Stereocontrolled syntheses of α-C-mannosyltryptophan and its analogues

Article abstract of DOI:10.1039/b414905j

The total synthesis of α-C-mannosyltryptophan (C-Man-Trp), a naturally occurring C-glycosylamino acid, was achieved from a commercially available α-methyl-D-mannoside in 10 steps including the following key steps: the C-glycosidation of a mannose derivative with a stannylacetylene, Castro indole synthesis, and Sc(ClO₄)₃-promoted coupling with L-serine-derived aziridine carboxylate. The glucose- and galactose-analogues of C-Man-Trp were also synthesized in a similar manner. Conformational analyses of the synthesized C-glycosyltryptophan and its synthetic intermediate are briefly discussed.

Full text of DOI:10.1039/b414905j

View Article Online / Journal Homepage / Table of Contents for this issue
A R T I C L E
Stereocontrolled syntheses of a-C-mannosyltryptophan and its
analogues
Toshio Nishikawa,*a,b Yuya Koide,a Shigeo Kajii,a Kyoko Wada,a Miyuki Ishikawaa and
Minoru Isobea
a Laboratory of Organic Chemistry, Graduate School of Bioagricultural Sciences, Nagoya
University, Chikusa, Nagoya, 464-8601, Japan. E-mail: nisikawa@agr.nagoyya-u.ac.jp;
Fax: (+)81-52-789-4111; Tel: (+)81-52-789-4112
b PRESTO, Japan Science and Technology Agency
Received 29th September 2004, Accepted 3rd December 2004
First published as an Advance Article on the web 18th January 2005
The total synthesis of a-C-mannosyltryptophan (C-Man-Trp), a naturally occurring C-glycosylamino acid, was
achieved from a commercially available a-methyl-D-mannoside in 10 steps including the following key steps: the
C-glycosidation of a mannose derivative with a stannylacetylene, Castro indole synthesis, and Sc(ClO4)3-promoted
coupling with L-serine-derived aziridine carboxylate. The glucose- and galactose-analogues of C-Man-Trp were also
synthesized in a similar manner. Conformational analyses of the synthesized C-glycosyltryptophan and its synthetic
intermediate are briefly discussed.
Introduction
The carbohydrate moieties of glycoproteins and glycolipids are
of great interest due to their numerous significant biological
functions, including their involvement in cell–cell interactions,
the immune response, the stabilization of proteins, local con-
formational changes of the protein backbone etc.1 Most carbo-
hydrate moieties are linked to asparagine through N-glycosidic
bonds, or to serine/threonine through O-glycosidic bonds. There
are a few other types of glycosides linked to tyrosine and
cysteine on the protein surface.2 However, until 1994, no C-
glycosidic linkage between amino acids and carbohydrates had
been identified among the proteins, whereas many synthetic C-
glycosylamino acids have been reported as stable mimics of
Fig. 1 Structure of a-C-mannosyltryptophan.
N- and O-glycosylamino acids; such synthetic compounds have
been employed as probes for analyzing the biological functions
of the corresponding naturally occurring sugar chains.3 In 1994,
Hofsteenge and co-workers discovered that tryptophan-7 of
Ribonuclease 2 (RNase 2) from human urine was modified by
a hexopyranose.4 Surprisingly, extensive NMR analysis of the
hexapeptide containing the modified tryptophan obtained from
enzyme digestion of the RNase 2 revealed that mannose was
connected to the 2-position (carbon atom) of the indole with an
a-configuration, as shown in Fig. 1.5 C-Mannosyltryptophan
(C-Man-Trp, 1) is the first example of a molecule with a C-
glycosidic linkage between amino acid and carbohydrate found
in proteins. Interestingly, the mannose moiety of C-Man-Trp
since the recognition sequence is contained in the TSR module
and the WS motif (Trp-Ser-x-Trp-Ser) of many proteins such
as extracellular matrix proteins, complement system proteins
and cytokine receptors.9 In fact, the C-Man-Trp residue has
also been found in a variety of biologically important proteins
such as interleukin 12b,10 four terminal components of the
human complement system,11 properdine,12 human platelet
thrombospondin-1,13 and the erythropoietin receptor.14 On the
other hand, C-Man-Trp (1) has been isolated as a monomer
from human urine15 and marine organisms.16 However, despite
these extensive studies, the biological function of this novel sugar
residue has not yet been clarified, although some possibilities
have been discussed in the literature.9,17,18 In order to elucidate
the biological function(s) of this residue, C-Man-Trp and its
related compounds are indispensable; however, a sufficient
amount of these compounds is not yet available from natural
sources. In this context, we recently successfully carried out
the total synthesis of C-Man-Trp (1)19 in order to supply the
materials necessary for biochemical research in this area of
study, and two other syntheses of C-Man-Trp based on different
synthetic strategies were also reported by Ito and Manabe20 and
Fujise and co-workers21 prior to our synthesis. We describe
herein the full details of our investigation of the synthesis
of C-Man-Trp (1), as well as its a-glucose and a-galactose
analogues.22
4
was reported not to adopt the typical C1 conformation, but
instead adopted multiple conformations, including the unusual
1C4 conformation and a twist-boat conformation, presumably
due to the severe steric hindrance of the tryptophan at the
anomeric position in the a-configuration, as well as due to the
lack of anomeric effect.
This novel post- or co-translational modification is catalyzed
by a microsome-associated enzyme, “C-mannosyltransferase”,
which has not been purified to date.6 However, the enzyme
activity has been detected in cell culture from many organisms
such as mammals, nematodes, birds, amphibians, fish, but
not in Escherichia coli, insects, or yeast.7 This enzyme was
found to recognize an amino acid sequence, Trp-x-x-Trp, to
glycosylate the first Trp of this motif.8 Such previous studies
have indicated that C-Man-Trp is more common than expected,
T h i s j o u r n a l i s
T h e R o y a l S o c i e t y o f C h e m i s t r y 2 0 0 5
O r g . B i o m o l . C h e m . , 2 0 0 5 , 3 , 6 8 7 – 7 0 0
6 8 7
©

View Article Online
Results and discussion
Synthetic plan
We considered two retrosynthetic plans for C-Man-Trp (1) and
its analogues, as shown in Scheme 1. One approach (route a)
is based on palladium-catalyzed heteroannulation developed
by Larock23 for the synthesis of an indole nucleus from C-
glycosylpropargylglycine 2 and an o-iodoaniline derivative.
Disconnection at the propargylic position of 2 led us to find a-
sugar acetylene 3 and L-serine derivative 4. This type of coupling
with a palladium catalyst has been reported by Knochel and
Jackson.24 Another approach (route b) would be to synthesize
the tryptophan moiety from C-glycosylindole 5, via the cor-
responding dehydrotryptophan. The C-glycosylindole 5 would
be synthesized by the Castro method from o-ethynylaniline
6,25 which could be obtained by Sonogashira coupling of the
sugar acetylene 3 and the o-iodoaniline derivative. Both of these
approaches would ultimately rely on the stereoselective synthesis
of the a-sugar acetylene 3. The stereocontrolled synthesis of such
sugar acetylenes and their synthetic applications have been ex-
tensively developed in our laboratory,26 where unsaturated sugar
acetylene 727 is prepared by C-glycosidation of tri-O-acetyl-D-
glucal. We would therefore synthesize C-ethynylmannose 3 from
dihydroxylation of 7 or by direct C-glycosidation of mannose
derivative 8. Vasella and co-workers have also extensively
developed an alternate route for the synthesis of sugar acetylenes
and their wide application,28 which includes the stereocontrolled
synthesis of 3 and its glucose analogue from the corresponding
1,6-anhydropyranose derivatives.29 The above synthetic plan
would be applicable for the synthesis of various analogues of
C-Man-Trp (1) in the sugar moiety.
(1)
Synthesis of a-C-ethynylhexopyranoside through
C-glycosidation
According to the synthetic plan as shown in Scheme 1, we
attempted the dihydroxylation of cyclic olefin of the known
compound 14a27 with OsO4 and NMO (eqn. (2)). However,
the desired product 15a was obtained in a poor yield, probably
because of the competitive oxidation of the acetylenic moiety.
The same reaction of a phenyl-substituted acetylene such as 14b
prepared from 14a31 also gave a poor yield of the corresponding
product 15b. These fruitless results led us to develop a new
method of carrying out the direct synthesis of a-ethynylmannose
332 from the mannose derivative 8 with a silyl or stannylacety-
lene.For the C-glycosidation of D-mannose, 1,6-di-O-acetyl-
In our initial efforts to synthesize the glucose analogue of
C-Man-Trp according to route a, the heteroannulation of a-C-
glucosylpropargylglycine derivative 10 and N-toluenesulfonyl-
2-iodoaniline (11) under Larock’s conditions23 gave not the
desired product 13, but instead the undesired regioisomer
12, iso-tryptophan, as a single product (eqn. (1)).30 To the
best of our knowledge, this is the first example of complete
reverse regioselectivity in a case of the Larock indole synthesis.
Therefore we focused our attention on the second approach
(route b) starting from a-sugar acetylene 7.
(2)
2,3,4-tri-O-benzyl-a-D-mannopyranose (16) was chosen as the
glycosyl donor, due to its stability and availability (eqn. (3)).
Thus, 16 was easily prepared from a commercially available
methyl-a-D-mannopyranoside in 2 steps involving benzylation
(NaH, BnBr in DMF) followed by acetolysis (conc. H2SO4
in Ac2O).33 Using substrate 16, we examined the reaction
conditions (Lewis acids and solvents) for C-glycosidation with
bis(trimethylsilyl)acetylene, according to conditions previously
developed in our laboratory.26 In the case of mannose, we
expected that steric hindrance of b-benzyloxy group at the
2-position and stereoelectronic effect would facilitate highly
a-selective C–C bond forming reactions via the axial attack
of silylacetylene at an oxonium ion. However, despite our
extensive efforts,34 we were unable to find any conditions
that would give the desired product; even reaction with the
relatively reactive 1-phenyl-2-(trimethylsilyl)acetylene gave only
a 20% yield of the corresponding product. Thus, we next
attempted the C-glycosidation with the much more reactive tri-
n-butylstannyl(trimethylsilyl)acetylene (20). Further extensive
examinations led us to conclude that the only combination to
give the desired a-C-ethynylmannose 21 as a single product in
high yield was the stannylacetylene 20 and TMSOTf in CH2Cl2
(entry 1 in Table 1). Interestingly, the acetyl group of the 6-
hydroxyl group of 16 exerted an influence on the yield of the
C-glycosidation; thus, C-glycosidation of the corresponding
benzyl ether 17 under the same conditions afforded product
22 in a lower yield (entry 2). These results imply that the
acetoxy group at the 6-position accommodates the reactivity
of the anomeric center, presumably by an arming/disarming
effect.35 These successful results encouraged us to apply these
conditions to synthesize the corresponding glucose and galac-
tose analogues.36 In the case of the C-glycosidation of glucose
and galactose derivatives, the 1-acetoxy-2,3,4,6-tetra-O-benzyl
derivatives 18 and 19 were found to be better substrates
than the corresponding 1,6-diacetoxy derivatives with regard
to the yields and reproducibility. The substrates 18 and 19
were easily prepared from the methyl-a-D-glucopyranoside and
Scheme 1 Synthetic plan of a-C-glycosyltryptophan exemplified by
C-Man-Trp (1).
6 8 8
O r g . B i o m o l . C h e m . , 2 0 0 5 , 3 , 6 8 7 – 7 0 0

View Article Online
Table 1 C-Glycosidation of 1-acetylhexopyranosides (16–19) with stannylacetylene 20
Substrate
Entry
Pyranose
R
a/b
Conditions for step 2
Product
Yield over 2 steps (%)
1
2
3
4
Mannose
Mannose
Glucose
Ac
Bn
Bn
Bn
1 : 0
1 : 3
0 : 1
0 : 1
16
17
18
19
A
B
B
A
21
22
23
24
83
48
71
54
Galactose
Table 2 Palladium-catalyzed coupling between a-ethylpyranose (21–24) and N-tosyl-2-iodoaniline (11)
Substrate
Sugar
Products
Entry
R
Conditions
Temp./◦C
Ethynylaniline
Yield (%)
Indole
Yield (%)
1
2
3
4
5
6
7
21
22
22
23
23
24
24
Mannose
Mannose
Mannose
Glucose
Glucose
Galactose
Galactose
Ac
Bn
Bn
Bn
Bn
Bn
Bn
A
A
B
A
B
A
B
rt
rt
60
60
60
60
60
25
26
26
27
27
28
28
96
57
75
0
88
0
29
30
30
31
31
32
32
0
0
0
44
0
46
0
86
methyl-a-D-galactopyranoside, respectively, in a conventional
manner involving benzylation of hydroxyl groups, acid hydroly-
sis of the methylglycoside, and acetylation of the hemiacetal.
Although the stereoselectivity of the C-glycosidation turned
out to be independent of the anomeric configuration of the
acetate, we employed the b-acetates 18 and 19, which were stereo-
selectively prepared by the acetylation of the corresponding
hemiacetal with acetic anhydride and Et3N in CH2Cl2.37 The C-
glycosidation of the substrates 18 and 19 with stannylacetylene
20 under the optimized conditions gave 23 and 24, respectively, in
good yields and with very high a-stereoselectivity (entries 3 and
4).38,39 Desilylation of the silylacetylenes was carried out with n-
Bu4NF (TBAF) in THF (condition A) or potassium carbonate
in methanol (condition B).
(4)
The resulting o-ethynylanilides 25–28 were then heated at
80 ◦C with CuI and triethylamine in DMF to give mannosylin-
dole 29 and 30, glucosylindole 31, and galactosylindole 32 in
good to high yields (Table 3). The tosyl protective group of
the glycosylindole 29–32 was removed with TBAF in refluxing
THF43 to afford 33–36 in high yields. Thus, the efficient and
highly stereocontrolled syntheses of a-C-glycosylindoles has
been established.
(5)
(3)
Synthesis of the tryptophan moiety via dehydrotryptophan
We initially attempted the direct synthesis of a dehydroman-
nosyltryptophan such as 37 from mannosylindole 29 and N-
Cbz-dehydroalanine methyl ester 36 under Yokoyama and Mu-
rakami’s conditions (eqn. (6));44 however, no coupling products
were detected, probably due to the steric hindrance around the
3-position of the indole.
Synthesis of a-glycosylindole
With the a-C-ethynylhexoses in hand, we next focused on the
construction of an indole nucleus from the terminal acetylenes
according to our synthetic plan. a-Ethynyl-D-mannose 21 and
22 were coupled with N-tosyl-2-iodoaniline (11) under Sono-
gashira’s conditions (condition A; in the presence of CuI and
a palladium catalyst)40 at room temperature to give manno-
sylethynylaniline 25 and 26 in 96 and 57% yields, respectively
(Table 2, entries 1 and 2).41 The yield of the coupling reaction
between 22 and 11 was improved by an alternative copper-free
condition (condition B) that consisted of a catalytic amount of
Pd(OAc)2 and Ph3P in triethylamine as a solvent42 (entry 3). In
sharp contrast, the Sonogashira coupling of the glucose and
galactose analogues 23 and 24 with 11 did not proceed at room
temperature. When the reaction temperature was elevated to
60 ◦C, the coupling with concomitant indole cyclization took
place to give indole 31 and 32 in 44 and 46% yields, respectively
(entries 4 and 6). The copper-free condition (condition B)
was found to be effective for the coupling reaction of 23
and 24, which proceeded at 60 ◦C to give good yields of the
products 27 and 28 without giving indoles 31 and 32 (entries 5
and 7).
(6)
We therefore synthesized a dehydrotryptophan in stepwise
fashion using an aldehyde 38 (Scheme 2). Vilsmeier formylation
of 33 and subsequent acetylation of the resulting free hydroxyl
group at the 6-position gave 38a45 in a good overall yield.
However, the transformation of the aldehyde 38a into the
dehydrotryptophan proved to be problematic. For example, the
coupling of N-Boc protected aldehyde 38b with conventional
Horner–Emmons reagents such as 39a and 39b46 was sluggish,
and gave poor yields of the corresponding dehydrotryptophans,
even when a large excess of the reagent was used. Fortu-
nately, we found that the aldehyde 38a, when treated with
O r g . B i o m o l . C h e m . , 2 0 0 5 , 3 , 6 8 7 – 7 0 0
6 8 9

