Stereoselective Synthesis of Diglycosyl Diacylglycerols with Glycosyl Donors Bearing a β-Stereodirecting 2,3-Naphthalenedimethyl Protecting Group

DOI: 10.1021/acs.joc.0c02121

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Journal of Organic Chemistry p. 16166 - 16181 (2020)

Update date:2022-08-04

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Authors:

Yagami, Nahoko

Vibhute, Amol M.

Tanaka, Hide-Nori

Komura, Naoko

Imamura, Akihiro

Ishida, Hideharu

Ando, Hiromune

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Article abstract of DOI:10.1021/acs.joc.0c02121

Diglycosyl diacylglycerols (DGDGs) are major components of Gram-positive bacterial plasma membranes and are involved in the immune response systems. The chemical synthesis of DGDGs has been highly demanded, as it will allow the elucidation of their biological functions at the molecular level. In this study, we have developed a novel β-stereodirecting 2,3-naphthalenedimethyl (NapDM) protecting group that is orthogonal to protecting groups commonly used in oligosaccharide synthesis. The NapDM group can be easily cleaved under TFA-mediated acidic conditions. Futhermore, we demonstrated the application of this protecting group to an acyl protecting-group-free strategy by utilizing the NapDM group for the synthesis of DGDGs. This strategy features the use of the β-stereodirecting NapDM group as an acid-cleavable permanent protecting group and late-stage glycosylation of monoglycosyl diacylglycerol acceptors, enabling the stereoselective synthesis of three different bacterial DGDGs with unsaturated fatty acid chain(s).

Full text of DOI:10.1021/acs.joc.0c02121

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Article

Stereoselective Synthesis of Diglycosyl Diacylglycerols with Glycosyl

Donors Bearing a β‑Stereodirecting 2,3-Naphthalenedimethyl

Protecting Group

Nahoko Yagami,^⊥Amol M. Vibhute,^⊥Hide-Nori Tanaka,*^,⊥Naoko Komura, Akihiro Imamura,

Hideharu Ishida, and Hiromune Ando *

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ABSTRACT: Diglycosyl diacylglycerols (DGDGs) are major com-

ponents of Gram-positive bacterial plasma membranes and are

involved in the immune response systems. The chemical synthesis

of DGDGs has been highly demanded, as it will allow the elucidation

of their biological functions at the molecular level. In this study, we

have developed a novel β-stereodirecting 2,3-naphthalenedimethyl

(NapDM) protecting group that is orthogonal to protecting groups

commonly used in oligosaccharide synthesis. The NapDM group can

be easily cleaved under TFA-mediated acidic conditions. Futhermore,

we demonstrated the application of this protecting group to an acyl

protecting-group-free strategy by utilizing the NapDM group for the synthesis of DGDGs. This strategy features the use of the β-

stereodirecting NapDM group as an acid-cleavable permanent protecting group and late-stage glycosylation of monoglycosyl

diacylglycerol acceptors, enabling the stereoselective synthesis of three diﬀerent bacterial DGDGs with unsaturated fatty acid

chain(s).

tuberculosis β-gentiobiosyl diacylglycerides and various ana-

logues using a benzoyl protecting group at the C-2-position for

β-glycosidic bond formation and showed that β-gentiobiosyl

diacylglyceride signaling through macrophage-inducible Ca²⁺-

dependent lectin receptor (Mincle) varied drastically depend-

ing upon the acyl chain length.^5gHowever, the C-2 acyl

functionality is incompatible with the incoming fatty acyl

chains. During these syntheses, the C-2 acyl functionality must

be replaced with an ether-type protecting group such as a

benzyl group before the introduction of fatty acid chains into

the 1,2-positions of the glycerol moiety. In addition, the acyl

protection at the C-2-position leads to the formation of

orthoester side products during the glycosylation reaction.⁶In

order to avoid these problems and improve synthetic

eﬃciency, Nishida et al. accomplished the chemical synthesis

of two diﬀerent DGDGs from Mycoplasma pneumoniae via β-

selective glycosylations using the nitrile solvent eﬀect⁷with

per-O-benzylated glycosyl donors having a nonmalodorous

thiosalicyl leaving group.^5cFurthermore, Fujimoto et al.

INTRODUCTION

■

Glycoglycerolipids are abundant in plants,¹algae,²and some

bacteria³and include diglycosyl diacylglycerols (DGDGs),

which are major components of Gram-positive bacterial plasma

membranes. DGDGs are composed of a polar disaccharide

head that is glycosidically linked to the 3-position of a

nonpolar 1,2-diacyl-sn-glycerol tail. Over the past decade,

several reports have shown that bacterial DGDGs are involved

in the immune response systems.⁴Kronenberg et al. reported

DGDG-containing glycolipids, from Streptococcus pneumoniae

and group B Streptococcus, presented by CD1d, were

recognized by human natural killer T cells.^4aA DGDG in

Enterococcus faecalis was recently reported to modulate

lipoprotein expression and activation of the host immune

system.^4cTherefore, bacterial DGDGs have attracted increas-

ing attention from researchers. However, the availability of

DGDGs from the natural sources is limited because of their

heterogeneity with respect to not only the sugar component

and glycosidic linkage of the disaccharide but also the length

and unsaturation of the acyl chain. To overcome this supply

problem and further elucidate their biological functions at the

molecular level, their chemical synthesis has been in high

demand. To date, most of synthetic studies on DGDGs

possessing β-glycosidic linkage(s)⁵utilize neighboring group

participation by a C-2 acyl functionality on glycosyl donors,

which enables a β-selective glycosylation reaction. For instance,

Williams et al. have chemically synthesized Mycobacterium

Special Issue: A New Era of Discovery in Carbohy-

drate Chemistry

Received: September 3, 2020

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recently reported the convergent synthesis of digalactosyl

diacylglycerols without the use of acyl groups; instead, they

employed allyl and alloc groups as permanent protecting

groups that can be easily removed under mild reaction

conditions using a ruthenium catalyst.^5h

Recently, we developed a β-selective glycosylation reaction

using glycopyranosyl donors bearing 2,3-trans-fused cyclic

protecting groups,⁸which was inspired by the β-selective

glycofuranosylation method developed by Lowary and co-

workers.⁹Cyclic protecting groups, such as o-xylylene (Xyln)

and 1,1,3,3-tetraisopropyldisiloxane-1,3-diyl (TIPDS) group,

have been proven to give excellent β-selectivity. Based on a

conformational study of the oxocarbenium intermediate of a

Xyln-protected donor via NMR analysis of a model derivative

and DFT computational simulations, the β-selective glyco-

sylation reaction is speculated to proceed predominantly via a

⁴H₃conformational intermediate. The preference for a H₃

conformation can be rationalized by the presence of a rigid 2,3-

trans-fused ring. Very recently, we achieved the chemical

synthesis of diglucosyl diacylglycols with diﬀerent saturated

fatty acyl chains using a TIPDS-protected glucosyl donor.⁵ⁱ

However, it was found that the TIPDS group was often

aﬀected during protecting group manipulations such as the

acid hydrolysis of acetals and etheriﬁcation under basic

conditions due to its acid and base susceptibility. Moreover,

this synthetic method still utilized the same late-stage

introduction of fatty acyl chains into the diglycosyl glycerols

as the aforementioned syntheses. Thus, these methods do not

facilitate the diversity of the glycan structure, only allowing the

synthesis of DGDGs with structural diversity in fatty acid

chains. Herein, we report the development of (i) the 2,3-

naphthalenedimethyl (NapDM) group as an acid-cleavable

equivalent of the β-stereodirecting Xyln group and (ii) an acyl

protecting-group-free strategy for the synthesis of DGDGs

based on the NapDM group, with the aim of expanding the

scope of the chemical synthesis of DGDGs (Figure 1). This

strategy utilizes the NapDM group as an acid-cleavable

permanent protecting group as well as late-stage glycosylation

of monoglycosyl diacylglycerol (MGDG) acceptors to

construct the glycan structure of DGDGs, enabling the

stereoselective synthesis of three diﬀerent DGDGs with

unsaturated fatty acyl chain(s) (unsaturated DGDGs): 3-O-

[6-O-(β-^D-glucopyranosyl)-β-D-glucopyranosyl]-1,2-di-O-ole-

noyl-sn-glycerol (1)^3bfound in Mycoplasma genitalium; a

derivative of 1 with galactose at the nonreducing end, 3-O-[6-

O-(β-^D-galactopyranosyl)-β-D-glucopyranosyl]-1,2-di-O-oleno-

yl-sn-glycerol (2); and 3-O-[6-O-(β-^D-glucopyranosyl)-β-D-

galactopyranosyl]-2-O-palmitoleoyl-1-O-stearoyl-sn-glycerol

(3)^4cfound in Mycoplasma pneumoniae (Figure 2).

Figure 1. Background for the chemical synthesis of DGDGs.

Figure 2. Structures of the targeted unsaturated DGDGs.

mediated acidic conditions,¹³the NapDM group in 7 was

selectively cleaved within 2 h at room temperature, giving the

corresponding diol 8 in 80% yield. This encouraging result

prompted us to utilize the NapDM protecting group for a

TFA-cleavable protection strategy in the chemical synthesis of

unsaturated DGDGs without using acyl protecting groups.

With glucosyl donor 7 in hand, we examined whether the

donor gave high β-selectivity on the glycosidation reaction

with the galactose acceptor 9, similar to that of the Xyln-

protected donor previously reported by our group (Scheme 2).

Using the NIS-TfOH promoter system, 7 was coupled with 9

at −80 °C to provide the disaccharide 10 in 99% yield with

excellent β-selectivity (β/α = >15:1). This stereoselectivity is

consistent with our previous results when using the Xyln donor

(93%, β/α = 11.5:1).⁸Therefore, we envisaged that the

NapDM group could be used as a β-stereodirecting protecting

group in glycosylation reactions.

