Sphingolipid bases. A revisitation of the O-methyl derivatives of sphingosine. Isolation and characterization of diacetate derivatives, with revised 13C nuclear magnetic resonance assignments for D-erythro-sphingosine

As described by Carter et al. (J. Biol. Chem. 1951. 192: 197-207), O-methyl derivatives of sphingosine are formed upon acid hydrolysis of sphingolipids in the presence of methanol. In the present study, we have isolated four O-methyl ethers of C18-sphingosine by medium pressure liquid chromatography of their diacetate derivatives, i.e., (2S,3R,4E)-1-acetoxy-2-acetamido-3-methoxy-4-octadecene, its (2S,3S) epimer, (2R,3E,5R)-1-acetoxy-2-acetamido-5-methoxy-3-octadecene, and its (2R,5S) epimer. Structures were determined by physical, chromatographic, and spectral properties. The 5-O-methyl ethers, which were the predominant byproducts of sphingolipid hydrolysis, were easily distinguished from the 3-O-methyl ethers by chromatography, and all four isomers could be differentiated by 1H and 13C nuclear magnetic resonance (NMR) spectroscopy. NMR analysis of the original N-acetate and diacetate samples of O-methylsphingosines I and II of Carter et al. demonstrated that they correspond to the 5-O-methyl ethers (2R,5R and 2R,5S, respectively), with purities of approximately 90-99%. Resolution enhancement of the 126-MHz 13C NMR spectra of the O-methyl ethers and D-erythro-C18-sphingosine (Ia) afforded distinct signals for nearly all carbon atoms. 13C NMR assignments of carbons 7-15 were made from their lanthanide-induced shifts, and revised assignments for olefinic carbons of Ia were established based upon 1H-13C shift correlation experiments.

Inhibitors of sterol synthesis. Metabolism-based design and construction of a new analog of 3 beta-hydroxy-5 alpha-cholest-8(14)-en-15-one and its effects in cultured mammalian cells and in rats

3 beta-Hydroxy-5 alpha-cholest-8(14)-en-15-one (I) is a potent regulator of cholesterol metabolism. In the present study, the 7 alpha-methyl-25,26,26,26,27,27,27-heptafluoro analog (X) of I has been synthesized with the goal of blocking not only the side chain oxidation of I but also its conversion to cholesterol. X was prepared in seven steps from the known 7 alpha-methyl analog (IX) of I. Treatment of the acetate of IX with a mixture of trifluoroacetic anhydride, hydrogen peroxide, and sulfuric acid gave 3 beta-acetoxy-7 alpha-methyl-24-hydroxy-5 alpha-chol-8(14)-en-15-one (XII) in remarkably high (68%) yield. Dehydration of XII via the orthonitrophenylselenide to the 23-ene, followed by addition of (CF3)2CFI gave (23R)-3 beta-acetoxy-7 alpha-methyl-23-iodo-25,26,26,26,27,27,27-heptafluoro-5 alpha-cholest-8(14)-en-15-one (XV). Reductive deiodination of XV with tributyltin hydride, followed by hydrolysis of the acetate gave 3 beta-hydroxy-7 alpha-methyl-25,26,26,26,27,27,27-heptafluoro-5 alpha-cholest-8(14)-en-15-one (X). The F7-7 alpha-methyl-15-ketosterol X lowered the levels of 3-hydroxy-3-methylglutaryl coenzyme A reductase activity in CHO-K1 cells with a potency equivalent to that of I. X showed significant hypocholesterolemic action upon oral administration to rats, with a potency far in excess of the 7 alpha-methyl-15-ketosterol IX lacking the F7 substitution. In marked contrast to I, X showed little or no suppression of food consumption in rats. Upon oral administration of X to rats, low levels of X (relative to cholesterol), characterized by chromatographic and gas chromatography-mass spectrometric methodologies, were observed in serum, liver, and small intestine. No material was observed with the expected properties of F7-7-methylcholesterol (or potential intermediates in its possible formation from X). In contrast to I, X lowered serum cholesterol levels at dosages at which no effect on food consumption was observed.

