N-aryl-O-glycosyl haloacetimidates as glycosyl donors

Article abstract of DOI:10.1080/07328301003597673

Reaction of 1-O-unprotected tetra-O-acetyl- and tetra-O-benzyl- glucopyranose with N-aryl haloacetimidoyl chlorides in the presence of sodium hydride and 15-crown-5 afforded N-aryl-O-glucopyranosyl haloacetimidates. Mainly the β-anomers were obtained in this anomeric O-acylation-type reaction. The glycosyl donor properties of these haloacetimidates were investigated with 6-O- and 4-O-unprotected glucopyranosides as acceptors. The results were compared with those obtained with the corresponding O-glucopyranosyl trichloroacetimidates as glycosyl donors and the same acceptors. It was found that N-(2-chloro-6-methylphenyl)-O-glucopyranosyl trifluoroacetimidates (16Ad, 16Bd) exhibit glycosyl donor properties closely related to those of the corresponding N-unsubstituted O-glucopyranosyl trichloroacetimidates (12A, 12B). Copyright Taylor & Francis Group, LLC.

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N-Aryl-O-glycosyl Haloacetimidates as
Glycosyl Donors
Uschi Huchel a , Pallavi Tiwari a & Richard R. Schmidt a
a Department of Chemistry , University of Konstanz , 78457,
Konstanz, Germany
Published online: 30 Mar 2010.
To cite this article: Uschi Huchel , Pallavi Tiwari & Richard R. Schmidt (2010) N-Aryl-O-glycosyl
Haloacetimidates as Glycosyl Donors, Journal of Carbohydrate Chemistry, 29:2, 61-75, DOI:
10.1080/07328301003597673
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Journal of Carbohydrate Chemistry, 29:61–75, 2010
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ISSN: 0732-8303 print / 1532-2327 online
DOI: 10.1080/07328301003597673
N-Aryl-O-glycosyl
Haloacetimidates as Glycosyl
Donors
Uschi Huchel, Pallavi Tiwari, and Richard R. Schmidt
Department of Chemistry, University of Konstanz 78457, Konstanz, Germany
Reaction of 1-O-unprotected tetra-O-acetyl- and tetra-O-benzyl-glucopyranose with N-
aryl haloacetimidoyl chlorides in the presence of sodium hydride and 15-crown-5 af-
forded N-aryl-O-glucopyranosyl haloacetimidates. Mainly the β-anomers were obtained
in this anomeric O-acylation-type reaction. The glycosyl donor properties of these
haloacetimidates were investigated with 6-O- and 4-O-unprotected glucopyranosides
as acceptors. The results were compared with those obtained with the corresponding O-
glucopyranosyl trichloroacetimidates as glycosyl donors and the same acceptors. It was
found that N-(2-chloro-6-methylphenyl)-O-glucopyranosyl trifluoroacetimidates (16Ad,
16Bd) exhibit glycosyl donor properties closely related to those of the corresponding N-
unsubstituted O-glucopyranosyl trichloroacetimidates (12A, 12B).
Keywords Carbohydrates; Glycosidation; N-Aryl-O-glycosyl haloacetimidates; Syn-
thesis; O-Imidoylation
INTRODUCTION
O-Glycosyl trichloroacetimidates have become highly useful glycosyl donors as
they combine the most convenient preparation with excellent glycosyl donor
properties under simple acid catalysis.[1–3] Replacement of the trichloromethyl
group, for instance, by the trifluoromethyl group[4] or the dichloro-cyanomethyl
group[5] was reported. So far, these modifications of the haloacetimidate leav-
ing group did not exhibit advantages over the trichloroacetimidate group in
glycosylation reactions.
Introduction of a substituent at the nitrogen of the imidate group can be
reached by replacing the convenient base-catalyzed reversible addition of the
anomeric hydroxy group to electron-poor nitriles permitting even anomeric
Received August 10, 2009; accepted January 1, 2010.
Address correspondence to Richard R. Schmidt, Fachbereich Chemie, Universita¨t
Konstanz, Fach 725, D-78457 Konstanz, Germany. E-mail: richard.schmidt@uni-
konstanz.de
61

U. Huchel et al.
62
Ar
N
Cl
OR
OR
X
Y
Ar
N
O
O
Z
RO
RO
RO
RO
O
X
OH
Base
OR
OR
Y
Z
Figure 1: Imidoylation of 1-O-unprotected sugars by N-substituted imidoyl halides.
stereocontrol for a reaction with N-substituted imidoyl halides (Fig. 1).[6,7]
Since this anomeric O-imidoylation reaction is generally irreversible, anomeric
stereocontrol can hardly be achieved.[7,8] However, the available modification of
the leaving group character may compensate for the less convenient prepara-
tion of such N-substituted O-glycosyl haloacetimidate donors. As O-glycosyl-N-
phenyl-trifluoroacetimidates (Fig. 1, Ar Ph, X Y Z F) have previously been
investigated as glycosyl donors in various glycosylation reactions,[8,9] earlier
comparative studies by our group in this direction will be disclosed.[7]
RESULTS AND DISCUSSION
At first the synthesis and the reactions of N-aryl O-glucopyranosyl
trichloroacetimidates were investigated (Sch. 1). To this end, aniline (1a)
was transformed via the N-trichloroacetyl intermediate 2a into known imi-
doyl chloride 3a.[10,11] Anomeric O-imidoylation of O-benzyl-protected glucose
5B with 3a in the presence of sodium hydride as base and 15-crown-5 as
complexing agent for sodium afforded the desired O-glucopyranosyl-N-phenyl
trichloroacetimidate 6Ba in excellent yield as anomeric mixture (α/β = 3:7).[12]
Following reaction of this donor with a primary and a secondary hydroxy group
as acceptor, as, for instance, is present in the 6-O- and 4-O-unprotected glu-
copyranosides 8 and 9, respectively, led under standard TMSOTf catalysis at
rt to a mixture of the known anomers of 10B[13,14] and 11B[15] in good yield
(Table 1, entry 1). Comparison of this glycosylation result with that for the
corresponding N-unsubstituted β-configurated O-glucopyranosyl trichloroace-
timidate 12B[12,13] (that is most closely related to the anomeric mixture of
6Ba) exhibited almost quantitative formation of 10B and 11B though in lower
anomeric selectivity (Table 1, entry 7). Hence, the preference for the α-anomers
in 10B and 11B with 6Ba as donor reflects the lower reactivity of 6Ba favor-
ing an SN2-type reaction, as also was observed for 12B at low temperatures

