Ultrasound irradiation promoted enzymatic transesterification of (R/S)-1-chloro-3-(1-naphthyloxy)-2-propanol.

(R)-1-Chloro-3-(1-naphthyloxy)-2-propanol, which is the key intermediate of (S)-propranolol, was successfully prepared via enantioselective transesterification catalyzed by lipase under ultrasound irradiation. Compared with conventional shaking, the enzyme activity and enantioselectivity were dramatically increased under ultrasound exposure. Effects of various reaction conditions on the synthetic activity of enzyme as well as enantioselectivity, including the type of enzyme, ultrasound power, solvent, acyl donor, temperature and substrate molar ratio, were investigated. Pseudomonas sp. lipase (PSL) showed an excellent catalytic performance under optimum conditions (enzyme activity: 78.3 ± 3.2 μmol·g⁻¹·min⁻¹, E value: 98 ± 6).