- Design, Synthesis, and Conformational Analysis of Proposed β-Turn Mimics from Isoxazoline-Cyclopentane Aminols
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Constrained aminols from oxazanorbornene derivatives have the geometrical features to be used as β-turn inducers. Four different stereoisomers were prepared and spectroscopically characterized (MD calculations, NMR-titration and VT-NMR experiments). Temperature coefficients in DMSO are indicative for the existence of an intramolecular hydrogen bond. Chirooptical properties revealed a β-turn arrangement of all the synthesized compounds, where, depending on the absolute configuration of the cyclopentane spacer, they can be labeled as left- or right-handed turns.
- Memeo, Misal Giuseppe,Mella, Mariella,Montagna, Valentina,Quadrelli, Paolo
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Read Online
- Synthesis of illudalic acid and analogous phosphatase inhibitors
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Developing an efficient, concise synthesis of the fungal natural product illudalic acid has been a long-standing challenge, made more pressing by the recent discovery that illudalic acid and analogs are selective phosphatase inhibitors. Syntheses of illudalic acid have become progressively more efficient over the decades yet remain strategically grounded in a 17-step synthesis reported in 1977. Here we validate a two-step process—convergent [4 + 2] benzannulation and one-pot coordinated functional group manipulations—for preparing the key trifunctional pharmacophore of illudalic acid. The modular building blocks are readily available in 2-3 steps, for a longest linear sequence (LLS) of 5 steps to illudalic acid from 3,3-dimethylcyclopentanone. A small collection of analogous indanes and tetralins featuring the same pharmacophore were prepared by a similar route. These compounds potently and selectively inhibit the human leukocyte common antigen-related (LAR) subfamily of protein tyrosine phosphatases (PTPs). Evidence supporting a postulated covalent ligation mechanism is provided herein.
- Ahmed, Kh Tanvir,Barrios, Amy M.,Batsomboon, Paratchata,Dudley, Gregory B.,Fulo, Harvey F.,Gaston, Robert,Rueb, Nicole J.
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supporting information
p. 10596 - 10600
(2021/12/27)
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- Biomimetic regioselective and high-yielding Cu(i)-catalyzed dimerization of sinapate esters in green solvent Cyrene: Towards sustainable antioxidant and anti-UV ingredients
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Naturally occurring sinapic acid and its esters are anti-UV and antiradical chemicals. This work aimed at designing an industrially relevant sustainable synthetic pathway allowing their selective β-β′ dimerization to enhance their properties with a view to use them in commercial applications such as functional additives for cosmetics, plastics and food/feed. A copper(i)-catalyzed procedure involving pyridine and O2 from air was developed and greened up using the REACH-compliant bio-based solvent Cyrene. Upon optimizing further through design of experiments, this sustainable synthetic process was successfully implemented to various sinapate esters and was validated on the multigram scale. Antiradical activities of the resulting β-β′ disinapate esters were benchmarked against commercial antioxidants, whereas their UV absorbance was compared to that of sinapoyl malate, a natural anti-UV compound found in plants and that of Octinoxate, a widely used commercial sunscreen ingredient. Results showed that these dimers were better radical scavengers, and not only exhibited a better UV absorbance but also covered both UV-A and UV-B regions.
- Mention, Matthieu M.,Flourat, Amandine L.,Peyrot, Cédric,Allais, Florent
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supporting information
p. 2077 - 2085
(2020/04/08)
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- Design and synthesis of the ring-opened derivative of 3-n-butylphthalide-ferulic acid-glucose trihybrids as potential anti-ischemic agents
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To improve aqueous solubility and anti-ischemic activity of 3-n-butylphthalide (NBP), we designed and synthesized the ring-opened derivative of NBP-ferulic acid-glucose trihybrids (S1-S8). These hybrids inhibited adenosine diphosphate (ADP)- or arachidonic acid (AA)-induced platelet aggregation, among them, S2 was 30-fold more water-soluble, and over 10-fold more potent in inhibition of platelet aggregation, as well as reduced ROS generation and protected primary neuronal cells from OGD/R-induced damage, in comparison with NBP. Additionally, S2 was more active than its three moieties alone or in combination, suggesting that the activity of S2 may be attributed to the synergistic effects of these moieties. Importantly, in vivo studies indicated that S2 not only possessed good pharmacokinetic profile, but also improved NBP distribution in rodent brain, suggesting that the glucose moiety in S2 may be recognized by glucose transporter 1 (GLUT1) on blood-brain barrier (BBB), promoting it to penetrate through BBB. Our findings suggest that S2 may be a promising candidate for the intervention of ischemic stroke, warranting further study.
