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C.-O. Abrahamsson et al. / Carbohydrate Research 343 (2008) 1473–1477
chromatography.4 All treated cells secreted alkali sensi-
tive proteoglycans to the extracellular space, and modi-
fications of naphthalene ring with one or two amino acid
residues did not affect proteoglycan biosynthesis or
GAG priming ability. Only compound 11 initiated the
synthesis of free GAG chains (Table 1). As a compari-
son, the GAG-priming capability of compound 1, in
T24 cells, was 7.2.14
was stirred for 19 h at rt. The reaction was neutralized
with Amberlite IR-120 H+, filtered and evaporated
to dryness to give 3 as a white solid (112 mg, quant.).
HRESIMS calcd for C16H16O7Na [M+Na]+: 343.0794;
found 343.0811.
1.3. 6-(2-Carboxynaphthyl) b-D-xylopyranoside (8)
The structure of the aglycon has been shown to play
an important role for the priming ability, and for the
structure of the GAG chains synthesized by the xylopyr-
anosides.15,16 The compounds used in this study may be
internalized but not distributed to correct intracellular
compartments to take part in GAG biosynthesis or
may not be recognized by the GAG-priming enzymes.
The results are similar to earlier studies using fluorescent
analogs,17 and it may be assumed that these compounds
are unsuitable to function as GAG-primers. However,
we note that compound 11, which did initiate priming,
is the most nonpolar (as indicated by HPLC retention
times) of the investigated analogs and it is reasonable
to assume that the polarity is important for the cellular
transportation and targeting.
Compound 8 was synthesized according to the proce-
dure for 4 to give a white amorphous solid. HRESIMS
calcd for C16H16O7Na [M+Na]+: 343.0794; found
343.0806.
1.4. General procedure for the synthesis of compounds
4–6 and 9–11
Compounds 3 or 8 was dissolved in pyridine (15 mL).
Ac2O (0.71 mL, 7.5 mmol) was added, and the mixture
was stirred for 4 h at rt. The soln was concentrated and
the residue was dissolved in EtOAc and washed three
times with HCl (10% aq) and the organic layer was dried
with MgSO4 and concentrated. The intermediate
(10 mg, 0.022 mmol) and glycine tBu-ester hydrochlo-
ride (4.9 mg, 0.029 mmol) were dissolved in CH2Cl2
(1.5 mL). DMAP (4.1 mg, 0.034 mmol) was added
and the soln was stirred for 15 min. DIC (4.4 lL,
0.028 mmol) in CH2Cl2 (0.1 mL) was added and the
soln was stirred under N2 at rt for 3 h. The mixture
was concentrated and chromatographed (SiO2, 1:10 hep-
tane–EtOAc). The intermediate (11.2 mg, 0.020 mmol)
was dissolved in MeOH (2 mL). NaOH (0.40 mL,
1 M) was added and the mixture was stirred for 5 h.
The reaction was quenched with Amberlite IR-120 H+
and concentrated to give 4 as white amorphous solid.
1. Experimental
1.1. General methods
CH2Cl2 for reactions was dried by passing through a
column of Al2O3 (neutral, activity grade I). NMR-spec-
tra were collected at 400 MHz (1H) and 100 MHz (13C)
on a Bruker DRX 400 spectrometer. Chemical shifts are
reported in ppm with the residual solvent peaks (1H)
and solvent signals (13C) as reference. High-resolution
mass-spectra were collected using a Micromass Q-Tof
ESI or aFABMS JEOL SX-102. All the title compounds
were further purified using reverse phase preparative
HPLC using a Waters C18 symmetry column.
1.5. General procedure for solid-phase dipeptide synthesis
Dipeptides were synthesized using dry CH2Cl2 as a sol-
vent in a mechanically agitated reactor tube. Pre-loaded
Merrifield resins with Boc-protected glycine (0.5 mmol/
g, 0.020 mmol) and Boc-protected alanine (0.7 mmol/g,
0.021 mmol) were used. The resins were swelled for 10
min followed by Boc-deprotection. The deprotection
was performed twice using 4:1 TFA–CH2Cl2 (2 mL).
The resins were then washed with CH2Cl2. The second
Boc-protected amino acid was added alongside with
DMAP and CH2Cl2 and the tube was agitated for
15 min and DIC was added. The mixture was agitated
for 3 h after which the resins were washed with CH2Cl2
and MeOH. The Boc-group on the second amino acid
was removed as described earlier. The resins were
swelled for 10 min, followed by the addition of 4
(10.7 mg, 0.024 mmol), DMAP and CH2Cl2 and
agitated for 15 min. DIC was added and the tube was
agitated for 3 h. The resins were then washed as previ-
ously described. Swelling in CH2Cl2, followed by cleav-
1.2. 6-(1-Carboxynaphthyl) b-D-xylopyranoside (3)
Compound 29 (95 mg, 0.47 mmol) and 1,2,3,4-tetra-O-
acetyl-b-D-xylopyranose (299 mg, 0.94 mmol) were dis-
solved in CH2Cl2 (10 mL) under N2. Et3N (0.07 mL,
0.47 mmol) followed by BF3ÁOEt2 (0.295 mL, 2.34
mmol) were added. The soln was stirred at rt for 3 h
and quenched by the addition of Et3N, concentrated
and chromatographed (SiO2, 40:1 CH2Cl2–acetone).
The intermediate (178.7 mg, 0.39 mmol) was dissolved
in MeOH (10 mL). NaOMe (0.62 mL, 0.25 M) was
added to the soln and stirred for 45 min at rt. The reac-
tion was neutralized with solid CO2, concentrated and
chromatographed (SiO2, 1:1 CHCl3–MeOH). The inter-
mediate (117.2 mg, 0.35 mmol) was dissolved in MeOH
(15 mL). NaOH (7 mL, 1 M) was added and the soln