A study directed to the total synthesis of β-erythroidine 1, a non-aromatic Erythrina alkaloid, was conducted based on a strategy involving construction of D-furanoerythrinan via Diels-Alder reaction of furodioxopyrroline and the conversion of the resulting furan to the δ-lactone via oxidative fission of the furan ring followed by one-carbon homologation. Oxidation of the furanoerythrinan 17 with N-bromoacetamide followed by treatment with Nafion-H gave the enol γ-lactone 27. Alkaline hydrolysis of 27 followed by methylation with diazomethane gave the keto-ester 31. Alkylation of 31a with dimethylsulfoxonium methylide gave 8-oxo-γ-erythrodine (5). One-carbon homologation of 31a by Yamakawa's method using chloromethyl phenyl sulfoxide resulted in the formation of 8-ozocycloerythroidine (6). Compounds 5 and 6 are structural isomers of natural 8-oxo-β-erthroidine (2).
一项针对非芳香性赤子豆
生物碱β-赤子豆碱1的总体合成研究,基于一种策略,即通过Diels-Alder反应构建D-
呋喃赤子豆烷,反应物为
呋喃二氧
吡咯烯,然后将生成的
呋喃通过氧化开环转化为δ-内酯,随后进行一碳同系物化。用N-
溴乙酰胺氧化
呋喃赤子豆烷17,然后用Nafion-H处理,得到了烯醇γ-内酯27。对27进行碱性
水解后,再用
偶氮甲烷进行甲基化,得到
酮酯31。用二甲基亚磺酰基
甲烷对31a进行烷基化,得到8-氧-γ-赤子豆碱(5)。采用山川法,通过
氯甲基苯基亚磺酰氧化物对31a进行一碳同系物化,形成8-氧环赤子豆碱(6)。化合物5和6是天然8-氧-β-赤子豆碱(2)的结构异构体。