New synthetic approach to per-O-acetyl-isocyanates, isothiocyanates and thioureas in the disaccharide and cyclodextrin series

Article abstract of DOI:10.1039/b600023a

An efficient method for the preparation of per-O-acetyl disaccharides and cyclodextrin isocyanates or isothiocyanates by the phosphine imide strategy is reported. Successful one-pot, high yield syntheses of cellobiose, lactose and sucrose isocyanates or/a

Full text of DOI:10.1039/b600023a

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PAPER
www.rsc.org/njc | New Journal of Chemistry
New synthetic approach to per-O-acetyl-isocyanates, isothiocyanates and
thioureas in the disaccharide and cyclodextrin series
Stephane Menuel,a Stanislaw Porwanskib and Alain Marsura*a
Received (in Montpellier, France) 4th January 2006, Accepted 31st January 2006
First published as an Advance Article on the web 3rd March 2006
DOI: 10.1039/b600023a
An efficient method for the preparation of per-O-acetyl disaccharides and cyclodextrin isocyanates
or isothiocyanates by the phosphine imide strategy is reported. Successful one-pot, high yield
syntheses of cellobiose, lactose and sucrose isocyanates or/and isothiocyanates pure b-anomers
have been completed starting from their corresponding monoazido-per-O-acetyl derivatives.
Transformation of the ACEtris-6-azido-per-O-methylated and the ACEtris-6-azido-per-O-acetylated-
a-cyclodextrins or of the 6A-azido-6A-deoxy-per-O-acetyl-b-cyclodextrin into the corresponding
isocyanates and/or isothiocyanates is also presented. Finally the conversion of the cyclodextrin
isothiocyanates by nucleophilic addition of primary and secondary amines into a large panel of
original thioureido-cyclodextrins derivatives is described.
of analytical chemistry, to obtain grafted cyclodextrin chro-
matographic phases.11 In comparison, the recent literature
Introduction
It is well known that compounds containing the urea or
reports two other procedures for urea synthesis. A first one,
using triphosgene,8a,b giving the peracetylated urea bridged
thiourea functionality are of extended biological interest in
several classes of drugs.1a–g In the carbohydrate field, glyco-
b-CD-dimer in medium yield (49%) and a scope-limited
sylureas have been shown also to be useful antidiabetic
second one, using a metal–carbonyl reagent as carbon mon-
agents.2a,b As a powerful easy access to urea functionality
oxide source.12
and other main quadrivalent functions of chemistry as e.g.
isocyanate, carbodiimide, thiourea. . . notably in the cyclodex-
Results and discussion
trin series, we earlier reported and demonstrated the high
safety, efficiency and versatility of the phosphine imide reac-
tion.3a–c The latter was proposed as a general method for
symmetrical or unsymmetrical urea synthesis, either from
azides,4 or amines,5 using CO2 or sCO2 (supercritical CO2)6
as solvent and/or reagent in the presence of free,3a–c or
polymer-supported triphenylphosphine.7
Continuing our research on the scope and limitations of the
phosphine imide reaction and considering results previously
obtained with CO2, we performed the reaction with CS2
expecting that CDs-isothiocyanates and/or other isothiocya-
nates, could be interestingly prepared in this way in pure form
and in high yields. Considering the mechanism hypothesis of
Scheme 1, based on our previous theoretical results with
CO2,13a,b and despite that our early attempts to obtain iso-
thiocyanates instead of isocyanates failed,14 we report here,
the first successful synthesis of the 6-monoisothiocyanato-per-
O-acetyl-b-cyclodextrin 3 and the ACEtris-6-isothiocyanato-
per-O-acetyl-a-cyclodextrin 4 (Scheme 2) through the ‘‘thio-
phosphine imide reaction’’ (so named by analogy with the
initial phosphine imide reaction with CO2) by the action of
Applied to the cyclodextrin series (CDs), the phosphine
imide reaction afforded for the first time, from the native or
peracetylated azido-Cds, a direct and very easy access to the
non-acetylated or peracetylated urea bridged CD-dimers,
respectively, in high yields, (91 to 94%)3a–c presently un-
matched by other methods.8a,b In the same way, sophisticated
supramolecular hosts such as dimers, trimers and tetramers of
ureido-CD-cyclams or aza-crown ether,3,9a,b were obtained by
this method. More recently, we introduced the URFT-cyclo-
dextrins (Upper Rim Fully Tethered)-CDs and ACEtris-ureido-
a-CD, new classes of tritopic podands which have been
designed to afford original mononuclear or dinuclear lantha-
nides and/or transition-metal complexes exhibiting interesting
luminescence, redox and amphiphilic properties.10a–e The re-
action was also further applied by another group, in the field
a
´
´
GEVSM SRSMC, UMR 7565 CNRS-Universite Henri Poincare-
Nancy-1, Faculte´ de Pharmacie, 5 rue A. Lebrun, B.P. 80403, 54001
Nancy Cedex, France. E-mail: Alain.Marsura@pharma.uhp-
nancy.fr; Fax: þ33 (0) 3 83682345; Tel: þ33 (0) 3 83682324
b Department of Organic Chemistry, University of Lodz, ul.
Naturowicza 68, 90-136 Lodz, Poland. E-mail:
porwany@chemul.uni.lodz.pl; Fax: þ48 42 678 16 09; Tel: þ48 42
636 42 61
Scheme 1
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1648 and 1654 cmꢁ1 and a quaternary carbon 13C-NMR signal
between 180 and 182 ppm, characteristic of the CQS double
bond of the thiourea function. To our knowledge, only one
example of a multistep synthesis of an a-CD isothiocyanate
was reported in the patent literature,15 but other CDs-isothio-
cyanates have not been obtained before.
