Directly linked polyazoles:: Important moieties in natural products

Directly linked 1,3-azoles are found as substructures in important naturally Occurring products that have interesting biological activities as well as fascinating structures. Therefore, many research groups are working on their total syntheses. Although new approaches have been developed to prepare these targets, classical 13-azole formation methodologies are still being used for this purpose. This report provides an overview of polyazole-containing natural products and the different strategies for the synthesis of directly linked 1,3-azole moieties. 1 Introduction 2 Biogenesis 3 Synthesis of Polythiazole Fragments 3.1 Construction of the Thiazole Ring 3.1.1 Hantzsch Cyclization 3.1.2 Formation and Oxidation of Thiazoline 3.1.3 Miscellaneous 3.2 Cross-Coupling Reactions 4 Synthesis of Polyoxazole Fragments 4.1 Construction of the Oxazole Ring 4.1.1 Blomlein-Lewy Cyclization 4.1.2 Polyoxazoles from Amino Acids and Peptide Derivatives 4.1.2.1 Formation and Oxidation of Oxazoline 4.1.2.2 Cyclodehydration of P-Keto Amides 4.1.2.3 Polyoxazoles from Dehydropeptides 4.1.3 Rhodium(II)-Catalyzed Cycloaddition Reactions 4.1.4 Chan-Type Rearrangement 4.1.5 Polyoxazoles from alpha-Chloroglycinates 4.1.6 Polyoxazoles from N-Acylisoxazol-5-ones 4.1.7 Miscellaneous 4.2 Cross-Coupling Reactions 5 Svnthesis of Thiazole-Oxazole Fragments 5.1 Polyazoles from Amino Acids 5.2 Hantzsch Cyclization Followed by Azoline Formation 6 Overview