Water-soluble glycodendrimers: Synthesis and stabilization of catalytically active Pd and Pt nanoparticles

Article abstract of DOI:10.1016/j.tetlet.2011.02.015

A new water-soluble glycodendrimer containing 9 terminal modified xylose branches was prepared from nona-azide terminated dendrimer by 'click' chemistry. The glycodendrimer was analyzed by ¹H, ¹³C NMR and mass spectroscopy and used to stabilize palladium (PdNPs) and platine (PtNPs) nanoparticles. These DSN are stable in water and were characterized by TEM. The platinum NPs showed a remarkable catalytically activity for olefin hydrogenation in water at room temperature.

Full text of DOI:10.1016/j.tetlet.2011.02.015

Tetrahedron Letters 52 (2011) 1842–1846
Contents lists available at ScienceDirect
Tetrahedron Letters
journal homepage: www.elsevier.com/locate/tetlet
Water-soluble glycodendrimers: synthesis and stabilization of catalytically
active Pd and Pt nanoparticles
Sylvain Gatard a, , Liyuan Liang b, Lionel Salmon c, Jaime Ruiz b, Didier Astruc b, Sandrine Bouquillon a,
⇑
⇑
a Institut de Chimie Moléculaire de Reims, CNRS UMR 6229, Université de Reims Champagne-Ardenne, BP 1039, 51687 Reims Cedex, France
b Institut des Sciences Moléculaires, Groupe Nanosciences Moléculaires et Catalyse, UMR CNRS N° 5255, Université Bordeaux I, 351, Cours de la Libération, 33405 Talence Cedex, France
c Laboratoire de Chimie de Coordination, UPR CNRS 8241, 205 Route de Narbonne, 31077 Toulouse Cedex 04, France
a r t i c l e i n f o
a b s t r a c t
Article history:
A new water-soluble glycodendrimer containing 9 terminal modified xylose branches was prepared from
nona-azide terminated dendrimer by ‘click’ chemistry. The glycodendrimer was analyzed by 1H, 13C NMR
and mass spectroscopy and used to stabilize palladium (PdNPs) and platine (PtNPs) nanoparticles. These
DSN are stable in water and were characterized by TEM. The platinum NPs showed a remarkable catalyt-
ically activity for olefin hydrogenation in water at room temperature.
Received 10 January 2011
Revised 28 January 2011
Accepted 1 February 2011
Available online 12 February 2011
Ó 2011 Elsevier Ltd. All rights reserved.
Keywords:
Glycodendrimer
Nanoparticles
Palladium
Platinum
Catalysis
Hydrogenation
Cheap molecules such as
D
-xylose and
L
-arabinose derived from
lysts.11 Amphiphilic glycodendrimers having
a chiral surface
corn are building blocks of choice for the formation of various com-
pounds with a broad spectrum of applications. Recently, we have
chosen to valorize these sugars in glycodendrimer chemistry,1 an
area developed by Roy’s group, that we wish to apply to catalysis
and vectorization.
found potential applications in enantioselective catalysis,1b–d,12
and the supramolecular interaction between sugars and proteins
such as for instance lectins,13 are involved in nanomedicine.1f,g,l,2c
Recently, we reported the syntheses of a series of large glyco-
dendrimers containing 27, 81, and 243 terminal modified xylose
branches by ‘click’ chemistry.1i However, the mildly basic condi-
tions (MeONa) used to cleave the acetate group in order to give
glycodendrimers with free hydroxyl groups resulted in their
decomposition. This led us to envisage a new synthetic route to
dendrimers decorated by unprotected sugar entities. We first used
the known dendrimer core14 1 (Scheme 1) to induce a Huisgen-
type 1,3 dipolar ‘click’ reaction of the azido-terminated dendrimer
Dendrimers2 can be used in various fields of nanosciences such
as nanoreactors,3 molecular micelles,4 drug vectors,5 sensors,6
green catalysts,7 supramolecular electronics,8 and light-harvesting
devices,9 and in these areas water solubility is a key factor.
