(m.n)-Homorubins. Syntheses and Structures.

Five new homorubin analogs of bilirubin with their two dipyrrinone components conjoined to (CH), (CH), and (CH) units were synthesized with propionic acid chains shortened to acetic and elongated to butyric, and examined by spectroscopy and molecular mechanics computations for an ability to form conformation-determining hydrogen bonds. With m designating the number of conjoining CH units and n indicating the number of CH units of the alkanoic acid chains of (m.n)-homorubins, (2.

Homorubins and Homoverdins.

The syntheses are described for centrally expanded bilirubin analogs: -homorubins with propionic and butyric acid groups in the positions corresponding to the propionic acids of bilirubin. Their syntheses were accomplished by coupling two equivalents of a reactive monopyrrole (5-(bromomethylene)pyrrolin-2-one) to a dipyrrylethane. The corresponding -homoverdins and dehydro- -homoverdins were prepared by dehydrogenating the rubins or their dimethyl esters using DDQ.