Synthesis of β-analogues of C-mannosyltryptophan, a novel C-glycosylamino acid found in proteins

Article abstract of DOI:10.1039/b516282c

α-C-Mannosyltryptophan (α-C-Man-Trp) has been found to be a novel post-translational modification of tryptophan found from some biologically important glycoproteins. In order to analyze the biological functions of α-C-Man-Trp, we have developed an efficie

Full text of DOI:10.1039/b516282c

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www.rsc.org/obc | Organic & Biomolecular Chemistry
Synthesis of b-analogues of C-mannosyltryptophan, a novel C-glycosylamino
acid found in proteins†
Toshio Nishikawa,*a,b Yuya Koide,a Akira Kanakubo,a Hiroshi Yoshimuraa and Minoru Isobea
Received 16th November 2005, Accepted 27th January 2006
First published as an Advance Article on the web 16th February 2006
DOI: 10.1039/b516282c
a-C-Mannosyltryptophan (a-C-Man-Trp) has been found to be a novel post-translational modification
of tryptophan found from some biologically important glycoproteins. In order to analyze the biological
functions of a-C-Man-Trp, we have developed an efficient synthetic strategy for a-C-Man-Trp and its
glucose and galactose analogues, starting from a-C-glycosidation of the corresponding hexapyranoside
derivatives with tinacetylene. According to the synthetic routes, we describe here syntheses of b-anomers
of C-Man-Trp, and its glucose and galactose analogues from the corresponding b-C-glycosylacetylenes.
During this study, we have developed a highly stereocontrolled synthesis of b-C-mannosylacetylene that
is required for the synthesis of b-C-Man-Trp, while the precedented method gave an anomeric mixture
of the C-mannosylacetylene. The synthetic C-Man-Trp and its analogues were analyzed by HPLC.
Introduction
a-C-Mannosyltryptophan (a-C-Man-Trp (1) in Fig. 1) was first
found as a novel linkage “C-glycoside” between a protein and car-
bohydrate from human ribonuclease 2 (RNase 2).1 Interestingly,
the mannose moiety of a-C-Man-Trp adopts a 1C4 conformation as
a major conformer due to a bulky tryptophan moiety occupying
the a-position of the anomeric center and a lack of anomeric
effect. Since its discovery, C-Man-Trp has been identified in
several biologically important proteins such as interleukin-12,2
the terminal four components of a complement system (C6,
Fig. 1 Structure and preferable conformation of a-C-Man-Trp (1).
C7, C8a, b and C9),3 properdin,4 thrombospondin,5 F-spondin,6
mucins (MUC5AC and MUC5B),7 and erythropoietin receptors.8
Extensive studies on the biosynthetic pathway have revealed that
“C-mannosyltransferase,” still not identified as an enzyme for
installation of mannose to tryptophan, recognizes the amino acid
sequence W–X–X–W to modify the first Trp of this motif.9 Since
the recognition sequence is included in conserved sequences such
as TSP-1 (W–X–X–W–X–X–W–X–X–C) and the WS motif (W–
S–X–W–S) in thrombospondin type 1 repeats (TSRs),10 it is likely
that other proteins with these motifs may be modified by C-
mannosylation. On the other hand, the biological functions of
a-C-Man-Trp have not been clarified, although several possibilities
have been studied.11 In order to identify a-C-Man-Trp from
proteins, peptide sequencing utilizing Edman degradation, the
MS/MS method,12 and specific antibodies against a-C-Man-
Trp13–15 have been employed; however, such methods have not
been able to exclude the possibility of other stereoisomers having a
different carbohydrate moiety with the same molecular weight as
that of a-C-Man-Trp. Although NMR spectroscopy is the only
way to discriminate these isomers, a sufficient amount of the
sample containing the modification is difficult to obtain. Thus,
a new analytical method to differentiate the isomers of a-C-Man-
Trp has been highly desired.3,6,8 To supply the a-C-Man-Trp for
analyzing its biological functions, we have previously synthesized
a-C-Man-Trp, and its glucose and galactose analogues,16,17 and
its probes for use in biochemical studies.18 The corresponding b-
isomers, however, have been reported to be obtained in only minute
amounts by heating L-tryptophan with D-mannose, galactose, and
glucose in the presence of acid.19 We therefore describe herein
stereocontrolled syntheses of the b series of C-Man-Trp and
its glucose and galactose analogues, which can be employed as
authentic samples for their trace analyses.
Synthetic plan for b-C-glycosyltryptophan
In our previous papers, we established the synthesis of a-C-
Man-Trp and its glucose and galactose analogues as outlined
in Scheme 1. Thus, C-glycosidation of glycosyl-1-acetate 2 with
tinacetylene in the presence of TMSOTf as a Lewis acid exclusively
gave the corresponding a-C-glycosylacetylene 3,20 which was
coupled with N-Ts-o-iodoanilide 4 by palladium catalyst to o-
ethylaniline derivatives 5. Copper(I)-mediated indole formation
was followed by deprotection of the Ts group to give a-C-
glycosylindole 6, which reacted with L-serine-derived aziridine
carboxylate 7 in the presence of Sc(ClO4)3 as a Lewis acid21
to afford a fully protected a-C-Gly-Trp 8. Finally, two-step
aLaboratory of Organic Chemistry, Graduate School of Bioagricultural
Sciences, Nagoya University, Chikusa, Nagoya, 464-8601, Japan. E-mail:
nisikawa@agr.nagoya-u.ac.jp; Fax: (+)81-52-789-4111; Tel: (+)81-52-
789-4115
bPRESTO, Japan Science and Technology Agency, 4-1-8 Honcho,
Kawaguchi, Saitama, 332-0012 Japan
† Electronic supplementary information (ESI) available: NMR data. See
DOI: 10.1039/b516282c
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resulting ketal B with triethylsilane in the presence of a Lewis
acid.24 The synthetic sequence enabled us to synthesize b-C-
glucosylacetylene 11b and b-C-galactosylacetylene 12b in highly
stereoselective manner.22 However, when the same procedure was
applied to D-mannopyranolactone, reduction of the correspond-
ing ketal proceeded in a low stereoselective manner, giving a 1 : 2
mixture of a- and b-C-mannosylacetylenes 13 (see Table 1). Kishi
has also reported that the reduction of an allyl-substituted ketal
of mannose gave a 1 : 1 mixture of the anomeric isomer. Many
efforts have been reported to achieve stereoselective synthesis of b-
C-mannosides,25,26 however, no stereocontrolled synthesis of b-C-
mannosylacetylene has been reported to date.27 We thus initiated
our studies from the perspective of improving the stereoselectivity
in the synthesis of b-C-mannosylacetylene 13b, a starting material
for b-C-Man-Trp.
The aforementioned results imply that the b-benzyloxy sub-
stituent at the C-2 position of the mannose derivative induces a
different conformation of the oxocarbenium cation from those
of the corresponding glucose and galactose derivatives. This
assumption might be supported by a recent study of Shuto and
co-workers,28 from which it was reported that conformationally
restricted ketal derived from a 4,6-benzylidene acetal-protected
mannopyranolactone undertook a highly stereoselective reduction
with Et3SiH and TMSOTf to exclusively afford b-C-mannoside.
We supposed that even if the transition state conformation is
different from those of the corresponding glucose and galactose
intermediates, the a-face of the oxocarbenium cation should
be less hindered and therefore sterically hindered silanes would
improve the stereoselectivity of the reduction. We thus examined
the influence of sterically hindered silanes in the reduction of
ketal 16, which was prepared from 2,3,4,6-tetra-O-benzylmannose
(14) via the corresponding lactone 15 (Scheme 3 and Table 1).29
To our delight, tris(trimethylsilyl)silane (TMS)3SiH, one of the
most hindered silanes, reduced the ketal 16 to afford b-C-
mannosylacetylene 13b as a single isomer (entry 2). Further
examination led us to find that triisopropylsilane (i-Pr3SiH)
exhibits a high stereoselectivity, giving 13b in 67% yield along
with a trace amount of 13a.30 Since the coupling constant between
Scheme 1 Synthesis of a-C-Man-Trp and its analogues.
deprotection furnished a-C-mannosyltryptophan (1, a-C-Man-
Trp), a-C-glucosyltryptophan (9, a-C-Glc-Trp), and a-C-
galactosyltryptophan (10, a-C-Gal-Trp). Based on this synthesis,
we planned to synthesize the b-series of the analogues starting
from b-C-glycosylacetylenes.
Highly stereoselective synthesis of b-C-mannosylacetylene
The b-C-glycosylacetylenes, including glucose, galactose, and
mannose, were required as the starting materials. Meldal and
Vasella et al.22 have reported the syntheses of these b-sugar
acetylenes as tetrabenzyl ether according to Kishi’s protocol,23
a widely employed and reliable synthetic method for b-C-
hexapyranosides (Scheme 2); addition of lithium acetylide to the
corresponding sugar lactones A followed by reduction of the
Scheme 2 General synthetic route for b-C-glycosylacetylenes.
