Exploring and exploiting the reactivity of glucuronic acid donors

Article

pubs.acs.org/joc

Exploring and Exploiting the Reactivity of Glucuronic Acid Donors

Ana-Rae de Jong, Bas Hagen, Vincent van der Ark, Herman S. Overkleeft, Jeroen D. C. Codee,*

́

and Gijsbert A. Van der Marel*

Leiden Institute of Chemistry, Leiden University, P.O. Box 9502, 2300 RA Leiden, The Netherlands

S

* Supporting Information

ABSTRACT: The relative reactivity of glucuronic acid esters was established in a series of competition experiments, in which two

thioglucoside and/or thioglucuronic acid ester donors competed for a limited amount of activator (NIS-TfOH). Although

glucuronic acid esters are often considered to be of very low reactivity, the series of competition reactions revealed that the reactivity

of the glucuronic acid esters studied is sufficient to provide productive glycosylation reactions. The latter is illustrated in the

synthesis of two Streptococcus pneumoniae trisaccharides, in which the applicability of the two similarly protected frame-shifted

thiodisaccharide donors, Glc-GlcA and GlcA-Glc, were compared. The Glc-GlcA disaccharide, featuring the glucuronic acid donor

moiety, proved to be the most productive in the assembly of a protected S. pneumoniae trisaccharide.

Bols,¹⁰but the relative reactivity of thioglucuronic acid esters

INTRODUCTION

D-Glucuronic acid is a prime constituent of many biologically

■

has never been explored.¹¹The establishment of the relative

reactivity of carbohydrate building blocks can not only pave the

relevant poly- and oligosaccharides and glycoconjugates. For

way for chemoselective glycosylation reaction sequences but also

example, the human body uses glucuronylation as a key step in

detoxification processes,¹in which xenobiotic or endobiotic

provides important insight into the glycosylation capacity of a

given donor. We here present the establishment of the relative

substances are rendered (more) water-soluble by the appendage

reactivity of glucuronic acid ester thiodonors in relation to the

of a glucuronic acid to allow secretion. Glucuronic acids are also

reactivity of a set of relevant thioglucosides. Guided by these results,

frequently encountered on saponins, a very diverse class of

glucuronic acid donors were probed for their use in the construction

glycosylated steroid- and triterpene-based compounds, forming

the active ingredient of many traditional folk medicines.²The

of Streptococcus pneumoniae type 3 di- and trisaccharides.

glycosaminoglycans (GAGs), a family of linear, anionic

RESULTS AND DISCUSSION

polysaccharides, which fulfill a plethora of biological functions,³

■

We investigated the relative reactivity of three different

thioglucuronic acid esters 1, 2, and 3, in combination with the

panel of thioglucosides (4−7) displayed in Table 1. Di-O-benzyl

glucuronic acid ester 1 was studied as a model glucuronic acid

ester having two “arming” benzyl protecting groups.¹²

Azidoglucuronate (donor 2) was used to investigate the effect

of a strongly electron-withdrawing functionality on the reactivity.

Glucuronic acid ester 3 was studied because it represents a

potentially useful building block in the preparation of fragments

of the Streptococcus pneumoniae type 3 capsular oligosaccharide

(vide infra). Thioglucosides 4−7 were used as reference

compounds because these represent commonly used glucosyl

donors featuring arming (benzyl ethers), semidisarming

(benzylidene acetal),¹³and disarming (benzoyl and acetyl esters)

protecting groups. Wong and co-workers have quantified the

are an important example of D-glucuronic acid containing

polysaccharides. Furthermore, various bacterial capsular poly-

saccharides feature glucuronic acids as prominent con-

tituents.⁴Because of their biological relevance, the synthesis of

D-glucuronic acid containing oligosaccharides has received

considerable attention.⁵For the preparation of glucuronic acid

containing oligosaccharides, two strategies can be used. In a

postglycosylation−oxidation approach, the oligosaccharide back-

bone is assembled with nonoxidized glucosyl building blocks and

the introduction of the carboxylic acid moiety takes place at the

oligosaccharide stage. In a preglycosylation−oxidation approach,

the oligosaccharide is prepared using glucuronic acid building

blocks. Because glucuronic acids are often considered to be

unreactive glycosyl donors because of the presence of the

electron-withdrawing carboxylic acid moiety, the postglycosylation−

oxidation approach is usually favored over the alternate

strategy.^5,6The reactivity of a large number of thioglycoside

donors⁷has been quantified by the groups of Ley,⁸Wong,⁹and

Received: July 29, 2011

Published: November 29, 2011

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benzoyl groups at C-2 and C-3 of the 4,6-O-benzylidene

glucoside leads to a donor (5) that is less reactive than

glucuronic acid methyl ester 1 (entry 4). The introduction of an

azide at C-2 of the glucuronic acid donor, as in 2, significantly

reduces the reactivity, as judged from entry 5, which shows that

only the disaccharide derived from donor 1 was formed. The

reactivity of glucuronic acid 3, a building block to be used in the

assembly of the S. pneumoniae oligomers, was assessed in

competion experiments with both glucuronides 1 and 2.¹⁵Donor

3 was less reactive than dibenzyl donor 1 and more reactive than

2 (entries 6 and 7). To establish the relative reactivity of the

uronic acid donors with respect to a glucosyl donor of known

reactivity, we competed the least reactive glucuronide, i.e. 2, with

tetra-O-benzoyl glucose donor 7. Glucosyl donor 7 has a relative

reactivity value (RRV) of 1.3, on a scale in which α-S-tolyl

peracetylmannose has a RRV of 1 and β-S-tolyl perbenzylglucose

a RRV of 2656, as established by Wong and co-workers.⁹In this

competition reaction (entry 8), the 2-azidoglucuronic acid donor

completely outcompeted the tetrabenzoyl glucosyl donor leading

to the formation of the glucuronic acid derived disaccharide as

the sole product in 94% yield. Taken together, these results show

that, although the C-5 carboxylic acid ester has a disarming effect

on glucosyl donor reactivity (Table 1, entry 2), glucuronic acids

should not by definition be classified as highly unreactive donors,

but placed in the continuum of reactivity among the 4,6-O-

benzylidene glucosides.

We then explored the utility of monomeric and dimeric donor

building blocks in the synthesis of Streptococcus pneumoniae type

3 oligosaccharides. S. pneumoniae is one of the most prevalent

commensal Gram-positive pathogens, causing a variety of

diseases such as bacteremia, otitis media, meningitis, and

sepsis.¹⁶A tridecavalent capsular polysaccharide vaccine, licensed

under the name of Prevnar/Prevenar-13, which is routinely

administered to infants and young children, presents one of the

most powerful weapons to prevent infections by this pathogen,

and polyvalent vaccines providing protection against more

S. pneumoniae serotypes are currently being introduced on the

market.¹⁷To study the immune response to this type of vaccines

and the virulence factors of the parent pathogen at the molecular

level, well-defined oligo- or polysaccharide structures are valuable

tools.¹⁸The anionic cellobiouronic acid polymer of S. pneumo-

niae type 3, built up from 1,3-linked [β-glucuronic acid-(1→4)-β-

glucose] disaccharide repeats¹⁹is one of the prominent

S. pneumoniae capsular polysaccharides. In the construction of

fragments of this polysaccharide two types of linkages have to be

installed: a β-glucuronic acid bond to the C-4-OH of a glucose

acceptor and a β-glucosyl bond to a glucuronic acid C-3-OH.

Although previous syntheses of this oligosaccharide have

employed a postglycosylation oxidation approach to circumvent

the assumed low reactivity of glucuronic acid building blocks,²⁰

the results described above indicate that the reactivity of

glucuronic acid donors such as 3 is sufficient to be of use in the

synthesis of oligosaccharides. We therefore investigated the

construction of these bonds using both monomeric and dimeric

glucuronic acid donor building blocks as described below.

First, the two relevant monomeric acceptors 10 and 14 were

assembled as depicted in Scheme 1. Glucuronic acid donor 3 and

S-tolyl glucose 12 were condensed with an azidohexanol spacer

under the agency of NIS/TfOH to provide 9 and 13 in 85% and

80% yield, respectively. Delevulinoylation gave the two acceptor

molecules 10 and 14 in 91% and 99% yield, respectively. The

glycosylation of glucoside 12 (1 equiv) with glucuronic acid ester

acceptor 10 (1.3 equiv) yielded disaccharide 11 in 62% yield.

Table 1. Competing Donors in Glycosylation of 8

a

b

product ratio

entry

donor A

donor B

donor A/donor B

yield (%)

1

2

3

4

5

6

7

8

1

4

1

2

4

6

5

2

3

7

1:1

1:8

90

87

84

90

95

89

84

94

1:8

2.3:1

1:0

9:1

0:1

1:0

a

For structures of the disaccharides, see the Experimental Section.

Product ratio was determined by NMR of the disaccharide mixtures.

b

reactivity of a large series of p-methylphenylthio (S-tolyl)-

glycosides using the NIS-TfOH promoter system.⁹To stay close

to this system, we also employed S-Tol donors and the same

activator. In our competition experiments (Table 1), two

thioglucuronic acid esters and/or thioglycosides competed for

a limited amount of activator (NIS, 1 equiv) in the presence of a

catalytic amount of TfOH (0.1 equiv) and an excess of the

model glycosyl acceptor methyl 2,3,4-tri-O-benzyl-α-^D-glucopyr-

anoside 8 (3 equiv).¹¹The ratio of formed disaccharides was

established by NMR spectroscopy using the fraction of

disaccharides, obtained after size-exclusion chromatography of

the crude reaction mixtures. The results of these experiments are

summarized in Table 1.

In the first competition reaction, glucuronic acid ester 1

competed with benzylidene-protected glucoside 4 leading to 1:1

mixture of the corresponding disaccharides (entry 1), indicating

that the combined deactivating effect of the C-5 carboxylic acid

ester and the C-4-O-acetate in 1 is similar to the disarming effect

of the benzylidene group in 4. The similar reactivity of glucu-

ronic acid 1 and benzylidene glucoside 4 was confirmed in

competition experiments, in which both donors competed

separately with donor 6 (entry 2 and 3). Diacetyl donor 6

turned out to be eight times more reactive than both donor 1 and

donor 4. In line with expectations, the C-5 carboxylic acid ester

reduces the reactivity of a glucosyl donor more than a CH₂OAc

moiety at C-5 (entry 2).¹⁴The conformationally and electroni-

cally disarming 4,6-benzylidene group¹³in 4 reduces the glucosyl

donor reactivity more than the two acetyls at the C-4 and

C-6 position (entry 3). This is in line with the relative reactivity

of the analogous mannosyl donors, on which we recently

reported.¹¹The introduction of stronger electron-withdrawing

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a

Scheme 1. Synthesis of Both Alternating Disaccharides

a

Reagents and conditions: (a) HO(CH₂)₆N₃, NIS, TfOH, DCM, 0 °C, 9: 85%, 13: 80%; (b) NH₂NH₂·H₂O, pyridine/AcOH, 10: 91%, 14: 99%;

(c) NIS, TfOH, DCM, 0 °C, 11: 62%, 15: 74%.

a

Scheme 2. Synthesis of the Dimeric Donors

a

Reagents and conditions: (a) NIS, TFA, DCM, 0 °C; (b) NaHCO₃(aq, sat), 16: 88%; (c) piperidine, 18: 84%; (d) ClC(NPh)CF₃, Cs₂CO₃,

acetone, 0 °C, 17: 83%, 19: 68%; (e) TfOH, DCM, 0 °C, 21: 12%, 25: 0%.

Glucuronic acid ester donor 3 (1.3 equiv) was condensed with

glucosyl acceptor 14 (1 equiv) to give the alternative

disaccharide 15 in slightly higher yield (74%). These results

show that the glucose donor−glucuronic acid acceptor

combination does not outperform the glucuronic acid donor−

glucose acceptor pair.

into the corresponding N-phenyl trifluoroacetimidate donors 17,

and 19 in 83% and 68% yield, respectively. The S-tolyl acceptors

20a and 24a were obtained en route to donors 12 and 3.

The condensation of glucuronic acid ester N-phenyl

trifluoroacetimidate 17 (1.3 equiv) with acceptor 20a (1 equiv)

using a catalytic amount of TfOH in DCM only led to a modest

yield of disaccharide 21 (12%). Increasing the concentration of

the reaction (0.05 to 0.5 M) did not give an improved yield but

led to formation of two major side products instead.

Disaccharide 22, featuring an anhydroglucose reducing end,

and S-tolyl glucuronic acid ester 23a were isolated in 29% and

10% yield, respectively. The formation of glucuronic acid ester

23a can be explained by aglycon transfer from glucoside 20a to

the activated glucuronic acid donor (Scheme 3).²⁵The activated

glucoside, formed in this event, collapses via the formation of

the 1,6-anhydro ring²⁶into a glucosyl acceptor 26a, with an

accessible axial hydroxyl group. This 1,6-anhydro glucoside

reacts with an activated glucuronic acid ester, leading to the

formation of disaccharide 22. To explore whether these side

reactions were due to the nucleophilicity of the anomeric

S-tolyl moiety in 20a, we prepared acceptor 20b, bearing the

Next, we explored the applicability of dimer donors in the

synthesis of two complementary trisaccharides. The required

dimer donors 21 and 25 were synthesized in an orthogonal

glycosylation reaction⁷between a S-tolyl acceptor and a trifluoro-

N-phenylimidate donor,²¹in turn obtained from the thioglyco-

side precursor 3 or 12 (Scheme 2).²²The preparation of imidate

17 started by substitution of the anomeric thio functionality in 3

for a trifluoroacetyl function using NIS and TFA in dry DCM.²³

Subsequent hydrolysis of the anomeric trifluoroacetate with

aqueous NaHCO₃led to hemiacetal 16 in 88%. These

conditions, however, were not efficient for the hydrolysis of

donor 12, as a result of intramolecular benzoyl migration.²⁴To

prevent the formation of the anomeric benzoate, we cleaved the

anomeric trifluoroacetate with piperidine, which yielded hemi-

acetal 18 in 84%. The hemiacetals 16 and 18 were converted

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Scheme 3. Aglycon Transfer during the Condensation of Glucuronic Acid Donor 17 and Acceptor 20a

a

Scheme 4. Preparation of the Dimeric Donors and the Construction of the Trisaccharides

a

Reagents and conditions: (a) NIS, TFA, DCM, 0 °C, then piperidine, 85%; (b) ClC(NPh)CF₃, Cs₂CO₃, acetone, 0 °C, 77%; (c) TfOH, DCM,

0 °C, 30a: 51%, 30b: 64%, 32: 68%; (d) NIS, TfOH, DCM, 0 °C, 33: 75%, 36: 51%; (e) hydrazine acetate, pyridine/AcOH, 34: 95%, 37: 93%;

(f) (i) KOH, dioxane/H₂O, (ii) H₂, Pd/C, BuOH/H₂O, 35: 44%/two steps; 38: 28%/two steps.

t

somewhat less nucleophilic thiophenyl aglycon.²⁷However, use

of this thioglucosyl acceptor also resulted in aglycon transfer,

yielding glucuronic acid ester 23b, and disaccharide 22 (41%

isolated yield). On the basis of these results, we reasoned that

activation of donor 17 was not the problem but that acceptors

20a and 20b were simply too reactive. This was confirmed in the

attempted synthesis of dimer 25 through the condensation of

glycosyl N-phenyl trifluoroacetimidate 19 (1.3 equiv) and

glucuronic acid ester acceptor 24a (1 equiv) (Scheme 2). No

disaccharide could be obtained from this reaction; instead, only

anhydroglucoside 26b was isolated in 34% yield.

acceptor 31 (Scheme 4). The condensation of glucuronic acid

imidate 17 with acceptor glucoside 31 yielded disaccharide 32

without any side products. Similarly, anhydroglucoside formation

was prevented in the reaction between glucosyl imidate 29

(1 equiv) and glucuronic acid acceptor 20a (1.3 equiv), which

gave disaccharide 30a in 51% yield. This disaccharide, however,

was obtained as a mixture of α/β-thioglucuronides (α/β 1/5).²⁹

Anomerisation was not observed when glucuronic acid ester 20b,

having a somewhat less electron rich thiophenyl function,²⁶was

used. Dimer 30b was uneventfully obtained from 29 (1.3 equiv)

and 20b (1 equiv) in 64% yield. Next, the disaccharide donors

30b and 32 were used for the formation of trisaccharides 33 and

36. Donor 30b, having the glucuronic acid donor moiety

(1 equiv) was coupled to spacer containing glucoside 14 (1.3

equiv), leading to the formation of trisaccharide 33 in 75% yield.

In order to prevent these side reactions, we decided to

downtune the donor reactivity of the S-tolyl glucosyl building

block by replacing the C-6-O-benzyl for a more electron-

withdrawing C-6-O-benzoyl group, resulting in donor 27²⁸and

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followed by addition of activated (flame-dried) molecular sieves 3 Å.

The reaction mixture was stirred for 30 min, followed by addition of

NIS (1.3 equiv relative to the donor). The reaction mixture was cooled

to 0 °C, followed by addition of TfOH (0.1 equiv), and the reaction

mixture was allowed to warm to rt. When TLC analysis showed

completion, the reaction mixture was neutralized with TEA and

quenched with Na₂S₂O₃(aq, satd). The organic layer was isolated, dried

over MgSO₄, filtered, and concentrated. Size-exclusion chromatography

(DCM/MeOH, 1/1, v/v) and/or column chromatography resulted in

the isolation of the products formed.

Benzyl (6-Azidohexyl 4-O-benzyl-2-O-benzoyl-3-O-levulinyl-β-^D-

glucopyranosyluronate) (9). Glucuronic acid ester 3 (410 mg,

0.6 mmol) and 6-azidohexanol (102 mg, 0.71 mmol, 1.18 equiv) were

coevaporated with toluene (2×) and dissolved in freshly distilled DCM

(24 mL, 0.03 M). Activated MS 3 Å were added, and the reaction

mixture was stirred for 30 min, followed by addition of NIS (202 mg,

0.9 mmol, 1.5 equiv). The reaction mixture was cooled to 0 °C, followed

by addition of TfOH (0.6 mL of a 0.1 M stock solution, 0.06 mmol, 0.1

equiv). The reaction mixture was allowed to warm to rt, and after 3 h,

TLC analysis (PE/EtOAc 12/8, v/v) showed total conversion into a

higher running spot. The reaction mixture was neutralized with TEA,

quenched with Na₂S₂O₃(aq, satd), and diluted with EtOAc, followed by

separation of the layers. The organic layer was washed with NaHCO₃

(aq, satd) and brine, dried over MgSO₄, filtered, and concentrated.

Column chromatography (PE/EtOAc 1/0 → 17:3) gave the title

compound in 85% yield (358 mg, 0.51 mmol). [α]²⁰_D: +24.2 (c = 0.7,

DCM). IR (neat, cm⁻¹): 2940, 2862, 2097, 1746, 1724, 1454, 1360,

1315, 1265, 1215, 1179, 1153, 1096, 1070, 1028, 1001, 735, 712, 700.

¹H NMR (400 MHz, CDCl₃, HH-COSY, HSQC): 7.99 (d, 2H, J = 7.6

Hz, H_arom), 7.57 (t, 1H, J = 7.6 Hz, H_arom), 7.46−7.42 (m, 2H, H_arom),

7.36−7.24 (m, 7H, H_arom), 7.18−7.14 (m, 3H, H_arom), 5.43 (t, 1H, J =

9.6 Hz, H-3), 5.25−5.18 (m, 3H, H-2, CH₂CO₂Bn), 4.62 (d, 1H, J =

7.6 Hz, H-1), 5.54 (d, 1H, J = 11.2 Hz, CHHPh), 4.81 (d, 1H,

CHHPh), 4.01−4.013 (m, 2H, H-4, H-5), 3.90−3.85 (m, CHH

N₃(CH₂)₆OH), 3.49−3.41 (CHH N₃(CH₂)₆OH), 3.04 (t, 2H, J = 7.2

Hz, N₃(CH₂)₆OH), 2.52−2.47 (m, 2H, CH₂Lev), 2.40−2.35 (m, 2H,

CH₂Lev), 2.00 (s, 3H, CH₃Lev), 1.50−1.45 (m, 2H, CH₂

N₃(CH₂)₆OH), 1.34−1.28 (m, 4H, 2 × CH₂N₃(CH₂)₆OH), 1.28−

1.15 (m, 2H, CH₂N₃(CH₂)₆OH). ¹³C NMR (100 MHz, CDCl₃, HH-

COSY, HSQC): 205.9 (CO Lev ketone), 171.9 (CO Lev), 168.0

(C-6), 165.3 (CO Bz), 137.6 (C_qC_arom), 135.0 (C_qC_arom), 133.4

(CH_arom), 129.9 (CH_arom), 129.5 (C_qC_arom), 129.2−128.0 (CH_arom),

125.4 (CH_arom), 101.4 (C-1), 77.6 (C-4 or C-5), 77.4 (C-4 or C-5), 74.2

(C-3), 72.0 (C-2), 70.2 (CH₂N₃(CH₂)₆OH), 67.7 (CH₂CO₂Bn), 51.3

(CH₂N₃(CH₂)₆OH), 37.8 (CH₂Lev), 29.2 (CH₂N₃(CH₂)₆OH), 28.7

(CH₂N₃(CH₂)₆OH), 28.0 (CH₂Lev), 26.4 (CH₂N₃(CH₂)₆OH), 25.5

(CH₂N₃(CH₂)₆OH). HRMS: [M + Na]⁺calcd for C₃₈H₄₃N₃O₁₀Na

724.28407, found 724.28369.

Benzyl (6-Azidohexyl 2-O-benzoyl-4-O-benzyl-β-^D-glucopyrano-

syluronate) (10). Glucuronic acid ester 9 (211 mg, 0.3 mmol) was

dissolved in a mixture of pyridine/AcOH (4/1, 6 mL), and hydrazine

monohydrate (90 μL, 1.50 mmol, 5 equiv) was added. The reaction

mixture was stirred for 2 h. The reaction mixture was diluted with

EtOAc, washed with 1 M HCl and NaHCO₃(aq, satd), dried over

MgSO₄, filtered, and concentrated. Column chromatography (PE/

EtOAc 9/1) gave the title compound as a transparent oil in 91% yield

(165 mg, 0.27 mmol). [α]²⁰_D: −1.5 (c = 1.6, DCM). IR (neat, cm⁻¹):

2932, 2884, 2860, 2095, 1732, 1601, 1497, 1454, 1396, 1362, 1315,

1267, 1215, 1177, 1098, 1069, 1028, 1009, 1001, 978, 908, 897, 750,

712, 698, 619. ¹H NMR (400 MHz, CDCl₃, HH-COSY, HSQC): 8.04

(d, 2H, J = 7.6 Hz, H_arom), 7.58 (t, 1H, J = 7.2 Hz, H_arom), 7.45−7.22

(m, 10H, H_arom), 7.20−7.18 (m, 2H, H_arom), 5.25 (d, 1H, J = 12.4 Hz,

CHHPh), 5.20 (d, 1H, J = 12.0 Hz, CHHPh), 5.10 (t, 1H, J = 8.2 Hz,

H-2), 4.70 (d, 1H, J = 11.2 Hz, CHHPh), 4.60 (d, 1H, J = 7.6 Hz, H-1),

5.54 (d, 1H, J = 11.2 Hz, CHHPh), 4.02 (d, 1H, J = 8.8 Hz, H-5), 3.95−

3.86 (m, 3H, H-3, H-4, CHH N₃(CH₂)₆OH), 3.48−3.23 (m, 1H, CHH

N₃(CH₂)₆OH), 3.06 (t, 2H, J = 7.0 Hz, CH₂N₃(CH₂)₆OH), 2.72 (bs,

1H, C-3-OH), 1.54−1.44 (m, 2H, CH₂N₃(CH₂)₆OH), 1.35−1.13 (m,

6H, 3x CH₂N₃(CH₂)₆OH). ¹³C NMR (100 MHz, CDCl₃, HH-COSY,

HSQC): 168.4 (CO), 166.3 (CO), 137.9 (C_qC_arom), 135.1 (C_qC_arom),

The condensation of dimer 32 (1 equiv), featuring the glucosyl

donor moiety, and acceptor 10 (1.3 equiv) led to the alternative

trimer 36 in 54% yield. In line with the results obtained with the

monomeric donors, the glucuronic acid donor−glucosyl acceptor

combination performed better than the corresponding glucosyl

donor−glucuronic acid acceptor couple, indicating that the

former disaccharide donor is the building block of choice for the

assembly of larger oligomers of S. pneumoniae type 3.

Finally, the obtained trisaccharides were deprotected as

follows. First, the levulinyl group was removed from trisaccharide

33 and 36 by treatment with hydrazine acetate in a pyridine/

AcOH mixture, yielding trisaccharides 34 and 37 in 95% and

93% yield, respectively. Then, the benzoyl esters and benzyl

esters were saponified using KOH in dioxane/H₂O and the azido

en benzyl protective groups were reduced with H₂gas and Pd/C

in a mixture of ^tBuOH and H₂O. The deprotected trisaccharides

35 and 38 were obtained in 44% and 28% yield over two steps,

respectively.

CONCLUSION

■

In summary, we determined the relative reactivity of a set of

thioglucuronic acid esters. From the established reactivities it has

become apparent that the reactivity of glucuronic acid is not as

low as often assumed. For example, 2,3-di-O-benzylglucuronic

acid methyl ester 1 was shown to be of equal reactivity as 2,3-

di-O-benzyl-4,6-O-benzylideneglucosyl donor 4, and the least

reactive glucuronide studied here, azidoglucuronic acid 2, out-

competed tetrabenzoyl glucose 7 completely. In the construc-

tion of dimers and trimers of the capsular polysaccharide of

Streptococcus pneumoniae type 3, the glycosylations involving the

glucuronic acid donors proceeded well, paving the way for the

preparation of larger oligomers.

EXPERIMENTAL SECTION

■

General Experimental Procedures. Chemical shifts (δ) are

given in ppm relative to TMS as internal standard. All ¹³C-APT spectra

are proton decoupled. IR spectra are reported in cm⁻¹. Reactions were

performed at rt unless stated otherwise and were followed by TLC

analysis with detection by UV absorption (254 nm) where applicable

and by spraying with 20% sulfuric acid in EtOH or with a solution of

(NH₄)₆Mo₇O₂₄·H₂O (25 g L⁻¹), followed by charring at 150 °C. Flash

column chromatography was performed on silica gel (0.04−0.063 nm)

and size-exclusion chromatography (SEC) was performed on Sephadex

LH-20. Experiments which required an inert atmosphere were carried

out under dry argon. Dichloromethane (p.a.) was distilled over P₂O₅

prior to use. Molecular sieves (3 Å) were flame-dried before use.