- Wu, Jianbing,Yin, Wei,Zhang, Yinqiu,Ye, Hui,Li, Yunman,Tian, Jide,Huang, Zhangjian,Zhang, Yihua
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supporting information
p. 1881 - 1886
(2020/03/13)
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- Synthesis and evaluation of new 4-peptidamido-2-fluorobenzyl phosphoramide mustard conjugates as prodrugs activated by prostate-specific antigen
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In our continued efforts to develop targeted prodrugs activated by prostate-specific antigen (PSA), we designed and synthesized novel phosphoramide mustard peptide conjugates using previously optimized PSA substrates. Initial Nu/Nu mouse PK studies indicated that prodrug I (glutaryl-Hyp-Ala-Ser-Chg-Gln-NH-2-F-Bn-phosphoramide mustard) exhibits high clearance with significant extrahepatic metabolism in vivo. Substrate optimization studies were thus carried out to further improve PSA specificity and enable the design of prodrugs with reduced in vivo clearance and enhanced tumor selectivity. To assess the utility of the newly optimized sequences as promoieties, they were coupled to phosphoramide mustard using a 4-amino-2-fluorobenzyl alcohol linker akin to prodrug I. In the presence of human PSA, prodrug I was rapidly cleaved with a half-life (t1/2) of 35 min. Prodrugs II (glutaryl-Ser-Ala-Ser-Chg-Gln-NH-2-F-Bn-phosphoramide mustard) and III (GABA ← mGly-Ala-Ser-Chg-Gln-NH-2-F-Bn-phosphoramide mustard) were hydrolyzed at slower rates with t1/2 values of 80 and 107 min, respectively. These results we observed here are different from our previously reported data but may be explained by the fact that PSA-activated release of phosphoramide mustard and reactive quinonimine methides resulted in mechanism-based inhibition of PSA, thereby preventing further hydrolysis of prodrugs I–III. Prodrug I was cytotoxic to PSA-producing LNCaP cells with an IC50 value of 7.3 μM and demonstrated 14-fold selectivity over the non-PSA-producing DU145. Despite its poor in vitro antiproliferative activity (IC50 = 30 μM), prodrug III was found to be more stable against non-PSA-mediated hydrolysis compared with prodrug I as revealed by metabolite profiling studies, which was in agreement with its improved stability in human hepatocyte cultures. These results suggested that a combination of the peptide sequence GABA ← mGly-Ala-Ser-Chg-Gln with optimal linkers and/or other cytotoxic agents can help achieve an adequate balance between PSA cleavage rate and enhanced resistance to non-PSA-mediated hydrolysis. [Figure not available: see fulltext.]
- Aloysius, Herve,Hu, Longqin
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- PRO-DRUGS OF ELIGLUSTAT
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The present invention is directed to pro-drugs of Eliglustat (formula A) and process for the preparation thereof. The present invention is further directed to pharmaceutical composition thereof and method of treatment using the same.
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Page/Page column 54
(2019/11/19)
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- Mechanistic Studies of the Deslongchamps Annulation
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The Cs2CO3-mediated annulations ("Deslongchamps annulations") of three spirocyclic benzoquinone monoketals 5b-d with an ester or acyl substituent at C-2 to two tert-butyl esters of λδ-unsaturated β-ketocarboxyl acids ("Nazarov reagents" 2a,b) were monitored 1H NMR spectroscopically. This revealed that a primary product, by all likelihood the Michael adduct, forms fast and prior to the appearance of the Deslongchamps adduct. These primary products form reversibly. This was proved by two crossover and four scavenging experiments. Therein, components already incorporat.
