Anomalous Zemplen deacylation reactions of α- and β-D-mannopyranoside derivatives

Article abstract of DOI:10.1016/S0008-6215(00)00283-4

Reaction of mono-, di-, and trisaccharide derivatives of methyl β-D- and octyl β-D-mannopyranosides bearing ester groups at isolated and non-isolated positions on the same molecule, under Zemplen conditions (catalytic amount of sodium methoxide in methanol) gave partially deacylated compounds, in which the O-acyl groups were retained at isolated sites. In the case of one disaccharide, all the benzoyl groups remained intact at the reducing end, while all the acetyl functions were removable from the nonreducing end. In another case, both isolated ester groups at positions 2 and 4 were retained at the reducing end. The isolated 2-O-acyl groups on methyl α-D-mannopyranoside compounds were more labile than on the corresponding β-mannosides under the same conditions. The mechanism of the reaction may be different for ester groups at isolated or non-isolated positions. In the latter case, acyl migration may take place and carry acyl groups into a less hindered position.

Full text of DOI:10.1016/S0008-6215(00)00283-4

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Carbohydrate Research 330 (2001) 183–190
Anomalous Zemple´n deacylation reactions of a- and
b-
D
-mannopyranoside derivatives
a
b
a
a
a,
´
Ka´roly Agoston, Andra´s Dobo´, Ja´nos Ra´ko´, Ja´nos Kere´kgya´rto´, Zolta´n Szurmai *
aInstitute of Biochemistry, Faculty of Sciences, Uni6ersity of Debrecen, PO Box 55, H-4010 Debrecen, Hungary
bCentral Research Institute for Chemistry of the Hungarian Academy of Sciences, PO Box 17,
H-1525 Budapest, Hungary
Received 5 June 2000; accepted 23 October 2000
Dedicated to Professor Andra´s Lipta´k on the occasion of his 65th birthday
Abstract
Reaction of mono-, di-, and trisaccharide derivatives of methyl b-
D
- and octyl b-D-mannopyranosides bearing ester
groups at isolated and non-isolated positions on the same molecule, under Zemple´n conditions (catalytic amount of
sodium methoxide in methanol) gave partially deacylated compounds, in which the O-acyl groups were retained at
isolated sites. In the case of one disaccharide, all the benzoyl groups remained intact at the reducing end, while all
the acetyl functions were removable from the nonreducing end. In another case, both isolated ester groups at
positions 2 and 4 were retained at the reducing end. The isolated 2-O-acyl groups on methyl a-D-mannopyranoside
compounds were more labile than on the corresponding b-mannosides under the same conditions. The mechanism of
the reaction may be different for ester groups at isolated or non-isolated positions. In the latter case, acyl migration
may take place and carry acyl groups into a less hindered position. © 2001 Published by Elsevier Science Ltd. All
rights reserved.
Keywords: Anomalous Zemple´n deacylation; Temporary ester groups; Mannosides
1. Introduction
galactose2 it was found that under Zemple´n
conditions, benzyl 2,3,4-tri-O-acetyl-a-
rhamnopyranosyl-(1“3)-2-O-benzoyl-4,6-O-
benzylidene-b- -galactopyranoside yielded a
L
-
Zemple´n deacylation1 is one of the com-
monly used deblocking reactions in carbohy-
drate chemistry. Using this transesterification
reaction, OH-functions can be regenerated un-
der mild conditions, in methanol with a cata-
lytic amount of sodium methoxide at room
temperature. In most cases the reaction goes
smoothly and, after the very simple workup
procedure, the expected product can be ob-
tained in good yield. However, during the
D
disaccharide in which the 2-O-benzoyl group
was retained. There were only sporadic data3–
5 on this type of reaction called anomalous
deacylation but later on it turned out to be
more general and was observed among gluco
derivatives, too.6,7 Thus, in galacto and gluco
compounds, acyl groups could not be re-
moved from position 2 with a catalytic
amount of sodium methoxide when an alkyl
or glycosyl substituent was present at position
3. Bacterial oligosaccharides were prepared by
this anomalous reaction and in special cases
acyl groups were shown to serve as temporary
synthesis of a-
L
-rhamnopyranosyl-(1“3)- -
D
* Corresponding author. Tel.: +36-52-316666; fax: +36-
52-512913.
E-mail address: szurmaiz@tigris.klte.hu (Z. Szurmai).
0008-6215/01/$ - see front matter © 2001 Published by Elsevier Science Ltd. All rights reserved.
PII: S0008-6215(00)00283-4

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K. Agoston et al. / Carbohydrate Research 330 (2001) 183–190
184
protecting groups.8,9 It is worth noting that a
similar finding has recently been reported for
deoxy compounds bearing acyl groups at iso-
lated positions.10 Among mannosides, the first
observation had been made11 with octyl 2,4,6-
methyl a-
mannopyranoside compounds.
