Synthesis of an Exhaustive Library of Naturally Occurring Gal f-Man p and Gal p-Man p Disaccharides. Toward Fingerprinting According to Ring Size by Advanced Mass Spectrometry-Based IM-MS and IRMPD

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Synthesis of an Exhaustive Library of Naturally Occurring Galf‑Manp

and Galp‑Manp Disaccharides. Toward Fingerprinting According to

Ring Size by Advanced Mass Spectrometry-Based IM-MS and IRMPD

B é n é dicte Favreau, Oznur Yeni,^§Simon Ollivier,^§Joë l Boustie, Franco

̧ ise Le D é v é hat, Jean-Paul Gu é gan,

̀

Mathieu Fanuel, H é lene Rogniaux, Richard Br é dy, Isabelle Compagnon, David Ropartz,

Laurent Legentil, and Vincent Ferrieres *

̀

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Supporting Information

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ABSTRACT: Nature oﬀers a huge diversity of glycosidic

derivatives. Among numerous structural modulations, the nature

of the ring size of hexosides may induce signiﬁcant diﬀerences on

both biological and physicochemical properties of the glycoconju-

gate of interest. On this assumption, we expect that small

disaccharides bearing either a furanosyl entity or a pyranosyl

residue would give a speciﬁc signature, even in the gas phase. On

the basis of the scope of mass spectrometry, two analytical

techniques to register those signatures were considered, i.e., the ion

mobility (IM) and the infrared multiple photon dissociation

(IRMPD), in order to build up cross-linked databases. ^D-Galactose

occurs in natural products in both tautomeric forms and presents

all possible regioisomers when linked to ^D-mannose. Consequently, the four reducing Galf-Manp disaccharides as well as the four

Galp-Manp counterparts were ﬁrst synthesized according to a highly convergent approach, and IM-MS and IRMPD-MS data were

second collected. Both techniques used aﬀorded signatures, speciﬁc to the nature of the connectivity between the two glycosyl

entities.

based on NMR⁸and mass spectrometry (MS) techniques⁹

INTRODUCTION

■

brilliantly complemented by modeling^10,11and machine

A huge diversity of glycans is observed in Nature. This results

learning approaches.¹²⁻¹⁴Despite these advances, no single

from the variety of sequencing, branching, connectivity

analytical technique is able to solve all of the structural

between monosaccharides, minor but very important func-

elements in carbohydrates, and techniques still have to be

tional group modulations, the traditional OH group being

improved in order to collect and cross-check data, to increase

opportunistically replaced by uronic acid, deoxy, or NHAc

reliability of the analysis. They must also consider minor

functions, and conjugation to lipids, nucleosides or proteins

through O- or N-, α- or β-glycosidic bonds, to name only the

most widespread modulations. This biodiversity is also

variations proposed by the living kingdom.

Mammals biosynthesize hexosyl-containing glycoconjugates

exclusively in the pyranose form. However, some micro-

widened by considering the possible tautomerism between

organisms are able to produce hexofuranosyl-containing

pyranosides and furanosides. As a consequence, glycoconju-

gates are involved in many biological processes such as

polysaccharides and conjugates. For instance, galactose,¹⁵⁻¹⁷

N-acetylgalactosamine,^18,19and fucose¹⁵in their furanose form

photosynthesis, intercellular and host−pathogen recognition

were identiﬁed in natural biomolecules with still unclear roles.

phenomena, and maturation of proteins.¹They can be also

Moreover, understanding why Nature sometimes prefers to

overexpressed by cancer cells²or used as markers of some

biosynthesize hexofuranosides instead of the thermodynami-

infection diseases.³To decipher the complex biological and

physicochemical properties of this family of biomolecules,

analytical strategies are still being developed.⁴Very recently,

Received: February 1, 2021

Published: April 20, 2021

low-temperature scanning tunneling microscopy allowed direct

imaging of diﬀerent conformers of some oligosaccharides with

a subnanometer resolution.⁵On the contrary, neutron

crystallography is able to study H-bond networks in protein

binding sites.^6,7Nevertheless, structural studies are mostly

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cally more stable pyranosidic counterparts, while the energy

cost is higher, is not evident.

An analysis of the natural occurrence of galactofuranosides

led us to focus on the galactofuranose (Galf)-mannopyranose

(Manp) sequence and thus the four possible regioisomers

(Figure 1). The disaccharides with a (1→2)-, (1→3)-, or (1→

patterns in larger polysaccharides. Upon fragmentation,

galactomannans will release speciﬁc disaccharidic fragments,

whose ﬁngerprints will match that of the synthetic library. The

MS/MS strategy has been applied to the identiﬁcation of the

monosaccharide content (analyses were done on the

monosaccharide fragments released upon fragmentation),⁴¹⁻⁴³

and IRMPD signatures of methyl furanoside and pyranoside

derived from N-acetylgalactosamine have been previously

reported.⁴⁰We anticipate, however, that monosaccharidic

fragments may isomerize upon fragmentation, especially the

thermodynamically less stable hexofuranosyl residues, and this

would adversely aﬀect the analysis of monosaccharide entities

in larger oligosaccharides. Therefore, we present the ﬁnger-

prints of Galf-Manp and Galp-Manp disaccharides, for future

analysis of oligosaccharides. The strategy oﬀers the advantage

that no additional eﬀorts will be further required in terms of

synthesis, as the eight disaccharides synthesized in this work

will provide the library necessary for the structural study of

larger polymers.

RESULTS AND DISCUSSION

■

Synthesis of Galf-Containing Disaccharides and of

Their Galp Isomers. To access the panel of the targeted

unprotected and reducing disaccharides, four mannopyranosi-

dic acceptors were ﬁrst synthesized for further coupling with

galactofuranosyl or galactopyranosyl donors. Considering the

ease of preparation and structural modulation of thioglyco-

sides, and the orthogonal properties toward other families of

glycosyl donors, the phenyl thiomannopyranoside 1 was

selected as the precursor for all acceptors (Scheme 1). The

Figure 1. Deﬁned disaccharides for IM-MS and IRMPD ﬁnger-

printing

6)-linkage, but not a (1→4)-bond, were identiﬁed in

microorganisms,¹⁵some of them being pathogenic, for

instance, Trypanosoma, Leishmania, and Aspergillus species.

Surprisingly, the β-^D-Galf-(1→4)-D-Manp sequence was

exclusively found in lichens.²⁰⁻²⁴On another side, the

corresponding pyranosidic Galp-Manp isomers were identiﬁed

in diﬀerent microorganisms: Klebsiella for the (1→2)-

disaccharide,²⁵Rahnella for the (1→3)-derivative,²⁶Leishma-

nia, Escherichia coli for the nondigestable epilactose with the

(1→4)-linkage,^27,28and Burkholderia,²⁹KLH protein,³⁰

Salmonella³¹for the β-D-Galp-(1→6)-D-Manp. This resulting

orthogonality in Nature strengthens the need for consolidating

analytical data to diﬀerentiate Galf and Galp residues.³²

Scheme 1. Synthesis of the Required Mannopyranosidic

Acceptors

In this context, we have initiated a program dealing with new

analytical approaches of hexofuranosides based on mass

spectrometry since this technique can be augmented to

provide further structural and conformational information.

We thus anticipated that ion-mobility mass spectrometry (IM-

MS)^33,34and infrared multiple photon dissociation

(IRMPD)³⁵spectroscopy are indeed suitable tools to assess

the impact of the ring size and the branching pattern of small

disaccharides on physicochemical properties. We thus expect

that these techniques provide speciﬁc signatures for distin-

guishing furanosides from pyranosides. IM-MS separates ions,

based on their gas-phase mobility in an electric ﬁeld,³⁶and can

be used to determine speciﬁc structures.^37,38IRMPD spec-

troscopy has been widely used, in combination with quantum

chemistry, to elucidate the conformation of biomolecular ions

in the gas phase.³⁹Previous results demonstrate that IRMPD

spectroscopy has suﬃcient structural resolution to yield

distinctive signatures and to unambiguously distinguish

GalpNAc residues from Galf NAc ones in the case of

monosaccharides.⁴⁰Here, we describe the synthesis of the

eight isomers of naturally occurring reducing disaccharides

Gal-Man, and we demonstrate that individual signatures can be

obtained using adequate MS-based strategies, namely IM-MS

and IRMPD spectroscopy. We expect that these signatures will

be useful for the identiﬁcation of the corresponding Gal-Man

primary position was ﬁrst selectively acetylated with vinyl

acetate thanks to the action of the Candida antartica lipase B

(CAL B) to aﬀord 2 isolated in 87% yield.⁴⁴This biocatalyzed

acylation was interestingly performed on a large 20 g scale, and

this consolidates our choice toward this compound as a key

intermediate in our synthesis strategy. Moreover, intermediate

2 can act as acceptor for direct O-3 glycosylation without

further protections. The pioneering works of Taylor,⁴⁵dealing

with the activation of the equatorial hydroxyl of 1,2-diols in

carbohydrates with organoborinic catalysts, oﬀers the oppor-

tunity to signiﬁcantly increase the nucleophilicity of OH-3 in

the manno-series. Consequently, this compound was indeed

the key intermediate in our approach since it was either

directly engaged in glycosylation reaction [(1→3)-disacchar-

ides] or converted into the other required acceptors for (1→

2)-, (1→4)-, and (1→6)-linkages, thus limiting the number of

intermediates and synthetic steps. The synthesis of acceptor 5

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Scheme 2. Synthesis of the Galf-Containing Disaccharides FP

with free OH-2 started with the speciﬁc benzoylation of 2 at

position 3 in the presence of the borinate ester 2-amino-

ethyldiphenyl borinate (2-ADPB). The building block 3 thus

obtained was then converted into the mannopyranoside 5 after

selective deacetylation under acidic conditions and benzylide-

nation. This synthetic way was preferred to the sequence

benzylidenation followed by 3-O-benzoylation since it was

anticipated the possible formation of the O-2/O-3 acetalization

concomitantly with the desired O-4/O-6 protection. Never-

theless, it took advantage of the cis arrangement of the

hydroxyl groups in compound 2 for obtaining the derivative 6

bearing free OH-4 by acid-catalyzed acetalization with

dimethoxypropane. Finally, a two-step benzoylation−deacety-

lation of 2 aﬀorded 8 with a free primary position.

With the acceptors in hand, it was anticipated that

glycosylation at positions 6 and 3 is easier than that at O-2

and O-4.⁴⁶Moreover, it is recognized that conditions should

be tuned according to the nature of the leaving group on the

glycosyl donors but also on the basis of its furanose or the

pyranose form. Our results did not depart from these general

observations. The synthesis of disaccharides FP-2−FP-6 was

ﬁrst considered starting with the known galactofuranosyl

bromide 9a (Scheme 2). As expected, the coupling reactions at

O-2 and, in a lesser extent at O-4, were less eﬃcient than the

ones at O-3 under the Taylor’s conditions and at the primary

hydroxyl group. The preferred promoter was the soluble silver

triﬂate in all cases except the O-3 linkage, for which it was

shown that silver oxide was more eﬃcient.⁴⁷For these steps,

the yields ranged from 24% for the less reactive O-2 on the

mannoside 5 to 93% and 95% for acceptors 2 and 8,

respectively. It was, however, observed that limitations to

aﬀord 10 and 15 resulted from low reactivity of the donor 9a

for 10 and formation of the corresponding orthoester for 15.

Nevertheless, glycosylation of 5 and 6 with the trichloroace-

timidate 9b in the presence of TMSOTf as the catalyst gave

the desired disaccharides 10 and 15 in improved 54% and 71%

yields, respectively.

The disaccharides 10, 13, 15, and 18 are characterized by

two small J_H1−H2coupling constants close or less to 1 Hz for

both residues near 5.7 and 5.4 ppm (see the Supporting

Information). Moreover, 2D-NMR analysis revealed that the

former signal is correlated with a peak around 85 ppm, while

the latter is correlated with the signal at 104 ppm. These data

corroborate both the α-mannopyranosidic and the expected β-

galactofuranosidic linkages, respectively. Concerning the

regioselectivity of the glycosylation of acceptor 2 catalyzed

by 2-ADPB, it was also established on the ¹³C NMR data since

the signal corresponding to C-3 was signiﬁcantly up-shifted

from 72.2 ppm for the monosaccharide 2 to 78.2 ppm for the

disaccharide 13. Finally, removal of protecting groups was

performed under standard conditions: acidic hydrolysis for the

acetals, Zemplen transesteriﬁcation for the esters, and

hydrolysis promoted by N-iodosaccharine⁴⁸for the thioglyco-

sides. It is noteworthy that the resulting reducing disaccharides

were obtained in aqueous solution generally as mixtures of

1

anomers as revealed by H NMR and corroborates previous

data for FP-2⁴⁹and FP-3.⁵⁰The targeted structures thus

tightly approach those ensuing hydrolysis of polysaccharides

extracted from biomass. The developed synthetic strategy

therefore allowed the synthesis of all possible regioisomers

Galf-Manp and complements well the one recently described

for three Galf-Manp derivatives but bearing an amino spacer

arm at the reducing end.⁵¹Both anomers were unambiguously

characterized thanks to the NMR spectra, with the help of

TOCSY 1D-data, which allows isolation of the signals

corresponding to the irradiated proton. Under these

conditions, the spectrum of the minor β-anomer in water

was fully assigned (see the Supporting Information).

This strategy was next extended to the preparation of the

Galp-Manp isomers (Scheme 3), except for the disaccharide

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Scheme 3. Synthesis of the Galp-Containing Disaccharides PP

Figure 2. Extracted monoisotopic ion mobility spectra for the eight synthesized products as (a) [M + Na]⁺(m/z 365.1) and (b) as [M + Li]⁺(m/z

349.1). Standard deviations are given for three replicates. For both parts, the left panel corresponds to the galactofuranosyl-containing disaccharides

and right panel to the pyranosyl-containaing ones. Color for the regiochemistry of the glycosidic bond: Gal-(1→2)-Man (red), Gal-(1→3)-Man

(green), Gal-(1→4)-Man (orange), and Gal-(1→6)-Man (blue).

PP-4, which is commercially available. Considering the

synthesis of PP-3, very eﬃcient glycosidic coupling was

obtained starting from the triol 2 and the bromide 20a in

the presence of the organoboron catalyst 2-ADPB and silver

oxide. The standard deprotection steps aﬀorded PP-3 in 53%

yield over the three steps. Unfortunately, a poor glycosylation

yield was obtained using the same donor 20a and the acceptor

5. The targeted intermediate 21 was nevertheless prepared

from the perbenzoylated galactopyranosyl trichloroacetimidate

20b⁵²and the same acceptor and isolated after removal of the

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benzylidene ring in 26% yield. Further deprotection steps gave

the desired product PP-2⁵³in satisfactory yield. Finally, and

surprisingly, the formation of the (1→6)-linkage raised some

diﬃculties. First attempts with the bromide 20a activated by

silver triﬂate transferred an acetyl group to the acceptor 8.

Unfortunately, adding diisopropylethyl amine as a base

(DIPEA) to avoid the acid-catalyzed transesteriﬁcation also

resulted in the formation of an orthoester in 73% yield (results

not shown). This was circumvented by using the trichlor-

oacetimidate 20b and trimethylsilyl triﬂate (TMSOTf), so that

the disaccharide 25 was isolated in a 78% yield. Action of

sodium methoxide followed by hydrolysis of the thiomanno-

side gave the wanted disaccharide PP-6.⁵⁴

Mass Spectrometry Analysis. As a preliminary mass

spectrometry analysis, the spectra of all disaccharides were

recorded using traditional MS/MS approaches. It was

evidenced that the Galf moiety cannot be diﬀerentiated from

its Galp isomer, as the products do not generate speciﬁc

fragments for a deﬁned Galf-Manp/Galp-Manp pair (see

Figure S1). We thus turned to gas phase analysis techniques

that are sensitive to both the spatial arrangement and the

regiochemistry of the ions: ion mobility (IM-MS) and IRMPD

spectroscopy.