Inhibitors of sterol synthesis. Synthesis and spectral properties of 3 beta-hydroxy-5 alpha-cholestan-15-one and its 17 beta-epimer and their effects on 3-hydroxy-3-methylglutaryl coenzyme A reductase activity

3 beta-Hydroxy-5 alpha-cholestan-15-one (2a) and its 14 beta-epimer 2b were prepared from 3 beta-acetoxy-5 alpha-cholest-8(14)-ene (3). Hydroboration of 3 at 45-50 degrees C gave a mixture of 5 alpha,14 alpha-cholestane-3 beta,15 alpha-diol and 5 alpha,14 beta-cholestane-3 beta,15 beta-diol, which were separated on silica gel as their 3 beta-tert-butyldimethylsilyl ethers 5a and 5b. Oxidation of 5a with pyridinium chlorochromate, followed by desilylation with tetrabutylammonium fluoride gave 2a. Analogous transformations of 5b gave 2b contaminated with 2a. Desilylation of 5b followed by oxidation with pyridinium chlorochromate resulted in a mixture composed mainly of 5 alpha,14 beta-cholestane-3,15-dione and 2b. Successive chromatographic separations on silica gel and reversed phase media gave 2b of high purity. Compound 2a was also prepared by lithium-ammonia reduction of 3 beta-hydroxy-5 alpha-cholest-8(14)-en-15-one (96% yield) and by selective reduction of 5 alpha-cholestane-3,15-dione with lithium tri-tert-butoxyaluminum hydride (90% yield). Isomers 2a and 2b were readily epimerized under acidic or basic conditions or under conditions used for gas chromatographic analysis. The purities of 2a and 2b were measured from nuclear magnetic resonance (NMR) spectra; chromatographic methods gave less reliable estimates of purity. NMR data also showed that ring C of the 14 beta sterols is predominantly in a chair conformation. The effects of 2a and 2b on the levels of 3-hydroxy-3-methylglutaryl coenzyme A reductase have been studied in Chinese hamster ovary cells.

Inhibitors of sterol synthesis: synthesis and spectral properties of derivatives of 3 beta-hydroxy-25,26,26,26,27,27,27-heptafluoro-5 alpha-cholest-8(14)-en-15-one fluorinated at carbon 7 or carbon 9 and their effects on 3-hydroxy-3-methylglutaryl coenzyme A reductase activity in cultured mammalian cells

As part of a program to prepare delta 8(14)-15-ketosterols that cannot readily be metabolized to cholesterol or side-chain oxygenated species, we have prepared 3 beta-hydroxy-7 alpha-fluoro-5 alpha-cholest-8(14)-en-15-one (VII) and the 9 alpha-hydroxy (IV), 9 alpha-fluoro (VI) and 7 alpha-fluoro (VIII) derivatives of 3 beta-hydroxy-25,26,26,26,27,27,27-heptafluoro-5 alpha-cholest-8(14)-en-15-one (II). Sterol IV was prepared by oxidation of the delta 8,14 dienol ethyl ether of the 3 beta-acetate of II with m-chloroperbenzoic acid, followed by mild alkaline hydrolysis of the 3 beta-acetate derivative of IV. Treatment of IV with hydrogen fluoride-pyridine gave VI. The 7 alpha-fluoro-15-ketosterols VII and VIII were synthesized by treating the 3 beta,15-bis-trimethylsilyl delta 7,14-dienol ether derivative of the appropriate delta 8(14)-15-ketosterol with N-fluoropyridinium triflate, followed by hydrolysis of residual trimethylsilyl ethers and purification by high-performance liquid chromatography. The combined results of 1H and 13C nuclear magnetic resonance (NMR) chemical shifts, 1H-1H coupling constants, 1H-19F long-range coupling constants and molecular modeling indicated that a 7 alpha-fluoro, 9 alpha-fluoro or 9 alpha-hydroxy substituent has negligible effect on the conformation of the 15-ketosterols. 1H and 13C-NMR data are also given for delta 6,8(14)- and delta 8(14),9(11)-15-ketosterols, synthetic byproducts that could not be detected readily in samples of the fluoro-15-ketosterols by chromatographic methods. Mass spectra of VI and of previously reported 9 alpha-fluoro and 9 alpha-hydroxy-delta 8(14)-15-ketosterols showed abundant M-62 or M-60 ions that appear to correspond to loss of ketene and HF or H2O. The 9 alpha-hydroxy-F7-15-ketosterol IV, the 7 alpha-fluoro-15-ketosterol VII and the 7 alpha-fluoro-F7-15-ketosterol VIII were of equivalent potency to the parent 3 beta-hydroxy-5 alpha-cholest-8(14)-en-15-one (I) in lowering the levels of 3-hydroxy-3-methylglutaryl coenzyme A reductase activity in CHO-K1 cells. The 9 alpha-fluoro-F7-15-ketosterol VI showed high potency but appeared to be slightly less active than I.

