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J7,7 = 10.1 Hz, J7,6 = 5.7 Hz, 1H, H-7), 3.76 (dd, J7,7 = 10.1 Hz,
J7,6 = 3.0 Hz, 1H, H-7), 4.17 (q, J = 7.1 Hz, 2H, CH2), 4.24 (dd,
J5,6 = 8.6 Hz, J5,4 = 6.3 Hz, H-5), 5.75 (ddd, J4,3 = 8.6 Hz, J4,5 = 6.3 Hz,
J4,2 = 1.3 Hz, 1H, H-4), 5.96 (dd, J2,3 = 11.7 Hz, J2,4 = 1.3 Hz, 1H, H-
2), 6.27 (dd, J3,2 = 11.7 Hz, J3,4 = 8.6 Hz, 1H, H-3). 13C NMR (CDCl3,
100 MHz): d ꢁ5.4 (2 ꢄ CH3), 14.1 (CH3), 18.3 (C), 25.4 (CH3), 25.9
(3 ꢄ CH3), 27.9 (CH3), 60.5 (CH2), 64.3 (CH2), 70.0 (CH), 73.8 (CH),
78.0 (CH), 109.1 (C), 122.2 (CH), 144.5 (CH), 166.1 (C@O). Anal.
Calcd for C18H34O6Si: C, 57.72; H, 9.15. Found: C, 57.85; H, 9.03.
(dd, J7,7 = 10.9 Hz, J7,6 = 3.3 Hz, H-7), 3.78 (dt, J6,5 = 7.1 Hz,
J6,7 = 3.5 Hz, J6,7 = 3.5 Hz, 1H, H-6), 4.19 (q, J = 7.1 Hz, 2H, CH2),
4.33 (t, J5,6 = 6.9 Hz, J5,4 = 6.9 Hz, 1H, H-5), 4.74 (1H, ddd,
J4,5 = 6.6 Hz, J4,3 = 5.1 Hz, J4,2 = 1.6 Hz, H-4), 6.08 (dd, J2,3 = 15.6 Hz,
J2,4 = 1.6 Hz, 1H, H-2), 7.10 (dd, J3,2 = 15.6 Hz, J3,4 = 5.1 Hz, 1H, H-
3). 13C NMR (CDCl3, 100 MHz): d ꢁ5.6 (CH3), ꢁ5.4 (CH3), ꢁ4.8
(CH3), ꢁ3.9 (CH3), 14.3 (CH3), 18.2 (C), 18.4 (C), 25.4 (CH3), 25.9
(6 ꢄ CH3), 27.7 (CH3), 60.3 (CH2), 64.6 (CH), 72.5 (CH), 76.5 (CH),
77.6 (CH), 108.8 (C), 122.3 (CH), 145.5 (CH), 166.2 (C@O). Anal.
Calcd for C24H48O6Si2: C, 58.97; H, 9.90. Found: C, 59.05; H, 9.84.
Compound (E)-9: ½a D25
ꢃ
+34.8 (c 0.46, CHCl3). 1H NMR (CDCl3,
400 MHz): d 0.08 (s, 3H, CH3), 0.09 (s, 3H, CH3), 0.91 (s, 9H,
3 ꢄ CH3), 1.29 (t, J = 7.1 Hz, 3H, CH3), 1.37 (s, 3H, CH3), 1.49 (s,
3H, CH3), 2.55 (d, J6,OH = 5.6 Hz, 1H, OH), 3.55 (dtd, J6,5 = 9.4 Hz,
J6,OH = 5.6 Hz, J6,7 = 5.5 Hz, J6,7 = 3.2 Hz, 1H, H-6), 3.66 (dd,
J7,7 = 10.0 Hz, J7,6 = 5.5 Hz, 1H, H-7), 3.79 (dd, J7,7 = 10.0 Hz,
J7,6 = 3.2 Hz, 1H, H-7), 4.13 (dd, J5,6 = 9.4 Hz, J5,4 = 6.7 Hz, 1H, H-5),
4.21 (q, J = 7.1 Hz, 2H, CH2), 4.85 (ddd, J4,5 = 6.7 Hz, J4,3 = 4.9 Hz,
J4,2 = 1.7 Hz, 1H, H-4), 6.15 (dd, J2,3 = 15.6 Hz, J2,4 = 1.7 Hz, 1H, H2),
7.12 (dd, J3,2 = 15.6 Hz, J3,4 = 4.9 Hz, 1H, H-3). 13C NMR (CDCl3,
100 MHz): d ꢁ5.5 (CH3), ꢁ5.4 (CH3), 14.2 (CH3), 18.3 (C), 25.3
(CH3), 25.9 (3 ꢄ CH3), 27.6 (CH3), 60.4 (CH2), 64.3 (CH2), 69.6
(CH), 76.9 (CH), 77.5 (CH), 109.5 (C), 122.3 (CH), 143.9 (CH),
166.2 (C@O). Anal. Calcd for C18H34O6Si: C, 57.72; H, 9.15. Found:
C, 57.91; H, 9.01.
