A new reactivity-based one-pot synthesis of N-acetyllactosamine oligomers

Article abstract of DOI:10.1021/jo0206420

Poly-N-acetyllactosamine oligomer is a type-2 glycan core from which a number of important bioactive glycoconjugates are assembled in vivo. Development of an effective synthesis of N-acetyllactosamine oligomers will therefore provide a new chemoenzymatic

Full text of DOI:10.1021/jo0206420

A New Rea ctivity-Ba sed On e-P ot Syn th esis of N-Acetylla ctosa m in e
Oligom er s
Tony K.-K. Mong, Cheng-Yuan Huang, and Chi-Huey Wong*
Department of Chemistry and the Skaggs institute for Chemical Biology, The Scripps Research Institute,
10550 North Torrey Pines Road, La J olla, California 92037
wong@scripps.edu
Received October 9, 2002
Poly-N-acetyllactosamine oligomer is a type-2 glycan core from which a number of important
bioactive glycoconjugates are assembled in vivo. Development of an effective synthesis of N-
acetyllactosamine oligomers will therefore provide a new chemoenzymatic entry to this class of
complex saccharides. This paper describes the design and synthesis of thioglycoside building blocks,
determination of their relative reactivity values, and demonstration of their use in the programmable
one-pot synthesis of various N-acetyllactosamine oligomers. Through a combination of segment
condensation, the strategy allows for the preparation of larger oligosaccharides with minimal
protecting group manipulation, as illustrated in the synthesis of an octasaccharide in a very short
period of time.
In tr od u ction
The programmable reactivity-based one-pot strategy
is based on thioglycoside building blocks with defined
relative reactivity values (RRV).6 Different from the
qualitative one-pot synthesis, the reactivity of each
thioglycoside building block is determined quantitatively
rather than by qualitative estimation.7 These RRV values
form a reactivity database that, together with the “Op-
tiMer” computer program, provides an optimized set of
thioglycoside building blocks for use in the reactivity-
based one-pot synthesis of a given oligosaccharide (Figure
2). Using this strategy, we have successfully prepared a
small oligosaccharide library,8 the breast cancer antigenic
determinant Globo H,9 and the colon cancer antigen
Lewis Y.10 We have now added the newly designed
building blocks for N-acetyllactosamine oligomers to our
database, which will further expand the scope of the one-
pot approach for the synthesis of other biologically
important oligosaccharides.
N-Acetyllactosamine oligomer is a type-2 glycan com-
posed of repeating â(1,3) linked N-acetyllactosamine
(LacNAc) residues.1 As a precursor to a number of blood
group antigens, these oligomers also serve as an acceptor
substrate for a number of glycosyltransferases in the
production of different glycoconjugates such as sialyl
Lewis- X, tumor-related fucosylated poly-N-acetyllac-
tosamine; it also serves as a spacer to present sugar
ligands from glycoproteins to their receptors (Figure 1).2,3
Since many of the glycosyltransferases with N-acetyllac-
tosamine oligomers as starting substrates are available,
development of effective syntheses of N-acetyllactosamine
oligomers will therefore provide a new chemoenzymatic
entry to a number of important glycoconjugates.4 Previ-
ous syntheses of N-acetyllactosamine oligomers often
begin with a fully protected lactosamine, which is ob-
tained either from lactal or glycosylation of galactosyl and
glucosaminyl precursors. The final product is obtained
after a series of protecting group and anomeric leaving
group manipulations.4,5 We report here our effort to
simplify this lengthy operation using the principle of
programmable reactivity-based one-pot synthesis of oli-
gosaccharide to design building blocks with defined
reactivity for the rapid assembly of various N-acetyllac-
tosamine oligomers.
Resu lts a n d Discu ssion
The initial design and synthesis of galactosyl and
glucosaminyl building blocks is a key step in our syn-
thetic venture. Selection of appropriate hydroxyl and
amino protecting groups was crucial to create a reactivity
profile for the different lactosaminyl building blocks and
subsequent implementation of reavtivity-based one-pot
(1) Minoru, U.; Minoru, F. Trends in Glycoscience and Glycotech-
nology 2001, 13, 177.
(6) Zhang, Z.; Ollmann, I. R.; Ye, X.-S.; Wischnat, R.; Baasov, T.;
Wong, C.-H. J . Am. Chem. Soc. 1999, 121, 734.
(7) (a) Yamada, H.; Takimoto, H.; Ikeda, T.; Tsukamoto, H.; Harada,
T.; Takahashi, T. Synlett 2001, 1751. (b) Pongdee, R.; Wu, B.;
Sulikowski, G. A. Org. Lett. 2001, 3, 3523. (c) Fridman, M.; Solomon,
D.; Yogev, S.; Baasov, T. Org. Lett. 2002, 4, 281.
(8) Ye, X.-S.; Wong, C.-H. J . Org. Chem. 2000, 65, 2410.
(9) Burkhart, F.; Zhang, Z.; Wacowich-Sgarbi, S.; Wong, C.-H.
Angew. Chem., Int. Ed. 2001, 40, 1274.
(10) Mong, T. K.-K.; Wong, C.-H. Angew. Chem., Int. Ed. 2002, 41,
4087.
(2) (a) Hakomori, S.-I.; Nudelman, E.; Levery, S. B.; Kannagi, R. J .
Biol. Chem. 1984, 259, 4672. (b) Hakomori, S.-I.; Zhang, Y. Chem. Biol.
1997, 4, 97. (c) Hakomori, S.-I. Biochim. Biophys. Acta 1999, 1473,
247-266.
(3) Sell, S. Prog. Path. 1990, 21, 1003-1019.
(4) Koeller, K. M.; Wong, C.-H. Chem. Eur. J . 2000, 6, 1243.
(5) (a) Alais, J .; Veyrie`res, A. Carbohydr. Res. 1990, 207, 11. (b)
Srivastava, G.; Hindsgaul, O. J . Carbohydr. Chem. 1991, 10, 927. (c)
Shimizu, H.; Ito, Y.; Kanie, O.; Ogawa, T. Bioorg. Med. Chem. Lett.
1996, 6, 2841.
10.1021/jo0206420 CCC: $25.00 © 2003 American Chemical Society
Published on Web 01/25/2003
J . Org. Chem. 2003, 68, 2135-2142
2135

Mong et al.
F IGURE 1. Poly-N-acetyllactosamine and their derivatives.
SCHEME 1 a
F IGURE 2. Illustration of the programmable one-pot syn-
thesis of oligosaccharide.
a
Reagents and conditions: (a) (i) NaOMe, MeOH/CH2Cl2, -0
°C; (ii) Bn(OMe)2, CSA, CH3CN, rt; (iii) Ac2O, pyr, ca.t DMAP,
CH2Cl2, 60% over three steps. (b) Et3SiH, TFA, CH2Cl2, 0 °C, 90%.
(c) DMTST, MS, CH2Cl2, -20 to 0 °C, 80%.
donor, while the later directs the â-glycosidic bond
formation.
F IGURE 3. Galactosyl and glucosaminyl thioglycoside build-
ing blocks.
