title: Synthesis of 18O-Labelled chlorophyll derivatives at carbonyl oxygen atoms by acidic hydrolysis of the ethylene ketal and acetal.
abstract: The ethylene ketal of pyropheophorbides, chlorophylls possessing the 13-keto carbonyl group and lacking the 13(2)-methoxycarbonyl group, reacted with H(2)(18)O (ca. 95% 18O atom) by acidic hydrolysis to give efficiently and regioselectively 13(1)-18O-oxo-labelled compounds (ca. 92% 18O). The resulting 18O-labelled chlorin was modified by several chemical reactions to afford some derivatives with little loss of the 18O atom. Following the same procedures, 3(1),13(1)-doubly-18O-labelled pyrochlorophyll derivatives were also prepared. All the synthetic 18O-labelled compounds were identified by FAB-mass and vibrational spectra. Especially, in the vibrational spectroscopic results including IR and resonance Raman spectra, an about 30 cm(-1) wavenumber down-shift of the 3- and/or 13-C[double bond]O stretching vibrational bands was observed by exchanging 3(1)- or 13(1)-oxo-oxygen atom from 16O to 18O.
authors.affiliation: Department of Bioscience and Biotechnology, Faculty of Science and Engineering, Ritsumeikan University, Kusatsu, Shiga 525-8577, Japan.
authors.forename: Hidetada
authors.initials: H
authors.lastname: Morishita
authors.forename: Hitoshi
authors.initials: H
authors.lastname: Tamiaki
mesh_terms: D000080:Acetals / Q000737:chemistry*; D002734:Chlorophyll / Q000031:analogs & derivatives* / Q000138:chemical synthesis* / Q000737:chemistry*; D000077194:Chlorophyll A; D004148:Dioxolanes / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D006868:Hydrolysis; D007553:Isotope Labeling / Q000379:methods; D009682:Magnetic Resonance Spectroscopy; D015394:Molecular Structure; D010084:Oxidation-Reduction; D010100:Oxygen / Q000737:chemistry*; D010103:Oxygen Isotopes; D011166:Porphyrins / Q000737:chemistry; D017550:Spectroscopy, Fourier Transform Infrared
chemical_list: D000080:Acetals; D004148:Dioxolanes; D010103:Oxygen Isotopes; D011166:Porphyrins; D002734:Chlorophyll; C040298:pyropheophorbide a; C006969:chlorin; D010100:Oxygen; D000077194:Chlorophyll A