SORBOSE REACTION IN MELT
2455
time, the structure of the selectively formed a-pyranose form was proven by
two-dimensional NMR techniques. We introduced two new solvent-free systems
here based on nontoxic and renewable resources for the conversion of L-sorbose.
EXPERIMENTAL
L-Sorbose (0.6 g, 3.3 mmol), urea (1.4 g, 26.7 mmol), and NH4Cl (0.2 g,
3.7 mmol) were heated in a 10-mL reaction flask at 80 ꢀC until a clear melt was
formed. Amberlyst 15 (150 mg) was added, and the reaction was stirred for 1.5 h
at that temperature. Methanol was added, solids were filtered off, and the solvent
evaporated. Then, 6 mL (5.8 g, 74.3 mmol) of pyridine and 3.5 mL of Ac2O (3.8 g,
37.0 mmol) were added to the mixture, and the mixture was first stirred for 1 h in
the ultrasounic bath and then overnight at room temperature without sonication.
The reaction was stopped by pouring the solution into saturated NaHCO3 solution.
The aqueous phase was extracted three times with CH2Cl2. The combined organic
layers were washed twice with 2N HCl and twice with water, dried over MgSO4,
and evaporated. The pure product was crystallized from ethyl acetate, affording a
colorless powder (0.215 g, 0.55 mmol, 16%).
1H NMR (300 MHz, CDCl3): d (ppm) ¼ 2.02, 2.04, 2.08, 2.10 (s, 12 H, OAc), 3.75
3
2
(dd, 1 H, H-6), 4.01 (dd, 1H, J(H-5, H-60) ¼ 5.91 Hz, H-60), 4.03 (dd, 1H, J(H-1,
H-10) ¼ 12.36 Hz, 166.24 Hz, H-1), 4.58 (dd, J1 ¼ 12.33 Hz, J2 ¼ 166.24 Hz, 1H,
H-10), 5.00–5.09 (m, 1H, H-5), 5.24–5.40 (m, 5H, H-3, H-4, urea); 13C NMR (75 Hz,
CDCl3): d (ppm) ¼ 20.5, 20.6, 20.5, 20.7 (CH3-Ac), 59.9 (C-5), 62.0 (C-1), 68.3 (C-4),
=
69.0 (C-5), 70.4 (C-3), 85.3 (C-2), 156.6 (urea), 168.6, 169.8, 170.1, 170.2 (C O, Ac).
1H NMR (600 MHz, CDCl3): d (ppm) ¼ 2.01, 2.04, 2.07, 2.10 (4 ꢁ s, 4 ꢁ 3H,
OAc), 3.74 [‘‘dd’’, 2J(H-6ax, H-6eq) ¼ 10.98 Hz, 3J(H-6ax, H-5) ¼ 10.98 Hz, 1 H,
H-6ax], 4.00 [dd, J(H-5, H-60) ¼ 5.91 Hz, J(H-6ax, H-6eq) ¼ 11.07 Hz, 1H, H-6eq],
3
2
2
2
4.04 [d, 1H, J(H-1, H-10) ¼ 12.37 Hz, H-1], 4.58 [d, J(H-1, H-10) ¼ 12.37 Hz, 1H,
3
H-10], 5.02–5.06 (m, 1H, H-5), 5.26 [d, J(H-3, H-4) ¼ 9.87 Hz, 1H, H-3], 5.35–5.38
(m, 2H, H-4, urea); 13CNMR (75 Hz, CDCl3): d (ppm) ¼ 20.5, 20.6, 20.6, 20.7 (CH3-
Ac), 59.8 (C-5), 62.0 (C-1), 68.3 (C-4), 69.0 (C-5), 70.4 (C-3), 85.3 (C-2), 156.7 (urea),
=
168.6, 169.8, 170.1, 170.2 (C O, Ac); FT-IR (ATR): v (cmꢂ1) ¼ 3487, 3458, 3341,
1753, 1744, 1697, 1665, 1620, 1614, 1591, 1564, 1547, 1535, 1441, 1433, 1377, 1371,
1275, 1229, 1211, 1138, 1103, 1061, 1032, 908; mp: 192 ꢀC. ESI-MS: m=z (%) ¼ 407.9
20
(MNH4þ, 100), 431.9 (MHþ þ MeCN, 37), 390.9 (MHþ, 15).½aꢃD ¼ ꢂ37.395 (c 1.000,
23:5
chloroform) (a-anomer) (literature[9]: ½aꢃD ¼ ꢂ34.4 (c 0.973, chloroform).
SUPPORTING INFORMATION
General experimental information, NOE spectrum of compound 7, and syn-
thesis of HMF from sorbose can be found via the Supplementary Content section
of this article’s web page.
ACKNOWLEDGMENTS
We thank the Suedzucker AG and the Fachagentur fuer Nachwachsende
Rohstoffe for financially supporting this project.