The contribution of dendrimers in the catalysis field is well
established, and many studies have clearly shown that dendrimers
have high catalytic activities. Crooks and his group have shown
that dendrimers can stabilize transition-metal nanoparticles in
solution. The presence of ‘hydrophobic areas’ within the dendrimer
allows the development of highly selective catalytic processes, the
dendrimer playing the role of an efficient ‘nanofilter’.3a–c The func-
tion of dendrimers as micelles has been pioneered by Newkome in
his seminal publication on ‘arborols’,4 and Tomalia, Meijer and
Zimmerman have also shown useful dendrimer encapsulation of
guest molecules in early reports.10 Recently, Astruc et al. described
the use of recyclable dendritic nanoreactors for the catalysis of ole-
fin metathesis reactions in water using the classical Grubbs cata-
with 20-(prop-2-ynyloxy) 2,3,4-tri-O-acetyl-b- -xylopyranoside.15
D
After cleavage of acetate groups in basic medium, this reaction
yielded a xylose-terminated water-soluble dendrimer containing
nine sugar termini (Scheme 1).
The nona-azide core 1 was treated with 20-(prop-2-ynyloxy)
2,3,4-tri-O-acetyl-b-D-xylopyranoside in the presence of CuSO4
(4 equivperbranch)instoichiometricamountandsodiumascorbate
(8 equiv per branch) in aqueous tetrahydrofuran (H2O/THF 1:1). The
excess of Cu salt was removed as [Cu(NH3)2(H2O)2][SO4] by washing
ten times with an ammonia solution. The desired protected glyco-
dendrimer 2 was purified by precipitation with CH2Cl2/Et2O in order
to remove the excess sugar, and the reaction yield was 52%.16 The
presence of signals in the 1H NMR spectrum at 7.40 ppm and the
13C NMR spectrum at 124.1 and 144.2 ppm unambiguously proved
⇑
Corresponding authors.
E-mail addresses: sylvain.gatard@univ-reims.fr (S. Gatard), sandrine.bouquillo-
n@univ-reims.fr (S. Bouquillon).
0040-4039/$ - see front matter Ó 2011 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tetlet.2011.02.015

S. Gatard et al. / Tetrahedron Letters 52 (2011) 1842–1846
1843
OAc
AcO
AcO
N
AcO
AcO
O
O
OAc
AcO
AcO
O
AcO
O
O
O
N
N
N
N
N
N
N3
N3
N
N
N3
Si
Si
Si
Si
Si
Si
O
O
AcO
18 eq.
OAc
OAc
AcO
O
AcO
OAc
N
N
N3
N
Si
Si
O
CuSO4 (36 eq.),
sodium ascorbate (72 eq.),
THF/water, 12h, rt
O
Si
Si
N
N
O
AcO
AcO
N3
Si
Si
N
N
N
Si
Si
OAc
N
Si
N
Si
N3
Si
AcO
Si
N3
N
OAc
N3
52 %
N
N
O
N
N
N3
O
N
O
N
O
OAc
N
OAc
OAc
O
OAc
OAc
OAc
AcO
O
OAc
1
O
O
OAc
AcO
2
NaOMe (27 eq.),
CH2Cl2/MeOH
12h, rt
86 %
OH
HO
HO
HO
HO
HO
O
O
OH
O
O
HO
O
HO
O
N
N
N
N
N
N
N
N
Si
Si
N
Si
OH
HO
O
N
N
N
Si
O
OH
O
O
Si
N
N
HO
Si
N
N
N
Si
OH
N
N
Si
HO
HO
Si
N
OH
OH
N
N
O
N
N
O
N
O
N
O
N
OH
O
OH
OH
OH
HO
O
OH
OH
O
O
OH
HO
3
Scheme 1. Synthesis of the glycodendrimer 3 in two steps from the nona-azide core 1.
the formation of the triazole ring, and the composition of compound
2 was further confirmed by elemental analysis.
was used as a template for the preparation of palladium nanopar-
ticles (PdNPs) and platinum nanoparticles (PtNPs) in water. Reac-
tions between K2MCl4 (M = Pd or Pt) and 3 in the presence of
NaBH4 as the reducing agent led in less than 10 min. to the forma-
tion of nanoparticles stabilized by the dendrimer 3 (Scheme 2).18
Brown solutions were obtained and the reduction of PdII to Pd0
was confirmed by the decrease of the shifts in 1H NMR of dendri-
mer 3, as previously reported.19
The TEM data (Figs. 1 and 2) show that DSNs with a diameter of
4.7 0.4 nm for PdNPs (3624 Pd atoms stabilized by 403 dendri-
mers) and of 14.0 3.0 nm for PtNPs (89795 Pt atoms for 9978
dendrimers) were formed. The TEM data also show that the PtNPs
are more monodisperse than the PdNPs and, therefore, appear to
be more suitable for careful catalytic studies.3
The acetylated glycodendrimer
2 was then quantitatively
deprotected in the presence of sodium methanolate to give glyco-
dendrimer 3 with free hydroxyl groups. Compound 3 was purified
by precipitation with MeOH/Et2O and characterized by 1H, 13C
NMR spectroscopy and mass spectroscopy.17 No signals were
found for methyl groups or carbonyl carbons in the 1H and 13C
NMR spectra, respectively. The mass spectrum of 3 contained
peaks at m/z 3233.4 and m/z 1628.2 corresponding to [M+Na]
and [M/2+Na], respectively.
