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Formal Synthesis (formal + synthesis)
Selected AbstractsA Stereoselective Formal Synthesis of (,)-FumagillolEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 18 2004Olivier Bedel Abstract A novel formal synthesis of fumagillol, a direct precursor of the antiangiogenic sesquiterpene fumagillin, is described. The main features of the synthesis are a stereoselective Claisen,Ireland rearrangement, a ring-closing metathesis, a chemo- and stereoselective dihydroxylation, and a Julia,Kocienski olefination. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004) [source] Formal Synthesis of Olivacine via IndolylborateHELVETICA CHIMICA ACTA, Issue 10 2008Minoru Ishikura Abstract Palladium-catalyzed tandem cyclization,cross-coupling reaction of indolylborate 2 and vinyl bromide 5 was successfully applied in a short formal synthesis of olivacine. The reaction of 2 with 5 in the presence of Pd(OAc)2 readily afforded three kinds of products, triene derivative 6 and vinylindole derivative 7, along with a small amount of the piperidine derivative 8 (Scheme,2). On the other hand, the reactions of 2 with bromide 10 or 15 were also examined (Schemes,4 and 5), and their outcome markedly depended on the relative ease of ring closure as a function of ring size. Irradiation of 6 with a high-pressure mercury lamp (,9; Scheme,2), followed by removal of the N -[(benzyloxy)carbonyl] group and subsequent oxidation afforded, after deprotection, pyridocarbazole 23, and the conversion of 23 to olivacine is known (Scheme,6). [source] Innentitelbild: Catalytic Selective Cyclizations of Aminocyclopropanes: Formal Synthesis of Aspidospermidine and Total Synthesis of Goniomitine (Angew. Chem.ANGEWANDTE CHEMIE, Issue 33 201033/2010) Je nach Reaktionsbedingungen kann die selektive Cyclisierung von Aminocyclopropanen entweder an N1 oder an C3 des Indolrings ablaufen, wie J. Waser und Mitarbeiter in ihrer Zuschrift auf S.,5903,ff. beschreiben. Die Methode wurde zur Synthese von Apocynaceae -Alkaloiden eingesetzt: Mit einem Kupfer(I)-Katalysator wurde die Kernstruktur von Aspidospermidin erhalten, und in Gegenwart einer Brønsted-Säure gelang die Totalsynthese von Goniomitin, das signifikante Zytotoxizität gegen Tumorzelllinien zeigte (IC50=150,400,nM). [source] Catalytic Selective Cyclizations of Aminocyclopropanes: Formal Synthesis of Aspidospermidine and Total Synthesis of Goniomitine,ANGEWANDTE CHEMIE, Issue 33 2010Filippo De, Simone Sanfte Kontrolle: Je nach Reaktionsbedingungen gelingt die Titelreaktion an der N1- oder der C3-Position eines Indolrings (siehe Schema). Das neben Aspidospermidin mithilfe dieser Strategie synthetisierte Goniomitin ist gegen mehrere Tumorzelllinien cytotoxisch (IC50=150,400,nM). Cbz=Benzyloxycarbonyl, Ts=4-Toluolsulfonyl. [source] A Concise Formal Synthesis of Diazonamide,A by the Stereoselective Construction of the C10 Quaternary Center,ANGEWANDTE CHEMIE, Issue 13 2010Cheng-Kang Mai Schutzgruppen überschätzt! Der Schlüsselschritt einer formalen Totalsynthese von Diazonamid,A ist die intramolekulare SNAr-Reaktion zwischen einem Oxindol und einem Bromoxazol. Interessanterweise verläuft diese Reaktion am besten, wenn das Oxindol-Stickstoffatom und die Phenolgruppe der Cyclisierungsvorstufe keine Schutzgruppen tragen und die milde Base Na2CO3 eingesetzt wird. [source] An Efficient Formal Synthesis of the Human Telomerase Inhibitor (±)-,-Rubromycin,ANGEWANDTE CHEMIE, Issue 43 2009Dominea Balanceakt: Das Gleichgewicht der elektronischen Faktoren im Naphthazarin- und Isocumarin-Fragment erleichtert die säurevermittelte Cyclisierung zum