- Indium-mediated diastereoselective allylation of N-tert-butanesulfinyl imines derived from α-ketoesters
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The indium-mediated allylation of α-aldimino and -ketimino esters 3 with allylic bromides proceeds with high diastereoselectivity to yield homoallylic α-amino ester derivatives 5, in both THF and water as solvents. The reactions are diastereospecific, the stereochemical outcome depending on the configuration of both the sulfur atom of the sulfinyl group and the C[dbnd]N double bond. Of particular interest are the reaction products using ethyl bromomethylacrylate as allylating reagent because amino diesters are obtained, which can be easily transformed into enantiomerically pure α-methylidene-γ-butyrolactams 6 with an alkoxycarbonyl group on the ring bearing the nitrogen atom.
- Maciá, Edgar,Foubelo, Francisco,Yus, Miguel
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Read Online
- A metal-free strategy for the cross-dehydrogenative coupling of 1,3-dicarbonyl compounds with 2-methoxyethanol
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Here, we report a metal-free approach for the construction of methylene-bridged bis-1,3-dicarbonyl compounds via cross-dehydrogenative coupling of 1,3-dicarbonyl compounds with 2-methoxyethanol. In addition, we have extended this methodology to synthesize tetra-substituted pyridine derivatives using 1,3-dicarbonyl, 2-methoxyethanol and NH4OAc in one step. The key advantages include accepting a wide range of substrates, utilizing O2 as the sole oxidant, and synthesizing biologically active compounds such as 1,4-dihydropyridine and pyrazole. This journal is
- Chang, Yu-Lun,Huang, Sheng-Hua,Kudale, Vishal Suresh,Wang, Jeh-Jeng,Zheng, Sheng
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p. 1226 - 1230
(2022/02/21)
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- An Economical Route to Lamivudine Featuring a Novel Strategy for Stereospecific Assembly
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An economical synthesis of lamivudine was developed by employing a new method to establish the stereochemistry about the heterocyclic oxathiolane ring. Toward this end, an inexpensive and readily accessible lactic acid derivative served the dual purpose of activating the carbohydrate's anomeric center for N-glycosylation and transferring stereochemical information to the substrate simultaneously. Both enantiomers of the lactic acid derivative are available, and either β-enantiomer in this challenging class of 2′-deoxynucleoside active pharmaceutical ingredients can be formed.
- Abdiaj, Irini,Ahmad, Saeed,Burns, Justina M.,Gopalsamuthiram, Vijayagopal,Gupton, B. Frank,Krack, Rudy,McQuade, D. Tyler,Nelson, Ryan C.,Snead, David R.,Stringham, Rodger W.
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supporting information
p. 1194 - 1198
(2020/07/15)
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- Introduction of fluorine atoms to vitamin D3 side-chain and synthesis of 24,24-difluoro-25-hydroxyvitamin D3
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During our ongoing studies of vitamin D, we focused on the vitamin D3 side-chain 24-position, which is the major metabolic site of human CYP24A1. In order to inhibit the metabolism of vitamin D3, 24,24-difluorovitamin D3analogues are important candidates. In this paper, we report the practical introduction of the difluoro-unit to the 24-position to synthesize 24,24-difluoro-CD ring (1) and 24,24-difluoro-25-hydroxyvitamin D3 (2).
- Kawagoe, Fumihiro,Mototani, Sayuri,Yasuda, Kaori,Nagasawa, Kazuo,Uesugi, Motonari,Sakaki, Toshiyuki,Kittaka, Atsushi
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- Method for producing glyoxylate through oxidation of glycollate
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The invention relates to a method for producing glyoxylate through oxidation of glycollate. The invention mainly aims to overcome the problem of low yield of glyoxylate in the prior art. The method provided by the invention comprises a reaction step of contacting a nitrogen oxide and oxygen-containing gas with glycollate to produce glyoxylate. A catalyst used in the invention comprises the following components by weight: a) 0.5 to 30 parts of at least one active component selected from a group consisting of iron and iron oxides; b) 0 to 10 parts of an auxiliary agent which is at least one metal selected from a group consisting of group IA or group IIA elements or oxides thereof; and c) 70 to 99 parts of a carrier. With such a technical scheme, the above problem is overcome, and the method is applicable to industrial production of glyoxylate through oxidation of glycollate.
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Paragraph 0080; 0081; 0082; 0083; 0084; 0085; 0086-0131
(2017/12/30)
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- POLYGLYOXYLATES, MANUFACTURE AND USE THEREOF
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Self-immolative polymers degrade by an end-to-end depolymerisation mechanism in response to the cleavage of a stabilizing end-cap from the polymer terminus. Examples include homopolymers, mixed polymers including block copolymers, suitable for a variety of applications. A polyglyoxylate can be end-capped or capped with a linker as in a block copolymer.
