3-Ethyl-6-methyl-isocytosines: Synthesis and solid state structural analysis

The syntheses and solid state structures of 3-ethyl-6- methyl-5-alkyl-isocytosines (alkyl=H, Me, Et, n-Pr, n-Bu) are presented. These heterocycles consistently self-assemble into N-H N hydrogen-bonded dimers, which further associate by N-H···O=C interactions, or N-H···O-H···O=C hydrogen bonds involving water of crystallization, generating extended supramolecular networks. Crystal packing analysis indicates that although hydrogen bonding is the primary intermolecular interaction in these molecular crystals, the dispersion forces may play a decisive role in determining their final three-dimensional arrangements. (C) 2000 Elsevier Science Ltd.