Ion Mobility−Mass Spectrometry. We ﬁrst analyzed the

synthesized disaccharides using positive electrospray ionization

(ESI) time-of-ﬂight mass spectrometry, hyphenated with a

high-resolution cyclic ion mobility cell (Waters Select Series

Cyclic IMS, Wilmslow, UK).⁵⁵Arrival time distributions

(ATDs) were then calibrated to give collision cross sections

(CCSs), which represent the eﬀective surface of the ions that

interacts with the buﬀer gas during ion mobility experiments.

We recorded the ion mobility of the [M + Na]⁺cations or [M

+ Li]⁺cations after four passes around the cyclic mobility cell,

i.e., approximately a path of four meters. The resolving power

of ion mobility is proportional to the path length of the ions,

which, for four passes, yields a theoretical CCS/δCCS

resolution of about 200, meaning that cyclic IM-MS can

resolve conformers that diﬀer by less than about 1 Å²in the

case of the disaccharides studied here (i.e., having CCSs of

around 170 Å²). As shown in the literature, this level of IM

resolution allows the gas-phase separation of isomers and

conformers prior to their mass measurement.⁵⁶⁻⁵⁸After mass

selection of each disaccharide using a quadrupole ﬁlter, we

recorded the set of gas-phase conformations for each ion,

translated into CCS distributions (CCSDs). As shown in

Figure 2 for the eight FP and PP disaccharides, a single

disaccharide can give a single conformer or multiple ones with

diﬀerent CCSs, intensities, and peak shapes. These features of

the CCSD act as a ﬁngerprint of each disaccharide. Notably,

ﬁtting gaussians under the curve can be used in order to

estimate the number of conformers in CCSDs (full,

deconvolved CCSDs are given in Figure S2).

0.5 Å²), two kinds of signatures could be observed: (i) the

isomers each display a single peak of diﬀerent CCS or (ii) the

isomers have shared CCSs but diﬀer through the global

distribution of the peaks. For instance, in (i), the case of FP-4

and PP-4, their pattern is rather similar with one major peak

(note, however, a slight broadening of the peak for FP-4,

which suggests the presence of two conformers) but these

single peaks have diﬀerent CCSs (173.4 Å²for FP-4 and 171.5

Å²for PP-4). In (ii), the case of FP-3 and PP-3, a diﬀerence of

less than 1 Å²is measured on the most extended conformation

(174.7 Å²versus 173.9 Å²). However, the overall pattern is

diﬀerent, with three conformations separated for FP-3

compared to two conformations for PP-3. Notably, the FP-

type samples appeared to produce more complex ATD

patterns than PP-type ones. This behavior might be related

to the greater ﬂexibility of the furanose moiety,^59,60resulting in

diﬀerent conformations.

The same reasoning can be made “vertically” to diﬀerentiate

isomers diﬀering in their regiochemistry. As an example, the

FP-2 sample had an intense signal at 171.0 Å²with another

peak of lower intensity at 174.1 Å². In contrast, the FP-3

sample exhibited a triplet of CCSDs, respectively, at 169.3,

171.7, and 174.7 Å². Although less pronounced diﬀerences in

CCSD patterns were observed for the PP-type samples, most

signatures remained distinctive. For example, the PP-3 showed

a doublet of CCSDs at 169.9 (minor species) and 173.9 Å²,

while the PP-4 displayed a doublet at 168.9 (minor species)

and 171.5 Å².

However, although the [M + Na]⁺adducts already provided

distinctive signatures in most cases, some ambiguities remained

regarding the samples FP-2 and PP-2. They had similar

proﬁles with a CCS diﬀerence below 1 Å². Moreover, regarding

the regiochemistry, samples PP-2 and PP-4 have the same

CCS and only diﬀered through minor conformations. The

samples were thus also analyzed as lithium adducts. As shown

in Figure 2b, we achieved a better distinction in the IM-MS

proﬁles for FP-2 and PP-2, both in terms of the CCS values of

the peaks and in terms of the number and intensities of the

conformers (both harbor two peaks at, respectively, 167.8 and

170.3 Å²and 166.7 and 168.4 Å²). The measurement of the

IM-MS of the [M + Li]⁺adduct also yielded a completely

diﬀerent pattern for PP-2 compared to PP-6. Although

samples PP-4 and PP-6 have strikingly similar CCSDs when

analyzed as [M + Li]⁺adducts (a main peak at 167.3 Å², with

similar peak shapes), the combination of the [M + Na]⁺and

[M+Li]⁺ﬁngerprints is unambiguous and allows identiﬁcation

of both the galactosyl conﬁguration and the regiochemistry of

the glycosidic bond.

Exploration of the IRMPD Sensitivity for the Identiﬁcation

of the Ring-Size and Regiochemistry. IRMPD (InfraRed

Multiple Photon Dissociation) spectroscopy is an advanced

MS-based scheme that adds a dimension of laser spectroscopy

to mass spectrometry analysis. Its main advantage is to allow

simultaneous measurements of the mass and the infrared

ﬁngerprint of an ion. Two ions of the same mass will generally

feature distinctive IR ﬁngerprints if they have diﬀerent spatial

arrangements (3D conformation or isomeric form).⁴³Here, we

explore the sensitivity of this technique to resolve the two

types of isomerism present in the synthesized model

disaccharides, namely the regiochemistry of the Gal-Man

bond and the form of the galactosyl entity as a ﬁve- or a six-

membered ring.

Second, we measured the CCSDs of the eight synthesized

products as [M + Na]⁺ions at m/z 365.1 (Figure 2a). The [M

+ Na]⁺cations are most commonly used for MS and IM-MS

analyses of neutral oligosaccharides as they oﬀer a good

compromise between ionization and ion transmission through

IM drift cells, more than ammonium adducts. Alkali metal

cations also favor the separation of conformers compared to

protonated adducts. Figure 2.a can ﬁrst be read “horizontally”

to diﬀerentiate isomers diﬀering by the Galf or Galp residue.

Here, considering the maximum standard deviations of CCSs

observed during replicates (diﬀerences are signiﬁcant if above

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As mentioned in the previous section, Li⁺and Na⁺adducts

are often used to increase ion signal and fragmentation in mass

spectrometry of carbohydrates.⁶¹In the context of IRMPD

spectroscopy, diﬀerent ion adducts will lead to diﬀerent

spectroscopic ﬁngerprints.^39,62As previously reported, ion

adducts can also be chosen to enhance the spectroscopic

diﬀerentiation of carbohydrate isomers.⁶²Generally, proto-

nated ions feature more distinguishing IR ﬁngerprints than

other charge states (i.e., deprotonated ions or alkali adducts).

In the present study, the disaccharides of interest are neutral

and do not easily protonate; therefore, we use ammonium

adducts for ionization and enhanced spectroscopic diagnostic.

The eight IRMPD spectra presented in Figure 3 were

obtained using the setup previously described.⁶³In short, the

in the same area. Additionally, PP-4 shows a broad and intense

feature around 3500 cm⁻¹.

Spectra are less distinctive of the regiochemistry of

furanosyl-containing disaccharides, but some diﬀerences can

be noticed. Besides the main band at 3650 cm⁻¹(furanose

diagnostic), all four spectra show a NH band in a close range

(from 3380 to 3390 cm⁻¹). In addition, FP-6 shows a weak

band at 3580 cm⁻¹(marked with a blue star); FP-4 features a

group of partly resolved bands in the 3500−3570 cm⁻¹region

(marked with an orange star); both FP-2 and FP-3 show a

broadening of their NH band toward the high wavenumber,

ranging to 3490 cm⁻¹(marked with red and green stars). FP-2

and FP-3 only diﬀer by the relative intensity of this shoulder

(FP-2: high, FP-3: low).

Overall, the IRMPD spectra bear a strong diagnostic of the

ring size: either one dominant band at 3650 cm⁻¹for furanose

or a doublet of bands at 3650/3575 cm⁻¹for pyranose. In the

case of Galp-containing disaccharides, the IR ﬁngerprint is also

diagnostic of the regiochemistry because all PP spectra are

distinguishable. For Galf-containing disaccharides, the IRMPD

approach proves less distinguising of the regiochemistry: FP-2

and FP-3 have close ﬁngerprints.

CONCLUSION

■

The results presented in this work, combining diﬀerent ﬁelds in

glycosciences, allowed us to highlight the impact of the ring

size of the nonreducing galactosyl residue for each possible

connectivity in the Galf-Manp disaccharides. On one hand, this

study showed that the metal adducts of the synthesized

compounds have diﬀerent gas-phase conformations, resulting

in speciﬁc signatures in IM-MS for all Gal-Man disaccharides,

according to the ring size for the galactosyl residue and to the

connectivity between both entities. The same structural

diﬀerences were strengthened on another hand, registering

IR signals of the disaccharides in the gas phase.

As a result, we expect that the IM-MS and IRMPD data can

be used as libraries of reference ﬁngerprints for further analysis

of unknown disaccharides and that they constitute the

fundamentals of bringing out Galf for pattern recognition in

longer oligosaccharides. Therefore, we expect that this study

paves the way to the screening of galactofuranose in natural

polysaccharides.

Figure 3. Left pannel: IRMPD spectra of galactofuranosyl-containing

disaccharides. Right panel: galactopyranosyl-containing disaccharides.

Color code for the regiochemistry of the glycosidic bond: Gal-(1→2)-

Man (red), Gal-(1→3)-Man (green), Gal-(1→4)-Man (orange), Gal-

(1→6)-Man (blue).

EXPERIMENTAL SECTION

■

Synthesis. General Experimental Details. All reagents were

purchased from commercial sources and were used without further

puriﬁcation unless noted. 2,3,5,6-Benzoylgalactofuranosyl bromide

9a⁶⁴and trichloroacetimidate 9b⁶⁵as well as 2,3,4,6-benzoylgalacto-

pyranosyl trichloroacetimidate 20b⁵²were synthesized according to

literature procedures. Unless otherwise stated, all reactions were

monitored by TLC on silica gel 60 F₂₅₄. TLC spots were detected

under 254 nm UV light or by staining with cerium ammonium

molybdate solution. For reactions that proceeded by heating, a

metallic heating mantle was used. Column chromatography was

performed on silica gel (50 μm). High-resolution masses were

recorded in positive mode using direct electrospray ionization on a

Waters Q-Tof 2 spectrometer.

standards were prepared in water/methanol (50/50), and 0.1%

of ammonium sulfate was added to promote the formation of

+

ionic complexes M·NH₄, which are easily detected by mass

spectrometry. The ions of interest are detected at 360 m/z and

isolated in the ion trap where they are irradiated by the laser to

record their IR ﬁngerprints. The IRMPD spectra are presented

between 3200 and 3700 cm⁻¹, which corresponds to the active

range of NH and OH vibrations (elongation modes).

First, all spectra display a common feature: an intense band

around 3650 cm⁻¹. In addition, another intense feature is

observed at 3575 cm⁻¹only for the pyranose form, which

makes a straightforward distinction between pyranose and

furanose ﬁngerprints. The 3200−3550 cm⁻¹range is unique

for each pyranose: PP-6 hardly presents any vibrational activity

besides the pyranose diagnostic doublet. PP-2 presents a

distinctive feature at 3547 cm⁻¹and a weak NH band at 3380

cm⁻¹. PP-3 and PP-4 show an intense and broad NH feature

NMR spectra were recorded on a Bruker Avance III 400

spectrometer operating at 400.13 MHz for ¹H, equipped with a

BBFO probe with a Z-gradient coil and a GREAT 1/10 gradient unit

1

or on a Bruker Avance III operating at 500.13 MHz for H equipped

1

with H and ¹³C cryo-probe. All experiments were carried out at 25

°C, and references for chemical shifts are external. Coupling constants

J were calculated in hertz (Hz). Proton and carbon NMR peaks were

unambiguously assigned by COSY (double quantum ﬁltered with

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gradient pulse for selection), HSQC (gradient echo-anti echo

selection and shape pulse), and HMBC (echo-anti echo gradient

selection, magnitude mode) correlation experiments as well as

TOCSY. Mutiplicity are annotated as s (singlet), d (doublet), t

(triplet), m (multiplet), or o (overlapping signals).

4.56 (dd, 1H, J = 12.1, 5.1 Hz, H-6), 4.46 (dd, 1H, J = 3.1, 1.6 Hz, H-

2), 4.44 (ddd, 1H, J = 9.8, 5.1, 2.2 Hz, H-5), 4.31 (dd, 1H, J = 12.1,

2.2 Hz, H-6′), 4.11 (t, 1H, J = 9.8 Hz, H-4), 2.09 (s, 3H, CH₃).

¹³C{1H} NMR (CDCl₃, 100 MHz): δ 171.7, 166.6 (CO), 133.8,

131.8, 130.0, 129.3, 128.7, 127.9 (C₆H₅), 88.0 (C-1), 75.1 (C-3),

72.1, 70.9 (C-2, C-5), 66.2 (C-4), 63.4 (C-6), 21.0 (CH₃). HRMS

(ESI) m/z: [M + Na]⁺Calcd for C₂₁H₂₂O₇SNa 441.0978; Found

441.0982.

Phenyl 3-O-Benzoyl-1-thio-α-^D-mannopyranoside (4). To a

solution of 3 (1.42 g, 2.41 mmol) in dry MeOH (30 mL) was

added acetyl chloride (360 μL, 5.09 mmol) under anhydrous

conditions. The reaction mixture was stirred at room temperature

for 17 h. The reaction was then stopped by the addition of saturated

aqueous NaHCO₃. The aqueous layer was extracted with DCM. The

combined organic layers were dried over MgSO₄, ﬁltered, and

concentrated under reduced pressure to aﬀord 4 (1.22 g, 96%) as a

white solid. ¹H NMR (CDCl₃, 400 MHz): δ 8.13−8.00 (m, 2H,

H_arom), 7.63−7.27 (m, 8H, H_arom), 5.55 (d, 1H, J = 1.6 Hz, H-1), 5.35

(dd, 1H, J = 9.7, 3.1 Hz, H-3), 4.44 (dd, 1H, J = 3.1, 1.6 Hz, H-2),

4.35 (t, 1H, J = 9.7 Hz, H-4), 4.26 (dt, 1H, J = 9.7, 3.3 Hz, H-5), 3.96

(dd, 1H, J = 12.1, 3.7 Hz, H-6), 3.86 (dd, 1H, J = 12.1, 2.8, H-6′).

¹³C{1H} NMR (CDCl₃, 100 MHz): δ 167.9, 167.0 (CO), 134.3,

1

The zg30 Bruker pulse program was used for 1D H NMR, with a

TD of 64k, a relaxation delay d1 = 2s and 32 scans or more. The

spectrum width was set to 18 ppm. 2D COSY experiments were

acquired using the cosygpdqf pulse program. Matrices consisting of

256−512 (t1) × 2048 (t2) complex data points were recorded. An

AQ time of 0.25−0.5 s was used. Processing was performed with a

QSINE function in both dimensions (SSB = 0). 2D TOCSY

experiments were acquired using the dipsi2sisp pulse program with a

mixing time of 150 ms in major cases. Matrices consisting of 256−400

(t1) × 4k−8k (t2) complex data points were recorded; 8−16 scans

are carried out per t1 increment with 1.5 s recovery delay (d1) and

AQ time of 0.3 to 0.7 s. Processing was performed with a QSINE

function in both dimensions (SSB = 2). ¹³C NMR spectra were

recorded at 100.61 MHz or at 125.13 MHz on cryo-probe. Several

sequences as jmod, dept135, or zgpg30 were used with n*1024 scans

depending on the concentration of the sample. TD was set to 64k and

a relaxation delay of 2 s for a spectral width of 220 ppm was used.

2D HSQC (¹H−¹³C) experiments were acquired using the

hsqcetgpsisp2.2 pulse program for high sensitivity with an AQ =

0.25 to 0.5 s, d1 = 1.5 s, ns = 2 to 24 depending on the concentration.

