Preparation of 2,6-anhydro-aldose acylhydrazones, -semicarbazones and -oximes from 2,6-anhydro-aldononitriles (glycosyl cyanides)

Article abstract of DOI:10.1016/S0008-6215(03)00163-0

Reductive transformation of per-O-acylated 2,6-anhydro-aldononitriles (glycopyranosyl cyanides of the D-galacto, D-gluco, D-xylo, and D-arabino configuration) with Raney-nickel-NaH₂PO₂ in pyridine-AcOH-water solvent mixture in the pr

Full text of DOI:10.1016/S0008-6215(03)00163-0

Carbohydrate Research 338 (2003) 1319ꢀ1325
/
www.elsevier.com/locate/carres
Note
Preparation of 2,6-anhydro-aldose acylhydrazones, -semicarbazones
and -oximes from 2,6-anhydro-aldononitriles (glycosyl cyanides)
Marietta To´th, La´szlo´ Somsa´k*
Department of Organic Chemistry, University of Debrecen, H-4010, P.O. Box 20, Debrecen, Hungary
Received 13 March 2003; accepted 1 April 2003
Abstract
Reductive transformation of per-O-acylated 2,6-anhydro-aldononitriles (glycopyranosyl cyanides of the
D-galacto, D-gluco, D-
xylo, and -arabino configuration) with Raney-nickelꢀNaH2PO2 in pyridineꢀAcOHꢀwater solvent mixture in the presence of
D
/
/
/
benzoylhydrazine, ethyl carbazate, and semicarbazide gave the corresponding anhydro-aldose benzoylhydrazones, -ethoxycarbo-
nylhydrazones, and -semicarbazones, respectively. Acid catalyzed transimination of the semicarbazones with thiosemicarbazide,
hydroxylamine, and O-benzylhydroxylamine, resulted in the formation of anhydro-aldose thiosemicarbazones, and E/Z mixtures of
anhydro-aldose oximes, and O-benzyl-(anhydro-aldose)-oximes, respectively.
# 2003 Elsevier Science Ltd. All rights reserved.
Keywords: C-Glycosyl compounds; Hydrazones; Oximes
1. Introduction
nosyl azomethines, see a recent work18 by Gyorgydea´k
¨
and co-workers and references cited therein.
Azomethines constitute a densely populated class of
compounds readily available by condensation of a
carbonyl compound with an ammonia derivative.1,2
Their widespread application in organic synthesis is
Recently, we have elaborated a method for the
preparation of tosylhydrazones from nitriles by Raney-
nickelꢀNaH2PO2 reduction of the cyano group and in
/
situ trapping of the intermediate with tosylhydrazine.19
The application of this protocol to glycosyl cyanides
based on the sensitivity of the CÄ/N double bond
(anhydro-aldononitriles, Scheme 1, 1ꢀ4) led to the till
/
towards attacks by nucleophiles and radicals, and on
additional various possibilities offered by substituents
on the nitrogen especially when they are of heteroatomic
nature.2ꢀ8 Such derivatives are very well known among
open chain carbohydrates as well and lend themselves to
several ensuing transformations.9 At variance, because
of the more limited availability of 2,6-anhydro-aldoses
(C-glycosyl aldehydes)10 azomethine derivatives at-
tached through carbon to the anomeric centre of
pyranoid sugar rings are less frequent: C-glycosyl
azomethines have been represented by anhydro-
aldoximes,11ꢀ14 nitrones,15 and nitronates16 of anhy-
dro-aldoses; as well as C-glycosyl imidoyltellurides
obtained from glycosyl tellurides.17 For N-glycopyra-
then unknown anhydro-aldose tosylhydrazones (e.g., 5)
which opened a new way to exo-glycals via their aprotic
Bamfordꢀ
Stevens reaction.20,21
/
Studies on the Raney-nickel catalyzed conversion of
nitriles to aldehydes in hydrogen atmosphere showed
that the intermediate (probably an imine) had to be
trapped to avoid formation of the corresponding
methylamine.22ꢀ25 1,2-Dianilino-ethane and semicarba-
zide as trapping agents proved very efficient, phenylhy-
drazine was less effective, and tosyl- and
benzoylhydrazine as well as hydroxylamine were re-
ported to deliver no useful results.22ꢀ25 For the conver-
sion of glycosyl cyanides to the corresponding
aldehydes, a modified protocol was used (Raney-nickel
and NaH2PO2 in a mixture of AcOH and pyridine) with
1,2-dianilino-ethane,26,27 while in the absence of a
trapping agent a 1-formyl-glycal could be isolated.28,29
Since our experiences with the formation of tosylhydra-
* Corresponding author. Tel.: ꢁ
453836.
E-mail address: somsak@tigris.klte.hu (L. Somsa´k).
/
36-52-512900; fax: ꢁ36-52-
/
0008-6215/03/$ - see front matter # 2003 Elsevier Science Ltd. All rights reserved.
doi:10.1016/S0008-6215(03)00163-0

1320
M. To´th, L. Somsa´k / Carbohydrate Research 338 (2003) 1319ꢀ1325
/
Scheme 1. (a) Raney-Ni, NaH2PO2, RNHNH2, pyridine, AcOH, water, 40 8C; (b) NH2OR×
/
HCl, abs. pyridine, abs. CH3CN, rt; (c)
NH2OBn×HCl, AcOH, rt; (d) NH2NHCSNH2, AcOH, 40 8C.
/
zones from nitriles19,20 contradicted the earlier ob-
servations,22ꢀ25 we started a systematic investigation
with respect to the trapping agent. Here we disclose our
results on the scope and limitations of the above
reductive transformation as to the preparation of new
C-glycosyl azomethine derivatives.
product in 82% yield. Semicarbazones 11, 13, and 15
were obtained in 63ꢀ89% yields.
/
Trials to use other ammonia derivatives as trapping
agents like phenylhydrazine, hydroxylamine, O-benzyl-
hydroxylamine, aniline, and benzylamine were success-
ful neither at room temperature nor at 40 8C. In the
reaction of 1 with phenylhydrazine and aniline complex
reaction mixtures unseparable with column chromato-
graphy were formed, with hydroxylamine, its O-benzyl
derivative, and also with benzylamine 1-formyl-galac-
2. Results and discussion
tal28,29 was isolated in 15ꢀ
69% yield. These experiences
/
together with the preparation19,20 of tosylhydrazones
like 5 indicated that a direct transformation of the nitrile
group in glycosyl cyanides into imine derivatives was
restricted to hydrazines substituted with electron with-
drawing acyl or analogous groups.
