Tandem Intramolecular Photocycloaddition−Retro-Mannich Fragmentation as a Route to Spiro[pyrrolidine-3,3′-oxindoles]. Total Synthesis of (±)-Coerulescine, (±)-Horsfiline, (±)-Elacomine, and (±)-6-Deoxyelacomine
作者:James D. White、Yang Li、David C. Ihle
DOI:10.1021/jo1002714
日期:2010.6.4
a tryptamine linked through its side-chain nitrogen to an alkylidene malonate residue results in an intramolecular [2 + 2] cycloaddition to the indole 2,3-double bond. The resultant cyclobutane undergoes spontaneous retro-Mannich fission to produce a spiro[indoline-3,3′-pyrrolenine] with relative configuration defined by the orientation of substituents in the transient cyclobutane. The tandem intramolecular
辐射通过其侧链氮连接至亚烷基丙二酸酯残基的色胺导致分子内[2 + 2]环加成至吲哚2,3-双键。所得环丁烷经历自发的逆曼尼希裂变,以产生螺环[二氢吲哚啉-3,3'-吡咯烷],其相对构型由瞬态环丁烷中的取代基的取向定义。串联分子内光环加成-逆曼尼希过程(缩写为TIPCARM)会导致螺吡咯烷,后者准备进行第二次逆曼尼希裂解,驱逐丙二酸酯单元并短暂生成吲哚啉。后者经历重排为β-咔啉,其在溴化氧化后经历进一步重排为羟吲哚。以色胺为原料 整个序列导致生物碱(±)-椰菜碱。从5-甲氧基色胺开始,一个平行的序列得到(±)-horsfiline。丙二烯基单元的修饰以在C 3处包括异丁基取代基提供了光致抗蚀剂,该光致抗蚀剂也经历了TIPCARM工艺。在这种情况下,得到2'-异丁基取代的螺[吲哚啉-3,3'-吡咯烷]。将其进行立体选择性氢化物还原,得到在螺碳处具有相对取向的产物,并且新的立体中心带有对应于生物