Jean-Bernard Baudin

A Blue-Absorbing Photolabile Protecting Group for in Vivo Chromatically Orthogonal Photoactivation

The small and synthetically easily accessible 7-diethylamino-4-thiocoumarinylmethyl photolabile protecting group has been validated for uncaging with blue light. It exhibits a significant action cross-section for uncaging in the 470-500 nm wavelength range and a low light absorption between 350 and 400 nm. These attractive features have been implemented in living zebrafish embryos to perform chromatic orthogonal photoactivation of two biologically active species controlling biological development with UV and blue-cyan light sources, respectively.

Excited-state relaxation dynamics of a PYP chromophore model in solution: influence of the thioester group

Abstract Cis–trans photoisomerization of a photoactive yellow protein chromophore model, the deprotonated trans S -phenyl thio- p -hydroxycinnamate, is studied in aqueous solution by subpicosecond transient absorption and gain spectroscopy. The excited-state deactivation is found to involve the formation, in 1.7 ps, of an intermediate state which decays in 2.8 ps. A persistent bleaching signal is observed at longer times indicating that the excited state not only relaxes to the ground state but also partly forms a stable photoproduct, possibly the cis isomer. This behavior is analogous to that of the native photoactive yellow protein.

Coumarinylmethyl Caging Groups with Redshifted Absorption

The small and synthetically easily accessible coumarinylmethyl backbone has been modified to generate a family of photolabile protecting groups with redshifted absorption. We relied on introducing electron-donating groups in the 7 position and electron-withdrawing groups in the 2-, and 2- and 3 positions. In particular, we showed that the diethylamino-thiocoumarylmethyl and the diethylamino-coumarylidenemalononitrilemethyl are relevant for uncaging with cyan light. They both exhibit a significant action cross section for uncaging in the 470-500 nm wavelength range and a low light absorption between 350 and 400 nm. These attractive features are favorable to perform chromatic orthogonal photoactivation with UV and blue-cyan light sources, respectively.

Alcohol Uncaging with Fluorescence Reporting: Evaluation of o-Acetoxyphenyl Methyloxazolone Precursors

This paper evaluates a series of photolabile protecting groups with built-in fluorescence reporting. They rely on readily available o-acetoxyphenyl methyloxazolones as activated precursors. Alcohol substrates are easily caged. The resulting photoactivable esters exhibit large one- and two-photon uncaging cross sections. The alcohol substrates are quantitatively released in a 1:1 molar ratio with a strongly fluorescent coumarin coproduct that serves as a reporter to quantify substrate delivery.

2‐Hydroxyazobenzenes to Tailor pH Pulses and Oscillations with Light

This paper evaluates the 2-hydroxyazobenzene platform for tailoring proton concentration pulses and oscillations with monochromatic light. The easily prepared 2-hydroxyazobenzenes exhibit large absorptions in the near-UV range. Photoisomerization was investigated by UV/Vis absorption, (1)H NMR spectroscopy, and steady-state fluorescence emission. In the whole investigated series, the trans stereoisomer of the 2-hydroxyazobenzene motif provides the corresponding cis derivative with an action cross section in the 10(3) M(-1) cm(-1) range. At the same time, photoisomerization is accompanied by a significant pK drop of the phenol group. According to the phenyl-substituent pattern, cis-to-trans thermal back-isomerization can be tuned in the 10 ms-100 s range. Up to 2 units of reversible pH drops or pH oscillations on the 10 s timescale have been obtained by appropriately tailoring single-wavelength illumination of 2-hydroxyazobenzene solutions.

A hyperpolar, multichromophoric cyclodextrin derivative: synthesis, and linear and nonlinear optical properties.

A chiral, highly polar, multichromophoric supermolecule has been designed by gathering seven push-pull chromophores onto a beta-cyclodextrin assembling unit through covalent flexible linkers. The photophysical and nonlinear optical properties of this mutichromophoric conical bundle were investigated and compared with those of the monomeric chromophore. The strongly absorbing multichromophoric system combines interesting features: it has a high molecular first-order hyperpolarisability and a very large dipolar moment (u = 38 D) which reveal a self-arrangement of the dipolar chromophores within the supermolecule. The confinement of the push-pull chromophores within the nanoscopic bundle affects their optical properties and promotes interactions: the multichromophoric supermolecule is hypochromically and hypsochromically shifted with respect to its monomeric analogue. In addition, the close proximity promotes excitonic coupling, as well as excimer formation phenomena.

N-aryl-ethenesulphenamides; thermal transformation of two N-)1-naphthyl)-ethenesulphenamides into 1H-benz[g]indoles

Abstract Reaction of vinylmagnesium bromide with morpholine or piperidine-N-sulphenyl chlorides 3a , b affords the N-ethenylthio-morpholine and -piperidine 4a , b . When treated with stoichiometric amounts of an arylamine and methanesulphonic (or trifluoroacetic) acid, the sulphenamides 4 are converted into N-aryl-ethenesulphenamides 6a - e . On heating in toluene, two of these sulphenamides 6d and 6e undergo [3.3]-sigmotropic rearrangements followed by cyclisation of the intermediate amino-thioaldehydes yielding the corresponding 1H-benz[g]indoles 8a , b .

Organic syntheses with sulfones noxxxvi: conversion of sulfones into aldehydes and ketones.

Abstract Alkyl and allyl sulfones can be converted into boronic esters, oxidation of which leads to aldehydes or ketones.

Unsaturated sulfinamides III. Conversion of several 4-(2'-alkenesulfinyl)-morpholines into the corresponding sulfinate esters, unsymmetrical bisallylic sulfones and olefins. isolation of some functionalised 2-alkenesulfinic acids

The boron trifluoride etherate-catalysed treatment of the unsaturated sulfinamides (1a–1e) with simple saturated alcohols afforded the corresponding alkyl sulfinates 2 whereas allylic alcohols provided the bisallylic sulfones 4. Efficient conditions for the acid-catalysed hydrolysis of the unsaturated sulfinamides 1 are described and some allylic sulfinic acids bearing an electron-withdrawing group 6 were isolated. Smooth fragmentation of the homoconjugated sulfinic acids gave the corresponding olefins 5 and 7.

Synthesis of indoles from N-aryl-1-alkenylsulphinamides

Abstract Reaction of 1-alkenylmagnesium bromides with N-sulphinyl-benzenamines affords the title sulphinamides 5 . On heating in toluene, these sulphinamides 5 are transformed into the corresponding indoles.