Kinetic study of 2 - butanol O - acylation and sec - butylamine N - acylation catalyzed by 1 Candida antarctica lipase B . 2 3

13 The aim of this work was to study the differential behavior shown by Candida antarctica 14 lipase B during the O-acylation and N-acylation of monofunctional alcohols and 15 monofunctional amines. To achieve this, 2-butanol and sec-butylamine were used as model 16 molecules. Yields, kinetics and enantioselectivity were studied for both reactions. Although a 17 steady-state ordered ternary complex bi-bi mechanism was obtained for the O-acylation of 2-18 butanol, a ping-pong bi-bi mechanism was obtained for the N-acylation in case of low sec-19 butylamine concentrations. The values of apparent kinetics parameters were calculated: the 20 enantiomeric ratios (E) were evaluated and confirmed the preference of Candida antarctica 21 lipase B for the (R)-enantiomer, which was consistent with the literature. The 22 enantioselectivity was calculated for the alcohol (E ≈ 3.17) and for the amine (E ≈ 1.34). 23 Concerning the O-acylation, the yields were found to be very similar for both enantiomers R 24 and S. However, both initial rates and yields of the (R)-enantiomer N-acylation were higher 25 than those of the (S)-enantiomer. In the last part of our study, the chemoselectivity of Candida 26 antarctica lipase B was evaluated, showing that Candida antarctica lipase B was a 27 chemoselective enzyme that preferentially catalyzed the O-acylation to the detriment of the 28 N-acylation (C ≈ 92, for the selective acylation of (R)-enantiomers). These results provide 29 new insights for the synthesis of products issued from the selective acylation of 30 multifunctional substrates such as amino-alcohols.