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Page/Page column 24
(2015/11/27)
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- Polyglyoxylates: A versatile class of triggerable self-immolative polymers from readily accessible monomers
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Self-immolative polymers, which degrade by an end-to-end depolymerization mechanism in response to the cleavage of a stabilizing end-cap from the polymer terminus, are of increasing interest for a wide variety of applications ranging from sensors to controlled release. However, the preparation of these materials often requires expensive, multistep monomer syntheses, and the degradation products such as quinone methides or phthalaldehydes are potentially toxic to humans and the environment. We demonstrate here that polyglyxoylates can serve as a new and versatile class of self-immolative polymers. Polymerization of the commercially available monomer ethyl glyoxylate, followed by end-capping with a 6-nitroveratryl carbonate, provides a poly(ethyl glyoxylate) that depolymerizes selectively upon irradiation with UV light, ultimately generating ethanol and the metabolic intermediate glyoxylic acid hydrate. To access polyglyoxylates with different properties, the polymerization and end-capping approach can also be extended to other glyoxylate monomers including methyl glyoxylate, n-butyl glyoxylate, and benzyl glyoxylate, which can be easily prepared from their corresponding fumaric or maleic acid derivatives. Random copolymers of these monomers with ethyl glyoxylate can also be prepared. Furthermore, using a multifunctional end-cap that is UV-responsive and also enables the conjugation of another polymer block via an azide-alkyne "click" cycloaddition, amphiphilic self-immolative block copolymers are also prepared. These block copolymers self-assemble into micelles in aqueous solution, and their poly(ethyl glyoxylate) blocks rapidly depolymerize upon UV irradiation. Overall, these strategies are expected to greatly expand the utility of self-immolative polymers by providing access for the first time to self-immolative polymers with tunable properties that can be readily obtained from simple monomers and can be designed to depolymerize into nontoxic products.
- Fan, Bo,Trant, John F.,Wong, Andrew D.,Gillies, Elizabeth R.
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supporting information
p. 10116 - 10123
(2014/08/05)
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- Determination of absolute configuration of the phosphonic acid moiety of fosfazinomycins
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Fosfazinomycins A and B produced by Streptomyces lavendofoliae share the same phosphonate moiety with one chiral centre of unknown configuration which was determined by synthesising both enantiomers of 2-hydroxy-2-phosphonoacetic acid methyl ester. A chiral cyclic phosphite was reacted with methyl glyoxylate in a Pudovik reaction to give a pair of diastereomeric α- hydroxyphosphonates, which were separated by HPLC. The configurations at C-2 were assigned on the basis of single crystal X-ray structure analysis. Deprotection of these diastereomers furnished the enantiomeric α-hydroxyphosphonic acids, of which the (S)-configured had the same sign of optical rotation as the phosphonic acid moiety of the two fosfazinomycins.
- Schiessl, Katharina,Roller, Alexander,Hammerschmidt, Friedrich
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p. 7420 - 7426
(2013/10/22)
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- Fe(II) complexes that mimic the active site structure of acetylacetone dioxygenase: O2 and NO reactivity
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Acetylacetone dioxygenase (Dke1) is a bacterial enzyme that catalyzes the dioxygen-dependent degradation of β-dicarbonyl compounds. The Dke1 active site contains a nonheme monoiron(II) center facially ligated by three histidine residues (the 3His triad); coordination of the substrate in a bidentate manner provides a five-coordinate site for O2 binding. Recently, we published the synthesis and characterization of a series of ferrous β-diketonato complexes that faithfully mimic the enzyme-substrate intermediate of Dke1 (Park, H.; Baus, J.S.; Lindeman, S.V.; Fiedler, A.T. Inorg. Chem. 2011, 50, 11978-11989). The 3His triad was modeled with three different facially coordinating N3 supporting ligands, and substituted β-diketonates (acacX) with varying steric and electronic properties were employed. Here, we describe the reactivity of our Dke1 models toward O2 and its surrogate nitric oxide (NO), and report the synthesis of three new Fe(II) complexes featuring the anions of dialkyl malonates. Exposure of [Fe( Me2Tp) (acacX)] complexes (where R2Tp = hydrotris(pyrazol-1-yl)borate with R-groups at the 3- and 5-positions of the pyrazole rings) to O2 at -70 °C in toluene results in irreversible formation of green chromophores (λmax ~750 nm) that decay at temperatures above -60 °C. Spectroscopic and computational analyses suggest that these intermediates contain a diiron(III) unit bridged by a trans μ-1,2-peroxo ligand. The green chromophore is not observed with analogous complexes featuring Ph2Tp and PhTIP ligands (where PhTIP = tris(2-phenylimidazoly-4-yl)phosphine), since the steric bulk of the phenyl substituents prevents formation of dinuclear species. While these complexes are largely inert toward O2, Ph2Tp-based complexes with dialkyl malonate anions exhibit dioxygenase activity and thus serve as functional Dke1 models. The Fe/acac X complexes all react readily with NO to yield highspin (S = 3/2) {FeNO}7 adducts that were characterized with crystallographic, spectroscopic, and computational methods. Collectively, the results presented here enhance our understanding of the chemical factors involved in the oxidation of aliphatic substrates by nonheme iron dioxygenases.
