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Metiamide
Metiamide is a histamine H2 receptor antagonist developed from another H2 antagonist, burimamide. It was an intermediate compound in the development of the successful anti-ulcer drug cimetidine (Tagamet). Development of metiamide from burimamide After discovering that burimamide is largely inactive at physiological pH, due to the presence of its electron-donating side chain, the following steps were undertaken to stabilize burimamide: * addition of a sulfide group close to the imidazole ring, giving thiaburimamide * addition of methyl group to the 4-position on the imidazole ring to favor the tautomer of thiaburimamide which binds better to the H2 receptor These changes increased the bioavailability metiamide so that it is ten times more potent than burimamide in inhibiting histamine-stimulated release of gastric acid. The clinical trials that began in 1973 demonstrated the ability of metiamide to provide symptomatic relief for ulcerous patients by increasing healing rate of p ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Metiamide Synthesis
Metiamide is a histamine H2 receptor antagonist developed from another H2 antagonist, burimamide. It was an intermediate compound in the development of the successful anti-ulcer drug cimetidine (Tagamet). Development of metiamide from burimamide After discovering that burimamide is largely inactive at physiological pH, due to the presence of its electron-donating side chain, the following steps were undertaken to stabilize burimamide: * addition of a sulfide group close to the imidazole ring, giving thiaburimamide * addition of methyl group to the 4-position on the imidazole ring to favor the tautomer of thiaburimamide which binds better to the H2 receptor These changes increased the bioavailability metiamide so that it is ten times more potent than burimamide in inhibiting histamine-stimulated release of gastric acid. The clinical trials that began in 1973 demonstrated the ability of metiamide to provide symptomatic relief for ulcerous patients by increasing healing rate of p ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
H2 Antagonist
H2 antagonists, sometimes referred to as H2RAs and also called H2 blockers, are a class of pharmaceutical drug, medications that block the action of histamine at the histamine H2 receptor, histamine H2 receptors of the parietal cells in the stomach. This decreases the production of gastric acid, stomach acid. H2 antagonists can be used in the treatment of dyspepsia, peptic ulcers and gastroesophageal reflux disease. They have been surpassed by proton pump inhibitors (PPIs); the PPI omeprazole was found to be more effective at both healing and alleviating symptoms of ulcers and reflux oesophagitis than the H2 blockers ranitidine and cimetidine. H2 antagonists are a type of antihistamine, although in common use the term "antihistamine" is often reserved for H1 antagonist, H1 antagonists, which relieve Allergy, allergic reactions. Like the H1 antagonists, some H2 antagonists function as inverse agonists rather than receptor antagonists, due to the constitutive activity of these re ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cimetidine
Cimetidine, sold under the brand name Tagamet among others, is a histamine H2 receptor antagonist that inhibits stomach acid production. It is mainly used in the treatment of heartburn and peptic ulcers. The development of longer-acting H2 receptor antagonists with fewer drug interactions and adverse effects, such as ranitidine and famotidine, decreased the use of cimetidine, and though it is still used, cimetidine is no longer among the more widely used of the H2 receptor antagonists. Cimetidine was developed in 1971 and came into commercial use in 1977. Cimetidine was approved in the United Kingdom in 1976, and was approved in the United States by the Food and Drug Administration for prescriptions in 1979. Medical uses Cimetidine is used to inhibit stomach acid production and is used in the treatment of heartburn and peptic ulcers. Other uses Some evidence suggests cimetidine could be effective in the treatment of common warts, but more rigorous double-blind clinical t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Nitrile
