Synthesis and biological evaluation of analogues of M6G

Article abstract of DOI:10.1016/j.ejmech.2011.05.076

Synthesis and biological evaluation of new derivatives of Morphine-6-Glucuronide (M6G) are described. M6G is an active metabolite of morphine which displays more analgesia than morphine with a superior side effect profile but with a less efficiently BBB p

Full text of DOI:10.1016/j.ejmech.2011.05.076

European Journal of Medicinal Chemistry 46 (2011) 4035e4041
Contents lists available at ScienceDirect
European Journal of Medicinal Chemistry
journal homepage: http://www.elsevier.com/locate/ejmech
Original article
Synthesis and biological evaluation of analogues of M6G
,
c
c
a
a,
*
Claire Trécant a, Alain Dlubala b , Pascal George , Philippe Pichat , Isabelle Ripoche , Yves Troin
*
a Clermont Université, ENSCCF, EA 987, LCHG, BP 10448, F-63000 Clermont-Ferrand, France
b Sanofi-Aventis, Route d’Avignon, 30390 Aramon, France
c Sanofi-Aventis R&D, 1 rue Pierre Brossolette, 91380 Chilly-Mazarin, France
a r t i c l e i n f o
a b s t r a c t
Article history:
Synthesis and biological evaluation of new derivatives of Morphine-6-Glucuronide (M6G) are described.
M6G is an active metabolite of morphine which displays more analgesia than morphine with a superior
side effect profile but with a less efficiently BBB penetration. These phenomena could be explained by the
presence of the glucuronide moiety, which confers a higher hydrophilic character compare to morphine.
In this context, we have prepared three analogues of M6G possessing a tetrazole, an oxadiazole, and
a triazolopyrimidine moiety instead of the carboxylic acid function on position 5 of the sugar. These three
analogues showed higher analgesic properties than morphine and M6G even by oral administration.
Ó 2011 Elsevier Masson SAS. All rights reserved.
Received 14 April 2011
Received in revised form
30 May 2011
Accepted 31 May 2011
Available online 12 June 2011
Keywords:
Morphine-6-glucuronide
Heterocycles
Analgesic activity
1. Introduction
new derivatives of M6G in which the acid function of the glucu-
ronide moiety is replaced by various heterocyclic rings and
Morphine is the most widely used opiate treatment for
moderate to severe pain in spite of several side effects as con-
stipation, respiratory depression and chemical dependency. Several
studies have showed that the analgesic effect of morphine was not
produced by the parent drug but by its active metabolite M6G,
which is formed upon administration of morphine in human.
Indeed, after administration, morphine is metabolized chiefly
through glucuronidation by uridine diphosphate glucuronosyl
transferase (UGT) enzymes. Morphine has two main metabolites,
namely morphine-3-glucuronide (M3G, 50%) and morphine-6-
glucuronide (M6G, 10%) [1,2]. Systematic studies on M3G and
M6G have been undertaken and showed, after intra-
particularly by a tetrazole unit. Despite of their physical and
chemical differences it has been showed that they exhibited
a remarkable similarity in their respective topology and geomet-
rical disposition [7]. Moreover we could hope that these new
derivatives have a better pharmacological profile by notably
limiting the metabolism and thus improving its “in vivo” stability.
We describe herein the synthesis of three new derivatives of M6G,
for which the carboxylic acid is replaced by a tetrazole, an oxa-
diazole ring and a triazolopyrimidine moiety together with the
evaluation of the analgesic activity.
2. Results and discussion
cerebroventricular injection, that M3G, with its low affinity for
m
receptors, was devoid of significant analgesic properties, when
M6G was more than 100-fold higher than morphine itself and have
reduced side effects [3,4] which were generally associated with the
uptake of morphine [5]. In apparent contradiction to its polar
properties, M6G, which is a more potent analgesic drug than
morphine itself, is able to penetrate the BBB, although to a lesser
extent than morphine. A lot of work has been devoted to the
synthesis of new analogues, such as chemically modified opiate
alkaloids, peptides and non-peptide derivatives but with limited
therapeutic success [6]. In this context we wish to describe here
We first envisaged the synthesis of the tetrazole derivative. For
its preparation we first needed to prepare a glycosidic donor,
possessing a tetrazole moiety in position 5 of the sugar. Starting
from commercially available glucuronamide 1 we chose the
sterically hindered benzoyl protective group rather than the
classical acetyl group in order to avoid acyl transfer reaction [8],
a side reaction often observed on glucuronidation, which strongly
decreased the yield. So, treatment of compound 1 with benzoyl
chloride in presence of pyridine led directly to a mixture of the
cyano derivatives 2a and 2b in a 2:1 ratio and 57% yield. In this
case concomitant dehydration was observed, reaction which
traditionally occurred by the use of thionyl chloride [9] or tri-
fluoroacetic acid (Scheme 1) [10].
* Corresponding authors. Tel.: þ33 4 73 40 71 39; fax: þ33 0 4 73 40 70 08.
E-mail address: Yves.Troin@univ-bpclermont.fr (Y. Troin).
0223-5234/$ e see front matter Ó 2011 Elsevier Masson SAS. All rights reserved.
doi:10.1016/j.ejmech.2011.05.076

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C. Trécant et al. / European Journal of Medicinal Chemistry 46 (2011) 4035e4041
H
N
N
NH2
CN
OBz
N
N
BzO
OBz
NC
O
HO
HO
i
O
O
ii
O
BzO
O
OH
+
OBz
OBz
BzO
BzO
BzO
OH
BzO
OBz
OBz
3
1
2a
2b
Scheme 1. Synthesis of glucuronamide derivative (3). Reagents and conditions : (i) BzCl, pyridine, CH2Cl2, 25 ꢀC, 12 h (57%); (ii) TMSN3, (Bu3Sn)2O, toluene, reflux, 12 h (59%).
PMB
PMB
N
N
N
N
PMB
O
PMB
O
N
N
N
N
N
N
N
N
N
N
N
N
ii
i
O
O
BzO
BzO
BzO
3
OH
BzO
+
OBz
OH
OBz
+
OBz
OBz
BzO
BzO
BzO
BzO
OBz
OBz
4a
4b
5a
5b
PMB
N
N
PMB
O
N
N
N
N
N
N
iii
O
BzO
BzO
+
BzO
BzO
BzO
BzO
OCNHCCl3
OCNHCCl3
6a
6b
Scheme 2. Synthesis of trichloroacetimidates derivatives (6a-6b). Reagents and conditions : (i) PMBCl, NEt3, THF, reflux 12 h (73%); (ii) NH2NH2, AcOH, DMF, 25 ꢀC 4 h (70%); (iii)
CCl3CN, DBU, CH2Cl2, 25 ꢀC, 1 h (65%).
The ratio 2a/2b was determined by NMR, considering the signal
of each anomeric proton (respectively H-1
(J ¼ 3.5 Hz) at 6.88 ppm
for 2a and H-1
(J ¼ 3.0 Hz) at 6.57 ppm for 2b). This unusual
Selective debenzoylation using hydrazine acetate in DMF gave
the two acetals 5a and 5b (70%, 5a/5b 2:1). The corresponding
alpha imidates 6a and 6b were obtained after treatment with
trichloroacetonitrile and DBU in a 3/1 ratio. The structure of these
two imidates and the ratio of the two tetrazoles were confirmed
by NMR spectroscopy. Isomerisation of tetrazoles during the
reaction could explain the difference between the ratio observed
for 5a/5b and 6a/6b as Lwowski and coll. have showed that this
isomerization is strongly dependent of the solvent and of the
steric hindrance [18].
a
b
coupling constant for 2b led us to undertake modeling calculations
using the BatchminÒ; program within the MM2 force field of the
Macromodel package [11] in order to confirm the 1C4 conformation.
