Treatment of steroidal sapogenin diosgenin 1 with Lewis acid ethereal trifluoroborane in acetic anhydride at room temperature afforded a new type of pseudosapugenin 23, 26-diacetyl-△22(23)- pseudo-sapogenin 3 and its...Treatment of steroidal sapogenin diosgenin 1 with Lewis acid ethereal trifluoroborane in acetic anhydride at room temperature afforded a new type of pseudosapugenin 23, 26-diacetyl-△22(23)- pseudo-sapogenin 3 and its C-20 isomer 4 in 54% and 19% yield respectively.The possible mechanism was also suggested.展开更多
Let R ＊θ G be the skew group ring with a F.C group G and the group homomrphism 8 from G to Aut（R）, the group of automorphisms of the ring R. In this paper,the necessary and sufficient condition such that R ＊θ G ...Let R ＊θ G be the skew group ring with a F.C group G and the group homomrphism 8 from G to Aut（R）, the group of automorphisms of the ring R. In this paper,the necessary and sufficient condition such that R ＊θ G will be Noetherian is given, which generalizes the results of LG. connel.展开更多
Let R be a ring, and let （F, C） be a cotorsion theory. In this article, the notion of F-perfect rings is introduced as a nontrial generalization of perfect rings and A-perfect rings. A ring R is said to be right dr-...Let R be a ring, and let （F, C） be a cotorsion theory. In this article, the notion of F-perfect rings is introduced as a nontrial generalization of perfect rings and A-perfect rings. A ring R is said to be right dr-perfect if F is projective relative to R for any F ∈ F. We give some characterizations of F-perfect rings. For example, we show that a ring R is right F-perfect if and only if F-covers of finitely generated modules are projective. Moreover, we define F-perfect modules and investigate some properties of them.展开更多
文摘Treatment of steroidal sapogenin diosgenin 1 with Lewis acid ethereal trifluoroborane in acetic anhydride at room temperature afforded a new type of pseudosapugenin 23, 26-diacetyl-△22(23)- pseudo-sapogenin 3 and its C-20 isomer 4 in 54% and 19% yield respectively.The possible mechanism was also suggested.
基金Supported by the NSF of Educational Department of Henan Province(20025100003)
文摘Let R ＊θ G be the skew group ring with a F.C group G and the group homomrphism 8 from G to Aut（R）, the group of automorphisms of the ring R. In this paper,the necessary and sufficient condition such that R ＊θ G will be Noetherian is given, which generalizes the results of LG. connel.
文摘Let R be a ring, and let （F, C） be a cotorsion theory. In this article, the notion of F-perfect rings is introduced as a nontrial generalization of perfect rings and A-perfect rings. A ring R is said to be right dr-perfect if F is projective relative to R for any F ∈ F. We give some characterizations of F-perfect rings. For example, we show that a ring R is right F-perfect if and only if F-covers of finitely generated modules are projective. Moreover, we define F-perfect modules and investigate some properties of them.
