Glycosyl hydroperoxides

Article abstract of DOI:10.1016/j.carres.2012.12.023

Synthesis of glycosyl hydroperoxides derived from 2,3,4,6-tetra-O-benzyl-d- glucopyranose and 2,3,4,6-di-O-isopropylidene-d-mannofuranose was performed via a Schmidt's imidate intermediate with hydrogen peroxide in an ethyl ether solution in the presence of an acid catalyst. Separation of the α- and β-anomers of the glycosyl hydroperoxides was achieved by chromatography.

Full text of DOI:10.1016/j.carres.2012.12.023

Carbohydrate Research 369 (2013) 54–57
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Carbohydrate Research
journal homepage: www.elsevier.com/locate/carres
Glycosyl hydroperoxides
⇑
Barbara Szechner, Bartłomiej Furman, Marek Chmielewski
Institute of Organic Chemistry of the Polish Academy of Sciences, Kasprzaka 44/52, 01-224 Warsaw, Poland
a r t i c l e i n f o
a b s t r a c t
Article history:
Synthesis of glycosyl hydroperoxides derived from 2,3,4,6-tetra-O-benzyl-D-glucopyranose and 2,3,4,6-
Received 7 November 2012
Received in revised form 29 December 2012
Accepted 31 December 2012
Available online 9 January 2013
di-O-isopropylidene-
hydrogen peroxide in an ethyl ether solution in the presence of an acid catalyst. Separation of the
- and b-anomers of the glycosyl hydroperoxides was achieved by chromatography.
Ó 2013 Elsevier Ltd. All rights reserved.
D-mannofuranose was performed via a Schmidt’s imidate intermediate with
a
Keywords:
Glycosidation
O-Glycosyl trichloroacetimidates
Glycosyl hydroperoxides
1. Introduction
ceed with high asymmetric induction and the crucial role played
by the counter ion was demonstrated.9
Recently, we have reported that the oxidation of 2-deoxysugars
or their glycosides to the corresponding glycosyl hydroperoxides
can be performed with hydrogen peroxide in the presence of an
acid catalyst using several reaction conditions.1,2 Glycosyl hydro-
peroxides derived from 2-deoxysugars 1 and 2,1,2 similarly to those
derived from 2,3-unsaturated sugars 3,3 are relatively stable; they
can be purified by silica gel chromatography and stored for weeks
in the refrigerator without visible decomposition. Easy synthesis of
stable hydroperoxides from 2-deoxy- and from 2,3-unsaturated
sugars has been rationalized as the readiness of these sugars to
form a glycosyl cation which can add the hydrogen peroxide mol-
ecule. 2-Deoxy- and 2,3-unsaturated-sugars are known to split off
easily an anomeric hydroxy- or alkoxy group.6,7 The proportion of
anomers is controlled by the kinetics of the addition. Epimerization
at the anomeric carbon atom has never been observed. It is worth
noting that DFT calculation of the conformational behavior of the
2. Results and discussion
Contrary to 2-deoxysugars, fully hydroxylated congeners elimi-
nate an alkoxyl or hydroxyl from the anomeric center to form a gly-
cosyl cation under conditions which cause decomposition of the
hydroperoxide group, therefore formation of the glycosyl hydroper-
oxide, according to our standard procedure, cannot be performed.
This prompted us to use sugars with an activated anomeric substitu-
ent. To this end we employed the well-known Schmidt’s trichloro-
acetimidates 4–6 obtained by the known procedures.10
Previously used methods based on: 50% hydrogen peroxide and
molybdenum trioxide, proposed by Snatzke and co-workers4 and
Taylor and co-workers,5 hydrogen peroxide in dioxane in the pres-
ence of concentrated sulfuric acid or a solution of hydrogen perox-
ide in tert-butanol2 when applied to imidates 4–6 did not provide
the expected hydroperoxides. Instead, hydrolysis of the trichloro-
acetimidate group took place resulting in sugars with the free ano-
meric hydroxyl group. These results impelled us to apply a method
of glycosylation with rigorously anhydrous reaction conditions.
