Chemical synthesis of a core 2 branched pentasaccharide containing a carboxylate group

Article abstract of DOI:10.1016/S0960-894X(00)00497-2

Design and synthesis of a carboxylate-containing pentasaccahride 1 with the Galβ(1-4) (Fucα1-3)GlcNAcβ(1-6){3-[1-carboxymethyl]-Galβ(1-3)}GalNAcα-OMe sequence, which is obtained through regioselective coupling of the 6-OH of a novel acceptor 9 with Lewis(x) donor 10 catalyzed by NIS-TfOH are described. (C) 2000 Elsevier Science Ltd.

Full text of DOI:10.1016/S0960-894X(00)00497-2

Bioorganic & Medicinal Chemistry Letters 10 (2000) 2485±2487
Chemical Synthesis of a Core 2 Branched Pentasaccharide
Containing a Carboxylate Group
Jie Xia, James L. Alderfer and Khushi L. Matta*
Molecular & Cellular Biophysics, Roswell Park Cancer Institute, Em & Carlton Streets, Bu€alo, NY 14263, USA
Received 19 July 2000; accepted 25 August 2000
AbstractÐDesign and synthesis of a carboxylate-containing pentasaccahride 1 with the Galb(1±4) (Fuca1±3)GlcNAcb(1±6){3-[1-
carboxymethyl]-Galb(1±3)}GalNAca±OMe sequence, which is obtained through regioselective coupling of the 6-OH of a novel acceptor
9 with Lewisx donor 10 catalyzed by NIS-TfOH are described. # 2000 Elsevier Science Ltd. All rights reserved.
In the last decade we have witnessed tremendous e€orts
in the syntheses of potential selectin ligands.1 However,
most of these studies have been centered on the synth-
eses of SLex type structures. In our laboratory, we have
clearly shown that the NeuAca2±3Galb(1±3)GalNAc
sequence of core 2, GlcNAcb(1±6)[Galb(1±3)]Gal-
NAca±, branched structure, as found in O-linked gly-
coprotein, plays a part in binding with L-, E-, and P-
selectins.2 Recently, Cummings and co-workers3 have
synthesized a series of sulfoglycopeptides and have
shown that a glycopeptide compound having Galb(1±
3)GalNAc along with SLex at the C6 position of Gal-
NAca was active. Moreover, studies of mice de®cient in
core 2 branching enzymes support the role of core 2
glycans in binding with L- and P-selectins.4 In our con-
tinued interest in the synthesis of core 2 branched
structures containing sulfate, fucose and sialic acid,5 we
report the design and synthesis of the title compound.
compound 7 with chloroacetic anhydride using NaHCO3
as a base in dry DMF a€orded compound 8. Removal of
the 4,6-O-benzylidene group from compound 8 gave the
desired disaccharide acceptor 9 in high yield (94%).
Because of the much higher reactivity of the primary
hydroxyl group, glycosylation of 6-HO of acceptor 9
with trisaccharide donor 10 8 provided compound 11 as
the only glycosylation product under controlled reac-
tion conditions (NIS-TfOH promoted system).9 The
b(1±6) linkage of compound 11 was con®rmed by
observation of a strong NOE cross peak between Hc-1
of sugar residue c and Ha-6a, Ha-6b of sugar residue a in
the 2D ROESY spectrum. b-Con®guration of sugar
residue c was con®rmed by the presentation of a large
coupling constant (3J1c,2c=7.8 Hz). Compound 11 was
then O-dechloroacetylated in the presence of thiourea
and 2,6-lutidine to give compound 12. Regioselective
sulfation of OH-6 of galactose residue b in compound 12
.
The synthesis of compound 1 was accomplished as illu-
strated in Schemes 1 and 2. Monosaccharide acceptor 3
was treated with 2,3,4,6-tetra-O-acetylgalactosyl bromide
4 in the presence of Hg(CN)26 to a€ord disaccharide 5 in
good yield (65%). O-deacetylation of disaccharide 5 in
MeOH±CH2Cl2 with 1 M sodium methoxide at room
temperature provided compound 6 in high yield (94%).
Tin acetal 7 prepared in situ from disaccharide 6 could be
selectively alkylated with methyl bromoacetate in the pre-
sence of tetrabutylammonium iodide at a reasonable
temperature (60±65ꢀC), giving compound 7 in acceptable
yield (59%) in two steps. Complete chloroacetylation of
was achieved by treatment with SO3 pyridine complex
in dry pyridine at low temperature to give compound 13
in good yield (85%). The systematic removal of pro-
tecting groups in 13 was accomplished in four steps to
give target molecule 1. Thus, removal of benzyl groups
from compound 13 was achieved by treatment with Pd±
C (10%) under hydrogen atmosphere at room tempera-
ture, resulting in compound 14. Compound 14 was then
treated with Ac2O±pyridine in the presence of DMAP,
providing compound 15. Removal of methyl and the
phthalimido groups from 15 was executed through a
one-pot, three-step procedure, by treatment of com-
pound 15 with a larger excess of anhydrous LiI in dry
pyridine at re¯uxing temperature, followed by treatment
with hydrazine hydrate in ethanol, then acetylation with
acetic anhydride±pyridine (1:1) in the presence of a cat-
*Corresponding author. Tel.: +1-716-845-2397; fax: +1-716-845-
3458; e-mail: klmatta@yahoo.com
0960-894X/00/$ - see front matter # 2000 Elsevier Science Ltd. All rights reserved.
PII: S0960-894X(00)00497-2

