Convergent synthesis of 4-o-phosphorylatedl-glycero-d-manno-heptosyl lipopolysaccharide core oligosaccharides based on regioselective cleavage of a 6,7-o-tetraisopropyldisiloxane-1,3-diyl protecting group

Article

pubs.acs.org/joc

Convergent Synthesis of 4‑O‑Phosphorylated L-glycero-D-manno-

Heptosyl Lipopolysaccharide Core Oligosaccharides Based on

Regioselective Cleavage of a 6,7‑O‑Tetraisopropyldisiloxane-1,3-diyl

Protecting Group

Christian Stanetty, Martin Walter, and Paul Kosma*

Department of Chemistry, University of Natural Resources and Life Sciences, A-1190 Vienna, Austria

S

* Supporting Information

ABSTRACT: The structurally conserved lipopolysaccharide

core region of many Gram-negative bacteria is composed of

trisaccharides containing 4-O-phosphorylated ^L-glycero-D-

manno-heptose (^L,D-Hep) units, which act as ligands for

antibodies and lectins. The disaccharides Glc-(1→3)-Hep4P

Hep-(1→3)-Hep4P and Hep-(1→7)-Hep4P and the branched

trisaccharide Glc-(1→3)-[Hep-(1→7)]-Hep4P, respectively,

have been synthesized from a methyl heptopyranoside

acceptor in less than 10 steps. The synthetic strategy was based on the early introduction of a phosphotriester at position 4

of heptose followed by a regioselective opening of a 6,7-O-(1,1,3,3-tetraisopropyl-1,3-disiloxane-1,3-diyl) group allowing for a

straightforward access to glycosylation at position 7. Perbenzylated N-phenyl triﬂuoroacetimidate glucosyl and heptosyl

derivatives served as α-selective glycosyl donors.

INTRODUCTION

■

Lipopolysaccharide (LPS) is a biomedically highly relevant

glycolipid located in the outer leaﬂet of the cell membrane of

Gram-negative bacteria.^1,2LPS is essential for many functions

of the bacterial membrane, providing stability, a protective

shield, and permeation control, and is thus indispensable for the

Figure 1. Common inner core oligosaccharide domains in enter-

obacterial LPS.

viability of bacteria.³LPS is also a major virulence factor which

is involved in a multitude of interactions with the adaptive and

innate immune system of respective host organisms.^4,5In

been reported to interact with C-type lectins such as lung

surfactant protein D (SP-D), concanavalin A, as well as

bacterial lectins from Burkholderia cenocepacia.¹⁷⁻²⁰

structural terms, LPS of Enterobacteriaceae comprises a highly

variable O-antigenic polysaccharide chain followed by a core

region which provides the link to the endotoxic lipid A

domain.⁶⁻⁸Within the core region, the inner part of

enterobacterial LPS is composed of the higher carbon sugars

3-deoxy-^D-manno-oct-2-ulosonic acid (Kdo) and L-glycero-D-

manno-heptose (^L,D-Hep) residues.⁹Speciﬁcally, phosphory-

lated heptosyl units are important antigens suitable for the

development of vaccines against pathogenic bacteria such as

Thus, the chemical synthesis of deﬁned heptosyl oligosac-

charides is a challenging task in order to further elucidate the

molecular basis of these biomedically relevant protein−LPS

interactions and to provide ligands for immunochemical

applications to be translated into future vaccine development.²¹

The chemical synthesis of suitably protected heptosyl building

blocks has been accomplished by de novo approaches as well as

by exquisite orthogonal protecting group manipulations

followed by selective glycosylation strategies to produce

spacer-equipped oligosaccharides corresponding to LPS-inner

core part structures related to Yersinia pestis, Pseudomonas

aeruginosa, N. meningitidis, and H. influenzae antigens.²²⁻²⁶The

latter target structures comprised 4-O-β-^D-glucopyranosylhep-

tosyl units with 6-O-phosphorylethanolamine substitution

introduced at the neighboring ^L,D-Hep residue.^27,28

Haemophilus influenzae and Neisseria meningitidis.^10,11

A

prototype phosphorylated heptose core structure as found in

Escherichia coli and Salmonella enterica LPS is shown in Figure

1.

The branched 4-O-phosphorylated heptosyl trisaccharide

core domain has recently been reported as essential part

mediating the binding to the cross-reactive antibacterial

monoclonal antibody WN1 222-5.¹²⁻¹⁵Of note, the paratope

of this antibody mimics the receptor binding site of Toll-like

receptor 4 (TLR-4), wherein the 4-O-phosphoryl heptosyl

domains are involved in multiple ionic and hydrogen-bonded

interactions.¹⁶In addition, L,D-heptosyl residues have recently

Received: October 16, 2013

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Figure 2. Retrosynthetic analysis for the synthesis of 4-O-phosphorylated heptosyl glycosides.

Scheme 1. Synthesis of Fully Diﬀerentiated 4-O-Phosphorylated Heptoside Acceptor Derivatives

The disaccharide fragment Hep4P-(1→3)-Hep4P has

previously been synthesized from an orthogonally protected

disaccharide precursor which was phosphorylated following

cleavage of the respective protective group at either of the 4-

positions.²⁹Herein we disclose a highly convergent approach

allowing access to α-glucosylated 4-O-phosphorylated hepto-

sides based on an early introduction of a 4-O-phosphotriester

moiety, thereby minimizing the number of protection and

deblocking steps. In addition, in combination with a

regioselective opening of a 1,1,3,3-tetraisopropyldisiloxane-1,3-

diyl (TIPDS) protecting group to give O-7 acceptor heptoside

derivatives, a straightforward assembly of several (1→7)- and

(1→3)-linked 4-O-phosphorylated heptosides, has been elabo-

rated.

converted into the corresponding 4-O-phosphotriester inter-

mediate (Figure 2).

Regioselective 2,3-O-orthoester opening should then allow

for extension at O-3, while regioselective opening of the

protecting group at the side chain would generate a 7-OH

glycosyl acceptor. Thus, several phosphorylated heptosyl LPS

ligands would be accessible from a common 4-O-phosphory-

lated building block, thereby minimizing the number of

protecting group manipulationsa highly important issue in

current oligosaccharide synthesis.³⁰The presence of a protected

phosphate moiety to be kept throughout the synthesis,

however, clearly implicates additional synthetic challenges to

be met during the assembly of the oligosaccharide.

Methyl ^L-glycero-D-manno-heptopyranoside 1, obtained pre-

viously by the Brimacombe approach,³¹was used for the

regioselective protection of the side-chain diol at C6 and C7.

Reaction of crystalline 1 with TIPDSCl₂in the presence of

imidazole gave directly the 6,7-O-TIPDS-protected derivative 2

in 87% yield (Scheme 1).

Starting from the TIPDS-protected heptoside 2, two

approaches for the diﬀerentiation of the remaining hydroxyl

groups were developed via initial selective syn-2,3-O-orthoester

formation. The ﬁrst approach utilized the 2,3-O-orthobenzoate

as a temporary protecting group that is suﬃciently stable to

allow phosphorylation using phosphoramidite-based coupling

methodology. Indeed, reaction of the intermediate orthoester

with dibenzyl N,N-diisopropylaminophosphoramidite/1H-tet-

RESULTS AND DISCUSSION

■

The common enterobacterial heptose region as shown in

Figure 1 reveals a repetitive substitution pattern comprising two

heptosyl units harboring a 4-O-phosphoryl substituent which

are extended at position 3 by another glycose residue (note: a

reversed pattern is seen in N. meniningitidis and H. influenzae

LPS, wherein a β-^D-glucopyranosyl residue is present at O-4).

The 3-O-α-^D-glucosyl substituted heptose residue is addition-

ally substituted at O-7 by a second heptose unit. Thus,

retrosynthetic analysis would suggest assembling these ligands

from a side-chain protected heptoside precursor to be

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razole³²followed by oxidation with m-CPBA gave a separable

mixture of the two diastereomers 3a/3b (∼3:1) in 89% yield.

The phosphoester substitution at position 4 was conﬁrmed by

further analyzed. As the imidate 13 has recently been reported

to be a suitable donor for the glycosylation of a 2,3,4,6-tetra-O-

acetylheptoside acceptor,³⁸the poor outcome of the glyco-

sylation reactions at the primary alcohol position of 10 may

thus have been due to the steric bulk imposed by the adjacent

FTIPDS group. Hence, an “armed” per-O-benzylated heptosyl

donor was envisaged to be more eﬀective and was prepared in a

straightforward sequence from the known³¹hexa-O-acetyl

heptose derivative 12 (Scheme 2). First, treatment of 12 with

1

the respective heteronuclear H/³¹P and ¹³C/³¹P spin-coupling

interactions. Selective acid-induced orthoester opening then

furnished 2-O-benzoate 4 in 72% yield together with minor

amounts of the corresponding 3-O-benzoate 5. The orthoester

mixture was also directly converted into 2,3-di-O-benzoate 6 in

a two-step yield of 89%. Alternatively, the intermediate

orthobenzoate was directly opened by the action of

camphorsulfonic acid to give 2-O-benzoate 7 (82%) which

was further transformed into the 3-O-Lev-protected compound

8 via a Steglich-type protocol in 96% yield. Almost complete

regioselectivity in the latter step was achieved by gradually

treating the reaction mixture with a solution of DCC (note: the

3,4-di-O-levulinated byproduct, however, was readily formed

when the reaction was performed under conventional reaction

conditions). Formation of the corresponding 4-O-Lev-pro-

tected isomer was not observed. Subsequent phosphotriester

formation at position 4 of the 3-O-Lev derivative 8 was

uneventful and delivered the orthogonally protected compound

9 in 81% yield.

Scheme 2. Synthesis of Heptosyl and Glucosyl Donors

Next, the 7-OH acceptor derivatives 10 and 11 were

approached by a selective partial cleavage of the 6,7-O-TIPDS

group of fully protected intermediates 6 and 9, respectively.

This methodology was originally developed by the group of

Ziegler^33,34for hexopyranosides and has so far been exclusively

used in this context. Initially, this protodesilylation was

attempted with HF-pyridine as reagent, according to the

published protocol, but turned out to be diﬃcult to elaborate

into a reliable procedure for the regioselective opening of the

exocyclic TIPDS group in heptoside derivatives 6 and 9,

respectively. Even when the reagent was added in moderate

excess and at low temperatures, the undesirable cleavage of

both silyl ether groups could not be completely suppressed.

Still, by close monitoring of the reaction and careful handling

during the workup, a good selectivity and high isolated yield

could be achieved for compound 10. Eventually, exchange of

the reagent to triethylamine trihydroﬂuoride (TREAT) allowed

for a better control of the reaction progress and resulted in a

reliable and scalable preparation of 10 and 11, respectively,

since complete desilylation by TREAT would require

substantially more reagent amounts, higher temperatures, and

extended reaction times.³⁵The 6-O-FTIPDS-protected accep-

tor 10 was stable upon storage for several months in a

refrigerator. Also, a trial experiment of acceptor 11 under

glycosylation conditions (at −40 °C in the presence of boron

triﬂuoride etherate) indicated that the 6-O-FTIPDS group was

not aﬀected.

The 4-O-phosphorylated heptoside acceptor derivatives 4,

10, and 11 then served as versatile precursors for ready

attachment of sugars at O-3 (4) as well as O-7 (10, 11),

allowing also for subsequent coupling steps to give O-7/O-3

disubstituted products.

For the synthesis of heptosyl oligosaccharides, trihaloaceti-

midate leaving groups developed by Schmidt have mainly been

used.^36,37Initially, the readily available per-O-acetylated N-

phenyltriﬂuoroacetimidate donor 13 was tested, since it usually

provides a good stereocontrol in the glycosylation step via 2-O-

acyl group participation leading to 1,2-trans glycosides. Several

glycosylation attempts utilizing 13 and the glycosyl acceptor

molecules 4 or 10, however, produced mainly orthoester

species accompanied by other byproducts which were not

thiophenol in the presence of excess boron triﬂuoride etherate

gave a separable mixture of the anomeric phenyl 1-thioglyco-

side in 88% yield. The anomeric mixture as well as the isolated

α-glycoside 14 was then processed into the phenyl penta-O-

benzyl-1-thioglycoside 16 in a combined yield of 80% via

sodium methoxide catalyzed transesteriﬁcation to give 15

followed by benzylation. Subsequent hydrolysis of the

thioglycoside with NBS gave the lactol 17 in 85% yield,

which was eventually converted into the N-phenyltriﬂuoroace-

timidate (NPTFA) derivative 18. The corresponding tetra-O-

benzyl ^D-glucopyranosyl NPTFA donor 19 was prepared

according to published procedures.³⁹Depending on the

mode of activation of the leaving group of donor 19 and the

solvent used, highly selective glucosylation reactions have been

reported leading to either β- or α-selective glycoside

formation.^39,40

Glycosylation of alcohol 10 using a slight excess of heptosyl

donor 18 was performed in dichloromethane in the presence of

0.05 equiv of TMSOTf. The coupling step proceeded smoothly

and gave a separable 4.9:1 anomeric mixture of disaccharides

20a and 20b in 83% yield (Scheme 3). No relevant side

reaction was observed when working at a temperature of −78

°C. TLC indicated that the glycosylation reaction was already

complete within 20 min. The α-anomeric conﬁguration of the

distal heptose unit in 20a was inferred from the value of the

heteronuclear J_C‑1,H‑1coupling constant (172 Hz)being in the

expected range for an α-^D-manno-conﬁgurationin contrast to

20b, which had a J_C‑1,H‑1coupling constant of 153.5 Hz. In

addition, the assigned substitution at position 7 was supported

by HMBC correlation signals from H-1 of the distal heptose (δ

5.02) to C-7 (δ 66.9) of the methyl heptoside unit in 20a as

well as, conversely, from H-7b (δ 3.74) to the anomeric carbon

of the distal heptose unit in 20b, respectively. Similarly, the

glycosylation reaction of the 3-O-levulinoyl derivative 11 was

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glycoside 27 was eventually isolated in 51% yield by HPLC

separation. As minor byproducts, the 1,6-anhydroheptose

derivative 25 and a 7-O-trimethylsilyl acceptor derivative were

also isolated.

Scheme 3. Synthesis of the (1→7) Linked 4-O-

Phosphorylated Heptobioside

Alternatively, the glycosylation sequence was reversed and

the (1→7)-linked heptobioside 22 was subjected to glyco-

sylation with the triﬂuoroacetimidate glucosyl donor 19. The

coupling reaction of 19 with 22 produced a separable mixture

of the anomeric trisaccharides in 82% yield and in high α-

selectivity (α/β = 9:1). The trisaccharide 27 was eventually

obtained after HPLC puriﬁcation in 74% isolated yield. Both

pathways delivered the protected trisaccharide 27 in com-

parable overall yield (17% versus 19%) but in a diﬀerent

number of steps (ﬁve versus seven steps when starting from 2).

In summary, the side-chain TIPDS protecting group pattern

turned out as a versatile means for chain elongation at the

primary alcohol group of ^L,D-heptose. No evidence for 6-O-

glycosylated products was found throughout these glycosylation

steps.

performed at −39 °C and provided a 4.1:1 anomeric mixture

(ratio based on the integration values of the downﬁeld-shifted

H-2 signals) of 21a and 21b in 72% yield. Disaccharide 21a was

isolated by HPLC and was then subjected to treatment with

hydrazine acetate to furnish the glycosyl acceptor derivative 22

in 84% yield.

Global deprotection of 6, 20a, 23, 24, and 27 was performed

by initial desilylation, followed by hydrogenation and ﬁnal

alkaline saponiﬁcation of the benzoate ester groups, and was

optimized using monosaccharide 6 (Scheme 6). The choice to

ﬁrst cleave the silyl-protecting group allowed for an additional

chromatographic puriﬁcation step prior to ﬁnal deprotection.

However, careful optimization of the desilylation conditions

and close monitoring was necessary to prevent partial

debenzylation of the phosphate moiety^41,42forming water-

soluble compounds, in particular, when the more reactive HF−

pyridine reagent was used. Treatment with TREAT, however,

provided a safe alternative. Hydrogenolysis of 28 followed by

alkaline transesteriﬁcation/ester hydrolysis of the dibenzoate 29

yielded the known 4-O-phosphoryl heptoside 30.^43,44The di-

and trisaccharide derivatives were treated similarly to the

deprotection of the monosaccharide 6. The desilylation of 23

and 24 was accomplished under mild TREAT conditions

aﬀording 34 and 37 without signiﬁcant phosphate−debenzyla-

tion. By contrast, the 7-O-heptosides 20a and 27, respectively,

required the more reactive HF−pyridine reagent under

carefully monitored reaction conditions to aﬀord 31 and 40

in good isolated yields and without hydrolysis of the benzyl

phosphate group. Hydrogenolysis and alkaline ester cleavage

was uneventful in all cases, complicated only by the fact that

benzoylated heptosides 32, 38, and 41 were insoluble in MeOH

at basic pH and needed addition of water to achieve

quantitative cleavage. The formed methylbenzoate and benzoic

acid were subsequently extracted with Et₂O or CHCl₃,

respectively. The NMR data of 30 and 39 were in good

agreement with published values.^29,44The structures of 33, 39,

and 42 were fully assigned on the basis of one- and two-

dimensional NMR measurements, and this data will be used in

ongoing STD-NMR experiments with heptose-binding lectins.

In contrast to the smooth glycosylation of the primary

alcohol 10, glycosylation at position 3 of acceptor 4 using

heptosyl imidate 18 met with diﬃculties (Scheme 4).

Speciﬁcally, the reaction required a higher temperature, and

the donor 18 was consumed by debenzylation at O-6/

intramolecular cyclization with formation of the known²⁴1,6-

anhydro sugar 25. In order to suppress this side reaction,

heptosyl donor 18 (2 equiv) was slowly added to a mixture of

acceptor and promotor, but the isolated yield of pure α-anomer

24 did not exceed 36% under various reaction conditions

tested. In contrast, the synthesis of the related 3-O-glucosyl

derivative 23 using donor 19 was robust (∼75% glycosylation

yield) and gave good isolated yields of the pure α-anomer

(>60%) with a temperature-dependent α to β ratio between 3:1

to 5:1 (with slightly increased α-selectivity observed for

glycosylations at higher temperatures). The α-anomeric

conﬁguration of the ^D-glucosyl residue in compound 23 was

inferred from the J_H‑1,H‑2coupling constant (3.4 Hz).

Based on the results obtained for the synthesis of the

disaccharides, trisaccharide 27 was targeted via a short route by

converting α-glucosyl-(1→3)-heptoside 23 into the corre-

sponding 7-O-acceptor 26 (Scheme 5). Again, regioselective

TIPDS cleavage of 23 by the action of TREAT was

accomplished in high yield thereby providing evidence that

this methodology is also applicable at the disaccharide stage.

Gratifyingly, the 6-O-FTIPDS group was compatible with the

ensuing coupling step using 1.5 equiv of donor 18 and 0.05

equiv of TMSO-triﬂate as promotor. Additional promotor,

however, had to be added, and the temperature was gradually

raised from −40 to 0 °C in order to drive the reaction to

completion. Thus, a 3.3:1 α/β anomeric mixture of

trisaccharides was formed in 69% yield, from which the α-

Scheme 4. Synthesis of (1→3) Linked 4-O-Phosphorylated Heptoside Derivative

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Scheme 5. Two Synthetic Pathways toward Phosphorylated Trisaccharide 27

Scheme 6. Global Deprotection of Oligosaccharides

such as Kdo and provide rapid access to 8-O-substituted Kdo

derivatives.

In conclusion, starting from a methyl heptoside, less than 10

steps were needed to complete the synthesis of a series of α-

(1→3)- and α-(1→7)-connected LPS heptose fragments

(Figure 3).

CONCLUSIONS AND OUTLOOK

■

A straightforward synthetic route toward LPS-oligosaccharide

fragments containing a central 4-O-phosphorylated heptosyl

residue has been established. This strategy capitalizes on the

introduction of the required phosphorylation pattern already at

the early stage of monosaccharide building blocks followed by a

regioselective partial cleavage of a side-chain TIPDS protecting

group as a robust and high-yielding method to generate fully

protected 7-O-heptosyl acceptor derivatives. In addition, the

presence of the resulting 6-O-ﬂuorosilyl protecting group after

regioselective TIPDS cleavage may also be exploited for

subsequent selective substitution at position 6 of heptoses.

The selective ring-opening of a side-chain locked TIPDS group

should also work for the synthesis of other higher-carbon sugars

EXPERIMENTAL SECTION

■

General Methods. All starting materials and reagents were

purchased from commercial sources and used without further

puriﬁcation. DCM was distilled from CaH₂and stored over molecular

sieves 4 Å. Residual moisture was conﬁrmed by Karl Fischer tritration

to be at least below 5 ppm. Reactions were monitored by TLC on

silica gel 60 F254 plates; spots were detected by UV light examination

or visualized by spraying with anisaldehyde−sulfuric acid and heating.

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Figure 3. Summary of di- and trisaccharide ligands derived from the TIPDS-protected 4-O-phosphotriester precursor.

Normal-phase column chromatography was performed on silica gel 60

(230−400 mesh) or on prepacked SPE columns (2 g/6 mL).

Preparative normal-phase HPLC was performed on column A (250 ×

20 mm, S-5 μm, 6 nm) or column B (250 × 10 mm, S-5 μm, 6 nm).

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

300 and 600 MHz instruments, respectively, employing standard

software provided by the manufacturer. ¹H NMR spectra were

referenced to tetramethylsilane (TMS, δ = 0) or by calibration with

the residual solvent peaks for solutions in organic solvents and to DSS

for solutions in D₂O. ¹³C NMR spectra were referenced to TMS (δ =

0), residual solvent peaks (CDCl₃, δ = 77.0, CD₃OD, δ = 49.0) in

organic solvents and to 1,4-dioxane (δ = 67.4) for solutions in D₂O.

³¹P NMR spectra in D₂O were referenced to external H₃PO₄(δ = 0).

Assignments were based on COSY, HSQC, and HMBC experiments.

HPLC−MS monitoring was done by injection of 0.01−0.1% solutions

(5−20 μL) on a system with two gradient pumps, degasser, and a

LCMS-2200 EV detector with mobile phase A = H₂O (0.1%

HCOOH) and mobile phase B = CH₃CN (0.1% HCOOH) on a

column (3.5 μm, 100 Å, 4.6 × 150 mm). Method A: ﬂow rate: 0.75

mL/min (0−22 min); gradient: 0−2 min: 85% B, 2−17 min: 85−40%

B, 17−22 min: 40% B. Method B: ﬂow rate: 0.75 mL/min (0−22

min); gradient: 0−2 min: 95% B, 2−17 min: 95−40% B, 17−22 min:

40% B. Accurate mass analysis (2 ppm mass accuracy) was carried out

from 10−100 mg/L solutions via LC−TOFMS measurements using

an autosampler, an HPLC system with binary pumps, degasser, and

column thermostat and ESI-TOF mass spectrometer.

General Procedure 1 for Cleavage of the 6-O-FTIPDS Group

with TREAT. The fully protected heptoside was coevaporated with

toluene, dissolved in dry DCM (1−6 mL), and transferred into a

Teﬂon ﬂask. TREAT (0.3 mL, ∼150 equiv of F⁻) was added dropwise

to the vigorously stirred solution, which was kept at rt for 15−21 h.

The solution was poured into a stirred mixture of cold 50% aq

NaHCO₃and EtOAc. Phases were separated, and the aqueous layer

was extracted twice with EtOAc. The combined organic layers were

washed with satd aq NaHCO₃and brine, dried (Na₂SO₄),

concentrated, and coevaporated with toluene. The crude material

was then puriﬁed by silica gel chromagraphy.

General Procedure 2 for Hydrogenolysis of Benzyl

Derivatives. A solution of the heptoside in dry MeOH (5−8 mL)

was purged with argon, and 10% Pd/C was added. The atmosphere

was exchanged for H₂, and the suspension was stirred at rt for the time

indicated. The atmosphere was exchanged to argon, and the

suspension was ﬁltered through Celite and washed repeatedly with

MeOH. The ﬁltrate was concentrated to yield the acidic form or was

treated with Et₃N and concentrated to aﬀord the target compound as

Et₃N species.

