Efficient synthesis of 1β-O-acyl glucuronides via selective acylation of allyl or benzyl d-glucuronate

Article abstract of DOI:10.1016/j.tet.2007.05.050

Acyl glucuronides are key metabolites for many carboxylic acid-containing drugs, notably those of the non-steroidal anti-inflammatory class. In the processes of drug safety assessment and new drug development, it is essential that acyl glucuronides, if formed in vivo, should be made conveniently available for bioevaluation. We recently showed that selective acylation of allyl glucuronate is a promising method for the synthesis of these metabolites in good yield and with excellent β-anomeric selectivity. We now give fuller details of the allyl ester method and further report that benzyl glucuronate performs at least equally well in the acylation step, offering the advantage of very mild deprotection by catalytic transfer (or conventional) hydrogenation. Depending on the compatibility of other functional groups, as discussed below, this will be the method of choice for many acyl glucuronide syntheses. The value of the method is demonstrated in particular by the synthesis of several acyl glucuronides that are known metabolites of important drugs.

Full text of DOI:10.1016/j.tet.2007.05.050

Tetrahedron 63 (2007) 7596–7605
Efficient synthesis of 1b-O-acyl glucuronides via selective
acylation of allyl or benzyl D-glucuronate
Elizabeth R. Bowkett,a John R. Harding,b James L. Maggs,c B. Kevin Park,c
Jennifer A. Perriea,y and Andrew V. Stachulskia,
*
aThe Robert Robinson Laboratories, Department of Chemistry, University of Liverpool, Liverpool L 69 7ZD, UK
bAstraZeneca UK Ltd, Drug Metabolism and Pharmacokinetics Department, Mereside, Alderley Park,
Macclesfield, Cheshire SK10 4 TG, UK
cDepartment of Pharmacology and Therapeutics, University of Liverpool, Liverpool L69 3GE, UK
Received 8 March 2007; revised 25 April 2007; accepted 10 May 2007
Available online 17 May 2007
Abstract—Acyl glucuronides are key metabolites for many carboxylic acid-containing drugs, notably those of the non-steroidal anti-inflam-
matory class. In the processes of drug safety assessment and new drug development, it is essential that acyl glucuronides, if formed in vivo,
should be made conveniently available for bioevaluation. We recently showed that selective acylation of allyl glucuronate is a promising
method for the synthesis of these metabolites in good yield and with excellent b-anomeric selectivity. We now give fuller details of the allyl
ester method and further report that benzyl glucuronate performs at least equally well in the acylation step, offering the advantage of very mild
deprotection by catalytic transfer (or conventional) hydrogenation. Depending on the compatibility of other functional groups, as discussed
below, this will be the method of choice for many acyl glucuronide syntheses. The value of the method is demonstrated in particular by the
synthesis of several acyl glucuronides that are known metabolites of important drugs.
Ó 2007 Elsevier Ltd. All rights reserved.
1. Introduction
important phase 2 metabolites for a wide range of carboxylic
acid-containing drugs, notably those of the non-steroidal
anti-inflammatory class.3 In a number of cases AGs have
been implicated in adverse side effects of such drugs,4,5
but direct evidence is lacking.
Glucuronidation is a vital phase 2 metabolic (conjugative)
process by which a wide range of drugs and other xeno-
biotics may be rendered water-soluble, detoxified and ex-
creted. While O-glucuronides of alcohols and phenols are
well known and generally behave as stable organic mole-
cules,1,2 acyl (ester) glucuronides (AGs) of carboxylic acids
are potentially reactive metabolites. In particular, AGs are
AGs may react (Scheme 1) as acylating agents, by hydrolysis
or direct displacement with other nucleophiles, such as those
present in body proteins (Pathway 1), or by acyl migration
O
Nu
R
OH
O
Pathway 1
Nu-H
HO
+
O
OH
HO
OH
O
HO
O
HO
HO
O
R
HO
O
Pathway 2
Acyl migration
O
O
OH
OH
4
4
R'-NH2
OH
O
HO
HO
3
3
OH
NH-R'
RCO2
RCO2
with
rearrangement
2
2
O
HO
(also 2- and 4-acyl
isomers)
Scheme 1. Reactivity of acyl glucuronides.
* Corresponding author. Tel.: +44 (0) 151 7943542; fax: +44 (0) 151 7943588; e-mail: stachuls@liv.ac.uk
Present address: Astra Zeneca, SPP4, Macclesfield Works, Silk Road Business Park, Macclesfield, Cheshire SK10 2NA, UK.
y
0040–4020/$ - see front matter Ó 2007 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tet.2007.05.050

E. R. Bowkett et al. / Tetrahedron 63 (2007) 7596–7605
7597
followed by condensation with amines (Amadori rearrange-
ment, Pathway 2).5 The acyl rearrangement process has been
studied in detail by NMR spectroscopy.6,7 In a recent per-
spective, the chemistry and biology of AGs has been re-
viewed in detail, examining in particular their potential as
reactive metabolites.8
alkylation of 3 with allyl or benzyl bromide in DMF gave
good (up to 76%) yields of crystalline 1 or 2, after chroma-
tography. Originally DBU was the base used in the prepara-
tion of 1 but we found it very difficult to remove all the DBU
residues. A resin-bound fluoride11 (Aldrich art. 387789) was
an effective base for either 1 or 2. Use of TBAF was also pos-
sible; this led to products containing variable amounts of
glucuronolactone, which were very largely removed by
chromatography.14 Recrystallisation of 1 from methanol
gave highly pure product; this was not possible for 2, but
small amounts (viz. 5%) of glucuronolactone did not inter-
fere with the following acylation step. Benzyl chloride did
not react satisfactorily, even with iodide catalysis.
In order to assess the biological activity and potential toxic-
ity of AGs, it is essential that they should be synthesised in
pure form, and especially as single 1b-anomers, for evalua-
tion. This is equally important for ongoing assessment of
recognised drugs and the development of new ones. Methods
for the synthesis of AGs have been reviewed.2,8 The prefer-
O
O
O
Br
OR
OR
OR
O
O
O
HO
HO
HO
HO
HO
O
CH2Ph
O
HO
OH
HO
HO
HO
O
O
1 R = CH2CH=CH2 (75%)
2 R = CH2Ph (58–76%)
3 R = H
8b R = CH2Ph
8d R = H
5c R = CH2CH=CH2
5d R = H
ence now is for syntheses using minimal rather than global
sugar protection, one of the most useful intermediates being
allyl glucuronate 1. Mitsunobu coupling of 1 with a range of
carboxylic acids followed by Pd(0) deprotection was shown
to be a viable method9 for the preparation of a range of AGs.
Yields were modest, however, and a/b mixtures were invari-
ably generated in the coupling step, requiring careful separa-
tion by preparative HPLC.9,10
2.2. Acylation step
The advantage of the selective acylation method (Scheme 2)
using 1 was explained previously.11a,b The kinetic anomeric
effect was exploited to greatly favour 1b-acylation through
the stereoelectronic enhancement of the nucleophilicity of
the 1b-alkoxide. There was some precedent in an earlier
report of the selective 1b-acylation of glucose derivatives
using activated esters.11c After considerable experimenta-
tion with different carboxyl activators and bases, we found
that the combination of HATU for carboxyl activation and
N-methylmorpholine (NMM) as base gave best results for
the acylation of 1. Bases weaker or stronger than NMM
were less effective. This method was successfully applied
to the selective acylation of 2 with a range of carboxylic
acids 4a–14a (Fig. 1 and Scheme 2), affording products
4b–14b with the yields given in Table 1. Where available
the direct comparison with the result when using 1,11 yield-
ing allyl esters 5c, 7–9c, 11c and 12c, is given.
Recently we showed11 that selective acylation of 1 was an
excellent alternative to the Mitsunobu procedure, affording
higher yields and essentially pure b-products (Scheme 2).
One drawback, when 1 was used, was the persistence of
Pd traces in the final products after deprotection of the allyl
ester using Pd(0) reagents.9,12 This is not a major concern for
the preparation of analytical standards, but would prohibit
biological evaluation of material prepared in this way. While
a resin-bound form of the reagent11 greatly reduced the Pd
levels, the use of a different ester seemed to us a promising
solution to the problem. We now give full details of the se-
lective acylation method using allyl ester 1 and report the
preparation and use of benzyl glucuronate 2 in this method.
An alternative uronium reagent, TBTU, gave a lower yield
(entry 7) but, in view of its significantly lower cost compared
to HATU, it may be regarded as a satisfactory alternative.