- Park, Heaweon,Bittner, Michael M.,Baus, Jacob S.,Lindeman, Sergey V.,Fiedler, Adam T.
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p. 10279 - 10289
(2013/01/15)
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- Looking glass mechanism-based inhibition of peptidylglycine α-amidating monooxygenase
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Carboxyl-terminal amidation, a required post-translational modification for the bioactivation of many peptide hormones, entails sequential enzymatic action by peptidylglycine α-monooxygenase (PAM, EC 1.14.17.3) and peptidylamidoglycolate lyase (PGL, EC 4.3.2.5). We have previously demonstrated that PAM and PGL exhibit strict tandem reaction stereospecificities, with PAM producing exclusively α-hydroxyglycine moieties of absolute configuration (S), and PGL being reactive only toward (S)-α-hydroxyglycines, and we have also shown that PAM exhibits strict P2-subsite stereospecificity toward both peptide substrates and peptidyl competitive inhibitors. Herein, it is reported that the inhibitory stereochemistry of olefinic mechanism-based amidation inhibitors differs from the strict subsite stereospecificity exhibited by PAM toward substrates and reversible competitive inhibitors. Kinetic analyses of mechanism-based irreversible inhibition of PAM by the (S)- and (R)-enantiomers of 5-acetamido-4-oxo-6-phenyl-2-hexenoic acid were carried out using the rigorous progress curve method. The two enantiomers were found to exhibit very similar values of KI and kinact and in both cases kinetic analysis confirmed that irreversible inhibition occurs strictly at the substrate binding site with no ESI complex being formed during the catalytic processing of these irreversible inhibitors. Molecular docking studies were carried out to help rationalize the sharp contrast in the stereospecificity of PAM toward irreversible inhibitors versus substrates and competitive inhibitors. The results revealed that, in contrast to substrates, both docked enantiomers of the olefinic irreversible inhibitors are well-positioned to undergo catalytic processing at the Cu center that gives rise to irreversible inhibition. Taken together, these results provide one of the first clear examples where the stereospecificity of a particular enzyme toward mechanism-based irreversible inhibitors differs from that for substrates and competitive inhibitors.
- Foster, Michael S.,Oldham, Charlie D.,May, Sheldon W.
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experimental part
p. 283 - 293
(2011/05/17)
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- Kinetics and products of gas-phase reactions of ozone with methyl methacrylate, methyl acrylate, and ethyl acrylate
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The kinetics and products of the gas-phase reactions of ozone with methyl methacrylate, methyl acrylate, and ethyl acrylate have been investigated at 760 Torr total pressure of air and 294 ± 2 K. The rate coefficients obtained (in cm3 molecule-1 s-1 units) were as follows: k(methyl methacrylate) = (6.7 ± 0.9) × 10-18, k(methyl acrylate) = (0.95 ± 0.07) × 10-18, and k(ethyl acrylate) = (1.3 ± 0.1) × 10-18. In addition to formaldehyde being observed as a product of the three reactions, the other major reaction products were methyl pyruvate from reaction of ozone with methyl methacrylate, methyl glyoxylate from reaction of ozone with methyl acrylate, and ethyl glyoxylate from reaction of ozone with ethyl acrylate. Possible reaction mechanisms leading to the observed products are presented and discussed.
- Bernard,Eyglunent,Daele,Mellouki
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experimental part
p. 8376 - 8383
(2011/02/16)
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- Highly enantioselective organocatalytic Michael addition of nitroalkanes to 4-oxo-enoates
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A useful Michael addition reaction using nitroalkanes as the nucleophile and 4-oxo-enoates as the Michael acceptor has been disclosed, and the reaction allows expedient access to functionalized chiral γ-keto esters in high yields and excellent enantioselectivities (up to 98% ee), with a low catalyst loading.
