Synthesis of an hexadentate tricyclic tetraazadiacetic ligand as precursor for MRI contrast enhancement agents

Article abstract of DOI:10.1016/j.tet.2009.06.117

A tricyclic tetraazadiacetic compound, which is a rigidified derivative of cyclo-PCTA12 ligand with an oxo-ethylene bridge replacing an ethylene one, was prepared. The synthetic route involved the macrocyclization between an activated amido-disulfonamide and the 2,6-bis(bromomethyl)pyridine. The acetate side chains were grafted on the macrocyclic backbone to lead to the highly rigid tricyclic ligand in 34% overall yield in four steps from the linear amido-disulfonamide precursor. The corresponding Gd(III) and Mn(II) complexes were then prepared in order to evaluate their potential as contrast agent for MRI.

Full text of DOI:10.1016/j.tet.2009.06.117

Tetrahedron 65 (2009) 7573–7579
Contents lists available at ScienceDirect
Tetrahedron
journal homepage: www.elsevier.com/locate/tet
Synthesis of an hexadentate tricyclic tetraazadiacetic ligand as precursor
for MRI contrast enhancement agents
a
a
,
a
b
*
Fabienne Dioury , Clotilde Ferroud , Alain Guy , Marc Port
a
Conservatoire national des arts et m e´ tiers, Service de Transformations Chimiques et Pharmaceutiques, UMR CNRS 7084, Case 303, 2 rue Cont e´ , 75003 Paris, France
Guerbet, BP 57400, 95943 Roissy CdG Cedex, France
b
a r t i c l e i n f o
a b s t r a c t
Article history:
A tricyclic tetraazadiacetic compound, which is a rigidified derivative of cyclo-PCTA12 ligand with an
oxo-ethylene bridge replacing an ethylene one, was prepared. The synthetic route involved the macro-
cyclization between an activated amido-disulfonamide and the 2,6-bis(bromomethyl)pyridine. The ac-
etate side chains were grafted on the macrocyclic backbone to lead to the highly rigid tricyclic ligand in
Received 24 March 2009
Received in revised form 26 June 2009
Accepted 29 June 2009
Available online 3 July 2009
34% overall yield in four steps from the linear amido-disulfonamide precursor. The corresponding Gd(III)
and Mn(II) complexes were then prepared in order to evaluate their potential as contrast agent for MRI.
Keywords:
Ó 2009 Elsevier Ltd. All rights reserved.
Contrast agent for MRI
Gadolinium complex
Manganese complex
PCTA12 derivative
Macrocyclic polyaza-polycarboxylic acid
1
. Introduction
reorientational correlation time of the paramagnetic complex (
Recently, it has been postulated that the rigidification of the chelate
s
R
).1,6
8
,9
Magnetic Resonance Imaging (MRI) is a non-invasive clinical
modality widely used in the diagnosis of human diseases. Some
MRI examinations require the use of contrast agents (CAs) to im-
prove visualization of abnormal structures or lesions, and the most
widespread pharmaceuticals routinely used for such purpose are
gadolinium-based CAs. They are complexes of Gd(III) with ligands
designed to form kinetic and thermodynamic stable chelates
thereby significantly reducing the toxicity of the free Gd(III) ion. It is
now well-established that polyamino-polyacetate ligands can
confer such a stability to the corresponding gadolinium complexes
and that well-designed macrocyclic compounds, which are preor-
ganized rigid rings of almost optimal size to cage the Gd(III) ion,
structure could be favourable to an higher longitudinal relaxivity.
10
The macrocyclic PCTA12 ligand is a rigidified analog of the well-
known DOTA ligand (Fig. 1) and the Gd-complexes formed with
PCTA12 and with other pyridine-containing (PC-type) ligands are
very stable and exhibit improved longitudinal relaxivity in com-
1,2
1,11–13
parison with that of the marketed gadolinium-based CAs.
O
HO
HO
O
N
N
N
N
OH
OH
HO C
2
N
N
CO H
2
N
N
3
O
O
CO H
generate Gd-complexes of higher stability. In terms of perfor-
2
mance, there is still a great effort to find new products endowed
with higher relaxivity, so that the CA could be administered at
a lower dose which is probably a key issue to move towards organ/
DOTA ligand
PCTA12 ligand
4
,5
tissue-specific agents and MRI molecular imaging.
The relaxation theory of paramagnetic substances was discussed
1,6,7
N
N
HO C
CO H
HO C
CO H
in details in previous reviews.
Relaxivity is a function of several
2
2
2
2
N
N
N
N
parameters, the most important being the number of water mole-
cules coordinated to the metal center (q, inner sphere term), the
H
N
N
lifetime of the coordinated water molecule
(
s
M
), and the
CO
2
H
O
rac-cyclo-PCTA12 ligand
rac-1
*
Corresponding author. Tel.: þ33 1 40 27 24 02; fax: þ33 1 42 71 05 34.
E-mail address: clotilde.ferroud@cnam.fr (C. Ferroud).
Figure 1. Some 12-membered polyamino-polyacetic macrocyclic ligands for the
complexation of Gd ion.
3
þ
0
040-4020/$ – see front matter Ó 2009 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tet.2009.06.117

7574
F. Dioury et al. / Tetrahedron 65 (2009) 7573–7579
With these structural aspects in mind, we have recently reported
the synthesis of the even more rigid cyclo-PCTA12 ligand (Fig. 1)
HO C
N
CO H
2
14
2
N
and that of its Gd-complex. We have shown that the rigidification
of the scaffold did not alter the inertness of the complex toward
N
N
NH
NH
H
N
H
N
transmetallation by Zn2þ ions and that the relaxivity was not
O
quenched by endogeneous anions such as chloride, citrate, and
phosphate.15 Moreover, the constrained Gd-cyclo-PCTA12 complex
proved to have an higher longitudinal relaxivity than that of the
parent Gd-PCTA12 always above than those of the other gadoli-
nium-based contrast agents used clinically at the present time. At
last, this previous work showed that the rigidification induced the
shortening of the residence lifetime of the inner-sphere water
O
rac-1
R
NH
NH2
O
+
NH2
NH2
EtO
NH
H
N
( )
+
_
310
O
R
molecules
(
s
M
¼34 ns versus 82 ns for Gd-PCTA12) thus
approaching the optimal value required to attain high relaxivity
once the chelate is immobilized bycovalent or non-covalent binding
to macromolecules.7
R : Amine protecting / activating group
Scheme 1. Synthetic pathway envisaged for the preparation of the target pyridine-
containing macrocycle 1.
These results encouraged us to study the influence of structural
modifications on PCTA12 skeleton. We so decided to prepare the
new cyclo-PCTA12 derivative 1 in which the last ethylene bridge
connecting two N-atoms is replaced by an oxo-ethylene bridge
O
R
(a)
+
NH2
EtO
NH
NH
H N
NH2
HCl
(Fig. 1). This macrocyclic ligand features four nitrogen atoms car-
2
rying two carboxymethyl side chains. This hexadentate ligand
rac-2
H
2
þ
N
could give either a non-ionic complex with Mn cation or a posi-
O
R
3
þ
tively charged species upon complexation with Gd cation. In the
latter case, the positive charge may benefit to tissue/organ speci-
ficity for MRI purpose16 and, as it was established for other hex-
rac-3 : R = H
rac-4 : R = SO Ar 58 %
50 %
(
b)
2
17
adentate PC-type structures, the lower denticity of the target
(c)
ligand 1 may favour higher relaxivity by allowing three water
N
N
1,16
molecules in the inner-sphere coordination.
This assumes that
OH
OH
Br
Br
the endo amide subunit in ligand 1 is involved in the nine-co-
ordinate ground state of gadolinium(III), probably by its carbonyl
oxygen atom, together with the other three nitrogen atoms of the
ring, and with the two carbonyl oxygen atoms of the carboxylate
pendant arms. So, in ligand 1, the endo amide subunit replaces and
plays the coordinating role of one of the three amine subunits
found in the parent ligands PCTA12 and cyclo-PCTA12 so that the
presence of a carboxamide function should not be damageable in
5
: 75-90%
Scheme 2. Preparations of the precursors for macrocyclization rac-4 and 5; reagents
and conditions: Ar¼(2-NO )C ; (a) EtOH, reflux, 3 days; (b) Ar-SO -Cl (2.7 equiv),
Na CO (3 equiv), Et O/THF/H O (63/20/17), rt, 1.5 day; (c) (i) HBr (aq, 48%) (16 equiv),
SO (aq, 96%) (3.6 equiv), reflux, 31 h; (ii) HBr (aq, 48%) (16 equiv), H SO (aq, 96%)
3.6 equiv), reflux, 63 h; (iii) Na CO
2
6
H
4
2
2
3
2
2
H
(
2
4
2
4
2
3
.
