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Synthesis and characterization of monoaryl esters of l-tartaric acid and their process for fries rearrangement
Chiral protected monoaryl esters (2a-2h) were synthesized from monoester of l-tartaric acid, having two asymmetric centers and C2 axis of symmetry. l-tartaric acid was protected and partially hydrolyzed to give the corresponding monoester. Monoester upon treatment with different substituted phenols gave desired monoaryl esters (2a-2h). Fries rearrangement of monoaryl esters was then tried under various conditions by using different Lewis acids. All the compounds were purified and characterized by using spectroscopic techniques like IR, 1H-NMR, 13C-NMR, HRMS-ESI, and elemental analysis. The structure of compound 2e was obtained by X-ray crystallography.
Khan, Sher Wali,Zaidi, Javaid Hussain,Khan, Gul Shahzada,Rashid, Haroon Ur,Umar, Muhammad Naveed,Jan, Abdul Khaliq,Galan, Carman,Haddow, Mairi
p. 1819 - 1827
(2015)
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[2]Catenane Synthesis via Covalent Templating
After earlier unsuccessful attempts, this work reports the application of covalent templating for the synthesis of mechanically interlocked molecules (MiMs) bearing no supramolecular recognition sites. Two linear strands were covalently connected in a perpendicular fashion by a central ketal linkage. After subsequent attachment of the first strand to a template via temporary benzylic linkages, the second was linked to the template in a backfolding macrocyclization. The resulting pseudo[1]rotaxane structure was successfully converted to a [2]catenane via a second macrocyclization and cleavage of the ketal and temporary linkages.
Pilon, Simone,Ingemann J?rgensen, Steen,van Maarseveen, Jan H.
supporting information
p. 2310 - 2314
(2021/01/20)

Practical Cleavage of Acetals by Using an Odorless Thiol Immobilized on Silica
A practical, efficient and general method was developed for the deprotection of a variety of aromatic and aliphatic acetals to their corresponding catechol or diol derivatives using thiol immobilized on silica gel. This is an application for the well-known commercial solid-supported thiol (SiliaMetS Thiol). The procedure is mild and amenable to scale-up. It does not require inert atmosphere and clean conversions were observed. This method is applicable to substituted 1,3-benzodioxole and aliphatic acetals with different functionalities. It offers the advantage of a general route with high yield, which can be undertaken at ambient temperature.
de Léséleuc, Mylène,Kukor, Andrew,Abbott, Shaun D.,Zacharie, Boulos
p. 7389 - 7393
(2019/12/03)

Selective Monoacylation of Diols and Asymmetric Desymmetrization of Dialkyl meso-Tartrates Using 2-Pyridyl Esters as Acylating Agents and Metal Carboxylates as Catalysts
With 2-pyridyl benzoates as acylating agents and Zn(OAc)2 as a catalyst, 1,2-diols, 1,3-diols, and catechol were selectively monoacylated. Furthermore, the highly enantioselective desymmetrization of meso-tartrates was achieved for the first time, utilizing 2-pyridyl esters and NiBr2/AgOPiv/Ph-BOX in CH3CN or CuCl2/AgOPiv/Ph-BOX in EtOAc catalyst systems (up to 96% ee). The latter catalyst system was also effective for the kinetic resolution of dibenzyl dl-tartrate.
Hashimoto, Yuki,Michimuko, Chiaki,Yamaguchi, Koki,Nakajima, Makoto,Sugiura, Masaharu
p. 9313 - 9321
(2019/08/12)

Enantioselective Dihydroxylation of Alkenes Catalyzed by 1,4-Bis(9-O-dihydroquinidinyl)phthalazine-Modified Binaphthyl–Osmium Nanoparticles
A series of unprecedented binaphthyl–osmium nanoparticles (OsNPs) with chiral modifiers were applied in the heterogeneous asymmetric dihydroxylation of alkenes. A remarkable size effect of the OsNPs, depending on the density of the covalent organic shells, on the reactivity and enantioselectivity of the dihydroxylation reaction was revealed. Successful recycling of the OsNPs was also demonstrated and high reaction efficiency and enantioselectivity were maintained.
Zhu, Jie,Sun, Xiao-Tao,Wang, Xiao-Dong,Wu, Lei
p. 1788 - 1792
(2018/04/30)

Chiroptical properties of 2,2’-bioxirane
The two enantiomers of 2,2′-bioxirane were synthesized, and their chiroptical properties were thoroughly investigated in various solvents by polarimetry, vibrational circular dichroism (VCD), and Raman optical activity (ROA). Density functional theory (DFT) calculations at the B3LYP/aug-cc-pVTZ level revealed the presence of three conformers (G+, G?, and cis) with Gibbs populations of 51, 44, and 5% for the isolated molecule, respectively. The population ratios of the two main conformers were modified for solvents exhibiting higher dielectric constants (G? form decreases whereas G+ form increases). The behavior of the specific optical rotation values with the different solvents was correctly reproduced by time-dependent DFT calculations using the polarizable continuum model (PCM), except for the benzene for which explicit solvent model should be necessary. Finally, VCD and ROA spectra were perfectly reproduced by the DFT/PCM calculations for the Boltzmann-averaged G+ and G? conformers.
Daugey,De Rycke,Brotin,Buffeteau
p. 342 - 350
(2018/01/15)

