RESUMO
Terpenoids, which have many biological activities and have occurred widely in nature, can be artificially synthesized. However, regioselective oxidation of terpenoids is difficult by chemical methods. In this study, (+)- and (-)-citronellene were biotransformed with Spodoptera litura to define the mechanism of metabolism of citronellene and gain a new natural terpenoid. (+)-Citronellene was converted to (2S,3S)-3,7-dimethyl-6-octene-1,2-diol and (2R,3S)-3,7-dimethyl-6-octene-1,2-diol (89.7%), (3S,6S)-(-)-3,7-dimethyl-1-octene-6,7-diol (3.8%), (3S)-(6E)-(+)-3,7-dimethyl-1,6-octadien-8-ol (4.2%), and (3S)-(6E)-(+)-3,7-dimethyl-1,6-octadien-8-oic acid (2.3%). In contrast, (-)-citronellene was converted to (2R,3R)-3,7-dimethyl-6-octene-1,2-diol and (2S,3R)-3,7-dimethyl-6-octene-1,2-diol (56.3%), (+)-iridan-7,8-diol (3.5%), and (3R)-(6E)-(-)-3,7-dimethyl-1,6-octadien-8-oic acid (40.2%). The main metabolic pathway of (+)- and (-)-citronellene by larvae of S. litura was oxidized at the terminal double bond and trans-allylic methyl position. Particularly on (+)-citronellene, the regioselective reaction was shown. On the oxidation of C-6, C-7, and C-8 positions, four new compounds (3S,6S)-(-)-3,7-dimethyl-1-octene-6,7-diol, (3S)-(6E)-(+)-3,7-dimethyl-1,6-octadien-8-oic acid, (+)-iridan-7,8-diol, and (3R)-(6E)-(-)-3,7-dimethyl-1,6-octadien-8-oic acid were produced in regioselective oxidation. It noted that stereoselective oxidation occurred between the enantiomers. The C-6 position was oxidized on the (+)-(3S) form, whereas cyclized and the C-7 position were oxidized on the (-)-(3R) form.
