Pyrano[2,3-b]dioxanes through Bisacetalic Annulation of 2-Ketosugars to Glycol
1 H, 2Ј-Ha), 3.75 (dd, 1 H, 2Ј-He), 4.28 (ddd, 1 H, 1Ј-Ha) ppm; 167.9 (3 COC6H5, COCH3) ppm. C30H24N2O8S (572.6): calcd. C
FULL PAPER
J1Ј,1Ј ϭ 10.0, J1Јe,2Јa ϭ 2.7, J1Јe,2Јe ϭ 0, J1Јa,2Јe ϭ 4.0, J1Јa,2Јa ϭ 62.92, H 4.23, N 4.89; found C 62.72, H 3.99, N 4.83.
J2Ј,2Ј ϭ 12.0 Hz (2 ethylene-H2); δ ϭ 3.81, 3.91 (d, 2 H, 1-H2), 4.59
(ddd, 1 H, 5-H), 4.70, 4.78 (d, 2 H, 6-H2), 5.57 (d, 1 H, 3-H), 5.97
2-Amino-4-[1Ј,4Ј-bis(benzoyloxy)but-2Ј-enylidene]thiazolin-5(4H)-
one Hydrobromide (38·HBr): A solution of bromo-enolone 19[17]
(dd, 1 H, 4-H) ppm; J1,1 ϭ 11.9, J3,4 ϭ 0.6, J4,5 ϭ 5.0, J5.6
ϭ
(1.0 g, 2.3 mmol) and thiourea (200 mg, 0.6 mmol) in dry acetone
(10 mL) was gently refluxed for 30 min. The crystalline product
that separated on cooling was filtered off, washed with acetone,
and dried to give 900 mg (79%) of the hydrobromide of 38. M.p.
176Ϫ178 °C. [α]2D0 ϭ 0.00 (c ϭ 2, CHCl3). 1H NMR (300 MHz,
[D6]DMSO): δ ϭ 5.02 (dd, 2 H, 4Ј-H2), 6.39 (dt, 1 H, 3Ј-H),
7.2Ϫ8.2 (m, 11 H, 2Ј-H, 2 C6H5) ppm; J2Ј,3Ј ϭ 15.6, J2Ј,4Ј ϭ 1.6,
J3Ј,4Ј ϭ 6.9 Hz. C21H17BrN2O5S (489.34): calcd. C 51.54, H 3.50,
N 5.72; found C 51.44, H 3.45, N 5.80.
4.8, 6.5, J6,6 ϭ 11.6 Hz (fructose protons). 13C NMR (75.5 MHz,
CDCl3): δ ϭ 61.3 (C-7), 65.6 (BzOCH2), 66.1 (C-3), 70.1 (C-10),
77.2 (C-4), 77.5 (C-3), 79.3 (C-2), 101.1 (C-5) ppm. MS (FD,
20 mA): m/zϭ 518 (95) [Mϩ]. C25H26O9 (518.5): calcd. C 67.17,
H 5.05; found C 67.06, H 5.03.
3. Pyranothiazoles
3,4,6-Tri-O-benzoyl-β-D-arabino-hexopyrano-2-ulosyl Thiouronium
Bromide (33): Thiourea (0.76 g, 10 mmol) was added to a solution
of ulosyl bromide 2 (5.55 g, 10 mmol) in acetone (150 mL), the
mixture was stirred at room temperature for 15 min, and was sub-
sequently evaporated to dryness in vacuo. The residue crystallized
from hot EtOAc to give 4.33 g (88%) of 33. M.p. 174Ϫ175 °C
(dec.). [α]2D0 ϭ Ϫ4.6 (c ϭ 1.1, acetone). 1H NMR (300 MHz,
[D6]DMSO): δ ϭ 4.43, 4.52 (dd, 2 H, 6-H2), 4.68 (ddd, 1 H, 5-H),
5.40 (dd, 1 H, 4-H), 5.84 (s, 1 H, H-1), 6.09 (d, 1 H, 3-H), 7.4Ϫ8.2
(m, 16 H, 3 C6H5, NH), 9.24, 10.38, 10.84 (3 broad 1H-s, 3 NH)
ppm; J3,4 ϭ J4,5 ϭ 10.0, J5,6 ϭ 2, 6, 4.4, J6,6 ϭ 12.5 Hz. 13C NMR
(75.5 MHz, [D6]DMSO): δ ϭ 62.5 (C-6), 67.8, 73.6, 74.3 (C-3, C-
4, C-5), 88.4 (C-1), 92.6 [SC(NH2)2], 128Ϫ133 (3 C6H5), 164.7,
164.9, 165.3 (3 COC6H5), 174.0 (C-2) ppm. MS (FD, 10 mA):
m/z ϭ 549 [Mϩ Ϫ Br]. C28H25BrN2O8S (629.5): calcd. C 53.42,
H 4.01, N 4.45; found C 53.46, H 3.87, N 4.38.