Mechanistically Driven Development of an Iron Catalyst for Selective Syn-Dihydroxylation of Alkenes with Aqueous Hydrogen Peroxide
Product release is the rate-determining step in the arene syn-dihydroxylation reaction taking place at Rieske oxygenase enzymes and is regarded as a difficult problem to be resolved in the design of iron catalysts for olefin syn-dihydroxylation with potential utility in organic synthesis. Toward this end, in this work a novel catalyst bearing a sterically encumbered tetradentate ligand based in the tpa (tpa = tris(2-methylpyridyl)amine) scaffold, [FeII(CF3SO3)2(5-tips3tpa)], 1 has been designed. The steric demand of the ligand was envisioned as a key element to support a high catalytic activity by isolating the metal center, preventing bimolecular decomposition paths and facilitating product release. In synergistic combination with a Lewis acid that helps sequestering the product, 1 provides good to excellent yields of diol products (up to 97% isolated yield), in short reaction times under mild experimental conditions using a slight excess (1.5 equiv) of aqueous hydrogen peroxide, from the oxidation of a broad range of olefins. Predictable site selective syn-dihydroxylation of diolefins is shown. The encumbered nature of the ligand also provides a unique tool that has been used in combination with isotopic analysis to define the nature of the active species and the mechanism of activation of H2O2. Furthermore, 1 is shown to be a competent synthetic tool for preparing O-labeled diols using water as oxygen source.
Borrell, Margarida,Costas, Miquel
supporting information
p. 12821 - 12829
(2017/09/25)

Based on the chiral diamine spiro skeleton chiral phosphorus nitrile catalyst, preparation method and application thereof
The invention provides a chiral phosphazene catalyst based on a spiro framework adopting chiral diamine, a preparation method and an application of the chiral phosphazene catalyst. The catalyst has a structure represented in the general formula: (RX-)3P=NR', chiral groups are introduced through R and R', and the catalyst has a structure with two seven-membered rings in centered connection through phosphorspirol. Optically pure tartaric acid or substituted hexahydrophthalic acid or 1,2-cyclopentanedicarboxylicacid,(1R,2S)-rel- is taken as a raw material, chiral diamine is generated through esterification, a Grignard reaction, an optional chlorination reaction, an azido reaction and a reduction reaction of the raw material, then chiral diamine and phosphorus pentachloride have a spirocyclization reaction to construct a phosphorspirol-centered screw ring, the chiral phosphazene molecular catalyst is obtained under the alkaline condition, and a method for substituting azido for hydroxyl directly has good application and popularization value. The catalyst has the advantages of high catalysis efficiency, good stereoselectivity, mild conditions, economy, environmental protection, simplicity and convenience in operation and the like as well as popularization and application prospects.
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Paragraph 11; 12; 14; 16; 18; 20; 22; 24; 26; 28; 29

(2017/08/16)

Cis-Dihydroxylation of electron deficient olefins catalysed by an oxo-bridged diiron(III) complex with H2O2
Room temperature oxidation of olefins catalysed by a symmetrical (μ-oxo)(μ-hydroxo)diiron(III) complex (1) based on the amino pyridyl ligand bpmen (bpmen = N,N′-dimethyl-N,N′-bis(2-pyridyl methyl)ethane-1,2-diamine) with hydrogen peroxide under the conditions of limiting substrate is described. Excellent substrate conversions have been achieved under ambient reaction conditions. The olefin oxidation efficacy of the 1/H2O2 system has been found to get improved in presence of acetic acid. The catalytic system has been shown to oxidise electron-deficient olefins to the corresponding cis-diols, while epoxidation is favoured in case of electron-rich olefins. The μ-oxo diiron(III) core of the catalyst 1 has been found be regenerated after the catalytic turnovers. Addition of a second batch of substrate and oxidant at the end of the olefin oxidation results in the formation of almost identical amounts of epoxides/diols. Moreover, the regenerated catalyst exhibits a significantly higher preference towards the oxidation of electron-deficient olefins.
Kejriwal, Ambica,Biswas, Sachidulal,Biswas, Achintesh N.,Bandyopadhyay, Pinaki
p. 77 - 84
(2016/01/09)

A quaternary phosphonium salt compound and its preparation method
The present invention discloses a quaternary phosphonium salt compound and a preparation method thereof. The method uses cheap and readily available L-tartaric acid as the raw material, and conducts carboxyl esterification, hydroxyl protection, Grignard reaction, azide substitution, azide reduction and final reaction with phosphorus pentachloride, so as to obtain the quaternary phosphonium salt compound. The quaternary phosphonium salt compound is a novel Bronsted acid catalyst (a hydrogen bond donor catalyst), and can be used in the catalysis of asymmetric Mannich reaction, Michael reaction and Henry reaction.
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Paragraph 0034-0038

(2017/03/08)