Unfortunately, no significant difference of energy between the two
conformations was observed (Scheme 1).
Among all the methods described to create the tetrazole ring
[12] the treatment of mixture of cyano derivatives 2a and 2b with
combination of trimethylsilylazide and bis(tributyltin) oxide gave
the best results. Using this experimental procedure, the tetrazole
glucuronide 3 [13] was obtained in 59% yield (Scheme 1). At this
step of the synthesis it was necessary to protect the tetrazole
moiety. We chose the p-methoxybenzyl group, stable in glycosyl-
ation conditions, introduced in soft conditions (PMBCl, Et3N) [14]
and cleaved in acidic media (TFA) [15], as protection of the tetra-
zole with a carbamate or an amide moiety was not possible, due to
a Huisgen rearrangement often encountered in tetrazole chemistry
[16] (Scheme 2).
The next step of the synthesis consisted of a glycosylation using
a
morphine derivative. As morphine is strongly scheduled
substance controlled by French authorities, we have used the 3-O-
pivaloyl N-ethylcarbamate morphine derivative 7 [19], which we
were allowed to use in academic laboratory, furnished by
FrancopiaÒ;, even if we should use drastic reduction conditions to
transform the carbamate moiety into a methyl group. Thus, glyco-
sylation of 7 with an excess of donor (6a/6b, 2.eq.) and promotor
(TMSOTf, 4eq.) at 0 ꢀC without anhydrous conditions, afforded the
compound 8 as a unique
of compound 8 was determined by NMR, considering the anomeric
proton (H-1 at 5.43 ppm with a coupling constant of 7 Hz).
b anomer in a good yield of 69%. Structure
Treatment of compound 3 with para-methoxybenzyl chloride in
presence of triethylamine led to a mixture of protected tetrazoles 4a
b
and 4b in a 2:1 ratio (73% combined yield, for 4a and 4b
a
/
b
: 2/1).
Cleavage of the p-methoxybenzyl group was performed using TFA,
to give the tetrazole 9 in a 60% yield. Simultaneous reduction of the
carbamate moiety and of the benzoate group was performed in
presence of LAH. Purification of the crude product on reverse phase
Among all the methods described in literature to perform gly-
cosydation, we chose the trichloroacetimidate method developed
by Schmidt [17].
PivO
PivO
PivO
PMB
H
N
N
O
N
O
ii
i
N
N
N
N
O
6a/6b
N
N
+
N
N
CO2Et
CO2Et
O
O
BzO
BzO
O
O
OBz
CO2Et
BzO
BzO
HO
OBz
8
7
9
HO
H
N
N
O
H
N
N
HO
iii
N
CF3COO
O
O
HO
OH
Scheme 3. Synthesis of morphinan derivative (10). Reagents and conditions : (i) TMSOTf, CH2Cl2, 0 ꢀC 30 mn (69%); (ii) TFA, reflux 15 mn (60%); (iii) LiAlH4, THF, reflux 1 h (16%).

C. Trécant et al. / European Journal of Medicinal Chemistry 46 (2011) 4035e4041
AcO
4037
HO
HO
H
N
N
O
O
O
i
ii
N
N
N
N
HO
N
N
O
O
N
N
N
CF3COO
O
O
O
AcO
HO
O
O
O
HO
AcO
HO
OH
OAc
OH
10
11
12
Scheme 4. Synthesis of morphinan derivative (12). Reagents and conditions : (i) Ac2O, reflux 12 h (55%); MeONa, IR-120 resin, 3 h (46%).
flash chromatography afforded compound 10 in a 16%yield, as its
trifluoroacetate salt. This low yield could be explained by the lot of
purifications necessary to obtain purity higher than 95% for bio-
logical evaluation [20] (Scheme 3).
Starting from the tetrazole 10 (Scheme 4) we prepared the
corresponding 1,3,4-oxadiazole 11 by treatment with acetic anhy-
dride. The Huisgen rearrangement [16,21] of the tetrazole 10 gave
the corresponding oxadiazole, with a methyl group in position 2, in
55% yield. Complete deacetylation of compound 11 using sodium
methoxyde gave, after purification on HPLC, the oxadiazole 12 in
46% yield (Scheme 4).
The preparation of a triazolopyrimidine derivative was also
envisaged by transformation of the tetrazole ring through reaction
with an imidoyl chloride via a Huisgen reaction. Only a few couple
of examples of this type of rearrangement has already been
described [22,23]. Transformation of a tetrazole ring into a tri-
azolopyrimidine has already been described by Karkas and coll [23].
on the anomeric position of a galactopyranoside.
Treatmentof the tetrazole 3 (Scheme 5) with 2-chloropyrimidine
and pyridine led to the corresponding triazolopyrimidines 13a and
13b in a 3:1 ratio. Here too, the presence of these two isomers could
be explained bya Huisgen rearrangement on the two isomeric forms
of the tetrazole. The N-H1 isomer furnished the pyrimidine 13a as
the NH2 form gave the pyrimidine 13b. Selective anomeric depro-
tection of the mixture of compounds 13a and 13b using hydrazine
acetate in DMF led to the unique triazolopyrimidine hemiacetal 14.
Isomerisation of [4,3-a]pyrimidine into the [1,5-a]pyrimidine could
be explained by a Dimroth [24] rearrangement which was also
observed when 13a was stored at room temperature under atmo-
spheric pressure.
analogue 17 in 40% yield. The structure of compound 17 was
established by NMR spectroscopy. The presence of a multiplet at
5.36 ppm corresponding to the proton gem to the hydroxyl group
and two multiplets at 4.30 and 4.10 ppm corresponding to the
hydrogens in alpha position of the hydroxyl group confirm the
structure of 17. The 13C spectra also showed the presence of two
secondary carbons at 40.1 and 26.2 ppm and a tertiary carbon at
71.1 ppm. The formation of this tetrahydrotetrazolopyrimidine
derivative could be explained by a partial reduction of the pyridine
ring to give the corresponding imine which is directly hydrated to
give the compound 17. Such partial reduction has already been
described on phenanthroline, pteridine [25e27] and uracile [28]
derivatives, but never on a pyrimidine moiety. We envisaged that,
in this case, the hydride transfer was not possible due to
a complexation of the nitrogen atoms of the pyrimidine and
morphine moiety with aluminum, as the reduction of the sugar 14,
led to the complete reduction of the pyrimidine.
In summary, we have synthesized three analogues of M6G
for which the carboxylic acid moiety was respectively replaced
by a tetrazole ring (compound 10), by a 1,3,4-oxadiazole moiety
(compound12) andbyatetrahydrotriazolopyrimidine(compound 17).
3. Biological evaluations
The anti-nociceptive activity was determined using the tail-flick
procedure in Swiss mice male (Iffa Credo, group of 12 animals for
each test). In the experiment, the tail reflex was elicited by placing
the tip of the tail over a slit through which the light of an infra-red
source was focused (55e60
ꢀC) and the time to tail withdrawal was
recorded. Heat intensity was settled for a withdrawal reflex within
0.5e3.5 s for basal recording of each animal. The cut-off time was
set at 8 s for this test in order to avoid tissue damage. Respon-
siveness to drug treatments was measured several times from 20 to
120 min after administration. The compounds were tested at
various doses between 1.25 and 30 mg/kg by subcutaneous
administration. The inhibition of tail-flick was expressed as
“percent maximum possible effect (%MPE) calculated using the
method previously described by D’Amour and Smith [29].
