TY - JOUR
T1 - Strain-promoted alkyne azide cycloaddition for the functionalization of poly(amide)-based dendrons and dendrimers
AU - Ornelas, Cátia
AU - Broichhagen, Johannes
AU - Weck, Marcus
PY - 2010/3/24
Y1 - 2010/3/24
N2 - Functionalization of a poly(amido)-based dendron with ethylene glycol chains (PEG) using coppercatalyzed alkyne azide cycloaddition (CuAAC) afforded dendrons with significant levels of copper contaminations, preventing the use of such materials for biological applications. We suggest that the presence of amide, PEG, and triazole functional groups allows for copper complexation, thereby preventing the separation of the copper catalyst from the final dendron. To minimize this problem, synthetic variations on CuAAC including the addition of "click" additives for copper sequestering as well as the use of copper wire as the copper source were investigated. None of these strategies, however, resulted in copper-free products. In contrast, we developed a copper-free strain-promoted alkyne azide cycloaddition (SPAAC) strategy that functionalized poly(amide)-based dendrons and dendrimers with PEG chains quantitatively under mild reaction conditions without any metal contamination. The SPAAC products were characterized by 1H and 13C NMR, 2D HSQC and COSY NMR, mass spectrometry, and elemental analysis. This is the first report on the use of SPAAC for dendrimer functionalization, and the results obtained here show that SPAAC is an important tool to the dendrimer and more general biomaterials community for the functionalization of macromolecular structures due to the mild and metal-free reaction conditions, no side products, tolerance toward functional groups, and high yields.
AB - Functionalization of a poly(amido)-based dendron with ethylene glycol chains (PEG) using coppercatalyzed alkyne azide cycloaddition (CuAAC) afforded dendrons with significant levels of copper contaminations, preventing the use of such materials for biological applications. We suggest that the presence of amide, PEG, and triazole functional groups allows for copper complexation, thereby preventing the separation of the copper catalyst from the final dendron. To minimize this problem, synthetic variations on CuAAC including the addition of "click" additives for copper sequestering as well as the use of copper wire as the copper source were investigated. None of these strategies, however, resulted in copper-free products. In contrast, we developed a copper-free strain-promoted alkyne azide cycloaddition (SPAAC) strategy that functionalized poly(amide)-based dendrons and dendrimers with PEG chains quantitatively under mild reaction conditions without any metal contamination. The SPAAC products were characterized by 1H and 13C NMR, 2D HSQC and COSY NMR, mass spectrometry, and elemental analysis. This is the first report on the use of SPAAC for dendrimer functionalization, and the results obtained here show that SPAAC is an important tool to the dendrimer and more general biomaterials community for the functionalization of macromolecular structures due to the mild and metal-free reaction conditions, no side products, tolerance toward functional groups, and high yields.
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U2 - 10.1021/ja910581d
DO - 10.1021/ja910581d
M3 - Article
C2 - 20184364
AN - SCOPUS:77949867607
VL - 132
SP - 3923
EP - 3931
JO - Journal of the American Chemical Society
JF - Journal of the American Chemical Society
SN - 0002-7863
IS - 11
ER -