(0.0994g, 0.130 mmol) were dissolved inanhydrous DCM(15 mL).
The stereochemistry of the anomeric linkages was confirmed
by measurement of the JH1-C1 coupling constants from C-coupled
HSQC experiments: JC(1a)-H(1a) 166 Hz; JC(1b)-H(1b) 162 Hz; JC(1c)-H(1c)
173 Hz; JC(1c¢)-H(1c¢) 171 Hz; JC(1d¢)-H(1d¢) 165 Hz; JC(1d)-H(1d) 166 Hz.
The solution was transferred via syringe to a flame-dried round-
˚
bottom flask containing activated 3 A molecular sieves (0.5 g) and
NIS (0.0336 g, 0.149 mmol) added. The solution was cooled to
0 ◦C and stirred under an atmosphere of argon for 10 min. After
this time silver trifluoromethanesulfonate (0.0333 g, 0.130 mmol)
was added and the reaction mixture stirred at 0 ◦C. After 1 h, t.l.c.
(petrol : ethyl acetate, 1 : 2) indicated formation of a major product
(Rf 0.20) and complete consumption of donor 6b (Rf 0.55). The
reaction mixture was diluted with DCM (15 mL), filtered through
p-Methoxyphenyl 3,4,6-tri-O-acetyl-2-deoxy-2-phthalimido-b-
D-glucopyranosyl-(1→2)-3,4,6-tri-O-acetyl-a-D-mannopyranosyl-
(1→6)-2,4-di-O-acetyl-[3,4,6-tri-O-acetyl-2-deoxy-2-phthalimido-
b-D-glucopyranosyl-(1→2)-3,4,6-tri-O-acetyl-a-D-mannopyra-
nosyl-(1→3)]-b-D-mannopyranosyl-(1→4)-3,6-di-O-acetyl-2-
deoxy-2-phthalimido-b-D-glucopyranoside (9b). Benzyl ether 9a
(0.136 g, 0.0591 mmol) was dissolved in methanol (2 mL) and THF
(2 mL). The solution was degassed and put under an atmosphere of
nitrogen. Palladium hydroxide (0.040 g) was added and the mixture
stirred at rt under an atmosphere of hydrogen. After 10 days,
t.l.c. (petrol : ethyl acetate, 1 : 4) indicated complete consumption
of starting material (Rf 0.35) and formation of a single product
R
Celiteꢀ, washed with sodium thiosulfate (2 ¥ 5 mL of a 10% w/v
solution) and sodium hydrogen carbonate (5 mL of a saturated
solution), dried (MgSO4), filtered and concentrated in vacuo. The
residue was purified by flash column chromatography (petrol :
ethyl acetate, 1 : 2 then toluene : ethyl acetate, 2 : 3) to afford
hexasaccharide 9a (0.182 g, 79%, 89% based on recovered acceptor
8) as a white, glassy solid, [a]D25 + 2.6 (c, 0.9 in CHCl3); nmax (KBr
R
-1
disk) 1748, 1717 (s, C O) cm ; dH (500 MHz, CDCl3) 1.84, 1.85,
(Rf 0.25). The reaction mixture was filtered through Celiteꢀ, the
=
R
1.87, 1.90, 1.96, 1.98, 2.01, 2.01, 2.03, 2.03, 2.07, 2.10, 2.13 (39H,
13 ¥ s, 13 ¥ CH3), 3.14–3.17 (2H, m, H-5b, H-5d¢), 3.46–3.52 (2H,
m, H-3b, H-6b), 3.54–3.59 (3H, m, H-4b, H-5a, H-5d, H-6c¢), 3.61–
3.66 (2H, m, H-6¢b, H-6d), 3.67–3.71 (1H, m, H-5c¢), 3.68 (3H, s,
OCH3), 3.74–3.81 (5H, m, H-6a, H-6¢a, H-6c, H-6¢c, H-6¢c¢), 3.84–