N-Aryl-O-glycosyl Haloacetimidates as Glycosyl Donors
63
a: R2 = R6 = H
b: R2 = CF3, R6 = H
R2
R6
c: R2 = OMe, R6 = H
d: R2 = Cl, R6 = Me
1a-d NH2
a
R2
R6
O
NH
CCl3
2a-d
c
b
Ph
N
R2
R6
Cl
3a
Cl
N
CCl3
4a-d
CHCl2
OR
O
RO
d
RO
OH
d
OR
5A: R = Ac
5B: R = Bn
OBn
O
OR
O
R2
O
R6
Ph
N
BnO
BnO
RO
O
RO
N
OR6
O
OBn
OR
6Ba
CCl3
CHCl2
R4O
7Aa, 7Ab, 7Bb, 7Bc
BnO
BnO
OMe
8: R4 = Bn, R6 = H
9: R4 = H, R6 = Bn
9, e
8, e
8, e
9, e
OR
O
OMe
OR
O
RO
RO
BnO
Bn
O
O
RO
RO
O
O
OR
BnO
BnO
O
OBn
OR
11A (R = Ac)
11B (R = Bn)
10A (R = Ac)
10B (R = Bn)
BnO
OMe
9, e
8, e
OR
O
RO
RO
O
NH
CCl3
12A: R = Ac
12B: R = Bn
OR
Scheme 1: N-Aryl-O-glucopyranosyl-haloacetimidate formation and glycosylation of
acceptors 8 and 9. Reagents and conditions: (a) Cl3C–COCl, Pyr; (b) POCl3, PCl5; (c) PPh3,
CCl4, CH2Cl2; (d) NaH, 15-crown-15, CH2Cl2, rt; (e) TMSOTf (0.1 eq), CH2Cl2, rt (see Table 1).

U. Huchel et al.
64
Table 1: Glycosylation results with glycosyl donors 6, 7, 12, and 16 and acceptors 8
and 9 leading to disaccharides 11A, B and 11A, Ba
Glycosyl
Product with Glycosyl
Product with Glycosyl
Entry
Donor (α/β)b
Acceptor 8 (R6 = H)
Acceptor 9 (R4 = H)
1
2
6Ba (3:7)
7Aa (β)
10B 82%, α:β = 4:1
11B 71%, α:β = 5:1
10A 80%, β
11A 71%, β
3
7Ab (2:3)
7Bb (1:7)
7Bc (1:9)
12A (β)
10A 70%, β
11A 62%, β
4
10B 77%, α:β = 5:1
10B 87%, α:β = 3:1
10A 82%, β
11B 69%, α:β = 5:1
11B 78%, α:β = 2:1
11A 74%, β
5
6
7
12B (β)
10B 98%, α:β = 3:2
11B 85%, α:β = 1:1
8
16Aa (1:3)
16Ab (1:2)
16Ac (1:4)
16Ad (2:1)
16Ba (β)
16Bb (1:5)
16Bc (β)
16Bd (β)
10A 74%, β
11A 67%, β
9
10A 59%, β
11A 53%, β
10
11
12
13
14
15
10A 80%, β
11A 71%, β
10A 85%, β
11A 74%, β
10B 85%, α:β = 1:1
10B 71%, α:β = 1:1
10B 91%, α:β = 1:1
10B 98%, α:β = 1:1
11B 74%, α:β = 1:1
11B 63%, α:β = 1:1
11B 82%, α:β = 1:1
11B 89%, α:β = 1:1
aAll reactions were carried out in dichloromethane as solvent and TMSOTf (0.1 equivalents) as
catalyst at rt.
bThe anomeric ratio was taken from the 1H NMR spectra.
or by using a less polar solvent; alternatively, through intimate ion pair for-
mation of the activated glycosyl donor, a memory effect could influence the
stereocontrol.[1,2]
Thereafter, the reaction of O-acetyl-protected 5A with imidoyl chloride
3a was investigated. However, presumably due to the lower reactivity of 5A
and the steric bulk of the trichloromethyl group, the reaction was met with
difficulties. Therefore, we took advantage of a dehalogenation procedure found
for the transformation of 2a into dichloroacetimidoyl chloride 4a with the help
of triphenylphosphine and carbon tetrachloride[17]; this procedure was simi-
larly applied to 2b–d, furnishing the corresponding imidoyl chlorides 4b–d.
Reaction of 5A with 4a and 4b readily provided O-acetyl-protected glucopyra-
nosyl dihaloacetimidates 7Aa and 7Ab; similarly, reaction of 5B with 4b and
4c afforded the O-benzyl-protected O-glucopyranosyl dichloroacetimidates
7Bb and 7Bc. The glycosylation results found for 7Aa with 8[18] and 9[15] as
acceptors (Table 1, entry 2) were closely related to those found for the related
β-configurated O-glucopyranosyl trichloroacetimidate 12A[1,2,16] with 8 and 9
as acceptors (Table 1, entry 6). Based on the neighboring group participation,
as expected, in both cases only the β-linked disaccharides 10B and 11B were
obtained. Introduction of an electron-withdrawing trifluoromethyl substituent
into the N-phenyl group as in 7Ab and 7Bb did not improve the glycosylation
yields with acceptors 8 and 9 (Table 1, entries 3 and 4). However, it is
noteworthy that donor 7Bb furnished mainly α-linked disaccharides (Table 1,

