Calix [4]arene diastereomeric pairs with combined axial chirality and inherent chirality were readily synthesized via monoalkylation of 1,2-substituted calix[4]arene crown-4 incorporating an axially chiral binaphthyl moiety with different electrophiles as a key step. The reaction showed high generality and distinct diastereoselectivity. The easy separation of the diaster-eomers, the good diastereoselectivity of the reaction, and the poor stereoselectivity of the chiral recognition of diastereomeric pairs were attributed to the remarkable steric effect of the axially chiral binaphthyl moiety. Absolute configurations were determined by X-ray crystallography.
Barnidipine hydrochloride is a long term dihydropyridine calcium channel blocker used for the treatment of hypertension. During the process development of barnidipine hydrochloride, four barnidipine impurities were detected by high-performance liquid chromatography (HPLC) with an ordinary column (Agilent ZORBAX Eclipse XDB-C18, 150 mm × 4.6 mm, 5 µm). All these impurities were identified, synthesized, and subsequently characterized by their respective spectral data (MS, 1 H-NMR, and 13 C-NMR). The identification of these impurities should be useful for quality control in the manufacture of barnidipine.
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