S YNTHESIS OF PRECURSORS FOR C- GLYCOSYL COMPOUNDS

O-(3,4,6-Tri-O-acetyl-2-(3,4,5,6-tetrachlorophtalimido)-2-deoxy--D-glucopyranosyl) trichloracetimidate 85^[158]

Trichloracetimidate 85 was prepared in thee steps according to Casro-Palomino and Schmidt^[158] in 25 % yield.

Rf = 0.43 (petroleum ether/EtOAc 2:1 with 0.1% Et3N), anisaldehyde; ¹H NMR (400 MHz, CDCl3)  [ppm] = 8.69 (s, 1 H, NH), 6.59 (d, J = 8.8 Hz, 1 H, H-1), 5.84 (dd, J = 10.5, 9.0 Hz, 1 H, H-3), 5.29 (dd, J = 10.1, 9.1 Hz, 1 H, H-4), 4.62 (dd, J = 10.5, 8.8 Hz, 1 H, H-2), 4.45 – 3.94 (m, 3 H, H-5, H-6), 2.12, 2.05, 1.92 (s, 3 H, CH3); ¹³C NMR (100

MHz, CDCl3)  [ppm] = 170.8, 170.6, 169.4, 160.6 (C=O), 140.9, 130.2, 126.9 (C^Ar), 93.5 (C-1), 90.3 (CCl3), 73.0, 70.7, 68.3, 61.6, 54.5 (C-2, C-3, C-4, C-5, C-6), 20.9, 20.7, 20.6 (CH3).

3,4,6-Tetra-O-benzyl-D-glucopyranolactone 101^[166]

2,3,4,6-tetra-O-Benzyl-D-glucopyranose 100 (7 g, 13 mmol) was dissolved in dry DMSO (40 mL) and Ac2O (24.3 mL, 0.26 mol) was added. The reaction mixture was stirred overnight at rt and concentrated. The residue was dissolved in CH2Cl2 and washed with water. The organic layer was dried (MgSO4)and the solvent was removed under reduced pressure. The residue was purified by FC (petroleum ether/EtOAc 4:1) yielding the lacton 101 (6.58 g, 94 %) as colorless oil.

Rf = 0.50 (petroleum ether/EtOAc 4:1), anisaldehyde; spectroscopic data corresponding to literature^[166]

2-Azido-2-deoxy-/-D-glucopyranose 114[171, 210-211]

To a mixture of sodiumazide (10.8 g, 165 mmol) in CH2Cl2 (30 mL) and H2O (30 mL), Tf2O (13.8 mL, 82 mmol) was added dropwise at 0 °C. The mixture was stirred for 2 h at 0 °C. The layers were separated and the aqueous layer was extracted with CH2Cl2 (2x 25 mL). The combined organic layers were washed with sat aq NaHCO3. The TfN3 solution was added slowly to a mixture of glucosamine hydrochloride (6.6 g, 30.6 mmol), K2CO3 (5.8 g, 42 mmol) and copper(II) sulfate hydrate (45 mg, 0.42 mmol) in H2O (90 mL). After addition of MeOH until layer unification (120 mL), the reaction mixture was stirred overnight at rt. After concentration under reduced pressure the crude product was used without further purification.

Rf = 0.35 (CH2Cl2/MeOH 5:1), anisaldehyde.

1,3,4,6-tetra-O-Acetyl-2-azido-2-deoxy-/-D-glucopyranoside 115^[212]

A solution of 2-azido-2-deoxy-/-D-glucopyranose 114 (6.1 g, 30 mmol) in pyridine (180 mL) and Ac2O (125 mL) was stirred at rt overnight. The solvents were removed under reduced pressure and the residue was dissolved in CH2Cl2 (50 mL). The organic layer was washed with 1M HCl (3x 15 mL) and with sat aq NaHCO3 (20

/EtOAc 2:1) yielding 1,3,4,6-tetra-O-acetyl-2-azido-2-deoxy-/-D-glucopyranoside 115 (10.4 g, 91 %) as an

/mixture of 3:7.

