Facile synthesis of glycosylated Fmoc amino acid building blocks assisted by microwave irradiation

Article abstract of DOI:10.1016/j.carres.2010.07.040

The synthesis of glycosylated Fmoc amino acids by reaction of mono- and disaccharide peracetates with Fmoc amino acids having free carboxyl groups was rapidly promoted by Lewis acids (SnCl₄, BF₃·Et ₂O) under microwave irradiation. The products are useful building blocks for the synthesis of glycopeptides.

Full text of DOI:10.1016/j.carres.2010.07.040

Carbohydrate Research 345 (2010) 2277–2281
Contents lists available at ScienceDirect
Carbohydrate Research
journal homepage: www.elsevier.com/locate/carres
Note
Facile synthesis of glycosylated Fmoc amino acid building blocks assisted
by microwave irradiation
Nianhuan Yao a, Gabriel Fung a, Hamed Malekan b, Long Ye b, Mark J. Kurth b, Kit S. Lam a,
⇑
a Division of Hematology and Oncology, Department of Internal Medicine, UC-Davis Cancer Center, School of Medicine, 4501 X Street, Sacramento, CA 95817, USA
b Department of Chemistry, One Shields Avenue, UC-Davis, CA 95616 , USA
a r t i c l e i n f o
a b s t r a c t
Article history:
The synthesis of glycosylated Fmoc amino acids by reaction of mono- and disaccharide peracetates with
Fmoc amino acids having free carboxyl groups was rapidly promoted by Lewis acids (SnCl4, BF3ÁEt2O)
under microwave irradiation. The products are useful building blocks for the synthesis of glycopeptides.
Ó 2010 Elsevier Ltd. All rights reserved.
Received 26 March 2010
Received in revised form 22 July 2010
Accepted 27 July 2010
Available online 1 August 2010
Keywords:
Fmoc amino acids
Glycosylation
Microwave irradiation
Carbohydrates are important components of glycoproteins,
playing pivotal roles in many biological processes, such as cell
adhesion, inflammation, the immune response, and tumor metas-
tasis.1 It is therefore of great interest to synthesize glycopeptides.
Currently, there are two approaches to synthesize glycopeptides
including the convergent approach2 and the building block ap-
proach.3 The former is based on glycosylation of a peptide in solu-
tion or on solid-phase. This direct O-glycosylation of a peptide
often results in low yields.4 Alternatively, the versatile and general
building block approach has a lot of advantages. A glycosylated
amino acid building block is easily introduced into a solid-phase
peptide synthesis using peptide chemistry. This method has been
widely applied to prepare a large variety of complex glycopeptides
and even larger glycopeptide libraries.5
sis of glycosylated Fmoc amino acids from Fmoc amino acids with
unprotected carboxyl groups and mono- and disaccharide perace-
tates should be efficiently carried out under microwave irradiation.
It has been reported that Fmoc amino acids are glycosylated
with peracetylated glycosides under the influence of Lewis acids
such as FeCl3, SnCl4 or BF3ÁEt2O as promoters and CH2Cl2, CH3CN
and toluene as solvents.7,9 A microwave reactor (Personal Chemis-
try, Emrys Optimizer) is compatible with various solvents and
reaction temperatures. Initially, glycosylated Fmoc-Ser-OH with
b-
Lewis acid and solvent could afford higher yield (Table 1) using
microwave reactor. Fmoc-Ser-OH (0.01 mmol) and b- -galactose
D-galactose pentaacetate was investigated to determine which
D
pentaacetate (0.01 mmol) were added to a 5-mL microwave vial,
followed by addition of 2 mL of solvent and Lewis acid
(0.01 mmol). The mixture was irradiated in the microwave oven
for 5 min. The product 1 was purified by preparative HPLC and con-
firmed to be of the b-configuration by 1H NMR spectroscopy. The
reaction conversion was directly determined by HPLC. FeCl3 pro-
vided lower conversion, suggesting that the heterogeneous system
(FeCl3/CH2ClCH2Cl or C6H6) may limit the reaction rates. The use of
CH2Cl2 as solvent resulted in a higher conversion than that of reac-
tions performed in CH2ClCH2Cl, C6H6 or CH3CN.
