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Asymmetric Synthesis
Enantioselective synthesis, also called asymmetric synthesis, is a form of chemical synthesis. It is defined by IUPAC as "a chemical reaction (or reaction sequence) in which one or more new elements of chirality are formed in a substrate molecule and which produces the stereoisomeric (enantiomeric or diastereomeric) products in unequal amounts." Put more simply: it is the synthesis of a compound by a method that favors the formation of a specific enantiomer or diastereomer. Enantiomers are stereoisomers that have opposite configurations at every chiral center. Diastereomers are stereoisomers that differ at one or more chiral centers. Enantioselective synthesis is a key process in modern chemistry and is particularly important in the field of pharmaceuticals, as the different enantiomers or diastereomers of a molecule often have different biological activity. Overview Many of the building blocks of biological systems such as sugars and amino acids are produced exclusively as ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sharpless Dihydroxylation Scheme
Sharpless is a surname. Notable people with the surname include: *Bevan Sharpless (1904–1950), American solar system astronomer *Christopher Sharpless (born 1945), American 1988 Winter Olympics bobsledder *Isaac Sharpless (1848–1920), American educator *Josh Sharpless (born 1988), American baseball player *Karl Barry Sharpless (born 1941), American chemist and Nobel prize winner *Mattie R. Sharpless (born 1942), American diplomat *Nathan J. Sharpless (1823–1893), American politician from Pennsylvania *Norman Sharpless (born 1966), American oncologist and director of the National Cancer Institute *Stewart Sharpless (1926–2013), American galactic astronomer **Sharpless catalog, a 20th-century astronomical catalog with 313 items *Disappearance of Toni Sharpless (born 1979), American nurse who disappeared in 2009 Fictional characters *A character in Madama Butterfly See also *Sharpless asymmetric dihydroxylation, a chemical reaction *Sharpless epoxidation, a chemical reacti ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Carvone
Carvone is a member of a family of chemicals called terpenoids. Carvone is found naturally in many essential oils, but is most abundant in the oils from seeds of caraway (''Carum carvi''), spearmint (''Mentha spicata''), and dill. Uses Food applications Both carvones are used in the food and flavor industry. As the compound most responsible for the flavor of caraway, dill, and spearmint, carvone has been used for millennia in food. Food applications are mainly met by carvone made from limonene. ''R''-(−)-Carvone is also used for air freshening products and, like many essential oils, oils containing carvones are used in aromatherapy and alternative medicine. Agriculture ''S''-(+)-Carvone is also used to prevent premature sprouting of potatoes during storage, being marketed in the Netherlands for this purpose under the name ''Talent''. Insect control ''R''-(−)-Carvone has been approved by the U.S. Environmental Protection Agency for use as a mosquito repellent. Stereoiso ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Transition State
In chemistry, the transition state of a chemical reaction is a particular configuration along the reaction coordinate. It is defined as the state corresponding to the highest potential energy along this reaction coordinate. It is often marked with the double dagger (‡) symbol. As an example, the transition state shown below occurs during the SN2 reaction of bromoethane with a hydroxide anion: The activated complex of a reaction can refer to either the transition state or to other states along the reaction coordinate between reactants and products, especially those close to the transition state. Peter Atkins and Julio de Paula, ''Physical Chemistry'' (8th ed., W.H. Freeman 2006), p.809 According to the transition state theory, once the reactants have passed through the transition state configuration, they always continue to form products. History of concept The concept of a transition state has been important in many theories of the rates at which chemical re ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Entropy
Entropy is a scientific concept, most commonly associated with states of disorder, randomness, or uncertainty. The term and the concept are used in diverse fields, from classical thermodynamics, where it was first recognized, to the microscopic description of nature in statistical physics, and to the principles of information theory. It has found far-ranging applications in chemistry and physics, in biological systems and their relation to life, in cosmology, economics, sociology, weather science, climate change and information systems including the transmission of information in telecommunication. Entropy is central to the second law of thermodynamics, which states that the entropy of an isolated system left to spontaneous evolution cannot decrease with time. As a result, isolated systems evolve toward thermodynamic equilibrium, where the entropy is highest. A consequence of the second law of thermodynamics is that certain processes are irreversible. The thermodynami ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Enthalpy Of Formation
In chemistry and thermodynamics, the standard enthalpy of formation or standard heat of formation of a compound is the change of enthalpy during the formation of 1 mole of the substance from its constituent elements in their reference state, with all substances in their standard states. The standard pressure value is recommended by IUPAC, although prior to 1982 the value 1.00 atm (101.325 kPa) was used. There is no standard temperature. Its symbol is Δf''H''⦵. The superscript Plimsoll on this symbol indicates that the process has occurred under standard conditions at the specified temperature (usually 25 °C or 298.15 K). Standard states are defined for various types of substances. For a gas, it is the hypothetical state the gas would assume if it obeyed the ideal gas equation at a pressure of 1 bar. For a gaseous or solid solute present in a diluted ideal solution, the standard state is the hypothetical state of concentration of the solute of exactly one mole p ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pyridoxine
