Homogeneous azidophenylselenylation of glucals

Article abstract of DOI:10.1016/j.mencom.2008.09.003

The homogeneous azidophenylselenylation of diversely protected mono-, di- and trisaccharide glucals was studied to evaluate the influence of protective groups, N₃ and I donors, temperature and solvent on the stereoselectivity of the formation of corresponding phenyl 2-azido-2-deoxy-1-seleno-α-D-gluco- and -manno-adducts.

Full text of DOI:10.1016/j.mencom.2008.09.003

Mendeleev
Communications
Mendeleev Commun., 2008, 18, 241–243
Homogeneous azidophenylselenylation of glucals
Yuri V. Mironov, Andrei A. Sherman and Nikolay E. Nifantiev*
N. D. Zelinsky Institute of Organic Chemistry, Russian Academy of Sciences, 119991 Moscow, Russian Federation.
Fax: +7 499 135 5328; e-mail: nen@ioc.ac.ru
DOI: 10.1016/j.mencom.2008.09.003
The homogeneous azidophenylselenylation of diversely protected mono-, di- and trisaccharide glucals was studied to evaluate the
influence of protective groups, N3 and I donors, temperature and solvent on the stereoselectivity of the formation of corresponding
phenyl 2-azido-2-deoxy-1-seleno-α-D-gluco- and -manno-adducts.
Table 1 APS reactions of triacetylglucal 1a (R1 = R2 = R3 = Ac).a
Glycosyl donors bearing an azido group at C-2 are important
intermediates for oligosaccharide synthesis especially for the
installation of α-galactosamine and α-glucosamine units.1 Among
the known methods2 for introduction of the azido group into
monosaccharide units, the azidophenylselenylation (APS reaction)
of glycals3 represents special interest as it allows the single-step
straightforward preparation of phenyl glycosides of corresponding
2-azido-2-deoxy-1-seleno-adducts, which could be directly used
as glycosyl donors.
Recently, we reported an efficient protocol4 for the APS
reaction in which a glycal is treated under homogenous con-
ditions with TMSN3 (instead of NaN3 used in others procedures3)
and Ph2Se2 in the presence of PhI(OAc)2 in dichloromethane
(DCM). This is an efficient stereoselective procedure for the
transformation of D-galactals into phenyl 2-azido-2-deoxy-
1-seleno-α-D-galactopyranosides, but in the case of triacetyl-
glucal 1a gave an inseparable mixture of gluco- and manno-
isomers 2a and 3a in a ratio of 2.7:1 (Scheme 1). Here we
describe the reaction conditions, i.e., solvent, temperature and
azide radical source, as well as the nature of blocking groups,
as factors influencing stereoselectivity in the APS reaction of
glucals. These characteristics are critical for the stereochemistry
of the azidonitration of glucals.2 In addition, we studied the
applicability of APS reaction to the transformation of oligo-
saccharide glucals as such reactions open a direct way towards
corresponding lactosaminyl and 3'-sialyllactosaminyl derivatives
like compounds 2m–q, which could be considered as convenient
Azide
donor
2a:3a
ratio
Other
products
Entry Solvent T/°C
[I] donor
t/h
1
2
3
C6F6
PhMe –10
CCl4 –10
6
TMSN3 PhI(OAc)2 12 3.2:1
TMSN3 PhI(OAc)2 18 3.0:1
TMSN3 PhI(OAc)2 18 2.9:1
4
5
DCM –10
EtOAc –10
TMSN3 PhI(OAc)2
TMSN3 PhI(OAc)2 18 1.5:1
4
2.7:1
6
7
8
9
10
11
12
13
14
15
16
17
THF
MeCN –10
DMF
Et2O
–10
TMSN3 PhI(OAc)2
TMSN3 PhI(OAc)2 18
TMSN3 PhI(OAc)2 18
TMSN3 PhI(OAc)2 48 no reaction
TMSN3 PhI(OAc)2 48 no reaction
TMSN3 PhI(OAc)2 24 2.7:1
TMSN3 PhI(OAc)2 144 2.7:1
TMSN3 PhI(OAc)2 48 1.5:1
TMSN3 PhI(OAc)2 144 1.5:1
TMSN3 PhI(OAc)2 48
TMSN3 PhI(OAc)2 144
TMSN3 PhI=O
TMSN3 PhI=O
8
1.3:1
1:1
1:1
–10
–10
PriOH –10
DCM –23
DCM –40
EtOAc –23
EtOAc –40
MeCN –23
MeCN –40
DCM –10
1:1
1:1
2.2:1
3
18b DCM –10
24 2.2:1
19
20
21
DCM –10
DMF –10
DCM –10®
room tem-
perature
C2H4Cl2 78
C2H4Cl2 78
TBAN3 PhI(OAc)2 12 2.1:1
NaN3 PhI(OAc)2 24 1.9:1
4
4
48 no reaction
22
23
4
4
3
3
5:6, 2:1
5:6, 2:1
None IBA
aIn all entries the conversion was > 60% as determined by TLC and 1H NMR
spectroscopy. bIn entry 17 the reaction was performed according to standard
procedure4 while in entry 18 PhI=O was added after TMSN3 that enlarged
the reaction time.
