Epimerization and stereochemistry of avoparcin

Area of Science:

• Medicinal Chemistry
• Organic Chemistry
• Biochemistry

Background:

• Avoparcin is a complex glycopeptide antibiotic with known antibacterial properties.
• Understanding the stereochemistry and potential epimerization is crucial for drug stability and efficacy.

Purpose of the Study:

• To investigate the epimerization of avoparcin and its stereochemical implications.
• To determine the absolute stereochemistry of the N-methyl terminal amino acid of the aglycone.
• To analyze the effect of protonation on antibacterial activity.

Main Methods:

• Isolation and characterization of the N-methyl terminal amino acid from native and epimerized avoparcin.
• Determination of absolute stereochemistry using optical rotation.
• Comparison of Circular Dichroism (CD) curves between beta-avoparcin and epi-beta-avoparcin.

Main Results:

• The N-methyl terminal amino acid of native avoparcin exhibits R-configuration (negative optical rotation).
• The same amino acid from epimerized avoparcin shows S-configuration (positive optical rotation).
• Distinct CD curves were observed for beta-avoparcin and epi-beta-avoparcin.

Conclusions:

• Avoparcin undergoes epimerization, leading to a change in the stereochemistry of its terminal amino acid.
• The study elucidates the absolute stereochemistry of avoparcin's components and their epimerized forms.
• Protonation of the N-methyl group may influence the antibacterial activity of avoparcin.