General Procedure for the Competition Experiments. Donor

A (0.1 mmol, 1 equiv), donor B (0.1 mmol, 1 equiv) and the acceptor

(methyl 2,3,4-tri-O-benzyl-α-^D-glucopyranoside, 3 equiv) were coevapo-

rated with toluene (2×). DCM was refluxed with P₂O₅and distilled

before use. Freshly distilled DCM (4 mL, donor concentration 0.05 M),

a Teflon stirrer bar, and activated (flame-dried) molecular sieves 3 Å

were added, and the mixture was stirred under argon for 30 min at rt.

NIS (1 equiv) was added, and the mixture was cooled to −40 °C. TfOH

(0.1 equiv, 0.1 mL of a 0.1 M stock solution in distilled DCM) was

added, and the mixture was allowed to warm to 0 °C in ∼3 h.

Triethylamine (0.1 mL) was added, and the mixture was diluted with

EtOAc, washed with satd aq Na₂S₂O₃(1×) and satd aq NaCl (2×),

dried over MgSO₄, and concentrated in vacuo. Elution over a Sephadex

LH-20 (DCM/MeOH, 1/1, v/v) enabled isolation of the disaccharide

products, which were analyzed with NMR spectroscopy. The yield

of the disaccharide fraction and the ratio of the disaccharides were

determined.

General Procedure for Glycosylations Using NIS/TfOH. The

donor and acceptor glucosides and/or glucuronic acid esters were

coevaporated with toluene (2×), dissolved in freshly distilled DCM,

112

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Article

133.6 (CH_arom), 130.0 (CH_arom), 129.6 (C_qC_arom), 128.7−128.1

(CH_arom), 101.2 (C-1), 79.8 (C-3 or C-4), 75.3 (C-3 or C-4), 75.0

(CH2 Bn), 74.7 (C-2 or C-5), 74.6 (C-2 or C-5), 70.1 (CH₂

N₃(CH₂)₆OH), 67.6 (CH₂CO₂Bn), 51.3 (CH₂N₃(CH₂)₆OH), 29.3

(CH₂N₃(CH₂)₆OH), 28.7 (CH₂N₃(CH₂)₆OH), 26.4 (CH₂

N₃(CH₂)₆OH), 25.5 (CH₂N₃(CH₂)₆OH). HRMS: [M + Na]⁺

calcd for C₃₃H₃₇N₃O₈Na 626.24729, found 626.24673.

3.91−3.85 (m, 2H, H-3, CHH N₃(CH₂)₆OH), 3.70−3.58 (m, 3H, H-5,

H-6), 3.47−3.41 (m, 1H, CHH N₃(CH₂)₆OH), 3.02 (t, 1H, J = 6.8 Hz,

CH₂N₃(CH₂)₆OH), 2.63−2.58 (m, 2H, CH₂Lev), 2.43−2.36 (m, 2H,

CH₂Lev), 2.10 (s, 3H, CH₃Lev), 1.50−1.44 (m, 2H, CH₂N₃(CH₂)₆-

OH), 1.31−1.15 (m, 6H, 3x CH₂N₃(CH₂)₆OH). ¹³C NMR (100 MHz,

CDCl₃, HH-COSY, HSQC): 206.3 (CO Lev ketone), 171.6 (CO

Lev), 165.0 (CO Bz), 138.1 (C_qC_arom), 137.8 (C_qC_arom), 133.3

(CH_arom), 129.9 (C_qC_arom), 129.8 (CH_arom), 128.5−127.6 (CH_arom),

101.2 (C-1), 79.8 (C-3), 73.8 (CH₂Bn), 76.7 (C-5), 76.6 (CH₂Bn),

73.4 (C-2), 71.2 (C-4), 69.7 (CH₂N₃(CH₂)₆OH), 69.7 (C-6), 51.2

(CH₂N₃(CH₂)₆OH), 37.8 (CH₂Lev), 29.8 (CH₃Lev), 29.3 (CH₂

N₃(CH₂)₆OH), 29.3 (CH₂N₃(CH₂)₆OH), 27.9 (CH₂Lev), 26.3 (CH₂

N₃(CH₂)₆OH), 25.4 (CH₂N₃(CH₂)₆OH). HRMS: [M + Na]⁺calcd

for C₃₈H₄₅N₃O₉Na 710.30480, found 710.30474.

Benzyl (6-Azidohexyl 2-O-benzoyl-4-O-benzyl-3-O-(2,6-di-O-

benzoyl-3-O-benzyl-4-O-levulinyl-1-thio-β-^D-glucopyranoside)-β-D-

glucopyranosyluronate)) (11). Glucuronic acid ester acceptor 10

(175 mg, 0.26 mmol, 1.3 equiv) and glucoside donor 12 (119 mg,

0.20 mmol, 1 equiv) were condensed according to the general procedure

for glycosylations and yielded the title compound as a white solid in 62%

yield (142 mg, 0.12 mmol). R_f: 0.29 (Tol/EtOAc 3/1). [α]_D: +5.4 (c =

1, DCM). IR (neat, cm⁻¹): 2938, 2095, 1721, 1452, 1362, 1315, 1263,

1211, 1177, 1146, 1094, 1069, 1026, 1001, 737, 710, 700. ¹H NMR (400

MHz, CDCl₃, HH-COSY, HSQC): 8.01 (d, 2H, J = 7.2 Hz, H_arom), 7.94

(d, 2H, J = 7.6 Hz, H_arom), 7.84 (d, 2H, J = 7.6 Hz, H_arom), 7.59−7.52

(m, 2H, H_arom), 7.50−7.30 (m, 7H, H_arom). 7.28−7.26 (m, 6H, H_arom),

7.17−7.10 (m, 7H, H_arom), 7.10−7.01 (m, 2H, H_arom), 5.33 (t, 1H, J =

8.8 Hz, H-2′), 5.21 (t, 1H, J = 9.6 Hz, H-2), 5.14−5.10 (m, 2H, CH₂

CO₂Bn), 4.98 (d, 1H, J = 10.8 Hz, CHHPh), 4.93 (d, 1H, J = 8.0 Hz,

H-1′), 4.51−4.47 (m, 3H, CH₂Bn, H-6), 4.46 (d, 1H, J = 6.0 Hz, H-1),

4.44 (d, 1H, J = 12.0 Hz, CHHPh), 4.24−4.17 (m, 2H, H-6′, H-5′), 4.03

(t, 1H, J = 9.6 Hz, H-4), 3.98 (d, 1H, J = 8.8 Hz, H-5), 3.77−3.69 (m,

3H, H-3, H-3′, CHH CH₂N₃(CH₂)₆OH), 3.23−3.18 (m, 1H, CHH

CH₂N₃(CH₂)₆OH), 3.04 (t, 2H, 7.2 Hz, CH₂N₃(CH₂)₆OH), 2.65−

2.60 (m, 2H, CH₂Lev), 2.50−2.42 (m, 1H, CHH Lev), 2.38−2.32 (m,

1H, CHH Lev), 2.09 (s, 3H, CH₃Lev), 1.30−1.22 (m, 4H, 2 × CH₂

N₃(CH₂)₆OH), 1.11−1.00 (m, 4H, 2 × CH₂N₃(CH₂)₆OH). ¹³C NMR

(100 MHz, CDCl₃, HH-COSY, HSQC): 206.1 (CO Lev ketone),

171.4 (CO), 168.2 (CO), 166.1 (CO Bz), 165.0 (CO), 164.4

(CO), 138.0 (C_qC_arom), 137.4 (C_qC_arom), 135.1 (C_qC_arom), 133.5

(CH_arom), 133.0 (CH_arom), 129.9−129.8 (CH_arom), 129.7−129.5 (C_q

C_arom), 128.6−127.11 (CH_arom), 100.5 (C-1), 100.2 (C-1′), 80.0 (C-3′),

76.6 (C-5′), 76.8 (C-4), 74.8 (CH₂Bn), 74.5 (C-5), 74.1 (CH₂Bn),

73.6 (C-4′), 73.3 (C-2′), 72.2 (C-3′), 70.5 (C-2), 69.3 (CH₂

N₃(CH₂)₆OH), 67.3 (CH₂CO₂Bn), 63.0 (C-6′), 51.2 (CH₂

N₃(CH₂)₆OH), 37.8 (CH₂Lev), 29.7 (CH₃Lev), 28.9 (CH₂

N₃(CH₂)₆OH), 28.5 (CH₂Lev), 27.8 (CH₂N₃(CH₂)₆OH), 26.2

(CH₂N₃(CH₂)₆OH), 25.2 (CH₂N₃(CH₂)₆OH). HRMS: [M + Na]⁺

calcd for C₆₅H₆₇N₃O₁₇Na 1184.43627, found 1184.43563.

6-Azidohexyl 2-O-Benzoyl-3,6-di-O-benzyl-β-^D-glucopyranoside

(14). Glucoside 13 (523 mg, 0.76 mmol) was dissolved in pyridine/

AcOH (4/1, 15 mL) followed by addition of hydrazine monohydrate

(0.22 mL, 3.8 mmol, 5 equiv). After 1 h, TLC analysis (PE/EtOAc 4/1,

v/v) showed total conversion of the starting material. The reaction

mixture was diluted with EtOAc, washed with 2 M HCl and NaHCO₃

(aq, satd), dried over MgSO₄, filtered, and concentratedd. Column

chromatography (PE/EtOAc 7/3) gave the target compound in 99%

yield (442 mg, 0.75 mmol). [α]²⁰_D: +2.6 (c = 0.7, DCM). IR (neat,

cm⁻¹): 2938, 2866, 2095, 1726, 1452, 1362, 1314, 1265, 1209, 1179,

1

1110, 1069, 1026, 984, 733, 698, 648. H NMR (400 MHz, CDCl₃,

1

HH-COSY, HSQC): H NMR: 8.08−8.03 (m, 2H, H_arom), 7.60−7.57

(m, 1H, H_arom), 7.47−7.44 (m, 2H, H_arom), 7.37−7.18 (m, 10H, H_arom),

5.24 (t, 1H, J = 8.8 Hz, H-2), 4.73 (d, 1H, J = 11.6 Hz, CHHPh), 4.69

(d, 1H, J = 11.6 Hz, CHHPh), 4.63 (d, 1H, J = 11.6 Hz, CHHPh), 4.58

(d, 1H, J = 11.6 Hz, CHHPh), 4.50 (d, 1H, J = 8.0 Hz, H-1), 3.94−3.85

(m, 1H, CHH N₃(CH₂)₆OH), 3.84−3.73 (m, 3H, H-4, H-6), 3.68 (t,

1H, J = 9.2 Hz, H-3), 3.57−3.52 (m, 1H, H-5), 3.44−3.38 (m, CHH

N₃(CH₂)₆OH), 3.01 (t, 1=2H, J = 6.8 Hz, CH₂N₃(CH₂)₆OH), 1.52−

1.41 (m, 2H, CH₂N₃(CH₂)₆OH), 1.13−1.15 (m, 6H, 3x CH₂

N₃(CH₂)₆OH). ¹³C NMR (100 MHz, CDCl₃, HH-COSY, HSQC):

165.2 (CO Bz), 138.0 (C_qC_arom), 137.8 (C_qC_arom), 133.2 (CH_arom),

130.0 (C_qC_arom), 130.0−129.8 (CH_arom), 128.6−127.9 (CH_arom), 101.3

(C-1), 82.1 (C-3), 74.5 (CH₂Bn), 74.2 (C-5), 73.8 (CH₂Bn), 73.5

(C-2), 72.3 (C-4), 70.4 (C-6), 69.7 (CH₂N₃(CH₂)₆OH), 51.2 (CH₂

N₃(CH₂)₆OH), 29.3 (CH₂N₃(CH₂)₆OH), 28.6 (CH₂N₃(CH₂)₆OH),

26.3 (CH₂N₃(CH₂)₆OH), 25.5 (CH₂N₃(CH₂)₆OH). HRMS:

[M + Na]⁺calcd for C₅₅H₅₄O₁₃Na 945.34566, found 945.34162.

6-Azidohexyl 3,6-Di-O-benzyl-4-O-(benzyl (2-O-benzoyl-4-O-ben-

zyl-3-O-levulinyl-β-^D-glucopyranosyluronate))-2-O-benzoyl-1-thio-

β-^D-glucopyranoside (15). Glucuronic acid ester donor 3 (151 mg,

0.22 mmol, 1.3 equiv) and glucoside acceptor 14 (100 mg, 0.17 mmol, 1

equiv) were glycosylated according to the general procedure for

glycosylations and yielded disaccharide 16 in 74% yield (144 mg, 0.13

mmol) as a transparent oil, which crystallized on standing. R_f: 0.46 (PE/

EtOAc 12/8, v/v). [α]_D: +26.0 (c = 1, DCM). IR (neat, cm⁻¹): 2940,

2095, 1721, 1452, 1364, 1315, 1263, 1211, 1177, 1148, 1094, 1069,

6-Azidohexyl 2-O-Benzoyl-3,6-di-O-benzyl-4-O-levulinyl-β-^D-

glucopyranoside (13). Glucoside donor 12 (654 mg, 1 mmol) and

6-azidohexanol (214 mg, 1.5 mmol, 1.5 equiv) were coevaporated with

toluene (2×) and dissolved in freshly distilled DCM (4.0 mL, 0.25 M).

Activated MS 3 Å were added, and the reaction mixture was stirred for

30 min, followed by addition of NIS (338 mg, 1.5 mmol, 1.5 equiv). The

reaction mixture was cooled to −25 °C, followed by addition of TfOH

(1 mL of 0.1 M stock solution, 0.1 mmol, 0.1 equiv). The reaction

mixture was allowed to warm to rt. TLC analysis (PE/EtOAc 3/2, v/v)

showed total consumption of the thioglucoside. The reaction mixture

was quenched with TEA and Na₂S₂O₃(aq, satd) and diluted with DCM,

followed by separation of the layers. The organic layer was washed with

NaHCO₃(aq, satd) and brine, dried over MgSO₄, filtered, and

concentrated. Column chromatography (PE/EtOAc 9/1 → 7/3) gave a

mixture of the title compound and 6-azidohexanol. This mixture was

dissolved in a mixture of pyridine/Ac₂O (1/1, 10 mL) and stirred

overnight (acetylation of 6-azidohexanol). The reaction mixture was

quenched with MeOH, diluted with EtOAc, washed with 2 M HCl,

NaHCO₃(aq, satd), dried over MgSO₄, filtered, and concentrated.

Column chromatography (PE/EtOAc 9/1 → 3/1) gave the title

compound as a transparent oil in 80% yield (550 mg, 0.80 mmol).

[α]²⁰_D: +16.0 (c = 1.1, DCM). IR (neat, cm⁻¹): 2936, 2862, 2095, 1721,

1452, 1362, 1314, 1267, 1206, 1177, 1148, 1094, 1069, 1026, 988, 970,

1

1026, 1001, 735, 710, 700. H NMR (400 MHz, CDCl₃, HH-COSY,

HSQC): 7.94−7.91 (m, 4H, H_arom), 7.58−7.54 (m, 2H, H_arom), 7.45−

7.24 (m, 17H, H_arom), 7.15−7.14 (m, 4H, H_arom), 7.14−7.04 (m, 3H,

H_arom), 5.31 (t, 1H, J = 9.2 Hz, H-3′), 5.23 (t, 1H, J = 10.0 Hz, H-2′),

5.17 (t, 1H, J = 8.8 Hz, H-2), 5.06 (d, 1H, J = 12.0 Hz, CHH CO₂Bn),

5.01 (d, 1H, J = 12.0 Hz, CHH CO₂Bn), 4.86 (d, 1H, J = 10.8 Hz,

CHHPh), 4.84 (d, 1H, J = 7.2 Hz, H-1′), 4.64 (d, 1H, J = 12.0 Hz,

CHHPh), 4.59 (d, 1H, J = 11.6 Hz, CHHPh), 4.49 (d, 1H, J = 12.0 Hz,

CHHPh), 4.49 (d, 1H, J = 12.4 Hz, CHHPh), 4.37 (d, 1H, J = 11.2 Hz,

CHHPh), 4.34 (d, 1H, J = 8.4 Hz, H-1), 4.11 (t, 1H, J = 9.2 Hz, H-4),

4.00 (d, 1H, J = 9.6 Hz, H-4′), 3.89 (d, 1H, J = 9.6 Hz, H-5′), 3.80-.3.70

(m, 2H, H-3, CHH CH₂N₃(CH₂)₆OH), 3.60 (dd, 1H, J = 3.6 Hz, J =

11.2 Hz, H-6), 3.49 (d, 1H, J = 10.4 Hz, H-6), 3.35−3.27 (m, 1H, CHH

CH₂N₃(CH₂)₆OH), 3.26−3.23 (m, 1H, H-5), 3.03−3.96 (m, 2H, CH₂

CH₂N₃(CH₂)₆OH), 2.47−2.44 (m, 2H, CH₂Lev), 2.34−2.31 (m, 2H,

CH₂Lev), 1.97 (s, 3H, CH₃Lev), 1.50−1.28 (m, 2H, CH₂CH₂

N₃(CH₂)₆OH), 1.28−1.26 (m, 2H, CH₂N₃(CH₂)₆OH), 1.24−1.11 (m,

4H, 2 × CH₂CH₂N₃(CH₂)₆OH). ¹³C NMR (100 MHz, CDCl₃, HH-

COSY, HSQC): 205.5 (CO Lev ketone), 171.5 (CO, 167.5 (CO),

1

910, 748, 712 698. H NMR (400 MHz, CDCl₃, HH-COSY, HSQC):

8.03−8.01 (m, 2H, H_arom), 7.59 (t, 1H, J = 7.6 Hz, H_arom), 7.77−7.73

(m, 2H, H_arom), 7.35−7.26 (m, 5H, H_arom), 7.14−7.10 (m, 5H, H_arom),

5.30 (t, 1H, J = 9.2 Hz, H-2), 5.14 (t, 1H, J = 9.6 Hz, H-4), 4.60 (s,

2H, CH₂Bn), 4.55 (s, 2H, CH₂Bn), 5.54 (d, 1H, J = 8.0 Hz, H-1),

113

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Article

165.0 (CO), 164.9 (CO), 138.3 (C_qC_arom), 137.8 (C_qC_arom),

137.5 (C_qC_arom), 136.6 (C_qC_arom), 134.8 (C_qC_arom), 133.4 (CH_arom),

132.9 (CH_arom), 130.0 (C_qC_arom), 129.8−129.1 (CH_arom), 128.6 (C_q

C_arom), 128.5−127.1 (CH_arom), 101.1 (C-1), 100.4 (C-1′), 80.2 (C-3),

77.6 (C-4′), 77.3 (C-4), 74.6 (C-5), 74.5 (CH₂Bn), 74.5 (C-5′), 74.4

(CH₂Bn), 74.0 (C-3′), 73.5 (CH₂Bn), 73.1 (C-2), 72.2 (C-2′),

69.3 (CH₂N₃(CH₂)₆OH), 67.5 (C-6), 67.4 (CH₂CO₂Bn), 51.1

(CH₂N₃(CH₂)₆OH), 37.7 (CH₂Lev), 29.4 (CH₃Lev), 29.1 (CH₂

N₃(CH₂)₆OH), 28.5 (CH₂N₃(CH₂)₆OH), 27.8 (CH₂

N₃(CH₂)₆OH), 26.2 (CH₂Lev), 25.3 (CH₂N₃(CH₂)₆OH). HRMS:

[M + Na]⁺calcd for C₆₅H₆₉N₃O₁₆Na 1170.45700, found 1170.45688.

Benzyl (2-O-Benzoyl-4-O-benzyl-3-O-levulinyl-α/β-^D-

glucopyranose)uronate) (16). Glucuronic acid ester 3 (3074 mg,

0.45 mmol) was dissolved in freshly distilled DCM (4.5 mL, 0.1M). The

reaction mixture was cooled to 0 °C, followed by addition of NIS

(111 mg, 0.50 mmol, 1.1 equiv) and TFA (38 μL, 0.50 mmol, 1.1 equiv).

The reaction mixture was allowed to warm to rt, and after 30 min,

TLC analysis (Tol/EtOAc 4/1, v/v) showed total conversion into a

lower running spot. The reaction mixture was quenched by addition of

Na₂S₂O₃(aq, satd) and NaHCO₃(aq, satd) and stirred for 30 min.

Then the reaction mixture was diluted with DCM, followed by

separation of the layers. The organic layer was dried over MgSO₄,

filtered, and concentrated. Column chromatography (PE/EtOAc

1/0 → 6/4) gave hemiacetal 16 as a transparent oil and as anomeric

mixture (α/β 4/1) in 88% yield (229 mg, 0.40 mmol). IR (neat, cm⁻¹):

3443, 1744, 1721, 1601, 1497, 1452, 1404, 1360, 1339, 1315, 1265,

1213, 1179, 1155, 1109, 1098, 1070, 1061, 1028, 986, 962, 908, 853,

750, 714, 698, 635, 621. α isomer: ¹H NMR (400 MHz, CDCl₃, HH-

COSY, HSQC): 8.01 (d, 2H, J = 7.6 Hz, H_arom), 7.44 (t, 1H, J = 5.2

Hz, H_arom), 7.41−7.22 (m, 10H, H_arom), 7.17−7.13 (m, 2H, H_arom),

5.78 (t, 1H, J = 10.0 Hz, H-3), 5.59 (d, 1H, J = 3.2 Hz, OH), 5.18 (s,

2H, CH₂Bn ester), 5.02 (dd, 1H, J = 3.6 Hz, J = 10.0 Hz, H-2), 4.63

(d, 1H, J = 10.0 Hz, H-5), 4.53 (d, 1H, J = 11.2 Hz, CHHPh), 4.50 (d,

1H, J = 11.2 Hz, CHHPh), 3.96 (t, 1H, J = 9.6 Hz, H-4), 3.62 (bs,

OH), 2.54−2.48 (m, 2H, CH₂Lev), 2.38−2.32 (m, 2H, CH₂Lev),

1.99 (s, 3H, CH₃Lev). ¹³C NMR (100 MHz, CDCl₃, HH-COSY,

HSQC): 206.0 (CO Lev ketone), 171.8 (CO Bn ester), 169.0

(CO Lev), 165.8 (CO Bz), 137.5 (C_qC_arom), 134.8 (C_qC_arom),

133.5 (CH_arom), 130.0 (CH_arom), 129.0 (CH_arom), 128.7 (C_qC_arom),

128.6−127.8 (CH_arom), 90.6 (C-1), 77.6 (C-4), 74.5 (CH₂Bn ether),

71.8 (C-2), 71.2 (C-3), 70.2 (C-5), 67.5 (C-6), 37.7 (CH₂Lev), 29.6

(CH₃Lev), 27.9 (CH₂Lev), 27.9 (CH₃STol). HRMS: [M + Na]⁺

calcd for C₃₂H₃₂O₁₀Na 599.18877, found 599.18776.

2-O-Benzoyl-3,6-di-O-benzyl-4-O-levulinyl-α/β-^D-glucopyranose

(18). Glucoside 11 (263 mg, 0.39 mmol) was dissolved in freshly

distilled DCM (39.3 mL, 0.1 M). The reaction mixture was cooled to

0 °C, followed by addition of NIS (97 mg, 0.43 mmol, 1.1 equiv) and

TFA (33 μL, 0.43 mmol, 1.1 equiv). The reaction mixture was allowed

to warm to rt. After 3 h, piperidine (128 μL, 1.29 mmol, 3 equiv) was

added, and the reaction mixture turned orange. The reaction was

quenched by addition of Na₂S₂O₃(aq, satd) and diluted with DCM,

followed by separation of the layers. The organic layer was dried over

MgSO₄, filtered, and concentrated. Column chromatography (PE/

EtOAc 1/0 → 6/4) gave hemiacetal 18 as a transparent oil in 84% yield

(186 mg, 0.33 mmol). IR (neat, cm⁻¹): 1717, 1452, 1404, 1362, 1271,

1207, 1177, 1153, 1098, 1067, 1026, 1001, 937, 914, 746, 712, 698. α

Anomer: ¹H NMR (400 MHz, CDCl₃, HH-COSY, HSQC): 8.05−8.03

(m, 2H, H_arom), 7.59−7.18 (m, 13H, H_arom), 5.52 (t, 1H, J = 3.2 Hz,

H-1), 5.15−5.04 (m, 2H, H-2, H-4), 4.71 (d, 1H, J = 11.6 Hz, CHHPh),

4.63 (d, 1H, J = 11.6 Hz, CHHPh), 4.50 (s, 2H, CH₂Bn), 4.26−4.16

(m, 2H, H-3, H-5), 3.53−3.49 (m, 2H, H-6), 2.67−2.48 (m, 2H, CH₂

Lev), 2.44−2.23 (m, 2H, CH₂Lev), 2.11 (s, 3H, CH₃Lev). ¹³C NMR

(100 MHz, CDCl₃, HH-COSY, HSQC): 206.4 (CO Lev ketone),

171.5 (CO Lev), 165.6 (CO Bz), 138.0 (C_qC_arom), 137.5 (C_q

C_arom), 133.2 (CH_arom), 129.8 (CH_arom), 129.7 (CH_arom), 129.5 (C_q

C_arom), 128.5−127.5 (CH_arom), 92.2 (C-1), 76.8 (C-3 or C-5), 74.7

(CH₂Bn), 73.8 (C-2 or C-4), 73.4 (CH₂Bn), 70.9 (C-2 or C-4), 69.0

(C-6), 68.5 (C-3 or C-5), 37.7 (CH₂Lev), 29.7 (CH₃Lev), 27.7 (CH₂

Lev). HRMS: [M + Na]⁺calcd for C₃₂H₃₄O₉Na 585.20950, found

585.20905.

