- Single-Crystal X-ray Diffraction Structure of the Stable Enol Tautomer Polymorph of Barbituric Acid at 224 and 95K
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The thermodynamically stable enol crystal form of barbituric acid, previously prepared as powder by grinding or slurry methods, has been obtained as single crystals by slow cooling from methanol solution. The selection of the enol crystal was facilitated by a density-gradient method. The structure at 224 and 95K confirms the enol inferred on the basis of powder data. The enol has bond lengths that are consistent with the expected bond order and with DFT calculations that include treatment of hydrogen bonding. In isolation, the enol is higher in energy than the tri-keto form by 50kJ mol-1 which must be more than compensated by enhanced hydrogen bonding. Both crystal forms have four normal H-bonds; the enol has two additional H-bonds with O-O distances of 2.49?. Conversion into the enol form occurs spontaneously in the solid state upon prolonged storage of the commercial tri-keto material. Slurry conversion of tri-one to enol in ethanol is reversed in direction in ethanol-D1.
- Marshall, Madalynn G.,Lopez-Diaz, Valerie,Hudson, Bruce S.
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Read Online
- Ultrasound-assisted rapid synthesis of 2-aminopyrimidine and barbituric acid derivatives
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Novel, inexpensive, and relatively expeditious procedure to achieve the synthesis of different 2-aminopyrimidine and barbituric acid derivatives is presented here, starting from readily available compounds such as guanidine hydrochloride, urea, 1,3-dialkylurea, or thiourea. Under ultrasonic irradiation, base-driven (Na2CO3, NaOH, or NaOC2H5) heterocyclization reactions of the aforementioned substrates with diethyl malonate, diethyl-2-alkyl malonate, pentane-2,4-dione, or ethyl-3-oxobutanoate yielded corresponding products. Significant advantages of this sonochemical synthetic protocol with regard to the conventional thermal methods include easy reaction setup and work-up steps, reasonably mild conditions, shorter reaction times (～30 min) and comparably high product yields. The characterization of the synthesized compounds was based on melting points, FT-IR, GC-MS, 1H-NMR techniques, and the obtained data were also checked from the previously published studies.
- Bayramo?lu, Duygu,Kurtay, Gülbin,Güllü, Mustafa
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p. 649 - 658
(2020/02/11)
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- Design and synthesis of some barbituric and 1,3-dimethylbarbituric acid derivatives: A non-classical scaffold for potential PARP1 inhibitors
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Six series based on barbituric acid 5a-e, 10a-d; thiobarbituric acid 6a-e, 11a-d and 1,3-dimethylbarbituric acid 7a-e, 12a-d were prepared and screened for their in vitro PARP1 inhibition. They revealed promising inhibition at nanomolar level especially compounds 5c, 7b, 7d and 7e (IC50 = 30.51, 41.60, 41.53 and 36.33 nM) with higher potency than olaparib (IC50 = 43.59 nM). Moreover, compounds 5b, 5d, 7a, 12a and 12c exhibited good comparable activity (IC50 = 65.93, 58.90, 66.57, 45.40 and 50.62 nM, respectively). Furthermore, the most active compounds 5c, 7b, 7d, 7e, 12a and 12c against PARP1 in vitro were evaluated in the BRCA1 mutated triple negative breast cancer cell line MDA-MB-436 where 5c and 12c showed higher potency compared to olaparib and result in cell cycle arrest at G2/M phase. 5c and 12c showed apoptotic effects in MDA-MB-436 and potentiated the cytotoxicity of temozolomide in A549 human lung epithelial cancer cell line. Compounds 5c and 12c represent interesting starting points towards PARP1 inhibitors.
- Eldin A. Osman, Essam,Hanafy, Noura S.,George, Riham F.,El-Moghazy, Samir M.
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- Prebiotic Origin of Pre-RNA Building Blocks in a Urea “Warm Little Pond” Scenario
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Urea appears to be a key intermediate of important prebiotic synthetic pathways. Concentrated pools of urea likely existed on the surface of the early Earth, as urea is synthesized in significant quantities from hydrogen cyanide or cyanamide (widely accepted prebiotic molecules), it has extremely high water solubility, and it can concentrate to form eutectics from aqueous solutions. We propose a model for the origin of a variety of canonical and non-canonical nucleobases, including some known to form supramolecular assemblies that contain Watson-Crick-like base pairs.The dual nucleophilic-electrophilic character of urea makes it an ideal precursor for the formation of nitrogenous heterocycles. We propose a model for the origin of a variety of canonical and noncanonical nucleobases, including some known to form supramolecular assemblies that contain Watson-Crick-like base pairs. These reactions involve urea condensation with other prebiotic molecules (e. g., malonic acid) that could be driven by environmental cycles (e. g., freezing/thawing, drying/wetting). The resulting heterocycle assemblies are compatible with the formation of nucleosides and, possibly, the chemical evolution of molecular precursors to RNA. We show that urea eutectics at moderate temperature represent a robust prebiotic source of nitrogenous heterocycles. The simplicity of these pathways, and their independence from specific or rare geological events, support the idea of urea being of fundamental importance to the prebiotic chemistry that gave rise to life on Earth.