Inhibitors of sterol synthesis. Effects of a new fluorinated analog of 3 beta-hydroxy-5 alpha-cholest-8(14)-en-15-one in rats

3 beta-Hydroxy-25,26,26,26,27,27,27-heptafluoro-5 alpha-cholest-8(14)-en-15-one (VII), an analog of 3 beta-hydroxy-5 alpha-cholest-8(14)-en-15-one (I) in which conversion to 26- and 25-oxygenated metabolites is blocked by the F7-substitution, was administered to male Sprague-Dawley rats at levels of from 0.025 to 0.15% by weight in a ground chow diet. Administration of VII resulted in lowering of the levels of serum cholesterol at dosages as low as 0.025% by weight in diet. In marked contrast to I, VII had little or no effect on food consumption. Whereas administration of I at a level of 0.1% by weight in diet resulted in a cessation of growth, VII, at approximately the same molar concentration in diet, had only slight or no effect on changes in total body weight. Significant levels of 25,26,26,26,27,27,27-heptafluorocholesterol (VIII) were observed in serum and liver, indicating the conversion of VII to VIII. Characterization of VIII in liver was based upon the results of gas chromatography, low and high resolution mass spectral studies, infrared spectroscopy, and 1H and 13C nuclear magnetic resonance spectroscopy. The levels of VIII in serum appeared to be related to dosage and duration of administration of VII.

Inhibitors of sterol synthesis: 3 beta-hydroxy-25,26,26,26,27,27,27- heptafluoro-5 alpha-cholestan-15-one, an analog of a potent hypocholesterolemic agent in which its major metabolism is blocked

The chemical synthesis of 3 beta-hydroxy-25,26,26,26,27,27,27-heptafluoro- 5 alpha-cholestan-15-one (IV) has been pursued to provide an analog of the potent hypocholesterolemic agent 3 beta-hydroxy-5 alpha-cholest-8(14)-en-15-one (I) in which its major metabolism is blocked. Reduction of 3 beta-acetoxy-5 alpha-chola-8(14),23-dien-15-one with lithium in liquid ammonia gave 3 beta-hydroxy-5 alpha-chol-23-en-15-one (VI). Addition of (CF3)2CFI to VI in the presence of triethylborane gave 3 beta-hydroxy-23R-iodo-25,26,26,26,27,27,27-heptafluoro-5 alpha-cholestan- 15-one, which was reduced to IV with tributyltin hydride. IV was found to be highly active in lowering the levels of HMG-CoA reductase activity in CHO-K1 cells, in lowering acyl coenzyme A:cholesterol acyltransferase activity in jejunal microsomes, and in lowering serum cholesterol levels in rats.

Inhibitors of sterol synthesis. An improved chemical synthesis of 26-oxygenated delta 8(14)-15-ketosterols having the 25R configuration

(25R)-3 beta,26-Dihydroxy-5 alpha-cholest-8(14)-en-15-one (I) was synthesized in four steps from (25R)-3 beta,26-diacetoxycholesta-5,7-diene (III) in 30% overall yield. Isomerization of III with HCl in chloroform-dichloromethane at -60 degrees C gave (25R)-3 beta,26-diacetoxy-5 alpha-cholesta-7,14-diene together with the 5 alpha-delta 8,14 and 5 beta-delta 8,14 isomers in a 5:1:1 ratio. Epoxidation of the crude diene mixture with m-chloroperbenzoic acid, followed by hydrolysis in acetone containing concentrated HClO4 (0.1%) gave (25R)-3 beta,26-diacetoxy-5 alpha-cholest-8(14)-en-15-one (VIII), accompanied by numerous minor byproducts, including the 5 alpha,14 beta-delta 7, 5 alpha, 14 beta-delta 8 and 5 beta,14 beta-delta 8 isomers of VIII. All four 15-ketosterol esters were isolated by chromatography and fully characterized by mass spectrometry and 1H and 13C nuclear magnetic resonance. Treatment of VIII with potassium carbonate in degassed methanol gave I.

