Synthesis of N-Urethane-protected gamma-amino-functionalized butenoates and tautomeric studies by means of NMR, X-ray crystallography and ab initio calculations

N-Urethane-protected gamma -amino-alpha -cyano-beta -hydroxybutenoates were synthesized as potential statine analogues and the stability of their poss ible tautomers was assessed using NMR, X-ray crystallography and ab initio calculations. The results establish that the cis-enol tautomeric form is th e most stable one both in solution (CDCl3) and in the solid phase. In full agreement with the experimental data, the theoretical calculations predicte d that the cis-enol tautomer would be the minimum energy tautomer.