Methyl 6,7-O-(1,1,3,3-Tetraisopropyl-1,3-disiloxane-1,3-diyl)-^L-

glycero-α-^D-manno-heptopyranoside (2). Compound 1 (300 mg,

1.338 mmol, crystallized from hot 2-propanol) was coevaporated with

toluene (3×) and then dissolved in dry DMF (4.7 mL). 1H-Imidazole

(228 mg, 3.35 mmol, 2.5 equiv) was added, and the solution was

cooled to −55 °C. TIPDSCl₂(0.444 mL, 1.40 mmol, 1.05 equiv) was

added via a syringe during 10 min, and the solution was slowly warmed

to room temperature during 2.5 h. The reaction mixture was diluted

with EtOAc (40 mL) and washed with satd aq NaHCO₃. The aqueous

layer was reextracted with EtOAc and washed with brine. The

combined organic phase was dried (Na₂SO₄) and concentrated. The

crude material was puriﬁed by ﬂash column chromatography on a silica

gel cartridge (100 g, toluene/EtOAc 2:3→1:4) to give compound 2

20

(546.5 mg, 87%) as a syrup: R_f0.29 (toluene/EtOAc 1:1); [α]_D

+48.4 (c 1.3, MeOH); ¹H NMR (600 MHz, CDCl₃) δ 4.71 (d, J = 1.3

Hz, 1H, H-1), 4.30 (dt, J = 3.0, 5.0 Hz, 1H, H-6), 4.03 (d, J = 5.0 Hz,

2H, H-7a, H-7b), 3.85 (dd, J = 1.8, 3.5 Hz, 1H, H-2), 3.84 (t, J = 9.5

Hz, 1H, H-4), 3.75 (dd, J = 3.4, 9.2 Hz, 1H, H-3), 3.58 (dd, J = 2.9, 9.6

Hz, 1H, H-5), 3.35 (s, 3H, OCH₃), 1.12−0.94 (m, 28H, TIPDS-CH₃,

TIPDS-CH); ¹³C NMR (151 MHz, CDCl₃) δ 100.8 (C-1), 75.3 (C-

6), 72.1 (C-3), 70.95 (C-5), 70.2 (C-2), 68.2 (C-4), 67.3 (C-7), 55.0

(OCH₃), 17.4, 17.4, 17.29, 17.27, 17.24, 17.21 (8 × TIPDS-CH₃),

12.9, 12.7, 12.4, 12.3 (TIPDS-CH); HRMS (⁺ESI-TOF) m/z [M +

Na]⁺calcd for C₂₀H₄₂NaO₈Si₂489.2310, found 489.2312.

Methyl 4-O-Dibenzyloxyphosphoryl-2,3-O-ethoxybenzylidene-

6,7-O-(1,1,3,3-tetraisopropyl-1,3-disiloxane-1,3-diyl)-^L-glycero-α-D-

manno-heptopyranoside (3a/3b). Triethyl orthobenzoate (0.59 mL,

2.61 mmol) and camphorsulfonic acid (25 mg, 0.11 mmol) were

added to a solution of triol 2 (1.00 g, 2.14 mmol) in dry DCM (18

mL). The reaction mixture was stirred at rt for 30 min, when TLC

(toluene/EtOAc 5:1 + Et₃N) indicated almost complete conversion to

the intermediate orthoester diastereoisomers (∼2:1 ratio). Et₃N (0.3

mL, 2.14 mmol) was added, and the solution was concentrated and

coevaporated with dry toluene. The residue was dissolved in dry DCM

(18 mL). Dibenzyl N,N-diisopropylphosphoramidite (1.08 mL, 3.21

mmol) was added followed by dropwise addition of a 0.45 M solution

of 1H-tetrazole in acetonitrile (6.2 mL, 2.785 mmol). The solution was

stirred for 45 min at rt and then cooled to −78 °C. A solution of m-

CPBA (0.96 g; approximately 77%, 4.29 mmol) in DCM (6 mL) was

added, and the reaction mixture was stirred for 75 min at this

F

dx.doi.org/10.1021/jo402312x | J. Org. Chem. XXXX, XXX, XXX−XXX

The Journal of Organic Chemistry

Article

temperature. Triethylamine (0.75 mL, 5.36 mmol) was added, and the

solution was warmed to rt. The reaction mixture was then added to a

stirred mixture of satd aq NaHCO₃(40 mL) and EtOAc (40 mL).

Phases were separated, and the aqueous layer was extracted with

EtOAc (30 mL). The combined organic layers were washed with satd

aq NaHCO₃(30 mL) and brine (30 mL), dried (Na₂SO₄), and

concentrated. The crude was puriﬁed by chromatography (SiO₂: 150

g, toluene/EtOAc 15:1→12:1; the column was preconditioned with

toluene/EtOAc 15:1 containing 0.3% Et₃N) to give 3a (0.532 g, 29%)

and 3b (1.103 g, 60%) as a syrup. Data for isomer 3a: R_f0.73

δ 165.8 (PhCO), 135.5 (d, J_C,P= 6.8 Hz, POCH₂PhC1), 135.4 (d,

J_C,P= 6.9 Hz, POCH₂PhC1′), 133.15, 130.0, 129.7, 128.60, 128.58,

128.5, 128.3, 128.2, 127.9 (PhC), 98.439 (C-1), 76.8 (C-4), 73.4 (C-

6), 72.2 (C-2), 71.0 (d, J_C,P= 1.6 Hz, C-5), 70.2 (d, J_C,P= 5.5 Hz,

POCH₂), 69.8 (d, J_C,P= 5.4 Hz, POCH₂), 68.5 (C-3), 68.15 (C-7),

55.2 (OCH₃), 17.62, 17.56, 17.4, 17.3, 17.25, 17.2, 17.1 (8 × TIPDS-

CH₃), 13.3, 13.2, 12.6 (4 × TIPDS-CH); HRMS (⁺ESI-TOF) m/z [M

+ H]⁺calcd for C₄₁H₆₀O₁₂PSi₂831.3355, found 831.3355.

20

Data for 5: R_f0.29 (hexane/EtOAc 3:1); [α]_D+21.4 (c 0.9,

1

CHCl₃); H NMR (600 MHz, CDCl₃) δ 8.16−8.13 (m, 2H, BzH2/

20

(toluene/EtOAc 3:1); [α]_D+25 (c 0.6, CHCl₃); ¹H NMR (600

H6), 7.53−7.50 (m, 1H, BzH4), 7.40−7.36 (m, 2H, BzH3/H5), 7.28−

7.25 (m, 3H, PhH), 7.22−7.18 (m, 1H, PhH), 7.18−7.14 (m, 4H,

PhH), 6.93 −6.90 (m, 2H, PhH), 5.52 (dd, J = 9.7, 3.2 Hz, 1H, H-3),

5.17 (app q, J = 9.3 Hz, 1H, H-4), 4.91 (dd, J = 11.8, J_H,P= 7.0 Hz, 1H,

POCH₂), 4.84 (dd, J = 11.8, J_H,P= 8.5 Hz, 1H, POCH₂), 4.73 (d, J =

2.1 Hz, 1H, H-1), 4.71 (dd, J = 11.7, J_H,P= 6.8 Hz, 1H, POCH₂), 4.54

(dd, J = 11.8, J_H,P= 8.0 Hz, 1H, POCH₂), 4.38 (app dt, J = 8.7, 1.3 Hz,

1H, H-6), 4.19−4.14 (m, 2H, H-2, H-7a), 3.85 (dd, J = 12.4, 1.4 Hz,

1H, H-7b), 3.75 (dd, J = 9.5, 1.2 Hz, 1H, H-5), 3.40 (s, 3H, OCH₃),

2.10 (d d, J = 6.8 Hz, 1H, 2-OH), 1.12−0.87 (m, 28H, TIPDS); ¹³C

NMR (151 MHz, CDCl₃) δ 165.7 (PhCO), 135.6 and 135.4 (d,

J_C,P= 7.7 Hz, POCH₂PhC1), 133.2, 130.2, 129.5, 128.4, 128.35, 128.3,

128.27, 128.1, 127.7, 127.4 (PhC), 100.5 (C-1), 73.7 (C-6), 73.3 (C-

3), 72.0 (d, J_C,P= 8.8 Hz, C-5), 71.8 (d, J_C,P= 6.1 Hz, C-4), 69.1 (C-

2), 69.06 (d, J_C,P= 5.5 Hz, POCH₂), 68.95 (d, J_C,P= 5.5 Hz, POCH₂),

67.9 (C-7), 55.3 (OCH₃), 17.6, 17.4, 17.4, 17.3, 17.2 (8 × TIPDS-

CH₃), 13.55, 13.4, 12.72, 12.69 (4 × TIPDS-CH); ³¹P NMR (243

MHz, CDCl₃) δ −2.77; HRMS (⁺ESI-TOF) m/z [M + H]⁺calcd for

C₄₁H₆₀O₁₂PSi₂: m/z = 831.3355, found 831.3363.

MHz, CDCl₃) δ 7.47−7.44 (m, 2H, 2 × PhH), 7.35−7.28 (m, 13H, 13

× PhH), 5.14 (dd, J = 11.9, J_H,P= 8.2 Hz, 1H, POCH₂), 5.10 (dd, J =

11.6, J_H,P= 6.9 Hz, 1H, POCH₂), 5.08−5.03 (m, 2H, POCH₂), 5.01

(app dt, J = 9.6, J_H,P= 6.8 Hz, 1H, H-4), 4.95 (bs, 1H, H-1), 4.60 (app

t, J = 6.9 Hz, H-3), 4.35 (app d, J = 9.1 Hz, 1H, H-6), 4.12 (dd, J =

12.2, 8.8 Hz, 1H, H-7a), 3.94 (dd, J = 6.9, 1.1 Hz, 1H, H-2), 3.88 (m,

3H, OCH₂, H-7b), 3.68 (dd, J = 10.0 Hz, 1.4 Hz, 1H, H-5), 3.34 (s,

3H, OCH₃), 1.19 (t, J = 7.1 Hz, 2H, OCH₂CH₃), 1.12−1.03 (m, 26H,

TIPDS), 1.00−0.92 (m, 2H, TIPDS); ¹³C NMR (151 MHz, CDCl₃) δ

139.07, 136.11, 136.0, 128.9, 128.5, 128.4, 128.3, 128.1, 127.82,

127.79, 126.0, 121.7 (Cq, orthoester), 98.4 (C-1), 76.3 (C-3), 75.2 (C-

2), 74.8 (d, J_C,P= 6.5 Hz, C-4), 73.55 (C-6), 69.45 (d, J_C,P= 5.5 Hz,

POCH₂), 69.3 (d, J_C,P= 5.5 Hz, POCH₂), 69.0 (d, J_C,P= 9.5 Hz, C-5),

68.3 (C-7), 59.0 (OCH₂CH₃), 55.4 (OCH₃), 17.7, 17.6, 17.43, 17.36,

17.35, 17.3, 17.2 (TIPDS-CH₃), 15.0 (OCH₂CH₃), 13.23, 13.20, 12.7,

12.6 (4 × TIPDS-CH). HRMS (⁺ESI-TOF) m/z [M + Na]⁺calcd for

C₄₃H₆₃NaO₁₂PSi₂881.3488, found 881.3491.

20

Data for 3b: R_f0.66 (toluene/EtOAc 3:1); [α]_D+9 (c 0.5,

1

CHCl₃); H NMR (600 MHz, CDCl₃) δ 7.71−7.65 (m, 2H, PhH),

Methyl 2,3-di-O-benzoyl-4-O-dibenzyloxyphosphoryl-6,7-O-

(1,1,3,3-tetraisopropyl-1,3-disiloxane-1,3-diyl)-^L-glycero-α-D-

manno-heptopyranoside (6). A solution of orthoester 3a/3b (1.09 g,

1.268 mmol) in DCM (22 mL) was treated with CSA (29 mg, 0.127

mmol) and water (75 μL) as described for the preparation of 4. The

crude material (1.163 g) was dissolved in pyridine (5.3 mL) and BzCl

(0.3 mL, 2.5 mmol) was added dropwise at rt and the reaction mixture

was stirred overnight. The reaction was quenched by addition of

MeOH (0.1 mL, 2.5 mmol) and stirring was continued for 30 min.

The solution was diluted with EtOAc (50 mL), washed with cold 1 M

HCl (with re-extraction of the aqueous phase). The combined organic

layers were washed with water, satd aq NaHCO₃, brine, dried

(Na₂SO₄) and concentrated. The crude material (1.291 g) was puriﬁed

by column chromatography (SiO₂: 20 g, DCM → DCM/EtOAc 30:1)

to give compound 6 (1.051 g, 88.6% for 2 steps) as a colorless oil that

crystallized upon storage, m.p.: 97−100 °C (EtOAc); R_f0.33

7.37−7.23 (m, 13H, PhH), 5.07−4.89 (m, 4H, 1.5 × POCH₂, H-1),

4.90 (dd, J = 11.8, J_H,P= 8.5 Hz, 1H, POCH₂), 4.86 (app t, J = 6.7 Hz,

1H, H-3), 4.55 (app dt, J = 10.4, J_H,P= 6.9 Hz, 1H, H-4), 4.51 (dd, J =

6.5, 1.0 Hz, 1H, H-2), 4.27 (app d, J = 8.8 Hz, 1H, H-6), 4.06 (dd, J =

12.1, 8.8 Hz, 1H, H-7a), 3.79 (dd, J = 12.2, J = 1.5 Hz, 1H, H-7b), 3.67

(dd, J = 9.9, 1.6 Hz, 1H, H-5), 3.35 (q, J = 7.1 Hz, 2H, OCH₂CH₃),

3.36 (s, 3H, OCH₃), 1.13 (t, J = 7.1 Hz, 3H, OCH₂CH₃), 1.07−0.85

(m, 28H, TIPDS); ¹³C NMR (151 MHz, CDCl₃) δ 137.0, 136.0,

135.9, 129.0, 128.5, 128.5, 128.4, 128.31, 128.27, 128.21, 128.18,

127.9, 127.83, 127.77, 126.5 (PhC), 120.9 (Cq, orthoester), 98.0 (C-

1), 77.4 (C-3), 75.75 (C-2), 75.05 (d, J_C,P= 6.5 Hz, C-4), 73.3 (C6),

69.33 (d, J_C,P= 5.5 Hz, POCH₂), 69.28 (d, J_C,P= 5.5 Hz, POCH₂),

68.6 (d, J_C,P= 8.9 Hz, C-5), 68.0 (C-7), 59.3 (OCH₂CH₃), 55.4

(OCH₃), 17.6, 17.5, 17.4, 17.3, 17.25, 17.22, 17.21, 17.1 (8 × TIPDS-

CH₃), 15.1 (OCH₂CH₃), 13.2, 13.1, 12.7, 12.6 (4 × TIPDS-CH).

HRMS (⁺ESI-TOF) m/z [M + Na]⁺calcd for C₄₃H₆₃NaO₁₂PSi₂

881.3488, found 881.3494.

20

1

(toluene/EtOAc 9:1); [α]_D−35 (c 0.5, CHCl₃); H NMR (600

MHz) δ 8.03−8.01 (m, 2H, BzH2/H6), 7.98−7.97 (m, 2H, BzH2/

H6), 7.60−7.57 (m, 1H, BzH4), 7.45−7.40 (m, 3H, BzH3/H5,

BzH4), 7.28−7.23 (m, 6H, BzH3/H5, 4 × PhH), 7.20−7.12 (m, 4H,

PhH), 6.91−6.88 (m, 2H, PhH), 5.76 (dd, J = 9.8, 3.5 Hz, 1H, H-3),

5.58 (dd, J = 3.5, 1.7 Hz, 1H, H-2), 5.32 (app q, J = 9.4 Hz, 1H, H-4),

4.91 (dd, J = 11.8, J_H,P= 7.1 Hz, 1H, POCH₂), 4.89 (d, J = 1.4 Hz, 1H,

H-1), 4.81 (dd, J = 11.8, J_H,P= 9.0 Hz, 1H, POCH₂), 4.68 (dd, J =

11.8, J_H,P= 6.7 Hz, 1H, POCH₂), 4.50 (dd, J = 11.8, J_H,P= 7.9 Hz, 1H,

POCH₂), 4.45 (app d, J = 8.6 Hz, 1H, H-6), 4.17 (dd, J = 12.4, 8.7 Hz,

1H, H-7a), 3.87 (dd, J = 12.4, 1.1 Hz, 1H, H-7b), 3.86 (app d, J = 9.5

Methyl 2-O-Benzoyl-4-O-dibenzyloxyphosphoryl-6,7-O-(1,1,3,3-

tetraisopropyl-1,3-disiloxane-1,3-diyl)-^L-glycero-α-D-manno-hepto-

pyranoside (4). Orthoester 3a/3b (1.61 g, 1.877 mmol) was dissolved

in DCM (32 mL), and CSA (44 mg, 0.188 mmol) was added at rt

followed by dropwise addition of H₂O (∼0.1 mL). The reaction

mixture was stirred at rt for 1 h. The organic layer was washed with

satd aq NaHCO₃(30 mL), and the aqueous layer was reextracted with

DCM (30 mL). The combined organic layers were washed with satd

aq NaHCO₃(30 mL) and brine (15 mL), dried (Na₂SO₄), and

concentrated. The crude (1.593 g) was puriﬁed by column

chromatography (SiO₂: 150 g, toluene/EtOAc 10:1→ 7:1→ 5:1) to

yield pure target compound 4 (1.129 g, 72%) as a syrup and a second

fraction containing a mixture of 2-O- and 3-O-monobenzoate 4 and 5

(280 mg, 18%). Data for 4: R_f0.30 (toluene/EtOAc 3:1); [α]_D²⁰+26

Hz, 1H, H-5), 3.43 (s, 3H, OCH₃), 1.13−0.94 (m, 28 H, TIPDS); ¹³

C

NMR (151 MHz, CDCl₃) δ 165.5 (PhCO), 165.4 (PhCO),

135.6 (d, J_C,P= 7.3 Hz, POCH₂PhC1), 135.4 (d, J_C,P= 7.7 Hz,

POCH₂PhC1), 133.3, 133.0, 130.0, 129.9, 129.4, 129.35, 128.41,

128.36, 128.3, 128.25, 128.2, 128.1, 127.7, 127.3 (PhC), 98.35 (C-1),

73.5 (C-6), 71.9 (d, J_C,P= 6.5 Hz, C-5), 71.85 (d, J = 4.4 Hz, C-4),

1

(c 0.3, CHCl₃); H NMR (600 MHz, CDCl₃) δ 8.06−8.04 (m, 2H,

BzH2/H6), 7.59−7.55 (m, 1H, BzH4), 7.43−7.39 (m, 2H, BzH3/

H5), 7.38−7.33 (m, 3H, PhH), 7.23−7.32 (m, 7H, PhH), 5.40 (dd, J =

3.6, 1.7 Hz, 1H, H-2), 5.08−5.00 (m, 4H, 2 × POCH₂), 4.80 (td, J =

9.4, J_H,P= 7.8 Hz, 1H, H-4), 4.79 (d, J = 1.4 Hz, 1H, H-1), 4.76 (d, J =

4.6 Hz, 1H, 3-OH), 4.35 (dt, J = 9.9, 4.6 Hz, 1H, H-3), 4.32 (d, J = 9.3

Hz, 1H, H-6), 4.08 (dd, J = 12.4, 8.7 Hz, 1H, H-7a), 3.79 (dd, J = 12.3,

1.2 Hz, 1H, H-7b), 3.60 (dd, J = 9.5, 1.0 Hz, 1H, H-5), 3.34 (s, 3H,

OCH₃), 1.10−0.83 (m, 28H, TIPDS); ¹³C NMR (151 MHz, CDCl₃)

70.9 (C-3), 70.4 (C-2), 69.1 (d, J_C,P= 6.2 Hz, POCH₂), 68.9 (d, J_C,P

=

5.2 Hz, POCH₂), 68.1 (C-7), 55.3 (OCH₃), 17.7, 17.6, 17.39, 17.36,

17.3, 17.25, 17.21, 17.17 (8 × TIPDS-CH₃), 13.6, 13.5, 12.7, 12.7 (4 ×

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

C₄₈H₆₄O₁₃PSi₂935.3618, found 935.3625.

Methyl 2-O-benzoyl-6,7-O-(1,1,3,3-tetraisopropyl-1,3-disiloxane-

1,3-diyl)-^L-glycero-α-D-manno-heptopyranoside (7). A solution of

triol 2 (2.00 g, 4.28 mmol) in dry DCM (40 mL) and triethyl

G

dx.doi.org/10.1021/jo402312x | J. Org. Chem. XXXX, XXX, XXX−XXX

The Journal of Organic Chemistry

Article

orthobenzoate (1.17 mL, 5.16 mmol) was treated with CSA (49 mg,

0.22 mmol) at rt. TLC monitoring (hexane/EtOAc 2:1) revealed

almost complete conversion into the intermediate orthoester after 10

min. After 30 min, H₂O (160 μL, ∼8.5 mmol) was added, and stirring

was continued for 1 h at rt. The solution was diluted with DCM (60

mL) and washed with satd aq NaHCO₃(90 mL). The aqueous layer

was reextracted with DCM (70 mL), and the combined organic layers

were washed with brine (60 mL), dried (Na₂SO₄), and concentrated.

The crude material (∼2.5 g) was puriﬁed by vacuum ﬂash

chromatography (SiO₂: 50 g, toluene/EtOAc 5:1) to give 7 (2.00 g,

81.7%) as a white solid foam: [α]_D+12.8 (c 2.1, CDCl₃); H NMR

(600 MHz, CDCl₃) δ 8.06−8.03 (m, 2H, BzH2/H6), 7.60−7.56 (m,

1H, BzH4), 7.45−7.41 (m, 2H, BzH3/H5), 5.32 (dd, J = 1.7, 2.9 Hz,

1H, H-2), 4.81 (d, J = 1.6 Hz, 1H, H-1), 4.38 (ddd, J = 1.4, 2.3, 8.5 Hz,

1H, H-6), 4.13−4.06 (m, 3H, H-4, H-7a, H-3), 4.00 (dd, J = 1.4, 12.2

Hz, 1H, H-7b), 3.66 (dd, J = 2.4, 9.2 Hz, 1H, H-5), 3.37 (s, 3H,

OCH₃), 2.77 (d, J = 1.8 Hz, 1H, 4-OH), 2.29 (d, J = 5.3 Hz, 1H, 3-

OH), 1.13−0.94 (m, 28H, TIPDS); ¹³C NMR (151 MHz, CDCl₃) δ

166.2 (PhCO), 133.4, 129.9, 129.5, 128.4 (PhC), 98.8 (C-1), 74.4

(C-6), 72.1 (C-2), 71.9 (C-5), 70.8 (C-3), 68.15 (C-4), 67.8 (C-7),

55.1 (OCH₃), 17.5, 17.42, 17.39, 17.30, 17.26, 17.2 (TIPDS-CH₃),

13.0, 12.7, 12.6, 12.4 (TIPDS-CH); HRMS (⁺ESI-TOF) m/z [M +

Na]⁺calcd for C₂₇H₄₆NaO₉Si₂593.2573, found 593.2575.

repeated chromatography on silica gel (SiO₂: 2 g cartridge, toluene→

toluene/EtOAc 3:1), then by preparative HPLC (column A, toluene/

20

EtOAc 10:1 to 5:1), to give 9 (97 mg, 81%): [α]_D−4.5 (c 0.9,

1

CHCl₃); H NMR (600 MHz, CDCl₃) δ 8.07−8.04 (m, 2H, BzH2/

H6), 7.62−7.58 (m, 1H, BzH4), 7.45−7.41 (m, 2H, BzH3/H5), 7.29−

7.23 (m, 10H, PhH), 5.54 (dd, J = 3.5, 9.8 Hz, 1H, H-3), 5.46 (dd, J =

1.8, 3.6 Hz, 1H, H-2), 5.03 (app q, J = 9.4 Hz, 1H, H-4), 5.01−4.91

(m, 4H, 2 × POCH₂), 4.79 (d, J = 1.6 Hz, 1H, H-1), 4.45−4.42 (m,

1H, H-6), 4.13 (dd, J = 8.7, 12.4 Hz, 1H, H-7a), 3.84 (dd, J = 1.2, 12.3

Hz, 1H, H-7b), 3.82−3.79 (m, 1H, H-5), 3.38 (s, 3H, OCH₃), 2.56−

2.47 (m, 2H, Lev-H3a/H3b), 2.46−2.32 (m, 2H, Lev-H2a/H2b), 1.97

(s, 3H, Lev-CH₃), 1.12−0.91 (m, 28H, TIPDS); ¹³C NMR (151 MHz,

CDCl₃) δ 206.1 (Lev-C4), 171.8 (Lev-C1), 165.5 (PhCO), 135.7

(d, J_C,P= 7.1 Hz, POCH₂PhC), 135.6 (d, J_C,P= 6.6 Hz, POCH₂PhC),

133.4, 130.0, 129.3, 128.49, 128.47, 128.44, 128.38, 127.95, 127.8

(PhC), 98.4 (C-1), 73.4 (C-6), 72.0 (d, J_C,P= 7.1 Hz, C-4), 71.65 (d,

J_C,P= 8.4 Hz, C-5), 70.3 (C-3), 70.0 (C-2), 69.3 (d, J_C,P= 5.3 Hz,

POCH₂), 69.2 (d, J_C,P= 5.6 Hz, POCH₂), 68.1 (C7), 55.2 (OCH₃),

37.7 (Lev-C3), 29.55 (Lev-CH₃), 27.9 (Lev-C2), 17.6, 17.5, 17.4, 17.3,

17.2, 17.1 (8 × TIPDS-CH₃), 13.36, 13.34, 12.64, 12.62 (4 × TIPDS-

CH); ³¹P NMR (243 MHz, CDCl₃) δ −3.47; HRMS (⁺ESI-TOF) m/z

[M + H]⁺calcd for C₄₆H₆₆O₁₄PSi₂929.3723, found 929.3731.

