Crystal structure and conformation of frentizole, [1-(6-methoxy-2-benzothiazolyl)-3-phenylurlea, an antiviral agent and an immunosuppressive drug

Crystals of Frentizole (from ethanol/water) are monoclinic, space group P2(1)/c, with a = 11.187(4), b = 7.392(2), c = 32.727(6) Angstrom, beta = 92.77(2)degrees, Z = 8, D-o = 1.47 g/cm(3), and D-c = 1.472 g/cm(3). There are two independent molecules in the crystallographic asymmetric unit with very different conformations. In molecule A the urea group is in the plane of the benzothiazole ring (0.9 degrees) whereas in molecule B the dihedral angle between them is 4.4 degrees. The dihedral angle between the planes of the phenyl group and the benzothiazole ring are +/- 157 degrees and +/-12 degrees, respectively, in the two molecules. The molecules are linked by a pair of N-H ... N hydrogen bonds involving the urea nitrogen and two other N-H ... N bonds involving the urea nitrogen and the nitrogen of the benzothiazole group.