Organic & Biomolecular Chemistry
Paper
N-[(9H-Fluoren-9-ylmethoxy)carbonyl]-O-(3,4,6-tri-O-acetyl-2- 9-H-Fmoc, 5-H, 6a,b-H, Tα, Tβ), 2.14 (s, 3H, CH3 (Ac)), 2.02 (s,
azido-2-deoxy-α-D-galactopyranosyl)-L-threonine-tert-butyl ester 3H, CH3 (AcNH)), 1.98 (2 × s, 6H, 2 × CH3 (Ac)), 1.44 (s,9H,
(Fmoc-Thr-(αAc3N3Gal)-OtBu) (3).38 A solution of 10.73 g CH3 (tBu)), 1.30 (d, 3H, JTγ,Tβ = 6.0 Hz, Tγ).
(26.00 mmol) Fmoc-Thr-OtBu 2 in 100 mL of dichloro-
N-[(9H-Fluoren-9-ylmethoxy)carbonyl]-O-(2-acetamido-3,4,6-
methane–toluene (1 : 1) was stirred for 1 h with activated pow- tri-O-acetyl-2-deoxy-α-D-galactopyranosyl)-L-threonine (Fmoc-
dered molecular sieves (4 Å) under an argon atmosphere and Thr-(αAc3GalNAc)-OH) (5).38 1.25 g (1.72 mmol) Fmoc-Thr-
exclusion of light. Then the mixture was cooled to 0 °C and (αAc3GalNAc)-OtBu 4 was dissolved in 8 mL of dichloro-
7.74 g (28.07 mmol) Ag2CO3 and 1.22 g (5.43 mmol) AgClO4 in methane and mixed with 15 mL of TFA and 2.5 mL of Milli-
8 mL of toluene were added. The mixture was stirred for pore-H2O. The mixture was stirred for 5 h at room temperature
30 min at 0 °C before 10.00 g (0.025 mol) αAc3N3Gal-Br 1 in under an argon atmosphere. Then it was diluted in 30 mL of
toluene (35 mL) and dichloromethane (35 mL) was added toluene. The crude product was concentrated to dryness,
dropwise to the mixture over 90 min. After stirring overnight at diluted in toluene, concentrated three times and purified by
room temperature, the mixture was diluted with 100 mL flash chromatography with silica (CH2Cl2–MeOH–AcOH,
dichloromethane and filtered through Hyflo®. Then the filtrate 95 : 5 : 1) to yield compound 5 (618 mg, 0.92 mmol, 54%); Rf =
was extracted twice with 150 mL of a saturated sodium hydro- 0.10 (CH2Cl2–MeOH–AcOH, 95 : 5 : 1).
gen carbonate solution, followed by washing twice with
200 mL of brine solution. The aqueous layer was separated
C33H38N2O13 (M = 670.66 g mol−1) [670.24].
1H-NMR (300 MHz, CDCl3), δ (ppm) = 7.76 (d, 2H, JH4,H3 =
from the organic layer, which was dried with magnesium JH5,H6 = 7.2 Hz, 4-H-, 5-H-Fmoc), 7.62 (d, 2H, JH1,H2 = JH7,
sulfate and filtered. The solvent was removed in vacuo and the H8 = 7.3 Hz, 1-H-, 8-H-Fmoc), 7.39 (t, 2H, JH3,H2/H4 = JH6,
crude product was purified by flash chromatography with H5/H7 = 7.2 Hz, 3-H-, 6-H-Fmoc), 7.33–7.30 (m, 2H, 2-H-,
silica (CH2Cl2–EtOAc, 10 : 1). Yield: 7.92 g (11.00 mmol, 45%), 7-H-Fmoc), 6.05 (d, 1H, JNH,Tα = 8.9 Hz, NH(Fmoc)), 5.91 (d,
Rf = 0.74 (CH2Cl2–EtOAc, 10 : 1).
1H, JNH,H2 = 9.3 Hz, NH (GalNAc)), 5.38 (d, 1H, JH4,H3 = 2.9
Hz, 4-H), 5.14 (dd, 1H, JH3,H4 = 2.7 Hz, JH3,H2 = 11.2 Hz,
C35H42N4O12 (M = 710.73 g mol−1) [710.28].
1H-NMR (300 MHz, CDCl3): δ (ppm) = 7.75 (d, 2H, JH4,H3 = 3-H), 4.98 (d, 1H, JH1,H2 = 3.3 Hz, 1-H), 4.66–4.58 (m, 1H,
JH5,H6 = 7.5 Hz, 4-H-, 5-H-Fmoc), 7.64 (d, 2H, JH1,H2 = JH7, 2-H), 4.52–4.38 (m, 2H, CH2 (Fmoc)), 4.29–4.04 (m, 6H,
H8 = 7.3 Hz, 1-H-, 8-H-Fmoc), 7.40 (t, 2H, JH3,H2/H4 = JH6, 9-H-Fmoc, 5-H, 6a,b-H, Tα,Tβ), 2.17 (s, 3H, CH3 (Ac)), 2.04
H5/H7 = 7.44 Hz, 3-H-, 6-H-Fmoc), 7.34–7.28 (m, 2H, 2-H-, (s, 3H, CH3 (AcNH)), 1.98 (2× s, 6H, 2× CH3 (Ac)), 1.29 (d, 3H,
7-H-Fmoc), 5.66 (d, 1H, JNH,Tα = 9.3 Hz, NH (Fmoc)), 5.47 (d, JTγ,Tβ = 6.2 Hz, Tγ).
