An Efficient Method for the Synthesis of 2,6-Branched Galacto-Oligo­saccharides and Its Applications to the Synthesis of Three Tetrasaccharides and a Hexasaccharide Related to the Arabinogalactans (AGs)

Jun Ning; Yuetao Yi; Zhe Yao

doi:10.1055/s-2003-42109

LETTER

An Efficient Method for the Synthesis of 2,6-Branched Galacto-Oligosaccharides and Its Applications to the Synthesis of Three Tetrasaccharides and a Hexasaccharide Related to the Arabinogalactans (AGs)

Jun Ning*, Yuetao Yi, Zhe Yao
Research Center for Eco-Environmental Sciences, Academia Sinica, P. O. Box 2871, Beijing 100085, P. R. China
Fax: +86(10)62923563; e-Mail: jning@mail.rcees.ac.cn;

Abstract

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Abstract

An efficient method for the synthesis of 2,6-branched galacto-oligosaccharides has been developed by using 6-O-Ac-2,3,4-tri-O-Bz-α-d-galactopyranosyl trichloroacetimidate, 2,6-di-O-Ac-3,4-di-O-Bz-α-d-galactopyranosyl trichloroacetimidate and 2-O-Ac-3,4,6-tri-O-Bz-α-d-galactopyranosyl trichloroacetimidate as synthons. Three tetrasaccharides and a hexasaccharides related to AGs from plants were readily prepared using this method.

