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K. R. Prasad, P. Anbarasan / Tetrahedron 62 (2006) 8303–8308
over 10 min, under argon atmosphere. The reaction mixture
was stirred for 0.5 h, quenched with water (3 mL) and ex-
tracted with ether (3ꢂ6 mL). The combined ethereal extracts
were washed with brine and dried over Na2SO4. Residue ob-
tained after evaporation of solvent was filtered through silica
and evaporated to yield crude alcohol. Using a similar pro-
cedure described for the synthesis of 10, the alcohol was
converted to the silylether 11. Alternately, the same reaction
can be effected using TBDMSCl as described below.
extracted with ether (3ꢂ5 mL). Combined ethereal extracts
were washed with brine and dried over Na2SO4. Residue
obtained after evaporation of solvent was purified by column
chromatography to yield 13 in 98% (0.12 g) as colorless oil.
[a]D +6.4 (c 2.8, CHCl3); IR (neat): 3473, 2933, 2857, 1471,
1378, 1255, 1157, 1106, 835, 777 cmꢀ1
;
1H NMR
(300 MHz, CDCl3) d 4.02–3.91 (m, 2H), 3.74–3.57 (m,
3H), 2.69 (t, J¼6.6 Hz, 1H), 1.31 (s, 6H), 1.12 (d,
J¼6.6 Hz, 3H), 0.80 (s, 9H), 0.07 (s, 6H); 13C NMR
(75 MHz, CDCl3) d 108.7, 81.4, 76.6, 67.7, 63.1, 27.1,
26.9, 25.7, 18.1, 18.0, ꢀ4.7, ꢀ4.9.
To a solution of crude alcohol (obtained above) in 3 mL of
DMF at room temperature were added imidazole (0.09 g,
1.38 mmol), DMAP (10 mg, 0.07 mmol), and TBDMSCl
(0.21 g, 1.38 mmol) and was heated up to 80 ꢁC. The reac-
tion mixture was stirred for 2 h at same temperature. After
the reaction was complete (TLC), it was cooled to room tem-
perature, poured into water (5 mL) and extracted with ether
(3ꢂ10 mL). The combined ethereal extracts were washed
with brine and dried over Na2SO4. Evaporation of solvent
followed by column chromatography of the resulting residue
afforded 11 as colorless oil in 77% (0.17 g) yield. [a]D ꢀ16
(c 2.3, CHCl3); IR (neat): 2954, 2896, 1673, 1463, 1380,
2.1.7. Preparation of (4S,5R)-5-((R)-1-tert-butyldi-
methylsilyloxyhex-5-enyl)-4-(p-toluenesulfonyloxy-
methyl)-2,2-dimethyl-1,3-dioxolane (14). To a solution of
12 (0.25 g, 0.73 mmol) and DMAP (0.22 g, 1.8 mmol) in
5 mL of CH2Cl2 at 0 ꢁC was added p-toluenesulfonyl
chloride (0.21 g, 1.1 mmol) under argon atmosphere. The
reaction mixture was stirred at room temperature for 5 h,
poured into water (8 mL) and extracted with ether
(3ꢂ10 mL). The ethereal extracts were washed with brine
and dried over Na2SO4. Residue obtained after evaporation
of solvent was subjected to column chromatography to yield
14 in 92% (0.33 g) as colorless oil. [a]D ꢀ7.2 (c 1.1, CHCl3);
IR (neat): 2929, 2857, 1598, 1461, 1369, 1253, 1189, 1095,
1255, 1159, 1074, 1008, 979, 894, 836, 777 cmꢀ1 1H
;
NMR (300 MHz, CDCl3) d 4.74 (br s, 1H), 4.50 (dd,
J¼6.6, 4.5 Hz, 1H), 4.03 (qd, J¼6.3, 4.5 Hz, 1H), 3.75 (s,
3H), 3.22 (s, 3H), 1.45 (s, 6H), 1.19 (d, J¼6.3 Hz, 3H),
0.87 (s, 9H), 0.07 (s, 3H), 0.05 (s, 3H); 13C NMR
(75 MHz, CDCl3) d 170.4, 111.1, 81.2, 72.2, 67.7, 61.7,
32.2, 27.0, 26.3, 25.7, 18.7, 18.0, ꢀ4.5, ꢀ4.9; HRMS for
C16H33NO5Si+Na calcd 370.2026; found 370.2021.
983, 835, 775, 665 cmꢀ1 1H NMR (300 MHz, CDCl3)
;
d 7.74 (d, J¼8.4 Hz, 2H), 7.28 (d, J¼8.4 Hz, 2H), 5.73
(ddt, J¼16.8, 10.2, 6.6 Hz, 1H), 4.98–4.87 (m, 2H), 4.15
(dd, J¼10.5, 3.0 Hz, 1H), 4.09–4.02 (m, 1H), 3.96 (dd,
J¼10.5, 5.7 Hz, 1H), 3.76–3.66 (m, 2H), 2.39 (s, 3H),
1.99–1.96 (m, 2H), 1.56–1.23 (m, 4H), 1.30 (s, 3H), 1.25
(s, 3H), 0.80 (s, 9H), ꢀ0.01 (s, 3H), ꢀ0.02 (s, 3H); 13C
NMR (75 MHz, CDCl3) d 144.8, 138.4, 132.8. 129.8.