View Article Online
Table 3 Synthesis of glycosylindole
Substrate
Synthesis of indole
Deprotection of Ts group
Entry
Sugar
R
Products
Yield (%)
Products
Yield (%)
1
2
3
4
25
26
27
28
Mannose
Mannose
Glucose
Ac
Bn
Bn
Bn
29
30
31
32
88
85
89
92
33
34
35
36
90
93
98
90
Galactose
N-acetamide malonate monomethyl ester (40) in acetic anhy-
dride and pyridine47 afforded dehydrotryptophan 41 in 49%
yield, with 39% recovered 38a. The product 41 was hydrogenated
with palladium on charcoal to give a mixture (1 : 2 – 2 :
3) of the diastereoisomer of amino acid 42a and 43a. The
structures, with the exception of the absolute configuration of
the amino acid moiety, were confirmed by the NMR spectra of
the corresponding acetates42b and 43b. The later experiments
revealed that the minor product 42a had the natural L-absolute
configuration of the tryptophan moiety, as shown in Scheme 2;
a fully protected C-Man-Trp methyl ester 45a with a definite L-
configuration (vide infra) was transformed into 42a in three steps,
including transesterification with KCN in EtOH, deprotection
definite amino acid residue. The Lewis acid-promoted coupling
between tryptophan and aziridine carboxylate developed by
Kozikowski (with Zn(OTf)2)48 and later by Bennani (with
Sc(OTf)3)49 appeared to be a candidate. However, the reaction of
mannosylindole 33 with L-serine-derived aziridine carboxylate
4450 in the presence of Zn(OTf)2 did not give any coupling
product, whereas the aziridine 44 decomposed under these
conditions (Table 4, entry 1). When Sc(OTf)3, reported as a
superior Lewis acid, was employed, the coupling proceeded
at 0 ◦C, but it gave a ca. 3 : 1 mixture of the regioisomers
45a and 45b, which were difficult to separate on a preparative
scale (entry 2). Concurrent with these experiments, we examined
a model reaction of 2-methylinodole and aziridine 44 in the
presence of Sc(OTf)3; however, a mixture of the corresponding
regioisomers was obtained. These unfavorable results led us
to re-examine the reaction conditions using 2-methylindole as
a test substrate. Extensive experimentation fortunately led us
1
of the benzyl groups, and acetylation. The H NMR spectra
of the product were identical to those of the minor product
42b obtained from 41 in Scheme 2. Thus, we synthesized the C-
Man-Trp derivatives 42a and 42b with the natural configuration;
however, it should be noted that the synthetic route contains
several drawbacks such as the multi-step sequence required for
the introduction of the amino acid functionality, the difficult
separation of the mixture of diastereoisomers, and the remaining
task of deprotection of the acetamide group.
51
to find that Sc(ClO4)3 effected highly regioselective coupling
between 2-methylindole and the aziridine 44 to afford the
desired regioisomer (i.e., the 2-methyltryptophan derivative). 52
Fortunately, the optimized condition could then be applied to
the reaction of mannosylindole 33 and aziridine 44 to give the
exclusive formation of the desired regioisomer 45a in good yield
(entry 3). Surprisingly, the coupling of a similar substrate 34,
which bears a benzyl ether on the 6-OH, with 44 gave a very low
yield of the desired product 46a53 (entry 4). This low yield may
be attributed to the steric hindrance of the benzyl ether of 34 and
the instability of the product 46 under the acidic conditions. The
same coupling of glucose and galactose analogues 35 and 36 gave
the desired products 47 and 48, respectively, in moderate yields
˚
(entries 5 and 6). In these cases, 5 A molecular sieves were added
to the reaction mixture in order to suppress the decomposition
54
of the products, which would otherwise have caused low yields.
Scheme 2 Synthesis of C-Man-Trp derivatives via dehydrotryptophan.
(7)
Synthesis of the tryptophan moiety via direct coupling between
an indole and a chiral aziridine derivative
Deprotection of esters and benzyl groups
Rather than pursue the above inefficient route, we focused our
attention on an alternative route that gives a configurationally
The methyl ester and the acetate of 45a were hydrolyzed with
aqueous lithium hydroxide in 2-propanol to give a 71% yield of
Table 4 Lewis acid-promoted coupling of glycosylindole (33–36) and aziridine (44)
Substrate
Product
Entry
Sugar
R
Lewis acid
Solvent
Temp./◦C
a/ba
Yield (%)
1
2
3
4
5
6
Mannose
Mannose
Mannose
Mannose
Glucose
33
33
33
34
35
36
Ac
Ac
Ac
Bn
Bn
Bn
Zn(OTf)2
Sc(OTf)3
Sc(ClO4)3
Sc(ClO4)3
Sc(ClO4)3
Sc(ClO4)3
CHCl3
80
0
0
0
0
45
45
45
46
47
48
—
0
CH2Cl2
CH2Cl2
CH2Cl2
CH2Cl2
CH2Cl2
3 : 1b
1 : 0
1 : 0
1 : 0
1 : 0
47
83
5
41
43
c
c
c
Galactose
0
a The ratio was determined by 1H NMR spectra. b The by-product 45b was isolated as a single diastereomer; the configuration of the newly asymmetric
center (* in eqn. (7)) was not determined. c 5 A MS were added.
˚
6 9 0
O r g . B i o m o l . C h e m . , 2 0 0 5 , 3 , 6 8 7 – 7 0 0

View Article Online
Table 5 Deprotection of esters
Conformational analysis of C-Man-Trp and its synthetic
intermediates
Substrate
Deprotection of esters
Hofsteenge and co-workers reported that C-Man-Trp in the
peptide fragment of RNase2 protein exists as a multiple con-
Entry
Sugar
R
Products
R
Yield (%)
1
former, including an unusual C4 conformation.4,5 During our
1
2
3
45a Mannose
47a Glucose
48a Galactose
Ac
Bn
Bn
49
50
51
H
Bn
Bn
70
86
85
synthetic studies described above, we noticed that the coupling
constant between H-1 and H-2 (JH1 H2) of the hexopyranose
–
ring depended on the substituent at the C-1 position. These
observations prompted us to analyze the conformation of the
a-C-glycosyl compounds synthesized in this study. The vicinal
coupling constants of the pyranose ring are the most informative
parameters for the analysis of conformation.56 Table 7 shows
the coupling constants of the synthetic C-glycosyltryptophan
(C-Man-Trp, C-Glu-Trp and C-Gal-Trp) and its synthetic
intermediates, along with typical data for the corresponding
a-O-glycoside.56
49 (entry 1 in Table 5). The deprotection of 46 was not carried
out because of the scarcity of the material. The methyl esters of
47a and 48a were removed under the same conditions to afford
50 and 51 in good yields.
a-Mannose acetylenes 21 and 22 adopt the typical 4C1
conformation, judging from the vicinal coupling constants of
the pyranose rings; a small coupling constant (2.5 Hz) between
H-1 and H-2, and large coupling constants (9–10 Hz) between
H-3 and H-4, and between H-4 and H-5, are observed. Since
ethynylaniline-substituted mannoses 25 and 26 exhibit nearly
the same coupling constants as those of 21 and 22, these
sugar acetylenes adopt the 4C1 conformation. On the other
(8)
hand, the larger coupling constants (JH1
= 5–6 Hz) of N-
On the other hand, hydrogenolytic deprotection of the benzyl
groups was found to be problematic, because of the competitive
side reaction of the cleavage of the pyranose ring (eqn. (8) and
Table 6). In the case of the mannose derivative 49, debenzylation
was best carried out with Pearlman catalyst (20% Pd(OH)2 on
charcoal) in the presence of concentrated HCl for 3 hours to give
C-Man-Trp (1) in good yield (entry 1). The same reaction in the
absence of acid proceeded very slowly, whereas the prolonged
reaction time decreased the yield of 1 because of the formation
–H2
tosylindole-substituted mannoses 29 and 30 clearly indicate a
4
1
conformation that differs from C1. Since the C4 conformer
exhibits a larger coupling constant between H-1 and H-2 (vide
infra), these compounds are likely to exist as an equilibrium
4
1
between C1 and C4 conformers, although the other coupling
constants (JH3 and JH4 H5) are not yet available. When the
–H4
–
Ts group of 29 and 30 was deprotected, the conformation of
the resulting mannosylindoles 33 and 34 returned to a nearly
4C1 conformation, judging from the coupling constants. In
sharp contrast, 3-formylindole-substituted mannose 38a clearly
adopts the 1C4 conformation,57 judging from the large coupling
constant (9.5 Hz) between H-1 and H-2, and the small coupling
constant (1.5 Hz) between H-4 and H-5. Fully protected C-
Man-Trp 45a and 46a also adopt a conformation close to
1C4. However, C-Man-Trp (1) and C-Man-Trp in the peptide
1
of the by-product 1a. The H and 13C NMR spectra of the
synthetic C-Man-Trp (1) were in good agreement with those of
15a
the natural product, which was isolated from human urine.
However, when the conditions were applied to the galactose
substrate 51, a mixture of C-Gal-Trp (52) and the by-product
52a was obtained in a ratio of approximately 2 : 1 (entry 2).
After some experimentation, we found that 5% Pd–C in the
presence of 1 N HCl was a good condition for the debenzylation
of 51, giving C-Gal-Trp (52) in good yield without 52a (entry 3).
When the glucose derivative 50 was treated under the conditions
optimized for the galactose derivative 51, a significant amount
of the by-product 53a was produced (entry 4). In this case, we
fortunately found that 5% Pd–C in the absence of the acid was
the condition required to afford C-Glu-Trp (53)55 without giving
53a (entry 5).
exhibit slightly smaller coupling constants for JH1 H2, and larger
–
coupling constants for JH4 H5, than those of 45a and 46a.
–
Consideration of these vicinal couplings together with the
contradictory NOESY correlation (Fig. 2) led us to conclude
that C-Man-Trp (1) and C-Man-Trp in the peptide largely
adopt the 1C4 conformation, but there exists a slight equilibrium
between the 1C4 and the 4C1 conformations.
In the glucose series, most of the synthetic intermediates
(23, 27, 31, and 35) adopt a typical 4C1 conformation, as
based on the three large coupling constants observed (JH2
,
–H3
JH3 H4 and JH4 H5). Unfortunately, the conformation of the fully
–
–
protected C-Glu-Trp 47a could not be analyzed due to the
1
heavily overlapping H NMR signals. The conformation of C-
Glu-Trp (53) is a slightly distorted form of 4C1, judging from the
observation of smaller coupling constants (JH2 H3, JH3
and
–
–H4
4
JH4 H5) than those observed in typical C1 conformers such as
–
23 and 27.58
(9)
Table 6 Deprotection of benzyl groups
Substrate
Sugar
Conditions
Catalyst
Product
Entry
R
Acid
Time/h
Yield (%)
Ratioa
1
2
3
4
5
49
51
51
50
50
Mannose
Galactose
Galactose
Glucose
H
Pd(OH)2/C
Pd(OH)2/C
5% Pd/C
5% Pd/C
5% Pd/C
12 N HCl
12 N HCl
1 N HCl
1 N HCl
none
3
3
25
17
35
71
83
70
70
73
1/1a (1 : 0)
Bn
Bn
Bn
Bn
52/52a (2 : 1)
52/52a (1 : 0)
53/53a (2 : 1)
53/53a (1 : 0)
Glucose
a The ratios were determined by 1H NMR spectra.
O r g . B i o m o l . C h e m . , 2 0 0 5 , 3 , 6 8 7 – 7 0 0
6 9 1

View Article Online
Fig. 2 Conformation of a-C-glycosyltryptophan and the observed NOESY correlations.
In the galactose series, galactosyl acetylene 24, ethynylaniline-
Conclusion
substituted galactose 28, and indolylgalactose 36 adopt the 4C1
conformation, as determined from the large coupling constants
(9–10 Hz) between H-2 and H-3. On the other hand, conforma-
tional analyses of N-Ts-indolylmannose 32, the fully protected
C-Gal-Trp 48a, and C-Gal-Trp (52) proved to be difficult
because no characteristic coupling constants were observed.
However, the contradictory NOESY correlations observed in
52 (Fig. 2) suggested that 52 exists as an equilibrium mixture
between the 4C1 and 1C4 conformers.
The syntheses of C-Man-Trp (1) and its glucose and galactose
analogues have been achieved in a highly stereoselective manner.
The present studies revealed that the protective group at the 6-
hydroxyl group of mannose derivatives significantly affected the
reactivity of several reactions, including C-glycosidation with
the the stannylacetylene and the Sc(ClO4)3-promoted coupling
of the glycosylindole and aziridine. The yields of the palladium-
catalyzed coupling of the sugar acetylene with an o-iodoaniline
derivative and the Sc(ClO4)3-promoted coupling depended on
the type of the carbohydrate.
The above studies also enabled us to supply a variety of C-
Man-Trp-related compounds for biochemical research. In fact,
we prepared some derivatives from the synthetic C-Man-Trp,
and employed these materials for a lectin assay and in a search
for C-Man-Trp binding proteins. These studies revealed that
C-Man-Trp could not be recognized by conventional mannose
lectins such as Con A (Concanavarin A) and MBL (Mannose-
Binding Lectin), and we also found several C-Man-Trp binding
proteins in mouse serum.59
1
These analyses suggested that the inversion (4C1 to C4) of
a-C-mannose and a-C-galactose is induced by some degree
of steric hindrance due to a substituent such as an N-Ts
protected indole and the presence of a tryptophan derivative
at the anomeric position. These inverted 1C4 conformations
may be stabilized by one equatorial hydroxyl group at the
C-2 or the C-4 position, respectively. In the case of a-C-
glucose, the four equatorial substituents may stabilized the 4C1
conformation, even when a bulky substituent such as an N-Ts-
protected indole or a tryptophan derivative occupies the C-1
position.
Table 7 Vicinal coupling constants of the pyranose moiety of the synthetic C-glycosides and their conformations
C-Glycosides
JH1−H2
JH2−H3
JH3−H4
JH4−H5
Favoured conformation
a-O-Man56
1.8
2.5
2.5
2.5
2.5
5.0
6.0
3.0
2.5
9.5
9.0
9.0
8.0
7.8
3.8
2.5
2.5
2.5
2.5
2.5
2.5
3.0
2.5
2.5
n.d.
n.d.
3.0
3.2
10.0
9.0
10.0
n.d.
9.0
n.d.
n.d.
n.d.
8.5
4.0
3.5
n.d.
5.0
9.8
9.0
n.d.
n.d.
9.0
n.d.
n.d.
8.0
8.5
1.5
1.0
n.d.
3.0
3.8
4C1
4C1
4C1
4C1
4C1
Man-acetylene 21
Man-acetylene 22
Man-ethynylaniline 25
Man-ethynylaniline 26
Man-(N-Ts)indole 29
Man-(N-Ts)indole 30
Man-indole 33
1
4C1ꢀ C4
4C1ꢀ C4
1
4C1
4C1
1C4
1C4
1C4
1C4
1C4
Man-indole 34
Man-formylindole 38a
Man-Trp (protected form) 45a
Man-Trp (protected form) 46a
a-C-Man-Trp (1)
a-C-Man-Trp (1) (in RNase2)4
5.5
a-O-Glu56
3.6
6.0
6.0
6.0
6.0
n.d.
5.5
9.5
9.5
10.0
8.0
10.0
n.d.
8.5
9.5
9.5
10.0
8.0
8.0
n.d.
8.5
9.5
9.5
10.0
10.0
10.0
n.d.
8.5
4C1
4C1
4C1
4C1
4C1
n.d.
4C1
Glu-acetylene 23
Glu-ethynylaniline 27
Glu-(N-Ts)indole 31
Glu-indole 35
Glu-Trp (protected form) 47a
a-C-Glu-Trp (53)
a-O-Gal56
3.8
6.0
6.0
2.5
5.0
3.5
4.5
10.0
9.0
10.0
5.0
9.0
6.5
3.8
3.0
3.0
3.0
3.0
3.0
3.5
1.0
1.0
3.0
6.0
3.0
4.5
3.5
4C1
4C1
4C1
n.d.
4C1
n.d.
Gal-acetylene 24
Gal-ethynylaniline 28
Gal-(N-Ts)indole 32
Gal-indole 36
Gal-Trp (protected form) 48a
a-C-Gal-Trp (52)
1
7.5
4C1ꢀ C4
6 9 2
O r g . B i o m o l . C h e m . , 2 0 0 5 , 3 , 6 8 7 – 7 0 0

