Conformation of two 1-benzenesulphonyl-2-oxo-5-alkylthiopyrrolidine cognition activators

Abstract

The molecular structures of the cognition activators (±)1-benzenesulphonyl-2-oxo-5-ethylthiopyrrolidine (1) and (±)1-benzenesulphonyl-2-oxo-5-isopropylthiopyrrolidine (2) were determined by means of X-ray diffraction and semi-empirical quantum mechanical methods. The conformational properties of the compounds, in the solid state andin vacuo (free molecule), were compared with those of the corresponding oxygenated derivatives bearing, in position 5, ethoxy and isopropyloxy substituents, respectively. The molecular arrangements of (1) and (2) in the solid state are similar, with the exception of the side chain on C(5), and they are retained alsoin vacuo. Both present an “envelope” conformation of the five-membered ring, and the relative positions of the five- and six-membered rings look similar and parallel those of their oxygenated parents. Fromin vacuo calculations another low-energy arrangement seems to be possible, and a detailed examination of the side-chain freedom in (1) and (2) gives more insight in the conformational properties of the compounds.