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Showing posts with label 3.4. 1. Show all posts
Showing posts with label 3.4. 1. Show all posts

Saturday 4 November 2017

3.4. 1,2,3,4-Tetra-O-Acetyl-β-d-Mannuronic Acid

Laura Beswick

Laura Beswick

2nd degree connection

PhD Student at Keele University


Keele University




Gavin J. Miller

Gavin J. Miller

2nd degree connection

Lecturer in Organic Chemistry at Keele University




3.4. 1,2,3,4-Tetra-O-Acetyl-β-d-Mannuronic Acid (4)

To a vigorously stirred solution of 1,2,3,4-tetra-O-acetyl-β-d-mannopyranose (3) (1.5 g, 4.30 mmol, 1.0 equiv.) in dichloromethane (20 mL) and water (10 mL) was added (2,2,6,6-tetramethylpiperidin-1-yl)oxyl radical (TEMPO) (336 mg, 2.2 mmol, 0.50 equiv.) and [bis(acetoxy)iodo]benzene (BAIB) (6.9 g, 21.5 mmol, 5.00 equiv.). The solution was stirred at RT for 5 h, whereupon TLC analysis (hexane/ethyl acetate, 1/1) showed complete conversion of starting material to a baseline Rf value spot. The reaction was quenched with aqueous Na2S2O3 solution (10% w/v, 30 mL), the organic layer removed and the aqueous layer acidified to pH 3 using 1M HCl, followed by extraction with ethyl acetate (2 × 30 mL). The organic extracts were combined, dried (MgSO4), filtered and concentrated in vacuo to afford 1,2,3,4-tetra-O-acetyl-β-d-mannuronic acid (4) as a white solid (1.2 g, 3.3 mmol, 75%). Rf = 0.81 (dichloromethane/methanol, 9/1);

 1H-NMR (300 MHz, CDCl3) δH5.96 (1H, d, J = 1.5 Hz, H1), 5.50 (1H, dd, J = 3.2, 1.5 Hz, H2), 5.48 (1H, appt, J = 9.1 Hz, H4), 5.21 (1H, dd, J = 9.1, 3.2 Hz, H3), 4.2 (1H, d, J = 9.1 Hz, H5), 2.21 (3H, s, C(O)CH3), 2.13 (3H, s, C(O)CH3), 2.10 (3H, s, C(O)CH3), 2.04 (3H, s, C(O)CH3).
 13C-NMR (100 MHz, CDCl3) δC 169.9 (C=O), 169.7 (C=O), 169.5 (C=O), 169.4 (C=O), 168.2 (C=O), 89.4 (C1), 72.3 (C5), 69.3 (C3), 66.9 (C2), 65.9 (C4), 20.4 (C(O)CH3), 20.4 (C(O)CH3), 20.3 (C(O)CH3), 20.2 (C(O)CH3); 
FT-HRMS NSI (ES) m/z Found: (M−H) 361.0767, C14H17O11 requires 361.0776; FT-IR vmax/cm−1 2986 (O–H), 1751 (C=O).







Molbank 2017 m947 sch001

Molbank 20172017(3), M947; doi:10.3390/M947
Communication
1,2,3,4-Tetra-O-Acetyl-β-d-Mannuronic Acid
Laura Beswick and Gavin J. Miller *Orcid
Lennard-Jones Laboratory, School of Chemical and Physical Sciences, Keele University, Keele, Staffordshire ST5 5BG, UK
*
Correspondence: Tel.: +44-1782-734442
Received: 3 July 2017 / Accepted: 11 July 2017 / Published: 14 July 2017


Abstract

: 
1,2,3,4-Tetra-O-acetyl-β-d-mannuronic acid was synthesized in three steps from commercial d-mannose in 21% yield. Regioselective 6-O-tritylation followed by per-acetylation and 6-OTr removal using HBr/AcOH gave the required primary alcohol substrate, which was then oxidised to the target compound using TEMPO/BAIB. None of the synthetic steps required column chromatography and the product was fully characterized by 1H-NMR, 13C-NMR, 2D NMR, MS and IR.


Image result for Keele University, Keele, Staffordshire

Image result for Keele University, Keele, Staffordshire

Keele University, Keele, Staffordshire


Image result for Lennard-Jones Laboratory, School of Chemical and Physical Sciences, Keele University,

Image result for Lennard-Jones Laboratory, School of Chemical and Physical Sciences, Keele University,



Image result for Lennard-Jones Laboratory, School of Chemical and Physical Sciences, Keele University,


Lennard-Jones Laboratory, School of Chemical and Physical Sciences, Keele University,

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