Stereoselective synthesis of Di- and trisaccharide fucoidan fragments bearing -D-glucuronic acid residue

Article abstract of DOI:10.1080/07328300802419865

The first stereoselective synthesis of disaccharide -d-GlcA-(1 2) - l-Fuc-OPr (1), trisaccharide (1 3) - l-Fuc-[ -d-GlcA-(1 2)]- -l-Fuc-OPr (3), and their selectively O-sulfated derivatives 2 and 4 bearing sulfo-groups at O(4) of the fucose units has been

Full text of DOI:10.1080/07328300802419865

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Stereoselective Synthesis of Di- and
Trisaccharide Fucoidan Fragments
Bearing α-D-Glucuronic Acid Residue
Natalia S. Zlotina a , Nadezhda E. Ustyuzhanina a , Alexey A.
Grachev a , Alexey G. Gerbst a & Nikolay E. Nifantiev a
a Laboratory of Glycoconjugate Chemistry , N.D. Zelinsky Institute of
Organic Chemistry, Russian Academy of Sciences , Moscow, Russia
Published online: 10 Dec 2008.
To cite this article: Natalia S. Zlotina , Nadezhda E. Ustyuzhanina , Alexey A. Grachev , Alexey G.
Gerbst & Nikolay E. Nifantiev (2008) Stereoselective Synthesis of Di- and Trisaccharide Fucoidan
Fragments Bearing α-D-Glucuronic Acid Residue , Journal of Carbohydrate Chemistry, 27:8-9, 429-445,
DOI: 10.1080/07328300802419865
To link to this article: http://dx.doi.org/10.1080/07328300802419865
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Journal of Carbohydrate Chemistry, 27:429–445, 2008
ꢀC
Copyright Taylor & Francis Group, LLC
ISSN: 0732-8303 print / 1532-2327 online
DOI: 10.1080/07328300802419865
Stereoselective Synthesis of Di-
and Trisaccharide Fucoidan
Fragments Bearing
α-D-Glucuronic Acid Residue*
Natalia S. Zlotina, Nadezhda E. Ustyuzhanina,
Alexey A. Grachev, Alexey G. Gerbst, and Nikolay E. Nifantiev
Laboratory of Glycoconjugate Chemistry, N.D. Zelinsky Institute of Organic Chemistry,
Russian Academy of Sciences, Moscow, Russia
The first stereoselective synthesis of disaccharide α-D-GlcA-(1 → 2)-α-L-Fuc-OPr (1),
trisaccharide (1 → 3)-α-L-Fuc-[α-D-GlcA-(1 → 2)]-α-L-Fuc-OPr (3), and their selectively
O-sulfated derivatives 2 and 4 bearing sulfo-groups at O(4) of the fucose units has been
performed. Compounds 1–4 represent the fragments of the chain of the fucoidan from
Cladosiphon okamuranus brown seaweed. Glucuronylation by a series of selectively O-
acetylated glucuronyl bromides was studied to obtain the target products. It has been
found that 3-O-acetylated donor 6 is the most efficient agent for α-glycoside bond for-
mation that can be connected with intramolecular remote participation of 3-O-acetyl
group favoring α-stereoselectivity.
Keywords Fucoidan, Cladosiphon okamuranus brown seaweed, fucosylation, glu-
curonylation, O-sulfation
INTRODUCTION
Brown seaweed polysaccharide fucoidans have been shown to be active an-
ticoagulant agents[2–5] as well as effective inhibitors of angiogenesis devel-
opment, P- and L-selectin-mediated inflammation, and some other biological
processes (see papers[3–5] and references therein). The backbones of fucoidans
consist mainly of partially sulfated α-L-fucose residues, but the exact structure
Received June 2, 2008; accepted August 19, 2008.
*Synthesis, NMR, and Conformational Studies of Fucoidan Fragments. Part 10. For
Part 9 see [1].
Address correspondence to Professor Nikolay E. Nifantiev, Laboratory of Glycoconju-
gate Chemistry, N.D. Zelinsky Institute of Organic Chemistry, Russian Academy of Sci-
ences, Leninsky Prospect, 47, Moscow B-334, 119991 Russia. E-mail: nen@ioc.ac.ru
429

N. S. Zlotina et al.
430
Figure 1: Structures of studied ogliosaccharides.
of these polysaccharides could not be determined in all details because of ir-
regularity and heterogeneity of their chains. Structural features of fucoidans
such as the types of glycoside bonds, pattern of sulfation, presence of nonfu-
cose monosaccharide residues, branched fragments, and other characteristics
depend on algae species. Recently we demonstrated that the fucoidans from
different brown seaweeds could vary dramatically in the profile of their biolog-
ical activity.[5] Thus, the polysaccharide from Cladosiphon okamuranus effec-
tively inhibits inflammation but not blood coagulation processes, whereas fu-
coidan from Laminaria saccharina possesses both anti-inflammatory and an-
ticoagulant activities. These two polysaccharides have similar backbones built
up of (1 → 3)-linked α-L-fucose residues, but differ in their branching parts.
Thus, the fucoidan from L. saccharina contains α-L-fucose or sulfo-group as a
substituent at O(2) of the fucose residues in the main chain,[6] whereas the
fucoidan from C. okamuranus bears the (1 → 2)-α-D-glucuronic acid unit as a
substituent.[7]
To determine the structural features of fucoidans responsible for their spa-
tial organization and biological properties, we carry out systematic synthesis,
NMR, and conformational analysis of fucoidan fragments and study their bio-
logical activity.[8,9] In this communication we report the first regio- and stere-
oselective synthesis of nonsulfated and selectively O-sulfated di- and trisac-
charides 1–4 (Fig. 1) related to the fragments of fucoidan from C. okamuranus.
RESULTS AND DISCUSSION
The most difficult aspect in the synthesis of target compounds 1–4 was the
stereoselective introduction of α-D-glucuronic residue. In order to choose an
efficient glucuronosyl donor for this process, model glycosylation of allyl 3,4-
O-isopropylidene-α-L-fucopyranoside (8)[10] with fully benzylated (5) and par-
tially O-acetylated 2-O-benzylglucuronosyl bromides (6, 7) was studied. Based
on our previous results,[11–13] we anticipated that the remote stereocontrolling
effect of the 3-O-acetyl group would favor α-glycoside formation.

