Application of Preferential Crystallization for Different Types of Racemic Compounds

Atropisomerism - A Neglected Way to Escape Out of Solubility Flatlands

Low solubility of drugs represents a major challenge during research and development. Ways to overcome this are either focused on formulation development or optimization of the molecular structure of the drug. The latter is not only governed by the constitution of the molecule but also by its stereochemistry. Development of enantiomers in contrast to racemic mixtures has become the state of the art over the last decades as this leads to higher potency and selectivity. Thus, enantiopure drugs require lower doses compared to their racemates. Additionally, selecting one enantiomer also leads to improved solubility of the drug compared to its racemic compound. While this effect is well known for enantiomers and racemic compounds where chirality is introduced via a chiral central atom, here we describe the first case where improved solubility is realized by selecting an axially chiral atropisomer.

Enantioseparation of flurbiprofen enantiomers using chiral ionic liquids by liquid-liquid extraction

Flurbiprofen is a kind of nonsteroidal anti-inflammatory drug, which has been widely used in clinic for treatment of rheumatoid arthritis and osteoarthritis. It has been reported that S-flurbiprofen shows good performance on clinic anti-inflammatory treatment, while R-enantiomer almost has no pharmacological activities. It has important practical values to obtain optically pure S-flurbiprofen. In this work, chiral ionic liquids, which have good structural designability and chiral recognize ability, were selected as the extraction selector by the assistance of quantum chemistry calculations. The distribution behaviors of flurbiprofen enantiomers were investigated in the extraction system, which was composed of organic solvent and aqueous phase containing chiral ionic liquid. The results show that maximum enantioselectivity up to 1.20 was attained at pH 2.0, 25°C using 1,2-dichloroethane as organic solvent, 1-butyl-3-methylimidazole L-tryptophan ([Bmim][L-trp]) as chiral selector. The racemic flurbiprofen initial concentration was 0.2 mmol L^-1 , and [Bmim][L-trp] concentration was 0.02 mol L^-1 . Furthermore, the recycle of chiral ionic liquids has been achieved by reverse extraction process of the aqueous phase with chiral selector, which is significant for industrial application of chiral ionic liquids and scale-up of the extraction process.

Chiral liquid membrane for enantioselective separation of racemic ibuprofen by l-tartaric acid derivatives

Use of a chiral liquid membrane is an attractive separation method for racemic ibuprofen, and the separation factor could be up to 1.38 under optimal experimental conditions.