307
ki at decreasing pH values and assigned it to the protonation of an acidic group possessing pK a of about 4.
Comparison of activation energy values for interaction of methyl thiolate with
oxirane and epoxides (24, 25) shows decreasing of reaction rate for epoxyacid
(Fig. 10.9) [47], while increasing of inhibition activity has been found experimentally for acid-substituted oxiranes [48]. According to [47] increased activity of epoxide (24) arises from interaction of carboxylate with imidazolium ion stabilizes the
noncovalent enzyme inhibitor complex and thus improves Ki.
ȿ
N-PRO
ȿ
N-PRO
∆
∆
Fig. 10.8 Geometrical arrangements of the transition states for interaction of oxirane with methyl
thiolete with explicit consideration of proton donors Н 2 О, NH 4
+
and HCO 2 H and corresponding
values of activation barriers calculated at COSMO/BLYP/6-311 + G(d) level of theory (the geometrical values obtained if only bulk effects of water as solvent are considered (given in parenthesis)) [46]
10 Quantum-Chemical Investigation of Epoxidic Compounds Transformation
ki at decreasing pH values and assigned it to the protonation of an acidic group possessing pK a of about 4.
Comparison of activation energy values for interaction of methyl thiolate with
oxirane and epoxides (24, 25) shows decreasing of reaction rate for epoxyacid
(Fig. 10.9) [47], while increasing of inhibition activity has been found experimentally for acid-substituted oxiranes [48]. According to [47] increased activity of epoxide (24) arises from interaction of carboxylate with imidazolium ion stabilizes the
noncovalent enzyme inhibitor complex and thus improves Ki.
ȿ
N-PRO
ȿ
N-PRO
∆
∆
Fig. 10.8 Geometrical arrangements of the transition states for interaction of oxirane with methyl
thiolete with explicit consideration of proton donors Н 2 О, NH 4
+
and HCO 2 H and corresponding
values of activation barriers calculated at COSMO/BLYP/6-311 + G(d) level of theory (the geometrical values obtained if only bulk effects of water as solvent are considered (given in parenthesis)) [46]
10 Quantum-Chemical Investigation of Epoxidic Compounds Transformation