20

1

Methyl 2,3-Di-O-benzoyl-4-O-dibenzyloxyphosphoryl-6-O-(3-ﬂu-

oro-1,1,3,3-tetraisopropyl-1,3-disiloxane-1-yl)-^L-glycero-α-D-

manno-heptopyranoside (10). Method A. Compound 6 (290 mg,

0.310 mmol) was dissolved in dry DCM (15 mL), transferred into a

Teﬂon ﬂask, and cooled in an ice bath. HF−pyridine reagent (88 μL,

∼10 equiv of F⁻) was added in four portions every 2 min to prevent

local overheating. The solution was stirred for 35 min at 0 °C. The

reaction was quenched by dropping the solution into stirred ice-cold

satd aq NaHCO₃(60 mL). The aqueous layer was extracted with

DCM (3 × 30 mL), and the combined organic layers were washed

with satd aq NaHCO₃, and brine, dried (Na₂SO₄), and concentrated.

The crude material (19.8 mg) was puriﬁed by column chromatography

(SiO₂: 17 g, toluene/EtOAc 2:3) to furnish 10 (245 mg, 83%).

Method B. A solution of compound 6 (20 mg, 21.4 μmol) in dry

DCM (1.0 mL) was treated with TREAT (174 μL, ∼150 equiv of F)

at 0 °C for 1 h according to general procedure 1. The residue (19.8

mg) was puriﬁed by column chromatography (SiO₂: 2 g cartridge,

hexane/EtOAc 3:1) to give 10 (18.3 mg, 90%) which solidiﬁed upon

storage in a refrigerator. Analytical data for 10: R_f0.20 (toluene/

Methyl 2-O-Benzoyl-3-O-(4-oxopentanoyl)-6,7-O-(1,1,3,3-tetra-

isopropyl-1,3-disiloxane-1,3-diyl)-^L-glycero-α-D-manno-heptopyra-

noside (8). A solution of DCC (304 mg, 1.472 mmol) in dry DCM

(2.4 mL) was slowly added in several portions for a period of 45 min

to a solution of diol 7 (700 mg, 1.23 mmol), levulinic acid (157 mg,

1.249 mmol), and DMAP (7.5 mg, 0.061 mmol) in dry DCM (14 mL)

at rt. The reaction mixture was then diluted with DCM (40 mL) and

ﬁltered over a plug of cotton. The organic layer was washed with satd

aq NaHCO₃(30 mL), and the aqueous layer was re-extracted with

DCM (40 mL). The combined organic phases were washed with brine

(30 mL), dried (Na₂SO₄), and concentrated. The residue was

dissolved in a small volume of DCM, ﬁltered, and concentrated.

The crude material (870 mg) was puriﬁed by MPLC-column

chromatography (SiO₂: 60 g, ﬂow-rate: 40 mL/min toluene/EtOAc

20

7:1) to aﬀord compound 8 (785 mg, 96%) as a glasslike solid: [α]_D

1

+8.4 (c 1.1, CHCl₃); H NMR (600 MHz, CDCl₃) δ 8.07−8.05 (m,

2H, BzH2/H6), 7.61−7.58 (m, 1H, BzH4), 7.47−7.42 (m, 2H, BzH3/

H5), 5.42 (dd, J = 1.8, 3.5 Hz, 1H, H-2), 5.31 (dd, J = 3.4, 9.8 Hz, 1H,

H-3), 4.78 (d, J = 1.7 Hz, 1H, H-1), 4.45−4.42 (m, 1H, H-6), 4.26 (dt,

J = 3.4, 9.7 Hz, 1H, H-4), 4.11 (dd, J = 8.6, 12.1 Hz, 1H, H-7a), 3.98

(dd, J = 1.3, 12.1 Hz, 1H, H-7b), 3.73 (dd, J = 2.2, 9.6 Hz, 1H, H-5),

3.38 (s, 3H, OCH₃), 2.83 (d, J = 3.4 Hz, 1H, 4-OH), 2.77 (ddd, J =

6.1, 7.7, 18.4 Hz, 1H, Lev-H3a), 2.66 (dt, J = 6.2, 18.4 Hz, 1H, Lev-

H3b), 2.57 (ddd, J = 5.7, 7.8, 17.0 Hz, 1H, Lev-H2a), 2.48 (dt, J = 6.4,

17.0 Hz, 1H, Lev-H2b), 2.08 (s, 3H, Lev-CH₃), 1.15−0.94 (m, 28H,

TIPDS); ¹³C NMR (151 MHz, CDCl₃) δ 207.15 (Lev-C4), 172.3

(Lev-C1), 165.4 (PhCO), 133.4, 129.8, 129.5, 128.4 (PhC), 98.7

(C-1), 73.8 (C-6), 72.8 (C-3), 72.5 (C-5), 70.0 (C-2), 68.1 (C-7), 65.5

(C-4), 55.0 (OCH₃), 38.1 (Lev-C3), 29.6 (Lev-C5), 28.1 (Lev-C2),

17.44, 17.42, 17.41, 17.36, 17.3, 17.2 (8 × TIPDS-CH₃) 13.0, 12.6,

12.35 (4 × TIPDS-CH); HRMS (⁺ESI-TOF) m/z [M + Na]⁺calcd for

C₃₂H₅₂NaO₁₁Si₂691.2940, found 691.2940.

20

EtOAc 5:1); [α]_D−51.8 (c 0.5, CHCl₃); ¹H NMR (600 MHz,

CDCl₃) δ 8.04−8.01 (m, 2H, BzH2/H6), 7.95−7.93 (m, 2H, BzH2/

H6), 7.60−7.57 (m, 1H, BzH4), 7.45−7.41 (m, 3H, BzH3/H5,

BzH4), 7.27−7.22 (m, 5H, BzH3/H5, 3 × PhH), 7.19−7.17 (m, 1H,

PhH), 7.14−7.10 (m, 4H, PhH), 6.91−6.89 (m, 2H, PhH), 5.80 (dd, J

= 3.5, 9.7 Hz, 1H, H-3), 5.59 (dd, J = 1.7, 3.5 Hz, 1H, H-2), 5.33 (app

q, J = 9.7 Hz, 1H, H-4), 4.90 (d, J = 1.9 Hz, 1H, H-1), 4.88 (dd, J =

7.1, 11.6 Hz, 1H, POCH₂), 4.78 (dd, J = 8.8, 11.8 Hz, 1H, POCH₂),

4.70 (dd, J = 6.9, 11.8 Hz, 1H, POCH₂), 4.55 (dd, J = 8.5, 11.8 Hz,

1H, POCH₂), 4.37−4.34 (m, H-6), 4.10 (dd, J = 1.9, 9.8 Hz, 1H, H-5),

3.93 (dd, J = 4.7, 11.1 Hz, 1H, H-7a), 3.86 (dd, J = 6.1, 11.1 Hz, 1H,

H-7b), 3.47 (s, 3H, OCH₃), 1.16−0.95 (m, 28H, TIPDS); ¹³C NMR

(151 MHz, CDCl₃) δ 165.6 (PhCO), 165.4 (PhCO), 135.6 (d,

J_C,P= 7.0 Hz, POCH₂PhC), 135.4 (d, J_C,P= 7.5 Hz, POCH₂PhC),

133.4, 133.0, 123.0, 129.9, 129.42, 129.38, 128.41, 128.39, 128.31,

Methyl 2-O-Benzoyl-4-O-dibenzyloxyphosphoryl-3-O-(4-oxo-

pentanoyl)-6,7-O-(1,1,3,3-tetraisopropyl-1,3-disiloxane-1,3-diyl)-^L-

glycero-α-^D-manno-heptopyranoside (9). A solution of 1H-tetrazole

in CH₃CN (∼0.45 M, dried over molecular sieves) was added

dropwise at rt to a solution of alcohol 8 (86 mg, 0.129 mmol) and

dibenzyl N,N-diisopropylphosphoramidite (60 μL, 0.18 mmol) in dry

DCM (1.7 mL). TLC (toluene/EtOAc 5:1) indicated complete

conversion to the intermediate phosphite species after 10 min. The

reaction mixture was cooled to −72 °C, and m-CPBA (71 mg, 0.315

mmol) was added in one portion. After the mixture was stirred for 40

min, Et₃N (54 μL, 0.386 mmol) was added. The solution was warmed

to rt and was separated between EtOAc and satd aq NaHCO₃. The

aqueous layer was again extracted with EtOAc, and the combined

organic layers were washed with satd aq NaHCO₃and brine, dried

(Na₂SO₄), and concentrated. The crude material was puriﬁed by

128.26, 128.24, 128.1, 127.8, 127.5 (PhC), 98.35 (C-1), 72.4 (d, J_C,P

=

6.3 Hz, C-4), 71.4 (C-6), 71.0 (C-3), 70.6 (C-2), 70.4 (d, J_C,P= 7.6

Hz, C-5), 69.2 (d, J_C,P= 5.9 Hz, POCH₂), 69.1 (d, J_C,P= 5.4 Hz,

POCH₂), 63.6 (C-7), 55.4 (OCH₃), 17.5, 17.4, 17.3, 17.2, 16.7, 16.6 (8

× FTIPDS-CH₃), 13.6, 13.1 (2 × FTIPDS-CH), 12.61 and 12.59 (2 d,

J = 16.5 Hz, FTIPDS-CH); HRMS (⁺ESI-TOF) m/z [M + H]⁺calcd

for C₄₈H₆₅FO_13PSi₂955.3680, found 955.3693.

Methyl 2-O-Benzoyl-4-O-dibenzyloxyphosphoryl-6-O-(3-ﬂuoro-

1,1,3,3-tetraisopropyl-1,3-disiloxane-1-yl)-3-O-(4-oxopentanoyl)-^L-

glycero-α-^D-manno-heptopyranoside (11). A solution of compound

9 (45 mg, 48.4 μmol) in dry DCM (1.2 mL) was treated with TREAT

(158 μL, ∼60 equiv of F) at 0 °C for 3.5 h according to general

procedure 1. The residue was puriﬁed by column chromatography

(SiO₂: 2 g cartridge, toluene/EtOAc 10:1→5:1→2:1) to give 11 as

H

dx.doi.org/10.1021/jo402312x | J. Org. Chem. XXXX, XXX, XXX−XXX

The Journal of Organic Chemistry

Article

colorless solid (37.8 mg, 82%). Alternatively, compound 11 was

prepared in a two-step sequence from 8: Alcohol 8 (350 mg, 0.522

mmol) was treated as described for 11 with phosphoramidite (245 μL,

0.731 mmol) and a solution of 1H-tetrazole in CH₃CN (∼0.45 M,

0.68 mmol, dried over molecular sieves) followed by oxidation with m-

CPBA (287 mg, 1.28 mmol). The crude material was directly

submitted to selective TIPDS cleavage as described above with

TREAT (1.7 mL, ∼60 equiv of F⁻) and puriﬁed by column

chromatography (SiO₂: 50 g, toluene/EtOAc 5:1) to aﬀord 11 (397

1.5, 3.3 Hz, 1H, H-2), 3.99−3.96 (m, 2H, H-5, H-6), 3.93 (app t, J =

9.6 Hz, 1H, H-4), 3.70 (dd, J = 3.3, 9.3 Hz, 1H, H-3), 3.48 (dd, J = 7.4,

11.0 Hz, 1H, H-7a), 3.39 (dd, J = 5.2, 11.0 Hz, 1H, H-7b); ¹³C NMR

(151 MHz, MeOD) δ 135.5, 133.0, 130.1, 128.6 (PhC), 90.3 (C-1),

74.25 (C-5), 73.6 (C-2), 73.4 (C-3), 71.0 (C-6), 68.0 (C-4), 65.0 (C-

7); HRMS (⁻ESI-TOF) m/z [M + HCOO]⁻calcd for C₁₄H₁₉O₈S

347.0806, found 347.0803.

Phenyl 2,3,4,6,7-Penta-O-benzyl-1-thio-^L-glycero-α-D-manno-

heptopyranoside (16). Thioglycoside 15 (310 mg, 1.025 mmol)

was coevaporated with toluene and dissolved in dry DMF (20 mL).

The solution was cooled to 0 °C, and NaH (60%, 226 mg, 5.65 mmol,

5.5 equiv) was added in portions. The resulting slurry was stirred for

∼0.5 h, and benzyl bromide (0.74 mL, 6.15 mmol, 6.0 equiv) was

added dropwise. The reaction mixture was warmed to rt and was

stirred for 18 h. Since mainly two polar spots were visible on TLC

(toluene/EtOAc 20:1, EtOAc/MeOH = 4:1), additional NaH (75 mg,

1.87 mmol, ∼1.8 equiv) was added at 0 °C. The ice bath was removed,

and stirring was continued for 20 min. BnBr (0.06 mL, 0.25 mmol,

0.24 equiv) was added, and the mixture was stirred for an additional 45

min without signiﬁcant additional formation of product. MeOH (0.84

mL, ∼20 equiv) was added leading to formation of H₂(caution!).

After 30 min, the reaction mixture was separated between Et₂O (50

mL) and satd aq NaHCO₃(100 mL). The aqueous layer was extracted

with Et₂O (50 mL), and the combined organic layers were washed

with satd aq NaHCO₃(50 mL), water (50 mL), and brine (50 mL).

The organic layer was dried (Na₂SO₄), ﬁltered, and concentrated, and

the residue was coevaporated with toluene. The crude material was

submitted to vacuum ﬂash chromatography (SiO₂: 30 g toluene →

toluene/EtOAc 120:1→80:1) to give 16 (625.5 mg, 81%) as a

20

mg, 80% for two steps) as a colorless foam: [α]_D−20 (c 1.1,

1

CHCl₃); H NMR (600 MHz, CDCl₃) δ 8.07−8.04 (m, 2H, BzH2/

H6), 7.61−7.58 (m, 1H, BzH4), 7.45- 7.42 (m, 2H, BzH3/H5), 7.30−

7.20 (m, 10H, PhH), 5.55 (dd, J = 3.5, 9.8 Hz, 1H, H-3), 5.46 (dd, J =

1.7, 3.6 Hz, 1H, H-2), 5.08 (app q, J = 9.8 Hz, 1H, H-4), 5.01−4.94

(m, 3H, POCH₂), 4.92 (dd, J = 6.8, 11.7 Hz, 1H, POCH₂), 4.81 (d, J =

1.6 Hz, 1H, H-1), 4.34−4.32 (m, 1H, H-6), 4.04 (dd, J = 2.0, 9.8 Hz,

1H, H-5), 3.90 (dd, J = 4.8, 11.1 Hz, 1H, H-7a), 3.83 (dd, J = 6.2, 11.1

Hz, 1H, H-7b), 3.42 (s, 3H, OCH₃), 2.49 (t, J = 7.1 Hz, 2H, Lev-H3a,

H3b), 2.41−2.28 (m, 2H, Lev-H2a, H2b), 1.97 (s, 3H, Lev-CH₃),

1.07−0.94 (m, 28H, FTIPDS); ¹³C NMR (151 MHz, CDCl₃) δ 206.1

(Lev-C4), 171.8 (Lev-C1), 165.5 (PhCO), 135.7 (d, J_C,P= 7.5 Hz, 2

× POCH₂PhC1), 133.4, 129.9, 129.35, 128.50, 128.47, 128.46, 128.42,

128.39, 128.0, 127.8 (PhC), 98.4 (C-1), 72.4 (d, J_C,P= 6.7 Hz, C-4),

71.2 (C-6), 70.5 (C-3), 70.3 (d, J_C,P= 7.8 Hz, C-5), 70.25 (C-2), 69.44

(d, J_C,P= 5.5 Hz, POCH₂), 69.36 (d, J_C,P= 5.5 Hz, POCH₂), 63.6 (C-

7), 55.3 (OCH₃), 37.65 (Lev-C3), 29.6 (Lev-CH₃), 27.9 (Lev-C2),

17.5, 17.4, 17.3, 17.2 (4 × FTIPDS-CH₃) 16.7 (2 × FTIPDS-CH₃),

16.6 (2 × FTIPDS-CH₃), 13.6, 13.1 (2 × FTIPDS-CH), 12.57 and

12.56 (2 d, J = 16.4 Hz, FTIPDS-CH); HRMS (⁺ESI-TOF) m/z [M +

H]⁺calcd for C₄₆H₆₇FO₁₄PSi₂949.3786, found 949.3792.

20

colorless oil: [α]_D+73.6 (c 0.8, CHCl₃); ¹H NMR (600 MHz,

CDCl₃) δ 7.39−7.36 (m, 4H, PhH), 7.34−7.19 (m, 26H, PhH), 5.75

(d, J = 1.7 Hz, 1H, H-1), 4.88 and 4.34 (2 d, J = 11.0 Hz, 2H, CH₂Ph),

4.84 and 4.52 (2 d, J = 11.8 Hz, 2H, CH₂Ph), 4.76 and 4.63 (2 d, J =

12.2 Hz, 2H, CH₂Ph), 4.57 (bs, 2H, CH₂Ph), 4.38 and 4.35 (2 d, J =

11.9 Hz, 2H, CH₂Ph), 4.25 (app t, J = 9.5 Hz, 1H, H-4), 4.15−4.11

(m, 2H, H-5, H-6), 3.98 (dd, J = 2.0, 2.9 Hz, 1H, H-2), 3.88 (dd, J =

3.0, 9.1 Hz, 1H, H-3), 3.69 (dd, J = 6.7, 10.0 Hz, 1H, H-7a), 3.46 (dd, J

= 5.1, 10.0 Hz, 1H, H-7b); ¹³C NMR (151 MHz, CDCl₃) δ 138.7,

138.7, 138.2, 138.1, 137.95 (PhC), 134.4 (SPhC-1), 130.7, 128.9,

128.4, 128.33, 128.29, 128.2, 127.9, 127.73, 127.71, 127.68, 127.6,

127.50, 127.47, 127.35, and 127.0 (PhC), 85.2 (C-1), 80.6 (C-3), 76.0

(C-2), 75.3 (C-6), 74.7 (CH₂Ph), 74.35 (C-4), 73.3 (CH₂Ph), 73.1

(C-5), 72.8 (CH₂Ph), 72.1 (CH₂Ph), 72.0 (CH₂Ph), 71.0 (C-7);

HRMS (⁺ESI-TOF) m/z [M + NH₄]⁺calcd for C₄₈H₅₂NO₆S

770.3510, found 770.3544.

Phenyl 2,3,4,6,7-Penta-O-acetyl-1-thio-^L-glycero-α-D-manno-

heptopyranoside (14). Peracetate 12³¹(1.00 g, 2.16 mmol) was

dissolved in dry DCM (10 mL), and the solution was stripped with

argon for several minutes. Thiophenol (0.44 mL, 4.3 mmol) and then

BF₃·OEt₂(1.33 mL, 10.8 mmol) were added dropwise, each within

∼15 min, and the solution was stirred at rt for 23 h. The reaction

mixture was poured into 1:1 DCM/satd aq NaHCO₃(100 mL). The

phases were separated, and the aqueous layer was extracted with DCM

(3×). The combined organic layer was washed twice with satd aq

NaHCO₃, 0.5% aq I₂-solution, 5% aq Na₂S₂O₃, and brine. The organic

phase was dried (Na₂SO₄) and concentrated. The crude material was

puriﬁed by vacuum ﬂash chromatography (SiO₂: 22 g, hexane/EtOAc

2:1) to give 14 as an anomeric mixture (980 mg, 88.4%, α/β ∼ 93:7)

that was used for the further steps. To obtain pure α-anomer, the

material was crystallized from hot dry EtOH (10 mL) to give 14 as

colorless crystals (657 mg, 59%), mp 109−111 °C (EtOH). The

anomers can alternatively be separated by chromatography using

Et₂O/hexane 3:2 as eluent. Analytical data for α-anomer 14: R_f0.21

(hexane/Et₂O 2:3); [α]_D²⁰+93.9 (c 1.9, CHCl₃); ¹H NMR (600 MHz,

CDCl₃) δ 7.43−7.40 (m, 2H, PhH), 7.34−7.26 (m, 3H, PhH), 5.62 (d,

J = 1.6 Hz, 1H, H-1), 5.52 (dd, J = 1.5, 3.4 Hz, 1H, H-2), 5.37 (app t, J

= 10.1, 1H, H-4), 5.31 (dd, J = 3.4, 10.1 Hz, 1H, H-3), 5.29 (ddd, J =

2.0, 5.6, 7.5 Hz, 1H, H-6), 4.55 (dd, J = 2.1, 10.0 Hz, 1H, H-5), 4.03

(dd, J = 5.8, 11.4 Hz, 1H, H-7a), 3.99 (dd, J = 7.5, 11.4 Hz, 1H, H-7b),

2.18, 2.12, 2.04, 2.01, and 1.90 (5s, 5 × 3H, CH₃CO); ¹³C NMR

(151 MHz, CDCl₃) δ 170.3, 170.2, 169.9, 169.8, 169.55 (5 × CO),

132.5, 130.9, 129.4, 127.9 (PhC), 85.6 (C-1), 70.9 (C-2), 69.7 (C-5),

69.6 (C-3), 67.0 (C-6), 64.8 (C-4), 61.8 (C-7), 20.9, 20.64, 20.59,

20.58, 20.5 (5 × CH₃CO); HRMS (⁺ESI-TOF) m/z [M + NH₄]⁺

calcd for C₂₃H₃₂NO₁₁S 530.1691, found 530.1680.

2,3,4,6,7-Penta-O-benzyl-^L-glycero-D-manno-heptopyranose

(17). Thioglycoside 16 (833 mg, 1.106 mmol) was dissolved in 24:1

acetone/water (28 mL) and stirred with external cooling using an

EtOH−ice bath. A solution of NBS (591 mg, 3.32 mmol) in 24:1

acetone/water (6 mL) was added dropwise within ∼5 min keeping the

temperature below −5 °C. After 15 min, the reaction was quenched by

pouring the reaction mixture into an ice-cold stirred mixture of satd aq

NaHCO₃(25 mL), 5% aq Na₂S₂O₃(25 mL), and EtOAc (50 mL).

The aqueous layer was extracted with EtOAc (20 mL) and the

combined organic layers were washed with satd aq NaHCO₃(30 mL),

water (30 mL), brine (30 mL), dried (Na₂SO₄) and concentrated. The

crude material (785 mg) was submitted to preparative MPLC (SiO₂:

60 g; ﬂow rate: 35 mL/min; hexane/EtOAc 3:1) to give 17 (621 mg,

1

85%) as a colorless oil: 0.32 (hexane/EtOAc 2:1); H NMR (600

MHz, CDCl₃, α/β ratio appr. 2:1, * denotes signals assigned to the β-

anomer) δ 7.38−7.17 (m, 25H, PhH), 5.25 (d, J = 1.9 Hz, 1H, H-1),

5.12 (d, J = 11.6 Hz, 1H, PhCH₂*), 4.88 (d, J = 11.4 Hz, 1H, PhCH₂),

4.86 (d, J = 8.2 Hz, 1H, PhCH₂*), 4.84 (d, J = 9.0 Hz, 1H, PhCH₂*),

4.81 (d, J = 11.6 Hz, 1H, PhCH₂), 4.73 (d, J = 11.6 Hz, 1H, PhCH₂*),

4.72 (bs, 2H, PhCH₂), 4.70 (d, J = 11.7 Hz, 1H, PhCH₂*), 4.66 (d, J =

11.6 Hz, 1H, PhCH₂*), 4.59−4.58 (m, 3H, H-1*, 2 × PhCH₂), 4.57

(d, J = 11.9 Hz, 1H, PhCH₂), 4.54 (d, J = 11.9 Hz, 1H, PhCH₂*), 4.54

(d, J = 12.1 Hz, 1H, PhCH₂*), 4.53 (d, J = 11.4 Hz, 1H, PhCH₂), 4.51

(d, J = 11.5 Hz, 1H, PhCH₂), 4.46 (d, J = 11.9 Hz, 1H, PhCH₂), 4.37−

4.34 (m, 2H, PhCH₂, PhCH₂*), 4.19 (t, J = 9.5 Hz, 1H, H-4), 4.16 (t,

Phenyl 1-Thio-^L-glycero-α-D-manno-heptopyranoside (15). Per-

acetate 14 (48 mg, 1.26 mmol) was dissolved in dry MeOH (15 mL),

1 M NaOMe (0.38 mL, ∼0.25 equiv) was added, and the reaction

mixture was stirred at rt for 4 h. The pH was adjusted ∼7.0 by addition

of DOWEX 50 cation-exchange resin (H⁺-form). The resin was

removed by ﬁltration and washed with MeOH, and the ﬁltrate was

concentrated to give 15 (373 mg, 98%) as a colorless syrup: R_f0.24

20

1

(EtOAc/MeOH 4:1); [α]_D+251.8 (c 1.2, MeOH); H NMR (600

MHz, MeOD) δ 7.52−7.48 (m, 2H, PhH), 7.35−7.31 (m, 2H, PhH),

7.30−7.26 (m, 1H, PhH), 5.48 (d, J = 1.6 Hz, 1H, H-1), 4.07 (dd, J =

I

dx.doi.org/10.1021/jo402312x | J. Org. Chem. XXXX, XXX, XXX−XXX

The Journal of Organic Chemistry

Article

J = 9.5 Hz, 1H, H-4*), 4.12−4.08 (m, 2H, H-6, H-6*), 3.96 (dd, J =

3.0, 9.2 Hz, 1H, H-3), 3.92 (dd, J = 1.7, 9.7 Hz, 1H, H-5), 3.86−3.83

(m, 2H, H-2*, H-7*a), 3.80−3.75 (m, 3H, H-2, H-7a, H-7*b), 3.72

(dd, J = 6.2, 9.8 Hz, 1H, H-7b), 3.63 (dd, J = 2.7, 9.4 Hz, 1H, H-3*),

3.42 (dd, J = 1.9, 9.6 Hz, 1H, H-5*); ¹³C NMR (151 MHz, CDCl₃) δ

138.9, 138.8, 138.7, 138.6, 138.45, 138.4, 138.33, 138.30, 138.2, 137.9,

128.5, 128.5, 128.4, 128.36, 128.34, 128.28, 128.25, 128.2, 128.05,

127.9, 127.86, 127.85, 127.80, 127.77, 127.74, 127.72, 127.69, 127.6,

127.54, 127.50, 127.46, 127.38 (PhC), 94.0 (C-1*), 92.8 (C-1), 83.9

(C-3*), 80.1 (C-3), 76.3 (C-2*), 75.3 (C-5*), 75.0 (C-6, C-6*), 74.71

(CH₂Ph*), 74.68 (C-2), 74.6 (CH₂Ph*), 74.5 (CH₂Ph), 74.4 (C-4),

74.0 (C-4*), 73.4 (CH₂Ph*), 73.25 (CH₂Ph), 72.75 (CH₂Ph*) 72.7

(CH₂Ph), 72.55 (CH₂Ph), 72.4 (CH₂Ph*), 72.1 (CH₂Ph), 71.7 (C-5),

70.5 (C-7*), 70.0 (C-7); HRMS (⁺ESI-TOF) m/z [M + NH₄]⁺calcd

for C₄₂H₄₈O₇N 678.3435, found 678.3431.

