1. Department of Chemistry, West University of Timisoara, Strada Pestalozzi 16, RO-1900 Timisoara, Romania, Department of Organic Chemistry, University of Agriculture Sciences, Calea Aradului 118, RO-1900 Timisoara, Romania, and Ecole des Mines d'Albi, Campus Jarlard, F 81013 Albi Cedex 09, France