A visible light promoted O-glycosylation with glycosyl trichloroacetimidates using eosin Y as an organo photoacid

Article abstract of DOI:10.1016/j.carres.2020.107963

A photoacid catalyzed O-glycosylation of alcohols with glycosyl trichloroacetimidates in the presence of commercially available phenolic photoacids, fluorescein, 4′,5′-dibromo-fluorescein, and eosin Y under visible light irradiation by blue LEDs was devel

Full text of DOI:10.1016/j.carres.2020.107963

Journal Pre-proof
A visible light promoted O-glycosylation with glycosyl trichloroacetimidates using
eosin Y as an organo photoacid
Jiao Liu, Shan Yin, Haimei Wang, Hongfang Li, Guanghui Ni
PII:
S0008-6215(20)30041-0
DOI:
https://doi.org/10.1016/j.carres.2020.107963
CAR 107963
Reference:
To appear in: Carbohydrate Research
Received Date: 22 January 2020
Revised Date: 23 February 2020
Accepted Date: 25 February 2020
Please cite this article as: J. Liu, S. Yin, H. Wang, H. Li, G. Ni, A visible light promoted O-glycosylation
with glycosyl trichloroacetimidates using eosin Y as an organo photoacid, Carbohydrate Research
(2020), doi: https://doi.org/10.1016/j.carres.2020.107963.
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2020 Published by Elsevier Ltd.

A visible light promoted O-glycosylation with glycosyl
trichloroacetimidates using eosin Y as an organo photoacid
Jiao Liu, Shan Yin, Haimei Wang, Hongfang Li and Guanghui Ni *
College of Pharmaceutic Science, Yunnan University of Chinese Medicine, Kunming,
China 650500
*
Corresponding author: niguanghui@ynutcm.edu.cn
Abstract
A photoacid catalyzed O-glycosylation of alcohols with glycosyl trichloroacetimidates in the
presence of commercially available phenolic photoacids, fluorescein,
4
',5'-dibromo-fluorescein, and eosin Y under visible light irradiation by blue LEDs was
developed. The method is operationally simple without neutralization and proceeds at room
temperature.
Keywords: O-glycosylation; photoacid catalysis; visible light photocatalysis
1
Carbohydrates, the prime biological molecules , play an extremely
2
important role in many biochemical processes . The chemical synthesis of
carbohydrates especially glycosylation reactions deserve further research, but
3
often related to moisture-sensitive reagents . Photo promoted glycosylation has
3-5
developed attributed to its mild condition and environmental friendliness .
Photoacids have been used as catalysts or promoters in the glycosylation,
6
acidities of the photoacids insignificantly increase in the photoexcited state .
Therefore, photoacids can promote glycosylation under light and terminate in
7
the dark without neutralization. Previously, naphthol derivatives and aryl
8
thioureas were used as photoacids in glycosylation reactions of which the
glycosyl donors were trichloroacetimidates using UV irradiation of a Blackray
1
00W lamp at 365nm.
Compared to UV light, the energy of visible light has better availability
9
and is more economical . Recently visible light promoted glycosylation with
4, 5, 10-16
milder conditions has been described
. Most of them are catalyzed by
homogeneous transition metal complexes which show absorption in the visible
range of the solar spectrum. The general usage is limited due to the high cost
and toxicities of the organometallic dyes. Eosin Y (1), the 2’,4’,5’,7’-
tetrabromo derivative of fluorescein, has been shown perspective on the
application of photo-induced organic synthesis due to low price, innocuousness
17, 18
and strong absorption in visible light
. An eosin Y catalyzed synthesis of
2
-deoxy-glycosides from glycals promoted by the visible light with blue

15
light-emitting diode (LED) irradiation was developed . With the blue LEDs
irradiation, eosin Y is excited then protonates the glycal as a photoacid,
generating the oxocarbenium intermediate (Scheme 1). Glycosyl
trichloroacetimidates are one of the most widely used glycosyl donors. The
corresponding trichloroacetimidates can be easily prepared in high yielding.
Common glycosylation reaction with glycosyl trichloroacetimidate and a
glycosyl acceptor in dry CH Cl is treated by trimethylsilyl triflate (TMSOTf)
2
2
o
o
or boron trifluoride etherate (BF •OEt ) as the promoter at about -40 C to -50 C
3
2
19
with a solution .
Scheme 1. The glycal and glycosyl trichloroacetimidate were protonated by
excited eosin Y.
This study has investigated glycosylation reactions of glycosyl
trichloroacetimidates with alcohols which were promoted by eosin Y and blue
LEDs. The
in the presence of eosin Y
photoacids 5-6 and 4Å molecular sieves (MS) under the irradiation by two 12W
blue LEDs (Table 1, entries 1-3). The corresponding glycoside was obtained
in the highest yield when eosin Y was used. The presence of bromine
α-glucosyl trichloroacetimidate
2 were coupled with cyclohexanol 3
1
or other commercially available phenolic
4
1
substituents (electron withdrawing group) increases the acidity of the phenolic
photocatalyst. We screened solvents (1,2-dichloroethane, CH CN, toluene, THF,
3
dioxane, Et O, and CH Cl ) and found CH Cl was the optimal one.
2
2
2
2
2
Glycosylation using eosin Y without blue LED irradiation didn’t occur (table 1,
entries 4), neither did glycosylation under blue LED irradiation without
photoacid(Table 1, entries 5). 2,6-Di-tert-butyl-4-methyl pyridine shuts down
the reaction completely(Table 1, entries 6). These results suggest a photoacid
catalyzed process is operative. The glycosyl trichloroacetimidates were
activated by eosin Y in the excited state (Scheme 1).