Usually, the preparation of monosaccharidyl and disacchar-
idyl isocyanates or isothiocyanates is achieved by isocyanation
or isothiocyanation with phosgene or thiophosgene,16a,b
hazardous reagent (CSCl2). In the following, we report the
first synthesis of pure monoisocyanates and monoisothiocya-
nates of three popular disaccharides, cellobiose, lactose and
sucrose along the original ACEtris-6-isocyanato-per-O-methyl-
a-cyclodextrin host using the phosphine imide reaction in
anhydrous conditions and without use of phosgene or thio-
phosgene (Scheme 3). For the preparation of the azido per-
acetylated disaccharide starting materials 13–14 we followed
the sequence: peracetylation, bromination, azidation, by using
known literature procedures,17 and for the 6-monoazido-6-
deoxy-sucrose heptaacetate 15 another literature method was
used.18 Finally, concerning the case of ACEtris-6-azido-per-O-
methylated-a-cyclodextrin 16 we followed our original pub-
lished synthesis.19
Isocyanates 17–19, isothiocyanates 21–22 and ACEtris-6-
isocyanato-per-O-methylated-a-cyclodextrin 20 were prepared
using CO2 or CS2 in the presence of triphenylphosphine in
anhydrous toluol and were obtained as pure white microcrys-
talline powders after a simple precipitation with cyclohexane.
No further purification was needed. The isothiocyanate of
sucrose cannot be isolated in a pure form and is not reported
here. Analytical and spectroscopic data of the compounds are
in perfect agreement with the proposed structures. Strong IR
absorptions at 2192–2155 cmꢁ1 together with 13C-NMR re-
sonances at 137.9 and 144.5 ppm confirm the presence of the
NQCQO and NQCQS moieties, respectively. 1H- and
13C-NMR spectra of the disaccharidyl derivatives show that
the sole b-anomer was obtained in the reaction.
To our knowledge, this practical one-pot preparation is the
first example reported, of a direct and scale-up preparation of
isocyanates and isothiocyanates of oligosaccharides at the
anomeric position from their corresponding azides. In com-
parison rare examples of oligosaccharidyl isothiocyanate
synthesis at the 6-primary alcohol position have been reported
earlier, from amines by reaction with thiophosgene,20 and two
other monosaccharidyl-isocyanates have been recently claimed
to be formed, but not isolated, using triphosgene in a biphasic
water–CH2Cl2 medium.8a,b
Scheme 2
carbon disulfide on the 6A-azido-6A-deoxy-per-O-acetyl-b-cy-
clodextrin
1
or the ACEtris-6-azido-per-O-acetyl-a-cyclo-
dextrin 2. In a separate second step, we described their
straightforward conversion into the corresponding thiourea
derivatives 5 to 12 by addition of primary and secondary
nucleophilic amines (Scheme 2). All the synthesised products
were obtained in fairly good yields, 88 and 96% (b- and a-CDs
isothiocyanates) and 55 to 93% (CDs thioureas), respectively.
The purification step is easy, limited to a simple precipitation
with cyclohexane, followed by a rapid flash chromatography
filtration on silica gel to discard triphenylphosphine oxide. The
reaction conditions are found to be close to those of the
phosphine imide reaction with CO2 except that a careful
control of anhydrous conditions must especially be respected,
with regards to the stronger sensitivity of the isothiocyanates
vs. the corresponding isocyanates. The reaction time to com-
plete formation of the isothiocyanates is 60 h, instead of the
shorter time (6 h) necessary for the conversion at rt into
thiourea derivatives from the latter. The reaction works well
with aliphatic or aromatic primary amines and also with
secondary amines. Analyses of 3 to 12 by FTIR and NMR
spectroscopy and elemental analyses are in total agreement
with the proposed structures. For the isothiocyanates 3 and 4,
the FTIR spectra show the presence of a weak absorption
band at 2100 cmꢁ1, characteristic of the NQCQS vibration,
also confirmed by the 13C-NMR corresponding signal at
162–163 ppm. Concerning the thiourea compounds 5 to 12,
the FTIR spectra show a characteristic absorption between
Elsewhere, considering details of the mechanism proposed
earlier for this reaction, our calculations13a,b clearly predicted
the in situ formation of an isocyanate as the key intermediate
and its evolution to a urea by a nucleophilic attack of a
primary or a secondary amine. Our previous experimental
work confirms this prediction and earlier allowed us to isolate
the 6-monoisocyanato-per-O-acetyl-b-cyclodextrin in a high
overall yield (92%),3a recently improved to 97%. It should be
noted here, that in the mechanisms of analogous reactions, key
intermediate isocyanates were often invoked in the urea for-
mation pathways.8a,b,12 Nevertheless, it should be pointed out
that sometimes, in these reactions, isocyanates cannot be
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Scheme 3 Reagents and conditions: i = P(Ph)3, CO2 (17–20) or CS2 (21, 22), toluol (anh.), rt.
isolated and as recently reported in literature,21 their effective
Experimental
existence appeared controversial with e.g. correlative func-
The structures of all compounds were assigned by 1H and 13
C
tional density calculations.
NMR spectroscopy on a Bruker-DRX 400 spectrometer;
FTIR spectra were recorded on a Bruker-Vector 22 spectro-
meter. Mass spectra were recorded on an ESI-MS Platform
Micromass Platform spectrometer. Elemental analyses were
obtained with a Thermofinnigan Flash EA1112 analyser. The
solvents were purified by standard methods.
Conclusion
In summary, we find that the proposed phosphine imide
reaction and its thio-variant, bring efficient high yielding, soft
and safe (without hazardous phosgene or analogues) synthetic
methodologies for CDs and disaccharide isothiocyanate and
isocyanate scale-up preparation. This very practical method
needs no fastidious protection/deprotection sequence or sophisti-
cated separation procedures and will also be promising for
further reactions with sensitive and/or sophisticated struc-
tures, with regards to the generally mild reaction conditions.
We argued that the proposed methods could be considered as
a valuable and interesting alternative to the sole usual phos-
gene/thiophosgene isocyanation/isothiocyanation. Further,
some of the above described isocyanates and/or isothiocya-
nates, notably the preorganised original trisubstituted-CDs
derivatives are reactive and truly precious starting materials
for the rapid development of new designed supramolecular
podands. Moreover, we demonstrate that the reaction offers
the opportunity and versatility to obtain a large panel of
monosubstituted and trisubstituted ureido- or thioureido-
CDs derivatives in one step and high yields. Now, the study
of the trisubstituted thioureido-CDs towards cation/anion
complexation is underway.
