Synthesis, regioselective hydrogenolysis, partial hydrogenation, and conformational study of dioxane and dioxolane-type (9′-anthracenyl)methylene acetals of sugars

Article abstract of DOI:10.1016/j.carres.2009.09.007

Dioxane-type (9′-anthracenyl)methylene acetal of methyl 2,3-di-O-methyl-α-d-glucopyranoside was cleaved with LiAlH₄/AlCl₃ (3:1) or with Na(CN)BH₃-HCl regioselectively to provide the 4- or 6-O-(9′-anthracenyl)methyl ether,

Full text of DOI:10.1016/j.carres.2009.09.007

Carbohydrate Research 344 (2009) 2444–2453
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Carbohydrate Research
journal homepage: www.elsevier.com/locate/carres
Synthesis, regioselective hydrogenolysis, partial hydrogenation,
and conformational study of dioxane and dioxolane-type
(90-anthracenyl)methylene acetals of sugars
b
c
a
Zsolt Jakab a, Attila Mándi a, Anikó Borbás a, , Attila Bényei , István Komáromi , László Lázár ,
*
Sándor Antus a,d, András Lipták a
a Research Group for Carbohydrates of the Hungarian Academy of Sciences, University of Debrecen, PO Box 94, H-4010 Debrecen, Hungary
b Institute of Physical Chemistry, Faculty of Science, University of Debrecen, PO Box 7, H-4010 Debrecen, Hungary
c Haemostasis, Thrombosis and Vascular Biology Research Group of the Hungarian Academy of Sciences, University of Debrecen, H-4032 Debrecen, Hungary
d Department of Organic Chemistry, University of Debrecen, PO Box 20, H-4010 Debrecen, Hungary
a r t i c l e i n f o
a b s t r a c t
Dioxane-type (90-anthracenyl)methylene acetal of methyl 2,3-di-O-methyl-
a-D-glucopyranoside was
Article history:
Received 15 July 2009
Received in revised form 26 August 2009
Accepted 9 September 2009
Available online 12 September 2009
cleaved with LiAlH4/AlCl3 (3:1) or with Na(CN)BH3–HCl regioselectively to provide the 4- or 6-O-(90-anth-
racenyl)methyl ether, respectively. Hydrogenolytic reaction of the exo and endo isomers of dioxolane-
type acetals proved to be directed by the configuration of the acetalic carbon as well as by the intramo-
lecular participation of the adjacent-free hydroxyl; ring-opening reaction of the endo isomer of the
methyl 2,3-O-(90-anthracenyl)methylene-
a-L-rhamnopyranoside took place with complete selectivity
Dedicated to Professor Károly Lempert on
the occasion of his 85th birthday
resulting in the axial (90-anthracenyl)methyl ether, whereas a 1:1 mixture of the axial and equatorial
ethers was formed upon the same reaction of the exo isomer. Catalytic hydrogenation of the sugar acetals
resulted in (90,100-dihydro-90-anthracenyl)methylene derivatives without affecting the acetalic center.
High-temperature molecular dynamics simulations and DFT (Density Functional Theory) geometry opti-
mizations were carried out to study the conformation of the dioxane-type (90,100-dihydro-90-anthrace-
nyl)methylene acetal.
Keywords:
(90-Anthracenyl)methylene acetal
Regioselective
Hydrogenolysis
High-temperature MD
DFT
Ó 2009 Elsevier Ltd. All rights reserved.
1. Introduction
cleaved under reductive conditions with Na(CN)BH3 and HCl/Et2O
in THF to give 6-O-(90-anthracenyl)methyl ethers, and can be selec-
Regioselective transformation of polyhydroxy compounds, such
as carbohydrates, necessitates the application of protective groups
which can be attached or cleaved in a selective manner to obtain
partially substituted molecules. Modification of simple sugars
and synthesis of higher oligosaccharides cannot be carried out
without the use of these methodologies.1
The acetal-type protecting groups possess significant advanta-
ges such as simultaneous protection of two hydroxyls, the easy re-
moval and the possibility of a partial deprotection. By the adequate
selection of the hydride donor and various protic or Lewis acid re-
agents as well as solvents, any of the two protected hydroxyls can
be liberated regioselectively.2
Most recently the 9-anthraldehyde acetal as a new protecting
group was proposed by Ellervik3 reporting the synthesis of
(90-anthracenyl)methylene acetals of the 2-(trimethylsilyl)ethyl
b-D-glucopyranoside and the phenyl 1-thio-b-D-galactopyranoside
in an acetal exchange reaction. The anthraldehyde acetals can be
tively removed in the presence of benzylidene acetals. Due to the
good crystalline properties and strong absorbance and fluores-
cence the (90-anthracenyl)methylene acetal and (90-anthrace-
nyl)methyl ether may become useful as new protecting groups.
These results prompted us to investigate the regioselective ring-
opening reaction and deprotection procedures of dioxane- and
dioxolane-type (90-anthracenyl)methylene-acetals of sugars.
2. Results and discussion
2.1. Synthesis and reactivity of dioxane-type (90-anthracenyl)-
methylene acetals
To prepare the dioxane-type acetal 2, methyl a-D-glucopyrano-
side 1 was treated with anthraldehyde dimethyl acetal in the pres-
ence of ( )10-camphorsulfonic acid (CSA). The OH groups of
positions 2 and 3 were methylated to obtain the fully protected
methyl 4,6-O-(90-anthracenyl)methylene-2,3-di-O-methyl-
glucopyranoside 3 (Scheme 1).
a-D-
* Corresponding author. Tel.: +36 52512900/22462; fax: +36 52512900/22342.
E-mail address: borbasa@puma.unideb.hu (A. Borbás).
0008-6215/$ - see front matter Ó 2009 Elsevier Ltd. All rights reserved.
doi:10.1016/j.carres.2009.09.007

Z. Jakab et al. / Carbohydrate Research 344 (2009) 2444–2453
2445
4
Upon treatment of compound 3 with LiAlH4/AlCl3 (3:1) the
of 3 into 4, however no reaction could be observed. Interestingly,
11
methyl 4-O-(90-anthracenyl)methyl-2,3-di-O-methyl-
a
-
D
-glucopy-
the reaction of 6 with Et3SiH in the presence of BF3ꢀOEt2 in dry
ranoside 4 could be isolated in crystalline form in a yield of 70%.
Transformation of 3 with Na(CN)BH3 and HCl/Et2O in dry THF5
mainly resulted in methyl 6-O-(90-anthracenyl)methyl-2,3-di-O-
CH2Cl2 resulted in two products, 13 and 14. Unreacted starting
material 6 also remained after 24 h. Compound 13 proved to be
methyl 6-O-(90,100-dihydro-90-anthracenyl)methyl-2,3-di-O-
methyl-
a
-D
-glucopyranoside 5, and its regioisomer 4 was also
methyl-a-D-glucopyranoside. The byproduct 14 could be purified
formed as a minor product.
after acetylation (14?15) and was identified as 1,5-anhydro-4-
It has been known since 1936 that 4,6-O-benzylidene acetals of
glucose can be catalytically reduced into the corresponding 4,6-
diols.6 However, catalytic hydrogenation of 3 surprisingly did not af-
fect the acetalic center, but affected the anthracenyl ring resulting in
methyl 4,6-O-(90,100-dihydro-90-anthracenyl)methylene-2,3-di-O-
O-acetyl-6-O-(90,100-dihydro-90-anthracenyl)methyl-2,3-di-O-
methyl-D-glucitol on the basis of NMR. This result has
experimentally proved the high stability of this type of acetal 6
and the formation of 14 is assumed to take place via compound 13.
Hydrogenolysis of the glycosidic acetal resulting in a glucitol deriv-
ative is extremely rare upon reductive cleavage of benzylidene-type
acetals,12 since glycosides are more stable than the aromatic acetals.
methyl-a-D-glucopyranoside 6 which was stable under hydrogen
atmosphere in the presence of Pd catalyst for as long as five days.
The structure of compound 6 was determined on the basis of 1H
and 13C NMR spectroscopyand X-ray crystallography as well. Molec-
ular modeling was also applied to investigate the conformation of
the (90,100-dihydro-90-anthracenyl)methylene moiety.