Key words

arabinogalactan - oligosaccharides - synthesis - glycosides - glycosylations

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References

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All new compounds gave satisfactory elemental analysis results. Selected physical data for some key compounds are as follows:
For 8: [α]_D +20.9 (c 1.0, CHCl₃). ¹H NMR (400 MHz, CDCl₃): δ = 8.66 (s, 1 H, CNHCCl₃), 8.08-7.26 (m, 15 H, 3 × PhH), 6.89 (d, J _1,2 = 3.6 Hz, 1 H, H-1), 6.06 (dd, 1 H, H-4), 6.05 (dd, 1 H, H-3), 5.94 (dd, 1 H, H-2), 4.72 (m, 1 H, H-5), 4.28-4.26 (m, 2 H, H-6a,6b), 1.99 (s, 3 H, CH₃CO). Anal. Calcd for C₃₁H₂₆NO₁₀CI₃: C, 54.84; H, 3.86. Found: C, 54.69; H, 3.98.
For 13: [α]_D +21.2 (c 1.0, CHCl₃). ¹H NMR (400 MHz, CDCl₃): δ = 8.71 (s, 1 H, CNHCCl₃), 8.06-7.33 (m, 15 H, 3 × PhH), 6.79 (d, J _1,2 = 3.6 Hz, 1 H, H-1), 6.11 (dd, 1 H, H-4), 5.86 (dd, 1 H, H-3), 5.72 (dd, 1 H, H-2), 4.80 (m, 1 H, H-5), 4.58 (dd, 1 H, H-6a), 4.40 (dd, 1 H, H-6b), 1.98 (s, 3 H, CH₃CO). Anal. Calcd for C₃₁H₂₆NO₁₀CI₃: C, 54.84; H, 3.86. Found: C, 54.72; H, 3.90. For 17: [α]_D +55 (c 1.0, CHCl₃). ¹H NMR (400 MHz, CDCl₃): δ = 8.73 (s, 1 H, CNHCCl₃), 8.04-7.31 (m, 10 H, 2 × PhH), 6.76 (d, J _1,2 = 3.6 Hz, 1 H, H-1), 6.00 (dd, 1 H, H-4), 5.81 (dd, 1 H, H-3), 5.68 (dd, 1 H, H-2), 4.65 (m, 1 H, H-5), 4.22 (m, 2 H, H-6a,b), 1.98, 1.97 (2 × s, 6 H, 2 CH₃CO). Anal. Calcd for C₂₆H₂₄Cl₃NO₁₀: C, 50.63; H, 3.92. Found: C, 50.79; H, 3.85.
For 19: [α]_D +67.8° (c 1.0, CHCl₃). ¹H NMR (400 MHz, CDCl₃): δ = 8.13-7.25 (m, 15 H, 3 × PhH), 5.85 (dd, 1 H, H-2), 5.81 (dd, 1 H, H-4), 5.58 (dd, 1 H, H-3), 4.79 (d, J _1,2 = 7.9 Hz, 1 H, H-1), 4.03 (m, 1 H, H-5), 3.97-3.54 (m, 4 H, H-6a,6b, CH ₂C₁₁H₂₃), 1.56-0.86 (m, 23 H, CH₂C₁₁ H ₂₃). Anal. Calcd for C₃₉H₄₈O₉: C, 70.89; H, 7.32. Found: C, 70.51; H, 7.39.
For 21: [α]_D +85.3 (c 1.0, CHCl₃). ¹H NMR (400 MHz, CDCl₃): δ = 8.04-7.22 (m, 25 H, 5 × PhH), 6.00 (dd, 1 H, H-4), 5.74 (dd, 1 H, H-2), 5.62 (dd, 1 H, H-4), 5.56 (dd, 1 H, H-3), 5.29 (dd, 1 H, H-3), 4.77 (d, J _1,2 = 7.9 Hz, 1 H, H-1), 4.52 (d, J _1,2 = 7.6 Hz, 1 H, H-1), 1.60-0.81 (m, 23 H, CH₂C₁₁ H ₂₃). Anal. Calcd for C₅₉H₆₆O₁₆: C, 68.72; H, 6.45. Found: C, 68.49; H, 6.52.