Yields with the DIC–HOBt combination11 (not tabled
here) were about 20% lower than with HATU. In cases
where there is a direct comparison, 2 performs at least as
well as 1, often giving a cleaner reaction. Selectivity for
the b-anomer was essentially complete by 1H NMR (at least
19:1 b/a, typically <2% a-anomer). Characteristic NMR
signals for the desired b-products are dH 5.5–6.0 (1H, d,
J¼7.5–8 Hz) for the anomeric proton and dC w95 for the
anomeric carbon.
O
O
OR1
OR1
R2CO2H
O
O
HO
HO
HO
HO
R2
O
HATU, NMM
MeCN, 20 °C
OH
HO
HO
O
1 R1 = CH2CH=CH2
2 R1 = CH2Ph
Scheme 2. 1b-Acyl glucuronide synthesis by selective acylation.
2. Discussion
A range of substituted benzoic acids 4a–6a (entries 1–4)
gave nearly identical yields, e.g., 4-bromobenzoic acid 5a,
which we used extensively11 in earlier studies with allyl ester
1. p-Toluic acid 6a reacted a little more slowly and here
3 equiv of NMM was desirable. The o-substituted acid 7a,
entry 4, gave just as good a result, suggesting that steric
2.1. Glucuronate esters
Previously 2 was prepared by a three-step synthesis from
D-glucuronic acid 3.13 We found that direct base-catalysed

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E. R. Bowkett et al. / Tetrahedron 63 (2007) 7596–7605
Table 1. Acyl glucuronide Bn esters 4b–14b by selective acylation of 2a,b
CO2R
CO2R
Br
Entry Carboxylic
acid
HATU, Yield Product Yield (%) Product
NMM (%)
(equiv)
CO2R
from 1
X
1
2
3
4
5
6
7
8
4-Chlorobenzoic 4a 1, 3
62 4b
4a, b, c, d X = Cl
5a, b, c, d X = Br
6a, b, d X = Me
7a, b, c, d
8a, b, c,d
4-Bromobenzoic 5a 1, 2
4-Methylbenzoic 6a 1, 3
2-Bromobenzoic 7a 1, 2
62 5b
58 6b
65 7b
63 8b
82 8b
46 8b
68 9b
67 10b
55 11b
60 12b
20 13b
40 14b
56e 14b
59
5c
52
66
7c
8c
Phenylacetic 8a
Phenylacetic 8a
Phenylacetic 8a
Ibuprofen 9a
1, 2
1, 3
1c, 2
1, 3
1, 2
Me
Me
CO2R
CO2R
65
9c
MeO
9
Naproxen 10a
10
11
12
13
14
Mycophenolic 11a 1, 3
44
52
11c
12c
10a, b, d
9a, b, c, d
Zomepirac 12a
Diclofenac13a
Valproic 14a
Valproic 14a
1, 3
Me
1, 2
O
Me
N
1, 2d
1e, 2
MeO
CO2R
O
RO2C
Cl
Comparable yields from allyl ester 1 are shown where available.
Me
a
General conditions: all reagents were combined and stirred at 20 ꢀC in
anhydrous acetonitrile for 3–4 h; workup was achieved by addition of
Amberlite IR-120 followed by brief stirring, filtration and evaporation.
Except for entry 14, the b/a ratio of the product was >19:1 (1H NMR).
Using TBTU (1 equiv), rather than HATU, with NMM (2 equiv).
Using DABCO (2 equiv) as base and adding 2 lastly.
OH
11a, b, c, d
O
12a, b, c,d
CO2R
b
c
d
e
CO2R
NH
Cl
Cl
Using 1 equiv acid chloride of 14a and 2 equiv NMM, rather than 14a and
HATU; product was 9:1 b/a.
13a, b, d
14a, b, d
diazabicyclo[2,2,2]octane (DABCO),
a stronger base
O
O
OCH2CH=CH2
OCH2Ph
(pKa¼8.5 vs 7.4 for NMM), is superior to NMM. It is neces-
sary to add 2 slowly to a solution of the other reagents in this
case to prevent its self-condensation. In this case we also
studied the reaction of the acid chloride of 14a with NMM
as base (entry 15); this procedure gave a better yield of
14b (56%) but with some loss of selectivity, 10% of the a-
O
O
HO
HO
HO
HO
c, R =
O
a, R = H b, R =
O
HO
HO
O
OH
O
HO
O
d, R =
HO
HO
1
anomer (d 6.3, d, J¼3.5 Hz) being detected by H NMR,
Figure 1. Carboxylic acids used in this study and their acyl glucuronide
derivatives.
and a confirmatory close-eluting peak of equal mass was
observed by LC–MS.18
2.3. Deprotection
hindrance is relatively unimportant. The reaction of phenyl-
acetic acid 8a using 3 equiv of NMM, entry 6, gave an excel-
lent yield, the highest seen for a reaction of 1 or 2 so far.
Among other examples, the important drugs ibuprofen 9a,
naproxen 10a, mycophenolic acid 11a and zomepirac 12a
all react well (entries 8–11). In the cases of 9a and 10a single
(2S) enantiomers of the starting acids were used; as noted
previously,11 some epimerisation occurs in the acylation
step. The major diastereoisomers of the products 9b and
10b were isolated and we assume these still have the (2S)
configuration. Phenolic protection of 11a was not necessary,
but the yield here should be regarded as unoptimised. Zome-
pirac 12a is a significant case as its AG has an in vitro half-
life of only 0.45 h (pH 7.4, 37 ꢀC)15 and allergic reactions
have led to its withdrawal from the market.16 Recent inves-
tigations17 have suggested that reactive oxidative metabo-
lites and thioester intermediates as well as the AG of 12a
might haptenate proteins and thereby contribute to the initi-
ation of drug-induced anaphylaxis.
We then addressed the question of deprotection, Scheme 3,
bearing in mind that the method should ideally be suffi-
ciently robust to tolerate a range of functionalities in the
carboxylic acid.
O
O
OH
O
H2 or
O
O
HO
HO
HO
HO
O
R
O
R
10% Pd-C
Solvent
HO
4b-6b and 8b-14b
Scheme 3. Deprotection of benzyl ester intermediates.
HO
O
O
4d-6d and 8d-14d
Various conditions were studied for the hydrogenolysis of
benzyl esters. Using the benzyl ester 8b of the acyl glucuro-
nide of phenylacetic acid (Table 2) as a model, we were
pleased to find that catalytic transfer hydrogenation using
cyclohexa-1,4-diene (10% Pd–C, THF+iPrOH, 60 ꢀC,
1.5 h) afforded the free acyl glucuronide 8d in essentially
quantitative yield, entry 1. As expected, cyclohexene (entry
2) was also a feasible donor but required a higher tempera-
ture (80 ꢀC); 1,2-dihydronaphthalene (entry 3) was too
Two further demanding drug examples were studied.
Diclofenac 13a, entry 12, gives a low yield (20%) with
much unreacted starting material; nevertheless the method
is still preferable to the Mitsunobu procedure9,10 because
of the excellent b/a product ratio. The hindered valproic
acid 14a (entry 13) reacts very slowly and here 1,8-
i
slow to be useful. Traditional hydrogenation in PrOH:

E. R. Bowkett et al. / Tetrahedron 63 (2007) 7596–7605
Table 2. Deprotection of benzyl esters 4b–6b and 8b–14b, Scheme 3
7599
Entry
Acyl glucuronide Bn ester
Hydrogenation
method (see below)
Reaction time (h)
Isolated acyl
glucuronide yield (%)
Product
1
2
3
4
5
6
7
8
Phenylacetic 8b
Phenylacetic 8b
Phenylacetic 8b
4-Chlorobenzoic 4b
4-Methylbenzoic 6b
4-Bromobenzoic 5b
Ibuprofen 9b
Aa
Bb
Cc
A
A
A
1.5
5
4
4.5
1.5
20
2
2
2
4
2
100
100
Low yield
95d
8d
8d
8d
4d
6d
5d
9d
10d
11d
12d
13d
14d
100
0e
A
100
100
95d
100
100
100
Naproxen 10b
A
9
Mycophenolicf 11b
Zomepirac 12b
Diclofenac 13b
Valproic 14b
Ag
A
10
11
12
A
A
3
a
Method A: using cyclohexa-1,4-diene (1 mL) as donor with 10% Pd–C (10% w/w), see Section 4. Conventional hydrogenation with H2 at 1 atm, other
conditions being the same, gave a similar result.
b
c
d
e
f
Method B: as method A but using cyclohexene as donor, heated for 5 h at 80 ꢀC.
Method C: using 1,2-dihydronaphthalene as donor, see text.
Purification using reverse-phase chromatography (see text and Section 4) was desirable.
Loss of Br observed (NMR, MS): the reaction was slow and 20 h were required for full deprotection.
Here it was possible to achieve debenzylation without reduction of the trisubstituted double bond, verified by NMR and LC–MS.
