Synthesis of biodegradable amphiphilic AB-type diblock copolymers of lactide and depsipeptide with pendant reactive groups

The syntheses of amphiphilic AB-type diblock copolymers composed of hydrophobic polylactide segment and hydrophilic polydepsipeptide segment with amino or carboxyl groups were performed. The protected cyclodepsipeptides cyclo[Glc-Lys(Z)] and cyclo[Glc-Asp(OBzl)] (where Glc is glycolic acid, Lys is lysine, Asp is aspartic acid, Z is benzyloxycarbonyl, and OBzl is benzyl) were first polymerized in tetrahydrofuran (THF) with potassium ethoxide as an initiator to obtain the corresponding protected polydepsipeptides. After the terminal hydroxyl groups of the protected polydepsipeptides were converted into the potassium alcoholates with K/naphthalene, L-lactide was polymerized in the presence of the corresponding polymeric alcoholates as macroinitiators in THF to obtain poly [Glc-Lys(Z)]-block-poly(L-lactide) and poly [Glc-Asp(OBzl)] block-poly(L-lactide). Subsequent deprotection of Z and OBzl groups gave the objective amphiphiles poly(Glc-Lys)-block-poly(L-lactide) and poly(Glc-Asp)-block-poly(L-lactide), respectively. (C) 2002 Wiley Periodicals, Inc.