Synthesis of glucosaminyl building blocks 7 and 9
followed standard procedure and started with the known
compound 5 (Scheme 1).6 For compound 7, deacetylation
under Zemple´n conditions was followed by C-4/C-6 hy-
droxyls benzylidenation and C3-OH acetylation to fur-
nish compound 6.11 The benzylidene ring of 6 was
reductively opened in the presence triethylsilane (Et3SiH)
and trifluoroacetic acid (TFA) to yield the glucosaminyl
synthesis of oligomers. Hence, galactosyl building block
4 and glucosaminyl building blocks 7, 9, and 14 were
prepared whereas 4 and 9 have been reported (Figure
3).10 All the glucosaminyl building blocks 7, 9, and 14
possess a free C-4 hydroxyl and a trichloroethoxylcarbo-
nyl protecting group (Troc) at the C-2 amino functional-
ity. The former provides an acceptor site for the galactosyl
2136 J . Org. Chem., Vol. 68, No. 6, 2003

One-Pot Synthesis of N-Acetyllactosamine Oligomers
determined to be 1.8 × 104 and 302, respectively (Scheme
3).6 The 60-fold difference is apparently attributed to a
change of electron-donating benzyl ether to electron-
withdrawing acetyl protecting group at C-3 hydroxyl. On
the basis of the obtained RRV values, we proceeded to
the syntheses of lactosaminyl building blocks (Scheme
3). However, galactosyl building block 4 could not be a
donor for glucosaminyl building block 14 because 14
(RRV ) 1.8 × 104) was more reactive than the 4 (RRV )
4150). Instead, peracetylated galactosyl bromide 15 was
used and acceptor 14 was glycosylated with 15 in the
presence of silver triflate (AgOTf) and 2,6-di-tert-butyl-
4-methylpyridine (DTBMP) furnishing the nonreducing
end lactosaminyl building block 16 in 70% yield.15
Precursor 17 of the bridging lactosaminyl building block
was prepared by glycosylating glucosaminyl acceptor 7
(RRV ) 302) with reactive galactosyl donor 4 (RRV )
4150) in the presence of N-iodosuccinimide and triflic acid
(NIS/TfOH).16 Conversion of 17 to the functional bridging
lactosaminyl building block 18 was achieved by removal
of the p-methoxyl benzyl ether (PMB) at the C′-3 hydroxyl
with 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ).
For the lactosaminyl building blocks 19 and 20, their
syntheses have been reported.10
For the functional tetrasaccharide building block 22,
its precursor 21 was first obtained by glycosylating
lactosaminyl building block 20 with 17 in the presence
of NIS/TfOH. However, unlike compound 17 and 19,
subsequent DDQ removal of the PMB ether of compound
21 led to product degradation. A milder deprotection
procedure with the use of 10% TFA in CH2Cl2 was used
to obtain the functional tetrasaccharide building block
22 in 80% yield. With the building blocks 16, 18, 20, and
22 in hand, the RRV data for 16 and 18 were determined
to be 1.3 × 104 and 246, respectively.
SCHEME 2 a
a
Reagents and conditions: (a) (i) Zn dust, CH2Cl2/Ac2O (1:1),
cat. DMAP; (ii) NaOMe, CH2Cl2/MeOH (1:1); (iii) TfN3, K2CO3, cat.
ZnCl2, CH2Cl2/MeOH/H2O (3:3:1); (iv) Bn(OMe)2, cat. CSA, CH3CN,
60% over 4 steps. (b) BnBr, NaH, Bu4NI, DMF, 0 °C to rt, 82%.
(c) Et3SiH, TFA, CH2Cl2, 0 °C, 90%. (d) 1,3-Dithiopropane, TEA,
MeOH/CH2Cl2 (1:1), 40 °C, 80%. (e) TrocCl, NaHCO3, THF, 90%.
building block 7,12 while for 9, thioglycoside 5 was first
converted to O-glycoside 8 with methyl 6-hydroxyhexan-
ate in the presence of dimethyl (thiomethyl) sulfonium
triflate (DMTST) and then followed the same reaction
course as for the synthesis of 7, the glucosaminyl building
block 9 was obtained.
Nevertheless, additional protecting group manipula-
tion was required for the synthesis of 14 because the C-2
amino Troc protection could not survive the basic condi-
tions necessary for benzylation of the C-3 hydroxyl
(Scheme 2). The solution was to install a temporary azide
protection first and subsequently reduce it to amine after
benzylation of the C-3 hydroxyl. Starting from known
compound 5, N-Troc protection was removed by zinc dust
reduction, and followed by Zemple´n deacetylation. The
free C-2 amino group was converted to an azide via a
modified diazo transfer reaction and the C-4/C-6 hy-
droxyls were protected as a benzylidene acetal to yield
compound 10.13 Benzylation of 10 with sodium hydride
and benzyl bromide gave compound 11, which was
subjected to reductive benzylidene ring opening with
Et3SiH and TFA to furnish 12. Subsequent Staudinger
reduction of the C-2 azide of 12 was sluggish and
successful reduction was achieved by the use dithiopro-
pane in the presence of TEA to give 13, which was reacted
with TrocCl in the presence of NaHCO3 to give the
desired acceptor 14.14
Synthesis of the N-acetyllactosamine oligomers is
depicted in Scheme 4. Guided by the RRVs, the less
reactive bridging lactosaminyl building block 18 (RRV
) 246) was first glycosylated with the more reactive
lactosaminyl building block 16 (RRV ) 1.3 × 104) in the
presence of NIS/TfOH at -35 °C and the reaction was
monitored by TLC. Complete consumption of donor 16
was followed by addition of the third lactosaminyl build-
ing block 20 along with another molar equivalent of NIS.
The resulting hexasaccharide 23 was obtained in 55%
yield. Synthesis of octasaccharide 24 was identical with
that of 23 except that the final acceptor used was
tetrasaccharide 22, and a higher reaction temperature
(-20 °C) was required for the second glycosylation. 24
was obtained in 35% yield. The lower yield of 24 as
compared to that of 23 is due to extensive chromato-
graphic purification. Global deprotection of 22, 23, and
24 was performed in three consecutive steps: (i) N-Troc
was removed by zinc reduction in the presence of acetic
anhydride with simultaneous acetylation of the free
amine, (ii) the acyl protecting groups were removed with
Zemple´n deacylation, and (iii) benzyl ethers were re-
moved with palladium-black catalyzed hydrogenation in
acidified methanol. N-Acetyllactosamine oligomers 1, 2,
and 3 were then fully characterized by HRMS and proton
NMR.
With the established competitive HPLC assay, the
RRVs of thioglycoside building blocks 7 and 14 were
(11) Furniss, B. S.; Hannaford, A. J .; Smith, P. W. G.; Tatchen, A.
R. Vogel’s Textbook of Practical Organic Chemistry, 5th ed.; Longman
Scientific & Technical: Harlow, Great Britain, 1989; p 650.
(12) DeNinno, M. P.; Etienne, J . B.; Duplantier, K. C. Tetrahedron
Lett. 1995, 36, 669.
(13) Nyffeler, P. T.; Liang, C.-H.; Koeller, K. M.; Wong, C.-H. J . Am.
Chem. Soc. 2002, 124, 10773.
(14) Staudinger; Meyer Helv. Chim. Acta 1919, 2, 635.
(15) Abbas, S. A.; Barlow, J . J .; Matta, K. L. Carbohydr. Res. 1983,
112, 201.
(16) Garegg, P. J . Adv. Carbohydr. Chem., Biochem. 1997, 52, 179.
J . Org. Chem, Vol. 68, No. 6, 2003 2137

Mong et al.
SCHEME 3 a
a
Reagents and conditions: (a) AgOTf, DTBMP, CH2Cl2/toluene (2:1), -10 °C, 70%. (b) NIS, cat. TfOH, CH2Cl2, -45 °C, 40%. (c) NIS,
cat. TfOH, CH2Cl2, -45 °C, 75%. (d) DDQ, CH2Cl2/PO4 buffer (10:1), 75%. (e) NIS, cat. TfOH, CH2Cl2, -30 °C, 88%. (f) TFA, CH2Cl2,
anisole, 0 °C to rt, 81%.
1
(35-75 µm). H NMR spectra were recorded on a 500- or 600-
Hz NMR spectrometer at 20 °C. Chemical shift (in ppm) was
determined relative to either tetramethylsilane in deuterated
chloroform (δ 0 ppm) or acetone in deuterated water (δ 2.05
ppm). Coupling constant(s) in hertz (Hz) were measured from
one-dimensional spectra. 13C Attatched Proton Test (C-Apt)
spectra were obtained with the NMR-500 spectrometer (125
Hz) and were calibrated with CDCl3 (δ 77.00 ppm).
Con clu sion
We have demonstrated the preparation of a series of
biologically relevant N-acetyllactosamine oligomers using
the reactivity-based one-pot approach combined with
segment condensation. This new combination takes
advantage of minimizing tedious protecting group ma-
nipulations and reaction intermediate isolation. It pro-
vides a useful strategy for the programmable synthesis
of large oligosaccharides and complements the automated
solid-phase synthesis strategy.17 We are in the process
of adding more newly designed building blocks to the
OptiMer database for use in the development of pro-
grammable one-pot synthesis to target other biologically
important oligosaccharides.
