Stereoselective synthesis of 1,1′-linked α-l-lyxopyranosyl β-d-glucopyranoside, the proposed biosynthetic precursor of the FG ring system of avilamycins

Article abstract of DOI:10.1016/j.carres.2008.05.004

The non-reducing disaccharide β-d-Glcp-(1?1)-α-l-Lyxp 1 had been proposed to be an early intermediate during the biosynthesis of avilamycin A [Boll, R.; Hofmann, C.; Heitmann, B.; Hauser, G.; Glaser, S.; Koslowski, T.; Friedrich, T.; Bechthold, A. J. Biol. Chem. 2006, 281, 14756-14763]. This work describes a comparison of two strategies for the synthesis of 1 and its 2-amino-2-deoxy analog with either the glucose or the lyxose moiety acting as the glycosyl donor. The best results in terms of stereoselectivity and yield were obtained with 2,3,4-tri-O-acetyl-α-l-lyxopyranosyl trichloroacetimidate 13. Reaction of 13 with 2,3,4,6-tetra-O-acetyl-d-glucopyranose gave the disaccharide as mixture of 1β,1′α and 1β,1′β isomers in a ratio of 10:1 and a yield of 50%. Reaction of 13 and 3,4,6-tri-O-acetyl-2-azido-2-deoxy-d-glucopyranose yielded the desired 1β,1′α disaccharide as a single isomer in 72% yield. Interestingly, the formation of α-glucosides was not observed in any case, regardless of the use of glucose as glycosyl donor or acceptor.

Full text of DOI:10.1016/j.carres.2008.05.004

Available online at www.sciencedirect.com
Carbohydrate Research 343 (2008) 1612–1623
Stereoselective synthesis of 1,10-linked
a-L-lyxopyranosyl b-D-glucopyranoside, the proposed
biosynthetic precursor of the FG ring system of avilamycins
Magnus S. Schmidt and Valentin Wittmann*
Fachbereich Chemie, Universita¨t Konstanz, D-78457 Konstanz, Germany
Received 21 March 2008; received in revised form 29 April 2008; accepted 4 May 2008
Available online 8 May 2008
Abstract—The non-reducing disaccharide b-D-Glcp-(1M1)-a-L-Lyxp 1 had been proposed to be an early intermediate during the
biosynthesis of avilamycin A [Boll, R.; Hofmann, C.; Heitmann, B.; Hauser, G.; Glaser, S.; Koslowski, T.; Friedrich, T.; Bechthold,
A. J. Biol. Chem. 2006, 281, 14756–14763]. This work describes a comparison of two strategies for the synthesis of 1 and its 2-amino-2-
deoxy analog with either the glucose or the lyxose moiety acting as the glycosyl donor. The best results in terms of stereoselectivity and
yield were obtained with 2,3,4-tri-O-acetyl-a-L-lyxopyranosyl trichloroacetimidate 13. Reaction of 13 with 2,3,4,6-tetra-O-acetyl-D-
glucopyranose gave the disaccharide as mixture of 1b,10a and 1b,10b isomers in a ratio of 10:1 and a yield of 50%. Reaction of 13 and
3,4,6-tri-O-acetyl-2-azido-2-deoxy-D-glucopyranose yielded the desired 1b,10a disaccharide as a single isomer in 72% yield. Interest-
ingly, the formation of a-glucosides was not observed in any case, regardless of the use of glucose as glycosyl donor or acceptor.
Ó 2008 Elsevier Ltd. All rights reserved.
Keywords: Avilamycin A; Glycosylation; Lyxose; Non-reducing disaccharides; Trichloroacetimidates
1. Introduction
many Gram-positive bacteria, including emerging prob-
lem organisms such as vancomycin-resistant enterococci,
methicillin-resistant staphylococci, and penicillin-resis-
tant pneumococci.2 Avilamycin inhibits protein biosyn-
thesis by binding to the 50S ribosomal subunit of
bacterial ribosomes.3–5 Everninomicin (Ziracin), which
is structurally very similar to avilamycin, was under
investigation for approval by Schering-Plough. Due to
The avilamycins are oligosaccharide antibiotics isolated
from Streptomyces viridochromogenes Tu57. Along with
everninomycins, curamycins, and flambamycins, they
belong to the orthosomycin group of antibiotics.1 Avila-
mycin A, the main compound produced by S. virido-
¨
chromogenes Tu57, was shown to be active against
¨
H3CO
O
O
O
O
Cl
R
CH3O
O
CH3O
O
O
O
O
O
OCH3
O
HO
CH3
O
O
O
O
HO
OH
O
HO
O
O
O
O
HO
O
B
G
OH
Cl
A
C
D
E
H
F
avilamycin A: R = C(O)CH3
avilamycin C: R = CH(OH)CH3
*
Corresponding author. Tel.: +49 7531 88 4572; fax: +49 7531 88 4573; e-mail: mail@valentin-wittmann.de
0008-6215/$ - see front matter Ó 2008 Elsevier Ltd. All rights reserved.
doi:10.1016/j.carres.2008.05.004

M. S. Schmidt, V. Wittmann / Carbohydrate Research 343 (2008) 1612–1623
1613
side effects and its poor water solubility, further develop-
ment was stopped in 2000.2 Thus, the development of no-
vel strategies for the synthesis of new orthosomycin-type
antibiotics with improved properties is of great interest.
Recent research carried out by Bechthold and
coworkers led to the conclusion that the non-reducing
disaccharide 1 composed of b-D-glucopyranose and a-
L-lyxose is an early intermediate during the biosynthesis
of avilamycin.6 At a late stage in the biosynthesis and
after having been methylated and acylated at several hy-
droxy groups, AviX12, a radical AdoMet enzyme, seems
to be implicated in epimerizing this disaccharide subunit
to its final configuration b-D-Manp-(1M1)-a-L-Lyxp
(marked in gray in the avilamycin structure), thereby
converting avilamycin to its bioactive conformation. It
has been shown that inactivation of the gene aviE2 of
S. viridochromogenes results in the breakdown of the
avilamycin biosynthesis.7 aviE2 is a decarboxylase that
catalyzes the formation of UDP-L-lyxose, which is a bio-
synthetic step prior to the formation of 1. Thus, it can be
hypothesized that feeding experiments with 1 will lead to
resumption of the avilamycin biosynthesis of this
mutant. Feeding of analogs of 1 potentially leads to
the formation of avilamycin derivatives with improved
properties such as higher water solubility. In this report,
we describe the stereoselective synthesis of 1 as well as
the deoxy-amino analog 2 (Chart 1).
selective synthesis of non-reducing disaccharides de-
mands for control of stereochemistry at two anomeric
centers.8–21 Accordingly, many syntheses of non-reduc-
ing disaccharides lead to mixtures of stereoisomers. In
addition, yields in the formation of 1-10-linked disaccha-
rides significantly exceed 50% only in rare cases. A few
examples of their stereoselective synthesis have been
reported, including the formation of b-mannoside-
containing 1,10-disaccharides22 by use of cyclic tin ace-
tals,23,24 a,a-trehalose25 by use of intramolecular aglycon
delivery26 and the preparation of sucrose.27,28 Cook et al.
