Crystal structure and Hirshfeld surface analysis of ethyl (3 E )-5-(4-fluoro-phen-yl)3-{[(4-meth-oxy-phen-yl)formamido]-imino}-7-methyl-2 H ,3 H ,5 H -[1,3]thia-zolo[3,2- a ]pyrimidine-6-carboxyl-ate 0.25-hydrate.

In the title compound, C 24 H 23 FN 4 O 4 S·0.25H 2 O, the di-hydro-pyrimidine ring is distinctly non-planar, with the flap C atom deviating by 0.297 (2) Å from the least-squares plane. In the crystal, zigzag chains are formed by N-H⋯N hydrogen bonds parallel to [010] and are connected into layers parallel to (100) by O-H⋯O, O-H⋯F, C-H⋯O, C-H⋯F and C-H⋯N hydrogen bonds. Additional C-H⋯O hydrogen bonds connect the layers into a three-dimensional network. A Hirshfeld surface analysis indicates that the most significant contributions to the crystal packing are from H⋯H (42.6%), O⋯H/H⋯O (16.8%) and C⋯H/H⋯C (15.5%) contacts.