LACTONIZATION OF 3,5,7-TRIOXO-7-PHENYLHEPTANOIC ACID AND ITS 2-METHYL HOMOLOG

3,5,7-Trioxo-7-phenylheptanoic acid and its 2-methyl homolog were cyclized by treatment with acetic anhydride to form the corresponding δ-lactones (or 4-hydroxy-2-pyrones). An alternative synthesis of this structural type was achieved by treatment of the trisodium salt of 1-phenyl-1,3,5-hexanetrione with carbonyl sulfide. The reaction apparently involved the corresponding triketo thiolacid, but spontaneous cyclization occurred to give the lactone. The biogenetic significance of these reactions is discussed. © 1969.