reported the stereoselective synthesis of b,b-trehalose by
using the trichloroacetimidate method.13
2. Results and discussion
For the synthesis of 1, we compared two strategies with
either the glucose or the lyxose moiety acting as the
glycosyl donor (Scheme 1). Because both b-glucopyr-
anosides and a-lyxopyranosides have a 1,2-trans config-
uration, they should be readily accessible by use of
protecting groups with neighboring group participation
such as acetyl and benzoyl groups.29–31 a-Lyxopyrano-
sides were also expected to be preferentially obtained
from benzyl protected donors due to the anomeric effect
and the steric influence of the protected hydroxy group
at the 2-position as is well known for a-mannopyrano-
sides.32,33 The selectivity at the anomeric center of the
glycosyl acceptor was more difficult to predict. From
anomeric O-alkylation reactions with gluco- and galac-
topyranoses under alkaline conditions it is known that
an equatorial anomeric OH group often reacts faster
and, therefore, b-glucosides may be selectively obtained
under kinetic control (kinetic anomeric effect).30,34,35
However, the base used for anomeric alkoxide forma-
tion, chelation control, solvent, and reaction tempera-
Non-reducing disaccharides are known in nature, with
sucrose (b-D-Fruf-(2M1)-a-D-Glcp) and trehalose (a-D-
Glcp-(1M1)-a-D-Glcp) being prominent examples. In
contrast to conventional glycoside syntheses, the stereo-
OH
OH
O
O
OH
OH
OH
OH
OH
O
OH
O
HO
HO
HO
HO
O
O
OH
NH2
1
2
ture also play
a role in determining anomeric
Chart 1.
stereoselectivity. Anomeric O-alkylation reactions of
OH
O
OH
OH
OH
O
HO
HO
O
OH
1
OAc
O
OR'
OR
O
OR
O
OR'
OR'
AcO
AcO
O
RO
RO
OR
OR
+
+
OH
HO
AcO
OR
Cl3C
O
O
CCl3
NH
R = Ac, Bn
R' = Ac, Bn
R = Ac, Bn
NH
Scheme 1. Retrosynthetic strategies investigated for the synthesis of 1,10-disaccharide 1.

1614
M. S. Schmidt, V. Wittmann / Carbohydrate Research 343 (2008) 1612–1623
lyxose have not yet been reported and were not
clearly predictable. TMSOTf-catalyzed glycosylation of
a
NH2
OR
OAc
H2N
O
O
OR
OR
OAc
OAc
2,3,4,6-tetra-O-benzyl-D-mannose with
a
mannosyl
RO
HO
AcOH, THF
trichloroacetimidate, however, predominantly led to an
10 R = H
11 R = Ac
Ac2O, pyr
85%
12
72%
OAc
a-glycoside.22
L- and D-Lyxose are both commercially avail-
able. However, because L-lyxose is significantly more
expensive, initial experiments were carried out with the
D-isomer. Although it was not expected that the stereo-
selectivities for the formation of the diastereomeric
disaccharides b-D-Glcp-(1M1)-a-L-Lyxp and b-D-Glcp-
(1M1)-a-D-Lyxp are the same due to the possible occur-
rence of matched/mismatched pairs,36 at least some
valuable lessons were expected to be learned from these
experiments.
O
Cl3CCN, K2CO3
OAc
OAc
CH2Cl2
83%
Cl3C
O
13
NH
b
OH
1.5% HCl in
MeOH, rfl
BnBr, KOH,
dioxane, rfl
O
OH
OH
MeO
10
14
80% AcOH,
1M HCl, 90 °C
OBn
OBn
O
2.1. Preparation of glycosyl donors and acceptors
O
OBn
OBn
OBn
OBn
MeO
HO
82% (3 steps)
Glucose derivatives 3,37 4,38 5,39 6, and 738 and D-lyxose
derivatives 840,41 and 942,43 were obtained according to
published procedures or were commercially available
(6, Chart 2). The synthesis of the required L-lyxose
derivatives is shown in Scheme 2. Peracetylated L-lyxo-
pyranose 1144 obtained from L-lyxose 10 by treatment
with acetic anhydride and pyridine was selectively
deprotected at the anomeric center using the method
15
16
OBn
O
OBn
OBn
Cl3CCN, NaH
CH2Cl2
Cl3C
O
NH
17
Scheme 2. Synthesis of L-lyxose derivatives 13 (a) and 17 (b).
´ˇ39
of Zhang and Kovac to give 12. Reaction with trichlo-
roacetonitrile and potassium carbonate45 gave a-trichlo-
roacetimidate 13 in a yield of 83%. Methyl glycoside
14,46,47 obtained by Fischer glycosylation42 of L-lyxose
10, was further processed similar to a procedure re-
ported for the preparation of the D-lyxo isomer of
16.43 Thus, 14 was benzylated with benzyl bromide
and KOH followed by cleavage of the crude methyl gly-
coside 15 under acidic conditions to give 16 in a yield of
82%. Compound 16 was converted to trichloroacetimi-
date 17, which turned out to be too reactive to be either
purified by column chromatography or stored for a pro-
longed time. Thus, it was freshly prepared before each
experiment and immediately used without further
purification.
dichloromethane under varying reaction conditions
(Scheme 3). As expected, the formation of a-glucosides
was not observed in any case. The glycosidic linkage
at the D-lyxose was formed as a mixture of a- and b-ano-
mers. Table 1 gives an overview of the ratio of products
18 (1b,10a-configuration) and 19 (1b,10b-configuration).
The use of TMSOTf gave low yields and low stereoselec-
tivities regardless of the amount of Lewis acid added
(entries 1–3). Switching to tin tetrachloride slightly
improved yield and stereoselectivity (entries 4–6). Best
results were obtained with BF3ꢀOEt2 (entries 7–11) with
yields up to 45% and an 18/19 ratio of 4:1. Ratios of
1
products 18/19 were determined from H NMR spectra
of the isolated product mixtures.
The anomeric configurations of the products 18 and 19
were determined by NMR spectroscopy. Whereas the
b-configuration of the glucose residues could be readily
2.2. Glycosylations with glucosyl donors
3
deduced from JH-1,H-2 coupling constants (18: 8.4 Hz,
To explore suitable reaction conditions for the forma-
tion of 1,10-disaccharides, glucosyl trichloroacetimidate
3 was reacted with acetylated D-lyxose acceptor 8 in
1
0
0
19: 8.0 Hz), JC-1 ;H-1 coupling constants obtained from
non-decoupled heteronuclear single quantum coherence
(HSQC) NMR spectra were used for determination of
the lyxose configuration. It is well established that a-
OAc
O
OR
O
1
OR
O
mannosides and a-rhamnosides have higher JC-1,H-1
OR
AcO
AcO
RO
RO
values (usually higher than 170 Hz) than the corre-
sponding b-glycosides (usually lower than 170 Hz),48–50
and it can be assumed that this trend is also applicable
OR
OH
R
R'
HO
O
CCl3
5 R = Ac, R' = OAc
6 R = Bn, R' = OBn
7 R = Ac, R' = N3
8 R = Ac
9 R = Bn
NH
3 R = OAc
4 R = N3
to lyxose. Thus, we assigned the product with the
1
0
0
JC-1 ;H-1 value of 174.1 Hz to be a-lyxoside 18 and that
with the value of 170.2 Hz to be the b-lyxoside 19.
Chart 2.

M. S. Schmidt, V. Wittmann / Carbohydrate Research 343 (2008) 1612–1623
1615
OR
O
OR
OR
OAc
1'
O
AcO
AcO
1
O
OAc
OAc
O
OR
O
OR
18 R = Ac
20 R = Bn
Lewis acid
AcO
AcO
OR
+
HO
AcO
DCM
0 ˚C → rt
O
CCl3
NH
OR
OAc
8 R = Ac
9 R = Bn
OR
O
OR
AcO
AcO
3
1'
1
O
O
OAc
19 R = Ac
21 R = Bn
Scheme 3. Synthesis of D-lyxopyranosyl b-D-glucopyranosides 18–21.
To study the influence of the protecting groups of the
glycosyl acceptor, trichloroacetimidate 3 was also re-
acted with benzylated lyxose acceptor 9 (Scheme 3).
