Intramolecular aglycon delivery enables the synthesis of 6-deoxy-β-d-manno-heptosides as fragments of Burkholderia pseudomallei and Burkholderia mallei capsular polysaccharide

Article

pubs.acs.org/joc

Intramolecular Aglycon Delivery Enables the Synthesis of 6‑Deoxy-

β‑^D-manno-heptosides as Fragments of Burkholderia pseudomallei

and Burkholderia mallei Capsular Polysaccharide

Marielle Tamigney Kenfack, Yves Bleriot, and Charles Gauthier*

́

Universite de Poitiers, Institut de Chimie IC2MP, UMR-CNRS 7285, Equipe Synthese Organique, 4 rue Michel Brunet, 86073

́

̀

Poitiers, France

S

* Supporting Information

ABSTRACT: Burkholderia pseudomallei and Burkholderia

mallei are potential bioterrorism agents. They express the

same capsular polysaccharide (CPS), a homopolymer featuring

an unusual [→3)-2-O-acetyl-6-deoxy-β-^D-manno-heptopyrano-

syl-(1→] as the repeating unit. This CPS is known to be one

of the main targets of the adaptive immune response in

humans and therefore represents a crucial subunit candidate

for vaccine development. Herein, the stereoselective synthesis

of mono- and disaccharidic fragments of the B. pseudomallei

and B. mallei CPS repeating unit is reported. The synthesis of 6-deoxy-β-^D-manno-heptosides was investigated using both inter-

and intramolecular glycosylation strategies from thio-manno-heptose that was modiﬁed with 2-naphthylmethyl (NAP) at C2. We

show here that NAP-mediated intramolecular aglycon delivery (IAD) represents a suitable approach for the stereocontrolled

synthesis of 6-deoxy-β-^D-manno-heptosides without the need for rigid 4,6-O-cyclic protection of the sugar skeleton. The IAD

strategy is highly modular, as it can be applied to structurally diverse acceptors with complete control of stereoselectivity.

Problematic hydrogenation of the acetylated disaccharides was overcome by using a microﬂuidic continuous ﬂow reactor.

results have so far been obtained.^4,8−10In the subunit vaccine

INTRODUCTION

■

category, there is strong evidence to suggest that the surface

polysaccharides produced by B. pseudomallei and B. mallei are

the main virulence factors that trigger the production of

protective antibodies in humans.¹¹⁻¹⁴As for Gram-negative

bacteria, B. pseudomallei and B. mallei express high-molecular-

weight capsular polysaccharides (CPS) at their surface that act

as protective antigens. Interestingly, almost all virulent strains

of B. pseudomallei and B. mallei, whether of human or animal

origin, are known to express the same major CPS structure

(type I O-PS), a homopolymer featuring an uncommon [→3)-

2-O-acetyl-6-deoxy-β-^D-manno-heptopyranose-(1→] as the re-

peating unit (Figure 1).¹⁵⁻¹⁷Consequently, it has been

hypothesized that a CPS-based vaccine, if eﬀective, could

serve to immunize against both melioidosis and glanders

infections.^17,18

Burkholderia pseudomallei and Burkholderia mallei are the

causative agents of melioidosis^1,2and glanders,³respectively.

The clinical diagnosis of these diseases, which can aﬀect both

humans and animals, includes diverse manifestations that range

from pneumonia and septicemia to skin abscesses.⁴Because of

their high infectivity via the respiratory route and their intrinsic

resistance to many common antibiotics, together with their low

infectious doses and high mortality rates, B. pseudomallei and B.

mallei are considered category B bioterrorism agents according

to the U.S. Center for Disease Control and Prevention.⁵

Recently, both pathogens have been added to a top-priority list

among 13 “tier 1” selected agents and toxins by the U.S.

Furthermore, it has been proven that B. mallei was used as a

biological warfare agent during World Wars I and II, whereas

the use of B. pseudomallei as a biological weapon was evaluated

by the U.S. and the former Soviet Union.⁶The ease with which

B. pseudomallei and B. mallei can be obtained, cultured, and

disseminated (possibly on a large scale) makes the ﬁght against

these bacteria a serious public concern. Importantly, no human

or veterinary clinical vaccines are currently available for

immunization against melioidosis and glanders.⁵

For all of the aforementioned reasons, the development of an

eﬀective vaccine against B. pseudomallei and B. mallei has

recently become an important research issue.^4,7Over the last 2

decades, various experimental melioidosis and glanders vaccines

have been tested in animal models, such as live-attenuated,

killed whole-cell, and subunit vaccines, but only mitigated

Figure 1. Structure of B. pseudomallei and B. mallei CPS

homopolymer.

Received: March 19, 2014

Published: April 24, 2014

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Nevertheless, there are some severe issues associated with the

isolation of polysaccharides from the large-scale culture of

pathogenic B. pseudomallei and B. mallei bacteria, which require

manipulation in biosafety level 3 laboratories.⁷The industrial

production of such a CPS-based vaccine is also hampered by

the tedious puriﬁcation procedures required to produce pure

CPS that is free of bacterial contaminants in suﬃcient

quantities.¹⁹In recent years, organic synthesis has provided

convenient processes by which to generate homogeneous

carbohydrate antigens in a more reproducible manner.^20,21The

target sugar epitopes can be synthesized that display diﬀerent

lengths and feature suitable linkers at their reducing ends. They

can be used to produce well-deﬁned glycoconjugates and/or to

study the minimal epitopes needed for recognition with

protective antibodies.²²For instance, the success of the

Cuban anti-Hib CPS-based tetanus toxoid construct is a

striking example of the advantages of organic synthesis for the

development of glycoconjugate vaccines.²³

suitable for use with commonly used protecting groups such as

PMB and NAP ethers. Third, the saponiﬁcation step that is

required to cleave the (2-cyanophenyl)acetyl ester resulting

from the radical fragmentation is somewhat incompatible with

the synthesis of partially acetylated carbohydrates, such as B.

pseudomallei and B. mallei CPS fragments.

Intramolecular aglycon delivery (IAD)^37,38is an alternative

approach for the stereoselective synthesis of 1,2-cis-glycosides.

IAD was originally pioneered by Hindsgaul³⁹and Stork⁴⁰to

tackle the problem of β-^D-mannoside synthesis. This method

was further implemented by Ito and Ogawa,⁴¹who developed

the PMB-⁴²⁻⁴⁴and NAP-mediated^45,46IAD for the synthesis of

challenging 1,2-cis-linkages. In this two-step protocol (Figure

2), a glycosyl donor equipped with a PMB or NAP group at the

From the organic chemistry perspective, the synthesis of the

B. pseudomallei and B. mallei CPS repeating unit is challenging.

The major diﬃculties are 3-fold: (1) the stereospeciﬁc

formation of a 1,2-cis-manno glycosidic bond, (2) the C6

one-carbon homologation to generate a 6-deoxy-^D-manno-

heptose, and (3) the introduction of a labile acetyl group at C2.

We report herein the chemical synthesis of the B. pseudomallei

and B. mallei CPS repeating unit. Stereoselective synthesis of

mono- and disaccharidic fragments (1−4) of (1→3)-linked 6-

deoxy-2-O-acetyl-β-^D-manno-heptopyranosides was studied

using inter- and intramolecular glycosylation strategies. For

the ﬁrst time, we have successfully showed that the 2-

naphthylmethyl (NAP)-mediated intramolecular aglycon deliv-

ery strategy is suitable for the complete stereocontrolled

synthesis of 6-deoxy-β-^D-manno-heptopyranosides without the

need for rigid 4,6-O-cyclic protection.

RESULTS AND DISCUSSION

■

Synthetic Approach. In the core and surface polysacchar-

ides of Gram-negative bacteria, ^L- and D-glycero-D-manno-

heptoses of the α-anomeric conﬁguration (1,2-trans) are

ubiquitous.²⁴Stereoselective syntheses of complex bacterial

oligosaccharides incorporating these α-manno-heptoses have

been achieved by taking advantage of the so-called neighboring

group participation eﬀect of having an acetyl at the C2

position.²⁵⁻³¹Nevertheless, the synthesis of β-linked-manno-

heptosides (1,2-cis)³²still represents a major challenge. As far

as we are aware, Crich and co-workers³³⁻³⁵are the only group

to have reported the stereocontrolled synthesis of 1,2-cis-

manno-heptosides in either the ^D- or L-glycero conﬁgurations.

Their approach relies on a 4,6-O-alkylidene-type acetal donor

that is required to achieve good β-stereoselectivity under donor

preactivation conditions. The methodology was also extended

to the preparation of 6-deoxy-β-^D-manno-heptosides.^34,36In

order to do so, they devised a 4,6-O-[1-cyano-2-(2-

iodophenyl)ethylidene] acetal-protected thioglycoside donor.

After β-stereoselective glycosylation, the target glycoside was

formed via a reductive radical fragmentation followed by an

oxidative treatment with DDQ. Although this very elegant

methodology represents pioneering work in the ﬁeld, certain

drawbacks are associated with its application to oligosaccharide

synthesis. First, it necessitates the formation of a diastereoiso-

meric mixture of ^L- and D-glycero-manno-heptopyranoses prior

to the synthesis of the 4,6-O-protected cyclic acetal. Second, the

oxidative treatment with DDQ under aqueous conditions is not

Figure 2. Retrosynthetic analysis of B. pseudomallei and B. mallei CPS

fragments via inter- or intramolecular glycosylation.

C2 position and an alcohol acceptor are tethered using DDQ to

form a mixed acetal via a single electron transfer mechanism.

After activation of the anomeric position, the aglycon is

stereoselectively delivered from the same side as the tether,

yielding excellent if not exclusive β-anomeric selectivity in most

substrates. In the case of our work, the IAD approach was

particularly appealing because the regenerated free OH at the

C2 position could be directly acetylated after the glycosylation

step.

As depicted in Figure 2, monosaccharide 1 and disaccharide

3, representing one or two repeating unit(s) of B. pseudomallei

and B. mallei CPS, respectively, were chosen as targets. Because

we were mindful of potential trans esteriﬁcation^47,48between

the alcohols at C2 and C3 in the ﬁnal compounds, we also

planned to synthesize the corresponding C3 O-propylated

compounds, 2 and 4. In this manner, the acetyl migration

would be avoided, and we reasoned that the propyl group could

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mimic the chain elongation/termination at the C3 position.

The reducing-end anomeric positions of the target compounds

were ﬁxed in the β-conﬁguration bearing an 5-amino-1-pentyl

linker, which would further serve to anchor the CPS fragments

to an immunogenic protein, such as CRM-197.⁴⁹Intermo-

lecular glycosylation with heptose donor A was also

investigated considering that we could modulate the β-

selectivity via the so-called “nitrile” eﬀect.⁵⁰NAP-mediated

IAD⁴⁵was favored over PMB owing to the superior yields

typically obtained for the mixed acetals formation as well as the

intramolecular glycosylation step.³⁸Regarding heptose A, two

diﬀerent protecting groups at the C3 position, namely, TBS and

allyl, were investigated. It was expected that both TBS and allyl

groups could be selectively removed allowing further chain

elongation at C3 to provide oligosaccharide fragments by

iteration of the optimized 1,2-cis-glycosylation protocol.

Moreover, a thiophenyl moiety was chosen at the anomeric

position because it can be activated in the presence of soft

electrophiles without aﬀecting the protecting groups.⁵¹

over two steps. Allylation of 5 was accomplished with

stannylene acetal chemistry⁵⁵using dibutyltin(IV) oxide

(Bu₂SnO) followed by treatment with allyl bromide (AllBr)

at 80 °C to aﬀord 8 in high yield (95%). The latter was

protected at C2 with a NAP group under the aforementioned

conditions to give 9 (89%). The regioselectivity of the reactions

was conﬁrmed by 2D NMR HMBC, which showed strong

cross-peak correlations between CH₂NAP and C2.

The regioselective reductive ring opening of the benzylidene

acetals^56,57in 7 and 9 to provide primary alcohol derivatives 10

and 11 was examined next (Table 1). Reaction of 7 with boron

tetrahydrofuran complex (BH₃·THF) in the presence of

catalytic amounts of scandium(III) triﬂate⁵⁸[Sc(OTf)₃] led

to desired alcohol 10 in 30% yield along with concomitant TBS

deprotection (entry 1). Substitution of Sc(OTf)₃with

trimethylsilyl triﬂuoromethanesulfonate (TMSOTf)⁵⁹led to

10 being produced in a much improved yield of 89% without

aﬀecting the TBS group (entry 2). DIBALH/tol-mediated

reduction⁶⁰of 7 furnished 10 in only 14% yield along with 3,6-

diol 12 and unreacted starting material (entry 3). Ring opening

of benzylidene acetal 9 was then attempted using BH₃·THF

(entry 4); however, predominant hydroboration of the double

bond led to decomposition. Reaction of 9 with DIBALH/tol

under diluted conditions was sluggish, aﬀording expected

regioisomer 11 in 41% (entry 6). More gratifying results were

obtained when 9 was treated with DIBALH/tol without

diluting the substrate (entry 7). Under these conditions, 11

was formed in 73% yield along with its regioisomer, 13 (15%),

in an inseparable mixture.

Synthesis of 6-Deoxy-manno-heptose Donors. The

synthesis of manno-heptose donors started with known 4,6-O-

benzylidene thiomannoside 5^52,53(Scheme 1). The bulky TBS

Scheme 1. Regioselective Synthesis of Mannose Derivatives

7 and 9

The C6 one-carbon homologation of derivatives 10 and 11

was then studied (Scheme 2). Two diﬀerent synthetic

approaches have been described in the literature for the chain

elongation toward 6-deoxy-^D-manno-heptoses.²⁶The strategy

developed by Boren

and co-workers⁶¹involved the Wittig

́

reaction of the C6 aldehyde group with methoxymethylene-

triphenylphosphorane followed by acid hydrolysis. In another

approach, Aspinall and co-workers^62,63displaced a 6-O-triﬂate

or mesylate group with cyanide ions followed by reduction with

DIBALH and acid hydrolysis. The latter strategy was adopted

for this project.

group was regioselectively introduced at C3 by reacting 5 with

tert-butyldimethylsilyl triﬂuoromethanesulfonate (TBSOTf) in

the presence of triethylamine (Et₃N). Subsequent reaction of

crude product 6 with 2-(bromomethyl)naphthalene (NAPBr)

in the presence of sodium hydride (NaH) gave 7⁵⁴in 79% yield

Therefore, alcohol 10 was treated with triﬂic anhydride

(Tf₂O) in the presence of 2,6-lutidine. Unexpectedly, the

Table 1. Regioselective Reductive Ring Opening of Benzylidene Acetals 7 and 9

a

yield (%)

10 or 11

entry

compd

reagent(s)

solvent

T (°C)

23

time (h)

13

c

b

1

2

3

4

5

6

7

9

BH₃·THF/Sc(OTf)₃

BH₃·THF/TMSOTf

DIBALH/tol

DCM

neat

21

3

30

89

c

23

bd

,

−78 to 23

23

24

0.5

2

14

c

e

BH₃·THF

e

c

DIBALH/DCM

−10 to 23

f

DIBALH/tol

tol

24

3

41

73

5

f

neat

15

a

b

c

d

e

Isolated yield. 3,6-Diol 12 was obtained as the major compound. Not detected. Starting material was recovered in 25% yield. Decomposition of

f

1

the starting material, leading to a complex mixture. Obtained as an inseparable mixture. Ratio was estimated by H NMR.

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Scheme 2. C6 One-Carbon Homologation toward Nitrile Derivatives 18 and 19

corresponding triﬂate derivative was converted in situ into

more stable 3,6-anhydro-mannose 14 in 62% yield, releasing

TBSOTf in the process. The ³J_1,2coupling constant of 8.0 Hz in

Scheme 3. Three-Step Nitrile Conversion to C7 Primary

Alcohols 20 and 21

1

the H NMR spectra of 14 indicated a C₄conformation. The

formation of 3,6-anhydro-mannose is not unprecedented, as

Kovac⁶⁴and Lowary⁶⁵isolated similar compounds under

ﬂuorinating conditions. By contrast, when allyl derivative 11

was treated with Tf₂O, only decomposition occurred and no

anhydro-mannose was isolated. To circumvent this problem,

tosylation²⁷of 10 with tosyl chloride (TsCl) in the presence of

catalytic DMAP in pyridine aﬀorded compound 15 in 82%

yield. The mixture of regioisomers 11 and 13 was tosylated

under the same conditions. At this step, secondary alcohol 13

did not react with TsCl; therefore, compounds 13 and 16

(88%) were readily separable by ﬂash chromatography. The

formation of chlorinated compound 17 was observed as a side

product when the reaction was run at high temperature. S_N2

reaction of tosylated 15 and 16 proceeded without

complication by using potassium cyanide (KCN) together

with 18-crown-6 in anhydrous CH₃CN (88% for 18, 67% for

19).²⁷

A three-step reduction of nitriles into C7 primary alcohols

was then investigated. As depicted in Scheme 3, nitrile

derivatives 18 and 19 were reduced with DIBALH at cryogenic

temp (−78 °C). Interestingly, the (i-Bu)₂Al-imine complex was

detected by LRMS. After acidic hydrolysis (THF/1 N HCl(aq)

9:1) of the imine, the resulting aldehydes were reduced to

desired alcohols 20 and 21 with sodium borohydride (NaBH₄).

When nitrile 18 was subjected to this procedure (Table 2), only

moderate yields of alcohol 20 were obtained (33−60%, entry

1). These yields, however, were not reproducible, and cleavage

of the TBS group occurred predominantly. Better results were

obtained with allyl derivative 19, which aﬀorded 21 in 87%

yield when using 1.2 equiv of DIBALH/tol (entry 2). It is

noteworthy that acidic hydrolysis with THF/1 N HCl was

crucial in order to convert all of the imine into aldehyde;

otherwise, 21 was formed in lower yield (56%, entry 3).

Moreover, use of DIBALH in DCM mainly led to degradation

of 19 into primary amine 22, as detected by LRMS (entry 4).

Subsequent benzylation of the C7 primary alcohol in 20 was

not as straightforward as expected (Table 3). Under standard

Table 2. Optimization of Nitrile Reduction Using DIBALH

a

entry

compd

reagent (1.2−1.5 equiv)

solvent

yield (%)

b

1

2

3

4

18

19

DIBALH/tol

DIBALH/DCM

tol

33−60

tol

87

c

tol

56

d

DCM

a

Isolated yield in alcohol 20 or 21 (over three steps from 18 or 19).

b

Yields were not reproducible, and unidentiﬁed byproducts were

c

formed. Crude was dissolved in EtOAc and washed with 1 N HCl

d

(3×) instead of reacting it for 1 h with THF/1 N HCl. Degradation

occurred. Amine 22 was detected by LRMS (m/z 556 [M + H]⁺).

conditions (NaH, BnBr), derivative 23 was formed in 50% yield

at best along with alcohol 24 (20%) because of the partial

cleavage of the TBS group (entry 1). We then tried using

neutral conditions of silver(I) oxide (Ag₂O), but 23 was

isolated in 36% yield along with 24 (12%) and unreacted 20

(entry 2). In contrast, benzylation of allyl derivative 21 gave a

nearly quantitative yield of 97% without formation of 24 when

standard conditions (NaH, BnBr) were used.

To summarize this section, novel 6-deoxy-^D-manno-heptose

donors 23 and 25 were synthesized in nine linear steps from

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promoter systems were screened, such as dimethyl(methyl-

thio)sulfonium triﬂuoromethanesulfonate (DMTST),⁶⁷p-nitro-

benzenesulfenyl triﬂate (p-NO₂PhSOTf),⁶⁸and dimethyl

disulﬁde (Me₂S₂)/Tf₂O⁶⁹together with 4 Å molecular sieves

as well as the hindered base 2,6-di-tert-butyl-4-methylpyridine

(DTBMP); the latter acts as an acid-scavenger. Other well-

known promoter systems, such as NIS/triﬂic acid (TfOH),

NIS/silver triﬂuoromethanesulfonate (AgOTf), iodine dicolli-

dine perchlorate (IDCP), and IBr, could not be employed

because of the incompatibility of the allyl group in 25 with

iodonium ions. We ﬁrst tried a normal activation procedure in

which 25 and 26 were premixed before adding the promoter

(entries 1−5). Glycosylation with DMTST in DCE from −10

to 40 °C aﬀorded predominantly α-anomer 27 (48%) along

with β-anomer 28 (35%) (entry 1). The mixture was readily

separable by silica gel chromatography. The stereochemistry of

the anomeric linkages was assigned on the basis of undecoupled

Table 3. Primary Alcohol Benzylation for the Synthesis of

Mannoheptoses 23 and 25

a

yield (%)

entry

compd

reagents

23 or 25

24

b

1

2

3

20

BnBr, NaH, DMF

BnBr, Ag₂O, DCM

BnBr, NaH, DMF

50

20

36

97

12

c

21

a

b

c

Isolated yield. Yields were not reproducible. Not detected.

1

2D NMR HSQC J_C1,H1coupling constants (168 Hz for 27;

154 Hz for 28). In order to increase the diastereoselectivity

toward the β-anomer, acetonitrile was added in the reaction to

take advantage of the β-stereodirective nitrile eﬀect.⁵⁰

Unfortunately, no signiﬁcant improvements were observed

using a 2:1 DCE/CH₃CN solvent mixture (entry 2), whereas a

slight increase in β-selectivity occurred in neat CH₃CN (90%,

ratio 27/28 ∼ 1.0:1.1, entry 3). No glycosides were formed

under the promotion of p-NO₂PhSOTf, as 25 was almost

totally recovered (entry 4). Activation of 25 using Me₂S₂/Tf₂O

only provided trace amounts of heptosides 27 and 28 (entry 5).

Preactivation conditions⁷⁰were then assessed at −78 °C in

which donor 25 was activated with diﬀerent promoters prior to

adding acceptor 26 to the mixture (entries 6−9). We reasoned

that this protocol could favor the in situ formation of a transient

α-anomeric triﬂate^71,72and allow the synthesis of β-heptoside

28 in increased yields via an S_N2-like reaction.⁷³Similar to the

known diol 5. Superior overall yields were obtained for allyl

derivative 25 (35%) compared to that of TBS derivative 23

(15%), which could be attributed to the increased stability of

the allyl group under both reductive and acidic conditions.

Throughout this robust synthetic sequence, we were able to

routinely prepare gram quantities of 25 (∼5 g), which was

stable for several months when stored at −20 °C. Thus,

optimization of the inter- and intramolecular glycosylation

conditions were preferentially performed with derivative 25

with the knowledge that under Pd-catalyzed hydrogenation the

allyl group could be converted into target C3 O-propylheptose

derivatives 2 and 4.