RESULTS AND DISCUSSION

■

In order to demonstrate the applicability of the NapDM

protecting group, we initially prepared a novel glucosyl donor 7

bearing a NapDM protecting group at the 2- and 3-positions

and carried out its acid cleavage (Scheme 1). 2,3-O-NapDM

protection¹⁰of the known 4,6-O-benzylidene acetal 4¹¹was

carried out using 2,3-bis(bromomethyl)naphthalene and NaH

in DMF to obtain the corresponding compound 5 in 95%

yield. The regioselective reductive opening of the benzylidene

acetal using Et₃SiH and PhBCl₂in CH₂Cl₂aﬀorded the

desired product 6, which had a free hydroxyl group at the 6-

position, in 94% yield. Subsequent benzylation successfully

aﬀorded the thioglycoside donor 7 in 83% yield. Under TFA-

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Scheme 1. Preparation of Glucosyl Donor 7

Scheme 3. Retrosynthetic Analysis of DGDGs 1−3

Abbreviations: DMF, N,N-dimethylformamide; Bn, benzyl; TFA,

triﬂuoroacetic acid.

Scheme 2. Glycosidation of Donor 7

known 4,6-O-p-anisylidene acetal 15¹⁷were protected with the

NapDM group using 2,3-bis(bromomethyl)naphthalene and

NaH under dilute conditions to give the NapDM-protected

thioglucoside 16 in 81% yield. Subsequent regioselective

reductive opening of the p-anisylidene acetal using Et₃SiH

and PhBCl₂aﬀorded 17, which was then silylated with tert-

butyldiphenylsilyl chloride to provide the fully protected

thioglycoside 18 in 70% yield over two steps. The

corresponding trichloroacetimidate 19 was prepared by

chemoselective hydrolysis of the anomeric phenylsulfenyl

group in 18, followed by treatment with Cl₃CCN and DBU.

Similarly, the 4,6-O-p-anisilidene acetal of galactose, 20,¹⁸was

converted into thioglycoside 23 and trichloroacetimidate 24 by

the above-mentioned reaction sequence.

The glycerol acceptor 14 was synthesized in two

straightforward steps from 3-O-benzoylated sn-glycerol 25,

which was prepared from a commercially available 1,2-O-

isopropylidene derivative following the procedure reported by

Santaniello et al.¹⁹Compound 25 was exposed to acetalization

with p-nitrobenzaldehyde, providing the two diastereomers

26a and 26b in 34 and 37% yields, respectively. The absolute

conﬁguration of the newly generated stereogenic center was

determined by X-ray crystallographic analysis of 26a (Scheme

5 and see Supporting Information). Debenzoylation under

Abbreviations: NIS, N-iodosuccinimide; TfOH, triﬂuoromethane-

sulfonic acid.

Having demonstrated the orthogonality and β-selectivity of

the NapDM protecting group, we turned our attention toward

the synthesis of unstaturated DGDGs without using acyl

protecting groups (Scheme 3). Retrosynthetic analysis of the

targeted DGDGs 1−3 indicated that they could be synthesized

by the β-selective glycosylation reaction of MGDG 12 with the

2,3-O-NapDM-protected glycosyl imidate 11, with subsequent

global deprotection under acidic conditions (Scheme 3). In a

recent report from Kulkarni et al., a MGDG acceptor has been

used in the synthesis of the lipid-anchor-attached core

trisaccharide of lipoteichoic acids of Streptococcus pneumonia

and Streptococcus oralis Uo5.¹⁴Acceptors with the structure 12

could be accessed from glycosyl thioglycoside 13 and glycerol

14 via the following three steps: β-selective glycosylation

reaction, removal of the p-nitrobenzylidene group on the

glycerol moiety, and introduction of unsaturated fatty acyl

chain(s). The use of an electron-deﬁcient p-nitrobenzylidene¹⁵

to protect the 1,2-diol of the sn-glycerol in 14 allows the

suppression of intermolecular isomerizations when 1,2-O-

isopropylidene-protected sn-glycerol was used as an acceptor.¹⁶

Furthermore, the p-nitrobenzylidene protecting group allows

for the chemoselective deprotection under mild conditions in

the presence of other acid-labile protecting groups such as the

p-methoxyphenylmethyl (MPM) group.

Zemplen conditions aﬀorded the p-nitrobenzylidene-protected

glycerol acceptors 14a and 14b in 92 and 89% yields,

respectively.

For the construction of glycosyl glycerol fragments,

acceptors 14a and 14b were glycosylated with thioglycoside

donors 18 and 23 in CH₂Cl₂at −80 °C by the NIS-TESOTf

activation method (Table 1).²⁰The use of TESOTf as an acid

source rather than TfOH not only decreased the amount of

acid required to 0.15 equiv due to its high solubility in organic

solvents but also avoided the undesired removal of the MPM

group from the glycosylated products that was observed when

using 0.3 equiv of TfOH. All the glycosylations proceeded β-

The synthesis commenced with the preparation of glucose

and galactose donors with suitable protection pattern (Scheme

4). The free hydroxyl groups at the 2- and 3-positions of the

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Scheme 4. Preparation of Donors 18, 19, 23, and 24

Scheme 5. Synthesis of Glycerol Acceptor 14

Abbreviations: TMSOTf, trimethylsilyl triﬂuoromethanesulfonate;

HMDSO, hexamethyldisiloxane; THF, tetrahydrofuran.

Table 1. Construction of Glycosyl Glycerol Framework

entry

donor

acceptor

reaction time

24 h

product

isolated yield

(Glc)

(Gal)

14a

β: 61%

α: 34%

β: 58%

α: 39%

β: 72%

α: 24%

β: 73%

α: 24%

14b

14a

14b

24 h

4 h

(Gal)

Abbreviations: PNP, p-nitrophenyl; TESOTf, triethylsilyl triﬂuor-

omethanesulfonate.

However, we speculate that the lesser β-selectivities while

using acceptors 14a,b could be attributed with the nitro-

benzylidene protecting group, making it mismatched acceptors,

because the better β-selectivity (β/α = 6.7:1) was obtained

during coupling of the Xyln donor with the 1,2-isopropylidene-

protected glycerol acceptor.

To establish a TFA-cleavable protection strategy for the

chemical synthesis of unsaturated DGDGs, we ﬁrst demon-

strated the synthesis of the targeted molecules 1 and 2

(Scheme 6). Chemoselective removal of the p-nitrobenzyli-

dene protecting groups in 27β and 28β using zinc and AcOH²¹

in wet THF provided the 1,2-diol compound 31, which was

subjected to acylation with oleic acid followed by desilylation

using TBAF to obtain the monoglucosyl diacylglycerol

acceptor 32. For the synthesis of 1, glucosylation of 32 with

glucosyl imidate 19 was performed at −80 °C in the presence

of a catalytic amount of BF₃·Et₂O, yielding the DGDG

framework 33 in 80% yield with excellent β-selectivity (β/α =

>15:1). After removal of the TBDPS group of 33 by treatment

with TBAF and AcOH, global deprotection of 34 was

conducted using a mixture of TFA and toluene as a solvent,

with anisole being used as a scavenger to furnish the desired

product 1 in a satisfactory yield. Turning to the next target

molecule 2, compound 32 was galactosylated with galactosyl

imidate 24 under the aforementioned reaction conditions.

Abbreviations: MPM, p-methoxyphenylmethyl; TBDPS, tert-butyldi-

phenylsilyl; NBS, N-bromosuccinimide; DBU, 1,8-diazabicyclo-

[5.4.0]undec-7-ene; TBAI, tetra-n-butylammonium iodide.

selectively without acetal isomerization to give the desired O-

glycosides 27−30 in high yields (entries 1−4). The structures

of the β-glycosides were conﬁrmed by the large J_1,2coupling

constants in the H NMR spectra (7−8 Hz), whereas smaller

J_1,2coupling constants (3−4 Hz) were observed for α-

glycosides. Moreover, the anomeric carbon signals of the β-

glycosides appeared at magnetic ﬁelds (approximately 103

ppm) lower than those of the α-glycosides (around 98 ppm).

The β-selectivities obtained with the galactose donor 23 (β/α

= 3:1, entries 3 and 4) were slightly higher than those obtained

with the glucose donor 18 (β/α = 1.5−1.8:1, entries 1 and 2).

These results indicated that the stereochemistry of the p-

nitrobenzylidene acetal exerted no inﬂuence on the β-

selectivity of the glycosylation with donors 18 and 23.

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Scheme 6. Synthesis of DGDGs 1 and 2

Abbreviations: DCC, N,N′-dicyclohexylcarbodiimide; DMAP, 4-dimethylaminopyridine; TBAF, tetra-n-butylammonium ﬂuoride.

However, the yield of the desired coupling product 35 was

only 50% without β-selectivity (β/α = ∼1:1). Additionally, the

corresponding galactosyl ﬂuoride was observed as a by-

product,²²which led to a change in the activator for

glycosylation to TMSOTf instead of BF₃·Et₂O, which

improved both the yield and β-selectivity (62%, β/α =

1.8:1). Unfortunately, it seemed to be a mismatched donor−

acceptor pairing between 24 and 32. The synthesis of the non-

natural DGDG 2 was then completed following the same

deprotection sequence as used for natural DGDG 1.

Based on the established acid-cleavable protection strategy,

we addressed the preparation of the synthetically challenging

DGDG 3, which possesses two diﬀerent acyl groups with

saturated and unsaturated chains (Scheme 7). The 1,2-diol

compound 37, derived from 29β and 30β via removal of the p-

nitrobenzylidene under reductive conditions, was exposed to

tin-mediated acylation²³with stearoyl chloride at the 1-

position of the glycerol moiety to give the monoacylated

compound 38 in 78% yield. Palmitoleoylation of the remaining

hydroxyl group and subsequent TBDPS removal provided the

diacylated product 39 in 74% yield over two steps. Since the 4-

O-MPM protecting group in the axial direction might reduce

the reactivity of a hydroxyl group at the 6-position of the

galactose moiety, the acid-labile group was cleaved using the

TMSCl/SnCl₂/anisole system²⁴to obtain the galactosyl

diacylglycerol acceptor 40 in 89% yield. Using a catalytic

amount of BF₃·Et₂O, coupling of 40 with glucosyl imidate 19

led to a good yield of the desired glucoside 41 (67%) with high

β-selectivity (β/α = 8:1). A tiny amount of the corresponding

regioisomer, glucosylated at the 4-position of the galactose

moiety, was also observed. The glucosylated position was then

conﬁrmed by acetylation of the remaining free hydroxyl group.

Finally, all the protecting groups were removed by a two-step

reaction sequence to successfully aﬀord the target DGDG 3.

