(S)-N-{3-[1-cyclopropyl-1-(2,4-difluoro-phenyl)-ethyl]-1H-indol-7-yl}-methanesulfonamide: a potent, nonsteroidal, functional antagonist of the mineralocorticoid receptor.

A novel, potent series of indole analogs were recently developed as MR antagonists, culminating in 14. This compound represents the first MR antagonist in this class of molecules, exhibiting picomolar binding affinity and in vivo blood pressure lowering at pharmaceutically relevant doses.

High performance liquid chromatographic enantioseparation development and analytical method characterization of the carboxylate ester of evacetrapib using an immobilized chiral stationary phase with a non-conventional eluent system.

Using multiple HPLC chromatographic modes and various chiral columns in the context of an automated screening system, a potential separation was initially identified for the methyl ester of evacetrapib and its stereoisomers using an immobilized polysaccharide-based HPLC column. The bonded nature of this column, the Chiralpak(®) IC, allows for enhanced separation development with a diverse solvent range not amenable to standard coated chiral stationary phases. The ternary eluent system ultimately identified provided isomer resolutions not obtainable via the more established hexane/alcohol or polar organic chromatographic modes. A systematic separation development process is described, first for the resolution of the isomers, and later incorporating five potential impurities. A robust separation system was eventually developed that effectively resolves all compounds within a reasonable analysis time.

Stereoselective high-performance liquid chromatography and analytical method characterization of evacetrapib using a brush-type chiral stationary phase: a challenging isomeric separation requiring a unique eluent system.

Using HPLC chiral separation screening, various columns representing the polysaccharide, macrocyclic antibiotic and brush classes were assessed in multiple chromatographic modes for the separation of evacetrapib, a potential cardiovascular drug, from its enantiomer, two diastereomers and several impurities. Screening data consistently pointed to the brush-type Whelk-O 1 chiral column as most promising for this task. A systematic separation optimization process is outlined using the (S,S) Whelk-O 1 chiral column, first for the resolution of the isomers, and later including six potential impurities. A relatively complex yet rugged separation system was eventually identified that effectively resolves all compounds within a reasonable analysis time, and should serve as an adequate tool for evacetrapib bulk drug enantiopurity measurement.

Investigation of the mechanism of racemization of litronesib in aqueous solution: unexpected base-catalyzed inversion of a fully substituted carbon chiral center.

Mitosis inhibitor (R)-litronesib (LY2523355) is a 1,3,4-thiadiazoline-bearing phenyl and N-(2-ethylamino)ethanesulfonamido-methyl substituents on tetrahedral C5. Chiral instability has been observed at pH 6 and above with the rate of racemization increasing with pH. A positively charged trigonal intermediate is inferred from the fact that p-methoxy substituent on the phenyl accelerated racemization, whereas a p-trifluoromethyl substituent had the opposite effect. Racemization is proposed to occur through a relay mechanism involving intramolecular deprotonation of the sulfonamide by the side chain amino group and attack of the sulfonamide anion on C5, cleaving the C5S bond, to form an aziridine; heterolytic dissociation of the aziridine yields an ylide. This pathway is supported by (1) a crystal structure providing evidence for a hydrogen bond between the sulfonamide NH and the amino group, (2) effects of substituents on the rate of racemization, and (3) computational studies. This racemization mechanism results from neighboring group effects in this densely functionalized molecule. Of particular novelty is the involvement of the side-chain secondary amino group, which overcomes the weak acidity of the sulfonamide by anchimeric assistance.

Enantiomeric separation of mineralocorticoid receptor (hMR) antagonists using the Chiralcel OJ-H HPLC column with novel polar cosolvent eluent systems.

This study demonstrates the increased versatility of the Chiralcel OJ-H stationary phase when using various alcohol/acetonitrile mobile phases. This chiral stationary phase has traditionally been employed in the normal phase mode and more recently with neat alcohols as eluents. Selected isomeric human mineralocorticoid receptor (hMR) antagonist pharmaceutical candidates and synthetic intermediates were separated using the Chiralcel OJ-H HPLC column with novel polar cosolvent eluent systems. The capacity factors, resolution, and selectivity of the chiral separations were assessed while varying the alcohol/acetonitrile composition and alcohol identity. The mixed polar eluents provide separations that are nearly always superior to both the traditional hexane-rich and single-alcohol "polar organic" eluents for the compounds tested in this article.

Enantiomeric separation of dansyl amino acids using macrocyclic antibiotics as chiral mobile phase additives by narrow-bore high-performance liquid chromatography.

Seven macrocyclic antibiotics were evaluated as chiral selectors for the enantiomeric separation of 11 dansyl amino acids using narrow-bore high-performance liquid chromatography (HPLC). The macrocyclic antibiotics were incorporated as mobile phase additives to determine the enantioselective effects on the chiral analytes. The resolution and capacity factor (k') of each analyte were assessed while varying the structure of macrocyclic antibiotic and the mobile phase buffer pH. The selectivity of the chiral selectors was measured as a function of changes in these parameters. All 11 dansyl amino acids were separated by at least one of the chiral selectors. Three-dimensional computer modeling of the more effective chiral selectors illustrated the importance of macrocyclic antibiotic structure concerning stereospecific analyte interaction.