In order to further improve yields, a number of conditions
including reaction time and promoter (Table 2) were conducted
in CH2Cl2. An increase in the amount of SnCl4 from 1 equiv to
2 equiv resulted in higher glycosylation. A further increase in the
amount of SnCl4, however, did not increase the yield of glycosyl-
ated Fmoc amino acid. Interestingly, variations in the amount of
BF3ÁEt2O did not lead to any change in yield, and prolonged micro-
wave irradiation was discovered to give side products. Further-
Several methods exist for the preparation of glycosylated Fmoc
amino acid building blocks.6 However, the previous approaches to
glycosylated amino acids require the synthetic glycosyl donors and
amino acids to be protected at both the
a-carboxyl and a-amino
groups. Kihlberg and co-workers reported that Fmoc amino acids
with unprotected carboxyl groups could be directly glycosylated
with commercial carbohydrate 1,2-trans peracetates.7 However,
these methods suffered from low yields or long reaction times.
Microwave irradiation has been demonstrated to dramatically
accelerate the conversion in synthetic chemistry.8 Seibel et al. re-
ported on the glycosylation of Fmoc-Ser-OBn in a microwave
oven.9 These building blocks cannot be directly used for the so-
lid-phase synthesis of glycopeptides. Therefore, the direct synthe-
⇑
Corresponding author. Tel.: +1 916 734 8012; fax: +1 916 734 7946.
E-mail address: kit.lam@ucdmc.ucdavis.edu (K.S. Lam).
0008-6215/$ - see front matter Ó 2010 Elsevier Ltd. All rights reserved.
doi:10.1016/j.carres.2010.07.040

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N. Yao et al. / Carbohydrate Research 345 (2010) 2277–2281
Table 1
Microwave-assisted glycosylation of Fmoc-Ser-OH under different reaction conditions
OH
OH
OAc
AcO
O
FmocHN
OAc
O
AcO
O
OAc
O
OAc
AcO
OH
FmocHN
OAc
Microwave
AcO
O
1
Entry
Promoter (1 equiv)
Solvent (2 mL)
Temperature (°C)
Conversion (%)
1
2
3
4
5
6
7
8
FeCl3
SnCl4
FeCl3
SnCl4
FeCl3
SnCl4
FeCl3
SnCl4
CH2ClCH2Cl
CH2ClCH2Cl
CH3CN
CH3CN
C6H6
C6H6
CH2Cl2
CH2Cl2
150
150
150
150
150
150
100
100
19
41
7
24
0
40
35
44
NMR spectra were recorded on a Bruker DRX spectrometer in DMSO-
d6 at 25 °C (500 MHz for 1H NMR). HRMS was performed with a Finn-
igan LTQ FT™ instrument. Analytical HPLC was performed on a
Waters 2996 HPLC system equipped with a 4.6 Â 150 mm Waters
Table 2
Microwave-assisted glycosylation of Fmoc-Ser-OH under different reaction conditions
Entry
Promoter
Time (min)
Conversion (%)
1
2
3
4
5
6
7
8
9
SnCl4 (2 equiv)
SnCl4 (3 equiv)
SnCl4 (4 equiv)
SnCl4 (5 equiv)
BF3ÁEt2O (1 equiv)
BF3ÁEt2O (2 equiv)
BF3ÁEt2O (4 equiv)
BF3ÁEt2O (6 equiv)
SnCl4 (2 equiv)
5
5
5
5
5
5
5
5
15
30
15
30
73
68
64
63
72
72
73
71
64
60
55
36
XterraÒ MS C18 5.0-
lm column, and employed a 20-min gradient
from 100% aqueous H2O (0.1% TFA) to 100% CH3CN (0.1% TFA) at a
flow rate of 1.0 mL/min. Preparative HPLC was performed on a Sys-
tem Gold 126NMP Solvent Module (Beckman) with a C18 column
(Vydac, 5
l
M, 2.5 cm i.d. Â 25 cm). A gradient elution of 0–60% B
over 25 min, followed by 60–100% B over 25 min, followed by
100% B for 5 min, was used at a flow rate of 7 mL/min (solvent A:
H2O–0.1% TFA; B: Acetonitrile–0.1% TFA).