- Menor Salván,Bouza, Marcos,Fialho, David M.,Burcar, Bradley T.,Fernández, Facundo M.,Hud, Nicholas V.
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p. 3504 - 3510
(2020/10/02)
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- Oxidation of Thioamides to Amides with Tetrachloro- and Tetrabromoglycolurils
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Tetrabromo- and tetrachloroglycolurils have been shown to act as good oxidants capable of converting thioamides to the corresponding amides. This approach offers such advantages as good yields (81–99%), short reaction times (10–25 min), simple workup procedure, and environmental safety.
- Arrous, S.,Boudebouz, I.,Parunov, I. V.
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p. 1874 - 1877
(2020/02/03)
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- A compound and its preparation and use (by machine translation)
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The present invention discloses a structure of the formula X compound or its pharmaceutically acceptable salt and its preparation and use: Wherein R1 is at least comprises a five-membered ring or a six-membered ring of chemical structure; R2 is a molecular weight greater than 100 and chemical structure containing electron-withdrawing group. (by machine translation)
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Paragraph 0091; 0092; 0093; 0095; 0102; 0104; 0111; 0113
(2018/03/25)
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- Selective and facile oxidative desulfurization of thioureas and thiobarbituric acids with singlet molecular oxygen generated from trans-3,5-dihydroperoxy-3,5-dimethyl-1,2-dioxolane
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An efficient and facile procedure using trans-3,5-dihydroperoxy-3,5-dimethyl-1,2-dioxolane has been developed for oxidative desulfurization of thioureas and thiobarbituric acids. The reactions proceeded smoothly very fast under mild conditions in basic media at room temperature to afford the respective ureas in excellent yields. Simple procedure and work up, mild conditions, high yields, short reaction times, use of highly potent and non-toxic oxidant are the main merits of the present method.
- Azarifar, Davood,Golbaghi, Maryam
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- Site-Selective Synthesis of 15N- and 13C-Enriched Flavin Mononucleotide Coenzyme Isotopologues
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Flavin mononucleotide (FMN) is a coenzyme for numerous proteins involved in key cellular and physiological processes. Isotopically labeled flavin is a powerful tool for studying the structure and mechanism of flavoenzyme-catalyzed reactions by a variety of techniques, including NMR, IR, Raman, and mass spectrometry. In this report, we describe the preparation of labeled FMN isotopologues enriched with 15N and 13C isotopes at various sites in the pyrazine and pyrimidine rings of the isoalloxazine core of the cofactor from readily available precursors by a five-step chemo-enzymatic synthesis.
- Neti, Syam Sundar,Poulter, C. Dale
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p. 5087 - 5092
(2016/07/06)
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- FeCl3·6H2O catalyzed aqueous media domino synthesis of 5-monoalkylbarbiturates: Water as both reactant and solvent
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A novel, simple and straightforward route to 5-monoalkylbarbiturates by FeCl3·6H2O catalyzed domino reactions of 6-aminouracils, water and α,β-unsaturated ketones, where water plays a key dual role as both reactant and solvent, is described. Significantly, all the reactions efficiently furnished exclusively 5-monoalkylbarbiturates and not pyrido[2,3-d]pyrimidines as generally produced from the reactions of 6-aminouracils and α,β-unsaturated carbonyls.
- Kalita, Subarna Jyoti,Mecadon, Hormi,Deka, Dibakar C.
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p. 10402 - 10411
(2014/03/21)
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- Reaction of 6-aminouracils with aldehydes in water as both solvent and reactant under FeCl3·6H2O catalysis: Towards 5-alkyl/arylidenebarbituric acids
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5-Alkyl/arylidenebarbituric acids were efficiently synthesized through an FeCl3·6H2O catalyzed domino reaction of 6-aminouracils, water and aldehydes with water serving a dual role as both solvent and reactant, under benign reaction conditions. A study on comparative substrate scope of 6-aminouracil versus barbituric acid showed similar efficacy towards 5-alkyl/arylidenebarbituric acids. The protocol is the first detailed report to prepare regioselectively 5-alkyl/arylidenebarbituric acids starting from 6-aminouracils, which is an alternative and competing strategy to hitherto all known reactions directly employing barbituric acids. the Partner Organisations 2014.
