Molecules 2016, 21, 1602
10 of 14
150 mL of EtOAc was added. After two phases were separated, aqueous phase was extracted by EtOAc
(120 mL 2). Combined organic phases were dried over Na2SO4, filtered and concentrated to give
×
crude uronic acid (7 g) directly for methylation. The above crude uronic acid (7 g,) was dissolved in
dry DMF (76 mL). Solid NaHCO3 (6.56 g, 78.10 mmol, 10 eq) and iodomethane (4.86 mL, 78.10 mmol,
10 eq) were added under a nitrogen atmosphere and stirred at RT overnight. The reaction mixture was
diluted with EtOAc (250 mL) and H2O (120 mL). After the two phases were separated, the aqueous
phase was extracted with EtOAc (100 mL
1 M Na2S2O3 (80 mL 1) and brine (80 mL
flash chromatography (hexane–EtOAc 6:4) to give compound 14 (4.13 g, yield: 81.8% of 4 steps) as
a crystalline glass. 1H-NMR (500 MHz, CDCl3)
: 7.39–7.28 (m, 15H, 3Ph), 5.52 (s, 1H, H-1), 5.01,
×
1). The combined organic phases were washed with
×
×
1). The crude product (6.16 g) was submitted to
δ
4.74 (AB system, J = 11.0 Hz, 2H, CH2Ph), 4.91, 4.83 (AB system, J = 11.5 Hz, 2H, CH2Ph), 04.67, 4.64
(AB system, J = 11.5 Hz, 2H, CH2Ph), 4.60 (d, J = 5.0 Hz, 1H, H-5), 4.57 (d, J = 7.5 Hz, 1H, H-1 ), 4.05 (d,
J = 7.0 Hz, 1H, H-6), 3.95 (t, J = 1.5 Hz, 1H, H-3), 3.90 (t, J = 9.5 Hz, 1H, H-40), 3.79–3.75 (m, 1H, H-6),
3.78 (s, 1H, H-4), 3.78 (t, J = 10.0 Hz, 1H, H-50), 3.76 (s, 3H, CH3O), 3.54–3.52 (m, 1H, H-20), 3.51–3.49
(m, 1H, H-30), 3.21 (s, 1H, H-2). 13C-NMR (CDCl3)
δ: 169.39 (CO), 138.44,138.22,137.60 (Ph), 128.52,
128.49, 128.42, 128.38, 127.92, 127.62 (Ph), 103.91 (C-10), 100.71 (C-1), 83.02 (C-30), 80.78 (C-20), 77.85
(C-3), 75.42 (C-4), 75.23, 74.42 (CH2Ph), 74.15 (C-5), 72.63 (C-50), 71.56 (C-40), 64.97 (C-6), 59.84 (C-2),
52.66 (CH3O). ESIMS m/z: [M + Na]+: 670.1001, [M + K]+: 686.068. Calculated for C34H37N3O10 + Na:
670.2371, C34H37N3O10K: 686.2111.
(6-O-Acetyl-2-azido-3-O-benzyl-2-deoxy-4-O-methyl-
D-glucopyranosyluronate)-O-(1 4)-1,6-anhydro-2-azido-3-O-benzyl-2-deoxy-
Compound 14 (1.679 g, 2.44 mmol), (1.45 g, 2.928 mmol, 1.3 eq) and 4 Å molecular sieves (1.6 g)
were stirred in dry DCM at RT for 1 h under nitrogen atmosphere. After cooling (
20 ◦C), TMSOTf
(0.106 mL, 0.2 eq respect to donor) in DCM (16 mL) was added dropwise over 30 min. A precipitate
formed and dissolved again. Additional compound (0.19 g, 0.3 eq) and TMSOTf (0.025 mL) were
added and after 15 min at
20 ◦C the mixture was allowed to warm up and maintained at RT for
α
-D-glucopyranosyl)-O-(1
→
4)-(methyl 2,3-di-O benzyl-
β-
→
β-D-glucopyranose (15).
