Premium
Structural Investigations of 13‐ O ‐Demethyl‐FK506 and Its Isomers Generated by in vitro Metabolism of FK506 Using Human‐Liver Microsomes
Author(s) -
Schüler Wolfgang,
Schmieder P.,
Kessler Horst,
Christians Uwe,
Holze Ines,
Sewing KarlFriedrich,
Schiebel HansMartin
Publication year - 1993
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.19930760614
Subject(s) - chemistry , stereochemistry , demethylation , epimer , amide , isomerization , metabolite , heteronuclear molecule , two dimensional nuclear magnetic resonance spectroscopy , chemical shift , conformational isomerism , nuclear magnetic resonance spectroscopy , molecule , biochemistry , organic chemistry , gene expression , dna methylation , gene , catalysis
FK506 is currently under investigation as immunosuppressant after organ transplantation and in immune diseases. The structure of a demethylated metabolite 1 of FK506 isolated after in vitro metabolism by human‐liver microsomes was established using two‐dimensional homo‐ and heteronuclear NMR experiments. The demethylation position was found to be at O C(13) using HMBC spectra. In contrast to FK506, 7 different isomers could be differentiated in COSY, HMBC, and HMQC spectra. The intensity of their signals was 50:18:11:9:6:6 (one isomer could not be quantified). This isomerization may be explained by epimerization at C(10) or alternative formations of the hemiketal ring between C(10) and C(13) or C(9) and C(13), in addition to cis/trans ‐isomerism about the amide bond (see Scheme ). The structural variation is possible by participation of the OH group at C(13) formed after demethylation and could be derived from HMBC spectra. Chemical exchange evidenced by ROESY spectra proved the rotational isomerism. NMR investigation of the structure of 13‐ O ‐demethyl‐FK 506 ( 1 ) revealed at least seven isomers.