A. Bhattacharjee et al. / Tetrahedron 59 (2003) 4623–4639
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mp 142–1438C. [a]2D5¼256.4 (c 1.0, CHCl3); MS (EI) m/z
347 (Mþ), 332; 1H NMR (300 MHz, CDCl3) d 1.17 (s, 3H),
1.36 (s, 3H), 1.67 (s, 3H), 3.16 (m, 1H), 3.28 (dd, J¼8.2,
9.9 Hz, 1H), 3.51 (dd, J¼7.0, 8.5 Hz, 1H), 3.93–4.01 (m,
3H), 3.95 (d, J¼13.9 Hz, 1H), 4.13 (d, J¼14.0 Hz, 1H), 4.14
(t, J¼8.5 Hz, 1H), 4.23 (d, J¼3.5 Hz, 1H), 4.28 (d,
J¼9.9 Hz, 1H), 5.76 (d, J¼3.5 Hz, 1H), 7.26–7.43 (m,
5H). 13C NMR (25 MHz, CDCl3) d 18.8 (q), 26.0 (q), 26.4
(q), 41.1 (d), 60.2 (t), 63.7 (d), 64.4 (t), 68.0 (t). 74.2 (d),
78.0 (s), 82.6 (d), 105.0 (d), 113.3 (s), 127.1 (d), 128.1 (d),
128.8 (d), 137.1 (s). Anal. calcd for C19H25NO5: C, 65.66;
H, 7.26; N, 4.04. Found C, 65.74; H, 7.30; N, 4.25.
1.38 (s, 3H), 2.44 (m, 1H), 3.30 (d, J¼6.2 Hz, 1H), 3.53 (t,
J¼11.2 Hz, 1H), 3.74–3.82 (m, 3H), 4.00 (d, J¼1.8 Hz,
1H), 4.04 (d, J¼13.9 Hz, 1H), 4.13 (d, J¼13.9 Hz, 1H), 4.50
(d, J¼3.7 Hz, 1H), 5.85 (d, J¼3.7 Hz, 1H), 7.23–7.41 (m,
5H); 13C NMR (75 MHz, CDCl3): d 18.6, 26.3, 26.6, 45.4,
60.7, 63.2, 63.5, 73.9, 75.8, 78.9, 83.8, 104.7, 111.7, 127.6,
128.4, 129.4, 136.6.
Compound 34. Yield 34%; sticky material; 1H NMR
(300 MHz, CDCl3) d 1.28 (s, 3H), 1.29 (d, J¼6.0 Hz, 3H),
1.39 (s, 3H), 2.06 (m, 1H), 3.32 (dd, J¼8.0, 5.1 Hz, 1H),
3.68 (dd, J¼12.4, 4.1 Hz, 1H), 3.78–3.83 (m, 4H), 4.37 (d,
J¼12.6 Hz, 1H), 4.44 (d, J¼3.7 Hz, 1H), 5.89 (d, J¼3.7 Hz,
1H), 7.23–7.44 (m, 5H). 13C NMR (75 MHz, CDCl3): d
21.1, 26.1, 26.7, 45.2, 62.6 (2£C), 65.0, 73.2, 74.8, 77.2,
84.1, 104.3, 111.7, 127.5, 128.4, 128.8, 137.1. Anal. calcd
for C19H25NO5: C, 65.69; H, 7.25. Found: C, 65.37; H, 7.03.
4.5.6. (2R,3R,3aR,6R,7S,7aR)-6-Acetoxymethyl-7-(N-
acetyl-N-benzyl)amino-2,3,3a,6,7,7a-hexahydro-2,3-iso-
propylidenedioxy-3a-methyl-5H-furo[3,2-b]pyran (30).
