Michel Baboulene

Optimization of the enzymatic synthesis of amino acid esters. Reaction in polyphasic medium

Abstract N-acetyl-L-Tyrosine Ethyl Ester (ATEE) was synthesized from N-acetyl- l -Tyrosine and ethanol, with immobilized chymotrypsin as catalyst. For this purpose, a biphasic liquid reaction mixture consisting of an organic chloroform phase and an aqueous phase was used. This system allows the shift of the reaction equilibrium towards ATEE synthesis by achieving continuous ATEE extraction in the organic phase. Synthesis rates of up to 90% were obtained by optimizing the reaction conditions and controlling the pH of the aqueous phase.

Regioselective bromohydroxylation of alkenes catalyzed by chloroperoxidase: Advantages of the immobilization of enzyme on talc

Abstract The bromohydroxylation of alkenes catalyzed by chloroperoxidase (CPO) from the mould Caldariomyces fumago adsorbed on different types of talc or in reverse micelles was compared to that of the same reaction catalyzed by the free enzyme in buffer. High reactivity was observed in all media, but the reaction was optimized with an enzyme-talc combination that produced the halohydrin with no oxidative by-products in a Markovnikov-type regioselective addition. The reaction was facilitated by the use of this solid and a recyclable biocatalyst, which gave rise to the halohydrin in a quantitative yield. The protective influence of the talc (hydrophilic or hydrophobic) with respect to hydrogen peroxide enabled use of large amounts of oxidizing agent and substrate, opening perspectives for CPO in the synthesis of fine chemicals.

An Improved Greener Esterification of Fatty Alcohols Using a Renewable Acid–Ionic Liquid Couple as Catalyst–Solvent

Abstract We have developed a simple and efficient method for the esterification of various organic acids with C4–C18 alcohols using the 1‐octyl‐3‐methylimidazolium tetrafluoroborate–para‐toluenesulphonic acid (OMIM/BF4–PTSA) couple, without organic solvent, either by classic heating or by microwave irradiation. The utilisation of the OMIM/BF4–PTSA couple presents considerable advantages: high yield, low temperature, short reaction time, isolation of the ester by simple decantation, easy reuse of the catalyst couple.

Ionic liquids as catalytic “green” reactants and solvents for nucleophilic conversion of fatty alcohols to alkyl halides

We show that ionic liquids such as 1-octyl-3-methylimidazolium bromide or iodide (OMIM/X) make excellent reagents and solvents for the transformation of fatty alcohols into fatty halides in the presence of paratoluene sulfonic acid (PTSA). The conversion used either direct or microwave heating with excellent yields. The ionic liquid was successfully regenerated and reused.

Noncovalent immobilization of chloroperoxidase onto talc: Catalytic properties of a new biocatalyst

Abstract The noncovalent adsorption of chloroperoxidase (CPO) from the mold Caldariomyces fumago onto a talc, a mineral support that is available in various forms in industrial quantities and low cost, was investigated at two different values of pH (3.0 and 6.0). pH was found to affect both adsorption and enzymatic activity owing to the isoelectric point of CPO (pI ≈ 4) and the chemical characteristics of the absorbing surface of the talc tested. The hydrophobic and chemically neutral talc, type 15M00, favored adsorption (up to 8 mg CPO-g −1 talc); however, it led to strong inhibition of enzymatic activity on adsorption at pH 3, although activity was conserved (≈61% for halogenation and up to 72% for oxidation) by performing the adsorption at pH 6. In contrast, the hydrophilic and slightly acidic, calcined talc, type CLST, was less favorable to adsorption (≤2.5 mg CPO-g −1 talc); however, the CLST-CPO combination had excellent enzymatic activity (80–126%) irrespective of the pH of adsorption and without modification of the pH optimum of the enzyme. The results were accounted for in terms of the interactions between CPO and the talc as a function of the adsorption pH. Adsorption onto talc may thus lead to an improvement in reaction selectivity of CPO particularly in the competing halohydroxylation-oxidation reactions, thereby widening the potential industrial applications of this enzyme.

New Preparation of Aminoboronic Acids

Abstract A new preparation of aminoboronic acids, starting from N-trimethylsilyl derivatives of olefinic amines and utilizing the hydroboration reaction, is described as a “one pot” reaction.

Improved synthesis of azaheteroarylboronic acids using tris-trimethylsilylborate under mild conditions

Abstract A new family of azaheteroarylboronic acids was synthesized with good yields (70% to 75%). The proposed strategy utilizes an improved transmetalation reaction from Grignard azine reagents and tris-trimethylsilylborate, little used until now.

Protection of primary and secondary amines in the hydroboration reaction

Abstract Trimethylsilyl groups are efficient to protect the NH bonds of olefinic amines in the hydroboration reaction with BMS; deprotection is easily run with methanol and affords aminoorganoboranes which can be used without any oxydation.

Hydroboration d'amines insaturees—IV : Hydroboration-alkylation de propargylamines par des dialkylboranes mixtes

Resume Hydroboration-alkylation of substituted or unsubstituted propargylamines with thexylalkylboranes rapidly gives good yields of ethylenic amines. A tendency towards rearranged products depends on the basicity of the starting acetylenic amines. Comparatively to corresponding alkynes, acetylenic amines are characterized—by anomalous regioselectivity of the hydroboration, and—by anomalous migratory aptitudes of thexyl and alkyl groups, depending on the amine basicity and modified by addition of trimethylamine oxide.

Hydroboration d'amines insaturees—II: Régio et stéréosélectivité de l'hydroboration-alkylation d'amines acétyléniques

Abstract The hydroboration reaction of acetylenic amines R 1 R 2 NCH(R 3 )CCR 4 was studied. We report the first results of a study of the reactivity of dialkylborane R 2 BH towards these amines which allow us to propose a new method for the synthesis of differently substituted β-ethylenic amines. The regioselectivity and the stereoselectivity of this reaction are examined and allow us to set out the possibility of a trans hydroboration.