| 1. |
- Adeyemi, Ahmed, et al.
(författare)
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Regio- and Stereoselective Synthesis of Allylic Spiroethers (Spirobenzofuranes) via an Intramolecular Mizoroki-Heck Reaction
- 2020
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Ingår i: Journal of Organic Chemistry. - : American Chemical Society (ACS). - 0022-3263 .- 1520-6904. ; 85:12, s. 7648-7657
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Tidskriftsartikel (refereegranskat)abstract
- The palladium(0)-catalyzed intramolecular annulation of 12 1,3-disubstituted cyclopentenes, derived from (+)-vincelactam, resulted in 5-exo cyclizations which furnished a series of 2,5-dimethyl-14(3R,4'S)-2H-spiro[benzofuran-3,1'-cyclopentan]2'-en-4'-yl)-1H-pyrroles in excellent diastereoselectivities and useful isolated yields. The double bond migration process that followed the arylpalladium insertion was controlled by a fine-tuning of the reaction system, which provided regioselectivities of up to 98:2. The selective Mizoroki-Heck reaction was used as the key transformation for preparing two new spirocyclic monoprotected amino acids as single stereoisomers.
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| 2. |
- Adolfsson, Dan E., 1989-, et al.
(författare)
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Intramolecular Povarov Reactions for the Synthesis of Chromenopyridine fused 2-Pyridone Polyheterocycles Binding to α-Synuclein and Amyloid-β fibrils
- 2020
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Ingår i: Journal of Organic Chemistry. - : American Chemical Society (ACS). - 0022-3263 .- 1520-6904. ; 85:21, s. 14174-14189
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- A BF3×OEt2 catalyzed intramolecular Povarov reaction was used to synthesize a library of 15 chromenopyridine fused thiazolino-2-pyridone peptidomimetics. The reaction works with a range of O-alkylated salicylaldehydes and amino functionalized thiazolino-2-pyridones, to generate polyheterocycles with diverse substitution. The synthesized compounds were screened for their ability to bind α-synuclein and amyloid β fibrils in vitro. Analogs substituted with a nitro group bind to mature amyloid fibrils, and the activity moreover depends on the positioning of this functional group.
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| 3. |
- Al-Smadi, Derar, 1983-, et al.
(författare)
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Chemical and Biochemical Approaches for the Synthesis of Substituted Dihydroxybutanones and Di-, and Tri-Hydroxypentanones
- 2019
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Ingår i: Journal of Organic Chemistry. - : American Chemical Society (ACS). - 0022-3263 .- 1520-6904. ; 84:11, s. 6982-6991
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Tidskriftsartikel (refereegranskat)abstract
- Polyhydroxylated compounds are building blocks for the synthesis of carbohydrates and other natural products. Their synthesis is mainly achieved by different synthetic versions of aldol-coupling reactions, catalyzed either by organocatalysts, enzymes or metal-organic catalysts. We have investigated the formation of 1,4-substituted 2,3-dihydroxybutan-1-one derivatives from para- and meta-substituted phenylacetaldehydes by three distinctly different strategies. The first involved a direct aldol reaction with hydroxyacetone, dihydroxyacetone or 2-hydroxyacetophenone, catalyzed by the cinchona derivative cinchonine. The second was reductive cross-coupling with methyl or phenyl glyoxal promoted by SmI2 resulting in either 5-substituted 3,4-dihydroxypentan-2-ones or 1,4 bis-phenyl substituted butanones, respectively. Finally, in the third case, aldolase catalysis was employed for synthesis of the corresponding 1,3,4-trihydroxylated pentan-2-one derivatives. The organocatalytic route with cinchonine generated distereomerically enriched syn products (de = 60−99 %), with moderate enantiomeric excesses (ee = 43−56%), but did not produce aldols with either hydroxyacetone or dihydroxyacetone as donor ketones. The SmI2-promoted reductive cross-coupling generated product mixtures with diastereomeric and enantiomeric ratios close to unity. This route allowed for the production of both 1-methyl- and 1-phenylsubstituted 2,3-dihydroxybutanones, at yields between 40−60%. Finally, the biocatalytic approach resulted in enantiopure syn (3R,4S) 1,3,4-trihydroxypentan-2-ones.
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| 4. |
- Albers, Michael F, et al.