2,3,4,6,7-Penta-O-benzyl-^L-glycero-D-manno-heptopyranosyl N-

Phenyltriﬂuoroacetimidate (18). Reducing sugar 17 (100 mg, 0.151

mmol) was dissolved in acetone (2.0 mL). K₂CO₃(42 mg, 0.303

mmol) and N-phenyltriﬂuoroacetimidoyl chloride (63 mg, 0.30 mmol)

were added rapidly, and the reaction mixture was stirred at rt for 4.5 h.

The suspension was ﬁltered through a plug of Celite and washed

thoroughly with acetone. After addition of one drop of triethylamine,

the solution was concentrated and the crude material was puriﬁed by

column chromatography (SiO₂: 15 g, toluene/EtOAc 20:1 + 0.2%

Et₃N) to give 18 (119 mg, 94.5%) as a colorless oil: ¹H NMR of main

isomer (600 MHz, CDCl₃) δ 7.37−7.18 (m, 28H, PhH), 6.73 −6.68

(m, 2H, PhH), 6.30 (bs, 1H, H-1), 4.87−4.83 (m, 2H, CH₂Ph), 4.76−

4.60 (bs, 1H, CH₂Ph), 4.63 (d, J = 11.7 Hz, 1H, CH₂Ph), 4.58−4.49

(m, 4H, 2 × CH₂Ph), 4.38−4.34 (m, 1H, CH₂Ph), 4.29−4.23 (m,

1H), 4.14−4.10 (m, 1H, H-6), 3.94−3.88 (m, 2H), 3.85 (dd, J = 6.8,

10.0 Hz, 1H, H-7a), 3.83−3.78 (bs, 1H), 3.70 (dd, J = 5.2, 10.0 Hz,

1H, H-7b); ¹³C NMR (151 MHz, CDCl₃) δ 143.5, 142.8, 142.55,

138.6, 138.4, 138.2, 138.0, 137.7, 128.8, 128.43, 128.37, 128.36,

128.32, 128.27, 128.05, 128.0, 127.82, 127.77, 127.72, 127.69, 127.6,

127.4, 119.4 (PhC), 79.3, 75.0 (C-6), 74.75 (CH₂Ph), 74.5, 73.7, 73.5

(CH₂Ph), 73.2, 72.7, 72.53, 72.48 (3 × CH₂Ph), 70.66 (C-7).

CH₂Ph), 4.21 (app t, J = 9.5 Hz, 1H, H-4′), 4.10 (ddd, J = 1.3, 5.4, 6.6

Hz, 1H, H-6′), 3.94−3.84 (m, 4H, H-7a, H-5, H-7a′, H-3′), 3.82 (dd, J

= 2.0, 3.0 Hz, 1H, H-2′), 3.79 (dd, J = 5.4, 10.0 Hz, 1H, H-7b′), 3.74

(dd, J = 1.5, 9.7 Hz, 1H, H-5′), 3.71 (dd, J = 6.0, 10.0 Hz, 1H, H-7b),

3.26 (s, 3H, OCH₃), 1.16−0.96 (m, 28H, TIPDS); ¹³C NMR (151

MHz, CDCl₃) δ 165.6 (CO), 165.4 (CO), 138.9, 138.8, 138.4,

138.21, 138.17, 135.6 (d, J_C,P= 7.9 Hz, POCH₂PhC1), 135.4 (d, J_C,P

=

7.6 Hz, POCH₂PhC1), 133.3, 133.0, 130.0, 129.9, 129.45, 129.4,

128.45, 128.4, 128.36, 128.25, 128.22, 128.18, 128.1, 127.77, 127.76,

127.73, 127.68, 127.64, 127.59, 127.5, 127.42, 127.41, 127.34, 127.31,

127.27 (PhC), 98.4 (C-1), 98.25 (C-1′), 80.1 (C-3′), 75.1 (C-6′),

74.55 (CH₂Ph), 74.3 (C-2′), 74.15 (C-4′), 73.35 (CH₂Ph), 72.8

(CH₂Ph), 72.5 (CH₂Ph), 72.15 (C-5′), 71.7 (C-4), 71.7 (CH₂Ph),

71.1 (C-3), 71.0 (C-7′), 70.7 (C-2), 70.0 (d, J_C,P= 8.7 Hz, C-5), 69.2

(d, J_C,P= 5.5 Hz, POCH₂), 69.0 (C-6), 68.85 (d, J_C,P= 5.4 Hz,

POCH₂), 66.9 (C-7), 55.6 (OCH₃), 17.64, 17.58, 17.5, 17.4 (4 ×

FTIPDS-CH₃), 16.8, 16.7 (bs, 2 × FTIPDS-CH₃), 13.8, 13.4 (2 ×

FTIPDS-CH), 12.6 (d, J_C,F= 16.5 Hz, 2 × FTIPDS-CH); ³¹P NMR

(243 MHz, CDCl₃) δ −2.76. HRMS (⁺ESI-TOF) m/z [M + NH₄]⁺

calcd for C₉₀H₁₁₀FO₁₉NPSi₂1614.692, found 1614.6907. Analytical

20

data for 20b: R_f0.4 (hexane/EtOAc 3:1); [α]_D−37.8 (c 1.0,

1

CHCl₃); H NMR (600 MHz, CDCl₃) δ 8.03−8.00 (m, 4H, 2 ×

BzH2/H6), 7.59−7.55 (m, 1H, Bz H4), 7.46−7.39 (m, 5H, Bz H4,

BzH3/H5, 2 × PhH), 7.37−7.35 (m, 2H, PhH), 7.33−7.15 (m, 26H,

BzH3/H5, PhH), 7.15 −7.11 (m, 3H, PhH), 7.10−7.06 (m, 2H, PhH),

6.82−6.79 (m, 2H, PhH), 5.82 (dd, J = 3.5, 9.8 Hz, 1H, H-3), 5.56

(dd, J = 1.6, 3.6 Hz, 1H, H-2), 5.39 (app q, J = 9.8 Hz, 1H, H-4),

4.96−4.83 (m, 5H, 4 × CH₂Ph, POCH₂), 4.85 (bs, 1H, H-1), 4.78

(dd, J_H,P= 8.6, J = 11.9 Hz, 1H, POCH₂), 4.66−4.58 (m, 3H, POCH₂,

CH₂Ph, H-6), 4.56−4.45 (m, 5H, 4 × CH₂Ph, POCH₂Ph), 4.39 (d, J =

11.0 Hz, 1H, CH₂Ph), 4.29 (bs, 1H, H-1′), 4.26 (t, J = 9.5, 1H, H-4′),

4.20−4.16 (m, 2H, H-7a, H-6′), 4.11 (br d, 1H, H-5), 4.01 (dd, J =

7.3, 10.5 Hz, 1H, H-7a′), 3.83 (dd, J = 4.0, 10.5 Hz, 1H, H-7b′), 3.79

(d, J = 2.8 Hz, 1H, H-2′), 3.74 (dd, J = 8.4, 10.2 Hz, 1H, H-7b), 3.48

(dd, J = 2.7, 9.6 Hz, 1H, H-3′), 3.39 (dd, J = 2.0, 9.6 Hz, 1H, H-5′),

3.16 (s, 3H, OCH₃), 1.07−0.95 (m, 28H, FTIPDS); ¹³C NMR (151

MHz, CDCl₃) δ 165.8 (CO), 165.5 (CO), 138.9, 138.8, 138.5,

Methyl (2,3,4,6,7-Penta-O-benzyl-^L-glycero-α-D-manno-hepto-

pyranosyl)-(1→7)-2,3-di-O-benzoyl-4-O-dibenzyloxyphosphoryl-6-

O-(3-ﬂuoro-1,1,3,3-tetraisopropyl-1,3-disiloxane-1-yl)-^L-glycero-α-D-

manno-heptopyranoside (20a) and Methyl (2,3,4,6,7-Penta-O-

benzyl-^L-glycero-β-D-manno-heptopyranosyl)-(1→7)-2,3-di-O-ben-

zoyl-4-O-dibenzyloxyphosphoryl-6-O-(3-ﬂuoro-1,1,3,3-tetraisoprop-

yl-1,3-disiloxane-1-yl)-^L-glycero-α-D-manno-heptopyranoside

(20b). Dry DCM (5 mL) and ground molecular sieves (4 Å, 300 mg)

were placed in a ﬂame-dried, two-necked 10 mL ﬂask. Acceptor 10

(207 mg, 0.217 mmol) and donor 18 (216 mg, 260 mmol, 1.2 equiv)

were combined and coevaporated with dry toluene, transferred into

the suspension, stirred under Ar for 30 min at rt, and then cooled to

−78 °C. A solution of TMSOTf (2 μL, 0.011 mmol, 0.05 equiv) in dry

DCM (in 200 μL) was added, and the reaction mixture was stirred for

1.5 h at −78 °C. The reaction was quenched by dropwise addition of

Et₃N (57 μL, 0.412 mmol) in DCM (∼1 mL). The suspension was

allowed to warm to rt, ﬁltered through Celite, and washed with DCM.

The organic phase was dried and concentrated. The residue was ﬁrst

subjected to chromatography on an MPLC column (SiO₂: 21 g, ﬂow

rate 20 mL/min with a stepwise gradient hexane/EtOAc 5:1 → 3:1) to

furnish a fraction containing the disaccharides. Final puriﬁcation was

achieved by preparative HPLC (in three portions on column A, ﬂow

rate 15 mL/min, hexane/EtOAc 7:1) to give ﬁrst α-anomer 20a (238

mg, 69%), followed by β-anomer 20b (46.6 mg, 13.5%) as a colorless

138.45, 138.0, 135.4 (d, J_C,P= 7.7 Hz, POCH₂PhC1), 135.38 (d, J_C,P

=

7.1 Hz, POCH₂PhC1), 133.3, 133.0, 130.1, 129.9, 129.41, 129.38,

128.5, 128.4, 128.33, 128.28, 128.25, 128.19, 128.15, 128.0, 127.85,

127.75, 127.7, 127.6, 127.53, 127.50, 127.4, 127.24, 127.23 (PhC),

102.3 (C-1′), 98.4 (C-1), 82.8 (C-3′), 76.6 (C-5′), 75.45 (C-6′), 74.7

(CH₂Ph), 74.2 (C-4′), 73.6 (CH₂Ph), 73.5 (C-2′), 73.3 (CH₂Ph), 72.2

(CH₂Ph), 72.0 (C-7′), 71.9 (CH₂Ph), 71.5 (d, J_C,P= 5.5 Hz, C-4), 71.2

(C-3), 70.8 (C-2), 69.3 (d, J_C,P= 5.5 Hz, POCH₂), 69.1 (d, J_C,P= 7.7

Hz, C-5), 68.8 (d, J_C,P= 5.5 Hz, POCH₂), 68.7 (C-6), 68.15 (C-7),

55.0 (OCH₃), 17.67, 17.66, 17.44, 17.37, 16.75, 16.70, 16.67 (8 ×

FTIPDS-CH₃), 13.7, 13.4 (2 × FTIPDS-CH), 12.6 (d, J_C,F= 16.5 Hz,

FTIPDS-CH), 12.5 (J_C,F= 16.5 Hz, FTIPDS-CH); ³¹P NMR (243

MHz, CDCl₃) δ −2.42. HRMS (⁺ESI-TOF) m/z [M + NH₄]⁺calcd

for C₉₀H₁₁₀FO₁₉NPSi₂1614.6927, found 1614.6921.

Methyl (2,3,4,6,7-Penta-O-benzyl-^L-glycero-α-D-manno-hepto-

pyranosyl)-(1→7)-2-O-benzoyl-4-O-dibenzyloxyphosphoryl-6-O-(3-

ﬂuoro-1,1,3,3-tetraisopropyl-1,3-disiloxane-1-yl)-3-O-(4-oxopenta-

noyl)-^L-glycero-α-D-manno-heptopyranoside (21a) and Methyl

(2,3,4,6,7-Penta-O-benzyl-^L-glycero-β-D-manno-heptopyranosyl)-

(1→7)-2-O-benzoyl-4-O-dibenzyloxyphosphoryl-6-O-(3-ﬂuoro-

1,1,3,3-tetraisopropyl-1,3-disiloxane-1-yl)-3-O-(4-oxopentanoyl)-^L-

glycero-α-^D-manno-heptopyranoside (21b). Acceptor 11 (25.0 mg,

26 μmol) and donor 18 (32.9 mg, 40 μmol, 1.5 equiv) were combined

and coevaporated with dry toluene. The residue was dissolved in dry

DCM (1.2 mL) and transferred into a ﬂame-dried ﬂask containing

ground molecular sieves 4 Å (30 mg). The suspension was stirred

under Ar for 30 min at rt and then cooled to −39 °C. A solution of

TMSOTf (0.37 μL, 2 μmol) in dry DCM (0.15 mL) was added

dropwise, and the suspension was stirred for 60 min. The reaction was

quenched by dropwise addition of Et₃N (6.9 μL, 50 μmol) in DCM

(0.5 mL) and was warmed to rt. The suspension was ﬁltered over a

plug of cotton and washed with DCM, and the ﬁltrate was

concentrated. The crude material (59.6 mg) was ﬁrst puriﬁed on

20

oils. Analytical data for 20a: R_f0.4 (hexane/EtOAc); [α]_D−15.6 (c

0.9, CHCl₃); ¹H NMR (600 MHz, CDCl₃) δ 8.04−8.01 (m, 2H,

BzH2/H6), 7.99−7.96 (m, 2H, BzH2/H6), 7.60−7.56 (m, 1H,

BzH4), 7.46−7.40 (m, 3H, BzH4, BzH3/H5), 7.38−7.36 (m, 2H,

PhH), 7.35−7.32 (m, 2H, PhH), 7.31−7.14 (m, 27H, BzH3/H5, 25 ×

PhH), 7.11−7.07 (m, 4H, PhH), 6.87−6.84 (m, 2H, PhH), 5.79 (dd, J

= 3.6, 9.8 Hz, 1H, H-3), 5.53 (dd, J = 1.8, 3.7 Hz, 1H, H-2), 5.30 (app

q, J = 9.7 Hz, 1H, H-4), 5.02 (d, J = 1.8 Hz, 1H, H-1′), 4.90 and 4.33

(2 d, 2 × J = 11.2 Hz, 2H, CH₂Ph), 4.88−4.84 (m, 2H, POCH₂,

CH₂Ph), 4.78−4.64 (m, 4H, 2 × POCH₂, 2 × CH₂Ph), 4.68 (bs, 1H,

H-1), 4.58−4.45 (m, 7H, 5 × CH₂Ph, POCH₂, H-6), 4.32 (d, 1H,

J

dx.doi.org/10.1021/jo402312x | J. Org. Chem. XXXX, XXX, XXX−XXX

The Journal of Organic Chemistry

Article

silica gel (SiO₂: 2 g cartridge, hexane/EtOAc 3:1→ 1:2) to give a

disaccharide fraction (41.2 mg) that was further puriﬁed by preparative

HPLC (column A, ﬂow rate 10 mL/min, hexane/acetone 5:1) to

provide pure α-anomer 21a (24.2 mg, 58%) followed by elution of the

β-anomer 21b (5.9 mg, 14%) both as a colorless oils. Analytical data

Methyl (2,3,4,6,7-Penta-O-benzyl-^L-glycero-α-D-manno-hepto-

pyranosyl)-(1→7)-2-O-benzoyl-4-O-dibenzyloxyphosphoryl-6-O-(3-

ﬂuoro-1,1,3,3-tetraisopropyl-1,3-disiloxane-1-yl)-^L-glycero-α-D-

manno-heptopyranoside (22). Disaccharide 21a (34 mg, 0.021

mmol) was dissolved in 6:4 pyridine/AcOH (1.2 mL). A solution of

N₂H₄·H₂O (3.2 μL, 0.043 mmol, 2 equiv) in 6:4 pyridine/AcOH (50

μL) was added, and the solution was stirred at rt for 40 min. The

reaction was quenched by addition of acetone (40 μL) and diluted

with EtOAc (20 mL). The organic layer washed with satd aq NaHCO₃

(5 mL) and brine, dried (NaSO₄), concentrated, and coevaporated

with toluene. The crude material (31.2 mg) was puriﬁed by column

chromatography (SiO₂: 2 g cartridge, stepwise gradient hexane/EtOAc

4:1 → 2:1) to give 22 (26.7 mg, 84%) as a glasslike solid: R_f0.65

(hexane/EtOAc 1:1); [α]_D+18.5 (c 1.3, CHCl₃); H NMR (600

MHz, CDCl₃) δ 8.07−8.04 (m, 2H, BzH2/H6), 7.58−7.55 (m, 1H,

BzH4), 7.42−7.39 (m, 1H, BzH3/H5), 7.37−7.35 (m, 2H, PhH),

7.33−7.31 (m, 2H, PhH), 7.29−7.14 (m, 33H, PhH), 5.37 (dd, J = 1.7,

3.6 Hz, 1H, H-2), 5.05−4.98 (m, 4H, 2 × POCH₂), 4.86 and 4.30 (2

d, J = 11.1 Hz, 2H, CH₂Ph), 4.83 and 4.52 (2 d, J = 11.8 Hz, 2H,

CH₂Ph), 4.81 (ddd, J = 6.1, 9.5, 9.5 Hz, 1H, H-4), 4.72 and 4.67 (2 d, J

= 12.2 Hz, 2H, CH₂Ph), 4.70 (d, J = 5.0 Hz, 1H, 3-OH), 4.58 (d, J =

1.3 Hz, 1H, H-1), 4.54 and 4.47 (2 d, J = 11.6 Hz, 2H, CH₂Ph), 4.48

and 4.42 (2 d, J = 11.8 Hz, 2H, CH₂Ph), 4.35−4.29 (m, 2H, H-3, H-

6), 4.19 (app t, J = 9.5 Hz, 1H, H-4′), 4.08 (ddd, J = 1.2, 5.5, 6.7 Hz,

1H, H-6′), 3.88−3.82 (m, 3H, H-7a, H-3′, H-7a′), 3.81−3.80 (m, 1H,

H-2′), 3.75 (dd, J = 5.7, 9.9 Hz, 1H, H-7b′), 3.72 (dd, J = 1.4, 9.8 Hz,

1H, H-5′), 3.70 (bd, J = 10.0 Hz, 1H, H-5), 3.61 (dd, J = 6.2, 9.9 Hz,

1H, H-7b), 3.21 (s, 3H, OCH₃), 1.11−0.82 (m, 28H, FTIPDS); ¹³C

NMR (151 MHz, CDCl₃) δ 165.9 (CO), 138.9, 138.7, 138.4, 138.2,

138.1,135.5 (d, J_C,P= 6.9 Hz, POCH₂PhC1),135.3 (d, J_C,P= 6.6 Hz,

POCH₂PhC1), 133.15, 130.0, 129.8, 128.65, 128.57, 128.56, 128.34,

128.30, 128.26, 128.22, 128.2, 127.74, 127.73, 127.68, 127.60, 127.57,

127.5, 127.4, 127.35 (PhC), 98.5 (C-1), 98.3 (C-1′), 80.3 (C-3′),

76.55 (d, J_C,P= 6.6 Hz, C-4), 75.0 (C-6′), 74.5 (CH₂Ph), 74.15 (C-2′),

74.1 (C-4′), 73.3 (CH₂Ph), 72.75 (CH₂Ph), 72.4 (CH₂Ph), 72.3 (C-

2), 72.0 (C-5′), 71.7 (CH₂Ph), 70.7 (C-7′), 70.2 (d, J_C,P= 5.3 Hz,

POCH₂Ph), 69.7 (d, J_C,P= 5.4 Hz, POCH₂Ph), 69.45 (d, J_C,P= 11.0

Hz, C-5), 68.9, 68.9 (C-3, C-6), 67.4 (C-7), 55.6 (OCH₃), 17.6, 17.5,

17.3, 16.74, 16.69 (FTIPDS-CH₃), 13.6, 13.2 (2 × FTIPDS-CH),

12.55 and 12.53 (2 d, J_F,C= 16.5 Hz, FTIPDS-CH); ³¹P NMR (243

MHz, CDCl₃) δ 0.64. HRMS (⁺ESI-TOF) m/z [M + Na]⁺calcd for

C₈₃H₁₀₂FNaO₁₈PSi₂1515.6219, found 1515.6245.

Methyl (2,3,4,6-Tetra-O-benzyl-α-^D-glucopyranosyl)-(1→3)-2-O-

benzoyl-4-O-dibenzyloxyphosphoryl-6,7-O-(1,1,3,3-tetraisopropyl-

1,3-disiloxane-1,3-diyl)-^L-glycero-α-D-manno-heptopyranoside (23).