ArSO
2
Cl)23,24 without any acid scavenger. In such conditions, there
0
term of water exchange rate (1/
s
M
) as it was reported for ligands
is no, or a very few amount of, competitive di-N,N -functionalized
compound formed and the mono-N-functionalized compound is
always isolated with high yields superior to 70%. In our case, by
allowing to react an equimolecular mixture of hydrochloric salt of
ethyl glycinate and trans-1,2-diamino-cyclohexane 2 for three days
in refluxing ethanol, diamine 2 was selectively transformed in the
desired amido-diamine 3. Moreover, amido-diamine 3 crystallizes
during the process and was isolated by simple filtration in 50% yield
with a satisfying purity allowing to use the crude product. It should
be noted that this process has been scaled up to a large scale (14 g),
once limited at the laboratory scale by the prolonged reflux to-
gether with the dilution which proved to be an important para-
meter. A 1.0 M concentration for both reagents led to an important
precipitation that prevented an effective stirring. A dilution to
0.25 M induced a decreased yield of the expected monocondensed
product 3 (38%). The best results were obtained with a 0.5 M con-
centration for both reagents. In that case, a GC–MS analysis of the
residual alcoholic surnageant revealed the presence of the desired
amido-diamine 3 together with the unreacted starting diamino
compound 2. As the glycinate reagent was totally consumed, we
added an excess of glycinate reagent in order to improve the yield.
Unfortunately, when a three fold excess of glycinate derivative was
added, either in one portion or in three successive portions, as
whose carboxylate pendant arms were replaced by carboxamide
pendant arms.3
1,32
The results presented here detail the synthetic
route developed to prepare the tricyclic PC-type ligand 1. Com-
plexation with Gd(III) and Mn(II) is also reported in order to ap-
preciate its potential activity as CA for MRI.
2
2
. Results and discussion
.1. Preparation of the ligand
It has been previously shown in the literature that two synthetic
routes could be envisaged for the preparation of such PCTA de-
rivatives depending on the stage at which the arms are grafted: ei-
ther on a pyridine-containing macrocyclic intermediate bearing
functionalizable secondary amine sites, or on a linear triamine
14,16,18–21
precursor before the macrocyclization process.
By com-
parison with other PCTA12 derivatives, the target macrocycle 1
bears only two acetate arms attached on amino sites a priori no so
crowded so that we decided to develop the first strategy which al-
lows variations on the nature of ligating chains (Scheme 1). The
construction of the linear amido-diamine precursor 3 could result
from the monoamidification of trans-1,2-diamino-cyclohexane with
a glycine derivative (Scheme 2). Moreover, we planned to apply the
2
3,24
usually practised for monofunctionalization,
the expected
Fukuyama’s 2-nitro-phenylsulfonamide strategy (R¼(2-NO
2
)C
6
H
4
-
amido-diamine 3 did not precipitate from the reactional medium.
The compound 3 was recovered in solution together with unreac-
ted starting diamine 2 and polyamido compounds. Furthermore,
when the ethyl glycinate derivative was replaced by the more re-
active methyl derivative, the reaction occurred in refluxing
2
2
SO
2
) to control and activate the macrocyclization process.
The mono-N-functionalizations of trans-1,2-diamino-cyclohex-
ane 2 are usually controlled by reacting a three fold excess of the
unexpensive diamine 2 relative to the derivatizing agent (Boc O,
2

F. Dioury et al. / Tetrahedron 65 (2009) 7573–7579
7575
methanol and, after 3 days, no conversion of diamino reagent 2 was
observed while the glycinate reagent was totally converted to pi-
perazine-2,5-dione. Even if all attempts to improve the moderate
yield failed, this protocol presents several advantages as it involves
commercially available and inexpensive reagents, a benign solvent
allowing the reaction to be conducted at high concentation, and it
affords a pure crude product easily isolated by filtration.
Subsequent activation/protection was realized by reacting the
previous triamino compound 3 with a small excess of 2-nitro-
2 3
phenylsulfonyl chloride in the presence of Na CO as a non nucle-
ophile acid scavenger. The reaction occurred at room temperature
and, once again, the crude product isolated by filtration in 58% yield
was pure enough to avoid any purification step. It should be noted
that the analysis of the residual filtrate revealed the presence of the
desired product 4 so that the yield could be increased by treatment
of this filtrate.
complex with a larger proportion of uncyclized [2þ1] adducts,
while replacing DMF by CH CN had also a dramatic effect for both
carbonates with higher proportions of competitive [2þ2] or [2þ1]
3
2
7
adducts.
The H and 13C NMR spectra of the macrocyclic disulfonamide 6
revealed the presence of two forms in 80/20 or 67/33 ratio in CDCl
or DMSO-d solution respectively. By increasing the temperature,
the H NMR spectrum of a DMSO-d solution showed coalescence
1
3
6
1
6
for all signals of both isomers between 393 and 413 K. It is in-
teresting to notice that we previously observed such a splitting for
14
the less rigid cyclo-PCTA12 analog, attributed to the presence, at
room temperature, of a mixture of rotamers probably due to pre-
vented free rotations generated by the bulky 2-nitro-phenyl-
sulfonyl and/or cyclohexyl subunits.
The cleavage of the 2-nitro-phenylsulfonamides was realized
2
8
following a conventional method, by treatment with thiophenate
in slightly warmed CH CN. In such conditions, the desulfonylated
The quite expensive 2,6-bis(bromomethyl)pyridine 5 reagent
was prepared from the 2,6-bis(hydroxymethyl)pyridine whose
bromination has been reported with hydrobromic acid in water
under reflux with26 or without an additional portion of concen-
trated sulfuric acid (Scheme 2). In both cases, the presence of
mono-brominated side-product had required an effective purifi-
3
macrocycle 7 was isolated in 86% yield as hydrochloride. It should
be interesting to note that this step can also be envisaged in DMF,
from the crude DMF solution of previous macrocycle 6. In that case,
the reaction medium of previous step was twice concentrated and
the reaction occurred overnight at room temperature with similar
yield.
25
2
5
26
cation step by column chromatography or by recristallization.
After optimization, two successive additions of both concentrated
hydrobromic and sulfuric acids, and a prolonged reflux in water (at
least 4 days), led to the desired product 5 which crystallized in the
crude mixture once cooled to room temperature. In these condi-
tions, the proportion of mono-brominated compound recovered
fell down to 1.5% (molar proportion), and yields up to 90% of the
expected di-brominated compound 5 were obtained on a large
scale (>20 g).
The subsequent di-N-alkylation step was then performed in
conditions previously described for the parent cyclo-PCTA12 se-
14
ries, with a stoechiometric amount of tert-butyl bromoacetate in
the presence of a slight excess of triethylamine in refluxing THF. The
desired product 8 was isolated after purification by column chro-
matography on silica gel in 44% overall yield (3 steps from the linear
disulfonalmide 4). At last, when treated with anhydrous hydrogen
chloride, the diester 8 was converted to the target macrocyclic
diacetic acid 1 as the HCl salt with highyield (77 to 90% with 1<x<3).
We verified that the desired macrocycle 1 could also result from
direct di-N-alkylation of macrocyclic diamine 7 with an excess of
sodium bromoacetate in alcaline aqueous medium (pH 10). In such
conditions, the conversionwas complete after a prolonged warming
(3 days) and no trace of per-alkylated products was detected.
With the two precursors 4 and 5 in hand, the macrocyclization
14,20,21
step was then envisaged (Scheme 3). As previously observed,
optimization of the conditions was necessary to minimize the
amounts of competitive adducts such as cyclic [2þ2] adducts,
uncyclized [2þ1] adducts (two amido-disulfonamides 4 condensed
on the bis-bromo compound 5), and other oligomers. By slow ad-
dition of a slight excess of 2,6-bis(bromomethyl)pyridine 5 to
a warmed DMF solution of amido-disulfonamide 4 in the presence
2.2. Preparation of the gadolinium and manganese
complexes
2 3
of an excess of K CO , an immediate condensation occurred with
the formation of the desired macrocycle 6 isolated in 59% yield after
chromatography. We studied the influence of both the nature of the
With the hexadentate ligand 1 in hand, we decided to prepare
the corresponding gadolinium (III) and manganese (II) complexes
in order to evaluate them as potential contrast agents for MRI.
