Analysis and applications of 13C NMR lanthanide induced shifts of 1,4-benzodiazepines

✍ Scribed by H.-H. Paul; H. Sapper; W. Lohmann; H.-O. Kalinowski

• Publisher: John Wiley and Sons
• Year: 1982
• Tongue: English
• Weight: 521 KB
• Volume: 19
• Category: Article
• ISSN: 0749-1581
• DOI: 10.1002/mrc.1270190113

✦ Synopsis

Abstract

Lanthanide induced shifts using Yb(fod)~3~ and Pr(fod)~3~ were used for the signal assignments of the ^13^C 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.