Photoinitiated glycosylation at 350 nm

Article abstract of DOI:10.1080/07328303.2011.601533

A method for photochemical activation of glycosyl donors is presented. Selenoglycosides were activated by single-electron transfer using a photooxidant, N-methylquinolinium hexafluorophosphate, as photosensitizer and a toluene cosolvent as cosensitizer under irradiation at 350 nm. In this way we were able to synthesize glycosides including (1→6)-linked disaccharides. Benzyl ethers and benzoate esters were compatible with these conditions, allowing potentially synthetically useful transformations. The major by-products were due to hydrolysis; the reactions required the presence of oxygen and were run in air.

Full text of DOI:10.1080/07328303.2011.601533

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Photoinitiated Glycosylation at 350 nm
Ian Cumpstey a & David Crich a
a Centre de Recherche de Gif, Institut de Chimie des Substances
Naturelles, CNRS , Avenue de la Terrasse, 91198 , Gif-sur-Yvette
CEDEX , France
Published online: 14 Dec 2011.
To cite this article: Ian Cumpstey & David Crich (2011) Photoinitiated Glycosylation at 350 nm,
Journal of Carbohydrate Chemistry, 30:7-9, 469-485, DOI: 10.1080/07328303.2011.601533
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Journal of Carbohydrate Chemistry, 30:469–485, 2011
ꢀ
C
Copyright Taylor & Francis Group, LLC
ISSN: 0732-8303 print / 1532-2327 online
DOI: 10.1080/07328303.2011.601533
Photoinitiated Glycosylation
at 350 nm
Ian Cumpstey and David Crich
Centre de Recherche de Gif, Institut de Chimie des Substances Naturelles, CNRS,
Avenue de la Terrasse, 91198 Gif-sur-Yvette CEDEX, France
A method for photochemical activation of glycosyl donors is presented. Selenoglycosides
were activated by single-electron transfer using a photooxidant, N-methylquinolinium
hexafluorophosphate, as photosensitizer and a toluene cosolvent as cosensitizer under
irradiation at 350 nm. In this way we were able to synthesize glycosides including
(1→6)-linked disaccharides. Benzyl ethers and benzoate esters were compatible with
these conditions, allowing potentially synthetically useful transformations. The major
by-products were due to hydrolysis; the reactions required the presence of oxygen and
were run in air.
Keywords Glycosylation; Photochemistry; Radical ions; Oxocarbenium ions; Oxida-
tion; Electron transfer
INTRODUCTION
The importance of oligosaccharides in biological systems is beyond question,
but their roles are in many cases poorly understood.[1] Their low availability
from natural sources necessitates their chemical synthesis, but general meth-
ods to achieve this remain elusive.[2] The development of new glycosylation
protocols contributes to the quest for the ideal glycosylation methodology. In
the vast majority of published glycosylation methods, a Lewis acid will coor-
dinate to an anomeric substituent, transforming it into a better leaving group
so that nucleophilic substitution with an alcohol nucleophile can occur. In an
alternative approach that avoids the use of Lewis acids, one-electron oxida-
tion of the anomeric substituent gives a radical cation. This then fragments
into a glycosyl cation that can react analogously with an alcohol nucleophile to
give a glycoside. Such one-electron chemistry has been achieved by chemical
Received May 12, 2011; accepted June 7, 2011.
Address correspondence to Ian Cumpstey, Centre de Recherche de Gif, Institut de
Chimie des Substances Naturelles, CNRS, Avenue de la Terrasse, 91198 Gif-sur-
Yvette CEDEX, France. E-mail: ian.cumpstey@sjc.oxon.org; or David Crich, Centre de
Recherche de Gif, Institut de Chimie des Substances Naturelles, CNRS, Avenue de la
Terrasse, 91198 Gif-sur-Yvette CEDEX, France. E-mail: david.crich@icsn.cnrs-gif.fr
469

I. Cumpstey & D. Crich
470
means.[3] Alternatively, electrochemical activation has been explored,[4] with
the advantage that the electrode potential can be tuned exactly to match the
requirements for activation of the glycoside in question.
Photochemical one-electron oxidation is potentially an attractive alterna-
tive technique; here the reaction is promoted by an external stimulus, but
takes place in solution, so complications of electrochemical glycosylation due to
reaction at an electrode surface or electrochemical cell design will be avoided,
simplifying reaction setup. Three papers have reported on this concept: Noy-
ori used a methyl ether–protected aryl 2-deoxyglycoside as a donor.[5] When
irradiated with a high-pressure mercury lamp in the presence of photosen-
sitizers and an alcohol, the glycoside was formed. Furuta used a methyl
ether–protected selenoglycoside as a donor, with a high-pressure mercury
lamp, and a 2,4,6-triphenylpyrilium salt as photosensitizer.[6] This method
gave a number of glycosides in low to high yields, including a (1→6)-linked dis-
accharide. Photoinduced activation of methyl ether–protected thioglycosides
using a 1,4-dicyanonaphthalene photocatalyst with irradiation at 350 nm gave,
with methanol as cosolvent, methyl glycosides among other products.[7] Benzyl
ether protection was incompatible with these glycosylation conditions, result-
ing in degradation, while acetate-protected donors were unreactive.
For our study of photochemical glycosylation, the results of which we re-
port in this paper, we evaluated N-methyl quinolinium hexafluorophosphate
(NMQ-PF6) as photosensitizer. This salt has been used for C Si bond cleav-
age,[8] or for acetal formation by oxidative C C bond cleavage.[9,10] The corre-
sponding tetrafluoroborate salt has also been used in photochemical oxidation
reactions.[11] Using this photosensitizer, we were able to activate selenoglyco-
sides as glycosyl donors[12] under rather mild activation conditions, irradiating
O
SePh
OAc
O
SePh
OMe
(i), (ii)
AcO
AcO
MeO
MeO
OAc
OMe
3
1
(i), (iii)
O
SePh
OBn
O
SePh
OBn
BnO
BnO
BnO
BnO
OBn
OBn
4
2
Scheme 1: (i) NaOMe, MeOH; (ii) MeI, NaH, DMF, 0◦C → rt, 81% (2 steps); (iii) BnBr, NaH, DMF,
0◦C → rt, 71% (2 steps).

