CONFORMATIONAL PREFERENCE FOR SEGETALIN-G AND SEGETALIN-H, CYCLIC-PEPTIDES WITH ESTROGEN-LIKE ACTIVITY FROM SEEDS OF VACCARIA-SEGETALIS

Three-dimensional structures in DMSO-d(6) of segetalins G [cyclo (-Gly -Val-Lys-Tyr-Ala-)] and H [cyclo (-Gly-Tyr-Arg-Phe-Ser-)], cyclic pent apeptides from seeds of Vaccaria segetalis, showing estrogen-like acti vity, were determined by the distance geometry calculation and restrai ned energy minimization from NMR data. The backbone structure of seget alin G contains one beta- turn: a beta II-like turn at Tyr(4)-Ala(5), and that of segetalin H one beta-turn: a beta II' turn at Gly(1)-Tyr(2 ) and one gamma-turn at Arg(3)-Phe(4)-Ser(5) sequence. The results of distance comparison analysis proposed a pharmacophore model of estroge n-like cyclic peptides, segetalins. (C) 1997 Elsevier Science Ltd.