- Kalita, Subarna Jyoti,Mecadon, Hormi,Chandra Deka, Dibakar
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p. 32207 - 32213
(2014/08/18)
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- Synthesis and antifungal activity of substituted 2,4,6-pyrimidinetrione carbaldehyde hydrazones
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Opportunistic fungal infections caused by the Candida spp. are the most common human fungal infections, often resulting in severe systemic infections - a significant cause of morbidity and mortality in at-risk populations. Azole antifungals remain the mainstay of antifungal treatment for candidiasis, however development of clinical resistance to azoles by Candida spp. limits the drugs' efficacy and highlights the need for discovery of novel therapeutics. Recently, it has been reported that simple hydrazone derivatives have the capability to potentiate antifungal activities in vitro. Similarly, pyrimidinetrione analogs have long been explored by medicinal chemists as potential therapeutics, with more recent focus being on the potential for pyrimidinetrione antimicrobial activity. In this work, we present the synthesis of a class of novel hydrazone-pyrimidinetrione analogs using novel synthetic procedures. In addition, structure-activity relationship studies focusing on fungal growth inhibition were also performed against two clinically significant fungal pathogens. A number of derivatives, including phenylhydrazones of 5-acylpyrimidinetrione exhibited potent growth inhibition at or below 10 μM with minimal mammalian cell toxicity. In addition, in vitro studies aimed at defining the mechanism of action of the most active analogs provide preliminary evidence that these compound decrease energy production and fungal cell respiration, making this class of analogs promising novel therapies, as they target pathways not targeted by currently available antifungals.
- Neumann, Donna M.,Cammarata, Amy,Backes, Gregory,Palmer, Glen E.,Jursic, Branko S.
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p. 813 - 826
(2014/01/23)
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- Organocatalyzed and uncatalyzed C=C/C=C and C=C/C=N exchange processes between knoevenagel and imine compounds in dynamic covalent chemistry
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Molecular diversity generation through reversible component exchange has acquired great importance in the last decade with the development of dynamic covalent chemistry. We explore here the recombination of components linked by C=C and C=N bonds through reversible double-bond formation, and cleavage in C=C/C=C and C=C/C=N exchange processes. The reversibility of the Knoevenagel reaction has been explored, and C=C/C=C C/C exchanges have been achieved among different benzylidenes, under organocatalysis by secondary amines such as L-proline. The substituents of these benzylidenes were shown to play a very important role in the kinetics of the exchange reactions. L-Proline is also used to catalyze the reversible C=C/C=C exchange between Knoevenagel derivatives of barbituric acid and malononitrile. Finally, the interconversion between Knoevenagel derivatives of dimethylbarbituric acid and imines (C=C/C=N exchange) has been studied and was found to occur rapidly in the absence of catalyst. The results of this study pave the way for the extension of dynamic combinatorial chemistry based on C=C/C=C and C=C/C=N exchange systems.
- Kulchat, Sirinan,Meguellati, Kamel,Lehn, Jean-Marie
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p. 1219 - 1236
(2015/04/14)
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- Diverse combinatorial design, synthesis and in vitro evaluation of new HEPT analogues as potential non-nucleoside HIV-1 reverse transcription inhibitors
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New analogues of 1-[(2-hydroxyethoxy)methyl]-6-(phenylthio)thymine (HEPT) were synthesized and evaluated for their in vitro activities against HIV-1 in MT-4 cell cultures. Chemical diversity was introduced in 4 of the six positions of the core and the influence of each substituent was studied. This library was built on the basis of a rational diversity analysis with the objective of maximizing diversity and thus, the activity range with a minimum number of synthesized compounds. Among them, 2{1,2,3,1} and 2{1,2,3,4} exhibited the most potent anti-HIV-1 activities (EC50 = 0.015 μg/mL; 0.046 μM, SI >1667) and (EC50 = 0.025 μg/mL; 0.086 μM, SI >1000), respectively, which were about 71-fold and 38-fold more active than the reference compound HEPT (EC50 = 1.01 μg/mL; 3.27 μM, SI >25).
- Puig-De-La-Bellacasa, Raimon,Gimenez, Laura,Pettersson, Sofia,Pascual, Rosalia,Gonzalo, Encarna,Este, Jose A.,Clotet, Bonaventura,Borrell, Jose I.,Teixido, Jordi
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experimental part
p. 159 - 174
(2012/09/05)
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- Microwave-assisted synthesis of 3-aryl-pyrimido[5,4-e][1,2,4]triazine-5, 7(1H,6H)-dione libraries: Derivatives of toxoflavin
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The parallel synthesis of a library of toxoflavin derivatives is described. The microwave-assisted approach involves the de novo generation of the heterocyclic scaffold and allows for facile introduction of a variety of fragments.
- Todorovic, Nick,Giacomelli, Andrew,Hassell, John A.,Frampton, Christopher S.,Capretta, Alfredo
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experimental part
p. 6037 - 6040
(2010/11/21)
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- PROCESS FOR STRAIGHTENING KERATIN FIBRES WITH A HEATING MEANS AND DENATURING AGENTS
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The invention relates to a process for straightening keratin fibres, comprising: (i) a step in which a straightening composition containing at least two denaturing agents is applied to the keratin fibres, (ii) a step in which the temperature of the keratin fibres is raised, using a heating means, to a temperature of between 110 and 250° C.