As can be seen from the results in Table 2, only the
use of tin tetrachloride as Lewis acid resulted in product
formation, this time, however, with an increased
Table 1. Results of glycosylation reactions of 3 and 8 according to
Scheme 3
Entry
3
8
Lewis
Lewis acid Yield 18/19
(equiv) (equiv) acid
(equiv)
TMSOTf 0.1
TMSOTf 0.5
(%)
1
2
1
1
1
1.1
1.1
1.1
1
1
1
1.05
1.05
1.05
1
1
1
1.05
1.05
1.05
1.05
1.05
19
17
24
31
31
31
39
31
45
40
36
2:1
2:1
3
TMSOTf
SnCl4
SnCl4
1
2:1
4
5
6
7
0.1
0.5
1
3.5:1
3.5:1
3.5:1
4:1
Table 2. Results of glycosylation reactions of 3 and 9 according to
Scheme 3
SnCl4
Entry
3
9
Lewis
Lewis acid Yield 20/21
BF3ꢀOEt2 0.1
BF3ꢀOEt2 0.25
BF3ꢀOEt2 0.5
(equiv) (equiv) acid
(equiv)
TMSOTf 0.1
BF3ꢀOEt2 0.1
SnCl4 0.1
(%)
8
4:1
1
2
3
1.4
1.4
1.4
1
1
1
—
—
45
—
—
10:1
9
4:1
10
11
1
1
BF3ꢀOEt2
BF3ꢀOEt2
1
2
4:1
4:1
a
OBn
O
OBn
OAc
O
OAc
O
OBn
O
OBn
OBn
AcO
AcO
AcO
AcO
O
OBn
+
HO
AcO
AcO
O
CCl3
NH
O
CCl3
NH
9
3
LA
O
LA
OAc
O
Coupling constants for 23 [Hz]:
3JNH,1 7.6; 3J1,2 4.5; 3J2,3 3.0;
3J3,4 3.4; 3J4,5a 1.4; 3J4,5b 1.5;
1JC-1,H-1 164.9
AcO
OBn
–
OBn
AcO
OH
Cl3C
NH OBn
OBn
OBn
LA
AcO
O
5
Cl3C
O
O
NH
OBn
22
23
b
O
OBn
O
OBn
OBn
O
OBn
OBn
OBn
Cl3C
NH2
OBn
OBn
LA
OBn
O
HO
23
24
9
Scheme 4. Possible mechanisms for the formation of 23. LA = Lewis acid.

1616
M. S. Schmidt, V. Wittmann / Carbohydrate Research 343 (2008) 1612–1623
stereoselectivity of 20/21 = 10:1. Using the stronger Le-
wis acids TMSOTf and BF3ꢀOEt2, respectively, no disac-
charide formation was observed. Instead, 2,3,4-tri-O-
benzyl-b-D-lyxopyranosyl trichloroacetamide 23, which
2.3. Glycosylations with lyxosyl donors
Scheme 6 shows the results obtained with L-lyxosyl tri-
chloroacetimidates 13 and 17, and tetra-O-acetyl-glucose
5. Reaction of acetylated L-lyxosyl donor 13 gave two
isomeric disaccharides in a ratio of 10:1, and a combined
yield of 50%. As expected, the major isomer was 1b,10a
compound 25. To our surprise, however, the minor iso-
mer turned out to be 1b,10b compound 26. Isomers with
an a-glucose configuration could not be observed. This
indicates on one hand that the kinetic anomeric effect,
that is, the higher reactivity of the b-anomer of 5 com-
pared to the a-anomer, is very effective for this pair of
glycosyl donor and acceptor. On the other hand, it
becomes obvious that the stereochemistry at the lyxose
moiety is not fully controlled either by the neighboring
group effect of the 2-O-acetyl group or by the anomeric
effect both of which would favor a-lyxose configuration.
In this respect, it is worth mentioning that reaction of 13
with the more nucleophilic glycosyl acceptor tetra-O-
benzyl-glucose 6 leads to a ratio of the 1b,10a and
1b,10b isomers of only 3:1 (data not shown), which can
be explained by an increased SN2 character of the reac-
tion. Attempts to react glucose acceptor 5 with the reac-
tive benzylated L-lyxosyl donor 17 were unsuccessful,
even with the mild Lewis acid tin tetrachloride. In this
case, the trichloroacetimidate-to-trichloroacetamide
rearrangement was too fast leading to formation of the
enantiomer of 23 in approximately 60% yield (Scheme
6). The mixture of 25 and 26 was separated by HPLC
1
according to NMR analysis exists in a C4 conforma-
tion, was isolated in a yield of 70%. The formation of
23 may be rationalized by nucleophilic attack of tri-O-
benzyl-lyxose 9 to trichloroacetimidate 3 in a Lewis
acid-catalyzed process outlined in Scheme 4a followed
by release of tetra-O-acetyl-glucose 5 and rearrangement
of trichloroacetimidate 22. Such rearrangements of tri-
chloroacetimidates to trichloroacetamides are well
known in carbohydrate chemistry and recently have
been applied in the preparation of glycosyl amines.51
More likely, however, is the Lewis acid-promoted for-
mation of lyxosyl cation 24 from either reactive 9 or
by cleavage of intermediately formed disaccharide 20
(or 21) and subsequent reaction with trichloroacetamide
to yield 23 (Scheme 4b). Trichloroacetamide is produced
during the glycosylation reaction or hydrolysis of 3 with
the water stemming from activation of 9. To examine
the mechanism depicted in Scheme 4b, tribenzyl lyxose
9 was reacted with trichloroacetamide and BF3ꢀOEt2
(0.1 equiv) under the same reaction conditions employed
above. After 12 h, lyxopyranosyl trichloroacetamide 23
was obtained in 60% yield, supporting the postulated
mechanism.
We next turned our attention to glycosylation reac-
tions with lyxose acceptors having the desired L-config-
uration (Scheme 5). Thus, glucosyl trichloroacetimidate
3 was treated with 12 and 16, respectively, and the Lewis
acid that turned out to be best for reactions with the cor-
responding D-isomers. Reaction of 3 and acetylated
acceptor 12 with BF3ꢀOEt2 (0.1 equiv) gave the disac-
charides 25 and 26 in an improved yield of 52%, how-
ever, with a reduced stereoselectivity of 25/26 = 1.5:1.
Glycosylation of benzylated acceptor 16 with trichloro-
acetimidate 3 and SnCl4 (0.03 equiv) resulted in disac-
charides 27 and 28 in a yield of 48% and a 1b,10a/
1b,10b ratio of 7:1.
´
and the pure isomers were deacetylated under Zemplen
conditions to give a-L-lyxopyranosyl b-D-glucopyran-
oside 1 and its 1b,10b isomer 29 in quantitative yields.
2.4. Preparation of amino-substituted disaccharide 2
The preparation of amino-deoxy disaccharide 2 is
shown in Scheme 7. When 2-azido-glucopyranosyl tri-
chloroacetimidate 4 was reacted with lyxose acceptor
12, the desired 1b,10a isomer 30 was formed in 41% yield
OR
O
OR
OR
OAc
O
1'
AcO
AcO
1
O
OAc
OAc
O
OR
a or b
25 R = Ac
27 R = Bn
AcO
AcO
O
OR
OR
+
HO
AcO
CH2Cl2
O
CCl3
NH
0 ˚C → rt
OAc
12 R = Ac
16 R = Bn
OR
O
O
OR
OR
AcO
AcO
3
1'
1
O
OAc
26 R = Ac
28 R = Bn
Scheme 5. Synthesis of L-lyxopyranosyl b-D-glucopyranosides 25–28. Reagents: (a) 3, 12 (1.1 equiv), BF3ꢀOEt2 (0.1 equiv) (52%, 25/26 = 1.5:1); (b) 3
(1.4 equiv), 16, SnCl4 (0.03 equiv) (48%, 27/28 = 7:1).

M. S. Schmidt, V. Wittmann / Carbohydrate Research 343 (2008) 1612–1623
1617
OAc
O
OAc
OAc
Cl3C
O
13
NH
25 + 26
BF3·OEt2 (0.1 equiv)
CH2Cl2, 0 °C → rt
50%
(10 : 1)
OAc
O
AcO
AcO
OH
OAc
OBn
5
O
OBn
OBn
Cl3C
O
NH
17
ent-23
SnCl4 (0.03 equiv)
CH2Cl2, 0 °C → rt
60%
NaOMe, MeOH
quant.