Using benzoylhydrazine under the above mentioned
Raney-nickelꢀNaH2PO2 reductive conditions at room
/
temperature brought about no transformation of 1.
However, a slight enhancement of the reaction tempera-
ture to 40 8C resulted in a rather clean transformation of
In order to get other C-glycosyl azomethines, acid
catalyzed transimination reactions of the hydrazone
derivatives were investigated next. Thus semicarbazones
7, 11, and 15 were reacted at room temperature in a
mixture of acetonitrile and pyridine with hydrochlorides
of hydroxylamine and O-benzylhydroxylamine to give
the corresponding oximes 16, 18, and 20 and their O-
each glycosyl cyanide 1ꢀ
12, and 14, respectively, in 58ꢀ
Ethyl-carbazate also served as a suitable trapping agent
at room temperature to give 8 (58%). Only a partial
transformation of 1 could be observed at room tem-
perature with semicarbazide, but at 40 8C the reaction
was complete in 1 h to give 7 as a crystalline crude
/
4 to benzoylhydrazones 6, 10,
/90% yields (Scheme 1).

M. To´th, L. Somsa´k / Carbohydrate Research 338 (2003) 1319ꢀ
/1325
1321
benzylated derivatives 17, 19, and 21, respectively, as
mixtures of E and Z isomers (see below) generally in
good yields. Under the same conditions, attempted
reactions of 7 with hydrochlorides of aniline and
benzylamine, hydrazine sulfate, and tosylhydrazine in
the presence of catalytic or stoichiometric amounts of
trifluoroacetic acid or p-toluenesulfonic acid gave not
even a trace of the expected transimination products.
Tosylhydrazone 5 also resisted transformations with O-
benzylhydroxylamine.
be valuable synthetic intermediates, and their ensuing
reactions are currently being investigated in our labora-
tory.
3. Experimental
3.1. General methods
Performing the reaction of 7 and 15 with BnONH2×
/
Melting points were measured on a Kofler hot-stage and
are uncorrected. Optical rotations were determined with
HCl in glacial AcOH gave the expected 17 and 21,
respectively, in very good yields. On the contrary, no
reaction occurred in this solvent with hydrochlorides of
aniline and benzylamine, while with tosylhydrazine and
a Perkinꢀ/Elmer 241 polarimeter at room temperature.
IR spectra were taken with a Perkinꢀ
/
Elmer 16 PC FT-
IR spectrometer. NMR spectra were recorded with
1
Bruker WP 360 SY (360/90 MHz for H/13C). Chemical
NH2OH×
Compound 7 was also transformed with thiosemicarba-
zide both in acetonitrileꢀpyridine (at room temperature
/HCl multicomponent mixtures were formed.
shifts are referenced to Me4Si (1H), to the residual
solvent signals (13C). TLC was performed on DC-
Alurolle Kieselgel 60 F254 (Merck); the plates were
visualized by gentle heating or with UV light. For
column chromatography, Kieselgel 60 (E. Merck) was
used. Organic solutions were dried on MgSO4, and
/
85% conversion) and in AcOH at 40 8C the latter giving
higher yield of 9 (84% vs. 43%) with a complete
conversion of the starting material.
Structural elucidation of the new products was
straightforward by NMR spectroscopy. In the 1H
concentrated in vacuo at 40ꢀ50 8C (water bath).
/
NMR spectra, characteristic doublets (J1,2
Hz) appeared at d ꢀ7.4ꢀ7.5 ppm for H-1 of benzoylhy-
drazones 6, 10, 12, 14, and at d ꢀ7.0ꢀ7.2 ppm for
ꢂ
/
4.9ꢀ7.4
/
/
/
/
/
3.2. General procedure I for the preparation of 2,6-
anhydro-aldose hydrazones 6, 8, 10, 12, 14, and
semicarbazones 7, 11, 13, 15
semicarbazones 7, 11, 13, 15, ethoxycarbonylhydrazone
8, and thiosemicarbazone 9. In the 13C spectra, reso-
nances for C-1 were visible at d ꢀ
10, 12, 14, at d ꢀ137ꢀ138 ppm for 7, 11, 13, 15, at dꢂ
142 ppm for 8, and dꢂ140 ppm for 9. In these spectra
only one set of signals was to be observed indicating that
no significant isomerization around the CÄN double
bond took place. The configuration of the CÄN bond
/
145ꢀ
/
146 ppm for 6,
/
/
/
Raney-nickel (1.5 g, from an aq. suspension, E. Merck)
was added at room temperature to a vigorously stirred
solution of pyridine (5.7 mL), AcOH (3.4 mL), and
water (3.4 mL, in case of 6, 8, 10, 12, and 14, or 1.7 mL,
in case of 7, 11, 13, and 15). Then NaH2PO2 (0.74 g, 8.4
mmol), benzoylhydrazine (0.23 g, 1.7 mmol, in case of 6,
10, 12, and 14), ethyl-carbazate (0.18 g, 1.7 mmol, in
case of 8), or an aq. sol. (1.7 mL) of semicarbazide (2
mmol, in case of 7, 11, 13, and 15) liberated from its
hydrochloride (0.22 g) by 1.02 equivalent of KOH and
/
/
/
was not investigated in detail in these derivatives: it can
be assumed that these are E as demonstrated with
1
tosylhydrazones.19,21 For the oximes, both the H and
13C spectra exhibited two sets of signals suggesting the
presence of E and Z isomers. In keeping with the
literature13, H-1 in E diastereomers resonated at lower
the corresponding glycosyl cyanide 1ꢀ4 (1 mmol) were
/
field (d ꢀ
6.8ꢀ6.9 ppm for 16Z, 18Z, and 20Z, J1,2
each; d ꢀ7.3ꢀ7.5 ppm for 17E, 19E, and 21E, d ꢀ
6.9 ppm for 17Z, 19Z, and 21Z, J1,2 6.7ꢀ7.3 Hz for
each). The signals for C-1 appeared around 146ꢀ147
ppm for each oxime 16ꢀ21.
