Approaches to the Synthesis of Cytochalasans. Part 3. Synthesis of a substituted tetrahydroisoindolinone moiety possessing the same relative configuration as proxiphomin
作者:Tibur Schmidlin、Werner Züurcher、Christoph Tamm
DOI:10.1002/hlca.19810640125
日期:1981.2.4
analysis of its O-acetyl derivative 16 [5]. Ring closure of the hydroxy acid 14 gave the lactone 17, corresponding to the natural product 1 as to the configuration. The presence of the N-benzyloxycarbonyl group in lactone 6 has been shown to be essential for the above-mentioned ‘inversion’ at C(9), because no configurational change occurred with the N-unprotected lactone 8 when treated under the same conditions
描述了对应于脯氨酰胺(1)的四氢异吲哚满酮部分的总合成,其带有用于连接大环的官能团。外消旋2-(苄氧基羰基-氨基)-3-苯基丙醛(2)与(4-甲基-2,4-己二烯基)丙二酸甲酯(3)的Knoevenagel-Cope缩合产生(E)-和(Z)的混合物-烯烃4a和4b,其在加热时经历分子内Diels-Alder环化(参见方案1)。从所得产物中分离出四氢异吲哚啉衍生物6。X射线分析6 [5]揭示了在C(3),C(4),C(5)和C(8)上与1中相同的相对配置,但在C(9)处没有。用KOH水解6伴随着C(9)构型的变化,生成羟基酸14,该羟基酸14被转化为羟基酯11(参见方案4)。X射线分析O-乙酰基衍生物16 [5]证实了顺式-内酰胺环在11中的存在。羟基酸14的闭环得到内酯17,其对应于天然产物1关于配置。已经证明内酯6中N-苄氧基羰基的存在对于C(9)的上述“转化”是必不可少的,因为当在相同