Similar results have now been obtained with
D
-, methyl b-
D
-, and octyl b- -
D
a methyl b-
D
- and another octyl b- -
D
mannopyranoside derivative as in the case of
compound 1. Mild acidic hydrolysis and sub-
sequent acetylation of methyl 3-O-allyl-4,6-
tri-O-benzoyl-3-O-benzyl-b- -mannopyra-
D
noside (1) prepared according to the ‘ulosyl
bromide’ approach.12 Thus, on Zemple´n dea-
cylation of 1, BzO-4,6 were removed but not
BzO-2, and octyl 2-O-benzoyl-3-O-benzyl-b-
O-benzylidene-b-
4,6-O-benzylidene-b-
D
- (3)18 and octyl 3-O-allyl-
D
-mannopyranoside (4)19
gave the triacetates 5 and 6, which, under
Zemple´n conditions, yielded exclusively the
monoacetates 7 and 8, respectively. In con-
trast, the a-mannoside derivative 10, prepared
from methyl 3-O-benzyl-4,6-O-benzylidene-a-
D
-mannopyranoside (2) was obtained in good
yield.11 Octyl 3,6-di-O-a-
b- -mannopyranoside, a trisaccharide sub-
D
-mannopyranosyl-
D
strate of glycosyltransferases was successfully
synthesised11 using 2 as the key compound.
We now report the anomalous Zemple´n
deacylation reactions of some other a- and
D
-mannopyranoside (9)20 gave a mixture of
the monoacetate 11 and the fully deacylated
product 12 (Fig. 1). The presence of the acetyl
groups in monoacetates 7, 8 and 11 were
b- -mannopyranoside derivatives.
D
1
indicated by H NMR, 13C NMR, and MS
data.
2. Results and discussion
During the synthesis of mannobioses 1414
and 16,11 13 gave easily 14 under Zemple´n
conditions but 15 having an isolated benzoyl
function could only be converted into 16 with
an equimolar amount of sodium methoxide in
methanol at the boiling point.11 In the present
study, when deacylation was performed at
room temperature with catalytic amount of
the reagent, surprisingly, all the benzoates re-
mained at the b-mannosidic unit yielding com-
pound 17 (Fig. 2).
The chemical synthesis of glycan chains of
oligomannose type N-glycoproteins is just one
of the ongoing research programmes in our
laboratories.11,13–17 After the preparation of a
series of protected mannose derivatives, the
investigation of the anomalous Zemple´n dea-
cylation reactions2,6–9 was continued among
Zemple´n reaction of disaccharide 18, syn-
thesised from 2 by selective mannosylation,11
surprisingly gave 19 as the only product, in
which not only the BzO-2 but the AcO-4
group was retained, as well. This experiment
suggests that, for an anomalous reaction to
occur, the isolated nature of the ester function
is more important than its proximity to the
steric relationship to the anomeric centre. This
suggestion was verified by the fact that methyl
2,4 - di - O - acetyl-3,6-di-O-benzyl-a- -manno-
D
pyranoside (20)13 was stable for hours, under
the usual reaction conditions. Moreover,
a model disaccharide 22 was prepared from
2117 by conventional acetylation, and then
converted into the 3-acetate 23 with a catalytic
amount of sodium methoxide. In contrast,
in the case of the methyl a-mannobioside
2417 the isolated acetyl group was not so
Fig. 1. Syntheses and deacylation reactions of mannose
derivatives.

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K. Agoston et al. / Carbohydrate Research 330 (2001) 183–190
185
tected disaccharide (26) was obtained after 30
min at room temperature (Fig. 3).
Finally, reactions of trisaccharides 27 and
30 were investigated. In the light of the results
mentioned above, not surprisingly, in the case
of the b-octyl compound 2711 after 45 min the
diacyl derivative 28 was successfully isolated.
As it was indicated by FABMS data, the
a-methyl derivative 30 prepared from 2917 by
standard reactions, gave a complex mixture
after 45 min. The sample contained traces of
31 and its triacetate and the corresponding
mono- and diacetates as the main compo-
nents. Within 2 h, the fully deprotected 31 was
the main product. The minor component was
1
not homogenous; H NMR showed the pres-
ence of the 2-acetate and the 4-acetate of 31 in
almost equal amounts (Fig. 4).
The accepted mechanism of Zemple´n deacyl-
ation is that methylate anion makes a nucle-
ophilic attack on the carbonyl carbon atom
and forms a methyl ester. Then, the ‘alcoho-
late’ anion abstracts a proton from methanol
through which process the methylate anion is
regenerated. The nucleophilic attack may be
unfavourable in a fully protected derivative
because of steric hindrance. Additionally, the
lone electron pairs of oxygen atoms, including
the ‘ring oxygen’ may give rise to a ‘stereoelec-
tronic hindrance’ discouraging attack by the
negatively charged methylate anion. Thus, the
reaction rate of removing ester groups from
isolated positions can be very low. The avail-
able data strongly suggest that, in the case of
non-isolated ester groups (e.g., 2,3,4,6-tetra-
Fig. 2. Deacylation of mannose derivatives bearing ester
groups at located and non-isolated positions.
Fig. 3. Zemple´n deacylations of mannobioses.
O-acetyl-a- -mannopyranosyl moiety), the
D
mechanism of the deacylation reaction may be
different. The nucleophilic attack takes place
at the less hindered carbonyl carbon atom.