In organic chemistry, a nitrile is any organic compound that has a functional group. The prefix ''cyano-'' is used interchangeably with the term ''nitrile'' in industrial literature. Nitriles are found in many useful compounds, including methyl cyanoacrylate, used in super glue, and nitrile rubber, a nitrile-containing polymer used in latex-free laboratory and medical gloves. Nitrile rubber is also widely used as automotive and other seals since it is resistant to fuels and oils. Organic compounds containing multiple nitrile groups are known as cyanocarbons. Inorganic compounds containing the group are not called nitriles, but cyanides instead. Though both nitriles and cyanides can be derived from cyanide salts, most nitriles are not nearly as toxic. Structure and basic properties The N−C−C geometry is linear in nitriles, reflecting the sp hybridization of the triply bonded carbon. The C−N distance is short at 1.16 Å, consistent with a triple bond. Nitriles a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Methyl Isothiocyanate
Methyl isothiocyanate is the organosulfur compound with the formula CH3N=C=S. This low melting colorless solid is a powerful lachrymator. As a precursor to a variety of valuable bioactive compounds, it is the most important organic isothiocyanate in industry. Synthesis It is prepared industrially by two routes. Annual production in 1993 was estimated to be 4,000 tonnes. The main method involves the thermal rearrangement of methyl thiocyanate: :CH3S−C≡N → CH3N=C=S It is also prepared via with the reaction of methylamine with carbon disulfide followed by oxidation of the resulting dithiocarbamate with hydrogen peroxide. A related method is useful to prepare this compound in the laboratory. MITC forms naturally upon the enzymatic degradation of glucocapparin, a glucoside found in capers. Reactions A characteristic reaction is with amines to give methyl thioureas: :CH3NCS + R2NH → R2NC(S)NHCH3 : Other nucleophiles add similarly. Applications Solutions of M ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Nucleophilicity
In chemistry, a nucleophile is a chemical species that forms bonds by donating an electron pair. All molecules and ions with a free pair of electrons or at least one pi bond can act as nucleophiles. Because nucleophiles donate electrons, they are Lewis bases. ''Nucleophilic'' describes the affinity of a nucleophile to bond with positively charged atomic nuclei. Nucleophilicity, sometimes referred to as nucleophile strength, refers to a substance's nucleophilic character and is often used to compare the affinity of atoms. Neutral nucleophilic reactions with solvents such as alcohols and water are named solvolysis. Nucleophiles may take part in nucleophilic substitution, whereby a nucleophile becomes attracted to a full or partial positive charge, and nucleophilic addition. Nucleophilicity is closely related to basicity. History The terms ''nucleophile'' and ''electrophile'' were introduced by Christopher Kelk Ingold in 1933, replacing the terms ''anionoid'' and ''cationoid'' p ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Thiol
In organic chemistry, a thiol (; ), or thiol derivative, is any organosulfur compound of the form , where R represents an alkyl or other organic substituent. The functional group itself is referred to as either a thiol group or a sulfhydryl group, or a sulfanyl group. Thiols are the sulfur analogue of alcohols (that is, sulfur takes the place of oxygen in the hydroxyl () group of an alcohol), and the word is a blend of "''thio-''" with "alcohol". Many thiols have strong odors resembling that of garlic or rotten eggs. Thiols are used as odorants to assist in the detection of natural gas (which in pure form is odorless), and the "smell of natural gas" is due to the smell of the thiol used as the odorant. Thiols are sometimes referred to as mercaptans () or mercapto compounds, a term introduced in 1832 by William Christopher Zeise and is derived from the Latin ('capturing mercury')''Oxford American Dictionaries'' (Mac OS X Leopard). because the thiolate group () bonds very strong ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cysteamine
Cysteamine is a chemical compound that can be biosynthesized in mammals, including humans, by the degradation of coenzyme A. The intermediate pantetheine is broken down into cysteamine and pantothenic acid. It is the biosynthetic precursor to the neurotransmitter hypotaurine. It is a stable aminothiol, i.e., an organic compound containing both an amine and a thiol functional groups. Cysteamine is a white, water-soluble solid. It is often used as salts of the ammonium derivative SCH2CH2NH3sup>+ including the hydrochloride, phosphocysteamine, and bitartrate. As a medication, cysteamine, sold under the brand name Cystagon among others, is indicated to treat cystinosis. Medical uses Cysteamine is used to treat cystinosis. It is available by mouth (capsule and extended release capsule) and in eye drops. When applied topically it can scavenge free radicals and lighten skin that's been darkened as a result of post-inflammatory hyperpigmentation, sun exposure and Melasma. Tent ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Birch Reduction
