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Takahashi Taxol Total Synthesis
The Takahashi Taxol total synthesis published by Takashi Takahashi in 2006 is one of several methods in taxol total synthesis.''A Formal Total Synthesis of Taxol Aided by an Automated Synthesizer'' Takayuki Doi, Shinichiro Fuse, Shigeru Miyamoto, Kazuoki Nakai, Daisuke Sasuga and Takashi Takahashi Chemistry an Asian J.; (Article); 2006; 1(3); 370-383. DOAbstract/ref> The method starts from geraniol and differs from the other 6 published methods that it is a formal synthesis (the final product is baccatin III which lacks the amide tail found in taxol itself) and that it is racemic (the product baccatin III is optically inactive). A key feature of the published procedure is that several synthetic steps (construction of rings A, B and C) were performed in an automated synthesizer on a scale up to 300 gram and that purification steps were also automated. A ring synthesis Ring A was synthesised starting from geraniol 1 and involved acylation (acetic anhydride, DMAP, Et3N) to 2, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Manganese
Manganese is a chemical element with the symbol Mn and atomic number 25. It is a hard, brittle, silvery metal, often found in minerals in combination with iron. Manganese is a transition metal with a multifaceted array of industrial alloy uses, particularly in stainless steels. It improves strength, workability, and resistance to wear. Manganese oxide is used as an oxidising agent; as a rubber additive; and in glass making, fertilisers, and ceramics. Manganese sulfate can be used as a fungicide. Manganese is also an essential human dietary element, important in macronutrient metabolism, bone formation, and free radical defense systems. It is a critical component in dozens of proteins and enzymes. It is found mostly in the bones, but also the liver, kidneys, and brain. In the human brain, the manganese is bound to manganese metalloproteins, most notably glutamine synthetase in astrocytes. Manganese was first isolated in 1774. It is familiar in the laboratory in the form ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hydrazone
Hydrazones are a class of organic compounds with the structure . They are related to ketones and aldehydes by the replacement of the oxygen =O with the = functional group. They are formed usually by the action of hydrazine on ketones or aldehydes. Synthesis Hydrazine, organohydrazines, and 1,1-diorganohydrazines react with aldehydes and ketones to give hydrazones. : Phenylhydrazine reacts with reducing sugars to form hydrazones known as osazones, which was developed by German chemist Emil Fischer as a test to differentiate monosaccharides. Uses Hydrazones are the basis for various analyses of ketones and aldehydes. For example, dinitrophenylhydrazine coated onto a silica sorbent is the basis of an adsorption cartridge. The hydrazones are then eluted and analyzed by HPLC using a UV detector. The compound carbonyl cyanide-''p''-trifluoromethoxyphenylhydrazone (abbreviated as FCCP) is used to uncouple ATP synthesis and reduction of oxygen in oxidative phosphorylation in mol ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
TBS Ether
Silyl ethers are a group of chemical compounds which contain a silicon atom covalently bonded to an alkoxy group. The general structure is R1R2R3Si−O−R4 where R4 is an alkyl group or an aryl group. Silyl ethers are usually used as protecting groups for alcohols in organic synthesis. Since R1R2R3 can be combinations of differing groups which can be varied in order to provide a number of silyl ethers, this group of chemical compounds provides a wide spectrum of selectivity for protecting group chemistry. Common silyl ethers are: trimethylsilyl (TMS), ''tert''-butyldiphenylsilyl (TBDPS), ''tert''-butyldimethylsilyl (TBS/TBDMS) and triisopropylsilyl (TIPS). They are particularly useful because they can be installed and removed very selectively under mild conditions. Common silyl ethers Formation Commonly silylation of alcohols requires a silyl chloride and an amine base. One reliable and rapid procedure is the Corey protocol in which the alcohol is reacted with a sil ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
TBSCl
''tert''-Butyldimethylsilyl chloride is an organosilicon compound with the formula (Me3C)Me2SiCl (Me = CH3). It is commonly abbreviated as TBSCl or TBDMSCl. It is a silane containing two methyl groups, a ''tert''-butyl group, and a reactive chloride. It is a colorless or white solid that is soluble in many organic solvents but reacts with water and alcohols. The compound is used to protect alcohols in organic synthesis. Examples can be found in the Nicolaou taxol total synthesis. ''tert''-Butyldimethylsilyl chloride reacts with alcohols in the presence of base to give ''tert''-butyldimethylsilyl ether Silyl ethers are a group of chemical compounds which contain a silicon atom covalently bonded to an alkoxy group. The general structure is R1R2R3Si−O−R4 where R4 is an alkyl group or an aryl group. Silyl ethers are usually used as protecting g ...s: :(Me3C)Me2SiCl + ROH → (Me3C)Me2SiOR + HCl These silyl ethers hydrolyze much more slowly than the trimethylsilyl e ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sodium Borohydride