N-Aryl-O-glycosyl Haloacetimidates as Glycosyl Donors
65
entry 4). The electron-donating 2-methoxy substituent in the N-phenyl group
as in 7Bc afforded almost glycosylation yields (Table 1, entry 5) as those found
for 12B (Table 1, entry 7).[1,2,16] This result is presumably due to bidentate
complexation of the catalyst by the leaving group, thus exhibiting a remote
activation effect, as previously found for the 3-methoxy-2-pyridyloxy (MOP)
leaving group.[19]
In order to generate better and less bulky N-aryl-haloacetimidate leav-
ing groups, the related trifluoroacetimidate analogs also were prepared
(Sch. 2). To this end, anilines 1a–d were transformed with N-trifluoroacetyl-
benzotriazole[20] (13) into the trifluoroacetanilides 14a–d. Reaction with triph-
enylphosphine/carbon tetrachloride in dichloromethane readily gave the N-
aryl imidoyl chlorides 15a–d that led with 5A and 5B in the presence of sodium
hydride and 15-crown-5 to the O-acetyl-protected glucopyranosyl trifluoroace-
timidates 16Aa–16Ad and to the O-benzyl-protected analogs 16Ba–16Bd, re-
spectively; generally, mainly or exclusively the β-anomers were formed. The
glycosidation reaction with acceptors 8 and 9 under the aforementioned con-
ditions clearly showed that donors 16 are superior to the trichloro- (6Ba) and
dichloroacetimidate analogs 7 (Table 1, entries 8–15). However, only the com-
pounds with 2,6-di-substitution in the N-phenyl ring (16Ad and 16Bd) led
to glycosylation results (Table 1, entries 11 and 15) as found for the corre-
sponding trichloroacetimidates 12A and 12B (Table 1, entries 6 and 7). Hence,
b
a
R2
O
R6
1a-d
R2
Cl
R6
N
NH
N
N
15a-d
14a-d
CF3
CF3
N
13
c
O
CF3
5A, B
a: R2 = R6 = H
b: R2 = CF3, R6 = H
OR
O
c: R2 = OMe, R6 = H
R2
R6
d: R2 = Cl, R6 = Me
RO
RO
O
N
16Aa-16Ad (R = Ac)
16Ba-16Bd (R = Bn)
OR
CF3
8, d
10A
9, d
11A
8, d
9, d
10B
11B
Scheme 2: N-Aryl-O-glucopyranosyl-trifluoroacetimidate formation and glycosylation of
acceptors 8 and 9. Reagents and conditions: (a) CH2Cl2; (b) PPh3, CCl4, CH2Cl2; (c) NaH,
15-crown-15, CH2Cl2, rt; (d) TMSOTf (0.1 eq), CH2Cl2, rt (see Table 1).

U. Huchel et al.
66
these compounds possess similar glycosyl donor properties as 12A and 12B,
which is presumably due to additional release of steric strain in the glycosy-
lation step. Catalysis of these glycosylation reactions with BF3·OEt2 was also
possible.[7] With glycosyl donors 16Ba–16Bd, the α,β-selectivities in the gly-
cosidation reactions dropped (Table 1, entries 12–15) as was also found for
trichloroacetimidate 12B when reacted in dichloromethane at rt.[1,2] Hence, it
seems that the ease of formation and the reactivity potential of the O-glycosyl
trichloroacetimidates (as, for instance, 12A, B) can be matched by structurally
varied N-aryl-O-glycosyl haloacetimidates.
CONCLUSION
N-Aryl-O-glucopyransoyl haloacetimidates were prepared and their glycosyl
donor properties were investigated. The best glycosyl donor properties were
found for N-(2-chloro-6-methylphenyl)-O-glucopyranosyl trifluoroacetimidates
(compounds 16Ad and 16Bd). Comparison of these glycosyl donors with the
corresponding O-glucopyranosyl trichloroacetimidates (12A and 12B) exhib-
ited very similar behavior. Interestingly, the less reactive N-aryl-O-(tetra-O-
benzyl-glucopyranosyl) dichloroacetimidates (7Bd and 7Bc), having mainly β-
configuration, furnished in the glycosylation reaction higher amounts of the
inversion products than the more reactive glycosyl donors 12B or 16Bd. Yet,
similar results were previously observed for 12B when the reactivity was de-
creased by lowering the reaction temperature.
EXPERIMENTAL
1
Solvents were purified by standard procedures: H NMR spectra: Bruker AC-
250 (250 MHz): internal standard tetramethylsilane (TMS); flash chromatog-
raphy: silica gel 60 (Baker: 0.04–0.063 mm); thin-layer chromatography (TLC):
foil plates, silica gel 60 F254 (Merck: layer thickness 0.2 mm); optical rotations:
Perkin-Elmer polarimeter 241 MC: 1-dm cell, 20◦C; elemental analyses: Her-
aeus CHN-O-Rapid; MALDI-MS: Kratos (Kompac Maldi 1); ESI-MS: Bruker
Esquire 3000 plus.
General Procedure A: Trichloroacetylation of Anilines (1a–d)
To a solution of aniline (2 eq) in dry dioxane (2 mL/1 mmol aniline) was
added trichloroacetyl chloride (1 eq) under cooling with ice. After stirring for
30 min, water was added and the reaction mixture extracted three times with
ethyl acetate (10 mL/1 mmol aniline). The organic phases were combined and
dried with MgSO4, the filtrate concentrated in vacuo, and the resulting product
purified.

N-Aryl-O-glycosyl Haloacetimidates as Glycosyl Donors
67
General Procedure B: Trifluoroacetylation of Anilines (1a–d)
The aniline (1 eq) was dissolved in dry dichloromethane (2 mL/1 mmol
aniline). To this solution was added N-trifluoro-acetyl-benzotriazole (13, 1.1 eq)
in portions and then the mixture was stirred for 3 h at rt. After concentration
of this mixture, pure product was obtained by flash chromatography.
General Procedure C: Synthesis of the Imidoyl Chlorides 4a–d
and 15a–d
The anilides (2a–d, 14a–d) (1 eq) and triphenylphosphane (1.1 eq) were
dissolved in a 1:1 mixture of carbon tetrachloride and dichloromethane (2 mL/1
mmol anilide) and the reaction mixture stirred for 4 h at 60◦C. Then half of the
solvent was removed in vacuo and the residue purified by flash chromatogra-
phy on ALOX (Aluminia N32–63 active) with dry toluene as solvent.
General Procedure D: Synthesis of N-aryl-O-glucopyranosyl
Haloacetimidates 6Ba, 7Aa, 7Ab, 7Bb, 7Bc, 16Aa–Ad and
16Ba–Bd
5A or 5B (1 mmol) was dissolved in dry dichloromethane (5 mL) under
argon and then 15-crown-5 (220 µL, 1.1 mmol) and sodium hydride (26 mg,
1.1 mmol) added under stirring at rt. After 5 min N-aryl-imidoyl chloride (1 to
1.1 mmol) was added and stirring continued for 30 min. The reaction mixture
was neutralized with acetic acid and then concentrated in vacuo. The residue
was purified by flash chromatography with dry solvents.
General Procedure E: Glycosylation Reactions Furnishing 10A, B
and 11A, B
Under argon the glycosyl donor (0.26 mmol) and the acceptor 8 or 9 (0.2
mmol) were dissolved in dry dichloromethane (0.4 mL). A catalytic amount of
TMSOTf (0.02 mmol) was then added at rt. After 1 h, the reaction mixture was
neutralized with triethylamine and concentrated in vacuo. Flash chromatogra-
phy with toluene/ethyl acetate (20:1) gave the disaccharides that were identical
with independently synthesized material: 10A, ref. 13; 10B, ref. 14; 11A, ref.
15; 11B, ref. 15.
2,2,2-Trichloroacetyl-anilide (2a) and
2,2,2-Trichloro-N-phenyl-acetimidoyl Chloride (3a)
These compounds were obtained as previously described.[10,11]

