Synthesis of urine drug metabolites: Glucuronosyl esters of carboxymefloquine, indoprofen, (S)-naproxen, and desmethyl (S)-naproxen

Article abstract of DOI:10.1081/CAR-120034003

A general procedure for the synthesis of 1-O-acyl-β-D-glucuronic acids using the benzyl 1-O-trichloroacetimidoyl-2,3,4-tri-O-benzyl-D- glucopyranuronate 6 as donor is exemplified by the synthesis of the urine metabolites of (S)-naproxen, desmethyl (S)-naproxen, indoprofen, and carboxymefloquine. The key intermediate benzyl 2,3,4-tri-O-benzyl-D- glucopyranuronate 5 is easily accessible in four steps (29%) from the peracetylated β-D-glucuronic acid 1. Copyright

Full text of DOI:10.1081/CAR-120034003

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Synthesis of Urine Drug Metabolites: Glucuronosyl
Esters of Carboxymefloquine, Indoprofen,
(S)‐Naproxen, and Desmethyl (S)‐Naproxen
Martina Lahmann a , Moa Andresen Bergström a , Dominika Turek b c & Stefan Oscarson b
a Department of Chemistry , Göteborg University , S‐412 96, Göteborg, Sweden
b Department of Organic Chemistry, Arrhenius Laboratory , Stockholm University ,
Stockholm, Sweden
c AstraZeneca R&D Södertälje , S‐151 85, So¨derta¨lje, Sweden
Published online: 18 Aug 2006.
To cite this article: Martina Lahmann , Moa Andresen Bergström , Dominika Turek & Stefan Oscarson (2004) Synthesis
of Urine Drug Metabolites: Glucuronosyl Esters of Carboxymefloquine, Indoprofen, (S)‐Naproxen, and Desmethyl
(S)‐Naproxen, Journal of Carbohydrate Chemistry, 23:2-3, 123-132, DOI: 10.1081/CAR-120034003
To link to this article: http://dx.doi.org/10.1081/CAR-120034003
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JOURNAL OF CARBOHYDRATE CHEMISTRY
Vol. 23, Nos. 2 & 3, pp. 123–132, 2004
Synthesis of Urine Drug Metabolites: Glucuronosyl
Esters of Carboxymefloquine, Indoprofen,
(S)-Naproxen, and Desmethyl (S)-Naproxen
1
Martina Lahmann,1, Moa Andresen Bergstrom,
Dominika Turek,2,# and Stefan Oscarson2
*
¨
1
¨
¨
Department of Chemistry, Goteborg University, Goteborg, Sweden
2Department of Organic Chemistry, Arrhenius Laboratory,
Stockholm University, Stockholm, Sweden
ABSTRACT
A general procedure for the synthesis of 1-O-acyl-b-D-glucuronic acids using the ben-
zyl 1-O-trichloroacetimidoyl-2,3,4-tri-O-benzyl-D-glucopyranuronate 6 as donor is
exemplified by the synthesis of the urine metabolites of (S)-naproxen, desmethyl
(S)-naproxen, indoprofen, and carboxymefloquine. The key intermediate benzyl
2,3,4-tri-O-benzyl-D-glucopyranuronate 5 is easily accessible in four steps (29%)
from the peracetylated b-D-glucuronic acid 1.
Key Words: (S)-Naproxen; Desmethyl (S)-naproxen; Indoprofen; Carboxymefloquine.
INTRODUCTION
The in vivo formation of b-D-glucuronic acid derivatives plays an important role in
the elimination and detoxification of xenobiotics and endogenous compounds in humans.
*
¨
Correspondence: Martina Lahmann, Department of Chemistry, Goteborg University, S-412 96
¨
Goteborg, Sweden; E-mail: martina.lahmann@chem.gu.se.
#
¨ ¨
Current address: AstraZeneca R&D Sodertalje, S-151 85 Sodertalje, Sweden.
¨
¨
123
DOI: 10.1081/CAR-120034003
0732-8303 (Print); 1532-2327 (Online)
www.dekker.com
Copyright # 2004 by Marcel Dekker, Inc.

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Lahmann et al.
Many compounds containing a carboxylic acid group are excreted as 1-O-acyl-b-D-
glucuronic acids produced via the UDP-glucuronosyl transferase system. A large number
of drugs, e.g., (S)-naproxen and indoprofen, are known to be metabolised via this pathway.