Rf = 0.37 (petroleum ether/EtOAc 2:1), anisaldehyde; spectroscopic data corresponding to literature.^[212]

2,4,6-tri-O-Acetyl-2-azido-2-deoxy--D-glucopyranosyl bromide 116^[213]

To a solution of azido sugar 115 (1.38 g, 3.7 mmol) in CH2Cl2 (40 mL) and EtOAc (8 mL), TiBr4 (1.7 g, 4.6 mmol) was added. The reaction mixture was stirred for 3 d at rt. Toluene (50 mL), MeCN (10 mL) and dry NaOAc (10 g) were added and the reaction mixture was stirred until decolorization. The suspension was filtered through celite and concentrated. The residue was purified by FC (petroleum ether/EtOAc 3:1) yielding the bromide 116 (1.06 g, 73 %) as colorless oil. followed by allyl alcohol (305 µL, 4.48 mmol). The reaction mixture was stirred for 1 h followed by the addition of Ag2CO3 (940 mg, 3.4 mmol). The suspension was stirred for 24 h in the dark. CH2Cl2 (200 mL) was added and the suspension was filtered through celite. The filtrate was washed with water (3x), once with brine, dried (MgSO4) and concentrated. The residue was purified by FC (petroleum ether/EtOAc 3:1) yielding the allyl protected azido sugar 117 (410 mg, 49 %) as colorless foam.

Rf = 0.31 (petroleum ether /EtOAc 3:1), anisaldehyde; ¹H NMR (400 MHz, CDCl3):  [ppm] = 5.93 (dddd, J = 17.3 Hz, 10.4 Hz, 6.2 Hz, 5.2 Hz, 1 H, OCH2CHCH2), 5.34 (dq, J = 17.2 Hz, 1.6 Hz, 1 H, OCH2CHCH2), 5.25 (dq, J = 10.4 Hz, 1.3 Hz, 1 H, OCH2CHCH2), 5.09 – 4.89 (m, 2 H, H-3, H-4), 4.43 (d, J = 8.1 Hz, 1 H, H-1), 4.42 – 4.37 (m, 1 H, OCH2CHCH2), 4.26 (dd, J = 12.3 Hz, 4.8 Hz, 1 H, H-6a), 4.16 (m, 1 H, OCH2CHCH2), 4.11 (dd, J = 12.3 Hz, 2.4 Hz, 1

H, H-6b), 3.69 – 3.59 (m, 1 H, H-5), 3.57 – 3.42 (m, 1 H, H-2), 2.07 (s, 6 H, CH3), 2.00 (s, 3 H, CH3); ¹³C NMR (100 MHz, CDCl3)  [ppm] = 170.7, 170.1, 169.7 (C=O), 133.1 (OCH2CHCH2), 118.5 (OCH2CHCH2), 100.9 1), 72.7 (C-3), 71.9 (C-5), 70.8 (OCH2CHCH2), 68.6 (C-4), 63.8 (C-2), 62.0 (C-6), 20.8, 20.8, 20.7 (CH3).

1-O-Allyl-2-azido-2-deoxy--D-glucopyranoside 118

Allyl protected azido sugar 117 (1.30 g, 3.5 mmol) was deacetylated according to GP 2. After lyophiliziation, the deacetlyated azido sugar 118 (810 mg, 95 %) was obtained as colorless solid.

1H NMR (400 MHz, D2O)  [ppm] = 6.12 – 5.96 (m, 1 H, OCH2CHCH2), 5.44 (d, J = 17.3 Hz, 1 H, OCH2CHCH2), 5.34 benzylbromide (0.93 mL, 7.9 mmol) was added dropwise at 0°C. Azido sugar 118 (0.81 g, 3.3 mmol) dissolved in DMF (8 mL) was added dropwise and stirred for 1.5 h at rt. Methanol was added, the mixture was diluted with EtOAc and neutralized with acetic acid. Water was added and the layers were separated. The organic layer was dried (MgSO4) and concentrated. The residue was purified by FC (petroleum ether/EtOAc 5:1) to obtain the benzyl protected azido sugar 119 (1.46 g, 2.84 mmol, 86 %).

