Synthesis and selective catalytic oxidation of new dimeric steroids (original) (raw)
Related papers
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.
Synthesis of C–C bonded dimeric steroids by olefin metathesis
Tetrahedron, 2009
Five new CC bonded steroidal homodimers derived from deoxycholic acid, pregnenolone, and progesterone were synthesized by an olefin metathesis reaction assisted by microwave heating. Microwave improved the yield and accelerated the reaction allowing the use of less catalyst with good results (2.5 mol %). Due to the bulky nature of the steroidal skeleton the more favorable E-dimers were formed as the sole or major products depending on the linker length.
Tetrahedron: Asymmetry, 1996
The asymmetric reduction of enantiomerically pure steroid ketones was carried out by using oxazaborolidine catalysts with a variety of achiral or chiral ligands. The efficiency of chiral ligands (1,2-amino alcohols) as well as the effect of the stereogenic centers in the substrate on the catalytic asymmetric reduction were studied. It was found that the diastereoselectivity is mainly controlled by the absolute configuration of the chiral ligand. The reduction gave either the 17et-or 1713-alcohol with high diastereomeric purity. This catalytic reduction represents a very practical solution to the problem of controlling C(17)stereochemistry in synthesis of steroid compounds.
Metathesis reactions of Δ 22-steroids
Tetrahedron Letters, 2009
Metathesis reactions of Δ22-steroids are studied. The cross metathesis reactions of model Δ22-steroids with excess of simple alkenes are sluggish or do not occur at all. In contrast, derivatives of both trans- and cis-Δ22-cholesterol undergo ring closing metathesis reactions but the former reacts faster. However, the side chain double bond in stigmasterol and ergosterol is too crowded for metathesis reactions promoted by currently available catalysts.
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.
The Journal of Organic Chemistry, 1993
Dimethylaluminum chloride-mediated ene reactions of aldehydes with (2)-3@-acetoxy-5,17(20)pregnadiene (3) at low temperatures followed by acetylation of the resulting alcohols have been shown to produce stereoselectively 22-acetoxylated steroid derivatives in good to excellent yields. Interestingly, the stereochemical outcome of these ene reactions has been found to be dependent upon the size of the aldehyde employed; the less sterically demanding aldehydes such as 4-methylpentanal and cyclohexanecarboxaldehyde afford the (20a,22a)-22-acetoxy products (4a) stereoselectively, whereas the relatively congested aldehydes such as benzaldehyde and other aromatic aldehydes produce predominantly the (20a,228)-22-acetates (4b). This novel stereochemical observation has been rationalized in terms of the relative stabilities of the two most plausible transition states where the difference in the relative bulk between the R group of the aldehyde RCHO and the Me2AlC1 coordinating to the aldehyde oxygen in an anti-fashion seems to be manifested in the stereochemical outcome at C-22 of the ene producta.