View Article Online
Peptide sequencing by the Edman degradation method and
mass spectrometry approaches such as MS/MS have been
employed for the identification of C-Man-Trp from proteins;60
however, because of the identical molecular weight of these
analogues, such analytical methods have not yet enabled dif-
ferentiation between types of sugar (mannose, glucose, or galac-
tose) nor determination of the configuration of the anomeric
(a, b) positions. At present, NMR analysis is the only means of
determining the chemical structures of carbohydrates including
their stereochemistries. However, in general, the amount of
sample required for NMR measurement is difficult to obtain
from natural proteins. We anticipate that peptide sequencing
utilizing the synthetic analogues of C-Man-Trp as authentic
samples will render it possible to conduct trace analysis in order
to discriminate between these analogues of identical molecular
weight. To this end, syntheses of the b-analogues of C-Man-Trp
are currently ongoing in our laboratories.
layer was washed with H2O (×2) and brine (×2), dried over
anhydrous Na2SO4, and concentrated under reduced pressure.
The residue was dissolved in CH3CN (ca. 100 ml), the solution
was washed with hexane (100 ml × 5) to remove the tin
residue,61 and concentrated. The residue was purified by silica
gel column chromatography (Et2O–hexane = 1 : 3) to give
a-ethynylmannose 21 (2.32 g, 83% in 2 steps) as an oil: [a]D27
+192 (c 0.86, CHCl3); IR (KBr) mmax 3276, 3031, 2872, 2112,
1
1740, 1454, 1237 cm−1; H NMR (300 MHz, CDCl3) d 2.07
(3H, s, OAc), 2.54 (1H, d, J = 2.5 Hz, C≡CH), 3.84 (1H, t, J =
2.5 Hz, H-2), 3.90 (1H, t, J = 9 Hz, H-4), 3.99 (1H, ddd, J =
9, 4.5, 2.5 Hz, H-5), 4.07 (1H, dd, J = 9, 3 Hz, H-3), 4.32 (1H,
dd, J = 12, 4.5 Hz, H-6), 4.38 (1H, dd, J = 12, 2.5 Hz, H-6),
4.59 (1H, d, J = 11 Hz, CHAHBPh), 4.62 (2H, br s, CH2Ph),
4.66 (1H, d, J = 12 Hz, CHCHDPh), 4.74 (1H, d, J = 12 Hz,
CHCHDPh), 4.80 (1H, t, J = 2.5 Hz, H-1), 4.94 (1H, d, J =
11 Hz, CHAHBPh), 7.27–7.41 (15H, m, aromatic); 13C NMR
(100 MHz, CDCl3) d 20.9, 63.5, 66.0, 71.9, 72.1, 73.0, 74.4,
75.3, 76.1, 77.7, 78.3, 80.1, 127.8, 128.2, 128.4, 137.8, 138.1,
170.9; MS (FAB) m/z 501 (M + H); Anal. Calcd. for C38H32O6:
C, 74.38; H, 6.44. Found: C, 74.38; H, 6.49.
Experimental
General
Optical rotations were measured on a JASCO DIP-370 digital
polarimeter. Infrared spectra (IR) were recorded on a JASCO
FT/IR-8300 spectrophotometer and are reported in wavenum-
bers (cm−1). Proton nuclear magnetic resonance (1H NMR)
spectra were recorded on a Bruker AMX-600 (600 MHz),
Bruker ARX-400 (400 MHz), Bruker AVANCE-400 (400 MHz)
and Varian Gemini-2000 (300 MHz) spectrometers. Data are
reported as follows; chemical shift, integration, multiplicity
(s = singlet, d = doublet, t = triplet, br = broadened, m =
multiplet), coupling constant and assignment. Carbon nuclear
magnetic resonance (13C NMR) spectra were recorded on Bruker
AMX-600 (150 MHz), Bruker ARX-400 (100 MHz), Bruker
AVANCE-400 (100 MHz) and Varian Gemini-2000 (75 MHz)
spectrometers. High resolution mass spectra (HRMS) were
recorded on a JEOL JMS-700 spectrometer and reported in
m/z. Elemental analyses were performed by the Analytical
Laboratory at the Graduate School of Bioagricultural Sciences,
Nagoya University. Reactions were monitored by thin-layer
chromatography (TLC) on 0.25 mm silica gel coated glass
plate 60 F254 (Merck, g 1.05715). Cica-reagent silica gel 60
(particle size 0.063–0.2 mm ASTM) was used for open-column
chromatography. Preparative thin-layer chromatographic sep-
arations were carried out on 0.5 mm silica gel plates 60
F254 (Merck, g 1.05774). Unless otherwise noted, non-aqueous
reactions were carried out in oven-dried (120 ◦C) or flame-dried
glassware under nitrogen atmosphere. Dry THF was distilled
from potassium metal with benzophenone. Dry CH2Cl2 was
distilled from CaH2 under nitrogen atmosphere. Et3N, n-BuNH2
and pyridine were dried over anhydrous KOH. Sc(ClO4)3 was
prepared according to the literature.49,50 All other commercially
available reagents were used as received.
(2,3,4,6-Tetra-O-benzyl-a-D-mannopyranosyl)ethyne (22).
(1) To an ice-cold solution of 17 (1.00 g, 1.72 mmol) and
stannylacetylene 20 (1.10 ml, 2.81 mmol) in dry CH2Cl2 (30 ml)
was added TMSOTf (0.70 ml, 3.37 mmol). After stirring at
0
◦C for 2 h, the mixture was quenched with sat. NaHCO3
solution and sat. Rochelle salt solution, and extracted with
CH2Cl2 (×3). The combined organic layer was washed with
H2O (×2) and brine (×1), dried over anhydrous Na2SO4, and
concentrated under reduced pressure. (2) The residue was
dissolved in THF (20 ml) and H2O (2 ml). To this solution
was added n-Bu4NF (1 M in THF, 3.7 ml, 3.7 mmol). After
stirring at rt for 1 h, sat. NH4Cl solution was added. The
resulting mixture was extracted with ether (×3). The combined
organic layer was washed with water (×2) and brine (×2), dried
over anhydrous Na2SO4, and concentrated. The residue was
dissolved in CH3CN (ca. 30 ml), and the solution was washed
with hexane (×4) and evaporated. The residue was purified by
column chromatography (Et2O–hexane = 1 : 3 → 1 : 2) to give
22 (450 mg, 48% in 2 steps) as an oil: [a]3D0 +22.7 (c 1.05, CHCl3),
lit.30 [a]D +23.5 (c 0.9, CHCl3); IR (KBr) mmax 3279, 3029, 2869,
2111, 1604, 1496, 1454, 1365, 1101 cm−1; 1H NMR (400 MHz,
CDCl3) d 2.50 (1H, d, J = 2.5 Hz, C≡CH), 3.72 (1H, dd, J =
11, 1.5 Hz, H-6), 3.79 (1H, dd, J = 11, 4.5 Hz, H-6), 3.83 (1H,
t, J = 2.5 Hz, H-2), 3.94–4.01 (2H, m, H-4, H-5), 4.03 (1H, dd,
J = 10, 2.5 Hz, H-3), 4.52 (1H, d, J = 10.5 Hz, CHAHBPh),
4.54 (1H, d, J = 12 Hz, CHCHDPh), 4.58 (1H, d, J = 11.5 Hz,
CHEHFPh), 4.61 (1H, d, J = 11.5 Hz, CHEHFPh), 4.65 (1H, d,
J = 12 Hz, CHCHDPh), 4.66 (1H, d, J = 12.5 Hz, CHGHHPh),
4.74 (1H, d, J = 12.5 Hz, CHGHHPh), 4.82 (1H, t, J = 2.5 Hz,
H-1), 4.88 (1H, d, J = 10.5 Hz, CHAHBPh) 7.13–7.40 (20H,
m, aromatic); 13C NMR (100 MHz, CDCl3) d 65.9, 69.1, 71.8,
72.0, 73.3, 74.7, 74.7, 75.2, 76.1, 77.4, 78.5, 80.1, 127.4, 127.6,
127.6, 127.7, 127.8, 128.0, 128.2, 128.2, 128.3, 128.3, 137.8,
138.2, 138.2, 138.3; HRMS (FAB) for C36H37O5 (M + H) calcd.
549.2641, found 549.2576; Anal. Calcd. for C36H36O5: C, 78.81;
H, 6.61. Found: C, 78.68; H, 6.89.
Synthesis of a-C-ethynylhexose through C-Glycosidation in
Table 1
(6-O-Acetyl-2,3,4-tri-O-benzyl-a-D-mannopyranosyl)ethyne
(21) (entry 1). (1) Diacetate 16 (3.00 g, 5.62 mmol) was
dissolved in dry CH2Cl2 (60 ml) and cooled to 0 ◦C. To this
solution were added tributylstannyl(trimethylsilyl)ethyne 20
(3.50 ml, 8.99 mmol) and TMSOTf (2.00 ml, 10.1 mmol)
successively. After stirring at rt for 15 h, the reaction was
quenched with sat. NaHCO3 solution and sat. Rochelle salt
solution, and then extracted with CH2Cl2 (×3). The combined
organic layer was washed with water (×2) and brine (×1), dried
over anhydrous Na2SO4, and concentrated. (2) The residue was
dissolved in THF (80 ml) and H2O (8 ml), and then n-Bu4NF
(1 M in THF, 11 ml, 11.0 mmol) was added. After stirring at rt
for 90 min, sat. NH4Cl solution was added, and the resulting
mixture was extracted with Et2O (×3). The combined organic
(2,3,4,5-Tetra-O-benzyl-a-D-glucopyranosyl)ethyne (23). (1)
Glucosylacetate 18 (1.07 g, 1.89 mmol) was azeotropically
dried from toluene and dissolved in dry CH2Cl2 (20 ml) and
tributylstannyl(trimethylsilyl)ethyne 20 (1.27 ml, 3.21 mmol)
was added. To this solution cooled to 4 ◦C was added TMSOTf
◦
(0.38 ml, 1.89 mmol). After stirring at 4 C for 3 h, additional
TMSOTf (0.38 ml, 1.89 mmol) and the stannylacetylene 20
(0.22 ml, 0.57 mmol) were added. The reaction mixture was
stirred at 4 ◦C for additional 15 h. The reaction was quenched
with sat. NaHCO3 solution, and the mixture was extracted with
CH2Cl2 (×3). The combined organic extracts were washed with
H2O (×2) and brine (×2), dried over Na2SO4, and concentrated.
O r g . B i o m o l . C h e m . , 2 0 0 5 , 3 , 6 8 7 – 7 0 0
6 9 3

View Article Online
(2) The residue was purified by column chromatography (silica
gel 150 g, Et2O–hexane = 1 : 10 → 1 : 3) to afford the
crude product (0.98 g) containing a small amount of stannane.
The crude product was dissolved in MeOH (19.6 ml) and
treated with K2CO3 (0.98 g) at rt for 1 h. The reaction was
quenched with saturated NH4Cl solution, and extracted with
AcOEt (×3). The combined organic extracts were washed with
H2O (×2) and brine (×2), dried over anhydrous Na2SO4, and
concentrated. To remove stannous residue, the residue was
dissolved in CH3CN and the solution was washed with hexane
(×3) and evaporated. The residue was purified by silica gel (40 g)
column chromatography (Et2O–hexane = 1 : 3 → 1 : 2) to afford
ethynylglucose 23 (0.71 g, 71% in 2 steps) as a colorless oil:
[a]D22 +41.0 (c 0.800, CHCl3), lit.62 [a]D +46.7 (c 1.7, CHCl3); IR
CHCHDPh), 7.20–7.42 (20H, m, aromatic); 13C NMR (75 MHz,
CDCl3) d 67.2, 68.6, 72.6, 73.1, 73.2, 73.4, 74.7, 74.8, 75.1, 76.3,
78.9, 80.1, 127.5, 127.6, 127.6, 127.8, 128.0, 128.3, 128.3, 128.4,
137.9, 138.2, 138.6, 138.7; MS (FAB) m/z 549 (M + H); Anal.
Calcd. for C36H36O5: C, 78.81; H, 6.61. Found: C, 78.79; H,
6.47.
Palladium catalyzed coupling between sugar acetylene and
N-tosyl-2-iodoaniline
Synthesis of 1-(6-O-acetyl-2,3,4-tri-O-benzyl-a-D-mannopy-
ranosyl)-2-o-(p-toluenesulfoamidyl)phenylethyne (25) under con-
dition A in Table 2 (entry 1). a-Ethynylmannose 21 (620 mg,
1.24 mmol), Pd2[dba]3·CHCl3 (31 mg, 0.031 mmol), Ph3P (31 mg,
0.12 mmol), CuI (23 mg, 0.12 mmol) and N-tosyl-2-iodoaniline
11 (892 mg, 2.40 mmol) were placed in a two-necked flask.
The flask was filled with argon and then dry THF (20 ml)
and n-BuNH2 (0.60 ml, 6.2 mmol) were added successively.
After stirring at rt for 3 h under argon, the reaction was
quenched with sat. NH4Cl solution and then extracted with
EtOAc (×3). The combined organic layer was washed with sat.
NH4Cl solution (×2), H2O (×2) and brine (×2), dried over
anhydrous Na2SO4 and concentrated. The residue was purified
by column chromatography (ether–hexane = 1 : 1) to give 25
(883 mg, 96%): [a]D24 +40 (c 0.97, CHCl3); IR (KBr) mmax 2870,
1
(KBr) mmax 3285, 3031, 2869, 2113, 1455, 1090 cm−1; H NMR
(300 MHz, CDCl3) d 2.59 (1H, d, J = 2.5 Hz, C≡CH), 3.62 (1H,
t, J = 9.5 Hz, H-4), 3.64 (1H, dd, J = 9.5, 6 Hz, H-2), 3.65 (1H,
dd, J = 11, 2 Hz, H-6), 3.74 (1H, dd, J = 11, 3.5 Hz, H-6), 3.96
(1H, t, J = 9.5 Hz, H-3), 3.95–4.01 (1H, m, H-5), 4.47 (1H, d,
J = 12 Hz, CHAHBPh), 4.47 (1H, d, J = 11 Hz, CHCHDPh),
4.60 (1H, d, J = 12 Hz, CHAHBPh), 4.69 (1H, d, J = 12 Hz,
CHEHFPh), 4.73 (1H, dd, J = 6, 2.5 Hz, H-1), 4.75 (1H, d,
J = 12 Hz, CHEHFPh), 4.83 (1H, d, J = 11 Hz, CHGHHPh),
4.83 (1H, d, J = 11 Hz, CHCHDPh), 4.99 (1H, d, J = 11 Hz,
CHGHHPh), 7.10–7.40 (20H, m, aromatic); 13C NMR (75 MHz,
CDCl3) d 66.6, 68.4, 73.1, 73.5, 73.6, 75.2, 75.7, 77.3, 77.6, 78.5,
78.7, 83.1, 127.7, 127.8, 127.8, 128.0, 128.1, 128.4, 128.6, 137.9,
138.2, 138.8; MS (FAB) m/z 549 (M + H); Anal. Calcd. for
C36H36O5: C, 78.81; H, 6.61. Found: C, 78.80; H, 6.60.
1
2218, 1740, 1239, 1092 cm−1; H NMR (400 MHz, CDCl3) d
2.10 (3H, s, OAc), 2.28 (3H, s, CH3 of Ts), 3.87 (1H, t, J =
2.5 Hz, H-2), 3.89–4.02 (3H, m, H-3, 4, 5), 4.35 (1H, dd, J =
12, 5 Hz, H-6), 4.41 (1H, dd, J = 12, 2 Hz, H-6), 4.61 (1H, d,
J = 10.5 Hz, CHAHBPh), 4.66 (2H, s, CH2Ph), 4.73 (1H, d, J =
12.5 Hz, CHCHDPh), 4.79 (1H, d, J = 12.5 Hz, CHCHDPh),
4.96 (1H, d, J = 10.5 Hz, CHAHBPh), 4.99 (1H, d, J = 2.5 Hz,
H-1), 7.00 (1H, td, J = 7.5, 1 Hz, aromatic), 7.00 (1H, br s, NH),
7.09 (2H, d, J = 8 Hz, aromatic), 7.15 (1H, dd, J = 7.5, 1.5 Hz,
aromatic), 7.23–7.44 (16H, m, aromatic), 7.57 (1H, dd, J = 8.5,
1 Hz, aromatic), 7.63 (2H, d, J = 8, Hz, aromatic); 13C NMR
(100 MHz, CDCl3) d 20.9, 21.5, 63.5, 66.6, 72.1, 72.2, 73.4, 74.4,
75.5, 76.1, 80.0, 84.0, 90.5, 112.5, 119.6, 124.2, 127.2, 127.8,
127.9, 128.3, 128.5, 128.5, 128.5, 130.0, 130.3, 132.6, 135.9,
137.7, 137.9, 137.9, 144.1, 171.0; MS (FAB) m/z 746 (M +
H); Anal. Calcd. for C44H43NO8S: C, 70.85; H, 5.81, N, 1.88.
Found: C, 70.86; H, 5.92; N, 1.77.
(2,3,4,5-Tetra-O-benzyl-a-D-galactopyranosyl)ethyne
(24).
(1) A two-necked round-bottomed flask was charged with
galactosylacetate 19 (565 mg, 0.971 mmol) azeotropically dried
from toluene and connected to a vacuum/argon line. The flask
was evacuated and then filled with argon. This evacuation/filling
cycle was repeated three times. The reagent was dissolved in
dry CH2Cl2 (17 ml) and tributylstannyl(trimethylsilyl)ethyne
20 (0.76 ml, 1.94 mmol) was added. To this solution cooled
to 5 ◦C was added TMSOTf (0.19 ml, 0.971 mmol). After
stirring at 5 ◦C for 3 h 55 min, additional TMSOTf (0.19 ml,
0.971 mmol) was added. The reaction mixture was stirred at
5
◦C for additional 12 h 35 min. The reaction was quenched
with saturated NaHCO3 solution and extracted with AcOEt
(×3). The combined organic extracts were washed with H2O
(×2) and brine (×2), dried over anhydrous Na2SO4, and
concentrated. The residue was purified by silica gel (60 g)
column chromatography (AcOEt–hexane = 1 : 7) to afford
the product (753 mg) containing a small amount of stannane.
(2) The product (753 mg) was dissolved in THF–H2O (21.5 :
1.1 ml) and n-Bu4NF (1.21 ml, 1.21 mmol, 1 M in THF) was
added. After stirring at rt for 1 h 35 min, n-Bu4NF (1.21 ml,
1.21 mmol, 1 M in THF) was added. The reaction mixture
was stirred at room temperature for additional 45 min. The
reaction was quenched with NH4Cl solution and extracted
with AcOEt (×3). The combined organic extracts were washed
with H2O (×2) and brine (×2), dried over anhydrous Na2SO4,
and concentrated. The residue was purified by silica gel (35 g)
column chromatography (AcOEt–hexane = 1 : 7) to afford
a-1-ethynylgalactose 24 (289 mg, 54% in 2 steps): [a]2D5 +38 (c
0.49, CHCl3), lit.36 [a]D +31.1 (c 1.7, CHCl3); IR (KBr) mmax
3287, 3031, 2112, 2871, 1455, 1100 cm−1; 1H NMR (300 MHz,
CDCl3) d 2.52 (1H, d, J = 2.5 Hz, C≡CH), 3.50 (1H, dd, J = 9,
7 Hz, H-6), 3.54 (1H, dd, J = 9, 6 Hz, H-6), 3.88 (1H, dd, J =
10, 3 Hz, H-3), 3.97 (1H, dd, J = 3, 1 Hz, H-4), 4.09 (1H, dd,
J = 9, 6 Hz, H-2), 4.12 (1H, br td, J = 6.5, 1 Hz, H-5), 4.39 (1H,
d, J = 12 Hz, CHAHBPh), 4.48 (1H, d, J = 12 Hz, CHAHBPh),
4.56 (1H, d, J = 11.5 Hz, CHCHDPh), 4.71 (1H, d, J = 12 Hz,
CHEHFPh), 4.74 (1H, d, J = 12 Hz, CHGHHPh), 4.79 (1H,
d, J = 12 Hz, CHGHHPh), 4.79 (1H, dd, J = 6, 2.5 Hz, H-1),
4.85 (1H, d, J = 12 Hz, CHEHFPh), 4.93 (1H, d, J = 11.5 Hz,
Synthesis of 1-(2,3,4,6-tetra-O-benzyl-a-D-mannopyranosyl)-
2-o-(p-toluenesulfoamidyl)phenylethyne (26) under condition B in
Table 2 (entry 3). A two-necked round-bottomed flask was
charged with a-ethynylmannose 21 (151 mg, 0.276 mmol), N-
tosyl-2-iodoaniline 11 (205 mg, 0.551 mmol) and PPh3 (7.2 mg,
0.027 mmol), and connected to a vacuum/argon line. The flask
was evacuated and then filled with argon. This evacuation/filling
cycle was repeated three times. Et3N (4.5 ml, distilled from
CaH2) was added and the solution was heated to 60 ◦C
with stirring. After these reagents were completely dissolved,
Pd(OAc)2 (3.1 mg, 0.014 mmol) was added and the mixture was
◦
stirred at 60 C for 2 h 20 min. The mixture was cooled to rt,
quenched with saturated NH4Cl solution, and extracted with
AcOEt (×3). The combined organic extracts were washed with
saturated NH4Cl solution (×2), H2O (×2) and brine (×2), dried
over anhydrous Na2SO4, and concentrated. The residue was
purified by silica gel (18 g) column chromatography (CH2Cl2 →
AcOEt–hexane = 1 : 4) to afford mannosyl-a-1-ethynylaniline 26
(165 mg, 75%): [a]D30 +46.6 (c 1.00, CHCl3); IR (KBr) mmax 3260,
3063, 3031, 2869, 2216, 1953, 1812 cm−1; 1H NMR (400 MHz,
CDCl3) d 2.25 (3H, s, CH3 of Ts), 3.76 (1H, dd, J = 10.5, 2 Hz,
H-6), 3.81 (1H, dd, J = 10.5, 5 Hz, H-6), 3.86 (1H, t, J =
2.5 Hz, H-2), 3.88–3.90 (1H, m, H-5), 3.97 (1H, dd, J = 9, 3 Hz,
H-3), 4.03 (1H, t, J = 9 Hz, H-4), 4.55 (1H, d, J = 10.5 Hz,
CHAHBPh), 4.57 (1H, d, J = 12 Hz, CHCHDPh), 4.64 (1H, d,
J = 12 Hz, CHEHFPh), 4.67 (1H, d, J = 12 Hz, CHEHFPh),
4.68 (1H, d, J = 12 Hz, CHCHDPh) 4.73 (1H, d, J = 12.5 Hz,
CHGHHPh), 4.79 (1H, d, J = 12.5 Hz, CHGHHPh), 4.90 (1H,
6 9 4
O r g . B i o m o l . C h e m . , 2 0 0 5 , 3 , 6 8 7 – 7 0 0

