title: Determination of stereochemistry of bacteriochlorophyll gF and 8(1)-hydroxy-chlorophyll aF from Heliobacterium modesticaldum.
abstract: The reaction center complex of heliobacteria contains three kinds of chlorophyll pigments, bacteriochlorophyll gF (BChl gF), its 13(2)-epimer BChl gF' and 8(1)-hydroxy-chlorophyll aF (8(1)-OH-Chl aF). Because the full stereochemistry of these naturally occurring chlorophyllous pigments has remained unknown, we determined the stereochemistry of both BChl gF and 8(1)-OH-Chl aF extracted from Heliobacterium modesticaldum. The configurations of the specific functional groups at ring-B as well as those at ring-D and -E were investigated by use of nuclear Overhauser effect correlations in their 1H-NMR spectra and circular dichroism spectra, as well as by modified Mosher's method in their chemical modification: (1) E-configuration was confirmed for the 8-ethylidene group at ring-B in BChl gF, (2) R-configuration was identified for the 1-hydroxyethyl group at ring-B in 8(1)-OH-Chl aF and (3) 13(2)-(R)-, 17-(S)- and 18-(S)-configurations at ring-D and -E in both BChl gF and 8(1)-OH-Chl aF were confirmed. These stereochemistries enabled us to discuss their biosynthesis and to propose possible routes for preparation of ethylidene and 1-hydroxyethyl groups at the 8-position.
authors.affiliation: Department of Bioscience and Biotechnology, Faculty of Science and Engineering, Ritsumeikan University, Kusatsu 525-8577, Japan.
authors.forename: Tadashi
authors.initials: T
authors.lastname: Mizoguchi
authors.forename: Hirozo
authors.initials: H
authors.lastname: Oh-oka
authors.forename: Hitoshi
authors.initials: H
authors.lastname: Tamiaki
mesh_terms: D001429:Bacteriochlorophylls / Q000032:analysis* / Q000737:chemistry; D002734:Chlorophyll / Q000031:analogs & derivatives* / Q000032:analysis* / Q000737:chemistry; D002942:Circular Dichroism; D003013:Clostridium / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy; D013237:Stereoisomerism
chemical_list: C504205:8(1)-hydroxy-chlorophyll aF; D001429:Bacteriochlorophylls; D002734:Chlorophyll