Photoinitiated Glycosylation
471
with 350-nm fluorescent tubes rather than a high-pressure mercury lamp, and
to synthesize disaccharides bearing synthetically useful protecting groups.
RESULTS AND DISCUSSION
Phenyl selenogalactosides with methyl ether 1 or benzyl ether 2[13] protection
for use as glycosyl donors were synthesized from the peracetate 3 by straight-
forward protecting group swap (Sch. 1). The phenyl selenoglucoside 4[12] was
synthesized in the same way, as described previously.
We first studied photochemical glycosylation with a model system with
a methyl ether–protected phenyl selenogalactoside 1 as glycosyl donor and
isopropanol 5 as acceptor. Using a mixture of acetonitrile, dichloromethane,
and toluene as solvent, 1.5 equiv. of the sensitizer NMQ-PF6, and 2 equiv.
of the acceptor alcohol 2, in air, under light irradiation (350 nm) after 2 h
20 min, we were able to isolate the glycosides 6 (54%) and the hemiacetal 7
(40%), which presumably arose from hydrolysis (Table 1, entry 1). In control
Table 1: Optimization of the reaction conditions
O
SePh
OMe
O
OH
PF6
MeO
MeO
MeO
MeO
O
O
N
MeO
MeO
OMe
+
HO
+
OMe
OMe
OMe
5
OMe
hν 350 nm
(see Table)
7
1
6
NMQ-PF6
(equiv.) Atmosphere
Entry
Solvent
Time
Outcome
1
MeCN/CH2Cl2/PhMe,
1.5
1.5
0
Air
2 h 20 min
>48 h
6 (1:1.6)a/54%; 7/40%b
No reaction
2:4:1
2c
3
MeCN/CH2Cl2/PhMe,
Air
2:4:1
MeCN/CH2Cl2/PhMe,
Air
2 h 20 min
1 h 30 min
Very little reaction
Very little reaction
2:4:1
4
MeCN/CH2Cl2/PhMe,
1.5
Argon
2:4:1
5
MeCN/PhMe, 5:2
MeCN/PhMe, 5:2
MeCN/PhMe, 5:2
0.3
0.3
0.3
Air
Air
Air
2 h
3 h
3 h
6 (1:1.8)a :7, 2.0:1d
1:6 (1:1.9)a :7, 2.7:1.6:1d
6 (1:1.8)a :7, 2.3:1d
6e
7f
Reaction between selenoglycoside donor 1 and isopropanol 5 (2 equiv.), carried out in Pyrex
flasks. Irradiation at 350 nm.
aα/β ratio, measured by integration of 1H NMR spectra.
bIsolated yields.
cReaction carried out in the dark.
dRatio of products from integration of crude 1H NMR spectra. Generally, only the glycosides
6, the hemiacetal 7, and Ph2Se2 are visible in the crude NMR spectra (the salt NMQ-PF6 is
insoluble in CDCl3).
eReaction carried out with molecular sieves 4 Å powder.
fReaction carried out with molecular sieves 4 Å balls.

I. Cumpstey & D. Crich
472
experiments, running the same reaction in the dark resulted in no reaction
after 48 h (Table 1, entry 2), and running the reaction without the sensitizer
NMQ-PF6 gave mostly (>90%) starting material after 2 h 20 min, although
some decomposition products and traces of hemiacetal 7 and glycosides 6 were
1
visible in the crude H NMR spectrum (Table 1, entry 3). This is consistent
with the anticipated mechanism for the glycosylation reaction involving the
photochemical activation of the sensitizer salt and subsequent activation of the
selenoglycoside as a donor by single-electron transfer. The yellow by-product
from the glycosylation reaction was confirmed to be diphenyl diselenide by LC-
APCI mass spectrometry, which showed peaks with a mass isotope distribu-
tion consistent with [Ph2Se2H]+ and with an identical LC trace to authentic
Ph2Se2.
When the reaction was run under Ar rather than air, very little reaction
was seen after 1 h 30 min (Table 1, entry 4), which suggests that oxygen is nec-
essary for the reaction. This prompted us to test using a catalytic quantity of
the photosensitizer. It has been shown that catalytic NMQ-PF6 in combination
with oxygen can be used as a photooxidant, where the oxygen reoxidizes the
reduced NMQ radical.[10] Indeed, running the reaction under these conditions
(0.3 equiv. NMQ-PF6) resulted in complete conversion of the selenoglycoside 1
into a mixture of glycosides 6 and hemiacetal 7 after 2 h (Table 1, entry 5).
Carrying out the reaction in dichloromethane and acetonitrile without toluene
gave a somewhat slower reaction (5 h was needed for the disappearance of
donor 1), which is consistent with toluene’s proposed role as a cosensitizer.[14]
Acetonitrile is needed as cosolvent as the sensitizer NMQ-PF6 is insoluble in
toluene (and many other solvents).
The major or exclusive by-product in these glycosylation reactions was the
hemiacetal 7,[15] presumably resulting from hydrolysis. We passed the air at-
mosphere used in the reaction through a column of CaCl2 as standard proce-
dure, in an attempt to dry it, but in fact this had little effect on the ratio of
glycosides 6 to hemiacetal 7 formed. It seems likely that one source of water
is from the reduction of the molecular oxygen that is necessary for the reac-
tion; that is, that water is produced in the reaction. When we added powdered
˚
sieves (4 A), we saw a significantly slower reaction, presumably due to the in-
creased light scattering and failure of the light to reach the photosensitizer
˚
(Table 1, entry 6). Ball sieves (4 A) did not have a significantly deleterious ef-
fect on the reaction rate and did give a marginal improvement in the ratio of
1
glycoside to hydrolysis product seen by crude H NMR spectroscopy (Table 1,
entry 7).
We went on to examine the scope of the reaction with other glycosyl
donors and acceptors. The results are given in Table 2. Significantly, ben-
zyl ether–protected galacto 2- and gluco 4-configured selenoglycosides could
be used as donors without any cleavage of the benzyl ethers or other side

