<p>Cyclic peptides having the structural formula (1) : wherein R represents an aliphatic acyl group having from 8 to 18 carbon atoms or a hydrogen atom; and their salts, esters and amides. The acylated peptides and their pharmaceutically acceptable salts, esters and amides, are active against Gram-positive bacteria including multi-drug-resistant Staphylococcus aureus (MDRSA) and methicillin-resistant Staphylococcus aureus (MRSA) .</p>