25
26
1
OH
OH
NaOMe, MeOH
quant.
O
O
OH
OH
HO
O
HO
OH
29
Scheme 6. Glycosylations with L-lyxosyl donors 13 and 17.
in addition to small amounts of the 1b,10b isomer
(1b,10a/1b,10b = 10:1). Using 2-azido-2-deoxy-glucose 7
and L-lyxosyl trichloroacetimidate 13, disaccharide 30
was obtained as single isomer in a yield of 72%. In both
cases, the formation of an a-glucosidic linkage was not
observed. Finally, 30 was deacetylated followed by
reduction of the azide group by catalytic hydrogenation
to give disaccharide 2 in quantitative yields.
OAc
O
AcO
AcO
BF3·OEt2 (0.1 equiv)
OAc
O
+
OAc
OAc
N3
O
CH2Cl2 , 0 ˚C → rt
CCl3
NH
HO
OAc
12
41% (+ 4% 1β,1'β-isomer)
4
O
OAc
OAc
OAc
O
1'
AcO
AcO
1
O
N3
OAc
O
OAc
O
OAc
30
OAc
BF3·OEt2 (0.1 equiv)
AcO
AcO
+
OH
Cl3C
O
N3
CH2Cl2 , 0 ˚C → rt
13
NH
7
72%
OH
O
OH
OH
O
OH
NaOMe, MeOH
quant.
H2, Pd-C, MeOH
HO
HO
2
30
O
quant.
N3
31
Scheme 7. Synthesis of a-L-lyxopyranosyl 2-amino-2-deoxy-b-D-glucopyranoside 2.

1618
M. S. Schmidt, V. Wittmann / Carbohydrate Research 343 (2008) 1612–1623
3. Conclusions
RP-HPLC was performed on a LC-20A prominence sys-
tem from Shimadzu. Used columns: Nucleosil 100-5 C-
In summary, two strategies for the synthesis of non-
reducing disaccharides 1 and 2 were compared with
either the glucose or the lyxose moiety acting as the gly-
cosyl donor. For both 1 and 2 the application of lyxosyl
trichloroacetimidate 13 turned out to be superior over
the use of a glucosyl donor in terms of stereoselectivity
and yield. Using BF3ꢀOEt2 as the Lewis acid, reaction
of 13 and tetra-O-acetyl-glucopyranose 5 gave protected
disaccharides 25 and 26 in a ratio of 10:1 and a yield of
50%. Reaction of 13 with 2-azido-2-deoxy-glucopyra-
nose 7 resulted in the formation of disaccharide 30 as
a single stereoisomer in a yield of 72%. Interestingly,
the formation of a-glucosides was not observed in any
case, regardless of the use of glucose as glycosyl donor
or acceptor whereas reaction of neighboring-group ac-
tive lyxosyl donor 13 only in one case led to exclusive
formation of a 1,2-trans-glycoside (30). Both disaccha-
rides b-D-Glcp-(1M1)-a-L-Lyxp and its 2-azido-2-deoxy
analog were deprotected in quantitative yields.
Currently, 1 and 2 are being subjected to feeding exper-
iments with a S. viridochromogenes strain with inacti-
vated aviE2 gene and results will be reported in due
course.
18 (analytical: 4 ꢁ 250 mm, flow 0.9 mL minꢂ1, semi-
preparative 8 ꢁ 250 mm, flow 3 mL minꢂ1
)
from
Knauer. Eluent: gradient of water with 0.1% TFA (elu-
ent A) in acetonitrile with 0.1% TFA (eluent B).
4.2. 2,3,4-Tri-O-acetyl-a/b-L-lyxopyranose (12)
To a solution of ethylenediamine (0.5 mL, 8.8 mmol) in
tetrahydrofuran (50 mL), acetic acid (0.5 mL, 7.5 mmol)
was added slowly upon which a white precipitate
occurred. Then 1,2,3,4-tetra-O-acetyl-a/b-L-lyxopyra-
nose 1144 (3.5 g, 11 mmol), which had been prepared
from L-lyxose 10 by treatment with Ac2O and pyridine
according to a published procedure,52 was added and
the mixture was stirred for 16 h at room temperature.
After addition of water (50 mL) the precipitate dissolved
completely. The mixture was extracted with CH2Cl2
(3 ꢁ 50 mL). The combined organic layer was washed
with 1 N HCl (50 mL), satd aq NaHCO3 (50 mL), and
water (50 mL), dried (MgSO4), and the solvent was
evaporated. Purification by FC (petroleum ether–EtOAc
3:2) yielded 12 (2.2 g, 72%) as a colorless oil. Prepara-
tion of the D-lyxo isomer of 12 had been reported
earlier.40,41
Rf = 0.28 (petroleum ether–EtOAc 1:1); 1H NMR
(250 MHz, CDCl3): d 5.40 (dd, J = 8.3, 3.6, 1H, H-3),
5.20 (‘t’, J = 3.6, 1H, H-2), 5.13–5.06 (m, 2H, H-1 and
H-4), 3.91–3.86 (m, 2H, H-5a, H-5b), 2.12 (s, 3H,
C(O)CH3), 2.08 (s, 3H, C(O)CH3), 2.06 (s, 3H,
C(O)CH3); (MALDI-TOF-MS): m/z 299.2 [M+Na]+,
315.2 [M+K]+; Anal. Calcd for C11H16O8: C, 47.83;
H, 5.84. Found: C, 48.17; H, 5.79.
4. Experimental
4.1. General methods
TLC was carried out on Silica Gel 60 F254 (Merck, layer
thickness 0.2 mm) with detection by UV light
(k = 254 nm) and/or by charring with 15% sulfuric acid
in ethanol. Flash column chromatography (FC) was
performed on Merck Silica Gel 60 (0.040–0.063 mm)
4.3. 2,3,4-Tri-O-acetyl-a-L-lyxopyranosyl trichloroace-
timidate (13)
with the solvent systems specified. H NMR and 13C
1
NMR spectra were recorded on Bruker AC 250 and
Bruker Avance DRX 600 instruments. Chemical shifts
are reported in ppm relative to solvent signals: CDCl3:
dH = 7.26 ppm, dC = 77.0 ppm; DMSO-d6: dH =
2.49 ppm, dC = 39.7 ppm; CD3OD: dH = 4.78 ppm,
dC = 49.3 ppm. Signals were assigned by first-order
analysis and, when feasible, assignments were supported
by two-dimensional 1H, 1H and 1H, 13C correlation
To a solution of 12 (0.5 g, 1.8 mmol) and trichloroaceto-
nitrile (0.63 mL, 6 mmol) in dry CH2Cl2 (10 mL) K2CO3
(0.63 g, 4.6 mmol) was added and the mixture was stir-
red for 1.5 h. The reaction mixture was filtered, concen-
trated, and the residue was purified by FC (petroleum
ether–EtOAc 2:1) to give 13 as colorless oil (0.63 g,
83%). The preparation of the D-lyxo isomer of 13 with
trichloroacetonitrile–DBU in a yield of 68% had been
reported earlier.41 Rf = 0.33 (petroleum ether–EtOAc
1
spectroscopy. JH–C coupling constants were obtained
from non-decoupled heteronuclear single quantum
coherence (HSQC) NMR spectra. 3JH–H and 1JH–C cou-
pling constants are reported in Hz. Within disaccha-
rides, signals of lyxose residues are labeled with
primed numbers. MALDI-TOF mass spectra were
recorded on a Bruker Biflex III spectrometer with
a-cyano-4-hydroxy-cinnamic acid (CHCA) as the
matrix. ESI-IT mass spectra were recorded on a Bruker
Esquire 3000 spectrometer. Elemental analysis was per-
formed on an elementar CHNS vario EL instrument.