pgae)
nxet
on
(oCtinued
473

(Cotinued)
474

Photoinitiated Glycosylation
475
reactions being observed. This represents a step forward in photochemical gly-
cosylation as previously only methyl ethers have been used, and these can
be rather difficult to deprotect, limiting the synthetic utility of any method
relying on their use. Benzoate esters on the acceptor were also unaffected. We
were able to synthesize (1→6)-linked disaccharides 9, 12, 14, 16, and 18 and
a carbohydrate–steroid conjugate 11 uneventfully. Again, significant quanti-
ties of the hemiacetals 7,[15] 15,[16] and 17[17] derived from the glycosyl donors
were formed as by-products. The glycosidic α/β ratios favored the β-configured
products in all cases to a greater or lesser extent, a phenomenon that may be
explained by the presence of acetonitrile as cosolvent,[18] but the diastereose-
lectivity was only modest in all cases.
Attempted glycosylation of secondary carbohydrate alcohols with donor 2
gave worse results. Disaccharides were clearly formed, as shown by mass spec-
trometry, but they were not obtained pure from other by-products. Activation
of an acetate-protected selenoglycoside 19 with diacetone galactose 8 as accep-
tor under the conditions of Table 2 gave a very slow reaction, requiring many
hours for the donor 19 to be completely consumed, as would be expected from
the armed–disarmed principle (and implying reversible oxidation of the se-
lenoglycoside). Possibly surprisingly though, in this case no glycoside and only
hydrolysis products 20,[17,22] 21,[23] and 22[24] were formed (Sch. 2).
O
NHAc
OAc
O
SePh
OAc
O
OAc
OH
O
OH
AcO
AcO
19
AcO
AcO
AcO
20
AcO
(i)
+
+
AcO
22
OAc
AcO
21
OAc
OAc
OAc
OAc
Scheme 2: (i) 8 (3 equiv.), NMQ-PF6 (0.3 equiv.), MeCN–toluene 5:2, air, hν 350 nm; 20 + 21:
70%; 22: 16%.
Thioglycosides were also briefly examined as donors and gave inferior re-
sults. A benzyl ether–protected thioglycoside donor 23 (Fig. 1) was activated
slowly and gave some disaccharide along with other by-products. A benzoate-
protected thioglycoside 24 failed to react under the conditions.
O
SPh
OBn
O
SEt
BnO
BnO
23
BzO
BzO
24
OBz
OBn
OBz
Figure 1: Thioglycosides tested as donors.

I. Cumpstey & D. Crich
476
CONCLUSIONS
Benzyl ether–protected or methyl ether–protected selenophenyl glycosides
can be used as donors in photochemical glycosylation reactions using N-
methylquinolinium hexafluorophosphate as photosensitizer. The reactions use
a catalytic amount of the photosensitizer and require oxygen or air for a sto-
ichiometric oxidant. The major by-products in these reactions are the donor-
derived hemiacetals.
EXPERIMENTAL
General Methods
Melting points were measured using a Bu¨chi B-540 melting point appara-
tus and are uncorrected. Proton nuclear magnetic resonance (1H) spectra were
recorded on Bruker Avance 500 (500 MHz) or Bruker Avance 300 (300 MHz)
spectrometers; multiplicities are quoted as singlet (s), doublet (d), doublet of
doublets (dd), doublet of doublet of doublets (ddd), triplet (t), apparent triplet
(at), quartet (q), and multiplet (m). Carbon nuclear magnetic resonance (13C)
spectra were recorded on Bruker Avance 500 (125 MHz) or Bruker Avance 300
(75 MHz) spectrometers. Selenium nuclear magnetic resonance (77Se) spectra
1
were recorded on a Bruker Avance 500 (95 MHz) spectrometer. H and 13C
spectra and 13C multiplicities were assigned using COSY, HSQC, and DEPT
experiments. All chemical shifts are quoted on the δ-scale in parts per million
(ppm). Residual solvent signals (CHCl3, 7.26) were used as an internal ref-
I
II
erence. In disaccharides, the descriptors and refer to the monosaccharide
residues numbered starting from the reducing terminus. In compounds that
were isolated as α/β mixtures, the descriptors α and β refer to the anomeric con-
figuration of the newly formed glycosidic bond (in disaccharides this means the
configuration of monosaccharide II). Coupling constants to selenium quoted
1
in H and 13C NMR spectra were measured from the satellite peaks in the
respective spectra. Low- and high-resolution (HRESIMS) electrospray (ESI)
mass spectra were recorded using a Waters Micromass LCT premier XE in-
strument or using the mass spectrometry service of the ICSN. Optical rota-
tions were measured on a Jasco P1010 polarimeter with a path length of 1 dm;
concentrations are given in g/100 mL. Microanalysis was carried out by the
microanalysis service of the ICSN. Thin layer chromatography (TLC) was car-
ried out on Merck Kieselgel sheets, precoated with 60F254 silica. Plates were
visualized with UV light and developed using 10% sulfuric acid. Flash column
chromatography was carried out on prepacked silica columns (Chromabond,
RediSep, PuriFlash, or SuperFlash). Photochemical experiments were carried
out using a Rayonet photochemical reactor equipped with 350-nm tubes. An-
hydrous solvents were bought and used as supplied.

Photoinitiated Glycosylation
477
N-Methylquinolinium hexafluorophosphate was prepared by methylation
of quinoline with methyl iodide followed by anion exchange and recrystalliza-
tion from water according to the literature procedure.[8] It was dried under
vacuum over P2O5 before use.
General Procedure for Photochemical Glycosylation
The selenoglycoside (0.074–0.21 mmol), the alcohol (3 equiv), and NMQ-
PF6 (0.3 equiv.) were dissolved in toluene (0.2 mL) and acetonitrile (0.5 mL) in
a flame-dried Pyrex flask (25 mL). Freshly activated molecular sieves (9 balls,
˚
4 A) were added. The reaction vessel was sealed and purged several times with
air that was dried by passing through a column of CaCl2. The reaction vessel
was suspended in the Rayonet photoreactor and irradiated (350 nm) for the
stated time. The temperature was maintained close to rt by passing a stream
of air through the photoreactor around the flask. When TLC showed complete
consumption of the selenoglycoside, silica gel was added, the mixture was con-
centrated in vacuo, and the residue purified by flash column chromatography.
Phenyl 2,3,4,6-Tetra-O-methyl-1-seleno-β-D-galactopyranoside 1
Sodium (40 mg, 1.7 mmol) was added to MeOH (30 mL). Phenyl 2,3,4,6-
tetra-O-acetyl-1-seleno-β-D-galactopyranoside 3 (6.87 g, 14.1 mmol) was added
to the resulting methoxide solution, and the mixture was stirred at rt. After
45 min, TLC (EtOAc) showed the presence of a single component (Rf 0.1). AcOH
(2 mL) was added, and the mixture was concentrated in vacuo.
The residue was dissolved in DMF (40 mL) and cooled to 0◦C under Ar.
NaH (60% in oil, 3.38 g, 85 mmol) was washed with heptane and then added
to the reaction mixture. MeI (4.8 mL, 78 mmol) was added, and the mixture
was stirred at rt. After 1 h, TLC (heptane–EtOAc, 1:1) showed the presence of
a single component (Rf 0.2). The reaction was quenched with MeOH (ca 6 mL)
and then concentrated in vacuo. The residue was partitioned between EtOAc
(100 mL) and a mixture of water (100 mL) and brine (100 mL). The aqueous
phase was re-extracted with EtOAc (3 × 100 mL), and the combined organic
extracts were dried (Na2SO4), filtered, and concentrated in vacuo. The residue
was purified by flash column chromatography (40 g silica, heptane–EtOAc,
10:1 → 2:1) to give the tetramethyl selenogalactoside 1 (4.26 g, 81%) as a col-
orless oil that crystallized on standing. Recrystallization gave white crystals,
m.p. 61–62◦C (heptane); [α]D25 –33.1 (c 1.0, CHCl3); 1H NMR (500 MHz, CDCl3)
δH 3.18 (1H, dd, J3,4 = 2.8 Hz, J2,3 = 9.1 Hz, H-3), 3.36, 3.52, 3.55, 3.56 (12H,
4 × s, 4 × OCH3), 3.44–3.49 (2H, m, H-2, H-5), 3.53 (1H, m (obs), H-6), 3.59
(1H, at, J = 8.5 Hz, H-6ꢁ), 3.69 (1H, d, J3,4 = 2.8 Hz, H-4), 4.69 (1H, d, J1,2
=
2
9.8 Hz, JH1,Se = 12.0 Hz, H-1), 7.24–7.65 (5H, m, Ar-H); 13C NMR (125 MHz,
CDCl3) δC 58.3, 59.3, 61.2, 61.4 (4 × q, 4 × OCH3), 70.7 (t, C-6), 75.1 (d, C-4),