2486
J. Xia et al. / Bioorg. Med. Chem. Lett. 10 (2000) 2485±2487
Scheme 1. (i) p-MeOPhCH(OCH3)2, PTS, CH3CN, rt, 12 h, 75%; (ii) 4 (1.5 equiv), Hg(CN)2, benzene:CH3NO2 (1:1), 40±45 ꢀC, 12 h, 65%; (iii)
CH3ONa±CH3OH (1 M), CH2Cl2:CH3OH (1:1), pH 10.0, rt, 2 h, 94%; (iv) (a) n-Bu2SnO/CH3OH, re¯uxing, 3±4 h; (b) n-Bu4NI±BrCH2COOCH3,
60±65 ꢀC, 48 h, two steps, 57%; (v) (ClCH2CO)2O (12 equiv)/NaHCO3(12 equiv)±DMF, rt, 12 h, 65%; (vi) HOAc (60%), 60±65 ꢀC, 1 h, 94%.
Scheme 2. (i) NIS-TfOH, CH2Cl2, 4A-MS, 65 to 60 ꢀC, 2 h, 45%; (ii) thiourea-2,6-lutidine, CH2Cl2, re¯uxing, 12 h, 85%; (iii) SO3±pyridine,
pyridine, 0 ꢀC, 6±9 h, 85%; (iv) Pd±C (ꢀ10%), H2, 9 h, 86%; (v) Ac2O:pyridine (1:1) DMAP, rt, 12 h, 75%; (vi) LiI-pyridine, 125±130 ꢀC, 6 h; (vii)
24 h, 35% in three steps.
.
CH3OH±NH2NH2 H2O (5:1), 80±85% C, 4±5 h, then, Ac2O:pyridine (1:1), DMAP, rt, 12 h; (viii) 1 M CH3ONa±CH3OH (cat), CH3OH±H2O, rt,

