1730
G. V. M. Sharma et al.
LETTER
(11) Jungheim, L. N. Tetrahedron Lett. 1989, 30, 1889.
Table 2 20 Mol% ZrCl4–NaI (1:1) Catalyzed Deprotection of
(12) Yadav, J. S.; Subba Reddy, B. V.; Rao, C. V.; Chand, P. K.;
Prasad, A. R. Synlett 2002, 137.
(13) Nishizawa, M.; Yamamoto, H.; Seo, K.; Imagawa, H.;
Sugihara, T. Org. Lett. 2002, 4, 1947.
Prenyl Esters
Entry Starting material
Producta
Time Yield
(h)
(%)
(14) Sharma, G. V. M.; Mahalingam, A. K.; Lavanya, B.; Radha
Krishna, P. Tetrahedron Lett. 2000, 41, 10323.
1
1.5
88
O
O
(15) Sharma, G. V. M.; Ilangovan, A.; Mahalingam, A. K. J. Org.
Chem. 1998, 63, 9103.
O
OH
(16) Sharma, G. V. M.; Ilangovan, A. Synlett 1999, 1963.
(17) General Experimental Procedure: A stirred solution of the
prenyl ether/ester (1 mmol) in CH3CN (5 mL) was treated
with ZrCl4 (0.046 g, 0.2 mmol), NaI (0.03 g, 0.2 mmol) and
heated at reflux until complete consumption of the starting
material (TLC analysis). The solvent was removed under
reduced pressure, the residue dissolved in EtOAc (2 × 10
mL) and washed with H2O (2 × 10 mL) and brine (15 mL).
The organic layer was dried (Na2SO4) and evaporated under
reduced pressure to afford a crude product which on
purification by column chromatography (silica gel, 60–120,
EtOAc–hexane, 5:95) furnished alcohol/acid. Spectral data
for selected compounds: Compound 4: IR (neat): 1510,
1745, 2362, 2858, 2936 cm–1. 1H NMR (200 MHz, CDCl3):
d = 1.36–1.43 (m, 8 H), 1.68 (s, 3 H), 1.71 (s, 3 H), 2.10 (s,
3 H), 3.57 (t, J = 6.5 Hz, 2 H), 3.88 (d, J = 4.7 Hz, 2 H), 4.05
(t, J = 6.4 Hz, 2 H), 5.29–5.32 (t, J = 6.5 Hz, 1 H). MS (EI):
m/z (%) = 228 [M+]. Compound 8: IR (neat): 1376, 1510,
1620, 2932, 2986 cm–1. 1H NMR (200 MHz, CDCl3): d =
1.38 (s, 6 H), 1.42 (s, 3 H), 1.52 (s, 3 H), 1.68 (s, 3 H), 1.73
(s, 3 H), 3.87 (d, J = 4.6 Hz, 2 H), 4.03 (ddd, J = 4.0, 6.6 Hz,
1 H), 4.25 (ddd, J = 4.0, 4.5 Hz, 2 H), 4.32 (dd, J = 2.5, 5.1
Hz, 1 H), 4.39 (dd, J = 1.5, 8.0 Hz, 1 H), 4.61 (dd, J = 2.5,
8.0 Hz, 1 H), 5.28–5.31 (t, J = 6.5 Hz, 1 H) 5.52 (d, J = 5.1
Hz, 1 H). MS (EI): m/z (%) = 328 [M+]. Compound 6a:
IR(neat): 1260, 1510, 1590, 2920, 3515 cm–1. 1H NMR (200
MHz, CDCl3): d = 1.36–1.64 (m, 8 H), 3.39–3.42 (t, J = 5.6
Hz, 2 H), 3.59–3.63 (t, J = 5.4 Hz, 2 H), 3.92 (d, J = 6.2 Hz,
2 H), 5.18–5.25 (m, 2 H) 5.84–5.86 (m, 1 H). MS (EI): m/z
(%) = 158 [M+]. Compound 7a: IR (neat): 1226, 1523, 2862,
2958, 3506 cm–1. 1H NMR (200 MHz, CDCl3): d = 1.36–
1.61 (m, 8 H), 1.72 (d, J = 6.4 Hz, 3 H), 3.37 (t, J = 6.5 Hz,
2 H), 3.62 (t, J = 6.4 Hz, 2 H), 3.96 (d, J = 4.8 Hz, 2 H), 5.61
(m, 2 H). MS (EI): m/z (%) = 172 [M+]. Compound 15: IR
(neat): 1220, 1345, 1565, 1745, 2885, 2930 cm–1. 1H NMR
(200 MHz, CDCl3): d = 0.94–1.20 (m, 6 H), 1.77 (s, 3 H),
1.82 (s, 3 H), 2.18 (m, 1 H), 4.31 (m, 1 H), 4.61 (d, J = 6.6
Hz, 2 H), 5.14 (s, 2 H), 5.32 (t, J = 6.4 Hz, 1 H) 7.39 (m, 5
H). MS (EI): m/z (%) = 319 [M+], 252 [M+ – 69]. Compound
16: IR (neat): 1225, 1350, 1545, 1750, 2865, 2935 cm–1. 1H
NMR (200 MHz, CDCl3): d = 1.22 (s, 9 H), 1.77 (s, 3 H),
1.81 (s, 3 H), 2.47 (t, J = 4.8 Hz, 2 H), 3.38 (t, J = 4.6 Hz, 2
H), 4.56 (d, J = 6.4 Hz, 2 H), 5.10 (br s, 1 H) 5.31 (t, J = 6.4
Hz, 1 H). MS (EI): m/z (%) = 258 [M+ + 1].
11
Ph
11a
O
2
3
1
85
90
O
Ph
O
OH
OH
12a
12
1.5
O
O
O
N
N
13a
13
4
2
88
O
O
O
OH
N
N
Boc
Boc
14
15
14a
5
6
2
2
91
88
O
O
O
OH
NHCbz
NHCbz
15a
O
O
O
OH
BocHN
BocHN
16a
16
a All the products were identified by IR, 1H NMR, mass and TLC
analysis with authentic samples.
(5) Gigg, R.; Warren, C. D. J. Chem. Soc., Perkin Trans. 1 1968,
1903.
(6) Gent, P. A.; Gigg, R.; Conant, R. J. Chem. Soc., Perkin
Trans. 1 1973, 1858.
(7) (a) Hubert, A. J.; Reimlinger, H. Synthesis 1969, 97.
(b) Prosser, T. J. Am. Chem. Soc. 1961, 83, 1701. (c) Pricc,
C. C.; Snyder, W. H. J. Am. Chem. Soc. 1961, 83, 1773.
(8) Tsuritani, T.; Shinokubo, H.; Oshima, K. Tetrahedron Lett.
1999, 40, 8121.
(9) Suresh Babu, B.; Chinna Raju, B.; Srinivas, P. V.;
Madhusudana Rao, J. Tetrahedron Lett. 2003, 44, 2525.
(10) (a) Vatele, J. M. Synlett 2001, 1989. (b) Vatele, J. M.
Synlett 2002, 507. (c) Vatele, J. M. Tetrahedron 2002, 58,
5689.
Synlett 2003, No. 11, 1728–1730 ISSN 1234-567-89 © Thieme Stuttgart · New York