Block synthesis with galacturonate trichloroacetimidates

Article abstract of DOI:10.1081/CAR-100108276

The disaccharide methyl (4-O-benzoyl-3-O-benzyl-2-O-acetyl-α-L-rhamno pyranosyl)-(1→4)-(allyl 2,3-di-O-benzy-β-D-galactopyranosid)uronate (13) was obtained in an excellent yield of 88% using methyl (allyl 2,3-di-O-benzyl-β-D-galactopyranosid)uronate (12) as the glycosyl acceptor and a slight excess of the 1,2-di-O-acetyl-rhamnoglycosyl donor 5a. Disaccharide 13 is a key intermediate that can be used either as a glycosyl acceptor or glycosyl donor for the preparation of rhamnogalacturonan fragments. Here, introduction of the trichloroacetimidate function at the anomeric center gave the disaccharide glycosyl donor 28, which could be applied in a blockwise glycosylation reaction to form the L-Rha-α(1→4)-D-GalA-α(1→4)-D-GalA trisaccharide 29. Generally, on condition that no neighboring group effect influenced the reaction at the anomeric center of the α-trichloroacetimidate galacturonate glycosyl donors (20-22,28), α-glycosidic linkages were nearly exclusively formed, except in the case of the 4-O-methylgalactopyranosyluronate 22.

Full text of DOI:10.1081/CAR-100108276

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BLOCK SYNTHESIS WITH GALACTURONATE
TRICHLOROACETIMIDATES
Birte Nolting a , Hanna Boye a & Christian Vogel b
a Department of Chemistry, Division of Organic Chemistry , University of Rostock ,
Buchbinderstrabe 9, Rostock, 18055, Germany
b Department of Chemistry, Division of Organic Chemistry , University of Rostock ,
Buchbinderstrabe 9, Rostock, 18055, Germany
Published online: 16 Aug 2006.
To cite this article: Birte Nolting , Hanna Boye & Christian Vogel (2001) BLOCK SYNTHESIS WITH GALACTURONATE
TRICHLOROACETIMIDATES , Journal of Carbohydrate Chemistry, 20:7-8, 585-610
To link to this article: http://dx.doi.org/10.1081/CAR-100108276
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J. CARBOHYDRATE CHEMISTRY, 20(7&8), 585–610 (2001)
BLOCK SYNTHESIS WITH GALACTURONATE
TRICHLOROACETIMIDATES1
Birte Nolting, Hanna Boye, and Christian Vogel*
University of Rostock, Department of Chemistry,
Division of Organic Chemistry, Buchbinderstrabe 9,
18055 Rostock, Germany
Dedicated with great appreciation to Professor Joachim Thiem on the
occasion of his 60th birthday.
ABSTRACT
The disaccharide methyl (4-O-benzoyl-3-O-benzyl-2-O-acetyl-ꢀ-L-rhamno
pyranosyl)-(1→4)-(allyl 2,3-di-O-benzyl-ꢁ-D-galactopyranosid)uronate (13)
was obtained in an excellent yield of 88% using methyl (allyl 2,3-di-O-benzyl-
ꢁ-D-galactopyranosid)uronate (12) as the glycosyl acceptor and a slight excess
of the 1,2-di-O-acetyl-rhamnoglycosyl donor 5a. Disaccharide 13 is a key in-
termediate that can be used either as a glycosyl acceptor or glycosyl donor for
the preparation of rhamnogalacturonan fragments. Here, introduction of the
trichloroacetimidate function at the anomeric center gave the disaccharide gly-
cosyl donor 28, which could be applied in a blockwise glycosylation reaction
to form the L-Rha-ꢀ(1→4)-D-GalA-ꢀ(1→4)-D-GalA trisaccharide 29. Gener-
ally, on condition that no neighboring group effect influenced the reaction at
the anomeric center of the ꢀ-trichloroacetimidate galacturonate glycosyl
donors (20–22,28), ꢀ-glycosidic linkages were nearly exclusively formed, ex-
cept in the case of the 4-O-methylgalactopyranosyluronate 22.
INTRODUCTION
Pursuing our program directed at the synthesis of pectin fragments, which
have a very complex structure and several biological functions and activities,2 we
looked for an option to use oligomeric galacturonates in glycosidic reactions to form
higher oligomers of defined structure. The repeating units in pectin fragments are
*Corresponding author. E-mail:christian.vogel@chemie.uni-rostock.de
585
Copyright © 2001 by Marcel Dekker, Inc.
www.dekker.com

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NOLTING, BOYE, AND VOGEL
often ꢀ(1→2) or ꢀ(1→4) linked between D-galacturonic acid itself and L-rhamnose
residues. Until now, the best synthetic method to prepare aD-GalA-ꢀ(1→4)-D-GalA
disaccharide or a D-GalA-ꢀ(1→2)-L-Rha-ꢀ(1→4)-D-GalA trisaccharide is applica-
tion of D-galactopyranosyluronic thioglycosides, in which the neighboring group in
the O-2-position does not exercise an influence on the anomeric center of the gly-
cosyl donor.3–6 Unfortunately, there is no suitable preparative procedure to synthe-
size a thioglycoside starting from a D-galacturonate precursor.7 Up to this day, the
synthetic pathway to galactopyranosyluronic thioglycosides starts from selective
protected thiogalactosides including the crucial oxidation step of the primary
hydroxyl group.5 Furthermore, our attempts to prepare ꢁ-D-galacturonate
trichloroacetimidates for an SN2-like ꢀ-glycosylation were unsuccessful.7 Fortu-
nately, the ꢀ-D-galacturonate trichloroimidates obtained provided predominantly
ꢀ-glycosidic linkages and this result creates the basis both for galacturonate glyco-
syl donors in ꢀ-glycosylation reactions prepared directly from D-galacturonic acid
and for the block synthesis with oligomeric galacturonate trichloroacetimidates.
RESULTS AND DISCUSSION
Recently, we have described the stepwise synthesis of a trisaccharide [D-
GalA-ꢀ(1→2)-L-Rha-ꢀ(1→4)-D-GalA], as an analogue for the repeating unit of the
backbone of rhamnogalacturonan I. The ꢀ(1→4) coupling between L-rhamnose and
D-galacturonic acid derivatives was realized using the trityl-cyanoethylidene con-
densation.6 Herein, we report a more efficient glycosylation procedure for this cou-
pling as well as an option for a block synthesis with rhamnogalacturonan fragments.
In order to improve the formation of a L-Rha-ꢀ(1→4)-D-GalA disaccharide,
the glycosylation step was systematically examined with several suitable
rhamnopyranosyl donors (5a,7–10, Scheme 2), synthesis of which started from the
orthoester derivative 1 (Scheme 1). The O-4 position of 1 was protected with dif-
ferent substituted benzoyl groups (2a–2c) to serve both as a marker in subsequent
biological investigations and, after reduction of the nitro group to an amino group,
as a tether for stains or dyes.
Regioselective opening8 of the orthoester structure in 2a–2c led to the O-2
acetyl protecting group of compounds 3a–3c which were involved in neighboring
participation in the later glycosylation, and favored formation of the desired 1,2-
trans linked products.10 As expected, conversion of the orthoester 1 into the diacyl
derivatives 3a–3c caused a considerable downfield shift of the H-2 and H-4 signals
(H-2, ꢂ 4.82 to 5.09 ꢃ 0.02 and H-4, ꢂ 3.49 to 5.10 ꢃ 0.02) in the 1H NMR spec-
tra. Benzylation of 3a–3c with benzyl trichloroacetimidate and a catalytic amount
of trifluoromethanesulfonic acid11 provided 4a–4c in 63% yield. The introduction
of a benzyl ether at the O-3 position functions both as a permanent protecting group
and for activation of the later glycosyl donors.10 Acetolysis12 of 4a–4c gave nearly
exclusively the ꢀ-acetates 5a–5c in excellent yields. Only in the case of 5a could a
small amount (7%) of the ꢁ-acetate (5aꢁ) be isolated. The ꢀ stereochemistry at the
anomeric center was evident only from the geminal 13CM1H coupling constants

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587
Scheme 1.
Scheme 2.

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NOLTING, BOYE, AND VOGEL
(JC-1,H-1).6,13 Since the observed values for 5a and 5b,c are 172.6 Hz and 171.1 Hz,
respectively, a comparison with JC-1,H-1ꢄ 161.6 Hz of 5aꢁ verified the expected
structures.
For the preparation of the trichloroacetimidate 7, the acetyl group at the
anomeric center was removed with hydrazine acetate14 and the resulting compound
6 treated with trichloroacetonitrile and DBU15 to provide the compound 7 in 92%
yield. Again, the value of 13CM1H coupling constant JC-1,H-1ꢄ 178.8 Hz estab-
lished the ꢀ configuration of the trichloroacetimidate group at the anomeric center.
The reaction of 5a with methylthiomethylsilane15 provided the correspond-
ing thioglycoside 8 in nearly quantitative yield. Finally, the rhamnosyl chloride 9
and the bromide 10 could be obtained in comparably good yields by treatment of
5a with dichloromethyl methyl ether and oxalyl bromide, respectively.16 In all
cases, 13CM1H coupling constant JC-1,H-1 with values higher than 169 Hz indicated
the 1,2-trans configuration of the substituents at the rhamnose derivatives 8–10.
For the comparative study, the rhamnoglycosyl donors 5a,7–10 were coupled
with the galacturonate glycosyl acceptor 12 in a ratio of 1:1. For every glycosyl
donor several promoters were tested, and the best result of each reaction type is de-
scribed in the Experimental. Thus, the highest yields of the ꢀ(1→4)-coupled dis-
accharide 13 were achieved with the glycosyl chloride 9 (73%) and the glycosyl
bromide 10 (76%) in the presence of silver trifluoromethanesulfonate.17 Compara-
ble results afforded the coupling of the 1-acetate 5a with the aid of trimethylsilyl
trifluoromethanesulfonate17 (66%), in the course of which the utilization of a
1.3:1 molar ratio of donor 5a and acceptor 12 increased effectively the yield of dis-
accharide 13 to 88%. Unfortunately, the glycosylation with the rhamnosyl
trichloroacetimidate 7 in the presence of boron trifluoride diethyl etherate16 gave
only comparable results (50% yield) due to the trityl-cyanoethylidene condensa-
tion of the 4-O-tritylated acceptor 12 with the donor 11.6 Suprisingly low was the
yield of disaccharide 13 when the thioglycoside 8 was used as glycosyl donor. Pro-
motion with N-iodosuccinimide/trifluoromethanesulfonic acid18 as well as with
dimethyl(methyl-thio)sulfonium triflate19 gave approximately 30% yields only,
whereas iodonium di-sym-collidine perchlorate18,20 and iodonium di-sym-collidine
triflate21 were completely inactive. The analytical data for compound 13 was re-
ported in an earlier paper6 by us and is in full agreement with the structure obtained
here. Noteworthy, the value of the 13CM1H coupling constant JC-1ꢅ,H-1ꢅ is 172.5 Hz
and indicates clearly the ꢀ-linkage between L-rhamnose and D-galacturonic acid.
Before the disaccharide 13 was used as a glycosyl donor in a block synthesis,
we investigated both the introduction of the trichloroacetimidate function at the
anomeric center and the influence on stereoselectivity during glycosylation of sev-
eral substituents in the O-3 and O-4 position of galacturonates 20–22 (Scheme 3),
which served here as model compounds. Thus, acetylation of galacturonate 125
with acetic anhydride in pyridine provided the 4-O-acetyl derivative 14, whereas
methylation of 12 was achieved with ethereal diazomethane under acid catalysis22
to afford the 4-O-methyl derivative 16. In the 1H NMR spectra the acetylation of
12 caused the expected downfield shift of the H-4 ring proton signal from ꢂ 4.31

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GALACTURONATE TRICHLOROACETIMIDATES
589
Scheme 3.
(12)5 to 5.78 (14). Otherwise, the methylation leads to an upfield shift of H-4 to ꢂ
3.97 (16). The synthesis of the 3,4-di-O-acetyl derivative 15 has been described in
an earlier paper.5 After deallylation of compounds 14–16 with the aid of palla-
dium(II) chloride,23 the introduction of the trichloroacetimidate group at the
anomeric center of resulting 17–19 in the presence of DBU furnished the ꢀ-D-
galactopyranosyl trichloroacetimidates 20ꢀ-22ꢀ after chromatographic purifica-
tion in good yields (ca. 73%). Furthermore, the ꢁ-trichloroacetimidates 20ꢁ-22ꢁ
1
could be characterized by H NMR spectroscopy obtained from enriched HPLC
fractions which still contained mostly the corresponding ꢀ-anomers. Typically, the
small coupling constants J1,2 of 3.2 ꢃ 0.2 Hz for compounds 20ꢀ-22ꢀ and the con-
siderable bigger ones of 7.8 ꢃ 0.5 Hz for 20ꢁ-22ꢁ illustrated the situation at the
anomeric center.
The glycosylation of the galacturonate acceptor 12 with donors 20ꢀ-22ꢀ in a
ratio of 1:1 promoted by trimethylsilyl trifluoromethanesulfonate revealed a
peculiar effect of the chosen substitution pattern (Scheme 3). Thus, the 3,4-di-O-
acetyl-ꢀ-D-galacturonate trichloroacetimidate 21 provided 67% yield of the
ꢀ(1→4)-coupled disaccharide 24ꢀ but only 5% of the ꢁ-coupled disaccharide 24ꢁ
was detected. By way of contrast, the more active 2,3-di-O-benzyl glycosyl donor
20 coupled with 12 furnished the corresponding disaccharides 23ꢀ in a yield of
59% but no ꢁ-coupled disaccharide 23ꢁ was observed. In earlier experiments the
coupling of 12 with 20 in the presence of boron trifluoride diethyl etherate fur-
nished the corresponding disaccharides 23ꢀ and 23ꢁ in a total yield of 53% and a
disappointingꢀ/ꢁ ratio of 1.6:1. The analytical data of the isolated 23ꢁ are de-
scribed in the Experimental. Finally, the methyl group in the O-4 position of the
glycosyl donor 22 gave rise to the lowest stereoselectivity (nearly 1:1 disaccharide
25ꢀ/25ꢁ) with a total yield of 52%. Subsequent experiments have shown that the
ꢀ- or ꢁ-configuration of the trichloroacetimidate group at the anomeric center of

