Rose bengal derivatives

Hearse, D.J., Kusama, Y. and Bernier, M. (1989). Rapid elec-trophysiological changes leading to arrhythmias in the aerobic rat heart. Photosensitization studies with rose bengal-derived reactive oxygen intermediates. Circ. Res. 65, 146-153. 

Bengali women to symbolize marriage. Only Bengali women wear the red spot at the center of the forehead. The decorative spot worn in the middle of the forehead by other Indian women is—today—pasted on. Much of the history of Rose Bengal has been reviewed elsewhere [241], Citations to Rose Bengal have increased in the last three or so years, and the diversity of its application has greatly expanded. Many of the Rose Bengal derivatives listed are now commercially available from either Molecular Probes or Aldrich. 

All Rose Bengal derivatives retain their general xanthene color and spectra if ionization of the -OH is supported by the solvent. The xanthene ring is symmetrical in the ionized form and we have assigned the ionized phenol the... 

Rose Bengal differs in reactivity from fluorescein and Eosin because of the iodines at C-2, C-4, C-5, and C-7 which differentiate the reactivity of the phenoxide from the carboxylate and make substitution at C-2 possible in lieu of substitution at C-6. Essentially three different kinds of Rose Bengal derivatives have been synthesized. The most common include derivatives with gegen ions other than sodium at both C-2 and C-6. Many esters of C-2 have been synthesized and compounds with a number of different gegen ions at C-6 have been reported. The rarest derivatives of Rose Bengal are the C-6 ethers, of which only three have been reported. 

Substitution at C-6. Because of the sterically imposing iodines ortho to the phenoxide, the reactivity of Rose Bengal dianion as a nucleophile is essentially entirely at the C-2 position, and most of the known Rose Bengal derivatives which have been prepared take advantage of this reactivity. Derivatives with a nonionizable substituent at C-6 are rare and only three C-6 ethers are known. All are C-2 esters, C-6 ethers, 6. 

Scheme I. Structure and Properties of Rose Bengal Derivatives...

The principle spectroscopic and photochemical properties of rose bengal derivatives recently synthesized by Lamberts and Neckers3f13,15 are shown in Thble I. These new derivatives cover the gamut of solubility, and are soluble in every solvent from water to pentane. In methylene chloride and chloroform the quantum yields of singlet oxygen are somewhat lower than they are in methanol, e.g., Table I. 

This had been proposed, namely for a Rose Bengal derivative because the yield and the rate of formation of the radicals are dependent on the light intensity. A more recent analysis of the process performed in a micellar environment seems to agree with an alternative path (steps 25 and 26) still explaining a biphotonic behaviour [174] a more reactive but unidentified intermediate would be formed by absorption of a photon by the triplet state. 

Figure 6. Rate of heat evolution during argon-ion laser-photoinitiated polymerization of 1-methyl-2-pyrrolidinone (MP), 9 ML of 2-ethyl-2-(hydroxymethyl)-l,3-propanediol triacrylate (TMPTA), and the dyes at a concentration of 10 m. Initiators 1) 19, 2) 18, 3) 10, 4) 16, 5) RBAX (rose bengal derivative prepared from rose bengal, which is first decarboxylated and then acetylated [36]),...

Figure 1. Electronic absorption spectra of rose bengal derivatives...

Several compounds that inhibit vesicular glutamate transport have been identified These include the dyes Evans Blue and Rose Bengal. In addition, the stilbene derivative 4,4 -diisothiocyanatostilbene-2,2 -disulfonic acid (DEDS), a compound commonly used as a specific inhibitor of anion channels, inhibits vesicular glutamate transport. Most known inhibitors have limited use as they are membrane impermeant, with the exception of Rose Bengal. 

Oxidation of dihydrocoptisine (124), derived from protopine, with m-chloroperbenzoic acid in dichloromethane afforded coptisinephenolbetaine (125) as the hydrochloride in 78% yield (Scheme 26) (82). This oxidation method was applied to dihydroberberine (90) to produce berberinephenolbetaine (121) (53). Additionally, photooxygenation of 90 in methanol containing Rose Bengal gave 121 in 80% yield, further photooxygenation of which led to the epidioxide 122, a 1,3-dipolar cycloaddition product with oxygen (84,85). 

The photochemistry of Eosin under both reductive and oxidative conditions has been studied by several groups [145-151], Photoreduction by amines such as tribenzylamine (R = CH2, R" = ) produces two leuco analogues, the dihydro derivative, and the cross-coupled product formed from the amine radical and the dye radical anion (2) [152], In addition, debromination of Eosin is reported during photobleaching with amines and phenols. The reader however is referred to the extensive studies of Rose Bengal dehalogenation by Paczkowski and Neckers [153]. Radiolysis of Eosin in methanol shows that debromination is a consequence of the photochemical decomposition of semireduced Eosin [154],... 

Singlet oxygen yields for several monomeric derivatives of Rose Bengal... 

The reader may, perhaps, recognize 8 as being a derivative prepared from Rose Bengal which is first decarboxylated and then acetylated. We refer to 8 as RBAX. RBAX is a xanthone, analogous to the thioxanthones which are common commercial UV photoinitiators. The latter are used with typical... 

Rose-Bengal sensitized photooxygenation of cyclic tryptophan derivative 119 gave l,3-diazocine-2,6-dione 120 (76H53). Murato and coworkers reductively cleaved / -carboline derivative 121 and isolated the novel diazocinoindole 122 (77CPB1559). 

The evidence from photosensitization derives from the Rose Bengal (RB) sensitized dimerization of acenaphthylene.1 15 It is observed that one RB molecule can yield, by repeated excitation, dimeric molecules with a high conversion. This requires that dimers move away from the RB molecules and that monomers move to occupy these vacant places. Evidence has been presented1 that the RB molecules are firmly fixed to the surface and thus the acenaphthylene monomers and dimers must be undergoing extensive motion on the surface during... 

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