Construction of the Bacteriochlorin Macrocycle with Concomitant Nazarov Cyclization To Form the Annulated Isocyclic Ring: Analogues of Bacteriochlorophyll <i>a</i>
作者:Shaofei Zhang、Jonathan S. Lindsey
DOI:10.1021/acs.joc.6b02878
日期:2017.3.3
propenone bearing the two halves (a hydrobilin analogue). Subsequent treatment (0.2 mM) with acid (Yb(OTf)3, CH3CN, 80 °C) promotes a double ring-closure process: (i) condensation between the α-position of pyrrole ring A and the α-acetal unit attached to pyrroline ring B forms the bacteriochlorin macrocycle, and (ii) Nazarov cyclization of the β-(propenoyl)-substituted ring C forms the isocyclic ring (E)
细菌叶绿素含有带有环第五环的细菌绿素大环。称为杂环或环E的第五个环带有131-氧代和132-羰基甲氧基取代基。在本文中,描述了获得稳定的合成细菌叶绿素类似物的一般途径。二氢联吡啶-甲醛(AD的一半)与被β-酮酸酯取代的二氢联吡啶(BC的一半)的Knoevenagel缩合(〜40 mM,rt,CH2Cl2,哌啶/ AcOH /分子筛)形成带有两个半团的丙烯酮(水联蛋白)类似物)。随后用酸(Yb(OTf)3,CH3CN,80°C)处理(0.2 mM)会促进双闭环过程:(i)吡咯环A的α位和与之连接的α缩醛单元之间的缩合吡咯啉环B形成细菌绿素大环,(ii)β-(丙烯酰基)-取代的环C的纳扎罗夫环化形成杂环(E)。在37-61%的位置构建了5个在2和3位(β-吡咯位,A环)和132个碳烷氧基(R = Me或Et)带有各种取代基(烷基/烷基,芳基和烷基/酯)的新细菌绿素。氢比林类似物的收率。相应的吡