Kuenzle C C
Biochem J. 1970 Sep;119(3):395-409. doi: 10.1042/bj1190395.
N.m.r., i.r. and optical spectra of model compounds were recorded. These were to help in elucidating the structures of the phenylazo derivatives of bilirubin conjugates isolated from human bile. Model compounds included commercial and human bile bilirubin, mesobilirubin, bilirubin dimethyl ester, dimethoxybilirubin dimethyl ester and the corresponding phenylazo derivatives. The phenylazo derivative of vinylneoxanthobilirubinic acid was also investigated. All compounds were of the type IXalpha, and no other isomer could be detected with the spectroscopic methods employed. The compounds crystallize as the lactams, except for dimethoxybilirubin dimethyl ester and its phenylazo derivative, which are held in the lactim ether configuration. With all other compounds no tautomeric forms other than the lactams could be detected, although small proportions of bilirubin must exist as the lactim. Bilirubin does not form a betaine, a structure that has been proposed by von Dobeneck & Brunner (1965) to explain the bathochromic shift of its optical spectrum as compared with the expected position of the absorption maximum at 420nm. However, this shift to 453nm can be explained on the basis of internal hydrogen bonds occurring between the carboxylic protons and the pyrrole rings of bilirubin, as proposed by Fog & Jellum (1963), and new evidence for such a bonding has been accumulated. The bilirubin sulphate described by Watson (1958), which is formed by treatment of bilirubin with concentrated sulphuric acid and acetic anhydride, was also investigated. The main product of this reaction was isolated as its phenylazo derivative, and was shown to be 3,18-di(ethylidene sulphate)-2,7,13,17-tetramethylbiladiene-ac-8,12-dipropionic acid. The reaction leading to this compound is an addition of sulphuric acid to the vinyl side chains of bilirubin according to Markownikoff's rule.
记录了模型化合物的核磁共振、红外和光谱。这些有助于阐明从人胆汁中分离出的胆红素缀合物的苯基偶氮衍生物的结构。模型化合物包括市售胆红素和人胆汁胆红素、中胆红素、胆红素二甲酯、二甲氧基胆红素二甲酯以及相应的苯基偶氮衍生物。还研究了乙烯基新胆红酸的苯基偶氮衍生物。所有化合物均为IXα型，采用所使用的光谱方法未检测到其他异构体。除二甲氧基胆红素二甲酯及其苯基偶氮衍生物以烯醇醚构型存在外，其他化合物均以内酰胺形式结晶。对于所有其他化合物，除了内酰胺形式外，未检测到其他互变异构形式，尽管少量胆红素必须以烯醇形式存在。胆红素不形成甜菜碱结构，冯·多贝内克和布鲁纳（1965年）曾提出该结构来解释其光谱的红移现象，相比之下，预期的吸收最大值在420nm处。然而，如福格和杰勒姆（1963年）所提出的，这种向453nm的红移可以基于胆红素羧基质子与吡咯环之间形成的分子内氢键来解释，并且已经积累了关于这种键合的新证据。还研究了沃森（1958年）描述的胆红素硫酸盐，它是通过用浓硫酸和乙酸酐处理胆红素形成的。该反应的主要产物以其苯基偶氮衍生物形式分离出来，并被证明是3,18 - 二（亚乙基硫酸盐）- 2,7,13,17 - 四甲基胆二烯 - ac - 8,12 - 二丙酸。导致该化合物的反应是根据马尔科夫尼科夫规则，硫酸加成到胆红素的乙烯基侧链上。