A suspension of acceptor 4 (100 mg, 0.120 mmol), donor 19 (130 mg,

0.180 mg, 1.50 equiv) and molecular sieves 4 Å (150 mg) in dry DCM

(2.5 mL) was stirred for 20 min at rt and then cooled to −7 °C. A

solution of TMSOTf (2.2 μL, 0.012 mmol, 0.10 equiv) in dry DCM

(0.5 mL) was added. TLC control (toluene/EtOAc 5:1) indicated

complete consumption of acceptor and donor after 5 min. The

reaction was quenched by slow addition of Et₃N (33.4 μL, 0.241

mmol) in DCM (0.3 mL) and stirring for several min. The suspension

was ﬁltered through a bed of Celite and washed with DCM, and the

ﬁltrate was concentrated. The crude material was passed over a short

bed of silica gel (SiO₂: 2 g cartridge, hexane/EtOAc 5:1) to furnish a

disaccharide-containing fraction which was further puriﬁed by

preparative HPLC on column A (hexane/EtOAc 6:1) to give ﬁrst a

fraction containing mainly the β-(1→3)-isomer (23 mg 14%): ¹H

NMR (600 MHz, CDCl₃) δ 8.00−7.97 (m, 2H, BzH2/H6), 7.48−7.45

(m, 1H, BzH4), 7.31−7.19 (m, 22H, BzH3/H5, PhH), 7.14−7.08 (m,

4H, PhH), 7.07−7.04 (m, 1H, PhH), 6.99−6.93 (m, 4H, PhH), 5.53

(dd, J = 2.2, 3.1 Hz, 1H, H-2), 5.22 (app q, J = 10.0 Hz, 1H, H-4), 5.16

(dd, J_H,P= 6.2, J = 12.1 Hz, 1H, POCH₂), 5.04 (dd, J_H,P= 7.2, 13.1 Hz,

1H, POCH₂), 5.03 (d, J_H,P= 7.2 Hz, 2H, POCH₂), 4.86 (d, J = 1.9 Hz,

1H, H-1), 4.77−4.74 (m, 3H, H-3, 2 × CH₂Ph), 4.64 and 4.35 (2d, J =

11.0 Hz, 2H, CH₂Ph), 4.61 (d, J = 11.1 Hz, 1H, CH₂Ph), 4.58 (d, J =

7.7 Hz, 1H, H-1′), 4.55−4.52 (m, 1H, H-6), 4.514 (d, J = 11.9 Hz, 1H,

CH₂Ph), 4.510 and 4.48 (2 d, J = 12.25 Hz, 2H, CH₂Ph), 4.15 (dd, J =

8.6, 12.4 Hz, 1H, H-7a), 3.86 (dd, J = 1.3, 12.4 Hz, 1H, H-7b), 3.82

20

for 21a: R_f= 0.22 (hexane/EtOAc 2:1); [α]_D−5.3 (c 0.7, toluene);

¹H NMR (600 MHz, CDCl₃) δ 8.07−8.05 (m, 2H, BzH2/H6), 7.62−

7.58 (m, 1H, BzH4), 7.45−7.41 (m, 2H, BzH3/H5), 7.39−7.36 (m,

2H, PhH), 7.34−7.32 (m, 2H, PhH), 7.31−7.15 (m, 33H, PhH), 5.55

(dd, J = 3.6, 9.9 Hz, 1H, H-3), 5.41 (dd, J = 1.7, 3.6 Hz, 1H, H-2), 5.03

(ddd, J = 8.6, 9.8, 9.8 Hz, 1H, H-4), 5.01 (d, J = 1.7 Hz, 1H, H-1′),

4.96 (dd, J = 7.1, 11.8 Hz, 1H, POCH₂), 4.95−4.90 (m, 3H, POCH₂),

4.89 and 4.31 (2 d, J = 11.3 Hz, 1H, OCH₂), 4.85 and 4.53 (2d, J =

11.85 Hz, 2H, CH₂Ph), 4.73 and 4.69 (2 d, J = 12.2 Hz, 2H, CH₂Ph),

4.56 and 4.49 (2 d, J = 11.75 Hz, 2H, CH₂Ph), 4.56 (d, J = 1.7 Hz, 1H,

H-1), 4.51 and 4.46 (2 d, J = 11.85 Hz, 1H, CH₂Ph), 4.47−4.44 (m,

1H, H-6), 4.20 (t, J = 9.5 Hz, 1H, H-4′), 4.09 (ddd, J = 1.4, 5.3, 6.8 Hz,

1H, H-6′), 3.89 (dd, J = 8.0, 9.8 Hz, 1H, H-7a), 3.88−3.83 (m, 3H, H-

5, H-7a′, H-3′), 3.82 (dd, J = 1.9, 2.9 Hz, 1H, H-2′), 3.77 (dd, J = 5.5,

10.1 Hz, 1H, H-7b′), 3.72 (dd, J = 1.6, 9.8 Hz, 1H, H-5′), 3.67 (dd, J =

5.9, 9.8 Hz, 1H, H-7b), 3.21 (s, 3H, OCH₃), 2.55−2.45 (m, 2H, Lev-

H2a/H2b), 2.43−2.31 (m, 2H, Lev-H3a/H3b), 1.98 (s, 3H, Lev-H5),

1.14−0.88 (m, 28H, FTIPDS); ¹³C NMR (151 MHz, CDCl₃) δ 206.1

(Lev-C4), 171.9 (Lev-C1), 165.6 (PhCO), 138.9, 138.7, 138.4,

138.2, 138.1, 135.7 (d, J = 7.9 Hz, POCH₂PhC1), 135.6 (d, J = 6.7 Hz,

POCH₂PhC1), 133.1, 130.0, 129.4, 128.54, 128.48, 128.39, 128.37,

128.36, 128.22, 128.18, 127.9, 127.8, 127.72, 127.67, 127.64, 127.58,

127.5, 127.43, 127.40, 127.34, 127.31 (PhC), 98.4 (C-1), 98.2 (C-1′),

80.1 (C-3′), 75.1 (C-6′), 74.5 (CH₂Ph), 74.14 (C-2′), 74.09 (C-4′),

73.3 (CH₂Ph), 72.8 (CH₂Ph), 72.4 (CH₂Ph), 72.1 (C-5′), 71.8 (d, J =

6.7 Hz, C-4), 71.6 (CH₂Ph), 71.0 (C-7′), 70.6 (C-3), 70.2 (C-2), 69.8

20

1

(d, J_C,P= 8.5 Hz, C-5), 69.4 (d, J_C,P= 5.5 Hz, POCH₂), 69.2 (d, J_C,P

=

5.6 Hz, POCH₂), 68.8 (C-6), 66.9 (C-7), 55.6 (OCH₃), 37.7 (Lev-

C3), 29.6 (Lev-C5), 27.9 (Lev-C2), 17.6, 17.55, 17.4, 17.35, 16.8,

16.73, 16.71 (8 × FTIPDS-CH₃), 13.7, 13.25 (2 × FTIPDS-CH),

12.58 and 12.56 (2 d, J_C,F= 16.8 Hz, FTIPDS-CH); ³¹P NMR (243

MHz, CDCl₃) δ −3.21. HRMS (⁺ESI-TOF) m/z [M + Na]⁺calcd for

C₈₈H₁₀₈FNaO₂₀PSi₂1613.6586, found 1613.6575. Analytical data for

20

1

21b: [α]_D−19.0 (c 1.4, CHCl₃); H NMR (600 MHz, CDCl₃) δ

8.06−8.04 (m, 2H, BzH2/H6), 7.60−7.57 (m, 1H, BzH4), 7.44−7.40

(m, 4H, BzH3/H5, 2PhH), 7.37−7.34 (m, 2H, PhH), 7.33−7.16 (m,

31H, PhH), 5.60 (dd, J = 3.6, 9.8 Hz, 1H, H-3), 5.43 (dd, J = 1.7, 3.6

Hz, 1H, H-2), 5.11 (ddd, J = 8.2, 9.8, 9.8 Hz, 1H, H-4), 4.97 (dd, J_H,P

= 7.3, J = 11.8 Hz, 1H, POCH₂), 4.95 and 4.82 (2 d, J = 12.4 Hz, 2H,

CH₂Ph), 4.96−4.86 (m, 5H, 3 POCH₂, 2 CH₂Ph), 4.76 (d, J = 1.5 Hz,

1H, H-1), 4.60−4.57 (m, 1H, H-6), 4.60 (d, J = 11.7 Hz, 1H, CH₂Ph),

4.54−4.47 (m, 4H, 2 × CH₂Ph), 4.38 (d, J = 10.8 Hz, 1H, CH₂Ph),

4.26 (bs, 1H, H-1′), 4.25 (app t, J = 9.4, 1H, H-4′), 4.18−4.14 (m, 2H,

H-6′, H-7a), 4.04 (bd, J = 10.0 Hz, 1H, H-5), 4.01 (dd, J = 7.2, 10.3

Hz, 1H, H-7a′), 3.83 (dd, J = 4.0, 10.3 Hz, 1H, H-7b′), 3.76 (d, J = 2.8

Hz, 1H, H-2′), 3.70 (dd, J = 8.5, 10.1 Hz, 1H, H-7b), 3.46 (dd, J = 2.9,

9.5 Hz, 1H, H-3′), 3.38 (dd, J = 2.0, 9.5 Hz, 1H, H-5′), 3.10 (s, 3H,

OCH₃), 2.56−2.47 (m, 2H, Lev-H3a/H3b), 2.46−2.34 (m, 2H, Lev-

H2a/H2b), 1.97 (s, 3H, Lev-H5), 1.05−0.87 (m, 28H, TIPDSF); ¹³C

NMR (151 MHz, CDCl₃) δ 206.2 (Lev-C4), 171.9 (Lev-C1), 165.7

(PhCO), 138.9, 138.75, 138.5, 138.45, 138.0, 135.7 (d, J_C,P= 8.0 Hz,

POCH₂PhC1), 135.5 (d, J = 6.6 Hz, POCH₂PhC1), 133.4, 123.0,

129.4, 128.54, 128.46, 128.44, 128.39, 128.35, 128.26, 128.24, 128.15,

128.1, 128.0, 127.9, 127.7, 127.6, 127.52, 127.50, 127.4, 127.2 (PhC),

102.3 (C-1′), 98.4 (C-1), 82.7 (C-3′), 76.6 (C-5′), 75.4 (C-6′), 74.7

(CH₂Ph), 74.2 (C-4′), 73.5 (CH₂Ph), 73.4 (C-2′), 73.3 (CH₂Ph), 72.2

(CH₂Ph), 71.9 (C-7′), 71.8 (CH₂Ph), 71.65 (d, J_C,P= 6.6 Hz, C-4),

70.6 (C-3), 70.5 (C-2), 69.4 (d, J_C,P= 5.5 Hz, POCH₂), 69.2 (d, J = 5.5

Hz, POCH₂), 69.0 (d, J = 8.1 Hz, C-5), 68.5 (C-6), 68.2 (C-7), 54.9

(OCH₃), 37.7 (Lev-C3), 29.6 (Lev-C5), 28.0 (Lev-C2), 17.69, 17.66,

17.4, 17.35, 16.75, 16.70, 16.65 (FTIPDS-CH₃), 13.7, 13.3 (2 ×

FTIPDS-CH), 12.54 and 12.49 (2 d, J_F,C= 16.5 Hz, FTIPDS-CH); ³¹

P

NMR (243 MHz, CDCl₃) δ −2.88. HRMS (⁺ESI-TOF) m/z [M +

Na]⁺calcd for C₈₈H₁₀₈FNaO₂₀PSi₂1613.6586, found 1613.6590.

K

dx.doi.org/10.1021/jo402312x | J. Org. Chem. XXXX, XXX, XXX−XXX

The Journal of Organic Chemistry

Article

(dd, J = 0.9, 9.6 Hz, 1H, H-5), 3.71 (dd, J = 1.7, 10.8 Hz, 1H, H-6a′),

3.53−3.49 (m, 2H, H-6b′, H-3′), 3.45−3.42 (m, 1H, H-5′), 3.34 (s,

3H, OCH₃), 3.34 (dd, J = 7.8, 9.1 Hz, 1H, H-2′), 3.15 (t, J = 9.4 Hz,

1H, H-4′), 1.13−0.82 (m, 28H, FTIPDS); ¹³C NMR (151 MHz,

CDCl₃) δ 165.8 (CO), 138.8, 138.6, 138.4, 138.3 (PhC), 136.4 (d,

J_C,P= 7.6 Hz, POCH₂PhC1), 136.1 (d, J = 7.7 Hz, POCH₂PhC1),

133.2, 130.0, 129.2, 128.4, 128.33, 128.30, 128.24, 128.16, 128.1,

127.9, 127.82, 127.79, 127.71, 127.68, 127.6, 127.5, 127.25, 126.8

(PhC), 98.4 (bs, C-1′), 98.3 (C-1), 84.4 (C-3′), 81.6 (C-2′), 77.7 (C-

4′), 75.2 (CH₂Ph), 75.0 (C-5′), 74.8 (CH₂Ph), 74.4 (CH₂Ph), 73.7

(C-6), 73.2 (CH₂Ph), 73.0 (bs, C-4), 72.2 (d, J_C,P= 6.3 Hz, C-5), 71.4

(bs, C-3), 68.9−68.7 (bs, 2 × POCH₂, C-6′), 68.2 (C-7), 67.8 (bs, C-

2), 55.2 (OCH₃), 17.7, 17.5, 17.4, 17.31, 17.26, 17.24, 17.16 (8 ×

TIPDS-CH₃), 13.6, 13.4, 12.73, 12.71 (4 × TIPDS-CH); HRMS

(⁺ESI-TOF) m/z [M + Na]⁺calcd for C₇₅H₉₃NaO₁₇PSi₂1375.5581,

found 1375.5601. Continued elution of the column gave α-isomer 23

(99.4 mg, 61%) as a colorless oil: [α]_D²⁰+20 (c 1.0, CHCl₃); ¹H NMR

(600 MHz, CDCl₃) δ 8.03−8.00 (m, 2H, Bz-H2/H6), 7.56 (t, J = 7.4

Hz, 1H, BzH4), 7.37 (t, J = 7.8 Hz, 2H, Bz-H3/H5), 7.33−7.30 (m,

2H, PhH), 7.28−7.16 (m, 24H, PhH), 7.09−7.05 (m, 2H, PhH),

6.96−6.91 (m, 2H, PhH), 5.38 (dd, J = 2.3, 3.2 Hz, 1H, H-2), 5.23 (d,

J = 3.4 Hz, 1H, H-1′), 5.11−4.96 (m, 5H, 2 × POCH₂, H-4), 4.90 (d, J

= 1.8 Hz, 1H, H-1), 4.79 and 4.53 (2d, J = 12.15 Hz, 2H, CH₂Ph), 4.75

(dd, J = 3.2, 9.4 Hz, 1H, H-3), 4.66 and 4.34 (2 d, J = 11.15 Hz, 2H,

CH₂Ph), 4.62 and 4.47 (2 d, J = 10.8 Hz, 2H, CH₂Ph), 4.58 (d, J = 8.5

Hz, 1H, H-6), 4.46 and 4.23 (2 d, J = 12.15 Hz, 2H, CH₂Ph), 4.02 (dd,

J = 8.6, 12.3 Hz, 1H, H-7a), 3.92 (d, J = 9.5 Hz, 1H, H-5), 3.92 (t, J =

9.4 Hz, 1H, H-3′), 3.77 (bd, J = 10.0 Hz, 1H, H-5′), 3.69 (d, J = 12.0

Hz, 1H, H-7b), 3.61 (d, J = 9.5 Hz, 1H, H-4′), 3.48 (dd, J = 3.5, 9.9

Hz, 1H, H-2′), 3.34 (s, 3H, OCH₃), 3.24 (dd, J = 2.6, 10.8 Hz, 1H, H-

6a′), 3.17 (bd, J = 11.0 Hz, 1H, H-6b′), 1.07−0.99 and 0.90−0.86 (m,

20H and 8H, TIPDS); ¹³C NMR (151 MHz, CDCl₃) δ 165.8 (C

O), 138.9, 138.6, 138.5, 138.0, 136.01, 135.96 (PhC), 135.9 (d.i., 2 ×

POCH₂PhC), 133.2, 129.9, 129.6, 128.5, 128.45, 128.38, 128.3,

128.24, 128.19, 128.12, 128.09, 128.07, 127.93, 127.88, 127.8, 127.6,

127.5, 127.45, 127.37, 127.2 (PhC), 98.2 (C-1′), 97.7 (C-1), 81.2 (C-

3′), 79.75 (C-2′), 77.2 (C-4′), 75.8 (C-3), 75.2 (CH₂Ph), 74.6 (d, J_C,P

= 6.9 Hz, C-4), 74.4 (CH₂Ph), 73.5 (C-6), 73.4 (CH₂Ph), 72.5 (C-2),

72.46 (CH₂Ph), 71.4 (bs, C-5), 71.3 (C-5′), 69.5 (d, J_C,P= 5.6 Hz,

POCH₂), 69.3 (d, J_C,P= 4.9 Hz, POCH₂), 68.03, 67.99 (C-6′, C-7),

55.3 (OCH₃), 17.6, 17.5, 17.4, 17.34, 17.32, 17.25 (8 × TIPDS-CH₃),

13.35, 13.2, 12.7, 12.6 (TIPDS-CH); HRMS (⁺ESI-TOF) m/z [M +

Na]⁺calcd for C₇₅H₉₃NaO₁₇PSi₂1375.5581, found 1375.5562.

Methyl (2,3,4,6,7-Penta-O-benzyl-^L-glycero-α-D-manno-hepto-

pyranosyl)-(1→3)-2-O-benzoyl-4-O-dibenzyloxyphosphoryl-6,7-O-

(1,1,3,3-tetraisopropyl-1,3-disiloxane-1,3-diyl)-^L-glycero-α-D-

manno-heptopyranoside (24). Acceptor 4 (57 mg, 0.069 mmol) was

coevaporated with dry toluene and dissolved in dry DCM (0.8 mL) in

a ﬂame-dried ﬂask. Ground molecular sieves (4 Å, 40 mg) were added,

and the suspension was stirred for 30 min at rt under Ar. A solution of

TBDMSOTf (1.57 μL, 0.007 mmol, 0.10 equiv) in dry DCM (in 0.1

mL) was added dropwise. Then a solution of donor 18 (103 mg, 0.123

mmol, 1.8 equiv) in dry DCM (1 mL) was added continuously within

1 h via a syringe pump. Additional TBDMSOTf solution (∼0.05

equiv) was added after 1.5 h, and the suspension was stirred for 1 h at

rt. The reaction was quenched by dropwise addition of Et₃N (10 μL)

in DCM (0.5 mL). The suspension was ﬁltered over Celite and

washed with DCM, and the ﬁltrate was concentrated. The crude

material was ﬁrst puriﬁed by MPLC (SiO₂: 18 g, ﬂow rate 15 mL/min,

DCM/EtOAc 30:1) to give the anhydro byproduct 25 (17.3 mg, 25%

of donor used) followed by a disaccharide-containing fraction (53.9

mg). Analytical data for 25: NMR data were in full agreement with

published values:²⁴HRMS (⁺ESI-TOF) m/z [M + NH₄]⁺calcd for

C₃₅H₄₀NO₆570.2850, found 570.2846.

7.07−7.03 (m, 2H, PhH), 5.41 (d, J = 1.7 Hz, 1H, H-1′), 5.40 (dd, J =

2.0, 3.2 Hz, 1H, H-2), 5.03−4.94 (m, 4H, H-4, 3 × POCH₂), 4.92 (dd,

J_H,P= 7.0, J = 11.8 Hz, 1H, POCH₂), 4.82 and 4.47 (2 d, J = 11.85 Hz,

2H, CH₂Ph), 4.76 and 4.31 (2 d, J = 11.55 Hz, 2H, CH₂Ph), 4.76 (d, J

= 1.9 Hz, 1H, H-1), 4.62 and 4.52 (2d, J = 12.1 Hz, 2H, CH₂Ph), 4.61

and 4.60 (2 d, J = 12.15 Hz, 2H, CH₂Ph), 4.55−4.45 (m, 1H, H-6),

4.43 (dd, J = 3.3, 9.5 Hz, 1H, H-3), 4.20 and 4.16 (2 d, J = 11.6 Hz,

2H, CH₂Ph), 4.19 (app t, J = 9.6 Hz, 1H, H-4′), 4.10 (dd, J = 8.6, 12.5

Hz, 1H, H-7a), 4.09−4.06 (m, 1H, H-6′), 4.03−4.01 (m, 1H, H-2′),

3.89 (dd, J = 7.4, 10.0 Hz, 1H, H-7a′), 3.87 (dd, J = 1.5, 9.8 Hz, 1H, H-

5′), 3.80−3.75 (m, 3H, H-7b, H-7b′, H-3′), 3.66 (bd, J = 9.4 Hz, 1H,

H-5), 3.28 (s, 3H, OCH₃), 1.07−0.82 (m, 28H, TIPDS); ¹³C NMR

(151 MHz, CDCl₃) δ 165.6 (CO), 139.2, 139.1, 139.0, 138.7,

138.57 (PhC), 135.7 (d, J_C,P= 7.7 Hz, POCH₂PhC1), 135.6 (d, J_C,P

=

6.6 Hz, POCH₂PhC1), 133.4, 130.0, 129.7, 128.6, 128.5, 128.42,

128.39, 128.37, 128.25, 128.1, 128.02, 128.00, 127.9, 127.2, 127.6,

127.53, 127.46, 127.4, 127.29, 127.27, 127.1, 127.05, 127.0, 126.8

(PhC), 100.35 (C-1′), 98.1 (C-1), 79.95 (C-3′), 75.6 (C-6′), 74.9 (C-

2′), 74.5 (dd, J_C,P= 6.6 Hz, C-4), 74.35 (C-3), 73.9 (C-4′), 73.7

(CH₂Ph), 73.6 (C-6), 73.23 (C-5′), 73.17 (CH₂Ph), 72.75 (CH₂Ph),

72.7 (C-2), 72.13 (CH₂Ph), 72.08 (d, J_C,P= 5.5 Hz, C-5), 71.6 (C-7′),

71.4 (CH₂Ph), 69.4 (d, J_C,P= 4.4 Hz, POCH₂), 69.3 (d, J_C,P= 5.5 Hz,

POCH₂), 68.2 (C-7), 55.1 (OCH₃), 17.6, 17.5, 17.4, 17.3, 17.24, 17.21,

17.1 (8 × TIPDS-CH₃), 13.6, 13.55, 12.73, 12.71 (4 × TIPDS-CH);

³¹P NMR (243 MHz, CDCl₃) δ −2.97; HRMS (⁺ESI-TOF) m/z [M +

NH₄]⁺calcd for C₈₃H₁₀₅NO₁₈P Si₂1490.6602, found 1490.6596.

Methyl (2,3,4,6-Tetra-O-benzyl-α-^D-glucopyranosyl)-(1→3)-2-O-

benzoyl-4-O-dibenzyloxyphosphoryl-6-O-(3-ﬂuoro-1,1,3,3-tetraiso-

propyl-1,3-disiloxane-1-yl)-^L-glycero-α-D-manno-heptopyranoside

(26). A solution of 23 (89.5 mg, 66.1 μmol) in dry DCM (3 mL) was

treated with TREAT (216 μL, ∼60 equiv of F⁻) at 0 °C for 2.5 h

according to general procedure 1. The residue (87 mg) was puriﬁed by

column chromatography (SiO₂: 2 g cartridge, hexane/EtOAc 5:1 →

20

4:1 → 3:1) to give compound 26 (78.4 mg, 88%) as an oil: [α]_D

1

+11.7 (c 1.0, CHCl₃); H NMR (600 MHz, CDCl₃) δ 8.02−8.00 (m,

2H, BzH2/H6), 7.56 −7.53 (m, 1H, BzH4), 7.38−7.34 (m, 2H,

BzH3/H5), 7.30−7.27 (m, 4H, PhH), 7.26−7.15 (m, 22H, PhH),

7.12−7.08 (m, 2H, PhH), 6.96−6.93 (m, 2H, PhH), 5.38 (app t, J =

3.0 Hz, 1H, H-2), 5.18 (d, J = 3.5 Hz, 1H, H-1′), 5.09−5.05 (m, 3H,

POCH₂), 5.04−4.99 (m, 2H, H-4, POCH₂), 4.95 (d, J = 2.6 Hz, 1H,

H-1), 4.72 and 4.50 (2d, J = 12.2 Hz, 2H, CH₂Ph), 4.68−4.63 (m, 3H,

H-3, CH₂Ph), 4.67 and 4.35 (2 d, J = 11.25 Hz, 2H, CH₂Ph), 4.52−

4.47 (m, 2H, H-6, CH₂Ph), 4.45 and 4.21 (2 d, J = 12.1 Hz, 2H,

CH₂Ph), 4.17 (dd, J = 2.4, 9.6 Hz, 1H, H-5), 3.90 (t, J = 9.4 Hz, 1H,

H-3′), 3.78−3.73 (m, 2H, H-5′, H-7a), 3.72−3.67 (m, 1H, H-7b), 3.61

(t, J = 9.5 Hz, 1H, H-4′), 3.47 (dd, J = 3.5, 9.8 Hz, 1H, H-2′), 3.41 (s,

3H, OCH₃), 3.25 (dd, J = 2.7, 11.0 Hz, 1H, H-6a′), 3.11 (bd, J = 10.8

Hz, 1H, H-6b′), 1.06−0.92 (m, 28H, FTIPDS); ¹³C NMR (151 MHz,

CDCl₃) δ 165.8 (CO), 138.85, 138.6, 138.4, 137.9, 135.9, 135.8 (2

× POCH₂PhC1), 133.2, 129.9, 129.6, 128.54, 128.48, 128.4, 128.3,

128.20, 128.16, 128.1, 128.01, 127.99, 127.96, 127.8, 127.6, 127.52,

127.4, 127.40, 127.29, 127.27 (PhC), 98.2 (C-1′), 97.9 (C-1), 81.3 (C-

3′), 79.7 (C-2′), 77.2 (C-4'), 76.2 (C-3), 75.2 (CH₂Ph), 74.7 (d, J_C,P

=

6.4 Hz, C-4), 74.4 (CH₂Ph), 73.4 (CH₂Ph), 72.58 (C-2), 72.56

(CH₂Ph), 71.3 (C-5′), 71.0 (bs, C-6), 70.2 (C-5), 69.6 (d, J_C,P= 5.6

Hz, POCH₂), 69.5 (d, J_C,P= 5.3 Hz, POCH₂), 67.9 (C-6′), 63.4 (C-7),

55.4 (OCH₃), 17.4, 17.3, 17.2, 17.1, 16.7, 16.6 (8 × FTIPDS-CH₃),

13.5, 13.1, 12.6, 12.5 (4 × FTIPDS-CH); HRMS (⁺ESI-TOF) m/z [M

+ Na]⁺calcd for C₇₅H₉₄FNaO₁₇PSi₂1395.5643, found 1395.5638.

