Total Synthesis of Haterumalides NA and NC via a Chromium-Mediated Macrocyclization
作者:Jennifer M. Schomaker、Babak Borhan
DOI:10.1021/ja8043695
日期:2008.9.17
haterumalides NA and NC were accomplished via the macrocyclization of a chlorovinylidene chromium carbenoid onto a pendant aldehyde to generate the C8-C9 bond with the desired stereoisomer as the major product. Utilizing the latter chemistry enables access to both C9 hydroxylated (haterumalides NC and ND) and C9 deoxygenated forms (haterumalides NA, NB, and NE; via deoxygenation of the C9-hydroxyl).
Intramolecular Hydrogen Abstraction Promoted by Amidyl Radicals. Evidence for Electronic Factors in the Nucleophilic Cyclization of Ambident Amides to Oxocarbenium Ions
A tandem 1,5-hydrogen atom transfer/radical oxidation/nucleophilic cyclization mechanism is proposed for the intramolecular hydrogenabstraction reaction promoted for primary carboxamidyl radicals. The electron-withdrawing capacity of the C-5 substituent can switch the reaction to give exclusively bicyclic spirolactams (6-oxa-1-azaspiro[4.5]decan-2-one) when R(1) = H or spirolactones (1,6-dioxaspiro[4
Stereoselective synthesis of C-ketosides by sequential intramolecular hydrogen atom transfer–intermolecular allylation reaction
作者:Angeles Martín、Inés Pérez-Martín、Luis M. Quintanal、Ernesto Suárez
DOI:10.1016/j.tetlet.2008.06.070
日期:2008.8
A tandem 1,5 or 1,6 hydrogen atom transfer (HAT)-radical allylation using carbohydrate models is described. The HAT reaction generated a C-glycos-1-yl radical intermediate, which added to allyltri-n-butyltin with high diastereoselectivity, to give C-ketosides with the quaternary carbon carrying two differently functionalized tethers. (C) 2008 Elsevier Ltd. All rights reserved.