Intermolecular Glycosylation. With heptose 25 in hand,

we next planned to study its stereoselective behavior as a donor

under standard intermolecular glycosylation conditions with

azidopentyl acceptor 26⁶⁶(Table 4). Diﬀerent thioglycoside

Table 4. Intermolecular Glycosylation of Thiodonor 25 with Azide 26 with or without Donor Preactivation

a

yield (%)

entry

reagent(s)

solvent

T (°C)

time (h)

27

48

28

35

b

c

1

DMTST

DCE

−10 to 40

−10 to 23

−10 to 40

−78 to 40

−78 to −30

−78 to 23

−78

2

b

c

2

DMTST

DCE/CH₃CN 2:1

CH₃CN

DCE

2

48

38

b

3

5

42

e

48

e

b

d

4

p-NO₂PhSOTf

Me₂S₂/Tf₂O

p-NO₂PhSOTf

Me₂S₂/Tf₂O

24

1

b

5

DCE

trace

e

trace

e

f

6

DCM

24

3

f

gh

,

gh

,

7

DCM

f

c

8

DMTST

DCM

16

2

49

g

32

g

f

9

Ph₂SO/Tf₂O

DCM

a

d

g

b

c

Isolated yield. Normal procedure without donor preactivation. DMTST was formed in situ by reacting Me₂S₂(3.0 equiv) and MeOTf (3.0 equiv).

e

f

p-NO₂PhSOTf was formed in situ by reacting p-NO₂PhSCl (1.2 equiv) and AgOTf (2.5 equiv). No reaction. Donor preactivation protocol.

Donor degradation into hemiacetal 30 occurred. Thiomethyl glycoside 29 was isolated as a minor compound (18%).

h

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normal procedure, p-NO₂PhSOTf did not allow the activation

of donor 25 (entry 6). Preactivation under the promotion of

Me₂S₂/Tf₂O led to degradation of 25 along with a minor

compound whose structure was assigned to α-thiomethyl

glycoside 29 (18%, ¹J_C1,H1= 165 Hz, entry 7). This compound

could come from S-glycosylation between activated donor 25

and methanethiol, which is formed in situ by the reaction of

acceptor 26 with highly reactive intermediate CH₃STf.

Preactivation with DMTST did not proceed successfully at

−78 °C; yield and selectivity comparable with the normal

procedure were obtained when the reaction was performed at rt

(entry 8). The powerful diphenylsulfoxide (Ph₂SO)/Tf₂O⁷⁴

promoter system was also explored under preactivation

conditions, but unfortunately, donor degradation occurred

predominantly (entry 9).

such as primary (41), secondary (42 and 43), and tertiary (44)

alcohols, in order to evaluate the scope of the reaction. Good to

excellent yields were achieved with diacetone galactose (36,

62%) and diacetone glucose (37, 83%), whereas the reaction

with the more hindered stigmastanol (43) and 1-adamantanol

(44) provided acetals 38 and 39 in moderate yields (40−44%).

The rather low isolated yields obtained for acetals 38 and 39

were mainly due to instability toward puriﬁcation on silica gel

because conversions were almost complete according to TLC.

Moreover, degradation of acetals 33, 34, 38, and 39 occurred in

deuterated solvents (CDCl₃and/or py-d₅) during extensive ¹H

and ¹³C NMR analysis. Noteworthy, acetals were always

formed in an inseparable R/S mixture with a predominance for

the S diastereoisomer (R/S ratio of 1:4 for 36), based on 2D

NMR NOE correlations together with the empirical rules

previously reported by Ito.⁴³

Mixed acetals 33−35 were then subjected to the IAD

reaction under diﬀerent activating conditions (Table 5).

Glycosylations were usually performed in diluted DCE at 40

°C in the presence of 5 Å molecular sieves in conjunction with

hindered base DTBMP, which has been shown to be a crucial

acid scavenger throughout the IAD process.³⁸When methyl

triﬂuoromethanesulfonate (MeOTf) was used as the promoter,

degradation of tethers 33 and 34 predominantly occurred

(entries 1 and 2). Cleavage of the TBS group in 33 was also

detected by LRMS. Changing MeOTf to p-NO₂PhSOTf

provided somewhat improved results, as target β-heptoside

46 was isolated as a single anomer, albeit in low yield (16%,

entry 3). Other isolated products consisted mainly of the

degradation product of tether 34 and unreacted starting

material. Under the promotion of DMTST, the acetals were

found to be more stable throughout the IAD process, and

increased yields of β-manno-heptosides 46 (45%) and 47

(62%) were obtained with complete β-stereoselectivity; no α-

heptosides were isolated or detected by NMR (entries 4 and 5).

The eﬃciency of the intramolecular glycosylation was strongly

solvent-dependent (entries 6−9). It was observed that

switching DCE to CH₃CN or toluene had a detrimental eﬀect

on the yields, whereas in THF, acetal 35 was degraded.

Moreover, no reaction occurred in DMF, and the starting

material was fully recovered. It was also observed that the

reaction rate and formation of byproducts were modulated by

the nature of the molecular sieves, namely, 4 or 5 Å MS.

Indeed, identical experiments using 4 Å MS accelerated the

reaction kinetic, providing 47 in decreased yield (36%, entry

10). During the latter reaction, α-(1→2)-linked disaccharide 49

was also isolated as a minor byproduct. It can be postulated that

49 originated from the intermolecular glycosylation of β-

manno-heptoside 47 with hydrolyzed acetal 48, which was

detected in the reaction mixture.

Although the intermolecular glycosylation strategy provided

somewhat low β-stereoselectivities, the good overall yield

(90%) obtained with the normal procedure prompted us to

apply the optimized conditions to the formation of disaccharide

31 (Scheme 4). Deallylation of 28 under Ir-catalyzed⁷⁵

Scheme 4. Attempt To Synthesize Disaccharide 31 via an

Optimized Intermolecular Glycosylation Reaction

conditions aﬀorded 32 in excellent yield (97%). Unfortunately,

glycosylation of acceptor 32 with thiodonor 25 under DMTST

promotion in acetonitrile gave only trace amounts of

disaccharide 31 even after forcing the conditions (6.0 equiv

DMTST, reﬂux, 24 h). Acceptor 32 was almost fully recovered

after the reaction together with hydrolyzed donor 30. This

coupling incompatibility between 25 and 32 could be due to

the unfavorable steric interactions between the two NAP

groups at C2. At this point, no further optimization of the

intermolecular process was undertaken, and synthetic eﬀorts

were exclusively focused toward the IAD approach.

Intramolecular Glycosylation. Formation of mixed

acetals between heptose derivatives and aminolinkers was the

ﬁrst step of the IAD protocol (Scheme 5). Thus, heptoses 23 or

25 were reacted with alcohols 26 or 40⁷⁶in the presence of

DDQ (1.2 equiv) and 4 Å MS in DCM at rt. Good to excellent

yields (62−81%) of mixed acetals 33−35 were isolated within

short reaction times (2−3 h). Other solvents (tol, CH₃CN,

THF, and DMF) were screened, but reactions were sluggish

and gave decreased yields. A reaction was also performed that

used CAN instead of DDQ as the oxidizing agent, but no acetal

formation occurred. A series of acceptors were then selected,

We then applied the optimized IAD conditions to more

complex acetals (Scheme 6). Complete β-stereoselectivities

(¹J_C1,H1= 155−158 Hz) were achieved in all cases with yields

ranging from 46 to 75% for heptosides 47, 50, 51, and 53.

Adamantanyl acetal 38 was, however, unstable under these

conditions and underwent hydrolysis to alcohol 48; only trace

amounts of β-heptoside 52 were detected. Therefore, instead of

starting from puriﬁed acetals (route A), the IAD reaction was

performed on the crude acetals mixture in order to minimize

degradation (route B). Under these conditions, adamantanyl β-

heptoside 52 was isolated in a satisfying 58% yield over two

steps. This one-pot procedure proved to be eﬃcient for the

synthesis of heptosides 47, 50, and 52, although similar overall

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a

Scheme 5. Synthesis of Mixed Acetals 33−39

a

Acetals with an asterisk were unstable and degraded in CDCl₃and/or py-d₅during NMR analysis. Naph = naphthyl.

Table 5. Optimization of the IAD Reaction with Acetals 33−35

a

yield (%)

entry

compd

reagent

MeOTf

solvent

product

β

α

b

1

2

3

4

5

6

7

8

9

10

33

34

35

DCE

45

46

47

25

c

MeOTf

DCE

d

b

p-NO₂PhSOTf

DCE

16

45

62

35

e

DMTST

DCE

e

DMTST

DCE

e

DMTST

CH₃CN

toluene

THF

e

DMTST

12

e

c

DMTST

e

f

DMTST

DMF

DCE

eg

,

h

b

DMTST

36

a

b

c

d

Isolated yields. Not detected. Acetal decomposition occurred leading to alcohol 48 as the major compound. p-NO₂PhSOTf was formed in situ

e

by reacting p-NO₂PhSCl (1.2 equiv) and AgOTf (2.5 equiv). DMTST was formed in situ by reacting Me₂S₂(3.0 equiv) and MeOTf (3.0 equiv).

f

g

h

No reaction. Reaction was performed with 4 Å MS for 2 h. Disaccharide 49 was isolated as a byproduct.

yields were achieved for heptosides 51 and 53. Notably, the

exclusive β-stereoselectivity achieved for the NAP-mediated

IAD reaction of 6-deoxy-manno-heptosides is rather unusual

because similar work with mannosides highlighted the

importance of 4,6-O-cyclic protection to reach high β-

stereoselectivity.^42,54Recently, Ito and co-workers⁴⁶have also

reported the synthesis of β-mannosides with complete control

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Scheme 6. Scope of the IAD Approach

of stereoselectivity through NAP-mediated IAD using 3,4,6-tri-

O-benzylated donors.

alcohol 55 in 55% yield. At this stage, acetyl migration from the

C2 to the C3 position could not be avoided (ratio C2/C3 ∼

4:1). Therefore, in order to minimize trans esteriﬁcation,

alcohol 55 was not puriﬁed but was directly coupled with an

equimolar amount of thiodonor 25 using the optimized one-

pot IAD protocol. In this way, disaccharide 56 was obtained in

58% yield with complete β-selectivity (¹J_C1′,H1′= 159 Hz). The

free alcohol in 56 was then acetylated to give 57 (96%). The

byproducts of the IAD reaction mainly consisted in the

formation of C2 alcohol 48 and unreacted acceptor 55 coming

from the decomposition of the naphthaldehyde acetal. No (1→

2)-linked disaccharide was isolated from the reaction mixture.

Final Deprotection of Mono- and Diheptosides. Pd-

catalyzed hydrogenation of monosaccharides 55 and 54 cleanly

yielded target heptosides 1 and 2, respectively, in the form of

their hydrochloride salts (Scheme 8). Importantly, Pd black

together with 1.0 equiv of HCl were needed for complete

deprotection. Indeed, hydrogenation was incomplete even after

a long reaction time (>48 h) with catalysts such as Pd/C or

Pd(OH)₂/C, whereas the use of a higher amount of HCl (>1.0

equiv) led to partial deacetylation. 1D and 2D NMR analysis of

heptoside 1 showed that the acetyl group partially migrated

from C2 (1a) to C3 (1b) (ratio of 1a/1b ∼ 1.7:1.0 in D₂O).

Such acetyl migration was recently observed by Wong and co-

workers in the synthesis of partially C2 acetylated β-(1→4)-

linked oligomannose derivatives.⁴⁸

Having shown that the IAD approach was suitable for the

synthesis of diverse β-heptosides, we undertook the synthesis of

disaccharidic B. pseudomallei and B. mallei CPS mimics 3 and 4

(Scheme 7). First, the IAD reaction was scaled up to 1 g,

aﬀording heptoside 54 in 58% yield over three steps upon

acetylation of crude alcohol 47. Ir-catalyzed deallylation of 54

provided only low and nonreproducible yields of alcohol 55

(<50%), which was presumably due to the catalyst deactivation

with trace pyridine found in 54. Deallylation of 54 using

stoichiometric palladium(II) chloride (PdCl₂) in MeOH gave

Scheme 7. Synthesis of Disaccharide 57 by Optimized IAD

Reaction

Deallylation of disaccharide 57 under standard conditions

(PdCl₂, MeOH/DCE) gave 58 (69%). Contrary to mono-

saccharide 55, no acetyl migration occurred in 58, even after

silica gel chromatography, as revealed by ¹H NMR.

Unexpectedly, hydrogenolysis of disaccharides 57 and 58 into

target heptosides 3 and 4 was found to be highly problematic.

Incomplete deprotection of the four benzyl groups occurred

using common catalysts such as Pd/C, Pd(OH)₂/C and Pd

black in various solvents including MeOH, THF, and AcOH as

well as in mixtures of the latter. Furthermore, performing the

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Scheme 8. Global Deprotection of Monosaccharides 54 and

55

Scheme 9. Final Deprotection of Disaccharides 57 and 58

hydrogenation under pressure (6 bar) did allow complete

debenzylation using Pd black in MeOH/THF/AcOH

(2.0:1.0:0.3). However, methylation occurred on the free

amine as well as other nonidentiﬁed side reactions, providing

only trace amounts of target compounds. We hypothesized that

the amine generated during the hydrogenation process was

poisoning the catalyst and consequently dramatically decreasing

the rate of debenzylation. Similar problems were encountered

by Lowary and co-workers during the hydrogenation of an ^L-

gluco-heptopyranose featuring a 8-azido-1-octyl chain and four

benzyl groups.⁷⁷They managed to overcome this diﬃculty by

performing a cumbersome four-step protocol involving (1)

selective azide reduction, (2) amine protection into a NHTFA,

(3) debenzylation, and (4) amine deprotection. This procedure

was obviously not suitable for the synthesis of our targets

because the NHTFA could not be selectively deprotected in the

presence of acetyl groups. Therefore, we instead turned our

attention to a microﬂuidic continuous ﬂow hydrogenation

reactor system. Gratifyingly, performing the hydrogenation

reaction with the H-Cube system in the full-H₂mode using

Pearlman’s catalyst cleanly produced disaccharidic heptosides 3

and 4 in the form of their HCl salts (Scheme 9). After only one

run, complete debenzylation occurred without any side

1

reactions on the free amine. As revealed by the H NMR

Figure 3. Selected area of the ¹H NMR spectra (500 MHz) of

heptosides after dissolution in D₂O: (a) monosaccharide 2; (b)

monosaccharides 1a/1b; (c) disaccharide 4; and (d) disaccharides 3a/

3b.

spectrum of heptoside 3, intramolecular migration of the acetyl

group between the C2′ (3a) and C3′ (3b) positions was

unavoidable, and an almost 1:1 mixture of the 3a/3b

regioisomers was formed upon dissolution in D₂O (Figure

3). As expected, no acetyl transfer occurred for C3 O-propyl

analogue 4.

NAP group at the C2 position. Notably, a rigid 4,6-O-

benzylidene protection was not required to reach full β-

selectivity. Global deprotection of disaccharides was problem-

atic under standard hydrogenation conditions but was found to

be eﬀective under microﬂuidic conditions. The B. pseudomallei

and B. mallei CPS fragments (1−4) were equipped with a 5-

amino-1-pentyl linker at the anomeric position, enabling their

subsequent conjugation with a carrier protein. This will allow

the preparation of glycoconjugate vaccines that could elicit

protective immune responses in vivo in mouse models of

CONCLUSIONS

■

In this study, we successfully applied the NAP-mediated IAD

reaction for the stereoselective synthesis of diverse 6-deoxy-β-^D-

manno-heptosides including four mono- and disaccharides

representing, respectively, one and two repeating units of B.

pseudomallei and B. mallei CPS homopolymer. Complete

stereoselectivity was achieved for the glycosylation reaction

using a newly developed thioheptose donor equipped with a

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mmol, 1.02 equiv), dried TBAI (1.23 g, 3.33 mmol, 1.2 equiv), and

AllBr (0.3 mL, 3.3 mmol, 1.2 equiv) were successively added. After

stirring for 24 h at 80 °C, the mixture was concentrated under reduced

pressure. The residue was puriﬁed by silica gel ﬂash chromatography

(PE/EtOAc 95:5 to 80:20) to aﬀord 8 (1.06 g, 95%) as a yellow oil: R_f

melioidosis and/or glanders. The synthesized heptosides could

also be used to assess the minimal epitopes required for

recognition with anti-CPS antibodies, work that is currently in

progress in our laboratory.

0.5 (PE/EtOAc 7:3); [α]_D²⁰= +227 (c 0.4, CHCl₃); H NMR (400

1

EXPERIMENTAL SECTION

MHz, CDCl₃) δ 7.53−7.26 (m, 10H, CH-Ar), 5.98−5.88 (m, 1H, H-

2All), 5.62 (d, J = 1.0 Hz, 1H, H-1), 5.60 (s, 1H, CH-acetal), 5.33

(ddd, J = 17.3, 4.8, 1.6 Hz, 1H, H-3aAll), 5.23 (ddd, J = 10.3, 4.0, 1.4

Hz, 1H, H-3bAll), 4.35 (dd, J = 6.1, 1.3 Hz, 1H, H-1aAll), 4.33−4.31

(m, 2H, H-5, H-2), 4.24 (td, J = 6.1, 1.3 Hz, 1H, H-1bAll), 4.22−4.18

(m, 1H, H-6a), 4.12 (t, J = 9.5 Hz, 1H, H-4), 3.88 (dd, J = 9.1, 3.4 Hz,

1H, H-3), 3.84 (t, J = 10.4 Hz, 1H, H-6b), 2.84 (d, J = 1.3 Hz, 1H,

OH); ¹³C NMR (100 MHz, CDCl₃) δ 137.6−133.5 (2 × C-Ar), 134.3

(C-2All), 131.7−126.1 (CH-Ar), 117.8 (C-3All), 101.8 (C-acetal),

87.9 (C-1), 79.1 (C-4), 75.4 (C-3), 72.2 (C-1All), 71.6 (C-5), 68.7 (C-

6), 64.7 (C-2); HRMS (ESI-TOF) m/z [M + H]⁺calcd for

C₂₂H₂₅O₅S, 401.1417; found, 401.1417.

■

General Methods. All starting materials and reagents were

purchased from commercial sources and used as received without

further puriﬁcation. Air- and water-sensitive reactions were performed

in ﬂame-dried glassware under an Ar atmosphere. Moisture-sensitive

reagents were introduced via a dry syringe. Anhydrous solvents were

supplied over molecular sieves and used as received. Petroleum ether

(PE) refers to the 40−60 °C boiling fraction. Powdered 4 or 5 Å

molecular sieves were activated before use by heating for ∼5 min

under high vacuum. Reactions were monitored by thin-layer

chromatography (TLC) with silica gel 60 F₂₅₄0.25 mm precoated

aluminum foil plates. Compounds were visualized by using UV₂₅₄and/

or orcinol (1 mg·mL⁻¹) in a 10% H₂SO₄(aq) solution and/or

Hanessian’s stain [2.5 g of (NH₄)₆Mo₇O₂₄·4H₂O, 1.0 g of

Ce(NH₄)₄(SO₄)₄·2H₂O, 90 mL of H₂O, and 10 mL of H₂SO₄] with

heating. Normal-phase ﬂash column chromatography was performed

on silica gel 60 Å (15−40 μm). Reversed-phase ﬂash column

chromatography was performed on C₁₈silica gel (25−40 μm).

NMR spectra were recorded at 297 K in the indicated solvent (CDCl₃,

MeOD, py-d₅, or D₂O) with a 400 or 500 MHz instrument, employing

Phenyl 3-O-Allyl-4,6-O-benzylidene-2-O-(2-naphthylmeth-

yl)-1-thio-α-^D-mannopyranoside (9). To an ice-cold solution of

alcohol 8 (8.6 g, 22 mmol, 1.0 equiv) in anhydrous DMF (47 mL) was

slowly added NaH (60% oil dispersion, 0.95 g, 24 mmol, 1.1 equiv)

under N₂, and the mixture was stirred for 20 min. NAPBr (5.7 g, 26

mmol, 1.2 equiv) was then added, and the mixture was gradually

warmed to rt. After being stirred for 1 h, the reaction was quenched

with MeOH (20 mL) and diluted with EtOAc. The organic layer was

successively washed with water and brine and dried over MgSO₄, and

the solutions were concentrated under reduced pressure. The residue

was puriﬁed by silica gel ﬂash chromatography (PE/EtOAc 9:1 to 8:2)

to furnish 9 (10.3 g, 89%) as a yellow oil: R_f0.7 (PE/EtOAc 8:2);

1

standard software provided by the manufacturer. H and ¹³C NMR

spectra were referenced to tetramethylsilane (TMS, δ_H= δ_C= 0.00

ppm) as the internal reference for spectra in CDCl₃, MeOD, and py-d₅

or to external sodium 3-trimethylsilyl-(2,2,3,3-²H₄)propanoate (TSP,

δ_H= 0.00 ppm) or 1,4-dioxane (δ_C= 67.19 ppm) for spectra in D₂O.

Assignments were based on ¹H, ¹³C, DEPT-135, COSY, HSQC,

undecoupled HSQC, HMBC, and NOESY experiments. Of the two

magnetically nonequivalent geminal protons at C-6, the one resonating

at lower ﬁeld is denoted 6a and the one at higher ﬁeld is denoted 6b.

Interchangeable assignments are marked with an asterisk. High-

resolution mass spectra (HRMS) were recorded on a ESI-Q-TOF

mass spectrometer.

[α]²_D⁰= +63.1 (c 0.4, CHCl₃); H NMR (400 MHz, CDCl₃) δ 7.88−

1

7.18 (m, 17H, CH-Ar), 5.97−5.87 (m, 1H, H-2All), 5.64 (s, 1H, CH-

acetal), 5.51 (d, J = 1.4 Hz, 1H, H-1), 5.31 (ddd, J = 17.3, 5.0, 1.6 Hz,

1H, H-3aAll), 5.20 (ddd, J = 10.4, 4.3, 1.5 Hz, 1H, H-3bAll), 4.94 (d, J

= 12.4 Hz, 1H, CHHNAP), 4.89 (d, J = 12.4 Hz, 1H, CHHNAP),

4.38−4.26 (m, 3H, H-1aAll, H-4, H-5), 4.19 (dd, J = 10.2, 4.4 Hz, 1H,

H-6a), 4.16−4.11 (m, 2H, H-1bAll, H-2), 3.95−3.86 (m, 2H, H-3, H-

6b); ¹³C NMR (100 MHz, CDCl₃) δ 135.4−132.1 (5 × C-Ar), 134.8

(C-2All), 131.9−126.1 (CH-Ar), 117.2 (C-3All), 101.7 (C-acetal),

87.6 (C-1), 79.2 (C-4), 78.2 (C-2), 76.1 (C-3), 73.4 (CH₂NAP), 72.2

(C-1All), 68.7 (C-6), 65.6 (C-5); MS (ESI-TOF) m/z 563.8 [M +

Na]⁺; HRMS (ESI-TOF) m/z [M + H]⁺calcd for C₃₃H₃₃O₅S,

541.2043; found, 541.2039.