Reaction in ethanol was significantly less clean.
g
THF, 1:1 (10% Pd–C, H2, 1 atm), not tabulated, was also
deprotected, as was 4b. The ketone functionality of 12b
was unaffected.
successful here. Isopropanol was the best solvent, giving
cleaner products than ethanol; addition of some THF (up to
1:1 v/v) was often beneficial for improved solubility. One
slight drawback of catalytic transfer hydrogenation was
that small traces of isopropyl ester (ca. 2% by NMR) were
sometimes seen in the final products if the heating in isopro-
panol was prolonged; such transesterification was not ob-
served when using conventional hydrogenation. For the
same reason ethanol is not recommended in this mode.
Finally, for comparison (see Section 4), we give details of the
deprotection procedure applied to allyl esters 5c and 11c,
using Pd(PPh3)4 or polymer-supported Pd(0) reagent,11 to
afford 4-bromobenzoyl acyl glucuronide 5d and mycophe-
nolic acid acyl glucuronide 11d. The latter was previously
obtained from 11a by enzymatic synthesis followed by
preparative HPLC separation from the co-formed aryl glucu-
ronide.21
In general highly pure product was obtained simply by filtra-
tion, evaporation of solvent and trituration of the residue
with a solvent, ether or dichloromethane (see Section 4). If
necessary, acyl glucuronides may be purified by conven-
tional chromatography eluting with ethanol–dichloro-
methane mixtures, preferably containing a little acetic acid
(as for material prepared by Pd(0) deprotection of an allyl
ester), or by reverse-phase chromatography. Details are
given in Section 4.
3. Conclusions
We have demonstrated an effective and versatile two-step
synthesis of AGs from readily available glucuronate esters
1 and 2 as single 1b-anomers, using the selective acylation
procedure. In the present variation, benzyl glucuronate 2 is
shown to acylate at least as well as allyl glucuronate 1 using
HATU–NMM. With the single exception of diclofenac 13a,
yields in the acylation step are highly satisfactory, in the
range 55–82%. Deprotection is effected under mild condi-
tions, using Pd(0) for allyl esters and catalytic transfer (or
conventional) hydrogenation for benzyl esters; these condi-
tions are compatible with a range of functional groups. The
examples given include AGs of important drug molecules,
some of which are known to have short half-lives in vitro
(<1 h in pH 7.4 buffer at 37 ꢀC). We believe this procedure
will be of great value in the pharmaceutical industry for eval-
uation of potentially reactive AG metabolites.
This method was studied for the other examples prepared in
Table 1, including examples with potentially reactive func-
tionalities (aryl halogens, C]C). In the case of 4-bromoben-
zoic acid derivative 5b (cyclohexa-1,4-diene, 10% Pd–C,
iPrOH, 60 ꢀC, 5 h), entry 6, the corresponding intermediate
was slowly debenzylated together with significant loss of
Br. Other donors, or conventional hydrogenation, were no
more successful. In the 4-chlorobenzoic acid series, how-
ever, entry 5, clean debenzylation of 4b was observed with-
out dechlorination. Addition of 1 equiv acid ion-exchange
resin before hydrogenation was beneficial in this case.
This is an important factor as a number of drugs contain
aryl–Cl bonds. The benzyl ester intermediate 11b from my-
cophenolic acid was also an important test case, since 11a is
widely used (generally as a prodrug ester or the Na salt) in
transplant surgery.19,20 Here (entry 9) no significant reduc-
tion of the trisubstituted C]C double bond was seen. The
zomepirac 12b and diclofenac 13b intermediates, entries
10 and 11, which both contain aryl–Cl bonds, were cleanly
O
OMe
O
AcO
AcO
AcO
Br
15
During the course of this work a new method for AG synthe-
sis has been reported22 via alkylation of an alkali metal salt

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E. R. Bowkett et al. / Tetrahedron 63 (2007) 7596–7605
of the carboxylic acid component with the bromosugar 15.
This yields the fully protected acyl glucuronide in good
yield and high b-selectivity; deprotection to give the free
AG is effected by successive deprotections with enzymes
that are able to operate at pH 5. This is clearly a promising
method although only three examples have been reported
so far.
pure material, removing glucuronolactone traces in
particular.
4.3. Benzyl a,b-D-glucuronate (2)
Benzyl bromide (1.25 mL, 10.5 mmol) was added for over
1 min to a solution of D-glucuronic acid 3 (1.84 g,
10 mmol) in DMF (10 mL) and 1 M TBAF in THF
(11 mL) with stirring at 0 ꢀC. The clear solution was left
for 18 h and allowed to warm to 20 ꢀC, whereupon reaction
i
4. Experimental
was complete by TLC (20% PrOH in CH2Cl2). Solvents
were evaporated followed by azeotroping with toluene
4.1. General experimental methods
(4ꢂ30 mL), then the residue was chromatographed, eluting
i
with 10–20% PrOH in CH2Cl2. Appropriate fractions (de-
All organic solvents were anhydrous and of AR grade.
Vacuum rotary evaporation was carried out at <30 ꢀC.
Analytical thin layer chromatography was performed using
Merck Kieselgel 60 F254 silica plates. Preparative column
chromatography was performed on Merck 938S silica gel.
Reverse-phase chromatography was carried out using
Lichroprep RP-18, 25–40 mm particle size (Merck). Infrared
spectra were obtained either for Nujol mulls in a Perkin–
Elmer RX1 FTIR instrument, or using an FTIR-4100 type
tected by UV and anisaldehyde) were combined and evapo-
rated to afford the anomeric mixture of esters (2) as a foam
(2.23 g); remaining traces of quaternary ammonium salts
were removed by addition of CH2Cl2 to afford a solid that
was filtered, washed with further CH2Cl2 and dried to give
2 as a hygroscopic white solid (1.65 g, 58%). Found: C,
55.0; H, 5.7. C13H16O7 requires C, 54.9; H, 5.5%; nmax
(cmꢁ1, FT) 3000–3600 (br), 1722, 1608, 1590 (both vw),
1498 (w) and 1394 (m); 1H NMR [(CD3)CO+D2O, for
a 1:1 a/b mixture]: 3.29 (0.5H, dd, J¼9.1 and 8.0 Hz,
H-2b), 3.49 (0.5H, dd, J¼9.3 and 3.6 Hz, H-2a), 3.52 (0.5H,
t, J¼9.3 Hz, H-3b), 3.64–3.70 (1H, m, H-4a and b), 3.78
(0.5H, t, J¼9.3 Hz, H-3a), 3.94 (0.5H, d, J¼9.6 Hz,
H-5b), 4.36 (0.5H, d, J¼9.7 Hz, H-5a), 4.62 (0.5H, d,
J¼7.8 Hz, H-1b), 5.20 (0.5H, d, J¼3.6 Hz, H-1a), 5.16–
5.24 (2H, m, PhCH2a and b) and 7.30–7.50 (5H, m, ArH);
13C NMR [(CD3)CO+D2O]: 67.7, 67.8, 72.9, 73.1, 73.3
(2ꢂ), 74.3, 75.8, 77.0, 77.3, 94.2, 98.6, 129.3, 129.4,
129.8, 137.2, 137.3, 170.6 and 171.4; m/z (CI, NH3): 302
(MNH+4, 45%) and 284 (M+, 60%). High-resolution mass
(CI) calculated for C13H20NO7 (MNH+4): 302.12399. Found:
302.12387.
1
A instrument (distinguished by suffix FT). Both H and
13C NMR spectra were recorded for the solvents noted using
either Bruker 250 or 400 MHz instruments (operating at
100 MHz only for 13C spectra) with tetramethylsilane as
internal standard. Mass spectra in the chemical ionisation
(CI) mode were obtained using a VG7070E mass spectrom-
eter. Both low and high-resolution electrospray mode (ES)
mass spectra were obtained using a Micromass LCT mass
spectrometer operating in the +ve or ꢁve ion mode as
indicated. Elemental microanalysis was performed by
Mr. Steve Apter of the Chemistry Department.
