2664
S. J. Eitelman, D. Horton / Carbohydrate Research 341 (2006) 2658–2668
R value comparable to that of acetylated aldehydrol 4.
3.7. Preparation of 2,3:4,5-di-O-isopropylidene-aldehydo-
D-arabinose (5)
f
New spots having very high R values (0.98) gradually
f
replaced those of the starting materials. Similarly, acet-
ylated aldehydrol 4 (0.1 g, 0.4 mmol) was not converted
into enol acetates 2 and 3 upon exposure to NaOAc
2
0
Using a slight modification of the method of Fischer,
D-arabinose (250 g, 1.66 mol) was dissolved in 37%
HCl (250 mL) and cooled to 0 ꢁC. Technical-grade
EtSH (250 mL) was added and the two layers were vig-
orously shaken. Copious crystallization occurred after
about 15 min. After 30 min, the crude D-arabinose
diethyl dithioacetal was recovered by filtration and then
(
50 mg, 0.6 mmol) in Ac O (1 mL) at 140 ꢁC. Some
2
spots of lower R values slowly appeared.
f
3.5. Reaction of 2,3-O-isopropylidene-aldehydo-D-glycer-
aldehyde with pyridine–Ac O–water. General procedure
for preparing acetylated aldehydrols
2
recrystallized from water; yield 380 g (91%), mp 124–
20
1
25 ꢁC, lit. mp 125–126 ꢁC.
To the vacuum-dried dithioacetal (20 g, 78 mmol) in
dry acetone (200 mL) was added 0.5 mL of concentrated
H SO . The mixture was stirred overnight at room tem-
perature, neutralized with aqueous ammonia, filtered,
and the filtrate evaporated to dryness. The residue was
extracted with CH Cl (150 mL), which was washed
Freshly distilled aldehyde 1 (0.542 g, 4 mmol) was dis-
solved in Ac O (4 mL) and pyridine (4 mL) was added,
2
2
4
followed by distilled water (0.4 mL, 22 mmol). The
mixture was kept for 16 h at room temperature, after
which time it was heated for 10 h at 60 ꢁC. TLC (sol-
2
2
vent B) showed one new spot (R = 0.55) and none of
f
with water (40 mL), dried (MgSO ), filtered, and then
evaporated to a light-brown syrup that was purified by
4
the starting aldehyde (R = 0.25). The crude mixture
f
was evaporated, purified by loose-layer chromatogra-
phy using 1:1 benzene–EtOAc and the resulting yellow
oil crystallized; yield 0.77 g (80%). The IR and NMR
spectra were identical to the already described alde-
hydrol acetate 4.
vacuum distillation to afford 2,3:4,5-di-O-isopropylid-
21
24
D
ene-D-arabinose diethyl dithioacetal as a syrup; ½aꢂ
22
KBr
ꢀ1
+
82 (MeOH), lit. [a]D +83; mmax 1380 cm (CMe );
2
1
H NMR (benzene-d ): d 4.67–3.90 (m, 6H, H-1,2,
,4,5,5 ), 2.74 (dq, 4H, SCH ), 1.40, 1.33, 1.25, 1.20 (s,
6
0
3
2
3
H, CMe ), 1.15 (dt, 6H, SCH –CH ); m/z 338 (4),
2
2
3
3.6. Preparation of 1,1,2,3,4,5,6-hepta-O-acetyl-
aldehydo-D-glucose aldehydrol
337 (6), 336 (35), 321 (5), 263 (3.0), 261 (1.0), 217 (33),
203 (9.0), 201 (2.0), 177 (3.5), 159 (15), 143 (96), 135
(90), 101 (22), 87 (18), 85 (15), 75 (18), 59 (55), 43
The following procedure is an improvement over the
(100). Anal. Calcd for C H O S : C, 53.39; H, 8.32;
S, 19.05. Found: C, 53.30; H, 8.21; S, 18.99.