To a suspension of LiAlH4 (0.1 g, 2.6 mmol) in THF
(10 mL), 29 (0.11 g, 0.3 mmol) was added in portions and
the reaction mixture was heated to reflux for 24 h. After
cooling to 08C and dropwise addition of saturated
ammonium chloride solution (5 mL) to destroy the excess
LiAlH4, the mixture was filtered and the filtrate was
extracted with chloroform. Removal of solvent gave an
oil, which was dissolved in pyridine (3 mL), and acetic
anhydride (2 mL) was added at 08C. The reaction mixture
was allowed to warm upto room temperature and left
overnight. Usual work up of the reaction mixture gave an
oil, which was chromatographed over silica gel to yield a
white solid. Recrystallization of the solid from diethyl
ether–petroleum ether afforded 30 (0.07 g, 50%), mp 123–
1248C. [a]2D5¼þ12.4 (c 0.55, CHCl3); MS (EI) m/z 433
(Mþ), 432, 418; IR (KBr) 2984, 2926, 1737, 1643 cm21; 1H
NMR (300 MHz, CDCl3) d 1.20 (s, 3H), 1.30 (s, 3H), 1.50
(s, 3H), 2.00 (s, 3H), 2.05 (s, 3H), 2.70 (m, 1H), 3.96 (dd,
J¼12, 3 Hz, 1H), 3.98 (d, J¼12 Hz, 1H), 4.04 (dd, J¼10.5,
9 Hz, 1H), 4.22 (dd, J¼10.5, 3.5 Hz, 1H), 4.26 (d,
J¼3.5 Hz, 1H), 4.56 (d, J¼17.4 Hz, 1H), 4.66 (d,
J¼17.4 Hz, 1H), 4.75 (dd, J¼12.3, 4.0 Hz, 1H), 5.64
(d, J¼3.5 Hz, 1H), 7.26–7.35 (m, 5H). 13C NMR
(25 MHz, CDCl3) d 15.4 (q), 20.7 (q), 23.0 (q), 25.9 (q),
26.2 (q), 38.6 (d), 50.7 (t), 55.1 (t), 61.6 (t), 63.4 (t), 70.8 (t),
80.2 (s), 82.5 (d), 104.1 (d), 113.3 (s), 126.4 (d), 127.0 (d),
128.4 (d), 137.4 (s), 170.4 (s), 172.7 (s). Anal. calcd for
C23H31NO7: C, 63.79; H, 7.22; N, 3.24. Found: C, 63.55; H,
7.31; N, 3.15.
Compound 35. Yield, 11%; sticky material; 1H NMR
(300 MHz) d 1.29 (s, 3H), 1.31 (d, J¼7.3 Hz, 3H), 1.42 (s,
3H), 3.09 (q, J¼7.2 Hz, 1H), 3.37 (d, J¼4.62 Hz, 1H), 3.54
(d, J¼13.3 Hz, 1H), 3.80 (dd, J¼13.3, 5.1 Hz, 1H), 3.88 (bd,
J¼3.2 Hz, 1H), 4.07 (d, J¼12.9 Hz, 1H), 4.12 (bs, 1H), 4.20
(d, J¼5.1 Hz, 1H), 4.37 (d, J¼12.9 Hz, 1H), 4.41 (d,
J¼3.7 Hz, 1H), 5.87 (d, J¼3.6 Hz, 1H), 7.31 (m, 5H). 13C
NMR (75 MHz, CDCl3) d 20.1 (CH3), 26.2 (CH3), 26.7
(CH3), 36.6 (CH), 63.4 (CH2), 69.3 (CH), 73.7 (CH2), 78.5
(CH), 83.2 (CH), 84.1 (CH), 85.1 (CH), 104.9 (CH), 111.7
(quaternary C), 127.5 (CH), 128.5 (CH), 128.8 (CH), 137.4
(quaternary C).
4.5.8. (3aR,5aS,6R,7R,8aR,8bS)-1-Benzyl-3,3-dimethyl-
1,3,3a,5a,6,7,8a,8b-octahydro-4H-furo[20,30:3,2]pyrano-
[4,5-c]isoxazole (36) and (3aR,5aS,6R,7R,8aR,8bR)-1-
benzyl-3,3-dimethyl-1,3,3a,5a,6,7,8a,8b-octahydro-4H-
furo[20,30:3,2]pyrano[4,5-c]isoxazole (37). The crude
material obtained from 9f was chromatographed over silica
gel using EtOAc–petroleum ether (1:1) to afford mixture of
two products (70%). The two products were purified by
further chromatography over silica gel followed by
fractional crystallization affording 36 and 37 (3:2) as two
diastereomers.
