STRUCTURES OF THE CONFIGURATIONAL ISOMERS OF 3,3' (1,2-ETHANEDIYL)BIS[2(3-FLUOROPHENYL)-1,3-THIAZOLIDINE-4-ONE], C20H18F2N2O2S2

The crystal and molecular structures of two configurational isomers (hereinafter HM and LM) of the title compound have been determined from single-crystal X-ray diffraction data. The HM isomer has crystallographically imposed 1BAR symmetry; then, the two asymmetric carbon atoms must have opposite chirality and the product is the 2R2'S-meso (or 2S2'R-meso) stereoisomer. The ethylenediamine group assumes the anti-periplanar conformation, the two phenyl rings are strictly planar, and the two thiazolidine rings present the same envelope conformation. The LM isomer is characterized by a -syn-clinal conformation of the ethylenediamine group, by the same envelope conformation of the two thiazolidine rings, and by the same chirality of the two asymmetric carbons atoms. Nevertheless in the crystal structure both enantiomers, 2R2'R and 2S2'S, are present.