U. Huchel et al.
68
N-(2-Trifluoromethylphenyl)-trichloroacetamide (2b)
Following general procedure A, from 1b (2.51 mL, 20 mmol) 2b (3.05 g, qu.)
was obtained as yellow crystals. m.p. 46◦C; Rf (toluene/ethyl acetate, 4:1) 0.68.
1H NMR (250 MHz, CDCl3): δ 8.75 (1 H, NH), 8.12 (mc, 1 H, 6-H), 7.85 (mc, 1
H, 3-H), 7.71–7.55 (m, 2 H, 4-H, 5-H). Anal. Calcd for C9H5Cl3F3NO (306.50):
C, 35.27; H, 1.64; N, 4.57. Found C, 35.20; H, 1.71; N, 4.67.
N-(2-Methoxyphenyl)-trichloroacetamide (2c)
Following general procedure A, from 1c (12 g, 1 mol) 2c (9.51 g, 36%) was
1
obtained as clear viscous mass. Rf (toluene) 0.31. H NMR (250 MHz, CDCl3):
δ 9.15 (1 H, NH), 8.30 (mc, 1 H, 6-H), 7.17 (mc, 1 H, 4-H), 7.01 (mc, 1 H, 5-H),
6.93 (mc, 1 H, 3-H), 3.91 (s, 3 H, OCH3). Anal. Calcd for C9H8Cl3NO2 (268.52):
C, 40.26; H, 3.00; N, 5.22. Found C, 40.45; H, 3.08; N, 5.23.
N-(2-Chloro-6-methylphenyl)-trichloroacetamide (2d)
Following general procedure A, from 1d (6.15 mL, 0.05 mol) 2d (6.10 g,
1
42%) was obtained as white crystals. m.p. 141◦C; Rf (toluene) 0.15. H NMR
(250 MHz, CDCl3): δ 7.23–6.98 (m, 3 H, 3-H, 4-H, 5-H), 2.11 (s, 3 H, CH3). Anal.
Calcd for C9H7Cl4NO (286.97): C, 37.67; H, 2.46; N, 4.88. Found C, 37.38; H,
2.28; N, 4.86.
N-Phenyl-dichloroacetimidoyl Chloride (4a)
Following general procedure C, from 2a (8.3 g, 35 mmol) 4a (2.72 g, 35%)
1
was obtained as colorless fluid. Rf (toluene) 0.89. H NMR (250 MHz, CDCl3):
δ 7.42–6.97 (m, 5 H, 2-H, 3-H, 4-H, 5-H, 6-H), 6.43 (s, 1 H, CHCl2). Anal. Calcd
for C8H6Cl3N (222.50): C, 43.18; H, 2.72; N, 6.30. Found C, 43.40; H, 2.73; N,
6.32.
N-(2-Trifluoromethylphenyl)-dichloroacetimidoyl Chloride (4b)
Following general procedure C, from 2b (1.53 g, 5 mmol) 4b (485 mg, 33%)
was obtained as yellow fluid. Rf (toluene/ethyl acetate, 4:1) 0.98. 1H NMR (250
MHz, CDCl3): δ 7.69 (mc, 1 H, 6-H), 7.58 (mc, 1 H, 4-H), 7.33 (mc, 1 H, 5-H),
6.90 (mc, 1 H, 3-H), 6.48 (s, 1 H, CHCl2). Anal. Calcd for C9H5Cl3F3N (290.50):
C, 37.21; H, 1.73; N, 4.82. Found C, 37.56; H, 1.78; N, 5.01.
N-(2-Methoxyphenyl)-dichloroacetimidoyl Chloride (4c)
Following general procedure C, from 2c (1.85 g, 7 mmol) 4c (743 mg, 43%)
1
was obtained as colorless oil. Rf (toluene) 0.81. H NMR (250 MHz, CDCl3): δ
7.28–6.87 (m, 4 H, 3-H, 4-H, 5-H, 6-H), 6.53 (s, 1 H, CHCl2), 3.84 (s, 3 H, CH3).

