A practical and stereoselective reduction of 3-keto-2-methyl esters or 3-keto-2-methyl amides into erythro-3-hydroxy-2-methyl esters or erythro-3-hydroxy-2-methyl amides with NaBH4 catalyzed by MnCl2
作者:Hideaki Fujii、Koichiro Oshima、Kiitiro Utimoto
DOI:10.1016/0040-4039(91)80775-2
日期:1991.10
Erythro-3-hydroxy-2-methylpropionates or erythro-3-hydroxy-2-methylpropionamides were prepared with high stereoselectivity by NaBH4reduction of the corresponding 3-keto esters or 3-keto amides in the presence of a catalytic amount of MnCl2.
In the presence of titanium tetrachloride, the borane/tetrahydrofuran complex can reduce 2-methyl-3-oxoamides into the corresponding syn-aminols in good yields and high diastereoselectivity. The use of borane/dimethyl sulfide instead of BH3/THF allows a partial reduction to syn-beta -hydroxyamides. (C) 2001 Elsevier Science Ltd. All rights reserved.
Highly Diastereoselective Synthesis of β-Hydroxy Amides from β-Keto Amides
β-Hydroxy amides with stereodefined geometry represent an important unit present in various natural products. The diastereoselective preparation of amides carrying a secondary or tertiary alcohol in β-position is described here.
Stereoselective reduction of 2-methyl-3-oxo esters (or amides) with sodium borohydride catalyzed by manganese(II) chloride or tetrabutylammonium borohydride. A practical preparation of erythro and threo-3-hydroxy-2-methyl esters (or amides)
lpropionamides were prepared with high stereoselectivity by NaBH4reduction of the corresponding 2-methyl-3-oxo esters or 2-methyl-3-oxo amides in the presence of a catalytic amount of manganese(II) chloride. On the other hand, reduction of these substrates with n-Bu4NBH4 provided threo-isomers selectively. erythro-Selective reduction of 2-methyl-3-oxo amides with NaBH3CN in 1N HCl-MeOH is also described