Synthese neuer Ringbausteine für Chlorophyll a und andere Chlorine aus Hagemanns-Ester

Total synthesis of naturally occurring products has been the most fecund field for developing new methodologies in Organic Chemistry. Interest in synthesis of chlorins has lead into investigation of new methodologies towards these natural products, including studies directed to total synthesis of chlorophyll a. With this objective we have developed a flexible synthetic concept for the synthesis of chlorins, which is based on the connection of four heterocyclic rings, leading to chlorin macrotetracycles. This work focused on the synthesis of new ring D building blocks from Hagemann's ester, which is an ease accessible starting material. Constitutional and sterochemical requirements have imposed the application of regio- and enantioselective protocols for obtaining appropriate intermediates to be transformed into the desired ring D units. The scope of enantioselective reductions of ketones as well as kinetic enzymatic resolution of alcohols derived from Hagemann's ester type was explored.