Inhibitors of sterol synthesis. Effects of fluorine substitution at carbon atom 25 of cholesterol on its spectral and chromatographic properties and on 3-hydroxy-3-methylglutaryl coenzyme A reductase activity in CHO-K1 cells

25-Fluorocholesterol (III) was prepared by treatment of 25-hydroxycholesterol (IV) with hydrogen fluoride-pyridine. Compounds III, IV, and cholesterol (I) were fully characterized by 1H and 13C NMR, and stereochemical assignments were established for the C-22 and C-23 protons. The side-chain proton assignments, which apply to most other sterols with a saturated eight-carbon side chain, were based on conformational analysis and comparisons with NMR data for 25,26,26,26,27,27,27-heptafluorocholesterol (II). The chromatographic behavior of I, II, and III were compared on thin-layer chromatography, high performance liquid chromatography, and gas chromatography. Major fragment ions in electron-impact mass spectra of III were analogous to ions of either cholesterol or desmosterol, and a similar analogy was observed for the trimethylsilyl ethers. The 25-hydroxysterol IV and the 25-fluorosterol III differed markedly in their effects on the levels of 3-hydroxy-3-methylglutaryl coenzyme A reductase activity in CHO-K1 cells. Whereas 25-hydroxycholesterol caused a approximately 66% lowering of reductase activity in cells at 0.1 microM, the 25-fluorosterol III had no effect at this concentration.

Inhibitors of sterol synthesis: effects of a 7 alpha-alkyl analog of 3 beta-hydroxy-5 alpha-cholest-8(14)-en-15-one on 3-hydroxy-3-methylglutaryl coenzyme A reductase activity in cultured mammalian cells and on serum cholesterol levels and other parameters in rats

The 7 alpha-methyl analog (II) of 3 beta-hydroxy-5 alpha-cholest-8(14)-en-15- one (I) was prepared by chemical synthesis and evaluated with respect to its effects on HMG-CoA reductase activity in CHO-K1 cells and on serum cholesterol levels in rats. The 7 alpha-methyl substitution had no detectable effect on the potency of I in lowering HMG-CoA reductase activity in the cultured cells. In contrast, the 7 alpha-methyl substitution had a marked effect on the action of I in the suppression of food consumption in rats. Whereas II was less potent than I in lowering serum cholesterol levels in rats, it did so at dosage levels at which only slight or moderate effects on food consumption were observed. Full 1H and 13C-NMR assignments for II and intermediates in its synthesis have been presented. Conformational analysis, based on 1H-1H coupling constants, NMR shieldings and force-field calculations, indicated that the 7 alpha-methyl substitution had virtually no effect on the conformation of the 15-ketosterol apart from minor distortions of ring B.

Inhibitors of sterol synthesis. Tritium-labeled 26-hydroxycholesterol of high specific activity from a byproduct of the Clemmensen reduction of diosgenin