I. Cumpstey & D. Crich
478
78.2 (d, C-5), 80.1 (d, C-2), 84.1 (d, 1JC1,Se = 87.1 Hz, C-1), 86.1 (d, C-3), 127.6,
129.0, 134.2 (3 × d, Ar-CH), 129.4 (s, Ar-C); 77Se NMR (95 MHz, CDCl3) δSe
421; m/z (ES+) 394 (M+NH4+, 100%); HRMS calcd for C16H28O5NSe (MNH4
)
+
394.1127; found 394.1142. Anal calcd for C16H24O5Se: C, 51.22; H, 6.45; found:
C, 51.22; H, 6.41%.
Phenyl 2,3,4,6-Tetra-O-benzyl-1-seleno-β-D-galactopyranoside 2
Sodium (20 mg, 0.87 mmol) was added to MeOH (10 mL). Phenyl 2,3,4,6-
tetra-O-acetyl-1-seleno-β-D-galactopyranoside 3 (2.10 g, 4.3 mmol) was added
to the resulting methoxide solution, and the mixture was stirred at rt. After
1 h 30 min, TLC (EtOAc) showed the presence of a single component (Rf 0.1).
The mixture was concentrated in vacuo.
The residue was dissolved in DMF (20 mL) and cooled to 0◦C under Ar.
NaH (60% in oil, 1.20 g, 30 mmol) was washed with heptane and then added
to the reaction mixture. BnBr (3.15 mL, 26 mmol) was added, and the mixture
was allowed to warm to rt in the ice–water bath. After 13 h, the reaction was
quenched with MeOH (ca 6 mL) and then concentrated in vacuo. The residue
was partitioned between EtOAc (100 mL) and water (100 mL). The organic
phase was dried (Na2SO4), filtered, and concentrated in vacuo. The residue was
purified by flash column chromatography (25 g silica, heptane–EtOAc, 20:1 →
2:1) to give the tetrabenzyl selenogalactoside 2 (2.07 g, 71%) as a pale yellow
oil. Recrystallization gave white crystals, m.p. 89–91◦C (Et2O–heptane); [α]D
25
–9.7 (c 1.0, CHCl3); 1H NMR (500 MHz, CDCl3) δH 3.59–3.62 (2H, m, H-3, H-5),
3.66–3.68 (2H, m, H-6, H-6ꢁ), 3.97 (1H, at, J = 9.5 Hz, H-2), 4.01 (1H, d, J3,4
=
2.2 Hz, H-4), 4.44, 4.49 (2H, 2 × d, PhCH2), 4.60, 4.97 (2H, 2 × d, PhCH2),
2
4.70–4.78 (4H, m, 2 × PhCH2), 4.85 (1H, d, J1,2 = 9.8 Hz, JH1,Se = 14.7 Hz,
H-1), 7.13–7.68 (25H, m, Ar-H); 13C NMR (125 MHz, CDCl3) δC 68.8 (t, C-6),
72.8, 73.7, 74.6, 75.6 (4 × t, 4 × PhCH2), 73.9 (d, C-4), 78.0 (d, C-2), 78.5, 84.4
(2 × d, C-3, C-5), 83.8 (d, C-1), 127.5, 127.6, 127.7, 127.8, 127.9, 127.9, 128.1,
128.3, 128.4, 128.5, 128.6, 129.0 (12 × d, Ar-CH), 129.4 (s, Ar-C), 134.0 (d, Ar-
CH), 138.0, 138.4, 138.4, 139.0 (4 × s, 4 × Ar-C); 77Se NMR (95 MHz, CDCl3) δSe
418; m/z (ES+) 698 (M+NH4+, 100%); HRMS calcd for C40H44O5NSe (MNH4
)
+
698.2385; found 698.2413. Anal calcd for C40H40O5Se: C, 70.68; H, 5.93; found:
C, 70.80; H, 6.15%.
Isopropyl 2,3,4,6-Tetra-O-methyl-α,β-D-galactopyranoside 6
Synthesized according to the general procedure from tetramethyl galacto
donor 1 (80 mg, 0.21 mmol) and isopropanol (60 µL, 0.81 mmol) with NMQ-PF6
(20 mg, 0.07 mmol) in toluene (0.4 mL) and acetonitrile (1 mL). Purification
by flash column chromatography (4 g silica, heptane–EtOAc, 10:1 → 2:1 →
1
0:1) gave the glycosides 6 (43 mg, 75%) as a colorless oil (α:β 1:1.6); H NMR