- Lu, Hai-Hua,Wang, Xu-Fan,Yao, Chang-Jiang,Zhang, Jian-Ming,Wu, Hong,Xiao, Wen-Jing
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supporting information; experimental part
p. 4251 - 4253
(2011/03/19)
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- Enantioselective epoxidation of α,β-enones promoted by (1R,3S,4S)-2-azanorbornyl-3-methanol as an organocatalyst
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(1R,3S,4S)-2-Azanorbornyl-3-methanol was synthesized form (R)-1-phenylethylamine and used as a catalyst for the enantioselective epoxidation of α,β-enones to afford the corresponding epoxides in good yields and high enantioselectivities at room temperature.
- Lu, Jun,Xu, Yun-He,Liu, Feng,Loh, Teck-Peng
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supporting information; scheme or table
p. 6007 - 6008
(2009/04/04)
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- A metathesis-based approach to the synthesis of 2-pyridones and pyridines
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(Chemical Equation Presented) The ring-closing metathesis reaction has been successfully employed to form a range of dihydropyridone intermediates, which are in the correct oxidation state to undergo a base-induced elimination to reveal the aromatic 2-pyridone. This mild and novel approach to six-membered heteroaromatic compounds then provides access to a wide variety of substituted pyridines in excellent overall yield.
- Donohoe, Timothy J.,Fishlock, Lisa P.,Procopiou, Panayiotis A.
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p. 285 - 288
(2008/09/19)
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- Syntheses of retipolide E and ornatipolide, 14-membered biaryl-ether macrolactones from mushrooms
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Two approaches for the total synthesis of the spiromacrolide retipolide E (5) are described, the first using a modified Mitsunobu reaction as key step for the formation of the strained 14-membered macrolactone, the second a nucleophilic aromatic substitution (SNAr). In the first approach an α-oxomacrolactone 15 was obtained, which could either be converted into ornatipolide (6) or further transformed into racemic retipolide E [(R,S)-5] by directed aldol condensation with a methyl arylpyruvate. The second approach allowed the synthesis of either racemic or enantiomerically pure retipolide E (5). In the latter case Evans' methodology was used for the introduction of stereogenic center via stereoselective alkylation. The oxazolidinone auxiliary was removed under mild conditions by exchange for 2-arylethanol 22 with Otera's distannoxane catalyst. Synthetic retipolide E allowed the identification of this biosynthetic intermediate in the fruit bodies of the North American mushroom Retiboletus retipes.
- Ingerl, Andrea,Justus, Karl,Hellwig, Veronika,Steglich, Wolfgang
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p. 6548 - 6557
(2008/02/03)
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- Preparation of new monomers aza-β3-aminoacids for solid-phase syntheses of aza-β3-peptides
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The preparation of new Nβ-Fmoc-protected aza-β3-amino acids (aza-β3-aa) with proteinogenic side chains as well as their Nβ-Fmoc, Nβ-Cbz or Nβ-Boc aza-β3-amino esters (from Pro, Asn, Asp, Glu, Gln) by successive nucleophilic substitutions will be described.
- Busnel, Olivier,Baudy-Floc'h, Miche?le
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p. 5767 - 5770
(2008/02/09)
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- Synthesis of postulated molecular probes: Stereoselective free-radical-mediated C-glycosylation in tandem with hydrogen transfer
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Reported herein is a strategy employing an addition reaction in tandem with a hydrogen-transfer reaction for the elaboration of C-glycoside-based sialyl Lewis X (sLeX) analogues. Significant stereocontrol was noted when alkyl radicals were reacted with a series of alkoxytaconates. Transition states were proposed to explain the obtained selectivity. Further reaction between an anomeric-centered fucosyl-derived radical and a galactosylated hydroxytaconate provided easy access to C,O-diglycosides as mimics of sLeX. In this case, two 1,3-distant stereocenters were created with high diastereoselectivity using free radical intermediates in a tandem process.
- Guindon, Yvan,Bencheqroun, Mohammed,Bouzide, Abderrahim
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p. 554 - 558
(2007/10/03)
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- Regioselective alkene carbon-carbon bond cleavage to aldehydes and chemoselective alcohol oxidation of allylic alcohols with hydrogen peroxide catalyzed by [cis-Ru(II)(dmp)2(H2O)2] 2+ (dmp = 2,9-dimethylphenanthroline)
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(Chemical Equation Presented) [cis-Ru(II)(dmp)2(H 2O)2]2+ (dmp = 2,9-dimethylphenanthroline) was found to be a selective oxidation catalyst using hydrogen peroxide as oxidant. Thus, primary alkenes were very efficiently oxidized via direct carbon-carbon bond cleavage to the corresponding aldehydes as an alternative to ozonolysis. Secondary alkenes were much less reactive, leading to regioselective oxidation of substrates such as 4-vinylcyclohexene and 7-methyl-1,6-octadiene at the terminal position. Primary allylic alcohols were chemoselectively oxidized to the corresponding allylic aldehydes, e.g., geraniol to citral.
