- One-Pot Preparation of (E)-α,β-Unsaturated Aldehydes by a Julia-Kocienski Reaction of 2,2-Dimethoxyethyl PT Sulfone Followed by Acid Hydrolysis
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(E)-α,β-Unsaturated aldehydes were synthesized by the Julia-Kocienski reaction of 2,2-dimethoxyethyl 1-phenyl-1H-tetrazol-5-yl (PT) sulfone 3 with various aldehydes, followed by acid hydrolysis. The reaction could be carried out in one pot, and various (E)-α,β-unsaturated aldehydes were obtained in a short time and with high yields.
- Ando, Kaori,Watanabe, Haruka,Zhu, Xiaoxian
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p. 6969 - 6973
(2021/05/06)
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- Iron-Catalyzed ?±,?-Dehydrogenation of Carbonyl Compounds
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An iron-catalyzed α,β-dehydrogenation of carbonyl compounds was developed. A broad spectrum of carbonyls or analogues, such as aldehyde, ketone, lactone, lactam, amine, and alcohol, could be converted to their α,β-unsaturated counterparts in a simple one-step reaction with high yields.
- Zhang, Xiao-Wei,Jiang, Guo-Qing,Lei, Shu-Hui,Shan, Xiang-Huan,Qu, Jian-Ping,Kang, Yan-Biao
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supporting information
p. 1611 - 1615
(2021/03/03)
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- Dihydropyrimidinones: Efficient one-pot green synthesis using Montmorillonite-KSF and evaluation of their cytotoxic activity
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A simple, efficient, cost-effective, recyclable and green approach has been developed for the synthesis of new dihydropyrimidinone analogs via the Biginelli reaction. The methodology involves a multicomponent reaction catalyzed by "HPA-Montmorillonite-KSF"as a reusable and heterogeneous catalyst. This method gives an efficient and much improved modification of the original Biginelli reaction, in terms of yield and short reaction times under solvent free conditions. All the derivatives were subjected to cytotoxicity screening against a panel of four different human cancer cell lines viz. colon (Colo-205), prostate (PC-3), leukemia (THP-1) and lung (A549) to check their effect on percentage growth. MTT [3-(4,5-dimethylthiazol-yl)-diphenyl tetrazoliumbromide] cytotoxicity assay was employed to check IC50 values. Of the synthesized analogs, 16a showed the best activity with IC50 of 7.1 ± 0.8, 13.1 ± 1.4, 13.8 ± 0.9 and 14.7 ± 1.1 μM against lung (A549), leukemia (THP-1), prostate (PC-3) and colon (Colo-205) cancer lines, respectively. The 16a analog was further checked for its effect on cancer cell properties through clonogenic (colony formation) and scratch motility (wound healing) assays and thereby was found that it reduced both the colony formation and migratory properties of the lung cancer cell line (A549). Further, molecular docking studies were performed with 16a to show its binding mode. This journal is
- Alharthi, Fahad A.,Alsalme, Ali,Dar, Bashir A.,Farooq, Saleem,Hamid, Abid,Hussain, Aashiq,Koul, S.
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p. 42221 - 42234
(2020/12/09)
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- Structure–Activity Relationship Studies on 6,7-Dimethoxy-2-phenethyl-1,2,3,4-tetrahydroisoquinoline Derivatives as Multidrug Resistance Reversers
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A series of derivatives were synthesized and studied with the aim to investigate the structure–activity relationships of the two P-glycoprotein (P-gp) modulators elacridar and tariquidar. Then, different aryl-substituted amides were inserted, and to explore the effects of varying the amide function, the corresponding isosteric ester derivatives and some alkylamine analogues were synthesized. The new compounds were studied to evaluate their P-gp interaction profile and selectivity toward the two other ABC transporters, multidrug-resistance-associated protein-1 (MRP-1) and breast cancer resistance protein (BCRP). Investigation of the chemical stability of the amide and ester derivatives toward spontaneous or enzymatic hydrolysis showed that these compounds were stable in phosphate-buffered saline and human plasma. This study allowed us to evaluate the selectivity of the three series on the three efflux pumps and to propose the structural requirements that define the P-gp interaction profile. We identified two P-gp substrates, a P-gp inhibitor, and three ester derivatives that were active on BCRP, which opens a new scenario in the development of ligands active toward this pump.