2.2. Synthesis and reactivity of dioxolane-type
(90-anthracenyl)methylene acetals
In order to study the selective removal of the (90-anthrace-
nyl)methyl ether moiety in the presence of acetyl, benzoyl, or
p-methoxybenzyl (PMB) groups the free hydroxyl of compound 4
was substituted by a simple acetylation, benzoylation, and p-meth-
oxybenzylation to furnish compounds 7–9, respectively. All three
fully protected derivatives 7–9 were treated with BF3ꢀOEt2 in dry
CH2Cl2 at 0 °C. Selective cleavage of the (90-anthracenyl)methyl
group of 7 and 8 liberating the OH-4 took place in 20 min to afford
compounds 107 and 11,8,9 respectively. In the case of compound 9
not only the (90-anthracenyl)methyl group but also the PMB group
was cleaved under these conditions to give the diol 12.10
Reductive ring-opening reaction of the partially hydrogenated
acetal derivative 6 was also studied. We assumed that the acetalic
center of 4,6-O-acetal ring anchored to the aliphatic 90-carbon is less
reactive under hydrogenolytic conditions than that of compound 3
anchored to an aromatic carbon. Compound 6 was treated with
LiAlH4/AlCl3 (3:1) under the conditions applied for the conversion
The vicinal cis-axial/equatorial hydroxyl groups of pyranosides
react with acetalating reagents to form dioxolane-type acetal
derivatives. The corresponding anthraldehyde dimethylacetal has
not been used as protecting group for vicinal diols so far. Methyl
a-L-rhamnopyranoside was considered to be an excellent model
compound to study the synthesis and hydrogenolysis of dioxo-
lane-type (90-anthracenyl)methylene acetals. Treatment of methyl
a-L-rhamnopyranoside 16 with anthraldehyde dimethylacetal re-
sulted in a 1:4.5 mixture of the 17endo and 17exo isomers, in a
moderate yield (55%). Since these isomers could not be completely
separated by column chromatography, the mixture was acetylated,
and the separation of the obtained mixture of 18endo and 18exo
was successful. After deacetylation of 18endo and 18exo, respec-
tively, the 17endo- and exo-acetals could be obtained in a crystal-
line form (Scheme 2).
The determination of the absolute configuration of the dioxo-
lane-type acetals is a rather complex task although the 1H NMR
OH
O
OH
HO
HO
O
O
O
MeO
OH
OMe
O
O
1
H
H
MeO
H
c
MeO
OMe
OMe
a
MeO
4
e
OMe
6
f, g, h
j
OR
O
O
O
O
O
O
RO
O
MeO
7 R = Ac
HO
OR
MeO
H
OMe
MeO
2 R = H
H
H
b
MeO
3 R = CH3
OMe
8 R = Bz
9 R = PMB
13
d
i
+
OR
O
HO
MeO
O
O
O
H
O
RO
H
H
HO
MeO
4
+
MeO
MeO
MeO
MeO
OMe
OMe
14 R = H
k
5
15 R = Ac
10 R = Ac
11 R = Bz
12 R = H
Scheme 1. Reagents and conditions: (a) anthraldehyde dimethylacetal, cat. CSA, dry MeCN, rt, 3 h, 79%; (b) MeI, NaH, DMF, 0 °C, 3 h, 90%; (c) from 3: LiAlH4, AlCl3 (3:1), Et2O,
CH2Cl2, rt, 4 h, 70%; (d) from 3: Na(CN)BH3 in THF, HCl/Et2O, rt, 5 min, 48% for 5, 12% for 4; (e) Pd(C), H2, EtOH, rt, 6 h, 90%; (f) Ac2O, pyridine, rt, 2 h, 80% for 7; (g) BzCl,
pyridine, CH2Cl2, 0 °C, 2 h, 89% for 8; (h) PMBCl, NaH, DMF, 0 °C, 2 h, 82% for 9; (i) BF3ꢀOEt2, CH2Cl2, 0 °C, 20 min, 75% for 10, 76% for 11, 79% for 12; (j) BF3ꢀOEt2, Et3SiH, CH2Cl2,
0 °C, overnight, 20% for 13; (k) Ac2O, pyridine, rt, 2 h, 14% for two steps.

2446
Z. Jakab et al. / Carbohydrate Research 344 (2009) 2444–2453
spectra can help if both isomers are available. Since the late seven-
ties the chemical shift values of acetalic protons and carbons have
been applied for the structure elucidation of the dioxolane-type
structures.13 The acetalic configuration of compounds 17 and 18
was proven by 1H NMR spectroscopy; H-acetalic signals of 17-
and 18endo isomers resonate at higher field (d 7.08 and
7.12 ppm) while H-acetalic signals of 17- and 18exo isomers reso-
nate at lower field (d 7.47 and 7.58 ppm). Resonance values of the
acetalic carbons are the following: 17endo: 102.2 ppm, 18endo:
101.8 ppm and 17exo: 100.3 ppm, 18exo: 100.8 ppm.
We studied ring-opening reaction of the dioxolane-type acetals
17endo and 17exo possessing an extremely bulky anthracenyl sub-
stituent at the acetalic center. It was earlier shown that the cleav-
age of the five-membered benzylidene-type acetal rings is directed
by the stereochemistry of the acetalic center. Namely, upon exo
arrangement of the bulky substituent, the reagent attacks the axial
oxygen atom forming the axial hydroxyl and equatorial benzyl-
ether derivatives, selectively. On the contrary, in the case of endo
arrangement of the bulky group, the equatorial oxygen atom is
attacked leading to the formation of the equatorial hydroxyl and
axial ether type products, also with full selectivity. Recently a rule
of thumb (x, x, x) was formulated for the ring-opening reactions of
the dioxolane acetals by the following way: exo isomer gives axial
hydroxyl.14 In good agreement with our expectations the cleavage
of 17endo with LiAlH4/AlCl3 (3:1) gave methyl 2-O-(90-anthrace-
formation of the axial ether derivative 20 upon hydrogenolysis of
17exo was assumed via this mechanism.
In order to prove our assumption compound 17exo was benzy-
lated, and the fully protected 21exo was subjected to reductive
ring-opening reaction using LiAlH4/AlCl3 (3:1) as the reagents.
The reaction gave exclusively the equatorial (90-anthrace-
nyl)methyl-ether derivative 22 as expected. In the course of
hydrogenolytic cleavage, hydrolysis of the dioxolane acetals also
occurred decreasing the yields of compounds 19, 20, and 22.
Catalytic hydrogenation of compound 17exo took place in a sim-
ilar manner as observed in the case of compound 3; the acetalic
center stayed intact and the 90,100-positions of the anthracenyl ring
were saturated to afford compound 23exo (Scheme 3).
The (90,100-dihydro-90-anthracenyl)methylene acetals of sugars
have not been known in the literature and this kind of structure
could be interesting in a sterical point of view. Therefore, confor-
mational studies of the presumed roof-like structure of the
(90,100-dihydro-90-anthracenyl)methylene acetal ring of 6 was per-
formed by means of computational and X-ray crystallographic
methods.
2.3. Computational study of the 9,10-dihydro-9-anthraldehyde
(24) and the (90,100-dihydro-90-anthracenyl)methylene acetal of
glucopyranoside (6) and comparison with the X-ray experiment
nyl)methyl-
a
-
L
-rhamnopyranoside 20, exclusively. Surprisingly,
First, a simple aldehyde was chosen as a model compound for
the computational studies. 100 ns constant temperature molecular
dynamics simulation has been carried out at 1200 K on the par-
tially hydrogenated 9,10-dihydro-9-anthraldehyde 24 in order to
explore the low energy regions of the conformational energy (hy-
per) surface. Hundred thousands geometries (snapshots) have
been saved and each of them was minimized applying the GAFF
empirical force field. Due to the relatively high temperature molec-
ular dynamics simulations it can be plausibly assumed, that the
low energy region of the conformational energy surface is suffi-
ciently sampled, that is, geometry optimization from the saved tra-
jectory snapshots will find all the conformers corresponding to
local energy minima which are non-negligibly populated. The
geometries obtained this way constituted three distinct clusters
of conformers. The geometry of a representative member of each
cluster (with the lowest energy) was further optimized at the
B3LYP/6-31G(d) level of theory. The computed energies and
treatment of 17exo with LiAlH4/AlCl3 (3:1) resulted in a 1:1 mix-
ture of the equatorial (90-anthracenyl)methyl-ether derivative 19
and the axial (90-anthracenyl)methyl-ether derivative 20. The loss
of selectivity in the ring-opening reaction of the 17exo acetal is
seemed to disagree with the rule of thumb. In fact, we supposed,
that the rule is valid, and the formation of the axial hydroxyl deriv-
ative 19 is due to the directing effect of the bulky exo-substituent
of the acetalic carbon. However, an opposite directing effect of
the free OH-4 next to the acetal ring also appears and gives rise
to the formation of the axial ether 20. We demonstrated earlier15,16
in the course of symmetrical acetals of sugars that an adjacent-free
hydroxyl could participate in the opening reaction of the acetal
ring. Being a free hydroxyl present at the acetal derivative first
the reagents reacted with the OH free forming an aluminate deriv-
ative, then the cleavage of the acetal occurred through an intramo-
lecular complexation of the adjacent oxygen of the acetal ring. The
OMe
OMe
OMe
OMe
O
O
O
HO
AcO
AcO
b
a
O
O
O
H
O
H
HO
O
O
O
HO
16
HO
H
17 endo
17 exo
18 endo
18 exo
c
c
OMe
OMe
O
O
HO
HO
O
O
H
O
O
H
17 exo
17 endo
Scheme 2. Reagents and conditions: (a) anthraldehyde dimethylacetal, cat. CSA, dry MeCN, rt, 1 d, 46% for 17exo, 9% for 17endo; (b) Ac2O, pyridine, rt, 1 h; (c) NaOMe, MeOH,
rt, 1 h.