Methyl (2,3,4,6-Tetra-O-benzyl-α-^D-glucopyranosyl)-(1→3)-

[(2,3,4,6,7-penta-O-benzyl-^L-glycero-α-D-manno-heptopyranosyl)-

(1→7)]-2-O-benzoyl-4-O-dibenzyloxyphosphoryl-6-O-(3-ﬂuoro-

1,1,3,3-tetraisopropyl-1,3-disiloxane-1-yl)-^L-glycero-α-D-manno-

heptopyranoside (27). Acceptor 26 (33.2 mg, 24.2 μmol) and donor

18 (30.2 mg, 36.0 μmol, 1.5 equiv) were combined, coevaporated with

dry toluene, dissolved in dry DCM (1.4 mL), and transferred into a

ﬂame-dried ﬂask containing ground molecular sieves 4 Å (50 mg). The

suspension was stirred under Ar for 30 min at rt and was then cooled

to −40 °C. A solution of TMSOTf (0.22 μL, 1.2 μmol, 0.05 equiv) in

dry DCM (0.1 mL) was added dropwise, and the reaction mixture was

The disaccharide fraction was further puriﬁed by preparative HPLC

(in three portions on column A, ﬂow rate 15 mL/min, hexane/EtOAc

7:1) to furnish α-anomer 24 (36.3 mg, 36%) as an oil; R_f0.56

20

1

(hexane/EtOAc 3:1): [α]_D−11.3 (c 1.6, CHCl₃); H NMR (600

MHz, CDCl₃) δ 8.07−8.03 (m, 2H, BzH2/H6), 7.58−7.54 (m, 1H,

BzH4), 7.39−7.35 (m, 4H, BzH3/H5, 2 × PhH), 7.09 (m, 31H, PhH),

L

dx.doi.org/10.1021/jo402312x | J. Org. Chem. XXXX, XXX, XXX−XXX

The Journal of Organic Chemistry

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stirred under Ar while gradually raising the temperature to −35 °C

during 1 h. Since TLC control (hexane/EtOAc 3:1) still indicated the

presence of starting materials, additional TMSOTf solution (0.11 μL

in 0.05 mL DCM) was added, and stirring was continued for 1 h. The

suspension was warmed to 0 °C, the addition of promotor was

repeated, and stirring was continued for 1 h. The reaction was

quenched by dropwise addition of a solution of Et₃N (6.7 μL) in

DCM (0.5 mL). The suspension was ﬁltered through a plug of cotton,

washed with DCM, and concentrated. Puriﬁcation of the residue was

performed ﬁrst on silica gel (SiO₂: 2 g cartridge, hexane/EtOAc 6:1 →

4:1 → 3:1 → 0:1) to collect the trisaccharide-containing fraction (43.4

mg). Final puriﬁcation was achieved by preparative HPLC (column A,

hexane/EtOAc 5:1) to aﬀord ﬁrst the 7-O-TMS disaccharide acceptor

(2.5 mg, data not shown) followed by 27 (24.7 mg, 51%) and fractions

containing anhydro derivative 25 and the β-(1→7)-linked trisaccharide

(8.9 mg, 18%, data not shown). Analytical data for 27: R_f0.55

(m, 3H, PhH), 7.00−6.95 (m, 4H, PhH), 5.55 (dd, J = 2.1, 3.0 Hz, 1H,

H-2), 5.23 (app q, J = 9.8 Hz, 1H, H-4), 5.18 (dd, J_H,P= 6.0, J = 12.2

Hz, 1H, POCH₂), 5.03 (dd, J_H,P= 7.1, J = 12.3 Hz, 1H, POCH₂), 5.01

(d, J = 1.5 Hz, 1H, H-1″), 4.98−4.96 (m, 2H, POCH₂Ph), 4.87 and

4.32 (2d, J = 11.2 Hz, 2H, CH₂Ph), 4.85 (d, J = 11.9 Hz, 1H, CH₂Ph),

4.81−4.76 (m, 2H, H-3, CH₂Ph), 4.75 and 4.60 (2 d, J = 11.2 Hz, 2H,

CH₂Ph), 4.69 and 4.65 (2 d, J = 12.3 Hz, 2H, CH₂Ph), 4.65 (d, J = 1.7

Hz, 1H, H-1), 4.63 and 4.33 (2 d, J = 11.0 Hz, 2H, CH₂Ph), 4.61 (d, J

= 7.7 Hz, 1H, H-1′), 4.55−4.50 (m, 3H, H-6, 2 × CH₂Ph), 4.48 and

4.42 (2 d, J = 11.7 Hz, 2H, CH₂Ph), 4.47 and 4.43 (2 d, J = 11.7 Hz,

2H, CH₂Ph), 4.41 and 4.34 (2 d, J = 12.0 Hz, 2H, CH₂Ph), 4.19 (app

t, J = 9.6 Hz, 1H, H-4″), 4.10−4.07 (m, 1H, H-6″), 3.91 (dd, J = 8.3,

9.5 Hz, 1H, H-7a), 3.88−3.82 (m, 3H, H-5, H-7a″, H-3″), 3.77−3.74

(m, 2H, H-2″, H-7b″), 3.72 (dd, J = 1.4, 9.6 Hz, 1H, H-5″), 3.71−3.66

(m, 2H, H-7b, H-6a′), 3.56−3.50 (m, 2H, H-6b′, H-3′), 3.46−3.43

(m, 1H, H-5′), 3.32 (dd, J = 7.8, 9.2 Hz, 1H, H-2′), 3.21 (s, 3H,

OCH₃), 3.19 (app t, J = 9.5 Hz, 1H, H-4′);¹³C NMR (151 MHz,

CDCl₃) δ 165.9 (CO), 139.0, 138.82, 138.79, 138.6, 138.45, 138.24,

138.19, 138.1 (PhC), 136.4 (d, J = 8.9 Hz, POCH₂PhC1), 136.0 (d, J =

7.7 Hz, POCH₂PhC1), 133.2, 130.0, 129.2, 128.5, 128.42, 128.36,

128.34, 128.29, 128.22, 128.17, 128.1, 127.9, 127.83, 127.80, 127.76,

127.74, 127.72, 127.64, 127.61, 127.59, 127.57, 127.56, 127.53, 127.52,

127.50, 127.39, 127.36, 127.31, 127.29, 127.22, 127.19, 126.75 (PhC),

98.3 (d.i., C-1 and C-1′), 98.2 (C-1″), 84.3 (C-3′), 81.6 (C-2′), 80.1

(C-3″), 77.5 (C-4′), 75.18 (CH₂Ph), 75.16 (C-6″), 74.8 (C-5′), 74.75,

74.5 (2 × CH₂Ph), 74.33 (C-2), 74.31 (CH₂Ph), 74.2 (C-4″), 73.3,

73.2, 72.71 (3 × CH₂Ph), 72.69 (C-4), 72.4 (CH₂Ph), 72.2 (C-5″),

71.7 (CH₂Ph), 71.4 (C-3), 71.0 (C-7″), 70.1 (C-5), 69.2 (C-6), 68.83

(d, J_C,P= 5.6 Hz, POCH₂), 68.77 (C-6′), 68.75 (d, J_C,P= 5.0 Hz,

POCH₂), 67.4 (C-2″), 67.1 (C-7), 55.5 (s, OCH₃), 17.70, 17.66, 17.5,

17.4, 16.8, 16.7 (FTIPDS-CH₃), 13.9 (2 × FTIPDS-CH), 13.3 (2 ×

20

1

(hexane/EtOAc 2:1); [α]_D+10.2 (c 1.1, CHCl₃); H NMR (600

MHz, CDCl₃) δ 8.04−8.01 (m, 2H, BzH2/H6), 7.58−7.54 (m, 1H,

BzH4), 7.38−7.31 (m, 6H, BzH3/H5, 4 × PhH), 7.29−7.13 (m, 47H,

PhH), 7.05−7.02 (m, 2H, PhH), 6.94−6.90 (m, 2H, PhH), 5.38 (dd, J

= 3.4, 2.0 Hz, 1H, H-2), 5.18 (d, J = 3.5 Hz, 1H, H-1′), 5.13−4.95 (m,

5H, H-4, 2 × POCH₂), 5.05 (d, J = 1.7 Hz, 1H, H-1″), 4.90−4.86 (m,

2H, CH₂Ph), 4.81 (d, J = 1.6 Hz, 1H, H-1), 4.82−4.77 (m, 1H, H-6),

4.73−4.63 (m, 4H, 4 × CH₂Ph), 4.61 (dd, J = 3.3, 9.6 Hz, 1H, H-3),

4.57−4.40 (m, 9H, 9 × CH₂Ph), 4.35−4.31 (m, 2H, CH₂Ph), 4.23 (d,

J = 12.0 Hz, 1H, CH₂Ph), 4.21 (app t, J = 9.5 Hz, 1H, H-4″), 4.13−

4.10 (m, 1H, H-6″), 4.06 (br d, J = 9.9 Hz, 1H, H-5), 3.93−3.86 (m,

4H, H-7a″, H-3′, H-3″, H-7a), 3.83 (dd, J = 2.0, 2.7 Hz, 1H, H-2″),

3.78−3.73 (m, 3H, H-7b″, H-5′, H-5″), 3.68 (dd, J = 5.7, 9.9 Hz, 1H,

H-7b), 3.60 (app t, J = 9.5 Hz, 1H, H-4′), 3.46 (dd, J = 3.5, 9.8 Hz,

1H, H-2′), 3.28 (s, 3H, OCH₃), 3.26−3.23 (m, 1H, H-6a′), 3.22−3.18

(m, 1H, H-6b′), 1.13−0.79 (m, 28H, FTIPDS); ¹³C NMR (151 MHz,

CDCl₃) δ 166.0 (CO), 138.93, 138.86, 138.8, 138.7, 138.6, 138.4,

138.3, 137.9 (PhC), 136.0 (d, J_C,P= 7.0 Hz, POCH₂PhC1), 135.9 (d,

J_C,P= 7.7 Hz, POCH₂PhC1), 133.2, 129.9, 129.6, 128.5, 128.45, 128.4,

128.34, 128.32, 128.25, 128.21, 128.18, 128.17, 128.1, 128.02, 127.97,

127.81, 127.76, 127.7, 127.62, 127.61, 127.56, 127.52, 127.48, 127.46,

127.45, 127.29, 127.28, 127.25, 127.21, 127.16 (PhC), 98.6 (C-1′),

98.1 (C-1″), 97.6 (C-1), 81.2 (C-3′), 80.5 (C-3″), 79.5 (C-2′), 77.2

(C-4′), 76.7 (C-3), 75.3 (C-6″), 75.15, 74.6 (2 × CH₂Ph), 74.3 (C-

2″), 74.24 (CH₂Ph), 74.17 (C-4″), 73.9 (d, J = 6.7 Hz, C-4), 73.4,

73.3, 72.7 (3 × CH₂Ph), 72.6 (C-2), 72.4 (CH₂Ph), 72.34 (C-5″),

72.31, 71.65 (2 × CH₂Ph), 71.5 (C-7″), 71.4 (C-5′), 69.7 (C-5), 69.4

(d, J_C,P= 5.4 Hz, POCH₂), 69.2 (d, J_C,P= 4.9 Hz, POCH₂), 68.65 (C-

6), 67.9 (C-6′), 66.8 (C-7), 55.6 (s, OCH₃), 17.6, 17.5, 17.4, 17.3,

16.8, 16.7 (FTIPDS-CH₃), 13.7, 13.4 (2 × FTIPDS-CH), 12.6 (d, J_F,C

FTIPDS-CH), 12.59 and 12.57 (2 d, J_F,C= 16.5 Hz, FTIPDS-CH); ³¹

P

NMR (243 MHz, CDCl₃) δ −2.69; HRMS (⁺ESI-TOF) m/z [M +

Na]⁺calcd for C₁₁₇H₁₃₆FNaO₂₃PSi₂2037.8625, found 2037.8579.

Methyl 2,3-Di-O-benzoyl-4-O-(dibenzyloxyphosphoryl)-^L-glycero-

α-^D-manno-heptopyranoside (28). Pyridine (580 μL) was added to a

solution of 70% HF−pyridine (205 μL) in an Eppendorf vial with

external cooling. An aliquot of the HF−pyridine solution (0.4 mL, ∼33

equiv of F⁻) was added to a solution of 6 (112 mg, 0.120 mmol) in dry

THF (3.4 mL) in a Teﬂon vessel, and the solution was stirred at rt for

3 h. Additional aliquots (0.1 and 0.285 mL) were added in two

portions, and stirring was continued for 75 min. The solution was

poured into a stirred mixture of cold 50% aq satd NaHCO₃and

EtOAc. The aqueous layer was extracted twice with EtOAc, and the

combined organic layers were washed with satd aq NaHCO₃and

brine, dried (Na₂SO₄), and concentrated. The residue was

coevaporated with toluene and submitted to column chromatography

(SiO₂: 2 g cartridge, Tol/EtOAc 5:1 → 3:1 → 2:1 → 1:1 → 2:3) to

give 28 (60 mg, 72.3%) as a glasslike solid. Alternatively, heptoside 6

(35 mg, 37 μmol) was treated according to general procedure 1. The

crude material (39.1 mg) was puriﬁed by chromatography (SiO₂: 2 g

cartridge, Hex/EtOAc 1:2 → 1:3 → 1:4 → EtOAc) to give 28 (23.6

= 16.5 Hz, FTIPDS-CH), 12.55 (d, J_F,C= 16.9 Hz, FTIPDS-CH); ³¹

P

NMR (243 MHz, CDCl₃) δ −3.04; HRMS (⁺ESI-TOF) m/z [M +

Na]⁺calcd for C₁₁₇H₁₃₆FNaO₂₃PSi₂2037.8625, found 2037.8564.

Alternative Preparation of Trisaccharide 27 from Acceptor 22.

Compound 22 (38.5 mg, 25.8 μmol) and donor 19 (55.0 mg, 77.3

μmol, 3.0 equiv) were combined and coevaporated with dry toluene.

The residue was dissolved in dry DCM (1.5 mL) and transferred into a

ﬂame-dried 10 mL ﬂask containing ground molecular sieves 4 Å (50

mg). The suspension was stirred for 5 min at rt and then cooled to

−22 °C. A solution of TBDMSOTf (0.29 μL, 1.3 μmol, 0.05 equiv) in

dry DCM (0.1 mL) was added dropwise, and the reaction mixture was

stirred under Ar for 2 h. The reaction was quenched by dropwise

addition of Et₃N (16 μL, 26 μmol) in DCM (0.5 mL) and warmed to

rt. The suspension was ﬁltered over a plug of cotton, washed with

DCM, and concentrated. The crude material was passed through a

short silica gel column (SiO₂: 2 g, stepwise gradient of hexane/acetone

7:1→ 3:1) to aﬀord a fraction containing the trisaccharides (50.7 mg).

This material was further puriﬁed by preparative HPLC (column A,

ﬂow rate 15 mL/min, hexane/EtOAc 7:1 → 6:1) to aﬀord pure α-

anomer 27 (38.2 mg, 73.5%) as a colorless oil. Continued elution

aﬀorded the β-(1→3)-linked glucosyl isomer as colorless syrup (4.1

20

1

mg, 91%) as a glasslike solid: [α]_D−80 (c 0.3, CHCl₃); H NMR

(600 MHz, CDCl₃) δ 8.08−8.06 (m, 2H, BzH2/H6), 7.85−7.83 (m,

2H, BzH2/H6), 7.64−7.61 (m, 1H, BzH4), 7.51−7.47 (m, 2H, BzH3/

H5), 7.45−7.42 (m, 1H, BzH4), 7.31−7.27 (m, 3H, PhH), 7.21−7.15

(m, 5H, BzH3/H5, 3 × PhH), 7.09−7.06 (m, 2H, PhH), 6.89−6.87

(m, 2H, PhH), 5.81 (dd, J = 9.8, 3.6 Hz, 1H, H-3), 5.60 (dd, J = 3.5,

1.6 Hz, 1H, H-2), 5.13 (app q, J = 9.7 Hz, 1H, H-4), 4.92 (dd, J = 11.6,

J_H,P= 8.8 Hz, 1H, POCH₂), 4.90 (d, J = 1.8 Hz, 1H, H-1), 4.82 (dd, J

= 11.7 Hz, J_P,H= 8.3 Hz, 1H, POCH₂), 4.74−4.68 (m, 2H, CH₂Ph),

4.24 (d, J = 6.3 Hz, 1H, 6-OH), 4.12−4.08 (m, 1H, H-6), 3.94 (dd, J =

11.1, 7.8 Hz, 1H, H-7a), 3.90 (dd, J = 9.8, 1.5 Hz, 1H, H-5), 3.70−3.65

(m, 1H, H-7b), 3.44 (s, 3H, OCH₃), 2.12 (d, J = 8.7 Hz, 1H, 7-OH);

¹³C NMR (151 MHz, CDCl₃) δ 165.4 (CO), 165.3 (CO), 135.1

(d, J_C,P= 6.5 Hz, POCH₂PhC1), 134.9 (d, J_C,P= 5.7 Hz,

POCH₂PhC1), 133.6, 133.1, 129.95, 129.8, 129.30, 129.26, 128.65,

128.54, 128.47, 128.38, 128.3, 127.9, 127.7 (PhC), 98.8 (C-1), 71.6 (d,

J_C,P= 5.3 Hz, C-4), 71.0 (d, J_C,P= 3.7 Hz, C-5), 70.6 (C-2), 70.1 (d,

J_C,P= 6.2 Hz, POCH₂), 70.0 (d, J_C,P= 4.2 Hz, C-3), 69.8 (d, J_C,P= 5.6

1

mg, 8%): H NMR (600 MHz, CDCl₃) δ 8.01−7.98 (m, 2H, BzH2/

H6), 7.47−7.43 (m, 1H, BzH4), 7.38−7.35 (m, 2H, PhH), 7.33−7.31

(m, 2H, PhH), 7.28−7.10 (m, 46H, BzH3/H5, 44 × PhH), 7.09−7.04

M

dx.doi.org/10.1021/jo402312x | J. Org. Chem. XXXX, XXX, XXX−XXX

The Journal of Organic Chemistry

Article

Hz, POCH₂), 68.3 (C-7), 55.4 (OCH₃); HRMS (⁺ESI-TOF) m/z [M

+ H]⁺calcd for C₃₆H₃₈O₁₂P 693.2095, found 693.2101.

(dd, J = 7.3, 10.5 Hz, 1H, H-7b), 3.25 (s, 3H, OCH₃); ¹³C NMR (151

MHz, CDCl₃) δ 165.4 (CO), 165.3 (CO), 138.9, 138.7, 138.34,

138.28, 138.1, 135.13 (d, J_C,P= 7.4 Hz, POCH₂PhC1), 135.07 (d, J_C,P

= 6.6 Hz, POCH₂PhC1), 133.5, 133.1, 129.95, 129.8, 129.4, 129.3,

128.64, 128.61, 128.56, 128.44, 128.41, 128.38, 128.35, 128.29, 128.28,

128.23, 128.21, 127.8, 127.75, 127.73, 127.69, 127.64, 127.62, 127.5,

127.45, 127.41, 127.37, 127.3 (PhC), 98.7 (C1), 98.4 (C-1′), 80.2 (C-

3′), 74.9 (C-6′), 74.5 (CH₂Ph), 74.2, 74.15 (C-2′, C-4′), 73.3

(CH₂Ph), 72.7 (CH₂Ph), 72.4 (CH₂Ph), 71.8 (CH₂Ph), 71.6 (C-5′),

71.4 (d, J_C,P= 5.2 Hz, C-4), 70.6 (C-2), 70.4 (d, J_C,P= 3.6 Hz, C-5),

70.1 (C-7′), 70.0 (d, J_C,P= 3.6 Hz, C-3), 69.9 (d, J_C,P= 5.9 Hz,

POCH₂), 69.7 (d, J_C,P= 5.6 Hz, POCH₂), 67.4 (C-7), 66.5 (C-6), 55.5

(OCH₃); ³¹P NMR (243 MHz, CDCl₃) δ −0.34. HRMS (⁺ESI-TOF)

m/z [M + NH₄]⁺calcd for C₇₈H₈₃O₁₈NP 1352.5342, found

1352.5315.

Methyl 2,3-Di-O-benzoyl-^L-glycero-α-D-manno-heptopyranoside

4-O-Phosphoric Acid (29). A solution of dibenzylphosphate 28 (117

mg, 0.169 mol) in MeOH (8 mL) was treated with 10% Pd/C (23

mg) for 2 h according to general procedure 2. The ﬁltrate was

20

concentrated to give 29 (87 mg, quant) as a glasslike solid: [α]_D

1

−55.1 (c 0.25, MeOD); H NMR (600 MHz, MeOD) δ 8.07−8.04

(m, 2H, BzH2/6), 7.98−7.95 (m, 2H, BzH2/6), 7.65−7.60 (m, 1H,

BzH4), 7.54−7.50 (m, 1H, BzH4), 7.50−7.45 (m, 2H, BzH3/5),

7.37−7.32 (m, 2H, BzH3/5), 5.62−5.60 (m, 2H, H-2, H-3), 5.06 (app

q, J = 10.3 Hz, 1H, H-4), 4.91 (bs, 1H, H-1), 4.17 (app t, J = 7.0 Hz,

1H, H-6), 4.02 (bd, J = 9.8 Hz, 1H, H-5), 3.79 (dd, J = 10.5, 6.8 Hz,

1H, H-7a), 3.76 (dd, J = 10.5, 7.1 Hz, 1H, H-7b), 3.50 (s, 3H, OCH₃);

¹³C NMR (151 MHz, MeOD) δ 167.2, 166.9 (2 × CO), 134.7,

134.16, 131.1, 131.0, 130.7, 129.6, 129.2 (PhC), 100.1 (C-1), 72.7 (d,

J_C,P= 2.2 Hz, C-3), 71.6 (d, J_C,P= 5.5 Hz, C-5), 71.5 (C-2), 71.1 (d,

J_C,P= 4.9 Hz, C-4), 69.8 (C-6), 63.3 (C-7), 55.8 (OCH₃); HRMS

(⁻ESI-TOF) m/z calcd for C₂₂H₂₅O₁₂P [M − H]⁻511.1011, found

511.1013; HRMS (⁺ESI-TOF) m/z [M + H]⁺calcd for C₂₂H₂₆O₁₂P

513.1156, found 513.1159.

Methyl (^L-glycero-α-D-manno-Heptopyranosyl)-(1→7)-2,3-di-O-

benzoyl-^L-glycero-α-D-manno-heptopyranoside 4-O-Phosphate

Monotriethylammonium Salt (32). A suspension of heptobioside

31 (147 mg, 0.110 mmol) in dry MeOH (4.8 mL) and Pd/C (14 mg)

was treated for 7 h according to general procedure 2. The ﬁltrate was

treated with Et₃N (31 μL, 0.22 mmol) and concentrated to aﬀord the

target compound as mono-Et₃N species 32 (84.1 mg, 95%) as a

Methyl ^L-glycero-α-D-manno-Heptopyranoside 4-O-Phosphate

Monosodium Salt (30). A solution of 29 (74 mg, 0.144 mmol) in

MeOH (5 mL) was treated with 0.1 M methanolic NaOMe solution

(13 mL). The solution (pH of ∼11) was stirred for 10 h at rt and

made neutral by addition of cation-exchange resin (H⁺-form). The

resin was ﬁltered oﬀ, and the ﬁltrate was concentrated. The residue

was dissolved in water, extracted with Et₂O and the aqueous phase was

passed through a PD-10 column (water). Product containing fractions

were pooled and lyophilized to give 47 mg (94%) of compound 30:

20

colorless oil: R_f0.1 (CHCl₃/MeOH/H₂O 14:6:1); [α]_D−15.4 (c

1

0.5, MeOH); H NMR (600 MHz, MeOD) δ = 8.06−8.04 (m, 2H,

BzH2/H6), 8.02−7.99 (m, 2H, BzH2/H6), 7.63−7.59 (m, 1H,

BzH4), 7.51−7.45 (m, 3H, BzH4, BzH3/H5), 7.35−7.31 (m, 2H,

BzH3/H5), 5.60 (dd, J = 1.6, 3.4 Hz, 1H, H-2), 5.54 (dd, J = 3.4, 9.9

Hz, 1H, H-3), 4.93 (app q, J = 9.9 Hz, 1H, H-4), 4.90 (d, J = 1.4 Hz,

1H, H-1), 4.87 (d, J = 1.4 Hz, 1H, H-1′), 4.46−4.42 (m, 1H, H-6),

3.99−3.96 (m, 1H, H-6′), 3.91−3.88 (m, 2H, H-5, H-7a), 3.86 (dd, J =

1.6, 3.2 Hz, 1H, H-2′), 3.85 (app t, J = 9.7 Hz, 1H, H-4′), 3.74−3.65

(m, 4H, H-3′, H-7b, H-7a′, H-7b′), 3.63 (dd, J = 1.7, 9.7 Hz, 1H, H-

5′), 3.50 (s, 3H, OCH₃), 3.07 (q, J = 7.3 Hz, 6H, NCH₂CH₃), 1.25 (t,

J = 7.3 Hz, 9H, NCH₂CH₃); ¹³C NMR (151 MHz, MeOD) δ 167.5

(CO), 167.0 (CO), 134.6, 134.0, 131.3, 131.1, 131.0, 130.8,

129.6, 129.15 (PhC), 102.3 (C-1′), 100.3 (C-1), 73.4 (d, J_C,P= 3.1 Hz,

C-5), 73.04 (d, J_C,P= 3.5 Hz, C-3), 72.99 (C-5′), 72.8 (C-3′), 72.1 (C-

2′), 71.7 (C-2), 71.0 (C-6′), 69.45 (d, J_C,P= 5.6 Hz, C-4), 68.8 (C-7),

68.1 (C-6), 67.9 (C-4′), 64.7 (C-7′), 55.85 (OCH₃), 47.7

(NCH₂CH₃), 9.55 (NCH₂CH₃); ³¹P NMR (243 MHz, MeOD) δ

1.98; HRMS (⁻ESI-TOF) m/z [M − H]⁻calcd for C₂₉H₃₆O₁₈P

703.1645, found 703.1642.

