The chemical synthesis of 1-O-(indol-3′-ylacetyl)-β- d -glucopyranose. The higher activity of the glucoside in comparison with exogenous indol-3-ylacetic acid in plant-section elongation tests

The synthesis of 1-O-(indol-3'-ylacetyl)-beta-d-glucopyranose via the fully benzylated 1-O-(indol-3'-ylacetyl)-d-glucopyranose is described. The configuration of the free ester glucoside was confirmed by complete hydrolysis with beta-glucosidase and by the n.m.r. spectrum of the tetra-acetyl derivative. 2. The growth-promoting effect of the glucoside in Avena coleoptile- and pea stem-section tests distinctly exceeds the responses stimulated by equimolar amounts of indol-3-ylacetic acid or equimolar mixtures of indol-3-ylacetic acid and glucose at all concentrations investigated. Time-sequence experiments revealed that the sections stimulated by the glucoside exhibit a markedly greater rate of elongation than those promoted by indol-3-ylacetic acid. 3. 1-O-(Indol-3'-ylacetyl)-beta-d-glucopyranose was isolated from intact Avena coleoptiles. 4. According to the results, the conjugation of indol-3-ylacetic acid with glucose could not be considered merely as a detoxication mechanism for indol-3-ylacetic acid in plant tissues.