Synthese und Struktur eines peptidisch verknüpften Chlorindimers als Modellsystem für das photosynthetische Reaktionszentrum

The key step of photosynthesis is the light induced electron transfer from a dimeric chlorophyll donor, called special pair, to a quinone acceptor. The present knowledge of photosynthesis is based on studies of naturally occurring photosynthetic reactions centers as well as on artificial model systems. The synthesis of enantiomerically pure chlorins with two different functional groups in an anellated norbornan ring was performed in order to obtain a chlorin based special pair model compound. This synthesis was based on a total synthetic model pathway using four monopyrrolic building blocks. The transformation of the two different functional groups either to an active ester group or to an amine function gave two chlorin subunits, which allowed to form a peptide linkage between them. A chlorin dimer with a well defined structure was obtained. The most favourable conformations of the chlorin dimer were revealed by semiempirical calculations.