42783-36-8Relevant articles and documents
Organic bifunctional catalyst and preparation method thereof as well as stereoregular biodegradable polyester and preparation method thereof
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Paragraph 0101-0104, (2021/07/10)
The invention relates to an organic bifunctional catalyst and a preparation method thereof, and stereoregular biodegradable polyester and a preparation method thereof. The organic bifunctional catalyst disclosed by the invention is obtained by reacting isocyanate or isothiocyanate with a pyridylamine compound. According to the catalyst, an O-carboxyl intracyclic anhydride monomer and a pyridine nucleophilic addition monomer of an amino acid source are activated by thiourea, and controllable ring opening polymerization can be performed on an OCA monomer under a mild condition by utilizing an amplification effect of adjacent groups, so that functional polyester with high isotacticity and controllable molecular weight is prepared. The solvent used for polymerization can be chloroform, toluene, dichloromethane and the like, the polymerization temperature range is 25-50 DEG C, and the stereoregularity is adjustable between 60% and 90%. Under the polymerization condition, the monomer conversion rate can reach 99% within 24-48 hours. The molecular weight of the obtained polyester is controllable, and the melting point reaches up to 150 DEG C. The molecular weight of the polyester is changed between 20,000 and 100,000, and the polyester has a wide prospect for industrial application.
Dynamic kinetic resolution via dual-function catalysis of modified cinchona alkaloids: Asymmetric synthesis of α-hydroxy carboxylic acids
Tang, Liang,Deng, Li
, p. 2870 - 2871 (2007/10/03)
A highly enantioselective catalytic transformation of racemic α-hydroxy acids to optically active α-hydroxy acids is reported. A new procedure was developed for the condensation of racemic α-hydroxy acids with trichloromethyl chloroformate (diphosgene) at room temperature in the presence of activated charcoal to form 5-substituted-1,3-dioxolane-2,4-diones in 90-100% yield. An efficient dynamic kinetic resolution of 5-aryl dioxolanediones was realized via a modified cinchona alkaloid-catalyzed alcoholytic opening of the dioxolanedione ring, generating a variety of optically active α-hydroxy esters in 91-96% ee and 61-85% chemical yield. In this dynamic kinetic resolution, the modified cinchona alkaloid was found to serve dual catalytic roles, mediating both the rapid racemization of the 5-aryl dioxolanediones and the enantioselective alcoholytic ring opening of the 5-aryl dioxolanediones. Consequently, both enantiomers of the 5-aryl dioxolanediones were converted to highly enantiomerically enriched aromatic α-hydroxy esters in yields (61-85%), far exceeding the maximum of 50% for a normal kinetic resolution. This development not only represents an expansion of the scope of asymmetric acyl-transfer catalysis of synthetic catalysts but also provides a new approach for the development of efficient chemical dynamic kinetic resolutions promoted by a single catalyst. 5-Alkyl dioxolanediones were resolved by a conventional but highly enantioselective kinetic resolution to provide α-hydroxy acids and esters in high optical purity and good yields. Copyright
Cephalosporin derivatives
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, (2008/06/13)
A series of novel 7-(Dα-aminophenylacetamido)- and 7-(D-α-hydroxyphenylacetamido)- Δ3 -cephem derivatives have been prepared wherein a heterocyclic thiomethyl moiety is located at the 3-position of the molecule. These compounds are useful as antibacterial agents for the treatment of diseases caused by Gram-positive and Gram-negative bacteria. Preferred members include 7-(D-α-hydroxyphenylacetamido)-3-(3-carbamoyl-1,2,4-triazol-5-yl)thiomethylceph-3-em-4-carboxylic acid and 7-(D-α-hydroxyphenylacetamido)-3-(2-carboxymethoxy-methyl-1,3,4-thiadiazol-5-yl)thiomethylceph-3-em-4-carboxylic acid. Alternative methods of preparation are provided for these compounds, including various synthetic routes leading to the required novel heterocyclic thiol intermediates.