- Kreibich, Michael,Petrovi?, Denis,Brückner, Reinhard
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supporting information
p. 1116 - 1133
(2018/02/14)
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- NEW PEPTIDE-LINKED ESTER PRODRUGS ACTIVATED BY PROSTATE-SPECIFIC ANTIGEN
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The present disclosure is directed to a series of target-selective chemotherapeutic ester prodrugs comprising PSA-cleavable peptides that promote the delivery of free doxorubicin and other chemotherapeutic agents into the prostate and/or prostate tumors with greater efficiency.
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Paragraph 72-73
(2018/08/26)
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- Development of catalytic deacylative alkylations (DaA) of 3-acyl-2-oxindoles: total synthesis of meso-chimonanthine and related alkaloids
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We present an effective deacylative alkylation strategy for the construction of a variety of 2-oxindoles bearing an all-carbon quaternary center at the pseudobenzylic position. A wide variety of products with quaternary centers could be accessed by employing simple Pd(0) catalysis under mild reaction conditions. Importantly, the same strategy works equally well for the dimeric 2-oxindole system, furnishing products with a vicinal quaternary center in favour of meso-isomer as the major product. Eventual application to the total syntheses of meso-chimonanthine and meso-folicanthine very well demonstrates the synthetic potential of this strategy.
- Kumar, Nivesh,Das, Mrinal Kanti,Ghosh, Santanu,Bisai, Alakesh
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supporting information
p. 2170 - 2173
(2017/02/19)
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- Synthesis of 2-oxindoles via 'transition-metal-free' intramolecular dehydrogenative coupling (IDC) of sp2 C-H and sp3 C-H bonds
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The synthesis of a variety of 2-oxindoles bearing an all-carbon quaternary center at the pseudo benzylic position has been achieved via a 'transition-metal-free' intramolecular dehydrogenative coupling (IDC). The construction of 2-oxindole moieties was carried out through formation of carbon-carbon bonds using KOt-Bu-catalyzed one pot C-alkylation of β-N-arylamido esters with alkyl halides followed by a dehydrogenative coupling. Experimental evidences indicated toward a radical-mediated path for this reaction.
- Kumar, Nivesh,Ghosh, Santanu,Bhunia, Subhajit,Bisai, Alakesh
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supporting information
p. 1153 - 1169
(2016/07/06)
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- Application of asymmetric alkylation of malonic diester with phase-transfer catalysis: Synthesis of LFA-1 antagonist BIRT-377
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An efficient asymmetric synthesis of LFA-1 antagonist BIRT-377 using enantioselective phase-transfer catalytic alkylation has been developed. The alkylation of α-monosubstituted tert-butyl methyl malonate was catalyzed by a quaternary ammonium salt derived from a cinchona alkaloid to obtain the product with a quaternary stereogenic carbon in high yield and with high enantioselectivity. The chiral α,α-disubstituted product thus obtained was transformed into BIRT-377 through alternating chemoselective deprotection of the two ester groups followed by Curtius rearrangement.
- Kanemitsu, Takuya,Furukoshi, Saeka,Miyazaki, Michiko,Nagata, Kazuhiro,Itoh, Takashi
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p. 214 - 218
(2015/03/04)
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- Synthesis and antitumor activity of feruloyl and caffeoyl derivatives This paper is dedicated to Prof. Wei-xiao Hu for his lifelong commitment to mentoring graduate students
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We developed two efficient protocols for the synthesis of feruloyl and caffeoyl derivatives from commercial vanillin and veratraldehyde. Pharmacological activities were assessed against a panel of human cancer cell lines in vitro. Most synthesized compounds demonstrated attractive cytotoxicity. Several new compounds demonstrated significant antiproliferative and cytotoxic activities against HeLa and Bewo tumor cell lines. In particular, 5-nitro caffeic adamantyl ester showed broad spectrum of tumor inhibition in 10 cell lines, and reduced tumor weight by 36.7% in vivo when administered at a dose of 40 mg kg-1.
