Solid solution of two diastereomers of [3a(R,S),7a(R,S)]-3-[(1′R)-1-phenylethyl]perhydro-1,3-benzothiazol-2-iminium chloride

Abstract

A mixture of two diastereomers with the configurations (3aS,7aS,1'R) and (3aR,7aR,1'R) forms co-crystals in which there is one unique molecule in the asymmetric unit, but the molecule displays disorder which is a result of the presence of the two diastereomers at the same crystallographic site. Theoretical calculations carried out by the DFT method with the 6-311++G(2df,p) basis set allowed for the estimation of the energy difference between the two diastereomers both in the isolated and the solid state, while the natural bond orbital (NBO), Mulliken, natural population (NPA) and CHelpG analyses helped to establish the electronic structure of the thazolidin-2-imine fragment.

Amplification of enantiomeric excess, mirror-image symmetry breaking and kinetic proofreading in Soai reaction models with different oligomeric orders

“…6 illustrate the complexity of the parameter interactions and show that in some cases the necessary condition of surpassing a minimum DE RS is not sufficient. The threshold of DE RS = 5 kcal mol À1 is relatively high when compared with literature data [76][77][78][79][80] of typical diastereomeric energy differences. For instance, diastereoisomeric energy differences between 0.2 and 2.4 kcal mol À1 were estimated for the asymmetric induction of aliphatic and cyclic ketones.…”

“…76 Similar values were reported from quantum calculations of several systems including Pd(II), 77 Pt(II) 78 complexes and heterocyclic compounds. 79 Records of higher diastereoisomeric energy differences are hardly found. Hence it is likely that the number of compounds displaying diastereoisomeric energy differences of DE RS > 5 kcal mol À1 is quite limited.…”

Failures of fractional crystallization: ordered co-crystals of isomers and near isomers

“…Mixed crystals, in which different molecules occupy the same site with at least approximately similar occupancies, were excluded. (For a list of 30 mixed crystals of diastereomers see Plutecka et al, 2010. ) While it is possible that some apparently mixed crystals might be better described as ordered molecular compounds in a larger or lower-symmetry unit cell, there was no way we could investigate that possibility.…”

Solid Solutions in the Xanthone–Thioxanthone Binary System: How Well Are Similar Molecules Discriminated in the Solid State?

“…For example, as we have shown in our recent work–solid solutions may form when a similarly shaped molecule that does not disrupt the hydrogen bonding network in the crystal structure or can participate in this bonding equally well is introduced in the system . Solid solutions have been discovered and studied for multicomponent systems of the following: enantiomers; − diastereomers; ,− molecules differing by single/double bonds between two carbon atoms; , molecules differing by halogen (and halogen/methyl) substituents; − molecules differing by S/O atoms; , molecules differing by F/H atoms; aromatic systems differing by presence/absence of a heteroatom; − molecules differing by methyl/ethyl substituents . Nevertheless, up to date, only somewhat rough and empirical guidelines could be established to define the criteria for solid solution formation, and there are cases when even very similar molecules do not mix in the solid state .…”