/
7.3ꢀ
/
7.5 ppm, for 16E, 18E, and 20E, d ꢀ
6.7 Hz for
6.8ꢀ
/
added to the mixture. The reaction was carried out at
room temperature in case of 8, or at 40 8C in case of 6,
10, 12, and 14, and 7, 11, 13, and 15. When the reaction
/
ꢂ
/
/
/
/
/
ꢂ
/
/
was complete (TLC, 1:1 EtOAcꢀhexane) the insoluble
/
/
materials were filtered off with suction, and washed with
CH2Cl2 or EtOAc (10 mL). The organic layer of the
filtrate was separated, washed with water (3 mL), 10%
/
In conclusion, we have shown that anhydro-aldono-
nitriles can readily be transformed into anhydro-aldose
aq HCl solution (2ꢃ/3 mL), cold, satd NaHCO3
hydrazones by Raney-nickelꢀ
presence of hydrazines bearing an electron withdrawing
substituent (e.g., Ã COR, ÃCONH2). An-
SO2Ar19ꢀ21, Ã
hydro-aldose semicarbazones are prone to acid cata-
lysed transiminations with hydroxylamine, O-
benzylhydroxylamine, or thiosemicarbazide to give the
corresponding oximes and thiosemicarbazones, respec-
tively. These new C-glycosyl azomethine derivatives can
/
NaH2PO2 reduction in the
solution (2ꢃ3 mL), water (3 mL), (in case of 6 and 12
/
washing was performed with water only), and then
dried. The solution was concentrated under reduced
pressure, and traces of pyridine were removed by
repeated co-evaporations with toluene. The residue
was purified either by crystallization or column chro-
/
/
/
matography (1:1 or 1:2 EtOAcꢀ/hexane) as indicated
with the description of the particular compounds.

1322
M. To´th, L. Somsa´k / Carbohydrate Research 338 (2003) 1319ꢀ1325
/
3.3. General procedure II for the preparation of 2,6-
anhydro-aldoximes 16 21
3.6. 3,4,5,7-Tetra-O-acetyl-2,6-anhydro-
manno-heptose semicarbazone (7)
D
-glycero-L-
/
ꢀ
White crystals from MeOH; mp 152ꢀ
/
155 8C; [a]D
ꢁ2 (c
/
An anhydro-aldose semicarbazone (7, 11, or 15, 1
mmol) was dissolved in the mixture of dry acetonitrile
(12.5 mL) and dry pyridine (4.2 mL). Hydroxylamine
hydrochloride (278 mg, 4 mmol, in case of 16, 18, and
20) or O-benzyl-hydroxylamine hydrochloride (638 mg,
4 mmol, in case of 17, 19, 21) was added in one portion.
The mixture was stirred at room temperature until
disappearance of the starting material (TLC, 1:1
1.04, CHCl3); IR (KBr) 3438, 1742, 1702, 1586, 1372,
1250, 1055 cmꢄ1; 1H NMR (Me2SO-d6): d 10.21 (brs, 1
H, NH), 7.01 (d, 1 H, J1,2
(brs, 2 H, NH2), 5.36ꢀ5.31 (m, 1 H, H-5), 5.26 (dd, 1 H,
J4,5 3.3 Hz, H-4), 5.14 (dd, 1 H, J3,4 10.1 Hz, H-3),
4.27 (dd, 1 H, J5,6 1.0, J6,7 6.0, J6,7?ꢂ6.0 Hz, H-6),
4.21 (dd, 1 H, J2,3 9.4 Hz, H-2), 4.07ꢀ3.92 (m, 2 H, H-
7, H-7?), 2.13, 2.00, 1.96, 1.93 (4 s, 12 H, 4ꢃ
OAc); 13
NMR (CDCl3): d 170.3, 170.1, 170.0 (CÄO), 157.7
ꢂ
/
6.1 Hz, H-1), 6.40ꢀ6.00
/
/
ꢂ
/
ꢂ
/
B
/
ꢂ
/
/
ꢂ
/
/
/
C
EtOAcꢀ
was washed by 10% aq HCl solution (3ꢃ
satd NaHCO3 solution (3ꢃ6 mL), water (3 mL), then
/
hexane). After dilution with EtOAc the solution
/
/6 mL), cold,
(NHCONH2) 137.8 (C-1), 77.1, 74.2, 71.6, 67.4, 66.4 (C-
2, C-3, C-4, C-5, C-6), 61.6 (C-7), 20.7, 20.5 (CH3).
Anal. Calcd for C16H23N3O10: C, 46.04; H, 5.55; N,
10.07; found: C, 46.14; H, 5.69; N, 10.21.
/
dried, and the solvent removed. The residue was purified
either by crystallization or column chromatography (1:1
or 1:2 EtOAcꢀhexane) as indicated with the description
/
of the particular compounds.
3.7. 3,4,5,7-Tetra-O-acetyl-2,6-anhydro-
manno-heptose ethoxycarbonylhydrazone (8)
D
-glycero-L-
Colourless syrup; [a]D
3274, 2982, 1732, 1538, 1372, 1230, 1056, 756; 1H NMR
(CDCl3): d 8.77 (brs, 1 H, NH), 7.13 (d, 1 H, J1,2 5.2
Hz, H-1), 5.49ꢀ5.47 (m, 1 H, H-5), 5.24 (dd, 1 H, J2,3
9.4, J3,4 10.0 Hz, H-3), 5.13 (dd, 1 H, J4,5 3.2 Hz, H-
4), 4.33ꢀ3.94 (m, 6 H, H-2, H-6, H-7, H-7?, CH2), 2.17,
2.05, 2.04, 2.01 (4 s, 12 H, 4ꢃ OAc), 1.31 (t, 3 H, CH3);
13C NMR (CDCl3): d 171.0, 170.7, 170.4, 170.2 (CÄ
O),
ꢁ
/
108 (c 0.98, CHCl3); IR (KBr)
3.4. General procedure III for the preparation of O-
benzyl-(2,6-anhydro-aldose)-oximes 17, 21
ꢂ
/
/
ꢂ
/
An anhydro-aldose semicarbazone (7, or 15, 1 mmol)
was dissolved in glacial AcOH (21 mL), and O-benzyl-
hydroxylamine hydrochloride (638 mg, 4 mmol) was
added in one portion. The mixture was stirred at room
temperature until the starting material disappeared
ꢂ
/
ꢂ
/
/
/
/
141.7 (C-1), 78.6, 74.6, 71.3, 67.8, 67.4 (C-2, C-3, C-4, C-
5, C-6), 62.0 (C-7, CH2), 21.1, 20.9, 20.8, 14.7 (CH3).
