Two-Photon Uncaging with Fluorescence Reporting:  Evaluation of the o-Hydroxycinnamic Platform

Abstract

This paper evaluates the o-hydroxycinnamic platform for designing efficient caging groups with fluorescence reporting upon one- and two-photon excitation. The model cinnamates are easily prepared in one step by coupling commercial or readily available synthons. They exhibit a large one-photon absorption that can be tuned in the near-UV range. Uncaging after one-photon excitation was investigated by 1H NMR, UV-vis absorption, and steady-state fluorescence emission. In the whole investigated series, the caged substrate is quantitatively released upon photolysis. At the same time, uncaging releases a strongly fluorescent coproduct that can be used as a reporter for quantitative substrate delivery. The quantum yield of double bond photoisomerization leading to uncaging after one-photon absorption mostly lies in the 10% range. Taking advantage of the favorable photophysical properties of the uncaging coproduct, we use a series of techniques based on fluorescence emission to measure the action uncaging cross sections with two-photon excitation of the present cinnamates. Exhibiting values in the 1-10 GM range at 750 nm, they satisfactorily compare with the most efficient caging groups reported to date. Noticeably, the uncaging behavior with two-photon excitation is retained in vivo as suggested by the results observed in living zebrafish embryos. Reliable structure property relationships were extracted from analysis of the present collected data. In particular, the careful kinetic analysis allows us to discuss the relevance of the o-hydroxycinnamic platform for diverse caging applications with one- and two-photon excitation.

Ethyl Cinnamate Derivatives as Promising High-Efficient Acaricides against <i>Psoroptes cuniculi</i>: Synthesis, Bioactivity and Structure–Activity Relationship

“…42 43) Compounds 10 and 13-15 were obtained by typical methyl-etherification or acetylation reaction of the corresponding hydroxyl-substituted trans-cinnamic acid esters (7)(8)(9). Compound 29 was synthesized by Horner-Wadsworth-Emmons (HWE) reaction of benzaldehyde with ethyl 2-(bis(2-(tert-butyl) phenoxy) phosphoryl) acetate in 73% yield.…”

“…(E)-Ethyl Cinnamate (6) 8 and 9) to yield the desired compounds according to the reported method 43) with slight modification. After removal of the solvent, the resulting residue was subjected to a short silica gel column chromatography (ϕ40 mm×L 40 mm) using petroleum ether-ethyl acetate as eluent to remove polar triphenylphosphine oxide.…”

Intracellular Photoactivation and Quantification Using Fluorescence Microscopy: Chemical Tools and Imaging Approaches

“…The Porter [27] and Jullien groups [28,29] developed a conceptually different fluorogenic, photoremovable protecting group. These trans-cinnamic acid derivatives release the molecule of interest triggered by a photoinduced cis-trans isomerization and subsequent intramolecular lactonization (Scheme 2b).…”

“…[27] In particular, compound 6 (Fig. 1) has the advantage of being efficiently activated under two-photon excitation conditions, [28,29] which is desirable because light of longer wavelength displays deeper penetration into non-translucent media. Exploiting the large contrast in fluorescence between the protected (transcinnamic acid) and activated (coumarin) product, the photoinduced release of cytosolic ethanol from the cinnamic ester in zebrafish embryos was quantified via fluorescence correlation spectroscopy.…”

“…Exploiting the large contrast in fluorescence between the protected (transcinnamic acid) and activated (coumarin) product, the photoinduced release of cytosolic ethanol from the cinnamic ester in zebrafish embryos was quantified via fluorescence correlation spectroscopy. [28,29] tive microscopy because the stoichiometric release of a fluorescent reporter makes it possible to quantify the amount of released (bio-)molecule.…”