Synthesis of bis-homo-prostaglandins

First Enantioselective Synthesis and Absolute Stereochemistry Assignment of New Monocyclic Sesquiterpenes from Artemisia chamaemelifolia

“…Application of the mild and efficient barium hydroxide-promoted Horner−Wadsworth−Emmons (HWE) reaction to the mixture 7 , using the barium derivative of diethyl-2-oxopropylphosphonate in THF at room temperature, gave 92% as an easily separable 1:3 mixture of the expected derivative (+)- 8 and diastereomeric bicyclic compounds 9 resulting from the intramolecular domino oxa-conjugate addition of the hydroxyl group to the intermediate enone system generated by the HWE reaction. Acetylation of (+)- 8 using the usual procedure (Ac 2 O, pyridine) and irreversible retro-Michael acetylation of 9 by heating under reflux with acetic anhydride and pyridinium p -toluenesulfonate (PPTS) furnished crystalline (+)- 10 (mp 40 °C) as a single E stereomer ( 3 J trans = 15.8 Hz) in 91% and 89% yield, respectively . The chemoselective 1,4-conjugate reduction of the α,β-enone system of (+)- 10 using Bu 3 SnH/cat.…”

Enantioselective Synthesis and Determination of the Absolute Configuration of Natural (−)-Elegansidiol

“…76°C) as a single E stereoisomer ( 3 J trans ϭ 15.9 Hz) in 81% yield by an irreversible retro-Michael addition process. [5] The conjugate reduction of α,β-unsaturated carbonyl compounds is an active area of organic synthesis and the arsenal of relevant synthetic tools has been strikingly enriched. [6] After several attempts, the best chemoselective 1,4-conjugate reduction of the α,β-enone system of (ϩ)-6 was achieved with Bu 3 SnH/palladium catalyst in the presence of anhydrous ZnCl 2 as the reducing system [7] to afford an 88% yield of solid (ϩ)-7 (m.p.…”