Then, the ‘alcoholate’ anion, by an in-
tramolecular nucleophilic attack against the
next-door-neighbour’s carbonyl carbon, may
cause acyl migration. Thus, by the possible
acyl migrations the ester groups may have less
hindered position for the nucleophilic attack.21
Consequently, the reaction rate of the deacyla-
tion reaction would be higher than the one for
the isolated ester functions. The significant
difference between the deacylation reactions
of a- and b-mannosides can be explained by
the configuration of C-1. In b-mannosides, the
Fig. 4. Zemple´n deacylations of mannotrioses.
stable in methanol in the presence of sodium
methoxide and a mixture of methyl a-
D
-
-
mannopyranosyl - (1“3) - 2 - O - acetyl - a -
D
mannopyranoside (25) and the fully depro-

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K. Agoston et al. / Carbohydrate Research 330 (2001) 183–190
186
molecule is more crowded around the car-
bonyl carbon of the C-2-O-acyl groups.
Therefore, under Zemple´n conditions ester
functions at C-2 are more stable in the b
anomers than those in the a anomers.
General description for Zemple´n deacylation
reactions.—To a soln of the model compound
(1 mmol) in dry MeOH (10 mL) was added
NaOMe (0.15 mmol). The mixture was kept at
rt for the required time (the reaction was
monitored by TLC), then neutralised with
Amberlite IR 120 (H+) resin, filtered, and
concd. The residue was purified by short-
column chromatography to give the partially
deacylated product.
In summary, Zemple´n deacylation reactions
of mannose derivatives were investigated bear-
ing ester groups at both isolated and non-iso-
lated positions. The obtained results showed
that isolated acyl groups in b- -mannopyran-
D
oside derivatives were stable under Zemple´n
conditions. Some lability was observed for
a-mannosides. This fact should be very impor-
tant during the final step in the syntheses of
oligosaccharides. Moreover, in certain com-
pounds, ester groups can be used for tempo-
rary protection.
Methyl
mannopyranoside (5).—A mixture of methyl
-mannopyra-
2,4,6-tri-O-acetyl-3-O-allyl-i- -
D
3-O-allyl-4,6-O-benzylidene-b-
D
noside (3; 322 mg, 1 mmol)18 and aq 60%
AcOH (6 mL) was kept at 60 °C for 30 min,
then concd and co-concd with toluene (3×5
mL). The residue was dissolved in pyridine (4
mL), Ac2O (4 mL) was added and the mixture
was kept at rt overnight, then concd and
co-concd with toluene (3×5 mL). Column
chromatography of the residue (19:1 CH2Cl2–
EtOAc) gave 5 (329 mg, 91%); mp 104–
105 °C (from EtOH); [h]D −77.2° (c 0.29,
3. Experimental
General.—Melting points (uncorrected)
were determined on a Kofler hot-stage ap-
paratus. Optical rotations were measured with
a Perkin–Elmer 241 polarimeter. NMR spec-
tra were recorded with a Bruker WP-200 SY
spectrometer. The reactions were monitored
by TLC on Kieselgel 60 F254 (E. Merck,
Darmstadt) with detection by charring with
H2SO4. Kieselgel 60 (E. Merck) was used for
short-column chromatography. Fast-atom
bombardment (FAB) mass spectrometric mea-
surements have been performed using a VG-
ZAB-2SEQ reverse geometry instrument
operating at an accelerating voltage of 8 kV.
A cesium ion gun producing 30 keV ions was
utilised for ion bombardment. Glycerol was
used as the FAB matrix. The electrospray
(ESI) mass spectrometric measurements have
been performed on PE SCIEX API 2000 triple
quadrupole mass spectrometer (PE SCIEX,
Toronto, Canada). The solvent applied was a
1:1 mixture of water–MeOH with 0.1%
AcOH. The MALDI-TOF measurements were
carried out with a Bruker Biflex III mass
spectrometer, equipped with a 337 nm nitro-
gen laser. The instrument was used in reflec-
tron mode at 19.0 kV voltage. 2,5-
Dihydroxybenzoic acid was used as matrix
and 100–200 laser shots were applied for each
spectrum.
1
CHCl3); H NMR (CDCl3): l 5.89–5.70 (m, 1
H, ꢀCHꢁ), 5.53 (dd, 1 H, J2,3 3.2 Hz, H-2),
5.29–5.16 (m, 2 H, CH2ꢁ), 5.17 (t, 1 H, J4,5 9.8
Hz, H-4), 4.48 (d, 1 H, J1,2 0.7 Hz, H-1), 4.30
(dd, 1 H, J5,6a 5.5, J6a,6b 12.2 Hz, H-6a),
4.19–3.87 (m, 3 H, H-6b and ꢀOCH2ꢀ), 3.61
(m, 1 H, H-5), 3.56 (dd, 1 H, J3,4 9.8 Hz, H-3),
3.53 (s, 3 H, OMe), 2.18, 2.09 and 2.08 (3 s,
each 3 H, 3 OAc); 13C NMR (CDCl3): l
170.67, 170.39 and 169.49 (3 CꢁO), 133.86
(ꢀCHꢁ), 117.41 (CH2ꢁ), 99.91 (C-1), 76.35 (C-
3), 72.25 (C-5), 70.17 (ꢀOCH2ꢀ), 67.33 (C-2,4),
62.65 (C-6), 57.18 (OMe), 20.84 and 20.69 (3
Me). ESIMS (+): m/z 383.2 [M+Na]+,
378.1 [M+NH4]+, 361.0 [M+H]+, 329.2
[M+H−MeOH]+. Anal. Calcd for C16H24O9
(360.14): C, 53.31; H, 6.72. Found: C, 53.49;
H, 6.70.