Z. Jakab et al. / Carbohydrate Research 344 (2009) 2444–2453
2447
OMe
OMe
OMe
O
O
O
b
BnO
HO
HO
O
H
O
H
O
H
O
O
O
17 endo
17 exo
21 exo
c
a, 50%
OMe
a, 58%
O
OMe
HO
OMe
OMe
O
O
H
O
HO
HO
BnO
O
HO
O
H
O
HO
O
O
H
HO
H
19
20
22
23 exo
Scheme 3. Reagents and conditions: (a) LiAlH4, AlCl3 (3:1), Et2O, CH2Cl2, 0 °C, 2 h; (b) BnBr, NaH, dry DMF, 0 °C, 1 h, 92%; (c) Pd(C), H2, EtOH, rt, 8 h, 95%.
populations of the stable conformers of compound 24 are given in
Table 1. As it is immediately apparent, the axial position of the
aldehyde group is substantially more preferable than the equato-
rial one. In addition, while the axial position of the aldehyde group
can exist in two (three, if the mirrored conformers are counted
independently) stable conformations differing only in the relative
orientation of the carbonyl oxygen, only one (two mirror related)
conformer found with equatorial aldehyde group. It is especially
interesting, that interchanging the aldehyde O and H atoms at
the conformer 24c causes a conformational (equatorial?axial)
transition to the most stable conformer 24a.
by B3LYP/6-31G(d) method (Table 2). Figure 2 shows the correla-
tion between X-ray geometry of 6 and DFT optimized geometry
of 6a.
3. Conclusion
Dioxane- and dioxolane-type (90-anthracenyl)methylene acetal
of sugars could be readily prepared by means of acetal exchange
reaction. Reductive hydrogenolysis of the (90-anthracenyl)methy-
lene acetal ring showed a similar pattern of regioselectivity as
observed in the case of benzylidene acetals. Reaction of methyl
4,6-O-(90-anthracenyl)methylene-2,3-di-O-methyl-
a-D-glucopy-
The computational protocol detailed above was applied for the
methyl 4,6-O-(90,100-dihydro-90-anthracenyl)methylene-2,3-di-O-
ranoside with LiAlH4/AlCl3 (3:1) or with Na(CN)BH3–HCl pro-
vided regioselectively the 4- or 6-O-(90-anthracenyl)methyl
ether, respectively. Hydrogenolytic reaction of the exo and endo
isomers of dioxolane-type acetals with AlH3 was directed by the
configuration of the acetalic carbon as well as the intramolecular
participation of the adjacent-free hydroxyl. Due to the joint
effects the endo isomer of the methyl 2,3-O-(90-anthrace-
methyl-a-D-glucopyranoside 6. It resulted in six structures which
are schematically depicted and the corresponding numerical re-
sults are summarized in Table 2. Not surprisingly, the partially
hydrogenated anthracenylmethylene group favors the equatorial
position to the sugar ring. On the other hand, acetalic C became ax-
ial to C-90 as it was expected, based on the conformational analysis
of the model compound 24.
nyl)methylene-a-L
-rhamnopyranoside afforded the axial (90-
The structure of methyl 4,6-O-(90,100-dihydro-90-(R)-anthrace-
nyl)methylene-a-D-glucopyranoside determined by X-ray mea-
surements (shown in Fig. 1), corresponds perfectly to 6a, which
is predicted as the most stable structure by GAFF empirical force
field and showed one of the considerably populated one suggested
anthracenyl)methyl ether exclusively, whereas the exo isomer
resulted in a 1:1 mixture of the axial and equatorial ethers upon
ring-opening reaction. The ring cleavage of the fully protected
exo isomer (21exo) afforded the expected equatorial (90-anth-
racenyl)methyl ether exclusively, in the lack of directing effect
Table 1
Computed empirical force field (GAFF) and zero point vibrational energy corrected density functional (B3LYP/6-31G(d)) energies and relative energies as well as the estimated
percentage populations (based on the corrected density functional energies and the Boltzmann energy distribution) of conformers for compound 24
Geometry
GAFF
B3LYP/6-31G(d)
E+ZPVE (a.u.) DE (kJ/mol)
Percentage population (at 300 K) (%)
E (kJ/mol)
D
E (kJ/mol)
24a
24b
24c
44.354
56.223
69.973
0
ꢁ653.822281
ꢁ653.821431
ꢁ653.813038
0
70.98
29.01
0.01
11.869
25.619
2.232
24.267

2448
Z. Jakab et al. / Carbohydrate Research 344 (2009) 2444–2453
Table 2
Computed empirical force field (GAFF) and zero point vibrational energy corrected density functional (B3LYP/6-31G(d)) energies and relative energies as well as the estimated
percentage populations (based on the corrected density functional energies and the Boltzmann energy distribution) of conformers for compound 6
Geometry
GAFF
B3LYP/6-31G(d)
E+ZPVE (a.u.) DE (kJ/mol)
Percentage population (at 300 K) (%)
E (kJ/mol)
D
E (kJ/mol)
6a
6b
6c
6d
6e
6f
245.396
246.792
252.835
269.563
274.761
281.164
0
ꢁ1382.220653
ꢁ1382.220375
ꢁ1382.221173
ꢁ1382.214537
ꢁ1382.214000
ꢁ1382.213114
1.366
2.095
0
17.423
18.823
21.159
28.75
21.46
49.71
0.05
0.03
0.01
1.396
7.439
24.167
29.365
35.768
Figure 1. Structure of compound 6 determined by single crystal X-ray diffraction
together with partial numbering scheme.
of an adjacent-free hydroxyl. The (90-anthracenyl)methyl group
could be removed selectively with BF3ꢀOEt2 in the presence of
acetyl or benzoyl groups. To remove the (90-anthracenyl)methy-
lene acetal catalytic hydrogenation proved to be inefficient, and
resulted in the stable (90,100-dihydro-90-anthracenyl)methylene
derivatives without affecting the acetalic center. Catalytic
hydrogenation of 9-anthraldehyde into 9-methyl-1,2,3,4,5,6,
7,8-octahydro-anthracene is known from the literature,17 the
unexpected stability of the 90,100-dihydro-90-anthracenyl)meth-
ylene derivatives of sugars was explained by computational
methods.
Figure 2. Correlation of X-ray structure of 6 and DFT optimized 6a structure.
The computational studies outlined above show that more than
one local energy minimum with non-negligible population exist
which correspond to axial acetalic orientations and they are sub-
stantially more stable than the equatorial ones. It means that
although the X-ray experiment shows the global minimum in a
solidphase, insolutiontheexistenceofotheraxial conformationalso
might have contribution to the observed properties. Another conse-

Z. Jakab et al. / Carbohydrate Research 344 (2009) 2444–2453
2449
quence of the axial acetal conformation and the roof-type shape of
the hydrogenated anthracenyl group is the loss of tight fit to the sur-
face of catalysator and this way the loss of full hydrogenation.
iodide (0.70 mL, 11.2 mmol, 2.71 equiv) was added dropwise and
the reaction temperature was kept at 0 °C for 1 h. Then it was al-
lowed to warm up to rt, and no starting material was indicated
by TLC after 2 h. To the mixture MeOH was added to decompose
the unreacted NaH and then it was concentrated, diluted with
CH2Cl2, washed twice with water, dried (MgSO4), and concen-
trated. After column chromatography (6:4 hexane/EtOAc) com-
4. Experimental
4.1. General methods
pound 3 (1.52 g, 90%) was isolated as a syrup: [a] +85 (c 0.16,
D
CHCl3); 1H NMR (200 MHz, CDCl3): d (ppm) 8.66 (d, 2H, J 8.7 Hz),
8.42 (s, 1H), 7.93 (dd, 2H, J 8.4 Hz, J 0.8 Hz), 7.55–7.36 (m, 4H),
6.89 (s, 1H, acetalic), 4.89 (d, 1H, J 3.8 Hz, H-1), 4.43 (dd, 1H, J
10.1 Hz, J 4.7 Hz), 4.26–4.11 (m, 1H), 4.09 (dd, 1H, J 14.3 Hz, J
7.2 Hz), 3.90 (t, 1H, J 10.2 Hz), 3.80–3.72 (m, 1H), 3.52 (2s, 6H,
2 ꢂ OCH3), 3.41 (s, 3H, OCH3), 3.34 (dd, 1H, J2,3 8.9 Hz, H-2); 13C
NMR (50 MHz, CDCl3): d (ppm) 131.4, 129.6, 129.6, 128.8, 126.9,
125.9, 124.9, 124.7 (aromatic), 100.6 (C-acetalic), 98.5 (C-1), 83.1,
81.4, 79.8 (C-2, C-3, C-4), 69.9 (C-6), 62.3 (C-5), 60.8, 59.2
(2 ꢂ OCH3), 55.5 (anomeric OCH3). MALDI-TOF MS m/z calcd for
C24H26O6: 410.17, found: 410.42 [M]+ and 433.38 [M+Na]+. Anal.
