First synthesis of pentasaccharide glycoform I of the outer core region of the Pseudomonas aeruginosa lipopolysaccharide

Article abstract of DOI:10.1021/jo801561p

(Chemical Equation Presented) The synthesis of a pentasaccharide representing the glycoform I, which is one of two naturally occurring glycoforms of the outer core of Pseudomonas aeruginosa lipopolysaccharide, and its analogues, differing in the N-substituent in the galactosamine unit, is reported. The main features of the synthetic scheme included the assembly of the pentasaccharide backbone by successive introduction of monosaccharide units, the use of glucosyl donors with specific location of acyl protecting groups capable of the remote anchimeric participation for highly stereoselective α-glucosylation, and efficient reduction of the azido group allowing high-yielding transformation of the intermediary azido pentasaccharide into final products.

Full text of DOI:10.1021/jo801561p

First Synthesis of Pentasaccharide Glycoform I of the Outer Core
Region of the Pseudomonas aeruginosa Lipopolysaccharide
Bozhena S. Komarova,† Yury E. Tsvetkov,† Gerald B. Pier,‡ and Nikolay E. Nifantiev*,†
Laboratory of Glycoconjugate Chemistry, N.D. Zelinsky Institute of Organic Chemistry, Russian Academy
of Sciences, Leninsky Prospect 47, 119991 Moscow, Russia, and Channing Laboratory, Brigham and
Women’s Hospital, HarVard Medical School, Boston, Massachusetts 02115
nen@ioc.ac
ReceiVed July 15, 2008
The synthesis of a pentasaccharide representing the glycoform I, which is one of two naturally occurring
glycoforms of the outer core of Pseudomonas aeruginosa lipopolysaccharide, and its analogues, differing
in the N-substituent in the galactosamine unit, is reported. The main features of the synthetic scheme
included the assembly of the pentasaccharide backbone by successive introduction of monosaccharide
units, the use of glucosyl donors with specific location of acyl protecting groups capable of the remote
anchimeric participation for highly stereoselective R-glucosylation, and efficient reduction of the azido
group allowing high-yielding transformation of the intermediary azido pentasaccharide into final products.
Introduction
In order to ascertain which of the two naturally occurring
glycoforms3 I and II (Figure 1) of the LPS outer core interact
with the CFTR receptor on respiratory epithelial cells, we
performed a systematic synthesis of the oligosaccharides
representing these two glycoforms. Here we describe the
synthesis of the N-(L-alanyl)pentasaccharide 36 corresponding
to glycoform I, as well as its N-acetyl- 32 and N-(N-acetyl-L-
alanyl)- 37 analogues. The latter compounds were prepared to
elucidate the role of the L-alanine residue and its amino group
in the host recognition of the presence of P. aeruginosa bacterial
cells.
Cystic fibrosis (CF) is a congenital disease wherein there is
a high susceptibility to Pseudomonas aeruginosa infection in
the lungs.1 By late adolescence, over 80% of CF patients will
be infected with this organism.2 It was previously shown that
the outer core region of the lipopolysaccharide of P. aeruginosa
influences a critical step in the elimination of this bacterium
from a normal host by binding to the CF transmembrane
conductance regulator (CFTR), the protein that is missing or is
dysfunctional in CF. This interaction is thought to induce
effective innate immune responses in normal hosts, which, when
missing in CF, allows the microbe to persist in the airway and
initiate colonization that will eventually lead to chronic infec-
tion.1
Results and Discussion
Three important points were taken into consideration while
planning the synthesis of the target pentasaccharides. First, they
(2) Li, Z.; Kosorok, M. R.; Farrell, P. M.; Laxova, A.; West, S. E.; Green,
C. G.; Collins, J.; Rock, M. J.; Splaingard, M. L. J. Am. Med. Assoc. 2005, 293,
581–588.
(3) Bystrova, O. V.; Lindner, B.; Moll, H.; Kocharova, N. A.; Knirel, Y. A.;
Za¨hringer, U.; Pier, G. B. Carbohydr. Res. 2003, 338, 1895–1905.
(4) Demchenko, A. V. Curr. Org. Chem. 2003, 7, 35–79.
(5) Demchenko, A. V. Synlett 2003, 1225–1240.
Corresponding author. Tel: +7 499 135 87 84. Fax: +7 499 135 87 84.
† N. D. Zelinsky Institute of Organic Chemistry.
‡ Harvard Medical School.
(1) Campodonico, V. L.; Gadjeva, M.; Paradis-Bleau, C.; Uluer, A.; Pier,
G. B. Trends Molec. Med. 2008, 14, 120–133.
10.1021/jo801561p CCC: $40.75
Published on Web 10/09/2008
2008 American Chemical Society
J. Org. Chem. 2008, 73, 8411–8421 8411

Komarova et al.
FIGURE 1. Glycoforms of the outer core region of P. aeruginosa lipopolysaccharide.
SCHEME 1. Retrosynthetic Scheme toward Protected Pentasaccharide Precursor
contain three 1,2-cis-glycoside bonds, which are still not easily
synthesized.4,5 These bonds are R-D-GalpN-OMe, R-D-Glcp-
(1f6)-ꢀ-D-Glcp, and R-D-Glcp-(1f4)-R-D-GalpN. The first
R-glycoside bond could be introduced at the stage of the
synthesis of the corresponding monosaccharide blocks, and
therefore, the effectiveness of this stage was not deemed to be
critical. On the contrary, the effectiveness of R-stereoselective
construction of the two other fragments (Scheme 1) may have
a decisive influence on the feasibility of the whole synthetic
scheme. As we showed recently,6,7 glucosyl N-phenyltrifluo-
roacetimidates with acyl groups at O-3 and/or O-6, which are
capable of remote anchimeric participation, provide the neces-
sary material for efficient and highly stereoselective R-gluco-
sylation.
groups at C-3 and C-4 of galactosamine, as well as the
interdependence of the reactivity of these two groups, are well
documented.8-10 It has been demonstrated that the 4-OH in the
GalNAc residue can be glycosylated successfully only if the
adjacent hydroxyl groups carry electron-donating protecting
groups. The hydroxyl group at the position 3 of GalNAc can
be glycosylated without special conditions,8,9 although an
example of unsuccessful glycosylation of a 4,6-benzylidene
derivative of N-trichloroacetylgalactosamine has been reported.11
However, when a glycosyl substituent is present at position 4
of GalNAc, glycosylation of 3-OH becomes impossible due to
steric hindrance.8,9 Thus, the most realistic way to 3,4-bis-
glycosylated GalNAc would include initial 3-O-glycosylation
followed by 4-O-glycosylation. As we have shown during the
synthesis of trisaccharides 1a-c,6 the same is true for 2-azido-
The second difficulty is the presence of a 3,4-branch in the
galactosamine fragment. Specific properties of the hydroxyl
(8) Paulsen, H. Angew. Chem., Int. Ed. 1982, 21, 155–173.
(9) Paulsen, H.; Jaquinet, J.-C.; Rust, W. Carbohydr. Res. 1982, 104, 195–
219.
(10) Jaquinet, J.-C.; Paulsen, H. Tetrahedron Lett. 1981, 22, 1387–1390.
(11) Be´lot, F.; Jacquinet, J.-C. Carbohydr. Res. 2000, 326, 88–97.
(6) Komarova, B. S.; Tsvetkov, Y. E.; Knirel, Y. A.; Za¨ringer, U.; Pier, G. B.;
Nifantiev, N. E. Tetrahedron Lett. 2006, 47, 3583–3587.
(7) Ustuzhanina, N.; Komarova, B.; Zlotina, N.; Krylov, V.; Gerbst, A.;
Tsvetkov, Y.; Nifantiev, N. Synlett 2006, 6, 0921-0923.
8412 J. Org. Chem. Vol. 73, No. 21, 2008

Synthesis of Pentasaccharide Glycoform I
SCHEME 2. Preparation of r-Stereoselective Glucosyl Donors
2-deoxygalactose: the successful preparation of the target
structure was possible if ꢀ-(1f3)-glucosylation of a galac-
tosamine acceptor preceded R-(1f4)-glucosylation. In contrast,
an alternative sequence of glycosylations, which involves
ꢀ-glucosylation of an R-(1f4)-linked Glc-GalN3 unit, did not
lead at all to the target trisaccharide backbone.
azido group reduction. The choice of the proper reducing agent
is usually complicated by the lack of a universal method.14
Taking the aforementioned considerations into account, two
retrosynthetic schemes for the synthesis of the pentasaccharide
could be proposed (Scheme 1). The first retrosynthetic step in
both schemes is the cleavage of the pentasaccharide backbone
on the R-L-Rhap-(1f6)-R-D-Glcp linkage to give tetrasaccharide
acceptor 3 and rhamnosyl donor 4. Then, according to the first
scheme (left), the tetrasaccharide 3 is divided onto glycosyl
donor 5 and linear trisaccharide acceptor 6, which could be
obtained in turn by glycosylation of monosaccharide acceptor
10 with disaccharide thioglycoside 9. In the second scheme
(right), tetrasaccharide 3 is divided onto glucosyl donor 7 and
branched trisaccharide acceptor 8. The latter could be assembled
from monosaccharide precursors 10, 11, and 14 via intermediate
disaccharide 12.
The known benzylidene derivative of 2-azido-2-deoxygalac-
tose 106 and ꢀ-thioglucoside 1315 were used as starting materials
in the synthesis of the pentasaccharide. A set of R-glucosyl
donors, namely N-phenyltrifluoroacetimidates 7, 5, and 11
(Scheme 2) with different protecting group patterns, was
prepared as follows: Selective benzoylation of the primary
hydroxyl group in diol 1516 afforded 6-monobenzoate 16, and
treatment with N-phenyltrifluoroacetimidoyl chloride (PTAIC)
in the presence of potassium carbonate gave glucosyl donor 7.
Similarly, imidate 5 was obtained from the known16 6-O-
acetylated hemiacetal 17, while 3,6-diacylated imidate 11 was
The target pentasaccharides contain different acyl substituents
on the nitrogen of the galactosamine unit, and it would be most
convenient to synthesize them from a single amino precursor.
Thus, the third point of the synthetic strategy was based on the
proper choice of a masked form of the amino group. Azide
seemed to be the best choice because it is stable under a variety
of conditions of glycosylation and protecting group manipula-
tions. It can be reduced into an amino group at one of the final
steps of the synthesis. Simultaneous reduction of the azido group
and debenzylation by catalytic hydrogenolysis12 would provide
the simplest way to such an amino precursor. However,
hydrogenolysis sometimes may give low yields, especially in
the case of complex oligosaccharides, because of catalyst
poisoning by amines arising from azides and perhaps other
obscure processes (see, for example, ref 13). That is why an
alternative synthetic pathway is sometimes necessary for the
(14) Amantini, D.; Fringuelli, F.; Pizzo, F.; Vaccaro, L. Org. Prep. Proc.
Int. 2002, 34, 109–147.
(15) Veeneman, G. H.; van Boom, J. H. Tetrahedron Lett. 1990, 31, 275–
278.
(12) Manabe, S.; Ishii, K.; Ito, Y. J. Org. Chem. 2007, 72, 6107–6115.
(13) Amin, M. N.; Ishiwata, A.; Ito, Y. Tetrehedron 2007, 63, 8181–8198.
(16) Koto, S.; Morishima, N.; Kihara, Y.; Suzuki, H.; Kosugi, S.; Zen, S.
Bull. Chem. Soc. Jpn. 1983, 56, 188–191.
J. Org. Chem. Vol. 73, No. 21, 2008 8413

Komarova et al.
SCHEME 3. First Approach to the Pentasaccharide
prepared from the known17 tribenzylated methyl glucoside 18.
Benzoylation of 18 and subsequent acetolysis of benzoate 19
produced diacetate 20. Tetrafluoroboric acid etherate was found
to be the promoter of choice that allowed for preparation of 20
with an excellent yield of 91% without affecting benzyl groups
at O-2 and O-4. Anomeric deacetylation of 20 followed by
treatment of the formed hemiacetal 21 with PTAIC gave target
imidate 11. All the glucosyl donors contain acyl group(s) at
O-6 or at O-3 and O-6, which is able to control anomeric
stereoselectivity owing to remote anchimeric participation.6,7
On the other hand, both imidates 5 and 11 bear a selectively
removable acetyl group at O-6, thus enabling further glycosy-
lation at this site. With the above monosaccharide precursors
in hand, we started the assembly of the pentasaccharide 28.