Globa l Dep r otection for N-Acetylla ctosa m in e Oligo-
m er s. To the solution of protected N-acetyllactosamine oligo-
mer 1, 2, or 3 in Ac2O/CH2Cl2 was added DMAP and activated
Zn dust (prewashed with 0.5 M HCl, followed by H2O, MeOH,
and Et2O). The reaction mixture was stirred at rt under Ar
for 4 h and filtered with Zn. After the solvent was evaporated
in a vacuum, the residue was dissolved in CH2Cl2, washed with
H2O and brine, dried (MgSO4), and concentrated for flash
column chromatography. The N-Troc deprotected product was
dissolved in CH2Cl2/MeOH (1:1) and added NaOMe (25% in
MeOH). The reaction mixture was stirred for 10 h and then
neutralized with IRC-50 resin (H+). After the resin was filtered
and the solvent removed, the deacylated product was dissolved
in MeOH/AcOH (5:1) and palladium-black (Pd-black) was
added. The reaction mixture was stirred at rt under 1 atm of
H2 for 18 h. After the Pd-black was filtered and the solvent
removed in a vacuum, the product was purified by C-18
reverse-phase chromatography (H2O/MeOH, 100:0 gradient to
50:50). For tetrasaccharide 1: 1H NMR (600 MHz, D2O) δ 4.51
(d, J ) 8.3 Hz, 1H; H-1), 4.32 (d, J ) 7.4 Hz, 1H; H-1), 4.29 (d,
J ) 7.9 Hz, 1H; H-1), 4.27 (d, J ) 7.9 Hz, 1H; H-1), 3.97 (d, J
) 3.1 Hz, 1H), 3.80-3.47 (m, 23H), 3.41-3.34 (m, 5H), 2.21
(t, J ) 7.5 Hz, 2H; aglycon-CH2), 1.85 (s, 3H; CH3CdO), 1.84
(s, 3H; CH3CdO), 1.42 (p, J ) 8.2 Hz, 2H; aglycon-CH2), 1.37
(p, J ) 6.5 Hz, 2H; aglycon-CH2), 1.17-1.12 (m, 2H; aglycon-
CH2); HRMS calcd for C35H60N2O23Na (M + Na)+ 899.3479,
found 899.3473. For hexasaccharide 2: 1H NMR (600 MHz,
Exp er im en ta l Section
Gen er a l. All chemicals were purchased as reagent grade
and used without further purification. Dichloromethane
(CH2Cl2), toluene, and acetonitrile (CH3CN) were distilled over
calcium hydride whereas tetrahydrofuran (THF) and ether
(Et2O) were distilled over sodium/benzophenone ketyl. Anhy-
drous DMF was purchased from a commercial source. Molec-
ular sieves (MS) used for glycosylation were AW-300, which
was ground into powdered form before use. Reactions were
monitored with analytical thin-layer chromatography (TLC)
on silica gel 60 F254 plates and visualized under UV (254 nm)
and/or by staining with acidic ceric ammonium molybdate.
Flash column chromatography was performed on silica gel
(17) Plante, O. J .; Palmacci, E. R.; Seeberger, P. H. Science 2001,
291, 1523.
2138 J . Org. Chem., Vol. 68, No. 6, 2003

One-Pot Synthesis of N-Acetyllactosamine Oligomers
SCHEME 4 a
a
Reagents and conditions: (a) (i) NIS, cat. TfOH, CH2Cl2, -35 °C; (ii) 20, NIS, -35 °C, 55%. (b) (i) NIS, cat. TfOH, CH2Cl2, -35 °C;
(ii) 22, NIS, -20 °C, 35%. (c) (i) Zn dust, Ac2O/CH2Cl2 (1:1), cat. DMAP; (ii) cat. NaOMe, MeOH; (iii) Pd-black, H2, MeOH/AcOH (4:1),
30% over 3 steps.
D2O) δ 4.52 (d, J ) 8.4 Hz, 1H; H-1), 4.51 (d, J ) 8.4 Hz, 1H;
H-1), 4.33 (d, J ) 7.9 Hz, 1H; H-1), 4.29 (d, J ) 7.9 Hz, 1H;
H-1), 4.28 (d, J ) 7.9 Hz, 1H; H-1), 4.27 (d, J ) 7.9 Hz, 1H;
H-1), 3.97 (br, 2H), 3.80-3.47 (m, 32H), 3.41-3.34 (m, 7H),
2.21 (t, J ) 7.9 Hz, 2H; aglycon-CH2), 1.85 (s, 6H; CH3CdO),
1.84 (s, 3H; CH3CdO), 1.42 (p, J ) 8.2 Hz, 2H; aglycon-CH2),
1.37 (p, J ) 6.5 Hz, 2H; aglycon-CH2), 1.17-1.13 (m, 2H;
aglycon-CH2); HRMS calcd for C49H83N3O33Na (M + Na)+
1264.4801, found 1264.4810. For octasaccharide 3: 1H NMR
(600 MHz, D2O) δ 4.51 (d, J ) 8.3 Hz, 3H; H-1), 4.33 (d, J )
7.9 Hz, 1H; H-1), 4.30-4.26 (m, 4H; H-1), 4.28 (d, J ) 7.9 Hz,
1H; H-1), 4.27 (d, J ) 7.9 Hz, 1H; H-1), 3.97 (br, 3H), 3.80-
3.47 (m, 41H), 3.41-3.34 (m, 9H), 2.21 (t, J ) 7.5 Hz, 2H;
aglycon-CH2), 1.85 (s, 9H; CH3CdO), 1.84 (s, 3H; CH3CdO),
1.42 (p, J ) 7.5 Hz, 2H; aglycon-CH2), 1.37 (p, J ) 6.5 Hz, 2H;
aglycon-CH2), 1.17-1.13 (m, 2H; aglycon-CH2); HRMS calcd
for C63H106N4O43Na (M + Na)+ 1629.6123, found 1629.6115.
Com p ou n d 6. 5 (2 g, 3.3 mmol) in MeOH/CH2Cl2 (1/1, 10
mL) was stirred at 0 °C and NaOMe (25% in MeOH, 0.1 mL)
was added. The reaction mixture was stirred at 0 °C under
Ar for 2 h and then neutralized with IRC-50 resin(H+). The
resin was filtered off and the reaction solvent was evaporated
in a vacuum, followed by coevaporation with toluene (×2). The
residue suspended in CH3CN and (()-10-camphorsulfonic acid
(CSA) (9 mg, 17 µmol) was added to the mixture. Benzaldehyde
dimethyl acetal (1.6 mL, 10 mmol) was added and reaction
mixture was stirred at room temperature for 2 h then neutral-
ized with triethylamine (TEA). The solvent was removed by
rotaevaporator. The resulting residue and DMAP (40 mg, 0.33
mmol) were dissolved in CH2Cl2. Acetic anhydride (Ac2O) (0.94
mL, 10 mmol) and pyridine (pyr) (1.6 mL, 20 mmol) were
added. The reaction mixture was stirred at room temperature
for 2 h and then washed t with 0.5 M HCl × 2, H2O, and brine
and dried (MgSO4). The organic phase was concentrated for
flash column chromatography (hexane/CH2Cl2/EtOAc, 2:1:0.5).
Compound 6 (1.17 g, 60% over 3 steps) was obtained as a white
1
glassy solid. For compound 6: H NMR (500 MHz, CDCl3) δ
7.42-7.32 (m, 8H; aromatic), 7.13 (d, J ) 8.1 Hz, 2H;
aromatic), 5.48 (s, 1H), 5.43 (d, J ) 9.5 Hz, 1H), 5.30 (t, J )
9.5 Hz, 1H), 4.78 (dd, J ) 36.7, 12.1 Hz, 2H), 4.73 (d, J ) 10.3
Hz, 1H; H-1), 4.33-4.29 (m, 1H), 3.81-3.75 (m, 2H), 3.65 (t, J
) 9.6 Hz, 1H), 3.54-3.49 (m, 1H), 2.37 (s, 3H; PhMe), 2.05 (s,
3H; MeCdO); 13C NMR (125 MHz, CDCl3) δ 170.79, 154.20,
138.61, 136.78, 133.41, 129.78, 129.13, 128.40, 128.22, 128.20,
126.09, 101.33, 88.22, 78.38, 74.53, 72.44, 70.59, 68.40, 55.51,
21.17, 20.82; HRMS calcd for C25H26Cl3NO7SNa (M + Na)+
612.0338, found 612.0381.
