Asymmetric Synthesis of 3,3′-Piperidinoyl Spirooxindoles and Discovery of Stereospecific Cycloadducts as Novel Hedgehog Pathway Modulators.

An enantioselective hetero-Diels–Alder reaction of alkylidene- oxindoles and 2-aza-3-silyloxy-1,3-butadienes, catalyzed by divalent transition metal complexes with N , N ′-dioxide ligands offered an efficient access to natural-product-based 3,3′-piperidinoyl spiroox-indole class of small molecules. exo -Cycloadducts formed via stereospecific cycloaddition with Z -olefin displayed potent activity in modulation of hedgehog pathway. [ABSTRACT FROM AUTHOR]