Generally, 256 experiences were acquired (t1). Fourier transform was

performed in both dimensions with a SINE function (SSB = 3). 2D

HMBC (¹H−¹³C) experiments were performed with either the

hmbcplrndqf or the impact-hmbc pulse program. D1 was set to 0.3 to

1.5 s, delay d6 for the evolution of long-range coupling was set to 65

ms, NS was depending on the concentration and the number of series

was set at 256 to 512(t1). All of the data were processed with a SINE

function in both dimensions (SSB = 3). To identify the ¹H frequency

of the mixture of anomers, the 1D-Tocsy experiment (selcssfdizs.2)

from the Bruker library was used with 150 ms for mixing time and 16

for TD0 when the highest selectivity was required.

133.7, 132.0, 130.0, 129.8, 129.3, 128.8, 127.9 (C₆H₅), 88.2 (C-1),

75.5 (C-3), 73.7 (C-5), 71.0 (C-2), 65.9 (C-4), 62.0 (C-6). HRMS

(ESI) m/z: [M + Na]⁺Calcd for C₁₉H₂₀O₆SNa 399.0873; Found

399.0875.

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

noside (5). To a solution of 1 (620 mg, 1.65 mmol) in dry

acetonitrile (10 mL) were added benzaldehyde dimethyl acetal (372

μL, 2.48 mmol) and camphorsulfonic acid (77 mg, 0.33 mmol) under

anhydrous conditions. The reaction mixture was allowed to stir at 55

°C for 8 h. Then the medium was concentrated under reduced

pressure and partitioned between DCM and aqueous saturated

NaHCO₃solution. The organic layer was washed with aqueous

saturated NaHCO₃solution (2×) and water. The combined organic

phases were dried over MgSO₄, ﬁltered, and concentrated under

reduced pressure. The resulting residue was puriﬁed by column

chromatography on silica gel (cyclohexane/EtOAc gradient from

100:0 to 70:30) to aﬀord 5 (573 mg, 75%) as a white solid. ¹H NMR

(CDCl₃, 400 MHz): δ 8.08 (dd, 2H, J = 8.4, 1.4 Hz, H_arom), 7.61−

7.43 (m, 7H, H_arom), 7.37−7.29 (m, 6H, H_arom), 5.63 (s, 1H, H-7),

5.61 (d, 1H, J = 1.4 Hz, H-1), 5.60 (dd, 1H, J = 10.2, 3.2 Hz, H-3),

4.59 (dd, 1H, J = 3.2, 1.4 Hz, H-2), 4.54 (td, 1H, J = 10.2, 4.9 Hz, H-

5), 4.37 (t, 1H, J = 10.2 Hz, H-4), 4.28 (dd, 1H, J = 10.2, 4.9 Hz, H-

6), 3.92 (t, 1H, J = 10.2 Hz, H-6′). ¹³C{1H} NMR (CDCl₃, 100

MHz): δ 165.6 (CO), 137.2, 133.6, 133.4, 132.0, 130.0, 129.7, 129.3,

129.2, 128.6, 128.4, 128.0, 126.3 (C₆H₅), 102.0 (C-7), 88.6 (C-1),

76.4 (C-4), 71.6, 71.4 (C-3, C-2), 68.7 (C-6), 65.3 (C-5). HRMS

(ESI) m/z: [M + Na]⁺Calcd for C₂₆H₂₄O₆SNa 487.1186; Found

487.1187.

Phenyl 6-O-Acetyl-2,3-O-isopropylydene-1-thio-α-^D-mannopyr-

anoside (6). To a solution of 2 (2.0 g, 3.37 mmol) in anhydrous

acetone (30 mL) were added 2,2-dimethoxypropane (1.6 mL, 12.74

mmol) and camphorsulfonic acid (147 mg, 0.637 mmol) under

anhydrous conditions. The mixture was stirred at room temperature

for 17 h. Then the reaction was stopped by the addition of

triethylamine and concentrated under reduced pressure. The resulting

residue was dissolved in DCM, and the organic layer was washed with

saturated aqueous NaHCO₃(3×) followed by water. The organic

layers were dried over MgSO₄, ﬁltered, and evaporated under reduced

pressure. The resulting residue was puriﬁed by column chromatog-

raphy on silica gel (cyclohexane/EtOAc gradient from 100:0 up to

80:20) to aﬀord 6 (1.95 g, 87%) as a colorless oil. ¹H NMR (CDCl₃,

400 MHz): δ 7.51−7.47 (m, 2H, H_arom), 7.34−7.27 (m, 3H, H_arom),

5.82 (s, 1H, H-1), 4.47−4.41 (m, 1H, H-6), 4.35 (dd, 1H, J = 5.6, 1.0

Hz, H-2), 4.22−4.15 (m, 3H, H-3, H-5, H-6′), 3.60 (dd, 1H, J = 10.2,

7.5 Hz, H-4), 2.02 (s, 3H, CH₃), 1.52 (s, 3H, CH₃), 1.37 (s, 3H,

CH₃). ¹³C{1H} NMR (CDCl₃, 100 MHz): δ 171.7 (CO), 133.0,

132.0, 129.2, 127.9 (C₆H₅), 110.0 (C(CH₃)₂), 84.0 (C-1), 78.1 (C-

3), 76.3 (C-2), 69.9 (C-4), 69.4 (C-5), 63.4 (C-6), 28.3, 26.4, 20.9

Further details, including NMR data, are described in the

Supporting Information.

Synthesis of Glycosyl Acceptors. Phenyl 6-O-Acetyl-1-thio-α-^D-

mannopyranoside (2). To a solution of phenyl 1-thio-α-^D-

mannopyranoside 1 (20 g, 73.5 mmol) in dry THF (600 mL) were

added vinyl acetate (17.6 mL, 0.19 mol) and Novozym 435 (3 g). The

reaction mixture was allowed to stire at 45 °C for 65 h. The reaction

mixture was ﬁltered and concentrated under reduced pressure. The

resulting residue was puriﬁed by column chromatography on silica gel

(DCM/MeOH gradient from 100:0 up to 90:10) to aﬀord 2 (19.97 g,

87%) as a beige solid. ¹H NMR (CDCl₃, 400 MHz): δ 7.50−7.44 (m,

2H, H_arom), 7.31−7.22 (m, 3H, H_arom), 5.58 (d, 1H, J = 1.3 Hz, H-1),

4.49 (dd, 1H, J = 12.6, 6.9 Hz, H-6), 4.37−4.31 (m, 2H, H-5, H6′),

4.27 (dd, 1H, J = 3.3, 1.3 Hz, H-2), 3.91 (dd, 1H, J = 9.4, 3.3 Hz, H-

2), 3.78 (t, 1H, J = 9.4 Hz, H-3), 2.03 (s, 3H, CH₃). ¹³C{1H} NMR

(CDCl₃, 100 MHz): δ 172.2 (CO), 133.7, 131.8, 129.1, 127.7

(C₆H₅), 87.9 (C-1), 72.2, 72.2 (C-2, C-3), 71.4 (C-5), 68.2(C-4),

63.9 (C-6), 21.0 (CH₃). HRMS (ESI) m/z: [M + Na]⁺Calcd for

C₁₄H₁₈O₆SNa 337.0716; Found 337.0718.

Phenyl 6-O-Acetyl-3-O-benzoyl-1-thio-α-^D-mannopyranoside

(3). To a solution of 2 (1.0 g, 3.2 mmol) in dry acetonitrile (20

mL) were added 2-aminoethyldiphenyl borinate (788 mg, 3.5 mmol),

benzoyl chloride (1.2 mL, 10.0 mmol), and N,N-diisopropylethyl-

amine (1.7 mL, 9.8 mmol) under anhydrous conditions. The reaction

mixture was stirred at 40 °C for 17 h. The reaction mixture was then

concentrated under reduced pressure, and the resulting residue was

partitioned between DCM and aqueous saturated NaHCO₃solution.

The organic layer was washed with aqueous saturated NaHCO₃

solution (2×) and brine, dried over MgSO₄, ﬁltered, and concentrated

under reduced pressure. The resulting residue was puriﬁed by column

chromatography on silica gel (DCM/MeOH gradient from 100:0 to

1

90:10) to aﬀord 3 (1.17 g, 84%) as a white solid. H NMR (CDCl₃,

400 MHz): δ 8.12−8.08 (m, 2H, H_arom), 7.62−7.28 (m, 8H, H_arom),

5.58 (d, 1H, J = 1.6 Hz, H-1), 5.34 (dd, 1H, J = 9.8, 3.1 Hz, H-3),

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(CH₃). HRMS (ESI) m/z: [M + Na]⁺Calcd for C₁₇H₂₂O₆SNa

377.1029; Found 377.1031.

128.05, 126,28, 125,74 (C₆H₅), 103.97 (C-7), 102.00 (C-1b), 85.96

(C-1a), 83.05 (C-4b), 81.53 (C-2b), 77.68 (C-3b), 76.43 (C-4a),

74.81 (C-2a), 70.56 (C-3a), 70.35 (C-5b), 68.67 (C-6a), 65.45 (C-

5a), 63.65 (C-6b). HRMS (ESI) m/z: [M + Na]⁺Calcd for

C₆₀H₅₀O₁₅SNa 1065.2763; Found 1065.2761.

Phenyl 6-O-Acetyl-2,3,4-tri-O-benzoyl-1-thio-α-^D-mannopyrano-

side (7). To a solution of 2 (10 g, 31.8 mmol) in dry pyridine (300

mL) was added dropwise benzoyl chloride (14.8 mL, 0.13 mol) at 0

°C under anhydrous conditions. The reaction mixture was stirred at

room temperature for 17 h. The reaction mixture was then

concentrated under reduced pressure. The residue was dissolved in

EtOAc, and the organic layer was washed with aqueous 1 M HCl,

followed by water, saturated aqueous NaHCO₃, and brine. The

resulting aqueous layers were extracted with EtOAc, and the

combined organic layers were dried over MgSO₄, ﬁltered, and

evaporated under reduced pressure. The resulting residue was puriﬁed

by column chromatography on silica gel (cyclohexane/EtOAc

gradient from 100:0 up to 80:20) to aﬀord 7 (18.12 g, 91%) as a

white solid. ¹H NMR (CDCl₃, 400 MHz): δ 8.13−8.08 (m, 2H,

H_arom), 8.03−7.98 (m, 2H, H_arom), 7.90−7.83 (m, 2H, H_arom), 7.71−

7.23 (m, 14H, H_arom), 6.02 (t, 1H, J = 10.1 Hz, H-4), 5.97 (dd, 1H, J

= 3.2, 1.6 Hz, H-2), 5.86 (dd, 1H, J = 10.1, 3.2 Hz, H-3), 5.79 (d, 1H,

J = 1.6 Hz, H-1), 4.88 (ddd, 1H, J = 10.1, 5.5, 2.7 Hz, H-5), 4.43 (dd,

1H, J = 12.2, 5.5 Hz, H-6), 4.30 (dd, 1H, J = 12.2, 2.7 Hz, H-6′).

¹³C{1H} NMR (CDCl₃, 100 MHz): δ 170.6, 165.7, 165.5, 165.4

(CO), 133.8, 133.7, 133.5, 132.8, 132.3, 130.0, 130.0, 129.9, 129.4,

129.4, 129.0, 128.9, 128.7, 128.6, 128.5, 128.3 (C₆H₅), 86.0 (C-1),

72.0 (C-2), 70.4 (C-3), 69.8 (C-5), 67.2 (C-4), 62.9 (C-6). HRMS

(ESI) m/z: [M + Na]⁺Calcd for C₃₅H₃₀O₉SNa 649.1503; Found

649.1501.

Phenyl 2,3,4-Tri-O-benzoyl-1-thio-α-^D-mannopyranoside (8). To

a solution of 7 (4.89 g, 7.82 mmol) in a mixture of dry DCM/dry

MeOH 1:1 (80 mL) was added acetyl chloride (830 μL, 11.73 mmol)

under anhydrous conditions. The mixture was stirred at room

temperature for 17 h. The reaction was then stopped by the addition

of saturated aqueous NaHCO₃. The resulting aqueous layer was

extracted with DCM (2×). The combined organic layers were dried

over MgSO₄, and solvent was removed under reduced pressure to

aﬀord 8 (4.34 g, 95%) as a white solid. The measured spectroscopic

data are in concordance with the literature.⁶⁶HRMS (ESI) m/z: [M +

Na]⁺Calcd for C₃₃H₂₈O₈SNa 607.1397; Found 607.1405.

Phenyl 2,3,5,6-Tetra-O-benzoyl-β-^D-galactofuranosyl-(1→2)-3-

O-benzoyl-1-thio-α-^D-mannopyranoside (11). To a solution of

disaccharide 10 (440 mg, 0.42 mmol) in DCM (5 mL) were added

1 drop of water and TFA (180 μL, 1.33 mmol). The mixture was

stirred during 1 h 30 at room temperature. The reaction was then

quenched by addition of triethylamine and concentrated under

reduced pressure. The residue was puriﬁed by column chromatog-

raphy on silica gel (DCM/MeOH gradient from 100:0 to 95:5) to

1

aﬀord 11 (171 mg, 42%) as a white solid. H NMR (CDCl₃, 400

MHz): δ 8.16−8.10 (m, 2H, H_arom), 8.00−7.93 (m, 4H, H_arom), 7.90−

7.86 (m, 2H, H_arom), 7.82−7.78 (m, 2H, H_arom), 7.64−7.27 (m, 16H,

H_arom), 7.25−7.15 (m, 4H, H_arom), 5.79 (dt, 1H, J = 7.5, 3.4 Hz, H-

5b), 5.68 (d, 1H, J = 1.7 Hz, H-1a), 5.62 (d, 1H, J = 4.5 Hz, H-3b),

5.52 (d, 1H, J = 0.8 Hz, H-2b), 5.44 (s, 1H, H-1b), 5.40 (dd, 1H, J =

9.8, 3.2 Hz, H-3a), 4.69 (dd, 1H, J = 3.2, 1.7 Hz, H-2a), 4.47 (t, 1H, J

= 9.8 Hz, H-4a), 4.43 (t, 1H, J = 4.5 Hz, H-4b), 4.37 (dd, 1H, J =

12.1, 7.5 Hz, H-6b), 4.31 (dt, 1H, J = 9.8, 3.6 Hz, H-5a), 4.24 (dd,

1H, J = 12.1, 3.4 Hz, H-6′b), 3.96 (d, 2H, J = 3.6 Hz, H-6a). ¹³C{1H}

NMR (CDCl₃, 100 MHz): δ 166.3, 166.0, 165.7, 165.6, 165.6 (CO),

133.9, 133.8, 133.6, 133.5, 133.3, 133.1, 132.3, 130.1, 129.9, 129.8,

129.7, 129.6, 129.5, 129.4, 129.1, 128.8, 128.7, 128.6, 128.5, 128.5,

128.4, 128.1 (C₆H₅), 103.8 (C-1b), 85.1 (C-1a), 82.9 (C-4b), 82.1

(C-2b), 77.7 (C-3b), 74.2 (C-2a), 74.1 (C-3a), 73.7 (C-5a), 70.3 (C-

5b), 66.4 (C-4a), 63.6 (C-6b), 62.3 (C-6a). HRMS (ESI) m/z: [M +

Na]⁺Calcd for C₅₃H₄₆O₁₅SNa 977.2450; Found 977.2452.

Phenyl β-^D-Galactofuranosyl-(1→2)-1-thio-α-D-mannopyrano-

side (12). To a solution of disaccharide 11 (122 mg, 0.013 mmol)

in anhydrous MeOH (2 mL) was added a solution of MeONa in

MeOH (0.054M, 473 μL, 25 μmol). The mixture was then stirred

overnight at room temperature. Then the solution was neutralized by

the addition of IR 120-H⁺form resin. After ﬁltration, the ﬁltrate was

evaporated under reduced pressure. The resulting residue was

suspended in water and the biphasic solution was washed with

DCM (3×). The aqueous phase was ﬁnally freeze-dried to aﬀord 12

Synthesis of Galactofuranosyl-Containing Disaccharides FP.

