442
S. Tsujihata, F. Nakatsubo/Carbohydrate Research 308 (1998) 439±443
ꢀ
was stirred at 0 C for 1 h. The reaction mixture
was diluted with ethyl acetate and washed with
water and brine. The organic phase was dried over
Na2SO4, and concentrated in vacuo to give a yel-
low syrup that was puri®ed on a silica gel column
(Wakogel C-200, 1:4 EtOAc±n-hexane) to give
compound 5 as a colorless syrup (1.50 g, 87.2%):
was neutralized with acetic acid and concentrated
in vacuo The residue was dissolved in chloroform
and washed with water and brine. The organic
phase was dried over Na2SO4 and concetrated in
vacuo to give a colorless powder that was puri®ed
on a silica gel column eluted with chloroform and
crystalized from methanol to give compound 8 as
colorless crystals (68.0 mg, 88.0%): mp 111 ꢀC; [ꢀ]d
+24.4ꢀ (c 1.00, CHCl3); Anal. Calcd for C11H18O6:
C, 53.65; H, 7.37; O, 38.98. Found: C, 53.74; H,
7.30; O, 38.96.
[ꢀ]d 25.5ꢀ (c 1.01, CHCl3); H NMR (CDCl3): ꢂ
1
1.19, 1.20, 1.23 (s, 27 H, Piv-H), 3.38 (s, 3 H, CH3),
4.10 (s, 2 H, ClCH2CO), 4.19 (dd, 1 H, J5,6a 7.63,
J6a,6b 12.07 Hz, H-6a), 4.22 (t, 1 H, J4,5 5.27 Hz, H-
4), 4.46 (dd, 1 H, J5,6b 3.78 Hz, H-6b), 4.86 (s, 1 H,
J1,2 0 Hz, H-1), 5.00 (dd, 1 H, J3,4 5.27 Hz, H-3), 5.01
(d, 1 H, J2,3 1.85 Hz, H-2), 5.44 (m, 1 H, 5-H); Anal.
Calcd for C24H39ClO10: C, 55.12; H, 7.46; O, 30.63;
Cl, 6.79. Found: C, 55.05; H, 7.71; O, 30.6; Cl, 6.65.
3,6-Di-O-pivaloyl-a-d-galactofuranose 1,2,5-
orthopivalate (7).ÐTo a solution of 5 (682 mg,
1.31 mmol) in anhydrous chloroform (6 mL) was
added dichloromethyl methyl ether (2.37 mL,
26.2 mmol) and tin(IV) chloride (1.02 mL,
0.873 mmol). The solution was stirred at room
temperature for 12 h. The reaction mixture was
diluted with ethyl acetate and sequentially washed
with cold water, saturated NaHCO3, and brine.
The organic phase was concentrated in vacuo to
give compound 6 as a crude oil (685 mg). To a
solution of crude 6 (685 mg) in pyridine (30 mL)
was added thiourea (298 mg, 391 mmol). The solu-
tion was stirred at 80 ꢀC for 6 h. The reaction mix-
ture was diluted with ethyl acetate and washed
with water and brine. The organic phase was con-
centrated in vacuo to give a brown powder that
was puri®ed on a silica gel column eluted with
chloroform and crystalized from methanol to give
compound 7 as colorless crystals (360 mg, 66.3%):
mp 134 C; [ꢀ]d +71.3ꢀ (c 1.02, CHCl3); H NMR
(CDCl3): ꢂ 1.02, 1.20 (s, 27 H, piv-H), 4.15 (m, 1 H,
H-5), 4.21±4.25 (overlapped, 2 H, H-6a,6b), 4.40 (t,
1 H, J4,5 1.80 Hz, H-4), 4.55 (dd, 1 H J2.3 0 Hz, J2,4
1.49, H-2), 5.13 (s, 1 H, J3,4 0 Hz, H-3), 5.90 (d, 1
H, J1,2 3.77, H-1); 13C NMR (CDCl3): ꢂ 103.4 (C-
1), 63.9, 74.8, 78.3, 81.0, 81.1 (C-2, 3, 4, 5, 6), 24.9,
27.0, 27.1 (Me±C), 37.3, 38.3 [C(CH3)], 126.6
(orthoester quaternary carbon), 177.6, 178.0 (car-
bonyl); Anal. Calcd for C21H34O8: C, 60.85; H,
8.27; O, 30.88. Found: C, 60.82; H, 8.22; O, 30.96.
a-d-Galactofuranose 1,2,5-orthopivalate (8).ÐTo
a solution of 7 (130 mg, 0.314 mmol) in methanol
(5 mL) was added 28% NaOMe in methanol
(1.12 mL, 4.71 mmol). The solution was stirred at
room temperature for 12 h. The reaction mixture
3,6-Di-O-benzyl-a-d-galactofuranose 1,2,5-ortho-
pivalate (9).ÐCompound 8 (65.4 mg, 0.266 mmol)
was dissolved in Me2NCHO (3 mL). Sodium
hydride (25.5 mg, 0.638 mmol, 60% in mineral oil)
and tetra-n-butyl ammonium iodide (23.5 mg,
0.0638 mmol) were added, followed by the slow
addition of benzyl bromide (75.8 ꢃL, 0.638 mmol)
ꢀ
at 0 C . The solution was stirred at room tem-
perature for 20 h. Methanol was then added to the
reaction mixture for the decomposition of excess
benzyl bromide. The reaction mixture was worked
up by the same manner as that of compound 5.
Crude compound 9 was puri®ed on a silica gel
column eluted with chloroform to give compound
9 as a colorless syrup (88.1 mg, 77.7%): [ꢀ]d
ꢀ
1
+38.8 (c 0.95, CHCl3); H NMR (CDCl3): ꢂ 0.98
(s, 9 H, piv-H), 3.57 (dd, 1 H, J5,6a 5.61, J6a,6b
8.50 Hz, H-6a), 3.72 (t, 1 H, J5,6b 8.50 Hz, H-6b),
3.96 (m, 1 H, H-5), 4.07 (s, 1 H, J3,4 0 Hz, H-3),
4.51, 4.57, 4.60 (d, d, s, 1 H, 1 H, 2 H, respectively,
benzyl-H), 4.58 (dd, 1 H, J2,3 0, J2,4 1.50 Hz, H-2),
4.65 (t, 1 H, J4,5 1.89 Hz H-4), 5.90 (d, 1 H, J1,2
3.75 Hz, H-1), 7.33 (s, 5 H, AH); 13C NMR
(CDCl3): ꢂ 103.4 (C-1), 69.8, 71.5, 73.5, 75.9, 80.3,
80.9, 84.1 (C-2, 3, 4, 5, 6 and benzyl-C), 25.0
(CH3), 37.3 [C(CH3)], 126.3 (orthoester quaternary
carbon); Anal. Calcd for C25H30O6: C, 70.40; H,
7.09; O, 22.51. Found: C, 70.12; H, 7.13; O, 22.75.
ꢀ
1
Acknowledgements
This investigation was supported in part by a
Grant-in-Aid for Scienti®c Research from the
Ministry of Education, Science, Sport and Culture
of Japan (no. 09460076).
References
[1] J.E. Gander, N.H. Jentoft, L.R. Drewes, and P.D.
Rick, J. Biol. Chem., 249 (1974) 2063±2072.