Kinetic study of the reaction between hydroxylated polybutadienes and isocyanates. 1. Reaction with tolylene diisocyanate (TDI)

A comparative kinetic study of the reaction of three different hydroxylated liquid polybutadienes (M _n ? 3000) — R - 45M, R-45HT, and H-034—and tolylene diisocyanate (TDI), was carried out in toluene solution. An analytical method was used to follow the kinetics of the reactions at four different temperatures. The reactions presented an apparent second-order rate law. In the second-order plots, a discontinuity was observed. The R-45M polybutadiene was about twice more reactive than R-45HT and H-034; these latter two polybutadienes presented similar reactivities.     

Synthesis and analysis of aminochromes by HPLC-photodiode array. Adrenochrome evaluation in rat blood

The catecholamine oxidation process induces cardiotoxicity and neurotoxicity. Catecholamines can oxidize to aminochromes through autoxidation or by enzymatic or non-enzymatic catalysis. Although some toxic effects seem to be related to the formation of aminochromes there is still scarce information concerning the identification and evaluation of these compounds in in vivo models. In this study five catecholamines were oxidized to their respective aminochromes: adrenaline/adrenochrome; noradrenaline/noradrenochrome; dopa/dopachrome; dopamine/dopaminochrome; and isoproterenol/isoprenochrome. The evaluation of the catecholamines oxidation profile was performed by HPLC with photodiode array detection and using either enzymatic (tyrosinase) or non-enzymatic [Ag(2)O, CuSO(4), NaIO(4) and K(3)Fe(CN)(6)] catalytic systems. The NaIO(4) was found to be the most efficient oxidant of catecholamines. An isocratic reverse-phase HPLC method was developed to analyse each pair of catecholamine-aminochrome. The analytical system was then applied to the detection of adrenochrome in rat blood at 490 nm. Thus, adrenochrome was administered i.p. to rats and its concentration in whole blood was monitored after 5, 15 and 25 min. Blood treatment for adrenochrome evaluation consists of an acidification for protein precipitation followed by a rapid neutralization. The results showed a rapid decrease of adrenochrome concentration in blood after its administration. The adrenochrome present in blood was characterized by UV and tandem mass spectrometry.     

PROPERTIES OF A NEW STATE OF HEMATOPORPHYRIN IN DILUTE AQUEOUS SOLUTION

Abstract —Dilute aqueous hematoporphyrin undergoes a transformation after standing at room temperature leading to a shift of the Soret peak from 395 nm to 405 nm, disappearance of visible bands I (610 nm) and IV (503 nm), a shift of the first emission band from 615 nm to 580 nm, and fluorescence polarization at room temperature. The transformation was accelerated by heating and was faster for more dilute solutions. It did not take place in ethanol, 99:1 glycerol-water, or in small egg lecithin liposomes. It was rapid in SDS micelles and did not occur in CTAB and Triton X-100 micelles. Low concentrations of divalent zinc and copper increased the rate of transformation, but the product was not the corresponding metal ion ligand. The transformation was fast with uroporphyrin I and fast but incomplete with hematoporphyrin derivative. The methyl esters of hematoporphyrin IX and uroporphyrin I did not transform. The tentative identification of the transformed product is a tightly-bound linear micelle, oriented such that the central hydrogens of the free base monomer units are anti-parallel.     

Generation of Singlet Molecular Oxygen by Lipid Hydroperoxides and Nitronium Ion†

Singlet molecular oxygen is a reactive species involved in biological oxidative processes. The major cellular targets of singlet molecular oxygen are unsaturated fatty acids in the membrane, as well as nucleic acids and proteins. The aim of this study was to investigate whether lipids and commercial hydroperoxides generate singlet molecular oxygen, in presence of nitronium and activated nitronium ion. For this purpose, monomol light emitted in the near-infrared region (λ = 1270 nm) was used to monitor singlet molecular oxygen decay in different solvents, with different hydroperoxides and in the presence of azide. Direct measurements of the singlet molecular oxygen spectrum at 1270 nm recorded during the reaction between lipids and commercial hydroperoxides and nitronium ions unequivocally demonstrated the formation of this excited species.     

The first intramolecular Heck-Matsuda reaction and its application in the syntheses of benzofurans and indoles

In this Letter, we report, for the first time, the development of an efficient method for the intramolecular Heck reaction of arenediazonium salts in the synthesis of benzofuran and indole derivatives. In addition, this methodology allowed the synthesis of a series of dihydrobenzofuran acetic acid derivatives via a domino Heck-Matsuda coupling-carbonylation reaction.