Table 1 Stereoselectivities of the reduction of ketal 16 with silanes
Conditions for 1)a
Products
Entry
Silane
Temp.
Conditions for 2)
Yieldb
13a : 13bc
1
2
3
Et3SiH
(TMS)3SiH
i-Pr3SiH
−40 ◦
C
C
C
TBAF
TBAF
K2CO3, MeOH
56% (from 14)
76 (from 16)
67 (from 16)
1 : 2
0 : 100
1 : 99
0 ◦
0 ◦
a All reactions were performed with BF3·OEt2 as a Lewis acid in CH3CN–CH2Cl2 (85 : 15). b The yields were isolated yields. c The ratios were determined
by 1H NMR.
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Scheme 3 Synthesis b-C-mannosylacetylene 13b.
the protons at the C-1 and C-2 positions of 13a and 13b are very
close (J = 2.0 Hz for 13a, J = 1.0 Hz for 13b), the a-configuration
of 13b was confirmed by the NOESY spectrum of tetraacetate 17
obtained by acetolysis of 13b22 (Scheme 4).
gave a mixture of 20 and 23 in a ca. 3.5 : 1 ratio,31 which could be
directly transformed into 26 by treatment with TBAF in refluxing
THF.32
Coupling of b-C-glycosylindoles 24–26 with aziridine carboxy-
late 7 was then carried out as shown in Table 3 to afford b-C-Man-
Trp and its glucose and galactose analogues in moderate yields.
Table 3 Sc(ClO4)3-promoted coupling of glycosylindole (24–26) with the
aziridine 7
Scheme 4 Proof of the configuration of 13b.
Synthesis of fully protected b-C-glycosyltryptophan
With three b-C-glycosylacetylenes (11b, 12b and 13b) from
glucose, galactose, and mannose in hand, we next transformed
these products to b-C-glycosylindoles, as shown in Table 2,
according to our previous studies. The details are including in
the supporting information†. It is worth noting that in the case
of mannosylacetylene 13b, the cross coupling between 13b and 4
Entry
Substrate
Product
Yield (%)
1
2
3
Glucose
Galactose
Mannose
24
25
26
27
28
29
62
39
49
Table 2 Pd-catalyzed coupling between glycosylacetylenes (11b–13b) and N-Ts-o-iodoanilide 4, and synthesis of b-C-glycosylindoles (24–26)
Pd coupling with 4
Synthesis of indole
Deprotection of Ts group
Entry
Glycosylacetylene
Products
Yield (%)
Products
Yield (%)
Products
Yield (%)
1
2
3
11b
12b
13b
Glucose
Galactose
Mannose
18
19
20
86
93
67a
21
22
23
91
90
87
24
25
26
94
92
Quant.
a The indole 23 was isolated in 19% as a by-product.
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Deprotection
HPLC analysis of the synthetic analogues of C-Man-Trp
Deprotection of the methyl ester and benzyl groups of 27, 28
and 29 would then be carried out according to the synthesis of
analogues of a-C-Man-Trp (1). However, many modifications of
the conditions were necessary for satisfactory yields of the final
products 33, 34 and 35.
First, methyl esters of the fully protected C–Gly–Trp (27–
29) were hydrolyzed with aqueous lithium hydroxide (Table 4).
In the syntheses of analogues of a-C-Man-Trp (1), 2-propanol
was employed as a solvent for the hydrolysis, however, the
corresponding b-analogues 27–29 were found to be not sufficiently
soluble in 2-propanol. After some experiments, we found a 1 : 1
mixture of acetonitrile and methanol to be a suitable solvent.33
Under the improved conditions, the esters of 29, 28, and 27 were
hydrolyzed to give 30, 31, and 32 in good to moderate yields
(entries 1, 2, and 4).
With all six possible isomers (1, 9, 10, 33, 34, and 35) of C-
Man-Trp in hand, we next analyzed the synthetic compounds
by HPLC with an ODS column attached to UV and fluorescence
detectors. Fortunately, all six isomers were clearly separated under
conventional conditions as shown in Fig. 2. Interestingly, only
b-C-Man-Trp (33) was eluted at a completely different retention
time from those of other analogues.
Conclusion
The synthesis of b-C-Man-Trp and its Glc, Gal analogues was
carried out in a highly stereoselective manner. The synthesized
materials should be useful as authentic samples for developing
new analytical methods.
Benzyl groups of tetrabenzyl b-C-Man-Trp 30 were then
removed under hydrogenolytic conditions with 5% Pd–C in
methanol (Table 4). Because of our initial concern regarding a
reductive opening of the pyranose ring that we encountered in the
synthesis of a-C-Man-Trp, we were reluctant to add hydrochloric
acid. However, debenzylation of 30 was very sluggish in the
absence of the acid. Fortunately, the debenzylation proceeded in
the presence of concentrated hydrochloric acid to give b-C-Man-
Trp (33) in moderate yield (entry 1). Under these conditions, the
ring-opening by-product was not observed. When deprotection
of tetrabenzyl C-Gal-Trp (31) was conducted with 5% Pd–C in
methanol in the presence of 1 N HCl for 42 hours, b-C-Gal-Trp
(34) was obtained in 54% yield along with the corresponding N-
methyl C-Gal-Trp in 9% yield (entry 2). However, we found that
a shorter time (18.5 hours) suppressed the side reaction to give a
69% yield of the desired product 34 with a trace amount of the
N-methyl product (entry 3). In the deprotection of tetrabenzyl
b-C-Glc-Trp (32), we found that both the substrate 32 and the
product 35 were not sufficiently soluble in methanol, resulting in
lower yields. A mixture of dioxane and water was found to be a
better solvent,19 and b-C-Glc-Trp 35 was thus obtained in good
yield (entry 4). The NMR spectra of these synthetic materials are
in good agreement with those of the literature.18
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 wavenumbers
(cm−1). Proton nuclear magnetic resonance (1H NMR) spectra
were recorded on a Bruker AMX-600 (600 MHz), a Bruker
ARX-400 (400 MHz), a Bruker AVANCE-400 (400 MHz) or a
Varian Gemini-2000 (300 MHz) spectrometer. 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 a Bruker AMX-600 (150 MHz), a
Bruker ARX-400 (100 MHz), a Bruker AVANCE-400 (100 MHz)
or a Varian Gemini-2000 (75 MHz) spectrometer. High resolution
mass spectra (HRMS) were recorded on a JEOL JMS-700 or
a LC-MATE spectrometer and are 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 plates 60 F254 (Merck. #1.05715).
Table 4 Deprotection of esters and benzyl groups
Deprotection of ester
Deprotection of benzyl groups
Entry
Substrate
Product
Yield
Cat.
Additive
Solvent
Time/h
Product
Yield (%)
1
2
3
4
29
28
—
27
Mannose
Galactose
—
30
31
—
32
86%
64
—
5% Pd–C
5% Pd–C
5% Pd–C
10% Pd–C
12 N HCl
1 N HCl
1 N HCl
1 N HCl
MeOH
MeOH
MeOH
Dioxane–H2O
25
42
18.5
7
33
34a
34
35
43
54
69
Quant.
Glucose
64
a N-Methyl-C-Gal-Trp was obtained as a by-product in 9% yield.
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Fig. 2 HPLC chromatogram of synthetic a-C-Man-Trp and its analogues. Conditions: column ODS-5 Develosil, size; 4.6 × 250 mm, mobile phase:
10% MeOH–H2O, 0.1% TFA, flow rate: 0.5 ml min−1
.
Cica-reagent silica gel 60 (particle size 0.063–0.2 mm ASTM)
and Silica Gel 60 N (spherical, neutral) were used for open-
column chromatography. Preparative thin-layer chromatographic
separations were carried out on 0.5 mm silica gel plates 60 F254
(Merck. #1.05774). Unless otherwise noted, non-aqueous reac-
tions were carried out in oven-dried (120 ◦C) or flame-dried
glassware under a nitrogen atmosphere. Dry THF was purchased
from Wako Pure Chemical Industries, Ltd. Dry CH2Cl2, CH3CN
and Et3N were distilled from CaH2 under a nitrogen atmosphere.
Sc(ClO4)3 was prepared according to the literature. All other
commercially available reagents were used as received.
was added a THF (56 ml) solution of the lactone 15 (5.82 g,
10.8 mmol, dried azeotropically with toluene). After stirring for
3.5 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. The residue (6.87 g) was purified by
silica gel column chromatography (150 g, AcOEt–hexane = 1 : 6)
to afford ketal 16 (5.52 g, 75% in 2 steps).
(2,3,4,6-Tetra-O-benzyl-b-D-mannopyranosyl)ethyne (13b).