Formation of the alpha trichloroacetimidate [22] was per-
formed, as previously described, using trichloroacetonitrile and
DBU as a base. The presence of a single anomer was confirmed by
NMR according to the anomeric proton at 7.00 ppm with a coupling
constant of 3.5 Hz. Glycosylation of the acceptor 7 with the donor
15 in the conditions previously described furnished the compound
16 in 31% yield. Complete reduction of the triazolopyrimidine 16
with LAH didn’t furnish the desired triazolopyrimidine but the M6G
N
N
N
H
N
N
N
N
i
N
N
ii
N
N
N
N
BzO
iii
N
N
N
+
O
BzO
OBz
O
O
O
BzO
BzO
BzO
OBz
OBz
OH
OBz
BzO
BzO
BzO
OBz
OBz
OBz
3
13a
13b
14
OH
NH
HO
PivO
O
N
N
O
N
N
iv
v
H
N
N
N
N
N
N
N
N
N
CF3COO
O
CO2Et
O
O
BzO
HO
O
O
BzO
BzO
HO
BzO
OH
BzO
OBz
16
OCNHCCl3
15
17
Scheme 5. Synthesis of morphinan derivative (17). Reagents and conditions : (i) 2-chloropyrimidine, pyridine, reflux 12 h (74%); (ii) NH2NH2.AcOH, DMF, 0 ꢀC, 1 h then room
temperature 2 h (68%); (iii) CCl3CN, DBU, CH2Cl2, room temperature 1.5 h (70%); (7), TMSOTf, CH2Cl2, 0 ꢀC 0.5 h (31%); LiAlH4, THF, reflux 1h (40%).

4038
C. Trécant et al. / European Journal of Medicinal Chemistry 46 (2011) 4035e4041
reported in ppm (d scale) and all J values are in Hz. The following
abbreviations are used: singlet (s), doublet (d), doubled doublet
(dd), triplet (t), multiplet (m). Melting points are uncorrected. Mass
spectra (Ion Spray) were performed on a Perkin Elmer Sciex PI300,
HRMS. Monitoring of the reactions was performed using silica gel
TLC plates (silica Merck 60 F254). Spots were visualized by UV light
at 254 nm. Flash chromatography columns were performed using
silica gel 60 (70e230 mesh). The reverse phase chromatographies
were performed either on a CombiFlash (RetrieveÒ;) apparatus
with a Redi Step C-18 column (Teledyne IscoÒ;), 43 g or with
a preparative apparatus NovacepÒ; equipped with a diode array
detector (230 nm) on Hyperprep 10 mm HSC8 column.
5.1. Synthesis of tetrazole (10)
Fig. 1. Tail-Flick (%MPE max), s.c. administration. *The anti-nociceptive activity of
morphine and M6G was in accordance with literature [19].
5.1.1. 1,2,3,4-Tetra-O-benzoyl-
a/b-D-glucurononitrile (2a/2b)
To a suspension of -glucuronamide 1 (25.0 g, 0.129 mol) in
D
pyridine (100 mL) was added over a period of 30 min, a solution of
benzoyl chloride (102 mL, 0.878 mol) in CH2Cl2 (90 mL). The
mixture was stirred overnight at room temperature, then CH2Cl2
(200 mL) and water (200 mL) were added. The organic layer was
washed with HCl 1N (200 mL), saturated NaHCO3 (3 ꢁ 200 mL),
brine (200 mL) and was dried over Na2SO4. The concentrated
residue was triturated with EtOH (200 mL) to give the nitrile 2a and
2b (43.4 g, 57%) as pale yellow solid. The
determined by 1H NMR. mp 209e212 ꢀC; 1H NMR (400 MHz,
CDCl3): 8.10-7.30 (m, 20H , H-aro), 6.88 (d, 1H , J 3.5 Hz,
þ 20H
H-1 ), 6.57 (d, 1H , J 3.0 Hz, H-1 ), 6.21 (t, 1H , J 9.5 Hz, H-3 ), 5.93
(t, 1H , J 9.5 Hz, H-4 ), 5.84 (t, 1H , J 4.0 Hz, H-3 ), 5.71-5.65 (m,
1H , H-2 , H-4 ), 5.64 (m, 1H , H-2 ), 5.16 (d, 1H , J 4.0 Hz,
þ 1H
H-5 ), 5.11 (d, 1H , J 9.5 Hz, H-5
); 13C NMR (100 MHz, CDCl3):
165.5, 165.1, 164.8, 164.6, 164.3, 163.8 (C]O), 134.4-128.0 (C-aro),
115.3 (C-6 ), 114.1 (C-6 ), 90.9 (C-1 ), 89.4 (C-1 ), 69.3, 69.2, 69.0
(C-2 , C-3 , C-4 , C-3
60.8 (C-5
a:b (2:1) ratio was
d
a
b
a
a
b
b
a
a
a
a
b
b
b
a
b
b
a
b
b
b
a
a
Fig. 2. Duration (%MPE 120 min after s.c. administration) * The results obtained for
morphine and M6G was in accordance with literature [19].
d
b
a
b
a
b
a
a
a
), 67.4 (C-4
b
), 66.7, 66.5 (C-2
b
b), 61.9 (C-5a),
); HRMS (ES) C34H25NO9Na [M þ Na]þ calc. 614.1427,
The results of the tail-flick test on compounds 10, 12 and 17 are
summarized in Fig. 1 [30]. The DE50 correspond to the efficient dose
of compound to obtain an analgesic activity of 50% of the MPE.
All the compounds tested showed powerful analgesic activity
starting at low doses. The % MPE was superior to 80% after acute
administration within doses of 1.25 mg/kg s.c. The three tested
analogues of M6G have long duration analgesic activity (>120 min,
Fig. 2) after unique dose injection. For comparison, the DE50 of
morphine is about 4.4 mg/kg (s.c., 30 min post injection) [31,32],
and about 2.7 mg/kg (s.c., 60 min post administration) for M6G.
The anti-nociceptive activity of compound 10 was also tested by
oral administration. The value of percent MPE maxobtained is about
78% at a dose of 10 mg/kg, p.o. and the DE50 was inferior to 2.5 mg/kg.
found 614.1422.
5.1.2. 1,2,3,4-Tetra-O-benzoyl-5-C-(tetrazol-5-yl)-a/b-D-
xylopyranose (3)
To a solution of nitrile 2a/2b (43.0 g, 72.8 mmol) in toluene
(500 mL) were added (Bu3Sn)2O (3.70 mL, 7.26 mmol) and TMSN3
(28.7 mL, 216 mmol) and the mixture was refluxed overnight. The
concentrated residue was purified by flash chromatography on
silica gel (Cyclohexane-Ethyl acetate 1:1 to 0:1) to give the tetrazole
3 (27.0 g, 59%) as a brown solid. The
by 1H NMR. mp 144e147 ꢀC; 1H NMR (400 MHz, CDCl3):
(m, 20H , H-aro), 7.06 (d, 1H , J 3.5 Hz, H-1 ), 6.50-6.44 (m,
, H-3 ), 6.21 (t, 1H , J 9.0 Hz, H-3 ), 6.13-6.01 (m,
, H-4 , H-2 ), 5.90-5.85 (m, 2H , H-2 , H-5 ), 5.66
, J 9.0 Hz, H-5 165.79, 165.2,
). 13C NMR (100 MHz, CDCl3):
164.7 (C]O, C]N), 134.4-128.1 (C-aro), 93.0 (C-1 ), 89.9 (C-1 ),
C-4 , C-4 ), 68.9
a:
b
(2:1) ratio was determined
d
8.19-7.28
a
þ 20H
þ 1H , H-1
þ 1H , H-4
b
b
b
a
b
a
b
1H
2H
(d, 1H
b
b
a
a
a
a
b
a
a
a
4. Conclusion
b
b
d
b
a
In summary, we have prepared three analogues of M6G with
various heterocyclic rings (tetrazole, oxadiazole, and triazolopyr-
imidine) possessing powerful analgesic activity. The results of the
tail-flick tests showed that the analgesic effect of the three
synthesized compounds have higher analgesic effect than
morphine and M6G by subcutaneous and oral administration. The
low doses necessary for long duration anti-nociceptive effects by
oral administration allowed us to envisage the use of this
compound as drug for treatment of severe pain.
