The reduction with isolated enzymes have also been studied and the advantage of this protocol is that it reduces the effect of other interfering enzymes which are present in a cell but the weak point is that the stability of isolated enzymes and use of expensive specific co-factor such as NADP (Nicotinamide adenine dinucleotide phosphate) (Scheme 11).

Scheme 11

For an example, the following symmetrical diketone could be reduced by enzyme horse liver alcohol dehydrogenase (HLADH) to give the corresponding chiral alcohol with high enantioselectivity (Scheme 12).

Scheme 12