10
11
12
SnCl4 (2 equiv)
BF3ÁEt2O (6 equiv)
BF3ÁEt2O (6 equiv)
1.2. General procedure for glycosylation of Fmoc amino acids
more, a wider range of amino acids and mono- and oligosaccha-
rides were explored to synthesize various glycosylated Fmoc ami-
no acid building blocks under microwave irradiation for 5 min
using SnCl4 or BF3ÁEt2O (2 equiv) as promoters and CH2Cl2 as sol-
vent. Their conversions are presented in Table 3. Glycosylation of
Fmoc-Ser-OH with different peracetylated glycosylation donors
such as galactose, glucose, xylose, lactose and maltose gave higher
yields (52–72%). In comparison, lower yields (31–47%) were ob-
tained in the glycosylation of Fmoc-Tyr-OH under identical condi-
tions. It was noteworthy that disaccharide peracetates of lactose
and maltose as glycosyl donors were found to give lower yields
than monosaccharide peracetates of galactose, glucose, and xylose.
In conclusion, we have developed a microwave-assisted glyco-
sylation of Fmoc amino acids with unprotected carboxyl groups,
which can be used to efficiently synthesize glycosylated Fmoc ami-
no acid building blocks. To our knowledge, this is the first report of
glycosylation of Fmoc amino acids without prior protection of the
amino acid carboxyl groups under microwave conditions. The reac-
tions were readily carried out under microwave irradiation for only
5 min, resulting in b-glycosides in moderate yields. The products
could be easily purified via flash chromatography. Furthermore,
Fmoc amino acids and carbohydrate peracetates are commercially
available. This method provides an easy access to numerous valu-
able building blocks, which can be directly used for constructing
parallel and combinatorial glycopeptide libraries as well as the
synthesis of various glycopeptides.
Fmoc amino acids (0.2 mmol) and mono- and disaccharideperac-
etates (0.26 mmol) were added to a 5-mL round-bottomed micro-
wave vial, followed by addition of 3 mL of CH2Cl2 and SnCl4, or
BF3ÁEt2O (0.4 mmol). The vessel was sealed and heated to 100 °C
for 5 min in a microwave reactor (Personal Chemistry, Emrys Opti-
mizer). The reaction temperature increased from 25 to 100 °C in
90 s and was maintained at 100 °C for the duration of the reaction.
The reaction conversion was determined by analytical HPLC. The
mixture was concentrated and purified by preparative HPLC. All of
the products were characterized by ESIMS and 1H NMR
spectroscopy.
a
1.3. N -(9-Fluorenylmethoxycarbonyl)-3-O-(2,3,4,6-tetra-O-
acetyl-b-D-galactopyranosyl)-L-serine (1)
White powder, purity, 97%; 1H NMR (500 MHz, DMSO-d6): d
7.90 (d, J 5 Hz, 2H), 7.72 (d, J 10 Hz, 2H), 7.43 (m, 2H), 7.33 (m,
2H), 5.25 (d, J 2.5 Hz, 1H), 5.15 (dd, J 9 Hz, 3.0 Hz, 1H), 4.91 (dd, J
9 Hz, 6.5 Hz, 1H), 4.76 (d, J 6.5 Hz, 1H), 4.28–4.34 (m, 2H), 4.19–
4.24 (m, 3H), 4.04 (m, 1H), 3.90 (m, 1H), 3.79 (m, 1H), 2.11 (s,
3H), 2.00 (s, 3H), 1.93 (s, 3H), 1.91 (s, 3H). HRESIFTMS [M+K]+:
calcd for C32H35KNO14 696.1695; found: 696.1697.
a
1.4. N -(9-Fluorenylmethoxycarbonyl)-3-O-(2,3,4,6-tetra-O-
acetyl-b-D-glucopyranosyl)-L-serine (2)
1. Experimental
White powder, purity, 99%; 1H NMR (500 MHz, DMSO-d6): d 7.90
(d, J 5 Hz, 2H), 7.72 (d, J 5 Hz, 2H), 7.43 (m, 2H), 7.33 (m, 2H), 5.25 (t, J
10 Hz, 1H), 4.90 (dd, 1H), 4.87 (d, J 10 Hz, 1H), 4.73 (t, J 5 Hz, 1H),
4.16–4.33 (overlap, 5H), 3.99 (m, 1H), 3.90 (m, 1H), 3.77 (dd, 1H),
2.01 (s, 3H), 1.98 (s, 3H), 1.93 (s, 3H), 1.90 (s, 3H). HRESIFTMS
[M+K]+: calcd for C32H35KNO14 696.1695; found: 696.1696.