Photoinitiated Glycosylation
479
(500 MHz, CDCl3) δH 1.17 (6H, d, J = 6.1 Hz, CH(CH3)CH3α,β), 1.22 (6H, d,
J = 6.1 Hz, CH(CH3)CH3α,β), 3.38, 3.47, 3.50, 3.56 (12H, 4 × s, 4 × OCH3α),
3.38, 3.51, 3.54, 3.57 (12H, 4 × s, 4 × OCH3β), 3.43–3.62 (m), 3.69 (1H, m, H-
4α), 3.90–3.95 (3H, m, 2 × Hα, Hβ), 4.26 (1H, d, J1,2 = 7.6 Hz, H-1β), 5.06 (1H,
d, J1,2 = 3.7 Hz, H-1α), 3.09 (1H, dd, J3,4 = 2.9 Hz, J2,3 = 9.6 Hz, H-3β), 3.27
(1H, at, J = 8.7 Hz, H-2β); 13C NMR (75 MHz, CDCl3) δC 21.3, 23.3 (2 × q,
CH(CH3)2α), 22.0, 23.7 (2 × q, CH(CH3)2β), 58.1, 58.4, 59.3, 61.4 (4 × q, 4 ×
OCH3α), 58.6, 60.9, 61.4 (3 × q, 4 × OCH3β), 68.9, 69.2, 77.7, 80.2 (4 × d, C-2α,
C-3α, C-5α, CH(CH3)2α), 71.0 (t, C-6β), 71.3 (t, C-6α), 72.0 (d, CH(CH3)2β), 73.1
(d, C-5β), 75.1 (d, C-4β), 76.1 (d, C-4α), 80.9 (d, C-2β), 84.0 (d, C-3β), 94.7 (d, C-
1α), 102.4 (d, C-1β); m/z (ES+) 579 (2M+Na+, 35), 301 (M+Na+, 100%); HRMS
calcd for C13H26O6Na (MNa+) 301.1627; found 301.1617.
And the hemiacetal 2,3,4,6-tetra-O-methyl-D-galactopyranose 7 (13 mg,
1
25%) as a colorless oil; H NMR (500 MHz, CDCl3) δH 3.17 (1H, dd, J2,3
=
9.7 Hz, J3,4 = 3.0 Hz, H-3β), 3.28 (1H, dd, J1,2 = 7.4 Hz, J2,3 = 9.7 Hz, H-2β),
3.39–3.65 (32H, m, 8 × OCH3, H-4β, H-5β, H-6β, H-6ꢁβ, H-2α, H-3α, H-6α, H-6ꢁα),
3.70 (1H, d, J3,4 = 1.9 Hz, H-4α), 4.12 (1H, at, J = 6.5 Hz, H-5α) 4.55 (1H, d,
J1,2 = 7.2 Hz, H-1β), 5.39 (1H, d, J1,2 = 3.5 Hz, H-1α); 13C NMR (125 MHz,
CDCl3) δC 58.2, 59.0, 59.3, 61.4 (4 × q, 4 × OCH3α), 58.4, 61.0 (2 × q, OCH3β),
69.3 (d, C-5α), 71.2 (t, C-6β), 71.5 (t, C-6α), 73.5 (d, C-5β), 75.2 (d, C-4β), 76.1 (d,
C-4α), 78.2 (d, C-2α), 80.2 (d, C-3α), 82.2 (d, C-2β), 84.1 (d, C-3β), 91.2 (d, C-1α+),
97.7 (d, C-1β); m/z (ES+) 275 (M+K+, 25), 259 (M+Na+, 95), 254 (M+NH4
,
100%); HRMS calcd for C10H20O6Na (MNa+) 259.1158; found 259.1151.
2,3,4,6-Tetra-O-methyl-α,β-D-galactopyranosyl-(1→6)-1,2:3,4-di-
O-isopropylidene-α-D-galactopyranose 9
Synthesized according to the general procedure from tetramethyl galacto
donor 1 (60 mg, 0.16 mmol) and diacetone galactose 8 (125 mg, 0.48 mmol)
with NMQ-PF6 (14 mg, 0.05 mmol) in toluene (0.2 mL) and acetonitrile (0.5
mL). Purification by flash column chromatography (4 g silica, heptane–EtOAc,
10:1 → 2:1 → 1:10) gave the recovered nucleophile 8 (90 mg), then the glyco-
1
sides 9 (54 mg, 71%) as a colorless oil (α:β 1:1.6); H NMR (500 MHz, CDCl3)
δH 1.30, 1.41, 1.42, 1.47, 1.50 (24H, 5 × s, 4 × C(CH3)2), 3.10 (1H, dd, J2,3
=
9.8 Hz, J3,4 = 3.2 Hz, H-3IIβ), 3.30 (1H, dd, J2,3 = 9.8 Hz, J1,2 = 7.8 Hz, H-2IIβ),
ꢁ
3.37–3.71 (m), 3.79 (1H, dd, J5,6 = 6.6 Hz, J6,6 = 10.7 Hz, H-6α), 3.94 (1H, at,
ꢁ
J = 6.6 Hz), 3.99–4.02 (2H, m), 4.05 (1H, dd, J5,6 = 3.5 Hz, J6,6 = 10.7 Hz, H-
6β), 4.20 (1H, dd, J3,4 = 7.9 Hz, J4,5 = 1.6 Hz, H-4Iβ), 4.26–4.30 (4H, m, H-2Iα,
H-2Iβ, H-4Iα, H-1IIβ), 4.55–4.59 (2H, m, H-3Iα, H-3Iβ), 5.03 (1H, d, J1,2 = 3.5 Hz,
H-1IIα), 5.49–5.51 (2H, m, H-1Iα, H-1Iβ); 13C NMR (125 MHz, CDCl3) δC 24.5,
24.6, 25.0, 25.2, 26.1, 26.1, 26.1 (7 × q, 4 × C(CH3)2), 58.0, 58.1, 58.5, 59.2,
59.3, 60.8, 61.3, 61.4 (8 × q, 8 × OCH3), 65.9, 67.8, 68.9, 70.7, 70.8, 70.9, 70.9,
71.6, 72.9, 74.9, 75.8, 77.7, 79.9 (13 × d, C-2Iα, C-2Iβ, C-3Iα, C-3Iβ, C-4Iα, C-4Iβ,