Our first approach to the assembly of the pentasaccharide is
shown in the Scheme 3. Thioglycoside acceptor 13 was
subjected to AgOTf-promoted glycosylation with imidate 7 to
prepare R-glucosyl-(1f6)-glucose block. However, unlike the
published data related to AgOTf-promoted glycosylation with
similar trichloracetimidates18 and our own previous results,6
AgOTf from a freshly opened package did not promote this
glycosylation. We thus assumed that the actual promoter in the
cited works was possibly traces of triflic acid, which is produced
from AgOTf upon hydrolysis. The replacement of AgOTf with
catalytic amount of triflic acid brought the reaction of 13 with
7 to completion within a few hours and provided disaccharide
thioglycoside 9 as a mixture of R,ꢀ-anomers in a ratio of 8.4:1.
The R-anomer was isolated by preparative HPLC in 63% yield.
The configuration of the (1f6)-glycoside bond was confirmed
by the characteristic coupling constant value J1′,2′ of 3.5 Hz for
of 22. Conversion of the benzylidene acetal 22 into 6-O-benzyl
ether 6 under the described conditions19 proceeded slowly so
that a substantial amount of starting compound 22 was observed
in the reaction mixture even with a prolonged reaction time,
which was 10 times longer than that usually needed for the
transformation of related disaccharide ꢀ-D-Glcp-(1f3)-R-D-
GalpN3-OMe substrates. As product 6 and starting material 22
were difficult to separate, isolation of 6 required a tedious
chromatographic separation accompanied by the loss of the
material. As a result, trisaccharide acceptor 6 was obtained in
only 46% yield. The modest yield at this step prompted us to
abandon this approach, despite the fact that trial glycosylation
of 6 with imidate 5 in the presence of catalytic amount of TfOH
gave tetrasaccharide 23 in reasonable yield (78% for R,ꢀ-
mixture) and with good R-stereoselectivity (R/ꢀ ratio 6.7:1).
We next explored a synthetic approach, which was based on
the successive introduction of monosaccharide units into the
growing oligosaccharide backbone (Scheme 4). The glucosyl
donor 14 was obtained from derivative 13 by conventional
chloroacetylation. Chloroacetyl groups can be selectively re-
moved when necessary in the presence of other acyl protecting
groups and thus provide the site for further R-glucosylation.
NIS-TfOH-promoted coupling of donor 14 and acceptor 10 gave
ꢀ-(1f3)-linked disaccharide 24. Contrary to the findings with
the trisaccharide derivatives 22, regioselective reductive opening
of the benzylidene ring of disaccharide 24 was accomplished
without complications and efficiently produced disaccharide
acceptor 12. Its R-glucosylation with imidate 11 in the presence
of catalytic amounts of TfOH and MS AW-300 gave branched
R-trisaccharide 25 along with minor amounts of the correspond-
ing ꢀ-anomer (R/ꢀ-ratio ∼11:1). Pure compound 25 was isolated
in 75% yield by preparative HPLC. The R-configuration of the
(1f4)-glucoside bond was confirmed by the corresponding
coupling constant value J1,2 (<4.4 Hz, the exact value could
not be determined due to signal overlap) in the 1H NMR
spectrum of 25. The chloroacetyl group was removed from 25
1
the nonreducing Glc unit in the H NMR spectrum of 9.
NIS-TfOH-promoted coupling of acceptor 10 with disaccha-
ride thioglycoside 9 yielded trisaccharide 22 in 70% yield. The
ꢀ-configuration of the newly formed (1f3)-glycosidic bond was
deduced from the J1′,2′ value of 7.9 Hz in the 1H NMR spectrum
(17) Koto, S.; Takebe, Y.; Zen, S. Bull. Chem. Soc. Jpn. 1972, 45, 291–293.
(18) Douglas, S. P.; Whitfield, D. M.; Krepinsky, J. J. J. Carbohydr. Chem.
1993, 12, 131–136.
(19) Sherman, A. A.; Mironov, Y. V.; Yudina, O. N.; Nifantiev, N. E.
Carbohydr. Res. 2003, 338, 697–703.
8414 J. Org. Chem. Vol. 73, No. 21, 2008

Synthesis of Pentasaccharide Glycoform I
SCHEME 4. Second Approach to the Pentasaccharide
nearly quantitatively on treatment with thiourea in the presence
of 2,4,6-collidine to give trisaccharide acceptor 8. The position
of the free OH group was deduced from the upfield shift of
signals for H-6 of the ꢀ-glucose residue (δ 4.51, 4.37 f 3.84,
hydrogenation in a mixture of MeOH-AcOH-HCO2H for 7
days afforded an isolatable product, which was shown to be
bismethylated amine 30. Reductive alkylation of free amines
with traces of formaldehyde present in methanol on prolonged
hydrogenolysis has been described.21
1
3.72) in the H NMR spectrum of 8 as compared to those of
starting 25.
Reduction with H2S was next tried for the transformation of
the azido group in 29 into an amine. Optimization of the reaction
conditions with respect to the solvent and including a basic
additive has shown that application of an aq THF-Et3N-
pyridine mixture instead of conventional aq pyridine22 provided
for a smooth transformation of 29 into 31 within 2.5 h. A
combination of aq acetonitrile-Et3N-diisopropylamine was
found to be even more effective. TLC showed that H2S under
these conditions completely reduced the azido group in 29 within
a few minutes. However, the reduction with H2S was accompanied
by the formation of sulfur-containing contaminants, presumably
polysulfides, amounts of which were proportional to the reaction
time. Although the latter reaction conditions allowed for a
significant decrease in the quantity of sulfur-containing contami-
nants, the resultant amine 31 and its N-acyl derivatives can retain
some of these byproducts even after silica gel column chromatog-
6-O-Benzoylated imidate 7 was applied to introduce the
second R-glucose residue. Its TfOH-promoted coupling with
acceptor 8 yielded target tetrasaccharide 26 isolated by prepara-
tive HPLC in 60% yield. The R-configuration of (1f6)-
glucoside bond was deduced from the corresponding coupling
1
constant value J1,2 (3.5 Hz) in the H NMR spectrum of 26.
Removal of the sole acetyl group by mild acidic methanolysis20
produced tetrasaccharide acceptor 27 in high yield. Its final
AgOTf-promoted glycosylation with rhamnosyl bromide 4
produced the target protected pentasaccharide 28 in 88% yield.
Benzoyl protecting groups in 28 were removed by treatment
with methanolic MeONa and then with aqueous 5 M NaOH, as
MeONa did not provide complete debenzoylation. Attempts at
reducing the azido group in the resultant compound 29 by
Pd(OH)2/C-catalyzed hydrogenation either with periodic addition
of ethyl trifluoracetate to bind free amine formed or without it
(Scheme 5) always led to complex mixtures of products. Only
(21) van Boeckel, C. A. A. In Modern Synthetic Methods; Scheffold, R.,
Ed.; Verlag Helvetica Chimica Acta: Basel, Switzerland, 1992; Vol. 6, pp 439-
418.
(20) Byramova, N. E.; Ovchinnikov, M. V.; Backinowsky, L. V.; Kochetkov,
N. K. Carbohydr. Res. 1983, 124, C8.
(22) Zimmerman, P.; Bommer, R.; Ba¨r, T.; Schmidt, R. R. J. Carbohydr.
Chem. 1988, 7, 435–452.
J. Org. Chem. Vol. 73, No. 21, 2008 8415

Komarova et al.
SCHEME 5. Azido Group Reduction and Final Deprotection
raphy or treatment with a strongly basic anion-exchanger Amberlyst
A-26 (OH-) judging from the poor reproducibility of further
catalytic hydrogenolysis of the benzyl groups.
Application of dithiothreitol (DTT) in CH2Cl2 for reduction
of the sugar azides is known.23 We have found that the
reducing system DTT-diisopropylamine in acetonitrile, being
less active than H2S, is free from the above disadvantage
because oxidized DTT can be easily separated by conven-
tional column chromatography.
Conclusions
In summary, the synthesis of the pentasaccharide 36 corre-
sponding to the glycoform I of the outer core region of the
Pseudomonas aeruginosa lipopolysaccharide, as well as its two
closely related analogues 32 and 37, was achieved. The synthetic
scheme, which was based on consecutive addition of monosac-
charide units, proved to be the most convenient. Anomeric
stereocontrol of remote acyl groups in glucosyl donors ensured
highly stereoselective R-glucosylation at the key steps of the
synthesis. New conditions for efficient reduction of sugar azides,
viz. DTT-diisopropylamine in acetonitrile, were the second key
feature of the synthesis. The biological evaluation of synthetic
pentasaccharides 32, 36, and 37 in relation to development of
cystic fibrosis is in progress.
Reduction of the azide group in 29 with DTT under the
described optimal conditions followed by acylation of amine
31 formed with N-Boc-L-alanine active ester 33 afforded
N-alanyl derivative 34 with an overall yield of 79%. The
1
characteristic doublet at δ 1.35 and singlet at δ 1.46 in the H
NMR spectrum revealed the presence of the N-Boc-L-alanyl
moiety in 34. Catalytic hydrogenolysis of 34 gave debenzylated
pentasaccharide 35. Subsequent removal of the N-Boc protecting
group with neat TFA provided target pentasaccharide 36 in a
quantitative yield corresponding to glycoform I. The structure
of 36 was confirmed by 1H and 13C NMR and MS data.
Conventional N-acetylation of the free amino group in 36
produced the second target N-(N-acetyl-L-alanyl) product 37.
N-Acetylated pentasaccharide 32 was obtained via H2S reduction
of the azido group followed by N-acetylation and hydrogenolysis
of benzyl groups with 55% overall yield from azide 29.
Experimental Section
For general experimental methods, see the Supporting Information.
Methyl 2,3,4-Tri-O-benzoyl-ꢀ-D-glucopyranosyl-(1f3)-[6-O-
acetyl-3-O-benzoyl-2,4-di-O-benzyl-r-D-glucopyranosyl-(1f4)]-2-
azido-6-O-benzyl-2-deoxy-r-D-galactopyranoside (8). A solution of
trisaccharide 25 (728 mg, 0.54 mmol), thiourea (190 mg, 2.5 mmol),
and 2,4,6-collidine (65 µL, 0.49 mmol) in a mixture of CH2Cl2
(23 mL) and MeOH (10 mL) was kept for 48 h at room temperature
and then taken to dryness. Flash chromatography of the residue
8416 J. Org. Chem. Vol. 73, No. 21, 2008

Synthesis of Pentasaccharide Glycoform I
(3:1 toluene-EtOAc) provided 8 (662 mg, 97%): Rf 0.26 (3:1
toluene-EtOAc); [R]21D +52.7 (c 1, CHCl3); 1H NMR (500 MHz,
and saturated aq NaHCO3, dried (Na2SO4), and concentrated. The
resulting solid was purified by flash chromatography (1:0.4:0.2, light
petroleum-EtOAc-Et2O) to provide 12 (1.33 g, 1.55 mmol, 76%)
as a colorless foam: Rf 0.2 (8:1 toluene-EtOAc); [R]23D +44.5 (c
II II
CDCl3, δH) 8.05-7.10 (m, 35H, Ar), 5.94 (t, J3 ,4 ) 9.8 Hz, 1H,
H-3II), 5.89 (t, J3
) 9.7 Hz, 1H, H-3III), 5.62 (dd, J2 ,3 ) 9.9
II II
II II
II II
III,4III
1
II II
Hz, J2 ,1 ) 8.0 Hz, 1H, H-2 ), 5.58 (t, J4 ,5 ) 9.7 Hz, 1H, H-4 ),
1, CHCl3); H NMR (500 MHz, CDCl3, δH) 7.97-7.20 (m, 20H,
III
5.42 (d, J1
) 3.2 Hz, 1H, H-1 ), 5.08 (d, J1 ,2 ) 8.0 Hz, 1H,
Ar), 5.90 (t, J3 ,4 ) 9.7 Hz, 1H, H-3II), 5.57 (dd, J2 ,3 ) 9.7 Hz,
II II II II
III,2III
II II
II II
II II
I
H-1II), 4.79 (d, J1 ,2 ) 3.5 Hz, 1H, H-1 ), 4.59-4.49 (m, 5H, PhCH2,
J2 ,1 ) 8.0 Hz, 1H, H-2II), 5.53 (t, J4 ,5 ) 9.7 Hz, 1H, H-4II),
I
I
′
PhCH2 , H-6AIII), 4.42 (d, JA′′,B′′ ) 11.9 Hz, 1H, PhCH2′′A), 4.41
5.08 (d, J1 ,2 ) 7.9 Hz, 1H, H-1II), 4.78 (d, J1 ,2 ) 3.5 Hz, 1H,
H-1I), 4.61 (d, JA,B ) 12.0, 1H, PhCH2A), 4.56 (d, JB,A) 12.0 Hz,
II II
I
I
) 3.3 Hz, 1H, H-6BIII), 4.34 (br
III,6AIII
III,5III
(dd, J6B
) 12.0 Hz, J6B
d, 1H, H-4I), 4.32 (d, JB′′,A′′ ) 11.9 Hz, 1H, PhCH2′′B), 4.30 (m,
1H, PhCH2B), 4.38 (d, J6 ,5 ) 4.2 Hz, 2H, H-6 ), 4.20 (br d, 1H,
II
II II
1H, H-5III), 4.02 (dd, J3 ,4 ) 2.5 Hz, J3 ,2 ) 10.9 Hz, 1H, H-3I),
3.94 (m, 1H, H-5I), 3.87 (m, 1H, H-6AI), 3.84 (m, 1H, H-6AII),
3.77 (m, 1H, H-5II), 3.76-3.60 (m, 5H, H-4III, H-6BII, H-2III, H-6BI,
H-2I), 3.39 (s, 3H, CH3O), 2.10 (s, 3H, CH3CO); 13C NMR (75
MHz, CDCl3, δC) 170.8 (CH3CO), 166.2, 165.6, 165.4, 164.6
(PhCO), 138.2, 137.7, (ipso-Ph (Bn)), 133.6, 133.1, 132.9, ((ipso-
Ph (Bz)), 130.1, 129.9, 129.7, 129.2, 128.9, 128.4, 128.3, 128.2,
128.1, 127.7, 127.5, 127.4 (Ar), 103.3 (C-1II), 98.9 (C-1I), 98.2
(C-1III), 78.6 (C-3I), 78.4 (C-4I), 78.1 (C-2III), 76.0 (C-4III), 74.6
(C-5II), 74.2 (C-3III, PhCH2′), 73.2 (PhCH2′′), 72.7 (C-3II), 72.6
(PhCH2), 71.3 (C-2II), 69.9 (C-5I), 69.21 (C-4II), 69.16 (C-5III), 68.9
(C-6I), 62.9 (C-6III), 60.8 (C-6II), 59.5 (C-2I), 55.3 (CH3O), 20.9
(CH3CO). Anal. Calcd for C70H69N3O20: C, 66.08; H, 5.47; N, 3.30.
