Cleavage of Calkyl-Caryl bond of [Pd-CH2CMe2Ph] complexes

Article abstract of DOI:10.1002/1521-3773(20011001)40:19<3641::AID-ANIE3641>3.0.CO;2-9

The extrusion of isobutene from the neophyl derivative 1 is catalyzed by the cationic palladium π-arene complex 2 in a process that involves the cleavage of the β C-C bond of the latter (see scheme). The inverse reactivity, that is olefin insertion, is observed when the reaction proceeds in the presence of ethylene.

Full text of DOI:10.1002/1521-3773(20011001)40:19<3641::AID-ANIE3641>3.0.CO;2-9

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Alkenes were distilled and treated with activated alumina to remove
impurities and alkyl hydroperoxide. The reaction was carried out in a glass
vial or a round-bottomed flask containing a magnetic stir bar under 1 atm
of molecular oxygen as described previously.[21] 2-Cyclohexen-1-one was
usually used as an internal standard. The homogeneous reaction solution
was periodically sampled and analyzed by gas chromatography on a TC-
WAX capillary column and by NMR spectroscopy. The amounts of oxygen
consumed were measured with a gas burette. It was confirmed for the
oxygenation of cyclooctene that no reaction proceeded without catalysts.
Turnover numbers were calculated as moles of products per mole of 1.
Cleavage of the Calkyl Caryl Bond of
[Pd CH2CMe2Ph] Complexes**
Â
Â
Juan Campora,* Enrique Gutierrez-Puebla,
Â
Jorge A. Lopez, Angeles Monge, Pilar Palma,*
Diego del Río, and Ernesto Carmona*
The cleavage and functionalization of strong C C single
bonds[1] by transition metal compounds is an important
transformation,[2±6] which is relevant to Ziegler± Natta catal-
ysis[7] and to other organometallic processes.[8, 9] Aryl elimi-
nation by activation of a b-Calkyl Caryl bond[5] is the micro-
scopic reverse of the migratory insertion of an alkene into a
M Caryl bond, a relevant step of the Heck reaction[8] and of the
SHOP process.[9] Herein we report on the conversion of a
Received: May 17, 2001 [Z17132]
[1] R. A. Sheldon, J. K. Kochi, Metal-Catalyzed Oxidations of Organic
Compounds, Academic Press, New York, 1981.
[2] Chlorohydrins: W. F. Richey, Kirk ± Othmer Encyclopedia of Chem-
ical Technology, Vol. 6, Wiley, New York, 1993, pp. 140.
[3] The Activation of Dioxygen and Homogeneous Catalytic Oxidation
(Eds.: D. H. R. Barton, A. E. Martell, D. T. Sawyer), Plenum, New
York, 1993.
[4] B. J. Wallar, J. D. Lipscomb, Chem. Rev. 1996, 96, 2625.
[5] B. Meunier, Chem. Rev. 1992, 92, 1411.
[6] J. T. Groves, R. Quinn, J. Am. Chem. Soc. 1985, 107, 5790.
[7] A. S. Goldstein, R. H. Beer, R. S. Drago, J. Am. Chem. Soc. 1994, 116,
2424.
[8] R. Neumann, M. A. Dahan, Nature 1997, 388, 353.
[9] C. L. Hill, I. A. Weinstock, Nature 1997, 388, 332.
[10] J. M. Thomas, R. Raja, G. Sanker, R. G. Bell, Nature 1999, 398, 227.
[11] R. G. Finke, H. Weiner, J. Am. Chem. Soc. 1999, 121, 9831.
[12] R. A. Sheldon, Top. Curr. Chem. 1993, 164, 22.
[13] C. L. Hill, C. M. Prosser-McCartha, Coord. Chem. Rev. 1995, 143, 407.
[14] T. Okuhara, N. Mizuno, M. Misono, Adv. Catal. 1996, 41, 113.
[15] I. V. Kozhevnikov, Chem. Rev. 1998, 98, 171.
‡
[Pd CH2CMe2Ph] moiety into the corresponding phenyl
‡
derivative, [Pd Ph] , and the subsequent functionalization of
the latter by conventional C2H4 migratory insertion chemistry
ˆ
to produce C6H5CH CH2.