Furthermore, we noticed that a diluted solution of 3 in water
showed considerable foaming, which is a good indication for the
surfactant properties of this dendrimer. The glycodendrimer 3

1844
S. Gatard et al. / Tetrahedron Letters 52 (2011) 1842–1846
OH
HO
HO
HO
HO
HO
OH
O
HO
HO
O
O
HO
HO
HO
HO
OH
O
O
O
O
O
HO
HO
OH
HO
O
N
O
O
N
N
N
N
N
O
N
N
N
N
N
N
OH
N
N
Si
Si
N
HO
HO
N
N
Si
Si
N
Si
OH
O
O
Si
HO
HO
O
O
HO
HO
HO
HO
HO
OH
HO
HO
HO
O
O
O
O
HO
HO
OH
OH
HO
N
OH
O
N
N
N
N
N
O
Si
Si
O
N
N
O
O
OH
OH
N
O
HO
N
N
Si
Si
N
N
O
HO
HO
N
N
N
O
N
N
N
N
Si
Si
Si
Si
OH
N
O
N
N
N
N
O
N
N
Si
O
Si
Si
N
Si
O
HO
HO
N
N
N
HO
OH
N
N
N
Si
Si
N
N
N
N
O
OH
N
Si
O
N
Si
N
N
N
N
O
Si
N
O
OH
OH
HO
OH
HO
N
N
Si
OH
OH
N
HO
O
N
Si
Si
O
O
O
O
N
N
OH
OH
OH
HO
N
N
O
Si
Si
N
N
O
N
N
O
OH
OH
HO
HO
OH
OH
O
N
O
N
N
Si
Si
N
O
OH
OH
N
O
O
O
O
N
N
N
N
Si
Si
Si
N
N
O
HO
Si
HO
N
N
N
HO
N
OH
OH
OH
OH
HO
N
N
OH
OH
N
N
O
N
Si
O
N
O
HO
Si
N
N
O
N
N
N
HO
O
N
O
OH
OH
OH
OH
OH
O
N
OH
OH
N
O
OH
OH
N
O
O
N
N
O
O
N
O
HO
O
OH
OH
OH
HO
OH
O
OH
OH
HO
O
O
HO
OH
O
OH
HO HO
OH
OH
OH
OH
OH
O
HO
HO
HO
O
O
O
O
HO
OH
HO
OH
O
HO
HO
HO
HO
HO
Pt or Pd
O
O
O
HO
HO
N
N
O
N
OH
O
N
N
HO
N
O
9 eq. K2PtCl4
or
9 eq. K2PdCl4
O
N
N
N
N
O
Si
N
Si
N
N
N
N
Si
N
N
Si
Si
N
Si
OH
HO
N
N
N
Si
Si
O
OH
O
O
Si
Si
N
N
O
HO
HO
OH
OH
HO
N
N
N
N
OH
HO
OH
N
Si
Si
N
N
O
Si
Water (6 mL), RT
NaBH4 (90 eq.)
HO
HO
HO
O
O
O
OH
Si
Si
Si
N
N
N
N
N
HO
HO
OH
O
O
N
OH
OH
O
O
HO
N
N
HO
HO
O
N
HO
N
O
N
N
Si
N
O
N
O
Si
N
N
N
HO
N
OH
OH
O
N
N
N
OH
OH
N
N
O
O
N
O
O
O
OH
OH
HO
N
N
O
N
N
OH
OH
OH
N
N
O
OH
OH
O
O
N
N
Si
O
Si
N
HO
O
HO
OH
OH
OH
Si
OH
OH
O
O
HO
OH
HO
N
N
N
Si
Si
O
OH
O
O
Si
Si
N
N
O
HO
HO
N
OH
N
N
N
Si
Si
N
N
N
HO
N
OH
OH
N
O
N
O
N
N
O
N
O
OH
OH
O
HO
O
OH
OH
OH
OH
OH
O
O
HO
Scheme 2. Formation and stabilization of Pd and Pt nanoparticles in water.
