Regio and stereoselective oxidations of unsaturated steroidal compounds with H2O2 mediated by CH3ReO3.
We have investigated the oxidative behavior of sterols such as cholesteryl acetate (1), 7-dehydrocholesteryl acetate (2), ergosteryl acetate (3), cholecalciferol acetate (Vitamin D(3) acetate) (4) and ergocalciferol acetate (Vitamin D(2) acetate) (5) with the oxidant system methyltrioxorhenium/H(2)O(2)/pyridine in order to check potential parameters controlling the selectivity. The reactions, performed in CH(2)Cl(2)/H(2)O at 25 degrees C, have shown good regio- and stereoselectivity. All oxidation products were isolated by high-performance liquid chromatography (HPLC) and characterized by MS(EI) or FAB, (1)H NMR, (13)C NMR, APT, COSY, HSQC, HMBC, ROESY and NOEDS measurements. Seven new oxygenated compounds were also obtained. Under the experimental conditions adopted in this work, only the diene steroids, i.e. 7-dehydrocholesteryl acetate and ergosteryl acetate, undergo hydrolytic oxirane ring opening, whereas Vitamin D(2) and D(3) acetates, containing the triene system and cholesteryl acetate yield only epoxides. The selectivity seems to be controlled by the nucleophilicity of double bonds and by stereoelectronic and steric effects.
Ballistreri
Francesco P
FP
Dipartimento di Scienze Chimiche, University of Catania, Viale A. Doria, I-95125 Catania, Italy.
Chillemi
Rosa
R
Sciuto
Sebastiano
S
Tomaselli
Gaetano A
GA
Toscano
Rosa M
RM
D002762:Cholecalciferol / Q000138:chemical synthesis / Q000737:chemistry; D002788:Cholesterol Esters / Q000138:chemical synthesis / Q000737:chemistry; D002851:Chromatography, High Pressure Liquid; D004872:Ergocalciferols / Q000138:chemical synthesis / Q000737:chemistry; D006861:Hydrogen Peroxide / Q000737:chemistry* / Q000378:metabolism; D009682:Magnetic Resonance Spectroscopy; D013058:Mass Spectrometry; D009942:Organometallic Compounds / Q000138:chemical synthesis / Q000737:chemistry*; D016877:Oxidants / Q000737:chemistry*; D010084:Oxidation-Reduction; D013237:Stereoisomerism; D013261:Sterols / Q000138:chemical synthesis / Q000737:chemistry*
D002788:Cholesterol Esters; D004872:Ergocalciferols; D009942:Organometallic Compounds; D016877:Oxidants; D013261:Sterols; D002762:Cholecalciferol; C411866:methyltrioxorhenium VII; D006861:Hydrogen Peroxide; C060123:cholesterol acetate