J. Xia et al. / Bioorg. Med. Chem. Lett. 10 (2000) 2485±2487
2487
alytic amount of DMAP. The above acetylated com-
pound was then treated with a catalytic amount of 1 M
sodium methoxide±methanol solution at room tem-
perature overnight to a€ord target molecule 1. The
structure and purity of 1 was fully con®rmed by TLC,
NMR, MS and FAB.10
3. Leppanen, A.; Mehta, P.; Ouyang, Y.-B.; Ju, T.; Helin, J.;
Moore, K. L.; Van Die, I.; Can®eld, W. M.; McEver, P. P.;
Cummings, R. D. J. Biol. Chem. 1999, 274, 24838.
4. Ellies, L. G.; Tsuboi, S.; Petryniak, B.; Lowe, J. B.;
Fukuda, M. J.; Marth, D. Immunity 1998, 9, 881.
5. (a) Jain, R. K.; Vig, R.; Rocke, R. D.; Mohammad, A.;
Matta, K. L. J. Am. Chem. Soc. 1994, 116, 12123. (b) Jain, R. K.;
Huang, B.-G.; Chandrasekaran, E. V.; Matta, K. L. Chem.
Commun. 1997, 23. (c) Xia, J.; Piskorz, C. F.; Locke, R. D.;
Chandrasekaran, E. V.; Alderfer, J. L.; Matta, K. L. Bioorg.
Med. Chem. Lett. 1999, 9, 2941. (d) Xia, J.; Piskorz, C. F.;
Alderfer, J. L.; Locke, R. D.; Matta, K. L. Tetrahedron Lett.
2000, 41, 2773. (e) Xia, J.; Alderfer, J. L.; Piskorz, C. F.; Matta,
K. L. Chem. Eur. J. 2000, 6, 3442. (f) Xia, J.; Alderfer, J. L.;
Piskorz, C. F.; Matta, K. L. Chem. Eur. J. 2000, 6, in press.
6. (a) Helferich, B.; Weis, K. Chem. Ber. 1956, 89, 314. (b)
Helferich, B.; Zirner, J. Chem. Ber. 1962, 95, 2604.
7. (a) David, S.; Hannessian, S. Tetrahedron 1985, 41, 643. (b)
Guibe, F. Tetrahedron 1997, 53, 13509. (c) Hanessian, S.; Reddy,
G.; Huynh, H. K.; Pan, J.; Pedatella, S. Bioorg. Med. Chem. Lett.
1997, 7, 2729. (d) Hanessian, S.; Huynh, H. K.; Reddy, G.;
McNaughton-Smith, G.; Ernst, B.; Kolb, H. C.; Magnani, J.;
Sweeley, C. Bioorg. Med. Chem. Lett. 1998, 8, 2803.
Our earlier studies show that core 2 branched structures
having 6-O-sulfate at galactose in the Galb(1±3)Gal-
NAc arm bind with selectins (L- and P-Selectins). Our
preliminary binding study of compound 1 indicated
that this molecule can bind with these two selectins (L-
and P-). Detailed inhibition studies will be reported
elsewhere.
In summary, we describe a convergent route for the
synthesis of a core 2 branched pentasaccharide contain-
ing a carboxylate group.
Acknowledgements
8. Huang, B.-G.; Locke, R. D.; Jain, R. K.; Matta, K. L.
Bioorg. Med. Chem. Lett. 1997, 7, 1157.
This work was supported by Grant Nos. CA35329 and
CA63218, and in part by Grant No. P30CA16056,
awarded by the National Cancer Institute. The authors
thank Dr. S. Dutta for mass spectrometry analyses.
9. (a) Konradsson, P.; Mootoo, D. R.; Medevitt, R. E.; Fraser-
Reid, B. J. Chem. Soc., Chem. Commun. 1990, 270. (b) Veene-
man, G. H.; Van Boom, J. H. Tetrahedron Lett. 1990, 31, 1331.
1
10. Selected physical data for compound 1: H NMR (D2O,
600 MHz) d 5.18 (d, 1H, J1,2=3.6 Hz, He-1), 4.83 (dd, 1H, He-
5), 4.84±4.83 (d, 1H, J1,2=4.0 Hz, Ha-1), 4.56 (d, J1,2=8.0 Hz,
Hc-1), 4.50 (d, 1H, J1,2=7.8 Hz, Hd-1), 4.46 (d, 1H, J1,2=7.6
Hz, Hb-1), 4.32 (dd, 1H, J=2.8 Hz, Ha-4), 4.20 (dd, 2H,
CH2COO), 4.16±3.90 (m, 13H, Ha-5, Hc-4, Hb-4, Hc-2), 3.85±
3.47 (m, 12H, He-4, Ha-6a, Hd-3, Hb-3, Hc-5, Hd-2, Hb-2), 3.38
(s, 3H, OCH3), 2.14 (s, 3H, Ac), 2.03 (s, 3H, Ac), 1.21 (d, 3H,
J=6.4 Hz, CHe3); 13C NMR (D2O, 100.6 MHz) d 170.78
(CˆO), 170.00 (CˆO), 169.68 (CˆO), 103.31, 100.72, 100.07,
97.42, 96.90, 89.83, 80.73, 76.09, 74.24, 73.90, 73.67, 72.40,
71.44, 71.29, 70.78, 68.25, 68.15, 67.99, 67.54, 67.37, 67.18,
66.11, 65.45, 64.04, 63.22, 63.14, 60.18, 57.26, 56.20, 51.01,
48.63, 48.30, 47.40, 39.99, 23.15 (Ac), 23.00 (Ac), 14.50 (CH3);
FABMS (m/z) (positive ion model) calcd for C37H60O30N2-
SNa: 1090.5 [M]+; found 1091.8 [M+1]+.
References and Notes
1. (a) Tsuboi, S.; Isogai, Y.; Hada, N.; King, J. K.; Hindsgaul,
O.; Fukuda, M. J. Biol. Chem. 1996, 271, 27213. (b) Wang, Z.
G.; Hindsgaul, O. Adv. Exp. Med. Biol. 1998, 435, 219. (c)
Shimanel, E. E.; McGarvey, G. J.; Jablonowski, J. A.; Wong,
C.-H. Chem. Rev. 1998, 98, 833. (d) Wong, C.-H. Acc. Chem.
Res. 1999, 32, 376.
2. (a) Jain, R. K.; Piskorz, C. F.; Huang, B.-G.; Locke, R. D.;
Han, H. L.; Koening, A.; Varki, A.; Matta, K. L. Glycobiology
1998, 8, 707. (b) Koenig, A.; Jain, R. K.; Vig, R.; Norgard
Sumnicht, K. E.; Matta, K. L.; Varki, A. Glycobiology 1997, 7,
79.