dicht funktionalisierten Spiroketal (siehe Bild; EOM=Ethoxymethyl) in einer formalen Synthese von (±)-,-Rubromycin. Eine Sequenz aus regioselektiver Allyloxylierung und Claisen-Umlagerung macht das hoch oxygenierte Naphthazarin-Fragment ausgehend von 2-Azido-1,4-naphthochinon zugänglich. [source] ChemInform Abstract: Synthesis of Isoxazoline N-Oxides and Application in the Formal Synthesis of Dehydroclausenamide (VIII).CHEMINFORM, Issue 47 2008Chun-Yin Zhu Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] Stereoselective Formal Synthesis of (-)-Centrolobine (I).CHEMINFORM, Issue 24 2007Kavirayani R. Prasad Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF. [source] Efficient Enantioselective Formal Synthesis of Ro 67-8867, a NMDA 2B Receptor Antagonist.CHEMINFORM, Issue 42 2005Ingrid Dechamps No abstract is available for this article. [source] A Simple Procedure for the Synthesis of ,-Hydroxy-,,,-(E)-alkenoic Esters: Formal Synthesis of (+)-Macrosphelides A and B.CHEMINFORM, Issue 29 2005K. Srinivasa Rao Abstract For Abstract see ChemInform Abstract in Full Text. [source] A Stereoselective Formal Synthesis of (-)-Fumagillol.CHEMINFORM, Issue 1 2005Olivier Bedel No abstract is available for this article. [source] Enantioselective Formal Synthesis of Uleine Alkaloids from Phenylglycinol-Derived Bicyclic Lactams.CHEMINFORM, Issue 49 2004Mercedes Amat Abstract For Abstract see ChemInform Abstract in Full Text. [source] A Fast Assembly of Pentacyclic Benz[f]indolo[2,3-a]quinolizidine Core by Tandem Intermolecular Formal Aza-[3 + 3] Cycloaddition/Pictet,Spengler Cyclization: A Formal Synthesis of (.+-.)-Tangutorine (I).CHEMINFORM, Issue 46 2004Shengjun Luo No abstract is available for this article. [source] Vicinal Stereocontrol During Nucleophilic Addition to Arene Chromium Tricarbonyl Complexes: Formal Synthesis of (.+-.)-erythro Juvabione.CHEMINFORM, Issue 43 2004Anthony J. Pearson No abstract is available for this article. [source] Oxone®-KI Induced Lactonization and Etherification of Unsaturated Acids and Alcohols: A Formal Synthesis of Mintlactone.CHEMINFORM, Issue 24 2004Massimo Curini Abstract For Abstract see ChemInform Abstract in Full Text. [source] Facile Conversion of 2-Azetidinones to 2-Piperidones: Application to a Formal Synthesis of Prosopis and Cassia Alkaloids.CHEMINFORM, Issue 48 2003Hyeon Kyu Lee Abstract For Abstract see ChemInform Abstract in Full Text. [source] Highly Enantioselective Syntheses of Functionalized ,-Methylene-,-butyrolactones via Rh(I)-Catalyzed Intramolecular Alder Ene Reaction: Application to Formal Synthesis of (+)-Pilocarpine.CHEMINFORM, Issue 44 2002Aiwen Lei Abstract For Abstract see ChemInform Abstract in Full Text. [source] ChemInform Abstract: Synthesis of Elemane Bis-lactones from Santonin , Synthesis of the Reported Structure of seco-Isoerivanin Pseudo Acid and Formal Synthesis of (+)-8-Deoxyvernolepin.CHEMINFORM, Issue 3 2001Gonzalo Blay Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] Formal Synthesis of the Anti-Angiogenic Polyketide (,)-Borrelidin under Asymmetric Catalytic ControlCHEMISTRY - A EUROPEAN JOURNAL, Issue 38 2010Ashoka V. R. Madduri Abstract Borrelidin (1) is a polyketide that possesses extremely potent anti-angiogenesis activity. This paper describes its formal total synthesis by the most efficient route to date. This modular approach takes optimal benefit of asymmetric catalysis and permits the synthesis of analogues; in addition, the high yields and selectivities obtained eliminate the need for separation of stereoisomers. The upper half of borrelidin has been accessed by iterative copper-catalysed asymmetric