OR3
N3
OR3
O
OR3
O
APS
reaction
synthetic blocks for the assembling of complex oligosaccharide
chains.
R2O
R1O
R2O
R1O
R2O
O
+
R1O
Commercially available triacetylglucal 1a was chosen as a
first model substrate in our study of APS reactions. The results
of experiments under varied conditions are summarized in
Table 1. The ratio of gluco- and manno-adducts 2a and 3a
was determined by integration of corresponding H-1 signals
[6.00 ppm (d, J1,2 3.6 Hz) for 2a; 5.47 ppm (br. s, J1,2 < 0.5 Hz)
for 3a]. All APS reactions gave the adducts in a high yield of
75–90% except for several cases noted in Table 1.
The solvent effect was studied first. Thus, the replacement
of DCM by a less polar solvent (C6F6, CCl4 or PhMe) leads to
an insignificant increase in the proportion of gluco-isomer 2a
(Table 1, entries 1–3), whereas the use of more polar solvents
(EtOAc, MeCN and THF) decreased the yield of 2a (entries 5–8)
and increased the formation of 3a. Solvents such as THF, DMF
and PriOH were not inert in the APS reaction (entries 6, 8, 10).
The insolubility of reagents in Et2O prevented the APS reaction
N3
SePh
SePh
1
2
3
N3
O
OAc
O
I
I
AcO
AcO
O
PhSe
O
O
4
5
OAc
SePh
O
AcO
AcO
I
O
O
6
Scheme 1 APS reaction of glucals 1.
– 241 –
© 2008 Mendeleev Communications. All rights reserved.

Mendeleev Commun., 2008, 18, 241–243
(entry 3). Unfortunately, the known methods for the introduc-
Table 2 APS reactions of diversely protected glucals.a,†
tion of other type of 4,6-O-acetal protections into carbohydrates7
are not efficient in the case of glucals. Thus, we had to focus on
the investigation of homo-3,4,6-tri-O-substituted glucal deriva-
tives 1e–l, which could be prepared from 1a in a high yield.8
The APS reaction proceeded non-selectively when an electron-
donating substituent was present in the acyl O-protecting group
(entry 4 in Table 1 vs. entries 4 and 5 in Table 2). The same results
were obtained in the case of alkyl substitutents at O(3) (entry 7).
In the case of tri-O-silylated glucals, the corresponding gluco-
products were formed stereospecifically when the bulky TIPS
Product(s) ratio
Entry
Glucal
R1
R2
R3
–CMe2–
–CMe2–
–CMe2–
and/or isolated yield
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
1b
1c
1d
1e
1f
1g
1h
1i
1j
1k
1l
1m
1n
1o
1p
1q
Ac
2b:3b, 1.7:1
2c:3c, 1:1
2d, 85%
2e:3e, 1:1
2f:3f, 1.6:1
2g:3g, 3.5:1
2h:3h, 1.3:1
2i:3i, 3:1
2j:3j, 1.5:1
2k, 81%
2l, 75%
2m:3m, 1:1, 89%
2n, 78%
2o, 87%
Piv
TIPS
Bz
Bz
Piv
Bz
Piv
MCA
Bn
TMS
TES
TIPS
TBS
Ac
TMS
TES
Ac
Piv
MCA MCA
Bn Bn
TMS TMS
TES TES
TIPS TIPS
TBS
Ac
TMS
TES
Ac
†
For typical procedure of APS reaction see ref. 4.