Found: C, 66.35; H, 5.52; N, 3.37.
H-4I), 4.07 (m, 1H, H-5II), 4.05 (dd, J3 ,4 ) 3.0 Hz, 1H, H-3I),
I
I
I
I
I
I
4.01 (s, 2H, ClCH2CO), 3.96 (m, J5 ,6 ) 5.6 Hz, 1H, H-5I), 3.78
I
I
(dd, J6A ,6B ) 10.0 Hz, J6A ,5 ) 5.5 Hz, 1H, H-6AI), 3.72-3.66
(m, 2H, H-6BI, H-2I), 3.38 (s, 3H, CH3O); 13C NMR (125 MHz,
CDCl3, δC) 167.0 (ClCH2CO), 165.6, 165.2 (PhCO), 137.9 (ipso-
Ph (Ph)), 133.7, 133.3, 133.2 (ipso-Ph (Bz)), 129.8, 129.7, 129.0,
128.5, 128.4, 128.3, 127.8, 127.7 (Ar), 101.8 (C-1II), 98.8 (C-1I),
78.5 (C-3I), 73.6 (PhCH2), 72.4 (C-3II), 72.2 (C-5II), 71.5 (C-2II),
69.2 (C-6I), 69.1 (C-4II), 68.62 (C-5I), 68.57 (C-4I), 63.7 (C-6II),
58.9 (C-2I), 55.3 (CH3O), 40.5 (ClCH2CO). Anal. Calcd for
C43H42ClN3O14: C, 60.04; H, 4.92; N, 4.88. Found: C, 60.11; H,
5.24; N, 4.83.
I
I
I
I
Ethyl 2,3,4-Tri-O-benzoyl-6-O-chloracetyl-1-thio-ꢀ-D-glucopy-
ranoside (14). To a solution of 13 (1.95 g, 3.64 mmol) in dry CH2Cl2
(60 mL) were added chloroacetyl chloride (0.726 mL, 9.1 mmol)
and pyridine (1.2 mL) at -5 °C, and the reaction mixture was stirred
for 20 min and then quenched with water (50 mL). The product
was extracted with CH2Cl2 (3 × 50 mL), and combined organic
solutions were successively washed with HCl 1 M and water and
concentrated. The residue was purified by column chromatography
(4:1 petroleum ether-EtOAc) to provide 14 (95%, 2.10 g, 3.43
O-(6-O-Acetyl-3-O-benzoyl-2,4-di-O-benzyl-D-glucopyranosyl) N-
Phenyltrifluoroacetimidate (11). A solution of PTAIC (468 mg,
2.26 mmol) in acetone (10 mL) was added to a solution of 21 (954
mg, 1.88 mmol) in acetone (25 mL) followed by K2CO3 (400 mg,
2.9 mmol). The reaction mixture was vigorously stirred for 7 h at
rt and filtered through a pad of Celite. The filtrate was concentrated
in vacuo, and the residue was purified by column chromatography
(40:1 toluene-EtOAc) to yield 11 (1.253 g, 1.85 mmol, 98%) as
a colorless foam: Rf 0.25 (35:1 toluene-EtOAc). Data for 11r: 1H
NMR (500 MHz, CDCl3, δH) 8.10-6.70 (m, 20 H, Ar), 6.54 (br s,
1H, H-1), 5.89 (t, J3,4 ) 9.6 Hz, 1H, H-3), 4.70-4.47 (m, 4H,
mmol): Rf 0.22 (4:1 petroleum ether-EtOAc); [R]25 +5.8 (c 1,
D
CHCl3); 1H NMR (300 MHz, CDCl3, δH) 8.00-7.25 (m, 15H, Ar),
5.92 (t, J3,4 ) J3,2 ) 9.5 Hz, 1H, H-3), 5.63-5.52 (m, 2H, H-2,
H-4), 4.85 (d, J1,2 ) 10.0 Hz, 1H, H-1), 4.46-4.41 (m, 2H, H-6),
4.12-4.05 (m, 3H, ClCH2CO, H-5), 2.80 (m, 2H, SCH2CH3), 1.30
(t, 3H, SCH2CH3); 13C NMR (75 MHz, CDCl3, δC) 167.0
(ClCH2CO), 165.7, 165.3, 165.1 (PhCO), 133.6, 133.3 (ipso-Ph
(Bz)), 129.8, 129.7, 129.1, 128.7, 128.6, 128.5, 128.4, 128.3 (Ph),
84.0 (C-1), 76.0, 74.0, 70.5, 69.2 (C-3, C-5, C-2, C-4), 64.1 (C-6),
40.6 (ClCH2CO), 24.3 (SCH2CH3), 14.9 (SCH2CH3). Anal. Calcd
for C31H29ClO9S: C, 60,73; H, 4.77; Cl, 5.78; S, 5.23. Found: C,
60.66; H, 4.80; Cl, 5.50; S, 4.97.
PhCH2), 4.39 (d, J6A,6B ) 12.2 Hz, 1H, H-6A), 4.29 (dd, J6B,6A
)
12.2 Hz, J6B,5 ) 3.9 Hz, 1H, H-6B), 4.13 (m, 1H, H-5), 3.80-3.71
(m, 2H, H-2, H-4), 2.09 (s, 3H, CH3CO); 13C NMR (125 MHz,
CDCl3, δH): 170.4 (CH3CO), 165.3 (PhCO), 143.4 (ipso-Ph (NPh)),
137.1, 136.8 (ipso-Ph (Bn)), 133.2 (ipso-Ph (Bz)), 129.8, 128.7,
128.4, 128.2, 128.1, 127.9, 127.8 (Ar), 124.3, 119.3 (Ph (NPh)),
92.5 (C-1), 75.9 (C-2), 75.1 (C-4), 74.6 (PhCH2), 73.7 (C-3), 72.7
(PhCH2), 71.2 (C-5), 62.4 (C-6), 20.8 (CH3CO). Data for 11ꢀ: 1H
NMR (500 MHz, CDCl3, δH) 8.05-6.71 (m, 20 H, Ar), 5.79 (br s,
1H, H-1), 5.58 (br t, 1H, H-3), 4.80 (d, JA,B ) 11.6 Hz, 1H
6-O-Benzoyl-2,3,4-tri-O-benzyl-D-glucopyranose (16). Benzoyl
chloride (23 µL, 0.20 mmol) was added to a solution of diol 15
(82 mg, 0.18 mmol) in pyridine (2 mL) and CH2Cl2 (2 mL) at -20
°C. The mixture was stirred for 10 min and then poured into ice-
cold aq saturated NaHCO3 solution, and the product 16 was
extracted three times with EtOAc. Combined organic extracts were
successively washed with 1 M HCl, water, and aq saturated
NaHCO3 and concentrated. The residue was purified by silica gel
column chromatography (7.5:1 toluene-EtOAc) to give hemiacetal
16 (73 mg, 0.13 mmol, 72%) as a 2.5:1 R,ꢀ-mixture: Rf 0.17 (8:1
toluene-EtOAc); 1H NMR (500 MHz, CDCl3, δH) 8.09-7.11 (m,
28.1H, Ar), 5.26 (br s, 1H, H-1R), 5.04-4.84 (m, 4.5H, PhCH2R,ꢀ),
4.82-4.59 (m, 5.5H, PhCH2R,ꢀ, H-1ꢀ, H-6Aꢀ, H-6AR), 4.54-4.46
PhCH2A), 4.65 (d, JB,A ) 11.6 Hz, 1H PhCH2B), 4.56 (d, JA,B
)
11.0 Hz, 1H PhCH2′A), 4.49 (d, JB,A ) 11.0 Hz, 1H PhCH2′B),
4.37 (d, J6A,6B ) 11.9 Hz, 1H, H-6A), 4.25 (dd, J6B,6A ) 11.9 Hz,
J6B,5 ) 3.2 Hz, 1H, H-6B), 3.84-3.73 (m, 2H, H-4,H-2), 2.08 (s,
3H, CH3CO); 13C NMR (125 MHz, CDCl3, δC) 170.4 (CH3CO),
165.3 (PhCO), 143.2 (ipso-Ph (NPh)), 137.0, 136.8 (ipso-Ph (Bn)),
133.3 (ipso-Ph (Bz)), 129.8, 128.7, 128.4, 128.3, 128.2, 128.1, 127.9
(Ar), 124.5, 119.2 (Ph (NPh)), 96.9 (C-1), 77.5 (C-2), 76.0 (C-3),
75.1 (C-4), 74.4, 74.0 (PhCH2), 73.3 (C-5), 62.4 (C-6), 20.7
(CH3CO). Data for 11: Anal. Calcd for C37H34F3NO8: C, 65.58; H,
5.06; N, 2.07. Found: C, 65.81; H, 5.07; N, 2.04.
R
R
(m, 1.4H, H-6BR, H-6Aꢀ), 4.25 (m, 1H, H-5R), 4.09 (t, J3
)
Methyl 2,3,4-Tri-O-benzoyl-6-O-chloracetyl-ꢀ-D-glucopyranosyl-
(1f3)-2-azido-6-O-benzyl-2-deoxy-r-D-galactopyranoside (12). To
a chilled (4 °C) solution of 24 (1.74 g, 2.03 mmol) in dry THF (86
mL) were added Me3N·BH3 (0.61 g, 8.42 mmol) and AlCl3 (1.64
g, 12.34 mmol) followed by water (75 µL, 4.13 mmol), and the
resulting mixture was vigorously stirred for 20 h at rt. The reaction
was quenched by adding HCl 1 M (140 mL) and water (130 mL).
The mixture was extracted with EtOAc (250 mL), the aqueous layer
was additionally extracted with EtOAc (3 × 50 mL), and the
combined organic extracts were successively washed with water
,4
J3 R ) 9.0 Hz, 1H, H-3R), 3.75-3.61 (m, 3.2H, H-3ꢀ, H-4ꢀ, H-4R,
R
,2
H-5ꢀ, H-2R), 3.53-3.43 (m, 1.4H, H-2ꢀ, OH); 13C NMR (125 MHz,
CDCl3, δC) 116.3 (PHCO), 138.5, 138.3, 137.8 (ipso-Ph (Bz)), 133.1
(ipso-Ph (Bn)), 129.9, 129.7, 128.5, 128.4, 128.1, 128.0, 127.9,
127.8 (Ph), 97.6 (C-1ꢀ), 91.1 (C-1R), 84.6 (C-3ꢀ), 83.2 (C-2ꢀ), 81.8
(C-3R), 80.3 (C-2R), 77.54 (C-4R), 77.47 (C-4ꢀ). 75.9, 75.8, 75.2,
74.6 (PhCH2R,ꢀ), 73.2 (C-5ꢀ), 69.0 (C-5R), 63.4 (C-6R,ꢀ). Anal. Calcd
for C34H34O7: C, 73.63; H, 6.18. Found: C, 73.91; H, 6.41.