Table 1. Optimization of the glycosylation reactions conditions
a
entry photoacid
Blue LEDs
additive
4
b
yield (%)
α/β
1
2
3
4
5
5
6
1
1
-
+
+
+
-
-
-
-
-
-
37
52
1.5:1
1.5:1
58
1.6:1
0
-
-
-
+
+
trace
0
6
1
2,6-di-tert-butyl-4-methyl pyridine
a
b
c
two 12 W, 450 nm LED flood lamps. MS 4 Å (100 wt % to 1) was used. α/β ratios were determined
by NMR analysis.
Based on these results, we explored the scope of the glycosylation promoted
by eosin Y and blue LEDs. The reaction could be carried out with
α-glucosyl
trichloroacetimidate and the alcohols 13. As shown in Scheme 2, the
2
7−
catalytic system is tolerant of a range of alcohols and functional groups,
including esters, acetals, and alkenes.
OBn
O
OBn
O
BnO
BnO
eosin Y, 4 Å MS
BnO
BnO
ROH
BnO
BnO OR
Blue LEDs, CH2Cl2
O
CCl3
NH
7~13
2
14~20
(1.2 eq)
Scheme 2. Scope of OH Nucleophiles.
The generality of the glycosylation method was also investigated using
cyclohexanol and the glycosyl donors galactosyl and mannosyl
trichloroacetimidates 21 and 22 to afford the corresponding glycoside 23 and
3
24.

Scheme 3. Scope of glycosyl trichloroacetimidates.
In conclusion, a novel glycosylation method has been developed using
glycosyl trichloroacetimidates as a donor and eosin Y as an organo photoacid
under visible light irradiation by blue LEDs. This method should be applied in a
range of glycosylation in the synthese of carbohydrate-containing products.
1
1
. Experimental
.1. General methods
Reagents were purchased from commercial sources without further purification.
®
Heavy wall cylindrical vessels were purchased from Synthware Glass (Capacity: 15
mL). Acetonitrile was dried further over activated 4 Å molecular sieves prior to use.
Anhydrous CH Cl was distilled from CaH prior to use. Flash column
2
2
2
chromatography was carried out using silica gel (300–400 mesh). Analytical thin layer
chromatography was carried out using silica gel 60 F254 plates, and compounds were
1
13
visualized through the use of UV light and orcinol. H and C NMR spectra were
1
recorded using a 400 MHz spectrometer. H NMR are reported in parts per million
(ppm) relative to tetramethylsilane and referenced to residual protium in the solvent.
Spectral features are tabulated in the following order: chemical shift (δ, ppm);
multiplicity (s-singlet, d-doublet, t-triplet, q-quartet, m-complex multiplet); number of
protons; coupling constant(s) (J, Hz). Solvents were purified commonly prior to use.
Experiments upon visible-light irradiation were carried out using two blue LED lamps
(24 W in total), purchased from Shenzhen Xinjia Lighting Co., Ltd.
1
1
.2. General procedures for the visible light-mediated glycosylation
.2.1 Experimental procedures in Table 1
An oven-dried heavy wall cylindrical vessels equipped with a magnetic stir bar,
was charged with the glucosyl trichloroacetimidate 2 (34.3 mg, 0.05 mmol),
cyclohexanol 3 (6.2µL, 0.06 mmol), eosin Y or other commercially available phenolic
photoacids 5-6 (0.01 mmol), powdered activated 4Å molecular sieves (34.3 mg), and
CH Cl (1 mL). The reaction mixture was exposed to visible light irradiation (two blue
2
2
LED lamps, 24 W in total) at room temperature. After disappearance of the glucosyl
trichloroacetimidate 2 detected by TLC, the precipitate was filtered off, and the
filtrate was concentrated. The crude product was purified by column chromatography

on silica gel (eluting with petroleum ether/ethyl acetate) to give the desired
corresponding glycoside 4α and 4β.
1
.2.2 Experimental procedures in Scheme 2
An oven-dried heavy wall cylindrical vessels equipped with a magnetic stir bar, was
charged with the glycosyl donors glucosyl trichloroacetimidate 2 (34.3 mg, 0.05
mmol), alcohols 7−13 (0.06 mmol), eosin Y (0.01 mmol), powdered activated 4Å
molecular sieves (34.3 mg), and CH Cl (1 mL). The reaction mixture was exposed to
2
2
visible light irradiation (two blue LED lamps, 24 W in total) at room temperature.
After disappearance of the glucosyl trichloroacetimidate 2 detected by TLC, the
precipitate was filtered off, and the filtrate was concentrated. The crude product was
purified by column chromatography on silica gel (eluting with petroleum ether/ethyl
acetate) to give the desired corresponding glycosides 14-20.
1
.2.3 Experimental procedures in Scheme 3
An oven-dried heavy wall cylindrical vessels equipped with a magnetic stir bar, was
charged with the galactosyl and mannosyl trichloroacetimidates 21 and 22 (34.3 mg,
0
.05 mmol), cyclohexanol 3 (6.2µL, 0.06 mmol), eosin Y (0.01 mmol), powdered
activated 4Å molecular sieves (34.3 mg), and CH Cl (1 mL). The reaction mixture
2
2
was exposed to visible light irradiation (two blue LED lamps, 24 W in total) at room
temperature. After disappearance of the glycosyl donors detected by TLC, the
precipitate was filtered off, and the filtrate was concentrated. The crude product was
purified by column chromatography on silica gel (eluting with petroleum ether/ethyl
acetate) to give the desired corresponding glycosides 23 and 24.
1
1
.3. Characterization of glycosides
8
.3.1. Cyclohexyl 2, 3, 4, 6-tetra-O-benzyl-α-D-glucopyranoside(4α)
1
colorless syrup; R 0.49 (petroleum ether : ethyl acetate=7: 1, v/v); H NMR (400
f
MHz, CDCl ) δ 7.31-7.14 (m, 18H), 7.08-7.00 (m, 2H), 4.92 (d, J = 10.8 Hz, 1H),
3
4
.88 (d, J = 3.7 Hz, 1H), 4.75 (d, J = 10.8 Hz, 1H), 4.73 (dd, J = 10.8 Hz, 1H), 4.67 (d,
J = 12.0 Hz, 1H), 4.58 (d, J = 12.0 Hz, 1H), 4.54 (d, J = 12.1 Hz, 1H), 4.43-4.37 (m,
2
1
3
1
1
2
H), 3.93 (t, J = 9.3 Hz, 1H), 3.81 (d, J = 10.0 Hz, 1H), 3.66 (dd, J = 10.6, 3.7 Hz,
H), 3.57 (dd, J = 5.8, 3.9 Hz, 1H), 3.54 (dd, J = 5.6, 3.5 Hz, 1H), 3.48 (dd, J = 9.6,
1
3
.8 Hz, 2H), 1.88-1.61(m, 4H), 1.48-1.06 (m, 6H). C NMR (100 MHz, CDCl ) δ
3
39.0, 138.3, 138.2, 138.0, 128.0, 128.3×3, 128.03, 127.9×2, 127.8, 127.7, 127.6,
27.6, 127.4, 94.6, 82.1, 80.0, 77.9, 75.6, 75.2, 75.1, 73.4, 72.9, 70.0, 68.6, 33.3, 31.4,
5.6, 24.4, 24.1.
8
1
.3.2. Cyclohexyl 2, 3, 4, 6-tetra-O-benzyl-β-D-glucopyranoside(4β)
1
white solid; R 0.54 (petroleum ether : ethyl acetate=7: 1, v/v); mp102.4-104.0℃ ; H
f
NMR (400 MHz, CDCl ) δ 7.28-7.15 (m, 18H), 7.10 (dd, J = 7.2, 2.0 Hz, 2H), 4.92 (d,
3

