THIOPHENE INTERCONVERSIONS IN TAGETES-PATULA HAIRY-ROOT CULTURES

On the basis of feeding experiments with S-35-labelled intermediates, we present a modified biosynthetic pathway of the bithienyls in Tagete s. The monothiophene -(but-3-en-1-ynyl)-5-(penta-1,3-diynyl)-thiophene , which is present in small amounts in Tagetes hairy roots, is the pre cursor of all bithienyls that have been described for this species but not of alpha-terthienyl. The current hypothesis that 5-(3-buten-1-yny l)-2,2'-bithienyl originates from 5'-methyl-5-(3-buten-1-ynyl)-2,2'-bi thienyl after oxidative decarboxylation proved untrue. The latter comp ound is only converted into 5'-but-3-en-1-ynyl-[2,2']bithiophenyl-5-yl )-methyl acetate, probably via but-3-en-1-ynyl-[2,2']bithiophenyl-5-yl )-methanol. Substitution of the butenynyl side chain of 5-(3-buten-1-y nyl)-2-2'-bithienyl results in the formation of 5-(3,4-dihydroxy-1-but ynyl)-2,2'-bithienyl and 5-(4-hydroxy-1-butynyl)-2,2'-bithienyl, which are subsequently converted into respectively 5-(3,4-diacetoxy-1-butyn yl)-2,2'-bithienyl and 5-(4-acetoxy-1-butynyl)-2,2'-bithienyl. The end products of this biosynthetic pathway are all bithienyl-acetate ester s.