Terminal effect of chiral residue on helical screw sense in achiral peptides

Structural and conformational properties of (Z)-?-(1-naphthyl)- dehydroalanine residue

“…This hydrogen-bonding manner should indicate that peptide 2 takes a 3 10 -helical conformation in solution. 24,33,34 As shown in Table V, the ROESY experiment in CDCl 3 showed marked cross peaks for neighboring NH proton pairs (N i H to N iϩ1 H: d NN ), meaning that peptide 2 forms a 3 10 -or ␣-helix. 45,46 On the other hand, cross peaks for C i ␣ H to N iϩ1 H (d ␣N ) were observed with moderate intensity, suggesting the presence of an extended conformation.…”

“…The program PEPCON, written by M. Sisido (private communication) for a conformational energy calculation 29 and graphics 32 of a given peptide, was modified to be applicable to ␤-aryldehyroalanine-containing peptides. [23][24][25][33][34][35][36] …”

A helical arrangement of ?-substituents of dehydropeptides: Synthesis and conformational study of sequential nona- and dodecapeptides possessing (Z)-?-(1-naphthyl)dehydroalanine residues

“…14 The program PEP-CON 30,31 for a conformational energy calculation and graphics of a given peptide was modified to be applicable to ␤-aryldehyroalanine-containing peptides. [32][33][34][35] The stepwise elongation 36,37 of the repeating unit -(Ala-⌬ Z Nap-Leu)-was used to find the stable conformations from all possible candidates. In the first step, energy minimization of the tripeptide, Ac-Ala-⌬ Z Nap-Leu-OMe (Ac ϭ acetyl), was carried out.…”

“…No such interactions were also observed in helical polypeptides possessing 1-naphthylalanines 65,66 or in 3 10 -helical sequential peptides possessing two or more ⌬ Z Phe residues. 10,33,34,37,53 The band of 228 nm should be assigned to the 1 B b band of 1-naphthyl group, because (poly)peptides possessing L-1-naphthylalanine residues has almost the same absorption band (225-230 nm). 65,66 Thus, the transition moment of 228 nm should be nearly located to the long axis of 1-naphthyl group.…”

Syntheses of organocatalysts with one-handed helix and their application to the kinetic resolution of second alcohol

“…As an achiral helical backbone, we used an oligopeptide composed of an amino isobutylic acid (Aib) and an a,b-dehydroxyphenyl alanine (DPhe) reported by Inai and coworkers [15]. Then, Boc-N-methyl-L-histidine 3, which has the catalytic activity, was attached at the terminal position of the achiral peptide 1 and 2 by DCC coupling to give peptides 4 and 5, respectively (Scheme 2).…”