2.1. Synthesis
2.1.1. General Methods
Optical rotations were measured at room temperature on a Perkin-Elmer 241 automatic polarimeter (PerkinElmer, Waltham, MA, USA). TLC analysis was performed on Kieselgel 60 F
254 (Merck, Kenilworth, NJ, USA) silica gel plates with visualization by immersing in a sulphuric-acid solution (5% in EtOH, VWR International Ltd., Radnor, PA, USA) followed by heating. Column chromatography was performed on silica gel 60 (Merck 0.063–0.200 mm). Organic solutions were dried over MgSO
4 and concentrated under a vacuum.
1H- and J-modulated
13C NMR spectroscopy (
1H: 400 and 500 MHz;
13C: 100.28 and 125.76 MHz) were performed on Bruker DRX-400 and Bruker Avance II 500 spectrometers (Bruker, Billerica, MA, USA) at 25 °C. Chemical shifts are referenced to SiMe
4 or sodium 3-(trimethylsilyl)-1-propanesulfonate (DSS, d = 0.00 ppm for
1H nuclei) and to residual solvent signals (CDCl
3:
δ = 77.16 ppm, CD
3OD:
δ = 49.15 ppm for
13C nuclei). The 1D and 2D NMR spectra of the synthesized compounds you can find the
Supplementary Materials (Figures S1–S19). HRMS measurements were carried out on a maXis II UHR ESI-QTOF MS instrument (Bruker, Billerica, MA, USA) in positive ionization mode. The following parameters were applied for the electrospray ion source: capillary voltage: 3.6 kV; end plate offset: 500 V; nebulizer pressure: 0.5 bar; dry gas temperature: 200 °C; and dry gas flow rate: 4.0 L/min. Constant background correction was applied for each spectrum; the background was recorded before each sample by injecting the blank sample matrix (solvent). Na-formate calibrant was injected after each sample, which enabled internal calibration during data evaluation. Mass spectra were recorded by otofControl version 4.1 (build: 3.5, Bruker, Billerica, MA, USA) and processed by Compass DataAnalysis version 4.4 (build: 200.55.2969).
General Method A for Zemplén Deacetylation (10 and 12)
To a stirred solution of acetyl-containing derivatives (
9 [
30] and
11) (0.074 mmol) in MeOH (4.0 mL), NaOMe (25 mg) was added, and the reaction mixture was stirred for 24 h at room temperature. After 24 h, the mixture was neutralized with Amberlite IR 120 H
+ ion exchange resin (
10) or with 60% AcOH solution (3 drops) (
12), filtered, washed with MeOH and concentrated.
General Method B for Cleavage of the Benzyl Groups by Catalytic Hydrogenation (11 and 33)
To a solution of the oxidized products (28 and 32) (0.556 mmol) in EtOH (27 mL), we added 20% Pd(OH)2-C (233 mg) and Et3SiH (1.15 mL, 7.225 mmol, 13.0 equiv.), and the reaction mixture was stirred at room temperature for 24 h. The reaction mixture was filtered through a pad of Celite, washed with MeOH and concentrated under reduced pressure.
General Method C for Introduction of the Sulphate Ester Groups (13 and 15)
SO3·Et3N complex (7.098 mmol, 5.0 equiv./–OH) was added to a solution of the appropriate trisaccharide polyols (11 and 33) (0.203 mmol) in dry DMF (10.9 mL). The reaction mixture was stirred at 50 °C for 24 h. Subsequently, the reaction was quenched with NaHCO3 solution (35.49 mmol, 5.0 equiv. to the complex), and the mixture was concentrated under reduced pressure.
General Method D for Deacetylation/Debenzoylation of the Sulphated Derivatives (14 and 15)
To a solution of the appropriate sulphated trisaccharides (13 and sulphated 33) (0.040 mmol) in MeOH (1.63 mL) a solution of NaOH (3 M, 871 µL) was added at 0 °C. The reaction mixture was allowed to warm up to room temperature and stirred for 24 h. Subsequently, the reaction mixture was neutralized with AcOH solution (60%), and the mixture was concentrated under reduced pressure.
General Method E for Glycosylation Reactions Using Thioglycoside Donor (18, 25 and 30)
To a solution of the appropriate 4-OH acceptor (
17 [
33] and
19) (3.231 mmol) and monosaccharide donor (
16 [
34],
24 and
29) (4.846 mmol, 1.5 equiv.) in dry CH
2Cl
2 (75.0 mL), 4 Å MS (50 pieces) were added and the reaction mixture was stirred at room temperature under argon. After 30 min, the stirred mixture was cooled to −40 °C under argon. At this temperature, NIS (7.269 mmol, 1.5 equiv. to the donor) and TfOH (2.181 mmol, 0.3 equiv. to NIS) dissolved in dry THF (3.0 mL) were added. The temperature was allowed to warm up to −20 °C (
18 and
25) or to −10 °C (
30) and the reaction mixture was stirred for 4 h. Then, the reaction mixture was quenched with Et
3N (500 µL), diluted with CH
2Cl
2 (500 mL), filtered and washed with a saturated aqueous solution of Na
2S
2O
3 (2 × 100 mL) and a saturated aqueous solution of NaHCO
3 (100 mL) and H
2O (2 × 100 mL) until neutral pH was reached. The organic layer was dried over MgSO
4 and concentrated.
General Method F for Regioselective Ring Opening Reaction of the 4,6-O-acetals (19 and 26)
The appropriate 4,6-O-acetals (18 and 25) (3.194 mmol) were dissolved in anhydrous CH2Cl2 (28 mL); then, 4 Å MS (~50 pieces) were added and the solution was stirred at room temperature for 30 min. After 30 min, the mixture was cooled to 0 °C; then, Et3SiH (6.12 mL, 38.33 mmol, 12.0 equiv.) and BF3·Et2O (788 μL, 6.388 mmol, 2.0 equiv.) were added. The reaction mixture was stirred at 0 °C for 5 h. Then, the mixture was diluted with CH2Cl2 (500 mL), washed with water (75 mL), saturated aqueous solution of NaHCO3 (2 × 75 mL), and water (2 × 75 mL) until a neutral pH was reached. The organic layer was dried over MgSO4 and concentrated.
General Method G for Cleavage of the (2-Naphthyl)methyl Group (27 and 31)
The appropriate trisaccharide derivatives (26 and 30) (1.265 mmol) were dissolved in a mixture of CH2Cl2 (21 mL) and water (2.1 mL); then, DDQ was added (1.898 mmol, 1.5 equiv.) and the reaction mixture was stirred for 30 min at room temperature. After 30 min, the reaction mixture was diluted with CH2Cl2 (400 mL) and washed with a saturated aqueous solution of NaHCO3 (2 × 50 mL) and water (2 × 50 mL) until a neutral pH was reached. The organic layer was dried over MgSO4 and concentrated under reduced pressure.
General Method H for Oxidation of the C-6-OH to Carboxylic Acid (28 and 32)
The appropriate 6-OH derivatives (27 and 31) (0.887 mmol) were dissolved in CH3CN (34 mL) and H2O (12 mL); then, BAIB (857 mg, 2.660 mmol, 3.0 equiv./−OH) and TEMPO (25 mg, 0.160 mmol, 0.18 equiv./OH) were added at 0 °C. The solution was stirred vigorously for 24 h at room temperature. After 24 h, the reaction mixture was quenched by the addition of 10% aqueous solution of Na2S2O3 (44 mL) and extracted with CH2Cl2 (3 × 100 mL), and the combined organic layers were dried over MgSO4, and concentrated.