72.0, 70.5, 70.4, 70.3, 69.5 (C-2
a
, C-2
b, C-3
a
, C-3
b
a
b
(C-5b
), 67.0 (C-5
a
); HRMS (ES) C34H26N4O9Na [M þ Na]þ calc.
657.1597, found 657.1595.
5.1.3. 1,2,3,4-Tetra-O-benzoyl-5-C-[2-(4-methoxybenzyl)-2H-
tetrazol-5-yl]-a/b-D-xylopyranose and 1,2,3,4-tetra-O-benzoyl-5-C-
[1-(4-methoxybenzyl)-1H-tetrazol-5-yl]-a/b-D-xylopyranose (4a/4b)
A solution of tetrazole 3 (21.0 g, 33.1 mmol) in THF (210 mL)
triethylamine (5.5 mL, 39.5 mmol) and 4-methoxybenzyl chloride
(5.0 mL, 36.7 mmol) was refluxed overnight. The concentrated
residue was purified on flash chromatography (Cyclohexane-Ethyl
acetate 4:1) to give the mixture of isomers 4a and 4b (18.5 g, 73%)
as pale yellow solid. The 4a:4b (2:1) ratio was determined by 1H
5. Experimental section
1H and 13C NMR spectra were recorded on a Brüker 400 MHz
apparatus using CDCl3 CD3OD or D2O. The chemical shifts are
NMR with a 2:1 a:b ratio for 4a and a 2:1 a:b
ratio for 4b. 1H NMR

C. Trécant et al. / European Journal of Medicinal Chemistry 46 (2011) 4035e4041
4039
(400 MHz, CDCl3) for
a
anomers :
d
8.21-7.29 (m, 20Ha þ 20Hb, H-
d 165.6, 165.4, 164.4, 162.0, 160.5, 159.9 (C]O, C]N), 134.0-124.8
aro), 7.23 (d, 2Hb, J 8.5 Hz, H-aroPMBb), 7.17 (d, 2Ha, J 8.5 Hz, H-
aroPMBa), 6.98 (d, 1Ha, J 3.5 Hz, H-1a), 6.96 (d, 1Hb, J 3.5 Hz, H-1b),
6.86 (d, 2Hb, J 8.5 Hz, H-aroPMBb), 6.75 (d, 2Ha, J 8.5 Hz, H-
aroPMBa), 6.42 (t,1Ha, J 10.0 Hz, H-3a), 6.33 (t,1Hb, J 10.0 Hz, H-3b),
6.13 (t, 1Ha, J 10.0 Hz, H-4a), 5.84 (dd, 1Ha, J 3.5 Hz, J 10.0 Hz, H-2a),
5.76-5.63 (m, 3Ha þ 5Hb, CH2PhOCH3a, CH2PhOCH3b, H-5a, H-2b,
H-4b, H-5b), 3.79 (s, 3Hb, OCH3b), 3.75 (s, 3Ha, OCH3a); NMR 13C
(C-aro), 114.6 (C-aroPMBb), 114.3 (C-aroPMBa), 93.1 (C-1a), 92.8 (C-
1b), 70.9 (C-2b ou C-3b ou C-4b), 70.7 (C-4a), 70.5 (C-2a), 70.0 (C-2b
ou C-3b ou C-4b), 69.8 (C-3a), 69.3 (C-2b ou C-3b ou C-4b), 66.9 (C-
5a), 66.0 (C-5b), 56.5 (CH2PhOCH3a), 55.3 (OCH3b), 55.1 (OCH3a),
51.8 (CH2PhOCH3b).
5.1.6. 3-O-Pivaloyl-N-ethoxycarbonylnormorphin-6-yl 2,3,4-tri-O-
(100 MHz, CDCl3) for
a
anomers :
d
165.8, 165.2, 164.5, 164.3, 164.2,
benzoyl-5-C-[2-(4-methoxybenzyl)-2H-tetrazol-5-yl]-b-D-
162.1 (C]O, C]N),134.4-124.7 (C-aro),114.5 (C-aroPMBa),114.3 (C-
aroPMBb), 90.0 (C-1a), 89.7 (C-1b), 71.1 (C-4a), 70.4, 70.2, (C-2a, C-
3a), 69.9, 69.6, 69.5 (C-2b, C-3b, C-4b), 67.0 (C-5a), 66.0 (C-5b), 56.7
(CH2PhOCH3a), 55.3 (OCH3b), 55.2 (OCH3a), 52.1 (CH2PhOCH3b);
HRMS (ES) C42H34N4O10Na [M þ Na]þ calc. 777.2173, found
777.2181.
xylopyranoside (8)
To a solution of imidate 6a/6b (3.6 g, 4.54 mmol) and acceptor 7
(1.0 g, 2.34 mmol) in CH2Cl2 (50 mL) at 0 ꢀC, under argon, was
added TMSOTf (1.7 mL, 9.38 mmol). The mixture was stirred at 0 ꢀC
for 30 min, then at room temperature for 30 min. After addition of
DIEA (1 mL) the mixture was stirred for 15 min then concentrated.
The residue was purified by chromatography on silica gel (Cyclo-
hexane-AcOEt 3:2) to afford the compound 8 (1.7 g, 69%) as a white
5.1.4. 2,3,4-Tri-O-benzoyl-5-C-[2-(4-(methoxybenzyl)-2H-tetrazol-
5-yl]-
a
/
b
-
D
-xylopyranose and 2,3,4-tri-O-benzoyl-5-C-[1-(4-
-xylopyranose (5a/5b)
powder. mp 185e188 ꢀC; ½a D23
ꢂ
¼ ꢃ 77 (c 1.0, CHCl3); 1H NMR
(methoxybenzyl)-1H-tetrazol-5-yl]-
a/
b
-D
(400 MHz, CDCl3): d 7.97-7.28 (m, 15H, H-aro), 7.17 (m, 2H, H-
To a solution of tetrazoles 4a and 4b (13.4 g, 17.8 mmol) in DMF
(100 mL) at 0 ꢀC was added hydrazine acetate (2.45 g, 26.6 mmol)
in small portions over 15 min. The mixture was stirred for 1h at
aroPMB), 6.72 (m, 3H, H-aroPMB, H-1), 6.54 (d, 1H, J 8.5 Hz, H-2),
6.13 (t, 1H, J 10.0 Hz, H-40), 5.90 (t, 1H, J 10.0 Hz, H-30), 5.72 (m, 1H,
H-8), 5.67 (m, 1H, H-20), 5.61 (d, 2H, J 5.0 Hz, CH2PhOCH3), 5.43 (d,
1H, J 7.0 Hz, H-10), 5.32 (d, 1H, J 10.0 Hz, H-50), 5.25 (m, 1H, H-7),
5.00-4.80 (m, 2H, H-9, H-5), 4.40 (m, 1H, H-6), 4.20 (m, 2H,
OCH2CH3), 4.00 (m, 1H, H-16a), 3.74 (s, 3H, OCH3), 3.00 (m, 1H, H-
16b), 2.84-2.74 (m, 2H, H-10), 2.48 (m, 1H, H-14), 1.89 (m, 2H, H-15),
1.30 (m, 12H, C(CH3)3, OCH2CH3); 13C NMR (100 MHz, CDCl3):
0
ꢀC then for 4 h at room temperature. The concentrated residue
was purified on flash chromatography (Cyclohexane-Ethyl acetate
7:3) to give the hemiacetals 5a and 5b (8.0 g, 70%) as a pale yellow
solid.
