Convergent Synthesis of Anti-Cancer Alkaloid, Mirabazols, using a New Coupling Reagent

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Convergent synthesis of (-) Mirabazole C and B,tetra thiazoline/thiazole alkaloids isolated from Blue-Green Alga, have been achieved. The successive thiazoline rings of (-) mirabazole C and B were formed by a single step cyclization mediated by TiC14 treatment of a tripeptideamide intermediates. Convergent synthesis of the key intermediates derived from three 2-methylcysteine residues was first achieved using a newly developed coupling reagent, 2-chloro-1,3-dimethylimidazolidium hexafluorophosphate (CIP). The effectiveness of CIP for the coupling of alpha, alpha-dialkyl amino acids and the reaction pathway of the activation were clarified by the syntheses of model pepitdes containing alpha, alpha-dimethylamino acid.