Inhibitors of sterol synthesis. A highly efficient and specific side-chain oxidation of 3 beta-acetoxy-5 alpha-cholest-8(14)-en-15-one for construction of metabolites and analogs of the 15-ketosterol

• Published in: Journal of lipid research Vol. 33; no. 4; pp. 579 - 598
• Main Authors: Herz, JE, Swaminathan, S, Pinkerton, FD, Wilson, WK, Schroepfer, GJ
• Format: Journal Article
• Language: English
• Published: Bethesda, MD Elsevier Inc 01.04.1992; American Society for Biochemistry and Molecular Biology; Elsevier
• Subjects: Acetic Anhydrides; Analytical, structural and metabolic biochemistry; Animals; Biological and medical sciences; CHO Cells; Cholenes - chemistry; Cholestenones - chemistry; Cholestenones - metabolism; Cholesterol - metabolism; Chromatography, High Pressure Liquid; Cricetinae; Fluoroacetates; Fundamental and applied biological sciences. Psychology; Hydrogen Peroxide - metabolism; Hydroxymethylglutaryl CoA Reductases - metabolism; Magnetic Resonance Spectroscopy; Molecular Structure; Other biological molecules; Oxidation-Reduction; Sulfuric Acids - metabolism; Terpenes, steroids. Hormones; Trifluoroacetic Acid - metabolism; Inhibitor; Molecular structure; Metabolism; Chemical synthesis; Mass spectrometry; Cholesterol
• ISSN: 0022-2275; 1539-7262
• DOI: 10.1016/S0022-2275(20)41623-2

As part of a program directed towards the chemical syntheses of potential metabolites and analogs of 3 beta-hydroxy-5 alpha-cholest-8(14)-en-15-one (I), a potent regulator of cholesterol metabolism, several routes have been explored for the preparation of 3 beta-hydroxy-15-keto-5 alpha-chol-8(14)-en-24-oic acid (IV). These investigations led to a remarkably specific and efficient side-chain oxidation of I. For example, treatment of the acetate of I with a mixture of trifluoroacetic anhydride, hydrogen peroxide, and sulfuric acid for 3.5 h at -2 degrees C gave a crude product consisting of 3 beta-acetoxy-24-trifluoroacetoxy-5 alpha-chol-8(14)-en-15-one (XI), 3 beta-acetoxy-24-hydroxy-5 alpha-chol-8(14)-en-15-one (XII), and 3 beta, 24-diacetoxy-5 alpha-chol-8(14)-en-15-one (XIII) in yields of 58%, 8%, and 3%, respectively, by HPLC analysis. XI was readily hydrolyzed to XII upon treatment with triethylamine in methanol at room temperature. Oxidation of XII with Jones reagent gave 3 beta-acetoxy-15-keto-5 alpha-chol-8(14)-en-24-oic acid (XVIII) from which its methyl ester (IX) was prepared by treatment with diazomethane. Mild alkaline hydrolysis of XVIII gave the 3 beta-hydroxy-delta 8(14)-15-keto C24 acid (IV). Hydrolysis of the crude product of the side-chain oxidation with K2CO3 in methanol gave 3 beta,24-dihydroxy-5 alpha-chol-8(14)-en-15-one (XIV) which was oxidized with Jones reagent to yield 3,15-diketo-5 alpha-chol-8(14)-en-24-oic acid (XV). Treatment of XV with diazomethane gave its methyl ester (XVI) which, upon controlled reduction with NaBH4, yielded methyl 3 beta-hydroxy-15-keto-5 alpha-chol-8(14)-en-24-oate (XVII). Compound IX was also prepared by an independent route. Full 1H and 13C NMR assignments are presented for 12 new compounds. IV caused a approximately 56% reduction of the level of 3-hydroxy-3-methylglutaryl coenzyme A reductase activity in CHO-K1 cells at a concentration of 2.5 microM. In contrast, the corresponding 3,15-diketo acid XV had no detectable effect on reductase activity under the same conditions.