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- SUBSTANCES FOR DYEING KERATINOUS FIBERS
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Disclosed are substances which contain unsaturated, non-aromatic dialdehydes of formula (Ia) and/or the tautomer (Ib) thereof, wherein R1, R2, and R3 are defined as indicated in claim 1, along with at least one CH-acidic compound of formulas (II) and/or (III), wherein R6, R7, R8, R9, R10, Y, X?, Het, and X1 are defined as indicated in claim 1, in a cosmetic carrier. Said substances color keratinous fibers, especially human hair, in an intensive, colorfast, natural brown shade.
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- 6-Methyl-2-(3-methyl-5-oxo-2,5-dihydropyrazolyl)-pyrimidin-4(1H)-one as CH acid in Michael reaction
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Addition of 6-methyl-2-(3-methyl-5-oxo-2,5-dihydropyrazol-1-yl)pyrimidin- 4(1H)-one, a compound with two CH-acidic centers, to 5-benzylidenepyrimidine-2, 4,6(1H,3H,5H)-trione proceeds with the participation of the atom C5 of pyrimidine ring. Un
- Erkin,Krutikov
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body text
p. 1525 - 1531
(2009/12/04)
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- Synthesis of novel galactopyranosyl-derived spiro barbiturates
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Malonic acid undergoes condensation readily with ureas to yield barbituric acids 2, which on bromination give 5,5-dibromobarbituric acids 3. Reaction of α-D-galactose with these 5,5-dibromo barbituric acids afforded 2,3-α-D-galactopyrano-1,4-dioxo-7,9-diaza-spiro[4,5]deca-6,8,10-triones 4. The structures of the products have been assigned on the basis of 1H NMR, 13C NMR, FAB-MS, optical activity, and elemental analysis. The title compounds are found to have antibacterial and antifungal activities.
- Ingle,Gaidhane,Dutta,Naha,Sengupta
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p. 661 - 671
(2007/10/03)
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- An expedient method for the synthesis of 6-substituted uracils under microwave irradiation in a solvent-free medium
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Condensation of malonic acid 1 and ureas 2a-f proceeds smoothly in the presence of acetic anhydride 3 under microwave irradiation in solvent-free conditions to give 6-hydroxy-uracils 4 in excellent yields. Under identical conditions, the condensation of cyanoacetic acid 5 and ureas 2a,b,g and h in the presence of acetic anhydride 3, followed by cyclization in the presence of sodium hydroxide affords 6-amino-uracils 6 in high yields. The work-up procedures are simple and products need no purification.
- Devi, Ipsita,Bhuyan, Pulak J.
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p. 5727 - 5729
(2007/10/03)
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- Facile desulfurization of thioamides and thioureas with tetrabutylammonium periodate under mild conditions
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Thioamides and thioureas were reacted with tetrabutylammonium periodate at room temperature to afford the corresponding amides and ureas, respectively, under aprotic conditions. Springer-Verlag 2005.
- Pourali, Ali Reza
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p. 733 - 737
(2007/10/03)
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- Method for the synthesis of amides and related products from esters or ester-like compounds
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A versatile, eco-friendly, and efficient method for the convenient conversion of esters and ester-like compounds into amides, peptides, carbamates, ureas, oxamides, oxamates, hydrazides, oxazolidinones, pyrazolones, oxazolidinediones, barbituric acids, and other molecules containing one or more OCN moieties in the presence of a diol or polyol is disclosed.
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Page/Page column 8
(2008/06/13)
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- Efficient and convenient deprotection of thiocarbonyl to carbonyl compounds using 3-carboxypyridinium and 2,2′-bipyridinium chlorochromates in solution, dry media, and under microwave irradiation
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A synthetic utility of 3-carboxypyridinium (CPCC) and 2,2′- bipyridinium (BPCC) chlorochromates in deprotection reactions is reported. Different types of thioamides, thioureas, thiono esters, and thioketones are deprotected to their corresponding carbonyl compounds with these reagents in good to excellent yields. The reactions were carried out in solution, under solvent-free conditions, and under microwave irradiation. The results show that with both reagents the rates of the reactions and the yields are usually highest under microwave irradiation. Springer-Verlag 2003.
- Mohammadpoor-Baltork, Iraj,Memarian, Hamid Reza,Bahrami, Kiumars
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p. 411 - 418
(2007/10/03)
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- Barbituric acid derivatives as inhibitors of TNF-alpha converting enzyme (TACE) and/or matrix metalloproteinases
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The present application describes novel barbituric acid derivatives of formula I: or pharmaceutically acceptable salt or prodrug forms thereof, wherein A, B, L, R1, W, Z, Ua, Xa, Ya, and Za are defined in the present specification, which are useful as TNF-α converting enzyme (TACE) and matrix metalloproteinses (MMP) inhibitors.
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- Selective conversion of thioamides and thioureas to their oxygen analogues using quinolinium fluorochromate
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The synthetic utility of quinolinium fluorochromate (QFC) in deprotection of thiocarbonyl compounds is reported. A variety of primary and secondary thioamides and thioureas are converted to their oxo derivatives in high yields. However, tertiary thioamides afford their amides in relatively poor yields. Selective deprotection of thioamides and thioureas in the presence of thionoesters and thioketones is noteworthy advantage of this method.
