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The preparative column chromatographic separation on small grained silica gel of the bacteriophaeophorbide-c- and -d-methyl esters into their homologous and isomeric components is described. The influence of particular regions of the molecule, which carry different alkyl-substituents, on the chromatographic separability is selectively enhanced through the variation of the eluent. Mass and 1H NMR spectra of the pure components are discussed.

The structural requirements for the regioselective photochemical ring-opening of chlorin derivatives and the corresponding rate of formation of the pertinent photobilins are reported. The structure of one of the photobilins is verified by X-ray analysis.

A new bacteriochlorophyll has been isolated by thin layer chromatography from all strains of the brown-colored Chlorobiaceae Chlorobium phaeobacteroides and Chlorobium phaeovibrioides. The new bacteriochlorophyll e —like the bacteriochlorophylls c and d—represents the major amount of bacteriochlorophyll in the cells in addition to small amounts of bacteriochlorophyll a. Bacteriochlorophyll e can be differentiated from the bacteriochlorophylls c and d by its absorption maxima in aceton and its different Rf-value in the thin layer chromatogram. The structure of the new bacteriochlorophyll e has been elucidated on the basis of mass spectra, 1H- and 13C-NMR-spectra, the UV/VIS-spectrum as well as IR-, ORD-, and CD-spectra. The new bacteriochlorophyll has the same relationship to bacteriochlorophyll c as chlorophyll b from green plants to chlorophyll a; therefore, bacteriochlorophyll e represents the first formyl-substituted chlorophyll from bacteria. Similar to the bacteriochlorophylls c and d, the new bacteriochlorophyll e consists of a mixture of at least three homologues which differ from each other by different substituents on the pyrrol rings II and III.

The esterifying alcohol of the bacteriochlorophyll a from Rhodospirillum rubrum was shown to be trans-trans-geranylgeraniol. Mass spectra of the corresponding bacteriopheophytins are used to determine the content and ratio of bacteriochlorophyll aP and bacteriochlorophyll aGg in various strains of phototrophic bacteria.

Chromic acid degradation of natural (-)-stercobilin (1) yields 2(R)-methyl-3(R)-ethylsuccinimide (+2), whereby the absolute configuration of 1 at the chiral centers C-1, C-2, C-7, and C-8 is established. The substituted oxo-tetrahydrodipyrromethane precursor, 5, for the total synthesis of (-)-stercobilins 3 and 4, in which the relative configuration between the asymmetric centers is known, yields 2(S)-methyl-3(S)-ethylsuccinimide (-2) under the same conditions of degradation. Nuclear magnetic resonance studies of 1 and 3 show that in 1 the hydrogen atoms at C-2 and C-2′, as well as those at C-7 and C-7′, are transrelative to one another. Accordingly, natural (-)-stercobilin possesses the 2′(S), 7′(S) configuration, and has the configuration formula 6(1 (R), 2(R), 2′(S), 7′(S), 7(R), 8(R)). These results, coupled with those of earlier studies, also establish the absolute configuration of the (+)-urobilin 7 and of the phycobilin 8 at C-7′.

Rhodospirillum rubrum and Rhodopseudomonas palustris contain a bacteriochlorophyll which is a farnesyl rather than a phytyl ester. The new bacteriochlorophyll (Bchl aF) can be distinguished from the well known bacteriochlorophyll a (Bchl aP) by 1H-n.m.r. spectroscopy and by t.l.c. of the corresponding pheophytins on silver nitrate impregnated silica gel. The chromophores of Bchl aP and Bchl aF are identical in structure and stereochemistry.

A new bacteriochlorophyll g has been isolated from Heliobacterium chlorum. Its visible absorption spectrum is different from those of all other known bacteriochlorophylls, and it is extremely sensitive to oxygen in the presence of light. A proposal for the structure of the new bacteriochlorophyll g is given on the basis of absorption, CD, and 1H-NMR spectra of the corresponding bacteriopheophytin g and two main transformation products of Bchl g.

In the presence of oxygen and light magnesium free derivatives of bacteriochlorophyll c form linear tetrapyrroles by oxidative ring cleavage. The structure of these photobilines has been determined by spectroscopic methods.