4.2. Allyl a,b-D-glucuronate (1)8
A commercial batch of polymer-bound fluoride (Sigma–
Aldrich) was stirred in anhydrous DMF at 20 ꢀC for 2 h,
filtered, washed with ether and air-dried. This product (15 g,
45 mmol) was stirred in anhydrous DMF (90 mL) under
N2 with D-glucuronic acid (5.82 g, 30 mmol) for 3 h, then al-
lyl bromide (3.99 g, 2.86 mL, 33 mmol) was added and the
mixture was stirred at 40 ꢀC for 20 h. The reaction mixture
was filtered and the resin was washed with DMF
(2ꢂ10 mL), then the combined filtrates were evaporated to
dryness to give crude product (5.74 g), which was purified
by chromatography, eluting with EtOAc–iPrOH–H2O,
5:3:1 to afford the ester 18 as a solid of variable mp, which
was an a/b mixture of varying ratios (5.29 g, 75%). Found:
m/z, 252.10829. C9H14NO7 (MNH+4) requires m/z,
252.10832; nmax (cmꢁ1) 3298 (br) and 1746. A batch of
Material prepared in this way typically contained small
quantities of glucuronolactone (ca. 5%), which was difficult
to remove by crystallisation (cf. 1) but did not interfere with
the next step. The use of polymer-bound fluoride, as
described for 1, was also effective (yield of 2, 76%).
4.4. Typical acylation procedure using (1)
4.4.1. Allyl 1-O-(4-bromo)benzoyl-b-D-glucopyranuro-
nate (5c).8 4-Bromobenzoic acid 5a (0.101 g, 0.5 mmol),
allyl glucuronate 1 (0.117 g, 0.5 mmol) and HATU
(0.190 g, 0.5 mmol) were stirred in dry acetonitrile (5 mL)
with N-methylmorpholine (0.110 mL, 0.101 g, 2 equiv) un-
der nitrogen at 20 ꢀC. The reaction was monitored by TLC
(10% EtOH–CH2Cl2) and after 2 h it was quenched by addi-
tion of Amberlyst A-15 (H+, 2 equiv). After evaporation the
residue was chromatographed, eluting with 7% EtOH–
CH2Cl2. Appropriate fractions were pooled and evaporated,
eventually under high vacuum, to afford the title compound
5c as a foam (0.123 g, 59%), with spectroscopic data as
reported.8 Found: C, 46.2; H, 4.1; m/z 438.9992 and
440.9966. C16H17BrO8 requires C, 46.1; H, 4.1%;
C16H1779BrO8Na and C16H1781BrO8Na require 439.0004
and 440.9984, respectively; nmax (cmꢁ1) 3386 (br), 1740,
1725 and 1589; 1H NMR [400 MHz, (CD3)2CO]: 3.63
(2H, m) and 3.72 (1H, m, 20H, 30-H and 40-H), 4.11 (1H, d,
1
a/b¼3:2 showed H NMR [(CD3)2CO]: 3.23 (0.4H, dd,
J¼7.8, 9.2 Hz, 2-Hb), 3.43 (0.6H, dd, J¼3.6, 9.4 Hz,
2-Ha), 4.46 (0.4H, t, J¼9.1 Hz, 4-Hb), 3.63–3.56 (1H, m,
4-Ha+3-Hb), 3.73 (0.6H, t, J¼9.1 Hz, 3-Ha), 3.87 (0.4H,
d, J¼9.7 Hz, 5-Hb), 4.29 (0.6H, dd, J¼0.7 and 9.7 Hz,
5-Ha), 4.58 (0.4H, d, J¼7.8 Hz, 1-Hb), 4.64 (2H, d,
J¼5.4 Hz, OCH2CH]CH2, a and b), 5.16 (0.6H, d,
J¼3.5 Hz, 1-Ha), 5.20 (1H, m, OCH2CH]CH2a and b),
5.37 (1H, m, OCH2CH]CH2a and b) and 5.87–6.00 (1H,
m, OCH2CH]CH2a and b). In some runs it was necessary
to recrystallise the product from methanol to obtain highly

E. R. Bowkett et al. / Tetrahedron 63 (2007) 7596–7605
7601
J¼9.5 Hz, 50-H), 4.63 (2H, m, OCH2CH]CH2), 5.18 and
5.35 (2H, 2m, OCH2CH]CH2),5.81 (1H, d, J¼7.8 Hz,
10-H), 5.91 (1H, m, OCH2CH]CH2), 7.67 and 8.00 (4H,
approx. dd, ArH); 13C NMR [(CD3)CO]: 71.0, 71.1, 72.0,
75.4, 75.8, 94.7, 117.2, 127.8, 128.0, 131.2, 131.5, 131.6,
163.6 and 167.5; m/z (ES+): 439, 441 (MNa+ for 79Br,
81Br, respectively).
m, 20-H+30-H+40-H+CH2Ar), 3.66 (3H, s, CH3O), 3.87
(1H, d, J¼9.5 Hz, 50-H), 4.51 (2H, m, OCH2CH]CH2),
5.10, 5.25 (2H, approx. 2d, CH2CH]CH2), 5.17 (3H, m,
ArCH2O+C]CHCH2Ar), 5.40 (1H, d, J¼8.1 Hz, 10-H)
and 5.85 (1H, m, CH2CH]CH2); 13C NMR [100 MHz,
(CD3)2CO]: 11.86, 15.99, 16.64, 23.60, 33.73, 35.20,
61.79, 66.50, 70.91, 72.97, 73.82, 77.40, 95.51, 107.67,
118.07, 118.76, 123.00, 124.48, 133.42, 134.87, 146.43,
154.45, 164.70, 169.19, 172.53 and 173.22; m/z (ES+): 559
(MNa+, 100%) and 575 (MK+, 5%). Found: m/z, 559.1797.
C26H32O12Na requires MNa+, 559.1791.
Similarly the following compounds were prepared.
4.4.2. 2-Bromobenzoic acid acyl glucuronide, allyl ester
(7c).8 Amorphous white solid. Found: C, 46.3; H, 4.1; m/z
439.0022 and 441.0002. C16H17BrO8 requires C, 46.1; H,
4.1%; C16H1779BrO8Na and C16H1781BrO8Na require
439.0004 and 440.9984, respectively. nmax (cmꢁ1) 3500
(br), 1754, 1720, 1587 and 1564; 1H NMR [200 MHz,
(CD3)2CO]: 3.50–3.80 (3H, 3m, 20H+30-H+40-H), 4.17
(1H, d, J¼9.4 Hz, 50-H), 4.66 (2H, m, OCH2CH]CH2),
5.21 and 5.37 (2H, 2m, OCH2CH]CH2), 5.83 (1H, d,
J¼7.8 Hz, 10-H), 5.85–6.05 (1H, m, OCH2CH]CH2),
7.50–7.60 (2H, m, ArH), 7.75–7.80 and 7.95–8.05 (2H,
2m, ArH); 13C NMR [100 MHz, (CD3)2CO]: 65.9, 72.4,
73.3, 76.9, 77.0, 96.0, 118.1, 122.3, 128.3, 132.6, 132.8,
134.3, 135.2, 164.3 and 168.5; m/z (ES+): 439, 441 (MNa+
for 79Br, 81Br, respectively), also weak 445, 447 (MK+).
4.4.6. Zomepirac acyl glucuronide, allyl ester (12c).
Amorphous white solid. Found: C, 56.3; H, 5.1; N, 2.8;
m/z 530.1219. C24H26ClNO9 requires C, 56.7; H, 5.1; N,
2.8%; C24H26ClNO9Na requires m/z 530.1194; nmax (cmꢁ1
)
3200–3600 (br), 1770, 1750 (sh), 1726, 1613, 1580 and
1550 (sh); 1H NMR [400 MHz, (CD3)2CO]: 1.74 (3H, s, pyr-
role 4-CH3), 3.46, 3.59 and 3.67 (3H, 3m, 20-H+30-H+40-H),
3.72 (3H, s, NCH3), 3.91 (2H, s, ArCH2CO), 4.06 (1H, d,
J¼9.5 Hz, 50-H), 4.68 (2H, m, OCH2CH]CH2), 5.23 and
5.38 (2H, 2 m, OCH2CH]CH2), 5.65 (1H, d, J¼8.1 Hz,
10-H), 5.90–6.00 (1H, m, OCH2CH]CH2), 6.03 (1H, s, pyr-
role 3-H), 7.55 and 7.69 (4H, approx. dd, ArH); 13C NMR
[100 MHz, (CD3)2CO]: 14.87, 33.24, 33.87, 66.55, 72.99,
73.88, 77.56, 77.66, 96.28, 113.74, 118.79, 129.26,
129.85, 130.87, 131.87, 133.48, 134.36, 138.33, 141.22,
169.23, 169.60 and 186.94; m/z (ES+): 530 (MNa+, 100%).