I. Cumpstey & D. Crich
480
C-5Iα, C-5Iβ, C-2IIα, C-3IIα, C-4IIα, C-4IIβ, C-5IIα, C-5IIβ), 66.5, 69.3, 70.8, 71.0
(4 × t, C-6Iα, C-6Iβ, C-6IIα, C-6IIβ), 80.7 (d, C-2IIβ), 83.5 (d, C-3IIβ), 96.4, 96.4,
96.8 (3 × d, C-1Iα, C-1Iβ, C-1IIα), 104.4 (d, C-1IIβ), 108.6, 108.7, 109.3, 109.4 (4 ×
s, 4 × C(CH3)2); m/z (ES+) 501 (M+Na+, 27), 496 (M+NH4+, 100%); HRMS
calcd for C22H38O11Na (MNa+) 501.2312; found 501.2305.
And then the hemiacetal 7 (13 mg, 25%) as a colorless oil.
Cholestan-3β-yl 2,3,4,6-Tetra-O-methyl-α,β-D-
galactopyranoside 11
Synthesized according to the general procedure from tetramethyl galacto
donor 1 (60 mg, 0.16 mmol) and cholestanol 10 (186 mg, 0.48 mmol) with NMQ-
PF6 (14 mg, 0.05 mmol) in toluene (2 mL) and acetonitrile (1 mL). Purification
by flash column chromatography (4 g silica, heptane–EtOAc, 10:1 → 2:1 → 0:1)
gave the recovered alcohol 10 (142 mg) as a white solid, then the glycosides 11
(49 mg, 51%) as a white solid (α:β 1:2); 1H NMR (500 MHz, CDCl3) δH 0.59–1.56
(92H, m, steroid-H), 3.09 (1H, dd, J2,3 = 9.8 Hz, J3,4 = 2.8 Hz, H-3β), 3.28 (1H,
dd, J1,2 = 7.6 Hz, J2,3 = 9.8 Hz, H-2β), 3.39–3.62 (34H, m, 2 × steroid-OCH,
8 × OCH3, H-4β, H-5β, H-6β, H-6ꢁβ, H-2α, H-3α, H-6α, H-6ꢁα), 3.69 (1H, d, J3,4
=
1.6 Hz, H-4α), 3.95 (1H, at, J = 6.6 Hz, H-5α), 4.31 (1H, d, J1,2 = 7.6 Hz, H-1β),
5.10 (1H, d, J1,2 = 3.5 Hz, H-1α); 13C NMR (125 MHz, CDCl3) δC 12.2, 12.4,
12.5, 18.8, 22.7, 23.0, 28.2, 35.7, 35.9, 45.0, 45.3, 54.5, 54.6, 56.5, 56.6, 56.7
(16 × d, q, steroid-CH and steroid-CH3), 21.4, 24.0, 24.4, 27.6, 28.4, 28.9, 29.0,
29.7, 32.2, 32.3, 34.7, 36.0, 36.3, 37.0, 37.2, 39.7, 40.2, 40.2 (18 × t, steroid-
CH2), 58.0, 58.3, 58.6, 59.3, 59.3, 60.9, 61.3, 61.4 (8 × q, 8 × OCH3), 68.9 (d,
C-5α), 71.0 (t, C-6β), 71.3 (t, C-6α), 73.0, 75.1, 78.9 (3 × d, C-4β, C-5β, steroid-
OCHβ), 76.1, 76.5, 77.7, 80.2 (4 × d, C-2α, C-3α, C-4α, steroid-OCHα), 80.9 (d,
C-2β), 84.0 (d, C-3β), 94.8 (d, C-1α), 102.3 (d, C-1β); m/z (ES+) 629 (M+Na+, 21),
624 (M+NH4+, 100%); HRMS calcd for C37H66O6Na (MNa+) 629.4757; found
629.4748.
2,3,4,6-Tetra-O-benzyl-α,β-D-galactopyranosyl-(1→6)-1,2:3,4-di-
O-isopropylidene-α-D-galactopyranose 12[19]
Synthesized according to the general procedure from tetrabenzyl galacto
donor 2 (109 mg, 0.16 mmol) and diacetone galactose 8 (125 mg, 0.48
mmol) with NMQ-PF6 (14 mg, 0.044 mmol) in toluene (0.2 mL) and ace-
tonitrile (0.5 mL). Purification by flash column chromatography (4 g silica,
heptane–EtOAc, 10:1 → 5:1) gave the glycosides 12 (74 mg, 59%) as a color-
less oil (α:β 1:1.4); 1H NMR (300 MHz, CDCl3) 1.32, 1.33, 1.34, 1.45, 1.46, 1.51,
1.54 (24H, 7 × s, 4 × C(CH3)2), 3.52–3.63 (6H, m, 2 × H-6, 2 × H-6ꢁ), 3.72 (1H,
ꢁ
ꢁ
dd, J6,6 = 10.7 Hz, J5,6 = 7.3 Hz, H-6), 3.76 (1H, dd, J6,6 = 10.4 Hz, J5,6
=
7.3 Hz, H-6), 3.81 (1H, dd, J6,6 = 10.4 Hz, J5,6 = 6.3 Hz, H-6ꢁ), 3.85 (1H, dd,
ꢁ
ꢁ