Stereoselective Synthesis of Di- and Trisaccharide Fucoidan Fragments
431
Scheme 1. (i) HBr, AcOH, Ac2O, CH2Cl2, 1.5h.
Compounds 6 and 7 were prepared in yields of 59% and 25%, respectively,
by treatment of fully benzylated precursor 5[14] with HBr in acetic acid in the
presence of Ac2O (Sch. 1). 3-O-Acetylated and 3,4-di-O-acetylated glucurono-
syl bromides 6 and 7 were easily separated by column chromatography. The
presence of the acetyl group at O(3) in 6 was confirmed by the downfield shift
1
of the corresponding H(3) signal (5.58 ppm) in the H NMR spectrum, while
the low-field signals for H(3) and H(4) (5.50 and 5.10 ppm, respectively) in the
spectrum of 7 confirmed its 3,4-di-O-acetylation.
Glycosylation of compound 8 with fully benzylated bromide 5 in the pres-
ence of AgOTf gave a mixture of α- and β-disaccharides 9 and 10 in a ratio of 2:1
and total yield of 89% (Sch. 2). The isomers were easily separated by column
chromatography on silica gel. The configuration of the glycoside bond formed
was confirmed by corresponding characteristic coupling constant values J1,2
(3.5 Hz for α-isomer, 7.8 Hz for β-isomer) in the 1H NMR spectra.
Glucuronylation of fucoside 8 by selectively O-acetylated bromides 6 and
7 proceeded more α-stereoselectively. Thus, 3-O-acetylated bromide 6 pro-
duced α-linked disaccharide 11 exclusively, whereas glycosylation with 3,4-di-
O-acetylated bromide 7 under the same conditions was less stereoselective and
gave a mixture of α- and β-isomers 12 and 13 in a ratio of 5:1.
We assumed that the higher α-stereoselectivity in glycosylation with acety-
lated donors 6 and 7 as compared to fully benzylated donor 5 is connected
with the remote participation of the 3-O-acetyl group resulting in the for-
mation of the stabilized glycosyl cation II (Fig. 2). Nucleophilic attack on
this cation is favored from the α-side, while in the case of the nonstabi-
lized intermediate I from fully benzylated donor 5, it is possible both from
α- and β-sides. Efficiency of remote participation of the 3-O-acetyl group was
Scheme 2. (i) AgOTf, CH2Cl2, −30◦C.

N. S. Zlotina et al.
432
Figure 2 Delocalization of positive charge in the glycosyl cation I via intramolecular
participation of acetyl group at O(3) (cation II) and O(4) (cation III).
confirmed by molecular calculations[13]; a similar stereo-effect has been ob-
served earlier in the reactions with fucosyl,[1,11] glucosyl,[12,13] xylosyl,[13,15] and
mannuronosyl[16] donors.
3,4-Di-O-acetylated bromide 7 is a less α-selective glycosylating agent than
mono-3-O-acetylated bromide 6 (Sch. 2). This could be connected with the
existence of the equilibrium between two sorts of the stabilized cationic in-
termediates II and III (Fig. 2). The interaction of the latter with a glycosyl ac-
ceptor proceeds preferentially from the β-side to give a β-linked disaccharide.
Similar stereocontrolling effects of O-acetyl groups were observed in glycosy-
lation by selectively 3-O- and 4-O-acetylated di-O-benzyl-α-D-mannuronosyl
thioglycosides.[16] The possibility of the formation of the intermediates of type
II and III and the comparison of the efficiencies of both stabilization effects as
well as of possible participation of a methoxycarbonyl substituent[17] at C(5)
are under investigation in this laboratory by computer calculations according
to the described procedure[11] with the use of special series of selectively sub-
stituted glucuronic acid derivatives and will be reported elsewhere.
Removal of the isopropylidene group in compound 9 by acidic hydrolysis
gave quantitatively corresponding diol 14, which was subjected to catalytic hy-
drogenolysis accompanied by the reduction of the allyl to the propyl group to
give the target disaccharide 1 in 61% yield (Sch. 3). To synthesize its sulfated
derivative 2, diol 14 was subjected to regioselective 3-O-benzylation using the
stannylene procedure[18] to give the disaccharide 15 in a yield of 84%. Its sul-
fation with the Py·SO3 complex and further catalytic hydrogenolysis followed
by saponification of the ester group in the compound 16 gave disaccharide 2.
The presence of a sulfo-group at O(4) in this compound was confirmed by a
characteristic downfield chemical shift of the H(4) signal (3.85 → 4.64 ppm) in
the comparison of the 1H NMR spectra for 1 and 2.
Disaccharides 11 and 12 are convenient synthetic blocks for assembling
larger oligosaccharides carrying glycosylated glucuronic acid. Particularly,
such structural motif represented by the terminal α-L-Fucf -(1 → 4)-α-D-GlcAp

Stereoselective Synthesis of Di- and Trisaccharide Fucoidan Fragments
433
Scheme 3. (i) CF3COOHaq, CH2Cl2; (ii) (a) H2, Pd/C; (b) 0.4 M NaOH; (iii) Bu2SnO, toluene;
BnBr, Bu4NBr; (iv) Py·SO3, DMF, Py, Amberlite (Na+).
disaccharide fragment was recently found[19] in the fucoidan from the brown
alga Chordaria flagelliformis.
Diol 14 was chosen as glycosyl acceptor block for the synthesis of trisac-
charides 3 and 4. It was supposed that this compound could be regioselectively
3-O-glycosylated with the use of one equivalent of fucosyl donor 17[1] due to the
difference in the reactivity of equatorial and axial OH-groups at C(3) and C(4).
However, this reaction afforded only unexpected 4-O-fucosylated trisaccharide
18 (Sch. 4). This result could be explained by decreasing of the reactivity of
the equatorial hydroxyl group at C(3) in diol 14 due to electronic and steric
effects of the neighboring 2-O-glucuronosyl residue. The structure of 18 was
1
confirmed by H NMR spectroscopy after its transformation into correspond-
ing acetylated derivative 19; the downfield location of the signal for H(3) (5.42
ppm) revealed the presence of the free OH-group at C(3) in 18.
To avoid the (1 → 4)-glycoside bond formation, diol 14 was converted into
4-O-acetylated derivative 20; its glycosylation with fucosyl donor 17 provided
the desired (1 → 3)-α-linked trisaccharide 21 in 78% yield (Sch. 5). The α-
configuration of the glycoside bond formed was confirmed by the character-
1
ꢁꢁ ꢁꢁ
istic coupling constant value J1 ,2 (3.5 Hz) in the H NMR spectrum of 21.
Scheme 4. (i) 0.1 M TMSOTf, CH2Cl2, –30◦C; (ii) AcCl, Py, CH2Cl2.

N. S. Zlotina et al.
434
Scheme 5. (i) CH3C(OEt)3, TsOH, CH2Cl2; AcOHaq, CH2Cl2; (ii) 0.1 M TMSOTf, CH2Cl2, –30◦C;
(iii) (a) H2, Pd/C; (b) 0.4 M NaOH.
Catalytic hydrogenolysis and saponification of acyl groups in compound 21
gave the target trisaccharide 3 in yield of 79%.
For the synthesis of disulfated trisaccharide 4, all acyl groups in the com-
pound 21 were saponified, and the carboxylic moiety of the uronic acid was es-
terified with excess of CH2N2 to give corresponding methyl uronate 22 bearing
three hydroxyl groups (Sch. 6). Subsequent stannylene activation and regiose-
lective benzoylation of the equatorial hydroxyl group in compound 22 afforded
3ꢁꢁ-O-benzoylated trisaccharide 23. In the course of the reaction the formation
of butyl uronate 24 was observed. Compounds 23 and 24 were separated by col-
1
umn chromatography and characterized by H NMR and mass-spectral data.
Sulfation of the mixture of uronates 23 and 24 and further deprotection of
products 25 and 26 gave the target trisaccaride 4 in a yield of 70%. The pres-
ence of the sulfate groups at C(4) and at C(4ꢁꢁ) in compound 4 was confirmed
by the downfield chemical shifts of the H(4) and H(4ꢁꢁ) signals to 4.87 ppm and
4.58 ppm, respectively, in the 1H NMR spectrum.
Additionally, we studied the possibility of the use of O-benzylated glu-
curonic lactone 29 as a glucuronosyl donor. It was synthesized from ethyl thio-
glycoside 27[20] by transformation into acid 28 followed by its intramolecular
cyclization in 92% yield (Sch. 7). The structure of 29 was confirmed by 1H NMR
Scheme 6. (i) LiOH, EtOH; CH2N2, CH2Cl2, (ii) Bu2SnO, toluene; BzCl; (iii) SO3·Py, DMF, Py,
Amberlite (Na+); (iv) (a) H2, Pd/C; (b) 0.4 M NaOH.

