105618-03-9

Separations of six dihydropyridine enantiomers on three commercially available cellulose-based chiral stationary phases (Chiralcel OD-RH, Chiralpak IB, and Chiralpak IC) were evaluated with high-performance liquid chromatography (HPLC). The best enantioseparation of the six chiral drugs was obtained with a Chiralpak IC (250?×?4.6?mm i.d., 5?μm) column. Then the influence of the mobile phase including an alcohol-modifying agent and alkaline additive on the enantioseparation were investigated and optimized. The optimal mobile phase conditions and maximum resolution for every analyte were as follows respectively: n-hexane/isopropanol (85:15, v/v) for nimodipine (R?=?5.80) and cinildilpine (R?=?5.65); n-hexane/isopropanol (92:8, v/v) for nicardipine (R?=?1.76) and nisoldipine (R?=?1.92); and n-hexane/isopropanol/ethanol (97:2:1, v/v/v) for felodipine (R?=?1.84) and lercanidipine (R?=?1.47). Relative separation mechanisms are discussed based on the separation results, and indicate that the achiral parts in the analytes' structure showed an important influence on the separation of the chiral column.

A short and facile synthesis of (S)-felodipine was developed starting from (R)-glycidol as the source of the chiral auxiliary. 2-Hydroxyethyl esters were found to undergo selective transesterification reactions in the presence of other esters. This selective transesterification reaction was applied to the synthesis of (S)-felodipine through selective substitution of the 2-hydroxyethyl group possessing chiral ester with sodium methoxide.

The enantioselective retention of eight 4-aryl-1,4-dihydropyridine (DHP) calcium-channel blockers on HPLC stationary phases supporting human serum albumin (HSA) or α1-acid glycoprotein (AGP) was investigated. All chiral neutral DHPs were resolved on the AGP column, whereas, on the HSA column, only isradipine showed a split chromatographic peak. Analyses performed on AGP with eluents containing dimethyloctylamine (DMOA) as thc displacer demonstrated that the protein has at least two binding sites for DHPs. The first family of binding sites is enantioselective, binds exclusively to the (R)-forms, and presumably interacts competitively with DMOA. The second family of binding sites appears to be non-enantioselective and is affected by a cooperative interaction with DMOA. For the selected set of DHPs, the lipophilicity scale in octan-1-ol/H2O (log P) was not collinear with log k(w)(IAM) values obtained with immobilized artificial membranes (IAM-HPLC) due to the inclusion of both neutral and basic congeners. Only for the neutral DHPs did log k(w)(IAM) behave as a better descriptor than log P for retention date on HSA and AGP. In fact, the behavior of the basic DHPs amlodipine and nicardipine on both proteins correlated better with the octan- 1-ol/H2O log P values. We, therefore, infer that the amphipathic nature of the IAM phase only mimics the interaction of non-ionizable compounds with serum proteins. In contrast, the IAM-HPLC retention data of protonated bases encode additional interaction mechanisms that are specific for phospholipids and not involved in ligand-protein interactions.

The absolute configuration of 4-(2,3-dichlorophenyl)-1,4-dihydropyridines was established by chemical correlation with (S)-(-)-felodipine, the absolute configuration of which had been determined by X-ray analysis.

The pure enantiomers of felodipine, 1, have been synthesized by chromatographic separation of diastereomeric esters with (R)-1-(p-toluenesulfonyl)-3-trityloxypropan-2-ol, 3, as an easily removable chiral auxiliary.Absolute configurations have been deduced