N-Aryl-O-glycosyl Haloacetimidates as Glycosyl Donors
69
Anal. Calcd for C9H8Cl3NO (252.52): C, 42.81; H, 3.19; N, 5.55. Found C, 43.31;
H, 3.29; N, 5.50.
N-(2-Chloro-6-methylphenyl)-dichloroacetimidoyl Chloride (4d)
Following general procedure C, from 2d (2.87 g, 10 mmol) 4d (1.19 g, 44%)
1
was obtained as viscous yellowish oil. Rf (toluene) 0.85. H NMR (250 MHz,
CDCl3): δ 7.29–6.99 (m, 3 H, 3-H, 4-H, 5-H), 6.53 (s, 1 H, CHCl2), 2.08 (s, 3 H,
CH3). Anal. Calcd for C9H7Cl4N (270.97): C, 39.89; H, 2.60; N, 5.18. Found C,
40.36; H, 2.69; N, 5.18.
N-Phenyl-O-(2,3,4,6-tetra-O-benzyl-α,β-D-glucopyranosyl)
Trichloroacetimidate (6Ba)
Following general procedure D, from 5B (540 mg, 1 mmol) and 3a (250 mg,
1 mmol) 6Ba (647 mg, 85%) was obtained as yellowish oil. Rf (toluene/ethyl
1
acetate, 4:1) 0.98, α/β 3:7. H NMR (250 MHz, CDCl3): δ 7.01–6.73 (m, 25 H,
2ꢁ-H, 3ꢁ-H, 4ꢁ-H, 5ꢁ-H, 6ꢁ-H, 4 Ph), 6.67 (d, 0.3 H, J1,2 = 3.6 Hz, 1-Hα), 5.91 (d,
0.7 H, J1,2 = 8.4 Hz, 1-Hβ), 5.12–4.51 (m, 8 H, 4 CH2Ph), 4.22 (dd, 0.3 H, J3,2
=
9.7, J3,4 = 9.8 Hz, 3-Hα), 3.90–3.62 (m, 5.7 H, 2-H, 3-Hβ, 4-H, 5-H, 6A-H, 6B-H).
C42H40Cl3NO6 (759): ESI-MS (negative mode): m/z = 792 (M-2 H+Cl)−, 758
(M H)−, 724 (M Cl)−.
N-Phenyl-O-(2,3,4,6-tetra-O-acetyl-α,β-D-glucopyranosyl)
Dichloroacetimidate (7Aa)
Following general procedure D, from 5A (340 mg, 1 mmol) and 4a (230 mg,
1 mmol) 7Aa (358 mg, 69%) was obtained as clear oil. Rf (toluene/ethyl acetate,
1
6:1) 0.18. H NMR (250 MHz, CDCl3): δ 7.40–6.79 (m, 5 H, NPh), 6.12 (s, 1 H,
CHCl2), 5.93 (d, 1 H, J1,2 = 8.2 Hz, 1-Hβ), 5.41–5.17 (m, 3 H, 2-H, 3-H, 4-H),
4.38–4.12 (dd, dd, 2-H, Jgem = 12.3, J6A,5 = 4.5, J6B,5 = 2.3 Hz, 6A-H, 6B-H),
3.90 (ddd, 1 H, J5,4 = 9.5, J5,6A = 4.5, J5,6B = 2.3 Hz, 5-H), 2.02–2.09 (4s, 12 H,
4 OAc). C22H25Cl2NO10 (534.43). FAB-MS (positive mode, matrix: NBOH with
NaI): m/z = 533/535 (M)+.
N-(2-Trifluoromethyl-phenyl)-O-(2,3,4,6-tetra-O-acetyl-α,β-D-
glucopyranosyl) Dichloroacetimidate (7Ab)
Following general procedure D, from 5A (340 mg, 1 mmol) and 4b (280 mg,
1 mmol) 7Ab (186 mg, 32%) was obtained as white foam. Rf (toluene/ethyl
acetate, 6:1) 0.24. 1H NMR (250 MHz, CDCl3): δ 7.68–7.14 (m, 3-H, 3ꢁ-H, 5ꢁ-H,
6ꢁ-H), 6.89–6.79 (m, 1 H, 4ꢁ-H), 6.60 (d, 0.4 H, J1,2 = 3.7 Hz, 1-Hα), 5.99 (s, 0.4
H, CHCl2), 5.97 (s, 0.6 H, CHCl2), 5.92 (d, 0.6 H, J1,2 = 7.9 Hz, 1-Hβ), 5.65 (dd,
0.4 H, J3,2 = 10.3, J3,4 = 10.3 Hz, 3-Hα), 5.40–5.11 (m, 2.6 H, 2-H, 3-Hβ, 4-H),
4.37–4.08 (m, 2.4 H, 5-Hα, 6A-H, 6B-H), 3.90–3.82 (ddd, 0.6 H, J5,4 = 9.8, J5,6A

U. Huchel et al.
70
= 4.5, J5,6B = 2.4 Hz, 5-Hβ), 2.11–1.99 (m, 12 H, 4 OAc). C23H24Cl2F3NO10
(601). FAB-MS (positive mode, matrix: NBOH with NaI): m/z = 601 (M)+, 624
(M+Na)+.
N-(2-Trifluoromethyl-phenyl)-O-(2,3,4,6-tetra-O-benzyl-α,β-D-
glucopyranosyl) Dichloroacetimidate (7Bb)
Following general procedure D, from 5B (540 mg, 1 mmol) and 4b (280 mg,
1 mmol) 7Bb (343 mg, 43%) was obtained as clear oil. Rf (toluene/ethyl ac-
1
etate, 8:1) 0.64. H NMR (250 MHz, CDCl3): δ 7.68–7.12 (m, 23 H, 3ꢁ-H, 5ꢁ-H,
6ꢁ-H, 4 Ph), 6.80 (mc, 0.8 H, 4ꢁ-Hβ), 6.71 (mc, 0.2 H, 4ꢁ-Hα), 6.56 (d, 0.2 H,
J1,2 = 3.8 Hz, 1-Hα), 6.02 (s, 0.8 H, CHCl2β), 5.98 (s, 0.2 H, CHCl2α), 5.82 (d,
0.8 H, J1,2 = 7.9 Hz, 1-Hβ), 5.08–3.52 (m, 8 H, 2-H, 3-H, 4-H, 5-H, 6A-H, 6B-H,
4 CH2Ph).
C43H40Cl2F3NO6 (793). FAB-MS (positive mode, matrix: NBOH with NaI):
m/z = 816 (M+Na)+.
N-(2-Methoxyphenyl)-O-(2,3,4,6-tetra-O-benzyl-α,β-D-
glucopyranosyl) Dichloroacetimidate (7Bc)
Following general procedure D, from 5B (540 mg, 1 mmol) and 4c (269 mg,
1 mmol) 7Bc (188 mg, 25%) was obtained as dark-yellow oil. Rf (toluene/ethyl
1
acetate, 16:1) 0.68. H NMR (250 MHz, CDCl3): δ 7.35–6.63 (m, 24 H, 1-Hα,
3ꢁ-H, 4ꢁ-H, 5ꢁ-H, 6ꢁ-H, 4 Ph), 6.01 (s, 0.9 H, CHCl2β), 5.98 (s, 0.1 H, CHCl2α),
5.91 (d, 0.9 H, J1,2 = 8.4 Hz, 1-Hβ), 5.07–4.42 (m, 8 H, 4 CH2Ph), 3.70–3.57 (m,
9 H, OCH3, 2-H, 3-H, 4-H, 5-H, 6A-H, 6B-H).
N-Phenyl-trifluoroacetamide (14a)
Following general procedure B, from 1a (0.93 g, 10 mmol) and 13 (2.32 g,
11 mmol) 14a (1.61 g, 85%) was obtained as white solid. m.p. 87.7◦C; Rf
(toluene/ethyl acetate, 20:1) 0.63. 1H NMR (250 MHz, CDCl3): δ 8.22–8.01 (1 H,
NH), 7.60 (mc, 2 H, 2-H, 6-H), 7.26 (mc, 1 H, 4 H). Anal. Calcd for C8H6F3NO
(189.13): C, 50.80; H, 3.20; N, 7.41. Found C, 50.61; H, 3.09; N, 7.34.
N-(2-Trifluoromethylphenyl)-trifluoroacetamide (14b)
Following general procedure B, from 1b (0.63 mL, 5 mmol) and 13 (1.16 g,
5.5 mmol) 14b (1.23 g, 48%) was obtained as white crystals. m.p. 66◦C; Rf
(toluene/ethyl acetate, 6:1) 0.82. 1H NMR (250 MHz, CDCl3): δ 8.22 (1 H, NH),
8.08 (mc, 1 H, 6-H), 7.72–7.57 (m, 2 H, 4-H, 5-H), 7.47 (mc, 1 H, 3-H). Anal.
Calcd for C9H5F6NO (257.16): C, 42.04; H, 1.96; N, 5.45. Found C, 42.52; H,
2.39; N, 5.45.

