Total Synthesis of (±)-Clavicipitic Acids I and II

A b s t ~o c t -Ergot alkaloids, clavicipitic acids (3 and 4) were -synthesized respectively in racemic forms from 4-(3-0x0-1-buteny1)indole ( 5 ) by way of 6 and 7. Names of clavicipitic acids I and " I1 were proposed for 2 and 4. - ~lavicipitic acid, a metabolite of C t a v i c e p s strain SD '58l) or C t a v i c e p s f u s i f o r m i s 139/2/1~,~) was originally assumed to be a single compound with a tentative structure (; ) , ' ) but later on, its structure was revised to z , ~) and furthermore, the acid itself was shown to be actually a mixture of two diastereoisomers concerning the side chain in z .~) Final proof that clavihpitic acid was composed of two compounds having structures (3) and ( 4 ) was obtained by the X-ray crystallographic -study on a major component (3) ,4) exhibiting a biogenetically unique structure where the N(b)-function of tryptophan participated with the isoprene unit in forming a nitrogen-containing seven-membered ring.