A New Method for the Synthesis of Medium- and Large-Sized Carbocycles
作者:Keiichi Masuya、Keiji Tanino、Isao Kuwajima
DOI:10.1055/s-1999-2696
日期:1999.5
A new synthetic method for medium and large-sized carbocycles has been developed. An acyclic compound having an olefin moiety and a 3-(methylthio)allyl acetate moiety at each of the terminal positions was designed as a cyclization precursor. The corresponding allyl cation intermediate, which was generated by treatment with EtAlCl2, underwent cyclization via an intramolecular addition reaction. The ring size of the product, which depends on the reaction site of the allyl cation, can be controlled by changing the nucleophilicity of the terminal olefin moiety.
Intramolecular (3+2) cycloaddition reactions involving benzyne and ynamides as three-atom components have been accomplished through the utilization of benzyne precursors having a linking functionality. The ambivalent nature of the intermediate indolium ylide, which exhibits both nucleophilic and electrophilic properties at its C2 atom, is thus brought to light in this approach.
Synthesis of chalcogenol esters from chalcogenoacetylenes
作者:Antonio L Braga、Tales L.C Martins、Claudio C Silveira、Oscar E.D Rodrigues
DOI:10.1016/s0040-4020(01)00200-9
日期:2001.4
Thiol and selenol esters were conveniently prepared in good yields by reacting chalcogenoacetylenes with trifluoroacetic acid in dichloromethane in the presence of silica. (C) 2001 Elsevier Science Ltd. Ah rights reserved.
Type-2 Isopentenyl Diphosphate Isomerase: Evidence for a Stepwise Mechanism
作者:Nicole A. Heaps、C. Dale Poulter
DOI:10.1021/ja208331q
日期:2011.11.30
studies with Thermus thermophilus IDI-2, we discovered that the olefinic hydrogens of a vinyl thiomethyl analogue of isopentenyl diphosphate exchanged with solvent when the enzyme was incubated with D(2)O without concomitant isomerization of the double bond. These results suggest that the enzyme-catalyzed isomerization reaction is not concerted.