2-O-Benzoyl-3,6-di-O-benzyl-4-O-levulinyl-1-O-(N-phenyltrifluoro-

acetimidoyl)-α/β-^D-glucopyranoside (19). Hemiacetal 18 (465 mg,

0.83 mmol) was dissolved in acetone (5.5 mL, 0.2 M), and the reaction

mixture was cooled to 0 °C. To this mixture were added N-phenyl-2,2,2-

trifluoroacetimidoyl chloride (0.25 mL, 1.66 mmol, 2 equiv) and

Cs₂CO₃(270 mg, 0.83 mmol, 1 equiv). The reaction mixture was

allowed to warm to rt, and after 2 h, TLC analysis showed total

conversion into a higher running spot (PE/EtOAc 12/8, v/v, R_f0.50).

The reaction mixture was filered over Celite and concentrated. Column

chromatography (PE/EtOAc 1/0 → 7/3) gave the title compound as a

transparent oil in 68% yield (α/β 9/1). IR (neat, cm⁻¹): 1717, 1364,

1315, 1265, 1207, 1152, 1119, 1098, 1070, 1026, 924, 885, 737, 712,

696. α Anomer ¹H NMR (50 °C, 400 MHz, CDCl₃, HH-COSY,

HSQC): 8.02−7.99 (m, 2H, H_arom), 7.61−7.58 (m, 1H, H_arom), 7.47−

7.43 (m, 3H, H_arom), 7.35−7.07 (m, 12H, H_arom), 7.00−6.96 (m, 2H,

H_arom), 6.62 (bs, 1H, H-1), 6.43 (d, 2H, J = 7.6 Hz, H_arom), 5.36 (dd,

1H, J = 3.6 Hz, J = 10.0 Hz, H-2), 5.29 (t, 1H, J = 9.6 Hz, H-4), 4.73 (d,

1H, J = 11.6 Hz, CHHPh), 4.68 (d, 1H, J = 11.6 Hz, CHHPh), 4.56 (d,

1H, J = 12.4 Hz, CHHPh), 4.53 (d, 1H, J = 12.0 Hz, CHHPh), 4.22

(t, 1H, J = 9.6 Hz, H-3), 4.14−4.11 (m, 1H, H-5), 3.66−3.57 (m, 2H,

H-6), 2.67−2.53 (m, 2H, CH₂Lev), 2.50−2.35 (m, 2H, CH₂Lev), 2.12

(s, 3H, CH₃Lev). ¹³C NMR (100 MHz, CDCl₃, HH-COSY, HSQC):

205.8 (CO Lev ketone), 171.3 (CO Lev ketone), 165.1 (CO

Bz), 143.1 (C_qC_arom), 138.0 (C_qC_arom), 133.5 (CH_arom), 129.8

(CH_arom), 129.3 (C_qC_arom),128.7−127.6 (CH_arom), 124.2 (CH_arom),

119.2 (CH_arom), 92.9 (C-1), 77.1 (C-3), 74.8 (CH₂Bn), 73.7 (CH₂Bn),

72.2 (C-2), 72.1 (C-5), 70.3 (C-4), 68.8 (C-6), 37.8 (CH₂Lev), 29.6

(CH₃Lev), 28.0 (CH₂Lev). HRMS: [M + Na]⁺calcd for

C₄₀H₃₈F₃NO₉Na 756.23909, found 756.23982.

Benzyl (2-O-Benzoyl-4-O-benzyl-3-O-levulinyl-1-O-(N-phenyltri-

fluoroacetimidoyl)-α/β-^D-glucopyranosyl)uronate (17). Hemiacetal

16 (190 mg, 0.33 mmol) was dissolved in acetone (1.65 mL, 0.2 M),

and the reaction mixture was cooled to 0 °C. To this mixture were

added N-phenyl-2,2,2-trifluoroacetimidoyl chloride (0.1 mL, 0.66 mmol,

2 equiv) and Cs₂CO₃(108 mg, 0.33 mmol, 1 equiv). The reaction

mixture was allowed to warm to rt, and after 2 h, TLC analysis showed

total conversion into a higher running spot (PE/EtOAc 12/8, v/v, R_f

0.55). The reaction mixture was filered over Celite and concentrated.

Column chromatography (PE/EtOAc 1/0 → 6/4) gave the title com-

pound as a transparent oil in 83% yield (α/β 3.4/1). IR (neat, cm⁻¹):

1746, 1719, 1452, 1404, 1358, 1317, 1263, 1209, 1153, 1107, 1096,

1

1070, 1040, 1028, 1003, 984, 908, 754, 739, 712, 696. α Isomer: H

NMR (50 °C, 400 MHz, CDCl₃, HH-COSY, HSQC): 8.00 (d, 2H,

J = 7.6 Hz, H_arom), 7.59−7.50 (m, 2H, H_arom), 7.41−7.16 (m, 12H,

H_arom), 7.11−7.07 (m, 3H, H_arom), 6.99 (t, 1H, J = 7.2 Hz, H_arom), 6.68

(bs, 1H, H-1), 5.81 (t, 1H, J = 10.0 Hz, H-3), 5.31 (dd, 1H, J = 2.4 Hz,

J = 10.0 Hz, H-2), 5.23 (s, 2H, CH₂Bn ester), 4.56−4.50 (m, 3H, H-5,

CH₂Bn ether), 4.08 (t, 1H, J = 9.6 Hz, H-4), 2.55−2.50 (m, 2H, CH₂

Lev), 2.42−2.38 (m, 2H, CH₂Lev), 2.02 (s, 3H, CH₃Lev). ¹³C NMR

(100 MHz, CDCl₃, HH-COSY, HSQC): 171.6 (CO), 167.8 (C

O), 165.3 (CO), 142.9 (C_qC_arom), 137.4 (C_qC_arom), 134.9 (C_q

C_arom), 133.6 (CH_arom), 130.1 (CH_arom), 128.9 (C_qC_arom), 128.7−127.9

(CH_arom), 124.4 (CH_arom), 119.1 (CH_arom), 92.4 (C-1), 77.2 (C-4), 74.9

(CH₂Bn ether), 72.8 (C-5), 71.3 (C-3), 70.4 (C-2), 67.8 (CH₂

Bn ester), 37.8 (CH₂Lev), 29.4 (CH₃Lev), 28.0 (CH₂Lev). HRMS:

[M + Na]⁺calcd for C₄₀H₃₆F₃NO₁₀Na 770.21835, found 770.21895.

p-Tolyl 3,6-Di-O-benzyl-4-O-(benzyl (2-O-benzoyl-4-O-benzyl-3-

O-levulinyl-β-^D-glucopyranosyluronate))-2-O-benzoyl-1-thio-β-D-

glucopyranoside (21). Donor 17 (256 mg, 0.34 mmol, 1.3 equiv) and

acceptor 20 (151 mg, 0.26 mmol) were coevaporated with toluene (2×)

and dissolved in freshly distilled DCM (6.8 mL, 0.05 M). Activated MS

3 Å were added, and the reaction mixture was stirred for 30 min. The

reaction mixture was cooled to 0 °C, followed by addition of TfOH

(0.2 mL of 0.1 M stock solution, 0.02 mmol, 0.1 equiv). The reaction

mixture was allowed to warm to rt. After 4 h, TLC analysis (PE/EtOAc

12/8, v/v) showed disappearance of the acceptor. The reaction mixture

was neutralized with TEA, diluted with DCM, washed with H₂O, dried

over MgSO₄, filtered, and concentrated. A yellow oil was obtained,

which was purified by SEC (DCM/MeOH 1/1), yielding disaccharide

37 in 12% yield (35 mg, 0.031 mmol). [α]²⁰_D: +2.0 (c = 0.6, DCM).

114

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IR (neat, cm⁻¹): 2914, 2872, 1744, 1728, 1495, 1452, 1400, 1360, 1315,

1263, 1215, 1177, 1144, 1092, 1069, 1051, 1026, 1001, 910, 845, 810,

750, 710, 698. ¹H NMR (400 MHz, CDCl₃, HH-COSY, HSQC): 7.95−

7.92 (m, 4H, H_arom), 7.60−7.55 (m, 2H, H_arom), 7.45−7.25 (m, 19H,

H_arom), 7.19−7.03 (m, 7H, H_arom), 6.95 (d, 2H, J = 7.6 Hz, H_arom), 5.33

(t, 1H, J = 9.2 Hz, H-3′), 5.23 (t, 1H, J = 9.6 Hz, H-2′), 5.16 (t, 1H, J =

9.6 Hz, H-2), 5.03 (d, 1H, J = 12.0 Hz, CHHPh), 4.96 (d, 1H, J = 12.0

Hz, CHHPh), 4.87 (d, 1H, J = 8.4 Hz H-1′), 4.87 (d, 1H, J = 11.2 Hz,

CHHPh), 4.58−4.53 (m, 3H, CH₂Bn, H-1), 4.47 (s, 2H, CH₂Bn),

4.35 (d, 1H, J = 12.0 Hz, CHHPh), 4.11 (t, 1H, J = 9.6 Hz, H-4), 4.04

(t, 1H, J = 9.2 Hz, H-4′), 3.90 (d, 1H, J = 9.6 Hz, H-5′), 3.73 (t, 1H, J =

8.8 Hz, H-3), 3.61 (dd, 1H, J = 3.6 Hz, J = 11.6 Hz, H-6), 3.53 (d, 1H,

J = 11.2 Hz, H-6), 3.28−3.25 (m, 1H, H-5), 2.46−2.44 (m, 2H, CH₂

Lev), 2.35−2.29 (m, 2H, CH₂Lev), 2.24 (s, 3H, CH₃STol), 1.97 (s,

3H, CH₃Lev). ¹³C NMR (100 MHz, CDCl₃, HH-COSY, HSQC):

205.6 (CO Lev ketone), 171.6 (CO), 167.5 (CO Bz), 165.0

(CO Bz), 138.2 (C_qC_arom), 138.1 (C_qC_arom), 137.9 (C_qC_arom), 137.5

(C_qC_arom), 134.8 (C_qC_arom), 133.4−133.0 (CH_arom), 130.0 (C_qC_arom),

129.8 (CH_arom), 129.5 (CH_arom), 129.0 (C_qC_arom), 128.6−127.2

(CH_arom), 100.5 (C-1′), 86.2 (C-1), 81.6 (C-3), 78.8 (C-5), 77.5

(C-4′), 77.1 (C-4), 74.8 (CH₂Bn), 74.5 (CH₂Bn), 74.5 (C-5′), 74.1

(C-3′), 73.5 (CH₂Bn), 72.2 (C-2′), 71.9 (C-2), 67.6 (C-6), 67.5 (CH₂

CO₂Bn), 37.7 (CH₂Lev), 29.5 (CH₃Lev), 27.8 (CH₂Lev), 21.1 (CH₃

STol). HRMS: [M + Na]⁺calcd for C₆₆H₆₂O₁₆SNa 1165.36508, found

1165.36484.

4.95 (s, CH₂Bn ether α), 5.54 (d, J = 11.2 Hz, CHHPh β), 4.49 (d, J =

11.2 Hz, CHHPh β), 4.08 (d, J = 9.6 Hz, H-5 β), 4.04 (t, J = 9.2 Hz,

H-4 α), 3.98 (t, J = 9.6 Hz, H-4 β), 2.59−2.26 (m, 2 × CH₂Lev, CH₃

Lev), 2.02 (s, CH₃Lev α), 1.98 (s, CH₃Lev β). ¹³C NMR (100 MHz,

CDCl₃, HH-COSY, HSQC): 205.7 (CO Lev ketone β), 205.6 (C

O Lev ketone α), 171.6 (CO), 171.5 (CO), 168.5 (CO), 165.4

(CO), 165.1 (CO), 165.0 (CO), 138.7−137.4 (C_qC_arom), 134.9

(C_qC_arom), 133.5−132.3 (CH_arom), 131.9 (CH_arom), 130.0−129.1

(CH_arom), 128.9−128.8 (C_qC_arom), 128.6−127.4 (CH_arom), 127.2 (C_q

C_arom), 86.6 (C-1 β), 86.3 (C-1 α), 74.1 (C-5 β), 77.2 (C-4 α), 77.0

(C-4 β), 75.1 (C-3 β), 74.6 (CH₂Bn β), 74.6 (CH₂Bn α), 71.3

(C-3 α), 70.8 (C-2 α), 70.7 (C-5 α), 70.3 (C-2 β), 67.4 (CH₂CO₂Bn

β), 67.4 (CH₂CO₂Bn α), 37.7 (CH₂Lev), 29.5 (CH₃Lev), 27.8 (CH₂

Lev), 21.0 (CH₃STol). HRMS: [M + Na]⁺calcd for C₃₉H₃₈O₉SNa

705.21287, found 705.21230.

Benzyl (Phenyl 2-O-benzoyl-4-O-benzyl-3-O-levulinyl-1-thio-α/β-

D-glucopyranosyluronate) (23b). The title compound was isolated as

a clear oil and as an anomeric mixture. IR (neat, cm⁻¹): 1744, 1721,

1404, 1358, 1315, 1265, 1207, 1179, 1155, 1092, 1070, 1026, 999, 972,

908, 733, 712, 698. ¹H NMR (400 MHz, CDCl₃, HH-COSY, HSQC):

8.04−8.00 (m, 3H, H_arom), 7.59−7.57 (m, 1.6H, H_arom), 7.47−7.15 (m,

27.6H, H_arom), 5.97 (d, 1H, 0.4H, J = 5.6 Hz, H-1 α), 5.66 (t, 1H, J = 9.2

Hz, H-3 α), 5.43 (t, 1H, J = 9.2 Hz, H-3 β), 5.29−5.15 (m, 4.3H, H-2 α,

CH₂CO₂Bn, H-2 β), 4.97 (d, 1H, J = 9.6 Hz, H-5 α), 4.86 (d, 1H, J =

10.0 Hz, H-1β), 4.59 (s, 1H, CH₂Bn α), 4.54 (d, 1H, J = CHHPh β),

5.50 (d, 1H, J = CHHPh β), 4.10 (d, 1H, J = 9.6 Hz, H-5 β), 4.07−4.05

(m, 1.53H, H-4 α, H-4 β), 2.57−2.55 (m, 1H, CHH Lev), 2.46−2.32

(m, 5H, CH₂Lev α and β), 2.03 (s, 1.36H, CH₃Lev α), 1.97 (s, 2.85H,

CH₃Lev β). ¹³C NMR (100 MHz, CDCl₃, HH-COSY, HSQC): 205.6

(CO Lev ketone), 171.7 (CO), 167.3 (CO), 165.3 (CO),

137.4 (C_qC_arom), 133.6−132.6 (CH_arom), 131.6 (C_qC_arom), 130.1−

130.0 (CH_arom), 129.0 (C_qC_arom), 128.9−127.8 (CH_arom), 86.6 (C-1 α),

86.0 (C-1 β), 78.2 (C-5 β), 77.3 (C-4 α), 77.2 (C-4 β), 75.4 (C-3 β),

74.7 (CH₂Bn β), 74.7 (CH₂Bn α), 71.7 (C-3 α), 71.2 (C-2 α), 71.0

(C-5 α), 70.4 (C-2 β), 67.5 (CH₂CO₂Bn β), 67.4 (CH₂CO₂Bn α),

37.8 (CH₂Lev α), 37.7 (CH₂Lev β), 29.5 (CH₃Lev), 27.9 (CH₂Lev).

HRMS: [M + Na]⁺calcd for C₃₈H₃₆O₉SNa 691.19722, found

691.19684.

1,6-Anhydro-2-O-benzyl-4-O-(benzyl (2-O-benzoyl-4-O-benzyl-3-

O-levulinyl-β-^D-glucopyranosyluronate))-2-O-benzoyl-β-D-glucopyr-

anoside (22). Donor 17 (1.15 g mg, 1.54 mmol, 1.8 equiv) and

acceptor 20 (491 mg, 0.86 mmol) were coevaporated with toluene (2×)

and dissolved in freshly distilled DCM (1.72 mL, 0.5 M). Activated MS

3 Å were added, and the reaction mixture was stirred for 30 min. The

reaction mixture was cooled to 0 °C, followed by addition of TfOH

(0.14 μL, 0.154 mmol, 0.1 equiv). After 5 min, TLC analysis (PE/

EtOAc 12/8, v/v) showed total conversion of the acceptor. The

reaction mixture was neutralized with TEA, diluted, washed with H₂O,

dried over MgSO₄, filtered, and concentrated. Column chromatography

(PE/EtOAc 1/0 → 7/3), followed by SEC DCM/MeOH 1/1) gave the

title compound as a clear oil in 10% yield (81 mg, 0.089 mmol). [α]²⁰

:

D

−6.0 (c = 1, DCM). IR (neat, cm⁻¹): 1746, 1719, 1362, 1316, 1265,

1,6-Anhydro-2-O-benzoyl-3-O-benzyl-4-O-levulinyl-β-^D-glucopyr-

1

1215, 1179, 1150, 1094, 1070, 1026, 1009, 1001, 750, 712, 698. H

anoside (26b). The title compound was isolated as a transparent oil

NMR (400 MHz, CDCl₃, HH-COSY, HSQC): 8.05 (d, 2H, J = 7.6 Hz,

H_arom), 7.95 (d, 2H, J = 7.2 Hz, H_arom), 7.61−7.06 (m, 21H, H_arom), 5.45

(s, 1H, H-1), 5.37 (1, 1H, J = 8.4 Hz, H-3′), 5.26 (t, 1H, J = 9.6 Hz,

H-2′), 5.06 (d, 1H, J = 12.0 Hz, CHHPh), 5.01 (d, 1H, J = 12.0 Hz,

CHHPh), 4.91 (s, 1H, H-2), 4.74 (d, 1H, J = 13.6 Hz, CHHPh), 4.71

(d, 1H, J = 7.6 Hz, H-1′), 4.54−4.44 (m, 4H, CH₂Bn, CHHPh, H-5),

3.99 (d, 1H, J = 7.6 Hz, H-6), 4.02−3.95 (m, 2H, H-4′, H-5′), 3.78 (s,

1H, H-3 or H-4), 3.74 (s, 1H, H-3 or H-4), 3.68 (t, 1H, J = 6.4 Hz,

H-6), 2.52−2.40 (m, 2H, CH₂Lev), 2.38−2.34 (m, 2H, CH₂Lev), 2.18

(s, 3H, CH₃Lev). ¹³C NMR (100 MHz, CDCl₃, HH-COSY, HSQC):

205.7 (CO Lev ketone), 171.7 (CO), 167.3 (CO), 165.7 (C

O), 165.1 (CO), 137.7 (C_qC_arom), 137.4 (C_qC_arom), 134.7 (C_q

C_arom), 133.3−133.2 (CH_arom), 131.9−129.3 (CH_arom), 128.8−128.5

(C_qC_arom), 128.5−127.5 (CH_arom), 100.2 (C-1′), 99.4 (C-1), 77.0 (C-4′

or C-5′), 76.9 (C-3 or C-4), 76.4 (C-3 or C-4), 74.7 (CH₂Bn), 74.6

(C-4′ or C-5′), 74.1 (C-3), 73.6 (C-5), 72.4 (CH₂Bn), 71.9 (C-2′), 68.9

(C-2), 67.5 (CH₂Bn ester), 64.8 (C-6), 37.6 (CH₂Lev), 29.6 (CH₃

Lev), 27.8 (CH₂Lev). HRMS: [M + Na]⁺calcd for C₅₂H₅₀O₁₅Na

937.30419, found 937.30413.

Benzyl (Tolyl 2-O-benzoyl-4-O-benzyl-3-O-levulinyl-1-thio-α/β-^D-

glucopyranosyluronate) (23a). The title compound was isolated

during the glycosylation of glucuronic acid ester 17 with glucoside 20a

in 53% yield (341 mg, 0.46 mmol, α/β 1/3). IR (neat, cm⁻¹): 1744,

1721, 1493, 1452, 1402, 1358, 1315, 1263, 1206, 1177, 1153, 1090,

1069, 1026, 997, 972, 908, 847, 810, 735, 710, 696, 640. ¹H NMR (400

MHz, CDCl₃, HH-COSY, HSQC): 8.05−8.00 (m, H_arom), 7.58−7.56

(m, H_arom), 7.47−7.14 (m, H_arom), 7.04−6.95 (m, H_arom), 5.89 (d, J = 5.6

Hz, H-1 α), 5.66 (t, J = 9.2 Hz, H-3 β), 5.42 (t, J = 9.2 Hz, H-3 β), 5.26

(dd, J = 4.8 Hz, J = 10.0 Hz, H-2 α), 5.21 (s, CH₂Bn ester), 5.14 (t, J =

9.6 Hz, H-2 β), 5.00 (d, J = 9.2 Hz, H-5 α), 4.79 (d, J = 10.0 Hz, H-1 β),

(185 mg, 0.41 mmol, 34% yield with respect to the donor 19). [α]²⁰

:

D

+30.9 (c = 3.6, DCM). IR (neat, cm⁻¹): 1717, 1362, 1337, 1315, 1265,

1207, 1179, 1148, 1109, 1098, 1070, 1047, 1026, 1009, 1001, 932, 903,

1

885, 733, 712, 700, 617. H NMR (400 MHz, CDCl₃, HH-COSY,

HSQC): 8.11−8.00 (m, 2H, H_arom), 7.59−7.57 (m, 1H, H_arom), 7.49−

7.44 (m, 2H, H_arom), 7.38−7.11 (m, 5H, H_arom), 5.60 (s, 1H, H-1), 5.00

(s, 1H, H-2 or H-4), 4.84 (s, 1H, H-5), 4.83 (d, 1H, J = 11.2 Hz,

CHHPh), 4.69 (d, 1H, J = 11.2 Hz, CHHPh), 4.65 (d, 1H, J = 5.2 Hz,

H-2 or H-4), 4.25 (d, 1H, J = 7.2 Hz, H-6), 3.80 (t, 1H, J = 6.8 Hz, H-

6), 3.65 (d, 1H, H-3), 2.79−2.54 (m, 4H, 2 × CH₂Lev), 2.11 (s, 3H,

CH₃Lev). ¹³C NMR (100 MHz, CDCl₃, HH-COSY, HSQC): 206.1

(CO Lev ketone), 171.9 (CO), 165.3 (CO), 137.4 (C_qC_arom),

133.4 (CH_arom), 129.7 (CH_arom), 129.4 (C_qC_arom), 128.4−127.5

(CH_arom), 99.5 (C-1), 75.6 (C-3), 73.6 (C-2 or C-4), 72.3 (CH₂Bn),

71.0 (C-5), 69.3 (C-2 or C-4), 65.1 (C-6), 37.7 (CH₂Lev), 29.6 (CH₃

Lev), 28.0 (CH₂Lev). HRMS: [M + Na]⁺calcd for C₂₅H₂₈O₇Na:

463.17272, found 463.17281.