Octyl 2,4,6-tri-O-acetyl-3-O-allyl-i-D-manno-
pyranoside (6).—Octyl 3-O-allyl-4,6-O-ben-
zylidene-b- -mannopyranoside (4; 210 mg, 0.5
D
mmol)19 was converted into 6 as described for
5. Column chromatography of the crude
product (97:3 CH2Cl2–EtOAc) yielded 6 (205
mg, 89%) as a syrup; [h]D −59.2° (c 0.32,
1
CHCl3); H NMR (CDCl3): l 5.86–5.72 (m, 1
H, ꢀCHꢁ), 5.61 (dd, 1 H, J2,3 3.3 Hz, H-2),
5.30–5.16 (m, 2 H, CH2ꢁ), 5.15 (t, 1 H, J4,5 9.8

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K. Agoston et al. / Carbohydrate Research 330 (2001) 183–190
187
0.7 Hz, H-1), 4.08 (m, 2 H, OCH2ꢀCHꢁ), 2.87
and 2.37 (2 bs, each 1 H, 2 OH, deuterable),
2.15 (s, 3 H, OAc), 1.61–1.26 (m, 12 H, 6
ꢀCH2ꢀ), 0.88 (t, 3 H, ꢀCH3); 13C NMR
(CDCl3): l 170.35 (CꢁO), 133.88 (CHꢁ),
118.21 (CH2ꢁ), 99.12 (C-1), 79.39 (C-3), 75.57
(C-5), 70.32 with double int. (2 ꢀOCH2ꢀ),
67.37 with double int. (C-2,4), 62.82 (C-6),
31.76, 29.31 with triple int., 25.62, 22.62 (6
ꢀCH2ꢀ), 20.87 (Me), 14.07 (CH2Me); ESIMS
(+): m/z 397.3 [M+Na]+, 392.2 [M+
NH4]+, 375.1 [M+H]+, 357.1 [M+H−
H2O]+, 317.2 [M+H−AllOH]+, 245.2
[M+H−CH3(CH2)7OH]+. Anal. Calcd for
C19H34O7 (374.23): C, 60.93; H, 9.16. Found:
C, 61.13; H, 9.11.
Hz, H-4), 4.53 (d, 1 H, J1,2 1.0 Hz, H-1), 4.29
(dd, 1 H, J5,6a 5.7, J6a,6b 12.1 Hz, H-6a),
4.17–3.81 (m,
3
H, ꢀOCH2ꢀCHꢁ and
ꢀOCH2ꢀCH2ꢀ), 4.15 (dd, 1 H, J5,6b 2.6 Hz,
H-6b), 3.59 (m, 1 H, H-5), 3.54 (dd, 1 H, J3,4
9.8 Hz, H-3), 3.48 (dt, 1 H, ꢀOCH2ꢀCH2ꢀ),
2.18, 2.08 and 2.07 (3 s, each 3 H, 3 OAc),
1.61–1.26 (m, 12 H, 6 ꢀCH2ꢀ), 0.88 (t, 3 H,
ꢀCH3); 13C NMR (CDCl3): l 170.81, 170.51,
169.62 (3 CꢁO), 134.04 (CHꢁ), 117.43 (CH2ꢁ),
99.06 (C-1), 76.69 (C-3), 72.36 (C-5), 70.48
with double int. (2 ꢀOCH2ꢀ), 67.68 with dou-
ble int. (C-2,4), 62.63 (C-6), 31.77, 29.67,
29.31 with double int., 25.82, 22.63 (6 ꢀCH2ꢀ),
20.80 with triple int. (3 Me), 14.08 (CH2Me);
ESIMS (+): m/z 481.3 [M+Na]+, 476.3
[M+NH4]+, 459.2 [M+H]+, 401.3 [M+
Methyl 2,4,6-tri-O-acetyl-3-O-benzyl-h-
D
-
H−AllOH]+,
329.3
[M+H−
mannopyranoside (10).—Methyl 3-O-benzyl-
CH3(CH2)7OH]+. Anal. Calcd for C23H38O9
(458.25): C, 60.23; H, 8.36. Found: C, 60.26;
H, 8.40.