2.1.2. Sodium [methyl (2,3,4-tri-O-methyl-α-d-glucopyranosyl)-(1→4)-(β-d-glucopyranosyl-uronate)-(1→4)-α-d-glucopyranoside] (10)
Compound
9 [
30] (50 mg, 0.074 mmol) was deacetylated according to general method A. The crude product was purified by silica gel chromatography (1:1 CH
2Cl
2/MeOH) to give
10 (39 mg, 89%) as a colourless syrup. [α]
D25 +114.6 (
c 0.24, MeOH);
Rf 0.37 (1:1 CH
2Cl
2/MeOH);
1H NMR (D
2O, 500 MHz)
δ 5.63 (d,
J = 3.2 Hz, 1H, H-1″), 4.74 (d,
J = 3.4 Hz, 1H, H-1), 4.52 (d,
J = 7.9 Hz, 1H, H-1′), 4.04 (d,
J = 9.7 Hz, 1H, H-5′), 3.87–3.77 (m, 3H, H-4′, H-6″a, H-6″b), 3.74–3.69 (m, 5H, H-3′, H-5, H-5″, H-6a,b), 3.56–3.52 (m, 5H, H-2, H-4″, OC
H3), 3.49, 3.47 (2 × s, 6H, 2 × OC
H3), 3.45–3.41 (m, 2H, H-3, H-3″), 3.36 (s, 3H, C-1-OC
H3), 3.35–3.31 (m, 1H, H-2′), 3.29–3.23 (m, 2H, H-2″, H-4) ppm;
13C NMR (D
2O, 125 MHz)
δ 172.2 (1C, C
q, COOH), 102.3 (1C, C-1′), 99.0 (1C, C-1), 95.8 (1C, C-1″), 81.5 (1C, C-3″), 80.2 (1C, C-2″), 78.6 (1C, C-4″), 78.2 (1C, C-4), 76.0 (1C, C-3′), 75.2 (1C, C-4′), 73.8 (1C, C-5′), 73.2 (1C, C-2′), 71.5 (1C, C-5″), 71.1 (1C, C-3), 71.0 (1C, C-2), 70.3 (1C, C-5), 60.1 (1C, O
CH
3), 59.8 (1C, C-6″), 59.7 (1C, O
CH
3), 59.5 (1C, C-6), 58.1 (1C, O
CH
3), 55.1 (1C, C-1-O
CH
3) ppm; UHR ESI-QTOF (positive ion):
m/
z calcd for [C
22H
38O
17 + Na]
+: 597.2001; found: 597.2002.
2.1.3. Sodium [methyl (α-d-glucopyranosyl)-(1→4)-(2,3-di-O-acetyl-β-d-glucopyranosyl-uronate)-(1→4)-α-d-glucopyranoside] (11)
Compound 28 (655 mg, 0.556 mmol) was debenzylated according to general method B. The crude product was purified by silica gel chromatography (4:6 CH2Cl2/MeOH) to give 11 (290 mg, 82%) as a colourless syrup. [α]D25 +92.1 (c 0.14, MeOH); Rf 0.43 (4:6 CH2Cl2/MeOH); 1H NMR (D2O, 400 MHz) δ 5.22 (t, J = 9.0 Hz, 1H, H-3′), 5.03 (d, J = 3.9 Hz, 1H, H-1″), 4.81–4.74 (m, 2H, H-1′, H-2′), 4.67 (d, J = 3.7 Hz, 1H, H-1), 3.97 (t, J = 9.4 Hz, 1H, H-4′), 3.84 (d, J = 9.7 Hz, 1H, H-5′), 3.72 (d, J = 11.0 Hz, 1H, H-6a), 3.66–3.59 (m, 5H, H-3, H-5″, H-6b, H-6″a,b), 3.54–3.52 (m, 1H, H-5), 3.49–3.44 (m, 3H, H-2, H-3″, H-4), 3.33–3.28 (m, 2H, H-2″, H-4″), 3.27 (s, 3H, C-1-OCH3), 1.99 (s, 6H, 2 × Ac-CH3) ppm; 13C NMR (D2O, 100 MHz) δ 174.5 (1C, Cq COOH), 173.7, 169.4 (2C, 2 × Cq Ac), 100.3 (1C, C-1′), 100.1 (1C, C-1″), 99.5 (1C, C-1), 79.5 (1C, C-4), 76.7 (1C, C-5′), 75.9 (1C, C-3′), 75.7 (1C, C-4′), 73.4 (1C, C-3″), 73.1 (1C, C-2′), 72.4 (1C, C-5″), 71.9 (1C, C-3), 71.7 (1C, C-2″), 71.5 (1C, C-2), 70.7 (1C, C-5), 69.6 (1C, C-4″), 60.5, 60.4 (2C, C-6, C-6″), 55.6 (1C, C-1-OCH3), 21.1, 20.7 (2C, 2 × Ac-CH3) ppm; UHR ESI-QTOF (positive ion): m/z calcd for [C23H35NaO19 + Na]+: 661.1562; found: 661.1559.
2.1.4. Sodium [methyl (α-d-glucopyranosyl)-(1→4)-(β-d-glucopyranosyl-uronate)-(1→4)-α-d-glucopyranoside] (12)
Compound 11 (70 mg, 0.110 mmol) was deacetylated according to general method A. The crude product was purified by a Sephadex G-25 column in H2O to give 12 (54 mg, 89%) as a colourless syrup. [α]D25 +51.8 (c 0.11, H2O); Rf 0.57 (7:6:1 CH2Cl2/MeOH/H2O); 1H NMR (D2O, 400 MHz) δ 5.36 (d, J = 3.8 Hz, 1H, H-1″), 4.68 (d, J = 4.1 Hz, 1H, H-1), 4.39 (d, J = 7.9 Hz, 1H, H-1′), 3.81–3.78 (m, 1H, H-6a), 3.73–3.67 (m, 2H, H-5′, H-6b), 3.66–3.62 (m, 6H, H-3, H-3′, H-4, H-5, H-6″a,b), 3.60–3.54 (m, 2H, H-3″, H-5″), 3.50–3.45 (m, 2H, H-2, H-4), 3.39 (dd, J = 3.9 Hz, J = 9.9 Hz, 1H, H-2″), 3.29 (s, 3H, C-1-OCH3), 3.28–3.24 (m, 2H, H-2′, H-4″) ppm; 13C NMR (D2O, 100 MHz) δ 174.9 (1C, Cq COOH), 102.2 (1C, C-1′), 98.9 (1C, C-1), 98.2 (1C, C-1″), 78.5 (1C, C-4), 76.3 (2C, C-3′, C-5′), 76.1 (1C, C-4′), 73.1 (1C, C-2′), 72.7 (1C, C-5″), 71.8 (1C, C-3″), 71.6 (1C, C-2″), 71.5 (1C, C-3), 70.9 (1C, C-2), 70.2 (1C, C-5), 69.2 (1C, C-4″), 60.1, 59.8 (2C, C-6, C-6″), 55.1 (1C, C-1-OCH3) ppm; UHR ESI-QTOF (positive ion): m/z calcd for [C19H31NaO17 + Na]+: 577.1351; found: 577.1351.