Syntheses
The 6A-azido-6A-deoxy-per-O-acetyl-b-cyclodextrin
1 was
synthesised by a known literature procedure.3a
ACETris-6-azido-per-O-acetyl-a-cyclodextrin 2. ACETris-6-
azido-a-cyclodextrin19 (1 g) in solution in a mixture of pyr-
idine–acetic anhydride (100 mL; 2 : 1 v/v) was stirred at 80 1C
under argon for 15 h. After evaporation the resulting oily
paste was dissolved in 150 mL of toluol and evaporated three
times with the same amount of toluol to dryness. The same
operation was carried out with methanol (150 mL) in order to
eliminate all traces of pyridine and acetic anhydride from the
residue. Finally 100 mL of water was added to give a solid
which was filtered and washed with water over a glass sinter. A
white pure powder of 2 was obtained (0.740 g, 46%). Found C
47.01, H 5.31, N 7.15; calc. for C66H87N9O42 (1678.43): C,
47.23; H, 5.22; N, 7.51%; FTIR KBr; umax/cmꢁ1 2105 (N3),
1759 (CO); dH (400 MHz; CDCl3) 5.54 (6H, t, J 9.8 Hz, 3-H),
5.04 (6H, d, J 3.53 Hz, 1-H), 4.55 (6H, dd, J1 3.27 Hz, J2 10.1
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Hz, 2-H), 4.40 (12H, 2s, 6-H), 4.18 (6H, m, 3-H), 3.78 (6H, dd,
J1 8.8 Hz, J2 8.9 Hz, 4-H), 2.12 (45H, m, CH3); dC(100 MHz;
CDCl3) 171.2–169.5 (CQO), 96.9 (C-1), 77.6 (C-4), 71.3, 71.2,
69.8 (C62, C-3, C-5), 63.5 (C-6a), 51.12 (C-6b), 21.2 (CH3);
ES-MS m/z: 1797.31 (M1 þ CHCl3), 1696.02 (M1 þ HOꢂ).
5.24–5.15 (7H, m, 1-H), 5.08–4.98 (7H, m, 2-H), 4.81–4.64
(12H, m, 6a-H), 4.53–4.29 (9H, m, 6b-H, 5-H), 4.23–3.98 (7H,
m, 4-H), 3.51 (3H, s, OCH3), 2.08 (70H, several s,
CH3–CQO); dC(100 MHz; CDCl3) 182.0 (CQS),
171.2–169.8 (CQO), 134.2, 132.7, 129.3, 127.2 (Carom), 97.2
(C-1), 77.1 (C-4), 72.0, 71.0, 70.0 (C-2, C-3, C-5), 63.3 (C-1a),
56.1 (OCH3), 21.2 (CH3–CO).
6A-Isothiocyanato-6A-deoxy-6-(icosa-O-acetyl)-b-cyclodextrin
3. 6A-Azido-6A-deoxy-per-O-acetyl-b-cyclodextrin 1 (2.0 g, 1
mmol),3 was added to a solution of triphenylphosphine (18.35
g, 70 equiv.) in an anhydrous CS2–DMF (10 : 6) mixture under
argon at rt. After 60 h, the solution was evaporated to dryness.
The residue was dissolved in 2 cm3 of anhydrous CH2Cl2 and
anhydrous hexane was added. The resulting precipitate was
filtered and washed on a glass sinter under argon (1.77 g,
88%). Found: C, 49.91; H, 5.35; N, 0.59; S, 1.38; calc. for
C83H109NO54S: C, 49.43; H, 5.45; N, 0.69; S, 1.59%; FTIR
N-[Icosa-O-acetyl-6A-deoxy-b-cyclodextrin-6A-yl]-N0-[dibutyl]
-thiourea 6. Di-N-butylamine (0.014 g, 1.1 equiv.), isothiocya-
nate 3 (0.20 g, 0.099 mmol); (0.197 g, 93%). Found: C, 50.97;
H, 5.88; N, 1.13; S, 1.42; calc. for C91H128N2O54S: C, 50.91; H,
5.96; N, 1.30; S, 1.49%; FTIR umax(KBr)/cmꢁ1 1756 (CQO),
1649 (CQS); dH (400 MHz; CDCl3) 5.40–5.28 (7H, m, 3-H),
5.18–5.08 (7H, m, 1-H), 4.86–4.78 (7H, m, 2-H), 4.62 4.56
(12H, m, 6a-H), 4.38–4.19 (9H, m, 6b-H, 5-H), 3.80–3.70 (7H,
m, 4-H), 2.65 (4H, t, J 7.4 Hz, CH2a), 2.12 (70H, several s,
CH3–CQO), 1.54 (4H, m, CH2b), 1.38 (4H, m, CH2g), 0.94
(6H, t, J 7.3 Hz, CH3 chain); dC(100 MHz; CDCl3) 181.7
(CQS), 171.0–169.6 (CQO), 97.2 (C-1), 76.5 (C-4), 71.3–70.0
(C-2, C-3, C-5), 63.0 (C-6a), 53.8 (C-6b), 49.8 (CH2a), 32.1
(CH2b), 21.1 (CH3–CO), 20.8 (CH2g), 14.2 (CH3 chain).
u
max(KBr)/cmꢁ1 2100 (NQCQS), 1750 (CQO); dH (400
MHz; CDCl3) 5.36–5.24 (7H, m, 3-H), 6.01 (7H, d, J 3.3 Hz,
1-H), 4.83–4.76 (7H, m, 2-H), 4.61–4.54 (12H, m, 6a-H),
4.35–4.24 (2H, m, 6b-H), 4.06–4.20 (7H, m, 5-H), 3.78–3.65
(7H, m, 4-H), 2.10 (60H, m, CH3); dC(100 MHz; CDCl3)
170.9, 170.7, 169.7 (CQO), 162.8 (NQCQS), 97.5, 97.3
(C-1), 78.0–77.1 (C-4), 70.9–69.9 (C-2, C-3, C-5), 62.8
(C-6a), 46.3 (C-6b), 21.1 (CH3).
N-[Icosa-O-acetyl-6A-deoxy-b-cyclodextrin-6A-yl]-N0-[benzyl]
-thiourea 7. Benzylamine (0.016 g, 1.5 equiv.), isothiocyanate 3
(0.20 g, 0.099 mmol); (0.195 g, 93%). Found: C, 50.80; H, 5.42;
N, 1.21; S, 1.41; calc. for C90H118N2O54S: C, 50.88; H, 5.56; N,
1.32; S, 1.50%; FTIR umax(KBr)/cmꢁ1 1759 (CQO), 1652
(CQS); dH (400 MHz; CDCl3) 7.41–7.26 (5H, m, Harom),
5.34–5.19 (7H, m, 3-H), 5.17–5.01 (7H, m, 1-H), 4.88–4.68
(7H, m, 2-H), 4.62–4.40 (6H, m, 6a-H), 4.36–3.96 (10H, m, 5-
H, 6b-H, CH2benzyl), 3.81–3.62 (7H, m, 4-H), 2.10 (45H, m,
CH3); dC(100 MHz; CDCl3) 171.1–170.9–169.7 (CQO),
129.0–128.3–127.9 (Carom), 97.3 (C-1), 77.3 (C-4), 71.3–69.2
(C-2, C-3, C-5), 62.9 (C-6), 21.1 (CH3).
