Some key experimental features of a modular synthesis of heparin-like oligosaccharides

Article abstract of DOI:10.1002/ejoc.200300210

The key features of a modular n+2 strategy for a completely stereoselective synthesis of oligosaccharides containing the GlcN-IdoA repeating unit of the major sequence of heparin are presented and discussed in detail. These key features include the regio-

Full text of DOI:10.1002/ejoc.200300210

FULL PAPER
Some Key Experimental Features of a Modular Synthesis of Heparin-Like
Oligosaccharides
[a]
[a]
[a]
[a]
´
´
Jose-Luis de Paz, Rafael Ojeda, Niels Reichardt, and Manuel Martın-Lomas*
Keywords: Carbohydrates / Glycosylation / Heparin / Oligosaccharides / Synthesis design
The key features of a modular n+2 strategy for a completely
stereoselective synthesis of oligosaccharides containing the
GlcN−IdoA repeating unit of the major sequence of heparin
are presented and discussed in detail. These key features in-
clude the regio- and stereoselective synthesis of disaccharide
building blocks and the reactivity of building blocks in the
iveness of which has previously been demonstrated by the
total synthesis of four hexasaccharides and two octasacchar-
ides, allows the size and the charge distribution of the target
oligosaccharide fragments to be controlled.
( Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim,
modular assembly process. The synthetic strategy, the effect- Germany, 2003
Introduction
ily to be discovered,[2] have shown the importance of these
factors in the regulation of FGF-induced mitogenesis sig-
naling.[1a,7]
In the framework of a program on the activation of fibro-
blast growth factors (FGFs) by glycosaminoglycans
(GAGs), we have previously synthesized hexasaccharides
1؊4 and octasaccharides 5 and 6 (Figure 1).[1] FGFs[2] are
the most thoroughly studied heparin-binding proteins,[3]
with the single exception of antithrombin III (AT III).[4]
However, the molecular basis of FGF activation is still a
matter of debate, as a consequence of the diversity and the
complexity of the FGF system.[2] The availability of homo-
geneous oligosaccharides with precisely defined molecular
structures, such as 1؊6, would most probably represent a
major contribution in the elucidation of the molecular
mechanism of the FGF activation process.[2] Compounds
1؊6 are composed of variously sulfated -glucosamine and
-iduronate units, as the major sequences in heparin.[5] In
terms of overall conformation, compounds 1؊6, like hep-
arin itself,[6] have well defined three-dimensional helical
structures.[1,7,8] This conformation, which can be assessed
by NMR and computational modeling,[8] determines the
spatial orientation of the negative charges. Since biological
interactions between GAGs and proteins are primarily elec-
trostatic in nature,[3] it is generally accepted that the charge
distribution, the charge orientation, and the size of the oli-
gosaccharide chain are major factors in determining the ac-
tivity and defining the specificity of GAG-FGF interac-
tions.[2,3] Indeed, the results obtained so far with com-
pounds 1؊6 and FGF-1, the first member of the FGF fam-
The syntheses of 1؊6 were performed by a convergent
nϩ2 modular strategy (Scheme 1).[1] As could be antici-
pated, the already well established glycosylation method-
ologies[9] and the plethora of existing protecting groups[10]
allowed these molecules to be designed and constructed by
the successive assembly of disaccharide building blocks.
This strategy, which allows the length of the final product
and the charge distribution along the oligosaccharide se-
quence to be controlled, has proven to be effective and ver-
satile. However, the elucidation of the molecular basis of
FGF activation requires the synthesis and purification of
sufficient quantities of a variety of such oligosaccharides
specifically designed to provide information on the recog-
nition, binding, and signaling processes. Therefore, for these
synthetic molecules to serve as a significant tool in these
studies, further simplification, optimization, and possibly
automation of the synthetic process are much needed. The
chemistry underlying these syntheses therefore has to be op-
timized and successfully translated into solid-phase meth-
odologies in order to be effective enough for subsequent
parallel syntheses and combinatorial developments.
A recent publication[11] on a related modular approach
to the synthesis of heparin oligosaccharides has prompted
us to present here a detailed report on ours, including new
unpublished data and relevant results in this context. These
findings provided the basis for our syntheses of 1؊6 but
were not explicitly discussed in our previous reports.[1] The
wide scope of those papers,[1] dealing with structural and
biological studies as well, did not allow proper attention to
be devoted to these practical details that now, having been
further developed and elaborated, may contribute valuable
knowledge to the wealth of existing data.[11,12]
[a]
Grupo de Carbohidratos, Instituto de Investigaciones
´
Quımicas, CSIC,
´
Americo Vespucio s/n, Isla de La Cartuja, 41092 Sevilla, Spain
Fax: (internat.) ϩ34-954-460565
E-mail: manuel.martin-lomas@iiq.cartuja.csic.es
Supporting information for this article is available on the
WWW under http://www.eurjoc.org or from the author.
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DOI: 10.1002/ejoc.200300210
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A Modular Synthesis of Heparin-Like Oligosaccharides
FULL PAPER
Figure 1. Six synthetic oligosaccharides, differing in length and/or sulfation pattern
Results and Discussion
laboratory equipment. Building block 8 is obtained from -
glucosamine hydrochloride through a diazo transfer reac-
tion[16] followed by benzylidenation and activation of the
Synthesis Strategy and Monosaccharide Building Blocks
The synthesis of GAG oligosaccharides is already well anomeric position as a trichloroacetimidate (Scheme 2).
developed.[12] The major achievement in the field has been The direct installation of the azide function from commer-
the work performed around the pentasaccharide constitut- cially available amino sugars was first reported by us for
ing the minimum heparin sequence for recognition and the preparation of 2-azido-2-deoxy--gluco, -manno, -ga-
binding to AT III.[4,13] Many of the strategies currently used lacto, and -allo derivatives[16a] and was later revisited and
in the synthesis of GAG oligosaccharides are somehow in- modified in an attempt to improve yield and reproducibili-
spired by these pioneering studies. This is indeed the case ty.[16b,16c] Both the original[16a] and the modified[16b] pro-
for our synthesis of oligosaccharides 1؊6,[1] based on the cedures have been extensively used in our laboratory over
retrosynthetic analysis shown in Scheme 1.[1] The key build- the years. For the reliable ten gram scale synthesis of 8 with
ing blocks are disaccharide structures such as I, which are excellent reproducibility we currently use the original meth-
effectively synthesized from the monosaccharide derivatives od[16a] under carefully controlled experimental conditions,
7 and 8. Building block 7 is most conveniently prepared as followed by direct benzylidenation to obtain 9[17] in
[14]
´
reported by Bonnaffe et al.
This method has a number 65Ϫ70% overall yield from -glucosamine hydrochloride
of advantages over other literature procedures previously (Scheme 2). Stereoselective silylation (Ǟ 10),[18] benzylation
used in our laboratory to produce -iduronic acid deriva- (Ǟ 11),[18a] desilylation (Ǟ 12),[19] and anomeric acti-
tives.[15] Those advantages include reproducibility, sim- vation[20] finally yield 8.[19,21] Compound 11 has been used
plicity, and ready scale-up potential. By this procedure, diol as starting material for the preparation of other glycosyl
7 is currently being synthesized in tens of grams in ordinary donors such as 18, 19, and 20 (Table 2), which are also used
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Scheme 1. General retrosynthetic analysis; R1 ϭ H, SO3Na; R2 ϭ Ac, SO3Na; R5 ϭ N3, NHAc; R3, R4, P1ϪP10 ϭ protecting groups;
TDS ϭ dimethylthexylsilyl
Scheme 2. Synthesis of donor 8; reagents and conditions: a) MeONa, MeOH; TfN3, DMAP; PhCH(OMe)2, pTsOH, DMF, 40 °C 71%;
b) TBSCl, imidazole, CH2Cl2, Ϫ10 °C 70%; c) BnBr, NaH, CH2Cl2, TBAI, 85%; d) TBAF, AcOH, THF, Ϫ40 °C quantitative; e) Cl3CCN,
DBU, CH2Cl2, 95%; DMAP ϭ 4-dimethylaminopyridine, TBS ϭ tert-butyldimethylsilyl, TBAF ϭ tetrabutylammonium fluoride, DBU ϭ
1,8-diazabicyclo[5.4.0]undec-7-ene
as monosaccharide building blocks for specific purposes in
with regard to the regioselectivity of the process, and a
our reported synthesis of compounds 1؊6.
multi-step route to obtain 2-OH protected -iduronate gly-
cosyl acceptors from 7 has been proposed as a preferred
Disaccharide Building Blocks
alternative.[11] A considerable volume of data from our lab-
A key step in our syntheses of compounds 1؊6 is the oratory, however, indicates that the direct glycosylation of
regio- and stereoselective condensation of diol 7 with tri- 7 followed by installation of the needed protecting group
chloroacetimidate 8.[1] This and other related glycosylations at position 2 of the resulting disaccharide is a convenient
of diol 7 are in routine use in our laboratory for the prep- procedure for the preparation of the key building blocks I.
aration of structures I.[1] The usefulness of this regio- and We have already reported that the C4 conformation of 7,
1
stereoselective glycosylation, which is key for the simplifi- which is stabilized by two cooperative intramolecular hy-
cation of the synthetic scheme, has recently been questioned drogen bonds (4-OH Ǟ 2-OH Ǟ 1OR),[1,15b,22] results in
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A Modular Synthesis of Heparin-Like Oligosaccharides
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Table 1. Reaction conditions for the glycosylation between diol 7 and trichloroacetimidate 8
Entry
Ratio 8/7 (equiv.)
Catalyst
Solvent
Inverse procedure
T (°C)
Yield (%)
1
2
3
4
5
6
1.5:1
1.5:1
1.5:1
0.6:1
1:1
TMSOTf
TMSOTf
TMSOTf
TMSOTf
TMSOTf
TMSOTf
Et2O
Et2O
Et2O
Et2O
CH2Cl2
CH2Cl2
No
Yes
Yes
Yes
Yes
Yes
0
Ϫ20
0
0
0
38[a]
35[a]
33[a]
46[b]
45[a]
62[b]
0.6:1
0
[a]
[b]
Yield calculated with respect to acceptor equivalents. Yield calculated with respect to donor equivalents.
decreased nucleophilicity of OH-2, which, on the other 23 (Scheme 4). The isolation of the major compound from
hand, is sterically hindered by the bulky dimethylthexylsilyl these reaction mixtures is most conveniently carried out
neighboring group. The successful use of these reactions in after treatment with the corresponding acylating agent to
the reported syntheses of 1؊6[1] supports this. The reaction give the 2-O-substituted disaccharide building block with
conditions have been carefully investigated, and the results the required protecting group pattern. In all cases the yield
of this study are summarized in Table 1. When the conden- of the two-step process was around 50%. The obtained re-
sation of 7 with 8 was carried out in dichloromethane as sults are summarized in Table 2.
solvent with a 0.6:1 donor/acceptor ratio by the inverse pro-
In order to evaluate the advantages and disadvantages of
cedure,[23] the desired disaccharide 13 was obtained in 62% constructing the key building blocks I by the above direct
yield. The reaction mixture also contained acceptor 7 (35%) regioselective glycosylations of diol 7, we also investigated
and small amounts of the α(1Ǟ2) disaccharide (14, charac- some alternative routes involving glycosylation of con-
terized as acetate 15), the β(1Ǟ2) disaccharide (16), and veniently 2-O-substituted derivatives of 7. For these alterna-
trisaccharide 17 (Scheme 3). No β(1Ǟ4) disaccharide was tive routes to compete effectively with the direct glycosyla-
observed, which constitutes a further indication of the diffi- tions of diol 7, the glycosyl acceptors have to be directly
culty of explaining the steric course of this glycosylation. and effectively prepared, lengthy multi-step processes being
As would be expected, an excess of donor resulted in an avoided. Thus, regioselective monosubstitution of diol 7
increase of the proportion of 17. No significant changes in was attempted both through selective cleavage of 2,4-
yield, regioselectivity, or stereoselectivity of this reaction benzylidene acetal derivatives[24] and by 2,4-stannylidene
were observed for other 2-azido-2-deoxy glycosyl donors acetal- or tributyltin ether-mediated selective acylation[25]
with different substitution patterns, such as in compounds (Scheme 5). With regard to the first approach, the 2,4-
18,[1a] 19,[1b] and 20[1c] (Table 2). Thus, a similar result was benzylidene acetal derivative of 7 could not be satisfactorily
obtained in the glycosylation of 7 with 18, from which sub- prepared, most probably due to insufficient reactivity of
sequent benzoylation of the reaction mixture allowed the benzaldehyde dimethyl acetal under the conventional acet-
isolation of the α(1Ǟ4) disaccharide (21, 51%) and small alation conditions. However, the p-methoxybenzylidene
amounts of the α(1Ǟ2) disaccharide (22) and trisaccharide acetal 28 was prepared in high yield (82%) from 7 and then
Scheme 3. Synthesis of disaccharide 13; reagents and conditions: a) TMSOTf, CH2Cl2, 0 °C 62% (13) ϩ35% of recovered 7; b) Ac2O,
Py, 93%; c) Ac2O, Py, quantitative. TMSOTf ϭ trimethylsilyl trifluoromethanesulfonate
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FULL PAPER
Table 2. Regio- and stereoselective glycosylations between acceptor 7 and different donors
Scheme 4. Synthesis of disaccharide 21; reagents and conditions: a) TMSOTf, CH2Cl2, 0 °C; BzCl, Py, 51% (21)
subjected to regioselective reductive opening to give the 2- afforded 31 in 77% yield (Scheme 5). Therefore, for the
O substituted -iduronate derivative 29 (85%) and a small selective activation to proceed, an -iduronate building
amount of the corresponding regioisomer, which could not block with a less sterically demanding protecting group at
be purified from the reaction mixture. The observed selec- the anomeric position and also easily accessible from cur-
tivity in the cleavage of acetal 28 opens a convenient route rently available intermediates had to be used. Phenylthiogly-
to the preparation of -iduronate building blocks for the coside 32 was chosen. (Scheme 6). Dibutylstannylidene-me-
modular synthesis of heparin-like oligosaccharides. In our diated benzoylation of 32 gave the 2-O-benzoyl derivatives
case this reaction permitted the preparation of building 33α and 33β (80% overall). The α anomer was subjected to
blocks such as 25, a key intermediate in the synthesis of 1 glycosylation with building block 8 to give 34 (65%,
and 5, by glycosylation of 29 with 8 (Ǟ 30, 85%), sub- Scheme 6). In this case the overall yield of the disaccharide
sequent removal of the p-methoxybenzyl group in 30 (Ǟ module (34) reached 52% in two steps, which was similar
13, 90%), and pivaloylation of 13 (Ǟ 25, 95%) (Scheme 5). to the yield obtained for a similar building block by direct
After these transformations 25 could be obtained in 51% glycosylation of diol 7. Interestingly enough, glycosylation
overall yield from 7 in five high-yielding steps. This yield is of lactone 31 with 8 gave an 8:1 anomeric mixture of glyco-
similar to that obtained by direct regioselective glycosyl- sides 35 in 88% yield. Treatment of this mixture with dibu-
ation of 7 and in situ pivaloylation of the resulting disac- tyltin oxide[26] in methanol gave a mixture of 13 and the
charide mixture (56%, Table 2). As for the second alterna- β anomer 13β, from which 13 was isolated in 75% yield.
tive, attempted selective activation of diol 7 with dibutyltin (Scheme 5). It may be concluded that even for acceptors 29
oxide in toluene followed by treatment with benzoyl chlo- and 33, which can be prepared in good yield after two-step
ride resulted in a mixture of lactone 31 and partially ben- processes and successfully glycosylated with 8, these multi-
zoylated derivatives in low yield. The presence of the β-ori- step approaches do not seem to be remarkably superior in
ented dimethylthexylsilyl group in 7 seemed to prevent ef- practical terms to direct regioselective glycosylation of the
fective formation of the intermediate 2,4-dibutylstannylid- -iduronate diol 7. It is also interesting to note that the
ene acetal. Treatment of 7 with bis(tributyltin) oxide glycosylation of 31 does not occur with complete stereo-
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Scheme 5. Reagents and conditions: a) (Bu3Sn)2O, toluene, reflux, 77%; b) 8, TMSOTf, CH2Cl2, Ϫ5 °C, 88%, α/β ϭ 8:1; c) Bu2SnO (1
equiv.), MeOH, reflux, 24 h, 75% (α anomer 13); d) pMeOPhCH(OMe)2, pTsOH, DMF, 25 mbar, 82%; e) NaBH3CN, TMSCl, CH3CN,
[1a]
˚
MS 3 A, Ϫ45 °C, 85%; f) 8, TMSOTf, CH2Cl2, Ϫ10 °C, 85%; g) DDQ, CH2Cl2/H2O 10:1, 0 °C, 90%; h) PivCl, Py, DMAP, 95%
Scheme 6. Synthesis of disaccharide 34; reagents and conditions: a) Bu2SnO, MeOH, reflux 1 h; dioxane, BzCl, Et3N, 0 °C, 80%; b) 8,
TMSOTf, CH2Cl2, 0 °C, 65%
selectivity, in contrast to the results obtained in the glycos- 1؊6 provided a series of useful data in this regard, dis-
ylation of 7, 29, 33 and other -iduronate derivatives. The cussed below.
