The antifolate trimetrexate: observation of the enzyme-binding conformation

The crystal structure of the title compound contains four 2,4-diamino-5-methyl-6-[(3,4,5-trimethoxyanilino)methyl]quinazoline molecules, two dimethyl sulfoxide molecules and three water molecules in the asymmetric unit, i.e. 4C(19)H(23)N(5)O(3)(.)-2C(2)H(6)OS . 3H(2)O. All four quinazoline molecules adopt trans,gauche conformations. An extensive hydrogen-bond network involving N . . . N base-pairing interactions, as well as the dimethyl sulfoxide and water molecules, stabilizes the crystal structure.