- Kogan, Vladimir,Quintal, Miriam M.,Neumann, Ronny
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p. 5039 - 5042
(2007/10/03)
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- Synthesis of a Gln-Phe hydroxy-ethylene dipeptide isostere
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(Chemical Equation Presented) The protected Gln-Phe hydroxyethylene dipeptide isostere 1 was synthesized as a precursor for preparation of potential inhibitors of Botulinum neurotoxin B metalloprotease. The method allows for the synthesis of additional hydroxyethylene dipeptide isosteres such as 2 with functionalized P1 side chains. The isosteres prepared were coupled with a dipeptide to produce protected pseudotetrapeptide derivatives.
- Haug, Bengt Erik,Rich, Daniel H.
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p. 4783 - 4786
(2007/10/03)
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- IR and UV spectra of ozonized phenol and guaiacol
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The UV and IR spectra of products formed at various stages of the ozonization of phenol and guaiacol in distilled water and the kinetics of ozone reactions with phenol and guaiacol were studied. The oxidation of phenol with ozone involved successive stages of the formation of acids and aldehyde acids with two and one C=C bonds and the stage of the formation of glyoxalic acid. The rates of these reactions were commensurate. The oxidation of the guaiacol aromatic ring by ozone occurred at a much higher rate than the oxidation of phenol. The end products of the ozonolysis of phenol were formic and oxalic acids. With guaiacol, esters of these acids were also formed. The results of the spectral study of the ozonolysis of phenol and guaiacol were in agreement with the conclusions drawn based on kinetic data.
- Mamleeva,Ben'Ko,Bokova,Tveritinova,Pryakhin,Lunin
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p. 926 - 929
(2007/10/03)
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- Method and product for skin lightening
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A method and cosmetic product for lightening skin is provided, the method including wiping the skin with a cosmetic towelette. Impregnated on the towelette is an alpha-hydroxy carboxylic acid or salt thereof and a sunscreen agent.
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- The aza-Diels-Alder reaction protocol - A useful approach to chiral, sterically constrained α-amino acid derivatives
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Different types of polycyclic α-amino acid derivatives are prepared from chiral imines by using well-established aza-Diels-Alder reaction conditions. Simply by varying the diene moiety, different products such as spirocyclic compounds 8 and 9, anthracene 10, and tetrahydroquinolines 15-21 are formed.
- Bertilsson, Sophie K,Ekegren, Jenny K,Modin, Stefan A,Andersson, Pher G
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p. 6399 - 6406
(2007/10/03)
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- Towelette product
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A disposable towelette product is provided which includes a flexible water-insoluble substrate such as a tissue impregnated with an alpha- or beta-hydroxycarboxylic acid in a cosmetically acceptable carrier vehicle. Impregnated cosmetic composition in water will have a pH no higher than 6.8. A silicone microemulsion is present to minimize any stickiness resulting from deposition of the hydroxycarboxylic acid by the towelette onto the skin. In the presence of fatty acid group containing surfactants, the silicone microemulsion controls foul odors that the surfactants may emit through hydrolysis at low pH.
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- Towelette product for minimizing facial fine lines and wrinkles
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A disposable towelette is provided which includes a flexible substrate such as a cellulosic tissue impregnated with an alpha-hydroxycarboxylic add delivered in a cosmetically acceptable carrier vehicle. There is further provided a method for cleansing skin and simultaneously inhibiting fine lines and wrinkles by wiping the skin with the impregnated towelette.
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- Method of purifying glyoxylic esters and distillation equipment for purifying glyoxylic esters
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A method for purifying glyoxylates includes (1) a coarse distillation process in which a crude glyoxylate in which water coexists is, in a film form, continuously subjected to coarse distillation, and (2) an azeotropic dehydration process in which the crude glyoxylate purified through the coarse distillation process is subjected to azeotropic dehydration in the presence of an azeotropic agent such as propyl acetate. By this method, high-purity glyoxylates can be efficiently and easily obtained at lower costs.
