Abstract
The catalytic asymmetric reduction of α-keto aldoxime O -methyl, O -benzyl,
and O -trityl ethers, derived from substituted acetophenones,
with borane/oxazaborolidines, by transfer hydrogenation,
and with yeast, was studied. The reduction with borane/oxazaborolidines
produced the corresponding α-hydroxy oxime ethers, α-hydroxy
hydroxylamine ethers, and β-amino alcohols in 39-78% yields
and up to 77% ee. The carbonyl group was selectively reduced
by transfer hydrogenation with formic acid-triethylamine
catalyzed by RhCl[(R ,R )-TsDPEN](C5 Me5 ),
and also with yeast, producing α-hydroxy oxime ethers,
up to 75% ee and 93% ee, respectively.
Key words
α-keto aldoximes - catalytic reduction - oxazaborolidines - transfer hydrogenation - yeast reduction