- Teodori, Elisabetta,Dei, Silvia,Bartolucci, Gianluca,Perrone, Maria Grazia,Manetti, Dina,Romanelli, Maria Novella,Contino, Marialessandra,Colabufo, Nicola Antonio
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p. 1369 - 1379
(2017/09/01)
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- Dehydrogenative Synthesis of Linear α,β-Unsaturated Aldehydes with Oxygen at Room Temperature Enabled by tBuONO
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Synthesis of linear α,β-unsaturated aldehydes via a room-temperature oxidative dehydrogenation has been realized by the cocatalysis of an organic nitrite and palladium with molecular oxygen as the sole clean oxidant. Linear α,β-unsaturated aldehydes could be efficiently prepared under aerobic catalytic conditions directly from the corresponding saturated linear aldehydes. Besides linear products, the aromatic analogy could also be smoothly achieved by the same standard method. The organic nitrite redox cocatalyst and alcohol solvent play a key role for realizing this method.
- Wang, Mei-Mei,Ning, Xiao-Shan,Qu, Jian-Ping,Kang, Yan-Biao
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p. 4000 - 4003
(2017/06/19)
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- Expanding the scope of the Babler–Dauben oxidation: 1,3-oxidative transposition of secondary allylic alcohols
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We report the catalytic chromium-mediated oxidation of secondary allylic alcohols to give α,β-unsaturated aldehydes with exclusive (E)-stereoselectivity. This facile procedure employs catalytic PCC (5?mol?%) and periodic acid (H5IO6) as a co-oxidant. This transformation occurs specifically with aromatic substituted allyl alcohols containing both electron withdrawing and electron donating substituents as well as a range of functional groups.
- Killoran, Patrick M.,Rossington, Steven B.,Wilkinson, James A.,Hadfield, John A.
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p. 3954 - 3957
(2016/08/09)
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- Oxygenative and Dehydrogenative [3 + 3] Benzannulation Reactions of α,β-Unsaturated Aldehydes and γ-Phosphonyl Crotonates Mediated by Air: Regioselective Synthesis of 4-Hydroxybiaryl-2-carboxylates
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Regioselective synthesis of 4-hydroxybiphenyl-2-carboxylates via the base-mediated oxygenative [3 + 3] benzannulation reaction of α,β-unsaturated aldehydes and γ-phosphonyl crotonates is reported. A hydroxyl group is installed in the final product on the originally phosphorus-bound carbon via a novel oxygenative and dehydrogenative transformation. The reaction proceeds rapidly in an open flask, uses atmospheric oxygen as an oxidant, and affords good yields of substituted biaryl phenols. (Chemical Equation Presented).
- Joshi, Prabhakar Ramchandra,Nanubolu, Jagadeesh Babu,Menon, Rajeev S.
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supporting information
p. 752 - 755
(2016/03/01)
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- Solvolysis, Electrochemistry, and Development of Synthetic Building Blocks from Sawdust
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Either aldehyde or cinnamyl ether products can be selectively extracted from raw sawdust by controlling the temperature and pressure of a solvolysis reaction. These materials have been used as platform chemicals for the synthesis of 15 different synthetic substrates. The conversion of the initial sawdust-derived materials into electron-rich aryl substrates often requires the use of oxidation and reduction chemistry, and the role electrochemistry can play as a sustainable method for these transformations has been defined.
- Nguyen, Bichlien H.,Perkins, Robert J.,Smith, Jake A.,Moeller, Kevin D.