‡
The cationic complex [Pd(CH2CMe2Ph)(dmpe)(PMe3)]
(1) (dmpe ˆ Me2PCH2CH2PMe2) can be generated by react-
ing the palladacycle [PdCH2CMe2-o-C6H4)(dmpe)] (2)[10] with
‡
[HPMe3] BAr4 (Arˆ 3,5-C6H3(CF3)2). At 608 C it under-
+
CH2CMe2Ph
PMe3
P
P
P
P
[HPMe3]+BAr4
BAr4
Pd
Pd
[16] N. Mizuno, M. Misono, Chem. Rev. 1998, 98, 199.
[17] C. L. Hill, Activation and Functionalization of Alkanes, Wiley, New
York, 1989, p. 243.
[18] M. T. Pope, A. Müller, Angew. Chem. 1991, 103, 56; Angew. Chem. Int.
Ed. Engl. 1991, 30, 34.
2
1-BAr4
(1)
+
P
[19] R. Neumann, Prog. Inorg. Chem. 1998, 47, 317.
[20] The TON of 26 reported in ref. [6] is still one of the highest for the
epoxidation of cis-cyclooctene with 1 atm of molecular oxygen alone.
[21] N. Mizuno, C. Nozaki, I. Kiyoto, M. Misono, J. Am. Chem. Soc. 1998,
120, 9267.
60 °C
Pd
BAr4
P
PMe3
3-BAr4
[22] B. Meunier, A. Robert, G. Pratviel, J. Bernadou, The Porphyrin
Handbook, Academic Press, New York, 2000, p. 119.
[23] The oxygenation of adamantane was carried out under the following
conditions: 1, 11 mmol; solvent, 1,2-dichloroethane/benzene ˆ 8 mL/
Â
Â
[*] Dr. J. Campora, Dr. P. Palma, Prof. Dr. E. Carmona, Dr. J. A. Lopez,
D. del Río
2 mL; adamantane, 12.4 mmol; pO , 1 atm; reaction temperature,
2
Â
Departamento de Química Inorganica-Instituto
356 K; reaction time, 118 h. The conversion was 4% and the
selectivities for 1-adamantanol, 2-adamantanol, and 2-adamantanone
were 79, 11, and 10%, respectively.
de Investigaciones Químicas
Universidad de Sevilla-Consejo Superior de Investigaciones
Científicas
C/Americo Vespucio s/n, Isla de la Cartuja
41092 Sevilla (Spain)
[24] R. A. Sheldon, J. K. Kochi, Oxidation and Combustion Reviews,
Vol. 5, 1973, p. 135; R. Neumann, M. Dahan, J. Am. Chem. Soc. 1998,
120, 11969.
[25] The amount of oxygen consumed was 1.5 mmol when the amount of
cyclooctene oxide produced was 2.9 mmol. The corresponding con-
version was 16%.
Fax : (‡34)95-4460565
E-mail: campora@cica.es
ppalma@cica.es
guzman@cica.es
[26] C. Nozaki, I. Kiyoto, Y. Minai, M. Misono, N. Mizuno, Inorg. Chem.
1999, 38, 5724.
Â
Dr. E. Gutierrez-Puebla, Dr. A. Monge
Instituto de Ciencia de Materiales
Consejo Superior de Investigaciones Científicas
Campus de Cantoblanco, 28049 Madrid (Spain)
Â
Ä
[**] This work was supported by the Direccion General de Ensenanza
Â
Superior e Investigacion Científica (Project 1FD97-0919), the Minis-
Â
terio de Educacion y Ciencia (PFPI grant to D. del Rio), and the Junta
de Andalucia. J. A. L. thanks the CONACYT and the University of
Guanajuato (Mexico) for a fellowship.
Supporting information (kinetic data and reaction rates for the
transformation 1 !3 calyzed by 4) for this article is available on the
WWW under http://www.angewandte.com or from the author.
Angew. Chem. Int. Ed. 2001, 40, No. 19
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goes very slow thermolysis ([Eq. (1) ], t1/2 ꢀ 60 h) to give the
C6H5CMe3, and smaller amounts of other unidentified
volatile materials. An uncharacterized mixture of inorganic
compounds is also formed. This complexity is, however,
foreseeable since the extrusion of isobutene from 4 would
generate a highly labile, thermally unstable 14-electron
[11]
phenyl derivative 3-BAr4
along with isobutene (GC-MS
analysis). A formally three-coordinate cationic complex
‡
[Pd(CH2CMe2Ph)(dmpe)] (4), in which the highly electro-
phylic metal is stabilized by an auxiliary p,h1 interaction with
the ipso-carbon atom of the phenyl group appears as a likely
intermediate.[12] Hence, we have prepared the BAr4 salt of
this cation [Eq. (2)] by the low-temperature protonation of
‡
phenyl complex, [PdPh(dmpe)] . Notwithstanding, we have
found that the b-Ph elimination reaction of 1 can be made
catalytic in the presence of 4 (10 mol%). Thus, a sample of
compound 1 converts cleanly under these conditions into
‡
+
ˆ
[Pd(Ph)(dmpe)(PMe3)] (3) and CH2 CMe2 (Scheme 1).
