Gradient-enhanced one-dimensional pulse schemes for quaternary and methylene carbon detection

Gradient-enhanced pulse schemes are presented for the detection of quaternary and methylene carbons. The new pulse schemes permit the detection of quaternary and methylene (- CH2) carbons or CH2 carbons alone from a single experiment. Efficient suppression of CH and CH3 carbons in all the pulse schemes is achieved by creating their antiphase magnetization and then dephasing using gradients. In the pulse schemes for detection of only CH2 carbons, the quaternary carbons are also suppressed either by dephasing using gradients or by rendering them unobservable by retaining in longitudinal order. The experimental results of the gradient pulse schemes are demonstrated on cholesteryl acetate and cyclosporin A. These one-dimensional techniques, because of their simplicity and the ease of performing the experiments, can be important for routine chemical applications. Copyright (C) 2003 John Wiley Sons, Ltd.