Abstract
A so far unknown chlorophyll has been isolated from several strains of brown-coloured chlorobacteria and has been designated bacteriochlorophyll e. Comparison of the physical and chemical properties of the new chlorophyll with those of bacteriochlorophylls c and d (Chlorobium chlorophylls) allows one to deduce its structural formula. The stereochemistry of the hydroxyethyl side chain of bacteriochlorophylls c, d and e can be determined by a modified Horeau analysis of these pigments, and the results thus obtained are in agreement with those derived from oxidative degradation experiments. The latter method allows one furthermore to prove the structure of bacteriochlorophylls c and d proposed by Holt, and to establish the absolute configuration at carbon atoms 7 and 8. The presence of a $\delta$-methylsubstituent in bacteriochlorophylls c and e is unambiguously demonstrated by nuclear magnetic resonance.