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p. 11953 - 11962
(2016/01/09)
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- Synthesis and assessment of the antioxidant and antitumor properties of asymmetric curcumin analogues
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In this study, 12 asymmetric curcumin (CUR) analogues and 5 symmetric curcumin derivatives were synthesized, the antioxidant activity of these derivatives were evaluated by radicals 1,1-diphenyl-2- picryl-hydrazyl (DPPH) assay, 2,2-azino-bis(3-ethylbenzthiazoline-6-sulfonic acid) (ABTS) assay, ROO. (TRAP) assay and O2-. (NET) assay and anti-proliferative activities of these analogues were assessed against the human hepatoma cell line (SMMC-7721), the human breast cancer cell line (MCF-7) and the human prostate cancer cell lines (PC-3). Most of the asymmetric compounds showed stronger antioxidant activities than Vitamin C (Vc). Curcumin analogues reducing free radicals contain two reaction mechanisms: H-atom and electron transfer mechanisms. Compound 14 showed the most significant antioxidant activity compared with curcumin and other derivatives. Shorted the carbon chain of 14 can reduce the OeH bond dissociation enthalpy (BED) to improve the antioxidant activity. The antioxidant activity of 25 was similar to curcumin. All of the compounds performed better in an anti-proliferate assay than curcumin, especially compound 25, which exhibited the preferential cytotoxic activity against MCF- 7 cells(25, IC50 = 9.11 μM, curcumin, IC50 = 70.2 μM). Considering these data, future studies should be performed to assess the therapeutic values of these asymmetric curcumin analogues.
- Li, Qingyong,Chen, Jian,Luo, Shuyue,Xu, Jialin,Huang, Qiaoxian,Liu, Tianyu
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p. 461 - 469
(2015/03/04)
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- Silicon-directed rhenium-catalyzed allylic carbaminations and oxidative fragmentations of γ-silyl allylic alcohols
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A highly regioselective allylic substitution of β-silyl allylic alcohols has been achieved that provides the branched isomer as a single product. This high level of regiocontrol is achieved through the use of a vinyl silane group that can perform a Hiyama coupling providing 1,3-disubstituted allylic amines. An unusual oxidative fragmentation product was also observed at elevated temperature that appears to proceed by a Fleming-Tamao-type oxidation-elimination pathway.
- Chavhan, Sanjay W.,Cook, Matthew J.
-
supporting information
p. 4891 - 4895
(2014/05/06)
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- Synthesis, biological evaluation and 3D-QSAR studies of new chalcone derivatives as inhibitors of human P-glycoprotein
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P-glycoprotein (P-gp) is an ATP-dependent multidrug resistance efflux transporter that plays an important role in anticancer drug resistance and in pharmacokinetics of medicines. Despite a large number of structurally and functionally diverse compounds, also flavonoids and chalcones have been reported as inhibitors of P-gp. The latter share some similarity with the well studied class of propafenones, but do not contain a basic nitrogen atom. Furthermore, due to their rigidity, they are suitable candidates for 3D-QSAR studies. In this study, a set of 22 new chalcone derivatives were synthesized and evaluated in a daunomycin efflux inhibition assay using the CCRF.CEM.VCR1000 cell line. The compound 10 showed the highest activity (IC50 = 42 nM), which is one order of magnitude higher than the activity for an equilipohillic propafenone analogue. 2D- and 3D-QSAR studies indicate the importance of H-bond acceptors, methoxy groups, hydrophobic groups as well as the number of rotatable bonds as pharmacophoric features influencing P-gp inhibitory activity.
- Parveen, Zahida,Brunhofer, Gerda,Jabeen, Ishrat,Erker, Thomas,Chiba, Peter,Ecker, Gerhard F.
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p. 2311 - 2319
(2014/04/17)
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- Development of a robust reagent for the two-carbon homologation of aldehydes to (E)-α,β-unsaturated aldehydes in water
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Synthesis of a new pinacolacetal-phosphonium salt and its reaction with aldehydes to give homologated acetals and two-carbon homologated unsaturated aldehydes is presented. The chemistry takes place in water under mild conditions and the sequence can be performed in one-flask operation.
