Cyclic Enolones

4-hydroxy-2-(or 5)ethyl-5-(or 2)-methyl-3(2H)fiiranone, 2-hydroxy-3-methyl-2-cyclo-penten-l-one, and/or 3-hydroxy-4,5-dimethyl-2(5H)-furanone have been shown to enhance sweemess in foods. Namiki and Nakamura [64] noted that a 5% sucrose solution plus 15 parts per million 2-hydroxy-3-methyl-2-cyclopenten-l-one is as sweet as a 20% sucrose solution. The major problem with these compounds is that they all carry an aroma that is typically caiamelic and seasoning-like and may not be desirable in the finished food product. 

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Thus, Tressl et al.219 characterised eight 2-(l-pyrrolidinyl)-2-cyclopentenones and 11 cyclopcnt(/ )azcpin-8( lf/)-oncs from proline-monosaccharide and proline-cyclic enolone systems. The compounds possessed bitter tastes, with the former exhibiting concomitant astringency. The bitter thresholds in water of Structure 33 and 34 were 50 and 10 ppm, respectively. 

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