The muraymycins, a family of nucleoside-lipopeptide antibiotics, were purified 
from the extract of Streptomyces sp. LL-AA896. The antibiotics were purified by 
chromatographic methods and characterized by NMR spectroscopy, degradation 
studies, and mass spectrometry. The structures of 19 compounds were established. 
The muraymycins constitute a new antibiotic family whose core structure contains 
a glycosylated uronic acid derivative joined by an aminopropane group to a 
hexahydro-2-imino-4-pyrimidylglycyl residue (epicapreomycidine) containing 
dipeptide that is further extended by a urea-valine moiety. Members of this 
family show broad-spectrum in vitro antimicrobial activity against a variety of 
clinical isolates (MIC 2 to >64 mug/mL). The muraymycins inhibited peptidoglycan 
biosynthesis. The fatty acid substituent and the presence or absence of the 
amino sugar play important roles in biological activity. One of the most active 
compounds, muraymycin A1, demonstrated protection in vivo against Staphylococcus 
aureus infection in mice (ED50 1.1 mg/kg).