CONCLUSIONS

■

We have developed an acid-cleavable and β-stereodirecting

NapDM protecting group for glycosyl donors for glycan

synthesis. This group not only served as a simultaneous

protecting group for the trans-equatorially oriented vicinal

diols but also inﬂuenced the outcome of the glycosylation

reaction, giving rise to the β-glycosides. The use of the

NapDM protecting group prevented the formation of

orthoester side products during the glycosylation reaction,

which can be a problem when using the C-2 acyl functionality.

The NapDM group was used to establish a TFA-cleavable

protection strategy for acyl protecting-group-free synthesis of

DGDGs. The key feature of this strategy was the β-

stereoselective glycosylation of MGDG acceptors with

NapDM-protected donors at a later stage. β-Stereoselective

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Scheme 7. Synthesis of DGDG 3

Abbreviation: TMSCl, trimethylsilyl chloride.

Bruker). Optical rotations were measured with a high-sensitivity

polarimeter SEPA-300 (Horiba, Kyoto, Japan).

glycosylation enabled the synthesis of three diﬀerent syntheti-

cally challenging unsaturated DGDGs. The strategy developed

in this study would allow rapid access to not only the natural

DGDGs but also functionalized derivatives, allowing for the

elucidation of their biological functions.

Synthetic Procedure. 3-O-[6-O-(β-^D-Glucopyranosyl)-β-D-glu-

copyranosyl]-1,2-di-O-oleoyl-sn-glycerol (1). To a solution of 34

(30 mg, 20 μmol) in TFA/toluene (10:1, 0.10 mL) was added anisole

(22 μL, 0.20 mmol) at 4 °C using an ice bath. After being stirred for

24 h at the same temperature as the reaction was monitored by TLC

(CHCl₃/MeOH = 5:1), the reaction was quenched by the addition of

NEt₃at 4 °C using an ice bath. The reaction mixture was

concentrated, and the resulting residue was puriﬁed by ﬂash column

chromatography on silica gel using toluene/EtOAc (10:1) as the

eluent and Sephadex LH-20 using CHCl₃/MeOH (1:1) as the eluent

EXPERIMENTAL SECTION

■

General Methods. All reactions were performed under an argon

atmosphere. All reactions that required heating were performed in an

oil bath. All chemicals were purchased from commercial suppliers and

used without further puriﬁcation. Compound 9 was purchased from

Sigma-Aldrich (St. Louis, MO). Molecular sieves were purchased

from FUJIFILM Wako Pure Chemical Corporation (Osaka, Japan)

and predried at 300 °C for 2 h in a muﬄe furnace and then dried in a

ﬂask at 300 °C for 2 h in vacuo prior to use. Dry solvents for reaction

media (CH₂Cl₂, toluene, THF, CH₃CN, DMF, and pyridine) were

purchased from Kanto Chemical Co. Inc. (Tokyo, Japan) and used

without puriﬁcation. TLC analyses were performed on Merck TLC

plates (silica gel 60F254 on glass plate). Compound detection on

TLC was carried out either by exposure to UV light (253.6 nm) or by

soaking in H₂SO₄solution (10% in EtOH) or phosphomolybdic acid

solution (20% in EtOH) followed by heating. Silica gel column

chromatography separations were performed with a ﬂash column

chromatography system. Silica gel (80 mesh and 300 mesh; Fuji

Silysia Co. (Aichi, Japan)) was used for ﬂash column chromatography.

The quantity of silica gel was typically 100 to 200 times the weight of

the crude sample. Sephadex (Pharmacia LH-20) was used for size-

exclusion chromatography. Solvent systems for chromatography are

to give 1 (13 mg, 68%) as a colorless syrup: [α]_D−18.0 (c 0.05,

CHCl₃); H NMR (500 MHz, CDCl₃/CD₃OD = 1:2) δ 5.38−5.26

(m, 5 H, 4 CH = CH, H-2^Gro), 4.43 (dd, 1 H, J_vic= 2.9 Hz, J_gem= 12.1

Hz, H-1a^Gro), 4.36 (d, 1 H, J_1,2= 7.8 Hz, H-1^Glc), 4.27 (d, 1 H, J_1,2

7.8 Hz, H-1^Glc), 4.22 (dd, 1 H, J_vic= 6.9 Hz, H-1b^Gro), 4.17 (dd, 1 H,

J_5,6a= 2.0 Hz, J_gem= 11.5 Hz, H-6a^Glc), 3.98 (dd, 1 H, J_vic= 5.5 Hz,

_gem= 11.0 Hz, H-3a^Gro), 3.87 (dd, 1 H, J_5,6a= 2.1 Hz, J_gem= 12.1 Hz,

H-6a^Glc), 3.79−3.74 (m, 2 H, H-6b^Glc, H-3b^Gro), 3.68 (dd, 1 H, J_5,6b

5.3 Hz, H-6b^Glc), 3.46−3.17 (m, 8 H, H-2^Glc, H-3^Glc, H-4^Glc, H-5^Glc, H-

^Glc, H-3^Glc, H-4^Glc, H-5^Glc), 2.35−2.31 (m, 4 H, 2 O(CO)CH₂),

2.03−1.98 (m, 8 H, 4 CHCHCH₂), 1.68−1.20 (m, 44 H, 22 CH₂),

0.91−0.88 (m, 6 H, 2 Me); ¹³C{¹H} NMR (125 MHz, CDCl₃/

CD₃OD = 1:2) δ 175.0, 174.8, 130.9, 130.7, 104.8, 104.6, 79.4, 79.3,

79.1, 78.9, 77.9, 77.7, 77.0, 75.0, 74.8, 71.7, 71.5, 71.3, 69.9, 68.9,

62.7, 49.9, 49.6, 35.1, 34.9, 33.0, 30.8, 30.7, 30.6, 30.4, 30.3, 30.2,

28.1, 26.0, 23.7, 14.5; HRMS (ESI) m/z [M + Na]⁺calcd for

C₅₁H₉₂O₁₅Na 967.6328; found [M + Na]⁺967.6328.

speciﬁed as v/v ratios. H and ¹³C NMR spectra were recorded on

3-O-[6-O-(β-^D-Galactopyranosyl)-β-D-glucopyranosyl]-1,2-di-O-

oleoyl-sn-glycerol (2). To a solution of 36 (8.1 mg, 5.4 μmol) in

toluene (0.1 mL) were added anisole (5.9 μL, 54 μmol) and TFA (1.0

mL) at 4 °C using an ice bath. After being stirred for 4 h at room

temperature as the reaction was monitored by TLC (CHCl₃/MeOH

= 5:1), the reaction mixture was concentrated. The residue was

puriﬁed by ﬂash column chromatography on silica gel using CHCl₃/

MeOH (20:1→15:1→5:1) as the eluent to give 2 (5.6 mg, 95%) as a

Avance III 500 spectrometers (Bruker, Billerica, MA, USA). Chemical

shifts are expressed in ppm (δ) relative to the Me₄Si signal (0.00

ppm). Each of the Glc units in compounds 1, 33, and 34 is numbered

using letters a and b: nonreducing end Glc(a), reducing end Glc(b)

(see Supporting Information). Structural assignments were made with

additional information from 2D NMR (¹H−¹H COSY, HMBC, and

HMQC) experiments. High-resolution mass spectrometry (ESI-TOF

MS) data were obtained with a mass spectrometer (micrOTOF,

white solid: [α]_D−16.6 (c 0.6, CHCl₃); ¹H NMR (500 MHz,

https://dx.doi.org/10.1021/acs.joc.0c02121

J. Org. Chem. XXXX, XXX, XXX−XXX

The Journal of Organic Chemistry

pubs.acs.org/joc

Article

CDCl₃/CD₃OD = 1:1) δ 5.38−5.26 (m, 5 H, 4 CH = CH, H-2^Gro),

4.41 (dd, 1 H, J_vic= 3.0 Hz, J_gem= 12.1 Hz, H-1a^Gro), 4.30 (d, 1 H, J_1,2

= 7.7 Hz, H-1^Gal), 4.27 (d, 1 H, J_1,2= 7.8 Hz, H-1^Glc), 4.24 (dd, 1 H,

Phenyl 4-O-benzyl-2,3-O-[2,3-bis(methyl)naphthele]-1-thio-β-^D-

glucopyranoside (6). To a solution of 5 (184 mg, 300 μmol) in

CH₂Cl₂(3.0 mL) was added 4 Å molecular sieves (184 mg). After

being stirred for 30 min at room temperature, the mixture was then

cooled to −80 °C using a low constant temperature bath.

Subsequently, Et₃SiH (112 μL, 660 μmol) and PhBCl₂(87 μL, 660

μmol) were added to the reaction mixture at −80 °C. After being

stirred for 30 min at the same temperature as the reaction was

monitored by TLC (n-hexane/EtOAc = 3:1), the reaction was

quenched by the addition of NEt₃and MeOH at −80 °C. The

resulting mixture was ﬁltered through a pad of Celite, and the pad was

washed with CHCl₃. The combined ﬁltrate and washings were

successively washed with saturated aqueous NaHCO₃, H₂O, and

brine. The organic layer was dried over Na₂SO₄, ﬁltered oﬀ, and

concentrated. The resulting residue was puriﬁed by ﬂash column

chromatography on silica gel using n-hexane/EtOAc (10:1) as the

_vic= 6.7 Hz, H-1b^Gro), 4.17 (dd, 1 H, J_5,6a= 1.5 Hz, J_gem= 11.1 Hz, H-

6a^Glc), 3.97 (dd, 1 H, J_vic= 5.4 Hz, J_gem= 11.0 Hz, H-3a^Gro), 3.87 (d, 1

H, J_3,4= 3.1 Hz, H-4^Gal), 3.83−3.73 (m, 4 H, H-5^Gal, H-6a^Gal, H-6b^Glc

H-3b^Gro), 3.58 (dd, 1 H, J_2,3= 9.6 Hz, H-2^Gal), 3.53−3.48 (m, 2 H, H-

^Gal, H-5^Glc), 3.47−3.38 (m, 3 H, H-3^Gal, H-6b^Gal, H-4^Glc), 3.25 (dd, 1

H, J_2,3= 8.1 Hz, H-2^Glc), 2.36−2.32 (m, 4 H, 2 O(CO)CH₂), 2.04−

2.00 (m, 8 H, 4 CH = CHCH₂), 1.63−1.17 (m, 44 H, 22 CH₂),

0.91−0.88 (m, 6 H, 2 Me); ¹³C{¹H} NMR (125 MHz, CDCl₃/

CD₃OD = 1:1) δ 174.6, 174.3, 130.4, 130.2, 104.6, 104.1, 78.7, 78.3,

76.9, 76.1, 75.8, 74.1, 74.0, 71.9, 70.9, 70.6, 69.5, 69.2, 68.5, 63.3,

62.0, 49.6, 34.8, 34.6, 34.2, 32.4, 32.4, 32.3, 30.2, 30.1, 30.0, 29.8,

29.8, 29.7, 29.6, 29.6, 27.7, 27.6, 25.5, 25.4, 25.4, 23.1, 14.3; HRMS

(ESI) m/z [M + Na]⁺calcd for C₅₁H₉₂O₁₅Na 967.6328; found [M +

Na]⁺967.6326.