These metabolic products were considered earlier only to be rapidly eliminated from the
body without any further biological interaction. Recent results, however, show that
adducts are formed both with low-molecular weight nucleophiles and proteins.[1] Detailed
metabolism studies including identification, characterisation, and toxicology testing are
quite often hampered by the limited access to sample material. Isolation of metabolites
from biological material, e.g., urine, is often difficult due to instability of the metabolic
products. In vitro biosynthesis affords the metabolites only in small amounts since simul-
taneous degradation occurs under physiological conditions. Therefore, the preparation of
glucuronic acid derivatives of drug metabolites has been a synthetic target for a long time,
and a general synthetic route has been desirable. However, the vast majority of these com-
pounds are glucuronides and only a few examples of anomeric ester metabolites have been
synthesised.[2–8]
The preparation of anomeric ester derivatives of glucuronic acid is connected to syn-
thetic problems. Although the anomeric hydroxyl group has a higher reactivity as com-
pared to the other hydroxyl groups, this difference is usually not sufficient to produce
an acyl glucuronic acid derivative using an unprotected or partially protected glucuronic
acid. Consequently, protecting groups have to be chosen, which are removable in the pre-
sence of the anomeric ester function. This circumstance excludes the use of many common
carboxyl-protecting groups as well as almost all acyl protecting groups, complicating the
stereoselective formation of the b-linked anomeric ester, which is normally controlled by
using a participating acyl protecting group at O-2. The benzyl ester 5[9,10] has been found
earlier to be a suitable precursor, but different esterification methods, e.g., Mitsunobu con-
ditions and carbodiimide based methods gave anomeric mixtures,[7,8,11] which often were
tedious or impossible to separate. Also, the preparation of the perbenzylated glucuronic
acid donor is cumbersome. Attempts to alkylate uronic acids directly seemed to be too
unpredictable,[12] thus, an oxidising step was required to generate the carboxylic function,
a step that can be problematic.
Herein we describe a general procedure for the synthesis of 1-O-acyl-b-D-glucuronic
acids exemplified by the synthesis of the urine metabolites of (S)-naproxen, desmethyl (S)-
naproxen, a metabolite derived from (S)-naproxen via a different pathway, indoprofen, and
carboxymefloquine. The acyl uronate of the latter is one of the metabolites of mefloquine
hydrochloride, a drug used for the prevention of malaria in areas with chloroquine-resist-
ant parasites.
RESULTS AND DISCUSSION
The methyl peracetyl b-uronate 1 (Sch. 1) was easily prepared by methanolysis of the
commercially available 3,6-glucurono lactone, followed by acetylation in Ac2O and
HClO4, and crystallisation.[13] The formation of the thioglycoside glucuronate 2 did not
proceed as well and b-stereoselectively as for glycosides. However, with 63% isolated
yield the reaction is an attractive alternative to the two step longer routes via the thio
orthoester or xanthate rearrangements, which are alternatives if the pure b-anomer is
required.[12,14] The acetates were removed with NaOMe in MeOH without any formation

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Synthesis of Urine Drug Metabolites
125
.
Scheme 1. (a) EtSH, BF3 Et2O,CH2Cl2, RT; 63% (b) 1. NaOMe, MeOH; 2. NaOH(aq.), 96% (c)
BnBr, NaH, DMSO, 158C; 57% (d) NIS, wet CH2Cl2, RT, 85%; (e) CCl3CN; cat.NaH, CH2Cl2, RT,
91%.
of b-elimination product. Addition of H2O and NaOH to the reaction mixture yielded the
sodium uronate 3, ready for introduction of the benzyl groups.
Alkylation of uronates is known to be difficult. However, use of the uronate salt
instead of an ester increased the yield[15] as well as replacement of DMF by DMSO[16]
along with careful monitoring of the temperature. The yields were acceptable (40–
65%), and the procedure is also suitable for oligosaccharic acids.[17] Hence, benzylation
of 3 with BnBr and NaH in DMSO produced 4 in 57% yield.
Attempts to activate the thioethyl group with various promoters in the presence of
different aglycons did not provide the wanted acyl glucuronic acids.[11] Consequently, the
thioethyl group was hydrolysed using NIS and a catalytic amount of AgOTf to produce
the benzyl 2,3,4-tri-O-benzyl-D-glucopyranuronate 5 (85%).[7,8,11] Conversion to the imi-
date 6 was accomplished by treatment of 5 with Cl3CCN in CH2Cl2 together with a catalytic
amount of NaH (91%, a/b 15: 1). Compound 6 is known to be an excellent donor for the
synthesis of b-alkyl glucuronides, employing SN2-type coupling conditions,[6,18,19] but has
been barely tried for acyl glucuronic acids.[6] (S)-Naproxen (Sch. 2) was smoothly converted
into its acyl-b-D-glucuronic acid 7 (60%), a minor amount of the a anomer was easily
removed by column chromatography. Hydrogenolysis over Pd/C at atmospheric pressure
rendered the unprotected metabolite 8[20,21] in almost quantitative yield.