2.1.5. Octa Sodium [methyl (2,3,4,6-tetra-O-sulfonato-α-d-glucopyranosyl)-(1→4)-(2,3-di-O-acetyl-β-d-glucopyranosyl-uronate)-(1→4)-2,3,6-tri-O-sulfonato-α-d-glucopyranoside] (13)
Compound 11 (129 mg, 0.203 mmol) was sulphated according to general method C. The crude product was purified by Sephadex LH-20 gel chromatography in H2O and transformed to sodium salt using Dowex Na+ ion exchange resin to give 13 (222 mg, 81%) as a white solid. [α]D25 +40.0 (c 0.16, H2O); Rf 0.33 (7:6:1 CH2Cl2/MeOH/H2O); 1H NMR (D2O, 400 MHz) δ 5.39 (d, J = 3.4 Hz, 1H, H-1″), 5.31 (t, J = 8.5 Hz, 1H, H-3′), 5.09 (d, J = 3.6 Hz, 1H, H-1), 4.91–4.86 (m, 2H, H-1′, H-2′), 4.58–4.50 (m, 2H, H-3, H-3″), 4.39–4.29 (m, 6H, H-2, H-4″, H-6a,b, H-6″a,b), 4.25–4.17 (m, 2H, H-2″, H-4′), 4.04–4.01 (m, 1H, H-5″), 3.98–3.89 (m, 3H, H-4, H-5, H-5′), 3.39 (s, 3H, C-1-OCH3), 2.07, 2.06 (2 × s, 6H, 2 × Ac-CH3) ppm; 13C NMR (D2O, 100 MHz) δ 174.0 (1C, Cq COOH), 173.4, 173.0 (2C, 2 × Cq Ac), 98.7 (1C, C-1′), 97.1 (1C, C-1), 96.2 (1C, C-1″), 77.0 (1C, C-5′), 75.7 (1C, C-3), 75.3 (1C, C-2), 75.1 (1C, C-3″), 75.0 (1C, C-3″), 74.4 (1C, C-4′), 74.2 (1C, C-2″), 73.9 (1C, C-4), 73.6 (1C, C-4″), 72.7 (1C, C-2″), 68.9 (1C, C-5″), 68.7 (1C, C-5), 65.9 (1C, C-6″), 65.8 (1C, C-6), 55.4 (1C, C-1-OCH3), 21.0, 20.3 (2C, 2 × Ac-CH3) ppm; UHR ESI-QTOF (positive ion): m/z calcd for [C23H28Na8O40S7 + Na2]2+: 698.8584; found: 698.8583.
2.1.6. Octa Sodium [methyl (2,3,4,6-tetra-O-sulfonato-α-d-glucopyranosyl)-(1→4)-(β-d-glucopyranosyl-uronate)-(1→4)-2,3,6-tri-O-sulfonato-α-d-glucopyranoside] (14)
Compound 13 (54 mg, 0.040 mmol) was deacetylated according to general method D. The crude product was purified by Sephadex LH-20 gel chromatography in H2O and transformed to sodium salt using Dowex Na+ ion exchange resin to give 14 (45 mg, 89%) as a white solid. [α]D25 +120.0 (c 0.02, H2O); Rf 0.45 (75:25 MeCN/H2O); 1H NMR (D2O, 400 MHz) δ 5.67 (d, J = 3.6 Hz, 1H, H-1″), 5.04 (d, J = 3.6 Hz, 1H, H-1), 4.57–4.50 (m, 3H, H-1′, H-3, H-3″), 4.34–4.30 (m, 1H, H-4″), 4.28–4.24 (m, 5H, H-2, H-2″, H-6a, H-6″a,b), 4.19 (dd, J = 2.3 Hz, J = 10.9 Hz, 1H, H-6b), 3.99–3.91 (m, 3H, H-4, H-5, H-5″), 3.80–3.71 (m, 3H, H-3′, H-4′, H-5′), 3.35 (s, 3H, C-1-OCH3), 3.34–3.29 (m, 1H, H-2′) ppm; 13C NMR (D2O, 100 MHz) δ 174.9 (1C, Cq COOH), 100.7 (1C, C-1′), 97.0 (1C, C-1), 96.1 (1C, C-1″), 77.0 (1C, C-4′), 76.9 (1C, C-3′), 76.2 (1C, C-3), 76.0 (1C, C-5′), 75.3 (1C, C-3″), 75.1 (1C, C-2″), 74.8 (1C, C-2), 73.6 (1C, C-4″), 73.0 (1C, C-2′), 72.8 (1C, C-4), 68.8 (1C, C-5), 68.5 (1C, C-5″), 66.3 (1C, C-6″), 65.9 (1C, C-6), 55.3 (1C, C-1-OCH3) ppm; UHR ESI-QTOF (positive ion): m/z calcd for [C19H24Na8O38S7 + Na2]2+: 656.8478; found: 656.8474.
2.1.7. Hexa Sodium [methyl (2-deoxy-2-sulfamido-6-O-sulfonato-α-d-glucopyranosyl)-(1→4)-(β-d-glucopyranosyl-uronate)-(1→4)-2,3,6-tri-O-sulfonato-α-d-glucopyranoside] (15)
Compound 33 (55 mg, 0.053 mmol) was sulphated according to general method C. The product was separated from the salt contaminants by Sephadex LH-20 gel chromatography in H2O, and the sulphated compound was debenzoylated according to general method D. The crude product was purified by Sephadex LH-20 gel chromatography in H2O and transformed to sodium salt using Dowex Na+ ion exchange resin to give 15 (25 mg, 45% for two steps) as a white solid. [α]D25 +51.8 (c 0.11, H2O); Rf 0.34 (8:2 CH3CN/H2O); 1H NMR (D2O, 500 MHz) δ 5.57 (d, J = 3.8 Hz, 1H, H-1″), 5.09 (d, J = 3.7 Hz, 1H, H-1), 4.60 (d, J = 8.0 Hz, 1H, H-1′), 4.57 (t, J = 9.4 Hz, 1H, H-3), 4.32–4.29 (m, 4H, H-2, H-6″a, H-6a,b), 4.10 (dd, J = 2.0 Hz, J = 11.1 Hz, 1H, H-6″b), 4.00–3.97 (m, 2H, H-5, H-4), 3.83–3.81 (m, 1H, H-5″), 3.79–3.75 (m, 2H, H-3′, H-5′), 3.73–3.71 (m, 1H, H-4′), 3.57–3.50 (m, 2H, H-3″, H-4″), 3.40 (s, 3H, C-3′-OCH3) 3.38–3.35 (m, 1H, H-2′), 3.20 (dd, J = 3.8 Hz, J = 10.0 Hz, 1H, H-2″) ppm; 13C NMR (D2O, 125 MHz) δ 175.1 (1C, C=O, COOH), 100.6 (1C, C-1′), 97.4 (1C, C-1″), 97.1 (1C, C-1), 77.0 (1C, C-4′), 76.5 (1C, C-3), 76.3 (1C, C-5′), 76.2 (1C, C-3′), 75.1 (1C, C-2), 72.8 (1C, C-4), 72.5 (1C, C-2′), 71.1 (1C, C-4″), 69.7 (1C, C-3′), 69.0 (1C, C-5″), 68.8 (1C, C-5), 66.3 (2C, C-6, C-6″), 57.9 (1C, C-2″), 55.3 (1C, C-1-OCH3) ppm; UHR ESI-QTOF (positive ion): m/z calcd for [C19H27NNa6O31S5 + Na2]2+: 554.4171; found: 554.4172.
