Complex Aliphatic and Alicyclic Extractives

These compounds will be described in the order of y- and J-lactones, cyanogenic glycosides, cyclohexane epoxides, cyclohexane diols, polycyclic compounds, and miscellaneous. 

Aliphatic lactones are important as aroma components in foods and flavors. Among them, y-lactones preferentially occur in plants and J-lactones are mainly found in animal products. The details on naturally-occurring lactones as aroma components are described in the literature (87). It is interesting that quercus lac-tone-a (1) and -b (2), two diastereomeric branched nonlactones, have been detected as ingredients in aged whiskeys (88, 134). These lactones were isolated from woods of some Quercus species which are widely used to make barrels for aging spirits such as whisky and brandy (72, 73). 

In 1972, Takeda et al. isolated six exocyclic a,-unsaturated y-lactones from the roots of Litsea japonica (138) (Ihble 6.2.1). These lactones, named litsenolide 

C2 (3-8), are three pairs of 2-alkylidene-3-hydroxy-4-methyl butanolides. The alkyl side chains are terminated with an ethyl (C-series), ethynyl (A-series), or ethynyl group (B-series). The two components in each pair are geometrical cis- and tra 5-isomers at the double bond conjugated with the lactone ring. It should be remembered that the carbon numbers of litsenolide Ci and C2 are two units larger than those of litsenolide Aj, A2, Bj and B2. 

A large group of y-lactones with a similar structural relationship to litsenolides were found in the trunk wood of Clinostemon mahuba (70, 71). Those are seven dihydromahuba lactones of series A (9-15) (Tkble 6.2.2), seven dihydroma-huba lactones of series B (16-22) (Thble 6.2.3), and eight mahuba lactones (23-30) (Ihble 6.2.4). 

---