N-Aryl-O-glycosyl Haloacetimidates as Glycosyl Donors
71
N-(2-Methoxyphenyl)-trifluoroacetamide (14c)
Following general procedure B, from 1c (6.00 g, 48.7 mmol) and 13 (11.6 g,
53.9 mmol) 14c (1.35 g, 62%) was obtained as white crystals. m.p. 39.9◦C; Rf
1
(toluene) 0.58. H NMR (250 MHz, CDCl3): δ 8.59 (mc, 1 H, NH), 8.34 (mc, 1
H, 6-H), 7.26–6.91 (m, 3 H, 3-H, 4-H, 5-H), 3.93 (s, 3 H, OCH3). Anal. Calcd
for C9H8F3NO2 (219.16): C, 49.32; H, 3.68; N, 6.39. Found C, 49.29; H, 3.68; N,
6.41.
N-(2-Chloro-6-methylphenyl)-trifluoroacetamide (14d)
Following general procedure B, from 1d (0.62 mL, 5 mmol) and 13 (1.16
g, 5.5 mmol) 14d (493 mg, 41%) was obtained as white crystals. m.p. 71◦C;
1
Rf (toluene/ethyl acetate, 2:1) 0.72. H NMR (250 MHz, CDCl3): δ 7.68 (1 H,
NH), 7.33–7.13 (m, 3 H, 3-H, 4-H, 5-H), 2.28 (s, 3 H, CH3). Anal. Calcd for
C9H7ClF3NO (237.69): C, 45.47; H, 2.96; N, 5.89. Found C, 45.65; H, 2.96; N,
5.91.
N-Phenyl-trifluoroacetimidoyl Chloride (15a)
Following general procedure C, from 14a (380 mg, 2 mmol) 15a (277 mg,
66%) was obtained as clear liquid. Rf (toluene) 0.90. 1H NMR (250 MHz,
CDCl3): δ 7.45 (mc, 2 H, 3-H, 5-H), 7.28 (mc, 1 H, 4-H), 7.09 (mc, 2 H, 2-H,
6-H). Anal. Calcd for C8H5ClF3N (207.6): C, 46.28; H, 2.43; N, 6.75. Found C,
46.29; H, 2.43; N, 6.78.
N-(2-Trifluoromethylphenyl)-trifluoroacetimidoyl Chloride (15b)
Following general procedure C, from 14b (514 mg, 2 mmol) 15b (338 mg,
61%) was obtained as clear viscous liquid. Rf (toluene/ethyl acetate, 12:1) 0.91.
1H NMR (250 MHz, CDCl3): δ 7.72 (mc, 1 H, 6-H), 7.58 (mc, 1 H, 4-H), 7.36 (mc,
1 H, 5-H), 6.93 (mc, 1 H, 3-H). Anal. Calcd for C9H4ClF6N (275.58): C, 39.22;
H, 1.46; N, 5.08. Found C, 38.94; H, 1.50; N, 5.36.
N-(2-Methoxyphenyl)-trifluoroacetimidoyl Chloride (15c)
Following general procedure C, from 14c (660 mg, 3 mmol) 15c (473 mg,
66%) was obtained as clear liquid. Rf (toluene) 0.83. 1H NMR (250 MHz,
CDCl3): δ 7.28 (mc, 1 H, 4-H), 7.08–6.96 (m, 3 H, 3-H, 5-H, 6-H), 3.89 (s, 3
H, OCH3). Anal. Calcd for C9H7ClF3NO (237.61): C, 45.49; H, 2.96; N, 5.89.
Found C, 45.68; H, 2.95; N, 6.28.

U. Huchel et al.
72
N-(2-Chloro-6-methylphenyl)-trifluoroacetimidoyl Chloride (15d)
Following general procedure C, from 14d (474 mg, 2 mmol) 15d (321 mg,
63%) was obtained as yellowish viscous oil. Rf (toluene/ethyl acetate, 6:1) 0.73.
1H NMR (250 MHz, CDCl3): δ 7.30–7.04 (m, 3 H, 3-H, 4-H, 5-H), 2.08 (s, 3 H,
CH3). Anal. Calcd for C9H6Cl2N (256.05): C, 42.22; H, 2.36; N, 5.46. Found C,
42.39; H, 2.52; N, 5.59.
N-Phenyl-O-(2,3,4,6-tetra-O-acetyl-α,β-D-glucopyranosyl)
Trifluoroacetimidate (16Aa)
Following general procedure D, from 5A (340 mg, 1 mmol) and 15a (230 mg,
1.1 mmol) 16Aa (197 mg, 38%) was obtained as colorless oil. Rf (toluene/ethyl
1
acetate, 4:1) 0.46, α/β 1:3. H NMR (250 MHz, CDCl3): δ Rotamere. 7.35–6.74
(5 H, 2ꢁ-H, 3ꢁ-H, 4ꢁ-H, 5ꢁ-H, 6ꢁ-H), 6.50 (0.25 H, 1-Hα), 5.75 (0.75 H, 1-Hβ), 6.54
(0.25 H, J3,2 = 10.3, J3,4 = 10.4 Hz, 3-Hα), 5.78–5.06 (2.75 H, 2-H, 3-Hβ, 4-H),
4.34–4.04 (2.25 H, 5-Hα, 6A-H, 6B-H), 3.74 (0.75 H, 5-Hβ), 2.11–1.99 (m, 12 H, 4
OAc). C22H24F3NO10 (518). FAB-MS (positive mode, matrix: NBOH with NaI):
m/z = 519 (M)+, 542 (M+Na)+.
N-(2-Trifluoromethylphenyl)-O-(2,3,4,6-tetra-O-acetyl-α,β-D-
glucopyranosyl) Trifluoroacetimidate (16Ab)
Following general procedure D, from 5A (340 mg, 1 mmol) and 15b (300 mg,
1.1 mmol) 16Ab (211 mg, 36%) was obtained as white foam. Rf (toluene/ethyl
1
acetate, 6:1) 0.31, α/β 1:2. H NMR (250 MHz, CDCl3): δ Rotamere. 7.33–6.77
(m, 4 H, 3ꢁ-H, 4ꢁ-H, 5ꢁ-H, 6ꢁ-H), 6.51 (mc, 0.34 H, 1-Hα), 5.76 (mc, 0.66 H, 1-Hβ),
5.31–5.07 (m, 3 H, 2-H, 3-H, 4-H), 4.33–4.03 (dddd, 2 H, Jgem = 12.4, J6A,5
=
4.5, J6B,5 = 2.4 Hz, 6A-H, 6B-H), 3.83–3.61 (m, 1 H, 5-H), 2.10–2.03 (m, 12 H,
4 OAc). C23H23F6NO10 (587.43). FAB-MS (positive mode, matrix: NBOH with
NaI): m/z = 587 (M)+, 610 (M+Na)+.
N-(2-Methoxyphenyl)-O-(2,3,4,6-tetra-O-acetyl-α,β-D-
glucopyranosyl) Trifluoroacetimidate (16Ac)
Following general procedure D, from 5A (340 mg, 1 mmol) and 15c (245 mg,
1 mmol) 16Ac (197 mg, 36%) was obtained as yellowish oil. Rf (toluene/ethyl
acetate, 4:1) 0.36, α/β 1:5. 1H NMR (250 MHz, CDCl3): δ Rotamere. 6.55 (0.2 H,
1-Hα), 5.80 (0.8 H, 1-Hβ), 5.57–5.08 (m, 3 H, 3 ring protons), 4.34–3.63 (m, 6 H,
OCH3, 4 ring protons), 2.11–1.98 (m, 12 H, 4 OAc). C23H26F3NO11 (549).
N-(2-Chloro-6-methylphenyl)-O-(2,3,4,6-tetra-O-acetyl-α,β-D-
glucopyranosyl) Trifluoroacetimidate (16Ad)
Following general procedure D, from 5A (340 mg, 1 mmol) and 15d
(265 mg, 1 mmol) 16Ad (173 mg, 32%) was obtained as clear oil. Rf (toluene/

