Silicon fluorides for acid-base catalysis in glycosidations

Article abstract of DOI:10.1002/adsc.201100933

Adduct formation between alcohols as glycosyl acceptors and phenylsilicon trifluoride (PhSiF₃) as catalyst permits acid-base-atalyzed glycosidations with O-glycosyl trichloroacetimidates as glycosyl donors. In this way, from various glycosyl do

Full text of DOI:10.1002/adsc.201100933

FULL PAPERS
DOI: 10.1002/adsc.201100933
Silicon Fluorides for Acid-Base Catalysis in Glycosidations
Amit Kumar,a Yiqun Geng,a and Richard R. Schmidta,b,*
a
Universitꢀt Konstanz, Fachbereich Chemie, Fach 725, D-78457 Konstanz, Germany
Fax : (+49)-7531-88-3135; e-mail: richard.schmidt@uni-konstanz.de
Chemistry Department – Faculty of Science, King Abdulaziz University, Jeddah 21589, Saudi Arabia
b
Received: November 30, 2011; Revised: February 10, 2012; Published online: May 15, 2012
Supporting information for this article is available on the WWW under http://dx.doi.org/10.1002/adsc.201100933.
Abstract: Adduct formation between alcohols as gly- substitution (SN2-type) reaction course with concomi-
cosyl acceptors and phenylsilicon trifluoride (PhSiF3) tant donor and acceptor activation is supported by
as catalyst permits acid-base-atalyzed glycosidations the results.
with O-glycosyl trichloroacetimidates as glycosyl
donors. In this way, from various glycosyl donors and
acceptors 1,2-trans- and some 1,2-cis-glycosides could Keywords: arylsilicon fluorides; bifunctional cataly-
be obtained with high anomeric selectivity. A prefer- sis; glycosidation; 1,2-trans glycosides; O-glycosyl tri-
ence for an intramolecular bimolecular nucleophilic chloroacetimidates; mechanism
Introduction
As boron has a high affinity to oxygen, however,
a markedly lower affinity to nitrogen, phenylboron
ꢀ
Acid-base catalysis for the acceleration of chemical fluorides as catalyst Y Z fulfill these criteria; with
reactions is an important concept that is also exten- their help and O-glycosyl trichloroacetimidates as gly-
sively employed by nature, for instance, in glycosyl- cosyl donors excellent results in 1,2-trans-glycoside
transferase reactions.[1] As the glycosyl donor and the bond formation were obtained, thus supporting the
acceptor are bound in the glycosyltransferase active prevalence of a concerted SN2-type transition state in
site in such a way that an intramolecular SN2-type these reactions.[3] As silicon forms much stronger
process is possible, complete stereocontrol is ob- bonds to fluorine and oxygen[4] than to nitrogen and
tained.
the pentacoordinated (or eventually hexacoordinat-
Glycosidation via first complex formation between ed)[5] silicon having a negative charge (see Scheme 2,
ꢀ
a catalyst Y Z, where Y is Lewis acidic and Z basic, a) is more prone to transfer the alkoxy group to the
ꢀ
and an alcohol RO H as acceptor permits in the gly- electrophilic anomeric carbon than the corresponding
cosidation step an activation of the glycosyl donor via boron complexes that possess higher bond energies,[6]
proton transfer as well as an activation of the accept- studies with phenylsilicon fluorides I–III[7] as glycosi-
or due to the transfer of a partial negative charge to dation catalysts were undertaken. The detection of sil-
the reacting oxygen.[2,3] When the donor and the ac- icon fluoride-hydrogen bonds (Si F···H) in fluoride-
ꢀ
ceptor-catalyst complex arrange in such a way that containing silicon complexes[8] favours SN2-type reac-
a hydrogen bond-mediated intramolecular SN2-type tions of the acceptor-catalyst adduct with the glycosyl
process is available (path a, Scheme 1, “RO-Y inside” donor.
transition state), also in the in vitro glycosidation, ex-
cellent stereocontrol should be observed. Thus, the
stereochemical outcome is dependent on the configu-
ration of the glycosyl donor. To support this conceptu-
ꢀ
al approach to glycosidation, the catalyst Y Z should Results and Discussion
not activate and thus eventually decompose the glyco-
syl donor (path b, Scheme 1), this should be only Compared with PhBF2 as catalyst, I–III are weaker
available to the fast and reversibly formed acceptor- Lewis acids and NMR studies exhibited that complex
catalyst complex that generates the increased proton formation, for instance, with 2-propanol (acceptor A),
acidity and concomitantly the increased acceptor nu- is fast, however the equilibrium is mainly on the left
cleophilicity.[2]
side. Hence, as expected, I–III do not activate and
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ꢀ
ꢀ
Scheme 1. Reaction of acceptors RO H in the presence of catalyst Y Z.
to initiate glycosidation in the presence of A as ac-
ceptor (entry 5), however excellent results were ob-
tained with PhSiF3 (III) as catalyst and A as acceptor.
At ꢀ408C practically only 1Ab was obtained
(entry 7) and, in support of a concerted reaction, the
results were only little influenced by solvent variation
(entries 9 and 10), yet strongly by temperature and
catalyst variation (entries 8, 11 and 12). Hence,
PhSiF3 as catalyst, CH2Cl2 as solvent and ꢀ408C as
reaction temperature were chosen as standard reac-
tion conditions. Similar results were obtained with
Scheme 2. Postulated transition state for SN2-type 1,2-trans- allyl alcohol (B) as primary alcohol, cholesterol (C)
and 1,2-cis-product formation.
and (+)-/(ꢀ)-menthol [(+)/(ꢀ)D] as secondary alco-
hol and tert-butanol (E) as tertiary alcohol (furnishing
1B,[11] 1C,[12] 1(+)/(ꢀ)D,[12] and 1E,[13] entries 13–18).
this way eventually decompose O-(a-d-glucopyrano- Although the steric demand of the acceptors B–E is
syl) trichloroacetimidate 1a[9] at 08C even after 2 h strongly increasing, only with tert-butanol (E,
(or longer reaction time) (Table 1, entries 1, 4, and 6). entry 18) did the yield and the b-selectivity drop
Thus, side reactions due to direct activation of O-gly- slightly. But in line with an SN2-type mechanism, the
cosyl trichloroacetimidates (Scheme 1, path b) leading reaction rates are affected by the increasing steric
eventually to a,b-mixtures of the desired product or bulk of the acceptors B–E. Also the relative place-
to O-glycosyl trichloroacetimidate rearrangement re- ment of the acceptor substituents leading to diaste-
actions are minimized. Hence, an important precondi- reomeric transition states affects the reaction rate and
tion for the prevalence of an acid-base-catalyzed SN2- the a/b-ratio as shown for (+)-/(ꢀ)-menthol
type glycosidation is fulfilled.
[(+)/(ꢀ)D, entries 16 and 17]. Comparisons with
However, when the acceptor A is added to the so- PhBF2 as catalyst at ꢀ408C under the same condi-
lution of catalyst I in CH2Cl2 and thereafter the donor tions (entries 11 and 14) demonstrate that both cata-
1a (inverse procedure) a fast reaction takes place lysts provide similar results.
leading at 08C and even at ꢀ408C mainly to b-prod-
Reaction of A with the anomeric O-b-d-glucopyra-
uct 1Ab (Table 1, entries 2 and 3).[10] Thus, the desired nosyl trichloroacetimidate 1b[10a] as glycosyl donor led
proton acidity and concomitantly the acceptor nucleo- only to low a-selectivity (entry 19), as the transition
philicity increase in the acceptor-catalyst complex is state for a concerted 1,2-cis glycoside bond formation
exhibited. The Lewis acidity of Ph2SiF2 (II) is too low is sterically disfavoured (Scheme 2, b). Hence, the ac-
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Silicon Fluorides for Acid-Base Catalysis in Glycosidations
Table 1. Phenylsilicon fluorides as glycosidation catalysts. Reaction of 1a and 1b with different acceptors.[a]
Entry
Donor
Acceptor
Promotor/Catalyst
(0.1 equiv.)
Reaction Conditions
Temperature
Product (Yield)
b/a-Ratio
Solvent
Time
1
2
3
4
5
6
7
8
1a
1a
1a
1a
1a
1a
1a
1a
1a
1a
1a
1a
1a
1a
1a
1a
1a
1a
1b
1b
1b
1b
None
A
A
none
A
none
A
A
A
A
A
A
B
B
F5C6SiF3
’’
’’
Ph2SiF2
’’
PhSiF3
’’
’’
’’
’’
PhBF2
TMSOTf
PhSiF3
PhBF2
PhSiF3
’’
’’
’’
’’
CH2Cl2
’’
’’
’’
’’
’’
’’
’’
0
0
2 h
no reaction/no decomp. of 1a
10 min
10 min
2 h
4 h
12 h
2 h
4 h
5 h
6 h
10 min
10 min.
