Comparison of the two anomers of methyl 2-(N-benzylamino)-2,3- dideoxy-4,6-O-phenylmethylene-3-C-phenylsulfonyl-D-glucopyranoside

Article abstract of DOI:10.1107/S0108270100007344

The title compounds, the α and β anomers of methyl 2-(N-benzylamino)-2,3-dideoxy-4,6-O-phenylmethylene-3-C- phenylsulfonyl-D-glucopyranoside, C₂₇H₂₉NO₆S, belong to the class of deoxyamino-sugars prepared by the addition of amines at C2. The endocyclic bond lengths of the pyranose ring in the α anomer are shorter than the corresponding bonds in the β anomer. The pyranose ring is in the chair form in the former, while it is in the boat form in the latter. These observed differences could be attributed to the C2 substitution of a bulky group. The phenylsulfonyl and benzylamino groups are in equatorial positions in the α anomer, while the benzylamino group is axial in the β anomer.

Full text of DOI:10.1107/S0108270100007344

organic compounds
Acta Crystallographica Section C
Crystal Structure
When the geometry of the pyranose rings in the two mol-
ecules is compared, the average endocyclic CÐC bond length
Communications
Ê
is 1.528 in (Iꢀ) and 1.537 A in (Iꢁ). The value of the former is
closer to the average values reported for glucopyranose rings
ISSN 0108-2701
(Jeffrey, 1990), whereas that of the latter is higher. The
average of the endocyclic bond angles around the C atoms is
ꢁ
Comparison of the two anomers of
methyl 2-(N-benzylamino)-2,3-di-
deoxy-4,6-O-phenylmethylene-3-C-
phenylsulfonyl-D-glucopyranoside
111.1 and 111.6 , respectively. These values are higher than the
reported average (Jeffrey, 1990). The bond angle around O5 in
(
Iꢁ) is wider than that in (Iꢀ).
a
b
Cheravakkattu G. Suresh, * Bindu Ravindran,
a
b
K. Narasimha Rao and Tanmaya Pathak
a
Division of Biochemical Sciences, National Chemical Laboratory, Pune 411 008,
b
India, and Organic Chemistry Division (Synthesis), National Chemical Laboratory,
Pune 411 008, India
Correspondence e-mail: suresh@ems.ncl.res.in
Received 9 March 2000
Accepted 16 May 2000
The pyranose±dioxane double-ring system in (Iꢀ) is in the
chair conformation. The dioxane ring alone has the chair form
in (Iꢁ), while the pyranose takes the boat form. The confor-
4
The title compounds, the ꢀ and ꢁ anomers of methyl
mations of the pyranoses are thus symbolized as C in (Iꢀ)
1
1
,4
2
phenylsulfonyl-d-glucopyranoside, C H NO S, belong to the
-(N-benzylamino)-2,3-dideoxy-4,6-O-phenylmethylene-3-C-
and B in (Iꢁ) (Collins & Ferrier, 1995). In (Iꢀ), the bulky
phenylsulfonyl and benzylamino groups attached to the
pyranose ring, as well as the phenyl group attached to dioxane,
are all equatorially positioned with respect to the double-ring
carbohydrate system, while the benzoylamino group is axial in
(Iꢁ) (Figs. 1 and 2).
The main conformational difference between the pyranose
rings in the two anomers corresponds to C1 puckering. The
observed difference, the chair conformation of the pyranose in
(Iꢀ) and the boat conformation in (Iꢁ), could presumably be
the result of C2 substitution. In (Iꢁ), the observed boat
conformation of the pyranose ring causes the benzylamino
and glycosidic O-methyl groups present at adjacent ring C
2
7
29
6
class of deoxyamino-sugars prepared by the addition of
amines at C2. The endocyclic bond lengths of the pyranose
ring in the ꢀanomer are shorter than the corresponding bonds
in the ꢁanomer. The pyranose ring is in the chair form in the
former, while it is in the boat form in the latter. These
observed differences could be attributed to the C2 substitution
of a bulky group. The phenylsulfonyl and benzylamino groups
are in equatorial positions in the ꢀ anomer, while the
benzylamino group is axial in the ꢁanomer.
