Synthesis of thiazole, imidazole and oxazole containing amino acids for peptide backbone modification

Novel 5-ring heterocyclic building blocks are synthesized. These can be inc orporated into analogs of peptide antibiotics such as microcin B17, which i s a potent DNA-gyrase inhibitor that exhibits eight thiazole and oxazole mo ieties. In particular, the syntheses of imidazole and bisoxazole amino acid s as novel peptidomimetics are reported, this includes a new procedure for the oxidative conversion of the intermediates oxazoline, imidazoline as wel l as oxazole-oxazoline into the corresponding heteroaromatic compounds. A m ixture of 1,8-diazabicyclo-[5.4.0.]-undec-7-ene/carbon tetrachloride/aceton itrile and pyridine proved to be a very effective and mild agent. Copyright (C) 1999 European Peptide Society and John Wiley & Sons, Ltd.