eluent to give 6 (174 mg, 94%) as a white solid: [α]_D+28.8 (c 3.0,

CHCl₃); ¹H NMR (500 MHz, CDCl₃) δ 7.86−7.05 (m, 16 H, 4 Ar),

5.34 (d, 1 H, J_gem= 13.0 Hz, ArCH₂), 5.30 (d, 1 H, J_gem= 14.0 Hz,

ArCH₂), 5.24 (d, 1 H, ArCH₂), 5.09 (d, 1 H, ArCH₂), 5.00 (d, 1 H,

3-O-[6-O-(β-^D-Glucopyranosyl)-β-D-galactopyranosyl]-2-O-pal-

mitoleoyl-1-O-stearoyl-sn-glycerol (3). To a solution of 42 (16 mg,

12 μmol) in TFA/toluene (10:1, 0.10 mL) was added anisole (6.2 μL,

58 μmol) at 4 °C using an ice bath. After being stirred for 4 h at room

temperature as the reaction was monitored by TLC (CHCl₃/MeOH

= 5:1), the reaction was quenched by the addition of NEt₃at 4 °C

using an ice bath. The reaction mixture was concentrated and the

resulting residue was puriﬁed by ﬂash column chromatography on

silica gel using CHCl₃/MeOH (5:1) as the eluent to give 3 (8.2 mg,

_gem= 11.0 Hz, ArCH₂), 4.67 (d, 1 H, ArCH₂), 4.64 (d, 1 H, J_1,2= 9.5

Hz, H-1), 3.78−3.56 (m, 2 H, H-3, H-6a), 3.64 (m, 1 H, H-6b),

3.49−3.43 (m, 2 H, H-2, H-4), 3.37 (m, 1 H, H-5), 1.83 (t, 1 H, J_6a,OH

= J_6b,OH= 6.5 Hz, OH); ¹³C{¹H} NMR (125 MHz, CDCl₃) δ 138.3,

134.9, 134.5, 133.1, 132.9, 131.9, 130.0, 129.0, 128.5, 128.5, 128.1,

127.9, 127.7, 127.5, 127.4, 126.5, 126.4, 86.6, 85.7, 79.1, 79.0, 77.6,

75.0, 73.1, 73.0, 62.4; HRMS (ESI) m/z [M + Na]⁺calcd for

C₃₁H₃₀O₅SNa 537.1706; found [M + Na]⁺537.1703.

78%): [α]_D+47.5 (c 0.1, CHCl₃); H NMR (500 MHz, CDCl₃/

CD₃OD = 1:2) δ 5.35−5.33 (m, 2 H, 2 CH = CH), 5.27 (m, 1 H, H-

Phenyl 4,6-di-O-benzyl-2,3-O-[2,3-bis(methyl)naphthele]-1-thio-

β-^D-glucopyranoside (7). To a solution of 6 (92 mg, 0.17 mmol) in

DMF (0.85 mL) was added NaH [60% in oil] (108 mg, 270 μmol) at

4 °C using an ice bath. The mixture was stirred for 30 min at the same

temperature, and benzyl bromide (101 μL, 850 μmol) was added at 4

°C using an ice bath. After being stirred for 20 h at the same

temperature as the reaction was monitored by TLC (n-hexane/EtOAc

= 3:1), the reaction was quenched by the addition of MeOH. The

resulting mixture was coevaporated with toluene, diluted with CHCl₃,

and washed with H₂O and brine. The organic layer was dried over

Na₂SO₄, ﬁltered oﬀ, and concentrated. The resulting residue was

puriﬁed by ﬂash column chromatography on silica gel using toluene/

CHCl₃(7:1) as the eluent to give 7 (85 mg, 83%) as a white foamy

^Gro), 4.44 (dd, 1 H, J_vic= 2.5 Hz, J_gem= 12.0 Hz, H-1a^Gro), 4.36 (d, 1

H, J_1,2= 8.0 Hz, H-1^Gal), 4.24 (d, 1 H, J_1,2= 7.5 Hz, H-1^Glc), 4.23 (m,

1 H, H-1b^Gro), 4.03−3.96 (m, 2 H, H-4^Gal, H-3a^Gro), 3.91−3.84 (m, 2

H, H-4^Glc, H-6a^Glc), 3.76 (dd, 1 H, J_2,3= 5.5 Hz, J_gem= 11.0 Hz, H-

3b^Gro), 3.72−3.65 (m, 2 H, H-5^Gal, H-6a^Gal), 3.53 (t, 1 H, J_2,3= J_3,4

9.5 Hz, H-3^Glc), 3.52 (dd, 1 H, H-2^Glc), 3.47 (dd, 1 H, J_5,6b= 3.5 Hz,

_gem= 10.0 Hz, H-6b^Glc), 3.94−3.23 (m, 3 H, H-3^Gal, H-6b^Gal, H-5^Glc),

3.21 (dd, 1 H, J_2,3= 9.0 Hz, H-2^Gal), 2.35−2.31 (m, 4 H, 2

O(CO)CH₂), 2.03−2.02 (m, 4 H, 2 CH = CHCH₂), 1.62−1.28 (m,

46 H, 23 CH₂), 0.95−0.88 (m, 6 H, 2 Me); ¹³C{¹H} NMR (125

MHz, CDCl₃/CD₃OD = 1:2) δ 174.9, 174.6, 130.7, 130.5, 105.0,

104.4, 79.1, 78.8, 78.6, 77.7, 77.5, 74.9, 74.7, 74.4, 72.1, 71.5, 71.4,

69.5, 69.1, 68.6, 63.8, 62.5, 49.5, 48.5, 35.0, 34.9, 32.8, 32.7, 30.6,

30.5, 30.5, 30.4, 30.2, 30.1, 30.0, 29.8, 28.0, 28.0, 25.8, 23.5, 14.4;

HRMS (ESI) m/z [M + Na]⁺calcd for C₄₉H₉₀O₁₅Na 941.6172;

found [M + Na]⁺941.6172.

material: [α]_D²⁵+24.0 (c 1.0, CHCl₃); H NMR (500 MHz, CDCl₃)

δ 7.79−7.21 (m, 21 H, 5 Ar), 5.31 (d, 1 H, J_gem= 13.0 Hz, ArCH₂),

5.25 (d, 1 H, J_gem= 14.5 Hz, ArCH₂), 5.21 (d, 1 H, ArCH₂), 5.04 (d,

1 H, ArCH₂), 4.92 (d, 1 H, J_gem= 11.0 Hz, ArCH₂), 4.60 (s, 1 H,

ArCH₂), 4.58 (s, 1 H, ArCH₂), 4.53 (d, 1 H, J_1,2= 7.5 Hz, H-1), 4.47

(d, 1 H, ArCH₂), 3.78−3.73 (m, 2 H, H-3, H-6a), 3.65 (dd, 1 H, J_5,6b

= 4.5 Hz, J_gem= 11.0 Hz, H-6b), 3.51−3.44 (m, 3 H, H-2, H-4, H-5);

¹³C{¹H} NMR (125 MHz, CDCl₃) δ 138.5, 138.3, 135.0, 134.6,

133.5, 133.0, 128.8, 128.4, 128.4, 128.3, 127.7, 127.6, 127.5, 127.5,

127.4, 126.4, 126.3, 86.6, 85.9, 78.9, 78.9, 77.6, 77.6, 75.0, 73.4, 73.1,

73.0, 69.2, 29.7; HRMS (ESI) m/z [M + Na]⁺calcd for

C₃₈H₃₆O₅SNa 627.2176; found [M + Na]⁺627.2177.

Phenyl 4,6-di-O-benzyl-1-thio-β-^D-glucopyranoside (8). Com-

pound 7 (8.1 mg, 13 μmol) was dissolved in toluene/TFA (1:10,

0.10 mL) at room temperature. After being stirred for 2 h at room

temperature as the reaction was monitored by TLC (n-hexane/EtOAc

= 1:1), the reaction mixture was coevaporated with toluene. The

residue was diluted with CHCl₃, and washed with H₂O and brine.

