Synthesis of Briarane Diterpenoids: Biomimetic Transannular Oxa-6π electrocyclization Induced by a UVA/UVC Photoswitch

• DOI: 10.1021/acs.orglett.6b03689
• Publication Date: 2017-01-12T17:51:16Z
• Authors: Andrew J. Hall; Stéphane P. Roche; Lyndon M. West
• Keywords: Lactones; Molecular Structure; Biomimetics; Cyclization; Ultraviolet Rays; Diterpenes; 01 natural sciences; Ethers; 0104 chemical sciences

A biomimetic synthesis of briareolate ester B (3) from briareolate ester L (1) via the intermediate briareolate ester G (2) has been achieved through a unique transannular oxa-6π electrocyclization induced by UVA light. UVC irradiation of 3 triggered a rapid retro-6π electrocyclization to establish an unprecedented photochromic switch. In the ground state, reaction of 1 led to the formation of a polycyclic γ-spiroketal γ-lactone 5, architecturally related to the ether-bridged cembranoids of the cladiellin class.