1
2:1); H NMR (600.1 MHz, CDCl3): d 8.75 (br s, 1H,
NH), 6.18 (d, J = 2.5, 1H, H-1), 5.46–5.37 (m, 2H,
H-2, H-3), 5.32–5.28 (m, 1H, H-4), 4.06 (dd, J = 11.3,
5.2, 1H, H-5a), 3.82 (dd, J = 11.3, 9.6, 1H, H-5b), 2.16
(s, 3H, C(O)CH3), 2.07 (s, 3H, C(O)CH3), 2.04 (s, 3H,
C(O)CH3); 13C NMR (150.9 MHz, CDCl3): d 169.7
(C(O)CH3), 169.6 (C(O)CH3), 160.2 (C(O)CH3), 94.6
(C-1), 67.8 (C-2), 68.2 (C-3), 66.0 (C-4), 62.0 (C-5),
21.0 (C(O)CH3), 20.8 (C(O)CH3), 20.7 (C(O)CH3);

M. S. Schmidt, V. Wittmann / Carbohydrate Research 343 (2008) 1612–1623
1619
1JH-1,C-1 = 179.9; (MALDI-TOF-MS): m/z 443.3
[M+Na]+, 459.2 [M+K]+; Anal. Calcd for C13H16-
Cl3NO8: C, 37.12; H, 3.83; N, 3.33. Found: C, 37.59;
H, 4.28; N, 3.22.
dry CH2Cl2 (0.25 mL) was added and the mixture was
stirred for 14 h at rt. The mixture was diluted with
CH2Cl2 (20 mL), washed with satd aq NaHCO3
(2 ꢁ 20 mL) and with brine (1 ꢁ 20 mL), dried
(MgSO4), and concentrated. Purification by FC (petro-
leum ether–EtOAc 2:1) yielded a 4:1 mixture of 18 and
19 (49 mg, 45%) as a colorless oil. Rf = 0.19 (petroleum
ether–EtOAc 1:1); 1H NMR (600.1 MHz, CDCl3): 18: d
5.27 (dd, J = 9.6, 3.6, 1H, H-30), 5.20–5.16 (m, 2H, H-3,
H-40), 5.10–5.05 (m, 2H, H-4, H-20), 5.01 (dd, J = 9.6,
8.4, 1H, H-2), 4.93 (d, J = 2.4, 1H, H-10), 4.66 (d,
J = 8.4, 1H, H-1), 4.23 (dd, J = 12.6, 4.8, 1H, H-6a),
4.08 (dd, J = 12.6, 2.4, 1H, H-6b), 3.84–3.80 (m, 2H,
H-5a0, H-5b0), 3.70 (m, 1H, H-5), 2.12 (s, 3H,
C(O)CH3), 2.08 (s, 6H, C(O)CH3), 2.05 (s, 3H,
C(O)CH3), 2.02 (s, 3H, C(O)CH3), 2.01 (s, 3H,
C(O)CH3), 2.00 (s, 3H, C(O)CH3); 19: d 5.42 (‘t’,
J = 9.8, 1H, H-3), 5.32 (dd, J = 9.5, 3.5, 1H, H-30),
4.76 (d, J = 8.0, 1H, H-1), 3.68 (ddd, J = 10.2, 5.2,
2.4, 1H, H-5), 3.53 (dd, J = 12.6, 3.3, 1H, H-5a0), 2.09
(s, 3H, C(O)CH3), 2.05 (s, 3H, C(O)CH3), 2.03 (s, 3H,
C(O)CH3), 2.00 (s, 3H, C(O)CH3); 13C NMR
4.4. 2,3,4-Tri-O-benzyl-a/b-L-lyxopyranose (16)
Under a N2 atmosphere, acetyl chloride (0.7 mL,
9.8 mmol) was dissolved in MeOH (30 mL). L-Lyxose
10 (2 g, 13.3 mmol) was added and the reaction mixture
was stirred under reflux for 2 h. After neutralization
with 0.5 M sodium methylate solution in MeOH the
reaction mixture was concentrated. The residue was dis-
solved in dioxane (15 mL) and suspended with KOH
(9 g, 0.16 mol) under reflux. Benzyl bromide (16 mL,
0.13 mol) was added dropwise and after 4 h under reflux
the reaction mixture was concentrated. After addition of
water (50 mL) the mixture was extracted with EtOAc
(3 ꢁ 50 mL). The combined organic layers were dried
(MgSO4) and the solvent was evaporated. The residue
was added to 80% aq AcOH (90 mL). After addition
of 1 N HCl (35 mL), the mixture was heated for 10 h
at 90 °C. Then the mixture was extracted with CH2Cl2
(2 ꢁ 100 mL). The combined organic layers were
washed with satd aq NaHCO3 (2 ꢁ 100 mL), dried
(MgSO4), and the solvent was evaporated. Purification
by FC (petroleum ether–EtOAc 3:1) yielded 16 (4.6 g,
82%) as a colorless oil. Preparation of the D-lyxo isomer
of 16 by similar procedures had been reported ear-
lier.42,43 Rf = 0.25 (petroleum ether–EtOAc 2:1); 1H
NMR (600.1 MHz, CDCl3): a-anomer: d 7.39–6.26 (m,
15H, Ph), 5.18 (dd, J = 10.1, 2.1, 1H, H-1), 5.01 (br d,
J = 10.1, 1H, OH), 4.77–4.48 (m, 6H, CH2), 4.08 (dd,
J = 12.6, 1.2, 1H, H-5a), 3.92–3.90 (m, 1H, H-3), 3.88
(‘t’, J = 3, 1H, H-2), 3.63–3.61 (m, 1H, H-5b); b-ano-
mer: d 7.39–6.26 (m, 15H, Ph), 5.12 (d, J = 2.1, 1H,
H-1), 4.77–4.48 (m, 6H, CH2), 3.91 (m, 1H, H-3), 3.85
(m, 1H, H-4), 3.81 (m, 2H, H-5a, H-5b), 3.73 (‘t’,
J = 3.6, H-2); 13C NMR (150.9 MHz, CDCl3): a-ano-
mer: d 138.6 (quaternary C), 138.5 (quaternary C),
138.3 (quaternary C), 128.5–127.4 (aromatic C), 93.0
(150.9 MHz, CDCl3): 18:
d
170.7–169.6 (7 ꢁ s,
C(O)CH3), 99.9 (C-1), 98.4 (C-10), 72.5 (C-3), 72.3 (C-
5), 71.1 (C-2), 69.1 (C-20), 68.0 (C-4), 67.9 (C-30), 66.5
(C-40), 61.7 (C-6), 60.6 (C-50), 20.9–20.7 (s,
1
1
0
0
7 ꢁ C(O)CH3); JH-1 ;C-1 ¼ 174:1; JH-1,C-1 = 166.3; 19:
1
d 96.0 (C1), 92.9 (C10); JH-1 ;C-1 ¼ 170:2; JH-1,C-1
=
1
0
0
166.3; (MALDI-TOF-MS): m/z 629.2 [M+Na]+, 645.2
[M+K]+; Anal. Calcd for C25H34O17: C, 49.51; H,
5.65. Found: C, 49.12; H, 6.04.
4.6. 2,3,4-Tri-O-benzyl-a-D-lyxopyranosyl 2,3,4,6-tetra-
O-acetyl-b-D-glucopyranoside (20) and 2,3,4-tri-O-benz-
yl-b-D-lyxopyranosyl 2,3,4,6-tetra-O-acetyl-b-D-gluco-
pyranoside (21)
Compounds 337 (246 mg, 0.5 mmol) and 942,43 (150 mg,
0.35 mmol) were dissolved at 0 °C in dry CH2Cl2
(2 mL). A solution of SnCl4 (1 M in CH2Cl2, 35 lL,
0.035 mmol) was added and the mixture was stirred
for 20 h at rt. The mixture was diluted with CH2Cl2
(20 mL), washed with satd aq NaHCO3 (2 ꢁ 20 mL)
and with brine (1 ꢁ 20 mL), dried (MgSO4), and the sol-
vent was evaporated. Purification by FC (petroleum
ether–EtOAc 2:1) yielded a 10:1 mixture of 20 and 21
(120 mg, 45%) as a colorless oil. Rf = 0.34 (petroleum
(C-1), 76.6 (C-3), 74.4 (C-4), 72.9 (C-2), 74.5 (CH2Ph),
1
74.2 (CH2Ph), 74.2 (CH2Ph), 56.6 (C-5); JH-1,C-1
=
1
170.0; b-anomer: d 93.9 (C-1); JH-1,C-1 = 165.9; (MAL-
DI-TOF-MS): m/z 443.3 [M+Na]+, 459.2 [M+K]+;
Anal. Calcd for C26H28O5: C, 74.26; H, 6.71. Found:
C, 73.87; H, 6.89.
