Synthesis of compounds containing the isoprene unit; a stereospecific synthesis of β-ionilideneacetic acid and dehydro-β-ionilideneacetic acid, a key intermediate to abscisic acid

Abstract

A stereospecific synthesis of dehydro-β-ionilideneacetic acid (7b), a key intermediate to the abscisic acid (1), starting from the dianion of 3-methylbut-2-enoic acid (2) and safranal (3b) is described. Dehydrobromination to the bromoaldehyde (11) was achieved by treatment of (10) with the resin Amberlyst A 26 in the F^– form. In the same way, treatment of β-cyclocitraf (3a) with (2) gives β-ionilideneacetic acid (7a) in good yield.