6A,6C,6E-Tris-isothiocyanato-6A,6C,6E-trideoxy-6B,6D,6F-tri-
O-acetyl-hexakis(2,3-di-O-acetyl) cyclomaltohexaose 4. ACETris-
azido-per-O-acetyl-a-cyclodextrin 2 (1 g, 0.67 mmol) was added
to a solution of triphenylphosphine (12.25 g, 70 equiv.) in an
anhydrous CS2–DMF (1 : 1) mixture under argon at rt. After
60 h, the solution was evaporated to dryness. The residue was
dissolved in 2 cm3 of anhydrous CH2Cl2 and anhydrous hexane
was added. The resulting precipitate was filtered and washed
with anhydrous hexane under argon (1.11 g, 96%). Found: C,
48.04; H, 5.05; N, 2.38 S, 5.18; calc. for C69H87N3O42S3: C,
47.99; H, 5.04; N, 2.43; S, 5.56%; FTIR umax(KBr)/cmꢁ1 2092
(NQCQS), 1749 (CQO); dH (400 MHz; CDCl3) 5.56 (6H, dd,
J1 8.5 Hz, J2 8.6 Hz, 3-H), 5.06 (6H, d, J 3.2 Hz, 1-H), 4.77 (6H,
dd, J1 3.2 Hz, J2 10.1 Hz, 2-H), 4.39 (6H, m, 6a-H), 4.23–4.14
(12H, m, 6b-H, 5-H), 3.79 (6H, dd, J 8.9 Hz, 4-H), 2.12 (45H, m,
CH3); dC(100 MHz; CDCl3) 171.0–169.5 (CQO), 162.9
(NQCQS), 96.9 (C-1), 77.6 (C-4), 71.3–71.2–69.8 (C-2, C-3,
C-5), 63.5 (C-6a), 47.1 (C-6b), 21.2 (CH3).
N-[Icosa-O-acetyl-6A-deoxy-b-cyclodextrin-6A-yl]-N0-[cyclo-
hexyl]-thiourea 8. Cyclohexylamine (0.007 g, 1.5 equiv.), iso-
thiocyanate 3 (0.1 g, 0.05 mmol); (0.097 g, 92%). Found: C,
50.47; H, 5.71; N, 1.25; S, 1.38; calc. for C89H122N2O54S: C,
50.50; H, 5.76; N, 1.32; S, 1.51%; FTIR umax(KBr)/cmꢁ1 1757
(CQO), 1654 (CQS); dC(100 MHz; CDCl3) 182.3 (CQS),
171.4–169.9 (CQO), 97.3 (C-1), 76.5 (C-4), 71.8–70.1–69.7 (C-
2, C-3, C-5), 63.0 (C-6a), 50.8 (C-6b), 33.2–30.7–25.9–25.2
(cyclohexyl), 21.2 (CH3CO).
Thioureas 5–12 general procedure. The desired amine was
added to a solution of isothiocyanate 3 or 4 in anhydrous
CH2Cl2 under argon at room temperature. After 6 h, the
solution was evaporated to dryness. The residue was dissolved
into 2 cm3 of CH2Cl2 and hexane was added. The resulting
precipitate was filtered, washed three times with hexane and
purified by flash chromatography on a silica gel column
(CH2Cl2–MeOH, 9 : 1).
6A,6C,6E-Tris[p-anisidinyl-thioureido]-6A,6C,6E-trideoxy-6B,6D,
6F-tri-O-acetyl-hexakis(2,3-di-O-acetyl) cyclomaltohexaose 9.
p-Anisidine (0.096 g, 6.0 equiv.), isothiocyanate 4 (0.2 g,
0.129 mmol); (0.178 g, 66%). Found: C, 51.46; H, 5.41; N,
3.87; S, 4.48; calc. for C90H114N6O45S3: C, 51.56; H, 5.44; N,
4.01; S, 4.58%; FTIR umax(KBr)/cmꢁ1 1749 (CQO), 1648
(CQS); dH (400 MHz; CDCl3) 6.72 (2H, d, J 8.8 Hz, Harom),
6.61 (2H, d, J 8.8 Hz, Harom), 5.59–5.49 (6H, m, 3-H), 5.08
(6H, d, J 3.3 Hz, 1-H), 7.74 (6H, dd, J1 3.5 Hz, J2 10.3 Hz, 2-
H), 4.4 (6H, s, 6a-H), 4.13–4.22 (12H, m, 6b-H, 5-H),
3.78–3.82 (6H, m, 4-H), 3.71 (9H, s, OCH3), 2.04 (45H, several
s, CH3–CQO); dC(100 MHz; CDCl3) 179.6 (CQS),
168.9–167.6 (CQO), 130.4, 130.3, 126.9, 126.7 (Carom), 94.7
N-[Icosa-O-acetyl-6A-deoxy-b-cyclodextrin-6A-yl]-N0-[p-ani-
sidinyl]-thiourea 5. p-Anisidine (0.012 g, 2 equiv.), isothiocya-
nate 3 (0.10 g, 0.05 mmol); (0.097 g, 91%). Found: C, 50.75; H,
5.55; N, 1.16; S, 1.38; calc. for C90H118N2O55S: C, 50.50; H,
5.51; N, 1.31; S, 1.49%; FTIR umax(KBr)/cmꢁ1 1748 (CQO),
1649 (CQS); dH (400 MHz; CDCl3) 6.63 (2H, d, J 8.8 Hz,
H
arom), 6.55 (2H, d, J 8.8 Hz, Harom), 5.33–5.26 (7H, m, 3-H),
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0
0
40–50
(C-1), 75.3 (C-4), 69.1–67.7 (C-2, C-3, C-5), 61.4 (C-1a), 53.7
(OCH3), 46.5 (C-6b), 19.1 (CH3–CO).