For 22: [α]_D +83.8 (c 1.0, CHCl₃). ¹H NMR (400 MHz, CDCl₃): δ = 8.10-7.22 (m, 45 H, 9 × PhH), 5.99 (dd, 1 H, H-4), 5.90 (dd, 1 H, H-4), 5.78-5.74 (m, 2 H, H-2,4), 5.68 (dd, 1 H, H-2), 5.59 (dd, 1 H, H-3), 5.53 (dd, 1 H, H-3), 5.24 (dd, 1 H, H-3), 4.79 (d, J _1,2 = 7.9 Hz, 1 H, H-1), 4.63 (d, J _1,2 = 7.8 Hz, 1 H, H-1), 4.46 (d, J _1,2 = 7.6 Hz, 1 H, H-1), 1.60-0.86 (m, 23 H, CH₂C₁₁ H ₂₃). Anal. Calcd for C₉₃H₉₂O₂₅: C, 69.39; H, 5.76. Found: C, 69.62; H, 5.81.
For 23: [α]_D +48.6° (c 1.0, CHCl₃). ¹H NMR (400 MHz, CDCl₃): δ = 7.98-7.12 (m, 60 H, 12 × PhH), 6.02 (dd, 1 H, H-4), 5.86 (dd, 1 H, H-4), 5.77 (dd, 1 H, H-4), 5.70 (dd, 1 H, H-2), 5.64 (dd, 1 H, H-2), 5.58-5.52 (m, 3 H, 3 × H-3), 5.49 (s, 1 H, H-1), 5.37 (d, J _2,3 = 1.5 Hz, 1 H, H-2), 5.35 (dd, 1 H, H-3), 4.70 (d, J _1,2 = 8.0 Hz, 1 H, H-1), 4.59 (d, J _1,2 = 7.6 Hz, 1 H, H-1), 4.53 (d, J _1,2 = 7.9 Hz, 1 H, H-1), 1.36-0.86 (m, 23 H, CH₂C₁₁ H ₂₃). ¹³C NMR (100 MHz, CDCl₃): δ = 166.19, 165.77, 165.48, 165.47, 165.41, 165.28, 165.23, 165.19, 165.16, 165.11, 165.0, 164.96 (12 PhCO), 106.51, 101.68, 101.44, 100.86 (4 C-1). Anal. Calcd for C₁₁₉H₁₁₂O₃₂: C, 69.58; H, 5.50. Found: C, 69.23; H, 5.59.
For 25: [α]_D +75.5 (c 1.0, CHCl₃). ¹H NMR (400 MHz, CDCl₃): δ = 8.13-7.23 (m, 30 H, 6 × PhH), 5.92 (dd, 1 H, H-4), 5.80 (dd, 1 H, H-2), 5.76 (dd, 1 H, H-4), 5.68 (dd, 1 H, H-2), 5.53 (dd, 1 H, H-3), 5.50 (dd, 1 H, H-3), 4.83 (d, J _1,2 = 7.9 Hz, 1 H, H-1), 4.63 (d, J _1,2 = 8.0 Hz, 1 H, H-1), 1.39-0.87 (m, 23 H, CH₂C₁₁ H ₂₃). Anal. Calcd for C₆₆H₇₀O₁₇: C, 69.83; H, 6.21. Found: C, 69.91; H, 6.37.
For 27: [α]_D +86.5 (c 1.0, CHCl₃). ¹H NMR (400 MHz, CDCl₃): δ = 8.05-7.15 (m, 45 H, 9 × PhH), 5.94 (dd, 1 H, H-4), 5.86 (dd, 1 H, H-4), 5.83 (d, 1 H, H-4), 5.77 (dd, 1 H, H-2), 5.68 (dd, 1 H, H-2), 5.55 (dd, 1 H, H-3), 5.52 (dd, 1 H, H-3), 5.32 (dd, 1 H, H-3), 4.87 (d, J _1,2 = 7.9 Hz, 1 H, H-1), 4.67 (d, J _1,2 = 7.9 Hz, 1 H, H-1), 4.52 (d, J _1,2 = 7.7 Hz, 1 H, H-1), 1.40-0.86 (m, 23 H, CH₂C₁₁ H ₂₃). Anal. Calcd for C₉₃H₉₂O₂₅: C, 69.39; H, 5.76. Found: C, 69.48; H, 5.81.
