Zirconocene-mediated Preparation of Precursors for Estratriene Synthesis
作者:Pavel Herrmann、Miloš Budešínský、Martin Kotora
DOI:10.1246/cl.2007.1268
日期:2007.10.5
Zirconium-mediated cyclization of an allyl-ene compound afforded organozirconium intermediate, which after alkylation (allylation and acylation) afforded either dienes or unsaturated ketones. These are considered to be precursors further elaboration of which should yield functionlized steroids.
Formal Total Synthesis of (±)-Estrone and Zirconocene-Promoted Cyclization of 2-Fluoro-1,7-octadienes and Ru-Catalyzed Ring Closing Metathesis
作者:Pavel Herrmann、Miloš Buděšínský、Martin Kotora
DOI:10.1021/jo800620d
日期:2008.8.1
A new and diastereoselective method for the synthesis of the estrone skeleton from a substituted styrene based on sequential 3-fold use of Cp2ZrBu2 (oxidative addition−alkylation and two cyclization−alkylation sequences) and a ruthenium complex catalyzed RC-metathesis of a sterically hindered diene was developed. The prepared estratetraene was obtained in 7 steps from a commercially available starting
A catalytic and stoichiometric approach to the synthesis of the steroid B-ring en route to estratrienes
作者:Pavel Herrmann、Martin Kotora
DOI:10.1016/j.tetlet.2007.03.018
日期:2007.4
Zirconocene catalyzed cyclization of 2-(5-methoxy-3-penten-1-yl)styrene in the presence of organomagnesium reagents was studied. The cyclization proceeded in high isolated yields (up to 84%) with excellent trans-selectivity (> 98%), which is unusual for the formation of cyclohexane derivatives. Catalytic cyclization in the presence of Cp2ZrCl2 proceeded as well with similar results. The reaction with (R,R)-(EBTHI)(2)ZrCl2 gave a cis/trans mixture of 5 in low yield and poor ee. (c) 2007 Elsevier Ltd. All rights reserved.
Synthesis of (±)-3-Methoxyestra-1,3,5(10)-trienes by the Repetitive Use of Negishi Reagent
repetitive use of Cp(2)ZrBu(2) (Negishi reagent) was applied in the synthesis of three 3-methoxyestra-1,3,5(10)-trienone isomers within four steps from the advanced intermediate 11. The overall synthesis is based on three zirconium-mediated reactions: (a) oxidative addition of a benzyl ether, (b) cyclization of an allyl-ene compound, and (c) cyclocarbonylation of a diene. The presented synthesis demonstrates