Phenyl 2,3,5,6-Tetra-O-benzoyl-β-^D-galactofuranosyl-(1→2)-3-O-

benzoyl-4,6-O-benzylidene-1-thio-α-^D-mannopyranoside (10). To

a solution of trichloroacetimidate galactofuranosyl 9b (72 mg, 0.1

mmol) and 5 (35 mg, 0.075 mmol) in anhydrous DCM (5 mL) were

added activated 4 Å molecular sieves (100 mg). The mixture was

cooled to 0 °C and stirred for 15 min before dropwise addition of

TMSOTf (0.02 M in DCM, 1.1 mL, 0.022 mmol). The temperature

was maintained at 0 °C, and the reaction was followed by TLC

(cyclohexane/EtOAc 8/2). After 2 h, no starting material remained so

triethylamine was added and the solution was ﬁltered on a pad of

Celite. The resulting ﬁltrate was evaporated under vacuo, and the

residue was puriﬁed by column chromatography on silica gel

(cyclohexane/EtOAc gradient from 90:10 up to 70:30) to give 10

1

(53 mg, 95%) as a pulverulent white powder. H NMR (D₂O, 400

MHz): δ 7.64−7.57 (m, 2H, H_arom), 7.47−7.40 (m, 3H, H_arom), 5.69

(s, 1H, H-1a), 5.15 (d, 1H, J = 1.0 Hz, H-1b), 4.32 (dd, 1H, J = 3.5,

1.3 Hz, H-2a), 4.21−4.16 (m, 1H, H-5a), 4.16−4.14 (m, 1H, H-2b),

4.11−4.05 (m, 2H, H-4b, H-3b), 3.93 (dd, 1H, J = 9.8, 3.5 Hz, H-3a),

3.88−3.76 (m, 3H, H-5b, H-6a), 3.75 (t, 1H, J = 9.8 Hz, H-4a), 3.70

(dd, 1H, J = 11.8, 4.4 Hz, H-6b), 3.65 (dd, 1H, J = 11.6, 7.3 Hz, H-

6′b). ¹³C{1H} NMR (D₂O, 100 MHz): δ 132.6, 132.3, 129.4, 128.4

(C₆H₅), 104.8 (C-1b), 84.8 (C-1a), 82.9 (C-4b), 81.1 (C-2b), 76.7

(C-3b), 75.5 (C-2a), 73.7 (C-5a), 70.6 (C-5b), 70.3 (C-3a), 67.2 (C-

4a), 62.7 (C-6b), 60.6 (C-6a). HRMS (ESI) m/z: [M + Na]⁺Calcd

for C₁₈H₂₆O₁₀SNa 457.1139; Found 457.1142.

β-^D-Galactofuranosyl-(1→2)-D-mannopyranose (FP-2). To a

solution of the disaccharide 12 (35 mg, 0.08 mmol) in a mixture of

acetonitrile/H₂O 1:1 (1 mL) was added N-iodosaccharine (87 mg,

0.28 mmol). The resulting mixture was stirred for 2 h 30 at room

temperature. Then the solvent was evaporated under reduced

pressure. The resulting residue was partitioned between DCM and

water. The resulting organic layer was further extracted with water

(2×). The combined aqueous layers were ﬁnally freeze-dried. The

resulting solid was puriﬁed by column chromatography on silica gel

(EtOAc/AcOH/H₂O/MeOH gradient from 9:0.5:0.5:0 up to

5:2:2:1) to aﬀord FP-2 (19 mg, 68%) as a solid. HRMS (ESI) m/

z: [M + Na]⁺Calcd for C₁₂H₂₂O₁₁Na 365.1054; Found 365.1057.

FP-2α (major). ¹H NMR (D₂O, 400 MHz): δ 5.32 (d, 1H, J = 1.6

Hz, H-1a), 5.12 (d, 1H, J = 2 Hz, H-1b), 4.15 (t, 1H, J = 2.2 Hz, H-

2b), 4.01 (dd, 1H, J = 3.4, 1.6 Hz, H-2a), 4.09−4.07 (m, 2H, H-3b,

H-4b), 3.89 (dd, 1H, J = 9.7, 3.4 Hz, H-3a), 3.87 (dd, 1H, J = 11.7,

2.0 Hz, H-6a), 3.85−3.81 (m, 1H, H-5a, H-5b), 3.65 (t, 1H, J = 9.7

Hz, H-4a), 3.76 (dd, 1H, J = 11.7, 6.0 Hz, H-6′a), 3.72 (dd, 1H, J =

11.8, 4.3 Hz, H-6b), 3.65 (dd, 1H, J = 11.8, 7.3 Hz, H-6′b). ¹³C{1H}

1

(42 mg, 54%) as an oil. H NMR (CDCl₃, 400 MHz): δ 8.20 (ddd,

2H, J = 7.1, 2, 1.5 Hz, H_arom), 8.00 (ddd, 2H, J = 8.3, 2.8, 1.7 Hz,

H_arom), 7.92 (ddd, 2H, J = 8.1, 2.9, 1.6 Hz, H_arom), 7.87 (ddd, 2H, J =

8.0, 2.9, 1.7 Hz, H_arom), 7.80 (ddd, 2H, J = 8.1, 2.9, 1.7 Hz, H_arom),

7.60 (tt, 1H, J = 7.5, 1.6 Hz, H_arom), 7.53 (ddd, 2H, J = 6.5, 2.9, 1.7

Hz, H_arom), 7.50−8.44 (m, 7H, H_arom), 7.40−7.27 (m, 12H, H_arom),

7.24−7.16 (m, 3H, H_arom), 5.68 (ddd, 1H, J = 7.5, 4.1, 3.0 Hz, H-5b),

5.67 (d, 1H, J = 1.6 Hz, H-1a), 5.63 (s, 1H, H-1b), 5.63 (dd, 1H, J =

4.1, 0.9 Hz, H-3b), 5.62 (dd, 1H, J = 10.3, 3.4 Hz, H-3a), 5.56 (d, 1H,

J = 0.9 Hz, H-2b), 5.43 (s, 1H, H-7), 4.82 (dd, 1H, J = 3.4, 1.5 Hz, H-

2a), 4.45 (dd, 1H, J = 10.3, 9.4 Hz, H-4a), 4.38 (t, 1H, J = 4.1 Hz, H-

4b), 4.30 (dd, 1H, J = 10.3, 5.0 Hz, H-6a), 4.27 (dd, 1H, J = 12.2, 7.5

Hz, H-6b), 4.55 (td, 1H, J = 10.3, 5.0 Hz, H-5a), 4.12 (dd, 1H, J =

12.2, 3.0 Hz, H-6′b), 3.96 (t, 1H, J = 10.3 Hz, H-6′a). ¹³C{1H} NMR

(CDCl₃, 100 MHz): δ 165.96, 165.70, 165.68, 165.48, 165.44 (CO),

137.28, 133.91, 133.61, 133.57, 133.44, 133.30, 133.10, 132.11,

130.06, 129.93, 129.80, 129.66, 129.55, 129.54, 129.37, 129.36,

129.26, 128.75, 128.69, 128.64, 128.59, 128.52, 128.46, 128.45,

6397

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Article

NMR (D₂O, 100 MHz): δ 105.7 (C-1b), 91.3 (C-1a), 82−7 (C-4b),

81.0 (C-2b), 76.5 (C-3b), 69.4 (C-3a),72.5 (C-5a), 70.6 (C-5b), 75.5

(C-2a), 67.1 (C-4a), 62.7 (C-6b), 60.8 (C-6a).

(2×). The combined aqueous layers were ﬁnally freeze-dried. The

resulting solid was puriﬁed by column chromatography on silica gel

(EtOAc/AcOH/H₂O/MeOH gradient from 9:0.5:0.5:0 up to

5:2:2:1) to aﬀord FP-3 (10 mg, 93%) as a solid. HRMS (ESI) m/

z: [M + Na]⁺Calcd for C₁₂H₂₂O₁₁Na 365.1054; Found 365.1058.

FP-3α (major). ¹H NMR (D₂O, 400 MHz): δ 5.24 (d, 1H, J = 1.8

Hz, H-1a), 5.18 (d, 1H, J = 1.5 Hz, H-1b), 4.18 (dd, 1H, J = 3.0, 1.5

Hz, H-2b), 4.15 (dd, 1H, J = 3.2, 1.8 Hz, H-2a), 4.10 (dd, 1H, J = 6.6,

3.0 Hz, H-3b), 4.09 (dd, 1H, J = 6.6, 3.8 Hz, H-4b), 3.95 (dd, 1H, J =

9.5, 3.2 Hz, H-3a), 3.92 (dd, 1H, J = 12.3, 2.3 Hz, H-6a), 3.90−3.85

(m, 2H, H-5a, H-5b), 3.77 (t, 1H, J = 9.5 Hz, H-4a), 3.77 (dd, 1H, J =

12.3, 6.1 Hz, H-6′a), 3.74 (dd, 1H, J = 11.6, 4.4 Hz, H-6b), 3.69 (dd,

1H, J = 11.6, 7.0 Hz, H-6′b). ¹³C{1H} NMR (D₂O, 100 MHz): δ

104.4 (C-1b), 93.9 (C-1a), 83.0 (C-4b), 81.4 (C-2b), 77.0 (C-3b),

75.1 (C-3a), 72.6 (C-5a), 70.7 (C-5b), 67.4 (C-2a), 65.1 (C-4a), 62.7

(C-6b), 61.1 (C-6a).

FP-2β (minor). ¹H NMR (D₂O, 400 MHz): δ 4.98 (s, 1H, H-1a),

5.27 (d, 1H, J = 1.7 Hz, H-1b), 4.23 (dd, 1H, J = 3.8, 1.7 Hz, H-2b),

4.11 (d, 1H, J = 3.6 Hz, H-2a), 4.16−4.12 (m, 1H, H-4b), 4.13 (dd,

1H, J = 6.2, 3.8 Hz, H-3b), 3.67 (dd, 1H, J = 9.8, 3.6 Hz, H-3a),

3.89−3.85 (o, 1H, H-6a), 3.85−3.81 (m, 1H, H-5b), 3.69−3.65 (o,

1H, H-5a), 3.90−3.87 (o, 1H, H-4a), 3.75−3.68 (o, 1H, H-6′a),

3.75−3.70 (o, 1H, H-6b), 3.67−3.63 (o, 1H, H-6′b). ¹³C{1H} NMR

(D₂O, 100 MHz): δ 108.2 (C-1b), 94.0 (C-1a), 83.0 (C-4b), 80.7 (C-

2b), 76.4 (C-3b), 69.4 (C-3a),72.2 (C-5a), 70.6 (C-5b), 76.7 (C-2a),

67.0 (C-4a), 62.7 (C-6b), 61.0 (C-6a).

Phenyl 2,3,5,6-Tetra-O-benzoyl-β-^D-galactofuranosyl-(1→3)-6-

O-acetyl-1-thio-α-^D-mannopyranoside (13). Bromide donor 9a

(200 mg, 0.3 mmol), acceptor 2 (47 mg, 0.15 mmol), and 2-

aminoethyl diphenylborinate (34 mg, 0.15 mmol) were suspended in

dry acetonitrile (4 mL) in the presence of activated 4 Å molecular

sieves under a nitrogen atmosphere. The mixture was stirred 30 min

at room temperature before addition of Ag₂O (35 mg, 0.15 mmol).

The mixture was then allowed to stir at room temperature in the dark,

and the reaction was followed by TLC (cylohexane/EtOAc 7:3 and

DCM/MeOH 9:1). After 2 h of stirring, no acceptor remained. Then,

the solution was ﬁltered on a plug of Celite, and the ﬁltrate was

evaporated under vacuum. The resulting crude was puriﬁed by

column chromatography on silica gel (cyclohexane/EtOAc gradient

FP-3β (minor). ¹H NMR (D₂O, 400 MHz): δ 5.20 (d, 1H, J = 1.4

Hz, H-1b), 4.92 (s, 1H, H-1a), 4.18 (dd, 1H, J = 3.0, 1.5 Hz, H-2b),

4.10 (d, 1H, J = 3.1 Hz, H-2a), 4.11 (dd, 1H, J = 6.6, 3.0 Hz, H-3b),

4.09 (dd, 1H, J = 6.6, 3.8 Hz, H-4b), 3.83−3.79 (m, 1H, H-3a), 3.94

(dd, 1H, J = 11.9, 2.2 Hz, H-6a), 3.90−3.85 (m, 1H, H-5b), 3.83−

3.74 (o, 1H, H-6′a), 3.74 (dd, 1H, J = 11.6, 4.4 Hz, H-6b), 3.69 (dd,

1H, J = 11.6, 7.0 Hz, H-6′b), 3.68 (dd, 1H, J = 9.9, 3.1 Hz, H-4a),

3.45 (ddd, 1H, J = 9.9, 6.3, 2.2 Hz, H-5a). ¹³C{1H} NMR (D₂O, 100

MHz): δ 104.1 (C-1b), 93.6 (C-1a), 82.9 (C-4b), 81.4 (C-2b), 77.4

(C-3a), 77.1 (C-3b), 76.0 (C-5a), 70.7 (C-5b), 67.7 (C-2a), 64.9 (C-

4a), 62.7 (C-6b), 61.0 (C-6a).

1

from 9:1 up to 7:3) to give 13 (127 mg, 95%) as a white solid. H

NMR (CDCl₃, 400 MHz): δ 8.14−7.90 (m, 8H, H_arom), 7.61−7.27

(m, 12H, H_arom), 5.95 (td, 1H, J = 5.3, 3.5 Hz, H-5b), 5.73 (dd, 1H, J

= 5.9, 2.1 Hz, H-3b), 5.62 (d, 1H, J = 1.3 Hz, H-1a), 5.49 (s, 1H, H-

1b), 5.48 (dd, 1H, J = 2.2, 0.8 Hz, H-2b), 4.93 (dd, 1H, J = 5.9, 3.5

Hz, H-4b), 4.81 (d, 2H, J = 5.3 Hz, H-6b), 4.42 (dd, 1H, J = 12.1, 5.8

Hz, H-6a), 4.34 (dd, 2H, J = 12.2, 2.1 Hz, H-6′a), 4.34−4.32 (m,

1H,H-2a), 4.32−4.28 (m, 1H, H-5a), 3.98−3.90 (m, 2H, H-3a, H-

4a), 2.06 (s, 3H, CH₃). ¹³C{1H} NMR (CDCl₃, 100 MHz): δ 171.4,

166.5, 166.3, 165.8, 165.7 (CO), 133.9, 133.6, 133.5, 133.4, 131.8,

130.1, 130.1, 130.0, 130.0, 129.6, 129.5, 129.2, 128.8, 128.7, 128.7,

128.6, 128.6, 127.8 (C₆H₅), 104.1 (C-1b), 87.4 (C-1a), 83.2 (C-2b),

81.4 (C-4b), 78.2 (C-3a), 77.0 (C-3b), 71.5 (C-5a), 70.2 (C-5b), 69.6

(C-2a), 66.3 (C-4a), 63.7 (C-6a), 63.2 (C-6b), 21.2 (CH₃). HRMS

(ESI) m/z: [M + Na]⁺Calcd for C₄₈H₄₄O₁₅SNa 915.2293; Found

915.2289.

Phenyl β-^D-Galactofuranosyl-(1→3)-1-thio-α-D-mannopyrano-

side (14). To a solution of 13 (400 mg, 0.448 mmol) in anhydrous

MeOH (5 mL) was added MeONa (0.54 M in MeOH, 170 μL, 0.090

mmol). The mixture was stirred for 17 h at room temperature. Then

the solution was neutralized by the addition of IR 120-H⁺form resin.

After ﬁltration, the ﬁltrate was evaporated under reduced pressure.

