THIONATION OF SEGETALIN-A AND SEGETALIN-B, CYCLIC-PEPTIDES WITH ESTROGEN-LIKE ACTIVITY FROM SEEDS OF VACCARIA SEGETALIS

Thionation of estrogen-like active cyclic peptides, segetalins A (1) a nd B (2), with Lawesson's reagent provided each two thiosegetalins; th iosegetalin Al [Gly-1-psi(CS-NH)-Val-2; Trp-5-psi(CS-NH)-Ala-6]segetal in A, thiosegetalin A2 [Gly-1-psi(CS-NH)-Val-2; Ala-6-psi(CS-NH)-Gly-1 ]segetalin A, thiosegetalin B1 [Gly-1-psi(CS-NH)-Val-2; Ala-3-psi(CS-N H)-Trp-4]segetalin B, and thiosegetalin B2 [Gly-1-psi(CS-NH)-Val-2; Tr p-4-psi(CS-NH)-Ala-1]segetalin B. Thiosegetalin A2 only showed estroge n-like activity against ovariectomized rats. On the basis of their con formations analysed by NMR experiments, the backbone conformation was considered to play an important role in estrogen-like activity for seg etalins. (C) 1997 Elsevier Science Ltd.