Reaction of carbohydrates and pentacoordinate oxaphosphorane and their biomimetic mechanism
The reaction of D-hexoses, D-pentose and organic pentacoordinate 1, 3, 2-dioxaphospholene were investigated. The observation showed that there were obvious differences of reaction ratio, intermediate, and final products in the reactions between hexoses an
Diisocyanates containing hydantoin groups and polyurethanes in which they are present
Diisocyanates of the formula (I) where R1is a C1-C10-hydrocarbon radical and R3is a C1-Cl2-hydrocarbon group and n is an integer from 1 to 10, are described.
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(2008/06/13)
Photochemistry of phosphate esters: α-keto phosphates as a photoprotecting group for caged phosphate
Irradiation of two families of α-keto phosphates yielded rearrangement products and deprotected phosphates as the major products. For both sets of reactants, the triplet excited state of the ketone reacted with quantum efficiencies that ranged from 0.10 to 0.38. Desyl phosphates yielded 2-phenylbenzo[6]furan independent of the nature of the solvent whereas phosphate esters of α-hydroxy-p-methoxyacetophenone rearranged to esters of p-methoxyphenylacetic acid. In all cases, the phosphate group with the remaining ligands intact was released in nearly quantitative yield. The desyl group was further developed as a cage ligand for cAMP. Upon photolysis, the desyl caged ester of cAMP (13) quantitatively released the nucleotide with a quantum efficiency of 0.33 ± 0.01 and a unimolecular rate constant of 7.1 × 108s-1. Additional synthetic, product, and mechanistic studies are reported for the two series of α-keto phosphates.
Givens, Richard S.,Athey, Phillip S.,Matuszewski, Bogdan,Kueper III, L. William,Xue, Jie-You,Fister, Thomas
p. 6001 - 6012
(2007/10/02)
Dynamic Equilibria between Pentavalent Protonated Oxyphosphoranes and Their Isomeric Tetravalent Enol Phosphonium Ions via Inter- and Intramolecular Proton Transfer
Low-temperature NMR (1H, 13C, 31P) measurements of the reaction of several pentavalent oxyphosphoranes with FSO3H in CH2Cl2 are described.Rapid equilibria between the neutral oxyphosphoranes and the enol phosphonium ions involving an intermolecular proton transfer can be obtained by implying certain structural constraints on the system, which means that less entropy has to be expended in order to obtain the rigid closed form of the protonated oxyphosphorane.Moreover, in one case evidence is presented for an intramolecular proton-exchange process which is also controlled by an intermediary pentavalent protonated oxyphosphorane.These reactions may be regarded as a model for intramolecular (biological) phosphorylation processes.
Castelijns, Marianne M. C. F.,Schipper, Pieter,Aken, Dirk van,Buck, Henk M.
p. 47 - 53
(2007/10/02)
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