- A novel application of a [3+2] cycloaddition reaction for the synthesis of the piperazinone rings of pseudotheonamides A1 and A2
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A novel approach to synthesize the piperazinone ring system of pseudotheonamide A1 and A2 is described. The key step is the intramolecular [3+2] cycloaddition reaction of a suitably orientated azide and an α,β-unsaturated ester.
- Gurjar, Mukund K,Karmakar, Sukhen,Mohapatra, Debendra K,Phalgune, Usha D
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- Synthesis of optically active α-(nonafluoro-tert-butoxy)carboxylic acids
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Three novel α-(nonafluoro-tert-butoxy)carboxylic esters were synthesized by two methods: the Mitsunobu reaction of optically active (S)-α-hydroxycarboxylic esters and the Williamson synthesis starting from the corresponding O-mesyl derivatives. Both procedures from ethyl (S)-lactate resulted in the formation of a fluorous optically active (R)-lactic acid ester derivative, while the reactions from methyl (S)-mandelate took place with racemization. The proposed mechanism of this racemization is described. The conversion of methyl (S)-phenyllactate under Mitsunobu conditions was also stereospecific, but the reaction of its O-mesyl derivative yielded a mixture of substitution and elimination products. The optical purity of the α-(nonafluoro-tert-butoxy)carboxylic acids prepared by the hydrolysis of the above esters was determined by 1H NMR spectroscopy.
- Csóka, Tamás,Nemes, Anikó,Szabó, Dénes
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p. 1730 - 1733
(2013/04/10)
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- Development of Novel Peptidomimetics Containing a Vinyl Sulfone Moiety as Proteasome Inhibitors
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Proteasome inhibition is a topic of great interest in anticancer research. The proteolytic activity of this multicatalytic complex relies on three subunits, β1, β2 and β5, containing a caspase-like, a trypsin-like and a chymotrypsin-like active site, respectively. Several studies have demonstrated that, of the three activities, the chymotrypsin-like activity was the most necessary for cell viability and protein processing. Thus, most efforts towards the development of proteasome inhibitors have focused on the selective inhibition of the β5 subunit active site. Herein, we report the design and synthesis of a series of conformationally constrained tripeptidyl vinyl sulfones were determined to be good inhibitors of the chymotrypsin-like activity of proteasome, with KI values in the sub-micromolar to micromolar range. These compounds were also tested against bovine pancreatic α-chymotrypsin and human cathepsinB and L, revealing a good selectivity for the target enzyme over these related enzymes. Molecular straitjackets! Conformationally constrained tripeptidyl vinyl sulfones were identified as good inhibitors of proteasome chymotrypsin-like activity, with KI values in the sub-micromolar to micromolar range. Derivatives were also tested against bovine pancreatic α-chymotrypsin and human cathepsins B andL, revealing a good selectivity for the target enzyme.
- Ettari, Roberta,Bonaccorso, Cinzia,Micale, Nicola,Heindl, Cornelia,Schirmeister, Tanja,Calabro, Maria Luisa,Grasso, Silvana,Zappala, Maria
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experimental part
p. 1228 - 1237
(2012/04/18)
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- PROCESS FOR PRODUCING OPTICALLY ACTIVE 2-SUBSTITUTED CARBOXYLIC ACID
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The present invention relates to a process for efficiently producing an optically active 2-bromocarboxylic acid and an optically active 2-sulfonyloxycarboxylic acid, which are important in the production of medicinal compounds and so forth. An optically active 2-sulfonyloxycarboxylic acid ester is subjected to deprotection under acid conditions to obtain an optically active 2-sulfonyloxycarboxylic acid. A metal bromide is caused to act on the acid to brominate it with configuration inversion at position 2 to thereby produce an optically active 2-bromocarboxylic acid. The resultant optically active 2-bromocarboxylic acid is isolated/purified by subjecting it to a step in which the acid is crystallized and separated as a salt with a base. Thus, an optically active 2-bromocarboxylic acid having a high chemical purity and high optical purity can be produced.
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- Simple synthesis of optically active 2-fluoropropanoic acid and analogs of high enantiomeric purity
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A very simple synthesis of optically active 2-fluoropropanoic acid 1 (R=CH3, R′=H) and analogs of high enantiomeric purity was developed using the sulfonates 2 of the corresponding optically active 2-hydroxycarboxylic esters and potassium fluor
- Fritz-Langhals, Elke,Schuetz, Gabi
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p. 293 - 296
(2007/10/02)
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