30 min
10 min
1 h
1 h
2 h
4 h
3 h
1A (86%)
1A (86%)
6:1
8:1
ꢀ40
0
no reaction/no decomp. of 1a
no reaction/no decomp. of 1a
no reaction/no decomp. of 1a
ꢀ40
0
ꢀ40
ꢀ78
ꢀ30
ꢀ40
ꢀ40
ꢀ40
ꢀ40
ꢀ40
ꢀ40
ꢀ40
ꢀ40
ꢀ40
ꢀ40
ꢀ40
ꢀ40
ꢀ40
1A (92%)
24:1
no reaction/no decomp. of 1a
9
MeCN
toluene
CH2Cl2
1A (89%)
1A (88%)
1A (76%)
1A (78%)
1B (90%)
1B (85%)
1C (81%)
1(ꢀ)D (88%)
1(+)D (81%)
1E (78%)
1A (84%)
1B (82%)
1B (86%)
1F (77%)
24:1
20:1
8:1
10
11
12
13
14
15
16
17
18
19
20
21
22
4:1
’’
’’
’’
’’
’’
’’
’’
’’
’’
’’
24:1
20:1
16:1
24:1
15:1
9:1
C
(ꢀ)D
(+)D
E
A
B
B
F
1:2
PhSiF3
PhBF2
PhSiF3
30 min
10 min
1 h
1:12
1:15
2:1
[a]
Inverse procedure, temperature in 8C.
ceptor-catalyst complex linked to the glycosyl donor H, I and J were investigated; they provided much
via a hydrogen bond is forced in the transition state better results (entries 3–5). Reaction of 1a with H led
in an “RO Y outside” arrangement that favours an to b-selective reaction at 6-OH (1Hb);[19] with I and J
ꢀ
acid catalyzed SN1-type reaction course. Thus, forma- regioselective reactions at 3-OH were observed, that
tion of an a/b-product mixture is admitted. This hy- again furnished mainly b-linked disaccharides 1Ib and
pothesis is strongly supported by the results with allyl 1Jb. The structural assignments were confirmed by
alcohol (B) (entry 20); the lower steric demand of the NMR data of the per-O-acetylated derivatives
this acceptor favours formation of the inversion prod-
uct, namely 1,2-cis-glycoside 1Ba that is also obtained
with PhBF2 as catalyst (entry 21). However, already
with F as acceptor the anomeric preference is re-
versed (entry 22).
To further demonstrate the efficacy of this method
important 1,2-trans linked di- and trisaccharides were
synthesized based on quite different carbohydrates
such as, for instance, F,[10a] G,[14] H,[15] I,[16] J and K as
acceptors (Figure 1, Figure 2 and Figure 3). Thus, with
6-O-unprotected glucoside F as acceptor and 1a as
glycosyl donor almost exclusive formation of gentio-
bioside 1Fb[17] was observed (Table 2, entry 1). How-
ever, the reaction of 4-O-unprotected glucoside G as
acceptor and 1a as donor was sluggish and led even
after 8 h only in low yield to the desired cellobioside
1Gb;[18] in addition, also the corresponding maltoside
1Ga[18] was formed (b/a=3:1, entry 2). Obviously, the
lower nucleophilicity of sugar hydroxy groups com-
pared with simple alcohols and the steric bulk of
a pentacoordinated (or hexacoordinated) silicon com-
plex having fully protected sugars attached gave infe-
rior results. Therefore, partially protected acceptors Figure 1. Hydroxy group containing acceptors A–K.
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AHCTUNGTRENNUNG
Then we extended the scope of this glycosidation
method to fucosyl donor 5a,[24] a compound type that
is generally employed for the synthesis of a-l-fuco-
pyranosides (Table 3).[25] In the presence of A as ac-
ceptor donor 5a could be even activated with Ph2SiF2
as catalyst affording 5A at 08C in good b-selectivity
(entries 1–3). Similar results were observed for PhSiF3
as catalyst (entries 4–7) that readily activated 5a even
at ꢀ608C (entry 5). Also primary alcohol B as accept-
or followed this SN2-type reaction course furnishing
with PhSiF3 as catalyst essentially only b-product 5Bb
(entry 9).[26] Similar glycosidation results were ob-
tained for A and B with PhBF2 as catalyst (entries 8
and 10). However, this outcome is in strong contrast
to the TMSOTf-catalyzed reaction (entry 11) that
generally favours an SN1-type reaction course and
hence led to a 1:1 ratio of 5Ba,b. Sterically more hin-
dered (ꢀ)-menthol [(ꢀ)D] as acceptor led to a
b/a 2:3 mixture of 5(ꢀ)D (entry 12), thus exhibiting
the known tendency of 5a to a-product formation
with less reactive acceptors and at higher tempera-
tures (entry 13). As 5a is a pseudoenantiomer of 3a it
was expected that the match/mismatch situation is re-
versed and enantiomeric (+)-menthol [(+)D] will
react faster than (ꢀ)D with 5a and eventually also
more b-product will be obtained; this was indeed ob-
served (entries 14 and 15). After these findings it was
not surprising that less reactive 6-O-unprotected glu-
coside acceptor F gave, as generally found for donors
Figure 2. Donors 1a, 1b, 2a–5a.
Figure 3. Products.
1Hb’, 1Ib’ and 1Jb’.[20] Comparisons with PhBF2 as of 5a-type,[25] exclusively the a-product 5Fa
catalyst showed that diols H and I led to better results (entry 16).[27] Hence, the SN1-type mechanism (pre-
ꢀ
with PhSiF3 as catalyst (entries 3 and 4) than with sumably via an “RO Y outside” transition state) pre-
PhBF2 (entries 6 and 7). This is presumably due to vails in this case.
the generation of hexacoordinated intermediates with
The structural assignments of new compounds were
PhSiF3. Similar results were obtained for the O-lacto- also confirmed through O-acetylation furnishing com-
syl trichloroacetimidate 2a;[3] with acceptors A, B, pounds 2Hb’, 3Hb’, 3Ib’, 3Jb’, 3Kb’ and 4Hb’.[20]
(ꢀ)D, F and H the desired b-glycosides 2Ab,[3] 2Bb,[3]
2(ꢀ)Db, 2Fb[3] and 2Hb were almost exclusively
formed (Table 2, entries 8–12).
Conclusions
Nearly the same results, as obtained for glucose-de-
rived glycosyl donor 1a and 2a, were found for galac- PhSiF3 does neither activate nor decompose O-glyco-
tosyl donor 3a (Table 2, entries 14–22).[17] Reactions syl trichloroacetimidates, however it reversibly gener-
with alcohols B, C and (+)/(ꢀ)D and also with 6-O- ates with alcohols adducts that activate the glycosyl
unprotected glucoside F as acceptor led practically ex- donor via a proton transfer. Even at low temperature
clusively to b-glycoside bond formation furnishing and with catalytic amounts of PhSiF3 the reaction is
3Bb,[11] 3Cb,[21] 3(+)/(ꢀ)Db and 3Fb.[22] Again, quite fast, thus confirming the concomitant nucleophi-
(+)-menthol [(+)D] as acceptor exhibited a slightly licity increase of the acceptor. With structurally differ-
lower reactivity than (ꢀ)D (entries 16, 17). Also par- ent, quite nucleophilic acceptors mainly 1,2-trans-gly-
tially O-protected acceptors H, I, J and K furnished cosides were obtained in good yields. The solvent,
mainly the b-products 3Hb, 3Ib, 3Jb and 3Kb, respec- temperature and the acceptor steric demand depend-
tively, although in partly lower yields (entries, 19–22). ence of these reactions supports the proposed SN2-
Good glycosidation results were also obtained for O- type intramolecular reaction course. Practically no
(2-azido-2-deoxy-a-d-galactopyranosyl) trichloroacet- glycosyl fluorides are obtained, thus reflecting the dif-
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Silicon Fluorides for Acid-Base Catalysis in Glycosidations
Table 2. Reaction of donors 1a–4a with different acceptors.[a]
Entry
Donor
Acceptor
Catalyst (0.1 equiv.)
Reaction Time
Product (Yield)
b/a-Ratio
1
2
3
4
5
6
7
8
1a
1a
1a
1a
1a
1a
1a
2a
2a
2a
2a
2a
2a
3a
3a
3a
3a
3a
3a
3a
3a
3a
4a
4a
F
G
H
I
J
H
I
A
PhSiF3
’’
’’
’’
3 h
8 h
3 h
4 h
1F (81%)
1G (30%)
1H (73%)
1I (70%)
24:1
3:1
24:1
8:1
5:1
15:1
’’
5 h
1J (52%)
PhBF2
’’
PhSiF3
’’
’’
’’
’’
30 min
30 min
2.5 h
2 h
6 h
6 h
1H (63%)
several products
2A (72%)
2B (78%)
2(ꢀ)D (78%)
2F (76%)
2H (74%)
2A (79%)
3B (91%)
3C (82%)
3(ꢀ)D (89%)
3(+)D (76%)
3F (78%)
3H (75%)
3I (64%)
3:1
9
B
15:1
24:1
24:1
8:1
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
(ꢀ)D
F
H
A
B
C
(ꢀ)D
(+)D
F
H
I
J
K
F
H
3 h
PhBF2
PhSiF3
15 min
30 min
2 h
1 h
2 h
6 h
3 h
4 h
6 h
5:1
24:1
15:1
20:1
20:1
24:1
20:1
9:1
9:1
9:1
15:1
4:1
’’
’’
’’
’’
’’
’’
’’
’’
’’
’’
3J (57%)
5 h
18 h
3 h
3K (53%)
4F (76%)
4H (70%)
[a]
All reactions were carried out in dichloromethane as solvent in the presence of PhSiF3 or PhBF2 (0.1 equivalents) as cata-
lyst at ꢀ408C; the inverse procedure was applied.
Table 3. Reaction of fucosyl donor 5a with various acceptors in the presence of different catalysts.[a]
Entry
Acceptor
Catalyst (0.1 equiv.)
Reaction Conditons
Product (Yield)
b/a-ratio
Temperature [8C]
Time
1
2
3
4
5
6
7
8
–
A
A
–
A
A
A
A
B
B
B
(ꢀ)D
(ꢀ)D
(+)D
(+)D
F
Ph2SiF2
’’
’’
PhSiF3
’’
’’
’’
PhBF2
PhSiF3
PhBF2
TMSOTf
r.t.
