Inhibitors of sterol synthesis. Chemical syntheses, properties and effects of 4,4-dimethyl-15-oxygenated sterols on sterol synthesis and on 3-hydroxy-3-methylglutaryl coenzyme A reductase activity in cultured mammalian cells

The chemical syntheses of a number of 4,4-dimethyl substituted 15-oxygenated sterols have been pursued to permit evaluation of their activity in the inhibition of the biosynthesis of cholesterol and other biological effects. Described herein are the first chemical syntheses of 4,4-dimethyl-14 alpha-ethyl-5 alpha-cholest-7-en-3 beta-ol-15-one, 3 beta,15 alpha-diacetoxy-4,4-dimethyl-14 alpha-ethyl-5 alpha-cholest-7-ene, 3 beta-acetoxy-4,4-dimethyl-14 alpha-ethyl-5 alpha-cholest-7-en-15 beta-ol, 4,4-dimethyl-14 alpha-ethyl-5 alpha-cholest-7-ene-3 beta,15 alpha-diol, 4,4-dimethyl-14 alpha-ethyl-5 alpha-cholest-7-ene-3 beta,15 beta-diol, 4,4-dimethyl-14 alpha-ethyl-5 alpha-cholest-7-en-15 alpha-ol-3-one, 3 beta-benzoyloxy-4,4-dimethyl-5 alpha-cholest-8(14)-ene-7 alpha,15 alpha-diol, 7 alpha,15 alpha-diacetoxy-3 beta-benzoyloxy-4,4-dimethyl-5 alpha-cholest-8(14)-ene, 4,4-dimethyl-5 alpha-cholest-8(14)-en-3 beta-ol-15-one and 3 beta,7 alpha,15 alpha-tri-o-bromobenzoyloxy-5 alpha-cholest-8(14)-ene. Also prepared for use in the biological experiments were 4,4-dimethyl-5 alpha-cholest-7-ene-3 beta,15 alpha-diol, 4,4-dimethyl-5 alpha-cholest-8-ene-3 beta,15 alpha-diol and 4,4-dimethyl-5 alpha-cholest-8(14)-ene-3 beta,7 alpha,15 alpha-triol. The effects of twelve 4,4-dimethyl substituted 15-oxygenated sterols and of four 4,4-dimethyl substituted 32-oxygenated sterols on sterol synthesis and on the level of 3-hydroxy-3-methylglutaryl coenzyme A reductase activity were evaluated in mouse L cells. With the exception of 4,4-dimethyl-5 alpha-cholest-8(14)-ene-3 beta,7 alpha,15 alpha-triol, all of the 4,4-dimethyl substituted 15-oxygenated sterols caused a 50% inhibition of sterol synthesis at less than 10(-6) M and six of the 4,4-dimethyl substituted 15-oxygenated sterols caused a 50% inhibition of sterol synthesis at less than 10(-7) M. 4,4-Dimethyl-14 alpha-ethyl-5 alpha-cholest-7-ene-3 beta,15 alpha-diol caused a 50% decrease in sterol synthesis at 10(-8) M. The potencies of the 4,4-dimethyl substituted 15-oxygenated and C-32-oxygenated sterols with respect to inhibition of sterol synthesis and suppression of 3-hydroxy-3-methylglutaryl coenzyme A reductase activity have been compared with those of the corresponding sterols lacking the 4,4-dimethyl substitution.     

Concerning the structure of 3 beta-benzoyloxy-5 beta-cholesta-8,14-diene, a major byproduct in the chemical synthesis of 5 alpha-cholest-8(14)-en-3 beta-ol-15-one

The X-ray crystal structure of 3 beta-(p-bromobenzoyloxy)-5 beta-cholesta-8,14-diene (space group P21, a = 10.698 A, b = 9.487 A, c = 15.024 A, beta = 96.05 degrees, Z = 2) was determined by the heavy atom method and refined to R = 0.075. This heavy atom derivative was synthesized from 5 beta-cholesta-8,14-diene-3 beta-ol, the benzoate ester of which was previously shown to be the major byproduct in the low-temperature isomerization of 7-dehydrocholesteryl benzoate in HCl/chloroform. The work presented here establishes unequivocally that the configuration of this isomerization byproduct at C-5 is 5 beta-H and that the configuration at C-17 was unchanged.     

