ACCEPTED MANUSCRIPT
The vessel was sealed and placed in an oil bath at 80 °C for 6 h. The reaction was allow to cool to 0 °C. To
the mixture was added an aqueous solution of NaOH (1.9 g, 47 mmol), and added dropwise 30% aqueous
soltuion of H2O2 (2.0 mL). After the diboration product disappeared on TLC, the reaction was cautiously
quenched with saturated aquous Na2S2O3 solution, diluted with water, and extracted with ethyl acetate (40
mL × 3). The combined organic layers were washed with brine, dried over Na2SO4, filtered, and
concentrated under reduced pressure. Purification of the crude by flash column chromatography on silica
gel (PE/EA: 12/1 to 10/1) provided triol 18 (1.31 g, 74%) as a white foam. [α]D29 −22.4 (c 0.6, CHCl3); IR
1
(KBr): 3392, 2931, 2897, 2857, 1472, 1462, 1387, 1111, 702 cm-1; H NMR (400 MHz, CDCl3) δ 7.70 –
7.62 (m, 8H), 7.45 – 7.32 (m, 12H), 5.12 (s, 1H), 4.25 (d, J = 7.3 Hz, 1H), 3.70 (t, J = 7.2 Hz, 1H), 3.58 –
3.43 (m, 3H), 3.23 (s, 1H), 1.05 (d, J = 2.0 Hz, 18H), 0.97 (s, 3H), 0.93 (d, J = 6.8 Hz, 3H), 0.88 (d, J = 6.6
Hz, 3H), 0.77 (s, 3H); 13C NMR (100 MHz, CDCl3) δ 141.3, 135.9, 135.9, 135.7, 135.7, 134.9, 134.9,
133.9, 129.8, 129.6, 129.6, 127.8, 127.6, 127.6, 121.1, 82.8, 76.2, 73.8, 73.3, 69.0, 49.4, 48.7, 44.6, 42.6,
37.2, 36.5, 35.5, 34.0, 33.3, 32.7, 31.9, 31.9, 31.8, 28.2, 27.1, 27.0, 20.6, 19.5, 19.4, 19.3, 16.9, 14.1, 13.2.
HRMS-ESI (m/z): [M+H]+ calcd for C59H82O5Si2: 926.5774, found: 927.5746.
4.1.5 Swern oxidation led to diketone 19
To a solution of oxalyl chloride (0.087 mL, 1.0 mmol) in dry DCM (4.0 mL) was slowly added dry
DMSO (0.144 mL, 2.0 mmol) at -78 °C under argon. After the evolution of gas ceased (ca. 30 min), a
solution of alcohol 18 (92.0 mg, 0.10 mmol) in dry DCM (4 mL) was slowly added to the resulting cold
solution. After 35 min, Et3N (0.21 mL, 1.5 mmol) was added and the reaction was left to reach ambient
temperature. After 2 h, the reaction was quenched by addition of water. The organic layer was separated
and the aqueous phase was extracted with DCM (15 mL × 3). The combined organic layers were washed
with brine, dried over Na2SO4, filtered, and concentrated under reduced pressure. Purification of the crude
by flash column chromatography on silica gel (PE/EA: 40/1 to 10/1) provided ketone 19 (52 mg, 56%) as a
white foam. [α]D29 −75.9 (c 0.5, CHCl3); IR (KBr): 3374, 3070, 2932, 2857, 1742, 1696, 1471, 1461, 1427,
1
1379, 1110, 702 cm-1; H NMR (400 MHz, CDCl3) δ 7.71 – 7.62 (m, 8H), 7.39 (m, J = 16.9, 9.6, 4.8 Hz,
12H), 5.55 (s, 1H), 5.11 (d, J = 4.7 Hz, 1H), 3.61 – 3.43 (m, 4H), 1.09 (d, J = 7.2 Hz, 3H), 1.06 (s, 9H),
13
1.05 (s, 9H), 1.01 (s, 3H), 0.94 (d, J = 6.6 Hz, 3H), 0.74 (s, 3H). C NMR (100 MHz, CDCl3) δ 219.5,
217.5, 141.5, 135.9, 135.8, 134.9, 134.9, 134.1, 134.0, 129.6, 129.6, 129.6, 127.7, 127.6, 127.6, 120.6, 85.9,
73.2, 68.7, 49.3, 45.3, 45.2, 43.0, 42.5, 41.2, 37.0, 36.7, 35.5, 35.3, 31.9, 31.2, 30.2, 27.2, 27.0, 26.7, 20.2,
19.6, 19.5, 19.3, 17.0, 13.9, 11.8. HRMS-ESI (m/z): [M+H]+ calcd for C59H78O5Si2: 923.5461, found:
923.5430.
4.1.6 Hemiketal 20
8