conjugate addition of methylmagnesium bromide, whereas synthesis of the lower half of the molecule was achieved by relying on asymmetric hydrogenation and cross-methathesis as key steps. [source] Application of Selective Palladium-Mediated Functionalization of the Pyrido[3,,2,:4,5]pyrrolo[1,2- c]pyrimidine Heterocyclic System for the Total Synthesis of Variolin B and Deoxyvariolin B,EUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 29 2010Alejandro Baeza Abstract The reaction of protected 3-bromo-2-(bromomethyl)-4-methoxypyrrolo[2,3- b]pyridine and tosylmethyl isocyanide (TosMIC) afforded a pyrido[3,,2,:4,5]pyrrolo[1,2- c]pyrimidine derivative in good yield. This compound was transformed through installation of the pyrimidine moiety in the C5 position, hydrolysis, and decarboxylation in an advanced intermediate for the total or formal synthesis of the naturalalkaloid variolin B. Reaction of 3-bromo-2-(bromomethyl)-4-chloropyrrolo[2,3- b]pyridine with N -tosylmethyl dichloroformimide as a synthetic TosMIC equivalent afforded trihalo-substituted pyrido[3,,2,:4,5]pyrrolo[1,2- c]pyrimidine. This compound was used in a new total synthesis of the alkaloid variolin B by selective and sequential C,N, C,C, and C,O palladium-mediated functionalization at the C9, C5, and C4 positions of the pyrido[3,,2,:4,5]pyrrolo[1,2- c]pyrimidine system. A formal synthesis of deoxyvariolin B is also described by using the same synthetic strategy. [source] A Stereoselective Formal Synthesis of (,)-FumagillolEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 18 2004Olivier Bedel Abstract A novel formal synthesis of fumagillol, a direct precursor of the antiangiogenic sesquiterpene fumagillin, is described. The main features of the synthesis are a stereoselective Claisen,Ireland rearrangement, a ring-closing metathesis, a chemo- and stereoselective dihydroxylation, and a Julia,Kocienski olefination. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004) [source] Formal Synthesis of Olivacine via IndolylborateHELVETICA CHIMICA ACTA, Issue 10 2008Minoru Ishikura Abstract Palladium-catalyzed tandem cyclization,cross-coupling reaction of indolylborate 2 and vinyl bromide 5 was successfully applied in a short formal synthesis of olivacine. The reaction of 2 with 5 in the presence of Pd(OAc)2 readily afforded three kinds of products, triene derivative 6 and vinylindole derivative 7, along with a small amount of the piperidine derivative 8 (Scheme,2). On the other hand, the reactions of 2 with bromide 10 or 15 were also examined (Schemes,4 and 5), and their outcome markedly depended on the relative ease of ring closure as a function of ring size. Irradiation of 6 with a high-pressure mercury lamp (,9; Scheme,2), followed by removal of the N -[(benzyloxy)carbonyl] group and subsequent oxidation afforded, after deprotection, pyridocarbazole 23, and the conversion of 23 to olivacine is known (Scheme,6). [source] Copper-Catalyzed Asymmetric 1,4-Hydroboration of Coumarins with Pinacolborane: Asymmetric Synthesis of DihydrocoumarinsADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 11-12 2010Hyohyun Kim Abstract An efficient asymmetric addition of pinacolborane to 4-substituted coumarins proceeded with high enantioselectivity in the presence of a copper(I)-QuinoxP complex as a catalyst to produce the corresponding 1,4-hydroboration products. Treatment of the intermediates with electrophiles, without isolation, resulted in enantioenriched dihydrocoumarins. The utility of this protocol was demonstrated in the formal synthesis of biologically active molecules. [source] Copper-Catalyzed Conjugate Addition