- Tajbakhsh,Mohammadpoor-Baltork,Alimohammadi
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p. 2638 - 2640
(2007/10/03)
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- Bismuth(III) nitrate pentahydrate: A convenient and selective reagent for conversion of thiocarbonyls to their carbonyl compounds
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A variety of thioamides and thioureas are rapidly transformed to their oxo derivatives with Bi(NO3)3·5H2O in excellent yields. However, thiono esters and thioketones are converted to their corresponding carbonyl compounds in only poor yields. Bi(NO3)3·5H2O is relatively non-toxic, insensitive to air and inexpensive. These features coupled with the selective deprotection of thioamides and thioureas in the presence of thiono esters and thioketones make this method an attractive alternative to the existing routes for deprotection of thiocarbonyl compounds.
- Mohammadpoor-Baltork, Iraj,Khodaei, Mohammad Mehdi,Nikoofar, Kobra
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p. 591 - 594
(2007/10/03)
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- Convenient transformation of thiocarbonyl to carbonyl group using benzyltriphenylphosphonium and n-butyltriphenylphosphonium peroxodisulfates
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Benzyltriphenylphosphonium and n-butyltriphenylphosphonium peroxodisulfates are stable and easily prepared oxidising agents. These reagents are able to convert different thioamides and thioureas to their oxygen analogues in good to excellent yields. Thiono esters are also transformed to esters in high yields. Thioketones such as thiobenzophenone and thiofluorenone are converted to their ketones in high yields while, 4-nitrothiobenzophenone, 2-aminothiobenzophenone and 4-chlorothiobenzophenone remained intact in the reaction mixture.
- Mohammadpoor-Baltork, Iraj,Sadeghi, Majid M. M.,Esmayilpour, Karim
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p. 348 - 350
(2007/10/03)
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- A facile and convenient method for deprotection of thiocarbonyls to their carbonyl compounds using oxone under aprotic and nonaqueous conditions
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The reaction of oxone as an inexpensive, stable, and commercially available reagent with thiocarbonyl compounds in refluxing acetonitrile has been studied. Primary, secondary, and tertiary thioamides and thioureas are converted to their oxo analogues efficiently. Thiono esters also are transformed to their corresponding esters, while thioketones remained intact under these conditions.
- Mohammadpoor-Baltork,Sadeghi,Esmayilpour
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- A convenient and inexpensive method for conversion of thiocarbonyl compounds to their oxo derivatives using oxone under solvent-free conditions
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A series of thioamides, thioureas and thioesters are transformed to their corresponding carbonyl compounds in good to excellent yields with oxone under solid phase conditions, while thioketones remained unchanged under these conditions.
- Mohammadpoor-Baltork, Iraj,Sadeghi, Majid M.,Esmayilpour, Karim
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p. 953 - 959
(2007/10/03)
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- Photochemical reactions of 5-fluoropyrimidine bases with selected alkylamines
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Novel photochemical reactions between 5-fluoropyrimidine bases and primary alkylamines are described. Photoreaction of 5-fluorouracil with alkylamines in aqueous solution (pH>8) leads to 5-alkylaminouracils as the main photoproducts. Similarly, photoreact
- Kanciurzewska, Anna,Raczkowski, Mateusz,Ciszewski, Krzysztof,Celewicz, Lech
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p. 761 - 763
(2007/10/03)
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- Composition of matter having bioactive properties
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Particles of coordinated complex comprising a basic, hydrous polymer and a capacitance adding compound, as well as methods for their production, are described. These complexes exhibit a high degree of bioactivity making them suitable for a broad range of applications through their incorporation into conventional vehicles benefiting from antimicrobial and similar properties.
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- Lock and key micelles and monomer building blocks therefor
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A lock unimolecular micelle includes at least one engineered acceptor specifically binding a ligand (or specifically a "key" unimolecular micelle) thereto. A key unimolecular micelle comprises a core molecule and a plurality of branches extending therefrom, at least one of the branches including a shank portion extending therefrom having a terminal moiety at an end thereof for binding to a complimentary acceptor of a lock unimolecular micelle. Together, the lock and key micelles form a unit, either irreversibly or reversibly bound wherein the lock micelles is a soluble receptor engineered to specifically bind to the specifically engineered key micelle.
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- Silyl modification of biologically active compounds. 5. Hydrolytic stability and biological activity of the trialkylsilyl derivatives of some heterocyclic bases
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The kinetics of the desilylation of the triorganosilyl derivatives of some biologically active heterocyclic bases and uridine were investigated by 1H NMR spectroscopy. A correlation was established between the relative rates of desilylation and the steric environment of the silicon atom. In trials on locomotor activity and muscular tone, the effect on memory processes, and the Porsolt test it was found that tris(tert-butylmethylsilyl)barbituric acid has higher sedative activity than barbituric acid. In contrast to uridine, 5′-O-tert-butyldimethylsilyluridine exhibits antitumor activity, suppressing the development of fibrosarcoma in human lungs (HT-1080) and fibroblasts in mice. 1999 Kluwer Academic/Plenum Publishers.
