130 



IV. BILE PIGMENTS 



doubtful. The spectroscopic and other properties of mesobilierythrin resem- 

 ble those of mesobilene-(b) more closely than those of mesobiliviolin. Like 

 mesobilene-(b) it is more hydrophilic than mesobiliviolin and passes from 

 ether into 0.1% acetic acid. For this reason a dehydromesobilene-(b) 

 formula (Fig. 19) should be considered. This formula satisfactorily explains 



M 



M 



P M M E 



/\ ApA ApA A„A .CO 



H H2 jj H H, 



Fig. 19. Structure suggested for mesobilierythrin. 



the formation of mesobilic-ythrin from mesobilane and mesobilene-(b) by 

 oxidation and its isomerization to mesobiliviolin. Siedel's synthesis, which 

 gives mesobilierythrin in poor yield, can hardly be considered certain evi- 

 dence for the structure, but the oxidation of mesobilene-(a) to mesobili- 

 erythrin by nitrous acid or autoxidation {2552,2559) cannot be satisfactorily 

 explained with the formula of Figure 19. The problem of the structure of 

 erythrins must therefore remain open. 



Properties. In the chromatogram the red ring of mesobilierythrin 

 migrates before the violet ring of mesobiliviolin {2550). No pure 

 crystalline preparation has yet been obtained. The position of the 

 absorption maxima of solutions of mesobilierythrin and of its zinc 

 complex are summarized in Table VII. 



TABLE VII 



Color and Absorption Spectra of Mesobilierythrin 

 and Its Zinc Complex Salt 



5.4. Bilipurpurins [Biladiene -(a,b)- ones -(c)] 

 and Related Substances 



5.4.1. Structure. Siedel and Fischer {2554) still assumed these sub- 

 stances to be isomerides of bilatrienes. Lemberg {1679) demonstrated, how- 