Reduction with (TMS)3SiH (entry 2 in Table 1). (1) The ketal
16 (3.25 g, 5.11 mmol) was dried azeotropically from toluene,
and dissolved in dry CH3CN (83 ml) and CH2Cl2 (15 ml). To
this solution cooled at 0 ◦C were added (TMS)3SiH (7.90 ml,
25.6 mmol) and BF3·Et2O (1.94 ll, 15.3 mmol). After 1.5 h, 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 (8.39 g) was purified by
silica gel column chromatography (150 g, AcOEt–hexane = 1 :
15 → 1 : 10 → 1 : 7) to afford b-C-trimethylsilylmannosylacetylene
(2.58 g, 81%). (2) The b-C-trimethylsilylmannosylacetylene
(2.58 g, 4.16 mmol) was dissolved in THF (74 ml)–H2O (4 ml),
and TBAF (4.16 ml, 4.16 mmol, 1 M in THF) was added.
After stirring at rt for 1.5 h, the reaction was quenched with
aqueous 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 column chromatography (120 g,
1-Trimethylsilylethynyl-2,3,4,6-tetra-O-benzyl-D-mannopyranose
(16). (1) A solution of mannolactol 14 (6.29 g, 11.6 mmol) in
DMSO (36 ml) and Ac2O (24 ml) was stirred at rt for 7 h, and the
◦
reaction mixture was quenched with H2O at 0 C. The resulting
mixture was extracted with AcOEt (×2). The combined organic
extracts were washed with water (×2) and brine (×2), dried over
anhydrous Na2SO4, and concentrated. The residue was dissolved
in Et2O, and passed through a short column packed with neutral
silica gel, and the eluate was concentrated to afford lactone 15.
This material 15 (5.82 g) was used for the next step without
further purification. (2) Trimethylsilylethyne (3.05 ml, 21.6 mmol)
was dissolved in dry THF (60 ml) and the solution was cooled
to −78 ◦C, and stirred at −78 ◦C for 20 min. To this solution
was added n-BuLi (10.3 ml, 16.2 mmol, 1.57 M in hexane). After
◦
◦
stirring at −78 C for 40 min, the solution was warmed to 0 C
and stirred at 0 ◦C for 40 min. This solution was again cooled
to −78 ◦C and stirred at −78 ◦C for 20 min. To this solution
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AcOEt–hexane = 1 : 6) to afford b-C-mannosylacetylene 13b
(2.13 mg, 93%) as a white solid: [a]3D0 −31.4 (c 1.05, CHCl3); IR
(KBr) mmax 3284, 3032, 2866, 2127, 1954, 1877, 1811, 1606 cm−1;
1H NMR (300 MHz, CDCl3) d 2.47 (1H, d, J = 2 Hz, C≡CH),
3.47 (1H, ddd, J = 9.5, 5, 2 Hz, H-5), 3.55 (1H, dd, J = 9.5,
3 Hz, H-3), 3.68–3.80 (2H, m, H-6), 3.92 (1H, t, J = 9.5 Hz,
H-4), 3.97 (1H, dd, J = 3, 1 Hz, H-2), 4.14 (1H, dd, J = 2,
1 Hz, H-1), 4.53 (1H, d, J = 11 Hz, CHAHBPh), 4.56 (1H, d,
J = 13 Hz, CHCHDPh), 4.60 (1H, d, J = 11.5 Hz, CHEHFPh),
4.63 (1H, d, J = 13 Hz, CHCHDPh), 4.65 (1H, d, J = 11.5 Hz,
CHEHFPh), 4.86 (1H, d, J = 11 Hz, CHAHBPh), 4.98 (2H, s,
CH2Ph), 7.12–7.50 (20H, m, aromatic); 13C NMR (75 MHz,
CDCl3) d 69.0, 69.3, 72.0, 73.4, 74.3, 74.5, 74.6, 75.2, 75.8, 79.9,
80.1, 83.4, 127.5, 127.6, 127.7, 127.7, 128.0, 128.1, 128.1, 128.2,
128.3, 128.4, 128.5, 138.1, 138.2, 138.3, 138.5; Anal. Calcd for
C36H36O5: C, 78.81; H, 6.61. Found: C, 78.81; H, 6.70.
Reduction with (i-Pr)3SiH (entry 3 in Table 1). The ketal
16 (55 mg, 0.086 mmol) was dried azeotropically with toluene
and dissolved in dry CH3CN–CH2Cl2 (1.40 ml–0.25 ml). To
this solution was added (i-Pr)3SiH (88 ll, 0.43 mmol). After
the solution was stirring at 0 ◦C for 25 min, BF3·OEt2 (33 ll,
0.26 mmol) was added. After 15 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 (52 mg) was dissolved in MeOH (1.0 ml), and K2CO3
(52 mg, 0.38 mmol) was added. After stirring at room temperature
for 20 min, 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. The residue was purified
by column chromatography (silica gel 1.6 g, AcOEt–hexane = 1 :
7 → 1 : 5) to afford b-C-mannosylacetylene 13b (32 mg, 67% in
2 steps).
0.025 mmol) was added. After stirring at 60 ◦C for 2 h 45 min,
the mixture was cooled to room temperature. The reaction was
then 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 column chromatography (30 g, CH2Cl2 →
Et2O–hexane = 1 : 1) to afford glucosyl-b-1-ethynylaniline 18
(346 mg, 86%) as yellow oil: [a]2D7 +20 (c 0.98, CHCl3); IR
(KBr) mmax 3031, 2868, 2343, 1495, 1454, 1400, 1342, 1167, 1091,
1
1028 cm−1; H NMR (CDCl3, 400 MHz) d 2.26 (3H, s, CH3 of
Ts), 3.50–3.83 (6H, m, H-2, H-3, H-4, H-5, H-6), 4.24 (1H, d, J =
9 Hz, H-1), 4.57 (1H, d, J = 12 Hz, CHAHBPh), 4.59 (1H, d, J =
11 Hz, CHCHDPh), 4.65 (1H, d, J = 12 Hz, CHAHBPh), 4.80 (1H,
d, J = 11 Hz, CHEHFPh), 4.83 (1H, d, J = 14 Hz, CHGHHPh),
4.85 (1H, d, J = 11 Hz, CHCHDPh), 4.90 (1H, d, J = 14 Hz,
CHGHHPh), 4.92 (1H, d, J = 11 Hz, CHEHFPh), 6.98 (1H, t, J =
7 Hz, aromatic), 7.11 (2H, d, J = 8 Hz, H-3ꢀꢀ of Ts), 7.15–7.38
(23H, m, aromatic, NH), 7.59 (1H, d, J = 8 Hz, aromatic), 7.68
(2H, d, J = 8 Hz, H-2ꢀꢀ of Ts); 13C NMR (CDCl3, 100 MHz) d
21.4, 68.9, 70.2, 73.6, 75.1, 75.5, 75.7, 77.6, 79.2, 80.7, 82.2, 86.1,
93.5, 113.2, 119.8, 124.2, 127.5, 127.7, 127.7, 127.8, 127.9, 127.9,
127.9, 128.0, 128.4, 129.6, 129.9, 132.1, 136.1, 137.7, 137.9, 138.0,
138.2, 138.4, 143.9; Anal. Calcd for C49H47NO7S: C, 74.12; H,
5.97; N, 1.76. Found: C, 74.05; H, 6.14; N, 1.62.
1-(2,3,4,6-Tetra-O-benzyl-b-D-galactopyranosyl)-2-o-(p-toluen-
sulfoamidyl)phenylethyne (19). Following the procedure for
18, 19 (2.50 g, 93%) was obtained as a yellow oil from
b-C-galactosylacetylene 12b (1.85 g, 3.38 mmol) and N-Ts-o-
iodoanilide 4 (2.51 g, 6.76 mmol) after column chromatography
(silicagel120g, CH2Cl2 →AcOEt–hexane=1:3):[a]2D7 −9.0(c1.5,
CHCl3); IR (KBr) mmax 3032, 2868, 1496, 1456, 1341, 1167,
1
1093, cm−1; H NMR (CDCl3, 300 MHz) d 2.22 (3H, s, CH3 of
Ts), 3.57 (1H, dd, J = 9.5, 3 Hz, H-3), 3.61–3.71 (3H, m, H-5,
H-6), 4.00 (1H, t, J = 9.5 Hz, H-2), 4.02 (1H, dd, J = 3, 0.5 Hz,
H-4), 4.19 (1H, d, J = 9.5 Hz, H-1), 4.46 (1H, d, J = 12 Hz,
CHAHBPh), 4.54 (1H, d, J = 12 Hz, CHAHBPh), 4.65 (1H, d,
J = 11.5 Hz, CHCHDPh), 4.73 (1H, d, J = 12 Hz, CHEHFPh),
4.78 (1H, d, J = 12 Hz, CHEHFPh), 4.79 (1H, d, J = 11 Hz,
CHGHHPh), 4.86 (1H, d, J = 11 Hz, CHGHHPh), 4.98 (1H, d,
J = 11.5 Hz, CHCHDPh), 6.98 (1H, dt, J = 7.5 1 Hz, aromatic),
7.06 (2H, br d, J = 8 Hz, aromatic), 7.17–7.41 (23H, m, aromatic,
NH), 7.59 (1H, br d, J = 8 Hz, aromatic), 7.64 (2H, br d, J =
8 Hz, aromatic); 13C NMR (CDCl3, 100 MHz) d 21.4, 68.7, 70.6,
72.7, 73.7, 74.0, 75.0, 75.7, 77.5, 78.8, 80.1, 83.5, 93.7, 120.3,
124.3, 127.5, 127.6, 127.8, 127.9, 128.1, 128.1, 128.3, 128.4, 128.5,
129.6, 129.8, 132.1, 138.1, 138.1; Anal. Calcd for C49H47NO7S: C,
74.12; H, 5.97; N, 1.76. Found: C, 74.12; H, 5.79; N, 1.66.
