Isolation and identification of the intermediates during pyrazole formation of some carbohydrate hydrazone derivatives

Article abstract of DOI:10.1016/S0008-6215(00)00019-7

Reaction of the oxidation product of L-ascorbic acid, dehydro-L-ascorbic acid, with o-phenylenediamine, followed by 2,4,6-trichlorophenylhydrazine (3) afforded 3-[1-(2,4,6-trichlorophenylhydrazono)-L-threo-2,3,4-trihydroxybut-1- yl]quinoxalin-2(1H)one (4), whose structure was deduced from studying its periodate oxidation, which gave the glyoxal derivative 3-[1-(2,4,6- trichlorophenylhydrazono)glyoxal-1-yl]quinoxalin-2(1H)one (5) that upon reduction afforded 3-[1-(2,4,6-trichlorophenylhydrazono)-2-hydroxyethy-1- yl]quinoxalin-2(1H)one (6). The reaction of 5 with 3 afforded the bishydrazone 3-[1,2-bis(2,4,6-trichlorophenylhydrazono)glyoxal-1- yl]quinoxalin-2(1H)one. The reaction of 5 with acetic anhydride in pyridine afforded the 2,3-dihydrofuro[2,3-b]quinoxaline derivative 2-acetoxy-3-[2- acetyl-2-(2,4,6-trichlorophenyl)hydrazono)]-2,3-dihydrofuro[2,3- b]quinoxaline. Acetylation of 4 with acetic anhydride in pyridine afforded the acyclic diacetate intermediate 3-[3,4-di-O-acetyl-2-deoxy-1-(2,4,6- trichlorophenylhydrazono)but-2-en-1-yl]quinoxalin-2(1H)one (12), which was also obtained from the reaction of 4 with boiling acetic anhydride. Compound 12 rearranged under the reaction conditions to give the pyrazole derivatives 3-[5-(acetoxymethyl)-1-(2,4,6-trichlorophenyl)pyrazol-3-yl]quinoxalin- 2(1H)one (14) and 2-acetoxy-3-[5-(acetoxymethyl)-1-(2,4,6- trichlorophenyl)pyrazol-3-yl)]quinoxaline (15), as well as the 2,3- dihydrofuro[2,3-b]quinoxaline derivative 2-(2-acetoxyethen-2-yl)-3-[2-(2,4,6- trichlorophenyl)hydrazono]-2,3-dihydrofuro[2,3-b]quinoxaline. Acetylation of 3-[5-(hydroxymethyl)-1-(2,4,6-trichlorophenyl)pyrazol-3-yl]quinoxalin- 2(1H)one (16) with acetic anhydride in pyridine or 12 with boiling acetic anhydride afforded 15 and 16, respectively. Treatment of 4 with diluted sodium hydroxide afforded the pyrazolo[2,3-b]quinoxaline (flavazole) derivative 1-(2,4,6-trichlorophenyl)-3-(L-threo-glycerol-1-yl)pyrazolo[2,3- b]quinoxaline whose acetylation afforded the acetyl derivative 3-(2,3,4-tri- O-acetyl-L-threo-glycerol-1-yl)-1-(2,4,6-trichlorophenyl)pyrazolo[2,3- b]quinoxaline. The assigned structures were based on spectral analysis. The activity of compound 4 against hepatitis B virus has been studied. (C) 2000 Elsevier Science Ltd.