2.1.8. Methyl [2,3-di-O-acetyl-4,6-O-(2-naphthyl)methylene-β-d-glucopyranosyl]-(1→4)-2,3,6-tri-O-benzyl-α-d-glucopyranoside (18)
Compound
17 [
33] (1.50 g, 3.231 mmol) was glycosylated with
16 [
34] (2.40 g, 4.846 mmol, 1.5 equiv.) according to general method E. The crude product was purified by silica gel chromatography (6:4
n-hexane/EtOAc) to give
18 (2.18 g, 80%) as a colourless syrup. [α]
D25 +33.7 (
c 0.32, CHCl
3);
Rf 0.39 (6:4
n-hexane/EtOAc);
1H NMR (CDCl
3, 500 MHz)
δ 7.74–7.19 (m, 22H, arom.), 5.53 (s, 1H, H
ac), 5.12 (t,
J = 9.4 Hz, 1H, H-3′), 4.92–4.89 (m, 2H, Bn-C
H2a, H-2′), 4.82 (d,
J = 10.9 Hz, 1H, Bn-C
H2b), 4.79–4.75 (m, 2H, 2 × Bn-C
H2a), 4.62 (d,
J = 12.3 Hz, 1H, Bn-C
H2b), 4.60 (d,
J = 3.6 Hz, 1H, H-1), 4.54 (d,
J = 7.9 Hz, 1H, H-1′), 4.42 (d,
J = 12.0 Hz, 1H, Bn-C
H2b), 4.17 (dd,
J = 4.9 Hz,
J = 10.5 Hz, 1H, H-6′a), 3.91 (t,
J = 9.4 Hz, 1H, H-4), 3.83 (t,
J = 9.2 Hz, 1H, H-3), 3.79 (dd,
J = 2.8 Hz,
J = 10.7 Hz, 1H, H-6a), 3.63–3.58 (m, 3H, H-4′, H-5, H-6b), 3.51 (dd,
J = 3.6 Hz,
J = 9.5 Hz, 1H, H-2), 3.45 (t,
J = 10.3 Hz, 1H, H-6′b), 3.37 (s, 3H, C-1-OC
H3), 3.20 (td,
J = 4.9 Hz,
J = 9.7 Hz, 1H, H-5′), 2.01, 1.96 (2 × s, 6H, 2 × Ac-C
H3) ppm;
13C NMR (CDCl
3, 125 MHz)
δ 170.1, 169.4 (2C, 2 × C
q Ac), 139.4, 138.3, 137.6, 134.3, 133.7, 132.8 (6C, 6 × C
q arom.), 128.8–123.7 (22C, arom.), 101.6 (1C, C
ac), 100.5 (1C, C-1′), 98.4 (1C, C-1), 79.9 (1C, C-3), 79.0 (1C, C-2), 78.4 (1C, C-4′), 77.1 (1C, C-4), 75.3, 73.7, 73.6 (3C, 3 × Bn-
CH
2), 73.1 (1C, C-2′), 72.2 (1C, C-3′), 69.8 (1C, C-5), 68.6 (1C, C-6′), 67.4 (1C, C-6), 66.0 (1C, C-5′), 55.4 (1C, C-1-O
CH
3), 20.8, 20.7 (2C, 2 × Ac-
CH
3) ppm; UHR ESI-QTOF (positive ion):
m/
z calcd for [C
49H
52O
13 + Na]
+: 871.3300; found: 871.3300.
2.1.9. Methyl [2,3-di-O-acetyl-6-O-(2-naphthyl)methyl-β-d-glucopyranosyl]-(1→4)-2,3,6-tri-O-benzyl-α-d-glucopyranoside (19), and Methyl [2,3-di-O-acetyl-β-d-glucopyranosyl]-(1→4)-2,3,6-tri-O-benzyl-α-d-glucopyranoside (20) and Methyl [2,3-di-O-acetyl-4-O-(2-naphthyl)methyl-β-d-glucopyranosyl]-(1→4)-2,3,6-tri-O-benzyl-α-d-glucopyranoside (21)
Reaction 1: Compound 18 (2.71 g, 3.194 mmol) was converted to 19 by general method F. The crude product was purified by silica gel chromatography (55:45 hexane/EtOAc, then 6:4 hexane/acetone) to give compound 19 (1.77 g, 65%) as a white foam and compound 20 (600 mg, 26%) as a white foam.
Reaction 2: To a solution of compound 18 (1.56 g, 1.839 mmol) in dry THF (5.6 mL), 4 Å MS and Me3N·BH3 (805 mg, 11.033 mmol, 6.0 equiv.) were added, and the reaction mixture was stirred for 30 min at room temperature. After 30 min, the reaction mixture was cooled to 0 °C, AlCl3 (1.47 g, 11.033 mmol, 6.0 equiv.) was added, and the mixture was stirred at room temperature for 3 h. After 3 h, the reaction mixture was diluted with CH2Cl2 (50 mL) and washed with H2O (2 × 10 mL). The organic layer was dried over MgSO4, filtered and concentrated. The crude product was purified by silica gel chromatography (65:35 n-hexane/EtOAc) to give compound 19 (1.19 g, 76%) as a colourless syrup and compound 21 (116 mg, 7.5%) as a colourless syrup.
Data of 19: [α]D25 −4.7 (c 0.17, CHCl3); Rf 0.40 (6:4 n-hexane/acetone); 1H NMR (CDCl3, 400 MHz) δ 7.83–7.15 (m, 22H, arom.), 4.93–4.70 (m, 6H, 3 × Bn-CH2a, NAP-CH2a, H-2′, H-3′), 4.59–4.41 (m, 6H, 3 × Bn-CH2a, NAP-CH2a, H-1, H-1′), 3.88–3.79 (m, 2H, H-3, H-4), 3.75 (dd, J = 2.5 Hz, J = 10.4 Hz, 1H, H-6a), 3.67 (t, J = 9.0 Hz, 1H, H-4′), 3.63–3.54 (m, 3H, H-5, H-6b, H-6′a), 3.49–3.44 (m, 2H, H-2, H-6′b), 3.35 (s, 3H, C-1-OCH3), 3.26 (dt, J = 5.3 Hz, J = 10.0 Hz, 1H, H-5′), 3.18 (bs, 1H, H-4′-OH), 2.05, 1.94 (2 × s, 6H, 2 × Ac-CH3) ppm; 13C NMR (CDCl3, 100 MHz) δ 171.0, 169.5 (2C, 2 × Cq Ac), 139.5, 138.3, 137.7, 135.0, 133.3, 133.1 (6C, 6 × Cq arom.), 128.7–125.6 (22C, arom.), 100.1 (1C, C-1′), 98.4 (1C, C-1), 80.9 (1C, C-4), 79.1 (1C, C-2), 77.0 (1C, C-3), 75.8 (1C, C-3′), 75.2, 73.9, 73.8, 73.6 (4C, 3 × Bn-CH2, NAP-CH2), 73.2 (1C, C-5′), 72.2 (1C, C-2′), 71.8 (1C, C-4′), 70.9 (1C, C-6′), 69.9 (1C, C-5), 67.7 (1C, C-6), 55.4 (1C, C-1-OCH3), 20.9, 20.8 (2C, 2 × Ac-CH3) ppm; UHR ESI-QTOF (positive ion): m/z calcd for [C49H54O13 + Na]+: 873.3457; found: 873.3457.