Anal. Calcd for C18H26N2O11: C, 48.43; H, 5.87; N,
6.28; found: C, 48.30; H, 5.66; N, 6.05.
(TLC, 1:1 EtOAcꢀ
extracted with EtOAc (3ꢃ
neutralized by cold, satd NaHCO3 solution, dried, and
the solvent removed. The residue was purified by
/
hexane), then poured onto ice-water,
/20 mL), the organic phase
column chromatography (1:2 EtOAcꢀhexane).
/
3.8. 3,4,5,7-Tetra-O-acetyl-2,6-anhydro-
manno-heptose thiosemicarbazone (9)
D-glycero-L-
Semicarbazone 7 (30 mg, 0.07 mmol) was dissolved in
glacial AcOH (1.5 mL), thiosemicarbazide (26 mg, 0.28
mmol) was added in one portion, and the mixture was
stirred at 40 8C until disappearance of the starting
3.5. 3,4,5,7-Tetra-O-acetyl-2,6-anhydro-
manno-heptose benzoylhydrazone (6)
D
-glycero-L-
Colourless syrup; [a]D
3422, 1750, 1372, 1226, 1166, 1052 cmꢄ1
(CDCl3): d 10.52 (brs, 1 H, NH), 7.84 (d, 2 H, Jꢂ
Hz, Bz), 7.51 (t, 2 H, Jꢂ7.4 Hz, Bz), 7.41 (d, 1 H, J1,2
7.4 Hz, H-1), 7.40 (t, 1 H, Jꢂ7.4 Hz, Bz), 5.49ꢀ5.47 (m,
1 H, H-5), 5.25 (dd, 1 H, J2,3 9.3, J3,4 10.1 Hz, H-3),
5.15 (dd, 1 H, J4,5 2.7 Hz, H-4), 4.20ꢀ4.04 (m, 3 H, H-
2, H-7, H-7?), 4.00 (dd, 1 H, J5,6 1.0, J6,7 6.1, J6,7?ꢂ
6.0 Hz, H-6), 2.15, 2.02, 2.00 (3 s, 12 H, 4ꢃ
OAc); 13C
NMR (Me2SO-d6) d 170.0, 169.7, 169.5, 163.2 (CÄO),
ꢄ
/
258 (c 1.05, CHCl3); IR (KBr)
1H NMR
7.4
material (TLC, 2:1 EtOAcꢀ
poured onto ice-water, extracted with EtOAc (3ꢃ
/
hexane). The solution was
4
;
/
/
mL), the organic phase neutralized by cold, saturated
NaHCO3 solution, dried, and the solvent removed. The
residue was purified by column chromatography (1:2 to
/
ꢂ
/
/
/
ꢂ
/
ꢂ
/
1:1 EtOAcꢀ
[a]D ꢄ338 (c 1.00, CHCl3); IR (KBr) 3456, 3336, 1748,
1
/hexane) to give 9 (84%). Colourless syrup;
ꢂ
/
/
/
B
/
ꢂ
/
/
1600, 1254, 1224, 1050 cmꢄ1; H NMR (Me2SO-d6): d
/
11.4 (brs, 1 H, NH), 8.29, 7.51 (2 brs, 2 H, NH2), 7.23
/
(d, 1 H, J1,2
5.28 (dd, 1 H, J4,5
10.3 Hz, H-3), 4.29 (dd, 1 H, J5,6
6.1 Hz, H-6), 4.23 (dd, 1 H, J2,3
3.95 (m, 2 H, H-7, H-7?), 2.13, 2.00, 1.96, 1.93 (4 s, 12H,
4ꢃ S), 170.5,
OAc); 13C NMR (CDCl3): d 179.4 (CÄ
ꢂ
/
5.5 Hz, H-1), 5.35ꢀ
3.0 Hz, H-4), 5.12 (dd, 1 H, J3,4
1.0, J6,7 6.7, J6,7?ꢂ
9.7 Hz, H-2), 4.07ꢀ
/
5.32 (m, 1 H, H-5),
145.7 (C-1), 132.9 (Bz quaterner), 131.9, 128.5, 127.7,
127.6 (Bz), 76.7, 73.4, 70.5, 67.9, 67.0 (C-2, C-3, C-4, C-
5, C-6), 61.9 (C-7), 20.5, 20.4 (CH3). Anal. Calcd for
C22H26N2O10: C, 55.23; H, 5.48; N, 5.85; found: C,
55.31; H, 5.35; N, 5.74.
ꢂ
/
ꢂ
/
B
/
ꢂ
/
/
ꢂ
/
/
/
/

M. To´th, L. Somsa´k / Carbohydrate Research 338 (2003) 1319ꢀ
/1325
1323
170.3 (CÄ
/
O), 139.6 (C-1), 76.9, 74.7, 71.7, 67.5, 66.4 (C-
Anal. Calcd for C19H22N2O8: C, 56.15; H, 5.46; N, 6.89;
found: C, 56.22; H, 5.55; N, 6.98.
2, C-3, C-4, C-5, C-6), 61.8 (C-7), 21.1, 20.9, 20.7 (CH3).
Anal. Calcd for C16H23N3O9S: C, 44.34; H, 5.35; N,
9.69; found: C, 44.22; H, 5.49; N, 9.81.
3.12. 3,4,5-Tri-O-acetyl-2,6-anhydro-D-gulo-hexose
semicarbazone (13)
3.9. 3,4,5,7-Tetra-O-benzoyl-2,6-anhydro-
gulo-heptose benzoylhydrazone (10)
D-glycero-D-
White crystals from MeOH; mp 190ꢀ
/
192 8C; [a]D
ꢄ438
/
(c 0.96, MeOH); IR 3434, 1750, 1702, 1250, 1226, 1036
1
cmꢄ1; H NMR (Me2SO-d6): d 10.19 (brs, 1 H, NH),
Colourless syrup; [a]D
3420, 1734, 1266, 1092, 708 cmꢄ1; 1H NMR (CDCl3): d
9.32 (brs, 1 H, NH), 8.20ꢀ7.27 (m, 26 H, OBz, NHBz,
H-1), 6.01, 5.73, 5.57 (3 pseudo t, 3 H, Jꢂ9.4ꢀ10.0 Hz,
H-3, H-4, H-5), 4.64ꢀ4.59 (m, 2 H, H-2, H-7), 4.47 (dd,
1 H, J6,7?ꢂ5.3, J7,7?ꢂ12.1 Hz, H-7?), 4.29ꢀ4.15 (m, 1 H,
H-6); 13C NMR (CDCl3): d 166.3, 165.9, 165.5, 164.3
(CÄO), 145.1 (C-1), 132.5 (Bz quaterner), 133.8, 133.7,
133.5, 133.3, 130.0, 129.9, 129.1, 129.8, 128.6, 128.4,
127.5 (OBz, Bz), 129.5, 128.7 (OBz quaterners), 78.7,
76.4, 73.6, 71.0, 69.5 (C-2, C-3, C-4, C-5, C-6), 63.3 (C-
7). Anal. Calcd for C42H34N2O10: C, 69.41; H, 4.72; N,
3.85; found: C, 69.52; H, 4.66; N, 3.76.