2,6-Di-O-benzoyl-3-O-benzyl-4-O-levulinyl-α/β-^D-glucopyranose

(28). Glucoside 27 (1.23 g, 1.80 mmol) was dissolved in DCM (18 mL,

0.1 M), and the reaction mixture was cooled to 0 °C. NIS (445 mg, 1.98

mmol, 1.1 equiv) and TFA (152 μL, 1.98 mmol) were added, and the

reaction mixture was allowed to warm to rt. After 3 h, the reaction

mixture was cooled to 0 °C, followed by addition of piperidine (535 μL,

5.40 mmol, 3 equiv). The reaction mixture was allowed to warm to rt,

and TLC analysis (PE/EtOAc 12/8, v/v) showed total conversion into

a lower running spot. The reaction mixture was quenched with Na₂S₂O₃

(aq, satd), diluted with DCM, followed by separation of the layers. The

organic layer was washed with 1 M HCl, NaHCO₃(aq, satd), dried over

MgSO₄, filtered, and concentrated. The yellow oil obtained was purified

by column chromatography (PE/EtOAc 1/0 → 6/4) yielding the title

115

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compound as a transparent oil in 85% yield (882 mg, 1.53 mmol). IR

(neat, cm⁻¹): 3412, 1719, 1601, 1452, 1362, 1315, 1267, 1207, 1177,

1152, 1110, 1098, 1069, 1049, 1026, 989, 972, 937, 764, 750, 712, 689. α

anomer: ¹H NMR (400 MHz, CDCl₃, HH-COSY, HSQC): 8.08−8.01

(m, 5H, H_arom), 7.60−7.53 (m, 2H, H_arom), 7.48−7.26 (m, 4H, H_arom),

7.21−7.18 (m, 4H, H_arom), 5.59 (t, 1H, J = 3.6 Hz, H-1), 5.31 (t, 1H, J =

9.2 Hz, H-4), 5.13 (dd, 1H, J = 3.2 Hz, J = 10.0 Hz, H-2), 4.76 (d, 1H,

J = 11.6 Hz, CHHPh), 4.69 (d, 1H, J = 11.6 Hz, CHHPh), 4.57 (d, 1H,

J = 10.0 Hz, H-6), 4.38−4.31 (m, 2H, H-5, H-6), 4.28 (t, 1H, J = 9.6 Hz,

H-3), 3.31 (d, 1H, J = 3.2 Hz, OH), 2.70−2.64 (m, 2H, CH₂Lev),

2.57−2.35 (m, 2H, CH₂Lev), 2.11 (s, 3H, CH₃Lev). ¹³C NMR (100

MHz, CDCl₃, HH-COSY, HSQC): 206.3 (CO ketone), 171.5 (C

O Lev), 166.4 (CO Bz), 165.7 (CO Bz), 138.0 (C_qC_arom), 133.6−

133.1 (CH_arom), 129.9 (CH_arom), 129.8 (C_qC_arom), 129.4−127.6

(CH_arom), 90.4 (C-1), 76.9 (C-3), 75.0 (CH₂Bn), 73.9 (C-2), 70.4

(C-4), 67.9 (C-5), 62.6 (C-6), 37.8 (CH₂Lev), 29.7 (CH₃Lev), 27.9

(CH₂Lev). HRMS: [M + Na]⁺calcd for C₃₂H₃₂O₁₀Na 599.18877,

found 599.18785.

were coevaporated with toluene (2×) and dissolved in freshly distilled

DCM (6.1 mL, 0.1 M), followed by addition of activated MS 3 Å. The

reaction mixture was stirred for 30 min and then cooled to 0 °C. TfOH

(305 μL of 0.2 M stock solution, 0.061 mmol, 0.1 equiv) was added, and

the reaction mixture was allowed to warm to rt. After 15 min, TLC

analysis (PE/EtOAc 12/8, v/v) showed total consumption of the

acceptor. The reaction mixture was neutralized with TEA, diluted with

DCM, washed with H₂O and brine, dried over MgSO₄, filtered, and

concentrated. Column chromatography (PE/EtOAc 1/0 → 1/1)

followed by SEC gave disaccharide 34 as a colorless oil in 64% yield

(444 mg, 0.39 mmol). [α]²⁰_D: +19.2 (c = 1, DCM). IR (neat, cm⁻¹):

1719, 1452, 1362, 1315, 1263, 1204, 1177, 1148, 1090, 1067, 1026, 991,

1

972, 910, 845, 933, 698, 638, 617. H NMR (400 MHz, CDCl₃, HH-

COSY, HSQC): 8.01 (d, 2H, J = 7.6 Hz, H_arom), 7.96 (d, 2H, J = 7.2 Hz,

H_arom), 7.92 (d, 2H, J = 7.6 Hz, H_arom), 7.67−7.65 (m, 1H, H_arom),

7.59−7.57 (m, 1H, H_arom), 7.54−7.50 (m, 2H, H_arom), 7.45−7.35 (m,

3H, H_arom), 7.33−7.23 (m, 10H, H_arom), 7.19−7.08 (m, 11H, H_arom),

7.00−6.98 (m, 2H, H_arom), 5.31 (t, 1H, J = 8.8 Hz, H-2′), 5.22 (t, 1H, J =

8.8 Hz, H-2), 5.19 (t, 1H, J = 9.2 Hz, H-4′), 5.13 (d, 1H, J = 12.8 Hz,

CHH CO₂Bn), 5.09 (d, 1H, J = 12.8 Hz, CHH CO₂Bn), 4.98 (d, 1H,

J = 11.2 Hz, CHHPh), 4.86 (d, 1H, J = 8.0 Hz, H-1′), 4.67 (d, 1H, J =

10.0 Hz, H-1), 4.51 (d, 1H, J = 10.8 Hz, CHHPh), 4.51−4.47 (m, 1H,

H-6′), 4.44 (s, 2H, CH₂Bn), 4.24 (t, 1H, J = 8.8 Hz, H-3), 4.21 (dd, 1H,

J = 6.0 Hz, J = 12.4 Hz, H-6′), 3.99 (t, 1H, J = 9.2 Hz, H-4), 3.90 (d, 1H,

J = 9.6 Hz, H-5), 3.74−3.69 (m, 1H, H-5′), 3.62 (t, 1H, J = 9.2 Hz,

H-3′), 2.62−2.58 (m, 2H, CH₂Lev), 2.50−2.38 (m, 1H, CHH Lev),

2.38−2.29 (m, 1H, CHH Lev), 2.07 (s, 3H, CH₃Lev). ¹³C NMR (100

MHz, CDCl₃, HH-COSY, HSQC): 206.0 (CO Lev ketone), 171.3

(CO), 167.2 (CO, 166.0 (CO), 165.0 (CO), 164.3 (CO0,

2,6-Di-O-benzoyl-3-O-benzyl-4-O-levulinyl-1-O-(N-phenyltrifluoro-

acetimidoyl)-α/β-^D-glucopyranoside (29). Hemiacetal 28 (149 mg,

0.26 mmol) was dissolved in acetone (2.6 mL, 0.1 M), and the reaction

mixture was cooled to 0 °C. To this mixture were added N-phenyl-2,2,2-

trifluoroacetimidoyl chloride (80 μL, 0.52 mmol, 2 equiv) and Cs₂CO₃

(85 mg, 0.26 mmol, 1 equiv). The reaction mixture was allowed to

warm to rt, and after 2 h, TLC analysis showed total conversion into a

higher running spot (PE/EtOAc 12/8, v/v, R_f0.76). The reaction

mixture was filered over Celite and concentrated. Column chromatog-

raphy (PE/EtOAc 1/0 → 6/4) gave the title compound as a transparent

oil in 77% yield (α/β: 8/1). IR (neat, cm⁻¹): 1717, 1452, 1364, 1315,

1265, 1207, 1152, 1109, 1098, 1069, 1026, 926, 908, 895, 773, 735, 710,

137.9 (C_qC_arom), 137.3 (C_qC_arom), 135.0 (C_qC_arom), 133.5 (CH_arom

,

1

133.0 (CH_arom), 132.9 (C_qC_arom), 132.1 (CH_arom), 129.8 (CH_arom),

129.7 (CH_arom), 129.7 (CH_arom), 129.4−129.3 (C_qC_arom), 128.8−127.4

(CH_arom), 100.4 (C-1′), 87.2 (C-1), 80.3 (C-3), 79.8 (C-3′), 78.1

(C-5), 76.7 (C-4), 74.9 (CH₂Bn), 74.0 (CH₂Bn), 73.3 (C-2′), 72.3

(C-2), 72.2 (C-3′), 70.5 (C-4′), 67.2 (CH₂CO₂Bn), 63.0 (C-6′), 37.7

(CH₂Lev), 29.6 (CH₃Lev), 27.7 (CH₂Lev). HRMS: [M + Na]⁺calcd

for C₆₅H₆₀O₁₆SNa 1151.34943, found 1151.34865.

696, 633, 617. α anomer: H NMR (50 °C, 400 MHz, CDCl₃, HH-

1

COSY, HSQC): H NMR: 8.07−7.93 (m, 4H, H_arom), 7.60−7.23 (m,

7H, H_arom), 7.19−6.96 (m, 8H, H_arom), 6.59 (bs, 1H, H-1), 6.45−6.43

(m, 1H, H_arom), 5.39−5.31 (m, 2H, H-2, H-4), 4.722 (s, 2H, CH₂Bn),

5.54 (d, 1H, J = 12.0 Hz, H-6), 4.39 (dd, 1H, J = 5.2 Hz, J = 12.4 Hz,

H-6), 4.28−4.24 (m, 2H, H-3, H-5), 2.69−2.44 (m, 4H, 2 × CH₂Lev),

2.08 (s, 3H, CH₃Lev). ¹³C NMR (100 MHz, CDCl₃, HH-COSY,

HSQC): 205.4 (CO Lev ketone), 171.3 (CO Lev), 166.1 (CO

Bz), 165.2 (CO Bz), 143.0 (C_qC_arom), 137.9 (C_qC_arom), 133.5

(CH_arom), 133.3 (CH_arom), 133.0 (CH_arom), 130.1 (C_qC_arom), 129.9

(CH_arom), 129.8 (C_qC_arom), 129.4−127.7 (CH_arom), 124.4 (CH_arom),

119.2 (CH_arom), 93.0 (C-1), 77.2 (C-3 or C-5), 75.0 (CH₂Bn), 72.3

(C-2), 71.1 (C-3 or C-5), 70.1 (C-4), 62.6 (C-6), 37.9 (CH₂Lev), 29.4

(CH₃Lev), 28.1 (CH₂Lev). HRMS: [M + Na]⁺calcd for C₄₀H₃₆F₃

NO₁₀Na 770.21835, found 770.21854.

Tolyl 3-O-Benzyl-4-O-(benzyl (2-O-benzoyl-4-O-benzyl-3-O-levu-

linyl-β-^D-glucopyranosyluronate))-2,6-di-O-benzoyl-1-thio-β-D-glu-

copyranoside (32). Glucuronic acid ester donor 17 (260 mg,

0.35 mmol, 1 equiv) and glucoside acceptor 31 (275 mg, 0.46 mmol, 1.3

equiv) were coevaporated with toluene (2×) and dissolved in freshly

distilled DCM (3.5 mL, 0.1 M). Activated MS 3 Å were added, and the

reaction mixture was stirred for 30 min. The reaction mixture was

cooled to 0 °C, followed by addition of TfOH (175 μL of 0.2 M stock

solution, 0.035 mmol, 0.1 equiv). The reaction mixture was allowed to

warm to rt. After 10 min, TLC analysis (Tol/EtOAc 16/4, v/v) showed

total consumption of the donor. The reaction mixture was neutralized

with TEA, diluted with DCM, washed with H₂O, dried over MgSO₄,

filtered, and concentrated, yielding a yellow oil. Column chromatog-

raphy (PE/EtOAc 1/0 → 6/4) followed by SEC (MeOH/DCM 1/1)

gave the title compound as a white solid in 68% yield (274 mg,

0.24 mmol). [α]²⁰_D: + 20.6 (c = 1.6, DCM). IR (neat, cm⁻¹): 1724, 1452,

1400, 1360, 1315, 1263, 1215, 1177, 1144, 1092, 1069, 1051, 1026,

980, 737, 710, 700. ¹H NMR (400 MHz, CDCl₃, HH-COSY, HSQC):

7.99−7.95 (m, 4H, H_arom), 7.88 (d, 2H, J = 7.6 Hz, H_arom), 7.59−7.51

(m, 2H, H_arom), 7.45−7.33 (m, 7H, H_arom), 7.28−7.14 (m, 10H,

H_arom), 7.12−7.05 (m, 7H, H_arom), 6.78 (d, 2H, J = 8.0 Hz, H_arom), 5.37

(t, 1H, J = 9.2 Hz, H-3′), 5.30 (t, 1H, J = 9.6 Hz, H-2′), 5.13 (t, 1H, J =

9.6 Hz, H-2), 5.05 (d, 1H, J = 12.0 Hz, CHHPh), 4.97 (d, 1H, J = 12.0

Hz, CHHPh), 4.90 (d, 1H, J = 7.6 Hz, H-1′), 4.89 (d, 1H, J = 11.6 Hz,

CHHPh), 4.64−4.53 (m, 2H, CHHPh, H-6), 4.48 (d, 1H, J = 11.2 Hz,

CHHPh), 4.44 (d, 1H, J = 11.2 Hz, CHHPh), 4.29 (dd, 1H, J = 4.4

Hz, J = 12.0 Hz, H-6), 4.05−4.00 (m, 2H, H-4, H-4′), 3.96 (d, 1H, J =

9.6 Hz, H-5′), 3.82 (t, 1H, J = 8.8 Hz, H-3), 3.56−3.53 (m, 1H, H-5),

2.56−2.32 (m, 4H, 2 × CH₂Lev), 2.16 (s, 3H, CH₃STol), 1.95 (s,

3H, CH₃STol). ¹³C NMR (100 MHz, CDCl₃, HH-COSY, HSQC):

205.6 (CO Lev ketone), 171.5 (CO), 167.3 (CO), 165.6

(CO), 165.0 (CO), 164.9 (CO), 138.1 (C_qC_arom), 137.8

(C_qC_arom), 137.2 (C_qC_arom), 134.7 (C_qC_arom), 134.0 (CH_arom), 133.9

Benzyl (Tolyl 2-O-benzoyl-4-O-benzyl-3-O-(3,6-di-O-benzyl-2-O-

benzoyl-4-O-levulinyl-1-thio-β-^D-glucopyranosyl)-α/β-D-glucopyra-

nosyluronate)) (30a). Glucoside donor 29 (88 mg, 0.12 mmol) and

glucuronic acid acceptor 20a (90 mg, 0.15 mmol, 1.3 equiv) were

coevaporated with toluene (2×) and dissolved in freshly distilled DCM

(1.2 mL, 0.1 M), followed by addition of activated MS 3 Å. The reaction

mixture was stirred for 30 min and then cooled to 0 °C. TfOH (120 μL

of 0.1 M stock solution, 0.012 mmol, 0.1 equiv) and the reaction

mixture were allowed to warm to rt. After 15 min, TLC analysis (PE/

EtOAc 12/8, v/v) showed total consumption of the donor. The reaction

mixture was neutralized with TEA, diluted with DCM, washed with

H₂O, dried over MgSO₄, filtered, and concentrated. Size-exclusion

chromatography (DCM/MeOH 1/1) gave the disaccharide 33 as a

transparent oil in 51% yield (69 mg, 0.06 mmol). IR (neat, cm⁻¹): 2920,

1719, 1601, 1493, 1452, 1402, 1632, 1315, 1263, 1209, 1177, 1148,

1092, 1067, 1026, 1001, 910, 845, 810, 737, 710, 698, 662, 637. The

identification was based on NMR analysis (400 MHz, CDCl₃, HSQC):

33α 5.76 (d, J = 4.8 Hz, H-1), 33β 4.59 (d, J = 9.6 Hz, H-1). ¹³C NMR

(100 MHz, CDCl₃, HH-COSY, HSQC): 33α 84.7 (C-1), 33β 87.5

(C-1). HRMS: [M + Na]⁺calcd for C₆₆H₆₂O₁₆SNa 1165.36508, found

1165.36444.

Benzyl (Phenyl 2-O-benzoyl-4-O-benzyl-3-O-(2,6-di-O-benzoyl-3-

O-benzyl-4-O-levulinyl-β-^D-glucopyranoside)-1-thio-β-D-glucopyra-

nosyluronate)) (30b). Glucoside donor 29 (593 mg, 0.79 mmol, 1.3

equiv) and glucuronic acid ester acceptor 20b (354 mg, 0.61 mmol)

116

dx.doi.org/10.1021/jo201586r | J. Org. Chem. 2012, 77, 108−125

The Journal of Organic Chemistry

Article

(CH_arom), 133.4 (CH_arom), 133.0 (CH_arom), 129.8−127.8 (CH_arom),

127.5 (C_qC_arom), 127.3 (CH_arom), 100.9 (C-1′), 85.6 (C-1), 81.7

(C-3), 77.8 (C-4 or C-4′), 77.3 (C-4 or C-4′), 76.7 (C-5), 75.0 (CH₂

Bn), 74.6 (C-5′), 74.6 (CH₂Bn), 73.8 (C-3′), 72.2 (C-2′), 71.7 (C-2),

67.5 (CH₂CO₂Bn), 62.3 (C-6), 37.6 (CH₂Lev), 29.4 (CH₃Lev), 27.8

(CH₂Lev), 21.0 (CH₃STol). HRMS: [M + Na]⁺calcd for

C₆₆H₆₂O₁₆SNa 1165.36508, found 1165.36540.

H-2″), 5.13 (t, 1H, J = 9.2 Hz, H-2′), 5.03 (d, 1H, J = 11.2 Hz, CHHPh),

4.94 (d, 1H, CHH CO₂Bn), 4.88 (d, 1H, CHH CO₂Bn), 4.78 (d, 1H,

J = 11.6 Hz, CHHPh), 4.76 (d, 1H, J = 8.0 Hz, H-1″), 4.69 (d, 1H, J =

8.0 Hz, H-1), 4.67−4.54 (m, 4H, H-6″, CH₂Ph), 4.54−4.45 (m, 4H, 2 ×

CH₂Ph), 4.25 (d, 1H, J = 10.0 Hz, H-5″), 4.25 (d, 1H, J = 8.0 Hz, H-1′),

4.12 (t, 1H, J = 8.8 Hz, H-3), 4.02−3.95 (m, 2H, H-4′, H-4), 3.90 (d,

1H, J = 9.6 Hz, H-5′), 3.91−3.55 (m, 3H, CHH N₃(CH₂)₆OH, H-4″,

H-3′), 3.46 (dd, 1H, J = 3.2 Hz, J = 8.0 Hz, H-6^a), 3.41 (t, 1H, J =

9.2 Hz, H-3″), 3.30 (d, 1H, J = 10.0 Hz, H-6^b), 3.28−3.24 (m, 1H, CHH

N₃(CH₂)₆OH), 3.08−3.05 (m, 1H, H-5), 3.0 (dt, 2H, J = 2.0 Hz, J = 6.8

Hz, CH₂N₃(CH₂)₆OH), 2.81 (d, 1H, J = 3.2 Hz, OH), 1.58−1.26 (m,

4H, 2 × CH₂N₃(CH₂)₆OH), 1.16−1.09 (m,4H, 2 × CH₂

N₃(CH₂)₆OH). ¹³C NMR (100 MHz, CDCl₃, HH-COSY, HSQC,

HMBC): 167.5 (CO CO₂Bn), 167.2 (CO Bz), 165.2 (CO Bz),

164.9 (CO Bz), 163.8 (CO Bz), 138.4−137.5 (C_qC_arom), 134.9

(C_qC_arom), 133.6−132.9 (CH_arom), 130.1 (C_qC_arom), 130.0−129.7

(CH_arom), 129.7−129.6 (C_qC_arom),129.3−127.0 (CH_arom), 101.3 (C-1′),

100.9 (C-1″), 100.4 (C-1), 82.0 (C-3″), 80.3 (C-3′), 79.7 (C-3), 77.5

(C-4), 77.3 (C-4′), 74.8 (CH₂Bn), 74.8 (C-5′), 74.8 (CH₂Bn), 74.7

(C-5), 74.6 (CH₂Bn), 74.1 (C-3′), 73.9 (C-2 and C-5″), 73.5 (CH₂

Bn), 73.4 (C-2″), 73.1 (C-2′), 70.3 (C-4″), 69.3 (CH₂N₃(CH₂)₆OH),

67.4 (C-6), 67.3 (CH₂CO₂Bn), 63.5 (C-6″), 51.1 (CH₂N₃(CH₂)₆OH),

29.1 (CH₂N₃(CH₂)₆OH), 28.5 (CH₂N₃(CH₂)₆OH), 26.2 (CH₂

N₃(CH₂)₆OH), 25.3 (CH₂N₃(CH₂)₆OH). HRMS: [M + Na]⁺calcd

for C₈₇H₈₇N₃O₂₁Na 1532.57243, found 1532.57327.

6-Azidohexyl 2-O-Benzoyl-3,6-di-O-benzyl-4-O-[benzyl (2-O-ben-

zoyl-4-O-benzyl-3-[2,6-di-O-benzoyl-3-O-benzyl-4-O-levulinyl-β-^D-

glucopyranosyl]-β-^D-glucopyranosyluronate)]-β-D-glucopyranoside

(33). Disaccharide 30b (102 mg, 0.09 mmol) and acceptor glucoside

13 (69 mg, 0.117 mmol, 1.3 equiv) were glycosylated according to the

general procedure for glycosylations using NIS/TfOH. Trisaccharide 37

was obtained as a transparent oil in 75% yield (108 mg, 0.067 mmol).

R_f: 0.49 (Tol/EtOAc 4/1, v/v). [α]²⁰_D: + 11.0 (c = 1, DCM, cm⁻¹). IR

(neat): 2872, 2095, 1722, 1452, 1418, 1402, 1362, 1315, 1263, 1209,

1

1177, 1140, 1092, 1069, 1026, 1001, 910, 847, 733, 700, 638, 617. H

NMR (400 MHz, CDCl₃, HH-COSY, HSQC, HMBC): 7.99 (d, 2H,

J = 7.2 Hz, H_arom), 7.88 (d, 2H, J = 7.2 Hz, H_arom), 7.75 (d, 3H, J = 7.2

Hz, H_arom), 7.74−7.57 (m, 1H, H_arom), 7.56−6.96 (m, 37H, H_arom), 5.30

(t, 1H, J = 9.2 Hz, H-2″), 5.21−5.16 (m, 2H, H-4″, H-2), 5.11 (t, 1H, J =

9.2 Hz, H-2′), 4.97 (d, 1H, J = 11.2 Hz, CHHPh), 4.96 (d, 1H, J = 12.0

Hz, CHH CO₂Bn), 4.91 (d, 1H, J = 12.0 Hz, CHH CO₂Bn), 4.79 (d,

1H, J = 10.4 Hz, CHHPh), 4.77 (d, 1H, J = 7.6 Hz, H-1″), 4.65 (d, 1H,

J = 8.0 Hz, H-1), 4.57 (d, 1H, CHHPh), 4.51 (dd, 1H, J = 2.8 Hz, J =

12.0 Hz, H-6″), 4.47 (d, 2H, J = 10.8 Hz, CH₂Bn), 4.43 (s, 2H, CH₂

Bn), 4.25 (d, 1H, J = 8.0 Hz, H-1′), 4.24−4.17 (m, 2H, CHHPh, H-6″),

4.06 (t, 1H, J = 8.8 Hz, H-3), 3.98 (t, 2H, J = 8.4 Hz, H-4, H-4′), 3.86

(d, 1H, J = 9.2 Hz, H-5′), 3.78 (dt, 1H, J = 3.2, J = 9.6 Hz, H-5″), 3.73−

3.65 (m, 1H, CHH N₃(CH₂)₆OH), 3.65−3.59 (m, 2H, H-3″, H-3′),

3.43 (dd, 1H, J = 3.6 Hz, J = 11.2 Hz, H-6), 4.44 (d, 1H, J = 11.2 Hz, H-

6), 3.33−3.21 (m, 1H, CHH N₃(CH₂)₆OH), 3.04−3.02 (m, 1H, H-5),

3.00−2.95 (m, 2H, CH₂N₃(CH₂)₆OH), 2.65−2.60 (m, 2H, CH₂Lev),

2.45−2.44 (m, 1H, CHH Lev), 2.38−2.32 (m, 1H, CHH Lev), 2.08 (s,

3H, CH₃Lev), 1.50−1.20 (m, 4H, 2 × CH₂N₃(CH₂)₆OH), 1.19−1.05

(m, 4H, 2 × CH₂N₃(CH₂)₆OH). ¹³C NMR (100 MHz, CDCl₃, HH-

COSY, HSQC, HMBC): 206.2 (CO Lev ketone), 171.4 (CO),

167.5 (CO), 166.3 (CO), 165.0 (CO), 165.0 (CO), 163.9

(CO), 138.4 (C_qC_arom), 138.1 (C_qC_arom), 137.4 (C_qC_arom), 135.0

(C_qC_arom), 133.5−132.9 (CH_arom), 130.1 (C_qC_arom), 130.0−129.2

(CH_arom), 128.7 (C_qC_arom), 128.6 (C_qC_arom), 128.5 (C_qC_arom), 128.4−

127.1 (CH_arom), 101.1 (C-1′), 100.9 (C-1″), 100.4 (C-1), 80.3 (C-3′),

80.0 (C-3″), 79.9 (C-3), 77.5 (C-4 or C-4′), 77.1 (C-4 or C-4′), 75.0

(CH₂Bn), 74.8 (C-5′), 74.7 (C-5), 74.6 (CH₂Bn), 74.0 (CH₂Bn), 73.8

(C-2), 73.5 (CH₂Bn), 73.4 (C-2″), 73.1 (C-2′), 72.3 (C-5″), 70.6

(C-4″),69.3 (CH₂N₃(CH₂)₆OH), 67.4 (CH₂CO₂Bn), 67.3 (C-6), 63.2

(C-6″), 51.2 (CH₂N₃(CH₂)₆OH), 37.8 (CH₂Lev), 29.7 (CH₃Lev),

29.2 (CH₂Lev), 28.6 (CH₂N₃(CH₂)₆OH), 27.8 (CH₂N₃(CH₂)₆OH),

26.2 (CH₂N₃(CH₂)₆OH), 26.3 (CH₂N₃(CH₂)₆OH), 25.4

(CH₂N₃(CH₂)₆OH). HRMS: [M + Na]⁺calcd for C₉₂H₉₃N₃O₂₃Na

1630.60921, found 1630.60872.

6-Azidohexyl 2-O-Benzoyl-3,6-di-O-benzyl-4-O-[benzyl (2-O-ben-

zoyl-4-O-benzyl-3-[2,6-di-O-benzoyl-3-O-benzyl-β-^D-glucopyrano-

syl]-β-^D-glucopyranosyluronate)]-β-D-glucopyranoside (34). Trisac-

charide 33 (82 mg, 0.051 mmol) was dissolved in a mixture of pyridine/

AcOH (4/1, 0.51 mL, 0.1 M), and the reaction mixture was cooled to

0 °C. Hydrazine acetate (24 mg, 0.26 mmol, 5 equiv) was added, and

the reaction mixture was allowed to warm to rt. After 15 min, TLC

analysis (Tol./EtOAc 4/1) showed total conversion into a higher running

spot (R_f0.5). The reaction mixture was cooled to 0 °C, quenched with

acetone, diluted with EtOAc, washed with 1 M HCl and NaHCO₃

(aq, satd), dried over MgSO₄, filtered, and concentrated. Column

chromatography (PE/EtOAc 1/0 → 6/4) gave the title compound as

a colorless oil in 95% yield (73 mg, 0.048 mmol). [α]²⁰_D: + 16.7 (c =

0.86, DCM). IR (neat, cm⁻¹): 3065, 3034, 2928, 2869, 2253, 2099,

1728, 1603, 1497, 1452, 1418, 1362, 1315, 1265, 1213 1179, 1157, 1086,

1069, 1026, 905, 849. ¹H NMR (400 MHz, CDCl₃, HH-COSY, HSQC,

HMBC): 8.00 (d, 2H, J = 7.2 Hz, H_arom), 4.94 (d, 2H, J = 7.2 Hz,

H_arom), 7.92−7.78 (m, 3H, H_arom), 7.58−7.51 (m, 1H, H_arom), 7.51−7.40

(m, 5H, H_arom), 7.40−6.97 (m, 33H, H_arom), 5.23−5.16 (m, 2H, H-2,

6-Aminohexyl 4-O-(3-O-(β-^D-Glucopyranosyl)-β-D-glucopyrano-

syluronic acid)-β-^D-glucopyranoside (35). Trisaccharide 34 (66 mg,

43.7 μmol) was dissolved in dioxane (874 μL, 0.05 M) followed by

addition of KOH (0.5 M KOH in H₂O, 1.05 mL, 0.52 mmol, 12 equiv).