9.6 Hz, 3-H, 30-H), 5.09 (1H,0t, J
9.6 Hz, J4 –3 9.6 Hz, 40-H),
0
0
0
4.94 (1H, t, J2 –3 9.0 Hz, J2 –1 8.3 Hz, 20-H), 4.87 (1H, t, J2–3 9.3
Hz, J2–1 8.8 Hz, 2-H), 4.73 (1H, d, J1–2 8.8 Hz, 1-H), 4.54 (1H, d,
J6b–6a 12.0 Hz, 6b-H), 4.53 (1H, d, J1 –2 8.3 Hz, 10-H), 4.39 (1H,
dd, J6 b–6 a 12.6 Hz, J6 b–5 4.04 Hz, 60b-H), 4.14 (1H, dd, J6a–6b
12.08 Hz, J6a–5 5.0 Hz, 6a-H4), 4.05 (1H, d, J6 a–6 b 12.6 Hz, 60a-
H), 3.81 (1H, t, J4–3 9.6 Hz, J4–5 9.3 Hz, 4-H), 3.69–3.65 (2H, m,
5-H, 50-H), 2.16, 2.14, 2.06, 2.05, 2.03, 2.03, 2.00 (21H, 7s, CH3,
Ac); dC(100 MHz; CDCl3) 170.9, 170.7, 170.6, 170.1, 169.8,
169.7, 169.4 (7CO, Ac), 137.9 (CO, NQCQO), 101.2 (C-10),
84.3 (C-1), 76.5 (C-4), 75.2 (C-5), 73.3 (C-3), 73.0, 72.9 (C-2, C-
50), 72.4 (C-30), 72.0 (C-20), 68.1 (C-40), 62.0, 61.9 (C-6, C-60),
21.26, 21.05, 20.98, 20.93, 20.92, 20.91, 20.87 (several s, 7CH3,
Ac); ES-MS m/z: 662.12 [M þ H]1.
6A,6C,6E-Tris[di-N-butyl-thioureido]-6A,6C,6E-trideoxy-6B,6D,
6F-tri-O-acetyl-hexakis(2,3-di-O-acetyl) cyclomaltohexaose 10.
Di-N-butylamine (0.075 g, 4.5 equiv.), isothiocyanate 4 (0.20
g, 0.129 mmol); (0.164 g, 60%). Found: C, 53.92; H, 6.89; N,
3.79; S, 4.45; calc. for C95H146N6O41S3: C, 54.00; H, 6.91; N,
3.98; S, 4.54%; FTIR umax(KBr)/cmꢁ1 1749 (CQO), 1648
(CQS); dH (400 MHz; CDCl3) 5.55 (6H, dd, J1 8.8 Hz, J2
10.1 Hz, 3-H), 5.04 (6H, d, J 3.5 Hz, 1-H), 4.78 (6H, dd, J1 3.5
Hz, J2 10.3 Hz, 2-H), 4.23 (6H, d, J 2.8 Hz, 6a-H), 4.21–4.15
(12H, m, 6b-H, 5-H), 3.78 (6H, dd, J1 8.9 Hz, J2 10.0 Hz, 4-H),
2.92 (12H, m, CH2a), 2.08 (45H, m, CH3–CQO), 1.9 (12H, m,
CH2b), 1.41 (12H, m, CH2g), 0.96 (18H, t, J 7.3 Hz, CH3
chain); dC(100 MHz; CDCl3) 181.3 (CQS), 171.0, 169.7
(CQO), 96.8 (C-1), 77.5 (C-4), 71.2, 71.1, 69.8 (C-2, C-3,
C-5), 63.5 (C-6a), 48.4 (C-6b), 30.0 (CH2a), 29.1 (CH2b), 21.2
(CH3–CO), 20.6 (CH2g), 14.0 (CH3 chain).
0
0
0
0
0
0
0
0
2,3,6,20,30,40,60-Hepta-O-acetyl-isocyanato-b-D-lactose 18.
(0.301 g, 91%). TLC (EtOAc–hexane; 7 : 3): Rf = 0.48; found
C, 48.98; H, 5.39; N, 2.24; calc. for C27H35NO18 C, 49.02; H,
5.33; N, 2.12%; FTIR umax(KBr)/cmꢁ1 2192 (NQCQO), 1752
0
0
(CQO), 1226, 1069; dH (400 MHz; CDCl3) 5.33 (1H, dd, J4 –3
6A,6C,6E-Tris[benzyl-thioureido]-6A,6C,6E-trideoxy-6B,6D,6F-
tri-O-acetyl-hexakis(2,3-di-O-acetyl) cyclomaltohexaose 11.
Benzylamine (0.062 g, 4.5 equiv.), isothiocyanate 4 (0.20 g,
0.129 mmol); (0.224 g, 85%). Found: C, 52.69; H, 5.52; N,
3.97; S, 4.29; calc. for C90H114N6O42S3: C, 52.77; H, 5.57; N,
4.10; S, 4.69%; FTIR umax(KBr)/cmꢁ1 1749 (CQO), 1654
(CQS); dH (400 MHz; CDCl3) 7.45–7.23 (15H, 1m, Harom),
5.59 (6H, dd, J1 9.3 Hz, J2 9.2 Hz, 3-H), 5.06 (6H, d, J 3.2 Hz,
1-H), 4.79 (6H, dd, J1 3.5 Hz, J2 10.3 Hz, 2-H), 4.42 (12H, m,
0
0
3.2 Hz, J4 –5 1.5 Hz, 400-H), 5.15 (1H, t, J3–2 9.3 Hz, J3–4 9.3 Hz,
0
0
0
3-H), 5.08 (1H, dd, J2 –3 10.0 Hz, J2 –1 8.0 Hz, 20-H), 4.94 (1H,
0
0
0
0
t, J3 –4 3.2 Hz, J3 –2 10.0 Hz, 30-H), 4.83 (1H, t, J2–3 9.0 Hz,
J2–1 09.0 Hz, 2-H), 4.70 (1H, d, J1–2 9.0 Hz, 1-H), 4.51 (1H, d,
10–2
J
8.0 Hz, 10-H), 4.50 (1H, d, J6b–6a 12.0 Hz, 6b-H),
4.13–4.03 (3H, m, 60b-H, 60a-H, 6b-H), 3.88–3.85 (1H, m, 50-
H), 3.80 (1H, t, J4–3 9.6 Hz, J4–5 9.6 Hz, 4-H), 3.66–3.63 (1H,
m, 5-H), 2.13, 2.12, 2.04, 2.02, 2.02, 2.02, 1.94 (21H, 7s, CH3,
Ac); dC(100 MHz; CDCl3) 170.7, 170.6, 170.5, 170.4, 170.1,
169.8, 169.4 (7CO, Ac), 137.9 (NQCQO), 101.5 (C-10), 84.2
(C-1), 76.3 (C-4), 75.1 (C-5), 73.3, (C-3), 73.1 (C-2), 71.3 (C-
30), 71.1 (C-50), 69.5 (C-20), 67.0 (C-40), 62.1 (C-6), 61.1 (C-60),
21.2, 21.1, 21.0, 20.9 (several s, 7CH3, Ac); ES-MS m/z: 662.24
[M þ H]1.
