Structural studies on H2-antagonists: crystal and molecular structure of N-cyano-N'-methyl-N"-(2-[(2-amino-5-thiazolyl)methylthio]ethyl) guanidine and N-cyano-3-[(2-guanidino-5-thiazolyl)methylthio]propionamidine.

The crystal and molecular structures of N-cyano-N'-methyl-N"-(2-[(2-amino-5-thiazolyl) methylthio] ethyl) guanidine and N-cyano-3-[(2-guanidino-5-thiazolyl)methylthio]propionamidine are reported. Both molecules are in an extended conformation. In all two crystals a system of hydrogen bonds links the molecules in a three-dimensional network. A comparison with the structure of cimetidine and famotidine is also included.