4,6-O-benzylidene-a- -mannopyranoside (9;
D
745 mg, 2 mmol)20 was converted into 10 as
described for 5. Column chromatography of
the crude product (19:1 CH2Cl2 –EtOAc) gave
10 (755 mg, 92%) as a syrup; [h]D 0° (c 0.65,
Methyl
2-O-acetyl-3-O-allyl-i- -manno-
D
pyranoside (7).—Compound 5 (180 mg, 0.5
mmol) was partially deacylated for 4 h. The
product was purified by column chromatogra-
phy (3:1 CH2Cl2 –acetone) to give 7 (112 mg,
81%) as an amorphous solid; [h]D −68.3° (c
1
CHCl3); H NMR (CDCl3): l 7.36–7.23 (m, 5
H, aromatic), 5.34 (dd, 1 H, J2,3 3.5 Hz, H-2),
5.22 (t, 1 H, J4,5 10 Hz, H-4), 4.73 (d, 1 H, J1,2
1.8 Hz, H-1), 4.52 (ABq, 2 H, PhCH2), 4.24
(dd, 1 H, J5,6a 5.5, J6a,6b 12 Hz, H-6a), 4.11
(dd, 1 H, J5,6b 2.2 Hz, H-6b), 3.83 (m, 2 H,
H-3,5), 3.37 (s, 3 H, OMe), 2.15, 2.09 and 2.00
1
2.66, CHCl3); H NMR (CDCl3): l 5.97–5.78
(m, 1 H, ꢀCHꢁ), 5.50 (dd, 1 H, J2,3 3.1 Hz,
H-2), 5.34–5.18 (m, 2 H, CH2ꢁ), 4.49 (d, 1 H,
J1,2 0.9 Hz, H-1), 4.09 (m, 2 H, ꢀOCH2ꢀ), 3.53
(s, 3 H, OMe), 2.73 and 2.46 (2 bs, each 1 H,
2 OH, deuterable), 2.14 (s, 3 H, OAc); 13C
NMR (CDCl3): l 170.36 (CꢁO), 133.90
(ꢀCHꢁ), 118.07 (CH2ꢁ), 100.02 (C-1), 79.07
(C-3), 75.67 (C-5), 70.20 (ꢀOCH2ꢀ), 67.22 (C-
2), 66.72 (C-4), 62.34 (C-6), 57.23 (OMe),
20.73 (Me). ESIMS (+): m/z 299.2 [M+
Na]+, 294.1 [M+NH4]+, 277.0 [M+H]+,
245.2 [M+H−MeOH]+, 218.8 [M+H−Al-
lOH]+. Anal. Calcd for C12H20O7 (276.12): C,
52.15; H, 7.30. Found: C, 51.98; H, 7.27.
13
(3 s, each 3 H, 3 OAc); C NMR (CDCl3): l
170.52, 170.12, 169.53 (3 CꢁO), 137.56,
128.18, 127.56 (all for Ph), 98.70 (C-1), 74.30
(C-3), 71.17 (ꢀOCH2ꢀ), 68.36, 67.92, 67.24,
62.61 (C-6), 54.98 (OMe), 20.82 and 20.62
with double int. (3 Me); FABMS (+): m/z
411 [M+H]+, 379 [M+H−MeOH]+, 351
[M+H−CH3COOH]+,
303
[M+H−
BnOH]+. Anal. Calcd for C20H26O9 (410.16):
C, 58.51; H, 6.39. Found: C, 58.79; H, 6.33.
Methyl 2-O-acetyl-3-O-benzyl-h- -manno-
D
pyranoside (11).—Compound 10 (616 mg, 1.5
mmol) was partially deacylated for 4 h. The
product was purified by column chromatogra-
phy (3:1 CH2Cl2–acetone) to give 11 (64 mg,
13%) as a glass [h]D −4.8° (c 0.62, CHCl3);
1H NMR (CDCl3): l 7.36–7.27 (m, 5 H,
aromatic), 5.34 (dd, 1 H, J2,3 3.0 Hz, H-2),
4.69 (d, 1 H, J1,2 1.5 Hz, H-1), 4.57 (ABq, 2 H,
PhCH2), 3.36 (s, 3 H, OMe), 2.83 and 2.38 (2
bs, each 1 H, 2 OH, deuterable), 2.11 (s, 3 H,
Octyl2-O-acetyl-3-O-allyl-i- -mannopyran-
D
oside (8).—Compound 6 (138 mg, 0.3 mmol)
was partially deacylated for 4 h. The product
was purified by column chromatography (4:1
CH2Cl2 –acetone) to give 8 (101 mg, 90%) as
an amorphous solid; [h]D −79.1° (c 0.55,
1
CHCl3); H NMR (CDCl3): l 5.97–5.78 (m, 1
H, ꢀCHꢁ), 5.49 (dd, 1 H, J2,3 2.7 Hz, H-2),
5.35–5.19 (m, 2 H, CH2ꢁ), 4.57 (d, 1 H, J1,2

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K. Agoston et al. / Carbohydrate Research 330 (2001) 183–190
188
784.3 [M+NH4]+, 605.2 [M−C6H10O5]+,
587.2 475.3 [M−
[M−C6H12O6]+,
C6H10O5−CH3(CH2)7OH]+;
MALDI-TOF
HRMS: Calcd for C41H50NaO14 (789.3093).
Found: 789.0450 [M+Na]+. Resolution:
3060.
OAc); 13C NMR (CDCl3): l 170.25 (CꢁO),
137.49, 128.51, 128.05 (all for Ph), 99.08 (C-1),
77.49 (C-3), 71.79 (C-5), 71.50 (ꢀOCH2ꢀ),
67.84, 66.85, 62.45 (C-6), 55.03 (OMe), 20.88
(Me); ESIMS (+): m/z 349.0 [M+Na]+,
344.2 [M+NH4]+, 327.1 [M+H]+, 309.1
[M+H−H2O]+, 295.3 [M+H−MeOH]+,
218.8 [M+H−BnOH]+. Anal. Calcd for
C16H22O7 (326.14): C, 58.87; H, 6.80. Found:
C, 58.95; H, 6.81.