Stereospecific 1,4-addition to an alpha,beta-unsaturated steroidal epoxide: syntheses of new 15-oxygenated sterols

3 beta-Benzoyloxy-14 alpha,15 alpha-epoxy-5 alpha-cholest-7-ene (1) is a key intermediate in the synthesis of C-7 and C-15 oxygenated sterols. Treatment of 1 with benzoyl chloride resulted in the formation of 3 beta,15 alpha-bis-benzoyloxy-7 alpha-chloro-5 alpha-cholest-8(14)-ene (2). Reaction of 2 with LiAlH4 or LiAlD4 resulted in the formation of 5 alpha-cholest-7-ene-3 beta,15 alpha-diol (3a) or [14 alpha-2H]5 alpha-cholest-7-ene-3 beta,15 alpha-diol (3b). Diol 3b was selectively oxidized by Ag2CO3/celite to [14 alpha-2H]5 alpha-cholest-7-en-15 alpha-ol-3-one (4). Treatment of 1 with MeMgI/CuI gave 7 alpha-methyl-5 alpha-cholest-8(14)-ene-3 beta,15 alpha-diol (5). Selective oxidation of 5 with pyridinium chlorochromate (PCC)/pyridine or oxidation with PCC resulted in the formation of 7 alpha-methyl-5 alpha-cholest-8(14)-en-3 beta-ol-15-one (6) and 7 alpha-methyl-5 alpha-cholest-8(14)-ene-3,15-dione, respectively. Reduction of 6 with LiAlH4 yielded 5 and 7 alpha-methyl-5 alpha-cholest-8(14)-ene-3 beta,15 beta-diol (6). Reaction of 1 with benzoic acid/pyridine gave 3 beta,7 alpha-bis-benzoyloxy-5 alpha-cholest-8(14)-en-15 alpha-ol (9). Treatment of 9 with LiAlH4 or ethanolic KOH resulted in the formation of 5 alpha-cholest-8(14)-ene-3 beta,7 alpha,15 alpha-triol (10). Dibenzoate 9, upon brief treatment with mineral acid, gave 3 beta-benzoyloxy-5 alpha-cholest-8(14)-ene-15-one (11). Oxidation of 9 with PCC yielded 3 beta,7 alpha-bis-benzoyloxy-5 alpha-cholest-8(14)-ene-15-one (12). Ketone 12 was also prepared by the selective hydride reduction of 5 alpha-cholest-8(14)-en-7 alpha-ol-3,15-dione (13) to give 5 alpha-cholest-8(14)-ene-3 beta,7 alpha-diol-15-one (14), which was then treated with benzoyl chloride to produce 12.     

Inhibitors of cholesterol biosynthesis. Further studies of the metabolism of 5 alpha-cholest-8(14)-en-3 beta-ol-15-one in rat liver preparations

5 alpha-Cholest-8(14)-en-3 beta-ol-15-one is a potent inhibitor of sterol biosynthesis in mammalian cells in culture and has significant hypocholesterolemic activity upon oral administration to rodents and non-human primates. The conversion of the 15-ketosterol to cholesterol upon incubation with the 10,000 x g supernatant fraction of rat liver homogenate preparations under aerobic conditions has been reported (D.J. Monger, E.J. Parish and G.J. Schroepfer, Jr. (1980) J. Biol. Chem. 255, 11122-11129). Presented herein are results of studies of the metabolism of [2,4-3H]5 alpha-cholest-8(14)-en-3 beta-ol-15-one obtained upon incubation with the microsomal, cytosolic and the 10,000 x g supernatant fractions of liver homogenates of female rats under a variety of conditions. The results of these studies indicated metabolism of the 15-ketosterol to materials with the chromatographic properties of fatty acid esters of the 15-ketosterol, fatty acid esters of C27-monohydroxysterols, a component similar to the 15-ketosterol (possibly an isomer of the delta 8(14)-15-ketosterol), and a polar component. Detailed studies of the C27-monohydroxysterols obtained from incubation of the 15-ketosterol under anaerobic conditions indicated the formation of labeled 5 alpha-cholesta-8,14-dien-3 beta-ol and 5 alpha-cholest-7-en-3 beta-ol which were characterized by their behavior on silicic acid column chromatography, by the behavior of their acetate derivatives on medium pressure liquid chromatography on alumina-AgNO3 columns, and by co-crystallization of the labeled sterols with authentic unlabeled standards. The identification of 5 alpha-cholesta-8,14-dien-3 beta-ol and 5 alpha-cholest-7-en-3 beta-ol as metabolites of the 15-ketesterol, coupled with previous studies of the metabolism of 5 alpha-cholesta-8,14-dien-3 beta-ol and of 5 alpha-cholest-8(14)-ene-3 beta, 15 alpha-diol and 5 alpha-cholest-8(14)-ene-3 beta, 15 beta-diol has permitted the formulation of a scheme for the overall metabolism of the 15-ketosterol to cholesterol.     