TBS
A
A
A
B
1p: 1H NMR, d: 6.26 (br. d, 1H, H-1, J1,2 6.0 Hz), 5.50 (m, 1H, H-8''),
5.38 (dd, 1H, H-7'', J7'',6'' 2.2 Hz, J7'',8'' 9.1 Hz), 5.36 (d, 1H, H-4', J4,3 3.2 Hz),
5.11 (m, 2H, H-2', NH), 4.92 (dd, 1H, H-3', J3,2 9.1 Hz, J3,4 3.0 Hz),
4.80 (m, 1H, H-4''), 4.57 (dd, 1H, H-2, J2,1 6.0 Hz, J2,3 2.0 Hz), 4.44 (d,
1H, H-1', J1,2 8.0 Hz), 4.40 (m, 1H, H-3), 4.37 (m, 1H, H-6A), 4.20 (m,
4H, H-6'A, H-6'B, H-9A'', H-9B''), 4.03 (m, 2H, H-6B, H-5''), 3.81 (m,
1H, H-5'), 3.71 (s, 3H, Me), 3.70 (m, 2H, H-4, H-5), 3.55 (d, 1H, H-6'',
J6,7 2.1 Hz), 2.47 (dd, 1H, H-3eq, J3,3 12.5 Hz, J3,4 4.3 Hz), 1.68 (t, 1H,
H-3eq, J3,3 = J3,4 = 12.3 Hz), 1.90–2.25 (m, 30H, Ac). 13C NMR, d: 169.5–
171.2 (C=O), 163.4 (C=O), 143.1 (C-1), 101.5 (C-2), 100.4 (C-1'), 97.3
(C-2'') 77.9, 75.3, 75.2, 74.0, 72.8, 71.9, 71.6, 71.5, 70.5, 68.9, 66.1,
64.4, 62.5, 61.8, 53.9 (C-5''), 39.2 (C-3''), 19.3–21.7 (Ac).
2p:3p, 75%
2q, 69%
TES
C
TES
aThe ratio of gluco- and manno-adducts were determined by integration of
corresponding H-1 signals in 1H NMR spectra [5.8–6.1 ppm (d, J1,2 4.5–5.5 Hz)
for gluco-adducts; 5.4–5.7 ppm (br. s, J1,2 < 0.5 Hz) for manno-adducts].
All APS reactions gave the products in total high yield (75–90%, as evaluated
by TLC and 1H NMR spectroscopy) except the cases noted.
R1O
R1O
OR1
OR1
CO2Me
O
CONH2
O O
OR1
O
OR1
OR1
O
1
OR1
O
R1O
R1O
1q: H NMR, d: 6.21 (br. d, 1H, H-1, J1,2 6.2 Hz), 4.41 (d, 1H, H-1',
R1O
AcHN
R1O
AcHN
O
J1',2' 7.9 Hz), 4.03 (m, 2H), 3.80–3.97 (m, 10H), 3.85 (m, 1H, H-2), 3.79
(m, 1H, H-3), 3.71–3.77 (m, 5H), 2.43 (dd, 1H, H-3eq, J3,3 12.8 Hz,
J3,4 4.1 Hz), 1.75 (t, 1H, H-3eq, J3,3 = J3,4 = 12.9 Hz), 0.80–1.10 (m,
135H, Et). 13C NMR, d: 142.3 (C-1), 100.4 (C-2), 100.0 (C-1'), 98.3
(C-2''), 74.0, 73.4, 71.6, 71.5, 71.2, 71.0, 70.5, 70.1, 69.8, 66.5, 63.1,
62.8, 60.1; 57.1, 53.0, 39.2 (C-3'').
