RESUMEN
An acid-promoted cyclization of α-azidobenzyl ketones has been developed for the synthesis of 6-substituted quinoline derivatives. A variety of synthetically useful 6-OTf or -OMs quinoline derivatives were obtained in moderate to good yields. The reaction proceeds via CâN bond formation without organophosphine, providing convenient access to structurally interesting and synthetically important 6-substituted quinoline derivatives in moderate to good yields. A mechanistic perspective that is different from the traditional intramolecular Schmidt reaction has been proposed.
RESUMEN
Bioassay-guided isolation of spiroaspertrione A from cultures of Aspergillus sp. TJ23 in 2017 demonstrated potent resensitization of oxacillin against methicillin-resistant Staphylococcus aureus by lowering the oxacillin minimal inhibitory concentration up to 32-fold. To construct this unique spiro[bicyclo[3.2.2]nonane-2,1'-cyclohexane] system, a protocol for ceric ammonium nitrate-induced intramolecular cross-coupling of silyl enolate is disclosed.
RESUMEN
The responses of the autumn phenophase of 20 woody plants to climate warming in Beijing in 1962-2007 were analyzed by using the plant phenological data and the meteorological data obtained from Chinese Phenology Observation Network of Chinese Academy of Sciences. The results showed that in Beijing region, the end date of autumn defined by phenology was extended remarkably at an average rate of 3.2 d x 10 a(-1), while the onset of autumn defined by phenology remained essentially unchanged, resulting in a 14 d prolongation in autumn in 1962-2007. The timing of first leaf coloring change for the woody plants showed an average delaying rate of 4.9 d x 10 a(-1), and the main affecting factor was the mean minimum temperature. Climate warming was probably the main reason for the delaying trend in autumn phenophase of woody plants in Beijing during the study period.