-40
0
r.t.
12 h
12 h
30 min
12 h
3 h
2 h
1 h
30 min
2 h
no reaction/no decomp.
no reaction/no decomp.
5A (85%)
14:1
no reaction/no decomp.
ꢀ60
ꢀ40
ꢀ20
ꢀ40
ꢀ40
ꢀ40
ꢀ40
ꢀ40
ꢀ20
ꢀ40
ꢀ20
ꢀ40
5A (84%)
5A (86%)
5A (82%)
5A (79%)
5B (90%)
5B
5B (82%)
5(ꢀ)D (72%)
5(ꢀ)D (70%)
5(+)D (72%)
5(+)D (75%)
5F (72%)
12:1
9:1
6:1
9:1
20:1
15:1
1:1
2:3
1:3
9
10
11
12
13
14
15
16
10 min
6 h
5 h
4 h
2.5 h
10 h
PhSiF3
’’
’’
’’
’’
3:2
1:2
a only
[a]
All reactions were carried out in CH2Cl2 with equimolar amounts of 5a and acceptor; the inverse procedure was applied.
ferent bond strength and nucleophilicity of the nega- are operative that are related to enzymatic glycosida-
ꢀ
ꢀ
tively charged Si OR vs. Si F moieties. Other reac- tions. Worth mentioning is the high regioselectivity
tion courses, particularly an SN1-type reaction, are that is observed for partially O-protected acceptors,
only competitive with less nucleophilic acceptors. where PhSiF3 shows a clear preference over PhBF2 as
Hence, in most cases acid-base-catalyzed highly ste- catalyst. Thus, protecting group manipulations, gener-
reocontrolled SN2-type intramolecular glycosidations
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Amit Kumar et al.
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2.6 g (92%). Rf =0.4 (petroleum ether/EtOAc, 2:8); [a]D:
ꢀ86.3 (c 1.0, CHCl3). H NMR (400 MHz, CDCl3): d=6.96
ally required in consecutive glycosidations, can be
minimized.
1
(d, J=9.0 Hz, 2H, Ar-H), 6.72 (d, J=9.0 Hz, 2H, Ar-H),
4.65 (d, J=7.7 Hz, 1H, 1-H), 3.99 (app d, Japp=3.0 Hz, 1H,
5-H), 3.89 (app t, Japp=8.2 Hz, 1H, 2-H), 3.84–3.78 (m, 2H,
6a-H and 6a’-H), 3.70 (s, 3H, OMe), 3.60 (dd, J=9.6,
3.2 Hz, 1H, 3-H), 3.49 (app t, Japp=5.2 Hz, 1H, 4-H), 0.83
(s, 9H, t-Bu), 0.00 (s, 3H, -SiCH3), ꢀ0.01 (s, 3H, -SiCH3);
13C NMR (100 MHz, CDCl3): d=155.4, 151.2, 118.7, 114.5,
102.5 (C-1), 74.9, 73.7, 71.7, 68.9, 62.6, 55.6, 25.8, 18.2,
ꢀ5.40, ꢀ5.47; HR-MS: m/z=423.1800, calcd. for
(C19H32NaO7Si) [M+Na]+: 423.1810.
Experimental Section
General Experimental Details
Solvents were purified by standard procedures. NMR spec-
tra were recorded at 228C with a 400 MHz spectrometer;
tetramethylsilane (TMS) or the resonance of the undeuter-
ated solvent were used as internal standards (solvent CDCl3,
d=7.26 ppm). Mass spectra were recorded with an ESI MS
mass spectrometer. Thin-layer chromatography was per-
formed on silica gel plastic plates; compounds were visual-
ized by treatment with a solution of (NH4)6Mo7O24·4H2O
p-Methoxyphenyl 6-O-(Trityl)-b-d-galactopyranoside
(K)
(20 g) and CeACHTUNGTRENNUNG(SO4)2 (0.4 g) in sulfuric acid (10%, 400 mL)
To a solution of p-methoxyphenyl b-d-galactopyranoside[28]
(1.0 g, 3.5 mmol) in dry pyridine (20 mL) was added trityl-Cl
(1.01 g, 4.0 mmol) and the solution was stirred for 12 h at
room temperature. Solvents were evaporated under vacuum
and the residual syrup was purified by flash chromatography
using petroleum ether/EtOAc (1:3) as eluent to afford pure
compound K as a white solid; yield: 1.5 g (81%). Rf =0.5
(petroleum ether/EtOAc, 2:8); [a]D: ꢀ20.8 (c 4.0, CHCl3).
1H NMR (400 MHz, CDCl3): d=7.49 (d, J=7.4 Hz, 6H, Ar-
H), 7.34–7.27 (m, 9H, Ar-H), 7.13 (d, J=9.0 Hz, 2H, Ar-H),
6.84 (d, J=9.0 Hz, 2H, Ar-H), 4.76 (d, J=7.8 Hz, 1H, 1-H),
4.02 (d, J=3.3 Hz, 1H, 5-H), 3.93 (app t, Japp=9.3 Hz, 1H,
2-H), 3.80 (s, 3H, OMe), 3.68 (app d, Japp=3.3 Hz, 1H, 4-
H), 3.65 (dd, J=7.4, 4.0 Hz, 1H, 3-H), 3.60–3.56 (m, 1H, 6a-
H), 3.42 (dd, J=9.8, 5.0 Hz, 1H, 6a’-H); 13C NMR
(100 MHz, CDCl3): d=155.4, 151.2, 143.7, 128.7, 127.9,
127.1, 118.7, 114.5, 102.4 (C-1), 86.9, 74.1, 73.9, 69.3, 63.1,
55.6; HR-MS: m/z=551.2032, calcd. for (C32H32NaO7) [M+
Na]+: 551.2040.
Methyl 2,3,4,6-tetra-O-benzyl-a,b-d-glucopyranosyl-(1!
6)-2,3-di-O-benzyl-a-d-glucopyranoside (1H): Following the
general procedure A for glycosylation afforded 1H as
a white solid; yield: 73%. Rf =0.4 (petroleum ether/EtOAc,
7:3); [a]D: +20.5 (c 1.1, CHCl3). 1H NMR (400 MHz,
CDCl3): d=7.32–7.17 (m, 28H), 7.07 (dd, J=7.0, 2.4 Hz,
2H), 4.92 (d, J=11.5 Hz, 1H), 4.88 (d, J=11.0 Hz, 1H),
4.83 (d, J=11.0 Hz, 1H), 4.78–4.73 (m, 1H), 4.71 (br s, 1H),
4.67 (dd, J=7.5, 4.9 Hz, 2H), 4.64–4.62 (m, 1H), 4.56–4.50
(m, 2H), 4.50 (br s, 1H), 4.45 (br s, 1H), 4.42 (t, J=5.6 Hz,
1H), 4.37 (d, J=7.6 Hz, 1H), 4.05 (dd, J=10.0, 1.6 Hz, 1H),
3.75–3.68 (m, 2H), 3.66 (d, J=1.9 Hz, 1H), 3.63 (d, J=
1.8 Hz, 1H), 3.60 (d, J=4.7 Hz, 1H), 3.59–3.54 (m, 1H),
3.53 (d, J=5.9 Hz, 1H), 3.50 (s, 1H), 3.44–3.41 (m, 1H),
3.40 (d, J=3.2 Hz, 2H), 3.26 (s, 3H); 13C NMR (100 MHz,
CDCl3): d=138.9, 139.8, 139.7, 139.5, 139.1, 137.9, 128.5
ꢀ127.5 (m), 104.3, 98.1, 82.4, 81.5, 79.7, 79.4, 75.4, 75.1, 74.5,
73.6, 73.5, 73.4, 73.1, 73.0, 70.7, 70.0, 69.1, 68.7, 55.2; HR-
MS: m/z=919.4019, calcd. for (C55H60NaO11) [M+Na]+:
919.4028.
and then by heating to 1208C. Flash chromatography was
performed on silica gel (230–400 mesh) at a pressure of
0.2 bar. Optical rotations were measured at 228C using
sodium D line light.
General Procedure for Glycosylation: Inverse
Pocedure (A)
To a solution of acceptor (1 equiv. in CH2Cl2 was added cat-
alyst (0.1 equiv.) (C6F5-SiF3, Ph2SiF2 or PhSiF3 in CH2Cl2) at
room temperature. The reaction mixture was cooled to
ꢀ408C. Donor (1 equiv.) was dissolved in minimum amount
of CH2Cl2 and after cooling to ꢀ408C, was added into the
reaction mixture at once. The mixture was allowed to stir at
the same temperature until TLC indicated the complete
consumption of the starting material. The reaction was
quenched with aqueous NaHCO3 and extracted with
CH2Cl2. The organic layer was washed with water, dried
over MgSO4, and concentrated under vacuum. The crude
product was purified by flash column chromatography with
petroleum ether/EtOAc to afford the desired glycoside.