After the mixture was stirred overnight, more KOH was added

portionwise (52 μL, 0.26 mmol, 6 equiv, then 26 μL, 0.13 mmol,

3 equiv). After 6 days, LCMS analysis confirmed that the esters were

saponified. The reaction mixture was neutralized with H⁺Amberlite,

filtered, and concentrated. Size-exclusion chromatography (DCM/

MeOH 1/1) gave a white solid, which was dissolved in H₂O/^tBuOH

mixture (1/2, v/v, 486 μL, 0.09 M). A drop of 1 M HCl (aq) was added

followed by addition of Pd/C. The reaction mixture was purged with H₂

gas and stirred overnight. The reaction mixture was filtered over a

Whatman filter and concentrated. The obtained residue was subjected

to gel filtration (HW-40, 0.15 M NH₄HCO₃in H₂O) and subsequent

lyophilization. The deprotected trimer was obtained as a white solid in

1

44% yield over two steps (12 mg, 19.4 μmol). H NMR (600 MHz,

CDCl₃, HH-COSY, HSQC, TOCSY, HMBC): 4.75 (d, 1H, J = 7.8 Hz,

H-1″), 4.49 (d, 1H, J = 7.8 Hz, H-1′), 3.93 (d, 1H, J = 11.4 Hz, H-6^a″),

3.91−3.77 (m, 2H, H-6^a, CHH N₃(CH₂)₆OH), 3.77−3.72 (m, 3H, H-5,

H-3′, H-6^b″), 3.67 (dd, 1H, J = 6.0 Hz, J = 12.4 Hz, H-6^b), 3.67−3.63

(m, 1H, CHH N₃(CH₂)₆OH), 3.61−3.54 (m, 4H, H-3, H-4, H-4′,

H-5′), 5.53 (t, 1H, J = 9.0 Hz, H-2), 3.47 (t, 1H, J = 9.6 Hz, H-3″),

3.45−3.40 (m, 1H, H-5″), 3.35 (t, 1H, J = 9.6 Hz, H-4″), 3.30 (t, 1H, J =

9.0 Hz, H-2″), 3.24 (t, 1H, J = 9.0 Hz, H-2), 2.94 (t, 2H, J = 7.8 Hz,

CH₂N₃(CH₂)₆OH), 1.64−1.59 (m, 4H, 2 × CH₂N₃(CH₂)₆OH),

1.37−1.36 (m, 4H, 2 × CH₂N₃(CH₂)₆OH). ¹³C NMR (150 MHz,

CDCl₃, HH-COSY, HSQC, TOCSY, HMBC): 176.3 (CO), 103.5

(C-1″), 103.0 (C-1′), 102.9 (C-1), 83.5 (C-5), 79.8 (C-4 or C-4′ or C-

5′), 77.0 (C-5″), 76.7 (C-3′), 76.5 (C-3″), 75.7 (C-4 or C-4′ or C-5′),

75.3 (C-3), 74.4 (C-2″), 74.1 (C-2′), 73.8 (C-2), 71.4 (CH₂N₃(CH₂)₆-

OH), 71.2 (C-4 or C-4′ or C-5′), 70.5 (C-4″), 61.7 (C-6″), 61.0 (C-6),

40.3 (CH₂N₃(CH₂)₆OH), 29.4 (CH₂N₃(CH₂)₆OH), 27.6 (CH₂

N₃(CH₂)₆OH), 26.2 (CH₂N₃(CH₂)₆OH), 25.5 (CH₂N₃(CH₂)₆-

OH). HRMS: [M + H]⁺calcd for C₂₄H₄₄NO₁₇618.26038, found

618.26016.

Benzyl (6-Azidohexyl 2-O-benzoyl-4-O-benzyl-3-O-[2,6-di-O-ben-

zoyl-3-O-benzyl-4-O-[benzyl (2-O-benzoyl-4-O-benzyl-3-O-levulin-

yl-β-^D-glucopyranosyluronate)]-β-D-glucopyranosyl]-β-D-glucopyra-

nosyluronate) (36). Disaccharide 32 (90 mg, 0.08 mmol) and

glucuronic acid ester acceptor 10 (61 mg, 0.10 mmol, 1.3 equiv) were

condensed according to the general procedure for glycosylations using

NIS/TfOH. The title compound was isolated as a white solid in 54%

yield. R_f0.36 (PE/EtOAc 13/7). [α]²⁰_D: +6.1 (c = 1, DCM). IR (neat,

cm⁻¹): 2095, 1728, 1452, 1362, 1315, 1261, 1215, 1177, 1142, 1094,

117

dx.doi.org/10.1021/jo201586r | J. Org. Chem. 2012, 77, 108−125

The Journal of Organic Chemistry

Article

1069, 1026, 978, 910, 750, 710, 698. ¹H NMR (400 MHz, CDCl₃, HH-

COSY, HSQC, HMBC): 8.00−7.88 (m, 2H, H_arom),7.86−7.76 (m, 4H,

H_arom), 7.61−7.56 (m, 2H, H_arom), 7.48−7.35 (m, 11H, H_arom), 7.28−

7.09 (m, 15H, H_arom), 7.08−7.01 (m, 8H, H_arom), 7.08−6.95 (m, 3H,

H_arom), 5.33−5.20 (m, 3H, H-3″, H-2′, H-2″), 5.10−5.03 (m, 3H, H-2,

CH₂CO₂Bn), 5.02 (d, 1H, J = 12.4 Hz, CHH CO₂Bn), 4.94 (d, 1H, J =

12.4 Hz, CHH CO₂Bn), 4.85 (d, 1H, J = 11.2 Hz, CHHPh), 4.82 (d,

1H, J = 8.0 Hz, H-1′), 4.76 (d, 1H, J = 10.8 Hz, CHHPh), 4.76 (d, 1H,

J = 8.0 Hz, H-1″), 4.53 (d, 1H, J = 11.6 Hz, H-6), 4.48−4.34 (m, 4H,

2 × CH₂Bn), 4.35 (d, 1H, J = 7.6 Hz, H-1), 4.19 (dd, 1H, J = 4.4 Hz,

J = 12.0 Hz, H-6), 4.12 (t, 1H, J = 8.0 Hz, H-3), 4.05 (t, 1H, J = 8.8 Hz,

H-4′), 3.97 (t, 1H, J = 9.2 Hz, H-4″), 3.93 (t, 1H, J = 8.4 Hz, H-4), 3.88

(d, 1H, J = 8.4 Hz, H-5 or H-5″), 3.84 (d, 1H, J = 9.6 Hz, H-5 or H-5″),

3.71−3.64 (m, 2H, H-3, CHH N₃(CH₂)₆OH), 3.49−3.47 (m, 1H,

H-5′), 3.20-.3.14 (m, 1H, CHH N₃(CH₂)₆OH), 3.02 (t, 2H, J = 6.8 Hz,

CH₂N₃(CH₂)₆OH), 2.47−2.38 (m, 2H, CH₂Lev), 2.36−2.23 (m, 2H,

CH₂Lev), 1.97 (s, 3H, CH₃Lev), 1.26−1.17 (m, 4H, 2 × CH₂

N₃(CH₂)₆OH), 1.14−0.96 (m, 4H, 2 × CH₂N₃(CH₂)₆OH). ¹³C NMR

(100 MHz, CDCl₃, HH-COSY, HSQC, HMBC): 205.6 (CO Lev

ketone), 171.5 (CO), 168.2 (CO), 167.3 (CO), 165.6 (CO),

165.1 (CO), 164.4 (CO), 137.9 (C_qC_arom), 137.8 (C_qC_arom),

137.2 (C_qC_arom), 135.0 (C_qC_arom), 134.6 (C_qC_arom), 133.4 (CH_arom),

133.1 (CH_arom), 132.9 (CH_arom), 129.9 (C_qC_arom), 129.8 (C_qC_arom),

129.7−127.2 (CH_arom), 100.8 (C-1″), 100.5 (C-1), 99.7 (C-1′), 80.7 (C-

3′), 79.1 (C-3), 77.8 (C-4′), 77.3 (C-4″), 76.9 (C-4), 74.7 (CH₂Bn),

74.6 (CH₂Bn), 74.6 (CH₂Bn), 74.5 (C-5 or C-5″), 74.4 (C-5 or C-5″),

73.9 (C-3″), 73.5 (C-2), 73.3 (C-2′), 72.6 (C-5′), 72.1 (C-2″), 69.3 (CH₂

N₃(CH₂)₆OH), 67.5 (CH₂CO₂Bn), 67.2 (CH₂CO₂Bn), 62.4 (C-6′),

51.2 (CH₂N₃(CH₂)₆OH), 37.6 (CH₂Lev), 29.5 (CH₃Lev), 28.9 (CH₂

N₃(CH₂)₆OH), 28.5 (CH₂Lev), 27.8 (CH₂N₃(CH₂)₆OH), 26.1 (CH₂

N₃(CH₂)₆OH), 25.2 (CH₂N₃(CH₂)₆OH). HRMS: [M + Na]⁺calcd

for C₉₂H₉₁N₃O₂₄Na 1644.58847, found 1644.58818.

100.8 (C-1″), 100.5 (C-1), 100.0 (C-1′), 80.6 (C-3′), 79.6 (C-3″), 79.4

(C-3), 77.8 (C-4′), 76.9 (C-4), 74.9 (CH₂Bn), 74.9 (C-4″), 74.8 (CH₂

Bn), 74.6 (CH₂Bn), 74.5 (C-5 and C-5″), 74.1 (C-2″), 73.5 (C-2), 73.2

(C-2′), 72.8 (C-5), 69.3 (CH₂N₃(CH₂)₆OH), 67.4 (CH₂CO₂Bn), 67.2

(CH₂CO₂Bn), 62.6 (C-6′), 51.2 (CH₂N₃(CH₂)₆OH), 28.9 (CH₂

N₃(CH₂)₆OH), 28.5 (CH₂N₃(CH₂)₆OH), 26.2 (CH₂N₃(CH₂)₆OH),

25.2 (CH₂N₃(CH₂)₆OH). HRMS: [M + Na]⁺calcd for C₈₇H₈₅-

N₃O₂₂Na 1546.55169, found 1546.55288.

6-Aminohexyl 3-O-(4-O-(β-^D-Glucopyranosyluronic acid)-β-D-glu-

copyranosyl)-β-^D-glucopyranosyluronic Acid (38). Trisaccharide 37

(61 mg, 40 μmol) was dissolved in dioxane (800 μL, 0.05 M) followed

by addition of KOH (0.5 M KOH in H₂O, 0.96 mL, 0.48 mmol,

12 equiv). After the mixture was stirred overnight, more KOH was

added portionwise (48 μL, 0.26 mmol, 6 equiv, then 24 μL, 0.13 mmol,

3 equiv, then 24 μL, 0.13 mmol, 3 equiv). After 6 days, LCMS analysis

confirmed that the esters were saponified. The reaction mixture was

neutralized with H⁺Amberlite, filtered, and concentrated. Size-exclusion

chromatography (DCM/MeOH 1/1) gave a white solid, which was

dissolved in H₂O/^tBuOH mixture (1/2, v/v, 500 μL, 0.08 M). A drop of

1 M HCl (aq) was added followed by addition of Pd/C. The reaction

mixture was purged with H₂gas and stirred overnight. The reaction

mixture was filtered over a Whatman filter and concentrated. The

obtained residue was subjected to gel filtration (HW-40, 0.15 M

NH₄HCO₃in H₂O) and subsequent lyophilization. The deprotected

trimer was obtained as a fine white powder in 28% yield over two steps

1

(7 mg, 11 μmol). H NMR (600 MHz, D₂O, 283 K, HH-COSY,

HSQC, HMBC): 4.77 (d, 1H, J = 7.8 Hz, H-1′), 4.46 (d, 1H, J = 8.4 Hz,

H-1″), 4.44 (d, 1H, J = 7.8 Hz, H-1), 3.94 (d, 1H, J = 11.4 Hz, H-6^a),

3.90−3.80 (m, 1H, CHH N₃(CH₂)₆OH), 3.77−3.68 (m, 4H, H-3, H-4′,

H-5, H-6^b′), 3.65−3.62 (m, 2H, H-3″, CHH N₃(CH₂)₆OH), 3.60−3.55

(m, 2H, H-5′, H-5″), 3.48−3.44 (m, 3H, H-2, H-3′, H-4), 3.35−3.31 (m,

2H, H-2′, H-2″), 2.94 (t, 2H, J = 7.2 Hz, CH₂N₃(CH₂)₆OH), 1.6−1.58

(m, 4H, 2 × CH₂N₃(CH₂)₆OH), 1.37−1.36 (m, 4H, 2 × CH₂

N₃(CH₂)₆OH). ¹³C NMR (150 MHz, D₂O, HH-COSY, HSQC,

HMBC): 176.7 (CO), 176.6 (CO), 103.4 (C-1′), 103.3 (C-1″),

102.9 (C-1), 84.3 (C-3 or C-4′), 79.9 (C-5′ or C-5″), 77.2 (C-5), 76.8

(C-3 or C-4′), 76.2 (C-2 or C-3′), 75.8 (C-5′ or C-5″), 75.1 (C-3″), 74.1

(C-2″), 73.9 (C-4), 76.9 (C-2′), 72.7 (C-2 or C-3′), 71.7 (CH₂

N₃(CH₂)₆OH), 71.2 (C-4″), 61.0 (C-6), 40.4 (CH₂N₃(CH₂)₆OH),

29.4 (CH₂N₃(CH₂)₆OH), 27.6 (CH₂N₃(CH₂)₆OH), 26.1 (CH₂

N₃(CH₂)₆OH), 25.4 (CH₂N₃(CH₂)₆OH). HRMS: [M + Na]⁺calcd

for C₂₄H₄₁NO₁₈Na 654.22158, found 654.22136.

Benzyl (6-Azidohexyl 2-O-benzoyl-4-O-benzyl-3-O-[2,6-di-O-ben-

zoyl-3-O-benzyl-4-O-[benzyl (2-O-benzoyl-4-O-benzyl-β-^D-gluco-

pyranosyluronate)]-β-^D-glucopyranosyl]-β-D-glucopyranosyluro-

nate) (37). Trisaccharide 36 (24 mg, 0.015 mmol) was dissolved in a

mixture of pyridine/AcOH (4/1, 300 μL, 0.05 M), and the resulting

mixture was cooled to 0 °C. Hydrazine acetate (7 mg, 0.075 mmol,

5 equiv) was added, and the reaction mixture was allowed to warm to rt.

After 30 min, TLC analysis (PE/EtOAc 12/8) showed total conversion

into a slightly higher running spot (R_f0.82). The reaction mixture was

cooled to 0 °C and quenched with acetone. The reaction mixture was

diluted with EtOAc, washed with 1 M HCl and NaHCO₃(aq, satd),

dried over MgSO₄, filtered, and concentrated. Column chromatography

(PE/EtOAc 1/0 → 7/3) gave the title compound as an transparent oil

which crystallized on standing in 93% yield (21 mg, 0.014 mmol).

[α]²⁰_D: +16.2 (c = 0.4, DCM). IR (neat, cm⁻¹): 3696, 303, 2986, 2307,

1732, 1603, 1558, 1452, 1421, 1398, 1373, 1263, 1217, 1179, 1157,

Methyl (p-Tolyl 2,3-di-O-benzyl-1-thio-β-^D-glucopyranosyluro-

nate) (40). Glucoside 39³⁰(1.0 g, 2.14 mmol) was dissolved in a

mixture of DCM/H₂O (2/1, 10.7 mL, 0.2 M) (Scheme 5). The reaction

mixture was cooled to 0 °C, followed by addition of BAIB (1.72 g, 5.35

mmol, 2.5 equiv) and TEMPO (67 mg, 0.43 mmol, 0.2 equiv), The

reaction mixture was allowed to warm to rt, and after 2 h, TLC analysis

(PE/EtOAc 1/1, v/v) showed total conversion of the starting material.

The reaction mixture was quenched by addition of Na₂S₂O₃(aq, satd),

followed by separation of the layers. The aqueous layer was extracted

with EtOAc (2×), and the combined organic layers were dried over

MgSO₄, filtered, concentrated, and coevaporated with toluene. The

yellow oil obtained was dissolved in DMF (10.7 mL, 0.2 M) followed by

addition of MeI (0.4 mL, 6.42 mmol, 3 equiv) and K₂CO₃(0.89 g

6.42 mmol, 3 equiv). After 30 min, TLC analysis (PE/EtOAc 1/1, v/v)

showed total conversion of the glucuronic acid. The reaction mixture

was quenched with MeOH, diluted with DCM, washed with with brine,

dried over MgSO₄, filtered, and concentrated. Column chromatography

(PE/EtOAc 1/0 → 6/4) gave the target compound in 69% yield over

two steps (0.73 g, 1.48 mmol). [α]²⁰_D: −38.8 (c = 1, DCM). IR

(neat, cm⁻¹): 2870, 1746, 1493, 1454, 1439, 1398, 1356, 1279, 1265,

1238, 1209, 1175, 1130, 1059, 1018, 986, 908, 839, 808, 733, 696, 633,

1

1096, 1070, 1028, 1001, 986, 949, 895. H NMR (400 MHz, CDCl₃,

HH-COSY, HSQC, HMBC): 8.09 (d, 2H, J = 7.8 Hz, H_arom), 7.91−

7.86 (m, 4H, H_arom), 7.75 (d, 2H, J = 8.4 Hz, H_arom), 7.55−7.11 (m, 29

H, H_arom), 7.05−6.95 (m, 8H, H_arom), 5.25 (t, 1H, J = 8.8 Hz, H-2′), 5.15

(t, 1H, J = 8.8 Hz, H-2″), 5.04 (t, 1H, J = 8.8 Hz, H-2), 5.02 (s, 2H, CH₂

CO₂Bn), 5.01 (d, 1H, J = 12.0 Hz, CHHPh CO₂Bn), 4.96 (d, 1H, J =

12.0 Hz, CHHPh CO₂Bn), 4.89 (d, 1H, J = 11.2 Hz, CHHPh), 4.81 (d,

1H, J = 10.4 Hz, CHHPh), 4.81 (d, 1H, J = 8.4 Hz, H-1′), 4.69 (d, 1H,

J = 7.6 Hz, H-1″), 4.54 (d, 1H, J = 11.2 Hz, CHHPh), 4.49−4.44 (m,

3H, H-6′^a, 2 × CHHPh), 4.43 (d, 1H, J = 11.6 Hz, CHHPh), 4.40 (d,

1H, J = 8.4 Hz, H-1), 4.33 (dd, 1H, J = 4.8 Hz, J = 11.6 Hz, H-6′^b), 4.10

(t, 1H, J = 9.6 Hz, H-3), 4.08 (t, 1H, J = 9.6 Hz, H-4′), 3.95 (t, 1H, J =

10.0 Hz, H-4), 3.92 (d, 1H, J = 10.8 Hz, H-5), 3.80−3.68 (m, 4H, H-3″,

H-4″, H-5″, CHH N₃(CH₂)₆OH), 3.63 (t, 1H, J = 8.8 Hz, H-3′), 3.49−

3.46 (m, 1H, H-5′), 3.21−3.15 (m, 1H, CHH N₃(CH₂)₆OH), 3.02 (t,

2H, J = 6.8 Hz, CH₂N₃(CH₂)₆OH), 1.28−1.24 (m, 4H, 2 × CH₂

N₃(CH₂)₆OH), 1.23−1.08 (m, 4H, 2 × CH₂spacer). ¹³C NMR

(100 MHz, CDCl₃, HH-COSY, HSQC, HMBC): 168.1 (CO CO₂Bn),

167.6 (CO CO₂Bn), 165.8 (CO Bz or CO₂Bn), 165.7 (CO

or CO₂Bn), 165.1 (CO Bz), 164.4 (CO Bz), 138.0−137.5

(C_qC_arom), 135.0−134.8 (C_qC_arom), 133.5−132.8 (CH_arom), 130.0−

129.4 (CH_arom), 128.9−128.7 (C_qC_arom), 128.6−127.2 (CH_arom),

1

615, 604. H NMR (400 MHz, CDCl₃, HH-COSY, HSQC): 7.47 (d,

2H, J = 8.0 Hz, H_arom), 7.41−7.28 (m, 10H, H_arom), 7.11 (d, 2H, J = 8.0

Hz, H_arom), 4.88 (d, 1H, J = 10.8 Hz, CHHPh), 4.85 (m, 2H, CH₂Bn),

4.74 (d, 1H, J = 10.4 Hz, CHHPh), 4.63 (d, 1H, J = 9.6 Hz, H-1), 3.88

(t, 1H, J = 8.8 Hz, H-4), 3.82−3.80 (m, 4H, H-5, OCH₃), 3.57 (t, 1H,

J = 8.8 Hz, H-3), 3.45 (t, 1H, J = 9.2 Hz, H-2), 2.93 (bs, 1H, OH),

2.33 (s, 3H, CH₃STol). ¹³C NMR (100 MHz, CDCl₃, HH-COSY,

118

dx.doi.org/10.1021/jo201586r | J. Org. Chem. 2012, 77, 108−125

The Journal of Organic Chemistry

Article

a

Scheme 5. Synthesis of Thioglycosides 1, 2, 3, 12, and 27

a

Reagents and conditions: (a) pTsOH, MeOH (used without further purification); (b) (i) TEMPO, BAIB, DCM/H₂O, (ii) MeI, K₂CO₃, DMF, 40:

67%/two steps, 42: 61%/three steps; (c) (i) Ac₂O, Pyr, 1: 78%, 2: 82%; (d) BH₃·THF, Cu(OTf)₂, DCM, 46a: 66%, 46b: 66%; (e) (i) TEMPO,

BAIB, DCM/H₂O, (ii) BnBr, K₂CO₃, DMF, 47a: 17%/two steps, 47b: 56%/two steps.; (f) (i) Bu₂SnO, Tol, (ii) NAP-Br, CsF, DMF, 44a:

65%, 44b: 60%; (g) BzCl, Pyr, 45a: 80%, 45b: 84%; (h) DDQ, DCM/H₂O, 24a: 68%, 24b: 97%; (i) LevOH, DMAP, DCM, 3: 78%, 12: 75%;

(j) (i) Bu₂SnO, Tol, (ii) BzBr, Tol, (iii) LevOH, DIC, DMAP, DCM, 27: 75%/three steps.

HSQC): 169.4 (CO CO₂Me), 138.0 (C_qC_arom), 137.7 (C_qC_arom),

132.7 (CH_arom), 129.6 (CH_arom), 129.1 (C_qC_arom), 128.4−127.7 (CH_arom),

88.5 (C-1), 85.1 (C-3), 79.5 (C-2), 77.4 (C-5), 75.5 (CH₂Bn), 75.3 (CH₂

Bn), 71.7 (C-4), 52.6 (OCH₃), 21.0 (CH₃STol). HRMS: [M + Na]⁺

calcd for C₂₈H₃₀O₆SNa 517.16553, found 517.16477.

suspended in MeOH (19.3 mL, 0.3 M), and a catalytic amount of

p-TsOH was added. After 4 h, TLC analysis showed total conversion

into a lower running spot (PE/EtOAc 3/1, v/v, R_f0.2). The reaction mix-

ture was neutralized with TEA and concentrated. The residue was dissolved

in EtOAc and washed with H₂O (2×), dried over MgSO₄, filtered, and

concentrated. Crude ¹H NMR (400 MHz, CDCl₃, HH-COSY, HSQC):

7.41 (d, 2H, J = 8.0 Hz, H_arom), 7.35−7.25 (m, 5H, H_arom), 7.09 (d, 2H,

J = 8.0 Hz, H_arom), 4.86 (d, 1H, J = 10.8 Hz, CHHPh), 4.76 (d, 1H, J =

11.2 Hz, CHHPh), 4.35 (d, 1H, J = 10.0 Hz, H-1), 3.81 (d, 1H, J = 11.6

Hz, H-6), 3.71 (d, 1H, J = 11.6 Hz, H-6), 3.51 (t, 1H, J = 8.8 Hz, H-3),

3.44 (d, 1H, J = 3.6 Hz, C-3-OH), 3.29 (t, 1H, J = 9.2 Hz, H-4), 3.26−

3.21 (m, 2H, H-2, H-5), 2.95 (bs, 1H, C-6-OH), 2.30 (s, 3H, CH₃

STol). Crude ¹³C NMR (100 MHz, CDCl₃, HH-COSY, HSQC): 138.6

(C_qC_arom), 137.6 (C_qC_arom), 133.6 (CH_arom), 129.7 (CH_arom), 128.4

(CH_arom), 128.0 (CH_arom), 127.1 (C_qC_arom), 86.2 (C-1), 84.4 (C-4),

79.3 (C-2), 75.3 (CH₂Bn), 69.8 (C-3), 64.5 (C-5), 61.8 (C-6), 21.0

(CH₃STol). The crude residue was dissolved in a mixture of DCM/

H₂O (2/1, 28.9 mL, 0.2M). The reaction mixture was cooled to 0 °C

and BAIB (4.66 g, 14.45 mmol, 2.5 equiv) and TEMPO (181 mg,

1.16 mmol, 0.2 equiv) were added.⁸After 2 h., TLC analysis (PE/EtOAc

1/1, v/v) showed total consumption of the starting material. The

reaction mixture was quenched by addition of Na₂S₂O₃(aq, satd) and

NaHCO₃(aq, satd). The reaction mixture was extracted with EtOAc

(2×) and the combined organic layers were dried over MgSO₄, filtered,

concentrated, and coconcentrated with toluene. The obtained yellow

oil was dissolved in DMF (29.0 mL, 0.2M), followed by addition of

methyl iodide (1.08 mL, 17.34 mmol, 3 equiv) and K₂CO₃(2.4 g,

17.34 mmol, 3 equiv). After 20 min, TLC analysis (PE/EtOAc 1/1, v/v)

showed total conversion of the glucuronate. The reaction mixture was

quenched by addition of MeOH and extracted with Et₂O (2×). The

combined organic layers were washed with brine, dried over MgSO₄, filtered,

and concentrated. Column chromatography (PE/EtOAc 1/0 → 1/1) gave

the title compound in 61% yield over 3 steps (1.51 g, 3.51 mmol).

