MethylN-acetyl phenylserinates (1,2), methylN-acetyl nitrophenylserinates (3,4), and methylN-benzoyl threoninates (5,6) were resolved conveniently into the enantiomers with high optical purities by enzymatic hydrolysis in the presence of α-chymotrypsin, subtilisin, or bromelain. Thethreoanderythroforms were treated separately and the latter form was usually more reactive. Chymotrypsin and subtilisin are highly specific for the enantiomer having the same configuration on carbon-2 (S) as the natural standard amino acids. In contrast, bromelain shows the reverse specificity on phenylserine derivatives. This is a notable exception to the usualS-stereospecificity pattern of proteases.Keywords: enzymatic hydrolysis, resolution of amino acids.