The acyl glucuronic acids of desmethyl (S)-naproxen 14[20,21] (Sch. 3) is another
metabolite of (S)-naproxen. A direct transformation of 7 or 8 into their demethylated
derivatives is hard to accomplish, therefore, (S)-naproxen was modified into the suitable
aglycon 12. The phenolic methyl group was removed with HBr or HI in quantitative
yield giving 9.[21] Attempts to selectively benzylate the phenolic position failed, and di-
benzylation led to racemisation in the a position. The coupling with a TBDMS protected
desmethyl (S)-naproxen was successful, but deprotection of the silyl ether failed, due
to many side reactions. Instead, 12 was prepared in a one pot manner. In pyridine, the
.
Scheme 2. (a) (S)-Naproxen, BF3 Et2O, CH2Cl2, 2308C; (b) Pd/C, EtOAc, H2, 1 atm, RT.

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126
Lahmann et al.
Scheme 3. (a) TBDMSCl, pyridine/CH2Cl2, RT; (b) þ BnOCCl; (c) þ SiO2, CH2Cl2; 36% (for
ꢀ
.
three steps); (d) 6, BF3 Et2O, CH2Cl2, 2308C, 67%; (e) Pd/C, EtOAc, H2, 1 atm, RT, 99%. ( Not
isolated intermediates.)
formation of the labile TBDMS ester with TBDMSCl was faster than the formation of the
corresponding phenolic ether, thus, producing intermediate 10. Addition of benzyl chlor-
oformate formed compound 11. During aqueous work-up most of the TBDMS ester was
cleaved, and after filtration through silica gel 12 was obtained in an overall 36% yield
(three steps). Coupling with 6 under the same conditions as above gave, after column chro-
matography, 13 (67%) as the pure b anomer. 14 was obtained by hydrogenolysis over Pd/
C (99%).
The couplings with indoprofen (Sch. 4), which was used as a racemic mixture, and
carboxymefloquine (Sch. 5) were more demanding due to their poor solubility in
CH2Cl2. A good stereoselectivity was achieved by coupling indoprofen and 6 in a
CH2Cl2–1,4-dioxane mixture (5 : 1) producing 15 containing only a small amount of
the a anomer (,3%) in 54% yield. Hydrogenolysis gave 16 (87%). The preparation of
the carboxymefloquine acyl glucuronic acid metabolite 17 was tried earlier using Mitsu-
nobu conditions.[11] The best b selectivity was obtained with excess of DIAD and PPh3 at
room temperature (66%, a/b 2 : 1). A lowered reaction temperature increased the total
yield, but enhanced the a formation as well (82% a/b 3 : 1). However, the best results
were obtained dissolving carboxymefloquine in a small amount of THF and adding a sol-
ution of donor 6 in CH2Cl2 at 08C (17, 60%, a/b 1 : 3). Deprotection was achieved in
EtOAc and Pd/C 5% producing 18 but the reaction was difficult to reproduce due to
the concomitant reduction of the aromatic system.
In conclusion, the imidate 6 is a good general donor also for the preparation of b
acyl glucuronides. The key intermediate benzyl 2,3,4-tri-O-benzyl-D-glucopyranose
.
Scheme 4. (a) Indoprofen, BF3 Et2O, CH2Cl2/1,4-dioxane, 2308C; (b) Pd/C, EtOAc-DMF, H2, 1
atm, RT.

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Synthesis of Urine Drug Metabolites
127
.
Scheme 5. (a) Carboxymefloquine, BF3 Et2O,CH2Cl2/THF, 08C; (b) Pd/C, EtOAc, H2, 1 atm, RT.
uronate (5) is easily accessible in four steps (29%) from the methyl peracetylated b-
uronate 1.
EXPERIMENTAL
General Methods
All organic solvents were distilled before use, except diethyl ether, which was stored
over sodium wire. Organic solutions were dried over magnesium sulphate, before concen-
tration, which was performed under reduced pressure at ,408C (bath temperature).
NMR spectra were recorded at 300 or 400 MHz (Varian) (1H) or at 75 or 100 MHz (13C),
respectively, in chloroform-d, deuterium oxide or methanol-d4. Tetramethylsilane was
used as internal standard (d ¼ 0) for 1H-spectra. 13C-spectra were referred to the chloro-
1
form signal (d ¼ 77.17). Acetone (d ¼ 31.0, 13C; d ¼ 2.21, H) was applied as internal
standard when deuterium oxide was used as solvent. Silica gel MERCK 60 (0.040–
0.063) was used for flash chromatography. Thin-layer chromatography was performed
on silica gel 60 F254 (Merck) glass plates with detection by UV-light and/or charring
with 8% sulphuric acid. Column chromatography was performed on silica gel (Matrix
Silica Si 60A, 35–70 mm). MALDI-TOF spectra were recorded on a Bruker Biflex III
using PEG 400 and PEG 1000 as calibration reference and 20,40,60-trihydroxy-acetophe-
none monohydrate (THAP) as matrix.