Calcd for C24H26O6: C, 70.23; H, 6.38. Found: C, 70.33; H, 6.32.
Optical rotations were measured at room temperature with a
Perkin–Elmer 241 automatic polarimeter. Melting points were
determined on a Kofler hot-stage apparatus and are uncorrected.
TLC was performed on Kieselgel 60 F254 (Merck) with detection
by 5% sulfuric acid in ethanol. Column chromatography was per-
formed on Silica Gel 60 (E. Merck 0.062–0.200 nm). The organic
solutions were dried over MgSO4 and concentrated in vacuum.
The 1H (200.13, 360.13, and 500.13 MHz) and 13C NMR (50.3,
90.54, and 125.76 MHz) spectra were recorded with Bruker WP-
200SY, Bruker AM-360, and Bruker DRX-500 spectrometers for
solutions in CDCl3. Internal references: TMS (0.00 ppm for 1H),
CDCl3 (77.00 ppm for 13C). MALDI-TOF MS spectra were recorded
on a Bruker Biflex III spectrometer in positive, linear mode using
saturated 2,4,6-trihydroxy-acetofenon in water as matrix. X-ray
diffraction data were collected at 293 K, Enraf Nonius MACH3 dif-
4.1.3. Methyl 4-O-(90-anthracenyl)methyl-2,3-di-O-methyl-
a-
D-glucopyranoside (4)
To a stirred suspension of the starting acetal 3 (2.1 g, 5.1 mmol) in
fractometer, Mo Ka radiation k = 0.71073 Å. The structure was
solved by SIR-92 program18 and refined by full-matrix least-squares
method on F2, with all non-hydrogen atoms refined with aniso-
tropic thermal parameters using the SHELXL-97 package,19 publica-
tion material was prepared with the WINGX-suite.20 All
hydrogen atoms were located geometrically and refined in the ri-
gid mode. The molecular dynamics simulations and the prelimin-
ary geometry optimizations using the suitably developed GAFF
empirical force field on the trajectory snapshot geometries were
carried out by means of the Amber molecular dynamics simulation
package.21 B3LYP/6-31G(d) density functional calculations were
carried out using the GAUSSIAN 03 package.22 At the B3LYP/6-
31G(d) minima the zero point vibrational energy correction at
the same level of theory were also computed. Ball-and-stick repre-
sentations of the conformers were generated by the Molekel23 and
VMD24 softwares.
dry CH2Cl2/Et2O (30 mL, 2:1) LiAlH4 (0.86 g, 4.5 equiv) and solution
of AlCl3 (1.0 g, 1.5 equiv) in Et2O (10 mL) were added carefully under
argon at 0 °C, then stirred for 4 h at rt. After complete conversion 2–
3 mL of EtOAc and 1–5 drops of water were added, the mixture was
diluted with EtOAc, washed three times with water, dried, and con-
centrated. The crude syrup was crystallized from EtOH to give pale
yellow crystalline product and mother liquor was purified by col-
umn chromatography (7:3 hexane/acetone) to give 4 with 70% over-
all yield (1.46 g): mp 145–146 °C; [a]
D +112 (c 0.10, CHCl3); 1H NMR
(500 MHz, CDCl3): d (ppm) 8.47 (d, 2H, J 9.0 Hz, H-10, H-80), 8.44 (s,
1H, H-100), 7.98 (d, 2H, J 8.5 Hz, H-40, H-50), 7.55–7.40 (m, 4H, H-20,
H-30, H-60, H-70), 5.81 (d, 1H, J 11.0 Hz, ArCH2), 5.71 (d, 1H, J
11.0 Hz, ArCH2), 4.80 (d, 1H, J1,2 3.6 Hz, H-1), 3.80 (s, 3H, OCH3),
3.75–3.60 (m, 4H), 3.55–3.50 (m, 1H), 3.53 (s, 3H, OCH3), 3.32 (s,
3H, OCH3), 3.29 (dd, 1H, J2,3 9.1 Hz, H-2), 1.80 (br s, 1H, OH); 13C
NMR (125 MHz, CDCl3): d (ppm) 131.4, 130.9, 129.0, 128.7, 128.5,
126.3, 124.9, 124.3 (aromatic), 97.2 (C-1), 83.5, 82.8, 76.6 (C-2, C-3,
C-4), 70.6 (C-5), 66.6 (ArCH2–), 61.7 (C-6), 61.3, 58.6 (2 ꢂ OCH3),
55.0 (OCH3 anomeric). Anal. Calcd for C24H28O6 (412.48): C, 69.88;
H, 6.84. Found: C, 69.96; H, 6.75.
4.1.1. Methyl 4,6-O-(90-anthracenyl)methylene-
a-D-
glucopyranoside (2)
To a mixture of methyl a-D-glucopyranoside 1 (3.0 g 15.4 mmol)
and anthraldehyde dimethylacetal3 (4.56 g 18.1 mmol) in MeCN
(20 mL) was added a catalytic amount of ( )10-camphorsulfonic
acid (CSA) and was stirred at room temperature for 3 h. The mixture
was neutralized by the addition of Et3N and concentrated, then co-
evaporated with toluene three times. The residue was crystallized
from Et2O–hexane to give 2 (4.64 g, 79%) as white needles: mp
4.1.4. Methyl 6-O-(90-anthracenyl)methyl-2,3-di-O-methyl-
a-
D-glucopyranoside (5) and compound (4)
To stirred suspension of the starting acetal
a
3 (0.39 g,
0.96 mmol) and Na(CN)BH3 (0.54 g, 9 equiv) in dry THF (5 mL) con-
taining 3 Å MS was added HCl in Et2O dropwise until the evolution
of gas ceased. After 5 min TLC showed complete conversion of the
starting material. The mixture was diluted with CH2Cl2 (100 mL),
washed with satd NaHCO3 and water, then dried (MgSO4), and con-
centrated. After column chromatography (1:1 hexane/EtOAc) com-
192-194 °C; [a]
D +106 (c 0.14, CHCl3); 1H NMR (200 MHz, CDCl3): d
(ppm) 8.59 (d, 2H, J 8.5 Hz), 8.46 (s, 1H), 7.97 (d, 2H, J 8.0 Hz),
7.58–7.37 (m, 4H), 6.80 (s, 1H, acetalic), 4.50 (d, 1H, J1,2 3.9 Hz, H-
1), 4.33 (dd, 1H, J 10.4 Hz, J 4.7 Hz), 4.0 (dt, 1H, J 9.9 Hz, J 4.7 Hz),
3.87 (dd, 1H, J 9.3 Hz, J 2.4 Hz), 3.82 (d, 1H, J 11.6 Hz), 3.7 (d, 1H, J
10.3 Hz), 3.50–3.35 (m, 2H), 3.31 (s, 3H, OCH3), 2.73 (d, 1H, J
8.7 Hz, OH); 13C NMR: (50 MHz, CDCl3): d (ppm) 131.5, 129.9,
129.6, 129.0, 126.6, 126.2, 124.8 (aromatic), 100.5 (C-acetalic),
99.9 (C-1), 82.1 (C-4), 72.5, 71.3 (C-2, C-3), 69.9 (C-6), 62.3 (C-5),
55.6 (OCH3). Anal. Calcd for C22H22O6 (382.41): C, 69.10; H, 5.80.
Found: C, 69.43; H, 5.71.
pound 5 (227 mg, 48%) was isolated as a syrup: [a] +63 (c 0.17,
D
CHCl3); 1H NMR (360 MHz, CDCl3): d (ppm) 8.39 (d, 3H), 7.95 (d,
2H, J 8.4 Hz), 7.47 (dt, 4H), 5.55 (d, 1H, J 11.5 Hz, ArCH2), 5.47 (d,
1H, J 11.6 Hz, ArCH2), 4.84 (s, 1H, J1,2 3.4 Hz, H-1), 3.90–3.75 (m,
2H), 3.68 (m, 1H, H-5), 3.60–3.33 (m, 12H, incl. 3 ꢂ OCH3), 3.17
(dd, 1H, J2,3 9.1 Hz, H-2); 13C NMR (90 MHz, CDCl3): d (ppm)
130.9, 130.5, 128.5, 128.3, 127.9, 125.7, 124.5, 124.0 (aromatic),
97.0 (C-1, JC1,H1 170 Hz), 82.5, 81.2, 70.2, 70.0 (C-2, C-3, C-4, C-5),
69.2 (ArCH2–), 65.3 (C-6), 60.5, 58.1 (2 ꢂ OCH3), 54.7 (OCH3 ano-
meric). Anal. Calcd for C24H28O6 (412.48): C, 69.88; H, 6.84. Found:
C, 70.06; H, 6.63.
4.1.2. Methyl 4,6-O-(90-anthracenyl)methylene-
2,3-di-O-methyl-a-D-glucopyranoside (3)
Compound 2 (1.58 g, 4.36 mmol) was stirred in dry DMF
(10 mL), treated with NaH (0.40 g, 60%, 3 equiv) at 0 °C. Methyl
Compound 4 was also formed (56 mg, 12%).

