Reversal of regioselectivity in acetylation and deacetylation of aryl-naphthalene diols and diacetates by Amano lipase

Abstract

The regioselectivity of hydrolysis by Amano lipase (AK lipase) from Pseudomonas fluorescens of aryl naphthalene 4′,7-diacetates 1a–c prepared by the Garratt–Braverman cyclization of bis-propargyl sulfones, ethers and sulfonamides and acetylation of the corresponding diol 2a–c were studied. In all of these cases, the selectivity of both hydrolysis and acetylation were excellent. However, the pattern of selectivity was found to be dependent upon the nature of the fused heterocyclic ring, namely, dihydrothiophene dioxide (sulfolene), dihydrofuran (phthalan) or dihydro isoindole (indoline). For the isoindole system, the hydrolysis as well as the acetylation occurred at C-7, whereas for the furan derivative, the reaction took place entirely at C-4′. Interestingly, for dihydrothiophene dioxide, reversal of selectivity was observed in hydrolysis and acetylation. The results are in contrast with those reported for similar reactions on aryl naphthalene 2′,5-diacetates and corresponding diols. The observed results can be explained by molecular docking using PCL crystal structure, representing the Pseudomonas lipase family.