scholarly journals p-Hydroxyphenacyl photoremovable protecting groups — Robust photochemistry despite substituent diversity

2011 ◽  
Vol 89 (3) ◽  
pp. 364-384 ◽  
Author(s):  
Richard S. Givens ◽  
Kenneth Stensrud ◽  
Peter G. Conrad ◽  
Abraham L. Yousef ◽  
Chamani Perera ◽  
...  
Keyword(s):  
Aqueous Media ◽  
Protecting Groups ◽  
Quantum Yields ◽  
Photochemical Rearrangement ◽  
Favorskii Rearrangement ◽  
Leaving Group ◽  
Predominant Form ◽  
Photoremovable Protecting Groups ◽  
Conjugate Base ◽  
Modest Effect

A broadly based investigation of the effects of a diverse array of substituents on the photochemical rearrangement of p-hydroxyphenacyl esters has demonstrated that common substituents such as F, MeO, CN, CO2R, CONH2, and CH3 have little effect on the rate and quantum efficiencies for the photo-Favorskii rearrangement and the release of the acid leaving group or on the lifetimes of the reactive triplet state. A decrease in the quantum yields across all substituents was observed for the release and rearrangement when the photolyses were carried out in buffered aqueous media at pHs that exceeded the ground-state pKa of the chromophore where the conjugate base is the predominant form. Otherwise, substituents have only a very modest effect on the photoreaction of these robust chromophores.

scholarly journals Fluorinated photoremovable protecting groups: the influence of fluoro substituents on the photo-Favorskii rearrangement

2008 ◽  
Vol 7 (5) ◽  
pp. 614 ◽  
Author(s):  
Kenneth F. Stensrud ◽  
Dominik Heger ◽  
Peter Šebej ◽  
Jakob Wirz ◽  
Richard S. Givens
Keyword(s):  
Protecting Groups ◽  
Favorskii Rearrangement ◽  
Photoremovable Protecting Groups

scholarly journals Biocompatible Ir(III) Complexes as Oxygen Sensors for Phosphorescence Lifetime Imaging

Molecules ◽  
2021 ◽  
Vol 26 (10) ◽  
pp. 2898
Author(s):  
Ilya S. Kritchenkov ◽  
Anastasia I. Solomatina ◽  
Daria O. Kozina ◽  
Vitaly V. Porsev ◽  
Victor V. Sokolov ◽  
...  
Keyword(s):  
Near Infrared ◽  
Biological Systems ◽  
Aqueous Media ◽  
Oxygen Sensors ◽  
Quantum Yields ◽  
Complete Agreement ◽  
Phosphorescence Lifetime ◽  
Lifetime Imaging ◽  
Nir Emission ◽  
Phosphorescence Lifetime Imaging

Synthesis of biocompatible near infrared phosphorescent complexes and their application in bioimaging as triplet oxygen sensors in live systems are still challenging areas of organometallic chemistry. We have designed and synthetized four novel iridium [Ir(N^C)2(N^N)]+ complexes (N^C–benzothienyl-phenanthridine based cyclometalated ligand; N^N–pyridin-phenanthroimidazol diimine chelate), decorated with oligo(ethylene glycol) groups to impart these emitters’ solubility in aqueous media, biocompatibility, and to shield them from interaction with bio-environment. These substances were fully characterized using NMR spectroscopy and ESI mass-spectrometry. The complexes exhibited excitation close to the biological “window of transparency”, NIR emission at 730 nm, and quantum yields up to 12% in water. The compounds with higher degree of the chromophore shielding possess low toxicity, bleaching stability, absence of sensitivity to variations of pH, serum, and complex concentrations. The properties of these probes as oxygen sensors for biological systems have been studied by using phosphorescence lifetime imaging experiments in different cell cultures. The results showed essential lifetime response onto variations in oxygen concentration (2.0–2.3 μs under normoxia and 2.8–3.0 μs under hypoxia conditions) in complete agreement with the calibration curves obtained “in cuvette”. The data obtained indicate that these emitters can be used as semi-quantitative oxygen sensors in biological systems.

