Synthetic routes to 2-hydroxy-3-methylcyclopent-2-en-1-one and related cyclopentane-1,2-diones: a review (original) (raw)

1983, Journal of Agricultural and Food Chemistry

Synthetic routes to 2-hydroxy-3-methylcyclopent-2-en-lone are reviewed. This compound is produced during the thermal and base-catalyzed degradation of certain carbohydrates and is a product of the destructive distillation of wood. As a component of the roasted coffee aroma complex and of maple syrup flavor extract, it has important organoleptic properties. A crystalline compound, subsequently identified as 3methylcyclopentane-1,2-dione, was fiist isolated 70 years ago from pyroligneous acid, obtained by the dry distillation of beechwood (Meyerfeld, 1912; Rojahn and Ruhl, 1926). Many reports of the d a t i o n of this substance among the products of pyrolytic degradation of wood and carbohydrates have ensued [see referenm in Erickson and Collins (1965), Sat0 et al. (1967), and Fiddler et al. (1970)l. The compound was also produced when ground spruce wood, previously extracted with acetone, was digested with sodium hydroxide solution (Enkvist et al., 1954). In 1963,3-methylcyclopentane-1,2-dione was identified, along with some other cyclic l,Zdiketones, as a component of the roasted coffee aroma complex (Gianturco et al., 1963), and shortly afterward, it was found in maple syrup flavor extract (Filipic et al., 1965). The latter authors point out that during the conversion of maple sap to syrup by boiling, "the solution passes through an alkaline phase ... being at a maximum pH of about 9 for some time ...". Such conditions are clearly conducive to the formation of this cyclopentane-l,2-dione from certain carbohydrates [cf.