Heteronuclear Multiple-Bond Connectivity HMBC Spectra

Heteronuclear Multiple-Bond Connectivity (HMBC) Spectra... 

A H(detected)- C shift correlation spectrum (common acronym HMQC, for heteronuclear multiple quantum coherence, but sometimes also called COSY) is a rapid way to assign peaks from protonated carbons, once the hydrogen peaks are identified. With changes in pulse timings, this can also become the HMBC (heteronuclear multiple bond connectivity) experiment, where the correlations are made via the... 

A modification of the HMQC referred to as the HMBC (Heteronuclear Multiple Bond Coherence) experiment can be optimized for transfer through multiple bonds based on the value of the multiple bond couplings, which is typically about 8 Hz for a three-bond coupling. The HMBC spectrum of dutasteride shown in Fig. 9 illustrates the utility of this experiment for assigning quaternary carbons, connecting isolated spin systems (e.g., Hig and Hig) to other spin systems in the molecule, and confirming assignments made from the COSY and HMQC spectra. 

HMBC ( -Detected Multiple-bond Heteronuclear Multiple Quantum Coherence Spectrum) NMR of 26a allowed one to show that the isopropyl group (Ha, Hfc) is connected to the olefmic carbon (Cc), whereas methyl (IF) and methylene (H-C, H- ) groups are bonded to another olefmic carbon (Cd) and fullerene carbon (Ch) through quaternary carbon (Ce) shown in 26a and 26b (Scheme 8). 

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