1H, JH4,H3 = 2.7 Hz, 4-H), 5.35 (dd, 1H, JH3,H4 = 3.0 Hz, JH3,
12-Hydroxy-4,7,10-trioxadodecanoic acid tert-butyl ester
H2 = 11.2 Hz, 3-H), 5.11 (d, 1H, JH1,H2 = 3.7 Hz, 1-H), (HO(CH2CH2O)3CH2CH2COOtBu) (6).39 To
a
solution of
4.46–4.43 (m, 1H, Tβ), 4.40–4.36 (m, 2H, 6a,b-H), 4.32–4.25 (m, 25.6 mL (188.0 mmol) anhydrous triethyleneglycol in 100 mL
3H, Tα, 5-H, 9-H-Fmoc), 4.10 (d, 1H, JCH2,CH = 6.3 Hz, CH2 of THF were added 40 mg (0.90 mmol) of sodium. When the
(Fmoc)), 3.64 (dd,1H, JH2,H1 = 3.4 Hz, JH2,H3 = 11.0 Hz, 2-H), sodium was dissolved, 9.6 mL of (66.00 mmol) tert-butyl acry-
2.15, 2.08, 2.04 (3 × s, 9H, 3 × CH3 (Ac)), 1.51 (s, 9H, CH3 late was added and then the mixture was stirred for 20 h and
(tBu)), 1.36 (d, 3H, JTγ,Tβ = 6.5 Hz, Tγ).
then neutralized with 8 mL of 1 M HCl. After removal of the
N-[(9H-Fluoren-9-ylmethoxy)carbonyl]-O-(2-acetamido-3,4,6- solvent, the residue was suspended in 100 mL of brine solu-
tri-O-acetyl-2-deoxy-α-D-galactopyranosyl)-L-threonine-tert-butyl tion and extracted thrice with 50 mL of ethyl acetate. The com-
ester
(Fmoc-Thr-(αAc3GalNAc)-OtBu)
(4).38 4.51
g
bined organic layers were dried over magnesium sulfate before
(69.00 mmol) zinc was activated with 2% aq. CuSO4 solution the solvent was removed. The resulting colorless oil was dried
and added to a mixture of 2.71 g (3.82 mmol) Fmoc-Thr- in vacuo to give a yield of 15.75 g (57.00 mmol, 86%); Rf = 0.32
(αAc3N3Gal)-OtBu 3 in 160 mL of THF–acetic anhydride–acetic (EtOAc). C13H26O6 (M = 278.34 g mol−1) [278.17].
acid (3 : 2 : 1). The mixture was then stirred at room tempera-
1H-NMR (300 MHz, CDCl3), δ (ppm) = 3.72–3.69 (m, 4H,
ture for 3 h. After completion of the reaction, the mixture was 3-CH2, 14-CH2), 3.67–3.58 (m, 10H, 5 × OCH2), 2.50 (t, 2H,
diluted with 500 mL, filtered through Hyflo®, concentrated JCH2, CH2 = 6.7 Hz, 2-CH2), 1.43 (s, 9H, tBu).
and purified by flash chromatography with silica (cHex–EtOAc,
1 : 2). Yield: 1.63 g (2.24 mmol, 59%); Rf = 0.24 (cHex–EtOAc, (N3(CH2CH2O)3CH2CH2COOtBu) (7).39 15.60 g (0.056 mol) of
1 : 2). C37H46N2O13 (M = 726.77 g mol−1) [726.30].
compound 6 was dissolved in 20 mL of dichloromethane and
12-Azido-4,7,10-trioxadodecanoic acid tert-butyl ester
1H-NMR (300 MHz, CDCl3), δ (ppm) = 7.73 (d, 2H, JH4,H3 = 19.2 mL of (136.2 mmol) NEt3 was added. Under cooling in an
JH5,H6 = 7.3 Hz, 4-H-, 5-H-Fmoc), 7.62 (d, 2H, JH1,H2 = JH7, ice-bath, 8.9 mL of (116.1 mmol) MsCl was added dropwise.
H8 = 7.1 Hz, 1-H-, 8-H-Fmoc), 7.39 (t, 2H, JH3,H2/H4 = JH6, After stirring for 4 h, precipitated NEt3·HCl was filtered
H5/H7 = 7.4 Hz, 3-H-, 6-H-Fmoc), 7.33–7.30 (m, 2H, 2-H-, through Hyflo® and the filtrate was extracted twice with 25 mL
7-H-Fmoc), 5.99 (d, 1H, JNH,Tα = 9.9 Hz, NH (Fmoc)), 5.55 of dichloromethane, washed thrice with 25 mL of ice-water
(d, 1H, JNH,H2 = 8.9 Hz, NH (GalNAc)), 5.38 (d, 1H, JH4,H3 = and twice with brine solution. Then the organic layers were
2.4 Hz, 4-H), 5.07 (dd, 1H, JH3,H4 = 2.4 Hz, JH3,H2 = 10.7 Hz, dried with magnesium sulfate and filtered. The solvent was
3-H), 4.86 (d, 1H, JH1,H2 = 2.7 Hz, 1-H), 4.62–4.57 (m, 1H, removed in vacuo and the remaining residue was dissolved in
2-H), 4.46–4.35 (m, 2H, CH2 (Fmoc)), 4.27–4.04 (m, 6H, 20 mL of DMF and mixed with 22.46 g (345.52 mmol) NaN3.
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