conformation of 31 is tightly locked, so the recent report
The protecting group strategy for the synthesis of these
that conformational constraint of the glycosyl acceptor re-
oligosaccharide fragments is dictated by the desired sulf-
sults in complete α stereoselectivity of the glycosyl-
ation pattern and the configurations of the glycosidic link-
ation[11,27] does not seem to hold for equatorially oriented
ages. In addition, depending on the studies to be performed
hydroxy groups.
with the target molecule, the necessary installation of an
appropriate chemical functionality at a specific position
also has to be considered when planning the synthesis. The
Assembly of Building Blocks
The assembly of these building blocks for the construc- importance of choosing the appropriate set of protecting
tion of the oligosaccharide sequences has to be carefully groups and of designing the most convenient strategy to
planned. The structure of the final product would deter- achieve the final target can be illustrated by comparison of
mine the synthetic strategy and the protecting group pattern a successful synthesis[1a] and an unsuccessful approach to
in the different building blocks. Obviously, the latter would the synthesis of oligosaccharides with the structure of the
strongly influence their reactivity and therefore their per- regular region of heparin (1 and 5). In our reported syn-
formance as glycosyl donors or glycosyl acceptors. To thesis of 1؊6 we decided to install an α-isopropyl group at
match donor-acceptor reactivity is essential for a reasonable the reducing end.[1] These oligosaccharides were primarily
outcome of the process. Our studies on the syntheses of synthesized for conformational studies, sedimentation equi-
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Scheme 7. Synthesis of disaccharide building blocks; reagents and conditions: a) EtSH, pTsOH (cat.), CH2Cl2, 89%; b) BzCN, Et3N
(cat.), MeCN, Ϫ40 °C, 91%; c) (HF)x·Py, THF, Ϫ15 °CǞ0 °C, 94%; d) Cl3CCN, K2CO3, 87%; e) (HF)x·Py, THF, Ϫ10 °C Ǟ 0 °C, 88%;
g) Cl3CCN, K2CO3, 95%
Scheme 8. Assembly of hexasaccharide 46; reagents and conditions: a) TMSOTf, CH2Cl2, 0 °C, 50% ϩ 44% of recovered 37; b) EtSH,
pTsOH (cat.), 84%; c) BzCN, Et3N (cat.), MeCN, Ϫ40 °C, 95%; d) TMSOTf, CH2Cl2, 0 °C, 60% ϩ 37% of recovered 45; e) (HF)x·Py,
THF, 0 °C, 90%; f) Cl3CCN, K2CO3, 85%; g) MeOH, TMSOTf, CH2Cl2, 0 °C, 31%
librium analysis experiments, and stimulation of FGF mi- gosaccharide intermediate that would permit the synthesis
togenic activity assays. The planned syntheses of 1 and 5 of a variety of molecules differently substituted at the re-
were successful when the α-isopropyl group was directly in- ducing end for different purposes rendered the synthesis im-
troduced in the reducing end building block.[1] Different practicable. The use of pivaloyl or benzoyl groups as partic-
strategies aiming to prepare a common, fully protected oli- ipating protecting groups instead of acetyl at position 2 of
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A Modular Synthesis of Heparin-Like Oligosaccharides
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the -iduronate also greatly facilitates the assembly process. bility of obtaining further derivatization at the anomeric
Thus, for the synthesis of 1[1a] we first decided to proceed position was then investigated. Desilylation[30] (Ǟ 47) and
through the fully protected hexasaccharide derivative 46. As anomeric activation[20] afforded trichloroacetimidate 48. In
indicated above, a successful synthesis of 46 would allow contrast with our reported synthetic approach to 1 and
different groupings to be installed at the reducing end for 5,[1a] which yielded these compounds in an effective manner,
structural and biological investigation or handles for bind- this synthetic route finally had to be abandoned, as at-
ing studies after desilylation and anomeric activation, giv- tempted glycosylation with 48 resulted in low yields and sel-
ing rise to a variety of derivatives. Following our general ectivity.
retrosynthesis analysis (Scheme 1), the required disacchar-
The total syntheses of 1Ϫ6 involved the successful as-
ide building blocks were prepared from 21 and 24 sembly of building blocks with different reactivities as gly-
(Scheme 7). The reducing end building block 37 was pre- cosyl donors and as glycosyl acceptors. To achieve a reason-
pared from 24 by removal of the benzylidene group[28] (Ǟ able assembly process that would finally allow the isolation
36), followed by regioselective benzoylation[29] (Ǟ 37). The of the four hexasaccharides (1Ϫ4) and the two octasacchar-
inner region building block 39 was prepared from 24 by ides (5, 6) for structural and biological investigation,[1] the
desilylation[30] (Ǟ 38) and anomeric activation[20,31] (Ǟ 39). coupling strategy and the experimental conditions had to
The nonreducing end building block 41 was prepared from be carefully established. Since the process was designed to
21 by a similar sequence (Ǟ 40 Ǟ 41). The assembly of allow further developments towards further simplification,
these building blocks was carried out as shown in Scheme 8. a limited number of well established effective protecting
Glycosylation of 37 with 39 at 0 °C with TMSOTf as pro- groups, a unique robust and versatile glycosylation method,
moter gave tetrasaccharide 42 in 50% yield. A substantial and standard experimental conditions seemed advisable.
amount of 37 (44%), as well as glycal 43,[15a] could be iso- The assembly was therefore always carried out with build-
lated from the reaction mixture. Removal of the benzylidene ing blocks with benzyl groups as permanent protecting
acetal[28] in 42 and selective benzoylation[29] of the resulting groups, benzoyl, pivaloyl, and Ϫ to a far lesser extent Ϫ
diol 44 afforded acceptor 45. Glycosylation of 45 with do- acetyl as temporary protecting groups, and benzylidene and
nor 41 at room temperature gave hexasaccharide 46 in 60% p-methoxybenzylidene acetals as versatile groups for ma-
yield. A considerable amount of unchanged 45 and glycal nipulation of hydroxy protection. All glycosylations were
50 were also isolated from the reaction mixture. The feasi- performed by the trichloroacetimidate procedure in di-
Table 3. Summary of glycosylation reactions for the synthesis of precursors of heparin-like oligosaccharides. O-D ϭ O-Disaccharide;
O-T ϭ O-Tetrasaccharide
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O-(2-Azido-3-O-benzyl-4,6-O-benzylidene-2-deoxy-α,β- -gluco-
D
chloromethane with trimethylsilyl triflate as promoter at
temperatures ranging from Ϫ20° to 20 °C. A summary of
the results is shown in Table 3. The stereoselectivity of the
glycosylations was complete in all cases and the yields of
isolated product ranged from 85% to 33%. The protecting
group patterns of donors and acceptors were the best com-
patible in the synthesis of 3 and 4, in which the sulfation
pattern allowed the synthesis to be based on benzoyl, p-
methoxybenzylidene, and p-methoxybenzyl groups. The
most difficult situation arose when acetamido groups rather
than azido groups had to be installed in either donor or
acceptor.[20] On the whole, the process is effective and in the
essential aspects can be translated into solid-phase syn-
thesis. The synthesis of structures containing the structural
features of the heparin major sequence has thus already
been completed and will be reported elsewhere.
pyranosyl) Trichloroacetimidate (8):[19,21] Trichloroacetonitrile
(0.5 mL, 5.1 mmol) and catalytic DBU were added to a solution of
12 (130 mg, 0.34 mmol) in dry CH2Cl2 (2 mL). After 3 h stirring,
the reaction mixture was concentrated in vacuo and the residue was
purified by chromatography over a short silica gel column (hexane/
EtOAc, 4:1 ϩ 1% Et3N) to furnish 8 (170 mg, 95%) as an α/β mix-
ture. The physical data were in good agreement with published val-
ues.[19,21]
2-Azido-4,6-O-benzylidene-2-deoxy-α,β-
D-glucopyranose
(9):[17]
NaN3 (62.2 g, 0.96 mol) was dissolved at room temperature in H2O
(156 mL) in a 1-L three-necked round-bottomed flask, fitted with
a dropping funnel, a septum, and an argon balloon. CH2Cl2
(194 mL) was added to the vigorously stirred solution at 0 °C. Tf2O
(32 mL, 0.19 mol) was added over 1 h. The mixture was stirred for
2 h at 0 °C, the organic layer was separated, and the aqueous layer
was extracted with CH2Cl2 (2 ϫ 78 mL). The combined organic
layers were washed with saturated aqueous NaHCO3 solution
(156 mL) and H2O (156 mL), dried with MgSO4, and filtered, to
yield a 0.4  solution of TfN3 (350 mL) (WARNING: TfN3 has
been reported to be explosive when not in solvent and should always
be used as a solution). A suspension of -glucosamine hydrochlo-
ride (5 g, 23 mmol) in MeOH (100 mL) was treated with a solution
of NaOMe in MeOH (0.5 , 55 mL, 28 mmol) and stirred at room
Conclusion
In conclusion, we have developed an effective, basically
modular strategy for the preparation of oligosaccharides
with the structure of the major sequence in heparin, permit- temperature for 10 min. Dilution with MeOH (245 mL) and treat-
ment with DMAP (3 g, 25 mmol) afforded a clear, colorless solu-
tion, to which the TfN3 solution (0.4 , 175 mL, 70 mmol) was
added at room temperature over 2 h. After the mixture had been
stirred at room temperature for 48 h, the solvent was evaporated at
30 °C. The oily, white suspension of the residue was dissolved in
MeOH (50 mL), treated with methanolic acetic acid solution until
neutral pH, and concentrated to dryness. The residue was dissolved
in DMF (30 mL) and treated with benzaldehyde dimethyl acetal
(5.2 mL, 35 mmol) and pTsOH (50 mg). After stirring at 40 °C for
48 h, the mixture was neutralized with solid NaHCO3 and concen-
ting the size and the charge distribution along the oligosac-
charide chain to be controlled. This basic strategy, dis-
cussed in this paper, has already allowed the practical syn-
thesis of four different series of hexa- and octasaccharides,[1]
which have been used for structural and biological investi-
gation.[1,7] Key points of these syntheses are the direct prep-
aration of disaccharide building blocks by regio- and ster-
eoselective glycosylation of an -iduronic ester diol with a
2-azido-2-deoxy--glucopyranosyl trichloroacetimidate, the
use of a limited number of well established protecting trated in vacuo. The residue was purified by flash column chroma-
tography (8:1 Ǟ 4:1 toluene/acetone) to yield 9 (4.83 g, 71%). The
groups and a unique glycosylation procedure. With these
elements, a reasonable assembly of building blocks can be
achieved matching donor and acceptor reactivities, afford-
ing the desired oligosaccharide sequences in acceptable
yield.
physical data were in good agreement with published values.[17]
tert-Butyldimethylsilyl 2-Azido-4,6-O-benzylidene-2-deoxy-β-D-gluco-
pyranoside (10):[18] tert-Butyldimethylsilyl chloride (148 mg,
0.98 mmol) was added under argon to a cooled (Ϫ10 °C) solution
of 9 (261 mg, 0.89 mmol) and imidazole (151 mg, 2.23 mmol) in
CH2Cl2 (1.3 mL). After the mixture had been stirred for 2 h, H2O
(1 mL) was added and the mixture was diluted with CH2Cl2
(50 mL) and washed with H2O (50 mL). The aqueous layer was
extracted with CH2Cl2 (2 ϫ 25 mL), and the combined organic
layers were dried with MgSO4 and concentrated to dryness. The
residue was purified by flash column chromatography (hexane/
EtOAc, 9:1) to afford 10 (254 mg, 70%). The physical data were in
good agreement with published values.[18]
Experimental Section
General Procedures: Thin layer chromatography (TLC) analyses
were performed on silica gel 60 F254 precoated aluminium plates
(Merck) and the compounds were detected by staining with sulfuric
acid/ethanol (1:9) or with anisaldehyde solution (anisaldehyde
(25 mL) with sulfuric acid (25 mL), ethanol (450 mL), and acetic
acid (1 mL)], followed by heating at over 200 °C. Column chroma-
tert-Butyldimethylsilyl 2-Azido-3-O-benzyl-4,6-O-benzylidene-2-de-
tography was carried out on silica gel 60 (0.2Ϫ0.5 mm, oxy-β-D
-glucopyranoside (11):[18a] NaH (60% dispersion in mineral
0.2Ϫ0.063 mm or 0.040Ϫ0.015 mm; Merck). Optical rotations were
determined with a PerkinϪElmer 341 polarimeter. 1H and 13C
NMR spectra were acquired with Bruker DPX 300, DRX 400, and
DRX 500 spectrometers, and chemical shifts are given in ppm (δ)
oil, 1.76 g, 43.9 mmol) was added to a cooled (0 °C) solution of 10
(11.93 g, 29.3 mmol) in dry CH2Cl2 (120 mL). After the mixture
had been stirred for 1 h, benzyl bromide (6.27 mL, 52.7 mmol) and
catalytic TBAI (200 mg) were added. After the mixture had then
relative to tetramethylsilane as an internal reference or relative to been stirred at room temperature for 24 h, MeOH (10 mL) was
D2O. Elemental analyses were performed with a Leco CHNS-932 added, and the mixture was diluted with CH2Cl2 (400 mL) and
apparatus, after drying of analytical samples over phosphorous
washed with saturated NH4Cl solution (100 mL) and H2O
pentoxide for 24 h. Mass spectra (fast atom bombardment, FAB (200 mL). The aqueous layers were extracted with CH2Cl2 (2 ϫ
MS) were carried out by the Mass Spectrometry Service, Facultad 100 mL), and the combined organic layers were dried with MgSO4
´
Quımica, Seville, with a Kratos MS-80 RFA spectrometer.
and concentrated in vacuo. The residue was purified by flash col-
3316
 2003 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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Eur. J. Org. Chem. 2003, 3308Ϫ3324

A Modular Synthesis of Heparin-Like Oligosaccharides
FULL PAPER
umn chromatography (hexane/EtOAc, 25:1) to furnish 11 (12.35 g,
pyranoside]uronate (15): [α]2D0 ϭ ϩ75.0 (c ϭ 1, CHCl3). TLC (hex-
85%). The physical data were in good agreement with published ane/EtOAc, 4:1). Rf ϭ 0.48. 1H NMR (500 MHz, CDCl3): δ ϭ
values.[18a]
7.46Ϫ7.24 (m, 15 H, Ph), 5.50 (s, 1 H, PhCHO), 5.21 (d, J1Ј,2Ј ϭ
3.7 Hz, 1 H, H-1Ј), 5.17 (br. s, 1 H, H-4), 5.02 (br. s, 1 H, H-1),
4.88Ϫ4.74 (2d, Jgem ϭ 11.2 Hz, 2 H, CH2Ph), 4.78Ϫ4.62 (2d,
Jgem ϭ 12.0 Hz, 2 H, CH2Ph), 4.55 (d, J4,5 ϭ 2.0 Hz, 1 H, H-5),
3.90 (dd, J2Ј,3Ј ϭ J3Ј,4Ј ϭ 9.5 Hz, 1 H, H-3Ј), 3.83 (m, 1 H, H-6Јa),
3.78 (m, 1 H, H-3), 3.73 (s, 3 H, COOCH3), 3.66Ϫ3.52 (m, 4 H,
H-2, H-4Ј, H-5Ј and H-6Јb), 3.14 (dd, 1 H, H-2Ј), 1.94 (s, 3 H,
OCOCH3), 1.65 [m, 1 H, CH(CH3)2], 0.88Ϫ0.86 [4s, 12 H, C(CH3)2
and CH(CH3)2], 0.30Ϫ0.18 [2s, 6 H, Si(CH3)2] ppm. FAB-MS:
m/z ϭ 870 [MNaϩ]. C44H57N3O12Si (848.0): calcd. C 62.32, H 6.78,
N 4.96; found C 62.39, H 7.15, N 4.70.
