Long-lived nuclear spin states in the solution NMR of four-spin systems

Abstract

The existence of long-lived nuclear spin states in four-spin systems is explored by solution-state NMR experiments. Long-lived states are proved to exist in three different natural product molecules, each containing either a AA′ BB′ or a AA′ XX′ proton spin system. The measured state lifetimes are between four and eight times the spin–lattice relaxation time constants.