Highly stereoselective palladium catalysed cross-coupling approaches to the total synthesis of phthoxazolin A

The first total synthesis of racemic Phthoxazolin A 4 is described, involving a convergent series of palladium cross-coupling reactions to stereoselectively construct the ZZ,E-trienyl unit. The most important steps involve using vinylboronate pinacol ester 1 as a vinyl dianion equivalent, by employing a Heck coupling of a vinyl iodide 9 with the vinyl boronate 1, followed by a deboronation-iodination sequence with inversion of alkene stereochemistry to provide a new alkenyl iodide 6. Final Stille coupling of the vinyl iodide 6 with an oxazolyl alkenyl stannane 40 provided Phthoxazolin A 4. (C) 2000 Elsevier Science Ltd. All rights reserved.