Synthesis and crystal structure of two new macrocyclic phosphoramidates containing glycine ethyl ester and 2,5-diaryl-1,3,4-oxadiazole

Two new isomeric macrocyclic phosphoramidates containing glycine ethyl eate r and 2.5-diaryl-1,3,1-oxadiazole units were synthesized. The crystal struc tures of trans-isomer I and a 1:1 inclusion compound (2a) of cis-isomer 2 w ith acetone, were determined by X-ray single crystal diffraction analysis. Compound 1 is centrosymmetric layer shape, one benzene ring is parallel wit h another oxadiazole ring and the centroid-to-centroid distance D is 3.737 Angstrom. In contrast, compound 2 is L-shaped and the two oxadiazole rings are almost perpendicular with a dihedral angle of 87.81 degrees. The phosph oramidate molecules are self-associated by intermolecular N-H . . .O=P hydr ogen bonds and intermolecular or intramolecular aromatic face-to-face pi-pi interaction of aromatic rings. (C) 2001 Elsevier Science B.V. All rights r eserved.