80-71-7

Methyl cyclopentenolone occurs in beechwood tar and has a caramel-like (burnt sugar) odor. It has been identified as a flavor component in food. Crystals of the compound usually contain 1 mol of water. Synthetic routes of production are of limited importance in comparison with isolation from beechwood tar. Homologs of cyclotene such as 3-ethyl-2-hydroxy-2-cyclopenten-1-one, C₇H₁₀O₂, Mr 126.16, 2-hydroxy-3,4-dimethyl-2-cyclopenten-1-one, C₇H₁₀O₂, Mr 126.16, and 2-hydroxy-3,5-dimethyl-2-cyclopenten-1-one, C₇H₁₀O₂, Mr 126.16, are also used as flavor ingredients and have similar caramel-like properties.
Cyclotene and its homologs are frequently used in flavor compositions for its caramel note, for example, in beverages and in confectionery.

Off-white solid

Reported to be found during the dry distillation of wood and in the corresponding tar oil. It has also been identified in fenugreek (FenaroWs Handbook of Flavor Ingredients, 1975).

Methyl cyclopentenolone is used sparingly in perfume compositions often in combination with Coumarin or Coumarin derivatives. It is an excellent fortifier for such materials in Lavender fragrances, New Mown Hay, "tabac" type fragrances, spicy bases, etc. It falls naturally into Celery seed oil, Lovage, Fenugreek, Tonka, Liatris, Flouve, etc. It is, however, in flavor compositions that Methyl cyclopentenolone has found its truly extensive application.

By ketonic hydrolysis of the corresponding dicarboxylic ester (Arctander, 1969)

The acute oral LD₅₀ value in guinea-pigs was reported as 1.4 g/kg (Dow Chemical Company, 1953) and that in rats as > 1.85 g/kg, while the acute dermal LD₅₀ value in guinea-pigs exceeded 2 g/kg (Moreno, 1976). Methylcyclopentenolone was lethal to mice and rats at ip doses of 0.5-1 g/kg (Shugaev, 1959), and at a concentration of 7 χ 10^-4 m was toxic to cultured human leucocytes (Withers, 1966).