Com p ou n d 7. Compound 6 (0.7 g, 1.2 mmol) in CH2Cl2 (8
mL) was stirred at 0 °C under Ar. Et3SiH (2 mL, 12 mmol)
was added and followed by TFA (0.9 mL, 12 mmol). The
reaction mixture was stirred for 1 h. Then the mixture was
diluted with CH2Cl2 (20 mL) and cautiously washed with sat.
NaHCO3 (×3), H2O, and brine and dried (MgSO4). The organic
phase was concentrated for flash column chromatography
(hexane/CH2Cl2/EtOAc, 3:1:1). 7 (0.63 g, 90%) was obtained
as a glassy white solid. For compound 7: 1H NMR (500 MHz,
CDCl3) δ 7.40-7.05 (m, 9H; aromatic), 5.31 (d, J ) 9.5 Hz,
1H), 5.04 (t, J ) 9.5 Hz, 1H), 4.76 (dd, J ) 52.8, 12.1 Hz, 2H),
4.66 (d, J ) 10.3 Hz, 1H), 4.56 (dd, J ) 18.4, 11.8 Hz, 2H),
3.82-3.77 (m, 2H), 3.73-3.66 (m, 2H), 3.57-3.52 (m, 1H), 3.02
(d, J ) 4.0 Hz, 1H), 2.31 (s, 3H; PhMe), 2.07 (s, 3H; MeCdO);
13C NMR (125 MHz, CDCl3) δ 171.69, 154.13, 138.31, 137.58,
133.15, 129.71, 128.58, 128.47, 127.88, 127.74, 87.26, 78.11,
76.16, 74.48, 73.76, 70.55, 70.25, 54.77, 21.13, 20.90; HRMS
calcd for
614.0543.
C
25H28Cl3NO7SNa (M + Na)+ 614.0544, found
Com p ou n d 8. 5 (3 g, 5.1 mmol) in CH2Cl2 (15 mL) was
suspended with MS (AW-300, 3.75 g) for 1 h at rt under Ar.
J . Org. Chem, Vol. 68, No. 6, 2003 2139

Mong et al.
The reaction mixture was cooled to -20 °C and dimethyl
thiomethyl sulfonium triflate (DMTST) (6.45 g, 25 mmol) in
CH2Cl2 (10 mL) [freshly prepared from mixing methyl triflate
(MeOTf) (2.8 mL, 25 mmol) and dimethyl disulfide (Me2S2) (2.2
mL, 25 mmol)] was added to the reaction mixture. The reaction
mixture was stirred until the temperature went from -20 to
0 °C and kept at 0 °C for 4 h. The reaction was quenched with
TEA. MS was filtered off and the filtrate was washed with
sat. NaHCO3, H2O, and brine and dried (MgSO4). The organic
phase was concentrated for flash chromatography (hexane/
EtOAc, 1.5:1). 8 (4 g, 80%) was obtained as a colorless oil. For
compound 8: 1H NMR (500 MHz, CDCl3) δ 5.39 (d, J ) 8.6
Hz, 1H), 5.32 (t, J ) 9.9 Hz, 1H), 5.07 (t, J ) 9.2 Hz, 1H),
4.72 (dd, J ) 48.5, 12.1 Hz, 2H), 4.65 (d, J ) 8.2 Hz, 1H), 4.28
(dd, J ) 12.1, 4.8 Hz, 1H), 4.13 (d, J ) 10.3 Hz, 1H),
3.92-3.88 (m, 1H; aglycon-CH2), 3.71-3.69 (m, 1H), 3.68 (s,
3H; CO2Me), 3.62 (dd, J ) 19.4, 8.8 Hz, 1H), 3.52-3.47 (m,
1H; aglycon-CH2), 2.33-2.29 (m, 2H; aglycon-CH2), 2.09 (s, 3H;
MeCdO), 2.03 (s, 3H; MeCdO), 1.67-1.55 (m, 2H; aglycon-
CH2), 1.40-1.34 (m, 2H; aglycon-CH2); 13C NMR (125 MHz,
CDCl3) δ 174.24, 170.69, 170.57, 169.45, 154.01, 100.76, 74.36,
71.89, 71.70, 69.71, 68.69, 56.29, 51.55, 33.72, 28.89, 25.19,
24.28, 20.73, 20.63, 20.60; HRMS calcd for C22H32Cl3NO12Na
(M + Na)+ 630.0882, found 630.0890.
Com p ou n d 10. Zn dust (2 g, activated with 0.1 M HCl
before use) was added to 5 (1 g, 1.7 mmol) in MeOH/AcOH/
CH2Cl2 (8 mL, 2:1:1) and the mixture was stirred at room
temperature under Ar for 1 h. Then the Zn dust was filtered
off and the organic filtrate was diluted with CH2Cl2, which
was washed with saturated NaHCO3 and brine, dried (MgSO4),
and concentrated for flash column chromatography (EtOAc)
to yield the N-Troc deprotected product. The crude product
from the previous step was dissolved in MeOH/CH2Cl2 (5 mL,
1:1) to which a solution of NaOMe (25% in MeOH, 0.1 mL)
was added. The reaction mixture was stirred at room temper-
ature for 2 h and neutralized with concentrated HCl. Solvent
was removed in a vacuum, and the crude deacetylated product
was taken directly into the diazo transfer reaction. To the
crude residue in MeOH/H2O (5 mL, 4:1) was added K2CO3 (0.5
g, 3.4 mmol), ZnCl2 (11 mg, 0.085 mmol), and freshly prepared
triflyl azide (TfN3) in CH2Cl2 (6 mL) (freshly prepared from
triflic anhydride and sodium azide) and the mixture was
stirred at room temperature for 18 h. After solvent removal,
the residue was taken up with a EtOAc and water mixtureand
product was extracted with EtOAc (×2). The pooled organic
phase was concentrated for flash column chromatography
(hexane/EtOAc, 1:4). The resulting C2-azido compound was
then dissolved in CH3CN (4 mL) and CSA (18 mg, 0.08 mmol)
and benzaldehyde dimethyl acetal (0.25 mL, 1.54 mmol) were
added. After the mixture was stirred at room temperature
under Ar for 12 h, the reaction was quenched with addition of
TEA. Subsequent solvent removal and flash column chromato-
graphic purification (hexane/CH2Cl2/EtOAc, 2:1:0.25) furnished
10 (0.41 g, 60% from 5) as a white glassy solid. For compound
10: 1H NMR (500 MHz, CDCl3) δ 7.48-7.36 (m, 7H; aromatic),
7.17 (d, J ) 8.1 Hz, 2H; aromatic), 5.52 (s, 1H), 4.48 (t, J )
10.3 Hz, 1H), 4.37 (dd, J ) 10.6, 4.4 Hz, 1H), 3.78-3.73 (m,
2H), 3.47-3.41 (m, 2H), 3.32 (t, J ) 9.5 Hz, 1H), 2.72 (d, J )
2.9 Hz, 1H), 2.37 (s, 3H; PhMe); 13C NMR (125 MHz, CDCl3)
δ 139.12, 136.68, 134.28, 129.91, 129.43, 128.40, 126.70,
126.21, 101.92, 86.81, 80.17, 74.10, 70.22, 68.42, 65.97, 21.20;
HRMS calcd for C20H21N3O4SNa (M + Na)+ 422.1145, found
422.1147.
purification (hexane/CH2Cl2/Et2O, 2.5:1:0 to 2.5:1:0.1). Com-
pound 11 (0.18 g, 82%) was obtained as a white glassy solid.
