308 
PACIFIC SCIENCE, Vol. XXII, July 1968 
H 
H 3 C^O^O 
A max 205 mp 
(log £ = 4.03) 
9 CH 3 
H 3 c^0'^0 
A max 235 mp 
(log £ = 4.10) 
b 
Fig. 14. UV absorption of parasorbic acid (a) 
and of dihydro-methyltriacetic acid lactone (DM- 
MTL) (b). 
h 3 c^ 0-^0 
A max 205 rrijj 
(log £ = A. 03) 
H 
I 
h 3 c' c, *c-h 
J s-trans 
HCT^O 
A max 205.5 mn 
(log £ =4.13) 
Ca 
0CH 3 s-trans 
,0. 
CO- 
A max 235 m(j 
(log £ = 4.19) 
och 3 
ch 2 c-h 
ch 2 -ch 2 -ch 2 
HO o 
A max 234 nrifj 
( log E = 4.23) 
c 
d 
Fig. 15. UV absorption of parasorbic acid (a), 
cis crotonic acid ( b ), dihydromethysticin (c), and 
tetrahydromethysticinic acid (d) . 
a methyl group, we obtain two groups of natural 
kawa pyrones, the kawain and the dihydro- 
kawain types. In the naturally occurring dihydro- 
kawains, the two part chromophores — the ben- 
zene ring with its variable oxygen functions and 
the DH-MTL moiety — are separated. The spec- 
tra of these substances may therefore be in- 
terpreted as addition spectra of the two partial 
chromophores. This is graphically demon- 
strated in Figure 16 for the spectrum of tetrahy- 
droyangonin (p-cresol methyl ether -J- DH- 
MTL). In contrast to the compounds of the 
dihydrokawain type we may consider that in the 
naturally occurring kawains the two part chromo- 
phores (styryl and DH-MTL moiety) have a 
mutual effect on each other. In spite of this it is 
surprising that the spectra of this class of com- 
pounds are also additive from given partial 
chromophores, that is, they may be predicted by 
calculation from the corresponding cinnamyl 
alcohols and the DH-MTL. On the other hand, 
measured and calculated spectra do not agree 
when, instead of the cinnamyl alcohols, the 
aromatic chromophore is represented by other 
styryl derivatives, such as allyphenols of the 
anethole type. 
A second large group of kawa lactones are 
not derived from DH-MTL but from MTL 
itself. The two parent substances differ from 
each other by a double bond in the lactone ring. 
The enone system is extended to a dienone 