View Article Online
d, J = 10.5 Hz, CHAHBPh), 5.00 (1H, d, J = 2 Hz, H-1), 6.98
(1H, td, J = 7.5, 1 Hz, aromatic), 7.03 (1H, s, NH), 7.06 (2H, d,
J = 8 Hz, Ts), 7.13–7.44 (22H, m, aromatic), 7.57 (1H, d, J =
8 Hz, aromatic), 7.62 (2H, d, J = 8 Hz, Ts); 13C NMR (75 MHz,
CDCl3) d 21.5, 66.6, 69.1, 72.0, 72.2, 73.5, 74.7, 75.2,75.3, 76.2,
80.1, 83.7, 90.4, 112.7, 119.5, 124.2, 127.2, 127.5, 127.7, 127.8,
127.9, 128.2, 128.3, 128.4, 128.5, 129.6, 130.2, 130.4, 132.6,
134.9, 135.9, 137.8, 138.1, 138.1, 138.3, 144.0; Anal. Calcd. for
C49H47NO7S: C, 74.12; H, 5.97, N, 1.76. Found: C, 74.12; H,
6.04; N, 1.59.
concentrated. The residue was purified by silica gel column
chromatography (ether–hexane = 1 : 2) to give 29 (3.28 g, 88%):
[a]2D7 +82.2 (c 1.15, CHCl3). IR (KBr) mmax 1736, 1455, 1369,
1
1175, 1090 cm−1; H NMR (400 MHz, CDCl3) d 2.01 (3H, s,
OAc), 2.28 (3H, s, CH3 of Ts), 3.83–3.97 (4H, m, H-3, 4, 5, 6),
4.28 (1H, dd, J = 5, 2.5 Hz, H-2), 4.40 (1H, dd, J = 12, 6 Hz,
H-6), 4.56 (1H, d, J = 11.5 Hz, CHAHBPh), 4.60 (1H, d, J =
12 Hz, CHCHDPh), 4.61 (1H, d, J = 12 Hz, CHEHFPh), 4.67
(2H, d, J = 12 Hz, CHCHDPh and CHEHFPh), 4.72 (1H, d, J =
11.5 Hz, CHAHBPh), 5.98 (1H, d, J = 5 Hz, H-1), 6.37 (1H, s,
indole), 7.06 (2H, d, J = 8.5 Hz, aromatic), 7.20 (1H, t, J =
7.5 Hz, indole), 7.25–7.36 (17H, m, aromatic), 7.67 (2H, d, J =
8.5 Hz, aromatic), 8.13 (1H, d, J = 8.5 Hz, indole); MS (FAB)
m/z 746 (M + H); Anal. Calcd. for C44H43NO8S: C, 70.85; H,
5.81, N, 1.88. Found: C, 70.84; H, 5.78; N, 1.78.
1-(2,3,4,6-Tetra-O-benzyl-a-D-glucopyranosyl)-2-o-(p-toluene-
sulfoamidyl)phenylethyne (27). Following the procedure of
the entry 3, 27 (854 mg, 88%) was obtained as a yellow oil
from a-1-ethynylglucose 23 (672 mg, 1.23 mmol) after silica
gel (100 g) column chromatography (Et2O–hexane = 1 : 3):
[a]2D9 +52.5 (c 0.83, CHCl3); IR (KBr) mmax 3261, 3032, 2870,
2226, 1492, 1454, 1345, 1161, 1090 cm−1; 1H NMR (300 MHz,
CDCl3) d 2.27 (3H, s, CH3 of Ts), 3.66 (1H, t, J = 10 Hz, H-4),
3.67 (1H, dd, J = 10.5, 2 Hz, H-6), 3.75 (1H, dd, J = 10.5,
3.5 Hz, H-6), 3.76 (1H, dd, J = 10, 6 Hz, H-2), 3.90 (1H, br
d, J = 10 Hz, H-5), 3.98 (1H, t, J = 10 Hz, H-3), 4.49 (1H, d,
J = 12.5 Hz, CHAHBPh), 4.50 (1H, d, J = 11 Hz, CHCHDPh),
4.61 (1H, d, J = 12.5 Hz, CHAHBPh), 4.80 (1H, d, J = 13 Hz,
CHEHFPh), 4.85 (1H, d, J = 11 Hz, CHCHDPh), 4.86 (1H, d,
J = 6 Hz, H-1), 4.90 (1H, d, J = 11 Hz, CHGHHPh), 5.01 (1H,
d, J = 13 Hz, CHEHFPh), 5.12 (1H, d, J = 11 Hz, CHGHHPh),
6.96 (1H, t, J = 8 Hz, aromatic), 7.08 (2H, d, J = 8 Hz, Ts),
7.12–7.16 (2H, m, aromatic), 7.22–7.44 (22H, m, aromatic),
7.59 (1H, d, J = 8 Hz, aromatic), 7.70 (2H, d, J = 8 Hz, Ts),
7.88 (1H, s, NH); 13C NMR (75 MHz, CDCl3) d 21.4, 67.6,
68.4, 73.5, 73.5, 74.0, 75.2, 75.8, 77.2, 78.3, 83.7, 84.3, 91.9,
111.7, 117.6, 123.4, 127.3, 127.7, 127.8, 128.1, 128.1, 128.4,
128.4, 128.6, 129.7, 130.0, 131.5, 136.4, 137.8, 137.9, 138.1,
138.7, 139.0, 143.9; HR-MS (FAB) for C49H48NO7S (M + H)
calcd. 794.3152, found 794.3178.
2-(2,3,4,6-Tetra-O-benzyl-a-D-mannopyranosyl)-1-(p-toluene-
sulfonyl)indole (30). Following the procedure for 29, 30
(135 mg, 85%) was obtained from ethynylaniline 26 (159 mg,
0.20 mmol) after silica gel (7 g) column chromatography
(AcOEt–hexane = 1 : 4): [a]2D9 +69.9 (c 0.80, CHCl3); IR
1
(KBr) mmax 3295, 3031, 2869, 1496, 1455, 1097 cm−1. H NMR
(400 MHz, CDCl3) d 2.22 (3H, s, CH3 of Ts), 3.57 (1H, d, J =
10, 3 Hz, H-6), 3.86–3.91 (2H, m, H-3, 5), 3.94–4.02 (2H, m,
H-4, 6), 4.28 (1H, dd, J = 6, 2.5 Hz, H-2), 4.54 (2H, s, CH2Ph),
4.55–4.69 (6H, m, CH2Ph ×3), 6.01 (1H, d, J = 6 Hz, H-1),
6.46 (1H, s, indole), 6.98 (2H, d, J = 8 Hz, Ts), 7.16–7.36 (23H,
m, aromatic), 7.69 (2H, d, J = 8 Hz, Ts), 8.11 (1H, d, J = 8 Hz,
aromatic);13C NMR (100 MHz, CDCl3) d 21.5, 68.1, 69.1, 71.6,
72.4, 73.3, 74.9, 75.4, 76.0, 76.4, 92.3, 112.1, 115.5, 121.0, 122.4,
123.7, 124.8, 126.8, 126.9, 127.4, 127.7, 127.8, 127.9, 128.0,
128.2, 128.4, 129.0, 129.4, 129.5, 129.6 137.5, 138.2, 138.4,
138.7, 139.1, 144.2, 144.4; HR-MS (FAB) for C49H48NO7S
(M + H) calcd. 794.3152, found 794.3168.
2-(2,3,4,6-Tetra-O-benzyl-a-D-glucopyranosyl)-1-(p-toluenesul-
fonyl)indole (31). Following the procedure for 29, 31 (301 mg,
89%) was obtained as a yellow oil from ethynylaniline
27 (338 mg, 0.427 mmol) after silica gel (16 g) column
chromatography (AcOEt–hexane = 1 : 5 → 1 : 4): [a]2D7 +157
(c 1.05, CHCl3); IR (KBr) mmax 3029, 2866, 1454, 1367, 1175,
1-(2,3,4,6-Tera-O-benzyl-a-D-galactopyranosyl)-2-o-(p-toluene-
sulfoamidyl)phenylethyne (28). Following the procedure of
entry 3, 28 (909 mg, 86%) was obtained as a yellow oil from
a-1-ethynylgalactose 24 (732 mg, 1.34 mmol) after silica gel
(100 g) column chromatography (Et2O–hexane = 1 : 3 → 1 :
1): [a]2D5 +157 (c 1.05, CHCl3); IR (KBr) mmax 3262, 3031, 2872,
2227, 1492, 1455, 1344, 1161, 1092 cm−1; 1H NMR (300 MHz,
CDCl3) d 2.29 (3H, s, CH3 of Ts), 3.51 (1H, dd, J = 10, 7 Hz,
H-6), 3.56 (1H, dd, J = 10, 6 Hz, H-6), 3.92 (1H, dd, J = 10,
3 Hz, H-3), 3.99 (1H, br d, J = 3 Hz, H-4), 4.05 (1H, br t, J =
6.5 Hz, H-5), 4.20 (1H, dd, J = 10, 6 Hz, H-2), 4.40 (1H, d,
J = 12 Hz, CHAHBPh), 4.49 (1H, d, J = 12 Hz, CHAHBPh),
4.58 (1H, d, J = 11.5 Hz, CHCHDPh), 4.83 (1H, d, J = 11.5 Hz,
CHEHFPh), 4.84 (1H, d, J = 13 Hz, CHGHHPh), 4.94 (1H,
d, J = 6 Hz, H-1), 4.95 (1H, d, J = 12 Hz, CHCHDPh), 4.96
(1H, d, J = 11.5 Hz, CHEHFPh), 5.06 (1H, d, J = 13 Hz,
CHGHHPh), 6.96 (1H, t, J = 7.5 Hz, aromatic), 7.09 (2H, d,
J = 8.5 Hz, Ts), 7.21–7.38 (20H, m, aromatic), 7.40–7.46 (3H,
m, aromatic), 7.57 (1H, d, J = 8 Hz, aromatic), 7.67 (2H, d,
J = 8.5 Hz, Ts), 7.88 (1H, s, NH); 13C NMR (CDCl3, 75 MHz)
d 21.4, 68.2, 68.7, 73.0, 73.2, 73.5, 73.8, 74.5, 74.9, 74.9, 80.8,
83.1, 92.4, 112.0, 117.7, 123.4, 127.3, 127.6, 127.7, 127.8, 127.9,
128.0, 128.3, 128.3, 128.3, 128.4, 128.5, 129.6, 129.9, 131.6,
136.4, 137.9, 138.4, 138.5, 138.7, 139.1, 143.9; Anal. Calcd. for
C49H47NO7S: C, 74.12; H, 5.97, N, 1.76. Found: C, 74.11; H,
5.77; N, 1.72.
1
1092 cm−1; H NMR (300 MHz, CDCl3) d 2.27 (3H, s, CH3
of Ts), 2.94 (1H, dd, J = 11, 2 Hz, H-6ꢀ), 3.43 (1H, br d, J =
10 Hz, H-5), 3.50 (1H, dd, J = 11, 3.5 Hz, H-6), 3.74 (1H, dd,
J = 10, 8 Hz, H-4), 4.14 (1H, t, J = 8 Hz, H-3), 4.23 (1H, dd,
J = 8, 6 Hz, H-2), 4.39 (1H, d, J = 12.5 Hz, CHAHBPh), 4.47
(1H, d, J = 11 Hz, CHCHDPh), 4.48–4.58 (3H, m, CH2Ph &
CHAHBPh), 4.75 (1H, d, J = 11 Hz, CHCHDPh), 4.77 (1H, d,
J = 11.5 Hz, CHGHHPh), 4.98 (1H, d, J = 11.5 Hz, CHGHHPh),
6.11 (1H, d, J = 6 Hz, H-1), 7.03 (2H, d, J = 8 Hz, Ts), 7.04
(1H, s, indole), 7.10–7.35 (22H, m, aromatic), 7.49 (1H, d, J =
8 Hz, indole), 7.68 (2H, d, J = 8 Hz, Ts), 8.19 (1H, d, J = 8 Hz,
indole); 13C NMR (75 MHz, CDCl3) d 21.4, 68.3, 68.8, 72.3,
72.7, 73.3, 74.3, 74.5, 77.4, 78.5, 81.5, 114.7, 115.2, 121.2, 123.7,
125.0, 126.6, 127.6, 127.7, 127.8, 127.9, 127.9, 128.1, 128.3,
128.4, 128.9, 129.6, 135.6, 136.5, 137.6, 137.8, 138.2, 138.3,
138.5, 144.5; Anal. Calcd. for C49H47NO7S: C, 74.12; H, 5.97,
N, 1.76. Found: C, 74.14; H, 6.08; N, 1.75.
2-(2,3,4,6-Tetra-O-benzyl-a-D-galactopyranosyl)-1-(p-toluene-
sulfonyl)indole (32). Following the procedure for 29, 32
(879 mg, 92%) was obtained as a yellow oil from ethynylaniline
28 (951 mg, 1.20 mmol) after silica gel (45 g) column
chromatography (AcOEt–hexane = 1 : 5): [a]2D7 +126 (c 0.525,
CHCl3); IR (KBr) mmax 3031, 2872, 1453, 1369, 1174, 1088 cm−1;
1H NMR (400 MHz, CDCl3) d 2.17 (3H, s, CH3 of Ts), 3.84
(1H, dd, J = 12, 3 Hz, H-6), 3.85 (1H, dd, J = 5, 3 Hz, H-3),
4.04 (1H, dd, J = 12, 8 Hz, H-6), 4.12 (1H, dd, J = 6, 3 Hz,
H-4), 4.16 (1H, d, J = 12 Hz, CHAHBPh), 4.21 (1H, d, J =
12 Hz, CHAHBPh), 4.26 (1H, dd, J = 5, 2.5 Hz, H-2), 4.33 (1H,
d, J = 12 Hz, CHCHDPh), 4.35–4.38 (1H, m, H-5), 4.48 (1H, d,
2-(6-O-Acetyl-2,3,4-tri-O-benzyl-a-D-mannopyranosyl)-1-(p-
toluenesulfonyl)indole (29). To a solution of ethynylaniline
25 (3.71 g, 4.99 mmol) in Et3N (60 ml) and DMF (30 ml)
was added CuI (187 mg, 0.98 mmol). After stirring at 80 ◦C
for 30 min, water was added. The mixture was extracted with
AcOEt (×3). The combined organic layer was washed with
aqueous NH4Cl solution (×2), water (×2) and brine (×2), and
O r g . B i o m o l . C h e m . , 2 0 0 5 , 3 , 6 8 7 – 7 0 0
6 9 5