Stereoselective Synthesis of Di- and Trisaccharide Fucoidan Fragments
435
Scheme 7. (i) LiOH, EtOH; (ii) NIS, TfOH, CH2Cl2.
data. Particularly, the 1C4 conformation of the pyranose ring was confirmed by
small (<1 Hz) coupling constant values J1,2, J2,3, J3,4, and J4,5
.
Unfortunately, we failed to involve lactone 29 into the glycosylation reac-
tion. The use of a number of Lewis acids (SnCl4, TMSOTf, BF3·Et2O, TiCl4)
or TfOH as promoters at –30◦C led only to destruction of the acceptor 8 after
a few hours without activating lactone 29, which remained unchanged in the
reaction mixtures.
CONCLUSIONS
The first regio- and stereoselective synthesis of di- and trisaccharides 1–4 re-
lated to the fucoidan from Cladosiphon okamuranus algae has been performed.
The efficiency of a series of glucuronosyl donors was compared to select the bet-
ter agent for stereoselective α-glycoside bond formation. It was shown that the
presence of an acetyl group at O(3) in the glucuronosyl donor strongly favored
the formation of the desired α-isomer. The results of conformational analysis
and studies of biological activity of compounds synthesized will be published
elsewhere.
EXPERIMENTAL
TLC was performed on Silica Gel 60 F254 (Merck) with detection by char-
ring with H3PO4. Column chromatography was performed on Silicagel 60–
200 µm (Fluka). Gel chromatography was performed on a Sephadex G-10 col-
umn (2 × 20 cm) by elution with water at a flow rate of 1 mL/min. Optical
rotations were determined with a Jasco DIP-360 digital polarimeter at 26 to
30◦C. All solvents used for syntheses were purified according to conventional
procedures.[21] NMR spectra for protected derivatives were recorded on Bruker
WM-250 and AM-300 spectrometers at 303 K. NMR spectra for oligosaccha-
rides 1–4 were recorded in D2O on a Bruker DRX-500 spectrometer. Gradient-
enhanced 2D gCOSY, gNOESY, and gHSQC experiments as well as TOCSY
experiments were used for resonance assignment. Mass spectra of the com-
pounds synthesized were recorded on a Finnigan LCQ mass spectrometer.

N. S. Zlotina et al.
436
Methyl 3-O-acetyl-2,4-di-O-benzyl-α-D-glucopyranosyluronate
bromide (6) and Methyl 3,4-di-O-acetyl-2-O-benzyl-α-D-
glucopyranosyluronate bromide (7)
To a solution of glucuronosyl bromide 5 (600 mg, 1.1 mmol) in CH2Cl2(5
mL), 0.01 M solution of HBr in acetic acid (0.5 mL) and Ac2O (0.1 mL) were
added at 0◦C. The mixture was kept for 1.5 h at 0◦C, then diluted with
CH2Cl2(50 mL) and washed with saturated aqueous solution of NaHCO3 (50
mL) and water (50 mL). The organic layer was separated and concentrated,
and column chromatography of the residue gave bromide 6 (324 mg, 59%) and
bromide 7 (122 mg, 25%).
Data for bromide 6: Rf = 0.5 (Tol:EtOAc, 7:1), 1H NMR (250 MHz,
CDCl3) δ 2.02 (s, 3H, CH3), 3.50 (dd, 1H, J1,2 = 3.7 Hz, J2,3 = 9.5 Hz, H-2),
3.75 (s, 3H, CH3), 3.82 (t, 1H, J3,4=J4,5
=
9.5 Hz, H-4), 4.44–4.70 (m, 5H, H-5,
2CH2Ph), 5.58 (t, 1H, H-3), 6.31 (d, 1H, H-1), 7.20–7.40 (m, 10H, 2Ph). ESI
[M+Na]+ 515.1.
Data for the bromide 7: Rf = 0.3 (Tol:EtOAc, 7:1), 1H NMR (250 MHz,
CDCl3) δ 2.02 (s, 6H, 2CH3), 3.58 (dd, 1H, J1,2 = 3.7 Hz, J2,3 = 9.7 Hz, H-
2), 3.73 (s, 3H, CH3), 4.50–4.65 (m, 3H, H-5, CH2Ph), 5.10 (t, 1H, J3,4 = J4,5
=
9.7 Hz, H-4), 5.50 (t, 1H, H-3), 6.31 (d, 1H, H-1), 7.20–7.40 (m, 5H, Ph). ESI
[M+Na]+ 467.0.
Allyl 3,4-O-isopropylidene-2-O-(methyl 2,3,4-tri-O-benzyl-α- and β-
D-glucopyranosyl uronate)-α-L-fucopyranosides (9 and 10)
A solution of glucuronosyl bromide 5 (28 mg, 0.052 mmol) and allyl fucoside
˚
8 (13 mg, 0.052 mmol) in CH2Cl2 (2 mL) was stirred with molecular sieves (4A)
(200 mg) under Ar for 30 min. Then AgOTf (15 mg, 0.057 mmol) was added at
–30◦C, and the mixture was stirred for 15 min at –30◦C, and then Et3N (0.1
ml) was added. The sieves and solid were filtered off through a Celite pad,
and the filtrate was washed with 1 M Na2S2O3solution (50 mL) and water (50
mL). The organic layer was concentrated, and column chromatography of the
residue gave disaccharides 9 (23 mg, 61%) and 10 (10 mg, 28%).
Data for compound 9: [α]D –26◦ (EtOAc, c = 1), Rf = 0.7 (Toluene:EtOAc
3:1). 1H NMR (300 MHz, CDCl3) δ 1.35 (d, 3H, J5,6 = 5.7 Hz, 3H-6), 1.37 and
1.55 (2s, 6H, 2CH3), 3.61 (dd, 1H, J1 ,2 = 3.5 Hz, J2 ,3 = 9.8 Hz, H-2ꢁ), 3.70 (s,
3H, CH3), 3.72–3.76 (m, 2H, H-2, H-4ꢁ), 4.04–4.70 (m, 13H, H-3, H-4, H-5, H-3ꢁ,
H-5ꢁ, 3CH2Ph, CH2 = CHCH2O), 4.95 (d, 1H, J1,2 = 3.2 Hz, H-1), 5.20 and 5.37
(m, 2H, CH2 = CHCH2O), 5.26 (d, 1H, H-1ꢁ), 5.95 (m, 1H, CH2 =CHCH2O),
7.20–7.45 (m, 15H, 3Ph).
ꢁ
ꢁ
ꢁ
ꢁ
Anal. Calcd for C40H48O11: C, 68.16; H, 6.86. Found: C, 68.19; H, 6.90.
Data for compound 10: [α]D –64◦ (EtOAc, = 1); Rf = 0.6 (Toluene:EtOAc,
3:1). 1H NMR (300 MHz, CDCl3) δ 1.33 (d, 3H, J5,6 = 5.7 Hz, 3H-6), 1.37 and
1.57 (2s, 6H, 2CH3), 3.60 (dd, 1H, J1 ,2 = 7.8 Hz, J2 ,3 = 9.8 Hz, H-2ꢁ), 3.70 (s,
3H, CH3), 4.00–4.70 (m, 15H, H-2, H-3, H-4, H-5, H-3ꢁ, H-4ꢁ, H-5ꢁ, 3CH2Ph,
ꢁ
ꢁ
ꢁ
ꢁ

