1H NMR and theoretical studies on the conformational equilibrium of tryptophan methyl ester

摘要: Abstract Selected 3JHH coupling constants and theoretical calculations were used to explain the conformational equilibrium of L-tryptophan methyl ester (Trp-OMe) in several solvents. The obtained 3JHαHβ values did not exhibit any significant variability thus indicate that there are no population variations for side chain Trp-O-Me depending on solvent. Moreover, potential energy surfaces at B3LYP/cc-pVDZ level produced eight minima analysed by QTAIM NBO methods. It was possible conclude Trp-OMe preferences due hyperconjugative effects involving nonbonding electron pairs main nitrogen atom certain antibonding orbitals ( σ C 4 -C 13 ⁎ , 1 -H 12 ) also steric from oxygen atoms this system.