General Procedure for Acetylation (B)
To a stirred solution of the hydroxy compound in dry
CH2Cl2 (2 mL) was added acetic anhydride (0.5 mL), dry
pyridine (0.5 mL) and few crystals of DMAP at room tem-
perature. The reaction mixture was stirred at room tempera-
ture until TLC indicated complete consumption of the start-
ing material (12 h). Then the reaction mixture was diluted
with CH2Cl2 (10 mL) and washed with diluted HCl. The or-
ganic layer was dried over MgSO4 and concentrated under
vacuum. The residue was purified by flash column chroma-
tography with petroleum ether/EtOAc.
p-Methoxyphenyl 6-O-(tert-Butyldimethylsilyl)-b-d-
galactopyranoside (J)
To a solution of p-methoxyphenyl b-d-galactopyranoside[28]
(2.0 g, 7.0 mmol) in dry pyridine (30 mL) was added
TBDMS-Cl (1.35 g, 9.0 mmol) and the solution was stirred
for 12 h at room temperature. Solvents were evaporated
under vacuum and the residual syrup was purified by flash
chromatography using petroleum ether/EtOAc (1:3) as
eluent to afford pure compound J as a white solid; yield:
Methyl 2,3,4,6-tetra-O-benzyl-b-d-glucopyranosyl-(1!6)-
4-O-acetyl-2,3-di-O-benzyl-a-d-glucopyranoside (1H’): Ace-
tylation under standard conditions (B) afforded 1H’ as a col-
ourless solid; yield: 90%. Rf =0.6 (petroleum ether/EtOAc,
7:3); [a]D: +11.0 (c 1.4, CHCl3). 1H NMR (400 MHz,
CDCl3): d=7.39–7.26 (m, 28H, Ar-H), 7.22–7.11 (m, 2H,
Ar-H), 5.00 (d, J=10.9 Hz, 1H, benzylic-H), 4.91–4.86 (m,
1494
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ꢁ 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Adv. Synth. Catal. 2012, 354, 1489 – 1499

Silicon Fluorides for Acid-Base Catalysis in Glycosidations
3H, benzylic-H), 4.85 (d, J=10.0 Hz, 1H, benzylic-H), 4.79–
4.73 (m, 2H, 4a-H and benzylic-H), 4.75 (d, J=9.7 Hz, 2H,
benzylic-H), 4.66 (br s, 1H, benzylic-H), 4.64–4.60 (m, 3H,
benzylic-H), 4.57 (br s, 1H, benzylic-H), 4.53 (d, J=3.6 Hz,
1H, 1a-H), 4.50 (d, J=11.6 Hz, 2H, benzylic-H), 4.41 (d, J=
7.8 Hz, 1H, 1b-H), 3.93 (br d, J=9.2 Hz, 2H, 5a-H and 6b-
H), 3.91 (br d, J=2.8 Hz, 1H, 6a-H), 3.72 (dd, J=10.7,
2.0 Hz, 1H, 6a’-H), 3.70–3.64 (m, 1H, 5b-H), 3.61 (dd, J=
8.1, 6.4 Hz, 2H, 4b-H and 6b’-H), 3.56–3.54 (m, 2H, 3a-H
and 2a-H), 3.44 (app t, Japp=8.3 Hz, 2H, 2b-H and 3b-H),
3.30 (s, 3H, OMe), 1.88 (s, 3H, -COCH3); 13C NMR
(100 MHz, CDCl3): d=169.9, 138.6, 138.5, 138.18, 138.16,
138.0, 128.5–127.6 (m), 104.0 (C-1b), 97.9 (C-1a), 84.6, 82.3,
79.6, 79.2, 77.2, 75.7, 75.4, 74.9, 74.8, 74.7, 73.5, 70.8, 69.1,
68.9, 68.8, 55.3, 20.8; HR-MS: m/z=961.4130, calcd. for
(C57H62NaO12) [M+Na]+: 961.4133.
side (1J): Following the general procedure A for glycosyla-
tion afforded 1J as a white solid; yield: 52%. Rf =0.5 (petro-
leum ether/EtOAc, 5:5); [a]D: +25.0 (c 1.1, CHCl3).
1H NMR (400 MHz, CDCl3): d=7.42–7.22 (m, 35H), 7.16
(dd, J=7.1, 2.4 Hz, 3H), 7.04 (d, J=9.0 Hz, 3H), 6.81 (d,
J=9.2 Hz, 3H), 5.05 (d, J=10.9 Hz, 1H), 4.94 (d, J=
10.9 Hz, 2H), 4.86–4.78 (m, 4H), 4.75 (d, J=7.9 Hz, 2H),
4.69 (dd, J=6.8, 3.6 Hz, 2H), 4.55 (br s, 2H), 4.52 (d, J=
5.7 Hz, 2H), 4.49–4.42 (m, 1H), 4.13 (d, J=3.0 Hz, 1H),
4.07 (qt, J=9.3 Hz, 2H), 3.97 (t, J=8.3 Hz, 1H), 3.88 (d, J=
7.1 Hz, 3H), 3.77 (s, 4H), 3.72 (dd, J=9.5, 3.2 Hz, 2H), 3.66
(d, J=8.1 Hz, 5H), 3.59 (dd, J=16.1, 10.1 Hz, 4H), 3.51–
3.45 (m, 1H), 0.90 (s, 2H), 0.89 (s, 10H), 0.07, 0.06 (2 s,
2H), 0.48, 0.40 (2 s, 6H); 13C NMR (100 MHz, CDCl3): d=
155.7, 151.5, 138.4, 137.9, 137.8, 128.49, 128.46, 128.0, 127.8,
127.7, 118.6, 114.4, 103.9, 102.3, 84.6, 83.1, 81.6, 77.2, 75.7,
75.0, 74.7, 73.5, 70.4, 68.8, 67.9, 62.4, 25.9, 18.2, ꢀ5.31,
ꢀ5.40; HR-MS: m/z=945.4221, calcd. for (C53H66NaO12Si)
[M+Na]+: 945.4216.
4-Methoxyphenyl 2,3,4,6-tetra-O-benzyl-a,b-d-glucopyra-
nosyl-(1!3)-2,6-di-O-benzyl-b-d-galactopyranoside
(1I):
Following the general procedure A for glycosylation afford-
ed 1I as a white solid; yield: 70%. Rf =0.5 (petroleum ether/
EtOAc, 6:4); [a]D: +18.2 (c 1.1, CHCl3). 1H NMR
(400 MHz, CDCl3): d=7.43–7.30 (m, 29H), 7.23–7.29 (m,
5H), 7.07 (d, J=9.1 Hz, 2H), 6.84 (d, J=9.1 Hz, 2H), 5.30
(d, J=3.6 Hz, 1H), 5.07–4.99 (m, 2H), 4.98 (s, 1H), 4.95 (d,
J=4.4 Hz, 1H), 4.93 (s, 1H), 4.90 (d, J=2.6 Hz, 1H), 4.88–
4.86 (m, 1H), 4.85 (d, J=1.5 Hz, 1H), 4.84–4.82 (m, 1H),
4.81–4.77 (m, 3H), 4.76 (s, 1H), 4.67–4.64 (m, 1H), 4.62 (br
s, 1H), 4.59 (br s, 2H), 4.57 (d, J=5.3 Hz, 2H), 4.53 (d, J=
8.0 Hz, 2H), 4.16 (d, J=2.8 Hz, 1H), 4.07–4.02 (m, 2H),
3.89 (dd, J=9.5, 3.3 Hz, 1H), 3.84 (d, J=2.9 Hz, 1H), 3.82
(s, 4H), 3.78 (dd, J=9.2, 3.7 Hz, 1H), 3.71–3.63 (m, 7H),
3.52–3.43 (m, 1H); 13C NMR (100 MHz, CDCl3): d=163.5,
155.2, 138.7=137.8 (m), 128.7–127.4, 118.5, 114.5, 103.3,
103.0, 91.3, 84.7, 81.8, 81.7, 81.2, 80.0, 78.4, 77.78, 77.73, 77.2,
75.74, 75.72, 75.2, 75.1, 75.0, 74.8, 74.5, 73.7, 73.57, 73.53,
73.0, 70.3, 69.6, 68.8, 68.7, 68.2, 55.6; HR-MS: m/z=
1011.4283, calcd. for (C61H64NaO12) [M+Na]+: 1011.4290.
4-Methoxyphenyl 2,3,4,6-tetra-O-benzyl-b-d-glucopyrano-
syl-(1!3)-4-O-acetyl-2,6-di-O-benzyl-b-d-galactopyranoside
(1I’): Acetylation under standard conditions (B) afforded 1I’
as a white solid; yield: 85%. Rf =0.4 (petroleum ether/
EtOAc, 7:3); [a]D: +13.8 (c 1.8, CHCl3). 1H NMR
(400 MHz, CDCl3): d=7.32–7.11 (m, 29H, Ar-H), 7.11–7.02
(m, 2H, Ar-H), 6.97 (d, J=9.1 Hz, 2H, Ar-H), 6.72 (d, J=
9.1 Hz, 2H, Ar-H), 5.44 (app d, Japp=3.2 Hz, 1H, 4a-H),
4.86–4.85 (m, 3H, benzylic-H), 4.80 (d, J=7.6, 1H, 1a-H),
4.77 (d, J=8.0, 1H, 1b-H), 4.70 (d, J=11.2 Hz, 2H, benzyl-
ic-H), 4.68 (d, J=11.8 Hz, 1H, benzylic-H), 4.58 (d, J=
10.2 Hz, 1H, benzylic-H), 4.53 (d, J=12.0 Hz, 1H, benzylic-
H), 4.47–4.42 (m, 3H, benzylic-H), 3.98 (dd, J=9.7, 3.4 Hz,
1H, 3a-H), 3.93–3.91 (m, 1H, 2a-H), 3.76 (app t, Japp=
6.5 Hz, 1H, 3b-H), 3.70 (s, 3H, OMe), 3.61–3.59 (m, 2H, 6a-
H and 6a’-H), 3.58–3.46 (m, 3H, 4b-H, 5b-H, 6b-H and 6b’-
H), 3.36 (app t, Japp=8.1 Hz, 1H, 2b-H), 3.27–3.25 (m, 1H,
5a-H), 2.05 (s, 3H, -COCH3); 13C NMR (100 MHz, CDCl3):
d=169.9, 155.3, 151.4, 138.6, 138.4, 138.3, 138.1,138.0, 128.7–
127.5 (m), 118.3, 114.5, 102.97 (C-1a), 102.90 (C-1b), 84.5,
82.5, 79.8, 77.8, 77.1, 75.8, 77.4, 75.2, 75.0, 74.8, 74.7, 73.7,
73.2, 70.3, 68.9, 68.7, 55.6, 20.9; HR-MS: m/z=1053.4399,
calcd. for (C63H66NaO13) [M+Na]+: 1053.4396.
