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)

Article abstract of DOI:10.1016/S0040-4020(01)81804-4

erythro-3-Hydroxy-2-methylpropionates or erythro-3-hydroxy-2-methylpropionamides were prepared with high stereoselectivity by NaBH₄ reduction 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.