This approach proved to be fully successful.
anomeric peroxy group shows for the
a-anomer hydroperoxide
higher anomeric effect than for the hydroxy (alkoxy) group.8
CH2OR
O
CH2OBn
BnOH2C
O
OOH
O
OBn
RO
BnO
OOH
OOH
The method based on etheral solution of hydrogen peroxide in
the presence of an acid catalyst2,5,11 led to the formation of the ex-
pected hydroperoxides. As acid catalysts we used sulfuric acid or
BF3 etherate. To remove traces of water, molecular sieves were
added to the reaction mixture. Compound 4 at À30 °C in the pres-
ence of BF3 etherate provided glucosyl hydroperoxides 7 and 8 in a
ratio of about 2.5:1, respectively and in 46.1% yield, whereas in the
presence of sulfuric acid, hydroperoxides 7 and 8 were formed in a
ratio of about 6:1, respectively and in 40.7% yield. On the other
OBn
2
3
1
R: Bn, Ac, Silyl
Compounds 1–3 were used for enantioselective epoxidation of
electrophilic olefins. The epoxidation reactions were shown to pro-
⇑
Corresponding author.
E-mail address: chmiel@icho.edu.pl (M. Chmielewski).
0008-6215/$ - see front matter Ó 2013 Elsevier Ltd. All rights reserved.
http://dx.doi.org/10.1016/j.carres.2012.12.023

B. Szechner et al. / Carbohydrate Research 369 (2013) 54–57
55
O
CH2OBn
HN
CH2OBn
HN
O
BnO
O
O
O
OBn
CCl3
CCl3
OBn
O
O
O
O
O
CCl3
NH
O
BnO
BnO
BnO
4
5
6
O
O
CH2OBn
CH2OBn
OOH
CH2OBn
OOH
BnO
O
O
OBn
O
O
OBn
O
O
O
OBn
O
O
O
O
BnO
OOH
BnO
OOH
BnO
BnO
8
BnO
11
9
7
10
CH3
O
O
CH2OBn CH3
O OOCOCH3
CH2OBn
OOCOCH 3
CH3
O
O
O
OBn
O
O
O
OBn
CH3
CH3
CH3
O
O
O
OOCOCH3 BnO
CH3
OOCOCH 3
CH3
BnO
BnO
13
BnO
12
14
15
hand compound 6 at À30 °C in the presence of BF3ÁEt2O provided
hydroperoxides 9 and 10 in the ratio 1:1.6, respectively and in
57.5% yield, whereas in the presence of sulfuric acid, hydroperox-
ides 9 and 10 were formed in the ratio of about 1:8.5, respectively
internal standard. Chemical shifts are reported as d values in
ppm and coupling constants are in Hertz. Infrared spectra were re-
corded on a FT-IR-1600 Perkin–Elmer spectrophotometer. The
optical rotations were measured with a JASCO J-2000 digital polar-
imeter. Thin layer chromatography (TLC) was performed on alumi-
num sheet Silica Gel 60 F254 (20 Â 20 Â 0.2) from Merck. Column
chromatography was carried out using Merck silica gel (230–400
mesh).
in 45% yield. a- and b-Glycosyl hydroperoxides can be separated by
chromatography. However, since the hydroperoxides thus ob-
tained were contaminated with minute amounts of trichloroaceta-
mide, for the further purification all hydroperoxides were
converted into the corresponding peroxides 12–15 by treatment
with 2-methoxypropene, following the known procedure.2 Subse-
quently pure hydroperoxides 7–10 were recovered by acidic
hydrolysis.2
3.2. General procedure of glycosyl hydroperoxides formation
To a solution of sugar trichloroacetimidate (2 mmol) in toluene
(10 mL) powdered MS 4 Å (50 mg) and a solution of H2O2 in diethyl
ether (ca. 2 M, 10 mL) were added. The reaction mixture was
cooled to À30 °C and boron trifluoride etherate (0.1 mL) or concen-
trated sulfuric acid (0.1 mL) was then added and the reaction was
monitored by TLC. When the reaction was completed the mixture
was diluted with DCM and washed with water until neutral. After
drying (Na2SO4) and evaporation of solvents the residue was flash-
Galactosyl trichloroacetimidate 5 under both reaction condition
gave a complicated mixture of decomposition products in which
we succeeded to identify 2,3,4,6-tetra-O-benzyl-D-galactonolac-
tone (11).12 This result suggests the initial formation of the glyco-
syl hydroperoxide which subsequently undergoes elimination of a
water molecule to provide the lactone.