Phenyl 4,6-O-Benzylidene-3-O-tert-butyldimethylsilyl-2-O-

(2-naphthylmethyl)-1-thio-α-^D-mannopyranoside (7). Diol

5^52,53(0.83 g, 2.3 mmol, 1.0 equiv) was dissolved in anhydrous

DMF (5 mL), and the solution was cooled to −10 °C. Et₃N (0.35 mL,

2.5 mmol, 1.1 equiv) and TBSOTf (0.58 mL, 2.5 mmol, 1.1 equiv)

were added, and the mixture was stirred for 2 h under N₂while

gradually being warmed to rt. The reaction was quenched by adding a

saturated NaHCO₃(aq) solution (25 mL). DCM was added, and the

organic layer was washed with brine, dried over MgSO₄, and

concentrated under reduced pressure to give phenyl 4,6-O-

benzylidene-3-O-tert-butyldimethylsilyl-1-thio-α-^D-mannopyranoside

(6) as a yellow solid: R_f0.7 (PE/EtOAc 5:5); [α]²_D⁰= +148.3 (c 0.5,

CHCl₃). To an ice-cold water solution of crude alcohol 6 (1.1 g, 2.3

mmol, 1.0 equiv) in anhydrous DMF (10 mL) was slowly added NaH

(60% oil dispersion, 101 mg, 2.5 mmol, 1.1 equiv) under N₂, and the

mixture was stirred for 20 min. NAPBr (611 mg, 2.8 mmol, 1.2 equiv)

was then added, and the mixture was gradually warmed to rt. After

being stirred for 3 h, the reaction was quenched with MeOH (3 mL)

and diluted with EtOAc (40 mL). The organic layer was successively

washed with water (3 × 50 mL) and brine (50 mL) and dried over

MgSO₄, and the solutions were concentrated under reduced pressure.

The residue was puriﬁed by silica gel ﬂash chromatography (PE/Et₂O

95:5 to 80:20) to give 7 (1.1 g, 79%, two steps) as a yellow oil: R_f0.5

(PE/Et₂O 9:1); [α]²_D⁰= +62.7 (c 0.4, CHCl₃); HRMS (ESI-TOF) m/z

Phenyl 4-O-Benzyl-3-O-tert-butyldimethylsilyl-2-O-(2-naph-

thylmethyl)-1-thio-α-^D-mannopyranoside (10). To a solution of

7 (1.7 g, 2.8 mmol, 1.0 equiv) in anhydrous DCM (28 mL) were

added BH₃·THF (1.0 M in THF, 10.5 mL, 10.5 mmol, 3.8 equiv) and

TMSOTf (75 μL, 420 μmol, 0.15 equiv) under N₂. The mixture was

stirred at rt for 3 h. The reaction was quenched with Et₃N (0.4 mL)

and MeOH (10 mL). The solutions were concentrated under reduced

pressure. The residue was puriﬁed by silica gel ﬂash chromatography

(pentane/EtOAc 9:1) to give 10 (1.5 g, 89%) as a yellow oil: R_f0.4

(PE/EtOAc 8:2); [α]²_D⁰= +83.6 (c 0.4, CHCl₃); ¹H NMR (400 MHz,

CDCl₃) δ 7.70−7.03 (m, 17H, CH-Ar), 5.30 (s, 1H, H-1), 4.81 (d, J =

12.0 Hz, 1H CHHNAP), 4.76 (d, J = 11.4 Hz, 1H, CHHPh), 4.66 (d, J

= 12.0 Hz, 1H, CHHNAP), 4.48 (d, J = 11.4 Hz, 1H, CHHPh), 3.97−

3.91 (m, 2H, H-5, H-3), 3.82−3.76 (m, 2H, H-2, H-4), 3.66−3.54 (m,

2H, H-6a, H-6b), 0.83 (s, 9H, C(CH₃)₃), 0.00 (s, 6H, 2 × CH₃Si); ¹³

C

NMR (100 MHz, CDCl₃) δ 138.5−133.2 (5 × C-Ar), 132.0−125.9

(CH-Ar), 86.9 (C-1), 81.0 (C-2), 75.9 (C-4), 75.3 (CH₂Ph), 73.8 (C-

3), 73.8 (C-5), 73.6 (CH₂NAP), 62.3 (C-6), 26.1 (C(CH₃)₃), 18.2

(C(CH₃)₃), −4.2 (CH₃Si), −4.4 (CH₃Si); MS (ESI-TOF) m/z 634.7

[M + NH₄]⁺, m/z 639.6 [M + Na]⁺; HRMS (ESI-TOF) m/z [M +

NH₄]⁺calcd for C₃₆H₄₈NO₅SSi, 634.3017; found, 634.3017.

1

[M + H]⁺calcd for C₃₆H₄₃O₅SSi, 615.2595; found, 615.2598. H and

¹³C NMR spectra data of 7⁵⁴were in agreement with those published

Phenyl 3-O-Allyl-4-O-benzyl-2-O-(2-naphthylmethyl)-1-thio-

α-^D-mannopyranoside (11). To 9 (10.3 g, 19.1 mmol, 1.0 equiv)

was added dropwise neat DIBALH (1.0 M in toluene, 140 mL, 140

mmol, 7.3 equiv) at −10 °C under N₂. The solution was then slowly

warmed to rt. After being stirred for 3 h, the reaction mixture was

poured into a cooled saturated aqueous K−Na-tartrate tetrahydrate

in the literature.

Phenyl 3-O-Allyl-4,6-O-benzylidene-1-thio-α-^D-mannopyra-

noside (8). To a solution of diol 5^52,53(1.0 g, 2.8 mmol, 1.0 equiv)

in toluene (11 mL) was added Bu₂SnO (0.76 g, 3.1 mmol, 1.0 equiv),

and the mixture was reﬂuxed for 4 h using a Dean−Stark apparatus.

The temperature was cooled to 80 °C, and then dried CsF (0.43 g, 2.8

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solution and stirred vigorously for 2 h. The aqueous layer was

extracted with EtOAc (450 mL), and the organic layer was washed

with a saturated NH₄Cl(aq) solution (250 mL) and brine (250 mL).

The solvents of the dried solution (MgSO₄) were concentrated under

reduced pressure. The residue was puriﬁed by silica gel ﬂash

chromatography (PE/EtOAc 9:1 to 8:2) to give an inseparable

mixture of regioisomers 11 and 13 (9.1 g, 88%, ratio 11/13 4.9:1.0) as

a white amorphous solid: R_f0.5 (PE/EtOAc 8:2); [α]²_D⁰= +40.9 (c 0.1,

Phenyl 3-O-Allyl-4-O-benzyl-2-O-(2-naphthylmethyl)-1-thio-

6-O-tosyl-α-^D-mannopyranoside (16). To a cooled solution (0 °C)

of a mixture of alcohols 11 and 13 (9.13 g, 16.8 mmol, 1.0 equiv) in

anhydrous py (84.1 mL) were added TsCl (9.62 g, 50.5 mmol, 3.0

equiv) and DMAP (206 mg, 1.68 mmol, 0.1 equiv) under Ar. The

mixture was stirred for 18 h at rt, quenched with MeOH (25 mL), and

diluted with EtOAc (300 mL). The organic phase was washed with a

10% HCl(aq) solution (3 × 100 mL), a saturated NaHCO₃(aq)

solution (100 mL), and brine (100 mL). Solvents of the dried solution

(MgSO₄) were concentrated under reduced pressure. The residue was

puriﬁed by silica gel ﬂash chromatography (PE/EtOAc 10:0 to 6:4) to

1

CHCl₃); H NMR of 11 (400 MHz, CDCl₃) δ 7.87−7.18 (m, 17H,

CH-Ar), 6.01−5.87 (m, 1H, H-2All), 5.52 (s, 1H, H-1), 5.34 (dd, J =

17.3, 1.3 Hz, 1H, H-3aAll), 5.22 (d, J = 10.4 Hz, 1H, H-3bAll), 4.96 (d,

J = 10.6 Hz, 1H, CHHPh), 4.89 (s, 2H, CH₂NAP), 4.67 (d, J = 10.6

Hz, 1H, CHHPh), 4.13−4.09 (m, 3H, H-1aAll, H-1bAll, H-5), 4.07 (s,

1H, H-2), 4.03 (t, J = 9.6 Hz, 1H, H-4), 3.85−3.78 (m, 3H, H-6a, H-

6b, H-3); ¹³C NMR of 11 (100 MHz, CDCl₃) δ 138.5−133.2 (5 × C-

Ar), 134.7 (C-2All), 131.9−126.1 (CH-Ar), 117.4 (C-3All), 86.4 (C-

1), 79.9 (C-3), 76.5 (C-2), 75.4 (CH₂Ph), 74.8 (C-4), 73.3 (C-5), 72.6

(CH₂NAP), 71.3 (C-1All), 62.4 (C-6); MS (ESI-TOF) m/z = 565.6

[M + Na]⁺; HRMS (ESI-TOF) m/z [M + NH₄]⁺calcd for

C₃₃H₃₈NO₅S, 560.2465; found, 560.2463.

give 16 (10.3 g, 88%) as a yellow oil: R_f0.5 (PE/EtOAc 8:2); [α]_D²⁰

=

1

+24.7 (c 0.3, CHCl₃); H NMR (400 MHz, CDCl₃) δ 7.84−7.17 (m,

21H, CH-Ar), 5.95−5.85 (m, 1H, H-2All), 5.47 (d, J = 1.5 Hz, 1H, H-

1), 5.31 (ddd, J = 17.3, 4.8, 1.6 Hz, 1H, H-3aAll), 5.20 (ddd, J = 10.3,

4.1, 1.5 Hz, 1H, H-3bAll), 4.91 (d, J = 10.7 Hz, 1H, CHHPh), 4.87 (d,

J = 12.5 Hz, 1H, CHHNAP), 4.80 (d, J = 12.5 Hz, 1H, CHHNAP),

4.49 (d, J = 10.7 Hz, 1H, CHHPh), 4.34−4.28 (m, 2H, H-6a, H-6b),

4.26−4.23 (m, 1H, H-5), 4.08−4.05 (m, 2H, H-1aAll, H-1bAll), 4.02

(dd, J = 3.1, 1.7 Hz, 1H, H-2), 3.92 (t, J = 9.5 Hz, 1H, H-4), 3.71 (dd, J

= 9.4, 3.1 Hz, 1H, H-3), 2.35 (s, 3H, CH₃Ts); ¹³C NMR (100 MHz,

CDCl₃) δ 138.2−131.7 (7 × C-Ar), 134.5 (C-2All), 129.8−125.9

(CH-Ar), 117.5 (C-3All), 85.9 (C-1), 79.9 (C-3), 76.1 (C-2), 75.3

(CH₂Ph), 74.1 (C-4), 72.3 (CH₂NAP), 71.2 (C-1All), 71.0 (C-5), 68.8

(C-6), 21.7 (CH₃Ts); MS (ESI-TOF) m/z 714.7 [M + NH₄]⁺, m/z

719.6 [M + Na]⁺; HRMS (ESI-TOF) m/z [M + H]⁺calcd for

C₄₀H₄₁O₇S₂, 697.2288; found, 697.2281.

Phenyl 3,6-Anhydro-4-O-benzyl-2-O-(2-naphthylmethyl)-1-

thio-α-^D-mannopyranoside (14). Tf₂O (88 μL, 0.52 mmol, 2.0

equiv) and 2,6-lutidine (66 μL, 0.58 mmol, 2.2 equiv) were dissolved

in anhydrous DCE (2.7 mL), and the mixture was stirred at −10 °C

under N₂. A solution of alcohol 10 (0.16 g, 0.26 mmol, 1.0 equiv) in

anhydrous DCE (2.5 mL) was then added. The reaction mixture was

stirred for 1 h at −10 °C and quenched with a saturated NaHCO₃(aq)

solution (10 mL). The aqueous phase was extracted with DCM (3 ×

15 mL). The organic layer was dried over MgSO₄and concentrated

under reduced pressure. The residue was dissolved in anhydrous DCM

(5 mL), and the mixture was reﬂuxed for 2 h under N₂. The solutions

were concentrated under reduced pressure. The residue was puriﬁed

by silica gel ﬂash chromatography (pentane/EtOAc 95:5 to 80:20) to

provide 14 (77 mg, 62%) as a white sticky oil: R_f0.30 (PE/EtOAc

Phenyl 3-O-Allyl-4-O-benzyl-6-chloro-2-O-(2-naphthylmeth-

yl)-1-thio-α-^D-mannopyranoside (17). To a cooled solution (0 °C)

of a mixture of alcohols 11 and 13 (0.51 g, 0.94 mmol, 1.0 equiv) in

anhydrous py (5 mL) were added TsCl (0.54 g, 2.8 mmol, 3.0 equiv)

and DMAP (12 mg, 0.1 mmol, 0.1 equiv) under N₂. The mixture was

stirred for 20 h and gradually warmed to rt. Additional TsCl (0.38 g,

1.9 mmol, 2 equiv) was added, and the mixture was stirred at 60 °C for

16 h. Then, the reaction mixture was cooled to rt and diluted with

EtOAc (20 mL). The organic phase was washed with a 10% HCl(aq)

solution (10 mL), a saturated NaHCO₃(aq) solution (10 mL), and

brine (10 mL). Solvents of the dried solution (MgSO₄) were

concentrated under reduced pressure. The residue was puriﬁed by

silica gel ﬂash chromatography (PE/EtOAc 10:0 to 8:2) to provide 17

(118 mg, 22%) and 16 (141 mg, 21%) as yellow oils. Analytical data of

9:1); [α]²_D⁰= +15.5 (c 0.2, CHCl₃); H NMR (400 MHz, CDCl₃) δ

1

7.83−7.05 (m, 17H, CH-Ar), 5.13 (d, J = 8.8 Hz, 1H, H-1), 4.84 (d, J

= 11.9 Hz, 1H, CHHNAP), 4.67 (d, J = 11.9 Hz, 1H, CHHNAP), 4.48

(d, J = 11.7 Hz, 1H, CHHPh), 4.45 (t, J = 2.7 Hz, 1H, H-5), 4.25 (d, J

= 11.7 Hz, 1H, CHHPh), 4.18 (dd, J = 6.0, 1.2 Hz, 1H, H-3), 4.15 (d, J

= 10.8 Hz, 1H, H-6a), 3.95 (dd, J = 10.8, 2.8 Hz, 1H, H-6b), 3.89 (dd,

J = 6.0, 2.7 Hz, 1H, H-4), 3.78 (dd, J = 8.8, 1.2 Hz, 1H, H-2); ¹³C

NMR (100 MHz, CDCl₃) δ 137.3−133.2 (5 × C-Ar), 132.2−126.1

(CH-Ar), 83.7 (C-1), 77.1 (C-4), 75.7 (C-3), 74.5 (C-5), 73.9 (C-2),

73.1 (CH₂NAP), 71.9 (CH₂Ph), 69.3 (C-6); HRMS (ESI-TOF) m/z

[M + H]⁺calcd for C₃₀H₂₉O₄S, 485.1781; found, 485.1776.

Phenyl 4-O-Benzyl-3-O-tert-butyldimethylsilyl-2-O-(2-naph-

thylmethyl)-1-thio-6-O-tosyl-α-^D-mannopyranoside (15). To a

cooled solution (0 °C) of alcohol 10 (1.2 g, 1.9 mmol, 1.0 equiv) in

anhydrous py (9.6 mL) were added TsCl (1.1 g, 5.7 mmol, 3.0 equiv)

and DMAP (25 mg, 0.20 mmol, 0.1 equiv) under N₂. The mixture was

stirred for 20 h, gradually warmed to rt, and diluted with EtOAc (60

mL). The organic phase was washed with a 10% HCl(aq) solution (2

× 25 mL), a saturated NaHCO₃(aq) solution (25 mL), and brine (25

mL). Solvents of the dried solution (MgSO₄) were concentrated under

reduced pressure. The residue was puriﬁed by silica gel ﬂash

chromatography (PE/EtOAc 95:5 to 85:15) to provide 15 (1.2 g,

82%): R_f0.5 (PE/EtOAc 7:3); [α]²_D⁰= +68.7 (c 0.2, CHCl₃); ¹H NMR

(400 MHz, CDCl₃) δ 7.76−7.02 (m, 21H, CH-Ar), 5.38 (s, 1H, H-1),

4.79 (d, J = 10.8 Hz, 1H, CHHNAP), 4.77 (d, J = 12.0 Hz, 1H,

CHHPh), 4.71 (d, J = 12.0 Hz, 1H, CHHNAP), 4.37 (d, J = 10.8 Hz,

1H, CHHPh), 4.18−4.10 (m, 3H, H-5, H-6a, H-6b), 3.96−3.91 (dd, J

= 9.0, 2.9 Hz, 1H, H-3), 3.81 (dd, J = 3.0, 1.9 Hz, 1H, H-2), 3.72 (t, J =

9.3 Hz, 1H, H-4), 2.26 (s, 3H, CH₃Ts), 0.83 (s, 9H, C(CH₃)₃), 0.01

(s, 6H, 2 × CH₃Si); ¹³C NMR (CDCl₃, 100 MHz) δ 144.6−133.1 (7

× C-Ar), 131.8−125.8 (CH-Ar), 86.3 (C-1), 80.8 (C-2), 75.4 (C-4);

75.2 (CH₂Ph), 73.8 (C-3), 73.1 (CH₂NAP), 71.3 (C-5), 68.9 (C-6),

26.1 (C(CH₃)₃), 21.7 (CH₃Ts), 18.2 (C(CH₃)₃), −4.2 (CH₃Si), −4.5

(CH₃Si); MS (ESI-TOF) m/z 788.9 [M + NH₄]⁺, m/z 793.8 [M +

Na]⁺; HRMS (ESI-TOF) m/z [M + H]⁺calcd for C₄₃H₅₁O₇S₂Si,

771.2840; found, 771.2842.

16: R_f0.9 (PE/EtOAc 8:2); [α]²_D⁰= +35.4 (c 0.4, CHCl₃); H NMR

1

(400 MHz, CDCl₃) δ 7.79−7.13 (m, 17H, CH-Ar), 5.91−5.79 (m,

1H, H-2All), 5.54 (d, J = 1.5 Hz, 1H, H-1), 5.26 (ddd, J = 17.3, 3.7, 1.6

Hz, 1H, H-3aAll), 5.14 (ddd, J = 10.4, 3.3, 1.5 Hz, 1H, H-3bAll), 4.93

(d, J = 10.8 Hz, 1H, CHHPh), 4.85 (d, J = 12.6 Hz, 1H, CHHNAP),

4.78 (d, J = 12.6 Hz, 1H, CHHNAP), 4.61 (d, J = 10.8 Hz, 1H,

CHHPh), 4.27−4.23 (m, 1H, H-5), 4.07−3.95 (m, 4H, H-1aAll, H-

1bAll, H-4, H-2), 3.76−3.74 (m, 2H, H-6a, H-6b), 3.70 (dd, J = 9.4,

3.0 Hz, 1H, H-3); ¹³C NMR (100 MHz, CDCl₃) δ 138.3−133.2 (5 ×

C-Ar), 134.6 (C-2All), 131.7−125.9 (CH-Ar), 117.5 (C-3All), 86.2

(C-1), 79.8 (C-3), 76.2 (C-2), 75.7 (C-4), 75.6 (CH₂Ph), 72.6 (C-5),

72.2 (CH₂NAP), 71.2 (C-1All), 44.8 (C-6); MS (ESI-TOF) m/z =

578.4 [M + NH₄]⁺; HRMS (ESI-TOF) m/z [M + H]⁺calcd for

C₃₃H₃₄ClO₄S, 561.1861; found, 561.1862.

Phenyl 4-O-Benzyl-3-O-tert-butyldimethylsilyl-6-cyano-2-O-

(2-naphthylmethyl)-1-thio-α-^D-mannopyranoside (18). Tosy-

lated 15 (0.86 g, 1.1 mmol, 1.0 equiv) was dissolved in anhydrous

CH₃CN (11 mL), and freshly activated 4 Å molecular sieves (0.8 g)

were added. The suspension was stirred for 30 min at rt under N₂, and

then KCN (0.36 g, 5.5 mmol, 5.0 equiv) and 18-crown-6 (588 mg,

2.22 mmol, 2.0 equiv) were added. The mixture was stirred for 24 h at

∼55 °C under N₂. The mixture was cooled to rt, diluted with EtOAc

(100 mL), and ﬁltered over Celite. The ﬁltrate was washed with a 10%

HCl(aq) solution (25 mL), a saturated NaHCO₃(aq) solution (25

mL), and water (25 mL). Solvents of the dried solution (MgSO₄) were

concentrated under reduced pressure. The residue was puriﬁed by

silica gel ﬂash chromatography (PE/EtOAc 95:5) to furnish 18 (0.61

g, 88%) as a yellow oil: R_f0.5 (PE/EtOAc 8:2); [α]²_D⁰= +99.6 (c 0.2,

CHCl₃); ¹H NMR (400 MHz, CDCl₃) δ 7.86−7.22 (m, 17H, CH-Ar),

4625

dx.doi.org/10.1021/jo500640n | J. Org. Chem. 2014, 79, 4615−4634

The Journal of Organic Chemistry

Article

5.46 (d, J = 1.6 Hz, 1H, H-1), 4.98 (d, J = 11.6 Hz, 1H, CHHPh), 4.93

(d, J = 11.9 Hz, 1H, CHHNAP), 4.83 (d, J = 11.9 Hz, 1H, CHHNAP),

4.61 (d, J = 11.6 Hz, 1H, CHHPh), 4.27 (ddd, J = 9.6, 6.8, 3.2 Hz, 1H,

H-5), 4.07 (dd, J = 9.1, 2.9 Hz, H-3), 3.96 (dd, J = 2.8, 1.8 Hz, 1H, H-

2), 3.82 (t, J = 9.3 Hz, 1H, H-4), 2.65 (dd, J = 16.8, 3.0 Hz, 1H, H-6a),

2.49 (dd, J = 16.9, 7.7 Hz, 1H, H-6b), 0.97 (s, 9H, C(CH₃)₃), 0.18 (s,

6H, 2 × CH₃Si); ¹³C NMR (100 MHz, CDCl₃) δ 137.9−133.1 (5 ×

C-Ar), 131.9−125.3 (CH-Ar), 117.3 (CN), 86.7 (C-1), 80.9 (C-2),

78.2 (C-4), 75.6 (CH₂Ph), 73.8 (C-3), 73.2 (CH₂NAP), 69.1 (C-5),

26.1 (C(CH₃)₃), 20.9 (C-6), 18.2 (C(CH₃)₃), −4.1 (CH₃Si), −4.5

(CH₃Si); MS (ESI-TOF) m/z 643.8 [M + NH₄]⁺, m/z 648.7 [M +

Na]⁺; HRMS (ESI-TOF) m/z [M + H]⁺calcd for C₃₇H₄₄NO₄SSi,

626.2755; found, 626.2756.