7
−
7
−
1 h. TEA was added till pH 7. After filtration and evaporation purification was performed by flash
chromatography (CH2Cl2–EtOAc, 95:5 to 92:8) to give 15 (1.387 g, 58%) and its beta anomer (0.465 g,
1
19.5%). H-NMR (500 MHz, CDCl3) (
α
anomer)
δ
: 7.4–7.26 (m, 20H, arom. Ph), 5.54 (d, J = 3.75 Hz,
1H, H-100), 5.50 (s, 1H, H-1), 5.04, 4.70 (AB system, J = 10.8 Hz, 2H, CH2Ph), 5.03, 4.82 (AB system,
J = 10.8 Hz, 2H, CH2Ph), 4.85 (s, 2H, CH2Ph), 4.63, 4.60 (AB system, J = 10.8 Hz, 2H, CH2Ph), 4.61 (d,
0
00
00
0
J = 7.7 Hz, 1H, H-1 ), 4.59 (s, 1H, H-5), 4.26 (br s, 2H, H-6 a + H-6 b), 4.12 (t, J = 9.1 Hz, 1H, H-4 ), 4.07
(d, J = 7.4 Hz, H-6a), 3.92 (d, J = 9.6 Hz, 1H, H-50), 3.88 (br s, 1H, H-300), 3.79–3.74 (m, 4H, H-3 + H-4 +
0
0
00
H-3 + H-6b), 3.74 (s, 3H, Me ester), 3.63 (t, J = 7.7 Hz, 1H, H-2 ), 3.50 (s, 3H, OMe), 3.48 (br s, 1H, H-5 ),
3.22–3.19 (m, 3H, H-2 + H-20 + H-400), 2.10 (s, 3H, CH3CO). 13C-NMR (CDCl3) (
α anomer) δ: 170.7
(C=O, acetyl), 168.3 (C=O, Me ester), 138.1–137.4 (Bn), 128.1–127.2 (Bn), 103.3 (C-10), 100.7 (C-1), 97.5
(C-100), 83.8 (C-30), 81.4 (C-20), 80.0 (C-400), 79.5 (C-4), 77.5 (C-300), 76.7 (C-3), 75.1 (C-5), 74.3 (C-40), 74.2
(C-50), 75.3–74.2 (CH2, Bn), 72.7 (CH2, Bn), 69.7 (C-500), 65.0 (C-6), 63.0 (C-200), 62.3 (C-600), 60.8 (OMe),
59.9 (C-2), 52.7 (CH3, Me ester), 20.8 (CH3CO). ESIMS m/z: [M + Na]+: 1003.1659, [M + K]+: 1019.1354
1
calculated for C50H56N6O15Na: 1003.3696, C50H56N6O15K: 1019.3435. H-NMR (500 MHz, CDCl3) (
β
anomer) δ: 7.37–7.24 (m, 20H, 4Ph), 5.49 (s, 1H, H-1), 4.98, 4.72 (AB system, J = 11.4 Hz, 2H, CH2Ph),
4.91, 4.66 (AB system, J = 10.7 Hz, 2H, CH2Ph), 4.83, 4.78 (AB system, J = 11.3 Hz, 2H, CH2Ph), 4.64,
4.60 (AB system, J = 11.3 Hz, 2H, CH2Ph), 4.57 (d, J = 7.5 Hz, 1H, H-10), 4.57 (d, J = 7.5 Hz, 1H, H-5),
4.42 (d, J = 7.6 Hz, H-100), 4.20 (m, 1H, H-40), 4.16 8d, J = 12.5 Hz, 1H, H-600a), 4.12 (dd, J = 12.5 and 4.6
Hz, 1H, H-600b), 4.05 (d, J = 7.9 Hz, 1H, H-6a), 3.94 (d, J = 9.7 Hz, 1H, H-6a), 3.94 (d, J = 9.7 Hz, 1H,
H-500), 3.88 (br s, 1H, H-3), 3.80 (s, 3H, Me ester), 3.75–3.72 (m, 2H, H-6b + H-4), 3.61 (t, J = 9.3 Hz, 1H,
0
00
00
00
H-3 ), 3.55 (t, J = 7.9 Hz, 1H, H-2 ), 3.47 (s, 3H, OMe), 3.30–3.25 (m, 3H, H-5 + H-3 + H-2 ), 3.20–3.18
(m, 2H, H-2 + H-400), 1.92 (s, 3H, CH3CO). 13C-NMR (CDCl3) (
β anomer) δ: 170.7 (CO, acetyl), 168.2
(CO0, Me ester), 129.0–126.2 (Bn), 103.8 (C-10), 101.6 (C-100), 100.6 (C-1), 82.4 (C-300), 81.8 (C-30), 80.8
00
0
(C-2 ), 79.8 (C-4 ), 78.4 (C-4 ), 77.6 (C-3), 76.8 (C-4), 75.5 (CH2, Bn), 75.3 (CH2, Bn), 74.8 (CH2, Bn), 74.4