Compound 36. 42%, mp 108–1098C. [a]2D5¼252.9 (c 0.27,
1
CHCl3); MS (EI) m/z 361 (Mþ), 346; H NMR (300 MHz,
CDCl3) d 1.15 (s, 3H), 1.27 (s, 3H), 1.31 (s, 6H), 2.42 (m,
1H), 3.58 (dd, J¼11.5, 12.0 Hz, 1H), 3.65 (dd, J¼5.5,
,2.0 Hz, 1H), 3.66 (d, J¼1.9 Hz, 1H), 3.80 (dd, J¼12.0,
5.1 Hz, 1H), 3.93 (d, J¼1.6 Hz, 1H), 4.09 (d, J¼13.4 Hz,
1H), 4.24 (d, J¼13.4 Hz, 1H), 4.47 (d, J¼3.6 Hz, 1H), 5.81
(d, J¼3.6 Hz, 1H), 7.20–7.40 (m, 5H); 13C NMR (25 MHz,
CDCl3) d 21.7 (q), 26.0 (q), 26.6 (q), 29.7 (q), 45.6 (d), 63.7
(d), 63.9 (t), 64.1 (t). 73.7 (d), 76.7 (d), 80.3 (d), 83.6 (d),
104.2 (d), 111.5 (s), 127.4 (d), 128.3 (d), 128.7 (d), 136.8
(s). Anal. calcd for C20H27NO5: C, 66.46; H, 7.54; N, 3.88.
Found: C, 66.59; H, 7.37; N, 3.98.
4.5.7. (3R,3aR,5aS,6R,7R,8aR,8bS)-1-Benzyl-6, 7-isopro-
pylidenedioxy-3-methyl-1,3,3a,5a,6,7,8a,8b-octahydro-
4H-furo[20,30:3,2]pyrano[4,5-c]isoxazole (33),
(3S,3aS,5aS,6R,7R,8aR,8bR)-1-benzyl-6,7-isopropylide-
nedioxy-3-methyl-1,3,3a,5a,6,7,8a,8b-octahydro-4H-
furo[20,30:3,2]-pyrano[4,5-c]isoxazole (34), (2aS,2bR,
4R,5R,5aS,7bR,8R)-2-benzyl-8-methyl-2b,4,5,5a-tetra-
hydro-4,5-isopropylidenedioxy-furo[20,30:4,5]-bicy-
clo[4.2.1]nonane (35). The crude product obtained after the
usual procedure of cycloaddition using 9e yielded after
chromatography over silica gel (10–30% EtOAc–pet-
roleum ether) the following compounds, each of which
was observed to have other diastereomers as contaminants;
hence optical rotations of the samples were not measured.
Compound 37. 28%, mp 154–1558C. [a]2D5¼þ56.6 (c 0.28,
1
CHCl3); MS (EI) m/z 361 (Mþ), 346; H NMR (300 MHz,
CDCl3) d 1.08 (s, 3H), 1.25 (s, 3H), 1.38 (s, 3H), 1.60
(s, 3H), 2.64 (dt, J¼11.3, 3.1 Hz, 1H), 2.86 (dd, J¼11.3,
6.0 Hz, 1H), 3.36 (dd, J¼11.3, 10.7 Hz, 1H), 3.76 (br s, 1H),
3.86 (dd, J¼6.0, 4.0 Hz, 1H), 3.94 (dd, J¼10.7, 3.3 Hz, 1H),
Compound 33. Yield, 17%; sticky material; 1H NMR
(300 MHz, CDCl3) d 1.24 (d, J¼6.3 Hz, 1H), 1.29 (s, 3H),