Stereo-Selective Preparation of Teneraic Acid, trans-(2S,6S)-Piperidine-2,6-dicarboxylic Acid, via Anodic Oxidation and Cobalt-Catalyzed Carbonylation.

Teneraic acid (piperidine-2,6-dicarboxylic acid) is a naturally occurring imino acid that comprises three stereoisomers due to its two asymmetric centers at C2 and C6. The configuration of natural teneraic acid is reported to correspond to trans-(2S,6S). However, a few studies are focused on the stereospecific synthesis of trans-(2S,6S)-teneraic acid. The present study investigates a convenient synthetic method that includes regiospecific anodic oxidation and stereospecific cobalt-catalyzed carbonylation to obtain trans-(2S,6S)-teneraic acid. Methyl (S)-N-benzoyl-α-methoxypipecolate, the key intermediate that displays a structure that corresponds to an intermediate (N-α-hydroxyalkyl amide) of intramolecular amidocarbonylation, was obtained via an anodic oxidation of methyl (S)-N-benzoylpipecolate. Subsequently, cobalt-catalyzed carbonylation converted the methyl (S)-N-benzoyl-α-methoxypipecolate to trans-(2S,6S)-N-benzoyl-teneraic acid dimethyl ester in good optical purity (>95% enantiomeric excess (ee)) and modest yield (63%). Finally, de-protection occurred via acidic hydrolysis to obtain trans-(2S,6S)-teneraic acid. The stereochemistry of synthesized teneraic acid was confirmed as corresponding to trans-(2S,6S) by comparing its physical properties with those of a cis-meso-isomer and those of a trans-(2S,6S)-isomer that were reported in previous studies.

The establishment and validation of efficient assays for anti-IIa and anti-Xa activities of heparin sodium and heparin calcium.

Heparin is used as an anticoagulant drug. The anticoagulation process is mainly caused by the interaction of heparin with antithrombin followed by inhibition of anticoagulant factor IIa and factor Xa. The anti-factor IIa and anti-factor Xa activities of heparin are critical for its anticoagulant effect; however, physicochemical methods that can reflect these activities have not been established. Thus, the measurements of anti-IIa and anti-Xa activities by biological assay are critical for the quality control of heparin products. Currently in the Japanese Pharmacopoeia (JP), the activities of heparin sodium and heparin calcium are measured by an anti-Xa activity assay (anti-Xa assay), but anti-IIa activity is not measured. Here, we established an anti-IIa activity assay (anti-IIa assay) and an anti-Xa assay having good accuracy and precision. When samples having a relative activity of 0.8, 1.0 and 1.2 were measured by the established anti-IIa and anti-Xa assays in nine laboratories, good accuracy (100.0-102.8% and 101.6-102.8%, respectively), good intermediate precision (1.9-2.1% and 2.4-4.2%, respectively) and good reproducibility (4.0-4.8% and 3.6-6.4%, respectively) were obtained. The established anti-IIa and anti-Xa assays have similar protocols, and could be performed by a single person without a special machine. The established assays would be useful for quality control of heparin.