1,6-Di-O-acetyl-3-O-benzoyl-2,4-di-O-benzyl-D-glucopyranose (20).
Benzoyl chloride (2.2 mL, 19.0 mmol) was added dropwise to a
chilled (4 °C) solution of 18 (4.29 g, 9.22 mmol) in pyridine (40
mL). The mixture was stirred for 10 h at rt and then poured into a
(23) Meijohannes, E.; Meldal, M.; Jensen, T.; Werdelin, O.; Galli-Stampino,
L.; Mouritsen, S.; Bock, K. J. Chem. Soc., Perkin Trans. 1 1997, 871–884.
J. Org. Chem. Vol. 73, No. 21, 2008 8417

Komarova et al.
mixture of crushed ice and saturated aq NaHCO3. The product 19
was extracted with EtOAc (4 × 100 mL). Combined organic
extracts were concentrated, and pyridine was coevaporated several
times with toluene. Pure 19 (3.35 g, 64%) was isolated by column
chromatography (3:1 light petroleum-EtOAc): Rf 0.19 (4:1 light
petroleum-EtOAc).
1H NMR (300 MHz, CDCl3, δH) δ 7.99-7.15 (m, 20 H, Ar), 5.89
(t, J3 ,4 ) 9.6 Hz, 1H, H-3II), 5.62 (t, J2 ,3 ) 8.0 Hz, 1H, H-2II),
II II
II II
5.61 (s, 1H, CHPh), 5.58 (t, J4 ,5 ) 9.7 Hz, 1H, H-4II), 5.17 (d,
II II
II
I
II II
I
I
J1 ,2 ) 7.9 Hz, 1H, H-1 ), 4.88 (d, J1 ,2 ) 3.3 Hz, 1H, H-1 ), 4.53
(dd, J6A ,6B ) 12.2 Hz, J6A ,5 ) 2.4 Hz, 1H, H-6AII), 4.44 (d,
II
II
II II
J4 ,3 ) 3.0 Hz, 1H, H-4I), 4.39 (dd, J6B ,6A ) 12.2 Hz, J6B ,5
)
I
I
II
II
II II
5.1 Hz, 1H, H-6BII), 4.25 (d, 1H, H-6AI), 4.16 (dd, J3 ,4 ) 3.2 Hz,
To a solution of 19 (3.35 g, 5.90 mmol) in acetic anhydride (22
mL) was slowly added tetrafluoroboric acid etherate (4 mL of 54
wt % solution in diethyl ether, 25 mmol) at 4 °C. The reaction
mixture was kept for 2.5 h at rt and poured into a mixture of crushed
ice and saturated aq NaHCO3. The mixture was extracted four times
with EtOAc, and the combined extracts were washed with water,
dried (Na2SO4), and concentrated. Purification of the residue by
column chromatography (10:1 toluene-acetone) afforded 20 (2.94
g, 5.36 mmol, 91%) as a 2.5:1 R,ꢀ-mixture: Rf 0.22 (3:1 light
I
I
J3 ,2 ) 10.7 Hz, 1H, H-3I), 4.11 (d, 1H, H-6BI), 4.05 (s, 2H,
I
I
ClCH2CO), 4.04 (m, 1H, H-5II), 3.84 (dd, J2 ,3 ) 10.8 Hz, J2 ,1
)
I
I
I
I
3.4 Hz, 1H, H-2I) 3.68 (s, 1H, H-5I), 3.43 (s, 3H, CH3O); 13C NMR
(75 MHz, CDCl3, δC) 166.9 (ClCH2CO), 165.7, 165.2, 165.0
(PhCO), 137.7 (ipso-Ph (CHPh)), 133.6, 133.2, 133.1 (ipso-Ph
(Bz)), 129.8, 129.7, 129.2, 129.0, 128.8, 128.7, 128.5, 128.2, 128.1,
126.1, 125.3 (Ph (Bz)), 102.1 (C-1II), 100.5 (CHPh), 99.5 (C-1I),
75.7 (C-4I, C-3I), 72.9 (C-3II), 72.2 (C-5II), 71.7 (C-2II), 69.1 (C-
6I), 69.0 (C-4II), 63.5 (C-6II), 63.0 (C-5I), 59.0 (C-2I), 55.5 (CH3O),
40.6 (ClCH2CO). Anal. Calcd for C43H40ClN3O14: C, 60.18; H, 4.70;
Cl, 4.13; N, 4.90. Found: C, 60.34; H, 4.89; Cl, 4.11; N, 4.95.
1
petroleum-EtOAc); H NMR (500 MHz, CDCl3, δH) 8.10-7.10
(m, 21H Ar), 6.40 (d, J1 ,2 ) 3.5 Hz, 1H, H-1R), 5.82 (t, J3 ,4
)
R
R
R
R
9.6 Hz, 1H, H-3R), 5.73 (d, J1 ,2 ) 8.0 Hz, 0.4H, H-1ꢀ), 5.62 (t,
ꢀ
ꢀ
J3 ,4 ) 9.1 Hz, 0.4H, H-3ꢀ), 4.70-4.42 (m, 3H CH2Ph), 4.33 (m,
ꢀ
ꢀ
Methyl 2,3,4-Tri-O-benzoyl-6-O-chloroacetyl-ꢀ-D-glucopyrano-
syl-(1f3)-[6-O-acetyl-3-O-benzoyl-2,4-di-O-benzyl-r-D-glucopyra-
nosyl-(1f4)]-2-azido-6-O-benzyl-2-deoxy-r-D-galactopyranoside (25).
A solution of a mixture of donor 11 (634 mg, 0.94 mmol) and
acceptor 12 (700 mg, 0.82 mmol) in CH2Cl2 (17.5 mL) was
transferred via cannula into a flask containing AW-300 molecular
sieves (1.8 g) under argon. The mixture was vigorously stirred for
1 h at rt, and then TfOH (17.5 µL, 0.20 mmol) was added. After
1 h, TLC showed complete conversion of donor 11, while acceptor
12 was still present in the reaction mixture. Therefore, more donor
11 (200 mg, 0.30 mmol) in CH2Cl2 (4.5 mL) was added via a
syringe. After another 1 h, the procedure was repeated with 0.100
g (0.15 mmol) of 11 dissolved in CH2Cl2 (1 mL). When TLC
showed full conversion of the acceptor 12, the reaction was
quenched by adding pyridine (16 µL, 0.20 mmol). The resulting
mixture was diluted with CH2Cl2 and filtered through a pad of
Celite, and the filtrate was washed with saturated aq NaHCO3
solution. The organic layer was concentrated, and the residue was
purified by flash chromatography (10:1 toluene-EtOAc) to give a
mixture of 25 and its ꢀ-isomer. Preparative HPLC (2:1 light
petroleum-EtOAc) of this mixture on a silica gel column (5 µm,
250 × 25 mm) provided 25 (820 mg, 0.61 mmol, 75%) as a
0.4H, H-6Aꢀ), 4.30 (d, J6 ,5 ) 3.0 Hz, 1H, H-6R), 4.27 (m, 0.4H,
H-6Bꢀ), 4.07 (m, 1H, H-5R), 3.80 (m, 0.4H, H-5ꢀ), 3.77-3.68 (m,
R
R
2.4H, H-4ꢀ, H-4R, H-2R), 3.66 (t, J2 ,3 ) 9.0 Hz, 0.4H, H-2ꢀ),
2.28-2.05 (m, 4.2H, CH3C(O)); 13C NMR (125 MHz, CDCl3, δC)
170.5, 169.3, 168.7, 165.5 (CdO), 137.1, 136.9, (ipso-Ph (Bn)),
133.3 (ipso-Ph (Bz)), 129.8-127.8 (Ar), 93.9 (C-1ꢀ), 89.1 (C-1R),
77.9 (C-2ꢀ), 76.3 (C-3ꢀ), 75.4 (C-4ꢀ), 75.4,75.1 (C-2R,C-4R), 74.7,
74.4, 74.2 (PhCH2), 73.5 (C-5ꢀ), 72.3 (PhCH2), 70.9 (C-5R), 62.54
(C-6ꢀ), 62.45 (C-6R), 21.0, 20.8 (CH3CO). Anal. Calcd for
C31H32O9: C, 67.87; H, 5.88. Found: C, 68.04; H, 5.92.
ꢀ
ꢀ
6-O-Acetyl-3-O-benzoyl-2,4-di-O-benzyl-D-glucopyranose (21).
Hydrazine acetate (761 mg, 8.27 mmol) was added to a solution
of 20 (2.94 g, 5.36 mmol) in DMF (30 mL). The solution was stirred
for 1 h, and then the reaction was quenched by adding saturated
aq NaHCO3 solution. The mixture was extracted four times with
EtOAc, and the combined extracts were washed with water, dried
(Na2SO4), and concentrated. Chromatographic purification on silica
gel (7:1 toluene-acetone) gave 21 (2.04 g, 4.03 mmol, 81%) as a
1
1.5:1 R,ꢀ-mixture: Rf 0.32 (5:1 toluene-acetone); H NMR (500
MHz, CDCl3, δH) for (1.5:1) 8.08-7.05 (m, 37.5H, Ar), 5.82 (t,
J3 ,4 ) 9.4 Hz, 1.5H, H-3R), 5.55 (t, J3 ,4 ) 9.1 Hz, 1H, H-3ꢀ),
R
R
ꢀ
ꢀ
R
R
R
ꢀ
ꢀ
5.31 (d, J1 ,2 ) 3.3 Hz, 1.5H, H-1 ), 4.86 (d, J1 ,2 ) 7.6 Hz, 1H,
H-1ꢀ), 4.82-4.42 (m, 5H, CH2Ph), 4.38 (d, J6A ,6B ) 11.7 Hz,
ꢀ
ꢀ
colorless foam: Rf 0.61 (3:1 toluene-EtOAc); [R]21 +58.8 (c 1,
D
1H, H-6Aꢀ), 4.32 (dd, J6A ,6B ) 12.0 Hz, J6A ,5 ) 1.8 Hz, 1.5H,
H-6AR), 4.27-4.18 (m, 4H, H-6BR, H-5R, H-6Bꢀ), 3.68-3.61 (m,
R
R
R
R
CHCl3); 1H NMR (500 MHz, CDCl3, δH) 8.05-7.10 (m, 35H, Ar),
5.87 (2t, 2H, H-3II, H-3III), 5.62 (dd, J2 ,3 ) 9.6 Hz, J2 ,1 ) 8.1
II II
II II
5H, H-4ꢀ, H-5ꢀ, H-4R, H-2R), 3.43 (dd, J2 ,3 ) 9.4 Hz, J2 ,1 ) 7.8
Hz, 1H, H-2ꢀ), 2.05 (s, 7.5H, CH3C(O)); 13C NMR (125 MHz,
CDCl3, δC) 170.7 (CH3CO), 165.6 (PhCO), 137.7, 137.1, 137.0
(ipso-Ph (Bn)), 133.1 (ipso-Ph (Bz)), 130.0, 129.7, 128.4, 128.3,
128.1, 127.9, 127.5 (Ar), 97.4 (C-1ꢀ), 90.7 (C-1R), 79.6 (C-2ꢀ), 77.2
(C-2R), 76.3 (C-3ꢀ), 75.9 (C-4ꢀ), 75.8 (C-4R), 74.5, 74.3 (PhCH2),
74.1 (C-3R), 73.8 (PhCH2), 72.8 (C-5ꢀ), 72.4 (PhCH2), 68.5 (C-
5R), 63.0 (C-6R, C-6ꢀ) 20.8 (CH3CO). Anal. Calcd for C29H30O8:
C, 68.76; H, 5.97. Found: C, 68.85; H, 5.97.
ꢀ
ꢀ
ꢀ
ꢀ
Hz, 1H, H-2II), 5.57 (t, J4 ,5 ) 9.7 Hz, 1H, H-4II), 5.27 (d, 1H,
II II
II
H-1III), 5.04 (d, J1 ,2 ) 8.0 Hz, 1H, H-1 ), 4.79 (d, J1 ,2 ) 3.5 Hz,
1H, H-1I), 4.57 (d, JA,B) 12.0 Hz, 1H, PhCH2A), 4.53 (m, 2H,
PhCH2′), 4.51 (m, 2H, H-6AII, H-6AIII), 4.49 (d, JB,A) 12.0 Hz,
II II
I
I
III,6AIII
III,5III
1H, PhCH2B), 4.43 (dd, J6B
) 12.1 Hz, J6B
) 2.8 Hz, 1H,
II
H-6BIII), 4.37 (dd, J6B ,6A ) 12.1 Hz, J6B ,5 ) 5.6 Hz, 1H, H-6B ),
4.35 (d, JA′′,B′′ ) 12.2 Hz, 1H, PhCH2′′A), 4.26 (d, JB′′,A′′ ) 12.2
Hz, 1H, PhCH2′′B), 4.24-4.21 (m, 2H, H-5III, H-4I), 4.03 (m, 1H,
H-5II), 4.02 (d, JA,B) 14.9 Hz, 1H, ClCH2COA), 3.98 (dd, 1H,
H-3I), 3.95 (d, JB,A) 14.9 Hz, 1H, ClCH2COB), 3.93 (m, 1H, H-5I),
II
II
II II
Methyl 2,3,4-Tri-O-benzoyl-6-O-chloracetyl-ꢀ-D-glucopyranosyl-
(1f3)-2-azido-4,6-O-benzylidene-2-deoxy-r-D-galactopyranoside (24).
