Telenzepine is a selective M1antimuscarinic used in the treatment of peptic ulcers. Telenzepine is atropisomeric, in other words the molecule has a stereogenic C–N-axis; in neutral aqueous solution it displays a half-life for racemization of the order of 1000 years. The enantiomers have been resolved. The activity is related to the (+)-isomer which is about 500-fold more active as the (–)-isomer at muscarinic receptors in the rat cerebal cortex.
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^Clayden, J.; Moran, W. J.; Edwards, P. J.; Laplante, S. R. (2009). "The Challenge of Atropisomerism in Drug Discovery". Angewandte Chemie International Edition48 (35): 6398–6401. doi:10.1002/anie.200901719. PMID19637174.edit