mPEG-P(5BZTMC) as pendant precursor for pro-drug conjugation

PolySciTech (www.polyscitech.com) provides block copolymers of 5-benzyloxy-trimethylene carbonate (e.g. Polyvivo AK78).  This polymer has an inherent benefit of added hydrophobicity from the benzyloxy unit however there is another usage of this material. The Benzyloxy unit acts as a leaving group and can be readily removed by reacting the polymer with hydrogen gas using palladium on carbon catalyst. This leaves a pendant hydroxyl available for a wide array of further conjugation reactions. An example of the usage of this and chemical details for a similar polymer can be seen here: Xie, Zhigang, Huili Guan, Changhai Lü, Xuesi Chen, and Xiabin Jing. "Synthesis and characterization of novel biotinylated biodegradable poly (ethylene glycol)- b-poly (carbonate-lactic acid) copolymers." Acta biomaterialia 1, no. 6 (2005): 635-641. http://www.sciencedirect.com/science/article/pii/S1742706105001121

“Abstract: Poly(ethylene glycol)-b-poly(5-benzyloxy-trimethylene carbonate-lactic acid) copolymers (PEG-b-P(BTMC-LA)) were synthesized by ring-opening polymerization of lactide and 5-benzyloxy trimethylene carbonate in the presence of mono-hydroxyl poly(ethylene glycol) with diethyl zinc as catalyst. They were further converted into deprotected copolymers with the pendant hydroxyl groups by hydrogenolysis in the presence of Pd(OH)2/C, and finally conjugated with biotin through the free hydroxyl groups. Gel permeation chromatography, Fourier transform infrared, differential scanning calorimetry and 1H nuclear magnetic resonance studies confirmed the copolymer structures and successful attachment of biotin to the copolymer. Keywords: Biotin; Diethyl zinc; Polycarbonate; Polylactide”