Stereoselective Synthesis of Di- and Trisaccharide Fucoidan Fragments
437
CH2 =CHCH2O), 4.58 (d, 1H, J1 ,2 = 7.8 Hz, H-1ꢁ), 4.98 (d, 1H, J1,2 = 3.6 Hz,
H-1), 5.24 and 5.37 (m, 2H, CH2 = CHCH2O), 5.81 (m, 1H, CH2 = CHCH2O),
7.20–7.48 (m, 15H, 3Ph).
ꢁ
ꢁ
Allyl 3,4-O-isopropylidene-2-O-(methyl 3-O-acetyl-2,4-di-O-
benzyl-α-D-glucopyranosyl uronate)-α-L-fucopyranoside (11)
Glycosylation of allyl fucoside 8 (10 mg, 0.041 mmol) with glucuronosyl
bromide 6 (20 mg, 0.041 mmol) as described for the synthesis of compounds 9
and 10 gave disaccharide 11 (21 mg, 80%): [α]D –22◦ (EtOAc, c = 1), Rf = 0.4
(Toluene:EtOAc 4:1). 1H NMR (300 MHz, CDCl3) δ 1.32 (d, 3H, J5,6 = 5.7 Hz,
ꢁ
ꢁ
3H-6), 1.37 and 1.50 (2s, 6H, 2CH3), 1.98 (s, 3H, CH3), 3.52 (dd, 1H, J1 ,2
=
3.5 Hz, J2 ,3 = 9.8 Hz, H-2ꢁ), 3.70 (s, 3H, CH3), 3.74–3.78 (m, 2H, H-2, H-4ꢁ),
4.05–4.70 (m, 10H, H-3, H-4, H-5, H-5ꢁ, 2CH2Ph, CH2 = CHCH2O), 4.88 (d, 1H,
J1,2 = 3.6 Hz, H-1), 5.20 and 5.35 (m, 2H, CH2 = CHCH2O), 5.30 (d, 1H, H-1ꢁ),
ꢁ
ꢁ
5.56 (t, 1H, J3 ,4 = 9.8 Hz, H-3ꢁ), 5.59 (m, 1H, CH2 =CHCH2O), 7.20–7.40 (m,
10H, 2Ph). ESI [M+Na]+ 679.4.
ꢁ
ꢁ
Allyl 3,4-O-isopropylidene-2-O-(methyl 3,4-di-O-acetyl-2-O-
benzyl-α- and β-D-glucopyranosyl uronate)-α-L-
fucopyranosides (12 and 13)
Glycosylation of allyl fucoside 8 (16 mg, 0.067 mmol) with glucuronyl bro-
mide 7 (30 mg, 0.067 mmol) as described for the synthesis of compounds 9 and
10 gave a mixture of disaccharides 12 and 13 in a ratio of 5:1 (35 mg, 85%).
The ratio of the isomers was established by NMR data of the mixture. Rf =
0.25 (Toluene:EtOAc, 4:1).
1
Data for compound 12: H NMR (300 MHz, CDCl3) δ 1.35 (d, 3H, J5,6
=
5.7 Hz, 3H-6), 1.37 and 1.55 (2s, 6H, 2CH3), 2.00 and 2.02 (2s, 6H, 2CH3),
3.60 (dd, 1H, J1 ,2 = 3.5 Hz, J2 ,3 = 9.8 Hz, H-2ꢁ), 3.71 (s, 3H, CH3), 3.75
(dd, 1H, J1,2 = 3.4 Hz, J2,3 = 9.8 Hz, H-2), 3.90–4.20 (m, 4H, H-4, H-5,
CH2 = CHCH2O), 4.39 (dd, 1H, J3,4 = 5.9 Hz, H-3), 4.46 (d, 1H, H-5ꢁ), 4.65 (q,
ꢁ
ꢁ
ꢁ
ꢁ
2H, CH2 = CHCH2O), 4.90 (d, 1H, H-1), 5.05 (t, 1H, J3 ,4 = 9.8 Hz, H-4ꢁ), 5.20
and 5.37 (m, 2H, CH2 = CHCH2O), 5.25 (d, 1H, H-1ꢁ), 5.50 (t, 1H, H-3ꢁ), 5.95
ꢁ
ꢁ
(m, 1H, CH2 =CHCH2O), 7.20–7.45 (m, 5H, Ph).
1
Data for compound 13: H NMR (300 MHz, CDCl3) δ 1.35 (d, 3H, J5,6
=
5.7 Hz, 3H-6), 1.37 and 1.55 (2s, 6H, 2CH3), 1.91 and 2.00 (2s, 6H, 2CH3), 3.55
(dd, 1H, J1 ,2 = 7.5 Hz, J2 ,3 = 9.8 Hz, H-2ꢁ), 3.71 (s, 3H, CH3), 3.75 (dd, 1H,
J1,2 = 3.4 Hz, J2,3 = 9.8 Hz, H-2), 3.90–4.20 (m, 4H, H-4, H-5, CH2 =CHCH2O),
4.39 (dd, 1H, J3,4 = 5.9 Hz, H-3), 4.46 (d, 1H, H-5ꢁ), 4.60 (d, 1H, H-1ꢁ), 4.65
ꢁ
ꢁ
ꢁ
ꢁ
ꢁ
ꢁ
(q, 2H, CH2 =CHCH2O), 4.95 (d, 1H, H-1), 5.05 (t, 1H, J3 ,4 = 9.8 Hz, H-
4ꢁ), 5.20 and 5.37 (m, 2H, CH2 = CHCH2O), 5.50 (t, 1H, H-3ꢁ), 5.80 (m, 1H,
CH2 = CHCH2O), 7.20–7.45 (m, 5H, Ph). ESI [M+Na]+ 631.2.

