Alkaloids from Croton species. Part III. The constitution of the proaporphines crotonosine, “homolinearisine”, base A, and the dihydroproaporphine linearisine
Abstract
A full report on the proaporphine alkaloids isolated from Croton linearis Jacq. is presented. Crotonosine is shown to have the structure (I; R = R1= H), base A is NO-dimethylcrotonosine and is identical with pronuciferine, “homolinearisine” is L-(–)-N-methylcrotonosine, and linearisine is 8,9-(or 11,12)-dihydro-L-(–)-N-methylcrotonosine.