Full text of DOI:10.1016/S0008-6215(00)00019-7

www.elsevier.nl/locate/carres
Carbohydrate Research 326 (2000) 34–42
Isolation and identification of the intermediates during
pyrazole formation of some carbohydrate hydrazone
derivatives
Laila F. Awad *
Chemistry Department, Faculty of Science, Alexandria Uni6ersity, Alexandria, Egypt
Received 15 November 1999; accepted 5 January 2000
Abstract
Reaction of the oxidation product of
by 2,4,6-trichlorophenylhydrazine (3) afforded 3-[1-(2,4,6-trichlorophenylhydrazono)-
L
-ascorbic acid, dehydro-
L
-ascorbic acid, with o-phenylenediamine, followed
-threo-2,3,4-trihydroxybut-1-
L
yl]quinoxalin-2(1H)one (4), whose structure was deduced from studying its periodate oxidation, which gave the
glyoxal derivative 3-[1-(2,4,6-trichlorophenylhydrazono)glyoxal-1-yl]quinoxalin-2(1H)one (5) that upon reduction
afforded 3-[1-(2,4,6-trichlorophenylhydrazono)-2-hydroxyethy-1-yl]quinoxalin-2(1H)one (6). The reaction of 5 with 3
afforded the bishydrazone 3-[1,2-bis(2,4,6-trichlorophenylhydrazono)glyoxal-1-yl]quinoxalin-2(1H)one. The reaction
of 5 with acetic anhydride in pyridine afforded the 2,3-dihydrofuro[2,3-b]quinoxaline derivative 2-acetoxy-3-[2-acetyl-
2-(2,4,6-trichlorophenyl)hydrazono)]-2,3-dihydrofuro[2,3-b]quinoxaline. Acetylation of 4 with acetic anhydride in
pyridine afforded the acyclic diacetate intermediate 3-[3,4-di-O-acetyl-2-deoxy-1-(2,4,6-trichlorophenylhydra-
zono)but-2-en-1-yl]quinoxalin-2(1H)one (12), which was also obtained from the reaction of 4 with boiling acetic
anhydride. Compound 12 rearranged under the reaction conditions to give the pyrazole derivatives 3-[5-(ace-
toxymethyl)-1-(2,4,6-trichlorophenyl)pyrazol-3-yl]quinoxalin-2(1H)one (14) and 2-acetoxy-3-[5-(acetoxymethyl)-1-
(2,4,6-trichlorophenyl)pyrazol-3-yl)]quinoxaline (15), as well as the 2,3-dihydrofuro[2,3-b]quinoxaline derivative
2-(2-acetoxyethen-2-yl)-3-[2-(2,4,6-trichlorophenyl)hydrazono]-2,3-dihydrofuro[2,3-b]quinoxaline. Acetylation of 3-[5-
(hydroxymethyl)-1-(2,4,6-trichlorophenyl)pyrazol-3-yl]quinoxalin-2(1H)one (16) with acetic anhydride in pyridine or
12 with boiling acetic anhydride afforded 15 and 16, respectively. Treatment of 4 with diluted sodium hydroxide
afforded the pyrazolo[2,3-b]quinoxaline (flavazole) derivative 1-(2,4,6-trichlorophenyl)-3-(
L
-threo-glycerol-
1-
yl)pyrazolo[2,3-b]quinoxaline whose acetylation afforded the acetyl derivative 3-(2,3,4-tri-O-acetyl-
L
-threo-glycerol-1-
yl)-1-(2,4,6-trichlorophenyl)pyrazolo[2,3-b]quinoxaline. The assigned structures were based on spectral analysis. The
activity of compound 4 against hepatitis B virus has been studied. © 2000 Elsevier Science Ltd. All rights reserved.
Keywords: L-Ascorbic acid; (2,4,6-Trichlorophenylhydrazone); Quinoxalin-2(1H)one; 2,3-Dihydrofuro[2,3-b]quinoxaline; [But-2-
en-1-yl]quinoxalin-2(1H)one; Pyrazole; Pyrazolo[2,3-b]quinoxaline
acid, as an excellent precursor for constructing
heterocyclic rings either by retaining the car-
bon skeleton of the furanone ring or by rear-
rangement via its opening [1–10]. El Ashry et
al. [6–9] have extensively studied the role of
carbohydrates as organic raw materials for the
synthesis of heterocycles. Although acetyla-
tion with boiling acetic anhydride of sugar
1. Introduction
Much attention has been devoted to the
chemistry of the 2,3,4-tetrahydrofurantrione,
obtained from the oxidation of
L
-ascorbic
* Tel.: +20-3-5554361.
0008-6215/00/$ - see front matter © 2000 Elsevier Science Ltd. All rights reserved.
PII: S0008-6215(00)00019-7

L.F. Awad / Carbohydrate Research 326 (2000) 34–42
35
hydrazones did not lead to pyrazole ring for-
mation, but instead gave the respective per-
acetyl derivatives [11,12], the corresponding
sugar osazones gave pyrazole derivatives un-
der similar conditions [13–17]. On the other
hand, the pyrazolyl quinoxaline derivative
could be obtained under the same conditions
from the product of the reaction of dehydro-
The reduction of 5 with sodium borohy-
dride afforded an orange crystalline product
3-[1-(2,4,6-trichlorophenylhydrazono)-2-hy-
droxyeth-1-yl]quinoxalin-2(1H)one (6), and its
reaction with 3 gave the bishydrazone deriva-
tive 7. The FAB mass spectra of 6 and 7
showed molecular ion peaks at m/z 397 and
589, respectively, which were in agreement
with their assigned structures. Inspection of
L
-ascorbic acid with o-phenylenediamine and
arylhydrazines namely, 3-[1-(arylhydrazono)-
-threo-2,3,4-trihydroxybut-1-yl]quinoxalin-
1
the H NMR spectral data of 6 and 7 mea-
L
sured in Me2SO-d6 revealed that both com-
pounds may exist in their solutions in
alternated chelated structures resulting from
intramolecular hydrogen bonding (chelate
NꢀH bond), as well as a solvent-bonded NꢀH
[20–22].