(2,3,4,6-Tetra-O-acetyl-b-D-mannopyranosyl)ethyne (17). To
an ice-cold solution of b-C-mannosylacetylene 13b (54 mg,
0.098 mmol) in Ac2O (1.6 ml) was added TMSOTf (0.13 ml,
0.63 mmol). After stirring at rt for 38 h 45 min, the reaction
was quenched with saturated NaHCO3 solution and extracted
with AcOEt (×3). The combined organic extracts were washed
with saturated NaHCO3 solution (×2), H2O (×2) and brine
(×2), dried over anhydrous Na2SO4, and concentrated. The
residue (98 mg) was purified by silica gel column chromatography
(10 g, Et2O–hexane = 1 : 2 → 1 : 1 → 2 : 1) to afford b-C-
tetraacetylmannosylacetylene 17 (22 mg, 62%) as a yellow oil. The
NMR spectra were identical to those of the literature, diagnostic
NOESY correlations were observed between H-1 (d 4.46, dd, J =
2, 1 Hz) and H-3 (d 5.06, dd, J = 10, 3.5 Hz) as well as H-1 and
H-5 (d 3.67, 1H, ddd, J = 10, 5.5, 2 Hz).
1-(2,3,4,6-Tetra-O-benzyl-b-D-mannopyranosyl)-2-o-(p-toluen-
sulfoamidyl)phenylethyne (20). Following the procedure for 18,
20 (2.05 g, 67%) was obtained as a yellow oil along with mannosyl-
b-1-tosylindole 23 (579 mg, 19%) from b-C-mannosylacetylene
13b (2.13 g, 3.89 mmol) and N–Ts-o-iodoanilide 4 (2.89 g,
7.77 mmol) after column chromatography (silica gel 120 g,
CH2Cl2 → AcOEt–hexane = 1 : 4 → 1 : 2): [a]3D0 −19.1 (c 0.24,
CHCl3); IR (KBr) mmax 3063, 3032, 2865, 1954, 1811, 1653, 1598,
1496, 1093 cm−1; 1H NMR (CDCl3, 300 MHz) d 2.26 (3H, s, CH3
of Ts), 3.55 (1H, ddd, J = 9, 5 Hz, H-5), 3.64 (1H, dd, J = 9, 3 Hz,
1-(2,3,4,6-Tetra-O-benzyl-b-D-glucopyranosyl)-2-o-(p-toluensul-
foamidyl)phenylethyne (18).
A two-necked round-bottomed
flask was charged with b-C-glucosylacetylene 11b (278 mg,
0.507 mmol), N-Ts-o-iodoanilide 4 (376 mg, 1.01 mmol) and
PPh3 (13.3 mg, 0.0507 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 (8.3 ml)
was added and then the mixture was heated to 60 ◦C. After
these reagents were completely dissolved, Pd(OAc)2 (5.6 mg,
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H-3), 3.73–3.85 (2H, m, H-6 × 2), 3.99 (1H, t, J = 9 Hz, H-4), 4.01
(1H, dd, J = 3, 1 Hz, H-2), 4.36 (1H, d, J = 1 Hz, H-1), 4.57 (1H, d,
J = 10.5 Hz, CHAHBPh), 4.58 (1H, d, J = 12 Hz, CHCHDPh), 4.65
(1H, d, J = 12 Hz, CHCHDPh), 4.68 (1H, d, J = 12 Hz, CHEHFPh),
4.72 (1H, d, J = 12 Hz, CHEHFPh), 4.90 (1H, d, J = 10.5 Hz,
CHAHBPh), 4.91 (1H, d, J = 12 Hz, CHGHHPh), 5.01 (1H, d, J =
12 Hz, CHGHHPh), 6.98 (1H, td, J = 3, 1 Hz, aromatic), 7.10–7.42
(26H, m, aromatic), 7.54 (1H, dd, J = 8, 1 Hz, aromatic), 7.68
(1H, dt, J = 8.5, 2 Hz, aromatic);13C NMR (CDCl3, 100 MHz) d
21.4, 69.5, 69.8, 72.4, 73.5, 74.6, 74.6, 75.3, 76.0, 79.9, 80.7, 83.6,
92.8, 113.2, 119.6, 124.1, 127.5, 127.5, 127.5, 127.6, 127.7, 127.8,
128.0, 128.1, 128.1, 128.3, 128.4, 128.5, 129.6, 129.8, 132.1, 136.1,
138.0, 138.2, 138.3, 143.8; Anal. Calcd for C49H47NO7S: C, 74.12;
H, 5.97; N, 1.76. Found: C, 74.11; H, 6.05; N, 1.53.