2d: 1H NMR, d: 7.20–7.70 (m, 5H, Ar), 5.96 (d, 1H, H-1, J1,2 5.2 Hz),
4.06 (dd, 1H, H-3, J3,2 9.2 Hz, J3,4 9.6 Hz), 4.17 (dd, 1H, H-6, J6,5 4.9 Hz,
J6,6 11.7 Hz), 4.12 (t, 1H, H-3, J3,2 = J3,4 = 9.3 Hz), 3.84 (dd, 1H, H-2),
3.80 (br. d, 1H, H-6B, J6A,6B 11.5 Hz), 3.58 (t, 1H, H-4, J4,3 = J4,5 = 9.2 Hz),
1.05 (m, 21H, Pri). 13C NMR, d: 137.6 (ipso-Ph), 126.7–131.0 (Ar),
101.6 (Me2CH), 85.3 (C-1), 82.2 (C-4), 72.6 (C-3), 68.5 (C-6), 67.1 (C-2),
65.5 (C-5), 29.2, 19.0, 18.1, 12.8.
2k: 1H NMR, d: 7.25–7.80 (m, 5H, Ar), 5.93 (d, 1H, H-1, J1,2 4.5 Hz),
4.19 (m, 1H, H-5), 4.07 (m, 1H, H-6A), 4.02 (br. d, 1H, H-2, J2,1 4.7 Hz),
4.00 (m, 1H, H-4), 3.95 (m, 1H, H-3), 3.77 (m, 1H, H-3), 0.90–1.10 (m,
63H, Pri). 13C NMR, d: 127.0–132.2 (Ar), 85.2 (C-1), 80.5, 70.3, 64.9,
62.8, 59.9, 18.0 (Me), 12.6, 12.5, 12.2 (Pri).
2l: 1H NMR, d: 7.20–7.70 (m, 35H, Ar), 5.89 (d, 1H, H-1, J1,2 4.7 Hz),
4.21 (m, 1H, H-5), 4.07 (m, 1H, H-6A), 3.99 (br. d, 1H, H-2, J2,1 4.7 Hz),
3.95 (m, 1H, H-4), 3.73 (2H, H-3, H-6B) 0.70–0.90 (3s, 27H, But).
13C NMR, d: 127.0–135.2 (Ar), 85.7 (C-1), 79.3, 70.3, 64.5, 62.7, 60.1,
26.7–26.9 (Me), 19.1, 18.1, 15.2 (But).
2m: 1H NMR, d: 7.25–7.75 (m, 5H, Ar), 6.01 (d, 1H, H-1, J1,2 5.1 Hz),
5.36 (d, 1H, H-4', J4,3 3.2 Hz), 5.10 (m, 2H, H-2', H-3), 4.90 (dd, 1H,
H-3', J3,2 9.2 Hz, J3,4 3.1 Hz), 4.48 (d, 1H, H-1', J1,2 8.0 Hz), 4.40 (m,
1H, H-6A), 4.15 (m, 2H, H-6'A, H-6'B), 4.06 (m, 1H, H-6), 3.83 (m, 1H,
H-5'), 3.72 (m, 2H, H-4, H-5), 3.55 (dd, 1H, H-2, J2,1 5.1 Hz, J2,3 9.1 Hz),
2.00–2.20 (6s, 18H, Ac). 13C NMR, d: 169.3–170.9 (C=O), 137.6 (ipso-Ph),
126.6–129.8 (Ar), 101.0 (C-1'), 83.2 (C-1), 74.0, 71.5, 71.5, 70.8, 70.5,
67.4, 66.4, 63.1, 61.7, 60.7, 19.9–22.1 (Ac).
2n: 1H NMR, d: 7.25–7.75 (m, 5H, Ar), 6.01 (d, 1H, H-1, J1,2 5.1 Hz),
5.36 (d, 1H, H-4', J4,3 3.2 Hz), 5.10 (m, 2H, H-2', H-3), 4.90 (dd, 1H,
H-3', J3,2 9.2 Hz, J3,4 3.1 Hz), 4.48 (d, 1H, H-1', J1,2 8.0 Hz), 4.40 (m,
1H, H-6A), 4.15 (m, 2H, H-6'A, H-6'B), 4.06 (m, 1H, H-6), 3.83 (m, 1H,
H-5'), 3.72 (m, 2H, H-4, H-5), 3.55 (dd, 1H, H-2, J2,1 5.1 Hz, J2,3 9.1 Hz),
2.00–2.20 (6s, 18H, Ac). 13C NMR, d: 169.3–170.9 (C=O), 137.6 (ipso-Ph),
126.6–129.8 (Ar), 101.0 (C-1'), 84.2 (C-1), 74.2, 71.5, 71.3, 70.1, 70.4,
67.7, 65.2, 63.1, 61.4, 60.8, 19.9–22.1 (Ac).
