Abstract
Chlorophylls(Chls)-c are widely distributed and abundant in chromophyte algae and some prokaryotes together with Chl-a and carotenoids. The pigments are proved to function in light-absorbing pigments in photosynthesis. However, the detailed molecular structures of Chls-c have not yet been determined in terms of the conformation of the unique acrylic residue at the 17-position as well as the stereochemistry at the chiral 132-position. In this study, Chl-c1 and Chl-c2 were efficiently extracted from a diatom Chaetoseros calcitrans and the former (8-ethyl) and the latter (8-vinyl) were carefully separated using HPLC. The conformation of the acrylate was unambiguously determined to be cisoid around the C17-C171 bond using 1H-1H NOE correlations. Moreover, we developed a novel chiral HPLC method for quantitative analysis of a pair of enantiomeric isomers at the 132-position, which enabled us to determine the stereochemistry to be 132-(R)-configuration in combination with CD spectroscopy.