Data of 20: [α]D25 +10.0 (c 0.10, CHCl3); Rf 0.14 (55:45 n-hexane/EtOAc); 1H NMR (CDCl3, 500 MHz) δ 7.41–7.26 (m, 15H, arom.), 4.87–4.73 (m, 6H, 2 × Bn-CH2a, Bn-CH2, H-2′, H-3′), 4.65 (d, J = 12.2 Hz, 1H, Bn-CH2b), 4.59 (d, J = 3.5 Hz, 1H, H-1), 4.42–4.38 (m, 2H, H-1′, Bn-CH2b), 3.82–3.80 (m, 2H, H-3, H-4), 3.73 (dd, J = 2.4 Hz, J = 10.5 Hz, 1H, H-6a), 3.62–3.60 (m, 3H, H-5, H-6b, H-6′a), 3.53 (td, J = 4.7 Hz, J = 9.3 Hz, 1H, H-4′), 3.49 (dd, J = 3.9 Hz, J = 8.9 Hz, 1H, H-2), 3.37 (s, 3H, C-1-OCH3), 3.33 (dd, J = 4.7 Hz, J = 11.7 Hz, 1H, H-6′b), 3.04 (dq, J = 3.1 Hz, J = 8.8 Hz, 1H, H-5′), 2.59 (d, J = 4.8 Hz, 1H, H-4′-OH), 2.07, 1.95 (2 × s, 6H, 2 × Ac-CH3), 1.70 (bs, 1H, H-6′-OH) ppm; 13C NMR (CDCl3, 125 MHz) δ 171.0, 169.4 (2C, 2 × Cq Ac), 139.4, 138.3, 137.6 (3C, 3 × Cq arom.), 128.8–127.2 (15C, arom.), 99.9 (1C, C-1′), 98.6 (1C, C-1), 79.9 (1C, C-4), 79.0 (1C, C-2), 77.0 (1C, C-3), 76.7 (1C, C-3′), 75.4 (1C, C-5′), 75.3, 73.9, 73.7 (3C, 3 × Bn-CH2), 72.0 (1C, C-2′), 69.9 (1C, C-5), 69.7 (1C, C-4′), 67.5 (1C, C-6), 61.9 (1C, C-6′), 55.5 (1C, C-1-OCH3), 21.0, 20.9 (2C, 2 × Ac-CH3) ppm; UHR ESI-QTOF (positive ion): m/z calcd for [C38H46O13 + Na]+: 733.2831; found: 733.2829.
Data of 21: [α]D25 +6.0 (c 0.10, CHCl3); Rf 0.45 (1:1 n-hexane/acetone); 1H NMR (CDCl3, 500 MHz) δ 7.84–7.16 (m, 22H, arom.), 4.93–4.43 (m, 11H, 3 × Bn-CH2, NAP-CH2, H-2′, H-1, H-1′), 3.85–3.82 (m, 2H, H-3, H-4), 3.79 (dd, J = 2.8 Hz, J = 10.7 Hz, 1H, H-6a), 3.64–3.59 (m, 2H, H-5, H-6b), 3.57–3.53 (m, 2H, H-4′, H-6′a), 3.49–3.44 (m, 2H, H-2, H-6′b), 3.39 (dd, J = 3.4 Hz, J = 9.4 Hz, 1H, H-3′), 3.36 (s, 3H, C-1-OCH3), 3.24 (dt, J = 5.6 Hz, J = 10.7 Hz, 1H, H-5′), 3.18 (bs, 1H, H-4′-OH), 2.57 (bs, 1H, H-3′-OH), 2.03 (s, 3H, Ac-CH3) ppm; 13C NMR (CDCl3, 125 MHz) δ 170.7 (1C, Cq Ac), 139.6, 138.4, 137.9, 135.1, 133.4, 133.2 (6C, 6 × Cq arom.), 128.7–125.6 (22C, arom.), 100.2 (1C, C-1′), 98.5 (1C, C-1), 80.1 (1C, C-4), 79.2 (1C, C-2), 77.2 (1C, C-3), 75.6 (1C, C-3′), 75.3 (1C, Bn-CH2), 74.5 (1C, C-2′), 74.0 (1C, C-4′), 73.9, 73.8, 73.7 (3C, 2 × Bn-CH2, NAP-CH2), 72.9 (1C, C-5′), 71.1 (1C, C-6′), 70.0 (1C, C-5), 67.9 (1C, C-6), 55.5 (1C, C-1-OCH3), 21.2 (1C, Ac-CH3) ppm; UHR ESI-QTOF (positive ion): m/z calcd for [C47H52O12 + Na]+: 831.3351; found: 831.3347.
2.1.10. Methyl (2,3-di-O-benzyl-4,6-O-benzylidene-α-d-glucopyranosyl)-(1→4)-[2,3-di-O-acetyl-6-O-(2-naphthyl)methyl-β-d-glucopyranosyl]-(1→4)-2,3,6-tri-O-benzyl-α-d-glucopyranoside (25)
Compound 19 (2.60 g, 3.055 mmol) was glycosylated with 24 (2.48 g, 4.582 mmol, 1.5 equiv.) according to general method E. The crude product was purified by silica gel chromatography (6:4 then 1:1 n-hexane/EtOAc) to give 25 (2.40 g, 61%) as a light yellow foam and 19 (764 mg, 20%) starting material as a light yellow foam. [α]D25 +2.5 (c 0.12, CHCl3); Rf 0.37 (65:35 n-hexane/acetone); 1H NMR (CDCl3, 400 MHz) δ 7.78–7.14 (m, 37H, arom.), 5.47 (1H, HAc), 5.15 (t, J = 9.2 Hz, 1H, H-3′), 5.08–4.45 (m, 16H, 5 × Bn-CH2, NAP-CH2, H-1, H-1′, H-1″, H-2′), 4.11–4.03 (m, 2H, H-4′, H-6″a), 3.91–3.78 (m, 3H, H-3, H-3″, H-4), 3.84–3.77 (m, 2H, H-5″, H-6a), 3.69–3.60 (m, 4H, H-5, H-6a,b’, H-6b), 3.49–3.43 (m, 3H, H-2, H-4″, H-6″b), 3.35 (s, 3H, C-1-OCH3), 3.36–3.33 (m, 1H, H-2″), 3.13–3.11 (m, 1H, H-5′), 1.96, 1.87 (2 × s, 6H, 2 × Ac-CH3) ppm; 13C NMR (CDCl3, 100 MHz) δ 171.2, 169.6 (2C, 2 × Cq Ac), 139.6, 138.7, 138.3, 137.9, 137.7, 137.5, 135.7, 133.3, 132.9 (9C, 9 × Cq arom.), 128.9–125.8 (37C, arom.), 101.3 (1C, Cac), 100.1 (1C, C-1′), 98.4 (1C, C-1), 98.3 (1C, C-1″), 82.1 (1C, C-4″), 80.3 (1C, C-4), 79.3 (1C, C-2), 79.2 (1C, C-2″), 78.1 (1C, C-3″), 77.1 (1C, C-3), 75.4, 75.2 (2C, 2 × Bn-CH2), 75.0 (1C, C-5′), 74.7 (2C, C-3′, C-4′), 73.7, 73.6, 73.5, 73.4 (4C, 3 × Bn-CH2, NAP-CH2), 72.7 (1C, C-2′), 69.8 (1C, C-5), 68.9 (1C, C-6″), 68.1 (1C, C-6), 67.9 (1C, C-6′), 63.5 (1C, C-5″), 55.4 (1C, C-1-OCH3), 21.0, 20.9 (2C, 2 × Ac-CH3) ppm; UHR ESI-QTOF (positive ion): m/z calcd for [C76H80O18 + Na]+: 1303.5237; found: 1303.5237.
