Effects of Covalent Modifications on the Solid-State Folding and Packing of N-Malonylglycine Derivatives

摘要

The synthesis and crystal structures of triamides 1-4 and diamide-esters 5 and 6are described. In crystalline form, 1, 2 and 4 adopt conformations containing, an intramolecular N-H-O=C hydrogen bond in a nine-membered ring. Triamide 3 and ester-diamides 5 and 6 experience only intermolecular hydrogen bonding in the solid state. We have previously concluded, on the basis of IR and 1H NNM measurements, that triamide 1 manifests several different internal hydrogen bonding patterns in methylene chloride solution. The conformation adopted by 1 in the solid state is similar to the folding pattern that we had earlier deduced to be most enthalpically favorable in non-polar solution, although an intermolecular hydrogen bond detected in the crystalline 1 does not occur at the dilutions used for the solution experiments. The intramolecularly hydrogen bonded solid state conformations of 2 and 4 are similar to those that predominate in methylene chloride solution. In contrast, the extended, intermolecularly hydrogen bonded conformation of 3 in the solid state differs from the intramolecularly hydrogen bonded form that is favored in dilute methylene chloride. The solid state conformations of diamide-esters 5 and 6 also differ from the forms that appear to be most highly populated in non-polar solution. The crystal packing, of 2-4 is discussed in detail. Although the juxtapositions of neighbors vary among, these triamides, in all three cases a pattern of alternating sheets of polar and non-polar fragments is observed.