Syntheses of Bile Pigments. Part 16. Synthesis of a vinyl-substituted 2,3-Dihydrobilinedione: Possible role of this new class of bile pigments in phycobilin biosynthesis
作者:Albert Gossauer、Fredy Nydegger、Eva Benedikt、Hans-Peter Köst
DOI:10.1002/hlca.19890720315
日期:1989.5.3
The total synthesis of racemic cis-2,3,181, 182, -tetrahydroprotobiliverdin IXα dimethyl ester (19b), which is identical with the dimethyl ester of rac-4, is described (Scheme 2). Under virtually neutral conditions, in solution, this bile pigment isomerized within a few min to racemic Z-phycocyanobilin dimethyl ester (rac-5b). Likewise, acid-catalyzed allyl rearrangement of 3-vinyl-substituted cis-
外消旋的全合成顺式-2,3,18 1,18 2,-tetrahydroprotobiliverdinIXα二甲酯(19B),这与的二甲基酯相同消旋- 4,描述(方案2)。在几乎中性的条件下,在溶液中,这种胆汁色素在几分钟内异构化为外消旋的Z-藻氰基胆碱二甲酯(rac - 5b)。同样,酸催化的3-乙烯基取代的顺式和反式-2,3-二氢联吡啶-1(10 H)-ones 11c和13c的烯丙基重排分别得到相应的亚乙基衍生物。然而,在这种情况下,E-异构体是由两种底物选择性地立体形成的。上述结果证明,如果protobiliverdinIXα(2)被酶转化为它的2,3,18 1,18 2 -四氢衍生物,后者会自发地异构化为phycocyanobi林。可以用相同的方法直接解释从在C(8)带有乙烯基的常见前体中合成细菌叶绿素a和b的过程。