Synthesis of antioxidative and anti-inflammatory drugs glucoconjugates

Article abstract of DOI:10.1016/S0008-6215(99)00311-0

Glucoconjugates of (±)-ibuprofen, (±)-α-tocopherol (vitamin E), gentisic acid, gallic acid, 2,6-bis(tert-butyl)-4-thiophenol, and N-acetyl-L-cysteine were prepared with the objective of increasing the bioavailability of such antioxidant and anti-inflammatory drugs. The O-glucosides were synthesized using benzylated α-D-glucopyranosyl trichloracetimidate as glycosyl donor. For the synthesis of the S-glucosides, the glycosyl donor 1,2,3,4,6-penta-O-acetyl-β-D-glucopyranose provided higher yields than the corresponding O-acetylated imidate. Copyright (C) 2000 Elsevier Science Ltd.

Full text of DOI:10.1016/S0008-6215(99)00311-0

www.elsevier.nl/locate/carres
Carbohydrate Research 325 (2000) 72–80
Note
Synthesis of antioxidative and anti-inflammatory drugs
glucoconjugates
Rainer K. Uhrig a,b,*, Martin A. Picard a,b, Konrad Beyreuther a, Manfred Wiessler b
a Zentrum fu¨r Molekularbiologie Heidelberg (ZMBH), Im Neuenheimer Feld 282, D-69120 Heidelberg, Germany
b Molekulare Toxikologie (C0300), Deutsches Krebsforschungszentrum (DKFZ), Im Neuenheimer Feld 280,
D-69120 Heidelberg, Germany
Received 11 June 1999; revised 22 November 1999; accepted 23 November 1999
Abstract
Glucoconjugates of (9)-ibuprofen, (9)-a-tocopherol (vitamin E), gentisic acid, gallic acid, 2,6-bis(tert-butyl)-4-
thiophenol, and N-acetyl- -cysteine were prepared with the objective of increasing the bioavailability of such
antioxidant and anti-inflammatory drugs. The O-glucosides were synthesized using benzylated a- -glucopyranosyl
trichloracetimidate as glycosyl donor. For the synthesis of the S-glucosides, the glycosyl donor 1,2,3,4,6-penta-O-
-glucopyranose provided higher yields than the corresponding O-acetylated imidate. © 2000 Elsevier
L
D
acetyl-b-
D
Science Ltd. All rights reserved.
Keywords: Glycosylation; Antioxidants; Anti-inflammatory drugs; Glucose transporter; Blood–brain barrier; Cancer; Alzheimer’s
disease
Whole-body autoradiography studies in rats
1. Introduction
with Glufosfamid, the b- -glucoside of the
D
chemotherapeutic agent Ifosfamide mustard
(IPM), provides evidence for a selective en-
richment of the glucoside in the brain. This
enrichment was not observed in the case of the
In recent years, evidence has accumulated
suggesting that oxidative stress and inflamma-
tion are a common feature of several chronic
and degenerative diseases [1]. Brain disorders,
such as Alzheimer’s disease, Parkinson’s dis-
ease and stroke, might be involved due to the
brain’s high vulnerability to oxidative stress
[2]. For cancer, epidemiological studies have
shown that nutrients containing vitamins and
other natural antioxidants (e.g., vitamin E,
gallic acid derivatives) might lower the risk [3].
Non-steroidal anti-inflammatory drugs have
been reported to be beneficial for arthritis [4].
b- -glucoside of IPM, which indicates that
L
specialized glucose transporters may be re-
sponsible for this effect [5,6]. Moreover, up-
take measurements of the glucosides of IPM
using oocytes of Xenopus lae6is as an in vitro
expression system for mammalian glucose
transporters show that this selective uptake of
the b- -glucoside is a characteristic feature of
D
a sodium-coupled glucose transporter called
SGLT-3 (=SAAT-1) [7]. The concept that
glucoconjugates are transported by cellular
glucose transporters has also been reported
for other glucoconjugates [8–11]. The expres-
* Corresponding author.
E-mail address: r.uhrig@dkfz-heidelberg.de (R.K. Uhrig)
0008-6215/00/$ - see front matter © 2000 Elsevier Science Ltd. All rights reserved.
PII: S0008-6215(99)00311-0

R.K. Uhrig et al. / Carbohydrate Research 325 (2000) 72–80
73
sion of the high-affinity Na+-
-glucose trans-
D
porter SGLT-1 in human brain was demon-
strated by Poppe et al. [12]. We present here
novel synthetic routes to the glucosides of
the antioxidants or anti-inflammatory drugs
gallic acid, 2,6-bis(tert-butyl)-4-thiophenol, N-
acetyl- -cysteine ethyl ester, (9)-ibuprofen
L
and an improved synthesis for glucosides of
(9)-a-tocopherol and gentisic acid, which
may help to overcome the problem of re-
stricted bioavailability of such drugs.
The synthesis of glucosides of a-tocopherol
(2b) has been described by three other groups
using various acetylated sugar analogues as
glycosyl donors [15–17]. Up to now, only the
2. Results and discussion
use of 1,2,3,4,6-penta-O-acetyl-b- -glucopyr-
D
anose (5) as glycosyl donor, as reported by
Lahmann and Thiem [17], gave good yields.
These authors obtained a 67% yield by using a
six-fold excess of a-tocopherol. With equimo-
lar amounts of the reagents, the yield was
diminished to about 40%. Deprotection of the
acetylated glucoside was nearly quantitative
[17].
Performing the glycosylation reaction of 2b
(1 equivalent) with 1 (1.2 equivalents), we
achieved only moderate yields of the benzy-
lated glucoside of 2b (30–40%). Due to the
very similar physical properties of this deriva-
tive and the aglycone itself, the glucoside
could only be purified by crystallization from
ethanol, thereby resulting in substantial loss.