2.1.11. Methyl (2,3,6-tri-O-benzyl-α-d-glucopyranosyl)-(1→4)-[2,3-di-O-acetyl-6-O-(2-naphthyl)methyl-β-d-glucopyranosyl]-(1→4)-2,3,6-tri-O-benzyl-α-d-glucopyranoside (26)
Compound 25 (506 mg, 0.395 mmol) was converted to 26 by general method F. The crude product was purified by silica gel chromatography (6:4 n-hexane/EtOAc, then 1:1 n-hexane/acetone) to give 26 (381 mg, 75%) as a white foam. [α]D25 +13.1 (c 0.13, CHCl3); Rf 0.40 (6:4 n-hexane/acetone); 1H NMR (CDCl3, 400 MHz) δ 7.78–7.12 (m, 37H, arom.), 5.15 (t, J = 9.3 Hz, 1H, H-3′), 5.08–4.34 (m, 18H, 6 × Bn-CH2, NAP-CH2, H-1, H-1′, H-1″, H-2′), 4.01 (t, J = 9.3 Hz,1H, H-4′), 3.89–3.86 (m, 2H, H-3, H-4), 3.83–3.72 (m, 3H, H-5″, H-6a, H-6′a), 3.70–3.61 (m, 4H, H-3″, H-5, H-6b, H-6′b), 3.49–3.47 (m, 4H, H-2, H-4″, H-6″a,b), 3.35 (s, 3H, C-1-OCH3), 3.35–3.32 (m, 1H, H-2″), 3.16–3.13 (m, 1H, H-5′), 2.26 (s, 1H, H-4″-OH), 1.96, 1.87 (2 × s, 6H, 2 × Ac-CH3) ppm; 13C NMR (CDCl3, 100 MHz) δ 171.4, 169.5 (2C, 2 × Cq Ac), 139.6, 138.8, 138.3, 138.0, 137.8, 137.7, 136.0, 133.3, 132.9 (9C, 9 × Cq arom.), 128.7–125.8 (37C, arom.), 100.1 (1C, C-1′), 98.4 (1C, C-1), 97.9 (1C, C-1″), 80.5 (1C, C-3″), 80.2 (1C, C-4), 79.8 (1C, C-2″), 79.2 (1C, C-2), 77.1 (1C, C-3), 75.4 (2C, C-4′, C-5′), 75.3, (2C, 2 × Bn-CH2), 74.6 (1C, C-3′), 73.7, 73.6, 73.5, 73.2, 73.0 (5C, 4 × Bn-CH2, NAP-CH2), 72.7 (1C, C-2′), 71.2 (1C, C-5″), 70.7 (1C, C-4″), 69.9 (1C, C-5), 69.6 (1C, C-6″), 68.4 (1C, C-6), 67.9 (1C, C-6′), 55.4 (1C, C-1-OCH3), 21.1, 20.9 (2C, 2 × Ac-CH3) ppm; UHR ESI-QTOF (positive ion): m/z calcd for [C76H82O18 + Na]+: 1305.5393; found: 1305.5393.
2.1.12. Methyl (2,3,6-tri-O-benzyl-α-d-glucopyranosyl)-(1→4)-(2,3-di-O-acetyl-β-d-glucopyranosyl)-(1→4)-2,3,6-tri-O-benzyl-α-d-glucopyranoside (27)
Compound 26 (1.622 g, 1.265 mmol) was converted to 27 by general method G. The crude product was purified by silica gel chromatography (9:1 CH2Cl2/acetone) to give 27 (1.125 g, 75%) as a colourless syrup. [α]D25 +8.6 (c 0.22, CHCl3); Rf 0.38 (9:1 CH2Cl2/acetone); 1H NMR (CDCl3, 400 MHz) δ 7.40–7.23 (m, 30H, arom.), 5.12 (t, J = 9.3 Hz, 1H, H-3′), 4.92–4.39 (m, 16H, 6 × Bn-CH2, H-1, H-1′, H-1″, H-2′), 3.82–3.40 (m, 15H, skeleton protons), 3.37 (s, 3H, C-1-OCH3), 3.06–3.03 (m, 1H, H-5′), 2.28 (s, 1H, H-4″-OH), 1.95, 1.88 (2 × s, 6H, 2 × Ac-CH3), 1.71–1.65 (m, 1H, H-6-OH) ppm; 13C NMR (CDCl3, 100 MHz) δ 170.3, 169.6 (2C, 2 × Cq Ac), 139.4, 138.8, 138.4, 138.0, 137.9, 137.6 (6C, 6 × Cq arom.), 128.8–127.2 (30C, arom.), 99.9 (1C, C-1′), 98.6 (1C, C-1), 98.1 (1C, C-1″), 80.7, 80.0, 79.8, 79.0, 77.1, 75.3, 75.2, 74.7, 72.7, 71.5, 70.6, 69.9 (12C skeleton carbons), 75.4, 73.9, 73.7, 73.4 (6C, 6 × Bn-CH2), 69.5 (1C, C-6″), 67.6 (1C, C-6), 61.5 (1C, C-6′), 55.5 (1C, C-1-OCH3), 21.1, 20.9 (2C, 2 × Ac-CH3) ppm; UHR ESI-QTOF (positive ion): m/z calcd for [C65H74O18 + Na]+: 1165.4767; found: 1165.4770.
2.1.13. Sodium [methyl (2,3,6-tri-O-benzyl-α-d-glucopyranosyl)-(1→4)-(2,3-di-O-acetyl-β-d-glucopyranosyl-uronate)-(1→4)-2,3,6-tri-O-benzyl-α-d-glucopyranoside (28)
Compound 27 (1.013 g, 0.887 mmol) was oxidized according to general method H. The crude product was purified by silica gel chromatography (97:3 to 9:1 CH2Cl2/MeOH) to give 28 (597 mg, 60%) as a white foam. [α]D25 +23.8 (c 0.13, CHCl3); Rf 0.27 (97:3 CH2Cl2/MeOH); 1H NMR (CDCl3, 400 MHz) δ 7.41–7.20 (m, 30H, arom.), 5.12 (t, J = 9.0 Hz, 1H, H-3′), 5.01 (d, J = 3.1 Hz, 1H, H-1″), 4.97–4.86 (m, 3H, Bn-CH2, H-2′), 4.75–4.42 (m, 12H, 5 × Bn-CH2, H-1, H-1′), 4.07 (t, J = 9.0 Hz, 1H, H-4′), 3.91–3.81 (m, 2H, H-3, H-4), 3.77–3.69 (m, 4H, H-3″, H-4″, H-5′, H-6″a), 3.65–3.58 (m, 4H, H-5, H-6a,b, H-6″b), 3.53 (t, J = 9.4 Hz, 1H, H-5″), 3.45 (dd, J = 3.6 Hz, J = 9.2 Hz, 1H, H-2), 3.39 (dd, J = 3.2 Hz, J = 9.8 Hz, 1H, H-2″), 3.36 (s, 1H, H-4″-OH), 3.33 (s, 3H, C-1-OCH3), 1.94, 1.84 (2 × s, 6H, 2 × Ac-CH3) ppm; 13C NMR (CDCl3, 100 MHz) δ 170.1, 169.4 (2C, 2 × Cq Ac), 139.0, 138.7, 138.3, 137.9, 137.6, 137.5 (6C, 6 × Cq arom.), 128.8–127.3 (30C, arom.), 100.0 (1C, C-1′), 98.4 (1C, C-1), 98.2 (1C, C-1″), 80.2 (1C, C-3″), 79.9 (1C, C-3), 79.5 (1C, C-2″), 79.1 (1C, C-2), 77.0 (1C, C-4), 76.5 (1C, C-4′), 75.6, 75.2 (2C, 2 × Bn-CH2), 74.8 (1C, C-5′), 73.8 (1C, C-3′), 73.8, 73.7, 73.6, 73.1 (4C, 4 × Bn-CH2), 72.2 (1C, C-2′), 71.3 (1C, C-4″), 70.7 (1C, C-5″), 69.8 (1C, C-5), 69.6 (1C, C-6), 67.6 (1C, C-6″), 55.4 (1C, C-1-OCH3), 20.9, 20.8 (2C, 2 × Ac-CH3) ppm; UHR ESI-QTOF (positive ion): m/z calcd for [C65H72O19 + Na]+: 1179.4560; found: 1179.4559.