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- Atmospheric oxidation mechanism of methyl propionate
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Smog chamber FTIR techniques were used to study the atmospheric oxidation of methyl propionate in 740 Torr of air in the presence of NOx at 296 ± 2K. Relative rate techniques were used to measure k(OH + CH3CH2C(O)OCH3
- Cavalli,Barnes,Becker,Wallington
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p. 11310 - 11317
(2007/10/03)
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- Linkers
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The invention relates to a compound having the formula I wherein R1 is hydroxy, (1-6C)alkoxy or NR4R5, R4 and R5 being independently hydrogen, (1-6C)alkyl, (3-7C)cycloalkyl, (2-6C)alkenyl, (4-6C)aryl or (5-7C)aralkyl, the aryl groups of which may be optionally substituted with halogen, (1-6C)alkyl or (1-6C)alkoxy; R2 is a halo atom, (1-8C)acyloxy, -O-C(O)-O-(1-6C)alkyl, -O-C(O)-O-(5-7C)aralkyl, -SR6, -S(O)R6, -SeR6 or -Se(O)R6, R6 being (1-6C)alkyl or (4-6C)aryl; and R3 is -Si(R7)3, R7 being independently (1-6C)alkyl or (4-6C)aryl. The compounds of the invention may be used as protective groups or as linkers in solid phase organic chemistry.
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- Thermal Hetero [3 + 2] Cycloaddition of Dipolar Trimethylenemethane to O-Alkyloximes. Straightforward Synthetic Routes to Substituted Pyrrolidines and Prolines
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Thermal hetero [3 + 2] cycloaddition reaction of a dipolar trimethylenemethane 2 with an O-alkyloxime produces a substituted pyrrolidine. Thus, heating of a mixture of an alkylidenecyclopropane 1 an anti-O-alkyloxime 3 proceeds smoothly in good yield to give a substituted pyrrolidine 4 bearing a ketene acetal group in its 3-position, which upon hydrolysis under mild conditions gives a 3-alkoxycarbonylpyrrolidine 5 in quantitative yield. On the other hand, the cycloaddition to a syn-oxime is extremely slow. The cycloaddition reaction can be achieved by starting with nearly equimolar quantities of the two starting materials, and the reaction is quite insensitive to the choice of solvent and to the presence of oxygen and water. In the reaction of a substituted methylenecyclopropane 1 (R ≠ H), the reaction may take place with high regio- and stereoselectivity, which is in consonance with the concerted nature of the cycloaddition reaction. The present synthesis represents one of the rare examples of the imine-based route to pyrrolidines, which have been much less explored than the 1,3-dipolar cycloaddition route using olefin and azomethine ylide.
- Yamago, Shigeru,Nakamura, Masaharu,Wang, Xiao Qun,Yanagawa, Masao,Tokumitsu, Shuzo,Nakamura, Eiichi
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p. 1694 - 1703
(2007/10/03)
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- The functionalisation of electron rich aromatic compounds with 1,3-oxazolidines and 1,3-dimethylimidazolidine
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N-Phenyl- and N-alkyl-oxazolidines react with alkyl chlorosilanes in the presence of electron rich aromatic compounds with the formation of the expected Mannich bases: 2-methoxycarbonyl-3-methyloxazolidine also reacts with 2-methylfuran in the presence of thionyl chloride to give an a-amino acid derivative: the iminium salt derived from 1,3-dimethylimidazolidine was also shown to react with 2-methylfuran.
- Heaney, Harry,Papageorgiou, George,Wilkins, Robert F.
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p. 14381 - 14396
(2007/10/03)
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- Stereocontrolled route to some optically active β-hydroxy phosphine oxides using the stereoselective addition of metallated phosphine oxides to proline-derived keto aminals
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An asymmetric Horner-Wittig addition reaction with a chiral auxiliary attached to the electrophile is described. The key step is the addition of metallated phosphine oxides to Mukaiyama's proline-derived keto aminals (for which improved syntheses are described) and a detailed study of the factors affecting the stereoselectivity of these reactions is presented. In particular, by suitable choice of metallation conditions, complementary stereoselectivities are observed: reactions in THF with no additives are syn selective (Felkin non-chelation control) whereas reactions in toluene with added lithium bromide are anti selective (Cram chelation control).
- O'Brien, Peter,Warren, Stuart
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p. 2117 - 2127
(2007/10/03)
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- Synthesis of dipeptides containing α-substituted amino acids; their use as chiral ligands in Lewis-acid-catalyzed reactions
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L-α-Methylphenylalanine, obtained by enzymatic resolution of the corresponding racemic amide with amidase from Ochrobactrum anthropi NCIMB 40321, was used in the synthesis of dipeptides containing α-substituted amino acids.The 2-hydroxynaphthalene-1-carboxaldehyde Schiff bases of the dipeptides (1 and 2) were tested as Ti(IV) and Al(III) complexes in asymmetric Lewis-acid-catalyzed reactions.Only the Al(III) complex of 2 showed moderate enantioselectivity in the cyanation reaction of benzaldehyde with TMS-CN.