The resulting residue was suspended in water, and the biphasic

solution was washed with DCM (3×). The aqueous phase was ﬁnally

freeze-dried to aﬀord 14 (190 mg, 98%) as a white powder. ¹H NMR

(D₂O, 400 MHz): δ 7.63−7.58 (m, 2H, H_arom), 7.47−7.40 (m, 3H,

H_arom), 5.57 (d, 1H, J = 1.7 Hz, H-1a), 5.19 (d, 1H, J = 1.6 Hz, H-1b),

4.44 (dd, 1H, J = 3.2, 1.7 Hz, H-2a), 4.24−4.20 (m, 1H, H-5a), 4.18

(dd, 1H, J = 3.2, 1.6 Hz, H-2b), 4.14−4.07 (m, 2H, H-3b, H-4b), 3.96

(dd, 1H, J = 9.7, 3.2 Hz, H-3a), 3.90−3.85 (m, 1H, H-5b), 3.82 (t,

1H, J = 9.7 Hz, H-4a), 3.85−3.76 (m, 2H, H-6a), 3.74 (dd, 1H, J =

11.8, 4.5 Hz, H-6b), 3.69 (dd, 1H, J = 11.8, 7.4 Hz, H-6′b). ¹³C{1H}

NMR (D₂O, 100 MHz): δ 132.6, 132.2, 129.4, 128.4 (C₆H₅), 104.3

(C-1b), 87.8 (C-1a), 82.9 (C-4b), 81.3 (C-2b), 77.0 (C-3b), 75.6 (C-

3a), 73.5 (C-5a), 70.7 (C-5b), 68.1 (C-2a), 65.3 (C-4a), 62.8 (C-6b),

60.7 (C-6a). HRMS (ESI) m/z: [M + Na]⁺Calcd for C₁₈H₂₆O₁₀SNa

457.1139; Found 457.1138.

Phenyl 2,3,5,6-Tetra-O-benzoyl-β-^D-galactofuranosyl-(1→4)-6-

O-acetyl-3,4-O-isopropylidene-1-thio-α-^D-mannopyranoside (15).

To a solution of galactofuranosyl trichloroacetimidate 9b (50 mg,

70 μmol) and 6 (18 mg, 50 μmol) in anhydrous DCM (5 mL) were

added activated 4 Å molecular sieves (100 mg). The mixture was

cooled to 0 °C and stirred for 15 min before dropwise addition of

TMSOTf (0.02 M in DCM, 750 μL, 15 μmol). The temperature was

maintained at 0 °C, and the reaction was followed by TLC

(cyclohexane/EtOAc 7:3). After 2 h, no starting material remained

so triethylamine was added and the solution was ﬁltered on a pad of

Celite. The resulting ﬁltrate was evaporated under vacuo and the

residue was puriﬁed by column chromatography on silica gel

(cyclohexane/EtOAc gradient from 9:1 up to 7:3) to give 15 (34

1

mg, 71%) as an oil. H NMR (CDCl₃, 400 MHz): δ 8.14−8.07 (m,

4H, H_arom), 8.00−7.96 (m, 2H, H_arom), 7.87−7.83 (m, 2H, H_arom),

7.63−7.27 (m, 17 H, H_arom), 6.18 (dt, 1H, J = 8.0, 3.5 Hz, H-5b), 5.84

(s, 1H, H-1a), 5.61 (dt, 1H, J = 5.4, 0.9 Hz, H-3b), 5.39−5.36 (m,

2H, H-2b, H-1b), 4.84 (dd, 1H, J = 5.4, 2.9 Hz, H-4b), 4.79 (dd, 1H,

J = 12.1, 3.5 Hz, H-6b), 4.74 (dd, 1H, J = 12.1, 8.0 Hz, H-6′b), 4.42−

4.31 (m, 3H, H-5a, H-6a), 4.35 (dd, 1H, J = 5.5, 0.9 Hz, H-2a), 4.27

(dd, 1H, J = 7.3, 5.5 Hz, H-3a), 3.92 (dd, 1H, J = 9.8, 7.3 Hz, H-4a),

1.96 (s, 3H, COCH₃), 1.65 (s, 3H, CH₃), 1.37 (s, 3H, CH₃).

¹³C{1H} NMR (CDCl₃, 100 MHz): δ 170.7, 166.4, 165.9, 165.9,

165.8 (CO), 133.7, 133.5, 133.4, 133.2, 133.0, 131.9, 130.2, 130.1,

130.0, 129.9, 129.7, 129.3, 129.2, 128.9, 128.7, 128.6, 128.5, 128.5,

127.9 (C₆H₅), 110.1 (C(CH₃)₂), 105.7 (C-1b), 84.1 (C-1a), 82.4 (C-

2b), 81.6 (C-4b), 77.4, 77.3 (C-3a, C-3b), 76.5 (C-2a), 75.1 (C-4a),

70.3 (C-5b), 68.3 (C-5a), 64.8 (C-6b), 62.8 (C-6a), 28.0, 26.6

(CH₃), 21.0 (COCH₃). HRMS (ESI) m/z: [M + Na]⁺Calcd for

C₅₁H₄₈O₁₅SNa 955.2606; Found 955.2605.

Phenyl 2,3,5,6-Tetra-O-benzoyl-β-^D-galactofuranosyl-(1→4)-6-

O-acetyl-1-thio-α-^D-mannopyranoside (16). To a solution of 15

(108 mg, 0.116 mmol) in DCM (5 mL) were added 1 drop of water

and TFA (44 μL, 0.579 mmol). The mixture was stirred during 15 h

at room temperature. Then the reaction was quenched by addition of

triethylamine, and the solvent was removed under reduced pressure.

The resulting residue was puriﬁed by column chromatography on

silica gel (cyclohexane/EtOAc gradient from 1:0 to 6:4) to aﬀord 16

β-^D-Galactofuranosyl-(1→3)-D-mannopyranose (FP-3). To a

solution of 14 (14 mg, 0.032 mmol) in a mixture of acetonitrile/

H₂O 1:1 (4 mL) was added N-iodosaccharine (35 mg, 0.113 mmol).

The mixture was stirred for 2 h at room temperature. Then Et₃N was

added, and the resulting reaction mixture was concentrated under

reduced pressure. The residue was partitioned between DCM and

water. The resulting organic layer was further extracted with water

1

(103 mg, 100%) as a white solid. H NMR (CDCl₃, 400 MHz): δ

8.12−7.89 (m, 7H, H_arom), 7.62−7.27 (m, 18H, H_arom), 6.00 (dt, 1H, J

= 6.2, 4.7 Hz, H-5b), 5.73 (dd, 1H, J = 5.2, 1.8 Hz, H-3b), 5.60 (d,

1H, J = 1.4 Hz, H-1a), 5.47 (dd, 1H, J = 1.9, 0.8 Hz, H-2b), 5.39 (s,

1H, H-1b), 4.91 (dd, 1H, J = 5.1, 4.6 Hz, H-4b), 4.81 (dd, 1H, J =

6398

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J. Org. Chem. 2021, 86, 6390−6405

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Article

11.9, 4.7 Hz, H-6b), 4.72 (dd, 1H, J = 11.9, 6.2 Hz, H-6′b), 4.49−

4.38 (m, 3H, H-5a, H-6a), 4.21 (dd, 1H, J = 2.6, 1.4 Hz, H-2a), 3.96−

3.90 (m, 2H, H-3a, H-4a), 2.00 (s, 3H, CH₃). ¹³C{1H} NMR

(CDCl₃, 100 MHz): δ 170.9, 166.3, 165.8, 165.7, 165.7 (CO), 133.9,

133.8, 133.6, 133.6, 133.4, 131.7, 130.1, 130.1, 130.0, 129.9, 129.5,

129.4, 129.3, 128.8, 128.7, 128.7, 128.7, 128.6, 127.8 (C₆H₅), 108.0

(C1-b), 87.2 (C-1a), 82.6 (C-2b), 82.0 (C-4b), 78.7 (C-4a), 77.2 (C-

3b), 71.9 (C-2a), 70.8 (C-3a), 70.4 (C-5b), 69.4 (C-5a), 63.1, 63.0

(C-6a, C-6b), 21.2 (CH₃). HRMS (ESI) m/z: [M + Na]⁺Calcd for

C₄₈H₄₄O₁₅SNa 915.2293; Found 915.2290.

Phenyl β-^D-Galactofuranosyl-(1→4)-1-thio-α-D-mannopyrano-

side (17). To a solution of 16 (275 mg, 0.31 mmol) in anhydrous

MeOH (3 mL) was added MeONa (0.54 M in MeOH, 120 μL, 0.062

mmol). The mixture was stirred for 17 h at room temperature. Then

the solution was neutralized by the addition of IR 120-H⁺form resin.

After ﬁltration, the ﬁltrate was evaporated under reduced pressure.

The resulting residue was suspended in water, and the biphasic

solution was washed with DCM (3×). The aqueous phase was ﬁnally

freeze-dried to aﬀord 17 (122 mg, 91%) as a white powder. ¹H NMR

(D₂O, 400 MHz): δ 7.58−7.54 (m, 2H, H_arom), 7.43−7.37 (m, 3H,

H_arom), 5.50 (d, 1H, J = 1.8 Hz, H-1a), 5.08 (d, 1H, J = 2.2 Hz, H-1b),

4.24 (dd, 1H, J = 3.3, 1.8 Hz, H-2a), 4.24−4.20 (m, 1H, H-5a), 4.13−

4.05 (m, 3H, H-2b, H-3b, H-4b), 3.95 (dd, 1H, J = 9.5, 3.3 Hz, H-3a),

3.85 (t, 1H, J = 9.6 Hz, H-4a), 3.83−3.78 (m, 3H, H-6a, H-5b), 3.69

(dd, 1H, J = 11.7, 4.6 Hz, H-6b), 3.64 (dd, 1H, J = 11.7, 7.3 Hz, H-

6′b). ¹³C{1H} NMR (D₂O, 100 MHz): δ 132.6, 132.3, 129.4, 128.3

(C₆H₅), 107.9 (C-1b), 87.9 (C-1a), 82.6 (C-4b), 81.0 (C-2b), 75.9

(C-3b), 75.2 (C-4a), 72.4 (C-5a), 71.3 (C-2a), 70.5 (C-5b), 69.7 (C-

3a), 62.7 (C-6b), 60.1 (C-6a). HRMS (ESI) m/z: [M + Na]⁺Calcd

for C₁₈H₂₆O₁₀SNa 457.1139; Found 457.1135.

β-^D-Galactofuranosyl-(1→4)-D-mannopyranose (FP-4). To a

solution of 17 (100 mg, 0.23 mmol) in a mixture of acetonitrile/

H₂O 1:1 (10 mL) was added N-iodosaccharine (249 mg, 0.81 mmol).

The mixture was stirred for 1 h at room temperature. Then the

reaction mixture was concentrated under reduced pressure, and the

residue was partitioned between DCM and water. The resulting

organic layer was further extracted with water (2×). The combined

aqueous layers were ﬁnally freeze-dried. The resulting solid was

puriﬁed by column chromatography on silica gel (EtOAc/AcOH/

H₂O/MeOH gradient from 9:0.5:0.5:0 up to 5:2:2:1) to aﬀord FP-4

(87 mg, 100%) as a solid. HRMS (ESI) m/z: [M + Na]⁺Calcd for

C₁₂H₂₂O₁₁Na 365.1054; Found 365.1058.

Then the reaction was quenched by addition of triethylamine, and the

resulting suspension was ﬁltered on Celite. The ﬁltrate was

concentrated under reduced pressure, and the residue was puriﬁed

by column chromatography on silica gel (cyclohexane/EtOAc

gradient from 1:0 up to 7:3) to aﬀord 18 (930 mg, 93%) as a

1

white powder. H NMR (CDCl₃, 400 MHz): δ 8.11−7.81 (m, 16H,

H_arom), 7.65−7.40 (m, 13H, H_arom), 7.38−7.21 (m, 10H, H_arom),

7.17−7.11 (m, 1H, H_arom), 5.98 (t, 1H, J = 10.0 Hz, H-4a), 5.98−5.95

(m, 1H, H-2a), 5.95−5.94 (m, 1H, H-5b), 5.86 (dd, 1H, J = 10.0, 3.2

Hz, H-3a), 5.76 (d, 1H, J = 1.5 Hz, H-1a), 5.61 (ddd, 1H, J = 5.1, 1.4,

0.6 Hz, H-3b), 5.56 (d, 1H, J = 1.4 Hz, H-2b), 5.39 (s, 1H, H-1b),

4.91 (ddd, 1H, J = 8.9, 6.5, 2.1 Hz, H-5a), 4.67−4.63 (m, 2H, H-6b),

4.61 (dd, 1H, J = 5.1, 3.7 Hz, H-4b), 4.05 (dd, 1H, J = 11.5, 2.3 Hz,

H-6a), 3.92 (dd, 1H, J = 11.5, 6.5 Hz, H-6′a). ¹³C{1H} NMR

(CDCl₃, 100 MHz): δ 166.2, 165.8, 165.7, 165.7, 165.6, 165.6, 165.3

(CO),133.7, 133.6, 133.4, 133.4, 133.3, 133.1, 132.3, 132.2, 130.1,

130.1, 130.0, 130.0, 129.9, 129.9, 129.8, 129.7, 129.6, 129.4, 129.4,

129.3, 129.2, 129.0, 129.0, 128.8, 128.8, 128.7, 128.6, 128.5, 128.5,

128.4, 128.4, 128.3 (C₆H₅), 106.6 (C-1b), 86.2 (C-1a), 82.0 (C-4b),

81.9 (C-2b), 77.7 (C-3b), 72.2 (C-5b), 71.4 (C-5a), 70.5, 70.5 (C-2a,

C-3a), 67.6 (C-4a), 66.9 (C-6a), 63.7 (C-6b). HRMS (ESI) m/z: [M

+ Na]⁺Calcd for C₆₇H₅₄O₁₇SNa 1185.2974; Found 1185.2972.

Phenyl β-^D-Galactofuranosyl-(1→6)-1-thio-α-D-mannopyrano-

side (19). To a solution of 18 (688 mg, 0.59 mmol) in anhydrous

MeOH (10 mL) was added MeONa (5.4 M in MeOH, 27 μL, 0.14

mmol). The mixture was stirred for 17 h at room temperature. Then

the solution was neutralized by the addition of IR 120-H⁺form resin.

After ﬁltration, the ﬁltrate was evaporated under reduced pressure.

The resulting residue was suspended in water and the biphasic

solution was washed with DCM (3×). The aqueous phase was ﬁnally

1

freeze-dried to aﬀord 19 (257 mg, 100%) as a powder. H NMR

(CD₃OD, 400 MHz): δ 7.57−7.53 (m, 2H, H_arom), 7.37−7.26 (m,

3H, H_arom), 5.37 (d, 1H, J = 1.2 Hz, H-1a), 4.93 (s, 1H, H-1b), 4.21

(ddd, 1H, J = 8.7, 6.3, 2.3 Hz, H-5a), 4.08 (dd, 1H, J = 2.9, 1.6 Hz, H-

2a), 4.02 (dd, 1H, J = 11.0, 2.3 Hz, H-6a), 4.00−3.95 (m, 3H, H-2b,

H-3b, H-4b), 3.74−3.64 (m, 4H, H-3a, H-4a, H-6′a, H-5b), 3.61 (d,

2H, J = 6.2 Hz, H-6b). ¹³C{1H} NMR (CD₃OD, 100 MHz): δ 135.7,

133.2, 132.9, 130.1, 128.6 (C₆H₅), 109.9 (C-1b), 90.5 (C-1a), 84.8

(C-4b), 83.0 (C-2b), 79.1 (C-3b), 74.4 (C-5a), 73.6 (C-2a), 73.1 (C-

3a), 72.5 (C-5b), 69.1 (C-4a), 68.2 (C-6a), 64.6 (C-6b). HRMS

(ESI) m/z: [M + Na]⁺Calcd for C₁₈H₂₆O₁₀SNa 457.1139; Found

457.1140.

FP-4α (major). ¹H NMR ((CD₃)₂CO, 500 MHz): δ 5.07 (d, 1H, J

= 1.7 Hz, H-1a), 5.01 (d, 1H, J = 2.5 Hz, H-1b), 3.99 (dd, 1H, J = 4.5,

2.5 Hz, H-2b), 4.091 (dd, 1H, J = 6.6, 3.3 Hz, H-4b), 4.04 (dd, 1H, J

= 6.6, 4.5 Hz, H-3b), 3.86−3.81 (m, 1H, H-4a), 3.84−3.82 (m, 1H,

H-2a), 3.83−3.79 (m, 1H, H-3a), 3.78−3.69 (m, 3H, H-6a, H-5a),

3.73 (dt, 1H, J = 6.4, 3.3 Hz, H-5b), 3.57−3.61 (m, 2H, H-6b).