Octyl h-
tyl-2-O-benzoyl-3-O-benzyl-i-
D
-mannopyranosyl-(1“6)-4-O-ace-
-mannopyran-
D
oside (19).—Compound 18 (86 mg, 0.1
mmol)11 was partially deacylated for 30 min.
Column chromatography (9:1 CH2Cl2–
MeOH) of the product yielded 19 (58 mg,
84%) as an amorphous solid; [h]D −52.6° (c
A mixture (300 mg) of 11 and methyl 3-O-
benzyl-a- -mannopyranoside (12) was also
D
eluted from which an analytical sample of
pure 12 was obtained by rechromatography as
an amorphous solid; [h]D +38.8° (c 0.47,
1
0.86, CHCl3); H NMR (CDCl3): l 8.09–7.20
(m, 10 H, aromatic), 5.78 (d, 1 H, J2,3 3.0 Hz,
H-2), 5.27 (t, 1 H, J4,5 9.2 Hz, H-4), 4.83 (bs,
1 H, H-1%), 4.59 (ABq, 2 H, PhCH2), 4.56 (bs,
1 H, H-1), 1.98 (s, 3 H, OAc), 1.54–1.11 (m,
12 H, 6 ꢀCH2ꢀ), 0.83 (t, 3 H, ꢀCH3); 13C
NMR (CDCl3): l 170.16, 166.01 (2 CꢁO),
137.39, 133.08, 129.98, 128.35, 127.77 (all for
2 Ph), 100.14 (C-1), 98.95 (C-1%), 76.60 (C-3),
72.91, 72.37, 71.56, 70.71 and 69.91 (2
ꢀOCH2ꢀ), 68.57, 68.04, 66.90 (C-6), 66.28,
60.91 (C-6%), 31.69, 29.29 with triple int.,
25.82, and 22.59 (6 ꢀCH2ꢀ), 20.91 (Me), 14.05
(CMe); FABMS (+): m/z 691 [M+H]+, 631
1
CHCl3); H NMR (CDCl3–D2O): l 7.36–7.26
(m, 5 H, aromatic), 4.65 (d, 1 H, J1,2 1.4 Hz,
H-1), 4.61 (ABq, 2 H, PhCH2), 4.01 (t, 1 H,
J4,5 9.7 Hz, H-4), 3.88–3.71 (m, 3 H, H-
2,6a,6b), 3.62 (dd, 1 H, J2,3 3.1, J3,4 9.7 Hz,
H-3), 3.44 (m, 1 H, H-5), 3.26 (s, 3 H, OMe);
13C NMR (CDCl3): l 137.61, 128.38, 128.15,
127.91 (all for Ph), 100.64 (C-1), 79.46 (C-3),
72.26 (C-5), 71.99 (ꢀOCH2ꢀ), 67.93, 64.89,
60.86 (C-6), 54.75 (OMe); Anal. Calcd for
C14H20O6 (284.13): C, 59.13; H, 7.09. Found:
C, 59.02; H, 7.11.
Octyl h-
O-benzoyl-i-
2,3,4,6-tetra-O-acetyl-a-
(1“3)-2,4,6-tri-O-benzoyl-b-
D
-mannopyranosyl-(1“3)-2,4,6-tri-
-mannopyranoside (17).—Octyl
-mannopyranosyl-
-mannopyra-
[M+H−CH3COOH]+,
583
[M+H−
D
BnOH]+, 569 [M+H−PhCOOH]+, 561
[M+H−CH3(CH2)7OH]+. Anal. Calcd for
C36H50O13 (690.33): C, 62.58; H, 7.30. Found:
C, 62.50; H, 7.35.