- Kaptein, Bernard,Monaco, Vania,Broxterman, Quirinus B.,Schoemaker, Hans E.,Kamphuis, Johan
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p. 231 - 238
(2007/10/02)
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- Oxidation of diazo compounds by triphenyl phosphite ozonide. Quenching of singlet oxygen by diazo compounds
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The reaction of triphenyl phosphite ozonide with various types of diazo compounds results in their oxidation, which is accomplished by singlet oxygen (1O2) evolved during thermal decomposition of the ozonide.A decrease in the ionization potential of the substrate results in an increase in the overall rate constant of quenching of 1O2.In the case of 9-diazofluorene, the main channel of 1O2 quenching is physical quenching. - Key words: phosphite ozonides, singlet oxygen; diazo compounds; ionization potential; rate constant of quenching of singlet oxygen.
- Shereshovets, V. V.,Korotaeva, N. M.,Vorob'ev, A. S.,Komissarov, V. D.,Furlei, I. I.
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p. 1479 - 1483
(2007/10/02)
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- SYNTHESES AND FLASH VACUUM PYROLYSES OF HIGHLY FUNCTIONALIZED α-N-HYDROXY AMINO ACIDS
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Flash vacuum pyrolisis (FVP) of N-acetoxy-N-vinylacetylmethionine sulfoxide and N-acetyl-N-hexadienoylglycine produced dihydropyridones, presumably by cycloaddition reactions of intermediate imines.
- Huang, Nai Zhong,Miller, Marvin J.,Fowler, Frank W.
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p. 1821 - 1826
(2007/10/02)
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- CH3OCH.+, a New Stable C2H4O.+ Isomer, and a Reassessment of the Oxirane.+ Potential Surface
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The .+ isomer of structure .+ has been shown to be unambiguously generated by CO2 loss from ionized methyl glyoxylate. ΔHf0 for this new ion was measured to be 224 +/- 1 kcal mol-1.The .+ ion produced by the loss of CH2O from ionized 1,3-dioxolane and by the loss of HCOOH from ionized methoxymethyl formate was proposed to have the structure .+, ΔHf0 = 206 +/- 2 kcal mol-1.Ionized oxirane in either its 2B1 or 2A1 state was proposed to be generated by loss of CO2 from ionized ethylene carbonate at a threshold energy corresponding to a ΔHf0 = 235 +/- 1 kcal mol-1.The structure assignments were aided by observations of collisional activation and metastable ion mass spectra.The common fragmentations of .+ and .+ ions, loss of CH3. and H., take place at similar high internal energies, leading to large kinetic energy releases in the metastable ion decompositions.Interpretations of the observations were in keeping with recent high-level ab initio molecular orbital theory calculations, but detailed mechanisms could not be established.
- Buschek, J. M.,Holmes, J. L.,Terlouw, J. K.
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p. 7321 - 7325
(2007/10/02)
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- The Synthesis of 4-Oxo-2-pentenoic Esters by Wittig Reaction Using α-Oxoesters
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The reaction of stabilized ylides with α-oxoesters gives high yields of 4-oxo-2-pentenoic esters.By suitable substitution of each reactant, highly substituted and hindered enones can be prepared in quantity, with excellent geometric selectivity.
- Schuda, Paul Francis,Ebner, Cynthia B.,Potlock, Steven J.
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p. 1055 - 1057
(2007/10/02)
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- Kinetics and Mechanism of Oxidation of Dimethyl Malonate by Chromic Acid in Presence and in Absence of Manganous Ions
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The kinetics of the chromic acid oxidation of dimethyl malonate in acetic acid-water solutions of H2SO4-H3PO4 in the presence and in absence of manganous ions have been studied at constant ionic strength, at different temperatures in the range 303-328 K and at various in the range 0.75-1.5 mol dm-3.A well defined induction period is observed.MnII ion markedly catalyses the oxidation of dimethyl malonate by chromic acid which have low activation energy.The catalysis is ascribed to the reaction, followed by a slow oxidative break down of the MnIII complex, producing free radical and MnII.Catalysis by MnII reached an upper limit when the maximum concentration of complexed ion formed.The special kinetic features of uncatalysed oxidations disappear, i.e. uncatalysed oxidation is dependent on total VI> while catalysed on fraction of ->.Energy, free energy and entropy of activation for uncatalysed reaction are 61.5 kJ mol-1, 98.7 kJ mol-1 and -117.1 J mol-1 K-1, and for catalysed reaction the values are 48.9, 80.7 and 104.6, respectively.
- Oswal, S. L.
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p. 738 - 742
(2007/10/02)
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- AN INTRAMOLECULAR DIELS-ALDER REACTION OF A Z-DIENE. GENERATION OF THE CHIRAL ISOINDOLONE NUCLEUS OF CYTOCHALASIN C.
