Attempts to Obtain Separations of Chiral Anticholinergic Drugs
Where a drug has enantiomeric forms, each should be measurable in the same sample, as now investigated with oxyphenonium and some quaternary atropine analogues. Resolution was attempted with a chiral-HPLC system, containing d-camphorsulphonic acid as a mobile phase component or (cf. W.U. Pirkle’s work) with chiral stationary phases. Neither approach was successful, due to the relatively long distance between the chiral centre and the quaternized nitrogen.
We therefore tried to resolve the optical antipodes of the acid parts of the cholinergics (easily obtained by hydrolysis). An HPLC system having β-eyclodextrin as the chiral stationary phase was chosen. Using aqueous mobile phases, cyclohexylphenylglycollic acid (the acid moiety in oxyphenonium), cyclohexylphenylacetic acid and mandelic acid (e.g. in homatropine) were resolved. However, tropic acid could not be separated into enantiomers with this system. Consideration is given to the influence of temperature and sample concentration on selectivity and resolution and to difficulties in quantitative analysis.
KeywordsChiral Centre Chiral Stationary Phase Mandelic Acid Chiral HPLC Racemic Acid
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