2-Azido-3-O-benzyl-4,6-O-benzylidene-2-deoxy-α,β-D-glucopyranose
(12):[19] Acetic acid (755 µL, 13.2 mmol) and TBAF (13.2 mL of a
1  solution in THF) were added to a cooled (Ϫ40 °C) solution of
11 (5.97 g, 12.0 mmol) in dry THF (60 mL). After 3 h, H2O (5 mL)
was added and the mixture was diluted with Et2O (250 mL) and
washed with H2O (150 mL). The aqueous layer was extracted with
Et2O (2 ϫ 50 mL), and the combined organic layers were dried
(MgSO4) and concentrated to dryness. The residue was purified
by flash chromatography (10:1 toluene/acetone) to yield 12 (4.60 g,
100%). The physical data were in good agreement with published
values.[19]
Methyl [Dimethylthexylsilyl 2-O-(2-azido-3-O-benzyl-4,6-O-benzyl-
idene-2-deoxy-β-D-glucopyranosyl)-3-O-benzyl-β-L-idopyranoside]-
Methyl [Dimethylthexylsilyl 4-O-(2-Azido-3-O-benzyl-4,6-O-benzyl-
uronate (16): [α]2D0 ϭ Ϫ19.5 (c ϭ 1, CHCl3). TLC (toluene/EtOAc,
15:1). Rf ϭ 0.13. 1H NMR (500 MHz, CDCl3): δ ϭ 7.49Ϫ7.12 (m,
15 H, Ph), 5.56 (s, 1 H, PhCHO), 5.13 (br. s, 1 H, H-1), 4.91Ϫ4.78
(2d, Jgem ϭ 11.0 Hz, 2 H, CH2Ph), 4.76Ϫ4.60 (2d, Jgem ϭ 11.5 Hz,
2 H, CH2Ph), 4.46 (d, J4,5 ϭ 2.0 Hz, 1 H, H-5), 4.32 (br. d, 1 H,
H-1Ј), 4.26 (dd, J5Ј,6Јa ϭ 5.1, J6Јa,6Јb ϭ 10.6 Hz, 1 H, H-6Јa), 4.05
(br. d, J4,OH ϭ 12.2 Hz, 1 H, H-4), 3.91 (m, 1 H, H-3), 3.79 (s, 3
H, COOCH3), 3.72Ϫ3.61 (m, 3 H, H-2, H-4Ј and H-6Јb), 3.59 (t,
J2Ј, 3Ј ϭ J3Ј, 4Ј ϭ 9.2 Hz, 1 H, H-3Ј), 3.43 (t, J1Ј,2Ј ϭ 8.7 Hz, 1 H,
H-2Ј), 3.25 (dt, J4Ј,5Ј ϭ J5Ј, 6Јb ϭ 9.5 Hz, 1 H, H-5Ј), 1.62 [m, 1 H,
CH(CH3)2], 0.88Ϫ0.86 [4s, 12 H, C(CH3)2 and CH(CH3)2],
0.22Ϫ0.17 [2s, 6 H, Si(CH3)2] ppm. FAB-MS: m/z ϭ 828 [MNaϩ].
C42H55N3O11Si (806.0): calcd. C 62.59, H 6.88, N 5.21; found C
62.55, H 7.33, N 4.75.
idene-2-deoxy-α-D-glucopyranosyl)-3-O-benzyl-β-L-idopyranoside]-
uronate (13): TMSOTf (50 µL of a 0.26  solution in dry CH2Cl2)
was added under argon to a cooled (0 °C) solution of 7 (114 mg,
0.26 mmol) in dry CH2Cl2 (4 mL). While the reaction was stirred,
a solution of 8 (82 mg, 0.16 mmol) in dry CH2Cl2 (1.5 mL) was
added dropwise. After 30 min, the mixture was neutralized with
saturated aqueous NaHCO3 solution, and CH2Cl2 (50 mL) was
then added at room temperature. The suspension was washed with
H2O (50 mL). The organic layer was dried (MgSO4) and concen-
trated in vacuo, and the residue was purified by flash column chro-
matography (30:1 toluene/EtOAc) to yield 13 (78 mg, 62%) and
unchanged acceptor 7 (40 mg, 35% of initial acceptor). Di- and
trisaccharides 14, 16, and 17 were also isolated from the reaction
mixture (14 was acetylated to afford 15 and ensure the NMR as-
signment).
Methyl [Dimethylthexylsilyl 2-O-(2-Azido-3-O-benzyl-4,6-O-benzyl-
Compound 13: [α]2D0 ϭ Ϫ4.3 (c ϭ 1, CHCl3). TLC (hexane/EtOAc,
4:1). Rf ϭ 0.30, (toluene/EtOAc, 15:1). Rf ϭ 0.32. 1H NMR
(500 MHz, CDCl3): δ ϭ 7.43Ϫ7.24 (m, 15 H, Ph), 5.51 (s, 1 H,
PhCHO), 5.02 (br. s, 1 H, H-1), 4.90 (d, J1Ј,2Ј ϭ 3.8 Hz, 1 H, H-
1Ј), 4.87Ϫ4.73 (2d, Jgem ϭ 10.7 Hz, 2 H, CH2Ph), 4.64Ϫ4.61 (2d,
Jgem ϭ 11.8 Hz, 2 H, CH2Ph), 4.55 (br. s, 1 H, H-5), 4.25 (dd,
J5Ј,6Јa ϭ 2.5, J6Јa,6Јb ϭ 8.9 Hz, 1 H, H-6Јa), 4.06 (br. s, 1 H, H-4),
3.97Ϫ3.92 (m, 2 H, H-3 and H-3Ј), 3.79 (s, 3 H, COOCH3),
idene-2-deoxy-α-
benzylidene-2-deoxy-α-
D
-glucopyranosyl)-4-O-(2-azido-3-O-benzyl-4,6-O-
D
-glucopyranosyl)-3-O-benzyl-β- -idopyrano-
L
side]uronate (17): TLC (toluene/EtOAc, 15:1). Rf ϭ 0.39. 1H NMR
(500 MHz, CDCl3): δ ϭ 7.41Ϫ7.04 (m, 25 H, Ph), 5.49Ϫ5.47 (2s,
2 H, PhCHO), 5.42 (d, J1ЈЈ,2ЈЈ ϭ 3.9 Hz, 1 H, H-1ЈЈ), 5.01 (br. s, 1
H, H-1), 4.88 (d, J1Ј,2Ј ϭ 3.6 Hz, 1 H, H-1Ј), 4, 1 H.81Ϫ4.60 (m, 6
H, CH2Ph), 4.43 (br. s, 1 H, H-5), 4.33 (dd, J5Ј,6Јa ϭ 5.0, J6Јa,6Јb
ϭ
10.0 Hz, H-6Јa), 4.26Ϫ3.97 (m, 6 H, H-3, H-4, H-3Ј, H-3ЈЈ, H-6ЈЈa,
H-5Ј or H-5ЈЈ), 3.88 (dt, J5,6a ϭ 5.1, J4,5 ϭ J5,6b ϭ 10.1 Hz, 1 H,
H-5Ј or H-5ЈЈ), 3.79 (br. s, 1 H, H-2), 3.75 (s, 3 H, COOCH3),
3.68Ϫ3.58 (m, 4 H, H-4Ј, H-4ЈЈ, H-6Јb and H-6ЈЈb), 3.36 (dd,
J2Ј,3Ј ϭ 9.9 Hz, 1 H, H-2Ј), 3.28 (dd, J2ЈЈ,3ЈЈ ϭ 9.8 Hz, 1 H, H-
2ЈЈ), 1.67 [m, 1 H, CH(CH3)2], 0.89Ϫ0.87 [4s, 12 H, C(CH3)2 and
CH(CH3)2], 0.32Ϫ0.20 [2s, 6 H, Si(CH3)2] ppm. FAB-MS: m/z ϭ
1194 [MNaϩ]. C62H74N6O15Si (1171.4): calcd. C 63.57, H 6.37, N
7.17; found C 63.21, H 6.07, N 7.00.
3.69Ϫ3.62 (m, 4 H, H-2, H-4Ј, H-5Ј and H-6Јb), 3.53 (dd, J2Ј,3Ј
ϭ
9.8 Hz, 1 H, H-2Ј), 3.03 (d, J2,OH ϭ 9.9 Hz, 1 H, OH), 1.66 [m,
1 H, CH(CH3)2], 0.90Ϫ0.88 [4s, 12 H, C(CH3)2 and CH(CH3)2],
0.24Ϫ0.19 [2s, 6 H, Si(CH3)2] ppm. 13C NMR (125 MHz, CDCl3):
δ ϭ 169.0, 137.7, 126.0, 101.6, 95.9, 94.9, 82.1, 77.2, 75.2, 73.7,
72.7, 71.5, 68.5, 63.2, 63.1, 52.5, 34.0, 25.1, 20.4, 18.5, Ϫ1.9 and
Ϫ3.2 ppm. FAB-MS: m/z ϭ 828 [MNaϩ]. C42H55N3O11Si (806.0):
calcd. C 62.59, H 6.88, N 5.21; found C 62.61, H 6.74, N 5.36.
Methyl [Dimethylthexylsilyl 2-O-(2-Azido-3-O-benzyl-4,6-O-benzyl-
idene-2-deoxy-α-D-glucopyranosyl)-3-O-benzyl-β-L-idopyranoside]-
Methyl [Dimethylthexylsilyl 4-O-(6-O-Acetyl-2-azido-3,4-di-O-
benzyl-2-deoxy-α-D-glucopyranosyl)-2-O-benzoyl-3-O-benzyl-β-L-
uronate (14): TLC (toluene/EtOAc, 15:1). Rf ϭ 0.39. 1H NMR
(500 MHz, CDCl3): δ ϭ 7.48Ϫ7.24 (m, 15 H, Ph), 5.53 (s, 1 H,
PhCHO), 5.50 (d, J1Ј,2Ј ϭ 3.8 Hz, 1 H, H-1Ј), 5.05 (br. s, 1 H, H-
1), 4.88Ϫ4.76 (2d, Jgem ϭ 10.8 Hz, 2 H, CH2Ph), 4.73Ϫ4.56 (2d,
Jgem ϭ 12.0 Hz, 2 H, CH2Ph), 4.50 (br. s, 1 H, H-5), 4.06 (dd,
idopyranoside]uronate (21): TMSOTf (39 µL, 0.22 mmol) was added
under argon to a cooled (0 °C) solution of 7 (1.90 g, 4.32 mmol)
in dry CH2Cl2 (100 mL). While the reaction mixture was stirred, a
solution of 18 (2.48 g, 4.32 mmol) in dry CH2Cl2 (25 mL) was ad-
ded dropwise. After 30 min, the mixture was neutralized with satu-
rated aqueous NaHCO3 solution, and CH2Cl2 (400 mL) was then
added. The suspension was washed with H2O (250 mL). The or-
ganic layer was dried (MgSO4) and concentrated in vacuo, and the
residue was separated by flash column chromatography (toluene/
EtOAc, 12:1) to obtain unchanged acceptor 7 (363 mg, 19%) and
fractions containing the desired disaccharide; these were combined,
concentrated, and dissolved in Py (15 mL). Benzoyl chloride
(4.1 mL, 35 mmol) was added and the solution was stirred at room
temperature. After 24 h, the mixture was diluted with CH2Cl2
J5Ј,6Јa ϭ 4.2, J6Јa,6Јb ϭ 9.8 Hz, 1 H, H-6Јa), 3.99 (br. d, J4,OH
ϭ
12.6 Hz, 1 H, H-4), 3.93 (dd, J2Ј,3Ј ϭ J3Ј,4Ј ϭ 9.4 Hz, 1 H, H-3Ј),
3.82 (m, 1 H, H-3), 3.79 (s, 3 H, COOCH3), 3.76Ϫ3.63 (m, 4 H,
H-2, H-4Ј, H-5Ј and H-6Јb), 3.48 (d, J14,OH ϭ 12.6 Hz, 1 H, OH),
3.37 (dd, 1 H, H-2Ј), 1.64 [m, 1 H, CH(CH3)2], 0.90Ϫ0.83 [4s, 12
H, C(CH3)2 and CH(CH3)2], 0.20Ϫ0.17 [2s, 6 H, Si(CH3)2] ppm.
FAB-MS: m/z ϭ 828 [MNaϩ].
Methyl [Dimethylthexylsilyl 4-O-Acetyl-2-O-(2-azido-3-O-benzyl-
4,6-O-benzylidene-2-deoxy-α-
D-glucopyranosyl)-3-O-benzyl-β-
L-ido-
Eur. J. Org. Chem. 2003, 3308Ϫ3324
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 2003 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
3317

´
J.-L. de Paz, R. Ojeda, N. Reichardt, M. Martın-Lomas
FULL PAPER
(400 mL), washed with H2O (300 mL), dried (MgSO4), and concen-
trated in vacuo. The residue was purified by flash column chroma-
tography (toluene/EtOAc, 12:1) to yield 21 (2.12 g, 51%). Disac-
charide 22 and trisaccharide 23 were also isolated from the reac-
tion mixture.
Methyl [Dimethylthexylsilyl 2-O-Acetyl-4-O-(2-azido-3-O-benzyl-
4,6-O-benzylidene-2-deoxy-α-D-glucopyranosyl)-3-O-benzyl-β-L-
idopyranoside]uronate (24): Compound 13 (204 mg, 0.25 mmol) was
dissolved in Py (2 mL) at 0 °C. Acetic anhydride (1 mL) was added,
and the mixture was stirred at 0 °C for 24 h and at room tempera-
ture for 48 h. The solution was diluted with CH2Cl2 (50 mL),
washed with H2O, dried (MgSO4), and concentrated in vacuo. The
residue was coevaporated twice with toluene (20 mL) and then
purified by column chromatography (hexane/EtOAc, 6:1) to afford
24 (200 mg, 93%): [α]2D0 ϭ ϩ29.5 (c ϭ 1, CHCl3). TLC (hexane/
EtOAc, 4:1). Rf ϭ 0.38. 1H NMR (500 MHz, CDCl3): δ ϭ
7.45Ϫ7.24 (m, 15 H, Ph), 5.51 (s, 1 H, PhCHO), 5.07 (br. s, 1 H,
H-1), 4.97 (br. s, 1 H, H-2), 4.76 (d, J1Ј,2Ј ϭ 3.5 Hz, 1 H, H-1Ј),
4.88Ϫ4.70 (2d, Jgem ϭ 11.1 Hz, 2 H, CH2Ph), 4.74Ϫ4.66 (2d,
Jgem ϭ 11.8 Hz, 2 H, CH2Ph), 4.47 (br. s, 1 H, H-5), 4.30 (dd,
J5Ј,6Јa ϭ 4.9, J6Јa,6Јb ϭ 10.1 Hz, 1 H, H-6Јa), 4.04Ϫ3.95 (m, 4 H,
H-3, H-4, H-3Ј and H-5Ј), 3.75 (s, 3 H, COOCH3), 3.64Ϫ3.59 (m,
2 H, H-4Ј and H-6Јb), 3.28 (dd, J2Ј,3Ј ϭ 9.9 Hz, 1 H, H-2Ј), 2.03
(s, 3 H, OCOCH3), 1.61 [m, 1 H, CH(CH3)2], 0.86Ϫ0.83 [4s, 12 H,
C(CH3)2 and CH(CH3)2], 0.24Ϫ0.14 (2s, 6 H, Si(CH3)2] ppm. 13C
NMR (125 MHz, CDCl3): δ ϭ 170.7, 168.8, 137.8, 126.1, 101.6,
98.4, 93.7, 82.6, 76.0, 74.8, 74.3, 73.6, 73.4, 72.9, 68.5, 67.7, 63.2,
63.1, 52.1, 34.1, 24.8, 21.0, 20.2, 18.4, Ϫ2.0, Ϫ3.6 ppm. FAB-MS:
m/z ϭ 870 [MNaϩ]. C44H57N3O12Si (848.0): calcd. C 62.32, H 6.78,
N 4.96; found C 62.37, H 6.98, N 4.89.
Compound 21: [α]2D0 ϭ ϩ18.0 (c ϭ 1, CHCl3). TLC (toluene/EtOAc,
12:1). Rf ϭ 0.26. 1H NMR (500 MHz, CDCl3): δ ϭ 8.11Ϫ7.22 (m,
20 H, Ph), 5.17 (br. s, 1 H, H-1), 5.07 (br. s, 1 H, H-2), 4.84Ϫ4.74
(2d, Jgem ϭ 11.7 Hz, 2 H, CH2Ph), 4.72 (d, J1Ј,2Ј ϭ 3.4 Hz, 1 H,
H-1Ј), 4.67Ϫ4.49 (2d, Jgem ϭ 10.7 Hz, 2 H, CH2Ph), 4.48 (br. s, 1
H, H-5), 4.38 (dd, J5Ј,6Јa ϭ 1.8, J6Јa,6Јb ϭ 12.4 Hz, 1 H, H-6Јa), 4.30
(dd, J5Ј,6Јb ϭ 2.3 Hz, 1 H, H-6Јb), 4.23 (m, 1 H, H-3), 4.07 (m, 1
H, H-5Ј), 4.01 (br. s, 1 H, H-4), 3.96Ϫ3.87 (2d, Jgem ϭ 10.7 Hz, 2
H, CH2Ph), 3.75 (s, 3 H, COOCH3), 3.53Ϫ3.43 (m, 2 H, H-3Јand
H-4Ј), 3.12 (dd, J2Ј,3Ј ϭ 10.1 Hz, 1 H, H-2Ј), 1.99 (s, 3 H, OC-
OCH3), 1.56 [m, 1 H, CH(CH3)2], 0.79Ϫ0.75 [4s, 12 H, C(CH3)2
and CH(CH3)2], 0.25Ϫ0.13 [2s, 6 H, Si(CH3)2] ppm. 13C NMR
(125 MHz, CDCl3): δ ϭ 170.6, 168.6, 166.6, 137.9, 127.7, 99.7,
94.0, 79.9, 77.3, 75.6, 75.0, 74.9, 74.6, 73.4, 73.0, 70.1, 68.7, 63.7,
62.3, 52.2, 34.0, 24.8, 20.9, 20.2, 18.4, Ϫ2.0, Ϫ3.4 ppm. FAB-MS:
m/z ϭ 976 [MNaϩ]. C51H63N3O13Si (954.2): calcd. C 64.20, H 6.66,
N 4.40; found C 64.47, H 6.64, N 4.24.
