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Synlett 2006(15): 2464-2468  
DOI: 10.1055/s-2006-950430
LETTER
© Georg Thieme Verlag Stuttgart · New York

Selective Reduction of Azido Groups in Monosaccharides with Triphenyl-phosphine

Qin Li, Qiu-Hua Fan, Li-He Zhang, Xin-Shan Ye*
The State Key Laboratory of Natural and Biomimetic Drugs, School of Pharmaceutical Sciences, Peking University, Xue Yuan Rd 38, Beijing 100083, P. R. of China
Fax: +86(10)62014949; e-Mail: xinshan@bjmu.edu.cn;
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Publication History

Received 13 May 2006
Publication Date:
08 September 2006 (online)

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Abstract

The regioselective reduction of one azido group in glycopyranoside and mannitol derivatives containing two azido functions with triphenylphosphine is described. In cyclic substrates with two secondary azides, equatorial azides were reduced in good yields in preference to axial azides. Steric, but not electronic, factors ­appear to determine the regiochemical outcome of the Staudinger reduction.

Key words

selective reduction - azido group - monosaccharides - triphenylphosphine - functional-group manipulation

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p -Tolyl 4,6- O -Benzylidene-2-acetamino-3-azido-2,3-dideoxy-1-thio-α-d-allopyranoside ( 1b): To a solution of 1a (64.2 mg, 0.15 mmol) in anhyd THF (4.0 mL) was added PPh3 (44.0 mg, 0.167 mmol, 1.1 equiv), and the mixture was stirred at 65 °C for 8 h. Then H2O (2.0 mL) was added, and the mixture was stirred at 65 °C for another 8 h. The reaction mixture was concentrated to dryness. The resulting residue was dissolved in py (3.0 mL) and Ac2O (1.5 mL) was added dropwise at 0 °C. The mixture was stirred for 6 h at r.t. and the solvent was removed under vacuum. The residue was purified by column chromatography on silica gel (PE-EtOAc, 3:1 to 2:1) yielding the title compound 1b (64.5 mg, 97%) as a colorless oil. 1H NMR (500 MHz, CDCl3): δ = 7.52-7.50 (m, 2 H), 7.40-7.36 (m, 3 H), 7.33 (d, 2 H, J = 8.0 Hz), 7.11 (d, 2 H, J = 8.5 Hz), 6.20 (d, 1 H, J = 9.5 Hz), 5.59 (s, 1 H), 5.32 (d, 1 H, J = 6.0 Hz), 4.66-4.59 (m, 2 H), 4.35 (dd, 1 H, J = 5.5, 10.5 Hz), 4.23 (t, 1 H, J = 3.0 Hz), 3.87 (dd, 1 H, J = 3.0, 10.5 Hz), 3.78 (t, 1 H, J = 10.5 Hz), 2.32 (s, 3 H), 2.08 (s, 3 H). 13C NMR (125 MHz, CDCl3): δ = 169.44, 137.86, 136.77, 132.01, 131.71, 129.90, 129.27, 128.34, 126.15, 102.05, 88.94, 78.37, 68.88, 59.93, 59.86, 48.93, 23.28, 21.04. HRMS: m/z calcd for C22H25N4O4S [M + H]+: 441.1591; found: 441.1595.