2o: 1H NMR, d: 7.20–7.70 (m, 5H, Ar), 6.00 (d, 1H, H-1, J1,2 5.1 Hz),
4.41 (d, 1H, H-1', J1',2' 7.8 Hz), 4.03 (dd, 1H, H-6A, J6A,5 4.0 Hz, J6A,6B
11.8 Hz), 3.81–3.92 (m, 7H, H-2', H-3', H-4', H-5', H-6B, H-6A', H-6B'),
3.80 (m, 2H, H-2, H-3), 3.73–3.77 (m, 2H, H-4, H-5), 0.90–1.00 (m,
36H, CH2), 0.50–0.70 (m, 54H, Me). 13C NMR, d: 126.5–131.0 (Ar),
101.2 (C-1'), 82.2 (C-1), 74.0, 71.6, 71.5, 70.8, 70.5, 68.9, 66.5, 63.1,
62.0, 60.8.
R1O
R1O
R1O
R1O
OR1
OR1
A
B
C
(entry 9). The temperature affected the reaction time rather than
the ratio of gluco- and manno-adducts (entries 11–16) both in
the nonpolar and polar solvents.
The formation of an azide radical was supposed to be the
first step in azidonitration and APS reactions. Therefore, the
stereoselectivity of the addition of the azide radical to the double
bond controls the ratio of gluco- and manno-products. For the
generation of the azide radical, different combinations of the
donors of the azide anion and hypervalent iodine reagents could
be used (entries 17–20).5 Among them PhI(OAc)2/TMSN3 is
the combination of choice.4 Attempts to apply azidoiodinane 46
as a possible source of azide radicals (entry 22) resulted in the
formation of an unstable mixture of two adducts, presumably,
compounds 5 and 6. β-Gluco-configuration in dominating product
and α-manno-configuration in minor one were deduced from the
proton coupling constants in the H NMR spectrum.† Location
1
of the PhSe group at C-2 of both compounds followed from the
unusual high-field position of C-2 signals (46.3 and 46.4 ppm,
respectively) in the 13C NMR spectrum.† Formation of com-
pounds 5 and 6 could be connected with the oxidation of Ph2Se2
into PhSe+ under the action of a hypervalent iodine reagent, as
products 5 and 6 are formed in the presense of o-iodobenzoic
acid (IBA) and the absense of an azide donor (entry 23).
Thus, the studied variations of reaction conditions did not reveal
any protocol to run APS transformation with higher gluco-stereo-
selectivity than under initially proposed conditions [TMSN3, Ph2Se2,
PhI(OAc)2, DCM, –10 °C]. Therefore, we investigated further
the influence of blocking groups on the outcome of the APS
reaction. Special attention was paid to glucals with non-acetyl
protecting groups based on tendencies observed in azidonitra-
tion reactions.2(b)
The results of APS reaction of differently substituted glucals
are given in Table 2. 4,6-O-Acetonated substrates with varied
protecting groups at O(3) demonstrated the same tendencies in
the formation of gluco- and manno-products 2 and 3, which
were observed in corresponding azidonitration reactions2(b)
(entries 1–3). Thus, glucal 1d with a bulky silyl group at O(3)
gave gluco-product 2d stereospecifically and in a high yield
– 242 –

Mendeleev Commun., 2008, 18, 241–243
and TBS substituents (entries 10, 11) were used. The smaller
Similarly to tri-O-acetylated 1a, the APS transformations
of peracetylated di- and trisaccharide derivatives 1m9 and 1p
were non-stereoselective (entries 12, 15), but the transformation
of their per-O-silylated analogues 1n,10 1o10 and 1q gave only
gluco-products 2n,o,q contrary to the corresponding mono-
saccharide analogues 1i and 1j (entries 8, 9).
silyl protections (TMS and TES groups) provided remarkably
lower stereoselectivity (entries 8, 9), but the portion of gluco-
product was higher in the case of substrate 1i with the TMS
substituent.