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NOLTING, BOYE, AND VOGEL
the donors 20–22 exerted no influence on the outcome of stereoselectivity of the
glycosylations here investigated. Therefore, in the following experiments we used
theꢀ/ꢁ mixtures of 20–22. The 1H NMR spectra showed vicinal coupling constants
J1ꢅ,2ꢅ of 3.4 ꢃ 0.3 Hz for the ꢀ-coupled disaccarides 23ꢀ, 24ꢀ and 25ꢀ, whereas
the ꢁ-coupled ones had a value of 7.6 Hz. Furthermore, the 13C NMR signals for
C-1ꢅ of 23ꢀ-25ꢀ were found to fall within the expected range of ꢂ 99.7 ꢃ 0.3. In
the case of 23ꢁ-25ꢁ values for C-1ꢅ signals were determined at ꢂ 102.4 ꢃ 0.1. The
other 1H and 13C NMR data were also fully consistent with the assigned structures.
Now, the preparation of galacturonates suitable as donors in ꢀ-glycosylation
reactions can be carried out directly from commercially available D-galacturonic
acid (D-GalA → 14,15 → 20,21) avoiding the crucial oxidation step in comparison
to an approach involving D-galactose-derived intermediates.
In a side-experiment, we made sure that disaccharide 23ꢀ could serve as a
precursor of a glycosyl acceptor. Thus, the deacetylation of 23ꢀ with 0.28 M
methanolic hydrochloric acid6 provided the deprotected O-4ꢅ position of the dis-
accharide 26ꢀ in a quantitative yield. This successful cleavage of an acetyl group
in 23ꢀ was documented in its 1H NMR spectrum by a significant upfield shift for
the H-4ꢅ ring proton signal from ꢂ 5.78 (23ꢀ) to 4.28 (26ꢀ).
Encouraged by the good results of the model glycosylations, the disaccharide
13 was transformed via deallylation (27) into the ꢀ-trichloroacetimidate 28
(Scheme 4) and coupled with the glycosyl acceptor 12 under exactly the same con-
ditions described above. Fortunately, the trisaccharide 29 was obtained after chro-
matographic purification in 70% isolated yield. Only traces of a trisaccharide
formed as a result of a ꢁ-glycosylation were noticed in the NMR spectra of the re-
action mixture. The 1H and 13C NMR spectra of 29 confirm the assigned structure.
Thus, the stereochemistry of the glycosidic linkage between the galacturonic acid
1
residues was established in the H NMR spectra by the signal for H-1ꢅ at ꢂ 5.26
with a small coupling constant J1ꢅ,2ꢅ of 3.1 Hz, whereas ꢁ-linked trisaccharide
shows a typically larger coupling constant J1ꢅ,2ꢅ of 7.6 Hz at ꢂ 4.39. Additionally,
the value of the C-1ꢅ signal at ꢂ 99.59 for 29 is shifted to ꢂ 102.22 in the case of
the ꢁ-linked derivative.
Scheme 4.

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591
In conclusion, the key intermediate 13 could be obtained in excellent 88%
yield using a slight excess of the 1,2-di-O-acetylrhamnosyl glycosyl donor 5a. The
disaccharide 13 can be used either as a glycosyl acceptor or glycosyl donor for the
preparation of rhamnogalacturonan fragments. Selective deacetylation of the O-2ꢅ-
position and coupling with a suitable galacturonate glycosyl donor led to the
D-GalA-ꢀ(1→2)-L-Rha-ꢀ(1→4)-D-GalA trisaccharide as described in a previous
paper.6 On the other hand, introduction of the trichloroacetimidate function at the
anomeric center gave the disaccharide glycosyl donor 28, which could be applied
in a glycosylation reaction to form the L-Rha-ꢀ(1→4)-D-GalA-ꢀ(1→4)-D-GalA
trisaccharide 29 in excellent yield. On condition that no neighboring group effect
controlled the reaction at the anomeric center of the ꢀ-trichloroacetimidate glyco-
syl donors 20–22 and 28, ꢀ-glycosidic linkages were nearly exclusively formed,
except in the case of the 4-O-methyl-galactopyranosyluronate 22. Thus, the
trichloroacetimidate glycosylation procedure offers for the first time the possibil-
ity to use D-galacturonate oligomers in a block synthesis in the course of which ꢀ-
glycosidic linkages were realized.
EXPERIMENTAL
General methods. Melting points were determined with a Boetius micro
apparatus BHMK 05 (Rapido, Dresden) and are uncorrected. Optical rotations
were measured for solutions in a 2-cm cell with an automatic polarimeter “GY-
ROMAT” (Dr. Kernchen Co.). NMR spectra were recorded with Bruker AC-250
or ARX-300 spectrometers, at 250 MHz or 300 MHz for 1H, and 62.9 MHz or 75.5
MHz for 13C, respectively. Chemical shifts are given relative to the signal of inter-
nal tetramethylsilane (ꢂ ꢄ 0). First order chemical shifts and coupling constants
were obtained from one-dimensional spectra, and assignment of proton resonances
was based on COSY experiments. Thin-layer chromatography (TLC) on precoated
plates of silica gel (Merck, Silica Gel 60, F254, 0.25 mm) was performed with the
following solvent systems (v/v): (A) 1:1, (B) 1.5:1, (C) 2:1, (D) 2.5:1, (E) 1:1.5,
and (F) 1:2 heptane-ethyl acetate. The spots were made visible by spraying with
methanolic 10% H2SO4 solution and charring them for 3–5 min with a heat gun.
Detection of benzyl derivatives was effected by UV fluorescence. Preparative flash
chromatography, MPLC and HPLC were performed by elution from columns of
slurry-packed Silica Gel 60 (Merck, 40–63 ꢆm) and Nucleosil 100–7 (Knauer, 7.0
ꢆm), respectively, with the above mentioned solvent systems. All solvents and
reagents were purified and dried according to standard procedures.24 After classi-
cal work-up of the reaction mixtures, the organic layers as a rule, were dried over
MgSO4, and then concentrated under reduced pressure (rotary evaporator).
Methyl 2,3-O-methylorthoacetyl-ꢀ-L-rhamnopyranoside (1). To a solu-
tion of methyl ꢀ-L-rhamnopyranoside25 (1.265 g, 7.1 mmol) in dry DMF (40 mL)
was successively added camphorsulfonic acid (165 mg, 0.71 mmol) and triethyl or-
thoacetate (3.3 mL, 17.2 mmol). The solution was stirred for 40 min at ambient

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592
NOLTING, BOYE, AND VOGEL
temperature under argon (TLC, Rf 0.40, solvent A). The reaction was terminated
by addition of triethylamine (1.8 mL, 12.8 mmol), and the mixture was concen-
trated. The residue was dissolved in chloroform (40 mL), and the organic solution
was extracted with ice-water (2 ꢇ 15 mL), cold aq sat NaHCO3 solution (2 ꢇ 15
mL), dried, and concentrated. The crude material was purified by MPLC (ethyl ac-
etate gradient 0%→40% in heptane) to yield 1 (1.15 g, 65%) as a colorless syrup:
1H NMR (CDCl3) ꢂ 1.16, 1.19 (2t, 6H, J ꢄ 8.2 Hz, OCH2CH3 endo/exo), 1.29
(d, 3H, J5,6 ꢄ 6.1 Hz, H-6), 1.52, 1.62 (2s, 6H, CH3 endo/exo), 2.96 (d, 1H,
J4,OH ꢄ 15.3 Hz, OH-4), 3.36 (s, 3H, OCH3), 3.45, 3.48 (2m, 4H, OCH2CH3
endo/exo), 3.49 (t, 1H, J4,5 ꢄ 7.0 Hz, H-4), 3.52 (m, 1H, H-5), 4.11 (d, 1 H, J1,2
ꢄ 1.8 Hz, H-1), 4.34 (dd, 1 H, J3,4 ꢄ 7.0 Hz, H-3), 4.82 (dd, 1H, J2,3 ꢄ 3.1 Hz,
H-2).
Anal. Calcd for C11H20O6 (248.28): C, 53.22; H, 8.12. Found: C, 53.16;
H, 8.03.
Acylation and opening of the orthoester ring of compound 1. To a solu-
tion of 1 (546 mg, 2.2 mmol) in dry pyridine (15 mL) was added the acylation agent
(2.5 mmol of benzoyl chloride, p-methylbenzoyl chloride or p-nitrobenzoyl chlo-
ride) at ꢈ20 °C under an inert atmosphere. The reaction mixture was stirred at that
temperature for one hour and then kept for an additional 8 h at ambient tempera-
ture (TLC, Rf ꢀ0.6, solvent A). Next, the slight excess of acyl chloride was de-
stroyed by addition of methanol (1 mL), and after stirring for a further 20 min, the
reaction mixture was concentrated and repeatedly co-concentrated with toluene-
ethyl acetate-ethanol (5:3:1, v/v/v). In the course of this work-up the orthoester was
already completely opened (TLC, Rf ꢀ0.4, solvent A). The residue was dissolved
in toluene, and the formed carbohydrate-free precipitate filtered off and washed
with toluene. The filtrate and washings were combined, dried and concentrated.
The crude products were purified by HPLC (eluent solvent B).
Methyl 2-O-acetyl-4-O-benzoyl-ꢀ-L-rhamnopyranoside (3a). (642 mg,
90%; TLC, Rf 0.43, solvent A), colorless crystals: mp 152°C (ethyl acetate-hep-
tane); [ꢀ]D25 ꢈ31.6° (c 1.0, chloroform); 1H NMR (CDCl3) ꢂ 1.25 (d, 3H, J5,6 ꢄ
6.4 Hz, H-6), 2.15 (s, 3H, OCOCH3), 3.38 (s, 3H, OCH3), 3.90 (m, 1H, H-5), 4.16
(dd, 1H, J3,4 ꢄ 9.8 Hz, H-3), 4.70 (d, 1H, J1,2 ꢄ 1.5 Hz, H-1), 5.11 (dd, 1H, J2,3 ꢄ
3.7 Hz, H-2), 5.12 (t, 1H, J4,5 ꢄ 9.8 Hz, H-4), 7.41, 7.55, 8.05 (3m, 5H, C6H5); 13C
NMR (CDCl3) ꢂ 17.40 (C-6), 20.91 (OCOCH3), 55.08 (OCH3), 65.88 (C-5), 68.38
(C-3), 72.13 (C-2), 75.13 (C-4), 98.26 (JC-1,H-1 ꢄ 170.9 Hz, C-1), 128.31, 128.36
129.41, 129.74, 130.01, 133.31 (OCOC6H5), 166.82 (OCOC6H5), 170.68
(OCOCH3).
Anal. Calcd for C16H20O7 (324.33): C, 59.25; H, 6.22. Found: C, 59.18; H,
6.19.
Methyl 2-O-acetyl-4-O-p-methylbenzoyl-ꢀ-L-rhamnopyranoside (3b).
(633 mg, 85%; TLC, Rf 0.38, solvent A), colorless crystals: mp 126°C (ethyl ac-
etate-heptane); [ꢀ]D25 ꢈ50.7° (c 1.0, chloroform); 1H NMR (CDCl3) ꢂ 1.23 (d, 3H,

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GALACTURONATE TRICHLOROACETIMIDATES
593
J
5,6 ꢄ 6.4 Hz, H-6), 2.12 (s, 3H, OCOCH3), 2.36 (s, 3H, pCH3C6H4OCO), 2.76 (bs,
1H, OH-3), 3.36 (s, 3H, OCH3), 3.90 (m, 1H, H-5), 4.12 (dd, 1H, J3,4 ꢄ 9.8 Hz,
H-3), 4.67 (d, 1H, J1,2 ꢄ 1.6 Hz, H-1), 5.08 (dd, 1H, J2,3 ꢄ 3.7 Hz, H-2), 5.08
(t, 1H, J4,5 ꢄ 9.8 Hz, H-4), 7.18, 7.88 (2m, 4H, pCH3C6H4OCO); 13C NMR
(CDCl3) ꢂ 17.32 (C-6), 20.82 (OCOCH3), 21.49 (pCH3C6H4OCO), 54.97 (OCH3),
65.84 (C-5), 68.24 (C-3), 72.47 (C-2), 74.85 (C-4), 98.20 (JC-1,H-1 ꢄ 171.1 Hz,
C-1), 126.58, 128.96, 129.69, 143.97 (pCH3C6H4OCO), 166.78 (pCH3C6H4OCO),
170.58 (OCOCH3).
Anal. Calcd for C17H22O7 (338.36): C, 60.35; H, 6.55. Found: C, 60.31, H,
6.59.
Methyl 2-O-acetyl-4-O-p-nitrobenzoyl-ꢀ-L-rhamnopyranoside (3c).
(674 mg, 83%; TLC, Rf 0.39, solvent A), pale yellow crystals: mp 143 °C (ethyl
acetate-heptane); [ꢀ]D19 ꢈ15.6° (c 1.0, chloroform); 1H NMR (CDCl3) ꢂ 1.26 (d,
3H, J5,6 ꢄ 6.1 Hz, H-6), 2.17 (s, 3H, OCOCH3), 2.34 (d, 1H, J3,OH ꢄ 8.2 Hz, OH-
3), 3.39 (s, 3H, OCH3), 3.95 (m, 1H, H-5), 4.16 (ddd, 1H, J3,4 ꢄ 9.8 Hz, H-3), 4.71
(d, 1H, J1,2 ꢄ 1.5 Hz, H-1), 5.09 (dd, 1H, J2,3 ꢄ 3.7 Hz, H-2), 5.12 (t, 1H, J4,5 ꢄ
9.8 Hz, H-4), 8.20, 8.28 (2m, 4H, pNO2C6H4OCO); 13C NMR (CDCl3) ꢂ 17.44 (C-
6), 20.92 (OCOCH3), 55.22 (OCH3), 65.70 (C-5), 68.42 (C-3), 72.70 (C-2), 76.14
(C-4), 98.30 (JC-1,H-1 ꢄ 171.2 Hz, C-1), 123.56, 130.78, 130.88, 134.96, 150.78
(pNO2C6H4OCO), 164.78 (pNO2C6H4OCO), 170.60 (OCOCH3).
Anal. Calcd for C16H19O9N (369.32): C, 52.03; H, 5.19; N, 3.79. Found: C,
51.99; H, 5.25; N, 3.81.
Benzylation of 3a–3c. A solution of 3a, 3b, or 3c (5.7 mmol) and benzyl
2,2,2-trichloroacetimidate (1.6 mL, 8.5 mmol) in dry dichloromethane (20 mL)
and dry heptane (30 mL) was treated with a catalytic amount of trifluo-
romethanesulfonic acid [55 ꢆL, 0.6 mmol, dissolved in dry dichloromethane (2
mL)] under an inert atmosphere at ꢈ10°C. The reaction mixture was stirred at
that temperature for 3.5 h, and then for a further 18 h at ambient temperature
(TLC solvent A). The solution was passed through a layer of alkaline alumina
and concentrated. After suspending the residue in heptane-diethyl ether (6:1, v/v,
70 mL) the carbohydrate-free precipitates were filtered off and washed with hep-
tane-diethyl ether (6:1, v/v, 30 mL). The filtrate and washings were combined,
concentrated, and the raw product was purified by MPLC (ethyl acetate gradient
0%→45% in heptane).
Methyl 2-O-acetyl-4-O-benzoyl-3-O-benzyl-ꢀ-L-rhamnopyranoside (4a).
(1.51 g, 64%; TLC, Rf 0.49, solvent A), colorless foam: [ꢀ]D25 ꢉ39.7° (c 1.0, chlo-
1
roform); H NMR (CDCl3) ꢂ 1.39 (d, 3H, J5,6 ꢄ 6.1 Hz, H-6), 2.30 (s, 3H,
OCOCH3), 3.49 (s, 3H, OCH3), 4.00 (m, 1H, H-5), 4.06 (dd, 1H, J3,4 ꢄ 9.8 Hz, H-
3), 4.53, 4.73 (2d, 2H, J ꢄ 12.5 Hz, CH2C6H5), 4.82 (d, 1H, J1,2 ꢄ 1.8 Hz, H-1),
5.44 (t, 1H, J4,5 ꢄ 9.8 Hz, H-4), 5.55 (dd, 1H, J2,3 ꢄ 3.4 Hz, H-2), 7.17–8.13 (4m,
10H, CH2C6H5, OCOC6H5); 13C NMR (CDCl3) ꢂ 17.45 (C-6), 20.88 (OCOCH3),
54.93 (OCH3), 66.41 (C-5), 68.34 (C-2), 70.96 (CH2C6H5), 72.91 (C-4), 74.21

