Plasmepsin inhibitory activity and structure-guided optimization of a potent hydroxyethylamine-based antimalarial hit.

Antimalarial hit 1 SR (TCMDC-134674) identified in a GlaxoSmithKline cell based screening campaign was evaluated for inhibitory activity against the digestive vacuole plasmepsins (Plm I, II, and IV). It was found to be a potent Plm IV inhibitor with no selectivity over Cathepsin D. A cocrystal structure of 1 SR bound to Plm II was solved, providing structural insight for the design of more potent and selective analogues.

[Cyclic analogs of substance P. III. Cyclo (6(sup)gamma----oligomethylenediamine----11) substance P(6-11)-hexapeptides].

Cyclic analogues of substance P of the formula cyclo-[Glu-Phe-Phe-Gly-Leu-Met-NH(CH2)nNH-], where n = 3-10, 12, and open-chain analogues (XVIIIa, b) H-Glu.(NHR)-Phe-Phe-Gly-Leu-Met-NHR, where R = -CH3, -CH2CH2CH3, were synthesized. By NMR spectroscopy it was found that cyclo-compounds with n = 3-8 have regularly arranged structures, stabilized by intramolecular hydrogen bonds.

[Cyclic analogs of substance P. I. Cyclo(11----epsilon 5)-[Lys5] substance P-(5-11)].

Two solution syntheses of cyclo(11----5 epsilon)-[Lys5]substance P-(5-11) (CLP) were carried out. The first synthesis involved the stepwise elongation of the peptide chain starting from glycine tert-butyl ester. At the stage of hexapeptide deprotection, the cleavage of Boc and But groups was accompanied by tert-butylation of the Met residue.

[Substance P. New cyclic analogs].

[Adpoc-Glu(N3)6, (Met-N3)11] substance P-(6-11)-peptide was reacted with diamines H2N(CH2) nNH2 (n = 3-10, 12) to give cyclopeptides. Subsequent careful cleavage of the Adpoc group leads to the formation of compounds of type cyclo-[H-Glu-Phe-Phe-Gly-Leu-Met-NH-(CH2) n-NH-] X HCl. The substances produce a specific two-phase myotropic effect in experiments on isolated guinea pig ileum.