Several examples of gadolinium complexes formed with PC-type
carbonate and that of the polar solvent used. Indeed, when K
2 3
CO
was replaced by Na CO , the crude mixture was much more
2
3
11,12,13,16,29,30
ligands exhibited a 1/1 stoichiometry.
We postulated
(
a)
ArO S N
(b)
5
+ rac-4
N
N
a similar stoichiometry for both target complexes and, by mixing
equimolar amounts of ligand 1 with gadolinium or manganese
chloride, in water, at pH 5.7–5.8, the expected Gd–1 and Mn–1
complexes were formed. Both complexes were isolated from alca-
line water solutions (KOH), then characterized in the solid state (IR)
and in solution (mass spectrometry). In both cases, the complexa-
tion induced a shift of the CO stretching vibration bands from 1740
N SO Ar
NH
NH
2
2
H
N
H
N
(
c)
O
O
rac-6 : 59 %
rac-7 : 86 %
e)
(
ꢀ
1
ꢀ1
and 1687 cm to lower wave numbers (1660–1540 cm ). More-
over, by mass spectrometry, only species of 1/1 stoichiometry were
detected together with mono-hydrated form(s) in the case of the
gadolinium complex.
t
N
t
CO Bu
2
HO C
N
CO H
BuO C
2
2
2
N
N
N
N
(
d)
H
N
H
N
O
.
x HCl
O
3. Conclusion
rac-8 : 44 % (from rac-4)
rac-1 : > 77 % (fromrac-8)
Scheme 3. Route to the target macrocycle 1; reagents and conditions:
In our course to increase the relaxivity of Gd(III) complexes used
ꢁ
Ar¼(2-NO
2
)C
3.2 equiv), acetonitrile, 70 C, 4 h; (c) (i) K
2.8 equiv), K CO
(þ2 equiv), rt, overnight; (iii) tert-butyl bromoacetate (2.2 equiv),
(ca. 80 equiv), Et O, rt, 5 days; (ii) HCl (ca.
6
H
4
; (a) K
2
CO
3
(4 equiv), DMF, 100 C, 75 min; (b) PhSH (2.8 equiv), K
2
CO
3
as CAs for MRI, we have synthesized a rigidified derivative of the
previously prepared cyclo-PCTA12 ligand, bearing an amide func-
tion in the skeleton. The synthetic route envisaged provided the
desired target ligand in 34% overall yield in four steps from the
linear amino precursor 4. The corresponding gadolinium and
ꢁ
ꢁ
(
(
2
CO
3
(4 equiv), DMF, 100 C, 2 h; (ii) PhSH
2
3
TEA (2.4 equiv), THF, reflux, 7 h; (d) (i) HCl
g
2
g
8
0 equiv), Et
2
O, reflux, overnight; (e) Ref. 25 (i) sodium bromoacetate (6.6 equiv),
ꢁ
NaOH (pH 10), MeOH/H
2
O (1/6), 80 C, 3 days; (ii) HClaq
.

7576
F. Dioury et al. / Tetrahedron 65 (2009) 7573–7579
manganese complexes of 1/1 stoichiometry were then prepared in
order to evaluate their potentiality as CA for MRI.
(ꢂ 98%); chemical ionizations (CI-HRMS) using CH
4
as the ionizing
gas were performed with a Jeol MS700 mass spectrometer; ioni-
zations by electrospray (ESI-HRMS) were acquired on a Thermo-
Fisher Scientific hybrid linear ion trap LTQ-Orbitrap mass spec-
trometer. Low-resolution mass spectra (LRMS) resulting from ion-
ization by electronic impact (EI-LRMS) were acquired on an Agilent
5973 Network MSD mass spectrometer; ionizations by electrospray
4
4
4
. Experimental section
.1. General information
(ESI-LRMS) were performed on a Waters Micromass ZQ2000 mass
.1.1. Chemicals
spectrometer. The mass analyses of both complexes were made by
direct introduction carried out by infusion over 2 min of an aqueous
All reactions were monitored for completion by thin layer chro-
matography (TLC) analyses performed on aluminium sheets pre-
coated with silica gel Si60 (F254, Merck, Ref 1.05554.0001) or with
reverse phase silica gel RP18 (F254s, Merck, Ref 1.05559.0001). Visu-
alization was accomplished by irradiation with UV light at 254 nm
and/ordeveloped in an iodine chamber or byspraying with ninhydrin
or with Dragendorf reagent (bismuth subnitratedpotassium iodate).
Whenwarming isnecessary, thetemperature mentionedisthatof the
oil bath. Preparative chromatography was performed by elution from
columns of silica gel 60 (particle size 0.063–0.200 mm, Merck, Ref
solution of the sample (1 mg/mL) within a flow rate of 30 mL/min.
The abundance indicated for each mass number (m/z values) is
given in percentage relative to the strongest peak of 100% abun-
dance (base peak). The isotopic distributions due to the presence of
Br, Cl, or Gd elements were described by giving the more abondant
m/z value of the distribution; the abundance given corresponds to
that major peak and is relative to the base peak.
The HPLC analyses used a Waters 996 Photodiode Array Detector
(210–400 nm); all the detections occurred at 260 nm; moreover, an
isocratic system of elution was always used. The analyses were re-
alized either with normal phase columns: A (Lichrosorb Si60, length:
2
1.07734.2500). The solution of anhydrous HCl in Et O 2.0 M was
purchased from Sigma-Aldrich Co (Ref 45,518–0). Desionized water
Ò
was produced on exchange resinwith Millipore system (Simplicity ).
25 cm, diameter: 4.6 mm, stationary phase: 5
length: 15 cm, diameter: 4.6 mm, stationary phase: 5
reverse phase columns: C (Kromasil C8, length: 15 cm, diameter:
.6 mm, stationary phase: 5 m); D (Kromasil 100-5C18 Akzo-Nobel,
length: 25 cm, diameter: 4.6 mm, stationary phase: 5 m). The re-
tention times t are expressed in minutes in the decimal system.
mm); B (Hypersil Si60,
Unless stated otherwise, all reagents were purchased from commer-
cial sources and used without additional purification.
mm) or with
4
m
4
.1.2. Physical measurements
m
1H and 13C NMR spectra were acquired on a Bruker AM400
R
spectrometer (400 MHz), at room temperature, in CDCl
¼7.26 ppm and CDCl at ¼77.1 ppm (central shift) as internal
standards for H and C NMR spectra respectively), in D O (HOD at
¼4.80 ppm as internal standard for H NMR spectra and 3-tri-
methylsilyl-1-propanesulfonic acid sodium salt as external refer-
ence for 13C NMR spectra), or in DMSO-d
(DMSO-d at
¼2.50 ppm
central shift) and at
dards for H and C NMR spectra respectively). C spectra reported
are proton decoupled. For the assignments of the NMR signals, we
chose to use the convention presented in Figure 2. Chemical shifts
3
(CHCl
3
at
The GC analyses were performed on an Agilent 6890 N gas
chromatograph using an apolar column SGE-BP1 (length: 15 m, di-
d
3
d
1
13
2
ameter: 0.22 mm, film thickness: 0.25
ture was fixed at 280 C; the He flow was constant and fixed to 1 mL/
m
m). The injector tempera-
1
ꢁ
d
ꢁ
min; the column oven temperature programming ramps were 50 C
ꢁ
ꢁ
ꢁ
ꢁ
6
6
d
(1 min) then 50 C to 300 C (20 C/min) then 300 C (1 min). The
retention times t are expressed in minutes in the decimal system.
