HIGH-PERFORMANCE LIQUID-CHROMATOGRAPHIC SEPARATION AND ISOLATION OF THE METHANOLIC ALLOMERIZATION PRODUCTS OF CHLOROPHYLL-A

Isocratic normal-phase HPLC on a silica column with diode-array detect ion provided a powerful means for the analytical separation and prepar ative isolation of seven methanolic allomerization products of chlorop hyll a. Diastereomeric selectivity was achieved for 13(2)(R,S)-hydroxy chlorophyll a, 13(2)(R,S)-methoxychlorophyll a and the Mg complex of o -15(1)-hydroxy-15(1)(R,S)-methoxyrhodochlorin-15- acid delta-lactone 1 5(2)-methyl 17(3)-phytyl ester. The Mg complex of 3(1),3(2)-didehydror hodochlorin-15-glyoxylic acid 13(1),15(2)-dimethyl 17(3)-phytyl ester was also isolated in high purity. Reversed-phase HPLC did not result i n an acceptable separation in spite of using several different brands of reversed-phase C-18 columns and mobile phase compositions. The iden tification of the anomerization products was based on UV-Vis and H-1 N MR spectra, retention times and co-elution with authentic samples. The observed formation of small amounts of numerous side-products is inte rpreted as further evidence for the free-radical mechanism of the allo merization.