Benzyl 2,3,4-tri-O-benzyl-D-glucopyranuronate (5).[10] Boron trifluoride diethyl
etherate (5 mL, 40.0 mmol) was added slowly to a cooled (0 8C) mixture of 1 (9.5 g,
˚
26.6 mmol), ethane thiol (2.4 mL, 32.4 mmol), and molecular sieves (1 g, MS 4 A) in
dry dichloromethane (50 mL) under nitrogen. After stirring at room temperature (12 hr),
the solution was poured onto a mixture of cracked ice (ꢁ300 mL) and dichloromethane
(200 mL). The organic layer was separated, washed with saturated sodium hydrogen-
carbonate and brine, dried, and concentrated. The crude product was purified by silica
gel chromatography (toluene ! 9 : 1, toluene–diethyl ether) to give methyl (ethyl
2,3,4-tri-O-acetyl-1-thio-D-glucopyranosid)uronate (2) (6.3 g, 16.7 mmol, 63 %) as an
a/b mixture. A solution of 2 (6.2 g, 16.4 mmol) in dry methanol (100 mL) was treated
with sodium methoxide (30 drops, 1 M in methanol). After 2 hr stirring at room tempera-
ture all acetate groups were removed (6 : 1, CH2Cl2–MeOH), and water (50 mL) and
sodium hydroxide (8 mL, 2 M) were added. After additional 30 min (TLC: 12 : 3 : 3 : 2,

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Lahmann et al.
EtOAc–MeOH–H2O–AcOH), the mixture was neutralised with Dowex 50 (Hþ) ion
exchange resin, filtered, and concentrated to yield sodium (ethyl 1-thio-D-glucopyranosid)-
uronate (3)[13] (4.2 g, 16.1 mmol, 96%). Sodium hydride (340 mg, 60 %, ꢁ2.5 equiv./
OH) was added to a stirred solution of 3 (200 mg, 0.77 mmol) and benzyl bromide
(1.0 mL, 8.4 mmol, ꢁ2.5 equiv./OH) in dry dimethyl sulphoxide (2.2 mL) at 158C
(water bath temperature). The water bath was changed to 208C after the reaction mixture
had turned solid (ca. 15 min) and left for 15 min, when the reaction was quenched by
addition of toluene (35 mL) and water (15 mL). The organic layer was separated, diluted
with ethyl acetate (50 mL), washed with acetic acid (5%, aq.) and brine, dried, concen-
trated, and filtered through silica gel (toluene ! 20 : 1, toluene–ethyl acetate) to give ben-
zyl (ethyl 2,3,4-tri-O-benzyl-1-thio-D-glucopyranosid)uronate (4) (260 mg, 0.43 mmol,
57%) as an a/b mixture. NMR (CDCl3): 13C[11], anomeric mixture, d 14.8, 15.1 (SEt),
24.0, 25.1 (SEt), 67.2, 67.3, 75.6–79.3, 81.2, 81.6, 83.7, 85.8, 85.9 C-1–C-5, CH2Ph),
128.3–128.4, 136.4, 137.8, 138.3 (Ph), 168.2 (C55O). A mixture of 4 (3.6 g, 6.0 mmol)
and NIS (1.35 g, 6.0 mmol) in wet dichloromethane (20 mL CH2Cl2, 0.5 mL H2O) was
treated with a catalytic amount of silver trifluoromethanesulphonate. After 15 min
(TLC: 4 : 1, pentan–ethyl acetate), the mixture was transferred into a separation funnel,
washed with sat. sodium thiosulphate and brine, dried and concentrated. The residue
was purified by silica gel chromatography (toluene ! 10 : 1, toluene–diethyl
ether ! 6 : 1, toluene–ethyl acetate) to give the title compound 5 (2.8 g, 5.1 mmol,
1
85%). NMR (CDCl3): H, anomeric mixture d 3.10 (b, 1H, OH), 3.30–3.95 (m, 3H,
H-2, H-3, H-4), 4.35–5.15 (m, 10H, H-1, H-5, 4 ꢂ CH2Ph), 7.00–7.30 (m, 4, Ph); 13C,
d a-anomer 67.5, 70.8, 73.6, 75.1, 75.8, 79.2, 79.4, 80.8 (C-2–C-5, CH2Ph), 91.7
(C-1), 127.9–128.8, 135.1, 137.7, 137.9, 138.4 (Ph), 168.2 (C55O); b-anomer: 97.8 (C-1).