(
d
¼39.5 ppm (central shift) as internal stan-
R
1
13
13
4.2. (± ± trans 2-Amino-N-(2-amino-cyclohexyl±-acetamide 3
d
are given in ppm. Coupling constants J are measured in Hz. For
The hydrochloride ethyl glycinate (22.85 g, 164 mmol, 1 equiv)
was added in one portion to a solution of (ꢃ) trans-1,2-diamino-
cyclohexane 2 (19 mL,158 mmol) in absolute ethanol (300 mL). The
resulting suspension was refluxed for 3 days during which the in-
soluble matter increased. After cooling to room temperature, the
white precipitate was filtered on b u¨ chner, washed with EtOH
(3ꢄ20 mL), then dried to give the title compound 3 as a white solid
1
a given H NMR spectrum, JH,H(1), JH,H(2), . can be used for easier
association of protons coupled each together. Splitting patterns are
designed as follows: s, singlet; d, doublet; t, triplet; ddd, doublet of
a doublet of doublet; m, multiplet. Concerning the two diaster-
eotopic protons of an AB system: (i) when
neighbouring signals with respective chemical shifts
integrates for 2 protons; in this case, the AB system is described by
d
A
zd
B
, the group of four
d ,
1
d
2
,
d
3
and
d
4
1
(13.63 g, 79.6 mmol, Yield: 50%) whose purity was checked by H
giving the two extreme chemical shifts
corresponding JH,H calculated between
d
1
and
and
d
4
together with the
(or and ); (ii)
RMN (ꢂ98%). GC: t
¼0.45–0.55, ninhydrin. Mp >260 C. H NMR (D
(m, 3H, CHH , CHH
(m, 2H, CHH and CHH
R
¼7.8 min. TLC: Si60, MeOH/NH
4
OH, 9:1 v/v,
¼1.27–1.45
2
ꢁ
1
d
1
d
2
d
3
d
4
R
f
2
O): d
when
a ‘doublet’ (d of AB); in this case, the ‘doublets’ are described by
giving and for the first one, and and for the second one.
d
A
<<d
B
, each proton A and B of the AB system is described by
c
d
, and He,ax,), 1.45–1.56 (m, 1H, Hb,ax), 1.75–1.85
), 1.90–2.00 (m, 1H, He,eq), 2.07–2.15 (m, 1H,
c
d
3
3
3
d
1
d
2
d
3
d
4
H
b,eq), 3.11 (ddd, JH,H(1)¼ JH,H(2)¼11.3 Hz, JH,H(3)¼4.2 Hz, 1H, H
a
),
¼25.7
), 57.1
13
Infrared spectra were measured as KBr discs with a Nicolet FTIR
Avatar 320 spectrometer.
Meltingpoints(Mp)wereobtainedusingaB u¨ chiTottoliapparatus.
High-resolution mass spectra (HRMS) analyses have been done
on samples whose purity was checked by HPLC and/or H NMR
3.74 (s, 2H, H
(C
(C
h
), 3.80–3.95 (m, 1H, H
or C ), 31.9 (C ), 33.3 (C
), 170.2 (CO) ppm. IR (KBr):
f
) ppm. C NMR (D
2
O): d
c
or C
d
), 26.2 (C
c
d
b
e
), 43.3 (C ), 53.6 (C
h
f
a
n
¼3202, 3018 (br), 2935 (br), 2865,
ꢀ
1
þ
1682, 1563, 1501 cm
.
EI-LRMS: m/z 171 [M] (1%), 141
1
þ
þ
þ
10
]
[MꢀCH
2
NH
2
]
(10%), 97 [MꢀH
2
NCH
2
CONH
2
]
(100%), 82 [C
6
H
þ
(12%), 81 (14%), 69 (22%), 56 [C
4
H
8
]
(40%). CI-HRMS: m/z calcd for
r
þ
s
t
q
p
C
8
H
18
N
3
O, 172.1450; found, 172.1454 [MþH] .
u
o
N
4.3. (± ± trans 2-(2-Nitro-phenylsulfonylamino±-N-[2-(2-nitro-
NH
NH
h
H
N
phenylsulfonylamino± cyclohexyl]-acetamide 4
g
b
c
a
f
e
O
A
solution of 2-nitro-phenylsulfonyl chloride (11.36 g;
d
4
9.72 mmol, 1.1 equiv/NH ) in a mixture of THF (125 mL) and
2
Triamine blocks
Tetraazamacrocycle backbone
diethyl ether (400 mL) was added dropwise (over ca. 30 min) to
a solution of diamino-acetamide 3 (4.00 g; 23.36 mmol) and
Na CO (7.42 g, 70.01 mmol, 1.5 equiv/NH ) in water (110 mL). The
2 3 2
Figure 2. Convention adopted to assign signals of 1H and 13C NMR spectra.

F. Dioury et al. / Tetrahedron 65 (2009) 7573–7579
7577
mixture was stirred at room temperature. After one day, a cristal-
lization had occurred and the monitoring of the surnageant phase
TLC), showed a partial conversion of the starting diamino com-
pound 3. A second portion of 2-nitro-phenylsulfonyl chloride
2.59 g; 11.34 mmol, 0.25 equiv/NH ) was added in one solid por-
4.5. (± ± trans 3,13-Bis(2-nitro-phenylsulfonyl±-3,10,13,19-
tetraaza-tricyclo[13.3.1.0 ]nonadeca-1(19±,15,17-trien-11-
one 6
4
,9
(
(
2
A
solution of 2,6-bis(bromomethyl)pyridine
5
(0.323 g,
tion and the reaction was stirred at room temperature overnight.
The white solid formed was filtered on b u¨ chner, washed with THF
1.221 mmol, 1.2 equiv) in DMF (18 mL) was added dropwise (over
ca. 65 min) to a suspension of disulfonamido-acetamide 4 (0.546 g,
(
(
(
2ꢄ10 mL), then dried to give the title compound 4 as a white solid
1.009 mmol) and anhydrous K
2
CO
3
(0.559 g, 4.049 mmol, 4 equiv)
ꢁ
7.36 g, 13.59 mmol, Yield: 58%) whose purity was checked by RMN
in DMF (18 mL) previously warmed at 100 C. At the end of the
addition, heating and stirring were maintained for an additional
10 min. The crude mixture was allowed to cool to room tempera-
ꢂ 98%). HPLC: Column A, EtOAc, 1.0 mL/min, t
R
¼5.3 to 5.4 min,
¼0.2–0.25,
):
¼1.00–
l
max <255 nm. TLC: Si60, EtOAc/cyclohexane, 6:4 v/v, R
f
ꢁ
1
irradiation with UV light. Mp 204 C. H NMR (DMSO-d
1
6
d
2 2
ture; the insoluble matter was filtered off and washed with CH Cl .
$
.35 (m, 4H, Hb,ax, He,ax, and 2H ), 1.45–1.70 (m, 4H, Hb,eq, He,eq, and
The filtrate was concentrated and the residue obtained was purified
by chromatography on silica gel (EtOAc/cyclohexane, 7:3 to 10:0
v/v) to give the title compound 6 (0.383 g, 0.594 mmol, Yield: 59%)
as a light yellow solid whose purity was checked by HPLC (95%).
$
), 3.27 and 3.31 (d of AB, 2JH,H¼16.6 Hz,
2
1
3
5
8
H ), 2.95–3.10 (m, 1H, H
H, CHH
.55 (m, 1H, H
CHar, and NHSO
a
2
h
), 3.49 and 3.53 (d of AB, JH,H¼16.6 Hz, 1H, CHH
h
), 3.43–
3
f
), 7.68 (d, JH,H¼9.0 Hz, 1H, NHCO), 7.75–7.91 (m, 6H,
2
), 7.94–8.01 (m, 2H, CHar), 8.01–8.06 (m, 1H, CHar),
HPLC: Column B, EtOAc/MeOH 98:2 v/v, 1.0 mL/min, t
R
¼5.4 min,
£
$
.10 (br s, 1H, NHCH
þ1H of H , or 2H of H
triplet shape with
pattern appears for each ‘d of AB’ relative to H
): or C ), 23.9 (C or C ), 31.4 (C ), 32.1 (C
¼23.8 (C
1.2 (C ), 56.6 (C ), 124.0, and 124.4 (CHarCNO ), 129.6, and 129.7
CHarCSO ), 132.4, 132.6, 133.7, and 133.9 (CHar), 132.9, and 134.2
quatSO ), 147.2, and 147.5 (CquatNO ), 166.7 (CO) ppm. IR (KBr):
¼3357 (br), 3098, 2935, 2860,1672, 1541, 1443, 1420, 1362,
2
) ppm. Uncertain assignment: 2H¼1H of
lmax <255 nm. TLC: Si60, EtOAc, R
f
¼0.2–0.4, irradiation with UV
£
ꢁ
H
c
d
c
, or 2H of H
d
. This signal can have a broad
light, spot became yellow on standing at daylight. Mp 145–148 C.
