title: Reduction of vinyl groups in naturally occurring chlorophylls-a.
abstract: 3,8-Divinyl-chlorophyll(Chl)-a possessing a phytyl ester was hydrogenated in acetone by rhodium catalyst on alumina to afford 3-vinyl-8-ethyl-, 3-ethyl-8-vinyl- and 3,8-diethyl-Chls. The ratio of produced 3-ethyl-8-vinyl- over 3-vinyl-8-ethyl-Chls was determined to be 1.2, indicating that the reactivity of the 3-vinyl group was slightly higher than that of the 8-vinyl group. Catalytic hydrogenation of divinyl-protochlorophyll-a possessing a porphyrin π-skeleton (C17C18) instead of the above chlorin moiety (C17H-C18H) gave an equal amount of mono-reduced regioisomers. The slight (or no) selectivity is different from that in the enzymatic reduction of divinyl-(proto)chlorophyllides-a lacking a phytyl ester in the biosynthetic pathway of Chl-a where the sole 8-vinyl group is transformed to the ethyl group.
authors.affiliation: Department of Bioscience and Biotechnology, Faculty of Science and Engineering, Ritsumeikan University, Kusatsu, Shiga 525-8577, Japan. tamiaki@se.ritsumei.ac.jp
authors.forename: Hitoshi
authors.initials: H
authors.lastname: Tamiaki
authors.forename: Daisuke
authors.initials: D
authors.lastname: Takekoshi
authors.forename: Tadashi
authors.initials: T
authors.lastname: Mizoguchi
mesh_terms: D002384:Catalysis; D002734:Chlorophyll / Q000737:chemistry*; D000077194:Chlorophyll A; D002851:Chromatography, High Pressure Liquid; D006859:Hydrogen / Q000737:chemistry; D009682:Magnetic Resonance Spectroscopy; D013056:Spectrophotometry, Ultraviolet
chemical_list: D002734:Chlorophyll; D006859:Hydrogen; D000077194:Chlorophyll A