Benzyl 1-O-trichloroacetimidoyl-2,3,4-tri-O-benzyl-D-glucopyranuronate (6). The
compound was prepared according to the literature.[18] A solution of 5 (800mg,
1.44 mmol), trichloroacetonitrile (1.5 mL, 14.9 mmol) in dry dichloromethane (15 mL) was
treated with sodium hydride (44 mg, 0.11 mmol, 60%). After 30min the reaction was com-
plete (TLC: 2 : 1, pentane–ethyl acetate). The mixture was concentrated and filtered through
silica gel (2 : 1, pentane–ethyl acetate) to obtain 6 (915 mg, 1.31 mmol, 91%, a/b 15 : 1) as a
pale yellow syrup. NMR (CDCl3): 1H, d 3.85 (dd, 1H, J ¼ 3.7 Hz, J ¼ 9.5 Hz), 8.89 (t, 1H,
J ¼ 9.5 Hz), 4.11 (t, 1H, J ¼ 9.5 Hz), 4.50 (m, 2H), 4.77 (m, 3H), 4.86 (d, 1H, J ¼
11.0Hz), 4.98 (d, 1H, J ¼ 11.0 Hz), 5.18, 5.19 (s, 2H), 5.90 (d, 1H, b-H-1, J ¼ 7.0Hz),
6.58 (d, 1H, a-H-1, J ¼ 3.7 Hz), 7.15–7.40 (m, 20H, Ph), 8.65 (s, 1H, NH); 13C, d a-anomer
67.6, 72.9, 73.2, 75.0, 75.5, 75.9, 78.9, 79.0, 80.7 (C-2–C-5, CH2Ph, 22CCl3), 94.1
(C-1), 127.8–128.7, 135.0, 137.7, 127.8, 137.8, 138.4 (Ph), 161.2 (C55NH), 168.2 (C55O).
Benzyl 1-O-[2(S)-6-methoxy-2-naphthyl)propionyl]-2,3,4-tri-O-benzyl-b-D-glu-
copyranuronate (7). A boron trifluoride diethyl etherate solution (250 mL, 50 mL
.
BF3 Et2O in 1 mL CH2Cl2) was added in five portions to a cooled (2308C) solution of
6 (460 mg, 0.66 mmol) and (S)-naproxen (150 mg, 0.65 mmol) in dry dichloromethane
(15 mL). After 1 hr the reaction was complete (TLC: 4 : 1, pentane–ethyl acetate), and
sodium hydrogencarbonate (250 mg) was added. The mixture was allowed to attain
room temperature, diluted with dichloromethane, filtered and concentrated. Purification
on silica gel (20 : 1 ! 8 : 1, pentane–ethyl acetate) gave the pure b-anomer 7 (300 mg,
0.39 mmol, 60%). [a]D 298 (c 0.15, MeOH); NMR (CDCl3): 1H, d 1.62 (d, 3H,
J ¼ 6.7 Hz), 3.59 (t, 1H, J ¼ 8.2 Hz), 3.71 (t, 1H, J ¼ 8.9 Hz), 3.78–3.93 (m, 2H), 3.91
(s, 3H), 4.07 (d, 1H, J ¼ 9.2 Hz), 4.41 (d, 1H), 4.48 (d, 1H), 4.58 (d, 1H), 4.65 (d, 1H),

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Synthesis of Urine Drug Metabolites
129
4.70 (d, 1H), 4.80 (d, 1H), 5.11 (s, 2H), 5.70 (d, 1H, b-H-1, J ¼ 7.3 Hz), 6.50–7.14
(m, 6H), 7.20–7.40 (m, 21H), 7.62–7.68 (m, 3H) 18.5 (Me), 45.6 (CH), 55.5 (OMe);
13C, d 18.5, 45.6, 55.5 (OCH3), 67.6, 74.9, 75.1, 75.2, 75.8, 79.3, 80.5 (C-2–C-4,
CH2Ph), 84.0 (C-5), 94.3 (C-1), 105.7, 119.2, 126.4–129.5, 134.0, 134.5, 135.1, 137.7,
137.9, 138.2, 157.9 (Ph) 168.2, 173.0 (C55O). Anal. Calcd for C48H46O9 H2O: C, 73.5;
H, 6.2, Found: C, 73.1; H, 6.0.
1-O-[2(S)-(6-Methoxy-2-naphthyl)propionyl]-b-D-glucopyranuronic acid (8).[20,21]
A mixture of 7 (290 mg, 0.38 mmol) and palladium on activated carbon (10%, 30 mg) in
ethyl acetate (20 mL) was degassed and set under a hydrogen atmosphere. The hydrogeno-
lysis was carried out at atmospheric pressure over night. The suspension was filtered through
a plug of Celite, which was washed with ethyl acetate (100 mL). After concentration, the
residue was dissolved in water (10 mL) and washed with diethyl ether (2 ꢂ 10 mL).