- Lukevits,Segal,Birgele,Zablotskaya
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p. 1076 - 1080
(2007/10/03)
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- An unexpected linear Bronsted correlation
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The reaction of barbiturate and 1,3-dimethylbarbiturate ions with o-, p- and 2,4-dinitrobenzaldehyde was studied. The reactions of barbiturate anion with o- and p-nitrobenzaldehyde exhibit a pH-rate profile different to that the corresponding to the reactions of barbiturate and 1,3-dimethylbarbiturate ions with 2,4-dinitrobenzaldehyde. The dependence of the rate constant on the viscosity of the medium in the pH range 2-4, for all the reactions, indicates the contribution of a diffusion-controlled proton transfer from the hydronium ion to an addition intermediate, T-, in the rate-determining step. Surprisingly, in the reaction of 2,4-dinitrobenzaldehyde with barbiturate and 1,3-dimethylbarbiturate anions, the Bronsted plot for general acid catalysis for carboxylic acids of pKa between 2 to 5 gives a linear relationship with a = 0-707 (r = 0.991), whereas a = 0 is expected, considering the pKa of the addition intermediate T-. On the other hand, the point for the rate constant, considering water as a general acid catalyst, falls approximately 105 times above the corresponding Bronsfed line. The tautomerism existing in the intermediate T- permits these surprising facts to be explained.
- Baumann, Klaus D.,Brighente, Ines M.C.,Pizzolatti, Moacir G.,Yunes, Rosendo A.
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p. 545 - 551
(2007/10/03)
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- Method for stimulating hair growth with cationic derivative of minoxidil using therapeutic iontophoresis
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This invention relates to a method of applying a cationic derivative of Minoxidil which is transported by means of iontophoresis to hair follicles where the cationic derivatives promote hair growth. Each of the cationic derivatives of Minoxidil are synthesized by reacting the Minoxidil parent compound with an organic or an inorganic acid to form the cationic derivative.
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- Facile desulfurization of cyclic thioureas by hydrogen peroxide in acetic acid.
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A simple, mild and synthetically useful method for the desulfurization of cyclic thioureas and related compounds, existing as thiol-thione tautomeric mixtures, by hydrogen peroxide in acetic acid is proposed. The effect of substituting different solvents for the acetic acid was investigated.
- Grivas,Ronne
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p. 225 - 229
(2007/10/02)
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- Barbiturate assay, tracers, immunogens and antibodies
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The present invention is directed to a fluorescence polarization immunoassay for barbiturates, to the various components needed for preparing and carrying out such an assay, and to methods of making these components. Specifically, tracers, immunogens and antibodies are disclosed, as well as methods for preparing them. The tracers and the immunogens are made from substituted barbiturate compounds. A fluorescein moiety is included in the tracer, while a poly(amino acid) forms a part of the immunogen. The assay is conducted by measuring the degree of polarization retention of plane-polarized light that has been passed through a sample containing antiserum and tracer.
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- Barbiturate assay, tracers, immunogens, antibodies and kit
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The present invention is directed to a fluorescence polarization immunoassay for barbiturates, to the various components needed for preparing and carrying out such an assay, and to methods of making these components. Specifically, tracers, immunogens and antibodies are disclosed, as well as methods for preparing them and a reagent kit containing them. The tracers and the immunogens are made from substituted barbiturate compounds. A fluorescein moiety is included in the tracer, while a poly(amino acid) forms a part of the immunogen. The assay is conducted by measuring the degree of polarization retention of plane-polarized light that has been passed through a sample containing antiserum and tracer.
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- HIGHLY ACCELERATED REACTIONS IN A MICROWAVE OVEN : SYNTHESIS OF HETEROCYCLES
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Efficient synthesis of a wide variety of heterocycles on 0.1 to 200 g scale was conducted in organic solvents in a commercial microwave oven in a few minutes at a low energy level.Erlenmeyer flasks were adequate reaction vessels since neither high pressure nor high temperature were involved.Fast monitoring of synthetic reactions was achieved by tlc separation and transfer of tlc spot material directly to a solids probe of a chemical ionization mass spectrometer.Microwave Oven-induced Reaction Enhancement (MORE) chemistry is not due to thermolysis: one reaction was conducted successfully in a reaction vial encased in a block of ice.