CH2 benzyl), 4.18 (12H, m, 6b-H, 5-H), 3.81 (12H, m, H6b
,
H5), 3.81 (dd, J1 = 9.1 Hz, J2 = 9.2 Hz, H4), 2.10 (45H, m,
CH3–CQO); dC(100 MHz; CDCl3) 171.0–169.7 (CQO),
132.4, 129.1, 128.2, 127.8 (Carom), 96.8 (C-1), 77.3 (C-4),
71.2–69.8 (C-2, C-3, C-5), 63.5 (C-6a), 44.8 (CH2 benzyl)
21.2 (CH3–CO).
2,3,4,10,30,40,6-Hepta-O-acetyl-60-isocyanato-60deoxy
su-
6A,6C,6E-Tris[cyclohexyl-thioureido]-6A,6C,6E-trideoxy-6B,6D,
6F-tri-O-acetyl-hexakis(2,3-di-O-acetyl) cyclomaltohexaose 12.
Cyclohexylamine (0.058 g, 4.5 equiv.), 4 (0.20 g, 0.129 mmol);
(0.143 g, 55%). Found: C, 51.57; H, 6.25; N, 4.03; S, 4.61; calc.
for C87H126N6O42S3: C, 51.61; H, 6.23; N, 4.15; S, 4.74%;
FTIR umax(KBr)/cmꢁ1 1757 (CQO), 1654 (CQS); dC(100
MHz; CDCl3) 181.8 (CQS), 171.0–169.5 (CQO), 96.9 (C-1),
77.6 (C-4), 71.2–69.7 (C-2, C-3, C-5), 63.5 (C-6a), 50.7 (C-6b),
33.0, 25.8, 25.1, 24.7 (cyclohexyl), 21.2 (CH3CO).
crose 19. (0.189 g, 57%). TLC (EtOAc–hexane; 7 : 3): Rf =
0.43; FTIR umax(KBr)/cmꢁ1 2140 (NQCQO), 1748, (CQO),
1225, 1040; dH (400 MHz; CDCl3) 5.66 (1H, d, J1–2 3.5 Hz, 1-
0
0
H), 5.47 (1H, d, J3 –4 7.0 Hz, 30-H), 5.44 (1H, t, J30 –2 10.6 Hz,
0
0
0
J3–4 9.8 Hz, 3-H), 5.32 (1H, dd, J4 –3 7.0 Hz, J4 –5 4.8 Hz, 40-
H), 5.09 (1H, t, J4–3 9.8 Hz, J4–5 9.8 Hz, 4-H), 4.90 (1H, dd,
J2–1 3.5 Hz, J2–3 10.6 Hz, 2-H), 4.11–4.08 (6H, m, 10a-H, 10b-
0
0
0
0
H, 6a-H, 6b-H, 5-H, 50-H), 3.68 (1H, dd, J6 a–6 b 13.1 Hz, J6 a–5
0
0
60b–60a
7.3 Hz, 60a-H), 3.55 (1H, dd, J
13.1 Hz, J6 b–5 4.8 Hz,
60b-H), 2.19, 2.12, 2.12, 2.10, 2.10, 2.07, 2.02, (21H, 7s, CH3,
Ac); dC(100 MHz; CDCl3) 171.1, 170.8, 170.7, 170.3, 170.2,
169.9, 169.8 (7CO, Ac), 139.4 (NQCQO), 104.0 (C-20), 90.2
(C-1), 80.9 (C-50), 77.4 (C-30), 76.0 (C-40), 70.3 (C-2), 69.7
(C-3), 69.5 (C-4), 68.4 (C-5), 63.6 (C-60), 63.0 (C-10), 62.0
(C-6), 21.5–20.9 (several s, 7CH3, Ac).
Isocyanates 17–19 general procedure. The hepta-O-acetyl
monoazido disaccharide (0.5 mmol) and triphenylphosphine
(0.655 g, 2.5 mmol) were dissolved in anhydrous toluol (10
mL). The resulting solution was stirred for 2 h at rt; and then
24 h under anhydrous CO2 bubbling. Cyclohexane (40 mL)
was then added to the solution, a white solid powder pre-
cipitated and was filtered on a glass sinter, washed several
times with small quantities of cyclohexane and dried under
vacuum to give the pure white isocyanate powder.
6A,6C, 6E -Tris-isocyanato-6A,6C, 6E-trideoxy-6B,6D,6F-tri-O-
methyl-hexakis(2,3-di-O-methyl) cyclomaltohexaose 20. Anhy-
drous DMF (50 mL), ACEtris-6-azido-per-O-methylated-a-
cyclodextrin,19 16, (0.2 g, 0.108 mmol) polystyrene bound
triphenylphosphine resin (2.0 g, 6 mmol) are placed in a solid
phase peptide synthesis reactor. The resulting mixture was
then stirred for 24 h at room temperature under anhydrous
CO2 bubbling. The mixture was filtered and evaporated until
2,3,6,20,30,40,60-Hepta-O-acetyl-isocyanato-b-D-cellobiose 17.
