Improved procedures for the degradation of gibberellic acid. The preparation of substrates for synthetic studies

Abstract

Gibberellic acid has been efficiently degraded to methyl 16-oxo-17-norgibberellate (8), to 16-oxo-17-norgibberellin A₁ methyl ester (9), and to (15), the 3α-epimer of (9). Both (9) and (15) were protected as their acetal derivatives (10) and (16) respectively and converted into the Δ² olefin ent-10β,13-dihydroxy-16,16-ethylenedioxy-17,20 dinorgibberell-2-ene-7,19-dioic acid 7-methyl ester 19,10-lactone (11).