Enantioselective synthesis of neoambrosin, parthenin, and dihydroisoparthenin
Enantioselective synthesis of the titled ambrosanolides is described. Use of the trimethylsilyl group as an anchor contributed to the stereoselective introduction of two methyl groups.
Anhydroparthenin (III), obtained from parthenin (I), when treated with dimethylamine is cleaved at the lactone ring and finally affords isomeric diadducts IV and V, formed by the addition of 2 moles of amine to carbonyl carbon and exomethylene carbon.The diadduct (IV) after catalytic hydrogenation and relactonisation gives a compound characterised as epi-allodamsin which is epimeric with damsin at C-1 and C-10.
Bhat, Uppoor G.,Kulkarni, Mandakini M.,Rojatkar, Supada R.,Nagasampagi, Bhimsen A.