~-hydroxy group in the stigmasterol molecule would also be oxidized, it was necessary to protect it. For this purpose, we first converted stig-rnasterol by acetylation with acetic anhydride in pyridine into the known acetate (lb) in quantitative yield.

Biotransformation of Cholesterol and 16α,17α-Epoxypregnenolone and Isolation of Hydroxylase inBurkholderia cepaciaSE-1

“…Based on the information from MS, 1 H NMR, and 13 C NMR, compound 2 was characterized as 7-oxocholesterol. This was in accord with the data in literature [ 19 ]. The chemical structures of compound 2 were seen in Figure 4 .…”

Biotransformation of cholesterol and 16,17‐alpha epoxypregnenolone by novel Cladosporium sp. strain IS547

“…The structure of the converted products of cholesterol was characterized, products 1 and 2 were 7-b-hydroxycholesterol and 7-oxocholesterol, respectively. This determination also agreed with the data found in the literature [20,21]. These products are the same as the products obtained by Dan Fan [22] 16 Cuiping Pang et al Optimal conditions for strain cultivation and 16,17-alpha epoxypregnenolone transformation The optimal experiment was used to investigate the biotransformation of 16,17-alpha epoxypregnenolone by Cladosporium sp.…”