Synthesis, Conformation, and Interactions with Small Molecules of Bis (Cyclic Dipeptides)

Abstract

SummavvBis (cyclic Jipeptides),cyclo(Ljs-Pro) cyclo(G1LPro) and S, S'-bis(cyclo(hemiCysPro)), were synthesized. These bis (cyclic dipeptides) very efficiently formed complexes with Ba2+ and Na+ owing to intramolecular cooperation of two cyclicdipeptide moieties, the bis-effect. Cyclo (Lis-Pro) cyclo (Glb-Pro) stacked sodium 8-anilino-1-naphthalensulfonate in aqueous solution. These properties of complexation were controlled by the nature of the bridge connecting two cyclic dipeptide moieties. The geometry of the complex between S, S'-bis (cyclo (hemiCys-Pro)) and metal ion was investigated with the help of circular dichroism, nuclear magnetic resonance, and Raman spectroscopy.Introduction. -A number of studies on the interactions between metal ions and synthetic cyclic peptides as ionophore models have been reported , hexa- [ 11, octa-[3], and decapeptides [3] form complexes with metal ions as a result of intramolecular cooperation of carbonyl groups. In cyclic dipeptides, the carbonyl groups cannot cooperate to form intramolecular complexes. However, cyclo (Sar), forms insoluble complexes with various metal ions in ethyl acetate [4]. The crystalline complex between cyclo (Sar), and LiC104 has a network structure,

Synthesis and conformation of the cyclic octapeptides cyclo(Phe‐Pro)4, cyclo(Leu‐Pro)4, and cyclo[Lys(Z)‐Pro]4

“…2 The cyclic pentapeptide cyclo(G1y-Pro-Gly-D-Ala-Pro) has been reported to form a 1:l complex with its three or even two carbonyl group^.^ The cyclic hexapeptide4 cyclo(G1y-Pro)s and the cyclic octapeptide? cyclo(Gly-Pro)4 have been shown to form a 1:l complex with the metal ion due to intramolecular cooperation of three and four carbonyl groups, respectively.…”