2(1H)one [6,7,18,19]. In this paper, the inter-
mediates during the pyrazole formation from
derivatives of the latter compound could be
isolated, which sheds some light on the mode
of the reaction.
The reaction of 5 with acetic anhydride in
pyridine gave the 2,3-dihydrofuro[2,3-b]quino-
xaline derivative 8 whose structure was de-
duced from its mode of formation as reported
by El Ashry and co-workers [8,18,19] for the
construction of the 2,3-dihydrofuro[2,3-b]-
2. Results and discussion
The reaction of
1,4-lactone, obtained from the oxidation of
-ascorbic acid (1) with p-benzoquinone, with
L
-threo-2,3-hexodiulosono-
1
quinoxaline skeleton. The H NMR spectrum
of 8 showed two singlets due to the OAc and
NAc and a singlet at l 6.28, which was at-
tributed to H-2 of the furan ring; such
downfield shift was due to its attachment to a
carbon bearing two heteroatoms. The forma-
tion of 8 could be explained by the possible
interaction of the C-2 oxygen of the quinoxa-
line ring on the aldehydic carbonyl group with
elimination of a water molecule and subse-
quent acetylation of the formed hydroxyl
group, as well as the NH of the hydrazone
moiety.
L
1 molar equivalent of o-phenylenediamine (2),
followed by 2,4,6-trichlorophenylhydrazine
(3), afforded a yellow product that showed in
its IR spectrum an amide carbonyl absorption
band at 1660 cm−1 and gave an elemental
analysis that agreed with the molecular for-
mula C18H15Cl3N4O4. Consequently, the
product was assigned the acyclic structure
3-[1-(2,4,6-trichlorophenylhydrazono)- -threo-
L
2,3,4-trihydroxybut-1-yl]quinoxalin-2(1H)one
(4), rather than the hydrated form of the
anhydro structure 2,2%-anhydro-[2-hydroxy-3-
In order to gain definitive proof of the
acyclic nature of 4, as well as a better under-
standing of its mode of transformation to the
pyrazole derivative [6,7], the acetylation of 4
under various conditions was studied. Thus
the treatment of 4 with acetic anhydride in
pyridine afforded an orange product 12, which
would be expected to be the triacetate 10 [19]
or the diacetate 9 [2], but the spectral data
ruled out this expectation. The IR spectrum of
12 showed acetoxy and amide carbonyl ab-
sorption bands at 1745 and 1661 cm−1, re-
spectively, indicating its acyclic nature, which
(1-(2,4,6-trichlorophenylhydrazono)-
2,3,4-trihydroxybutyl]quinoxaline]
L
-threo-
[2,19]
(Scheme 1). Although its mass spectrum
showed the highest ion peak at m/z 440 that
agreed with the anhydro structure, this ion
can be attributed to the loss of a molecule of
water from the molecular ion peak of 4. Thus,
a confirmation for the acyclic nature of 4
becomes desirable. This was achieved from the
results of its periodate oxidation that afforded
a yellow crystalline product whose structure
was established by spectral analysis (see Sec-
tion 3) to be 3-[1-(2,4,6-trichlorophenylhydra-
1
was also established from its H NMR spec-
trum. Two exchangeable protons were as-
zono)glyoxal-1-yl]quinoxalin-2(1H)one
favoring the acyclic nature of 4.
(5)
signed at the downfield region at l 11.70 and

36
L.F. Awad / Carbohydrate Research 326 (2000) 34–42
stepwise elimination of a molecule of acetic
acid under the basic conditions of the reaction
with the formation of the azoalkene interme-
diate 11 (Scheme 2). The formation and isola-
tion of azoalkenes from sugar hydrazones is a
well-known reaction [23]. However, in this
case the product was tautomerized to the iso-
lated hydrazono alkene namely, 3-[3,4-di-O-
acetyl-2-deoxy-1-(2,4,6-trichlorophenylhydrazo
no)but-2-en-1-yl]quinoxalin-2(1H)one (12).