The organic layer was dried over Na₂SO₄, ﬁltered oﬀ, and

concentrated. The resulting residue was puriﬁed by ﬂash column

chromatography on silica gel using n-hexane/EtOAc (3:1) as the

eluent to give 8 (3.6 mg, 80%): the optical and spectroscopic data

([α]_D, ¹H and ¹³C NMR, MS) were identical to the reported value.²⁶

4,6-Di-O-benzyl-2,3-O-[2,3-bis(methyl)naphthele]-β-D-glucopyr-

anosyl]-(1→6)-1,2:3,4-di-O-isopropylidene-α-^D-galactopyranose

(10). To a solution of Glc thioglycoside 7 (73 mg, 0.12 mmol) and 9

(31 mg, 0.12 mmol) in CH₂Cl₂(1.2 mL) were added 4 Å molecular

sieves (60 mg) and NIS (41 mg, 0.18 mmol). After being stirred for

30 min at room temperature, the mixture was then cooled to −80 °C

Phenyl 4,6-O-benzylidene-2,3-O-[2,3-bis(methyl)naphthele]-1-

thio-β-^D-glucopyranoside (5). To a solution of 4²⁵(130 mg, 360

μmol) in DMF (7.4 mL) was added NaH [60% in oil] (72 mg, 1.8

mmol) at 4 °C using an ice bath. The mixture was stirred for 30 min

at room temperature, and 2,3-bis(bromomethyl)naphthalene (72 mg,

0.40 mmol) was added at 4 °C using an ice bath. After being stirred

for 5 h at room temperature as the reaction was monitored by TLC

(n-hexane/EtOAc = 3:1), the reaction was quenched by the addition

of MeOH. The resulting mixture was coevaporated with toluene,

diluted with CHCl₃, and washed with H₂O and brine. The organic

layer was dried over Na₂SO₄, ﬁltered oﬀ, and concentrated. The

resulting residue was puriﬁed by ﬂash column chromatography on

silica gel using toluene/CHCl₃(7:1) as the eluent to give 5 (179 mg,

95%) as a white solid: [α]_D+18.9 (c 0.5, CHCl₃); H NMR (500

MHz, CDCl₃) δ 7.55−7.14 (m, 16 H, 4 Ar), 5.50 (s, 1 H, >CHAr),

5.34 (d, 1 H, J_gem= 14.0 Hz, ArCH₂), 5.33 (d, 1 H, J_gem= 13.0 Hz,

ArCH₂), 5.27 (d, 1 H, ArCH₂), 5.05 (d, 1 H, J_gem= 10.0 Hz, ArCH₂),

4.73 (d, 1 H, J_1,2= 10.0 Hz, H-1), 4.33 (dd, 1 H, J_5,6a= 4.5 Hz, J_gem

10.5 Hz, H-6a), 3.88 (t, 1 H, J_2,3= J_3,4= 8.5 Hz, H-3), 3.88 (t, 1 H,

_5,6b= 10.5 Hz, H-6b), 3.59−3.43 (m, 3 H, H-2, H-4, H-5); ¹³C{¹H}

NMR (125 MHz, CDCl₃) δ 137.1, 134.8, 134.2, 133.0, 132.9, 132.3,

130.6, 129.1, 129.0, 128.5, 128.3, 127.9, 127.6, 127.3, 126.5, 126.4,

126.4, 101.8, 87.7, 81.2, 79.5, 78.7, 77.6, 73.0, 72.5, 70.4, 68.7; HRMS

(ESI) m/z [M + Na]⁺calcd for C₃₁H₂₈O₅SNa 535.1550; found [M +

Na]⁺535.1552.

https://dx.doi.org/10.1021/acs.joc.0c02121

J. Org. Chem. XXXX, XXX, XXX−XXX

The Journal of Organic Chemistry

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Article

using a low constant temperature bath. Subsequently, TfOH (3.2 μL,

36 μmol) was added to the reaction mixture at −80 °C. After being

stirred for 3 h at the same temperature as the reaction was monitored

by TLC (toluene/EtOAc = 4:1), the reaction was quenched by the

addition of NEt₃at −80 °C. The resulting mixture was ﬁltered

through a pad of Celite, and the pad was washed with CHCl₃. The

combined ﬁltrate and washings were successively washed with

saturated aqueous Na₂S₂O₃, H₂O, and brine. The organic layer was

dried over Na₂SO₄, ﬁltered oﬀ, and concentrated. The resulting

residue was puriﬁed by column chromatography on sephadex LH-20

using CHCl₃/MeOH (1:1) as the eluent to give the glycosylated

product 10 (90 mg, 99%, β/α = >15:1). The β-isomer was partially

separated by ﬂash column chromatography on silica gel using

toluene/EtOAc (20:1→10:1) as the eluent to give 10β in pure

HRMS (ESI) m/z [M + Na]⁺calcd for C₁₀H₁₁NO₅Na 248.0529;

found [M + Na]⁺248.0525.

Phenyl 4,6-O-anisylidene-2,3-O-[2,3-bis(methyl)naphthele]-1-

thio-β-^D-glucopyranoside (16). To a solution of 15²⁷(2.30 g, 5.89

mmol) in DMF (116 mL) was added NaH [60% in oil] (696 mg, 17.4

mmol) at 4 °C using an ice bath. The mixture was stirred for 30 min

at room temperature, and 2,3-bis(bromomethyl)naphthalene (2.04 g,

6.48 mmol) was added at 4 °C using an ice bath. After being stirred

for 12 h at room temperature as the reaction was monitored by TLC

(n-hexane/EtOAc = 3:1), the reaction was quenched by the addition

of MeOH. The resulting mixture was coevaporated with toluene,

diluted with EtOAc, and washed with H₂O and brine. The organic

layer was dried over Na₂SO₄, ﬁltered oﬀ, and concentrated. The

resulting residue was puriﬁed by ﬂash column chromatography on

silica gel using toluene/CHCl₃(1:1) as the eluent to give 16 (2.44 g,

form. 10β: [α]_D+28.9 (c 1.4, CHCl₃); ¹H NMR (500 MHz,

81%) as a yellow solid: [α]_D+20.7 (c 1.0, CHCl₃); H NMR (500

MHz, CDCl₃) δ 7.79−6.88 (m, 15 H, 4 Ar), 5.46 (s, 1 H, >CHAr),

5.34 (d, 1 H, J_gem= 14.0 Hz, ArCH₂), 5.33 (d, 1 H, J_gem= 13.0 Hz,

ArCH₂), 5.26 (d, 1 H, ArCH₂), 5.04 (d, 1 H, ArCH₂), 4.72 (d, 1 H,

J_1,2= 9.5 Hz, H-1), 4.31 (dd, 1 H, J_5,6a= 5.0 Hz, J_gem= 11.0 Hz, H-

6a), 3.87 (t, 1 H, J_2,3= J_3,4= 8.5 Hz, H-3), 3.81 (s, 3 H, OMe), 3.69

(dd, 1 H, J_5,6b= 10.0 Hz, H-6b), 3.53 (dd, 1 H, H-2), 3.51−3.46 (m, 2

H, H-4, H-5); ¹³C{¹H} NMR (125 MHz, CDCl₃) δ 160.2, 134.7,

134.2, 133.0, 133.0, 132.9, 132.2, 130.6, 129.7, 129.0, 129.0, 128.5,

128.2, 127.8, 127.7, 127.6, 127.3, 126.5, 126.3, 125.3, 113.6, 101.7,

87.7, 81.2, 79.4, 78.7, 73.0, 72.0, 70.4, 68.6, 55.3; HRMS (ESI) m/z

[M + Na]⁺calcd for C₃₂H₃₀O₆SNa 565.1655; found [M + Na]⁺

565.1659.

CDCl₃) δ 7.80−7.21 (m, 16 H, 4 Ar), 5.58 (d, 1 H, J_1,2= 5.0 Hz, H-

^Gal), 5.39 (d, 1 H, J_gem= 13.0 Hz, ArCH₂), 5.24 (s, 2 H, 2 ArCH₂),

5.00 (d, 1 H, ArCH₂), 4.94 (d, 1 H, J_gem= 11.0 Hz, ArCH₂), 4.61 (dd,

1 H, J_4,5= 2.5 Hz, J_3,4= 8.0 Hz, H-4^Gal), 4.56 (d, 1 H, J_gem= 12.0 Hz,

ArCH₂), 4.54 (d, 1 H, ArCH₂), 4.49 (d, 1 H, ArCH₂), 4.43 (d, 1 H,

_1,2= 7.5 Hz, H-1^Glc), 4.33 (m, 2 H, H-2^Gal, H-3^Gal), 4.10−4.06 (m, 2

H, H-5^Gal, H-6a^Gal), 3.80 (m, 1 H, H-6b^Gal), 3.76 (t, 1 H, J_2,3= J_3,4

8.5 Hz, H-3^Glc), 3.70 (dd, 1 H, J_5,6a= 2.0 Hz, J_gem= 9.0 Hz, H-6a^Glc),

3.64 (dd, 1 H, J_5,6b= 4.5 Hz, H-6b^Glc), 3.48 (t, 1 H, J_4,5= 8.5 Hz, H-

^Glc), 3.45−3.41 (m, 2 H, H-2^Gal, H-5^Gal), 1.58−1.33 (m, 12 H, 4

Me); ¹³C{¹H} NMR (125 MHz, CDCl₃) δ 138.6, 138.2, 135.4, 135.2,

133.0, 132.8, 130.7, 129.5, 128.3, 128.3, 127.9, 127.8, 127.6, 127.5,

127.2, 126.3, 126.0, 109.3, 108.6, 102.6, 96.4, 84.1, 80.4, 74.8, 73.4,

73.0, 72.6, 71.3, 70.7, 70.6, 69.2, 68.9, 67.7, 26.2, 26.0, 25.0, 24.4;

HRMS (ESI) m/z [M + Na]⁺calcd for C₄₄H₅₀O₁₁Na 777.3245;

found [M + Na]⁺777.3240.

Phenyl 2,3-O-[2,3-bis(methyl)naphthele]-6-O-tert-butyldiphenyl-

silyl-4-O-p-methoxybenzyl-1-thio-β-^D-glucopyranoside (18). To a

solution of 16 (1.70 g, 3.14 mmol) in CH₂Cl₂(31.0 mL) was added 4

Å molecular sieves (1.70 g). After being stirred for 30 min at room

temperature, the mixture was then cooled to −80 °C using a low

constant temperature bath. Subsequently, Et₃SiH (1.20 mL, 6.90

mmol) and PhBCl₂(913 μL, 6.90 mmol) were added to the reaction

mixture at −80 °C. After being stirred for 2 h at the same temperature

as the reaction was monitored by TLC (n-hexane/EtOAc = 3:1), the

reaction was quenched by the addition of NEt₃and MeOH at −80

°C. The resulting mixture was ﬁltered through a pad of Celite, and the

pad was washed with CHCl₃. The combined ﬁltrate and washings

were successively washed with saturated aqueous NaHCO₃, H₂O, and

brine. The organic layer was dried over Na₂SO₄, ﬁltered oﬀ, and

concentrated. The resulting residue was puriﬁed by ﬂash column

chromatography on silica gel using n-hexane/EtOAc (7:1) as the

eluent to give 17. After exposure to high vacuum overnight, this

compound was dissolved in DMF (31.4 mL). TBDPSCl (3.20 mL,

3.14 mmol) and imidazole (1.71 g, 25.1 mmol) were added to the

reaction mixture at room temperature. After being stirred for 2 h at

the same temperature as the reaction was monitored by TLC (n-

hexane/EtOAc = 3:1), the reaction was quenched by the addition of

MeOH. The resulting mixture was coevaporated with toluene, diluted

with EtOAc, and washed with H₂O and brine. The organic layer was

dried over Na₂SO₄, ﬁltered oﬀ, and concentrated. The resulting

residue was puriﬁed by column chromatography on Sephadex LH-20

using CHCl₃/MeOH (1:1) as the eluent to give 18 (4.05 g, 70% over

1,2-O-[(S)-p-Nitrobenzylidene)]-sn-glycerol (14a). To a solution

of 26a (121 mg, 366 μmol) in MeOH/THF (2:1, 3.7 mL) was added

NaOMe [28% solution in MeOH] (7.1 mg, 37 μmol) at 4 °C using

an ice bath. After being stirred for 3.5 h at room temperature as the

reaction was monitored by TLC (n-hexane/EtOAc = 3:1), the

reaction was quenched by the addition of Muromac (H⁺) at 4 °C

using an ice bath. The resulting mixture was ﬁltered through a pad of

Celite, and the pad and resin were washed with EtOAc. The

combined ﬁltrate and washings were concentrated and the resulting

residue was puriﬁed by ﬂash column chromatography on silica gel

using n-hexane/EtOAc (1:1) as the eluent to give 14a (77 mg, 92%)