[α]_D20+73.6 (c 0.35, H₂O) [lit.⁴³[α]_D+60.1 (c 0.22, H₂O); lit.⁴⁴

[α]_D+30 (c 1.0, H₂O)]; NMR data agree with ref 44. A diﬀerent

chemical shift of C-4 has been reported in ref 43 (72.39 ppm): ¹³C

NMR (151 MHz, D₂O) δ 101.5 (C-1), 71.9 (C-3), 71.4 (d, J_C,P= 6.9

Hz, C-5), 70.35 (C-2), 69.9 (d, J_C,P= 4.4 Hz, C-4), 69.25 (C-6), 63.3

(C-7), 55.6 (OCH₃); ³¹P NMR (243 MHz, D₂O) δ 4.87; HRMS

(⁻ESI-TOF) m/z calcd for C₈H₁₇O₁₀P [M − H]⁻303.0487, found

303.0483; HRMS (⁺ESI-TOF) m/z [M + H]⁺calcd for C₈H₁₈O₁₀P

305.0632, found 305.0634.

21

20

Methyl (2,3,4,6,7-Penta-O-benzyl-^L-glycero-α-D-manno-hepto-

pyranosyl)-(1→7)-2,3-di-O-benzoyl-4-O-dibenzyloxyphosphoryl-^L-

glycero-α-^D-manno-heptopyranoside (31). Disaccharide 20a (223.5

mg, 139.9 μmol) was coevaporated with toluene, dissolved in dry

DCM (6 mL), and transferred into a Teﬂon-ﬂask. HF−pyridine 70%

(188 μL, ∼51 equiv of F⁻) was added dropwise to the solution, and

the mixture was vigorously stirred at rt for 3 h. The solution was added

dropwise into a stirred mixture of ice-cold satd aq NaHCO₃(40 mL)

and EtOAc (30 mL). The aqueous layer was extracted with EtOAc (30

mL), and the combined organic layer was washed with H₂O and brine

(10 mL), dried (Na₂SO₄), and concentrated. The residue (208 mg)

was puriﬁed by chromatography (2 g cartridge, hexane/EtOAc 5:1 →

3:1 → 2:1) to aﬀord compound 31 (150 mg, 80%) as a colorless oil: R_f

Methyl (^L-glycero-α-D-manno-Heptopyranosyl)-(1→7)-L-glycero-

α-^D-manno-heptopyranoside 4-O-Phosphate Monosodium Salt

(33). Dibenzoate 32 (16.8 mg, 20.9 μmol) was dissolved in dry

MeOH (1.0 mL) and 1 M methanolic NaOMe (0.15 mL, 146 μmol)

was added, leading to the formation of a turbid emulsion. The reaction

mixture was stirred for 19 h at rt and subjected to HPLC−MS analysis

(method B) which indicated ∼30% of unchanged 32. Additional

reagent (0.15 mL, 146 μmol) and MeOH (0.5 mL) were added, and

stirring was continued for 8 h. The pH of reaction mixture was

adjusted to ∼5 by addition of cation-exchange resin (Dowex, H⁺-

form). The resin was ﬁltered oﬀ and washed with MeOH, and the

ﬁltrate was made nearly neutral by adding 0.1 M NaOMe to give a pH

of∼7−8. The solution was concentrated, and the residue (∼13.4 mg)

was dissolved in D₂O (1 mL) and washed twice with chloroform (1

mL). The combined organic layers were re-extracted with D₂O (0.8

mL), and the combined aqueous phases were concentrated to remove

residual CHCl₃. A solution of 1 M methanolic NaOMe (40 μL) was

added, and the mixture was stirred overnight at rt and processed as

described above. The combined aqueous layers were neutralized by

adding 0.1 M NaOMe (pH ∼7−8), purged with a stream of argon, and

lyophilized. Since NMR analysis indicated ∼5% of residual sodium

benzoate in the material, the extraction process was repeated to give

20

1

0.27 (hexane/EtOAc 3:2); [α]_D−19.5 (c 1.2, CHCl₃); H NMR

(600 MHz, CDCl₃) δ 8.08−8.06 (m, 2H, BzH2/H6), 7.87−7.84 (m,

2H, Bz, H2/H6), 7.64−7.60 (m, 1H, BzH4), 7.50−7.46 (m, 2H,

BzH3/H5), 7.46−7.42 (m, 1H, BzH4), 7.39−7.37 (m, 2H, PhH),

7.35−7.32 (m, 2H, PhH), 7.30−7.18 (m, 26H, BzH3/H5, PhH),

7.18−7.16 (m, 1H, PhH), 7.14−7.12 (m, 2H, PhH), 7.09−7.05 (m,

2H, PhH), 6.89−6.87 (m, 2H, PhH), 5.78 (dd, J = 3.5, 9.9 Hz, 1H, H-

3), 5.55 (dd, J = 1.6, 3.4 Hz, 1H, H-2), 5.12 (app q, J = 9.7 Hz, 1H, H-

4), 5.04 (d, J = 1.7 Hz, 1H, H-1′), 4.91 (d, J = 10.9 Hz, 1H, CH₂Ph),

4.89 (dd, J_H,P= 8.1 Hz, J = 11.6 Hz, 1H, POCH₂), 4.81 (d, J = 11.9 Hz,

1H, CH₂Ph), 4.79 (dd, J_H,P= 7.8 Hz, J = 11.7 Hz, 1H, POCH₂), 4.74

(d, J = 1.2 Hz, 1H, H-1), 4.74 (d, J = 12.3 Hz, 1H, CH₂Ph), 4.72−4.66

(m, 3H, POCH₂Ph, CH₂Ph), 4.61 (d, J = 11.8 Hz, 1H, CH₂Ph), 4.55

(d, J = 11.7 Hz, 1H, CH₂Ph), 4.53 (d, J = 11.5 Hz, 1H, CH₂Ph), 4.51

(bs, 2H, CH₂Ph), 4.36 (d, J = 10.7 Hz, 1H, CH₂Ph), 4.21 (app t, J =

9.5 Hz, 1H, H-4′), 4.17−4.10 (m, 2H, H-6, H-6′), 3.90 (dd, J = 3.0,

9.2 Hz, 1H, H-3′), 3.85−3.81 (m, 2H, H-2′, H-7a′), 3.80−3.73 (m,

4H, H-5′, H-7b′, H-7a, OH), 3.70 (dd, J = 1.3, 9.7 Hz, 1H, H-5), 3.62

20

1

pure compound 33 (10.2 mg, 94.4%): [α]_D+71.2 (c 1.5, H₂O); H

NMR (600 MHz, D₂O, pH ∼6−7) δ 4.91 (d, J = 1.7 Hz, 1H, H-1′),

4.75 (d, J = 1.6 Hz, 1H, H-1), 4.29−4.26 (app q, J = 9.7 Hz, 1H, H-4),

4.27−4.25 (m, 1H, H-6), 4.03 (ddd, J = 1.7, 5.5, 7.4 Hz, 1H, H-6′),

3.98 (dd, J = 1.6, 3.0 Hz, 1H, H-2′), 3.93 (dd, J = 1.7, 3.6 Hz, 1H, H-

2), 3.89 (dd, J = 3.5, 9.4 Hz, 1H, H-3), 3.86−3.81 (m, 2H, H-3′, H-4′),

N

dx.doi.org/10.1021/jo402312x | J. Org. Chem. XXXX, XXX, XXX−XXX

The Journal of Organic Chemistry

Article

3.77 (dd, J = 4.2, 10.9 Hz, 1H, H-7a), 3.73 (dd, J = 7.6, 11.2 Hz, 1H,

H-7a′), 3.71−3.67 (m, 2H, H-7b, H-7b′), 3.63−3.59 (m, 2H, H-5, H-

5′), 3.38 (s, 3H, OCH₃); ¹³C NMR (151 MHz, D₂O) δ 101.6 (C-1),

101.4 (C-1′), 72.2 (C-5′), 71.7 (d, J_C,P= 7.0 Hz, C-5), 71.64 (C-3),

71.57 (C-3′), 70.8 (C-2′), 70.4 (C-2), 70.3 (d, J_C,P= 4.8 Hz, C-4), 69.6

(C-6′), 69.3 (C-7), 67.7 (C-6), 66.9 (C-4′), 63.8 (C-7′), 55.6

(OCH₃); ³¹P NMR (243 MHz, D₂O) δ 3.81; HRMS (⁻ESI-TOF) m/z

[M-H]⁻calcd for C₁₅H₂₇O₁₆P 495.1120, found 495.1122.

was adjusted to pH ∼7−8 by adding cation-exchange resin (H⁺-form),

the resin was ﬁltered oﬀ, and the ﬁltrate was concentrated. The residue

was dissolved in D₂O and was thoroughly washed with Et₂O. The

combined aqueous layers were acidiﬁed with cation-exchange resin and

ﬁltered. The ﬁltrate was treated with 0.4 M methanolic NaOMe (0.1

mL) and lyophilized to give 36 (10.7 mg, quant) as a colorless

amorphous solid: [α]_D+87.5 (c 1.1, D₂O); H NMR (600 MHz,

D₂O, pH ∼10) δ 5.19 (d, J = 3.9 Hz, 1H, H-1′), 4.67 (d, J = 1.2 Hz,

1H, H-1), 4.32 (q, J = 10.1 Hz, 1H, H-4), 4.12 (ddd, J = 1.9, 5.4, 7.5

Hz, 1H, H-6), 4.02 (dd, J = 1.6, 3.2 Hz, 1H, H-2), 3.87 (dd, J = 3.3, 9.9

Hz, 1H, H-3), 3.81−3.77 (m, 3H, H-5′, H-3′, H-6a′), 3.76−3.72 (m,

2H, H-6b′, H-7a), 3.70 (dd, J = 5.2, 11.4 Hz, 1H, H-7b), 3.64 (dd, J =

1.7, 10.0 Hz, 1H, H-5), 3.38 (dd, J = 3.8, 9.8 Hz, 1H, H-2′), 3.35 (app

t, J = 9.0, 1H, H-4′), 3.34 (s, 3H, OCH₃).¹³C NMR (151 MHz, D₂O):

δ 102.3 (C-1′), 102.0 (C1), 80.1 (d, J_C,P= 2.2 Hz, C-3), 74.3 (C-3′),

73.3 (C-5′), 73.04 (d, J_C,P= 3.4 Hz, C-5), 72.96 (C-2′), 71.6 (C-2),

70.5 (C-4′), 69.4 (C-6), 68.5 (d, J_C,P= 4.8 Hz, C-4), 63.0 (C-7), 61.6

(C-6′), 55.7 (OCH₃); ³¹P NMR (243 MHz, D₂O) δ 4.70; HRMS

(⁻ESI-TOF) m/z [M − H]⁻calcd for C₁₄H₂₆O₁₅P 465.1015, found

465.1013.

21

1

Methyl (2,3,4,6-Tetra-O-benzyl-α-^D-glucopyranosyl)-(1→3)-2-O-

benzoyl-4-O-dibenzyloxyphosphoryl-^L-glycero-α-D-manno-hepto-

pyranoside (34). Compound 23 (24.6 mg, 18.2 μmol) was treated and

processed according to general procedure 1. The crude material was

puriﬁed by column chromatography (SiO₂: 2 g cartridge, stepwise

gradient of hexane/EtOAc 1:1→1:3) to give pure 34 (16 mg, 79%) as

a syrup: [α]_D²⁰−12.0 (c 1.1, CHCl₃); ¹H NMR (600 MHz, CDCl₃) δ

8.02−7.99 (m, 2H, BzH2/H6), 7.57 (dd, J = 1.2, 7.5 Hz, 1H, BzH4),

7.41−7.38 (m, 2H, BzH3/H5), 7.29−7.17 (m, 23H, PhH), 7.13−7.07

(m, 3H, PhH), 7.05−7.02 (m, 2H, PhH), 6.94−6.91 (m, 2H, PhH),

5.47−5.46 (m, 1H, H-2), 5.25−5.18 (m, 2H, POCH₂), 5.06 −5.01 (m,

3H, H-4, H-1′, POCH₂), 4.95 (dd, J = 7.7, 11.8 Hz, 1H, POCH₂), 4.93

(d, J = 1.8 Hz, 1H, H-1), 4.63 and 4.35 (2d, J = 11.2 Hz, 2H, CH₂Ph),

4.62 and 4.58 (2 d, J = 12.0 Hz, 2H, CH₂Ph), 4.53 (bd, J = 5.3 Hz, 1H,

6-OH), 4.48 and 4.26 (2 d, J = 12.1 Hz, 2H, CH₂Ph), 4.45 and 4.30 (2

d, J = 10.95 Hz, 2H, CH₂Ph), 4.26 (dd, J = 3.0, 9.4 Hz, 1H, H-3),

4.20−4.16 (m, 1H, H-6), 3.89 (br dd, J = 8.2, 10.8 Hz, 1H, H-7a), 3.83

(dd, J = 8.8, 9.8 Hz, 1H, H-3′), 3.79 (dd, J = 1.5, 9.6 Hz, 1H, H-5),

3.67 (dt, J = 2.1, 10.1 Hz, 1H, H-5′), 3.64−3.59 (m, 1H, H-7b), 3.62

(dd, J = 8.7, 10.0 Hz, 1H, H-4′), 3.50 (dd, J = 3.7, 9.8 Hz, 1H, H-2′),

3.39 (s, 3H, OCH₃), 3.25 (dd, J = 2.5, 11.0 Hz, 1H, H-6a′), 3.21 (dd, J

= 1.7, 10.9 Hz, 1H, H-6b′), 2.04 (bd, J = 8.5 Hz, 1H, 7-OH); ¹³C

NMR (151 MHz, CDCl₃) δ 165.75 (CO), 138.7, 138.55, 138.2,

Methyl (2,3,4,6,7-Penta-O-benzyl-^L-glycero-α-D-manno-hepto-

pyranosyl)-(1→3)-2-O-benzoyl-4-O-dibenzyloxyphosphoryl-^L-glyc-

ero-α-^D-manno-heptopyranoside (37). Compound 24 (53 mg, 36.0

μmol) was treated as described in general procedure 1. The crude

material (45 mg) was puriﬁed by column chromatography (SiO₂: 2 g

cartridge, Hex/EtOAc 1:3 → 1:4) to aﬀord 37 (37.7 mg, 83.6%) as a

20

colorless oil: R_f0.20 (hexane/EtOAc 1:2); [α]_D−42.4 (c 1.2,

1

CHCl₃); H NMR (600 MHz, CDCl₃) δ 8.14−8.12 (m, 2H, BzH2/

H6), 7.63−7.59 (m, 1H, BzH4), 7.49−7.45 (m, 2H, BzH3/H5), 7.40−

7.37 (m, 2H, PhH), 7.36−7.12 (m, 26H, PhH), 7.07−7.01 (m, 5H,

PhH), 6.93 −6.90 (m, 2H, PhH), 5.54 (dd, J = 1.4, 3.1 Hz, 1H, H-2),

5.32 (d, J = 1.4 Hz, 1H, H-1′), 5.08 (dd, J_H,P= 8.7, 11.5 Hz, 1H,

POCH₂), 5.05−5.00 (m, 2H, 2 × POCH₂), 4.92 (app q. J = 9.7 Hz,

1H, H-4), 4.81 and 4.36 (2 d, J = 11.6 Hz, 2H, CH₂Ph), 4.80 and 4.47

(2 d, J = 11.8 Hz, 2H, CH₂Ph), 4.76 (dd, J_H,P= 6.4, J = 11.9 Hz, 1H,

POCH₂), 4.69 (d, J = 1.3 Hz, 1H, H-1), 4.66 and 4.55 (2 d, J = 12.2

Hz, 2H, CH₂Ph), 4.54 (d, J = 5.7 Hz, 1H, 6-OH), 4.44−4.40 (m, 3H,

CH₂Ph, H-3), 4.17 (app t, J = 9.6, 1H, H-4′), 4.17−4.15 (m, 1H, H-

6′), 4.08 (d, J = 11.5 Hz, 1H, CH₂Ph), 4.08−4.04 (m, 1H, H-6), 4.02

(dd, J = 1.1, 9.8 Hz, 1H, H-5′), 3.96−3.90 (m, 2H, CH₂Ph, H-7a), 3.88

(dd, J = 6.7, 9.9 Hz, 1H, H-7a′), 3.83 (dd, J = 5.5, 9.8 Hz, 1H, H-7b′),

3.71 (dd, J = 1.2, 9.8 Hz, 1H, H-5), 3.65 (dd, J = 2.9, 9.5 Hz, 1H, H-

3′), 3.65−3.60 (m, 1H, H-7b), 3.59 (dd, J = 1.8, 2.8 Hz, 1H, H-2′),

2.06 (bd, J = 9.6 Hz, 1H, 7-OH); ¹³C NMR (151 MHz, CDCl₃) δ

165.1 (CO), 139.1, 138.9, 138.8, 138.6, 138.5 (PhC), 135.1 (d, J_C,P

= 7.7 Hz, POCH₂PhC1), 135.0 (d, J_C,P= 6.6 Hz, POCH₂PhC1), 133.4,

130.0, 129.7, 128.9, 128.75, 128.65, 128.6, 128.3, 128.12, 128.09,

128.07, 128.03, 127.96, 127.55, 127.39, 127.36, 127.34, 127.31, 127.27,

127.23, 127.17, 127.1, 126.95, 126.8 (PhC), 99.6 (C-1′), 99.0 (C-1),

80.1 (C-3′), 75.21 (C-6′), 75.17 (C-2′), 73.95 (d, J_C,P= 5.5 Hz, C-4),

73.83 (C-4′), 73.78 (CH₂Ph), 73.2 (CH₂Ph), 72.90 (C-5′), 72.88

(CH₂Ph), 72.3 (C-2), 72.1 (CH₂Ph), 71.8 (CH₂Ph), 71.7 (d, J_C,P= 4.4

Hz, C-3), 71.1 (d, J_C,P= 3.3 Hz, C-5), 71.0 (C-7′), 70.3 (d, J_C,P= 5.5

Hz, POCH₂), 69.9 (dt, J_C,P= 4.4 Hz, POCH₂), 68.1 (C-6), 63.1 (C-7),

55.15 (OCH₃); ³¹P NMR (243 MHz, CDCl₃) δ 1.72; HRMS (⁺ESI-

TOF) m/z [M + NH₄]⁺calcd for C₇₁H₇₉NO₁₇P 1248.5080, found

1248.5088.

137.85 (PhC), 135.7 (d, J_C,P= 6.2 Hz, POCH₂PhC1), 135.3 (d, J_C,P

=

7.1 Hz, POCH₂PhC1), 133.4, 129.8, 129.4, 128.62, 128.60, 128.56,

128.4, 128.23, 128.16, 128.1, 127.95, 127.9, 127.82, 127.78, 127.7,

127.5, 127.4, 127.34, 127.32, 127.30 (PhC), 99.1 (C-1′), 98.1 (C-1),

81.4 (C-3′), 80.05 (C-2), 77.9 (d, J = 5.0 Hz, C-3), 77.1 (C-4′), 75.1

(CH₂Ph), 74.4 (CH₂Ph), 73.4 (CH₂Ph), 73.1 (CH₂Ph), 72.3 (C-2),

72.1 (d, J_C,P= 5.1 Hz, C-4), 71.53 (C-5′), 71.47 (d, J_C,P= 2.2 Hz, C-5),

70.02, 69.99 (2 × POCH₂), 68.3 (C-6), 67.8 (C-6′), 63.15 (C-7), 55.4

(OCH₃); ³¹P NMR (243 MHz, CDCl₃) δ 0.60; HRMS (⁺ESI-TOF)

m/z [M + H]⁺calcd for C₆₃H₆₈O₁₆P 1111.4239, found 1111.4237.

Methyl (α-^D-Glucopyranosyl)-(1→3)-2-O-benzoyl-L-glycero-α-D-

manno-heptopyranoside 4-O-Phosphate Triethylammonium Salt

(35). A suspension of disaccharide 34 (25 mg, 22.5 μmol) and 10%

Pd/C (2.5 mg) was hydrogenated for 7 h at rt and processed as

described in general procedure 2. A solution of Et₃N (4 μL) in MeOH

(100 μL) was added, and the ﬁltrate was concentrated to aﬀord

20

compound 35 (14.3 mg, 95%) as a syrup: [α]_D+60.6 (c 1.4,

1

MeOH); H NMR (600 MHz, MeOD) δ 8.13−8.10 (m, 2H, BzH2/

H6), 7.63−7.60 (m, 1H, BzH4), 7.50−7.46 (m, 2H, BzH3/H5), 5.39

(dd, J = 1.6, 3.3 Hz, 1H, H-2), 5.13 (d, J = 4.0 Hz, 1H, H-1′), 4.78 (bs,

1H, H-1), 4.78 (app q, J = 10.1 Hz, 1H, H-4), 4.21 (dt, J = 1.5, 6.8 Hz,

1H, H-6), 4.16 (dd, J = 3.4, 9.8 Hz, 1H, H-3), 3.80 (dd, J = 1.5, 9.9 Hz,

1H, H-5), 3.73 (dd, J = 7.1, 10.8 Hz, 1H, H7-a), 3.68 (dd, J = 6.8, 11.0

Hz, 1H, H-7b), 3.66 (dd, J = 2.3, 12.2 Hz, 1H, H-6a), 3.60 (dd, J = 3.7,

12.0 Hz, 1H, H-6b), 3.56 (app t, J = 9.5 Hz, 1H, H-3′), 3.55−3.52 (m,

1H, H-5′), 3.42 (s, 3H, OCH₃), 3.37 (dd, J = 3.9, 9.8 Hz, 1H, H-2′),

3.34 (app t, J = 9.5 Hz, 1H, H-4′), 3.15 (q, J = 7.3 Hz, 7H,

NCH₂CH₃), 1.29 (t, J = 7.3 Hz, 11H, NCH₂CH₃); ¹³C NMR (151

MHz, MeOD) δ 167.5 (CO), 134.5, 131.13, 131.06, 129.6, 103.4

(C-1′), 99.95 (C-1), 79.4 (d, J_C,P= 2.5 Hz, C-3), 74.5 (C-3′), 74.4 (C-

2), 74.1 (C-5′), 73.8 (C-2′), 72.7 (d, J_C,P= 3.4 Hz, C-5), 70.7 (C-4′),

70.6 (d, J_C,P= 4.9 Hz, C-4), 69.9 (C-6), 63.1 (C-7), 61.8 (C-6′), 55.6

(OCH₃), 47.6 (NCH₂CH₃), 9.3 (NCH₂CH₃); ³¹P NMR (243 MHz,

MeOD) δ 1.97. HRMS (⁻ESI-TOF) m/z [M − H]⁻calcd for

C₂₁H₃₀O₁₆P 569.1277, found 569.1277.

Methyl (^L-glycero-α-D-manno-Heptopyranosyl)-(1→3)-2-O-ben-

zoyl-^L-glycero-α-D-manno-heptopyranoside 4-O-Phosphoric Acid

(38). A suspension of heptoside 37 (36.5 mg, 29.6 μmol) and Pd/C

(10 w%, 8.4 mg) in dry MeOH (1.8 mL) was processed according to

general procedure 2. The ﬁltrate was concentrated to aﬀord 38 as a

1

syrup (18.3 mg, ∼quant): R_f0.13 (CHCl₃/MeOH/H₂O 10:5:1); H

NMR (600 MHz, MeOD, pH ∼2) δ 8.12−8.09 (m, 2H, BzH2/H6),

7.64−7.60 (m, 1H, BzH4), 7.51−7.47 (m, 2H, BzH3/H5), 5.45 (dd, J

= 1.7, 3.2 Hz, 1H, H-2), 5.11 (s, 1H, H-1′), 4.88−4.82 (m, H-4), 4.82

(d, J = 1.6 Hz, 1H, H-1), 4.28 (dd, J = 3.3, 9.5 Hz, 1H, H-3), 4.15−

4.09 (m, 1H, H-6), 4.02−3.97 (m, 2H, H-6′, H-2′), 3.85 (bd, J = 9.8

Hz, 1H, H-5), 3.84 (app t, J = 9.7 Hz, 1H, H-4′), 3.77−3.68 (m, 4H,

H-7a, H-7b, H-7a′, H-7b′), 3.70 (dd, J = 1.5, 9.8 Hz, 1H, H-5′), 3.53

Methyl (α-^D-Glucopyranosyl)-(1→3)-L-glycero-α-D-manno-hepto-

pyranoside 4-O-Phosphate Disodium Salt (36). A solution of 35

(13.6 mg, 20.2 μmol) in dry MeOH (1.0 mL) was treated with 1 M

NaOMe (100 μL, ∼100 μmol) for 14 h at rt. The pH of the solution

O

dx.doi.org/10.1021/jo402312x | J. Org. Chem. XXXX, XXX, XXX−XXX

The Journal of Organic Chemistry

Article

(dd, J = 3.2, 9.5 Hz, 1H, H-3′), 3.44 (s, 3H, OCH₃); ¹³C NMR (151

MHz, MeOD) δ 167.1 (CO), 134.55, 131.05, 131.0, 129.6, 103.85

(C-1′), 100.1 (C-1), 75.2 (C-3), 74.2 (C-5′), 73.83 (C-2), 73.80 (C-

4), 72.4 (C-3′), 71.8 (d, J_C,P= 4.4 Hz, C-5), 71.6 (C-2′), 71.1 (C-6′),

69.8 (C-6), 67.7 (C-4′), 65.4, 63.2 (C-7, C-7′), 55.7 (OCH₃); ³¹P

NMR (243 MHz, D₂O) δ 0.80; HRMS (⁻ESI-TOF) m/z [M − H]⁻

calcd for C₂₂H₃₃O₁₇P 599.1383, found 599.1382.

