Successful Combination of (Methoxydimethyl)methyl (MIP) and (2-Naphthyl)methyl (NAP) Ethers for the Synthesis of Arabinogalactan-Type Oligosaccharides

Magdolna Csávás; Anikó Borbás; László Szilágyi; András Lipták

doi:10.1055/s-2002-31893

LETTER

Successful Combination of (Methoxydimethyl)methyl (MIP) and (2-Naphthyl)methyl (NAP) Ethers for the Synthesis of Arabinogalactan-Type Oligosaccharides

Magdolna Csávás^a, Anikó Borbás^a, László Szilágyi^b, András Lipták*^a
^a Research Group for Carbohydrates of the Hungarian Academy of Sciences, 4010 Debrecen, P.O. Box 55, Hungary
^b Department of Organic Chemistry, University of Debrecen, 4010 Debrecen, P.O. Box 20, Hungary
Fax: +36(52)512913; e-Mail: liptaka@tigris.klte.hu;

Abstract

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Abstract

In order to characterise the presumed epitopes of arabinogalactans, isolated from the extract of the cell-cultured Echinacea purpurea, two oligosaccharides were synthesized. The whole synthetic route was based on the successful combination of the (methoxydimethyl)methyl (MIP) and the (2-naphthyl)methyl ether (NAP) protecting groups. A β-(1→6)-linked trigalactoside was prepared, which contained a NAP ether at position 2′.This protecting group was selectively removed using either DDQ or Pd-C/H₂ and the acceptor was ready for further glycosylation.We have used two arabinofuranosyl donor compounds: 2,3,5-tri-O-acetyl arabinofuranosyl trichloroacetimidate and a peracetylated α-(1→5)-linked diarabinofuranosyl trichloroacetimidate. For the deprotection of the tetra- and pentasaccharides a common procedure was used. All of the synthesized compounds were characterized by ¹H and ¹³C NMR spectroscopy, as well as by MALDI-TOF mass-spectrometry.

Key words

arabinogalactan - oligosaccharides - protecting groups - (methoxydimethyl)methyl ether (MIP) - (2-naphthyl)methyl ether (NAP)

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References

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Spectroscopic data of compound 9: ¹H NMR (500 MHz, CDCl₃): δ 5.44 (d, 1 H, J _1,2 = 5.6 Hz, A-1), 4.26-4.28 (m, 1 H, A-2), 4.59 (dd, 1 H, J _2,3 = 7.9 Hz, J _3,4 = 2.3 Hz, A-3), 4.19 (dd, 1 H, J _4,5 = 1.9 Hz, A-4), 3.98-4.1 (m, 1 H, A-5), 4.15 (d, 1 H, J _5,6 = 8.6 Hz, A-6a), 3.58 (dd, 1 H, J _6a,6b = 10.3 Hz, A-6b), 4.26 (d, 1 H, J _1,2 = 5.2 Hz, B-1), 3.82 (dd, 1 H, J _2,3 = 8.3 Hz, B-2), 4.25 (s, 1 H, B-3), 4.07 (dd, 1 H, J _4,5 = 1.9 Hz, B-4), 3.94-3.96 (m, 1 H, B-5), 4.05 (dd, 1 H, J _5,6 = 2.3 Hz, J _6a,6a = 7.7 Hz, B-6a), 3.94-3.98 (m, 1 H, B-6b), 4.72 (d, 1 H, J _1,2 = 8.1 Hz, C-1), 5.23 (dd, 1 H, J _2,3 = 10.5 Hz, C-2), 5.01 (d, 1 H, J _3,4 = 3.4 Hz, C-3), 5.38 (dd, 1 H, J _4,5 = 0.9 Hz, C-4), 3.92-3.95 (m, 1 H, C-5), 4.15 (d, 2 H, J _6a,6b = 6.7 Hz, C-6a, C-6b), 5.45 (s, 1 H, d-1), 5.13 (s, 1 H, D-2), 4.99 (d, 1 H, J _3,4 = 3.7 Hz, D-3), 4.68 (dd, 1 H, J _4,5 = 7.1 Hz, D-4), 4.48 (dd, 1 H, J _5,6a = 3.4 Hz, J _6a,6b = 12.5 Hz, D-5a), 4.32 (dd, 1 H, J _5,6b = 2.5 Hz, D-5b), 1.25, 1.28, 1.38, 1.49, 1.52 (s, 24 H, 6 CH _3ip), 1.95, 2.02, 2.08, 2.01, 2.13, 2.15 (s, 21 H, 7 CH _3acetyl).
¹³C NMR (500 MHz, CDCl₃): 95.71 (A-1), 69.59 (A-2), 70.47 (A-3), 71.16 (A-4), 66.80 (A-5), 69.40 (A-6), 100.78 (B-1), 73.94 (B-2), 79.55 (B-3), 73.46 (B-4), 70.36 (B-5), 68.38 (B-6), 101.02 (C-1), 68.46 (C-2), 70.44 (C-3), 66.74 (C-4), 72.85 (C-5), 60.88 (C-6), 103.07 (D-1), 80.52 (D-2), 76.62 (D-3), 80.49 (D-4), 63.58 (D-5), 20.28, 20.36, 20.51, 20.54, 20.68 (CH_3acetyl), 23.75, 24.51, 25.60, 25.69, 26.02, 27.71 (CH_3ip), 108.03, 108.55, 110.34 (C_quat).
[α]_D: -45.32 (c 0.26, CHCl₃). MALDI-TOF measurements: 1073.25 [M + Na]⁺

