G. V. M. Sharma, K. Veera Babu / Tetrahedron: Asymmetry 18 (2007) 2175–2184
2179
2H, –CH2C6H4), 7.23–7.31 (m, 5H, C6H5); IR (neat): 3422,
3063, 2978, 2929, 2870, 1605, 1453 cmꢀ1; FABMS: 231
(M+Na)+, 226 (M+NH4)+.
200 MHz): d 0.05 (s, 6H, 2 · –CH3), 0.90 (s, 9H, 3 ·
–CH3), 1.08 (d, 3H, J = 5.9 Hz, –CH3), 1.99 (br s, 1H,
–OH), 3.62–3.74 (m, 1H, –CH), 3.94–3.99 (m, 1H, –CH),
5.16 (s, 1H, olefinic), 5.21 (dd, 1H, J = 0.85, 5.9 Hz, ole-
finic), 5.74–5.88 (m, 1H, olefinic); 13C NMR (75 MHz,
CDCl3): d ꢀ4.87, ꢀ4.26, 17.56, 25.94, 70.84, 78.26,
116.95, 137.11; IR (neat): 3446, 2923, 2853, 1643,
1102 cmꢀ1; HRMS m/z: [M+Na]+ calcd for C11H24O2Na-
Si, 239.1443; found, 239.1454.
4.1.2. (2R,3R)-2-[(1S)-1-(Benzyloxy)ethyl]-3-(chloromethyl)-
oxirane 15. To a stirred solution of 14 (2.2 g, 11.23 mmol)
in CCl4 (20 mL), Ph3P (3.24 g, 12.34 mmol) and NaHCO3
(cat.) were added and then heated at reflux for 3 h. The
reaction mixture was evaporated and the residue purified
by column chromatography (Silica gel, EtOAc/hexane,
5:95) to afford 15 (2.2 g, 88%) as a yellow syrup.
[a]D = ꢀ20.7 (c 0.38, CHCl3); 1H NMR (CDCl3,
300 MHz): d 1.28 (d, 3H, J = 6.4 Hz, –CH3), 2.8 (dd, 1H,
J = 1.9, 5.3 Hz, –CH), 3.13 (ddd, 1H, J = 1.9, 5.7,
11.33 Hz, –CH), 3.33–3.42 (m, 2H, –CH2), 3.54–3.60 (m,
1H, –CH), 4.57 (d, 2H, J = 7.6 Hz, –CH2C6H4), 7.26–
7.31 (m, 5H, C6H5); IR (neat): 3063, 2926, 2864, 1606,
1451 cmꢀ1; ESIMS: 226 (M)+.
4.1.6. Ethyl (4R,5S)-5-(benzyloxy)-4-[1-(tert-butyl)-1,1-di-
methylsilyl]oxy-2-hexenoate 18a. A solution of 17 (1.4 g,
4.5 mmol) in CH2Cl2 (15 mL) was cooled to ꢀ78 ꢁC and
subjected to ozonolysis for 15 min and quenched with
(CH3)2S (2 mL). The solvent was evaporated, and the resi-
due dissolved in benzene (30 mL) and treated with (eth-
oxycarbonylmethylene)triphenyl phosphorane (1.36 g,
5.4 mmol) at reflux. After 2 h, solvent was evaporated
and the residue purified by column chromatography (Silica
gel, EtOAc/hexane, 5:95) to furnish 18a (E:Z/4:1) (1.32 g,
77%) as a yellow syrup. E-Isomer: [a]D = ꢀ12.25 (c 0.55,
CHCl3); 1H NMR (CDCl3, 200 MHz): d 0.05 (s, 6H,
2 · –CH3), 0.94 (s, 9H, 3 · –CH3), 1.15 (d, 3H,
J = 6.3 Hz, –CH3), 1.32 (t, 3H, J = 7.3 Hz, –CH3), 3.43–
3.51 (m, 1H, –CH), 4.20 (q, 2H, J = 6.6 Hz, –CH2), 4.34
(br s, 1H, –CH), 4.53 (q, 2H, J = 12.1 Hz, –CH2C6H5),
6.01 (d, 1H, J = 15.7 Hz, olefinic), 6.93 (dd, 1H, J = 4.4,
15.7 Hz, olefinic), 7.26–7.32 (m, 5H, C6H5); IR (neat):
3031, 2955, 2858, 1721, 1658, 1465 cmꢀ1; ESIMS: 396
(M+NH4)+, 378 (M)+. Z-Isomer: [a]D = ꢀ8.7 (c 0.4,
CHCl3); 1H NMR (CDCl3, 300 MHz): d 0.07 (s, 6H,
2 · –CH3), 0.89 (s, 9H, 3 · –CH3), 1.10 (d, 3H,
J = 6.4 Hz, –CH3), 1.29 (t, 3H, J = 7.2 Hz, –CH3), 3.48–
3.54 (m, 1H, –CH), 4.16 (q, 2H, J = 7.2 Hz, –CH2), 4.64
(q, 2H, J = 12.5 Hz, –CH2C6H5), 5.51 (m, 1H, –CH), 5.74
(d, 1H, J = 10.9 Hz, olefinic), 6.16 (dd, 1H, J = 8.3,
11.7 Hz, olefinic), 7.20–7.33 (m, 5H, C6H5); IR (neat):
4.1.3. (3R,4S)-4-(Benzyloxy)-1-penten-3-ol 16. To a sus-
pension of Na (0.45 g, 19.6 mmol) in dry ether (10 mL), a
solution of 15 (2.1 g, 9.8 mmol) in dry ether (10 mL) was
added at 0 ꢁC and stirred at room temperature for 12 h.
