Differential analgesic activity of the enantiomers of atropine derivatives does not correlate with their muscarinic subtype selectivity

Hydrolytic dynamic kinetic resolution of racemic 3-phenyl-2-oxetanone to chiral tropic acid

Tropic acid was synthesized in a good yield and with high enantioselectivity (81% ee) under non-biphasic conditions via the novel hydrolytic dynamic kinetic resolution of racemic 3-phenyl-2-oxetanone (tropic acid β-lactone) in the presence of a chiral quaternary ammonium phase-transfer catalyst and strongly basic anion exchange resin as the hydroxide ion donor.

Enantiomeric differentiation of atropine/hyoscyamine by (13) C NMR spectroscopy and its application to Datura stramonium extract

INTRODUCTION

The two enantiomers of hyoscyamine, an alkaloid found in many plant species, have distinct pharmacological and biological properties. Methods for the discrimination of both enantiomers are almost exclusively based on chiral HPLC/UV. Determination of the enantiomeric ratio (e.r.) of hyoscyamine is a challenging problem since this compound tends to racaemise, forming atropine during acid-base extraction.

OBJECTIVE

To develop a protocol for the calculation of enantiomeric ratio of hyoscyamine in a plant extract using a (13) C NMR method.

METHODOLOGY

Samples were prepared by extraction of dried Datura stramonium seeds. Observation of C12 and C15 NMR signals of hyoscyamine in the presence of one equivalent of TFA and sub-stoichiometric amount of Yb(hfc)(3) allowed the calculation of the e.r. of S-(-) and R-(+)-hyoscyamine.The method was optimised with various mixtures of (+) and (-)-hyoscyamine ranging from 50:50 (racaemic mixture, i.e. atropine) to 98.5:1.5. The e.r. measured by NMR on the signals of aromatic C12 and C15 were in agreement with the gravimetrically prepared samples. The method was then applied to an extract of Datura stramonium and S-(-)-hyoscyamine was the unique enantiomer.

CONCLUSION

The study showed that the e.r. determination of atropine/hyoscyamine was achieved with a routine NMR spectrometer, using CLSR/TFA on pure compounds as well as on the crude extract of Datura stramonium.

Synthesis and Radiolabelling of Ipratropium and Tiotropium for Use as PET Ligands in the Study of Inhaled Drug Deposition

Ipratropium bromide [(1R,3r,5S,8r,2′RS)-3-(3′-hydroxy-2′-phenylpropionyloxy)-8-isopropyl-8-methyl-8-azabicyclo[3.2.1]octan-8-ium bromide] and tiotropium bromide [(1R,2R,4S,5S,7s)-7-[2′-hydroxy-2′,2′-di(thiophen-2′′-yl)acetoxy]-9,9-dimethyl-9-aza-3-oxatricyclo[3.3.1.02,4]nonan-9-ium bromide] are inhaled drugs used in the treatment of chronic obstructive pulmonary disease (COPD) and asthma. Tertiary amine precursors have been synthesized and radiolabelled with carbon-11 by N-alkylation with [11C]CH3I. The [11C]ipratropium and [11C]tiotropium positron emission tomography (PET) ligands are obtained with high radiochemical purity, in 0.3 and 0.5% non-decay corrected yields based on [11C]CO2 at end-of-synthesis and specific activities of 11 and 18 GBq μmol−1, respectively, calculated at end-of-synthesis. These PET radioligands can be used in the study of inhaled drug deposition.