P
P
P
P
[H(OEt2)2]BAr4
80° C
Kinetic measurements show a zero-order dependence on
Pd
Pd
(2)
BAr4
+
+
2
4-BAr4
P
P
P
P
Pd
Pd
the palladacycle 2 with [H(OEt2)2]BAr4. Similarly to related
palladium metallacycles[12] selective cleavage of the Pd Caryl
bond is observed, leading to 4-BAr4 in quantitative yield
[Eq. (2)]. Spectroscopic data for 4 (see Experimental Section)
are in accord with the proposed structure. In particular, the
ipso-carbon atom displays a 13C{1H} signal at d ˆ 119.6 (dd,
2JC,P ˆ 6, 12 Hz). This matches closely the corresponding
resonance in the PMe3 analogue and in the structurally
related, X-ray characterized compound [Pd(CH2CMe2-
4
[Pd(dmpe)(PMe3)CH2CMe2Ph] +
,
1
[PdPh(dmpe)(PMe3)]+, 3 +
Scheme 1. b-Ph elimination reaction of 1 in the presence of 4.
Ph)(OTf)(PMe3)][12] (d ˆ 123.5, dd, JC,P ˆ 4, 12 Hz and d ˆ
2
2
1, while the concentration of 4 remains steady during the
21.8, d, JC,P ˆ 13 Hz, respectively). The above observation is
in agreement with the existence of a Pd Cipso p,h1 bonding
interaction, which was confirmed by an X-ray structure
determination[13] (Figure 1). Other Pd complexes that display
process. The apparent rate constant exhibits a direct depend-
ency on the concentration of 4, a value of 2.7 Â 10 4 s has
1
been obtained at 608C for the overall first-order rate constant.
It seems likely that C C bond cleavage is the rate-determin-
ing step.
As already pointed out, the b-Ph elimination can be
considered as the microscopic reverse of the olefin insertion
step of the Heck reaction. Whereas it is evident that the
electrophilicity of the cationic palladium center has a decisive
influence in the deinsertion, it seems probable that the
irreversibility of this process is a consequence of the steric
requirements posed by the insertion of isobutene into the
Pd Ph bond. In accord with these assumptions, C2H4 is able to
induce the reverse reactivity, and undergoes insertion under
the conditions of Equation (3) to produce a mixture of the
ethyl derivative 5, isobutene, and styrene. Scheme 2 depicts a
+
CH2CMe2Ph
P
Figure 1. Structure of the cation 4 (ORTEP view; the BAr4 counterion
has been omitted for clarity). Selected bond lengths [Š] and angles [8]: Pd1-
C10 2.065(7), C7-C10 1.531(11), Pd1-C2 2.343(6), Pd1-P1 2.220(2), Pd1-C1
2.511(8), Pd1-P2 2.363(2), C2-C7 1.530(10); P1-Pd1-P2 86.67(7), Pd1-C10-
C7 98.3(5), C2-Pd1-C10 66.2(3), Pd-C2-C7 87.5(4).
C2H4, 3 atm
Pd
10 mol% 4
P
PMe3
BAr4
1-BAr4
CH2CH3
PMe3
(3)
similar Pd ´´´ aryl interactions (either p, h1 or p, h2) have been
reported.[14] It is also worth noting that the structural data
obtained for 4 are strikingly similar to those calculated by
Rösch et al.[15] by density functional theory (DFT) methods
+
P
P
Ph
+
+
Pd
‡
for [Pd(CH2CH2Ph)(C(NH2)2] , which was considered as a
BAr4
model for the insertion step of the Heck reaction.
