H2BC & Edited H2BC Selective observation of ²J_CH

Long-range correlation peaks in HMBC measurements appear depending on the magnetization transfer time 1/2 ⁿJ_CH. However, the value of ⁿJ_CH is not deter-mined by the bond number, and so the correlation peaks give no information on  the bond number. In particular, the close values of ²J_CH and ³J_CH make it difficult to discriminate the corresponding correlations. H2BC (Heteronuclear 2-Bond Correlation) detects only two-bond away correlations, clarifying the assignments. Furthermore, multiplicity edited H2BC may discriminate attached carbon numbers.

Edited H2BC spectrum of strychnine
¹J ^max = 170 Hz, ¹J   ^min = 125 Hz, y_points = 128, T = 22 msec

By linking correlation peaks in H2BC and HSQC spectra, ¹³C connectivities can be revealed. Thus, the combination of H2BC and HSQC gives a method for determining sequences of ¹³C bonding with ¹H.

Reference

N.T. Nyberg, J.Ø. Duus and O.W. Sørensen, J. Am. Chem. Soc., 127, 6154 (2005)
N.T. Nyberg, J.Ø. Duus and O.W. Sørensen, Magn. Reson. Chem., 43, 971 (2005)