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Organic & Biomolecular Chemistry
separation of the crystallised exo-isomer 3 in Table 1 was con- at −40 °C for 4 h, the reaction mixture was quenched with
centrated under reduced pressure. The residue was subjected TBAF (1 M solution in THF, 1 mL) and immediately filtered
to flash column chromatography (ethyl acetate–hexanes = 1/15) through Celite. The filtrate was washed successively with water
to obtain the pure endo-isomer 4 that was used to acquire and brine, dried over MgSO4 and concentrated under reduced
characterisation data. [α]2D4 +169.4 (c 0.59 in CHCl3); IR (thin pressure. The residue was purified by flash column chromato-
film) ν/cm−1 3044, 2948, 1500, 1448, 1373, 1106, 1105, 823, graphy (ethyl acetate–hexanes = 1/2) to furnish 2-alcohol 6
749, 695; 1H NMR (400 MHz, CDCl3) δ 7.54–7.47 (4 H, m, (272 mg, 72%). [α]D23 +230.4 (c 3.60 in CHCl3); IR (thin film)
Ar-H), 7.41–7.31 (8 H, m, Ar-H), 7.13 (2 H, d, J 7.9, Ar-H), 5.97 ν/cm−1 3460, 3021, 2924, 1732, 1493, 1372, 1234, 1098, 1028,
(1 H, s, CHPh), 5.84 (1 H, d, J 0.5 Hz, 1-H), 5.50 (1 H, s, CHPh), 755; 1H NMR (600 MHz, CDCl3) δ 7.46 (2 H, d, J 7.9, Ar-H),
4.52 (1 H, dd, J 7.5, 6.2, 3-H), 4.48 (1 H, dd, J 6.2, 0.5, 2-H), 7.37–7.34 (5 H, m, Ar-H), 7.11 (2 H, d, J = 7.9 Hz, Ar-H), 5.54
4.30–4.21 (1 H, m, 5-H), 4.17 (1 H, dd, J 10.3, 5.2, 6-Ha), 3.79 (1 (1 H, s, CHPh), 5.45 (1 H, s, 1-H), 5.34 (1 H, dd, J 10.2, 3.2,
H, dd, J 9.9, 7.5, 4-H), 3.68 (1 H, t, J 10.3, 6-Hb), 2.33 (3 H, s, 3-H), 4.45 (ddd, J 10.0, 10.0, 4.8, 5-H), 4.39 (1 H, d, J 1.8, 2-H),
CH3); 13C NMR (100 MHz, CDCl3) 138.4 (C), 137.1 (C), 136.9 4.22 (1 H, dd, J 4.8, 10.2, 4-H), 4.16 (1 H, t, J = 10.0 Hz, 6-Ha),
(C), 133.1 (CH), 129.9 (CH), 129.4 (CH), 129.0 (CH), 128.6 (C), 3.84 (1 H, t, J 10.0, 6-Hb), 2.66 (1 H, br s, 2-OH), 2.32 (3 H, s,
128.4 (CH), 128.1 (CH), 126.4 (CH), 126.2 (CH), 104.0 (CH), Ar-CH3), 2.12 (3 H, s, COCH3); 13C NMR (150 MHz, CDCl3) δ
101.7 (CH), 84.4 (CH), 80.7 (CH), 78.5 (CH), 73.9 (CH), 68.5 169.9 (C), 138.1 (C), 137.1 (C), 132.7 (CH), 132.4 (CH), 129.9
(CH2), 61.6 (CH), 21.1 (CH3); HRMS (FAB, [M + Na]+) m/z calcd (CH), 129.3 (C), 129.1 (CH), 128.4 (CH), 128.2 (CH), 126.2 (CH),
for C27H26O5NaS 485.1399, found 485.1400.
101.9 (CH), 88.7 (CH), 76.2 (CH), 71.0 (CH), 70.7 (CH), 68.4
4-Methylphenyl 2,3-di-O-acetyl-4,6-O-benzylidene-1-thio-α-D- (CH2), 65.0 (CH), 21.1 (CH3), 21.0 (CH3); HRMS (ESI, [M + Na]+)
mannopyranoside (5). A mixture of compound 1 (200 mg, m/z calcd for C22H24O6SNa 439.1191, found 439.1187.
