Facile synthesis of linear-dendritic cholesteryl-poly(epsilon-caprolactone)-b-(L-lysine)(G2) by thiol-ene and azide-alkyne "click" reactions

The construction of a linear-dendritic block copolymer consisting of terminal cholesteryl moiety, poly(epsilon-caprolactone), and a second generation L-lysine dendron has been accomplished by the combination of copper(I) catalyzed azide-alkyne and UV-triggered thiol-ene "click" reactions. Ring-opening polymerization of E-caprolactone initiated by 5-hexyn-1-ol and Mitsunobu coupling with 4-pentenoic acid provide hetero-telechelic poly(epsilon-caprolactone) bearing terminal alkyne and alkene groups. It is then employed in the sequential "click" reactions with the azide-functionalized dendritic wedge and thiocholesterol. Near to quantitative functionalization of the intermediate and final products has been attained as confirmed by NMR spectroscopy and MALDI-TOF spectrometry.