Genera/ procedure:The linear depsipeptide is dissolved together with 2 equiv. of o-phenylene chlorophosphite in diethyl phosphite and heated under nitrogen at a bath temperature of 100-C. For cyclization a solution of 3 equiv. of triethylamine dissolved in 10 ml of diethyl phosphite is added dropwise to the reaction mixture with vigorous stirring. The reaction mixture is stirred for 30 min at the above temperature, then cooled and evaporated under oil-pump vacuum. The oily residue is dissolved in methylene dichloride, extracted with 10% NaHC03 solution, and then with water. After evaporation, the residue is chromatographed on Sephadex LH 20 (eluant : methanol); the oligomeric cyclodepsipeptides are obtained from the fractionated eluates.