Stereochemical Studies of Monoterpene Compounds. III. Stereochemistry and Intramolecular Hydrogen Bonding of 1-Hydroxy-p-menth-3-en-2-one and Its Reduction Products

1-Hydroxy-p-menth-3-en-2-one (1) was prepared from α-terpinene by the t-butyl chromate oxidation, trans- and cis-p-Menth-3-ene-1,2-diols (4 and 5), 1-hydroxyisocarvomenthone (2), and 1-hydroxycarvomenthone (3) were also prepared from the compound 1 by lithium aluminum hydride reduction or by hydrogenation. The configurations of these compounds, 1–5, were identified on the basis of chemical evidence, and then the preferred conformation was determined by infrared spectroscopy on the basis of the conception of intramolecular hydrogen bonding. 1 and 2 were found to exist predominantly in the hydrogen-bonded conformations, 1a and 2a, respectively. With respect to 3, the existence of the conformational equilibrium, 3a\ightleftharpoons3b, was demonstrated by the presence of the free and bonded hydroxyl bands. Moreover, 4 and 5 were proved to take the preferred conformations of 4a and 5a respectively.