5.79 (d, J = 1.5 Hz, 2H), 4.10 (d, J = 2.8 Hz, 2H), 3.80 (d, J =
4.7 Hz, 2H); dC (75 MHz, CD3OD): 130.3 (2C), 72.0 (2C), 69.1
(2C). NMR data are in accordance with literature values.23
and concentrated under reduced pressure. Purification by flash
column chromatography (heptane–EtOAc, 9 : 1 → 8 : 2) gave
70 mg (94%) of the target compound as a solid (7 : 2 mixture of
diastereomers). It was not possible to separate the two isomers by
chromatography, but pure (+)-conduritol C tetraacetate (40 mg)
could be obtained by recrystallisation from MeOH. Rf 0.23
(heptane–EtOAc, 1 : 1); mmax(KBr)/cm−1: 1756, 1372, 1229. For
1,2,7,8-Tetradeoxy-3-benzoyl-5,6-di-O-(tert-butyldimethylsilyl)-
L-talo-octa-1,7-dienitol (8)
◦
Zinc (234 mg, 3.58 mmol) was added to a deoxygenated solution
of methyl furanoside 6 (180 mg, 0.358 mmol) in THF–H2O (4 :
1, 3 mL). The mixture was sonicated at 40 ◦C for 1 h, at which
point TLC revealed full conversion into aldehyde 7. The reaction
mixture was filtered through Celite, which was then rinsed with
THF–H2O (4 : 1, 2 mL). Benzoate B (129 mg, 0.537 mmol) and
indium (205 mg, 1.79 mmol) were added and the reaction was
sonicated under argon at 40 ◦C for 1 h. The mixture was filtered
through Celite, which was then washed with Et2O (30 mL). The
organic phase was washed with 1 M HCl (20 mL), saturated
NaHCO3 (2 × 20 mL) and H2O (20 mL), dried and absorbed on
Celite. Purification by flash column chromatography (heptane–
EtOAc, 25 : 0 → 24 : 1) gave the target compound (140 mg, 78%)
as a clear oil (7 : 2 mixture of diastereomers). Rf 0.48 (heptane–
EtOAc, 3 : 1); mmax(KBr)/cm−1: 3498, 2956, 1723, 1260. For the
major isomer 8: dH (500 MHz, CDCl3): 8.09–8.01 (m, 2H), 7.59
(m, 1H), 7.45–7.39 (m, 2H), 6.20–6.07 (m, 2H), 5.74 (d, J =
7.2 Hz, 1H), 5.48 (d, J = 17.3 Hz, 1H), 5.49–5.21 (m, 3H), 4.42
(m, 1H), 4.04 (d, J = 8.6 Hz, 1H), 3.67 (dd, J = 4.2, 8.9 Hz, 1H),
0.98–0.88 (m, 18H), 0.18–0.02 (m, 12H); dC (75 MHz, CDCl3):
165.9, 134.8, 132.9, 131.7, 130.6, 129.9, 128.4, 120.6, 116.8, 76.3,
75.6, 74.8, 72.0, 26.0, 25.9, 18.2, 18.2, −3.4, −4.4, −4.7, −5.0.
Anal. calcd. for C27H46O5Si2: C, 63.98; H, 9.15. Found: C, 63.73;
H, 8.90%.