ꢄ
/
438 (c 0.97, CHCl3); IR (KBr)
7.01 (d, 1 H, J1,2
5.25 (dd, 1 H, J3,4
10.1 Hz, H-4), 4.88 (ddd, 1 H, J5,6
H-5), 4.11 (dd, 1 H, J2,3 9.3 Hz, H-2), 3.97 (dd, 1 H,
6,6?ꢂ10.7 Hz, H-6), 3.50 (t, 1 H, H-6?), 1.98, 1.97, 1.93
(3 s, 9 H, 3ꢃ
OAc); 13C NMR (Me2SO-d6): d 169.9,
169.6 (CÄO), 156.5 (NHCONH2), 137.0 (C-1), 76.7,
ꢂ
ꢂ
/
5.9 Hz, H-1), 6.20 (brs, 2 H, NH2),
9.4 Hz, H-3), 5.03 (dd, 1 H, J4,5
5.3, J5,6?ꢂ10.7 Hz,
/
/
ꢂ
/
/
/
ꢂ
/
/
/
ꢂ
/
/
/
/
J
/
/
/
/
72.7, 69.5, 68.8 (C-2, C-3, C-4, C-5), 65.6 (C-7), 20.5,
20.4 (CH3). Anal. Calcd for C13H19N3O8: C, 45.22; H,
5.55; N, 12.17; found: C, 45.44; H, 5.78; N, 12.29.
3.13. 3,4,5-Tri-O-acetyl-2,6-anhydro-D-manno-hexose
benzoylhydrazone (14)
3.10. 3,4,5,7-Tetra-O-benzoyl-2,6-anhydro-
gulo-heptose semicarbazone (11)
D-glycero-D-
Colourless syrup; [a]D
3442, 1748, 1662, 1374, 1226, 1052 cmꢄ1
(CDCl3): d 10.14 (brs, 1 H, NH), 7.82 (d, 2 H, Jꢂ
Hz, Bz), 7.52 (t, 2 H, Jꢂ6.9 Hz, Bz), 7.44ꢀ7.38 (m, 2 H,
Bz, H-1), 5.37ꢀ5.36 (m, 1 H, H-5), 5.27 (dd, 1 H, J3,4
10.0 Hz, H-3), 5.13 (dd, 1 H, J4,5 2.1 Hz, H-4), 4.11
(dd, 1 H, J1,2 6.4, J2,3 9.6 Hz, H-2), 4.02 (d, 1 H,
J5,6 1.0, J6,6?ꢂ12.9 Hz, H-6), 3.74 (d, 1 H, J5,6?B1.0
Hz, H-6?), 2.15, 2.02 (2 s, 9 H, 3ꢃ
OAc); 13C NMR
(CDCl3): d 170.3, 170.1, 164.5 (CÄO, Bz), 145.8 (C-1),
ꢄ
/
58 (c 0.95, CHCl3); IR (KBr)
1H NMR
6.9
;
Colourless syrup; [a]D
3480, 1732, 1268, 1094, 708 cmꢄ1; H NMR (Me2SO-
d6): d 10.23 (brs, 1 H, NH), 8.05ꢀ7.80 (6 H, OBz), 7.75ꢀ
7.36 (m, 14 H, OBz), 7.20 (d, 1 H, J1,2 5.4 Hz, H-1),
6.11 (brs, 2 H, NH2), 6.04, 5.71, 5.66 (3 pseudo t, 3 H,
Jꢂ9.3ꢀ10.1 Hz, H-3, H-4, H-5), 4.72 (dd, 1 H, J2,3
10.1 Hz, H-2), 4.58ꢀ
4.42 (m, 3 H, H-6, H-7, H-7?); 13C
NMR (CDCl3): d 166.2, 166.0, 165.9, 165.2 (CÄO),
ꢁ
/
418 (c 1.05, CHCl3); IR (KBr)
1
/
/
/
/
/
/
ꢂ
/
ꢂ
/
ꢂ
/
ꢂ
/
ꢂ
/
/
/
ꢂ
/
B
/
/
/
/
/
/
/
157.8 (NHCONH2), 137.3 (C-1), 133.5, 133.3, 133.2,
129.8, 129.7, 128.4 (OBz), 129.5, 129.0, 128.8 (OBz
quaterners), 77.0, 76.2, 74.2, 69.9, 69.5 (C-2, C-3, C-4,
C-5, C-6), 63.2 (C-7). Anal. Calcd for C36H31N3O10: C,
64.96; H, 4.69; N, 6.31; found: C, 64.85; H, 4.77; N,
6.45.
132.5 (Bz quaterner), 129.1, 127.6 (Bz), 78.7, 70.9, 68.6,
67.5 (C-2, C-3, C-4, C-5), 68.0 (C-6), 21.0, 20.7 (CH3).
Anal. Calcd for C19H22N2O8: C, 56.15; H, 5.46; N, 6.89;
found: C, 56.23 H, 5.39; N, 6.94.