D
D
noside11 (15; 23.4 mg, 25 mmol) was partially
deacetylated for 45 min. Column chromatog-
raphy of the crude product (17:3 CH2Cl2–
MeOH) resulted in 17 (15.3 mg, 80%); glass;
[h]D −52.6° (c 1.53, CHCl3); 1H NMR
(CDCl3): l 8.09–7.26 (m, 15 H, aromatic),
5.75 (t, 1 H, J3,4 =J4,5 9.8 Hz, H-4), 5.66 (d, 1
H, J2,3 2.8 Hz, H-2), 4.88 (bs, 1 H, H-1%), 4.75
(bs, 1 H, H-1), 4.68 (dd, 1 H, J5,6a 2.8, J6a,6b
12.2 Hz, H-6a), 4.43 (dd, 1 H, J5,6b 5.0 Hz,
H-6b), 1.50–1.14 (m, 12 H, 6 ꢀCH2ꢀ), 0.82 (t,
Methyl 2,3,4,6-tetra-O-acetyl-h-
pyranosyl-(1“6)-3-O-acetyl-2,4-di-O-benzyl-
h- -mannopyranoside (22).—Methyl 2,3,4,6-
D-manno-
D
tetra-O-acetyl-a-
D
-mannopyranosyl-(1“6)-
2,4-di-O-benzyl-a-
D
-mannopyranoside17 (21;
70.5 mg, 0.1 mmol) was acetylated in 1:1
pyridine–Ac2O (8 mL) at rt overnight, then
the mixture was concd and co-concd with
toluene (3×5 mL). Column chromatography
of the residue (17:3 CH2Cl2 –EtOAc) resulted
in 22 (syrup, 69 mg, 92%); [h]D +45.5° (c
13
3 H, CH3); C NMR (CDCl3): l 166.17 with
double int. and 165.37 (3 CꢁO), 133.64,
133.15, 133.01, 130.01, 129.90, 129.73, 129.65,
128.79, 128.67, 128.38 (all for 3 Ph), 102.46
(C-1), 99.00 (C-1%), 73.08, 72.23, 71.49, 70.88,
70.54, 69.82 (ꢀOCH2ꢀ), 69.18, 66.11, 63.30
(C-6), 60.99 (C-6%), 31.70, 29.39, 29.18 with
double int., 25.75, and 22.60 (6 ꢀCH2ꢀ), 14.06
(CMe); ESIMS (+): m/z 789.4 [M+Na]+,
1
1.73, CHCl3); H NMR (CDCl3): l 7.38–7.25
(m, 10 H, aromatic), 5.37 (dd, 1 H, J3%,4% 9.5
Hz, H-3%), 5.33 (dd, 1 H, J2%,3% 3.3 Hz, H-2%),
5.27 (t, 1 H, J4%,5% 9.5 Hz, H-4%), 5.21 (dd, 1 H,
J3,4 8.8 Hz, H-3), 4.97 (d, 1 H, J1%,2% 1.5 Hz,
H-1%), 4.69 and 4.59 (2 ABq, each 2 H, 2
PhCH2), 4.68 (d, 1 H, J1,2 1.8 Hz, H-1), 3.35

´
K. Agoston et al. / Carbohydrate Research 330 (2001) 183–190
189
MeOH) to yield 28 (3.8 mg, 25%) as an amor-
(s, 3 H, OMe), 2.14, 2.07, 2.04, 1.98, and 1.96
(5 s, each 3 H, 5 OAc); C NMR (CDCl3): l
1
13
phous solid; H NMR (1:1 CDCl3–CD3OD):
l 8.10–7.47 (m, 5 H, aromatic), 5.69 (d, 1 H,
J2,3 2.9 Hz, H-2), 5.44 (t, 1 H, J3,4=J4,5 9.8
Hz, H-4), 4.92 (d, 1 H, J1¦,2¦ 1.5 Hz, H-1¦),
4.87 (d, 1 H, J1%,2% 1.3 Hz, H-1%), 4.67 (bs, 1 H,
H-1), 2.14 (s, 3 H, OAc), 1.51–1.19 (m, 12 H,
6 ꢀCH2ꢀ), 0.85 (t, 3 H, ꢀCH3). ESIMS (+):
m/z 785.5 [M+Na]+, 780.4 [M+NH4]+,
763.3 [M+H]+, 601.3 [M−C6H10O5]+, 439.3
[M−C12H20O10]+; MALDI-TOF HRMS:
Calcd for C35H54NaO18 (785.3202). Found:
785.1443 [M+Na]+. Resolution: 2991.
170.59, 169.75, 169.66 (all for 5 CꢁO), 137.97,
137.82, 128.33, 127.72, 127.44 (all for 2 Ph),
98.52 and 97.53 (C-1,1%), 75.66, 74.50
(ꢀOCH2ꢀ), 73.81, 73.25, 72.87 (ꢀOCH2ꢀ),
70.82, 69.41, 68.96, 68.28, 66.56 (C-6), 66.05,
62.41 (C-6%), 54.78 (OMe), 20.63 (CMe); ES-
IMS (+): m/z 769.3 [M+Na]+, 764.2 [M+
NH4]+,
747.4
[M+H]+,
715.3
[M+H−MeOH]+, 331.0 [C14H19O9]+. Anal.
Calcd for C37H46O16 (746.28): C, 59.50; H,
6.21. Found: C, 60.00; H, 6.18.
Methyl 2,3,4,6-tetra-O-acetyl-h- -manno-
D
Methyl h-
acetyl-2,4-di-O-benzyl-h-
D
-mannopyranosyl-(1“6)-3-O-
pyranosyl-(1“3)-[2,3,4,6-tetra-O-acetyl-h-
mannopyranosyl-(1“6)]-2,4-di-O-acetyl-h-
D
-
-
D
-mannopyranoside
D
(23).—Compound 22 (44.8 mg, 60 mmol) was
partially deacylated for 30 min and the crude
product was subjected to column chromatog-
raphy (19:1 CH2Cl2–MeOH) to yield syrupy
23 (27.1 mg, 78%); [h]D +43.7° (c 1.4,
mannopyranoside (30).—A mixture of methyl
2,3,4,6-tetra-O-acetyl-a- -mannopyranosyl-
(1“3)-[2,3,4,6-tetra-O-acetyl-a- -mannopy-
ranosyl-(1“6)]-2,4-di-O-benzyl-a- -manno-
D
D
D
pyranoside (29; 517 mg, 0.5 mmol),17 AcOH
(20 mL), EtOH (20 mL) and Pd–C (100 mg)
was stirred under a H2 atmosphere at rt for 2
days. The catalyst was filtered off, the filtrate
was concd and co-concd with toluene (4×30
mL). The product was purified by column
chromatography (3:2 CH2Cl2–EtOAc) to give
trisaccharide 30 (423 mg, 90%) as a foam; [h]D
1
CHCl3); H NMR (CDCl3): l 7.35–7.22 (m,
10 H, aromatic), 5.19 (dd, 1 H, J2,3 3.3, J3,4 9.2
Hz, H-3), 3.29 (s, 3 H, OMe), 1.92 (s, 3 H,
OAc); 13C NMR (CDCl3): l 170.10 (CꢁO),
138.02, 137.62, 128.41, 127.88, 127.69, 127.29
(all for 2 Ph), 100.27 and 98.56 (C-1,1%), 75.58,
74.51 (ꢀOCH2ꢀ), 73.81, 73.37, 72.89
(ꢀOCH2ꢀ), 72.28, 71.66, 70.73, 66.33 (C-6),
65.96, 60.75 (C-6%), 54.85 (OMe), 20.98
(CMe); ESIMS (+): m/z 601.3 [M+Na]+,
596.5 [M+NH4]+, 579.4 [M+H]+, 547.3
[M+H−MeOH]+, 417.4 [M−C6H9O5]+;
MALDI-TOF HRMS: Calcd for C29H38NaO12
(601.2255). Found: 601.1524 [M+Na]+. Res-
olution: 3862.
