Synthesis and conformational analysis of the Amadori compound N-(2,3:4,5-di-O-isopropylidene-1-deoxy-β-d-fructopyranos-1-yl)-l-tyrosine benzyl ester

The title compound, a precursor in the synthesis of other analogues of Amadori type, was prepared and characterized by X-ray structure analysis and NMR spectroscopy. The molecule crystallized in the orthorhombic space group P212121 with a = 10.441(2), b = 10.894(2), c = 24.686(4)Å, Z = 4. The molecule is flexible even in solid state; at 100 K two orientations of the benzyloxy group are present in the unit cell. Therefore, molecular mechanics and molecular dynamics simulations were used to study its conformational changes. The results obtained were compared with experimental observations. The comparative analysis revealed that the two conformers detected in the crystal are different from the energetically favourable conformations in Me2SO solutions. Rotations about both C-N bonds affect the global molecular conformation. The β-d-fructopyranose moiety blocked with two dioxolane rings is the less flexible part of the molecule; in the solid state and in Me2SO-d6 it is in the skew conformation.