688
S. Wakamura et al. / Tetrahedron Letters 42 (2001) 687–689
antenna of a male O. postica. Single EAG response was
observed at Kovat’s Index (KI) 2548 on a polar HP-
INNOWax column, and KI 2200 on a non-polar HP-1
column. The EAG-active compound was eluted gas-
chromatographically as an almost pure material with
5% ether in n-hexane from column chromatography
using 200 mg of Florisil. The EAG response coincided
well with an FID peak on the GC, which was predom-
inant in the fraction that represented approximately 17
ng per female abdominal tip.
The 1H NMR spectrum of accumulated EAG-active
component (ca. 8.5 mg from 500 females) (Fig. 2)
showed the presence of two epoxide protons [l 2.82
(1H, dt), 3.36 (1H, dd)], in which a coupling constant of
J=2.2 Hz confirmed the trans-epoxide structure. Four
vinyl proton signals [l 5.07 (1H, ddd), 5.36 (1H, dtt),
5.44 (1H, dtt), 5.66 (1H, dt)] and one doubly allylic
proton signal [l 2.96 (2H, dd)] were also observed. The
COSY spectrum confirmed the partial structure shown
in Fig. 2, and it guided us to only one possible struc-
ture, (6Z,9Z)-trans-11,12-epoxyhenicosa-6,9-diene. We
would like to propose to name this novel pheromone
‘posticlure’, in reference to the species name.
On a GC-MS analysis operated in an EI mode, the
EAG-active compound showed a mass spectrum (Fig.
1) similar to that of an unsaturated epoxide with a
distinct molecular ion at m/z 306 (M+, 21%, base m/z
155) and diagnostic ions at m/z 290 ([M−16]+, 3.2%)
and 288 ([M−18]+, 2.6%). The Kovat’s Indices (KI and
DKI) supported this interpretation. Micro-scale reduc-
tion of ca. 85 ng of the compound with diimide4 at
65°C for 1 h produced a single compound that gave a
mass spectrum typical for a mono-epoxide with a C21
straight chain; m/z 310 (M+, 7.3%, base m/z 83), 294
([M−16]+, 3.7%), 292 ([M−18]+, 0.9%), 183 (65%), and
169 (62%). The latter two ions indicated the epoxy ring
at the 10,11-position. The KI value (2467) on the polar
HP-INNOWax column was almost the same to that for
the trans-isomer (2468) of synthetic 10,11-epoxyheni-
cosane but different from that for the cis-isomer (2484).
Posticlure has stereoisomerism, that is, 11S,12S and
11R,12R configurations are possible. Both enantiomers
were stereoselectively synthesized using a Sharpless
epoxidation6 of trans-allylic alcohol derived from n-
decanal as a key reaction. The chiral epoxidation
employing (+)-diethyl tartrate produced an optically
active epoxy intermediate, which was converted to
(11S,12S)-posticlure with 59% e.e. (Fig. 3). The
antipode was prepared by employing (−)-diethyl tar-
trate. Preparative HPLC with a chiral column (Chiral-
pak AD) furnished optically pure samples, which
1
showed almost the same H NMR, GC-MS and GC
data as those of the EAG-active compound.
On this chiral HPLC, the natural pheromone showed
only one peak with the same retention time of synthetic
(11S,12S)-posticlure. Furthermore, males were cap-
tured by this (11S,12S)-isomer but not by (11R,12R)-
isomer in field experiments conducted in Okinawa in
June 2000. These results led to the assignment of the
11S,12S configuration to the natural sex pheromone of
O. postica females.
The EAG-active compound (ca. 85 ng) was partially
hydrogenated, in order to produce two mono-unsatu-
rated epoxides, by reaction with diimide at 55°C for 1
h. Since preparation of their dimethyl disulfide
(DMDS) derivatives5 was unsuccessful, this derivation
was accomplished after conversion of the epoxides to
secondary alcohols by LiAlH4 reduction. The products
were subjected to GC-MS analysis. Mass spectra of one
derivative showed a molecular ion at m/z 404 (22%)
and a diagnostic ion at m/z 173 (base), which indicated
the original double bond to be at 9-position, although
the other diagnostic ion at m/z 231 was not observed
probably because of the effect of the alcohol group.
Another DMDS derivative showed diagnostic ions at
m/z 273 (65%) and 131 (base), and indicated the double
bond at 6-position.
Many mono-epoxy compounds derived from (3Z,6Z,
9Z)-trienes and (6Z,9Z)-dienes, which are biosynthe-
sized from linolenic and linoleic acids, have been iden-
tified as sex pheromone components secreted by females
in several families of Lepidoptera.7,8 Males of many
more species were found to be attracted to the synthetic
epoxides.9 All those epoxides, however, have a cis
Figure 2. 1H NMR spectrum of natural posticlure (6Z,9Z)-trans-11,12-epoxyhenicosa-6,9-diene. Signals at l 3.38 and l 3.49 are
unrelated. These were not observed for synthetic posticlure.