OZONOLYSIS OF AZOLES AND ITS APPLICATION TO THE ORGANIC-SYNTHESIS

Our recent studies concerning to the ozonolysis of various azoles are reviewed in this paper. While azoles are remarkably stable under the-a cidic, basic, oxidative and/or reductive conditions due to their aroma tic characters, azoles are specifically labile toward ozone. These cha racters of azoles satisfy the requirement for the protection-deprotect ion of the functional group. Pyrroles are easily prepared from primary amines, and the side chains of these pyrroles are functionalized by b ase catalyzed alkylation, hydride reduction, and aminolysis. By the oz onolysis, pyrroles are converted into the corresponding amides. Throug h this series of the reactions, pyrroles are demonstrated to be useful as the protecting group of amino functions for the synthesis of alpha -aminoalcohols, alpha-aminoketones, alpha-aminoaldehydes, and some pep tides. Oxazole ring is also useful as the protecting group of carboxyl group in peptide synthesis, and the ring opening is carried out by oz onolysis. In this deprotection, oxazoles are converted into acid anhyd rides, which are the reactive forms of carboxyl. group and are directl y available for the further peptide formation. This is the most remark able example that the protecting group takes a role of the precursor o f the active form of the functional group.