138.4−133.2 (5 × C-Ar), 128.5−125.9 (CH-Ar), 86.5 (C-1), 80.9 (C-

2), 79.4 (C-4), 75.5 (CH₂Ph), 73.8 (C-3), 73.5 (CH₂NAP), 72.8 (C-

5), 60.9 (C-7), 33.8 (C-6), 26.1 (C(CH₃)₃Si), 18.2 (C(CH₃)₃Si), −4.2

(CH₃Si), −4.5 (CH₃Si); HRMS (ESI-TOF) m/z [M + NH₄]⁺calcd

for C₃₇H₅₀NO₅SSi, 648.3173; found, 648.3177.

Phenyl 3-O-Allyl-4-O-benzyl-6-deoxy-2-O-(2-naphthylmeth-

yl)-1-thio-^D-manno-heptopyranoside (21). To a solution of nitrile

19 (1.2 g, 2.1 mmol, 1.0 equiv) in anhydrous toluene (21 mL) was

added dropwise DIBALH (1.0 M in toluene, 2.5 mL, 2.5 mmol, 1.2

equiv) −78 °C under Ar. The mixture was stirred for 25 min and

gradually warmed to −35 °C. The mixture was diluted with EtOAc (20

mL), and the organic phase was washed with a 10% HCl(aq) solution

(3 × 10 mL), a saturated NaHCO₃(aq) solution (10 mL), and brine

(10 mL). The solvents of the dried solution (MgSO₄) were

concentrated under reduced pressure. The crude imine was dissolved

in a mixture of 1 N HCl(aq)/THF (1:9, 21 mL) and stirred for 1 h at

rt. The mixture was diluted with EtOAc (25 mL), and the organic

phase was washed with water (2 × 10 mL) and brine (10 mL). The

solvents of the dried solution (MgSO₄) were concentrated under

reduced pressure. Crude aldehyde was dissolved in MeOH/DCM

(2:1, 32 mL), and NaBH₄(88 mg, 2.3 mmol, 1.1 equiv) was added.

The mixture was stirred at rt for 20 min under N₂. The reaction

mixture was quenched with acetone (10 mL) and diluted with DCM

(20 mL). The organic layer was washed with water (10 mL) and brine

(10 mL). The solvents of the dried solution (MgSO₄) were

concentrated under reduced pressure. The residue was puriﬁed by

silica gel ﬂash chromatography (PE/EtOAc 9:1 to 7:3) to give 21

(1.02 g, 87%, three steps) as a white amorphous solid: R_f0.3 (PE/

Phenyl 3-O-Allyl-4-O-benzyl-6-cyano-2-O-(2-naphthylmeth-

yl)-1-thio-α-^D-mannopyranoside (19). Tosylated 16 (0.97 g, 1.4

mmol, 1.0 equiv) was dissolved in anhydrous CH₃CN (13.9 mL), and

freshly activated 4 Å molecular sieves (0.8 g) were added. The

suspension was stirred for 30 min at rt under N₂, and then KCN (0.72

g, 11 mmol, 8.0 equiv) and 18-crown-6 (0.74 g, 2.8 mmol, 2.0 equiv)

were added. The mixture was stirred at 80 °C for 1 h. The solution was

cooled to rt, diluted with EtOAc (15 mL), and ﬁltered over Celite. The

ﬁltrate was washed with a 10% HCl(aq) solution (10 mL), brine (10

mL), and water (10 mL). Solvents of the dried solution (MgSO₄) were

concentrated under reduced pressure. The residue was puriﬁed by

silica gel ﬂash chromatography (PE/EtOAc 95:5 to 85:15) to furnish

19 (0.52 g, 67%) as a white crystalline solid: R_f0.5 (PE/EtOAc 8:2);

mp 113−116 °C (DCM); [α]²_D⁰= +57.3 (c 0.1, CHCl₃); H NMR

1

(400 MHz, CDCl₃) δ 7.89−7.29 (m, 17H, CH-Ar), 6.00−5.86 (m,

1H, H-2All), 5.52 (s, 1H, H-1), 5.34 (d, J = 17.5 Hz, 1H, H-3aAll),

5.23 (d, J = 10.6 Hz, 1H, H-3bAll), 5.02 (d, J = 11.1 Hz, 1H, CHHPh),

4.91 (d, J = 12.5 Hz, 1H, CHHNAP), 4.85 (d, J = 12.5 Hz, 1H,

CHHNAP), 4.66 (d, J = 11.1 Hz, 1H, CHHPh), 4.29 (ddd, J = 9.5, 7.2,

3.1 Hz, 1H, H-5), 4.14−4.05 (m, 3H, H-1aAll, H-1bAll, H-2), 3.87 (t, J

= 9.3 Hz, 1H, H-4), 3.75 (dd, J = 9.3, 2.9 Hz, 1H, H-3), 2.74 (dd, J =

16.8, 3.4 Hz, 1H, H-6a), 2.60 (dd, J = 16.9, 7.5 Hz, 1H, H-6b); ¹³C

NMR (100 MHz, CDCl₃) δ 138.1−133.2 (5 × C-Ar), 134.4 (C-2All),

131.8−125.9 (CH-Ar), 117.7 (C-3All), 86.4 (C-1), 79.8 (C-3), 77.4

(C-4), 76.2 (C-2), 75.6 (CH₂Ph), 72.4 (CH₂NAP), 71.1 (C-1All), 68.8

(C-5), 21.1 (C-6); MS (ESI-TOF) m/z 569.6 [M + NH₄]⁺, m/z 574.6

[M + Na]⁺; HRMS (ESI-TOF) m/z [M + H]⁺calcd for C₃₄H₃₄NO₄S,

552.2203; found, 552.2197.

EtOAc 8:2); [α]²_D⁰= +57.9 (c 0.1, CHCl₃); H NMR (400 MHz,

1

CDCl₃) δ 7.81−7.14 (m, 17H, CH-Ar), 5.94−5.81 (m, 1H, H-2All),

5.45 (d, J = 1.0 Hz, 1H, H-1), 5.26 (dd, J = 17.5, 1.5 Hz, 1H, H-3aAll),

5.14 (dd, J = 10.5, 1.2 Hz, 1H, H-3bAll), 4.91 (d, J = 10.8 Hz, 1H,

CHHPh), 4.83 (s, 2H, CH₂NAP), 4.56 (d, J = 10.8 Hz, 1H, CHHPh),

4.16−4.07 (m, 1H, H-5), 4.04−4.03 (m, 2H, H-1aAll, H-1bAll), 3.99

(br s, 1H, H-2), 3.71−3.69 (m, 2H, H-4, H-3), 3.58−3.55 (m, 2H, H-

7a, H-7b), 2.09−2.02 (m, 1H, H-6a), 1.79−1.70 (m, 1H, H-6b); ¹³C

NMR (100 MHz, CDCl₃) δ 138.1−133.2 (5 × C-Ar), 134.7 (C-2All),

131.8−126.1 (CH-Ar), 117.4 (C-3All), 85.9 (C-1), 79.9 (C-3), 78.5

(C-4), 76.2 (C-2), 75.6 (CH₂Ph), 72.6 (CH₂NAP), 72.4 (C-5), 71.2

(C-1All), 60.8 (C-7), 34.1 (C-6); MS (ESI-TOF) m/z = 579.6 [M +

Na]⁺; HRMS (ESI-TOF) m/z [M + H]⁺calcd for C₃₄H₃₇O₅S,

557.2356; found, 557.2347.

Phenyl 4-O-Benzyl-3-O-tert-butyldimethylsilyl-6-deoxy-2-O-

(2-naphthylmethyl)-1-thio-α-^D-manno-heptopyranoside (20).

To a solution of nitrile 18 (0.31 g, 500 μmol, 1.0 equiv) in anhydrous

toluene (5 mL) was added dropwise DIBALH (1.0 M in toluene, 1.5

mL, 1.5 mmol, 3.0 equiv) at −78 °C under Ar. After being stirred for

15 min, the reaction mixture was diluted with EtOAc (30 mL), and the

organic phase was washed with brine (15 mL) and dried over MgSO₄.

The solutions were concentrated under reduced pressure. The crude

imine was dissolved in a mixture of 1 N HCl(aq)/THF (1:9, 5 mL).

After being stirred for 1 h at rt, the mixture was diluted with EtOAc

(15 mL), and the organic phase was washed with brine (10 mL). The

solvents of the dried solution (MgSO₄) were concentrated under

reduced pressure. The crude aldehyde was dissolved in MeOH/DCM

(2:1, 7.5 mL), and NaBH₄(21 mg, 550 μmmol, 1.1 equiv) was added.

The mixture was stirred at rt for 1 h under N₂. The reaction was

quenched with acetone (10 mL) and diluted with DCM (20 mL), and

the organic layer was washed with brine (2 × 15 mL). The solvents of

the dried solution (MgSO₄) were concentrated under reduced

pressure. The residue was puriﬁed by silica gel ﬂash chromatography

(PE/EtOAc 95:5 to 70:30) to give 20 (101 mg, 60%, three steps) as a

Phenyl 4,7-Di-O-benzyl-3-O-tert-butyldimethylsilyl-6-deoxy-

2-O-(2-naphthylmethyl)-1-thio-α-^D-manno-heptopyranoside

(23). To a cooled (0 °C) solution of alcohol 20 (191 mg, 303 μmol,

1.0 equiv) in anhydrous DMF (1.2 mL) was slowly added NaH (60%

oil dispersion, 36 mg, 910 μmol, 3.0 equiv) under N₂. The mixture was

stirred for 30 min at this temperature. BnBr (72 μL, 610 μmol) was

then added dropwise, and the mixture was gradually warmed to rt.

After being stirred for 20 h, the reaction was quenched with MeOH (4

mL) and diluted with EtOAc (25 mL). The organic layer was washed

with water (2 × 15 mL), and the solvents of the dried solution

(MgSO₄) were concentrated under reduced pressure. The residue was

puriﬁed by silica gel ﬂash chromatography (pentane/Et₂O 95:5 to

90:10) to give 23 (110 mg, 50%) as a yellow oil: R_f0.7 (PE/EtOAc

8:2); [α]²_D⁰= +72.3 (c 0.2, CHCl₃); H NMR (400 MHz, CDCl₃) δ

1

7.71−7.02 (m, 22H, CH-Ar), 5.37 (d, J = 1.6 Hz, 1H, H-1), 4.81 (d, J

= 11.8 Hz, 1H, CHHNAP), 4.78 (d, J = 11.2 Hz, 1H, CHHPh), 4.71

(d, J = 11.9 Hz, CHHNAP), 4.49 (d, J = 11.3 Hz, 1H, CHHPh), 4.23

(s, 2H, CH₂Ph), 4.01 (td, J = 9.5, 2.3 Hz, 1H, H-5), 3.94 (dd, J = 9.0,

2.9 Hz, 1H, H-3), 3.80 (dd, J = 3.0, 1.8 Hz, 1H, H-2), 3.56 (t, J = 9.3

Hz, 1H, H-4), 3.37−3.28 (m, 2H, H-7), 2.11−2.04 (m, 1H, H-6a),

1.71−1.63 (m, 1H, H-6b), 0.83 (s, 9H, C(CH₃)₃), 0.00 (s, 3H,

CH₃Si), −0,01 (s, 3H, CH₃Si); ¹³C NMR (100 MHz, CDCl₃) δ

138.7−133.4 (6 × C-Ar), 131.4−126.0 (CH-Ar), 86.2 (C-1), 81.0 (C-

2), 79.8 (C-4), 75.3 (CH₂Ph), 74.0 (C-3), 73.4 (CH₂NAP), 72.9

(CH₂Ph), 70.5 (C-5), 67.1 (C-7), 31.8 (C-6), 26.1 (C(CH₃)₃), 18.2

(C(CH₃)₃), −4.2 (CH₃Si), −4.5 (CH₃Si); MS (ESI-TOF) m/z =

579.6 [M + Na]⁺; HRMS (ESI-TOF) m/z [M + NH₄]⁺calcd for

C₄₄H₅₆NO₅SSi, 738.3643; found, 738.3644.

yellow oil: R_f0.1 (PE/Et₂O 7:3); [α]²_D⁰= +68.5 (c 0.3, CHCl₃); H

1

NMR (400 MHz, CDCl₃) δ 7.70−7.05 (m, 17H, CH-Ar), 5.30 (d, J =

1.7 Hz, 1H, H-1), 4.81 (d, J = 10.4 Hz, 1H, CHHNAP), 4.78 (d, J =

9.7 Hz, 1H, CHHPh), 4.68 (d, J = 11.9 Hz, CHHNAP), 4.45 (d, J =

11.3 Hz, 1H, CHHPh), 4.02 (td, J = 9.3, 2.8 Hz, 1H, H-5), 3.94 (dd, J

= 9.0, 2.9 Hz, 1H, H-3), 3.78 (dd, J = 3.0, 1.8 Hz, 1H, H-2), 3.57 (t, J =

9.4 Hz, 1H, H-4), 3.48−3.44 (m, 2H, H-7), 1.93−1.86 (m, 1H, H-6a),

1.64−1.56 (m, 1H, H-6b), 0.83 (s, 9H, 3 × C(CH₃)₃), 0.00 (s, 3H,

CH₃Si), −0.01 (s, 3H, CH₃Si); ¹³C NMR (100 MHz, CDCl₃) δ

4626

dx.doi.org/10.1021/jo500640n | J. Org. Chem. 2014, 79, 4615−4634

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Article

Phenyl 3-O-Allyl-4,7-di-O-benzyl-6-deoxy-2-O-(2-naphthyl-

methyl)-1-thio-α-^D-manno-heptopyranoside (25). To a cooled

(0 °C, ice water/water bath) solution of alcohol 21 (1.03 g, 1.84

mmol, 1.0 equiv) in anhydrous DMF (7.4 mL) was slowly added NaH

(60% oil dispersion, 0.37 g, 9.2 mmol, 4.0 equiv) under Ar. The

mixture was stirred for 30 min at this temperature. Then, TBAI (100

mg, 0.28 mmol, 0.15 equiv) followed by BnBr (0.66 mL, 5.5 mmol, 3.0

equiv) was added, and the mixture was gradually warmed to rt. After

being stirred for 7 h, the reaction was quenched with MeOH (8 mL)

and diluted with EtOAc (25 mL). The organic layer was washed with

water (3 × 15 mL) and brine (15 mL), and the solvents of the dried

solution (MgSO₄) were concentrated under reduced pressure. The

residue was puriﬁed by silica gel ﬂash chromatography (PE/EtOAc

10:0 to 9:1) to give 25 (1.2 g, 97%) as a yellow oil: R_f0.7 (PE/EtOAc

CHHPh), 4.95 (d, J = 10.7 Hz, 1H, CHHPh), 4.64 (d, J = 10.7 Hz,

1H, CHHPh), 4.53 (d, J = 12.1 Hz, 1H, CHHNAP), 4.43 (d, J = 12.1

Hz, 1H, CHHNAP), 4.29 (s, 1H, H-1), 3.98 (ddt, J = 12.7, 5.3, 1.4 Hz,

1H, H-1aAll), 3.92 (ddt, J = 12.8, 5.4, 1.3 Hz, 1H, H-1bAll), 3.88 (d, J

= 2.8 Hz, 1H, H-2), 3.84 (dt, J = 9.4, 6.2 Hz, 1H, H-1a_linker), 3.71−3.60

(m, 3H, H-7ab, H-4), 3.39−3.29 (m, 3H, H-3, H-5, H-1b_linker), 3.23

(td, J = 6.9, 1.5 Hz, 2H, H-5_linker), 2.34−2.25 (m, 1H, H-6a), 1.88−

1.80 (m, 1H, H-6b), 1.67−1.57 (m, 4H, H-2_linker, H-4_linker), 1.47−1.41

(m, 2H, H-3_linker); ¹³C NMR (100 MHz, CDCl₃) δ 138.7−133.2 (5 ×

C-Ar), 134.7 (C-2All), 128.3−125.7 (CH-Ar), 116.8 (C-3All), 101.5

1

(C-1, J_C,H= 154 Hz), 82.5 (C-3), 78.5 (C-4), 75.4 (CH₂Ph), 74.1

(CH₂Ph), 73.8 (C-2), 72.9 (CH₂NAP), 72.3 (C-5), 70.7 (C-1All), 69.4

(C-1_linker), 66.6 (C-7), 51.4 (C-5_linker), 31.9 (C-6), 29.3 (C-2_linker), 28.7

(C-4_linker), 23.5 (C-3_linker); HRMS (ESI-TOF) m/z [M + NH₄]⁺calcd

for C₄₀H₅₁N₄O₆, 683.3803; found, 683.3803.

8:2); [α]²_D⁰= +34.6 (c 0.1, CHCl₃); H NMR (400 MHz, CDCl₃) δ

1

7.85−7.16 (m, 22H, CH-Ar), 5.99−5.86 (m, 1H, H-2All), 5.56 (d, J =

1.2 Hz, 1H, H-1), 5.32 (dd, J = 17.1, 1.6 Hz, 1H, H-3aAll), 5.19 (dd, J

= 10.5, 1.4 Hz, 1H, H-3bAll), 4.96 (d, J = 10.6 Hz, 1H, CHHPh), 4.92

(d, J = 12.5 Hz, 1H, CHHNAP), 4.87 (d, J = 12.5 Hz, 1H, CHHNAP),

4.65 (d, J = 10.6 Hz, 1H, CHHPh), 4.38 (s, 2H, CH₂Ph), 4.17−4.13

(m, 1H, H-5), 4.09 (d, J = 5.4 Hz, 2H, H-1aAll, H-1bAll), 4.05 (s, 1H,

H-2), 3.76−3.74 (m, 2H, H-3, H-4), 3.53−3.41 (m, 2H, H-7a, H-7b),

2.31−2.24 (m, 1H, H-6a), 1.91−1.82 (m, 1H, H−6b); ¹³C NMR (100

MHz, CDCl₃) δ 138.7−133.2 (6 × C-Ar), 134.8 (C-2All), 131.4−

126.1 (CH-Ar), 117.3 (C-3All), 85.7 (C-1), 80.1 (C-3), 78.9 (C-4),

76.4 (C-2), 75.5 (CH₂Ph−C4), 73.0 (CH₂Ph−C7), 72.5 (CH₂NAP),

71.3 (C-1All), 70.3 (C-5), 67.1 (C-7), 32.0 (C-6); MS (ESI-TOF) m/

z = 669.7 [M + Na]⁺; HRMS (ESI-TOF) m/z [M + H]⁺calcd for

C₄₁H₄₃O₅S, 647.2826; found, 647.2815.

Methyl 3-O-Allyl-4,7-di-O-benzyl-6-deoxy-2-O-(2-naphthyl-

methyl)-1-thio-α-^D-manno-heptopyranoside (29). To a solution

of glycosyl donor 25 (20 mg, 31 μmol, 1.0 equiv), Me₂S₂(8.4 μL, 93

μmol, 3.0 equiv), and DTBMP (19 mg, 93 μmol, 3.0 equiv) in

anhydrous DCM (310 μL) was added freshly activated 4 Å powdered

molecular sieves (80 mg). The mixture was stirred for 50 min at rt

under Ar. Then, the reaction mixture was cooled to −78 °C, and Tf₂O

(15.6 μL, 93 μmol, 3.0 equiv) was added dropwise. The mixture was

stirred for 15 min at −78 °C before acceptor 26 (8.0 mg, 62 μmol, 2.0

equiv) in anhydrous DCM (150 μL) was added dropwise. The

reaction mixture was stirred at −78 °C for 2 h and then gradually

warmed to −30 °C. The reaction was quenched with Et₃N (500 μL),

ﬁltered over Celite, and rinsed with DCM. The ﬁltrate was

concentrated under reduced pressure and puriﬁed by silica gel ﬂash

chromatography (PE/Et₂O 100:0 to 95:5) to give 29 (7.2 mg, 18%) as

a yellow oil: R_f0.5 (PE/EtOAc 8:2); [α]²_D⁰= +20.6 (c 0.1, CHCl₃); ¹H

NMR (400 MHz, CDCl₃) δ 7.84−7.25 (m, 17H, CH-Ar), 5.95−5.85

(m, 1H, H-2All), 5.30 (dd, J = 17.3, 1.2 Hz, 1H, H-3aAll), 5.22 (s, 1H,

H-1), 5.17 (dd, J = 10.5, 1.0 Hz, 1H, H-3bAll), 4.93 (d, J = 12.7 Hz,

1H, CHHNAP), 4.94 (d, J = 10.8 Hz, 1H, CHHPh), 4.86 (d, J = 12.7

Hz, 1H, CHHNAP), 4.63 (d, J = 10.8 Hz, 1H, CHHPh), 4.50 (d, J =

11.9 Hz, 1H, CHHPh), 4.46 (d, J = 11.9 Hz, 1H, CHHPh), 4.09−4.05

(m, 3H, H-5, H-1aAll, H-1bAll), 3.89 (br s, 1H, H-2), 3.75 (dd, J = 8.5,

2.8 Hz, 1H, H-3), 3.71 (t, J = 9.2 Hz, 1H, H-4), 3.62 (dd, J = 8.0, 5.7

Hz, 2H, H-7a, H-7b), 2.32−2.25 (m, 1H, H-6a), 2.01 (s, 3H, SCH₃),

1.90−1.81 (m, 1H, H-6b); ¹³C NMR (100 MHz, CDCl₃) δ 138.7−

133.2 (5 × C-Ar), 134.9 (C-2All), 128.4−126.1 (CH-Ar), 117.1 (C-

3All), 83.4 (C-1), 80.3 (C-3), 79.1 (C-4), 76.3 (C-2), 75.4 (CH₂Ph),

72.9 (CH₂Ph), 72.5 (CH₂NAP), 71.3 (C-1All), 69.1 (C-5), 67.1 (C-7),

32.0 (C-6), 13.7 (SCH₃); HRMS (ESI-TOF) m/z [M + H]⁺calcd for

C₃₆H₄₁O₅S, 585.2669; found, 585.2664.