N-Aryl-O-glycosyl Haloacetimidates as Glycosyl Donors
73
ethyl acetate, 6:1) 0.36, α/β 3:2. 1H NMR (250 MHz, CDCl3): δ Rotamere.
7.36–7.02 (m, 3 H, 3ꢁ-H, 4ꢁ-H, 5ꢁ-H), 6.38 (0.65 H, 1-Hα), 6.14 (0.35 H, 1-Hβ),
5.49–4.98 (m, 3 H, 2-H, 3-H, 4-H), 4.27–3.97 (m, 3 H, 5-H, 6A-H, 6B-H), 2.08 (s, 3
H, CH3), 2.05–1.91 (m, 12 H, 4 OAc). C23H25ClF3NO10 (567.94). FAB-MS (posi-
tive mode, matrix: NBOH with NaI): m/z = 590 (M+Na)+, 740 (M+NaI+Na)+.
N-Phenyl-O-(2,3,4,6-tetra-O-benzyl-α,β-D-
glucopyranosyl) Trifluoroacetimidate (16Ba)
Following general procedure D, from 5B (540 mg, 1 mmol) and 15a (230 mg,
1.1 mmol) 16Ba (320 mg, 45%) was obtained as clear syrup. Rf (toluene/ethyl
1
acetate, 9:1) 0.69. H NMR (250 MHz, CDCl3): δ 7.43–6.68 (m, 25 H, 2ꢁ-H, 3ꢁ-
H, 4ꢁ-H, 5ꢁ-H, 6ꢁ-H, 4 Ph), 3.80–3.58 (m, 15 H, 1-H, 2-H; 3-H, 4-H, 5-H, 6A-H,
6B-H, 4 CH2Ph). C42H40F3NO6 (711). FAB-MS (positive mode, matrix: NBOH
with NaI): m/z = 711 (M)+, 734 (M+Na)+.
N-(2-Trifluoromethylphenyl)-O-(2,3,4,6-tetra-O-benzyl-α,β-D-
glucopyranosyl) Trifluoroacetimidate (16Bb)
Following general procedure D, from 5B (540 mg, 1 mmol) and 15b
(300 mg, 1.1 mmol) 16Bb (405 mg, 52%) was obtained as clear syrup. Rf
(toluene/ethyl acetate, 9:1) 0.61, α/β 1:5. 1H NMR (250 MHz, CDCl3): δ
7.53–6.65 (m, 24 H, 3ꢁ-H, 4ꢁ-H, 5ꢁ-H, 6ꢁ-H, 4 Ph), 6.44 (d, 0.17 H, J1,2 = 3.8
Hz, 1-Hα), 5.67 (d, 0.83 H, J1,2 = 8.0 Hz, 1-Hβ), 5.02–4.43 (m, 8 H, 4 CH2Ph),
4.08–3.39 (m, 6-H, 2-H, 3-H, 4-H, 5-H, 6A-H, 6B-H). C43H39F6NO6 (779). FAB-
MS (positive mode, matrix: NBOH with NaI): m/z = 779 (M)+, 802 (M+Na)+.
N-(2-Methoxphenyl)-O-(2,3,4,6-tetra-O-benzyl-α,β-D-
glucopyranosyl) Trifluoroacetimidate (16Bc)
Following general procedure D, from 5B (540 mg, 1 mmol) and 15c (245 mg,
1.1 mmol) 16Bc (310 mg, 42%) was obtained as yellowish oil. Rf (toluene/ethyl
acetate, 9:1) 0.60. 1H NMR (250 MHz, CDCl3): δ 7.40–6.67 (m, 24 H, 3ꢁ-H, 4ꢁ-H,
5ꢁ-H, 6ꢁ-H, 4 Ph), 5.01–3.58 (m, 18 H, OCH3, 1-H, 2-H, 3-H, 4-H, 5-H, 6A-H,
6B-H, 4 CH2Ph). C43H42F3NO7 (742).
N-(2-Chloro-4-methylphenyl)-O-(2,3,4,6-tetra-O-benzyl-α,β-D-
glucopyranosyl) Trifluoroacetimidate (16Bd)
Following general procedure D, from 5B (540 mg, 1 mmol) and 15d
(265 mg, 1.1 mmol) 16Bd (743 mg, 98%) was obtained as colorless oil. Rf
(toluene/ethyl acetate, 2:1) 0.93. 1H NMR (250 MHz, CDCl3): δ Rotamere.
7.37–6.85 (m, 23 H, 3ꢁ-H, 4ꢁ-H, 5ꢁ-H, 4 Ph), 5.54 (1 H, 1-Hβ), 4.93–4.42 (m,

