Photoaffinity-labeled Auxins

Two light-sensitive analogs of 2,4-dichlorophenoxyacetic acid, namely 4-azido-2-chlorophenoxyacetic acid and 3-azido-5-chlorophenoxyacetic acid, have been synthesized for use as auxin photoaffinity labels. The preparation and biological activity of the compounds are described. Both contain the photolabile azido group; the 2,4-substituted compound shows auxin activity and the 3,5-substituted compound does not. These photoaffinity analogs of 2,4-dichlorophenoxyacetic acid may be useful in the identification of the auxin receptor molecules in plant cells and eventually of the receptor sites within these molecules.