J = 10.9 Hz, 1H), 4.85 (d, J = 10.9 Hz, 1H), 4.74 (d, J = 10.8 Hz, 1H), 4.70 (d, J =
0.9 Hz, 1H), 4.63 (d, J = 10.9 Hz, 1H), 4.53 (d, J = 12.2 Hz, 1H), 4.49 (d, J = 12.0
Hz, 1H), 4.46 (d, J = 10.8 Hz, 1H), 4.43 (d, J = 7.9 Hz, 1H), 3.70-3.61 (m, 2H),
1
3
1
.60-3.53 (m, 2H), 3.47 (t, J = 9.2 Hz, 1H), 3.41-3.38 (m, 1H), 3.38-3.34 (m, 1H),
.96-1.79 (m, 2H), 1.74-1.63 (m, 2H), 1.51-1.14 (m, 6H). C NMR (100 MHz,
1
3
CDCl ) δ 138.7, 138.6, 138.3, 138.1, 128.4, 128.3×2, 128.2, 128.0, 127.8, 127.7×2,
3
1
2
27.6, 127.5×2, 101.9, 84.8, 82.2, 78.0, 77.7, 75.6, 75.0, 74.8, 73.4, 69.2, 33.8, 32.0,
5.6, 24.1, 23.9.
8
1
.3.3. Isopropyl 2, 3, 4, 6-tetra-O-benzyl-α-D-glucopyranoside(14α)
1
colorless syrup; R 0.41 (petroleum ether : ethyl acetate=7: 1, v/v); H NMR (400
f
MHz, CDCl ) δ 7.39-7.23 (m, 18H), 7.16-7.10 (m, 2H), 5.00 (d, J = 10.8 Hz, 1H),
3
4
.88 (d, J = 3.7 Hz, 1H), 4.83 (d, J = 10.8 Hz, 1H), 4.81 (d, J = 10.8 Hz, 1H), 4.77 (d,
J = 12.0 Hz, 1H), 4.65 (d, J = 12.0 Hz, 1H), 4.61 (d, J = 12.2 Hz, 1H), 4.49-4.44 (m,
2
3
3
1
7
H), 3.99 (t, J = 9.3 Hz, 1H), 3.93-3.87 (m, 1H), 3.87-3.82 (m, 1H), 3.73 (dd, J = 10.5,
.5 Hz, 1H), 3.68-3.60 (m, 2H), 3.55 (dd, J = 9.6, 3.7 Hz, 1H), 1.22 (d, J = 6.3 Hz,
1
3
H), 1.18 (d, J = 6.1 Hz, 3H). C NMR (100 MHz, CDCl ) δ 139.0, 138.3×2, 138.0,
3
28.4, 128.3×2, 128.1, 127.9×3, 127.8, 127.7, 127.6, 127.5, 94.8, 82.1, 79.9, 77.9,
5.6, 75.1, 73.4, 73.1, 70.0, 69.0, 68.6, 23.1, 21.1.
8
1
.3.4. Isopropyl 2, 3, 4, 6-tetra-O-benzyl-β-D-glucopyranoside(14β)
1
white solid; R 0.47 (petroleum ether : ethyl acetate=7: 1, v/v); mp103.8-105.7℃ ; H
f
NMR (400 MHz, CDCl ) δ 7.37-7.25 (m, 18H), 7.18 (d, J = 5.5 Hz, 2H), 4.98 (d, J =
3
1
0.9 Hz, 1H), 4.93 (d, J = 10.9 Hz, 1H), 4.82 (d, J = 10.9 Hz, 1H), 4.79 (d, J = 11.3
Hz, 1H), 4.71 (d, J = 10.9 Hz, 1H), 4.60 (t, J = 10.7 Hz, 1H), 4.54 (d, J = 10.8 Hz,
1
1
3
H), 4.47 (d, J = 7.8 Hz, 1H), 4.03 (dt, J = 12.3, 6.1 Hz, 1H), 3.74 (d, J = 10.7 Hz,
H), 3.67 (d, J = 5.3 Hz, 1H), 3.63 (d, J = 8.8 Hz, 1H), 3.56 (t, J = 9.2 Hz, 1H),
1
3
.48-3.42 (m, 2H), 1.32 (d, J = 6.2 Hz, 3H), 1.25 (d, J = 6.1 Hz, 3H). C NMR (100
MHz, CDCl ) δ 138.7, 138.5, 138.3, 138.1, 128.3×3, 128.1, 127.9, 127.8, 127.7,
3
1
2
27.6×2, 127.5×2, 102.1, 84.8, 82.3, 78.0, 75.6, 74.9, 74.8×2, 73.4, 72.3, 69.1, 23.7,
2.2.
7
1
.3.5. n-Octyl 2, 3, 4, 6-tetra-O-benzyl-α-D-glucopyranoside(15α)
1
colorless syrup; R 0.48 (petroleum ether : ethyl acetate=7: 1, v/v); H NMR (400
f
MHz, CDCl ) δ 7.38-7.24 (m, 18H), 7.15-7.12 (m, 2H), 4.99 (d, J = 10.9 Hz, 1H),
3
4
.83 (d, J = 10.8 Hz, 1H), 4.81 (d, J = 10.8 Hz, 1H), 4.77 (d, J = 12.0 Hz, 1H), 4.76 (d,
J = 3.0 Hz, 1H), 4.64 (d, J = 12.1 Hz, 1H), 4.60 (d, J = 12.2 Hz, 1H), 4.47 (d, J = 11.7
Hz, 2H), 3.99 (t, J = 9.2 Hz, 1H), 3.78 (d, J = 10.1 Hz, 1H), 3.72 (dd, J = 10.5, 3.5 Hz,
1
1
H), 3.66-3.58 (m, 3H), 3.55 (dd, J = 9.6, 3.6 Hz, 1H), 3.41 (dt, J = 9.7, 6.8 Hz, 1H),
.64-1.56 (m, 2H), 1.45-1.22 (m, 10H), 0.88 (t, J = 6.7 Hz, 3H). C NMR (100 MHz,
1
3
CDCl ) δ 139.0, 138.4, 138.3, 138.0, 128.4, 128.3, 128.0, 127.9×2, 127.8, 127.6,
3
1
2
1
27.5, 97.0, 82.1, 80.1, 77.8, 75.6, 75.0, 73.5, 73.1, 70.1, 68.6, 68.2, 31.8, 29.4, 29.2,
6.2, 22.6, 14.1.
.3.6. n-Octyl 2, 3, 4, 6-tetra-O-benzyl-β-D-glucopyranoside(15β)
7