Complex 4 undergoes intricate thermolysis in CH2Cl2, THF,
or Et2O as the solvent to give isobutene, along with C6H6,
5-BAr4
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spin system, dA ˆ 13.6, dX ˆ 32.7, JA,X
ˆ
29.6 Hz; 13C{1H} NMR (CD2Cl2, 208C):
2
d ˆ 18.9 (dd, JC,P ˆ 19, 34 Hz; CH2), 32.7
4
3
(d, JC,P ˆ 5 Hz; CMe2), 41.6 (d, JC,P
ˆ
2
3 Hz; CMe2), 119.6 (dd, JC,P ˆ 6, 12 Hz;
Cq arom.), 122.2 (d, JC,P ˆ 2 Hz; CH arom.),
128.6 (s; CH arom.), 133.1 (s; CH arom.).
5: A solution of 1 (0.33 g, 0.25 mmol), 4
(0.030 g, 0.025 mmol), and toluene (50 mL;
internal GC standard) in diethyl ether
(20 mL) was transferred to
a Fischer±
Porter pressure reactor, charged with eth-
ylene (3 bar) and heated at 608C for 24 h.
GC analysis of the resulting yellow solution
revealed the formation of styrene
(0.25 mmol), isobutene (0.20 mmol), tert-
butylbenzene (ca. 0.03 mmol), and minor
amounts of unidentified volatile products.
A
31P{1H} spectrum of this crude mixture
showed full conversion to (ca. 90%
5
purity). The solution was evaporated and
the residue extracted with petroleum ether
and filtered. Evaporation to dryness left
the crude product as an oily solid, which
was obtained as pale green crystals by
recrystallization from a petroleum ether/
Et2O (2:1) mixture. Yield: 0.18 g, 60%.
Elemental analysis (%) calcd for
C43H42BF24P3Pd: C 42.16, H 3.46; found:
C 42.21, H 3.27; 1H {31P} NMR (CD2Cl2,
3
208C): d ˆ 1.11 (t, JH,H ˆ 8.0 Hz, 3H;
CH3CH2), 1.41 (q, 2H; CH3CH2); 31P{1H}
NMR (CD2Cl2, 208C): d ˆ 18.6 (dd,
Scheme 2. Proposed reaction pathway for the overall transformation of 1 to 5.
2
2JP, P ˆ 386, 39 Hz), 16.1 (dd, JP, P ˆ 39,
2
26 Hz), 30.1 (dd, JP, P ˆ 386, 26 Hz);
2
13C{1H} NMR (CD2Cl2, 208C): d ˆ 11.9 (d, JC,P ˆ 87 Hz; CH2), 15.2 (m,
likely reaction pathway for the overall transformation. Like in
partially hidden by dmpe signals, CH3).
Received: May 23, 2001 [Z17164]
the Heck reaction, the phenethyl intermediate 6, undergoes
‡
facile b-H elimination. In our base-free system, the [Pd H]
complex inserts another molecule of C2H4 and gives rise to a
‡
[Pd Et] group which becomes stabilized by the coordination
of PMe3.[16] It is interesting to note here the ability of the
dmpe ligand to promote the olefin extrusion or insertion as
compared to the corresponding PMe3 system.[12] This might be
rationalized on the basis of the smaller steric hindrance posed
by the dmpe ligand to the planar transition state required for
the mentioned processes.[15, 17]
In summary, we have shown that the unstrained Calkyl Caryl
bond of the neophyl ligand becomes readily activated when
bonded to an electrophilic palladium center. Effecting this
thermal activation under ethylene allows the coupling of this
molecule with the phenyl fragment that results from the
[1] a) R. H. Crabtree, Chem. Rev. 1985, 85, 245; b) W. D. Jones, Nature
1993, 364, 676; c) D. Milstein, B. Rybtchinsky, Angew. Chem. 1999,
111, 918; Angew. Chem. Int. Ed. 1999, 38, 870; d) P. Steenwikel, R. A.
Gossage, G. van Koten, Chem. Eur. J. 1998, 4, 759.
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Mathieu, B. Donnadieu, J. Am. Chem. Soc. 1997, 119, 3218; c) K.
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119, 11244.
[3] a) D. M. Grove, G. van Koten, J. N. Louwne, J. G. Noltes, A. L. Spek,
H. J. C. Ubbels, J. Am. Chem. Soc. 1982, 104, 6609; b) J. Therjeiden, G.
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c) M. Albrecht, R. A. Gossage, A. L. Spek, G. van Koten. J. Am.
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Rangoni, Angew. Chem. 1997, 109, 142; Angew. Chem. Int. Ed. Engl.
1997, 36, 119.
cleavage of the Calkyl
isobutene.
