Derivatives of Coenzyme F430 with a Covalently Attached α-Axial Ligand. Part II : Partial Synthesis of the Five Coenzyme F430 Tetramethyl Esters and of a Derivative with a Coordinating Nπ-Methyl-L-histidine Ligand Covalently Attached to the Side Chain at C(3) of F430 via a Peptidic Linker

✍ Scribed by Carsten Bauer; Bernhard Jaun

• Publisher: John Wiley and Sons
• Year: 2003
• Tongue: German
• Weight: 222 KB
• Volume: 86
• Category: Article
• ISSN: 0018-019X
• DOI: 10.1002/hlca.200390348

✦ Synopsis

Abstract

Coenzyme F430 pentamethyl ester 2 was partially hydrolyzed to a mixture of the five F430 tetramethyl esters 7–11, which were separated by HPLC and identified by means of a full NMR characterization. The tetramethyl ester with a free COOH group at the side chain at C(3) of F430 was coupled to the N‐terminus of the peptidic spacerligand construct 12 selected and studied as described before. The UV/VIS and NMR spectra in CH~2~Cl~2~/3,3,3‐trifluoroethanol 6 : 1 show that the new derivative, the Ni^II^(3^3^‐dehydroxy‐8^3^,12^2^,13^3^,18^2^‐tetra‐O‐methyl‐F430‐3^3^‐yl)‐L‐prolyl‐L‐prolyl‐N^π^‐methyl‐L‐histidine methyl ester (13), is an intramolecular, pentacoordinate, paramagnetic complex. In the same solvent system, the parent 3^3^,8^3^,12^2^,13^3^,18^2^‐penta‐O‐methyl‐F430 (2) is four coordinate and diamagnetic even in the presence of equimolar 1__H__‐imidazole. Protonation of the axially coordinating histidine residue of 13 gave the diamagnetic tetracoordinate base‐off form, which allowed us to establish the constitution of 13 by NMR.