- An enzymatic domain for the formation of cyclic ethers in complex polyketides
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Champion cyclist: In vitro studies on the pederin biosynthetic pathway identify pyran synthases (PS) as a new family of polyketide synthase domains that stereoselectively form diverse five- and six-membered ether rings by oxa-conjugate cyclization during carbon-chain elongation. These domains could be useful tools for chemoenzymatic synthesis.
- Poeplau, Petra,Frank, Sarah,Morinaka, Brandon I.,Piel, Joern
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- 6-HETEROARYLOXY BENZIMIDAZOLES AND AZABENZIMIDAZOLES AS JAK2 INHIBITORS
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The present disclosure provides 6-heteroaryloxy benzimidazole and azabenzimidazole compounds and compositions thereof useful for inhibiting JAK2.
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- [3 + 2] Cycloreversion of Bicyclo[m.3.0]alkan-3-on-2-yl-1-oxonium Ylides to Alkenyloxyketenes. Stereospecific Aspect
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Rhodium(II)-catalyzed intramolecular reaction of diazoketones 1 bearing a cyclic ethereal moiety transiently formed bicyclo[m.3.0]octan-3-one-1-oxonium-2-ylides (2), which underwent sigmatropic and stereospecific [3 + 2] cycloreversion reaction to form alkenyloxyketenes 3. The ketenes were efficiently trapped by methanol to form the corresponding esters 4. Mechanistic studies revealed that the size of ethereal ring can be variable at least from THF to the THP, oxepane, and oxocane moiety, i.e., m = 3-6. On the other hand, the size of the ylide ring containing the carbonyl unit is limited to a five-membered ring. The cycloreversion was found to be stereospecific as was proven by the reactions of diastereoisomeric pairs bearing a methyl group at the bond-cleaving position. From threo isomers 7, (E)-alkenyloxyacetates 15 were exclusively formed (77-84%), whereas from erythro isomers 8, (Z)-isomers 16 were formed (80-88%). Mechanism of the cleavage from diazoacetonyl-substituted cyclic ethers to alkenyloxyketenes via bicyclic oxonium ylides was analyzed on the basis of calculations employing the hybrid density functional B3LYP and the highly correlated quadratic configuration interaction QCISD method to reveal that the concerted [3 + 2] cycloreversion is the key step of this reaction.
- Oku, Akira,Sawada, Yuichi,Schroeder, Marc,Higashikubo, Ichiro,Yoshida, Tomohiro,Ohki, Shigeji
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p. 1331 - 1336
(2007/10/03)
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- Stereoselective access to tetrahydropyranylacetic acid derivatives. Simple synthesis of (+)-(S,S)-(cis-6-methyltetrahydropyran-2-yl)acetic acid
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The reaction of the lactols 1a-1d, with malonic acid in hot dimethyl sulfoxide, in the presence of piperidinium acetate as catalyst, gives the corresponding (tetrahydrofuran-2-yl)acetic acids 2a, c and (tetrahydropyran-2-yl)acetic acids 2b, d in high yield (65-75%). While the synthesis of the (6-methyltetrahydropyran-2-yl)acetic acid (2d) is highly stereoselective (cis/trans ratio 20:1), no stereoselection was observed with the (5-methyltetrahydrofuran-2-yl)acetic acid (2c) (cis/trans ratio 1:1). This reaction was applied for the synthesis of natural (+)-(S,S)-(cis-6-methyltetrahydropyran-2-yl)acetic acid (7), minor constituent of the glandular secretion of the civet cat.
- Ragoussis,Theodorou
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- SYSTHESIS AND INTRAMOLECULAR RING CLEAVAGE OF 2-OXETANONES
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Intermolecular 2+2 aldehyde-ketene cycloaddition, followed by Lewis acid induced intramolecular ring opening of the 2-oxetanone product have been used to prepare tetrahydrofuran and tetrahydropyran ring systems.
- Mead, Keith T.,Samuel, Beverly
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p. 6573 - 6576
(2007/10/02)
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- A CONVENIENT ROUTE TO NORPYRENOPHORIN
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A norpyrenophorin precursor has been achieved by a three-step synthesis in good yield.
- Maciejewski, Lucien,Martin, Marius,Ricart, Gui,Brocard, Jacques
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p. 1757 - 1762
(2007/10/02)
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- An Efficient Synthesis of 2-Acylpyrroles
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Pyrrolylmagnesium bromide reacted with thiol- and selenolesters in the presence of cuprous iodide to afford 2-acylpyrroles regioselectively.
- Nakahara, Yoshiaki,Fujita, Akira,Ogawa, Tomoya
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p. 1491 - 1496
(2007/10/02)
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- Substituted hexahydropyrrolo[1,2-a]-quinolines, hexahydro-1H-pyrido[1,2-a]-q
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Tricyclic benzo fused compounds of the formula STR1 and pharmaceutically acceptable cationic and acid addition salts thereof, wherein n is zero, 1 or 2, and t is 1 or 2; M is CH or N, R1 is H or certain acyl groups; Q is CO2 R4, COR5, C(OR7)R5 R6, CN, CONR9 R10, CH2 NR9 R10, CH2 NHCOR11, CH2 NHSO2 R12, 5-tetrazolyl or when n is 1, Q and OR1 together form a lactone or certain reduced derivatives thereof; and Z is certain alkyl, alkoxy, alkoxyalkyl, aralkyl, aralkoxy, aryloxyalkyl or aralkoxyalkyl groups, are valuable central nervous system active agents, methods for their use, pharmaceutical compositions containing them and certain intermediates therefor.
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- Elimination and Addition Reactions. 36. Acceleration of Nucleophilic Eliminative Ring Fission by Bond Strain
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Rates of eliminative ring fission of cyclic ethers bearing carbanion stabilizing groups have been measured with a view to assessing the contribution of ring strain to the ease of cleavage of bonds in elimination reactions. (Ethylsulfonylmethyl)oxiran (4)
- Palmer, Robert J.,Stirling, Charles J. M.
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p. 7888 - 7892
(2007/10/02)
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