ABSTRACT
The highly enantioselective synthesis of 4-aryl-3,4-dihydrocoumarins was realized through direct annulation of phenols with enals catalyzed by dihydroisoquinoline-type NHC (DHIQ-NHC), an N-heterocyclic carbene derived from l-phenylalanine. The catalytic reaction proceeds with a wide scope of electron-rich phenols and enals providing structurally diverse 4-aryl-3,4-dihydrocoumarins in good to excellent yields and enantioselectivity. This method was useful in the synthesis of natural products and biologically relevant compounds from readily available starting materials.
ABSTRACT
A series of chiral triazolium salts have been synthesized from methyl l-phenylalaninate hydrochloride. The NHCs derived from this class of novel triazolium salts were found to be highly efficient catalysts in the annulation reaction of enals and 2-naphthols. These reactions proceeded with high chemoselectivity and wide substrate scope affording enantioenriched ß-arylsplitomicins in good yields with up to 96% ee.
ABSTRACT
OBJECTIVE: To sequence PrM and E gene of the Japanese encephalitis virus isolated from Gansu province in 2008 and analysis the genotype of new JEV isolates and the molecular characterization of E gene. METHODS: Computer software was used to analyze nucleic acid sequence and deduced amino acid sequence, and draw phylogenetic trees, including ClustalX2.09, MegAlign and Mega4. RESULTS: The six JEV strains were clustered in genotype I. 87.5%-87.9% identity in nucleotide sequence and 96.8%-97.2% identity in amino acid sequence were found in E gene when compared with the vaccine strain SA14-14-2. Eleven common amino acid differences were observed in E protein between new isolates and the vaccine strain. CONCLUSION: Genotype I JEVs were isolated from mosquitoes collected in Gansu province. The amino acid difference occurred in sites that were not the key ones affecting the antigenic of JEV.
