Influence of the peptide chain length on the stability of double‐stranded β‐helical species of D , L ‐alternating oligovalines in chloroform solution

The type and distribution of the β‐helixes occurring in chloroform solutions of Boc‐(L‐Val‐D‐Val) 6 ‐OMe and Boc‐(L‐Val‐D‐Val) 8 ‐OMe have been studied by using 1 H‐nmr techniques. Right‐ and left‐handed ↑↓β 4.4 ‐helices and left‐handed β 5.6 ‐helices occur with the dodecapeptide. β 4.4 ‐Helices of opposite handedness occur also with the hexadecapeptide, but ↑↓β 5.6 ‐helices could not be detected with this oligomer. At equilibrium, at 25°C, the double helix of the dodecapeptide is only moderately populated. These results indicate that increasing the chain length has a destabilizing effect on the ↑↓β 5.6 ‐helices of D , L ‐alternating oligovalines in chloroform solution.