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Analysis and applications of 13 C NMR lanthanide induced shifts of 1,4‐benzodiazepines
Author(s) -
Paul H.H.,
Sapper H.,
Lohmann W.,
Kalinowski H.O.
Publication year - 1982
Publication title -
organic magnetic resonance
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.483
H-Index - 72
eISSN - 1097-458X
pISSN - 0030-4921
DOI - 10.1002/mrc.1270190113
Subject(s) - lanthanide , chemistry , dihedral angle , substituent , crystallography , metal , reagent , bond length , chemical shift , ion , medicinal chemistry , crystal structure , molecule , organic chemistry , hydrogen bond
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.