1
Freeze-drying of the water phase gave 8 (152 mg, 0.38 mmol, 99 %). NMR (D2O): H,
1.57 d (d, J ¼ 6.7Hz, 3H), 3.40–3.60 (m, 3H), 3.85–4.15 (m, 5H), 5.60 (d, b-H-1,
J ¼ 7.9Hz), 7.30–7.50 (m, 3H), 7.75–7.85 (m, 3H);[21] 13C, d 18.0 (Me), 44.9 (CH), 54.7
(OMe), 66.0, 71.2, 71.9, 75.3 (C-2–C-5), 94.1 (C-1), 105.6, 118.8, 126.0 (2ꢂ),
127.3, 128.7, 129.2, 133.4, 134.6, 157.0 (Ph) 171.7, 175.0 (C55O); MS-FAB [M þ H]: 411.
2(S)-(6-Benzyloxycarbonyloxy-2-naphthyl)propionic acid (12). 2(S)-(6-Hydroxy-
2-naphthyl) propionic acid (9)[21] (600 mg, 2.8 mmol) was dissolved in a solution of butyl-
dimethylsilyl chloride (840 mg, 5.6 mmol) in pyridine (3 mL) and dichloromethane
(10 mL) at room temperature. After 30 min the silyl ester was formed according to TLC
(9 : 1, toluene–ethyl acetate), and benzyl chloroformate (1.2 mL, 8.4 mmol) was added.
To complete the conversion, an additional portion benzyl chloroformate (0.6 mL,
4.2 mmol) was added after 30 min. After 1 hr, the reaction mixture was diluted with
dichloromethane (30 mL), washed with water (2 ꢂ 15 mL), dried, and concentrated.
The residue was filtered through a plug of silica gel (CH2Cl2) to cleave any residual
silyl ester and purified by flash silica gel chromatography [2 : 1, pentane–diethyl ether
(cont. 0.5% AcOH)] to give 12 (460 mg, 1.0 mmol, 36%) as long needles (m.p. 157–
1
1588C). NMR: H (CDCl3), d 1.59 (d, J ¼ 7.2 Hz, Me), 3.89 (q, 1H, CH), 5.30 (s, 2H,
Cbz), 7.30–7.83 (11H, Ph, Cbz); 13C (MeOD), d 18.2 (PhMe), 45.4 (CH), 70.6 (Cbz),
118.0, 121.0, 126.4, 126.7, 128.4, 128.7, 128.8, 128.9, 129.6, 131.6, 133.0, 134.9, 137.4
(Ph, Cbz), 148.9 (Cbz), 153.8 (Ph), 180.4 (COOH). MALDI-TOF MS: Calcd for
C21H18O5 351.1154 [M]; Found 376.16 [M þ Na]þ, 389.15 [M þ K]þ. HRMS: Calcd
for C21H19O5 351.1127 [M þ H]þ; Found 351.125 [M þ H]þ.
Benzyl 1-O-[2(S)-(6-benzyloxycarbonyloxy-2-naphthyl)propionyl]-2,3,4-tri-O-
benzyl-b-D-glucopyranuronate (13). A solution of 6 (500 mg, 0.72 mmol) and 12
(200 mg, 0.57 mmol) in dry dichloromethane (15 mL) was cooled (2308C). A 250 mL
.
of a boron trifluoride diethyl etherate solution in dichloromethane (50 mL BF3 Et2O in
1 mL CH2Cl2) was added in five portions. After 1 hr the reaction was complete (TLC:
6 : 1, pentane–ethyl acetate), and sodium hydrogencarbonate (250 mg) was added. The
mixture was allowed to attain room temperature, diluted with dichloromethane, filtered,
and concentrated. Purification on silica gel (20 : 1 ! 6 : 1, pentane–ethyl acetate) gave
the pure b-anomer 13 (340 mg, 0.38 mmol, 67%). [a]D 2128 (c 1.03, CH2Cl2); NMR
(CDCl3): 1H, d 1.59 (d, J ¼ 7.2 Hz, Me), 3.57 (t, J ¼ 8.7 Hz, 1H, H-2), 3.70
(t, J ¼ 8.7 Hz, 1H, H-3), 3.81 (t, J ¼ 9.6 Hz, 1H, H-4), 3.87 (q, 1H, CH), 4.07, 4.41,
4.49, 4.60, 4.77, 5.10, 5.30 (CH2Ph), 5.69 (d, J ¼ 7.5 Hz, 1H, H-1), 7.06–7.76 (m, 31H,
Ph, Cbz); 13C, d 18.5 (PhMe), 45.6 (CH), 67.5, 70.6, 74.8, 75.0, 75.6, 79.2, 80.5, 84.0, 94.3

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130
Lahmann et al.
