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Synthesis and crystal structures of two structurally related kryptoracemates
Author(s) -
Kramer Philipp,
Bolte Michael
Publication year - 2017
Publication title -
acta crystallographica section c
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.304
H-Index - 17
ISSN - 2053-2296
DOI - 10.1107/s2053229617009408
Subject(s) - enantiomer , crystal structure , crystallography , chemistry , molecule , stereochemistry , hydrogen bond , space group , crystal (programming language) , point reflection , intermolecular force , x ray crystallography , physics , organic chemistry , condensed matter physics , diffraction , computer science , programming language , optics
Kryptoracemates are racemic compounds (pairs of enantiomers) that crystallize in Sohnke space groups (space groups that contain neither inversion centres nor mirror or glide planes nor rotoinversion axes). Thus, the two symmetry‐independent molecules cannot be transformed into one another by any symmetry element present in the crystal structure. Usually, the conformation of the two enantiomers is rather similar if not identical. Sometimes, the two enantiomers are related by a pseudosymmetry element, which is often a pseudocentre of inversion, because inversion symmetry is thought to be favourable for crystal packing. We obtained crystals of two kryptoracemates of two very similar compounds differing in just one residue, namely rac ‐ N ‐[(1 S ,2 R ,3 S )‐2‐methyl‐3‐(5‐methylfuran‐2‐yl)‐1‐phenyl‐3‐(pivalamido)propyl]benzamide, C 27 H 32 N 2 O 3 , (I), and rac ‐ N ‐[(1 S ,2 S ,3 R )‐2‐methyl‐3‐(5‐methylfuran‐2‐yl)‐1‐phenyl‐3‐(propionamido)propyl]benzamide dichloromethane hemisolvate, C 25 H 28 N 2 O 3 ·0.5CH 2 Cl 2 , (II). The crystals of both compounds contain both enantiomers of these chiral molecules. However, since the space groups [ P 2 1 2 1 2 1 for (I) and P 1 for (II)] contain neither inversion centres nor mirror or glide planes nor rotoinversion axes, there are both enantiomers in the asymmetric unit, which is a rather uncommon phenomenon. In addition, it is remarkable that (II) contains two pairs of enantiomers in the asymmetric unit. In the crystal, molecules are connected by intermolecular N—H…O hydrogen bonds to form chains or layered structures.