Syntheses of Gibberellins A93 and A94, Natural Products Detected in Wheat Grain.

Extracts of mature wheat grain have been analysed by GC–MS and found to contain two new metabolites. The syntheses of the two new gibberellins, 1β-hydroxy-2β,3β-epoxyGA9 4 and 1β-hydroxy-2β,3β-epoxyGA20 5 from the fungal gibberellins, GA7 and GA3 are described. A range of protecting groups for the 7-carboxylic acid which can be removed under mild conditions, are compared. The allyl ester proved most valuable in the manipulation of these multifunctional molecules and it is removed with tetrakis(triphenylphosphine)palladium(0), triphenylphosphine and potassium isobutyrate. The structures of the new natural products in wheat were confirmed to be 4 and 5 by comparison with the GC–MS data from the synthetic samples and are assigned the trivial names GA94 and GA93 respectively.