A short synthesis of quinazolinocarboline alkaloids rutaecarpine, hortiacine, euxylophoricine A and euxylophoricine D from methyl N-(4-chloro-5H-1,2,3-dithiazol-5-ylidene)anthranilates

Reactions of methyl N-(4-chloro-5H-1,2,3-dithiazol-5-ylidene)anthranilates with tryptamine at room temperature produced 2-cyano-3-[2-(indol-3-yl)ethyl]-4(3H)-quinazolinones, which underwent cyclization on heating with TFAA/HCl(g) to afford quinazolinocarboline alkaloids rutaecarpine (1a), hortiacine (1b), euxylophoricine A (1c) and euxylophoricine D (1d) in excellent yields.