Proportion of the
a and b anomers of 2,3;5,6-di-O-iso-
propylidenemannofuranosyl hydroperoxides 9 and 10, with a
significant predominance of the b anomer, resulted from the
reaction with the use of H2SO4. The steric course of the reaction
indicates the formation of the glycosyl hydroperoxide with the
participation of a glycosyl donor, supporting SN2-type mechanism,
suggested by Schmidt and co-workers.13
chromatographed affording a- and b-anomers. To remove contam-
ination with trichloroacetamide, products were converted into
mixed peroxides (with 2-methoxypropene) from which hydroper-
oxides were recovered by acidic hydrolysis following our previ-
ously reported precedure.2
It should be noted that formation of tert-butyl glycosyl perox-
ides has been achieved in the past from 2,3,4,6-tetra-O-acetylman-
nosyl or rhamnosyl bromides via the cyclic 1,2-peroxyorthoester
stage,14 or from 2,3,4,6-tetra-O-benzylglucosyl fluoride via nucleo-
philic substitution.15 Other mixed peroxides were formed via the
addition of glycosyl hydroperoxides to vinyl ether grouping.2,16
Our experiments and previous results14,15 have shown that,
contrary to 2-deoxysugars and 2,3-unsaturated sugars, the forma-
tion of glycosyl hydroperoxides derived from fully hydroxylated
monosaccharides, requires activation of the anomeric center.
3.3. 2,3,4,6-Tetra-O-benzyl-a- and b-D-glucopyranosyl
hydroperoxides (7 and 8)
A mixture of glucosyl trichloroacetimidates 4 in the presence of
BF3 etherate provided hydroperoxides 7 and 8 in a ratio 2.5:1 in
46.1% yield, whereas in the presence of H2SO4 7 and 8 were
obtained in
a ratio 6:1 in 40.7% yield. Contaminated with
trichloroacetamide hydroperoxides 7 and 8 were transformed into
corresponding peroxides 12 and 13 which after chromatographical
purification were deprotected to afford analytically pure 7 and 8,
respectively.
3. Experimental
3.4. 2,3,4,6-Tetra-O-benzyl-a-D-glucopyranosyl (1-methoxy-1-
methyl)ethyl peroxide (12)
3.1. General methods
[a]
+87 (c 1.14, CCl4); 1H NMR (C6D6) d: 7.31–7.04 (m, 20 H,
D
aromatic), 5.67 (d, 1H, J 4.22 Hz, H-1), 4.98–4.90 (m, 2H, 2 PhCH),
1H and 13C NMR spectra were recorded on a Brucker DRX 500
Avance Spectrometer, using deuteriated solvents and TMS as an

56
B. Szechner et al. / Carbohydrate Research 369 (2013) 54–57
4.73–4.66 (m, 1H, PhCH), 4.59 (d, 1H, J 11.5 Hz, PhCH), 4.48–4.42
(m, 2H, 2 PhCH), 4.37–4.33 (m, 3H, 2 PhCH, H-5), 4.12 (ps t, 1H, J
9.7 Hz, H-3), 3.96 (ps t, 1H, J 9.5 Hz, H-4), 3.85 (dd, 1H, J6,6a 10.8,
J5,6 3.2 Hz, H-6), 3.76 (dd, 1H, J6,6a 10.8, J5,6a 1.5 Hz, H-6a), 3.66
(dd, 1H, J2,3 10.0, J1,2 4.3 Hz, H-2), 3.2 (s, 3H, OMe), 1.38 and 1.35
(2 s, 6H, 2 Me); 13C NMR (C6D6) d: 139.7, 139.4, 139.1, 138.7,
128.53, 128.52, 128.42, 128.39, 128.29, 128.06, 127.93, 127.89,
127.87, 127.62, 127.55, 127.44, 105.8, 99.8, 82.3, 80.6, 78.1, 75.5,
75.1, 73.5, 72.8, 71.8, 69.19, 49.20, 23.08, 23.04; IR (CCl4) v:
3033, 2943, 2867, 1102, 1073 cmÀ1; Anal. calcd for C38H44O8:
C,72.59, H, 7.05, found: C, 72.65, H, 7.10.