Deprotection by hydrogenolysis with palla-
dium on charcoal gave yields between 70 and
80%. The severe loss of the protected glu-
coside during the purification procedure could
be avoided by direct hydrogenation of the
mixture resulting from the glycosylation step,
The synthesis of the O-glucosides was per-
formed in dry dichloromethane and under an
atmosphere of nitrogen using the benzylated
trichloroacetimidate (1) as glycosyl donor [13].
For the O-acyl glucoside, the reaction was
performed at room temperature without any
catalyst [14]. The synthesis of the O-aryl glu-
cosides was performed using boron trifluoride
diethyl etherate as catalyst at −40 °C. Depro-
tection of the sugar moiety was achieved by
hydrogenation with palladium on charcoal.
Coupling of aglycones containing more than
one potential glycosylation site required addi-
tional protection and deprotection steps,
which are described in the respective sections.
The 1-O-acyl glucoside 4a of (9)-ibupro-
fen (2a) was prepared by the autocatalytic
reaction of 2a with 1 yielding 67% of the
protected glucoside. Deprotection was per-
formed by hydrogenation with palladium on
charcoal in dichloromethane–acetone yielding
4a (76%), which, however, showed a poor
stability and decomposed slowly even at
−20 °C.

74
R.K. Uhrig et al. / Carbohydrate Research 325 (2000) 72–80
methylene protective group was not cleaved
by the usual catalyst (10% Pd–C). The cleav-
age required a more reactive catalyst such as
20% palladium on charcoal. Since we found
no method of cleaving the ethyl ester after
deprotection of the glucoside, we changed the
order of reaction steps by cleaving the ethyl
ester before hydrogenation. The ester cleavage
was performed by using potassium hydroxide
in 1,2-dimethoxyethane (89%), followed by
hydrogenolysis with 20% palladium on char-
coal in acetone containing 10% water (94%).
followed by column chromatography. Thus,
the overall yield in 4b could be increased to
67%, a result similar to the synthesis of Lah-
mann and Thiem [17]. The advantage of our
approach is that only equimolar amounts of
the reactants are needed.
The only described synthesis of the b- -glu-
D
coside of gentisic acid (4c) used a Ko¨nigs–
Knorr reaction of 2c with 2,3,4,6-tetra-O-
acetyl-a- -glucopyranosyl bromide (15%)
D
[18,19]. The glycosylation of 2c with 1 yielded
91% of the glucoside. Deacetylation with bar-
ium hydroxide in methanol, followed by ester
saponification with a mixture of potassium
and barium hydroxide in methanol, gave a
partly deprotected glucoside (55%). Hy-
drogenolysis with palladium on charcoal in
dichloromethane led to the fully deprotected
glucoside 4c (80%).
For the synthesis of thioglucosides 8e,f
1,2,3,4,6-penta-O-acetyl-b- -glucopyranose
D
(5) was used as glycosyl donor. The reaction
was performed in dry dichloromethane at
room temperature using boron trifluoride di-
ethyl etherate as catalyst and a five-fold excess
of 5. Deprotection could be performed under
mild alkaline conditions.
Until now only O-acyl glucosides of gallic
acid (‘a- and b-glucogallin’) were obtained by
chemical synthesis [20–22]. The only routes to
O-aryl glucosides of gallic acid are enzymatic
synthesis or by direct isolation from plants
[23–28]. Gallic acid possesses four reactive
groups, three of which have to be protected to
achieve a regioselective glycosylation. Gallic
acid ethyl ester is commercially available and
protection of the C-3,4 hydroxyl groups could
be performed by reaction with dichloro-
diphenylmethane in pyridine, yielding 2d
(61%). The major advantage of this protective
group is that it can be removed by hydrogena-
tion [29].
The glycosylation was performed with 1 as
described above, yielding 60% of 3d. However,
the subsequent hydrogenation was more
difficult than expected and the diphenyl-
For the synthesis of the b- -glucoside of
D
2,6-bis(tert-butyl)-4-thiophenol (8e), direct
glycosylation of the highly sensitive 2,6-bis-
(tert-butyl)-4-thiophenol gave only poor yields

R.K. Uhrig et al. / Carbohydrate Research 325 (2000) 72–80
75
deprotected glucoside 8f, with however partial
of 8e (ꢀ10–20%) using 5 as glycosyl donor.
However, this yield could be increased by up
to 74% by in situ generation of the highly
reactive educt using its acetonide, the syn-
thetic antioxidant probucol (4,4%-isopropyli-
denedithio)bis[2,6-di-tert-butylphenol] (6e) as
precursor. Deprotection under mild alkaline
conditions (4:2:1 MeOHꢀwaterꢀEt3N) yielded
74% of the unprotected glucoside 8e.
racemization at the cysteine moiety.
3. Experimental
General methods1.—Thin-layer chromatog-
raphy (TLC) was performed on precoated
plates of silica gel (Polygram Sil G/UV254,
Machery & Nagel), detection by UV absorp-
tion and/or spraying with 0.1% vanillin in 50%
H2SO4 followed by heating at 160 °C. Column
chromatography was performed on silica gel
(Kieselgel 60, 63–200 mesh, Machery &
Nagel). Ratios of solvent mixtures for chro-
matography are specified in terms of volume.
NMR spectra were recorded at 250 MHz (1H)
or 63 MHz (13C) on a Bruker AM 250 with
Me4Si (l 0) as internal standard by ‘Zentrale
Spektroskopie, DKFZ’, Heidelberg. Mass
spectrometry was performed on a Finnigan
MAT TSQ 7000 by ‘Zentrale Spektroskopie,
DKFZ’, Heidelberg. Elemental analysis were
performed with a Carlo Erba Elemental Ana-
lyzer CHNS EA 1108 by ‘Mikroanalytische
Abteilung, Max-Planck-Institut fu¨r Medizini-
sche Forschung’, Heidelberg.