4-Methoxyphenyl 2,3,4,6-tetra-O-benzyl-b-d-glucopyrano-
syl-(1!3)-2,4-di-O-acetyl-6-O-tert-butyldimethylsilyl-b-d-
galactopyranoside (1J’): Acetylation under standard condi-
tions (B) afforded 1J’ as a white solid; yield: 85%. Rf =0.4
(petroleum ether/EtOAc, 7:3); [a]D: +28.0 (c 0.7, CHCl3).
1H NMR (400 MHz, CDCl3): d=7.40–7.21 (m, 24H, Ar-H),
7.16 (d, J=7.0 Hz, 2H, Ar-H), 6.97 (d, J=9.1 Hz, 2H, Ar-
H), 6.79 (d, J=9.1 Hz, 2H, Ar-H), 5.56–5.53 (m, 2H, 2a-H
and 4a-H), 4.87 (d, J=11.2 Hz, 1H, benzylic-H), 4.83 (d, J=
11.5 Hz, 1H, benzylic-H), 4.80 (d, J=6.8 Hz, 1H, 1a-H),
4.74 (d, J=11.2 Hz, 2H, benzylic-H), 4.60 (dd, J=11.2,
6.8 Hz, 2H, benzylic-H), 4.55–4.52 (m, 1H, 3a-H), 4.51 (d,
J=7.6 Hz, 1H, 1b-H), 4.03 (dd, J=12.5, 6.3 Hz, 1H, 6a-H)
3.70 (s, 3H, OMe), 3.74–3.65 (m, 4H, 5a-H, 6a’-H’, 6b-H
and 6b’-H), 3.58–3.54 (m, 2H, 3b-H and 4b-H), 3.47 (m, 1H,
5b-H), 3.38 (app t, Japp=8.2 Hz, 1H, 2b-H), 2.11 (s, 3H,
-COCH3), 2.03 (s, 0.77H, -COCH3), 1.91 (s, 3H, -COCH3),
1.85 (s, 0.77H, -COCH3), 0.89 (s, 11H, t-Bu), 0.02, 0.01 (2s,
8H, -SiCH3); 13C NMR (100 MHz, CDCl3): d=169.8, 169.5,
155.6, 151.7, 138.6 138.0, 128.4–127.6 (m), 118.1, 114.5, 104.1-
AHCTUNGTREG(NNUN C-1a), 100.8 (C-1b), 84.3, 81.9, 77.8, 76.2, 75.5, 75.0, 73.4,
70.0, 69.2, 62.1, 55.6, 25.8, 20.88, 20.81, 18.2, ꢀ5.44, ꢀ5.53;
HR-MS: m/z=1029.4421, calcd. for (C57H70NaO14Si) [M+
Na]+: 1029.4427.
(ꢀ)-Menthyl 4-O-acetyl-2,4,6-tri-O-benzyl-b-d-galactopyr-
anosyl-(1!4)-2,3,6-tri-O-benzyl-b-d-glucopyranoside
[2(ꢀ)D]: Following the general procedure A for glycosyla-
tion afforded 2(ꢀ)D as a yellow oil; yield: 78%. Rf =0.4 (pe-
troleum ether/EtOAc, 9:1); [a]D: ꢀ3.6 (c 1.1, CHCl3).
1H NMR (400 MHz, CDCl3): d=7.43–7.04 (m, 30H, Ar-H),
5.00 (d, J=10.8 Hz, 1H, benzylic-H), 4.90 (d, J=10.8 Hz,
1H, benzylic-H), 4.86 (d, J=10.8 Hz, 1H, benzylic-H), 4.76
(dd, J=8.8, 2.4 Hz, 1H, 3b-H), 4.70 (d, J=11.1 Hz, 1H ben-
zylic-H), 4.62 (d, J=10.8 Hz, 2H, benzylic-H), 4.56 (d, J=
9.6 Hz, 1H, 1b-H), 4.52 (d, J=11.2 Hz, 2H, benzylic-H),
4.45 (br. s, 1H, benzylic-H), 4.42–4.36 (m, 2H, 1a-H and
benzylic-H), 4.25 (d, J=12.0 Hz, 1H, benzylic-H), 3.98–3.91
(m, 2H, 4b-H and 3a-H), 3.83–3.63 (m, 3H, 5b-H, 6b-H and
2b-H), 3.57–3.42 (m, 3H, 4a-H, 6a-H and 6b’-H), 3.38–3.32
(m, 3H, 2a-H, 5a-H and 6a’-H), 2.39–2.27 (m, 1H), 2.12 (q,
J=14.1 Hz, 1H), 1.91 (s, 3H, -COCH3), 1.66 (d, J=10.8 Hz,
2H), 1.38–1.14 (m, 3H), 1.04–0.68 (m, 12H); 13C NMR
(100 MHz, CDCl3): d=171.1, 139.3, 138.8, 138.5, 138.4,
4-Methoxyphenyl 2,3,4,6-tetra-O-benzyl-a,b-d-glucopyra-
nosyl-(1!3)-6-O-tert-butyldimethylsilyl-a-d-galactopyrano-
Adv. Synth. Catal. 2012, 354, 1489 – 1499
ꢁ 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
asc.wiley-vch.de
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Amit Kumar et al.
FULL PAPERS
138.0, 128.3–127.3 (m), 102.7 (C-1b), 100.7 (C-1a), 83.1, 81.7,
77.77, 77.73, 77.0, 75.4, 75.2, 75.1, 75.0, 74.8, 74.6, 73.4, 73.3,
72.8, 68.4, 67.7, 48.1, 40.9, 34.5, 31.5, 25.3, 23.3, 22.2, 21.0,
3.79 (d, J=2.7 Hz, 1H), 3.78–3.70 (m, 1H), 3.67–3.63 (m,
3H), 3.53–3.47 (m, 2H), 3.47–3.41 (m, 2H), 3.39 (dd, J=7.5,
4.2 Hz, 2H), 3.22 (s, 3H), 2.25 (d, J=2.2 Hz, 1H); 13C NMR
(100 MHz, CDCl3): d=138.9, 139.8, 139.7, 139.5, 139.1,
137.9, 128.5–127.5 (m), 104.3, 98.1, 82.4, 81.5, 79.7, 79.4, 75.4,
75.1, 74.5, 73.6, 73.4, 73.1, 73.0, 70.7, 70.0, 69.1, 68.7, 55.1;
HR-MS: m/z=919.4036, calcd. for (C55H60NaO11) [M+
Na]+: 919.4028.
20.9,
16.0;
HR-MS:
m/z=1085.5373,
calcd.
for
(C66H78NaO12) [M+Na]+: 1085.5385.
Methyl 4-O-acetyl-2,4,6-tri-O-benzyl-b-d-galactopyrano-
syl-(1!4)-2,3,6-tri-O-benzyl-a,b-d-glucopyranosyl-(1!6)-
2,3-di-O-benzyl-a-d-glucopyranoside (2H): Following the
general procedure A for glycosylation afforded 2H as
a white solid; yield: 74%. Rf =0.4 (petroleum ether/EtOAc,
7:3); [a]D: +22.5 (c 1.2, CHCl3). 1H NMR (400 MHz,
CDCl3): d=7.38–7.26 (m, 40H), 7.24 (d, J=1.9 Hz, 4H),
7.20–7.08 (m, 5H), 5.19 (d, J=3.7 Hz, 1H), 5.04–4.95 (m,
2H), 4.90 (d, J=10.9 Hz, 1H), 4.80 (dd, J=10.1, 3.1 Hz,
2H), 4.76 (d, J=4.9 Hz, 1H), 4.73 (d, J=3.9 Hz, 3H), 4.70
(d, J=2.7 Hz, 2H), 4.64 (s, 1H), 4.63–4.59 (m, 4H), 4.56 (br
s, 1H), 4.52 (d, J=6.5 Hz, 2H), 4.49–4.43 (m, 3H), 4.37 (d,
J=12.1 Hz, 3H), 4.25 (t, J=9.2 Hz, 2H), 4.06 (dd, J=10.8,
2.1 Hz, 1H), 3.99–3.94 (m, 1H), 3.92 (br s, 2H), 3.80 (dd,
J=9.8, 2.6 Hz, 2H), 3.77–3.66 (m, 5H), 3.60 (d, J=9.3 Hz,
1H), 3.58–3.54 (m, 1H), 3.52 (s, 1H), 3.52–3.48 (m, 5H),
3.35 (s, 1H), 3.34 (s, 3H), 1.93 (s, 1H), 1.91 (s, 3H);
13C NMR (100 MHz, CDCl3): d=170.3, 139.0, 138.9, 138.6,
138.57, 138.1, 138.0, 128.7–127.5 (m), 127.1, 103.7, 102.7,
98.2, 82.9, 81.4, 81.3, 79.6, 77.7, 77.6, 75.4, 75.1, 75.0, 74.98,
74.94, 74.5, 73.5, 73.2, 73.1, 72.7, 70.4, 70.2, 68.4, 68.0, 67.6,
Methyl 2,3,4,6-tetra-O-benzyl-b-d-galactopyranosyl-(1!