- Mcnulty, James,Zepeda-Velazquez, Carlos,McLeod, David
-
supporting information
p. 3146 - 3149
(2013/11/06)
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- Rhodium-catalyzed hydroformylation of alkynes employing a self-assembling ligand system
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Hydroformylation of alkynes is an underdeveloped atom-economic and redox-neutral method to prepare enals. Applying a new electron poor self-assembling ligand system provides the first general rhodium-catalyst for the chemo- and stereoselective hydroformylation of dialkyl- as well as diaryl-substituted alkynes to furnish enals in excellent chemo- and stereoselectivity.
- Agabekov, Vladislav,Seiche, Wolfgang,Breit, Bernhard
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p. 2418 - 2422
(2013/07/11)
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- Synthesis of methoxylated goniothalamin, aza-goniothalamin and γ-pyrones and their in vitro evaluation against human cancer cells
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The present work describes the preparation of three novel series of compounds based on the structure of goniothalamin, a natural styryl lactone which has been found to display cytotoxic and antiproliferative activities against a variety of cancer cell lines. A focused library of 29 novel goniothalamin analogues was prepared and evaluated against seven human cancer cell lines. While the γ-pyrones and the aza-goniothalamin analogues were less potent than the lead compound, 2,4-dimethoxy analogue 88 has shown to be more potent in vitro than goniothalamin against all cancer cell lines evaluated. Furthermore, it was more potent than doxorubicin against NCI-ADR/RES, OVCAR-03 and HT-29 while being less toxic to human keratinocytes (HaCat). The 3,5-dimethoxy analogue 90 and 2,4,5-trimethoxy analogue 92 also displayed promising antiproliferative activity when compared to goniothalamin (1). These results provide new elements for the design and synthesis of novel representatives of this family of natural compounds.
- Barcelos, Rosimeire Coura,Pastre, Julio Cezar,Caixeta, Vanessa,Vendramini-Costa, Débora Barbosa,De Carvalho, Jo?o Ernesto,Pilli, Ronaldo Aloise
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p. 3635 - 3651
(2012/07/27)
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- Design, synthesis, and biological evaluation of the first podophyllotoxin analogues as potential vascular-disrupting agents
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We designed and synthesized two novel series of azapodo-phyllotoxin analogues as potential antivascular agents. A linker was inserted between the trimethoxyphenyl ring E and the tetracyclic ABCD moiety of the 4-aza-1,2-didehydropodophyllotoxins. In the first series, the linker enables free rotation between the two moieties; in the second series, conformational restriction of the E nucleus was considered. We have identified several new compounds with inhibitory activity toward tubulin polymerization similar to that of CA-4 and colchicine, while displaying low cytotoxic activity against normal and/or cancer cells. An aminologue and a methylenic analogue were shown to disrupt endothelial cell cords on Matrigel at subtoxic concentrations, and an original assay of drug washout allowed us to demonstrate the rapid reversibility of this effect. These two new analogues are promising leads for the development of vascular-disrupting agents in the podophyllotoxin series.
- Labruere, Raphael,Gautier, Benoit,Testud, Marlene,Seguin, Johanne,Lenoir, Christine,Desbene-Finck, Stephanie,Helissey, Philippe,Garbay, Christiane,Chabot, Guy G.,Vidal, Michel,Giorgi-Renault, Sylviane
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experimental part
p. 2016 - 2025
(2011/12/15)
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- ASYMMETRIC ONE- AND TWO-PHOTON FLUOROPHORES FOR SIMULTANEOUS DETECTION OF MULTIPLE ANALYTES USING A COMMON EXCITATION SOURCE
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A family of one- and two-photon dyes that have overlapping fluorescence excitation maxima between 365 nm and 425 nm and that are specifically functionalized for coupling to biomolecules. The dyes have defined Stokes shifts such that they produce a continuum of emission wavelengths. The dyes are asymmetrical bis stilbenes. The asymmetry of these dyes facilitates functionalization of the dyes with carboxyl, thiol, aldehyde-reactive or amine-reactive groups, which in turn facilitates coupling with macromolecules. Furthermore, the dyes of the present invention are photostable and have high quantum yields (fluorescence intensity).