A solution of compounds 14 (2.14 g, 3.49 mmol) and 10 (0.89 g,
2.89 mmol) in CH2Cl2 (45 mL) was added through a cannula into
a flask containing 4 Å molecular sieves (4.90 g) under argon; the
resulting mixture was stirred for 1 h at rt and cooled to -20 °C.
Then NIS (0.86 mg, 3.51 mmol) was added followed by TfOH
(100 µL, 1.13 mmol), and the mixture was stirred for 1.5 h at -20
°C. The reaction was quenched by adding pyridine (1 mL), the
mixture was filtered through a pad of Celite, and the filtrate was
poured into saturated NaHCO3. The mixture was extracted three
times with CHCl3, and the combined organic solutions were
successively washed with 1 M aq Na2S2O3, saturated aq NaHCO3,
and concentrated. Column chromatography (8:1 toluene-EtOAc)
of the residue gave disaccharide 24 (1.86 g, 75%) as a colorless
3.83 (dd, J6A ,6B ) 10.1 Hz, 1H, H-6AI), 3.74 (t, J4
) 9.6 Hz,
I
I
III,5III
1H, H-4III), 3.67-3.63 (m, 2H, H-2III, H-6BI), 3.60 (dd, J2 ,3
)
I
I
11.0 Hz, J2 ,1 ) 3.5 Hz, 1H, H-2I), 3.39 (s, 3H, CH3O) 2.10 (s,
3H, CH3CO); 13C NMR (125 MHz, CDCl3, δC) 170.0 (ClCH2CO),
167.1 (CH3CO), 165.8 (PhCO), 137.9 (ipso-Ph (Ph)), 133.7, 133.2,
133.1 (ipso-Ph (Bz)), 130.4, 129.9, 129.3, 128.7, 128.5, 128.4,
128.3, 128.3, 127.8, 127.7, 127.5 (Ar), 103.2 (C-1II), 98.8 (C-1I),
98.6 (C-1III), 78.9 (C-4I), 78.4 (C-3I), 78.2 (C-2III), 76.0 (C-4III),
74.2 (C-3II), 74.1 (PhCH2′), 73.1 (PhCH2′′), 72.8 (PhCH2), 72.7
(C-3III), 72.2 (C-5II), 71.2 (C-2II), 70.2 (C-5I), 69.2 (C-4II), 69.1
(C-5III), 69.0 (C-6I), 63.4 (C-6II), 62.9 (C-6III), 59.5 (C-2I), 55.3
(CH3O), 40.6 (ClCH2CO), 21.1 (CH3CO). Anal. Calcd for
C72H70ClN3O21: C, 64.12; H, 5.23; Cl, 2.63; N, 3.12. Found: C,
64.08; H, 5.28; Cl, 2.79; N, 3.15.
I
I
foam: Rf 0.15 (8:1 toluene-EtOAc); [R]31 +76.1 (c 1, CHCl3);
D
8418 J. Org. Chem. Vol. 73, No. 21, 2008

Synthesis of Pentasaccharide Glycoform I
Methyl 6-O-Benzoyl-2,3,4-tri-O-benzyl-r-D-glucopyranosyl-
(1f6)-2,3,4-tri-O-benzoyl-ꢀ-D-glucopyranosyl-(1f3)-[6-O-acetyl-
3-O-benzoyl-2,4-di-O-benzyl-r-D-glucopyranosyl-(1f4)]-2-azido-
6-O-benzyl-2-deoxy-r-D-galactopyranoside (26). A solution of donor
7 (423 mg, 0.58 mmol) and acceptor 8 (590 mg, 0.46 mmol) in
dry CH2Cl2 (35 mL) was poured via cannula into a flask containing
AW-300 molecular sieves (3.6 g), and the mixture was stirred for
1 h before TfOH (8 µL, 0.090 mmol) was added. After 1 h, a new
portion of donor 7 (270 mg, 0.37 mmol) in CH2Cl2 (5 mL) was
added, and the mixture was stirred for 16 h. The reaction was
quenched with pyridine (40 µL, 0.49 mmol), the resulting mixture
was diluted with CH2Cl2 and filtered through a pad of Celite, and
the filtrate was washed successively with saturated aq NaHCO3
solution and water and concentrated. Column chromatography of
the residue (gradient elution 13:1f9:1 toluene-EtOAc) gave a
mixture of tetrasaccharide 26 and its ꢀ-anomer. Preparative HPLC
(17:1 toluene-acetonitrile) of this mixture afforded individual 26
(498 mg, 0.27 mmol, 59%) as well as its ꢀ-anomer (66 mg, 8%).
JA′′′′,B′′′′ )12.0 Hz, JB′′′′′,A′′′′ )12.0 Hz, 2H, PhCH2′′′′B, PhCH2′′′′′A),
4.32 (br d, 1H, H-4I), 4.28 (m, 2H, H-6AIII, PhCH2′′′′′B), 4.22 (m,
1H, H-5I), 4.17 (dd, 1H, H-6BIII), 4.14 (dd, J3 ,4 ) 2.2 Hz, 1H,
H-3I), 4.09-3.99 (m, 3H, H-5IV, H-5II, H-3III), 3.92 (m, 2H, H-6AI,
H-6AIV), 3.88-3.81 (m, 2H, H-5III, H-6AII), 3.77 (m, 1H, H-6BIV),
3.73-3.61 (m, 4H, H-2I, H-6BII, H-4IV, H-6BI), 3.54-3.47 (m, 3H,
I
I
H-2IV, H-2III, H-4III), 3.35 (s, 3H, CH3O), 3.12 (br s, 1H, OH); 13
C
NMR (125 MHz, CDCl3, δC) 165.4, 165.1 (PhCO), 138.6, 138.4,
137.8 (ipso-Ph (Bn)), 133.4, 133.2, 133.0, 132.8 (ipso-Ph (Bz)),
102.8 (C-1II), 98.7 (C-1I), 98.1 (C-1IV), 97.5 (C-1III), 81.8 (C-3III),
80.2 (C-4III), 78.3 (C-2IV), 78.2 (C-4I), 77.4 (C-2III), 77.3 (C-3I),
76.4 (C-4IV), 75.8 (PhCH2), 74.8 (PhCH2′), 73.9 (C-3II or C-3IV),
73.7 (PhCH2′′′), 73.3 (C-5II, PhCH2′′, PhCH2′′′′′), 73.1 (C-3II or
C-3IV), 72.7 (PhCH2′′′′), 71.7 (C-5I), 71.6 (C-2II), 70.4 (C-5IV), 69.5
(C-4II), 69.3 (C-6II), 69.2 C-5III), 67.2 (C-6I), 63.3 (C-6III), 61.9
(C-6IV), 59.9 (C-2I), 55.3 (CH3O). Anal. Calcd for C102H99N3O25:
C, 69.34; H, 5.65; N, 2.38. Found: C, 69.35; H, 5.51; N, 2.33.
Methyl 6-O-Benzoyl-2,3,4-tri-O-benzyl-r-D-glucopyranosyl-
(1f6)-2,3,4-tri-O-benzoyl-ꢀ-D-glucopyranosyl-(1f3)-[2,3,4-tri-O-
benzoyl-r-L-rhamnopyranosyl-(1f6)-3-O-benzoyl-2,4-di-O-benzyl-
r-D-glucopyranosyl-(1f4)]-2-azido-6-O-benzyl-2-deoxy-r-D-
galactopyranoside (28). A solution of tetrasaccharide acceptor 27
(356 mg, 0.20 mmol) and rhamnosyl bromide 4 (165 mg, 0.31
mmol) in dry CH2Cl2 (16.5 mL) was added via a cannula under
argon into a flask containing tetramethylurea (36 µL, 0.30 mmol)
and AW-300 molecular sieves (1.9 g). The mixture was stirred for
90 min at room temperature, and then a solution of AgOTf (76
mg, 0.30 mmol) in dry toluene (4 mL) was added. After the mixture
was stirred for 2 h, full conversion of acceptor 27 was observed.