6)-4-O-acetyl-2,3-di-O-benzyl-a-d-glucopyranoside
(3H’):
Acetylation under standard conditions (B) afforded 3H’ as
a white solid; yield: 90%. Rf =0.6 (petroleum ether/EtOAc,
1
7:3); [a]D: +7.4 (c 2.0, CHCl3). H NMR (400 MHz, CDCl3):
d=7.27 (m, 30H, Ar-H), 4.94 (d, J=10.8 Hz, 1H, benzylic-
H), 4.90 (d, J=11.6 Hz, 1H, benzylic-H), 4.85 (d, J=
11.6 Hz, 1H, benzylic-H), 4.80 (br s, 1H, benzylic-H), 4.76
(app t, Japp=8.4 Hz, 1H, 4a-H), 4.71 (d, J=12.3 Hz, 2H,
benzylic-H), 4.67 (br s, 1H, benzylic-H), 4.63 (d, J=9.7 Hz,
2H, benzylic-H), 4.61–4.57 (m, 1H, benzylic-H), 4.52 (d, J=
3.5 Hz, 1H, 1a-H), 4.39 (d, J=8.5 Hz, 1H, benzylic-H), 4.34
(d, J=7.7 Hz, 1H, 1b-H), 3.95–3.91 (m, 2H, 4a-H and 3b-
H), 3.86 (dd, J=6.2, 3.4 Hz, 2H, 4b-H and 6b-H), 3.77 (app
t, Japp=7.7 Hz, 1H, 2b-H), 3.58 (app d, Japp=9.0 Hz, 1H,
3a-H), 3.56–3.51 (m, 3H, 2a-H, 5a-H and 6a-H), 3.51–3.48
(m, 2H, 5b-H and 6b’-H), 3.48–3.45 (m, 1H, 6a’-H), 3.25 (s,
3H, OMe), 1.84 (s, 3H, -COCH3); 13C NMR (100 MHz,
CDCl3): d=170.0, 138.8, 138.6, 138.5, 138.0, 137.9, 128.6–
127.3 (m), 104.3 (C-1b), 97.8 (C-1a), 82.0, 79.7, 79.6, 79.3,
77.2, 75.4, 75.0, 74.6, 73.59, 73.50, 73.4, 73.1, 71.0, 69.3, 68.9,
68.6, 55.3, 20.8; HR-MS: m/z=961.4123, calcd. for
(C57H62NaO12) [M+Na]+: 961.4133.
55.2,
20.9;
HR-MS:
m/z=1303.5609,
calcd.
for
(C77H84NaO17) [M+Na]+: 1303.5601.
Methyl 4-O-acetyl-2,4,6-tri-O-benzyl-b-d-galactopyrano-
syl-(1!4)-2,3,6-tri-O-benzyl-b-d-glucopyranosyl-(1!6)-4-
O-acetyl-2,3-tri-O-benzyl-a-d-glucopyranoside (2H’): Acety-
lation under standard conditions (B) afforded 2H’ as a col-
ourless solid; yield: 90%. Rf =0.6 (petroleum ether/EtOAc,
8:2); [a]D: +18.8 (c 1.5, CHCl3). 1H NMR (400 MHz,
CDCl3): d=7.48–7.02 (m, 44H, Ar-H), 4.97 (d, J=11.2 Hz,
1H, benzylic-H), 4.91 (d, J=9.1 Hz, 1H, benzylic-H), 4.87
(br s, 1H, benzylic-H), 4.84–4.75 (m, 3H, 3c-H and benzylic-
H), 4.71 (dd, J=11.6, 7.6 Hz, 2H, 4a-H and benzylic-H),
4.66 (d, J=11.6 Hz, 1H benzylic-H), 4.63 (d, J=11.1 Hz,
2H, benzylic-H), 4.60 (d, J=4.5 Hz, 1H, 1a-H), 4.57–4.50
(m, 3H, benzylic-H), 4.45 (d, J=7.2 Hz, 1H, 1b-H), 4.39 (d,
J=7.2 Hz, 2H, benzylic-H), 4.36 (d, J=7.5 Hz, 1H, 1c-H),
4.24 (d, J=11.9 Hz, 1H, benzylic-H), 3.92–3.88 (m, 5H, 4c-
H, 5c-H, 3a-H, 6c-H and 4b-H), 3.70–3.65 (m, 3H, 6a-H, 6b-
H and 3b-H), 3.60–3.47 (m, 3H, 2a-H, 6c’-H and 2b-H),
3.40–3.33 (m, 4H, 6a’-H, 6b’-H, 5b-H, and H-2c), 3.27 (s,
3H, OMe), 1.91 (s, 3H, -COCH3), 1.88 (s, 3H,-COCH3);
13C NMR (100 MHz, CDCl3): d=170.3, 170.0, 139.0, 138.7,
138.6, 138.5, 138.4, 138.1, 138.06, 138.02, 128.6–127.36 (m),
104.0 (C-1b), 102.6 (C-1c), 97.8 (C-1a), 82.7, 81.8, 79.7, 79.2,
77.7, 77.2, 75.4, 75.0, 74.9, 74.5, 73.4, 73.3, 73.1, 72.7, 70.9,
69.2, 68.9, 67.6, 55.3, 20.9, 20.8; HR-MS: m/z=1345.5710,
calcd. for (C79H86NaO18) [M+Na]+: 1345.5706.
4-Methoxyphenyl 2,3,4,6-tetra-O-benzyl-a,b-d-galactopyr-
anosyl-(1!3)-2,6-di-O-benzyl-b-d-galactopyranoside
(3I):
Following the general procedure A for glycosylation afford-
ed 3I as white solid; yield: 63 mg (64%). Rf =0.5 (petroleum
ether/EtOAc, 6:4); [a]D: +28.0 (c 1.0, CHCl3). 1H NMR
(400 MHz, CDCl3): d=7.45–7.32 (m, 26H), 7.24 (m, 8H),
7.07 (d, J=9.1 Hz, 2H), 6.83 (d, J=9.1 Hz, 2H), 5.33 (d, J=
3.4 Hz, 1H), 5.04–4.95 (m, 3H), 4.90 (d, J=7.8 Hz, 1H),
4.87 (d, J=5.7 Hz, 1H), 4.85–4.75 (m, 4H), 4.73 (d, J=
7.9 Hz, 2H), 4.69–4.61 (m, 2H), 4.58 (d, J=7.2 Hz, 1H),
4.56–4.47 (m, 1H), 4.42 (br s, 2H), 4.11 (d, J=2.8 Hz, 1H),
4.04 (dd, J=9.4, 7.9 Hz, 2H), 3.94 (dd, J=6.5, 2.9 Hz, 2H),
3.92–3.88 (m, 1H), 3.85 (dd, J=7.3, 4.4 Hz, 2H), 3.81 (s,
3H), 3.79–3.74 (m, 1H), 3.65 (br s, 1H), 3.63–3.51 (m, 4H),
2.97 (d, J=14.9 Hz, 1H); 13C NMR (101 MHz, CDCl3): d=
155.2, 151.6, 138.4, 138.3, 138.2, 137.7, 128.6–127.3 (m),
118.5, 114.5, 103.6, 102.9, 82.2, 81.0, 79.1, 78.7, 78.4, 77.2,
75.2, 75.19, 74.6, 73.7, 73.5, 73.4, 73.2, 69.6, 68.89, 68.1, 55.6;
HR-MS: m/z=1011.4285, calcd. for (C61H64NaO12) [M+
Na]+: 1011.4290.
4-Methoxyphenyl 2,3,4,6-tetra-O-benzyl-b-d-galactopyra-
nosyl-(1!3)-4-O-acetyl-2,6-di-O-benzyl-b-d-galactopyrano-
side (3I’): Acetylation under standard conditions (B) afford-
ed 3I’ as a white solid; yield: 90%. Rf =0.4 (petroleum
ether/EtOAc, 7:3); [a]D: +32.2 (c 2.1, CHCl3). 1H NMR
(400 MHz, CDCl3): d=7.30 (m, 27H, Ar-H), 7.24 (m, 4H,
Ar-H), 7.03 (d, J=9.1 Hz, 2H, Ar-H), 6.78 (d, J=9.1 Hz,
2H, Ar-H), 5.44 (app d, Japp=2.4 Hz, 1H, 4a-H), 4.96–4.89
(m, 3H, 1b-H and benzylic-H), 4.86 (d, J=7.2 Hz, 1H, 1a-
H), 4.78 (app t, Japp=9.9 Hz, 2H, benzylic-H), 4.71 (d, J=
11.3 Hz, 2H, benzylic-H), 4.67 (d, J=10.0 Hz, 1H, benzylic-
Methyl 2,3,4,6-tetra-O-benzyl-a,b-d-galactopyranosyl-(1!
