Asymmetric Synthesis of (R)-(-)-O-desmethylangolensin using (R,R)-(-)-Pseudoephedrine as Chiral Auxiliary

by Rana Haikal

Institution: University of Helsinki
Year: 2015
Keywords: Orgaaninen kemia
Record ID: 1144492
Full text PDF: http://hdl.handle.net/10138/154744


O-Desmethylangolensin (O-DMA) is a product of anaerobic intestinal bacterial metabolism of the isoflavone daidzein, which is found mainly in soy foods. Because of its structural similarity to natural estrogen, it was found to have a strong binding affinity to human estrogen receptor β, thus explaining its anticarcinogenic activity among other biological actions. Because of its biological importance, the main aim of this study is to propose a synthetic route using (R,R)-(-)-Pseudoephedrine as chiral auxiliary to synthesize enantiopure (R)-(-)-O-DMA. Pseudoephedrine has been previously found to be an excellent chiral auxiliary; its amide is stable, easily prepared and its enolate is highly reactive and can undergo many useful transformations including alkylation reactions. 4-Hydroxyphenylacetic acid was used as starting material. Diastereoselective α-methylation of the pseudoephedrine amide was done using LDA in THF with subsequent addition of methyl iodide. The method was found successful; however, the yield (55%) and %ee (4.5%) were low, thus further adjustments are needed.