1.1. General methods
All solvents and chemical reagents were purchased from Sigma–
Aldrich Chemical Co. (Milwaukee, WI) and were of analytical grade.

N. Yao et al. / Carbohydrate Research 345 (2010) 2277–2281
2279
Table 3
Glycosylation of Fmoc amino acids
Entry
Fmoc amino acid
Donor
Product
Conversion (%)
SnCl4
BF3ÁEt2O
OAc
Fmoc-Ser-OH
AcO
AcO
O
O
OAc
1
2
3
b-
b-
D
-Galactose pentaacetate
-Glucose-pentaacetate
73
64
62
72
61
64
OH
OH
FmocHN
O
OH
FmocHN
OAc
O
O
O
AcO
AcO
OAc
D
OH
FmocHN
O
O
O
AcO
AcO
OAc
D-Xylose tetraacetate
OH
FmocHN
O
OAc
OAc
O
AcO
O
O
O
OAc
4
5
b-
b-
D
-Lactose octaacetate
-Maltose octaacetate
49
52
57
52
AcO
O
OAc
OH
AcO
FmocHN
O
OAc
OAc
O
O
O
OAc
AcO
D
AcO
OAc
OH
AcO
FmocHN
O
OAc
Fmoc-Thr-OH
AcO
AcO
O
O
OH
OH
OAc
6
b-
b-
D
-Galactose pentaacetate
-Glucose-pentaacetate
54
58
OH
FmocHN
O
O
FmocHN
OAc
O
O
AcO
AcO
OAc
7
8
9
D
54
45
45
49
62
43
OH
OH
FmocHN
O
O
O
OAc
AcO
AcO
D
-Xylose tetraacetate
FmocHN
O
OAc
OAc
O
O
OAc
AcO
O
O
AcO
b-
b-
D
-Lactose octaacetate
-Maltose octaacetate
OAc
OH
AcO
FmocHN
O
OAc
OAc
O
O
O
O
OAc
AcO
10
11
D
45
34
43
38
AcO
OAc
OH
AcO
FmocHN
O
OAc
Fmoc-Tyr-OH
AcO
AcO
O
O
OH
OAc
b-D-Galactose pentaacetate
OH
OH
FmocHN
O
FmocHN
O
O
OAc
O
AcO
AcO
OAc
12
b-
D-Glucose-pentaacetate
33
47
OH
FmocHN
O
(continued on next page)

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N. Yao et al. / Carbohydrate Research 345 (2010) 2277–2281
Table 3 (continued)
Entry
Fmoc amino acid
Donor
Product
Conversion (%)
SnCl4
BF3ÁEt2O
O
O
AcO
OAc
AcO
13
35
40
D-Xylose tetraacetate
OH
FmocHN
O
OAc
OAc
O
AcO
O
O
O
AcO
OAc
OAc
AcO
14
15
b-
b-
D
-Lactose octaacetate
24
28
35
31
OH
FmocHN
O
OAc
OAc
O
O
O
O
AcO
AcO
AcO
OAc
OAc
D-Maltose octaacetate
OH
FmocHN
O
a
1.5. N -(9-Fluorenylmethoxycarbonyl)-3-O-(2,3,4-tri-O-acetyl-
b- -xylopyranosyl)- -serine (3)
1.99 (s, 3H), 1.92 (s, 3H), 1.13 (d, J 5 Hz, 3H). HRESIFTMS [M+K]+:
calcd for C33H37KNO14, 710.1851, found: 710.1854.
D
L
a
White powder, purity, 96%; 1H NMR (500 MHz, DMSO-d6): d
1.9. N -(9-Fluorenylmethoxycarbonyl)-3-O-(2,3,4,6-tetra-O-
7.90 (d, J 10 Hz, 2H), 7.73 (d, J 10 Hz, 2H), 7.43 (m, 2H), 7.33 (m,
2H), 5.12 (t, J 5 Hz, 1H), 4.80 (d, J 5 Hz, 1H), 4.73 (m, 2H), 4.25–
4.33 (m, 2H), 4.20–4.23 (m, 2H), 3.88 (m, 1H), 3.74 (m, 1H), 2.00
(s, 3H), 1.96 (s, 3H), 1.93 (s, 3H). HRESIFTMS [M+K]+: calcd for
acetyl-b-D-glucopyranosyl)-L-threonine (7)
White powder, purity, 97%; 1H NMR(500 MHz, DMSO-d6): d7.90
(d, J 10 Hz, 2H), 7.74 (d, J 5 Hz, 2H), 7.42 (t, J 5 Hz, 2H), 7.32 (t, J
5 Hz, 2H), 6.75 (d, J 5 Hz, 1H), 5.26 (t, J 10 Hz, 1H), 4.90 (dd, 1H),
4.88 (d, J 10 Hz, 1H), 4.70 (t, J 5 Hz, 1H), 4.27–4.31 (m, 2H), 4.17–
4.24 (m, 3H), 4.11 (dd, 1H), 3.97 (m, 1H), 1.98 (s, 6H), 1.97 (s,
3H), 1.94 (s, 3H), 1.13 (d, J 5 Hz, 3H). HRESIFTMS [M+K]+: calcd
for C33H37KNO14, 710.1851, found: 710.1854.