U. Huchel et al.
74
8 H, 4 CH2Ph), 3.92–3.11 (m, 6 H, 2-H, 3-H, 4-H, 5-H, 6A-H, 6B-H), 2.02 (s, 3
H, CH3). C43H41ClF3NO6 (760.24). EI-MS: m/z = 759 (M H)+.
ACKNOWLEDGEMENTS
This work was supported by the Deutsche Forschungsgemeinschaft, the Fonds
der Chemischen Industrie, the Bundesministerium fu¨r Erna¨hrung, Land-
wirtschaft und Forsten, and BASF AG, Ludwigshafen.
REFERENCES AND NOTES
1. Schmidt, R.R. New methods for the synthesis of glycosides and oligosac-
charides—are there alternatives to the Koenigs-Knorr method? Angew. Chem.
Int. Ed. Engl. 1986, 25, 212–235.
2. Schmidt, R.R.; Kinzy, W. Anomeric oxygen activation for glycoside synthesis. The
trichloroacetimidate method. Adv. Carbohydr. Chem. Biochem. 1994, 50, 21–123.
3. Zhu, X.; Schmidt, R.R. New principles of glycoside bond formation. Angew. Chem.
Int. Ed. 2009, 48, 1900–1935.
4. Schmidt, R.R.; Michel, J.; Roos, M. Direkte Synthese von O-α- und O-β-
Glycosylimidaten. Liebigs Ann. Chem. 1984, 1343–1357.
5. Schmelzer, U.; Zhang, Z.; Schmidt, R.R. Dichloro-cyano-acetimidates as glycosyl
donors. J. Carbohydr. Chem. 2007, 26, 223–238.
6. Michel, J. α- und β-O-Glycosylimidate: Ihre Herstellung und Anwendung in der
Glycosid- und Oligosaccharid-Synthese. Dissertation Universita¨t Konstanz, 1983. Ver-
lag W. Hartung-Gorre, Konstanz, ISBN-3-923200-24-2.
7. Huchel, U. Neue Methoden zur diastereoselektiven Glycosylierung. Dissertation,
Universita¨t Konstanz, 1998, Verlag Papierflieger, Clausthal-Zellerfeld, ISBN 3-89720-
221-2.
8. Adinolfi, M.; Barone, G.; Iadonisi, A.; Schiatarella, M. Iodine/triethylsilane as a
convenient promoter system for the activation of disarmed glycosyl trichloro- and N-
(phenyl)trifluoroacetimidates. Synlett 2002, 269–279; Adinolfi, M.; Iadonisi, A.; Ravida`,
A.; Schiatarella, M. Versatile use of Ytterbium (III) Triflate and acid washed molec-
ular sieves in the activation of Glycosyl Trifluoroacetimidate Donors. Assemblage of
a biologically relevant Tetrasaccharide sequence of Globo H. J. Org. Chem. 2005, 70,
5316–5319.
9. Yu, B.; Tao, H. Glycosyl trifluoroacetimidates. Part 1: preparation and application
as new glycosyl donors. Tetrahedron Lett. 2001, 42, 2405–2409; Yu. B.; Tao, H. Glycosyl
trifluoroacetimidates. Part 2. Synthesis of dioscin and xiebai saponin I. J. Org. Chem.
2002, 67, 9099–9102.
10. Lee, J. B.; Nolan, T.J. Sugar Esters: III. New reagent for deoxyhalo sugar prepara-
tion. Can. J. Chem. 1966, 44, 1331.
¨
11. Goerdeler, J.; Panshiri, F. M.; Vollrath, W. Uber Imidoyl–isothiocyanate III. Chem.
Ber. 1975, 108, 3071–3078.
12. For a discussion of anomeric O-acylation and O-alkylation reactions see reference
1 and Schmidt, R.R. Displacement by substitution processes: synthesis of glycosides.
Comprehensive Organic Synthesis, Vol. 6, Trost, B.M.; Fleming, I.; Winterfeldt, E. Eds.,
Pergamon Press, Oxford, 1991, pp. 33–64.

N-Aryl-O-glycosyl Haloacetimidates as Glycosyl Donors
75
13. Ito, Y.; Ogawa, T. Benzeneselenenyltriflate as a promoter of thioglycosides: a
new method for O–glycosylation using thioglycosides. Tetrahedron Lett. 1988, 29,
1061–1064.
14. Pougny, J.R.; Jacquinet, J.C.; Nasr, M.; Duchet, D.; Milat, M.L.; Sinay¨, P. A novel
synthesis of 1,2-cis-disaccharides. J. Am. Chem. Soc. 1977, 99, 6762–6763.
15. Garegg, P.J.; Hultberg, H.; Wallin, S.A. A novel reductive ring-opening of carbohy-
drate benzylidene acetals. Carbohydr. Res. 1982, 108, 97–101.
16. Schmidt, R. R.; Stumpp, M. Glycosylimidate, 10. Glycosylphosphate aus Glycosyl
(trichloracetimidaten). Liebigs Ann. Chem. 1984, 680–691.
17. Petrova, T.D.; Savchenko, T.I.; Platonov, V.E.; Yacobson, G.G. Preparation and sev-
eral reaction of N-(pentafluorophenyl)haloacetimidoyl chlorides. Investiya Sibirskogo
Otdeleniya Akademii Nank SSSR, Seriya Khimicheeskikh Nank 1981, 5, 109–116.
18. Liptak, A.; Jodal, I.; Nanasi, P. Stereoselective ring-cleavage of 3-O-benzyl- and
2,3-di-O-benzyl-4,6-O-benzylidenehexopyranoside derivatives with the LiAlH4–AlCl3
reagent. Carbohydr. Res. 1975, 44, 1–11.
19. Hanessian, S.; Bacquet, C.; Leliang, N. Chemistry of the glycosidic linkage. Excep-
tionally fast and efficient formation of glycosides by remote activation. Carbohydr. Res.
1980, 80, C17; Hanessian, S. In Preparative Carbohydrate Chemistry Chapter 16: Gly-
coside Synthesis Based on the Remote Activation Concept: An Overview. Marcel Dekker,
Inc., New York, 1997, pp. 381–388, and references therein.
20. Katriztky, A.R.; Yang, B.; Semenzin, D. (Trifluoroacetyl)benzotriazole: a conve-
nient trifluoroacetylating reagent. J. Org. Chem. 1997, 62, 726–728.