About the "physiological size" of fluorine substituents: comparison of sensorially active compounds with fluorine and methyl substituted analogs

The taste of four fluoro substituted derivs. is almost indistinguishable from that of the parent compd. 4-(4-hydroxyphenyl)butan-2-one, the main flavor component of raspberries. The same holds for the comparison between the corresponding acetate, another raspberry ingredient, and its 1-fluoro analog. In contrast, Me substituents profoundly alter the organoleptic properties. The prepn. of the fluorinated derivs, involved the three principal options existing for the incorporation of fluorine into org. mol. skeletons: the use of prefabricates (i.e., of fluoroarom. building blocks), the formation of chlorofluorocarbene cycloadducts followed by their solvolytic ring opening and the addn. of fluoride to olefinic double bonds. [on SciFinder (R)]