For compound 11: 1H NMR (500 MHz, CDCl3) δ 7.49-7.27
(m, 12H; aromatic), 7.14 (d, J ) 8.1 Hz, 2H; aromatic), 5.56
(s, 1H), 4.90 (d, J ) 10.6 Hz, 1H), 4.77 (d, J ) 10.6 Hz, 1H),
4.42 (d, J ) 10.3 Hz, 1H), 4.38 (dd, J ) 10.6, 5.1 Hz, 1H), 3.77
(t, J ) 10.3 Hz, 1H), 3.65 (t, J ) 9.2 Hz, 1H), 3.60 (t, J ) 9.2
Hz, 1H), 3.46-3.41 (m, 1H), 3.32 (dd, J ) 10.3, 8.8 Hz, 1H),
2.35 (s, 3H; PhMe); 13C NMR (125 MHz, CDCl3) δ 139.14,
137.50, 137.03, 134.52, 129.89, 129.06, 128.43, 128.33, 128.29,
128.01, 126.40, 125.92, 101.19, 86.50, 81.26, 80.96, 75.21,
70.41, 68.47, 64.42, 21.19; HRMS calcd for C27H27N3O4SNa (M
+ Na)+ 512.1614, found 512.1604.
Com p ou n d 12. To compound 11 (0.18 g, 0.37 mmol) and
Et3SiH (0.6 mL, 3.7 mmol) in CH2Cl2 (2 mL) was added TFA
(0.3 mL, 3.7 mmol). The reaction mixture was stirred under
Ar at 0 °C for 1 h and quenched with NaHCO3. The product
was extracted with CH2Cl2 (×2) and the organic phase was
washed with brine, dried (MgSO4), and concentrated for flash
column chromatography (hexane/CH2Cl2/EtOAc, 3:1:0.3). Com-
pound 12 (0.16 g, 90%) was obtained as a colorless viscous oil.
For compound 12: 1H NMR (500 MHz, CDCl3) δ 7.46 (d, J )
6.6 Hz, 2H; aromatic), 7.36-7.29 (m, 10H; aromatic), 7.06 (d,
J ) 7.7 Hz, 2H; aromatic), 4.84 (dd, J ) 35.6, 10.6 Hz, 2H),
4.56 (dd, J ) 24.6, 12.1 Hz, 2H), 4.35 (d, J ) 9.9 Hz, 1H), 3.78-
3.71 (ddd, J ) 23.1, 10.2, 4.8 Hz, 2H), 3.59 (dt, J ) 9.6, 2.2
Hz, 1H), 3.43-3.40 (m, 1H), 3.34 (t, J ) 9.1 Hz, 1H), 3.26 (t,
J ) 9.3 Hz 1H), 2.73 (d, J ) 2.6 Hz, 1H), 2.31 (s, 3H; PhMe);
13C NMR (125 MHz, CDCl3) δ 138.69, 137.77, 137.64, 134.14,
19.72, 128.57, 128.42, 128.18, 128.06, 127.79, 127.64, 126.96,
86.06, 84.52, 77.91, 75.41, 73.67, 71.84, 70.20, 64.25, 21.12;
HRMS calcd for C27H29N3O4SNa (M + Na)+ 514.1771, found
514.1780.
Com p ou n d 13. To compound 12 (0.15 g, 0.31 mmol) in
MeOH/CH2Cl2 (2 mL, 1:1) was added 1,3-dithiopropane (0.15
mL, 1.5 mmol) and TEA (0.20 mL, 1.5 mmol). The reaction
mixture was stirred at 40 °C under Ar overnight and then
coevaporated with toluene (×2). The residue was dissolved in
CH2Cl2 and washed with H2O and brine, dried (MgSO4), and
concentrated for flash column chromatography purification
(hexane/CH2Cl2/EtOAc, 2:1:0.5). Compound 13 (0.12 g, 80%)
was obtained as a white glassy solid. For compound 13: 1H
NMR (500 MHz, CDCl3) δ 7.42 (d, J ) 8.1 Hz, 2H; aromatic),
7.38-7.26 (m, 10H; aromatic), 7.05 (d, J ) 7.7 Hz, 2H;
aromatic), 4.94 (d, J ) 11.3 Hz, 1H), 4.75 (d, J ) 11.7 Hz, 1H),
4.57 (dd, J ) 22.0, 12.1 Hz, 2H), 4.40 (d, J ) 9.5 Hz, 1H), 3.78
(ddd, J ) 34.1, 9.9, 4.8 Hz, 2H), 3.68 (t, J ) 9.2 Hz, 1H), 3.50-
3.46 (m, 1H), 3.33 (t, J ) 9.1 Hz, 1H), 2.28 (t, J ) 9.6 Hz 1H),
2.30 (s, 3H; PhMe), 1.69 (br, 2H;); 13C NMR (125 MHz, CDCl3)
δ 138.43, 138.17, 137.64, 133.34, 129.61, 128.56, 128.43,
128.02, 127.97, 127.88, 127.80, 127.71, 89.06, 86.30, 77.71,
75.14, 73.73, 72.95, 70.92, 54.69, 21.09; HRMS calcd for C27H31
-
NO4SNa (M + Na)+ 488.1866, found 488.1868.
Com p ou n d 14. To compound 13 (0.12 g, 0.29 mmol) in THF
(3 mL) was added NaHCO3 (49 mg, 0.58 mmol) and 2,2,2-
trichloroethyl chloroformate (TrocCl) (48 µL, 0.35 mmol). The
reaction mixture was stirred at room temperature under Ar
for 4 h and then filtered, and THF was removed in a vacuum.
The residue was dissolved in CH2Cl2 and washed with H2O
and brine, dried (MgSO4), and concentrated for flash column
chromatography (hexane/CH2Cl2/EtOAc, 3:1:0.5 to 3:1:1). Com-
pound 14 (0.17 g, 90%) was obtained as a white glassy solid.
For compound 14: 1H NMR (500 MHz, CDCl3) δ 7.40-7.26
(m, 12H; aromatic), 7.05 (d, J ) 8.1 Hz, 2H; aromatic), 5.11
(d, J ) 7.7 Hz, 1H), 4.90 (d, J ) 10.2 Hz, 1H), 4.76 (s, 4H),
4.57 (dd, J ) 11.8, 20 Hz, 2H), 3.80-3.73 (m, 3H), 3.67 (t, J )
8.8 Hz, 1H), 3.52-3.50 (m, 1H), 3.35 (dd, J ) 19.1, 9.9 Hz,
1H), 2.77 (br, 1H), 2.30 (s, 3H; PhMe); 13C NMR (125 MHz,
CDCl3) δ 153.78, 138.21, 137.98, 137.69, 133.19, 129.70, 128.58,
128.46, 128.15, 128.01, 127.82, 127.73, 86.04, 81.77, 77.82,
74.73, 74.44, 73.73, 72.98, 70.57, 56.05, 21.11; HRMS calcd
for C30H32Cl3NO6SNa (M + Na)+ 662.0908, found 662.0902.
Com p ou n d 11. A solution of compound 10 (0.18 g, 0.45
mmol) in DMF (2 mL) was added to a suspension of NaH (13
mg, 0.54 mmol), Bu4NI (17 mg, 0.045 mmol), and BnBr (0.11
mL, 0.9 mmol) in DMF (3 mL) at 0 °C. The reaction mixture
was stirred under Ar and brought to room temperature. After
3 h the reaction was quenched with the addition of MeOH.
