Regio and stereoselective oxidations of unsaturated steroidal compounds with H 2O 2 mediated by CH 3ReO 3 (original) (raw)
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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.
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.
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.
Oxidation of sterols: Energetics of C–H and O–H bond cleavage
Food Chemistry, 2012
Phytosterols, as components of human diet, received much attention because of their cholesterol-lowering and antioxidant properties. We have theoretically studied sterols oxidation in terms of O-H and C-H bond dissociation enthalpies (BDE). In 17 D 5-and D 7-sterols, BDEs were obtained for reported sites of oxidation attack. Obtained results indicate that D 7-sterols are more susceptible to oxidation attack in comparison to D 5-sterols. In sterol nuclei, the lowest BDE was found for C7-H bond in D 5-sterols and for C14-H in D 7-sterols. When D 5-sterol has a C@C double bond in the side chain, the lowest BDEs are usually found for C-H bonds in a-positions to this bond. The homolytic cleavage of hydroxyl O-H bond requires larger energy in comparison to the studied C-H bonds. We have shown that the C-H bonds with lowest BDE values actually correspond to the dominant sites of oxidation attack. .
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.