J = 8.5 Hz, aromatic); 13C NMR (CDCl3, 100 MHz) d 21.4, 68.6,
72.5, 73.2, 73.4, 73.9, 74.7, 77.1, 77.2, 77.7, 85.5, 111.0, 115.1,
121.3, 123.5, 124.8, 126.9, 127.4, 127.5, 127.7, 127.9, 128.1, 128.2,
128.4, 128.5, 129.2, 129.3, 135.6, 136.9, 137.9, 138.2, 138.3, 138.9,
139.0, 144.2; Anal. Calcd for C49H47NO7S: C, 74.12; H, 5.97; N,
1.76. Found: C, 74.13; H, 6.06; N, 1.78.
2-(2,3,4,6-Tetra-O-benzyl-b-D-mannopyranosyl)-1-(p-toluene-
sulfonyl)indole (23). Following the procedure for 21, 23 (17.2 mg,
87%) was obtained as a yellow oil from mannosyl-b-1-ethynylani-
line 20 (19.8 mg, 0.025 mmol) after column chromatography (5 g,
AcOEt–hexane = 1 : 4): [a]3D0 −94.6 (c 0.76, CHCl3); IR (KBr) mmax
1
3309, 3064, 3031, 2864, 1952, 1597, 1497, 1454 cm−1; H NMR
(CDCl3, 400 MHz) d 2.28 (3H, s, CH3 of Ts), 3.68–3.74 (1H, m,
H-5), 3.79–3.86 (2H, m, H-6), 3.88 (1H, dd, J = 9.5, 2.5 Hz, H-3),
4.01 (1H, t, J = 9.5 Hz, H-4), 4.25 (1H, d, J = 11.5 Hz, CHAHBPh),
4.50 (1H, d, J = 11.5 Hz, CHAHBPh), 4.53 (1H, br d, J = 2.5 Hz,
H-2), 4.60 (1H, d, J = 12 Hz, CHCHDPh), 4.61 (1H, d, J = 11 Hz,
CHEHFPh), 4.65 (1H, d, J = 12 Hz, CHGHHPh), 4.70 (1H, d,
J = 12 Hz, CHCHDPh), 4.75 (1H, d, J = 12 Hz, CHGHHPh), 4.95
(1H, d, J = 11 Hz, CHEHFPh), 5.13 (1H, s, H-1), 6.89–7.45 (26H,
m, aromatic, NH), 7.55 (2H, br d, J = 8 Hz, aromatic), 8.08 (1H,
d, J = 8 Hz, aromatic); 13C NMR (CDCl3, 100 MHz) d 21.5, 69.9,
71.8, 73.4, 74.3, 74.9, 75.1, 75.6, 77.2, 80.3, 84.3, 112.4, 115.1,
120.9, 122.4, 123.9, 124.4, 126.3, 126.8, 127.3, 127.4, 127.5, 127.5,
127.6, 127.8, 127.9, 128.0, 128.0, 128.1, 128.3, 128.3, 128.4, 129.5,
129.6, 129.8, 130.1, 135.1, 137.1, 137.9, 138.1, 138.2, 138.5, 138.5,
139.1, 144.9; Anal. Calcd for C49H47NO7S: C, 74.12; H, 5.97; N,
1.76. Found: C, 74.13; H, 6.06; N, 1.83.
2-(2,3,4,6-Tetra-O-benzyl-b-D-glucopyranosyl)-1-(p-toluene-
sulfonyl)indole (21). Glucosyl-b-1-ethynylaniline 18 (493 mg,
0.623 mmol) was dissolved in Et3N (9.9 ml) and DMF (4.9 ml),
and CuI (23 mg, 0.13 mmol) was added. This solution was
stirred at 80 ◦C for 2.5 h. The reaction was 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
column chromatography (15 g, AcOEt–hexane = 1 : 5) to afford
glucosyl-b-1-tosylindole 21 (447 mg, 91%) as a yellow oil: [a]D27
−46.5 (c 1.03, CHCl3); IR (KBr) mmax 3031, 2865, 1598, 1497,
1453, 1368, 1176, 1092 cm−1; 1H NMR (CDCl3, 300 MHz) d 2.20
(3H, s, CH3 of Ts), 3.68–4.04 (6H, m, H-2, H-3, H-4, H-5, H-6),
4.47 (1H, d, J = 12 Hz, CHAHBPh), 4.52 (1H, d, J = 11 Hz,
CHCHDPh), 4.58 (1H, d, J = 12 Hz, CHAHBPh), 4.64 (1H, d, J =
11 Hz, CHEHFPh), 4.77 (1H, d, J = 11 Hz, CHCHDPh), 4.88 (1H,
d, J = 11 Hz, CHEHFPh), 4.94 (1H, d, J = 11.5 Hz, CHGHHPh),
4.98 (1H, d, J = 11.5 Hz, CHGHHPh), 5.39 (1H, br d, J = 9 Hz,
H-1), 6.68 (1H, s, H-3ꢀ), 6.92 (2H, br d, J = 8 Hz, aromatic), 6.97
(2H, br dd, J = 8, 1 Hz, aromatic), 7.07–7.36 (20H, m, aromatic)
7.39 (1H, br d, J = 7.5 Hz, aromatic), 7.78 (2H, d, J = 8 Hz
aromatic), 8.08 (1H, d, J = 9 Hz, aromatic); 13C NMR (CDCl3,
75 MHz) d 21.4, 69.1, 73.3, 74.3, 74.9, 75.7, 78.3, 79.0, 81.2, 87.6,
115.2, 121.3, 123.6, 125.0, 127.0, 127.5, 127.6, 127.7, 127.8, 127.9,
128.1, 128.3, 128.5, 128.5, 129.1, 129.5, 135.6, 137.0, 137.9, 138.1,
138.3, 138.6, 144.4; Anal. Calcd for C49H47NO7S: C, 74.12; H,
5.97; N, 1.76. Found: C, 74.07; H, 6.00; N, 1.64.
2-(2,3,4,6-Tetra-O-benzyl-b-D-glucopyranosyl)-1H-indole (24).
To a solution of glucosyl-b-1-tosylindole 21 (377 mg, 0.476 mmol)
in THF (11 ml) was added TBAF (2.3 ml, 2.4 mmol, 1 M in THF).
This solution was heated at reflux temperature with stirring for
2 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. The residue was purified by silica
gel column chromatography (5 g, CH2Cl2) to afford glucosyl-b-
1-indole 24 (287 mg, 94%) as a yellow oil: [a]2D7 −14.8 (c 1.01,
CHCl3); IR (KBr) mmax 3406, 3032, 2902, 2865, 1455, 1359, 1135,
1062 cm−1; 1H NMR (CDCl3, 400 MHz) d 3.55–3.85 (6H, m, H-2,
H-3, H-4, H-5, H-6), 4.02 (1H, s, J = 10.5 Hz, H-1) 4.50 (1H, d,
J = 10 Hz, CHAHBPh), 4.56 (1H, d, J = 11.5 Hz, CHCHDPh),
4.59 (1H, d, J = 10 Hz, CHAHBPh), 4.62 (1H, d, J = 11.5 Hz,
CHCHDPh), 4.63 (1H, d, J = 11 Hz, CHEHFPh), 4.88 (1H, d, J =
11 Hz, CHEHFPh), 4.91 (1H, d, J = 10.5 Hz, CHGHHPh), 4.98
(1H, d, J = 10.5 Hz, CHGHHPh), 6.58 (1H, s, indole), 7.00–7.40
2-(2,3,4,6-Tetra-O-benzyl-b-D-galactopyranosyl)-1-(p-toluene-
sulfonyl)indole (22). Following the procedure for 21, 22 (2.24 g,
90%) was obtained as
a yellow oil from galactosyl-b-1-
ethynylaniline 19 (2.50 g, 3.16 mmol) after column chromatogra-
phy (120 g, AcOEt–hexane = 1 : 5): [a]2D7 −49.7 (c 0.35, CHCl3); IR
(KBr) mmax 3031, 2869, 1598, 1497, 1497, 1454, 1367, 1092 cm−1;
1H NMR (CDCl3, 300 MHz) d 2.18 (3H, s, CH3 of Ts), 3.54–4.14
(5H, m, H-3, H-4, H-5, H-6), 4.32 (1H, t, J = 9.5 Hz, H-2),
4.42 (1H, d, J = 12 Hz, CHAHBPh), 4.46 (1H, d, J = 12 Hz,
CHAHBPh), 4.58 (1H, d, J = 11 Hz, CHCHDPh), 4.68 (1H, d,
J = 11 Hz, CHEHFPh), 4.74 (1H, d, J = 11.5 Hz, CHGHHPh),
4.82 (1H, d, J = 11.5 Hz, CHGHHPh), 4.89 (1H, d, J = 11 Hz,
CHCHDPh), 5.00 (1H, d, J = 11 Hz, CHEHFPh), 5.41 (1H, d,
J = 9.5 Hz, H-1), 6.71 (1H, s, H-3ꢀ), 6.88 (2H, br d, J = 8.5 Hz,
aromatic), 7.00 (2H, dd, J = 8, 1 Hz, aromatic), 7.07–7.42 (21H,
m, aromatic), 7.73 (2H, d, J = 8.5 Hz, aromatic), 8.06 (1H, d,
(23H, m, aromatic), 7.60 (1H, s, aromatic), 8.48 (1H, s, NH); 13
C
NMR (CDCl3, 75 MHz) d 68.9, 73.5, 75.0, 75.1, 75.7, 75.7, 77.9,
79.1, 82.5, 86.5, 101.6, 111.1, 119.8, 120.6, 121.9, 127.7, 127.8,
127.9, 127.9, 128.0, 128.2, 128.4, 128.4, 128.5, 135.7, 136.1, 137.5,
138.0, 138.1, 138.6; Anal. Calcd for C42H41NO5: C, 78.85; H, 6.46;
N, 2.19. Found: C, 78.86; H, 6.61; N, 2.19.
2-(2,3,4,6-Tetra-O-benzyl-b-D-galactopyranosyl)-1H-indole (25).
Following the procedure for 24, 25 (1.67 g, 92%) was obtained as a
yellow solid from galactosyl-b-1-tosylindole 22 (2.24 g, 2.83 mmol)
after column chromatography (silica gel 90 g, AcOEt–hexane = 1 :
4): [a]2D2 −20.8 (c 1.05, CHCl3); IR (KBr) mmax 3423, 3032, 2869,
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1497, 1455, 1364, 1294, 1101 cm−1; 1H NMR (CDCl3, 300 MHz)
d 3.64 (2H, dd, J = 6.5, 1.5 Hz, H-6), 3.68–3.78 (2H, m, H-3,
H-5), 3.98 (1H, t, J = 9.5 Hz, H-2), 4.06–4.10 (1H, m, H-4),
4.09 (1H, d, J = 10 Hz, CHAHBPh), 4.45 (1H, d, J = 11.5 Hz,
CHCHDPh), 4.47 (1H, d, J = 9.5 Hz, H-1), 4.50 (1H, d, J =
11.5 Hz, CHCHDPh), 4.56 (1H, d, J = 10 Hz, CHAHBPh), 4.64
(1H, d, J = 11 Hz, CHEHFPh), 4.79 (2H, s, CH2Ph), 5.00 (1H, d,
J = 11 Hz, CHEHFPh), 6.55 (1H, br d, J = 1.5 Hz, H-3ꢀ), 7.02–
7.42 (23H, m, aromatic), 7.59 (1H, br d, J = 8 Hz, aromatic), 8.59
(1H, s, NH); 13C NMR (CDCl3, 75 MHz) d 68.7, 72.7, 73.5, 74.3,
74.9, 75.2, 76.1, 77.4, 78.9, 84.0, 101.6, 111.1, 119.6, 120.6, 121.8,
127.6, 127.7, 127.8, 127.9, 128.0, 128.1, 128.3, 128.3, 128.4, 128.5,
135.9, 136.0, 137.9, 138.4, 138.7; Anal. Calcd for C42H41NO5: C,
78.85; H, 6.46; N, 2.19. Found: C, 78.86; H, 6.35; N, 2.23.
