S. Sankaranarayanan et al. / Tetrahedron: Asymmetry 13 (2002) 1373–1378
1377
propyl ether (25 ml) was stirred at room temperature
until 28% conversion (cf. GLC). It was filtered, the
solid residue washed with ether and the extract concen-
trated in vacuo to give a mixture. From this, the
individual components viz. (3S,7R)-7 (0.313 g, 22%)
and (3R,7R)-6 (0.87 g, 72.5%) were isolated by column
chromatography (silica gel, 0–15% EtOAc/hexane).
(3R,7R)-6: [h]2D2=+2.5 (c 1.02, CHCl3). Its spectral
properties were similar to those of (3RS,7R)-6.
(3S,7R)-7: [h]2D2=−5.2 (c 0.88, CHCl3); IR: 1730, 1480,
1380, 1230 cm−1; 1H NMR: l 0.88 (d, J=6 Hz, 6H), 1.3
(br. s, 12H), 1.58 (s, 3H), 1.62 (s, 3H), 2.1–2.3 (m
containing a s at l 2.14, 5H), 4.12 (t, J=6 Hz, 2H),
5.06 (t, J=7 Hz, 1H). Anal. calcd for C17H32O2: C,
76.06; H, 12.02. Found: C, 76.18; H, 11.86%.
The above mesylate in ether (10 ml) was added drop-
wise to a stirred suspension of LiAlH4 (0.197 g, 5.2
mmol) in ether (30 ml) and the mixture gently heated
under reflux for 6 h. Excess hydride was decomposed
by dropwise addition of aqueous saturated Na2SO4
solution, the supernatant decanted from the crystalline
mass and the solid washed with ether. The combined
organic extract was carefully concentrated to obtain
pure 8 after column chromatography (silica gel, pen-
tane). Yield: 0.37 g (66%); [h]2D2=−6.2 (c 0.84, CHCl3);
1
IR: 1480, 1380 cm−1; H NMR: l 0.8–1.0 (m, 9H), 1.34
(br. s, 12H), 1.58 (s, 3H), 1.62 (s, 3H), 2.1–2.2 (m, 2H),
5.06 (t, J=7 Hz, 1H). Anal. calcd for C15H30: C, 85.63;
H, 14.37. Found: C, 85.79; H, 14.19%.
3.11. (3S,7R)-3,7,11-Trimethyl-10-dodecen-1-ol, 6
3.15. (4R,8R)-4,8-Dimethyldecanal, I
A solution of (3S,7R)-7 (1.2 g, 4.48 mmol) in 2N
alcoholic KOH (25 ml) was stirred for 18 h. Most of
the solvent was removed in vacuo, the residue taken in
ether and the ethereal extract washed with water and
brine. After drying, the organic extract was concen-
trated in vacuo and the residue was chromatographed
(silica gel, 0–15% EtOAc/hexane) to furnish (3S,7R)-6.
Yield: 1.0 g (ꢀquantitative); [h]2D2=−4.6 (c 0.98,
CHCl3).
To a cooled (0°C) and stirred solution of 8 (0.3 g, 1.43
mmol) in CH2Cl2 (15 ml) was added m-CPBA (0.538 g,
1.72 mmol) in portions. After stirring for 3 h at the
same temperature, the mixture was kept at 0°C for 18
h. Then the mixture was filtered to remove the solid
precipitate and the extract successively washed with
aqueous NaHSO3, water, aqueous NaHCO3 (10%),
water, brine and dried. Concentration of the extract
gave the crude epoxide 9 which was directly used for
1
the next step. IR: 1480, 1380, 1230 cm−1; H NMR: l
3.12. (3S,7S)-3,7,11-Trimethyl-10-dodecenyl acetate, 7
0.88 (d, J=6 Hz, 6H), 0.93 (d, J=6 Hz, 3H), 1.3 (br. s,
14H), 1.54 (s, 3H), 1.58 (s, 3H), 3.28 (t, J=5.5 Hz, 1H).