2.1.14. Methyl (2-azido-3,4-di-O-benzoyl-6-O-benzyl-2-deoxy-α-d-glucopyranosyl)-(1→4)-[2,3-di-O-benzoyl-6-O-(2-naphthyl)methyl-β-d-glucopyranosyl]-(1→4)-2,3,6-tri-O-benzyl-α-d-glucopyranoside (30)
Compound
17 [
33] (240 mg, 0.516 mmol, 1.4 equiv.) was glycosylated with
29 (390 mg, 0.369 mmol) according to general method
E. The crude product was purified by silica gel chromatography (6:4
n-hexane/acetone) to give
30 (345 mg, 64%) as a colourless syrup. [α]
D25 +31.4 (
c 0.17, CHCl
3);
Rf 0.46 (6:4
n-hexane/acetone);
1H NMR (CDCl
3, 500 MHz)
δ 7.98–6.93 (m, 47H, arom.), 5.82 (td,
J = 6.3 Hz,
J = 10.5 Hz, 1H, H-3″), 5.71 (td,
J = 6.2 Hz,
J = 9.5 Hz, 1H, H-3′), 5.50 (td,
J = 5.4 Hz,
J = 10.0 Hz, 1H, H-4″), 5.42–5.33 (m, 2H, H-1″, H-2′), 5.13 (dd,
J = 5.1 Hz,
J = 11.6 Hz, 1H, Bn-
CH
2a), 4.86–4.78 (m, 2H, H-1′, Bn-C
H2b), 4.75–4.33 (m, 7H, H-1, 2 × Bn-
CH
2, NAP-
CH
2), 4.30–4.26 (m, 2H, H-4′, Bn-C
H2a), 4.15–4.12 (m, 1H, H-5″), 4.08 (dd,
J = 4.2 Hz,
J = 12.0 Hz, 1H, Bn-
CH
2b), 4.01–3.95 (m, 1H, H-4), 3.92–3.88 (m, 1H, H-3), 3.84–3.76 (m, 2H, H-6′a,b), 3.69–3.64 (m, 1H, H-6a), 3.54–3.52 (m, 2H, H-5, H-5′), 3.49–3.47 (m, 1H, H-2), 3.46–3.42 (m, 1H, H-6b), 3.34 (dt,
J = 4.0 Hz,
J = 10.6 Hz, 1H, H-2″), 3.26 (s, 3H, C-3′-OC
H3), 3.25–3.18 (m, 2H, H-6″a,b) ppm;
13C NMR (CDCl
3, 125 MHz)
δ 165.5, 165.3, 165.2, 165.1 (4C, 4 × C=O Bz), 139.6, 139.3, 137.7, 137.3, 135.9, 132.9, 129.5, 129.2, 129.0, 128.9 (11C, 11 × C
q arom.), 133.3–125.8 (47C, arom.), 100.2 (1C, C-1′), 98.8 (1C, C-1″), 98.4 (1C, C-1), 80.3 (1C, C-3), 79.1 (1C, C-2), 77.0 (1C, C-4), 75.4 (1C, C-3′), 75.3 (1C, Bn-
CH
2), 75.0 (1C, C-4′), 74.9 (1C, C-5′), 73.8, 73.7, 73.6, 73.5 (4C, NAP-
CH
2, 3 × Bn-
CH
2), 72.9 (1C, C-2′), 70.3 (1C, C-3″), 70.0 (1C, C-5″), 69.6 (1C, C-5), 69.3 (1C, C-6′), 69.0 (1C, C-4″), 67.8 (1C, C-6), 67.5 (1C, C-6″), 61.4 (1C, C-2″), 55.3 (1C, C-1-O
CH
3) ppm; UHR ESI-QTOF (positive ion):
m/
z calcd for [C
86H
81N
3O
19 + Na
2]
2+: 752.7624; found: 752.7623.
2.1.15. Methyl (2-azido-3,4-di-O-benzoyl-6-O-benzyl-2-deoxy-α-d-glucopyranosyl)-(1→4)-(2,3-di-O-benzoyl-β-d-glucopyranosyl)-(1→4)-2,3,6-tri-O-benzyl-α-d-glucopyranoside (31)
Compound 30 (330 mg, 0.226 mmol) was converted to 31 according to general method G. The crude product was purified by silica gel chromatography (6:4 n-hexane/EtOAc) to give 31 (245 mg, 82%) as a colourless syrup. [α]D25 +5.4 (c 0.13, CHCl3); Rf 0.38 (6:4 n-hexane/EtOAc); 1H NMR (CDCl3, 500 MHz) δ 7.90–7.17 (m, 40H, arom.), 5.80 (t, J = 10.1 Hz, 1H, H-3″), 5.69 (t, J = 9.5 Hz, 1H, H-3′), 5.48 (t, J = 9.8 Hz, 1H, H-4″), 5.36 (d, J = 3.8 Hz, 1H, H-1″), 5.29 (t, J = 8.9 Hz, 1H, H-2′), 5.00 (d, J = 11.1 Hz, 1H, Bn-CH2a), 4.86 (d, J = 11.1 Hz, 1H, Bn-CH2b), 4.80 (d, J = 12.3 Hz, 1H, Bn-CH2a), 4.71 (d, J = 11.9 Hz, 1H, Bn-CH2a), 4.68–4.64 (m, 2H, H-1′, Bn-CH2b), 4.58–4.55 (m, 2H, H-1, Bn-CH2b), 4.48 (d, J = 12.1 Hz, 1H, Bn-CH2b), 4.34 (d, J = 12.0 Hz, 1H, Bn-CH2b), 4.18 (t, J = 9.4 Hz, 1H, H-4′), 4.11 (t, J = 7.1 Hz, 1H, H-5″), 3.93–3.83 (m, 2H, H-3, H-4), 3.75 (d, J = 12.0 Hz, 1H, H-6′a), 3.62 (d, J = 10.9 Hz, 1H, H-6a), 3.57–3.49 (m, 5H, H-2, H-5, H-6′a, H-6″a,b), 3.39 (d, J = 10.1 Hz, 1H, H-6b), 3.35–3.29 (m, 2H, H-2″, H-5′), 3.27 (s, 3H, C-3′-OCH3), 2.12–2.10 (m, 1H, H-6′-OH) ppm; 13C NMR (CDCl3, 125 MHz) δ 165.5, 165.2, 165.2, 165.1 (4C, 4 × C=O Bz), 139.4, 138.3, 137.6, 137.2, 129.4, 129.2, 128.9, 128.8 (8C, 11 × Cq arom.), 133.4–127.5 (40C, arom.), 100.1 (1C, C-1′), 99.1 (1C, C-1″), 98.4 (1C, C-1), 80.0 (1C, C-3), 79.0 (1C, C-2), 77.1 (1C, C-4), 75.5 (1C, Bn-CH2), 75.4 (1C, C-3′), 74.7 (1C, C-4′), 74.5 (1C, C-5′), 73.8, 73.7, 73.6 (3C, 3 × Bn-CH2), 72.8 (1C, C-2′), 70.5 (1C, C-3″), 70.2 (1C, C-5″), 69.6 (1C, C-5), 69.1 (1C, C-4″), 67.8 (1C, C-6″), 67.5 (1C, C-6), 61.5 (1C, C-6′), 61.2 (1C, C-2″), 55.4 (1C, C-1-OCH3) ppm.