1
ether–EtOAc 3:1); H NMR (600.1 MHz, CDCl3): 20:
4.5. 2,3,4-Tri-O-acetyl-a-D-lyxopyranosyl 2,3,4,6-tetra-
O-acetyl-b-D-glucopyranoside (18) and 2,3,4-tri-O-acetyl-
b-D-lyxopyranosyl 2,3,4,6-tetra-O-acetyl-b-D-glucopy-
ranoside (19)
d 7.37–7.27 (m, 15H, Ph), 5.16 (‘t’, 9.6, 1H, H-3), 5.08
(‘t’, J = 9.6, 1H, H-4), 4.97 (dd, J = 9.6, 8.4, 1H, H-2),
4.86 (d, J = 3.6, 1H, H-10) 4.75–4.77 (m, 6H, CH2),
4.64–4.61 (m, 1H, H-1), 4.26 (dd, J = 12.6, 4.8, 1H,
H-6a), 4.09 (dd, J = 12.6, 2.4, 1H, H-6b), 3.93 (m, 1H,
H-40), 3.81 (dd, J = 8.4, 3.6, 1H, H-30), 3.76 (m, 2H,
H-5a0, H-5b0), 3.63 (‘t’, J = 3.6, 1H, H-20), 3.70 (m,
1H, H-5), 2.06 (s, 3H, C(O)CH3), 2.02 (s, 3H,
Compounds 337 (100 mg, 0.2 mmol) and 840,41 (60 mg,
0.21 mmol) were dissolved at 0 °C in dry CH2Cl2
(2 mL). A solution of BF3ꢀOEt2 (11 lL, 0.1 mmol) in

1620
M. S. Schmidt, V. Wittmann / Carbohydrate Research 343 (2008) 1612–1623
C(O)CH3), 2.00 (s, 3H, C(O)CH3), 1.83 (s, 3H,
C(O)CH3); 13C NMR (150.9 MHz, CDCl3): 20: d
170.3 (C(O)CH3), 169.4 (C(O)CH3), 169.1 (C(O)CH3),
169.0 (C(O)CH3), 138.6 (quaternary C), 138.5 (quater-
nary C), 138.2 (quaternary C), 128.5–127.7 (aromatic
C), 100.6 (C-10), 99.8 (C-1), 78.7 (C-30), 74.8 (C-20),
74.7 (C-40), 72.8 (C-3), 72.1 (C-5), 71.4 (C-2), 68.1 (C-
4), 62.3 (C-50), 61.8 (C-6), 20.8 (s C(O)CH3), 20.6
(C(O)CH3), 20.6 (C(O)CH3), 20.5 (C(O)CH3);
4.8.2. Method b. Compounds 13 (970 mg, 2.31 mmol)
and 539 (730 mg, 2.1 mmol) were dissolved at 0 °C in
dry CH2Cl2 (10 mL). BF3ꢀOEt2 (29 lL, 0.23 mmol)
was added and the mixture was stirred for 18 h at rt.
The mixture was diluted with CH2Cl2 (20 mL), washed
with satd aq NaHCO3 (2 ꢁ 20 mL) and with brine
(1 ꢁ 20 mL), dried (MgSO4), and the solvent was
evaporated. Purification by FC (petroleum ether–EtOAc
2:1) yielded a 10:1 mixture of 25 and 26 (640 mg, 50%)
as a white solid. Rf = 0.23 (petroleum ether–EtOAc
3:2); (MALDI-TOF-MS): m/z 629.3 [M+Na]+, 645.3
[M+K]+; Anal. Calcd for C25H34O17: C, 49.51; H,
5.65. Found: C, 49.80; H, 6.10.
1
1
0
0
JH-1 ;C-1 ¼ 170:0; JH-1,C-1 = 160.6; 21: d 99.8 (C-1),
1
1
95.5 (C10); JH-1 ;C-1 ¼ 164:2; JH-1,C-1 = 160.8; (MAL-
DI-TOF-MS): m/z 773.4 [M+Na]+, 789.4 [M+K]+;
Anal. Calcd for C40H46O14: C, 63.99; H, 6.18. Found:
C, 63.57; H, 6.04.
0
0
The diastereoisomers 25 and 26 were separated by
RP-HPLC (40–90% B over 30 min).
4.7. N-(2,3,4-Tri-O-benzyl-b-D-lyxopyranosyl)-trichloro-
acetamide (23)
Compound 25: RP-HPLC (semi-preparative column):
tR = 7.6 min; 1H NMR (600.1 MHz, CDCl3): d 5.32 (dd,
1H, J = 3.0, 2.4, H-20), 5,23 (ddd, J = 9.9, 9.8, 5.6, 1H,
H-40), 5.19 (dd, J = 9.9, 3.3, 1H, H-30), 5.22 (‘t’,
J = 9.4, 1H, H-3) 5.13 (‘t’, J = 9.6, 1H, H-4), 5.12 (d,
J = 2.2, 1H, H-10), 5.09 (dd, J = 9.8, 8.2, 1H, H-2),
4.81 (d, J = 7.8, 1H, H-1), 4.26 (dd, J = 12.6, 4.8, 1H,
H-6a), 4,13 (dd, J = 12.6, 2.4, 1H, H-6b), 3.93 (dd,
J = 10.2, 5.4, 1H, H-5a0), 3.72 (m, 1H, H-5), 3.54 (‘t’,
J = 10.2, 1H, H-5b0), 2.10 (s, 6H, C(O)CH3), 2.07 (s,
3H, C(O)CH3), 2.03 (s, 3H, C(O)CH3), 2.02 (s, 3H,
C(O)CH3), 2.01 (s, 3H, C(O)CH3), 2.00 (s, 3H,
C(O)CH3); 13C NMR (150.9 MHz, CDCl3): d 170.8
(C(O)CH3), 170.4 (C(O)CH3), 170.0 (C(O)CH3), 169.6
(C(O)CH3), 169.4 (C(O)CH3), 169.4 (C(O)CH3), 168.8
(C(O)CH3), 95.0 (C-1), 94.0 (C-10), 72.6 (C-30), 72.1
(C-5), 70.8 (C-2), 68.7 (C-20), 67.9 (C-3), 67.8 (C-4),
66.4 (C-40), 61.5 (C-6), 60.0 (C-50), 20.8 (C(O)CH3),
20.8 (C(O)CH3), 20.7 (C(O)CH3), 20.7 (C(O)CH3),
20.6 (C(O)CH3), 20.6 (C(O)CH3), 20.5 (C(O)CH3);
To a solution of 2,3,4-tri-O-benzyl-D-lyxopyranose
942,43 (200 mg, 0.48 mmol) in dry CH2Cl2 (3 mL) was
added BF3ꢀOEt2 (6 lL, 0.048 mmol) and trichloroaceta-
mide (81 mg, 0.5 mmol). The reaction mixture was stir-
red for 12 h. After neutralization and evaporation,
purification by FC (petroleum ether–EtOAc 7:1) yielded
23 as a colorless oil (160 mg, 60%). Rf = 0.55 (petroleum
ether–EtOAc 2:1); 1H NMR (600.1 MHz, CDCl3): d
8.79 (d, J = 7.6, 1H, NH), 7.38–7.27 (m, 15H, Ph),
5.65 (dd, J = 7.6, 4.5, 1H, H-1); 4.67–4.48 (m, 6H,
CH2), 4.07 (dd, J = 4.5, 3.0, 1H, H-2), 3.96 (‘t’,
J = 3.4; 1H, H-3), 3.93 (dd, J = 12.9, 1.4, 1H, H-5a),
3,71 (dd, J = 13.1, 1.5, 1H, H-5b), 3.66 (ddd, J ꢃ 3.9,
2.0, 1.9, 1H, H-4); 13C NMR (150.9 MHz, CDCl3): d
162.5 (C@O), 137.6 (quaternary C), 137.5 (quaternary
C), 137.0 (quaternary C), 128.5–127.7 (aromatic C),
76.8 (C-1), 76.1 (C-3), 74.0 (C-4), 71.0 (C-2), 74.5
(CH2Ph), 74.1 (CH2Ph), 74.1 (CH2Ph), 58.6 (C-5);
1J H-1,C-1 = 164.9; (ESI-IT-MS): m/z 686.6 [M+Na]+,
602.6 [M+K]+; Anal. Calcd for C28H28Cl3NO5: C,
59.53; H, 5.00, N, 2.48. Found: C, 59.13; H, 5.03, N,
2.50.