Inhibitory effect of 15-oxygenated sterols on cholesterol synthesis from 24,25-dihydrolanosterol

Several 15-oxygenated sterols were examined as to their inhibitory activity toward cholesterol synthesis from [24,25-3H]-24,25-dihydrolanosterol in the 10,000 X g supernatant fraction of a rat liver homogenate. At 40 microM, three 15 alpha-hydroxylated compounds, 14 alpha-ethylcholest-7-ene-3 beta,15 alpha-diol, 14 alpha-methylcholest-7-ene-3 beta,15 alpha-diol, and lanost-7-ene-3 beta,15 alpha-diol, were found to be extremely potent inhibitors (more than 90% inhibition) of dihydrolanosterol metabolism. The inhibitory effect of the C-15 substituents appeared to be in the order of: 15 alpha-hydroxyl greater than 15-ketone greater than 15 beta-hydroxyl.     

15 beta-Methyl-5 alpha,14 beta-cholest-7-ene-3 beta,15 alpha-diol. Synthesis, structure, and inhibition of sterol synthesis in animal cells

Treatment of 3 beta-benzoyloxy-14 alpha,15 alpha-epoxy-5 alpha-cholest-7-ene with methyl magnesium iodide gave, as the major product, 15 beta-methyl-5 alpha,14 beta-cholest-7-ene-3 beta,15 alpha-diol. The product was characterized as the free sterol and in the form of its 3 beta-acetoxy and 3 beta-p-bromobenzoate derivatives. Unambiguous assignment of structure was based upon X-ray analysis of the latter derivative. 15 beta-Methyl-5 alpha,14 beta-cholest-7-ene-3 beta,15 alpha-diol was found to be a potent inhibitor of sterol synthesis in cultured mammalian cells. The 15 beta-methyl-3 beta,15 alpha-dihydroxysterol caused a 50% reduction of the level of HMG-CoA reductase activity and a 50% reduction in the incorporation of labeled acetate into digitonin-precipitable sterols in L cells at a concentration of 3.0 x 10(-6) M.     

Inhibitors of sterol synthesis. Concerning the structure of 15 beta-methyl-5 alpha,14 beta-cholest-7-ene-3 beta,15 alpha-diol, an inhibitor of cholesterol biosynthesis

The chemical synthesis of 3 beta-p-bromobenzoyloxy-15 beta-methyl-5 alpha,14 beta-cholest-7-en-15 alpha-ol from 15 beta-methyl-5 alpha, 14 beta-cholest-7-ene-3 beta,15 alpha-diol is described. The structure of the former compound was unambiguously determined by X-ray crystallographic analysis. The space group of the crystal was P2 with unit cell parameters a = 12.611 A, b = 9.826 A, c = 13.221 A, b = 91.71 degrees and Z = 2. The structure was solved by the heavy atom method and refined to a final R of 0.041. Asymmetry parameters indicated that ring A is a symmetrical chair, that rings B and C are half chairs, and that ring D is a 15 alpha-envelope.     

Chemical synthesis of 4,4'-dimethyl-7-oxygenated sterols. Inhibitors of 3-hydroxy-3-methylglutaryl reductase

The chemical syntheses of 4,4'-dimethylcholest-5-en-3 beta-ol-7-one, 4,4'-dimethylcholest-5-ene-3 beta, 7 beta-diol and 4,4'-dimethylcholest-5-ene-3 beta, 7 alpha-diol are described. All of these compounds were found to be potent inhibitors of 3-hydroxy-3-methylglutaryl (HMG-CoA) reductase activity in cultured mouse L cells. The synthetic scheme developed in this study utilizes commercial cholesterol as the starting material and provides a simplified method for the preparation of 4,4'-dimethyl-7-oxygenated steroids.     

