Segmental motion in pseudomonic acid A: a carbon-13 spin-lattice relaxation time study at two field strengths

The mobility of pseudomonic acid A in dimethyl sulfoxide-d6 solution has been determined from 13C spin-lattice relaxation time measurements at two field strengths. The central tetrahydropyran ring reorientates isotropically with a rotational correlation time of approximately 280 picoseconds/ radian . Both side-chains exhibit marked segmental motion with correlation times decreasing to only approximately 50 picoseconds/ radian at the end of the nonanoic acid side-chain.