- Bose, Ajay K.,Manhas, Maghar S.,Ghosh, Malay,Raju, Vegesna S.,Tabei, Keiko,Urbanczyk-Lipkowska, Zofia
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p. 741 - 744
(2007/10/02)
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- Triazinyl reactive dyes containing additional fiber reactive groups bound through the sulfonylalkylaminoalkylamino bridge
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The invention relates to novel useful reactive dyes of the formula I STR1 in which: F is a radical selected from the group consisting of metal-free or metal-containing monoazo or disazo dyes containing at least one --SO3 H group, anthraquinone dyes, sulfophthalocyanine dyes, formazan dyes, phenazine dyes, oxanine dyes and nitroaryl dyes, R is hydrogen, C1 -C4 alkyl which is unsubstituted or substituted with --COOH or --SO3 H, cyanoethyl, or hydroxyethyl, X is fluorine, chlorine, bromine, --SO3 H, phenylsulfonyl or C1 -C4 -alkylsulfonyl, P is 1 or 2 and A is a radical of the formula STR2 in which: the groups designated "alk" are independently of each other straight or branched polymethylene radicals having 2 to 6 carbon atoms, and Z is β-halogenoethyl, vinyl, β-sulfatoethyl, β-thiosulfatoethyl or βacetoxyethyl.
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- Barbituric acids as carbon acids. Acidity relationships and 1H and 2H transfer in 1,3-dimethyl-5-tert-butyl- and 5-tert-butylbarbituric acids
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Slow ionization and reprotonation at the C5 carbon atom has been observed for 1,3-dimethyl-5-tert-butyl- (1,3-Me2-5-t-Bu), 5-tert-butyl- (5-t-Bu), 1,3-diisopropyl-(1,3-iPr2), and 1,5-diisopropyl- (1,5-i-Pr2) barbituric acids (BA) in aqueous solution at 25.0 deg C and I = 0.1 mol/dm3 (NaCl).For 1,3-Me2-5-t-Bu(BA) (pK = 9.41) deprotonation follows the rate law kf = k1H2O + k1OH-> with k1H2O = 4.0E-4/s, k1OH = 192 dm3/mol.s and reprotonation the rate law kr = k-1H2O + k-1H+> with k-1H2O = 8.9E-3/s, k-1H = 1.12E6 dm3/mol.s (pH range 6.91-12.89).For the 2H(C5) derivative the corresponding dedeuteration rates are k1H2O = 7.7E5/s (kH/kD = 5.5) and K1OH = 54 dm3/mol.s (kH/kD = 3.5).Deprotonation is catalysed by general bases (kB dm3/mol.s, kH/kD), 2,6-lutidine (0.0108, 10.0), dabco (29.6, 5.5), NH3 (1.06, 7.1), EtNH2 (14.7, 5.8), Et2NH (18.0,7.2), Et3N(1.30,7.2), but a linear correlation with pKBH is not observed, and structural effects appear to play an important role.The measurement of precise primary kinetic isotope ratios (kH/kd) in water is discussed.In 5-t-Bu(BA)(KH3) ionization at C5 (pK = 8.09+/-0.12) to produce the enolate anion (EH2-) comes into competition with ionization at imide nitrogen (pK = 7.88 +/- 0.04) to produce the keto monoanion (KH2-).In strongly alkaline solution the species deprotonated at both imide nitrogen centers (KH2- is preferred by about 20:1 over the enolate dianion (EH2-)) (C5, and imide nitrogen deprotonated).Such ionizations complicate a study of proton exchange at C5 but this has been clarified by use of the 2H(C5) substituted acid (KDH2)).Deprotonation at C5 occurs via pH independent (k1H2O = 2.59E-3/s, kH/D = 8.1) and OH(1-) dependent (k1OH = 800 dm3/mol.s, kH/kD = 3.4) reactions and via the OH(1-) dependent reactions of KH2(1-) (k2OH = 0.54 dm3/mol.s).Coresspondigly, pathways for reprotonation of the enolate anions are available through the H(1+) dependent (k-1H = 3.2E5 dm3/mol.s) and pH independent (k-1H2O = 1.62E-3/s) reactions of EH1- and through the pH independent reaction of EH(2-) (k-2H2O ca. 0.4/s).The known rates of C5 deprotonation (k1H2O) and reprotonation (k-1H) for barbituric acids have been correlated with carbon acidity (Kc) via linear Broenstead relationships of slope 0.80 and 0.20, respectively (pKc range 2.2-9.6).Barbituric acid carbon acidity is thus demonstrated to be controlled largely by substituent effects on the deprotonation reaction.
- Buckingham, D. A.,Clark, C. R.,McKeown, R. H.,Wong. O.
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p. 466 - 476
(2007/10/02)
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- One-Electron Redox Potentials of Purines and Pyrimidines
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One-electron redox potentials of some purine and pyrimidine derivatives were determined by pulse radiolysis from electron transfer equilibria involving their and other free radicals.The redox potentials were determined at pH 13 by using p-methoxyphenol (E=0.4 V), Trolox C (E=0.19 V), and tryptophan (E=0.56 V) as references.The lowest oxidation potential measured for DNA bases was guanosine (E=0.72 V vs.NHE), and the highest was for 1-methylpyrimidines (E ca. 1.6 V) Uric acid (E=0.26 V) and isobarbituric acid (E=0.13 V) were found to have the lowest potentials.
- Jovanovic, Slobodan V.,Simic, Michael G.
