Solid-state structure and solution conformation of the nootropic agent N[2-(N,N-Diisopropylamino)ethyl]-2-oxo-1-pyrrolidinacetamide sulphate. X-ray and homonuclear two-dimensional 1H NMR studies☆

Abstract The crystal and molecular structure of the nootropic agent N -[2-( N,N -diisopropyl-amino)ethyl]-2-oxo-1-pyrrolidinacetamide sulphate was determined by X-ray analysis. The conformational properties in the solution state were deduced from the 1 H-NMR spectrum run in 2 H 2 O at 500 MHz. Spectral assignments were made with the aid of the COSY 45 shift correlation experiment. Crystals were triclinic with unit cell dimensions a = 13.410(10), b = 11.382(8), c = 6.697(4) » , α = 83.80(3), β = 88.61(3)and γ = 72.25(6)° ; space group P 1 . The structure was determined from 1047 three-dimensional counter data and refined to a value of 7.5% for the conventional discrepancy factor R . One molecule of the solvent acetonitrile is incorporated per two of the (C 14 H 28 N 3 O 2 ) + -(HSO 4 ) − . The five-membered heterocyclic ring is in an envelope ( C s ) conformation and the “flap” atom deviates by 0.31 » from the plane of the other four. This plane forms a dihedral angle of 71.4° with the amide group, with the CO fragment directed toward the ring. All bond angles and distances are in good agreement with expected standard values. A strong OH⋯O intermolecular bond (2.61 » ) links the cation of the hydrogen-sulphate anion, while the loosely held MeCN molecule is trapped in the polar pockets. The molecular conformation in the solid was compared with results from 1 H NMR spectral analysis which showed that in solution wide torsional oscillations can occur about the bonds of the chain bonded to the N(1) atom.