A single-step acylation of rutin and naringin, catalyzed by immobilized Candida antarctica lipase B in 2-methyl-2- butanol, occurred preferentially on the primary hydroxyl group. Using palmitic methyl ester as acyl donor, the acylation rate of naringin was 10-fold higher than that of rutin. Under optimal conditions, i.e. a molar ratio acyl donor/naringin of 7: 1 and 200 mbar, 92% naringin was acylated.