3.87 (2H, m, H-5c, H-6d¢), 3.99–4.02 (2H, m, H-2c, H-6¢d), 4.11
(1H, dd, J3,4 9.4 Hz, J4,5 7.4 Hz, H-4a), 4.16–4.20 (3H, m, H-2c¢,
H-3a, H-6¢d¢), 4.23 (1H, dd, J1,2 8.3 Hz, J2,3 10.4 Hz, H-2a), 4.28
(1H, dd, J1,2 8.4 Hz, J2,3 10.8 Hz, H-2d), 4.35 (1H, dd, J1,2 8.5 Hz,
J2,3 10.8 Hz, H-2d¢), 4.39, 4.84 (2H, ABq, J 12.0 Hz, PhCH2),
4.44 (1H, s, H-1c¢), 4.45, 4.67 (2H, ABq, J 12.8 Hz, PhCH2), 4.50
(1H, s, H-1b), 4.58, 4.91 (2H, ABq, J 12.9 Hz, PhCH2), 4.83-4.86
(1H, m, H-3c), 4.95 (1H, s, H-1c), 4.97-5.00 (2H, m, H-1d, H-4d),
5.03 (1H, dd, J2,3 3.1 Hz, J3,4 10.0 Hz, H-3c¢), 5.05-5.09 (2H, m, H-
4c, H-4d¢), 5.11-5.13 (1H, m, H-2b), 5.13 (1H, s, H-1d¢), 5.28 (1H,
at, J 10.0 Hz, H-4c¢), 5.47 (1H, dd, J3,4 9.1 Hz, H-3d), 5.54 (1H,
d, J1,2 8.0 Hz, H-1a), 5.56 (1H, dd, J3,4 9.1 Hz, H-3d¢), 6.65–6.79
(5H, m, 5 ¥ Ar-H), 7.03–7.05 (2H, m, 2 ¥ Ar-H), 7.33–7.54 (12H,
m, 12 ¥ Ar-H), 7.63–7.87 (12H, m, 12 ¥ Ar-H); dC (125.8 MHz,
CDCl3) 20.5, 20.6, 20.6, 20.6, 20.7, 20.8, 20.8, 20.9, 20.9, 21.1,
21.2 (11 ¥ q, 13 ¥ CH3), 54.3 (d, C-2d), 54.5 (d, C-2d¢), 55.6 (d, C-
2a), 55.7 (q, OCH3), 61.5 (t, C-6d), 61.7 (t, C-6d¢), 62.4 (t, C-6c¢),
62.6 (t, C-6c), 65.3 (d, C-4c¢), 65.5 (d, C-4c), 66.8 (t, C-6b), 67.9
(t, C-6a), 68.4 (d, C-4d), 68.6 (d, C-4d¢), 68.7 (d, C-5c¢), 69.2 (d,
C-5c), 69.7 (d, C-3c), 70.4 (d, C-3c¢), 70.7 (d, C-3d), 70.8 (d, C-
3d¢), 71.1 (d, C-2b), 71.4 (d, C-5d), 71.6 (d, C-5d¢), 73.4 (d, C-2c),
73.6 (d, C-5b), 73.7, 74.2, 74.6 (3 ¥ t, 3 ¥ PhCH2), 74.5 (d, C-2c¢),
74.7 (d, C-5a), 75.0 (d, C-4b), 76.2 (d, C-3a), 78.2 (d, C-4a), 79.9
(d, C-3b), 96.4 (d, C-1d), 97.3 (d, C-1c¢), 97.3 (d, C-1d¢), 97.5 (d,
C-1a), 97.8 (d, C-1b), 99.8 (d, C-1c), 114.5, 118.4, 123.6, 125.9,
127.6, 128.1, 128.2, 128.5, 128.9, 129.0, 129.0, 133.5, 134.0, 134.4,
134.5, 134.7 (16 ¥ d, 31 ¥ Ar-C), 131.6, 138.1, 138.3, 138.4, 150.9,
Celiteꢀ washed with methanol (2 ¥ 10 mL) and ethyl acetate (2 ¥
10 mL) and the combined organic washings were concentrated
in vacuo. The residue was dissolved in pyridine (5 mL), acetic
anhydride (2 mL) was added, and the reaction mixture was stirred
under an atmosphere of argon. After 16 h, t.l.c. (1 : 4 petrol :
ethyl acetate) indicated formation of a single product (Rf 0.30) and
complete consumption of triol intermediate (Rf 0.25). The reaction
mixture was concentrated in vacuo and the residue was co-distilled
with toluene 4 times. The residue was purified by flash column
chromatography (1 : 4 petrol : ethyl acetate) to afford peracetate
9b (0.110 g, 86% over two steps) as a white foam, [a]D20–7.2 (c,
-1
=
0.25 in CHCl3); nmax (KBr disk) 1749, 1718, 1636 (s, C O) cm ;
dH (500 MHz, CDCl3) 1.86, 1.88, 1.96, 1.98, 2.00, 2.02, 2.03, 2.04,