as a colorless syrup: [α]_D+14.0 (c 0.5, CHCl₃); H NMR (500

MHz, CDCl₃) δ 8.24 (d, 2 H, J_H,H= 8.7 Hz, Ar), 7.65 (d, 2 H, Ar),

6.06 (s, 1 H, >CHAr), 4.36 (m, 1 H, H-2^Gro), 4.20 (dd, 1 H, J_vic= 6.4

Hz, J_gem= 8.3 Hz, H-1a^Gro), 3.93 (dd, 1 H, J_vic= 6.9 Hz, H-1b^Gro),

3.86 (dd, 1 H, J_vic= 3.6 Hz, J_gem= 12.0 Hz, H-3a^Gro), 3.75 (dd, 1 H,

J_vic= 5.3 Hz, H-3b^Gro), 1.85 (brs, 1 H, OH); ¹³C{¹H} NMR (125

MHz, CDCl₃) δ 148.4, 144.9, 127.3, 123.6, 102.4, 76.8, 66.8, 62.6;

HRMS (ESI) m/z [M + Na]⁺calcd for C₁₀H₁₁NO₅Na 248.0529;

found [M + Na]⁺248.0525.

1,2-O-[(R)-p-Nitrobenzylidene)]-sn-glycerol (14b). To a solution

of 26b (77 mg, 0.23 mmol) in MeOH/THF (2:1, 2.3 mL) was added

NaOMe [28% solution in MeOH] (4.4 mg, 23 μmol) at 4 °C using

an ice bath. After being stirred for 3.5 h at room temperature as the

reaction was monitored by TLC (n-hexane/EtOAc = 3:1), the

reaction was quenched by the addition of Muromac (H⁺) at 4 °C

using an ice bath. The resulting mixture was ﬁltered through a pad of

Celite, and the pad and resin were washed with EtOAc. The

combined ﬁltrate and washings were concentrated and the resulting

residue was puriﬁed by ﬂash column chromatography on silica gel

using n-hexane/EtOAc (1:1) as the eluent to give 14b (46 mg, 89%)

two steps) as a white foamy material: [α]_D−38.7 (c 0.8, CHCl₃);

¹H NMR (500 MHz, CDCl₃) δ 7.79−6.81 (m, 25 H, 6 Ar), 5.34 (d, 1

H, J_gem= 13.5 Hz, ArCH₂), 5.28 (d, 1 H, J_gem= 14.0 Hz, ArCH₂), 5.22

(d, 1 H, ArCH₂), 5.12 (d, 1 H, ArCH₂), 4.87 (d, 1 H, J_gem= 10.5 Hz,

ArCH₂), 4.61 (d, 1 H, J_1,2= 10.0 Hz, H-1), 4.57 (d, 1 H, ArCH₂),

3.93 (dd, 1 H, J_5,6a= 1.5 Hz, J_gem= 11.0 Hz, H-6a), 3.84 (dd, 1 H, J_5,6b

= 4.0 Hz, H-6b), 3.81 (s, 3 H, OMe), 3.76 (t, 1 H, J_2,3= J_3,4= 9.0 Hz,

H-3), 3.59 (t, 1 H, J_4,5= 9.0 Hz, H-4), 3.47 (dd, 1 H, H-2), 3.36 (td, 1

as a colorless syrup: [α]_D−13.3 (c 0.5, CHCl₃); H NMR (500

MHz, CDCl₃) δ 8.25 (d, 2 H, J_H,H= 8.7 Hz, Ar), 7.68 (d, 2 H, Ar),

5.90 (s, 1 H, >CHAr), 4.42 (m, 1 H, H-2^Gro), 4.15 (dd, 1 H, J_vic= 6.3

Hz, J_gem= 8.1 Hz, H-1a^Gro), 4.03 (dd, 1 H, J_vic= 5.8 Hz, H-1b^Gro),

3.83 (dd, 1 H, J_vic= 3.8 Hz, J_gem= 11.9 Hz, H-3a^Gro), 3.70 (dd, 1 H,

J_vic= 5.3 Hz, H-3b^Gro), 1.73 (brs, 1 H, OH); ¹³C{¹H} NMR (125

MHz, CDCl₃) δ 148.6, 144.0, 127.5, 123.6, 102.7, 77.3, 67.0, 63.0;

H, H-5), 1.06 (s, 9 H, Bu); ¹³C{¹H} NMR (125 MHz, CDCl₃) δ

159.2, 135.8, 135.6, 135.0, 134.8, 133.8, 133.5, 133.0, 133.0, 132.9,

131.8, 130.6, 129.7, 129.6, 129.6, 129.6, 128.8, 128.5, 127.7, 127.6,

127.5, 127.4, 127.3, 126.4, 126.3, 113.8, 86.6, 86.1, 79.8, 79.1, 77.6,

76.2, 74.8, 73.3, 73.1, 62.9, 55.3, 26.8, 19.2; HRMS (ESI) m/z [M +

Na]⁺calcd for C₄₈H₅₀O₆SSiNa 805.2990; found [M + Na]⁺805.2991.

https://dx.doi.org/10.1021/acs.joc.0c02121

J. Org. Chem. XXXX, XXX, XXX−XXX

The Journal of Organic Chemistry

pubs.acs.org/joc

Article

2,3-O-[2,3-Bis(methyl)naphthele]-6-O-tert-butyldiphenylsilyl-4-

O-p-methoxybenzyl-^D-glucopyranosyl trichloroacetimidate (19).

To a solution of 18 (257 mg, 0.33 mmol) in 90% aqueous acetone

(3.33 mL) was added NBS (175 mg, 0.98 mmol) at room

temperature. After being stirred for 10 min at the same temperature

as the reaction was monitored by TLC (n-hexane/EtOAc = 2:1), the

reaction mixture was diluted with EtOAc, and washed with saturated

aqueous Na₂S₂O₃, H₂O, and brine. The organic layer was dried over

Na₂SO₄and concentrated. The residue was puriﬁed by ﬂash column

chromatography on silica gel using n-hexane/EtOAc (4:1→2:1) as the

eluent to give the corresponding hemiacetal. After exposure to high

vacuum overnight, this compound was dissolved in CH₂Cl₂(31.0

mL). CCl₃CN (0.33 mL, 3.29 mmol) and DBU (0.15 mL, 1.00

mmol) were added to the solution at room temperature. After being

stirred for 30 min at the same temperature as the reaction was

monitored by TLC (n-hexane/EtOAc = 2:1), the reaction mixture

was evaporated. The resulting residue was puriﬁed by ﬂash column

chromatography on silica gel using n-hexane/EtOAc (5:1→3:1) as the

quenched by the addition of NEt₃and MeOH at −80 °C. The

resulting mixture was ﬁltered through a pad of Celite, and the pad was

washed with CHCl₃. The combined ﬁltrate and washings were

successively washed with saturated aqueous NaHCO₃, H₂O, and

brine. The organic layer was dried over Na₂SO₄, ﬁltered oﬀ, and

concentrated. The resulting residue was puriﬁed by ﬂash column

chromatography on silica gel using n-hexane/EtOAc (2:1) as the

eluent to give 22 (73 mg, 73%) as a white solid: [α]_D²⁵+22.6 (c 0.3,

CHCl₃); ¹H NMR (500 MHz, CDCl₃) δ 7.82−6.39 (m, 15 H, 4 Ar),

5.41 (d, 1 H, J_gem= 13.5 Hz, CH₂Ar), 5.28 (d, 1 H, J_gem= 14.5 Hz,

CH₂Ar), 5.14 (d, 1 H, CH₂Ar), 4.92 (d, 1 H, CH₂Ar), 4.69 (d, 1 H,

J_gem= 10.5 Hz, CH₂Ar), 4.62 (d, 1 H, J_1,2= 9.5 Hz, H-1), 4.40 (d, 1

H, CH₂Ar), 3.97 (t, 1 H, J_2,3= 9.5 Hz, H-2), 3.67 (d, 1 H, J_3,4= 2.5

Hz, H-4), 3.79 (dd, 1 H, J_5,6a= 4.0 Hz, J_gem= 8.5 Hz, H-6a), 3.75 (dd,

1 H, H-3), 3.66 (s, 3 H, OMe), 3.54−3.49 (m, 2 H, H-5, H-6b);

¹³C{¹H} NMR (125 MHz, CDCl₃) δ 131.2, 129.9, 128.8, 127.7,

127.4, 127.0, 126.1, 113.4, 87.2, 82.7, 78.7, 77.6, 75.6, 74.3, 73.2, 62.5,

55.1; HRMS (ESI) m/z [M + Na]⁺calcd for C₃₂H₃₂O₆SNa 567.1812;

found [M + Na]⁺567.1819.

