Helical Foldamer Containing a Combination of Cyclopentane-1,2-diamine and 2,2-Dimethylmalonic Acid

We have developed new helical oligomers using a combination of (1<i>S</i>,2<i>S</i>)-cyclopentane-1,2-diamine [(<i>S</i>,<i>S</i>)-CPDA] and 2,2-dimethylmalonic acid (DMM) residues as building blocks. In solution, the preferred secondary structure of the (<i>S</i>,<i>S</i>) tetramer <b>6</b> was a right-handed (<i>P</i>) helix, and that of the (<i>R</i>,<i>R</i>) tetramer <i>ent</i>-<b>6</b> was a left-handed (<i>M</i>) helix. In the crystalline state, both <b>6</b> and the (<i>S</i>,<i>S</i>) pentamer <b>7</b> folded into (<i>P</i>) 11-helices, and <i>ent</i>-<b>6</b> folded into an (<i>M</i>) 11-helix with hydrogen bonds that were oriented in alternating directions