Analytical Chemistry and Spectroscopy
Wiley InterScience Backfile Collection 1832-2000
Chemistry and Pharmacology
Lanthanide induced shifts using Yb(fod)3 and Pr(fod)3 were used for the signal assignments of the 13C spectra of the 1,4-benzodiazepines diazepam, desmethyldiazepam, prazepam and flurazepam, and for characterizing their solution conformation with respect to the substituents at N-1 and C-5. The phenyl substituent at C-5 is found to be nearly coplanar with the π-bond between C-5 and N-4, and the substituents at N-1 seem to be orientated towards the carbonyl group with dihedral angles of either 60° or 120° between the bonds N-1 and C-2 and C-12 and C-13. The metal ions seem to bind to O-2 with metal-oxygen distances between 0.19 and 0.26 nm and bond angles between 117° and 167°. Contact shifts induced by Pr(fod)3 are slightly larger than obtained for Yb(fod)3, whereas the latter reagent causes a stronger broadening.
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