Exploring the stereochemical outcome (E/Z) of tandem metal-mediated reactions leading to 3-arylidene isobenzofuran-1-ones

ORGN 535

Kailey B. Voellinger, Brian F. Ohman, and Erin T. Pelkey, pelkey@hws.edu. Department of Chemistry, Hobart and William Smith Colleges, 300 Pulteney St., Geneva, NY 14456
Aristolactams alkaloids are highly oxygenated natural products found in the roots of certain plants.  Recently, aristolactams have been shown to possess anticancer properties, specifically towards the L1210 Leukemia cell line.  We envisioned a novel synthetic strategy to this class of natural products through a regio- and stereocontrolled, palladium-mediated cyclization of 2-ethynylbenzoic acids leading to isobenzofuran-1-ones as the key synthetic step.  We have successfully prepared the requisite alkynes via a Sonogashira cross-coupling reaction.  We next subjected our alkyne substrate to a palladium-mediated cascade reaction and obtained a stereochemical mixture (E/Z) of 3-arylidene isobenzofuran-1-one products.  In order to distinguish between the stereoisomers of the cascade reaction, we prepared the (Z)-stereoisomer by an independent synthesis.  Progress toward the completing the synthesis of the aristolactam alkaloids will also be reported.