3.14. 3,4,5-Tri-O-acetyl-2,6-anhydro-D-manno-hexose
semicarbazone (15)
3.11. 3,4,5-Tri-O-acetyl-2,6-anhydro-
benzoylhydrazone (12)
D-gulo-hexose
White crystals from EtOAcꢀ
142.5 8C; [a]D 168 (c 1.04, CHCl3); IR (KBr) 3474,
1744, 1698, 1582, 1372, 1228, 1054 cmꢄ1 1H NMR
(CDCl3): d 9.95 (brs, 1 H, NH), 7.08 (d, 1 H, J1,2 4.9
Hz, H-1), 6.02 (brs, 2 H, NH2), 5.48 (pseudo t, 1 H,
J3,4 9.8 Hz, H-3), 5.35ꢀ5.33 (m, 1 H, H-5), 5.11 (dd, 1
H, J4,5 3.2 Hz, H-4), 4.04 (d, 1 H, J5,6 1.0, J6,6?ꢂ
13.6 Hz, H-6), 3.98 (dd, 1 H, J2,3 9.8 Hz, H-2), 3.72 (d,
1 H, J5,6?B1.0 Hz, H-6?), 2.17, 2.03, 2.01 (3 s, 9 H, 3ꢃ
OAc); 13C NMR (CDCl3): d 170.3, 170.2, 170.1 (CÄ
O),
/
hexane; mp 141.5ꢀ
/
White crystals from MeOH; mp 225ꢀ
/
227 8C dec.; [a]D
ꢄ
/
ꢄ
/
438 (c 1.07, CHCl3); IR (KBr) 1746, 1660, 1544, 1372,
;
1224, 772 cmꢄ1; H NMR (acetone-d6): d 11.04 (brs, 1
H, NH), 7.91 (d, 2 H, Jꢂ7.4 Hz, Bz), 7.57 (t, 2 H, Jꢂ
7.4 Hz, Bz), 7.49 (d, 1 H, J1,2 5.8 Hz, H-1), 7.48 (t, 1
H, Jꢂ7.4 Hz, Bz), 5.34 (dd, 1 H, J3,4 9.7 Hz, H-3),
5.03 (t, 1 H, J4,5 9.7 Hz, H-4), 4.95 (dd, 1 H, J2,3 9.8
Hz, H-2), 4.24ꢀ4.14 (m, 1 H, H-5), 4.11 (dd, 1 H, J5,6
5.8, J6,6?ꢂ11.2 Hz, H-6), 3.56 (dd, 1 H, J5,6?ꢂ10.7 Hz,
H-6?), 2.00, 1.96 (2 s, 9 H, 3ꢃ
OAc); 13C NMR
(Me2SO-d6): d 169.6, 169.5, 163.1 (CÄO), 145.9 (C-1),
ꢂ
/
1
/
/
ꢂ
/
ꢂ
/
/
/
ꢂ
/
ꢂ
/
B
/
/
ꢂ
/
ꢂ
/
ꢂ
/
/
ꢂ
/
/
/
/
/
/
/
157.7 (NHCONH2), 137.9 (C-1), 77.5, 71.2, 68.5, 66.8
(C-2, C-3, C-4, C-5), 67.8 (C-7), 20.8, 20.5 (CH3). Anal.
Calcd for C13H19N3O8: C, 45.22; H, 5.55; N, 12.17;
found: C, 45.29; H, 5.68; N, 12.24.
/
132.9 (Bz quaterner), 131.9, 128.4, 127.6 (Bz), 76.9, 72.3,
69.7, 68.7 (C-2, C-3, C-4, C-5), 65.4 (C-6), 20.4 (CH3).

1324
M. To´th, L. Somsa´k / Carbohydrate Research 338 (2003) 1319ꢀ1325
/
3.15. 3,4,5,7-Tetra-O-acetyl-2,6-anhydro-
manno-heptose oxime (16)
D
-glycero-
L
-
13C NMR (CDCl3): d 166.3, 166.1, 165.5, 165.3 (CÄ
/
O),
146.8 (C-1), 133.6, 133.5, 133.4, 133.2, 129.9, 129.8,
128.5, 128.4 (OBz), 129.6, 129.0, 128.8 (OBz quaterners),
76.4, 76.3, 74.0, 70.5, 69.5 (C-2, C-3, C-4, C-5, C-6), 63.2
(C-7). Recognizable signals for 18Z: 1H NMR (CDCl3):
White crystals from CH2Cl2ꢀ
/
hexane; mixture of E and
Z isomers; IR: 3332, 1748, 1720, 1376, 1262, 1244, 1218,
13
1
1064, 958 cmꢄ1; Lit. IR: 3332 cmꢄ1. 16E: H NMR
(CDCl3): d 8.65 (brs, 1 H, OH), 7.37 (d, 1 H, J1,2 6.7
Hz, H-1), 5.48ꢀ5.45 (m, 1 H, H-5), 5.29 (dd, 1 H, J3,4
10.4 Hz, H-3), 5.11 (dd, 1 H, J4,5 3.7 Hz, H-4), 4.15ꢀ
4.09 (m, 2 H, H-7, H-7?), 4.05 (dd, 1 H, J2,3 9.8 Hz, H-
2), 3.98 (dd, 1 H, J5,6 1.0, J6,7 6.7, J6,7?ꢂ6.1 Hz, H-
6), 2.18, 2.06, 2.03, 2.00 (4 s, 12 H, 4ꢃ
OAc); 13C NMR
O), 147.1 (C-
d 8.41 (s, 1 H, OH), 6.87 (d, 1 H, J1,2
6.03, 5.69, 5.55 (3 pseudo t, 3 H, Jꢂ9.2ꢀ
H-4, H-5), 5.26 (dd, 1 H, J2,3
9.7 Hz, H-2); 13C NMR
(CDCl3): d 73.9, 70.7, 69.9, 69.8, 69.6 (sugar carbons).
ꢂ/6.7 Hz, H-1),
ꢂ
/
/
/
9.7 Hz, H-3,
/
ꢂ
/
ꢂ
/
ꢂ
/
/
ꢂ
/
B
/
ꢂ
/
/
/
3.18. O-Benzyl-(3,4,5,7-tetra-O-benzoyl-2,6-anhydro-
glycero- -gulo-heptose)-oxime (19)
D-
(CDCl3): d 170.7, 170.4, 170.3, 170.1 (CÄ
/
D
1), 76.3, 74.4, 71.4, 67.6, 66.9 (C-2, C-3, C-4, C-5, C-6),
61.7 (C-7), 20.8 (CH3). Recognizable signals for 16Z: 1H
Colourless syrup; mixture of E and Z isomers; IR (KBr)
1732, 1266, 1094, 708 cmꢄ1. 19E: 1H NMR (CDCl3): d
NMR (CDCl3): d 8.92 (s, 1 H, OH), 6.78 (d, 1 H, J1,2
ꢂ
/
6.7 Hz, H-1), 5.21 (dd, 1 H, J3,4 10.4 Hz, H-3), 5.17
(dd, 1 H, J4,5
ꢂ
/
8.05ꢀ
H-1), 5.95, 5.72, 5.60 (3 pseudo t, 3 H, Jꢂ
H-3, H-4, H-5), 4.91 (s, 2 H, CH2ÃBn), 4.64 (dd, 1 H,
7,7?ꢂ12.3 Hz, H-7), 4.46 (dd, 1 H, H-7?), 4.39 (dd, 1 H,
J1,2 7.0, J2,3 10.0 Hz, H-2), 4.26 (ddd, 1 H, J6,7
2.3, J6,7?ꢂ
4.7 Hz, H-6); 13C NMR (CDCl3): d 166.3,
165.9, 165.5, 165.3 (CÄO), 146.0 (C-1), 137.1 (Bn
/
7.75 (m, 8 H, OBz), 7.55ꢀ/7.22 (m, 18 H, OBz, Bn,
ꢂ
/
3.0 Hz, H-4), 4.88 (1 H, dd, J2,3
ꢂ9.2
/
/
9.4ꢀ10.0 Hz,
/
Hz, H-2); 13C NMR (CDCl3): d 71.3, 69.8, 67.1 (sugar
carbons).