2450
Z. Jakab et al. / Carbohydrate Research 344 (2009) 2444–2453
4.1.5. Methyl 4,6-O-(90,100-dihydro-90-anthracenyl)methylene-
2,3-di-O-methyl- -glucopyranoside (6)
stirred for 20 min, then PMBCl (50 lL, 1.2 equiv) was added and
a
-D
stirred for 4 h. Then the reaction mixture was diluted carefully
with MeOH and concentrated. The residue was dissolved in CH2Cl2,
washed twice with water, dried (MgSO4), and concentrated. After
Compound 3 (0.45 g, 1.1 mmol) was dissolved in 96% EtOH
(25 mL) and stirred under H2 atmosphere in the presence of 10%
Pd/C (75 mg) for 6 h. The catalyst was removed by filtration through
a layer of Celite, washed with EtOH, and the solvent was evaporated.
The residue was crystallized from MeOH to give 6 (360 mg, 79%) as
column chromatography (7:3 hexane/EtOAc) compound
9
(135 mg, 82%) was isolated as a syrup: [ +118 (c 0.09, CHCl3);
a
]
D
1H NMR (500 MHz, CDCl3): d (ppm) 8.41 (s, 1H, H-100), 8.41 (d,
2H, J 8.5 Hz, H-10, H-80), 7.97 (d, 2H, J 8.0 Hz, H-40, H-50), 7.50–
7.40 (m, 4H, H-20, H-30, H-60, H-70), 7.18 (d, 2H, J 8.5 Hz), 6.81 (d,
2H, J 8.5 Hz), 5.77 (d, 1H, J 11.0 Hz, ArCH2), 5.66 (d, 1H, J 11.0 Hz,
H- ArCH2), 4.86 (s, 1H, J1,2 3.5 Hz, H-1), 4.30 (s, 2H, pCH3OPhCH2),
3.82 (t, 1H, J 8.0 Hz), 3.76–3.65 (m, 9H, incl. 2 ꢂ OCH3) 3.65–3.60
(m, 4H, incl. OCH3), 3.39–3.35 (m, 4H, incl. OCH3); 13C NMR
(125 MHz, CDCl3): d (ppm) 159.2, 131.6, 131.0, 130.2, 129.2,
128.0, 126.2, 124.9, 124.6, 113.8 (aromatic), 97.3 (C-1), 83.8,
82.7, 76.7, 70.1 (C-2, C-3, C-4, C-5), 73.0 (pCH3OPhCH2), 66.5 (ant-
hr-CH2), 66.6 (C-6), 61.5, 58.7 (2 ꢂ OCH3), 55.2, 55.1 (pCH3OPhCH2,
anomeric OCH3). Anal. Calcd for C32H36O7 (532.62): C, 72.16; H,
6.81. Found: C, 72.32; H, 6.71.
white needles: mp 172–174 °C; [a]
+51 (c 0.19, CHCl3); 1H NMR
D
(200 MHz, CDCl3): d (ppm) 7.40–7.10 (m, 8H, aromatic), 4.72 (d,
1H, J1,2 3.7 Hz, H-1), 4.63 (d, 1H, J 5.2 Hz, H-acetalic), 4.22 (d, 1H, J
4.4 Hz, H-90), 4.17 (d, 1H, J 16.9 Hz, H-100a), 3.99 (dd, 1H, J 10 Hz, J
4.6 Hz), 3.78 (d, 1H, J 18.1 Hz, H-100b), 3.60–3.40 (m, 8H, incl.
2 ꢂ OCH3), 3.33 (s, 3H, anomeric OCH3), 3.30 (t, 1H, J 10.1 Hz), 3.14
(t, 1H, J 9.4 Hz), 3.12 (dd, 1H, J2,3 9.3 Hz, H-2); 13C NMR (50 MHz,
CDCl3): d (ppm) 137.3, 137.2, 135.1, 134.9, 130.0, 129.8, 127.4,
127.3, 126.7, 125.6 (aromatic), 103.5 (C-acetalic), 98.3 (C-1), 81.8,
80.9, 79.8 (C-2, C-3, C-4), 68.6 (C-6), 61.9 (C-5), 60.6, 59.3 (2 ꢂ OCH3),
55.0 (anomeric OCH3), 51.0 (C-90), 35.8 (C-100). MALDI-TOF MS m/z
calcd for C24H28O6: 412.19, found: 435.40 [M+Na]+. Anal. Calcd for
C24H28O6: C, 69.88; H, 6.84. Found: C, 70.03; H, 6.69.
4.1.9. Methyl 6-O-acetyl-2,3-di-O-methyl-a-D-glucopyranoside
(10)
4.1.6. Methyl 6-O-acetyl-4-O-(90-anthracenyl)methyl-2,3-di-O-
methyl-
a
-
D
-glucopyranoside (7)
To a solution of 7 (42 mg, 0.09 mmol) in dry CH2Cl2 (1 mL) at
L) and the mixture was stirred for
To a solution of 4 (250 mg, 0.61 mmol) in pyridine (2 mL) was
added Ac2O (1 mL), and stirred for 2 h. Then the reaction mixture
was concentrated and co-evaporated twice with toluene. After col-
umn chromatography (7:3 hexane/EtOAc) compound 7 was iso-
0 °C was added BF3ꢀOEt2 (2
l
20 min. When TLC (4:6 hexane/EtOAc) showed a complete con-
version of the starting material (Rf 0.65) into the title compound
(Rf 0.22) one drop of Et3N was added and the solvent was evap-
orated. After column chromatography (3:7 hexane/EtOAc, Rf
lated (220 mg, 80%) as a syrup: [
a]
+144 (c 0.11, CHCl3); 1H
D
NMR (500 MHz, CDCl3): d (ppm) 8.42 (d, 2H, J 9.0 Hz, H-10, H-80),
8.40 (s, 1H, H-100), 7.96 (d, 2H, J 8.5 Hz, H-40, H-50), 7.60–7.40 (m,
4H, H-20, H-30, H-60, H-70), 5.75 (d, 1H, J 11.5 Hz, ArCH2), 5.70 (d,
1H, J 11.5 Hz, ArCH2), 4.80 (s, 1H, J1,2 3.5 Hz, H-1), 4.12–4.08 (m,
1H), 3.95 (dd, 1H, J 12.0 Hz, J 3.5 Hz), 3.81 (s, 3H, OCH3), 3.75–
3.60 (m, 3H), 3.59 (s, 3H, OCH3), 3.33 (s, 3H, OCH3), 3.40–3.30
(dd, 1H, J 4.0 Hz), 1.77 (s, 3H, COCH3); 13C NMR (125 MHz, CDCl3):
d (ppm) 170.3 (CO) 131.5, 131.0, 129.0, 128.6, 126.4, 125.0, 124.3
(aromatic), 97.2 (C-1), 83.9, 82.5, 76.0, 68.4 (C-2, C-3, C-4, C-5),
66.3 (ArCH2), 62.9 (C-6) 61.5, 58.7 (2 ꢂ OCH3), 55.1 (anomeric
OCH3) 20.2 (OCOCH3). Anal. Calcd for C26H30O7 (454.51): C,
68.71; H, 6.65. Found: C, 68.52; H, 6.77.
0.27) compound 107 (18 mg, 75%) was isolated as a syrup: [
a]
D
+85 (c 1.28, CHCl3), lit.7 +85 (CH2Cl2); 1H NMR (360 MHz, CDCl3):
d (ppm) 4.86 (d, 1H, J1,2 3.5 Hz, H-1), 4.45 (d, 1H, J6a,6b 12.1 Hz,
J6a,5 4.8 Hz, H-6a), 4.27 (d, 1H, J6b,5 2.1 Hz, H-6b), 3.80–3.70 (m,
1H, H-5), 3.65 (s, 3H, OCH3), 3.55–3.35 (m, 8H, 2 ꢂ OCH3, H-3,
H-4), 3.25 (dd, 1H, J2,3 9.4 Hz, H-2), 2.77 (br s, 1H, 4-OH), 2.12
(s, 3H, OCOCH3); 13C NMR (90 MHz, CDCl3): d (ppm) 97.5 (C-1),
82.5, 81.7 (C-2, C-3), 69.9, 69.3 (C-4, C-5), 63.2 (C-6), 61.3,
58.6 (2 ꢂ OCH3), 55.3 (anomeric OCH3), 20.8 (OCOCH3). Anal.
Calcd for C11H20O7 (264.27): C, 49.99; H, 7.63. Found: C, 50.38;
H, 7.42.