Comment
Amino-sugars, in general, are one of the most important
classes of carbohydrates. The CÐN equatorial bonds at the C2
position of carbohydrates play a signi®cant role because
naturally occurring amino-sugars, such as d-glucosamine,
d-galactosamine, d-lividosamine etc., have their CÐN bonds
at C2 in an equatorial con®guration. Not many synthetic
routes are available for the introduction of N-monoalkylated
and N-dialkylated amines to the C2 atom of pyranoses in
equatorial con®gurations. As part of an ongoing programme
on the development of novel synthetic routes for the
preparation of new classes of deoxyamino-sugars, we have
been studying the stereoselective addition of various amines
to phenylsulfonyl-modi®ed carbohydrates. In this context, we
have determined the structures of the ꢀ, (Iꢀ), and ꢁ, (Iꢁ),
anomers of a phenylsulfonyl-modi®ed monosaccharide with
amino substitution at C2.
Figure 1
A perspective view of (Iꢀ). Displacement ellipsoids are drawn at the 50%
probability level and H atoms have been omitted for clarity.
1
030 # 2000 International Union of Crystallography ꢀ Printed in Great Britain ± all rights reserved
Acta Cryst. (2000). C56, 1030±1032

organic compounds
atoms to orient away from each other. In a chair conformation
of the pyranose rings, these groups would have come sterically
closer. Another difference between the anomers is in the
disposition of the phenyl ring of the phenylsulfonyl. This
phenyl ring is positioned away from C2 benzylamino in (Iꢁ)
compared to its position in (Iꢀ). Among the three planar
phenyl rings, that of benzylamino is almost orthogonal to the
other two in both structures, whereas the phenyl rings of
phenylmethylene and phenylsulfonyl make angles of 26.6 (2)
Experimental
Methyl 2,3-dideoxy-4,6-O-phenylmethylene-3C-phenylsulfonyl-ꢀ-d-
erythro-hex-2-enopyranoside and the corresponding -ꢁ-d-erythro-
hex-2-enopyranoside were reacted separately with benzylamine at
elevated temperatures (Ravindran et al., 2000). The desired amino-
sugars were recrystallized from methanol.
Compound (Ia)
Crystal data
ꢁ
and 63.5 (2) with respect to each other in (Iꢀ) and (Iꢁ),
respectively.
�
3
C
27
H29NO
6
S
D
x
= 1.312 Mg m
r
M = 495.57
Cu Kꢀradiation
In the case of hexapyranoses, the presence of a hydroxyl
group at C4 is expected to forbid the orientation of the
primary alcohol group C6ÐOH in a tg conformation (Jeffrey,
1990). However, in both the molecules reported here, this
group is in a tg conformation as a result of dioxan ring
formation.
Monoclinic, P21
Ê
a = 10.418 (2) A
Cell parameters from 25
re¯ections
Ê
b = 8.880 (6) A
ꢁ
ꢂ= 10±30
ꢃ= 1.501 mm
T = 293 (2) K
Ê
c = 13.560 (2) A
� 1
ꢁ
ꢁ= 91.36 (1)
V = 1254.1 (9) A
Z = 2
Ê
3
Needle, colourless
0.80 Â 0.31 Â 0.25 mm
Data collection
Enraf±Nonius CAD-4 diffract-
ometer
Rint = 0.017
ꢁ
ꢂ
max = 75.62
!
±2ꢂscans
Absorption correction: scan
North et al., 1968)
min = 0.668, Tmax = 0.687
h = 0 ! 13
k = 0 ! 10
(
T
l = � 16 ! 16
3 standard re¯ections
frequency: 60 min
intensity decay: 0.1%
2
2
2
810 measured re¯ections
667 independent re¯ections
563 re¯ections with I > 2ꢄ(I)
Re®nement
2
Re®nement on F
2
(Á/ꢄ)max = 0.002
2
Ê
� 3
Áꢅmax = 0.25 e A
R[F > 2ꢄ(F )] = 0.033
wR(F ) = 0.090
S = 1.054
2
Ê
� 3
Áꢅmin = � 0.34 e A
Extinction correction: SHELXL93
(Sheldrick, 1993)
2
3
667 re¯ections
18 parameters
Extinction coef®cient: 0.0119 (8)
Absolute structure: Flack (1983)
Flack parameter = 0.00 (2)
H-atom parameters constrained
2
2
2
w = 1/[ꢄ(F
0.1489P]
where P = (F
o
) + (0.0620P)
+
2
2
c
o
+ 2F
)/3
Figure 2
A perspective view of (Iꢁ). Displacement ellipsoids are drawn at the 50%
probability level and H atoms have been omitted for clarity.