(0.312 g, 95%). TLC (EtOAc–hexane; 7 : 3): Rf = 0.43; found
C, 49.09; H, 5.37; N, 2.22; calc. for C27H35NO18: C, 49.02; H,
5.33; N, 2.12%; FTIR umax(KBr)/cmꢁ1 2190 (NQCQO), 1751
(CQO), 1229, 1043. dH (400 MHz; CDCl3) 5.16 (2H, t large, J
ꢀc
This journal is the Royal Society of Chemistry and the Centre National de la Recherche Scientifique 2006
New J. Chem., 2006, 30, 603–608 | 607

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dryness. The residue was treated with anhydrous DMF (2 mL)
and precipitated with cyclohexane (100 mL). The pure product
was obtained as a white powder (0.156 g, 78%). FTIR
References
1 As antitumor agents see: (a) H. Gurulingappa, M. L. Amador, M.
Zhao, M. A. Rudek, M. Hidalgo and S. R. Khan, Bioorg. Med.
Chem. Lett., 2004, 14, 2213; (b) C. Monneret, R. Risse, P. Ardouin
´
u
max(KBr)/cmꢁ1 2261 (NQCQO), dH (400 MHz; CDCl3)
4.96 (6H, m, 1-HA–F), 3.76 (12H, m, 2-HA–F, 3-HA–F), 3.68
(6H, m, 4-HA–F), 3.57 (18H, s, O–CH3), 3.49 (6H, m, 5-HA–F),
3.43 (18H, s, O–CH3), 3.33 (9H, s, O–CH3), 3.09 (12H, m, 6-
HACE1BDF); dC(100 MHz; CDCl3) 127.8 (NQCQOB,D,F),
100.6 (C-1A–F), 83.8 (C-4A–F), 82.7 (C-2 A–F), 81.6 (C-3 A–F),
71.6 (C-5 A–F), 62.2 (C-6 A–F), 59.5 (O–CH3), 58.4 (O–CH3).
and A. Gouyette, Eur. J. Med. Chem., 2000, 35, 137; (c) as an
antimalarial agent: J. N. Dominguez, L. Caritza, J. Rodrigues, N.
Gamboa de Dominguez, J. Gut and P. J. Rosenthal, J. Med.
Chem., 2005, 48, 3654; (d) as ACAT inhibitors see: A. Tanaka and
T. Terasawa, Drugs Future, 2000, 25, 171; (e) H. Ban, M. Muraoka
and N. Ohashi, Tetrahedron, 2005, 61, 10081; (f) thiourea deriva-
tives: V. G. de Vries, US Pat. 5003106, 1991; (g) T. K. Venkata-
chalam and F. M. Uckun, Synth. Commun., 2005, 35, 2039.
2 (a) N. G. Oikonomakos, M. Kosmopoulou, S. E. Zographos, D.
D. Leonidas, E. D. Chrysina, L. Somsa
Docsa, B. Toth and P. Gergely, Eur. J. Biochem., 2002, 269,
1684–1696; (b) L. Somsak, V. Nagy, Z. Hadaly, T. Docsa and P.
´
k, V. Nagy, J.-P. Praly, T.
Isothiocyanates 21–22 general procedure. The hepta-O-acetyl
monoazido disaccharide (0.5 mmol) and triphenylphosphine
(0.655 g, 2.5 mmol) were dissolved in anhydrous toluol (10
mL). The resulting solution was stirred for 2 h at rt, then CS2
(1.90 g, 25 mmol) was added to the solution and the resulting
mixture was stirred for a further 48 h under argon. Cyclohex-
ane (40 mL) was then added to the solution, a white solid
powder precipitated and was filtered on a glass sinter, washed
several times with small quantities of cyclohexane and dried
under vacuum to give the pure white isothiocyanate powder.
´
´
Gergely, Curr. Pharm. Des., 2003, 9, 1177–1189.
3 (a) F. Sallas, A. Marsura, V. Petot, I. Pinter, J. Kovacs and L.
Jicsinszky, Helv. Chim. Acta, 1998, 81, 632; (b) F. Charbonnier, A.
Marsura and I. Pinter, Tetrahedron Lett., 1999, 40, 6581; (c) F.
´
Charbonnier, A. Marsura, K. Roussel, J. Kovacs and I. Pinter,
Helv. Chim. Acta, 2001, 84, 535.
4 J. Kovacs, F. Sallas, I. Pinter, A. Marsura and L. Jicsinszky, J.
Inclusion Phenom. Mol. Recognit. Chem., 1996, 25, 53.
5 S. Porwanski, S. Menuel, X. Marsura and A. Marsura, Tetra-
hedron Lett., 2004, 45, 5027.
6 S. Menuel, M. Wagner, D. Barth and A. Marsura, Tetrahedron
Lett., 2005, 46, 3307.
7 S. Porwanski, B. Kryczka and A. Marsura, Tetrahedron Lett.,
2002, 43, 8441.
8 (a) I. Maya, O. Lopez, S. Maza, J. G. Fernandez-Bolanos and J.
Fuentes, Tetrahedron Lett., 2003, 44, 8539; (b) O. Lopez, S. Maza,
I. Maya, J. Fuentes and J. G. Fernandez-Bolanos, Tetrahedron,
2005, 61, 9058, (and references cited therein).
9 (a) S. Menuel, J. P. Joly, A. Marsura, Proceedings of the 12th
International Symposium on Cyclodextrin, ed. D. Duchene and E.
Fattal, APGI, Montpellier, 2004, pp. 153–158; (b) S. Menuel, J. P.
Joly and A. Marsura, presented in part at the E.S.F. Conference on
Supramolecular Chemistry, Strasbourg, 2005.
10 (a) R. Heck, F. Dumarcay and A. Marsura, Chem.–Eur. J., 2002, 8,
2438; (b) R. Heck and A. Marsura, Tetrahedron Lett., 2004, 45,
281; (c) R. Heck and A. Marsura, Tetrahedron Lett., 2003, 44,
1533; (d) M. J. J. Peirera Silva, J. M. Haider, M. Chavarot, P. R.
Ashton, R. M. Williams, L. De Cola, R. Heck, A. Marsura and Z.
Pikramenou, Supramol. Chem., 2003, 15, 563; (e) M. Badis, A. Van
der Heyden, R. Heck, A. Marsura, B. Gauthier-Manuel, A.
Zywocinski and E. Rogalska, Langmuir, 2004, 20, 5338.
11 L.-F. Zhang, L. Chen, T.-C. Lee and S.-C. Ng, Tetrahedron:
Asymmetry, 1999, 10, 4107.
12 P. A. Enquist, P. Nilsson, Johan Edin and M. Lahred, Tetrahedron
Lett., 2005, 46, 3335.
13 (a) P. Friant-Michel, A. Marsura, J. Kovacs, I. Pinter and J.-L.