3.9. 2,3;5,6-Di-O-isopropylidene-
(1-methoxy-1-methyl)ethyl peroxide (14)
a-D-mannofuranosyl
[a]
D +63.5 (c 1.1, CCl4); 1H NMR (C6D6) d: 5.72 (s, 1 H, H-1), 4.56
(ddd,1H, J4,5 7.7, J5,6 5.7, J5,6a 6.4 Hz, H-5), 4.44 (d, 1H, J2,3 5.9 Hz, H-
2), 4.38 (dd, 1H, J2,3 5.9, J3,4 3.4 Hz, H-3), 4.25 (dd, 1H, J4,5 7.7, J3,4
3.7 Hz, H-4), 4.22 (dd, 1H, J6,6a 8.5, J5,6 5.7 Hz, H-6), 4.10 (dd, 1H,
J6,6a 8.5, J5,6a 6.4 Hz, H-6a), 3.21 (s, 3H, OMe), 1.43 (s, 3H, Me),
1.33 (s, 3H, Me), 1.30 (s, 6H, 2ÁMe), 1.27 (s, 3H, Me), 1.04 (s, 3H,
Me); 13C NMR (C6D6) d: 112.7, 109.8, 109.0, 105.2, 83.3, 82.1,
79.9, 73.6, 67.2, 49.0, 27.0, 26.1, 25.6, 23.0, 22.9; IR (KBr) v: 2994,
2946, 1382, 1265, 1212 cmÀ1; Anal. calcd for C16H28O8: C, 55.16,
H, 8.10, found: C, 55.22, H, 8.07.
3.5. 2,3,4,6-Tetra-O-benzyl-b-D-glucopyranosyl (1-methoxy-1-
methyl)ethyl peroxide (13)
3.10. 2,3;5,6-Di-O-isopropylidene-b-
(1-methoxy-1-methyl)ethyl peroxide (15)
D-mannofuranosyl
[a
]
D À1.14 (c 1.0, CCl4); 1H NMR (C6D6) d: 7.44–7.0 (m, 20H, aro-
matic), 5.14 (d, 1H, J1,2 8.4 Hz, H-1), 5.04–4.94 (m, 2H, 2 PhCH),
4.85–4.76 (m, 2H, 2 PhCH), 4.66 (m, 2H, 2 PhCH), 4.48–4.36 (m,
2H, 2 PhCH), 3.77 (ps t, 1H, J 9.5 Hz), 3.71–3.65 (m, 3H, H-5, H-6,
H-6a), 3.54 (ps t, 1H, J 8.6 Hz) 3.44–3.40 (dm, J1,2 8.6 Hz, H-2),
3.29 (s, 3H, OMe), 1.43 and 1.35 (2 s, 6H, 2 Me); 13C NMR (C6D6)
d: 139.45, 139.23, 139.02, 138.98, 128.52, 128.49, 128.47, 128.44,
128.29, 127.90, 127.85, 127.63, 127.61, 127.54, 106.08, 105.49,
85.36, 80.37, 77.84, 75.58, 75.43, 74.91, 74.88, 73.58, 69.14,
49.12, 23.46, 22.77; IR (CCl4) v: 2904, 2869, 1213, 1072 cmÀ1; Anal.
calcd for C38H44O8: C,72.59, H, 7.05, found: C, 72.64, H, 6.99.
[
a
]
À52.5 (c 1.2, CCl4); 1H NMR (C6D6) d: 5.16 (d, 1H, J 4.7 Hz,
D
H-1), 4.63 (m, 1H, H-5), 4.26–4.22 (m, 2H, H-6, H-3), 4.17–4.11 (m,
2H, H-2, H-6a), 3.51 (dd, 1H, J 7.4, 4.0 Hz, H-4), 3.23 (s, 3H, OMe),
1.54, 1.47, 1.37, 1.32, 1.31, 1.14 (6Ás, 18H, 6ÁMe); 13C NMR (C6D6)
d: 114.0, 109.1, 105.4, 104.0, 80.3, 79.2, 78.3, 74.0, 67.3, 49.1,
27.2, 25.8, 25.7, 25.6, 23.1, 23.0; IR (CCl4) v: 2988, 2941, 1381,
1371, 1214 cmÀ1; Anal calcd for C16H28O8: C, 55.16, H, 8.10, found:
C, 55.08, H, 8.13.
3.11. 2,3;5,6-Di-O-isopropylidene-a-D-mannofuranosyl
hydroperoxide (9)
3.6. 2,3,4,6-Tetra-O-benzyl-a-D-glucopyranosyl hydroperoxide
(7)
[a]
+43 (c 1.11, CHCl3); 1H NMR (CDCl3) d: 9.19 (s, 1H, OOH),
D
5.44 (s, 1H, H-1), 4.78 (dd, 1H, J2,3 5.8, J3,4 3.7 Hz, H-3), 4.65 (d,
1H, J2,3 5.9 Hz, H-2), 4.43 (m, 1H, H-5), 4.18 dd, 1H, J4,5 7.0, J3,4
3.6 Hz, H-4), 4.12 (d, 2H, J5,6 5.4 Hz, H-6, H-6a), 1.48, 1.47, 1.39,
1.33 (4Ás, 12H, 4ÁMe), 13C NMR (CDCl3) d: 113.2, 110.5, 109.3,
82.6, 81.5, 79.4, 73.2, 66.4, 26.8, 25.9, 25.1, 24.5; IR (CHCl3) v:
3519, 2940, 1383, 1375, 1069 cmÀ1; Anal. calcd for C12H20O7: C,
52.17, H, 7.30, found: C, 52.27, H, 7.24.
