Enzyme-catalyzed chemoselective transesterification reactions on hydroxymethylated phenolic compounds

The chemoselective capabilities of porcine pancreatic lipase (PPL) in tetrahydrofuran and Candida rugosa lipase (CRL) in diisopropyl ether have been investigated for selective acetylation and deacetylation of hydroxymethylated phenols and hydroxyaryl alkyl ketones and their peracetylated derivatives. Both PPL and CRL exhibited exclusive selectivity for the acetylation of alcoholic hydroxyl group over the phenolic hydroxyl group(s) of the hydroxymethylated phenols 1-5 and aryl alkyl ketones 6-9, and for the deacetylation of ester group involving the phenolic hydroxyl group over the ester group involving alcoholic hydroxyl of the peracetates 19-24. The preliminary results indicate that this strategy of chemoselective acetylation can also be used in the enantiomeric resolution of racemic ketones 6-9. Single crystal X-ray diffraction studies have confirmed the structures of compounds 4, 15, and 17. (C) 1999 Academic Press.