Synthesis, characterization, antimicrobial and antileishmanial activities of amide derivatives of L-tartaric acid
Sixteen (16) chiral, amides were synthesized from commercially available L-tartaric acid, having two asymmetric centers and C2 axis of symmetry. The diacid functionality of L-tartaric acid was protected as dimethyl ester and dihydroxy groups as acetonoid. The partial hydrolysis of acetonoid of dimethyl ester gave the corresponding monoester. Monoester upon treatment with different substituted aromatic amines gave desired amides (1-8). Amides (1-8) afforded deprotected compounds (9-16) after reacting with acetyl chloride and methanol. All the compounds were characterized by using spectroscopic techniques such as IR, 1H-NMR, 13C-NMR, and EIMS. The compounds gave reasonable elemental analyses. The structure of compound 6 was unambiguously obtained by X-ray crystallography. Protected (1-8) and deprotected amides (9-16) were tested for their antileishmanial (against Leshmania tropica KWH23 Promastigotes) and antimicrobial activities at different concentrations against different strains of bacteria and fungi.
Khan, Sher Wali,Zaidi, Javid H.,Nasser, Nahed,El-Sayed,Khan, Khalid Mohammed,Yousuf, Sammer,Khan, Momin,Nadhman, Akhtar,Umar, M. Naveed,Perveen, Shahnaz,Miana, Ghulam Abbas
p. 70 - 79
(2016/03/12)

Design of Highly Stable Iminophosphoranes as Recyclable Organocatalysts: Application to Asymmetric Chlorinations of Oxindoles
A new family of tartaric acid derived chiral iminophosphoranes has been developed as highly effective organocatalysts in the asymmetric chlorinations of 3-substituted oxindoles with a high level of enantioselectivity. Importantly, these catalysts are air- and moisture-stable. Recovery of the catalyst after simple chromatographic separation for reuse in the model reaction was achieved; the catalyst can be recycled six times without loss of any enantioselectivity. Several advantages of this catalytic process are high conversion after a very short reaction time at ambient temperature, low catalytic loading, and scale-up to multigram quantities with an excellent enantiomeric excess value of >99%, which meets the enantiomeric purity required for pharmaceutical purposes.
Gao, Xing,Han, Jianwei,Wang, Limin
supporting information
p. 4596 - 4599
(2015/09/28)

Sesquiterpene dimers esterified with diverse small organic acids from the seeds of Sarcandra glabra
11 new sesquiterpene dimers, sarglabolides A-K (1-11), and five known ones were isolated from the seeds of Sarcandra glabra. Their structures were elucidated by spectroscopic data analysis and chemical evidence. Sarglabolide A (1) was verified to exclusively possess a seventeen-membered macrocyclic ester ring formed by the scaffold of the sesquiterpene dimer and small organic acids, different from the eighteen-membered rings of the other reported analogues. The chiral small organic acid moieties were assigned to l-malic acid, d-malic acid, and d-tartaric acid based on the combination of spectroscopy, chemical derivatization and HPLC analysis. Dimers 1, 12 and 13 can significantly inhibit NO production in LPS-induced macrophages with IC50 values at 3.04, 4.65 and 2.33 μmol/L, respectively.
Wang, Peng,Luo, Jun,Zhang, Yang-Mei,Kong, Ling-Yi
p. 5362 - 5370
(2015/07/15)

Synthesis and the absolute configuration of both enantiomers of 4,5-dihydroxy-3-(formyl)cyclopent-2-enone acetonide as a new chiral building block for prostanoid synthesis
The synthesis of both enantiomers of 4,5-dihydroxy-3-(formyl)cyclopent-2-enone acetonide (5) was accomplished in five steps starting from meso-tartaric acid (6). The key steps involved are preparation of the isopropylidene protected 3-[(dimethoxyphosphoryl)methyl]-4,5-dihydroxycyclopent-2-enone (9), resolution of the diastereoisomeric products 10 of the Horner reaction of racemic 9 with (R)-glyceraldehyde acetonide and the final regioselective ozonolysis of the exocyclic carbon-carbon double bond of the separated dienones 10 leading to both enantiomeric title compounds 5. The absolute configuration of both enantiomers was initially assigned based on the comparison of the chiroptical properties obtained from the DFT calculations with the experimental data and finally confirmed by X-ray analysis.
Lukasik, Beata,Mikolajczyk, Marian,Bujacz, Grzegorz,Zurawiski, Remigiusz
p. 807 - 816
(2015/02/19)

An optimized synthetic route for the preparation of the versatile chiral building block 1,4-di-O-benzylthreitol
An improved five-step procedure has been applied to synthesize enantiopure l- and d-1,4-di-O-benzylthreitol out of readily available l- and d-tartaric acid. Through the use of modern reagents and enhanced work-up conditions these useful auxiliaries were o
Meier, Bettina,Kollroser, Manfred,Presser, Armin
p. 305 - 309
(2014/03/21)

Li+-induced selective gelation of discrete homochiral structural isomers derived from l-tartaric acid
Two chiral structural isomers have been synthesized by molecular engineering of l-tartaric acid. In the presence of LiOH isomer 1 forms a thermally stable, fluorescent gel which exhibits interesting nano-cluster morphology, anomalous optical and rheological properties whilst 2 forms a non-fluorescent solution under similar conditions. The current-voltage (I-V) curve followed a non-linear trend, rationally in close proximity to the diode characteristic curve. This journal is the Partner Organisations 2014.
Dubey, Mrigendra,Kumar, Ashish,Gupta, Rakesh Kumar,Pandey, Daya Shankar
supporting information
p. 8144 - 8147
(2014/07/21)