Figure 1. PtNPs: (a) TEM image and (b) size distribution.
Figure 2. PdNPs: (a) TEM image and (b) size distribution.

S. Gatard et al. / Tetrahedron Letters 52 (2011) 1842–1846
1845
Isophorone
H2 (1 atm)
1.2x10-3 M in Pt (0.01 eq)
O
O
Isophorone : 1 eq.
H2O (6 mL), 26h, rt
With
Without
No e.e.
Glyco. Glyco.
Conv. (GC) 86 % 30 %
(R)-(+)-Pulegone
H2 (1 atm)
1.2x10-3 M in Pt (0.01 eq)
(R)-(+)-Pulegone : 1 eq.
H2O (6 mL), 50h, rt
O
O
With
Without
Glyco. Glyco.
No d.e.
Conv. (GC) 95 % 8 %
Scheme 3. Hydrogenation reactions in the presence of Pt nanoparticles stabilized by the glycodendrimer 3.
2. (a) Hecht, S.; Fréchet, J. M. J. Angew. Chem., Int. Ed. 2001, 40, 74; (b) Tomalia, D.
A.; Naylor, A. M.; Goddard, W. A. III. Angew. Chem., Int. Ed. 1990, 29, 138; (c)
Bosman, A. W.; Janssen, H. M.; Meijer, E. W. Chem. Rev. 1999, 99, 1665; (d)
Astruc, D.; Boisselier, E.; Ornelas, C. Chem. Rev. 2010, 110, 1857; (e) Newkome,
G. R.; Shreiner, C. Chem. Rev. 2010, 110, 6338.
3. (a) Crooks, R. M.; Zhao, M.; Sun, L.; Chechik, V.; Yeung, L. K. Acc. Chem. Res.
2001, 34, 181; (b) Niu, Y.; Crooks, R. M. C. R. Chimie 2003, 6, 1049; (c) Scott, R.
W. J.; Wilson, O. M.; Crooks, R. M. J. Phys. Chem. B 2005, 109, 692; (d) Krämer,
M.; Pérignon, N.; Haag, R.; Marty, J.-D.; Thomann, R.; Lauth-de Viguerie, N.;
Mingotaud, C. Macromolecules 2005, 38, 8308; (e) Astruc, D.; Ornelas, C.; Ruiz, J.
Acc. Chem. Res. 2008, 41, 841.
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Moorefield, C. N.; Baker, G. R.; Behera, R. K.; Escamillia, G. H.; Saunders, M. J.
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C. M.; Tsiourvas, D. Langmuir 1997, 13, 5870; (c) Jansen, J. F. G. A.; den Berg, E.
M. M.; Meijer, E. W. Science 1999, 266, 1226; (d) Liu, M.; Kono, K.; Fréchet, J. M.
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Klopsch, R.; Lorenz, K.; Frey, H.; Weener, J. W.; Meijer, E. W.; Paulus, W.;
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Rev. 2009, 38, 1759.
Solutions containing PtNPs were used in hydrogenation reac-
tions with isophorone and (R)-(+)-pulegone (Scheme 3). The
hydrogenation reactions were conducted under an H2 atmosphere
at room temperature in water.20 Remarkably, for the isophorone,
we found that the conversion of the substrate in the presence of
PtNPs stabilized by glycodendrimer 3 proceeded more rapidly than
the same reaction performed in the absence of glycodendrimer.
Similar observations were made for the hydrogenation of (R)-(+)-
pulegone for which the influence of glycodendrimer 3 was much
more significant (Scheme 3).
Unfortunately, no stereoselectivity was observed even in the
presence of the chiral sugar used as the decorating entities. Cata-
lytic experiments are underway in order to tentatively benefit from
the chiral character of the glycodendrimer, as well as to recycle the
catalyst.
In conclusion, we have described here the preparation of a new
Si-based dendrimer decorated with
D-xylose groups using click
chemistry. This water-soluble dendrimer can be used for the prep-
aration and stabilization of Pd and Pt nanoparticles in water. Preli-
minary catalytic hydrogenation studies in water in the absence of
co-solvent using Pt stabilized nanoparticles showed promising
results.
