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The zymogen alpha-chymotrypsinogen A is bound to mesoporous silica MCM-41 with a protein loading of 170 mg/g solid (MCM-Z) by a simple stirring in aqueous tris-HCl buffer (pH 7.2). The bound zymogen is then activated with trypsin to obtain alpha-chymotrypsin immobilized on MCM-41 (MCM-E.I) that displays an effective enzyme activity corresponding to 65 mg protein/g of solid support (3250 BTEE units/g). A direct immobilization of commercially available alpha-chymotrypsin (MCM-E.II) gives lower loading (1250 BTEE units/g). Protein content of the solid support after immobilization is confirmed by thermogravimetric analysis (TGA). The enzyme is tightly bound to the support and can be used over 100 recycles over 1 week in aqueous as well as reverse micellar media. The immobilized enzyme (MCM-E.I) has been used for resolution of N-acetyl-dl-amino acid esters and racemic trans-4-methoxy-3-phenylglycidic acid (PGA) methyl ester.

Michael additions were achieved quantitatively at room temperature with a broad spectrum of acceptors and donors, using a magnesium-lanthanum mixed oxide, a strong solid base. The best solvent for the reaction is dimethylformamide, but good yields were also obtained using toluene as solvent. The results obtained with magnesium-lanthanum are comparable to those reported for super bases. The catalyst can be separated from the reaction mixture and recycled five times without loss of activity with no other treatment.Keywords: basic catalysis; magnesium-lanthanum mixed oxide; Michael additions; recyclability; solvent effectsThe Michael addition is a reaction for C À C bond formation, involving the nucleophilic addition of a carbanion to a,b-unsaturated carbonyl compounds and is therefore base-catalysed. This reaction has found multiple industrial applications for the production of monomers, [1,2] corrosion inhibitors, [3] coatings, [4] and pharmaceuticals.[5] This reaction is industrially catalysed by liquid bases such as alkoxides, tertiary amines, non-ionic bases, [6,7] and superbases such as proazaphosphatranes. [8 -10] A variety of solid bases has also been described including barium hydroxide, [11] KF supported on g-Al 2 O 3 , [12] a-Al 2 O 3 , [13] phosphates, [14,15] on hydrotalcites, [16,17] amines anchored at surfaces, [18] and organic resins.[19]Most of these solids are weak bases which are effective only with a restricted class of electrophilic olefins such as a,b-unsaturated esters or conjugated enones. Recycling of the catalyst has seldom been demonstrated except for KF/natural phosphate which can be recycled after calcination at 973 K, which represents a severe limitation to its practical use. We report here the properties of Mg-La mixed oxides for different Michael additions. This catalyst has been recently used for the transesterification of diethyl carbonate by alcohols.[20] A comparison of substrates with different pK a allows us to estimate the possibilities of the catalyst and also gives an evaluation of the basic strength at the surface.[21] We used here donors with pK a values, measured in DMSO, [22] varying from 8 for thiocresol to 16.4 for diethyl malonate and 17.2 for nitromethane.The Mg-La mixed oxide was obtained by co-precipitation of Mg and La nitrates (0.386 and 0.129 mol, in water 0.5 L, for an atomic ratio Mg/La ¼ 3) at a constant pH ¼ 10 using a mixture of KOH (1 mol) and K 2 CO 3 (0.26 mol) in 0.52 L of distilled water. The samples (about 0.15 g) were activated at 923 K in an air flow, using a temperature ramp of 10 K/min. Just before use, they were reactivated at 773 K in air and not rehydrated.The chemical analyses of the solid catalyst give the composition: La: 39.8%; K: 5.4%; H 2 O: 37%. The Mg/ La ratio in the solid is then 4.26, compared to 3 in the solution, therefore the precipitation of La is not complete at pH 10. The powder XRD pattern of the uncalcined Mg-La mixed oxide contains diffraction lines of a hydrated lanthanum carbonate as well as magnesium and lanth...