4.4.3. Phenylacetic acid acyl glucuronide, allyl ester (8c).8
Amorphous white solid. Found: C, 57.3; H, 5.8; m/z
375.1073. C17H20O8 requires C, 58.0; H, 5.7%; C17H20-
O8Na requires m/z 375.1056; nmax (cmꢁ1) 3396 (br),
4.5. Typical acylation procedure using (2)
1
1750, 1728 and 1550; H NMR [(CD3)2CO]: 3.46, 3.58
and 3.68 (3H, 3m, 20-H+30-H+40-H), 3.76 (2H, s,
ArCH2CO), 4.04 (1H, d, J¼9.6 Hz, 50-H), 4.65 (2H, m,
OCH2CH]CH2), 5.21 and 5.37 (2H, 2m, OCH2CH]CH2),
5.61 (1H, d, J¼8.1 Hz, 10-H), 5.90–6.00 (1H, m,
OCH2CH]CH2) and 7.25–7.35 (5H, m, ArH); 13C NMR
[100 MHz, (CD3)2CO]: 41.5, 66.5, 73.0, 73.9, 77.5, 95.9,
118.8, 128.2, 129.6, 130.6, 130.8, 133.4, 135.2, 169.2 and
171.2; m/z (ES+): 375 (MNa+, 100%).
4.5.1. Benzyl 1-O-(2-phenyl)acetyl-b-D-glucopyranuro-
nate (8b). Phenylacetic acid 8a (0.068 g, 0.5 mmol), benzyl
glucuronate 2 (0.142 g, 0.5 mmol) and HATU (0.190 g,
0.5 mmol) were stirred in dry acetonitrile (5 mL) with N-
methylmorpholine (0.110 mL, 0.101 g, 1 mmol) under nitro-
gen at 20 ꢀC. The reaction was monitored by TLC (10%
EtOH–CH2Cl2, Merck Kieselgel analytical plates) and after
2 h workup as described for 5c but using Amberlite IR-120H
resin gave 8b as a white solid (0.165 g, 82%); mp 119–
120 ꢀC. Found: C, 60.2; H, 5.3. C21H22O8$H2O requires C,
60.0; H, 5.7%; nmax (cmꢁ1, FT) 3100–3600 (br), 1757 (sh),
1730, 1643 and 1496; 1H NMR [400 MHz, (CD3)2CO]:
3.46, 3.59, 3.69 (3H, 3t, J¼9–9.5 Hz, 2-H, 3-H and 4-H),
3.74 (2H, s, ArCH2CO), 4.08 (1H, d, J¼9.6 Hz, 5-H),
4.66–4.76 (3H, m, D2O exch., 3ꢂOH), 5.21 (2H, s,
PhCH2O), 5.61 (1H, d, J¼8.1 Hz, 1-H) and 7.25–7.43
(10H, m, ArH); 13C NMR [400 MHz, (CD3)2CO]: 41.0,
67.3, 72.7, 73.5, 77.1, 77.2, 95.5, 127.8, 128.9, 129.0,
129.2, 129.3, 130.4, 134.8, 136.8, 169.0 and 170.1; m/z
(ES+): 425 (MNa+, 100%), 827 (2MNa+). High-resolution
mass (EI) calculated for C21H22O8Na (MNa+): 425.1212.
Found: 425.1212.
4.4.4. (2S)-Ibuprofen acyl glucuronide, allyl ester (9c).
White solid, mp 123–124 ꢀC. Found: C, 62.6; H, 7.1;
m/z 445.1826. C22H30O8 requires C, 62.6; H, 7.1%;
C22H30O8Na requires m/z 445.1838; nmax (cmꢁ1) 3200–
3600 (br), 3538, 1744, 1720 (sh), and 1515; 1H NMR
[(CD3)2CO]: 0.90 (6H, d, J¼6.6 Hz, (CH3)2CH), 1.46 (3H,
d, J¼7.2 Hz, CH3CHAr), 1.86 (1H, m, (CH3)2CH), 2.46
(2H, d, J¼7.2 Hz, CHCH2Ar), 3.45, 3.63 and 3.83 (4H,
3m, 20-H+30-H+40-H+ArCHCH3), 4.03 (1H, d, J¼9.4 Hz,
50-H), 4.64 (2H, m, OCH2CH]CH2), 5.19 and 5.34 (2H,
2m, OCH2CH]CH2), 5.62 (1H, d, J¼8.2 Hz, 10-H), 5.92
(1H, m, OCH2CH]CH2), 7.13 and 7.26 (4H, approx. dd,
ArH); 13C NMR [100 MHz, (CD3)2CO]: 19.6, 23.1, 31.1,
45.9, 66.5, 73.0, 73.8, 77.5, 95.9, 118.6, 118.8, 128.6,
130.5, 133.5, 139.0, 141.6, 169.1 and 174.1; Mass spec.
(ES+): m/z 445 (MNa+, 100%), 867 (weak, 2MNa+).
Similarly the following compounds were prepared.
4.5.2. Benzyl 1-(4-chlorobenzoyl)-b-D-glucopyranuro-
nate (4b). White solid, mp 154–155 ꢀC. Found: C, 56.6;
4.4.5. Mycophenolic acid acyl glucuronide, allyl ester
(11c). Amorphous white solid. Found: C, 57.9; H, 5.9.
C26H32O12 requires C, 58.2; H, 6.0%; nmax (cmꢁ1) 3400
(v br), 1750 (sh), 1732, 1710 (sh) and 1621; 1H NMR
[400 MHz, (CD3)2CO]: 1.68 (3H, s, CH3C]C), 2.03 (3H,
s, CH3Ar), 2.16, 2.33 (4H, 2t, COCH2CH2), 3.20–3.50 (5H,
H, 4.6. C20H19ClO8 requires C, 56.8; H, 4.5%; nmax (cmꢁ1
,
FT) 3100–3600 (br), 1740 (sh), 1720, 1593, 1489 and 752;
1H NMR [400 MHz, (CD3)2CO]: 3.64–3.72 (2H, m) and
3.79 (1H, m, 20-H, 30-H and 40-H), 4.19 (1H, d, J¼9.6 Hz,
5-H), 5.21 (2H, s, PhCH2O), 5.84 (1H, d, J¼8.0 Hz, 1-H),

7602
E. R. Bowkett et al. / Tetrahedron 63 (2007) 7596–7605
7.28–7.42 (5H, 2m, PhCH2O), 7.56 and 8.06 (4H, 2d, ArH of
4-Cl benzoyl); 13C NMR [100 MHz, (CD3)2CO]: 67.8, 73.1,
74.0, 77.5, 77.7, 96.5, 129.3, 129.4, 129.5, 129.7, 130.2,
132.9, 137.2, 140.8, 165.1 and 169.4; m/z (ES+): 445
(100%), 447 (MNa+ for 35Cl and 37Cl). High-resolution
mass (ES) calculated for C20H1935ClO8Na (MNa+):
445.0666. Found: 445.0673.
d, J¼8.1 Hz, ArH) and 7.30–7.45 (5H, m, ArH of Bn ester);
13C NMR [100 MHz, (CD3)2CO]: 19.8, 23.0, 31.3, 46.0,
67.6, 73.1, 73.9, 77.60, 77.63, 96.0, 128.6, 129.1, 129.3,
129.7, 130.5, 137.3, 139.0, 141.6, 169.3 and 174.1; Mass
spec. (ES+): m/z 495 (MNa+, 100%), 967 (weak, 2MNa+).
4.5.7. (2S)-Naproxen acyl glucuronide, benzyl ester
(10b). White solid, mp 186–187 ꢀC. Found: C, 64.2; H,
5.9. C27H28O9$0.5H2O requires C, 64.1; H, 5.7%; nmax
(cmꢁ1, FT) 3573 (sh), 3200–3600 (br), 1728, 1630, 1604,
4.5.3. Benzyl 1-(4-bromobenzoyl)-b-D-glucopyranuro-
nate (5b). White solid, mp 143.5–144.5 ꢀC. Found: C,
51.2; H, 4.1. C20H19BrO8 requires C, 51.4; H, 4.1%; nmax
1
1502 and 752; H NMR [400 MHz, (CD3)2CO]: 1.55 (3H,
1
(cmꢁ1, FT) 3100–3600 (br), 1722, 1590, 1485 and 748; H
d, J¼7.1 Hz, CH3CH), 3.42, 3.57 and 3.64 (3H, 3m, 20-H,
30-H and 40-H), 3.91 (3H, s, CH3O), 3.98 (1H, q,
J¼7.1 Hz, CH3CH), 4.05 (1H, d, J¼9.4 Hz, 50-H), 5.15
(2H, s, PhCH2O), 5.63 (1H, d, J¼8.2 Hz, 10-H), 7.14 (1H,
m), 7.27–7.35 (5H, m), 7.45 (1H, m) and 7.74–7.77 (4H,
m, ArH); 13C NMR [100 MHz, (CD3)2CO]: 19.7, 39.1,
46.2, 56.0, 67.5, 73.0, 73.9, 77.6, 96.0, 106.9, 120.1,
127.3, 127.6, 128.4, 129.1, 129.2, 129.6, 130.3, 130.5,
135.2, 136.8, 137.2, 159.1, 169.3 and 174.0; m/z (ES+):
519 (MNa+, 100%). High-resolution mass (ES) calculated
for C27H28O9Na: 519.1631. Found: 519.1630.