Acetylation of the analogues of 4 with boil-
ing acetic anhydride gave pyrazolyl derivatives
of the type 14 [6,7]. However, the reaction of
4 with acetic anhydride under the same condi-
tions gave a mixture of products that could be
13.95 and attributed to the NH protons of the
amide and the hydrazone moieties, respec-
tively. At the lower-frequency region only two
acetyl signals were assigned at l 2.01 and 2.20,
and since the two singlets at l 5.10 (2 H) and
l 7.07 (1 H) were attributed to methylene
protons and a methine proton each without
coupling, respectively, the structure 12 rather
than the other possible structures was assigned
for the product. The formation of the diac-
etate 12 can be explained taking into consider-
ation the mechanism suggested for the
cyclization of the sugar osazone acetate [16].
The first step involved the formation of the
expected triacetate 10, which undergoes a
Scheme 1.

L.F. Awad / Carbohydrate Research 326 (2000) 34–42
37
Scheme 2.
tion to that of the chemical shift of the C-2
proton of 8. At the downfield region only one
exchangeable proton was assigned to the sin-
glet at l 13.90 due to the hydrazono NH
proton. Accordingly the structure 13 was as-
signed for the product and its formation can
be explained by an intramolecular nucle-
ophilic attack of the C-2-enolized oxygen of
the amide group to the C-2 of the butenyl
moiety of the intermediate diacetate 12 with
rearrangement of the double bond and subse-
quent elimination of a molecule of acetic acid
with ring closure to give the furoquinoxaline
derivative 13.
Ring closure of 12 to 3-[5-(hydroxymethyl)-
1 - (2,4,6 - trichlorophenyl)pyrazol - 3 - yl]quino-
xalin-2(1H)one (16) was induced under alka-
line conditions. Thus, treatment of 12 with
aqueous sodium hydroxide solution under
reflux, followed by acidification with acetic
acid, afforded 16 as a pale-yellow crystalline
product.
separated, and the products were identified as
12, 13, 14 and 15. The structures of 3-[5-(ace-
toxymethyl)-1-(2,4,6-trichlorophenyl)pyrazol-
3-yl]quinoxalin-2(1H)one (14) and 2-acetoxy-
3-[5-(acetoxymethyl)-1-(2,4,6-trichlorophenyl)
pyrazol-3-yl]quinoxaline (15) were assigned
based on their spectral characteristics (see Sec-
tion 3).
The structure of red product 13 was de-
duced from its FAB mass spectrum, which
showed a molecular ion peak at m/z 464,
agreeing with the elemental analysis data for
the molecular formula C20H13Cl3N4O3. Its IR
spectrum showed the absence of the amide
carbonyl absorption and the presence of OAc
1
absorption at 1737 cm−1. The H NMR spec-
trum of 13 showed a singlet at l 2.20 corre-
sponding to an acetyl group. The two singlets
at l 4.85 (2 H) and 6.30 (1 H) were attributed
to a methylene and a methine proton, respec-
tively. The latter appeared at a similar loca-

38
L.F. Awad / Carbohydrate Research 326 (2000) 34–42
On the other hand, treatment of 12 with
3. Experimental
boiling acetic anhydride afforded the expected
pyrazolyl derivatives 14 and 15. Acetylation of
16 with acetic anhydride in pyridine afforded
a mixture of two products that were identical
as 14 and 15, as confirmed from their spectral
data. Accordingly, from the above data the
formation of the pyrazole derivatives 14 and
15 can now be explained to be formed from
the intermediate diacetate 12 that undergoes
an elimination of a molecule of acetic acid
from the acetoxy group on C-3 and N–H
proton of the hydrazone moiety with the for-
mation of 14, which was acetylated at the
enolized amide group to give 15 under the
reaction conditions.
Ring closure to pyrazolo[2,3-b]quinoxaline
(flavazole) 17 has been attempted by treat-
ment of 4 with dilute aqueous sodium hydrox-
ide. The FAB mass spectrum of 17 showed a
protonated molecular ion peak at m/z 441. Its
IR spectrum showed the disappearance of the
amide carbonyl absorption as well as the NH
absorption bands, which is in agreement with
its formation.
Acetylation of 17 with acetic anhydride in
pyridine afforded a yellow hygroscopic acetyl
derivative 18 whose structure was assigned
based on its spectral data (see Section 3).
The favored conformation of acyclic sugar
derivatives has been studied based on the vici-
nal proton–proton coupling constants [24–
28]. Thus, examination of the extended zig-zag
conformation of 18 indicated that H-1 and
H-2 are in a gauche arrangement, which
should require the J1,2 value to be B4 Hz.
However, J1,2 was found to be 8.0 Hz, indicat-
ing that H-1 and H-2 are in an antiparallel
disposition. This could be achieved by the
rotation around the C-1ꢀC-2 bond with a
better steric arrangement for the bulky sub-
stituents at C-1. The J2,3 of 4 Hz and J2,3% of 7
Hz indicated that both of H-3 and H-3% would
be in a gauche and antiparallel disposition to
that of H-2.
