New Synthesis of (Methoxycarbonyl)-Indolizidin-7-one and -Quinolizidin-2-one: an Access to alpha-Amino Acids with Indolizidine and Quinolizidine Backbone

Two protected beta-amino acids containing the indolizidine or quinolizidine skeleton have been synthesised. The key step of the strategy is represented by the new synthesis of indolizidinone and quinolizidinone II carried out by the opening of the tricyclic 1,3-dipolar cycloaddition products 17 or 18 with DABCO. A new and more convenient method for the synthesis of the cyclic hydroxylamines 13 and 14 precursors of nitrones is also reported