A novel green route for the synthesis of N-phenylacetamides, benzimidazoles and acridinediones using Candida parapsilosis ATCC 7330

Abstract

Biocatalytic preparation of various substituted N-phenylacetamides was carried out for the first time using whole cells of Candida parapsilosis ATCC 7330 under mild reaction conditions with excellent conversions (up to 93%) and good yields (up to 81%). Arylamine N-acetyltransferase (NAT) from whole cells of Candida parapsilosis ATCC 7330 is implicated in the N-acylation which is known to transfer the acetyl group from acetyl CoA (coenzyme A) to aromatic amines. Mechanistic investigation carried out using deuterated ethanol to find the source of acetyl CoA revealed that the reaction proceeds through the formation of acetaldehyde in situ, which is a potential source for the acetyl group of cytoplasmic acetyl CoA. Furthermore, experiments on regioselectivity, carried out with 2-phenylenediamine (2-PDA) resulted in a cyclised product 2-methyl benzimidazole (conversion 99%). The biocatalyst also mediates the cyclization of 3-(phenylamino)cyclohex-2-enones in the presence of the in situ generated acetaldehyde to form acridine-1,8-diones (conversion up to 70%), which is a green process reported here for the first time.