For the synthesis of cysteine glucosides two
methods have been described so far. Mon-
signy et al. [30] used a 3-iodo- -serine deriva-
L
tive as glycosyl acceptor in a reaction with an
acetylated glycosyl isothiouronium salt. Al-
though they achieved a very good yield (72%)
for the thioglycosylation step, a great deal of
synthetic work was required for the prepara-
tion of the adducts. Interestingly, Baran and
Drabarek [31] successfully synthesized a cys-
teine glucoside via a Ko¨nigs–Knorr reaction
using silver salts as catalyst and 2,3,4,6-tetra-
O-acetyl-a- -glucopyranosyl bromide as gly-
D
cosyl donor in a 50% yield.
General procedure for the synthesis of O-acyl
glucosides (GP 1).—A solution of the acyl
compound and the benzylated a- -glucopyra-
D
nosyl trichloracetimidate (1) was reacted at
room temperature (rt) until no further reac-
tion was detectable (TLC). The mixture was
washed with 0.05 M NaOH and brine. After
drying over Na2SO4, the solvents were re-
moved under reduced pressure. The products
were purified by column chromatography or
crystallization.
For the regioselective glycosylation of N-
acetyl- -cysteine, the carboxy group was pro-
L
tected as its ethyl ester (46%). The
glycosylation step with 5 yielded 45% of the
acetylated glucoside. Deprotection with 10%
triethylamine in methanol gave 60% of the
General procedure for the synthesis of O-aryl
glucosides (GP 2).—A solution of BF3·Et2O in
dry CH2Cl2 was slowly added to a solution of
the aromatic compound and benzylated a-
D-glucopyranosyl trichloracetimidate (1) at
−40 °C under nitrogen atmosphere. The mix-
ture was stirred until no further reaction was
detectable (TLC). The excess of BF3·Et2O
was decomposed with NaHCO3. After dilu-
tion with CH2Cl2, the mixture was washed
1 Note of the Editor: The normally required polarimetric
data for chiral compounds were not available for this
manuscript.

76
R.K. Uhrig et al. / Carbohydrate Research 325 (2000) 72–80
C-5%, 4 CH2C6H5), 94.73, 94.42 (C-1), 84.74,
84.59 (C-2), 80.92, 80.76 (C-3), 77.29, 77.16
(C-4), 75.79, 75.48 (C-5), 75.60, 75.55, 74.92,
74.75, 74.35, 73.49 (4 CH2C6H5), 68.10 (C-6),
45.20 (ROOC–CHCH3–R%), 44.98, 44.93
(CH2CH(CH3)2), 30.06, 29.98 (CH2CH-
(CH3)2), 22.34, 22.28 (CH2CH(CH3)2)), 18.49,
18.44 (ROOC–CHCH3 –R%); ESIMS: C47-
H52O7 (728.92), m/z 751.3 (60), [M+Na]+.
with water, dried over Na2SO4 and the sol-
vents were removed under reduced pressure.
The raw product was purified by column chro-
matography or crystallization.
General procedure for the synthesis of the
S-Glucosides (GP 3).—A solution of BF3·Et2O
in dry CH2Cl2 was slowly added to a solution
of the aromatic compound and 1,2,3,4,6-
penta-O-acetyl-b- -glucopyranose (5) at rt
D
1-(i- -Glucopyranosyloxy)-(9)-ibuprofen
D
under nitrogen atmosphere. The mixture was
stirred overnight and stopped by decomposi-
tion of the catalyst over NaHCO3. After dilu-
tion with CH2Cl2, the mixture was washed
with water, dried with Na2SO4 and the sol-
vents were removed under reduced pressure.
The raw product was purified by column chro-
matography or crystallization.
(4a).—A solution of compound 3a (212 mg,
0.29 mmol) in CH2Cl2 (20 mL) and acetone (5
mL) was reacted under a hydrogen atmo-
sphere in the presence of 20% palladium on
charcoal (205 mg) according to GP 4. After
purification by column chromatography (4:1
Et2O–acetone), a colourless film of 4a (81 mg,
1
0.22 mmol, 76%) was obtained; H NMR
General procedure for the deprotection of
benzyl groups (GP 4).—A slurry of palladium
on charcoal was added to the solution of the
protected glucoside under a nitrogen atmo-
sphere. The atmosphere was changed from
nitrogen to hydrogen and the reaction was
continued until no further reaction was de-
tectable. After filtration the solvents were re-
moved under reduced pressure and the
product was purified by column chromatogra-
phy or crystallization.
(CD3OD) (two sets of signals, diastereomers):
l 7.20 (m, 2 H, H-2%, H-6%), 7.11 (d, 2 H, H-3%,
H-5%), 5.50 (d, 1 H, J1,2 7.8 Hz, H-1), 3.75 (m,
2 H, H-6a, H-6b), 3.60 (m, 1 H, ROOC–
CHCH3–R%), 3.30 (m, 4 H, H-2, H-3, H-4,
H-5), 2.42 (d, 2 H, CH2CH(CH3)2), 1.80 (m, 1
H, CH2CH(CH3)2), 1.52 (m, 3 H, ROOC–
CHCH3–R%), 0.89 (d, 6 H, CH2CH(CH3)2);
13C NMR (CD3OD) (two sets of signals,
diastereomers): l 175.22, 175.15 (COOR),
141.72 (C-4%), 138.86, 238.79 (C-1%), 130.35,
130.29 (C-2%, C-6%), 128.44 (C-3%, C-5%), 96.05,
95.99 (C-1), 78.86 (C-5), 78.11, 78.04 (C-2),
73.98, 73.92 (C-3), 70.99, 70.92 (C-4), 62.28,
62.19 (C-6), 46.27, 46.21 (ROOC–CHCH3–
R%), 46.03 (CH2CH(CH3)2), 31.40 (CH2CH-
(CH3)2)), 22.71 (CH2CH(CH3)2)), 19.43, 19.20
(ROOC–CHCH3 –R%); Anal. Calcd for
C19H28O7 (368.42): C, 61.94; H, 7.7. Found: C,
61.21; H, 7.81.