Methyl (p-Tolyl 4-O-acetyl-2,3-di-O-benzyl-1-thio-β-^D-glucopyr-

anosyluronate) (1). Glucuronic acid methyl ester 40 (264 mg,

0.53 mmol) was dissolved in pyridine (1.8 mL, 0.3 M). The reaction

mixture was cooled to 0 °C, followed by addition of acetic anhydride

(0.15 mL, 1.60 mmol, 3 equiv). After 15 min, TLC analysis (PE/EtOAc

1/1, v/v) showed total conversion into a higher running spot. The

reaction mixture was quenched with MeOH, diluted with EtOAc,

washed with 1 M HCl, NaHCO₃(aq, satd), dried over MgSO₄, filtered,

and concentrated. Column chromatography (PE/EtOAc 1/0 → 8/2)

gave the title compound as a white solid in quantitative yield (286 mg,

0.53 mmol). [α]²⁰_D: + 21.2 (c = 1, DCM). IR (neat, cm⁻¹): 2874, 1753,

1732, 1495, 1454, 1435, 1369, 1356, 1310, 1234, 1206, 1179, 1121,

1090, 1078, 1045, 1028, 1018, 986, 962, 947, 899, 820, 806, 743, 698,

671, 646, 629, 617. ¹H NMR (400 MHz, CDCl₃, HH-COSY, HSQC):

7.49 (d, 2H, J = 7.6 Hz, H_arom), 7.40−7.7.22 (m, 10H, H_arom), 7.12 (d,

2H, J = 8.0 Hz, H_arom), 5.11 (t, 1H, J = 9.6 Hz, H-4), 4.87 (d, 1H, J =

10.0 Hz, CHHPh), 4.79 (d, 1H, J = 11.6 Hz, CHHPh), 4.69 (d, 1H, J =

10.8 Hz, CHHPh), 4.66 (d, 1H, J = 11.6 Hz, CHHPh), 4.57 (d, 1H, J =

9.6 Hz, H-1), 3.88 (d, 1H, J = 10.0 Hz, H-5), 3.73 (s, 3H, CO₂CH₃),

3.67 (t, 1H, J = 9.2 Hz, H-3), 3.52 (t, 1H, J = 9.6 Hz, H-2), 2.33 (s, 3H,

CH₃STol), 1.91 (s, 3H, CH₃Ac). ¹³C NMR (100 MHz, CDCl₃, HH-

COSY, HSQC): 169.5 (CO), 167.6 (CO), 138.3 (C_qC_arom), 137.9

(C_qC_arom), 137.8 (C_qC_arom), 133.2−132.8 (CH_arom), 129.8 (CH_arom),

129.6 (C_qC_arom), 128.6−127.7 (CH_arom), 87.9 (C-1), 83.3 (C-3), 79.7

(C-2), 76.3 (C-5), 75.4 (CH₂Bn), 75.2 (CH₂Bn), 69.3 (C-4), 52.7

(OCH₃), 21.1 (CH₃STol), 20.6 (CH₃Ac). HRMS: [M + Na]⁺calcd

for C₃₀H₃₂O₇SNa 559.17610, found 559.17561.

Methyl (p-Tolyl 2-azido-3-O-benzyl-2-O-deoxy-1-thio-β-^D-gluco-

pyranosyluronate) (42). Glucosamine 41³¹(2.83 g, 5.78 mmol) was

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[α]²⁰_D: + 82.8 (c = 1, DCM). IR (neat, cm⁻¹): 2874, 2108, 1744, 1493,

1454, 1439, 1379, 1354, 1267, 1236, 1207, 1175, 1065, 1018, 957, 908,

837, 810, 737, 698, 677, 617. ¹H NMR (400 MHz, CDCl₃, HH-COSY,

HSQC): 7.46 (d, 2H, J = 7.6 Hz, H_arom), 7.37−7.25 (m, 5H, H_arom),

7.11 (d, 2H, J = 8.0 Hz, H_arom), 4.88 (d, 1H, J = 10.8 Hz, CHHPh),

4.82 (d, 1H, J = 10.8 Hz, CHHPh), 4.35 (d, 1H, J = 10.0 Hz, H-1),

3.78−3.75 (m, 5H, H-4, H-5, OCH₃), 3.38 (t, 1H, J = 8.4 Hz, H-3),

3.26 (t, 1H, J = 9.6 Hz, H-2), 2.31 (s, 3H, CH₃STol). ¹³C NMR (100

MHz, CDCl₃, HH-COSY, HSQC): 168.9 (CO), 138.6 (C_qC_arom),

137.3 (C_qC_arom), 133.9 (CH_arom), 129.4 (CH_arom), 128.1 (CH_arom),

127.8 (CH_arom), 127.6 (CH_arom), 126.2 (C_qC_arom), 86.2 (C-1), 83.2

(C-3), 77.3 (C-4 or C-5), 75.1 (CH₂Bn), 71.3 (C-4 or C-5), 63.6

(C-2), 60.0 (C-6), 52.4 (OCH₃), 20.7 (CH₃STol). HRMS: [M +

Na]⁺calcd for C₂₁H₂₃N₃O₅SNa 452.12506, found 452.12362.

Methyl (p-Tolyl 4-O-acetyl-2-azido-3-O-benzyl-2-O-deoxy-1-thio-

β-^D-glucopyranosyluronate) (2). Azide glucuronate 42 (1.07 g,

2.50 mmol) was dissolved in pyridine (8.33 mL, 0.3 M). The reaction

mixture was cooled to 0 °C, and acetic anhydride (1.0 mL, 10.58 mmol,

4.2 equiv) was added. After 15 min, TLC analysis (PE/EtOAc 1/1, v/v)

showed total conversion of the starting material. The reaction mixture

was quenched by subsequent addition of MeOH and H₂O, diluted with

EtOAc, washed with 1 M HCl and NaHCO₃(aq, satd), dried over

MgSO₄, filtered, and concentrated yielding the target compound as a

colorless oil in 82% (0.97 g, 2.1 mmol). [α]²⁰_D: −10.7 (c = 1.5, DCM).

IR (neat, cm⁻¹): 2108, 1746, 1356, 1277, 1233, 1213, 1186, 1163, 1126

1111, 1074, 1053, 1007, 986, 955, 903, 841, 812, 752, 698, 677, 650. ¹H

NMR (400 MHz, CDCl₃, HH-COSY, HSQC): 7.51 (d, 2H, J = 7.6 Hz,

H_arom), 7.34−7.24 (m, 6H, H_arom), 7.19−7.15 (m, 2H, H_arom), 5.00 (t,

1H, J = 9.6 Hz, H-4), 4.80 (d, 1H, J = 11.2 Hz, CHHPh), 4.66 (d, 1H,

J = 10.8 Hz, CHHPh), 4.36 (d, 1H, J = 10.4 Hz, H-1), 3.87 (d, 1H, J =

10.0 Hz, H-5), 3.74 (s, 3H, OCH₃), 3.53 (t, 1H, J = 9.2 Hz, H-3), 3.45

(t, 1H, J = 9.6 Hz, H-2), 2.36 (s, 3H, CH₃STol), 1.94 (s, 3H, CH₃Ac).

¹³C NMR (100 MHz, CDCl₃, HH-COSY, HSQC): 134.7 (CH_arom),

68.8 (C-6). HRMS: calcd for [C₃₀H₂₈O₅S + NH₄]⁺518.19957, found

518.19942. Mp: 176 °C.

Tolyl 2-O-Benzoyl-4,6-O-benzylidene-3-O-(naphthalen-2-ylmeth-

yl)-1-thio-β-^D-glucopyranoside (45a). Compound 45a³²was pre-

pared as described for compound 45b, starting with 44a (2.83 g, 5.49

mmol) in 80% yield (2.70 g, 4.37 mmol).

Phenyl 2-O-Benzoyl-4,6-O-benzylidene-3-O-(naphthalen-2-yl-

methyl)-1-thio-β-^D-glucopyranoside (45b). To a stirred solution of

44b (5.1 g, 10.1 mmol) in pyridine/CH₂Cl₂(1:1 v/v, 50 mL, 0.2 M) at

0 °C, was added benzoyl chloride (1.3 mL, 11.1 mmol, 1.1 equiv) and

a catalytic amount of DMAP. The mixture was stirred at room

temperature until TLC (toluene/EtOAc, 3:1, v/v) indicated complete

consumption of the starting material. The reaction was quenched with

MeOH, the mixture diluted with EtOAc. The organic phase was washed

with aq 1 M HCl (2×), once with H₂O, and once with brine. The

organic layer was dried over MgSO₄, filtered, and concentrated in vacuo.

Crystallization from MeOH gave the title compound as a white solid in

84% yield (8.5 mmol, 5.1 g). [α]_D: +28.6 (c = 1, CH₂Cl₂). IR (neat):

3063, 2945, 2880, 1715, 1599, 1584, 1479, 1450, 1412, 1385, 1364,

1315, 1263, 1246, 1213, 1167, 1115, 1094, 1082, 1059, 1026, 991, 962,

1

935, 918, 905, 860, 835. H NMR (400 MHz, CDCl₃, HH-COSY,

HSQC) δ: 7.95 (d, 2H, J_vic= 7.2 Hz, CH arom), 7.67 (d, 1H, J_vic= 7.2

Hz, CH arom), 7.60−7.51 (m, 5H, CH arom), 7.46−7.35 (m, 10H, CH

arom), 7.33−7.21 (m, 3H, CH arom), 7.19 (d, 1H, J_vic= 8.4 Hz, CH

arom), 5.63 (s, 1H, CH benzylidene), 4.96 (d, 1H, J_gem= 12.0 Hz,

ArCHH NAP), 4.83 (d, 1H, J_gem= 12.8 Hz, ArCHH NAP), 4.82 (d, 1H,

J_1,2= 9.6 Hz, H-1), 4.42 (dd, 1H, J_6a,5= 4.8 Hz, J_6a,6b= 10.6 Hz, H-6a),

3.93 (t, 1H, J_4,3= J_4,5= 9.2 Hz, H-4), 3.88−3.83 (m, 2H, H-3, H-6b),

3.57 (dt, 1H, J_5,4= J_5,6b= 9.6 Hz, J_5,6a= 4.8 Hz, H-5). ¹³C NMR (100

MHz, CDCl₃, HH-COSY, HSQC) δ: 165.2 (CO Bz), 137.3, 135.3,

133.3, 133.2 (C_qarom), 133.1, 133.0 (CH arom), 132.3 (C_qarom),

130.0 (CH arom), 129.9 (C_qarom), 129.3−125.9 (CH arom), 101.5

(CH benzylidene), 87.2 (C-1), 81.7 (C-4), 79.2 (C-3), 74.4 (ArCH₂

NAP), 72.1 (C-2), 70.7 (C-5), 68.8 (C-6). HRMS: calcd for

[C₃₇H₃₂O₆S + NH₄]⁺622.22578, found 622.22589. Mp: 179 °C.

Phenyl 2-O-Benzoyl-4-O-benzyl-3-O-(naphthalen-2-ylmethyl)-1-

thio-β-^D-glucopyranoside (46a). Glucoside 46a³²was prepared as

described for glucoside 46b, starting from 45a (2.56 g 4.13 mmol), in

66% yield (1.64 g, 2.71 mmol).

Phenyl 2-O-Benzoyl-4-O-benzyl-3-O-(naphthalen-2-ylmethyl)-1-

thio-β-^D-glucopyranoside (46b). To a stirred solution of glycoside

45b (3.0 g, 5 mmol) in dichloromethane (25 mL, 0.2 M) were added

BH₃−THF (1 M in THF, 25 mmol, 5 equiv) and Cu(OTf)₂(0.09 g,

0.25 mmol, 0.05 equiv) at 0 °C. After TLC analysis (toluene/EtOAc,

9:1 v/v) indicated complete conversion of the starting material,

the mixture was quenched with NEt₃(14 mL) and MeOH (20 mL).

The mixture was filtered over a pad of Celite, concentrated, and

coevaporated with methanol. Column chromatography (toluene/

EtOAc, 49:1 → 19:1) gave the compound as a white solid in 66%

yield (2.0 g, 3.3 mmol). [α]_D: 56.2 (c = 1, CH₂Cl₂). IR (neat): 3516,

3059, 3026, 2947, 2916, 2862, 1717, 1684, 1601, 1584, 1479, 1452,

1439, 1404, 1360, 1325, 1288, 1261, 1209, 1180, 1153, 1113, 1101,

1086, 1069, 1030, 1018, 993, 966, 949, 930, 903, 889, 880, 858, 820. ¹H

NMR (400 MHz, CDCl₃, HH-COSY, HSQC) δ: 7.95 (d, 2H, J_vic= 8.4

Hz, CH arom), 7.68−7.66 (m, 1H, CH arom), 7.61−7.58 (m, 1H, CH

arom), 7.56−7.50 (m, 3H CH arom), 7.43−7.21 (m, 15H CH arom),

5.28 (dd, 1H, J_2,1= 10.0 Hz, J_2,3= 9.2 Hz, H-2), 4.93−4.87 (m, 2H, 2×

ArCHH), 4.82 (d, 1H, J_1,2= 10.0 Hz, H-1), 4.80 (d, 1H, J_gem= 11.2 Hz,

ArCHH), 4.69 (d, 1H, J_gem= 11.2 Hz, ArCHH), 3.96−3.91 (m, 1H, H-

6a), 3.91 (t, 1H, J_3,2= J_3,4= 9.2 Hz, H-3), 3.78−3.72 (m, 1H, H-6b),

3.73 (t, 1H, J_4,3= J_4,5= 9.4 Hz, H-4), 3.54−3.50 (m, 1H, H-5), 1.92 (t,

1H, J_6‑OH,6= 6.8 Hz, 6-OH). ¹³C NMR (100 MHz, CDCl₃, HH-COSY,

HSQC) δ: 165.4 (CO Bz), 137.9, 135.2 C_qarom), 133.4 (CH arom),

133.2, 133.0, 132.7 (C_qarom), 132.6, 129.9 (CH arom), 129.8 (C_q

arom), 128.7, 128.5, 128.3, 128.2, 128.2, 128.0, 127.8, 127.0, 126.2,

126.1, 126.0 (CH arom), 86.3 (C-1), 84.0 (C-3), 79.7 (C-5), 77.8

(C-4), 75.5, 75.4 (2× ArCH₂), 75.5 (C-2), 62.2 (C-6). HRMS: calcd for

[C₃₇H₃₄O₆S + NH₄]⁺624.24144, found 624.24156.

130.0 (CH_arom), 128.5 (CH_arom), 128.1 (CH_arom), 128.0 (CH_arom), 86.0

(C-1), 81.8 (C-3), 76.3 (C-5), 75.5 (CH₂Bn), 70.8 (C-4), 63.9 (C-2),

52.8 (OCH₃), 21.2 (CH₃STol), 20.6 (CH₃Ac). [M + Na]⁺calcd for

C₂₃H₂₅N₃O₆SNa: 494.13563, found 494.13521.

Tolyl 4,6-O-Benzylidene-3-O-(naphthalen-2-ylmethyl)-1-thio-β-^D-

glucopyranoside (44a):.³²Compound 44a was prepared as described

for compound 44b, starting with 43a (5.0 g, 13.35 mmol) in 65% yield

(4.47 g, 8.68 mmol) over two steps.

Phenyl 4,6-O-Benzylidene-3-O-(naphthalen-2-ylmethyl)-1-thio-β-

D-glucopyranoside (44b). To a suspension of 43b (7.2 g, 20.0 mmol)

in toluene (70 mL, 0.3 M) was added dibutyltin oxide (5.0 g, 20.0

mmol, 1.0 equiv), and the mixture was heated to reflux for 3 h, during

which the mixture became clear. The orange-brown solution was

concentrated in vacuo. The crude tin ketal was dissolved in N,N-

dimethylformamide (100 mL, 0.2 M), and 2-(bromomethyl)-

naphthalene (5.3 g, 24.0 mmol, 1.2 equiv) and cesium fluoride (4.0 g,

26.0 mmol, 1.3 equiv) were added. After TLC analysis (toluene/EtOAc,

4:1 v/v) indicated completion of the reaction, the mixture was washed

twice with water and once with brine, dried over MgSO₄, filtered, and

concentrated in vacuo. The product was crystallized from EtOAc/Et₂O

to give the product as a white solid in 60% yield (6.0 g, 12.0 mmol).

[α]_D: −26.8 (c = 1, CH₂Cl₂). IR (neat): 3375, 3061, 3034, 2990, 2955,

2922, 2901, 2889, 2872, 2855, 1719, 1599, 1551, 1449, 1441, 1398,

1368, 1342, 1317, 1304, 1271, 1240, 1213, 1194, 1165, 1132, 1088,

1067, 1024, 1007, 991, 968, 934, 918, 889, 876, 853, 833, 812. ¹H NMR

(400 MHz, CDCl₃, HH-COSY, HSQC) δ: 7.82−7.78 (m, 3H, CH

arom), 7.74−7.72 (m, 1H, CH arom), 7.56−7.31 (m, 13H, CH arom),

5.58 (s, 1H, CH benzylidene), 5.10 (d, 1H, J_gem= 11.6 Hz, ArCHH

NAP), 4.96 (d, 1H, J_gem= 12.0 Hz, ArCHH NAP), 4.62 (d, 1H, J_1,2

=

10.0 Hz, H-1), 4.39 (dd, 1H, J_6a,5= 4.8 Hz, J_6a,6b= 10.4 Hz, H-6a), 3.82

(t, 1H, J_6b,5= J_6b,6a= 10.0 Hz, H-6b), 3.77−3.66 (m, 2H, H-3, H-4),

3.58−3.47 (m, 2H, H-2, H-5), 2.57 (d, 1H, J_2‑OH,2= 2.0 Hz, 2-OH). ¹³

C

NMR (100 MHz, CDCl₃, HH-COSY, HSQC) δ: 137.3, 135.7 (C_q

arom), 133.3 (CH arom), 131.4 (C_qarom), 128.5, 128.4, 128.1, 127.8,

127.1, 126.2, 126.1 (CH arom), 101.5 (CH benzylidene), 88.7 (C-1),

81.6, 81.2 (C-3, C-4), 75.0 (ArCH₂NAP), 72.5 (C-2), 70.9 (C-5),

Benzyl (Tolyl 2-O-benzoyl-4-O-benzyl-3-O-naphthylmethyl-1-

thio-β-^D-glucopyranosyluronate) (47a). Glucoside 46a (1.47 g,

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2.37 mmol) was dissolved in DCM/H₂O (2/1, 11.8 mL, 0.2 M) and

chilled to 0 °C. To this reaction mixture were added BAIB (1.91 g, 5.93

mmol, 2.5 equiv) and TEMPO (74 mg, 0.47 mmol, 0.2 equiv), and the

reaction mixture was allowed to warm to rt. After 1 h, TLC analysis

(PE/EtOAc 3/1 + 1% AcOH, v/v) showed total conversion into a lower

running spot. The reaction mixture was quenched with Na₂S₂O₃(aq,

satd) and stirred for 30 min. Then, the reaction mixture was diluted with

DCM, washed with brine, dried over MgSO₄, filtered, concentrated, and

coevaporated with toluene. An orange oil was obtained, which was

dissolved in DMF (11.84 mL, 0.2 M), followed by addition of BnBr

(0.56 mL, 4.74 mmol, 2 equiv) and K₂CO₃(0.66 g, 4.74 mmol, 2

equiv). TLC analysis showed total conversion into a higher running spot

(PE/EtOAc 1/1, v/v, R_f0.48). The reaction mixture was quenched with

MeOH, diluted with DCM, washed with H₂O and brine, dried over

MgSO₄, filtered, and concentrated. A yellow solid was obtained, which

was purified by column chromatography (PE/EtOAc 1/0 → 8/2)

yielding the title compound as a white solid in 17% over two steps

(0.31 g, 0.43 mmol). [α]²⁰_D: +18.6 (c = 1, DCM). IR (neat, cm⁻¹):

1728, 1452, 1398, 1352, 1315, 1263, 1204, 1175, 1144, 1090, 1069,

4.69 (d, 1H, J = 11.2 Hz, CHHPh), 4.54 (d, 1H, J = 11.2 Hz,

CHHPh), 3.99 (d, 1H, J = 9.6 Hz, H-5), 3.90 (dt, 1H, J = 3.6 Hz, J =

8.8 Hz, H-3), 3.79 (t, 1H, J = 9.2 Hz, H-4), 2.79 (d, 1H, J = 3.6 Hz,

OH), 2.30 (s, 3H, CH₃STol). ¹³C NMR (100 MHz, CDCl₃, HH-

COSY, HSQC): 167.7, (CO), 166.1 (CO), 138.6 (C_qC_arom),

137.7 (C_qC_arom), 135.0 (C_qC_arom), 133.9 (CH_arom), 133.5 (CH_arom),

130.0 (CH_arom), 129.6 (CH_arom), 129.3 (C_qC_arom), 128.6−127.9

(CH_arom), 127.4 (C_qC_arom), 86.2 (C-1), 79.3 (C-4), 78.0 (C-5), 76.6

(C-3), 74.8 (CH₂Bn ether), 72.6 (C-2), 67.3 (CH₂CO₂Bn), 21.1

(CH₃STol). HRMS: [M + Na]⁺calcd for C₃₄H₃₂O₇SNa 607.17610,

found 607.17534.

Benzyl (Phenyl 2-O-benzoyl-4-O-benzyl-1-thio-β-^D-glucopyrano-

side) uronate (24b). Glucuronic acid esters 24b was prepared from

47b (1.0 g, 1.40 mmol) as described for glucuronic acid ester 24a in

97% yield (0.78 g, 1.36 mmol). [α]_D: −14.0 (c = 1, CH₂Cl₂). IR (neat):

3576, 3063, 3028, 2911, 1740, 1715, 1601, 1584, 1497, 1481, 1452,

1439, 1391, 1362, 1329, 1315, 1296, 1258, 1225, 1213, 1169, 1113,

1

1067, 1026, 999, 949, 926, 891, 847, 827, 804. H NMR (400 MHz,

CDCl₃, HH-COSY, HSQC) δ: 8.07 (d, 2H, J_vic= 7.2 Hz, CH arom),

7.59 (t, 1H, J_vic= 7.4 Hz, CH arom), 7.44−7.37 (m, 4H, CH arom),

7.36−7.33 (m, 5H, CH arom), 7.32−7.16 (m, 8H, CH arom), 5.22 (s,

2H,), 5.02 (t, 1H, J_2,1= J_2,3= 8.8 Hz, H-2), 4.81 (d, 1H, J_1,2= 10.0 Hz,

H-1), 4.69 (d, 1H, J_gem= 11.2 Hz, PhCHH Bn), 4.56 (d, 1H, J_gem= 11.2

1

1026, 972, 955, 812, 750, 710, 698. H NMR (400 MHz, CDCl₃, HH-

COSY, HSQC): 7.94 (d, 2H, J = 7.6 Hz, H_arom), 7.66−7.49 (m, 16H,

H_arom), 7.47−7.06 (m, 6H, H_arom), 7.10 (d, 2H, J = 8.0 Hz, H_arom), 5.24

(t, 1H, J = 9.6 Hz, H-2), 5.20 (m, 2H, CH₂CO₂Bn), 4.88 (d, 1H, J =

10.8 Hz, CHHAr), 4.79−4.68 (m, 2H, CH₂Ar, H-1), 4.53 (d, 1H, J =

10.0 Hz, CHHAr), 4.11 (d, 1H, J = 9.6 Hz, H-5), 3.97 (t, 1H, J = 9.6

Hz, H-4), 3.87 (t, 1H, J = 8.8 Hz, H-3), 2.30 (s, 3H, CH₃STol). ¹³C

NMR (100 MHz, CDCl₃, HH-COSY, HSQC): 167.7 (CO), 164.9

(CO), 138.4 (C_qC_arom), 137.5 (C_qC_arom), 135.0−133.1 (CH_arom),

133.0 (C_qC_arom), 129.7−125.7 (CH_arom), 86.9 (C-1), 83.1 (C-3), 79.2

(C-4), 78.3 (C-5), 75.3 (CH₂Ar), 75.0 (CH₂Ar), 71.6 (C-2), 67.3 (CH₂

CO₂Bn), 21.1 (CH₃STol). HRMS: [M + Na]⁺calcd for C₄₅H₄₀O₇SNa

747.23870, found 747.23875.

Hz, PhCHH Bn), 4.02 (d, 1H, J_5,4= 9.6 Hz, H-5), 3.93 (dt, 1H, J_3,2

=

J_3,4= 8.8 Hz, J_3,3‑OH= 2.0 Hz, H-3), 3.83 (t, 1H, J_4,3= J_4,5= 9.2 Hz,

H-4), 2.72 (d, 1H, J_3‑OH,3H= 2.8 Hz, 3-OH). ¹³C NMR (100 MHz,

CDCl₃, HH-COSY, HSQC) δ: 167.9 (CO C-6), 166.3 (CO Bz),

137.9, 135.2 (C_qarom), 133.7, 133.4 (CH arom), 131.7 (C_qarom),

130.2 (CH arom), 129.5 (C_qarom), 129.1, 128.8, 128.7, 128.7, 128.6,

128.6, 128.5, 128.1 (CH arom), 86.3 (C-1), 79.5 (C-4), 78.2 (C-5), 76.8

(C-3), 75.1 (CH₂Bn), 72.8 (C-2), 67.6 (CH₂Bn ester). HRMS: calcd

for [C₃₃H₃₀O₇S + Na]⁺593.16045; found 593.16005.

Benzyl (Tolyl 2-O-benzoyl-4-O-benzyl-3-levulinyl-1-thio-β-^D-glu-

copyranosyluronate) (3). Glucuronic acid ester 24a (0.44 g, 0.75

mmol) was dissolved in DCM (7.5 mL, 0.1 M) followed by subsequent

addition of LevOH (98 μL, 0.97 mmol, 1.3 equiv), DIC (114 μL, 0.97

mmol, 1.3 equiv), and DMAP (cat.). After 30 min, TLC analysis showed

total conversion into a lower running spot (PE/EtOAc 12/8, v/v, R_f

0.48). The reaction mixture was filtered, diluted with EtOAc, washed

with 1 M HCl, NaHCO₃(aq, satd), dried over MgSO₄, filtered, and

concentrated. Column chromatography (PE/EtOAc 1/0 → 7/3) gave

the title compound as a white solid in 78% yield (398 mg, 0.58 mmol).

