Vanadium,bis[N-[(1S)-1-(carboxy-κO)ethyl]-N-(hydroxy-κO)-l-alaninato(2-)-κN,κO

Abstract

[12705-99-6] C12H18N2O10V (MW 401.22) InChI = 1S/2C6H11NO5.V/c2*1-3(5(8)9)7(12)4(2)6(10)11;/h2*3-4,12H,1-2H3,(H,8,9)(H,10,11);/q;;+4/p-4/t2*3-,4-;/m00./s1 InChIKey = KJVYZWGBSKNRTK-SYJLBKBESA-J [amavadine acts as (electro)catalyst for the oxidation of some organic thiols (especially biological ones), displays peroxidase- and catalase-type activities, and acts as a catalyst precursor for peroxidative oxidations, peroxidative halogenation and carboxylation of alkanes and other hydrocarbons, for oxidations of thioanisole and alcohols, and for epoxidations of allylic alcohols] Alternate Names: bis[N-[(1S)-1-(carboxy-κO)ethyl]-N-(hydroxy-kO)-l-alaninato(3-)-kN,kO]vanadate(IV)(2-); amavadin; amavadine (name used in the text). Physical Data and Specific Features: pale blue solid; does not show melting point, but the blue color disappears at 170°C.1 Its molecular weight depends on the counterions (cations). It is a rare vanadium(IV) complex without an oxovanadium(IV) center that is stable in aqueous solutions. Amavadine containing vanadium in oxidation state 5 (presenting a red color) can be obtained in aqueous solutions by oxidation of its reduced form (which is blue) by hydrogen peroxide,2, 3 tert-butyl hydroperoxide (TBHP)2 or Ce(IV).4 Solubility: it is soluble in water, in some nonaqueous organic solvents such as DMSO, DMF, and acetone. It is also soluble by conversion to the complex with the oxidized metal (oxidation state 5).5 It is insoluble in many usual solvents, such as 1-propanol, 2-propanol, 1-butanol, diethyl ether, dichloromethane, nitrobenzene, THF, and toluene.2 Preparative and Purification Methods: in 1973,6 N-hydroxyimino-(2,2′)-dipropionic acid (proligand of natural amavadine) was synthesized by reacting N-hydroxylamine with 2-bromoproprionic acid at basic pH, followed by conversion to the acid form by cation exchange chromatography. In 1986,7 the same initial reaction was carried out at neutral pH and the proligand was precipitated by addition of zinc acetate solution at pH 4. The solid obtained was dissolved in acidic medium and its purification was achieved by cation exchange chromatography. These synthetic procedures lead to a mixture of isomers and the purification of the proligand is accomplished by chromatographic techniques.8 The 2:1 vanadium(IV) complex is obtained by addition of a vanadyl [oxovanadium(IV)] salt to the proligand in aqueous solution.8 In 2005,9 the first enantioselective synthesis of amavadine was achieved by addition of hydroxylamine to the triflate of R-lactic acid ester at low temperature (−80 °C). The final steps are similar to those mentioned above 7, 8 (overall yield about 43%).2 The synthesis of the V complex is analogous to that indicated formerly.7, 8 Precipitation of amavadine requires a divalent cation or two monovalent cations, enabling its crystallization, for example, Ca2+ or hydrated hydronium.2, 10 Handling, Storage, and Precautions: with vanadium in the oxidation state 4, either as a solid or in aqueous solution, amavadine is stable to air and moisture. Although it is considered nontoxic, thorough toxicity studies have not been reported.