¹³C{1H} NMR (D₂O, 125 MHz): δ 109.07 (C-1b), 94.81 (C-1a),

83.80 (C-4b), 81.92 (C-2b), 77.27 (C-3b), 75.62 (C-4a), 72.00 (C-

5a), 71.74 (C-2a), 71.32 (C-5b), 70.22 (C-3a), 63.46 (C-6b), 61.27

(C-6a).

β-^D-Galactofuranosyl-(1→6)-D-mannopyranose (FP-6). To a

solution of 19 (270 mg, 0.62 mmol) in a mixture of acetonitrile/

H₂O 1:1 (10 mL) was added N-iodosaccharine (731 mg, 2.36 mmol).

The mixture was stirred for 1 h at room temperature. Then the

reaction mixture was concentrated under reduced pressure, and the

residue was partitioned between DCM and water. The resulting

organic layer was further extracted with water (2×). The combined

aqueous layers were ﬁnally freeze-dried. The resulting solid was

puriﬁed by column chromatography on silica gel (EtOAc/AcOH/

H₂O/MeOH gradient from 9:0.5:0.5:0 up to 5:2:2:1) to aﬀord FP-6

(193 mg, 89%) as a solid. HRMS (ESI) m/z: [M + Na]⁺Calcd for

C₁₂H₂₂O₁₁Na 365.1054; Found 365.1058.

FP-4β (minor). ¹H NMR ((CD₃)₂CO, 500 MHz): δ 5.01 (d, 1H, J

= 2.5 Hz, H-1b), 4.75 (d, 1H, J = 1.1 Hz, H-1a), 4.093 (dd, 1H, J =

6.6, 3.3 Hz, H-4b), 4.04 (dd, 1H, J = 6.6, 4.5 Hz, H-3b), 3.98 (dd, 1H,

J = 4.5, 2.5 Hz, H-2b), 3.86 (dd, 1H, J = 3.3, 1.1 Hz, H-2a), 3.78 (dd,

1H, J = 12.1, 2.2 Hz, H-6a), 3.75 (t, 1H, J = 9.6 Hz, H-4a), 3.726 (dt,

1H, J = 6.4, 3.3 Hz, H-5b), 3.70 (dd, 1H, J = 12.1, 4.6 Hz, H-6′a),

3.60 (dd, 1H, J = 9.6, 3.3 Hz, H-3a), 3.57−3.61 (m, 2H, H-6b), 3.31

(ddd, 1H, J = 9.6, 4.6, 2.2 Hz, H-5a). ¹³C{1H} NMR (D₂O, 125

MHz): δ 109.07 (C-1b), 94.70 (C-1a), 83.93 (C-4b), 81.88 (C-2b),

77.27 (C-3b), 76.09 (C-5a), 75.04 (C-4a), 73.08 (C-3a), 71.99 (C-

2a), 71.32 (C-5b), 63.41 (C-6b), 61.23 (C-6a).

Phenyl 2,3,5,6-Tetra-O-benzoyl-β-^D-galactofuranosyl-(1→6)-

2,3,4-tri-O-benzoyl-1-thio-α-^D-mannopyranoside (18). To a sol-

ution of donor 9a (850 mg, 1.29 mmol) and acceptor 8 (502 mg, 0.86

mmol) in anhydrous dichloromethane (10 mL) were added activated

4 Å molecular sieves. The media was stirred during 15 min at room

temperature under nitrogen atmosphere. Then AgOTf (244 mg, 0.95

mmol) was added, and the reaction was stirred in the dark for 6 h.

FP-6α. ¹H NMR (CD₃OD, 500 MHz): δ 5.06 (d, 1H, J = 1.8 Hz,

H-1a), 4.95 (s, 1H, H-1b), 4.02 (dd, 1H, J = 4.7, 3.2 Hz, H-4b),

3.99−3.96 (m, 2H, H-2b, H-3b), 3.96 (dd, 1H, J = 10.9, 2.5 Hz, H-

6a), 3.89 (ddd, 1H, J = 9.6, 5.6, 2.5 Hz, H-5a), 3.79 (dd, 1H, J = 3.3,

1.8 Hz, H-2a), 3.75−3.71 (m, 1H, H-5b), 3.75 (dd, 1H, J = 9.2, 3.3

Hz, H-3a), 3.65 (dd, 1H, J = 10.9, 5.6 Hz, H-6′a), 3.64−3.59 (m, 2H,

H-6b), 3.61 (t, 1H, J = 9.6 Hz, H-4a). ¹³C{1H} NMR (CD₃OD, 125

MHz): δ 109.45 (C-1b), 95.60 (C-1a), 84.97 (C-4b), 82.12 (C-2b),

78.82 (C-3b), 72.41 (C-2a), 72.31, 72.28 (C-5a, C-5b), 71.92 (C-3a),

68.96 (C-4a), 68.17 (C-6a), 64.18 (C-6b).

FP-6β. ¹H NMR (CD₃OD, 500 MHz): δ 4.95 (s, 1H, H-1b), 4.73

(d, 1H, J = 0.9 Hz, H-1a), 4.02−4.01 (o, 1H, H-3b), 4.02−3.96 (o,

1H, H-6a), 4.00−3.98 (o, 1H, H-4b), 3.98−3.96 (o, 1H, H-2b),

3.91−3.88 (o, 1H, H-5b), 3.81 (dd, 1H, J = 3.3, 0.9 Hz, H-2a), 3.66−

3.60 (m, 3H, H-6′a, H-6b), 3.56 (t, 1H, J = 9.6 Hz, H-4a), 3.44 (dd,

1H, J = 9.6, 3.3 Hz, H-3a), 3.35 (ddd, 1H, J = 9.6, 5.9, 2.6 Hz, H-5a).

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¹³C{1H} NMR (CD₃OD, 100 MHz): δ 109.56 (C-1b), 95.35 (C-1a),

85.00 (C-4b), 82.16 (C-2b), 78.80 (C-3b), 76.37 (C-5a), 75.01 (C-

3a), 72.72 (C-2a), 72.31 or 72.28 (C-5b), 68.48 (C-4a), 68.06 (C-

6a), 64.18 (C-6b).

was concentrated under reduced pressure, and the residue was

partitioned between DCM and water. The resulting organic layer was

further extracted with water (2×). The combined aqueous layers were

ﬁnally freeze-dried. The resulting solid was puriﬁed by column

chromatography on silica gel (EtOAc/AcOH/H₂O/MeOH gradient

from 9:0.5:0.5:0 up to 5:2:2:1) to aﬀord PP-2 (10 mg, 72%) as a

solid. HRMS (ESI) m/z: [M + Na]⁺Calcd for C₁₂H₂₂O₁₁Na

365.1054; Found 365.1056.

Synthesis of Galactopyranosyl-Containing Disaccharides PP.

Phenyl 2,3,4,6-Tetra-O-benzoyl-β-^D-galactopyranosyl-(1→2)-3-O-

benzoyl-1-thio-α-^D-mannopyranoside (21). To a solution of

trichloroacetimidate galactopyranosyl 20b (207 mg, 0.28 mmol)

and 5 (100 mg, 0.21 mmol) in anhydrous DCM (10 mL) were added

activated 4 Å molecular sieves (100 mg). The mixture was cooled to 0

°C and stirred for 15 min before dropwise addition of TMSOTf (0.02

M in DCM, 3.2 mL, 0.06 mmol). The temperature was maintained at

0 °C and reaction was followed by TLC (cyclohexane/EtOAc 8/2).

After 2 h, no starting material remained, so triethylamine was added

and the solution was ﬁltered on a pad of Celite. The ﬁltrate was

evaporated in vacuo. The resulting residue was dissolved in DCM (10

mL), and water (10 μL) and TFA (124 μL, 1.62 mmol) were added

successively. The reaction mixture was stirred at room temperature for

24 h. Then triethylamine was added, and the reaction media was

washed with water (3×), dried over MgSO₄, and evaporated. The

residue was puriﬁed by column chromatography on silica gel

(cyclohexane/EtOAc gradient from 90:10 up to 60:40) to give 21

(53 mg, 26% over two steps) as an oil. ¹H NMR (CDCl₃, 400 MHz):

δ 8.12 (dd, 2H, J = 8.5, 1.3 Hz, H_arom), 8.09 (dd, 2H, J = 8.6, 1.3 Hz,

H_arom), 7.94 (dd, 2H, J = 8.5, 1.2 Hz, H_arom), 7.88 (dd, 2H, J = 8.4, 1.3

Hz, H_arom), 7.76 (dd, 2H, J = 8.4, 1.2 Hz, H_arom), 7.68 (tt, 1H, J = 7.5,

1.3 Hz, H_arom), 7.59−7.51 (m, 3H, H_arom), 7.49−7.18 (m, 12H,

H_arom), 7.14 (td, 2H, J = 7.3, 1.3 Hz, H_arom), 7.07 (dd, 2H, J = 7.3, 1.3

Hz, H_arom), 5.89 (dd, 1H, J = 3.5, 0.9 Hz, H-4b), 5.81 (dd, 1H, J =

10.5, 7.8 Hz, H-2b), 5.61 (dd, 1H, J = 10.5, 3.5 Hz, H-3b), 5.24 (d,

1H, J = 2.1 Hz, H-1a), 5.21 (dd, 1H, J = 9.7, 3.1 Hz, H-3a), 4.75 (d,

1H, J = 7.8 Hz, H-1b), 4.56 (dd, 1H, J = 3.1, 2.1 Hz, H-2a), 4.53 (t,

1H, J = 9.7 Hz, H-4a), 4.14 (dd, 1H, J = 6.5, 0.9 Hz, H-5b), 4.04

(apparent td, 1H, J = 9.7, 3.0 Hz, H-5a), 4.00 (dd, 1H, J = 11.4, 6.5

Hz, H-6b), 3.93 (dd, 1H, J = 11.4, 6.5 Hz, H-6′b), 3.79 (dd, 1H, J =

12.1, 3.6 Hz, H-6a), 3.68 (dd, 1H, J = 12.1, 2.4 Hz, H-6′a). ¹³C{1H}

NMR (CDCl₃, 100 MHz): δ 166.77, 165.89, 165.57, 165.48 (COPh),

134.03, 133.89, 133.56, 133.53, 133.38, 130.31, 130.13, 130.07,

129.95, 129.92, 129.90, 129.64, 129.45, 129.33, 129.22, 129.14,

128.88, 128.80, 128.72, 128.54, 128.46, 128.35, 127.25 (C₆H₅),

101.44 (C-1b), 85.28 (C-1a), 77.90 (C-2a), 73.80 (C-3a), 73.55 (C-

5a), 71.60 (C-5b), 71.01 (C-3b), 70.24 (C-2b), 68.00 (C-4b), 65.11

(C-4a), 61.97 (C-6a), 61.70 (C-6b). HRMS (ESI) m/z: [M + Na]⁺

Calcd for C₅₃H₄₆O₁₅SNa 977,2455; Found 977,2536.

Phenyl β-^D-Galactopyranosyl-(1→2)-1-thio-α-D-mannopyrano-

side (22). To a solution of 21 (36 mg, 0.05 mmol) in anhydrous

MeOH (1 mL) was added MeONa (0.054 M in MeOH, 200 μL, 11

μmol). The mixture was stirred for 17 h at room temperature. Then

the solution was neutralized by the addition of IR 120-H⁺form resin.

After ﬁltration, the ﬁltrate was evaporated under reduced pressure.

The resulting residue was suspended in water and the biphasic

solution was washed with DCM (3×). The aqueous phase was ﬁnally

freeze-dried to aﬀord 22 (20 mg, 91%) as a powder. ¹H NMR (D₂O,

400 MHz): δ 7.64−7.57 (m, 2H, H_arom), 7.47−7.39 (m, 3H, H_arom),

5.67 (d, 1H, J = 1.4 Hz, H-1a), 4.91 (dd, 1H, J = 3.4, 1.1 Hz, H-4b),

4.46 (d, 1H, J = 7.5 Hz, H-1b), 4.44 (dd, 1H, J = 3.5, 1.4 Hz, H-2a),

4.17 (ddd, 1H, J = 9.9, 4.5, 2.9 Hz, H-5a), 3.94 (dd, 1H, J = 9.9, 3.5

Hz, H-3a), 3.85−3.81 (m, 2H, H-6a), 3.81 (dd, 1H, J = 12.0, 7.9 Hz,

H-6b), 3.80 (t, 1H, J = 9.9 Hz, H-4a), 3.74 (dd, 1H, J = 12.0, 3.9 Hz,

H-6′b), 3.66 (ddd, 1H, J = 7.9, 3.9, 1.1 Hz, H-5b), 3.64 (dd, 1H, J =

11.1, 3.3 Hz, H-3b), 3.57 (dd, 1H, J = 11.1, 7.5 Hz, H-2b). ¹³C{1H}

NMR (D₂O, 100 MHz): δ 132.71, 132.14, 129.45, 128.47 (C₆H₅),

101.45 (C-1b), 85.83 (C-1a), 78.17 (C-2a), 75.25 (C-5b), 73.56 (C-

5a), 72.47 (C-3b), 70.40 (C-2b), 70.32 (C-3a), 68.60 (C-4b), 66.97

(C-4a), 61.11 (C-6b), 60.19 (C-6a). HRMS (ESI) m/z: [M + Na]⁺

Calcd for C₁₈H₂₆O₁₀SNa 457.1139; Found 457.1141.

PP-2α (major). ¹H NMR ((CD₃)₂CO, 500 MHz): δ 5.22 (d, 1H, J

= 1.8 Hz, H-1a),4.38−4.33 (m, 1H, H-1b), 3.98 (dd, 1H, J = 3.4, 1.8

Hz, H-2a), 3.85−3.84 (m, 1H, H-3b), 3.77 (dd, 1H, J = 9.5, 3.4 Hz,

H-3a), 3.75−3.72 (m, 2H, H-5a, H-6b), 3.74−3.72 (m, 2H, H-6a),

3.65 (dd, 1H, J = 11.7, 4.0 Hz, H-6′b), 3.65 (t, 1H, J = 9.5 Hz, H-4a),

3.60 (ddd, 1H, J = 7.8, 4.2, 0.9 Hz, H-5b), 3.59−3.56 (m, 1H, H-4b),

3.57−3.55 (m, 1H, H-2b). ¹³C{1H} NMR ((CD₃)₂CO, 125 MHz): δ

103.3 (C-1b), 92.92 (C-1a), 79.16 (C-2a), 75.99 (C-5b), 73.3 (C-

4b), 73.09 (C-5a), 71.10 (C-2b), 70.32 (C-3a), 69.25 (C-3b), 67.87

(C-4a), 61.66 (C-6b), 60.86 (C-6a).

PP-2β (minor). ¹H NMR ((CD₃)₂CO, 500 MHz): δ 4.84 (d, 1H, J

= 0.9 Hz, H-1a), 4.44 (d, 1H, J = 7.7 Hz, H-1b), 4.05 (dd, 1H, J = 2.9,

0.9 Hz, H-2a), 3.85−3.84 (o, 1H, H-3b), 3.81 (o, 2H, H-6a), 3.73 (o,

1H, H-6b), 3.67 (o, 1H, H-6′b), 3.64 (o, 1H, H-2b), 3.62 (o, 1H, H-

5b), 3.58−3.54 (o, 1H, H-3a), 3.56 (o, 1H, H-4b), 3.54 (o, 1H, H-

4a), 3.25 (ddd, 1H, J = 8.3, 5.9, 2.2 Hz, H-5a). ¹³C{1H} NMR

((CD₃)₂CO, 125 MHz): δ 105.22 (C-1b), 94.37 (C-1a), 81.50 (C-

2a), 77.14 (C-5a), 76.21 (C-5b), 73.44 (C-4b), 73.14 (C-3a), 71.81

(C-2b), 69.28 (C-3b), 67.70 (C-4a), 61.52 (C-6a), 61.61 (C-6b).