N. S. Zlotina et al.
438
Allyl 2-O-(methyl 2,3,4-tri-O-benzyl-α-D-glucopyranosyluronate)-
α-L-fucopyranoside (14)
To a solution of the disaccharide 9 (95 mg, 0.135 mmol) in H2Cl2 (2 mL),
90% aqueous solution of CF3COOH (0.1 mL) was added. The mixture was kept
for 15 min, then concentrated and coevaporated with toluene (10 mL). Flash
chromatography of the residue gave diol 14 (81 mg, 90%): [α]D –16◦ (c = 1,
EtOAc), Rf = 0.3 (Toluene:EtOAc, 2:1). 1H NMR (300 MHz, CDCl3) δ 1.33
(d, 3H, J5,6 = 5.6 Hz, 3H-6), 3.60–3.65 (m, 2H, H-2, H-2ꢁ, H-4ꢁ), 3.70 (s, 3H,
CH3), 3.86 (t, 1H, J3 ,4 = 9.5 Hz, H-4ꢁ), 3.99 (q, 1H, H-5), 4.06–4.16 (m, 4H,
ꢁ
ꢁ
ꢁ
H-3, H-3 , CH2 =CHCH2O), 4.47 (d, 1H, J4 ,5 = 10.1 Hz, H-5ꢁ), 4.63–4.93 (m,
8H, H-1, H-1ꢁ, 3CH2Ph), 5.20 and 5.35 (m, 2H, CH2 =CHCH2O), 5.98 (m, 1H,
CH2 =CHCH2O), 7.20–7.40 (m, 15H, 3Ph).
ꢁ
ꢁ
Anal. Calcd for C37H44O11: C, 66.85; H, 6.67. Found: C, 66.86; H, 6.70.
Allyl 3-O-benzyl-2-O-(methyl 2,3,4-tri-O-benzyl-α-D-
glucopyranosyluronate)-α-L-fucopyranoside (15)
To a solution of diol 14 (30 mg, 0.045 mmol) in toluene (5 mL), Bu2SnO
(12 mg, 0.050 mmol) was added. The mixture was refluxed with azeotropic
removal of water for 45 min to the volume of 1 mL and then cooled to 25◦C.
BnBr (5 µL, 0.05 mmol) and Bu4NBr (16 mg, 0.05 mmol) were added, and the
mixture was kept for 1 h at 25◦C. Column chromatography of the mixture gave
the disaccharide 15 (29 mg, 84%): Rf = 0.4 (Toluene:EtOAc, 3:1). 1H NMR (300
ꢁ
ꢁ
MHz, CDCl3) δ 1.24 (d, 3H, J5,6 = 5.6 Hz, 3H-6), 3.48 (dd, 1H, J1 ,2 = 3.6 Hz,
J2 ,3 = 9.5 Hz, H-2ꢁ), 3.70–3.75 (m, 4H, H-2, H-4, H-5, H-4ꢁ), 3.70 (s, 3H, CH3),
ꢁ
ꢁ
3.90 (dd, 1H, J3,4 = 9.5 Hz, H-3), 4.06–4.16 (m, 3H, H-3ꢁ, CH2 =CHCH2O), 4.53
(d, 1H, J4 ,5 = 10.1 Hz, H-5ꢁ), 4.63–4.93 (m, 8H, 4CH2Ph), 5.01 (d, 1H, J1,2
=
ꢁ
ꢁ
3.3 Hz, H-1), 5.09 (d, 1H, H-1ꢁ), 5.20 and 5.45 (m, 2H, CH2 =CHCH2O), 5.98
(m, 1H, CH2 = CHCH2O), 7.20–7.40 (m, 20H, 4Ph). ESI [M+Na]+ 777.3.
Allyl 3-O-acetyl-2-O-(methyl 2,3,4-tri-O-benzyl-α-D-
glucopyranosyl uronate)-4-O-(2-O-benzyl-3-O-acetyl-4-O-
benzoyl-α-L-fucopyranosyl)-α-L-fucopyranoside (19)
A solution of fucosyl trichloroacetimidate 17 (13 mg, 0.024 mmol) and diol
14 (16 mg, 0.024 mmol) in CH2Cl2 (2 mL) was stirred with molecular sieves
˚
(4A) (200 mg) under Ar for 30 min. Then 0.1 M solution of TMSOTf in CH2Cl2
(10 µl) was added at –40◦C. The mixture was stirred for 1 h at –30◦C, then
quenched with Et3N (0.1 mL), filtered through Celite, and concentrated. Col-
umn chromatography of the residue gave trisaccharide 18, which was further
treated with a mixture of AcCl (0.1 mL) and Py (0.1 mL). The mixture was kept
for 10 min and then evaporated with toluene (5 mL). Column chromatography

