1335013-07-4Relevant academic research and scientific papers
Lewis acid mediated asymmetric Diels-Alder reactions of chiral 2-phosphonoacrylates
Zhu, Jia-Liang,Chen, Po-Erh,Huang, Hue-Wen
, p. 23 - 36 (2013/02/23)
2-Phosphonoacrylates containing four chiral alcohol auxiliaries were efficiently prepared and evaluated in Lewis acid mediated Diels-Alder reactions. Under the activation of SnCl4, all reactions performed in CH 2Cl2 at -65 °C exclusively afforded the endo (endo-to-carboxylate) cycloadducts with dr's ranging from 50:50 to >99:1. The best facial selectivity was obtained from the substrate bearing a (-)-phenylmenthyl group, to give adducts as (dr >99:1) or almost as (dr = 99:1) single diastereomers. Detailed strategies for the structural elucidation of the cycloadducts as well as a rationalization of the observed stereoselectivity are described.
Control of the regio- and diastereoselectivity for the preparation of highly functionalized terpenic cyclopentanes through radical cyclization
Arteaga, Jesus F.,Dieguez, Horacio R.,Gonzalez-Delgado, Jose A.,Quilez Del Moral, Jose F.,Barrero, Alejandro F.
experimental part, p. 5002 - 5011 (2011/11/06)
The titanocene-mediated cyclization of suitably functionalized acyclic C10 epoxy-polyprenes leads, with moderate stereoselectivity, to high yields of functionalized terpenic cyclopentanes with three contiguous stereogenic centers. These highly functionalized cyclopentanes are useful intermediates for the synthesis of several natural compounds that include this interesting subunit in their structure. Both the regioselectivity of the process leading to cyclopentanes and the stereoselectivity of the cyclization could be controlled by using malonyl derivatives or α,β-unsaturated nitriles as radical acceptors. The titanocene-mediated cyclization of suitably functionalized acyclic C10 epoxy-polyprenes proceeds with acceptable stereochemical control and excellent yields. The process takes place through 5-exo-trig ring closures and gives cyclopentanes with three contiguous stereogenic centers with peripheral functional groups that are suitable for constructing structurally complex natural products. Copyright