1
colorless syrup; R 0.55 (petroleum ether : ethyl acetate=7: 1, v/v); H NMR (400
f
MHz, CDCl ) δ 7.37-7.21 (m, 18H), 7.20-7.15 (m, 2H), 4.95 (t, J = 11.4 Hz, 2H),
3
4
.80 (t, J = 11.4 Hz, 2H), 4.72 (d, J = 11.0 Hz, 1H), 4.61 (d, J = 12.2 Hz, 1H), 4.55 (d,
J = 12.0 Hz, 1H), 4.53 (d, J = 10.8 Hz, 1H), 4.39 (d, J = 7.8 Hz, 1H), 3.96 (dt, J = 9.4,
6
1
2
1
1
2
.5 Hz, 1H), 3.74 (dd, J = 10.8, 1.9 Hz, 1H), 3.70-3.66 (m, 1H), 3.64 (t, J = 6.0 Hz,
H), 3.58 (t, J = 9.1 Hz, 1H), 3.54-3.49 (m, 1H), 3.49-3.42 (m, 2H), 1.71-1.58 (m,
1
3
H), 1.44-1.22 (m, 10H), 0.87 (t, J = 6.9 Hz, 3H). C NMR (100 MHz, CDCl ) δ
3
38.6, 138.5, 138.2, 138.1, 128.3×2, 128.0, 127.9, 127.8, 127.7, 127.6, 127.5×2,
03.6, 84.7, 82.2, 77.9, 75.6, 74.9, 74.8, 74.7, 73.4, 70.1, 69.0, 31.8, 29.7, 29.4, 29.2,
6.1, 22.6, 14.0.
7
1
.3.7. Cyclohexylmethyl 2, 3, 4, 6-tetra-O-benzyl-α-D-glucopyranoside(16α)
1
colorless syrup; R 048 (petroleum ether : ethyl acetate=7: 1, v/v); H NMR (400 MHz,
f
CDCl ) δ 7.31-7.15 (m, 18H), 7.08-7.04 (m, 2H), 4.92 (d, J = 10.9 Hz, 1H), 4.75 (d, J
3
=
10.8 Hz, 1H), 4.74 (d, J = 10.8 Hz, 1H), 4.69 (d, J = 12.2 Hz, 1H), 4.66 (d, J = 3.8
Hz, 1H), 4.58- 4.50 (m, 2H), 4.43-4.36 (m, 2H), 3.90 (t, J = 9.3 Hz, 1H), 3.72-3.62 (m,
2
3
2
1
7
H), 3.58-3.51 (m, 2H), 3.48 (dd, J = 9.6, 3.6 Hz, 1H), 3.35 (dd, J = 9.5, 7.3 Hz, 1H),
.13 (dd, J = 9.5, 6.0 Hz, 1H), 1.79-1.58 (m, 6H), 1.22-1.07 (m, 3H), 0.89-0.77 (m,
1
3
H). C NMR (100 MHz, CDCl ) δ 139.0, 138.4, 138.3, 138.0, 128.4, 128.3×2, 128.0,
3
27.9×2, 127.7×2, 127.6, 127.5, 97.0, 82.1, 80.3, 77.8, 75.6, 75.1, 73.9, 73.5, 73.0,
0.1, 68.6, 37.6, 30.3, 30.0, 26.6, 25.8, 25.7.
7
1
.3.8. Cyclohexylmethyl 2, 3, 4, 6-tetra-O-benzyl-β-D-glucopyranoside(16β)
1
white solid; R 0.52 (petroleum ether : ethyl acetate=7: 1, v/v); mp100.2-102.3℃ ; H
f
NMR (400 MHz, CDCl ) δ 7.37-7.15 (m, 18H), 7.12-7.05 (m, 2H), 4.89 (d, J = 10.9
3
Hz, 1H), 4.85 (d, J = 11.0 Hz, 1H), 4.74 (d, J = 10.9 Hz, 1H), 4.71 (d, J = 11.0 Hz,
1
4
1
H), 4.64 (d, J = 10.9 Hz, 1H), 4.52 (d, J = 10.8 Hz, 2H), 4.46 (d, J = 11.1 Hz, 1H),
.30 (d, J = 7.8 Hz, 1H), 3.72 (dd, J = 9.4, 6.0 Hz, 1H), 3.67 (dd, J = 10.8, 1.8 Hz,
H), 3.62-3.47 (m, 3H), 3.42-3.34 (m, 2H), 3.25 (dd, J = 9.4, 7.0 Hz, 1H), 1.82-1.55
1
3
(m, 6H), 1.29 -1.10 (m, 3H), 0.95-0.88 (m, 2H). C NMR (100 MHz, CDCl ) δ 139.8,
3
1
7
39.6, 139.4, 139.3, 129.5×2, 129.31, 129.1, 129.0, 128.8, 128.7×2, 105.1, 85.9, 83.5,
9.1, 76.8×2, 76.1, 76.0, 74.6, 70.2, 39.2, 31.3, 31.0, 27.7, 27.0, 26.9.
1
3
1
.3.9. Menthyl 2,3,4,6-tetra-O-benzyl-α-D-glucopyranoside (17α)
1
colorless syrup; R 0.54 (petroleum ether : ethyl acetate=7: 1, v/v); H NMR (400
f
MHz, CDCl ) δ 7.28-7.17 (m, 18H), 7.08-7.04 (m, 2H), 4.95 (d, J = 3.6 Hz, 1H), 4.90
3
(
1
d, J = 10.9 Hz, 1H), 4.76 (d, J = 10.8 Hz, 1H), 4.74 (d, J = 10.8 Hz, 1H), 4.64 (d, J =
1.7 Hz, 1H), 4.60 (d, J = 11.8 Hz, 1H), 4.56 (d, J = 12.1 Hz, 1H), 4.53 (d, J = 10.8
Hz, 1H), 4.39 (d, J = 12.0 Hz, 1H), 3.97-3.91 (m, 1H), 3.91-3.87 (m, 1H), 3.68 (dd, J
10.5, 3.8 Hz, 1H), 3.60-3.53 (m, 2H), 3.47 (dd, J = 9.8, 3.6 Hz, 1H), 3.27 (td, J =
0.6, 4.3 Hz, 1H), 2.36-2.33 (m, 1H), 2.05 (d, br, 1H), 1.58-1.49 (m, 2H), 1.27-1.16
=
1
(
m, 2H), 1.02-0.81 (m, 3H), 0.77 (dd, J = 6.8, 2.0 Hz, 6H), 0.63 (d, J = 6.9 Hz, 3H).
1
3
C NMR (100 MHz, CDCl ) δ 138.9, 138.4, 138.3, 138.1, 128.3×2, 128.2, 127.9,
3