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p. 974 - 978
(2007/10/02)
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- A C-13 nuclear magnetic resonance study of the pyrimidine synthesis by the reactions of 1,3-dicarbonyl compounds with amidines and ureas
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The detailed mechanistic pathways are elucidated for the reactions of acetylacetone, methyl acetoacetate, and dimethyl malonate with a variety of amidines and ureas.In many cases the identification of a single intermediate allows the definition of the reaction path and identification of two steps.Intermediates characterized include ring-closed dihydroxytetrahydropyrimidines, dihydrohydroxypyrimidinones, open-chain enamides, and carbonyl addition compounds.
- Katritzky, Alan R.,Yousaf, Taher I.
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p. 2087 - 2093
(2007/10/02)
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- RADIOLYSIS OF DIHYDROURACIL AND DIHYDROTHYMINE IN AQUEOUS SOLUTIONS CONTAINING OXYGEN; FIRST- AND SECOND-ORDER REACTIONS OF THE ORGANIC PEROXYL RADICALS; THE ROLE OF ISOPYRIMIDINES AS INTERMEDIATES
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The nature and yields of the products of radiolysis of aqueous solutions of dihydrouracil containing both N2O and O2 strongly depend on pH and dose rate.At a dose rate of 0.3 Gy s-1 and at pH 3, the major products are barbituric acid (G 2.4), labile material (G 2.8), and uracil (G 0.1).The labile material is converted into uracil upon treatment with acid and is largely composed of 5,6-dihydro-6-hydroxyuracil.At pH 7 barbituric acid is absent and uracil becomes the major product (G 4.5); some labile material is also formed (G 0.7).At pH 5 the pattern of the product distribution changes as a function of dose rate.With increasing dose r ate G(uracil) decreases whereas G(barbituric acid) increases.The predominant radical formed in the dihydrouracil system is the 6-peroxyl radical, and it has been found, using pulse radiolysis with both optical and conductometric detection, that this peroxyl radical can eliminate O2-. to give uracil via an unstable isomeric form of the pyrimidine (isouracil).The elimination is base-catalysed so that, under alkaline conditions, uracil is the major radiolysis product.At lower pH, and also at higher dose rates, bimolecular decay of the peroxyl radical competes with the O2-. elimination process, barbituric acid being a specific product of the bimolecular decay route.The mechanism of these processes are discussed.Irradiation of dihydrothymine-N2O-O2 solutions gave similar results.
- Al-Sheikhly, Mohamed I.,Hissung, Alfred,Schuchmann, Heinz-Peter,Schuchmann, Man Nien,Sonntag, Clemens von,et al.
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p. 601 - 608
(2007/10/02)
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- Protolytic Kinetics of Some Pyridine Derivatives in Non-buffered Aqueous Solution
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The deprotonation rates of the conjugate acids of 2,2'-bipyridine and pyridine, and the protonation rates of 2-aminopyridine and 4-aminopyridine were measured in non-buffered aqueous solution by means of a stopped-flow pH jump method.These pyridine derivatives showed quite slow protolytic behavior, similar to that of 1,10-phenanthroline and cyclopentadienes: the deprotonation rate constants of conjugate acids of 2,2'-bipyridine and pyridine are (4.8 +/- 0.7)*10-1 and (6.0 +/- 2.2)*10-2 s-1, respectively.The deprotonation rates of barbituric acid and acetylcyclopentadiene as authentic samples were also measured.Their deprotonation rate constants are in good agreement with the literature values, this demonstrates the validity and the applicability of the stopped-flow pH jump method.This method is superior to the NMR method for the determination of the protontransfer rates of azaaromatic compounds.
- Ando, Isao,Ujimoto, Kikujiro,Kurihara, Hirondo
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p. 713 - 716
(2007/10/02)
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- Determination of the Rate Constants of the Reactions CO2 + OH(-) --> HCO3(-) and Barbituric Acid --> Barbiturate Anion + H(+) Using the Pulse Radiolysis Technique
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The kinetics of the reactions of CO2 + OH(-) --> HCO3(-) (i) and barbituric acid --> barbiturate anion + H(+) (ii) have been remeasured using as a new approach the pulse radiolysis technique with optical and conductivity detection.The rate constants obtained in the present study, ki (21 deg C) = 6900 +/- 700 M-1s-1 and kii (19 deg C) = 22 +/- 2 s-1 agree within experimental errors with values obtained earlier by other methods. - Key words: Fast Reaction Kinetics, Pulse Conductometry, Peroxyl Radicals, Radiation Chemistry
- Schuchmann, Man Nien,Sonntag, Clemens
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p. 1184 - 1186
(2007/10/02)
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- Method for the preparation of carbonic acid monoester salts
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A method is disclosed for the preparation of salts of monoesters of the carbonic acid, the improvement consisting in that the alcohols corresponding to the esters are reacted with carbon dioxide and a compound of an alkali metal or an alkaline earth metal. A distinct advantage over the use of the alcoholates is obtained inasmuch as the reaction is less violent, side-reactions are put aside and the costs are lowered.
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