Pyridine (0.5 mL) was added, and the reaction mixture was diluted
with CH2Cl2 (70 mL), filtered through a pad of Celite, and
successively washed with a mixture of saturated aq NaHCO3 and
Na2S2O3 1 M (1:1) and water. After concentration of the organic
solution and purification of the residue by flash chromatography
(15:1 toluene-EtOAc), pentasaccharide 28 (395 mg, 0.18 mmol,
Data for 26: Rf 0.55 (5:1 toluene-EtOAc); [R]19 +53.7 (c 1,
D
CHCl3); 1H NMR (300 MHz, CDCl3, δH) 8.03-7.03 (m, 55H, Ar),
5.87 (t, J3
) 9.9 Hz, 1H, H-3IV), 5.85 (t, J3 ,4 ) 9.9 Hz, 1H,
II II II II
II II
IV,4IV
H-3II), 5.53 (dd, J2 ,3 ) 9.6 Hz, J2 ,1 ) 8.2 Hz, 1H, H-2II), 5.46
II
(t, J4 ,5 ) 9.8 Hz, 1H, H-4 ), 5.25 (d, J1
) 3.2 Hz, 1H, H-1IV),
IV,2IV
II II
5.04 (d, J1 ,2 ) 8.0 Hz, 1H, H-1II), 4.89 (d, JA,B) 10.6 Hz, 1H,
II II
PhCH2A), 4.82 (m, 1H, PhCH2′A), 4.81 (br d, 1H, H-1I), 4.73 (m,
2H, PhCH2B, PhCH2′′A), 4.67 (d, J1
) 3.5 Hz, 1H, H-1III),
III,2III
4.61-4.53 (m, 4H, PhCH2′B, PhCH2′′B, PhCH2′′′), 4.49 (m, 1H,
H-6AIV), 4.45 (d, JA′′′′,B′′′′ ) 12.5 Hz, 1H, PhCH2′′′′A), 4.40 (d,
JB′′′′,A′′′′) 11.9 Hz, 1H, PhCH2′′′′B), 4.37-4.30 (m, 4H, H-6AIII,
PhCH2′′′′′A, H-5IV, H-6BIV), 4.28 (br d, 1H, H-4I), 4.25 (dd, 1H,
H-6BIII), 4.21 (d, 1H, PhCH2′′′′′′B), 4.15 (dd, J3 ,4 ) 2.3 Hz, J3 ,2
I
I
I
I
) 11.2 Hz, 1H, H-3I), 4.06 (m, 1H, H-5I), 4.03 (m, 1H, H-5II),
3.94-3.88 (m, 3H, H-6AI, H-5III, H-3III), 3.85 (dd, J6A ,5 ) 4.7
II II
Hz, J6A ,6B ) 10.4 Hz, 1H, H-6AII), 3.73-3.66 (m, 3H, H-4IV,
II
II
H-2I, H-6BII), 3.61 (dd, J2
) 10.1 Hz, J2
) 3.2 Hz, 1H,
IV,3IV
IV,1IV
H-2IV), 3.58 (m, 1H, H-6BI), 3.53-3.48 (m, 2H, H-4III, H-2III), 3.32
(s, 3H, CH3O), 2.10 (s, 3H, CH3CO); 13C NMR (75 MHz, CDCl3,
δC) 170.5 (CH3CO), 165.4, 165.1, 164.7 (PhCO), 138.4, 138.3,
137.7, 137.6, (ipso-Ph (Bn)), 133.3, 133.0, 132.9 (ipso-Ph (Bz)),
130.2, 129.9, 129.7, 129.6, 129.3, 129.0, 128.9, 128.5, 128.1, 127.9,
127.7, 127.6, 127.2, 125.3 (Ar), 102.6 (C-1II), 98.7 (C-1I), 97.9
(C-1IV), 97.3 (C-1III), 82.0 (C-3III), 80.4 (C-4III), 78.2 (C-2IV), 78.1
(C-4I), 77.2 (C-3I), 77.0 (C-2III), 76.1 (C-4IV), 75.7 (PhCH2), 74.8
(PhCH2′), 74.0 (C-3IV), 73.8 (PhCH2′′′), 73.6 (C-5I), 73.3 (PhCH2′′,
PhCH2′′′′′), 73.1 (C-3II), 72.7 (PhCH2′′′′), 71.4 (C-2II), 70.8 (C-
5II), 70.0 (C-4II), 69.4 (C-6II), 69.1 (C-5III), 68.9 (C-5IV), 67.8 (C-
6I), 63.4 (C-6III), 63.0 (C-6IV), 59.7 (C-2I), 55.2 (CH3O), 20.9
(CH3CO). Anal. Calcd for C104H101N3O26: C, 69.05; H, 5.63; N,
2.32. Found: C, 68.99; H, 5.51; N, 2.27.
88%) was obtained: Rf 0.38 (8:1 toluene-EtOAc); [R]21 +88.0
D
(c 1, CHCl3); 1H NMR (500 MHz, CDCl3, δH) 8.14-7.05 (m, 70H,
Ar), 6.00-5.90 (m, 3H, H-3V, H-3II, H-3IV), 5.82 (br d, 1H, H-2V),
5.70 (t, 1H, H-4V), 5.57-5.50 (m, 2H, H-2II, H-4II), 5.37 (d, J1
IV,2IV
) 2.7 Hz, 1H, H-1IV), 5.21 (d, J1 ,2 ) 7.9 Hz, 1H, H-1 ), 5.93 (d,
II
II II
I
V
I
I
V,2V
J1 ,2 ) 3.2 Hz, 1H, H-1 ), 4.84 (d, J1 ) 3.7 Hz, 1H, H-1 ), 4.82
(m, 2H, PhCH2), 4.73 (d, 1H, H-1III), 4.71-4.47 (m, 8H, PhCH2),
4.40-4.35 (m, 3H, H-6AIII, H-5V, PhCH2), 4.28-4.17 (m, 5H,
H-6BIII, PhCH2, H-4I, H-3I, H-5IV), 4.13-4.02 (m. 3H, H-6AIV,
H-5I, H-5II), 3.93-3.87 (m, 3H, H-6AI, H-3III, H-5III), 3.84-3.75
(m, 2H, H-6AII, H-4IV), 3.74-3.68 (m, 3H, H-2I, H-6BI, H-6BII),
3.66 (dd, 1H, H-2IV), 3.52-3.46 (m, 3H, H-4III, H-2III, H-6BIV),
3.36 (s, 3H, CH3O), 1.36 (d, 3H, H-6V); 13C NMR (125 MHz,
CDCl3, δC) 166.1, 166.0, 165.6, 165.1, 165.0 (PhCO), 138.1, 138.0,
137.7, 137.6 (ipso-Ph (Bn)), 133.3, 133.1, 133.0, 132.8 (ipso-Ph
(Bz)), 101.9 (C-1II), 98.9 (C-1I), 98.4 (C-1V), 98.0 (C-1IV), 97.5
(C-1III), 81.9 (C-3III), 80.2 (C-4III), 78.5 (C-2IV), 78.3 (C-4I), 77.2
(C-2III), 76.2 (C-4IV), 76.0 (C-3I), 75.7, 74.9, 74.4 (PhCH2), 74.3
(C-3IV), 73.4 (C-3II), 73.2 (C-5I, PhCH2), 72.9 (PhCH2), 72.1 (C-
4V), 71.9 (C-2II), 70.9 (C-2V), 70.6 (C-5II), 70.4 (C-5IV), 70.2 (C-
3V), 70.1 (C-4II), 69.4 (C-6II), 69.3 (C-5III), 68.0 (C-6I), 67.5 (C-
6IV), 66.8 (C-5V), 63.4 (C-6III), 59.7 (C-2I), 55.1 (CH3O), 17.6 (C-
6V). Anal. Calcd for C129H121N3O32: C, 69.62; H, 5.48; N, 1.89.
Found: C, 69.42; H, 5.70; N, 1.85.
Methyl 6-O-Benzoyl-2,3,4-tri-O-benzyl-r-D-glucopyranosyl-
(1f6)-2,3,4-tri-O-benzoyl-ꢀ-D-glucopyranosyl-(1f3)-[3-O-benzoyl-
2,4-di-O-benzyl-r-D-glucopyranosyl-(1f4)]-2-azido-6-O-benzyl-2-
deoxy-r-D-galactopyranoside (27). To a chilled solution of 26 (474
mg, 0.26 mmol) in a mixture of CH2Cl2 (15 mL) and MeOH (30
mL) was added a solution of HCl in MeOH prepared by adding
AcCl (3.4 mL, 47.9 mmol) to MeOH (15 mL). The reaction mixture
was kept at room temperature for 5 h, diluted with toluene, and
evaporated, and HCl was removed by coevaporation with toluene.
Purificationoftheresiduebyflashchromatography(9:1toluene-EtOAc)
yielded27(402mg,0.23mmol,88%):Rf 0.24(10:1toluene-EtOAc);
Methyl 2,3,4-Tri-O-benzyl-r-D-glucopyranosyl-(1f6)-ꢀ-D-glu-
copyranosyl-(1f3)-[r-L-rhamnopyranosyl-(1f6)-2,4-di-O-benzyl-
r-D-glucopyranosyl-(1f4)]-2-azido-6-O-benzyl-2-deoxy-r-D-galac-
topyranoside (29). To a solution of pentasaccharide 28 (56 mg,
0.025 mmol) in CH2Cl2 (1 mL) and MeOH (1 mL) was added 1 M
MeONa in methanol (0.4 mL). After 16 h at rt, TLC (5:1
CH2Cl2-MeOH) showed the formation of a single product. The
solution was made neutral by Amberlyte IRA-120 (H+), and then
the resin was filtered off and the filtrate was concentrated. NMR
spectra of the product showed the presence of one benzoyl group,
[R]20 +54.7 (c 1, CHCl3); 1H NMR (500 MHz, CDCl3, δH)
D
II II
IV,4IV
8.04-7.06 (m, 55H, Ar), 5.88 (t, J3 ,4 ) 10.0 Hz, J3
) 10.0
Hz, 2H, H-3II, H-3IV), 5.69 (t, J2 ,3 ) 8.2 Hz, 1H, H-2II), 5.61 (t,
II II
J4 ,5 ) 9.8 Hz, 1H, H-4II), 5.31 (d, J1
) 3.2 Hz, 1H, H-1IV),
IV,2IV
II II
5.05 (d, J1 ,2 ) 7.9 Hz, 1H, H-1II), 4.95 (d, JA,B ) 10.7 Hz, 1H,
PhCH2A), 4.87 (d, JA′,B′ ) 11.2 Hz, 1H, PhCH2′A), 4.81 (m, 2H,
H-1I, PhCH2B), 4.75 (d, JA′′,B′′ ) 12.4 Hz, 1H, PhCH2′′A), 4.66 (d,
II II
) 3.5 Hz, 1H, H-1III), 4.64-4.56 (m, 4H, PhCH2′′B, PhCH2′′′,
PhCH2′B), 4.47 (d, JA′′′′,B′′′′ ) 12.0 Hz, 1H, PhCH2′′′′A), 4.41 (d,
III,2III
J1
J. Org. Chem. Vol. 73, No. 21, 2008 8419

Komarova et al.
presumably at O-3 of the rhamnose residue. A solution of the
product in MeOH (3.5 mL) was treated with aq solution of NaOH
5 M (0.5 mL) for 20 h, neutralized with Amberlyte IRA-120 (H+),
filtered, and concentrated. The residue was treated with Amberlyst
A-26 (HCO3-) in MeOH to remove benzoic acid. The resin was
filtered off and the solution was concentrated to provide product
29 (35 mg, 0.025 mmol) quantitatively: Rf 0.41 (10:1
CH2Cl2-MeOH); [R]23D +78.8 (c 1, MeOH); 1H NMR (500 MHz,
and water (0.3 mL) were added to dissolve the gel. After a few
minutes, TLC showed the complete conversion of starting 29.
Amberlyst A-26 (OH-) was added until the solution became
colorless. The resin was filtered, and the solution was concentrated
1
to give amine 31: H NMR (500 MHz, CD3OD) 7.40-7.05 (m,
) 3.4 Hz, 1H, H-1IV), 5.00-4.97 (d, 1H,
IV,2IV
30H, Ar), 5.01 (d, J1
PhCH2), 4.95 (d, J1
) 3.6 Hz, 1H, H-1III), 4.88 (d, 1H, PhCH2),
III,2III
4.83-4.74 (m, 3H, PhCH2), 4.73 (m, 2H, H-1I, H-1V), 4.70-4.56
II
II II
IV,2IV
CD3OD, δH) 7.40-7.06 (m, 30H, Ar), 5.03 (d, J1
) 3.2 Hz,
(m, 5H, PhCH2), 4.39 (d, J1 ,2 ) 7.9 Hz, 1H, H-1 ), 4.30 (m, 1H,
1H, H-1IV), 4.99 (d, JA,B ) 11.1 Hz, 1H, PhCH2), 4.91 (d, J1
)
H-5IV), 4.25 (br d, 1H, H-4I), 4.14 (d, JA,B ) 11.9 Hz, 1H, PhCH2′),
III,2III
3.6 Hz, 1H, H-1III), 4.89-4.85 (m, 2H, PhCH2, H-1I), 4.83-4.54
4.07 (t, J3
) 9.4 Hz, 1H, H-3IV), 4.01 (m, 3H, H-5I, PhCH2),
IV,4IV
(m, 9H, PhCH2, H-1V), 4.49 (d, J1 ,2 ) 7.9 Hz, 1H, H-1II), 4.33
3.95-3.90 (m, 2H, H-6AIV, H-6AII), 3.88-3.83 (m, 3H, H-3III,
H-6AIII, H-2V), 3.82-3.76 (m, 3H, H-6BIII, H-3I, H-6AI), 3.76-3.70
II II
(br d, 1H, H-4I), 4.28 (m, 1H, H-5IV), 4.20 (dd, J3 ,4 ) 2.5 Hz, J3 ,2
I
I
I
I
) 11.0 Hz, 1H, H-3I), 4.17, (d, 1H, PhCH2), 4.09-4.04 (m, 2H,
H-3IV, H-5I), 4.03 (d, 1H, PhCH2), 3.93-3.85 (m, 4H, H-6AIV,
H-6AII, H-2V, H-3III), 3.84-3.76 (m, 3H, H-6AIII, H-6AI, H-6BII),
(m, 4H, H-5III, H-5V, H-3V, H-6BIII), 3.63 (dd, J6A
) 11.1 Hz,
IV,6BIV
IV,5IV
J6A
) 3.4 Hz, 1H, H-6BIV), 3.60-3.55 (m, 2H, H-5II, H-6BI),
3.54-3.49 (m, 3H, H-2III, H-4III, H-4IV), 3.41-3.35 (m, 2H, H-4V,
H-3II), 3.32 (dd, 1H, H-2IV), 3.31 (s, 3H, OCH3), 3.23-3.18 (m,
3H, H-2II, H-4II, H-2I), 1.30 (d, 3H, H-6V); 13C NMR (125 MHz,
CD3OD) 140.2, 139.9, 139.6 (ipso-Ph (Bn)), 129.5, 129.3, 129.2,
129.1, 128.9, 128.8, 128.6, 128.4 (Ar), 107.3 (C-1II), 102.1 (C-
1V), 101.3 (C-1I), 98.8 (C-1IV), 98.4 (C-1III), 83.4 (C-3III), 82.8 (C-
3I), 81.7 (C-2IV), 81.4 (C-2III), 79.4 (C-4IV), 78.1 (C-3II), 77.8 (C-
4I), 76.6 (PhCH2), 76.4 (C-5II), 76.2, 76.0 (PhCH2), 75.2 (C-2II),
74.6 (C-3III), 74.3, 74.1 (PhCH2), 74.0 (C-4V), 72.9 (C-5III), 72.5
(C-5I, C-4II), 72.2 (C-3V, C-2V), 71.4 (C-6I, C-5IV), 70.2 (C-6II),
70.0 (C-5V), 67.8 (C-6IV), 61.8 (C-6III), 55.6 (OCH3), 52.2 (C-2I),
18.9 (C-6V).