View Article Online
(11 g) column chromatography (AcOEt–hexane = 1 : 5): [a]D23
+122 (c 0.449, CHCl3); IR (KBr) mmax 3427, 3032, 2870, 1455,
J = 12 Hz, CHCHDPh), 4.52 (1H, d, J = 12 Hz, CHEHFPh),
4.56 (1H, d, J = 12 Hz, CHGHHPh), 4.57 (1H, d, J = 12 Hz,
CHEHFPh), 4.76 (1H, d, J = 12 Hz, CHGHHPh), 5.83 (1H, d,
J = 2.5 Hz, H-1), 6.92–6.99 (5H, m, aromatic), 7.11–7.39 (20H,
m, aromatic), 7.44 (1H, d, J = 8 Hz, indole), 7.52 (2H, d, J =
8 Hz, Ts), 8.18 (1H, d, J = 8 Hz, indole); 13C NMR (75 MHz,
CDCl3) d 21.3, 65.6, 66.5, 71.8, 72.2, 72.9, 73.1, 73.4, 74.7,
75.1, 75.9, 113.3, 115.3, 120.9, 123.9, 124.5, 126.3, 127.4, 127.5,
127.7, 127.8, 128.1, 128.3, 128.3, 128.4, 129.7, 130.1, 135.5,
137.5, 137.6, 137.8, 138.4, 138.5, 138.6, 144.7; Anal. Calcd. for
C49H47NO7S: C, 74.12; H, 5.97; N, 1.76. Found: C, 74.12; H,
6.03; N, 1.68.
1
1072 cm−1; H NMR (400 MHz, CDCl3) d 3.63 (1H, dd, J =
10, 8 Hz, H-4), 3.65 (1H, dd, J = 11, 4 Hz, H-6), 3.69 (1H, dd,
J = 11, 2 Hz, H-6), 3.72 (1H, ddd, J = 10, 4, 2 Hz, H-5), 3.96
(1H, dd, J = 10, 8 Hz, H-3), 4.02 (1H, dd, J = 10, 6 Hz, H-2),
4.47 (1H, d, J = 11 Hz, CHAHBPh), 4.51 (1H, d, J = 12 Hz,
CHCHDPh), 4.61 (1H, d, J = 12 Hz, CHCHDPh), 4.78 (1H, d,
J = 11 Hz, CHEHFPh), 4.79 (1H, d, J = 11 Hz, CHAHBPh),
4.81 (1H, d, J = 10.5 Hz, CHGHHPh), 4.84 (1H, d, J = 11 Hz,
CHEHFPh), 4.97 (1H, d, J = 10.5 Hz, CHGHHPh), 5.39 (1H, d,
J = 6 Hz, H-1), 6.71 (1H, s, indole), 7.06–7.10 (2H, m, aromatic),
7.14 (1H, t, J = 8 Hz, indole), 7.20–7.39 (20H, m, aromatic),
7.57 (1H, d, J = 8 Hz, indole), 8.82 (1H, s, NH of indole); 13
C
Typical experimental procedure for deprotection of Ts group in
Table 3
NMR (100 MHz, CDCl3) d 69.1, 70.4, 73.2, 73.5, 73.8, 74.8,
75.6, 78.2, 80.7, 82.6, 102.7, 110.9, 119.8, 120.5, 121.9, 127.6,
127.6, 127.7, 127.7, 127.9, 128.0, 128.1, 128.2, 128.3, 128.4,
128.6, 134.5, 135.7, 137.8, 138.0, 138.2, 138.6; Anal. Calcd. for
C42H41NO5: C, 78.85; H, 6.46; N, 2.19. Found: C, 78.86; H, 6.52;
N, 2.27.
2-(6-O-Acetyl-2,3,4-tri-O-benzyl-a-D-mannopyranosyl)-1-indole
(33). To a solution of tosyindole 29 (205 mg, 0.276 mmol) in
THF (6 ml) was added n-Bu4NF (1M, 1.4 ml, 1.4 mmol). After
stirring at rt for 50 min, the reaction mixture was quenched
with sat. NH4Cl solution. The resulting mixture was extracted
with Et2O (×2). The combined organic layer was washed with
water (×2), sat. NH4Cl solution (×1) and brine (×1), dried
over anhydrous Na2SO4, and concentrated. The residue was
dissolved in pyridine (1 ml) and Ac2O (1 ml). The solution
was stirred at rt for 30 min, and then diluted with toluene.
The mixture was evaporated in vacuo and subjected to silica
gel column chromatography (ether–hexane = 1 : 1) to give 33
(147 mg, 90% in 2 steps) as a colorless oil: [a]2D7 +68 (c 0.82,
CHCl3). IR (KBr) vmax 3030, 2874, 1734, 1456, 1364, 1239,
2-(2,3,4,6-Tetra-O-benzyl-a-D-galactopyranosyl)-1H-indole(36).
Following the procedure for 33, 36 (641 mg, 90%) was obtained
as a yellow oil from 32 (879 mg, 1.11 mmol) after silica gel
(22 g) column chromatography (AcOEt–hexane = 1 : 5): [a]D23
+80.9 (c 1.13, CHCl3); IR (KBr) mmax 3425, 3031, 2869, 1455,
1
1090 cm−1; H NMR (300 MHz, CDCl3) d 3.52 (1H, dd, J =
10, 5 Hz, H-6), 3.77 (1H, dd, J = 10, 7 Hz, H-6), 3.84 (1H,
dd, J = 9, 3 Hz, H-3), 3.90 (1H, t, J = 3 Hz, H-4), 3.96 (1H,
m, H-5), 4.34 (1H, br dd, J = 9, 5 Hz, H-2), 4.45 (1H, d, J =
12 Hz, CHAHBPh), 4.53 (1H, d, J = 12 Hz, CHAHBPh), 4.59
(1H, d, J = 11.5 Hz, CHCHDPh), 4.68 (1H, br d, J = 11 Hz,
CHEHFPh), 4.72 (2H, s, CH2Ph), 4.78 (1H, br d, J = 11 Hz,
CHEHFPh), 4.88 (1H, d, J = 11.5 Hz, CHCHDPh), 5.39 (1H, d,
J = 5 Hz, H-1), 6.60 (1H, s, indole), 7.08 (1H, td, J = 7, 1 Hz,
indole), 7.14 (1H, td, J = 7, 1 Hz, indole), 7.21–7.38 (21H, m,
1
1096, 1027 cm−1; H NMR (400 MHz, CDCl3) d 2.09 (3H, s,
OAc), 3.59 (1H, dt, J = 8, 4 Hz, H-5), 3.89–3.94 (2H, m, H-3,
4), 4.17 (1H, br t, J = 3 Hz, H-2), 4.34 (2H, d, J = 4 Hz, H-6),
4.58 (1H, d, J = 11 Hz, CHAHBPh), 4.65 (1H, d, J = 12 Hz,
CHCHDPh), 4.71 (2H, br s, CH2Ph), 4.72 (1H, d, J = 12 Hz,
CHCHDPh), 4.84 (1H, d, J = 11 Hz, CHAHBPh), 5.24 (1H, d,
J = 3 Hz, H-1), 5.86 (1H, s, indole), 7.07 (1H, t, J = 7.5 Hz,
aromatic), 7.16 (1H, t, J = 7.5 Hz, aromatic), 7.22–7.40 (16H,
m, aromatic), 7.46 (1H, d, J = 7.5 Hz, aromatic), 8.35 (1H,
br s, NH); 13C NMR (100 MHz, CDCl3) d 20.9, 63.6, 70.9,
72.3, 72.8, 73.5, 74.5, 74.9, 75.1, 78.7, 100.8, 110.8, 120.0, 120.4,
122.3, 127.8, 127.8, 128.0, 128.0, 128.1 128.3, 128.4, 128.6,
134.3, 135.8, 138.0, 138.0, 138.1, 170.9; MS (FAB) m/z 592
(M + H); Anal. Calcd. for C37H37NO6S: C, 75.11; H, 6.30, N,
2.37. Found: C, 75.13; H, 6.35; N, 2.29.
aromatic), 7.56 (1H, d, J = 8 Hz, indole), 8.87 (1H, s, NH); 13
C
NMR (75 MHz, CDCl3) d 68.7, 69.8, 73.0, 73.3, 74.0, 74.1, 74.6,
77.7, 78.6, 101.8, 110.9, 119.6, 120.4, 121.6, 127.6, 127.7, 128.0,
128.2, 128.4, 128.4, 128.5, 135.2, 135.7, 138.1, 138.2, 138.5; Anal.
Calcd. for C42H41NO5: C, 78.85; H, 6.46; N, 2.19. Found: C,
78.84; H, 6.50; N, 2.26.
2-(6-O-Acetyl-2,3,4-tri-O-benzyl-a-D-mannopyranosyl)-1H-3-
formylindole (38a). To ice-cold dry DMF (5 ml) was added
POCl3 (59 ll, 0.63 mmol). To this solution was added indole
33 (146 mg, 0.25 mmol). After stirring for 15 min, the mixture
was diluted with an ice-cold aqueous solution of KOH (3.52 g
in 20 ml water) and stirred at 90 ◦C for 30 min. The mixture
was allowed to stand overnight at rt, and then extracted with
EtOAc (×3). The combined organic extracts were washed with
H2O (×2) and sat. NH4Cl solution (×2) and brine (×2), dried
over anhydrous Na2SO4, and concentrated. The residue was
dissolved in pyridine (2 ml) and Ac2O (2 ml). After the solution
was stirred at rt for 20 min, the mixture was concentrated in
vacuo. The residue was purified by column chromatography
(Et2O–hexane = 2 : 1) to give aldehyde 38a (131 mg, 85% in 2
steps): [a]2D7 −6.82 (c 1.02, CHCl3); IR (KBr) mmax 2927, 1740,
1651, 1455, 1368, 1233, 1103, 1039 cm−1; 1H NMR (400 MHz,
CDCl3) d 2.01 (3H, s, OAc), 3.61 (1H, dd, J = 4, 1.5 Hz, H-4),
3.82 (1H, dd, J = 9.5, 2.5 Hz, H-2), 3.89 (1H, dd, J = 4, 2.5 Hz,
H-3), 4.10 (1H, d, J = 12 Hz, CHAHBPh), 4.14 (1H, dd, J =
12.5, 4 Hz, H-6), 4.20 (1H, d, J = 12 Hz, CHAHBPh), 4.27 (1H,
ddd, J = 9, 4, 1.5 Hz, H-5), 4.40 (1H, d, J = 12 Hz, CHCHDPh),
4.49 (1H, d, J = 12 Hz, CHCHDPh), 4.60 (1H, d, J = 12 Hz,
CHEHFPh), 4.77 (1H, d, J = 12Hz, CHEHFPh), 4.77 (1H,
dd, J = 12.5, 9 Hz, H-6), 5.60 (1H, d, J = 9.5 Hz, H-1), 7.00
(2 H, m, aromatic), 7.08–7.40 (16H, m, aromatic), 8.37 (1H, m,
aromatic), 9.08 (1H, br s, NH), 10.26 (1H, s, CHO); 13C NMR
(75 MHz, CDCl3) d 20.7, 61.5, 65.0, 72.1, 72.3, 73.1, 73.7, 75.1,
75.3, 75.7, 111.1, 116.0, 122.2, 122.7, 123.8, 125.9, 127.9, 127.9,
2-(2,3,4,6-Tetra-O-benzyl-a-D-mannopyranosyl)-1H-indole (34).
Following the procedure for 33, 34 (101 mg, 93%) was obtained
from 30 (135 mg, 0.170 mmol) after silica gel (6 g) column
chromatography (AcOEt:hexane = 1 : 4): [a]3D0 +53.0 (c 0.99,
CHCl3); IR (KBr) mmax 3311, 3087, 3062, 3030, 2867, 2630, 1953,
1881, 1811 cm−1; 1H NMR (400 MHz, CDCl3) d 3.54–3.62 (1H,
m, H-5), 3.69–3.78 (2H, m, H-6 × 2), 3.88 (1H, dd, J = 8.5,
2.5 Hz, H-3), 3.92 (1H, t, J = 8.5 Hz, H-4), 4.16 (1H, t, J =
2.5 Hz, H-2), 4.50 (1H, d, J = 11 Hz, CHAHBPh), 4.55 (1H, d,
J = 12 Hz, CHCHDPh), 4.60 (1H, d, J = 12 Hz, CHCHDPh),
4.62 (1H, d, J = 12 Hz, CHEHFPh), 4.71 (1H, d, J = 12 Hz,
CHEHFPh), 4.72 (1H, d, J = 12.5 Hz, CHGHHPh), 4.78 (1H, d,
J = 12.5 Hz, CHGHHPh), 4.83 (1H, d, J = 11 Hz, CHAHBPh),
5.24 (1H, m, H-1), 5.80 (1H, br s, indole), 7.00–7.55 (24H, m,
aromatic), 8.46 (1H, br s, NH);13C NMR (75 MHz, CDCl3) d
69.6, 71.2, 72.2, 72.7, 73.3, 74.5, 74.8, 75.1, 75.2, 79.0, 100.2,
110.9, 119.7, 120.2, 122.1, 127.5, 127.6, 127.7, 127.9, 128.1,
128.3, 128.4, 128.5, 134.6, 135.8, 137.9, 138.2, 138.2; MS (FAB)
m/z 640 (M + H); HR-MS (FAB) for C42H41NO5 (M + H),
calcd. 640.3063, found 640.2963; Anal. Calcd. for C42H41NO5:
C, 78.85; H, 6.46, N, 2.19. Found: C, 78.86; H, 6.42; N, 2.13.
2-(2,3,4,6-Tetra-O-benzyl-a-D-glucopyranosyl)-1H-indole (35).
Following the procedure for 33, 35 (353 mg, 98%) was obtained
as an orange oil from 31 (446 mg, 0.563 mmol) after silica gel
6 9 6
O r g . B i o m o l . C h e m . , 2 0 0 5 , 3 , 6 8 7 – 7 0 0

