I 1287 (OTTO) Indole, GR 99% Cas 120-72-9 - used in the preparation of gramine, which is obtained by Mannich reaction dimethylamine and formaldehyde. I 1287 (OTTO) Indole, GR 99% Cas 120-72-9 - used as a starting material for the preparation of oxindole and indole-3-carboxaldehyde. In Diels-Alder reaction, it acts as dienophile and reacts with 2-aminofuran to get strychnine.