ORDER
REPRINTS
594
NOLTING, BOYE, AND VOGEL
(C-3), 98.81 (C-1), 127.40, 127.66, 128.06, 128.25, 129.68, 129.86, 132.97, 137.58
(CH2C6H5, OCOC6H5), 165.53 (OCOC6H5), 170.22 (OCOCH3).
Anal. Calcd for C23H26O7 (414.45): C, 66.66; H, 6.32. Found: C, 66.67; H,
6.28.
Methyl 2-O-acetyl-3-O-benzyl-4-O-p-methylbenzoyl-ꢀ-L-rhamnopyra-
noside (4b). (1.54 g, 63%; TLC, Rf 0.54, solvent A), colorless foam: [ꢀ]D23 ꢉ23.2°
1
(c 1.0, chloroform); H NMR (CDCl3) ꢂ 1.24 (d, 3H, J5,6 ꢄ 6.1 Hz, H-6), 2.17
(s, 3H, OCOCH3), 2.44 (s, 3H, pCH3C6H4OCO), 3.37 (s, 3H, OCH3), 3.90 (m, 1H,
H-5), 3.91 (dd, 1H, J3,4 ꢄ 9.8 Hz, H-3), 4.41, 4.60 (2d, 2H, J ꢄ 12.5 Hz, CH2C6H5),
4.68 (d, 1H, J1,2 ꢄ 1.8 Hz, H-1), 5.29 (t, 1H, J4,5 ꢄ 9.8 Hz, H-4), 5.40 (dd, 1H, J2,3
ꢄ 3.4 Hz, H-2), 7.11–7.89 (3m, 9H, CH2C6H5, pCH3C6H4OCO); 13C NMR
(CDCl3) ꢂ 17.50 (C-6), 21.08 (OCOCH3), 21.67 (pCH3C6H5OCO), 55.04 (OCH3),
66.50 (C-5), 68.33 (C-2), 70.92 (CH2C6H5), 72.65 (C-4), 74.07 (C-3), 98.85 (C-1),
127.08, 127.48, 127.75, 128.17, 129.04, 129.86, 137.65, 143.82 (CH2C6H5,
pCH3C6H4OCO), 165.72 (pCH3C6H4OCO), 170.46 (OCOCH3).
Anal. Calcd for C24H28O7 (428.48): C, 67.28; H, 6.59. Found: C, 67.24; H,
6.65.
Methyl 2-O-acetyl-3-O-benzyl-4-O-p-nitrobenzoyl-ꢀ-L-rhamnopyra-
24
noside (4c). (1.65 g, 63%; TLC, Rf 0.50, solvent A), pale yellow foam: [ꢀ]D
ꢉ31.7° (c 1.0, chloroform); 1H NMR (CDCl3) ꢂ 1.23 (d, 3H, J5,6 ꢄ 6.4 Hz, H-6),
2.18 (s, 3H, OCOCH3), 3.39 (s, 3H, OCH3), 3.89 (m, 1H, H-5), 3.92 (dd, 1H, J3,4
ꢄ 9.8 Hz, H-3), 4.34, 4.59 (2d, 2H, J ꢄ 12.5 Hz, CH2C6H5), 4.70 (d, 1H, J1,2 ꢄ 1.8
Hz, H-1), 5.26 (t, 1H, J4,5 ꢄ 9.8 Hz, H-4), 5.42 (dd, 1H, J2,3 ꢄ 3.4 Hz, H-2),
7.07–8.15 (3m, 9H, CH2C6H5, pNO2C6H4OCO); 13C NMR (CDCl3) ꢂ 17.55 (C-
6), 21.06 (OCOCH3), 55.20 (OCH3), 66.13 (C-5), 68.05 (C-2), 70.87 (CH2C6H5),
73.89 (C-4), 73.91 (C-3), 98.83 (C-1), 123.47, 127.73, 127.93, 128.23, 130.86,
135.13, 137.44, 150.59 (CH2C6H5, pNO2C6H4OCO), 163.79 (pNO2C6H4OCO),
170.37 (OCOCH3).
Anal. Calcd for C23H25O9N (459.45): C, 60.13; H, 5.48; N, 3.05. Found:
C, 60.04; H, 5.55; N, 3.12.
Acetolysis of 4a–4c. A solution of 4a, 4b, or 4c (3.5 mmol) in acetic anhy-
dride-acetic acid-sulfuric acid (100:40:1, v/v/v, 15 mL) was stirred for 30 min at
ambient temperature (TLC solvent A). After addition of cold aq 10% K2SO4 (200
mL), the solution was stirred for a further 30 min. Subsequently, the reaction mix-
ture was extracted with chloroform (3 ꢇ 50 mL), and the combined organic phases
were washed successively with cold sat aq NaHCO3 (2 ꢇ 50 mL), water (2 ꢇ 50
mL), dried, and concentrated. The residue was co-concentrated with toluene (3 ꢇ)
to remove remaining traces of acetic acid. Finally, the residue was purified by
MPLC (ethyl acetate gradient 0%→50% in heptane) providing nearly exclusively
the ꢀ-anomers of 5a–5c.
1,2-Di-O-acetyl-4-O-benzoyl-3-O-benzyl-ꢀ-L-rhamnopyranose (5a).
(1.30 g, 84%; TLC, Rf 0.55, solvent A), colorless foam: [ꢀ]D25 ꢉ22.7° (c 1.0, chlo-

ORDER
REPRINTS
GALACTURONATE TRICHLOROACETIMIDATES
595
roform); 1H NMR (CDCl3) ꢂ 1.26 (d, 3H, J5,6 ꢄ 6.2 Hz, H-6), 2.12, 2.18 (2s, 6H,
2 ꢇ OCOCH3), 3.93 (dd, 1H, J3,4 ꢄ 9.9 Hz, H-3), 3.96 (m, 1H, H-5), 4.43, 4.63
(2 d, 2H, J ꢄ 12.4 Hz, CH2C6H5), 5.34 (t, 1H, J4,5 ꢄ 9.9 Hz, H-4), 5.40 (dd, 1H,
J2,3 ꢄ 3.3 Hz, H-2), 6.08 (d, 1H, J1,2 ꢄ 1.9 Hz, H-1), 7.10–8.01 (4m, 10H,
CH2C6H5, OCOC6H5); 13C NMR (CDCl3) ꢂ 17.52 (C-6), 20.90 (2 ꢇ OCOCH3),
67.26 (C-2), 68.99 (C-5), 71.11 (CH2C6H5), 72.24 (C-4), 73.77 (C-3), 91.13
(JC-1,H-1 ꢄ 172.6 Hz, C-1), 127.67, 127.81, 128.22, 128.37, 129.80, 129.25,
133.25, 137.29 (CH2C6H5, OCOC6H5), 165.51 (OCOC6H5), 168.37, 170.07
(2 ꢇ OCOCH3).
Anal. Calcd for C24H26O8 (442.46): C, 65.15; H, 5.92. Found: C, 65.16;
H, 5.87.
1,2-Di-O-acetyl-3-O-benzyl-4-O-benzoyl-ꢁ-L-rhamnopyranose (5aꢁ).
(108 mg, 7%; TLC, Rf 0.47, solvent A), colorless foam: [ꢀ]D24 ꢉ73.3° (c 1.0, chlo-
roform); 1H NMR (CDCl3) ꢂ 1.46 (d, 3H, J5,6 ꢄ 6.1 Hz, H-6), 2.26, 2.39 (2s, 6H,
2 ꢇ OCOCH3), 3.84 (m, 1H, H-5), 3.87 (dd, 1H, J3,4 ꢄ 9.8 Hz, H-3), 4.55, 4.79
(2d, 2H, J ꢄ 12.5 Hz, CH2C6H5), 5.46 (t, 1H, J4,5 ꢄ 9.8 Hz, H-4), 5.80 (dd, 1H,
J2,3 ꢄ 3.4 Hz, H-2), 5.95 (d, 1H, J1,2 ꢄ 1.2 Hz, H-1), 7.26–8.13 (4m, 10H,
CH2C6H5, OCOC6H5); 13C NMR (CDCl3) ꢂ 17.41 (C-6), 20.72, 20.90
(2 ꢇ OCOCH3), 66.91 (C-2), 70.66 (CH2C6H5), 71.58 (C-5), 72.06 (C-4), 75.49
(C-3), 90.92 (JC-1,H-1 ꢄ 161.6 Hz C-1), 127.77, 127.83, 128.25, 128.35, 128.81,
129.46, 129.77, 133.26, 136.86 (CH2C6H5, OCOC6H5), 165.46 (OCOC6H5),
168.70, 170.52 (2 ꢇ OCOCH3).
Anal. Calcd for C24H26O8 (442.46): C, 65.15; H, 5.92. Found: C, 65.11; H,
5.86.
1,2-Di-O-acetyl-3-O-benzyl-4-O-p-methylbenzoyl-ꢀ-L-rhamnopyranose
(5b). (1.49 g, 93%; TLC, Rf 0.53, solvent A), colorless syrup: [ꢀ]D24 ꢉ15.7° (c
1.0, chloroform); 1H NMR (CDCl3) ꢂ 1.23 (d, 3H, J5,6 ꢄ 6.1 Hz, H-6), 2.12, 2.18
(2s, 6H, 2 ꢇ COCH3), 2.43 (s, 3H, pCH3C6H4OCO), 3.91 (dd, 1H, J3,4 ꢄ 9.8 Hz,
H-3), 3.93 (m, 1H, H-5), 4.41, 4.61 (2d, 2H, J ꢄ 12.5 Hz, CH2C6H5), 5.33 (t, 1H,
J
4,5 ꢄ 9.8 Hz, H-4), 5.39 (dd, 1H, J2,3 ꢄ 3.4 Hz, H-2), 6.07 (d, 1H, J1,2 ꢄ 1.8 Hz,
H-1), 7.12–7.91 (3m, 9H, CH2C6H5, pCH3C6H4OCO); 13C NMR (CDCl3) ꢂ 17.53
(C-6), 20.94, 21.72 (2 ꢇ OCOCH3), 22.67 (pCH3C6H4OCO), 67.31 (C-2), 69.09
(C-5), 71.10 (CH2C6H5), 72.05 (C-4), 73.74 (C-3), 91.16 (JC-1,H-1 ꢄ 171.7 Hz,
C-1), 127.67, 127.83, 128.02, 128.27, 129.11, 129.90, 137.36, 144.05 (CH2C6H5,
pCH3C6H4OCO), 165.60 (pCH3C6H4OCO), 168.43, 170.13 (2 ꢇ OCOCH3).
Anal. Calcd for C25H28O8 (456.49): C, 65.78; H, 6.18. Found: C, 6.84; H,
6.14 %.
1,2-Di-O-acetyl-3-O-benzyl-4-O-(p-nitrobenzoyl)-ꢀ -L-rhamnopyranose
(5c). (1.60 g, 94%; TLC, Rf 0.53, solvent A), colorless foam: [ꢀ]D23 ꢉ18.4° (c
0.5, chloroform); 1H NMR (CDCl3) ꢂ 1.24 (d, 3H, J5,6 ꢄ 6.4 Hz, H-6), 2.15, 2.20
(2s, 6H, OCOCH3), 3.93 (dd, 1H, J3,4 ꢄ 9.8 Hz, H-3), 3.96 (m, 1H, H-5), 4.38, 4.63
(2d, 2H, J ꢄ 12.5 Hz, CH2C6H5), 5.33 (t, 1H, J4,5 ꢄ 9.8 Hz, H-4), 5.43 (dd, 1H, J2,3
ꢄ 3.4 Hz, H-2), 6.08 (d, 1H, J1,2 ꢄ 1.8 Hz, H-1), 7.09–8.28 (3m, 9H, CH2C6H5,

