Regioselective 15-bromination and functionalization of a stable synthetic bacteriochlorin.
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5-Methoxy-8,8,18,18-tetramethyl-2,12-di-p-tolylbacteriochlorin (MeO-BC) undergoes regioselective electrophilic bromination with NBS to give the 15-bromo analogue (MeO-BC-Br15) in 85% yield. By contrast, the bacteriochlorin lacking the 5-methoxy group (8,8,18,18-tetramethyl-2,12-di-p-tolylbacteriochlorin, H-BC) gives a mixture of two monobromo- and two dibromobacteriochlorins. Deuterium exchange of both bacteriochlorins (H-BC and MeO-BC) in acidic media (TFA-d) occurs preferentially at the beta-pyrrole positions (3, 13) > unhindered meso-positions (5, 15 for H-BC; 15 for MeO-BC) > hindered meso-positions (10, 20). The 15-bromo-5-methoxybacteriochlorin MeO-BC-Br15 was subjected to three types of Pd-mediated coupling reactions (Suzuki, Sonogashira, Hartwig-Buchwald) to give six bacteriochlorins bearing functional groups at the 15-position (49% to 85% yield). The groups include 4-(tert-butoxycarbonylmethoxy)phenyl, 4-pyridyl, 3,5-diformylphenyl, phenylethynyl, TIPS-ethynyl, and N-benzamido. The presence of the 15-ethynyl moiety shifts the position of the long-wavelength Qy band from 732 nm to approximately 753 nm. The ability to introduce a range of groups at a specific site enables synthetic bacteriochlorins to be tailored for a variety of applications. (+info)
Synthesis of desformylflustrabromine and its evaluation as an alpha4beta2 and alpha7 nACh receptor modulator.
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Desformylflustrabromine (dFBr; 1) and desformylflustrabromine-B (dFBr-B; 2) have been previously isolated from natural sources, and the former has been demonstrated to be a novel and selective positive allosteric modulator of alpha4beta2 nicotinic acetylcholine (nACh) receptors. The present study describes the synthesis of water-soluble salts of 1 and 2, and confirms and further investigates the actions of 1 and 2 using two-electrode voltage clamp recordings. (+info)
Analysis of exposure biomarker relationships with the Johnson SBB distribution.
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Application of the Johnson bivariate S(B) distribution, or alternatively the S(BB) distribution, is presented here as a tool for the analysis of concentration data and in particular for characterizing the relationship between exposures and biomarkers. Methods for fitting the marginal S(B) distributions are enhanced by maximizing the Shapiro-Wilk W statistic. The subsequent goodness of fit for the S(BB) distribution is evaluated with a multivariate Z statistic. Median regression results are extended here with methods for calculating the mean and standard deviation of the conditional array distributions. Application of these methods to the evaluation of the relationship between exposure to airborne bromopropane and the biomarker of serum bromide concentration suggests that the S(BB) distribution may be useful in stratifying workers by exposure based on using a biomarker. A comparison with the usual two-parameter log-normal approach shows that in some cases the S(BB) distribution may offer advantages. (+info)
Simple and regioselective bromination of 5,6-disubstituted-indan-1-ones with Br2 under acidic and basic conditions.
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Bromination of 5,6-dimethoxyindan-1-one with Br(2) in acetic acid at room temperature produced exclusively the corresponding 2,4-dibromo compound in 95% yield. Reaction of 5,6-dimethoxyindan-1-one with Br(2) in the presence of KOH, K(2)CO(3) or Cs(2)CO(3 )at ~0 degrees C( )gave the monobrominated product 4-bromo-5,6-dimethoxyindan-3-one in 79%, 81% and 67% yield, respectively. 5,6-Dihydroxyindan-1-one was dibrominated on the aromatic ring affording 4,7-dibromo-5,6-dihydroxyindan-1-one both in acetic acid at room temperature and in the presence of KOH at ~0 degrees C. 5,6-Difluoroindan-1-one and 1-indanone were alpha-monobrominated in acetic acid and alpha,alpha-dibrominated under KOH conditions at room temperature. (+info)
Bromine--the red cloud approaching.
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Bromine is a strong and prevalent irritating agent that can spread both as liquid and as fumes. It has a characteristic reddish-brown color. The mainstay of the medical management is supportive and symptomatic therapy that should be given as soon as possible to prevent further damage. Medical personnel, especially the emergency department staff, should be familiar with its health effects, including the safety precautions needed when caring for casualties following such an exposure. (+info)
Biaryl product formation from cross-coupling in palladium-catalyzed borylation of a Boc protected aminobromoquinoline compound.
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The palladium catalyzed borylation of a Boc protected aminobromoquinoline compound with bis(pinacolato)diboron yielded a biaryl compound, resulting from cross coupling, as the major product, instead of the intended boronate, even though no strong base was used. Such results indicate that under certain conditions and with certain substrates, cross coupling can be a major problem during borylation, leading to unintended consequences. (+info)
A novel synthesis of bromobenzenes using molecular bromine.
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Certain substituted bromobenzenes have been synthesized in acceptable yields using a novel Sandmeyer type reaction. The reactions are relatively quick and possibly proceed via a radical mechanism. (+info)
Structure of the alamethicin pore reconstructed by x-ray diffraction analysis.
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