Conformation of Symmetric Bilirubin Analogs from13C-Nuclear Magnetic Resonance Spin Lattice T1Relaxation Times

Abstract
Symmetric analogs of bilirubin with propionic acid groups shortened and lengthened (and esterified as methyl esters) adopt similar conformations in deuterated dimethylsulfoxide solvent, as determined from their 13C-NMR spin lattice relaxation times. Segmental motion of the alkanoic acid chain carbons indicates internal hydrogen bonding with solvent participation.