6)-2,3-di-O-benzyl-a-d-glucopyranoside (3H): Following the
general procedure A for glycosylation afforded 3H as
a white solid; yield: 75%. Rf =0.4 (petroleum ether/EtOAc,
7:3); [a]D: +35.0 (c 1.0, CHCl3). 1H NMR (400 MHz,
CDCl3): d=7.37–6.83 (m, 30H), 4.89 (d, J=11.5 Hz, 1H),
4.85 (d, J=2.0 Hz, 1H), 4.82 (br s, 1H), 4.66 (d, J=2.0 Hz,
1H), 4.65–4.60 (m, 4H), 4.54 (br s, 1H), 4.50 (t, J=3.6 Hz,
1H), 4.47 (br s, 1H), 4.37–4.29 (m, 3H), 4.04–3.97 (m, 1H),
1496
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Silicon Fluorides for Acid-Base Catalysis in Glycosidations
H), 4.60 (d, J=11.7 Hz, 1H, benzylic-H), 4.51 (d J=
11.2 Hz, 2H, benzylic-H), 4.39 (br s, 2H, benzylic-H), 4.02
(app t, Japp=7.2 Hz, 2H, 2a-H and 2b-H), 3.86–3.84 (m,
1H, 5a-H), 3.80 (app t, Japp=5.9 Hz, 1H, 3a-H), 3.77 (s,
3H, OMe), 3.64 (dd, J=10.0, 4.4 Hz, 1H, 3b-H), 3.58–3.49
(m, 3H, 5b-H, 6a-H and 6a’-H), 3.44–3.37 (m, 2H, 6b-H and
6b’-H), 2.10 (s, 3H, -COCH3); 13C NMR (100 MHz, CDCl3):
d=170.2, 155.3, 151.5, 138.8, 138.4, 137.9, 137.5, 128.7–127.7
(m), 118.2, 114.5, 102.9 (C-1b), 100.0 (C-1a), 87.3, 86.9, 79.9,
77.2, 75.8, 75.2, 73.6, 72.8, 70.3, 70.2, 70.0, 69.6, 69.1, 68.41,
68.40 68.0, 55.6, 20.9; HR-MS: m/z=1053.4386, calcd. for
(C63H66NaO13): [M+Na]+: 1053.4396.
26H), 7.17–7.09 (m, 6H), 7.04 (d, J=9.1 Hz, 2H), 6.71 (d,
J=9.1 Hz, 2H), 5.21 (s, 1H), 4.95–4.82 (m, 3H), 4.79–4.72
(m, 2H), 4.69 (dd, J=5.7, 2.7 Hz, 1H), 4.65 (d, J=4.7 Hz,
2H), 4.62 (s, 1H), 4.56 (d, J=7.6, 1H), 4.50 (dd, J=11.6,
2.5 Hz, 2H), 4.40 (d, J=11.9 Hz, 1H), 4.34 (d, J=11.9 Hz,
1H), 4.25 (br s, 2H), 4.09 (t, J=6.5 Hz, 1H), 4.0–3.98 (m,
1H), 3.90 (br s, 1H), 3.84–3.80 (m, 1H), 3.78 (d, J=2.9 Hz,
1H), 3.67 (s, 4H), 3.58–3.50 (m, 3H), 3.46 (ddd, J=12.4, 7.5,
2.8 Hz, 4H), 3.38 (dd, J=11.0, 4.0 Hz, 2H), 3.19 (dd, J=8.2,
2.7 Hz, 1H), 2.98 (d, J=6.3 Hz, 1H), 2.80 (s, 1H), 2.59 (d,
J=11.6 Hz, 2H); 13C NMR (100 MHz, CDCl3): d=155.2,
151.3, 143.9, 138.3, 138.2, 137.6, 128.7–127.4 (m), 126.9,
118.6, 114.4, 104.2, 102.0, 100.0, 86.7, 83.2, 82.3, 78.8, 77.2,
75.3, 74.6, 74.0, 73.7, 73.4, 73.3, 73.0, 68.5, 55.6; HR-MS: m/
z=1073.4429, calcd. for (C66H66NaO12) [M+Na]+:
1073.4446.
4-Methoxyphenyl 2,3,4,6-tetra-O-benzyl-a,b-d-galactopyr-
anosyl-(1!3)-6-O-tert-butyldimethylsilyl-b-d-galactopyrano-
side (3J): Following the general procedure A for glycosyla-
tion afforded 3J as a white solid; yield: 54%. Rf =0.5 (petro-
leum
ether/EtOAc,
5:5);
[a]D:
+45.5
(c
1.1,
Methyl 2-azido-3,4-di-O-benzyl-6-O-tert-butyldimethylsil-
yl-d-2-deoxy-a,b-galactopyranosyl-(1!6)-2,3-di-O-benzyl-a-
d-glucopyranoside (4H): Following the general procedure A
for glycosylation afforded 4H as a white solid; yield: 69 mg
(53%). Rf =0.4 (petroleum ether/EtOAc, 8:2); [a]D: +12.5
(c 1.1, CHCl3). 1H NMR (400 MHz, CDCl3): d=7.75–7.55
(m, 8H), 7.34–7.23 (m, 30H), 7.21–7.16 (m, 10H), 7.14–7.08
(m, 4H), 5.19 (d, J=3.5 Hz, 1H), 4.93 (t, J=10.9 Hz, 2H),
4.85 (br s, 2H), 4.84–4.79 (m, 3H), 4.78–4.75 (m, 1H), 4.74
(br s, 1H), 4.72 (br s, 1H), 4.69 (s, 1H), 4.66 (app t, Japp=
5.7 Hz, 4H), 4.62 (d, J=2.4 Hz, 1H), 4.59 (t, J=3.9 Hz,
1H), 4.57 (d, J=2.2 Hz, 2H), 4.38 (d, J=7.8 Hz, 1H), 4.13
(d, J=8.4 Hz, 1H), 3.94–3.88 (m, 2H), 3.87–3.81 (m, 4H),
3.74 (d, J=9.0 Hz, 2H), 3.71–3.64 (m, 4H), 3.59 (d, J=
9.0 Hz, 1H), 3.56 (d, J=3.4 Hz, 1H), 3.54 (d, J=1.9 Hz,
1H), 3.52 (s, 1H), 3.46 (br s, 1H), 3.44 (d, J=3.4 Hz, 1H),
3.43–3.41 (m, 1H), 3.34–3.31 (m, 1H), 3.28 (s, 3H), 3.28 (s,
1H), 3.25 (d, J=3.0 Hz, 1H), 0.99 (s, 3H), 0.96 (s, 10H):
13C NMR (100 MHz, CDCl3): d=135.9, 138.63, 138.61,
138.0, 135.9, 135.8, 135.63, 135.60, 128.3–126.78 (m), 103.9,
99.2, 98.2, 84.8, 82.5, 81.8, 81.5, 80.6, 79.7, 77.2, 76.2, 75.87,
75.81, 75.3, 75.1, 74.8, 73.3, 73.1, 71.6, 70.2, 70.0, 68.6, 55.3
26.9, 26.8, 19.2 , 19.1; HR-MS: m/z=1002.4336, calcd. for
(C57H65N3NaO10Si) [M+Na]+: 1002.4331.
CHCl3).1H NMR (400 MHz, CDCl3): d=7.28 (m, 23H), 7.01
(d, J=9.1 Hz, 2H), 6.77 (d, J=9.1 Hz, 2H), 5.33–5.11 (m,
1H), 4.97 (d, J=10.8 Hz, 1H), 4.91 (d, J=11.5 Hz, 1H),
4.80 (d, J=10.7 Hz, 1H), 4.74 (d, J=6.3 Hz, 1H), 4.70 (d,
J=4.1 Hz, 2H), 4.61 (d, J=7.6 Hz, 1H), 4.59 (d, J=11.6 Hz,
1H), 4.45 (d, J=11.9 Hz, 1H), 4.38 (br s, 2H), 4.07- 4.00 (m,
2H), 3.94 (s, 1H), 3.92–3.85 (m, 2H), 3.82 (dd, J=6.0,
4.0 Hz, 2H), 3.74 (s, 3H), 3.64 (dd, J=9.4, 3.2 Hz, 1H),
3.59–3.47 (m, 6H), 2.70 (s, 1H), 2.65 (d, J=2.3 Hz, 1H),
0.85 (s, 1H), 0.84 (s, 9H), 0.04, 0.03 (2 s, 6H); 13C NMR
(101 MHz, CDCl3): d=155.2, 151.4, 138.4, 138.3, 137.7,
128.7–127.4 (m), 118.6, 114.4, 104.4, 102.2, 91.9, 83.4, 82.3,
78.8, 77.3, 75.3, 75.2, 74.7, 73.6,73.5, 73.2, 73.0, 70.4, 68.6,
67.8, 62.1, 55.6, 25.9, 18.2, ꢀ5.3, ꢀ5.4; HR-MS: m/z=
945.4218, calcd. for (C53H66NaO12Si) [M+Na]+: 945.4216.
4-Methoxyphenyl 2,3,4,6-tetra-O-benzyl-b-d-galactopyra-
nosyl-(1!3)-6–2,4-di-O-acetyl-O-tert-butyldimethylsilyl-b-d-
galactopyranoside (3J’): Acetylation under standard condi-
tions (B) afforded 3J’ as a white solid; yield: 87%. Rf =0.4
(petroleum ether/EtOAc, 7:3); [a]D: +18.5 (c 1.2, CHCl3).
