An expeditious total synthesis of kalkitoxins: determination of the absolute stereostructure of natural kalkitoxin

Kalkitoxin, a potent neurotoxin isolated from the marine cyanobacteria Lyngbya majuscula, and its congeners () were efficiently synthesized utilizing Hrubyʹs diastereoselective 1,4-addition and the Wipfʹs 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 .