2.1.16. Sodium [methyl (2-azido-3,4-di-O-benzoyl-6-O-benzyl-2-deoxy-α-d-glucopyranosyl)-(1→4)-(2,3-di-O-benzoyl-β-d-glucopyranosyl-uronate)-(1→4)-2,3,6-tri-O-benzyl-α-d-glucopyranoside (32)
Compound 31 (230 mg, 0.174 mmol) was oxidized according to general method H. The crude product was purified by silica gel chromatography (6:4 n-hexane/acetone) to give 32 (172 mg, 73%) as a colourless syrup. [α]D25 +4.4 (c 0.18, CHCl3); Rf 0.38 (6:4 n-hexane/acetone); 1H NMR (CDCl3, 500 MHz) δ 7.90–7.16 (m, 40H, arom.), 5.85 (t, J = 10.1 Hz, 1H, H-3″), 5.59 (t, J = 9.2 Hz, 1H, H-3′), 5.41 (t, J = 9.7 Hz, 1H, H-4″), 5.29 (d, J = 3.5 Hz, 1H, H-1″), 5.27 (t, J = 8.6 Hz, 1H, H-2′), 4.99 (d, J = 11.2 Hz, 1H, Bn-CH2a), 4.80 (d, J = 11.2 Hz, 1H, Bn-CH2b), 4.75–4.71 (m, 2H, 2 × Bn-CH2a), 4.65 (d, J = 7.7 Hz, 1H, H-1′), 4.58–4.55 (m, 2H, 2 × Bn-CH2b), 4.53 (d, J = 3.5 Hz, 1H, H-1), 4.47 (d, J = 11.8 Hz, 1H, H-1, Bn-CH2b), 4.44–4.40 (m, 1H, H-5″), 4.32–4.27 (m, 2H, H-4′, Bn-CH2b), 3.94–3.85 (m, 3H, H-3, H-4, H-5′), 3.62–3.56 (m, 3H, H-6a, H-6″a,b), 3.50–3.47 (m, 2H, H-2, H-5), 3.39 (d, J = 10.2 Hz, 1H, H-6b), 3.33 (dd, J = 3.8 Hz, J = 10.1 Hz, 1H, H-2″), 3.25 (s, 3H, C-3′-OCH3) ppm; 13C NMR (CDCl3, 125 MHz) δ 165.4, 165.3, 165.0, 164.9 (4C, 4 × C=O Bz), 138.9, 138.2, 137.5, 136.8, 129.3, 129.0, 128.9, 128.8 (8C, 11 × Cq arom.), 133.5–127.5 (40C, arom.), 99.7 (2C, C-1′, C-1″), 98.4 (1C, C-1), 80.2 (1C, C-3), 79.1 (1C, C-2), 77.1 (1C, C-4′), 76.5 (1C, C-4), 75.9 (1C, Bn-CH2), 74.3 (1C, C-3′), 74.0, 73.8 (2C, 2 × Bn-CH2), 73.7 (1C, C-5′), 73.5 (1C, Bn-CH2), 72.3 (1C, C-2′), 70.6 (1C, C-3″), 69.9 (1C, C-5″), 69.5 (1C, C-5), 69.3 (1C, C-4″), 68.8 (1C, C-6″), 67.3 (1C, C-6), 61.3 (1C, C-2″), 55.4 (1C, C-1-OCH3) ppm; UHR ESI-QTOF (positive ion): m/z calcd for [C75H70N3NaO20 + Na2]2+: 700.7117; found: 700.7117.
2.1.17. Sodium [methyl (2-amino-3,4-di-O-benzoyl-2-deoxy-α-d-glucopyranosyl)-(1→4)-(2,3-di-O-benzoyl-β-d-glucopyranosyl-uronate)-(1→4)-α-d-glucopyranoside (33)
Compound 32 (165 mg, 0.122 mmol) was debenzylated in the presence of CH3COOH (8.0 µL, 0.134 mmol, 1.1 equiv.) according to general method B. The crude product was purified by silica gel chromatography (9:1 CH3CN/H2O) to give 33 (111 mg, 89%) as a colourless syrup. [α]D25 +64.4 (c 0.09, MeOH); Rf 0.31 (9:1 CH3CN/H2O); 1H NMR (MeOD, 500 MHz) δ 7.95–7.23 (m, 20H, arom.), 5.93–5.89 (m, 1H, H-3′), 5.79–5.72 (m, 1H, H-3″), 5.51–5.49 (m, 2H, H-1″, H-2′), 5.45–5.40 (m, 1H, H-4″), 5.16 (d, J = 7.1 Hz, 1H, H-1′), 4.64–4.62 (m, 2H, H-1, H-4′), 4.33–4.29 (m, 2H, H-5′, H-5″), 3.80–3.53 (m, 8H, H-2, H-3, H-4, H-5, H-6a,b, H-6′a,b), 3.46–3.38 (m, 1H, H-2″), 3.28 (s, 3H, C-3′-OCH3) ppm; 13C NMR (MeOD, 125 MHz) δ 174.8 (1C, C=O, COOH), 167.6, 167.4, 166.9, 166.5 (4C, 4 × C=O Bz), 130.5, 130.3, 130.2 (4C, 4 × Cq arom.), 134.7–129.2 (20C, arom.), 100.8 (1C, C-1′), 100.6 (1C, C-1), 97.5 (1C, C-1″), 79.8 (1C, C-4), 76.8 (1C, C-5′), 76.7 (1C, C-3′), 75.5 (1C, C-4′), 73.5 (1C, C-2′), 73.0 (1C, C-3), 72.9 (1C, C-2), 72.7 (1C, C-3″), 71.8 (1C, C-5), 71.6 (1C, C-5″), 70.3 (1C, C-4″), 60.7 (2C, C-6, C-6″), 55.5 (1C, C-1-OCH3), 55.2 (1C, C-2″) ppm; UHR ESI-QTOF (positive ion): m/z calcd for [C47H49NO20 + Na]+: 970.2740; found: 970.2743.