3
1
£,$
J
H,H z 5.5 Hz; in this case, another coupling
H NMR (CDCl
3
)
:
d
¼1.04–1.22 (m, 3H, CHH , CHH
c
d
, and He,ax),
13
h
.
C NMR (DMSO-
), 45.0 (C ),
1.48–1.72 (m, 4H, Hb,ax, Hb,eq, CHH
c
, and CHH ), 2.10–2.22 (m, 1H,
d
3
3
d
5
6
d
c
d
c
d
e
b
h
H
e,eq), 2.94–3.03 (m, 1H, H
f
), 3.71 (ddd,
J
H,H(1)¼ JH,H(2)¼11.4 Hz,
3
2
f
a
2
J
H
H,H(3)¼3.7 Hz, 1H, H
a
), 3.87 and 3.96 (AB,
J
H,H(1)¼16.1 Hz, 2H,
2
(
(
2
b
), 4.28 and 4.32 (d of AB,
J
H,H(2)¼14.3 Hz, 1H, CHH
), 4.46 and 4.50 (d of AB,
g
), 5.02 and 5.06 (d of AB,
g
), 4.29 and
2
C
2
2
4.33 (d of AB, JH,H(3)¼17.3 Hz, 1H, CHH
a
2
n
J
H,H(2)¼14.3 Hz, 1H, CHH
ꢀ
1
2
3
1
5
167 cm . CI-HRMS: m/z calcd for C20
H N
24 5
O
9
S
2
, 542.1015; found,
JH,H(3)¼17.3 Hz, 1H, CHH
a
), 7.11 (d, JH,H(4)¼7.7 Hz, 1H, H
q
or H
H,H(6)¼4.7 Hz, 1H,
r
), 7.58–7.77 (m, 6H,
s
),
42.1014 [MþH]þ.
7.14 (d,
NH), 7.55 (dd,
CHar), 7.96–8.02 (m, 1H, CHar), 8.14–8.20 (m, 1H, CHar) ppm.
3
J
H,H(5)¼7.7 Hz, 1H, H
or H
3
q
s
), 7.31 (d, J
3
3
J
H,H(4)¼ JH,H(5)¼7.7 Hz, 1H, H
.4. 2,6-Bis(bromomethyl±pyridine 525,26
13
C
),
),
4
£
,$
NMR (CDCl
47.8 (C ), 52.0 (C
122.9 (C or C ), 124.1, and 124.8 (CHarCNO
131.9, 133.79, and 133.83 (CHar), 132.7, and 133.9 (CquatSO
(C ), 147.7, and 148.3 (CquatNO ), 154.0 (C or C ), 154.7 (C
168.3 (C , there is two distinct forms in 80/20
molar proportions; the following description refers to the major
form. Signals relative to the three populations of NCH
not be certainly assigned so that were used to design these
positions. IR (KBr):
3
)
:
d
¼23.9 (C
c
or C
d
), 25.4 (C
c
or C
d
), 29.9 (C
b
), 33.4 (C
e
CAUTION: Lachrymator compound!
A
concentrated (96%)
a
f
), 53.0 (C
b
), 55.5 (C
g
), 60.0 (C
a
), 120.8 (C
q
or C
s
aqueous solution of sulphuric acid (20 mL, 0.36 mol, 3.6 equiv) was
added to a solution of 2,6-bis(hydroxymethyl)pyridine (15.054 g,
0
acid (200 mL,1.76 mol,16 equiv). The mixture was refluxed for 31 h.
Second portions of both concentrated aqueous solution of hydro-
bromic acid (200 mL, 1.76 mol, 16 equiv) and concentrated aqueous
solution of sulphuric acid were then added (20 mL, 0.36 mol,
q
s
2
), 131.3, 131.5, 131.7,
), 137.6
or C
2
.11 mol) in a concentrated (48%) aqueous solution of hydrobromic
r
2
p
t
p
t
)
£
g 3
) ppm. In CDCl
$
2
nuclei could
a, b, g
3
.6 equiv) and the reflux was maintained for 63 h.
A cristallization occurred when the mixture cooled to room
n
¼3378 (br), 2930, 2857, 1670, 1543, 1439, 1373,
ꢀ
1
1163 cm . CI-HRMS: m/z calcd for C27
645.1448 [MþH] .
29
H N
6
O
9
S
2
, 645.1437; found,
þ
temperature. The orange acidic surnageant was collected. The
white solid remaining was solubilized in water (900 mL) and the
solution was basified (pH ꢂ10) by portionwise addition of solid
4.6. (± ± trans 3,10,13,19-Tetraaza-tricyclo[13.3.1.04,9]nonadeca-
1(19±,15,17-trien-11-one 7
Na
2
CO
3
. At basic pH, a cristallization occurred. The whitish solid
formed was filtered on b u¨ chner, washed with water (2ꢄ30 mL),
then taken up with diethyl ether (700 mL) and water (200 mL). The
ethereal layer was dried, then concentrated to obtain a first crop of
the title compound 5 (16.308 g; 0.062 mol, Yield (1st crop): 56%) as
Thiophenol (0.850 mL, 8.278 mmol,1.4 equiv/NSO
in one portion to a suspension of macrocyclic disulfonamide 6
(1.909 g, 2.961 mmol) and anhydrous K CO (1.308 g, 9.466 mmol,
2
Ar) was added
2
3
1
a white solid whose purity was checked by H NMR (ꢂ98%). The
1.6 equiv/NSO
2
Ar) in acetonitrile (30 mL). The resulting mixture was
ꢁ
acidic surnageant was similarly treated. The combined ethereal
layers were dried, then concentrated to obtain a grey solid (5.280 g)
that revealed to be a mixture of the desired title compound 5 and of
warmed up to 70 C for 4 h. The crude mixture was then allowed to
cool to room temperature then it was diluted with CH
and H O (27 mL). The heterogeneous mixture was vigorously stirred
then acidified by addition of an aqueous solution of HCl 6 M (3 mL,
18 mmol). The aqueous layer was repeatedly washed with CH Cl
2 2
Cl (30 mL)
2
the intermediate 2-bromomethyl-6-hydroxymethyl-pyridine in
1
9
4:6 molar proportions respectively ( H NMR estimation). This
2
2
second part was purified by filtration on silica gel (diethyl ether/
petroleum ether 40–60 C, 1:9 v/v) to give a second crop of the title
(9ꢄ30 mL). The washed aqueous layer was then basified by addition
ꢁ
of an aqueous solution of NaOH 6 M (5 mL, 30 mmol) then extracted
compound 5 as a white solid (5.087 g, 0.0192 mol) whose purity
was checked by H NMR (ꢂ98%). Yield (1stþ2nd crops): 74%. GC:
with CH
2
Cl
2
(3ꢄ100 mL). The combined organic layers were dried
1
and concentrated to give the title compound 7 (0.699 g, 2.547 mmol,
t
8
2
CH
[
7
(
R
¼6.8 min. TLC: Si60, CH
2
Cl
2
, R
f
¼0.6, irradiation with UV light. Mp
Yield: 86%) as a sticky light yellow solid whose purity was checked by
ꢁ
1
25,26
1
6 C. H NMR (CDCl
3
): conform to reported data.
EI-LRMS: m/z
H NMR and HPLC (ꢂ98%). HPLC: Column C, MeOH/H
H 0.1%, 0.8 mL/min, t max¼261.6 nm. TLC:
¼1.4 to 1.5 min,
RP18, MeOH, R , ninhydrin.
¼0–0.2 (trail), irradiation with UV light, I
¼0.93–1.10 (m, 2H, Hc,ax or Hd,ax, and He,ax), 1.17–
1.32 (m, 2H, Hb,ax, and Hc,ax or Hd,ax), 1.54–1.68 (m, 2H, Hc,eq and
2
O 95:5
þ
þ
65 [M] (21%), 184, 186 [MꢀBr] (100%), 157, 159 [Mꢀ2
v/vþHCO
2
R
l
þ
þ
þ
2
BrþHBr] ¼[C
5
H
4
BrN] (5%), 144, 146 [C
5
H
5
Br] (2%), 105
f
2
þ
þ
þ
1
$
MꢀBr
2
]
(29%), 104 (25%), 78 [Mꢀ2 CH
2
BrþH] ¼[C
5
H
4
N] , (16%),
3
H NMR (CDCl ) : d
þ
þ
þ
þ
7 [Mꢀ2 CH
2
Br] ¼[C
5
H
3
N] (15%), 63 [C
5
H
3
]
4 3
(7%), 51 [C H ]
3
3
3
6%).
