A series of proline-based amino pyridine dipeptide organocatalysts was synthesized and applied in direct asymmetric intermolecular aldol reaction. These catalysts showed good solubility in organic solvents, good yiel...A series of proline-based amino pyridine dipeptide organocatalysts was synthesized and applied in direct asymmetric intermolecular aldol reaction. These catalysts showed good solubility in organic solvents, good yields （73%--97%） and enantioselectivitives（74%--94%）. Among them, dipeptide organocatalyst（2） was found to be the most efficient one for the asymmetric aldol reaction between cyclohexanone and 4-nitrobeznaldehyde. After optimizing the catalytic reaction conditions, we found that the catalyst showed high yield（97%）, enantioselectivity（e.e., up to 92%） and anti-diastcreoselectivity（up to 95：5） at mild room temperature without any additives.展开更多
Here,we characterize the temporal and spatial dynamics of forest community structure and species diversity in a subtropical evergreen broad-leaved forest in China.We found that community structure in this forest chang...Here,we characterize the temporal and spatial dynamics of forest community structure and species diversity in a subtropical evergreen broad-leaved forest in China.We found that community structure in this forest changed over a 15-year period.Specifically,renewal and death of common species was large,with the renewal of individuals mainly concentrated within a few populations,especially those of Aidia canthioides and Cryptocarya concinna.The numbers of individual deaths for common species were concentrated in the small and mid-diameter level.The spatial distribution of community species diversity fluctuated in each monitoring period,showing a more dispersed diversity after the 15-year study period,and the coefficient of variation on quadrats increased.In 2010,the death and renewal of the community and the spatial variation of species diversity were different compared to other survey years.Extreme weather may have affected species regeneration and community stability in our subtropical monsoon evergreen broad-leaved forests.Our findings suggest that strengthening the monitoring and management of the forest community will help better understand the long-and short-term causes of dynamic fluctuations of community structure and species diversity,and reveal the factors that drive changes in community structure.展开更多
基金Supported by the National Natural Science Foundation of China(Nos.20802025 and 20082011)
文摘A series of proline-based amino pyridine dipeptide organocatalysts was synthesized and applied in direct asymmetric intermolecular aldol reaction. These catalysts showed good solubility in organic solvents, good yields （73%--97%） and enantioselectivitives（74%--94%）. Among them, dipeptide organocatalyst（2） was found to be the most efficient one for the asymmetric aldol reaction between cyclohexanone and 4-nitrobeznaldehyde. After optimizing the catalytic reaction conditions, we found that the catalyst showed high yield（97%）, enantioselectivity（e.e., up to 92%） and anti-diastcreoselectivity（up to 95：5） at mild room temperature without any additives.
基金funded by the Guangxi Natural Science Foundation Program (2022GXNSFAA035583 and 2020GXNSFAA159108)National Natural Science Foundation of China (32060305)+2 种基金Foundation of Key Laboratory of Ecology of Rare and Endangered Species and Environmental Protection (Guangxi Normal University)Ministry of Education, China (ERESEP 2021Z06)Chinese Forest Biodiversity Monitoring Network
文摘Here,we characterize the temporal and spatial dynamics of forest community structure and species diversity in a subtropical evergreen broad-leaved forest in China.We found that community structure in this forest changed over a 15-year period.Specifically,renewal and death of common species was large,with the renewal of individuals mainly concentrated within a few populations,especially those of Aidia canthioides and Cryptocarya concinna.The numbers of individual deaths for common species were concentrated in the small and mid-diameter level.The spatial distribution of community species diversity fluctuated in each monitoring period,showing a more dispersed diversity after the 15-year study period,and the coefficient of variation on quadrats increased.In 2010,the death and renewal of the community and the spatial variation of species diversity were different compared to other survey years.Extreme weather may have affected species regeneration and community stability in our subtropical monsoon evergreen broad-leaved forests.Our findings suggest that strengthening the monitoring and management of the forest community will help better understand the long-and short-term causes of dynamic fluctuations of community structure and species diversity,and reveal the factors that drive changes in community structure.