1-(2,3,4,6-Tetra-O-benzyl-i- -glucopyran-
D
osyloxy)-(9)-ibuprofen (3a).—A solution of
compound 2a (2.2 g, 11 mmol) in dry CH2Cl2
(100 mL) was reacted with a solution of 1
(8.6 g, 12.0 mmol) in dry CH2Cl2 (25 mL) for
4 h according to GP 1. After purification
by column chromatography (9:1 hexane–
EtOAc), 3a (5.37 g, 7.37 mmol, 67%) was
1
obtained as an oil; H NMR (CDCl3) (two
sets of signals, diastereomers): l 7.15 (m, 24
H, 4 CH2C6H5, H-2%, H-3%, H-5%, H-6%), 5.60
(d, 1 H, J1,2 8.0 Hz, H-1), 4.45 (m, 15 H, 4
CH2C6H5, H-2, H-3, H-4, H-5, H-6a, H-6b,
ROOC–CHCH3–R%), 2.35 (d, 2 H, CH2CH-
(CH3)2), 1.75 (m, 1 H, CH2CH(CH3)2), 1.50
(d, 3 H, ROOC–CHCH3–R%), 0.85 (m, 6 H,
CH2CH(CH3)2); 13C NMR (CDCl3) (two sets
of signals, diastereomers): l 173.06 (COOR),
140.76, 140.62 (C-4%), 138.44, 138.08, 137.97,
137.88, 137.20, 136.73 (C-1%, 4 CH2C6H5),
129.49, 129.28 (C-2%, C-6%), 128.34, 128.06,
127.93, 127.85, 127.83, 127.76, 127.66, 127.59,
127.56, 127.53, 127.46, 127.30, 127.26 (C-3%,
6 - (i - - Glucopyranosyloxy) - (9) - h - toco-
D
pherol (4b).—Compound 2b (2.15 g, 5 mmol)
and 1 (3.97 g, 6 mmol) were reacted in the
presence of BF3·Et2O (120 ml, 1 mmol) in dry
CH2Cl2 (110 mL) for 3 h according to GP 1.
Following flash chromatography (9:1 hexane–
EtOAc) the mixture of 2b and 3b (3.57 g) in
EtOAc (370 mL) was hydrogenated for 4 h in
the presence of 10% palladium on charcoal
(3.7 g) according to GP 4. After purification
by column chromatography (20:1 EtOAc–
MeOH), white crystals of 4b (2 g, 3.37 mmol,
67%) formed spontaneously; mp 143–145 °C;
1H NMR (CDCl3): l 5.22 (bs, 1 H, OH), 4.72

R.K. Uhrig et al. / Carbohydrate Research 325 (2000) 72–80
77
(bs, 1 H, OH), 4.61 (bs, 1 H, OH), 4.57 (dd, 1
H, J1,2 7.7 Hz, H-1), 3.74 (m, 5 H, H-2, H-3,
J4,5 9.5 Hz, H-4, H-6a, H-6b), 3.18 (m, 1 H,
H-5), 2.76 (bs, 1 H, OH), 2.47 (m, 2 H, H-3%),
2.08 (m, 9 H, 5%-CH3, 7%-CH3, 8%-CH3), 1.73
(m, 2 H, H-4%), 1.31 (m, 24 H, 2%-CH3,
C16H33), 0.86 (m, 12 H, C16H33); 13C NMR
(CDCl3): l 148.41 (C-6%), 145.4 (C-1a%), 128.36
(C-8%), 126.61 (C-7%), 122.78 (C-4a%), 117.37
(C-5%), 104.30 (C-1), 69.74, 74.31, 74.81, 75.15
(C-2%, C-2, C-3, C-4, C-5), 61.76 (C-6), 40.74,
39.37, 37.29, 37.44, 37.58, 37.67 (C16H33),
32.79 (2%-CH3), 31.13 (C-3%), 27.97, 24.47,
24.80, 23.46, 23.70, 22.63, 22.72, 20.69, 21.08,
19.69, 19.75 (C-7%, C16H33), 11.81, 12.92, 13.77
(5%-CH3, 7%-CH3, 8%-CH3); Anal. Calcd for
C35H6O7 (592.85): C, 70.91; H, 10.2. Found:
C, 70.64; H, 10.34.