The Birch reduction is an organic reaction that is used to convert arenes to cyclohexadienes. The reaction is named after the Australian chemist Arthur Birch and involves the organic reduction of aromatic rings in an amine solvent (traditionally liquid ammonia) with an alkali metal (traditionally sodium) and a proton source (traditionally an alcohol). Unlike catalytic hydrogenation, Birch reduction does not reduce the aromatic ring all the way to a cyclohexane. An example is the reduction of naphthalene in ammonia and ethanol: Reaction mechanism and regioselectivity A solution of sodium in liquid ammonia consists of the intensely blue electride salt a(NH3)xsup>+ e−. The solvated electrons add to the aromatic ring to give a radical anion, which then abstracts a proton from the alcohol. The process then repeats at either the ''ortho'' or ''para'' position (depending on substituents) to give the final diene. The residual double bonds do not stabilize further radical add ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Formamide
Formamide is an amide derived from formic acid. It is a colorless liquid which is miscible with water and has an ammonia-like odor. It is chemical feedstock for the manufacture of sulfa drugs and other pharmaceuticals, herbicides and pesticides, and in the manufacture of hydrocyanic acid. It has been used as a softener for paper and fiber. It is a solvent for many ionic compounds. It has also been used as a solvent for resins and plasticizers. Some astrobiologists suggest that it may be an alternative to water as the main solvent in other forms of life. Formamides are compounds of the type RR′NCHO. One important formamide is dimethylformamide, (CH3)2NCHO. Production Historical production In the past, formamide was produced by treating formic acid with ammonia, which produces ammonium formate, which in turn yields formamide upon heating: :HCOOH + NH3 → HCOO− :HCOO− → HCONH2 + H2O Formamide is also generated by aminolysis of ethyl formate: :HCOOCH2CH3 + NH3 → H ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Molar Equivalent
An equivalent (symbol: officially equiv; unofficially but often Eq) is the amount of a substance that reacts with (or is ''equivalent'' to) an arbitrary amount (typically one mole) of another substance in a given chemical reaction. It is an archaic unit of measurement that was used in chemistry and the biological sciences (see '). The mass of an equivalent is called its equivalent weight. Formula : ''milligrams to = mg x V / MW'' :: Example for elemental compounds: (mg element / elemental compound mass fraction) x V / MV : '' to milligrams = mEq x MW / V'' Common examples mEq to milligram Milligram to mEq Formal definition In a more formal definition, the ''equivalent'' is the amount of a substance needed to do one of the following: * react with or supply one mole of hydrogen ions () in an acid–base reaction * react with or supply one mole of electrons in a redox reaction. The "hydrogen ion" and the "electron" in these examples are respectively called the "reactio ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Acidity
In computer science, ACID ( atomicity, consistency, isolation, durability) is a set of properties of database transactions intended to guarantee data validity despite errors, power failures, and other mishaps. In the context of databases, a sequence of database operations that satisfies the ACID properties (which can be perceived as a single logical operation on the data) is called a ''transaction''. For example, a transfer of funds from one bank account to another, even involving multiple changes such as debiting one account and crediting another, is a single transaction. In 1983, Andreas Reuter and Theo Härder coined the acronym ''ACID'', building on earlier work by Jim Gray who named atomicity, consistency, and durability, but not isolation, when characterizing the transaction concept. These four properties are the major guarantees of the transaction paradigm, which has influenced many aspects of development in database systems. According to Gray and Reuter, the IBM Informa ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