Inhibitors of sterol synthesis. Chemical synthesis, structure, and biological activities of (25R)-3 beta,26-dihydroxy-5 alpha-cholest-8(14)-en-15-one, a metabolite of 3 beta-hydroxy-5 alpha-cholest-8(14)-en-15-one

3 beta-Hydroxy-5 alpha-cholest-8(14)-en-15-one (I) is a potent inhibitor of sterol synthesis with significant hypocholesterolemic activity. (25R)-3 beta,26-Dihydroxy-5 alpha-cholest-8(14)-en-15-one (II) has been shown to be a major metabolite of I after incubation with rat liver mitochondria. Described herein is the chemical synthesis of II from diosgenin. As part of this synthesis, improved conditions are described for the conversion of diosgenin to (25R)-26-hydroxycholesterol. Benzoylation of the latter compound gave (25R)-cholest-5-ene-3 beta,26-diol 3 beta,26-dibenzoate which, upon allylic bromination followed by dehydrobromination, gave (25R)-cholesta-5,7-diene-3 beta,26-diol 3 beta,26-dibenzoate. Hydrogenation-isomerization of the delta 5.7-3 beta,26-dibenzoate to (25R)-5 alpha-cholest-8(14)-ene-3 beta,26-diol 3 beta,26-bis(cyclohexanecarboxylate) followed by controlled oxidation with CrO3-dimethylpyrazole gave (25R)-3 beta,26-dihydroxy-5 alpha-cholest-8(14)-en-15-one 3 beta,26-bis(cyclohexanecarboxylate). Acid hydrolysis of the delta 8(14)-15-ketosteryl diester gave II. 13C NMR assignments are given for all synthetic intermediates and several major reaction byproducts. The structure of II was unequivocally established by X-ray crystal analysis. II was found to be highly active in the suppression of the levels of 3-hydroxy-3-methylglutaryl coenzyme A reductase in cultured mammalian cells and to inhibit oleoyl coenzyme A-dependent esterification of cholesterol in jejunal microsomes.     

Inhibitors of sterol biosynthesis. Synthesis and activities of ring C oxygenated sterols

The chemical syntheses of a number of C27 ring C oxygenated sterols have been pursued to permit evaluation of their activity in the inhibition of sterol biosynthesis in cultured mammalian cells. Thus, 5 alpha-cholest-7-ene-3 beta, 11 alpha-diol, 3 alpha-hydroxy-5 alpha-cholest-9(11)-en-12-one, and the previously unreported 11 alpha-hydroxy-5 alpha-cholest-7-en-3-one, 5 alpha-cholest-9(11)-ene-3,12-dione, and 3 beta-hydroxy-5 alpha-cholest-9 (11)-en-12-one have been synthesized. The effects of these compounds on the synthesis of digitonin-precipitable sterols from labeled acetate in mouse L cells and on the levels of 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase activity in the same cells have been investigated and compared with previously published data on other ring C oxygenated sterols. 5 alpha-Cholest-7-ene-3 beta, 11 alpha-diol was shown to be the most potent inhibitor of sterol synthesis.     

Studies of the oxysterol inhibition of tumor cell growth

The oxysterols 3 beta-hydroxy-5 alpha-cholest-8-en-11-one, 3 beta-hydroxy-5 alpha-cholest-8-en-7-one, 3 beta-hydroxy-5 alpha-cholest-8(14)-en-7-one, 3 beta-hydroxy-4,4'-dimethylcholest-5-ene-7 one, 4,4'-dimethylcholest-5-ene-3 beta, 7 alpha-diol, 4,4'-dimethylcholest-5-ene-3 beta, 7 beta-diol, lanost-8-ene-3 beta, 25-diol, 25-hydroxylanost-8-en-3-one, 9 alpha, 11 alpha-epoxy-5 alpha-cholest-7-en-3 beta-ol, 3 beta-hydroxycholest-5 alpha-en-22-one, and 3 beta-hydroxycholest-5-en-22-one oxime were evaluated with respect to their ability to inhibit cell growth. All of the sterols were found to possess cytotoxicity when incubated with hepatoma (HTC) and lymphoma (RDM-4) cells in culture at 10-30 microM concentrations.     

Inhibitors of sterol synthesis. 14 alpha-ethyl-5 alpha-cholest-7-ene-3 beta,15 alpha-diol induces changes in the sterol composition and the morphology of CHO-K1 cells

Incubation of CHO-K1 cells in lipid-deficient medium containing 14 alpha-ethyl-5 alpha-cholest-7-ene-3 beta,15 alpha-diol (0.1 microM) for 4 days was associated with a profound change in cellular sterol composition as reflected by a marked accumulation of lanosterol and 24,25-dihydrolanosterol. A striking elongation of the cells was also observed. Incubation of CHO-K1 cells in lipid-deficient medium containing lanosterol (10 microM) also caused a significant accumulation of lanosterol which was also associated with a marked elongation of the cells.     