4.1.10. Methyl 6-O-benzoyl-2,3-di-O-methyl-
4.1.7. Methyl 4-O-(90-anthracenyl)methyl-6-O-benzoyl-
a
-
D
-glucopyranoside (11)
To a solution of 8 (47 mg, 0.09 mmol) in dry CH2Cl2 (1 mL) at
L) and the mixture was stirred for
2,3-di-O-methyl-
To a solution of 4 (123 mg, 0.30 mmol) in dry CH2Cl2 (2 mL) and
dry pyridine (2 mL) was added BzCl (42 L, 1.2 equiv) at 0 °C and
a-D-glucopyranoside (8)
0 °C was added BF3ꢀOEt2 (2
l
l
20 min. TLC (4:6 hexane/EtOAc) showed a complete conversion
of the starting material (Rf 0.72) into the title compound (Rf
0.32). Then one drop of TEA was added and the solution was
evaporated. After column chromatography (3:7 hexane/EtOAc, Rf
0.52) compound 118,9 (22 mg, 76%) was isolated as a syrup:
the mixture was stirred for 2 h. Then the reaction mixture was
diluted with CH2Cl2, washed twice with water, dried (MgSO4) and
concentrated. After column chromatography (7:3 hexane/EtOAc)
compound 8 (138 mg, 89%) was isolated as a syrup: [a] +102 (c
D
0.12, CHCl3); 1H NMR (500 MHz, CDCl3): d (ppm) 8.43 (d, 2H, J
9.0 Hz, H-10, H-80), 8.26 (s, 1H, H-100), 7.88 (d, 2H, J 8.5 Hz, H-40, H-
50), 7.82 (d, 2H, J 9.0 Hz,) 7.55–7.45 (m, 3H) 7.40–7.30 (m, 4H, H-20,
H-30, H-60, H-70), 5.83 (d, 1H, J 11.5 Hz, ArCH2), 5.76 (d, 1H, J
11.5 Hz, ArCH2), 4.82 (s, 1H, J1,2 3.5 Hz, H-1), 4.42 (dd, 1H, J 11.8 Hz,
J 2.0 Hz), 4.23 (dd, 1H, J 12.0 Hz, J 3.5 Hz), 3.85 (s, 3H, OCH3), 3.85–
3.76 (m, 4H), 3.55 (s, 3H, OCH3), 3.36 (s, 4H, incl. OCH3); 13C NMR
(125 MHz, CDCl3): d (ppm) 165.8 (COPh) 132.9, 131.4, 131.0, 129.8,
129.5, 129.1, 128.7, 128.4, 126.4, 125.0, 124.2 (aromatic), 97.2 (C-
1), 84.0, 82.7, 76.3, 68.6 (C-2, C-3, C-4, C-5), 66.5 (ArCH2), 63.2 (C-6)
61.5, 58.7 (2 ꢂ OCH3), 55.2 (anomeric OCH3). Anal. Calcd for
C31H32O7 (516.58): C, 72.08; H, 6.24. Found: C, 72.66; H, 6.01.
[a
]
+81 (c 0.11, CHCl3), lit.9 +75 (CH2Cl2); 1H NMR (360 MHz,
D
CDCl3): d (ppm) 8.06 (d, 2H, J 7.4 Hz, o-H aromatic), 7.57 (t, 1H,
J 7.4 Hz, p-H aromatic), 7.44 (t, 2H, J 7.7 Hz, m-H aromatic),
4.87 (d, 1H, J1,2 3.5 Hz, H-1), 4.67 (d, 1H, J6a,6b 12.1 Hz, J6a,5
4.9 Hz, H-6a), 4.55 (d, 1H, J6b,5 2.1 Hz, H-6b), 3.9–3.8 (m, 1H, H-
5), 3.66 (s, 3H, OCH3), 3.55–3.4 (m, 8H, 2 ꢂ OCH3, H-3, H-4),
3.25 (dd, 1H, J2,3 9.1 Hz, H-2), 2.96 (br s, 1H, 4-OH); 13C NMR
(90 MHz, CDCl3): d (ppm) 166.8 (OCOPh), 133.2 (m aromatic),
129.7, 128.4 (o and p aromatic), 97.4 (C-1), 82.6, 81.7 (C-2, C-3),
70.1, 69.5 (C-4, C-5), 63.7 (C-6), 61.3, 58.6 (2 ꢂ OCH3), 55.2 (ano-
meric OCH3). Anal. Calcd for C16H22O7 (326.34): C, 58.89; H, 6.79.
Found: C, 58.63; H, 6.89.
4.1.8. Methyl 4-O-(90-anthracenyl)methyl-6-
O-p-methoxybenzyl-2,3-di-O-methyl-a-D-glucopyranoside (9)
To a solution of 4 (127 mg, 0.31 mmol) in dry DMF (3 mL) was
added NaH (20 mg, 80%, 1.5 equiv) at 0 °C and the mixture was
4.1.11. Methyl 2,3-di-O-methyl-
To a solution of 9 (67 mg, 0.13 mmol) in dry CH2Cl2 (1 mL) at
0 °C was added BF3ꢀOEt2 (2 L) and the mixture was stirred for
20 min. TLC (1:1 hexane/EtOAc) showed complete conversion of
a-D-glucopyranoside (12)
l

Z. Jakab et al. / Carbohydrate Research 344 (2009) 2444–2453
2451
the starting material (Rf 0.82) into the title compound (Rf 0.22).
Then one drop of TEA was added and the solution was evaporated.
After column chromatography (1:1 hexane/EtOAc) compound 1210
acetylated endo and Rf 0.49 acetylated exo isomers). The mixture was
diluted with CH2Cl2, washed twice with water, dried, and concen-
trated. The isomers were separated with column chromatography
on silica gel (8:2 hexane/EtOAc) to yield 1.276 g of 18endo and
410 mg of 18exo isomers. Deacetylation of compounds 18endo and
18exo with cat. amount of NaOMe in MeOH (3 mL) followed by neu-
tralization with Amberlite IR-120 H+ resin, evaporated and 17endo
(1.03 g, 90%) and 17exo (324 mg, 88%) were yielded, respectively.
In summary, 5.124 g 17exo (46%) and 1.03 g 17endo (9%) were
isolated.
(24 mg, 86%) was isolated as a syrup: [a] +170 (c 0.98, CHCl3),
D
lit.10b +174; 1H and 13C NMR data were in very good agreement
with those reported in the literature.10b
4.1.12. Methyl 6-O-(90,100-dihydro-90-anthracenyl)methyl-2,3-
di-O-methyl-
a-D-glucopyranoside (13) and 1,5-anhydro-6-O-
(90,100-dihydro-90-anthracenyl)methyl-2,3-di-O-methyl-
D
-glucitol (14)
Compound 17exo: mp 201–202 °C; [a]
+26 (c 0.22, CHCl3); 1H
D
To a solution of 6 (250 mg, 0.60 mmol) in dry CH2Cl2 (2 mL) was
NMR (500 MHz, CDCl3): d (ppm) 8.50 (d, 2H, J 9.0 Hz, H-10, H-80),
8.46 (s, 1H, H-100), 7.97 (d, 2H, J 8.4 Hz, H-40, H-50), 7.50–7.40 (m,
5H, H-20, H-30, H-60, H-70, H-acetalic), 4.99 (s, 1H, H-1), 4.76 (t,
1H, J 6.5 Hz, H-3), 4.56 (d, 1H, J2,3 6.2 Hz, H-2), 3.85–3.75 (m, 2H,
H-4, H-5), 3.44 (s, 1H, OH), 3.39 (s, 3H, OCH3), 1.43 (d, 3H, J6,5
6 Hz, CH3-6); 13C NMR (125 MHz, CDCl3): d (ppm) 131.2, 130.5,
130.3, 129.0, 126.2, 124.8, 124.6, 123.7 (aromatic), 100.3 (C-aceta-
lic), 98.8 (C-1), 80.3 (C-3), 76.0 (C-2), 70.4 (C-4), 65.1 (C-5), 54.7
(OCH3), 17.4 (C-6). MALDI-TOF MS m/z calcd for C22H22O5:
366.15, found: 367.37 [M+H]+ and 389.34 [M+Na]+ and 397.24
[M+K]+. Anal. Calcd for C22H22O5: C, 72.12, H 6.05. Found: C,
72.01; H, 6.15.
added Et3SiH (484
lL, 5 equiv) at 0 °C, then BF3ꢀOEt2 (154
lL,
2 equiv) was also added and the mixture was stirred overnight at
rt. After TLC (7:3 hexane/acetone) indicated the formation of two
products, the reaction mixture was diluted with CH2Cl2, washed
with water, satd NaHCO3, then again with water, dried (MgSO4),
and concentrated. After column chromatography (8:2?7:3 hex-
ane/acetone) compound 13 (Rf 0.42, 49 mg, 20%), compound 14
(Rf 0.46, 52 mg) and unreacted 6 (34 mg, 14%) were isolated as syr-
ups. Compound 13: [a]
+62 (c 0.14, CHCl3); 1H NMR (500 MHz,
D
CDCl3) d (ppm) 7.36–7.19 (m, 8H, aromatic), 4.78 (d, 1H, J1,2
3.6 Hz, H-1), 4.22 (t, 1H, J 7.3 Hz, H-90), 4.13 (d, 1H, J 18.5 Hz, H-
100a), 3.88 (d, 1H, J 18.5 Hz, H-100b), 3.65–3.56 (m, 6H), 3.61 (s,
3H, OCH3), 3.48 (s, 3H, OCH3), 3.47–3.36 (m, 2H), 3.35 (s, 3H,
OCH3), 3.15 (dd, 1H, J 9.1 Hz, H-1); 13C NMR (125 MHz, CDCl3): d
(ppm) 137.1, 137.0, 136.1, 128.8, 128.7, 127.7, 127.7, 126.5,
126.1, 126.0 (aromatic), 97.3 (C-1), 82.6, 81.6 (C-2, C-3) 75.6 (C-
110), 71.0, 69.8 (C-4, C-5), 70.9 (C-6), 61.0, 58.5 (2 ꢂ OCH3), 55.0
(OCH3 anomeric), 47.5 (C-90), 35.1 (C-100). MALDI-TOF MS m/z
calcd for C24H30O6: 414.20, found: 437.42 [M+Na]+. Anal. Calcd
for C24H30O6 (414.49): C, 69.54; H, 7.30. Found: C, 69.43; H, 7.38.
