Chiral HPLC resolution of monoepoxides derived from 6,9-dienes and its application to stereochemistry assignment of fruit-piercing noctuid pheromone
✍ Scribed by Masanobu Yamamoto; Yaeko Takeuchi; Yoshihisa Ohmasa; Hiroyuki Yamazawa; Tetsu Ando
- Publisher
- John Wiley and Sons
- Year
- 1999
- Tongue
- English
- Weight
- 105 KB
- Volume
- 13
- Category
- Article
- ISSN
- 0269-3879
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✦ Synopsis
The resolution of insect pheromonal cis-monoepoxy racemates derived from (Z,Z)-6,9-dienes was examined employing chiral HPLC columns, and the results showed that a normal-phase column (Chiralpak AD) was suitable for both 6,7-and 9,10epoxides with a C 17 -C 23 straight chain, as was a reversed-phase column (Chiralcel OJ-R) for the 6,7-epoxides. To determine the absolute configuration of each separated enantiomer applying a modified Mosher's method, the epoxy ring was opened by methanolysis, and the 1 H-NMR data of (S)-and (R)-MTPA esters of the methoxyalcohols produced were analyzed. Further, the hydrogenated product of each enantiomer was chromatographed on the OJ-R column referring to the corresponding authentic chiral compounds with a saturated chain, which were prepared by a Sharpless epoxidation reaction. These analyses showed that the levorotatory 6,7-and 9,10-epoxides with shorter t R s possess 6S,7R and 9R,10S configuration, respectively, and the dextrorotatory enantiomers with longer t R s possess the opposite configuration. Utilizing this chiral HPLC, it was revealed that an abdominal tip extract of the fruit-piercing moth, Oraesia excavata Butler (Lepidoptera: Noctuidae), included (9S,10R)-(Z)-9,10-epoxy-6henicosene as a main sex pheromone component. The synthetic 9,10-epoxide with this configuration, which was separated from the racemate, exhibited stronger activity in electrophysiological and field tests against male moths than the enantiomer.