Melting points were determined with a
Melt–Temp apparatus and are uncorrected.
IR spectra were recorded for the compounds
in a matrix of KBr with a Unicam SP1025
1
spectrophotometer. H NMR spectra were de-
termined with a Bruker AC 250 MHz spec-
trometer. The chemical shifts are expressed on
the l (ppm) scale using Me4Si as the standard.
Mass spectra were recorded using electron
ionization (EI) on a Finnigan MAT 312 spec-
trometer and fast-atom bombardment (FAB)
on a Kratos MS 50 spectrometer. Thin-layer
chromatography (TLC) was performed on E.
Merck Silica Gel 60 F254. The spots were
detected by their characteristic color and by
UV light absorption. The biological testing
was carried out at the Liver Institute,
Menoufia University, Egypt. Microanalyses
were performed at the microanalytical labora-
tory at the Faculty of Science, Alexandria
University.
3 - [1 - (2,4,6 - Trichlorophenylhydrazono) -
threo - 2,3,4 - trihydroxybut - 1 - yl]quinoxalin - 2-
(1H)one (4).—A mixture of -ascorbic acid
L
-
L
(1) (4.4 g, 25 mmol) and p-benzoquinone (2.7
g, 25 mmol) in EtOH (40 mL) was stirred for
90 min at room temperature (rt). The resulting
solution was treated with a soln of o-
phenylenediamine (2) (2.7 g, 25 mmol) in
MeOH (25 mL) and water (100 mL), and
heated until boiling. Then a solution of 2,4,6-
trichlorophenylhydrazine (3) (5.28 g, 25
mmol) in EtOH (100 mL) was added. The
reaction mixture was boiled for 5–10 min,
whereupon a yellow crystalline product was
separated out. It was filtered, washed with
EtOH, dried, and recrystallized from EtOH to
give a yellow crystals of 4 (8.4 g, 74% yield):
mp 225–227 °C; IR (KBr): 3366 (OH), 3175,
3085 (NH), 1646 (OCN), 1540, 1514 cm−1
(CꢁN). EIMS: m/z (%): 442 (8, [M+
+
’
2−H2O]), 440 (8, [M+ −H2O]), 426 (7,
’
+
[M+ +4–2 H2O]), 424 (25, [M +2–2
H2O]), 422 (26, [M −2 H2O]), 396 (21, 426−
’
’
Compound 4 was tested for its activity
against hepatitis B virus (HBV) in Hep G2
2.2.15 cells. The concentration of the tested
compound was 10 mM. It showed high viral
replication inhibition values of 89.5, 88.1 and
87.1% after 1, 2 and 3 weeks, respectively. It
has a low cytotoxicity (7.7%).
+
’
CH2-O), 394 (36, 424−CH2O), 392 (47, 422−
CH2-O), 381 (21), 379 (32), 377 (37), 366
(7, 426−CH2OHꢀCHO), 364 (24, 424−
CH2OHꢀCHO), 362 (28, 422−CH2OHꢀ
CHO), 199 (26, [C6H3Cl3N]+), 197 (91, [C6H3-

L.F. Awad / Carbohydrate Research 326 (2000) 34–42
39
Cl3N]+), 195 (100, [C6H3Cl3N]+). Anal. Calcd
for C18H15Cl3N4O4 (457.5): C, 47.23; H, 3.30;
N, 12.24. Found: C, 47.42; H, 2.89; N, 12.24.
3 - [1 - (2,4,6 - Trichlorophenylhydrazono)gly-
oxal-1-yl]quinoxalin-2(1H)one (5).—A mix-
ture of 4 (2.20 g, 4.80 mmol) and sodium
metaperiodate (3.2 g, 15 mmol) in distilled
water (100 mL) was stirred overnight at rt.
The product obtained was filtered off, washed
with water, dried, and crystallized from EtOH
to give yellow crystals of 5 (1.5 g, 79% yield):
mp 258–260 °C; IR (KBr) 3170, 3112 (NH),
1710 (CO), 1665, (CON) 1609 and 1534 cm−1
(CꢁN); FABMS (CHCl3–NBOH): m/z (%)
The resulting solution was filtered and left to
cool, whereupon a red crystalline product sep-
arated out. It was filtered, washed with EtOH,
and recrystallized from EtOH to give reddish
crystals of 7 (0.1 g, 67% yield): mp 215–
217 °C; IR (KBr) 3170 (NH) and 1648 cm−1
(CON); FABMS: (CHCl3–NBOH) m/z (%);
593 (13, [M+4]+) 591 (24, [M+2]+); 589
1
(24, [M]+); H NMR (Me2SO-d6): l 7.27–
7.40, 7.53–7.85 (2 m, 8 H, ArꢀH), 8.35 (s, 1
H, HCꢁN), 10.27, 10.84, 12.50, 12.70 and
12.90 (5 s, 2 H, D2O exchangeable 2 NH),
11.25 (s, 1 H, D2O exchangeable, OCNH).