Synthesis X-ray crystallography and antimicrobial activity of protected and deprotected amides
Twenty four chiral protected and deprotected amides were synthesized by using commercially available L-tartaric acid, having two asymmetric centers and C2 axis of symmetry. In the synthetic sequence, diacid functionality of L-tartaric acid was protected as dimethyl ester and dihydroxy groups as acetonoid. The partial hydrolysis of acetonoid of dimethyl ester gives the corresponding monoesters. Monoester upon treatment with different substituted aromatic amines gave desired amides (1a-1l). Amides (1a-1l) afforded compounds (2a-2l) after reacting with acetyl chrloride and methanol. All the compounds were purified and characterized by using sophisticated spectroscopic techniques including IR, 1H-NMR, 13C-NMR and elemental analysis. The structure of compounds 1a and 2l were unambiguously obtained by X-ray crystallography. Protected (1a-1l) and deprotected amides (2a-2l) were tested for their antimicrobial activities at different concentrations against different strains of bacteria and fungi and found to be antimicrobial.
Khan, Sher Wali,Zaidi, Javed Hussain,Yousuf, Sammer,Khan, Khalid Mohammed,Ambreen, Nida,Khan, Momin,Perveen, Shahnaz,Miana, Ghulam Abbas
p. 875 - 885
(2013/07/26)

Chiral-anion-dependent inversion of diastereo- and enantioselectivity in carbonyl crotylation via ruthenium-catalyzed butadiene hydrohydroxyalkylation
The ruthenium catalyst generated in situ from H2Ru(CO)(PPh 3)3, (S)-SEGPHOS, and a TADDOL-derived phosphoric acid promotes butadiene hydrohydroxyalkylation to form enantiomerically enriched products. Notably, the observed diastereo- and enantioselectivity is the opposite of that observed using BINOL-derived phosphate counterions in combination with (S)-SEGPHOS, the same enantiomer of the chiral ligand. Match/mismatch effects between the chiral ligand and the chiral TADDOL-phosphate counterion are described. For the first time, single-crystal X-ray diffraction data for a ruthenium complex modified by a chiral phosphate counterion are reported.
McInturff, Emma L.,Yamaguchi, Eiji,Krische, Michael J.
supporting information
p. 20628 - 20631
(2013/02/23)

General and efficient α-oxygenation of carbonyl compounds by TEMPO induced by single-electron-transfer oxidation of their enolates
A generally applicable method for the synthesis of protected α-oxygenated carbonyl compounds is reported. It is based on the single-electron-transfer oxidation of easily generated enolates to the corresponding α-carbonyl radicals. Coupling with the stable free radical TEMPO provides α-(piperidinyloxy) ketones, esters, amides, acids or nitriles in moderate-to-excellent yields. Enolate aggregates influence the outcome of the oxygenation reactions significantly. Competitive reactions have been analyzed and conditions for their minimization are presented. Chemoselective reduction of the products led to either N-O bond cleavage to α-hydroxy carbonyl compounds or reduction of the carbonyl functionality tomonoprotected 1,2-diols or O-protected amino alcohols. The oxygenation of enolates proves to be the most general and effective methodology for the synthesis of O-protected α-oxy carbonyl compounds and nitriles A. The scope and limitations of the electron-transfer-induced radical coupling reaction with TEMPO are presented. The reaction pathways are outlined. Methods for the deprotection to α-hydroxy carbonyl compounds B are provided and discussed. Copyright
Dinca, Emanuela,Hartmann, Philip,Smrcek, Jakub,Dix, Ina,Jones, Peter G.,Jahn, Ullrich
supporting information
p. 4461 - 4482
(2012/10/30)

Investigation of tartaric acid amide formation by thermolysis of tartaric acids with alkylamines
N,N'-dialkyltartramides were obtained by conventional thermolysis at 200 °C without a solvent, of the L-, D- or meso-tartaric acids with butyl-, hexyl- and octylamine, respectively. The products proved in all cases to be mixtures of all the possible stereoisomers, in ratios that depended on the stereochemistry of the tartaric acid applied, retaining an excess of the configuration of the starting material. Isomerization of the initially formed diamide did not take place under the reaction conditions. Mechanistically the transformation was rationalized in terms of two competing pathways - the direct substitution of the alkylamine into the carboxylic acid group, - in competition with ketene formation and subsequent amide formation. As a method for stereoselective synthesis of optically active N,N'-dialkyltartramides, the method may be considered obsolete and of little practical value; however, it provided new insight into the mechanisms of amide formation. ARKAT-USA, Inc.
Gonzalez, Susana V.,Carlsen, Per
experimental part
p. 325 - 336
(2011/08/22)

Olefin cis-dihydroxylation with bio-inspired iron catalysts. evidence for an FeII/FeIV catalytic cycle
Iron(II) complexes of a series of N-acylated dipyridin-2-ylmethylamine ligands (R-DPAH) have been investigated as catalysts for the cis-dihydroxylation of olefins to model the action of Rieske dioxygenases that catalyze arene cis-dihydroxylation. The Rieske dioxygenases have a mononuclear iron active site coordinated to a 2-histidine-1-carboxylate facial triad motif. The R-DPAH ligands are designed to provide a facial N,N,O-ligand set that mimics the enzyme active site. The iron(II) complexes of the R-DPAH ligands activate H 2O2 to effect the oxidation of olefin substrates into cis-diol products. As much as 90% of the H2O2 oxidant is converted into cis-diol, but a large excess of olefin is required to achieve the high conversion efficiency. Reactivity and mechanistic comparisons with the previously characterized Fe(TPA)/H2O2 catalyst/oxidant combination (TPA = tris(pyridin-2-ylmethyl)amine) lead us to postulate an FeII/FeIV redox cycle for the Fe(R-DPAH) catalysts in which an FeIV(OH)2 oxidant carries out the cis-hydroxylation of olefins. This hypothesis is supported by three sets of observations: (a) the absence of a lag phase in the conversion of the H 2O2 oxidant into a cis-diol product, thereby excluding the prior oxidation of the Fe(II) catalyst to an Fe(III) derivative as established for the Fe(TPA) catalyst; (b) the incorporation of H218O into the cis-diol product, thereby requiring O-O bond cleavage to occur prior to cis-diol formation; and (c) the formation of cis-diol as the major product of cyclohexene oxidation, rather than the epoxide or allylic alcohol products more commonly observed in metal-catalyzed oxidations of cyclohexene, implicating an oxidant less prone to oxo transfer or H-atom abstraction.
Oldenburg, Paul D.,Feng, Yan,Pryjomska-Ray, Iweta,Ness, Daniel,Que Jr., Lawrence
experimental part
p. 17713 - 17723
(2011/03/17)