(C-1), 117.8, 121.0, 126.6–129.6, 131.5, 135.0, 134.9, 137.0, 137.7, 137.8, 138.2 (Ph,
Cbz), 148.9 (Cbz), 153.8 (Ph), 168.2, 172.6 (C55O). MALDI-TOF MS: Calcd for
C55H50O11 886.34 [M]; Found 909.66 [M þ Na]þ, 925.30 [M þ K]þ. HRMS: Calcd for
C55H50O11Na 909.3245 [M þ Na]þ; Found 909.288 [M þ Na]þ.
1-O-[2(S)-(6-Hydroxy-2-naphthyl)propionyl]-b-D-glucopyranuronic acid (14).[20,21]
A mixture of 13 (340mg, 0.38mmol) and palladium on activated carbon (10%, 30mg) in
ethyl acetate (20 mL) was degassed and set under a hydrogen atmosphere. The hydroge-
nolysis was carried out at atmospheric pressure over night. The suspension was filtered
through a plug of Celite, which was washed with ethyl acetate (100 mL). After concen-
tration, the residue was dissolved in water (10 mL) and washed with diethyl ether
(2 ꢂ 10 mL). Freeze-drying gave 14 (150 mg, 0.38 mmol, 99%). [a]D þ 1458 (c 0.4,
1
H2O); NMR (D2O, 258C): H, d 1.56 (d, J ¼ 7.3 Hz, Me), 3.57 (t, J ¼ 8.7 Hz, 1H),
3.50–3.68 (m, 2H), 4.07 (m, 2H), 5.63 (d, J ¼ 8.0 Hz, H-1), 7.14 (dd, 1H, PhH), 7.19
(d, 1H, PhH), 7.41 (dd, 1H, PhH), 7.71 (m, 3H, PhH).21 13C, d 17.5 (CH3), 45.0 (CH),
71.1, 71.7, 75.2 (C2, C3, C4, C5), 94.1 (C1), 109.2, 118.6, 126.3, 126.5, 127.2, 129.9,
133.8, 134.8, 153.8 (Ph), 175.8 (C55O).
Benzyl 1-O-indoprofenyl-2,3,4-tri-O-benzyl-b-D-glucopyranuronate (15). A sol-
.
ution of boron trifluoride diethyl etherate in dichloromethane (110 mL BF3 Et2O in
1 mL CH2Cl2) was added in five portions to a cooled (2308C) solution of 6 (200 mg,
0.28 mmol) and racemic indoprofen (100 mg, 0.36 mmol) in dry dichloromethane221,4-
dioxane (5 : 1, 10 mL) under argon. Stirring was continued over night, while the mixture
slowly attained room temperature TLC: 2 : 1, pentane–ethyl acetate. The reaction mixture
was diluted with dichloromethane (10 mL) and neutralized by addition of 10% sodium
hydrogencarbonate (20 mL). The organic layer was separated, dried and concentrated.
Purification on silica gel (20 : 1 ! 8 : 1, pentane–ethyl acetate) gave 13 (150 mg,
0.15 mmol, 54%, a , 3%) as a diastereomeric mixture (1 : 1). NMR (CDCl3, diastereo-
1
meric mixture), H, d 1.55 (d, 3H, Me), 3.44–3.94 (m, 5H, H-2–H-5, CH), 4.00–4.90
(m, 8H, CH2Ph, CH2N), 5.15 (d, 2H, CH2Ph), 5.86, 5.70 (d, J ¼ 8.2 Hz, 1H, H-1, diaster-
eomers), 6.90–7.89 (28H, Ph); 13C, d 18.2, 18.4 (Me), 45.0, 45.1 (CH), 50.5, 50.8 (CH2N),
67.6, 67.7, 74.5, 74.9, 75.1, 75.2, 75.8, 75.9, 79.1, 79.3, 80.5, 80.6, 83.7, 84.0 (CH2Ph,
C-2–C-5), 94.3, 94.5 (C-1), 119.5, 119.6, 122.7, 122.8, 124.3, 124.4, 127.4–128.8,
132.3–140.2 (Ph), 167.6, 167.7, 168.3, 168.4, 172.8 (C55O). Anal. Calcd for
C51H47NO9: C 74.9, H 5.8, N 1.7; Found: C 74.6, H 5.9, N 1.8.