Hd,eq), 1.87 (ddd, JH,H(1)¼ JH,H(2)¼10.7 Hz, JH,H(3)¼4.2 Hz, 1H, H
a
),

7578
F. Dioury et al. / Tetrahedron 65 (2009) 7573–7579
3
), 10.75 (br s, 1H, NH) ppm. 13C NMR
or C ), 28.0 (CH ), 28.2 (CH ), 31.6
), 56.3 (C ), 58.7 (C ), 60.3 (C ),
), 81.3 (C(CH ), 120.3 (C ), 120.6 (C or
or C ), 160.0 (C or C ), 171.2 (CO), 172.6 (CO),
172.8 (CO) ppm. In this description, signals relative to the five pop-
ulations ofNCH nucleicouldnotbecertainlyassignedsothat
and were used to design these positions. This signal has an un-
common shape: very small and broad. This unique signal accounts
1
.94–2.09 (m, 2H, Hb,eq, and He,eq), 2.70 (br s, 2H, NH), 3.34 and 3.39
3JH,H(1)¼ JH,H(2)¼7.5 Hz, 1H, H
r
2
(
3
d of AB, JH,H(1)¼17.3 Hz, 1H, CHH
a f
), 3.59–3.70 (m, 1H, H ), 3.69 and
3
(CDCl ):
d
¼24.4 (C
c
or C
d
), 26.0 (C
c
d
3
3
.73 (d of AB, 2
J
H,H(2)¼16.8 Hz, 1H, CHH
), 3.71 and 3.75 (d of AB,
(C
68.2 (C
), 136.9 (C
), 33.2 (C
), 80.3 (C(CH
), 158.8 (C
£
), 47.6 (C
), 51.6 (C
and C
or C
#
h
b
e
a
f
b
g
d
3
2
2
J
H,H(1)¼17.3 Hz,1H, CHH
H, CHH
), 3.94 and 3.98 (d of AB, JH,H(2)¼16.8 Hz, 1H, CHH
and 4.12 (d of AB,
a
), 3.89 and 3.93 (d of AB, JH,H(3)¼15.7 Hz,
a
)
3 3
)
3 3
q
s
q
2
1
b
h
), 4.08
), 6.90 (d,
), 6.94 (d, JH,H(5)¼7.7 Hz, 1H, H or H ),
.49 (dd, JH,H(4)¼ JH,H(5)¼7.7 Hz, 1H, H ), 8.05 (br s, 1H, NH) ppm.
In the following description, signals relative to nuclei designed by o
and u letters (Fig. 2) could not be certainly assigned so that were
C
s
r
p
t
p
t
2
$
J
H,H(3)¼15.7 Hz, 1H, CHH
b
3
3
J
H,H(4)¼7.7 Hz, 1H, H
q
or H
s
q
s
2
a, b, g, d,
3
3
£
7
r
3
$
#
a
,
b
or C
or C
for the two populations of CH
2931, 2851, 1736, 1675, 1577, 1556, 1451, 1365, 1215, 1147 cm . ESI-
HRMS: m/z calcd for C27
2
. IR (KBr):
n
¼3329, 3210, 3065, 2972,
1
3
ꢀ1
used to design these positions. C NMR (CDCl
3
):
), 52.2 (C
), 120.8 (C
d
¼24.6 (C
), 56.2 (C
or C
c
d
),
),
),
2
5
4.9 (C
6.3 (C
c
or C
or C
and C
d
), 32.6 (C
e
), 33.5 (C
b
), 51.3 (C
h
f
o
u
43
H N
4 5
O , 503.32280; found, 503.32255
þ
o
u
), 62.4 (C
a
), 119.3 (C or C
q
s
q
s
), 136.6 (C
r
[MþH] .
£
£
159.9 (C
p
t
), 173.7 (C
g
) ppm. This unique signal accounts for
¼3327 (br), 2925, 2852,
the two populations of Cquat,ar. IR (KBr):
n
4.8. (± ± trans 11-Oxo-3,10,13,19-tetraaza-tricyclo[13.3.1.04,9]-
nonadeca-1(19±,15,17-triene-3,13-diacetic
acid hydrochloride 1
ꢀ
1
1658, 1650, 1575, 1526, 1448, 1431 cm . CI-HRMS: m/z calcd for
þ
C
15
H
23
N
4
O, 275.1872; found, 275.1872 [MþH] .
4
.7. (± ± trans tert-Butyl (13-tert-butoxycarbonylmethyl-11-
4.8.1. From macrocyclic diester 8
4
,9
oxo-3,10,13,19-tetraaza-tricyclo[13.3.1.0 ]nonadeca-
(19±,15,17-trien-3-yl±acetate 8
A solution of anhydrous HCl in Et
77 equiv) was poured over the macrocyclic di-tert-butyl ester 8
0.195 g, 0.387 mmol). A white precipitate appeared after several
minutes. The mixture was vigorously stirred at room temperature
for 5 days, then a second portion of anhydrous HCl in Et O (2.0 M,
2
O (2.0 M, 15 mL, 30 mmol,
1
(
ꢁ
CAUTION:thepurifiedisolatedproduct8mustbestoredatꢀ18 C.
A solution of 2,6-bis(bromomethyl)pyridine 5 (1.778 g, 6.711 mmol,
.2 equiv) in DMF (50 mL) was added dropwise (over 70 min) to
a suspension of disulfonamido-acetamide 4 (3.004 g, 5.547 mmol)
2
1
15 mL, 30 mmol, 77 equiv) was added and the suspension was
refluxed overnight. The precipitate was then filtered and washed
andanhydrousK
2
CO
3
(3.080 g, 22.283 mmol,4 equiv)inDMF(50 mL)
with Et
0.299 mmol for x¼3 or 0.350 mmol for x¼1, 77%<Rdt<90%). Its
purity was checked by HPLC (97%). HPLC: Column D, MeOH/H
0.1%, 0.7 mL/min,
¼0.1–0.5 (trail), irradiation
2
O to give the title compound 1 as a white powder (0.149 g,
ꢁ
previously warmed at 100 C. At the end of the addition, heating and
stirring were maintained for an additional 50 min. The crude mixture
was concentrated to reduce the volume twofold. A second portion of
2
O
75:25 v/vþHCO
2
H
t
R
¼3.2–3.6 min (br),
anhydrous K
added followed by the addition of thiophenol (1.6 mL, 15.582 mmol,
.4 equiv/NSO Ar). The resulting suspension was stirred at room
temperature overnight. The crude mixture was then diluted with
CH Cl (50 mL) and H O (40 mL). The heterogeneous mixture was
2
CO
3
(1.506 g, 10.898 mmol, 1 equiv/NSO
2
Ar) was then
l
max¼262.7 nm. TLC: RP18, MeOH, R
f
ꢁ
1
with UV light, I
2
, Dragendorf. Mp 214 C (decomposition). H NMR
¼1.07–1.41,1.41–1.75, and 1.75–2.00 (3 m, 7H, CHH
), 2.10–2.35 (m, 1H, CHH ), 3.05, and 3.21–3.34 (br s
) , 3.46–3.60, and 3.73 (m and br s, 0.37H
f
) , 3.85–4.10 (m, 2H), 4.12–4.35 (m, 4H), 4.36–4.50 (m,
1
2
(D
2
O, pDz1):
, H , and H
and m, 0.63H and 0.37H, H
a
d
b
,
H
c
d
e
b
£
2
2
2
£
vigorously stirred then acidified by addition of an aqueous solution of
HCl 6 M (10 mL). The upper aqueous layer was repeatedly washed
and 0.63H, H
1H), 4.56–4.80 (m, 3H) , 7.50–7.70 (m, 2H, H
1H, H
molar proportions. A part of this signal is under the HOD one (seen
$
q
, and H
s
), 8.02–8.15 (m,
£
withCH
2
Cl
2
(12ꢄ50 mL). Thewashedaqueouslayer wasthen basified
r
) ppm. Presence of two forms in aqueous solution; 63/37
$
byadditionof solidNaOH(3 g)thenextracted withCH
2 2
Cl
(3ꢄ50 mL).