sion of 3c (1.0 g, 1.36 mmol) in MeOH (100
mL) was mixed with a saturated Ba(OH)2
solution (30 mL). Subsequently, EtOH, iso-
propanol and tert-butanol (each 15 mL) were
added and the mixture was stirred for 25 h at
rt. The mixture was neutralized with 1 M HCl
and diluted in Et2O. Following drying over
Na2SO4, the organic solvents were removed
under reduced pressure. The raw product and
KOH powder (1 g) were suspended in a satu-
rated solution of Ba(OH)2 (30 mL), 1,2-
dimethoxyethane (100 mL) and water (70 mL)
and reacted for 5 days at rt. Repeating the
work-up procedure of the first step resulted in
spontaneous crystallization of colourless
needles of 3c% (550 mg, 0.81 mmol, 60%); mp
1
137–138 °C; H NMR (CDCl3): l 10.20 (bs, 1
H, OH), 7.61 (d, 1 H, H-6%), 7.3 (m, 21 H, 4
CH2C6H5, J4%/6% 3.0 Hz, H-4%), 6.91 (d, 1 H,
J3%/4% 9.1 Hz, H-3%), 4.75 (m, 9 H, 4 CH2C6H5,
H-1), 3.7 (m, 6 H, H-2, H-3, H-4, H-5, H-6a,
Methyl 2-acetoxy-5-(2,3,4,6-tetra-O-benzyl-
i-D-glucopyranosyloxy)benzoate
(3c).—To
compound 2c (1.7 g, 8.08 mmol), prepared as
described elsewhere [18,19], BF3·Et2O (300 ml,
2.5 mmol) in dry CH2Cl2 (80 mL) and 1 (6.6 g,
5 mmol) were added according to a slight
modification of GP 2. The imidate 1 (6.6 g, 5
mmol) was added to the mixture of 2c (1.7 g,
8.08 mmol) in three portions (3.3 g (2.5 mmol)
at 0 h and 1.65 g (1.25 mmol) at 1.5 and 3 h,
respectively). Extraction was performed with
EtOAc instead of CH2Cl2. After purification
by column chromatography (5:1 hexane–
EtOAc), 3c (5.4 g, 7.37 mmol, 91%) was ob-
tained. Recrystallization from MeOH gave
white crystals; mp 79–80 °C; 1H NMR
(CDCl3): l 7.70 (d, 1 H, H-6%), 7.25 (m, 21 H,
4 CH2C6H5, H-4%), 7.01 (d, 1 H, H-3%), 4.75
(m, 9 H, 4 CH2C6H5, H-1), 3.81 (s, 3 H,
OCH3), 3.65 (m, 6 H, H-2, H-3, H-4, H-5,
13
H-6b); C NMR (CDCl3): l 173.00 (COOH),
158.02 (C-3%), 149.60 (C-6%), 138.41, 138.06,
137.94, 137.82, 128.39, 128.33, 128.18, 127.91,
127.87, 127.79, 127.67, 127.28 (4 CH2C6H5),
118.58 (C-4%), 118.16 (C-1%), 112.89 (C-2%),
111.27 (C-5%), 102.56 (C-1), 84.60, 81.99,
77.66, 76.48 (C-2, C-3, C-4, C-5), 75.76, 75.14,
75.00, 73.48 (4 CH2C6H5), 68.75 (C-6); ES-
IMS: C41H40O9 (676.76), m/z 699.8 (80), [M+
Na]+.
2-Hydroxy-5-(i- -glucopyranosyloxy)ben-
D
zoate (4c).—Compound 3c% (40 mg, 0.062
mmol) was reacted with 20% palladium on
charcoal (50 mg) in acetone (20 mL) and
water (2 mL) for 4 h according to GP 4.
Without further purification, white crystals of
4c (20 mg, 55.8 mmol, 80%) formed sponta-
neously out of the aqueous solution; mp 98–
13
H-6a, H-6b), 2.31 (s, 3 H, COCH3); C NMR
(CDCl3): l 169.90 (COOR), 164.39 (COCH3),
154.71 (C-3%), 145.71 (C-6%), 138.44, 138.1,
138.03, 138.01, 128.39, 128.33, 128.17, 127.89,
127.84, 127.78, 127.71, 127.65, 127.60 (4
CH2C6H5), 124.73 (C-4%), 123.77 (C-1%), 122.35
(C-2%), 120.01 (C-5%), 101.90 (C-1), 84.61,
81.91, 77.55, 75.21 (C-2, C-3, C-4, C-5), 75.74,
75.11, 75.01, 73.50 (4 CH2C6H5), 68.66 (C-6),
52.19 (OCH3), 20.91 (COCH3); Anal. Calcd
for C44H44O10 (732.82): C, 72.12; H, 6.05.
Found: C, 72.51; H, 5.96.
1
99 °C; H NMR (D2O): l 7.55 (d, 1 H, H-6%),
7.30 (dd, 1 H, H-4%), 6.95 (d, 1 H, H-3%), 5.00
(d, 1 H, J1,2 7.4 Hz, H-1), 3.95 (dd, 1 H, J5,6a
2.1 Hz, J6a,6b 12.4 Hz H-6a), 3.25 (dd, 1 H,
H-6b, J5,6b 5.6 Hz), 3.10 (m, 4 H, H-2, H-3,
H-4, H-5); 13C NMR (D2O): l 176.67
(COOH), 160.45 (C-5%), 153.94 (C-2%), 130.23
(C-4%), 122.70 (C-6%), 122.45 (C-3%), 118.22 (C-
1%), 106.02 (C-1), 80.80 (C-5), 80.30 (C-2),
77.65 (C-3), 74.18 (C-4), 65.27 (C-6); Anal.
Calcd for C13H16O9·2H2O (352.29): C, 44.32;
H, 5.72. Found: C, 44.56; H, 5.96.
2-Hydroxy-5-(2,3,4,6-tetra-O-benzyl-i-
D
-
glucopyranosyloxy)benzoate (3c%).—A suspen-

78
R.K. Uhrig et al. / Carbohydrate Research 325 (2000) 72–80
Ethyl 3,4-(diphenylmethylendioxy)-5-hy-
C(C6H5)2, 4 CH2C6H5), 102.28, 105.07, 114.81
(C-1, C-2%, C-6%), 75.25, 77.38, 81.81, 84.47
(C-2, C-3, C-4, C-5), 73.48, 74.98, 75.04, 75.72
(4 CH2C6H5), 68.29 (C-6), 60.9 (OCH2CH3),
14.27 (OCH2CH3); Anal. Calcd for C56H52O10
(885.02): C, 76.00; H, 5.92. Found: C, 75.82;
H, 6.09.
droxybenzoate (2d).—Ethyl 3,4,5-trihydroxy-
benzoate (396 mg, 2 mmol) was dissolved in
acetone (0.9 mL) and pyridine (0.16 mL).