(25R)-26-Hydroxycholesterol (I) was synthesized in six steps from (22Z,25R)-cholesta-5,22-diene-3 beta,26-diol (II) in 31% overall yield. The 26-tert-butyldiphenylsilyl ether of II was converted via its 3 beta-tosylate to (22Z,25R)-6 beta-methoxy-26-(tert- butyldiphenylsilyloxy)-3 alpha,5-cyclo-5 alpha-cholest-22-ene (V). Removal of the 26-silyl group of V gave (22Z,25R)-6 beta-methoxy-3 alpha,5-cyclo-5 alpha-cholest-22-en-26-ol, which was hydrogenated over platinum oxide and then hydrolyzed to I. Catalytic reduction in the presence of deuterium or tritium gas gave [2H]-I or [3H]-I, respectively. Analysis of the [2H]-I by mass spectrometry showed that all the deuterium was located in the sterol side chain, mainly as d2, d3, and d4 species. The 2H and 13C nuclear magnetic resonance (NMR) spectra of [2H]-I indicated that most of the deuterium was located at C-22 and C-23, with lesser amounts at C-24 and minor amounts at C-20, C-21, C-25, and C-27. NMR spectra of [2H]-I and its alpha-methoxy-alpha-(trifluoromethyl)phenylacetate diester showed no detectable 20S epimer and approximately 2% of the 25S epimer. The [3H]-I was prepared analogously to [2H]-I using carrier-free tritium and showed a specific activity of 16.9 Ci/mmol. All synthetic intermediates were characterized fully by 1H and 13C NMR, and representative 1H-1H coupling constants are given for the ring A protons of i-steroids.

Inhibitors of sterol synthesis. Chemical synthesis and properties of 3 beta-hydroxy-25,26,26,26,27,27,27-heptafluoro-5 alpha-cholest-8(14)-en-15-one and 25,26,26,26,27,27,27-heptafluorocholesterol and their effects on 3-hydroxy-3-methylglutaryl coenzyme A reductase activity in cultured mammalian cells

A side-chain fluorinated delta 8(14)-15-ketosterol has been synthesized from 3 beta-acetoxy-24-hydroxy-5 alpha-chol-8(14)-en-15-one (VII) as part of a program to prepare new analogs of 3 beta-hydroxy-5 alpha-cholest-8(14)-en-15-one (I), a potent regulator of cholesterol metabolism. 3 beta-Hydroxy-25,26,26,26,27,27,27-heptafluoro-5 alpha-cholest-8(14)-en-15-one (VIII) was prepared in five steps from VII in 38% overall yield. Dehydration of VII via the ortho-nitrophenylselenide to the 23-ene, followed by addition of (CF3)2CFI gave 3 beta-acetoxy-23R-iodo-25,26,26,26,27,27,27-heptafluoro-5 alpha-cholest-8(14)-en-15-one. Reductive deiodination with tributyltin hydride, followed by hydrolysis of the acetate gave VIII. 25,26,26,26,27,27,27-Heptafluorocholest-5-en-3 beta-ol (XXI) was prepared in eight steps in 31% overall yield from 3 alpha,6 alpha-diacetoxy-5 beta-cholanic acid (XIII). Compound XIII was reduced with borane-methyl sulfide to the corresponding 24-hydroxysteroid, which was converted to 3 alpha,6 alpha-diacetoxy-25,26,26,26,27,27,27-heptafluoro-5 beta-cholestane (XVIII) by reactions analogous to those developed for the preparation of VIII from VII. Conversion of XVIII via the 3 alpha,6 alpha-diol to the 3 alpha,6 alpha-ditosylate, followed by heating with potassium acetate in dimethylformamide and subsequent hydrolysis gave XXI. Full 1H and 13C NMR assignments are presented for VIII, XXI, and intermediates involved in their synthesis. 13C NMR assignments for 3 alpha,6 alpha-dihydroxy-5 beta-steroids have been corrected, and stereochemical assignments were established for the side-chain methylene protons of VIII, XXI, and most synthetic intermediates. Compound VIII lowered the levels of HMG-CoA reductase activity in CHO-K1 cells and in HepG2 cells with a potency comparable to that of 3 beta-hydroxy-5 alpha-cholest-8(14)-en-15-one (I). In contrast, 25,26,26,26,27,27,27-heptafluorocholest-5-en-3 beta-ol had little or no effect on reductase activity in CHO-K1 cells. These combined results indicate that metabolism of 3 beta-hydroxy-5 alpha-cholest-8(14)-en-15-one (I) to 26- and 25-oxygenated species is not required for the suppressive action of I on the levels of HMG-CoA reductase activity in CHO-K1 cells and HepG2 cells.