The 5a:5b (2:1) ratio was determined by 1H NMR with a 5:1
a:b
ratio for 5a and a 5:1
anomers :
a
:
b
ratio for 5b. 1H NMR (400 MHz, CDCl3) for
8.14-7.15 (m, 17Ha þ 17Hb, H-aro), 6.96 (d, 2Ha, J
d 176.4, 165.7, 165.1, 164.5, 159.9 (C]O, C]N), 155.0, 150.5, 133.1, (C-
a
d
aro), 130.7 (C-8), 129.8, 129.7,129.6,128.3, 128.2, 128.1, (C-aro),127.4
(C-7), 122.2 (C-1), 119.3 (C-2), 114.3 (C-aroPMB), 99.4 (C-10), 89.9 (C-
5), 72.9 (C-30, C-6), 72.5 (C-20), 71.5 (C-40), 68.7 (C-50), 61.6
(OCH2CH3), 56.6 (CH2PhOCH3), 55.2 (OCH3), 50.2 (C-9), 44.3 (C-13),
39.8 (C-14), 37.2 (C-16), 35.3 (C-15), 35.0 (C(CH3)3), 30.2 (C-10), 29.8
(C(CH3)3), 14.7 (OCH2CH3); HRMS (ES) C59H57N5O14Na [M þ Na]þ
calc. 1082.3800, found 1082.3802.
9.0 Hz, H-aroPMBa), 6.71 (d, 2Hb, J 9.0 Hz, H-aroPMBb), 6.36-6.26
(m, 1Ha þ 1Hb, H-3a, H-3b), 6.02 (t, 1Ha, J 10.0 Hz, H-4a), 5.88 (d,
1Ha, J 3.5 Hz, H-1a), 5.86 (d, 1Hb, J 3.5 Hz, H-1b), 5.85-5.74 (m,
1Ha þ 3Hb, H-5a, H-5b, CH2PhOCH3b), 5.63 (s, 2Ha, CH2PhOCH3a),
5.51-5.42 (m, 1Ha þ 1Hb, H-4b, H-2a), 5.31 (dd, 1Hb, J 3.5 Hz, J
10.0 Hz, H-2b), 3.82 (s, 3Hb, OCH3b), 3.75 (s, 3Ha, OCH3a); 13C NMR
(100 MHz, CDCl3) for
a anomeres : d 165.8, 165.5, 164.7, 162.9, 150.5
(C]O, C]N), 133.7-124.8 (C-aro), 114.5 (C-aroPMBb), 114.2 (C-
aroPMBa), 90.9 (C-1a), 90.8 (C-1b), 72.1 (C-2a), 71.8 (C-2b ou C-3b
ou C-4b), 71.2 (C-4a), 70.2 (C-2b ou C-3b ou C-4b), 70.0 (C-3a), 69.3
(C-2b ou C-3b ou C-4b), 64.1 (C-5a), 63.4 (C-5b), 56.7 (CH2PhO-
CH3a), 55.4 (OCH3b), 55.2 (OCH3a), 52.0 (CH2PhOCH3b); HRMS (ES)
C35H31N4O9 [M þ H]þ calc. 651.2091, found 651.2111.
5.1.7. 3-O-Pivaloyl-N-ethoxycarbonylnormorphin-6-yl 2,3,4-tri-O-
benzoyl-5-C-(tetrazol-5-yl)-b-D-xylopyranoside (9)
A solution of compound 8 (1.6 g, 1.51 mmol) in TFA (4.5 mL,
60.6 mmol) was refluxed for 15 min. The mixture was concentrated
then co-concentrated with toluene (2 ꢁ 10 mL). The residue was
purified by chromatography on silica gel (Cyclohexane-Ethyl
acetate 1:2) to give the tetrazole 9 (850 mg, 60%) as a pale yellow
5.1.5. 2,3,4-Tri-O-benzoyl-5-C-[2-(4-(methoxybenzyl)-2H-tetrazol-
solid. mp 169e171 ꢀC; ½a D23
ꢂ
¼ ꢃ 66 (c 1.0, CHCl3); 1H NMR
5-yl]-
a
-D-xylopyranosyle trichloroacetimidate and 2,3,4-tri-O-
(400 MHz, CDCl3): d 7.98-7.24 (m, 15H, H-aro), 6.76 (d, 1H, J 8.0 Hz,
benzoyl-5-C-[1-(4-methoxybenzyl)-1H-tetrazol-5-yl]-
xylopyranosyle trichloroacetimidate (6a/6b)
a
-D-
H-1), 6.58 (d, 1H, J 8.0 Hz, H-2), 6.01 (t,1H, J 10.0 Hz, H-30), 5.98-5.95
(m, 1H, H-8), 5.72 (m, 1H, H-40), 5.62 (m, 1H, H-20), 5.41 (d, 1H, J
10.0 Hz, H-50), 5.34-5.26 (m, 2H, H-10 et H-7), 5.02-4.96 (m, 1H, H-
9), 4.85 (m, 1H, H-5), 4.38-4.31 (m, 1H, H-6), 4.22-4.13 (m, 2H,
OCH2CH3), 4.07-3.98 (m, 1H, H-16a), 3.10-2.83 (m, 2H, H-16b, H-
10a), 2.82-2.72 (m, 1H, H-10b), 2.47 (m, 1H, H-14), 1.93-1.85 (m, 2H,
H-15), 1.47 (s, 12H, C(CH3)3), 1.33-1.25 (m, 3H, OCH2CH3); 13C NMR
To a solution of hemiacetal 5a and 5b (6.0 g, 9.23 mmol) in
CH2Cl2 (170 mL) were added DBU (278 L, 1.86 mmol) and tri-
chloroacetonitrile (14.6 ml, 184 mmol). The mixture was stirred for
1h then a solution of acetic acid (105 L, 1.83 mmol) in water
m
m
(50 mL) was added. The organic layer was washed with water
(50 mL) dried over Na2SO4 and concentrated. The residue was
purified by chromatography on silica gel (silica gel previously
washed with a 5% solution of Et3N in ethyl acetate) (Cyclohexane-
Ethyl acetate 7:3) to afford the imidates 6a and 6b (4.7 g, 65%) as
pale yellow solid. The 6a:6b (3:1) ratio was determined by 1H NMR.
(100 MHz, CDCl3):
d 165.6, 165.1, 165.0 (C]O, C]N), 133.5, 132.4,
130.0, 129.8, 128.5, 128.4, 128.3 (C-aro, C-8, C-7), 122.5 (C-1), 119.9
(C-2), 90.9 (C-10), 77.0 (C-6), 72.03 (C-20 ou C-30), 71.9 (C-20 ou C-30),
70.7 (C-40), 68.3 (C-50), 61.8 (OCH2CH3), 49.7 (C-9), 44.5 (C-13), 40.0
(C-14), 37.1 (C-16), 35.5 (C-15), 29.7 (C-10), 27.2 (C(CH3)3), 14.7
(OCH2CH3); HRMS (ES) C51H49N5O13Na [M þ Na]þ calc. 962.3225,
found 962.3211.
