This invention provides a method of producing a large amount of an α-form or β-form of N-pyranosyl-tryptophan having a specified structure and preparing an antibody therefrom. The method comprises a step of allowing a pyranose compound to react with a 3-pyrazyl-indole compound in the presence of a first base to obtain a 1-pyranosyl-3-pyrazyl-indole compound, and a step of treating the 1-pyranosyl-3-pyrazyl-indole compound with an acid, treating the resultant with a hydrogenation catalyst, and further treating the resultant with a second base to synthesize N-pyranosyl-tryptophan, thereby producing an antibody therefrom.