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I. Izquierdo et al. / Tetrahedron: Asymmetry 9 (1998) 1015–1027
(chloroform:methanol=10:1) of the residue gave 1-azido-1-deoxy-D-glycero-D-galacto-4-octulose (4, 2.3
g, 84%) as a syrup that was not characterized but hydrogenated in water (100 mL) with 10% Pd–C (460
mg) for 20 h, at which time TLC (chloroform:methanol=5:2) revealed (B) the absence of 4 and the
presence of a non-mobile compound. The catalyst was filtered off, washed with water and the combined
filtrate and washings concentrated to a thick syrup. Addition of methanol caused crystallization to afford 7
(1.7 g, 88%): m.p.: 172°C (dec.); [α]27+1.5 (c 1.1, water). NMR data (DMSO-d6–D2O): 1H, δ 3.82–3.80
D
0
(m, 2H, H-2,3), 3.61 (d, 1H, J4,5=6.5 Hz, H-5), 3.56 (dd, 1H, J7,8=3.2, J8,8 =11 Hz, H-8), 3.47 (ddd, 1H,
0
0
0
H-7), 3.42 (d, 1H, J6,7=8.4 Hz, H-6), 3.35 (dd, 1H, J7,8 =5.9, H-8 ), 2.88 (dd, 1H, J1,2=5.0, J1,1 =11.5 Hz,
H-1), 2.83 (dd, 1H, J3,4=4.9 Hz, H-4), and 2.55 (dd, 1H, J1 ,2=3.5 Hz, H-10); 13C, δ 79.5 (C-3), 77.9 (C-
0
2), 71.7 (C-6), 71.6 (C-7), 69.9 (C-5), 67.6 (C-4), 63.9 (C-8), and 51.9 (C-1). Anal. calcd for C8H17NO6;
C, 43.04; H, 7.68; N, 6.27. Found: C, 43.26; H, 7.39; N, 6.43.
Conventional acetylation of 7 (100 mg, 0.45 mmol) in dry pyridine (5 mL) with acetic anhy-
dride (2 mL) and a catalytic amount of DMAP gave, after work-up and column chromatography
(ether:acetone=10:1), the corresponding N-acetyl-2,3,5,6,7,8-hexa-O-acetyl derivative 8 (175 mg, 75%)
as a syrup; [α]25 +44 (c 1.5); ν
1756 and 1749 (MeCOO), and 1660 cm−1 (MeCON). NMR data:
KBr
D
max
1H, δ 5.59 (dd, 1H, J4,5=5.3, J5,6=3.3 Hz, H-5), 5.32 (dd, 1H, J6,7=7.2 Hz, H-6), 5.31 (bd, 1H, H-3),
5.15 (m, 1H, H-2), 5.13 (ddd, 1H, H-7), 4.45 (bd, 1H, H-4), 4.29 (dd, 1H, J7,8=3.1, J8,8 =12.4 Hz, H-8),
4.06 (dd, 1H, J7,8 =6.3 Hz, H-8 ), 4.05 (dd, 1H, J1,2=7.3, J1,1 =12.1 Hz, H-1), 3.36 (dd, 1H, J1 ,2=3.7 Hz,
H-10), 2.12, 2.11, 2.08, 2.04, 2.03, 2.02, and 2.01 (7 s, 21H, 7 Ac); 13C, δ 170.7, 170.5, 170.2, 170.0,
169.9, and 169.6 (7 MeCO), 76.4 (C-2,6), 69.6 (C-3), 68.9 (C-7), 68.8 (C-5), 62.6 (C-4), 62.0 (C-8), 52.5
(C-1), 22.4, 21.0, 20.9, 20.8, and 20.7 (7 MeCO). Mass spectrum (LSIMS): m/z 540.16914 (M++Na). For
C22H31NO13Na 540.16931 (deviation 0.3 ppm).
0
0
0
0
0
3.5. Attempted cyclisation of 7-→12
To a stirred solution of iodine (254 mg, 1 mmol) in dry pyridine (8.5 mL), triphenylphosphine (263 mg,
1 mmol) and imidazole (150 mg, 2 mmol) were added at room temperature. Then, compound 7 (223 mg,
1 mmol) was added and after 5 min TLC (methanol with a few drops of triethylamine) revealed (B) the
presence of a faster-running compound. DABCO (223 mg, 2 mmol) was then added and after 1 h acetic
anhydride (1 mL) was added and the reaction mixture left at room temperature overnight. Conventional
work-up and column chromatography (ether:acetone=5:1) afforded crystalline N-acetyl-2,3,5,7,8-penta-
O-acetyl-1,4-dideoxy-1,4-imino-D-erythro-L-altro-octitol (9, 120 mg, 25%): m.p.: 217–218°C; [α]27
D
27
+11, [α]
+26.5 (c 1.1); νmKBaxr 3278 (OH), 1748, 1744, and 1740 (MeCO2), and 1633 cm−1 (MeCON).
405
1
NMR data: H, δ 5.55 (bs, 1H, OH), 5.22 (d, 1H, H-2), 5.18 (d, 1H, J4,5=10.8 Hz, H-5), 5.09 (s, 1H,
H-3), 4.98 (ddd, 1H, H-7), 4.49 (dd, 1H, J7,8=2.2, J8,8 =12.1 Hz, H-8), 4.32 (d, 1H, H-4), 4.26 (dd, 1H,
0
0
0
0
0
J7,8 =5.2 Hz, H-8 ), 4.01 (dd, 1H, J1,2=5.8, J1,1 =12.2 Hz, H-1), 3.71 (d, 1H, H-1 ), 3.70 (d, 1H, J6,7=9.7
Hz, H-6), 2.20, 2.16, 2.12, 2.05, 2.04, and 1.99 (6 s, 18H, 6 Ac); 13C, δ 173.5, 171.0, 169.7, 169.6, and
168.7 (6 MeCO), 75.2 (C-3), 74.7 (C-2), 69.2 (C-7), 69.0 (C-5), 66.9 (C-6), 63.5 (C-8), 62.7 (C-4), 53.3
(C-1), 22.9, 21.0, 20.9, and 20.8 (6 MeCO). Anal. calcd for C20H29NO12: C, 50.52; H, 6.16; N, 2.95.
Found: C, 50.90; H, 6.61; N, 3.02.
3.6. N-Benzyloxycarbonyl-1,4-dideoxy-1,4-imino-8-O-mesitylenesulphonyl-D-erythro-L-altro-octitol 11
To an ice–water cooled and stirred solution of 7 (400 mg, 1.8 mmol) in water (5 mL) containing sodium
hydrogen carbonate (400 mg), benzyl chloroformate (800 µL, 5.6 mmol) was added dropwise. After 6 h
TLC (isopropanol:methanol:ammonia=6:2:1) revealed (B) the presence of a faster-running compound.