Rf = 0.45 (petroleum ether /EtOAc 5:1), anisaldehyde; ¹H NMR (400 MHz, CDCl3)  [ppm] = 7.40-7.12 (m, 15 H,

2-Azido-3,4,6-tri-O-benzyl-2-deoxy-/-D-glucopyranose 97^[167]

[Ir(MePh2P)2(C8H12)]PF6 (12 mg, 14 µmol) was suspended in dry THF (3 mL) under N2. The suspension was evacuated and then saturated with H2. After stirring for 10 min the red suspension turned colorless. The solution was evacuated again to remove excess hydrogen and added dropwise over 15 minutes to a solution of the allyl protected sugar 119 (244 mg, 0.47 mmol) in dry THF (4 mL). After 5 min TLC (petroleum ether/EtOAc 5:1) showed complete conversion of the starting material. THF (20 mL), water (3 mL) and NBS (300 mg) were added and the reaction mixture was stirred for 15 min. The reaction mixture was concentrated, dissolved in CH2Cl2 and extracted with sat aq NaHCO3. The aqueous layer was extracted once more with CH2Cl2 and the combined organic layers were concentrated. The residue was purified by FC (petroleum ether/EtOAc 3:1) yielding 97 (192 mg, 86 %) as colorless solid.

Rf = 0.28 (petroleum ether/EtOAc 3:1), anisaldehyde; ¹H NMR (400 MHz, CDCl3):  [ppm] = 7.33-7.06 (m, 15 H, added. The reaction mixture was stirred overnight at rt. The solvents were removed under reduced pressure and the residue was coevaporated with toluene (2x). The residue was purified by FC (petroleum ether/EtOAc 5:1) yielding lactone 98 (1.62 g, 54 %) as a colorless oil.

3,4,6-tri-O-Acetyl-2-amino-2-deoxy--D-glucopyranosyl bromide hydrobromide 125^[174]

To dry glucosamine hydrochloride (5 g, 23.3 mmol), AcBr (8.4 mL, 112.5 mmol) was added and stirred at rt for 3 d in a sealed flask. The crude product was dissolved in hot CHCl3 and filtered to remove unreacted glucosamine hydrochloride. After removal of the solvent using oil pump vacuum and condensation trap, the crude product was intensively washed with dry Et2O. After drying, the sugarbromide 125 (9.3 g, 90 %) was obtained as slightly brown solid.

Rf = 0.44 (EtOAc), anisaldehyde; mp 148–150 °C.

2-(4-Bromophenyl)-4,4,5,5-tetramethyl-1,3,2-dioxaborolane 123^[214]

1,4-Dibromobenzene (5 g, 21.1 mmol) was dissolved in dry THF (50 mL) under N2 and cooled to –78°C, followed by dropwise addition of n-BuLi (2.5 M in hexane, 8.4 mL, 21.1 mmol). After stirring for 20 min at –78°C, triisopropylborate (14.8 mL, 63.3 mmol) was added dropwise and the solution was stirred for 10 min at –78°C.

The reaction was allowed to warm to rt and stirred for 1 h, cooled to 0°C and quenched with sat aq NH4Cl (20 mL). After acidification with 1 M HCl, the reaction mixture was extracted with EtOAc (3x) and dried (MgSO4).

Pinacol (2.5 g, 21.1 mmol) was added to the organic layer prior to the removal of the solvent under reduced pressure. The residue was purified by FC (petroleum ether/EtOAc 15:1) yielding the pinacol ester 123 (4.01 g, 67 %) as colorless solid.

Rf = 0.45 (petroleum ether/EtOAc 15:1), iodine; ¹H NMR (400 MHz, CDCl3):  [ppm] = 7.67-7.65 (m, 2 H, Ar-H), 7.51-7.49 (m, 2 H, Ar-H), 1.34 (s, 12 H, CH3) ¹³C NMR (100 MHz, CDCl3):  [ppm] =136.5, 131.1, 126.4 (C^Ar), 84.2 (C(CH3)2), 25.0.(CH3), ¹¹B NMR (128 MHz, CDCl3):  [ppm] = 30.6.

