Reduction of Chlorophyllides, Chlorophylls and Chlorophyll Derivatives by Sodium Borohydride.

Abstract

Dilute methanolic solutions of sodium borohydride effect a selective reduction of the C3 formyl group of chlorophyll b. The product, Mg-phytyl pheophorbide b, has a visible absorption spectrum characteristic of the a series of pigments. Its infra-red absorption spectrum in non-polar solvents has a strong absorption band at about 1650 cm-1, as does that of chlorophyll a. The band disappears when Mg is removed. In higher concentrations the C3 keto group of chlorophyll a and of the C3 methanol derivative of chlorophyll b is reduced. The "red" absorption maxima are shifted from about 660 m[mu]. in ether to about 630 m[mu]. The formyl and keto groups of Mg-free compounds are likewise reduced. Pheoporphyrin as and phylloerythrin are reduced to their respective 9-oxy-desoxo derivatives. An intermediate reduction product was not observed during reduction of the C3 keto group.