The cyclic hexadepsipeptide antibiotic L-156602 (1) was found to be an inhibitor of ~aphyIatoxin C5a binding to its receptor (ICso=l.7 &tg/mL). This compound also caused nonspecific degranulation of neutrophils, but not through interactions with the C5a or other receptors. The effects of chemical modification of the structure of 1 on C5a mceptor inhibition and nonspecific actions are sported.