Tripodal peptides with chiral conformations stabilized by interstrand hydrogen bonds

Article abstract of DOI:10.1021/ja00043a007

C₃ symmetric trispeptides are described that form chiral conformations and are therefore eminently suited to provide a new family of chiral receptor molecules when extended by appropriate binding sites. These trispeptides are composed of C₃ symmetric trisamines as anchors and three symmetrically extending chiral amino acid residues. Their conformations in apolar solvents fall into two main classes. One is comprised of propeller-like conformations of preferred chiral sense that are stabilized by a belt of intramolecular H-bonds (hydrogen bonds) between adjacent strands. The other class has two of its strands connected by two H-bonds to form a 10-membered ring, while the third strand may hydrogen-bond to one of the other two. The effect of the anchors and amino acids on the relative stability of the H-bonded, chiral conformations has been established by a combination of spectroscopic and theoretical means. Trispeptides derived from more lipophilic α-amino acids show a higher population of the chiral conformations. Moreover, trispeptides that are based on tris(2-aminoethyl)amine (TREN) as anchor form stronger H-bonds than those relying on 1,3,5-tris(aminomethyl)benzene (TRAM).