2-Pyridone and 3-oxo-1,2,6-thiadiazine-1,1-dioxide derivatives: a new class of hydrogen bond equivalents of uracil.

Hydrogen bond complex stability between adenine (A) and hydrogen bond equivalents of uracil: 2-pyridone derivatives (U(X2O)X) and 3-oxo-1,2,6-thiadiazine-1,1-dioxide derivatives (U(SO2)X) was studied, and as the result, the hydrogen bond energy of U(X2O)X-A and a complex of UX(SO2)X-A, was about 1.5 kcal/mol more stable than that of the corresponding adenine-uracil derivatives complex, respectively. The energy difference between the imide tautomer and enol tautomer was smaller than those of uracil derivatives. U(SO2)F can form a stable complex with A, and its imide tautomer is stable.