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Treatment of mesityloxide with basic condensing agents resulted in formation of isoxylitones-A, B, C and D and isophorone. These compounds were purely isolated and assigned their structures from spectroscopic and chemical evidences. Isoxylitone-A and isoxylitone-B were conformers of 1-acetyl-2, 4, 6, 6-tetramethyl-1, 3-cyclohexadiene separat ed by the rotational barrier of acetyl group and interconversional barrier of cyclohexadiene ring. Isoxylitone-C was 4-isopropenyl-1, 5, 5-trimethyl-l-cyclohexen-3-one. Isoxylitone-D was 5, 5-dimethyl-3-(1-isobutenyl)-2-cyclohexen-1-one.

The relationship between structure and activity in bacteriostasis was compared to the relationship between structure and reactivity in metal chelate formation for various kojic acid analogs. The metal chelating property with Cu 2 + and Cd 2 + was closely related to the acid dissociation constant. Since structure-activity analyses showed that the neutral molecule is the active form, and since the pKA value as the electronic parameter is related to the activity only for the neutral molecule but not for the ionized form, it was postulated that metal chelate formation is not significant for manifestation of the bacteriostatic activity of this series of compounds. This postulation was confirmed in experiments under conditions in which the metal was depleted or excessive. The bacteriostatic activity of kojic acid analogs against such bacteria as S. aurells 209P, E. coli K-12 and Ps. fiuorescens was neither retarded nor enhanced.