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Zinc complex of methyl 31-octadecyl-bacteriopheophorbide-d was prepared from modification of naturally occurring chlorophyll-a. The 31-epimerically pure samples were obtained by HPLC separation and their stereochemistry including the absolute configuration at the secondary alcoholic 31-position was determined by combination of esterification to methoxy(trifluoromethyl)phenylacetate and NMR spectroscopy (Mosher''s method). Both the epimers were monomeric in a polar organic solvent and self-aggregated in a non-polar solvent to give oligomers as well as dimers possessing red-shifted visible absorption bands. Visible spectra of the non-polar organic solutions were dependent upon the 31-chirality and such a diastereoselective control on the self-aggregation led to the formation of self-aggregates with different supramolecular structures. [Copyright &y& Elsevier]

The ethylene ketal of pyropheophorbides, chlorophylls possessing the 13-keto carbonyl group and lacking the 132-methoxycarbonyl group, reacted with H218O (ca. 95% 18O atom) by acidic hydrolysis to give efficiently and regioselectively 131-18O-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, 31,131-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&z.dbnd6;O stretching vibrational bands was observed by exchanging 31- or 131-oxo-oxygen atom from 16O to 18O. [Copyright &y& Elsevier]