C29H31KNO12, 624.1483, found: 624.1486.
a
1.6. N -(9-Fluorenylmethoxycarbonyl)-3-O-[(2,3,6-tri-O-acetyl-
4-O-(2,3,4,6-tetra-O-acetyl-b-D-galactopyranosyl)-b-D-
glucopyranosyl]- -serine (4)
L
a
White powder, purity, 98%; 1H NMR (500 MHz, DMSO-d6): d 7.90
(d, J 10 Hz, 2H), 7.71 (d, J 10 Hz, 2H), 7.43 (m, 2H), 7.33 (m, 2H), 5.22
(br s, 1H), 5.15 (m, 2H), 4.84 (dd, 1H), 4.80 (d, J 5.0 Hz, 1H), 4.73 (d, J
10 Hz, 1H), 4.65 (dd, 1H), 4.29 (m, 3H), 4.21 (m, 3H), 4.05 (m, 1H),
4.00 (m, 2H), 3.81–3.88 (m, 2H), 3.75–3.79 (m, 2H), 2.11 (s, 3H),
2.07 (s, 3H), 2.00 (s, 6H), 1.93 (s, 3H), 1.89 (s, 6H). HRESIFTMS
[M+K]+: calcd for C44H51KNO22, 984.2540, found: 984.2542.
1.10. N -(9-Fluorenylmethoxycarbonyl)-3-O-(2,3,4-tri-O-acetyl-
b-D
-xylopyranosyl)-
L-threonine (8)
White powder, purity, 98%; 1H NMR (500 MHz, DMSO-d6): d
7.90 (d, J 10 Hz, 2H), 7.73 (d, J 5 Hz, 2H), 7.42 (t, J 5 Hz, 2H), 7.32
(t, J 5 Hz, 2H), 6.75 (d, J 5 Hz, 1H), 5.10 (t, J 5 Hz, 1H), 4.76 (d, J
5 Hz, 1H) 4.75 (m, 1H), 4.69 (t, J 5 Hz, 1H), 4.23–4.31 (m, 4H),
4.12 (dd, J 5 Hz, 5 Hz, 1H), 4.93 (dd, J 5 Hz, 5 Hz, 1H), 2.01 (s,
3H), 2.00 (s, 6H), 1.12 (d, J 5 Hz, 3H). HRESIFTMS [M+K]+: calcd
for C30H33KNO12, 638.1640, found: 638.1642.
a
1.7. N -(9-Fluorenylmethoxycarbonyl)-3-O-[(2,3,6-tri-O-acetyl-
4-O-(2,3,4,6-tetra-O-acetyl-b-D-glucopyranosyl)-b-D-
glucopyranosyl]- -serine (5)
L
a
1.11. N -(9-Fluorenylmethoxycarbonyl)-3-O-[(2,3,6-tri-O-
White powder, purity, 97%; 1H NMR (500 MHz, DMSO-d6): d 7.90
(d, J 10 Hz, 2H), 7.71 (d, J 10 Hz, 2H), 7.43 (m, 2H), 7.33 (m, 2H), 5.29
(m, 1H), 5.27 (br s, 1H), 5.22 (t, J 10 Hz, 1H), 4.98 (dd, 1H), 4.87 (dd,
1H), 4.84 (d, J 10 Hz, 1H), 4.63 (t, J 5 Hz, 1H), 4.14–4.36 (m, 4H), 3.86–
4.01 (m, 4H), 3.76 (dd, 1H), 3.40–3.70 (overlap), 2.06 (s, 3H), 2.01 (s,
3H), 1.98 (s, 6H), 1.95 (s, 3H), 1.91 (s, 3H), 1.88 (s, 3H). HRESIFTMS
[M+K]+: calcd for C44H51KNO22, 984.2540, found: 984.2542.
