Epimerization and stereochemistry of avoparcin.

Abstract

The epimerization of avoparcin entities is discussed in some detail. The absolute stereochemistry of avoparcin is now known since the N-methyl terminal amino acid of the aglycone was isolated and shown to exhibit negative optical rotation, and hence has the R-configuration. The same amino acid was isolated from an epimerized solution of avoparcin and found to have positive rotation and hence the S-configuration. A comparison is made of the circular dichroism curves of .beta.-avoparcin and epi-.beta.-avoparcin. Some discussion on the effect of protonation of the terminal N-methyl group on the antibacterial activity of avoparcin is included.