Rivail, THEOCHEM, 1997, 395–396, 61; (b) B. Paizs, I. Pinter, J.
Kovacs, W. Viviani, A. Marsura, J. L. Rivail and G. Czismadia,
THEOCHEM, 1997, 395–396, 41.
2,3,6,20,30,40,60-Hepta-O-acetyl-isothiocyanato-b-D-cellobiose 21.
(0.211 g, 64%). FTIR umax(KBr)/cmꢁ1 2157 (NQCQS), 1752
(CQO); TLC (EtOAc–hexane; 7 : 3): Rf = 0.3; dH (400 MHz;
0
0
CDCl3) 5.16 (2H, t large, J3 –4 9.6 Hz, J3–2 9.3 Hz, 3-H, 030-H),
0
0
0
0
2 –30
5.09 (1H, t, J4 –3 9.6 Hz, J4 –5 9.6 Hz, 40-H), 4.92 (1H, t, J
9.0
0
0
Hz, J2 –1 8.3 Hz, 20-H), 4.87 (1H, t, J2–3 9.3 Hz, 0J20–1 8.8 Hz, 2-H),
4.72 (1H, d, J1–2 8.8 Hz, 1-H), 4.53 (1H, d, J1 –2 8.3 Hz, 10-H),
0
0
4.52 (1H, d, J6b–6a 12.0 Hz, 6b-H), 4.38 (1H, dd, J6 b–6 a 12.6 Hz,
0
0
J6 b–5 4.04 Hz, 60b-H), 4.14 (1H, dd, J6a–6b 12.08 Hz, J6a–5 5.04
0
0
0
Hz, 6a-H), 4.05 (1H, dd, J6 a–6 b 12.6 Hz, J6 a–5 2.0 Hz, 60a-H), 3.81
(1H, t, J4–3 9.6 Hz, J4–5 9.3 Hz, 4-H), 3.68–3.66 (2H, m, 5-H, 50-
H), 2.15, 2.10, 2.06, 2.05, 2.03, 2.03, 2.00 (21H, 7s, CH3, Ac);
dC(100 MHz; CDCl3) 170.8, 170.6, 170.5, 170.1, 170.0, 169.7,
169.4 (7CO, Ac), 144.5 (NQCQS), 101.2 (C-10), 84.3 (C-1), 76.2
(C-4), 75.3 (C-5), 73.2 (C-3), 72.5, 72.4 (C-2, C-50), 72.0 (C-30),
71.9 (C-20), 68.1 (C-40), 62.0, 61.9 (C-6, C-60), 21.3, 21.2, 21.1,
21.0, 20.9, 20.8 (several s, 7CH3, Ac); ES-MS m/z: 700 [M þ Na]1.
2,3,6,20,30,40,60-Hepta-O-acetyl-isothiocyanato-b-D-lactose 22.
(0.223 g, 66%). TLC (EtOAc–hexane; 7 : 3): Rf = 0.40; FTIR
u
max(KBr)/cmꢁ1 2153 (NQCQS), 1751 0(CQO), 1232, 1050; dH
0
0
0
(400 MHz; CDCl3) 5.37 (1H, d large, J4 –3 3.2 Hz, J4 –5 1.0 Hz,
40-H), 5.19 (1H, t, J3–2 9.1 Hz, J3–4 9.4 Hz, 3-H), 5.12 (1H, t,
14 I. Pinter and A. Marsura, 1999, unpublished work.
15 M. Hiramatsu, T. Suzuki, H. Satozono and Y. Misuzawa, Ger.
Offen. DE 19627474 A1, 1997.
16 (a) C. Ortiz-Mellet, J. Defaye and J. M. Garcia Fernandez,
Chem.–Eur. J., 2002, 8, 1982; (b) J. M. Garcia Fernandez, C.
Ortiz-Mellet, S. Maciejewski and J. Defaye, Chem. Commun., 1996,
2741.
20–30
20–10
10.0 Hz, J
30–40
30–20
3.3 Hz, J
J
8.0 Hz, 20-H), 4.97 (1H, t, J
10.0 Hz, 30-H), 4.87 (1H, d, J2–3 9.1 Hz, J2–1 9.0 Hz, 2-H), 4.66
0
0
(1H, d, J1–2 9.0 Hz, 1-H), 4.51 (1H, d, J1 –2 8.3 Hz, 10-H), 4.50
(1H, d, J6b–6a 12.0 Hz, 6b-H), 4.16–4.07 (3H, m, 6b-H, 60a-H,
6b-H), 3.90–3.86 (1H, m, 50-H), 3.84 (1H, dd, J4–3 9.4 Hz, J4–5
9.6 Hz, 4-H), 3.70–3.67 (1H, m, 5-H), 2.17, 2.15, 2.08, 2.07,
2.06, 2.05, 1.98 (21H, 7s, CH3, Ac); dC(100 MHz; CDCl3) 170.7,
170.6, 170.5, 170.4, 170.1, 169.9, 169.4 (7CO, Ac), 144.5
(NQCQS), 101.5 (C-10), 84.3 (C-1), 76.3 (C-4), 75.1 (C-5),
73.3, (C-3), 73.1 (C-2), 71.3, 71.1 (C-5, C-30), 69.5 (C-20), 67.0
(C-40), 62.2, 61.1 (C-6, C-60), 21.3, 21.2, 21.1, 21.03, 21.02,
21.01, 20.9 (several s, 7 CH3, Ac).
17 C. Peto, G. Batta, Z. Gyorgydeak and F. Sztaricskai, Liebigs Ann.
¨
Chem., 1991, 505.
¨
18 S. Singh, C. M. Maynard, R. J. Doyle and K. G. Taylor, J. Org.
Chem., 1984, 46, 976.
19 R. Heck, L. Jicsinzky and A. Marsura, Tetrahedron Lett., 2003, 44,
5411.
20 J. M. Garcia-Fernandez, C. Ortiz-Mellet, J. L. Jimenez-Blanco, J.
F. Mota, A. Gadelle, A. Coste-Sarguet and J. Defaye, Carbohydr.
Res., 1995, 268, 57.
21 F. E. Hong and Y. Chang, Organometallics, 2004, 23, 718.
ꢀc
608 | New J. Chem., 2006, 30, 603–608 This journal is the Royal Society of Chemistry and the Centre National de la Recherche Scientifique 2006