acetyl-4-O-(2,3,4,6-tetra-O-acetyl-b-
glucopyranosyl]- -threonine (9)
D-galactopyranosyl)-b-D-
L
White powder, purity, 96%; 1H NMR (500 MHz, DMSO-d6): d
7.90 (d, J 10 Hz, 2H), 7.72 (d, J 10 Hz, 2H), 7.42 (t, J 10 Hz, 5 Hz,
2H), 7.33 (t, J 5 Hz, 2H), 6.69 (d, J 10 Hz, 1H), 5.22 (br s, 1H),
5.12–5.17 (m, 2H), 4.82–4.85 (m, 2H), 4.73 (d, J 5 Hz, 1H), 4.63 (t,
J 10 Hz, 1H), 4.22–4.29 (m, 6H), 4.11 (dd, 1H), 4.00–4.05 (m, 3H),
3.75–3.79 (m, 2H), 2.10 (s, 3H), 2.05 (s, 3H), 2.00 (s, 6H), 1.97 (s,
3H), 1.95 (s, 3H), 1.89 (s, 3H), 1.12 (d, J 5 Hz, 3H). HRESIFTMS
[M+H]+: calcd for C45H54NO22, 960.3137, found: 960.3140.
a
1.8. N -(9-Fluorenylmethoxycarbonyl)-3-O-(2,3,4,6-tetra-O-
acetyl-b-D-galactopyranosyl)-L-threonine (6)
White powder, purity, 99%; 1H NMR (500 MHz, DMSO-d6): d
7.90 (d, J 10 Hz, 2H), 7.73 (d, J 10 Hz, 2H), 7.42 (t, J 10 Hz, 2H),
7.33 (t, J 10 Hz, 2H), 6.60 (d, J 5 Hz, 1H), 5.25 (d, J 5.0 Hz, 1H),
5.17 (dd, J 10 Hz, 5.0 Hz, 1H), 4.87 (dd, 1H), 4.79 (d, J 10 Hz, 1H),
4.30 (m, 1H), 4.29 (m, 1H), 4.22 (m, 2H), 4.17 (t, J 10 Hz, 1H),
4.10 (dd, J 10 Hz, 5.0 Hz, 1H), 4.02 (t, J 5 Hz, 2H), 2.09 (s, 3H),
a
1.12. N -(9-Fluorenylmethoxycarbonyl)-3-O-[(2,3,6-tri-O-
acetyl-4-O-(2,3,4,6-tetra-O-acetyl-b-
glucopyranosyl]- -threonine (10)
D-glucopyranosyl)-b-D-
L
White powder, purity, 98%; 1H NMR (500 MHz, DMSO-d6): d
7.89 (d, J 10 Hz, 2H), 7.73 (d, J 10 Hz, 5 Hz, 2H), 7.42 (t, J 10 Hz,

N. Yao et al. / Carbohydrate Research 345 (2010) 2277–2281
2281
2H), 7.32 (t, J 5 Hz, 2H), 6.78 (d, J 5 Hz, 1H), 5.29 (dd, 1H), 5.27 (br s,
1H), 4.98 (t, J 10 Hz, 1H), 4.88 (dd, 1H), 4.87 (d, J 10 Hz, 1H), 4.61 (t,
J 10 Hz, 1H), 4.10–4.31 (m, 7H), 3.98–4.09 (m, 5H), 2.05 (s, 3H),
2.00 (s, 3H), 1.99 (s, 3H), 1.98 (s, 3H), 1.95 (s, 3H), 1.94 (s, 6H),
9H), 3.03 (dd, 1H), 2.82 (dd, 1H), 2.10 (s, 3H), 2.03 (s, 3H), 2.02
(s, 6H), 1.99 (s, 3H), 1.96 (s, 3H), 1.89 (s, 3H). HRESIFTMS [M+K]+:
calcd for C50H55KNO22, 1060.2853, found: 1060.2855.
a
1.13 (d, J 10 Hz, 3H). HRESIFTMS [M+H]+: calcd for C45H54NO22
,
1.17. N -(9-Fluorenylmethoxycarbonyl)-O-[(2,3,6-tri-O-acetyl-
960.3137, found: 960.3140.