(5-Azido-1-pentyl) 3-O-Allyl-4,7-di-O-benzyl-6-deoxy-2-O-

(2-naphthylmethyl)-α-^D-manno-heptopyranoside (27) and (5-

Azido-1-pentyl) 3-O-Allyl-4,7-di-O-benzyl-6-deoxy-2-O-(2-

naphthylmethyl)-β-^D-manno-heptopyranoside (28). Represen-

tative Procedure for Intermolecular Glycosylation without Donor

Preactivation. To a solution of donor 25 (20 mg, 31 μmol, 1.0 equiv)

and 5-azido-1-pentanol⁶⁶(26, 8.0 mg, 62 μmol, 2.0 equiv) in

anhydrous CH₃CN (620 μL) were added freshly activated 4 Å

powdered molecular sieves (80 mg) and DTBMP (19 mg, 93 μmol,

3.0 equiv). The mixture was stirred for 40 min at rt under Ar. Then,

Me₂S₂(8.4 μL, 93 μmol, 3.0 equiv) followed by MeOTf (10.5 μL, 93

μmol, 3.0 equiv) was added at −10 °C. The mixture was stirred for 5 h

and gradually warmed to rt. The reaction was quenched with Et₃N

(500 μL), ﬁltered over Celite, and rinsed with DCM. The ﬁltrate was

concentrated under reduced pressure and puriﬁed by silica gel ﬂash

chromatography (PE/EtOAc 10:0 to 7:3) to give 27 (8.8 mg, 42%)

and 28 (10 mg, 48%) as yellow oils. Analytical data for 27: R_f0.30

(PE/EtOAc 9:1); [α]²_D⁰= +24.2 (c 0.2, CHCl₃); ¹H NMR (400 MHz,

CDCl₃) δ 7.84−7.26 (m, 17H, CH-Ar), 6.10−5.91 (m, 1H, H-2All),

5.33 (dd, J = 17.3, 1.4 Hz, 1H, H-3aAll), 5.18 (dd, J = 10.5, 1.1 Hz, 1H,

H-3bAll), 4.95 (d, J = 10.7 Hz, 1H, CHHPh), 4.96 (d, J = 12.5 Hz, 1H,

CHHPh), 4.89 (d, J = 12.5 Hz, 1H, CHHPh), 4.74 (s, 1H, H-1), 4.65

(d, J = 10.6 Hz, 1H, CHHPh), 4.50 (d, J = 11.9 Hz, 1H, CHHNAP),

4.45 (d, J = 11.9 Hz, 1H, CHHNAP), 4.13−4.11 (m, 2H, H-1aAll, H-

1bAll), 3.77−3.74 (m, 2H, H-2, H-3), 3.71−3.69 (m, 2H, H-5, H-4),

3.67−3.62 (m, 2H, H-7a, H-7b), 3.54 (dt, J = 9.6, 6.7 Hz, 1H, H-

1a_linker), 3.24 (dt, J = 9.6, 6.3 Hz, 1H, H-1b_linker), 3.11 (t, J = 6.7 Hz,

2H, H-5_linker), 2.32−2.25 (m, 1H, H-6a), 1.84−1.76 (m, 1H, H-6b),

1.49−1.39 (m, 4H, H-2_linker, H-4_linker), 1.24−1.20 (m, 2H, H-3_linker);

¹³C NMR (100 MHz, CDCl₃) δ 138.7−133.2 (5 × C-Ar), 135.1 (C-

(5-Azido-1-pentyl) 4,7-Di-O-benzyl-6-deoxy-2-O-(2-naph-

thylmethyl)-β-^D-manno-heptopyranoside (32). 1,5-Cycloocta-

diene-bis(methyldiphenylphosphine)-iridium hexaﬂuorophosphate

(2.9 mg, 3.0 μmol, 0.1 equiv) was dissolved in anhydrous THF (700

μL), and the resulting red solution was degassed under Ar. Hydrogen

was bubbled through the solution for 5 min, and then the resulting

yellow solution was once again degassed under Ar. A solution of

heptoside 28 (23 mg, 34 μmol, 1.0 equiv) in anhydrous THF (700

μL) was added. The mixture was stirred for 1 h at rt under Ar. Then, a

solution of iodine (17.4 mg, 69 μmol, 2.0 equiv) in THF/H₂O (1 mL,

4:1 v/v) was added to the mixture, which was stirred for another 1 h at

rt. The excess of iodine was then quenched by adding a freshly

prepared 10% Na₂S₂O₃(aq) solution. The aqueous phase was extracted

with EtOAc (3 × 5 mL). The combined organic layers were washed

with a saturated NaHCO₃(aq) solution (10 mL) and brine (10 mL).

The solvents of the dried solution (MgSO₄) were concentrated under

reduced pressure. The residue was puriﬁed by silica gel ﬂash

chromatography (pentane/Et₂O 8:2 to 6:4) to aﬀord 32 (20.7 mg,

1

2All), 128.5−126.1 (CH-Ar), 116.7 (C-3All), 98.0 (C-1, J_C,H= 168

Hz), 80.3 (C-3), 79.1 (C-4), 75.5 (CH₂Ph), 74.8 (C-2), 73.1

(CH₂Ph), 72.9 (CH₂NAP), 71.3 (C-1All), 68.5 (C-5), 67.0 (C-7),

66.9 (C-1_linker), 51.3 (C-5_linker), 31.9 (C-6), 29.0 (C-2_linker), 28.7 (C-

4_linker), 23.5 (C-3_linker); MS (ESI-TOF) m/z = 688.7 [M + Na]⁺;

HRMS (ESI-TOF) m/z [M + NH₄]⁺calcd for C₄₀H₅₁N₄O₆, 683.3803;

found, 683.3799. Analytical data for 28: R_f0.26 (PE/EtOAc 9:1);

[α]_D²⁰= −19.2 (c 0.1, CHCl₃); ¹H NMR (400 MHz, CDCl₃) δ 7.87−

7.27 (m, 17H, CH-Ar), 5.90−5.80 (m, 1H, H-2All), 5.25 (ddd, J =

17.2, 4.0, 1.7 Hz, 1H, H-3aAll), 5.13 (dd, J = 10.4, 1.5 Hz, 1H, H-

3bAll), 5.11 (d, J = 12.8 Hz, 1H, CHHPh), 5.03 (d, J = 12.8 Hz, 1H,

97%, two steps) as a colorless oil: R_f0.30 (PE/EtOAc 8:2); [α]_D²⁰

=

−28.8 (c 0.3, CHCl₃); ¹H NMR (400 MHz, CDCl₃) δ 7.86−7.24 (m,

17H, CH-Ar), 5.20 (d, J = 12.1 Hz, 1H, CHHNAP), 4.89 (d, J = 10.9

Hz, 1H, CHHPh), 4.80 (d, J = 12.1 Hz, 1H, CHHNAP), 4.62 (d, J =

10.9 Hz, 1H, CHHPh), 4.54 (d, J = 12.0 Hz, 1H, CHHPh), 4.44 (d, J

= 12.0 Hz, 1H, CHHPh), 4.41 (s, 1H, H-1), 3.87−3.82 (m, 2H, H-

4627

dx.doi.org/10.1021/jo500640n | J. Org. Chem. 2014, 79, 4615−4634

The Journal of Organic Chemistry

Article

1a_linker, H-2), 3.70−3.60 (m, 3H, H-7ab, H-4), 3.41−3.33 (m, 3H, H-

1b_linker, H-3, H-5), 3.25 (t, J = 6.8 Hz, 2H, H-5_linker), 2.33−2.26 (m,

1H, H-6a), 1.87−1.77 (m, 1H, H-6b), 1.71−1.58 (m, 4H, H-2_linker, H-

4_linker), 1.49−1.42 (m, 2H, H-3_linker); ¹³C NMR (100 MHz, CDCl₃) δ

138.5−133.2 (5 × C-Ar), 128.5−126.1 (CH-Ar), 101.8 (C-1), 80.7

(C-3), 78.1 (C-2), 75.3 (CH₂NAP), 75.0 (CH₂Ph), 74.4 (C-4), 72.9

(CH₂Ph), 72.0 (C-5), 69.6 (C-1_linker), 66.5 (C-7), 51.4 (C-5_linker), 32.1

(C-6), 29.4 (C-2_linker), 28.7 (C-4_linker), 23.6 (C-3_linker); HRMS (ESI-

TOF) m/z [M + NH₄]⁺calcd for C₃₇H₄₇N₄O₆, 643.3489; found,

643.3490.

m/z = 796.7 [M + Na]⁺; HRMS (ESI-TOF) m/z [M + NH₄]⁺calcd

for C₄₆H₅₅N₄O₆S, 791.3837; found, 791.3832.

2-Naphthaldehyde(1,2:3,4-di-O-isopropylidene-α-^D-galacto-

pyranos-6-yl)(phenyl 3-O-allyl-4,7-di-O-benzyl-6-deoxy-1-thio-

α-^D-manno-heptopyranosid-2-yl) Acetal (36). According to the

general procedure for the synthesis of mixed acetals, donor 25 (20.4

mg, 0.031 mmol) was reacted with acceptor 41 (9 mg, 34 μmol, 1.1

equiv) in the presence of DDQ (8.4 mg, 37 μmol, 1.2 equiv).

Puriﬁcation by silica gel ﬂash chromatography (PE/EtOAc 9:1 to 8:2 +

5% Et₃N) gave 36 (17.4 mg, 62%) as a yellow oil: R_f0.2 (PE/EtOAc

8:2); [α]²_D⁰= +42.9 (c 0.2, CHCl₃); H NMR (400 MHz, py-d₅) δ

1

General Procedure for the Synthesis of Mixed Acetals 33−

39. To a mixture of donor 23 or 25 (1.0 equiv) and alcohol acceptor

(1.2−1.5 equiv) in anhydrous DCM (20 mL·mmol⁻¹) was added

freshly activated 4 Å powdered molecular sieves (4 mg·mg⁻¹of

donor). The mixture was stirred at rt for 40 min under Ar. Then, DDQ

(1.2 equiv) was added, and the deep-green mixture was stirred for 3 h

at rt under Ar. The reaction was quenched by adding a saturated

NaHCO₃(aq) solution, stirred until the color turned bright yellow

(∼10 min), and diluted with DCM. The mixture was ﬁltered over

Celite and rinsed with DCM, and the organic phase was washed with a

saturated NaHCO₃(aq) and brine. The solvents of the dried solution

(MgSO₄) were concentrated under reduced pressure. The residue was

puriﬁed by silica gel ﬂash chromatography to give mixed acetals.

2-Naphthaldehyde(5-amino-N-benzyloxycarbonyl-1-

pentyl)(phenyl 4,7-di-O-benzyl-3-O-tert-butyldimethylsilyl-6-

deoxy-1-thio-α-^D-manno-heptopyranosid-2-yl) Acetal (33). Ac-

cording to the general procedure for the synthesis of mixed acetals,

donor 23 (104 mg, 150 μmol) was reacted with acceptor 40⁷⁶(70 mg,

210 μmol, 1.5 equiv) in the presence of DDQ (40 mg, 170 μmol, 1.2

equiv). Puriﬁcation by silica gel ﬂash chromatography (pentane/Et₂O

95:5 to 75:25) gave 33 (88 mg, 64%) as a yellow oil: R_f0.7 (PE/

EtOAc 7:3); HRMS (ESI-TOF) m/z [M + NH₄]⁺calcd for

C₅₇H₇₃N₂O₈SSi, 973.4851; found, 973.4846. The mixed acetals were

unstable and decomposed in the NMR tube (CDCl₃or py-d₅).

2-Naphthaldehyde(5-amino-N-benzyloxycarbonyl-1-

pentyl)(phenyl 3-O-allyl-4,7-di-O-benzyl-6-deoxy-1-thio-α-^D-

manno-heptopyranosid-2-yl) Acetal (34). According to the

general procedure for the synthesis of mixed acetals, donor 25 (16

mg, 24 μmol) was reacted with acceptor 40⁷⁶(7 mg, 29 μmol, 1.2

equiv) in the presence of DDQ (7 mg, 29 μmol, 1.2 equiv).

Puriﬁcation by silica gel ﬂash chromatography (PE/EtOAc 95:5 to 7:3

+ 5% Et₃N) gave 34 (13.2 mg, 62%) as a yellow oil: R_f0.2 (PE/Et₂O

8.42−7.42 (m, 22H, CH-Ar), 6.43 (s, 1H, H-acetal), 6.37 (s, 1H, H-

1_A), 6.07−5.98 (m, 1H, H-2All), 5.66 (d, J = 4.7 Hz, 1H, H-1_B), 5.42

(d, J = 17.4 Hz, 1H, H-3aAll), 5.17 (d, J = 10.8 Hz, 1H, H-3bAll), 5.10

(d, J = 11.1 Hz, 1H, CHHPh), 5.03 (s, 1H, H-2_A), 4.79 (s, 1H, H-3_B),

4.78 (d, J = 10.5 Hz, 1H, CHHPh), 4.61 (t, J = 7.7 Hz, 1H, H-5_A), 4.52

(br s, 1H, H-2_B), 4.46−4.37 (m, 4H, H-5_B, H-4_B, CH₂Ph), 4.30 (dd, J

= 13.1, 5.1 Hz, 1H, H-1aAll), 4.26−4.19 (m, 2H, H-6a_B, H-1bAll),

4.16−4.09 (m, 2H, H-3_A, H-4_A), 3.94 (dd, J = 10.3, 3.9 Hz, 1H, H-

6b_B), 3.64 (t, J = 6.2 Hz, 2H, H-7ab_A), 2.52−2.45 (m, 1H, H-6a_A),

2.03−1.94 (m, 1H, H-6b_A), 1.56 (s, 3H, CH₃), 1.49 (s, 3H, CH₃), 1.36

(s, 3H, CH₃), 1.31 (s, 3H, CH₃); ¹³C NMR (100 MHz, py-d₅) δ

139.8−133.9 (6 × C-Ar), 135.8 (C-2All), 131.8−124.2 (CH-Ar), 117.2

(C-3All), 109.7 (C-iso), 109.0 (C-iso) 103.8 (CH-acetal), 97.2 (C-1_B),

87.6 (C-1_A), 81.2 (C-3_A), 79.6 (C-4_A), 75.7 (C-2_A), 75.6 (CH2Ph),

73.3 (CH2Ph), 72.2 (C-4_B), 71.6 (C-3_B), 71.3 (C-2_B), 71.2 (C-1All),

70.5 (C-5_A), 68.3 (C-5_B), 67.4 (C-7_A), 64.3 (C-6_B), 32.7 (C-6_A), 26.7−

24.9 (4 × CH₃); HRMS (ESI-TOF) m/z [M + NH₄]⁺calcd for

C₅₃H₆₄NO₁₁S, 922.4195; found, 922.4191.

2-Naphthaldehyde(1,2:5,6-di-O-isopropylidene-α-^D-gluco-

furanos-3-yl)(phenyl 3-O-allyl-4,7-di-O-benzyl-6-deoxy-1-thio-

α-^D-manno-heptopyranosid-2-yl) Acetal (37). According to the

general procedure for the synthesis of mixed acetals, donor 25 (15 mg,

23 μmol) was reacted with acceptor 42 (9.1 mg, 35 μmol, 1.5 equiv) in

the presence of DDQ (6.3 mg, 28 μmol, 1.2 equiv). Puriﬁcation by

silica gel ﬂash chromatography (PE/EtOAc 95:5 to 80:20 + 5% Et₃N)

gave 37 (17.2 mg, 83%) as a yellow amorphous solid: R_f0.6 (PE/

EtOAc 8:2); [α]²_D⁰= +41.5 (c 0.3, CHCl₃); H NMR (400 MHz, py-

1

d₅) δ 8.40−7.24 (m, 22H, CH-Ar), 6.42 (s, 1H, H-acetal), 6.20 (s, 1H,

H-1_A), 6.14 (d, J = 3.5 Hz, 1H, H-1_B), 6.14−6.05 (m, 1H, H-2All),

5.49 (dd, J = 17.2, 1.4 Hz, 1H, H-3aAll), 5.26 (dd, J = 10.6, 1.0 Hz, 1H,

H-3bAll), 5.08−5.07 (m, 2H, H-2_A, CHHPh), 4.90 (dd, J = 14.3, 6.2

Hz, 1H, H-5_B), 4.79 (d, J = 3.6 Hz, 1H, H-2_B), 4.76 (d, J = 3.0 Hz, 1H,

H-3_B), 4.71 (d, J = 11.2 Hz, 1H, CHHPh), 4.63−4.57 (m, 2H, H-5_A,

H-4_B), 4.48−4.38 (m, 4H, CH₂Ph, H-1aAll, H-6a_B), 4.34−4.25 (m,

2H, H-6b_B, H-1bAll), 4.10 (dd, J = 9.3, 2.8 Hz, 1H, H-3_A), 4.02 (t, J =

9.3 Hz, 1H, H-4_A), 3.67−3.58 (m, 2H, H-7ab_A), 2.52−2.45 (m, 1H, H-

6a_A), 2.02−1.93 (m, 1H, H-6b_A), 1.57 (s, 3H, CH₃), 1.55 (s, 3H,

CH₃), 1.43 (s, 3H, CH₃), 1.11 (s, 3H, CH₃); ¹³C NMR (100 MHz, py-

d₅) δ 139.8−133.9 (6 × C-Ar), 135.8 (C-2All), 132.3−124.2 (CH-Ar),

117.3 (C-3All), 112.2 (C-iso), 109.8 (C-iso), 106.3 (C-1_B), 105.3

(CH-acetal), 87.9 (C-1_A), 84.1 (C-2_B), 82.1 (C-4_B), 80.6 (C-3_A), 79.6

(C-4_A), 79.5 (C-3_B), 76.3 (C-2_A), 75.6 (CH₂Ph), 73.9 (C-5_B), 73.3

(CH₂Ph), 71.5 (C-1All), 70.6 (C-5_A), 67.9 (C-6_B), 67.3 (C-7_A), 32.7

(C-6_A), 27.4−26.1 (4 × CH₃); MS (ESI-TOF) m/z = 927.8 [M +

Na]⁺; HRMS (ESI-TOF) m/z [M + NH₄]⁺calcd for C₅₃H₆₄NO₁₁S,

922.4195; found, 922.4190.

2-Naphthaldehyde(1-adamantanyl)(phenyl 3-O-allyl-4,7-di-

O-benzyl-6-deoxy-1-thio-α-^D-manno-heptopyranosid-2-yl)

Acetal (38). According to the general procedure for the synthesis of

mixed acetals, donor 25 (15 mg, 23 μmol) was reacted with acceptor

44 (5.3 mg, 35 μmol, 1.5 equiv) in the presence of DDQ (6.3 mg, 28

μmol, 1.2 equiv). Puriﬁcation by silica gel ﬂash chromatography (PE/

EtOAc 10:0 to 8:2 + 5% Et₃N) gave 38 (7.2 mg, 40%) as a white solid:

R_f0.6 (PE/EtOAc 8:2); [α]_D²⁰= +159.7 (c 0.1, CHCl₃); HRMS (ESI-

TOF) m/z [M + H]⁺calcd for C₅₁H₅₇O₆S, 797.3870; found, 797.3851.

The mixed acetals were unstable and decomposed in the NMR tube

(CDCl₃or py-d₅).

20

7:3); [α]_D= +61.3 (c 0.2, CHCl₃); HRMS (ESI-TOF) m/z [M +

NH₄]⁺calcd for C₅₄H₆₃N₂O₈S, 899.4300; found, 899.4294. The mixed

acetals were unstable and decomposed in the NMR tube (CDCl₃or

py-d₅).

2-Naphthaldehyde(5-azido-1-pentyl)(phenyl 3-O-allyl-4,7-

di-O-benzyl-6-deoxy-1-thio-α-^D-manno-heptopyranosid-2-yl)

Acetal (35). According to the general procedure for the synthesis of

mixed acetals, donor 25 (20 mg, 32 μmol) was reacted with acceptor

26⁶⁶(5.3 mg, 41 μmol, 1.3 equiv) in the presence of DDQ (8.6 mg, 38

μmol, 1.2 equiv). Puriﬁcation by silica gel ﬂash chromatography (PE/

Et₂O 95:5 to 7:3 + 5% Et₃N) gave 35 (20.2 mg, 81%) as a yellow oil:

R_f0.4 (PE/Et₂O 7:3); [α]_D²⁰= +72.7 (c 0.3, CHCl₃); H NMR (400

1

MHz, py-d₅) δ 8.38−7.23 (m, 22H, CH-Ar), 6.24 (s, 1H, H-acetal),

6.07−5.96 (m, 1H, H-2All), 6.03 (d, J = 1.5 Hz, 1H, H-1), 5.42 (ddd, J

= 17.3, 4.1, 1.7 Hz, 1H, H-3aAll), 5.17 (dd, J = 10.4, 1.6 Hz, 1H, H-

3bAll), 5.12 (d, J = 11.2 Hz, 1H, CHHPh), 4.87 (s, 1H, H-2), 4.78 (d,

J = 11.2 Hz, 1H, CHHPh), 4.63−4.57 (m, 1H, H-5), 4.44 (d, J = 11.9

Hz, 1H, CHHPh), 4.40 (d, J = 11.9 Hz, 1H, CHHPh), 4.34 (ddt, J =

13.0, 5.3, 1.4 Hz, 1H, H-1aAll), 4.24 (ddt, J = 13.2, 5.4, 1.5 Hz, 1H, H-

1bAll), 4.08 (d, J = 2.3 Hz, 1H, H-3), 4.07 (d, J = 2.2 Hz, 1H, H-4),

3.76−3.60 (m, 4H, H-7ab, H-1ab_linker), 3.10 (t, J = 6.6 Hz, 1H, H-

5_linker), 2.52−2.45 (m, 1H, H-6a), 2.02−1.94 (m, 1H, H-6b), 1.59−

1.52 (m, 2H, H-2_linker), 1.49−1.35 (m, 4H, H-4_linker, H-3_linker); ¹³C

NMR (100 MHz, py-d₅) δ 139.8−133.9 (6 × C-Ar), 135.9 (C-2All),

132.4−124.2 (CHAr), 117.1 (C-3All), 104.1 (CH-acetal), 88.3 (C-1),

80.9 (C-3), 79.6 (C-4), 75.9 (C-2), 75.6 (CH₂Ph), 73.4 (CH₂Ph), 71.4

(C-1All), 70.7 (C-5), 67.4 (C-7), 65.9 (C-1_linker), 51.7 (C-5_linker), 32.8

(C-6), 29.9 (C-2_linker), 29.2 (C-4_linker), 24.1 (C-3_linker); MS (ESI-TOF)

2-Naphthaldehyde(stigmastan-3-yl)(phenyl 3-O-allyl-4,7-di-

O-benzyl-6-deoxy-1-thio-α-^D-manno-heptopyranosid-2-yl)

Acetal (39). According to the general procedure for the synthesis of

4628

dx.doi.org/10.1021/jo500640n | J. Org. Chem. 2014, 79, 4615−4634

The Journal of Organic Chemistry

Article

1

mixed acetals, donor 25 (20.2 mg, 31 μmol) was reacted with acceptor

43 (14 mg, 34 μmol, 1.1 equiv) in the presence of DDQ (8.4 mg, 37

μmol, 1.2 equiv). Puriﬁcation by silica gel ﬂash chromatography (PE/

EtOAc 10:0 to 95:5 + 5% Et₃N) gave 39 (15 mg, 44%) as a yellow oil:

R_f0.6 (PE/EtOAc 8:2); [α]_D²⁰= +55.0 (c 0.3, CHCl₃); HRMS (ESI-

TOF) m/z [M + H]⁺calcd for C₇₀H₉₃O₆S 1061.6687, found

1061.6677. The mixed acetals were unstable and decomposed in the

NMR tube (CDCl₃and py-d₅).