D-erythro-sphingosine lowers 3-hydroxy-3-methylglutaryl coenzyme A reductase activity in Chinese hamster ovary cells

D-Erythro-sphingosine lowered the levels of HMG-CoA reductase activity in CHO-K1 cells. Significant suppression of reductase activity was observed at 5 microM, 10 microM, and 15 microM concentrations of the sphingolipid base and approximately 50% lowering was found at 10 microM. In contrast, L-threo-sphingosine had no effect on the levels of reductase activity under the conditions studied. Direct addition of D-erythro-sphingosine, at concentrations up to 100 microM, to rat liver microsomes had no effect on the levels of HMG-CoA reductase activity. The concentrations of D-erythro-sphingosine required to lower reductase activity in CHO-K1 cells correspond to reported levels of sphingosine in mammalian cells.

Efficient preparation of steroidal 5,7-dienes of high purity

Protected forms of dehydroepiandrosterone, delta 5 cholenic acid, (25R)-26-hydroxycholesterol and diosgenin were converted to the corresponding delta 5,7 dienes by successive treatment with 1,3-dibromo-5,5-dimethylhydantoin (dibromantin), tetrabutylammonium bromide and tetrabutylammonium fluoride. The crude products, which contained the delta 5,7 species contaminated by minor amounts of the delta 5 and delta 4,6 steroids, were purified by silica gel-AgNO3 chromatography to give the following steroids in approximately 99% purity and at least 50% yield: 3 beta-acetoxyandrosta-5,7-dien-17-one, methyl 3 beta-acetoxychola-5,7-dien-24-oate, (25R)-3 beta,26-diacetoxycholesta-5,7-diene and (25R)-3 beta-acetoxyspirosta-5,7-diene. Analogous treatment of acetate derivatives of pregnenolone and stigmasterol gave 3 beta-acetoxypregna-5,7-dien-20-one and 3 beta-acetoxystigmasta-5,7,22-triene in approximately 50% yield but of lower purity. Full 1H and 13C NMR assignments are given for seven delta 5,7 steroid acetates and the corresponding delta 5 starting materials. Coupling constants for rings A, B and C of delta 5,7 steroids are presented and stereochemical assignments have been made for the following 1H NMR signals: the C-11 protons of delta 5,7 steroids, the C-16 protons of sterols and bile acids, the C-22 and C-23 protons of bile acid esters and the C-28 protons of stigmasterol derivatives.

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.

Inhibitors of sterol synthesis. Chemical synthesis and spectral properties of 3 beta-hydroxy-5 alpha-cholesta-8(14),24-dien-15-one, 3 beta,25-dihydroxy-5 alpha-cholest-8(14)-en-15-one, and 3 beta,24-dihydroxy-5 alpha-cholest-8(14)-en-15-one and their effects on 3-hydroxy-3-methylglutaryl coenzyme A reductase activity in CHO-K1 cells

Side-chain functionalized delta 8(14)-15-ketosterols have been synthesized from 3 beta-acetoxy-24-hydroxy-5 alpha-chol-8(14)-en-15-one (VI) 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. Oxidation of VI to the 24-aldehyde VII, followed by Wittig olefination with isopropyltriphenylphosphonium iodide gave 3 beta-acetoxy-5 alpha-cholesta-8(14),24-dien-15-one (VIII), which was hydrolyzed to the free sterol IX. Oxymercuration of VIII followed by hydrolysis of the 3 beta-acetate gave 3 beta,25-dihydroxy-5 alpha-cholest-8(14)-en-15-one (IV). Hydroboration-oxidation of VIII followed by hydrolysis of the 3 beta-acetate gave 3 beta,24-dihydroxy-5 alpha-cholest-8(14)-en-15-one (V) as a 5:4 mixture of the 24R and 24S epimers. 1H and 13C nuclear magnetic resonance (NMR) assignments and mass spectral fragmentation patterns, supported by high-resolution measurements, are presented for IV and its 3 beta-acetate, V, VII, VIII, and IX. Characterization of IV by NMR and of trimethylsilyl ethers of IV and V by gas chromatography-mass spectrometry was compatible with spectral data for samples of IV and V isolated previously after incubation of I with rat liver mitochondria in the presence of NADPH. Sterols IV, V, and IX were very potent in lowering of the level of 3-hydroxy-3-methylglutaryl coenzyme A reductase activity in Chinese hamster ovary cells; their potency was comparable to that of I.