To a solution of 31 obtained in MeOH (1 mL) were added acetic
anhydride (3 µL) and Amberlyst A-26 (HCO3-). The mixture was
stirred for 20 min and filtered through a membrane filter, and the
filtrate was concentrated to provide N-acetylated product (18.1 mg,
80%), Rf 0.2 (CHCl3-MeOH, 9:1). It was dissolved in MeOH (1
mL), Pd(OH)2/C (13 mg) was added, the mixture was stirred for
18 h under a hydrogen atmosphere, and then the catalyst was filtered
off through a pad of Celite. The filtrate was concentrated, and the
residue was purified by size-exclusion chromatography on a TSK
HW-40 (S) column (2.5 × 40 cm) in 0.1 M aq AcOH to yield 32
(7.6 mg, 55% over three steps from azide 29): Rf 0.2 (5:5:4:1
BuOH-EtOH-H2O-NH3 aq); [R]23D +75.2 (c 1, H2O); 1H NMR
3.76-3.68 (m, 5H, H-6BIII, H-5III, H-5V, H-3V, H-2I), 3.62 (dd,
IV IV
J6B
) 11.0 Hz, J6B,5 ) 3.6 Hz, 1H, H-6BIV), 3.58-3.49 (m,
,6A
4H, H-6BI, H-4IV, H-2III, H-4III), 3.41-3.36 (m, 2H, H-3II, H-4V),
3.32 (m, 1H, H-2IV), 3.31 (s, 3H, CH3O), 3.23 (t, J4 ,5 ) 9.4 Hz,
II II
1H, H-4II), 3.19 (t, J2 ,3 ) 8.8 Hz, 1H, H-2 ), 1.30 (d, 3H, H-6 );
13C NMR (125 MHz, CD3OD, δC) 140.1, 139.9, 139.6, 139.5 (ipso-
Ph (Bn)), 133.9, 130.7, 129.6, 129.4, 129.2, 129.1, 129.0, 128.8,
128.7, 128.6, 128.5, 128.4 (Ar), 106.4 (C-1II), 102.2 (C-1V), 100.5
(C-1I), 98.7 (C-1IV), 98.3 (C-1III), 83.4 (C-3III), 81.6 (C-2IV), 81.3
(C-4III), 79.5 (PhCH2), 79.1 (C-2III), 78.2 (C-3I), 77.94 (C-4I), 77.86
(C-4V), 76.6 (PhCH2), 76.2 (C-4IV), 76.1 (PhCH2), 74.8 (C-2II), 74.7
(C-3IV), 74.3 (PhCH2), 74.1 (C-3II), 74.0 (PhCH2), 72.8 (C-5III),
72.5 (C-4II), 72.3 (C-5I), 72.2 (C-2V), 72.1 (C-3V), 71.3 (C-5IV),
71.0 (C-6I), 69.9 (C-5V or C-5II), 69.7 (C-6II), 67.7 (C-6IV), 61.7
(C-6III), 61.1 (C-2I), 18.5 (C-6V), 55.5 (CH3O); HR ESI MS calcd
for [M + K + H]+2 (C73H89N3O24 + K + H)/2 715.7776, found
715.7725.
II
V
II II
Methyl r-D-Glucopyranosyl-(1f6)-ꢀ-D-glucopyranosyl-(1f3)-
[r-L-rhamnopyranosyl-(1f6)-r-D-glucopyranosyl-(1f4)]-2-deoxy-
2-dimethylamino-r-D-galactopyranoside (30). Pd(OH)2/C (20%, 7
mg) was added to a solution of azide 29 (8 mg, 0.0057 mmol) in
MeOH (1 mL) containing formic acid (0.5%, v/v) and acetic acid
(5%, v/v), and the mixture was stirred in a hydrogen atmosphere.
After 3 days, a new portion of the catalyst (4.5 mg) was added,
and stirring under hydrogen was continued for 4 days. The catalyst
was filtered off through a membrane filter (0.45 µm), and the filtrate
was concentrated to give 30 (2.5 mg, 52%): Rf 0.09 (5:5:4:1
(300 MHz, D2O) 4.94 (d, J1
) 3.3 Hz, 1H, H-1III), 4.89 (d,
III,2III
IV,2IV
J1
) 3.1 Hz, 1H, H-1IV), 4.80-4.74 (m, 2H, H-1I, H-1V), 4.45
II I I
I I
II II
(d, J1 ,2 ) 7.7 Hz, 1H, H-1 ), 4.39 (dd, J2 ,3 ) 11.2 Hz, J2 ,1 )
3.4 Hz, 1H, H-2I), 4.29 (m, J5
) 10.0 Hz, 1H, H-5IV), 4.16 (br
IV,6IV
BuOH-EtOH-H2O-NH3 aq); 1H NMR (500 MHz, D2O, δH) 5.26
s, 1H, H-4I), 4.05 (m, 1H, H-3I), 4.00-3.95 (m, 2H, H-5I, H-2V),
3.86-3.51 (m, 16H, H-6I, H-6AII, H-6AIV, H-3IV, H-6AIII, H-3V,
H-6BII, H-6BIII, H-6BIV, H-5V, H-3III, H-5III, H-5II, H-4IV, H-2III),
3.48-3.35 (m, 7H, H-2IV, H-4III, H-3II, H-4V, CH3O), 3.25 (t, 1H,
I
(d, J1 ,2 ) 2.9 Hz, 1H, H-1 ), 4.99 (d, J1
) 3.5 Hz, 1H, H-1V),
I
I
IV,2IV
III,2III
4.97 (d, J1
) 3.7 Hz, 1H, H-1III), 4.79 (br s, 1H, H-1V), 4.72
(d, 1H, H-1II), 4.57 (br dd, 1H, H-3I), 4.5 (br d, 1H, H-4I), 4.08
(m, 1H, H-5IV), 4.04-3.98 (m, 2H, H-5I, H-2V), 3.92-3.59 (m,
16H, H-6AII, H-6I, H-6AIV, H-6AIII, H-2I, H-6BII, H-3V, H-6BIV,
II
II
V
V
H-4 ), 3.08 (t, 1H, H-2 ), 2.01 (s, 3H, CH3CO), 1.31 (d, J6 ,5 )
6.2 Hz, 3H, H-6V); 13C NMR (125 MHz, D2O) 176.0 (CH3CO),
105.9 (C-1II), 102.5 (C-1V), 100.5 (C-1IV), 99.7 (C-1I), 99.4 (C-
1III), 77.7 (C-3I), 77.2 (C-4I), 77.0 (C-3II), 75.6 (C-5II), 74.7 (C-
5III), 74.3 (C-2II), 74.1 (C-3IV), 73.4 (C-4V), 73.2 (C-5I, C-2IV, C-3III),
72.6 (C-2III), 72.0 (C-4II), 71.5 (C-5IV, C-3V), 71.3 (C-2V), 70.5
(C-4III), 70.4 (C-4IV), 70.1 (C-5V), 68.5 (C-6II), 67.7 (C-6IV), 61.8
(C-6I), 61.7 (C-6III), 56.6 (CH3O), 50.4 (C-2I), 23.5 (CH3CO), 18.4
(C-6V); HR ESI MS calcd for [M + Na]+ C33H57NO25 + Na
890.3117, found 890.3115.
Methyl r-D-Glucopyranosyl-(1f6)-ꢀ-D-glucopyranosyl-(1f3)-
[r-L-rhamnopyranosyl-(1f6)-r-D-glucopyranosyl-(1f4)]-2-[N-
(tert-butoxycarbonyl)-L-alanylamino]-2-deoxy-r-D-galactopyrano-
side (35). Azido Group Reduction with DTT. To a solution of azide
29 (33.9 mg, 0.024 mmol) in a mixture of dry MeCN and diisopro-
pylamine (600 µL, 3:1) was added DTT (7.5 mg, 0.049 mmol). After
1 h, the conversion of the starting material was approximately 50%,
but then the reaction stopped. More DTT (8.5 mg, 0.055 mmol) was
added and the mixture was stirred for next 24 h after which time the
full conversion of azide 29 was observed. The reaction mixture was
taken to dryness. Amine 31, identical to that obtained by reduction
with H2S with respect to the Rf value and NMR data, can be purified
H-6BIII, H-3IV, H-5V, H-5III, H-5II, H-3III, H-4IV), 3.57 (dd, J2
III,3III
III,1III
) 9.9 Hz, J2
) 3.7 Hz, 1H, H-2III), 3.53-3.48 (m, 2H, H-2IV,
H-3II), 3.47-3.41 (m, 5H, CH3O, H-4III, H-4V), 3.31-3.25 (m, 2H,
H-4II, H-2II), 2.99 (br s, 6H, (CH3)2N), 1.30 (d, J6
) 6.2 Hz,
V,5V
3H, H-6V); 13C NMR (125 MHz, D2O, δC) 105.9 (C-1II), 102.3
(C-1V), 100.6 (C-1IV), 100.0 (C-1III), 97.1 (C-1I), 78.3 (C-4I), 77.0
(C-3II), 76.0 (C-5III), 74.5 (C-5II), 74.3 (C-2II), 73.9 (C-3IV), 73.3
(C-4III, C-3III), 73.0 (C-2IV), 72.4 (C-2III), 71.4 (C-3V), 71.2 (C-
2V), 70.6 (C-4V), 70.1 (C-4IV), 70.0 (C-5V), 69.2 (C-6II), 67.7 (C-
6IV), 63.0 (C-2I), 61.7 (C-6I, C-6III), 56.0 (CH3O), 42.4 ((CH3)2N),
18.2 (C-6V); HR ESI MS calcd for [M + H]+ C33H59NO24 + H
854,3505, found 854.3505.
Methyl r-D-Glucopyranosyl-(1f6)-ꢀ-D-glucopyranosyl-(1f3)-
[r-L-rhamnopyranosyl-(1f6)-r-D-glucopyranosyl-(1f4)]-2-aceta-
mido-2-deoxy-r-D-galactopyranoside (32). Azido Group Reduction
with Hydrogen Sulfide. Azide 29 (22.9 mg, 0.016 mmol) was
dissolved in a mixture of CH3CN (0.65 mL), triethylamine (0.5
mL), water (0.1 mL), and diisopropylamine (0.2 mL) under Ar,
and H2S was bubbled through the solution until the reaction mixture
turned into a slightly yellow gel (∼1 min). More CH3CN (1 mL)
8420 J. Org. Chem. Vol. 73, No. 21, 2008

Synthesis of Pentasaccharide Glycoform I
II II
by column chromatography (gradient elution 10:1 f 5:1 CHCl3-
MeOH). To a solution of the raw reaction mixture in dry DMF (1
mL) were added succinimidyl active ester 33 (10.3 mg, 0.036 mmol)
and Et3N (2 µL, 0.014 mmol), and the solution was stirred for 24 h at
rt. Then the mixture was diluted with toluene (2 mL) and taken to
dryness. Column chromatography of the residue (gradient elution 15:1
f 10:1 CHCl3-MeOH) provided L-alanyl pentasaccharide 34 (29.0
mg, 0.019 mmol, 79%): Rf 0.20 (11:1 CHCl3-MeOH); [R]16D +57.6
(c 1, MeOH); 1H NMR (500 MHz, CD3OD) 7.40-7.05 (m, 30H, Ar),
5.00-4.93 (m, 3H, H-1III, H-1IV, PhCH2), 4.89-4.72 (m, 4H, PhCH2),
4.72-4.56 (m, 7H, H-1I, H-1V, PhCH2), 4.47-4.41 (d, 2H, H-1II, H-2I),
4.33 (m, 1H, H-5IV), 4.21 (br s, 1H, H-4I), 4.19-4.12 (m, 2H, H-3IV,
PhCH2), 4.12-3.98 (m, 5H, H-3I, CHCH3 (Ala), H-5I, PhCH2),
3.96-3.68 (m, 11H, H-6AII, H-6AIV, H-3III, H-6AIII, H-2V, H-6AI,
H-6BII, H-5V, H-5III, H-3V, H-6BIII), 3.64 (m, 1H, H-6BIV), 3.61-3.52
(m, 4H, H-5II, H-4IV, H-6BI, H-2III), 3.49 (m, 1H, H-4III), 3.41-3.33
(m, 3H, H-3II, H-4V, H-2IV), 3.28 (s, 3H, CH3O), 3.27-3.12 (m, 2H,
H-4II, H-2II), 1.40 (s, 9H, (CH3)3CO), 1.29 (m, 6H, CH3 (Ala), H-6V);
13C NMR (125 MHz, CD3OD) 176.0 (CdO (Ala)), 140.1, 140.0,
139.8, 139.7, 139.6 (ipso-Ph (Ph)), 129.5, 129.4, 129.3, 129.2, 129.1,
129.0, 128.8, 128.7, 128.6, 128.4 (Ph), 106.0 (C-1II), 102.3 (C-1V),
99.7 (C-1I), 99.2 (C-1IV), 98.3 (C-1III), 83.4 (C-3III), 81.6 (C-2IV), 81.4
(C-2III), 80.6 ((CH3)3CO), 79.4 (C-4IV), 79.2 (C-4III), 78.0 (C-4V), 77.7
(C-4I, C-3I), 76.6 (C-5II, PhCH2), 76.2, 75.9 (PhCH2), 74.7 (C-2II),
74.4 (C-3IV), 74.3 (PhCH2), 74.1 (C-3II), 73.9 (PhCH2), 73.0 (C-5III),
72.3 (C-4II, C-3V), 72.1 (C-2V), 72.0 (C-5I), 71.0 (C-5IV, C-6I), 69.9
(C-5V, C-6II), 67.9 (C-6IV), 61.9 (C-6III), 55.7 (CH3O) 51.5 (CH3CH
(Ala)), 50.8 (C-2I), 28.8 (CH3 (Boc)), 18.9 (C-6V), 18.7 (CH3CH (Ala)).