Photoinitiated Glycosylation
481
J = 7.9 Hz, J = 9.8 Hz), 3.90 (1H, d, J = 2.2 Hz), 3.98 (1H, dd, J = 10.1 Hz,
ꢁ
J = 2.8 Hz), 4.02 (1H, d, J = 1.6 Hz), 4.04–4.11 (4H, m), 4.15 (1H, dd, J5,6
=
3.5 Hz, J6,6 = 10.7 Hz, H-6ꢁ), 4.23 (1H, dd, J = 1.9 Hz, J = 7.9 Hz), 4.31–4.35
(3H, m, H-2Iα, H-2Iβ), 4.41–4.51 (5H, m, H-1IIβ, 2 × PhCH2), 4.58–4.64 (4H,
m, 2 × PhCHHꢁ), 4.72–4.87 (7H, m, 3 × PhCH2, PhCHHꢁ), 4.93–4.97 (2H, m,
2 × PhCHHꢁ), 5.03 (1H, d, J1,2 = 3.8 Hz, H-1IIα), 5.07 (1H, d, J = 11.0 Hz,
PhCHHꢁ), 5.53 (1H, d, J1,2 = 5.0 Hz, H-1Iα), 5.58 (1H, d, J1,2 = 4.7 Hz, H-1Iβ),
7.26–7.48 (40H, m, Ar-H); 13C NMR (75 MHz, CDCl3) δC 24.6, 24.7, 25.1, 25.2,
26.1, 26.2, 26.3 (7 × q, 4 × C(CH3)2), 66.0, 67.5, 69.3, 70.6, 70.8, 70.8, 70.9,
71.0, 71.6, 73.4, 73.7, 75.1, 76.6, 79.1, 79.2, 82.0 (16 × d, C-2Iα, C-3Iα, C-4Iα,
C-5Iα, C-2IIα, C-3IIα, C-4IIα, C-5IIα, C-2Iβ, C-3Iβ, C-4Iβ, C-5IIβ, C-2IIβ, C-3IIβ, C-
4IIβ, C-5IIβ), 66.5, 68.8, 68.8, 69.7 (4 × t, C-6Iα, C-6IIα, C-6Iβ, C-6IIβ), 72.8, 73.2,
73.3, 73.5, 73.6, 74.6, 74.9, 74.9 (8 × t, 8 × PhCH2), 96.4, 96.5 (2 × d, C-1Iα,
C-1Iβ), 97.7 (d, C-1IIα), 104.8 (d, C-1IIβ), 108.6, 108.7, 109.3, 109.4 (4 × s, 4 ×
C(CH3)2), 127.4, 127.5, 127.5, 127.6, 127.6, 127.6, 127.8, 127.8, 127.9, 127.9,
128.0, 128.2, 128.2, 128.3, 128.3, 128.3, 128.4, 128.5, 128.5, 128.7 (20 × d, Ar-
CH), 138.1, 138.2, 138.8, 138.8, 138.9, 138.9, 139.1, 139.2 (8 × s, Ar-C); m/z
(ES+) 800 (M+NH4+, 100%); HRMS calcd for C46H58O11N (MNH4+) 800.4010;
found 800.4015.
ꢁ
Then a mixture of the hemiacetal 15 and unreacted alcohol 8 (127 mg).
Methyl 2,3,4,6-Tetra-O-benzyl-α,β-D-galactopyranosyl-(1→6)-
2,3,4-tri-O-benzoyl-α-D-glucopyranoside 14[20]
Synthesized according to the general procedure from tetrabenzyl galacto
donor 2 (50 mg, 0.074 mmol) and gluco acceptor 13 (112 mg, 0.22 mmol) with
NMQ-PF6 (7 mg, 0.022 mmol) in toluene (0.2 mL) and acetonitrile (0.5 mL). Pu-
rification by flash column chromatography (4 g silica, heptane–EtOAc, 6:1 →
1
2:1) gave the glycosides 14 (34 mg, 45%) as a colorless oil (α:β 1:1.4); H NMR
(500 MHz, CDCl3) 3.35, 3.36 (6H, 2 × s, OCH3α, OCH3β), 3.42–4.40 (18H, m,
H-5Iα, H-6Iα, H-6ꢁIα, H-2IIα, H-3IIα, H-4IIα, H-5IIα, H-5Iβ, H-6Iβ, H-6ꢁIβ, H-2II
,
β
H-3IIβ, H-4IIβ, H-5IIβ, H-6IIα, H-6ꢁIIα, H-6IIβ, H-6ꢁIIβ), 4.44 (1H, d, J1,2 = 7.6 Hz,
H-1IIβ), 4.55–5.03 (17H, m, H-1IIα, 8 × PhCH2), 5.16 (1H, d, J1,2 = 3.7 Hz, H-
1Iα), 5.19 (1H, d, J1,2 = 3.4 Hz, H-1Iβ), 5.21–5.27 (2H, m, H-2Iα, H-2Iβ), 5.41
(1H, at, J = 9.9 Hz, H-4Iβ), 5.53 (1H, at, J = 9.9 Hz, H-4Iα), 6.11–6.18 (2H,
m, H-3Iα, H-3Iβ), 7.20–8.00 (70H, m, Ar-H); 13C NMR (75 MHz, CDCl3) δC 55.6
(q, 2 × OCH3), 66.7, 68.8, 68.8, 69.1 (4 × t, C-6Iα, C-6IIα, C-6Iβ, C-6IIβ), 68.6,
69.1, 69.4, 69.7, 70.1, 70.6, 70.8, 72.3, 73.5, 73.6, 75.2, 76.6, 78.7, 79.8, 82.2
(15 × d, C-2Iα, C-3Iα, C-4Iα, C-5Iα, C-2IIα, C-3IIα, C-4IIα, C-5IIα, C-2Iβ, C-3Iβ, C-
4Iβ, C-5IIβ, C-2IIβ, C-3IIβ, C-4IIβ, C-5IIβ), 73.0, 73.2, 73.3, 73.3, 73.6, 74.6, 74.9,
75.3 (8 × t, 8 × PhCH2), 96.8, 96.9 (2 × d, C-1Iα, C-1Iβ), 98.0 (d, C-1IIα), 104.4
(d, C-1IIβ), 127.6, 127.6, 127.7, 127.7, 127.7, 127.7, 127.8, 127.9, 128.0, 128.0,