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Spectroscopic data of compound 14: ¹H NMR (500 MHz, CDCl₃): δ 5.59 (s, 1 H, H-1), 5.32 (d, 1 H, J _2,3 = 2.16 Hz, H-2), 5.28 (dd, 1 H, J _3,4 = 6.5 Hz, H-3), 4.32-4.35 (m, 1 H, H-4), 3.95 (dd, 1 H, J _4,5a = 4.3 Hz, J _5a,5b = 12.9 Hz, H-5a), 3.75 (dd, 1 H, J _4,5b = 3.8 Hz, H-5b), 5.14 (s, 1 H, H-1′), 5.16 (s, 1 H, H-2′), 4.94 (d, 1 H, J _3,4 = 4.3 Hz, H-3′), 4.26-4.30 (m, 1 H, H-4′), 4.45 (dd, 1 H, J _4,5a = 3.9 Hz, J _5a,5b = 12.9 Hz, H-5′a), 4.23 (dd, 1 H, J _4,5b = 4.7 Hz, H-5′b), 3.76 (s, 3 H, -OCH ₃), 2.09-2.18 (s, 15 H, CH _3acetyl), 6.78-7.02 (m, 4 H, -Ph). ¹³C NMR (500 MHz, CDCl₃): 104.49 (C-1), 81.74 (C-2), 76.04 (C-3), 81.38 (C-4), 64.87 (C-5), 105.18 (C-1′), 80.68 (C-2′), 76.96 (C-3′), 80.49 (C-4′), 62.96 (C-5′), 55.31 (-OCH₃), 20.30, 20. 43, 20.48 (CH_3acetyl), 169.11, 169.50, 169.85, 169.93, 170,26 (CH₃ CO-), 114.25, 117.97 (-Ph), 149.72, 154.89 (-Ph_quat).
[α]_D: -30.35 (c 0.32, CHCl₃). MALDI-TOF measurements: 621.51 [M + Na]⁺

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Spectroscopic data of compound 17: ¹H NMR (500 MHz, CDCl₃): δ 5.42 (d, 1 H, J _1,2 = 5.2 Hz, A-1), 4.24-4.27 (m, 2 H, A-2, B-3), 4.56 (d, 1 H, J _3,4 = 2.3 Hz, A-3), 4.18 (dd, 1 H, J _4,5 = 8 Hz, A-4), 3.94-3.98 (m, 1 H, A-5), 3.58 (d, 1 H, A-6a), 4.13 (dd, 1 H, J _5,6b = 2.3 Hz, J _6a,6b = 10.3 Hz, A-6b), 4.26 (d, 1 H, J _1,2 = 8.5 Hz, B-1), 3.81 (dd, 1 H, J _2,3 = 6 Hz, B-2), 4.03 (dd, 1 H, J _3,4 = 1.8 Hz, B-4), 3.92-3.95 (m, 1 H, B-5), 3.92-3.96 (m, 1 H, B-6a), 4.03-4.06 (m, 1 H, B-6b), 4.69 (d, 1 H, J _1,2 = 8 Hz, C-1), 5.22 (dd, 1 H, J _2,3 = 10 Hz, C-2), 4.98 (dd, 1 H, J _3,4 = 3.5 Hz, C-3), 5.36 (dd, 1 H, J _4,5 = 1.1 Hz, C-4), 3.89-3.93 (m, 1 H, C-5), 4.13-4.16 (m, 2 H, C-6a, C-6b), 4.17 (s, 1 H, D-1), 5.08 (s, 1 H, D-2), 5.15 (d, 1 H, J _3,4 = 1.6 Hz, D-3), 4.56-4.5 (m, 1 H, D-4), 4.14 (d, 1 H, J _4,5a = 1.1 Hz, D-5a), 3.58 (dd, 1 H, J _4,5ab = 1.6 Hz, J _5a,5b = 9.8 Hz, d-5b), 5.46 (s, 1 H, E-1), 5.18 (s, 1 H, E-2), 4.91 (dd, 1 H, J = 4.9 Hz, J = 0.8 Hz, E-3), 4.29-4.34 (m, 1 H, E-4), 4.44 (dd, 1 H, J _4,5a = 3.1 Hz, J _5a,5b = 11.8 Hz, E-5a), 4.21-4.24 (m, 1 H, E-5b), 1.26, 1.30, 1.31, 1.36, 1.49, 1.53 (s, 24 H, CH _3ip), 1.95, 2.04, 2.06, 2.07, 2.08, 2.09, 2.10, 2.12, 2.15 (CH _3acetyl).
¹³C NMR (200 MHz, CDCl₃): 96.00 (A-1), 69.91 (A-2), 70.74 (A-3), 71.40 (A-4), 67.04 (A-5), 69.55 (A-6), 101.07 (B-1), 74.08 (B-2), 79.84 (B-3), 73.75 (B-4), 70.74 (B-5), 68.62 (B-6), 101.30 (C-1), 68.75 (C-2), 70.74 (C-3), 67.04 (C-4), 70.74 (C-5), 61.13 (C-6), 104.91 (D-1), 80.84 (D-2), 77.63 (D-3), 80.98 (D-4), 63.35 (D-5), 104.91 (E-1), 81.34 (E-2), 76.13 (E-3), 81.84 (E-4), 64.87 (E-5), 20.58, 20.75 (CH_3acetyl), 24.08, 24.73, 25.87, 26.00, 26.29, 27.94, 29.19, 30.83 (CH_3ip), 108.12, 108.85, 110.57 (C_quat), 169.27, 169.35, 169.80, 169.88, 170.15, 170.27, 170.36, 170.48 (CH₃ CO).
[α]_D: -66.18 (c 0.3173, CHCl₃). MALDI-TOF measurements: 1289.87 [M + Na]⁺

