Complete ¹H NMR assignment of cholesteryl benzoate

Area of Science:

• Organic Chemistry
• Spectroscopy
• Structural Biology

Background:

• Cholesterol derivatives are crucial in biological systems and drug development.
• Complete spectral assignment of complex molecules like cholesteryl benzoate is challenging but vital for structural elucidation.
• Nuclear Magnetic Resonance (NMR) spectroscopy is a powerful tool for determining molecular structure.

Purpose of the Study:

• To achieve complete assignment of the 750 MHz 1H NMR spectrum of cholesteryl benzoate (1b).
• To establish all chemical shifts and coupling constants, including long-range values.
• To investigate the structural and electronic effects of benzoylation on cholesterol.

Main Methods:

• Utilized Heteronuclear Single Quantum Coherence (HSQC) experiments to extract coupling constant values from overlapped spectral regions.
• Employed 1H iterative full spin analysis within PERCH NMR software.
• Leveraged previously published data and conducted new HSQC studies on related compounds, including deuterated cholesterol.

Main Results:

• Successfully assigned all chemical shifts and coupling constants for cholesteryl benzoate (1b).
• The assignment of cholesteryl benzoate (1b) and deuterated cholesterol (1c) allowed for the estimation of hydrogen shifts upon benzoylation.
• Experimental vicinal coupling constants for 1b showed excellent correlation with values calculated using Altona software.
• X-ray diffraction revealed an extended conformation of the side chain in solid-state cholesteryl benzoate.

Conclusions:

• Complete spectral assignment of cholesteryl benzoate (1b) and deuterated cholesterol (1c) was achieved using advanced NMR techniques.
• The study provides valuable insights into the structural modifications of cholesterol upon benzoylation.
• The findings validate the utility of combined NMR and computational methods for complex molecule analysis.