α-Hydroxy ketones are frequently involved in biologically important compounds and,therefore,the determination of the stereochemistry of these structural elements has attracted the attention in natural products chemis...α-Hydroxy ketones are frequently involved in biologically important compounds and,therefore,the determination of the stereochemistry of these structural elements has attracted the attention in natural products chemistry.In this paper a simpler Mosher′s method was developed from the modified Mosher′s method.It only need one configuration of MTPA to determine the absolute configurations of four α-hydroxy ketones with their（S）-and（R）-MTPA esters using（）1H NMR.The signals of protons on the same side with phenyl ring will be in the higher field than those of on the different side ones.Consequently according to the model the main configuration of compounds 1,2,3 and 4 were determined as S,R,R and S, respectively.展开更多
The molecular conformation of cyclodextrins (β CD,γ CD) bearing benzoyl moiety was studied by circular dichroism and 1H NMR.The circular dichroism intensity of mono[6 (benzoyl ethylendiamino)] β CD (1) was reduced ...The molecular conformation of cyclodextrins (β CD,γ CD) bearing benzoyl moiety was studied by circular dichroism and 1H NMR.The circular dichroism intensity of mono[6 (benzoyl ethylendiamino)] β CD (1) was reduced by adding of guests.In contrast,the circular dichroism intensity of mono(6 o benzoyl) γ CD (2) was increased by adding of guests.The benzoyl moiety of 1 was extruded outside from the cavity of β CD by guests,while the benzoyl moiety of 2 was included together with guests in the cavity of γ CD.展开更多
This paper reports the improved synthesis of 4-O-ethylepipicropodophyllin 5 in two steps starting from Podophyllotoxin 1. The method is more efficient and convenient than the synthetic route from references.
文摘α-Hydroxy ketones are frequently involved in biologically important compounds and,therefore,the determination of the stereochemistry of these structural elements has attracted the attention in natural products chemistry.In this paper a simpler Mosher′s method was developed from the modified Mosher′s method.It only need one configuration of MTPA to determine the absolute configurations of four α-hydroxy ketones with their（S）-and（R）-MTPA esters using（）1H NMR.The signals of protons on the same side with phenyl ring will be in the higher field than those of on the different side ones.Consequently according to the model the main configuration of compounds 1,2,3 and 4 were determined as S,R,R and S, respectively.
文摘The molecular conformation of cyclodextrins (β CD,γ CD) bearing benzoyl moiety was studied by circular dichroism and 1H NMR.The circular dichroism intensity of mono[6 (benzoyl ethylendiamino)] β CD (1) was reduced by adding of guests.In contrast,the circular dichroism intensity of mono(6 o benzoyl) γ CD (2) was increased by adding of guests.The benzoyl moiety of 1 was extruded outside from the cavity of β CD by guests,while the benzoyl moiety of 2 was included together with guests in the cavity of γ CD.
文摘This paper reports the improved synthesis of 4-O-ethylepipicropodophyllin 5 in two steps starting from Podophyllotoxin 1. The method is more efficient and convenient than the synthetic route from references.
