Decarboxylative photorelease coupled with fluorescent up/down reporter function based on the aminophthalimide-serine system.

The fluorescence of caged phthalimide-serine couples 2 and 4 is up/down modulated by decarboxylative photorelease with fluorescence decrease (2) vs. moderate fluorescence increase (4) serving as reporter function.

Regio- and stereochemistry of [2 + 2] photocycloadditions of imines to alkenes: a computational and experimental study.

The [2 + 2] photocycloaddition of isoxazolines to alkenes has been studied by means of CASPT2/6-31G*//CASSCF/6-31G*. The reaction outcome is influenced by the relative ratio of imine deactivation and photocycloaddition. Analysis of the conical intersection points involved in the photoreaction shows that fast deactivation is prevented when an electron-withdrawing group is placed in any position that can affect the imine moiety.

Chiral photocages based on phthalimide photochemistry.

A new class of photoremovable protecting groups, based on a photoinduced decarboxylation reaction coupled with the elimination of the caged molecule, is described for 2-phthalimido-3-hydroxy-propionate derivatives. When derived from enantiopure N-phthaloyl- serine or threonine, the chirality of the starting amino acid is transmitted to the protected (caged) molecule. These photocages possess good properties for their use in biological systems, and the introduction of chirality opens new possibilities for the study of diastereoselective photochemistry and stereodifferentiation processes involving the release of the caged molecule.

Analysis of polymeric phenolics in red wines using different techniques combined with gel permeation chromatography fractionation.

A multiple-step analytical method was developed to improve the analysis of polymeric phenolics in red wines. With a common initial step based on the fractionation of wine phenolics by gel permeation chromatography (GPC), different analytical techniques were used: high-performance liquid chromatography-diode array detection (HPLC-DAD), HPLC-mass spectrometry (MS), capillary zone electrophoresis (CZE) and spectrophotometry. This method proved to be valid for analyzing different families of phenolic compounds, such as monomeric phenolics and their derivatives, polymeric pigments and proanthocyanidins.

The N-cyclopropylimine-1-pyrroline photorearrangement as a synthetic tool: scope and limitations.

The scope and limitations of the photorearrangement of N-cyclopropylimines to 1-pyrrolines are presented. The influence on the reactivity of different substituents throughout the cyclopropane ring and at the iminic position of the N-cyclopropylimine structure is discussed. The observed effects are interpreted from computational studies.

Mechanism of the N-cyclopropylimine-1-pyrroline photorearrangement.

We present here a combined experimental and computational investigation into the photorearrangement of N-cyclopropylimines to yield pyrrolines. We show that the photochemistry, regiochemistry, and stereochemistry of the reaction can be understood in terms of a mechanism involving barrierless evolution in three different (S(2), S(1), S(0)) singlet states and sequential decay through two different (S(2)/S(1), and S(1)/S(0)) conical intersection funnels. We provide evidence that the reaction mechanism involves the generation of a nonequilibrated (i.