The selective 1D INEPT (SINEPT) experiment allows to detect long-range proton-carbon connectivities from a 1D ¹³C spectrum. The experiment is very useful to assign quaternary carbon chemical shifts.

Easy implementation on AVANCE spectrometers.

The 1D SINEPT pulse sequence ( 84JMR314-57 ) can easily derived from the conventional 1D refocused INEPT experiment by applying all proton pulses selective for an specific ¹H resonance and optimizing the interpulse delays as a function of ⁿJ(CH) (typically 5-10 Hz) (see refocused INEPT block).

Several modified sequences has been proposed:

• The 1D SINEPT experiment has been used to detect non-protonated ¹⁵N nuclei ( 84JACS1150 ).
• A Selective 1D DEPT (SDEPT) experiment ( 92BMR263 and 94MRC343 ) has also been proposed with the same purpose. The pulse sequence is derived from the conventional DEPT experiment in which all proton pulses are made selective for a selected proton.
• A 2D selective J-INEPT experiment can be derived if the proton evolution period is made variable. This experiment allows to measure long-range ¹H-¹³C coupling constants directly from a selective 2D J-resolved experiment.
• The experiment has been largely used for resonance assignment and structure elucidation. A review of applications on natural products has been published ( 91TET3521 ).

The 1D SINEPT experiment can be recorded in a fully automated way. Minor changes from a predefined parameter set are required. Important parameters to consider are:

• Selectivity of the selective pulses: the user must define the offset, the shape, the duration and the power level needed for a defined excitation profile.
• Optimization of the J-coupling interpulse delays as a function of ⁿJ(CH) in the same way as described for the INEPT experiment. Standard values are 100 and 66 ms (5 Hz) for the refocusing and refocusing periods, respectively.

For further details on practical implementation of the 1D SINEPT experiment on AVANCE spectrometers see Tutorial: Selective 1D INEPT experiment

The 1D SINEPT experiment affords a 1D ¹H-decoupled ¹³C spectrum only showing the ¹³C resonances whose are two or three bonds away of the selected ¹H resonance. The intensities of these signals will depend of the delays optimization.

2D COLOC and 2D HMBC experiment are useful alternative to trace out all long-range proton-carbon connectivities from a single 2D spectrum.