2p: 1H NMR, d: 7.20–7.70 (m, 5H, Ar), 5.99 (d, 1H, H-1, J1,2 5.2 Hz),
5.50 (m, 1H, H-8''), 5.38 (dd, 1H, H-7'', J7'',6'' 2.2 Hz, J7'',8'' 9.1 Hz), 5.36
(d, 1H, H-4', J4,3 3.2 Hz), 5.11 (m, 2H, H-2', NH), 4.92 (dd, 1H, H-3',
J3,2 9.1 Hz, J3,4 3.0 Hz), 4.80 (m, 1H, H-4''), 4.57 (dd, 1H, H-2, J2,1 6.0 Hz,
J2,3 2.0 Hz), 4.44 (d, 1H, H-1', J1,2 8.0 Hz), 4.40 (m, 1H, H-3), 4.37 (m,
1H, H-6A), 4.20 (m, 4H, H-6'A, H-6'B, H-9A'', H-9B''), 4.03 (m, 2H,
H-6B, H-5''), 3.81 (m, 1H, H-5'), 3.72 (s, 3H, OMe), 3.70 (m, 2H, H-4,
H-5), 3.55 (d, 1H, H-6'', J6,7 2.1 Hz), 2.47 (dd, 1H, H-3eq, J3,3 12.5 Hz,
J3,4 4.3 Hz), 1.68 (t, 1H, H-3eq, J3,3 = J3,4 = 12.3 Hz), 1.90–2.25 (m, 30H,
Ac). 13C NMR, d: 126.5–131.0 (Ar), 126.5–131.0 (Ar), 100.4 (C-1'), 97.3
(C-2'') 83.2 (C-1), 77.9, 75.3, 75.2, 74.0, 72.8, 71.9, 71.6, 71.5, 70.5, 68.6,
65.7, 63.2, 62.7, 62.3, 61.2 (C-2), 54.9 (C-5''), 39.9 (C-3''), 19.3–21.6 (Ac).
2q: 1H NMR, d: 7.20–7.70 (m, 5H, Ar), 5.95 (d, 1H, H-1, J1,2 5.0 Hz),
4.02 (m, 2H), 3.94 (m, 1H, H-2), 3.81–3.96 (m, 10H), 3.79 (m, 1H, H-3),
3.72–3.78 (m, 5H), 2.42 (dd, 1H, H-3eq, J3,3 12.8 Hz, J3,4 4.1 Hz), 1.75
(t, 1H, H-3eq, J3,3 = J3,4 = 12.9 Hz), 0.80–1.10 (m, 135H, Et). 13C NMR,
d: 133.1–127.4 (Ar), 100.4 (C-2''), 100.3 (C-1'), 98.1 (C-2''), 84.1 (C-1),
74.0, 73.2, 71.5, 71.0, 70.5, 70.1, 69.1, 66.3, 63.1, 62.4, 60.1, 56.2, 53.0,
39.2 (C-3''), 10.4–12.7 (Et), 0.4–2.9 (Et).
3m: 1H NMR, d: 7.20–7.70 (m, 5H, Ar), 5.72 (d, 1H, H-1, J1,2 1.4 Hz),
5.37 (d, 1H, H-4', J4',3' 3.5 Hz), 5.32 (dd, 1H, H-3, J3,2 9.0 Hz, J3,4 3.2 Hz),
5.15 (dd, 1H, H-2', J2',1' 8.0 Hz, J2',3' 10.0 Hz), 4.97 (dd, 1H, H-3', J3',2'
10.0 Hz, J3',4' 3.4 Hz), 4.55 (d, 1H, H-1', J1',2' 8.0 Hz), 4.36 (m, 3H,
H-6A, H-6'A, H-6'B), 4.30 (m, 1H, H-2), 4.05 (m, 2H, H-5', H-6B), 3.93
(m, 2H, H-4, H-5), 2.00–2.20 (6s, 18H, Ac). 13C NMR, d: 169.6–170.9
(C=O), 137.5 (ipso-Ph), 126.5–131.0 (Ar), 101.2 (C-1'), 82.2 (C-1), 74.0,
71.6, 71.5, 70.8, 70.5, 68.9, 66.5, 63.1, 62.0, 60.8, 19.6–22.0 (Ac).
