Page 11 - Volume 3, Issue 2, July 2010

© Benaki Phytopathological Institute
Mosquito oviposition aggregation pheromone 41
esis as the key step. The secondary hydrox-
yl group was epimerized under Mitsunobu
conditions furnishing alcohol 22 . Acid hydro-
lysis led to the corresponding lactol, which
was subjected to oxidation to afford the final
product (7 steps from 19, 30.7% yield).
Kotsuki reported an enantiospecific syn-
thesis of mosquito pheromone originating
from L-tartrate as chiral source (Kotsuki et
al. , 1990). The synthesis employed an effi-
cient carbon-carbon bond forming reaction
of triflate with copper(I)-catalyzed Grignard
reagent (Figure 11).
The one-pot procedure from tosyl-triflate
24 through initial reaction first with 3-bute-
nylmagnesium bromide/CuBr and further
alkylation with lithium di- n-nonylcuprate
provided intermediate 25 in 58% overall
yield from 24. Conversion of 25 to hydroxy
δ- lactone 26 was accomplished by one-pot
ozonolysis, dimethyl sulfide reduction, Ag 2O
oxidation, acidification to make free hydroxy
acid and finally lactonization. Acetylation of
hydroxy lactone with simultaneous inver-
sion of configuration was accomplished by
applying Ikegami’s procedure (Torisawa et
al., 1984) (10 steps, 28.4% yield).
From D -isoascorbic acid, a general ap-
proach to (–)-(5R,6S )-6-acetoxy-5-hexade-
canolide, viaa four carbonatomsbis-epoxide
equivalent was reported by Gravier-Pelletier
(Gravier-Pelletier et al., 1994) (Figure 12). Al-
kylation resulted in the opening of the free
epoxide allowing the introduction of the
carbon chain. Nucleophilic opening of the
second epoxide, being masked into the pro-
tected glycol, by ethylpropiolate, led after
hydrogenation of the triple bond and lac-
tonization to the optically pure pheromone
1a (8 steps, 22% yield).
Figure 10
Figure 11