6. (a) Daniel, M.-C.; Ruiz, J.; Astruc, D. J. Am. Chem. Soc. 2003, 125, 1150; (b) Daniel,
M.-C.; Ruiz, J.; Nlate, S.; Blais, J.-C.; Astruc, D. J. Am. Chem. Soc. 2003, 125, 2617;
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J. Chem. Commun. 2004, 2637; (e) Ashton, P. R.; Balzani, V.; Clemente-Leon, M.;
Colonna, B.; Credi, A.; Jayaraman, N.; Raymo, F. M.; Stoddart, J. F.; Venturi, M.
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Acknowledgments
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This work was supported by the CPER framework (Pentoraf pro-
gram). We are grateful to the Public Authorities of Champagne-
Ardenne and FEDER for material funds. Authors also acknowledge
the CNRS, the French Ministry of Research, the universities of Re-
ims Champagne Ardenne and Bordeaux 1, and the Agence Natio-
nale pour la Recherche (ANR-07-CP2D-05-01) for their financial
support.
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14. Dendrimer 1 was prepared by CpFe+-induced nona-allylation of mesitylene in
[CpFe(
g
6-mesitylene)][PF6],14a followed by decomplexation using visible-
light,14b,c hydrosilylation with HSiMe2CH2Cl and reaction with NaN3 as

1846
S. Gatard et al. / Tetrahedron Letters 52 (2011) 1842–1846
already reported. For a recent application, see ref.14d. (a) Moulines, F.; Astruc,
filtered. The organic phase was concentrated to dryness in vacuo, and the crude
product was dissolved in a minimum of MeOH and precipitated with an excess
of diethylether. The glycodendrimer 3 was obtained as a white solid in 86%
D. Angew. Chem., Int. Ed., 1988, 27, 1347. (b) Catheline, D.; Astruc, D. J.
Organomet. Chem. 1983, 248, C9. (c) Catheline, D.; Astruc, D. J. Organomet. Chem.
1984, 272, 417. (d) Boisselier, E.; Diallo, A. K.; Salmon, L.; Ornelas, C.; Ruiz, J.;
Astruc, D. J. Am. Chem. Soc. 2010, 132, 2729.
yield (m = 107 mg). Data for glycodendrimer
3 C135H237N27O45Si9 : MW
3211.27 g molꢀ1; NMR 1H (250 MHz, CD3OD, 25 °C): 0.00 (s, 54 H, Si(CH3)2),
0.59 (s, 18H, CH2CH2CH2Si), 1.11 (s, 18H, CH2CH2CH2Si), 1.64 (s, 18H,
CH2CH2CH2Si), 3.14–3.35 (m, 9H+9H+9H, H5a+H2+H3 sugar), 3.47 (m, 9H, H4),
3.86 (dd, J = 5 Hz, J = 12.5 Hz, H5e), 3.94 (s, Si-CH2-Ntriazole), 4.31 (d, J = 7.5 Hz,
15. Ding, H.; Yang, R.; Song, Y.; Xiao, Q.; Wu, J. Nucleosides, Nucleotides and Nucleic
Acids 2008, 27, 368.
16. Preparation of glycodendrimer 2: To a solution of dendrimer 1 (1.0 equiv) in a
THF/water 1:1 (v:v) mixture were added 20-(prop-2-ynyloxy) 2,3,4-tri-O-
9H, H1), 4.76 (m, 18H, H1 sugar), 4.93 (s, 18H, -OH), 7.03 (s, 3H, HAr), 7.81
0
acetyl-b-
D-xylopyranoside (2.0 equiv per branch), CuSO4.5H2O (4.0 equiv per
(s, 9H, Htriazole). NMR 13C{1H} (250 MHz, CD3OD, 25 °C): ꢀ3.03 (s, CH3), 16.3
(CH2), 19.4 (CH2), 42.4 (CH2), 43.4 (CH2), 45.6 (C), 63.6 (CH2), 67.4 (CH2), 71.5
(CH), 75.2 (CH), 78.1 (CH), 104.7 (CH), 123.5 (CH), 126.4 (CH), 145.8 (CH2),
147.7 (C). MS m/z for C135H237N27O45Si9Na found (calcd): 3233.4 (3234.3) and
for C67.5H118.5N13.5O22.5Si4.5Na found (calcd) 1628.2 (1628.7).