1
3
27.6, 127.5, 98.6, 82.0, 81.0, 80.6, 78.1, 75.4, 75.0, 73.4, 73.2, 70.3, 68.7, 48.7, 43.0,
4.3, 31.7, 24.6, 23.0, 22.2, 21.1, 16.0.
8
1
.3.10. Menthyl 2,3,4,6-tetra-O-benzyl-β-D-glucopyranoside (17β)
1
white solid; R 0.60 (petroleum ether : ethyl acetate=7: 1, v/v); mp 65.2-67.5℃ ; H
f
NMR (400 MHz, CDCl ) δ 7.34-7.25 (m, 18H), 7.22-7.17 (m, 2H), 4.93 (t, J = 10.7
3
Hz, 2H), 4.80 (t, J = 11.1 Hz, 2H), 4.68 (d, J = 10.9 Hz, 1H), 4.59 (t, J = 10.6 Hz, 2H),
4
1
1
.54 (d, J = 12.2 Hz, 1H), 4.47 (d, J = 7.8 Hz, 1H), 3.71-3.56 (m, 4H), 3.50 (td, J =
0.6, 4.1 Hz, 1H), 3.44-3.37 (m, 2H), 2.42-2.28 (m, 1H), 2.13 (d, J = 12.2 Hz, 1H),
1
3
.66 (d, br, 2H), 1.36-1.22 (m, 2H), 1.02-0.86 (m, 9H), 0.82 (d, J = 6.9 Hz, 3H). C
NMR (100 MHz, CDCl ) δ 138.8, 138.6, 138.4, 138.3, 128.3×2, 128.0, 127.7×2,
3
1
4
27.6×2, 127.5, 100.7, 85.0, 82.2, 78.0, 77.7, 75.5, 74.9, 74.9, 74.8, 73.7, 69.4, 48.1,
0.9, 34.5, 31.5, 25.3, 23.2, 22.2, 21.1, 16.0.
2
0
1
.3.11. Cholesteryl 2, 3, 4, 6-tetra-O-benzyl-α-D-glucopyranoside(18α)
1
white solid; R 0.55 (petroleum ether : ethyl acetate=7: 1, v/v); mp135.7-137.9℃ ; H
f
NMR (400 MHz, CDCl ) δ 7.37-7.24 (m, 18H), 7.15-7.12 (m, 2H), 5.28 (d, J = 5.0
3
Hz, 1H), 5.01 (d, J = 10.8 Hz, 1H), 4.94 (d, J = 3.6 Hz, 1H), 4.83 (d, J = 10.8 Hz, 1H),
4
.81 (d, J = 11.2 Hz, 1H), 4.76 (d, J = 12.0 Hz, 1H), 4.65 (d, J = 12.0 Hz, 1H), 4.61 (d,
J = 12.1 Hz, 1H), 4.46 (d, J = 10.8 Hz, 1H), 4.44 (d, J = 12.4 Hz, 1H), 4.00 (t, J = 9.3
Hz, 1H), 3.88 (d, J = 8.9 Hz, 1H), 3.74 (dd, J = 10.6, 3.6 Hz, 1H), 3.68-3.64 (m, 1H),
3
1
.63-3.60 (m, 1H), 3.55 (dd, J = 9.6, 3.6 Hz, 1H), 3.52-3.41 (m, 1H), 2.48-2.37 (m,
H), 2.28 (dd, J = 13.3, 3.4 Hz, 1H), 2.06-1.75 (m, 5H), 1.62-1.40 (m, 8H), 1.40-1.30
(
3
m, 2H), 1.26-1.20 (m, 1H), 1.17-1.10 (m, 5H), 1.04-0.97 (m, 8H), 0.92 (d, J = 6.5 Hz,
H), 0.87 (d, J = 1.7 Hz, 3H), 0.86 (d, J = 1.7 Hz, 3H) , 0.68 (s, 3H). C NMR (100
1
3
MHz, CDCl ) δ 140.8, 139.0, 138.2, 138.0, 128.4, 128.3×2, 128.1, 127.9×2, 127.8,
3
127.7, 127.6, 127.5, 121.7, 94.6, 82.1, 79.9, 77.9, 76.5, 75.6, 75.1, 73.4, 73.0, 70.0,
68.6, 56.8, 56.1, 50.1, 42.3, 39.9, 39.8, 39.5, 37.1, 36.8, 36.2, 35.8, 31.9, 31.9, 28.2,
28.0, 27.8, 24.3, 23.8, 22.8, 22.5, 21.0, 19.4, 18.7, 11.8.
2
0
1
.3.12. Cholesteryl 2, 3, 4, 6-tetra-O-benzyl-β-D-glucopyranoside(18β)
1
colorless syrup; R 0.6 (petroleum ether : ethyl acetate=7: 1, v/v); H NMR (400 MHz,
f
CDCl ) δ 7.35-7.26 (m, 18H), 7.19-7.15 (m, 2H), 5.34 (d, J = 5.2 Hz, 1H), 4.97 (d, J
3
=
10.9 Hz, 1H), 4.92 (d, J = 10.9 Hz, 1H), 4.81 (d, J = 10.9 Hz, 1H), 4.78 (d, J = 11.0
Hz, 1H), 4.72 (d, J = 10.9 Hz, 1H), 4.60 (d, J = 12.2 Hz, 1H), 4.54 (d, J = 12.0 Hz,
1
1
H), 4.53 (d, J = 11.2 Hz, 1H), 4.50 (d, J = 7.8 Hz, 1H), 3.73 (dd, J = 10.7, 1.7 Hz,
H), 3.66 (d, J = 5.0 Hz, 1H), 3.63 (d, J = 3.1 Hz, 1H), 3.61-3.58 (m, 1H), 3.56-3.52
(m, 1H), 3.48-3.45 (m, 1H), 3.43 (d, J = 9.0 Hz, 1H), 2.46-2.37 (m, 1H), 2.37-2.28 (m,
1
1
3
H), 2.05-2.02 (m, 1H), 2.03-1.99 (m, 1H), 1.98-1.91 (m, 1H), 1.90-1.78 (m, 2H),
.66-1.43 (m, 8H), 1.39-1.30 (m, 2H), 1.28-1.10 (m, 8H), 1.03 (s, 3H), 1.02-0.94 (m,
H), 0.92 (d, J = 6.5 Hz, 3H), 0.87 (d, J = 1.7 Hz, 3H), 0.86 (d, J = 1.7 Hz, 3H) , 0.68
1
3
(s, 3H). C NMR (100 MHz, CDCl ) δ 140.6, 138.7, 138.6, 138.3, 138.2, 128.4,
3
1
7
28.3×2, 128.2, 128.0, 127.9, 127.7×2, 127.6×2, 127.5, 121.9, 102.3, 84.9, 82.4, 79.7,
8.0, 77.6, 77.2, 75.7, 75.0, 74.9, 74.8, 73.4, 69.2, 56.8, 56.2, 50.2, 42.3, 39.8, 39.5,

