Macrocyclic peptides, 8. Enantiomeric differentiations of various (R)‐ and (S)‐ ammonium and (R)‐ and (S)‐α‐amino acid ester salts by macrocyclic pseudopeptides

Abstract

Enantiomeric differentiations of various (R)-and (5')ammonium and (R)and (S)-a-amino acid ester salts bySUMMARY The interactions of the hydrobromides of (R)and (S)-alanine-N-methylanilides (1) with 24-, 27and 36-membered ring pseudopeptides (H-24, H-27 and H-36, respectively) derived from glycine and (2 S, 3'S)-4-methyl-2-(2'-0~0-3'-isobutyl-l'-piperazinyl)pentanoic acid were studied by means of ' H and I3C NMR measurements in CDCI, . It was found from these results that H-24 and H-27 distinguished ( R )and (S)-isomers of 1, while H-36 did not entirely. Moreover, the enantioface-differentiating abilities of these cyclic peptides were investigated by means of 'H NMR measurements in CDCI, using ( R )and (S)-1-phenylethylammonium and ( R )and (S)-p-methoxy-1-phenylethylammonium bromides as the substrates, showing that the enantioselectivity of H-36 is superior to those of H-24 and H-27. Also, the chiral recognition ability of H-24 for the hydrochlorides of (R)and (S)-alanine (Ala), -leucine (Leu), -methionhe (Met), -phenylalanine (Phe), -proline (Pro) and -valine (Val) methyl esters were examined by 'H and I3C NMR measurements in CDCI, . Among these hydrochlorides, HCI . Phe-OCH, was distinguished more effectively with H-24.

Conformations of cyclic octapeptides and the influence of heterocyclic ring constraints upon calcium binding †

“…Acetonitrile was used as the solvent to allow comparisons with previous determinations of calcium binding constants. 3,8,43 Broadening and shifting of signals in the NMR spectra of 1 and 2 in d 3 -acetonitrile were observed upon addition of calcium perchlorate. The binding constants for the respective 1 : 1 complexes were calculated from the change in the chemical shift of a number of protons (Fig.…”

“…[3][4][5][6][7] The influences of conformationally constraining groups incorporated in the macrocyclic ring have also been investigated. 3,4,[8][9][10][11][12] Typically, these constraints have taken the form of proline and/or N,NЈ-ethylene bridges.…”

Synthesis and solid-state spectroscopic investigation of some novel diorganotin(IV) complexes of tetraazamacrocyclic ligands

“…The amide functions of oxoazamacrocycles are generally reduced by B 2 H 6 /THF, providing versatile synthesis of cyclic amines. The cyclic amine-amide and cyclic peptides have many properties analogous to linear peptides and their metal complexes show functionalities resembling those of metalloproteins, thereby, making them of biological interest [15]. A large number of workers [16][17][18] are currently engaged in the synthesis of polyamide macrocycles and their coordination chemistry which is of particular interest in view of two potential donor atoms, i.e., amide nitrogen and amide oxygen [17,[19][20][21][22][23][24][25][26].…”

Selective BH3-Reduction of Amide Carbonyl Groups of Lithium Salts of N-t-Butoxycarbonyl (S)-O-Benzyl Tyrosyl (S)-Proline and N,N′-Ethylene-Bridged Dipeptides

“…Previously, the N,N'-ethylene-bridged dipeptides used as starting materials for the piperazine derivatives described here were utilized as the units of many kinds of macrocyclic pseudo-peptides 8-10 because these dipeptides can be obtained conveniently and economically in a large scale from commercial α-amino acids only in two steps 4,5 via acid-catalyzed cyclization. These macrocycles included several metal ions 8,10 and differentiated various enantiomers, 9,10 effectively. Therefore, the piperazine derivatives (basic amino acids) obtained in this work can be used as the units of new types of macrocycles whose functionalities are expected to be superior to those of previous [8][9][10] macrocycles.…”

“…These macrocycles included several metal ions 8,10 and differentiated various enantiomers, 9,10 effectively. Therefore, the piperazine derivatives (basic amino acids) obtained in this work can be used as the units of new types of macrocycles whose functionalities are expected to be superior to those of previous [8][9][10] macrocycles.…”