7651-83-4Relevant articles and documents
A solution- and solid-state investigation of medium effects on charge separation in metastable photomerocyanines
Patel, Dinesh G.,Paquette, Michelle M.,Kopelman, Roni A.,Kaminsky, Werner,Ferguson, Michael J.,Frank, Natia L.
, p. 12568 - 12586 (2010)
The effects of solution-state dielectric and intermolecular interactions on the degree of charge separation in metastable spirooxazine photomerocyanines (PMCs) is investigated. We report the first X-ray diffraction (XRD) analyses of an open form, a metastable photomerocyanine, of the spirooxazine class of photochromic molecules in two derivatives: spiro[azahomoadamantane- isoquinolinoxazine] (1) and spiro[azahomoadamantane-phenanthrolinoxazine] (2). Using the results of XRD analysis of the open photomerocyanine forms, in conjunction with computation, solvatochromism, and solution NMR studies, we have investigated the effect of the medium on the ground-state structure of these photomerocyanines. Solvatochromism and NMR chemical shift studies of 1 and 2 support the assignment of a quinoidal structure in nonpolar solvents and a zwitterionic structure in high-polarity solvents. The effect of azahomoadamantyl substitution is explored by comparing 1 and 2 with the analogous indolyl derivatives, spiro[indoline-isoquinolinoxazine] (3) and spiro[indoline- phenanthrolinoxazine] (4) through XRD analysis of the closed spirooxazine (SO) forms, solution-state kinetic experiments, solvatochromism, and NMR studies. Longer Cspiro-O bond lengths in the SO form and slower rates of thermal PMC → SO isomerization for the azahomoadamantyl derivatives are associated with greater zwitterionic character in the PMC form, as found in the solvatochromism studies. XRD analysis of photomerocyanines 1 and 2 indicate a greater contribution from the canonical zwitterionic resonance form relative to the quinoidal form in the solid state. Structural differences observed in two pseudopolymorphs of 2-PMC suggest that the degree of charge-separated character is influenced by the crystal packing environment. These results provide direct structural evidence for the effects of the medium polarity on charge-separated states of photomerocyanines.
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Tsizin,Yu.S.
, (1974)
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Total synthesis of (±)-cortistatin J from furan
Nilson, Mark G.,Funk, Raymond L.
supporting information; experimental part, p. 12451 - 12453 (2011/10/09)
A concise, diastereoselective total synthesis of (±)-cortistatin J has been completed in 20 steps from furan. Key steps include an intramolecular [4 + 3] cyclization of a disubstituted furan with a (Z)-2-(trialkylsilyloxy)-2- enal to construct the tetracyclic core and a (Z)-vinylsilane/iminium ion cyclization to form the A ring.
Highly potent and selective zwitterionic agonists of the δ-opioid receptor. Part 1
Middleton, Donald S.,Maw, Graham N.,Challenger, Clare,Jessiman, Alan,Johnson, Patrick S.,Million, William A.,Nichols, Carly L.,Price, Jenny A.,Trevethick, Michael
, p. 905 - 910 (2008/12/20)
A series of zwitterionic δ-opioid agonists, with targeted physicochemistry, as a strategy to limit potential for CNS exposure, were prepared. These agents were found to possess exquisite potency and selectivity over mu and κ-opiate activity. Furthermore,