Phenyl 2,3,4,6-Tetra-O-acetyl-β-^D-galactopyranosyl-(1→3)-6-O-

acetyl-1-thio-α-^D-mannopyranoside (23). Bromide donor 20a (956

mg, 2.3 mmol), acceptor 2 (487 mg, 1.55 mmol), and 2-aminoethyl

diphenylborinate (349 mg, 1.55 mmol) were suspended in anhydrous

CH₃CN (20 mL) in the presence of activated 4 Å molecular sieves

under a nitrogen atmosphere. The mixture was stirred for 15 min at

room temperature before addition of Ag₂O (359 mg, 1.55 mmol).

The mixture was then allowed to stir at room temperature in the dark

for 3 h. Then the solution was ﬁltered on a plug of Celite, and the

ﬁltrate was evaporated under vacuum. The resulting crude was

puriﬁed by column chromatography on silica gel (cyclohexane/EtOAc

gradient from 10:1 up to 6:4) to give 23 (1.46 g, 73%) as a white

1

solid. H NMR (CDCl₃, 400 MHz): δ 7.50−7.46 (m, 2H, H_arom),

7.34−7.27 (m, 3H, H_arom), 5.59 (d, 1H, J = 1.3 Hz, H-1a), 5.43 (dd,

1H, J = 3.4, 1.0 Hz, H-4b), 5.25 (dd, 1H, J = 10.6, 7.9 Hz, H-2b), 5.07

(dd, 1H, J = 10.6, 3.4 Hz, H-3b), 4.62 (d, 1H, J = 7.9 Hz, H-1b),

4.40−4.30 (m, 2H, H-6a), 4.34−4.28 (m, 1H, H-5a), 4.19 (dd, 1H, J

= 11.4, 5.3 Hz, H-6b), 4.13 (dd, 1H, J = 11.4, 7.6 Hz, H-6′b), 4.09

(dd, 1H, J = 3.4, 1.3 Hz, H-2a), 4.05 (ddd, 1H, J = 7.6, 5.3, 1.0 Hz, H-

5b), 3.91 (t, 1H, J = 9.0 Hz, H-4a), 3.74 (dd, 1H, J = 9.0, 3.4 Hz, H-

3a), 2.17 (s, 3H, CH₃), 2.11 (s, 3H, CH₃), 2.08 (s, 3H, CH₃), 2.02 (s,

3H, CH₃), 2.01 (s, 3H, CH₃). ¹³C{1H} NMR (CDCl₃, 100 MHz): δ

171.0, 170.6, 170.2, 170.1, 170.1 (CO), 133.0, 131.9, 129.3, 128.0

(C₆H₅), 102.1 (C-1b), 87.1 (C-1a), 84.5 (C-3a), 71.6 (C-2a), 71.5

(C-5b), 70.9 (C-5a), 70.5 (C-3b), 69.2 (C-2b), 66.9 (C-4a), 66.3 (C-

4b), 63.5 (C-6a), 61.8 (C-6b), 21.0, 20.8, 20.7, 20.7 (CH₃). HRMS

(ESI) m/z: [M + Na]⁺Calcd for C₂₈H₃₆O₁₅SNa 667.1667; Found

667.1665.

Phenyl β-^D-Galactopyranosyl-(1→3)-1-thio-α-D-mannopyrano-

side (24). To a solution of 23 (350 mg, 0.54 mmol) in anhydrous

MeOH (5 mL) was added MeONa (0.054 M in MeOH, 2 mL, 0.11

mmol). The mixture was stirred for 17 h at room temperature. Then

the solution was neutralized by the addition of IR 120-H⁺form resin.

After ﬁltration, the ﬁltrate was evaporated under reduced pressure.

The resulting residue was suspended in water and the biphasic

solution was washed with DCM (3×). The aqueous phase was ﬁnally

1

freeze-dried to aﬀord 24 (235 mg, 100%) as of a white powder. H

NMR (D₂O, 400 MHz): δ 7.62−7.57 (m, 2H, H_arom), 7.46−7.40 (m,

3H, H_arom), 5.58 (d, 1H, J = 1.6 Hz, H-1a), 4.54 (d, 1H, J = 7.6 Hz,

H-1b), 4.42 (dd, 1H, J = 3.3, 1.7 Hz, H-2a), 4.20 (ddd, 1H, J = 9.7,

5.5, 2.5 Hz, H-5a), 4.07 (dd, 1H, J = 9.7, 3.1 Hz, H-3a), 3.94 (d, 1H, J

= 3.3 Hz, H-4b), 3.86 (t, 1H, J = 9.6 Hz, H-4a), 3.88−3.75 (m, 4H,

H-6a, H-6b), 3.74−3.70 (m, 1H, H-5b), 3.68 (ddd, 1H, J = 9.9, 3.3,

β-^D-Galactopyranosyl-(1→2)-D-mannopyranoside (PP-2). To a

solution of 22 (18 mg, 4 μmol) in a mixture of acetonitrile/H₂O 1:1

(5 mL) was added N-iodosaccharine (45 mg, 15 μmol). The mixture

was stirred for 2 h at room temperature. Then the reaction mixture

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0.5 Hz, H-3b), 3.62 (dd, 1H, J = 9.9, 7.6 Hz, H-2b). ¹³C{1H} NMR

(D₂O, 100 MHz): δ 132.7, 132.1, 129.4, 128.4 (C₆H₅), 101.0 (C-1b),

87.7 (C-1a), 78.6 (C-3a), 75.3 (C-5b), 73.6 (C-5a), 72.6 (C-3b), 70.7

(C-2b), 69.1 (C-2a), 68.6 (C-4b), 65.4 (C-4a), 61.0, 60.7 (C-6a, C-

6b). HRMS (ESI) m/z: [M + Na]⁺Calcd for C₁₈H₂₆O₁₀SNa

457.1139; Found 457.1143.

β-^D-Galactopyranosyl-(1→3)-D-mannopyranose (PP-3). To a

solution of 24 (231 mg, 0.53 mmol) in a mixture of acetonitrile/

H₂O 1:1 (5 mL) was added N-iodosaccharine (576 mg, 1.86 mmol).

The mixture was stirred for 2 h at room temperature. Then the

reaction mixture was concentrated under reduced pressure, and the

residue was partitioned between DCM and water. The resulting

organic layer was further extracted with water (2×). The combined

aqueous layers were ﬁnally freeze-dried. The resulting solid was

puriﬁed by column chromatography on silica gel (EtOAc/AcOH/

H₂O/MeOH gradient from 9:0.5:0.5:0 up to 5:2:2:1) to aﬀord PP-3

(132 mg, 73%) as a solid. HRMS (ESI) m/z: [M + Na]⁺Calcd for

C₁₂H₂₂O₁₁Na 365.1054; Found 365.1055.

Phenyl β-^D-Galactopyranosyl-(1→6)-1-thio-α-D-mannopyrano-

side (26). To a solution of 25 (77 mg, 0.084 mmol) in anhydrous

MeOH (1 mL) was added MeONa (0.054 M in MeOH, 312 μL,

0.017 mmol). The mixture was stirred for 17 h at room temperature.

Then the solution was neutralized by the addition of IR 120-H⁺form

resin. After ﬁltration, the ﬁltrate was evaporated under reduced

pressure. The resulting residue was suspended in water and the

biphasic solution was washed with DCM (3×). The aqueous phase

1

was ﬁnally freeze-dried to aﬀord 26 (34 mg, 94%) as a powder. H

NMR (CD₃OD, 400 MHz): δ 7.58−7.50 (m, 2H, H_arom), 7.37−7.25

(m, 3H, H_arom), 5.39 (d, 1H, J = 1.5 Hz, H-1a), 4.28 (d, 1H, J = 7.7

Hz, H-1b), 4.22 (ddd, 1H, J = 9.7, 5.3, 2.2 Hz, H-5a), 4.13 (dd, 1H, J

= 11.2, 2.3 Hz, H-6b), 4.09 (dd, 1H, J = 3.3, 1.5 Hz, H-2a), 3.86 (dd,

1H, J = 11.2, 5.4 Hz, H-6′b), 3.85−3.67 (m, 5H, H-3a, H-4a, H-6a,

H-4b), 3.57 (dd, 1H, J = 9.7, 7.6 Hz, H-2b), 3.51−3.47 (m, 1H, H-

5b), 3.46 (dd, 1H, J = 9.7, 3.4 Hz, H-3b). ¹³C{1H} NMR (CD₃OD,

100 MHz): δ 135.5, 133.4, 130.2, 128.7 (C₆H₅), 105.3 (C-1b), 90.7

(C-1a), 76.8 (C-5b), 74.8 (C-3b), 74.6 (C-5a), 73.6 (C-2a), 73.0 (C-

3a), 72.6 (C-2b), 70.3 (C-4a or C-4b), 69.8 (C-6a), 68.7 (C-4a or C-

4b), 62.5 (C-6b). HRMS (ESI) m/z: [M + Na]⁺Calcd for

C₁₈H₂₆O₁₀SNa 457.1139; Found 457.1143.

β-^D-Galactopyranosyl-(1→6)-α-D-mannopyranose (PP-6). To a

solution of 26 (53 mg, 0.122 mmol) in a mixture of ACN/H₂O 1:1

(10 mL) was added N-iodosaccharine (130 mg, 0.427 mmol). The

mixture was stirred for 1 h at room temperature. Then the reaction

mixture was concentrated under reduced pressure, and the residue

was partitioned between DCM and water. The resulting organic layer

was further extracted with water (2×). The combined aqueous layers

were ﬁnally freeze-dried. The resulting solid was puriﬁed by column

chromatography on silica gel (EtOAc/AcOH/H₂O/MeOH gradient

from 9:0.5:0.5:0 up to 5:2:2:1) to aﬀord PP-6 (39 mg, 93%) as a

solid.

PP-3α (major). ¹H NMR (D₂O, 400 MHz): δ 5.24 (d, 1H, J = 1.9

Hz, H-1a), 4.55 (d, 1H, J = 7.6 Hz, H-1b), 4.14 (dd, 1H, J = 3.2, 1.9

Hz, H-2a), 4.08 (dd, 1H, J = 9.4, 3.2 Hz, H-3a), 3.96−3.94 (m, 1H,

H-4b), 3.94−3.88 (m, 2H, H-6a), 3.90−3.85 (m, 1H, H-5a), 3.82−

3.74 (m, 3H, H-4a, H-6b), 3.76−3.71 (m, 1H, H-5b), 3.71 (dd, 1H, J

= 9.8, 3.3 Hz, H-3b), 3.626 (dd, 1H, J = 9.8, 7.6 Hz, H-2b). ¹³C{1H}

NMR (D₂O, 100 MHz): δ 101.00 (C-1b), 93.74 (C-1a), 78.11 (C-

3a), 75.30 (C-5b), 72.63 (C-3b), 72.32 (C-5a), 70.75 (C-2b), 68.39

(C-2a), 68.66 (C-4b), 65.27 (C-4a), 61.1 (C-6a), 60.96 (C-6b).

PP-3β (minor). ¹H NMR (D₂O, 400 MHz): δ 4.92 (d, 1H, J = 0.7

Hz, H-1a), 4.56 (d, 1H, J = 7.7 Hz, H-1b), 4.17 (dd, 1H, J = 3.1, 0.7

Hz, H-2a), 3.96−3.94 (o, 1H, H-4b), 3.92 (dd, 1H, J = 9.7, 3.1 Hz, H-

3a), 3.92 (dd, 1H, J = 12.5, 2.5 Hz, H-6a), 3.82−3.77 (o, 2H, H-6b),

3.76−3.71 (o, 1H, H-5b), 3.75 (dd, 1H, J = 12.5, 6.4 Hz, H-6′a),

3.72−3.69 (o, 1H, H-3b), 3.71 (t, 1H, J = 9.7 Hz, H-4a), 3.631 (dd,

1H, J = 10.0, 7.7 Hz, H-2b), 3.44 (ddd, 1H, J = 9.7, 6.4, 2.5 Hz, H-

5a). ¹³C{1H} NMR (D₂O, 100 MHz): δ 100.75 (C-1b), 93.53 (C-

1a), 80.18 (C-3a), 72.62 (C-5b), 75.90 (C-5a), 75.32 (C-3b), 70.75

(C-2b), 68.79 (C-2a), 68.65 (C-4b), 65.07 (C-4a), 61.09 (C-6b),

60.99 (C-6a).

PP-6α (major). ¹H NMR (D₂O, 400 MHz): δ 5.18 (d, 1H, J = 1.6

Hz, H-1a), 4.45 (d, 1H, J = 7.8 Hz, H-1b), 4.18 (dd, 1H, J = 11.4, 1.8

Hz, H-6a), 4.07−3.96 (m, 1H, H-5a), 3.94 (dd, 1H, J = 3.3, 1.6 Hz,

H-2a), 3.93 (d, 1H, J = 3.3 Hz, H-4b), 3.91 (dd, 1H, J = 11.4, 5.9 Hz,

H-6′a), 3.86 (dd, 1H, J = 9.7, 2.2 Hz, H-3a), 3.81 (dd, 1H, J = 11.6,

7.9 Hz, H-6b), 3.77 (o, 1H, H-6′b), 3.75 (t, 1H, J = 9.7 Hz, H-4a),

3.75−3.70 (m, 1H, H-5b), 3.66 (dd, 1H, J = 9.8, 3.3 Hz, H-3b), 3.57

(dd, 1H, J = 9.8, 7.8 Hz, H-2b). ¹³C{1H} NMR (D₂O, 100 MHz): δ

103.3 (C-1b), 94.1 (C-1a), 75.1 (C-5b), 72.6 (C-3b), 71.3 (C-5a),

70.7 (C-2b), 70.6 (C-2a), 70.1 (C-3a), 68.8 (C-6a), 68.6 (C-4b), 66.5

(C-4a), 61.0 (C-6b). HRMS (ESI) m/z: [M + Na]⁺Calcd for

C₁₂H₂₂O₁₁Na 365.1054; Found 365.1058.

Phenyl 2,3,4,6-Tetra-O-benzoyl-β-^D-galactopyranosyl-(1→6)-

2,3,4-O-benzoyl-1-thio-α-^D-mannopyranoside (25). To a solution

of galactopyranosyl trichloroacetimidate 20b (329 mg, 0.44 mmol)

and 8 (200 mg, 0.34 mmol) in anhydrous DCM (15 mL) were added

activated 4 Å molecular sieves (100 mg). The mixture was stirred for

30 min at room temperature before the dropwise addition of

TMSOTf (0.02 M in DCM, 5.1 mL, 0.10 mmol). After 3 h,

triethylamine was added, and the solution was ﬁltered on a pad of

Celite. The resulting ﬁltrate was evaporated under vacuo, and the

residue was puriﬁed by column chromatography on silica gel

(cyclohexane/EtOAc gradient from 9:1 up to 8:2) to give 25 (309

PP-6β (minor). ¹H NMR (D₂O, 400 MHz): δ 4.91 (t, 1H, J = 1.0

Hz, H-1a), 4.46 (d, 1H, J = 7.8 Hz, H-1b), 4.23 (dd, 1H, J = 11.2, 1.9

Hz, H-6a), 3.95 (dd, 1H, J = 3.3, 1.6 Hz, H-2a), 3.94 (o, 1H, H-4b),

3.85 (o, 1H, H-6′a), 3.77 (o, 2H, H-6b), 3.71 (o, 1H, H-5b), 3.71−

3.66 (m, 2H, H-3a, H-4a), 3.66 (dd, 1H, J = 9.8, 3.3 Hz, H-3b), 3.57

(dd, 1H, J = 9.8, 7.8 Hz, H-2b), 3.55 (o, 1H, H-5a). ¹³C{1H} NMR

(D₂O, 100 MHz): δ 103.3 (C-1b), 93.7 (C-1a), 75.1 (C-5b), 75.0 (C-

5a), 72.9 (C-3a), 72.6 (C-3b), 71.2 (C-2a), 70.7 (C-2b), 68.8 (C-6a),

68.6 (C-4b), 66.4 (C-4a), 61.0 (C-6b).