ORDER
REPRINTS
596
NOLTING, BOYE, AND VOGEL
pNO2C6H4OCO); 13C NMR (CDCl3) ꢂ 17.56 (C-6), 20.79, 21.93 (2 ꢇ OCOCH3),
67.05 (C-2), 68.69 (C-5), 71.07 (CH2C6H5), 73.25 (C-4), 73.63 (C-3), 91.06
(JC-1,H-1 ꢄ 171.7 Hz, C-1), 123.53, 127.92, 128.05, 128.31, 130.89, 134.92,
137.14, 150.84 (CH2C6H5, pNO2C6H4OCO), 163.69 (pNO2C6H4OCO), 168.31,
170.02 (2 ꢇ OCOCH3).
Anal. Calcd for C24H25O10N (487.46): C, 59.14; H, 5.17; N, 2.87. Found: C,
59.06; H, 5.26; N, 2.95.
2-O-Acetyl-4-O-benzoyl-3-O-benzyl-ꢀ,ꢀ-L-rhamnopyranose (6). A so-
lution of 5a (1.18 g, 2.7 mmol) and hydrazine acetate (247 mg, 2.7 mmol) in dry
acetonitrile (10 mL) was stirred for 4 h at 40°C (TLC, Rf 0.35, solvent A). Subse-
quently, the reaction mixture was concentrated, the residue dissolved in chloro-
form (30 mL), and the organic layer extracted with brine (2 ꢇ 15 mL), water (2 ꢇ
15 mL), dried, and concentrated. The crude product was purified by HPLC (eluent
solvent A) to yield 6 (961 mg, 90%, 10:1 ratio of the ꢀ,ꢁ -anomers) as a colorless
foam: 1H NMR (CDCl3) ꢂ 1.23 (d, J5,6 ꢄ 6.1 Hz, H-6ꢀ), 1.29 (d, J5,6 ꢄ 6.1 Hz, H-
6ꢁ), 2.18 (s, OCOCH3ꢀ), 2.24 (s, OCOCH3ꢁ), 3.22 (bs, 1-OHꢀ/ꢁ), 3.64 (m, H-
5ꢁ), 4.01 (dd, J3,4 ꢄ 9.8 Hz, H-3ꢀ), 4.10 (dd, J3,4 ꢄ 9.8 Hz H-3ꢁ), 4.14 (m, H-5ꢀ),
4.39, 4.63 (2d, J ꢄ 12.5 Hz, CH2C6H5ꢁ), 4.42, 4.61 (2d, J ꢄ 12.5 Hz, CH2C6H5ꢀ),
5.22 (d, J1,2 ꢄ 0.9 Hz, H-1ꢁ), 5.22 (d, J1,2 ꢄ 2.1 Hz, H-1ꢀ), 5.24 (t, J3,4 ꢄ 9.8 Hz,
H-4ꢁ), 5.30 (t, J3,4 ꢄ 9.8 Hz, H-4ꢀ), 5.43 (dd, J2,3 ꢄ 3.4 Hz, H-2ꢀ), 5.56 (dd, J2,3
ꢄ 3.4 Hz, H-2ꢁ), 7.05–8.00 (4m, CH2C6H5ꢀ/ꢁ, OCOC6H5ꢀ/ꢁ); 13C NMR
(CDCl3) ꢂ 17.55 (C-6ꢁ), 17.58 (C-6ꢀ), 21.00 (OCOCH3ꢁ), 21.08 (OCOCH3ꢀ),
66.66 (C-5ꢀ/ꢁ), 68.75 (C-2ꢀ), 69.09 (C-2ꢁ), 70.74 (CH2C6H5ꢁ), 70.77
(CH2C6H5ꢀ), 72.27 (C-4ꢁ), 72.89 (C-4ꢀ), 73.62 (C-3ꢀ), 75.97 (C-3ꢁ), 92.48 (JC-
ꢄ 173.2 Hz, C-1ꢀ), 93.03 (JC-1,H-1 ꢄ 161.6 Hz, C-1ꢁ), 127.57, 127.76,
1,H-1
127.84, 127.96, 128.19, 128.28, 128.34, 128.40, 128.67, 128.75, 128.87, 129.49,
129.77, 129.81, 133.15, 133.30, 137.09, 137.50 (CH2C6H5ꢀ/ꢁ, OCOC6H5ꢀ/ꢁ),
165.72 (OCOC6H5ꢀ/ꢁ), 170.61 (OCOCH3ꢀ), 170.62 (OCOCH3ꢁ).
Anal. Calcd for C22H24O7 (400.43): C, 65.99; H, 27.97. Found: C, 66.05; H,
28.01.
2-O-Acetyl-4-O-benzoyl-3-O-benzyl-ꢁ-L-rhamnopyranosyl trichloroace-
timidate (7). To a solution of 6 (100 mg, 0.25 mmol) in dry dichloromethane (4
mL) were added trichloroacetonitrile (760 ꢆL, 7.6 mmol) and 1,8-diazabicy-
clo[5.4.0]undec-7-ene (DBU, 21 ꢆL, 0.15 mmol) under argon at ꢈ20 °C. The re-
action mixture was stirred at that temperature for one hour, and then, for an addi-
tional 30 min at room temperature (TLC, Rf 0.59, solvent A). Finally, the mixture
was concentrated, the residue suspended in chloroform (20 mL) and filtered over
Celite. The remaining solids were washed with chloroform (3 ꢇ 10 mL), the com-
bined filtrate and washings were dried, and concentrated. The residue was purified
24
by HPLC (eluent solvent D) to provide 7 (125 mg, 92%) as a colorless foam: [ꢀ]D
ꢉ7.3° (c 1.0, chloroform); 1H NMR (CDCl3) ꢂ 1.28 (d, 3H, J5,6 ꢄ 6.1 Hz, H-6),
2.21 (s, 3H, OCOCH3), 4.00 (dd, 1H, J3,4 ꢄ 9.8 Hz, H-3), 4.07 (m, 1H, H-5), 4.44,
4.62 (2d, 2H, J ꢄ 12.5 Hz, CH2C6H5), 5.39 (t, 1H, J4,5 ꢄ 9.8 Hz, H-4), 5.54 (dd,

ORDER
REPRINTS
GALACTURONATE TRICHLOROACETIMIDATES
597
1H, J2,3 ꢄ 3.4 Hz, H-2), 6.25 (d, 1H, J1,2 ꢄ 2.1 Hz, H-1), 7.09–7.99 (4m, 10H,
CH2C6H5, OCOC6H5), 8.71 (bs, 1H, NH); 13C NMR (CDCl3) ꢂ 17.53 (C-6), 20.93
(OCOCH3), 66.84 (C-2), 69.65 (C-5), 71.22 (CH2C6H5), 72.01 (C-4), 73.22 (C-3),
90.72 [C(BNH)CCl3], 95.09 (JC-1,H-1 ꢄ 178.8 Hz, C-1), 127.81, 127.89, 127.96,
128.23, 128.37, 128.60, 128.83, 129.51, 129.83, 133.28, 136.94 (CH2C6H5,
OCOC6H5), 159.82 [C(BNH)CCl3], 165.58 (OCOC6H5), 170.07 (OCOCH3).
Anal. Calcd for C24H24O7NCl3 (544.82): C, 52.91; H, 20.56; N, 2.57; Cl,
19.52. Found: C, 52.96; H, 20.59; N, 2.62; Cl, 19.40.
Methyl 2-O-acetyl-4-O-benzoyl-3-O-benzyl-1-thio-ꢀ-L-rhamnopyra-
noside (8). To a solution of 5a (664 mg, 1.5 mmol) in dry dichloromethane (10
mL) were added methylthiotrimethylsilane (2.1 mL, 14.7 mmol) and boron triflu-
oride diethyl etherate (1.0 mL, 7.3 mmol) under argon at 0 °C. After one hour at
that temperature, the reaction mixture was stirred at room temperature for 8 h
(TLC, Rf 0.61, solvent A). Then, the reaction was terminated by addition of N-
ethyldiisopropylamine (3 mL). Finally, the mixture was diluted with chloroform
(30 mL), extracted with water (2 ꢇ 15 mL), dried, and concentrated. The residue
was purified by HPLC (eluent solvent D) to give 8 (633 mg, 98%) as a colorless
foam: [ꢀ]D24 ꢈ49.3° (c 1.0, chloroform); 1H NMR (CDCl3) ꢂ 1.25 (d, 3H, J5,6 ꢄ
6.4 Hz, H-6), 1.84 (s, 3H, OCOCH3), 2.17 (s, 3H, SCH3), 3.87 (dd, 1H, J3,4 ꢄ 9.8
Hz, H-3), 4.20 (m, 1H, H-5), 4.38, 4.58 (2d, 2H, J ꢄ 12.5 Hz, CH2C6H5), 5.14 (d,
1H, J1,2 ꢄ 1.5 Hz, H-1), 5.32 (t, 1H, J4,5 ꢄ 9.8 Hz, H-4), 5.49 (dd, 1H, J2,3 ꢄ 3.4
Hz, H-2), 7.09–7.97 (4m, 10H, CH2C6H5, OCOC6H5); 13C NMR (CDCl3) ꢂ 13.74
(SCH3), 17.49 (C-6), 21.05 (OCOCH3), 67.14 (C-5), 69.78 (C-2), 71.07
(CH2C6H5), 72.97 (C-4), 74.44 (C-3), 83.73 (JC-1,H-1 ꢄ 169.3 Hz, C-1), 127.66,
127.95, 128.22, 128.33, 128.63, 128.80, 129.72, 129.79, 133.13, 137.21
(CH2C6H5, OCOC6H5), 165.59 (OCOC6H5), 170.28 (OCOCH3).
Anal. Calcd C23H26O6S (430.52): C, 64.17; H, 6.09; S, 7.45. Found: C, 64.19;
H, 6.05; S, 7.58.
2-O-Acetyl-4-O-benzoyl-3-O-benzyl-ꢀ-L-rhamnopyranosyl chloride (9).
To a stirred solution of 5a (266 mg, 0.6 mmol) in dry dichloromethane (6 mL) were
added dichloromethyl methyl ether (58 ꢆL, 0.7 mmol) and a catalytic amount of an-
hydrous ZnBr2 (2.3 mg, 0.001 mmol) under argon at room temperature. After stir-
ring for 15 min (TLC, Rf 0.57, solvent A), the mixture was filtered through cotton
wool, and concentrated. After drying under high vacuum, the chromatographically
pure syrup 9 (246 mg, 98%) was used without further purification: [ꢀ]D25 ꢈ8.7° (c
1.0, chloroform); 1H NMR (CDCl3) ꢂ 1.29 (d, 3H, J5,6 ꢄ 6.1 Hz, H-6), 2.19 (s, 3H,
OCOCH3), 4.18 (m, 1H, H-5), 4.22 (dd, 1H, J3,4 ꢄ 9.8 Hz, H-3), 4.42, 4.61 (2d, 2H,
J ꢄ 12.5 Hz, CH2C6H5), 5.36 (t, 1H, J4,5 ꢄ 9.8 Hz, H-4), 5.52 (dd, 1H, J2,3 ꢄ 3.4
Hz, H-2), 6.03 (d, 1H, J1,2 ꢄ 1.8 Hz, H-1), 7.11–7.61 (4m, 10H, CH2C6H5,
OCOC6H5); 13C NMR (CDCl3) ꢂ 17.17 (C-6), 20.91 (OCOCH3), 69.77 (C-5), 70.62
(C-2), 71.33 (CH2C6H5), 72.01 (C-4), 72.59 (C-3), 90.05 (JC-1,H-1 ꢄ 183.9 Hz, C-1),
127.80, 127.98, 128.28, 128.39, 128.69, 129.22, 129.40, 129.45, 129.80, 129.84,
133.31, 137.04 (CH2C6H5, OCOC6H5), 165.51 (OCOC6H5), 169.99 (OCOCH3).

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NOLTING, BOYE, AND VOGEL
Anal. Calcd for C22H23O6Cl (418.87): C, 63.08; H, 5.53; Cl, 8.46. Found: C,
63.11; H, 5.49; Cl, 8.41.
2-O-Acetyl-4-O-benzoyl-3-O-benzyl-ꢀ-L-rhamnopyranosyl bromide
(10). To a solution of 5a (443 mg, 1.0 mmol) in dry dichloromethane (6 mL) was
added oxalyl bromide (139 ꢆL) under argon at ꢈ40 °C. After an additional hour at
that temperature, the reaction mixture was kept for 4 h at ambient temperature
(TLC, Rf 0.60, solvent A). Next, the mixture was concentrated and repeatedly co-
concentrated with toluene. Finally, the residue was rapidly processed by HPLC
(eluent solvent D) to provide 10 (454 mg, 98%) as a colorless syrup: [ꢀ]D23 ꢈ63.6°
(c 1.0, chloroform); 1H NMR (CDCl3) ꢂ 1.28 (d, 3H, J5,6 ꢄ 6.10 Hz, H-6), 2.18 (s,
3H, OCOCH3), 4.12 (m, 1H, H-5), 4.34 (dd, 1H, J3,4 ꢄ 9.8 Hz, H-3), 4.41, 4.60
(2d, 2H, J ꢄ 12.2 Hz, CH2C6H5), 5.37 (t, 1H, J4,5 ꢄ 9.8 Hz, H-4), 5.57 (dd, 1H, J2,3
ꢄ 3.4 Hz, H-2), 6.36 (d, 1H, J1,2 ꢄ 1.5 Hz, H-1), 7.11–8.01 (4m, 10H, CH2C6H5,
OCOC6H5); 13C NMR (CDCl3) ꢂ 17.05 (C-6), 20.93 (OCOCH3), 69.65 (C-5),
71.12 (C-2), 71.97 (CH2C6H5), 72.74 (C-4), 73.38 (C-3), 85.39 (JC-1,H-1 ꢄ 184.6
Hz, C-1), 127.84, 127.98, 128.08, 128.31, 128.42, 129.45, 129.80, 129.89, 133.34,
137.01 (CH2C6H5, OCOC6H5) 165.50 (OCOC6H5), 169.92 (OCOCH3).
Anal. Calcd for C22H23O6Br (463.87): C, 57.03; H, 5.00; Br, 17.23. Found:
C, 57.00; H, 4.96; Br, 17.15.
Methyl (4-O-benzoyl-3-O-benzyl-2-O-acetyl-ꢀ-L-rhamnopyranosyl)-
(1→4)-(allyl 2,3-di-O-benzyl-ꢁ-D-galactopyranosid)uronate (13). A. via
donor 5a. Compound 5a (221 mg, 0.5 mmol), methyl (allyl 2,3-di-O-benzyl-ꢁ-D-
galactopyranosid) uronate5 (12, 214 mg, 0.5 mmol), and molecular sieves (4 Å, 4.0
g) were dried under high vacuum at ambient temperature for one hour. Then, the
solids were suspended in dry dichloromethane (8 mL), and the reaction mixture
was stirred for two hours, under argon, at room temperature in the dark. Subse-
quently, trimethylsilyl trifluoromethanesulfonate (150 ꢆL, 0.9 mmol) was added,
and stirring was continued for a further 18 h (TLC, Rf 0.53, solvent A). The reac-
tion mixture was then passed through a layer of alkaline alumina by elution with
chloroform. The eluate was washed with water (2 ꢇ 10 mL), dried, and concen-
trated. Finally, the residue was purified by HPLC (eluent solvent B) to yield start-
ing materials 5a (15 mg, 7%) and 12 (21 mg, 10%), and desired 13 (268 mg, 66%)
as a colorless foam. The analytical data of 13 is in full agreement with the data from
the literature.6 The utilization of a 1.3:1 molar ratio of glycosyl donor 5a and ac-
ceptor 12 increased effectively the yield of 13 (357 mg, 88%).
B. via donor 7. Compound 7 (272 mg, 0.5 mmol), glycosyl acceptor 12
(214 mg, 0.5 mmol), and molecular sieves (4 Å, 4.0 g) were dried under high vac-
uum at ambient temperature for 30 min. The solids were then suspended in dry
dichloromethane (12 mL), and the reaction mixture was stirred for one hour, under
argon, at room temperature in the dark. After cooling to ꢈ30°C, boron trifluoride
diethyl etherate (123 ꢆL, 1.0 mmol) was added, and stirring was continued for two
hours at that temperature. Next, the reaction mixture was allowed to warm-up to

