Crystal structure of a depsipeptide, Boc-(Leu-Leu-Lac)3-Leu-Leu-OEt

A sequential polydepsipeptide, Boc-(Leu-Leu-Lac)3-Leu-Leu-OEt (1) (Lac = L-lactic acid residue) has been synthesized by the segment condensation method. The sequential unit of 1, -Leu-Leu-Lac-, is consisted of two amino acid residues and one hydroxy acid residue. X-ray diffraction measurement with an imaging plate detector and a direct-methods procedure of Shake-and-Bake successfully revealed the crystal structure of 1. In the solid state, the 11-mer depsipeptide, 1, have clear alpha-helical conformation even with the three ester linkages.