Stereoselective Synthesis of Di- and Trisaccharide Fucoidan Fragments
439
of the residue gave compound 19 (20 mg, 74%): Rf = 0.5 (Toluene:EtOAc, 4:1).
1H NMR (300 MHz, CDCl3) δ 1.07 (d, 3H, J5 ,6 = 5.6 Hz, 3H-6ꢁꢁ), 1.31 (d, 3H,
ꢁꢁ ꢁꢁ
ꢁ
ꢁ
ꢁ
ꢁ
J5,6 = 5.6 Hz, 3H-6), 1.98 (s, 3H, CH3), 3.63 (dd, 1H, J1 ,2 = 3.8 Hz, J2 ,3 = 9.5
Hz, H-2 ), 3.70 (s, 3H, CH3), 3.74 (t, 1H, J3 ,4 = 9.5 Hz, H-4ꢁ), 3.8 (m, 3H, H-2,
ꢁ
ꢁ
ꢁ
H-4, H-5), 4.02 (dd, 1H, J1 ,2 = 3.4 Hz, J2 ,3 = 9.6 Hz, H-2ꢁꢁ), 4.07 (t, 1H, H-3ꢁ),
ꢁꢁ ꢁꢁ
ꢁꢁ ꢁꢁ
4.08–4.16 (m, 2H, CH2 =CHCH2O), 4.50 (d, 1H, J4 ,5 = 9.6 Hz, H-5ꢁ), 4.59 (q,
1H, H-5ꢁꢁ), 4.63–4.93 (m, 8H, 4CH2Ph), 5.04 (d, 1H, H-1ꢁ), 5.10 (2d, 2H, H-1,
H-1ꢁꢁ), 5.20 and 5.35 (m, 2H, CH2 =CHCH2O), 5.42 (d, 1H, H-3), 5.54 (dd, 1H,
H-3ꢁꢁ), 5.63 (d, 1H, H-4ꢁꢁ), 5.99 (m, 1H, CH2 =CHCH2O), 7.20–8.00 (m, 25H,
5Ph). ESI [M+Na]+ 1111.4.
ꢁ
ꢁ
Allyl 4-O-acetyl-2-O-(methyl 2,3,4-tri-O-benzyl-α-D-
glucopyranosyluronate)-α-L-fucopyranoside (20)
To a solution of disaccharide 14 (100 mg, 0.15 mmol) in CH2Cl2 (3 mL),
CH3C(OEt)3 (0.1 mL) and TsOH (15 mg) were added. The mixture was kept
for 1 h, and then 80% aqueous AcOH (0.5 mL) was added. After 30 min the
solution was evaporated with toluene (10 mL). Column chromatography of the
residue gave compound 20 (95 mg, 90%): [α]D –13◦ (EtOAc, = 1), Rf = 0.2
1
(Toluene:EtOAc, 4:1). H NMR (300 MHz, CDCl3) δ 1.14 (d, 3H, J5,6 = 5.6
Hz, 3H-6), 2.22 (s, 3H, CH3), 3.55 (dd, 1H, J1 ,2 = 3.6 Hz, J2 ,3 = 9.5 Hz, H-2ꢁ),
3.69 (dd, 1H, J1,2 = 3.5 Hz, J2,3 = 9.6 Hz, H-2), 3.70 (s, 3H, CH3), 3.73 (t, 1H,
ꢁ
ꢁ
ꢁ
ꢁ
J3 ,4 = 9.5 Hz, H-4ꢁ), 4.06 (t, 1H, H-3ꢁ), 4.08–4.16 (m, 3H, H-5, CH2 =CHCH2O),
ꢁ
ꢁ
ꢁ
4.23 (dd, 1H, H-3 ), 4.43 (d, 1H, J4 ,5 = 10.1 Hz, H-5ꢁ), 4.63–4.93 (m, 7H, H-1ꢁ,
3CH2Ph), 4.97 (d, 1H, H-1), 5.20 and 5.35 (m, 2H, CH2 =CHCH2O), 5.32 (d, 1H,
H-4), 5.98 (m, 1H, CH2 =CHCH2O), 7.20–7.40 (m, 15H, 3Ph). ESI [M+Na]+
729.3.
ꢁ
ꢁ
Allyl 4-O-acetyl-2-O-(methyl 2,3,4-tri-O-benzyl-α-D-
glucopyranosyluronate)-3-O-(2-O-benzyl-3-O-acetyl-4-O-
benzoyl-α-L-fucopyranosyl)-α-L-fucopyranoside (21)
Glycosylation of disaccharide 20 (100 mg, 0.142 mmol) with fucosyl
trichloroacetimidate 17 (78 mg, 0.144 mmol) as described for the preparation
of compound 18 gave trisaccharide 21 (134 mg, 87%): [α]D –160◦ (EtOAc, =1),
Rf = 0.4 (Toluene:EtOAc, 5:1). 1H NMR (300 MHz, CDCl3) δ 1.12 (d, 3H,
J5,6 = 5.6 Hz, 3H-6), 1.19 (d, 3H, J5 ,6 = 5.6 Hz, 3H-6ꢁꢁ), 1.98 (s, 3H, CH3),
ꢁꢁ ꢁꢁ
ꢁ
ꢁ
ꢁ
ꢁ
ꢁ
ꢁ
ꢁ
3.51 (dd, 1H, J1 ,2 = 3.7 Hz, J2 ,3 = 9.5 Hz, H-2 ), 3.68 (t, 1H, J3 ,4 = 9.5 Hz,
H-4ꢁ), 3.70 (s, 3H, CH3), 3.75 (dd, 1H, J1,2 = 3.2 Hz, J2,3 = 9.5 Hz, H-2), 3.83 (t,
1H, H-3 ), 4.01 (dd, 1H, J1 ,2 = 3.5 Hz, J2 ,3 = 9.6 Hz, H-2ꢁꢁ), 4.03 (d, 1H, H-4),
ꢁ
ꢁꢁ ꢁꢁ
ꢁꢁ ꢁꢁ
4.08–4.16 (m, 2H, CH2 =CHCH2O), 4.41 (dd, 1H, H-3), 4.47 (d, 1H, H-1ꢁ), 4.49
(d, 1H, J4 ,5 = 9.6 Hz, H-5ꢁ), 4.63–4.93 (m, 8H, 4CH2Ph), 4.98 (d, 1H, H-1), 5.01
(q, 1H, H-5ꢁꢁ), 5.31 (d, 1H, H-1ꢁꢁ), 5.20 and 5.35 (m, 2H, CH2 =CHCH2O), 5.45 (d,
ꢁ
ꢁ

N. S. Zlotina et al.
440
1H, H-4), 5.60 (d, 1H, H-4ꢁꢁ), 5.71 (dd, 1H, H-3ꢁꢁ), 5.99 (m, 1H, CH2 =CHCH2O),
7.20–8.00 (m, 25H, 5Ph). ESI [M+Na]+ 1111.3.
Allyl 2-O-(methyl 2,3,4-tri-O-benzyl-α-D-glucopyranosyl uronate)-
3-O-(2-O-benzyl-α-L-fucopyranosyl)-α-L-fucopyranoside (22)
Trisaccharide 21 (100 mg, 0.092 mmol) was dissolved in a mixture of EtOH
(5 mL), THF (5 mL), and H2O (1 mL) and the solution obtained was treated
with 2 N LiOH (10 mL). After stirring for 12 h, (5 mL) and 2 N NaOH (5 mL)
were added and the mixture was vigorously stirred for another 24 h. Then the
mixture was diluted with CHCl3 (100 mL) and washed with 1 M HCl (50 mL)
and water (50 mL). The organic layer was separated and concentrated. The
crude residue was dissolved in CH2Cl2 (2 mL) and 1.2 M solution of CH2N2
in Et2O (0.5 mL) was added. An excess of CH2N2 was removed by Ar current.
Flash chromatography of the residue gave methyl uronate 22 (62 mg, 75%):
1
[α]D –80◦ (CHCl3, = 1); Rf = 0.3 (Toluene:EtOAc, 2:1). H NMR (300 MHz,
CDCl3) δ 1.23 (d, 3H, J5 ,6 = 5.6 Hz, 3H-6ꢁꢁ), 1.32 (d, 3H, J5,6 = 5.6 Hz, 3H-
ꢁꢁ ꢁꢁ
ꢁ
ꢁ
6), 3.55 (dd, 1H, J1,2 = 3.5 Hz, J2,3 = 9.5 Hz, H-2), 3.64 (dd, 1H, J1 ,2 = 3.7
ꢁ
Hz, J2 ,3 = 9.5 Hz, H-2 ), 3.68 (t, 1H, J3 ,4 = 9.5 Hz, H-4ꢁ), 3.70 (s, 3H, CH3),
3.73 (m, 2H, H-4, H-4ꢁꢁ), 3.86 (m, 2H, H-3ꢁ, H-2ꢁꢁ), 3.90 (q, 1H, H-5), 3.95 (dd,
1H, H-3), 4.10–4.16 (m, 3H, H-3ꢁꢁ, CH2 =CHCH2O), 4.57 (m, 2H, H-5ꢁ, H-5ꢁꢁ),
4.63–4.93 (m, 8H, 4CH2Ph), 4.84 (d, 1H, H-1ꢁ), 4.95 (d, 1H, H-1), 5.08 (d, 1H,
H-1ꢁꢁ), 5.20 and 5.38 (m, 2H, CH2 =CHCH2O), 6.00 (m, 1H, CH2 =CHCH2O),
7.20–8.00 (m, 20H, 4Ph).
ꢁ
ꢁ
ꢁ
ꢁ
Anal. Calcd for C50H60O15: C, 66.65; H, 6.71. Found: C, 66.68; H, 6.70.
Allyl 2-O-(methyl 2,3,4-tri-O-benzyl-α-D-glucopyranosyl uronate)-
3-O-(2-O-benzyl-3-O-benzoyl-α-L-fucopyranosyl)-α-L-
fucopyranoside (23) and Allyl 2-O-(butyl
2,3,4-tri-O-benzyl-α-D-glucopyranosyl uronate)-3-O-(2-O-benzyl-
3-O-benzoyl-α-L-fucopyranosyl)-α-L-fucopyranoside (24)
To a solution of compound 22 (43 mg, 0.048 mmol) in toluene (5 mL),
Bu2SnO (18 mg, 0.072 mmol) was added. The mixture was refluxed with
azeotropic removal of water for 1 h to the volume of 1 mL and then cooled
to 25◦C. BzCl (6 µL, 0.05 mmol) was added and the mixture was kept at 60◦C
for 1 h. Column chromatography of the residue gave compound 23 (30 mg, 62%)
and compound 24 (7 mg, 15%).
Data for compound 23: Rf = 0.6 (Toluene:EtOAc, 2:1). 1H NMR (300 MHz,
CDCl3) δ 1.22 (d, 3H, J5 ,6 = 5.6 Hz, 3H-6ꢁꢁ), 1.30 (d, 3H, J5,6 = 5.6 Hz, 3H-
ꢁꢁ ꢁꢁ
6), 3.54 (dd, 1H, J1 ,2 = 3.7 Hz, J2 ,3 = 9.5 Hz, H-2ꢁ), 3.70–3.74 (m, 6H, H-4,
H-4ꢁ, H-4ꢁꢁ, CH3), 3.84 (dd, 1H, J1,2 = 3.3 Hz, J2,3 = 9.5 Hz, H-2), 3.90 (q, 1H,
ꢁ
ꢁ
ꢁ
ꢁ

