JOURNAL OF POLYMER SCIENCE PART A: POLYMER CHEMISTRY DOI 10.1002/POLA
hindrance is supported by the 1H and 13C spectra of T2. In Fig-
ure 7, we generally see doubling peaks for most chemical equiv-
alent germinal or ring protons. Specifically, the two methylene
groups adjacent to pyridine rings show different chemical shifts.
Moreover, two protons of the same methylene group have dif-
ferent chemical shifts. As a comparison, a singlet is observed
for those protons at bis(picolylamine) chelator ligand system.
Two pyridine rings have different proton chemical shifts too,
and similar effects were observed in the 13C NMR spectra. We
believe the ‘‘doubling’’ of the otherwise equivalent protons is
caused by the rigidity of the L-lactide backbone. As such, T2 or
its likes do not form complex with [Re(CO)3]þ core.
mun 2009, 493–512; (c) Jennings, L. E.; Long, N. J. Chem Commun
2009, 3511–3524; (d) Maresca, K. P.; Hiller, S. M.; Femia, F. J.; Zim-
merman, C. N.; Levadala, M. K.; Banerjee, S. R.; Hicks, J.; Sundar-
arajan, C.; Valliant, J.; Zubieta, J.; Eckelman, W. C.; Joyal, J. L.;
Babich, J. W. Bioconjug Chem 2009, 20, 1625–1633.
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2548–2550; (b) Saitoh, M.; Fujisaki, S.; Ishii, Y.; Nishiguchi, T.
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11 Thomas, A. A.; Kim, I. T.; Kisera, P. F. Tetrahedron Lett
2008, 46, 8921–8925.
CONCLUSIONS
12 (a) Stephenson, K. A.; Banerjee, S. R.; Besanger, T.; Sogbein,
O. O.; Levadala, M. K.; McFarlane, N.; Lemon, J. A.; Boreham, D.
R.; Maresca, K. P.; Brennan, J. D.; Babich, J. W.; Zubieta, J.; Val-
liant, J. F. J Am Chem Soc 2004, 126, 8598–8599; (b) Levadala, M.
K.; Banerjee, S. R.; Maresca, K. P.; Babich, J. W.; Zubieta, J. Syn-
thesis 2004, 11, 1759–1766; (c) Bartholoma, M.; Valliant, J.; Mar-
esca, K. P.; Babich, J.; Zubieta, J. Chem Commun 2009, 493–512.
The successful synthesis of well-defined oligomers of (L)-LA and
LA–PEG cooligomer is expected to provide new insights into the
design of systems on drug payload and controlled release. A
range of substrates were explored for DMAP-catalyzed transes-
terification. The coordination of fac-[Re(CO)3]þ by these oligom-
ers opens up an avenue to creating reagents for applications in
SPECT image or chemotherapy using these biocompatible
oligomers. In fact, failure of T2 complex implies that we have to
consider steric effects in designing those biocompatible oligom-
ers. Further research and related evaluation on oligomers la-
beled with radioactive nuclides such as 99mTc and 186/188Re is in
progress and will be reported in due course.
13 Alberto, R.; Schibli, R.; Egli, A.; Schubiger, P. A.; Herrmann,
W. A.; Artus, G.; Abram, U.; Kaden, T. A. J Organomet Chem
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This work was supported by the National Natural Science
Foundation of China (No. 81071250) and Hundreds Talent
Program of Chinese Academy of Sciences (No. 26200601).
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