0.35 mmol), PhCHO (37 μL, 0.37 mmol) and freshly dried 3 Å
molecular sieves (200 mg) in CH2Cl2 (2.0 mL) was stirred at pyranoside (7). A mixture of compound
4-Methylphenyl 2,3-di-O-acetyl-4-O-benzyl-1-thio-α-D-manno-
(250 mg,
1
−78 °C under an N2 atmosphere. TMSOTf (6.3 μL, 0.035 mmol) 0.44 mmol), PhCHO (46 μL, 0.46 mmol) and freshly dried 3 Å
was added to the solution, and the mixture was kept stirring at molecular sieves (250 mg) in CH2Cl2 (2.5 mL) was stirred at
the same temperature for 1.5 h. Then, Ac2O (79 μL, −78 °C under an N2 atmosphere. TMSOTf (8 μL, 0.044 mmol)
0.84 mmol) and TMSOTf (18.9 μL, 0.104 mmol) were sequen- was added to the solution, and the mixture was kept stirring at
tially added to the reaction mixture, and the reaction bottle the same temperature for 1.5 h. Ac2O (99 μL, 1.05 mmol) and
was shifted to an ice-bath. The reaction mixture was stirred for TMSOTf (24 μL, 0.13 mmol) were sequentially added to the
1 h at 0 °C, quenched with MeOH and filtered through Celite. reaction solution, and the resulting mixture was stirred for
The filtrate was concentrated under reduced pressure to get a another 1 h at 0 °C. BH3·THF (1 M solution in THF, 1.3 mL,
residue, which was purified by flash column chromatography 1.3 mmol) was added to the reaction mixture, followed by
(ethyl acetate–hexanes = 1/3) to obtain the diacetate 5 (123 mg, addition of TMSOTf (39.4 μL, 0.22 mmol), and the solution
77%). [α]2D4 +158.9 (c 3.2 in CHCl3); IR (thin film) ν/cm−1 3036, was kept stirring for another 5 h at 0 °C. Et3N was added, fol-
2933, 1750, 1493, 1371, 1237, 1101, 966; 1H NMR (400 MHz, lowed by slow addition of MeOH at 0 °C. The mixture was fil-
CDCl3) δ 7.48–7.46 (2 H, m, Ar-H), 7.38–7.34 (5 H, m, Ar-H), tered through a pad of Celite, and the filtrate was concentrated
7.12 (2 H, d, J 8, Ar-H), 5.59–5.58 (2 H, m, 1-H, CHPh), 5.40 under reduced pressure. The residue was partitioned in ethyl
(1 H, dd, J 9.6, 3.6, 3-H), 5.34 (1 H, d, J 1.2, 2-H), 4.45 (1 H, acetate and water and the combined organic layer was washed
ddd, J 9.6, 5.2, 4.8, 5-H), 4.24 (1 H, dd, J 10.4, 4.8, 6-Ha), 4.10 with brine, dried over MgSO4, filtered, concentrated under
(1 H, t, J 9.6, 4-H), 3.85 (1 H, t, J 10.4, 6-Hb), 2.32 (3 H, s, reduced pressure, and purified by flash column chromato-
Ar-CH3), 2.14 (3 H, s, COCH3), 2.02 (s, 3 H, CH3); 13C NMR graphy (ethyl acetate–hexanes = 1/2) to acquire the 6-alcohol 7
(100 MHz, CDCl3) δ 169.8 (C × 2), 138.5 (C), 137.0 (C), 132.9 (110 mg, 75%). [α]2D6 +63.7 (c 1.4 in CHCl3); IR (thin film)
(CH × 2), 130.0 (CH × 2), 129.2 (CH), 128.9 (C), 128.3 (CH × 2), ν/cm−1 3491, 2919, 2850, 1749, 1239, 1088; 1H NMR (400 MHz,
126.3 (CH × 2), 102.0 (CH), 87.2 (CH), 76.3 (CH), 71.5 (CH), CDCl3) δ 7.36–7.26 (7 H, m, Ar-H), 7.10 (2 H, d, J 7.6, Ar-H),
68.5 (CH), 68.4 (CH2), 65.1 (CH), 21.2 (CH3), 20.9 (CH3), 20.8 5.48 (1 H, dd, J 3.4, 2.0, 2-H), 5.34–5.31 (2 H, m, 3-H, 1-H), 4.71
(CH3); HRMS (ESI, [M + Na]+) m/z calcd for C24H26O7SNa (1 H, d, J 11.6, CH2Ph), 4.65 (1 H, d, J 11.6, CH2Ph), 4.25 (1 H,
481.1297, found 481.1290.
4-Methylphenyl 3-O-acetyl-4,6-O-benzylidene-1-thio-α-D-man- 2), 2.31 (3 H, s, Ar-CH3), 2.10 (3 H, s, 3 H, COCH3), 1.97 (3 H, s,
nopyranoside (6). A mixture of compound
(515 mg, COCH3); 13C NMR (100 MHz, CDCl3) δ 169.9 (C), 169.8 (C),
dt, J 9.6, 3.2, 5-H), 3.97 (1 H, t, J 9.6, 4-H), 3.81 (2 H, br s, 6-H ×
1
0.90 mmol), PhCHO (37 μL, 0.37 mmol) and freshly dried 3 Å 138.4 (C), 137.9 (C), 132.9 (CH), 130.0 (CH), 129.1 (C), 128.5
molecular sieves (515 mg) in CH2Cl2 (10.0 mL) was stirred at (CH), 127.9 (CH), 127.7 (CH), 86.2 (CH), 75.0 (CH2), 72.9 (CH ×
−78 °C under an N2 atmosphere. TMSOTf (16 μL, 0.09 mmol) 2), 72.0 (CH), 71.4 (CH), 61.6 (CH2), 21.1 (CH3), 20.8 (CH3 × 2);
was added to the solution, and the mixture was kept stirring at HRMS (FAB, M+) m/z calcd for C17H21O7 422.1729, found
the same temperature for 1.5 h. Ac2O (102 μL, 1.08 mmol) and 422.1721.
TMSOTf (180 μL, 0.18 mmol) were sequentially added to the
reaction solution, and the stirring continued with gradually pyranoside (8). A mixture of compound
warming up the reaction temperature to −40 °C. After stirring 0.35 mmol), PhCHO (37 μL, 0.37 mmol) and freshly dried 3 Å
4-Methylphenyl 2,3-di-O-acetyl-6-O-benzyl-1-thio-α-D-manno-
1
(200 mg,
2610 | Org. Biomol. Chem., 2013, 11, 2605–2612
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