(författare)
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Amino acid building blocks for Fmoc solid-phase synthesis of peptides phosphocholinated at serine, threonine, and tyrosine
- 2013
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Ingår i: Journal of Organic Chemistry. - : American Chemical Society (ACS). - 0022-3263 .- 1520-6904. ; 78:6, s. 2715-2719
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Tidskriftsartikel (refereegranskat)abstract
- Phosphocholination of eukaryotic host cell proteins has recently been identified as a novel post-translational modification important for bacterial pathogenesis. Here, we describe the first straightforward synthetic strategy for peptides containing phosphocholinated serine, threonine, or tyrosine residues using preformed functional amino acid building blocks, fully compatible with standard Fmoc solid-phase peptide synthesis.
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| 5. |
- Almqvist, Fredrik, et al.
(författare)
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Neighboring Group Participation in a Regio- and Stereoselective Chlorination of a Bicyclo[2.2.2]octanone
- 1996
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Ingår i: Journal of Organic Chemistry. - : American Chemical Society (ACS). - 1520-6904 .- 0022-3263. ; 61:20, s. 6947-6951
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Tidskriftsartikel (refereegranskat)abstract
- The zinc chloride-mediated acetylation of the optically active silyl enol ether 2a gave the beta-diketone 3a (48%) together with the regio- and stereoselectively chlorinated compound 4 (27%). The yield of 4 increased to 70% by starting from the O-acetyl derivative 2c. The chlorination most likely occurs via neighboring group participation by the endo acetoxy group.
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| 6. |
- Almqvist, Fredrik, et al.
(författare)
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Synthesis of Optically Active endo, endo Bicyclo[2.2.2]octane-2,5- diol, Bicyclo[2.2.2]octan-2,5-dione and Related Compounds
- 1996
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Ingår i: Journal of Organic Chemistry. - : American Chemical Society (ACS). - 1520-6904 .- 0022-3263. ; 61:11, s. 3794-3798
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Tidskriftsartikel (refereegranskat)abstract
- Optically active C-2-symmetric (1S,2S,4S,5S)-bicyclo[2.2.2]octane-2,5-diol ((+)-12; 98% ee) and several selectivity protected optically active intermediates useful for synthetic transformations were synthesized via a 1,2-carbonyl transposition route starting from the easily available optically active (1R,4S,6S)-6-hydroxybicyclo[2.2.2]octan-2-one ((-)-2). The synthetic route also allowed the preparation of optically active (1S,4S)-bicyclo[2.2.2]octane-2,5-dione ((+)-14; 98% ee).
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| 7. |
- Alonso, Diego, et al.
(författare)
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Deprotection of Sulfonyl Aziridines
- 1998
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Ingår i: J. Org. Chem.. - : American Chemical Society (ACS). ; :63, s. 9455-9461
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Tidskriftsartikel (refereegranskat)
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| 8. |
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| 9. |
- An, N., et al.
(författare)
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Mechanistic insight into self-propagation in organo-mediated Beckmann rearrangement: A combined experimental and computational study.
- 2013
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Ingår i: Journal of Organic Chemistry. - 0022-3263 .- 1520-6904. ; 78:9, s. 4297-4302
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Tidskriftsartikel (refereegranskat)abstract
- Organo-mediated Beckmann rearrangement in the liquid phase, which has the advantage of high efficiency and straightforward experimental procedures, plays an important role in the synthesis of amides from oximes. However, the catalytic mechanisms of these organic-based promoters are still not well understood. In this work, we report a combined experimental and computational study on the mechanism of Beckmann rearrangement mediated by organic-based promoters, using TsCl as an example. A novel self-propagating cycle is proposed, and key intermediates of this self-propagating cycle are confirmed by both experiments and DFT calculations. In addition, the reason why cyclohexanone oxime is not a good substrate of the organo-mediated Beckmann rearrangement is discussed, and a strategy for improving the yield is proposed.
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| 10. |
- Andersson, Hanna, 1979, et al.
(författare)
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Photochemically Induced Aryl Azide Rearrangement: Solution NMR Spectroscopic Identification of the Rearrangement Product
- 2017
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Ingår i: Journal of Organic Chemistry. - : American Chemical Society (ACS). - 0022-3263 .- 1520-6904. ; 82:3, s. 1812-1816
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Tidskriftsartikel (refereegranskat)abstract
- Photolysis of ethyl 3-azido-4,6-difluorobenzoate at room temperature in the presence of oxygen results in the regioselective formation of ethyl 5,7-difluoro-4-azaspiro[2.4]hepta-1,4,6-triene-1-carboxylate, presumably via the corresponding ketenimine intermediate which undergoes a photochemical four-electron electrocyclization followed by a rearrangement. The photorearrangement product was identified by multinuclear solution NMR spectroscopic techniques supported by DFT calculations.
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