Thierry Besson

Microwave acceleration of the Pechmann reaction on graphite/montmorillonite K10: application to the preparation of 4-substituted 7-aminocoumarins

Abstract Efficient synthesis of 7-aminocoumarins was performed via the Pechmann reaction by microwave irradiation of the reactants on solid support (graphite/montmorillonite K10). In this convenient new methodology, the strong thermal effect due to graphite/microwaves interaction is associated with the acidic catalyst role of the clay.

Microwave radiation can increase the rate of enzyme-catalysed reactions in organic media

Abstract Irradiating a hydrated lipase enzyme suspended in organic media using microwaves (2.45 GHz, 50°C) enhanced the reaction rate by 2–3 fold over classical heating and the apparent non-thermal effects observed were dependent on the hydration state of the enzyme in the organic medium.

Synthesis and in vitro antitumour evaluation of benzothiazole-2-carbonitrile derivatives

Novel benzothiazole derivatives have been synthesised via the corresponding imino-1,2,3-dithiazoles. The cytotoxicity of some of these polyheterocyclic compounds was studied. Our results show that 2-cyano derivatives exhibit a medium in vitro antitumour activity.

Microwave-assisted synthesis of galacto-oligosaccharides from lactose with immobilized β-galactosidase from Kluyveromyces lactis

Galacto-oligosaccharides (GOS) were synthesized from lactose by immobilized and free β-galactosidase from Kluyveromyces lactis (Lactozym 3000 L HP-G) using either focused microwave irradiation or conventional heating. Immobilization of the β-galactosidase on to Duolite A-568 increased the synthesis of GOS. GOS selectivity (GOS synthesis/lactose hydrolysis ratio) increased when the water activity of the media was reduced, notably with a high initial lactose concentration but also by using co-solvents in the media. The advantage of microwave heating on GOS formation was also examined. Addition of solvent and carrying out the reaction under microwave irradiation resulted an increase in the production of GOS. The selectivity for GOS synthesis can be increased by 217-fold under microwave irradiation, using immobilized β-glucosidase and with added co-solvents such as hexanol.

Microwave-assisted Niementowski reaction. Back to the roots

In a search to speed up an aspect of the drug discovery processes, the Niementowski synthesis of the 3H-quinazolin-4-one core was reinvestigated using microwave irradiation. The experimental methodology and microwave conditions described here are well established, allowing significant rate enhancements and good yields compared to conventional reaction conditions.

Novel series of 8H-quinazolino[4,3-b]quinazolin-8-ones via two Niementowski condensations

Efficient microwave-assisted multi-step synthesis of 8H-quinazolino[4,3-b]quinazolin-8-one was investigated. The synthesis involved two Niementowski condensations from anthranilic acids. Homogeneous or heterogeneous conditions were studied with the aim to develop convenient syntheses of the desired compounds.

Stability improvement of immobilized Candida antarctica lipase B in an organic medium under microwave radiation

The influence of microwave heating on the stability of immobilized Candida antarctica lipase B was studied at 100 degrees in an organic medium. The microwave radiation was carried out before enzymatic reaction (storage conditions) or during the enzymatic catalysis (use conditions). In both cases, enzymatic stability was higher under microwave heating than under conventional thermal heating, in strictly identical operating conditions. Furthermore, the gain of enzymatic stability under microwave heating appears to be higher in a more polar solvent, which interacts strongly with the microwave field. Our results suggest that microwave radiation has an effect, not related to temperature, on the process of enzymatic inactivation.

Multistep synthesis of thiazoloquinazolines under microwave irradiation in solution

Abstract Thiazolo[5,4- f ]quinazolines are synthesised in six or seven steps from 2-amino-5-nitrobenzonitrile. Both heterocyclic rings are fused onto the central benzene ring via imino-1,2,3-dithiazoles which are readily obtained from primary aromatic amines and 4,5-dichloro-1,2,3-dithiazolium chloride (Appel salt). Four of the steps were improved in yield or reaction time or both, compared to conventional heating, by microwave irradiation of solutions of the reactants in a focused open microwave oven.

Influence of microwave irradiation on enzymatic properties: applications in enzyme chemistry

Although microwave-assisted reactions are widely applied in various domains of organic chemistry, their use in the area of enzyme chemistry has been rather limited, due to the high temperatures associated with the microwave heating: Because current technology, allows a good control of reaction parameters, several examples of microwave-assisted enzyme chemistry have been reported, using stable and effective biocatalysts (modified enzymes). The purpose of this review is to highlight the applications and studies on the influence of microwave irradiation on enzymatic properties and their application in enzyme chemistry.

Antimicrobial evaluation of 3,1-benzoxazin-4-ones, 3,1-benzothiazin-4-ones, 4-alkoxyquinazolin-2-carbonitriles and N-arylimino-1,2,3-dithiazoles

Abstract Novel 3,1-benzoxazinones, 3,1-benzothiazinones and 4-alkoxyquinazolines have been synthesized via N -aryl-1,2,3-dithiazoles derivatives. The antibacterial and antifungal activity of these compounds were measured; the dithiazoles are significantly active against fungi.