1
1
0
0
JH-1 ;C-1 ¼ 175:5; JH-1,C-1 = 162.8.
Compound 26: RP-HPLC (semi-preparative column):
tR = 6.6 min; 1H NMR (600.1 MHz, CDCl3): d 5.20
(‘t’, J = 4.7, 1H, H-30), 5.19 (‘t’, J = 9.4, 1H, H-3),
5.16 (‘t’, J = 3.3, 1H, H-20), 5.10 (‘t’, J = 9.7, 1H, H-
4), 5.06 (dd, J = 9.8, 8.2, 1H, H-2), 5.04 (d, J = 4.2,
1H, H-10), 4.93 (‘q’, J = 5.5, 2.9 1H, H-40) 4.64 (d,
J = 7.8, 1H, H-1), 4.30 (dd, J = 12.9, 2.5, 1H, H-5a0),
4.27 (dd, J = 12.6, 2.4, 1H, H-6a), 4.13 (dd, J = 12.6,
2.4, 1H, H-6b), 3.74 (ddd, J = 10.2, 5.4, 2.4, 1H, H-5),
3.52 (dd, J = 13.2, 3.6, 1H, H-5b0), 2.12 (s, 3H,
C(O)CH3), 2.09 (s, 3H, C(O)CH3), 2.07 (s, 3H,
C(O)CH3), 2.03 (s, 3H, C(O)CH3), 2.02 (s, 3H,
C(O)CH3), 2.01 (s, 3H, C(O)CH3), 2.00 (s, 3H,
C(O)CH3); 13C NMR (150.9 MHz, CDCl3): d 170.6
(C(O)CH3), 170.2 (C(O)CH3), 170.0 (C(O)CH3), 169.8
(C(O)CH3), 169.5 (C(O)CH3), 169.4 (C(O)CH3), 168.9
(C(O)CH3), 100.9 (C-1), 97.6 (C-10), 72.5 (C-3), 72.1
(C-5), 71.0 (C-2), 68.4 (C-40), 68.2 (C-4), 66.5 (C-30,
C-20), 61.7 (C-6), 59.5 (C-50), 21.0 (C(O)CH3),
20.9 (C(O)CH3), 20.8 (C(O)CH3), 20.7 (C(O)CH3),
4.8. 2,3,4-Tri-O-acetyl-a-L-lyxopyranosyl 2,3,4,6-tetra-
O-acetyl-b-D-glucopyranoside (25) and 2,3,4-tri-O-acetyl-
b-L-lyxopyranosyl 2,3,4,6-tetra-O-acetyl-b-D-glucopyran-
oside (26)
4.8.1. Method a. Compounds 337 (764 mg, 1.55 mmol)
and 12 (450 mg, 1.61 mmol) were dissolved at 0 °C in
dry CH2Cl2 (8 mL). BF3ꢀOEt2 (20 lL, 0.16 mmol) was
added and the mixture was stirred for 17 h at rt. The
mixture was diluted with CH2Cl2 (20 mL), washed with
satd aq NaHCO3 (2 ꢁ 20 mL) and with brine
(1 ꢁ 20 mL), dried (MgSO4), and the solvent was evap-
orated. Purification by FC (petroleum ether–EtOAc 2:1)
yielded a 1.5:1 mixture of 25 and 26 (490 mg, 52%) as a
white solid.

M. S. Schmidt, V. Wittmann / Carbohydrate Research 343 (2008) 1612–1623
1621
20.7 (C(O)CH3), 20.6 (C(O)CH3), 20.6 (C(O)CH3);
1H, H-30), 5.27 (dd, J = 10.2, 4.8, 1H, H-40), 5.17 (d,
J = 2.4, 1H, H-10), 5.06–5.04 (m, 2H, H-3, H-4), 4.64
(d, J = 8.4, 1H, H-1), 4.25 (dd, J = 12.6, 4.8, 1H,
H-6a), 4,09 (dd, J = 12.6, 2.4, 1H, H-6b), 3.97 (dd,
J = 10.2, 5.4, 1H, H-5a0), 3.71–3.63 (m, 3H, H-2, H-5,
H-5b0), 2.15 (s, 3H, C(O)CH3), 2.11 (s, 3H, C(O)CH3),
2.09 (s, 3H, C(O)CH3), 2.06 (s, 3H, C(O)CH3), 2.02 (s,
3H, C(O)CH3), 2.01 (s, 3H, C(O)CH3); 13C NMR
1
1
0
0
JH-1 ;C-1 ¼ 167:8; JH-1,C-1 = 161.6.
4.9. 2,3,4-Tri-O-benzyl-a-L-lyxopyranosyl 2,3,4,6-tetra-
O-acetyl-b-D-glucopyranoside (27) and 2,3,4-tri-O-ben-
zyl-b-L-lyxopyranosyl 2,3,4,6-tetra-O-acetyl-b-D-gluco-
pyranoside (28)
Compounds 337 (600 mg, 1.2 mmol) and 16 (360 mg,
0.86 mmol) were dissolved at 0 °C in dry CH2Cl2
(4 mL). A solution of SnCl4 (1 M in CH2Cl2, 26 lL,
0.026 mmol) was added and the mixture was stirred
for 20 h at rt. The mixture was diluted with CH2Cl2
(20 mL), washed with satd aq NaHCO3 (2 ꢁ 20 mL)
and with brine (1 ꢁ 20 mL), dried (MgSO4), and the sol-
vent was evaporated. Purification by FC (petroleum
ether–EtOAc 3:1) yielded a 7:1 mixture of 27 and 28
(310 mg, 48%) as a colorless oil. Rf = 0.35 (petroleum
(150.9 MHz, CDCl3):
d
170.8 (C(O)CH3), 170.7
(C(O)CH3), 170.6 (C(O)CH3), 170.5 (C(O)CH3), 169.9
(C(O)CH3), 169.8 (C(O)CH3), 95.6 (C-1), 93.9 (C-10),
72.6 (C-3), 72.1 (C-5), 68.7 (C-20), 68.2 (C-30), 67.9
(C-4), 66.0 (C-40), 63.1 (C-2), 61.4 (C6), 60.4 (C-50),
21.8 (C(O)CH3), 21.7 (C(O)CH3), 21.6 (C(O)CH3),
21.6 (C(O)CH3), 21.5 (C(O)CH3), 21.5 (C(O)CH3);
JH-1 ;C-1 ¼ 176:3; 1J H-1,C-1 = 162.7; (MALDI-TOF-
MS): m/z 712.3 [M+Na]+, 628.2 [M+K]+; Anal. Calcd
for C23H31N3O15: C, 46.86; H, 5.30; N, 7.13. Found:
C, 46.80; H, 5.10; N, 6.79.
