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Derivatives of Coenzyme F430 with a Covalently Attached α ‐Axial Ligand. Part II
Author(s) -
Bauer Carsten,
Jaun Bernhard
Publication year - 2003
Publication title -
helvetica chimica acta
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.74
H-Index - 82
eISSN - 1522-2675
pISSN - 0018-019X
DOI - 10.1002/hlca.200390348
Subject(s) - chemistry , imidazole , protonation , stereochemistry , histidine , intramolecular force , ligand (biochemistry) , organic chemistry , ion , biochemistry , receptor , enzyme
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 spacerligand 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.