Anal. Calcd for C22H12Cl6N6O (589.08): C,
44.85; H, 2.05; N, 14.26. Found: C, 45.36; H,
1.78; N, 13.73.
1
399 (9, [MH]++2), 397 (9%, [MH]+); H
NMR (Me2SO-d6): l 7.25–7.40, 7.50–7.85 (2
m, 6 H, ArꢀH), 9.5 (s, 1 H, HCꢁO), 11.20 (s,
1 H, D2O exchangeable, CONH), 12.6 (s, 1 H,
D2O exchangeable, ꢁNꢀNH). Anal. Calcd for
C16H9Cl3N4O2·H2O (413.64): C, 46.45; H,
2.68; N, 13.54. Found: C, 46.05; H, 2.70; N,
13.23.
2-Acetoxy-3-[2-acetyl-2-(2,4,6-trichloro-
phenyl)hydrazono)]-2,3-dihydrofuro[2, 3-b]-
quinoxaline (8).—A solution of 5 (0.33 g, 0.83
mmol) in pyridine (5 mL) was cooled in an
ice-bath, then treated with Ac2O (5 mL) with
stirring. The reaction mixture was left at rt
overnight, then poured onto crushed ice. The
product separated out, was filtered off,
washed repeatedly with water, and dried. It
was crystallized from EtOH in yellow crystals
(0.27 g, 82% yield): mp 191–192 °C; IR (KBr)
1772 (OAc), 1721 (NAc), 1637 and 1618 cm−1
3 - [1 - (2,4,6 - Trichlorophenylhydrazono) - 2 -
hydroxyeth-1-yl]quinoxalin-2(1H)one (6).—To
a stirred solution of 5 (0.3 g, 0.63 mmol) in
abs EtOH (50 mL), NaBH4 (0.18 g, 4.7 mmol)
was added. The reaction mixture was stirred
for 2 h at rt. It was then acidified with AcOH
and diluted with water. The product separated
out and was filtered, washed with water, and
crystallized from EtOH to give an orange
crystalline product 6 (0.2 g, 80% yield): mp
232–234 °C; IR (KBr) 3416 (OH), 3113 NH,
1667 (CON), 1549 cm−1 (CꢁN); FABMS
(CHCl3 –NBOH) m/z (%), 399 (14, [M+2]+)
397 (18, [M]+), 381 (13, [M+2−H2O]+), 379
1
(CꢁN); H NMR (Me2SO-d6): l 2.05 (s, 3 H,
OCOCH3), 2.70 (s, 3 H, NCOCH3), 6.28 (s, 1
H, H-2), 7.70–7.90, 8.05, 8.15, 8.20 (m, 3 d, 6
H, ArꢀH). Anal. Calcd for C20H13Cl3-
N4O4·H2O (497.72): C, 48.26; H, 3.03; N,
11.26. Found: C, 48.73; H, 2.89; N, 10.68.
3-[3,4-Di-O-acetyl-2-deoxy-1-(2,4,6-tri-
chlorophenylhydrazono)but - 2 - en - 1 - yl]quino-
xalin-2(1H)one (12).—A solution of 4 (0.3 g,
0.65 mmol) in pyridine (7 mL) was treated
with Ac2O (7 mL) at 0 °C. The reaction pro-
ceeded as above to give an orange crystalline
product 12 (0.3 g, 88% yield): mp 175–178 °C;
IR (KBr) 3150 (NH) 1745 (OAc), 1661 (OCN)
1
(14, [M−H2O]+); H NMR (Me2SO-d6): l
4.60, 4.73 (2 d, 2 H, CH2), 6.05, 6.40 (2 m, 1
H, D2O exchangeable, OH) 7.27–7.70, 7.52–
7.80, 7.85 (2 m, d, 6 H, ArꢀH), 10.24, 12.45,
12.84 (3 s, 1 H, D2O exchangeable NH) and
11.24 (s, 1 H, D2O exchangeable OCNH).
Anal. Calcd for C16H11Cl3N4O2 (397.65): C,
48.32; H, 2.78; N, 14.09. Found: C, 47.83; H,
2.99; N, 13.84.