Compound 14 containing impurities was purified and charac-
terized after acetylation.
Compound 17endo: mp 182–184 °C; [
a
]
ꢁ32 (c 0.13; CHCl3);
D
1H NMR (500 MHz, CDCl3): d (ppm) 8.70 (d, 2H, J 9.5 Hz, H-10, H-
80), 8.45 (s, 1H, H-100), 7.94 (d, 2H, J 8.5 Hz, H-40, H-50), 7.50–7.40
(m, 4H, H-20, H-30, H-60, H-70), 7.08 (s, 1H, acetalic), 5.08 (s, 1H,
H-1), 4.36 (bt, 1H, J 6.5 Hz, J 7.0 Hz, H-3), 4.30 (d, 1H, J2,3 7.5 Hz,
H-2), 3.78–3.74 (m, 1H, H-5), 3.62 (dd, 1H, J4,5 8.5 Hz, J4,3 6.0 Hz,
H-4), 3.41 (s, 3H, OCH3), 3.01 (br s, 1H, OH), 1.22 (d, 3H, J6,5
6.5 Hz, CH3-6); 13C NMR (125 MHz, CDCl3): d (ppm) 131.4, 130.5,
129.1, 126.4, 124.8, 124.6, 124.0 (aromatic), 102.2 (C-acetalic),
98.4 (C-1), 78.0, 77.4 (C-2, C-3), 73.5 (C-4), 66.3 (C-5), 55.0
(OCH3), 18.0 (C-6). Anal. Calcd for C22H22O5 (366.41): C, 72.12; H,
6.05. Found: C, 72.26; H, 5.90.
4.1.13. 4-O-Acetyl-1,5-anhydro-6-O-(90,100-dihydro-
Compound 18exo (4-O-acetyl): mp 213-214 °C; [
a]
+90 (c
D
90-anthracenyl)methyl-2,3-di-O-methyl-
D-glucitol (15)
0.14; CHCl3); 1H NMR (360 MHz, CDCl3): d (ppm) 8.54 (d, 2H, J
9.0 Hz, H-10, H-80), 8.48 (s, 1H, H-100), 7.98 (d, 2H, J 8.0 Hz, H-
40, H-50), 7.58 (s, 1H, H-acetalic), 7.55–7.40 (m, 4H, H-20, H-30,
H-60, H-70), 5.35 (dd, 1H, J4,5 9.2 Hz, H-4), 5.06 (s, 1H, H-1),
4.84 (dd, 1H, J3,4 7.7 Hz, H-3), 4.62 (d, 1H, J2,3 5.8 Hz, H-2),
3.95–3.88 (m, 1H, H-5), 3.43 (s, 3H, OCH3), 2.11 (s, 3H, OCOCH3),
1.34 (d, 3H, J6,5 6.3 Hz, CH3-6); 13C NMR (90 MHz, CDCl3): d
(ppm) 170.2 (CO), 131.4, 130.7, 130.6, 129.1, 126.5, 124.8,
123.9 (aromatic), 100.8 (C-acetalic), 98.8 (C-1), 77.9, 76.3, 70.2
(C-2, C-3, C-4), 63.2 (C-5), 55.1 (OCH3), 20.9 (COCH3), 17.2 (C-
6). Anal. Calcd for C24H24O6 (408.44): C, 70.57; H, 5.92. Found:
C, 70.60; H, 5.99.
The isolated 14 (52 mg) containing impurities was acetylated
with Ac2O (0.5 mL) in pyridine (1 mL). The mixture was diluted with
CH2Cl2, washed twice with water, dried, and concentrated. After col-
umn chromatography (7:3 hexane/acetone) compound 15 (37 mg,
14% for two steps) was isolated as a syrup: [a]D +16 (c 0.14, CHCl3);
1H NMR (500 MHz, CDCl3): d (ppm) 7.31–7.19 (m, 8H, aromatic),
4.66 (t, 1H, J 9.3 Hz), 4.18 (t, 1H, J 7.1 Hz, H-90), 4.12 (d, 1H, J
18.0 Hz, H-100a), 4.02 (dd, 1H, J 11.3 Hz, J 5.3 Hz), 3.87 (d, 1H, J
18.5 Hz, H-100b), 3.63 (dd, 1H, J 8.2 Hz, J 6.6 Hz), 3.56–3.45 (m, 7H,
incl. 2 ꢂ OCH3), 3.40–3.20 (m, 4H), 3.17 (t, 1H, J 9.0 Hz), 3.04 (t, 1H,
J 11.0 Hz), 2.0 (s, 3H, OCOCH3); 13C NMR (125 MHz, CDCl3): d
(ppm) 169.8 (CO), 137.2, 137.0, 136.3, 136.2, 129.0, 128.8, 128.7,
127.6, 127.6, 126.5, 126.4, 126.2, 126.1 (aromatic), 84.9, 79.3, 78.0
(C-2, C-3, C-4), 75.8 (C-110), 71.0 (C-6), 70.7 (C-5), 67.5 (C-1), 60.52
(OCH3), 58.8 (OCH3), 47.6 (C-90), 35.2 (C-100), 20.9 (OCOCH3). MAL-
DI-TOF MS m/z calcd for C25H30O6: 426.20, found: 449.39 [M+Na]+.
Anal. Calcd for C25H30O6: C, 70.40; H, 7.09. Found: C, 70.29; H, 7.17.
Compound 18endo (4-O-acetyl): mp 194–196 °C; [
a
]
D
+43 (c
0.16; CHCl3); 1H NMR (500 MHz, CDCl3): d (ppm) 8.69 (d, 2H, J
9 Hz, H-10, H-80), 8.49 (s, 1H, H-100), 7.98 (d, 2H, J 8.3 Hz, H-40, H-
50), 7.55–7.40 (m, 4H, H-20, H-30, H-60, H-70), 7.12 (s, 1H, H-acetalic),
5.20 (dd, 1H, J4,5 9.5 Hz, H-4), 5.14 (s, 1H, H-1), 4.57 (dd, 1H, J3,4
5.7 Hz, H-3), 4.43 (d, 1H, J2,3 7.6 Hz, H-2), 3.95–3.88 (m, 1H, H-5),
3.45 (s, 3H, OCH3), 2.02 (s, 3H, OCOCH3), 1.34 (d, 3H, J6,5 6.4 Hz,
CH3-6); 13C NMR (125 MHz, CDCl3): d (ppm) 169.6 (CO), 131.4,
130.8, 130.7, 129.1, 126.4, 124.8, 124.4, 123.4 (aromatic), 101.8
(C-acetalic), 98.8 (C-1), 77.4, 75.8, 74.5 (C-2, C-3, C-4), 63.9 (C-5),
55.1 (OCH3), 20.9 (COCH3), 18.1 (C-6), Anal. Calcd for C24H24O6
(408.44): C, 70.57; H, 5.92. Found: C, 70.46; H, 6.06.
4.1.14. Methyl 2,3-O-(90-anthracenyl)methylene-
a-L-
rhamnopyranoside (17exo, 17endo) and methyl-4-O-acetyl-2,3-
O-(90-anthracenyl)methylene-
18endo)
a-L-rhamnopyranoside (18exo,
Crystalline methyl
a-L
-rhamnopyranoside 1625 (5.35 g,
30.2 mmol) was converted into the title compound according to
the method described for 2. The crude product was crystallized from
EtOAc–hexane to give the 17exo isomer (4.80 g, 43%). The mother li-
quor containing the exo and endo isomers could not be separated by
crystallization therefore it was acetylated with Ac2O (2 mL) in pyri-
dine (3 mL). TLC (8:4 hexane/EtOAc) showed two new spots (Rf 0.41
4.1.15. Methyl 3-O-(90-anthracenyl)methyl-
a-L-rhamnopyrano-
side (19) and methyl 2-O-(90-anthracenyl)methyl-
a-L-rhamno-
pyranoside (20)
Prepared from 17exo (100 mg, 0.27 mmol) according to the
same procedure as described for 4. After column chromatography

2452
Z. Jakab et al. / Carbohydrate Research 344 (2009) 2444–2453
(7:3 hexane/acetone) compound 19 (20 mg, 20%) and compound
20 (36 mg, 32%) were isolated as syrups.