stirred at the same temperature for 3 h, and directly subjected
to silica gel column chromatography (15 g, AcOEt–hexane = 1 :
4 → 1 : 3) to give 27 (176 mg, 62%) as a brown oil: [a]2D7 +8.4
(c 0.22, CHCl3); IR (KBr) mmax 3311, 3032, 2922, 1954, 1718,
1455, 1210, 1062 cm−1; 1H NMR (CDCl3, 400 MHz) d 3.19 (1H,
dd, J = 15, 4 Hz, CHAHBCHCOOMe), 3.53 (1H, dd, J = 15,
6.5 Hz, CHAHBCHCOOMe), 3.53–3.58 (1H, m, H-5), 3.60 (3H, s,
COOCH3), 3.62 (1H, t, J = 9 Hz, H-2), 3.69 (1H, dd, J = 10.5,
2 Hz, H-6), 3.76 (1H, dd, J = 10.5, 3 Hz, H-6), 3.75–3.85 (2H,
m, H-3, H-4), 4.15 (1H, d, J = 11 Hz, CHAHBPh), 4.43 (1H, d,
J = 11.5 Hz, CHCHDPh), 4.45 (1H, d, J = 11 Hz, CHEHFPh),
4.52 (1H, d, J = 11 Hz, CHAHBPh), 4.56 (1H, d, J = 9 Hz,
H-1), 4.58 (1H, d, J = 11.5 Hz, CHCHDPh), 4.65–4.72 (1H, m,
CHCOOCH3), 4.74 (1H, d, J = 11 Hz, CHGHHPh), 4.76 (1H,
d, J = 11 Hz, CHEHFPh), 4.80 (1H, d, J = 11 Hz, CHGHHPh),
5.08 (1H, d, J = 12 Hz, CHIHJPh), 5.12 (1H, d, J = 12 Hz,
CHIHJPh), 6.64 (1H, d, J = 8.5 Hz, aromatic), 6.90 (2H, d, J =
7 Hz, aromatic), 7.06 (2H, br t, J = 7.5 Hz, aromatic), 7.09–7.39
(24H, m, aromatic), 7.53 (1H, d, J = 8 Hz aromatic), 8.41 (1H, s,
NH of indole); 13C NMR (100 MHz, CDCl3) d 26.9, 52.2, 54.9,
66.9, 68.4, 73.5, 74.2, 74.5, 75.0, 75.5, 77.6, 79.0, 81.0, 86.9, 108.9,
111.2, 118.8, 119.5, 122.4, 127.6, 127.7, 127.8, 128.0, 128.1, 128.2,
128.3, 128.4, 128.4, 128.5, 132.5, 135.6, 137.0, 137.7, 138.2, 138.5,
156.3, 172.6; HRMS (FAB) Calcd for C54H55N2O9 (M + H):
875.3908, Found: 875.3887.
2-(2,3,4,6-Tetra-O-benzyl-b-D-mannopyranosyl)-1H-indole (26)
from 23. Following the procedure for 24, 26 (10 mg, quant.)
was obtained as a yellow solid from mannosyl-b-1-tosylindole 23
(12 mg, 0.015 mmol) after column chromatography (silica gel 5 g,
AcOEt–hexane = 1 : 4): [a]3D0 −7.8 (c 1.30, CHCl3); IR (KBr) mmax
3440, 3062, 2863, 1952, 1586, 1455, 1101 cm−1; 1H NMR (CDCl3,
300 MHz) d 3.61 (1H, m, H-5), 3.76–3.81 (2H, m, H-6), 3.80 (1H,
dd, J = 9.5, 2.5 Hz, H-3), 4.02 (1H, dd, J = 2.5, 1 Hz, H-2), 4.10
(1H, t, J = 9.5 Hz, H-4), 4.23 (1H, d, J = 11 Hz, CHAHBPh),
4.54 (1H, d, J = 12 Hz, CHCHDPh), 4.63 (1H, d, J = 10.5 Hz,
CHEHFPh), 4.64 (1H, d, J = 12 Hz, CHCHDPh), 4.68 (1H, d,
J = 1 Hz, H-1), 4.73 (1H, d, J = 12 Hz, CHGHHPh), 4.77 (1H,
d, J = 12 Hz, CHGHHPh), 4.78 (1H, d, J = 11 Hz, CHAHBPh),
4.94 (1H, d, J = 10.5 Hz, CHEHFPh), 6.34 (1H, d, J = 1.5 Hz,
indole), 7.02–7.40 (23H, m, aromatic), 7.57 (1H, br d, J = 8 Hz,
aromatic), 8.84–8.90 (1H, br, NH); 13C NMR (CDCl3, 100 MHz)
d 69.4, 72.4, 73.5, 74.6, 74.8, 75.0, 75.3, 78.5, 79.7, 84.4, 99.5,
111.0, 119.5, 120.4, 121.7, 127.4, 127.5, 127.6, 127.7, 127.7, 127.8,
128.1, 128.2, 128.3, 128.3, 128.5, 129.6, 135.6, 135.8, 138.0, 138.2,
138.3, 138.3; Anal. Calcd for C42H41NO5: C, 78.85; H, 6.46; N,
2.19. Found: C, 78.83; H, 6.61; N, 2.15.
2-(2,3,4,6-Tetra-O-benzyl-b-D-galactopyranosyl)-L-(N-carbo-
benzyloxyl)-tryptophan methyl ester (28). Following the proce-
dure for 27, 28 (60 mg, 39%) was obtained as a yellow oil from
galactosylindole 25 (112 mg, 0.175 mmol) and aziridine 7 (82 mg,
0.35 mmol) after column chromatography (12 g, AcOEt–hexane
= 1 : 4): [a]2D7 +10.1 (c 0.36, CHCl3); IR (KBr) mmax 3298, 3032,
2871, 1721, 1455, 1212, 1071 cm−1; 1H NMR (CDCl3, 400 MHz)
d 3.19 (1H, dd, J = 15, 4 Hz, CHAHBCHCOOMe), 3.53 (1H, dd,
J = 15, 6.5 Hz, CHAHBCHCOOMe), 3.53–3.58 (1H, m, H-5),
3.60 (3H, s, COOCH3), 3.62 (1H, t, J = 9 Hz, H-2), 3.69 (1H,
dd, J = 10.5, 2 Hz, H-6), 3.76 (1H, dd, J = 10.5, 3 Hz, H-6),
3.75–3.85 (2H, m, H-3, H-4), 4.15 (1H, d, J = 11 Hz, CHAHBPh),
4.43 (1H, d, J = 11.5 Hz, CHCHDPh), 4.45 (1H, d, J = 11 Hz,
CHEHFPh), 4.52 (1H, d, J = 11 Hz, CHAHBPh), 4.56 (1H, d, J =
9 Hz, H-1), 4.58 (1H, d, J = 11.5 Hz, CHCHDPh), 4.65–4.72 (1H,
m, CHCOOCH3), 4.74 (1H, d, J = 11 Hz, CHGHHPh), 4.76 (1H,
d, J = 11 Hz, CHEHFPh), 4.80 (1H, d, J = 11 Hz, CHGHHPh),
5.08 (1H, d, J = 12 Hz, CHIHJPh), 5.12 (1H, d, J = 12 Hz,
CHIHJPh), 6.64 (1H, d, J = 8.5 Hz, aromatic), 6.90 (2H, d, J =
7 Hz, aromatic), 7.06 (2H, br t, J = 7.5 Hz, aromatic), 7.09–7.39
(24H, m, aromatic), 7.53 (1H, d, J = 8 Hz aromatic), 8.41 (1H, s,
NH of indole); 13C NMR (100 MHz, CDCl3) d 26.9, 52.1, 54.7,
66.7, 68.5, 73.5, 74.3, 74.4, 74.9, 77.2, 77.5, 84.7, 108.8, 111.2,
118.9, 119.5, 122.3, 127.5, 127.7, 127.7, 127.8, 127.9, 128.1, 128.2,
128.2, 128.3, 128.4, 128.4, 128.7, 128.8, 132.9, 135.5, 136.6, 137.1,
137.8, 138.6, 172.5; HRMS (FAB) Calcd for C54H55N2O9 (M +
H): 875.3908, Found: 875.3887.
2-(2,3,4,6-Tetra-O-benzyl-b-D-mannopyranosyl)-1H-indole (26)
from 23.
A mixture of b-1-ethynylmannose 20 (2.05 g,
2.59 mmol) and mannosyl-b-1-tosylindole 23 (579 mg, 0.73 mmol)
was dissolved in THF (79 ml), and TBAF (10 ml, 10 mmol, 1 M in
THF) was added. This solution was stirred at reflux temperature
for 6 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. The residue was purified by column
chromatography (silica gel 110 g, AcOEt–hexane = 1 : 4) to afford
mannosyl-b-1-indole 26 (1.57 g, 74%) as a yellow solid.
2-(2,3,4,6-Tetra-O-benzyl-b-D-glucopyranosyl)-L-(N-carbobenzy-
loxyl)-tryptophan methyl ester (27). Sc(ClO4)3 (221 mg,
0.645 mmol) placed in a reaction vessel was freeze-dried with
benzene for 1 h, then cooled to 0 ◦C. To this flask was added MS
5A (300 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 a separate
flask, glucosylindole 24 (206 mg, 0.322 mmol) and aziridine 7
(152 mg, 0.645 mmol) were dried azeotropically with benzene,
and dissolved in dry CH2Cl2 (6 ml). The solution was added to
the reaction vessel via cannular tubing. The reaction mixture was
2-(2,3,4,6-Tetra-O-benzyl-b-D-mannopyranosyl)-L-(N-carbobenzy-
loxyl)-tryptophan methyl ester (29). Following the procedure
for 27, 29 (140 mg, 49%) was obtained as a yellow oil from
mannosylindole 26 (210 mg, 0.329 mmol) and aziridine 7 (154 mg,
0.657 mmol) after column chromatography (15 g, AcOEt–
hexane = 1 : 4 → 1 : 3): [a]D27 +5.7 (c 0.35, CHCl3); IR (KBr)
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mmax 3429, 3032, 2868, 1721, 1497, 1455, 1215, 1098 cm−1; 1H
NMR (CDCl3, 400 MHz) d 3.18 (1H, dd, J = 15, 6.5 Hz,
and brine, dried over anhydrous Na2SO4, and concentrated. The
residue was purified by preparative TLC (10% MeOH–CH2Cl2)
to give 31 (38 mg, 64%). (2) A two-necked flask was charged
with 5% Pd–C (11.6 mg) and connected to an inlet adaptor. The
flask was evacuated and then filled with nitrogen. A solution of 31
(11.6 mg, 0.013 mmol) in MeOH (0.34 ml) and 1 N HCl (4 ll) were
added. The flask was then evacuated and then filled with hydrogen.
