Correlation of Proton Chemical Shifts by Two-Dimensional Fourier Transform NMR

The first two-dimensional Fourier transform NMR experiment of Jeener (1) has proved to be of considerable historical importance in the development of two-dimensional NMR spectroscopy (2,3) but in its original form (a 90”-t,-90”~t, sequence) it has been surprisingly little used. On the other hand, the corresponding heteronuclear chemical shift correlation experiments (4) have been quite popular (S-8). Recently Nagayama et at. (9) have proposed a modification of the Jeener experiment in which acquisition is delayed by a further period t1 so that it starts at the peak of the spin echo. They have demonstrated that this “spin-echo correlated spectroscopy ” technique (SECSY) can be extremely useful in the assignment of proton spectra of fairly large molecules, since it identifies the resonances connected by a scalar spin-spin coupling. The purpose of the present communication is to show that the original Jeener experiment can have some advantages in this application. For the proton spectroscopy of large molecules, the refocusing effect which occurs at time 2t, is not usually an important consideration since the linewidths are largel