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599
room temperature and stirring was continued for a further 18 h (TLC solvent A).
Subsequently, the reaction mixture was passed through a layer of alkaline alumina
by elution with chloroform. The eluate (ca. 40 mL) was extracted with cold aq sat
NaHCO3 (2 ꢇ 20 mL), water (2 ꢇ 20 mL), dried and concentrated. Finally, the
residue was purified by HPLC (eluent solvent C) to provide starting material 12 (45
mg, 21%), syrupy 6 (26 mg, 13%) as a by-product, and desired 13 (207 mg, 51%).
C. via donor 8. Glycosyl donor 8 (215 mg, 0.5 mmol), acceptor 12 (214
mg, 0.5 mmol), and molecular sieves (4 Å, 4.0 g) were dried under high vacuum at
ambient temperature for one hour. The solids were then suspended in dry
dichloromethane (7 mL), and the suspension was stirred for two hours, under ar-
gon, at room temperature in the dark. Subsequently, to the reaction mixtue were
added N-iodosuccinimide (158 mg, 0.7 mmol), and after chilling to ꢈ40°C, a so-
lution of trifluoromethanesulfonic acid (6 ꢆL) in dry diethyl ether (4 mL). After
stirring for two hours at that temperature, the equal amount of N-iodosuccinimide
and trifluoromethanesulfonic acid was again added. After an additional two hours,
the chilling was terminated, and the mixture was stirred for 18 h at ambient tem-
perature (TLC solvent A). A solution of N-ethyldiisopropylamine (3 mL) in
methanol (4 mL) was then added, the reaction mixture was passed through a layer
of alkaline alumina by elution with chloroform. The eluate (ca. 40 mL) was ex-
tracted with cold aq 10% sodium thiosulfate (2 ꢇ 20 mL), ice-water (20 mL), cold
aq 3% hydrochloric acid (2 ꢇ 20 mL), ice-water (20 mL), cold sat aq NaHCO3 (2
ꢇ 20 mL), ice-water (2 ꢇ 20 mL), dried, and concentrated. Finally, the residue was
purified by HPLC (eluent solvent solvent B) to afford starting material 12 (114 mg,
53%), syrupy 6 (10 mg, 5%) as a by-product, and desired 13 (122 mg, 30%).
D. via donor 9. Glycosyl donor 9 (209 mg, 0.5 mmol), acceptor 12 (214
mg, 0.5 mmol), 2,6-di-tert-butyl-4-methylpyridine (123 mg, 0.6 mmol), and
molecular sieves (4 Å, 4.0 g) were dried under high vacuum at ambient tempera-
ture for one hour. The solids were then suspended in dry dichloromethane (10 mL),
and the suspension was stirred for one hour, under argon, at room temperature in
the dark. Subsequently, after chilling to ꢈ65°C, silver trifluoromethanesulfonate
(141 mg, 0.55 mmol) was added. After stirring for two hours at that temperature,
the chilling was terminated and the mixture was stirred for 18 h at ambient tem-
perature (TLC solvent A). The reaction mixture was then passed through a layer of
alkaline alumina by elution with chloroform. The eluate (ca. 40 mL) was extracted
with cold aq 3% hydrochloric acid (2 ꢇ 20 mL), ice-water (20 mL), cold sat aq
NaHCO3 (2 ꢇ 20 mL), ice-water (2 ꢇ 20 mL), dried, and concentrated. Finally,
the residue was purified by HPLC (eluent solvent B) to yield starting material 12
(13 mg, 6%), syrupy 6 (10 mg, 5%) as a by-product, and desired 13 (296 mg, 73%).
E. via donor 10. Exactly the same procedure as above (pathway D) was
used for the glycosylation with 10 (232 mg, 0.5 mmol) to give starting material 12
(17 mg, 8%), syrupy 6 (8 mg, 4%) as a by-product, and desired 13 (308 mg,
76%).Methyl (allyl 4-O-acetyl-2,3-di-O-benzyl-ꢁ-D-galactopyranosid)uronate

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NOLTING, BOYE, AND VOGEL
(14). To a stirred solution of methyl (allyl 2,3-di-O-benzyl-ꢁ-D-galactopyra-
nosid)uronate (12, 429 mg, 1.0 mmol) in dry pyridine (10 mL) was added acetic
anhydride (5 mL) at 0°C. After 5 h at ambient temperature (TLC, Rf 0.45, solvent
A), the mixture was poured into ice-water (60 mL), and the aqueous layer was ex-
tracted with chloroform (2 ꢇ 25 mL). The combined organic extracts were diluted
with heptane (100 mL), washed with cold aq 1% hydrochloric acid (2 ꢇ 20 mL),
ice-water (1 ꢇ 20 mL), cold aq sat NaHCO3 (1 ꢇ 20 mL), ice-water (1 ꢇ 20 mL),
dried, and concentrated. The residue was purified by HPLC (eluent
solvent C) to provide 14 (461 mg, 98 %) as a colorless foam: [ꢀ]D23 ꢉ35.8° (c 1.0,
chloroform); 1H NMR (CDCl3) ꢂ 2.12 (s, 3H, OCOCH3), 3.61 (d, 1H, J3,4 ꢄ 3.4
Hz, H-3), 3.69 (dd, 1H, J2,3 ꢄ 9.8 Hz, H-2), 3.77 (s, 3H, OCH3), 4.15 (d, 1H, H-5),
4.15 (m, 1H, CH2CHBCH2), 4.45 (d, 1H, J1,2 ꢄ 7.3 Hz, H-1), 4.50 (m, 1H,
CH2CHBCH2), 4.54, 4.72, 4.76, 4.90 (4d, 4H, J ꢄ 10.7 Hz, J ꢄ 11.3 Hz, 2
ꢇ CH2C6H5), 5.20, 5.34 (2m, 2H, CH2CHBCH2), 5.78 (dd, 1H, J4,5 ꢄ 0.9 Hz, H-
4), 5.95 (m, 1H, CH2-CHBCH2), 7.26–7.33 (m, 10H, CH2C6H5); 13C NMR
(CDCl3) ꢂ 20.81 (OCOCH3), 52.63 (OCH3), 67.72 (C-4), 70.53, 72.22 (2 ꢇ
CH2C6H5), 72.48 (C-5), 75.42 (CH2CHBCH2), 78.23 (C-2), 78.58 (C-3), 102.35
(C-1), 117.64 (CH2CHBCH2), 127.64, 127.80, 127.95, 128.04, 128.10, 128.25,
128.36, 128.40, 128.86, 129.83, 137.51, 138.36 (2 ꢇ CH2C6H5), 133.66
(CH2CHBCH2), 167.36 (C-6), 170.04 (OCOCH3).
Anal. Calcd for C26H30O8 (470.52): C, 66.37; H, 6.43. Found: C, 66.34; H,
6.40.
Methyl (allyl 2,3-di-O-benzyl-4-O-methyl-ꢁ-D-galactopyranosid)uronate
(16). To a solution of 12 (429 mg, 0.1 mmol) in dry dichloromethane (10 mL)
were successively added boron trifluoride diethyl etherate (20 ꢆL, 0.15 mmol) and,
dropwise, an ethereal diazomethane solution (until the yellow color of the reaction
mixture persisted) under argon at 0 °C. When the reaction was complete (TLC, Rf
0.32, solvent A), the excess of diazomethane was destroyed with boron trifluoride
diethyl etherate. The solution was then passed through a layer of alkaline alumina,
and concentrated. The residue was applied to a HPLC (eluent solvent A) to provide
16 ( 367 mg, 83%) as a colorless foam: [ꢀ]D26 ꢈ9.7° (c 1.0, chloroform); 1H NMR
(CDCl3) ꢂ 3.52 (dd, 1H, J3,4 ꢄ 3.1 Hz, H-3), 3.54 (s, 3H, H3CO-4) 3.80 (dd, 1H,
J
2,3 ꢄ 10.1 Hz, H-2), 3.81 (s, 3H, OCH3), 3.97 (dd, 1H, J4,5 ꢄ 1.2 Hz, H-4), 3.99
(d, 1H, H-5), 4.13, 4.48 (2m, 2H, CH2CHBCH2), 4.38 (d, 1H, J1,2 ꢄ 7.6 Hz,
H-1), 4.73, 4.92 (2d, 2H, J ꢄ 10.7 Hz, CH2C6H5), 4.76 (s, 2H, CH2C6H5), 5.18,
5.32 (2m, 2H, CH2CHBCH2), 5.94 (m, 1H, CH2CHBCH2), 7.23–7.39 (m, 10H,
2 ꢇ CH2C6H5); 13C NMR (CDCl3) ꢂ 52.53 (OCH3), 61.19 (H3CO-4), 70.13, 72.98
(2 ꢇ CH2C6H5), 73.60 (C-5), 75.33 (CH2CHBCH2), 77.61 (C-2), 78.87 (C-3),
80.85 (C-4), 102.29 (C-1), 117.23 (CH2CHBCH2), 127.60, 127.66, 127.75,
127.86, 127.98, 128.16, 128.27, 128.40, 128.48, 128.89, 138.05, 138.51 (2
ꢇ CH2C6H5), 133.92 (CH2CHBCH2), 168.87 (C-6).
Anal. Calcd for C25H30O7 (442.51): C, 67.86; H, 6.83. Found: C, 67.90; H,
6.81.

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601
Deallylation of 14–16. To a stirred solution of 14, 15 or 16 (0.5 mmol) in
a mixture of acetic acid and water (20:1, 15 ml) were added sodium acetate trihy-
drate (681 mg, 5 mmol) and palladium(II)chloride (355 mg, 2.0 mmol). After stir-
ring for 4–6 h at 40–45°C (TLC solvent A), the reaction mixture was filtered, and
the solids were washed with chloroform. The combined filtrate and washings (ꢀ30
mL) were extracted with sat aq NaHCO3 (3 ꢇ 15 mL), water (2 ꢇ 15 mL), dried,
and concentrated. The residue was purified by HPLC (eluent solvent E).
Methyl 4-O-acetyl-2,3-di-O-benzyl-ꢀ/ꢁ-D-galactopyranuronate (17).
(164 mg, 79%; TLC, Rf 0.20, solvent A, Rf 0.41, solvent F, 4:1 ratio of the ꢀ,ꢁ-
1
anomers), colorless syrup: H NMR (CDCl3) ꢂ 2.10, 2.11 (OCOCH3), 3.51 (d,
J
1,OH ꢄ 2.5 Hz, HO-1), 3.60 (dd, J3,4 ꢄ 3.1 Hz, H-3ꢁ), 3.67 (dd, J2,3 ꢄ 10.1 Hz,
H-2ꢁ), 3.73, 3.76 (2s, OCH3ꢀ/ꢁ), 3.82 (dd, J3,4 ꢄ 3.7 Hz, H-3ꢀ), 4.02 (dd,
J2,3 ꢄ 9.8 Hz, H-2ꢀ), 4.16 (d, H-5ꢁ), 4.52–4.84 (d,s, 2 ꢇ CH2C6H5ꢀ/ꢁ), 4.76
(d, J1,2 ꢄ 7.6 Hz, H-1ꢁ), 4.80 (d, H-5ꢀ), 5.37 (d, J1,2 ꢄ 3.4 Hz, H-1ꢀ), 5.78 (dd,
J4,5 ꢄ 0.91 Hz, H-4ꢁ), 5.85 (dd, J4,5 ꢄ 1.5 Hz, H-4ꢀ), 7.27–7.36 (m, 2 ꢇ
CH2C6H5ꢀ/ꢁ); 13C NMR (CDCl3) ꢂ 20.72, 20.80 (OCOCH3), 52.54, 52.70
(OCH3ꢀ/ꢁ), 67.51 (C-4ꢁ), 68.48 (C-4ꢀ), 72.03, 73.77 (2 ꢇ CH2C6H5), 72.22 (C-
5ꢁ), 72.48 (C-5ꢀ), 77.93 (C-2ꢁ), 78.43 (C-3ꢁ), 78.56 (C-2ꢀ), 79.14 (C-3ꢀ), 92.07
(C-1ꢀ), 97.33 (C-1ꢁ), 127.67, 127.73, 127.80, 127.83, 127.88, 127.95, 127.98,
128.02, 128.11, 128.19, 128.27, 128.34, 128.37, 128.93, 129.52, 137.39, 137.62,
137.85, 138.23 (2 ꢇ CH2C6H5ꢀ/ꢁ), 167.04, 168.31 (C-6ꢀ/ꢁ), 169.89, 169.93
(OCOCH3ꢀ/ꢁ).
Anal. Calcd C23H26O8 (430.45): C, 64.18; H, 6.08. Found: C, 64.20; H, 6.09.
Methyl 2,3-di-O-acetyl-4-O-benzyl-ꢀ/ꢁ-D-galactopyranuronate (18).
(153 mg, 80%; TLC, Rf 0.22, solvent A, Rf 0.46, solvent F): colorless foam. For
further analytical data see Ref. 5.
Methyl 2,3-di-O-benzyl-4-O-methyl-ꢀ/ꢁ-D-galactopyranuronate (19).
(155 mg, 77%; TLC, Rf 0.21, solvent A, Rf 0.44, solvent F; 4:1 ratio of the ꢀ,ꢁ-
1
anomers), colorless crystals: mp 49–51 °C, H NMR (CDCl3) ꢂ 3.29 (d, J1,OH
ꢄ 7.3 Hz, HO-1), 3.53, 3.55 (2s, H3CO-4ꢀ/ꢁ), 3.58 (dd, J2,3 ꢄ 9.7 Hz, H-2ꢁ), 3.78,
3.79 (2s, OCH3ꢀ/ꢁ), 3.88 (dd, J3,4 ꢄ 3.1 Hz, H-3ꢁ), 3.98 (dd, J2,3 ꢄ 8.5 Hz, H-2ꢀ),
3.99 (dd, J4,5 ꢄ 0.91 Hz, H-4ꢁ), 4.00 (d, H-5ꢁ), 4.01 (dd, J3,4 ꢄ 3.1 Hz, H-3ꢀ),
4.07 (dd, J4,5 ꢄ 1.2 Hz, H-4ꢀ), 4.60 (d, H-5ꢀ), 4.60–4.84 (d,s, 2 ꢇ CH2C6H5ꢀ/ꢁ),
4.77 (d, J1,2 ꢄ 7.6 Hz, H-1ꢁ), 5.34 (d, J1,2 ꢄ 2.7 Hz, H-1ꢀ), 7.27–7.38 (m, 2
ꢇ CH2C6H5ꢀ/ꢁ); 13C NMR (CDCl3) ꢂ 52.38 (OCH3ꢀ) 52.51 (OCH3ꢁ), 61.19
(H3CO-4ꢀ), 61.25 (H3CO-4ꢁ), 70.36, 72.88 (2 ꢇ CH2C6H5ꢀ), 73.60, 75.74 (2
ꢇ CH2C6H5ꢁ), 73.66 (C-5ꢁ), 73.71 (C-5ꢀ), 75.07 (C-3ꢁ), 75.74 (C-3ꢀ), 77.58
(C-2ꢁ), 78.23 (C-2ꢀ), 80.74 (C-4ꢀ), 80.87 (C-4ꢁ), 91.92 (C-1ꢀ), 97.48 (C-1ꢁ),
127.54, 127.60, 127.66, 127.76, 127.84, 127.92, 128.02, 128.07, 128.19, 128.25,
128.33, 128.37, 128.48, 128.83, 128.90, 137.83, 138.00, 138.17, 138.26 (2
ꢇ CH2C6H5ꢀ/ꢁ), 168.74 (C-6ꢁ), 169.52 (C-6ꢀ).

