- Synthesis of protected α-amino acids: Via decarboxylation amination from malonate derivatives
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A general and efficient strategy for the synthesis of protected α-amino acids is reported. The method uses malonate derivatives as the starting materials and Cs2CO3 as a base at 60 degrees, giving α-amino acid derivatives in moderate yields by releasing CO2. This methodology shows broad substrate scope (primary and secondary acids), excellent functional group tolerance and high efficiency to give the desired products under mild reaction conditions. It also allows the construction of β and γ-amino acids and other unnatural products.
- Dai, Qipu,Fu, Hui,Hu, Changwen,Li, Peihe,Li, Xiaoying,Wang, Zheng
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p. 4439 - 4446
(2020/10/20)
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- INDAZOLE COMPOUNDS
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Indazole compounds, processes for their preparation, pharmaceutical compositions containing such compounds and their use in therapy.
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Page/Page column 29
(2012/03/26)
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- Transition-Metal-Free carboxylation of organozinc reagents using CO 2 in DMF solvent
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An efficient process for the carboxylation of functionalized organozinc reagents with CO2 under transition-metal-free conditions was developed by employing DMF solvent in the presence of LICl.
- Kobayashi, Koji,Kondo, Yoshinori
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supporting information; experimental part
p. 2035 - 2037
(2009/09/08)
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- Direct oxidative cleavage of α- and β-dicarbonyls and α-hydroxyketones to diesters with KHSO5
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Presented is a methodology to oxidatively cleave α-hydroxyketones and α- or β-diones using the environmentally benign reagent KHSO 5, prepared easily from Oxone, to diesters in one simple transformation. In addition, we undertook a mechanistic study to provide a plausible mechanistic interpretation. These reactions may prove to be valuable alternatives to other related metal-mediated processes.
- Yan, Jun,Travis, Benjamin R.,Borhan, Babak
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p. 9299 - 9302
(2007/10/03)
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- A New Class of Linear Tetrapyrroles: Acetylenic 10,10a-Didehydro-10a-homobilirubins
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Novel bilirubin analogues with dipyrrinones conjoined to an acetylene rather than a methylene group were synthesized and examined spectroscopically. Despite the increased separation of the dipyrrinones forced by replacing a -CH2- by a -C≡C- unit, molecular dynamics calculations show that, like bilirubin, they may still engage in intramolecular hydrogen bonding to carboxylic acid groups when the propionic acid chains are slightly lengthened, e.g., butanoic acids. Unlike bilirubin, however, which is bent in the middle and has a ridge-tile shape, the acetylene orients the attached dipyrrinones along a linear path, and intramolecular hydrogen bonding preserves a twisted linear molecular shape. The extended planes of the dipyrrinones intersect along the -C≡C- axis at an angle of 136° for the conformation stabilized by intramolecular hydrogen bonding in the bis-butyric acid rubin (lb). With shorter acid chains (propionic), only one CO2H can engage an opposing dipyrrinone in intramolecular hydrogen bonding, and in this energy-minimum conformation of the linear pigment 1a, the intersection of the extended planes of the dipyrrinones has an angle of 171°. Spectroscopic evidence for such linearized and twisted structures was found in the pigments' NMR spectral data and their exciton UV-vis and induced circular dichroism spectra.
- Tu, Bin,Ghosh, Brahmananda,Lightner, David A.
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p. 8950 - 8963
(2007/10/03)
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- Ozonolysis of β-(Alkoxycarbonyl)- and β-Acyl-Substituted Vinyl Ethers. Cycloaddition Chemistry of the Derived α-Keto Ester O-Oxides and α-Diketone O-Oxides
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Ozonolyses of a series of vinyl ethers 1a-h having electron-withdrawing substituent(s) at the β-position were carried out in methanol and also in aprotic solvents in the presence of 1,3-dipolarophiles.Methanol-trapping experiments revealed that the cleavage of the primary ozonides from vinyl ethers 1a,b,d-f is regioselective, providing in each case the corresponding α-keto ester O-oxides 3a,b and α-diketone O-oxides 3d-f.These electron-deficient carbonyl oxides 3a,b,d-f could undergo cycloadditions with a variety of 1,3-dipolarophiles, particularly nitrones, and give in each case the corresponding cycloadducts.
- Sugiyama, Tomohito,Yamakoshi, Hideyuki,Nojima, Masatomo
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p. 4211 - 4218
(2007/10/02)
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- NOUVEAUX DECONTAMINANTS. ACTION DES PERACIDES A GROUPE ESTER SUR QUELQUES TOXIQUES INSECTICIDES OU DE GUERRE
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A new peroxyacid-ester series has been obtained and used in the destruction of toxic agents.These structures oROCOC6H4CO3H and ROCO(CH2)nCO3H are more stable than the unsubstituted compounds.The reaction with paraoxon (O,O-diethyl O-paranitrophenylphosphate) and HD (2,2'-dichlorodiethylsulfide) goes to completion in a very short time.The influence of the R group and the length of the chain (n=2......12) has been studied.The addition of some long chain tetraalkyl-ammonium salts enhances the rate of the reaction by micellar catalysis.
- Lion, C.,Hedayatullah, M.,Bauer, P.,Boukou-Poba, J. P.,Charvy, C.,et al.
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p. 555 - 560
(2007/10/02)
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- ENZYMATIC REACTIONS IN ORGANIC SYNTHESIS 4- HYDROLYSES OF DIESTERS
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Enzymatic hydrolyses allowed discriminations of esters functions present in the same molecule.
- Jeso, B. De,Drouillard, S.,Degueil-Castaing, M.,Saux, A.,Maillard, B.
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p. 1691 - 1698
(2007/10/02)
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