Many previous workers were concerned with optical rotation of terpin-l-en-4-ol (terpinen-4-ol) isolated from the various essential oils to give several different optical values. The present report was carried out to check the optical purity of terpinen-4-ol by means of the integration for signal of 4R-and 4S-terpinen-4-ol in NMR spectra using a chiral shift reagent. From the results obtained, the value of [α]D²⁰+48.3°, which has been reported by NAVES was found to be a reliable one of 4S-(+)-terpinen-4-ol. Furthermore, some monoterpenes such as a-thujene, sabinene and sabinene hydrate are known to be very sensitive to acid and rearrange to terpinen-4-ol accompanied by partial racemization. Therefore, the low optical rotations given for terpinen-4-ol isolated from various essential oils by previous workers, seem to be caused by isomerization of terpenes which are labile to acid, during the isolation of this alcohol.
Terpinen-4-olの光学活性について(不斉シフト試薬を用いた核磁気共鳴による光学純度の測定)