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NOLTING, BOYE, AND VOGEL
Anal. Calcd for C22H26O7 (402.44): C, 65.66; H, 6.51. Found: C, 65.71; H,
6.47.
Introduction of the trichloracetimidate group at the anomeric center of
17–19. To a solution of 17, 18 or 19 (1.0 mmol) in dry dichloromethane (7 mL)
was added trichloroacetonitrile (3.7 mL, 37 mmol) and 1,8-diazabicyclo[5.4.0]un-
dec-7-ene (DBU, 28 ꢆL, 0.2 mmol) under argon at ꢈ20°C. The reaction mixture
was stirred at that temperature for one hour, and then for an additional hour at room
temperature (TLC, Rf ꢀ0.4, solvent A). Finally, the mixture was concentrated, the
residue suspended in ethyl acetate (40 mL) and filtered over Celite. The remaining
solids were washed with ethyl acetate (3 ꢇ 10 mL), the combined filtrate and wash-
ings were dried, and concentrated. The residue was purified by HPLC (eluent
solvent B).
Methyl 4-O-acetyl-2,3-di-O-benzyl-ꢀ-D-galactopyranosyluronate trich-
loroacetimidate (20ꢀ). (408 mg, 71%; TLC, Rf 0.39, solvent A), colorless syrup:
[ꢀ]D25 ꢉ86.4° (c 1.0, chloroform); 1H NMR (CDCl3) ꢂ 2.10 (s, 3H, OCOCH3), 3.75
(s, 3H, OCH3), 4.06 (4d, 2H, J2,3 ꢄ 10.1 Hz, J3,4 ꢄ 3.1 Hz, H-2, H-3), 4.61, 4.71, 4.76,
4.78 (4d, 4H, J ꢄ 11.3 Hz, J ꢄ 11.9 Hz, 2 ꢇ CH2C6H5), 4.70 (d, 1H, H-5), 5.89 (dd,
1H, J4,5 ꢄ 1.5 Hz, H-4), 6.66 (d, 1H, J1,2 ꢄ 3.1 Hz, H-1), 7.27–7.32 (m, 10H, 2
ꢇ CH2C6H5), 8.64 (s, 1H, NH); 13C NMR (CDCl3) ꢂ 20.66 (OCOCH3), 52.71
(OCH3), 68.25 (C-4), 71.15 (C-5), 72.07, 73.21 (2 ꢇ CH2C6H5), 74.16, 74.41 (C-2,
C-3), 90.91 [C(BNH)CCl3], 93.27 (C-1), 127.39, 127.60, 127.74, 128.04, 128.24,
128.30, 137.42, 137.93 (2 ꢇ CH2C6H5, 4 signals are isochronic), 160.54
[C(BNH)CCl3], 167.32 (C-6), 169.78 (OCOCH3).
Anal. Calcd C25H26O8NCl3 (574.84): C, 52.24; H, 4.56; N, 2.45; Cl, 18.50.
Found: C, 52.20; H, 4.52; N, 2.39; Cl, 18.46.
Methyl 4-O-acetyl-2,3-di-O-benzyl-ꢁ-D-galactopyranosyluronate trich-
loroacetimidate (20ꢁ). (ꢀ2%, enriched fractions still contained mostly the
1
ꢀ-anomer; TLC, Rf 0.40, solvent A), colorless syrup: H NMR (CDCl3) ꢂ 2.11 (s,
OCOCH3), 3.76 (s, OCH3), 4.00 (dd, 1H, J3,4 ꢄ 3.1 Hz, H-3), 4.11 (dd, 1H, J2,3
ꢄ 10.1 Hz, H-2), 4.64–4.82 (d,s, 4H, 2 ꢇ CH2C6H5), 4.67 (d, 1H, H-5), 5.88 (d, 1H,
J1,2 ꢄ 7.3 Hz, H-1), 5.86 (dd, 1H, J4,5 ꢄ 1.2 Hz, H-4), 7.27–7.34 (m, 10H, 2 ꢇ
CH2C6H5), 8.64 (s, NH); 13C NMR (CDCl3) ꢂ 20.78 (OCOCH3), 52.80 (OCH3),
67.92 (C-4), 71.31, 72.50 (2 ꢇ CH2C6H5), 71.53 (C-5), 74.74, 74.95 (C-2, C-3),
90.94 [C(BNH)CCl3], 94.41 (C-1), 127.51, 127.86, 128.16, 128.51, 128.76, 128.93,
137.39, 137.54 (2 ꢇ CH2C6H5, 4 signals are isochronic), 160.55 [C(BNH)CCl3],
166.85 (C-6), 169.60 (OCOCH3).
Methyl 3,4-di-O-acetyl-2-O-benzyl-ꢀ-D-galactopyranosyluronate trich-
loroacetimidate (21ꢀ). (395 mg, 75%; TLC, Rf 0.44, solvent A), colorless foam:
[ꢀ]D24 ꢉ58.5° (c 1.0, chloroform); 1H NMR (CDCl3) ꢂ 1.93, 2.00 (2s, 6H, OCOCH3),
3.66 (s, 3H, OCH3), 4.01 (dd, 1H, J2,3 ꢄ 10.7 Hz, H-2), 4.56, 4.63 (2d, 2H, J ꢄ 11.9
Hz, CH2C6H5), 4.72 (d, 1H, H-5), 5.35 (dd, 1H, J3,4 ꢄ 3.4 Hz, H-3), 5.75 (dd, 1H, J4,5
ꢄ 1.2 Hz, H-4), 6.63 (d, 1H, J1,2 ꢄ 3.4 Hz, H-1), 7.22–7.28 (m, 5H, CH2C6H5), 8.63

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GALACTURONATE TRICHLOROACETIMIDATES
603
(s, 1H, NH); 13C NMR (CDCl3) ꢂ 20.43, 20.66 (2 ꢇ OCOCH3), 52.71 (OCH3), 68.78
(C-3), 68.92 (C-4), 70.59 (C-5), 72.00 (C-2), 72.94 (CH2C6H5), 90.71
[C(BNH)CCl3], 93.79 (C-1), 127.48, 127.73, 127.86, 128.25, 128.33, 137.31
(CH2C6H5), 160.56 [C(BNH)CCl3], 166.76 (C-6), 169.49, 169.83 (2 ꢇ OCOCH3).
Anal. Calcd for C20H22O9NCl3 (526.75): C, 45.60; H, 4.21; N, 2.66; Cl,
20.19. Found: C, 45.49; H, 4.18; N, 2.78; Cl, 20.06.
Methyl 3,4-di-O-acetyl-2-O-benzyl-ꢁ-D-galactopyranosyluronate trich-
loroacetimidate (21ꢁ). (ꢀ2%, only the ꢀ-anomer was isolated pure, while the en-
riched fractions of the ꢁ-anomer still contained ꢀ-anomer; TLC, Rf 0.41, solvent A),
1
colorless foam: H NMR (CDCl3) ꢂ 1.88, 2.03 (2s, 6H, OCOCH3), 3.66 (s, 3H,
OCH3), 3.89 (dd, 1H, J2,3 ꢄ 10.1 Hz, H-2), 4.53, 4.83 (2d, 2H, J ꢄ 12.8 Hz,
CH2C6H5), 4.39 (d, 1H, H-5), 5.06 (dd, 1H, J3,4ꢄ 3.4 Hz, H-3), 5.65 (dd, 1H, J4,5 ꢄ
1.5 Hz, H-4), 5.78 (d, 1H, J1,2 ꢄ 8.2 Hz, H-1), 7.24–7.28 (m, 5H, CH2C6H5), 8.72 (bs,
1H, NH); 13C NMR (CDCl3) ꢂ 20.52, 20.66 (2 ꢇ OCOCH3), 52.69 (OCH3), 68.43
(C-3), 71.76 (C-5), 73.02 (CH2C6H5), 74.77 (C-4), 74.98 (C-2), 90.83
[C(BNH)CCl3], 97.87 (C-1), 127.52, 127.77, 127.86, 127.90, 128.38, 137.45
(CH2C6H5), 160.99 [C(BNH)CCl3], 165.93 (C-6), 169.51, 169.68 (2 ꢇ OCOCH3).
Methyl 2,3-di-O-benzyl-4-O-methyl-ꢀ-D-galactopyranosyluronate trich-
loroacetimidate (22ꢀ). (399 mg, 73%; TLC, Rf 0.47, solvent A), colorless
syrup: [ꢀ]D24 ꢉ28.8° (c 1.0, chloroform); 1H NMR (CDCl3) ꢂ 3.55 (s, 3H, H3CO-
4), 3.80 (s, 3H, OCH3), 4.01 (dd, 1H, J3,4 ꢄ 3.1 Hz, H-3), 4.10 (dd, 1H, J4,5 ꢄ 1.5
Hz, H-4), 4.20 (dd, 1H, J2,3 ꢄ 9.8 Hz, H-2), 4.56 (d, 1H, H-5), 4.73 (s, 2H,
CH2C6H5), 4.53, 4.82 (2d, 2H, J ꢄ 11.9 Hz, CH2C6H5), 6.65 (d, 1H, J1,2 ꢄ 3.4 Hz,
H-1), 7.26–7.38 (m, 10H, 2 ꢇ CH2C6H5), 8.59 (s, 1H, NH); 13C NMR (CDCl3) ꢂ
52.65 (OCH3), 61.52 (H3CO-4), 72.89, 73.12 (2 ꢇ CH2C6H5), 73.07 (C-5), 75.23
(C-2), 76.70 (C-3), 78.37 (C-4), 90.91 [C(BNH)CCl3], 94.56 (C-1), 127.40,
127.54, 127.73, 127.78, 128.25, 128.37, 138.00, 138.12 (2 ꢇ CH2C6H5, 4 signals
are isochronic), 160.62 [C(BNH)CCl3], 168.61 (C-6).
Anal. Calcd C24H26O7NCl3 (546.83): C, 52.72; H, 4.79; N, 2.56; Cl, 19.45.
Found: C, 52.65; H, 4.68; N, 2.82; Cl, 19.31.
Methyl 2,3-di-O-benzyl-4-O-methyl-ꢁ-D-galactopyranosyluronate trich-
loroacetimidate (22ꢁ). (ꢀ2%, enriched fractions still contained mostly the
1
ꢀ-anomer; TLC, Rf 0.48, solvent A); H NMR (CDCl3) ꢂ 3.27 (s, 3H, H3CO-4),
3.81 (s, 3H, OCH3), 4.02 (dd, 1H, H-3), 4.08 (dd, 1H, H-4), 4.12 (dd, 1H, J2,3
ꢄ 9.8 Hz, H-2), 4.48 (d, 1H, H-5), 4.72–4.85 (d,s, 4H, 2 ꢇ CH2C6H5), 4.77 (d, 1H,
J1,2 ꢄ 7.6 Hz, H-1), 7.27–7.38 (m, 10H, 2 ꢇ CH2C6H5), 8.59 (s, 1H, NH); 13C
NMR (CDCl3) ꢂ 51.16 (OCH3), 61.47 (H3CO-4), 69.39 (C-5), 72.54, 73.04 (2
ꢇ CH2C6H5), 75.26 (C-2), 77.10 (C-3), 77.31 (C-4), 90.93 [C(BNH)CCl3], 95.21
(C-1), 127.40, 127.64, 127.72, 127.95, 128.03, 128.30, 137.95, 138.08 (2
ꢇ CH2C6H5, 4 signals are isochronic), 160.98 [C(BNH)CCl3], 167.81 (C-6).
Glycosylation of Acceptor 12 with the Glycosyl Donors 20, 21, or 22. The
Compounds 20ꢀꢁ, 21ꢀꢁ or 22ꢀꢁ (0.5 mmol), glycosyl acceptor 12 (214 mg, 0.5