Esterification of (3RS,7S)-6 (1.08 g, 4.78 mmol), vinyl
acetate (0.62 g, 7.2 mmol) and CRL (0.2 g) in diiso-
propyl ether (20 ml) was carried out until 30% conver-
sion (cf. GLC). Usual isolation as above gave (3S,7S)-7
(0.320 g, 25%) and (3R,7S)-6 (0.702 g, 65%). (3R,7S)-6:
[h]D22=+1.8 (c 0.88, CHCl3); (3S,7S)-7: [h]2D2=−5.9 (c
1.22, CHCl3).
To a stirred and cooled (0°C) solution of 9 in THF–
H2O (20 ml, 2:1) was added H5IO6 (0.498 g, 2.18 mmol)
in portions. After stirring for 1 h, the mixture was
extracted with ether, the ether layer washed with
aqueous NaHSO3, water and brine and finally dried.
Removal of solvent followed by column chromatogra-
phy over silica gel (0–10% ether/hexane) furnished the
pheromone I. Yield: 0.132 g (50%); [h]2D2=−7.2 (c 1.4,
CHCl3) (lit.7b [h]D22=−7.4 (c 2.04, CHCl3)); IR: 2720,
3.13. (3R,7S)-3,7,11-Trimethyl-10-dodecen-1-ol, 6
1
Esterification of the above (3R,7S)-6 (1.0 g, 4.42
mmol), vinyl acetate (0.57 g, 6.6 mmol) and CRL (0.2
g) in diisopropyl ether (20 ml) was carried out until
40% conversion (cf. GLC). Usual isolation as above
gave (3R,7S)-6 (0.340 g, 34%). [h]2D2=+3.3 (c 1.12,
CHCl3).
1720 cm−1; H NMR: l 0.8–1.0 (m, 9H), 1.1–1.5 (m,
12H), 2.3 (t, J=6 Hz, 2H), 9.8 (t, J=1.5 Hz, 1H).
3.16. (3R,7S)-3,7,11-Trimethyl-10-dodecenal, 10
To a stirred solution of (3R,7S)-6 (0.591 g, 2.62 mmol)
in CH2Cl2 (30 ml) was added PCC (0.850 g, 3.9 mmol)
in one lot. After stirring for 3 h, when the reaction was
complete (cf. TLC), the mixture was diluted with ether
(30 ml) and the supernatant passed through a pad (2¦)
of silica gel. Concentration of the extract in vacuo
furnished pure 10. Yield: 0.498 g (85%). [h]2D2=+3.9 (c
1.4, CHCl3); IR: 2720, 1720, 1480, 1380 cm−1; 1H
NMR: l 0.88 (d, J=6 Hz, 6H), 1.3–1.8 (m containing
two s at l 1.55 and 1.60, 16H), 2.1–2.3 (m, 4H), 5.06 (t,
J=7 Hz, 1H), 9.78 (t, J=1.5 Hz, 1H).
3.14. (6R,10R)-2,6,10-Trimethyl-2-dodecene, 8
To a cooled (0°C) and stirred mixture of (3S,7R)-6 (0.6
g, 2.65 mmol) and triethylamine (0.5 ml, 3.4 mmol) in
CH2Cl2 (25 ml) was added mesyl chloride (0.232 ml, 3.0
mmol) in drops. After 1 h, when the reaction was
complete, the mixture was poured in ice cooled water
containing NH4Cl (10%). The organic layer was sepa-
rated, the aqueous portion extracted with CHCl3, the
total organic extract washed with aqueous saturated
NH4Cl solution and dried. The solvent was removed to
get the corresponding mesylate which was directly used
3.17. Ethyl (5R,9S)-5,9,13-Trimethyl-2(E),10-tetra-
decadienoate, 11
1
for the next step. IR: 1640, 1480, 1380, 1180 cm−1; H
NMR: l 0.9 (d, J=6 Hz, 6H), 1.29 (br. s, 12H), 1.54 (s,
3H), 1.60 (s, 3H), 2.1–2.2 (m, 2H), 2.9 (s, 3H), 4.31 (t,
J=6 Hz, 2H), 5.06 (t, J=7 Hz, 1H).
As described earlier, Wittig–Horner reaction between
triethyl phosphonoacetate (0.695 g, 3.10 mmol) and 10
(0.498 g, 2.22 mmol) using NaH (0.139 g, 2.90 mmol,