1
5
28
4 2
8
literature procedure. Penta-O-acetyl-aldehydo-D-glu-
1
9
cose
(0.5 g, 1.3 mmol) was dissolved in pyridine
In an adaptation of the method of Zinner and co-
2
2
(
2.5 mL) and Ac O (6.25 mL), and the mixture was kept
workers the di-O-isopropylidene-D-arabinose diethyl
dithioacetal (3.36 g, 10.0 mmol) was dissolved in acetone
(60 mL) and then to the stirred mixture HgO (yellow,
6.0 g, 28 mmol), HgCl2 (6.0 g, 22 mmol), and water
(6 mL) were added in succession. After heating for 2 h
at 56 ꢁC the mixture was filtered into a receiver contain-
ing HgO (3 g). The resultant mixture was evaporated to
dryness, extracted with CH Cl (100 mL), washed with
2
at room temperature. TLC (solvent A) showed that
after 2 h the starting material (R = 0.17) had been
f
replaced by a new major (R = 0.51) and minor
f
(
(
R = 0.57) product. The mixture was poured onto ice
f
50 g) and then extracted twice with CH Cl (25 mL).
2
2
The dried (MgSO ) extract was evaporated to a black
4
residue, which crystallized on refrigeration. Recrystalli-
zation from EtOH gave the title compound as white
2
2
5% KI solution (30 mL), and then twice with water
(30 mL). Evaporation gave the crude aldehyde; yield
1.4 g (60%), whose IR spectrum showed both OH and
C@O absorptions. Distillation at 80 ꢁC and 30 mtorr
8
needles; yield 287 mg (45%) (lit. 25%), mp 119–120 ꢁC
8
(
lit. mp 118.5–119.5 ꢁC); mixed mp with an authentic
1
sample, 117–119 ꢁC; H NMR (CDCl ): d 6.80 (d, 1H,
= 4.5 Hz, H-1), 5.55–5.30 (m, 3H, H-2,3,4), 5.00
,2
3
1
J
gave the pure aldehyde 5; yield 1.1 g (47%); H NMR
1
(
br q, 1H, J4,5 = 5.5 Hz, H-5), 4.28 (dd, 1H, J5,6 = 4.0,
(acetone-d ): d 9.71 (d, 1H, J = 2.0 Hz, H-1), 4.37
6
1,2
J
6
0
¼ 12:5 Hz, H-6), 4.10 (dd, 1H, J = 5.5 Hz, H-
5,6
(dd, 1H, J = 5.0 Hz, H-2), 4.20–3.80 (m, 4H, H-3,4,5
6
0
;6
2,3
0
), 2.00 (21H, OAc); m/z: 433 (2.0), 419 (1.5), 347
and 5 ), 1.41, 1.32 and 1.29 (12H, CMe ).
2
(
(
(
(
30), 331 (4.0), 330 (1.0), 317 (2.0), 289 (5.0), 275
3.0), 259 (2.0), 245 (6.0), 242 (29), 228 (2.5), 217
9.0), 215 (8.0), 200 (9.0), 187 (9.0), 173 (5.0), 169
8.0), 168 (4.0), 158 (7.0), 157 (39), 145 (35), 144 (4),
3.8. Hydration of the arabino aldehyde (5)
To the foregoing aldehyde (80 mg) in acetone-d6
1
43 (5), 140 (10), 139 (6.0), 128 (3.0), 127 (5.0), 126
(0.3 mL) was added deuterium oxide (0.1 mL). Analysis
by H NMR showed a decrease in the intensity of the H-
1 signal (d 9.71) and the appearance of a new doublet at
d 5.01 (J12 = 5.0 Hz) attributable to the hydrated form
1
(
(
3.0), 115 (31), 103 (23), 102 (5.0), 98 (16), 97 (5), 43
100). Anal. Calcd for C H O : C, 48.78; H, 5.73.
2
0
28 14
Found: C, 48.79; H, 5.50.