Sitagliptin is the first new anti-diabetic drug in DPP-Ⅳ inhibitor class. The general synthesis of sitagliptin is by coupling of the β-amino acid fragment with the heterocycle fragment. Though the specific β-amino ...Sitagliptin is the first new anti-diabetic drug in DPP-Ⅳ inhibitor class. The general synthesis of sitagliptin is by coupling of the β-amino acid fragment with the heterocycle fragment. Though the specific β-amino acid can be easily made from the corresponding R-amino acid by Arndt-Eistert hornologation, the optically pure precursor R-amino acid is difficult to prepare. We herein reported a practical protocol to make the trifluorophenyl substituted R-amino acid 4 in 〉99.9% ee and 40.3% yield by the enzymatic resolution employing enantioselective hydrolysis and a general separation procedure. This protocol requires only cheap starting materials and friendly reaction condition. The procedure not only allows people to prepare the drug substance, but also provides an alternative method for prepareing the rare α-amino acid and the subsequent β-amino acid.展开更多
Reaction of Cp2TiCl2-Mg synthetic equivalent of practical Ti(II) reagent with propargyl alcohol derivatives affords allenyl titanium compounds in good yields.thus, providing an efficient and practical methods for synt...Reaction of Cp2TiCl2-Mg synthetic equivalent of practical Ti(II) reagent with propargyl alcohol derivatives affords allenyl titanium compounds in good yields.thus, providing an efficient and practical methods for synthesis of both allenyl and homopropargyl alcohols by the successive treatment with aldehydes and ketones.展开更多
A practical and cheap method for synthesis of C-4 carboxylic acid substituted kainic acid analogue 5 and its epimer 6 from trans-4-hydroxyproline is described. Using this method, more interesting intermediates and ana...A practical and cheap method for synthesis of C-4 carboxylic acid substituted kainic acid analogue 5 and its epimer 6 from trans-4-hydroxyproline is described. Using this method, more interesting intermediates and analogues could be obtained easily.展开更多
How to generate pictures real and esthetic objects is an important subject of computer graphics. The techniques of mapping textures onto the surfaces of an object in the 3D space are efficient ap- proaches for the pur...How to generate pictures real and esthetic objects is an important subject of computer graphics. The techniques of mapping textures onto the surfaces of an object in the 3D space are efficient ap- proaches for the purpose.We developed and implemented algorithms for generating objects with appear ances stone,wood grain,ice lattice,brick,doors and windows on Apollo workstations. All the algorithms have been incorporated into the 3D geometry modelling system(GEMS)developed by the CAD Center of Tsinghua University.This paper emphasizes the wood grain and the ice lattice algorithms.展开更多
Improved stereoselective syntheses of the targeted compounds （＋）-valiolamine 1 and （＋）-valienamine 2 starting from naturally abundant （–）-shikimic acid are described. A common key intermediate compound 7 was ...Improved stereoselective syntheses of the targeted compounds （＋）-valiolamine 1 and （＋）-valienamine 2 starting from naturally abundant （–）-shikimic acid are described. A common key intermediate compound 7 was first synthesized from （–）-shikimic acid in 9 steps. The compound 7 was then converted to （＋）-valiolamine 1 in 3 steps, and was also converted to （＋）-valienamine 2 in 4 steps. In summary, （＋）-valiolamine 1 and （＋）-valienamine 2 were synthesized from （–）-shikimic acid in 12 （or 13） steps in 40% and 39% overall yields, respectively.展开更多
基金supported in part by grant from Science and Technology Program of Guangdong Province(No. 2007B031503005).
文摘Sitagliptin is the first new anti-diabetic drug in DPP-Ⅳ inhibitor class. The general synthesis of sitagliptin is by coupling of the β-amino acid fragment with the heterocycle fragment. Though the specific β-amino acid can be easily made from the corresponding R-amino acid by Arndt-Eistert hornologation, the optically pure precursor R-amino acid is difficult to prepare. We herein reported a practical protocol to make the trifluorophenyl substituted R-amino acid 4 in 〉99.9% ee and 40.3% yield by the enzymatic resolution employing enantioselective hydrolysis and a general separation procedure. This protocol requires only cheap starting materials and friendly reaction condition. The procedure not only allows people to prepare the drug substance, but also provides an alternative method for prepareing the rare α-amino acid and the subsequent β-amino acid.
文摘Reaction of Cp2TiCl2-Mg synthetic equivalent of practical Ti(II) reagent with propargyl alcohol derivatives affords allenyl titanium compounds in good yields.thus, providing an efficient and practical methods for synthesis of both allenyl and homopropargyl alcohols by the successive treatment with aldehydes and ketones.
文摘A practical and cheap method for synthesis of C-4 carboxylic acid substituted kainic acid analogue 5 and its epimer 6 from trans-4-hydroxyproline is described. Using this method, more interesting intermediates and analogues could be obtained easily.
文摘How to generate pictures real and esthetic objects is an important subject of computer graphics. The techniques of mapping textures onto the surfaces of an object in the 3D space are efficient ap- proaches for the purpose.We developed and implemented algorithms for generating objects with appear ances stone,wood grain,ice lattice,brick,doors and windows on Apollo workstations. All the algorithms have been incorporated into the 3D geometry modelling system(GEMS)developed by the CAD Center of Tsinghua University.This paper emphasizes the wood grain and the ice lattice algorithms.
基金We thank the National Natural Science Foundation of China （No. 20972048） for the financial support of this work.
文摘Improved stereoselective syntheses of the targeted compounds （＋）-valiolamine 1 and （＋）-valienamine 2 starting from naturally abundant （–）-shikimic acid are described. A common key intermediate compound 7 was first synthesized from （–）-shikimic acid in 9 steps. The compound 7 was then converted to （＋）-valiolamine 1 in 3 steps, and was also converted to （＋）-valienamine 2 in 4 steps. In summary, （＋）-valiolamine 1 and （＋）-valienamine 2 were synthesized from （–）-shikimic acid in 12 （or 13） steps in 40% and 39% overall yields, respectively.