The reaction mixture was quenched with methanol
(5 mL), evaporated and the residue purified by column
chromatography (Silica gel, EtOAc/hexane, 15:85) to fur-
nish 16 (1.49 g, 84%) as a yellow syrup. [a]D = +14.9 (c
1
0.7, CHCl3); H NMR (CDCl3, 300 MHz): d 1.12 (d, 3H,
J = 6.1 Hz, –CH3), 2.07 (br s, 1H, –OH), 3.53–3.59 (m,
1H, –CH), 4.18–4.21 (m, 1H, –CH), 4.56 (q, 2H,
J = 11.7 Hz, –CH2C6H4), 5.16–5.33 (m, 2H, olefinic),
5.76–5.87 (m, 1H, olefinic), 7.28–7.31 (m, 5H, C6H5); IR
(neat): 3444, 3065, 2927, 1661, 1452 cmꢀ1; ESIMS: 193
(M+H)+.
4.1.4.
((1R)-1-[(1S)-1-(Benzyloxy)ethyl]-2-propenyloxy)-
(tert-butyl)dimethylsilane 17. To a stirred solution of 16
(0.9 g, 4.7 mmol) in CH2Cl2 (10 mL), imidazole (0.8 g,
11.72 mmol) and TBDMS–Cl (0.78 g, 5.2 mmol) were
added at 0 ꢁC and stirred at room temperature for 3 h. Sol-
vent was evaporated and the residue purified by column
chromatography (Silica gel, EtOAc/hexane, 5:95) to give
17 (1.2 g, 84%) as a yellow syrup. [a]D = +59.2 (c 0.15,
CHCl3); 1H NMR (CDCl3, 300 MHz): d 0.02 (s, 6H,
2 · –CH3), 0.90 (s, 9H, 3 · –CH3), 1.14 (d, 3H,
J = 6.4 Hz, –CH3), 3.37–3.43 (m, 1H, –CH), 4.10–4.13
(m, 1H, –CH), 4.55 (s, 2H, –CH2C6H4), 5.10–5.27 (m,
2H, olefinic), 5.80–5.91 (m, 1H, olefinic), 7.27–7.30 (m,
3033, 2932, 2889, 1725, 1664 cmꢀ1
(M+NH4)+, 378 (M)+.
;
ESIMS: 396
4.1.7. Ethyl (4R,5S)-5-(Benzyloxy)-4-[1-(tert-butyl)-1,1-
dimethylsilyl]oxyhexanoate 19. To a solution of 18a
(1.3 g, 3.44 mmol) in ethyl acetate (5 mL), PtO2 (10 mg)
was added and stirred at room temperature for 3 h under
a hydrogen atmosphere. The reaction mixture was filtered,
evaporated and the residue purified by column chromato-
graphy (Silica gel, EtOAc/hexane, 4:96) to afford 19 (1.2 g,
1
92%) as a yellow syrup. [a]D = ꢀ21.1 (c 0.25, CHCl3); H
5H, C6H5); IR (neat): 3067, 2931, 2857, 1456 cmꢀ1
ESIMS: 329 (M+Na)+, 307 (M+H)+.
;
NMR (CDCl3, 300 MHz): d 0.10 (s, 6H, 2 · –CH3), 0.95
(s, 9H, 3 · –CH3), 1.19 (d, 3H, J = 6.3 Hz, –CH3), 1.31
(t, 3H, J = 7.1 Hz, –CH3), 1.76–1.95 (m, 2H, –CH2), 2.37
(t, 2H, J = 7.8 Hz, –CH2), 3.37–3.53 (m, 1H, –CH), 3.72–
3.81 (m, 1H, –CH), 4.17 (q, 2H, J = 7.1 Hz, –CH3), 4.57
(d, 2H, J = 4.7 Hz, –CH2C6H5), 7.31–7.35 (m, 5H,
C6H5); IR (neat) 3031, 2955, 2931, 2858, 1735,
1463 cmꢀ1; HRMS m/z: [M+Na]+ calcd for C21H36O4Na-
Si, 403.2280; found, 403.2279.
4.1.5. (2S,3R)-3-[1-(tert-Butyl)-1,1-dimethylsilyl]oxy-4-pen-
ten-2-ol 6. To a solution of 17 (2.0 g, 6.6 mmol) in aq
CH2Cl2 (40 mL; 19:1), DDQ (5.94 g, 26.2 mmol) was
added and stirred at reflux for 3 h after which it was
quenched with saturated NaHCO3 (10 mL) solution, fil-
tered and washed with CH2Cl2 (20 mL). The filtrate was
washed with water (10 mL), brine (10 mL), dried over
Na2SO4, evaporated under reduced pressure and the resi-
due purified by column chromatography (Silica gel,
EtOAc/hexane, 15:85) to furnish 6 (1.22 g, 86%) as a syrup.
[a]D = +51.7 (c 0.25, CHCl3); 1H NMR (CDCl3,
4.1.8. (4R,5S)-5-(Benzyloxy)-4-[1-(tert-butyl)-1,1-dimethyl-
silyl]oxyhexanoic acid 5. To a solution of 19 (1.2 g,
3.14 mmol) in THF/MeOH/water (3:1:1, 15 mL), LiOH
(0.226 g, 9.4 mmol) was added and stirred at room