Table 2. Intramolecular and Intermolecular Hydrogen Bond Parameters from Various Conformations of P1–P3 Obtained in Crystals and DFT Studies (Mentioned in Parentheses)a.
| peptide | H-bonded ring size | H-bonds | D···A (Å) | H···A (Å) | ∠ D–H···A (°) |
|---|---|---|---|---|---|
| P1 (AH) | intermolecular | ||||
| N1–H1···O7a | 2.85 | 1.98 | 170.3 | ||
| N2–H2···O8a | 3.24 | 2.51 | 140.3 | ||
| N6–H6···O3b | 3.12 | 2.29 | 157.4 | ||
| N7–H7···O1W | 2.92 (3.0) | 2.14 (2.0) | 148.3 (167.3) | ||
| O6···O1W | 3.23 | ||||
| O4···O1W | (2.7) | (1.7) | (177.1) | ||
| intramolecular | |||||
| C10 | N3–H3···O0 | 3.03 (3.3) | 2.21 (2.3) | 155.7 (173.1) | |
| C10 | N4–H4···O1 | 3.03 (3.2) | 2.31 (2.2) | 138.6 (168.0) | |
| C10 | N5–H5···O2 | 3.01 (3.1) | 2.16 (2.1) | 162.1 (162.6) | |
| C10 | N8–H8···O5 | 3.21 (3.2) | 2.38 (2.2) | 157.1 (165.7) | |
| C10 | N9–H9···O6 | 3.24 (3.2) | 2.36 (2.2) | 173.3 (167.4) | |
| P1 (RHH) | C10 | N3–H3···O0 | (3.4) | (2.4) | (172.8) |
| C10 | N4–H4···O1 | (3.1) | (2.1) | (167.2) | |
| C10 | N5–H5···O2 | (3.1) | (2.1) | (163.9) | |
| C12 | N7–H7···O4 | (2.9) | (2.0) | (159.3) | |
| C10 | N8–H8···O5 | (3.3) | (2.3) | (166.7) | |
| C10 | N9–H9···O6 | (3.3) | (2.3) | (170.1) | |
| P2 (AH) | C10 | N3–H3···O0 | 2.94 (3.4) | 1.96 (2.4) | 173.9 (177.8) |
| C10 | N4–H4···O1 | 2.92 (3.1) | 1.96 (2.1) | 164.6 (169.8) | |
| C10 | N5–H5···O2 | 2.98 (3.3) | 2.02 (2.3) | 164.5 (165.1) | |
| O3···O1W | 4.05 (3.0) | 4.11 (2.1) | 79.7 (150.9) | ||
| O4···O1W | 2.96 (3.0) | 2.61 (2.1) | 101.2 (154.2) | ||
| N7···O1W | 2.99 (3.1) | 2.03 (2.1) | 165.0 (166.9) | ||
| C9 | N6–H6···O4 | 2.82 (3.0) | 1.85 (2.0) | 169.8 (171.9) | |
| C10 | N8–H8···O5 | 2.87 (3.2) | 1.92 (2.2) | 161.7 (166.2) | |
| C10 | N9–H9···O6 | 3.22 (3.5) | 2.28 (2.5) | 157.6 (168.2) | |
| P2 (LHH) | intermolecular | ||||
| N1–H1···O7c | 3.14 | 2.31 | 164.2 | ||
| N2– H2···O8c | 3.03 | 2.19 | 167.4 | ||
| intramolecular | |||||
| C10 | N4–H4···O1 | 3.13 (3.1) | 2.28 (2.1) | 168.9 (168.0) | |
| C10 | N5–H5···O2 | 3.43 (3.7) | 2.60 (2.7) | 163.3 (167.1) | |
| C12 | N6–H6···O3 | 2.88 (3.1) | 2.02 (2.1) | 173.0 (169.1) | |
| C12 | N7–H7···O4 | 2.94 (3.0) | 2.12 (2.0) | 158.4 (159.5) | |
| C10 | N8–H8···O5 | 2.99 (3.2) | 2.16 (2.2) | 160.7 (169.3) | |
| C10 | N9–H9···O6 | 3.09 (3.2) | 2.25 (2.2) | 165.1 (173.4) | |
| P2 (RHH) | intermolecular | ||||
| N1–H1···O2Wd | 3.24 | 2.37 | 169.6 | ||
| N2–H2···O1Wd | 2.97 | 2.21 | 144.5 | ||
| N3–H3···O0 | 3.16 (3.18) | 2.45 (2.23) | 139.0 (156.8) | ||
| intramolecular | |||||
| C13 | N4–H4···O0 | 2.94 (3.3) | 2.07 (2.3) | 171.6 (170.8) | |
| C13 | N5–H5···O1 | 3.00 (3.3) | 2.14 (2.3) | 162.4 (164.7) | |
| C12 | N6–H6···O3 | 2.92 (3.1) | 2.04 (2.1) | 173.6 (171.0) | |
| C12 | N7– H7···O4 | 2.90 (3.0) | 2.05 (2.1) | 162.0 (166.8) | |
| C10 | N8–H8···O5 | 3.05 (3.1) | 2.21 (2.2) | 159.9 (166.8) | |
| C10 | N9–H9···O6 | 3.35 (3.4) | 2.49 (2.4) | 166.4 (169.1) | |
| P3 (LHH) | intermolecular | ||||
| N1–H1···O8e | 2.82 | 1.97 | 160.9 | ||
| N2–H2···O1w | 3.28 | 2.40 | 171.9 | ||
| intramolecular | |||||
| C10 | N3–H3···O0 | 2.95 (3.3) | 2.09 (2.3) | 167.8 (172.9) | |
| C10 | N4– H4···O1 | 2.93 (3.1) | 2.14 (2.1) | 149.3 (168.1) | |
| C10 | N5– H5···O2 | 3.15 (3.3) | 2.39 (2.3) | 145.5 (162.8) | |
| C12 | N6–H6 ···O3 | 2.87 (3.1) | 2.01 (2.0) | 165.6 (171.9) | |
| C12 | N7–H7···O4 | 2.97 (3.2) | 2.16 (2.2) | 152.5 (156.3) | |
| C10 | N8–H8···O5 | 3.01 (3.2) | 2.21 (2.2) | 150.5 (168.6) | |
| C10 | N9–H9···O6 | 2.96 (3.2) | 2.10 (2.2) | 163.8 (167.6) | |
| P3 (RHH) | intermolecular | ||||
| N1–H1···O8f | 2.86 | 2.00 | 172.5 | ||
| N2–H2···O9f | 3.08 | 2.31 | 148.6 | ||
| intramolecular | |||||
| C10 | N3–H3···O0 | 3.05 (3.4) | 2.21 (2.4) | 164.8 (172.4) | |
| C10 | N4–H4···O1 | 2.90 (3.1) | 2.11 (2.1) | 151.8 (167.3) | |
| C10 | N5–H5···O2 | 3.19 (3.3) | 2.43 (2.4) | 147.2 (162.3) | |
| C12 | N6–H6···O3 | 2.91 (3.0) | 2.05 (2.0) | 170.9 (173.6) | |
| C12 | N7–H7···O4 | 3.19 (3.6) | 2.35 (2.7) | 164.2 (163.8) | |
| C10 | N8–H8···O5 | 3.00 (3.1) | 2.19 (2.2) | 155.9 (167.6) | |
| C10 | N9–H9···O6 | 3.11 (3.3) | 2.27 (2.3) | 164.2 (165.4) | |
a
AH: Ambidextrous helix, LHH: left-handed helix, and RHH: right-handed helix.