Studies on the enzymatic conversion of oxygen-substituted sterols to cholesterol.

Abstract The intermediary role of oxygenated sterols in the conversion of cholest-7-en-3β-ol to cholesta-5,7-dien-3β-ol by rat liver homogenates is considered, assuming that an oxygen molecule may attack the double bond of cholest-7-en-3β-ol. Labeled cholestan-7α,8α-epoxy-3β-ol, cholestane-3β,7β,8α-triol, cholest-8-ene-3β,7ξ-diols, cholestane-3β,7α,8α-triol, cholestane-3β,-8α-diol-7-one, and cholest-8(14)-ene-3β,7α-diol have been synthesized. All these compounds, but cholestane-3β,7α,8α-triol, are efficiently transformed to cholesterol under oxygen atmosphere. However, they cannot be considered as obligatory intermediates in the biosynthesis of cholesterol from cholest-7-en-3β-ol since under anaerobiosis they are transformed to cholest-7-en-3β-ol. The implications of these findings and the mechanisms involved are discussed

Piazza San Marco (Venice, Italy)

Postcard depicting women dining in the Piazza San Marco (Saint Mark's Square) in Venice, Italy

A ready synthesis of 5\u3b1,14\u3b2-cholest-7-en-3\u3b2-ol

Reduction of 3\u3b2-acetoxy-8\u3b1,14\u3b1-epoxy-5\u3b1-cholestan-7- one or 3\u3b2-acetoxy-5\u3b1-cholest-8(14)-en-7-one with zinc dust in methanolic N-sulphuric acid yields 3\u3b2-acetoxy-5\u3b1,14\u3b2-cholest-7- ene with minor amounts of 3\u3b2-acetoxy-5\u3b1,14\u3b2-cholestan-7-one, and constitutes a novel, simple synthesis of 14\u3b2-steroids

Side-chain inversion of steroidal olefins promoted by hydrogen chloride

The reaction of hydrogen chloride on 7-, 8(14)-, and 14-ene steroids was investigated. A 14\u3b1-chloro compound is the product of kinetically controlled addition of the acid. A 14\u3b2-chloro compound with the side chain in the 17\u3b1 configuration originates in diethyl ether at temperatures lower than -30\ub0C in the presence of hydrogen chloride, via a carbocation at C14. There is evidence that the inversion occurs through two distinct rearrangements involving the intermediary formation of a 12,14\u3b1-cyclo-12,13-seco-5\u3b1-cholest-13(17)-ene

A simple method for the reduction of the 7,8-double bond of steroidal 5,7-dienes

1,4-Cycloadducts of various steroidal 5,7-dienes and 4-phenyl-1-2-4-triazoline-3,5-dione gave a separable mixture (3 : 2) of the corresponding \u3945- and \u3947-sterols in good yield when treated with lithium dissolved in refluxing rthylamine

Epoxidation of 7-double bond of cholesta-5,7-dien-3\u3b2-OL by permanganate

The 5,7-diene system of ring B unsaturated steroids is transformed by neutral or alkaline permanganate mainly into a 5\u3b1,6\u3b1-dihydroxy-7\u3b1,8\u3b1-epoxide and minor amounts of more polar compounds

A novel synthesis of 3\u3b2-hydroxy-5\u3b1-cholest-8(14)-en-15-one

Jones oxidation of 5\u3b1-cholesta-8,14-dien-3\u3b2-yl acetate furnishes 9\u3b1-hydroxy-15-oxo-5\u3b1-cholest-8(14)-en-3\u3b2-yl acetate (4a). Treatment of (4a) with zinc dust and sulphuric acid followed by saponification gives 3\u3b2-hydroxy-5\u3b1-cholest-8(14)-en-15-one. On the basis of chemical and spectroscopic evidence, the product obtained by oxidation of 5\u3b1-cholest-8,14-dien-3\u3b2-ol is formulated as 9\u3b1-hydroxy- 5\u3b1-cholest-8(14)-ene-3,15-dione (4b) and not as 14\u3b1-hydroxy- 5\u3b1-cholest-8-ene-3,7-dione (3) as reported by others