Stereoselectivity in hydrosilylative reduction of substituted cyclohexanone derivatives with chiral rhodium-bis(oxazolinyl)pyridine catalyst
摘要:
Stereoselectivity in the reduction of substituted cyclohexanones, 4-tert-butylcycohexanone, 2-methylcycohexanone, 2-phenylcyclohexanone, and 2-methoxycarbonyl-methylcyclohexanone, was examined with chiral rhodium-bis(oxazolinyl)pyridine catalyst and diphenylsilane. 4-tert-Butylcyclohexanone gave the corresponding trans(equatorial)-alcohol predominantly; the ratio of the trans/cis alcohols, 67:33. Other 2-substituted cyclohexanones showed exclusive enantioselectivities for each diastereomer in terms of the kinetic resolution; e.g. from 2-phenylcyclohexanone, 99 % ee of (1S, 2R)-trans-2-phenylcyclohexanol and 96 % ee of (1S, 2S)-cis-2-phenylcyclohexanol in 92 % yield (the trans/cis ratio = 51:49).
Biocatalytic access to nonracemic γ-oxo esters via stereoselective reduction using ene-reductases
作者:Nikolaus G. Turrini、Răzvan C. Cioc、Daan J. H. van der Niet、Eelco Ruijter、Romano V. A. Orru、Mélanie Hall、Kurt Faber
DOI:10.1039/c6gc02493a
日期:——
The asymmetric bioreduction of [small alpha],[small beta]-unsaturated [gamma]-keto esters usingene-reductasesfrom the OldYellowEnzymefamily proceeds with excellent stereoselectivity and high conversion levels, covering a broad range of acyclic and...
(+) and (−)-Dihydropinidine and (+)- and (−)-epidihydropinidine were synthesized from hydroxy esters 1 and 2 which had been prepared by yeast reduction of methyl (2-oxocyclohexyl)acetate. The enantiomeric excess at the C-1 positions of 1 and 2 were both determined as more than 99% ee.