After concentration in a vacuum, the residue was dissolved in
CH2Cl2 and washed with 0.1 M HCl, H2O, and brine, dried
(MgSO4), and concentrated for flash column chromatography
2140 J . Org. Chem., Vol. 68, No. 6, 2003

One-Pot Synthesis of N-Acetyllactosamine Oligomers
Com p ou n d 16. Glucosaminyl acceptor 14 (0.53 g, 0.83
mmol), 2,6-di-tert-butyl-4-methylpyridine (DTBMP) (0.51 g, 2.5
mmol), and MS (4 Å, 2 g) were suspended in dry CH2Cl2/
toluene (15 mL, 2:1) and stirred at room temperature for
2 h under Ar. The mixture was cooled to -23 °C and R-bro-
moacetogalactoside 15 (0.5 g, 1.2 mmol) and silver triflate
(AgOTf) (0.3 g, 1.2 mmol) were added. The reaction mixture
was stirred at -10 °C for 1.5 h, additional R-bromoacetoga-
lactoside 15 (0.3 g, 0.83 mmol) and AgOTf (0.2 g, 0.83 mmol)
were added, and the reaction mixture was stirred again for 1
h. The MS were filtered off and the filtrate was washed with
0.1 M HCl, saturated NaHCO3, and brine, dried (MgSO4), and
concentrated for flash column chromatography (hexane/
CH2Cl2/EtOAc, 3:1:1). Compound 16 (0.56 g, 70%) was obtained
as white glassy solid. For compound 16: 1H NMR (500 MHz,
CDCl3) δ 7.41-7.27 (m, 12H; aromatic), 7.05 (d, J ) 8.5 Hz,
1H; aromatic), 5.28 (d, J ) 3.3 Hz, 1H), 5.18 (d, J ) 7.7 Hz,
1H), 5.13 (dd, J ) 10.6, 8.0 Hz, 1H), 4.92 (d, J ) 9.2 Hz, 1H),
4.90 (d, J ) 10.5 Hz, 1H), 4.87 (dd, J ) 10.2, 3.7 Hz, 1H), 4.74
(dd, J ) 38.5, 12.1 Hz, 2H), 4.71 (d, J ) 11.7 Hz, 1H), 4.60 (d,
J ) 12.8 Hz, 1H), 4.59 (d, J ) 8.0 Hz, 1H), 4.51 (d, J ) 12.1
Hz 1H), 4.03-3.96 (m, 2H), 3.90 (dd, J ) 11.4, 6.3 Hz, 1H),
3.85 (t, J ) 8.8 Hz, 1H), 3.76 (br, 2H), 3.61 (t, J ) 7.0 Hz, 1H),
3.45 (d, J ) 8.8 Hz, 1H), 3.33 (q, J ) 8.8 Hz, 1H), 2.30 (s, 3H;
PhMe), 2.09 (s, 3H; MeCdO), 1.99 (s, 3H; MeCdO), 1.97 (s,
6H; MeCdO); 13C NMR (125 MHz, CDCl3) δ 170.17, 170.53,
169.25, 153.69, 138.29, 138.15, 137.87, 133.44, 129.69, 128.52,
128.26, 128.01, 127.94, 127.84, 127.71, 99.98, 85.54, 79.30,
79.05, 76.28, 74.57, 74.37, 73.57, 70.84, 69.43, 67.94, 66.76,
60.57, 55.99, 21.12, 20.73, 20.61, 20.60, 20.55; HRMS calcd
for C44H50Cl3NO15SNa (M + Na)+ 992.1859, found 992.1862.
obtained as a white glassy solid. For compound 18: 1H NMR
(500 MHz, CDCl3) δ 7.39 (d, J ) 8.1 Hz, 2H; aromatic), 7.34-
7.24 (m, 15H; aromatic), 7.04 (d, J ) 7.7 Hz, 2H; aromatic),
5.38 (d, J ) 9.9 Hz, 1H), 5.02 (t, J ) 9.5 Hz, 1H), 4.83 (t, J )
9.0 Hz, 1H), 4.79 (d, J ) 12.1 Hz, 1H), 4.76 (dd, J ) 39.7, 12.1
Hz, 2H), 4.71 (d, J ) 11.7 Hz, 1H), 4.66 (d, J ) 12.1 Hz, 1H),
4.61 (d, J ) 12.1 Hz, 1H), 4.58 (d, J ) 10.6 Hz, 1H), 4.49 (d,
J ) 11.7 Hz, 1H), 4.43 (dd, J ) 15.0, 11.7 Hz, 2H), 4.37 (d, J
) 7.7 Hz, 1H), 3.82 (t, J ) 9.5 Hz, 1H), 3.81 (dd, J ) 10.6, 3.3
Hz, 2H), 3.76-3.71 (m, 2H), 3.58-3.53 (m, 2H), 3.51 (br,
1H; H-5), 3.49-3.44 (m, 2H), 2.73-2.64 (m, 2H; Lev-CH2),
2.51-2.43 (m, 2H; Lev-CH2), 2.28 (s,3H; PhMe), 2.12 (s, 3H;
MeCdO), 1.89 (s, 3H; MeCdO); 13C NMR (125 MHz, CDCl3) δ
206.77, 172.33, 170.59, 154.10, 138.13, 138.03, 137.45, 133.16,
129.54, 128.46, 128.41, 128.34, 128.30, 127.85, 127.72, 127.65,
127.61, 127.56, 100.02, 95.47, 86.98, 78.95, 75.92, 75.03, 74.37,
74.28, 73.91, 73.86, 73.43, 73.32, 72.97, 67.87, 67.68, 54.92,
37.90, 29.69, 27.85, 21.03, 20.67; HRMS calcd for C50H56Cl3-
NO14SNa (M + Na)+ 1054.2379, found 1054.2363.
Tetr a sa cch a r id e 21. Lactosaminyl donor 17 (0.52 g, 0.45
mmol), acceptor 20 (0.4 g, 0.38 mmol), and MS (AW-300, 1 g)
were suspended in dry CH2Cl2 (4 mL) under Ar at room
temperature for 1 h. The reaction mixture was then brought
to -30 °C, followed by addition of NIS (0.1 g, 0.45 mmol) and
0.5 M TfOH in Et2O (0.1 mL, 0.05 mmol). The reaction mixture
was stirred at -30 °C for 3 h and quenched with sat. NaHCO3
and solid Na2S2O3. MS was filtered off and the filtrate was
washed with sat. Na2S2O3, sat. NaHCO3, H2O, and brine, dried
(MgSO4), and concentrated for flash column chromatography
(toluene/EtOAc, 5.5:4.5). Compound 21 (0.6 g, 88%) was
obtained as a white glassy solid. For compound 21: 1H NMR
(500 MHz, CDCl3) δ 7.34-7.17 (m, 32H; aromatic), 6.88 (d, J
) 8.4 Hz, 2H; aromatic), 6.25 (d, J ) 9.9 Hz, 1H), 5.26 (d, J )
9.2 Hz, 1H), 5.21 (t, J ) 9.5 Hz, 1H), 5.15 (d, J ) 9.9 Hz, 1H),
5.05 (d, J ) 9.5 Hz, 1H), 5.02 (d, J ) 11.4 Hz, 1H), 4.98 (d, J
) 9.9 Hz, 1H), 4.91 (d, J ) 11.7 Hz, 1H), 4.90 (d, J ) 12.5 Hz,
1H), 4.74-4.66 (m, 4 H), 4.56 (d, J ) 11.7 Hz, 1H), 4.50-4.56
(m, 3H), 4.41-4.32 (m, 9H), 3.93-3.82 (m, 6 H), 3.79 (s, 3H;
OMe), 3.78-3.75 (m, 2H), 3.68 (br, 2H), 3.65 (s, 3H; CO2Me),
3.60-3.56 (m, 2H), 3.52-3.34 (m, 8H), 2.85-2.80 (m, 1H; Lev-
CH2), 2.73-2.56 (m, 2H; Lev-CH2), 2.53-2.39 (m, 4H; Lev-
CH2), 2.30-2.27 (m, 3H; Lev-CH2, aglycon-CH2), 2.21 (s, 3H;
MeCdO), 2.12 (s, 3H; MeCdO), 1.87 (s, 3H; MeCdO), 1.85 (s,
3H; MeCdO), 1.63-1.51 (m, 4 H; aglycon-CH2), 1.37-1.31 (m,
2H; aglycon-CH2); 13C NMR (125 MHz, CDCl3) δ 209.24,
206.28, 174.06, 171.04, 170.73, 170.62, 169.97, 159.15, 154.61,
154.21,138.89, 138.51, 137.95, 137.89, 137.69, 137.54, 129.92,
129.00, 128.38, 128.33, 128.13, 128.04, 127.88,127.78, 127.72,
127.67, 127.62, 127.57, 127.27, 127.10, 113.67, 101.38, 101.12,
100.56, 100.12, 95.86, 95.51, 79.79, 77.69, 75.53, 75.00, 74.90,
74.79, 74.59, 74.28, 74.21, 74.17, 73.98, 73.63, 73.41, 73.34,
73.27, 72.96, 72.73, 72.42, 72.38, 72.19, 72.09, 71.28, 69.23,
68.11, 67.93, 67.76, 67.71, 56.44, 55.80, 55.16, 51.42, 37.61,
33.72, 29.86, 29.78, 28.92, 27.74, 25.18, 24.30, 20.63; HRMS
calcd for C101H118Cl6N2O32Na (M + Na)+ 2103.569, found
2103.564.
