Effects of covalent modifications on the solid-state folding and packing of N-malonylglycine derivatives

Article abstract of DOI:10.1021/ja00038a057

The syntheses and crystal structures of triamides 1-4 and diamide esters 5 and 6 are described. In crystalline form, 1, 2, and 4 adopt conformations containing an intramolecular N-H?C=T 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 NMR 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 earlier deduced to be most enthalpically favorable in nonpolar 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 nonpolar 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 nonpolar fragments is observed.