Cyclisation reactions. Part 5. Synthesis of pallescensin A, a furanoid sesquiterpene by cationic cyclisation of an ω-furyldiolefin and of the corresponding epoxy-olefin

Abstract

A biomimetic synthesis of pallescensin A (1), a furanoid sesquiterpene of natural origin is effected by concerted cyclisation of (6E)-9-(3-furyl)-2,6-dimethylnona-2,6-diene (2). The diene (2) has also been converted into a mono-epoxide (3) and the latter cyclised stereoselectively into 3-β-hydroxypallescensin A(4) which is subsequently deoxygenated to (±)-pallescensin A.