1
0
0
1
ether–EtOAc 3:1); H NMR (600.1 MHz, CDCl3): 27:
d 7.36–7.27 (m, 15H, Ph) 5.22 (‘t’, J = 9.0, 1H, H-3),
5.14 (d, J = 2.4, 1H, H-10), 5.10 (‘t’, J = 9.0, 1H, H-4),
5.05 (dd, J = 10.8, 9.0, 1H, H-2), 4.80–4.60 (m, 7H,
CH2, H-1), 4.28 (dd, J = 12.0, 4.8, 1H, H-6a), 4.11
(dd, J = 12.0, 2.4, 1H, H-6b), 4.05–3.99 (m, 1H, H-40),
3.82 (‘t’, J = 2.4, 1H, H-20), 3.79 (dd, J = 11.4, 6.0,
1H, H-5a0), 3.73–3.67 (m, 1H, H-5), 3.66 (dd, J = 9.0,
2.4, 1H, H-30), 3.39 (‘t’, J = 11.4, 1H, H-5b0), 2.09 (s,
3H, C(O)CH3), 2.03 (s, 3H, C(O)CH3), 2.01 (s, 3H,
C(O)CH3), 2.00 (s, 3H, C(O)CH3); 13C NMR
(150.9 MHz, CDCl3): 27: d 170.7 (C(O)CH3), 170.6
(C(O)CH3), 170.2 (C(O)CH3), 169.4 (C(O)CH3), 138.8
(quaternary C), 138.4 (quaternary C), 138.1 (quaternary
C), 128.5–127.5 (aromatic C), 94.5 (C-10), 94.4 (C-1),
78.6 (C-30), 74.4 (C-20), 74.0 (C-40), 72.6 (C-3), 71.9 (C-
5), 70.7 (C-2), 68.3 (C-4), 61.8 (C-50), 61.7 (C-6), 20.8
(C(O)CH3), 20.7 (C(O)CH3), 20.6 (C(O)CH3), 20.5
4.11. General procedure for the deacetylation of disac-
charides 25, 26, and 30
To a solution of the peracetylated disaccharide in
MeOH is added a solution of sodium methylate (0.5 M
in MeOH, 0.15 equiv). The mixture is stirred for 10–
48 h at rt. After neutralization with acidic ion exchanger
(DOWEX 50 W X8, H+ form), the mixture is filtered
and lyophilized to yield the deacetylated disaccharide
in quantitative yield.
4.12. a-L-Lyxopyranosyl b-D-glucopyranoside (1)
Compound 25 was deacetylated according to the general
procedure in Section 4.11. RP-HPLC (semi-preparative
column) (5–65% B in 30 min): tR 3.3 min; 1H NMR
(600.1 MHz, CDCl3): d 5.10 (d, J = 2.7, H-10), 4.52 (d,
J = 7.9, 1H, H-1), 3.86–3.78 (m, 3H, H-40, H-5a0,
H-6a), 3.75 (dd, J = 8.7, 2.7, 1H, H-20), 3.67–3.59 (m,
3H, H-30, H-5, H-6b), 3.37 (‘t’, J = 8.8, 1H, H-4),
3.31–3.26 (m, 2H, H-3, H-5b0), 3.21 (‘t’, J=7.9, 1H,
H-2); 13C NMR (150.9 MHz, CDCl3): d 98.7 (C-1),
97.4 (C-10), 77.8 (C-3), 77.4 (C-4), 74.1 (C-2), 71.8
(C-20), 70.8 (C-50), 67.8 (C-40), 64.1 (C-30), 64.0 (C5),
1
1
0
0
(C(O)CH3); JH-1 ;C-1 ¼ 173:2; JH-1,C-1 = 163.8; 28: d
1
100.8 (C-10), 100.7 (C-1); JH-1 ;C-1 ¼ 164:7; JH-1,C-1
=
1
0
0
162.8; (MALDI-TOF-MS): m/z 773.4 [M+Na]+, 789.4
[M+K]+; Anal. Calcd for C40H46O14: C, 63.99; H,
6.18. Found: C, 63.55; H, 6.04.
4.10. 2,3,4-Tri-O-acetyl-a-L-lyxopyranosyl 3,4,6-tri-O-
acetyl-2-azido-2-deoxy-b-D-glucopyranoside (30)
1
1
0
0
62.2 (C6); JH-1 ;C-1 ¼ 174:7; JH-1,C-1 = 166.6; (MAL-
Compounds 13 (280 mg, 0.66 mmol) and 738 (200 mg,
0.6 mmol) were dissolved at 0 °C in dry CH2Cl2
(3 mL). BF3ꢀOEt2 (8 lL, 0.07 mmol) was added and
the mixture was stirred for 2 h at rt. The mixture was di-
luted with CH2Cl2 (20 mL), washed with satd aq NaH-
CO3 (2 ꢁ 20 mL) and with brine (1 ꢁ 20 mL), dried
(MgSO4), and the solvent was evaporated. Purification
by FC (petroleum ether–EtOAc 2:1) yielded 30
(255 mg, 72%) as a white solid. Rf = 0.35 (petroleum
ether–EtOAc 1:1); 1H NMR (600.1 MHz, CDCl3): d
5.38 (d, J = 3.6, 2.4 1H, H-20), 5.34 (dd, J = 10.2, 3.6,
DI-TOF-MS): m/z 335.2 [M+Na]+, 341.4 [M+K]+.
4.13. b-L-Lyxopyranosyl b-D-glucopyranoside (29)
Compound 26 was deacetylated according to the general
procedure in Section 4.11. RP-HPLC (semi-preparative
1
column) (5–65% B in 30 min): tR = 3.2 min; H NMR
(600.1 MHz, CDCl3): d 4.76 (d, J = 1.7, H-10), 4.31 (d,
J = 6, 1H, H-1), 3.87 (dd, J = 2.9, 12.6, 1H, H-5a0),
3.71–2.68 (m, 1H, H-40), 3.62 (dd, J = 10.8, 4.8, 1H,
H6a), 3.55–3.42 (m, 3H, H-30, H-20, H-6b), 3.12–3.00

1622
M. S. Schmidt, V. Wittmann / Carbohydrate Research 343 (2008) 1612–1623
(m, 4H, H-2, H-3, H-4, H-5), 3.08 (dd, J = 12.6, 8.4, 1H,
H-5b0); 13C NMR (150.9 MHz, CDCl3): d 102.3 (C-1),
102.2 (C-10), 76.8 (C-3), 75.9 (C-4), 73.6 (C-2), 71.6 (C-
20), 79.5 (C-5), 67.7 (C-30), 67.0 (C-40), 62.3 (C50), 60.6
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4.14. a-L-Lyxopyranosyl 2-azido-2-deoxy-b-D-gluco-
pyranoside (31)
Compound 30 was deacetylated according to the general
procedure in Section 4.11. RP-HPLC (semi-preparative
1
column) (5–45% B in 30 min): tR = 3.3 min; H NMR
(600.1 MHz, CDCl3): d 5.13 (d, J = 2.4, H-10), 4.64 (d,
J = 9.6, 1H, H-1), 3.87–3.76 (m, 4H, H-20, H-30, H-40,
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(C-4), 66.1 (C-40), 65.6 (C-2), 72.8 (C-50), 60.3 (C6);
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1
0
0
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Financial support by the Deutsche Forschungsgemeins-
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acknowledged. We thank Professor A. Bechthold
for valuable discussions regarding the avilamycin
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