1-O-Indoprofenyl-b-D-glucopyranuronic acid (16). A mixture of 15 (60 mg,
73 mmol) and palladium on activated carbon (10%, 50 mg) in ethyl acetate-DMF (9 : 1,
10 mL) was degassed and set under a hydrogen atmosphere for 7 hr at atmospheric press-
ure. The suspension was filtered through a plug of Celite, washed with ethyl acetate
(100 mL). After concentration, the residue was dissolved in water (10 mL) and washed
with diethyl ether (2 ꢂ 10 mL). Freeze-drying gave 16 (30 mg, 63 mmol, 87%) as a dia-
1
stereomeric mixture (1 : 1). NMR (MeOD, diastereomeric mixture), H, d 1.52, 1.54
(d, 3H, Me, diastereomers), 3.32–3.58 (m, 3H), 3.90 (m, 2H), 5.00 (s, 2H), 5.51, 5.52
(d, J ¼ 7.8 Hz, H-1), 7.42 (m, 4H), 7.57 (t, 1H), 7.67 (m, 2H), 7.84 (m, 3H); 13C, d
19.2, 19.3 (Me), 46.1, 46.2 (CH), 52.6 (CH2N), 73.1, 73.7, 75.6, 75.7 (C-2–C-5), 96.0
(C-1), 121.7, 121.8, 124.3, 124.7, 129.6, 133.7, 133.9, 138.3, 139.7, 142.5 (Ph), 169.9,
174.7, 174.9 (C55O). MS-FAB [M þ H]: 458.
Benzyl 1-O-carboxymefloquine-2,3,4-tri-O-benzyl-D-glucopyranuronate (17).
Carboxymefloquine (30 mg, 97 mmol) was dissolved in a small amount of dry THF

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Synthesis of Urine Drug Metabolites
131
(ꢁ 75 mL) and 6 (74 mg, 107 mmol) dissolved in dichloromethane (500 mL), was added.
The mixture was cooled (08C) before 50 mL of a boron trifluoride diethyl etherate solution
.
in dichloromethane (50 mL BF3 Et2O in 1 mL CH2Cl2) was added under argon. After
10 min, 6 was consumed (TLC: 4 : 1, toluene–ethyl acetate) and Et3N (50 mL) was
added. After concentration the crude material was purified on silica gel (9 : 1, toluene–
ethyl acetate) to give 17 (49 mg, 58 mmol, 60%) as an anomeric mixture (a/b 1 : 3).
NMR (CDCl3, anomeric mixture): 1H, d 5.97 (d, J ¼ 6.6 Hz, bH-1), 6.62 (d, J ¼ 3.3 Hz,
aH-1); 13C, d 67.8, 67.9, 73.4, 74.1,75.1, 75.4, 75.5, 75.7, 76.0, 78.5, 78.9, 79.0, 80.1,
81.0, 83.7, 92.5 (aC-1), 95.0 (bC-1), 118.5, 119.2, 127.7, 129.9, 128.0–129.9, 134.8,
136.0, 137.2–138.0 (Ph), 162.9, 163.5, 168.3, 168.4 (C55O). MALDI-TOF MS: Calcd
for C46H37F6NO8 845.24 [M]; Found 868.13 [M þ Na]þ, 884.04 [M þ K]þ. HRMS:
Calcd for C46H37F6NO8Na 868.2316 [M þ Na]þ; Found 868.211 [M þ Na]þ.
1-O-Carboxymefloquine D-glucopyranuronic acid (18). A mixture of 17 (220 mg,
0.26 mmol) and palladium on activated carbon (5%, 20 mg) in ethyl acetate (10 mL) was
degassed and set under hydrogen atmosphere for 5 hr at atmospheric pressure. The suspen-
sion was filtered through a plug of Celite, washed with ethyl acetate (100 mL). After con-
centration, the residue was dissolved in water (10 mL) and washed with diethyl ether
(2 ꢂ 10 mL). Freeze-drying gave 18 (115 mg, 0.24 mmol, 91%, a/b 1 : 2). NMR
1
(acetone-d6, anomeric mixture): H, d 3.6–4.2 (m, 4H H-2–H-5), 6.01 (d, J ¼ 7 Hz,
bH-1), 6.62 (sb, aH-1), 8.05 (m, 1H), 8.36 (m, 1H), 8.55 (18a, J ¼ 5.1 Hz) and 8.58
(18b, J ¼ 5.1 Hz) (d, 1H), 9.10 (m, 1H); 13C, d 72.3, 73.0, 73.1, 73.9, 75.0 (C-2–C-5),
96.3 (aC-1), 97.7 (bC-1), 120.7, 121.0, 121.4, 124.0, 124.1, 128.0–132.2, 139.2, 140.1,
145.8, 149.2, 149.5, 165.0, and 165.2 (C55O). MALDI-TOF MS: Calcd for
C18H13F6NO8 485.05 [M]; Found 486.8 [M þ H]þ, 508.8 [M þ Na]þ.
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Received June 24, 2003
Revised December 9, 2003
Accepted January 16, 2004

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