the major isomer 10: mp 100–101 C (MeOH) (lit.24 mp 96–
97.5 ◦C); [a]D + 200.7 (c 1.5, CHCl3) (lit.25 [a]2D4 +194 (c 1.1,
CHCl3)); dH (300 MHz, CDCl3): 5.78 (m, 1H), 5.68–5.62 (m,
4H), 5.18 (dd, J = 1.4, 8.4 Hz, 1H), 2.12 (s, 3H), 2.06 (s, 3H),
2.03 (s, 3H), 2.02 (s, 3H); dC (75 MHz, CDCl3): 170.6, 170.4,
170.1, 169.9, 127.6, 127.2, 70.6, 69.9, 69.6, 67.7, 21.1, 21.0, 20.9,
20.8. Anal. calcd. for C14H18O8: C, 53.50; H, 5.77. Found: C,
53.74; H, 5.82%. NMR data are in agreement with literature
values.12 For the minor isomer: dH (300 MHz, CDCl3): 5.86 (d,
J = 1.5 Hz, 2H), 5.40 (dd, J = 1.0, 5.6 Hz, 2H), 5.32 (d, J =
5.1 Hz, 2H), 2.09 (s, 6H), 2.06 (s, 6H). dC (75 MHz, CDCl3):
170.2 (2C), 170.0 (2C), 127.8 (2C), 69.4 (2C), 68.3 (2C), 21.1
(2C), 21.0 (2C). NMR data are in accordance with the reported
spectra for conduritol A tetraacetate.26
Deacetylation of 10 (102 mg) with K2CO3 in MeOH followed
by purification by flash chromatography (CH2Cl2–MeOH, 9 :
1 → 8 : 2) afforded 43 mg (90%) of (+)-conduritol C. Rf 0.20
(CHCl3–MeOH, 3 : 1); mmax(KBr)/cm−1: 3367, 1054, 1022. dH
(500 MHz, CD3OD): 5.65 (dt, J = 2.2, 10.3 Hz, 1H), 5.56 (m,
1H), 4.27–4.22 (m, 2H), 4.02 (m, 1H), 3.53 (dd, J = 2.1, 7.5 Hz,
1H); dC (50 MHz, CD3OD): 130.9, 130.1, 76.2, 74.1, 70.7, 69.6.
NMR data are in accordance with the literature values.24
1,2,4,7,8-Pentadeoxy-3-benzoyl-4-benzylamino-5,6-O-
isopropylidene-D-allo-octa-1,7-dienitol (11)
1,2,7,8-Tetradeoxy-3,4,5,6-tetra-O-acetyl-L-talo-octa-1,7-
dienitol (9)
Zinc (1.7 g, 26.0 mmol) and TMSCl (0.20 mL, 1.63 mmol)
were added to a deoxygenated solution of methyl furanoside
1 (1.0 g, 3.18 mmol)◦in anhydrous THF (15 mL). The mixture
was sonicated at 40 C under N2 for 2 h, at which point TLC
revealed full conversion into aldehyde 2. The reaction mixture
was filtered through Celite, and the Celite pad was washed with
anhydrous THF (2 mL). Benzylamine (1.0 mL, 14.2 mmol)
Compound 8 (424 mg, 0.84 mmol) and NaOH (134 mg,
3.35 mmol) were dissolved in dry MeOH (10 mL) and stirred
under argon for 1.5 h. CH2Cl2 (40 mL) was added and the
solution was washed with saturated NH4Cl (2 × 20 mL) and
H2O (2 × 20 mL). The combined aqueous phases were extracted
with CH2Cl2 (10 mL) and the combined organic phases were
dried and concentrated under reduced pressure. The residue was
dissolved in THF (10 mL), and a 0.5 M solution of TBAF
in THF (4.0 mL) was added. The solution was stirred under
argon for 30 min, after which Ac2O (0.79 mL, 8.4 mmol), Et3N
(1.40 mL, 10.1 mmol) and DMAP (catalytic) were added. After
stirring for another 1.5 h, the reaction mixture was diluted
with Et2O (40 mL) and washed with saturated NaHCO3 (2 ×
20 mL) and H2O (2 × 20 mL). The combined aqueous phases
were extracted with CH2Cl2 (10 mL) and the combined organic
phases were dried and absorbed on Celite. Purification by flash
column chromatography (heptane–EtOAc, 9 : 1 → 8 : 2) gave
the target compound (184 mg, 64%) as a solid (7 : 2 mixture of
diastereomers). Rf 0.18 (heptane–EtOAc, 3 : 1); mmax(KBr)/cm−1:
1746, 1372, 1215. For the major isomer 9: dH (500 MHz, CDCl3):
5.82 (ddd, J = 6.5, 10.6, 17.2 Hz, 1H), 5.69 (ddd, J = 5.1, 10.4,
17.5 Hz, 1H), 5.52 (m, 1H), 5.40 (m, 1H), 5.33–5.21 (m, 6H),
2.09 (s, 3H), 2.08 (s, 3H), 2.07 (s, 3H), 2.05 (s, 3H); dC (75 MHz,
CDCl3): 170.1, 169.9, 169.8, 169.7, 132.0, 130.8, 119.9, 118.2,
73.2, 71.4, 70.1, 70.1, 21.1, 21.0, 20.9, 20.9. Anal. calcd. for
C16H22O8: C, 56.14; H, 6.48. Found: C, 56.36; H, 6.48%. NMR
data are in accordance with literature data.12
˚
and 3 A molecular sieves (10 g) were added and the reaction
was stirred for 2 h at ambient temperature and then filtered.