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Aldol/elimination reactions of β-ketoamides with methyl glyoxylate result in highly selective production of Z-α, β-unsaturated amides.An intramolecular Diels-Alder reaction of a triply activated dienophile derived from chiral dienylamine 7ZE stereospecifically affords chiral bicyclic lactam 11 at room temperature.
- Hensel, M. J.,Palmer, J. T.,Learn, K. S.,Fuchs, P. L.
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p. 1297 - 1314
(2007/10/02)
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- SYNTHESIS OF DIPEROXIDES AND THEIR THERMAL DECOMPOSITION
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Diperoxides were synthesized from glycolic and lactic esters.Their thermal decomposition was realized in benzene and isopropyl alcohol, and the rate constants and apparent activation energies of the process were determined.On the basis of the kinetic data and of the nature of the isolated decomposition products a mechanism is proposed for the thermal decomposition of diperoxides.
- Kirillov, A. I.,Ivanova, L. F.,Shilov, G. I.
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p. 301 - 305
(2007/10/02)
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- A SIMPLE AND EFFICIENT SYNTHESIS OF ETHYL AND METHYL GLYOXYLATE
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Ethyl and methyl glyoxylate are both prepared in high yields from an exchange reaction between the appropriate alkyl dialkoxyacetate and glyoxylic acid, followed by reaction with phosphorus pentoxide.
- Hook, James M.,Road, Lensfield
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- A CONVENIENT METHOD FOR THE SYNTHESIS OF Α-KETOESTERS FROM ALDEHYDES
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An efficient two step, two carbon homologation of aldehydes to α-ketoesters is described.
- Horne, David,Gaudino, John,Thompson, Wayne J.
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p. 3529 - 3532
(2007/10/02)
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- Participation of Sulphonamide Nitrogen in the Rearrangement of the 2-Azabicyclooctane Skeleton: an Efficient Synthesis of the 6-Azabicyclooctan-4-one System
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Treatment of the 2-azabicyclooct-5-ene imino Diels-Alder adduct (2) with N-bromosuccinimide in aqueous dimethoxyethane gives the rearranged bromohydrin (4a), whose structure is confirmed by X-ray crystallographic analysis, and which serves as a precursor to the 6-azabicyclooctan-4-one (7).
- Holmes, Andrew B.,Raithby, Paul R.,Thompson, John,Baxter, Andrew J. G.,Dixon, John
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p. 1490 - 1492
(2007/10/02)
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- A CONVENIENT METHOD FOR THE PREPARATION OF ENOL ACETATES OF α-KETO ESTERS BY THE ALKYLATION OF CYANOHYDRIN SILYL ETHERS DERIVED FROM GLYOXYLIC ESTERS WITH BENZYL AND ALLYL HALIDES
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Cyanohydrin silyl ethers, prepared by trimethylsilylcyanation of glyoxylic esters, smoothly react with LDA (lithium diisopropylamide) to yield the lithium salts, which in turn react with alkyl halides such as allyl bromide to give, after acetylation, the corresponding enol acetates of α-keto esters in good yields.
- Mukaiyama, Teruaki,Oriyama, Takeshi,Murakami, Masahiro
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p. 985 - 988
(2007/10/02)
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- Dimethyl 1,1-Dicyanoethene-2,2-dicarboxylate, a New Electophilic Olefin
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Dimethyl 1,1-dicyanoethene-2,2-dicarboxylate (DDED), a new electrophilic tetrasubstituted olefin, was synthesized via Knoevenagel condensation.DDED spontaneously copolymerizes with electron-rich olefins such as styrene and p-methylstyrene.In the copolymerization, the bulky growing styryl radicals add to the dicyano-bearing carbon of DDED.Cyclobutane adducts are obtained in thermal reactions with styrene, p-methylstyrene, p-methoxystyrene and vinyl ethers via a tetramethylene intermediate.Bond formation occurs at diester end of DDED due to the greater stabilization provided by the dicyano group and the minimal steric requirements of the attacking methylene.
- Hall, H. K.,Sentman, R. C.
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- ELECTROCHEMICAL OXIDATION OF DIOXENE AND CHLORODIOXENE IN ALCOHOL SOLUTIONS
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2,3-Dialkoxy-1,4-dioxanes and 2-chloro-2,3-dialkoxy-1,4-dioxanes are formed during the anodic oxidation of dioxene and chlorodioxene respectively in the presence of various alcohols.The reaction of the products with sodium methoxide gave ortho esters of a new type.During hydrolysis of 2-chloro-2,3-dimethoxydioxane glyoxylic acid or its ester are obtained depending on the conditions.
- Krasavtsev, I. I.
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p. 1775 - 1777
(2007/10/02)
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