Caryl bond to produce styrene along with
Experimental Section
4: [H(OEt2)2]BAr4 (0.22 g, 0.25 mmol) was added to a cooled ( 308C)
solution of the metallacyclic complex 2[10] (0.97 g, 0.25 mmol) in CH2Cl2
(20 mL). After the cooling bath had been removed, the mixture was stirred
at room temperature for 30 min. The solvent was removed under vacuum
and the residue was extracted with Et2O (20 mL). The product was isolated
as colorless crystals by partial concentration of the solvent, addition of
some petroleum ether, and cooling to 208C overnight. Yield: 0.28 g,
91%. Elemental analysis (%) calcd for C48H41BF24P2Pd: C 46.01, H 3.30;
[6] a) G. Sini, S. A. Macgregor, O. Eisenstein, J. H. Teuben, Organo-
metallics 1994, 13, 1049; b) X. Yang, L. Jia, T. J. Marks, J. Am. Chem.
Soc. 1993, 115, 3392; c) X. Xinmin, C. L. Sterns, T. J. Marks, J. Am.
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1991, 10, 3344; b) C. M. Older, J. M. Stryker, J. Am. Chem. Soc. 2000,
122, 2784; c) M. Suzuki, Y. Takaya, T. Takemori, J. Am. Chem. Soc.
1994, 116, 10779.
1
3
found: C 46.08, H 3.29; H NMR (CD2Cl2, 208C): d ˆ 1.09 (dd, JH,P ˆ 5.5,
8.1 Hz, 2H; CH2), 1.37 (s, 6H; CMe2), 7.42 (m, 1H; CH arom.), 7.67 (m, 2H;
CH arom.), 7.73 (m, 2H; CH arom.); 31P{1H} NMR (CD2Cl2, 208C) AX
Angew. Chem. Int. Ed. 2001, 40, No. 19
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1433-7851/01/4019-3643 $ 17.50+.50/0
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COMMUNICATIONS
[8] a) W. Cabri, I. Candiani, Acc. Chem. Res. 1995, 28, 2; b) A. de Meijere,
F. E. Meyer, Angew. Chem. 1994, 106, 2473; Angew. Chem. Int. Ed.
Engl. 1994, 33, 2379.
A Readily Available, Highly Potent E-Selectin
Antagonist
[9] W. Keim, Angew. Chem. 1990, 102, 251; Angew. Chem. Int. Ed. Engl.
1990, 29, 235.
Gebhard Thoma,* Rolf Bänteli, Wolfgang Jahnke,
John L. Magnani, and John T. Patton
Â
Â
[10] J. Campora, E. Carmona, J. A. Lopez, P. Palma, D. del Rio, P. Valerga,
C. Graiff, A. Tiripicchio, Inorg. Chem. 2001, 40, 4116.
[11] The identity of complex 3 was confirmed by its independent synthesis
from [Pd(Ph)(Br)(PMe3)2] and equimolecular amounts of dmpe and
NaBPh4.
Excessive infiltration of leukocytes from blood vessels into
surrounding tissues can cause acute or chronic inflammatory
disorders such as reperfusion injuries, stroke, psoriasis,
rheumatoid arthritis, or respiratory diseases.[1] An early step
in the cascade of events which finally leads to leukocyte
extravasationÐtheir rolling on activated endothelial cellsÐis
mediated by selectin ± carbohydrate interactions.[2] The ad-
verse effects could thus be prevented by selectin blockade.
The tetrasaccharide sialyl Lewisx (1, Scheme 1) is a weak[3]
ligand for E-, P- and L-selectin[4] and became a lead to
discover more potent inhibitors.[5] To assess our E-selectin
antagonists we used a static, cell-free ligand-binding assay
which measures inhibition under equilibrium conditions.[6]
Sialyl Lewisx (IC50 ˆ 1000 ± 2000 mm) was tested on each plate
to allow direct comparison of data from different test plates.
Thus, we obtained relative IC50 values (see Table 1). To
further profile our compounds we developed a dynamic in
vitro assay which allows to monitor E-selectin-dependent
rolling of neutrophils on activated endothelial cells under
shear stress and, hence, mimics the nonequilibrium in vivo
conditions[7] (see Table 1). Recently we described the promis-
ing E-selectin inhibitor 2 (Scheme 1), which showed good
activities in both the static (rel. IC50 ˆ 0.030) and the dynamic
(IC50 ˆ 10 mm) assay.[8] Here we report on our search for
simplified analogues of 2 which led to the discovery of 3
(Scheme 1) being the most potent small-molecule E-selectin
antagonist to date (IC50 ˆ 1 ± 2 mm in the dynamic flow assay).
