Proof-of-principle direct double cyclisation of a linear C<sub>15</sub>-precursor to a dibrominated bicyclic medium-ring ether relevant to<i>Laurencia</i>species
作者:D. Christopher Braddock、Dan-Tiberiu Sbircea
DOI:10.1039/c4cc06402j
日期:——
Bicyclic medium ring ethers of relevance toLaurenciaspecies have been obtained by direct double brominative cyclisation of an acyclic precursor.
A Unifying Stereochemical Analysis for the Formation of Halogenated C<sub>15</sub>-Acetogenin Medium-Ring Ethers From <i>Laurencia</i> Species via Intramolecular Bromonium Ion Assisted Epoxide Ring-Opening and Experimental Corroboration with a Model Epoxide
作者:Karl J. Bonney、D. Christopher Braddock
DOI:10.1021/jo301580c
日期:2012.11.2
unifying stereochemical analysis for the formation of the constitutional isomeric halogenated C15-acetogenin medium-ring ether natural products from Laurencia species is presented, where an intramolecularbromoniumion assisted epoxide ring-opening reaction of enantiomerically pure epoxides can account for ring-size, the position of the halogen substituents, and relative and absolute configurations of
Large-scale preparation of (9Z,12E)-[1-13C]-octadeca-9,12-dienoic acid, (9Z,12Z,15E)-[1-13C]-octadeca-9,12,15-trienoic acid and their [1-13C] all-cis isomers
Several grams of labelled trans linoleic and linolenic acids with high chemical and isomeric purities (> 97%) have been prepared for human metabolism studies. A total of 12.5 g of (9Z,12E)-[1-C-13]-octadeca-9,12-dienoic acid and 6.3 g of (9Z,12Z,15E)-[1-C-13]-octadeca-9,12,15-trienoic acid were obtained in, respectively: seven steps (7.8% overall yield) and 11 steps (7% overall yield) from 7-bromo-heptan-1-ol. The trans bromo precursors used for the labelling were synthesised by using copper-catalysed couplings. The trans fatty acids were then obtained via the nitrile derivatives. A total of 23.5 g of (9Z,12Z)-[1-C-13]-octadeca-9,12-dienoic acid and 10.4 g of (9Z,12Z,15Z)-[1-C-13]-octadeca-9,12,15-trienoic acid were prepared in five steps in, respectively, 32 and 18% overall yield. Large quantities of bromo and chloro precursors were synthesised from the commercially available acid according to Barton's procedure. In all cases, the main impurities ( > 0.5%) of each labelled fatty acid have been characterised. (C) 2000 Elsevier Science Ireland Ltd. All rights reserved.