Methyl [Dimethylthexylsilyl 2-O-(6-O-Acetyl-2-azido-3,4-di-O-
benzyl-2-deoxy-α-D-glucopyranosyl)-4-O-benzoyl-3-O-benzyl-β-L-
idopyranoside]uronate (22): [α]2D0 ϭ ϩ70.4 (c ϭ 0.98, CHCl3). TLC
(toluene/EtOAc, 12:1). Rf ϭ 0.39. 1H NMR (500 MHz, CDCl3):
Methyl (Dimethylthexylsilyl 3-O-Benzyl-2,4-O-p-methoxybenzylid-
ene-β-L-idopyranoside)uronate (28): A catalytic amount of pTsOH
δ ϭ 8.06Ϫ7.11 (m, 20 H, Ph), 5.20 (br. s, 1 H, H-4), 5.15 (d, J1Ј,2Ј
3.5 Hz, 1 H, H-1Ј), 5.08 (br. s, 1 H, H-1), 4.86Ϫ4.73 (2d, Jgem
11.8 Hz, 2 H, CH2Ph), 4.70 (d, J4,5 ϭ 1.8 Hz, 1 H, H-5), 4.51Ϫ4.32
(2d, Jgem ϭ 11.1 Hz, 2 H, CH2Ph), 4.23 (dd, J2,3 ϭ J3,4 ϭ 2.6 Hz,
1 H, H-3), 4.06Ϫ4.02 (m, 2 H, H-6Јa and CH2Ph), 3.83 (dd,
ϭ
was added to a solution of diol 7 (1.84 g, 4.17 mmol) and p-meth-
oxybenzaldehyde dimethylacetal (1.43 mL, 8.34 mmol) in DMF
(10 mL). The reaction was carried out under reduced pressure
(20Ϫ30 mbar) by use of a rotary evaporator at 45 °C for 3.5 h. The
major part of the solvent was then removed by reduced pressure,
and the residue was taken up in ethyl acetate (100 mL), washed
with saturated NaHCO3 solution and brine, dried with MgSO4,
filtered, and concentrated in vacuo. Column chromatography (hex-
ane/EtOAc, 20:1 Ǟ 10:1) afforded 28 (1.91 g, 82%) as a colorless
oil. [α]2D0 ϭ ϩ30.1 (c ϭ 1.03, CHCl3). TLC (hexane/EtOAc, 3:1).
ϭ
J5Ј,6Јb ϭ 1.6, J6Јa,6Јb ϭ 12.1 Hz, 1 H, H-6Јb), 3.78 (d, Jgem
ϭ
10.6 Hz, 1 H, CH2Ph), 3.71 (s, 4 H, H-2 and COOCH3), 3.46 (m,
1 H, H-5Ј), 3.26 (t, J3Ј,4Ј ϭ J4Ј,5Ј ϭ 9.3 Hz, 1 H, H-4Ј), 3.17 (dd, 1
H, H-3Ј), 2.94 (dd, J2Ј,3Ј ϭ 10.4 Hz, 1 H, H-2Ј), 1.95 (s, 3 H, OC-
OCH3), 1.65 [m, 1 H, CH(CH3)2], 0.89Ϫ0.87 [4s, 12 H, C(CH3)2
and CH(CH3)2], 0.33Ϫ0.21 [2s, 6 H, Si(CH3)2] ppm. FAB-MS:
m/z ϭ 976 [MNaϩ]. MS-HRFAB: calcd. for C51H63N3O13SiNa:
976.4028, found 976.4069. C51H63N3O13Si (954.2): calcd. C 64.20,
H 6.66, N 4.40; found C 63.75, H 6.86, N 4.48.
1
Rf ϭ 0.65. H NMR (500 MHz, CDCl3): δ ϭ 7.38Ϫ7.34 (m, 9 H,
Ph), 7.02 (s, 1 H, CH3OPhCHO), 5.44 (s, 1 H, H-1), 4.87 (d, 1 H,
H-5), 4.72 (d, Jgem ϭ 11.9 Hz, 1 H, CH2Ph), 4.67 (d, 1 H, CH2Ph),
4.32Ϫ4.30 (m, 1 H, H-4), 4.25Ϫ4.22 (m, 1 H, H-3), 3.91 (d, J2,3
ϭ
4.1 Hz, 1 H, H-2), 3.78 (s, 6 H, COOCH3, CH3OPhCHO),
1.70Ϫ1.66 [m, 1 H, CH(CH3)2], 0.91Ϫ0.88 [4s, 12 H, C(CH3)2 and
CH(CH3)2], 0.28Ϫ0.18 [2s, 6 H, Si(CH3)2] ppm. 13C NMR
(125 MHz, CDCl3): δ ϭ 169.9, 160.5, 137.7, 131.6, 129.1, 128.7,
128.1, 128.0, 114.0, 96.7, 93.5, 77.9, 77.0, 74.1, 72.5, 72.1, 70.7,
69.8, 55.7, 52.7, 34.6, 25.0, 20.7, 20.4, 19.1, 18.9, Ϫ1.7, Ϫ2.7 ppm.
FAB-MS: m/z ϭ 581 [MNaϩ].
Methyl [Dimethylthexylsilyl 2-O-(6-O-Acetyl-2-azido-3,4-di-O-
benzyl-2-deoxy-α-
D-glucopyranosyl)-4-O-(6-O-acetyl-2-azido-3,4-di-
O-benzyl-2-deoxy-α-
D
-glucopyranosyl)-3-O-benzyl-β- -idopyrano-
L
side]uronate (23): [α]2D0 ϭ ϩ89.5 (c ϭ 1.33, CHCl3). TLC (toluene/
EtOAc, 12:1). Rf ϭ 0.14. 1H NMR (500 MHz, CDCl3): δ ϭ
7.47Ϫ7.14 (m, 25 H, Ph), 5.36 (d, J1ЈЈ,2ЈЈ ϭ 3.9 Hz, 1 H, H-1ЈЈ),
4.98 (m, 2 H, H-1 and H-1Ј), 4.93 (d, Jgem ϭ 10.4 Hz, 1 H, CH2Ph),
4.86Ϫ4.80 (2d, Jgem ϭ 10.5 Hz, 2 H, CH2Ph), 4.76Ϫ4.73 (m, 3 H,
Methyl (Dimethylthexylsilyl 3-O-Benzyl-2-O-p-methoxybenzyl-β-L-
CH2Ph), 4.70Ϫ4.64 (2d, Jgem ϭ 11.9 Hz, 2 H, CH2Ph), 4.56 (d, idopyranoside)uronate (29): Acetal 28 (1.42 g, 2.7 mmol) and pow-
˚
Jgem ϭ 11.4 Hz, 1 H, CH2Ph), 4.51 (d, Jgem ϭ 11.3 Hz, 1 H, dered molecular sieves (3 A) in CH3CN (50 mL) were stirred at
CH2Ph), 4.43 (d, J4,5 ϭ 1.6 Hz, 1 H, H-5), 4.33 (dd, J5Ј,6Јa ϭ 1.7,
J6Јa, 6Јb ϭ 12.3 Hz, 1 H, H-6Јa), 4.20Ϫ3.95 (m, 8 H, H-3, H-4, H-
3Ј, H-3ЈЈ, H-6ЈЈa, H-6Јb, H-6ЈЈb, H-5Ј or H-5ЈЈ), 3.84 (m, 1 H, H-
room temperature for 30 min, then cooled to Ϫ45 °C and treated
with NaBH3CN (1  solution in THF, 8.2 mL). After the mixture
had been stirred for 5 min, a solution of TMSCl (0.88 mL in 16 mL
5Ј or H-5ЈЈ), 3.77 (br. s, 1 H, H-2), 3.73 (s, 3 H, COOCH3), of CH3CN) was added dropwise to the reaction mixture. After 1 h,
3.56Ϫ3.51 (2t, J3,4 ϭ J4,5 ϭ 9.4 Hz, 2 H, H-4Ј and H-4ЈЈ), 3.28 (dd, TLC analysis indicated the complete conversion of the starting ma-
J1Ј,2Ј ϭ 3.6, J2Ј,3Ј ϭ 9.9 Hz, 1 H, H-2Ј), 3.26 (dd, J2ЈЈ,3ЈЈ ϭ 10.0 Hz, terial. The solution was diluted with CH2Cl2 (50 mL) and filtered
1 H, H-2ЈЈ), 1.94Ϫ1.93 (2s, 6 H, OCOCH3), 1.67 [m, 1 H, through Celite, and the filtrate was washed with saturated NaHCO3
CH(CH3)2], 0.89Ϫ0.87 [4s, 12 H, C(CH3)2 and CH(CH3)2], solution. The aqueous layer was further extracted with CH2Cl2 (2
0.31Ϫ0.20 [2s, 6 H, Si(CH3)2] ppm. FAB-MS: m/z ϭ 1282 [MNaϩ]. ϫ 100 mL), and the organic layers were combined, dried with
C66H83N6O17Si (1260.5): calcd. C 62.89, H 6.64, N 6.67; found C
62.61, H 6.73, N 6.23.
MgSO4, and concentrated in vacuo. Purification over silica gel
(hexane/EtOAc, 10:1 Ǟ 4:1) gave 29 (1.21 g, 85%) as a colorless
3318
 2003 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
Eur. J. Org. Chem. 2003, 3308Ϫ3324

A Modular Synthesis of Heparin-Like Oligosaccharides
FULL PAPER
oil. [α]2D0 ϭ ϩ71.6 (c ϭ 1.16 CHCl3). TLC (hexane/EtOAc, 3:1).
Rf ϭ 0.36. H NMR (500 MHz, CDCl3): δ ϭ 7.33Ϫ6.82 (m, 9 H, of saturated NaHCO3 solution and the mixture was extracted with
temperature, the stannylene complex was hydrolyzed by addition
1
Ph), 5.03 (s, 1 H, H-1), 4.80 (d, Jgem ϭ 11.8 Hz, 1 H, CH2Ph), 4.53
EtOAc (2 ϫ 150 mL). The joined organic extracts were washed
(d, Jgem ϭ 12.0 Hz, 1 H, CH2PhOMe), 4.52 (d, 1 H, CH2Ph), 4.45 with brine and dried with MgSO4. Purification by column chroma-
(m, 2 H, CH2PhOMe, H-5), 3.93 (m, 1 H, H-4), 3.86 (d, J4,OH
11.9 Hz, OH), 3.79Ϫ3.76 (2s, 6 H, COOCH3, CH3OPhCH2), 3.73
ϭ
tography afforded the lactone 31 (1.36 g, 77%) as a colorless oil.
[α]2D0 ϭ ϩ41.0 (c ϭ 8.58, CHCl3). TLC (hexane/EtOAc, 2:1). Rf ϭ
1
(t, J2,3 ϭ J3,4 ϭ 3.1 Hz, 1 H, H-3), 3.46 (d, 1 H, H-2), 1.67Ϫ1.63 [m, 0.69. H NMR (300 MHz, CDCl3): δ ϭ 7.38Ϫ7.33 (m, 5 H, Ph),
1 H, CH(CH3)2], 0.89Ϫ0.88 [4s, 12 H, C(CH3)2 and CH(CH3)2], 5.48 (s, 1 H, H-1), 4.73 (d, J1gem ϭ 12 Hz, 1 H, CH2Ph), 4.59 (d,
0.25Ϫ0.17 [2s, 6 H, Si(CH3)2] ppm. 13C NMR (125 MHz, CDCl3): 1 H, CH2Ph), 4.53 (d, J2,3 ϭ 4.1 Hz, 1 H, H-2), 4.26 (d, J15,4
ϭ
δ ϭ 169.4, 159.4, 137.4, 129.8, 129.6, 128.6, 128.1, 127.6, 113.8,
94.8, 77.3, 77.2, 75.8, 75.0, 74.7, 74.0, 72.2, 67.8, 55.3, 52.1, 34.0,
24.9, 20.2, 18.6, 10.3, Ϫ1.7, Ϫ3.5 ppm.
4 Hz, 1 H, H-5), 4.13 (br. s, 1 H, H-4), 3.83Ϫ3.81 (m, 1 H, H-3),
2.90 (br. s, 1 H, OH), 1.64Ϫ1.55 [m, 1 H, CH(CH3)2], 0.87Ϫ85 [4s,
12 H, C(CH3)2 and CH(CH3)2], 0.22Ϫ0.09 [2s, 6 H, Si(CH3)2]
ppm. 13C NMR (75 MHz, CDCl3): δ ϭ 170.4, 137.4, 129.1, 128.7,
128.5, 88.9, 79.0, 78.0, 72.7, 72.5, 71.4, 34.5, 25.1, 20.6, 20.4, 19.0,
18.8, Ϫ1.6, Ϫ2.7 ppm. FAB-MS: m/z ϭ 431 [MNaϩ].
Methyl (Dimethylthexylsilyl 4-O-(2-Azido-3-O-benzyl-4,6-O-benzyl-
idene-2-deoxy-α-
D-glucopyranosyl)-3-O-benzyl-2-O-p-methoxy-
benzyl-β- -idopyranoside)uronate (30): Alcohol 29 (199 mg,
L
0.38 mmol) and glycosyl donor 8 (239 mg, 0.45 mmol) were dried
together overnight under high vacuum, taken up in CH2Cl2 (2 mL)
under argon, cooled to Ϫ10 °C, and treated with a freshly prepared
TMSOTf solution (0.15 , 100 µL, 0.015 mmol, 0.04 equiv.). TLC
analysis indicated completion of the reaction after 20 min. The re-
action mixture was quenched with saturated NaHCO3 solution
(1 mL), diluted with CH2Cl2 (10 mL), and extracted twice with
CH2Cl2/H2O. The collected organic fractions were washed with
brine and dried with MgSO4, and the solvent was removed under
reduced pressure. Chromatographic purification (toluene/EtOAc,
40:1) yielded disaccharide 30 (298 mg, 85%) as a colorless gum.