3All), 101.4 (C-1, J_C1,H1= 155 Hz), 83.3 (C-3), 78.8 (C-4), 75.1

(CH₂Ph), 72.8 (CH₂Ph), 72.4 (C-5), 69.8 (C-1All), 69.3 (C-1_linker),

68.4 (C-2), 66.9 (C-7), 66.1 (CO₂CH₂Ph), 41.2 (C-5_linker), 32.7 (C-6),

30.2 (C-2_linker), 29.8 (C-4_linker), 23.8 (C-3_linker); MS (ESI-TOF) m/z =

656.7 [M + Na]⁺; HRMS (ESI-TOF) m/z [M + H]⁺calcd for

C₃₇H₄₈NO₈, 634.3374; found, 634.3369.

(5-Azido-1-pentyl) 3-O-Allyl-4,7-di-O-benzyl-6-deoxy-β-^D-

manno-heptopyranoside (47). The title compound was synthe-

sized from acetals 35 (340 mg, 430 μmol) according to the general

procedure for IAD from isolated mixed acetals. Puriﬁcation by silica

gel ﬂash chromatography (PE/EtOAc 9:1 to 7:3) gave 47 (142 mg,

62%) as a colorless oil: R_f0.2 (PE/EtOAc 8:2); [α]²_D⁰= −29.6 (c 0.02,

CHCl₃); ¹H NMR (400 MHz, CDCl₃) δ 7.36−7.23 (m, 10H, CH-Ar),

6.00−5.90 (m, 1H, H-2All), 5.31 (ddd, J = 17.1, 3.6, 1.5 Hz, 1H, H-

3aAll), 5.20 (ddd, J = 10.4, 3.3, 1.2 Hz, 1H, H-3bAll), 4.90 (d, J = 10.8

Hz, 1H, CHHPh), 4.61 (d, J = 10.8 Hz, 1H, CHHPh), 4.53 (d, J =

12.1 Hz, 1H, CHHPh), 4.43 (d, J = 12.1 Hz, 1H, CHHPh), 4.35 (s,

1H, H-1), 4.23 (ddt, J = 12.7, 5.8, 1.2 Hz, 1H, H-1aAll), 4.13 (ddt, J =

12.5, 5.6, 1.1 Hz, 1H, H-1bAll), 4.08 (d, J = 2.3 Hz, 1H, H-2), 3.79 (dt,

J = 9.4, 6.4 Hz, 1H, H-1a_linker), 3.68−3.57 (m, 2H, H-7ab), 3.53 (t, J =

9.1 Hz, 1H, H-4), 3.47 (dd, J = 8.8, 2.9 Hz, 1H, H-3), 3.44−3.35 (m,

2H, H-1b_linker, H-5), 3.26 (t, J = 6.7 Hz, 2H, H-5_linker), 2.30−2.23 (m,

1H, H-6a), 1.79−1.71 (m, 1H, H-6b), 1.65−1.56 (m, 4H, H-2_linker, H-

4_linker), 1.46−1.39 (m, 2H, H-3_linker); ¹³C NMR (100 MHz, CDCl₃) δ

138.6−138.3 (2 × C-Ar), 134.6 (C-2All), 128.4−127.5 (CH-Ar), 117.6

(5-Amino-N-benzyloxycarbonyl-1-pentyl) 4,7-Di-O-benzyl-

3-O-tert-butyldimethylsilyl-6-deoxy-β-^D-manno-heptopyrano-

side (45). To a solution of acetal 33 (88 mg, 92 μmol, 1.0 equiv) in

anhydrous DCE (9.2 mL) were added DTBMP (76 mg, 0.37 mmol,

4.0 equiv) and freshly activated 4 Å powdered molecular sieves (250

mg). The suspension was stirred for 40 min at rt under Ar. Then,

MeOTf (35 μL, 0.31 mmol, 3.4 equiv) was added, and the mixture was

stirred for 48 h at 40 °C under Ar. After the mixture was cooled to rt,

the reaction was quenched with Et₃N (2 mL), stirred for another 10

min, diluted with EtOAc (10 mL), and ﬁltered over Celite. The ﬁltrate

was concentrated under reduced pressure and puriﬁed by silica gel

ﬂash chromatography (pentane/EtOAc 95:5 to 80:20) to give 45

(16.3 mg, 25%) as a colorless oil: R_f0.2 (PE/EtOAc 7:3); [α]_D²⁰

=

−11.3 (c 0.1, CHCl₃); ¹H NMR (400 MHz, CDCl₃) δ 7.27−7.11 (m,

15H, CH-Ar), 4.98 (s, 2H, CO₂CHHPh), 4.72 (d, J = 11.3 Hz, 1H,

CH₂Ph), 4.45 (d, J = 11.1 Hz, 1H, CHHPh), 4.41 (d, J = 12 Hz, 1H,

CHHPh), 4.30 (d, J = 12.0 Hz, 1H, CHHPh), 4.28 (s, 1H, H-1), 3.76

(s, 1H, H-2), 3.69−3.62 (m, 2H, H-1a_linker, H-3), 3.55−3.43 (m, 2H,

H-7ab), 3.36−3.22 (m, 3H, H-4, H-5, H-1b_linker), 3.07 (d, J = 6.1 Hz,

1H, H-5_linker), 2.12−2.05 (m, 1H, H-6a), 1.64−1.56 (m, 1H, H-6b),

1.54−1.46 (m, 2H, H-2_linker), 1.42−1.35 (m, 2H, H-4_linker), 1.29−1.23

(m, 2H, H-3_linker), 0.83 (s, 9H, C(CH₃)₃), 0.01 (s, 3H, CH₃Si), 0.00 (s,

3H, CH₃Si); ¹³C NMR (100 MHz, CDCl₃) δ 156.5 (CO), 138.7−

136.7 (3 × C-Ar), 128.6−127.6 (CH-Ar), 99.9 (C-1), 79.4 (C-4), 75.8

(C-3), 75.4 (CH₂Ph), 72.9 (CH₂Ph), 72.0 (C-2), 71.8 (C-5), 69.7 (C-

1_linker), 66.7 (CO₂CH₂Ph), 66.4 (C-7), 41.0 (C-5_linker), 31.8 (C-6),

29.8 (C-4_linker), 29.3 (C-2_linker), 25.9 (C(CH₃)₃), 18.1 (C(CH₃)₃), −4.4

(CH₃Si), −4.5 (CH₃Si); MS (ESI-TOF) m/z 730.9 [M + Na]⁺;

HRMS (ESI-TOF) m/z [M + H]⁺calcd for C₄₀H₅₈NO₈Si, 708.3926;

found, 708.3924.

1

(C-3All), 99.7 (C-1, J_C,H= 156 Hz), 81.7 (C-3), 77.9 (C-4), 75.3

(CH₂Ph), 72.8 (CH₂Ph), 71.8 (C-5), 70.7 (C-1All), 69.3 (C-1_linker),

68.5 (C-2), 66.2 (C-7), 51.3 (C-5_linker), 31.8 (C-6), 29.1 (C-2_linker),

28.6 (C-4_linker), 23.3 (C-3_linker); MS (ESI-TOF) m/z = 543.7 [M +

NH₄]⁺, m/z = 548.6 [M + Na]⁺; HRMS (ESI-TOF) m/z [M + NH₄]⁺

calcd for C₂₉H₄₃N₄O₆, 543.3177; found, 543.3177.

3-O-Allyl-4,7-di-O-benzyl-6-deoxy-β-^D-manno-heptopyrano-

syl-[1→6]-1,2:3,4-di-O-isopropylidene-α-^D-galactopyranose

(50). The title compound was synthesized from acetals 36 (17.4 mg,

19 μmol) according to the general procedure for IAD from isolated

mixed acetals. Puriﬁcation by silica gel ﬂash chromatography (PE/

EtOAc 9:1 to 5:5) gave 50 (7.7 mg, 62%) as a yellow oil. R_f0.1 (PE/

EtOAc 6:4); [α]²_D⁰= −34.4 (c 0.1, CHCl₃); H NMR (400 MHz,

1

CDCl₃) δ 7.35−7.26 (m, 10H, CH-Ar), 5.99−5.89 (m, 1H, H-2All),

5.53 (d, J = 5.0 Hz, 1H, H-1_B), 5.30 (ddd, J = 17.1, 4.7, 1.6 Hz, 1H, H-

3aAll), 5.19 (ddd, J = 10.4, 3.9, 1.5 Hz, 1H, H-3bAll), 4.91 (d, J = 10.9

Hz, 1H, CHHPh), 4.61 (d, J = 10.9 Hz, 1H, CHHPh), 4.58 (dd, J =

8.3, 2.5 Hz, 1H, H-3_B), 4.51 (d, J = 11.9 Hz, 1H, CHHPh), 4.49 (d, J =

0.7 Hz, 1H, H-1_A), 4.46 (d, J = 11.9 Hz, 1H, CHHPh), 4.30 (dd, J =

5.1, 2.4 Hz, 1H, H-2_B), 4.22 (ddt, J = 12.6, 5.7, 1.3 Hz, 1H, H-1aAll),

4.17 (dd, J = 7.8, 1.5 Hz, 1H, H-4_B), 4.16 (br s, 1H, H-2_A), 4.10 (ddt, J

= 12.6, 5.7, 1.3 Hz, 1H, H-1bAll), 4.04−3.98 (m, 2H, H-6a_B, H-5_B),

3.68 (dd, J = 11.8, 3.2 Hz, 1H, H-6b_B), 3.65−3.60 (m, 2H, H-7ab_A),

3.56 (t, J = 9.2 Hz, 1H, H-4_A), 3.46 (dd, J = 9.1, 3.1 Hz, 1H, H-3_A),

3.38 (td, J = 9.5, 2.6 Hz, 1H, H-5_A), 2.29−2.22 (m, 1H, H-6a_A), 1.83−

1.74 (m, 1H, H-6b_A), 1.52 (s, 3H, CH₃), 1.42 (s, 3H, CH₃), 1.32 (s,

3H, CH₃), 1.25 (s, 3H, CH₃); ¹³C NMR (100 MHz, CDCl₃) δ 138.5−

138.4 (2 × C-Ar), 134.6 (C-2All), 128.3−127.5 (CH-Ar), 117.5 (C-

3All), 109.4 (C-iso), 108.7 (C-iso), 100.1 (C-1_A, ¹J_C,H= 158 Hz), 96.3

(C-1_B), 81.5 (C-3_A), 77.9 (C-4_A), 75.3 (CH₂Ph), 72.8 (CH₂Ph), 72.1

(C-5_A), 71.4 (C-4_B), 70.7 (C-3_B), 70.6 (C-1All), 70.4 (C-2_B), 68.8 (C-

6_B), 68.3 (C-2_A), 67.8 (C-5_B), 66.5 (C-7_A), 31.9 (C-6_A), 26.1−24.4 (4

× CH₃); HRMS (ESI-TOF) m/z [M + H]⁺calcd for C₃₆H₄₉O₁₁,

657.3269; found, 657.3267.

General Procedure for IAD from Isolated Mixed Acetals 34−

39. To a solution of mixed acetals (1.0 equiv) and DTBMP (3.0

equiv) in anhydrous DCE (100 mL·mmol⁻¹) was added freshly

activated 5 Å powdered molecular sieves (4 mg·mg⁻¹of acetal). The

suspension was stirred for 50 min at rt under Ar. Me₂S₂(3.0 equiv)

followed by MeOTf (3.0 equiv) was then injected, keeping rigorous

anhydrous conditions. The mixture was stirred for 24 h at 40 °C under

Ar. After the mixture was cooled to rt, the reaction was quenched with

Et₃N, stirred for 10 min, diluted with DCM, and ﬁltered over Celite.

The ﬁltrate was concentrated under reduced pressure and puriﬁed by

silica gel ﬂash chromatography.

(5-Amino-N-benzyloxycarbonyl-1-pentyl) 3-O-Allyl-4,7-di-O-

benzyl-6-deoxy-β-^D-manno-heptopyranoside (46). The title

compound was synthesized from acetals 34 (15.8 mg, 18 μmol)

according to the general procedure for IAD from isolated mixed

acetals. Puriﬁcation by silica gel ﬂash chromatography (PE/EtOAc

95:5 to 60:40) gave 46 (5.1 mg, 45%) as a colorless oil: R_f0.2 (PE/

EtOAc 6:4); [α]²_D⁰= −10.2 (c 0.2, CHCl₃); H NMR (400 MHz, py-

1

d₅) δ 7.54−7.28 (m, 15H, CH-Ar), 6.13−6.04 (m, 1H, H-2all), 5.45

(ddd, J = 17.2, 4.0, 1.8 Hz, 1H, H-3aAll), 5.36 (s, 2H, CO₂CH₂Ph),

5.20 (d, J = 11.3 Hz, 1H, CHHPh), 5.17 (ddd, J = 10.5, 3.6, 1.2 Hz,

1H, H-3bAll), 4.79 (d, J = 11.3 Hz, 1H, CHHPh), 4.60 (d, J = 12.1 Hz,

1H, CHHPh), 4.56 (s, 1H, H-1), 4.51 (d, J = 12.1 Hz, 1H, CHHPh),

4.47 (d, J = 2.8 Hz, 1H, H-2), 4.43 (ddt, J = 13.0, 5.2, 1.9 Hz, 1H, H-

1aAll), 4.22 (ddt, J = 13.0, 5.3, 1.9 Hz, 1H, H-1bAll), 4.06 (t, J = 9.3

Hz, 1H, H-4), 3.96 (dt, J = 9.6, 6.4 Hz, 1H, H-1a_linker), 3.88 (td, J = 8.9,

5.9 Hz, 1H, H-7a), 3.78−3.74 (m, 2H, H-7b, H-3), 3.73 (dd, J = 9.6,

2.5 Hz, 1H, H-5), 3.53 (dt, J = 9.5, 6.4 Hz, 1H, H-1b_linker), 3.36 (dd, J

= 13.0, 6.7 Hz, 2H, H-5_linker), 2.55−2.48 (m, 1H, H-6a), 2.00−1.91 (m,

1H, H-6b), 1.67−1.58 (m, 4H, H-2_linker, H-4_linker), 1.49−1.43 (m, 2H,

H-3_linker); ¹³C NMR (100 MHz, py-d₅) δ 157.1 (CO₂CH₂Ph), 139.7−

138.2 (3 × C-Ar), 135.9 (C-2All), 128.7−123.7 (CH-Ar), 116.2 (C-

3-O-Allyl-4,7-di-O-benzyl-6-deoxy-β-^D-manno-heptopyrano-

syl-[1→3]-1,2:5,6-di-O-isopropylidene-α-^D-glucofuranose (51).

The title compound was synthesized from acetals 37 (10 mg, 11

μmol) according to the general procedure for IAD from isolated mixed

acetals. Puriﬁcation by silica gel ﬂash chromatography (PE/EtOAc 9:1

to 6:4) gave 51 (3.3 mg, 46%) as a yellow oil: R_f0.2 (PE/EtOAc 6:4);

[α]²_D⁰= −3.1 (c 0.06, CHCl₃); H NMR (400 MHz, CDCl₃) δ 7.37−

1

7.25 (m, 10H, CH-Ar), 6.00−5.90 (m, 1H, H-2All), 5.88 (d, J = 3.7

Hz, 1H, H-1_B), 5.31 (ddd, J = 17.1, 3.9, 1.5 Hz, 1H, H-3aAll), 5.20

(ddd, J = 10.4, 3.3, 1.2 Hz, 1H, H-3bAll), 4.91 (d, J = 10.9 Hz, 1H,

CHHPh), 4.61 (d, J = 10.9 Hz, 1H, CHHPh), 4.59 (s, 1H, H-1_A), 4.53

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(d, J = 11.9 Hz, 1H, CHHPh), 4.48 (s, 1H, H-3_B), 4.47 (s, 1H, H-2_B),

4.46 (d, J = 11.9 Hz, 1H, CHHPh), 4.34 (dd, J = 12.3, 6.2 Hz, 1H, H-

5_B), 4.25−4.20 (m, 2H, H-4_B, H-1aAll), 4.16−4.10 (m, 2H, H-6a_B, H-

1bAll), 4.05−3.99 (m, 2H, H-2_A, H-6b_B), 3.67−3.60 (m, 2H, H-7ab_A),

3.57 (t, J = 9.3 Hz, 1H, H-4_A), 3.48 (dd, J = 8.7, 2.9 Hz, 1H, H-3_A),

3.40 (dd, J = 9.5, 2.5 Hz, 1H, H-5_A), 2.30−2.22 (m, 1H, H-6a_A), 1.84−

1.76 (m, 1H, H-6b_A), 1.50 (s, 3H, CH₃), 1.42 (s, 3H, CH₃), 1.35 (s,

3H, CH₃), 1.27 (s, 3H, CH₃); ¹³C NMR (100 MHz, CDCl₃) δ 138.5−

3.58 (m, 2H, H-7ab), 3.54 (t, J = 9.2 Hz, 1H, H-4), 3.46 (dd, J = 8.9,

3.1 Hz, 1H, H-3), 3.37 (td, J = 9.6, 2.5 Hz, 1H, H-5), 2.30−2.23 (m,

1H, H-6a), 1.96−1.79 (m, 4H, 2 × CH₂-stig), 1.78−1.72 (m, 1H, H-

6b), 1.71−1.41 (m, 11H, CH-stig, 5 × CH₂-stig), 1.35−0.94 (m, 19H,

5 × CH-stig, 7 × CH₂-stig), 0.94−0.92 (m, 1H, CH-stig), 0.90 (d, J =

6.5 Hz, 3H, CH₃-stig), 0.85 (d, J = 7.5 Hz, 3H, CH₃-stig), 0.82 (s, 3H,

CH₃-stig), 0.81 (d, J = 6.9 Hz, 3H, CH₃-stig), 0.77 (s, 3H, CH₃-stig),

0.64 (s, 3H, CH₃-stig), 0.63−0.56 (m, 1H, CH-stig); ¹³C NMR (100

MHz, CDCl₃) δ 138.7, 138.5 (2 × C-Ar), 134.8 (C-2All), 128.5−127.6

(CH-Ar), 117.6 (C-3All), 97.4 (C-1, ¹J_C,H= 157 Hz), 81.8 (C-3), 77.9

(C-4), 75.3 (CH₂Ph), 72.8 (CH₂Ph), 71.7 (C-5), 70.6 (C-1All), 69.1

(C-2), 66.5 (C-7), 56.5, 56.1, 54.3, 45.8, 44.7 (5 × CH-stig), 42.7 (C-

stig), 40.0, 36.9 (2 × CH₂-stig), 36.1 (CH-stig), 35.6 (C-stig), 35.4

(CH-stig), 34.3, 33.9, 32.1 (3 × CH₂-stig), 31.7 (C-6), 29.7, 29.2 (2 ×

CH₂-stig), 29.1 (CH-stig), 28.8, 26.0, 24.2, 23.0, 21.2 (5 × CH₂-stig),

19.8, 19.0, 18.7, 12.2, 12.1, 11.9 (6 × CH₃-stig); HRMS (ESI-TOF)

m/z [M + H]⁺calcd for C₅₃H₈₁O₆, 813.6028; found, 813.6011.

(5-Azido-1-pentyl) 3-O-Allyl-4,7-di-O-benzyl-6-deoxy-α-^D-

manno-heptopyranosyl-[1→2]-3-O-allyl-4,7-di-O-benzyl-6-

deoxy-β-^D-manno-heptopyranoside (49). The title compound

was isolated as a byproduct along with β-glycoside 47 from the

reaction of mixed acetal 35 (280 mg, 360 μmol) according to the

general procedure for IAD from isolated mixed acetals. Freshly

activated 4 Å powdered molecular sieves was used instead of 5 Å MS.

Puriﬁcation by silica gel ﬂash chromatography (PE/EtOAc 9:1 to 6:4)

gave 47 (66 mg, 35%) as a major compound along with 49 (11 mg,

3%), both as colorless oils. Analytical data for 49: R_f0.1 (PE/EtOAc

138.3 (2 × C-Ar), 134.6 (C-2All), 128.4−127.6 (CH-Ar), 117.6 (C-

1

3All), 111.9 (C-iso), 109.0 (C-iso), 105.2 (C-1_B), 97.6 (C-1_A, J_C,H

=

156 Hz), 83.2 (C-2_B), 81.4 (C-3_A), 80.5 (C-4_B), 78.5 (C-3_B), 77.6 (C-

4_A), 75.3 (CH₂Ph), 73.3 (C-5_B), 72.9 (CH₂Ph), 72.5 (C-5_A), 70.8 (C-

1All), 68.9 (C-2_B), 66.7 (C-6_B), 66.2 (C-7_A), 31.8 (C-6_A), 26.8−25.4

(4 × CH₃); HRMS (ESI-TOF) m/z [M + NH₄]⁺calcd for

C₃₆H₅₂NO₁₁, 674.3535; found, 674.3533.

