Use of a novel ring-closure reaction for total synthesis of chlorin-fullerene- and chlorin-quinone-dyads as model systems for photosynthesis

The aim of this dissertation was the total synthesis of model compounds for an elementary step of photosynthesis, the light induced charge separation. In contrast to many known model systems in literature, in which porphyrins have been used as electron donors, the donor used in this case was the chromophore of the naturally photosynthetic pigments, a chlorin derivative (dihydroporphyrine). As an electron acceptor a fullerene C60 has been used, which is known to be an excellent electron and energy acceptor since a few years. Another acceptor, which has been used was a quinone, which serves also as an acceptor in the naturally photosynthetic systems. Based on a model synthesis a total synthetic approach to a chlorin derivative with an anellated sulfolene ring could be achieved. This chlorin derivative, which is a precursor for a dimethylene chlorin (heterocyclic o-quinodimethane), could be used for many functionalisations by Diels-Alder reactions. Further a new ring closure method has been developed which has some advantages in preparative use. This new ring closure method involves a thermic cyclization of a carboethoxy-substituted hydrobiline derivative to the corresponding chlorin macrocycle. The cyclization is part of a cascade of reactions during which also the dienophile like fullerene C60 or quinone is covalently linked to the chlorin framework by a Diels-Alder reaction. This led to the desired dyads, in which the luminescence is quenched, which indicates an intramolecular transfer of electrons or energy from the chlorin moiety to the acceptor moiety

Verwendung einer neuartigen Ringschlussreaktion zur Totalsynthese von Chlorin-Fulleren- und Chlorin-Chinon-Dyaden als Modellsysteme fuer die Photosynthese

The aim of this dissertation was the total synthesis of model compounds for an elementary step of photosynthesis, the light induced charge separation. In contrast to many known model systems in literature, in which porphyrins have been used as electron donors, the donor used in this case was the chromophore of the naturally photosynthetic pigments, a chlorin derivative (dihydroporphyrine). As an electron acceptor a fullerene C60 has been used, which is known to be an excellent electron and energy acceptor since a few years. Another acceptor, which has been used was a quinone, which serves also as an acceptor in the naturally photosynthetic systems. Based on a model synthesis a total synthetic approach to a chlorin derivative with an anellated sulfolene ring could be achieved. This chlorin derivative, which is a precursor for a dimethylene chlorin (heterocyclic o-quinodimethane), could be used for many functionalisations by Diels-Alder reactions. Further a new ring closure method has been developed which has some advantages in preparative use. This new ring closure method involves a thermic cyclization of a carboethoxy-substituted hydrobiline derivative to the corresponding chlorin macrocycle. The cyclization is part of a cascade of reactions during which also the dienophile like fullerene C60 or quinone is covalently linked to the chlorin framework by a Diels-Alder reaction. This led to the desired dyads, in which the luminescence is quenched, which indicates an intramolecular transfer of electrons or energy from the chlorin moiety to the acceptor moiety

Kodierung verhaltensrelevanter Gesangsparameter bei Chorthippus biguttulus

Heuschrecken nutzen die akustische Kommunikation zum Auffinden eines geeigneten Paarungspartners. Sie produzieren artspezifische Gesänge, die aus Silben und Pausen festgelegter Dauer bestehen. Den Weibchen dienen diese Gesänge nicht nur zur Erken-nung der Artzugehörigkeit – und somit zur Vermeidung von Hybriden -, sondern dar-über hinaus als Informationsquelle über die Qualität der Männchen. Den Männchen hilft der weibliche Antwortgesang beim Auffinden der Weibchen. Die Attraktivität verschiedener artifizieller Gesangsattrappen für Männchen und Weib-chen wurde in Verhaltensexperimenten untersucht. Es zeigte sich ein starker Zusam-menhang zwischen der Attraktivität und den gewählten Parametern, insbesondere der Pausendauer. Die Reaktionen von auditorischen Neuronen des Metathorax und des Oberschlundganglions auf diese Stimuli wurden charakterisiert. Die durch diese Neuro-ne transportierte Informationsmenge bezüglich der variierten Parameter sowie ihr zeitli-cher Verlauf wurde bestimmt. Durch die Kombination von Verhaltensversuchen und elektrophysiologischen Untersu-chungen an denselben Tieren konnte ein Zusammenhang zwischen Verhalten und Spi-keantworten bei einer aufsteigenden Zelle hergestellt werden. Für diese Zelle wird ein Modell zur Pausendauerdetektion vorgestellt. Hierbei werden mittlere Pausendauern – die für Weibchen attraktiv sind – mit höheren Spikezahlen beantwortet als kurze und lange Pausen. Dies kommt durch unterschiedliche Zeitverläufe von Adap¬tation und Rückkehr aus der Adaptation bei den exzitatorischen und inhibitorischen Eingängen der Zelle zustande.Grasshoppers use acoustic communication to find a sexual partner. They produce species-specific songs, which consist of syllables and pauses of a fixed duration. The male songs enable the females not only to recognize conspecifics – and thus to avoid hybridization – but also to obtain information about the quality of the males. Males take advantage of the females’ response songs in localizing the female. The attractiveness of various artificial stimuli for males and females was studied in behavioral experiments. A strong correlation between the attractiveness and the chosen parameters - especially the pause duration - could be found. The responseproperties of auditory neurons in the metathoracic ganglion and the supraoesophageal ganglion have been characterized. The transmitted information and its temporal course was determined. By performing behavioral and electrophysiological experiments with the same animals, I found a correlation between behaviour and spike responses in an ascending neuron (AN3). The tuning of this cell for pause duration was modelled as the result of different time courses of adaptation of the cells excitatory and inhibitory inputs. In this model pauses of intermediate duration – which are most attractive to females – generate more action potentials than shorter or longer pauses

Verwendung einer neuartigen Ringschlussreaktion zur Totalsynthese von Chlorin-Fulleren- und Chlorin-Chinon-Dyaden als Modellsysteme fuer die Photosynthese

The aim of this dissertation was the total synthesis of model compounds for an elementary step of photosynthesis, the light induced charge separation. In contrast to many known model systems in literature, in which porphyrins have been used as electron donors, the donor used in this case was the chromophore of the naturally photosynthetic pigments, a chlorin derivative (dihydroporphyrine). As an electron acceptor a fullerene C60 has been used, which is known to be an excellent electron and energy acceptor since a few years. Another acceptor, which has been used was a quinone, which serves also as an acceptor in the naturally photosynthetic systems. Based on a model synthesis a total synthetic approach to a chlorin derivative with an anellated sulfolene ring could be achieved. This chlorin derivative, which is a precursor for a dimethylene chlorin (heterocyclic o-quinodimethane), could be used for many functionalisations by Diels-Alder reactions. Further a new ring closure method has been developed which has some advantages in preparative use. This new ring closure method involves a thermic cyclization of a carboethoxy-substituted hydrobiline derivative to the corresponding chlorin macrocycle. The cyclization is part of a cascade of reactions during which also the dienophile like fullerene C60 or quinone is covalently linked to the chlorin framework by a Diels-Alder reaction. This led to the desired dyads, in which the luminescence is quenched, which indicates an intramolecular transfer of electrons or energy from the chlorin moiety to the acceptor moiety