4-O-(2,3,4,6-tetra-O-acetyl-b-D-gulcopyranosyl)-b-D-
gulcopyranosyl]- -tyrosine (15)
L
a
1.13. N -(9-Fluorenylmethoxycarbonyl)-O-(2,3,4,6-tetra-O-
acetyl-b-
D
-galactopyranosyl)-
L
-tyrosine (11)
White powder, purity, 98%; 1H NMR(500 MHz, DMSO-d6): d7.88
(d, J 5 Hz, 2H), 7.63 (d, J 5 Hz, 2H), 7.41 (m, 2H), 7.31 (m, 2H), 7.23
(d, J 10 Hz, 2H), 7.04 (d, J 5 Hz, 1H), 6.87 (d, J 10 Hz, 1H), 5.40 (dd,
1H), 5.39 (br s, 1H), 5.30 (d, J 5 Hz, 1H), 5.22–5.26 (m, 2H), 4.97 (t, J
10 Hz, 2H), 4.88–4.93 (m, 2H), 4.12–4.22 (m, 6H), 3.98–4.03 (m,
3H), 3.03 (m, 1H), 2.82 (m, 1H), 2.02 (s, 3H), 2.00 (s, 3H), 1.99 (s,
6H), 1.96 (s, 6H), 1.94 (s, 3H). HRESIFTMS [M+K]+: calcd for
White powder, purity, 99%; 1H NMR(500 MHz, DMSO-d6): d7.88
(d, J 10 Hz, 2H), 7.63 (dd, J 10 Hz, 5 Hz, 2H), 7.41 (m, 2H), 7.31 (m,
2H), 7.23 (d, J 10 Hz, 2H), 7.00 (d, J 10 Hz, 2H), 5.73 (d, J 5 Hz, 1H),
5.40 (dd, 1H), 5.39 (br s, 1H), 5.32 (dd, 1H), 5.15 (d, J 5 Hz, 1H), 5.13
(t, J 5 Hz, 1H), 4.28 (dd, 1H), 4.12–4.20 (m, 3H), 4.01 (dd, J 5 Hz,
5 Hz, 1H), 3.90 (dd, J 5 Hz, 5 Hz, 1H), 3.05 (dd, J 10 Hz, 5 Hz, 1H),
3.81 (dd, J 10 Hz, 5 Hz, 1H), 2.14 (s, 3H), 2.04 (s, 3H), 1.97 (s, 3H),
1.83 (s, 3H). HRESIFTMS [M+H]+: calcd for C38H40NO14, 734.2449,
found: 734.2451.
C50H55KNO22, 1060.2853, found: 1060.2855.
Acknowledgments
This work was supported by US Department of Defense Breast
Cancer Research Program’s Multidisciplinary Postdoctoral Training
Award contract no. W81XWH-06-1-0447 (N. Yao), NIH
R01CA115483, and U19CA113298. We thank Mr. David Olivos for
editorial assistance.
a
1.14. N -(9-Fluorenylmethoxycarbonyl)-O-(2,3,4,6-tetra-O-
acetyl-b-D-gulcopyranosyl)-L-tyrosine (12)
White powder, purity, 97%; 1H NMR(500 MHz, DMSO-d6): d7.88
(d, J 5 Hz, 2H), 7.64 (d, J 5 Hz, 2H), 7.40 (m, 2H), 7.30 (m, 2H), 7.22
(d, J 5 Hz, 2H), 6.90 (d, J 5 Hz, 2H), 5.73 (d, J 5 Hz, 1H), 5.45 (dd, 1H),
5.37 (t, J 5 Hz, 1H), 5.05 (dd, 1H), 5.03 (d, J 10 Hz, 1H), 4.97 (t, J 5 Hz,
1H), 4.10–4.19 (m, 5H), 4.01 (dd, 1H), 3.03 (dd, 1H), 2.83 (dd, 1H),
2.00 (s, 3H), 1.99 (s, 3H), 1.97 (s, 3H), 1.96 (s, 3H). HRESIFTMS
[M+H]+: calcd for C38H40NO14, 734.2449, found: 734.2451.
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White powder, purity, 98%; 1H NMR(500 MHz, DMSO-d6): d7.88
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a
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