Cis-dihydroxylation of alkenes with oxone catalyzed by iron complexes of a macrocyclic tetraaza ligand and reaction mechanism by ESI-MS spectrometry and DFT calculations
[FeIII(L-N4Me2)Cl2]+ (1, L-N4Me2 = N,N′-dimethyl-2,11-diaza[3.3](2,6) pyridinophane) is an active catalyst for cis-dihydroxylation of various types of alkenes with oxone at room temperature using limiting amounts of alkene substrates. In the presence of 0.7 or 3.5 mol % of 1, reactions of electron-rich alkenes, including cyclooctene, styrenes, and linear alkenes, with oxone (2 equiv) for 5 min resulted in up to >99% substrate conversion and afforded cis-diol products in up to 67% yield, with cis-diol/epoxide molar ratio of up to 16.8:1. For electron-deficient alkenes including α,β-unsaturated esters and α,β-unsaturated ketones, their reactions with oxone (2 equiv) catalyzed by 1 (3.5 mol %) for 5 min afforded cis-diols in up to 99% yield with up to >99% substrate conversion. A large-scale cis-dihydroxylation of methyl cinnamate (9.7 g) with oxone (1 equiv) afforded the cis-diol product (8.4 g) in 84% yield with 85% substrate conversion. After catalysis, the L-N4Me2 ligand released due to demetalation can be reused to react with newly added Fe(ClO4)2?4H2O to generate an iron catalyst in situ, which could be used to restart the catalytic alkene cis-dihydroxylation. Mechanistic studies by ESI-MS, isotope labeling studies, and DFT calculations on the 1-catalyzed cis-dihydroxylation of dimethyl fumarate with oxone reveal possible involvement of cis-HO-Fe V O and/or cis-O FeV O species in the reaction; the cis-dihydroxylation reactions involving cis-HO-FeV O and cis-O FeV O species both proceed by a concerted but highly asynchronous mechanism, with that involving cis-HO-FeV O being more favorable due to a smaller activation barrier.
Chow, Toby Wai-Shan,Wong, Ella Lai-Ming,Guo, Zhen,Liu, Yungen,Huang, Jie-Sheng,Che, Chi-Ming
experimental part
p. 13229 - 13239
(2010/12/19)

On the interactions of alkyl 2-hydroxycarboxylic acids with alkoxysilanes 2. Complexation and esterification of di- and tricarboxylic acids
The selective esterifications of l-malic, l-tartaric and citric acids with tetramethoxysilane Si(OMe)4, in methanol (MeOH) have been demonstrated for the first time. The interactions between these acids and Si(OMe)4, and also between
Ansell, Richard J.,Meegan, Jonathan E.,Barrett, Simon A.,Warrinner, Stuart L.
scheme or table
p. 1460 - 1470
(2009/06/05)

FeCl3-catalysed cleavage of 1,2-butanediacetal protected diols
Catalytic FeCl3 in acetic acid has been employed as a cost-effective, low-toxicity reagent for the removal of butane 1,2-diacetal protecting groups under mild conditions. Georg Thieme Verlag Stuttgart.
Tzschucke, C. Christoph,Pradidphol, Narathip,Diéguez-Vázquez, Alejandro,Kongkathip, Boonsong,Kongkathip, Ngampong,Ley, Steven V.
experimental part
p. 1293 - 1296
(2009/04/06)

A structural and functional model for dioxygenases with a 2-His-1-carboxylate triad
(Chemical Equation Presented) An attractive model: The iron complex shown on the left models the 2-His-1-carboxylate active sites of Rieske dioxygenases both in terms of structure and function. 18O-labeling studies of olefin dihydroxylation support the involvement of a high-valent iron-oxo species.
Oldenburg, Paul D.,Ke, Chun-Yen,Tipton, A. Alex,Shteinman, Albert A.,Que Jr., Lawrence
p. 7975 - 7978
(2007/10/03)

Supported ruthenium nanoparticle catalyst for cis -dihydroxylation and oxidative cleavage of alkenes
The present invention relates to the use of nanosized metal particles (e.g., ruthenium) grafted on inert solid support for oxidation of alkenes. The supported metal catalyst can effect cis-dihydroxylation and oxidative cleavage of alkenes to give the respective cis-diols and carbonyl products.
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Page/Page column 3; 5

(2008/06/13)