3
1
9.1, 37.3, 36.8, 36.2, 35.8, 32.0, 31.9, 30.0, 28.2, 28.0, 24.3, 23.8, 22.8, 22.6, 21.1,
9.4, 18.7, 11.9.
1
.3.13. Methyl 2,3,4-tri-O-benzoyl-6-O-(2ʹ,3ʹ,4ʹ,6ʹ-tetra-O-benzyl-α-D-gluco
2
1, 22
pyranosyl)-α-D-Glucopyranoside(19α)
colorless syrup; R 0.43 (petroleum ether : ethyl acetate=3: 1, v/v); H NMR (400
1
f
MHz, CDCl ) δ 7.96 (dd, J = 13.9, 8.0 Hz, 4H), 7.86 (d, J = 8.0 Hz, 2H), 7.56-7.45 (m,
3
2
H), 7.44-7.25 (m, 25H), 7.16-7.12 (m, 2H), 6.14 (t, J = 9.3 Hz, 1H), 5.53 (t, J = 9.9
Hz, 1H), 5.23 (d, J = 3.6 Hz, 1H), 5.21 (s, 1H), 4.91 (d, J = 10.9 Hz, 1H), 4.82 (d, J =
1.0 Hz, 1H), 4.78 (d, J = 3.4 Hz, 1H), 4.75 (t, J = 4.5 Hz, 2H), 4.63 (d, J = 12.2 Hz,
1
1
4
H), 4.54 (d, J = 12.1 Hz, 1H), 4.45 (d, J = 11.0 Hz, 1H), 4.38 (d, J = 12.1 Hz, 1H),
.32 (dd, J = 8.7, 6.7 Hz, 1H), 3.96 (t, J = 9.3 Hz, 1H), 3.92-3.81 (m, 2H), 3.68-3.48
1
3
(m, 5H), 3.43 (s, 3H). C NMR (100 MHz, CDCl ) δ 165.8, 165.2, 138.9, 138.6,
3
1
1
7
38.4, 137.9, 133.3, 133.0, 129.9, 129.6, 129.3, 129.1, 129.0, 128.4, 128.3, 128.2,
27.9×3, 127.7, 127.6, 127.4, 97.2, 96.7, 81.7, 80.0, 77.6, 75.5, 74.7, 73.4, 73.1, 72.2,
0.6, 70.2, 69.6, 68.6, 68.3, 66.6, 55.6.
1
.3.14. Methyl 2,3,4-tri-O-benzoyl-6-O-(2ʹ,3ʹ,4ʹ,6ʹ-tetra-O-benzyl-β-D-gluco
21, 22
pyranosyl) -α-D-Glucopyranoside(19β)
colorless syrup; R 0.48 (petroleum ether : ethyl acetate=3: 1, v/v); H NMR (400
1
f
MHz, CDCl ) δ 8.02-7.88 (m, 4H), 7.89-7.81 (m, 2H), 7.50 (td, J = 7.3, 1.4 Hz, 2H),
3
7
=
1
.42-7.24 (m, 25H), 7.14 (dd, J = 7.1, 2.3 Hz, 2H), 6.18 (t, J = 9.8 Hz, 1H), 5.48 (t, J
9.9 Hz, 1H), 5.26 (dd, J = 10.1, 3.6 Hz, 1H), 5.21 (d, J = 3.6 Hz, 1H), 5.06 (d, J =
0.8 Hz, 1H), 4.91 (d, J = 10.9 Hz, 1H), 4.80 (d, J = 10.8 Hz, 1H), 4.77 (d, J = 11.0
Hz, 1H), 4.69 (d, J = 10.8 Hz, 1H), 4.53 (d, J = 7.7 Hz, 1H), 4.50 (d, J = 10.4 Hz, 1H),
4
1
2
1
1
7
.48 (d, J = 11.2 Hz, 1H), 4.44 (d, J = 12.2 Hz, 1H), 4.41-4.35 (m, 1H), 4.13 (dd, J =
0.9, 1.8 Hz, 1H), 3.81 (dd, J = 10.9, 7.5 Hz, 1H), 3.69-3.57 (m, 4H), 3.50-3.41 (m,
1
3
H), 3.38 (s, 3H). C NMR (100 MHz, CDCl ) δ 165.9, 165.8, 165.5, 138.6, 138.5,
3
38.2, 138.1, 133.4×2, 133.1, 129.9×2, 129.7, 129.3, 129.1, 129.0, 128.4×3, 128.3×2,
28.2, 128.0, 127.9, 127.8, 127.7, 127.6, 104.0, 96.8, 84.6, 82.4, 77.7, 75.7, 75.0, 74.9,
4.8, 73.5, 72.2, 70.6, 69.9, 69.0, 68.9, 68.7, 55.6.
1
.3.15. 1,2,3,4-Di-O-isopropylidene-α-D-galactopyranosyl 2ʹ,3ʹ,4ʹ,6ʹ-tetra-
8
O-benzyl-α-D-Glucopyranoside(20α)
colorless syrup; R 0.31 (petroleum ether : ethyl acetate=4: 1, v/v); H NMR (400
MHz, CDCl ) H NMR (400 MHz, CDCl ) δ 7.33-7.13 (m, 18H), 7.07-7.05 (m, 2H),
1
f
1
3
3
5
.45 (d, J = 5.0 Hz, 1H), ), 4.92 (d, J = 3.5 Hz, 1H), 4.90 (d, J = 10.9 Hz, 1H), 4.75 (d,
J = 10.8 Hz, 1H), 4.73 (d, J = 11.2 Hz, 1H), 4.67 (d, J = 11.9 Hz, 1H), 4.62 (d, J =
1.9 Hz, 1H), 4.55 (d, J = 12.0 Hz, 1H), 4.52 (d, J = 10.0 Hz, 1H), 4.40 (d, J = 10.8
Hz, 1H), 4.39 (d, J = 12.0 Hz, 1H), 4.28 (dd, J = 7.9, 1.9 Hz, 1H), 4.24 (dd, J = 5.0,
.4 Hz, 1H), 3.99-3.94 (m, 1H), 3.91 (t, J = 9.3 Hz, 1H), 3.78-3.55 (m, 6H), 3.51 (dd,
1
2
1
3
J = 9.6, 3.6 Hz, 1H), 1.46 (s, 3H), 1.38 (s, 3H), 1.25 (s, 3H), 1.24 (s, 3H). C NMR
100 MHz, CDCl ) δ 139.0, 138.4×2, 138.0, 128.3, 127.9×2, 127.8, 127.7, 127.6,
(
3

