Hinokiic acid reacts with hydrogen halide to produce oily addition products (II) and (III). Absorbing 1 mole of bromine, the acid produces a dibromohinokiic acid (IV), C
14H
21Br
2COOH, which partly melts at 50-55°, and then at 110-113°, and seems to be a mixture of isomers. By catalytic hydrogenation with PdO, hinokiic acid absorbs 2 moles of hydrogen to yield a dihydroisohinokiic acid (V), m. p. 154°, [α]
D13=+77.13°. Reduction with PtO
2-catalyst produces tetrahydrohinokiic acid, m. p. 143-144°, [α]
D20=+61.29°, which is also obtained by the further hydrogenation of the dihydro compound using PtO
2 as a catalyst. From these result, it is assumed that hinokiic acid possesses a tricyclic skeleton and a double bond. Dihydroisohinokiic acid is formed primarily by the saturation of the double bond and the tetrahydro acid seems to be a dicyclic compound formed by the secondary reduction accompanied by the fission of the bridged ring, such as the cyclopropane type. As hinokiic acid is reduced by Bouveault-Blanc's reaction to produce dihydrohinokiic acid (VII), m. p. 92-93°, [α]
D13=-22.96°, which is an isomer of the dihydroisohinokiic acid, the double bond is found to be situated on the α, β-position to the carboxyl group. The ester of hinokiic acid is also reduced by Bouveault-Blanc's reaction to hinokilol (VIII), C
14H
21CH
2OH, b. p.
4.5 142-143°, [α]
D22=-14.59°, which is oxidized to hinokiic acid by CrO
3 via hinokilal (IX), C
14H
21CHO, and also to dihydroisohinokilol (X), C
14H
23CH
2OH, b. p.
4 130-132°, [α]
D22=+7.69°, by the hydrogenation with PdO catalyst.
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