Conformation of 7-chloro-5-phenyl-d5 −3(S)-methyl-dihydro-1,4-benzodiazepin-2-one in solution

7-Chloro-5-phenyl-d₅-3(S)-methyldihydro-1,4-benzodiazepin-2-one ( 1a ) was synthesized and its conformation in solution determined using a computer assisted LIS-NMR method. It was found, with Fr(fod)-d₂₇ as a shift reagent, that a lanthanide coordinates to a carbonyl oxygen at a 2.02 Å distance (bond angle 158.07°, torsional angle 39.53°), while the substrate 1a adopts an expected quasi-boat conformation with a C(3)-methyl group exposed in a quasi-equatorial position.