13
The combined organic layers were dried and concentrated to give
macrocyclic diamine 7 as a light yellow solid (1.190 g, ꢅ4.337 mmol,
Yield (crude, 2 steps) ꢅ78%). tert-Butyl bromoacetate (1.4 mL,
by HOD irradiation experiment). C NMR (D
23.40 , 23.45, 23.53 , 23.64
(C b* , C c* , C , C d* and C e* ), 24.1 (C
31.6 (C ), 48.9*, and 49.6 (C ), 50.1, 51.7, 56.1, 56.6, 57.7, 58.1, 58.9,
59.5, 61.5 (C , C , C , and CH CO H), 67.5, and 68.3 (C ),123.5,124.6,
125.5, 126.1 (C , and C ), 141.2, 142.0 (C ), 148.8, 149.7, 150.2, 150.6
(C , and C ), 167.8, 168.9, 169.5, 169.8, 170.5, 171.1 (COO, and CONH).
2
O, pDz1)
*
:
d
¼23.39
*
,
*
*
*
d
b
), 29.4 (C
c
),
e
f
9
.603 mmol, 1.1 equiv/NH) was added to a solution of the crude
h
o
u
2
2
*
a
macrocyclic diamine 7 (1.190 g, 4.337 mmol) and triethylamine
1.4 mL, 10.044 mmol, 1.2 equiv/NH) in tetrahydrofuran (45 mL). The
q
s
r
(
p
t
*
13
mixture wasrefluxed for 7 h (after 10–15 min, awhite precipitate was
formed and remained until the end of the reaction). The crude mix-
Nearly all the C signals are doubled due to the presence of two
forms in aqueous solution; signals marked referred to the minor
ture was concentrated, then taken up in CH
2
Cl
2
(100 mL) and water
form. IR (KBr):
n
¼3361 (br), 3216 (br), 3000, 2944, 2865, 1740, 1687,
ꢀ
1
(
30 mL). The organic layerwasfurther washed withwater(2ꢄ30 mL),
1595, 1576, 1564, 1453, 1408 (br) cm . ESI-HRMS: m/z calcd for
ꢀ
ꢀ
dried and concentrated. The residue obtained was purified by chro-
matography on silica gel (EtOAc/cyclohexane, 5:5 v/v) to give the title
compound 8 as a white solid (1.215 g, 2.417 mmol, 44% overall yield
from 4 (3 steps)) whose purity was checked by HPLC (ꢂ94%). HPLC:
C
C
19
H
H
25
N
26ClN
4
O
5
389.18304, found 389.18207 [MꢀH] ; m/z calcd for
19
4
O
5
425.15972, found 425.15874 [MþCl] .
4.8.2. From macrocyclic diamine 7
An aqueous solution of NaOH (3 M, 1.9 mL, 5.7 mmol, 5.7 equiv)
was added in one portion to a solution of macrocyclic diamine 7
Column D, MeOH/H
¼4.2 min (br),
.6 (trail), irradiationwith UV light, I
2
O
75:25 v/vþHCO
2
H
0.1%, 0.7 mL/min,
¼0.1–
t
R
l
max¼262.7, and 263.9 nm. TLC: Si60, EtOAc, R
f
ꢁ
1
0
2
, Dragendorf. Mp 126–128 C. H
¼0.98–1.15 (m,1H, He,ax),1.18–1.32 (m, 3H, Hb,ax, Hc,ax
and Hd,ax),1.40 (s, 9H, CH ),1.47 (s, 9H, CH ),1.57–1.66 (m,1H, Hc,eq or
d,eq), 1.72–1.80 (m, 1H, Hc,eq or Hd,eq), 2.03–2.10 (m, 1H, Hb,eq), 2.40–
.55 (m, 1H, He,eq), 2.72–2.85 (m, 1H, H ), 2.91 and 2.95 (d of AB,
(0.276 g, 1.00 mmol) in MeOH/H
2
O 1/1 v/v (4 mL). The resulting
$
ꢁ
NMR (CDCl
3
) :
d
,
basic solution (pH z 10) was warmed at 80 C and a freshly pre-
pared solution of sodium bromoacetate (bromoacetic acid (0.309 g,
2.22 mmol, 2.2 equiv) and NaOH (0.127 g, 3.17 mmol, 3.1 equiv)) in
water (2 mL) was added in one portion. After 22 h, the monitoring of
the reaction (TLC on RP18) revealed an uncomplete conversion of
compound 7. Three portions of sodium bromoacetate were suc-
cessively added (4.3 equiv in all, after 22 h, 29 h, and 2.5 days of
warming). The crude mixture was then allowed to cool to room
3
3
H
2
a
2
2
J
H,H(1)¼18.1 Hz, 1H, CHH
H, CHH
), 3.23 and 3.28 (d of AB, JH,H(1)¼18.1 Hz,1H, CHH
large, 2H, H ),3.46–3.59(m, 2H, H andCHH ),4.00–4.15(m, 2H, CHH
and CHH ), 4.34
), 4.25 and 4.29 (d of AB, JH,H(3)¼16.6 Hz, 1H, CHH
and 4.38 (d of AB, JH,H(4)¼16.1 Hz, 1H, CHH ), 6.93 (d, JH,H(1)¼7.5 Hz,
H,H(2)¼7.5 Hz, 1H, H or H ), 7.52 (dd,
a
), 3.13 and 3.17 (d of AB, JH,H(2)¼17.6 Hz,
2
1
g
a
), 3.39 (s
b
f
g
d
,
2
3
d
2
3
3
temperature, washed with CH
(pHz1) by addition of a molar aqueous solution of HCl in the
2
Cl
2
(3ꢄ10 mL), then acidified
3
1
H, H
q
s
or H ), 6.97 (d,
J
q
s

F. Dioury et al. / Tetrahedron 65 (2009) 7573–7579
7579
presence of CH
washed with CH
2
Cl
2
(10 mL). The acidic aqueous layer was repeatedly
Cl
(3ꢄ10 mL). The washed aqueous layer was
ashless filter paper (Whatman, 542) to give the manganese complex
as a whitish fine powder. IR (Solid):
2
2
n
¼3420 (br), 3227, 2934, 2860,
ꢀ
1
concentrated to give a deliquescent light-brown solid (1.724 g)
whose HPLC analysis showed a chromatogram identical to that
previously obtained from the deprotection of tert-butyl diester 8.
The excess of crude matter may result from the excesses of both
NaOH introduced to insure alkaline medium, and bromoacetic acid,
and from a partial elimination of water.
1660, 1590, 1390, 1206, 1151 cm
.
ESI-LRMS: m/z: 333.2
þ
HþHþK]þ (4–10%),
[MꢀCH
2
CO
H
2
Hþ2H] (7–10%), 371.1 [MꢀCH
2 2
CO
þ
þ
482.0 [C19
þMnþ2K]
24
N O
4
5
MnK] ¼[Mꢀ2HþMnþK] (100%), 520.0 [Mꢀ3H
þ
þ
(15%), 556.0 [Mꢀ2HþMnþKþKCl]
(10%), 629.9
þ
þ
[Mꢀ2HþMnþKþ2KCl] (25–30%), 925.4 [2Mꢀ4Hþ2MnþK] (8%),
999.4 [2Mꢀ4Hþ2MnþKþKCl]þ (10%).
4
.9. Gadolinium complexation
References and notes
The initial pH 1.0 of a solution of macrocyclic ligand 1 (0.132 g,
1
. Caravan, P.; Ellison, J. J.; McMurry, T. J.; Lauffer, R. B. Chem. Rev. 1999, 99, 2293–
2352.
0
(
0
.265 mmol (if x¼3) to 0.310 mmol (if x¼1)) in deionized H
2
O
5 mL) was adjusted at pH 5.7 with an aqueous solution of KOH
.5 M. Gadolinium(III) chloride hexahydrate (0.115 g, 0.310 mmol)
2. Rohrer, M.; Bauer, H.; Mintorovitch, J.; Requardt, M.; Weinmann, H.-J. Invest.
Radiol. 2005, 40, 715–724.
3
. Port, M.; Id e´ e, J.-M.; Medina, C.; Robic, C.; Sabatou, M.; Corot, C. Biometals 2008,
was added in one portion which induced a decrease of pH down to
pH 4.2 value so that pH was readjusted up to 5.7 (KOH 0.5 M). The
21, 469–490.
4. Jacques, V.; Desreux, J. F. Top. Curr. Chem. 2002, 221, 123–164.
5. Aime, S.; Barge, A.; Cabella, C.; Crich, S. G.; Gianolio, E. Curr. Pharm. Biotechnol.
ꢁ
resulting mixture (final volume 10 mL) was warmed at 80 C for
2
004, 5, 509–518.