I. Cumpstey & D. Crich
482
128.3, 128.3, 128.4, 128.4, 128.4, 128.5, 128.5, 128.5, 128.5, 128.5 (20 × d, Ar-
CH), 129.0, 129.2, 129.3, 129.3, 129.4, 129.5 (6 × s, 6 × Bz-C), 129.8, 129.8,
130.0, 130.0, 130.1, 133.2, 133.4, 133.5, 133.5 (9 × d, Ar-CH), 138.0, 138.3,
138.7, 138.8, 138.9, 139.0 (6 × d, Bn-C), 165.5, 165.7, 165.9, 165.9, 166.0 (5 × s,
C = O); m/z (ES+) 1051 (M+Na+, 15), 1046 (M+NH4+, 100%); HRMS calcd for
C62H60O14Na (MNa+) 1051.3881; found 1051.3920.
And then the hemiacetal 15 (12 mg, 30%) as a colorless oil, and then the
recovered alcohol 13 (93 mg) as a white solid.
2,3,4,6-Tetra-O-benzyl-α,β-D-glucopyranosyl-(1→6)-1,2:3,4-di-O-
isopropylidene-α-D-galactopyranose16[21]
Synthesized according to the general procedure from tetrabenzyl gluco
donor 4 (50 mg, 0.074 mmol) and diacetone galactose 8 (57 mg, 0.22 mmol) with
NMQ-PF6 (7 mg, 0.022 mmol) in toluene (0.2 mL) and acetonitrile (0.5 mL). Pu-
rification by flash column chromatography (4 g silica, heptane–EtOAc, 10:1 →
1
6:1) gave the glycosides 16 (24 mg, 42%) as a colorless oil (α:β 1:2.5); H NMR
(300 MHz, CDCl3) 1.32, 1.46, 1.51, 1.54 (24H, 4 × s, 4 × C(CH3)2), 3.42–3.68
(m), 4.00 (1H, at, J = 9.2 Hz, Hβ), 4.03–4.12 (2H, m, Hα, Hβ), 4.17 (1H, dd,
J = 3.8 Hz, J = 10.6 Hz, Hβ) 4.25 (1H, dd, J = 1.9 Hz, J = 7.9 Hz, Hβ),
4.31–4.34 (2H, m, H-2Iα, H-2Iβ), 4.36 (1H, dd, J = 1.9 Hz, J = 7.9 Hz, Hα),
4.45–5.08 (m, H-1IIα, H-1IIβ), 4.36 (1H, dd, J = 1.9 Hz, J = 7.9 Hz, Hα),
4.45–5.08 (m, H-1IIα, H-1IIβ, 8 × PhCH2), 5.53 (d, J1,2 = 5.1 Hz, H-1Iα), 5.57
(d, J1,2 = 4.9 Hz, H-1Iβ), 7.13–7.44 (40H, m, Ar-H); 13C NMR (75 MHz, CDCl3)
δC 24.6, 25.2, 26.2, 26.2 (4 × q, 2 × C(CH3)2β), 24.8, 25.1, 26.2, 26.3 (4 × q,
2 × C(CH3)2α), 65.8, 70.4, 70.8, 70.8, 71.0, 77.7, 80.0, 82.1 (8 × d, C-2Iα, C-3Iα,
C-4Iα, C-5Iα, C-2IIα, C-3IIα, C-4IIα, C-5IIα), 66.4, 68.5 (2 × t, C-6Iα, C-6IIα), 67.5,
70.6, 70.9, 71.6, 74.9, 77.9, 81.8, 84.7 (8 × d, C-2Iβ, C-3Iβ, C-4Iβ, C-5Iβ, C-2IIβ, C-
3IIβ, C-4IIβ, C-5IIβ), 68.9, 69.8 (2 × t, C-6Iβ, C-6IIβ), 72.5, 73.6, 75.1, 75.8 (4 × d,
4 × PhCH2α), 73.6, 74.5, 75.1, 75.8 (4 × d, 4 × PhCH2β), 96.4 (d, C-1Iα), 96.5 (d,
C-1Iβ), 97.2 (d, C-1IIα), 104.5 (d, C-1IIβ), 108.7, 109.3, 109.5 (4 × s, 4 × C(CH3)2),
127.6, 127.7, 127.7, 127.8, 128.0, 128.0, 128.0, 128.1, 128.1, 128.3, 128.5, 128.8
(12 × d, Ar-CH), 138.3, 138.3, 138.5, 138.9, 139.1 (5 × s, Ar-C); m/z (ES+)
800 (M+NH4+, 100%); HRMS calcd for C46H58O11N (MNH4+) 800.4010; found
800.3994.
And then the hemiacetal 17 (16 mg, 40%), and then the recovered alcohol
8 (46 mg).
Methyl 2,3,4,6-Tetra-O-benzyl-α,β-D-glucopyranosyl-(1→6)-2,3,4-
tri-O-benzoyl-α-D-glucopyranoside 18[20]
Synthesized according to the general procedure from tetrabenzyl gluco
donor 4 (50 mg, 0.074 mmol) and gluco acceptor 13 (112 mg, 0.22 mmol) with

Photoinitiated Glycosylation
483
NMQ-PF6 (7 mg, 0.022 mmol) in toluene (0.2 mL) and acetonitrile (0.5 mL). Pu-
rification by flash column chromatography (4 g silica, heptane–EtOAc, 10:1 →
1
6:1) gave the glycosides 18 (34 mg, 45%) as a colorless oil (α:β 1:2.4); H NMR
(500 MHz, CDCl3) 3.38 (3H, s, OCH3β), 3.42–3.68 (14H, m, 2 × HIIα, 4 × HII
,
β
3 × H-6α, 2 × H-6β, OCH3α), 3.80–3.88 (3H, m, HIIα, H-6α, H-6β), 3.97 (1H, at,
J = 9.1 Hz, HIIα), 4.12 (1H, d, J = 10.7 Hz, H-6ꢁβ), 4.33 (1H, m, H-5Iα), 4.37–4.93
(11H, m, H-1IIα, H-1IIβ, H-5Iβ, 7 × PhCH2, PhCHHꢁβ), 5.06 (1H, d, J = 10.7 Hz,
PhCHHꢁβ), 5.21–5.27 (4H, m, H-1Iα, H-1Iβ, H-2Iα, H-2Iβ), 5.48 (1H, at, J = 9.8
Hz, H-4Iβ), 5.53 (1H, at, J = 10.1 Hz, H-4Iα), 6.14 (1H, at, J = 9.5 Hz, H-3Iα),
6.18 (1H, at, J = 9.8 Hz, H-3Iβ), 7.13–7.99 (70H, m, Ar-H); 13C NMR (125 MHz,
CDCl3) δC 55.7, 55.7 (2 × q, 2 × OCH3), 66.8, 68.5 (2 × t, C-6Iα, C-6IIα), 68.7
(d, C-5Iα), 68.8, 69.0 (2 × t, C-6Iβ, C-6IIβ), 69.2 (d, C-5Iβ), 69.8, 70.4, 70.8, 72.4,
77.7, 80.0, 81.9 (7 × d, C-2Iα, C-3Iα, C-4Iα, C-2IIα, C-3IIα, C-4IIα, C-5IIα), 70.1,
70.7, 72.3, 75.1, 77.8, 82.5, 84.7 (7 × d, C-2Iβ, C-3Iβ, C-4Iβ, C-2IIβ, C-3IIβ, C-4II
,
β
C-5IIβ), 73.3, 73.6, 74.9, 75.6 (4 × t, 4 × PhCH2α), 73.6, 74.9, 75.1, 75.8 (4 ×
t, 4 × PhCH2β), 96.9, 96.9 (2 × d, C-1Iα, C-1Iβ), 97.4 (d, C-1IIα), 104.2 (d, C-
1IIβ), 127.6, 127.6, 127.7, 127.8, 127.8, 127.9, 127.9, 128.0, 128.0, 128.1, 128.1,
128.3, 128.4, 128.5, 128.5, 128.5, 128.5 (17 × d, Ar-CH), 129.1, 129.2, 129.2,
129.3, 129.4, 129.4 (6 × s, Bz-C), 129.8, 130.0, 130.1, 133.2, 133.5, 133.5 (6 ×
d, Bz-CH), 138.1, 138.3, 138.3, 138.6, 138.7, 138.8, 139.0 (7 × d, Bn-C), 165.4,
165.6, 165.9, 166.0 (4 × s, C = O); m/z (ES+) 1046 (M+NH4+, 100%); HRMS
calcd for C62H64O14N (MNH4+) 1046.4321; found 1046.4310.
Then the hemiacetal 17 (19 mg, 47%) as a white solid.
REFERENCES
1. (a) Cummings, R.D. The repertoire of glycan determinants in the human glycome.
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