Asymmetrische Diels-Alder-Reaktion zum Aufbau des AB-Ring-Bausteins und Synthese der ABEFG-Substruktur der Chinocycline

Although the Quinocyclines were isolated in the 1950´s, a synthesis of these structurally very interesting compounds has not been reported yet. One goal of this work was to develop an enantioselective access to the AB-ring building block of the Quinocyclines via an asymmetric catalyzed Diels-Alder reaction. Different dienophiles and catalysts have been tested but an intermolecular approach did not deliver the desired product. Therefore, an intramolecular approach with an ester dienophile has been investigated. With the CBS-catalyst it was possible to conduct an intramolecular enantioselective Diels-Alder reaction and to obtain the desired lactone. This [4+2]-cycloaddition product has been converted into the AB ring building block in three steps and in good yields. The second goal of this PhD thesis was to find a synthetic access to the unique EF-(pyrrolopyrrole)-ring substructure of the Quinocyclines. Different approaches have been investigated but all cyclization conditions to close the E-ring as last step failed. Based on these results, it was reasonable to introduce the E-ring in an already activated form and to close the F-ring as the last step. The activated E-Ring was introduced via the reaction of a lithiated iminoether with a lactone. The synthesis of the unique heterocycle structure was possible via an acid catalyzed cyclization with a tosylated amidine as reactant. The EF-ring heterocycle structure could be synthesized in a few steps in very good yields.