View Article Online
128.0, 128.1, 128.2, 128.3, 128.3, 128.6, 128.7, 135.0, 137.1,
137.3, 137.8, 146.4, 170.9, 186.0; MS (FAB) m/z 620 (M +
H); Anal. Calcd. for C44H43NO8S: C, 73.65; H, 6.02, N, 2.26.
Found: C, 73.67; H, 6.06; N, 2.17.
3-[Ethyl-2(S)-acetamidopropanoyl]-2-(2,3,4,6-tetra-O-acetyl-
a-D-mannosyl)-1H-indole (42b). A solution of 42a (2.0 mg,
0.0036 mmol) in Ac2O (0.2 ml) and pyridine (0.2 ml) was stirred
at rt for 24 h. The mixture was evaporated in vacuo and purified
by preparative TLC (AcOEt) to give tetraacetate 42b (2.0 mg,
91%): [a]2D5 +42.6 (c 0.28, CHCl3); IR (KBr) mmax 2927, 1749,
1372, 1225, 1048 cm−1; 1H NMR (400 MHz, CDCl3) d 1.05 (3H,
t, J = 7 Hz, COOCH2CH3), 1.89 (3H, s, Ac), 2.01 (3H, s, Ac),
2.08 (3H, s, Ac), 2.14 (3H, s, Ac), 2.19 (3H, s, Ac), 3.28 (1H, dd,
J = 14.5, 6.5 Hz, CHAHBCHCOOEt), 3.37 (1H, dd, J = 14.5,
7.5 Hz, CHAHBCHCOOEt), 3.93–4.01 (1H, m, OCHAHBCH3),
4.04–4.11 (2H, m, H-5, OCHAHBCH3), 4.20 (1H, dd, J = 12,
3.5 Hz, H-6), 4.72 (1H, dd, J = 12, 8 Hz, H-6), 4.78 (1H, q,
J = 7 Hz, CHCOOEt), 5.19 (1H, dd, J = 6.5, 5 Hz, H-4), 5.34
(1H, d, J = 7 Hz, H-1), 5.36 (1H, dd, J = 6.5, 3 Hz, H-3), 5.71
(1H, dd, J = 7, 3 Hz, H-2), 6.32 (1H, br d, J = 7.5 Hz, NHAc),
7.12 (1H, td, J = 7.5, 1 Hz, indole), 7.21 (1H, td, J = 7.5, 1 Hz,
indole), 7.36 (1H, d, J = 8 Hz, indole), 7.53 (1H, d, J = 7.5 Hz,
indole), 8.46 (1H, br s, NH of indole); 13C NMR (100 MHz,
CDCl3) d 13.8, 20.7, 20.8, 20.8, 23.0, 27.1, 29.7, 53.1, 61.2,
61.5, 67.4, 67.7, 68.0, 69.0, 73.8, 110.5, 111.4, 118.8, 120.1,
123.0, 128.5, 129.7, 135.5, 169.6, 169.7, 170.3, 172.5; MS (FAB)
m/z 605 (M + H); HRMS (FAB+) for C19H37O12N2 (M + H),
605.2347, found 605.2325.
2-(6-O-Acetyl-2,3,4-tri-O-benzyl-a-D-mannopyranosyl)-1H-3-
(ethyl-2-acetoamido-1-propenoyl)-1H-indole (41). Aldehyde
38a (66 mg, 0.11 mmol) and N-acetamide malonate monomethyl
ester (40) (24 mg, 0.17 mmol) were dissolved in pyridine (3 ml)
and Ac2O (1 ml). After stirring at rt for 3 h, 40 (10 mg,
0.072 mmol) was added and stirring was continued for 3 h.
Silica gel (2 g) was added and the mixture was heated at 60 ◦C
for 14 h and then filtered through a pad of Super Cel. The
filtrate was concentrated and the residue was dissolved in
H2O and extracted with EtOAc (×3). The combined extracts
were washed with sat. NH4Cl solution, dried over anhydrous
Na2SO4, and concentrated. The residue was purified by column
chromatography (Et2O–hexane = 3 : 1) to give 41 (40 mg, 49%)
and the recovered aldehyde 38a (26 mg, 39%): [a]2D6 +1.53 (c
0.60, CHCl3); IR (KBr) mmax 1740, 1721, 1678, 1496, 1455, 1372,
1
1240, 1104, 1029 cm−1; H NMR (400 MHz, CDCl3) d 1.29
(3H, t, J = 7 Hz, OCH2CH3), 2.02 (3H, s, Ac), 2.33 (3H, s, Ac),
3.67 (1H, dd, J = 4.5, 3 Hz, H-4), 3.89 (1H, dd, J = 4.5, 2.5 Hz,
H-3), 4.03 (1H, m, H-2), 4.14 (1H, m, H-5), 4.19 (1H, dd, J =
12, 3.5 Hz, H-6), 4.27 (2H, m, OCH2CH3), 4.51 (2H, s, CH2Ph),
4.58 (1H, d, J = 12 Hz, CHAHBPh), 4.62–4.70 (3H, m, H-6
and CH2Ph), 4.73 (1H, d, J = 12 Hz, CHAHBPh), 5.33 (1H, br
d, J = 7.5 Hz, H-1), 6.93 (1H, br s, NHAc), 7.04 (1H, d, J =
7.5 Hz, aromatic), 7.09–7.36 (16H, m, aromatic), 7.44 (1H, d,
3-[Ethyl-2(R)-acetamidopropanoyl]-2-(2,3,4,6-tetra-O-acetyl-
a-D-mannosyl)-1H-indole (43b). Following the procedure for
42b, tetraacetate 43b (6.0 mg, 34%) was obtained from 43a
(5.5 mg, 0.012 mmol) after preparative TLC (AcOEt): [a]D27
+33.2 (c 0.53, CHCl3); IR (KBr) mmax 2936, 1743, 1668, 1372,
=
J = 8 Hz, aromatic), 7.49 (1H, s, CH CCOOEt), 8.85 (1H, br s,
1
1227, 1051 cm−1; H NMR (400 MHz, CDCl3) d 1.12 (3H, t,
NH of indole); 13C NMR (75 MHz, CDCl3) d 14.1, 20.8, 23.0,
53.4, 61.3, 62.0, 66.5, 72.0, 72.5, 73.2, 74.4, 75.0, 75.7, 108.7,
111.4, 120.6, 122.7, 123.1, 125.4, 126.0, 127.8, 127.9, 128.1,
128.4, 128.5, 128.6, 135.5, 136.2, 137.5, 137.6, 137.9, 165.1,
168.8, 171.0; MS (FAB) m/z 747 (M + H); HR-MS (FAB) for
C44H47N2O9 (M + H) calcd. 747.3282, found 747.3199.
J = 7 Hz, COOCH2CH3), 1.88 (3H, s, Ac), 2.02 (3H, s, Ac),
2.10 (3H, s, Ac), 2.12 (3H, s, Ac), 2.19 (3H, s, Ac), 3.21 (1H, dd,
J = 15, 8.5 Hz, CHAHBCHCOOEt), 3.35 (1H, dd, J = 15, 6 Hz,
CHAHBCHCOOEt), 4.01–4.17 (3H, m, H-5, COOCH2CH3),
4.22 (1H, dd, J = 12, 3.5 Hz, H-6), 4.71 (1H, dd, J = 12, 7.5 Hz,
H-6), 4.85 (1H, td, J = 8, 6 Hz, CHCOOEt), 5.20 (1H, dd, J =
6.5, 5 Hz, H-4), 5.33 (1H, dd, J = 6.5, 3 Hz, H-3), 5.43 (1H, d,
J = 6.5 Hz, H-1), 5.72 (1H, dd, J = 6.5, 3 Hz, H-2), 6.31 (1H,
br d, J = 7.5 Hz, NHAc), 7.13 (1H, td, J = 7.5, 1 Hz, indole),
7.21 (1H, td, J = 7.5, 1 Hz, indole), 7.36 (1H, d, J = 8 Hz,
indole), 7.58 (1H, d, J = 8 Hz, indole), 8.50 (1H, br s, indole
NH); 13C NMR (100 MHz, CDCl3) d 13.9, 20.7, 20.7, 20.8,
22.9, 27.0, 53.0, 61.4, 67.5, 68.0, 69.0, 73.9, 110.5, 111.4, 118.8,
120.1, 123.1, 128.1, 129.5, 135.6, 169.5, 169.8, 170.0, 170.2,
170.7, 172.4; MS (FAB) m/z 605 (M + H); HRMS (FAB) for
C19H37O12N2 (M + H), 605.2347, found 605.2346.
Reduction of dehydrotryptophan 41. Dehydrotryptophan 41
(22 mg, 0.029 mmol) was dissolved in MeOH (0.8 ml) and
Pd(OH)2/C (22 mg) was added. The reaction vessel was filled
with hydrogen gas. After stirring vigorously at rt for 32 h,
the mixture was filtered through a pad of Super Cel, and the
filtrate concentrated. The residue was purified by preparative
TLC (10% MeOH–CH2Cl2) to give 42a (2.2 mg, 16%, polar)
and 43a (5.5 mg, 39%, less polar).
3-[Ethyl-2(S)-acetamidopropanoyl]-2-a-D-mannosyl-1H-indole
(42a). 1H NMR (400 MHz, CDCl3) d 1.11 (3H, t, J = 7.5 Hz,
OCH2CH3), 1.76 (3H, s, Ac), 1.92 (3H, s, Ac), 3.16 (1H, dd,
J = 14.5, 10 Hz, CHAHBCHCOOEt), 3.32 (1H, dd, J = 14.5,
6 Hz, CHAHBCHCOOEt), 3.80–4.15 (6H, m, H-3, 4, 5, 6,
OCH2CH3), 4.26 (1H, br d, J = 8.5 Hz, H-2), 4.48 (3H, br s,
OH x3), 4.67 (1H, m, CHCOOEt), 4.93 (1H, dd, J = 12.5, 9 Hz,
H-6), 5.10 (1H, d, J = 8.5 Hz, H-1), 7.03 (1H, t, J = 7.5 Hz,
aromatic), 7.09 (1H, t, J = 7.5 Hz, aromatic), 7.21 (1H, d, J =
8 Hz, aromatic), 7.35 (1H, br d, J = 6 Hz, NHAc), 7.49 (1H, d,
J = 8 Hz, aromatic), 9.34 (1H, br s, NH of indole); MS (FAB)
m/z 479 (M + H).
Sc(OTf)3-promoted coupling between mannosylindole 33 and
aziridine 44 (entry 2 in Table 4)
Mannosylindole 33 (50 mg, 0.085 mmol) and aziridine 44 (40 mg,
0.17 mmol) were dissolved in dry CH2Cl2 (2.0 ml). To this
solution cooled to 0 ◦C was added Sc(OTf)3 (83 mg, 0.17 mmol).
After stirring at the same temperature for 3 h, sat. NaHCO3
solution was added. The resulting mixture was extracted with
EtOAc (×3). The combined organic layer was washed with H2O
(×2) and brine (×2), dried over anhydrous Na2SO4, passed
through a column packed with Na2CO3, and evaporated. The
residue was purified by column chromatography (silica gel 30 g,
ether–hexane = 1 : 1 to 3 : 1) to give 45 (33 mg, 47%, 45a : 45b =
3-[Ethyl-2(R)-acetamidopropanoyl]-2-a-D-mannosyl-1H-indole
(43a). 1H NMR (400 MHz, CDCl3) d 1.23 (3H, t, J = 7 Hz,
OCH2CH3), 1.58 (3H, s, Ac), 1.98 (3H, s, Ac), 3.14 (1H, dd,
J = 14.5, 9.5 Hz, CHAHBCHCOOEt), 3.34 (1H, dd, J = 14.5,
5.5 Hz, CHAHBCHCOOEt), 3.85–4.21 (8H, m, H-3, 4, 5, 6,
OCH2CH3, OH × 2), 4.28 (1H, dd, J = 8.5, 2 Hz, H-2), 4.81
(1H, td, J = 9.5, 5 Hz, CHCOOEt), 4.96 (1H, dd, J = 13,
9.5 Hz, H-6), 5.13 (1H, d, J = 8.5 Hz, H-1), 5.22 (1H, br s,
OH), 6.63 (1H, br s, NHAc), 7.03 (1H, t, J = 7 Hz, aromatic),
7.08 (1H, t, J = 7 Hz, aromatic), 7.20 (1H, d, J = 7.5 Hz,
aromatic), 7.43 (1H, d, J = 7.5 Hz, aromatic), 9.39 (1H, br s,
NH of indole); MS (FAB) m/z 479 (M + H).
1
ca. 3 : 1 from H NMR) as an oil. A portion of this oil was
separated by preparative TLC (ether–hexane = 1 : 1; CH2Cl2
×3) to give pure 45a and 45b.
2-(6-O-Acetyl-2,3,4-tri-O-benzyl-a-D-mannopyranosyl)-L-(N-
carbobenzyloxyl)tryptophan methyl ester (45a). [a]2D3 +14.5 (c
0.35, CHCl3); IR (KBr) vmax 3328, 3031, 2449, 1724, 1518, 1454,
1
1221, 1028 cm−1; H NMR (400 MHz, CDCl3) d 1.89 (3H, s,
OAc), 3.15 (1H, dd, J = 14.5, 10.5 Hz, CHAHBCHCOOCH3),
3.37 (1H, dd J = 14.5, 4.5 Hz, CHAHBCHCOOCH3), 3.55 (1H,
O r g . B i o m o l . C h e m . , 2 0 0 5 , 3 , 6 8 7 – 7 0 0
6 9 7