Pyridoxine (PN) is a form of vitamin B6 found commonly in food and used as a dietary supplement. As a supplement it is used to treat and prevent pyridoxine deficiency, sideroblastic anaemia, pyridoxine-dependent epilepsy, certain metabolic disorders, side effects or complications of isoniazid use, and certain types of mushroom poisoning. It is used by mouth or by injection. It is usually well tolerated. Occasionally side effects include headache, numbness, and sleepiness. Normal doses are safe during pregnancy and breastfeeding. Pyridoxine is in the vitamin B family of vitamins. It is required by the body to metabolise amino acids, carbohydrates, and lipids. Sources in the diet include meat, fish, fruit, vegetables, and grain. Medical uses As a treatment (oral or injection), it is used to treat or prevent pyridoxine deficiency, sideroblastic anaemia, pyridoxine-dependent epilepsy, certain metabolic disorders, side effects of isoniazid treatment and certain types ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Rheumatoid Arthritis
Rheumatoid arthritis (RA) is a long-term autoimmune disorder that primarily affects synovial joint, joints. It typically results in warm, swollen, and painful joints. Pain and stiffness often worsen following rest. Most commonly, the wrist and hands are involved, with the same joints typically involved on both sides of the body. The disease may also affect other parts of the body, including skin, eyes, lungs, heart, nerves, and blood. This may result in a anemia, low red blood cell count, pleurisy, inflammation around the lungs, and pericarditis, inflammation around the heart. Fever and low energy may also be present. Often, symptoms come on gradually over weeks to months. While the cause of rheumatoid arthritis is not clear, it is believed to involve a combination of genetic and environmental factors. The underlying mechanism involves the body's immune system attacking the joints. This results in inflammation and thickening of the synovium, joint capsule. It also affects the und ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Chelation Therapy
Chelation therapy is a medical procedure that involves the administration of chelating agents to remove heavy metals from the body. Chelation therapy has a long history of use in clinical toxicology and remains in use for some very specific medical treatments, although it is administered under very careful medical supervision due to various inherent risks, including the mobilization of mercury and other metals through the brain and other parts of the body by the use of weak chelating agents that unbind with metals before elimination, exacerbating existing damage. To avoid mobilization, some practitioners of chelation use strong chelators, such as selenium, taken at low doses over a long period of time. Chelation therapy also has a history of fraudulent use in Alternative medicine, to treat claimed effects of heavy-metal exposure on problems as disparate as heart disease, cancer and autism. Chelation therapy must be administered with care as it has a number of possible side effec ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Penicillamine
Penicillamine, sold under the brand name of Cuprimine among others, is a medication primarily used for the treatment of Wilson's disease. It is also used for people with kidney stones who have high urine cystine levels, rheumatoid arthritis, and various heavy metal poisonings. It is taken by mouth. Penicillamine was approved for medical use in the United States in 1970. It is on the World Health Organization's List of Essential Medicines. Medical uses It is used as a chelating agent: * In Wilson's disease, a rare genetic disorder of copper metabolism, penicillamine treatment relies on its binding to accumulated copper and elimination through urine. Succimer (dimercaptosuccinic acid) is increasingly used in place of penicillamine. * Penicillamine was the second line treatment for arsenic poisoning, after dimercaprol (BAL). It is no longer recommended. In cystinuria, a hereditary disorder in which high urine cystine levels lead to the formation of cystine stones, penicilla ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Escitalopram
Escitalopram ( ), sold under the brand names Lexapro and Cipralex, among others, is an antidepressant medication of the selective serotonin reuptake inhibitor (SSRI) class. It is mainly used to treat major depressive disorder, generalized anxiety disorder, panic disorder, obsessive–compulsive disorder (OCD), and social anxiety disorder. Escitalopram is taken by mouth. For commercial use, it is formulated as an oxalate salt exclusively. Common side effects include headache, nausea, sexual problems, mild sedation, and trouble sleeping. More serious side effects may include suicidal thoughts in people up to the age of 24 years. It is unclear if use during pregnancy or breastfeeding is safe. Escitalopram is the (''S'')-enantiomer of citalopram (which exists as a racemate), hence the name es-citalopram. Escitalopram was approved for medical use in the United States in 2002. Escitalopram is rarely replaced by twice the dose of citalopram; escitalopram is saf ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Racemic
In chemistry, a racemic mixture or racemate () is a mixture that has equal amounts (50:50) of left- and right-handed enantiomers of a chiral molecule or salt. Racemic mixtures are rare in nature, but many compounds are produced industrially as racemates. History The first known racemic mixture was racemic acid, which Louis Pasteur found to be a mixture of the two enantiomeric isomers of tartaric acid. He manually separated the crystals of a mixture, starting from an aqueous solution of the sodium ammonium salt of racemate tartaric acid. Pasteur benefited from the fact that ammonium tartrate salt gives enantiomeric crystals with distinct crystal forms (at 77 °F). Reasoning from the macroscopic scale down to the molecular, he reckoned that the molecules had to have non-superimposable mirror images. A sample with only a single enantiomer is an ''enantiomerically pure'' or ''enantiopure'' compound. Etymology The word ''racemic'' derives from Latin , meaning pertaining to a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Citalopram
Citalopram, sold under the brand name Celexa among others, is an antidepressant of the selective serotonin reuptake inhibitor (SSRI) class. It is used to treat major depressive disorder, obsessive compulsive disorder, panic disorder, and social phobia. The antidepressant effects may take one to four weeks to occur. It is typically taken oral administration, orally (swallowed by mouth). In some Europe, European countries, it is sometimes given intravenous, intravenously (injected into a vein) to initiate treatment, before switching to the oral route of administration for continuation of treatment. It has also been used intravenously in other parts of the world in some other circumstances. Common side effects include nausea, trouble sleeping, sexual problems, shakiness, feeling tired, and sweating. Serious side effects include an increased risk of suicide in those under the age of 25, serotonin syndrome, glaucoma, and QT prolongation. It should not be used in persons who take o ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