- -
-
Page/Page column sheet 4; 11
(2009/03/07)
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- Caulerpenyne-colchicine hybrid: Synthesis and biological evaluation
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The synthesis of an analog of caulerpenyne having a trimethoxyaryl moiety was achieved in 11% overall yield over 11 steps. Its biological activity has been evaluated as inhibitor of in vitro tubulin polymerization or angiogenesis.
- Bourdron, Julien,Commeiras, Laurent,Barbier, Pascale,Bourgarel-Rey, Veronique,Pasquier, Eddy,Vanthuyne, Nicolas,Hubaud, Jean-Claude,Peyrot, Vincent,Parrain, Jean-Luc
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p. 5540 - 5548
(2007/10/03)
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- Design, synthesis, and SAR analysis of cytotoxic sinapyl alcohol derivatives
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Five series totalling 51 of sinapyl alcohol derivatives were designed and synthesized. Their cytotoxicity analyses were performed on six human tumor cell lines such as PC-3, CNE, KB, A549, BEL-7404, and HeLa. Certain sinapyl alcohol derivatives showed significant cytotoxic activities. Compound 14d exhibited especially potent cytotoxicity against the BEL-7404 cell line with an IC 50 value of 0.7 μM, which showed more cytotoxic activity than the positive control, cisplatin. The structure-cytotoxicity relationships were discussed and the CoMFA analysis was performed using the cytotoxic data against HeLa cells as a template.
- Zou, Hong Bin,Dong, Sheng Yi,Zhou, Chang Xin,Hu, Li Hong,Wu, Yi Hang,Li, Hai Bo,Gong, Jing Xu,Sun, Lian Li,Wu, Xiu Mei,Bai, Hua,Fan, Bo Tao,Hao, Xiao Jiang,Stoeckigt, Joachim,Zhao, Yu
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p. 2060 - 2071
(2007/10/03)
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- Efficient one-pot, two-step synthesis of (E)-cinnmaldehydes by dehydrogenation-oxidation of arylpropanes using DDQ under ultrasonic irradiation
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A general, efficient and new approach to the synthesis of cinnamaldehydes with trans-selectivity has been accomplished starting from arylpropanes. One-pot, two-step dehydrogenation and oxidation of arylpropanes with excess DDQ in dioxane containing a few drops of acetic acid gave (E)-cinnmaldehydes under ultrasound irradiation.
- Joshi, Bhupendra P.,Sharma, Anuj,Sinha, Arun K.
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p. 2590 - 2593
(2007/10/03)
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- Ultrasound-assisted convenient synthesis of hypolipidemic active natural methoxylated (E)-arylalkenes and arylalkanones
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An ultrasound-assisted convenient method was developed for the conversion of toxic methoxylated cis-isomer of arylalkenes into its hypolipidemic active trans-isomer. Treatment of cis-isomer or mixture of all three isomers (1a-1j) with ammonium formate and 10% Pd/C gave arylalkanes (2a-2j), which upon oxidation with DDQ in anhydrous dioxane containing a little amount of silica gel, provided (E)-arylalkenes (3a-3g) in 42-72% yield depending upon the substituents attached at the aryl ring. The same method, upon addition of a few drops of water, provided hypolipidemic active arylalkanones (3h-3j) in 59-65% yield.
- Joshi, Bhupendra P.,Sharma, Anuj,Sinha, Arun K.