Com p ou n d 17. Galactosyl donor 4 (1.5 g, 2.16 mmol) and
glucosaminyl acceptor 7 (0.85 g, 1.44 mmol) and MS (AW-300,
3 g) were suspended in dry CH2Cl2 (15 mL) under Ar at room
temperature for 1 h. The reaction mixture was then brought
to -45 °C and N-iodosuccinimide (NIS) (0.49 g, 2.16 mmol)
and 0.5 M trifluoromethane-sulfonic acid in Et2O (TfOH) (0.43
mL, 0.0216 mmol) were added. The reaction mixture was
stirred at -45 °C for 2 h and quenched with addition of sat.
NaHCO3 and solid Na2S2O3. MS were filtered off and the
filtrate was washed with sat. Na2S2O3, sat. NaHCO3, H2O, and
brine, dried (MgSO4), and concentrated for flash column
chromatography (toluene/CH2Cl2/EtOAc, 4:1:1). Compound 17
(0.8 g, 40%) was obtained as a white glassy solid. For
compound 17: 1H NMR (500 MHz, CDCl3) δ 7.39 (d, J ) 8.1
Hz, 2H; aromatic), 7.35-7.21 (m, 17H; aromatic), 7.01 (d, J )
8.1 Hz, 2H; aromatic), 6.87 (d, J ) 8.5 Hz, 2H; aromatic), 5.40
(d, J ) 9.9 Hz, 1H), 5.13 (dd, J ) 10.3, 7.9 Hz, 1H), 5.01 (t, J
) 9.6 Hz, 1H), 4.90 (d, J ) 11.7 Hz, 1H), 4.74 (dd, J ) 31.9,
12.1 Hz, 2H), 4.62 (d, J ) 12.1 Hz, 1H), 4.56 (d, J ) 10.3 Hz,
1H), 4.55 (d, J ) 12.1 Hz, 1H), 4.48 (d, J ) 12.1 Hz, 1H), 4.45
(d, J ) 12.1 Hz, 1H), 4.41 (d, J ) 12.1 Hz, 1H), 4.39 (s, 2H),
4.35 (d, J ) 7.7 Hz, 1H), 3.88-3.84 (m, 2H), 3.78 (s, 3H; OMe),
3.76-3.72 (m, 3H), 3.57-3.55 (d, J ) 8.4 Hz, 1H), 3.54-3.52
(m, 1H), 3.50 (dd, J ) 8.8, 4.8 Hz, 1H), 3.38 (dd, J ) 7.7, 5.6
Hz, 1H), 3.34 (dd, J ) 9.9, 2.5 Hz, 1H), 2.62-2.59 (m, 2H; Lev-
CH2), 2.41 (t, J ) 6.6 Hz, 2H; Lev-CH2), 2.26 (s, 3H; PhMe),
2.09 (s, 3H; MeCdO), 1.85 (s, 3H; MeCdO); 13C NMR (125
MHz, CDCl3) δ 206.24, 171.00, 170.58, 159.13, 154.10, 138.42,
137.87, 137.54, 132.94, 129.88, 129.49, 129.02, 128.54, 128.37,
128.23, 128.02, 127.78, 127.73, 127.69, 127.67, 127.52, 127.29,
113.65, 100.34, 95.46, 86.92, 79.63, 78.92, 74.30, 74.21, 73.86,
73.28, 73.02, 72.29, 71.91, 71.34, 67.94, 67.86, 55.12, 55.11,
54.86, 37.56, 29.72, 27.71, 20.98, 20.58; HRMS calcd for
Tetr a sa cch a r id e 22. To compound 21 (0.2 g, 0.17 mmol)
in CH2Cl2 (4 mL) were added TFA (0.3 mL) and anisole (0.3
mL) at 0 °C and the reaction mixture was warmed to room
temperature over 1 h. Saturated NaHCO3 was added to quench
the reaction and product was extracted with CH2Cl2 (×3). The
pooled organic phase was washed with H2O and brine, dried
(MgSO4), and concentrated for flash column chromatography
(hexane/CH2Cl2/EtOAc, 1:1:2). Compound 22 (0.16 g, 81%) was
obtained as a white glassy solid. For compound 22: 1H NMR
(500 MHz, CDCl3) δ 7.35-7.20 (m, 30H), 6.27 (d, J ) 9.5 Hz,
1H), 5.29 (br, 1H), 5.06 (d, J ) 8.4 Hz, 1H), 5.03 (d, J ) 11.7
Hz, 1H), 4.98 (d, J ) 9.9 Hz, 1H), 4.90 (d, J ) 12.1 Hz, 1H),
4.85 (t, J ) 9.5, 1H), 4.74-4.62 (m, 7H), 4.51-4.34 (m, 11H),
3.95-3.75 (m, 9H), 3.68 (br, 2H), 3.65 (s, 3H; CO2Me), 3.61-
3.41 (m, 11H), 2.86-2.65 (m, 3H; Lev-CH2), 2.52-2.41 (m, 5H;
OH, Lev-CH2), 2.29-2.26 (m, 3H; Lev-CH2, aglycon-CH2), 2.20
C
58H64Cl3NO15SNa (M + Na)+ 1174.2954, found 1174.2963.
Com p ou n d 18. To compound 17 (0.3 g, 0.26 mmol) in
CH2Cl2/phosphate buffer mixture (3 mL, 10:1) was added DDQ
(0.8 g, 3 mmol) and the reaction mixture was stirred at room
temperature for 2 h. The mixture was diluted with CH2Cl2,
and washed with sat. NaHCO3, H2O, and brine, dried (MgSO4),
and concentrated for flash column chromatography (hexane/
EtOAc, 1.5:1 gradient to 1:1). Compound 18 (0.2 g, 75%) was
J . Org. Chem, Vol. 68, No. 6, 2003 2141

Mong et al.
(s, 3H; MeCdO), 2.14 (s, 3H; MeCdO), 1.89 (s, 3H; MeCdO),
1.87 (s, 3H; MeCdO), 1.63-1.52 (m, 4 H; aglycon-CH2), 1.37-
1.31 (m, 2H; aglycon-CH2); 13C NMR (125 MHz, CDCl3) δ
209.40, 206.65, 174.06, 172.32, 170.76, 170.60, 169.99, 154.62,
154.21, 138.88, 138.13, 137.90, 137.86, 137.67, 137.39, 128.40,
128.37, 128.33, 128.13, 127.90, 127.87, 127.85, 127.73, 127.69,
127.62, 127.57, 127.53, 127.47, 127.12, 101.37, 101.08, 100.15,
100.11, 95.65, 95.51, 77.69, 75.92, 75.51, 75.13, 75.02, 74.97,
74.72, 74.62, 74.27, 74.18, 74.01, 73.63, 73.37, 73.34, 73.28,
73.01, 72.90, 72.84, 72.43, 72.31, 69.22, 68.09, 67.75, 67.53,
56.41, 55.08, 51.42, 37.87, 37.61, 33.72, 29.88, 29.73, 28.92,
27.83, 27.77, 25.18, 24.30, 20.68, 20.62; HRMS calcd for
C93H110Cl6N2O31Na (M + Na)+ 1983.512, found 1983.519.