- Chen, Hui-Zhen,Chen, You-Bao,Lv, Ya-Ping,Zeng, Fang,Zhang, Juan,Zhou, Yong-Lie,Li, Han-Bing,Chen, Li-Fei,Zhou, Bin-Jie,Gao, Jian-Rong,Xia, Chun-Nian
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supporting information
p. 4367 - 4371
(2015/02/06)
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- DDQ-mediated direct Intramolecular-Dehydrogenative-Coupling (IDC): Expeditious approach to the tetracyclic core of ergot alkaloids
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An efficient route to 2-oxindoles bearing an all-carbon quaternary center at the pseudobenzylic position has been developed via a DDQ-mediated Intramolecular-Dehydrogenative-Coupling (IDC). The methodology involves a one-pot C-alkylation of β-N-arylamido esters (7) concomitant with dehydrogenative-coupling in the presence of stoichiometric amount of DDQ. A tentative mechanistic route has been proposed for the oxidative coupling. The methodology provides a two-step entry to the ergoline structure of ergot alkaloids.
- Bhunia, Subhajit,Ghosh, Santanu,Dey, Dhananjay,Bisai, Alakesh
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supporting information
p. 2426 - 2429
(2013/06/27)
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- Intramolecular dehydrogenative coupling of sp2 C-H and sp 3 C-H bonds: An expeditious route to 2-oxindoles
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An intramolecular-dehydrogenative-coupling (IDC) using "transition- metal-free" oxidation conditions has been achieved to synthesize a variety of 2-oxindoles bearing an all-carbon quaternary stereogenic center at the benzylic position. The methodology involves a one-pot C-alkylation of β-N-arylamido esters (3, 6) with alkyl halides using potassium tert-butoxide concomitant with a dehydrogenative coupling. A radical-mediated pathway has been tentatively proposed for the oxidative process.
- Ghosh, Santanu,De, Subhadip,Kakde, Badrinath N.,Bhunia, Subhajit,Adhikary, Amit,Bisai, Alakesh
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supporting information
p. 5864 - 5867
(2013/02/22)
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- Biomimetic synthetic studies on lactonamycin: An expedient synthesis of dihydroxy-isoindolinone-carboxylates
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The synthesis of dihydroxy-isoindolinone-carboxylates from a dioxinone keto-ester and N-protected sarcosine without the use of phenolic protection is described. Base-induced aromatization of the dioxinone diketo-ester followed by lactamization furnished the desired dihydroxy-isoindolinone moiety, which could be used as an EF-ring precursor toward the synthesis of lactonamycin.
- Jacques, Sylvain A.,Patel, Bhavesh H.,Barrett, Anthony G.M.
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scheme or table
p. 6072 - 6075
(2011/11/30)
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- Delineating origins of stereocontrol in asymmetric Pd-catalyzed α-hydroxylation of 1,3-ketoesters
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Systematic studies of reaction conditions and subsequent optimization led to the identification of important parameters for stereoselectivity in the asymmetric α-hydroxylation reaction of 1,3-ketoesters. Enantioselectivities of up to 98% can be achieved for cyclic substrates and 88% for acyclic ketoesters. Subsequently, the combination of cyclic/acyclic ketoester, catalyst, and oxidant was found to have a profound effect on reaction rates and turnover-limiting steps. The stereochemistry of the reaction contradicts that observed for other similar electrophilic substitution reactions. This was rationalized by transition-state modeling, which revealed a number of cooperative weak interactions between oxidant, ligand, and counterion, together with C-H/π interactions that cumulatively account for the unusual stereoselectivity.
- Smith, Alexander M. R.,Rzepa, Henry S.,White, Andrew J. P.,Billen, Denis,Hii, King Kuok
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supporting information; experimental part
p. 3085 - 3096
(2010/07/17)
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- Synthesis of trans-caffeate analogues and their bioactivities against HIV-1 integrase and cancer cell lines
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Forty caffeate analogues were synthesized via a convenient method starting from vanillin with moderate to good yields. The testing of biological activity of these compounds against HIV-1 integrase indicates that four compounds: bornyl caffeate, bornyl 2-nitrocaffeate, 5-nitrocaffeic acid and 5-nitrocaffeic acid phenethyl ester (5-nitroCAPE) possess a good HIV integrase inhibitory activity, IC50 19.9, 26.8, 25.0 and 13.5 μM, respectively. Twelve caffeate analogues were tested by MTT assay on growth of human hepatocellular carcinoma BEL-7404, human breast MCF-7 adenocarcinoma, human lung A549 adenocarcinoma and human gastric cancer BCG823 cell lines, respectively. And the best result is IC50 5.5 μM for CAPE against BEL-7404.