branch), and sodium ascorbate (8.0 equiv per branch). The mixture was stirred
at room temperature under an argon atmosphere for 12 h. The mixture was
concentrated and CH2Cl2 was added. The organic layer was washed with
aqueous ammonium hydroxide until a colorless aqueous layer was obtained
and then with water to neutrality. The organic phase was concentrated to
dryness in vacuo. The crude product was dissolved in a minimum of CH2Cl2 and
precipitated with excess of diethylether. The glycodendrimer 2 was obtained
18. General procedure for the preparation of PtNPs and PdNPs:
A solution of
glycodendrimer 3 (2.6 mg, 8.02.10ꢀ7 mol) in water (2 mL) was placed in a
Schlenk flask under argon. A solution of K2PtCl4 (3 mg, 7.22.10ꢀ6 mol, 1 equiv
per triazole) or K2PdCl4 (2.3 mg, 7.22.10ꢀ6 mol, 1 equiv per triazole) in water
(2 mL) was added. The solution was stirred for 5 min, NaBH4 (2.7 mg,
7.22.10ꢀ5 mol, 10 equiv per Pt) in solution in water (2 mL) was added, and
the solution turned a little bit brown indicating the nanoparticle formation.
19. Ornelas, C.; Salmon, L.; Ruiz, J.; Astruc, D. Chem. Commun. 2007, 4946.
20. General procedure for hydrogenation reactions with PtNPs: PtNPs were freshly
prepared in a Schlenk flask in an aqueous solution (1.2.10ꢀ3 M in Pt), and
100 equiv of the substrate were added. The Schlenk flask was filled with H2 and
the solution was allowed to stir at 25 °C. After respectively, for the isophorone
and the (R)-(+)-pulegone, 26 and 50 h, the mixture is analyzed by gas
chromatography (injector temperature, 250 °C; split injection mode; carrier
as a colorless oil in 52% yield. Data for glycodendrimer 2 C189H291N27O72Si9
:
MW 4346.27 g molꢀ1; yield 52%; NMR 1H (250 MHz, CDCl3, 25 °C, TMS) 0.05 (s,
54 H, Si(CH3)2), 0.63 (s, 18H, CH2CH2CH2Si), 1.09 (s, 18H, CH2CH2CH2Si), 1.62 (s,
18H, CH2CH2CH2Si), 1.97–2.03 (m, 81 H, CH3 sugar), 3.36 (m, 9H, H5a sugar),
3.83 (s, 18H, Si-CH2–Ntriazole), 4.10 (dd, J = 5 Hz, J = 12.5 Hz, 9H, H5e sugar), 4.60
0
(d, J = 7.5 Hz, 9H, H1sugar), 4.66-4.93 (m, 18H+9H+9H, H1 +H3+H4 sugar), 5.13
(m, 9H, H2 sugar), 6.93 (s, 3H, HAr), 7.40 (s, 9H, Htriazole). NMR 13C{1H}
(250 MHz, CDCl3, 25 °C, TMS) ꢀ3.44 (CH3), 15.4 (CH2), 18.1 (CH2), 21.2 (CH3),
41.4 (CH2), 42.2 (CH2), 44.3 (C), 62.6 (CH2), 63.1 (CH2), 69.3 (CH), 71.2 (CH),
71.9 (CH), 100.4 (CH), 121.6 (CH), 124.1 (CH), 144.2 (C), 146.2 (C), 169.9 (C),
170.3 (C), 170.4 (C). Anal. Found (Calcd) for C189H291N27O72Si9 + 5H2O: C 51.17
(51.17), H 6.59 (6.84), N 8.35 (8.52).
gas, nitrogen at 1 mL minꢀ1
; initial oven temperature, 60 °C, 1 min; rate,
17. Preparation of glycodendrimer 3: The acetylated dendrimer
2
(168 mg,
10 °C minꢀ1; final temperature, 250 °C, 2 min; detector, 300 °C; solvent, diethyl
ether). The retention times were found to be approx. 8 min for the isophorone
and 7 min for the corresponding hydrogenated product.
38.7 mmol) was dissolved in 1/1 MeOH-CH2Cl2 and 0.5 M solution of
a
NaOMe (1.5 equiv per branch, 2.08 mL) was then added. After stirring for 24 h
at room temperature, the mixture was neutralized with Amberlite IR120 and