(1-Adamantanyl) 3-O-Allyl-4,7-di-O-benzyl-6-deoxy-β-^D-

manno-heptopyranoside (52). Representative Procedure for the

One-Pot IAD. To a mixture of donor 25 (25 mg, 40 μmol, 1.0 equiv)

and acceptor 44 (8.8 mg, 0.06 mmol, 1.5 equiv) in anhydrous DCM

(800 μL) was added freshly activated 4 Å powdered molecular sieves

(100 mg). The mixture was stirred at rt for 40 min under Ar. Then,

DDQ (11 mg, 50 μmol, 1.3 equiv) was added, and the deep-green

mixture was stirred for 1 h at rt under Ar. The reaction was quenched

by adding a saturated NaHCO₃(aq) solution (3 mL) and stirred until

the color turned to bright yellow (∼10 min). The solution was diluted

with DCM (10 mL) and ﬁltered over Celite. The organic phase was

washed with a saturated NaHCO₃(aq) solution (5 mL) and brine (5

mL). The solvents of the dried solution (MgSO₄) were concentrated

under reduced pressure and coevaporated with toluene (3×). To a

solution of crude acetals 38 in anhydrous DCE (9.7 mL) were added

DTBMP (24 mg, 120 μmol, 3.0 equiv) and freshly activated 5 Å

powdered molecular sieves (124 mg). The suspension was stirred for

50 min at rt under Ar. Me₂S₂(10.5 μL, 0.12 mmol, 3.0 equiv) and

MeOTf (13.2 μL, 0.12 mmol, 3.0 equiv) were then injected to the

mixture, which was stirred for 20 h at 40 °C. After cooling to rt, the

reaction was quenched by adding Et₃N, stirred for 10 min, diluted with

DCM (10 mL), and ﬁltered over Celite. The ﬁltrate was concentrated

under reduced pressure and puriﬁed by silica gel ﬂash chromatography

(PE/EtOAc 10:0 to 6:4) to give 52 (12.1 mg, 58%, two steps) as a

colorless oil: R_f0.1 (PE/EtOAc 6:4); [α]²_D⁰= −14.8 (c = 0.1, CHCl₃);

¹H NMR (400 MHz, CDCl₃) δ 7.37−7.24 (m, 10H, CH-Ar), 6.00−

5.91 (m, 1H, H-2All), 5.31 (ddd, J = 17.2, 3.6, 1.6 Hz, 1H, H-3aAll),

5.20 (ddd, J = 10.4, 3.2, 1.5 Hz, 1H, H-3bAll), 4.90 (d, J = 10.9 Hz,

1H, CHHPh), 4.68 (d, J = 0.9 Hz, 1H, H-1), 4.61 (d, J = 10.9 Hz, 1H,

CHHPh), 4.46 (s, 2H, CH₂Ph), 4.24 (ddt, J = 12.7, 5.8, 1.4 Hz, 1H, H-

1aAll), 4.13 (ddt, J = 12.7, 5.7, 1.4 Hz, 1H, H-1bAll), 3.94 (dd, J = 3.1,

0.9 Hz, 1H, H-2), 3.63−3.59 (m, 2H, H-7ab), 3.52 (t, J = 9.1 Hz, 1H,

H-4), 3.48 (dd, J = 8.9, 3.0 Hz, 1H, H-3), 3.38 (td, J = 9.8, 2.4 Hz, 1H,

H-5), 2.27−2.16 (m, 1H, H-6a), 2.11 (s, 3H, 3 × CH-ada), 1.84−1.73

(m, 6H, 3 × CH₂-ada), 1.70−1.66 (m, 1H, H-6b), 1.63−1.54 (m, 6H,

3 × CH₂-ada); ¹³C NMR (100 MHz, CDCl₃) δ 138.6−138.5 (2 × C-

Ar), 134.8 (C-2All), 128.4−127.6 (CH-Ar), 117.6 (C-3All), 92.8 (C-1,

¹J_C,H= 155 Hz), 82.1 (C-3), 78.1 (C-4), 75.4 (CH₂Ph), 75.3 (C-Ada),

7:3); [α]²_D⁰= −19.6 (c 0.2, CHCl₃); H NMR (400 MHz, CDCl₃) δ

1

7.37−7.22 (m, 20H, CH-Ar), 5.96−5.88 (m, 2H, 2 × H-2All), 5.28

(ddd, J = 17.3, 3.7, 1.6 Hz, 2H, 2 × H-3aAll), 5.16 (ddd, J = 10.4, 3.4,

1.2 Hz, 2H, 2 × H-3bAll), 4.95 (d, J = 10.9 Hz, 1H, CHHPh), 4.89 (d,

J = 10.9 Hz, 1H, CHHPh), 4.82 (s, 1H, H-1_B), 4.61 (d, J = 11.1 Hz,

1H, CHHPh), 4.58 (d, J = 10.9 Hz, 1H, CHHPh), 4.53 (d, J = 12.1

Hz, 1H, CHHPh), 4.51 (d, J = 12.0 Hz, 1H, CHHPh), 4.44 (d, J =

12.0 Hz, 1H, CHHPh), 4.41 (d, J = 12.0 Hz, 1H, CHHPh), 4.27 (ddt,

J = 12.8, 5.6, 1.4 Hz, 1H, H-1aAll), 4.26 (s, 1H, H-1_A), 4.22 (d, J = 3.2

Hz, 1H, H-2_B), 4.20 (d, J = 2.6 Hz, 1H, H-2_A), 4.18 (ddt, J = 12.0, 5.3,

1.4 Hz, 1H, H-1aAll), 4.09 (ddt, J = 12.8, 5.8, 1.3 Hz, 1H, H-1bAll),

3.88 (ddt, J = 12.3, 5.9, 1.3 Hz, 1H, H-1bAll), 3.74 (td, J = 9.3, 6.4 Hz,

1H, H-1a_linker), 3.67−3.55 (m, 5H, H-4_A, H-7ab_A, H-7ab_B), 3.47−3.30

(m, 6H, H-4_B, H-3_A, H-3_B, H-5_A, H-5_B, H-1b_linker), 3.20 (t, J = 6.8 Hz,

2H, H-5_linker), 2.31−2.22 (m, 2H, H-6a_A, H-6a_B), 1.85−1.68 (m, 2H,

H-6b_A, H-6b_B), 1.59−1.51 (m, 4H, H-2_linker, H-4_linker), 1.40−1.34 (m,

2H, H-3_linker); ¹³C NMR (100 MHz, CDCl₃) δ 138.6−138.4 (4 × C-

Ar), 134.8−134.6 (2 × C-2All), 128.3−127.5 (CH-Ar), 117.3−117.2

1

(2 × C-3All), 100.1 (C-1_A, J_C,H= 155 Hz), 98.9 (C-1_B, J_C,H= 164

Hz), 81.6 (C-3_A), 80.5 (C-3_B), 77.7 (C-4_A, C-4_B), 75.4 (CH₂Ph), 75.3

(CH₂Ph), 72.8 (CH₂Ph), 72.7 (CH₂Ph), 72.4 (C-5_B), 72.1 (C-5_A),

70.4 (C-2_B), 70.3 (C-1All), 69.6 (C-1All), 69.4 (C-1_linker), 68.0 (C-2_A),

66.7 (C-7_A*), 66.3 (C-7_B*), 51.2 (C-5_linker), 31.9 (C-6_A), 31.8 (C-6_B),

29.2 (C-2_linker), 28.5 (C-4_linker), 23.3 (C-3_linker); MS (ESI-TOF) m/z =

945.2 [M + Na]⁺; HRMS (ESI-TOF) m/z [M + NH₄]⁺calcd for

C₅₃H₇₁N₄O₁₁, 939.5114; found, 939.5111.

(5-Azido-1-pentyl) 2-O-Acetyl-3-O-allyl-4,7-di-O-benzyl-6-

deoxy-β-^D-manno-heptopyranoside (54). To a solution of alcohol

47 (483 mg, 0.92 mmol, 1.0 equiv) in anhydrous py (15.4 mL) were

added Ac₂O (15.4 mL) and cat. DMAP (11 mg, 92 μmol, 0.1 equiv).

The mixture was stirred at rt for 15 min under N₂. Then, the mixture

was concentrated under reduced pressure and coevaporated with

toluene (3×). The residue was puriﬁed by silica gel ﬂash

chromatography (PE/EtOAc 95:5 to 80:20) to give 54 (475 mg,

91%) as a yellow oil: R_f0.4 (PE/EtOAc 8:2); [α]²_D⁰= −20.1 (c 0.2,

CHCl₃); ¹H NMR (400 MHz, CDCl₃) δ 7.34−7.27 (m, 10H, CH-Ar),

5.93−5.84 (m, 1H, H-2All), 5.48 (dd, J = 3.4, 1.0 Hz, 1H, H-2), 5.29

(ddd, J = 17.2, 3.7, 1.6 Hz, 1H, H-3aAll), 5.17 (ddd, J = 10.3, 3.2, 1.2

Hz, 1H, H-3bAll), 4.90 (d, J = 10.7 Hz, 1H, CHHPh), 4.60 (d, J = 10.7

Hz, 1H, CHHPh), 4.53 (d, J = 12.0 Hz, 1H, CHHPh), 4.43 (d, J =

12.0 Hz, 1H, CHHPh), 4.42 (d, J = 1.0 Hz, 1H, H-1), 4.18 (ddt, J =

12.5, 5.4, 1.4 Hz, 1H, H-1aAll), 4.00 (ddt, J = 12.5, 5.9, 1.3 Hz, 1H, H-

1bAll), 3.74 (td, J = 9.3, 6.3 Hz, 1H, H-1a_linker), 3.64−3.55 (m, 2H, H-

72.9 (CH₂Ph), 71.5 (C-5), 70.7 (C-1All), 70.2 (C-2), 66.7 (C-7), 42.5

(3 × CH₂-ada), 36.3 (3 × CH₂-ada), 31.7 (C-6), 30.7 (3 × CH-ada);

HRMS (ESI-TOF) m/z [M + H]⁺calcd for C₃₄H₄₈NO₆, 566.3476;

found, 566.3472.

(Stigmastan-3-yl) 3-O-Allyl-4,7-di-O-benzyl-6-deoxy-β-^D-

manno-heptopyranoside (53). The title compound was synthe-

sized from acetals 39 (14.6 mg, 0.014 mmol) according to the general

procedure for IAD from isolated mixed acetals. Puriﬁcation by silica

gel ﬂash chromatography (PE/EtOAc 9:1 to 7:3) gave 53 (8.5 mg,

75%) as a colorless oil: R_f0.2 (PE/EtOAc 7:3); [α]²_D⁰= +12.8 (c 0.1,

CHCl₃); ¹H NMR (400 MHz, CDCl₃) δ 7.34−7.28 (m, 10H, CH-Ar),

6.00−5.91 (m, 1H, H-2all), 5.31 (ddd, J = 17.3, 3.6, 1.6 Hz, 1H, H-

3aAll), 5.20 (ddd, J = 10.4, 3.1, 1.6 Hz, 1H, H-3bAll), 4.90 (d, J = 10.9

Hz, 1H, CHHPh), 4.61 (d, J = 10.9 Hz, 1H, CHHPh), 4.51 (s, 1H, H-

1), 4.50 (d, J = 11.9 Hz, 1H, CHHPh), 4.45 (d, J = 11.9 Hz, 1H,

CHHPh), 4.23 (ddt, J = 12.8, 5.8, 1.3 Hz, 1H, H-1aAll), 4.12 (ddt, J =

12.7, 5.8, 1.3 Hz, 1H, H-1bAll), 4.03 (d, J = 3.0 Hz, 1H, H-2), 3.64−

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7ab), 3.55−3.52 (m, 1H, H-3), 3.46−3.41 (m, 2H, H-4, H-5), 3.38 (td,

J = 9.4, 6.6 Hz, 1H, H-1b_linker), 3.24 (t, J = 6.9 Hz, 1H, H-5_linker), 2.34−

2.26 (m, 1H, H-6a), 2.18 (s, 3H, CH₃CO), 1.81−1.73 (m, 1H, H-6b),

1.62−1.53 (m, 4H, H-2_linker, H-4_linker), 1.42−1.33 (m, 2H, H-3_linker);

¹³C NMR (100 MHz, CDCl₃) δ 170.7 (CO), 138.7−138.4 (2 × C-Ar),

134.5 (C-2All), 128.5−127.7 (CH-Ar), 117.6 (C-3All), 99.0 (C-1),

80.3 (C-3), 78.2 (C-4), 75.4 (CH₂Ph), 72.9 (CH₂Ph), 72.2 (C-5), 70.6

(C-1All), 69.6 (C-1_linker), 68.5 (C-2), 66.3 (C-7), 51.4 (C-5_linker), 31.9

(C-6), 29.1 (C-2_linker), 28.7 (C-4_linker), 23.3 (C-3_linker), 21.2 (CH₃CO);

HRMS (ESI-TOF) m/z [M + H]⁺calcd for C₃₁H₄₂N₃O₇, 568.3017;

found, 568.3013.

CHHPh), 4.90 (d, J = 10.9 Hz, 1H, CHHPh), 4.61 (d, J = 10.9 Hz,

1H, CHHPh), 4.58 (s, 1H, H-1_B), 4.57 (d, J = 10.6 Hz, 1H, CHHPh),

4.54 (d, J = 11.9 Hz, 1H, CHHPh), 4.44 (d, J = 12.1 Hz, 1H,

CHHPh), 4.43 (d, J = 11.9 Hz, 1H, CHHPh), 4.36 (d, J = 12.1 Hz,

1H, CHHPh), 4.26 (s, 1H, H-1_A), 4.23 (ddt, J = 12.1, 5.7, 1.3 Hz, 1H,

H-1aAll), 4.11 (ddt, J = 12.7, 5.6, 1.3 Hz, 1H, H-1bAll), 3.97−3.92 (m,

2H, H-3_A, H-2_B), 3.71 (td, J = 9.4, 6.3 Hz, 1H, H-1a_linker), 3.66−3.52

(m, 4H, H-7ab_A, H-7ab_B), 3.49−3.29 (m, 6H, H-3_B, H-4_A, H-4_B, H-5_A,

H-5_B, H-1b_linker), 3.24 (t, J = 6.8 Hz, 2H, H-5_linker), 2.36−2.19 (m, 2H,

H-6a_A, H-6a_B), 2.17 (s, 3H, CH₃CO), 1.83−1.77 (m, 2H, H-6b_A, H-

6b_B), 1.61−1.52 (m, 4H, H-4_linker, H-2_linker), 1.40−1.32 (m, 2H, H-

3_linker); ¹³C NMR (100 MHz, CDCl₃) δ 171.1 (CO), 138.7−138.5 (4

× C-Ar), 134.6 (C-2All), 128.4−127.6 (CH-Ar), 117.6 (C-3All), 98.6

(C-1_A, ¹J_C,H= 157 Hz), 96.7 (C-1_B, ¹J_C,H= 159 Hz), 81.9 (C-3_B), 78.0

(C-4_A), 77.7 (C-3_A), 77.1 (C-4_B), 75.4 (CH₂Ph), 74.7 (CH₂Ph), 72.9

(CH₂Ph), 72.7 (CH₂Ph), 72.3 (C-5_A), 72.1 (C-5_B), 70.7 (C-1All), 69.7

(C-1_linker), 68.5 (C-2_A), 68.4 (C-2_B), 66.5 (C-7_A), 66.3 (C-7_B), 51.4

(C-5_linker), 32.0 (C-6_B), 31.8 (C-6_A), 29.1 (C-2_linker), 28.7 (C-4_linker),

23.4 (C-3_linker), 21.3 (CH₃CO); HRMS (ESI-TOF) m/z [M + H]⁺

calcd for C₅₂H₆₆N₃O₁₂, 924.4641; found, 924.4636.

(5-Azido-1-pentyl) 2-O-Acetyl-4,7-di-O-benzyl-6-deoxy-β-^D-

manno-heptopyranoside (55). To a solution of 54 (10 mg, 18

μmol, 1.0 equiv) in anhydrous MeOH (900 μL) was added PdCl₂(2

mg, 13 μmol, 0.6 equiv). The mixture was stirred for 4 h at 40 °C

under N₂. Then, the mixture was cooled to rt, diluted with DCM (5

mL), and ﬁltered over Celite. The ﬁltrate was concentrated under

reduced pressure and coevaporated with toluene (3×). Crude alcohol

55 was used for the next step without further puriﬁcation to avoid

acetyl migration between the C2 and C3 positions. For analytical

measurements, the residue was puriﬁed by silica gel ﬂash

chromatography (PE/EtOAc 10:0 to 6:4) to give 55 (5.1 mg, 55%)

as a yellow oil in a mixture of C2/C3 regioisomers (ratio C2/C3 ∼

(5-Azido-1-pentyl) 2-O-Acetyl-3-O-allyl-4,7-di-O-benzyl-6-

deoxy-β-^D-manno-heptopyranosyl-[1→3]-2-O-acetyl-4,7-di-O-

benzyl-6-deoxy-β-^D-manno-heptopyranoside (57). To a solution

of alcohol 56 (25 mg, 30 μmol, 1.0 equiv) in anhydrous py (2 mL)

were added Ac₂O (2 mL) and cat. DMAP (1 mg). The mixture was

stirred at rt for 30 min under N₂. The mixture was concentrated under

reduced pressure and coevaporated with toluene (3×). The residue

was puriﬁed by silica gel ﬂash chromatography (PE/EtOAc 90:10 to

70:30) to give 57 (26 mg, 96%) as a yellow oil: R_f0.2 (PE/EtOAc

1

2.8:1.0): R_f0.1 (PE/EtOAc 7:3); [α]²_D⁰= −16.9 (c 0.1, CHCl₃); H

NMR (400 MHz, CDCl₃) δ 7.35−7.27 (m, 10H, CH-Ar), 5.35 (dd, J

= 3.5, 0.9 Hz, 1H, H-2), 4.80 (d, J = 11.1 Hz, 1H, CHHPh), 4.70 (d, J

= 11.1 Hz, 1H, CHHPh), 4.55 (d, J = 12.0 Hz, 1H, CHHPh), 4.47 (d,

J = 1.0 Hz, 1H, H-1), 4.44 (d, J = 12.0 Hz, 1H, CHHPh), 3.85 (br d, J

= 8.4 Hz, 1H, H-3), 3.78−3.72 (m, 1H, H-1a_linker), 3.70−3.62 (m, 2H,

H-7ab), 3.45 (dd, J = 9.6, 2.2 Hz, 1H, H-5), 3.42 (t, J = 6.2 Hz, 1H, H-

4), 3.39−3.36 (m, 1H, H-1b_linker), 3.25 (t, J = 6.9 Hz, 2H, H-5_linker),

2.34−2.27 (m, 1H, H-6a), 2.25 (s, 3H, CH₃CO), 1.86−1.78 (m, 1H,

H-6b), 1.61−1.54 (m, 4H, H-2_linker, H-4_linker), 1.42−1.36 (m, 2H, H-

3_linker); ¹³C NMR (100 MHz, CDCl₃) δ 171.3 (CO), 138.5, 138.0 (2 ×

C-Ar), 128.6−127.6 (CH-Ar), 98.7 (C-1), 79.7 (C-4), 75.1 (CH₂Ph),

73.3 (C-3), 72.9 (CH₂Ph), 72.0 (C-5), 71.7 (C-2), 69.5 (C-1_linker),

66.2 (C-7), 51.3 (C-5_linker), 31.9 (C-6), 28.9 (C-2_linker), 28.6 (C-4_linker),

23.3 (C-3_linker), 21.1 (CH₃CO); HRMS (ESI-TOF) m/z [M + NH₄]⁺

calcd for C₂₈H₄₁N₄O₇, 545.2969; found, 545.2970.

7:3); [α]²_D⁰= −22.4 (c 0.5, CHCl₃); H NMR (400 MHz, CDCl₃) δ

1

7.42−7.20 (m, 20H, CH-Ar), 5.93−5.83 (m, 1H, H-2All), 5.37 (d, J =

3.0 Hz, 1H, H-2_B), 5.35 (d, J = 3.2 Hz, 1H, H-2_A), 5.31 (ddd, J = 17.3,

3.8, 1.6 Hz, 1H, H-3aAll), 5.18 (ddd, J = 10.3, 3.3, 1.4 Hz, 1H, H-

3bAll), 4.93 (d, J = 10.8 Hz, 1H, CHHPh), 4.63 (s, 1H, H-1_B), 4.62 (d,

J = 10.8 Hz, 1H, CHHPh), 4.52 (d, J = 12.1 Hz, 1H, CHHPh), 4.47

(d, J = 12.0 Hz, 1H, CHHPh), 4.45 (d, J = 10.0 Hz, 2H, CH₂Ph), 4.42

(d, J = 12.0 Hz, 1H, CHHPh), 4.37 (d, J = 12.1 Hz, 1H, CHHPh),

4.25 (s, 1H, H-1_A), 4.18 (ddt, J = 12.5, 5.4, 1.3 Hz, 1H, H-1aAll), 4.02

(ddt, J = 12.5, 5.8, 1.3 Hz, 1H, H-1bAll), 3.86 (dd, J = 8.5, 3.6 Hz, 1H,

H-3_A), 3.72 (td, J = 9.4, 6.3 Hz, 1H, H-1a_linker), 3.55−3.51 (m, 5H, H-

3_B, H-7ab_A, H-7ab_B), 3.51−3.46 (m, 2H, H-5_B, H-4_B), 3.36−3.29 (m,

3H, H-1b_linker, H-5_A, H-4_A), 3.24 (t, J = 6.8 Hz, 2H, H-5_linker), 2.33−

2.24 (m, 2H, H-6a_A, H-6a_B), 2.19 (s, 3H, CH₃CO), 1.96 (s, 3H,

CH₃CO), 1.82−1.71 (m, 2H, H-6b_A, H-6b_B), 1.62−1.52 (m, 4H, H-

4_linker, H-2_linker), 1.42−1.33 (m, 2H, H-3_linker); ¹³C NMR (100 MHz,

CDCl₃) δ 171.4 (CO), 170.1 (CO), 138.7−138.4 (4 × C-Ar), 134.3

(C-2All), 128.6−127.4 (CH-Ar), 117.4 (C-3All), 98.5 (C-1_A), 95.2 (C-

1_B), 80.1 (C-3_B), 78.2 (C-4_B), 77.8 (C-3_A), 76.8 (C-4_A), 75.2

(CH₂Ph), 74.7 (CH₂Ph), 72.9 (CH₂Ph), 72.6 (CH₂Ph), 72.1 (C-5_B),

71.9 (C-5_A), 70.4 (C-1All), 69.7 (C-1_linker), 68.1 (C-2_B), 67.8 (C-2_A),

66.4 (C-7_A*), 66.2 (C-7_B*), 51.3 (C-5_linker), 31.9 (C-6_A*), 31.8 (C-

6_B*), 28.9 (C-2_linker), 28.6 (C-4_linker), 23.3 (C-3_linker), 20.9 (2 ×

CH₃CO); HRMS (ESI-TOF) m/z [M + H]⁺calcd for C₅₄H₆₈N₃O₁₃,

966.4747; found, 966.4730.