- Xia, Chun-nian,Li, Hai-bo,liu, Feng,Hu, Wei-xiao
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supporting information; experimental part
p. 6553 - 6557
(2009/09/06)
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- Synthesis and biological evaluation of pyrophosphate mimics of thiamine pyrophosphate based on a triazole scaffold
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Novel triazole-based pyrophosphate analogues of thiamine pyrophosphate (TPP) have been synthesised and tested for inhibition of pyruvate decarboxylase (PDC) from Zymomonas mobilis. The thiazolium ring of thiamine was replaced by a triazole in an efficient two-step procedure. Pyrophosphorylation then gave extremely potent triazole inhibitors with KI values down to 20 pM, compared to a KD value of 0.35 μM for TPP. This triazole scaffold was used for further investigation and six analogues containing mimics of the pyrophosphate group were synthesised and tested for inhibition of PDC. Several effective analogues were found with KI values down to around 1 nM.
- Erixon, Karl M.,Dabalos, Chester L.,Leeper, Finian J.
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experimental part
p. 3561 - 3572
(2009/02/05)
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- Process for preparing C7 intermediates and their use in the preparation on N-substituted pyrrole derivatives
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The present invention relates to a process for preparing C7 intermediates and their use in the preparation of pyrrole derivatives of a class that is effective at inhibiting the biosynthesis of cholesterol in humans, and more particularly to improved synthetic methods for preparing 3,5-dihydroxy-7-pyrrol-1-yl heptanoic acids. The invention further relates to intermediates in this process.
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Page/Page column 5
(2010/11/28)
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- PROCESS FOR PREPARING C5 INTERMEDIATES AND THEIR USE IN THE PREPARATION OF N-SUBSTITUTED PYRROLE DERIVATIVES
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The present invention relates to a process for preparing C5 intermediates and their use in the preparation of pyrrole derivatives of a class that is effective at inhibiting the biosynthesis of cholesterol in humans, and more particularly to improved synthetic methods for preparing 3,5-dihydroxy-7-pyrrol-1-yl heptanoic acids from 1,4-diketo starting materials. The invention further relates to intermediates in this process.
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Page/Page column 27
(2010/11/29)
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- One-pot preparation of caffeic acid esters from 3,4-dihydroxybenzaldehyde
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A convenient one-pot process for preparing various esters of caffeic acid from 3,4-dihydroxybenzaldehyde has been developed. The alcohols or phenols react with Meldrum's acid to form malonic acid mono-esters, which, without separating, immediately react with 3,4-dihydroxybenzaldehyde to afford the desired esters in good yield. The 1H NMR data and X-ray diffraction analyses indicate that these α,β-unsaturated esters are in trans (E) form in accord with natural esters.
- Hu, Wei-Xiao,Xia, Chun-Nian,Wang, Guo-Hong,Zhou, Wei
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p. 586 - 588
(2007/10/03)
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- Synthesis and structure-activity relationships of truncated bisubstrate inhibitors of aminoglycoside 6′-N-acetyltransferases
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Truncated aminoglycoside-coenzyme A bisubstrate analogues were efficiently prepared using a convergent approach where the amine and the thiol are coupled in one pot with the addition of a linker, without the need for protecting groups. These derivatives were tested for their effect on the activity of the resistance-causing enzyme aminoglycoside 6′-N-acetyltransferase Ii, and key structure-activity relationships are reported. Moreover, one of the inhibitors is able to block aminoglycoside resistance in cells expressing this enzyme.