Boric acid catalyzed chemoselective esterification of α- hydroxycarboxylic acids
Boric acid catalyzes the selective esterification of α- hydroxycarboxylic acids without causing significant esterification to occur with other carboxylic acids. The procedure is simple, high-yielding, and applicable to the esterification of α-hydroxy carboxylates in the presence of other carboxylic acids including β-hydroxyacids within the same molecule.
Houston, Todd A.,Wilkinson, Brendan L.,Blanchfield, Joanne T.
p. 679 - 681
(2007/10/03)

Ruthenium nanoparticles supported on hydroxyapatite as an efficient and recyclable catalyst for cis-dihydroxylation and oxidative cleavage of alkenes
Impregnation of hydroxyapatite with colloidal ruthenium results in the formation of a catalyst that effects cis-dihydroxylation and oxidative cleavage of alkenes to their respective cis-1,2-diols and carbonyl products in good to excellent yields (see scheme). The supported ruthenium catalyst can be easily recycled and reused for consecutive reaction runs without significant deterioration of the catalytic activities. R1, R2 = H, alkyl, aryl.
Ho, Chi-Ming,Yu, Wing-Yiu,Che, Chi-Ming
p. 3303 - 3307
(2007/10/03)

An improved synthesis of aziridine-2,3-dicarboxylates via azido alcohols - Epimerization studies
The reasons for epimerization of 3-azido-2-hydroxysuccinates observed during the ring opening of epoxides or cyclic sulfites with sodium azide is now clarified. It is caused by the high acidity of the proton at the 3-position. This is proven by a proton deuterium exchange in assays with either D 2O or DCl containing solvents. The anti-3-azido-2-hydroxysuccinates serve as intermediates for enantiomerically pure trans-aziridine-2,3- dicarboxylates for which an optimized synthetic pathway is presented. The first example of an enantiomerically pure mixed diester of the aziridine-2,3- dicarboxylic acid the synthesis of the allyl ethyl ester is reported herein.
Breuning, Alexander,Vicik, Radim,Schirmeister, Tanja
p. 3301 - 3312
(2007/10/03)

Absolute stereochemistry of chiral, C60 fullerene bis-adducts
To determine the absolute configuration of chiral fullerene bis-adducts, we have studied the double Bingel reaction of C60 with chiral tether (2S,3S)-(-)-9 derived from (R,R)-(+ -tartaric acid, and have succeeded in isolating two possible chiral bis-adducts 10a (5%) and 10b (2%) in addition to the Cs-symmetrically added derivative 10c (40%). The CD spectra of chiral bis-adducts [CD(+)281]-10a and [CD(-)281]-10b show very intense Cotton effects, which are almost of mirror image, indicating that their chiral C60 π-electron systems are enantiomeric each other. The 1H and 13C NMR spectra of 10a and 10b indicate that they have C2-symmetrical structures, and the vicinal coupling constants between two equivalent protons H-2 and H-2′ were determined as 1.2 Hz for 10a and 1.8 Hz for 10b, respectively by the 13C satellite band method. From the conformational analyses, the absolute configurations of these chiral C60 fullerene bis-adducts were unambiguously determined as [CD(+)281]-(S,S,fC)-10a and [CD(-)281]-(S,S,fA) -10b, respectively.
Yoshida, Kazuhiro,Osawa, Shuichi,Monde, Kenji,Watanabe, Masataka,Harada, Nobuyuki
p. 23 - 32
(2007/10/03)

A mild and effective method for the transesterification of carboxylic acid esters
An extraordinarily versatile transesterification of simple or highly functionalized esters of aliphatic and aromatic carboxylic acids in high yields is catalyzed by dibutyltin oxide [Eq. (1)]. The reaction is compatible with several functional groups, for example, acetals, ketals, aliphatic bromides, enol ethers, urethanes, as well as free hydroxy, phenolic, and amino groups, and even with water.
Baumhof, Patrick,Mazitschek, Ralph,Giannis, Athanassios
p. 3672 - 3674
(2007/10/03)

Studies toward the synthesis of pinolidoxin, a phytotoxic nonenolide from the fungus Ascochyta pinodes. Determination of the configuration at the C-7, C-8, and C-9 chiral centers and stereoselective synthesis of the C6- C18 fragment
The absolute stereochemistry at the C-7, C-8, and C-9 chiral centers of pinolidoxin (1) has been determined by chemical and spectral methods. First, the synthesis of four stereoisomeric fully benzoylated 2,3-erythro-1,2,3,4- heptanetetrols, corresponding to the C6-C18 portion of the natural substance, has been accomplished starting from meso-tartaric acid. As next step, the selection of the synthetic tetrabenzoate possessing 'natural' stereochemistry (10a') suitable for absolute configuration determination, has been carried out by correlation with its 'natural' homologue derived from degradation of pinolidoxin. Determination of the stereochemistry at the title chiral centers has been carried out by application of the Mosher's method both to 7a', a compound stereochemically related to 10a', and to pinolidoxin itself. The stereoselective synthesis of a protected form of the C6-C18 portion of pinolidoxin, to be used in its total synthesis, has also been accomplished starting from commercially available D-erythronolactone.
De Napoli, Lorenzo,Messere, Anna,Palomba, Daniela,Piccialli, Vincenzo,Evidente, Antonio,Piccialli, Gennaro
p. 3432 - 3442
(2007/10/03)