3 - [1,2 - Bis(2,4,6 - trichlorophenylhydrazono)-
glyoxal-1-yl]quinoxalin-2(1H)one (7).—A so-
lution of 5 (0.1 g, 0.25 mmol) in EtOH (40
mL) was boiled under reflux with 2,4,6-
trichlorophenylhydrazine (3) (0.053 g, 0.25
mmol) and two drops of AcOH for 30 min.
1
and 1610 cm−1 (CꢁN); H NMR (CDCl3): l
2.01 (s, 3 H, COCH3), 2.20 (s, 3 H, COCH3),
5.10 (s, 2 H, CH2), 7.07 (s, 1 H, CH), 7.35–
7.45, 7.53–7.60 and 7.85 (2 m, s, 6 H, ArꢀH),
11.70 (bs, 1 H, D2O exchangeable, OCNH)
and 13.95 (s, 1 H, D2O exchangeable ꢁNNH).
Anal. Calcd for C22H17Cl3N4O5 (523.76): C,
50.44; H, 3.27; N, 10.69. Found: C, 50.61; H,
3.30; N, 11.27.

40
L.F. Awad / Carbohydrate Research 326 (2000) 34–42
H, ArꢀH) and 13.90 (s, 1 H, D2O exchange-
Reaction of 4 with boiling acetic anhydride.
able, NH). Anal. Calcd for C20H13Cl3N4O4
(463.70): C, 51.80; H, 2.83; N, 12.08. Found
C, 51.71; H, 2.89; N, 11.90.
A suspension of compound 4 (0.5 g, 1.09
mmol) in Ac2O (25 mL) was heated under
reflux. The reflux was continued for 30 min
after the solid was dissolved. The resulting
solution was cooled and then poured into
ice-cold water. The product obtained was
filtered off, washed with water, and dried. The
crude product was chromatographed on silica
gel by eluting with 2:1 EtOAc–petroleum
ether to give 12, 13, 14 and 15.
3 - [5 - (Hydroxymethyl) - 1 - (2,4,6 - trichloro-
phenyl)pyrazol-3-yl]quinoxalin-2-(1H)one (16).
—A solution of 12 (1 g, 1.9 mmol) in EtOH
(25 mL) was treated with a NaOH solution (1
N, 25 mL). The reaction mixture was heated
under reflux for 4 h. The clear solution ob-
tained was neutralized with AcOH and left to
cool, whereupon a yellow product separated
out. The product was filtered, washed with
water, and crystallized from EtOH to give 16
(0.46 g, 58% yield): mp 235–237 °C; IR (KBr)
3440 (OH), 1662 (OCN), 1553 cm−1 (CꢁN);
1H NMR (CDCl3): l 4.55 (s, 2 H, CH2),
7.20–7.45, 7.7 and 8.05 (m, s and d, 7 H,
ArꢀH+CꢀH), 11.05 (s, 1 H, D2O exchange-
able, NH). Anal. Calcd for C18H11Cl3N4O2
(421.67): C, 51.27; H, 2.63; N, 13.28. Found:
C, 51.09; H, 3.08; N, 12.86.
3-[3,4-Di-O-acetyl-2-deoxy-1-(2,4,6-tri-
chlorophenylhydrazono)but - 2 - en - 1 - yl]quino-
xalin-2-(1H)one (12).—The compound was
identical to that obtained from 4 and Ac2O–
pyridine (0.1 g, 18% yield).
3-[5-(Acetoxymethyl-1-(2,4,6-trichlorophe-
nyl)pyrazol-3-yl]quinoxalin-2 (1H)one (14).—
The compound was obtained as pale-yellow
needles (0.05 g, 10% yield): mp 195–197 °C;
IR (KBr) 1744 (OAc), 1656 (OCN), 1610 and
1
1578 cm−1 (CꢁN); H NMR (CDCl3): l 2.05
3 - [5 - (Acetoxymethyl) - 1 - (2,4,6 - trichloro-
phenyl)pyrazol-3-yl]quinoxalin-2 (1H)one (14)
and 2-acetoxy-3-[5-acetoxymethyl)-1-(2,4,6-
trichlorophenyl) pyrazol-3-yl]quinoxaline (15)
Method A. A suspension of 12 (0.1 g, 0.19
mmol) in Ac2O (10 mL) was heated under
reflux for 20 min. The clear solution obtained
was poured onto crushed ice with stirring, the
product obtained was filtered off, washed with
water, and dried. The crude product was frac-
tionally crystallized from cold acetone to give
14 (0.02 g, 23% yield) and 15 (0.04 g, 42%
yield).