1H NMR (400 MHz, CDCl3):
d 8.77 (s, 1H-b, NHb), 8.69 (s, 1Ha, NHa),
8.20-7.29 (m, 15Ha þ 17Hb, H-aro), 7.18 (d, 2Ha, J 8.5 Hz,
H-aroPMBa), 6.99 (d, 2Hb, J 8.5 Hz, H-aroPMBb), 6.94 (m,1Ha þ 1Hb,
H-1a, H-1b), 6.74 (d, 2Ha, J 8.5 Hz, H-aroPMBa), 6.36 (t, 1Ha, J
10.0 Hz, H-3a), 6.29 (t, 1Hb, J 10.0 Hz, H-3b), 6.10 (t, 1Ha, J 10.0 Hz,
H-4a), 5.80-5.69 (m, 2Ha þ 3Hb, H-2a, CH2PhOCH3b, H-5a, H-5b),
5.64 (s, 2Ha, CH2PhOCH3a), 5.62-5.55 (m, 2Hb, H-4b, H-2b), 3.84 (s,
3Hb, OCH3b), 3.75 (s, 3Ha, OCH3a); 13C NMR (100 MHz, CDCl3):
5.1.8. Morphin-6-yl-5-C-(tetrazol-5-yl)-b-D-xylopyranoside (10)
To a suspension of LAH (300 mg, 7.91 mmol) in THF (12 mL), was
added a solution of tetrazole 9 (500 mg, 0.532 mmol) in THF
(12 mL). The mixture was refluxed for 1h, ethyl acetate was added
and the pH was adjusted to 1 with HCl 1N. The mixture was

4040
C. Trécant et al. / European Journal of Medicinal Chemistry 46 (2011) 4035e4041
concentrated and the residue was purified by reverse-phase chro-
matography (C18) (H2O pure then (H2O þ 0.1%TFA)eCH3CN 80:20).
A second purification ((H2O þ 0.1%TFA)eCH3CN from 95:5 to 20:80)
was necessary to obtained the final compound 10 as a withe solid
(C-10),10.2 (CH3-oxadiazole). HRMS (ES) C25H30N3O8 [M þ H]þ calc.
500.2033, found 500.2021.
5.3. Synthesis of pyrimidine (17)
(42 mg, 16%). mp 204e207 ꢀC; ½a D23
ꢂ
¼ ꢃ 116 (c 0.5, MeOH); 1H NMR
(400 MHz, D2O):
d
6.74 (d, 1H, J 8.0 Hz, H-1), 6.65 (d, 1H, J 8.0 Hz, H-
5.3.1. 1,2,3,4-Tetra-O-benzoyl-5-C-([1,2,4]triazolo [4,3-a]pyrimidin-
2), 5.73 (m, 1H, H-8), 5.30 (m, 1H, H-7), 5.23 (d, 1H, J 5.5 Hz, H-5),
4.94-4.88 (m, 2H, H-10, H-50), 4.48 (m, 1H, H-6), 4.15 (m, 1H, H-9),
3.80 (t, 1H, J 9.5 Hz, H-40), 3.69 (t, 1H, J 9.5 Hz, H-30), 3.54 (m, 1H, H-
20), 3.37 (m, 1H, H-16a), 3.24 (m, 1H, H-10a), 3.10 (m, 1H, H-16b),
2.95 (s, 3H, NCH3), 2.95-2.83 (m, 2H, H-10b, H-14), 2.32-2.02 (m, 2H,
3-yl)-
([1,2,4]triazolo [1,5-a]pyrimidin-3-yl)-
A solution of 1,2,3,4-tetra-O-benzoyl-5-C-(tetrazol-5-yl)-a/b-D-
xylopyranose 3 (3.0 g, 4.73 mmol) and 2-chloropyrimidine (813 mg,
7.10 mmol) in pyridine (38 mL) was refluxed overnight. The reac-
tion mixture was concentrated and the residue was purified by
chromatography on silica gel (Cyclohexane-AcOEt 3:7) to give the
mixture of pyrimidines 13a and 13b (2.4 g, 74%) as pale yellow solid.
a
/
b
-
D
-xylopyranose (13a) and 1,2,3,4-tetra-O-benzoyl-5-C-
a/b-D
-xylopyranose (13b)
H-15); 13C NMR (100 MHz, D2O):
d 145.5 (C]N), 137.8, 134.0 (C-
ipso), 131.1 (C-8), 129.0 (C-ipso), 126.0 (C-7), 123.3 (C-ipso), 120.4 (C-
2), 117.7 (C-1), 102.3 (C-10), 88.1 (C-5), 75.0 (C-30), 73.3 (C-6), 73.0
(C-20), 72.4 (C-40), 69.3 (C-50), 60.5 (C-9), 47.1 (C-16), 41.5 (C-13),
40.9 (NCH3), 38.4 (C-14), 32.4 (C-15), 20.8 (C-10); HMRS (ES)
C23H28N5O7 [M þ H]þ calc.486.1989, found 486.1982.
The a:b ratio (2/1 for 13a and 7/3 for 13b) were determined on the
1H NMR spectra.
For 13a : 1H NMR(400 MHz, CDCl3):
d
8.93 (m, 1H
, H-50
þ 20H
, J 4.0 Hz, J 7.0 Hz, H-60
), 6.57 (t, 1H , J 9.5 Hz, H-3
), 6.29 (m, 2H , H-3 , H-4
, H-2 ), 5.93 (dd, 1H , J 3.5 Hz, J 10.0 Hz, H-
, H-5 165.5,
); 13C NMR (100 MHz, CDCl3):
165.2, 165.1, (C]O), 164.6 (C-30 ), 164.4 (C-30 ), 155.1 (C-8a0
C-8a0 ), 154.2 (C-50 or C-70 ), 154.0 (C-50 or C-70 ), 140.3 (C-50
or
C-70 ), 140.1 (C-50 or C-70
), 134.4, 134.2, 133.8, 133.7, 133.5, 132.5,
132.4, 130.2-128.3 (C-aro), 110.4 (C-6’ , C-6’ ), 93.0 (C-1 ), 89.7
), 70.7 (C-2 or C-3 or C-4 ), 70.4
), 69.4 (C-3 or C-4 ), 69.1 (C-3
a
a
, H-50
or H-70
b, H-aro),
a or
H-70
8.64 (m, 1H
7.04 (d, 1H
6.93 (dd, 1H
6.52 (d,1H , J 7.5 Hz, H-1
2H , H-4 , H-5
þ 1H
), 5.90-5.86 (m, 1H
a
), 8.87 (m, 1H
, H-50
, J 3.5 Hz, H-1
, J 3.5 Hz, J 6.5 Hz, H-60
b
, H-50
or H-7’
), 7,00 (dd, 1H
b
or H-70
b
), 8.73 (m, 1H
a
a
a),
b
a
b
b
b), 8.22-7.25 (m, 20H
5.2. Synthesis of 1,3,4-oxadiazole (12)
a
a
a
a
),
),
b
a
5.2.1. 3-O-Acetylmorphin-6-yl 2,3,4-tri-O-acetyl-5-C-(2-methyl-
b
b
b
b
b), 6.11-6.01 (m,
1,3,4-oxadiazol-5-yl)-
b
-D
-xylopyranoside (11)
a
b
a
a
b
a
A solution of tetrazole 10 (134 mg, 0.28 mmol) in acetic anhy-
dride (3 mL) was refluxed overnight then the reaction mixture was
concentrated. The residue was co-concentrated with toluene
(2 ꢁ 10 mL) and purified by chromatography on silica gel (CHCl3-
MeOH 98:2 to 95:5) to give the oxadiazole 11 (102 mg, 55%) as pale
2a
b
b
d
b
a
b
a,
b
b
a
a
b
b
a
a
a
b
b
b
yellow solid. mp 180e186 ꢀC; ½a D23
ꢂ
¼ ꢃ 82 (c 1.0, CHCl3); 1H NMR
(C-1
a
), 71.4 (C-2
), 70.1 (C-2
), 68.7 (C-5
685.1935 found 685.1985.