(5-Azido-1-pentyl) 3-O-Allyl-4,7-di-O-benzyl-6-deoxy-β-^D-

manno-heptopyranosyl-[1→3]-2-O-acetyl-4,7-di-O-benzyl-6-

deoxy-β-^D-manno-heptopyranoside (56). To a mixture of donor

25 (650 mg, 1.01 mmol, 1.2 equiv) and crude acceptor 55 (442 mg,

0.838 mmol, 1.0 equiv) in anhydrous DCM (20 mL) was added

freshly activated 4 Å powdered molecular sieves (2.6 g). The mixture

was stirred at rt for 40 min under Ar. Then, DDQ (247 mg, 1.09

mmol, 1.3 equiv) was added, and the deep-green mixture was stirred

for 3.5 h at rt under Ar. The reaction was quenched by adding a

saturated NaHCO₃(aq) solution, stirred until the color turned bright

yellow, and diluted with DCM. The mixture was ﬁltered over Celite

and rinsed with DCM, and the organic phase was washed with a

saturated NaHCO₃(aq) solution and brine. The solvents of the dried

solution (MgSO₄) were concentrated under reduced pressure and

coevaporated with toluene (3×) to give mixed acetals as a colorless

solid [R_f0.30 (PE/EtOAc 8:2); HRMS (ESI-TOF) m/z [M + NH₄]⁺

calcd for C₆₉H₈₁N₄O₁₂S, 1189.5566; found, 1189.5559]. Crude acetals

were dissolved in anhydrous DCE (210 mL), then DTBMP (516 mg,

2.51 mmol, 3.0 equiv) and freshly activated 5 Å powdered molecular

sieves (3.93 g) were added. The suspension was stirred for 50 min at rt

under Ar. Me₂S₂(226 μL, 2.51 mmol, 3.0 equiv) and MeOTf (285 μL,

2.51 mmol, 3.0 equiv) were then injected to the mixture, which was

stirred for 17 h at 40 °C. After cooling to rt, the reaction was quenched

by adding Et₃N, stirred for 10 min, and ﬁltered over Celite. The ﬁltrate

was concentrated under reduced pressure and puriﬁed by silica gel

ﬂash chromatography (PE/EtOAc 9:1 to 75:25) to give disaccharide

56 (300 mg, 58%, two steps) as a colorless oil: R_f0.2 (PE/EtOAc 7:3);

(5-Azido-1-pentyl) 2-O-Acetyl-4,7-di-O-benzyl-6-deoxy-β-^D-

manno-heptopyranosyl-[1→3]-2-O-acetyl-4,7-di-O-benzyl-6-

deoxy-β-^D-manno-heptopyranoside (58). To a solution of

disaccharide 57 (50 mg, 52 μmol, 1.0 equiv) in a mixture of

anhydrous MeOH/DCM (5.2 mL, 1:1 v/v) was added PdCl₂(6.1 mg,

34 μmol, 0.7 equiv). The mixture was stirred for 1 h at 40 °C. After

cooling to rt, the solution was diluted with DCM (10 mL) and ﬁltered

over Celite. The ﬁltrate was concentrated under reduced pressure and

puriﬁed by silica gel ﬂash chromatography (PE/EtOAc 10:0 to 7:3) to

give 58 (33 mg, 69%): R_f0.10 (PE/EtOAc 8:2); [α]²_D⁰= −22.4 (c 0.3

CHCl₃); ¹H NMR (400 MHz, CDCl₃) δ 7.42−7.32 (m, 20H, CH-Ar),

5.36 (d, J = 3.3 Hz, 1H, H-2_A), 5.25 (d, J = 3.3 Hz, 1H, H-2_B), 4.93 (d,

J = 10.3 Hz, 1H, CHHPh), 4.84 (d, J = 11.1 Hz, 1H, CHHPh), 4.71

(d, J = 11.1 Hz, 1H, CHHPh), 4.67 (d, J = 0.7 Hz, 1H, H-1_B), 4.53 (d,

J = 12.0 Hz, 1H, CHHPh), 4.49 (d, J = 14.3 Hz, 1H, CHHPh), 4.45

(d, J = 12.0 Hz, 1H, CHHPh), 4.42 (d, J = 14.1 Hz, 1H, CHHPh),

[α]²_D⁰= −17.0 (c 0.5, CHCl₃); H NMR (400 MHz, CDCl₃) δ 7.40−

1

7.18 (m, 20H, CH-Ar), 6.00−5.90 (m, 1H, H-2All), 5.37 (d, J = 3.5

Hz, 1H, H-2_A), 5.34 (ddd, J = 17.3, 3.8, 1.5 Hz, 1H, H-3aAll), 5.20

(ddd, J = 10.4, 3.3, 1.3 Hz, 1H, H-3bAll), 4.97 (d, J = 10.6 Hz, 1H,

4631

dx.doi.org/10.1021/jo500640n | J. Org. Chem. 2014, 79, 4615−4634

The Journal of Organic Chemistry

Article

4.38 (d, J = 10.3 Hz, 1H, CHHPh), 4.25 (d, J = 0.7 Hz, 1H, H-1_A),

3.91−3.85 (m, 2H, H-3_B, H-3_A), 3.72 (td, J = 9.4, 6.3 Hz, 1H, 1a_linker),

3.65−3.58 (m, 4H, H-7ab_B, H-7ab_A), 3.51−3.42 (m, 2H, H-5_B, H-4_B),

3.35−3.29 (m, 3H, H-4_A, H-1b_linker, H-5_A), 3.24 (t, J = 6.9 Hz, 2H, H-

5_linker), 2.33−2.24 (m, 2H, H-6a_A, H-6a_B), 2.19 (s, 3H, CH₃CO), 1.97

(s, 3H, CH₃CO), 1.86−1.72 (m, 2H, H-6b_A, H-6b_B), 1.61−1.52 (m,

4H, H-4_linker, H-2_linker), 1.40−1.34 (m, 2H, H-3_linker); ¹³C NMR (100

MHz, CDCl₃) δ 171.6, 170.7 (2 × CO), 138.7−138.3 (4 × C-Ar),

128.7−127.5 (CH-Ar), 98.6 (C-1_A), 95.2 (C-1_B), 79.9 (C-4_B), 77.9 (C-

3_A), 76.9 (C-4_A), 75.2 (CH₂Ph), 74.8 (CH₂Ph), 73.2 (C-3_B), 73.0

(CH₂Ph), 72.7 (CH₂Ph), 72.2 (C-5_B), 71.9 (C-5_A), 71.6 (C-2_B), 69.8

(C-1_linker), 67.8 (C-2_A), 66.5 (C-7_A), 66.3 (C-7_B), 51.4 (C-5_linker), 32.0

(C-6_B), 31.9 (C-6_A), 29.1 (C-2_linker), 28.7 (C-4_linker), 23.4 (C-3_linker),

21.3 (2 × CH₃CO); HRMS (ESI-TOF) m/z [M + Na]⁺calcd for

C₅₁H₆₃N₃O₁₃Na, 948.4253; found, 948.4253.

NMR (500 MHz, D₂O) δ 5.56 (d, J_2,3= 3.1 Hz, 1H, H-2), 4.80 (br s,

1H, H-1), 3.85 (dt, J = 10.1, 6.4 Hz, 1H, H-1a_linker), 3.81−3.73 (m, 2H,

H-7ab), 3.68 (dt, J = 10.1, 6.4 Hz, 1H, H-1b_linker), 3.65−3.58 (m, 2H,

H-1a_Pr, H-3), 3.53 (dt, J = 9.3, 6.5 Hz, 1H, H-1b_Pr), 3.49−3.44 (m, 2H,

H-4, H-5), 2.22−2.12 (m, 1H, H-6a), 2.18 (s, 3H, CH₃CO), 1.75−

1.51 (m, 7H, H-6b, H-4ab_linker, H-2ab_linker, H-2_Pr), 1.45−1.37 (m, 2H,

H-3ab_linker), 0.87 (t, J = 7.4 Hz, 3H, H-3_Pr); ¹³C NMR (100 MHz,

MeOD) δ 172.2 (CO), 100.2 (C-1), 81.4 (C-3), 74.4 (C-5), 72.6 (C-

1_Pr), 71.5 (C-4), 70.2 (C-1_linker), 70.0 (C-2), 59.4 (C-7), 40.7 (C-

5_linker), 35.9 (C-6), 30.0 (C-2_linker), 28.2 (C-4_linker), 24.1 (C-3_linker), 24.0

(C-2_Pr), 20.9 (CH₃CO), 10.8 (C-3_Pr); ¹³C NMR (125 MHz, D₂O) δ

174.0 (CO), 99.0 (C-1), 79.8 (C-3), 73.3 (C-5), 72.7 (C-1_Pr), 70.3 (C-

1_linker, C-4), 69.8 (C-2), 58.4 (C-7), 40.0 (C-5_linker), 34.1 (C-6), 28.8

(C-2_linker), 27.0 (C-4_linker), 22.8 (C-3_linker, C-2_Pr), 20.9 (CH₃CO), 10.3

(C-3_Pr); MS (ESI-TOF) m/z = 364.5 [M + H]⁺; HRMS (ESI-TOF)

m/z [M + H]⁺calcd for C₁₇H₃₄NO₇, 364.2330; found, 364.2333.

(5-Amino-1-pentyl) 2-O-Acetyl-6-deoxy-β-^D-manno-hepto-

pyranosyl-[1→3]-2-O-acetyl-6-deoxy-β-^D-manno-heptopyra-

noside Hydrochloride (3). Representative Procedure for Pd-

Catalyzed Hydrogenation of Disaccharides. A solution of benzylated

58 (14.3 mg, 15.4 μmol) in MeOH (6.0 mL) containing concentrated

HCl (1.3 μL, 15.4 μmol, 1.0 equiv) was passed through a 20%

Pd(OH)₂/C cartridge (CatCart30) using a H-Cube continuous ﬂow

hydrogenation system in full-H₂mode. The temperature was set at 30

°C, and the ﬂow rate was ﬁxed at 1.0 mL·min⁻¹. After one run, the

cartridge was rinsed with MeOH (6.0 mL) and then H₂O (6.0 mL).

The solutions were concentrated under reduced pressure, and the

residue was subjected to C₁₈reversed-phase ﬂash chromatography

(H₂O/MeOH 10:0 to 8:2) followed by freeze-drying to give 3 (5.8

mg, 70%) as a white amorphous powder. Disaccharide 3 existed as a

mixture of C2/C3 (3a/3b) regioisomers [ratio 3a:3b ∼ 1.8:1.0

(MeOD); ∼ 1.0:1.0 (D₂O)] resulting from the migration of the C2′

acetyl group: [α]²_D⁰= −2.0 (c 0.05 MeOH); ¹H NMR of 3a (400 MHz,

MeOD) δ 5.45 (d, J_2,3= 3.4 Hz, 1H, H-2_A), 5.22 (d, J_2,3= 3.4 Hz, 1H,

H-2_B), 4.77 (br s, 1H, H-1_B), 4.62 (br s, 1H, H-1_A), 3.90−3.67 (m, 6H,

H-1a_linker, H-3_B, H-7ab_A, H-7ab_B), 3.65−3.55 (m, 2H, H-1b_linker, H-3_A),

3.46−3.29 (m, 4H, H-4_A, H-4_B, H-5_A, H-5_B), 2.92 (t, J = 7.5 Hz, 2H,

H-5ab_linker), 2.23−2.07 (m, 2H, H-6a_A, H-6a_B), 2.10 (s, 3H, CH₃CO),

2.09 (s, 3H, CH_3Ac), 1.72−1.59 (m, 6H, H-6b_A, H-6b_B, H-4ab_linker, H-

2ab_linker), 1.49−1.41 (m, 2H, H-3ab_linker); ¹³C NMR of 3a (100 MHz,

MeOD) δ 172.7, 172.2 (2 × CO), 100.0 (C-1_A), 97.6 (C-1_B), 79.9 (C-

3_B), 74.7, 74.0 (C-5_A, C-5_B), 73.3 (C-3_A), 73.0 (C-2_B), 72.4, 70.7 (C-

4_A, C-4_B), 70.4 (C-1_linker), 70.0 (C-2_A), 59.3 (C-7_A, C-7_B), 40.7 (C-

5_linker), 35.9, 35.7 (C-6_A, C-6_B), 30.0 (C-2_linker), 28.2 (C-4_linker), 24.1

(C-3_linker), 20.9 (2 × CH₃CO); HRMS (ESI-TOF) m/z [M + H]⁺

calcd for C₂₃H₄₂NO₁₃, 540.2656; found, 540.2649.

(5-Amino-1-pentyl) 2-O-Acetyl-6-deoxy-β-^D-manno-hepto-

pyranoside Hydrochloride (1). Representative Procedure for Pd-

Catalyzed Hydrogenation of Monosaccharides. To a solution of

benzylated 55 (11.2 mg, 21.2 μmol, 1.0 equiv) in MeOH (1.1 mL) was

added 1 N HCl(aq) (2.1 μL, 1.0 equiv). The solution was degassed

with Ar, and Pd black (10 mg) was added. The suspension was stirred

under an atmosphere of H₂at rt for 48 h. The mixture was ﬁltered

over Celite to remove the catalyst, and the cake was rinsed with

MeOH. The solutions were concentrated under reduced pressure and

coevaporated with toluene (3×). The residue was dissolved in distilled

H₂O and subjected to C₁₈reversed-phase ﬂash chromatography

(H₂O/MeOH 10:0 to 8:2) followed by freeze-drying to give 1 (6.3

mg, 92%) as a white hydroscopic solid. Monosaccharide 1 existed as a

mixture of C2/C3 (1a/1b) regioisomers [ratio 1a/1b ∼ 2.5:1.0

(MeOD); ∼ 1.7:1.0 (D₂O)] resulting from the migration of the acetyl

group: [α]²_D⁰= −65.1 (c 0.1, MeOH); ¹H NMR (400 MHz, MeOD) δ

5.31 (dd, J_1,2= 0.9 Hz, J_2,3= 3.5 Hz, 1H, H-2 1a), 4.68 (dd, J_3,4= 9.7

Hz, J_2,3= 3.1 Hz, 0.4H, H-3 1b), 4.62 (d, J_1,2= 0.9 Hz, 1H, H-1 1a),

4.54 (d, J_1,2= 0.8 Hz, 0.4H, H-1 1b), 4.00 (dd, J_1,2= 0.8 Hz, J_2,3= 3.1

Hz, 0.4H, H-2 1b), 3.90−3.80 (m, 1.4H, H-1a_linker1a/1b), 3.77−3.68

(m, 2.8H, H-7ab 1a/1b), 3.65−3.53 (m, 2.8H, H-4 1b, H-3 1a, H-

1b_linker1a/1b), 3.45−3.24 (m, 2.8H, H-4 1a/1b, H-5 1a/1b), 2.96−

2.89 (m, 2.8H, H-5ab_linker1a/1b), 2.22−2.13 (m, 1.4H, H-6a 1a/1b),

2.12 (s, 1.2H, CH₃CO 1b), 2.10 (s, 3H, CH₃CO 1a), 1.74−1.58 (m,

7H, H-6b 1a/1b, H-4ab_linker1a/1b, H-2ab_linker1a/1b), 1.54−1.41 (m,

1

2.8H, H-3ab_linker1a/1b); H NMR (500 MHz, D₂O) δ 5.37 (d, J_2,3

=

3.3 Hz, 1H, H-2 1a), 4.85 (dd, J_3,4= 9.9 Hz, J_2,3= 3.2 Hz, 0.6H, H-3

1b), 4.81 (br s, 1H, H-1 1a), 4.72 (br s, 1H, H-1 1b), 4.13 (d, J_2,3= 3.2

Hz, 0.6H, H-2 1b), 3.90−3.64 (m, 8H, H-1ab_linker1a/1b, H-3 1a, H-4

1b, H-7ab 1a/1b), 3.52−3.43 (m, 2.6H, H-4 1a/1b, H-5 1a/1b),

3.03−2.97 (m, 3.2H, H-5ab_linker1a/1b), 2.20−2.13 (m, 1.6H, 6a 1a/

1b), 2.18 (s, 4.8H, CH₃CO 1a/1b), 1.77−1.59 (m, 8H, H-6b 1a/1b,

H-4ab_linker1a/1b, H-2ab_linker1a/1b), 1.48−1.37 (m, 3.2H, H-3ab_linker

1a/1b); ¹³C NMR (100 MHz, MeOD) δ 172.6 (CO 1a), 172.5 (CO

1b), 101.2 (C-1 1b), 100.2 (C-1 1a), 77.7 (C-3 1b), 74.5 (C-5 1a),

74.4 (C-5 1b), 73.4 (C-3 1a, C-2 1a), 72.6 (C-4 1a), 70.1 (C-2 1b, C-

1linker 1a/1b), 69.5 (C-4 1b), 59.4 (C-7 1b), 59.4 (C-7 1a), 40.7 (C-

5_linker1a), 40.6 (C-5_linker1b), 35.9 (C-6 1a), 35.8 (C-6 1b), 30.0 (C-

2_linker1b), 29.9 (C-2_linker1a), 28.2 (C-6 1a/1b), 24.0 (C-3_linker1a),

24.0 (C-3_linker1b), 21.0 (CH₃CO 1a/1b); MS (ESI-TOF) m/z =

322.4 [M + H]⁺; HRMS (ESI-TOF) m/z [M + H]⁺calcd for

C₁₄H₂₈NO₇, 322.1860; found, 322.1863.

(5-Amino-1-pentyl) 2-O-Acetyl-6-deoxy-3-O-propyl-β-^D-

manno-heptopyranosyl-[1→3]-2-O-acetyl-6-deoxy-β-^D-manno-

heptopyranoside Hydrochloride (4). Benzylated 57 (9.9 mg, 10

μmol, 1.0 equiv) was reacted according to the representative

procedure for Pd-catalyzed hydrogenation of disaccharides and gave

4 (3.7 mg, 64%) as a white amorphous powder: [α]²_D⁰= −2.2 (c 0.1

1

MeOH); H NMR (400 MHz, MeOD) δ 5.44 (br s, 1H, H-2_A), 5.36

(d, J_2,3= 2.9 Hz, 1H, H-2_B), 4.76 (br s, 1H, H-1_B), 4.62 (br s, 1H, H-

1_A), 3.88−3.77 (m, 2H, H-1a_linker, H-3_A), 3.77−3.68 (m, 4H, H-7ab_A,

H-7ab_B), 3.61−3.52 (m, 2H, H-1b_linker, H-1a_Pr), 3.45−3.25 (m, 6H, H-

1b_Pr, H-4_A, H-4_B, H-5_A, H-5_B, H-3_B), 2.91 (t, J = 7.3 Hz, 2H, H-

5ab_linker), 2.23−2.14 (m, 2H, H-6a_A, H-6a_B), 2.09 (s, 3H, CH₃CO),

2.06 (s, 3H, CH₃CO), 1.71−1.59 (m, 4H, H-4ab_linker, H-2ab_linker, H-

6b_A, H-6b_B), 1.59−1.52 (m, 2H, H-2ab_Pr), 1.49−1.40 (m, 2H, H-

3ab_linker), 0.90 (t, J = 7.3 Hz, 3H, H-3_Pr); ¹³C NMR (100 MHz,

MeOD) δ 172.8, 171.9 (2 × CO), 99.9 (C-1_A), 97.6 (C-1_B), 81.4 (C-

3_B), 80.1 (C-3_A), 74.7, 74.0 (C-5_A, C-5_B), 72.6 (C-1_Pr), 71.3, 70.7 (C-

4_A, C-4_B), 70.4 (C-1_linker), 70.1 (C-2_A), 69.9 (C-2_B), 59.3 (C-7_A, C-7_B),

40.7 (C-5_linker), 35.7, 35.9 (C-6_A, C-6_B), 30.0 (C-2_linker), 28.2 (C-4_linker),

24.1 (C-3_linker), 24.0 (C-2_Pr), 20.9, 20.8 (2 × CH₃CO), 10.8 (C-3_Pr);

HRMS (ESI-TOF) m/z [M + H]⁺calcd for C₂₆H₄₈NO₁₃, 582.3126;

found, 582.3113.

(5-Amino-1-pentyl) 2-O-Acetyl-6-deoxy-3-O-propyl-β-^D-

manno-heptopyranoside Hydrochloride (2). Benzylated 54

(13.6 mg, 24.0 μmol, 1.0 equiv) was reacted according to the

representative procedure for Pd-catalyzed hydrogenation of mono-

saccharides and gave 2 (8.3 mg, 95%) as a white hydroscopic solid:

[α]²_D⁰= −21.6 (c 0.2, MeOH); H NMR (400 MHz, MeOD) δ 5.46

1

(dd, J_2,3= 1.5 Hz, J_1,2= 1.0 Hz, 1H, H-2), 4.62 (d, J_1,2= 1.0 Hz, 1H, H-

1), 3.84 (dt, J = 9.7, 6.1 Hz, 1H, H-1a_linker), 3.75−3.69 (m, 2H, H-7ab),

3.61−3.54 (m, 2H, H-1a_Pr, H-1b_linker), 3.43 (dt, J = 8.9, 6.4 Hz, 1H, H-

1b_Pr), 3.38−3.34 (m, 3H, H-3, H-4, H-5), 2.92 (t, J = 7.6 Hz, 2H, H-

5ab_linker), 2.23−2.13 (m, 1H, H-6a), 2.08 (s, 3H, CH₃CO), 1.71−1.59

(m, 5H, H-6b, H-4ab_linker, H-2ab_linker), 1.59−1.52 (m, 2H, H-2ab_Pr),

1

1.49−1.42 (m, 2H, H-3ab_linker), 0.90 (t, J = 7.4 Hz, 3H, H-3_Pr); H

4632

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The Journal of Organic Chemistry

Article

Carmentes, A.; Costa, L.; Cardoso, F.; Campa, C.; Diaz, M.; Roy, R.

Science 2004, 305, 522.

(24) Kosma, P. Chemical synthesis of the core oligosaccharide of

bacterial lipopolysaccharide. In Microbial Glycobiology: Structures,

Relevance and Applications; Moran, A. P., Ed.; Elsevier: London,

2009; pp 429−454.

ASSOCIATED CONTENT

* Supporting Information

NMR spectra for all synthetic compounds and HRMS spectra

of target heptosides 1−4. This material is available free of

charge via the Internet at http://pubs.acs.org.

■

S

(25) Hansson, J.; Oscarson, S. Curr. Org. Chem. 2000, 4, 535.

(26) Kosma, P. Curr. Org. Chem. 2008, 12, 1021.

(27) Yun, M.; Yoon, S.; Shin, Y.; Chun, K. H.; Nam Shin, J. E. Arch.

Pharm. Res. 2004, 27, 143.

(28) Ohara, T.; Adibekian, A.; Esposito, D.; Stallforth, P.; Seeberger,

P. Chem. Commun. 2010, 46, 4106.

(29) Yamasaki, R.; Nagahara, K.; Kishimoto, K.; Takajyo, A. Biosci.

Biotechnol. Biochem. 2012, 76, 772.

(30) Yang, Y.; Oishi, S.; Martin, C.; Seeberger, P. J. Am. Chem. Soc.

AUTHOR INFORMATION

Corresponding Author

*E-mail: charles.gauthier@univ-poitiers.fr; Tel: +33 (0)5 49 45

38 65; Fax: +33 (0)5 49 45 35 01.

■

Notes

The authors declare no competing ﬁnancial interest.

2013, 135, 6262.

ACKNOWLEDGMENTS

■

(31) Jaipuri, F. A.; Collet, B. Y. M.; Pohl, N. L. Angew. Chem., Int. Ed.

2008, 47, 1707.

This work was supported by a grant from the Agence Nationale

de la Recherche Programme Jeunes Chercheuses Jeunes

Chercheurs (ANR-JCJC-12-JS07-0003-01). We thank the

Unite de Chimie des Biomolecules at Institut Pasteur, Paris,

́ ́

for kindly sharing their H-Cube instrument.

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Intramolecular aglycon delivery enables the synthesis of 6-deoxy-β-d-manno-heptosides as fragments of Burkholderia pseudomallei and Burkholderia mallei capsular polysaccharide

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