eluent to give 19 (174 mg, 64% over two steps, α/β = 2.4:1): H

NMR (500 MHz, CDCl₃) δ 8.66 (s, 1 H, NH^α), 8.49 (s, 1 H, NH^β),

7.79−6.85 (m, 20 H, 5 Ar), 6.52 (d, 1 H, J_1,2= 3.5 Hz, H-1^α), 5.76 (d,

1 H, J_1,2= 8.0 Hz, H-1^β), 5.42 (d, 1 H, J_gem= 12.5 Hz, CH₂Ar^β),

5.31−5.23 (m, 5 H, 5 CH₂Ar), 5.09 (d, 1 H, CH₂Ar^β), 5.06 (d, 1 H,

Phenyl 2,3-O-[2,3-bis(methyl)naphthele]-6-O-tert-butyldiphenyl-

silyl-4-O-p-methoxybenzyl-1-thio-β-^D-galactopyranoside (23). To a

solution of 22 (58 mg, 0.11 mmol) in DMF (1.1 mL) were added

TBDPSCl (137 μL, 533 μmol) and imidazole (73 mg, 533 μmol) at

room temperature. After being stirred for 1 h at the same temperature

as the reaction was monitored by TLC (n-hexane/EtOAc = 1:1), the

reaction was quenched by the addition of MeOH. The resulting

mixture was coevaporated with toluene, diluted with EtOAc, and

washed with H₂O and brine. The organic layer was dried over

Na₂SO₄, ﬁltered oﬀ, and concentrated. The resulting residue was

puriﬁed by ﬂash column chromatography on silica gel using n-hexane/

EtOAc (10:1) as the eluent to give 23 (84 mg, quant) as a white solid:

_gem= 13.0 Hz, CH₂Ar^α), 4.93 (d, 1 H, J_gem= 10.5 Hz, CH₂Ar^β), 4.92

(d, 1 H, J_gem= 10.5 Hz, CH₂Ar^α), 4.64 (d, 2 H, 2 CH₂Ar), 4.16 (t, 1

H, J_2,3= J_3,4= 9.5 Hz, H-3^α), 3.91−3.70 (m, 10 H, H-2^α, H-4^α, H-5^α,

H-6a^α, H-6b^α, H-2^β, H-3^β, H-4^β, H-6a^β, H-6b^β), 3.82 (s, 3 H, OMe^α),

3.81 (s, 3 H, OMe^β), 3.48 (td, 1 H, J_5,6a= J_5,6b= 2.5 Hz, J_4,5= 7.5 Hz,

H-5^β), 1.04 (s, 9 H, Bu^α), 0.99 (s, 9 H, Bu^β); ¹³C{¹H} NMR (125

MHz, CDCl₃) δ 161.1, 159.4, 135.8, 135.7, 135.0, 134.9, 133.6, 133.2,

132.9, 132.8, 130.5, 129.9, 129.8, 129.6, 129.6, 128.3, 127.7, 127.6,

127.4, 127.4, 126.4, 126.2, 113.9, 95.4, 91.3, 81.2, 78.5, 77.6, 76.3,

75.2, 74.3, 74.1, 71.9, 62.5, 55.3, 31.6, 26.8, 22.6, 19.3, 14.1; HRMS

(ESI) m/z [M + Na]⁺calcd for C₄₄H₄₆Cl₃NO₇SiNa 856.2001; found

[M + Na]⁺856.2002.

[α]_D+65.3 (c 0.5, CHCl₃); H NMR (500 MHz, CDCl₃) δ 7.50−

6.19 (m, 25 H, 6 Ar), 5.45 (d, 1 H, J_gem= 12.0 Hz, CH₂Ar), 5.25 (d, 1

H, J_gem= 14.5 Hz, CH₂Ar), 5.06 (d, 1 H, CH₂Ar), 4.89 (d, 1 H,

CH₂Ar), 4.70 (d, 1 H, J_gem= 10.5 Hz, CH₂Ar), 4.56 (d, 1 H, J_1,2= 9.5

Hz, H-1), 4.34 (d, 1 H, CH₂Ar), 4.00 (d, 1 H, J_3,4= 2.0 Hz, H-4), 3.95

(t, 1 H, J_2,3= 9.5 Hz, H-2), 3.78−3.75 (m, 3 H, H-3, H-6a, H-6b),

3.60 (s, 3 H, OMe), 3.55 (t, 1 H, J_5,6a= J_5,6b= 7.0 Hz, H-5), 1.07 (s, 9

Phenyl 4,6-O-anisylidene-2,3-O-[2,3-bis(methyl)naphthele]-1-

thio-β-^D-galactopyranoside (21). To a solution of 20²⁸(853 mg,

2.18 mmol) in DMF (21.8 mL) were added NaH [60% in oil] (262

mg, 6.54 mmol) and TBAI (402 mg, 1.09 mmol) at 4 °C using an ice

bath. The mixture was stirred for 30 min at room temperature, and

2,3-bis(bromomethyl)naphthalene (820 mg, 2.40 mmol) was added

at 4 °C using an ice bath. After being stirred for 19 h at room

temperature as the reaction was monitored by TLC (n-hexane/EtOAc

= 2:1), the reaction was quenched by the addition of MeOH. The

resulting mixture was coevaporated with toluene, diluted with EtOAc,

and washed with H₂O and brine. The organic layer was dried over

Na₂SO₄, ﬁltered oﬀ, and concentrated. The resulting residue was

puriﬁed by ﬂash column chromatography on silica gel using n-hexane/

EtOAc (1:1→1:2) as the eluent to give 21 (1.18 g, quant) as a white

H, Bu); ¹³C{¹H} NMR (125 MHz, CDCl₃) δ 158.6, 135.6, 135.2,

134.8, 134.7, 134.1, 133.3, 133.3, 133.1, 133.0, 131.2, 130.9, 130.9,

129.7, 129.7, 129.4, 128.7, 127.8, 127.7, 127.5, 127.4, 126.6, 126.3,

126.1, 113.0, 87.1, 82.6, 78.7, 77.6, 75.1, 74.3, 74.1, 73.1, 71.3, 62.1,

55.1, 26.9, 26.5, 19.2, 19.0; HRMS (ESI) m/z [M + Na]⁺calcd for

C₄₈H₅₀O₆SSiNa 805.2990; found [M + Na]⁺805.2994.

2,3-O-[2,3-Bis(methyl)naphthele]-6-O-tert-butyldiphenylsilyl-4-

O-p-methoxybenzyl-^D-galactopyranosyl trichloroacetimidate (24).

To a solution of 23 (40 mg, 51 μmol) in acetone/H₂O (2.4 mL/60

μL) was added NBS (18 mg, 0.10 mmol) at room temperature. After

being stirred for 15 min at room temperature as the reaction was

monitored by TLC (EtOAc/n-hexane = 1:3), the reaction mixture

was diluted with CHCl₃, and washed with H₂O and brine, dried over

Na₂SO₄, and concentrated. The residue was puriﬁed by ﬂash column

chromatography on silica gel using EtOAc/n-hexane (1:4 to 1:2) as

the eluent to give a hemiacetal. This compound was exposed to high

vacuum overnight. The resulting residue was dissolved in CH₂Cl₂(1.0

mL), and CCl₃CN (51 μL, 0.51 mmol) and DBU (23 μL, 0.15 mmol)

were added to the solution at 0 °C. After being stirred for 40 min at

room temperature as the reaction was monitored by TLC (EtOAc/n-

hexane = 1:3), the reaction mixture was concentrated. The residue

was puriﬁed by ﬂash column chromatography on silica gel using n-

hexane/EtOAc (4:1) as the eluent to give 24 (31 mg, 72%, α/β = 5:1

foamy material: [α]_D+31.9 (c 0.8, CHCl₃); H NMR (500 MHz,

CDCl₃) δ 7.76−6.70 (m, 15 H, 4 Ar), 5.47 (s, 1 H, >CHAr), 5.29 (d,

1 H, J_gem= 13.5 Hz, CH₂Ar), 5.22 (d, 1 H, J_gem= 14.5 Hz, CH₂Ar),

5.09 (d, 1 H, CH₂Ar), 5.06 (d, 1 H, CH₂Ar), 4.60 (d, 1 H, J_1,2= 9.0

Hz, H-1), 4.32 (dd, 1 H, J_5,6a= 1.5 Hz, J_gem= 12.5 Hz, H-6a), 4.28 (d,

1 H, J_3,4= 3.0 Hz, H-4), 4.00 (dd, 1 H, J_5,6b= 1.5 Hz, H-6b), 3.90 (t, 1

H, J_2,3= 9.0 Hz, H-2), 3.75 (dd, 1 H, H-3), 3.75 (s, 3 H, OMe), 3.48

(s, 1 H, H-5); ¹³C{¹H} NMR (125 MHz, CDCl₃) δ 159.9, 134.7,

134.7, 132.9, 132.8, 132.4, 130.3, 130.0, 128.8, 127.8, 127.8, 127.6,

127.5, 127.4, 126.3, 126.1, 113.3, 100.9, 86.1, 80.8, 77.6, 75.2, 74.6,

73.5, 72.7, 70.0, 69.2, 55.2; HRMS (ESI) m/z [M + Na]⁺calcd for

C₃₂H₃₀O₆SNa 565.1655; found [M + Na]⁺565.1665.

over two steps) as a white foamy material: H NMR (500 MHz,

Phenyl 2,3-O-[2,3-bis(methyl)naphthele]-4-O-p-methoxybenzyl-

1-thio-β-^D-galactopyranoside (22). To a solution of 21 (100 mg,

185 μmol) in CH₂Cl₂(1.90 mL) was added 4 Å molecular sieves (100

mg). After being stirred for 30 min at room temperature, the mixture

was then cooled to −80 °C using a low constant temperature bath.