1,3,4,6-tetra-O-Acetyl-2-amino-2-deoxy--D-glucopyranoside hydrochloride 140A^[215]

Hydrochloride 140A was synthesized from glucosamine hydrochloride according to Bergmann et al.^[215] in 33 % over three steps.

Ethyl-3,4,6-tri-O-acetyl-2-deoxy-1-thio-2-(2,2,2-trichloroethoxycarbonylamino)--D-glucopyranoside 140^[179]

The thiosugar 140 was synthesized from hydrochloride 140A according to Ellervik et al.^[179] in 60 % yield over two steps. The spectroscopic data were in agreement with the published ones.

Rf = 0.45 (petroleum ether/EtOAc 1:1), anisaldehyde.

2,3,4,6-tetra-O-Benzyl-D-galacto-1,5-lactone 151^[166]

2,3,4,6-tetra-O-Benzyl-D-galactopyranose 150 (4 g, 7.39 mmol) was dissolved in dry DMSO (90 mL) and Ac2O (22 mL) was added. The reaction was stirred at rt overnight. The solvents were removed under reduced pressure and coevaporated with toluene (3x). The residue was purified by FC (PE/EtOAc 3:1) yielding lactone 151 (3.95 g, 99 %) as colorless oil.

Rf = 0.50 (petroleum ether/EtOAc 3:1), anisaldehyde; ¹H NMR (400 MHz, CDCl3):  [ppm] = 7.43-7.23 (m, 20 H, Ar-H), 5.19 (d, J = 11.0 Hz, 1 H, CH2), 4.94 (d, J = 11.2 Hz, 1 H, CH2), 4.80-4.67 (m, 3 H, CH2), 4.61 (d, J = 11.2 Hz, 1 H, CH2), 4.52-4.43 (m, 3 H, CH2, H-4), 4.36-4.32 (m, 1-H, H-4), 4.17-4.16 (m, 1 H, H-3), 3.89 (dd, J = 9.5 Hz, 2.2 Hz, 1 H, H-5), 3.73-3.64 (m, 2 H, H-6); ¹³C NMR (100 MHz, CDCl3):  [ppm] = 170.1 (C=O), 137.9, 137.7, 137.5, 128.6-127.7 (C^Ar), 80.3 (C-5), 77.5 (C-2, C-4), 75.4 (C^Bn), 74.9 (C^Bn), 73.8 (C^Bn), 73.0 (C^Bn), 72.7 (C-3), 67.7 (C-6).

4-O-(2,3,4,6-tetra-O-Acetyl--D-galactopyranosyl)-1,2,3,6-tetra-O-acetyl-/-D-glucopyranose 159^[216]

Lactose (10 g, 29.2 mmol) was suspended in pyridine (280 mL) and Ac2O (140 mL). The suspension was stirred at rt for 12 h. After removal of the solvent under reduced pressure, the residue was dissolved in CH2Cl2, washed with 1 M HCl (3x) and aq sat NaHCO3. The aqueous layers were each extracted with CH2Cl2 (2x) and the combined organic layers dried (MgSO4). After removal of the solvent under reduced pressure the crude product (19.82 g, quant) was used without further purification.

Rf = 0.51 (petroleum ether/EtOAc 1:2), anisaldehyde.

4-O-(2,3,4,6-tetra-O-Acetyl--D-galactopyranosyl)-2,3,6-tri-O-acetyl--D-glucopyranosyl bromide 160^[184]

Peracetylated lactose 159 (1 g, 1.47 mmol) was dissolved under exclusion from light in 2 mL CH2Cl2 and cooled to 0°C. HBr solution (33 % in AcOH, 2.5 mL) was added, the reaction mixture was stirred for 2 h, poured into ice water and extracted with EtOAc. The organic layer was washed with saturated sat aq NaHCO3 (4x) and dried (Na2SO4). The residue was washed with petroleum ether (3x). Thus, the bromide 160 (973 mg, 95 %) could be obtained as colorless solid. added. The suspension was stirred at rt and freshly distilled allyl alcohol (194 µL, 2.86 mmol) was added. The suspension was stirred for 1 h at rt. Ag2CO3 (0.59 g, 2.14 mmol) was added and stirring was continued for 24 h.

