C-13, N-15 and Cd-113 NMR and molecular orbital studies of novel bile acidN-(2-aminoethyl)amides and their Cd2+-complexes

Lithocholic acid N-(2-aminoethyl)amide (1) and deoxycholic acid N-(2-aminoe thyl)amide (2) have been prepared and characterized by H-1, C-13 and N-15 N MR. The accurate molecular masses of 1 and 2 have been determined by ESI MS . The formation of the Cd2+-complexes (1+Cd and 2+Cd) in CD3OD solution hav e been detected by H-1, C-13, N-15 and Cd-113 NMR. The C-13 NMR chemical sh ift assignments of 1 and 2 and their Cd2+-complexes are based on DEPT-135 a nd z-GS H-1,C-13 HMQC experiments as well as comparison with the assignment s of the related structures. The N-15 NMR chemical shift assignments of the ligands and their Cd2+-complexes are based on z-GS H-1,N-15 HMBC experimen ts. (1)3C NMR chemical shift differences between 1 and its 1:1 Cd2+-complex based on ab initio calculations at Hartree-Fock SCI-PCM level using 3-21G( d) basis set are in agreement with the experimental shift changes observed on Cd2+-complexation.