NMR [400 MHz, (CD3)2CO]: 3.66 (2H, m) and 3.77 (1H,
m, 2-H, 3-H and 4-H), 4.18 (1H, d, J¼9.5 Hz, 5-H), 5.21
(2H, s, PhCH2O), 5.83 (1H, d, J¼7.8 Hz, 1-H), 7.34 and
7.42 (5H, 2m, PhCH2O), 7.74 and 8.06 (4H, 2d, ArH of
4-Br benzoyl); 13C NMR [100 MHz, (CD3)2CO]: 67.7, 73.1,
74.0, 77.4, 77.7, 96.5, 129.3, 129.3, 129.4, 129.7, 129.9,
132.9, 133.2, 137.2, 165.2 and 169.4; m/z (ES+): 489
(100%), 491 (MNa+ for 79Br and 81Br). High-resolution
mass (ES) calculated for C20H1979BrO8Na (MNa+):
489.0161. Found: 489.0180.
4.5.4. Benzyl 1-(4-methylbenzoyl)-b-D-glucopyranuro-
nate (6b). Amorphous white solid. Found: C, 62.4; H, 5.5.
C21H22O8 requires C, 62.7; H, 5.5%; nmax (cmꢁ1, FT) 3100–
4.5.8. Mycophenolic acid acyl glucuronide, benzyl ester
(11b). White solid, mp 54 ꢀC. Found: C, 60.2; H, 5.9.
C30H34O12$0.5H2O requires C, 60.5; H, 5.9%; nmax
(cmꢁ1, FT) 3100–3600 (br), 1732, 1620, 1452 and 748
(w); 1H NMR [400 MHz, (CD3)2CO]: 1.82 (3H, s,
CH3C]C), 2.16 (3H, s, CH3Ar), 2.30 and 2.47 (4H, 2m,
CH2CH2CO), 3.40 (2H, d, J¼6.9 Hz, ArCH2CH), 3.45,
3.60 and 3.72 (3H, 3m, 2-H, 3-H and 4-H), 3.80 (3H, s,
CH3O), 4.08 (1H, d, J¼9.6 Hz, 5-H), 5.21 (2H, s, PhCH2O),
5.28 (2H, s, ArCH2O, lactone), 5.30 (1H, t, J¼7.0 Hz,
C]CHCH2), 5.57 (1H, d, J¼8.1 Hz, 1-H) and 7.30–7.43
(5H, m, ArH); 13C NMR [100 MHz, (CD3)2CO]: 12.0,
16.7, 19.3, 23.7, 33.8, 35.3, 58.3, 61.9, 67.7, 70.6, 73.1,
73.9, 77.5, 95.6, 107.7, 118.1, 123.1, 124.5, 129.4, 129.6,
134.9, 137.2, 146.4, 154.5, 164.8, 169.5, 172.6 and 173.4;
m/z (ES+): 609 (100%, MNa+). High-resolution mass (ES)
calculated for C30H34O12Na: 609.1948. Found: 609.1968.
1
3600 (br), 1724, 1612, 1500 and 746; H NMR [400 MHz,
(CD3)2CO]: 2.41 (3H, s, Ar CH3), 3.67 (2H, m) and 3.78
(1H, m, 20-H, 30-H and 40-H), 4.16 (1H, d, J¼9.6 Hz, 50-H),
5.20 (2H, s, PhCH2O), 5.83 (1H, d, J¼7.9 Hz, 10-H), 7.33
(6H, m, ArH), 7.41 (1H, m, ArH) and 8.00 (2H, m, ArH);
13C NMR [100 MHz, (CD3)2CO]: 22.0, 39.2, 67.7, 73.1,
74.0, 77.6, 96.2, 128.1, 129.3, 129.5, 129.7, 130.5, 130.9,
137.3, 145.75, 165.9 and 169.5; m/z (ES+): 425 (MNa+,
100%) and 827 (2MNa+, 12%). High-resolution mass (ES)
calculated for C21H22O8Na (MNa+): 425.1212. Found:
425.1198.
4.5.5. Benzyl 1-(2-bromobenzoyl)-b-D-glucopyranuro-
nate (7b). Amorphous white solid. Found: C, 52.2; H, 4.4.
C20H19BrO8 requires C, 51.4; H, 4.1%; nmax (cmꢁ1, FT)
3100–3600 (br), 1755, 1720, 1587 and 741; 1H NMR
[400 MHz, (CD3)2CO]: 3.61, 3.68 and 3.76 (3H, 3m, 20-H,
30-H and 40-H), 4.20 (1H, d, J¼9.5 Hz, 5-H), 5.22 (2H, s,
PhCH2O), 5.84 (1H, d, J¼7.9 Hz, 1-H), 7.20–7.40 (5H, m,
PhCH2O), 7.52 (2H, m, ArH), 7.77 (1H, m, ArH) and 7.98
(1H, m, ArH); 13C NMR [100 MHz, (CD3)2CO]: 67.7,
73.1, 73.9, 77.5, 77.7, 96.6, 122.9, 128.9, 129.2, 129.3,
129.7, 132.3, 133.1, 134.9, 135.8, 137.3, 164.9 and 169.4.
High-resolution mass (ES) calculated for C20H1979BrO8Na
(MNa+): 489.0161. Found: 489.0161.
4.5.9. Zomepirac acyl glucuronide, benzyl ester (12b).
Amorphous white solid. Found: C, 60.1; H, 5.1; N, 2.4.
C28H28ClNO9 requires C, 60.3; H, 5.1; N, 2.5%; nmax
(cmꢁ1, FT) 3100–3600 (br), 1747, 1610 (sh), 1589, 1452
and 754; 1H NMR [400 MHz, (CD3)2CO]: 1.71 (3H, s,
CH3Ar), 3.50, 3.63 and 3.73 (3H, 3m, 2-H, 3-H and 4-H),
3.69 (3H, s, CH3N), 3.86 (2H, narrow AB q, ArCH2CO),
4.11 (1H, d, J¼9.6 Hz, 5-H), 5.21 (2H, s, PhCH2O), 5.67
(1H, d, J¼8.4 Hz, 1-H), 6.01 (1H, s, pyrrole 3-H), 7.28–
7.43 (5H, 2m, PhCH2O), 7.52 and 7.66 (4H, approx. 2d,
ArH of 4-ClPh); 13C NMR [100 MHz, (CD3)2CO]: 14.9,
33.2, 33.9, 67.8, 72.9, 73.8, 77.4, 77.6, 96.2, 129.2, 129.3,
129.4, 129.7, 129.9, 130.9, 131.9, 134.3, 137.2, 138.4,
141.2, 169.5, 169.6 and 187.0; m/z (ES+): 580 and 582
(MNa+ for 35Cl and 37Cl). High-resolution mass (ES+) calcu-
lated for C28H28ClNO9Na [MNa+]: 580.1350. Found:
580.1340.
4.5.6. (2S)-Ibuprofen acyl glucuronide, benzyl ester (9b).
Amorphous white solid. Found: C, 65.8; H, 6.8; m/z
495.1992. C26H32O8 requires C, 66.1; H, 6.8%; nmax
(cmꢁ1, FT) 3100–3600 (br), 1739, 1512 and 746;
C26H32O8Na requires m/z 445.1995; 1H NMR [(CD3)2CO]:
0.88 (6H, d, J¼7.1 Hz, (CH3)2CH), 1.45 (3H, d, J¼7.1 Hz,
CH3CHAr), 1.85 (1H, m, (CH3)2CH), 2.45 (2H, d,
J¼7.2 Hz, CHCH2Ar), 3.43, 3.57 and 3.66 (3H, 3m, 20-
H+30-H+40-H), 3.81 (1H, q, J¼7.1 Hz, ArCHCH3), 4.04
(1H, d, J¼9.6 Hz, 50-H), 5.18 (2H, s, PhCH2O), 6.00 (1H,
d, J¼7.9 Hz, 10-H), 7.10 (2H, d, J¼8.1 Hz, ArH), 7.23 (2H,
4.5.10. Diclofenac acyl glucuronide, benzyl ester (13b).
Amorphous white solid. nmax (cmꢁ1, FT) 3100–3600 (br),
1739, 1579, 1502, 1452 (s) and 744; H NMR [400 MHz,
(CD3)2CO]: 3.52, 3.61 and 3.71 (3H, 3m, 2-H, 3-H and
1

E. R. Bowkett et al. / Tetrahedron 63 (2007) 7596–7605
7603
4-H), 3.93 (2H, AB q, ArCH2CO), 4.10 (1H, d, J¼9.6 Hz, 5-
H), 5.19 (2H, s, PhCH2O), 5.68 (1H, d, J¼8.0 Hz, 1-H), 6.48
(1H, d, J¼8.0 Hz, ArH), 6.77 (1H, br s, NH), 6.95 (1H, t,
J¼7.4 Hz, ArH), 7.10–7.20 (2H, m, ArH), 7.28–7.45 (6H,
m, ArH) and 7.46 (2H, d, J¼8.1 Hz, ArH); 13C NMR
[100 MHz, (CD3)2CO]: 39.1, 67.7, 73.0, 73.9, 77.3, 77.6,
96.3, 119.1, 123.2, 125.6, 126.2, 129.2, 129.3, 129.3,
129.7, 130.3, 131.1, 132.4, 137.3, 139.2, 144.2, 169.3 and
172.0. High-resolution mass (ES+) calculated for
C27H2535Cl2NO8Na: 584.0855. Found: 584.0864.
