Strategies for the Synthesis of Cyclic Ethers of Marine Natural Products

This account describes our studies on the synthesis of natural products that contain cyclic ethers in their structures. An overview of the main methodologies is presented and several total syntheses developed by the group are described. We also discuss new applications based on the use of Prins and Nicolas reactions as key steps in the preparation of oxygenated heterocyclic compounds. 1 Introduction 1.1 Natural Sources and Biogenesis 2 Carbon–Oxygen Bond-Formation Approach 2.1 Intramolecular Opening of Epoxy Alcohols and Related Bromo Cyclizations 2.2 Intramolecular Hetero-Michael Reaction of Alkoxy γ-Benzoyloxy α,β-Unsaturated Esters 2.3 Intramolecular Nicholas Reaction 3 Ring-Closing Metathesis of Unsaturated Linear Ethers 4 Prins Cyclization Promoted by Iron(III) salts 4.1 General Strategy 4.2 Cyclization Using Alkynols and the Formation of Vinyl ­Halides 4.3 The Use of Trimethylsilyl and Electron-Withdrawing Substituents in the Synthesis of 2,6-Disubstituted Tetrahydropyrans 4.4 Catalytic Prins Cyclization 4.5 Synthesis of Oxepanes 5 Summary