Then a solution of diphenyldichloromethane
(0.38 mL, 2 mmol) in acetone (0.45 mL) was
added slowly and the mixture was stirred for
16 h. The reaction was stopped by carefully
adding a solution of NaOH (0.16 g) in water
(0.45 mL) and stirring for a further 2 h. The
oily phase was separated and extracted with
Et2O. The aqueous phase was acidified with
concd HCl (pH 2–3) and also extracted with
Et2O. The combined organic solutions were
washed with 10% NaHCO3 and water and
dried over Na2SO4. Solvents were removed
under reduced pressure and after column
chromatography (9:1 petroleum ether–
EtOAc) white crystals of 2d (440 mg, 1.21
mmol, 61%) formed spontaneously; mp 148–
3,4 - (Diphenylmethylendioxy) - 5 - (2,3,4,6-
tetra - O - benzyl) - i -
D
- glucopyranosyloxy)-
benzoic acid (3d%).—Compound 3d (4.5 g, 5
mmol) and KOH powder (3 g) were reacted in
1,2-dimethoxyethane (175 mL). After 20 h the
reaction was quenched with water (90 mL),
neutralized with 1 M HCl (pH 6–7) and ex-
tracted with Et2O. The organic solution was
washed with a saturated solution of NaHCO3
and water and dried over Na2SO4. After re-
moving the solvents under reduced pressure
3d% (3.8 g, 4.45 mmol, 89%) was obtained as a
white powder; mp 59–61 °C; 1H NMR
(CDCl3): l 7.26, 7.54 (m, 32 H, H-2%, H-6%,
C(C6H5)2, 4 CH2C6H5), 5.14 (2 H, J1,2 7 Hz,
H-1, J3,4 10.9 Hz, H-3), 4.97 (1 H, J2,3 10.9,
H-2), 4.83 (3 H, CH2C6H5), 4.52 (m, 3 H, J4,5
11 Hz, H-4, J6a,6b 12.2 Hz, H-6a, H-6b), 3.68
1
150 °C; H NMR (CDCl3): l 7.37, 7.56 (m, 12
H, H-4, H-6, C(C6H5)2), 5.67 (s, OH), 4.32 (q,
2 H, J 7.12 Hz, OCH2CH3), 1.34 (t, 3 H,
OCH2CH3); 13C NMR (CDCl3): l 166.23
(COOR), 148.28 (C(C6H5)2), 138.03, 138.93,
139.46 (C-3, C-4, C-5), 129.37, 128.31, 126.3
(C(C6H5)2), 124.65 (C-1), 103.29, 113.99 (C-2,
C-6), 61.12 (OCH2CH3), 14.25 (OCH3CH3);
Anal. Calcd for C22H18O5 (362.38): C, 72.92;
H, 5.01. Found: C, 73.08; H, 5.11.
13
(m, 6 H, H-5, CH2C6H5); C NMR (CDCl3):
l 171.00 (COOH), 148.57 (C(C6H5)2), 138.04,
138.13, 138.55, 139.34, 139.4, 140.21, 140. 66
(C-3%, C-4%, C-5%, C(C6H5)2), 118.96, 123.43,
126.32, 126.36, 127.56, 127.63, 127.68, 127.74,
127.83, 127.9, 128.29, 128.35, 129.36, 129.42
(C-1%, C(C6H5)2, 4 CH2C6H5), 102.26, 105.61,
115.56 (C-1, C-2%, C-6%), 75.23, 77.42, 81.80,
84.47 (C-2, C-3, C-4, C-5), 73.50, 75.01, 75.75
(CH2C6H5), 68.32 (C-6); Anal. Calcd for
C54H48O10 (856.96): C, 75.96; H, 5.65. Found:
C, 75.95; H, 5.80.
Ethyl 3,4-(diphenylmethylendioxy)-5-(2,3,-
4,6-tetra-O-benzyl-i- -glucopyranosyloxy)-
D
benzoate (3d).—Compound 2d (362 mg, 1
mmol) and 1 (793 mg, 1.2 mmol) were reacted
in the presence of BF3·Et2O (120 ml, 1 mmol)
in neat CH2Cl2 (25 mL) for 3 h according to
GP 1. After crystallization from EtOH, white
crystals of 3d (530 g, 0.599 mmol, 60%)
5-(i- -Glucopyranosyloxy)benzoic acid (4d).