Table 1
Selected geometric parameters (A, ) for (Iꢀ).
Ê
ꢁ
The CÐO bond shortening at C1 of the pyranose and the
preferred gauche conformations about the glycosidic bond
S1ÐC3
O5ÐC1
O5ÐC5
C1ÐO1
C1ÐC2
1.832 (2)
1.417 (3)
1.418 (3)
1.394 (4)
1.537 (3)
O1ÐC7
C2ÐN1
C2ÐC3
C3ÐC4
C4ÐC5
1.436 (3)
1.455 (3)
1.537 (3)
1.522 (3)
1.518 (3)
(
exo-anomeric effect) are known in carbohydrates (Perez &
Marchessault, 1978). The structure of (Iꢀ) reported here
belongs to the gauche±gauche class which is the allowed class
for ꢀ anomers. The trans±gauche form is favourable in ꢁ
anomers (Norrestam et al., 1981). Nevertheless, according to
glycosodic torsion angles (Table 1), the ꢁanomer has gauche±
gauche conformation. Presumably, this not so common form of
C1ÐO5ÐC5
O1ÐC1ÐO5
O1ÐC1ÐC2
O5ÐC1ÐC2
C1ÐO1ÐC7
N1ÐC2ÐC3
N1ÐC2ÐC1
C3ÐC2ÐC1
C4ÐC3ÐC2
111.1 (2)
C4ÐC3ÐS1
C2ÐC3ÐS1
O4ÐC4ÐC5
O4ÐC4ÐC3
C5ÐC4ÐC3
O5ÐC5ÐC4
O5ÐC5ÐC6
C4ÐC5ÐC6
C2ÐN1ÐC21
110.17 (15)
109.5 (2)
106.8 (2)
110.5 (2)
109.4 (2)
109.6 (2)
109.0 (2)
109.5 (2)
114.9 (2)
111.4 (2)
108.2 (2)
112.8 (2)
112.8 (3)
109.5 (2)
112.6 (2)
113.4 (2)
110.5 (2)
ꢁ
anomers is found in this structure due to the boat form
instead of the more common chair form of the pyranose ring.
The crystal structures are stabilized by the stacking and
hydrophobic interactions of the phenyl rings. In (Iꢁ), there is
an intermolecular hydrogen bond between the amino nitrogen
and the sulfone oxygen (O3) of the translated molecule along
c. In (Iꢀ), this nitrogen is involved in a weak intramolecular
hydrogen bond with the oxygen (O1) of the glycosidic
O-methyl group.
C5ÐO5ÐC1ÐO1
C5ÐO5ÐC1ÐC2
O5ÐC1ÐO1ÐC7
O1ÐC1ÐC2ÐN1
O5ÐC1ÐC2ÐC3
C1ÐC2ÐC3ÐC4
C2ÐC3ÐC4ÐC5
64.4 (2)
C1ÐO5ÐC5ÐC4
C1ÐO5ÐC5ÐC6
O4ÐC4ÐC5ÐO5
C3ÐC4ÐC5ÐO5
O4ÐC4ÐC5ÐC6
O6ÐC6ÐC5ÐO5
O6ÐC6ÐC5ÐC4
67.0 (2)
� 173.2 (2)
176.8 (2)
� 63.7 (2)
57.2 (3)
� 57.4 (3)
70.5 (3)
47.0 (3)
45.7 (3)
� 42.9 (3)
51.1 (3)
� 173.4 (2)
� 53.5 (3)
Acta Cryst. (2000). C56, 1030±1032
Cheravakkattu G. Suresh et al. ꢀ ꢀand ꢁanomers of C27
H
29NO
6
S
1031

organic compounds
Compound (Ib)
Table 2
Selected geometric parameters (A, ) for (Iꢁ).
