The bisindolesuccinic acid methyl ester 10 was obtained by an iodine-promoted coupling of the dianion 9. The diester was converted to the N-benzylimide 12, which was oxidatively cyclized to the indolo[2,3-a]pyrrolo[3,4-c]carbazole 15. The diester 10 could be directly transformed to the known indolocarbazole diester 27via acid-induced intramolecular cyclization in TFA. The same methodology gave arcyriaflavin A 4 from the succinimide 18b.
双
吲哚基
琥珀酸甲酯10是通过
碘促进的双阴离子9的耦合反应获得的。该二酯被转化为N-苄基
亚胺12,随后经过氧化环合得到
吲哚[2,3-a]
吡咯[3,4-c]
咔唑15。二酯10可以直接通过
三氟乙酸中的酸诱导分子内环合反应转化为已知的
吲哚咔唑二酯27。同样的合成方法从琥珀
酰亚胺18b得到了亮菌素A 4。