Spiro-fused Pyrrolidine, Piperidine, and Oxindole Scaffolds from Lactams

Abstract

Expedient routes to three classes of novel spiro-fused pyrrolidine, piperidine, and indoline heterocycle scaffolds are described. These three-dimensional frameworks, which conform to the "rule of three", are suitably protected to allow for site-selective manipulation and functionalization. Different modes of substrate control were explored, which allow for good to excellent levels of diastereoselectivity and dispense with the need for additional chiral reagents or catalysts. The concepts developed were applied in short, formal syntheses of (±)-coerulescine and (±)-horsfiline.