3H, J 6.2 Hz, CH3-6); 13C NMR (90 MHz, CDCl3): d (ppm) 138.5,
131.4, 130.8, 129.1, 128.7, 128.2, 127.5, 126.6, 125.0, 123.8 (aro-
matic), 100.1 (C-1), 80.59, 79.60 (C-3, C-4), 75.2 (PhCH2), 68.5, 67.3
(C-2, C-5), 63.9 (anthr-CH2), 54.81 (OCH3), 17.9 (C-6). MALDI-TOF
MS m/z calcd for C29H30O5: 458.55, found: 481.52 [M+Na]+. Anal.
Calcd for C29H30O5: C, 75.96; H, 6.59. Found: C, 76.05; H, 6.51.
Compound 19: [
a]
+22 (c 0.06, CHCl3); 1H NMR (500 MHz,
D
OCH3): d (ppm) 8.50 (s, 1H, H-100), 8.36 (d, 2H, J 8.9 Hz, H-10, H-
80), 8.03 (d, 2H, J 8.5 Hz, H-40, H-50), 7.60–7.40 (m, 4H, H-20, H-30,
H-60, H-70), 5.73 (d, 1H, J 11.3 Hz, Ar-CH2), 5.53 (d, 1H, J 11.2 Hz,
Ar-CH2), 4.76 (s, 1H, H-1), 4.29 (d, 1H, J2,1 1.5 Hz, H-2), 3.86 (dd,
1H, J3,4 9.2 Hz, J 3.25 Hz, H-3), 3.69–3.64 (m, 1H, H-5), 3.51 (t,
1H, J4,5 9.3 Hz, H-4), 3.38 (s, 3H, OCH3), 1.29 (d, 3H, J6,5 6.25 Hz,
CH3-6); 13C NMR (125 MHz, CDCl3): d (ppm) 131.4, 130.9, 129.3,
128.9, 127.8, 126.8, 125.1, 123.6 (aromatic), 100.5 (C-1), 80.0,
71.6, 68.0, 67.5 (C-2, C-3, C-4, C-5), 63.6 (ArCH2), 54.9 (OCH3),
17.6 (C-6). Anal. Calcd for C22H24O5 (368.42): C, 71.72; H, 6.57.
Found: C, 71.40; H, 6.88.
4.1.18. Methyl 2,3-O-(90,100-dihydro-90-anthracenyl)methylene-
a-
L
-rhamnopyranoside (23)
Prepared from 17exo (2.14 g, 5.84 mmol) according to the same
method as described for the synthesis of 6. After 8 h the reaction
was completed according to TLC (6:4 hexane/aceton, Rf 0.55). After
column chromatography compound 23exo (2.06 g, 95%) was iso-
lated as a syrup: [
a]
D
ꢁ22 (c 0.17, CHCl3); 1H NMR (360 MHz,
Compound 20: [
a
]
D
+34 (c 0.12, CHCl3); 1H NMR (500 MHz,
CDCl3): d (ppm) 7.35–7.10 (m, 8H, aromatic), 5.44 (d, 1H, J
2.8 Hz, H-acetalic), 4.67 (s, 1H, H-1), 4.24 (d, 1H, J 18.3 Hz, Ar-
CH2), 4.16 (s, 1H), 3.89 (dd, 1H, J 7.4 Hz, J 5.2 Hz), 3.81 (d, 1H, J
18.4 Hz, Ar-CH2), 3.50–3.40 (m, 1H, H-5), 3.25 (s, 3H, OCH3),
3.20–3.10 (m, 2H), 2.15 (br s, 1H, OH), 1.19 (d, 3H, J6,5 6.2 Hz,
CH3-6); 13C NMR (90 MHz, CDCl3): d (ppm) 137.6, 137.6, 134.1,
134.0, 129.6, 129.2, 127.7, 127.6, 126.9, 126.0, 125.8 (aromatic),
107.4 (C-acetalic), 97.7 (C-1), 79.0, 75.5, 71.4, (C-2, C-3, C-4), 64.8
(C-5), 54.7 (OCH3), 51.7 (C-90), 35.9 (C-100), 17.2 (C-6). MALDI-
TOF MS m/z calcd for C22H24O5: 368.16, found: 391.41 [M+Na]+.
Anal. Calcd for C22H24O5: C, 71.72; H, 6.57. Found: C, 71.62; H, 6.67.
CDCl3): d (ppm) 8.32 (s, 1H, H-100), 8.29 (d, 2H, J 9.0 Hz, H-10, H-
80), 7.88 (d, 2H, J 8.4 Hz, H-40, H-50), 7.55–7.37 (m, 4H, H-20, H-30,
H-60, H-70), 5.60 (d, 1H, J 11.3 Hz, Ar-CH2), 5.37 (d, 1H, J 11.2 Hz,
Ar-CH2), 5.00 (s, 1H, H-1), 3.81 (dd, 1H, J2,3 3.7 Hz, J2,1 1.1 Hz, H-
2), 3.62 (dd, 1H, J3,4 9.4 Hz, H-3), 3.58–3.50 (m, 1H, H-5), 3.36 (s,
3H, OCH3), 3.19 (t, 1H, J4,5 9.4 Hz, H-4), 1.24 (d, 3H, J6,5 6.2 Hz,
CH3-6); 13C NMR (125 MHz, CDCl3): d (ppm) 131.3, 130.8, 129.0,
128.7, 127.8, 126.5, 125.0, 123.9 (aromatic), 97.8 (C-1), 78.0,
73.6, 71.4, 67.7 (C-2, C-3, C-4, C-5), 64.4 (ArCH2), 54.8 (OCH3),
17.5 (C-6). Anal. Calcd for C22H24O5 (368.42): C, 71.72; H, 6.57.
Found: C, 71.56; H, 6.65.
Starting from 17endo (150 mg, 0.41 mmol) the previous ring
opening method gave only 20 (88 mg, 58%).
5. Supplementary data
Complete crystallographic data for the structural analysis of
4.1.16. Methyl 2,3-O-(90-anthracenyl)methylene-4-O-benzyl-
-rhamnopyranoside (21exo)
To a solution of 17exo (220 mg, 0.6 mmol) in dry DMF (3 mL)
was added NaH (35 mg, 2 equiv) at 0 °C and stirred for 30 min.
Benzyl bromide (79 L, 1.2 equiv) was added to the mixture and
a-
4,6-O-(90,100-dihydro-90-anthracenyl)methylene-2,3-di-O-methyl-
L
a-D-glucopyranoside (6) have been deposited with the Cambridge
Crystallographic Data Centre, CCDC No. 736551. Copies of this
information may be obtained free of charge from the Director,
Cambridge Crystallographic Data Centre, 12 Union Road, Cam-
bridge, CB2 1EZ, UK. (fax: +44-1223-336033, e-mail: depos-
it@ccdc.cam.ac.uk or via: www.ccdc.cam.ac.uk).
l
stirred for another 30 min. After complete conversion 2–3 mL of
EtOAc and 1–5 drops of water were added, the mixture was diluted
with EtOAc, washed three times with water, dried, and concen-
trated. After column chromatography (8:2 hexane/EtOAc, Rf 0.48)
compound 21exo (253 mg, 92%) was isolated as an amorf material.
Crystallization of 22exo from hexane/EtOAc afforded pale yellow
Acknowledgement
This work was supported by the Hungarian National Fund
(NK48798 to A.L. and K62802 to A.B.).
crystals: mp 142 °C;
[a
]
D
+47.2 (c 0.04, CHCl3);1H NMR
(360 MHz, CDCl3): d (ppm) 8.50 (s, 1H, aromatic), 8.46 (d, 2H, J
8.9 Hz, aromatic), 8.00 (d, 2H, J 8.2 Hz, aromatic), 7.56–7.41 (m,
4H, aromatic), 7.37 (s, 1H, H-acetalic), 7.35–7.25 (m, 5H), 5.03–
4.97 (m, 2H), 4.95 (d, 1H, J 11.9 Hz, PhCHH), 4.77 (d, 1H, J
11.8 Hz, PhCHH), 4.62 (d, 1H, J 6.3 Hz), 3.94–3.84 (m, 1H, H-5),
3.58 (dd, 1H, J 9.6 Hz, J 6.9 Hz), 3.39 (s, 3H, OCH3), 1.43 (d, 3H, J
6.2 Hz, CH3-6); 13C NMR (90 MHz, CDCl3): d (ppm) 137.8, 131.5,
130.7, 130.6, 129.2, 128.4, 128.3, 127.7, 126.4, 125.0, 124.8, 123.9
(aromatic), 100.3 (C-acetalic), 99.0 (C-1), 80.5, 76.4, 76.2, 63.6 (C-
2, C-3, C-4, C-5), 72.3 (PhCH2), 18.1 (C-6). MALDI-TOF MS m/z calcd
for C29H28O5: 456.53, found: 456.51 [M]+ 479.50 [M+Na]+. Anal.
Calcd for C29H28O5: C, 76.30; H, 6.18. Found: C, 76.46; H, 6.09.
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