Synthese von (+)- und (-)-Homononactinsäure. Totalsynthese des Makrotetrolids Tetranactin durch "Reverse Coupe du Roi ". Strukturvorschlag für Isodinactin

The syntheses of (-)- and (+)-homononactic acid were achieved in 4 steps and 6 steps, respectively, starting with the reaction of 2-lithio-5-vinylfuran and (S)-(-)-ethyloxirane. The vinyl group was transformed to the branched aldehyde by a regiospecific oxo reaction. Oxidation to the carboxylic acid, esterification, and hydrogenation of the furan ring formed four diastereomers of methyl homononactate. Two of these isomers were used directly for the synthesis of tetranactin, the others could be recycled by epimerisation and separation. The achiral macrolide antibiotic was constructed from two molecules of chiral (+)-homononactyl-(-)-homononactic acid by ester formation via the acid chloride and subsequent lactonisation via the (active) thiocarboxylic S-(3-cyano-4,6-dimethyl-2-pyridinyl) ester. The structure of isodinactin was corrected by comparing the optical rotations of methyl nonactate and methyl homononactate from natural origin with those of the optically pure synthetic compounds.