A novel expeditious entry into gibberellins. The total synthesis of (±)-GA 5

Abstract

A 16-step synthesis of (±)GA 5 ( 12 ), starting from m-methoxytienzoic acid, is described. Refunctionalization of the kinetic cycloadduct 4, obtained in 96 % yield from the Diels-Alder reaction of furan 3 in water in the presence of B-cyclodextrin, to ketone a, followed by Wittig olefination and selective quaternization to 11 , leads to the correctly functlonalized A-ring for eventual transformation to the title compound. A short and versatile entry into gibberellins: GA 5 ( 2 ) in 16 steps from m-methoxybenzoic acid via (1), the result of an intramolecular Diels-Alder reaction.