A selective method for the preparation of aliphatic methyl esters in the presence of aromatic carboxylic acids
2,2-Dimethoxypropane, methanol and a catalytic amount of HCl selectively esterify aliphatic carboxylic acids, in the presence of aromatic carboxylic acids, at room temperature and in high yields.
Rodriguez,Nomen,Spur,Godfroid
p. 8563 - 8566
(2007/10/03)

Selective esterification of aliphatic nonconjugated carboxylic acids in the presence of aromatic or conjugated carboxylic acids catalysed by NiCl2.6H2O
Unhindered aliphatic nonconjugated carboxylic acids were esterified selectively in the presence of aromatic or conjugated acids on heating in the corresponding alcoholic solutions at reflux for 3-13 hr with 10 mol% of NiCl2.6H2O catalyst.
Ram, Ram N.,Charles
p. 7335 - 7340
(2007/10/03)

Rhutenium-Catalyzed cis-Dihydroxylation of Alkenes: Scope and Limitations
Oxidative ruthenium catalysis (0.07 molequiv RuCl3*(H2O)3, 1.5 molequiv NaIO4, EtOAc/CH3CN/H2O 3:3:1), beyond the usual C-C bond cleavage to give dicarbonyls, have been shown to syn-dihydroxylate a wide range of alkenes (except for strained bicyclic alkenes, sterically hindered trisubstituted alkenes, and most tetrasubstituted alkenes) to give vicinal diols rapidly (within minutes) and efficiently.The minor products are the usual oxidative fission products, namely, ketones and aldehydes or carboxylic acids, and sometimes ketols.Longer reaction times lower the yields of most diols, probably owing to oxidative glycol cleavage.Reactions with substrates containing one or more electron-withdrawing groups in conjugation with or adjacent to the alkene moiety are generally slower but give better yields.The diastereoselectivity of the present "flash" dihydroxylation, anti to the existing α-stereogenic center, with cycloalkenes is excellent whereas that with acyclic alkenes is moderate to poor.Sodium metaperiodate is still the best co-oxidant for the catalytic reaction.Aqueous acetonitrile (approximately 86percent) as an alternative solvent system was found to give better yields of 1,2-diols than the original solvent system in some cases. - Keywords: alkenes, catalysis, dihydroxylations, electrophilicity, ruthenium compounds.
Shing, Tony K. M.,Tam, Eric K. W.,Tai, Vincent W.-F.,Chung, Ivan H. F.,Jiang, Qin
p. 50 - 57
(2007/10/03)

Chiral γ-(tetrahydropyranyloxy)allylstannane: a new chiral reagent for the asymmetric synthesis of syn 1,2-diols
(2R,3S)-3-Allyloxy-3,4,5,6-tetrahydro-2H-pyran-2-methanol was prepared in high yield from tri-O-acetyl-D-glucal, an easily available and cheap chiral source.The hydroxy group was protected as the t-butyldiphenylsilyl ether, and the allyl group was converted to the corresponding allyl stannane via formation of allyl carbanion and subsequent trapping with tributylstannyl chloride.The γ-alkoxy allyl stannane 1 bearing the (2R,3S)-2--3,4,5,6-tetrahydro-2H-pyran-3-yloxy auxiliary at the allyl terminus was prepared by this procedure.The reaction of 1 with aldehydes in the presence of AlCl3*OEt2 or AlCl3 gave the corresponding syn adducts 2 with high diastereoselectivities; the ratio of syn/anti > 97:3.The diastereomeric excess of the syn adducts 2, that is, the ratio 2/(2 + the (S,S) isomer of 2), varied from 85 to 94percent.Removal of the protecting group of 2 gave the (R,R) diols 3.The high diastereo- and enantioselectivity in the formation of the (R,R) isomer is accounted for by an anti S'E transition state 18. allylstannane / γ-alkoxyallylstannane / asymmetric synthesis / syn-1,2-diol / Lewis acid / allylstannane-aldehyde condensation / γ-(tetrahydropyranyloxy)allylstannane / anti S'E
Kadota, Isao,Kobayashi, Katsumi,Okano, Hiroshi,Asao, Naoki,Yamamoto, Yoshinori
p. 615 - 623
(2007/10/02)

Asymmetric Dihydroxylation of Olefins with a Simple Chiral Ligand
A C2 symmetrical chiral ligand derived from (R,R)-trans-1,2-diaminocyclohexane is highly effective in the asymmetric cis-dihydroxylation of aromatic and aliphatic di- and trisubstituted olefins under stoichiometric conditions.
Hanessian, Stephen,Meffre, Patrick,Girard, Mario,Beaudoin, Serge,Sanceau, Jean-Yves,Bennani, Youssef
p. 1991 - 1993
(2007/10/02)

A CONVENIENT METHOD FOR ENZYMATIC BENZYL-ALKYL TRANSESTERIFICATION UNDER MILD NEUTRAL CONDITIONS
Lipases from Candida cylindracea and from Pseudomonas fluorescens efficiently catalyse the benzyl to alkyl transesterification in organic solvents under mild conditions in nearly quantitative yields.
Gutman, Arie L.,Shkolnik, Eleonora,Shapira, Michal
p. 8775 - 8780
(2007/10/02)