D
1
—Compound 3d% (54 mg, 0.061 mmol) was
reacted for 4 h in the presence of 20% palla-
dium on charcoal (20 mg) in acetone (10 mL)
and water (1 mL) according to GP 4. Com-
pound 4d (20 mg, 0.057 mmol, 94%) was
obtained as a white powder without further
purification; mp 143–145 °C; 1H NMR
(CD3OD): l 7.36, 7.18 (2 s, 2 H, H-2%, H-6%),
4.76 (CD3OD, 1 H, J1,2 7.4 Hz, H-1), 3.69,
3.84 (m, 2 H, H-6a, H-6b), 3.49 (m, 4 H, H-2,
formed spontaneously; mp 106–109 °C; H
NMR (CDCl3): l 7.26, 7.52 (m, 32 H, H-2%,
H-6%, C(C6H5)2, 4 CH2C6H5), 5.15 (m, 2 H, J1,2
6.5 Hz, H-1, H-2), 4.97 (d, 1 H, H-3), 4.82 (3
H, CH2C6H5), 4.53 (m, 3 H, H-4, H-6a, H-6b),
4.28 (q, 2 H, J 7.1 Hz, OCH2CH3), 3.68 (m, 6
H, H-5, CH2C6H5), 1.30 (t, 3 H, OCH2CH3);
13C NMR (CDCl3): l 165.65 (COOR), 148.57
(C(C6H5)2), 138.09, 138.16, 138.55, 139.44,
139.51, 139.81, 140.09 (C-3%, C-4%, C-5%,
C(C6H5)2), 118.7, 124.81, 126.3, 126.35,
127.52, 127.61, 127.65, 127.76, 127.83, 127.92,
128.28, 128.33, 128.37, 129.28, 129.34 (C-1%,
13
H-3, H-4, H-5); C NMR (CD3OD): l 169.89
(COOH), 141.61, 146.70, 146.78 (C-3%, C-4%,
C-5%), 122.28 (C-1%), 112.16, 113.57 (C-2%, C-

R.K. Uhrig et al. / Carbohydrate Research 325 (2000) 72–80
79
6%), 104.32 (C-1(b)), 101.48 (C-1(a)), 73.36,
74.61, 74.78 (C-2, C-3, C-4, C-5 (a)), 71.06,
74.86, 77.6, 78.23 (C-2, C-3, C-4, C-5 (b)),
62.18 (C-6). Anal. Calcd for C13H16O10·H2O
(350.28): C, 44.58; H, 5.14. Found: C, 44.36;
H, 5.14.
C(CH3)3)), 30.77 (2 C(CH3)3); Anal. Calcd for
C20H32O6S·0.5H2O (409.53): C, 58.68; H, 8.07;
S, 7.82. Found: C, 58.62; H, 7.94; S, 7.87.
N-Acetyl-
L
-cysteine ethyl ester (6f).—To a
-cysteine (10 g, 61.5
solution of N-acetyl-
L
mmol) in EtOH (300 mL), SOCl2 (5 mL, 67.5
mmol) was added dropwise under a nitrogen
atmosphere, avoiding temperatures higher
than 30 °C. The reaction was stopped after 3 h
by adding water (200 mL). After extraction
with EtOAc, drying over Na2SO4 and remov-
ing the solvents under reduced pressure 6f (5.4
4-[2,6-Bis(tert-butyl)-phenyl] 2,3,4,6-tetra-
O-acetyl-1-thio-i- -glucopyranoside (7e).—
D
Compound 5 (390 mg, 1 mmol) was reacted
for 16 h with probucol (103.4 mg, 0.2 mmol)
in the presence of BF3·Et2O (26 mL, 0.2 mmol)
in CH2Cl2 (5 mL) according to GP 3. After
purification by column chromatography (4:1
petroleum ether–EtOAc), white crystals of 7e
(170 mg, 0.29 mmol, 74%) formed sponta-
1
g, 28.3 mmol, 46%) was obtained as an oil; H
NMR (CDCl3): l 6.42 (bs, 1 H, NH), 4.87 (dt,
1 H, J2,3 4.1 Hz, H-2), 4.26 (q, 2 H, J 7.2 Hz,
OCH2CH3), 3.03 (m, 2 H, J3,SH 8.9 Hz, H-3),
2.08 (s, 3 H, COCH3), 1.33 (m, 4 H, SH,
OCH2CH3); 13C NMR (CDCl3): l 169.84,
170.09 (COOR, COCH3), 62 (OCH2CH3),
53.53 (C-2), 26.86 (C-3), 23.11 (COCH3),
14.17 (OCH2CH3); Anal. Calcd for C7H13-
NO3S (191.25): C, 43.96; H, 6.85; S, 7.32.
Found: C, 43.66; H, 6.88; S, 7.25.
1
neously; mp 142–144 °C, H NMR (CDCl3):
l 7.30 (s, 2 H, H-3%, H-5%), 5.35 (s, 1 H, OH),
5.2 (dd, 1 H, J2,3 9.3 Hz, H-2), 4.02 (dd, 1 H,
J4,5 9.9 Hz, H-4), 4.87 (dd, 1 H, J3,4 9.8 Hz,
H-3), 4.57 (d, 1 H, J1,2 10 Hz, H-1), 4.31 (dd,
1 H, J6a,6b 12.2 Hz, H-6a), 4.12 (dd, 1 H,
H-6b), 3.72 (ddd, 1 H, J5,6a 4.5 Hz, J5,6b 2.2
Hz, H-5), 2.10, 2.07, 2.00, 1.99 (4 s, 12 H, 4
13
COCH3), 1.44 (s, 18 H, 2 C(CH3)3); C NMR
N-Acetyl-3-(2,3,4,6-tetra-O-acetyl-i-
copyranosyl)- -cysteine ethyl ester (7f).—
D
-glu-
(CDCl3): l 169.06, 169.38, 170.20, 170.63
(COCH3), 154.87 (C-1%), 136.48 (C-2%, C-6%),
132.00 (C-3%, C-5%), 119.48 (C-4%), 85.89
(C-1), 67.99, 69.81, 74.30, 75.88 (C-2, C-3,
C-4, C-5), 62.21 (C-6), 34.33 (2 C(CH3)3),
30.14 (2 CH(CH3)3), 20.54, 20.58, 20.75, 20.82
(COCH3); Anal. Calcd for C28H40O10S·0.5H2O
(577.69): C, 58.22; H, 7.15; S, 5.54. Found: C,
58.41; H, 7.04; S, 5.64.