View Article Online
dd, J = 3.5, 1 Hz, H-4), 3.75 (3H, s, COOCH3), 3.83–3.88 (2H,
m, H-2, H-3), 4.04 (1H, d, J = 13 Hz, CHAHBPh), 4.06 (1H,
dd, J = 12, 4 Hz, H-6), 4.12 (1H, d, J = 13 Hz, CHAHBPh),
4.17 (1H, br dd, J = 9, 4 Hz, H-5), 4.34 (1H, d, J = 12 Hz,
CHCHDPh), 4.46 (1H, d, J = 12 Hz, CHCHDPh), 4.56 (1H,
d, J = 12 Hz, CHEHFPh), 4.64 (1H, br dt, J = 10.5, 4.5 Hz,
CHCOOCH3), 4.73 (1H, d, J = 12 Hz, CHEHFPh), 4.78 (1H,
dd, J = 12, 9 Hz, H-6), 4.87 (1H, d, J = 12 Hz, CHGHHPh),
4.99 (1H, d, J = 12 Hz, CHGHHPh), 5.20 (1H, d, J = 9 Hz,
H-1), 6.37 (1H, d, J = 5 Hz, NH-Cbz), 6.70 (1H, d, J = 7.5 Hz,
indole), 7.01 (1H, t, J = 7.5 Hz, indole), 7.09–7.39 (21H, m,
aromatic), 7.64 (1H, d, J = 7.5 Hz, indole), 8.18 (1H, s, NH of
indole); 13C NMR (75 MHz, CDCl3) d 20.8, 26.7, 52.3, 54.6,
61.3, 64.3, 66.7, 70.8, 71.7, 72.5, 73.5, 74.7, 75.0, 109.1, 111.2,
118.8, 119.7, 122.5, 127.7, 127.8, 128.1, 128.2, 128.3, 128.5,
133.3, 135.7, 136.3, 137.1, 137.3, 137.8, 156.2, 170.8, 173.2; MS
(FAB) m/z 827 (M + H); HR-MS (FAB) for C49H51O10N2 (M +
H), 827.3544, found 827.3536.
were dried azeotropically with benzene, and dissolved in dry
CH2Cl2 (1.5 ml). The solution was added to the reaction
vessel via cannula. The reaction mixture was stirred at the
same temperature for 2 h and directly subjected to column
chromatography (silica gel 10 g, AcOEt–hexane = 1 : 6 → 1 :
4) followed by repeated preparative TLC (AcOEt–hexane = 1 :
4; Et2O–hexane = 1 : 2) to give 53 (3.3 mg, 4.9%) as a yellow
oil: [a]3D0 +14.5 (c 0.165, CHCl3); 1H NMR (400 MHz, CDCl3)
d 3.11 (1H, dd, J = 14, 10 Hz, CHAHBCHCOOCH3), 3.37
(1H, dd, J = 14, 4.5 Hz, CHAHBCHCOOCH3), 3.76–3.82 (3H,
m, H-3, H-4, H-6), 3.77 (3H, s, COOCH3), 3.85–3.91 (2H, m,
H-2, H-6), 4.08 (1H, d, J = 12.5 Hz, CHAHBPh), 4.17 (1H,
d, J = 12.5 Hz, CHAHBPh), 4.24 (1H, br t, J = 7 Hz, H-5),
4.39 (1H, d, J = 12 Hz, CHCHDPh), 4.41 (1H, d, J = 15 Hz,
CHEHFPh), 4.46 (1H, d, J = 15 Hz, CHEHFPh), 4.51 (1H, d,
J = 12 Hz, CHCHDPh), 4.55 (1H, d, J = 12 Hz, CHGHHPh),
4.66 (1H, d, J = 12 Hz, CHGHHPh), 4.66 (1H, ddd, J = 10, 5.5,
4.5 Hz, CHCOOCH3), 4.90 (1H, d, J = 12 Hz, CHIHJPh), 5.02
(1H, d, J = 12 Hz, CHIHJPh), 5.11 (1H, d, J = 9 Hz, H-1),
6.43 (1H, d, J = 5.5 Hz, NHCbz), 6.74 (2H, dd, J = 8, 1 Hz,
aromatic), 7.04 (1H, t, J = 8 Hz, aromatic), 7.11–7.41 (25H, m,
aromatic), 7.66 (1H, d, J = 8 Hz, aromatic), 8.21 (1H, s, NH
of indole); HR-MS (FAB) for C54H55O9N2 (M + H), 875.3908,
found 875.3903.
2-(6-O-Acetyl-2,3,4-tri-O-benzyl-a-D-mannopyranosyl)-3-[me-
thyl-(3-N-benzyloxycarboxylamido)-2-propionyl-1H-indole (45b).
IR (KBr) vmax 3356, 3032, 2925, 1729, 1455, 1243, 1075,
1
1028 cm−1; H NMR (600 MHz, CDCl3) d 1.96 (3H, s, OAc),
3.55 (3H, s, COOCH3), 3.62 (1H, br d, J = 4 Hz, H-4), 3.68
(1H, br dt, J = 14, 7 Hz, CHAHBNHCbz), 3.89–3.94 (2H, m,
H-3 and CHAHBNHCbz), 3.95 (1H, br d, J = 9, 1.5 Hz, H-2),
4.14 (1H, d, J = 12.5 Hz, PhCHAHBO), 4.14–4.21 (2H, m,
H-5 and H-6), 4.24 (1H, d, J = 12.5 Hz, PhCHAHBO), 4.38
(1H, t, J = 7.5 Hz, ArCHCOOMe), 4.42 (1H, d, J = 12 Hz,
PhCHCHDO), 4.49 (1H, d, J = 12 Hz, Ph–CHCHDO), 4.62
(1H, d, J = 12 Hz, PhCHEHFO), 4.75 (1H, dd, J = 12, 8 Hz,
H-6). 4.78 (1H, d, J = 12 Hz, PhCHEHFO), 4.98 (1H, d, J =
12 Hz, PhCHGHHO), 5.01 (1H, d, J = 12 Hz, PhCHGHHO),
5.38 (1H, d, J = 9.5 Hz, H-1), 5.40 (1H, t, J = 6 Hz, NHCbz),
6.97 (2H, br d, J = 7 Hz, aromatic), 7.09 (1H, t, J = 7.5 Hz,
aromatic), 7.13 (2H, t, J = 7.5 Hz, aromatic), 7.16–7.38 (19H,
m, aromatic), 7.61 (1H. br d, J = 8 Hz, aromatic), 8.31 (1H,
br s, NH of indole); 13C NMR (150 MHz, CDCl3) d 20.8,
42.1, 42.8, 51.8, 61.9, 64.8, 66.4, 71.6, 72.0, 73.5, 73.9, 75.0,
75.2, 75.7, 109.4, 111.1, 119.2, 119.9, 122.3, 127.3, 127.7, 127.8,
127.9, 128.0, 128.0, 128.3, 128.4, 128.5, 128.6, 133.5, 135.5,
136.8, 137.5, 137.6, 138.1, 156.3, 171.0, 173.6; HR-MS (FAB)
for C49H51O10N2 (M + H), 827.3544, found 827.3453.
2-(2,3,4,6-O-Tetrabenzyl-a-D-glucopyranosyl)-L-(N-carboben-
zyloxy)tryptophan methyl ester (47a) (entry 5 in Table 4).
Following the procedure for 46, 47a (30.2 mg, 41%) was
obtained as a yellow oil from glucosylindole 35 (54 mg,
0.085 mmol) after column chromatography (silica gel 10 g,
Et2O–hexane = 1 : 3 → 1 : 2 → 1 : 1): [a]2D2 +75.3 (c 1.00,
CHCl3); IR (KBr) mmax 3407, 3032, 2869, 1719, 1454, 1071 cm−1;
1H NMR (400 MHz, CDCl3) d 3.23 (1H, dd, J = 14.5,
5 Hz, CHAHBCHCOOCH3), 3.41 (1H, dd, J = 14.5, 8 Hz,
CHAHBCHCOOCH3), 3.61 (3H, s, COOCH3), 3.56–3.72 (4H,
m, H-4, H-5, H-6 and H-6), 3.91–3.99 (2H, m, H-2, H-3),
4.46 (1H, d, J = 12 Hz, CHAHBPh), 4.50 (1H, d, J = 11 Hz,
CHCHDPh), 4.57 (1H, m, CHCOOCH3), 4.58 (1H, d, J =
12 Hz, CHAHBPh), 4.63 (1H, d, J = 11 Hz, CHEHFPh), 4.71
(1H, d, J = 11 Hz, CHEHFPh), 4.77 (1H, d, J = 11 Hz,
CHCHDPh), 4.80 (1H, d, J = 11 Hz, CHGHHPh), 4.90 (1H, d,
J = 11 Hz, CHGHHPh), 5.03 (2H, s, CH2Ph), 5.46–5.50 (2H, m,
H-1, NHCbz), 7.06–7.37 (28H, m, aromatic), 7.53 (1H, d, J =
8 Hz, indole), 9.26 (1H, s, NH of indole); 13C NMR (100 MHz,
CDCl3) d 26.9, 52.1, 55.1, 66.8, 69.4, 69.6, 73.5, 73.6, 73.8,
74.6, 75.0, 78.2, 80.8, 81.8, 109.5, 111.2, 118.4, 119.8, 122.2,
127.6, 127.7, 127.8, 128.0, 128.2, 128.3, 128.3, 128.4, 128.4,
128.7, 128.9, 132.0, 135.4, 136.6, 137.3, 138.2, 138.3, 138.5,
155.8, 172.8; HR-MS (FAB) Calcd. for C54H54N2O9 (M + H):
875.3908. Found: 875.3833.
Sc(ClO4)3-promoted coupling between mannnosylindole 33 and
aziridine 44 (entry 3 in Table 4). Caution! We have never en-
countered any problem with the explosion of Sc(ClO4)3; however,
we suggest that Sc(ClO4)3 should be handled with special care,
because metal perchlorates have potentially explosive properties.
In particular, drying of the reagent with heating under vacuum
should be conducted in a hood with a safety shield.
2-(2,3,4,6-O-Tetrabenzyl-a-D-galctopyranosyl)-L-N-(carboben-
zyloxy)tryptophan methyl ester (48a). Following the procedure
for 46, 48a (65 mg, 43%) was obtained as a yellow oil from
galactosylindole 36 (111 mg, 0.174 mmol) after column
chromatography (silica gel 15 g, AcOEt–hexane = 1 : 6 → 1 : 4):
[a]2D2 +23.2 (c 0.75 CHCl3); IR (KBr) mmax 3411, 3332, 3031, 2869,
Sc(ClO4)3 (60 mg, 0.175 mmol) was placed in the reaction
vessel and dried with a Kugelrohr distillation apparatus under
reduced pressure (1.4 mmHg) at 150 ◦C for 14 h, and then
cooled to 0 ◦C. In a separate flask, mannnosylindole 33 (52 mg,
0.087 mmol) and aziridine 44 (41 mg, 0.175 mmol) were dried
azeotropically with benzene, and dissolved in CH2Cl2 (1.5 ml).
This solution was added to the reaction vessel via cannula. The
reaction mixture was stirred at the same temperature for 5 h and
directly subjected to column chromatography (Et2O–hexane =
1 : 2 → 1 : 1) to give 45a (59 mg, 83%) as a colorless oil.
◦
1722, 1455, 1089 cm−1; H NMR (400 MHz, CDCl3, 40 C) d
3.15 (1H, dd, J = 14, 6 Hz, CHAHBCHCOOCH3), 3.21–3.30
(1H, m, CHAHBCHCOOCH3), 3.52 (3H, s, COOCH3), 3.74
(1H, dd, J = 11, 4 Hz, H-6), 3.86 (1H, dd, J = 6.5, 3 Hz, H-3),
3.96 (1H, dd, J = 11, 7 Hz, H-6), 4.00 (1H, dd, J = 6.5, 3.5 Hz,
H-2), 4.04 (1H, dd, J = 4.5, 3 Hz, H-4), 4.11 (1H, br dt, J =
7.5, 4 Hz, H-5), 4.32 (1H, br d, J = 11.5 Hz, CHAHBPh), 4.43
(1H, d, J = 12 Hz, CHCHDPh), 4.45 (1H, br d, J = 11.5 Hz,
CHAHBPh), 4.49 (1H, d, J = 12 Hz, CHCHDPh), 4.52–4.58
(1H, m, CHCOOCH3), 4.58 (1H, d, J = 12 Hz, CHEHFPh),
4.62 (1H, d, J = 12 Hz, CHGHHPh), 4.70 (1H, d, J = 12 Hz,
CHEHFPh), 4.73 (1H, d, J = 12 Hz, CHGHFPh), 4.96–5.00
(2H, m, CH2Ph), 5.36 (1H, d, J = 3.5 Hz, H-1), 5.34–5.44
(1H, br, NH–Cbz), 7.03–7.07 (2H, m, aromatic), 7.12 (1H, t,
1
2-(2,3,4,6-Tetra-O-benzyl-a-D-mannopyranosyl)-L-(N-carbo-
benzyloxy)tryptophan methyl ester (46a) (entry 4 in Table 4).
Sc(ClO4)3 (54 mg, 0.156 mmol) placed in the reaction◦vessel
was freeze-dried with benzene for 1 h, then cooled to 0 C. To
˚
this flask were added 5 A MS (75 mg) and the vessel was
connected to a vacuum/argon line. The flask was evacuated
and then filled with argon. This evacuation/filling cycle was
repeated three times. In an separated flask, mannnosylindole
34 (50 mg, 0.078 mmol) and aziridine 44 (37 mg, 0.156 mmol)
6 9 8
O r g . B i o m o l . C h e m . , 2 0 0 5 , 3 , 6 8 7 – 7 0 0

View Article Online
J = 7.5 Hz, indole), 7.16–7.32 (25H, m, aromatic), 7.51 (1H,
d, J = 8 Hz, indole), 8.84 (1H, br s, NH of indole); 13C NMR
(150 MHz, CDCl3) d 27.0, 52.2, 55.0, 66.6, 66.8, 67.2. 73.0,
73.2, 73.2, 73.7, 73.9, 74.2, 76.5, 78.3, 111.0, 118.5, 119.5, 122.1,
127.7, 127.8, 127.9, 128.1, 128.3, 128.4, 128.5, 128.5, 132.5,
135.3, 137.4, 138.3, 138.4, 155.9, 172.8; HRMS (FAB) Calcd.
for C54H54N2O9 (M + H): 875.3908. Found: 875.3915.
indole), 7.31 (1H, t, J = 8 Hz, indole), 7.54 (1H, d, J = 8 Hz,
indole), 7.74 (1H, d, J = 8 Hz, indole); 13C NMR (150 MHz,
D2O) d 28.5 (CH2CHCOOH), 57.8 (CHCOOH), 62.4 (C-6), 70.1
(C-4), 70.4 (C-1), 72.5 (C-2), 73.4 (C-3), 78.2 (C-5), 111.1 (C-3
of indole), 114.7 (C-7 of indole), 121.4 (C-4 of indole), 122.6
(C-5 of indole), 125.5 (C-6 of indole), 130.0 (C-3a), 135.9 (C-2
of indole), 138.4 (C-7a), 177.4 (COOH); HRMS (FAB) Calcd.
for C17H22N2O7 (M + H): 367.1505, Found: 367.1500.
Deprotection of ester and benzyl groups
2-a-D-Glucopyranosyl-L-tryptophan (53) (entry 2 in Table 5;
entry 5 in Table 6). (1) To a solution of 47a (11.8 mg,
0.014 mmol) in 2-propanol (0.6 ml) was added 1 N LiOH
solution (41 ll, 0.041 mmol). After stirring at rt for 1.5 h,
sat. NH4Cl solution was added. The pH of the mixture was
adjusted to 2 with 1 N HCl and then extracted with EtOAc (×3).
The combined organic layers were washed with water (×2) and
brine (×2), dried over anhydrous Na2SO4, and concentrated. The
residue was purified by preparative TLC (10% MeOH–CH2Cl2)
to give 50 (10.0 mg, 86%). (2) A two-necked flask was charged
with Pd/C (13 mg) and connected to inlet adaptor. The flask was
evacuated and then filled with nitrogen. A solution of 50 (13 mg,
0.015 mmol) in MeOH (0.40 ml) was added. The flask was then
evacuated and then filled with hydrogen. After vigorous stirring
for 34.5 h, the mixture was filtered through a pad of Hyflo Super-
Cel, and the precipitate was washed with MeOH and H2O. The
combined filtrate was concentrated. The residue (6.3 mg) was
purified by preparative TLC (CHCl3–MeOH–H2O = 65 : 65 : 15)
to give 53, which was further purified by reverse phase column
chromatography (Cosmosil 75C18, H2O as eluant) to give 53
(4.0 mg, 73%): [a]3D0 +19.5 (c 0.200, H2O); 1H NMR (600 MHz,
D2O) d 3.47 (1H, dt, J = 8.5, 4 Hz, H-5), 3.51 (2H, br d, J =
7 Hz, CH2CHCOOH), 3.56 (1H, t, J = 8.5 Hz, H-4), 3.79 (2H,
br d, J = 4 Hz, H-6), 4.04 (1H, t, J = 8.5 Hz, H-3), 4.08–4.11
(1H, m, CHCOOH), 4.10 (1H, dd, J = 8.5, 5.5 Hz, H-2), 5.58
(1H, d, J = 5.5 Hz, H-1), 7.22 (1H, t, J = 7.5 Hz, indole), 7.30
(1H, t, J = 7.5 Hz, indole), 7.55 (1H, d, J = 7.5 Hz, indole), 7.74
(1H, d, J = 7.5 Hz, indole); 13C NMR (150 MHz, D2O) d 28.5
(CH2CHCOOH), 58.1 (CHCOOH), 63.3 (C-6), 72.4 (C-4), 72.5
(C-1), 74.4 (C-2), 76.7 (C-3), 78.2 (C-5), 111.5 (C-3 of indole),
114.9 (C-7 of indole), 121.3 (C-4 of indole), 122.7 (C-5 of indole),
125.5 (C-6 of indole), 129.9 (C-3a), 135.6 (C-2 of indole), 138.5
(C-7a), 177.5 (COOH); HR-MS (FAB) Calcd. for C17H22N2O7
(M + H): 367.1505. Found: 367.1507.
2-a-D-Mannopyranosyl-L-tryptophan (1). (1) To a solution
of 45 (21.8 mg, 0.0264 mmol) in 2-propanol (1.1 ml) was
added 1 N LiOH solution (0.079 ml). After stirring at rt for
2 h, the mixture was quenched with sat. NH4Cl solution. The
mixture was acidified to pH 1 with 1 N HCl and then extracted
with EtOAc (×2). The combined organic extracts were washed
with water (×2) and brine (×2), dried over anhydrous Na2SO4,
concentrated under reduced pressure. The residue was purified
by preparative TLC (10% MeOH–CH2Cl2 × 2) to give carboxylic
acid 49 (14.1 mg, 70%) as a colorless oil. (2) Pd(OH)2/C (19 mg)
was placed in a reaction vessel, and a solution of 49 (19 mg,
0.025 mmol) in MeOH (1.0 ml) and a solution of conc. HCl
(0.4 ll, 0.005 mmol) in MeOH (0.4 ml) were successively added
via cannula. After the reaction vessel was filled with H2, the
mixture was vigorously stirred for 3 h at rt. The resulting mixture
was filtered through a pad of Hyflo Super-Cel and the filtrate was
concentrated under reduced pressure. The residue was purified
by TLC (CHCl3–MeOH–H2O = 65 : 65 : 15) and lyophilized
to give 1 (6.5 mg, 71%) as a white amorphous solid: [a]2D3 +29.6
1
(c 1.20, H2O); H NMR (600 MHz, D2O) d 3.36 (1H, dd, J =
15.5, 9 Hz, CHAHBCHCOOH), 3.56 (1H, dd, J = 15.5, 5 Hz,
CHAHBCHCOOH), 3.74 (1H, dd, J = 12.5, 3 Hz, H-6), 3.90
(1H, dt, J = 9, 3 Hz, H-5), 3.96 (1H, dd, J = 5, 3 Hz, H-4), 4.03
(1H, dd, J = 9, 5 Hz, CHCOOH), 4.13 (1H, dd, J = 5, 3 Hz,
H-3), 4.26 (1H, dd, J = 12.5, 9 Hz, H-6), 4.44 (1H, dd, J = 8,
3 Hz, H-2), 5.18 (1H, d, J = 8 Hz, H-1), 7.22 (1H, t, J = 8 Hz,
indole), 7.32 (1H, t, J = 8 Hz, indole), 7.54 (1H, d, J = 8 Hz,
indole), 7.75 (1H, d, J = 8 Hz, indole); 13C NMR (150 MHz,
D2O) d 28.7, 58.0, 61.8, 68.9, 70.5, 71.7, 73.3, 81.8, 111.1, 114.7,
121.5, 122.7, 125.7, 129.9, 136.2, 138.8, 177.2; MS (FAB) m/z
367 (M + H); HRMS (FAB) for C17H23O7N2 (M + H), 367.1505,
found 367.1506.
2-a-D-Galctopyranosyl-L-tryptophan (52) (entry 3 in Table 5;
entry 3 in Table 6). (1) To a solution of 48a (17.5 mg,
0.020 mmol) in 2-propanol (0.5 ml) was added 1 N LiOH
solution (0.06 ml, 0.06 mmol). After stirring at rt for 25 h,
sat. NH4Cl solution was added. The mixture was adjusted to
pH 2 with 1 N HCl and then extracted with EtOAc (×3). The
combined organic layers were washed with water and brine,
dried over anhydrous Na2SO4, and concentrated. The residue
was purified by preparative TLC (10% MeOH–CH2Cl2) to
give 51 (14.5 mg, 85%). (2) A two-necked flask was charged
with Pd/C (9.4 mg) and connected to inlet adaptor. The flask
was evacuated and then filled with nitrogen. A solution of 51
(9.4 mg, 0.011 mmol) in MeOH (0.28 ml) and 1 N HCl (2.0 ll)
were added. The flask was then evacuated and then filled with
hydrogen. After vigorous stirring for 25 h, the mixture was
filtered through a pad of Hyflo Super-Cel, and the precipitate
was washed with MeOH and H2O. The combined filtrate was
concentrated. The residue (5.1 mg) was purified by preparative
TLC (CHCl3–MeOH–H2O = 65 : 65 : 15) to give 52, which
was further purified by reverse phase column chromatography
(Cosmosil 75C18, H2O as eluant) to give 52 (2.8 mg, 70%): [a]D30
+22.2 (c 0.185, H2O); 1H NMR (600 MHz, D2O) d 3.50 (1H, dd,
J = 15, 5.5 Hz, CHAHBCHCOOH), 3.56 (1H, dd, J = 15, 8 Hz,
CHAHBCHCOOH), 3.76 (1H, dd, J = 12, 3.5 Hz, H-6), 3.90
(1H, dt, J = 9, 3.5 Hz, H-5), 4.02 (1H, dd, J = 12, 9 Hz, H-6),
4.08 (1H, dd, J = 8, 5.5 Hz, CHCOOH), 4.17 (1H, t, J = 3.5 Hz,
H-4), 4.19 (1H, dd, J = 7.5, 3.5 Hz, H-3), 4.29 (1H, dd, J = 7.5,
4.5 Hz, H-2), 5.55 (1H, d, J = 4.5 Hz, H-1), 7.22 (1H, t, J = 8 Hz,
Acknowledgements
We are grateful to Professor K. Kitajima (Nagoya University)
and Dr J. Hofsteenge (FMI, Basel) for valuable discussions. We
also thank Dr K. Adachi (Marine Biotechnology Institute Co.,
Ltd., Japan) and Dr M. Herderich (Wu¨rzburg University) for
informing us of the revised structure of C-Man-Trp. Elemental
analyses and 600 MHz NMR spectroscopy were performed by
Mr M. Kitamura and K. Koga (analytical laboratory of this
school), whom we thank. Financial support was provided by
Scientific Research on Priority Area “Functional Glycomics”
(No. 502), the 21st COE grant and a Grant-in-Aid for Scientific
Research from MEXT, and PRESTO, Japan Science and
Technology Agency (JST).
References and notes
1 For reviews: (a) R. A. Dwek, Chem. Rev., 1996, 96, 683–720; (b) A.
Varki, Essentials of Glycobiology: Cold Spring Harbor Laboratory
Press, New York, 1999, pp. 1–15.
2 C. M. Taylor, Tetrahedron, 1988, 54, 11317–11362.
3 For review of synthetic C-glycosyl amino acids, see: (a) A. Dondoni
and A. Marra, Chem. Rev., 2000, 100, 4395–4422; (b) F. Schweizer,
Angew. Chem., Int. Ed., 2002, 41, 230–253.
4 J. Hofsteenge, D. R. Mu¨ller, T. Beer, A. Lo¨ffler, W. J. Richter and J.
Vliegenthart, Biochemistry, 1994, 33, 13524–13530.
5 T. Beer, J. Vliegenthart, A. Lo¨ffler and J. Hofsteenge, Biochemistry,
1995, 34, 11785–11789.
O r g . B i o m o l . C h e m . , 2 0 0 5 , 3 , 6 8 7 – 7 0 0
6 9 9