Asymmetric Synthesis of Syn 1,2-Diols via the Reaction of Aldehydes with Chiral γ-(Tetrahydropyranyloxy)allylstannanes
Asymmetric synthesis of syn 1,2-diols 3 has been accomplished via the reaction of the chiral γ-alkoxy-substituted allylstannane 1 with aldehydes in the presence of AlCl3 or AlCl3*OEt2, followed by a five-step operation to remove the chiral auxiliary.
Yamamoto, Yoshinori,Kobayashi, Katsumi,Okano, Hiroshi,Kadota, Isao
p. 7003 - 7005
(2007/10/02)

Highly Enantioselective Dihydroxylation of Trans-Disubstituted and Monosubstituted Olefins
Extremely high levels of asymmetric induction have been achieved in osmium tetraoxide oxidation of trans-disubstituted and monosubstituted olefins by using chiral N,N'-dineohexyl-2,2'-bipyrrolidine ligand.
Oishi, Tohru,Hirama, Masahiro
p. 5834 - 5835
(2007/10/02)

Enantioselective Vicinal Hydroxylation of Terminal and E-1,2-Disubstituted Olefins by a Chiral Complex of Osmium Tetraoxide. An Effective Controller System and a Rational Mechanistic Model
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Corey, E. J.,Jardine, Paul DaSilva,Virgil, Scott,Yuen, Po-Wai,Connell, Richard D.
p. 9243 - 9244
(2007/10/02)

Asymmetric Dihyroxylation of Alkenes with Osmium Tetroxide: Chiral N,N'-Dialkyl-2,2'-bipyrrolidine Complex
Asymmetric osmylation of alkenes by using N,N'-dialkyl-2,2'-bipyrrolidines as the chiral ligands shows a high asymmetric induction and a marked dependence of the enantioselectivity on both the N-alkyl group and the reaction solvent.
Hirama, Masahiro,Oishi, Tohru,Ito, Sho
p. 665 - 666
(2007/10/02)

Enantioface Differentiation in Cis Dihydroxylation of C-C Double Bonds by Osmium Tetroxide with Use of a Chiral Diamine with D2 Symmetry
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Tomioka, Kiyoshi,Nakajima, Makoto,Koga, Kenji
p. 6213 - 6215
(2007/10/02)

AN ECONOMICAL LARGE SCALE PREPARATION OF (2S,3S)-4,5-DIMETHYL-2-PHENYL-1,3-DIOXOLAN
An economical 5-step synthesis of (2S,3S)-4,5-dimethyl-2-phenyl-1,3-dioxolan from (2R,3R)-tartaric acid is described.
Kocienski, Philip,Street, Stephen D. A.
p. 1087 - 1092
(2007/10/02)

A Study of Stereoselective Hydrolysis of Symmetrical Diesters with Pig Liver Esterase
Pig liver esterase (PLE) catalyzed hydrolysis of dimethyl esters of symmetrical dicarboxylic acids, including meso-diacids, cis-1,2-cycloalkanedicarboxylic acids, and diacids with a prochiral center, was studied with 14 substrates.The products of these stereoselective hydrolyses are chiral monoesters of dicarboxylic acids, with an enantiomeric excess (e.e.) from 10percent to 100percent.Some of these optically active monoesters are valuable synthons in natural products synthesis.An additivity pattern of α- and β-substituents with the glutaric esters on the stereoselectivity of enzymatic hydrolysis was observed.Analysis of the experimental results leads to a model of enzyme stereoselectivity of diester hydrolysis in which the substitution pattern at α- and β-C-atoms is found to determine the absolute configuration of the resulting monoester.
Mohr, Peter,Waespe-Sarcevic, Nada,Tamm, Christoph,Gawronska, Krystyna,Gawronsky, Jacek K.
p. 2501 - 2511
(2007/10/02)

Stoffwechselproducte von Mikroorganismen. Strukturaufklaerung von Elaiophylin: Spektroskopische Untersuchungen und Abbau
The structure of the antibiotic elaiophylin (azalomycin B) was elucidated by extended spectroscopic investigations and chemical degradation.Elaiophylin (26) is a macrodiolide with a 16 membered dilactone ring.The synthesis of 7-acetoxy-6-ethyl-3-octanone (14), the acetyl derivative of an important degradation product, is described.
Kaiser, Hanspeter,Keller-Schierlein, Walter
p. 407 - 424
(2007/10/02)

STEREOCHEMISTRY OF α,α'-DIFLUOROSUCCINIC ACIDS
Treatment of both dimethyl (-)-D-tartrate (IVa) and dimethyl (+)-L-tartrate (Va) with sulfur tetrafluoride gave dimethyl meso-α,α'-difluorosuccinate (Ia).The same reagent converted dimethyl meso-tartrate (IIIa) to a racemic mixture of dimethyl D- and L-α,α'-difluorosuccinate (IIa).This outcome resulting from the replacement of hydroxyl by fluorine with inversion of configuration at one and retention of configuration at the other chiral carbon atom can be rationalized by assuming the formation of a cyclic intermediate.This is opened by a subsequent SN2 reaction with fluoride ion followed by a four-center displacement of sulfuroxy group by fluorine.The respective configuration of the dimethyl α,α'-difluorosuccinates Ia and IIa were established by (1)H and (19)F NMR using an optically active chemical shift reagent and confirmed by converting the esters to the corresponding acids and these in turn to the cis- and trans-α,α'-difluorosuccinic anhydrides, respectively.
Bell, H. M.,Hudlicky, M.
p. 191 - 200
(2007/10/02)