[α]2D0 ϭ ϩ21.6 (c ϭ 0.33, CHCl3). TLC (toluene/EtOAc, 12:1). Rf ϭ
Methyl (Phenyl 3-O-Benzyl-1-thio-α,β-L-idopyranoside)uronate (32):
Methyl (acetyl 2,4-di-O-acetyl-3-O-benzyl-α,β--idopyranoside)u-
ronate[15a] (1.44 g, 3.40 mmol) in CH2Cl2 (30 mL) was cooled to 0
°C and treated first with BF3·Et2O (2.15 mL, 17 mmol) and then
with thiophenol (0.38 mL, 3.7 mmol). The reaction mixture was
stirred at room temperature overnight and neutralized by addition
of saturated NaHCO3 solution (50 mL). The organic layer was
separated, washed with brine, dried with MgSO4, and concentrated
in vacuo. The crude material was purified by column chromatogra-
phy (hexane/EtOAc, 4:1) to obtain the thioglycoside as a mixture
of anomers. The thioglycoside (1.28 g, 2.7 mmol) was dissolved in
methanol, cooled to 0 °C, and treated with a catalytic amount
(20 mg) of sodium. The cooling bath was removed after complete
solution of the sodium, and the reaction mixture was stirred at
room temperature until TLC analysis indicated complete conver-
sion of the starting material. After neutralization with acidic resin
(Amberlite IR-120) and filtration, the solvent was removed under
reduced pressure and the crude material (780 mg, 73% over two
steps) was used as such for the next step. Data for the β Anomer:
[α]2D0 ϭ Ϫ86.3 (c ϭ 0.93, CHCl3). TLC (hexane/EtOAc, 1:1). Rf ϭ
1
0.47. H NMR (500 MHz, CDCl3): δ ϭ 7.52Ϫ6.61 (m, 19 H, Ph),
5.49 (s, 1 H, PhCHO), 5.04 (d, J1,2 ϭ 1.4 Hz, 1 H, H-1), 4.84 (d,
J1Ј,2Ј ϭ 3.5 Hz, 1 H, H-1Ј), 4.75 (d, Jgem ϭ 11.2 Hz, 1 H, CH2Ph),
4.64 (d, Jgem ϭ 11.6 Hz, 1 H, CH2Ph), 4.60 (d, 1 H, CH2Ph), 4.49
(d, 1 H, CH2Ph), 4.45 (d, Jgem ϭ 11.2 Hz, 1 H, CH2Ph), 4.40 (s, 1
H, H-4), 4.35 (dd, J5Ј,6Јa ϭ 5.0, J6Јa,6Јb ϭ 9.9 Hz, 1 H, H-6Јa),
4.20Ϫ4.16 (m, 1 H, H-5Ј), 4.13 (d, 1 H, CH2Ph), 3.73Ϫ3.71 (m, 4
H, COOCH3, H-3Ј), 3.54 (dd, J5Ј,6Јb ϭ 3.5 Hz, 1 H, H-6Јb), 3.54
(t, J3Ј,4Ј ϭ J4Ј,5Ј ϭ 10.2 Hz, 1 H, H-4Ј), 3.43Ϫ3.41 (m, 4 H,
CH3OPhCH2, H-2), 3.11 (dd, J2Ј,3Ј ϭ 10.0 Hz, 1 H, H-2Ј),
1.69Ϫ1.65 [m, 1 H, CH(CH3)2], 0.90Ϫ0.88 [4s, 12 H, C(CH3)2 and
CH(CH3)2], 0.31Ϫ0.19 [2s, 6 H, Si(CH3)2] ppm. 13C NMR
(125 MHz, CDCl3): δ ϭ 169.1, 158.8, 138.3, 137.9, 131.0, 129.1,
128.9, 128.6, 128.2, 128.1, 127.9, 127.8, 127.5, 126.4, 126.3, 113.7,
113.6, 101.4, 99.0, 96.2, 82.8, 76.1, 75.8, 75.3, 74.7, 74.3, 73.9, 73.3,
72.9, 68.5, 63.1, 54.8, 51.9, 34.1, 29.7, 24.9, 22.7, 20.2, 18.6,
14.1 ppm. FAB-MS: m/z ϭ 949 [MNaϩ].
1
0.4. H NMR (500 MHz, CDCl3): δ ϭ 7.50Ϫ7.22 (m, 10 H, Ph),
5.55 (s, 1 H, H-1), 5.21 (d, J4,5 ϭ 1.4 Hz, 1 H, H-5), 4.77 (d, Jgem ϭ
11.8 Hz, 1 H, CH2Ph), 4.61 (d, 1 H, CH2Ph), 4.16 (m, 1 H, H-4),
4.12Ϫ4.11 (m, 1 H, H-2), 3.81Ϫ3.80 (m, 4 H, COOCH3, H-3) ppm.
13C NMR (75 MHz, CDCl3): δ ϭ 171.1, 137.7, 136.7, 131.4, 129.4,
129.0, 128.9, 128.6, 128.4, 128.1, 128.0, 127.7, 89.9, 74.7, 72.7, 69.3,
69.1, 68.8, 53.0 ppm.
Methyl (Phenyl 2-O-Benzoyl-3-O-benzyl-1-thio-α,β-L-idopyrano-
side)uronate (33): A mixture of 32 (800 mg, 2.06 mmol) and
Bu2SnO (565 mg, 2.27 mmol) in methanol was heated at reflux un-
der an inert gas for 1 h until the turbid solution became clear. The
solvent was removed in vacuo, and the resulting foam was dried
under high vacuum for one hour. The stannylene acetal was then
dissolved in dioxane (30 mL), cooled to 0 °C, and treated with ex-
cess BzCl (2.39 mL, 20.6 mmol) and Et3N (2.9 mL, 21 mmol).
Upon addition of the base, rapid formation of an insoluble salt
was observed. TLC analysis indicated complete consumption of the
starting material after 30 min. After neutralization with acidic resin
(Amberlite IR-120) and filtration by suction through a pad of Ce-
lite, the solvent was removed by evaporation under reduced press-
ure, coevaporating three times with toluene. The crude residue was
then subjected to column chromatography (hexane/EtOAc, 4:1 Ǟ
1:1) to afford the pure 2-O-benzoyl derivative 33 as a mixture of
anomers (814 mg, 80%). [α]2D0 ϭ Ϫ11.8 (c ϭ 0.17, CHCl3). TLC
(hexane/EtOAc, 2:1). Rf ϭ 0.37. 1H NMR (500 MHz, CDCl3): δ ϭ
8.08Ϫ7.26 (m, 30 H, Ph), 5.73 (s, 1 H, H-1α), 5.51Ϫ5.49 (m, 1 H,
H-2α), 5.41 (m, 2 H, H-5α, H-2β), 5.31 (d, J1,2 ϭ 1.5 Hz, 1 H, H-
Hydrolysis of the p-Methoxybenzyl Ether of 30: Disaccharide 30
(103 mg, 0.13 mmol) was dissolved in a mixture of CH2Cl2/H2O
(10:1, 3 mL), and DDQ (0.13 mmol, 44 mg) was added slowly
whilst stirring at room temperature. After 40 min, TLC analysis
indicated the complete hydrolysis of the starting material. The reac-
tion mixture was diluted with CH2Cl2 (10 mL) and quenched by
addition of H2O (2 mL). After extraction with CH2Cl2/saturated
NaHCO3 solution, followed by the washing of the organic fraction
with brine, drying over MgSO4, and removal of the solvent under
reduced pressure, the crude residue was subjected to column chro-
matography (hexane/EtOAc, 4:1) to afford disaccharide 13 (97 mg,
90%) as a colorless gum. The spectroscopic data of the compound
were in agreement with the data reported above.
Dimethylthexylsilyl (3-O-Benzyl-β-L-idopyranuroside)-6,2-lactone
(31): Diol (1.91 g, 4.33 mmol) and (Bu3Sn)2O (1.11 mL,
7
2.17 mmol) were dissolved in toluene (60 mL) and heated at reflux
for 4 h with use of a DeanϪStark device for the continuous re-
moval of reaction water. After the mixture had cooled to room
Eur. J. Org. Chem. 2003, 3308Ϫ3324
www.eurjoc.org
 2003 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
3319

´
J.-L. de Paz, R. Ojeda, N. Reichardt, M. Martın-Lomas
FULL PAPER
1β), 4.90 (d, Jgem ϭ 12 Hz, 1 H, CH2Ph), 4.78 (d, Jgem ϭ 11.7 Hz, Methanolysis of Lactone 35: Disaccharide 35 (84 mg, 0.11 mmol)
1 H, CH2Ph), 4.71 (d, 1 H, CH2Ph), 4.69 (d, 1 H, CH2Ph), 4.62 (s, and Bu2SnO (54 mg, 0.22 mmol) were suspended in MeOH (4 mL)
1 H, H-5β), 4.15 (m, 1 H, H-4α), 4.03 (m, 2 H, H-3β, H-4β), 3.94
(m, 1 H, H-3α), 3.83 (2s, 6 H, COOCH3), 2.83 (d, J4,OH ϭ 12 Hz,
1 H, OH) ppm. FAB-MS: m/z ϭ 494 [MNaϩ].
and heated at reflux for 5 h, after which TLC analysis indicated the
complete methanolysis of the lactone. The Bu2SnO complex was
hydrolyzed by addition of saturated NaHCO3 solution (2 mL), and
the desired ester was extracted with CH2Cl2 (20 mL). After drying
over MgSO4 and evaporation of the solvent under reduced press-
ure, the obtained residue was subjected to column chromatography
to afford disaccharide 13 (80 mg, 0.1 mmol, 75%) as a colorless
foam. The β anomer 13β was also isolated from the reaction mix-
ture. Spectroscopic data for the α anomer were found to be ident-
ical with those for compound 13 described above. Physical data for
β anomer 13β: TLC (toluene/EtOAc, 4:1). Rf ϭ 0.59. [α]2D0 ϭ Ϫ47.3
Methyl (Phenyl 4-O-(2-Azido-3-O-benzyl-4,6-O-benzylidene-α-
D-
glucopyranosyl)-2-O-benzoyl-3-O-benzyl-1-thio-α- -idopyranoside)-
L
uronate (34): Acceptor 33α (160 mg, 0.32 mmol) and donor 7
(222 mg, 0.42 mmol) were dried under high vacuum, dissolved in
CH2Cl2 (4 mL), cooled to 0 °C, and treated with a freshly prepared
TMSOTf solution in CH2Cl2 (0.17 , 100 µL, 0.017 mmol, 4%).
After stirring for 1 h, the reaction mixture was quenched with satu-
rated NaHCO3 solution (1.5 mL), the mixture was extracted with
CH2Cl2/H2O, the organic fraction was dried with MgSO4, and the
solvent was removed under reduced pressure. Column chromatog-
raphy of the crude residue afforded the disaccharide 34 (183 mg,
65%). [α]2D0 ϭ Ϫ97.8 (c ϭ 0.72, CHCl3). TLC (toluene/EtOAc, 5:1).
Rf ϭ 0.61. 1H NMR (500 MHz, CDCl3): δ ϭ 8.13Ϫ7.21 (m, 25 H,
Ph), 5.80 (s, 1 H, H-1), 5.48 (s, 1 H, PhCHO), 5.41 (s, 1 H, H-2),
5.38 (d, J4,5 ϭ 1.6 Hz, 1 H, H-5), 4.98 (d, Jgem ϭ 11.7 Hz, 1 H,
CH2Ph), 4.77 (d, 1 H, CH2Ph), 4.70 (d, J1Ј,2Ј ϭ 3.6 Hz, 1 H, H-1Ј),
4.35Ϫ3.96 (m, 2 H, CH2Ph, H-6Јa), 4.21 (br. s, 1 H, H-3), 4.10 (br.
s, 1 H, H-4), 4.01 (m, 1 H, H-4Ј), 3.82 (d, Jgem ϭ 10.7 Hz, 1 H,
1
(c ϭ 0.64, CHCl3). H NMR (500 MHz, CDCl3): δ ϭ 7.46Ϫ7.25
(m, 15 H, Ph), 5.50 (s, 1 H, PhCHO), 5.01 (d, J1,2 ϭ 1.0 Hz, 1 H,
H-1), 4.87 (d, Jgem ϭ 11.2 Hz, 1 H, CH2Ph), 4.76 (d, 1 H, CH2Ph),
4.62 (d, Jgem ϭ 12.3 Hz, 1 H, CH2Ph), 4.56 (d, 1 H, CH2Ph), 4.50
(d, J4,5 ϭ 1.9 Hz, 1 H, H-5), 4.21 (d, J1Ј,2Ј ϭ 8.1 Hz, 1 H, H-1Ј),
4.09 (dd, J6Јa,6Јb ϭ 10.5, J5Ј,6Јa ϭ 5.0 Hz, 1 H, H-6Јa), 4.01 (m, 1
H, H-4), 3.95 (m, 1 H, H-3), 3.81 (s, 3 H, COOCH3), 3.69Ϫ3.58
(m, 3 H, H-6Јb, H-4Ј, H-2), 3.53 (t, J2Ј,3Ј ϭ J3Ј,4Ј ϭ 9.3 Hz, 1 H,
H-3Ј), 3.34Ϫ3.31 (m, 1 H, H-2Ј), 3.27Ϫ3.22 (ddd, 1 H, H-5Ј), 2.56
(d, J2,OH ϭ 8.9 Hz, 1 H, OH), 1.66Ϫ1.62 [m, 1 H, CH(CH3)2],
0.87Ϫ0.86 [4s, 12 H, C(CH3)2 and CH(CH3)2], 0.23Ϫ0.17 [2s, 6 H,
Si(CH3)2] ppm. 13C NMR (125 MHz, CDCl3): δ ϭ 168.9, 137.7,
137.5, 137.0, 129.1, 128.6, 128.4, 128.3, 128.1, 127.9, 127.8, 127.7,
126.0, 103.9, 101.3, 94.6, 81.2, 79.4, 77.2, 76.3, 76.1, 74.9, 73.9,
72.3, 68.5, 68.4, 66.2, 66.0, 52.2, 34.1, 25.0, 20.3, 20.1, 18.6, 18.4,
1.0, Ϫ1.9, Ϫ3.2 ppm. FAB-MS: m/z ϭ 828 [MNaϩ].
CH2Ph), 3.78 (s, 3 H, COOCH3), 3.61 (t, J5Ј,6Јa ϭ J6Јa,6Јb
ϭ
10.2 Hz, 1 H, H-5Ј), 3.54Ϫ3.49 (m, 2 H, H-3Ј, H-6Јb), 3.23Ϫ3.20
(m, 1 H, H-2Ј) ppm. 13C NMR (125 MHz, CDCl3): δ ϭ 169.2,
165.5, 137.8, 137.5, 137.1, 135.5, 133.3, 131.4, 130.0, 129.6, 129.1,
129.0, 128.8, 128.5, 128.3, 128.1, 127.9, 127.7, 127.6, 126.1, 101.3,
100.4, 87.1, 82.3, 76.9, 76.8, 76.7, 74.7, 72.8, 72.3, 69.2, 68.5, 68.3,
63.5, 63.3, 52.3, 2937 ppm. FAB-MS: m/z ϭ 882 [MNaϩ].
Methyl [Dimethylthexylsilyl 2-O-Acetyl-4-O-(2-azido-3-O-benzyl-2-
deoxy-α-D-glucopyranosyl)-3-O-benzyl-β-L-idopyranoside]uronate
Dimethylthexylsilyl 4-O-(2-Azido-3-O-benzyl-4,6-O-benzylidene-2-
deoxy-α,β-D-glucopyranosyl)-3-O-benzyl-β-L-idopyranoside)-6,2-
(36): EtSH (87 µL, 1.2 mmol) and catalytic pTsOH were added to
a solution of 24 (100 mg, 0.12 mmol) in dry CH2Cl2 (1.5 mL). After
stirring for 3 h under argon, the mixture was neutralized with solid
NaHCO3, diluted with CH2Cl2 (25 mL), washed with H2O
(25 mL), dried (MgSO4), and concentrated to dryness. The purifi-
cation of the residue was carried out by flash chromatography (hex-
ane/EtOAc, 3:2) to yield 36 (80 mg, 89%). [α]2D0 ϭ ϩ52.0 (c ϭ 1,
lactone (35): Alcohol 31 (186 mg, 0.46 mmol) and glycosyl donor 8
(316 mg, 0.60 mmol) were dissolved in CH2Cl2 (1 mL), and the sol-
vents were evaporated under reduced pressure to afford a stable
foam, which was dried under high vacuum for several h. The mix-
ture was dissolved in CH2Cl2 (3 mL) under an inert gas, cooled to
Ϫ5 °C, and activated by addition of TMSOTf solution (100 µL of
a 0.03  solution in CH2Cl2, 0.04 equiv.). After 30 min, the cooling
bath was removed and the reaction mixture was warmed to room
temperature. After 2.5 h no further evolution was observed, and
the reaction was quenched by the addition of saturated NaHCO3
solution (5 mL). After dilution with CH2Cl2 (10 mL), the phases
were separated and the aqueous layer was further extracted with
CH2Cl2 (2 ϫ 10 mL). The combined organic extracts were dried
with MgSO4 and concentrated in vacuo. Purification by silica gel
(hexane/EtOAc, 10:1 Ǟ 4:1) afforded the disaccharide 35 (312 mg,
88%) as a mixture of anomers (α/β: 8:1), [α]2D0 ϭ ϩ32.0 (c ϭ 1.5,
CHCl3). TLC (hexane/EtOAc, 3:2). Rf
ϭ
0.18. 1H NMR
(500 MHz, CDCl3): δ ϭ 7.38Ϫ7.27 (m, 10 H, Ph), 5.05 (br. s, 1 H,
H-1), 4.96 (br. s, 1 H, H-2), 4.78 (d, J1Ј,2Ј ϭ 3.3 Hz, 1 H, H-1Ј),
4.85Ϫ4.75 (2d, Jgem ϭ 11.2 Hz, 2 H, CH2Ph), 4.73Ϫ4.66 (2d,
Jgem ϭ 11.7 Hz, 2 H, CH2Ph), 4.47 (br. s, 1 H, H-5), 4.00 (m, 1 H,
H-4), 3.98 (m, 1 H, H-3), 3.82Ϫ3.57 (m, 5 H, H-3Ј, H-4Ј, H-5Ј, H-
6Јa and H-6Јb), 3.75 (s, 3 H, COOCH3), 3.17 (dd, J2Ј,3Ј ϭ 10.2 Hz,
1 H, H-2Ј), 2.09 (s, 3 H, OCOCH3), 1.60 [m, 1 H, CH(CH3)2],
0.87Ϫ0.82 [4s, 12 H, C(CH3)2 and CH(CH3)2], 0.20Ϫ0.13 [2s, 6 H,
Si(CH3)2] ppm. 13C NMR (125 MHz, CDCl3): δ ϭ 170.7, 169.0,
138.0, 128.0, 97.8, 93.6, 79.6, 74.9, 73.9, 73.4, 73.2, 72.9, 72.2, 71.1,
67.6, 63.0, 62.2, 52.3, 34.1, 24.9, 20.9, 20.2, 18.4, Ϫ2.1, Ϫ3.6 ppm.