(s, 3 H, COCH3), 5.05 (s, 2 H, CH2), 7.30–
7.43, 7.55, 7.80, 8.10 (m, d, s, d, 7 H, ArꢀH+
CH) and 11.65 (s, 1 H, D2O exchangeable,
OCNH). Anal. Calcd for C20H13Cl3N4O3
(463.70): C, 51.80; H, 2.82; N, 12.08. Found:
C, 52.13; H, 2.88; N, 11.99.
2 - Acetoxy - 3[5 - (acetoxymethyl) - 1 - (2,4,6-
trichlorophenyl)pyrazol-3-yl)]quinoxaline (15).
—The compound was separated as a white
crystalline product (0.13 g, 24% yield): mp
155–156 °C; IR (KBr) 1756 (OAc) and 1612,
1
1570 cm−1 (CꢁN); H NMR (CDCl3): l 2.00
(s, 3 H, COCH3), 2.30 (s, 3 H, COCH3), 5.0 (s,
2 H, CH2) and 7.40–7.55, 7.73–7.80, 7.95–
8.02, 8.17–8.20 (4 m, 7 H, ArꢀH+CH). Anal.
Calcd for C22H15Cl3N4O4 (505.74): C, 52.24;
H, 2.99; N, 11.07. Found: C, 52.37; H, 3.06;
N, 10.63.
Method B. A cold solution of 16 (0.12 g,
0.28 mmol) in pyridine (3 mL) was treated
with Ac2O (5 mL). The reaction mixture was
left at rt overnight, then poured onto crushed
ice and proceeded as in Method A to give 14
(0.03 g, 23% yield) and 15 (0.06 g, 43% yield).
2 - (2 - Acetoxyethen - 2 - yl) - 3 - [2-(2,4,6-tri-
chlorophenyl)hydrazono] - 2,3 - dihydrofuro[2,3-
b]quinoxaline (13).—The compound was sepa-
rated as a red crystalline product (0.05 g, 10%
yield): mp 205–207 °C; IR (KBr): 3077 (NH),
1737 (OAc) and 1576 cm−1 (CꢁN) FABMS
(CHCl3 –NBOH): m/z (%) 464 (20, [M]+), 403
(6, [M−OAc]+); 1H NMR (CDCl3): l 2.20 (s,
1 H, COCH3), 4.85 (s, 2 H, CH2), 6.30 (s, 1 H,
CH), 7.35, 7.67–7.78, 7.85, 7.95 (s, m, 2 d, 6
1 - (2,4,6 - Trichlorophenyl) - 3 - ( -threo-gly-
L
cerol-1-yl)pyrazolo[2,3-b]quinoxaline (17).—A
suspension of 4 (0.5 g, 1.09 mmol) in NaOH
solution (0.01 M, 500 mL) was heated under
reflux for 3 h. The resulting solution was
filtered off while hot, then left to cool, where-
upon a yellow crystalline product was ob-
tained. The product was filtered, washed with
water, dried and crystallized from EtOH (0.2

L.F. Awad / Carbohydrate Research 326 (2000) 34–42
41
Acknowledgements
g, 63% yield): mp 125–127 °C; IR (KBr) 3406
(OH), 1551 cm−1 (CꢁN); FABMS (CHCl3–
NBOH) m/z (%); 443 (90, [MH+2]+), 441
(90, [MH]+), 423 (3, [MH−H2O]+), 391 (5,
324−CH2OH). Anal. Calcd for C18H13Cl3-
N4O3 (439.68): C, 49.16; H, 2.98; N, 12.74.
Found: C, 48.83; H, 3.36; N, 12.27.
The author expresses her gratitude and
thanks to Professor E.S.H. El Ashry for his
encouragement, and his helpful discussions
and review of the manuscript. Thanks are also
due to Professor Dr R.R. Schmidt for making
available some spectral measurements and to
Mr Kalaus Ha¨gele for measuring the mass
spectra. The author thanks DANIDA for the
support of the biological testing.
3-(2,3,4-Tri-O-acetyl- -threo-glycerol-1-yl)-
L
1-(2,4,6-trichlorophenyl)pyrazolo[2,3-b]quino-
xaline (18).—A cold solution of 17 (0.2 g,
0.45 mmol) in pyridine (5 mL) was treated
with Ac2O (5 mL). The reaction was then
carried out as for 8. The crude product was
chromatographed on silica gel. Elution with
1:1 EtOAc–petroleum ether gave 18 as a yel-
low crystals (0.27 g, 65% yield): mp 58–60 °C;
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