An Expeditious Total Synthesis of Kalkitoxins: Determination of the Absolute Stereostructure of Natural Kalkitoxin.

Abstract Kalkitoxin, a potent neurotoxin isolated from the marine cyanobacteria Lyngbya majuscula , and its congeners ( 1 – 7 ) were efficiently synthesized utilizing Hruby's diastereoselective 1,4-addition and the Wipf's oxazoline-thiazoline conversion as key steps. These synthetic efforts in combination with spectral studies of natural kalkitoxin clearly determined the absolute stereostructure of kalkitoxin to be 7 .