Partial syntheses of 2-hydroxygibberellins; characterisation of two new gibberellins, A46 and A47

Abstract

A general method for the conversion of 3-hydroxygibberellins into the methyl esters of 2-hydroxygibberellins is described. Thus the structures of two new gibberellins have been established by partial syntheses of their methyl esters, namely, GA₄₆(12)(ent-2α-hydroxygibberell-16-ene-7,19,20-trioic acid) from seed of Echinocystis macrocarpa and GA₄₇(10)(ent-2β,3α,10-trihydroxy-20-norgibberell-16-ene-7,19-dioic acid 19,10-lactone) from cultures of Gibberella fujikuroi, strain GF-1a. The partial syntheses of the methyl esters of gibberellins A₄₀(9), A₃₄(4), and 3-epi-A₃₄(11) are described. The anomalous opening of the epoxide (23) is noted.