Phosphoric Acid Catalyzed Desymmetrization of Bicyclic Bislactones Bearing an All-Carbon Stereogenic Center: Total Syntheses of (−)-Rhazinilam and (−)-Leucomidine B
the presence of a catalytic amount of an imidodiphosphoric acid, enantioselective desymmetrization of bicyclicbislactones by reaction with alcohols took place smoothly to afford enantiomerically enriched monoacids having an all‐carbon stereogeniccenter. Concise catalytic enantioselective syntheses of both (−)‐rhazinilam and (−)‐leucomidine B were subsequently developed using (S)‐methyl 4‐ethyl‐4‐formylpimelate
C18-oxo eburnamine-vincamine alkaloids (+)-eburnaminol, (−)-larutenine, and (−)-cuanzine. Key to the approach is a substrate-controlled iridium-catalyzed asymmetric hydrogenation/lactamization cascade that leads to the formation of the common tetracyclic skeleton with essential cis-C20/C21 stereochemistry (93% yield, 98% ee, >20:1 dr, gram scale). Access to the targeted alkaloids is effected late in the
在这里,我们公开了代表性的C18-氧代依布胺-长春胺生物碱(+)-依布那醇、(-)-月桂藤碱和(-)-川嗪的不同全合成。该方法的关键是底物控制的铱催化不对称氢化/内酰胺化级联,导致形成具有基本顺式-C20/C21立体化学的常见四环骨架(93%产率,98% ee ,>20:1 dr ,克级)。通过实施许多面向多样性的转化和后期修饰,可以在合成后期实现对目标生物碱的获取。