FAB-MS: m/z ϭ 782 [MNaϩ]. C37H53N3O12Si (759.9): calcd. C
58.48, H 7.03, N 5.53; found C 58.80, H 7.32, N 5.17.
CHCl3). TLC (toluene/EtOAc, 9:1). Rf
(500 MHz,CDCl3, data for the α anomer): δ ϭ 7.48Ϫ7.27 (m, 15
H, Ph), 5.53 (s, 1 H, PhCHO), 5.49 (s, 1 H, H-1), 4.93 (d, Jgem
ϭ
0.55. 1H NMR
ϭ
10.9 Hz, 1 H, CH2Ph), 4.90 (d, J1Ј,2Ј ϭ 3.9 Hz, 1 H, H-1Ј), 4.75 (d,
1 H, CH2Ph), 4.74 (d, Jgem ϭ 11.9 Hz, 1 H, CH2Ph), 4.62 (d, 1 H,
CH2Ph), 4.51 (d, J2,3 ϭ 4.1 Hz, 1 H, H-2), 4.44 (d, J4,5 ϭ 4.0 Hz,
Methyl [Dimethylthexylsilyl 2-O-Acetyl-4-O-(2-azido-6-O-benzoyl-
1 H, H-5), 4.42 (m, 1 H, H-6Јa), 3.99 (m, 1 H, H-4), 3.97 (m, 2 H, 3-O-benzyl-2-deoxy-α-
H-3, H-3Ј), 3.85 (m, 1 H, H-5Ј), 3.67 (m, 2 H, H-4Ј, H-6Јb), 3.87 side]uronate (37): BzCN (72 µL of a 0.9  solution in dry CH3CN)
(dd, J2Ј,3Ј ϭ 10.1 Hz, 1 H, H-2Ј), 1.59 [m, 1 H, CH(CH3)2], and catalytic Et3N were added to a cooled (Ϫ40 °C) solution of 36
D-glucopyranosyl)-3-O-benzyl-β-L-idopyrano-
0.86Ϫ0.83 [4s, 12 H, C(CH3)2 and CH(CH3)2], 0.14Ϫ15 [2s, 6 H,
(47 mg, 62 µmol) in dry CH3CN (1 mL). After 4 h, additional
Si(CH3)2] ppm. 13C NMR (125 MHz, CDCl3): δ ϭ 167.5, 137.7, BzCN was added (18 µL of a 0.9  solution in dry CH3CN) until
137.2, 136.7, 128.9, 128.7, 128.4, 128.2, 128.0, 127.9, 126.1, 101.4, starting material had disappeared. After 7 h, MeOH was added and
100.2, 88.7, 82.3, 80.8, 76.8, 76.1, 75.8, 75.1, 72.5, 70.7, 68.4, 63.7,
62.8, 34.1, 24.8, 20.1, 20.0, 18.5, 18.4, Ϫ2.1, Ϫ3.1 ppm. FAB-MS: was evaporated, and the residue was dissolved in MeOH and con-
m/z ϭ 796 [MNaϩ].
centrated to dryness. The purification was carried out by flash
the mixture was allowed to reach room temperature. The solvent
3320
 2003 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
Eur. J. Org. Chem. 2003, 3308Ϫ3324

A Modular Synthesis of Heparin-Like Oligosaccharides
FULL PAPER
chromatography (hexane/EtOAc, 4:1) to afford 37 (48 mg, 91%).
(br. s, 1 H, H-2), 4.89Ϫ4.70 (2d, Jgem ϭ 11.0 Hz, 2 H, CH2Ph),
4.78Ϫ4.70 (2d, Jgem ϭ 11.6 Hz, 2 H, CH2Ph), 4.74 (d, J1Ј,2Ј ϭ
[α]2D0 ϭ ϩ72.7 (c ϭ 1, CHCl3). TLC (hexane/EtOAc, 4:1). Rf ϭ
1
0.17. H NMR (500 MHz, CDCl3): δ ϭ 8.02Ϫ7.24 (m, 15 H, Ph), 3.6 Hz, 1 H, H-1Ј), 4.68 (m, 1 H, H-5), 4.26 (dd, J5Ј,6Јa ϭ 4.8,
5.06 (d, J1,2 ϭ 1.4 Hz, 1 H, H-1), 4.99 (m, 1 H, H-2), 4.88 (d, J6Јa,6Јb ϭ 10.1 Hz, 1 H, H-6Јa), 4.11 (m, 1 H, H-3), 4.05 (m, 1 H,
J1Ј,2Ј ϭ 3.5 Hz, 1 H, H-1Ј), 4.87Ϫ4.81 (2d, Jgem ϭ 10.9 Hz, 2 H,
H-4), 3.97 (dd, 1 H, H-3Ј), 3.88 (ddd, 1 H, H-5Ј), 3.78 (s, 3 H,
CH2Ph), 4.71Ϫ4.65 (2d, Jgem ϭ 11.7 Hz, 2 H, CH2Ph), 4.62 (dd, COOCH3), 3.65Ϫ3.61 (m, 2 H, H-4Ј and H-6Јb), 3.38 (dd, J12Ј,3Ј
ϭ
J6Јa,6Јb ϭ 12.5, J5Ј,6Јa ϭ 2.4 Hz, 1 H, H-6Јa), 4.48 (br. s, 1 H, H-5), 9.9 Hz, 1 H, H-2Ј), 2.05 (s, 3 H, OCOCH3) ppm. FAB-MS: m/z ϭ
4.39 (dd, J5Ј,6Јb ϭ 2.0 Hz, 1 H, H-6Јb), 4.10Ϫ4.08 (m, 2 H, H-4 871 [MNaϩ].
and H-5Ј), 3.98 (m, 1 H, H-3), 3.79 (m, 1 H, H-3Ј), 3.78 (s, 3 H,
Methyl 4-O-(6-O-Acetyl-2-azido-3,4-di-O-benzyl-2-deoxy-α-
D-gluco-
COOCH3), 3.51 (m, 1 H, H-4Ј), 3.16 (dd, J2Ј,3Ј ϭ 10.2 Hz, 1 H, H-
2Ј), 3.08 (d, J4Ј,OH ϭ 3.3 Hz, 1 H, OH), 2.11 (s, 3 H, OCOCH3),
1.60 [m, 1 H, CH(CH3)2], 0.88Ϫ0.83 [4s, 12 H, C(CH3)2 and
CH(CH3)2], 0.22Ϫ0.13 [2s, 6 H, Si(CH3)2] ppm. 13C NMR
(125 MHz, CDCl3): δ ϭ 170.6, 169.0, 167.6, 137.9, 127.9, 97.7,
93.7, 78.8, 75.2, 74.3, 73.3, 72.94, 72.87, 71.2, 70.5, 67.6, 63.0, 62.9,
52.2, 34.1, 24.8, 21.0, 20.2, 18.4, Ϫ2.0, Ϫ3.5 ppm. FAB-MS: m/z ϭ
886 [MNaϩ]. C44H57N3O13Si·H2O (882.1): calcd. C 59.91, H 6.74,
N 4.76; found C 60.15, H 6.76, N 4.65.
pyranosyl)-2-O-benzoyl-3-O-benzyl-α,β- -idopyranosuronate (40):
L
An excess of (HF)n·Py complex (3.1 mL) was added to a cooled
(Ϫ10 °C) solution of 21 (1.067 g, 1.12 mmol) in dry THF (30 mL).
The reaction mixture was then warmed up to 0 °C and stirred un-
der argon. After 24 h, CH2Cl2 (200 mL) was added and the mixture
was washed with H2O (2 ϫ 100 mL) and saturated NaHCO3 solu-
tion (50 mL) until neutral pH. The organic layer was dried
(MgSO4) and concentrated in vacuo. The residue was purified by
flash column chromatography (hexane/EtOAc, 2:1) to afford 40
(800 mg, 88%) as an α/β mixture. TLC (hexane/EtOAc, 2:1). Rf ϭ
Methyl 2-O-Acetyl-4-O-(2-azido-3-O-benzyl-4,6-O-benzylidene-2-
deoxy-α-D-glucopyranosyl)-3-O-benzyl-α,β-L-idopyranosuronate
1
0.25. H NMR (500 MHz, CDCl3): δ ϭ 8.14Ϫ7.06 (m, 20 H, Ph),
5.45 (br. d, J1α,OH ϭ 8.4 Hz, 0.5 H, H-1α), 5.21 (br. d, J1β,OH
ϭ
(38): An excess of (HF)n·Py complex (3 mL) was added to a cooled
(Ϫ15 °C) solution of 24 (1.17 g, 1.37 mmol) in dry THF (30 mL).
The reaction mixture was then warmed up to 0 °C and stirred un-
der argon. After 24 h, CH2Cl2 (200 mL) was added and the mixture
was washed with H2O (2 ϫ 50 mL) and saturated NaHCO3 solu-
tion (100 mL) until neutral pH. The organic layer was dried
(MgSO4) and concentrated in vacuo. The residue was purified by
flash chromatography (hexane/EtOAc, 2:1) to yield 38 (893 mg,
9.0 Hz, 0.5 H, H-1β), 5.06 (br. s, 1 H, H-2 α and β), 4.91 (br. s, 0.5
H, H-5α), 4.91Ϫ4.85 (m, 1 H, CH2Ph), 4.80Ϫ4.74 (2d, Jgem ϭ 11.5,
Jgem ϭ 11.7 Hz, 1 H, CH2Ph), 4.66Ϫ4.62 (m, 2 H, H-1Ј, CH2Ph),
4.59 (br. s, 0.5 H, H-5β), 4.47 (m, 1 H, CH2Ph), 4.37 (m, 1 H, H-
6Јa), 4.31 (m, 1 H, H-3), 4.25Ϫ4.19 (m, 1.5 H, H-6Јb, OHα),
4.01Ϫ3.82 (m, 4 H, H-5Ј, H-4, CH2Ph), 3.64 (m, 0.5 H, OHβ), 3.79
(s, 3 H, COOCH3 α and β), 3.41 (m, 2 H, H-3Ј and H-4Ј), 3.19
(dd, J1Ј,2Ј ϭ 3.7, J2Ј,3Ј ϭ 9.2 Hz, 1 H, H-2Ј), 2.00 (s, 3 H, OCOCH3
α and β) ppm. FAB-MS: m/z ϭ 834 [MNaϩ]. C43H45N3O13 (811.9):
calcd. C 63.62, H 5.59, N 5.18; found C 63.22, H 5.95, N 4.94.
1
94%) as an α/β mixture: TLC (hexane/EtOAc, 2:1). Rf ϭ 0.17. H
NMR (500 MHz, CDCl3): δ ϭ 7.45Ϫ7.24 (m, 15 H, Ph), 5.52Ϫ5.51
(2s, 1 H, PhCHO α and β), 5.31 (br. d, J1α,OH ϭ 8.4 Hz, 0.5 H, H-
1α), 5.10 (br. d, J1β,OH ϭ 10.7 Hz, 0.5 H, H-1β), 4.90Ϫ4.66 (m, 6
H, H-2, H-5α, H-1Јα, CH2Ph), 4.63 (d, J1Ј,2Ј ϭ 3.4 Hz, 0.5 H, H-
1Јβ), 4.58 (d, J4,5 ϭ 1.9 Hz, 0.5 H, H-5β), 4.27 (dd, J5Ј,6Јa ϭ 4.7,
J6Јa,6Јb ϭ 10.1 Hz, 1 H, H-6Јa), 4.12Ϫ3.75 (m, 4 H, H-3, H-4, H-
3Ј, H-5Ј), 3.67Ϫ3.61 (m, 2 H, H-4Ј, H-6Јb), 3.79Ϫ3.77 (2s, 3 H,
COOCH3 α and β), 3.38 (dd, J2Ј,3Ј ϭ 9.9 Hz, 0.5 H, H-2Јβ), 3.34
(dd, J1Ј,2Ј ϭ 3.6, J2Ј,3Ј ϭ 9.9 Hz, 0.5 H, H-2Јα), 2.09Ϫ2.05 (2s, 3 H,
O-(Methyl 4-O-(6-O-Acetyl-2-azido-3,4-di-O-benzyl-2-deoxy-α-
D-
glucopyranosyl)-2-O-benzoyl-3-O-benzyl-α,β- -idopyranosyluronate)
L
Trichloroacetimidate (41): Cl3CCN (593 µL, 5.9 mmol) and K2CO3
(55 mg, 0.39 mmol) were added to a solution of 40 (320 mg,
0.39 mmol) in dry CH2Cl2 (4 mL). After stirring at room tempera-
ture for 4 h, the mixture was then filtered and concentrated in va-
cuo, and the residue was purified by chromatography over a short
silica gel column (hexane/EtOAc, 2:1) to yield 41 (357 mg, 95%) as
an α/β mixture. TLC (hexane/EtOAc, 2:1). Rf ϭ 0.53 and 0.38 (β
and α). 1H NMR (500 MHz, CDCl3): δ ϭ 8.67 (s, 0.6 H, NHβ),
8.64 (s, 0.4 H, NHα), 8.13Ϫ7.10 (m, 20 H, Ph), 6.55 (br. s, 0.6 H,
H-1β), 6.29 (d, J1,2 ϭ 1.8 Hz, 0.4 H, H-1α), 5.43 (m, 0.4 H, H-2α),
5.33 (br. s, 0.6 H, H-2β), 5.00 (br. s, 0.4 H, H-5α), 4.93Ϫ4.88 (m,
1 H, CH2Ph), 4.79Ϫ4.65 (m, 3.6 H, H-5β, H-1Ј, CH2Ph),
4.52Ϫ4.46 (m, 1 H, CH2Ph), 4.38Ϫ4.35 (m, 1.4 H, H-6Јa, H-3α),
4.25Ϫ4.23 (m, 1.6 H, H-6Јb, H-3β), 4.15 (br. s, 0.4 H, H-4α),
4.03Ϫ3.88 (m, 3.6 H, H-5Ј, H-4β, CH2Ph), 3.79Ϫ3.78 (2s, 3 H,
COOCH3 α and β), 3.51Ϫ3.41 (m, 2 H, H-3Ј and H-4Ј), 3.23Ϫ3.19
(m, 1 H, H-2Ј), 1.99 (s, 3 H, OCOCH3 α and β) ppm. C45H45
Cl3N4O13 (956.2): calcd. C 56.52, H 4.74, N 5.86; found C 56.17,
H 4.98, N 5.79.
OCOCH3
α and β) ppm. FAB-MS: m/z ϭ
728 [MNaϩ].
C36H39N3O12·2H2O (741.8): calcd. C 58.29, H 5.84, N 5.67; found
C 58.29, H 6.03, N 5.67.
O-(Methyl 2-O-Acetyl-4-O-(2-azido-3-O-benzyl-4,6-O-benzylidene-
2-deoxy-α-D-glucopyranosyl)-3-O-benzyl-α,β-L-idopyranosyluronate)
Trichloroacetimidate (39): Cl3CCN (3.8 mL, 39 mmol) and K2CO3
(187 mg, 1.35 mmol) were added to a solution of 38 (893 mg,
1.29 mmol) in dry CH2Cl2 (10 mL). After stirring at room tempera-
ture for 3 h, the mixture was then filtered off and concentrated in
vacuo, and the residue was purified by chromatography over a
short silica gel column (hexane/EtOAc, 3:1) to yield 39 (935 mg,
87%) as an α/β mixture. 39β: TLC (hexane/EtOAc, 2:1). Rf ϭ 0.61.