[a]
D +31.3 (c 1.16, CHCl3); 1H NMR (CDCl3) d: 9.25 (s, 1H, OOH),
7.37–7.24 (m, 18 H, aromatic), 7.15–7.10 (m, 2H, aromatic), 5.32 (d,
1H, J 4.1 Hz, H-1), 4.92 (d, 1H, PhCH) and 4.82–4.69 (m, 4 PhCH)
and 4.59–4.46 (m, 3 PhCH), 3.96–3.91 (m, 1H, H-4); 3.85 (ps t,
1H, J 9.5, H-5); 3.72–3.64 (m, 3H, H-2, H-6, H-6a), 3.56 (ps t, J
9.5, H-3); 13C NMR (125 Hz, CDCl3) d: 138.5, 138.0, 137.63,
137.58, 128.51, 128.43, 128.39, 128.37, 128.05, 128.02, 127.96,
127.85, 127.74, 127.67, 101.1, 81.6, 79.0, 77.5, 75.7, 75.1, 73.6,
3.12. 2,3;5,6-Di-O-isopropylidene-b-D-mannofuranosyl
hydroperoxide (10)
73.4, 71.0, 68.6; IR (film) v: 3484, 3282, 2913, 1453, 1047 cmÀ1
Anal. calcd for C34H36O7: C, 73.36, H, 6.52, found: C, 73.12, H, 6.65.
;
[
a
]
D À19.9 (c 0.52, CHCl3); 1H NMR (CDCl3) d: 9.48 (s, 1H, OOH),
3.7. 2,3,4,6-Tetra-O-benzyl-b-D-glucopyranosyl hydroperoxide
(8)
5.31 (d, 1H, J1,2 3.9 Hz, H-1), 4.84–4.80 (m, 2H, H-6, H-6a), 4.42 (dt,
1H, J5,6 = J5,6a 6.3, J4,5 3.6 Hz, H-5), 4.33 (dd, 1H, J2,3 9.1, J3,4 6.3 Hz,
H-3), 3.97 (dd, 1H, J4,5 6.2. J3,4 4.2 Hz, H-4), 1.55, 1.49, 1.38, 1.35
(4Ás, 16H, 4ÁMe); 13C NMR (CDCl3) d: 114.9, 109.4, 104.1, 80.4,
78.9, 78.8, 73.8, 66.7, 26.7, 25,2, 25.1, 24.9; IR (CHCl3) v: 3522,
3337, 2991, 2940, 1384, 1374, 1069, 1037 cmÀ1; Anal. calcd for
[a]
+28 (c 1.13, CHCl3); 1H NMR (CDCl3) d: 9.75 (s, 1H, OOH),
D
7.37–7.24 (m, 18 H, aromatic), 7.15–7.10 (m, 2H, aromatic), 5.0
(d, 1H, J 7.1 Hz, H-1), 4.90–4.80 (m, 2H, 2 PhCH); 4.81–4.73 (m,
2H, 2 PhCH), 4.53–4.45 (m, 2H, 2 PhCH), 3.75 (m, 4H), 3.61–3.55
(m, 2H); 13C NMR (CDCl3) d: 138.4, 137.9, 137.8, 137.4, 128.49,
128.39, 128.36, 128.21, 128.02, 127.96, 127.93, 127.81, 127.79,
127.64, 105.9, 84.5, 79.4, 76.7, 75.4, 75.0, 74.6, 74.2, 73.5, 68.6;
IR (film) v: 3450, 2926, 2869, 1454, 1098 cmÀ1; Anal. calcd for
C
12H20O7: C, 52.17, H, 7.30, found: C, 52.03, H, 7.26.
Acknowledgement
Financial support by the European Union within European Re-
gional Development Fund, Project POIG.01.01.02.-14-102/09 is
gratefully acknowledged.
C34H36O7: C, 73.36, H, 6.52, found: C, 73.14, H, 6.39.
3.8. 2,3;5,6-Di-O-isopropylidene-a- and b-D-mannofuranosyl
hydroperoxides (9 and 10)
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