4.5. (4S,5S,6R,2Z)-6,7-Bis[(tert-butyldimethylsilyl)oxy]-4,5-
(isopropylidenedioxy)hept-2-en-1-ol (12)
Diisobutylaluminum hydride (79.5 mL of a 1.2 M toluene solu-
tion, 95.4 mmol) was added dropwise to a solution of ester (Z)-
10 (12.9 g, 26.4 mmol) in dry CH2Cl2 (120 mL) for 1 h at ꢁ15 °C.
The resulting mixture was stirred at the same temperature for an-
other 15 min and then quenched with MeOH (18.7 mL). The mix-
ture was warmed to room temperature and poured into a 30% aq
K/Na tartrate (397 mL). After stirring for 1 h, the mixture was then
extracted with CH2Cl2 (3 ꢄ 267 mL). The combined organic layers
were dried over Na2SO4, the solvent was evaporated under reduced
pressure, and the residue was subjected to flash chromatography
on silica gel (7:1 hexane–EtOAc) to give 11.6 g (98%) of alcohol
4.3. Ethyl (4S,5S,6R,2Z)-6,7-bis[(tert-butyldimethylsilyl)oxy]-
4,5-(isopropylidenedioxy)hept-2-enoate (10)
(Z)-12 as a colourless oil: ½a D25
ꢃ
ꢁ24.8 (c 0.23, CHCl3). 1H NMR
(CDCl3, 400 MHz): d 0.06 (s, 9H, 3 ꢄ CH3), 0.08 (s, 3H, CH3), 0.87
(s, 9H, 3 ꢄ CH3), 0.90 (s, 9H, 3 ꢄ CH3), 1.34 (s, 3H, CH3), 1.44 (s,
3H, CH3), 1.86 (t, J1,OH = 5.5 Hz, 1H, OH), 3.66 (dd, J7,7 = 10.8 Hz,
J7,6 = 4.7 Hz, 1H, H-7), 3.72 (dd, J7,7 = 10.8 Hz, J7,6 = 3.9 Hz, 1H, H-
7), 3.86 (ddd, J6,5 = 6.4 Hz, J6,7 = 4.7 Hz, J6,7 = 3.9 Hz, 1H, H-6),
4.16–4.25 (m, 2H, H-1, H-5), 4.30–4.36 (m, 1H, H-1), 4.95 (m, 1H,
H-4), 5.79–5.87 (m, 2H, H-2, H-3). 13C NMR (CDCl3, 100 MHz): d
ꢁ5.4 (2 ꢄ CH3), ꢁ4.5 (CH3), ꢁ4.0 (CH3), 18.2 (C), 18.4 (C), 25.3
(CH3), 25.9 (6 ꢄ CH3), 27.8 (CH3), 58.7 (CH2), 64.8 (CH2), 72.4
(CH), 72.7 (CH), 77.7 (CH), 108.1 (C), 128.8 (CH), 132.5 (CH). Anal.
Calcd for C22H46O5Si2: C, 59.14; H, 10.38. Found: C, 59.03; H, 10.48.
To a solution of (Z)-8 (10.4 g, 27.9 mmol) in dry DMF (18.5 mL)
were successively added imidazole (3.79 g, 55.7 mmol) and tert-
butydimethylsilyl chloride (5.88 g, 39.0 mmol) at room tempera-
ture, and the resulting mixture was stirred at 70 °C. After 4 h no
starting material was detected (judged by TLC), the stirring was
stopped and the mixture was allowed to cool to room temperature.
The mixture was then partitioned between ice water (190 mL) and
Et2O (240 mL). The organic layer was dried over Na2SO4, the
solvent was evaporated in vacuo, and the residue was purified by
flash chromatography on silica gel (70:1 hexane–EtOAc). This
procedure yielded 12.9 g (95%) of (Z)-10 as a colourless oil: ½a D25
ꢃ
4.6. (4S,5S,6R,2E)-6,7-Bis[(tert-butyldimethylsilyl)oxy]-4,5-
(isopropylidenedioxy)hept-2-en-1-ol (13)