- Gao, Feng,Yan, Xuxu,Shakya, Tushar,Baettig, Oliver M.,Ait-Mohand-Brunet, Samia,Berghuis, Albert M.,Wright, Gerard D.,Auclair, Karine
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p. 5273 - 5281
(2007/10/03)
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- Inhibitors of aminoglycoside 6'-N-acetyltransferases, compositions and uses thereof
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The present invention relates to inhibitors of aminoglycoside 6''-N-acetyltransferases of Formula I: R-X-Y-Z Formula I wherein: R is selected from the group consisting of: R1 is selected from the group consisting of OH and R2 is selected from the group consisting of OH and R3 is selected from the group consisting of NH2 and OH; R4 is selected from the group consisting of NH2 and R5 is selected from the group consisting of OMe, OEt OPr, and O-iPr; X is selected from the group consisting of NH and O; Y is selected from the group consisting of: R6 is selected from the group consisting of OH, CH3, and OCH3; n is an integer ranging from 1 to 10; and Z is selected from the group consisting of: and R7 is selected from the group consisting of OH, OMe, OEt OPr, O-iPr, O-tBu and
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Page/Page column 15
(2008/06/13)
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- Facile preparation and purification of mono tert-butyl malonate
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Reaction of Meldrum's acid with tert-BuOH gives tert-BuO 2CCH2CO2H, which can be easily purified via its corresponding crystalline ammonium salt and subsequent acidification. Copyright Taylor & Francis LLC.
- Tararov, Vitali I.,Korostylev, Andrei,Koenig, Gerd,Boerner, Armin
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p. 187 - 191
(2007/10/03)
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- Synthesis and biological characterisation of [3H]BBL454, a new CCK2 selective radiolabelled agonist displaying original pharmacological properties
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[3H]BBL454, a new CCK2 selective tritiated agonist was prepared via the reductive tritiation of a 5-aminopentyn-1-yl moiety introduced on the N-terminal end of a pentapeptide derivative of cholecystokinin. The binding properties of this labelled compound were determined on CHO cells transfected with the rat CCK2 receptor. [3H]BBL454 is able to discriminate two affinity states of the CCK2 receptor a supplementary indication of its validity for further exploring the heterogeneity of this receptor.
- Bellier, Bruno,Dugave, Christophe,Etivant, Frederic,Genet, Roger,Gigoux, Veronique,Garbay, Christiane
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p. 369 - 372
(2007/10/03)
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- Self-condensation of activated malonic acid half esters: A model for the decarboxylative Claisen condensation in polyketide biosynthesis
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The reaction of a malonic acid half oxyester with a N-hydroxysuccinimidyl ester-forming reagent resulted in self-condensation to provide the corresponding 1,3-acetonedicarboxylic acid diester. This new method does not require a divalent metal chelator or a coordinating solvent for successful condensation.
- Ryu, Youngha,Scott, A. Ian
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p. 7499 - 7502
(2007/10/03)
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- Design, synthesis and antimalarial activity of novel, quinoline-based, zinc metallo-aminopeptidase inhibitors
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PfA-M1, a neutral zinc aminopeptidase of Plasmodium falciparum, is a new potential target for the discovery of antimalarials. The design and synthesis of a library of 45 quinoline-based inhibitors of PfA-M1 is reported. The best inhibitor displays an IC50 of 854 nM. The antimalarial activity on a CQ-resistant strain and the specificity towards mammalian aminopeptidase N are also discussed.
- Flipo, Marian,Florent, Isabelle,Grellier, Philippe,Sergheraert, Christian,Deprez-Poulain, Rebecca
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p. 2659 - 2662
(2007/10/03)
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- Acylation through ketene intermediates
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Carboxylic acids possessing a strong electron-withdrawing group in the α-position undergo facile dehydration upon reaction with carbodiimides to form the corresponding substituted ketenes that can react in situ with alcohols providing esters in a high yield. The ketene formed by the treatment of ethyl 2-methylmalonate with DCC was trapped in situ by a [4+2] cycloaddition with a second DCC molecule. The chemoselectivity of the acylation through the ketene intermediates was found to be substantially different from that of conventional acylation reagents showing a very low sensitivity toward the steric bulk of alcohols. A comparison of the sensitivity of the acylation to the steric bulk of alcohols supports the presence of a pseudopericyclic pathway for the nucleophilic addition of alcohols to ketenes derived from ethyl malonic and diethylphosphonoacetic acid.
- Shelkov, Rimma,Nahmany, Moshe,Melman, Artem
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p. 8975 - 8982
(2007/10/03)
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- An efficient method for generation of α-oxoketenes: Cycloreversion of enolized Meldrum's acid derivatives
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A series of 6-methoxy- or siloxy-4H-1,3-dioxin-4-ones was synthesized from Meldrum's acids. These dioxinones underwent 4+2 cycloreversion to methoxy- or siloxycartbonylketenes and ketones quantitatively at 20-50°C. The ketenes were characterized by IR spectroscopy as well as by trapping with t-butanol. The ready cycloreversion of these enolized Meldrum's acid derivatives strongly indicates that the anomalously high susceptibility of Meldrum's acids to nucleophilic reagents is due to the participation of carboxyketenes generated through the cycloreversion of tautomeric 6-hydroxydioxinones.
