The reaction yield of the esterification of (R,S) ibuprofen with n-propanol, catalyzed by physically adsorbed Candida antarctica lipase B on anionic resin, is improved by the addition of benzo-[18]-crown-6 or meso-tetraphenylporphyrin but reduced by the presence of metal-porphyrins. The interaction of benzo-[18]-crown-6 or meso-tetraphenyl porphyrin with the lid of pure lipase B on C. antarctica, would produce the activation of the lipase increasing the reaction rate but not the enantioselectivity.