[α]²⁰_D: 1.56 (c = 5.6, DCM). IR (neat, cm⁻¹): 1742, 1719, 1452, 1402,

1360, 1315, 1263, 1206, 1177, 1155, 1090, 1069, 1026, 997, 970, 910,

Phenyl 2-O-Benzoyl-4-O-benzyl-3-O-(naphthalen-2-methyl)-1-

thio-β-^D-glucopyranosiduronate (47b). Glucuronic acid esters 47b

was prepared from 46b (1.8 g, 3.0 mmol) as described for glucuronic

acid ester 47a in 56% yield (1.19 g, 1.68 mmol). [α]_D: +30.6 (c = 1,

CH₂Cl₂). IR (neat): 3059, 3026, 2967, 2955, 2907, 2862, 2853, 1742,

1713, 1601, 1584, 1495, 1476, 1454, 1389, 1391, 1360, 1327, 1315,

1285, 1260, 1211, 1194, 1169, 1157, 1113, 1070, 1020, 1003, 953,

924,899, 862, 849, 824, 804. ¹H NMR (400 MHz, CDCl₃, HH-COSY,

HSQC) δ: 7.93 (d, 2H, J_vic= 7.2 Hz, CH arom), 7.65 (m, 1H, CH

arom), 7.59−6.99 (m, 24H, CH arom), 5.28 (t, 1H, J_2,1= J_2,3= 9.4 Hz,

H-2), 4.86 (d, 1H, J_gem= 11.2 Hz, ArCHH), 4.80−4.72 (m, 3H, H-1, 2×

ArCH₂), 4.54 (d, 1H, J_gem= 10.8 Hz, ArCHH₂), 4.07 (d, 1H, J_5,4= 9.6

1

847, 808, 750, 712, 698. H NMR (400 MHz, CDCl₃, HH-COSY,

Hz, H-5), 3.99 (t, 1H, J_4,3= J_4,5= 9.2 Hz, H-4), 3.88 (t, 1H, J_3,2= J_3,4

=

8.8 Hz, H-3).¹³C NMR (100 MHz, CDCl₃, HH-COSY, HSQC) δ:

167.7 (CO C-6), 165.0 (CO Bz), 137.6, 135.1, 134.9 (C_qarom),

133.2, 133.1 (CH arom), 132.0 (C_qarom), 129.8, 129.8 (CH arom),

129.6 (C_qarom), 128.9, 128.9, 128.6, 128.6, 128.5, 128.5, 128.4, 128.4,

128.2, 128.2, 127.9, 127.9, 127.6, 126.9, 126.0, 125.9, 125.8 (CH arom),

86.9 (C-1), 83.1 (C-3), 79.3 (C-4), 78.4 (C-5), 75.4, 75.1 (ArCH₂), 71.7

(C-2), 67.5 (PhCH₂Bn ester). HRMS: calcd for [C₄₄H₃₈O₇S + Na]⁺

733.22305, found 733.22300.

HSQC): 8.05 (d, 2H, J = 7.6 Hz, H_arom), 7.57 (t, 1H, J = 7.6 Hz, H_arom),

7.46−7.42 (m, 2H, H_arom), 7.36−7.21 (m, 10H, H_arom), 7.16−7.14 (m,

2H, H_arom), 7.02 (d, 2H, J = 8.0 Hz, H_arom), 5.43 (t, 1H, J = 9.2 Hz, H-

3), 5.20 (s, 2H, CH₂Bn ester), 5.14 (t, 1H, J = 9.6 Hz, H-2), 4.79 (d,

1H, J = 10.0 Hz, H-1), 4.54 (d, 1H, J = 11.2 Hz, CHHPh), 4.49 (d, 1H,

J = 11.2 Hz, CHHPh), 4.08 (d, 1H, J = 10.0 Hz, H-5), 3.98 (t, 1H, J =

9.6 Hz, H-3), 2.50−2.40 (m, 2H, CH₂Lev), 2.39−2.25 (CH₂Lev), 1.97

(s, 3H, CH₃Lev). ¹³C NMR (100 MHz, CDCl₃, HH-COSY, HSQC):

205.6 (CO Lev ketone), 171.6 (CO), 167.2 (CO), 165.0 (C

O), 138.6 (C_qC_arom), 137.3 (C_qC_arom), 134.8 (C_qC_arom), 133.7

(CH_arom), 133.3 (CH_arom), 129.8 (CH_arom), 129.6 (CH_arom), 129.1 (C_q

C_arom),128.5−127.7 (CH_arom), 127.4 (C_qC_arom),, 86.5 (C-1), 78.1 (C-5),

77.0 (C-4), 75.3 (C-3), 74.6 (CH₂Bn ether), 70.2 (C-2), 67.4 (CH₂Bn

ester), 37.5 (CH₂Lev), 29.4 (CH₃Lev), 29.7 (CH₂Lev), 21.1 (CH₃

STol). HRMS: [M + K]⁺calcd for C₃₉H₃₈O₉SK 721.18681, found

721.18661.

p-Tolyl 2-O-Benzoyl-3,6-di-O-benzyl-4-levulinyl-1-thio-β-^D-gluco-

pyranoside (12). Glucoside 20a (1.14 g, 1.99 mmol) was dissolved in

DCM (10.0 mL, 0.2 M) followed by subsequent addition of LevOH

(301 μL, 2.99 mmol, 1.5 equiv), DIC (319 μL, 2.99 mmol, 1.5 equiv),

and a catalytic amount of DMAP. After 10 min, TLC analysis (PE/

EtOAc 3/1, v/v) showed total conversion of the starting material into a

lower running spot. The reaction mixture was filtered, diluted with EtOAc,

washed with 1 M HCl, NaHCO₃(aq, satd), dried over MgSO₄, filtered,

and concentrated. Column chromatography (PE/EtOAc 1/0 → 7/3)

Benzyl (Tolyl 2-O-benzoyl-4-O-benzyl-1-thio-β-^D-glucopyranosy-

luronate) (24a). Glucuronic acid ester 47a (0.68 g, 0.94 mmol) was

dissolved in a mixture of DCM/H₂O (4/1, 9.4 mL, 0.1 M), and the

reaction mixture was cooled to 0 °C. DDQ (427 mg, 1.88 mmol,

2 equiv) was added, and the reaction mixture was allowed to warm to rt.

After 3 h, TLC analysis (PE/EtOAc 12/8, v/v) showed total conversion

into a lower running spot. The reaction mixture was diluted with

DCM, washed with Na₂S₂O₃(aq, satd), dried over MgSO₄, filtered, and

concentrated. Column chromatography PE/EtOAc 1/0 → 7/3) gave

the title compound a clear oil in 68% yield (438 mg, 0.64 mmol).

[α]²⁰_D: −21.0 (c = 1, DCM). IR (neat, cm⁻¹): 3466, 3065, 3032, 2953,

2920, 2872, 1728, 1601, 1493, 1452, 1398, 1356, 1315, 1263, 1198,

1

1175, 1092, 1070, 1026, 997, 908, 845, 808, 750, 710, 698, 636. H

NMR (400 MHz, CDCl₃, HH-COSY, HSQC): 8.09 (d, 2H, J = 8.0 Hz,

H_arom), 7.59−7.57 (t, 1H, J = 8.0 Hz, H_arom), 7.47−7.43 (m, 2H, H_arom),

7.37−7.18 (m, 12H, H_arom), 7.02 (d, 2H, J = 8.0 Hz, H_arom), 5.21 (s, 2H,

CH₂CO₂Bn), 4.98 (t, 1H, J = 9.6 Hz, H-2), 4.73 (d, 1H, J = 9.6 Hz, H-1),

121

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Chart 1. Overview of the Disaccharides

gave the title compound in 75% yield (1.0 g, 1.50 mmol). [α]_D: + 23.1

(c = 0.3, DCM). IR (neat, cm⁻¹): 2864, 1740, 1717, 1495, 1452, 1418,

1400, 1362, 1317, 1287, 1260, 1213, 1179, 1153, 1112, 1090, 1063,

1040, 1028, 1007, 982, 964, 932, 908, 883, 843, 820, 804, 748,, 708, 694,

(t, 1H, J = 9.2 Hz, H-2), 5.23 (t, 1H, J = 9.6 Hz, H-4), 4.77 (d, 1H, J =

10.0 Hz, H-1), 4.64 (dd, 1H, J = 2.4 Hz, J = 12.4 Hz, H-6), 4.61 (d, 1H,

J = 10.8 Hz, CHHPh), 4.58 (d, 1H, J = 11.6 Hz, CHHPh), 4.35 (dd,

1H, J = 6.0 Hz, J = 12.4 Hz, H-6), 3.93 (t, 1H, J = 9.2 Hz, H-3), 3.88−

3.84 (m, 1H, H-5), 2.73−2.59 (m, 2H, CH₂Lev), 2.57−2.51 (m, 1H,

CHH Lev), 2.50−2.37 (m, 1H, CHH Lev), 2.20 (s, 3H, CH₃STol),

2.10 (s, 3H, CH₃Lev). ¹³C NMR (100 MHz, CDCl₃, HH-COSY,

HSQC): 206.0 (CO Lev ketone), 171.3 (CO Lev), 165.9 (CO

Bz), 164.8 (CO Bz), 138.1 (C_qC_arom), 137.3 (C_qC_arom), 133.7−

133.0 (CH_arom), 129.7 (CH_arom), 129.7 (CH_arom), 129.5 (C_qC_arom),

129.5 (CH_arom), 129.4 (CH_arom), 128.3 (CH_arom), 128.2 (CH_arom), 128.1

(C_qC_arom), 128.0 (CH_arom), 127.8 (CH_arom), 127.5 (CH_arom), 86.1 (C-1),

81.2 (C-3), 76.1 (C-5), 74.3 (CH₂Bn), 71.9 (C-2), 70.1 (C-4), 62.8

(C-6), 37.6 (CH₂Lev), 29.5 (CH₃Lev), 27.7 (CH₂Lev), 20.9 (CH₃

STol). HRMS: [M + H]⁺calcd for C₃₂H₃₁O₉H calcd 560.20408, found

560.19972.

1

685, 619. H NMR (400 MHz, CDCl₃, HH-COSY, HSQC): 8.05 (d,

2H, J = 7.6 Hz, H_arom), 7.57−7.55 (m, 1H, H_arom), 7.46−7.42 (m, 2H,

H_arom), 7.38−7.22 (m, 7H, H_arom), 7.19−7.11 (m, 5H, H_arom), 7.98 (d,

2H, J = 7.6 Hz, H_arom), 5.29 (t, 1H, J = 9.6 Hz, H-2), 5.11 (t, 1H, J =

9.6 Hz, H-4), 4.78 (d, 1H, J = 10.0 Hz, H-1), 4.57 (s, 2H, CH₂Bn), 4.53

(s, 2H, CH₂Bn), 3.89 (t, 1H, J = 9.2 Hz, H-3), 3.72−3.60 (m, 3H, H-5,

H-6), 2.71−2.51 (m, 2H, CH₂Lev), 2.47−2.31 (m, 2H, CH₂Lev), 2.26

(s, 3H, CH₃STol), 2.10 (s, 3H, CH₃Lev). ¹³C NMR (100 MHz,

CDCl₃, HH-COSY, HSQC): 206.1 (CO Lev ketone), 171.3 (CO

Lev), 164.8 (CO Bz), 138.0 (C_qC_arom), 137.9 (C_qC_arom), 137.4 (C_q

C_arom), 133.1 (CH_arom), 132.8 (CH_arom), 129.7 (CH_arom), 129.5

(CH_arom), 129.4 (C_qC_arom), 128.7 (C_qC_arom), 127.3−127.4 (CH_arom),

86.3 (C-1), 81.3 (C-3), 77.7 (C-5), 74.0 (CH₂Bn), 73.3 (CH₂Bn), 72.0

(C-2), 70.7 (C-4), 69.5 (C-6), 37.6 (CH₂Lev), 29.5 (CH₃Lev), 27.7

(CH₂Lev), 20.9 (CH₃STol). HRMS: [M + Na]⁺calcd for C₃₉H₄₀-

O₈SNa: 691.23361, found 691.23359.

Methyl 2,3,4-Tri-O-benzyl-6-O-(methyl 4-O-acetyl-2,3-di-O-ben-

zyl-α/β-^D-glucopyranosyluronate)-α-D-glucopyranoside (49). The

title compound was isolated as a white solid (Chart 1). IR (neat,

cm⁻¹): 2920, 2909, 2872, 1748, 1454, 1362, 1292, 1265, 1231, 1156,

1

p-Tolyl 2,6-O-benzoyl-3-O-benzyl-1-thio-β-^D-glucopyranoside

(27). Glucoside 48³³(2.40 g, 4.86 mmol) was suspended in toluene

(16.2 mL, 0.3 M) followed by addition of Bu₂SnO (1.21 g, 4.86 mmol,

1 equiv). The reaction mixture was heated to reflux and stirred for 3 h.

A clear reaction mixture was obtained, which was concentrated and

coevaporated with toluene, yielding a transparent oil. The oil obtained

was dissolved in toluene (16.2 mL, 0.3 M) followed by addition of BzCl

(622 μL, 5.35 mmol, 1.1 equiv). After 3 h, TLC analysis (PE/EtOAc

1/1, v/v) showed total conversion into higher running spot. The reaction

mixture was diluted with EtOAc, washed with H₂O, dried over MgSO₄,

filtered, and concentrated. The white residue was dissolved in DCM

(24.3 mL, 0.2 M) followed by addition of DIC (0.74 mL, 6.32 mmol,

1.3 equiv), LevOH (0.22 mL, 2.17 mmol, 1.3 equiv), and DMAP (cat.).

After 1 h, TLC analysis showed total conversion into a lower running

spot (PE/EtOAc 12/8, v/v, R_f0.33). The reaction mixture was filtered,

diluted with DCM, washed with 1 M HCl and NaHCO₃(aq, satd),

dried over MgSO₄, filtered, and concentrated. Column chromatography

(PE/EtOAc 1/0 → 6/4) gave the title compound as a white solid in

75% yield (2.52 g, 3.65 mmol). [α]_D: + 14.2 (c = 1, DCM). IR (neat,

cm⁻¹): 1742, 1717, 1493, 1450, 1402, 1377, 1364, 1315, 1261, 1233,

1204, 1175, 1157, 1123, 1111, 1084, 1067, 1038, 1028, 976, 964, 914,

1138, 1090, 1047, 1028, 908, 733, 696. H NMR (400 MHz, CDCl₃,

HH-COSY, HSQC): 7.90 (d, 2H, J = 7.2 Hz, H_arom), 7.43 (t, 1H, J = 7.2

Hz, H_arom), 7.35−7.22 (m, 23H, H_arom), 7.15−7.13 (m, 2H, H_arom),

7.03−7.01 (m, 2H, H_arom), 5.40 (dd, 1H, J = 3.6 Hz, J = 9.2 Hz, H-3′),

5.27 (t, 1H, J = 9.6 Hz, H-2′), 5.19 (s, 2H, CH₂Bn ester), 4.88 (d, 1H,

J = 12.4 Hz, CHHPh), 4.72 (d, 1H, J = 10.8 Hz, CHHPh), 4.63 (d, 1H,

J = 8.0 Hz, H-1′), 4.58 (d, 1H, J = 12.0 Hz, CHHPh), 4.55−4.47 (m,

2H, CH₂Bn), 4.46 (d, 1H, J = 3.2 Hz, H-1), 4.25 (d, 1H, J = 11.2 Hz,

CHHPh), 4.08 (d, 1H, J = 9.2 Hz, H-6), 4.05−4.02 (m, 2H, H-4′, H-5′),

3.86 (t, 1H, J = 9.2 Hz, H-3), 3.69−3.63 (m, 2H, H-5, H-6), 3.40 (dd,

1H, J = 3.6 Hz, J = 9.6 Hz, H-2), 3.32 (t, 1H, J = 9.6 Hz, H-4), 3.17 (s,

3H, OCH₃), 2.52−2.41 (m, 2H, CH₂Lev), 2.38−2.27 (m, 2H, CH₂

Lev), 1.98 (s, 3H, CH₃Lev). ¹³C NMR (100 MHz, CDCl₃, HH-COSY,

HSQC): 205.7 (CO Lev ketone), 171.8 (CO), 167.5 (CO),

165.0 (CO), 138.7 (C_qC_arom), 138.1 (C_qC_arom), 138.0 (C_qC_arom),

137.4 (C_qC_arom), 134.9 (C_qC_arom), 133.2 (CH_arom), 129.8 (CH_arom),

129.2 (C_qC_arom), 128.6−127.5 (CH_arom), 101.3 (C-1′), 97.8 (C-1), 81.8

(C-3), 79.7 (C-2), 77.2 (C-4, C-4′, C-5′), 75.5 (CH₂Bn), 74.7 (CH₂

Bn), 74.7 (CH₂Bn), 74.1 (C-3′), 73.3 (CH₂Bn), 71.7 (C-2′), 69.4

(C-5), 68.4 (C-6), 67.5 (CH₂Bn ester), 54.9 (OCH₃), 37.7 (CH₂Lev),

29.5 (CH₃Lev), 27.9 (CH₂Lev). HRMS: [M + Na]⁺calcd for

C₄₄H₄₉O₁₂Na 770.32968, found 770.33962.

1

804, 750, 710, 700, 687. H NMR (400 MHz, CDCl₃, HH-COSY,

HSQC): 8.08−8.04 (m, 4H, H_arom), 7.61−7.57 (m, 2H, H_arom), 7.61−

7.57 (m, 2H, H_arom), 7.48−7.44 (m, 4H, H_arom), 7.43−7.31 (m, 2H,

H_arom), 7.24−7.10 (m, 5H, H_arom), 6.83 (d, 2H, J = 8.0 Hz, H_arom), 5.28

Methyl 2,3,4-Tri-O-benzyl-6-O-(methyl 3-O-acetyl-2-azido-2-

deoxy-3-O-benzyl-α/β-^D-glucopyranosyluronate)-α-D-glucopyrano-

side (50). The title compound was isolated as a clear oil and as an

122

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anomeric mixture (α/β: 1/7.7). IR (neat, cm⁻¹): 2112, 1748, 1265,

1229, 1161, 1136, 1086, 1047, 1029, 908, 733, 696. ¹H NMR β anomer

(400 MHz, CDCl₃, HH-COSY, HSQC): 7.37−7.26 (m, 20H, H_arom),

5.09 (t, 1H, J = 9.6 Hz, H-4′), 4.99 (d, 1H, J = 10.8 Hz, CHHPh), 4.93

(d, 1H, J = 11.2 Hz, CHHPh), 4.85−4.77 (m, 3H, CHHPh, CH₂Ph),

4.69−4.61 (m, 3H, CHHPh, CH₂Ph), 4.60 (d, 1H, J = 3.6 Hz, H-1),

4.18 (d, 1H, J = 8.0 Hz, H-1′), 4.10 (dd, 1H, J = 1.6 Hz, J = 10.8 Hz,

H-6), 4.00 (t, 1H, J = 9.2 Hz, H-4), 3.82−3.80 (m, 1H, H-5), 4.76 (d,

1H, J = 10.0 Hz, H-5′), 3.67 (s, 3H, CO₂Me), 3.66−3.64 (m, 1H, H-6),

3.57−3.48 (m, 3H, H-2, H-2′, H-3), 3.43 (t, 1H, J = 9.6 Hz, H-3′, 3.37

(s, 3H, CH₃Ac), 1.96 (s, 3H, OCH₃). ¹³C NMR (100 MHz, CDCl₃,

HH-COSY, HSQC): 169.4 (CO), 167.3 (CO), 138.7−137.4 (C_q

C_arom), 128.4−127.6 (CH_arom), 102.0 (C-1′), 98.1 (C-1), 82.0 (C-4),

79.8 (C-3′), 77.7 (C-2′, C-2, C-3), 75.7 (CH₂Bn), 75.1 (CH₂Bn), 74.8

(CH₂Bn), 73.4 (CH₂Bn), 72.8 (C-5), 70.9 (C-4′), 69.7 (C-5), 68.8

(C-6), 65.4 (C-2, C-2′, C-3), 55.2 (OCH₃), 52.7 (CO₂Me), 20.6 (CH₃

Ac). HRMS: [M + Na]⁺calcd for C₄₈H₅₁O₁₀Na 810.33744, found

810.32286.

29.5 (CH₃Lev), 27.9 (CH₂Lev). HRMS: [M + Na]⁺calcd for

C₅₄H₅₈O₁₅Na 969.36679, found 969.36717.

Methyl 2,3,4-Tri-O-benzyl-6-O-(2,3-di-O-benzyl-4,6-O-benzyli-

dene-β-^D-glucopyranosyl)-α-D-glucopyranoside (52).³⁴The title

compound was isolated a white solid. IR (neat, cm⁻¹): 2924, 2914,

2868, 1454, 1364, 1314, 1265, 1209, 1157, 1134, 1086, 1070, 1049,

1

1028, 999, 912, 820, 733, 696, 678. H NMR (400 MHz, CDCl₃,

HH-COSY, HSQC): diagnostic peaks: 5.55 (s, 1H, CHPh β), 5.53

(s, 1.51H, CHPh α), 4.93 (d, 1.13H, J = 3.2 Hz, H-1′ βα), 4.32 (dd,

1.14H, J = 5.2 Hz, J = 10.0 Hz, H-6′ β), 4.21 (dd, 1.61H, J = 5.2 Hz,

J = 10.0 Hz, H-6′ α).

Methyl 2,3,4-Tri-O-benzyl-6-O-(4,6-O-benzylidene-2,3-di-O-ben-

zoyl-β-^D-glucopyranosyl)-α-D-glucopyranoside (53). The title com-

pound was isolated as a white solid. [α]_D: +12.0 (c = 1, DCM). IR

(neat): 2930, 1728, 1452, 1362, 1315, 1265, 1209, 1179, 1159, 1090,

1069, 1053, 1026, 999, 914, 853, 733, 696. ¹H NMR (400 MHz, CDCl₃,

HH-COSY, HSQC): 7.93 (d, 2H, J = 6.8 Hz, H_arom), 7.90 (d, 2H, J =

7.2 Hz, H_arom), 7.46−7.37 (m, 5H, H_arom), 7.35−7.17 (m, 19H, H_arom),

7.01−6.99 (m, 2H, H_arom), 5.77 (t, 1H, J = 9.6 Hz, H-3′), 5.54 (t, 1H, J =

9.2 Hz, H-2′), 5.52 (s, 1H, CHPh), 4.89 (d, 1H, J = 10.8 Hz, CHHPh0,

4.78 (d, 1H, J = 7.6 Hz, H-1′), 4.75 (d, 1H, J = 12.0 Hz, CHHPh), 4.68

(d, 1H, J = 11.2 Hz, CHHPh), 4.65 (d, 1H, J = 9.6 Hz, CHHPh), 4.50

(d, 1H, J = 3.2 Hz, H-1), 4.45 (d, 1H, J = 10.8 Jz. CHHPh), 4.41 (dd,

1H, J = 5.2 Hz, J = 10.4 Hz, H-6′), 4.23 (d, 1H, J = 11.2 Hz, CHHPh),

4.12 (d, 1H, J = 9.6 Hz, H-6), 3.96−3.82 (m, 3H, H-6′, H-3, H-4′),

3.75−3.62 (m, 3H, H-6, H-4, H-5′), 3.44 (dd, 1H, J = 3.2 Hz, J = 9.6 Hz,

H-2), 3.39−3.36 (m, 1H, H-5), 3.23 (s, 3H, OCH₃). ¹³C NMR (100

MHz, CDCl₃, HH-COSY, HSQC): 165.6 (CO Bz), 165.0 (CO

Bz), 138.7 (C_qC_arom), 138.1 (C_qC_arom), 138.1 (C_qC_arom), 136.9 (C_q

C_arom), 136.7 (C_qC_arom), 133.4−133.0 (CH_arom), 129.9−129.0

(CH_arom), 128.7 (C_qC_arom), 128.4 (C_qC_arom), 128.4 (C_qC_arom),

128.3−127.4 (CH_arom), 126.1−125.1 (CH_arom), 101.6 (C-1), 101.4

(CHPh), 98.0 (C-1′), 81.8 (C-3′ or C-4′), 79.4 (C-2), 78.6 (C-3′ or C-

4′), 77.3 (C-5), 75.5 (CH₂Bn), 74.7 (CH₂Bn), 73.3 (CH₂Bn), 72.3

(C-2′), 72.0 (C-3′), 69.4 (C-4), 68.5 (C-6′), 68.3 (C-6), 66.6 (C-5′),

55.0 (OCH₃). HRMS: [M + Na]⁺calcd for C₅₅H₅₄O₁₃Na 945.34566,

found 945.34537.

Methyl 2,3,4-Tri-O-benzyl-6-O-(benzyl 2-O-benzoyl-4-O-benzyl-

3-O-levulinyl-β-^D-glucopyranosyluronate)-α-D-glucopyranoside

(51a). The title compound was isolated as a white solid. [α]_D: + 0.8

(c = 0.8, DCM). IR (neat, cm⁻¹): 2918, 1744, 1454, 1360, 1265, 1213,

1177, 1155, 1092, 1070, 1028, 999, 735, 712, 698. ¹H NMR (400 MHz,

CDCl₃, HH-COSY, HSQC): 7.91−7.89 (m, 2H, H_arom), 7.43 (t, 1H, J =

7.2 Hz, H_arom), 7.35−7.22 (m, 23H, H_arom), 7.15−7.03 (m, 2H, H_arom),

7.02−7.01 (m, 2H, H_arom), 5.40 (t, 1H, J = 9.2 Hz, H-3′), 5.27 (t, 1H, J =

9.6 Hz, H-2′), 5.19 (s, 2H, CH₂Bn ester), 4.88 (d, 1H, J = 10.8 Hz,

CHHPh), 4.72 (d, 1H, J = 12.4 Hz, CHHPh), 4.68 (d, 1H, J = 10.8 Hz,

CHHPh), 4.63 (d, 1H, J = 8.0 Hz, H-1′), 4.58 (d, 1H, J = 12.0 Hz,

CHHPh), 4.55−4.47 (m, 3H, CH₂Ph, CHHPh), 4.46 (d, 1H, J = 3.2

Hz, H-1), 4.25 (d, 1H, J = 11.2 Hz, CHHPh), 4.08 (d, 1H, J = 9.2 Hz,

H-6′), 4.05−3.95 (m, 2H, H-4′, H-5′), 3.86 (t, 1H, J = 9.2 Hz, H-3),

3.69−3.63 (m, 2H, H-5, H-6), 3.40 (dd, 1H, J = 3.6 Hz, J = 9.6 Hz,

H-2), 3.53 (t, 1H, J = 9.6 Hz, H-4), 3.17 (s, 3H, OCH₃), 2.51−2.41 (m,

2H, CH₂Lev), 2.38−2.24 (m, 2H, CH₂Lev), 1.98 (s, 3H, CH₃Lev).

¹³C NMR (100 MHz, CDCl₃, HH-COSY, HSQC): 205.7 (CO Lev

ketone), 171.8 (CO), 167.5 (CO), 165.0 (CO), 138.7 (C_q

C_arom), 138.1 (C_qC_arom), 138.0 (C_qC_arom), 137.4 (C_qC_arom), 134.9 (C_q

C_arom), 133.2 (CH_arom), 129.8 (CH_arom), 129.2 (C_qC_arom), 128.6−127.5

(CH_arom), 101.3 (C-1′), 97.8 (C-1), 81.8 (C-3), 79.7 (C-2), 77.2 (C-4,

C-4′, C-5′), 75.5 (CH₂Bn), 74.7 (CH₂Bn), 74.7 (CH₂Bn), 74.1 (C-3′),

73.3 (CH₂Bn), 71.7 (C-2′), 69.4 (C-5), 68.4 (C-6), 67.5 (CH₂Bn

ester), 54.9 (OCH₃), 37.7 (CH₂Lev), 29.5 (CH₃Lev), 27.9 (CH₂Lev).