After vigorous stirring for 18.5 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 (4 mg) was purified by preparative TLC (CHCl3–MeOH–
H2O = 65 : 65 : 15) to give 35, which was further purified by
reversed phase column chromatography (Cosmosil 75C18, H2O as
an eluate) to give 34 (3.3 mg, 69%) as a white solid: [a]2D1 +3.0
CHAHBCHCOOMe), 3.25 (1H, dd,
J
=
15, 5.5 Hz,
CHAHBCHCOOMe), 3.61 (3H, s, COOCH3), 3.59–3.66 (1H, m,
H-5), 3.69–3.80 (2H, m, H-6), 3.82 (1H, m, H-3), 4.05 (1H, m,
H-2), 4.13 (1H, t, J = 9.5 Hz, H-4), 4.23 (1H, d, J = 10.5 Hz,
CHAHBPh), 4.42 (1H, d, J = 12 Hz, CHCHDPh), 4.53–4.62 (1H,
m, CHCOOCH3), 4.56 (1H, d, J = 12 Hz, CHCHDPh), 4.61 (1H,
d, J = 10.5 Hz, CHEHFPh), 4.68–4.78 (3H, m, H-1, CH2Ph),
4.86 (1H, d, J = 10.5 Hz, CHAHBPh), 4.93 (1H, d, J = 10.5 Hz,
CHEHFPh), 5.02 (1H, d, J = 12 Hz, CHIHJPh), 5.06 (1H, d, J =
12 Hz, CHIHJPh), 5.44 (1H, d, J = 7 Hz, NH–Cbz), 7.03–7.39
(28H, m, aromatic), 7.49 (1H, d, J = 7.5 Hz aromatic), 8.96 (1H, s,
NH of indole); 13C NMR (100 MHz, CDCl3) d 27.1, 52.4, 54.9,
66.9, 69.3, 72.0, 72.5, 73.4, 74.7, 75.1, 75.2, 77.2, 77.7, 79.8, 84.7,
106.4, 111.1, 118.7, 119.4, 122.2, 127.4, 127.6, 127.6, 127.7, 127.9,
128.0, 128.0, 128.1, 128.2, 128.3, 128.4, 128.4, 128.5, 133.0, 135.3,
136.2, 138.0, 138.2, 138.4, 155.8, 172.4; HRMS (FAB) Calcd for
C54H55N2O9 (M + H): 875.3908, Found: 875.3887.
1
(c 0.17, H2O); H NMR (D2O, 600 MHz) d 3.30 (1H, dd, J =
15, 9.5 Hz, CHAHBCHCOOH), 3.60 (1H, dd, J = 15, 4.5 Hz,
CHAHBCHCOOH), 3.80 (1H, dd, J = 14, 12 Hz, H-6), 3.81 (1H, s,
H-6), 3.85 (1H, dd, J = 9.5, 3 Hz, H-3), 3.94–3.97 (1H, m, H-5),
4.09 (1H, dd, J = 9.5, 4.5 Hz, CHCOOH), 4.11 (1H, t, J = 9.5 Hz,
H-2), 4.11 (1H, br s, H-4), 4.68 (1H, d, J = 9.5 Hz, H-1), 7.23 (1H,
ddd, J = 8, 7, 1 Hz, indole), 7.33 (1H, ddd, J = 8, 7, 1 Hz, indole),
2-b-D-Mannopyranosyl-L-tryptophan (33). (1) To a solution of
29 (130 mg, 0.149 mmol) in CH3CN–MeOH (3 ml/3 ml) was added
1 N LiOH solution (0.30 ml, 0.30 mmol). After stirring at rt for
14 h, sat. NH4Cl solution was added. The pH of the mixture was
adjusted to 2 with 1 N HCl and then extracted with AcOEt (×3).
The combined organic layer was washed with water and brine,
dried over anhydrous Na2SO4, and concentrated. The residue
was purified by column chromatography (silica gel 10 g, MeOH–
CH2Cl2 = 1 : 20) to give 30 (110 mg, 86%). (2) A two-necked flask
was charged with 5% Pd–C (31 mg) and connected to an inlet
adaptor. The flask was evacuated and then filled with nitrogen. A
solution of 30 (31 mg, 0.037 mmol) in MeOH (0.94 ml) and 1 N
HCl (14 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 (15.2 mg) was purified by preparative
TLC (CHCl3–MeOH–H2O = 65 : 65 : 15) to give 33, which
was further purified by reversed phase column chromatography
(Cosmosil 75C18, H2O as an eluate) to give 33 (5.8 mg, 43%) as a
white solid: [a]2D2 +14.1 (c 0.17, H2O); 1H NMR (D2O, 600 MHz)
d 3.26 (1H, dd, J = 15, 9.5 Hz, CHAHBCHCOOH), 3.61 (1H, dd,
J = 15, 4.5 Hz, CHAHBCHCOOH), 3.66 (1H, ddd, J = 9.5, 6.5,
2 Hz, H-5), 3.76 (1H, t, J = 9.5 Hz, H-4), 3.81 (1H, dd, J = 12,
6.5 Hz, H-6), 3.88 (1H, dd, J = 9.5, 3 Hz, H-3), 4.01 (1H, dd, J =
9.5, 4.5 Hz, CHCOOH), 4.04 (1H, dd, J = 12, 2 Hz, H-6), 4.29
(1H, d, J = 3 Hz, H-2), 5.08 (1H, s, H-1), 7.23 (1H, dd, J = 8, 7, Hz,
indole), 7.31 (1H, dd, J = 8, 7, Hz, indole), 7.53 (1H, d, J = 8 Hz,
indole), 7.75 (1H, d, J = 8 Hz, indole); 13C NMR (120 MHz, D2O)
d 28.6, 58.0, 63.9, 69.7, 74.3, 76.5, 76.6, 82.9, 109.3, 114.6, 121.2,
122.5, 125.3, 129.8, 136.1, 138.3, 177.3; HRMS (FAB) Calcd for
C17H23N2O7 (M + H): 367.1505, Found: 367.1500.
7.55 (1H, d, J = 8 Hz, indole), 7.77 (1H, d, J = 8 Hz, indole); 13
C
NMR (120 MHz, D2O) d 28.4, 58.0, 64.2, 72.0, 72.8, 76.6, 76.8,
81.8, 111.0, 114.7, 121.6, 122.5, 125.8, 129.6, 136.2, 138.8, 177.1;
HRMS (FAB) Calcd for C17H23N2O7 (M + H): 367.1505, Found:
367.1532.
2-b-D-Glucopyranosyl-L-tryptophan (35). (1) To a solution of
27 (172 mg, 0.197 mmol) in CH3CN–MeOH (7.9 ml/7.9 ml) was
added 1 N LiOH solution (0.39 ml, 0.39 mmol). After stirring
at rt for 15 h, sat. NH4Cl solution was added. The pH of the
mixture was adjusted to 2 with 1 N HCl and then extracted with
AcOEt (×3). The combined organic layer was washed with water
and brine, dried over anhydrous Na2SO4, and concentrated. The
residue was purified by silica gel column chromatography (15 g,
MeOH–CH2Cl2 = 1 : 20) to give 32 (109 mg, 64%). (2) A two-
necked flask was charged with 10%Pd–C (6.4 mg) and connected
to an inlet adaptor. The flask was evacuated and then filled with
nitrogen. A solution of 32 (6.4 mg, 0.0074 mmol) in dioxane–H2O
(0.19 ml : 0.032 ml) was added. The flask was then evacuated and
then filled with hydrogen. After vigorous stirring for 36 h, 1 N HCl
(2 ll) was added and stirring was continued for 7 h. The mixture
was filtered through a pad of Hyflo Super-Cel, and the precipitate
was rinsed with MeOH–CH3Cl–H2O (65 : 65 : 15). The combined
filtrate was concentrated. The residue was washed with MeOH
and the precipitate was further washed with CHCl3–MeOH–H2O
(65 : 65 : 15) to give 35 (3.1 mg, quant.) as a white solid: [a]D27
1
+2.6 (c 0.16, H2O); H NMR (D2O, 600 MHz) d 2.88 (1H, dd,
J = 15, 9 Hz, CHAHBCHCOOH), 3.15 (1H, dd, J = 15, 4.5 Hz,
CHAHBCHCOOH), 3.34 (1H, t, J = 9.5 Hz, H-4), 3.41 (1H, t,
J = 9.5 Hz, H-3), 3.41 (1H, ddd, J = 9.5, 5, 2 Hz, H-5), 3.53 (1H,
dd, J = 12.5, 5 Hz H-6), 3.54 (1H, t, J = 9.5 Hz, H-2), 3.53–3.57
(1H, m, CHCOOH), 3.64 (1H, dd, J = 12.5, 2 Hz, H-6), 4.47 (1H,
d, J = 9.5 Hz, H-1), 6.92 (1H, t, J = 7.5 Hz, indole), 7.02 (1H,
t, J = 7.5 Hz, indole), 7.23 (1H, d, J = 8 Hz, indole), 7.48 (1H,
d, J = 8 Hz, indole); 13C NMR (120 MHz, CDCl3) d 29.8, 58.6,
63.2, 72.1, 75.4, 76.1, 79.6, 82.3, 112.2, 114.2, 121.5, 122.1, 125.4,
129.6, 135.2, 138.6; HRMS (FAB) Calcd for C17H23N2O7 (M + H):
367.1505, Found: 367.1524.