1
7
27.5, 109.2, 108.6, 97.1, 96.3, 82.0, 79.8, 77.6, 75.6, 75.0, 73.5, 72.3, 70.8, 70.7,
0.6, 70.2, 68.4, 66.2, 65.7, 26.2, 26.1, 24.9, 24.6.
1
.3.16. 1,2,3,4-Di-O-isopropylidene-α-D-galactopyranosyl 2ʹ,3ʹ,4ʹ,6ʹ-tetra-O-
8
benzyl-β-D- Glucopyranoside(20β)
colorless syrup; R 0.30 (petroleum ether : ethyl acetate=5: 1, v/v); H NMR (400
1
f
MHz, CDCl ) δ 7.41-7.33 (m, 2H), 7.28- 7.18 (m, 16H), 7.09-7.05 (m, 2H), 5.50 (d, J
3
=
5.0 Hz, 1H), 4.98 (d, J = 11.1 Hz, 1H), 4.89 (d, J = 10.9 Hz, 1H), 4.74 (d, J = 10.9
Hz, 1H), 4.70 (d, J = 11.0 Hz, 1H), 4.65 (d, J = 11.1 Hz, 1H), 4.54 (d, J = 12.4 Hz,
1
4
4
H), 4.51 (d, J = 7.6 Hz, 1H), 4.49 (d, J = 12.2 Hz, 1H), 4.43 (d, J = 10.5 Hz, 1H),
.39 (d, J = 7.8 Hz, 1H), 4.25 (dd, J = 5.0, 2.4 Hz, 1H), 4.18 (dd, J = 7.9, 1.8 Hz, 1H),
.10 (dd, J = 10.8, 3.7 Hz, 1H), 4.05 (d, J = 7.2 Hz, 1H), 3.69-3.61 (m, 3H), 3.58-3.51
1
3
(m, 2H), 3.43-3.34 (m, 2H), 1.43 (s, 3H), 1.39 (s, 3H), 1.24 (s, 3H), 1.24 (s, 3H). C
NMR (100 MHz, CDCl ) δ 138.7, 138.1×2, 128.6, 128.3×2, 128.2, 127.9, 127.8,
3
1
7
27.7, 127.6, 127.5, 127.4, 109.4, 108.6, 104.4, 96.4, 84.5, 81.6, 77.7, 75.6, 74.9, 74.7,
4.3, 73.5, 71.4, 70.6, 70.5, 69.7, 68.7, 67.3, 26.0×2, 25.0, 24.41.
1
4
1
.3.17. Cyclohexyl 2, 3, 4, 6-tetra-O-benzyl-α-D-galactopyranoside(23α)
1
colorless syrup; R 0.35 (petroleum ether : ethyl acetate=7: 1, v/v); H NMR (400
f
MHz, CDCl ) δ 7.35-7.15 (m, 20H), 4.93 (d, J = 3.6 Hz, 1H), 4.88 (d, J = 11.5 Hz,
3
1
4
H), 4.78 (d, J = 11.6 Hz, 1H), 4.71 (d, J = 12.0 Hz, 1H), 4.66 (d, J = 11.6 Hz, 1H),
.60 (d, J = 12.0 Hz, 1H), 4.50 (d, J = 11.5 Hz, 1H), 4.41 (d, J = 11.8 Hz, 1H), 4.33 (d,
J = 11.8 Hz, 1H), 4.00-3.96 (m, 1H), 3.96-3.93 (m, 1H), 3.92-3.86 (m, 2H), 3.51-3.40
(
m, 3H), 1.83-1.76 (m, 2H), 1.70-1.62 (m, 2H), 1.53-1.41 (m, 1H), 1.39-1.29 (m, 1H),
1
3
1
1
7
.28-1.19 (m, 1H), 1.21-1.09 (m, 3H). C NMR (100 MHz, CDCl ) δ 139.0, 138.8,
3
38.2, 128.3×3, 128.2×2, 127.9, 127.6×2, 127.5×2, 127.4×2, 95.5, 79.2, 76.6, 75.4,
5.3, 74.7, 73.4, 73.2, 73.0, 69.3, 69.2, 33.4, 31.6, 25.6, 24.5, 24.2.
1
4
1
.3.18. Cyclohexyl 2, 3, 4, 6-tetra-O-benzyl-β-D-galactopyranoside(23β)
1
colorless syrup; R 0.32 (petroleum ether : ethyl acetate=7: 1, v/v); H NMR (400
f
MHz, CDCl ) δ 7.31-7.17 (m, 20H), 4.89 (d, J = 10.9 Hz, 1H), 4.86 (d, J = 11.8 Hz,
3
1
4
H), 4.68 (d, J =12.0 Hz, 1H), 4.67 (d, J = 10.8 Hz, 1H), 4.62 (d, J = 11.8 Hz, 1H),
.55 (d, J = 11.7 Hz, 1H), 4.38 (d, J = 7.7 Hz, 1H), 4.36-4.32 (m, 2H), 3.79 (d, J = 2.5
Hz, 1H), 3.73 (dd, J = 9.7, 7.7 Hz, 1H), 3.60 (ddd, J = 13.2, 9.3, 3.8 Hz, 1H),
3
1
1
7
.51-3.50 (m, 2H), 3.46-3.41 (m, 2H), 1.97-1.82 (m, 2H), 1.69-1.51 (m, 2H),
1
3
.47-1.29 (m, 2H), 1.21-1.12 (m, 4H). C NMR (100 MHz, CDCl ) δ 138.7, 138.5,
3
38.5, 128.3×2, 128.2, 128.0, 127.8, 127.7, 127.6×2, 127.5×2, 127.4, 95.7, 80.3, 75.4,
5.2, 75.1, 74.7, 73.3, 72.6, 72.2, 71.8, 69.4, 33.2, 31.3, 25.6, 24.0, 23.7.
1
4
1
.3.19. Cyclohexyl 2, 3, 4, 6-tetra-O-benzyl-α-D-mannopyranoside(24α)
1
colorless syrup; R 0.35 (petroleum ether : ethyl acetate=7: 1, v/v); H NMR (400
f
MHz, CDCl ) δ 7.33-7.15 (m, 18H), 7.13-7.04 (m, 2H), 4.92 (d, J = 1.7 Hz, 1H), 4.80
3
(d, J = 10.7 Hz, 1H), 4.69 (d, J = 12.5 Hz, 1H), 4.63 (d, J = 12.9 Hz, 1H), 4.60 (d, J =
1
2.3 Hz, 1H), 4.55 (d, J = 11.7 Hz, 2H), 4.45 (t, J = 11.3 Hz, 2H), 3.94-3.88 (m, 1H),