1H NMR (400 MHz, CDCl3): d=7.45–7.21 (m, 20H, Ar-H),
6.96 (d, J=9.1 Hz, 2H, Ar-H), 6.77 (d, J=9.1 Hz, 2H, Ar-
H), 5.53 (app t, Japp=8.4 Hz, 1H, 2a-H), 5.45 (app d,
Japp=3.6 Hz, 1H, 4a-H), 4.91 (d, J=11.7 Hz, 1H, benzylic-
H), 4.79 (dd, J=11.6 Hz, 2H, benzylic-H), 4.66 (d, J=
10.5 Hz, 3H, benzylic-H), 4.55 (d, J=11.7 Hz, 1H, benzylic-
H), 4.50–4.42 (m, 3H, 1a-H, 1b-H and benzylic-H), 3.94 (dd,
J=10.0, 3.6 Hz, 1H, 3b-H), 3.86 (app d, Japp=2.4 Hz, 1H,
4b-H), 3.75 (s, 3H, OMe), 3.73–3.66 (m, 3H, 3a-H, 5a-H
and 6a-H), 3.63–3.58 (m, 3H, 5b-H, 6b-H and 6b’-H), 3.51
(app t, Japp=6.4 Hz, 1H, 2b-H), 3.45 (dd, J=9.7, 2.9 Hz,
1H, 6a’-H), 2.07 (s, 3H, -COCH3), 1.84 (s, 3H, -COCH3),
0.88 (s, 9H, t-Bu), 0.02, 0.05 (2s, 6H, SiCH3); 13C NMR
(100 MHz, CDCl3): d=171.0, 169.5, 155.3, 151.6, 138.87,
138.81, 138.4, 138.0, 128.4–127.7 (m), 118.1, 114.4, 104.3 (C-
1a), 100.9 (C-1b), 82.0, 79.2, 77.3, 75.6, 74.9, 74.4, 73.5, 72.8,
70.9, 70.0, 68.7, 62.3, 55.6, 25.8, 20.86, 20.84, 18.2, ꢀ5.46,
ꢀ5.56; HR-MS: m/z=1029.4432, calcd. for (C57H70NaO14Si)
[M+Na]+: 1029.4427.
Methyl 2-azido-3,4-di-O-benzyl-6-O-tert-butyldimethylsil-
yl-2-deoxy-b-d-galactopyranosyl-(1!6)-4-O-acetyl-2,3-di-O-
benzyl-a-d-glucopyranoside (4H’): Acetylation under stan-
dard conditions (B) afforded 4H’ as a colourless solid; yield:
90%. Rf =0.6 (petroleum ether/EtOAc, 8:2); [a]D: +8.2 (c
1
1.6, CHCl3). H NMR (400 MHz, CDCl3): d=7.68–7.64 (m,
4H, Ar-H), 7.41–7.25 (m, 28H, Ar-H), 7.16–7.10 (m, 2H,
Ar-H), 5.04 (d, J=10.9 Hz, 1H, benzylic-H), 4.93–4.82 (m,
5H, 4a-H and benzylic-H), 4.73 (dd, J=11.3, 5.6 Hz, 2H,
benzylic-H), 4.66–4.60 (m, 3H, benzylic-H), 4.56 (d, J=
3.6 Hz, 1H, 1a-H), 4.43 (d, J=7.7 Hz, 1H, 1b-H), 3.94 (dd,
J=9.3, 3.5 Hz, 3H, 5b-H, 6a-H and 6a’-H), 3.88 (br s, 2H,
3a-H and 4b-H), 3.68–3.62 (m, 2H, 2a-H and 2b-H), 3.53
(dd, J=9.6, 3.4 Hz, 2H, 3b-H and 5a-H), 3.44 (app t, Japp=
8.0 Hz, 1H, 6b-H), 3.31 (br s, 1H, 6b’-H), 3.30 (s, 3H,
OMe), 1.85 (s, 1H, -COCH3), 1.82 (s, 3H, -COCH3), 1.02 (s,
9H, t-Bu), 1.00 (s, 2H, t-Bu); 13C NMR (100 MHz, CDCl3):
d=169.7, 138.7, 138.6, 138.0, 135.8, 135.6, 133.2, 129.6,
128.6–127.2 (m), 103.9 (C-1b), 98.0 (C-1a), 84.6, 82.6, 79.6,
79.3, 77.5, 75.8, 75.7, 75.4, 75.1, 74.7, 73.5, 70.7, 69.0, 62.8,
55.4, 29.7, 26.8, 20.8, 19.3; HR-MS: m/z=1044.4422, calcd.
for (C59H67N3NaO11Si) [M+Na]+:1044.4437.
4-Methoxyphenyl 2,3,4,6-tetra-O-benzyl-a,b-d-galactopyr-
anosyl-(1!3)-6-O-trityl-b-d-galactopyranoside (3K): Follow-
ing the general procedure A for glycosylation afforded 3K
as a white solid; yield: 54 mg (53%). Rf =0.5 (petroleum
ether/EtOAc, 5:5); [a]D: +46.9 (c 2.2, CHCl3). 1H NMR
(400 MHz, CDCl3): d=7.41–7.34 (m, 6H), 7.33–7.19 (m,
Adv. Synth. Catal. 2012, 354, 1489 – 1499
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Amit Kumar et al.
FULL PAPERS
1
Isopropyl 3,4-di-O-benzoyl-2-O-benzyl-a,b-l-fucopyrano-
side (5A): Following the general procedure A for glycosyla-
tion afforded 5A as a colourless solid; yield: 86%. Rf =0.5
(petroleum ether/EtOAc, 8:2); [a]D: ꢀ64.9 (c 1.1, CHCl3).
1H NMR (b-Isomer, 400 MHz, CDCl3): d=8.13 (dd, J=8.0,
1.2 Hz, 2H, Ar-H), 7.89 (dd, J=8.0, 1.0 Hz, 2H, Ar-H), 7.71
(dd, J=10.6, 4.3 Hz, 1H, Ar-H), 7.60–7.55 (m, 4H, Ar-H),
7.42–7.37 (m, 4H, Ar-H), 7.31 (dd, J=8.0, 1.8 Hz, 3.0H, Ar-
H), 7.26–7.25 (m, 3H, Ar-H), 5.68 (br d, J=3.6 Hz, 1H, 4-
H), 5.50 (dd, J=10.1, 3.6 Hz, 1H, 3-H), 5.00 (d, J=11.5 Hz,
1H, benzylic-H), 4.82 (d, J=11.6 Hz, 1H, benzylic-H), 4.75
(d, J=8.0 Hz, 1H, 1-H), 4.28–4.19 (m, 1H), 4.11–4.05 (m,
1H, 5-H), 3.97 (dd, J=10.1, 7.8 Hz, 1H, 2-H), 1.49 (d, J=
9.6, 5.5 Hz, 14H), 0.77 (d, J=6.9 Hz, 2H); H NMR (a-iso-
mer,400 MHz, CDCl3): d=7.99 (d, J=7.5 Hz, 1H, Ar-H),
7.63–7.61 (m, 2H, Ar-H), 5.51 (app d, Japp=3.6 Hz, 1H, 4-
H), 5.43 (app d, Japp=8.2 Hz, 1H, 3-H), 5.17 (d, J=3.6 Hz,
1H, 1-H), 4.52–4.48 (m, 1H, benzylic-H), 4.09–4.00 (m, ben-
zylic-H), 3.95–3.90 (m, 1H, 5-H), 3.80 (dd, J=8.2, 3.2 Hz,
1H, 2-H), 3.57–3.53 (m, 1H); 13C NMR (100 MHz, CDCl3):
d=165.8, 165.6, 138.1, 137.7, 133.2, 132.97, 132.90, 130.0,
129.9, 129.83, 129.81, 129.7, 129.69, 129.67, 128.4–127.6 (m),
127.4, 104.5 (C-1b), 93.9 (C-1a), 81.9, 77.2, 76.9, 76.2, 74.9,
73.5, 73.2, 72.9, 72.6, 71.7, 70.8, 69.1, 65.1, 48.8, 47.5, 43.4,
39.9, 34.4, 34.3, 31.8, 31.5, 25.5, 24.7, 22.8, 22.7,22.4, 22.3,
21.3, 21.1, 16.5, 16.2, 15.8, 15.1; HR-MS: m/z=623.2974,
calcd. for (C37H44NaO7) [M+Na]+: 623.2979.
1
6.2 Hz, 4H, -CH3), 1.43–139 (m, 7H); H NMR (a-Isomer,
400 MHz, CDCl3) d 8.12–8.08 (m, 0.4H, Ar-H), 7.98–7.92
(m, 0.4H, Ar-H), 5.84 (dd, J=10.4, 3.3 Hz, 1H, 3-H), 5.79
(br d, J=2.4 Hz, 1H, 4-H), 5.73 (app t, Japp=2.4, Hz, 1H,
2-H), 5.20 (d, J=3.6 Hz, 1H, 1-H), 3.80–3.78 (m, 1H, 5-H);
13C NMR (100 MHz, CDCl3): d=166.1, 165.5, 138.1, 133.2,
132.9, 129.9, 129.8–129.5 (m), 128.5–128.0 (m), 127.5, 102.3
Acknowledgements
This work was supported by the University of Konstanz and
the Fonds der Chemischen Industrie.
(C-1b), 95.6ACHTUNGTRENNUNG(C-1a), 74.5, 73.2, 72.7, 71.7, 69.2, 64.7, 31.9,
29.7, 29.6, 29.3, 23.5, 22.7, 22.2, 16.4, 14.1; HR-MS: m/z=
527.2051, calcd. for (C30H32NaO7) [M+Na]+: 527.2040.
(ꢀ)-Menthyl 3,4-Di-O-benzoyl-2-O-benzyl-a,b-l-fucopyr-
anoside [5(ꢀ)D]: Following the general procedure A for
glycosylation afforded 5(ꢀ)D as a colourless oil; yield: 72%.
Rf =0.5 (petroleum ether/EtOAc, 9:1); [a]D: ꢀ80.9 (c 1.1,
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J=6.9 Hz, 2H); H NMR (b-isomer, 400 MHz, CDCl3): d=
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