+81.5 (c 0.26, CHCl3). 1H NMR (CDCl3, 400 MHz): d 0.04 (s, 6H,
2 ꢄ CH3), 0.06 (s, 6H, 2 ꢄ CH3), 0.87 (s, 9H, 3 ꢄ CH3), 0.89 (s, 9H,
3 ꢄ CH3), 1.29 (t, J = 7.1 Hz, 3H, CH3), 1.36 (s, 3H, CH3), 1.48 (s,
3H, CH3), 3.56 (dd, J7,7 = 10.7 Hz, J7,6 = 5.6 Hz, 1H, H-7), 3.60 (dd,
J7,7 = 10.7 Hz, J7,6 = 4.5 Hz, 1H, H-7), 3.83 (m, 1H, H-6), 4.17 (q,
J = 7.1 Hz, 2H, CH2), 4.45 (dd, J5,4 = 7.1 Hz, J5,6 = 3.7 Hz, 1H, H-5),
5.77 (ddd, J4,3 = 8.7 Hz, J4,5 = 7.1 Hz, J4,2 = 1.3 Hz, 1H, H-4), 5.87
(dd, J2,3 = 11.6 Hz, J2,4 = 1.3 Hz, 1H, H-2), 6.39 (dd, J3,2 = 11.6 Hz,
J3,4 = 8.7 Hz, 1H, H-3). 13C NMR (CDCl3, 100 MHz): d ꢁ5.5 (CH3),
ꢁ5.4 (CH3), ꢁ4.6 (CH3), ꢁ4.3 (CH3), 14.2 (CH3), 18.1 (C), 18.4 (C),
24.8 (CH3), 25.9 (3 ꢄ CH3), 26.0 (3 ꢄ CH3), 27.3 (CH3), 60.3 (CH2),
65.0 (CH2), 72.8 (CH), 73.2 (CH), 79.6 (CH), 108.3 (C), 120.7 (CH),
146.4 (CH), 165.7 (C@O). Anal. Calcd for C24H48O6Si2: C, 58.97; H,
9.90. Found: C, 58.90; H, 9.97.
According to the same procedure described for the preparation
of (Z)-12, ester (E)-11 (2.04 g, 4.17 mmol) was transformed to
compound (E)-13 (1.79 g, 96%, 7:1 hexane–EtOAc); ½a D25
ꢁ62.3 (c
ꢃ
0.39, CHCl3). 1H NMR (CDCl3, 400 MHz): d 0.05 (s, 6H, 2 ꢄ CH3),
0.06 (s, 3H, CH3), 0.09 (s, 3H, CH3), 0.88 (s, 9H, 3 ꢄ CH3), 0.90 (s,
9H, 3 ꢄ CH3), 1.35 (s, 3H, CH3), 1.47 (s, 3H, CH3), 3.67 (dd, J7,7
=
10.8 Hz, J7,6 = 4.3 Hz, 1H, H-7), 3.73 (dd, J7,7 = 10.8 Hz, J7,6 = 3.5 Hz,
1H, H-7), 3.81 (ddd, J6,5 = 6.9 Hz, J6,7 = 4.3 Hz, J6,7 = 3.5 Hz, H-6),
4.17 (m, 2H, 2 ꢄ H-1), 4.24 (dd, J5,6 = 6.9 Hz, J5,4 = 6.4 Hz, 1H, H-
5), 4.60–4.63 (m, 1H, H-4), 5.89–5.91 (m, 2H, H-2, H-3). 13C NMR
(CDCl3, 100 MHz): d ꢁ5.5 (CH3), ꢁ5.4 (CH3), ꢁ4.6 (CH3), ꢁ3.9
(CH3), 18.2 (C), 18.4 (C), 25.4 (CH3), 25.9 (6 ꢄ CH3), 27.9 (CH3),
63.1 (CH2), 64.7 (CH2), 72.5 (CH), 77.5 (CH), 77.9 (CH), 108.1 (C),
128.4 (CH), 132.6 (CH). Anal. Calcd for C22H46O5Si2: C, 59.14; H,
10.38. Found: C, 59.29; H, 10.20.
4.4. Ethyl (4S,5S,6R,2E)-6,7-bis[(tert-butyldimethylsilyl)oxy]-
4,5-(isopropylidenedioxy)hept-2-enoate (11)
Using the same procedure as described for the preparation of
derivative (Z)-10, ester (E)-9 (2.21 g, 5.90 mmol), imidazole
(0.80 g, 11.8 mmol) and TBDMSCl (1.25 g, 8.29 mmol) afforded
after flash chromatography on silica gel (70:1 hexane–EtOAc)
4.7. N-{[(3S,4S,5S,6R)-6,7-Bis[(tert-butyldimethylsilyl)oxy]-4,5-
(isopropylidenedioxy)hept-1-en-3-yl]}-2,2,2-trichloroacetamide
(14) and N-{[(3R,4S,5S,6R)-6,7-bis[(tert-butyldimethylsilyl)oxy]-
4,5-(isopropylidenedioxy)hept-1-en-3-yl]}-2,2,2-trichloroacet-
amide (15)
2.05 g (71%) of compound (E)-11 as a colourless oil: ½a D25
ꢁ60.6 (c
ꢃ
0.20, CHCl3). 1H NMR (CDCl3, 400 MHz): d 0.06 (s, 6H, 2 ꢄ CH3),
0.10 (s, 3H, CH3), 0.11 (s, 3H, CH3), 0.89 (s, 9H, 3 ꢄ CH3), 0.90 (s,
9H, 3 ꢄ CH3), 1.28 (t, J = 7.1 Hz, 3H, CH3), 1.37 (s, 3H, CH3), 1.50
(s, 3H, CH3), 3.68 (dd, J7,7 = 10.9 Hz, J7,6 = 3.8 Hz, 1H, H-7), 3.72
4.7.1. Microwave-assisted synthesis
To a suspension of NaH (1.13 g, 47.1 mmol, 60% dispersion in
mineral oil, freed of oil with anhydrous THF) in THF (34.5 mL),