L
Compound 5 (10.9 g, 28 mmol) was reacted
for 3 h with 6f (5.4 g, 28 mmol) in the
presence of BF3·Et2O (6.9 ml, 56 mmol) in
CH2Cl2 (40 mL) according to GP 3. After
purification by column chromatography
(EtOAc) white crystals of 7f (6.56 g, 12.6
mmol, 45%) formed spontaneously; mp 75–
1
78 °C, H NMR (CDCl3): l 6.47 (bs, 1 H,
4-[2,6-Bis(tert-butyl)-phenyl]
1-thio-i-
D-
NH), 5.23 (dd, 1 H, J3,4 9.4 Hz, 3-H), 5.07,
4.98 (2 dd, 2 H, J2,3 9.3, H-2, J4,5 10 Hz, H-4),
4.79 (m, 1 H, H-2%), 4.54 (d, 1 H, J1,2 10 Hz,
H-1), 4.21 (m, 4 H, H-3%, J 7.2 Hz,
OCH2CH3), 3.72 (ddd, 1 H, J5,6a 6 Hz, J5,6b
4.6 Hz, H-5), 3.23 (dd, 1 H, H-6b), 3.05 (dd,
1 H, J6a,6b 14 Hz, H-6a), 2.10 (s, 3 H,
(NH)COCH3), 2.07, 2.05, 2.03, 2.01 (4 s, 12
H, 4 (O)COCH3), 1.29 (m, 3 H, OCH2CH3);
13C NMR: l 169.31, 169.38, 169.82, 169.97,
170.32, 170.53 (COOR, 5 COCH3), 83.25 (C-
1), 68.06, 69.78, 73.53, 76.11 (C-2, C-3, C-4,
C-5), 61.83, 61.85 (C-6, OCH2CH3), 51.89 (C-
2%), 31.68 (C-3%), 22.86 ((NH)COCH3)), 20.47,
20.49, 20.63 (4 (O)COCH3), 14.1 (OCH2CH3);
Anal. Calcd for C21H31NO12S (521.54): C,
48.36; H, 5.99; N, 2.69; S, 6.15. Found: C,
48.45; H, 6.08; N, 2.83; S, 6.27.
glucopyranoside (8e).—Compound 7e (4.2 g,
7.4 mmol) was reacted for 6 h in a solution of
MeOH (200 mL), water (100 mL) and Et3N
(50 mL). After removing the solvents under
reduced pressure and column chromatogra-
phy, white–yellowish crystals of 8e (2.2 g, 5.4
mmol, 74%) formed spontaneously; mp 81–
1
83 °C; H NMR (CD3OD): l 7.41 (s, 2 H,
H-3%, H-5%), 4.80 (s, 1 H, OH), 4.40 (d, 1 H,
J1,2 9.8 Hz, H-1), 3.86 (dd, 1 H, H-6b), 3.67
(m, 1 H, J6a,6b 12 Hz, H-6a), 3.30 (m, 3 H,
H-2, H-3, H-4), 3.16 (m, 1 H, J5,6a 5.4 Hz, J5,6b
1.8 Hz, H-5), 1.41 (s, 18 H, 2 C(CH3)3);
13C NMR (CD3OD): l 155.73 (C-1%), 139.82
(C-2%, C-6%), 131.48 (C-3%, C-5%), 123.67 (C-4%),
90.31 (C-1), 71.55, 73.62, 79.72, 81.95 (C-2,
C-3, C-4, C-5), 63.15 (C-6), 35.68 (2

80
R.K. Uhrig et al. / Carbohydrate Research 325 (2000) 72–80
Stu¨ben, M. Wießler, Cancer Chemother. Pharmacol., 35
(1995) 364–370.
N-Acetyl-3-(i-
D
-glucopyranosyl)- -cysteine
L
ethyl ester (8f).—Compound 7g (156.3 mg,
0.3 mmol) was reacted in a solution of 10%
Et3N in neat MeOH (24 mL) under a nitrogen
atmosphere. After 16 h the solvents were
removed under reduced pressure. After col-
umn chromatography (6:1 petroleum ether–
EtOAc) a colourless oil of 8f (67 mg, 0.18
mmol, 60%) was obtained; 1H NMR
(CD3OD) (two sets of signals, diastereomers):
l 5.32 (bs, 1 H, NH), 4.65 (m, 1 H, H-2%), 4.37
(d, 1 H, J1,2 9.5 Hz, H-1), 4.13 (m, 2 H, J 7.2
Hz, OCH2CH3), 3.86 (d, 2 H, J3,4 10.6 Hz,
H-3, J4,5 10 Hz, H-4), 3.67 (m, 2 H, J5,6a 8.1
Hz, H-5), 3.44 (dd, 1 H, J2,3 9.1 Hz, H-2), 3.08
(m, 4 H, J6a,6b 13.8 Hz, H-6a, H-6b, 3), 1.99 (s,
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13
3 H, COCH3), 1.26 (m, 3 H, (O)CH2CH3); C
NMR (CD3OD) (two sets of signals,
diastereomers): l 172.17, 173.36 (COOR,
COCH3), 88.85, 86.79 (C-1), 71.39, 71.65,
73.1, 74.25, 74.51, 75.6, 79.57, 82.26 (C-2, C-3,
C-4, C-5), 62.81 (OCH2CH3), 62.66 (C-6),
54.42 (C-2%), 33.77, 31.99 (C-3%), 22.4, 20.85
(COCH3), 14.45 (1 C, OCH2CH3); Anal.
Calcd for C21H31NO12S (371.41): C, 42.04; H,
6.78; N, 3.77; S, 8.63. Found: C, 42.48; H,
6.41; N, 3.57; S, 8.12.
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We thank the Deutsche Forschungsgemein-
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