α‑Oxo-γ-Butyrolactam, N‑Containing Pronucleophile in Organocatalytic One-Pot Assembly of Butyrolactam-Fused Indoloquinolizidines

The ambident reactivity of α-oxo-γ-butyrolactam has been explored in an organocatalytic one-pot Michael/Pictet–Spengler sequence. The synthetically interesting and medicinally important pentacyclic butyrolactam-fused indoloquinolizidines can be efficiently constructed in a highly stereocontrolled manner. Importantly, the chemistry described herein provides a general catalytic method for the enantioselective synthesis of butyrolactam-incorporated chemical entities.