Semirubin. A Novel Dipyrrinone Strapped by Intramolecular Hydrogen Bonds
作者:Michael T. Huggins、David A. Lightner
DOI:10.1021/jo000393k
日期:2000.9.1
monomeric in nonpolarsolvents, where their esters are dimeric. The corresponding 10-oxo analogue (3) of 1 serves as a model for 10-oxo-bilirubin, a presumed bilirubin metabolite in alternate pathways for bilirubin excretion. Like 1, 3 is found to engage in intramolecular hydrogen bonding. Unlike the methyl ester of 1, the ethyl ester of 3 is not intermolecularly hydrogen bonded in nonpolarsolvents.
the dipyrrinone, as in the hexanoic acid of [6]-semirubin, tight intramolecular hydrogen bonding between the carboxylic acid group and the lactam moiety (intramolecular Kassoc ≫25,000) is found in CHCl3 with no evidence of dimers. In contrast, the analogous dipyrrinthione, [6]-thiosemirubin, eschews intramolecular hydrogen bonds, as determined using NMR spectroscopy and vapor pressure osmometry, preferring
双吡咯酮的内酰胺基团积极参与酰胺-酰胺氢键,在非极性溶剂(在 CHCl 3 中,K D ∼25,000 M -1在 22 °C 中)形成二聚体缔合复合物。相应的硫代酰胺(dipyrrinthones),由 dipyrrinones 通过与 Lawesson's 试剂反应制备,也在非极性溶剂中形成分子间氢键二聚体,尽管缔合常数要弱得多(在 CHCl 3 中,K D ∼200 M -1 at 22 ° C)。当羧酸基团连接到双吡喃酮的 C(9) 时,如在 [6]-半红素的己酸中,羧酸基团和内酰胺部分之间的紧密分子内氢键(分子内K assoc ≫25,000) 存在于 CHCl 3 中,没有二聚体的证据。相比之下,类似的双吡喃硫酮,[6]-硫代蜜红素,避开了分子内氢键,如使用 NMR 光谱和蒸汽压渗透法测定的那样,更喜欢形成硫代酰胺 - 硫代酰胺类型的分子间氢键二聚体。