1. β-turns in proteins
2. Proline motifs in peptides and their biological processing
3. A Hypothetical Structural Role for Proline Residues in the Flanking Segments of Protein-Protein Interaction Sites
4. Spectral data for peptide 1: 1H NMR (CD2Cl2, 25 °C, 500 MHz) δ 0.911 (d, J = 6.4 Hz, 3H), 0.932 (d, J = 6.4 Hz, 3H), 1.5 – 1.7 (m, 2H), 1.695 (ddd, J = 13.1, 7.9 and 5.2 Hz, 1H), 1.998 (s, 3H), 2.5 – 2.7 (m, 2H), 2.941 (s, 3H), 2.950 (s, 3H), 3.8 – 3.9 (m, 2H), 3.932 (ABX, J = 17.2 and 4.2 Hz, 1H), 4.045 (ABX, J = 17.2 and 4.7 Hz, 1H), 4.1 – 4.2 (m, 2H), 4.405 (ddd, J = 9.2, 8.2 and 5.3 Hz, 1H), 4.864 (dd, J = 9.5 and 6.7 Hz, 1H), 6.323 (bs, 1H), 7.014 (bs, 1H), 7.647 (d, J = 7.9 Hz, 1H); HRMS (FAB, NBA) m/z 397.2329 [(M)+; calcd. for C18H31O5N5 397.2318]. Spectral data for peptide 2: 1H NMR (CD2Cl2, 25 °C, 500 MHz) δ 0.887 (d, J = 6.4 Hz, 3H), 0.923 (d, J = 6.4 Hz, 3H), 1.5 – 1.7 (m, 2H), 1.739 (ddd, J = 13.4, 8.9 and 4.6 Hz, 1H), 1.9 – 2.1 (m, 2H), 2.004 (s, 3H), 2.1 – 2.2 (m, 2H), 2.942 (s, 3H), 2.883 (s, 3H), 3.499 (ddd, J = 10.0, 7.5, 7.4 Hz, 1H), 3.658 (ddd, J = 10.0, 7.2, 4.9 Hz, 1H), 3.623 (ABX, J = 17.1 and 3.7 Hz, 1H), 4.023 (ABX, J = 17.3 and 3.8 Hz, 1H), 4.077 (ABX, J = 17.3 and 5.5 Hz, 1H), 4.431 (ABX, J = 17.1 and 5.8 Hz, 1H), 4.444 (dd, J = 7.6 and 4.6 Hz, 1H), 4.4 – 4.5 (m, 1H), 6.725 (d, J = 8.6 Hz, 1H), 6.852 (bs, 1H), 7.132 (bs, 1H); HRMS (FAB, NBA) m/z 412.2553 [(M + H)+; calcd. for C19H34O5N5 412.2570]. Spectral data for peptide 3: 1H NMR (CD2Cl2, 25 °C, 500 MHz) δ 0.906 (d, J = 6.4 Hz, 3H), 0.926 (d, J = 6.1 Hz, 3H), 1.4 – 1.7 (m, 8H), 2.002 (s, 3H), 2.1 – 2.3 (m, 1H), 2.948 (s, 6H), 3.144 (ddd, J = 13.0, 13.0 and 2.8 Hz, 1H), 3.6 – 3.7 (m, 1H), 3.949 (ABX, J = 17.3 and 4.0 Hz, 1H), 4.020 (ABX, J = 17.3 and 4.3 Hz, 1H), 4.095 (d, J = 4.3 Hz, 2H), 4.4 – 4.5 (m, 1H), 5.1 – 5.2 (m, 1H), 6.350 (d, J = 8.2 Hz, 1H), 6.5 – 6.7 (m, 1H), 6.8 – 7.0 (m, 1H); HRMS (FAB, NBA) m/z 425.2646 [(M)+; calcd. for C20H35O5N5 425.2628]
5. Conformation-directing effects of a single intramolecular amide-amide hydrogen bond: variable-temperature NMR and IR studies on a homologous diamide series