Studies on Terramycin and Its Related Compounds. V

Intramolecular Acylation with Polyphosphoric Acid

Abstract

In connection with the synthesis of terracinoic acid, intramolecular cyclization of β-phenylpropionic acid and its esters, indicated by the general formula C₆H₅-CRR′-CH₂-COOR″ (R=R′=R″=H or CH₃), with polyphosphoric acid was examined. The yield was found to be no different from that by the Friedel-Crafts method. The methoxyl group was found not to be affected by polyphosphoric acid but did affect yield of indanone, especially in the case of ortho-substituted, with which the formation of indanone was not found (Table I). Polyphosphoric acid was found to be a suitable condensation agent since it did not affect the methoxyl group and the ester can be used per se for the cyclization reaction. However, the separation of the ester and the indanone was difficult when the boiling points of the two were similar, as in the present case.