(CH₂Ph), 74.4 (CH₂Ph), 74.25 (C-4″), 74.1 (C-2″), 73.4 (CH₂Ph),

73.3 (CH₂Ph), 73.0 (CH₂Ph), 72.7 (CH₂Ph), 72.28 (C-2), 72.26

(CH₂Ph), 71.9 (d, J_P,C= 4.4 Hz, C-4), 71.8 (CH₂Ph), 71.7 (C-5″),

71.5 (C-5′), 71.1 (d, J_P,C= 2.2 Hz, C-5), 70.3 (C-7″), 70.0 (d, J_P,C

=

5.8 Hz, POCH₂), 69.9 (d, J_P,C= 5.5 Hz, POCH₂), 67.7 (C-6′, C-7),

66.6 (C-6), 55.5 (OCH₃); ³¹P NMR (243 MHz, CDCl₃) δ 0.45;

HRMS (⁺ESI-TOF) m/z [M + Na]⁺calcd for C₁₀₅H₁₀₉NaO₂₂P

1775.704, found 1775.7015.

Methyl (^L-glycero-α-D-manno-Heptopyranosyl)-(1→3)-L-glycero-

α-^D-manno-heptopyranoside 4-O-Phosphate Monosodium Salt

(39). A solution of 1 M methanolic NaOMe (0.29 mL, 0.290 mmol)

was added to a solution of 38 (17.6 mg, 29.3 μmol) in dry MeOH (1.8

mL) to give a pH ≥ 12. The turbid emulsion was stirred for 41 h at rt.

Additional reagent (0.29 mL) and MeOH (1.8 mL) were added, and

stirring was continued for 24 h. Another portion (4 mL MeOH and

0.6 mL 1 M NaOMe) was then added, and stirring was continued for 3

more days. The solution was acidiﬁed by adding cation-exchange resin

(H⁺-form), the resin was ﬁltered oﬀ, washed with MeOH, and the

ﬁltrate was concentrated. The residue was partitioned between water

and chloroform to remove methyl benzoate. The aqueous layer was

neutralized by addition of 1 M NaOMe solution and submitted to

lyophilization to yield a white powder (14.7 mg, 97%). Since the

product contained ∼1% of residual 38, hydrolysis of an aqueous

solution was continued using 1 M NaOMe in MeOH (57 μL)

overnight at rt. Workup as described aﬀorded compound 39 (12.0 mg,

Methyl (α-^D-Glucopyranosyl)-(1→3)-[(L-glycero-α-D-manno-hep-

topyranosyl)-(1→7)]-2-O-benzoyl-^L-glycero-α-D-manno-heptopyra-

noside 4-O-Phosphate Monotriethylammonium Salt (41). A

suspension of heptoside 40 (27.5 mg, 15.7 μmol) and 10% Pd/C

(6.3 mg) in dry MeOH (2.75 mL) was hydrogenated at atmospheric

pressure for 5.5 h at rt. The suspension was ﬁltered through Celite and

was washed repeatedly with MeOH. Triethylamine (2.6 μL, 18.8

μmol) was added to the ﬁltrate, and the ﬁltrate was concentrated to

aﬀord 41 (13.6 mg, quantitative) as a colorless oil: R_f0.32 (DCM/

20

1

MeOH/H₂O 5:4:1); [α]_D+72.3 (c 1.4, MeOD); H NMR (600

MHz, MeOD) δ 8.12−8.09 (m, 2H, BzH2/H6), 7.63−7.60 (m, 1H,

BzH4), 7.50−7.47 (m, 2H, BzH3/H5), 5.39 (dd, J = 3.3, 1.7 Hz, 1H,

H-2), 5.12 (d, J = 4.0 Hz, 1H, H-1″), 4.85 (d, J = 1.6 Hz, 1H, H-1′),

4.79 (d, J = 1.6 Hz, 1H, H-1), 4.79 (app q, J = 10.2 Hz, 1H, H-4),

4.38−4.33 (m, 1H, H-6), 4.16 (dd, J = 9.8, 3.4 Hz, 1H, H-3), 3.95 (app

td, J = 6.6, 1.4 Hz, 1H, H-6′), 3.85−3.80 (m, 3H, H-4′, H-2′, H-7a),

3.75 (dd, J = 10.0, 1.4 Hz, 1H, H-5), 3.71 (dd, J = 9.6, 3.4 Hz, 1H, H-

3′), 3.68−3.63 (m, 3H, H-7a′, H-7b, H-6a″), 3.63−3.58 (m, 3H, H-

7b′, H-5′, H-6b″), 3.56 (app t, J = 9.4 Hz, 1H, H-3″), 3.54−3.51 (m,

1H, H-5″), 3.43 (s, 3H, OCH₃), 3.37 (dd, J = 9.7, 3.9 Hz, 1H, H-2″),

3.33 (app t, J = 9.2 Hz, 1H, H-4″), 3.17 (q, J = 7.3 Hz, 6H,

NCH₂CH₃), 1.30 (t, J = 7.3 Hz, 9H, NCH₂CH₃); ¹³C NMR (151

MHz, MeOD) δ 167.5 (PhCO), 134.5, 131.09, 131.06, 129.6, 103.5

(C-1″), 102.3 (C-1′), 99.95 (C-1), 79.3 (d, J_P,C= 2.9 Hz, C-3), 74.5

(C-3″), 74.3 (C-2), 74.15 (C-5″), 73.8 (C-2″), 73.4 (d, J_P,C= 3.8 Hz,

C-5), 72.9 (C-5′), 72.8 (C-3′), 72.1 (C-2′), 70.9 (C-6′), 70.7 (C-4″),

70.5 (d, J_P,C= 5.3 Hz, C-4), 68.9 (C-7), 68.3 (C-6), 67.85 (C-4′), 64.6

(C-7′), 61.8 (C-6″), 55.8 (OCH₃), 47.75 (NCH₂CH₃), 9.3

(NCH₂CH₃); ³¹P NMR (243 MHz, MeOD) δ 1.82. HRMS (⁻ESI-

TOF) m/z [M − H]⁻calcd for C₂₈H₄₂O₂₂P 761.1911, found

761.1917.

79%) as a colorless powder: [α]_D+86.3 (c 0.8, D₂O) [lit.²⁹[α]_D

20

+85 (c 0.8, H₂O)]; NMR data agree with published values;²⁹³¹P NMR

(243 MHz, D₂O) δ 2.71; HRMS (⁻ESI-TOF) m/z [M − H]⁻calcd

for C₁₅H₂₈O₁₆P 495.1120, found 495.1122.

Methyl (2,3,4,6-Tetra-O-benzyl-α-^D-glucopyranosyl)-(1→3)-

[(2,3,4,6,7-penta-O-benzyl-^L-glycero-α-D-manno-heptopyranosyl)-

(1→7)]-2-O-benzoyl-4-O-dibenzyloxyphosphoryl-^L-glycero-α-D-

manno-heptopyranoside (40). A solution of HF−pyridine 70% (26.4

μL, ∼55 equiv of F⁻) was added dropwise to a solution of trisaccharide

27 (37.3 mg, 18.5 μmol, predried by coevaporation with toluene) in

dry DCM (2.5 mL) in a Teﬂon ﬂask under vigorous stirring. The

solution was stirred for 1 h at rt and was added dropwise into a stirred

mixture of ice-cold satd aq NaHCO₃(15 mL) and EtOAc (30 mL).

The aqueous layer was extracted with EtOAc (15 mL), and the

combined organic layer was washed with brine (15 mL), dried

(Na₂SO₄) ,and concentrated. The residue (37 mg) was puriﬁed by

chromatography (SiO₂: 2 g cartridge, hexane/EtOAc 2:1 → 3:2 →

1:1) to give compound 40 (26.5 mg, 82%) as a colorless oil: R_f0.25

Methyl (α-^D-Glucopyranosyl)-(1→3)-[(L-glycero-α-D-manno-hep-

topyranosyl)-(1→7)]-^L-glycero-α-D-manno-heptopyranoside 4-O-

Phosphate Monosodium Salt (42). A solution of benzoate 41 (13.6

mg, 15.7 μmol) in dry MeOH (2.7 mL) was stirred with 1 M

methanolic NaOMe (0.24 mL, 240 μmol) for 30 min at rt. D₂O (1.2

mL) was then added to dissolve the formed precipitate. Stirring was

continued for 5.5 h, and the solution was made neutral (pH ≈ 7) by

addition of cation-exchange resin (H⁺form). The resin was ﬁltered oﬀ

and washed with MeOH, and the ﬁltrate was concentrated. The

residue was dissolved in D₂O and ﬁltered over a bed of cation-

exchange resin (H⁺-form). The ﬁltrate was thoroughly extracted with

Et₂O. The combined organic layers were extracted with D₂O, and the

aqueous layer was reextracted with Et₂O. The combined aqueous

layers were neutralized by addition of 0.1 M NaOH (pH ≈ 7) and

lyophilized to give compound 42 (9.5 mg, 89%) as a white powder: R_f

0.14 (DCM/MeOH/H₂O 5:4:1); [α]_D²⁰+98.6 (c 1.0, D₂O); ¹H NMR

(600 MHz, D₂O, pH ≈ 7) δ 5.19 (d, J = 3.9 Hz, 1H, H-1″), 4.88 (d, J

= 1.6 Hz, 1H, H-1′), 4.68 (d, J = 1.5 Hz, 1H, H-1), 4.32 (app q, J =

10.1 Hz, 1H, H-4), 4.26 (ddd, J = 8.4, 3.9, 1.9 Hz, 1H, H-6), 4.03 (dd,

J = 3.3, 1.7 Hz, 1H, H-2), 4.02−3.99 (m, 1H, H-6′), 3.97−3.96 (m,

1H, H-2′), 3.86 (dd, J = 9.9, 3.3 Hz, 1H, H-3), 3.83−3.77 (m, 5H, H-

4′, H-6a″, H-3′, H-5″, H-3″), 3.76−3.69 (m, 3H, H-7a, H-6b″, H-7a′),

3.66 (dd, J = 11.3, 5.1 Hz, 1H, H-7b′), 3.65 (dd, J = 11.0, 8.5 Hz, 1H,

H-7b), 3.63 (dd, J = 9.9, 1.9 Hz, 1H, H-5), 3.60−3.56 (m, 1H, H-5′),

3.39 (dd, J = 9.9, 3.9 Hz, 1H, H-2″), 3.36 (app t, J = 9.5 Hz, 1H, H-

4″), 3.35 (s, 3H, OCH₃); ¹³C NMR (151 MHz, D₂O) δ 102.3 (C-1″),

102.0 (C-1), 101.5 (C-1′), 80.1 (d, J_P,C= 2.3 Hz, C-3), 74.3 (C-3″),

73.4 (d, J_P,C= 3.3 Hz, C-5), 73.3 (C-5″), 72.95 (C-2″), 72.4 (C-5′),

71.8 (C-3′), 71.5 (C-2), 70.9 (C-2′), 70.5 (C-4″), 69.9 (C-6′), 68.9

(C-7), 68.5 (d, J_P,C= 4.7 Hz, C-4), 67.9 (C-6), 67.1 (C-4′), 64.1 (C-

7′), 61.6 (C-6″), 55.8 (OCH₃); ³¹P NMR (243 MHz, D₂O) δ 4.53;

20

(hexane/EtOAc 2:1); [α]_D+3.9 (c 1.3, CHCl₃); ¹H NMR (600

MHz, CDCl₃) δ 8.02−7.99 (m, 2H, BzH2/H6), 7.59−7.55 (m, 1H,

BzH4), 7.41−7.35 (m, 4H, BzH3/H5, 2 × PhH), 7.34−7.14 (m, 46H,

PhH), 7.12−7.06 (m, 3H, PhH), 7.05−7.01 (m, 2H, PhH), 6.94−6.91

(m, 2H, PhH), 5.44 (dd, J = 3.1, 1.9 Hz, 1H, H-2), 5.22 (dd, J = 11.8

Hz, J_H,P= 7.8 Hz, 1H, POCH₂), 5.19 (dd, J = 11.8 Hz, J_H,P= 9.0 Hz,

1H, POCH₂), 5.07−5.01 (m, 4H, H-4, POCH₂, H-1′, H-1″), 4.94 (dd,

J = 11.7 Hz, J_H,P= 7.1 Hz, 1H, POCH₂), 4.90 (d, J = 11.2 Hz, 1H,

CH₂Ph), 4.82 and 4.53 (2 d, J = 11.95 Hz, 2H, CH₂Ph), 4.82 (d, J =

1.7 Hz, 1H, H-1), 4.73 and 4.67 (2 d, J = 12.35 Hz, 2H, CH₂Ph), 4.64

and 4.58 (2 d, J = 12.0 Hz, 2H, CH₂Ph), 4.63 (d, J = 11.2 Hz, 1H,

CH₂Ph), 4.59 and 4.54 (2 d, J = 11.75 Hz, 2H, CH₂Ph), 4.52−4.47

(m, 3H, CH₂Ph), 4.45 and 4.30 (2 d, J = 10.95 Hz, 2H, CH₂Ph),

4.38−4.33 (m, 2H, CH₂Ph), 4.28−4.15 (m, 5H, CH₂Ph, H-6, H-3, H-

4″, 6-OH), 4.13−4.10 (m, 1H, H-6″), 3.91 (dd, J = 9.2, 3.1 Hz, 1H, H-

3″), 3.86−3.82 (m, 3H, H-3′, H-2″, H-7a″), 3.78 (dd, J = 9.7, 1.7 Hz,

1H, H-5″), 3.76 (dd, J = 9.8, 6.1 Hz, 1H, H-7b″), 3.73 (dd, J = 10.4,

5.6 Hz, 1H, H-7a), 3.68−3.59 (m, 4H, H-5′, H-5, H-4′, H-7b), 3.50

(dd, J = 9.8, 3.6 Hz, 1H, H-2″), 3.25 (dd, J = 11.0, 2.3 Hz, 1H, H-6a′),

3.24 (s, 3H, OCH₃), 3.22 (dd, J = 11.1, 1.7 Hz, 1H, H-6b′); ¹³C NMR

(151 MHz, CDCl₃) δ 165.7 (PhCO), 138.9, 138.7, 138.55, 138.37,

138.36, 138.21, 138.17, 137.8 (PhC), 135.7 (d, J = 6.6 Hz,

POCH₂PhC1), 135.3 (d, J = 7.7 Hz, POCH₂PhC1), 133.4, 129.8,

129.5, 128.62, 128.59, 128.56, 128.4, 128.3, 128.24, 128.21, 128.15,

128.1, 127.9, 127.81, 127.76, 127.71, 127.69, 127.53, 127.51, 127.48,

127.43, 127.42, 127.33, 127.30, 127.27 (PhC), 99.15 (C-1′), 98.4 (C-

1″), 98.0 (C-1), 81.4 (C-3′), 80.4 (C-3″), 79.9 (C-2′), 77.9 (d, J_P,C

=

5.5 Hz, C-3), 77.1 (C-4′), 75.09 (CH₂Ph), 75.0 (C-6″), 74.53

P

dx.doi.org/10.1021/jo402312x | J. Org. Chem. XXXX, XXX, XXX−XXX

The Journal of Organic Chemistry

Article

HRMS (⁻ESI-TOF) m/z [M − H]⁻calcd for C₂₁H₃₈O₂₁P 657.1649,

(19) Marchetti, R.; Malinovska, L.; Lameignere, E.; Adamova, L.; de

Castro, C.; Cioci, G.; Stanetty, C.; Kosma, P.; Molinaro, A.;

Wimmerova, M.; Imberty, A.; Silipo, A. Glycobiology 2012, 22, 1387.

(20) Sulak, O.; Cioci, G.; Lameignere, E.; Balloy, V.; Round, A.;

Gutsche, I.; Malinovska, L.; Chignard, M.; Kosma, P.; Aubert, D. F.;

Marolda, C. L.; Valvano, M. A.; Wimmerova, M.; Imberty, A. PLOS

Pathog. 2011, 7 (9), e1002238.

(21) For reviews, see: (a) Hansson, J.; Oscarson, S. Curr. Org. Chem.

2000, 4, 535. (b) Oscarson, S. Top. Curr. Chem 1997, 186, 171.

(c) Kosma, P. Synthesis of the core region of bacterial lip-

opolysaccharides. In Microbial Glycobiology: Structures, Relevance and

Applications; Moran, A., P. Brennan, P., Holst, O., von Itzstein, M.,

Eds.; Elsevier: Amsterdam, 2009; p 429. (d) Oscarson, S. Carbohydr.

Polym. 2001, 44, 305 and references cited therein.

found 657.1643.

ASSOCIATED CONTENT

■

S

* Supporting Information

¹H NMR and ¹³C NMR spectra for known and new

compounds (2, 4−11, 14−18, and 20−42) and β-isomeric

byproducts. This material is available free of charge via the

Internet at http://pubs.acs.org.

AUTHOR INFORMATION

■

Corresponding Author

(22) Young, Y.; Oishi, S.; Martin, C. E.; Seeberger, P. H. J. Am. Chem.

Soc. 2013, 135, 6262.

*E-mail: paul.kosma@boku.ac.at.

(23) Young, Y.; Martin, C. E.; Seeberger, P. H. Chem. Sci. 2012, 3,

896.

(24) Anish, C.; Guo, X.; Wahlbrink, A.; Seeberger, P. H. Angew.

Notes

The authors declare no competing ﬁnancial interest.

Chem., Int. Ed. 2013, 52, 9524.

ACKNOWLEDGMENTS

(25) Bernlind, C.; Oscarson, O. J. Org. Chem. 1998, 63, 7780.

(26) Segerstedt, E.; Mannerstedt, K.; Johansson, M.; Oscarson, S. J.

Carbohydr. Chem. 2004, 23, 443.

(27) Olsson, J. D. M.; Oscarson, S. Tetrahedron: Asymmetry 2009, 20,

875.

■

We thank Florian Adanitsch and Markus Blaukopf for helpful

discussions and Philip Lackner and Daniel Schmidt for

technical support. We thank the Austrian Science Fund FWF

for ﬁnancial support (Grant No. P 22909).

(28) Mannerstedt, K.; Segerstedt, E.; Olsson, J.; Oscarson, S. Org.

Biomol. Chem. 2008, 6, 1087.

(29) Ekelof, K.; Oscarson, S. J. Carbohydr. Chem. 1995, 14, 299.

(30) Boltje, T. J.; Buskas, T.; Boons, G.-J. Nature Chem. 2009, 1, 611.

(31) Brimacombe, J. S.; Kabir, A. K. M. S. Carbohydr. Res. 1986, 152,

329.

̈

REFERENCES

■

(1) Raetz, C. R. H.; Whitfield, C. Annu. Rev. Biochem. 2002, 71, 635.

(2) Holst, O.; Muller-Loennies, S. Microbial polysaccharide

̈

structures. In Comprehensive Glycoscience. From Chemistry to Systems

Biology; Kamerling, J. P., Boons, G.-J., Lee, Y. C., Suzuki, A., Taniguchi,

N., Voragen, A. G. J., Eds.; Elsevier Inc.: Amsterdam, 2007; Vol. 1, p

123.

(3) Gronow, S.; Brade, H. J. Endotoxin Res. 2001, 7, 3.

(4) Beutler, B.; Rietschel, E. T. H. Nature Rev. Immun. 2003, 3, 169.

(5) Bryant, C. E.; Spring, D. R.; Gangloff, M.; Gay, N. J. Nature Rev.

Microbiol. 2010, 8, 8.

(6) Holst, O.; Molinaro, A. Core region and lipid A components of

lipopolysaccharides, P. In Microbial glycobiology: structures, relevance

and applications; Moran, A., Brennan, P., Holst, O., von Itzstein, M.,

Eds.; Elsevier: Amsterdam, 2009; p 29.

(7) Wilkinson, S. G. Prog. Lipid Res. 1996, 35, 283.

(8) Holst, O. FEMS Microbiol. Lett. 2007, 271, 3.

(9) Holst, O. Chemical structure of the core region of lip-

opolysaccharides. In Endotoxin in Health and Disease; Brade, H.,

Opal, S. M., Vogel, S. N., Morrison, D., Eds.; Marcel-Dekker, Inc.:

New York, 1999; p 115.

(10) Tsai, C.-M.; Jankowska-Stephens, E.; Mizanur, R. M.; Cipollo, J.

F. J. Biol. Chem. 2009, 284, 4616.

(11) Yamasaki, R.; Maruyama, T.; Yabe, U.; Asuka, S. J. Biochem.

2005, 137, 487.

(12) Di Padova, F. E.; Brade, H.; Barclay, G. R.; Poxton, I. R.; Liehl,

E.; Schuetze, E.; Kocher, H. P.; Ramsay, G.; Schreier, M. H.;

McClelland, D. B.; Rietschel, E. T. Infect. Immun. 1993, 61, 3863.

(32) Bannwarth, W.; Trzeciak, A. Helv. Chim. Acta 1987, 70, 175.

(33) Ziegler, T.; Dettmann, R.; Duszenko, M.; Kolb, V. Carbohydr.

Res. 1996, 295, 7.

(34) Ziegler, T.; Dettmann, R.; Duszenko, M.; Kolb, V. J. Carbohydr.

Chem. 1994, 13, 81.

(35) Nelson, T. D.; Crouch, R. D. Synthesis 1996, 1031.

(36) Schmidt, R. R.; Kinzy, W. In Advances in Carbohydrate Chemistry

and Biochemistry; Horton, D., Ed.; Academic Press: San Diego, 1994;

Vol. 50, p 21.

(37) Paulsen, H.; Wulff, A.; Brenken, M. Liebigs Ann. Chem. 1991,

1127.

(38) Artner, D.; Stanetty, C.; Mereiter, K.; Zamyatina, A.; Kosma, P.

Carbohydr. Res. 2011, 346, 1739.

(39) Yu, B.; Tao, H. Tetrahedron Lett. 2001, 42, 2405.

́

(40) Adinolfi, M.; Iadosini, A.; Ravida, A. Synlett 2006, 583.

(41) Wildemann, D.; Erdmann, F.; Hernandez, A. B.; Stoller, G.;

Zhou, X. Z.; Fanghaenel, J.; Schutkowski, M.; Lu, K. P.; Fischer, G. J.

Med. Chem. 2006, 49, 2147.

(42) Dowden, J.; Moreau, C.; Brown, R. S.; Berridge, G.; Galione, A.;

Potter, B. V. L Angew. Chem., Int. Ed. 2004, 43, 4637.

(43) Grzeszczyk, B.; Holst, O.; Muller-Loennies, S.; Zamojski, A.

̈

Carbohydr. Res. 1998, 307, 55.

(44) Stewart, A.; Bernlind, C.; Martin, A.; Oscarson, S.; Richards, J.

C.; Schweda, E. K. H. Carbohydr. Res. 1998, 313, 193.

(13) Muller-Loennies, S.; Brade, L.; MacKenzie, C. R.; Di Padova, F.

̈

E.; Brade, H. J. Biol. Chem. 2003, 278, 25618.

(14) Muller-Loennies, S.; Brade, L.; Brade, H. Int. J. Med. Microbiol.

̈

2007, 297, 321.

(15) Gomery, K.; Muller-Loennies, S.; Brooks, C. L.; Brade, L.;

̈

Kosma, P.; Di Padova, F.; Brade, H.; Evans, S. V. Proc. Natl. Acad. Sci.

U.S.A. 2012, 109, 20877.

(16) Park, B. S.; Song, D. H.; Kim, H. M.; Choi, B. S.; Lee, H.; Lee, J.

O. Nature 2009, 458, 1191.

(17) Wang, H.; Head, J.; Kosma, P.; Brade, H.; Muller-Loennies, S.;

̈

Sheikh, S.; McDonald, B.; Smith, K.; Cafarella, T.; Seaton, B.; Crouch,

E. Biochemistry 2008, 47, 710.

(18) Jaipuri, F. A.; Collet, B. Y.M.; Pohl, N. L. Angew. Chem., Int. Ed.

2008, 47, 1707.

Q

dx.doi.org/10.1021/jo402312x | J. Org. Chem. XXXX, XXX, XXX−XXX

Article Doi

Convergent synthesis of 4-o-phosphorylatedl-glycero-d-manno-heptosyl lipopolysaccharide core oligosaccharides based on regioselective cleavage of a 6,7-o-tetraisopropyldisiloxane-1,3-diyl protecting group

DOI: 10.1021/jo402312x

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