Glycosyl N-Tosyl Benzimidate as a New Building Block for Chemical Glycosylation

Shaojing Liu; Yannan Peng; Peng Wang; Ming Li

doi:10.1055/s-0031-1290920

Synlett, Inhaltsverzeichnis

Synlett 2012; 23(10): 1501-1504
DOI: 10.1055/s-0031-1290920

letter

Glycosyl N-Tosyl Benzimidate as a New Building Block for Chemical Glycosylation

Shaojing Liu

Key Laboratory of Marine Medicine, Ministry of Education, School of Medicine and Pharmacy, Ocean University of China, 5 Yushan Road, Qingdao, Shandong 266003, P. R. of China, Fax: +86(532)82033054 eMail: lmsnouc@ouc.edu.cn

,

Yannan Peng

Key Laboratory of Marine Medicine, Ministry of Education, School of Medicine and Pharmacy, Ocean University of China, 5 Yushan Road, Qingdao, Shandong 266003, P. R. of China, Fax: +86(532)82033054 eMail: lmsnouc@ouc.edu.cn

,

Peng Wang

Key Laboratory of Marine Medicine, Ministry of Education, School of Medicine and Pharmacy, Ocean University of China, 5 Yushan Road, Qingdao, Shandong 266003, P. R. of China, Fax: +86(532)82033054 eMail: lmsnouc@ouc.edu.cn

,

Ming Li*

Key Laboratory of Marine Medicine, Ministry of Education, School of Medicine and Pharmacy, Ocean University of China, 5 Yushan Road, Qingdao, Shandong 266003, P. R. of China, Fax: +86(532)82033054 eMail: lmsnouc@ouc.edu.cn

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Abstract

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Abstract

Seven novel glycosyl N-tosyl benzimidates were prepared by the reactions of the corresponding hemiacetals with imidoyl chloride in 55–88% yields, which were smoothly converted to glycosides, upon treatment with alcohols and catalytic TMSOTf, in 57–99% yields.

Key words

glycosylation - glycosyl N-tosyl benzimidate - glycosyl donor - oligosaccarides synthesis - saponins synthesis

Volltext

Referenzen

References

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10 A Typical Procedure for the Preparation of Glycosyl N-Tosyl Benzimidate To a solution of mannosyl hemiactal (500 mg, 0.84 mmol) in acetone (3 mL) was added K₂CO₃ (290 mg, 2.10 mmol, 2.50 equiv) and N-tosylbenzimidoyl chloride (296 mg, 1.0 mmol, 1.20 equiv) at ambient temperature. After stirring for 2 h the solid was filtered off, and the filtrate was concentrated under vacuum, and the residue was purified by silica gel chroma-tography (EtOAc–PE = 1:4) to give imidate 2a as a white solid (617 mg, 0.72 mmol, 86%). [α]_D ²⁰ = –30.1 (c 1.09 CHCl₃). ¹H NMR (600 MHz, CDCl₃): δ = 8.11 (d, J = 7.2 Hz, 2 H), 8.03 (m, 4 H), 7.93 (d, J = 7.14 Hz, 2 H), 7.82 (m, 4 H), 7.68 (t, J = 7.68 Hz, 1 H), 7.59 (m, 4 H), 7.50 (t, J = 7.14 Hz, 1 H), 7.43 (m, 5 H), 7.35 (t, J = 7.74 Hz, 2 H), 7.28 (d, J = 8.28 Hz, 2 H), 7.20 (d, J = 8.28 Hz, 2 H), 6.38 (d, J = 1.62 Hz, 1 H), 6.20 (t, J = 10.44 Hz, 1 H), 5.91 (m, 2 H), 4.73 (dd, J = 2.16, 12.06 Hz, 1 H), 4.59 (m, 1 H), 4.47 (dd, J = 4.38, 12.12 Hz, 1 H), 2.34 (s, 3 H). ¹³C NMR (150 MHz,CDCl₃): δ = 166.5, 166.1, 165.6, 165.4, 164.9, 143.5, 138.6, 133.9, 133.8, 133.5, 133.4, 133.3, 130.0, 129.9, 129.8, 129.5, 128.8, 128.7, 128.65, 128.6, 128.5, 127.0, 94.6, 71.8, 69.7, 68.9, 66.0, 62.5, 21.6. ESI-MS: m/z = 876.2 [M + Na]⁺. HRMS: m/z calcd for C₄₈H₃₉O₁₂NNaS [M + Na]⁺: 876.2091; found: 876.2085
11 Typical Procedure for the Glycosylation A solution of 2a (100 mg, 0.12 mmol, 1.40 equiv) and 3a (27 mg, 0.086 mmol) in anhyd CH₂Cl₂ (2 mL) was stirred for 30 min in the presence of freshly activated 5 Å MS (150 mg) under argon atmosphere. At this point, the mixture was cooled to 0 °C, then TMSOTf (1.50 μL, 0.0086 mmol, 0.1 equiv) was added. After the resulting mixture was stirred for another 2 h, Et₃N (1.20 μL, 0.0086 mmol, 0.1 equiv) was added to quench the reaction. The solid was filtered off, and the filtrate was concentrated under vacuum, the residue was applied to silica gel chromatography (EtOAc–PE = 1:9) to afford the disaccharide 4aa (61 mg, 0.069 mmol, 80%). [α]_D ²² –104.5 (c 0.32, CHCl₃). ¹H NMR (600 MHz, CDCl₃): δ = 8.16 (d, J = 8.22 Hz, 2 H), 8.07 (d, J = 8.28 Hz, 2 H), 8.00 (d, J = 8.28 Hz, 2 H), 7.89 (d, J = 7.74 Hz, 2 H), 7.59 (m, 2 H), 7.52 (t, J = 7.14 Hz, 1 H), 7.42 (m, 8 H), 7.27 (m, 2 H), 7.17 (d, J = 7.74 Hz, 2 H), 6.32 (t, J = 10.44 Hz, 1 H), 5.95 (dd, J = 3.30, 9.84 Hz, 1 H), 5.73 (s, 1 H), 5.69 (m, 1 H), 5.26 (s, 1 H), 4.75 (t, J = 12.66 Hz, 2 H), 4.49 (d, J = 11.04 Hz, 1 H), 4.37 (m, 2 H), 4.31 (m, 1 H), 3.61 (dd, J = 7.68, 9.36 Hz, 1 H), 2.35 (s, 3 H), 1.62 (s, 3 H), 1.39 (s, 3 H), 1.33 (d, J = 6.60 Hz, 3 H). ¹³C NMR (150 MHz, CDCl₃): δ = 166.3, 165.8, 165.6, 165.5, 138.1, 133.5, 133.4, 132.7, 130.1, 129.9, 129.8, 129.4, 129.2, 128.7, 128.5, 128.4, 109.8, 98.4, 84.0, 82.2, 76.8, 76.7, 70.6, 70.2, 69.1, 66.6, 66.2, 62.3, 28.4, 26.7, 21.2, 17.4. ESI-MS: m/z = 911.8 [M + Na]⁺. HRMS: m/z calcd for C₅₀H₄₈O₁₃NaS [M + Na]⁺: 911.2713; found: 911.2709
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