1216
W.Lu et al./ Carbohydrate Research 340 (2005) 1213–1217
washed with water. Purification by chromatography
(1:5:1, CHCl3–hexane–Et2O) gave 2 (3.53 g, 78%) as a
(500 mg, 0.80 mmol), followed by Ac2O (5 mL, freshly
distilled), and the solution was cooled to ꢀ78 ꢁC (CO2/
acetone bath). To this was added a freshly prepared
solution of 1:1 TMSOTf–CH2Cl2 (0.320 mL) dropwise
over a period of 3 min, and the solution was stirred at
ꢀ78 ꢁC for 60 min under Ar. The cold bath was re-
moved, and a 1:1 mixture of satd NaHCO3–CH2Cl2
(50 mL) was immediately added with vigorous stirring,
and the mixture was stirred for 30 min. The organic
layer was separated, and the aq layer was extracted with
CH2Cl2 (2 · 30 mL). The organic layers were combined,
washed with water, dried (Na2SO4) and then concen-
trated first on a rotary evaporator under aspirator pres-
sure and then using a high-vacuum rotary evaporator to
remove the remaining Ac2O. The resulting clear, color-
less oil (crude 5) became a white solid after being sub-
jected to high vacuum overnight. To a suspension of
this crude material in dry MeOH (5 mL) was added
0.5 mL of a 0.3 M solution of NaOMe in MeOH. The
reaction was stirred for 6 h and became clear. The reac-
tion was diluted with ether (70 mL) and washed with
water and satd brine, dried (Na2SO4), and concentrated.
The residue was purified by flash chromatography (sil-
ica, 20% EtOAc–hexane to 30% EtOAc–hexane) to give
6 (318 mg, 75%) as a colorless oil that became a white
solid after being subjected to high vacuum overnight.
22
D
white solid: mp 114–115 ꢁC, lit12 116–117 ꢁC; ½aꢁ
20
D
1
ꢀ2.8 (c 1.0 CHCl3), lit.12 ½aꢁ ꢀ2.9; H NMR: d 2.05
(s, 3H, COCH3) 3.48–3.61 (m, 3H, H-2, H-4, H-5),
3.67 (overlapping dd, J3,4 8.3, J3,2 8.3 Hz, 1H, H-3),
4.24 (dd, J5,6a 4.3, J6a,6b 11.7 Hz, 1H, H-6a), 4.35 (d,
J6a,6b 11.7 Hz, 1H, H-6b), 4.49–4.84 (m, 6H), 4.92–5.02
(m, 3H), 7.21–7.40 (m, 20H); 13C NMR: d 20.8 (CH3),
63.0 (C-6), 71.0 (CH2), 72.7 (C-4), 74.7 (CH2), 74.8
(CH2), 75.6 (CH2), 77.2 (C-2), 82.0 (C-5), 84.5 (C-3),
102.2 (C-1), 127.6, 127.7, 127.8, 127.9, 128.0, 128.2,
128.3, 128.4, 137.0, 137.6, 138.1, 138.3, 170.6. LREIMS:
m/z (relative intensity) 491.2 (MꢀCH2Ph, 8), 383.1 (5),
253.1 (52), 181.1 (20), 91.0 (100); HREIMS: Calcd for
C29H31O7, m/z 491.2059; found, m/z 491.2059.
1.1.3. Preparation of benzyl 2,3,4-tri-O-benzyl-b-D-gluco-
pyranoside (3). A suspension of glucosyl 6-acetate 2
(3.53 g, 6.05 mmol) in 50 mL of 0.025 M NaOMe in
MeOH was stirred for 5 h. The reaction mixture was
then poured into 200 mL of ice water and stirred for
30 min. The resulting precipitate was filtered and
washed with satd NaHCO3 and water, and then it was
dried under high vacuum to give spectroscopically pure
3 (3.18 g, 97%) as a white powder. Recrystallization
from EtOH gave white needles: mp 102–104 ꢁC, lit.12
22
1
Mp 64–66 ꢁC; ½aꢁ ꢀ64.7 (c 1.0, CHCl3), H NMR: d
D
22
D
20
D
104–106 ꢁC; ½aꢁ ꢀ8.8 (c 1.0, CHCl3), lit.12 ½aꢁ ꢀ9.2;
3.32 (ddd, J5,6a 2.6, J5,6b 5.4, J5,4 8.1 Hz, 1H, H-5),
3.51 (dd, J3,2 5.4, J3,4 9.4 Hz, 1H, H-3), 3.78 (dd, J6a,6b
11.8 Hz, 1H, H-6b), 3.93 (m, 3H, H-6a, H-4, H-2),
4.42–4.64 (m, 5H), 4.84–4.99 (m, 4H), 7.23–7.46 (m,
20H); 13C NMR: d 62.2 (C-6), 70.9 (C-4), 71.3 (CH2),
73.8 (CH2), 73.9 (C-2), 74.6 (CH2), 74.9 (CH2), 75.8
(C-5), 82.1 (C-3), 100.3 (C-1), 127.2, 127.3, 127.4,
127.5, 127.54, 127.8, 127.9, 128.1, 137.2, 127.9, 138.1,
138.4; LREIMS: m/z (relative intensity) 449.2
(MꢀCH2Ph, 3), 341.1 (13), 253.1 (52), 181.1 (15), 91.0
(100); HREIMS: Calcd for C27H29O6, m/z 449.1964;
found, m/z 449.1964.
1H and 13C NMR spectra were in agreement with those
published.1d Alternatively, compound 3 can be prepared
by subjecting crude 2 (after precipitation and drying) to
NaOMe–MeOH. Using this approach, pure 3 was ob-
tained in an 78–80% yield (from 1) after chromatogra-
phy (silica, 20% EtOAc–hexane to 30% EtOAc–hexane).
1.1.4. Preparation of benzyl 2,3,4,6-tetra-O-benzyl-b-D-
mannopyranoside (4). Compound 4 was prepared in
60–63% yield using the KOH method described above
for glucose, except the product was recrystallized in
5% EtOAc–hexane. White solid: mp 69–71 ꢁC, lit.6 70–
22
D
20
D
1
71 ꢁC; ½aꢁ ꢀ65.2 (c 1.0, CHCl3), lit.6 ½aꢁ ꢀ69.6; H
Acknowledgments
NMR: d 3.42–3.49 (m, 2H), 3.73–3.91 (m, 4H), 4.40–
4.63 (m, 7H), 4.85–5.01 (m, 4H), 7.14–7.50 (m, 25H);
13C NMR: d 69.7, 70.7, 71.4, 73.4, 73.8, 74.0, 75.0,
75.9, 82.4, 100.4 (C-1), 127.3, 127.4, 127.5, 127.6,
127.62, 127.7, 127.8, 127.9, 128.0, 128.3, 137.5, 138.1,
138.3, 138.4, 138.7. LREIMS: m/z (relative intensity)
539.2 (MꢀCH2Ph, 5), 431.2 (12), 253.1 (55), 181.1
(23), 91.0 (100); HREIMS: Calcd for C34H35O6, m/z
539.2433; found, m/z 539.2434.
We thank the Natural Sciences and Engineering Re-
search Council of Canada (NSERC) for financial sup-
port. L.N. thanks the Government of Iran for a
Scholarship. S.D.T. also thanks the Government of On-
tario for a PremiereÕs Research Excellence (PREA)
Award.
Supplementarydata
1.2. Benzyl 2,3,4-tri-O-benzyl-b-D-mannopyranoside (6)
Supplementary data associated with this article can be
A 100 mL round bottom flask was flame dried and then
flushed with Ar. To this was added carbohydrate 4