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Spectroscopic data of compound 1: ¹H NMR (500 MHz, D₂O): δ 5.21 (A-1α, J _1,2 = 3.8 Hz), 4.53 (A-1β, J _1,2 = 7.9 Hz), 3.41 (A-2β), 3.60 (A-3β), 4.49 (B-1, J _1,2 = 7.8 Hz), 3.58 (B-2), 3.72 (B-3), 4.40 (C-1, J _1,2 = 7.8 Hz), 3.44 (C-2), 3.60 (C-3), 5.24 (D-1, J _1,2 = 3.7 Hz), 4.12 (D-2), 3.90 (D-3), 4.17 (D-4), 3.67 and 3.75 (D-5a and d-5b).¹³C NMR (500 MHz, H₂O): 92.07 (A-1α), 96.09 (A-1ι), 71.52 (A-2ι), 72.39 (A-3β), 69.16 (A-6β), 101.61 (B-1), 75.66 (B-2), 72.49 (B-3), 68.73 (B-6), 103.07 (C-1), 70.43 (C-2), 72.41 (C-3), 60.69 (C-6), 107.93 (D-1), 80.64 (D-2), 76.57 (D-3), 83.95 (D-4), 61.07 (D-5).
[α]_D: -1.55 (c 0.1931, H₂O).MALDI-TOF measurements: 657.14 [M + Na]⁺

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Spectroscopic data of compound 2: ¹H NMR (500 MHz, D₂O): δ 5.20 (A-1α, J _1,2 = 3.98 Hz,), 4.52 (A-1β, J _1,2 = 8.16 Hz), 3.72 (A-2α), 3.44 (A-2ι), 3.59 (A-3), 3.91 (A-4), 4.48 (B-1, J _1,2 = 8.16 Hz), 3.59 (B-2), 3.71 (B-3), 3.91 (B-4), 4.40 (C-1, J _1,2 = 8.16 Hz), 3.48 (C-2), 3.59 (C-3), 3.87 (C-4), 5.03 (D-1, J _1,2 = 2.39 Hz,), 4.08 (D-2), 5.23 (E-1), 4.12 (E-2).
¹³C NMR (500 MHz, H₂O): 92.08 (A-1α), 96.10 (A-1β), 71.55 (A-2), 72.41 (A-3), 60.69 (A-6), 101.69 (B-1), 75.60 (B-2), 74.85 (B-3), 102.84 (C-1), 70.43 (C-2), 72.35 (C-3), 69.17 and 68.73 (B-6 and C-6), 107.10 (D-1), 80.60 (D-2), 76.24 (D-3), 82.25 (D-4), 66.55 (D-5), 107.98 (E-1), 80.60 (E-2), 76.90 (E-3), 83.63 (E-4), 60.89 (E-5).
MALDI-TOF measurements:791.13 [M + Na]⁺.