3
.86 (dd, J = 9.2, 2.9 Hz, 1H), 3.81- 3.75 (m, 1H), 3.72 (dd, J = 10.6, 4.9 Hz, 2H),
3
.68-3.62 (m, 1H), 1.80-1.65 (m, 2H), 1.63-1.42 (m, 2H), 1.41-1.38 (m, 1H)1.28-1.04
1
3
(m, 6H). C NMR (100 MHz, CDCl ) δ 138.7, 138.5×2, 128.3×2, 128.2, 128.0, 127.8,
3
1
7
27.7, 127.6×2, 127.5×2, 127.4, 95.7, 80.3, 75.4, 75.2, 75.1, 74.7, 73.3, 72.6, 72.2,
1.8, 69.4, 33.2, 31.3, 25.6, 24.0, 23.7.
1
4
1
.3.20. Cyclohexyl 2, 3, 4, 6-tetra-O-benzyl-β-D-mannopyranoside(24β)
1
colorless syrup; R 0.32 (petroleum ether : ethyl acetate=7: 1, v/v); H NMR (400
f
MHz, CDCl ) δ7.41 (d, J = 6.1 Hz, 2H), 7.31-7.17 (m, 16H), 7.16-7.10 (m, 2H), 4.95
3
(d, J = 12.6 Hz, 1H), 4.84 (d, J = 11.5 Hz, 2H), 4.54 (d, J = 3.1 Hz, 2H), 4.47 (d, J =
1
3
1
0.8 Hz, 1H) , 4.43 (t, J = 5.9 Hz, 2H), 4.36 (d, J = 11.8 Hz, 1H), 3.80-3.74 (m, 3H),
.68-3.62 (m, 2H), 3.43 (dd, J = 9.3, 3.1 Hz, 1H), 3.37 (ddd, J = 9.6, 6.3, 1.8 Hz, 1H),
.91 (d, J = 10.4 Hz, 1H), 1.75-1.60 (m, 3H), 1.39-1.50 (m, 1H), 1.18-1.34 (m, 5H).
1
3
C NMR (100 MHz, CDCl ) δ 139.0, 138.6, 138.4, 138.3, 128.4, 128.3×2, 128.0×2,
3
1
6
27.8, 127.6, 127.5×2, 127.4, 127.3, 99.5, 82.6, 76.6, 75.9, 75.1, 74.2, 73.7, 73.4, 71.4,
9.9, 33.5, 31.6, 25.7, 23.8, 23.7.
Acknowledgements
This work was supported by the National Natural Science Foundation of China
[
grant number 81560558].
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,
2

A novel glycosylation method involving the visible-light irradiation of
solutions of glycosyl trichloroacetimidates, alcohols, and eosin Y results in
O-glycosylation.
The usage of eosin Y avoiding of triflic acid and TMSOTf which pose obvious
storage and handling issues.

Declaration of interests
☒
The authors declare that they have no known competing financial interests or personal relationships
that could have appeared to influence the work reported in this paper.
☐
The authors declare the following financial interests/personal relationships which may be considered
as potential competing interests: