UV-MALDI-TOF-MS analysis of a monodisperse polyamidoamine obtained by one-pot lipase-catalyzed regioselective aminolysis and Michael addition

M. K. FATEMA; L. N. MONSALVE; H. NONAMI; R. ERRA-BALSELLS; A. BALDESSARI

Osaka, Japón

Congreso; The 57th Annual Conference on Mass Spectrometry; 2009

The Mass Spectrometry Society of Japan

UV-MALDI-TOF-MS Analysis of a Monodisperse Polyamidoamine Obtained by One-pot Lipase-catalyzed Regioselective Aminolysis and Michael Addition (1Plant Biophysics/Biochem. Research Laboratory Faculty of Agriculture, Ehime University, Japan 2UMYMFOR, Departamento de Química Orgánica, Universidad de Buenos Aires, Ciudad Universitaria, Buenos Aires, Argentina 3CIHIDECAR, Departamento de Química Orgánica, Facultad de Ciencias Exactas, Universidad de Buenos Aires, Argentina) M. K. Fatema,1 Leandro N. Monsalve,2 Hiroshi Nonami,1 Rosa Erra-Balsells3 and Alicia Baldessari2 Short Abstract: The application of lipases in polymer synthesis is a well known fact. Polyesters and polyacrylamides are good examples of it. Lipases also show catalytic activity on Michael reactions. We have taken advantage of the double activity displayed by the lipase of Candida antarctica B (CAL B). We have performed the enzymatic synthesis of a biodegradable polyamidoamine from ethyl acrylate (1) and N-methyl-1,3-propanediamine (2) as starting materials.  The polymeric material was prepared by the incubation of a 0.012M solution of reactants in either hexane or diisopropyl ether (DIPE) with CAL B for 72 hours in an orbital shaker at 30°C. Several solvents, concentrations, enzyme:substrate ratios, enzymes from different sources and temperatures have been tested in order to achieve optimal reaction conditions. The polyamidoamine have been characterized by: 1H and 13C, COSY, HSQC and HMBC NMR, FT-IR and UV-MALDI-TOF-MS. NMR experiments showed that the structure of the polymer obtained by this procedure, turned out to be very regular. This fact indicates that the behaviour of the lipase in the enzymatic polymerization is highly regioselective; aminolysis occurred exclusively on the primary amino group in 2 while the secondary amino group in 2 was the nucleophile in the Michael addition. UV-MALDI-TOF-MS experiments let to determine the Mn and Mw of the product and several structures in both ending groups of the polymeric chain: amide or carboxylic acid in R1 and amine or ether in R2. This is the first report of the synthesis of a polyamidoamine catalyzed by a lipase, affording a monodisperse, regular product in a highly regioselective fashion. This reaction could not be achieved previously by following the traditional synthetic methods. Regarding the biomedical applications of the polyamidoamines, the green and mild reaction conditions and the ease of handling of the enzymatic catalyst are obvious advantages of the present method. Keywords: Polyamidoamine, Michael Addition, UV-MALDI –TOF MS.