2-Amino-4-[1Ј,4Ј-bis(benzoyloxy)but-2Ј-enylidene]thiazolin-5(4H)-
one (38): A suspension of 38·HBr (245 mg, 0.5 mmol) and solid
NaHCO3 (100 mg) in moist methanol was stirred for 30 min at
room temperature; this was followed by evaporation to dryness in
vacuo. The residue was extracted with hot iPrOH (3 ϫ 5 mL) from
which 38 crystallized on cooling. Collection and recrystallization
gave 157 mg (77%). M.p. 160Ϫ162 °C. 1H NMR (300 MHz,
CDCl3): δ ϭ 4.99 (dd, 2 H, 4Ј-H2), 5.45 (bs, 2 H, NH2), 6.40 (dt,
1 H, 3Ј-H), 7.25Ϫ7.74 (m, 7 H, 2Ј-H, 6 ArH), 8.10 (dd, 2 H,
2 ArH), 8.25 (dd, 2 H, 2 ArH) ppm; J2Ј,3Ј ϭ 15.6, J2Ј,4Ј ϭ 1.6,
J3Ј,4Ј ϭ 5.8 Hz. MS (FD, 14 mA): m/z ϭ 408 [Mϩ]. C21H16N2O5S
(408.43): calcd. C 61.76, H 3.95, N 6.86; found C 61.61, H 3.88,
N 6.81.
Acknowledgments
(2R,3R,4R,7aS)-6-Acetimido-3,4-bis(benzoyloxy)-2-(benzoyloxy-
methyl)-3,4-dihydro-2H,7aH-pyrano[5,6-d]thiazoline (34): A mixture
of 33 (2.50 g, 4 mmol), pyridine (20 mL), and Ac2O (0.4 mL) was
stirred at 0 °C for 20 min, whereby a colorless precipitate formed.
The mixture was subsequently poured into ice-water (50 mL),
stirred for 1 h, and the crystals formed were collected by filtration
to give 2.08 g (91%) of 34. M.p. 108Ϫ109 °C. [α]2D0 ϭ ϩ16.0 (c ϭ
1.1, CHCl3). 1H NMR (300 MHz, CDCl3): δ ϭ 2.04 (s, 3 H, NAc),
4.16 (ddd, 1 H, 2-H), 4.44 and 4.56 (dd, 2 H, CH2OBz), 5.31 (s, 1
H, 7a-H), 5.50 (dd, 1 H, 3-H), 5.89 (d, 1 H, 4-H), 7.2Ϫ8.0 (m,
We would like to thank Mrs. Ingrid Svoboda for measuring the X-
ray data, Prof. Dr. H. J. Lindner for solving the crystal structure,
and Dr. S. Immel for expert graphics with his Molarchϩ program.
This work was partly supported by the Fonds der Chemischen
Industrie.
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K. Maurer, M. Mahn, Ber. Dtsch. Chem. Ges. 1927, 60,
15 H, 3 C6H5) ppm; J2,CH ϭ 3.4, 6.6, J2,3 ϭ 9.6, J3,4 ϭ 9.3 Hz. 13
C
[2b]
1318Ϫ1329.
2, 411Ϫ414.
6, 307Ϫ311.
M. G. Blair, Methods Carbohydr. Chem. 1963,
R. J. Ferrier, Methods Carbohydr. Chem. 1972,
NMR (75.5 MHz, CDCl32): δ ϭ 23.9 (AcCH3), 64.1 (CH2), 68.9,
74.7, 76.8 (C-2, C-3, C-4), 90.0 (C-7a), 96.7, 96.9 (C-4a, C-6),
128.3Ϫ133.8 (3 C6H5), 166.9, 166.1, 165.3, 165.0 (COCH3,
3 COC6H5) ppm. MS (FD): m/z ϭ 572 [Mϩ], 450 [M Ϫ HOBz].
C30H24N2O9S (572.6): calcd. C 62.92, H 4.23, N 4.89; found
C 62.88, H 4.22, N 4.84.
[2c]
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ium bromide 33 (1.25 g, 2 mmol) in pyridine (10 mL) and Ac2O
(650 mg, 6.4 mmol) was stirred at ambient temperature for 2 h, re-
sulting in a mixture of 34 (Rf ϭ 0.12 in CH2Cl2/EtOAc, 20:1) and
35 (Rf ϭ 0.30); this was followed by heating to 50 °C for 5 h, after
which conversion into 35 was complete (TLC). The mixture was
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Chem. 1985, 1659Ϫ1668.
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F. W. Lichtenthaler, M. Lergenmüller, S. Peters, Z. Varga,
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[9] [9a]
580 mg (75%) of 35 as a yellowish, amorphous product. [α]2D0
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3 H, NAc), 4.66 and 4.89 (dd, 2 H, CH2OBz), 5.08 (ddd, 1 H, 2-
H), 5.85 (dd, 1 H, H-3), 6.31 (dd, 1 H, 4-H), 9.38 (broad s, 1 H,
ϭ
1
[9b]
Commun. 1995, 967Ϫ968.
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[10]
NH) ppm; J2,CH ϭ 4.7 and 7.5, J2,3 ϭ 3.6, J2,4 ϭ 1.1, J3,4 ϭ 3.4,
2
J
C,H gem ϭ 12.1 Hz. 13C NMR (75.5 MHz, CDCl3): δ ϭ 22.8 (CH3),
[11] [11a]
F. Brüschweiler, K. Stöckel, T. Reichstein, Helv. Chim.
61.72(CH2OBz), 66.1, 68.6, 77.5 (C-2, C-3, C-4), 128.5Ϫ133.6 (m,
[11b]
Acta 1969, 52, 2276Ϫ2303.
T. Reichstein, K. Stöckel, T. R. Watson, Helv. Chim. Acta 1979,
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3 C6H5), 128.8, 147.5, 150.9 (C-4a, C-6, C-7a), 165.1, 165.7, 166.1,
Eur. J. Org. Chem. 2004, 4901Ϫ4910
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