Organic Letters
Letter
considered an important milestone toward developing red/
NIR-absorbing photocages for life sciences.
suggestions regarding photochemistry and Anna Grad
for her help during the work.
́
(RCNS)
Finally, the dark stability of the compounds was examined.
To our satisfaction all compounds were found to be stable, as
aqueous media (Figure S16). In addition, the stability of the
most promising candidate for biological experiments, com-
glutathione (Figure S17). Negligible changes (<10% within 2
h) were found within the time frame of the usual biological
experiments, demonstrating the potential applicability of 2 as a
caging group.
In conclusion, inspired by the photophysical features of π-
extended coumarin fluorophores, we introduced a new class of
coumarinylmethyl caging groups with red-shifted absorption,
high molar absorption coefficients, efficient uncaging cross
sections, and good aqueous solubility. All three compounds
can be activated by green light, leading to the release of a caged
model compound. These new photocages also show excep-
tionally high two-photon cross sections, making them ideal
candidates for two-photon uncaging experiments, work that is
currently underway in our group. This new design strategy
opens the way toward easily functionalized, water-soluble red-
shifted photocages for various applications in life sciences.
Nevertheless, further understanding of the photochemistry is
crucial toward the development of efficient photocages in this
region of visible light. This work, together with the
development of further red-shifted coumarin photocages with
improved features, is currently in progress in our laboratory,
and the results will be reported in due course.
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ASSOCIATED CONTENT
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ACKNOWLEDGMENTS
Present work was supported by the “Lendu
Hungarian Academy of Sciences (LP2013-55/2013), the
National Research, Development and Innovation Office
Van, B. T.; Yamada, A.; Oyama, R.; Sasaki, M.; Katan, C. Design and
Synthesis of Two-Photon Responsive Chromophores for Near-
Infrared Light-Induced Uncaging Reactions. Synthesis 2017, 49
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NKFIH-K-123917), and by the Higher Education Institu-
Responsive Chromophores for Application to Uncaging Reactions.
tional Excellence Programme of the Ministry of Human
Capacities in Hungary, within the framework of the therapeutic
thematic programme of the Semmelweis University. The
authors thank Prof. Attila Demeter (RCNS) for his valuable
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