. Aime, S.; Fasano, M.; Terreno, E. Chem. Soc. Rev. 1998, 27, 19–29.
7. Chan, K. W.-Y.; Wong, W.-T. Coord. Chem. Rev. 2007, 251, 2428–2451.
2
4 h. The pH was then raised to 8.7 value (KOH 0.5 M). A white
precipitate appeared after a prolonged stirring at room tempera-
ture, and persisted by decreasing the pH down to 8.2 value. The
6
8
9
. Jaszberenyi, Z.; Sour, A.; Toth, E.; Benmelouka, M.; Merbach, A. E. Dalton Trans.
005, 2713–2719.
. Ranganathan, R. S.; Raju, N.; Fan, H.; Zhang, X.; Tweedle, M. F.; Desreux, J. F.;
2
precipitate was filtered off on a 0.2
WAT200539). The clear yellow aqueous filtrate was concentrated
2.5 mL) and CH CN (15 mL) was then added. A solid sticked to the
reaction flask was formed. The filtrate was removed and a second
portion of CH CN (15 mL) was poured. After vigorous stirring, the
powder formed was filtered on an hardened ashless filter paper
Whatman, 542) to give the gadolinium complex as a whitish solid
0.134 g). IR (Solid):
¼3385 (br), 2934, 2860, 1581, 1545, 1397, 1212,
mm PES filter (Waters,
Jacques, V. Inorg. Chem. 2002, 41, 6856–6866.
10. Stetter, H.; Frank, W.; Mertens, R. Tetrahedron 1981, 37, 767–772.
(
3
11. Aime, S.; Botta, M.; Crich, S. G.; Giovenzana, G. B.; Jommi, G.; Pagliarin, R.; Sisti,
M. Inorg. Chem. 1997, 36, 2992–3000.
3
12. Aime, S.; Botta, M.; Frullano, L.; Crich, S. G.; Giovenzana, G.; Pagliarin, R.;
Palmisano, G.; Sirtori, F. R.; Sisti, M. J. Med. Chem. 2000, 43, 4017–4024.
13. Aime, S.; Gianolio, E.; Corpillo, D.; Cavallotti, C.; Palmisano, G.; Sisti, M.; Gio-
(
(
1
venzana, G. B.; Pagliarin, R. Helv. Chim. Acta 2003, 86, 615–632.
14. Dioury, F.; Sambou, S.; Guen e´ , E.; Sabatou, M.; Ferroud, C.; Guy, A.; Port, M.
Tetrahedron 2007, 63, 204–214.
15. Port, M.; Raynal, I.; Vander Elst, L.; Muller, R. M.; Dioury, F.; Ferroud, C.; Guy, A.
Contrast Media Mol. Imaging 2006, 1, 121–127.
n
ꢀ
1
$
þ
158
154 cm . ESI-LRMS: m/z: 371.1 [MꢀCH
2
CO
2
HþHþK] (100%), 546.1
1
58
þ
58
158
þ
þ
[C
19
H
24 GdN
4
O
5
] ¼[Mꢀ2Hþ Gd] , 564.1 [Mꢀ2Hþ GdþH
2
O] ,
2
O] , 620.1
1
þ
þ
158
þ
5
[
[
[
84.1 [Mꢀ3Hþ GdþK] , 602.1 [Mꢀ3Hþ GdþKþH
16. Kim, W. D.; Kiefer, G. E.; Maton, F.; McMillan, K.; Muller, R. N.; Sherry, A. D.
1
58
158
þ
Mꢀ3Hþ GdþKþ2H
2
O]
and/or [Mꢀ2Hþ GdþKCl] , 658.0
Inorg. Chem. 1995, 34, 2233–2243.
1
58
þ
158
þ
17. Kim, W. D.; Hrncir, D. C.; Kiefer, G. E.; Sherry, A. D. Inorg. Chem. 1995, 34, 2225–
Mꢀ3Hþ GdþKþKCl] , 696.0 [Mꢀ2Hþ Gdþ2KCl] , 734.0
2
232.
8. Dioury, F.; Sylvestre, I.; Siaugue, J.-M.; Wintgens, V.; Ferroud, C.; Favre-R e´ g-
uillon, A.; Foos, J.; Guy, A. Eur. J. Org. Chem. 2004, 4424–4436.
158 158
þ
þ
þ
þ
Mꢀ3Hþ GdþKþ2KCl] , 770.0 [Mꢀ2Hþ Gdþ3KCl] , 807.9
1
158 158 $
[
Mꢀ3Hþ GdþKþ3KCl] , 881.9 [Mꢀ3Hþ GdþKþ4KCl] . The rel-
19. Siaugue, J. M.; Segat-Dioury, F.; Sylvestre, I.; Favre-Reguillon, A.; Foos, J.; Madic,
ative abundances of the other mass numbers were not mentioned as
variable from one analysis to another.
C.; Guy, A. Tetrahedron 2001, 57, 4713–4718.
2
2
0. Galaup, C.; Carrie, M.-C.; Tisnes, P.; Picard, C. Eur. J. Org. Chem. 2001, 2165–2175.
1. Galaup, C.; Couchet, J. M.; Picard, C.; Tisnes, P. Tetrahedron Lett. 2001, 42, 6275–
278.
6
4
.10. Manganese complexation
2
2
2. Kan, T.; Fukuyama, T. Chem. Commun. 2004, 353–359.
3. Lagrifouille, P.; Wittung, P.; Eriksson, M.; Jensen, K. K.; Norden, B.; Buchardt, O.;
Nielsen, P. E. Chem.dEur. J. 1997, 3, 912–919.
The initial pH 1.0 of a solution of macrocyclic ligand 1 (0.052 g,
24. Balsells, J.; Mejorado, L.; Phillips, M.; Ortega, F.; Aguirre, G.; Somanathan, R.;
Walsh, P. J. Tetrahedron: Asymmetry 1998, 4135–4142.
0
.104 mmol (if x¼3) to 0.122 mmol (if x¼1)) in deionized H
2
O (2 mL)
was adjusted at pH 5.7 with an aqueous solution of KOH 0.5 M.
Manganese(II) chloride tetrahydrate (0.024 g, 0.124 mmol) was
added in one portion which induced a decrease of pH down to 3.5
value so that pH was readjusted to 5.8 (KOH 0.5 M). The resulting
mixture (final volume 6 mL) was stirred at room temperature for
25. Darbre, T.; Dubs, C.; Rusanov, E.; Stoeckli-Evans, H. Eur. J. Inorg. Chem. 2002,
3284–3291.
2
2
6. Zhang, X. PCT Int. Appl., WO 9713763, 1997.
7. The [2þ1]/[2þ2]/[1þ1] adducts ratio can be estimated by HPLC: UV-detection
at 260 nm, Column B, EtOAc/MeOH 98.5:1.5 v/v, 1.0 mL/min: t
5, and 6.2–6.5 min respectively.
R
¼3.0–3.1, 4.3–4.
2
4 h. The pH was then raised to 8.5 (KOH 0.5 M) and the fine brown
28. Fukuyama, T.; Jow, C.-K.; Cheung, M. Tetrahedron Lett. 1995, 36, 6373–6374.
2
9. Nachman, I.; Port, M.; Raynal, I.; Rousseaux, O. PCT Int. Appl., WO03074523,
003.
precipitate formed was filtered off on a 0.2 m PES filter (Waters,
WAT200539). The grey coloured filtrate became purple coloured by
standing at room temperature. The clear grey-purple aqueous filtrate
was concentrated (5 mL), and CH
solid obtained after slow evaporation to dryness was taken up in
CH CN(20 mL) andthe resulting powder was filtered on an hardened
m
2
30. Hovland, R.; Glogard, C.; Aasen, A. J.; Klaveness, J. Org. Biomol. Chem. 2003, 1,
644–647.
3
1. T o´ th, E.; Pubanz, D.; Vauthey, S.; Helm, L.; Merbach, A. E. Chem.dEur. J. 1996, 2,
607–1615.
3
CN (25 mL) was then added. The
1
32. Aime, S.; Barge, A.; Bruce, J. I.; Botta, M.; Howard, J. A. K.; Moloney, J. M.; Parker,
3
D.; de Sousa, A. S.; Woods, M. J. Am. Chem. Soc. 1999, 121, 5762–5771.