Three new D-ring unsaturated sterols from the Mediterranean sponge Topsentia aurantiaca: structure determination and complete nuclear magnetic resonance assignment.

Three novel sterols with a rare D-ring unsaturation were isolated from the marine sponge Topsentia aurantiaca and identified as 5 alpha-cholest-14-ene-3 beta,16 alpha-diol (2), 24R-ethyl-5 alpha-cholest-14-ene-3 beta,16 alpha-diol (3), and 24S-ethyl-5 alpha-cholest-14-ene-3 beta,16 alpha-diol (4). The sponge also elaborates a further D-ring unsaturated sterol, 5 alpha-cholest-15-en-3 beta-ol (1), which has been previously described only as a synthetic product. All the 1H and 13C nuclear magnetic resonances of compounds 1 and 2 were assigned to the relevant protons and carbons by bidimensional COSY, HETCOR, and HMQC nuclear magnetic resonance experiments.     

Sterol hydroperoxide metabolism by Salmonella typhimurium

In order to rationalize multiphasic dose-response data evincing mutagenicity towards Salmonella typhimurium TA1537 for sterol hydroperoxides 3 beta-hydroxy-5 alpha-cholest-6-ene-5-hydroperoxide and 3 beta-hydroxycholest-5-ene-7 alpha-hydroperoxide their metabolism by the bacterial test strain was investigated. The 5 alpha-hydroperoxide was isomerized to the 7 alpha-hydroperoxide and reduced to 5 alpha-cholest-6-ene-3 beta,5-diol; the 7 alpha-hydroperoxide was reduced to cholest-5-ene-3 beta,7 alpha-diol and transformed to 3 beta-hydroxycholest-5-en-7-one. The 3 beta,5 alpha-diol and 3 beta,7 alpha-diol were not interconverted nor was either transformed to the 7-ketone.     

Inhibitors of sterol synthesis. Characterization of beta,gamma-unsaturated analogs of 3 beta-hydroxy-5 alpha-cholest-8(14)-en-15-one and their effects on 3-hydroxy-3-methylglutaryl coenzyme A reductase activity in CHO-K1 cells

Treatment of 3 beta-hydroxy-5 alpha-cholest-8(14)-en-15-one (1), a potent regulator of cholesterol metabolism, with perchloric acid in methanol resulted in its partial isomerization to the beta,gamma-unsaturated 15-ketosterols, 3 beta-hydroxy-5 alpha,14 beta-cholest-8-en-15-one (2) and 3 beta-hydroxy-5 alpha,14 beta-cholest-7-en-15-one (3), which were easily separated from 1 by chromatography. Isomers 1, 2, and 3 could be distinguished by their chromatographic retention times as well as by their physical and spectral properties. Reduction of 2 with sodium borohydride gave 5 alpha,14 beta-cholest-8-ene-3 beta,15 beta-diol (4), for which the C-15 configuration was established from the lanthanide-induced shifts of its 3 beta-tert-butyldimethylsilyl ether. 1H and 13C NMR chemical shift differences between 2, 3, and 4 indicated the involvement of variable populations of conformers that differ in the flexible C-D ring system and in the side chain. Compounds 2, 3, and 4 lowered the levels of 3-hydroxy-3-methylglutaryl coenzyme A reductase activity in CHO-K1 cells.     

Taraxastane-type triterpenoids from Saussurea petrovii.

Two taraxastane triterpenoids, i.e. taraxast-20-ene-3beta,30-diol (1) and 20alpha,21alpha-epoxy-taraxastane-3beta,22alpha-diol (2), as well as four known triterpenes taraxast-20(30)ene-3beta,21alpha-diol (3), taraxast-20(30)-ene-3beta-ol (4), taraxast-20-ene-3beta-ol (5) and taraxastane-3beta,20alpha-diol (6) were isolated from the Chinese medicinal plant Saussurea petrovii. Their structures were elucidated by spectroscopic methods. These compounds, especially 1 and 2, exhibit significant antitumor and antibacterial activity.     

Synthesis of polyhydroxysterols (V): efficient and stereospecific synthesis of 24-methylene-cholest-5-ene-3beta,7alpha-diol and its C-7 epimer

This paper describes the efficient and stereospecific synthesis of cytotoxic dihydroxylated sterols, 24-methylene-cholest-5-ene-3beta,7alpha-diol 1, and its C-7 epimer, 24-methylene-cholest-5-ene-3beta,7beta-diol 2. The crux of the synthesis is that the selective allylic oxidation of 24-methylene-cholesteryl acetate proceeds to 24-methylene-7-keto-cholesteryl acetate without extensive byproduct formation from reaction at the Delta24(28) double bond. This methodology may be useful for the preparation of other oxysterols with non-standard side chains.     