1H NMR (500 MHz, CDCl3): δ ϭ 8.67 (s, 1 H, NH), 7.44Ϫ7.22
(m, 15 H, Ph), 6.40 (br. s, 1 H, H-1), 5.53 (s, 1 H, PhCHO), 5.13
(br. s, 1 H, H-2), 4.98 (d, J4,5 ϭ 1.7 Hz, 1 H, H-5), 4.91Ϫ4.71 (2d,
Methyl [Dimethylthexylsilyl O-(2-Azido-3-O-benzyl-4,6-O-benzyl-
Jgem ϭ 11.0 Hz, 2 H, CH2Ph), 4.82Ϫ4.65 (2d, Jgem ϭ 11.6 Hz, 2 idene-2-deoxy-α-
H, CH2Ph), 4.80 (d, J1Ј,2Ј ϭ 3.7 Hz, 1 H, H-1Ј), 4.29 (dd, J5Ј,6Јa O-benzyl-α- -idopyranosyluronate)-(1Ǟ4)-O-(2-azido-6-O-benzoyl-
4.9, J6Јa,6Јb ϭ 10.1 Hz, 1 H, H-6Јa), 4.15 (m, 1 H, H-4), 3.97Ϫ3.92 3-O-benzyl-2-deoxy-α- -glucopyranosyl)-(1Ǟ4)-2-O-acetyl-3-O-
(m, 2 H, H-3 and H-3Ј), 3.78 (s, 3 H, COOCH3), 3.78 (m, 1 H, H- benzylβ- -idopyranoside]uronate (42): TMSOTf (100 µL of a 0.18 
5Ј), 3.67Ϫ3.63 (m, 2 H, H-4Ј and H-6Јb), 3.36 (dd, J12Ј,3Ј
10.0 Hz, 1 H, H-2Ј), 2.09 (s, 3 H, OCOCH3) ppm. FAB-MS: m/z ϭ
D-glucopyranosyl)-(1Ǟ4)-O-(methyl 2-O-acetyl-3-
ϭ
L
D
L
ϭ
solution in dry CH2Cl2) was added under argon to a cooled (0 °C)
solution of 37 (394 mg, 0.46 mmol) and 39 (573 mg, 0.68 mmol) in
871 [MNaϩ]. 39α: TLC (hexane/EtOAc, 2:1). Rf ϭ 0.50. H NMR dry CH2Cl2 (5 mL). After 1.5 h, saturated NaHCO3 solution
1
(500 MHz, CDCl3): δ ϭ 8.66 (s, 1 H, NH), 7.42Ϫ7.24 (m, 15 H, (10 mL) and CH2Cl2 (250 mL) were added, and the mixture was
Ph), 6.20 (d, J1,2 ϭ 1.4 Hz, 1 H, H-1), 5.50 (s, 1 H, PhCHO), 5.27
www.eurjoc.org
washed with H2O (200 mL). The organic layer was dried (MgSO4)
3321
Eur. J. Org. Chem. 2003, 3308Ϫ3324
 2003 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

´
J.-L. de Paz, R. Ojeda, N. Reichardt, M. Martın-Lomas
FULL PAPER
and concentrated in vacuo, and the residue was purified by flash
H, H-3c), 3.79 (t, J12,3 ϭ J3,4 ϭ 10.1 Hz, 1 H, H-3b), 3.69Ϫ3.54
column chromatography (toluene/EtOAc, 12:1 and hexane/EtOAc, (m, 5 H, H-3d, H-4d, H-5d, H-6d, H-6Јd), 3.73 and 3.37 (2s, 6 H,
4:1) to yield 42 (352 mg, 50%) and unchanged acceptor (175 mg,
44%). Glycal 43 was also isolated from the reaction mixture. 42:
COOCH3 a and c), 3.29 (dd, J11,2 ϭ 3.4 Hz, 1 H, H-2b), 3.12 (dd,
J12,3 ϭ 9.7, J1,2 ϭ 3.5 Hz, 1 H, H-2d), 2.38 (d, 1 H, OH-4), 1.91
(m, 1 H, OH-6), 2.10 and 2.01 (2s, 6 H, OCOCH3 a and c), 1.59
[α]2D0 ϭ ϩ39.4 (c ϭ 0.58, CHCl3). TLC (hexane/EtOAc, 4:1). Rf ϭ
1
0.19. H NMR (500 MHz, CDCl3): δ ϭ 8.08Ϫ7.24 (m, 30 H, Ph), [m, 1 H, CH(CH3)2], 0.88Ϫ0.83 [4s, 12 H, C(CH3)2 and CH(CH3)2],
5.51 (s, 1 H, PhCHO), 5.39 (d, J1,2 ϭ 4.2 Hz, 1 H, H-1c), 5.06 (d,
0.22Ϫ0.14 [2s, 6 H, Si(CH3)2] ppm. 13C NMR (125 MHz, CDCl3):
J11,2 ϭ 1.4 Hz, 1 H, H-1a), 4.96 (br. s, 1 H, H-2a), 4.92 (dd, 1 H, δ ϭ 170.7, 169.7, 169.3, 169.0, 166.2, 137.8, 127.7, 98.1, 97.9, 97.1,
H-2c), 4.89 (d, J1,2 ϭ 3.7 Hz, 1 H, H-1d), 4.79 (d, J1,2 ϭ 3.5 Hz, 1 93.5, 79.3, 78.2, 75.14, 75.06, 74.85, 74.76, 73.7, 73.6, 73.5, 73.2,
H, H-1 b), 4.88Ϫ4.80 (m, 3 H, H-6b and CH2Ph), 4.74Ϫ4.62 (m, 72.9, 72.6, 72.1, 71.0, 70.1, 70.0, 69.9, 67.7, 63.3, 62.8, 62.3, 62.1,
7 H, H-5c and CH2Ph), 4.49 (d, J114,5 ϭ 1.6 Hz, 1 H, H-5a), 4.34
52.3, 51.8, 34.1, 24.9, 20.9, 20.8, 20.2, 18.4, Ϫ1.9, Ϫ3.5 ppm. FAB-
(dd, J5,6Ј ϭ 2.3, J6,6Ј ϭ 12.5 Hz, 1 H, H-6Јb), 4.19 (dd, J115,6 ϭ 4.8, MS: m/z ϭ 1485 [MNaϩ]. C73H90N6O24Si (1463.7): calcd. C 59.90,
J6,6Ј ϭ 10.1 Hz, 1 H, H-6d), 4.08Ϫ4.03 (m, 3 H, H-4b, H-5b, H-
4a), 3.98Ϫ3.96 (m, 2 H, H-3a, H-4c), 3.91 (dd, J112,3 ϭ J3,4
5.4 Hz, 1 H, H-3c), 3.83Ϫ3.76 (m, 3 H, H-5d, H-3b, H-3d),
3.67Ϫ3.60 (m, 2 H, H-4d, H-6Јd), 3.73 and 3.37 (2s, 6 H, COOCH3
H 6.20, N 5.74; found C 59.85, H 6.35, N 5.40.
ϭ
Methyl [Dimethylthexylsilyl O-(2-Azido-6-O-benzoyl-3-O-benzyl-2-
deoxy-α-
benzyl-α-
D
-glucopyranosyl)-(1Ǟ4)-O-(methyl 2-O-acetyl-3-O-
L
-idopyranosyluronate)-(1Ǟ4)-O-(2-azido-6-O-benzoyl-3-
a and c), 3.29 (dd, J112,3 ϭ 10.3 Hz, 1 H, H-2b), 3.25 (dd, J112,3
ϭ
O-benzyl-2-deoxy-α-
D-glucopyranosyl)-(1Ǟ4)-2-O-acetyl-3-O-
10.0 Hz, 1 H, H-2d), 2.10 and 2.06 (2s, 6 H, OCOCH3 a and c),
1.60 [m, 1 H, CH(CH3)2], 0.89Ϫ0.84 (4s, 12 H, C(CH3)2 and
CH(CH3)2], 0.23Ϫ0.15 (2s, 6 H, Si(CH3)2] ppm. 13C NMR
(125 MHz, CDCl3): δ ϭ 170.7, 169.7, 169.0, 168.9, 166.1, 137.8,
126.0, 101.5, 98.8, 98.0, 97.1, 93.5, 82.5, 78.3, 75.6, 75.1, 75.0, 74.9,
74.8, 73.9, 73.8, 73.7, 73.5, 72.9, 72.7, 70.0, 69.9, 68.5, 67.7, 63.4,
63.2, 62.8, 62.2, 52.3, 51.8, 34.1, 24.9, 20.9, 20.7, 20.2, 18.4, Ϫ1.9,
benzyl-β- -idopyranoside]uronate (45): BzCN (21 mg, 0.16 mmol)
L
and catalytic Et3N were added to a cooled (Ϫ35 °C) solution of 44
(215 mg, 0.15 mmol) in dry CH3CN (3 mL). After 1 h, MeOH was
added and the mixture was warmed up to room temperature and
stirred for 15 min. The solvent was then removed in vacuo, and the
residue was dissolved in MeOH and concentrated twice more. The
purification was carried out by flash column chromatography (hex-
ane/EtOAc, 3:1) to afford 45 (219 mg, 95%). [α]2D0 ϭ ϩ53.2 (c ϭ 1,
CHCl3). TLC (hexane/EtOAc, 2:1). Rf ϭ 0.26. 1H NMR
Ϫ3.5 ppm. FAB-MS: m/z
ϭ
1573 [MNaϩ]. C80H94N6O24Si
(1551.8): calcd. C 61.92, H 6.11, N 5.42; found C 61.59, H 6.41,
N 5.25.
(500 MHz, CDCl3): δ ϭ 8.10Ϫ7.24 (m, 30 H, Ph), 5.36 (d, J11,2
ϭ
4.0 Hz, 1 H, H-1c), 5.06 (d, J11,2 ϭ 1.5 Hz, 1 H, H-1a), 4.96Ϫ4.91
(m, 3 H, H-2a and c, and H-1d), 4.86 (d, Jgem ϭ 10.4 Hz, 1 H,
CH2Ph), 4.80Ϫ4.74 (m, 4 H, H-1b, H-6d, CH2Ph), 4.70Ϫ4.62 (m,
7 H, H-6b, H-5c, CH2Ph), 4.49 (d, J14,5 ϭ 1.7 Hz, 1 H, H-5a), 4.36
(dd, J5,6Ј ϭ 2.4, J6,6Ј ϭ 12.5 Hz, 1 H, H-6Јd), 4.27 (dd, J5,6Ј ϭ 2.0,
J6,6Ј ϭ 12.5 Hz, 1 H, H-6Јb), 4.07Ϫ4.02 (m, 4 H, H-4a, H-4c, H-
4b, H-5b), 3.97 (dd, 1 H, H-3a), 3.92 (dd, 1 H, H-3c), 3.80 (m, 2
H, H-3b and H-5d), 3.73 and 3.42 (2s, 6 H, COOCH3 a and c),
3.62 (dd, 1 H, H-3d), 3.48 (ddd, 1 H, H-4d), 3.29 (dd, J11,2 ϭ 3.5,
J2,3 ϭ 10.3 Hz, 1 H, H-2b), 3.13 (dd, J11,2 ϭ 3.5, J2,3 ϭ 10.2 Hz, 1
H, H-2d), 2.99 (d, J14,OH ϭ 3.5 Hz, 1 H, OH), 2.10 and 2.02 (2s, 6
H, OCOCH3 a and c), 1.62 [m, 1 H, CH(CH3)2], 0.88Ϫ0.84 [4s, 12
H, C(CH3)2 and CH(CH3)2], 0.23Ϫ0.14 [2s, 6 H, Si(CH3)2] ppm.
13C NMR (125 MHz, CDCl3): δ ϭ 170.7, 169.7, 169.1, 168.9,
167.4, 166.1, 137.8, 127.7, 98.1, 98.0, 97.1, 93.5, 78.7, 78.3, 75.14,
75.10, 74.9, 74.5, 73.7, 73.6, 73.5, 73.3, 72.9, 72.6, 71.2, 70.5, 69.9,
69.79, 69.76, 67.7, 63.4, 62.4, 52.3, 51.8, 34.1, 24.9, 20.9, 20.8, 20.2,
18.4, Ϫ1.9, Ϫ3.5 ppm. C80H94N6O25Si (1567.8): calcd. C 61.29, H
6.04, N 5.36; found C 61.41, H 6.32, N 5.06.
Methyl
benzylidene-2-deoxy-α-
2-O-Acetyl-1,5-anhydro-4-O-(2-azido-3-O-benzyl-4,6-O-
-glucopyranosyl)-3-O-benzyl- -xylo-hex-1-
D
L
enitoluronate (43): [α]D20 ϭ Ϫ2.8 (c ϭ 1, CHCl3). TLC (hexane/
EtOAc, 4:1). Rf ϭ 0.12; (toluene/EtOAc, 8:1). Rf ϭ 0.20. 1H NMR
(500 MHz, CDCl3): δ ϭ 7.46Ϫ7.24 (m, 15 H, Ph), 6.80 (s, 1 H, H-
1), 5.53 (s, 1 H, PhCHO), 4.91Ϫ4.89 (m, 2 H, H-1Ј and CH2Ph),
4.73 (d, Jgem ϭ 10.9 Hz, 1 H, CH2Ph), 4.69Ϫ4.61 (2d, J11gem
ϭ
12.1 Hz, 2 H, CH2Ph), 4.57 (br. s, 1 H, H-5), 4.36 (t, J113,4 ϭ J4,5 ϭ
1.6 Hz, 1 H, H-4), 4.28 (dd, J5Ј,6Јa ϭ 3.9, J6Јa,6Јb ϭ 9.3 Hz, 1 H, H-
6Јa), 4.10 (d, 1 H, H-3), 4.00 (dd, J113Ј,4Ј ϭ 9.5 Hz, 1 H, H-3Ј), 3.83
(s, 3 H, COOCH3), 3.74Ϫ3.62 (m, 3 H, H-4Ј, H-5Ј and H-6Јb),
3.26 (dd, J111Ј,2Ј ϭ 3.6, J2Ј,3Ј ϭ 10.1 Hz, 1 H, H-2Ј), 2.06 (s, 3 H,
OCOCH3) ppm. FAB-MS: m/z ϭ 710 [MNaϩ]. C36H37N3O11
(687.7): calcd. C 62.87, H 5.42, N 6.11; found C 62.52, H 5.31,
N 6.14.
Methyl [Dimethylthexylsilyl O-(2-azido-3-O-benzyl-2-deoxy-α-
glucopyranosyl)-(1Ǟ4)-O-(methyl 2-O-acetyl-3-O-benzyl-α- -ido-
pyranosyluronate)-(1Ǟ4)-O-(2-azido-6-O-benzoyl-3-O-benzyl-2-
deoxy-α- -glucopyranosyl)-(1Ǟ4)-2-O-acetyl-3-O-benzyl-β- -ido- Methyl [Dimethylthexylsilyl O-(6-O-Acetyl-2-azido-3,4-di-O-benzyl-
2-deoxy-α- -glucopyranosyl)-(1Ǟ4)-O-(methyl 2-O-benzoyl-3-O-
benzyl-α- -idopyranosyluronate)-(1Ǟ4)-O-(2-azido-6-O-benzoyl-3-
O-benzyl-2-deoxy-α- -glucopyranosyl)-(1Ǟ4)-O-(methyl 2-O-acetyl
3-O-benzyl-α- -idopyranosyluronate)-(1Ǟ4)-O-(2-azido-6-O-
-glucopyranosyl)-(1Ǟ4)-2-O-acetyl-
-idopyranoside]uronate (46): TMSOTf (50 µL of a
D-
L
D
L
pyranoside]uronate (44): EtSH (13 µL, 0.17 mmol) and catalytic
pTsOH were added to a solution of 42 (54 mg, 35 µmol) in dry
CH2Cl2 (1.5 mL). After stirring for 3 h under argon, the mixture
was neutralized with saturated NaHCO3 solution, diluted with
D
L
D
L
CH2Cl2 (25 mL), washed with H2O (25 mL), dried (MgSO4), and benzoyl-3-O-benzyl-2-deoxy-α-
D
concentrated to dryness. The purification of the residue was carried
out by flash column chromatography (hexane/EtOAc, 1:1) to yield
44 (43 mg, 84%). [α]2D0 ϭ ϩ49.7 (c ϭ 0.75, CHCl3). TLC (hexane/
3-O-benzyl-β-L
0.14  solution in dry CH2Cl2) was added at room temperature,
under argon, to a solution of 45 (147 mg, 94 µmol) and 41 (134 mg,
EtOAc, 1:1). Rf ϭ 0.29. 1H NMR (500 MHz, CDCl3): δ ϭ 0.14 mmol) in dry CH2Cl2 (2 mL). After 30 min, saturated
8.08Ϫ7.24 (m, 25 H, Ph), 5.38 (d, J111,2 ϭ 4.3 Hz, 1 H, H-1c), 5.06 NaHCO3 solution and CH2Cl2 (100 mL) were added, and the mix-
(d, J111,2 ϭ 1.2 Hz, 1 H, H-1a), 4.95Ϫ4.91 (m, 3 H, H-1d, H-2a, ture was washed with H2O (75 mL). The organic layer was dried
H-2c), 4.86 (d, Jgem ϭ 10.2 Hz, 1 H, CH2Ph), 4.83Ϫ4.78 (m, 3 H, (MgSO4) and concentrated in vacuo, and the residue was purified
H-1b, H-6b, CH2Ph), 4.72Ϫ4.62 (m, 7 H, H-5c, CH2Ph), 4.49 (d,
J14,5 ϭ 1.4 Hz, 1 H, H-5 a), 4.35 (dd, J5,6Ј ϭ 2.3, J6,6Ј ϭ 12.3 Hz,
by flash column chromatography (toluene/acetone, 16:1 and hex-
ane/EtOAc, 3:1) to yield 46 (133 mg, 60%) and unchanged acceptor
1 H, H-6Јb), 4.11Ϫ3.99 (m, 4 H, H-4a, H-4c, H-4b, H-5b), 3.96 (t, (55 mg, 37%). Glycal 50 was also isolated from the reaction mix-
J12,3 ϭ J3,4 ϭ 2.6 Hz, 1 H, H-3a), 3.93 (t, J12,3 ϭ J3,4 ϭ 5.4 Hz, 1 ture.