(0.028 g, 75%) as a foam; see Section 4.8.1. for characterisa-
tion of this product.
Similarly the following compound was prepared.
4.7.2. Mycophenolic acid acyl glucuronide (11d).18 Col-
ourless foam. Found: C, 53.6; H, 5.8. C23H28O12$H2O
requires C, 53.7; H, 5.6%; nmax (cmꢁ1, FT) 2500–3600
1
(br), 1730, 1620, 1452 and 791 (w); H NMR [400 MHz,
(CD3)2CO]: 1.81 (3H, s, CH3C]C), 2.15 (3H, s, ArCH3),
2.30, 2.51 (4H, 2m, COCH2CH2), 3.38 (2H, d, J¼6.9 Hz,
ArCH2CH), 3.43, 3.53 and 3.58 (3H, 3m, 20-H+30-H+40-
H), 3.70 (1H, d, J¼9.5 Hz, 50-H), 3.78 (3H, s, CH3O), 5.27
(1H, t, J¼6.25 Hz, C]CHCH2), 5.30 (2H, s, ArCH2O)
and 5.45 (1H, d, J¼8.1 Hz, 10-H); 13C NMR [(CD3)2CO]:
11.9, 16.7, 23.6, 33.8, 35.2, 61.9, 64.2, 70.9, 72.9, 73.8,
77.0, 77.5, 95.5, 107.7, 118.1, 123.1, 124.5, 134.9, 146.4,
154.5, 164.8, 172.6 and 173.3. High-resolution mass (ESꢁ)
calculated for C23H27O12 [MꢁH]+: 495.1503. Found:
495.1514.
4.5.11. Valproic acid acyl glucuronide, benzyl ester (14b).
Amorphous white solid. nmax (cmꢁ1, FT) 3100–3600 (br),
1788, 1741, 1601, 1456 and 766; 1H NMR [400 MHz,
(CD3)2CO]: 0.88 (6H, m, 2ꢂCH3), 1.30 (4H, m,
2ꢂCH3CH2), 1.46, 1.60 (4H, 2m, 2ꢂCH2CH), 2.46 (1H,
m, CH(CH2)2), 3.45, 3.57 and 3.71 (3H, 3m, 2-H, 3-H and
4-H), 4.05 (1H, d, J¼9.5 Hz, 5-H), 5.21 (2H, s, PhCH2O),
5.59 (1H, d, J¼8.2 Hz, 1-H) and 7.31–7.41 (5H, m, ArH);
13C NMR [100 MHz, (CD3)2CO]: 15.7, 21.2, 21.3, 35.3,
35.3, 46.0, 67.4, 73.0, 73.7, 77.4, 77.6, 95.3, 128.9, 129.1,
129.5, 137.2, 169.3 and 175.3; m/z (ES+): 433 (100%),
MNa+. High-resolution mass (ES+) calculated for
C21H30O8Na: 433.1838. Found: 433.1823.
4.8. Typical deprotection procedure (benzyl ester)
4.8.1. 1-O-(2-Phenyl)acetyl-b-D-glucopyranuronic acid
(8d). A solution of benzyl ester 8b (0.121 g, 0.3 mmol)
i
in PrOH (5 mL) and THF (5 mL) was stirred at 60 ꢀC
4.6. Typical deprotection procedure (allyl ester) using
Pd(PPh3)4
with cyclohexa-1,4-diene (1 mL) and 10% Pd–C (10 mg)
for 1.5 h. Reaction was then complete by TLC (10%
EtOH–CH2Cl2): the catalyst was filtered off and the filtrate
evaporated to give a residue, which on trituration with ether
afforded the product 8d as an amorphous solid (0.094 g,
quant.). Found: C, 54.2; H, 5.4. C14H16O8 requires C,
53.9; H, 5.1%; nmax (cmꢁ1, FT) 3502, 3433 and 3292
superimposed on 2500–3600 (br), 1753, 1620 (sh), 1394
4.6.1. 1-O-(4-Bromo)benzoyl-b-D-glucopyranuronic acid
(5d). Pd(PPh3)4 (0.014 g, 0.012 mmol) and morpholine
(0.011 g, 0.12 mmol) were added to 5c (0.050 g,
0.12 mmol) with stirring in THF (0.5 mL) at 0 ꢀC for
0.75 h. Evaporation of solvent left a yellow gum, which
was purified by chromatography, eluting with EtOH–
CH2Cl2–CH3CO2H, 2:8:0.1, increasing the polarity later to
3:1:0.1. Pooling and evaporation of appropriate fractions
(UVand anisaldehyde detection) gave the free acyl glucuro-
nide 5d (0.034 g, 80%) as a clear gum with spectroscopic
data as reported previously.8 In addition traces of Pd reagent
1
(w) and 768; H NMR [(CD3)2CO]: 3.37, 3.49, 3.57 (3H,
3t, J¼9–9.5 Hz, 20H, 30-H and 40-H), 3.62 (2H, s,
ArCH2CO), 3.88 (1H, d, J¼9.5 Hz, 5-H), 4.90–5.40 (3H,
m, D2O exch., 3ꢂOH), 5.48 (1H, d, J¼8.1 Hz, 1-H) and
7.11–7.22 (5H, m, ArH); 13C NMR [400 MHz,
(CD3)2CO]: 41.5, 73.0, 73.8, 77.1, 77.3, 95.8, 128.3,
129.4, 131.1, 135.2, 170.6 and 171.4; m/z (ES+): 335
(MNa+, 100%) and 647 (2MNa+). High-resolution mass
(ES) calculated for C14H16O8Na (MNa+): 335.0743.
Found: 335.0728.
1
were detected by H NMR (excess ArH integral) and MS.
For 5d: H NMR [(CD3)2CO]: 3.55–3.75 (3H, 3m, 2-H+3-
1
H+4-H), 3.87 (1H, d, J¼9.2 Hz, 5-H), 5.78 (1H, d,
J¼7.7 Hz, 1-H), 7.75 (2H, d, J¼8.5 Hz, ArH) and 8.06
(2H, d, J¼8.6 Hz, ArH).
Similarly the following compounds were prepared.
4.7. Typical deprotection procedure (allyl ester) using
resin-bound Pd(0)
4.8.2. 1-(4-Chlorobenzoyl)-b-D-glucopyranuronic acid
(4d). Colourless foam. nmax (cmꢁ1, FT) 3637 (sh), 2500–
3650 (br), 1716, 1593, 1431 and 760; H NMR [400 MHz,
1
4.7.1. 1-O-Phenylacetyl-b-D-glucopyranuronic acid (8d).
PS–PPh3–Pd(0), purchased from Argonaut Technologies,
was stirred in THF–DMF, 1:1 (1 mL per 0.1 g of resin) for
0.5 h, filtered, washed with further THF and dried before
use. This material (0.24 g, 0.024 mmol), allyl ester 8c
(CD3)2CO]: 3.56 (2H, m) and 3.62 (1H, m, 2-H, 3-H and
4-H), 3.98 (1H, d, J¼9.4 Hz, 5-H), 5.70 (1H, d, J¼7.5 Hz,
1-H), 7.44 (2H, d) and 7.96 (2H, d, ArH); 13C NMR
[100 MHz, (CD3)2CO]: 72.9, 73.8, 77.1, 77.4, 96.4, 129.5,
130.2, 132.8, 140.8, 165.2 and 170.4; m/z (ESꢁ):
331(100%), 333 ([MꢁH]+ for 35Cl, 37Cl). High-resolution
mass (ES) calculated for C13H1235ClO8 ([MꢁH]+):
331.0221. Found: 331.0208.
(0.042 g,
0.12 mmol)
and
morpholine
(0.011 g,
0.12 mmol) were stirred in THF (0.4 mL) and DMF
(0.1 mL) at 20 ꢀC under N2 for 3 h. Amberlite IR-120 (H+)
resin (0.1 g, 0.19 mmol) was added followed by stirring
for 0.5 h, then the resin was filtered off and washed with
the same solvent (10 mL) followed by evaporation of filtrate
and washings to dryness. Chromatography of the crude prod-
uct, eluting with 15% and then 50% EtOH–CH2Cl2, afforded
on evaporation of appropriate fractions the product 8d
4.8.3. 1-(4-Methylbenzoyl)-b-D-glucopyranuronic acid
(6d). Colourless foam. Found: C, 54.5; H, 6.4.