3p: 1H NMR, d: 7.20–7.70 (m, 5H, Ar), 5.99 (d, 1H, H-1, J1,2 5.2 Hz),
5.50 (m, 1H, H-8''), 5.38 (dd, 1H, H-7'', J7'',6'' 2.2 Hz, J7'',8'' 9.1 Hz), 5.36
(d, 1H, H-4', J4,3 3.2 Hz), 5.11 (m, 2H, H-2', NH), 4.92 (dd, 1H, H-3',
J3,2 9.1 Hz, J3,4 3.0 Hz), 4.80 (m, 1H, H-4''), 4.57 (dd, 1H, H-2, J2,1 6.0 Hz,
J2,3 2.0 Hz), 4.44 (d, 1H, H-1', J1,2 8.0 Hz), 4.40 (m, 1H, H-3), 4.37 (m,
1H, H-6A), 4.20 (m, 4H, H-6'A, H-6'B, H-9A'', H-9B''), 4.03 (m, 2H,
H-6B, H-5''), 3.81 (m, 1H, H-5'), 3.72 (s, 3H, OMe), 3.70 (m, 2H, H-4,
H-5), 3.55 (d, 1H, H-6'', J6,7 2.1 Hz), 2.47 (dd, 1H, H-3eq, J3,3 12.5 Hz,
J3,4 4.3 Hz), 1.68 (t, 1H, H-3eq, J3,3 = J3,4 = 12.3 Hz), 1.90–2.25 (m, 30H,
Ac). 13C NMR, d: 169.6–171.4 (C=O), 126.5–131.0 (Ar), 101.5 (C-2),
100.4 (C-1'), 97.3 (C-2''), 75.3, 75.2, 74.0, 72.8, 71.9, 71.6, 71.5, 70.8,
70.5, 68.9, 66.1, 64.4, 62.5, 62.8, 60.0 (C-2), 53.9 (C-5''), 39.1 (C-3''),
19.3–21.7 (Ac).
Synthesis of glucals 1p and 1q using known procedures11–14
will be published elsewhere.
In conclusion, we have demonstrated that the stereoselec-
tivity in the APS reaction of glucals depends on O-protecting
groups in the glucal that gives the possibility to direct to a certain
extent the stereochemical result of the reaction towards the
formation of either gluco- or manno-products.
This work was supported by the Russian Foundation for
Basic Research (grant no. 07-03-00225). A.A.S. acknowledges
the support of INTAS (YS fellowship grant no. 03-55-1026). We
are grateful to Yu. E. Tsvetkov, L. O. Kononov and A. I. Zinin
for helpful discussions and to A. S. Shashkov and A. A. Grachev
for recording the NMR spectra.
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5 (in the mixture with 6, see entries 22 and 23, Table 1): 1H NMR, d:
7.10–8.10 (m, 4H, Ar), 5.81 (d, 1H, H-1, J1,2 9.4 Hz), 5.17 (t, 1H, H-3,
J3,2 = J3,4 = 9.1 Hz), 5.08 (t, 1H, H-4, J4,3 = J4,5 = 9.1 Hz), 4.30 (m, 1H,
H-6), 4.06 (dd, 1H, H-6', J5,6' 2.2 Hz, J6',6 12.5 Hz), 3.74 (ddd, 1H, H-5,
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(Ar), 94.4 (C-1), 93.4 (C-I), 72.4 (C-5), 72.2 (C-3), 69.2 (C-4), 61.7 (C-6),
46.3 (C-2), 20.7 (Ac).
6 (in the mixture with 5, see entries 22 and 23, Table 1): 1H NMR, d:
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Received: 16th July 2008; Com. 08/3182
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