3322
 2003 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
Eur. J. Org. Chem. 2003, 3308Ϫ3324

A Modular Synthesis of Heparin-Like Oligosaccharides
FULL PAPER
Compound 46: [α]2D0 ϭ ϩ41.8 (c ϭ 1, CHCl3). TLC (toluene/ace-
raphy over a short silica gel column (hexane/EtOAc, 3:2) to yield
tone, 14:1). Rf ϭ 0.32. 1H NMR (500 MHz, CDCl3): δ ϭ 48 (50 mg, 85%) as an α/β mixture. TLC (hexane/EtOAc, 3:2). Rf ϭ
1
8.07Ϫ7.15 (m, 50 H, Ph), 5.53 (d, J11,2 ϭ 4.2 Hz, 1 H, H-1e), 5.36
0.39 and 0.33 (β and α). H NMR (500 MHz, CDCl3) (0.5:0.5 α/
(d, J11,2 ϭ 4.2 Hz, 1 H, H-1c), 5.14 (dd, 1 H, H-2e), 5.05 (br. s, 1 β): δ ϭ 8.67Ϫ8.65 (2s, 1 H, NH α and β), 8.07Ϫ7.17 (m, 50 H,
H, H-1a), 4.95 (br. s, 1 H, H-2a), 4.89Ϫ4.78 (m, 4 H, H-1d, H-1f,
CH2Ph and H-2c), 4.81Ϫ4.48 (m, 17 H, CH2Ph, H-5a, H-5c, H-
5e, H-6b, H-6Јb, H-6d, H-1b), 4.38Ϫ4.30 (m, 3 H, CH2Ph and H-
Ph), 6.40 (br. s, 0.5 H, H-1aβ), 6.20 (d, J11,2 ϭ 1.8 Hz, 0.5 H, H-
1aα), 5.54 (2d, J11,2 ϭ 3.7 Hz, 1 H, H-1e α and β), 5.40Ϫ5.35 (2d,
J11,2 ϭ 4.5 Hz, 1 H, H-1c α and β), 5.15 (2dd, 1 H, H-2e α and β),
6Јd), 4.23 (m, 2 H, H-6f and CH2Ph), 4.17Ϫ4.13 (m, 2 H, H-6Јf 4.98Ϫ4.49 (m, 22 H, CH2Ph, H-5a, H-5c, H-5e, H-6b, H-6Јb, H-
and H-3e), 4.03Ϫ3.93 (m, 7 H, H-4b, H-4d, H-5b or d, H-4a, H- 6d, H-1b, H-1d, H-1f, H-2a, H-2c), 4.38Ϫ4.31 (m, 3 H, CH2Ph and
4c, H-4e, H-3a), 3.86 (m, 2 H, H-5f, H-3c), 3.78 (m, 2 H, H-5b or H-6Јd), 4.26Ϫ4.23 (m, 2 H, H-6f and CH2Ph), 4.17Ϫ3.73 (m, 16
d, H-3b), 3.64 (t, J12,3 ϭ J3,4 ϭ 9.6 Hz, 1 H, H-3d), 3.54 (t, J12,3
J3,4 ϭ 9.9 Hz, 1 H, H-3f), 3.45 (t, J14,5 ϭ 9.4 Hz, 1 H, H-4f),
3.72Ϫ3.23 (3s, 9 H, COOCH3 a, c and e), 3.28Ϫ3.18 (m, 3 H, H-
ϭ
H, H-6Јf, H-4b, H-4d, H-5b, H-5d, H-5f, H-4a, H-4c, H-4e, H-3a,
H-3c, H-3e, H-3b, COOCH3), 3.65 (t, J12,3 ϭ J3,4 ϭ 9.5 Hz, 1 H,
H-3d), 3.55 (t, J12,3 ϭ J3,4 ϭ 10.0 Hz, 1 H, H-3f), 3.47Ϫ3.44 (m, 4
2 b, d and f), 2.09Ϫ1.95 (3s, 9 H, OCOCH3 a, c and f), 1.58 [m, H, H-4f, COOCH3), 3.36Ϫ3.24 (m, 5 H, H-2b, d and COOCH3),
1 H, CH(CH3)2], 0.87Ϫ0.83 [4s, 12 H, C(CH3)2 and CH(CH3)2], 3.18 (dd, J11,2 ϭ 3.4 Hz, 1 H, H-2f), 2.12Ϫ1.95 (5s, 9 H, OCOCH3
0.22Ϫ0.13 [2s, 6 H, Si(CH3)2] ppm. 13C NMR (125 MHz, CDCl3): a, c and f) ppm. MS-HRFAB: Calcd. for C117H119Cl3N10O37Na
δ ϭ 170.7, 170.5, 169.7, 169.1, 169.0, 168.9, 166.05, 165.98, 165.2,
137.7, 127.7, 99.0, 98.3, 97.9, 97.4, 97.0, 93.5, 80.0, 78.1, 75.4, 75.3,
75.0, 74.9, 74.8, 74.1, 73.8, 73.7, 73.6, 73.5, 73.0, 72.9, 72.6, 70.5,
70.1, 70.02, 69.95, 69.9, 69.8, 67.7, 63.5, 62.1, 52.3, 51.9, 51.6, 34.1,
24.9, 20.9, 20.8, 20.7, 20.2, 18.4, Ϫ1.9, Ϫ3.5 ppm. MS-HRFAB:
calcd. for C123H137N9O37SiNa 2382.88; found 2382.82 [MNaϩ].
2383.667; found 2383.509 [MNaϩ].
Methyl [Methyl O-(6-O-Acetyl-2-azido-3,4-di-O-benzyl-2-deoxy-α-
D
-glucopyranosyl)- (1Ǟ4)-O-(methyl 2-O-benzoyl-3-O-benzyl-α-
idopyranosyluronate)-(1Ǟ4)-O-(2-azido-6-O-benzoyl-3-O-benzyl-2-
deoxy-α- -glucopyranosyl)-(1Ǟ4)-O-(methyl 2-O-acetyl 3-O-
benzyl-α- -idopyranosyluronate)-(1Ǟ4)-O-(2-azido-6-O-benzoyl-3-O-
benzyl-2-deoxy-α- -glucopyranosyl)-(1Ǟ4)-2-O-acetyl-3-O-
benzyl-α- -idopyranoside]uronate (49): TMSOTf (50 µL of a 0.04 
L-
D
L
Methyl O-(6-O-Acetyl-2-azido-3,4-di-O-benzyl-2-deoxy-α-
pyranosyl)-(1Ǟ4)-O-(methyl 2-O-benzoyl-3-O-benzyl-α-
idopyranosyluronate)-(1Ǟ4)-O-(2-azido-6-O-benzoyl-3-O-benzyl-2-
D-gluco-
D
L
-
L
solution in dry CH2Cl2) and MeOH (24 µL, 0.76 mmol) were ad-
ded under argon to a cooled (0 °C) solution of 48 (90 mg, 38 µmol)
in dry CH2Cl2 (0.5 mL). After 1 h, saturated NaHCO3 solution and
CH2Cl2 (50 mL) were added and the mixture was washed with H2O
(30 mL). The organic layer was dried (MgSO4) and concentrated
in vacuo, and the residue was purified by flash column chromatog-
raphy (hexane/EtOAc, 2:1) to yield 49 (26 mg, 31%) and 47 (25 mg,
deoxy-α-
benzyl-α-
D
-glucopyranosyl)-(1Ǟ4)-O-(methyl 2-O-acetyl 3-O-
L
-idopyranosyluronate)-(1Ǟ4)-O-(2-azido-6-O-benzoyl-3-
O-benzyl-2-deoxy-α-
D-glucopyranosyl)-(1Ǟ4)-2-O-acetyl-3-O-
benzyl-α,β- -idopyranosuronate (47): An excess of (HF)n·Py com-
L
plex (0.2 mL) was added to a cooled (Ϫ15 °C) solution of 46
(210 mg, 89 µmol) in dry THF (5 mL). The reaction mixture was
warmed to 0 °C and stirred for 24 h under argon. The mixture was
diluted with CH2Cl2 (50 mL) and washed with H2O (2 ϫ 25 mL)
and saturated NaHCO3 solution (25 mL) until neutral pH. The
aqueous layer was extracted with CH2Cl2 (2 ϫ 25 mL), and the
organic layers were dried (MgSO4) and concentrated to dryness.
The residue was purified by flash column chromatography (hexane/
EtOAc, 3:2) to afford 47 (178 mg, 90%) as an α/β mixture. TLC
(hexane/EtOAc, 3:2). Rf ϭ 0.13. 1H NMR (500 MHz, CDCl3)
(0.6:0.4 α/β): δ ϭ 8.08Ϫ7.15 (m, 50 H, Ph), 5.54 (d, J11,2 ϭ 4.4 Hz,
1 H, H-1e), 5.38 (d, J11,2 ϭ 4.6 Hz, 1 H, H-1c), 5.30 (br. d, J11,OH ϭ
8.8 Hz, 0.6 H, H-1aα), 5.15 (t, J12,3 ϭ 4.6 Hz, 1 H, H-2e), 5.10 (dd,
J11,OH ϭ 11.4, J1,2 ϭ 2.4 Hz, 0.4 H, H-1aβ), 4.93Ϫ4.49 (m, 22 H,
CH2Ph, H-5a, H-5c, H-5e, H-6b, H-6Јb, H-6d, H-1b, H-1d, H-1f,
H-2 a, H-2c), 4.38Ϫ4.31 (m, 3 H, CH2Ph and H-6Јd), 4.26Ϫ4.22
(m, 2 H, H-6f and CH2Ph), 4.17Ϫ3.63 (m, 17 H, H-6Јf, H-4b, H-
4d, H-5b, H-5d, H-5f, H-4a, H-4c, H-4e, H-3a, H-3c, H-3e, H-3b,
H-3d, COOCH3), 3.55 (t, J12,3 ϭ J3,4 ϭ 10.1 Hz, 1 H, H-3f), 3.42
(m, 4 H, H-4f, COOCH3), 3.30Ϫ3.24 (m, 5 H, H-2b, d and CO-
OCH3), 3.18 (dd, J11,2 ϭ 3.5 Hz, 1 H, H-2f), 2.16Ϫ1.95 (3s, 9 H,
OCOCH3 a, c and f) ppm.
1
29%). TLC (hexane/EtOAc, 2:1). Rf ϭ 0.12. H NMR (500 MHz,
CDCl3): δ ϭ 8.08Ϫ7.17 (m, 50 H, Ph), 5.54 (d, J11,2 ϭ 4.3 Hz, 1
H, H-1e), 5.37 (d, J11,2 ϭ 4.6 Hz, 1 H, H-1c), 5.15 (t, J12,3 ϭ J1,2 ϭ
4.6 Hz, 1 H, H-2e), 4.91Ϫ4.87 (m, 6 H, H-1d, H-1f, H-1a, H-2a,
H-2c, CH2Ph), 4.83Ϫ4.49 (m, 17 H, CH2Ph, H-5a, H-5c, H-5e, H-
6b, H-6Јb, H-6d, H-1b), 4.36Ϫ4.31 (m, 3 H, CH2Ph and H-6Јd),
4.26Ϫ4.23 (m, 2 H, H-6f and CH2Ph), 4.16Ϫ4.10 (m, 2 H, H-3e,
H-6Јf), 4.05Ϫ3.84 (m, 10 H, H-4b, H-4d, H-5b, H-5d, H-5f, H-4a,
H-4c, H-4e, H-3a, H-3c), 3.76 (m, 4 H, H-3b, COOCH3), 3.66 (t,
J12,3 ϭ J3,4 ϭ 9.5 Hz, 1 H, H-3d), 3.55 (t, J12,3 ϭ J3,4 ϭ 9.4 Hz, 1
H, H-3f), 3.45 (m, 7 H, H-4f, OCH3, COOCH3), 3.28Ϫ3.25 (m, 5
H, H-2b, d and COOCH3), 3.21 (dd, J11,2 ϭ 3.5 Hz, 1 H, H-2f),
2.06, 2.01, 1.95 (3s, 9 H, OCOCH3) ppm.
Methyl 4-O-(6-O-Acetyl-2-azido-3,4-di-O-benzyl-2-deoxy-α-
D
-gluco-
L-xylo-hex-1-
pyranosyl)-1,5-anhydro-2-O-benzoyl-3-O-benzyl-
enitoluronate (50): [α]D20 ϭ ϩ12.0 (c ϭ 1, CHCl3). TLC (hexane/
EtOAc, 3:1). Rf ϭ 0.19. 1H NMR (500 MHz, CDCl3): δ ϭ
8.02Ϫ7.14 (m, 20 H, Ph), 6.91 (s, 1 H, H-1), 4.99 (d, J11Ј,2Ј
3.5 Hz, 1 H, H-1Ј), 4.88 (d, Jgem ϭ 10.7 Hz, 1 H, CH2Ph),
-glu- 4.84Ϫ4.81 (m, 2 H, CH2Ph), 4.68 (d, Jgem ϭ 12.1 Hz, 1 H, CH2Ph),
copyranosyl)- (1Ǟ4)-O-(methyl 2-O-benzoyl-3-O-benzyl-α- 4.64Ϫ4.61 (m, 2 H, H-5 and CH2Ph), 4.56 (d, Jgem ϭ 11.0 Hz, 1
idopyranosyluronate)-(1Ǟ4)-O-(2-azido-6-O-benzoyl-3-O-benzyl-2- H, CH2Ph), 4.39 (m, 1 H, H-4), 4.33 (dd, J5Ј,6Јa ϭ 2.0, J6Јa,6Јb
deoxy-α- -glucopyranosyl)-(1Ǟ4)-O-(methyl 2-O-acetyl 3-O- 12.3 Hz, 1 H, H-6Јa), 4.28 (d, J13,4 ϭ 1.7 Hz, 1 H, H-3), 4.20 (dd,
benzyl-α- -idopyranosyluronate)-(1Ǟ4)-O-(2-azido-6-O-benzoyl-3- J5Ј,6Јb ϭ 3.5, J6Јa,6Јb ϭ 12.3 Hz, 1 H, H-6Јb), 3.97 (dd, J13Ј,4Ј
O-benzyl-2-deoxy-α- -glucopyranosyl)-(1Ǟ4)-2-O-acetyl-3-O-benzyl- 9.0 Hz, 1 H, H-3Ј), 3.83 (s, 3 H, COOCH3), 3.79 (m, 1 H, H-5Ј),
α,β- -idopyranosuronate) trichloroacetimidate (48): Cl3CCN (75 µL,
ϭ
O-(Methyl O-(6-O-acetyl-2-azido-3,4-di-O-benzyl-2-deoxy-α-
D
L
-
ϭ
D
L
ϭ
D
L
3.54 (dd, J14Ј,5Ј ϭ 9.5 Hz, 1 H, H-4Ј), 3.28 (dd, J12Ј,3Ј ϭ 10.4 Hz, 1
H, H-2Ј), 2.02 (s, 3 H, OCOCH3) ppm. FAB-MS: m/z ϭ 816
[MNaϩ]. MS-HRFAB: calcd. for C43H43N3O12Na 816.2744; found
816.2716 [MNaϩ]. C43H43N3O12 (793.8): calcd. C 65.06, H 5.46, N
5.29; found C 64.78, H 5.47, N 5.21.
0.74 mmol) and K2CO3 (4 mg, 30 µmol) were added to a solution
of 47 (55 mg, 25 µmol) in dry CH2Cl2 (2 mL). After stirring over-
night at room temperature, the mixture was then filtered off and
concentrated in vacuo, and the residue was purified by chromatog-
Eur. J. Org. Chem. 2003, 3308Ϫ3324
www.eurjoc.org
 2003 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
3323

´
J.-L. de Paz, R. Ojeda, N. Reichardt, M. Martın-Lomas
FULL PAPER
Herault, J. Lormeau, A. Bernat, J. M. Herbert, J. Med. Chem.
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nology (Grant BQU2002Ϫ03734). We thank the Ministry of Edu-
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