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).
基于激活的
丁二烯与二
氧吡咯啉进行Diels-Alder反应的策略,实现了erythrinan类
生物碱的全合成。
异喹啉吡咯二
酮(15)与
1,3-双氧取代的
丁二烯反应,以区域特异性和立体选择性的方式生成erythrinan衍
生物(20)和(21)。通过
锂硼氢化物还原加合物(20)或(21),随后进行酸
水解得到
烯酮(33)。对33进行甲磺酰化,随后在中性条件下进行
脱甲
氧羰基化得到二
烯酮(43)。对43进行Meerwein-Ponndorf还原,随后进行
甲基化得到erysotramidine(2a)和8-
氧代erythraline(2b)。对8-
氧代衍
生物(2)进行
铝氢化还原得到dl-erysotrine(1a)和dl-erythraline(1b)。