Inhibitors of sterol synthesis. Chromatography of acetate derivatives of oxygenated sterols

The separation of the acetate derivatives of a number of oxygenated sterols was achieved by medium pressure liquid chromatography on silica gel columns and by normal and reversed phase high performance liquid chromatography. We have explored the application of these chromatographic systems for the analysis of oxygenated sterols of plasma samples from two normal human subjects. The addition of highly purified [14C]cholesterol to plasma permitted the detection and quantitation of oxygenated sterols formed by autoxidation of cholesterol during processing of the samples. Special attempts to suppress autoxidation of cholesterol included the use of an all-glass closed system for saponification and extraction under argon followed by rapid removal of cholesterol from the polar sterols by reversed phase medium pressure liquid chromatography. Chromatographic analyses of the [3H]acetate derivatives of the polar sterols provided a sensitive approach for the detection and quantitation of the individual oxygenated sterols. Oxygenated sterols detected in plasma included cholest-5-ene-3 beta,26-diol, (24S)-cholest-5-ene-3 beta,24-diol, and cholest-5-ene-3 beta,7 alpha-diol. After correction for their formation by autoxidation of cholesterol during processing of the samples, very little or none of the following sterols were observed: cholest-5-ene-3 beta,7 beta-diol, 5 alpha,6 alpha-epoxy-cholestan-3 beta-ol, 5 beta,6 beta-epoxy-cholestan-3 beta-ol, and cholestane- 3 beta, 5 alpha,6 beta-triol, and the 25-hydroxy, 22R-hydroxy, 21-hydroxy, 20 alpha-hydroxy, and 19-hydroxy derivatives of cholesterol.     

Inhibitors of sterol synthesis. Chemical syntheses and spectral properties of 26-oxygenated derivatives of 3 beta-hydroxy-5 alpha-cholest-8(14)-en-15-one and their effects on 3-hydroxy-3-methylglutaryl coenzyme A reductase activity in CHO-K1 cells.

26-Oxygenated derivatives of delta 8(14)-15-ketosterols have been synthesized from (25R)-3 beta,26-diacetoxy-5 alpha-cholest-8(14)-en-15-one (IX) as part of a program to prepare potential metabolites and analogs of 3 beta-hydroxy-5 alpha-cholest-8(14)-en-15-one (I), a potent regulator of cholesterol metabolism. Partial hydrolysis of IX gave a mixture, from which the 3 beta,26-diol II and the 26-acetate (XI) and 3 beta-acetate (X) monoesters were isolated. Mitsunobu reaction of XI followed by hydrolysis gave (25R)-3 alpha,26-dihydroxy-5 alpha-cholest-8(14)-en-15-one (VI). Oxidation of XI with pyridinium chlorochromate followed by hydrolysis of the acetate gave (25R)-26-hydroxy-5 alpha-cholest-8(14)-ene-3,15-dione (VII). Oxidation of X with Jones reagent followed by hydrolysis of the acetate gave (25R)-3 beta-hydroxy-15-keto-5 alpha-cholest-8(14)-en-26-oic acid (IVa). Jones oxidation of II gave (25R)-3,15-diketo-5 alpha-cholest-8(14)-en-26-oic acid (VII). 1H and 13C nuclear magnetic resonance assignments and analyses of mass spectral fragmentation data are presented for each of the new compounds and their derivatives. The 3,15-diketone VII was found to be highly active in lowering the levels of 3-hydroxy-3-methylglutaryl coenzyme A reductase activity in CHO-K1 cells, with a potency comparable to that of I. In contrast, 3 alpha,26-diol VI was less potent than I or VII. The two carboxylic acid analogs IVa and VIII were considerably less potent than VI in lowering the levels of HMG-CoA reductase activity.     

A new chemical synthesis of 5alpha-cholest-8(14)-en-3beta,5alpha-diol

Reduction of 3beta-benzoyloxy-14alpha,15alpha-epoxy-5alpha-cholest-7-ene with lithium in ethylenediamine gave 5alpha-cholest-8(14)-en-3beta, 5alpha-diol in high yield. This procedure offers an alternate synthesis through the reductive rearrangement of an alpha,beta-unsaturated steroidal epoxide.