For 28: [α]_D +56.0 (c 1.0, CHCl₃). ¹H NMR (400 MHz, CDCl₃): δ = 8.07-7.20 (m, 60 H, 12 × PhH), 6.01 (dd, 1 H, H-4), 5.88 (dd, 1 H, H-4), 5.79 (dd, 1 H, H-4), 5.70 (dd, 1 H, H-2), 5.68 (dd, 1 H, H-2), 5.54-5.49 (m, 3 H, 3 × H-3), 5.46 (dd, 1 H, H-3), 5.45 (s, 1 H, H-1), 5.36 (d, J _2,3 = 1.2 Hz, 1 H, H-2), 4.65 (d, 1 H, J _1,2 = 8.2 Hz, H-1), 4.63 (d, 1 H, J _1,2 = 8.2 Hz, H-1), 4.51 (d, 1 H, J _1,2 = 7.6 Hz, 1 H, H-1). 1.35-0.85 (m, 23 H, CH₂C₁₁ H ₂₃). ¹³C NMR (100 MHz, CDCl₃): δ = 166.21, 165.73, 165.47, 165.43, 165.40, 165.33,165.33, 165.29, 165.21, 165.07, 165.07, 164.98 (12 PhCO), 106.27, 101.46, 101.19, 100.93 (4 C-1). Anal. Calcd for C₁₁₉H₁₁₂O₃₂: C, 69.58; H, 5.50. Found: C, 69.74; H, 5.46.
For 1: [α]_D -6.5 (c 1.0, H₂O). ¹H NMR (400 MHz, D₂O): δ = 5.26 (s, 1 H, H-1), 4.48 (d, J _1,2 = 6.0 Hz, 1 H, H-1), 4.39 (d, J _1,2 = 7.6 Hz, 1 H, H-1), 4.30 (d, J _1,2 = 6.0 Hz, 1 H, H-1), 1.58-0.83 (m, 23 H, CH₂C₁₁ H ₂₃). MALDI-TOF MS: m/z calcd for C₃₅H₆₄O₂₀: 804.88 [M] , found: 827.54 (M + Na)⁺.
For 2: [α]_D -8.6 (c 1.0, H₂O). ¹H NMR (400 MHz, D₂O): δ = 5.33 (s, 1 H, H-1), 4.55 (d, J _1,2 = 6.0 Hz, 1 H, H-1), 4.46 (d, J _1,2 = 6.0 Hz, 1 H, H-1), 4.38 (d, J _1,2 = 6.0 Hz, 1 H, H-1), 1.66-0.92 (m, 23 H, CH₂C₁₁ H ₂₃). MALDI-TOF MS: m/z calcd for C₃₅H₆₄O₂₀: 804.88 [M], found: 827.81 (M + Na)⁺.
For 30: [α]_D +82.7 (c 1.0, CHCl₃). ¹H NMR (400 MHz, CDCl₃): δ = 8.08-7.26 (m, 10 H, 2 × PhH), 5.71 (dd, 1 H, H-4), 5.38 (dd, 1 H, H-3), 4.51 (d, J _1,2 = 7.7 Hz, 1 H, H-1), 4.13 (dd, 1 H, H-2), 3.98(dd, 1 H, H-6a), 3.93 (m, 1 H, H-5), 3.78 (dd, 1 H, H-6b), 3.64-3.59 (m, 2 H, CH ₂C₁₁H₂₃), 1.36-0.86 (m, 23 H, CH₂C₁₁ H ₂₃). Anal. Calcd for C₃₂H₄₄O₈: C, 69.04; H, 7.97. Found: C, 69.19; H, 8.04.
For 31: [α]_D +88.3 (c 1.0, CHCl₃). ¹H NMR (400 MHz, CDCl₃): δ = 8.07-7.24 (m, 25 H, 5 × PhH), 5.83 (dd, 1 H, H-4), 5.78 (dd, 1 H, H-4), 5.73 (dd, 1 H, H-2), 5.50 (dd, 1 H, H-3), 5.29 (dd, 1 H, H-3), 4.84 (d, J _1,2 = 7.9 Hz, 1 H, H-1), 4.37 (d, J _1,2 = 7.7 Hz, 1 H, H-1), 1.35-0.86 (m, 23 H, CH₂C₁₁ H ₂₃). Anal. Calcd for C₆₁H₆₈O₁₇: C, 68.27; H, 6.39. Found: C, 68.19; H, 6.35.
For 33: [α]_D +73.4 (c 1.0, CHCl₃). ¹H NMR (400 MHz, CDCl₃): δ = 8.01-7.13 (m, 40 H, 8 × PhH), 5.87 (dd, 1 H, H-4), 5.78 (dd, 1 H, H-2), 5.74 (dd, 1 H, H-4), 5.52-5.47 (m, 3 H, 3 × H-3), 5.36 (s, 1 H, H-1), 5.21 (d, J _1,2 = 0.9 Hz, 1 H, H-2), 4.80 (d, J _1,2 = 7.9 Hz, 1 H, H-1), 4.51 (d, J _1,2 = 7.8 Hz, 1 H, H-1), 1.4-0.86 (m, 23 H, CH₂C₁₁ H ₂₃). Anal. Calcd for C₈₅H₈₆O₂₃: C, 69.19; H, 5.87. Found: C, 69.44; H, 5.91.
