title: Determination of enantiomeric excess of nipecotic acid as 1-(7-nitrobenzo[c][1,2,5]oxadiazol-4-yl) derivatives.
abstract: For the enantiopure synthesis of novel chiral GABA uptake inhibitors, nipecotic acid (1) is an important key precursor. To characterize accurately the pharmacological activity of these interesting target compounds, the determination of the correct enantiomeric purity of nipecotic acid as the starting material is indispensable. In this report, a sensitive high-performance liquid chromatography (HPLC) based method for the separation and quantitation of both enantiomers of nipecotic acid as 1-(7-nitrobenzo[c][1,2,5]oxadiazol-4-yl) derivatives (5) on a Chiralpak ID-3 column (Daicel, Illkirch, France) was established. UV/Vis-detection at 490 nm was chosen to ensure a selective determination of even highly enantioenriched samples. Reliability was demonstrated by validation of specificity, linearity, lower limit of quantification (LLOQ), accuracy, and precision. By spiking highly enantiopure samples with small amounts of racemic rac-5, it was proven that the established HPLC method is able to detect even slight changes in enantiomeric excess (ee) values. Thus, accurate determination of ee values up to 99.87% ee for (R)-5 and 99.86% ee for (S)-5 over a linear concentration range of 1-1500 μM for (R)-5 and of 1-1455 μM for (S)-5 could be demonstrated.
authors.affiliation: Department of Pharmacy - Center of Drug Research, Ludwig-Maximilians-Universität München, Munich, Germany.
authors.forename: Simone K
authors.initials: SK
authors.lastname: Schmidt
authors.affiliation: Department of Pharmacy - Center of Drug Research, Ludwig-Maximilians-Universität München, Munich, Germany.
authors.forename: Georg
authors.initials: G
authors.lastname: Höfner
authors.affiliation: Department of Pharmacy - Center of Drug Research, Ludwig-Maximilians-Universität München, Munich, Germany.
authors.forename: Klaus T
authors.initials: KT
authors.lastname: Wanner
mesh_terms: D002851:Chromatography, High Pressure Liquid / Q000379:methods*; D009557:Nipecotic Acids / Q000737:chemistry*; D009574:Nitro Compounds / Q000737:chemistry*; D010069:Oxadiazoles / Q000737:chemistry*; D015203:Reproducibility of Results; D013237:Stereoisomerism
chemical_list: D009557:Nipecotic Acids; D009574:Nitro Compounds; D010069:Oxadiazoles; C030278:nipecotic acid
keywords: NBD-F; amino acid; derivatization; enantiopurity; high performance liquid chromatography; validation