scholarly journals Competing pathways for photoremovable protecting groups: the effects of solvent, oxygen and encapsulation

2020 ◽  
Vol 19 (10) ◽  
pp. 1364-1372
Author(s):  
Thomas Field ◽  
Julie Peterson ◽  
Chicheng Ma ◽  
Pradeepkumar Jagadesan ◽  
José P. Da Silva ◽  
...  
Keyword(s):  
Reaction Mechanism ◽  
Protecting Groups ◽  
Photoremovable Protecting Groups ◽  
Competing Pathways

Photolysis of p-hydroxyphenacyloxy arenes releases free phenols in good yields governed by their pKa. At high pKa, new byproducts (Bvs. A) reveal a change in reaction mechanism.

scholarly journals A general strategy for visible-light decaging based on the quinone cis-alkenyl lock

2019 ◽  
Vol 55 (34) ◽  
pp. 4965-4968 ◽  
Author(s):  
David P. Walton ◽  
Dennis A. Dougherty
Keyword(s):  
Visible Light ◽  
Protecting Groups ◽  
General Strategy ◽  
Thermal Cyclization ◽  
Coumaric Acid ◽  
Photoremovable Protecting Groups

Combining the fast thermal cyclization of o-coumaric acid derivatives with the intramolecular photoreduction of quinones gives new visible-light photoremovable protecting groups absorbing well above 450 nm.

scholarly journals Synthesis of Caged Nucleosides with Photoremovable Protecting Groups Linked to Intramolecular Antennae

2005 ◽  
Vol 88 (4) ◽  
pp. 891-904 ◽  
Author(s):  
Joulia Smirnova ◽  
Dominik Wöll ◽  
Wolfgang Pfleiderer ◽  
Ulrich E. Steiner
Keyword(s):  
Protecting Groups ◽  
Photoremovable Protecting Groups

Kinetics of the equilibration of 3-hydroxyphthalide and o-formylbenzoic acid. Hemiacetal breakdown with a carboxylic acid leaving group

1986 ◽  
Vol 64 (6) ◽  
pp. 1196-1200 ◽  
Author(s):  
Robert A. McClelland ◽  
Poule E. Sørensen
Keyword(s):  
Carboxylic Acid ◽  
Ring Opening ◽  
Temperature Jump ◽  
Acid Catalyst ◽  
Concerted Mechanism ◽  
Leaving Group ◽  
Relaxation Study ◽  
Acid Catalyzed ◽  
Kinetics Of ◽  
Conjugate Base

A temperature-jump relaxation study is reported for the equilibration: 3-hydroxyphthalide (SH) [Formula: see text]o-formylbenzoate (R−) [Formula: see text]o-formylbenzoic acid (RH). A kinetic analysis is carried out in which SH and R− interconvert with catalysis in the ring opening direction by water and by added general bases. Excellent Brønsted plots based upon a series of oxyacid buffer catalysts are obtained. These have slopes β for the base-catalyzed ring opening of 0.81 and α for the reverse acid-catalyzed ring closing of 0.19. A mechanism where S−, the conjugate base of SH, is a discrete intermediate can be ruled out on the basis of the Brønsted values and the magnitudes of the rate constants. The lifetime of S− is estimated to lie in the range 10−11–10−15 s. Two mechanisms can be proposed. A fully concerted mechanism "enforced" by lifetimes less than 10−13 s involves direct interconversion of SH and R− with no intermediate. A preassociated mechanism "enforced" by lifetimes in the 10−11–10−12 s range requires, in the ring closing direction, that an acid catalyst be hydrogen bonded to the carbonyl in R−.

Molecular Engineering of Photoremovable Protecting Groups for Two-Photon Uncaging

2008 ◽  
Vol 120 (49) ◽  
pp. 9667-9671 ◽  
Author(s):  
Sylvestre Gug ◽  
Frédéric Bolze ◽  
Alexandre Specht ◽  
Cyril Bourgogne ◽  
Maurice Goeldner ◽  
...  
Keyword(s):  
Molecular Engineering ◽  
Protecting Groups ◽  
Two Photon ◽  
Photoremovable Protecting Groups
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