%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