- Total synthesis of tryprostatins A and B
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Three distinct synthetic routes to the 2-prenyl tryptophan core skeleton of tryprostatins and their total syntheses are described. The strategies include a traditional gramine-mediated coupling reaction, Fuerstner indole synthesis, and our radical-mediated indole synthesis from o-alkenylphenyl isocyanide. The establishment of reliable conditions for the radical-mediated construction of indoles via a low-temperature radical initiator V-70 (2,2′-azobis(4- methoxy-2,4-dimethylvaleronitrile)) led to the highly efficient syntheses of tryprostatins A and B.
- Yamakawa, Takayuki,Ideue, Eiji,Iwaki, Yuzo,Sato, Ayumu,Tokuyama, Hidetoshi,Shimokawa, Jun,Fukuyama, Tohru
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scheme or table
p. 6547 - 6560
(2011/09/20)
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- Total synthesis of the duocarmycins
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The total synthesis of (+)-duocarmycin A and SA through a common indoline intermediate is described. The key reactions include selective lithiation of a 2,6-dibromoiodobenzene derivative and diastereoselective addition to a chiral nitroalkene, copper-mediated aryl amination, and addition of aryllithium to azlactones. Copyright
- Yamada, Ken,Kurokawa, Toshiki,Tokuyama, Hidetoshi,Fukuyama, Tohru
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p. 6630 - 6631
(2007/10/03)
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- Porphyrins with Exocyclic Rings. 2. Synthesis of Geochemically Significant Tetrahydrobenzoporphyrins from 4,5,6,7-Tetrahydro-2H-isoindoles
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Benzo- and tetrahydrobenzoporphyrins are widespread constituents of oil shales and petroleum.Although the origins of these materials are not known, a case is made for divinylchlorophyll a, a widespread pigment in marine algae, being the precursor to many of these geoporphyrins.Total syntheses of four tetrahydrobenzoporphyrins related to etioporphyrin III are described.Tetrahydroisoindoles were prepared by condensation of isocyanoacetates with 1-nitrocyclohexene in the presence of DBU or by reaction of aminomalonates with 2-formylcyclohexanone.Condensation of 3-unsubstituted 4,5,6,7-tetrahydro-2H-isoindoles 23c and 23d with (acetoxymethyl)pyrroles in the presence of Montmorillonite clay gave dipyrrylmethanes 28a and 36a in excellent yield.Hydrogenolysis of the benzyl esters and subsequent acid-catalyzed condensation with pyrrole aldehydes 37a and /or 37b gave a series of a,c-biladiene dihydrobromides.Copper(II) mediated cyclization of the a,c-biladienes 32, 33, 35, and 38, followed by demetallation with 15percent sulfuric acid-trifluoroacetic acid, gave four isomeric tetrahydrobenzoporphyrins 10-13 in unusually high yield.This work provides a general route for the synthesis of these important porphyrin molecular fossils.
- May, Donald A.,Lash, Timothy D.
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p. 4820 - 4828
(2007/10/02)
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- A GENERAL METHOD FOR THE SYNTHESIS OF 1-SUBSTITUTED (OR UNSUBSTITUTED)-4-CARBOMETHOXY-2-IMIDAZOLIN-5-ONES
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A general method for the synthesis of the title compounds by employing the reagent methyl N-(dicarbomethoxymethyl)methanimidate is described.The preparation, properties and reactions of the reagent are also reported.
- Hosmane, Ramachandra S.,Lim, Benjamin B.
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p. 1915 - 1918
(2007/10/02)
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- Reagents for Bioorganic Synthesis. 2. Methyl N-(Dicarboxymethyl)methanimidate
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Preparation, properties, and reactions of the reagent methyl N-(dicarbomethoxymethyl)methanimidate (1) are reported.Dropwise addition of dimethyl aminomalonate to refluxing trimethyl orthoformate/TFA afforded 1.Treatment of 1 with ammonia and various primary amines gave the corresponding unsubstituted and 1-substituted 4-carbomethoxy-5-hydroxyimidazoles 7-12, either as the parent hydroxy compounds (a) or as the (alkyl)ammonium salts (b).The reaction of 1 with water and sodium hydrosulfide provided dimethyl N-formylaminomalonate (13) and dimethyl N-(thioformyl)aminomalonate (14), respectively.The reaction of 1 with excess sodium hydrosulfide resulted in the formation of methyl N-(thioformyl)aminoacetate (17).Conversions of methylammonium 4-carbomethoxy-1-methylimidazol-5-olate (8b) and benzylammonium 4-carbomethoxy-1-benzylimidazol-5-olate (9b) into 5-(benzylamino)-4-(benzylcarbamoyl)-1-methylimidazole (18) and 1-benzyl-5-(benzylamino)-4-(benzylcarbamoyl)imidazole (19), respectively, were each accomplished in a single-pot procedure, employing phenylphosphonic dichloride as the key reagent.
- Lim, Benjamin B.,Hosmane, Ramachandra S.
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p. 5111 - 5115
(2007/10/02)
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- DERIVATIVES OF IMINOMALONIC ESTER
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The synthesis of (alkylimino)malonic esters was realized by the reaction of alkylamines with mesoxalic or dibromomalonic ester. (Halogenimino)malonic esters were obtained for the first time by the reaction of aminomalonic ester with tert-butyl hypochlorite or sodium hypobromite.A new method was developed for the synthesis of (acylimino)malonic esters by the successive bromination and dehydrobromination of (acylamino)malonic esters.The addition of various nucleophiles (water, amines, formamide) at the C=N bond of (acylimino)malonic esters was studied.
- Prosyanik, A. V.,Fedoseenko, D. V.,Markov, V. I.
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p. 1494 - 1503
(2007/10/02)
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