ChemInform Abstract: Recent Developments in Oxidative Processes in Steroid Chemistry (original) (raw)
Related papers
Optimization of the allylic oxidation in the synthesis of 7-keto-Δ5-steroidal substrates
Steroids, 2003
A variety of 5 -steroids were converted into ␣, -unsaturated 7-ketones using a modification of the already known method of t-butyl hydroperoxide in the presence of copper iodide in acetonitrile. The same alteration was applied to another oxidative procedure, which had never been used before on steroidal substrates. The same oxidative agent was used in the presence of copper iodide, and tetra-n-butylammonium bromide was used as a phase-transfer catalyst in a two-phase system of water/methylene chloride. It was found that the allylic oxidation proceeded more efficiently when t-butyl hydroperoxide was added to the reaction mixture in portions. The initial addition of the total amount of oxidant or its dropwise addition afforded low yields. This observation contributes to the investigation of the reaction mechanism, and high-yield conversions of steroidal 5,6-enes into the corresponding conjugated 7-ones in short reaction times are reported.
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.
ChemInform, 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.
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
Improved chromium-catalyzed allylic oxidation of Δ5-steroids with t-butyl hydroperoxide
Journal of Molecular Catalysis A: Chemical, 2006
Various chromium VI -catalyzed conditions have been tested to improve the oxidation of 5 -steroids with t-BuOOH to their corresponding 5-en-7-ones. The use of PDC or the association of CrO 3 with an amine as the catalyst and CH 2 Cl 2 or PhCF 3 as the solvent led usually to the best yields. A minor reaction pathway was the epoxidation of the double bond.
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.
Unusual oxidative transformations of a steroidal 16α,17α,22-triol
Steroids, 2010
A number of unexpected reactions were observed during attempts to invert configuration at C16 in 16␣,17␣,22-triol 3a. The PDC oxidation of 3a produced the D-seco-aldehyde 4a. Analogous compound 4b was obtained by Swern oxidation of the 16␣,17␣-dihydroxy-22-O-TES-ether 3b in addition to the desired 16-ketone 7. The unprotected triol 3a yielded pentacyclic products 5 and 6 under similar conditions. The Mitsunobu reaction of the triol 3a afforded 16-ketone 8 with inverted configuration of the side chain. During heating of a solution of 3a in THF with NaH at reflux autoxidation to the 16-ketone cyclic hemiketal 5, identical to one of the Swern oxidation products, took place.