Stereoselective Synthesis of Di- and Trisaccharide Fucoidan Fragments
441
H-5), 3.97 (t, 1H, H-3ꢁ), 4.10–4.16 (m, 3H, H-3, CH2 = CHCH2O), 4.59 (d, 1H,
H-5ꢁ), 4.63–4.93 (m, 9H, H-5ꢁꢁ, 4CH2Ph), 4.76 (d, 1H, H-1ꢁ), 4.92 (d, 1H, H-
1ꢁꢁ), 5.04 (d, 1H, H-1), 5.21 and 5.38 (m, 2H, CH2 =CHCH2O), 5.64 (dd, 1H,
H-3ꢁꢁ), 6.00 (m, 1H, CH2 =CHCH2O), 7.20–8.00 (m, 20H, 4Ph). ESI [M+Na]+
1027.4.
Data for compound 24: Rf = 0.7 (Toluene:EtOAc, 2:1). ESI [M+Na]+
1069.2.
Ethyl 2,3,4-tri-O-benzyl-1-thio-β-D-glucopyranoside Uronic
Acid (28)
To a solution of ethyl thioglycoside 27 (50 mg, 0.096 mmol) in CH2Cl2 (2
mL) and EtOH (2 mL), 2 M aqueous solution of LiOH (0.5 mL) was added. The
mixture was kept for 1 h at 25◦C, and then MeOH (4 mL) and Amberlite (H+)
were added to pH = 7. The resin was filtered off, and the solution was evap-
orated with toluene (5 mL). Column chromatography of the residue gave acid
28 (40 mg, 82%): Rf = 0.4 (CH2Cl2:EtOH, 10:1). 1H NMR (250 MHz, CDCl3)
δ
1.35 (t, 3H, CH3), 2.79 (m, 2H, CH2), 3.49 (t, 1H, J1,2 = J2,3 = 9.9 Hz, H-2), 3.71
(t, 1H, J3,4 = 9.9 Hz, H-3), 3.87 (t, 1H, J4,5 = 9.9 Hz, H-4), 3.96 (d, 1H, H-5), 4.57
(d, 1H, H-1), 4.65–5.01(m, 6H, 3CH2Ph), 7.15–7.40 (m, 15H, 3Ph). ESI [M+H]+
509.2, [M+Na]+ 531.2.
2,3,4-Tri-O-benzyl-β-D-glucopyranurono-1,6-lactone (29)
A solution of acid 28 (20 mg, 0.039 mmol) in CH2Cl2(2 mL) was stirred
˚
with molecular sieves (4A) (150 mg) under Ar for 30 min. Then NIS (10 mg,
0.04 mmol) and TfOH (0.03 mmol, 3 µL) were added to the mixture at –5◦C.
After stirring for 10 min at –5◦C, Et3N (0.1 mL) was added. The sieves were
filtered off through a Celite pad, and the filtrate was washed with 1 M Na2S2O3
solution (50 mL) and water (50 mL). The organic layer was concentrated, and
column chromatography of the residue gave the lactone 29 (16 mg, 92%): Rf =
1
0.6 (Toluene:Acetone, 10:1), H NMR (250 MHz, CDCl3) δ 3.50 (s, 1H, H-2),
3.66 (s, 1H, H-4), 3.70 (s, 1H, H-3), 4.30–4.44 (m, 2H, CH2Ph), 4.52 (s, 1H, H-
5), 4.58–4.70 (m, 4H, 2CH2Ph), 5.80 (s, 1H, H-1), 7.20–7.40 (m, 15H, 3Ph). ESI
[M+Na]+ 469.2.
Propyl 2-O-(α-D-glucopyranosyl Uronic Acid)-α-L-fucopyranoside,
Sodium Salt (1)
A mixture of diol 14 (50 mg, 0.075 mmol) and 10% Pd/C (20 mg) in EtOAc
(3.5 mL) and MeOH (3.5 mL) was stirred under H2 atmosphere for 2 h. Then
the catalyst was filtered off through a Celite pad, and the solution was con-
centrated. The residue was dissolved in distilled water (1 mL) and 2 N NaOH

