Zum Aufbau von Anhydro-tetracyclinen

The synthesis of 3-carboxymethyl-5-chloro-8,9-dimethoxy-10-methyl-l.2.3.4-tetrahydro-anthracene-l-one (XXIIIb), a key intermediate, in the synthesis of anhydrotetracyclines (IIa-c),is described. First the monomethylether XVIa of chloro-terranaphthoicacid was built up in a five-step reaction sequence starting with 3-methoxy-acetophenone. The tetrahydro-anthracenone-carbonicacid XXIIc, giving the desired compound XXIIIb in an Arndt-Eistert chain prolongation, was produced by ring closure of the condensation product of sodium-triethyl-carboxy-succinicacid with the bromide of dimethyl-chloro-terranaphthol (XIXb).