Glycosylation of 2,2'-indolylindolines

Constant stirring of indole-3-acetic acid methyl ester at room temperature results in the formation of 2,2'-indolyindoline (2) in 91% yield. Reaction of 2 with D-glucose in refluxing alcohol results in the formation of glycosylated derivatives. The presence of indole N-H resonance at delta 9.0-9.6 in the proton NMR of the glycosidic substrate indicates that glycosylation occurs on indoline.