N. S. Zlotina et al.
442
(0.5 ml) was added. The mixture was kept at 25◦C for 2 h, and then the disac-
charide 1 (25 mg, 82%) was isolated by gel chromatography on Sephadex G-10:
1
[α]D –27◦ (H2O, = 1). H NMR (500 MHz, D2O) δ 0.92 (t, 3H, CH3CH2CH2O),
1.21 (d, 3H, J5,6 = 5.3 Hz,3H-6), 1.67 (m, 2H, CH3CH2CH2O), 3.43 and 3.63
J4 ,5 = 9.3 Hz,H-4ꢁ), 3.58 (dd,
ꢁ
ꢁ
ꢁ
ꢁ
(2m, 2H, CH3CH2CH2O), 3.45 (t, 1H, J3 ,4
=
1H, J1 ,2 = 3.7 Hz, J2 ,3 = 9.3 Hz, H-2ꢁ), 3.73 (t, 1H, H-3ꢁ), 3.82 (dd, 1H, J1,2
=
ꢁ
ꢁ
ꢁ
ꢁ
3.9 Hz, J2,3 = 9.1 Hz, H-2), 3.85 (d, 1H, J3,4 = 3.3 Hz, H-4), 4.00 (d, 1H, H-
5ꢁ), 4.12 (dd, 1H, H-3), 4.20 (q, 1H, H-5), 5.02 (d, 1H, H-1), 5.10 (d, 1H, H-1ꢁ).
HRESIMS: m/z [M+Na]+ Calcd for C15H25Na2O11: 427.119. Found: 427.117.
Propyl 4-O-sulfonato-2-O-(α-D-glucopyranosyl Uronic
Acid)-α-L-fucopyranoside, Disodium Salt (2)
To a solution of disaccharide 15 (40 mg, 0.057 mmol) in DMF (0.5 mL) and
pyridine (0.5 mL), Py·SO3 complex (45 mg, 0.285 mmol) was added, and the
mixture was kept at 40◦C for 1 h. Then MeOH (5 mL), NaHCO3 (100 mg),
and Amberlite IR-120 (Na+) were added and the mixture was stirred for 2 h.
Resin and solid were filtered off, and the filtrate was concentrated. Flash chro-
matography of the residue (CHCl3:MeOH, 30:1) on silica gel gave disaccharide
16. Catalytic hydrogenolysis and subsequent saponification of the ester group
in compound 16 as described for the preparation of 1 gave disaccharide 2 (26
mg, 70%): 1H NMR (500 MHz, D2O) δ 0.92 (t, 3H, CH3CH2CH2O), 1.28 (d,
3H, J5,6 = 5.3 Hz,3H-6), 1.67 (m, 2H, CH3CH2CH2O), 3.43 and 3.63 (2m, 2H,
ꢁ
ꢁ
ꢁ
ꢁ
ꢁ
ꢁ
ꢁ
CH3CH2CH2O), 3.45 (t, 1H, J3 ,4 = J4 ,5 = 9.3 Hz,H-4 ), 3.58 (dd, 1H, J1 ,2 = 3.7
Hz, J2 ,3 = 9.3 Hz, H-2ꢁ), 3.73 (t, 1H, H-3ꢁ), 3.85 (dd, 1H, J1,2 = 3.9 Hz, J2,3
=
ꢁ
ꢁ
9.1 Hz, H-2), 4.00 (d, 1H, H-5ꢁ), 4.12 (dd, 1H, H-3), 4.20 (q, 1H, H-5), 4.64 (d,
1H, J3,4 = 3.1 Hz, H-4), 5.04 (d, 1H, H-1), 5.14 (d, 1H, H-1ꢁ). HRESIMS: m/z
[M+Na]+ Calcd for C15H24Na3O14S: 529.058. Found: 529.057.
Propyl 2-O-(α-D-glucopyranosyl Uronic Acid)-3-O-
(α-L-fucopyranosyl)-α-L-fucopyranoside, Sodium Salt (3)
Catalytic hydrogenolysis of the disaccharide 21 (45 mg, 0.041 mmol) and
subsequent saponification of the ester group in the product as described for
the preparation of the compound 1 gave trisaccharide 3 (18 mg, 79%): [α]D
–
1
92◦ (H2O, = 1). H NMR (500 MHz, D2O) δ 0.91 (t, 3H, CH3CH2CH2O), 1.21
(d, 3H, J5 ,6 = 5.4 Hz,3H-6ꢁꢁ), 1.24 (d, 3H, J5,6 = 5.2 Hz,3H-6), 1.67 (m, 2H,
ꢁꢁ ꢁꢁ
ꢁ
ꢁ
CH3CH2CH2O), 3.44 and 3.61 (2m, 2H, CH3CH2CH2O), 3.48 (t, 1H, J3 ,4
=
ꢁ
J4 ,5 = 9.3 Hz,H-4 ), 3.59 (dd, 1H, J1 ,2 = 3.7 Hz, J2 ,3 = 9.3 Hz, H-2ꢁ), 3.68
ꢁ
ꢁ
ꢁ
ꢁ
ꢁ
ꢁ
ꢁ
ꢁꢁ
ꢁꢁ ꢁꢁ
ꢁꢁ ꢁꢁ
(t, 1H, H-3 ), 3.79 (d, 1H, J3 ,4 = 3.4 Hz, H-4 ), 3.81 (dd, 1H, J1 ,2 = 3.4 Hz,
J2 ,3 = 9.1 Hz, H-2ꢁꢁ), 3.94 (dd, 1H, H-3ꢁꢁ), 4.01 (d, 1H, H-5ꢁ), 4.03 (dd, 1H, J1,2
=
ꢁꢁ ꢁꢁ
3.5 Hz, J2,3 = 9.3 Hz, H-2), 4.07 (q, 1H, H-5), 4.08 (d, 1H, J3,4 = 3.6 Hz, H-4),
4.13 (dd, 1H, 1H, H-3), 4.49 (d, 1H, H-5ꢁꢁ), 5.04 (d, 1H, H-1), 5.16 (d, 1H, H-1ꢁ),

Stereoselective Synthesis of Di- and Trisaccharide Fucoidan Fragments
443
5.12 (d, 1H, H-1ꢁꢁ). HRESIMS: m/z [M+Na]+ Calcd for C21H35Na2O15: 573.177.
Found: 573.178.
Propyl 4-O-Sulfonato-2-O-(α-D-glucopyranosyl Uronic Acid)-3-O-
(4-O-sulfonato-α-L-fucopyranosyl)-α-L-fucopyranoside,
Trisodium Salt (4)
Sulfation of the mixture of methyl and butyl uronates 23 (29 mg, 0.029
mmol) and 24 (6 mg, 0.006 mmol) and further catalytic hydrogenolysis and
saponification of acyl groups in 25 and26 as described for the preparation of
1
compound 2 gave trisaccharide 4 (18 mg, 70%): [α]D –67◦ (H2O, = 0.75), H
NMR (500 MHz, D2O) δ 0.91 (t, 3H, CH3CH2CH2O), 1.29 (d, 3H, J5,6 = 5.4
Hz,3H-6), 1.31 (d, 3H, J5 ,6 = 5.2 Hz,3H-6ꢁꢁ), 1.67 (m, 2H, CH3CH2CH2O), 3.43
ꢁꢁ ꢁꢁ
and 3.61 (2m, 2H, CH3CH2CH2O), 3.49 (t, 1H, J3 ,4 = J4 ,5 = 9.4 Hz,H-4ꢁ), 3.65
ꢁ
ꢁ
ꢁ
ꢁ
(dd, 1H, J1 ,2 = 3.7 Hz, J2 ,3 = 9.4 Hz, H-2ꢁ), 3.68 (t, 1H, H-3ꢁ), 3.86 (dd, 1H,
ꢁ
ꢁ
ꢁ
ꢁ
J1 ,2 = 3.4 Hz, J2 ,3 = 9.1 Hz, H-2ꢁꢁ), 4.03 (dd, 1H, J1,2 = 3.5 Hz, J2,3 = 9.3
Hz, H-2), 4.08 (dd, 1H, H-3ꢁꢁ), 4.10 (d, 1H, H-5ꢁ), 4.18 (q, 1H, H-5), 4.31 (dd, 1H,
J3,4 = 3.6 Hz, H-3), 4.58 (d, 1H, H-4ꢁꢁ), 4.78 (q, 1H, H-5ꢁꢁ), 4.87 (d, 1H, H-4), 5.11
(d, 1H, H-1), 5.16 (d, 1H, H-1ꢁ), 5.30 (d, 1H, H-1ꢁꢁ). HRESIMS: m/z [M+Na]+
Calcd for C21H33Na4O21S2: 777.058. Found: 777.057.
ꢁꢁ ꢁꢁ
ꢁꢁ ꢁꢁ
ACKNOWLEDGMENTS
This work was supported by the Russian Foundation for Basic Research (grant
06-03-33080). We also thank Dr. Yu. E. Tsvetkov for helpful discussions and
critical reading of the manuscript.
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