AROMA CHEMICALS : - IFEAT

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Figure 3 : Chiral delta-decalactones in nature 8 osmanthus oil cheddar cheese peach raspberry 100 80 60 40 20 0 20 40 60 80 100 S-isomer R-isomer Figure 4 : Chiral delta-lactones in cheddar cheese 3 C10 Figure 3. Chiral delta-lactones in cheddar cheese (Ref. 3) C11 C12 C13 C14 100 80 60 40 20 0 20 40 60 80 100 S-isomer R-isomer Chiral lactones are found also in insects. It has been proposed 6 that the pheromone responsible for some aspects of the social behavior of queens and workers of the Oriental hornet, Vespa orientalis, is delta-hexadecalactone which should be a chiral lactone, but the absolute configuration has not been defined as yet. Also, (S)-gamma-decalactone was found in the Japanese beetle, Osmoderma opicum 7 . Applications of chiral lactones An isomer of a lactone from nature can be used to create flavours and fragrances with a more ‘natural’ note. Also, there is the possibility of using other isomers from nature to make innovative, artificial flavours and fragrances. 132
Lactones as aroma chemicals Preparation of chiral lactones There are two approaches to obtain a chiral lactones, stereoselective synthesis and optical resolution of a racemic mixture obtained by asymmetric synthesis, as shown in Figure 5. Optical resolution is achieved by chromatographic or chemical or enzymatic methods. It is important to carefully consider the most appropriate method since each process has both good and bad points. Figure 5 : Preparation of chiral lactones How to access chiral lactones Chemical synthesis to make one isomer (1) stereoselective synthesis (2) asymmetric synthesis Chiral Lactones Optical resolution to separate one isomer (1) chromatography ex. LC with chiral stationary phase (2) chemical methods ex. diastereomer salt formation (3) enzymatic methods ex. using lipases In the case of the Soda Aromatic Company, optically enriched gamma-decalactone, gammaundecalactone, and gamma-dodecalactone are manufactured and have been launched on the market. Conclusions The progressive growth in availability of the range of chiral lactones is expected to result in both the reduced usage of racemic lactones, which have a less ‘natural’ organoleptic character, and to the creation of new types of flavours and fragrances. Sigeru Wada is a graduate of the Department of Applied Chemistry of Keio University in Tokyo and has 15 years experience in the synthesis of aroma chemicals. He joined the Soda Aromatic Company in 1985. During 1998-1999, he engaged in research on synthetic organic chemistry as an associated researcher at University of Pittsburgh in U.S.A.. 133
Page 2 and 3: Six-membered ring compounds are cal
Page 4 and 5: Gamma-C9 lactone appears in four no
Page 6 and 7: Table 4. Odour characteristics of g
Page 10: References 1. Youichi Yamamoto and

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