Solvent effects on the relative stability for tautomerism of (R)-4-amino-1,2- oxazolidin-3-one(Cycloserine).Ab initio and Density functional theory calculations

Relative tautomerization energies, dipole moments and polarizabilities for the tautomers of (R)-4-amino-1,2oxazolidin-3-one (Cycloserine) was studied by quantum-chemical calculations, using the HF and DFT(B3LYP) level of theory with the 6-311++G(d,p) basis set in the gas phase and different solvents using SCRF model, with full geometry optimization. Entropies, enthalpies, Gibbs free energies and equilibrium constants for the tautomerization process of cycloserine were calculated. The calculations showed that, the NH tautomer form is the most stable than OH tautomer form in the gas phase and other solvents. Then important molecular parameters and selected IR frequencies results in the gas phase and solvents were extracted. The stability of the tautomers relate to the nature of solvents. In the solution and with increase of polarity; NH isomers were more stable.