Cytosine-containing hybrid dipeptides: N-[2-(4-amino-2-oxo-1,2-dihydropyrimidin-1-yl)propionyl]-L-phenylalanine N-[2-(4-amino-2-oxo-1,2-dihydropyrimidin-1-yl)propionyl]-L-serine monohydrate and N-[2-(4-amino-2-oxo-1,2-dihydropyrimidin-1-yl)propionyl]-L-lysine.

The title compounds are cytosine-incorporating hybrid dipeptides showing affinities for 9-ethyl-7-methylguanine (7mG). Four molecules of the L-phenylalanine (L-Phe) derivative, C16H14N4O4, are present in the asymmetric unit, with similar folded conformations but with slightly different torsion angles involving the L-Phe group. The L-serine (L-Ser) derivative crystallizes as a monohydrate, C10H14N4O5.H2O, the two independent molecules having extended conformations, whereas the two independent molecules of the L-lysine (L-Lys) system in the final compound, C13H21N5O4, are folded. The cytosine-cytosine base pair (pyrimidine NN interactions) was observed only for the L-lysine derivative. Conformational comparisons with previous structures of cytosine hybrid dipeptides may show the relationships between side-chain position and binding phases for 7mG.