View Article Online
6 M.-A. Doucey, D. Hess, R. Cacan and J. Hofsteenge, Mol. Biol. Cell,
1998, 9, 291–300.
7 J. Krieg, W. Glasner, A. Vicentini, M.-A. Doucy, A. Lo¨ffer, D. Hess
and J. Hofsteenge, J. Biol. Chem., 1997, 272, 26687–26692.
8 J. Krieg, S. Hartmann, A. Vicentini, W. Gla¨sner, D. Hess and J.
Hofsteenge, Mol. Biol. Cell, 1998, 9, 301–309.
36 a-C-Glycosidations of 1-haloglucose derivatives with stanny-
lacetylenes have been reported: (a) D. Zhai, W. Zhai and R. M.
Williams, J. Am. Chem. Soc., 1988, 110, 2501–2505; (b) L. Jobron, C.
Leteux, A. Veyrieres and J.-B. Beau, J. Carbohydr. Chem., 1994, 13,
507–512.
37 For an example of the synthesis of b-acetylglucoside and galactoside.
See: M. Bols and H. C. Hansen, Acta Chem. Scand., 1993, 47, 818–
822.
9 A. Furmanek and J. Hofsteenge, Acta Biochem. Pol., 2000, 47, 781–
789.
10 M.-A. Doucey, D. Hess, M. J. J. Blommers and J. Hofsteenge,
Glycobiology, 1999, 9, 435–441.
11 J. Hofsteenge, M. Blommers, D. Hess, A. Furmanek and O.
Miroshnichenko, J. Biol. Chem., 1999, 274, 32786–32794.
12 S. Hartmann and J. Hofsteenge, J. Biol. Chem., 2000, 275, 28569–
28574.
13 J. Hofsteenge, K. G. Huwiler, B. Macek, D. Hess, J. Lawler, D. F.
Mosher and J. Peter-Katalinic, J. Biol. Chem., 2001, 276, 6485–6498.
14 A. Furmanek, D. Hess, H. Rogniaux and J. Hofsteenge, Biochemistry,
2003, 42, 8452–8458.
15 (a) K. Horiuchi, O. Yonekawa, K. Iwahara, T. Kanno, T. Kurihara
and Y. Fujise, J. Biochem., 1994, 115, 362–366; (b) B. Gutsche, C.
Grun, D. Scheutzow and M. Herderich, Biochem. J., 1999, 343, 11–
19.
16 A. Garcia, L. A. Lenis, C. Jimenez, C. Debitus, E. Quinoa and R.
Riguera, Org. Lett., 2000, 2, 2765–2767.
17 G. E. Richite, B. E. Moffat, R. B. Sim, P. Morgan, R. A. Dwek and
P. M. Rudd, Chem. Rev., 2002, 102, 305–319.
18 C-Man-Trp found in urine and serum was reported to be a potential
candidate as a marker molecule for renal function, see: R. Takahira,
K. Yonemura, O. Yonekawa, K. Iwahara, T. Kanno, Y. Fujise and
A. Hishida, Am. J. Med., 2001, 110, 192–197.
19 (a) T. Nishikawa, M. Ishikawa and M. Isobe, Synlett, 1999, 123–125;
(b) T. Nishikawa, M. Ishikawa, K. Wada and Isobe, Synlett, 2001,
945–947.
20 (a) S. Manabe and Y. Ito, J. Am. Chem. Soc., 1999, 121, 9754–9755;
(b) S. Manabe, Y. Marui and Y. Ito, Chem. Eur. J., 2003, 9, 1435–1447.
21 H. Fujise, H. Horiuchi, K. Adachi, H. Sano and K. Suzuki, World
Patent WO99/0411; (Chem. Abstr., 1999, 130).
22 Syntheses of C-Glu-Trp and C-Gal-Trp described in this paper were
preliminarily presented at the annual meeting of the Japan Society
for Bioscience, Biotechnology and Agrochemistry, Abstracts, p. 18,
Kyoto, Japan, March 2001.
23 (a) R. C. Larock and E. K. Yum, J. Am. Chem. Soc., 1991, 113,
6689–6690; (b) R. C. Larock, E. K. Yum and M. D. Refvik, J. Org.
Chem., 1998, 63, 7652–7662.
24 (a) M. C. Yeh and P. Knochel, Tetrahedron Lett., 1989, 30, 4799–
4802; (b) N. J. Dunn, R. F. W. Jackson, J. Pietruszka and D. Turner,
J. Org. Chem., 1995, 60, 2210–2215.
25 (a) C. E. Castro, E. J. Gaughan and D. C. Owsley, J. Org. Chem., 1966,
31, 4071–4078; (b) J. Fujiwara, Y. Fukutani, H. Sano, K. Maruoka
and H. Yamamoto, J. Am. Chem. Soc., 1983, 105, 7177–7179.
26 (a) M. Isobe, R. Nishizawa, S. Hosokawa and T. Nishikawa, Chem.
Commun., 1998, 2665–2676; (b) M. Isobe and K. Kira, J. Synth. Org.
Chem., 2000, 58, 23–30; (c) M. Isobe and K. Kira, J. Synth. Org.
Chem., 2000, 58, 99–107.
27 Y. Ichikawa, M. Isobe, M. Konobe and T. Goto, Carbohydr. Res.,
1987, 171, 193–199.
28 (a) A. Vasslla, Pure Appl. Chem., 1998, 70, 426–430; (b) J. Alzeer
and A. Vasella, Helv. Chim. Acta, 1995, 78, 242; (c) R. Bu¨rli and A.
Vasella, Helv. Chim. Acta, 1996, 79, 1159–1168.
38 In the case of glucose and galactose, a trace amount of the
corresponding b-anomer (>20 : 1) was detected in the 1H NMR
spectra.
39 Dondoni and co-workers have reported the synthesis of a-
ethynylglucose 23 and a-ethynylgalactose 24 under the same condi-
tions as we have developed for the synthesis of C-Man-Trp. See:(a) A.
Dondoni, G. Mariotti and A. Marra, Tetrahedron Lett., 2000, 41,
3483–3486; (b) A. Dondoni, G. Moriotti and A. Marra, J. Org.
Chem., 2002, 67, 4475–4486.
40 K. Sonogashira, Y. Tohda and N. Hagihara, Tetrahedron Lett., 1975,
4467–4470.
41 The coupling of 21 with an unprotected o-iodoaniline as a coupling
partner gave a good yield of the desired product; however, the
resulting o-ethynylaniline did not undergo indole cyclization even
under forcing conditions.
42 W. B. Austin, N. Bilow, W. J. Kelleghan and K. S. Lau, J. Org. Chem.,
1989, 54, 52280–2286.
43 A. Yasuhara and T. Sakamoto, Tetrahedron Lett., 1998, 39, 595–596.
44 Y. Yokoyama, T. Matsumoto and Y. Murakami, J. Org. Chem., 1995,
60, 1486–1487.
45 The mannose moiety of 38a has the unusual 1C4 conformation,
judging from coupling constant (9.5 Hz) between H-1 and H-2 in
its 1H NMR spectra.
46 (a) U. Schmidt, A. Lieberknecht and J. Wild, Synthesis, 1984, 53–
60; (b) U. Schmidt, H. Griesser, V. Leitenberger, A. Liberknecht, R.
Mangold, R. Meyer and B. Riedel, Synthesis, 1992, 487–490.
47 U. Hengartner, D. Valentine Jr., K. K. Johnson, M. M. Larscheid, F.
Pigott, F. Scheidl, J. W. Scott, R. C. Sun, J. M. Townsend and T. H.
Williams, J. Org. Chem., 1979, 44, 3741–3747.
48 K. Sato and A. P. Kozikowski, Tetrahedron Lett., 1989, 30, 4073–
4076.
49 Y. L. Bennani, G.-D. Zhu and J. C. Freeman, Synlett, 1998, 754–756.
50 (a) K. Nakajima, F. Takai, T. Tanaka and K. Okawa, Bull. Chem.
Soc. Jpn., 1978, 51, 1577–1578; (b) S. Kato, H. Harada and T. Morie,
J. Chem. Soc., Perkin Trans. 1, 1997, 3219–3225.
51 I. Hachiya and S. Kobayashi, Tetrahedron Lett., 1994, 35, 3319–
3321.
52 For the scope and limitation of the synthesis of tryptophan with
Sc(ClO4)3 as a Lewis acid, see: T. Nishikawa, S. Kajii, K. Wada, M.
Ishikawa and M. Isobe, Synthesis, 2002, 1658–1662.
53 The same coupling with other Lewis acid such as BF3·OEt2 and
Sc(OTf)3 was reported by Ito and co-workers to give a miserable
result, see ref. 20(b).
˚
˚
54 Addition of 3 A MS instead of 5 A MS retarded the reaction. For the
effect of molecular sieves in reactions with lanthanide triflates, see:T.
Tokiwano, K. Fujiwara and A. Murai, Chem. Lett., 2000, 272–273,
and references cited therein.
55 The same compound was synthesized by Manabe and Ito, based on
a different synthetic strategy – see ref. 20.
56 V. S. Raghavendra Rao, P. K. Qasba, and P. V. Balaji, R. Chan-
drasekaran, Conformation of Carbohydrates, Harwood Academic
Publishers, Amsterdam, Netherlands, 1998, pp. 49–90.
29 J. Stichler-Bonaparte and A. Vasellla, Helv. Chim. Acta, 2001, 84,
2355–2367.
57 For examples of the 1C4 conformation of C- and O-mannosides, see:
(a) T. G. George, P. Szolcsanyi, S. G. Koenig, D. E. Paterson, Y.
Isshiki and A. Vasella, Helv. Chim. Acta, 2004, 87, 1287–1298; (b) T.
Kumazawa, S. Sato, S. Matsuba and J. Onodera, Carbohydr. Res.,
2001, 332, 103–108; (c) H. Yamada, M. Nakatani, T. Ikeda and Y.
Marumoto, Tetrahedron Lett., 1999, 40, 5573.
30 T. Nishikawa, K. Wada and M. Isobe, Biosci., Biotechnol., Biochem.,
2002, 66, 2273–2278.
31 The phenylacetylene 14b was synthesized from 14a in 2 steps:
desilylation of the TMS group with TBAF and then Sonogashira
coupling with N-tosyl-2-idodoaniline.
32 Compound 3 (R = Bn, X = H, 22) has been reported as a minor
product in the synthesis of a b-ethylymannose derivative. See: T.
Lowray, M. Meldal, A. Helmboldt, A. Vasella and K. Bock, J. Org.
Chem., 1998, 63, 9657–9668.
58 For examples of the 1C4 conformation of C- and O-glucosides, see:
(a) H. Abe, M. Terauchi, A. Matsuda and S. Shuto, J. Org. Chem.,
2003, 68, 7439–7447; (b) C. Rousseau and O. R. Martin, Org. Lett.,
2003, 5, 3765–3766.
33 (a) R. Shah, J. Baptista, G. R. Perdomo, J. P. Carver and J. J.
Krepinsky, J. Carbohydr. Chem., 1987, 6, 645–660; (b) G. Zhang,
Z. Guo and Y. Hui, Synth. Commun., 1997, 27, 1907–1917.
34 We tested various Lewis acids such as BF3·OEt2, TMSOTf, SnCl4
and TiCl4 (in CH2Cl2 or CH3CN).
35 For the arming/disarming effect, see: (a) D. R. Mootoo, P. Kon-
radsson, U. Udodong and B. Fraser-Reid, J. Am. Chem. Soc., 1988,
110, 5583–5584; (b) C. S. Burgey, R. Vollerthum and B. Fraser-Reid,
J. Org. Chem., 1996, 61, 1609–1618.
59 T. Nishikawa, S. Kajii, C. Sato, Z. Yasukawa, K. Kitajima and M.
Isobe, Bioorg. Med. Chem., 2004, 12, 2343–2348.
60 For the Edmann degradation of C-Man-Trp, see: J. Hofsteenge, A.
Lo¨ffler, D. R. Mu¨ller, W. J. Richter, T. de Beer and J. F. G. Vligenthart,
in Techniques in Protein Chemistry, VII, ed. D. R. Marshak,
Academic Press, New York, 1996, pp. 163–171.
61 J. M. Berge and S. M. Roberts, Synthesis, 1979, 471–472.
62 G. Goekjian, T.-C. Wu, H.-Y. Kang and Y. Kishi, J. Org. Chem.,
1991, 56, 6422–6434.
7 0 0
O r g . B i o m o l . C h e m . , 2 0 0 5 , 3 , 6 8 7 – 7 0 0