Highly Efficient and Selective Syntheses of Phycobilin Derivatives toward Analysis of structure and Function of Phytochrome

光敏色素是植物中主要的光敏染色体蛋白之一，以红光/远红光光可逆方式介导多种光响应发育过程。藻蓝胆素（phycocyanobilin，PCB）是捕光色素藻蓝蛋白（phycocyanin，PS）的发色团，其结构与PS B相似，是一种线性四吡咯，可替代PS B与脱辅基蛋白复合。为了分析光敏色素中发色团的结构要求，我们对藻胆素衍生物的合成进行了研究，成功地合成了游离酸形式的P-β B、PCB和在A-、B-、C-和D-环上修饰的PCB衍生物。1)2-甲苯磺酰基吡咯的甲苯磺酰基在酸性条件下重排到5-位，2）2-溴-5-甲苯磺酰基吡咯在酸性条件下有效转化为相应的5-甲苯磺酰基吡咯啉酮，3） ...更多信息 为了研究光敏色素B（Phytochrome B，PhyB）的光谱特性对生色团的结构要求，我们设计并化学合成了20个PCB类似物，并将它们与PhyB脱辅基蛋白（PhyB）重组。结果表明，A环主要起与PHYB连接的锚作用，因为C2和C3位侧链的修饰对加合物的形成和差谱没有显著影响。相反，B环和C环的侧链对于将发色团适当地定位在PHYB的发色团口袋中以及对于光可逆光谱变化是至关重要的。加合物的光可逆光谱变化需要D环的侧链结构。从这些研究中，我们得出结论，每个吡咯环的线性四吡咯发色团在发色团组装和PhyB的光致变色性能发挥不同的作用。少

Phytochrome, one of the major photosensory chromo proteins in plants, mediates a variety of light responsive developmental processes in a red/far-red photo reversible manner. The chromophore named phytochromobilin (PФB) is a linear tetrapyrrole similar in structure to phycocyanobilin (PCB), which is a chromophore of the light-harvesting pigment phycocyanin and used as a substitute for PФB to reconstitute with apoproteins. In order to analyze the structural requirements of the chromophore in phytochrome, we studied on the syntheses of phycobilin derivatives and succeeded to synthesize PФB, PCB, and PCB derivatives modified at the A-, B-, C-, and D-rings in free acid forms.Total syntheses of PФB and PCB were achieved by employing our original synthetic reactions, I.e., 1) rearrangement of the tosyl group of 2-tosylpyrroles to the 5-position under acidic conditions, 2) efficient transformation of 2-bromo-5-tosylpyrroles to the corresponding 5-tosylpyrrolinones under acidic conditions, 3) … More Wittig-type coupling reaction between 5-tosylpyrrolinones and 2-formylpyrrole, 4) palladium catalyzed deprotection of allyl esters of propanoic acid side-chains.To analyze the structural requirements of the chromophore for the spectral properties of phytochrome B (PhyB), we have designed and chemically synthesized 20 analogs of PCB and reconstituted them with PhyB apoprotein (PHYB). It was found that the A-ring -acts mainly as the anchor for legation to PHYB, because the modification of the side chains at the C2 and C3 positions did not significantly influence the formation or difference spectra of adducts. In contrast, the side chains of the B- and C-rings are crucial to position the chromophore properly in the chromophore pocket of PHYB and for photo reversible spectral changes. The side-chain structure of the D-ring is required for the photo reversible spectral change of the adducts. From these studies, we concluded that each pyrrole ring of the linear tetrapyrrole chromophore plays a different role in chromophore assembly and the photo chromic properties of PhyB. Less