C14H16O8$0.5 PrOH requires C, 54.4; H, 5.8%; nmax
i
(cmꢁ1, FT) 2500–3650 (br), 1703, 1610, 1425 and 750;

7604
E. R. Bowkett et al. / Tetrahedron 63 (2007) 7596–7605
1H NMR [400 MHz, (CD3)2CO]: 2.41 (3H, s, ArCH3), 3.66
(2H, m) and 3.75 (1H, m, 20-H, 30-H and 40-H), 4.10 (1H,
d, J¼9.4 Hz, 50-H), 5.82 (1H, d, J¼7.6 Hz, 10-H), 7.35
(2H, m, ArH) and 7.98 (2H, m, ArH); 13C NMR
[100 MHz, (CD3)2CO]: 22.0, 73.0, 73.9, 77.1, 77.6, 96.1,
128.1, 130.5, 131.1, 145.7, 165.9 and 170.5; m/z (ESꢁ):
311 ([MꢁH]+), 100%. High-resolution mass (ES) calculated
for C14H15O8 ([MꢁH]+): 311.0767. Found: 311.0764.
4.8.8. Valproic acid acyl glucuronide (14d). Hard colour-
less gum. nmax (cmꢁ1, FT) 2500–3700 (br), 1734 and
1460; H NMR [400 MHz, CD3CN+D2O]: 0.85–0.90 (6H,
1
2m, 2ꢂCH3CH2, non-eq.), 1.25–1.32 (4H, m), 1.40–1.50
and 1.50–1.60 (4H, m), 2.40–2.50 (1H, m, COCH(CH2)2),
3.38, 3.48 and 3.56 (3H, 3m, 2-H, 3-H+4-H), 3.91 (1H, d,
J¼9.5 Hz, 5-H) and 5.48 (1H, d, J¼8.2 Hz, 1-H); 13C
NMR [100 MHz, THF-d8]: 13.0, 13.0, 19.7, 19.8, 33.6,
33.7, 44.6, 71.3, 72.1, 75.6, 76.5, 93.7, 168.8 and
173.3; m/z (ESꢁ): 319 (100%), (MꢁH)+. High-resolution
mass (ESꢁ) calculated for C14H23O8: 319.1393. Found:
319.1404.
4.8.4. (2S)-Ibuprofen acyl glucuronide (9d). Colourless
foam. Found: C, 58.8; H, 7.3. C19H26O8$0.5H2O requires
C, 58.3; H, 6.9%; nmax (cmꢁ1, FT) 2500–3650 (br), 1734,
1600 (sh, w), 1512, 1454 and 802 (w); 1H NMR
[400 MHz, (CD3)2CO]: 0.75 [6H, d, J¼6.6 Hz,
(CH3)2CH], 1.32 (3H, d, J¼7.1 Hz, CH3CHAr), 1.71 (1H,
m, (CH3)2CH), 2.31 (2H, d, J¼7.2 Hz, ArCH2CH), 3.32,
3.46 and 3.53 (3H, 3m, 2-H, 3-H and 4-H), 3.68 (1H, q,
J¼7.1 Hz, CH3CHAr), 3.85 (1H, d, J¼9.4 Hz, 5-H), 5.47
(1H, d, J¼8.1 Hz, 1-H), 6.98 and 7.11 (4H, 2d, ArH); 13C
NMR [100 MHz, (CD3)2CO]: 19.9, 23.1, 35.4, 46.0, 72.9,
73.8, 77.1, 77.6, 95.9, 126.5, 128.7, 130.5, 139.0, 141.6,
170.3 and 174.1. High-resolution mass (ESꢁ) calculated
for C19H25O8: 381.1549. Found: 381.1539.
4.9. Purification of acyl glucuronides
In general acyl glucuronides of high purity are obtained from
benzyl esters by the preceding method. If further purification
is necessary, we recommend either conventional chromato-
graphy as applied to 5d and 8d above (allyl ester method),
or the use of reverse-phase silica ‘LiChroprep’. For the latter,
on a 0.1 g scale of product, the crude product is applied to
a column of LiChroprep (2 g) and eluted with a gradient of
acetonitrile (typically from 20 to 60% for most AGs) in
0.1% AcOH–H2O. Appropriate fractions are then pooled
and evaporated. This procedure makes use of the greatly
enhanced stability of AGs at mildly acidic pH; similarly
0.1% aq formic acid has been used, see Ref. 21.
4.8.5. (2S)-Naproxen acyl glucuronide (10d). Colourless
foam. nmax (cmꢁ1, FT) 2500–3650 (br), 1747, 1631, 1606,
1508, 1455 and 850 (w); H NMR [400 MHz, (CD3)2CO]:
1
1.56 (3H, d, J¼7.1 Hz, CH3CH), 3.44, 3.54 and 3.65 (3H,
3m, 20-H, 30-H and 40-H), 3.90 (3H, s, CH3O), 3.96 (1H, d,
J¼9.4 Hz, 50-H), 3.98 (1H, q, J¼7.1 Hz, CH3CH), 5.63
(1H, d, J¼8.1 Hz, 10-H), 7.13 (1H, m, ArH), 7.45 (1H, m,
ArH) and 7.76 (4H, m, ArH); 13C NMR [100 MHz,
(CD3)2CO]: 19.7, 46.3, 56.0, 62.4, 73.0, 73.9, 77.7, 96.0,
106.9, 120.1, 127.3, 127.7, 128.4, 128.9, 130.5, 135.2,
136.9, 159.1, 170.3 and 174.1. High-resolution mass (ESꢁ)
calculated for C20H21O9: 405.1186. Found: 405.1177.
Acknowledgements
We are grateful to the EPSRC and Astra Zeneca for funding
(DTA award to ERB and CASE award to JAP). The Waters
Quattro II mass spectrometer was purchased and maintained
with grants from the Wellcome Trust. Professors D. Holt and
A. Johnston of Analytical Services International Ltd. are
thanked for a generous gift of mycophenolic acid.
4.8.6. Zomepirac acyl glucuronide (12d). Colourless foam.
nmax (cmꢁ1, FT) 2500–3600 (br), 1747, 1610 (sh), 1589,
1452 and 754; H NMR [400 MHz, (CD3)2CO]: 1.72 (3H,
References and notes
1
s, ArCH3), 3.52, 3.65 and 3.72 (3H, 3m, 2-H, 3-H and
4-H), 3.71 (3H, s, CH3N), 3.89 (2H, s, ArCH2CO), 4.05 (1H,
d, J¼9.4 Hz, 5-H), 5.67 (1H, d, J¼8.0 Hz, 1-H), 6.01 (1H,
s, pyrrole 3-H), 7.52 and 7.67 (4H, 2d, ArH); 13C NMR
[100 MHz, (CD3)2CO]: 14.9, 31.2, 33.3, 72.9, 73.8, 77.1,
77.5, 96.1, 113.8, 126.5, 129.4, 129.9, 131.9, 134.4, 138.4,
141.2, 169.6, 170.4 and 187.0. High-resolution mass (ESꢁ)
calculated for C21H21NO935Cl: 466.0905. Found: 466.0885.
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nmax (cmꢁ1, FT) 3639 (sh, w), 2500–3650 (br), 1734, 1581,
1504, 1450 (s), 769 and 744; 1H NMR [400 MHz,
(CD3)2CO]: 3.52, 3.59 and 3.68 (3H, 3m, 2-H, 3-H and
4-H), 3.94 (2H, s, ArCH2CO), 4.03 (1H, d, J¼9.5 Hz, 5-H),
5.68 (1H, d, J¼7.9 Hz, 1-H), 6.47 (1H, d, J¼7.8 Hz, ArH),
6.78 (1H, br s, NH), 6.94 (1H, m, ArH), 7.07–7.19 (2H, m,
ArH), 7.30 (1H, m, ArH) and 7.44 (2H, m, ArH); 13C NMR
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119.1, 123.5, 125.6, 126.6, 126.7, 129.2, 130.3, 131.0,
132.5, 139.1, 144.3, 170.2 and 171.9; m/z (ESꢁ): 470
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