Stable-isotope labeled metabolites of the phytohormone, indole-3-acetic acid

1,3-Dicyclohexylcarbodiimide-mediated condensation of [3a,4,5,6,7,7a-C-13(6)]indole-3-acetic acid with the bis(tert-butyl) esters of L-aspartic or L-glutamic acids, followed by removal of the ester groups by dilute alkali, afforded N-([3a,4,5.6,7,7a-C-13(6)]indol-3-ylacetyl)-L-aspartic and N-([3a,4,5,6,7,7a-C-13(8)]indol-3-ylacetyl)-L-glutamic acids, labeled forms of compounds involved in the regulation of plant growth and development. The corresponding conjugates of (R,S)-2,3-dihydro-2-oxoindole-3-acetic acid, which are likewise of physiological significance, were labeled with N-15 in the amino acid moieties and were synthesized via the N-hydroxysuccinimide ester.