Studies on the Regioselectivity of the Cyclization of Tryptophanol-Derived Oxazolopiperidone Lactams

Abstract

Cyclization of the lactam carbonyl on the indole ring in tryptophanol-derived oxazolopiperidone lactams 2 and 6, under the classical POCl3-promoted Bischler-Napieralski conditions and under neutral conditions via the corresponding thiolactam, has been studied. Whereas tricyclic lactam 2 only leads to products coming from an α-amidoalkylation process, bicyclic lactam 6 undergoes cyclization on the lactam carbonyl, leading to the expected indolo[2,3-a]quinolizidine derivatives.