HRMS: [M + Na]⁺calcd for C₅₅H₅₄O₁₃Na 945.34566, found

945.34717.

Methyl 2,3,4-Tri-O-benzyl-6-O-(4,6-di-O-acetyl-2,3-di-O-benzyl-

α/β-^D-glucopyranosyl)-α-D-glucopyranoside (54). The title com-

pound was isolated as a clear oil and as an anomeric mixture (α/β:

1/1.2). IR (neat): 2930, 2907, 2872, 1744, 1497, 1454, 1362, 1329,

1265, 1237, 1194, 1157, 1136, 1090, 1044, 1028, 910, 845, 822, 733,

696, 635, 604. ¹H NMR (400 MHz, CDCl₃, HH-COSY, HSQC):

Diagnostic peaks: 4.35 (d, 1H, J = 7.2 Hz, H-1β), 3.36 (2.68H OCH₃

α), 3.33 (3.07H OCH₃β). HRMS: [M + Na]⁺calcd for C₅₂H₅₈O₁₃Na

913.37696, found 913.37733.

Methyl 2,3,4-Tri-O-benzyl-6-O-(methyl 4-O-benzyl-2-O-benzoyl-

3-O-levulinyl-β-^D-glucopyranosyluronate)-α-D-glucopyranoside

(51b). The title compound was isolated as a transparent oil. [α]_D: +3.6

(c = 1.2, DCM). IR (neat, cm⁻¹): 2913, 1748, 1452, 1404, 1358, 1315,

1265, 1225, 1202, 1175, 1155, 1092, 1070, 1028, 1001, 910, 933, 912,

Methyl 2,3,4-Tri-O-benzyl-6-O-(2,3,4,6-tetra-O-benzoyl-β-^D-glu-

copyranosyl)-α-^D-glucopyranoside (55):.³⁵The title compound was

1

isolated as a white solid. H NMR (400 MHz, CDCl₃, HH-COSY,

HSQC): 7.99 (d, 2H, J = 7.2 Hz, H_arom), 7.89 (m, 4H, H_arom), 7.82 (d,

2H, H_arom), 7.53−7.46 (m, 2H, H_arom), 7.42−7.19 (m, 25H, H_arom), 7.05

(m, 2H, H_arom), 5.90 (t, 1H, J = 9.6 Hz, H-3′), 5.68 (t, 1H, J = 9.6 Hz,

H-4′), 5.60 (t, 1H, J = 9.6 Hz, H-2′), 4.89 (d, 1H, J = 11.2 Hz, CHHPh),

4.82 (d, 1H, J = 7.6 Hz, H-1′), 4.73 (d, 1H, J = 12.4 Hz, CHHPh), 4.68

(d, 1H, J = 10.8 Hz, CHHPh), 4.63−4.58 (m, 2H, CHHPh, H-6),

4.54−4.48 (m, 3H, H-1, H-6, CHHPh), 4.28 (d, 1H, J = 11.2 Hz,

CHHPh), 4.16−4.09 (m, 2H, H-6′, H-5′), 3.88 (t, 1H, J = 9.2 Hz, H-3),

3.76−3.67 (m, 2H, H-5, H-6′), 3.44−3.35 (m, 2H, H-2, H-4), 3.21 (s,

3H, OCH₃). ¹³C NMR (100 MHz, CDCl₃, HH-COSY, HSQC): 166.1

(CO Bz), 165.8 (CO Bz), 165.1 (CO Bz), 164.9 (CO), 138.7

(C_qC_arom), 138.1 (C_qC_arom), 138.1 (C_qC_arom), 133.4 (CH_arom), 133.2

(CH_arom), 133.1 (CH_arom), 129.8 (CH_arom), 129.7 (CH_arom), 129.7 (C_q

C_arom), 129.5 (C_qC_arom), 129.1 (C_qC_arom), 128.7−127.4 (CH_arom),

101.3 (C-1′), 97.9 (C-1), 81.8 (C-3), 79.7 (C-2), 77.3 (C-4), 75.5 (CH₂

Bn), 74.7 (CH₂Bn), 73.3 (CH₂Bn), 72.8 (C-3′), 72.1 (C-5′), 71.7

(C-2′), 69.7 (C-4′), 69.4 (C-5), 68.2 (C-6), 63.2 (C-6′), 55.0 (OCH₃).

Methyl 2,3,4-Tri-O-benzyl-6-O-(2-O-benzoyl-3,6-di-O-benzyl-4-

levulinyl-β-^D-glucopyranosyl)-β-D-glucopyranoside (56). The title

compound was isolated as a transparent oil, which crystallized on

standing. [α]_D: + 23.6 (c = 0.9, DCM). IR (neat, cm⁻¹): 2874, 1721,

1

698. H NMR (400 MHz, CDCl₃, HH-COSY, HSQC): 7.90 (d, 2H,

H_arom), 7.46 (t, 1H, J = 7.6 Hz, H_arom), 7.34−7.23 (m, 20H, H_arom),

7.05−7.02 (m, 2H, H_arom), 5.42 (t, 1H, J = 8.8 Hz, H-3′), 5.26 (t, 1H, J =

9.6 Hz, H-2′), 4.88 (d, 1H, J = 10.8 Hz, CHHPh), 4.72 (d, 1H, J = 12.0

Hz, CHHPh), 4.68 (d, 1H, J = 11.2 Hz, CHHPh), 4.65−4.62 (m, 3H,

CHHPh, CHHPh, H-1′), 4.58 (d, 1H, J = 12.0 Hz, CHHPh), 4.50 (d,

1H, J = 10.8 Hz, CHHPh), 4.59 (d, 1H, J = 3.6 Hz, H-1), 4.27 (d, 1H,

J = 11.2 Hz, CHHPh), 4.09−4.06 (m, 1H, H-6), 4.03−3.98 (m, 2H,

H-4′, H-5′), 3.86 (t, 1H, J = 9.2 Hz, H-3), 3.73 (s, 3H, CO₂Me), 3.69−

3.63 (m, 1H, H-6), 3.40 (dd, 1H, J = 3.2 Hz, J = 9.6 Hz, H-2), 3.32 (t,

1H, J = 9.6 Hz, H-4), 3.17 (s, 3H, OCH₃), 2.54−2.46 (m, 2H, CH₂

Lev), 2.44−2.38 (m, 2H, CH₂Lev), 2.00 (s, 3H, CH₃Lev). ¹³C NMR

(100 MHz, CDCl₃, HH-COSY, HSQC): 205.6 (CO Lev ketone),

171.8 (CO), 168.1 (CO, 165.0 (CO), 138.7 (C_qC_arom), 138.1

(C_qC_arom), 138.1 (C_qC_arom), 133.2 (CH_arom), 129.8 (CH_arom), 129.3

(C_qC_arom), 128.4−127.5 (CH_arom), 101.3 (C-1′), 97.8 (C-1), 81.8 (C-

3), 79.7 (C-2′), 77.4 (C-4), 77.2 (C-5′), 75.5 (CH₂Bn), 74.7 (CH₂Bn),

74.7 (CH₂Bn), 74.5 (C-4′), 74.2 (C-3′), 73.3 (CH₂Bn0, 71.7 (C-2′),

69.5 (C-5′), 68.5 (C-6), 54.9 (OCH₃), 52.6 (CO₂Me), 37.7 (CH₂Lev),

123

dx.doi.org/10.1021/jo201586r | J. Org. Chem. 2012, 77, 108−125

The Journal of Organic Chemistry

Article

1452, 1362, 1315, 1265, 1207, 1152, 1092, 1061, 1028, 912, 935, 696.

REFERENCES

■

¹H NMR (400 MHz, CDCl₃, HH-COSY, HSQC): 7.92 (d, 1H, J = 6.4

(1) (a) Shipkova, M.; Wieland, E. Clin. Chim. Acta 2005, 358, 2−23.

(b) Shipkova, M.; Armstrong, V. W.; Oellerich, M.; Wieland, E. Ther.

Drug. Monit. 2003, 25, 1−16. (c) Stachulski, A. V.; Harding, J. R.;

Lindon, J. C.; Maggs, J. L.; Park, B. K.; Wilson, I. D. J. Med. Chem.

2006, 49, 6931−6945. (d) Stachulski, A. V.; Jenkins, G. N. Nat. Prod.

Rep. 1998, 15, 173−186. (e) Kaspersen, F. M.; Van Boeckel, C. A. A.

Xenobiotica 1987, 17, 1451−1471.

(2) (a) Vincken, J.-P.; Heng, L.; Groot, A. D.; Gruppen, H.

Phytochemistry 2007, 68, 275−297. (b) Hostettmann, K.; Marston, A.

Saponins; Cambridge University Press: Cambridge, 1995. (c) Yu, B.;

Sun, J. S. Chem. Asian J. 2009, 4, 642−654. (d) Yu, B.; Zhang, Y. C.;

Tang, P. P. Eur. J. Org. Chem. 2007, 5145−5161.

(3) (a) Spillmann, D.; Lindahl, U. Curr. Opin. Struct. Biol. 1994, 4,

677−682. (b) Capila, I.; Linhardt, R. J. Angew. Chem., Int. Ed. 2002, 41,

391−412.

(4) (a) Griffiths, A. J.; Davies, D. B. Carbohydr. Pol. 1991, 14, 241−

279. (b) Griffiths, A. J.; Davies, D. B. Carbohydr. Pol. 1991, 14, 339−

365.

(5) (a) van den Bos, L. J.; Codee

Dinkelaar, J.; Overkleeft, H. S.; van der Marel, G. A. Eur. J. Org. Chem.

2007, 3963−3976. (b) Codee, J. D. C.; Christina, A. E.; Walvoort,

M. T. C.; Overkleeft, H. S.; van der Marel, G. A. Top. Curr. Chem.

2011, 301, 253−289. (c) Wadouachi, A.; Kovensky, J. Molecules 2011,

16, 3933−3968.

Hz, H_arom), 7.46−7.43 (m, 1H, H_arom), 7.32−7.21(m, 15H, H_arom),

7.14−7.13 (m, 5H, H_arom), 6.99−6.97 (m, 2H, H_arom), 5.39 (t, 1H, J =

9.6 Hz, H-2′), 5.12 (t, 1H, J = 9.2 Hz, H-4′), 4.87 (d, 1H, J = 11.2 Hz,

CHHPh), 4.73 (d, 1H, J = 12.0 Hz, CHHPh), 4.65 (d, 1H, CHHPh),

4.60−4.53 (m, 6H, 2 × CH₂Bn, CHHPh, H-1′), 4.49 (d, 1H, J = 3.6

Hz, H-1), 4.41 (d, 1H, J = 10.8 Hz, CHHPh), 4.23 (d, 1H, J = 11.2 Hz,

CHHPh), 4.13 (d, 1H, J = 12.4 Hz, H-6), 3.91−3.84 (m, 2H, H-3,

H-3′), 3.69−3.62 (m, 4H, H-6, H-5, H-6′, H-5′), 3.44 (dd, 1H, J = 3.6

Hz, J = 9.6 Hz, H-2), 3.38 (t, 1H, J = 9.2 Hz, H-4), 3.20 (s, 3H, OCH₃),

2.61−2.57 (m, 2H, CH₂Lev), 2.41−2.36 (m, CH₂Lev), 2.11 (s, 3H,

CH₃Lev). ¹³C NMR (100 MHz, CDCl₃, HH-COSY, HSQC): 206.1

(CO Lev ketone), 171.5 (CO), 164.7 (CO Bz), 138.8−137.6

(C_qC_arom), 133.0 (CH_arom), 129.7 (CH_arom), 129.5 (C_qC_arom), 128.4−

127.3 (CH_arom), 101.0 (C-1′), 97.9 (C-1), 81.8 (C-3 or C-3′), 79.8 (C-3

or C-3′), 79.6 (C-2), 77.2 (C-4), 75.4 (CH₂Bn), 74.5 (CH₂Bn), 73.7

(C-5′), 73.6 (CH₂Bn),73.5 (CH₂Bn), 73.3 (CH₂Bn), 72.2 (C-2′), 71.1

(C-4′), 69.7 (C-6′), 69.3 (C-5), 67.9 (C-6), 54.9 (OCH₃), 37.6 (CH₂

Lev), 29.7 (CH₃Lev), 27.8 (CH₂Lev). HRMS: [M + Na]⁺calcd for

C₆₀H₆₄O₁₄Na 1031.41883, found 1031.41796.

́

, J. D. C.; Litjens, R. E. J. N.;

Methyl 2,3,4-Tri-O-benzyl-6-O-(2,6-di-O-benzoyl-3-O-benzyl-4-

levulinyl-β-^D-glucopyranosyl)-β-D-glucopyranoside (57). The title

compound was isolated as an transparent oil, which crystallized on

standing. [α]_D: + 17.4 (c = 1, DCM). IR (neat, cm⁻¹): 3057, 2928,

1719, 1452, 1420, 1362, 1315, 1263, 120, 1177, 1152, 1092, 1069, 1026,

́

(6) For some recent examples, see: (a) Wang, Z.; Xy, Y.; Yang, B.;

Tiruchinapally, G.; Sun, B.; Liu, R.; Dulaney, S.; Liu, J.; Huang, X.

Chem.Eur. J. 2010, 16, 8365−8375. (b) Zeng, Y.; Wang, Z.;

Whitfield, D.; Huang, X. J. Org. Chem. 2008, 73, 7952−7962. (c) Wu,

X. Y.; Cui, L. N.; Lipinski, T.; Bundle, D. R. Chem.Eur. J. 2010, 16,

3476−3488. (d) Polat, T.; Wong, C.-H. J. Am. Chem. Soc. 2007, 129,

12795−12800.

1

1013, 912, 897, 731, 698. H NMR (400 MHz, CDCl₃, HH-COSY,

HSQC): 8.05 (d, 2H, J = 8.4 Hz, H_arom), 7.93 (d, 2H, J = 8.4 Hz, H_arom),

7.54 (t, 1H, J = 7.6 Hz, H_arom), 7.46−7.40 (m, 3H, H_arom), 7.32−7.22

(m, 16H, H_arom), 7.21−7.14 (m, 4H, H_arom), 7.00−6.98 (m, 2H, H_arom),

5.42 (t, 1H, J = 9.6 Hz, H-2′), 5.28 (t, 1H, J = 9.6 Hz, H-4′), 4.86 (d, 1H,

J = 11.2 Hz, CHHPh), 4.71 (d, 1H, J = 12.0 Hz, CHHPh), 4.65 (d, 1H,

J = 11.2 Hz, CHHPh), 4.60−4.57 (m, 3H, H-1′, CH₂Ph), 4.56−4.53 (m,

2H, CHHPh, H-6′), 4.47 (d, 1H, J = 3.6 Hz, H-1), 4.41 (d, 1H, J = 11.2

Hz, H-6′), 4.36 (dd, 1H, J = 5.6 Hz, J = 11.2 Hz, H-6′), 4.22 (d, 1H, J =

11.2 Hz, CHHPh), 4.08 (d, 1H, J = 8.8 Hz, H-6), 3.90 (t, 1H, J = 9.6

Hz, H-3′), 3.84 (t, 1H, J = 9.6 Hz, H-3), 3.81−3.77 (m, 1H, H-5′),

3.68−3.63 (m, 2H, H-5, H-6), 3.41 (dd, 1H, J = 3.6 Hz, J = 9.6 Hz, H-

2), 3.33 (t, 1H, J = 9.6 Hz, H-4), 3.18 (s, 3H, OCH₃), 2.67−2.59 (m,

2H, CH₂Lev), 2.51−2.45 (m, 2H, CH₂Lev), 2.11 (s, 3H, CH₃Lev).

¹³C NMR (100 MHz, CDCl₃, HH-COSY, HSQC): 206.2 (CO Lev

ketone), 171.5 (CO Lev), 166.2 (CO Bz), 164.8 (CO Bz),

138.9 (C_qC_arom), 138.2 (C_qC_arom), 138.2 (C_qC_arom), 137.6 (C_qC_arom),

133.1 (CH_arom), 129.9 (CH_arom), 129.8 (C_qC_arom), 129.6 (C_qC_arom),

128.4−127.4 (CH_arom), 101.3 (C-1′), 97.9 (C-1), 81.9 (C-3), 79.8

(C-3′), 79.7 (C-2), 77.1 (C-4), 75.5 (CH₂Bn), 74.6 (CH₂Bn), 73.9

(CH₂Bn), 73.4 (CH₂Bn), 73.2 (C-2′), 72.3 (C-5′), 70.5 (C-4′), 69.3

(C-5), 68.1 (C-6), 63.1 (C-6′), 55.0 (OCH₃), 37.8 (CH₂Lev), 29.7

(CH₃Lev), 27.9 (CH₂Lev). HRMS: [M + Na]⁺calcd for C₆₀H₆₂O₁₅Na

1045.39809, found 1045.39751.

́

(7) (a) Codee, J. D. C.; Litjens, R. E. J. N.; van den Bos, L. J.;

Overkleeft, H. S.; van der Marel, G. A. Chem. Soc. Rev. 2005, 34, 769−

782. (b) Wang, Y.; Ye, X.-S.; Zhang, L.-H. Org. Biomol. Chem. 2007, 5,

2189−2200.

(8) Douglas, N. L.; Ley, S. V.; Lucking, U.; Warriner, S. L. J. Chem.

̈

Soc., Perkin Trans. 1 1998, 51−65.

(9) (a) Zhang, Z. Y.; Ollmann, I. R.; Ye, X. S.; Wischna, R.; Baasov,

T.; Wong, C.-H. J. Am. Chem. Soc. 1999, 121, 734−753. (b) Koeller,

K. M.; Wong, C.-H. Chem. Rev. 2000, 100, 4465−4493. (c) Ritter, T. K.;

Mong, K. K. T.; Liu, H. T.; Nakatani, T.; Wong, C.-H. Angew. Chem., Int.

Ed. 2003, 42, 4657−4660. (d) Lee, J.-C.; Greenberg, W. A.; Wong, C.-H.

Nat. Prot. 2006, 1, 3143−3152. (e) Wu, C.-Y.; Wong, C.-H. Top. Curr.

Chem. 2011, 301, 223−252.

(10) Pedersen, C. M.; Marinescu, L. G.; Bols, M. Chem. Commun.

2008, 2465−2467.

(11) For the establishment of relative reactivities of mannuronic acids,

see: Walvoort, M. T. C.; de Witte, W.; van Dijk, J.; Dinkelaar, J.; Lodder,

G.; Overkleeft, H. S.; Codee

2011, 13 (16), 4360−4363.

́

, J. D. C.; van der Marel, G. A. Org. Lett.

(12) (a) Mootoo, D. R.; Konradson, P.; Ududong, U.; Fraser-Reid, B.

J. Am. Chem. Soc. 1988, 110, 5583−5584. (b) Fraser-Reid, B.; Wu, Z.;

Ududong, U.; Ottoson, H. J. Org. Chem. 1990, 55, 6068−6070.

ASSOCIATED CONTENT

■

S

* Supporting Information

¹H NMR, H−H COSY NMR, HSQC NMR, and ¹³C APT

NMR spectra for all new compounds. This material is available

free of charge via the Internet at http://pubs.acs.org.

(c) Fraser-Reid, B.; Cristob

1−30.

́ ́

al-Lopez, J. Top. Curr. Chem. 2011, 301,

(13) (a) Fraser-Reid, B.; Wu, Z.; Webster Andrews, C.; Skowronski,

E. J. Am. Chem. Soc. 1991, 113, 1434−1435. (b) Jensen, H. H.;

Nordstrøm, M.; Bols, M. J. Am. Chem. Soc. 2004, 126, 9205−9213.

(14) (a) Schmidt, R. R.; Grundler, G. Synthesis 1981, 885−887.

(b) Schmidt, R. R.; Stumpp, M.; Michel, J. Tetrahedron Lett. 1982, 23,

405−408. (c) Veeneman, G. H.; van Leeuwen, S. H.; van Boom, J. H.

Tetrahedron Lett. 1990, 31, 1331−1334.

AUTHOR INFORMATION

■

Corresponding Author

*E-mail: (G.A.V.d.M.) marel_g@chem.leidenuniv.nl; (J.D.C.C.)

jcodee@chem.leidenuniv.nl.

(15) The effect of the nature of the ester (methyl versus benzyl) on

the reactivity of the glucuronyl donor was found to be very small: the

methyl ester was 1.3 times more reactive than the benzyl ester (1.3:1,

94% yield).

(16) Nair, H.; Nokes, D. J.; Gessner, B. D.; Dherani, M.; Madhi,

S. A.; Singleton, R. J.; O’Brien, K. L.; Roca, A.; Wright, P. F.; Bruce, N.;

ACKNOWLEDGMENTS

■

This research was supported by Top Institute Pharma and The

Netherlands Organization of Scientific Research (NWO).

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dx.doi.org/10.1021/jo201586r | J. Org. Chem. 2012, 77, 108−125

The Journal of Organic Chemistry

Article

Chandran, A.; Theodoratou, E.; Sutanto, A.; Sedyaningsih, E. R.;

Ngama, M.; Munywoki, P. K.; Kartasasmita, C.; Simoes, E. A.; Rudan,

̃

I.; Weber, M. W.; Campbell, H. Lancet 2009, 12 (374), 893−902.

(17) (a) Rennels, M. B.; Edwards, K. M.; Keyserling, H. L.; Reisinger,

K. S.; Hogerman, D. A.; Madore, D. V.; Chang, I.; Paradiso, P. R.;

Malinoski, F. J.; Kimura, A. Pediatrics 1998, 101, 604−611. (b) Duggan,

S. T. Drugs 2010, 70, 1973−1986.

(18) (a) Riedmann, E. M. Human Vaccines 2011, 7 (7), 716−716.

(b) Yeh, S. H.; Gurtman, A.; Hurley, D. C.; Block, S. L.; Schwartz,

R. H.; Patterson, S.; Jansen, K. U.; Love, J.; Gruber, W. C.; Emini, E.

A.; Scott, D. A. Pediatrics 2010, 126 (3), E493−e505.

(19) (a) Hotchkiss, R. D.; Goebel, W. F. J. Biol. Chem. 1937, 121,

195−203. (b) Reeves, R. E.; Goebel, W. F. J. Biol. Chem. 1941, 139,

511−519.

(20) (a) Lefeber, D. J.; Kamerling, J. P.; Vliegenthart, J. F. G.

Chem.Eur. J. 2001, 7 (20), 441−4421. (b) Lefeber, D. J.; Arev

́

alo,

E. A.; Kamerling, J. P.; Vliegenthart, J. F. G. Can. J. Chem. 2002, 80,

76−81.

(21) (a) Yu, B.; Tao, H. Tetrahedron Lett. 2001, 42, 2405−2407.

(b) Yu, B.; Sun, J. Chem. Commun. 2010, 46, 4668−4679.

(22) A chemoselective glycosylation with donor 12 and acceptor 24a

proved to be unproductive due to formation of anhydroglucoside 26b.

(23) Dinkelaar, J.; Witte, M. D.; van den Bos, L. J.; Overkleeft, H. S.;

van der Marel, G. A. Carbohydr. Res. 2006, 341, 1723−1729.

(24) Ensley, H. E.; Yu, H. Tetrahedron Lett. 2003, 44, 9363−9366.

́

(25) See, for example: (a) Codee, J. D. C.; Stubba, B.; Schiattarella, M.;

Overkleeft, H. S.; van Boeckel, C. A. A.; van Boom, J. H.; van der Marel,

G. A. J. Am. Chem. Soc. 2005, 127, 3767−3773. (b) Geurtsen, R.;

Boons, G. J. Tetrahedron Lett. 2002, 43, 9429−9431. (c) Li, Z.;

Gildersleeve, G. C. J. Am. Chem. Soc. 2006, 128, 11612−11619, and

references cited therein.

(26) Malysheva, N. N.; Torgov, V. I.; Klimov, E. M.; Kochetkov,

N. K. Russ. Chem. Bull. 1974, 23, 2075−2077.

(27) (a) Lahmann, M.; Oscarson, S. Can. J. Chem. 2002, 80, 889−

903. (b) Shiao, T. C.; Roy, R. Top. Curr. Chem. 2011, 301, 69−108.

(28) The reactivity difference between the C-6-O-benzyl donor 12

and C-6-O-benzoyl glucoside 27 was established in two competition

reactions in which both donors competed with donor 4 as described

above. Donor 12 turned out to be 19 times more reactive than donor

4, where donor 27 was 3-fold less reactive than this thioglycoside.

(29) The anomerization of thio-glycosides in the presence of Lewis

acids has been reported before. See, for example: (a) Connolly, D. T.;

Roseman, S.; Lee, Y. C. Carb. Res. 1980, 87, 227−239. (b) Satoh, H.;

Manabe, S.; Ito, Y.; Luthi, H. P.; Laino, T.; Hutter, J. J. Am. Chem. Soc.

̈

2011, 133, 5610−5619.

(30) Lu, L.-D.; Schie, C.-R.; Kulkarni, S. S.; Pan, G.-R.; Lu, X.-A.;

Hung, S.-C. Org. Lett. 2006, 8, 5995−5998.

(31) Mong, T.K.-K.; Huang, Y.; Wong, C.-H. J. Org. Chem. 2003, 68,

2135−2142.

(32) Wang, C.-C.; Kulkarni, S. S.; Lee, J.-C.; Luo, S.-Y.; Hung, S.-C.

Nat. Prot. 2008, 3, 97−113.

(33) Tuley, P.; Wong, C.-H. J. Am. Chem. Soc. 2007, 129 (42),

̈

12795−12800.

(34) Tanaka, H.; Sakamoto, H.; Sano, A.; Nakamura, S.; Nakajima,

M.; Hashimoto, S Chem. Commun. 1999, 13, 1259−1260.

(35) Kamat, M. N.; Meo, C. D.; Demchenko, A. V. J. Org. Chem.

2007, 72, 6947−6955.

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Exploring and exploiting the reactivity of glucuronic acid donors

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