Subsequently, Et₃SiH (68 μL, 407 μmol) and PhBCl₂(54 μL, 407

μmol) were added to the reaction mixture at −80 °C. After being

stirred for 10 min at the same temperature as the reaction was

monitored by TLC (n-hexane/EtOAc = 3:1), the reaction was

CDCl₃) δ 8.60 (s, 1 H, NH^β), 8.51 (s, 1 H, NH^α), 7.85−6.69 (m, 25

H, 5 Ar), 6.44 (d, 1 H, J_1,2= 3.5 Hz, H-1^α), 6.40−6.20 (m, 4 H, Ar^α,

Ar^β), 5.74 (d, 1 H, J_1,2= 8.0 Hz, H-1^β), 5.54 (d, 1 H, J_gem= 12.2 Hz,

ArCH₂), 5.41 (d, 1 H, J_gem= 12.9 Hz, ArCH₂), 5.33 (d, 1 H, J_gem

15.0 Hz, ArCH₂), 5.23 (d, 1 H, J_gem= 14.4 Hz, ArCH₂), 5.16−5.06

(m, 3 H, 2 ArCH₂, ArCH₂), 4.92 (d, 1 H, ArCH₂), 4.79 (d, 1 H,

_gem= 10.3 Hz, ArCH₂), 4.70 (d, 1 H, J_gem= 10.2 Hz, ArCH₂), 4.49

α β

(d, 1 H, ArCH₂), 4.36 (d, 1 H, J_gem= 10.2 Hz, ArCH₂), 4.30 (dd, 1

https://dx.doi.org/10.1021/acs.joc.0c02121

J. Org. Chem. XXXX, XXX, XXX−XXX

The Journal of Organic Chemistry

pubs.acs.org/joc

Article

H, J_2,3= 10.0 Hz, H-2^α), 4.23 (dd, 1 H, J_3,4= 2.7 Hz, H-3^α), 4.18 (d, 1

H, H-4^α), 4.13−4.05 (m, 4 H, H-5^α, H-2^β, H-3^β, H-4^β), 3.86−3.56

(m, 11 H, Me^α, Me^β, H-6a^α, H-6b^α, H-5^β, H-6a^β, H-6b^β), 1.07−1.05

132.9, 130.5, 129.7, 129.6, 129.6, 129.5, 128.9, 127.8, 127.7, 127.5,

127.4, 127.4, 126.4, 126.3, 123.5, 113.8, 102.8, 102.5, 84.3, 80.6, 77.6,

76.5, 75.7, 74.8, 73.3, 72.9, 69.3, 68.0, 62.8, 55.3, 26.8, 19.3; HRMS

(ESI) m/z [M + Na]⁺calcd for C₅₂H₅₅O₁₁NSiNa 920.3437; found

[M + Na]⁺920.3437.

(m, 18 H, Bu^α, Bu^β); ¹³C{¹H} NMR (125 MHz, CDCl₃) δ 161.2,

159.0, 135.6, 135.6, 135.5, 135.5, 135.1, 133.3, 133.1, 133.0, 130.7,

130.1, 129.8, 129.6, 128.1, 127.7, 127.7, 127.7, 127.4, 126.4, 126.2,

113.4, 113.2, 95.9, 91.5, 77.8, 76.0, 75.7, 75.3, 74.9, 73.7, 73.1, 72.7,

61.9, 55.1, 55.1, 29.7, 26.9, 26.9, 11.2; HRMS (ESI) m/z [M + Na]⁺

calcd for C₄₄H₄₆Cl₃NO₇SiNa 856.2001; found [M + Na]⁺856.2000.

3-O-Benzoyl-1,2-O-(p-nitrobenzylidene)-sn-glycerol (26). To a

solution of 25¹⁹(218 mg, 1.11 mmol) and p-nitrobenzaldehyde (503

mg, 3.33 mmol) in THF (11.0 mL) were added HMDSO (1.40 mL,

6.59 mmol) and TMSOTf (0.11 mL, 0.61 mmol) at 0 °C. After being

stirred for 10 min at the same temperature, Et₃SiH (886 μL, 5.56

mmol) was added to the reaction mixture at 0 °C. After being stirred

for 30 min at the same temperature as the reaction was monitored by

TLC (n-hexane/EtOAc = 3:1), the reaction was quenched by the

addition of saturated aqueous NaHCO₃at 0 °C. The resulting

mixture was diluted with EtOAc and washed with H₂O and brine. The

organic layer was dried over Na₂SO₄, ﬁltered oﬀ, and concentrated.

The resulting residue was puriﬁed by ﬂash column chromatography

on silica gel using n-hexane/EtOAc (10:1→3:1) as the eluent to give

26a (124 mg, 34%) as a colorless syrup along with the diastereomer

26b (135 mg, 37%) as a colorless syrup.

27α: [α]_D²⁵+61.0 (c 1.0, CHCl₃); ¹H NMR (500 MHz, CDCl₃) δ

8.04−6.84 (m, 24 H, 6 Ar), 5.65 (s, 1 H, >CHAr), 5.31−5.24 (m, 3

H, 3 CH₂Ar), 5.12 (d, 1 H, J_gem= 13.5 Hz, CH₂Ar), 5.01 (d, 1 H, J_1,2

= 3.5 Hz, H-1^Glc), 4.89 (d, 1 H, J_gem= 10.5 Hz, CH₂Ar), 4.58 (d, 1 H,

CH₂Ar), 4.37 (m, 1 H, H-2^Gro), 4.19−4.09 (m, 2 H, H-1a^Gro, H-

1b^Gro), 4.04 (t, 1 H, J_2,3= J_3,4= 9.5 Hz, H-3^Glc), 3.89−3.83 (m, 4 H,

H-5^Glc, H-6a^Glc, H-6b^Glc, H-3a^Gro), 3.83 (s, 3 H, OMe), 3.66 (dd, 1 H,

H-2^Glc), 3.64−3.58 (m, 2 H, H-4^Glc, H-3b^Gro), 1.05 (s, 9 H, Bu);

¹³C{¹H} NMR (125 MHz, CDCl₃) δ 159.3, 148.2, 144.4, 135.8,

135.6, 135.2, 135.0, 133.5, 133.3, 132.9, 132.8, 130.5, 129.7, 129.7,

129.6, 129.5, 129.1, 127.9, 127.7, 127.6, 127.5, 127.4, 127.3, 126.4,

126.2, 123.5, 123.4, 113.8, 102.3, 98.3, 82.6, 79.8, 77.6, 76.9, 74.9,

74.9, 74.2, 73.0, 71.9, 67.7, 67.5, 63.0, 55.3, 29.7, 26.8, 26.8, 19.3;

HRMS (ESI) m/z [M + Na]⁺calcd for C₅₂H₅₅O₁₁NSiNa 920.3437;

found [M + Na]⁺920.3432.

3-O-{2,3-O-[2,3-Bis(methyl)naphthele]-6-O-tert-butyldiphenylsil-

yl-4-O-p-methoxybenzyl-^D-glucopyranosyl}-1,2-O-[(R)-p-nitroben-

zylidene]-sn-glycerol (28). To a solution of Glc thioglycoside 18 (83

mg, 106 μmol) and 14b (36 mg, 160 μmol) in CH₂Cl₂(2.1 mL) were

added 4 Å molecular sieves (0.21 g) and NIS (50 mg, 156 μmol).

After being stirred for 30 min at room temperature, the mixture was

then cooled to −80 °C using a low constant temperature bath.

Subsequently, TESOTf (3.5 μL, 16 μmol) was added to the reaction

mixture at −80 °C. After being stirred for 24 h at the same

temperature as the reaction was monitored by TLC (n-hexane/EtOAc

= 1:1), the reaction was quenched by the addition of NEt₃at −80 °C.

The resulting mixture was ﬁltered through a pad of Celite, and the

pad was washed with CHCl₃. The combined ﬁltrate and washings

were successively washed with saturated aqueous Na₂S₂O₃, H₂O, and

brine. The organic layer was dried over Na₂SO₄, ﬁltered oﬀ, and

concentrated. The resulting residue was puriﬁed by ﬂash column

chromatography on silica gel using n-hexane/EtOAc (3:1→3:2) as the

eluent to give 28β (55 mg, 58%) as a colorless syrup along with 28α

(37 mg, 39%) as a colorless syrup.

26a: [α]_D²⁵−19.4 (c 2.0, CHCl₃); ¹H NMR (500 MHz, CDCl₃) δ

8.26−7.26 (m, 9 H, Ar), 6.10 (s, 1 H, >CHAr), 4.63 (m, 1 H, H-2^Gro),

4.52 (m, 2 H, H-3a^Gro, H-3b^Gro), 4.31 (dd, 1 H, J_vic= 6.5 Hz, J_gem= 8.5

Hz, H-1a^Gro), 3.99 (dd, 1 H, J_vic= 6.0 Hz, H-1b^Gro); ¹³C{¹H} NMR

(125 MHz, CDCl₃) δ 166.3, 144.6, 133.4, 129.7, 129.6, 128.5, 127.4,

123.6, 102.6, 77.6, 74.4, 67.4, 64.3; HRMS (ESI) m/z [M + Na]⁺

calcd for C₁₇H₁₅O₆NNa 352.0792; found [M + Na]⁺352.0790.

26b: [α]_D²⁵+25.0 (c 0.3, CHCl₃); ¹H NMR (500 MHz, CDCl₃) δ

8.09−7.24 (m, 9 H, Ar), 5.96 (s, 1 H, >CHAr), 4.65 (m, 1 H, H-2^Gro),

4.55 (dd, 1 H, J_vic= 4.5 Hz, J_gem= 12.0 Hz, H-3a^Gro), 4.43 (dd, 1 H,

_vic= 5.0 Hz, H-3b^Gro), 4.24 (dd, 1 H, J_vic= 7.0 Hz, J_gem= 8.5 Hz, H-

1a^Gro), 4.11 (dd, 1 H, J_vic= 5.5 Hz, H-1b^Gro); ¹³C{¹H} NMR (125

MHz, CDCl₃) δ 166.2, 148.5, 144.1, 133.3, 129.7, 129.5, 128.4, 127.5,

123.6, 103.0, 74.8, 67.5, 64.3; HRMS (ESI) m/z [M + Na]⁺calcd for

C₁₇H₁₅O₆NNa 352.0792; found [M + Na]⁺352.0792.

28β: [α]_D²⁵+44.0 (c 0.5, CHCl₃); ¹H NMR (500 MHz, CDCl₃) δ

3-O-{2,3-O-[2,3-Bis(methyl)naphthele]-6-O-tert-butyldiphenylsil-

yl-4-O-p-methoxybenzyl-^D-glucopyranosyl}-1,2-O-[(S)-p-nitroben-

zylidene]-sn-glycerol (27). To a solution of Glc thioglycoside 18

(118 mg, 151 μmol) and 14a (51 mg, 226 μmol) in CH₂Cl₂(3.0 mL)

were added 4 Å molecular sieves (0.30 g) and NIS (52 mg, 231

μmol). After being stirred for 30 min at room temperature, the

mixture was then cooled to −80 °C using a low constant temperature

bath. Subsequently, TESOTf (5.1 μL, 23 μmol) was added to the

reaction mixture at −80 °C. After being stirred for 24 h at the same