2-b-D-Galactopyranosyl-L-tryptophan (34). (1) To a solution of
28 (60 mg, 0.069 mmol) in CH3CN–MeOH (2.7 ml/2.7 ml) was
added 1 N LiOH solution (0.14 ml, 0.14 mmol). After stirring at
rt for 6 h 40 min, sat. NH4Cl solution was added. The mixture
was adjusted to pH 2 with 1 N HCl and then extracted with
AcOEt (×3). The combined organic layer was washed with water
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18 T. Nishikawa, S. Kajii, C. Sato, Z. Yasukawa, K. Kitajima and M.
Isobe, Bioorg. Med. Chem., 2004, 12, 2343–2348.
Acknowledgements
19 B. Gutsche, C. Grun, D. Scheutzow and M. Herderich, Biochem. J.,
1999, 343, 11–19.
20 For accounts of the chemistry of sugar acetylene developed in this
laboratory, see: (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., Jpn., 2000, 58, 23–30; (c) M. Isobe and K.
Kira, J. Synth. Org. Chem., Jpn., 2000, 58, 99–107.
NMR measurements of 600 MHz and elemental analyses were
performed by Mr Koga and Mr M. Kitamura in the analytical
division of the faculty, whom we thank. This work was financially
supported by PRESTO, JST and Scientific research on priority
area “Functional Glycomics” from MEXT.
21 T. Nishikawa, S. Kajii, K. Wada, M. Ishikawa and M. Isobe, Synthesis,
2002, 1658–1662.
References
22 T. Lowary, M. Meldal, A. Helmboldt, A. Vasella and K. Bock, J. Org.
Chem., 1998, 63, 9657–9668.
1 (a) J. Hofsteenge, D. R. Mu¨ller, T. Beer, A. Lo¨ffler, W. J. Richter and
J. Vliegenthart, Biochemistry, 1994, 33, 13524–13530; (b) T. Beer, J.
Vliegenthart, A. Lo¨ffler and J. Hofsteenge, Biochemistry, 1995, 34,
11785–11789.
2 M.-A. Doucey, D. Hess, M. J. J. Blommers and J. Hofsteenge,
Glycobiology, 1999, 9, 435–441.
23 M. D. Lewis, J. K. Cha and Y. Kishi, J. Am. Chem. Soc., 1982, 104,
4976–4978.
24 For the first application of Kishi’s procedure to the synthesis of b-
C-glycosylacetylene, see: J.-M. Lancelin, P. H. A. Zollo and P. Sinay,
Tetrahedron Lett., 1983, 24, 4833–4836.
25 The stereoselective synthesis of b-C-mannosides has been a general
challenging subject as the synthesis of b-O-mannosides in carbohydrate
chemistry. For a recent review on b-O-mannoside synthesis, see: S. C.
Ennis and M. I. Osborn, in Carbohydrate, ed. H. M. I. Osborn,
Academic Press, Oxford, 2003, pp. 239–276.
26 For leading references, see: (a) J. Beignet, J. Tiernan, C. H. Woo, B. M.
Kariuki and L. R. Cox, J. Org. Chem., 2004, 69, 6341–6356; (b) G.
Stork and J. J. L. Clair, J. Am. Chem. Soc., 1996, 118, 247–248; (c) T.
Skrydstrup, D. Mazeas, M. Elmouchir, G. Doisnneau, C. Riche, A.
Chiaroni and J.-M. Beau, Chem.–Eur. J., 1997, 3, 1342–1356; (d) J. P.
Praly, G.-R. Chen, J. Gola and G. Hetzer, Eur. J. Org. Chem., 2000,
2831–2838.
3 J. Hofsteenge, M. Blommers, D. Hess, A. Furmanek and O. Mirosh-
nichenko, J. Biol. Chem., 1999, 274, 32786–32794.
4 S. Hartmann and J. Hofsteenge, J. Biol. Chem., 2000, 275, 28569–28574.
5 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.
6 A. Gonzalez de Peredo, D. Klein, M. Macek, D. Hess, J. Peter-Katalinic
and J. Hofsteenge, Mol. Cell. Proteomics, 2002, 1, 11–18.
7 J. Perez-Vilar, S. H. Randell and R. C. Boucher, Glycobiology, 2004, 14,
325–337.
8 A. Furmanek, D. Hess, H. Rogniaux and J. Hofsteenge, Biochemistry,
2003, 42, 8452–8458.
9 J. Krieg, S. Hartmann, A. Vicentini, W. Gla¨sner, D. Hess and J.
Hofsteenge, Mol. Biol. Cell, 1998, 9, 301–309.
10 (a) J. C. Adams and J. Lawler, Curr. Biol., 1993, 3, 188–190; (b) J. C.
Adams and R. P. Tucker, Dev. Dyn., 2000, 218, 280–299.
11 (a) J. F. G. Vligenthart and F. Casset, Curr. Opin. Struct. Biol., 1998, 8,
565–571; (b) A. Furmanek and J. Hofsteenge, Acta Biochim. Pol., 2000,
47, 781–789.
27 Dondoni reported the synthesis of various sugar acetylenes: (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.
28 M. Terauchi, H. Abe, A. Matsuda and S. Shuto, Org. Lett., 2004, 6,
3751–3754.
29 For examples of the reduction of ketals with silanes other than Et3SiH,
see: (a) Y. Wang, S. A. Babirad and Y. Kishi, J. Org. Chem., 1992, 57,
468–481; (b) S. A. Babirad, Y. Wang and Y. Kishi, J. Org. Chem., 1987,
52, 1372–1375; (c) A. Dondoni and M.-C. Scherrmann, Tetrahedron
Lett., 1993, 34, 7319–7322; (d) E. Alvarez, R. Perez, M. Rico, R. M.
Rodriguez and J. D. Martin, J. Org. Chem., 1996, 61, 3003–3016. For
examples of the reduction of cyclic ketals, see: K. C. Nicolaou, C.-K.
Hwang and D. A. Nugiel, J. Am. Chem. Soc., 1989, 111, 4136–4137.
30 Generality of the reduction with (TMS)3SiH and i-Pr3SiH is currently
underway.
12 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.
13 J. Krieg, W. Gla¨sner, A. Viventini, M.-A. Douncy, A. Lffler, D. Hess
and J. Hofsteenge, J. Biol. Chem., 1997, 272, 26687–26692.
14 H. Fujise, H. Horiuchi, K. Adachi, H. Sano and K. Suzuki, patent,
WO99/0411; Chem. Abstr. 1999, 130.
15 Y. Ihara, S. Manabe, M. Kaneda, H. Kawano, T. Nakayama, I. Sekine,
T. Kondo and Y. Ito, Glycobiology, 2005, 15, 383–392.
16 (a) T. Nishikawa, M. Ishikawa and M. Isobe, Synlett, 1999, 123–125;
(b) T. Nishikawa, M. Ishikawa, K. Wada and M. Isobe, Synlett, 2001,
945–947; (c) T. Nishikawa, Y. Koide, S. Kajii, K. Wada, M. Ishikawa
and M. Isobe, Org. Biomol. Chem., 2005, 3, 687–700.
31 Similar cyclization was observed in the Sonogashira coupling (Pd and
CuI catalyst) in the synthesis of a-C-Man-Trp, its glucose and galactose
analogues, see ref. 16.
32 A. Yasuhara, Y. Kanamori, M. Kaneko, A. Numata, Y. Kondo and T.
Sakamoto, J. Chem. Soc., Perkin Trans. 1, 1999, 529–534.
33 L. Dong and M. J. Miller, J. Org. Chem., 2002, 67, 4759–4770.
17 For the synthesis of C-Man-Trp from the other groups, see: (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.
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The Royal Society of Chemistry 2006
Org. Biomol. Chem., 2006, 4, 1268–1277 | 1277
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