b
b
or C-3
or C-3
, C-5
b
b
b
or C-4
or C-4
b
b
b
b
(400 MHz, CDCl3):
d
6.77 (d, 1H, J 8.0 Hz, H-1), 6.59 (d, 1H, J 8.0 Hz,
(C-2a
a
a
a
H-2), 5.71 (m, 1H, H-8), 5.37 (m, 2H, H-40 et H-30), 5.27 (m, 1H, H-7),
5.18 (m, 1H, H-20), 4.99 (d, 1H, J 7.5 Hz, H-10), 4.95 (d, 1H, J 5.5 Hz,
H-5), 4.87 (m, 1H, H-50), 4.31 (m, 1H, H-6), 3.71 (m, 1H, H-9), 3.07
(m, 1H, H-10a), 2.97-2.89 (m, 2H, H-16a, H-14), 2.62-2.52 (m, 8H,
H-10b, CH3-oxadiazole, NCH3, H-16b), 2.33 (s, CH3CO), 2.28 (m, 1H,
H-15a), 2.14 (s, 3H, CH3CO), 2.04 (s, 3H, CH3CO), 1.98 (m, 1H, H-15b),
or C-4
a
a
). HRMS (ES) C38H29N4O9 [M þ H]þ calc.
For 13b : 1H NMR (400 MHz, CDCl3):
H-50 , H-70 , H-50 , H-70
), 8.22-7.30 (m, 20H
(dd, 1H ), 7.07-7.02 (m, 1H
, J 6.5 Hz, J 4.5 Hz, H-60
), 6.47 (m, 1H , H-1 , H-3 ), 6.27-6.16 (m, 1H
þ 1H
, H-3 , H-4 ), 6.06 (m, 1H , H-2 ), 5.89 (dd, 1H
), 5.73 (d, 1H , J 10.0 Hz, H-5 ), 5.53 (d, 1H
). 13C NMR (100 MHz, CDCl3):
165.8, 165.6, 165.3, 165.0, 164.8,
164.5, 164.2 (C]O), 164.0 (C-20 ), 163.8 (C-20 ), 155.3 (C-3a0
, C-
3a0 ), 155.1 (C-70 ), 155.0 (C-70 ), 136.0 (C-50 , C-50
), 134.0, 133.7,
133.4-133.2, 130.2-128.2 (C-aro), 110.7 (C-60 ), 110.6 (C-60
), 92.9
(C-1 ), 90.0 (C-1 ), 72.5 (C-3 or C-4 ), 72.0 (C-3 or C-4 ), 71.3 (C-
), 70.6 (C-2 ), 70.4 (C-2 , C-3 ), 69.4 (C-5 , C-5 ). HRMS (ES)
d
8.80-8.71 (m, 2H
þ 20H
þ 1H
a
þ 2H
b,
a
a
b
b
a
b, H-aro), 7.10
a
a
a
b
a
, H-60
þ 2H
b,
,
H-1
H-4
a
a
a
b
b
b
a
b
b
1.93 (s, 3H, CH3CO). 13C NMR (100 MHz, CDCl3):
d
175.9, 170.0, 169.4,
b
b
a, J 3.5 Hz, J
169.3, 165.3, 161.2 (C]O, C]N), 150.3, 132.0 (C-ipso), 130.9 (C-8),
130.6, 130.4 (C-ipso), 127.5 (C-7), 122.6 (C-1), 119.5 (C-2), 100.0 (C-
10), 89.1 (C-5), 73.6 (C-6), 71.8 (C-30 or C-40), 71.0 (C-20), 69.6 (C-30 or
C-40), 67.9 (C-50), 58.5 (C-9), 46.0 (C-16), 42.7 (C-13), 41.7 (NCH3),
38.9 (C-14), 33.8 (C-15), 21.5 (C-10), 20.7, 20.6, 20.4 (CH3CO), 11.0
(CH3-oxadiazole). HRMS (ES) C33H38N3O12 [M þ H]þ calc. 668.2455,
found 668.2560.
10.0 Hz, H-2
H-5
a
a
a
b, J 9.0 Hz,
b
d
a
b
a
b
a
b
a
b
a
b
b
a
b
b
b
b
4a
b
a
a
a
b
C38H29N4O9 [M þ H]þ calc. 685.1935, found 685.1953.
5.2.2. Morphin-6-yl 5-C-(2-methyl-1,3,4-oxadiazol-5-yl)-b-D-
xylopyranoside (12)
5.3.2. 3,4-Tri-O-benzoyl-5-C-([1,2,4]triazolo [1,5-a]pyrimidin-2-yl)-
-xylopyranose (14)
To a solution of a mixture of pyrimidines 13a and 13b (500 mg,
To a solution of oxadiazole 11 (100 mg, 0.15 mmol) in methanol
(2 mL) was added, at room temperature, sodium methoxyde
(32 mg, 0.59 mmol). The reaction mixture was stirred for 3 h then
resine Amberlyte Hþ was added. The mixture was filtered, the
filtrate was concentrated under reduced pressure and the residue
was purified by reverse-phase chromatography (C18) (H2O þ 0.1%
TFA)-CH3CN 95:5 to 20:80) to give the oxadiazole 12 (34 mg, 46%)
a/b-D
0.73 mmol) in DMF (19 mL) was added, at 0 ꢀC, hydrazine acetate
(101 mg, 1.10 mmol) in small portions over a period of 10 min. The
reaction mixture was stirred at 0 ꢀC for 1 h then 2 h at room
temperature. The mixture was concentrated and the residue was
purified by chromatography on silica gel (Cyclohexane-AcOEt 1:4)
to give the corresponding hemiacetal 14 (284 mg, 67%) as white
as white crystals. mp 215e218 ꢀC; 1H NMR (300 MHz, D2O):
d 6.83
(d, 1H, J 8.0 Hz, H-1), 6.74 (d, 1H, J 8.0 Hz, H-2), 5.84 (m, 1H, H-8),
5.46 (m, 1H, H-7), 5.32 (d, 1H, J 6.5 Hz, H-5), 5.00 (d, 1H, J 8.0 Hz,
H-10), 4.90 (m, 1H, H-50), 4.59 (m, 1H, H-6), 4.26 (m, 1H, H-9), 3.92
(t, 1H, J 9.5 Hz, H-40), 3.74 (t, 1H, J 9.5 Hz, H-30), 3.59 (m, 1H, H-20),
3.45-3.38 (m, 1H, H-16a), 3.29 (d, 1H, H-10a), 3.17 (m, 1H, H-16b),
3.03-2.92 (m, 5H, NCH3, H-10b, H-14), 2.63 (s, 3H, CH3-oxadiazole),
crystals. The NMR spectra showed an
(400 MHz, CDCl3) for anomer :
a
:
b
ratio of 4:1; 1H NMR
d 8.77 (dd, 1H, J 2.0 Hz, J 7.0 Hz, H-
a
50 or H-70), 8.69 (m, 1H, H-50 or H-70), 8.02-7.27 (m, 15H, H-aro), 7.04
(m, 1H, H-60), 6.43 (t, 1H, J 10.0 Hz, H-3), 6.11 (t, 1H, J 10.0 Hz, H-4),
5.95 (d, 1H, J 3.5 Hz, H-1), 5.88 (d, 1H, J 10.0 Hz, H-5), 5.49 (dd, 1H, J
3.5 Hz, J 10.0 Hz, H-2); 13C NMR (100 MHz, CDCl3) for
a anomer :
2.40-2.11 (m, 2H, H-15); 13C NMR (75 MHz, D2O):
d
131.2 (C-8),
d
165.8, 165.7, 165.0 (C]O), 164.9 (C-20), 155.2 (C-3a0), 155.1 (C-70),
126.3 (C-7), 120.6 (C-2), 118.2 (C-1), 102.5 (C-10), 88.2 (C-5), 75.0
(C-30), 73.5 (C-6), 73.0 (C-20 or C-40), 71.4 (C-20 or C-40), 69.3 (C-50),
60.7 (C-9), 47.4 (C-6), 41.1 (NCH3), 38.7 (C-14), 32.6 (C-15), 21.1
136.1 (C-50), 133.2-132.9, 129.3-128.2 (C-aro), 110.8 (C-60), 90.8 (C-
1), 72.2 (C-2), 71.7 (C-4), 70.5 (C-3), 66.3 (C-5). HRMS (ES)
C31H25N4O8 [M þ H]þ calc. 581.1672, found 581.1661.