Ê
ꢁ
Crystal data
S1ÐC3
O5ÐC1
O5ÐC5
C1ÐO1
C1ÐC2
O1ÐC7
1.763 (7)
1.414 (7)
1.433 (7)
1.382 (7)
1.537 (9)
1.438 (8)
C2ÐN1
C2ÐC3
C3ÐC4
C4ÐC5
N1ÐC21
1.453 (7)
1.574 (8)
1.522 (8)
1.516 (8)
1.442 (9)
C
27 6
H29NO S
Z = 1
= 1.343 Mg m
Cu Kꢀradiation
�
3
M
r
= 495.57
Triclinic, P1
D
x
Ê
a = 8.3190 (10) A
Ê
b = 13.197 (2) A
c = 5.750 (2) A
Cell parameters from 18
re¯ections
Ê
ꢁ
ꢁ
ꢂ= 29.5±46.0
� 1
ꢀ
ꢁ
= 100.84 (2)
ꢁ
ꢃ= 1.536 mm
T = 293 (2) K
C1ÐO5ÐC5
O1ÐC1ÐO5
O1ÐC1ÐC2
O5ÐC1ÐC2
C1ÐO1ÐC7
N1ÐC2ÐC1
N1ÐC2ÐC3
C1ÐC2ÐC3
C4ÐC3ÐC2
115.6 (4)
112.4 (5)
110.1 (5)
113.0 (5)
111.0 (5)
108.5 (5)
115.6 (5)
111.5 (5)
110.1 (5)
C4ÐC3ÐS1
C2ÐC3ÐS1
O4ÐC4ÐC5
O4ÐC4ÐC3
C5ÐC4ÐC3
O5ÐC5ÐC6
O5ÐC5ÐC4
C6ÐC5ÐC4
C21ÐN1ÐC2
116.0 (4)
109.8 (4)
105.8 (4)
109.0 (5)
110.4 (5)
107.0 (5)
113.1 (5)
109.6 (5)
115.6 (5)
= 98.61 (2)
ꢁ
ꢆ= 89.430 (10)
Ê
V = 612.9 (2) A
Irregular ¯akes, colourless
0.40 Â 0.14 Â 0.06 mm
3
Data collection
AFC-7S diffractometer
Rint = 0.052
ꢂmax = 70.09
ꢁ
!
±2ꢂscans
Absorption correction: sphere
Weber, 1969)
min = 0.709, Tmax = 0.722
h = 0 ! 10
(
T
k = � 16 ! 16
l = � 6 ! 6
C5ÐO5ÐC1ÐO1
C5ÐO5ÐC1ÐC2
O5ÐC1ÐO1ÐC7
O1ÐC1ÐC2ÐN1
O5ÐC1ÐC2ÐC3
C1ÐC2ÐC3ÐC4
C2ÐC3ÐC4ÐC5
� 87.1 (6)
38.3 (7)
� 62.2 (7)
� 161.5 (5)
� 56.7 (6)
14.0 (6)
C1ÐO5ÐC5ÐC6
C1ÐO5ÐC5ÐC4
O6ÐC6ÐC5ÐO5
O6ÐC6ÐC5ÐC4
O4ÐC4ÐC5ÐO5
C3ÐC4ÐC5ÐO5
O4ÐC4ÐC5ÐC6
141.3 (5)
20.5 (7)
2
2
739 measured re¯ections
261 independent re¯ections (plus
3 standard re¯ections
every 150 re¯ections
intensity decay: 0.2%
178.6 (5)
� 58.4 (7)
179.4 (5)
� 62.8 (6)
60.1 (6)
1
46 Friedel-related re¯ections)
2
407 re¯ections with I > 2ꢄ(I)
Re®nement
40.9 (6)
2
Re®nement on F
2
(Á/ꢄ)max = � 0.005
Ê
� 3
Áꢅmax = 0.20 e A
2
R[F > 2ꢄ(F )] = 0.069
wR(F ) = 0.203
S = 1.106
2
Ê
� 3
Áꢅmin = � 0.31 e A
Extinction correction: SHELXL93
(Sheldrick, 1993)
2
3
425 re¯ections
18 parameters
Supplementary data for this paper are available from the IUCr electronic
archives (Reference: VJ1104). Services for accessing these data are
described at the back of the journal.
Extinction coef®cient: 0.100 (10)
Absolute structure: Flack (1983)
Flack parameter = 0.00 (4)
H-atom parameters constrained
2
2
2
w = 1/[ꢄ(F
0.4772P]
where P = (F
o
) + (0.1392P)
+
2
2
c
o
+ 2F
)/3
References
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1
032 Cheravakkattu G. Suresh et al. ꢀ ꢀand ꢁanomers of C27
Acta Cryst. (2000). C56, 1030±1032
6
H29NO S