/
J
/
ꢂ
/
ꢂ
/
ꢂ
/
3.16. O-Benzyl-(3,4,5,7-tetra-O-acetyl-2,6-anhydro-
glycero-L-manno-heptose)-oxime (17)
D-
/
/
quaterner), 133.6, 133.5, 133.4, 133.3, 129.9, 129.8,
128.5, 128.4, 128.0 (OBz, Bn), 129.7, 129.1, 128.9,
128.8 (OBz quaterners), 76.6, 76.4, 73.8, 70.5, 69.5 (C-
2, C-3, C-4, C-5, C-6), 76.3 (CH2-Bn), 63.2 (C-7).
Recognizable signals for 19Z: 1H NMR (CDCl3): d
Colourless syrup; mixture of E and Z isomers; IR (KBr)
1
1746, 1372, 1220, 1056 cmꢄ1. 17E: H NMR (C6D6): d
7.50 (d, 1 H, J1,2
5.62 (dd, 1 H, J3,4
H-5), 5.17 (dd, 1 H, J4,5
Jꢂ16.2 Hz, CH2ÃBn), 4.93 (d, 1 H, CH2Ã
1 H, J7,7?ꢂ11.0 Hz, H-7), 4.02 (dd, 1 H, H-7?), 3.89 (dd,
1 H, J2,3 9.8 Hz, H-2), 3.28 (dd, 1 H, J5,6 1.0, J6,7
6.7, J6,7?ꢂ6.1 Hz, H-6), 1.72, 1.60, 1.59, 1.55 (4 s, 12 H,
4ꢃ
OAc); 13C NMR (CDCl3): d 170.4, 170.2, 170.0,
169.7 (CÄO), 146.2 (C-1), 137.4 (Bn quaterner), 128.4,
Bn), 76.4, 74.3, 71.3, 67.5,
ꢂ
ꢂ
/
7.3 Hz, H-1), 7.23ꢀ
10.3 Hz, H-3), 5.50ꢀ
3.1 Hz, H-4), 4.96 (d, 1 H,
Bn), 4.07 (dd,
/
6.98 (m, 5 H, Bn),
/
/5.47 (m, 1 H,
ꢂ
/
6.88 (d, 1 H, J1,2
pseudo t, 3 H, Jꢂ
(dd, 1 H, J2,3
10.0 Hz, H-2); 13C NMR (CDCl3): d
146.1 (C-1), 76.7 (CH2ÃBn), 76.2, 73.8, 70.7, 70.6 (sugar
carbons).
ꢂ/7.0 Hz, H-1), 5.99, 5.70, 5.53 (3
/
/
/
/
9.3ꢀ10.0 Hz, H-3, H-4, H-5), 5.19
/
/
ꢂ
/
ꢂ
/
B
/
ꢂ
/
/
/
/
/
128.1, 127.9 (Bn), 76.2 (CH2Ã
/
66.7 (C-2, C-3, C-4, C-5, C-6), 61.6 (C-7), 20.7, 20.6,
20.5 (CH3). Recognizable signals for 17Z: 1H NMR
3.19. 3,4,5-Tri-O-acetyl-2,6-anhydro-D-manno-hexose
oxime (20)
(C6D6): d 6.81 (d, 1 H, J1,2
J3,4 9.7 Hz, H-3), 5.20 (dd, 1 H, J4,5
4.84 (dd, 1 H, J2,3 9.7 Hz, H-2), 3.23 (dd, 1 H, J5,6
1.0, J6,7 6.7, J6,7?ꢂ
6.1 Hz, H-6); 13C NMR (CDCl3):
146.0 (C-1), 75.2 (CH2ÃBn), 70.2, 66.9 (sugar
carbons), 21.9 (CH3).
ꢂ
/
7.3 Hz, H-1), 5.57 (t, 1 H,
ꢂ
/
ꢂ/3.6 Hz, H-4),
Colourless syrup; mixture of E and Z isomers; IR 3416,
1746, 1372, 1226, 1058 cmꢄ1. 20E: 1H NMR (CDCl3): d
ꢂ
/
B
/
ꢂ
/
/
8.41 (brs, 1 H, OH), 7.37 (d, 1 H, J1,2
5.36ꢀ5.33 (m, 1 H, H-5), 5.32 (pseudo t, 1 H, J3,4
Hz, H-3), 5.11 (dd, 1 H, J4,5 3.6 Hz, H-4), 4.05 (dd, 1
H, J5,6 1.9, J6,6?ꢂ13.4 Hz, H-6), 3.97 (dd, 1 H, J2,3
9.8 Hz, H-2), 3.72 (d, 1 H, J5,6?B1.0 Hz, H-6?), 2.17,
2.03 (2 s, 9 H, 3ꢃ
OAc); 13C NMR (CDCl3): d 170.6,
170.4, 170.1 (CÄO), 147.4 (C-1), 76.6, 71.2, 68.6, 67.3
ꢂ/6.7 Hz, H-1),
d
/
/
ꢂ/9.8
ꢂ
/
ꢂ
/
/
ꢂ
/
3.17. 3,4,5,7-Tetra-O-benzoyl-2,6-anhydro-
gulo-heptose oxime (18)
D-glycero-
D-
/
/
/
Colourless syrup; mixture of E and Z isomers; IR: 3436,
1
(C-2, C-3, C-4, C-5), 68.1 (C-6), 21.1, 20.8 (CH3).