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p. 3075 - 3080
(2007/10/03)
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- Structure-activity relationship of piperine and its synthetic analogues for their inhibitory potentials of rat hepatic microsomal constitutive and inducible cytochrome P450 activities
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Inhibitors of drug metabolism have important implications in pharmaco- toxicology and agriculture. We have reported earlier that piperine, a major alkaloid of black and long peppers inhibits both constitutive and inducible cytochrome P450 (CYP)-dependent drug metabolising enzymes. In the present study, an attempt has been made to prepare several novel synthetic analogues so as to relate various modifications in the parent molecule to the inhibition of CYP activities. Two types of mono-oxygenase reactions arylhydrocarbon hydroxylase (AHH) and 7-methoxycoumarin-O-demethylase (MOCD) have been studied. Inhibition studies were investigated in rat microsomal fraction prepared from untreated, 3MC- and PB- treated rat liver in vitro. Modifications were introduced into the piperine molecule: (i) in the phenyl nucleus, (ii) in the side chain and (iii) in the basic moiety. Thus, 38 compounds have been subjected to such studies, and simultaneously an attempt has also been made to arrive at the structure-activity relationship of synthetic analogues. In general, most of the inhibitory potential of the parent molecule is lost with modification in either of the three components of piperine. Saturation of the side chain resulted in significantly enhanced inhibition of CYP while modifications in the phenyl and basic moieties in few analogues offered maximal selectivity in inhibiting either constitutive or inducible CYP activities. Thus few novel analogues as CYP inactivators have been synthesized which may have important consequences in pharmacokinetics and bioavailability of drugs. (C) 2000 Elsevier Science Ltd.
- Koul, Surrinder,Koul, Jawahir L.,Taneja, Subhash C.,Dhar, Kanaya L.,Jamwal, Deshvir S.,Singh, Kuldeep,Reen, Rashmeet K.,Singh, Jaswant
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p. 251 - 268
(2007/10/03)
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- Formation of acetaldehyde enolate from vinyl acetate and its reaction with aromatic and heterocyclic aldehydes: An efficient synthesis of enals and polyenals
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Two carbon homologation of aromatic and heterocyclic aldehydes is achieved by reacting them with acetaldehyde enolate anion generated in situ by cleaving vinyl acetate in the presence of barium hydroxide.
- Mahata,Barun,Ila,Junjappa
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p. 1345 - 1347
(2007/10/03)
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- Synthesis of cinnamaldehydes by oxidation of arylpropenes with 2,3-dichloro-5,6-dicyanoquinone
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Alkoxylated 1-aryl-1-propenes [1-(4-methoxyphenyl)-1-propene, 1-(3,4-dimethoxyphenyl)-1-propene, 1-(3,4,5-trimethoxyphenyl)-1-propene] and 3-aryl-1-propenes [3-(4-methoxyphenyl)-1-propene, 3-(3,4-dimethoxyphenyl)-1-propene 3-(3,4,5-trimethoxyphenyl)-1-propene] gave cinnamaldehydes in 71-84% yield on treatment with 2,3-dichloro-5,6-dicyanoquinone (DDQ) (slight excess) at room temperature for 0.5-2 h in the two-phase system dichloromethane-water (4:1). Arylpropenes lacking electron-donating alkoxy groups (1-phenyl-1-propene, 3-phenyl-1-propene) or carrying an acetoxy group [1-(4-acetoxy-3-methoxyphenyl)-1-propene, 3-(4-acetoxy-3-methoxyphenyl)-1-propene] were converted into cinnamaldehydes in low to moderate yields on oxidation with a large excess of DDQ in combination with long reaction times (> 12 h). All the 1-aryl-1-propones examined were rapidly converted into a mixture of mono-and bis-(3-aryl-2-propenyl) ethers of 2,3-dichloro-5,6-dicyanohydroquinone (DDHQ) on DDQ oxidation. The rate of formation of DDHQ ethers from alkoxy-substituted 3-aryl-1-propenes was slightly lower. 3-Phenyl-1-propene and also 3-(4-acetoxy-3-methoxyphenyl)-1-propene were largely unchanged at the initial stage of the oxidation. Significant differences in the compositions of the DDHQ ether mixtures obtained from 1-aryl-1-propenes and 3-aryl-1-propones were not observed. Acta Chemica Scandinavica 1998.
- Iliefski, Tommy,Li, Shiming,Lundquist, Knut
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p. 1177 - 1182
(2007/10/03)
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- Phase transfer Wittig reaction with 1,3-dioxolan-2-yl-methyltriphenyl phosphonium salts: An efficient method for vinylogation of aromatic aldehydes
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Aldehydes were efficiently transformed into allylic dioxolanes by a Wittig-type reaction, using 1,3-dioxolan-2-yl-methyltriphenylphosphonium bromide under phase transfer conditions. The substituent kinetic effects were studied, and related to Hammett values and electrochemical potentials.