Ion Mobility−Mass Spectrometry. The synthesized disaccharides

were analyzed on a Select Series Cyclic IMS (Waters, Wilmslow, UK),

equipped with a cyclic Traveling Wave Ion Mobility Spectrometry

(TWIMS) cell.⁵⁵Arrival time distributions (ATDs) were recorded

with the Quartz v. 6 software and processed with the MassLynx v. 4.2

software (both from Waters, Wilmslow, UK). ATDs are reported

according to Gabelica et al.⁶⁷

Samples were dissolved at 1 μg/mL in 50/50 methanol/water (v/

v), doped with 0.5 mM NaCl, and then infused at 5 μL/min in the

electrospray ion source. Samples were also analyzed at 1 μg/mL

doped with 0.1 mM LiCl. All IM-MS analyses were performed in

triplicates. The disaccharides were analyzed in positive-ion mode (in

the m/z 50−1200 range), with MS/MS selection of m/z 365.1 in the

quadrupole prior to ion mobility separation. The detailed

instrumental parameters are given in the Supporting Information.

The following sequence of events was used to perform IMS

analyses at a TW height of 22 V and TW velocity of 375 m/s: (i)

1

mg, 78%) as an oil. H NMR (CDCl₃, 400 MHz): δ 8.07−7.98 (m,

6H, H_arom), 7.95−7.86 (m, 4H, H_arom), 7.81−7.76 (m, 4H, H_arom),

7.63−7.55 (m, 4H, H_arom), 7.55−7.33 (m, 16H, H_arom), 7.31−7.21

(m, 6H, H_arom), 5.95 (dd, 1H, J = 3.4, 1.0 Hz, H-4b), 5.90 (dd, 1H, J

= 2.9, 1.6 Hz, H-2a), 5.86 (dd, 1H, J = 10.4, 8.0 Hz, H-2b), 5.82 (dd,

1H, J = 9.7, 2.7 Hz, H-4a), 5.79 (dd, 1H, J = 9.7, 2.9 Hz, H-3a), 5.66

(d, 1H, J = 1.6 Hz, H-1a), 5.54 (dd, 1H, J = 10.4, 3.4 Hz, H-3b), 4.91

(d, 1H, J = 8.0 Hz, H-1b), 4.94−4.88 (m, 1H, H-5a), 4.56 (dd, 1H, J

= 11.3, 6.7 Hz, H-6b), 4.34 (dd, 1H, J = 11.3, 6.7 Hz, H-6′b), 4.22

(dd, 1H, J = 6.7, 1.0 Hz, H-5b), 4.17 (dd, 1H, J = 11.8, 1.9 Hz, H-6a),

4.04 (dd, 1H, J = 11.8, 6.1 Hz, H-6′a). ¹³C{1H} NMR (CDCl₃, 100

MHz): δ 166.10, 165.72, 165.68, 165.57, 165.54, 165.49, 165.47

(COPh), 133.66, 133.63, 133.42, 133.38, 133.36, 133.25, 133.05,

132.15, 130.15, 130.10, 129.97, 129.93, 129.90, 129.88, 129.72,

129.49, 129.31, 129.27, 129.08, 129.01, 128.94, 128.77, 128.71,

128.63, 128.61, 128.42, 128.41, 128.27, 128.24 (C₆H₅), 101.95 (C-

1b), 86.12 (C-1a), 71.85 (C-5a), 71.52 (C-5b), 72.00 (C-2a, C-3b),

70.45 (C-3a), 69.66 (C-2b), 69.02 (C-6a), 68.21 (C-4b), 67.45 (C-

4a), 61.92 (C-6b). HRMS (ESI) m/z: [M + Na]⁺Calcd for

C₆₇H₅₄O₁₇SNa 1185.2979; Found 1185.2961.

6401

https://doi.org/10.1021/acs.joc.1c00250

J. Org. Chem. 2021, 86, 6390−6405

The Journal of Organic Chemistry

pubs.acs.org/joc

Article

injection in the IMS cell (10 ms); (ii) separation (see Table S1); and

(iii) ejection to TOF analyzer (13.2 ms). As long as the ions remain in

the fourth pass, their arrival times do not change: the slight diﬀerences

in separation times serve the purpose of setting a window to observe

the full ATD.

Data were processed using Driftscope 2.9 and MassLynx 4.2

(Waters, Wilmslow, UK) to extract the monoisotopic ion mobility

spectra. ATDs were then calibrated to give CCSDs using MajorMix

calibration solution (Waters, Wilmslow, UK)^68,69(R²= 0.999).

IRMPD. IRMPD spectra are obtained using a commercial mass

spectrometer equipped with an electrospray ion source and a Paul

trap (LCQ classic ThermoFisher) with custom-made modiﬁcations.

The trap was drilled to allow irradiation of the ion cloud by the beam

of a YAG-pumped tunable infrared OPO/OPA system (laserVision),

which delivers 8 ns, 10 Hz, 13 mJ pulses in the 2700−3700 cm⁻¹. A

mechanical shutter ensures the synchronization of the laser injection

with the desired stage of the MS sequence.

The samples were prepared at 30 μM in water/methanol (50/50),

and 0.1% of ammonium sulfate was added to promote the formation

of ionic complexes [M + NH₄]⁺. The ions are produced by

electrospray ionization and directed to the ion trap through a set of

ion multipoles and isolated based on their mass-to-charge ratio at m/z

360. The isolated ions are further held in the trap for a period of 800

ms, during which they are irradiated by the laser. If the IR wavelength

is resonant with one of the vibrational frequencies of the ions,

multiple photons can be absorbed and their energy redistributed

through internal vibrational coupling (IVR). This increases the

internal energy of the ion, which results in fragmentation, in a very

similar way to traditional collisional activation. The trapped ion

(remaining parent and photofragments) are then ejected from the

trap and the resulting mass spectrum is recorded. This sequence is

repeated thorough the spectral range of interest and the photo-

fragmentation yield is plotted as a function of the wavenumber. The

data shown are averaged three times.

Oznur Yeni − Univ Rennes, Ecole Nationale Supérieure de

Chimie de Rennes, CNRS, ISCR − UMR 6226, F-35000

Rennes, France; Université de Lyon, CNRS, Université

Claude Bernard Lyon 1, CNRS, Institut Lumiére Matiére, F-

69622 Lyon, France; INRAE, UR BIA, F-44316 Nantes,

France; INRAE, BIBS Facility, F-44316 Nantes, France;

Univ Rennes, CNRS, ISCR − UMR 6226, F-35000 Rennes,

France

Simon Ollivier − Univ Rennes, Ecole Nationale Supérieure de

Chimie de Rennes, CNRS, ISCR − UMR 6226, F-35000

Rennes, France; Université de Lyon, CNRS, Université

Claude Bernard Lyon 1, CNRS, Institut Lumiére Matiére, F-

69622 Lyon, France; INRAE, UR BIA, F-44316 Nantes,

France; INRAE, BIBS Facility, F-44316 Nantes, France;

Univ Rennes, CNRS, ISCR − UMR 6226, F-35000 Rennes,

France; orcid.org/0000-0002-7671-1736

Joël Boustie − Univ Rennes, Ecole Nationale Supérieure de

Chimie de Rennes, CNRS, ISCR − UMR 6226, F-35000

Rennes, France; Université de Lyon, CNRS, Université

Claude Bernard Lyon 1, CNRS, Institut Lumiére Matiére, F-

69622 Lyon, France; INRAE, UR BIA, F-44316 Nantes,

France; INRAE, BIBS Facility, F-44316 Nantes, France;

Univ Rennes, CNRS, ISCR − UMR 6226, F-35000 Rennes,

France

Franco̧ ise Le Dévéhat − Univ Rennes, Ecole Nationale

Supérieure de Chimie de Rennes, CNRS, ISCR − UMR

6226, F-35000 Rennes, France; Université de Lyon, CNRS,

Université Claude Bernard Lyon 1, CNRS, Institut Lumiére

Matiére, F-69622 Lyon, France; INRAE, UR BIA, F-44316

Nantes, France; INRAE, BIBS Facility, F-44316 Nantes,

France; Univ Rennes, CNRS, ISCR − UMR 6226, F-35000

Rennes, France

ASSOCIATED CONTENT

Jean-Paul Guégan − Univ Rennes, Ecole Nationale Supérieure

de Chimie de Rennes, CNRS, ISCR − UMR 6226, F-35000

Rennes, France; Université de Lyon, CNRS, Université

Claude Bernard Lyon 1, CNRS, Institut Lumiére Matiére, F-

69622 Lyon, France; INRAE, UR BIA, F-44316 Nantes,

France; INRAE, BIBS Facility, F-44316 Nantes, France;

Univ Rennes, CNRS, ISCR − UMR 6226, F-35000 Rennes,

France

Mathieu Fanuel − Univ Rennes, Ecole Nationale Supérieure de

Chimie de Rennes, CNRS, ISCR − UMR 6226, F-35000

Rennes, France; Université de Lyon, CNRS, Université

Claude Bernard Lyon 1, CNRS, Institut Lumiére Matiére, F-

69622 Lyon, France; INRAE, UR BIA, F-44316 Nantes,

France; INRAE, BIBS Facility, F-44316 Nantes, France;

Univ Rennes, CNRS, ISCR − UMR 6226, F-35000 Rennes,

France; orcid.org/0000-0001-8384-8266

■

sı

* Supporting Information

The Supporting Information is available free of charge at

https://pubs.acs.org/doi/10.1021/acs.joc.1c00250.

¹H and ¹³C NMR spectra of acceptors as well as

galactofuranosyl- and galactopyranosyl-containing dis-

accharides, IM-MS and IRMPD technical descriptions,

and MS/MS and IRMPD spectra of the eight

disaccharides (PDF)

AUTHOR INFORMATION

■

Corresponding Author

̀

Vincent Ferrieres − Univ Rennes, Ecole Nationale Supérieure

de Chimie de Rennes, CNRS, ISCR − UMR 6226, F-35000

Rennes, France; Université de Lyon, CNRS, Université

Claude Bernard Lyon 1, CNRS, Institut Lumiére Matiére, F-

69622 Lyon, France; INRAE, UR BIA, F-44316 Nantes,

France; INRAE, BIBS Facility, F-44316 Nantes, France;

Univ Rennes, CNRS, ISCR − UMR 6226, F-35000 Rennes,

France; Email: vincent.ferrieres@ensc-rennes.fr

̀

Hélene Rogniaux − Univ Rennes, Ecole Nationale Supérieure

de Chimie de Rennes, CNRS, ISCR − UMR 6226, F-35000

Rennes, France; Université de Lyon, CNRS, Université

Claude Bernard Lyon 1, CNRS, Institut Lumiére Matiére, F-

69622 Lyon, France; INRAE, UR BIA, F-44316 Nantes,

France; INRAE, BIBS Facility, F-44316 Nantes, France;

Univ Rennes, CNRS, ISCR − UMR 6226, F-35000 Rennes,

France; orcid.org/0000-0001-6083-2034

Authors

Bénédicte Favreau − Univ Rennes, Ecole Nationale Supérieure

de Chimie de Rennes, CNRS, ISCR − UMR 6226, F-35000

Rennes, France; Université de Lyon, CNRS, Université

Claude Bernard Lyon 1, CNRS, Institut Lumiére Matiére, F-

69622 Lyon, France; INRAE, UR BIA, F-44316 Nantes,

France; INRAE, BIBS Facility, F-44316 Nantes, France;

Univ Rennes, CNRS, ISCR − UMR 6226, F-35000 Rennes,

France

Richard Brédy − Univ Rennes, Ecole Nationale Supérieure de

Chimie de Rennes, CNRS, ISCR − UMR 6226, F-35000

Rennes, France; Université de Lyon, CNRS, Université

Claude Bernard Lyon 1, CNRS, Institut Lumiére Matiére, F-

69622 Lyon, France; INRAE, UR BIA, F-44316 Nantes,

France; INRAE, BIBS Facility, F-44316 Nantes, France;

6402

https://doi.org/10.1021/acs.joc.1c00250

J. Org. Chem. 2021, 86, 6390−6405

The Journal of Organic Chemistry

pubs.acs.org/joc

Article

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Univ Rennes, CNRS, ISCR − UMR 6226, F-35000 Rennes,

France

Isabelle Compagnon − Univ Rennes, Ecole Nationale

Supérieure de Chimie de Rennes, CNRS, ISCR − UMR

6226, F-35000 Rennes, France; Université de Lyon, CNRS,

Université Claude Bernard Lyon 1, CNRS, Institut Lumiére

Matiére, F-69622 Lyon, France; INRAE, UR BIA, F-44316

Nantes, France; INRAE, BIBS Facility, F-44316 Nantes,

France; Univ Rennes, CNRS, ISCR − UMR 6226, F-35000

Rennes, France; orcid.org/0000-0003-2994-3961

David Ropartz − Univ Rennes, Ecole Nationale Supérieure de

Chimie de Rennes, CNRS, ISCR − UMR 6226, F-35000

Rennes, France; Université de Lyon, CNRS, Université

Claude Bernard Lyon 1, CNRS, Institut Lumiére Matiére, F-

69622 Lyon, France; INRAE, UR BIA, F-44316 Nantes,

France; INRAE, BIBS Facility, F-44316 Nantes, France;

Univ Rennes, CNRS, ISCR − UMR 6226, F-35000 Rennes,

France; orcid.org/0000-0003-4767-6940

Laurent Legentil − Univ Rennes, Ecole Nationale Supérieure

de Chimie de Rennes, CNRS, ISCR − UMR 6226, F-35000

Rennes, France; Université de Lyon, CNRS, Université

Claude Bernard Lyon 1, CNRS, Institut Lumiére Matiére, F-

69622 Lyon, France; INRAE, UR BIA, F-44316 Nantes,

France; INRAE, BIBS Facility, F-44316 Nantes, France;

Univ Rennes, CNRS, ISCR − UMR 6226, F-35000 Rennes,

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Complete contact information is available at:

https://pubs.acs.org/10.1021/acs.joc.1c00250

Author Contributions

^§O.Y. and S.O. contributed equally to this work.

Notes

(15) Peltier, P.; Euzen, R.; Daniellou, R.; Nugier-Chauvin, C.;

The authors declare no competing ﬁnancial interest.

̀

Ferrieres, V. Recent knowledge and innovations related to

hexofuranosides: structure, synthesis and applications. Carbohydr.

Res. 2008, 343, 1897−1923.

ACKNOWLEDGMENTS

■

(16) Richards, M. R.; Lowary, T. L. Chemistry and Biology of

Galactofuranose-Containing Polysaccharides. ChemBioChem 2009,

10, 1920−1938.

(17) Marino, C.; Rinflerch, A.; de Lederkremer, R. M. Galactofur-

anose antigens, a target for diagnosis of fungal infections in humans.

Future Sci. 2017, 3, FSO199.

(18) Arbatsky, N. P.; Shashkov, A. S.; Mamyan, S. S.; Knirel, Y. A.;

Zych, K.; Sidorczyk, Z. Structure of the O -specific polysaccharide of a

serologically separate Proteus penneri strain 22. Carbohydr. Res. 1998,

310, 85−90.

The authors thank the Agence Nationale de la Recherche

(ANR) for ﬁnancially supporting the ALGAIM-MS project

(ANR-18-CE29-0006-02, https://algaims-35.webself.net/

accueil). The NMR platform PRISM (Université de Rennes

1, https://biosit.univ-rennes1.fr/prism-plate-forme-rennaise-

dimagerie-et-spectroscopie-multimodales) is also acknowl-

1

edged for recording H and ¹³C spectra at 500 and 125

MHz, respectively.

(19) Michael, F. S.; Szymanski, C. M.; Li, J.; Chan, K. H.; Khieu, N.

H.; Larocque, S.; Wakarchuk, W. W.; Brisson, J. R.; Monteiro, M. A.

The structures of the lipooligosaccharide and capsule polysaccharide

of Campylobacter jejuni genome sequenced strain NCTC 11168. Eur.

J. Biochem. 2002, 269, 5119−5136.

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Synthesis of an Exhaustive Library of Naturally Occurring Gal f-Man p and Gal p-Man p Disaccharides. Toward Fingerprinting According to Ring Size by Advanced Mass Spectrometry-Based IM-MS and IRMPD

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