Recognizable signals for 20Z: 1H NMR (CDCl3): d
1732, 1452, 1316, 1108, 1094, 1070, 708 cmꢄ1. 18E: H
NMR (CDCl3): d 8.29 (brs, 1H, OH), 8.05ꢀ
H, OBz), 7.57ꢀ7.19 (m, 12 H, OBz), 7.32 (d, 1 H, J1,2
6.7 Hz, H-1), 6.00, 5.75, 5.65 (3 pseudo t, 3 H, Jꢂ9.7ꢀ
9.8 Hz, H-3, H-4, H-5), 4.62 (dd, 1 H, J6,7?ꢂ2.4, J7,7?ꢂ
12.2 Hz, H-7?), 4.48 (dd, 1 H, J2,3 9.8 Hz, H-2), 4.44
(dd, 1 H, J6,7 4.9 Hz, H-7), 4.27ꢀ4.15 (m, 1 H, H-6);
/
7.75 (m, 8
8.69 (brs, 1 H, OH), 6.79 (d, 1 H, J1,2
5.28 (pseudo t, 1 H, J3,4 9.8 Hz, H-3), 5.17 (dd, 1 H,
J4,5 3.7 Hz, H-4), 4.78 (dd, 1 H, J2,3 9.8 Hz, H-2),
4.03 (dd, 1 H, J5,6 2.5, J6,6?ꢂ12.8 Hz, H-6?), 3.74 (d, 1
H, J5,6?B
1.0 Hz, H-6?); 13C NMR (CDCl3): d 70.9,
70.2, 67.8, 67.4 (sugar carbons).
ꢂ
/
6.7 Hz, H-1),
/
ꢂ
/
ꢂ
/
/
/
ꢂ
/
ꢂ
/
/
/
ꢂ
/
/
ꢂ
/
/
ꢂ
/
/

M. To´th, L. Somsa´k / Carbohydrate Research 338 (2003) 1319ꢀ
/1325
1325
8. Friestad, G. K. Tetrahedron 2001, 57, 5461ꢀ
9. Collins, P. M.; Ferrier, R. J. Monosaccharides*
/
5496.
3.20. O-Benzyl-(3,4,5-tri-O-acetyl-2,6-anhydro-
manno-hexose)-oxime (21)
D-
/
Their
Chemistry and Their Roles in Natural Products; John
Wiley & Sons: Chichester, 1995; pp 112ꢀ115.
10. For a collection of synthetic methods of anhydro-aldoses
see a recent review: Somsa´k, L. Chem. Rev. 2001, 101, 81ꢀ
135 (Section III. C).
11. Kim, S.; Lee, I. Y.; Yoon, J.-Y.; Oh, D. H. J. Am. Chem.
/
White crystals from diethyl etherꢀ
and Z isomers; IR (KBr) 1748, 1372, 1220, 1058 cmꢄ1
21E: 1H NMR (CDCl3): d 7.41ꢀ
7.25 (m, 6 H, Bn, H-1),
5.33 (brs, 1 H, H-5), 5.28 (dd, 1 H, J3,4 10.4 Hz, H-3),
5.07 (brs, 3 H, CH2ÃBn, H-4), 4.03 (dd, 1 H, J5,6 2.5
Hz, H-6), 3.92 (dd, 1 H, J1,2 6.7, J2,3 9.8 Hz, H-2),
3.68 (d, 1 H, J5,6? 1.0, J6,6?ꢂ12.8 Hz, H-6?), 2.16, 2.00,
1.82 (3 s, 9 H, 3ꢃ
OAc); 13C NMR (CDCl3): d 170.4,
170.2, 169.8 (CÄO), 146.4 (C-1), 137.5 (Bn quaterner),
Bn), 76.8, 71.1,
/
hexane; mixture of E
.
/
/
ꢂ
/
/
ꢂ
/
Soc. 1996, 118, 5138ꢀ
12. Pham-Huu, D.-P.; Petrusˇova, M.; BeMiller, J. N.; Petrusˇ,
L. Synlett 1998, 1319ꢀ1320.
13. Pham-Huu, D.-P.; Petrusˇova, M.; BeMiller, J. N.; Petrusˇ,
L. J. Carbohydr. Chem. 2000, 19, 93ꢀ110.
14. Baker, K. W. J.; Gibb, A.; March, A. R.; Paton, R. M.
Tetrahedron Lett. 2001, 42, 4065ꢀ4068.
/
5139.
ꢂ
/
ꢂ
/
B
/
/
/
/
/
/
128.5, 128.2, 128.0 (Bn), 76.3 (CH2Ã
/
/
68.6, 67.2 (C-2, C-3, C-4, C-5), 68.1 (C-6), 21.1, 20.8,
20.6 (CH3). Recognizable signals for 21Z: 1H NMR
15. Dondoni, A.; Junquera, F.; Merchan, F. L.; Merino, P.;
Scherrmann, M. C.; Tejero, T. J. Org. Chem. 1997, 62,
(CDCl3): d 6.75 (d, 1 H, J1,2
H, J2,3
ꢂ6.7 Hz, H-1), 4.74 (dd, 1
/
5484ꢀ
16. Martin, O. R.; Khamis, F. E.; Rao, S. P. Tetrahedron Lett.
1989, 30, 6143ꢀ6146.
/
5496.
ꢂ
/
9.2 Hz, H-2), 2.15, 1.99, 1.85 (3 s, 9 H, 3ꢃ
/
OAc); 13C NMR (CDCl3): d 70.8, 70.7, 67.7, 67.4 (sugar
carbons).
/
17. Yamago, S.; Miyazoe, H.; Goto, R.; Hashidume, M.;
Sawazaki, T.; Yoshida, J. J. Am. Chem. Soc. 2001, 123,
3697ꢀ
18. Kova´cs, L.;
dea´k, Z. Tetrahedron 2001, 57, 4609ꢀ
19. To´th, M.; Somsa´k, L. Tetrahedron Lett. 2001, 42, 2723ꢀ
2725.
20. To´th, M.; Somsa´k, L. J. Chem. Soc., Perkin. Trans. 1
/
3705.
Acknowledgements
˝
Osz, E.; Domokos, V.; Holzer, W.; Gyorgy-
¨
.
/4621.
This work was supported by the Hungarian Scientific
Research Fund (Grant: OTKA T32124).
/
2001, 942ꢀ943.
/
21. To´th, M.; Kove´r, K. E.; Be´nyei, A.; Somsa´k, L. manu-
¨
script in preparation.
References
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