HSQC-ADEQUATE correlation: a new paradigm for establishing a molecular skeleton

Area of Science:

• Nuclear Magnetic Resonance (NMR) Spectroscopy
• Organic Chemistry
• Structural Elucidation

Background:

• Identifying adjacent carbon atoms is crucial for determining molecular structures.
• Existing methods like HMBC (Heteronuclear Multiple Bond Correlation) and H2BC have limitations, particularly with non-protonated carbons.
• The 1,1-ADEQUATE experiment offers an alternative but typically requires correlation with HSQC (Heteronuclear Single Quantum Coherence) spectra.

Purpose of the Study:

• To develop an improved NMR method for tracing carbon-carbon connectivity.
• To explore the use of unsymmetrical indirect covariance processing for NMR data.
• To create a combined HSQC-ADEQUATE spectrum for easier interpretation of carbon skeletons.

Main Methods:

• Applied unsymmetrical indirect covariance processing to multiplicity-edited GHSQC (edited Heteronuclear Single Quantum Coherence) and 1,1-ADEQUATE spectra.
• Developed a novel HSQC-ADEQUATE correlation spectrum.
• Utilized the 1,1-ADEQUATE experiment's reliance on (1)J(CC) coupling for identifying adjacent carbons, including non-protonated ones.

Main Results:

• Successfully generated an HSQC-ADEQUATE correlation spectrum.
• Demonstrated the utility of this spectrum for tracing the carbon skeleton of strychnine.
• Showcased the advantage of 1,1-ADEQUATE in identifying non-protonated adjacent carbons, unlike HMBC and H2BC.

Conclusions:

• The HSQC-ADEQUATE spectrum provides a powerful tool for extracting carbon-carbon connectivity information.
• This method facilitates the convenient tracing of molecular carbon skeletons.
• The developed technique offers an advancement in NMR-based structural analysis, particularly for complex molecules.