- Sato, Masayuki,Ban, Hitoshi,Kaneko, Chikara
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p. 6689 - 6692
(2007/10/03)
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- Scope and Mechanism of Deprotection of Carboxylic Esters by Bis(tributyltin) Oxide
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Methyl and ethyl esters of aliphatic and aromatic carboxylic acids as well as benzyl carboxylates, thiol esters and double esters such as (pivaloyloxy)methyl carboxylates have been successfully cleaved with bis(tributyltin) oxide to give the free carboxylic acids in good yields.The reaction is carried out in aprotic solvents under essentially neutral conditions and thus this method can serve as an ideal procedure for the cleavages of esters with other functional groups and/or protecting groups acid and/or base sensitive.We demonstrated that the reaction displays a high level of chemoselectivity between methyl and ethyl esters versus tert-butyl esters and γ-lactones.Bis(tributyltin) oxide is also a highly efficient reagent for the cleavage of acetates of primary and secondary alcohols and phenols.The limitations we found in the use of this reagent include the lack of cleavage of esters sterically hindered around the carboxyl carbon and the carbinol group (i.e., esters of tertiary alcohols) and in carboxylic esters that contain a fluoroalkyl substituent.A resonable mechanistic explanation is discussed to account for the reaction pathway of the acyloxygen cleavage of (-)-(1R)-menthyl acetate.
- Salomon, Claudio J.,Mata, Ernesto G.,Mascaretti, Oreste A.
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p. 7259 - 7266
(2007/10/02)
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- Intramolecular Cyclopropanation: Stereospecific Synthesis of (E)- and (Z)-1-Aminocyclopropane-1-carboxylic Acids
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tert-Butyl-substituted allyl malonates, prepared in two steps from malonic acid, are diazotized in high yields.The diazomalonates 7 undergo a stereospecific copper(I)-catalyzed cyclopropanation to give 1-(tert-butoxycarbonyl)-3-oxa-2-oxobicyclohexanes 8 which can be converted to the protected (E)- or (Z)-1-aminocyclopropane-1-carboxylic acids 10 or 15 via Curtius- or Hoffmann-type rearrangements, respectively.The sequences are short (six steps from malonic acid) and proceed with good overall yields (20-40percent overall from malonic acid).The free amino acids 12 and 13 can be liberated in two steps.
- Koskinen, Ari M. P.,Munoz, Luis
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p. 879 - 886
(2007/10/02)
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- Process for preparing malonic monoester
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A malonic monoester is prepared in a good yield by a single step reaction by reacting malonic acid with an alcohol in the presence of a base and an activator of malonic acid selected from the group consisting of an acyl halide or halocarbonate and an acid anhydride or dicarbonate.
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- SYNTHESIS OF N1-(p-GLYCOSYLOXYCINNAMOYL)SPERMIDINES
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The synthesis of O-glycosylated N1-(p-hydroxycinnamoyl)spermidines was investigated. p-Hydroxycinnamate glycosides of some amino sugars, including a synthetic intermediate of a unique antibiotic, cinodine, were prepared and converted into the amide of spermidine.
- Saito, Yoshihiro,Watanabe, Tsuyoshi,Hashimoto, Hironobu,Yoshimura, Juji
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p. 171 - 188
(2007/10/02)
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- REMOTE SUBSTITUENT EFFECTS IN MICROBIAL REDUCTIONS OF 3-KETOGLUTARATE AND 3-KETOADIPATE ESTERS
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The enantioselectivity of yeast mediated reductions of prochiral 3-ketoglutarate and 3-ketoadipate esters to the corresponding 3-hydroxyesters can be influenced by simple differences in the ester groups.
- Brooks, Dee W.,Lee, Nola Castro de,Peevey, Richard
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p. 4623 - 4626
(2007/10/02)
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