Synthesis of freelingyne, an acetylenic sesquiterpene from Eremophila freelingii

Abstract

The application of the 2-methyl-4-triphenylphosphoranylidenebut-2-en-4-olide (6) in the total synthesis of natural freelingyne (19) and its geometrical isomer (1)[(4Z)- and (4E)-isomers of (6E)-9-(3-furyl)-2,6-dimethylnona-2,4,6-trien-8-yn-4-olide] is described. A coupling reaction between 3-furylcopper (16) and the iodoacetylene (15) provided the (3-furyl)-enyne (17b), hydrolysis of which, followed by oxidation, led to the aldehyde (5). Condensation between the ylide (6) and the aldehyde (5) produced a mixture of isomers of free-lingyne, one of which, assigned the structure (19) from X-ray measurements, was identical with the naturally derived material.