For 34: [α]_D +77.6 (c 1.0, CHCl₃). ¹H NMR (400 MHz, CDCl₃): δ = 8.01-7.13 (m, 50 H, 10 × PhH), 5.89 (dd, 1 H, H-4), 5.85 (dd, 1 H, H-4), 5.72 (dd, 1 H, H-4), 5.70 (dd, 1 H, H-2), 5.55-5.47 (m, 3 H, 3 × H-3), 5.43 (s, 1 H, H-1), 5.36 (d, J _1,2 = 1.1 Hz, 1 H, H-2), 5.35 (dd, 1 H, H-3), 5.25 (dd, 1 H, H-3), 4.82 (d, J _1,2 = 7.8 Hz, 1 H, H-1), 4.52 (d, J _1,2 = 7.8 Hz, 1 H, H-1), 4.46 (d, J _1,2 = 7.9 Hz, 1 H, H-1), 1.89, 1.88 (2 × s, 6 H, 2 × CH₃CO), 1.36-0.86 (m, 23 H, CH₂C₁₁ H ₂₃). ¹³C NMR (100 MHz, CDCl₃): δ = 170.18, 169.23 (2 × CH₃ CO), 166.08, 165.57, 165.44, 165.44, 165.40, 165.27, 165.20, 165.11, 165.04, 164.87 (10 × PhCO), 106.03, 101.98, 100.94, 100.22 (4 × C-1) 20.53, 20.44 (2 × CH₃CO). Anal. Calcd for C₁₀₉H₁₀₈O₃₂: C, 67.83; H, 5.64. Found: C, 67.68; H, 5.69.
For 37: [α]_D +37.5 (c 1.0, CHCl₃). ¹H NMR (400 MHz, CDCl₃): δ = 5.41 (s, 1 H, H-1), 5.30 (s, 1 H, H-1), 4.65 (d, J _1,2 = 7.6 Hz, 1 H, H-1), 4.47 (d, J _1,2 = 7.7 Hz, 1 H, H-1), 4.39 (d, J _1,2 = 7.7 Hz, 1 H, H-1), 4.32 (d, J _1,2 = 7.5 Hz, 1 H, H-1). ¹³C NMR (100 MHz, CDCl₃): δ = 106.17, 106.02, 101.92, 101.22, 100.90, 100.82 (6 × C-1). Anal. Calcd for C₁₆₅H₁₅₀O₄₆: C, 69.08; H, 5.27. Found: C, 69.54; H, 5.17.
For 3: [α]_D -17.5 (c 1.0, H₂O). ¹H NMR (400 MHz, D₂O):
δ = 5.22 (s, 1 H, H-1), 4.38, 4.36, 4.11 (d, 3 H, 3 × H-1), 1.54-0.79 (m, 23 H, CH₂C₁₁ H ₂₃). MALDI-TOF MS: m/z calcd for C₃₅H₆₄O₂₀: 804.88 [M], found: 827.65 (M + Na)⁺.
For 4: [α]_D -6.8 (c 1.0, H₂O). ¹H NMR (400 MHz, D₂O): δ = 5.25 (s, 1 H, H-1), 5.23 (s, 1 H, H-1), 4.52 (d, J _1,2 = 6.8 Hz, 1 H, H-1), 4.01-4.39 (m, 3 H, H-1), 1.56-0.84 (m, 23 H, CH₂C₁₁ H ₂₃). ¹³C NMR (100 MHz, D₂O): δ = 108.23, 108.23, 103.45, 103.45, 103.25, 102.17 (6 × C-1). MALDI-TOF MS: m/z calcd for C₄₆H₈₂O₂₉: 1099.14 [M], found: 1122.26 (M + Na)⁺.

An Efficient Method for the Synthesis of 2,6-Branched Galacto-Oligo­saccharides and Its Applications to the Synthesis of Three Tetrasaccharides and a Hexasaccharide Related to the Arabinogalactans (AGs)

An Efficient Method for the Synthesis of 2,6-Branched Galacto-Oligosaccharides and Its Applications to the Synthesis of Three Tetrasaccharides and a Hexasaccharide Related to the Arabinogalactans (AGs)