Hexa sa cch a r id e 23. Lactosaminyl building blocks 16
(0.155 g, 0.16 mmol), 18 (0.1 g, 0.097 mmol), and MS (AW-
300, 0.5 g) were suspended in dry CH2Cl2 (2 mL) under Ar at
room temperature for 1 h, then cooled to -45 °C. NIS (36 mg,
0.16 mmol) and 0.5 M TfOH in Et2O (30 µL, 15 µmol) were
added to the mixture. The solution was then stirred at -35
°C for 1.5 h and the progress of the reaction was monitored
by TLC (developed by hexane/EtOAc, 4:3). When all 16 was
reacted, the third lactosaminyl building block 20 (0.25 g, 0.24
mmol) was added, together with additional NIS (44 mg, 0.194
mmol) and 0.5 M TfOH in Et2O (20 µL, 10 µmol). The mixture
was stirred at -35 °C for an additional 2.5 h and quenched
with sat. NaHCO3 and solid Na2S2O3. MS were filtered off and
the filtrate was washed with sat. Na2S2O3, sat. NaHCO3, H2O,
and brine, dried (MgSO4), and concentrated for flash column
chromatography (hexane/EtOAc, 3:4). Hexasaccharide 23 (0.15
g, 55% with respect to 18) was obtained as a white glassy solid.
For compound 23: 1H NMR (500 MHz, CDCl3) δ 7.32-7.20
(m, 40H; aromatic), 6.33 (d, J ) 9.2 Hz, 1H), 6.36 (d, J ) 9.9
Hz, 1H), 5.25 (d, J ) 3.3 Hz, 1H), 5.21 (br, 2H), 5.13 (dd, J )
10.3, 8.1 Hz, 1H), 5.10-4.97 (m, 5H), 4.90 (dd, J ) 11.0, 8.8
Hz, 2H), 4.84 (dd, J ) 10.3, 3.3 Hz, 1H), 4.76-4.66 (m, 8H),
4.61 (d, J ) 8.1 Hz, 1H; H-1), 4.51-4.45 (m, 6H), 4.40-4.34
(m, 8H), 3.99 (t, J ) 8.8 Hz, 1H), 3.95-3.91 (m, 2H), 3.88-
3.81 (m, 7H), 3.73 (br, 6H), 3.68 (br, 2H), 3.66 (s, 3H; CO2Me),
3.56-3.51 (m, 5H), 3.49-3.42 (m, 5H), 2.84 (br, 2H; Lev-CH2),
2.58-2.42 (m, 4H; Lev-CH2), 2.29 (t, J ) 7.3 Hz, 4H; Lev-CH2,
aglycon-CH2), 2.22 (s, 3H; MeCdO), 2.21 (s, 3H; MeCdO), 2.11
(s, 3H; MeCdO), 1.98 (s, 3H; MeCdO), 1.97 (s, 3H; MeCdO),
1.96 (s, 3H; MeCdO), 1.86 (s, 3H; MeCdO), 1.85 (s, 3H;
MeCdO), 1.61-1.52 (m, 4H; aglycon-CH2), 1.37-1.31 (m, 2H;
aglycon-CH2); 13C NMR (125 MHz, CDCl3) δ 209.67, 209.38,
174.12, 170.80, 170.73, 170.65, 170.12, 170.10, 170.00, 169.95,
169.31, 154.68, 154.49, 154.26, 138.96, 138.87, 138.70, 137.97,
137.92, 137.71, 137.66, 128.54, 128.46, 128.40, 128.14, 128.06,
128.02, 127.95, 127.82, 127.78, 127.75, 127.66, 127.22, 127.19,
127.15, 101.46, 101.31, 101.18, 100.33, 100.28, 100.18, 95.88,
95.84, 95.54, 79.71, 78.14, 77.83, 75.65, 75.36, 75.11, 75.06,
74.77, 74.71, 74.62, 74.35, 74.26, 74.10, 74.04, 73.75, 73.71,
73.56, 73.41, 73.38, 73.35, 73.11, 72.80, 72.44, 70.96, 70.39,
69.64, 69.32, 68.09, 67.93, 67.79, 66.75, 60.61, 57.43, 56.49,
55.86, 51.49, 37.68, 37.45, 33.77, 30.21, 29.91, 28.98, 27.83,
27.65, 25.24, 24.35, 20.75, 20.67, 20.58, 20.52; ESI-MS calcd
for C130H152Cl9N3O46Na (M + Na)+ 2829, found 2829.
Octa sa cch a r id e 24. Lactosaminyl building blocks 16 (0.1
g, 0.1 mmol), 18 (0.1 g, 0.097 mmol), and MS (AW-300, 0.5 g)
were suspended in dry CH2Cl2 (2.5 mL) at room temperature
under Ar for 1 h and then brought to -45 °C. NIS (23 mg, 0.1
mmol) and 0.5 M TfOH in Et2O (30 µL, 15 µmol) were then
added to the mixture. The reaction mixture was stirred at -35
°C for 1.5 h and the reaction was monitored by TLC (developed
by toluene/EtOAc, 2:1). When all 16 was reacted, tetrasaccha-
ride building block 22 (0.26 g, 0.13 mmol) was added, followed
by an additional NIS (29 mg, 0.13 mmol) and 0.5 M TfOH in
Et2O (20 µL, 10 µmol). The reaction temperature was raised
to -20 °C and stirred for another 2.5 h. The reaction was
quenched with sat. NaHCO3 and solid Na2S2O3. MS were
filtered off and the filtrate was washed with sat. Na2S2O3, sat.
NaHCO3, H2O, and brine, dried (MgSO4), and concentrated
for flash column chromatography (toluene/CH2Cl2/EtOAc,
4:2:3). Octasaccharide 24 (0.14 g, 35% with respect to 18) was
obtained as a white glassy solid. For compound 24: 1H NMR
(600 MHz, CDCl3) δ 7.49-7.27 (m, 55H; aromatic), 6.45-6.34
(m, 3H), 5.42-4.91 (m, 15H), 4.90-4.69 (m, 10H), 4.65-4.41
(m, 20H), 4.11-3.73 (m, 30H), 3.70-3.50 (m, 15H), 3.03-2.87
(m, 3H; Lev-CH2), 2.69-2.51 (m, 6H; Lev-CH2), 2.47-2.32 (m,
8H; Lev-CH2, aglycon-CH2, MeCdO), 2.30 (s, 3H; MeCdO),
2.19 (s, 3H; MeCdO), 2.08 (s, 3H; MeCdO), 2.07 (s, 3H;
MeCdO), 2.06 (s, 3H; MeCdO), 2.04 (s, 3H; MeCdO), 1.95 (s,
3H; MeCdO), 1.94 (s, 3H; MeCdO), 1.93 (s, 3H; MeCdO),
1.76-1.63 (m, 4H; aglycon-CH2), 1.50-1.42 (m, 2H; aglycon-
CH2); 13C NMR (125 MHz, CDCl3) δ 209.64, 209.34, 174.08,
170.79, 170.70, 170.63, 170.07, 170.05, 169.96, 169.25, 154.62,
154.44, 154.23, 138.83, 138.62, 137.90, 137.84, 137.80, 137.64,
137.61, 128.48, 128.40, 128.33, 128.30, 128.10, 128.05, 127.96,
127.92, 127.72, 127.69, 127.60, 127.18, 127.14, 101.39, 101.23,
101.18, 100.27, 100.11, 95.82, 95.50, 79.64, 78.05, 77.73, 76.94,
75.57, 75.30, 75.00, 74.73, 74.65, 74.57, 74.21, 74.07, 73.99,
73.71, 73.65, 73.50, 73.34, 73.30, 73.25, 73.05, 72.90, 72.75,
72.39, 70.90, 70.34, 69.57, 69.25, 68.05, 67.87, 67.76, 66.70,
60.56, 57.37, 56.42, 55.79, 51.43, 37.62, 37.39, 33.71, 30.14,
29.86, 29.84, 28.92, 27.78, 27.60, 25.18, 24.28, 20.69, 20.61,
20.51, 20.46; MALDI-TOF MS calcd for C173H200Cl12N4O60Na
(M + Na)+ 3736, found 3736.
Su p p or tin g In for m a tion Ava ila ble: Spectral data for all
the compounds 1-3, 6-8, 10-14, 16-18, and 21-24. This
material is available free of charge via the Internet at
http://pubs.acs.org.
J O0206420
2142 J . Org. Chem., Vol. 68, No. 6, 2003