%0 Journal Article %A Ema, Tadashi %A Jittani, Masahito %A Furuie, Kenji %A Utaka, Masanori %A Sakai, Takashi %D 2002 %T 5-[4-(1-Hydroxyethyl)phenyl]-10,15,20-triphenylporphyrin as a Probe of the Transition-State Conformation in Hydrolase-Catalyzed Enantioselective Transesterifications %U https://acs.figshare.com/articles/journal_contribution/5-_4-_1-Hydroxyethyl_phenyl_-10_15_20-triphenylporphyrin_as_a_Probe_of_the_Transition-State_Conformation_in_Hydrolase-Catalyzed_Enantioselective_Transesterifications/3690576 %R 10.1021/jo0109063.s001 %2 https://acs.figshare.com/ndownloader/files/5780934 %K enantioselectivity %K zinc porphyrin 1 b %K ΔΔ %K mol %K CHIRAZYME %K transition state %K PS %K Pseudomonas %K conformation %K lipase %K Hydroxyethyl %K model %X 5-[4-(1-Hydroxyethyl)phenyl]-10,15,20-triphenylporphyrin (1a) and zinc porphyrin 1b were designed and synthesized to experimentally examine the validity of the transition-state model previously proposed for the lipase-catalyzed kinetic resolution of secondary alcohols. The lipases from Pseudomonas cepacia (lipase PS), Candida antarctica (CHIRAZYME L-2), Rhizomucor miehei (CHIRAZYME L-9), and Pseudomonas aeruginosa (lipase LIP) exhibited excellent enantioselectivity (E >100 at 30 °C). Subtilisin Carlsberg from Bacillus licheniformis (ChiroCLEC-BL) also showed high enantioselectivity for 1a (E = 140 at 30 °C), and the thermodynamic parameters were determined: ΔΔH = −6.8 ± 0.8 kcal mol-1, ΔΔS = −13 ± 3 cal mol-1 K-1. Lipases and subtilisin showed R- and S-preference for 1, respectively. The mechanisms underlying the experimental observations are explained in terms of the transition-state models. The large secondary alcohol 1 is a powerful tool for investigating the conformation of the transition state of the enzyme-catalyzed reactions. The fact that 1 was resolved with high enantioselectivity strongly suggests that the gauche conformation, but not the anti conformation, is taken in the transition state, in agreement with the transition-state models involving the stereoelectronic effect. %I ACS Publications