ORDER
REPRINTS
604
NOLTING, BOYE, AND VOGEL
mmol), and molecular sieves (4 Å, 4.0 g) were dried under high vacuum at ambient
temperature for one hour. The solids were then suspended in dry dichloromethane
(8 mL), and the reaction mixture was stirred for two hours under an inert atmosphere
at room temperature in the dark. After cooling to ꢈ70°C, trimethylsilyl trifluo-
romethanesulfonate (83 ꢆL, 0.5 mmol) was added, and stirring was continued for 3
h at that temperature. The reaction mixture was then allowed to warm-up to room
temperature and stirring was continued for an additional 18 h (TLC solvent A).
Now, the reaction mixture was passed through a layer of alkaline alumina by elu-
tion with chloroform. The eluate (ca. 30 mL) was extracted with cold aq sat
NaHCO3 (2 ꢇ 15 mL), water (2 ꢇ 15 mL), dried, and concentrated.
Methyl (methyl 4-O-acetyl-2,3-di-O-benzyl-ꢀ-D-galactopyranosy-
luronate)-(1→4)-(allyl 2,3-di-O-benzyl-ꢁ-D-galactopyranosid)uronate (23ꢀ).
The crude disaccharide was purified by HPLC (eluent solvent B) to provide un-
changed acceptor 12 (40 mg, 18%) and the disaccharides 23ꢀ (206 mg, 59%; TLC,
Rf 0.38, solvent A), colorless foam: [ꢀ]D24 ꢉ66.5° (c 1.0, chloroform), 1H NMR
(CDCl3) ꢂ 1.99 (s, 3H, OCOCH3), 3.45 (dd, 1H, J3,4 ꢄ 2.8 Hz, H-3), 3.48, 3.53 (2s,
6H, OCH3, OCH3ꢅ), 3.67 (dd, 1H, J2,3 ꢄ 9.8 Hz, H-2), 3.79 (dd, 1H, J2ꢅ,3ꢅ ꢄ 10.1
Hz, H-2ꢅ), 3.95 (d, 1H, H-5), 4.04 (dd, 1H, J3ꢅ4ꢅ ꢄ 3.1 Hz, H-3ꢅ), 4.17 (m, 1H,
OCH2CHBCH2), 4.39 (d, 1H, J1,2 ꢄ 7.63 Hz, H-1), 4.52 (m, 1H,
OCH2CHBCH2), 4.46 (dd, 1H, H-4), 4.46–4.97 (d,s, 8H, 4 ꢇ CH2C6H5), 5.03 (d,
1H, H-5ꢅ), 5.18 (d, 1H, J1ꢅ,2ꢅ ꢄ 3.4 Hz, H-1ꢅ), 5.24, 5.36 (2m, 2H,
OCH2CHBCH2), 5.78 (dd, 1H, J4ꢅ,5ꢅ ꢄ 1.4 Hz, H-4ꢅ), 5.99 (m, 1H,
OCH2CHBCH2), 7.27–7.37 (m, 20H, 4 ꢇ CH2C6H5); 13C NMR (CDCl3) ꢂ 20.67
(OCOCH3), 52.12 (OCH3), 52.29 (OCH3ꢅ), 68.80 (C-4ꢅ), 69.65 (C-5ꢅ), 71.85,
72.45, 72.97, 70.53 (4 ꢇ CH2C6H5), 73.44 (C-2ꢅ), 73.51 (C-5), 74.91
(OCH2CHBCH2), 75.74 (C-3), 76.01 (C-4), 77.21 (C-2), 79.51 (C-3ꢅ), 100.11
(C-1ꢅ), 102.79 (C-1), 117.49 (OCH2CHBCH2), 127.39, 127.51, 127.54, 127.67,
127.86, 127.92, 128.04, 128.11, 128.14, 128.25, 128.28, 128.37, 128.83, 128.86,
137.79, 137.91, 138.20, 138.40 (4 ꢇ CH2C6H5, 6 signals are isochronic), 133.89
(OCH2CHBCH2), 168.05, 168.51 (C-6ꢅ,C-6), 169.86 (OCOCH3).
Anal. Calcd for C47H52O14 (840.92): C, 67.13; H,6.23. Found: C, 67.12, H,
6.24.
Here additionally, is the analytical data of disaccharide 23ꢁ isolated in a 24%
yield (ꢀ:ꢁ ratio of 1.6:1) when boron trifluoride was used as a promoter. (TLC, Rf
24
1
0.28, solvent A), colorless foam: [ꢀ]D ꢉ63.7° (c 1.0, chloroform); H NMR
(CDCl3) ꢂ 2.06 (s, 3H, OCOCH3), 3.50 (dd, 1H, J3ꢅ4ꢅ ꢄ 3.4 Hz, H-3ꢅ), 3.58 (dd,
1H, J3,4 ꢄ 2.8 Hz, H-3), 3.63 (dd, 1H, J2,3 ꢄ 9.8 Hz, H-2), 3.73, 3.91 (2s, 6H,
OCH3, OCH3ꢅ), 3.77 (dd, 1H, J2ꢅ,3ꢅ ꢄ 9.8 Hz, H-2ꢅ), 3.90 (d, 1H, H-5ꢅ), 4.09 (d,
1H, H-5), 4.13 (m, 1H, OCH2CHBCH2), 4.42 (d, 1H, J1,2 ꢄ 7.6 Hz, H-1), 4.50
(m, 1H, OCH2CHBCH2), 4.60 (dd, 1H, H-4), 4.14, 4.53 (2d, 2H, J ꢄ 10.7 Hz,
CH2C6H5), 4.68, 4.76 (2d, 2H, J ꢄ 12.2 Hz, CH2C6H5), 4.74 (s, 2H, CH2C6H5),
4.75, 5.11 (2d, 2H, J ꢄ 11.0 Hz, CH2C6H5), 4.83 (d, 1H, J1ꢅ,2ꢅ ꢄ 7.6 Hz, H-1ꢅ),
5.19, 5.32 (2m, 2H, OCH2CHBCH2), 5.65 (dd, 1H, J4ꢅ,5ꢅ ꢄ 0.9 Hz, H-4ꢅ), 5.93 (m,
1H, OCH2CHBCH2), 7.19–7.46 (m, 20H, 4 ꢇ CH2C6H5); 13C NMR (CDCl3) ꢂ

ORDER
REPRINTS
GALACTURONATE TRICHLOROACETIMIDATES
605
20.67 (OCOCH3), 52.29 (OCH3), 52.70 (OCH3ꢅ), 67.74 (C-4ꢅ), 70.30, 72.08,
73.04, 75.24 (4 ꢇ CH2C6H5), 72.09 (C-5ꢅ), 72.85 (C-4), 73.37 (C-2ꢅ), 74.01 (C-5),
75.12 (OCH2CHBCH2), 80.84 (C-3), 79.28 (C-2), 78.27 (C-3ꢅ), 102.37 (C-1),
102.67 (C-1ꢅ), 117.38 (OCH2CHBCH2), 127.23, 127.49, 127.54, 127.64, 127.81,
127.89, 127.92, 128.05, 128.19, 128.30, 137.67, 138.14, 138.50, 138.90 (4
ꢇ CH2C6H5, 10 signals are isochronic), 133.86 (OCH2CHBCH2), 166.98, 167.73
(C-6, C-6ꢅ), 169.95 (OCOCH3).
Anal. Calcd for C47H52O14 (840.92): C, 67.13; H, 6.23. Found: C, 67.11; H,
6.20.
Methyl (methyl 3,4-di-O-acetyl-2-O-benzyl-ꢀ/ꢁ-D-galactopyranosy-
luronate)-(1→4)-(allyl 2,3-di-O-benzyl-ꢁ-D-galactopyranosid)uronate (24ꢀ,
24ꢁ). The crude disaccharide was purified by HPLC (eluent solvent B) to pro-
vide unchanged acceptor 12 (15 mg, 7%) and desired 24ꢀ (266 mg, 67%; TLC, Rf
0.25, solvent A) as a colorless foam: [ꢀ]D23 ꢉ83.7° (c 1.0, chloroform); 1H NMR
(CDCl3) ꢂ 1.93, 1.96 (2s, 6H, OCOCH3), 3.409 (s, 3H, OCH3), 3.42 (dd, 1H, J3,4
ꢄ 3.1 Hz, H-3), 3.57 (s, 3H, OCH3ꢅ), 3.75 (dd, 1H, J2,3 ꢄ 10.1 Hz, H-2), 3.88
(dd, 1H, J2ꢅ,3ꢅ ꢄ 10.7 Hz, H-2ꢅ), 3.93 (d, 1H, H-5), 4.15 (m, 1H, CH2CHBCH2),
4.38 (d, 1H, J1,2 ꢄ 7.6 Hz, H-1), 4.48 (m, 1H, CH2CHBCH2), 4.49 (dd, 1H,
J
4,5 ꢄ 0.7 Hz, H-4), 4.55, 4.74 (2d, 2H, J ꢄ 12.8 Hz, CH2C6H5), 4.57, 4.68 (2d,
2H, J ꢄ 12.5 Hz, CH2C6H5), 4.81, 4.97 (2d, 2H, , J ꢄ 10.7 Hz, CH2C6H5), 5.10 (d,
1H, J4ꢅ,5ꢅ ꢄ 1.8 Hz, H-5ꢅ), 5.20 (m, 1H, CH2CHBCH2), 5.29 (d, 1H, J1ꢅ,2ꢅ ꢄ 3.7
Hz, H-1ꢅ), 5.30 (dd, 1H, J3ꢅ,4ꢅ ꢄ 3.4 Hz, H-3ꢅ), 5.34 (m, 1H, CH2CHBCH2), 5.69
(dd, 1H, J4ꢅ,5ꢅ ꢄ 1.5 Hz, H-4ꢅ), 5.96 (m, 1H, CH2CHBCH2), 7.21–7.41 (m, 15H,
3 ꢇ CH2C6H5); 13C NMR (CDCl3) ꢂ 20.44, 20.76 (2 ꢇ OCOCH3), 52.13 (OCH3),
52.30 (OCH3ꢅ), 69.13 (C-5ꢅ), 69.18 (C-3ꢅ), 69.78 (C-4ꢅ), 70.31, 72.35, 72.56 (3
ꢇ CH2C6H5), 71.74 (C-2ꢅ), 73.38 (C-5), 75.09 (CH2CHBCH2), 75.79 (C-4),
77.77 (C-2), 79.34 (C-3), 99.41 (C-1ꢅ), 102.81 (C-1), 117.35 (CH2CHBCH2),
127.33, 127.48, 127.64, 127.72, 127.89, 128.22, 128.28, 128.40, 128.92, 137.76,
137.97, 138.21 (3 ꢇ CH2C6H5), 133.91 (CH2CHBCH2), 168.04 (C-6ꢅ), 168.22
(C-6), 169.67, 169.7049 (2 ꢇ OCOCH3).
Anal. Calcd for C42H48O15 (792.83): C, 63.63; H, 6.10. Found: C, 63.60; H,
6.11.
Disaccharide 24ꢁ. (20 mg, 5%; TLC, 0.23, solvent A), colorless foam:
22
1
[ꢀ]D ꢉ54.8° (c 1.0, chloroform); H NMR (CDCl3) ꢂ 2.04, 2.11 (2s, 6H,
OCOCH3), 3.50 (dd, 1H, J3,4 ꢄ 3.1 Hz, H-3), 3.70 (dd, 1H, J2ꢅ,3ꢅ ꢄ 10.1 Hz, H-2ꢅ)
3.76 (s, 3H, OCH3ꢅ), 3.81 (dd, 1H, J2,3 ꢄ 10.1 Hz, H-2), 3.98 (s, 3H, OCH3), 4.01
(d, 1H, H-5), 4.09 (d, 1H, H-5ꢅ), 4.22 (m, 1H, CH2CHBCH2), 4.46 (d, 1H, J1,2 ꢄ
7.6 Hz, H-1), 4.51 (d, 1H, J1ꢅ,2ꢅ ꢄ 7.6 Hz, H-1ꢅ), 4.56 (dd, 1H, H-4), 4.58 (m, 1H,
CH2CHBCH2), 4.66–5.15 (6d, 6H, 3 ꢇ CH2C6H5), 5.27, 5.40 (2m, 2H,
CH2CHBCH2), 5.40 (dd, 1H, J3ꢅ,4ꢅ ꢄ 3.4 Hz, H-3ꢅ), 5.63 (dd, 1H, J4ꢅ,5ꢅ ꢄ 0.9 Hz,
H-4ꢅ), 6.02 (m, 1H, CH2CHBCH2), 7.28–7.47 (m, 15H, 3 ꢇ CH2C6H5); 13C NMR
(CDCl3) ꢂ 20.56, 20.97 (2 ꢇ OCOCH3), 52.09, 52.27 (OCH3, OCH3ꢅ), 67.96 (C-
5ꢅ), 70.33, 72.30, 72.51 (3 ꢇ CH2C6H5), 71.75 (C-2ꢅ), 73.38 (C-5), 73.85 (C-3ꢅ),

ORDER
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606
NOLTING, BOYE, AND VOGEL
74.66 (C-4ꢅ), 75.12 (CH2CHBCH2), 75.74 (C-4), 77.71 (C-2), 79.29 (C-3),
102.34 (C-1ꢅ), 102.76 (C-1), 117.33 (CH2CHBCH2), 127.33, 127.48, 127.64,
127.72, 127.89, 128.22, 128.28, 128.40, 128.92, 137.71, 137.92, 138.59 (3
ꢇ CH2C6H5), 133.86 (CH2CHBCH2), 166.40 (C-6ꢅ), 167.61 (C-6), 169.64,
169.99 (2 ꢇ OCOCH3).
Anal. Calcd for C42H48O15 (792.83): C, 63.63; H, 6.10. Found: C, 63.75; H,
6.08.
Methyl (methyl 2,3-di-O-benzyl-4-O-methyl-ꢀ/ꢁ-D-galactopyranosy-
luronate)-(1→4)-(allyl 2,3-di-O-benzyl-ꢁ-D-galactopyranosid)uronate (25ꢀ,
25ꢁ). The 1.3:1 ꢀ/ꢁ-mixture of 25ꢀ,25ꢁ was purified by HPLC (eluent solvent
B) to provide unchanged acceptor 12 (51 mg, 24%) and a not separated mixture of
1
25ꢀ and 25ꢁ (211 mg, 52%; TLC, Rf 0.26, solvent A) as a colorless syrup: H
NMR (CDCl3) ꢂ 3.45 (s, 3H, OCH3), 3.53 (s, OCH3ꢅꢁ), 3.53 (s, OCH3ꢅꢀ), 3.55
(dd, J3ꢅ,4ꢅ ꢄ 3.1 Hz, H-3ꢅꢁ), 3.58 (dd, 1H, J3,4 ꢄ 3.4 Hz, H-3), 3.67 (dd, J2ꢅ,3ꢅ ꢄ 9.8
Hz, H-2ꢅꢁ), 3.76 (dd, 1H, J2,3 ꢄ 9.5 Hz, H-2), 3.81 (s, 3H, H3CO-4), 3.81 (dd, J3ꢅ,4ꢅ
ꢄ 3.4 Hz, H-3ꢅꢀ), 3.93 (d, H-5ꢅꢁ), 3.97 (dd, H-4ꢅꢁ), 4.00 (dd, J2ꢅ,3ꢅ ꢄ 9.5 Hz,
H-2ꢅꢀ), 4.08 (dd, H-4ꢅꢀ), 4.09 (d, 1H, H-5), 4.17 (m, 1H, CH2CHBCH2), 4.32
(dd, 1H, H-4), 4.39 (d, J1ꢅ,2ꢅ ꢄ 7.6 Hz, H-1ꢅꢁ), 4.51 (m, 1H, CH2CHBCH2), 4.54
(d, 1H, J1,2 ꢄ 7.6 Hz, H-1), 4.54–4.95 (d, s, 4 ꢇ CH2C6H5), 4.88 (d, 1H, H-5ꢅꢀ),
5.16 (d, J1ꢅ,2ꢅ ꢄ 3.1 Hz, H-1ꢅꢀ), 5.20, 5.36 (2m, 2H, OCH2CHBCH2), 5.96 (m,
1H, CH2CHBCH2), 7.26–7.38 (m, 4 CH2C6H5); 13C NMR (CDCl3) ꢂ 51.95
(OCH3ꢅꢁ), 52.22 (OCH3ꢅꢀ), 52.71 (OCH3), 61.12 (H3CO-4), 67.75, 67.81, 70.57,
71.24, 72.36, 72.51, 72.57, 73.12, 73.38, 73.74, 73.85, 76.83, 77.20, 77.59, 77.83,
78.40, 79.44, 79.47, 79.74 (C-1, C-2, C-3, C-4, 2 ꢇ CH2C6H5, CH2CHBCH2,
C-2ꢅꢀ/ꢁ, C-3ꢅꢀ/ꢁ, C-4ꢅꢀ/ꢁ, C-5ꢅꢀ/ꢁ, 2 ꢇ CH2C6H5ꢅꢀ/ꢁ), 99.46 (C-1ꢅꢀ), 102.40
(C-1ꢅꢁ), 102.79 (C-1), 117.55 (CH2CHBCH2), 127.28, 127.36, 127.45, 127.49,
127.60, 127.75, 127.83, 127.89, 128.08, 128.14, 128.20, 128.25, 128.31, 128.34,
128.52, 128.84 137.35, 138.03, 137.91, 138.30, 138.41, 138.53, (2 ꢇ CH2C6H5,
2 ꢇ CH2C6H5ꢅꢀ/ꢁ), 133.91 (CH2CHBCH2), 168.02 (C-6ꢅꢁ), 168.13 (C-6),
169.66 (C-6ꢅꢀ).
Anal. Calcd for C46H52O13 (812.91): C, 67.97; H,6.45. Found: C, 67.90; H,
6.52.
Methyl (methyl 2,3-di-O-benzyl-ꢀ-D-galactopyranosyluronate)-(1→4)-
(allyl 2,3-di-O-benzyl-ꢁ-D-galactopyranosid)uronate (26ꢀ). A suspension of
23ꢀ (210 mg, 0.25 mmol) in methanolic hydrochloric acid (0.28 M, 15 mL, pre-
pared by adding 0.3 mL acetyl chloride to 15 mL dry methanol) was stirred for 72
h under an inert atmosphere at ambient temperature (TLC, solvent A). The reaction
mixture was then neutralized by filtration through a layer of alkaline alumina.
Evaporation of the eluate provided analytical pure 26ꢀ (198 mg, 99%; TLC, Rf
0.18, solvent A) as a colorless foam: [ꢀ]D24 ꢉ56.6° (c 1.0, chloroform); 1H NMR
(CDCl3) ꢂ 2.35 (bs, 1H, 4ꢅ-OH), 3.37 (dd, 1H, J3,4 ꢄ 2.8 Hz, H-3), 3.46, 3.47 (2s,
6H, OCH3, OCH3ꢅ), 3.60 (dd, 1H, J2,3 ꢄ 10.1 Hz, H-2), 3.75 (dd, 1H, J3ꢅ4ꢅ ꢄ 3.4

