Molecular structure, supramolecular organization and thermotropic phase behavior of N-acylglycine alkyl esters with matched acyl and alkyl chains

摘要

Graphical abstractDisplay OmittedHighlights?N-Acylglycine alkyl esters (NAGEs) with matched acyl and alkyl chains exhibit sharp phase transitions.?Phase transition enthalpy and entropy of NAGEs are linearly dependent on the chain length.?X-Ray structure showsN-myristoylglycine myristyl ester (NMGME) adopts a linear geometry.?The crystal packing of NMGME is stabilized by NH?O and CH?O hydrogen bonds.?PXRD studies suggest that structure of all NAGEs would be similar to that of NMGME.AbstractN-Acylglycines (NAGs), the endogenous single-tailed lipids present in rat brain and other mammalian tissues, play significant roles in cell physiology and exhibit interesting pharmacological properties. In the present study, a homologous series ofN-acylglycine alkyl esters (NAGEs) with matched chains were synthesized and characterized. Results of differential scanning calorimetric studies revealed that all NAGEs exhibit a single sharp phase transition and that the transition enthalpy and entropy show a linear dependence on theN-acyl and ester alkyl chain length. The structure ofN-myristoylglycine myristyl ester (NMGME), solved by single-crystal X-ray diffraction, showed that the molecule adopts a linear geometry and revealed that the structure ofN-myristoyl glycyl moiety in NMGME is identical to that inN-myristoylglycine. The molecules are packed in layers with the polar functional groups of the ester and amide functionalities located at the center of the layer. The crystal packing is stabilized by NH?O hydrogen bonds between the amide CO and NH groups of adjacent molecules as well as by CH?O hydrogen bonds between the amide carbonyl and the methylene CH adjacent to the ester carbonyl of neighboring molecules as well as between ester carbonyl and methylene group of the glycine moiety of adjacent molecules. Powder X-ray diffraction studies showed a linear dependence of thed-spacings on the acyl chain length, suggesting that all NAGEs adopt a structure similar to the packing exhibited in the crystal lattice of NMGME.]]>