benzyl (2R,3S)-2-methyl-3-hydroxybutanoate + NADP(+) = benzyl 2-methyl-3-oxobutanoate + NADPH + H(+)
benzyl (2r,3s)-2-methyl-3-hydroxybutanoate + nadp(+) = benzyl 2-methyl-3-oxobutanoate + nadph + h(+)