Identification of novel polyphenol oxidase inhibitors by enzymatic one-potsynthesis and deconvolution of combinatorial libraries

The feasibility of enzymatic synthesis of combinatorial libraries using mul tifunctional starting materials [i.e., 2,4-dihydroxy-N-(2-hydroxyethyl)benz amide, 1; 4-hydroxyphenethyl alcohol, 2; 3,5-dihydroxybenzyl alcohol, 3; an d 4-hydroxybenzyl alcohol, 4] with six vinyl esters, in a one-pot reaction, was investigated. Candida antarctica lipase was employed as a biocatalyst. The resulting 24-compound library contained all the expected species with no significant bias toward particular combinations of substrates. As expect ed, the library contained a substance(s) that showed significant inhibition of polyphenol oxidase, which was used as a model target. The deconvolution was accomplished via resynthesis of ten partial libraries, which were prep ared with either an equimolar mixture of the four alcohols and a single vin yl ester, or a single alcohol and equimolar mixture of the activated esters . Analysis of the inhibition pattern observed with these partial libraries suggested that 4-hydroxybenzyl benzoate (4e) should be the most potent inhi bitor. This conclusion was confirmed by the preparation and comparison of a ll 24 components of the initial library. Finally, it was shown that 4e was a competitive inhibitor of polyphenol oxidase, with a K-i of 40 muM. This v alue compared favorably with a K-i of 400 muM, which was determined for par ent phenol 4. (C) 2001 John Wiley & Sons, Inc.