To a solution of pentasaccharide 34 (29.0 mg, 0.019 mmol) in
MeOH (1 mL) was added Pd(OH)2/C (20%, 37 mg), and the reaction
mixture was stirred under a slight overpressure of hydrogen for 3 days.
Then water (0.2 mL) was added to enhance the solubility of
debenzylated products and the stirring was continued for another day.
The catalyst was filtered off, the filtrate was concentrated, and the
residue was freeze-dried from water to give crude 35 (18.4 mg, 98%).
An analytical sample of 35 was obtained by reversed-phase HPLC on
a C-18 column (5 µm, 250 × 10 mm, 8:2 H2O-CH3CN): Rf 0.44
(5:5:2 CHCl3-MeOH-H2O), 0.65 (5:5:4:1 BuOH-EtOH-
4.79 (br s, 1H, H-1V), 4.51 (d, J1 ,2 ) 8.0 Hz, 1H, H-1II), 4.46 (dd,
J2 ,3 ) 11.2 Hz, 1H, H-2I), 4.31 (m, 1H, H-5IV), 4.24 (d, J4 ,3 ) 2.7
I
I
I I
Hz, 1H, H-4I), 4.17 (dd, J3 ,4 ) 2.8 Hz, J3 ,2 ) 11.2 Hz, 1H, H-3I),
4.04-4.01 (m, 2H, H-5I, H-2V), 3.89-3.55 (m, 17H, H-6I, H-6AII,
CHCH3 (Ala), H-6AIV, H-6AIII, H-3IV, H-6BII, H-3IV, H-3V, H-6BIV,
I
I
I I
H-6BIII, H-5V, H-5III, H-3III, H-5II, H-4IV, H-2III), 3.52 (dd, J2
)
IV,3IV
) 3.5 Hz, 1H, H-2IV), 3.48-3.42 (m, 3H, H-4III, H-3II,
IV,1IV
10.0 Hz, J2
H-4V), 3.41 (s, 3H, CH3O), 3.30 (t, J4 ,5 ) 9.5 Hz, 1H, H-4II), 3.14
II II
II
II II
(t, J2 ,3 ) 8.6 Hz, 1H, H-2 ), 1.46 (d, JCH3,CH ) 7.1 Hz, 3H, CH3CH
(Ala)), 1.31 (d, J6,5 ) 6.3 Hz, 3H, H-6V); 13C NMR (125 MHz, D2O,
δC) 105.7 (C-1II), 102.5 (C-1V), 100.5 (C-1IV), 99.7 (C-1I), 99.6 (C-
1III), 77.2 (C-4I, C-3II), 77.1 (C-3I), 75.9 (C-5II), 74.8 (C-5III), 74.5
(C-2II), 74.2 (C-3IV), 73.6 (C-4V), 73.4 (C-2IV), 73.3 (C-3III), 73.2 (C-
5I), 72.8 (C-2III), 72.1 (C-4II), 71.8 (C-3V), 71.7 (C-5IV), 71.5 (C-2V),
70.8 (C-4III), 70.6 (C-4IV), 70.3 (C-5V), 68.7 (C-6II), 67.8 (C-6IV), 62.0
(C-6I), 61.9 (C-6III), 56.7 (CH3O), 51.0 (CH3CH (Ala)), 50.9 (C-2I),
18.6 (CH3CH (Ala)), 18.5 (C-6V); HR ESI MS calcd for [M + Na]
C34H60N2O25 + Na 919.3383, found 919.3417; calcd for [M + H]
C34H60N2O25 + H 897.3563, found 897.3593.
Methyl r-D-Glucopyranosyl-(1f6)-ꢀ-D-glucopyranosyl-(1f3)-
[r-L-rhamnopyranosyl-(1f6)-r-D-glucopyranosyl-(1f4)]-2-(N-
acetyl-L-alanylamino)-2-deoxy-r-D-galactopyranoside (37). To a
solution of 36 (9.4 mg, 0.009 mmol) in dry MeOH (400 µL) were
added acetic anhydride (1.9 µL, 0.020 mmol) and triethylamine
(3.9 µL, 0.028). The solution was kept for 16 h at rt, then more
Ac2O (1.7 µL, 0.015 mmol) was added. After being kept for 2 h,
the reaction mixture was diluted with toluene (0.5 mL) and
concentrated. The residue was purified by size-exclusion chroma-
tography (Sephadex G-15 column, 348 × 30 mm) in water to give
37 (6.0 mg, 0.006 mmol, 69%): Rf 0.41 (5:5:4:1 BuOH-EtOH-
H2O-NH3(aq)); [R]23D +55.6 (c 1, H2O); 1H NMR (500 MHz, D2O,
δH) 4.96 (d, J1
) 3.7 Hz, 1H, H-1III), 4.94 (d, J1,2 ) 3.5 Hz,
III,2III
1H, H-1IV), 4.79-4.77 (m, 2H, H-1V, H-1IV), 4.49 (d, J1 ,2 ) 8.0
II II
I
Hz, 1H, H-1II), 4.43 (dd, J2 ,3 ) 11.2 Hz, J2 ,1 ) 3.6 Hz, 1H, H-2 ),
I
I
I I
4.33-4.27 (m, 2H, H-5IV, CH3CH(NHAc)CO), 4.20 (d, J4 ,3 ) 2.5
I
I
I
Hz, 1H, H-4I), 4.15 (dd, J3 ,4 ) 2.6 Hz, J3 ,2 ) 11.3 Hz, 1H, H-3 ),
4.04-3.99 (m, 2H, H-5I, H-2V), 3.88-3.74 (m, 10H, H-6I, H-6AII,
H-6AIV, H-6AIII, H-6BII, H-3IV, H-3V, H-6BIV, H-6BIII), 3.72 (m,
1H, H-5V), 3.70-3.54 (m, 5H, H-3III, H-5III, H-5II, H-4IV, H-2III),
I
I
I
I
13
1
H2O-NH3aq); [R]D +69.4 (c 1, H2O); H NMR (500 MHz, D2O,
δH) 4.99 (d, J1 ) 2.9 Hz,
) 3.5 Hz, 1H, H-1III), 4.97 (d, J1
III,2III
IV,2IV
) 10.0 Hz, J2
) 3.5 Hz, 1H, H-2IV), 3.48-3.40
II II II II
IV,3IV
3.49 (dd, J2
IV,1IV
1H, H-1IV), 4.85 (d, J1 ,2 ) 3.6 Hz, 1H, H-1I), 4.81 (s, 1H, H-1V),
I
I
(m, 6H, H-3II, H-4III, H-4V, CH3O), 3.30 (t, J4 ,5 ) J4 ,3 ) 9.4
Hz, 1H, H-3II), 3.11 (t, J2,3 ) 8.5 Hz, 1H, H-2II), 2.04 (s, 3H,
CH3CO), 1.39 (d, JCH3,CH ) 7.2 Hz, 3H, CH3CH(NHAc)CO), 1.33
4.52 (d, J1 ,2 ) 7.9 Hz, 1H, H-1II), 4.45 (dd, J2 ,3 ) 11.2 Hz, 1H,
H-2I), 4.32 (m, 1H, H-5IV), 4.23 (br s, 1H, H-4I), 4.18-4.10 (m, 2H,
H-3I, CHCH3 (Ala)), 4.06-4.01 (m, 2H, H-5I, H-2V), 3.91-3.56 (m,
16H, H-6I, H-6AII, H-6AIII, H-3IV, H-6BII, H-6AIV, H-3V, H-6BIV,
II II
I I
(d, J6
) 6.2 Hz, 3H, H-6V); 13C NMR (125 MHz, D2O, δC)
V,5V
175.5, 174.1 (CH3CO, CH3CH(NHAc)CO), 104.1 (C-1II), 101.1 (C-
1V), 99.1 (C-1IV), 98.3 (C-1I), 98.1 (C-1III), 75.8 (C-4I), 75.7 (C-
3II), 75.3 (C-3I), 74.4 (C-5II), 73.3 (C-5III), 73.1 (C-2II), 72.9 (C-
3IV), 72.1 (C-4V), 71.9 (C-2IV), 71.8 (C-3III, C-5I), 71.3 (C-2III),
70.6 (C-4II), 70.2 (C-5IV, C-3V), 70.0 (C-2V), 69.3 (C-4III), 69.1
(C-4IV), 68.8 (C-5V), 67.1 (C-6II), 66.3 (C-6IV), 60.5 (C-6I), 60.4
(C-6III), 55.5 (CH3O), 49.9 (CH3CH(NHAc)CO), 49.4 (C-2I), 21.7
(CH3CO), 17.0 (CH3CH(NHAc)CO), 16.6 (C-6V); HR ESI MS [M
+ Na] calcd for C36H62N2O26 + Na 961.3489, found: 961.3468.
H-6BIII, H-5V, H-5III, H-3III, H-5II, H-4IV, H-2III), 3.52 (dd, J2
)
IV,3IV
10.0 Hz, 1H, H-2IV), 3.50-3.42 (m, 6H, H-3II, H-4III, H-4V, CH3O),
3.34 (t, 1H, H-4II), 1.46 (s, 9H, CH3 (Boc)), 1.35 (d, 3H, JCH,CH3
)
V
7.2 Hz, CH3CH (Ala)), 1.32 (d, 3H, J6 ,5 ) 6.2 Hz, H-6 ); 13C NMR
(125 MHz, D2O, δC): 105.5 (C-1II), 102.5 (C-1V), 100.7 (C-1IV), 99.8
(C-1I), 99.6 (C-1III), 77.7 (C-4I), 77.2 (C-3II), 76.9 (C-3I), 76.0 (C-5II),
74.8 (C-5III), 74.5 (C-2II), 74.1 (C-3IV), 73.6 (C-4V), 73.4 (C-3III, C-2IV),
73.2 (C-5I), 72.8 (C-2III), 71.9 (C-4II), 71.7 (C-3V, C-5IV), 71.4 (C-
2V), 70.8 (C-4III), 70.6 (C-4IV), 70.2 (C-5V), 68.4 (C-6II), 67.7 (C-6IV),
61.9 (C-6I, C-6III), 56.9 (CH3O), 52.0 (CH3CH (Ala)), 50.7 (C-2I), 29.2
(CH3 (Boc)), 18.4 (C-6V, CH3CH (Ala)); HR ESI MS calcd for [M +
K + H]+2 (C39H68N2O27 + K + H)/2 518.1862, found 518.1842.
Methyl r-D-Glucopyranosyl-(1f6)-ꢀ-D-glucopyranosyl-(1f3)-
[r-L-rhamnopyranosyl-(1f6)-r-D-glucopyranosyl-(1f4)]-2-(L-ala-
nylamino)-2-deoxy-r-D-galactopyranoside (36). Lyophilized 35 (8.9
mg, 0.009 mmol) was dissolved in neat TFA (400 µL), the solution
was kept for 5 min at 20 °C, and then taken to dryness (bath
temperature <35 °C). The residual TFA was removed by coevaporation
with toluene (2 × 1 mL). The residue was lyophilized from water to
give 36 (9.0 mg, 100%): Rf 0.09 (5:5:4:1 BuOH-EtOH-H2O-
V
V
Acknowledgment. We are grateful for the financial support
from 10th Program of the Division of Chemistry and Material
Sciences RAS as well as NIH Grant No. RO1 AI48917-04. We
acknowledge A. I. Zinin (N. D. Zelinsky Institute of Organic
Chemistry, RAS, Moscow) for helpful discussions.
1
Supporting Information Available: Selected H, 13C, 2-D
NMR spectra and procedures, which were not given in the
article, are included. This material is available free of charge
via the Internet at http://pubs.acs.org.
NH3aq); [R]23D +70.3 (c 1, H2O); 1H NMR (500 MHz, D2O, δH) 4.97
I
(d, 1H, H-1III), 4.96 (d, 1H, H-1IV), 4.83 (d, J1 ,2 ) 3.6 Hz, 1H, H-1 ),
JO801561P
I
I
J. Org. Chem. Vol. 73, No. 21, 2008 8421