New Photoremovable Protecting Groups for Carboxylic Acids with High Photolytic Efficiencies at Near‐UV Irradiation. Application to the Photocontrolled Release of L‐Glutamate

Abstract

We report here the syntheses and the photolytic properties of 3-(4,5-dimethoxy-2-nitrophenyl)-2-butyl (DMNPB) esters as new photoremovable groups for carboxylic acids, and their use for the caging of L-glutamate. A high-yielding synthesis of the DMNPB esters led to a 4:1 threo/erythro diastereomeric mixture, which could be separated by HPLC. While these esters were stable in neutral buffer, photolysis at 364 nm induced a > or =95 % release of the carboxylic acid, with a 0.26 quantum yield for L-glutamate formation. L-Glutamate release was also possible by two-photon photolysis with an action cross section of 0.17 GM at 720 nm. Laser photolysis at 350 nm generated a transient species at around 410 nm, attributed to a quinonoid aci-nitro intermediate that decayed in the submillisecond time range (t(1/2)=0.53 ms) for the faster gamma-L-glutamyl threo-esters. Given the absorbance of these esters (lambda(max)=350 nm; epsilon=4500), the threo DMNPB esters represent new caging groups that can be efficiently photolyzed at near-UV wavelengths. An efficient and rapid photolytic release of L-glutamate has been demonstrated on hippocampal neurons in primary culture.

Retraction: Development of Anionically Decorated 2‐(ortho‐Nitrophenyl)‐Propyl‐Caged Neurotransmitters for Photolysis in vitro and in vivo

“…Recently, dimethoxy [32] and anisyl [33] derivatives of NPP caged Glu have been reported (Table 1). However, these caged compounds require a significant amount of organic cosolvent to enable these caged compounds to be used on brain slices.…”

“…We found that dcANPP-Glu produced changes in membrane voltage that were similar to those evoked by photolysis of MNI-Glu. [17,20] For MNI-Glu we have used a laser energy 10 mW for 0.2 ms at a wavelength of 720 nm, and probe concentration 10 mm, [17] whereas we used 10 mW at 720 nm for 0.1 ms with 8 mm dcANPP-Glu; this implies that the two-photon cross-section of dcANPP-Glu is twice that of MNI-Glu, and almost identical to DMNPB-Glu [14,32] but significantly lower than ANPP-Glu [33] and BNSF-Glu. [14] Finally, we should add that we observed no photoevoked currents at 800 nm.…”

Two‐Photon Uncaging with the Efficient 3,5‐Dibromo‐2,4‐dihydroxycinnamic Caging Group

“…[2] This value makes the ortho-hydroxycinnamic caging platform one of the most efficient available to date. [2,3,[14][15][16] Figure 1. Optical-syringe strategy (a zebrafish embryo is used for illustration).…”

“…Such a value exceeds by a factor of 40 the uncaging action cross section for the most popular 4,5-dimethoxy-2-nitrobenzyl photolabile protecting group [10] and satisfactorily compares with the most efficient caging groups reported to date. [2,3,[13][14][15] To facilitate implementation of the optical-syringe strategy, uncaging and excitation of the reporting fluorescent molecule should be done with the same excitation source. Coumarin 4 and caged substrate 3 do absorb light in the same wavelength range (e 4 (l max =377 nm) = 2.1 10 4 m À1 cm À1 ).…”

Phototriggering of Cell Adhesion by Caged Cyclic RGD Peptides

“…[11,12] Their UV spectra are shown in Figure 1. The photolytic properties of the caged peptide in solution were then determined quantitatively.…”