Synthesis of Erythrina and related alkaloids. XVI Diels-Alder approach : Total synthesis of dl-erysotrine, dl-erythraline, dl-erysotramidine, dl-8-oxoerythraline and their 3-epimers.
Total synthesis of erythrinan alkaloids was achieved by a strategy based on the Diels-Alder reaction of activated butadienes to a dioxopyrroline. The reaction of isoquinolinopyrrolinedione (15) with 1, 3-bis-O-substituted butadienes proceeded in a regiospecific and stereoselective manner to give erythrinan derivatives (20) and (21). Lithium borohydride reduction of the adduct (20) or (21), followed by acid hydrolysis afforded the enone (33). Mesylation of 33 and subsequent demethoxycarbonylation of 42 under neutral conditions gave the dienone (43). Meerwein-Ponndorf reduction of 43 and subsequent methylation afforded erysotramidine (2a) and 8-oxoerythraline (2b). Aluminum hydride reduction of the 8-oxo derivatives (2) furnished dl-erysotrine (1a) and dl-erythraline (1b).
Total Synthesis of (±)-8-Oxo-erythrinine, (±)-8-Oxo-erythraline, and (±)-Clivonine
作者:Maomao He、Chunrong Qu、Bingbing Ding、Hao Chen、Yangyan Li、Guofu Qiu、Xianming Hu、Xuechuan Hong
DOI:10.1002/ejoc.201500265
日期:2015.5
Total syntheses of the erythrina alkaloids (±)-8-oxo-erythrinine and (±)-8-oxo-erythraline have been developed, based on a substrate-controlled intramolecular 6-exo-trig selective radical spirocyclization that establishes the quaternary center of the B-rings. An improved totalsynthesis of (±)-clivonine has also been reported, based on an intramolecular 6-endo-trig free-radical cyclization of a highly
Development of a Divergent Synthetic Route to the Erythrina Alkaloids: Asymmetric Syntheses of 8-Oxo-erythrinine, Crystamidine, 8-Oxo-erythraline, and Erythraline
developed. Inspired by a proposed biosynthetic mechanism, the medium‐sized chiral biaryl lactam was asymmetrically transformed into the common core A–D rings by a stereospecific singletoxygen oxidation of the phenol moiety, followed by a transannular aza‐Michael reaction to the dienone functionality. The late‐stage manipulation of the oxidation and oxygenation states of the functional groups on the peripheral