128.0, 114.7, 109.7, 79.2, 74.4, 71.5, 70.0, 33.6, 32.0,
26.9, 26.8, 25.8, 25.0, 21.6, 18.0, ꢀ4.2, ꢀ4.6. HRMS for
C25H42O6SSi+Na calcd 521.2371; found 521.2369.
2.1.5. Preparation of (4S,5R)-5-((R)-1-tert-butyldi-
methylsilyloxyhex-5-enyl)-4-(hydroxymethyl)-2,2-di-
methyl-1,3-dioxolane (12). To a solution of 10 (0.33 g,
0.82 mmol) in 3 mL of methanol at 0 ꢁC was added
NaBH4 (0.078 g, 2.1 mmol) in portion wise. The reaction
mixture was stirred for 1 h at the same temperature and
slowly warmed up to room temperature and stirred at room
temperature for 2 h. After the reaction was complete (indi-
cated by TLC), it was poured into water (5 mL) and
extracted with ether (3ꢂ10 mL). Combined ethereal extracts
were washed with brine and dried over Na2SO4. Residue
obtained after evaporation of solvent was purified by column
chromatography to yield 12 in 95% (0.27 g) as colorless oil.
[a]D +12.1 (c 2.4, CHCl3); IR (neat): 3469, 2985, 2857,
1471, 1461, 1378, 1253, 1164, 1101, 1004, 937, 836,
2.1.8. Preparation of (4S,5R)-5-((R)-1-tert-butyldi-
methylsilyloxyethyl)-4-(p-toluenesulfonyloxymethyl)-
2,2-dimethyl-1,3-dioxolane (15). To a solution of 13
(0.12 g, 0.41 mmol) and DMAP (0.12 g, 1 mmol) in 5 mL
of CH2Cl2 at 0 ꢁC was added p-toluenesulfonyl chloride
(0.11 g, 0.6 mmol) under argon atmosphere. The reaction
mixture was stirred at room temperature for 5 h, poured
into water (5 mL), and extracted with ether (3ꢂ5 mL). The
ethereal extracts were washed with brine and dried over
Na2SO4. Residue obtained after evaporation of solvent was
subjected to column chromatography to yield 15 in 92%
(0.17 g) as colorless oil. [a]D ꢀ19.1 (c 1.1, CHCl3); IR
(neat): 2931, 2857, 1598, 1461, 1369, 1255, 1178, 1097,
775 cmꢀ1 1H NMR (300 MHz, CDCl3) d 5.70 (ddt,
;
J¼16.8, 10.2, 6.6 Hz, 1H), 4.94–4.84 (m, 2H), 3.93 (dt,
J¼8.1, 4.8 Hz, 1H), 3.77–3.55 (m, 4H), 2.37 (br s, 1H),
1.98–1.95 (m, 2H), 1.60–1.24 (m, 4H), 1.31 (s, 3H), 1.30
(s, 3H), 0.81 (s, 9H), 0.01 (s, 6H); 13C NMR (75 MHz,
CDCl3) d 138.5, 114.7, 108.6, 80.5, 77.0, 71.9, 62.9, 33.7,
31.9, 27.0, 26.9, 25.8, 25.3, 18.1, ꢀ4.2, ꢀ4.7; HRMS for
C18H36O4Si+Na calcd 367.2281; found 367.2281.
981, 835, 777, 665 cmꢀ1 1H NMR (300 MHz, CDCl3)
;
d 7.78 (d, J¼8.1 Hz, 2H), 7.33 (d, J¼8.1 Hz, 2H), 4.21
(dd, J¼10.2, 2.7 Hz, 1H), 4.16–3.90 (m, 3H), 3.74 (dd, J¼
7.5, 4.5 Hz, 1H), 2.43 (s, 3H), 1.35 (s, 3H), 1.31 (s, 3H),
1.12 (d, J¼6.3 Hz, 3H), 0.83 (s, 9H), 0.03 (s, 3H), 0.01 (s,
3H); 13C NMR (75 MHz, CDCl3) d 144.8, 132.8, 129.7,
127.9, 109.8, 79.8, 74.1, 70.2, 67.3, 26.9, 26.8, 25.7, 21.6,
18.2, 17.9, ꢀ4.7, ꢀ4.9; HRMS for C21H36O6SSi+Na calcd
467.1900; found 467.1877.
2.1.6. Preparation of (4S,5R)-5-((R)-1-tert-butyldi-
methylsilyloxyethyl)-4-(hydroxylmethyl)-2,2-dimethyl-
1,3-dioxolane (13). To a solution of 11 (0.15 g, 0.43 mmol)
in 3 mL of methanol at 0 ꢁC was added NaBH4 (0.04 g,
1 mmol) in portions. The reaction mixture was stirred for
1 h at the same temperature and was slowly warmed up to
room temperature and stirred for 1 h. After the reaction
was complete (TLC), it was poured into water (5 mL) and
2.1.9. Preparation of (4S,5R)-5-((R)-1-tert-butyldi-
methylsilyloxyhex-5-enyl)-4-methyl-2,2-dimethyl-1,3-di-
oxolane (16). To a solution of 14 (0.25 g, 0.5 mmol) in 3 mL