C. Trécant et al. / European Journal of Medicinal Chemistry 46 (2011) 4035e4041
4041
5.3.3. 2,3,4-Tri-O-benzoyl-5-C-([1,2,4]triazolo [1,5-a]pyrimidin-2-
yl)- -D-xylopyranosyle trichloroacetimidate (15)
To a solution of hemiacetal 14 (650 mg, 1.12 mmol) in CH2Cl2
(15 mL) were added, at room temperature, DBU (186 L, 1.24 mmol)
and trichloroacetonitrile (2.20 mL, 21.9 mmol). The reaction
mixture was stirred for 1.5 h at room temperature and an aqueous
(61 mg, 40%). mp 201 ꢀC ½a D23
ꢂ
¼ ꢃ 118 (c 0.5, MeOH); 1H NMR
a
(300 MHz, D2O): d 6.80 (d, 1H, J 8.0 Hz, H-1), 6.72 (d, 1H, J 8.0 Hz, H-
2), 5.83 (m, 1H, H-8), 5.43 (m, 1H, H-7), 5.36 (m, 1H, H-50), 5.29 (d,
1H, J 5.5 Hz, H-5), 4.91 (d, 1H, J 8.0 Hz, H-10), 4.52 (m, 1H, H-6), 4.51
(d, 1H, J 9.5 Hz, H-50), 4.32-4.20 (m, 2H, H-9, H-600a), 4.10 (m, 1H, H-
600b), 3.78 (t, 1H, J 9.5 Hz, H-40), 3.68 (t, 1H, J 9.5 Hz, H-30), 3.53 (dd,
1H, J 8.0 Hz, J 9.5 Hz, H-20), 3.40 (m, 1H, H-16a), 3.25 (m, 1H, H-10a),
3.12 (m, 1H, H-16b), 3.05-2.89 (m, 5H, H-10b, H-14, NCH3), 2.35-2.11
m
solution of acetic acid (70 mL, 1.22 mmol in 7 mL of water) was
added. The layers were separated, the organic layer was washed
with water (7 mL) and the combined organic layers were dried over
Na2SO4 and concentrated. The residue was purified by chroma-
tography on silica gel (silica previously washed with a 5% solution
of NEt3 in AcOEt) (Cyclohexane-AcOEt 1:1) to afford the imidate 15
(m, 4H, H-15, H-700); 13C NMR (75 MHz, D2O):
d 131.2 (C-8), 126.1 (C-
7), 120.5 (C-2), 117.8 (C-1), 102.5 (C-10), 88.3 (C-5), 74.9 (C-30), 73.7
(C-6), 72.9 (C-20), 71.7 (C-40), 71.1 (C-500), 70.4 (C-50), 60.6 (C-9), 47.2
(C-16), 40.9 (NCH3), 40.1 (C-600), 38.5 (C-14), 32.4 (C-15), 26.2 (C-700),
20.9 (C-10). HRMS (ES) C27H34N5O8 [M þ H]þ calc. 556.2407, found
556.2390.
(565 mg, 70%) as a yellow solid. mp 72e73 ꢀC ½a D23
¼ 117 (c 0.1,
ꢂ
CHCl3); 1H NMR (400 MHz, CDCl3):
d
8.81-8.76 (m, 2H, H-50, H-70),
8.69 (s, 1H, NH), 8.00-7.29 (m, 15H, H-aro), 7.11 (dd, 1H, J 4.0 Hz, J
7.0 Hz, H-60), 7.00 (d, 1H, J 3.5 Hz, H-1), 6.43 (t, 1H, J 10.0 Hz, H-3),
6.20 (t, 1H, J 10.0 Hz, H-4), 5.81 (dd, 1H, J 3.5 Hz, J 10.0 Hz, H-2), 5.71
Acknowledgments
(d, 1H, J 10.0 Hz, H-5); 13C NMR (100 MHz, CDCl3):
d 165.6, 165.3,
The authors thank FRANCOPIAÒ; for its financial support and for
the generous gift of compound 7.
164.7 (C]O), 164.0 (C-20), 160.4 (C]N), 155.4 (C-3a’), 155.1 (C-70),
135.9 (C-50), 133.5-133.2, 129.9-128.2 (C-aro), 110.7 (C-60), 93.3 (C-
1), 71.1 (C-4), 70.6 (C-2), 70.1 (C-3), 69.4 (C-5).
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(470 mg, 31%) as a yellow solid. mp 171.5 ꢀC ½a D23
¼ ꢃ65 (c 0.5,
ꢂ
CHCl3); 1H NMR (400 MHz, CDCl3):
d 8.80 (dd, 1H, J 2.0 Hz, 4.0 Hz,
H-500 or H-700), 8.75 (dd, 1H, J 2.0 Hz, 7.0 Hz, H-500 or H-700), 8.02-7.29
(m, 15H, H-aro), 7.10 (dd, 1H, J 4.0 Hz, J 7.0 Hz, H-600), 6.71 (d, 1H, J
8.0 Hz, H-1), 6.52 (d,1H, J 8.0 Hz, H-2), 6.21 (m,1H, H-40), 5.95 (t,1H,
J 9.0 Hz, H-30), 5.75-5.69 (m, 2H, H-20, H-8), 5.47 (d, 1H, J 7.0 Hz,
H-10), 5.34 (d, 1H, J 9.5 Hz, H-50), 5.23 (m, 1H, H-7), 4.98 (d, 1H, J
5.5 Hz, H-5), 4.93 (m, 1H, H-9), 4.46 (m, 1H, H-6), 4.20-4.05 (m, 2H,
OCH2CH3), 3.99 (m, 1H, H-16a), 3.00 (m, 1H, H-16b), 2.90-2.70 (m,
2H, H-10), 2.48 (m, 1H, H-14), 1.88 (m, 2H, H-15), 1.31-1.25 (m, 12H,
C(CH3)3, OCH2CH3); 13C NMR (100 MHz, CDCl3):
d 165.7, 165.2, 164.7
(C]O), 155.4 (C-3a00), 154.9 (C-70), 136.0 (C-50), 133.1-128.2 (C-aro,
C-7, C-8), 122.2 (C-1), 119.2 (C-2), 110.6 (C-60), 99.4 (C-10), 89.9 (C-5),
73.0 (C-6), 72.7 (C-30), 72.2 (C-20), 71.3 (C-40, C-50), 61.5 (OCH2CH3),
49.8 (C-9), 44.3 (C-13), 39.8 (C-14), 37.2 (C-16), 35.3 (C-15), 30.0 (C-
10), 27.2 (C(CH3)3), 14.7 (OCH2CH3). HRMS (ES) C55H52N5O13
[M þ H]þ calc. 990.3562 found 990.3596.
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(H2O þ 0.1%TFA)-CH3CN 80:20) to eliminate the aluminium salts.
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