The reaction mixture was filtered through celite. The filtrate was washed with water, sat aq NaHCO3 and with brine. The organic layer was dried (MgSO4) and concentrated. The residue was purified by FC (petroleum ether/EtOAc 1:1) to obtain the allyl protected compound 161 (547 mg, 57 %) as a colorless foam.

Rf = 0.29 (petroleum ether/EtOAc 1:1), anisaldehyde; ¹H NMR (400 MHz, CDCl3):  [ppm] = 5.91-5.78 (m, 1 H, H-2^All), 5.34-5.33 (m, 1 H, H-4^Gal), 5.28-5.15 (m, 3 H, H-3^Glc, H-3^All), 5.09 (dd, J = 7.9 Hz, 10.4 Hz, 1 H, H-2^Gal), 4.97-4.89 (m, 2 H, H-2^Glc, H-3^Gal), 4.52 (d, J = 7.9 Hz, 1 H, H-1^Glc), 4.49-4.46 (m, 2 H, H-6a^Glc, H-1^Gal), 4.28-4.25 (m, 1 H, H-1^All), 4.15-4.01 (m, 4 H, H-1^All, H-6b^Glc, H-6ab^Gal), 3.88-3.84 (m, 1 H, H-5^Gal), 3.79 (t, J = 9.4 Hz, 1 H, H-4^Glc), 3.60-3.56 (m, 1 H, H-5^Glc), 2.14, 2.11, 2.05, 2.03, 1.95 (s, 21 H, CH3); ¹³C NMR (100 MHz, CDCl3):  [ppm] =170.5,

170.4, 170.2, 170.1, 169.9 169.7, 169.2 (C=O), 133.5 (C-2^All), 117.7 (C-3^All), 101.2 (C-1^Gal), 99.4 (C-1^Glc), 76.4 suspended in dry DMF (3 mL) at 0°C and BnBr (700 µL, 5.9 mmol) was added. After 15 min the deacetylated sugar 162 (271 mg, 0.7 mmol) in dry DMF (3 mL) was added dropwise. The reaction mixture was stirred for 1.5 h at rt. Methanol and EtOAc were added and the reaction mixture was neutralized with acetic acid. Water was added and the layers were separated. The aqueous layer was extracted with EtOAc (1x) and the combined evacuated and then saturated with H2. After 10 minutes the red suspension turned colorless. The solution was evacuated again to remove excess hydrogen and added dropwise over 15 min to a solution of the allyl protected sugar 163 (4.18 g, 4.13 mmol) in dry THF (40 mL). After 5 min TLC (petroleum ether/EtOAc 4:1) showed complete conversion of the starting material. THF (200 mL), water (10 mL) and NBS (1.08 g, 6 mmol) were added and the reaction mixture was stirred for 30 min. The reaction mixture was concentrated, dissolved

in CH2Cl2 and extracted with sat aq NaHCO3. The aqueous layer was extracted with CH2Cl2 and the combined organic layers were concentrated. The obtained crude product 164 (2.85 g, 71 %) was used in the next step without further purification.

Rf = 0.19 (petroleum ether/EtOAc 3:1), anisaldehyde.

4-O-(2,3,4,6-tetra-O-Benzyl--D-galactopyranosyl)-2,3,6-tri-O-benzyl-D-glucono-1,5-lactone 165

Anomer deprotected sugar 164 (2.73 g, 2.8 mmol) was dissolved in dry DMSO (35 mL), Ac2O (6 mL) was added and the solution was stirred at rt for 12 h. The solvent was removed under reduced pressure and the residue was coevaporated with toluene (3x). The product was purified by FC (petroleum ether/EtOAc 3:1) yielding the lactone 165 (2.72 g, 2.8 mmol, quant) as colorless oil.

Rf = 0.38 (petroleum ether/EtOAc 3:1), anisaldehyde; ¹H NMR (400 MHz, CDCl3):  [ppm] = 7.36-7.19 (m, 35 H, residue was distilled under reduced pressure (20 mbar) yielding the colorless liquid 89A (23.94 g, 53 %).