Vanadium phytase

The most practical method that is used in the industrial synthesis of esomeprazole involves titanium-catalyzed oxidation with an alkyl hydroperoxide, and a dialkyltartrate as chiral ligand, in an organic solvent such as dichloromethane. A variety of oxidoreductases are known to catalyze the enantioselective oxidation of prochiral sulfides, usually as whole-cell biotransformations in aqueous media, but no simple metal complexes have been shown to be effective in water and the development of practical systems employing aqueous hydrogen peroxide as the primary oxidant is still an important challenge. In this context it is worth mentioning the enantioselective sulfoxidation of prochiral sulfoxides catalyzed by the semisynthetic peroxidase, vanadium-phytase, in an aqueous medium. 

F. van Rantwijk, and R. A. Sheldon, Enantioselective sulfoxidation mediated by vanadium-incorporated phytase a hydrolase acting as a peroxidase,... 

Since vanadium chloroperoxidase from Curvularia inaequalis is structurally closely related to acid phosphatases and transition metal oxoanions are potent inhibitors of the related phytases, (Figure 10.8) [35,36], Sheldon and coworkers investigated the peroxidase activity of phytase from Aspergillus ficuum in the presence of sodium orthovanadate Na3V04 [37-39]. Oxidation of thioanisole with H2O2 proceeded to produce the sulfoxide in quantitative yield in the presence of [VO4]-phytase. The reaction rate showed saturation kinetics with respect to the vanadate concentration, indicating a maximum rate of 120pmol/h (TOF = 11 min ) and a dissociation constant for the vanadate ion of 15.4 pM. 

Scheme 10.9 Enantioselective oxidation of thioanisole in the presence of H2O2 catalyzed by vanadium-incorporated phytase [37].

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