Inhibition of gibberellin 3β-hydroxylase by novel acylcyclohexanedione derivatives

The 2-acyl-5-carboxycyclohexane-1,3-diones are plant growth retardants which are believed to act by competing with the natural co-substrate, 2-oxoglutarate, at the active site of dioxygenases involved in the later stages of the biosynthesis of the gibberellin (GA) plant hormones. A number of 2-acyl-carboxycyclohexanediones and related compounds were synthesized and compared with pyridine dicarboxylic acids and hydroxybenzoic acids as inhibitors of a GA 3 beta-hydroxylase from Cucurbita maxima endosperm. The most effective inhibitors of this enzyme possessed a 1,3-dioxo-2-acylcyclohesane-5-carboxylic acid structure. The nature of the 2-acyl group had a relatively minor effect on the potency of enzyme inhibition in vitro. A related chloro-substituted compound was shown to be a potential affinity label for this GA hydroxylase. (C) 1998 Elsevier Science Ltd. All rights reserved.