Sodium borohydride, also known as sodium tetrahydridoborate and sodium tetrahydroborate, is an inorganic compound with the formula Na BH4. This white solid, usually encountered as an aqueous basic solution, is a reducing agent that finds application in papermaking and dye industries. It is also used as a reagent in organic synthesis. The compound was discovered in the 1940s by H. I. Schlesinger, who led a team seeking volatile uranium compounds.Hermann I Schlesinger and Herbert C Brown (1945)Preparation of alkali metal compounds. US Patent 2461661. Granted on 1949-02-15; expired on 1966-02-15. Results of this wartime research were declassified and published in 1953. Properties The compound is soluble in alcohols, certain ethers, and water, although it slowly hydrolyzes. Sodium borohydride is an odorless white to gray-white microcrystalline powder that often forms lumps. It can be purified by recrystallization from warm (50 °C) diglyme. Sodium borohydride is soluble ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Organic Reduction
Organic reductions or organic oxidations or organic redox reactions are redox reactions that take place with organic compounds. In organic chemistry oxidations and reductions are different from ordinary redox reactions, because many reactions carry the name but do not actually involve electron transfer.March Jerry; (1985). Advanced Organic Chemistry reactions, mechanisms and structure (3rd ed.). New York: John Wiley & Sons, inc. Instead the relevant criterion for organic oxidation is gain of oxygen and/or loss of hydrogen, respectively.''Organic Redox Systems: Synthesis, Properties, and Applications'', Tohru Nishinaga 2016 Simple functional groups can be arranged in order of increasing oxidation state. The oxidation numbers are only an approximation: When methane is oxidized to carbon dioxide its oxidation number changes from −4 to +4. Classical reductions include alkene reduction to alkanes and classical oxidations include oxidation of alcohols to aldehydes. In oxidati ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
1,8-Diazabicycloundec-7-ene
1,8-Diazabicyclo .4.0ndec-7-ene, or more commonly DBU, is a chemical compound and belongs to the class of amidine compounds. It is used in organic synthesis as a catalyst, a complexing ligand, and a non-nucleophilic base. Occurrence Although all commercially available DBU is produced synthetically, it may also be isolated from the sea sponge '' Niphates digitalis''. The biosynthesis of DBU has been proposed to begin with 1,6-hexanedial and 1,3-diaminopropane. Uses As a reagent in organic chemistry, DBU is used as a catalyst, a complexing ligand, and a non-nucleophilic base. It is also used as a curing agent for epoxy resins. It is used in the separation of fullerenes in conjunction with trimethylbenzene. It reacts with C70 and higher fullerenes, but not with to C60 It is also used as a catalyst in the production of polyurethanes. It also exhibited its dual character (base and nucleophile) in the synthesis of aryl- and styryl-terminal acetylenes. See also * 1,5-Diazabicy ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Isomerization
In chemistry, isomerization or isomerisation is the process in which a molecule, polyatomic ion or molecular fragment is transformed into an isomer with a different chemical structure. Enolization is an example of isomerization, as is tautomerization. When the isomerization occurs intramolecularly it may be called a rearrangement reaction. When the activation energy for the isomerization reaction is sufficiently small, both isomers will exist in a temperature-dependent equilibrium with each other. Many values of the standard free energy difference, \Delta G^\circ, have been calculated, with good agreement between observed and calculated data. Examples and applications Alkanes Skeletal isomerization occurs in the cracking process, used in the petrochemical industry. As well as reducing the average chain length, straight-chain hydrocarbons are converted to branched isomers in the process, as illustrated the following reaction of ''n''-butane to ''i''-butane. :\overset -> ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Aldehyde
In organic chemistry, an aldehyde () is an organic compound containing a functional group with the structure . The functional group itself (without the "R" side chain) can be referred to as an aldehyde but can also be classified as a formyl group. Aldehydes are common and play important roles in the technology and biological spheres. Structure and bonding Aldehydes feature a carbon center that is connected by a double bond to oxygen and a single bond to hydrogen and single bond to a third substituent, which is carbon or, in the case of formaldehyde, hydrogen. The central carbon is often described as being sp2-Orbital hybridisation, hybridized. The aldehyde group is somewhat polar molecule, polar. The C=O bond length is about 120-122 picometers. Physical properties and characterization Aldehydes have properties that are diverse and that depend on the remainder of the molecule. Smaller aldehydes are more soluble in water, formaldehyde and acetaldehyde completely so. The volatile ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Camphorsulfonic Acid
Camphorsulfonic acid, sometimes abbreviated CSA or 10-CSA is an organosulfur compound. Like typical sulfonic acids, it is a relatively strong acid that is a colorless solid at room temperature and is soluble in water and a wide variety of organic substances. This compound is commercially available. It can be prepared by sulfonation of camphor with sulfuric acid and acetic anhydride: : Although this reaction appears to be a sulfonation of an unactivated methyl group, the actual mechanism is believed to involve a retro- semipinacol rearrangement, deprotonation next to the tertiary carbocation to form an alkene, sulfonation of the alkene intermediate, and finally, semipinacol rearrangement to re-establish the ketone function. In organic synthesis, CSA and its derivatives can be used as resolving agents for chiral amines and other cations. The synthesis of osanetant was an example of this. 3-bromocamphor-8-sulfonic acid was used in the synthesis of enantiopure devazepide. Ca ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