of Diboron Reagents to ,,,-Unsaturated Amides: Highly Reactive Copper-1,2- Bis(diphenylphosphino)benzene Catalyst SystemADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 6 2009Heesung Chea Abstract An efficient copper catalyst system for the ,-boration of ,,,-unsaturated amides has been developed. Copper-bisphosphine complexes with small bite angles generate efficient catalyst systems for the successful conjugate addition of bis(pinacolato)diboron to a variety ,,,-unsaturated amides under mild conditions. This method was utilized in the formal synthesis of (S)-fluoxetine. [source] A Formal Total Synthesis of Eleutherobin Using the Ring-Closing Metathesis (RCM) Reaction of a Densely Functionalized Diene as the Key Step: Investigation of the Unusual Kinetically Controlled RCM StereochemistryCHEMISTRY - A EUROPEAN JOURNAL, Issue 1 2006Damiano Castoldi Dr. Abstract Asymmetric oxyallylation reactions and ring-closing metathesis have been used to synthesize compound 3, a key advanced intermediate used in the total synthesis of eleutherobin reported by Danishefsky and co-workers. The aldehyde 6, which is readily prepared from commercially available R -(,)-carvone in six steps in 30,% overall yield on multigram quantities, was converted into the diene 5 utilizing two stereoselective titanium-mediated Hafner,Duthaler oxyallylation reactions. The reactions gave the desired products (8 and 12) in high yields (73 and 83,%, respectively) as single diastereoisomers, with the allylic alcohol already protected as the p -methoxyphenyl (PMP) ether, which previous work has demonstrated actually aids ring-closing metathesis compared to other protective groups and the corresponding free alcohol. Cyclization under forcing conditions, using Grubbs' second-generation catalyst 13, gave the ten-membered carbocycle (E)- 14 in 64,% yield. This result is in sharp contrast to similar, but less functionalized, dienes, which have all undergone cyclization to give the Z stereoisomers exclusively. A detailed investigation of this unusual cyclization stereochemistry by computational methods has shown that the E isomer of the ten-membered carbocycle is indeed less thermodynamically stable than the corresponding Z isomer. In fact, the selectivity is believed to be due to the dense functionality around the ruthenacyclobutane intermediate that favors the trans -ruthenacycle, which ultimately leads to the less stable E isomer of the ten-membered carbocycle under kinetic control. During the final synthetic manipulations the double bond of enedione (E)- 16 isomerized to the more thermodynamically stable enedione (Z)- 4, giving access to the advanced key-intermediate 3, which was spectroscopically and analytically identical to the data reported by Danishefsky and co-workers, and thereby completing the formal synthesis of eleutherobin. [source] Synthesis of ,-Methoxyacrylate Natural Products Based on Box-PdII -Catalyzed Intermolecular Methoxycarbonylation of AlkynolesCHEMISTRY - AN ASIAN JOURNAL, Issue 10 2010Satoshi Motodate Abstract Bis(oxazoline)-palladium(II) catalyzed carbonylation of homopropargyl alcohols afforded acyclic methoxyacrylate 2 and 6-membered lactone 3,a,k in good combined yield. In the case of propargyl alcohols, 5-membered lactones 3,p, 3,q, 16 were obtained in moderate yields. The one-pot synthesis of kawa lactones 3,a, 3,r, 3,s and formal synthesis of dihydroxycystothiazole,A and dihydroxycystothiazole,C are presented. To elucidate the stereochemistry of (+)-annularin G and (,)-annularin H, the first asymmetric syntheses of these natural products were achieved. [source] | ||||||||||||||||||||||