|Concomitant polymorphism in stereoselective synthesis of a $\beta$-benzyl $\beta$-hydroxy aspartate analogue |
(Article) Publié: Acta Crystallographica Section C Crystal Structure Communications, vol. 67 p.o301-o305 (2011)
Ref HAL: hal-00606460_v1
Two concomitant polymorphs, (I) and (II), of a beta-benzyl- beta-hydroxyaspartate analogue [systematic name: dibenzyl 2-benzyl-2-hydroxy-3-(4-methylphenylsulfonamido)succinate], C32H31NO7S, crystallize from a mixture of ethyl acetate and cyclohexane at ambient temperature. The structure of (I) has triclinic (P1) symmetry and that of (II) monoclinic (P21/c) symmetry. Both crystal structures are made up of a stacking of homochiral racemic dimers (2S,3S and 2R,3R) which are internally connected by a similar R2 2(9) hydrogen-bonding pattern consisting of intermolecular N--H...O and O--H... O hydrogen bonds. The centroid of the racemic dimer lies on an inversion centre. The main structural difference between the two polymorphs is the conformational orientation of two of the four aromatic rings present in the molecule. Polymorph (II) is found to be twinned by reticular merohedry with twin index 3 and twin fractions 0.854 (1) and 0.146 (1).