2.05, 2.07, 2.09, 2.11, 2.12, 2.13 (48H, 14 ¥ s, 16 ¥ CH3), 3.37 (1H,
dd, J 3.6 Hz, J 10.1 Hz, H-6b), 3.44–3.49 (1H, m, H-5b), 3.64
(1H, dd, J 6.3 Hz, J 10.2 Hz, H-6¢b), 3.70 (3H, s, OCH3), 3.74–
3.88 (10H, m, H-3b, H-5a, H-5c, H-5c¢, H-5d, H-6a, H-6c, H-6c¢,
H-6¢c, H-6‘c’), 3.89–3.91 (1H, m, H-5d¢), 3.93–3.97 (2H, m, H-4a,
H-6¢a), 4.05 (1H, d, J 2.4 Hz, H-2c), 4.06–4.10 (2H, m, H-6d, H-
6d¢), 4.24 (1H, d, J 2.4 Hz, H-2c¢), 4.31–4.47 (6H, m, H-1c¢, H-2a,
H-2d, H-2d¢, H-6¢d, H-6¢d¢), 4.58 (1H, s, H-1b), 4.62 (1h, s, H-1c),
4.77 (1H, dd, J2,3 3.3 Hz, J3,4 10.3 Hz, H-3c), 4.95–4.99 (2H, m,
H-3c¢, H-4b), 5.12–5.19 (3H, m, H-4c, H-4d, H-4d¢), 5.24 (1H, d,
J 3.4 Hz, H-2b), 5.27 (1H, at, J 10.1 Hz, H-4c¢), 5.28 (1H, d, J1,2
8.9 Hz, H-1d), 5.44 (1H, d, J1,2 8.5 Hz, H-1d¢), 5.67 (1H, dd, J2,3
10.8 Hz, J3,4 9.2 Hz, H-3d), 5.76 (1H, d, J1,2 8.4 Hz, H-1a), 5.77
(1H, dd, J2,3 10.8 Hz, J3,4 9.1 Hz, H-3d¢), 5.81 (1H, dd, J2,3 10.8 Hz,
J3,4 9.1 Hz, H-3a), 6.70–6.73 (2H, m, 2 ¥ Ar-H), 6.76–6.81 (2H,
m, 2 ¥ Ar-H), 7.70–7.86 (12H, m, 12 ¥ Ar-H); dC (125.8 MHz,
CDCl3) 20.6, 20.6, 20.7, 20.7, 20.8, 20.9, 20.9, 21.0, 21.0, 21.0,
21.2, 21.3, 22.8 (13 ¥ q, 16 ¥ CH3), 54.5 (d, C-2d¢), 54.5 (d, C-2a),
54.6 (d, C-2d), 55.7 (q, OCH3), 62.0 (t, C-6d), 62.2 (t, C-6d¢), 62.3
(t, C-6a), 62.4 (m, C-6c, C-6c¢), 65.2 (d, C-4c), 65.3 (d, C-4c¢), 67.9
(t, C-6b), 68.7 (d, C-4d), 68.9 (d, C-4d¢), 68.9 (m, C-5c, C-5c¢), 69.4
(d, C-2b), 69.4 (d, C-3c), 69.6 (d, C-4b), 70.0 (d, C-3a), 70.3 (d,
C-3c¢), 70.8 (m, C-3d, C-3d¢), 72.1 (d, C-5d¢), 72.4 (d, C-5d), 72.7
(d, C-5a), 73.0 (d, C-5b), 74.0 (d, C-2c¢), 74.2 (d, C-3b), 74.3 (d,
C-2c), 74.5 (d, C-4a), 96.9 (d, C-1b), 97.3 (m, C-1d, C-1d¢), 97.4
(d, C-1a), 97.7 (d, C-1c¢), 98.6 (d, C-1c), 114.6, 118.6, 123.7, 123.9,
128.9, 131.4 (6 ¥ d, 16 ¥ Ar-C), 134.5, 134.7, 151.0, 155.8 (4 ¥ s, 8 ¥
Ar-C), 169.5, 169.5, 169.7, 170.0, 170.3, 170.4, 170.4, 170.5, 170.6,
155.4 (6 ¥ s, 11 ¥ Ar-C), 169.4, 169.4, 169.6, 169.8, 170.3, 170.3,
+
=
170.4, 170.7, 170.7, 170.9 (10 ¥ s, 19 ¥ C O); m/z (ESI ) species
observed (MNa+), (MNH4 ); (MNa+) peaks observed: 2322.49
+
(61), 2323.49 (81), 2324.49 (49), 2325.50 (18), 2326.50 (6), peaks
calculated: 2322.70 (78), 2323.70 (100), 2324.71 (71), 2325.71 (36),
+
2326.71 (14), 2327.72 (5), 2328.72 (1.0); (MNH4 ) peaks observed:
2317.53 (70), 2318.54 (100), 2319.54 (62), 2320.54 (24), 2321.54
(8), peaks calculated: 2317.75 (78), 2318.75 (100), 2319.75 (71),
2320.76 (36), 2321.76 (14), 2322.76 (5), 2323.76 (1%).
This journal is
The Royal Society of Chemistry 2009
Org. Biomol. Chem., 2009, 7, 3128–3140 | 3137
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