Invasive Stink Bugs and Related Species (Pentatomoidea)

686 Invasive Stink Bugs and Related Species (Pentatomoidea)

for the L-Selectride® reduction of 24, they were not able to reproduce the >95% endo-selectivity reported
by Tashiro and Mori (2008). Instead, reduction of ketone 24 with L-Selectride® (Figure 15.4) produced a
~77:23 mixture of the endo-alcohols (ent- 17 and ent-16) and the exo-alcohols 25 and 26 (Khrimian et al.
2011). The alcohols 25 and 26 were separated by silica gel chromatography and oxidized back to ketones
ent- 20 and ent- 19 with (diacetoxyiodo)benzene in the presence of (2,2,6,6-tetramethyl-1-piperidinyl)oxyl
(TEMPO) (Figure 15.4). Thus, the decreased selectivity in the L-Selectride® reduction of the diastereo-
meric mixture 24 fortuitously offered an expedient way of producing pure ketones ent- 20 and ent- 19 ,
obviating the need for the kinetic resolution step used by Tashiro and Mori (2008) (Figure 15.3).
The second asymmetric synthesis of the E. lewisi pheromone developed by Tashiro and Mori (2008)
was entirely diastereoselective and employed Hodgson’s intramolecular cyclopropanation (Hodgson
et al. 2007). Alcohol 27 , prepared from (R)-citronellal in two steps (Mori 2007), was treated with

CHO a CHO

COCI COCHN 2

HO AcO

HO

O

AcOO

OOO

CHO

OH

CO 2 Et

CO 2 Et

HO

(R)-citronellal 11 12

13 14

15

16 18

17

17

(^181917)
20 21 22
23 10 3.3% yield
b
cde
f g
i
j
m
kl
h, i
CO 2 Et
FIGURE 15.3 Synthesis of Eysarcoris lewisi pheromone 10 via Lipase PS-D diastereomeric resolution of bicyclic alcohols
16 and 17. a) CH 2 O, EtCO 2 H/Py; b) 1. LiAlH 4 , 2. MeC(OEt) 3 /EtCO 2 H; c) 1. KOH, 2. NaOEt, 3. (COCl) 2 ; d) CH 2 N 2 ; e) Cu/
CuSO 4 ; f) LiB(sec-Bu) 3 H; g) Lipase PS-D/CH 2 =CHOAc; h) KOH; i) TPAP/NMO; j) OsO 4 /NaIO 4 ; k) (o-MeC 6 H 4 O) 2 P(O)
CHMeCO 2 Et/NaH; l) (C 6 H 5 ) 3 PMeBr/n-BuLi; m) (i-Bu) 2 AlH.