Syntheses of Bile Pigments. Part 16. Synthesis of a vinyl-substituted 2,3-Dihydrobilinedione: Possible role of this new class of bile pigments in phycobilin biosynthesis |
| |
Authors: | Albert Gossauer Fredy Nydegger Eva Benedikt Hans-Peter Kst |
| |
Institution: | Albert Gossauer,Fredy Nydegger,Eva Benedikt,Hans-Peter Köst |
| |
Abstract: | The total synthesis of racemic cis-2,3,181, 182, -tetrahydroprotobiliverdin IXα dimethyl ester ( 19b ), which is identical with the dimethyl ester of rac- 4 , is described (Scheme 2). Under virtually neutral conditions, in solution, this bile pigment isomerized within a few min to racemic Z-phycocyanobilin dimethyl ester (rac- 5b ). Likewise, acid-catalyzed allyl rearrangement of 3-vinyl-substituted cis- and trans-2,3-dihydrodipyrrin-1(10H)-ones 11c and 13c , respectively, yielded the corresponding ethylidene derivatives. In this case, however, the E-isomer was formed stereo selectively from both substrates. The above results prove that, if protobiliverdin IXα ( 2 ) is transformed enzymatically to its 2,3,181, 182-tetrahydro derivative, the latter would isomerize spontaneously to phycocyanobi-lin. The biosynthesis of bacteriochlorophyll a and b from a common precursor bearing a vinyl group at C(8)may be straightforwardly explained in the same way. |
| |
Keywords: | |
|
|