40823-41-4Relevant academic research and scientific papers
STUDIES ON THE CHEMO- AND STEREOSELECTIVITY OF SODIUM BOROHYDRIDE-POLYETHYLENE GLYCOL 400-MEDIATED REDUCTIONS
Santaniello, Enzo,Ferraboschi, Patrizia,Fiecchi, Alberto,Grisenti, Paride,Manzocchi, Ada
, p. 701 - 704 (2007/10/02)
Chemo- and stereoselectivity of reductions by the NaBH4/polyethylene glycol (PEG) 400 system have been studied and compared to the traditional NaBH4 reductions in methanol.When the stereoselectivity was tested on 3- and 7-keto steroids 1a and 1b, respectively, interesting improvements were observed.Aldehydes were reduced faster than ketones and in the case of 3-oxo-pregn-4-en-20β-carboxaldehyde, 2a, the aldehyde was reduced completely leaving the unsatured ketone moiety unchanged.Absorption on inorganic support or addition of a few cationic species led to inactive or much less active reducing species.
Stereoselectivity in Reduction of Steroidal 7-Ketones
Maruyama, Sanae,Ogihara, Noriko,Adachi, Itsuko,Ohotawa, Junko,Morisaki, Masuo
, p. 1847 - 1852 (2007/10/02)
Several 7-ketones of lanostane, 4,4-dimethylcholestane and cholestane derivatives were subjected to catalytic hydrogenation on platinum, reduction with complex hydrides and reduction with sodium in tert-butanol, and the product ratios (7α-ol/7β-ol) were determined by gas chromatography or high-performance liquid chromatography.Catalytic hydrogenation of 3β hydroxylanostan-7-one and 3β-hydroxy-4,4-dimethylcholestan-7one yielded the 7β-alcohols as the major products, whereas their 3-acetates gave prinsipally the 7α-alcohols.Reductionof various 7-ketones with sodium in tert-butanol gave mainly the 7β-equitoiral alcohols, while the epimeric 7α-ols were the major products on reduction with litium tri-sec- butilborohydride.The stereoselectivity of reduction with sodium borohydride and lihium aluminium hydride was highly dependent on the neighboring double bond and 4,4-dimethiyl and/or 14α-methyl substituent(s). Keywords---reduction; 7-oxygenated sterol; stereoselectivity; lithium tri-sec-butylborohydride; 3β-hydroxy-4,4-dimethylcholestan-7one