Zinc (1.5 g, 22.3 mmol) and benzoate B (1.15 g, 4.77 mmol)
were added and the reaction mixture was sonicated at 40 ◦C
under N2. After 4 h the mixture was filtered through Celite,
which was then rinsed with Et2O (150 mL). The filtrate was
washed with saturated NaHCO3 (4 × 100 mL), saturated NaCl
(2 × 50 mL) and H2O (2 × 50 mL), and the organic phase
dried and absorbed onto Celite. Purification by dry column
chromatography (hexane–EtOAc, 9 : 1 → 8 : 2) gave 568 mg
(44%) of 11 as a clear oil. Rf 0.42 (hexane–EtOAc, 3 : 1); [a]D −25
(c 1.9, CHCl3); mmax(neat)/cm−1: 2986, 1723, 1271; dH (300 MHz,
CDCl3): 8.08–8.01 (m, 2H), 7.57–7.52 (m, 1H), 7.46–7.39 (m,
2H), 7.28–7.21 (m, 5H), 6.04–5.88 (m, 3H), 5.45–5.28 (m, 3H),
5.20 (ddd, J = 1.1, 1.8, 10.3 Hz, 1H), 4.63 (m, 1H), 4.14 (d,
J = 12.3 Hz, 1H), 3.88 (dd, J = 6.1, 10.1 Hz, 1H), 3.65 (d, J =
12.6 Hz, 1H), 3.14 (dd, J = 2.5, 10.2 Hz, 1H), 1.48 (s, 3H), 1.31
(s, 3H); dC (75 MHz, CDCl3): 165.6, 140.7, 134.6, 133.2, 132.6,
130.4, 129.8, 128.6, 128.5, 128.2, 127.2, 118.5, 117.7, 108.9, 79.4,
78.5, 77.2, 59.7, 53.2, 28.2, 25.7. Anal. calcd. for C25H29NO4: C,
73.68; H, 7.17; N, 3.44. Found: C, 73.26; H, 7.14; N, 3.25%.
1,2,4,7,8-Pentadeoxy-3-benzoyl-4-(N-benzyl)acetamido-5,6-O-
isopropylidene-D-allo-octa-1,7-dienitol (12)
(+)-Conduritol C tetraacetate (10)
Compound 8 (81 mg, 0.24 mmol) was dissolved in deoxygenated
CH2Cl2 (5 mL) and Grubbs’ 2nd-generation catalyst (10 mg,
0.012 mmol) was added. The solution was stirred under N2
for 1.5 h at 40 C. Activated carbon (200 mg) was then added
and the reaction was stirred for an additional 18 h at room
temperature. The mixture was filtered through Celite, dried
Aminodiene 11 (446 mg, 1.10 mmol) was dissolved in CH2Cl2
(20 mL), and Ac2O (0.41 mL, 4.38 mmol), Et3N (0.92 mL,
6.57 mmol) and DMAP (13 mg, 0.11 mmol) were added. The
solution was stirred at 40 ◦C for 2 days. The resulting orange
solution was diluted with CH2Cl2 (30 mL), washed with 1 M
AcOH (2 × 10 mL) and H2O (10 mL), dried, and absorbed onto
◦
O r g . B i o m o l . C h e m . , 2 0 0 5 , 3 , 4 1 2 4 – 4 1 2 8
4 1 2 7