To simplify 2 we designed compound 4 (Scheme 1) with a
glucal-derived moiety instead of the glucosamine residue.
Furthermore, the benzamide in 2 was replaced by the
corresponding anilide. We expected compound 4 to be readily
available from the earlier described advanced intermediate 5,
which can be assembled from building blocks 6 ± 9 in eight
steps in an overall yield of >30% (Scheme 2).[9] The primary
hydroxyl group of 5 was oxidized to yield the carboxylic acid
10, which was then coupled with 3,4-dimethoxyaniline to give
11 (Scheme 2). Hydrogenolytic removal of the benzyl pro-
tecting groups proceeded smoothly (12), but subsequent
cleavage of all three benzoyl groups to obtain 4 failed.
Transesterification using NaOMe (1.1 equiv) gave clean
removal of the gal-4 and the gal-6 benzoyl groups leading to
partly protected compound 13[10] (Scheme 2). The gal-2
benzoate remained untouched. Harsher conditions (aqueous
NaOH; 508C) resulted in decomposition, most probably
Â
Â
[12] J. Campora, J. A. Lopez, P. Palma, P. Valerga, E. Carmona, Angew.
Chem. 1999, 111, 199; Angew. Chem. Int. Ed. Engl. 1999, 38, 147.
[13] Crystal data for 4: C48H41BF24P2Pd, Mr ˆ 1252.96, monoclinic, space
group Pn, a ˆ 10.3940(9), b ˆ 9.9127(8), c ˆ 24.819(2) Š, b ˆ
94.565(2)8, Vˆ 2549.0(4) Š3, Z ˆ 2, 1calcd ˆ 1.632 Mgm
,
Tˆ
3
173(2) K, l ˆ 0.71073 Š, m ˆ 0.549 mm 1, F(000) ˆ 1252, crystal size
0.4 Â 0.2 Â 0.15 mm, V range 2.63 to 23.308; 11 ꢁ h ꢁ 11, 2 ꢁ k ꢁ
11, 23 ꢁ l ꢁ 23; 6033 reflections (4624 independent, Rint ˆ 0.02) were
collected at 177 K on a Brucker± Siemens Smart CCD diffractometer,
GOF ˆ 1.02, R1 ˆ 0.026 and wR2 ˆ 0.06 for [I > 2(I)], R and R1 ˆ 0.031
and wR2 ˆ 0.062 for all data. Data were collected over a hemisphere of
the reciprocal space by a combination of three exposure sets. Each
exposure of 10 s covered 0.38 in w. The unit cell dimensions were
determined by a least-squares refinement using reflections with I >
20s and 68 < 2q < 468. The distance between the crystal and the
detector was 6.05 cm. Coverage of the unique set was over 92%
complete to at least 238 in q. The first 50 frames were recollected at
the end of the data collection to monitor crystal decay. The structure
was solved by Multan and Fourier methods. Full-matrix least-squares
refinement was carried out minimizing w(Fo2 Fc2†2. Hydrogen atoms
were included in their calculated positions. Refinement on F 2 for all
reflections. Weighted R factors (Rw) and all goodnesses of fit S were
based on F 2, conventional R factors (R) were based on F. Most of the
calculations were carried out with the SHELXTL program.[18]
Crystallographic data (excluding structure factors) for the structure
reported in this paper have been deposited with the Cambridge
Crystallographic Data Centre as supplementary publication no.
CCDC-162439. Copies of the data can be obtained free of charge on
application to CCDC, 12 Union Road, Cambridge CB21EZ, UK (fax:
(‡44)1223-336-033; e-mail: deposit@ccdc.cam.ac.uk).
Â
Â
[14] a) L. R. Falvello, J. Fornies, R. Navarro, V. Sicilia, M. Tomas, Angew.
Chem. 1990, 102, 952; Angew. Chem. Int. Ed. Engl. 1990, 29, 891;
Â
Â
b) L. R. Falvello, J. Fornies, R. Navarro, V. Sicilia, M. Tomas, J. Chem.
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[*] Dr. G. Thoma, Dr. R. Bänteli, Dr. W. Jahnke
Novartis Pharma AG
P.O. Box, 4002 Basel (Switzerland)
Fax : (‡41)61-3246735
E-mail: gebhard.thoma@pharma.novartis.com
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GlycoTech Corporation
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