1
+50.8° (c 1.09, CHCl3); H NMR (CDCl3): l
5.38–5.02 (m, 8 H, H-2,4,2%,3%,4%,2¦,3¦,4¦), 5.00
(bs, 1 H, H-1¦), 4.83 (bs, 1 H, H-1%), 4.69 (bs,
1 H, H-1), 4.34–3.46 (m, 10 H, skeleton pro-
tons), 3.41 (s, 3 H, OMe), 2.22, 2.16, 2.13,
2.12, 2.07, 2.05, 199, and 1.98 (8 s, 30 H, 10
OAc); 13C NMR (CDCl3): l 170.46, 170.31,
169.84, 169.61, 169.42 (all for 10 CꢁO), 98.64,
98.15, and 97.06 (C-1,1%,1¦), 74.02 (C-3),
70.67, 69.82, 69.23, 68.83, 68.48, 68.25, 68.11,
66.61 (C-6), 65.83, 62.26 with double int. (C-
6,6%), 54.92 (OMe), 20.67 and 20.48 (10 Me);
FABMS (+): m/z 939 [M+H]+. Anal. Calcd
for C39H54O26 (938.29): C, 49.88; H, 5.80.
Found: C, 50.00; H, 5.82.
Methyl h-
D
-mannopyranosyl-(1“3)-2-O-
acetyl-h- -mannopyranoside
D
(25).—Com-
pound 24 (65 mg, 0.1 mmol)17 was partially
deacylated for 30 min into an inseparable
mixture of 25 and 26. FABMS (+):Calcd for
C15H26O12 (25, 398.14) and C13H24O11 (26,
356.13). Found: m/z 399 [M+H]+, 367 [M+
H−MeOH]+ for 25 and 357 [M+H]+, 379
[M+Na]+, 325 [M+H−MeOH]+ for 26.
Zemple´n reactions of compound 30
Octyl
h-D
-mannopyranosyl-(1“3)-[h-
D-
Procedure A. Compound 30 (94 mg, 0.1
mannopyranosyl-(1“6)]-4-O-acetyl-2-O-ben-
mmol) was deacylated for 1 day to give
zoyl-i-
D
-mannopyranoside (28).—Compound
methyl 3,6-di-O-(a-
D
-mannopyranosyl)-a- -
D
2711 (22 mg, 0.02 mmol) was partially deacy-
lated for 45 min. The product was purified by
column chromatography (7:3 CH2Cl2–
mannopyranoside (31, 48 mg, 93%) as a glass;
[h]D +79.3° (c 0.16, water), +103.2° (c 0.22,
MeOH); lit. [h]D +83.9° (water),22 +96.7°

´
K. Agoston et al. / Carbohydrate Research 330 (2001) 183–190
190
(MeOH);23 1H NMR (D2O): l 5.09 (d, 1 H,
J1%,2% 1.4 Hz, H-1%), 4.90 (d, 1 H, J1¦,2¦ 1.4
Hz, H-1¦), 4.72 (d, 1 H, J1,2 1.4 Hz, H-1),
13C NMR (D2O): l 104.90 (C-1%), 103.50 (C-
1), 101.89 (C-1¦), 81.08 (C-3), 75.80, 75.19,
73.33, 73.09, 72.86, 72.46, 72.02, 69.22,
68.12, 67.69 (C-6), 63.44 (C-6% and C-6¦),
57.34 (OMe). FABMS (+): m/z 519 [M+
H]+.
Procedure B. Compound 30 (94 mg, 0.1
mmol) was partially deacylated. The reaction
was monitored by TLC (2:1:1 n-butanol–
MeOH–water). After 45 min the FABMS
spectrum of a sample showed that it was a
complex mixture in which the mono- and
diacetate of 31 were the main components:
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583
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1
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We thank the National Research Founda-
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Education Foundation (FKFP 0329/1997)
for financial support, and Mrs. Gyo¨ngyi
Gye´ma´nt for measuring the MALDI-TOF
mass spectra.
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