A Highly β-Stereoselective Catalytic Epoxidation of Δ 5 -Unsaturated Steroids with a Novel Ruthenium(II) Complex under Aerobic Conditions (original) (raw)
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Steroids, 2006
We have investigated the oxidative behavior of sterols such as cholesteryl acetate (1), 7-dehydrocholesteryl acetate (2), ergosteryl acetate (3), cholecalciferol acetate (Vitamin D3 acetate) (4) and ergocalciferol acetate (Vitamin D2 acetate) (5) with the oxidant system methyltrioxorhenium/H2O2/pyridine in order to check potential parameters controlling the selectivity. The reactions, performed in CH2Cl2/H2O at 25°C, have shown good regio- and stereoselectivity. All
ChemInform Abstract: Recent Developments in Oxidative Processes in Steroid Chemistry
ChemInform, 2012
Oxygenated steroids are bioactive compounds and valuable intermediates in the synthesis of biologically active products and APIs. This review will cover the literature from 2005/06 to the present concerning allylic oxidation, epoxidation and syn-dihydroxylation of alkenes, alcohol oxidation, and remote functionalization reactions of steroidal substrates.
Journal of Molecular Catalysis A-chemical, 2004
A general catalytic and relatively environment friendly method for β-epoxidation of Δ5-steroids has been developed, which uses silica supported cobalt as catalysts and molecular oxygen as the oxidant. The reactions are regio- and stereoselective.A whole range of Δ5-steroids, with different functional groups such as hydroxyl, carbonyl or acetyl, as well as different side chains, were conveniently converted to the corresponding biologically interesting 5β,6β-epoxides with high degree of stereoselectivity and high yields.A general catalytic and relatively environment friendly method for β-epoxidation of Δ5-steroids has been developed, which uses silica supported cobalt as catalysts and molecular oxygen as the oxidant. The reactions are regio- and stereoselective.
The oxidation of Δ2, Δ2,4 and Δ4,6 steroids with RuO4
Steroids, 2004
In order to find new ways for the functionalization of the A and B rings of the steroid nucleus, the reaction of 5alpha-androst-2-en-17beta-ol 17-acetate (1), cholesta-2,4-diene (4) and cholesta-4,6-dien-3beta-ol 3-acetate (7) was examined using stoichiometric amounts of ruthenium tetraoxide to yield 1,2-cis diols and/or alpha-hydroxy ketones. The reaction of 5alpha-cholest-2-en-3-ol 3-acetate (9) with ruthenium tetraoxide was also carried out and afforded, apart from an alpha-hydroxy ketone, also a diketone and a seco-dicarboxylic acid. The structures of all new steroids, including stereochemical details, were deduced by analysis of spectral data.
Recent Highlights in Green Oxidative Chemical Processes Applied to Steroid Chemistry
InTech eBooks, 2016
Steroids and their oxidation products are widely distributed in living organisms and are important intermediates for the synthesis of many biologically active molecules. Due to their pharmacological and synthetic relevance, several oxidative chemical processes for the functionalization of the steroid nucleus have been developed. Green chemistry principles have been incorporated in some oxidative transformations of steroids, allowing significant advances in synthetic chemistry applied to these compounds. This chapter presents a selection of relevant applications of pharmaceutical green chemistry to steroid's oxidative processes. Special emphasis is given to catalytic processes encompassing heterogeneous nanocatalysts, whose application in this context is increasing over the past years. This chapter is organized according to the reaction type that includes alcohol oxidation, epoxidation of alkenes, and allylic oxidation of alkenes to enones, among other relevant oxidative transformations. Biocatalytic oxidative methods applied to steroid synthesis are not included in this review.
Journal of the Chemical Society, Perkin Transactions 1, 2001
In order to find new ways of introducing oxygenated functions in the 15-, 9-and 11-position on steroid rings and at the same time test the reactivity of a conjugated diene steroid toward methyltrioxorhenium (MTO)-catalyzed oxidation with the urea-hydrogen peroxide adduct (UHP), the reactions of 5α-cholesta-8,14-dien-3β-yl acetate 1 with the MTO-UHP system are performed in aprotic solvents. These oxidations are performed both at 0 ЊC and 25 ЊC in CHCl 3 or diethyl ether as solvent and in the presence of pyridine ligand. From the reaction of diene 1 in CHCl 3 we isolate two new sterols, 9β-hydroxy-15-oxo-5α-cholest-8(14)-en-3β-yl acetate 3 and 9α,11α,15α-trihydroxy-5α-cholest-8(14)-en-3β-yl acetate 7, while oxidation in Et 2 O in the presence of pyridine ligand allows us to isolate the new epoxysteroid 9α,11α-epoxy-15α-hydroxy-5α-cholest-8(14)-en-3β-yl acetate 13. The structure of all new steroids is secured on the basis of chemical evidence and interpretation of spectral data, which include H-H COSY, HMBC and NOESY experiments. These results represent a new and mild method for the functionalization of C and D rings from an 8,14-diene steroid, to give 15-oxygenated sterols, a class of compounds remarkable for their inhibitory action on sterol synthesis in animal cell culture systems.