- Daubresse, Nicolas,Francesch, Charlette,Rolando, Christian
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p. 10761 - 10770
(2007/10/03)
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- Synthesis of cinnamaldehydes, esters of cinnamic acids and acylals of cinnamaldehydes by oxidation of arylpropenes with 2,3-dicyano-5,6- dichlorobenzoquinone (DDQ)
-
1-Arylpropenes and 3-arylpropenes give cinnamaldehydes (yield= 80%) on oxidation with 2,3-dichloro-5,6-dicyanobenzoquinone (DDQ) in the presence of water. The conversion to aldehydes is promoted by electron-donating groups at the aromatic ring. On DDQ oxidation in the presence of methanol, methyl esters of cinnamic acids are the predominant products. DDQ oxidation of 1- or 3-(3,4-dimethoxyphenyl)-1-propene in the presence of acetic acid gives an acylal [the diacetate of (E)-3-(3,4-dimethoxyphenyl)-2-propene-1, 1-diol].
- Iliefski, Tommy,Li, Shiming,Lundquist, Knut
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p. 2413 - 2416
(2007/10/03)
-
- Fully Regiocontrolled Synthesis of (+/-)-12a,12b-Secocolchicine and Studies Concerning its Cyclisation to the Alkaloid Colchicine
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A fully regiocontrolled synthesis of the title compound 6, an AC-ring analogue of the alkaloid colchicine 1, is reported.The key step associated with the sequence used was condensation of lithium halogenocarbenoid 10 - a synthetic equivalent for the inaccessible 7-methoxytropon-3-yl anion 12-with 3,4,5-trimethoxycinnamaldehyde 17 to produce the 1,2-addition product 18 as a mixture of diastereoisomers.Elaboration of compound 18 provided benzoate 23 which, on treatment with base, underwent ring-expansion to give troponoid 24 in excellent yield.Replacement of the C-7 benzoate group in compound 24 by an acetamido moiety was readily achieved and produced compound 6 in good overall yield.Unsuccessful attempts to convert compound 6 and the deacetamido analogue 38 into colchinine and deacetamidocolchicine 3, respectively, are described.
- Banwell, Martin G.,Lambert, John N.,Gravatt, G. Lance
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p. 2817 - 2830
(2007/10/02)
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- Polystyrene-Bound Phenylselenic Acid: Catalytic Oxydations of Olefins, Ketones, and Aromatic Systems
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A new synthesis of polystyrene-bound phenylselenic acid, from reaction of mercurated polystyrene and selenium dioxide, is described.A triphasic system of the polymer (in catalytic amounts), aqueous hydrogen peroxide, and dichloromethane is shown to be an effective medium for the conversion of olefins into trans diols and ketones into esters.A biphasic system of the polymer and tert-butyl hydroperoxide in refluxing chloroform effects the selective oxidation of benzylic alcohols to the carbonyl species.In a similar catalytic system hydroxy aromatic compounds can be converted into quinones.Conversion of 1,5-dihydroxynaphthalene into juglone can be realized in 70percent yield.
- Taylor, Richard T.,Flood, Lawrence A.
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p. 5160 - 5164
(2007/10/02)
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- Cumulated Ylides, XII. A Stereoselective Synthetic Method for (Z)-α,β-Unsaturated Aldehydes
-
(2-Ethoxyvinyl)triphenylphosphonium bromide (5) is converted with sodium amide into the corresponding phosphaallenylide 6 which adds ethanol forming the ylide 7. 7 is also obtained by the reaction of 5 with sodium ethanolate.The Wittig reaction of 7 with aldehydes 2 proceeds with high (Z)-stereoselectivity to give (Z)-α,β-unsaturated acetals 8 which are cleaved under well defined conditions with p-toluenesulfonic acid or with wet silica gel to (Z)-α,β-unsaturated aldehydes 9.
- Bestmann, Hans Juergen,Roth, Kurt,Ettlinger, Manfred
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p. 161 - 171
(2007/10/02)
-