ORDER
REPRINTS
GALACTURONATE TRICHLOROACETIMIDATES
607
Hz, H-3ꢅ), 3.87 (d, 1H, H-5), 3.91 (dd, 1H, J2ꢅ,3ꢅ ꢄ 10.1 Hz, H-2ꢅ), 4.09 (m, 1H,
OCH2CHBCH2), 4.28 (dd, 1H, H-4ꢅ), 4.32 (d, 1H, J1,2 ꢄ 7.63 Hz, H-1), 4.39
(dd, 1H, H-4), 4.45 (m, 1H, OCH2CHBCH2), 4.48–4.88 (d,s, 8H, 4 ꢇ CH2C6H5),
4.88 (d, 1H, H-5ꢅ), 5.11 (d, 1H, J1ꢅ,2ꢅ ꢄ 3.4 Hz, H-1ꢅ), 5.15, 5.29 (2m, 2H,
OCH2CHBCH2), 5.91 (m, 1H, OCH2CHBCH2), 7.16–7.31 (m, 20H, 4
ꢇ CH2C6H5); 13C NMR (CDCl3) ꢂ 52.08, 52.25 (OCH3, OCH3ꢅ), 68.35 (C-4ꢅ),
70.47 (C-5ꢅ), 70.56, 72.32, 72.34, 72.93 (4 ꢇ CH2C6H5), 73.50(C-5), 73.91 (C-2ꢅ),
74.95 (OCH2CHBCH2), 75.66 (C-3ꢅ), 76.96 (C-4), 77.64 (C-2), 79.73 (C-2),
99.60 (C-1ꢅ), 102.84 (C-1), 117.48 (OCH2CHBCH2), 127.35, 127.47, 127.61,
127.67, 127.83, 128.00, 128.15, 128.22, 128.28, 128.31, 128.45, 128.78, 128.87,
137.81, 137.87, 138.28, 138.35 (4 ꢇ CH2C6H5), 133.93 (OCH2CHBCH2),
168.07, 169.41 (C-6ꢅ, C-6 ).
Anal. Calcd for C45H50O13 (798.88): C, 67.66; H, 6.31. Found: C, 67.70; H,
6.29.
Methyl (4-O-benzoyl-3-O-benzyl-2-O-acetyl-ꢀ-L-rhamnopyranosyl)-
(1→4)-2,3-di-O-benzyl-ꢀ-D-galactopyranuronate (27). The deallylation of 13
(406 mg, 0.5 mmol) was carried out exactly as described for the preparation of
17–19. After processing (TLC, Rf 0.18, solvent A), the crude product was purified
24
by HPLC (eluent solvent E) to yield 27 (289 mg, 75%) as a colorless foam: [ꢀ]D
ꢉ42.9° (c 1.0, chloroform); 1H NMR (CDCl3) ꢂ 1.20 (s, 3H, J5ꢅ,6ꢅ ꢄ 6.1 Hz, H-6ꢅ),
2.10 (s, 3H, OCOCH3), 3.75 (s, 3H, OCH3), 3.81 (m, 1H, H-5ꢅ), 3.86 (dd, 1H, J3ꢅ,4ꢅ
ꢄ 10.1 Hz, H-3ꢅ), 3.89 (dd, 1H, J2,3 ꢄ 9.8 Hz, H-2), 4.00 (dd, 1H, J3,4 ꢄ 3.7 Hz,
H-3), 4.28, 4.55 (2d, 2H, J ꢄ 12.2 Hz, CH2C6H5ꢅ), 4.48 (dd, 1H, J4,5 ꢄ 1.8 Hz, H-
4), 4.67 (d, 1H, H-5), 4.73, 4.80 (2d, 2H, J ꢄ 12.5 Hz, CH2C6H5), 4.73 (s, 2H,
CH2C6H5), 5.16 (d, 1H, J1ꢅ,2ꢅ ꢄ 1.8 Hz, H-1ꢅ), 5.23 (t, 1H, J4ꢅ,5ꢅ ꢄ 10.1 Hz, H-4ꢅ),
5.36 (d, 1H, J1,2 ꢄ 3.4 Hz, H-1), 5.58 (dd, 1H, J2ꢅ,3ꢅ ꢄ 3.1 Hz, H-2ꢅ), 7.04–8.00 (5m,
20H, 3 ꢇ CH2C6H5, OCOC6H5); 13C NMR (CDCl3) ꢂ 17.56 (C-6ꢅ), 21.06
(OCOCH3), 52.47 (OCH3), 67.24 (C-5ꢅ), 68.18 (C-2ꢅ), 70.19 (C-5), 71.12
(CH2C6H5), 72.62 (C-4ꢅ), 73.03, 73.59 (2 ꢇ CH2C6H5), 74.27 (C-3ꢅ), 74.62 (C-2),
76.03 (C-4), 77.09 (C-3), 92.09 (C-1), 99.73 (C-1ꢅ), 127.42, 127.64, 127.69,
127.81, 128.11, 128.34, 128.48, 128.54, 128.60, 129.77, 133.10, 137.64, 137.65,
137.68 (3 ꢇ CH2C6H5, OCOC6H5), 165.69 (OCOC6H5), 168.78 (C-6), 169.95
(OCOCH3).
Anal. Calcd for C43H46O13 (770.83): C, 67.70; H, 6.02. Found: C, 67.53; H,
6.13.
Methyl (4-O-benzoyl-3-O-benzyl-2-O-acetyl-ꢀ-L-rhamnopyranosyl)-
(1→4)-2,3-di-O-benzyl-ꢀ-D-galactopyranosyluronate trichloroacetimidate
(28). The trichloroacetimidate group was introduced in 27 (385 mg, 0.5 mmol) as
described for 20–22 (TLC, Rf 0.51, solvent A). Finally, the raw product was puri-
fied by HPLC (eluent solvent C) to afford 28 (316 mg, 69%) as a colorless foam:
[ꢀ]D24 ꢉ51.8° (c 1.0, chloroform); 1H NMR (CDCl3) ꢂ 1.21 (s, 3H, J5ꢅ,6ꢅ ꢄ 6.4 Hz,
H-6ꢅ), 2.12 (s, 3H, OCOCH3), 3.75 (s, 3H, OCH3), 3.82 (m, 1H, H-5ꢅ), 3.84 (dd,

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NOLTING, BOYE, AND VOGEL
1H, J3ꢅ,4ꢅ ꢄ 9.8 Hz, H-3ꢅ), 4.08 (dd, 1H, J3,4 ꢄ 9.8 Hz, H-3), 4.09 (dd, 1H, J2,3
ꢄ 3.4 Hz, H-2), 4.27, 4.55 (2d, 2H, J ꢄ 12.2 Hz, CH2C6H5), 4.51 (dd, 1H, J4,5 ꢄ
1.2 Hz, H-4), 4.61 (d, 1H, Hz, H-5), 4.78 (s, 2H, CH2C6H5), 4.80, 4.87 (2d, 2H, J
ꢄ 11.6 Hz, CH2C6H5), 5.20 (d, 1H, J1ꢅ,2ꢅ ꢄ 1.8 Hz, H-1ꢅ), 5.24 (t, 1H, J4ꢅ,5ꢅ ꢄ 9.8
Hz, H-4ꢅ), 5.60 (dd, 1H, J2ꢅ,3ꢅ ꢄ 3.1 Hz, H-2ꢅ), 6.66 (d, 1H, J1,2 ꢄ 2.13 Hz, H-1),
7.03–7.95 (5m, 20H, 3x CH2C6H5, OCOC6H5), 8.66 (s, 1 H, NH); 13C NMR
(CDCl3) ꢂ 17.58 (C-6ꢅ), 21.05 (OCOCH3), 52.54 (OCH3), 67.34 (C-5ꢅ), 68.10
(C-2ꢅ), 71.01 (CH2C6H5), 72.38 (C-5), 72.54 (C-4ꢅ), 72.86, 73.24 (2 ꢇ CH2C6H5),
74.09 (C-2), 74.30 (C-3ꢅ), 76.12 (C-4), 77.02 (C-3), 90.98 [C(BNH)CCl3],
94.30 (C-1), 99.93 (C-1ꢅ), 127.48, 127.58, 127.66, 127.75, 127.81, 127.93,
127.99, 128.02, 128.11, 128.19, 128.33, 128.49, 128.66, 129.48, 129.55,
129.77, 129.89, 133.10, 137.56, 137.64, 137.77 (3 ꢇ CH2C6H5, OCOC6H5),
160.56 [C(BNH)CCl3], 165.64 (OCOC6H5), 167.89 (C-6), 169.87 (OCOCH3).
Anal. Calcd for C45H46O13NCl3 (915.22): C, 59.00; H, 5.06; N, 1.53; Cl,
1.16. Found: C, 58.92; H, 5.01; N, 1.59; Cl, 1.14.
Methyl (4-O-benzoyl-3-O-benzyl-2-O-acetyl-ꢀ-L-rhamnopyranosyl)-
(1→4)-(methyl 2,3-di-O-benzyl-ꢀ-D-galactopyranosyluronate)-(1→4)-(allyl
2,3-di-O-benzyl-ꢁ-D-galactopyranosid)uronate (29). The glycosylation of 12
(214 mg, 0.5 mmol) with the donor 28 (458 mg, 0.5 mmol) was processed as de-
scribed for the synthesis of 23 with 20 (TLC, Rf 0.28, solvent A). The crude trisac-
charide was purified by HPLC (eluent solvent B) to provide unchanged acceptor 12
23
(18 mg, 17%) and desired 29 (407 mg, 70%) as a colorless foam: [ꢀ]D ꢉ29.6°
(c 1.0, chloroform); 1H NMR (CDCl3) ꢂ 1.17 (d, 3H, J5ꢊ,6ꢊ ꢄ 6.1 Hz, H-6ꢊ), 2.04
(s, 3H, OCOCH3), 3.45 (dd, 1H, J3,4 ꢄ 3.1 Hz, H-3), 3.47 (s, 3H, OCH3), 3.67 (dd,
1H, J2,3 ꢄ 9.8 Hz, H-2), 3.69 (s, 3H, OCH3ꢅ), 3.75 (m, 1H, H-5ꢊ), 3.79 (dd, 1H, J3ꢊ,4ꢊ
ꢄ 10.1 Hz, H-3ꢊ), 3.91 (dd, 1H, J2ꢅ,3ꢅ ꢄ 9.8 Hz, H-2ꢅ), 3.98 (d, 1H, H-5), 4.07 (dd,
1H, J3ꢅ,4ꢅ ꢄ 3.4 Hz, H-3ꢅ), 4.19, 4.36 (2m, 2H, CH2CHBCH2), 4.41 (d, 1H, J1,2 ꢄ
7.6 Hz, H-1), 4.49 (dd, 1H, J4,5 ꢄ 1.2 Hz, H-4), 4.56 (dd, 1H, J4ꢅ,5ꢅ ꢄ 1.2 Hz, H-4ꢅ),
4.46–4.99 (d and s, 10H, 5 ꢇ CH2C6H5), 4.84 (d, 1H, H-5ꢅ), 5.10 (d, 1H, J1ꢊ,2ꢊ
ꢄ
1.5 Hz, H-1ꢊ), 5.16 (t, 1H, J4ꢊ,5ꢊ ꢄ 10.1 Hz, H-4ꢊ), 5.23 (m, 1H, CH2CHBCH2),
5.26 (d, 1H, J1ꢅ,2ꢅ ꢄ 3.1 Hz, H-1ꢅ), 5.37 (m, 1H, OCH2CHBCH2), 5.49 (dd, 1H,
J2ꢊ,3ꢊ ꢄ 3.4 Hz, H-2ꢊ), 6.00 (m, 1H, CH2CHBCH2), 6.99–7.95 (5m, 30H, 5 ꢇ
CH2C6H5, OCOC6H5); 13CNMR (CDCl3) ꢂ 17.61 (C-6ꢊ), 21.02 (OCOCH3), 52.03
(OCH3), 52.41 (OCH3ꢅ), 66.99 (C-5ꢊ), 67.49 (C-5), 68.10 (C-2ꢊ), 70.65 (C-5ꢅ),
70.81, 71.27, 72.21, 72.68, 73.12 (5 ꢇ CH2C6H5), 72.42 (C-4ꢊ), 72.82 (C-2ꢅ), 73.53
(C-3ꢅ), 74.77 (CH2CHBCH2), 74.88 (C-3ꢊ), 75.73 (C-4), 76.11 (C-4ꢅ), 77.65
(C-2), 79.40 (C-3), 99.59 (C-1ꢅ), 100.03 (C-1ꢊ), 102.81 (C-1), 117.59
(CH2CHBCH2), 127.14, 127.26, 127.48, 127.52, 127.58, 127.64, 127.75, 127.81,
127.86, 127.92, 128.02, 128.08, 128.11, 128.17, 128.23, 128.30, 128.33, 128.42,
128.46, 128.61, 128.81, 129.69, 129.77, 130.62, 133.01, 137.45, 137.73, 137.79,
138.09, 138.20 (5 ꢇ CH2C6H5, OCOC6H5), 133.83 (CH2CHBCH2), 165.64
(OCOC6H5), 168.11 (C-6), 169.07 (C-6ꢅ), 169.67 (OCOCH3).
Anal. Calcd for C67H72O18 (1165.30): C, 69.06; H, 6.24. Found: C, 68.97; H,
6.28.

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609
ACKNOWLEDGMENTS
The authors are indebted to the Deutschen Forschungsgemeinschaft as well
as to the Fonds der Chemischen Industrie for financial support.
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Received June 25, 2000
Accepted April 26, 2001

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