PN-II-RU-TE-2014-4-0654

Unprecedented polyesters as coating for solid surfaces with application in medicine and nanotechnology

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Results for Objective 1

O1. Synthesis and characterization of new lactides, preparation of large quantities

 

During the first objective of the project, the main activities were focused on the synthesis of novel lactide molecules and their structural investigation. It is important to mention here that only the successful and most interesting results obtained were discussed and reported.

We synthesized a total number of 6 new lactides:

- 3 symmetrical lactides: diallyl 3,3'-(3,6-dioxo-1,4-dioxane-2,5-diyl)dipropanoate, 3,6-diallyl-1,4-dioxane-2,5-dione, 3,6-bis(4-iodophenyl)-1,4-dioxane-2,5-dione;

- 3 unsymmetrical lactides: N-(3-(3,6-dioxo-1,4-dioxan-2-yl)propyl)-2,2,2-trifluoroacetamide, 3-(prop-2-yn-1-yl)-1,4-dioxane-2,5-dione, 3,6-dioxo-1,4-dioxane-2-carboxylic acid);

 Their structure was confirmed by means of liquid NMR spectroscopy and mass spectrometry. In order to arrive to the desired lactides, in most of the cases, prior functionalization of the starting materials was necessary. Generally, amino acids were transformed in α-hydroxyacids which were further submitted either to symmetrical lactonization reaction by azeotropic water separation using a Dean-Stark apparatus, or to asymmetrical lactonization with bromoacetyl bromide under basic conditions. In some cases, multi-step reaction procedures were applied in order to attach specific functions (ally, propargyl, carboxyl or iodine) to the starting derivatives, before submitting them to lactonization reactions. In all cases, the lactides were isolated and purified in relatively small yields due to the fact that the solubility of the lactide is very high in the solvent where the cyclization took place and the reaction doesn’t stop at the lactide, but further drives to polymerization reaction. For some lactides we found good solution to increase the yield and to synthesize them in high quantities. Nevertheless, the lactides were used in ring opening polymerization initiated at the surface of magnetic nanoparticles.