Pulse schemes for detection of quaternary carbons with and without proton decoupling

Four new pulse sequences are proposed for the detection of quaternary carbons. The primary, secondary and tertiary (CH 3 , CH 2 and CH) carbons are suppressed by creating their multiple quantum coherences, which are dephased by the pulsed field gradients in these schemes. Two of the schemes incorporate proton decoupling during acquisition resulting in the enhanced sensitivity of detection. The other two schemes, which do not involve the proton decoupling during acquisition, enable the observation of the long-range carbon-proton couplings, if any. Description of the pulse schemes is provided and the experiments are demonstrated on three samples, a hexapeptide [(CH 3 ) 3 C-O-CO-Val-Val-Val-Aib-Val-Aib-OCH 3 , where Aib is methyl-alanyl residue], cholesteryl acetate and friedelan-7-one.