Synthesis of 1-C-(tetra-O-acetyl-β-d-galactopyranosyl)-2,3-diiodo-1-propene and its reaction with primary amines

Article abstract of DOI:10.1016/j.carres.2009.06.021

Iodination of 1-C-(tetra-O-acetyl-β-d-galactopyranosyl)allene affords an E/Z-mixture of 1-C-(tetra-O-acetyl-β-d-galactopyranosyl)-2,3-diiodo-1-propene. S_N2 displacement of the allylic iodide with primary amines affords an E/Z-mixture of allylic

Full text of DOI:10.1016/j.carres.2009.06.021

Carbohydrate Research 344 (2009) 2096–2099
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Note
Synthesis of 1-C-(tetra-O-acetyl-b-D-galactopyranosyl)-2,3-diiodo-1-propene
and its reaction with primary amines q
a
b,
Uthai Sakee a, , Chiradet Nasuk , Ronald Grigg
*
*
a Center of Excellence for Innovation in Chemistry (PERCH-CIC), Department of Chemistry, Faculty of Science, Mahasarakham University, Mahasarakham 44150, Thailand
b Molecular Innovation, Diversity and Automated Synthesis (MIDAS) Centre, School of Chemistry, University of Leeds, Leeds LS2 9JT, United Kingdom
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 8 April 2009
Received in revised form 18 May 2009
Accepted 19 June 2009
Available online 25 June 2009
Iodination of 1-C-(tetra-O-acetyl-b-D-galactopyranosyl)allene affords an E/Z-mixture of 1-C-(tetra-O-
acetyl-b-D-galactopyranosyl)-2,3-diiodo-1-propene. SN2 displacement of the allylic iodide with primary
amines affords an E/Z-mixture of allylic amines under a variety of conditions. Due to its experimental
simplicity and low cost of reagents, this procedure may find wide use in the laboratory for functionaliza-
tion of sugar allenes.
Ó 2009 Elsevier Ltd. All rights reserved.
Keywords:
Allenes
Iodinations
Galactose
Benzylamines
Vinyl/allyl iodides
Carbohydrate-based starting materials are widely used in target-
oriented syntheses of optically active compounds.1 C-Glycosylic
compounds (‘C-glycosides’) with unsaturated aglycones are useful
for further functionalization purposes because of their potential
for the introduction of new stereogenic centers in the side chain.2
The addition of iodine to allene is well established;3–5 however, this
type of reaction has not been reported for sugar allenes. In this com-
munication, we report the addition of iodine to 1-C-(tetra-O-acetyl-
reaction mixture. The vinyl proton resonance for the major Z-2 (d
6.36) is 0.04 ppm upfield from the corresponding resonance for
the E-isomer E-2 (d 6.40). This assignment was also confirmed by
appropriate NOE experiments (Fig. 1).
Irradiation at the resonance frequency of H3 in the Z-isomer Z-2
(d 6.36) resulted in an enhancement of the H4 and H1a resonances of
8.5 and 6.3%, respectively, whilst irradiation at the analogous reso-
nance frequency of the E-isomer E-2 (d 6.40) did not result in any
enhancement of H1a or H1b but gave a 5.1% enhancement of H4.
The crude (1:1.9-E/Z)-mixture of allylic iodides 2 was subjected
to SN2 displacement with benzylamine nucleophiles 4a, b varying
both solvent (CH2Cl2, THF) and base (Et3N, K2CO3). Part of this
study is summarized in Table 2.
b-D
-galactopyranosyl)allene (1)6 in a variety of organic solvents and
the subsequent SN2 displacement of the allylic iodide in the diiodo
addition products with primary amines. We found that in all cases
an E/Z-mixture of E-2 and Z-2 was formed and that the E/Z ratio
was influenced by the solvent, time, and temperature7 (Table 1).
In Table 1 EtOH is identified as the best solvent for the reactions
studied. The products were formed by addition of iodine to the ter-
The geometry of E-5a and Z-5a was determined by NOE exper-
iments as shown in Figure 2.
minal
p-bond of the allene moiety. The other regioisomer resulting
In conclusion, we have established a simple route from 1-C-(tet-
from I2 addition to the internal
p
-bond of allene (1) was not ob-
ra-O-acetyl-b-
D-galactopyranosyl)allene (1) to (E/Z)-1-C-(tetra-O-
served. Selectivity for (Z)-2 increased with increasing reaction time
and temperature (Table 1, entries 5, 7, and 8), and further studies
of this trend are needed. The E/Z-isomerization of the diiodides is
presumed to proceed via a radical mechanism7 involving excess
I2 (Scheme 1).
acetyl-b- -galactopyranosyl)-2,3-diiodo-1-propene (2) in >95%
D
yield. Regioselective substitution of the allylic diiodide by benzyl-
amines can be achieved in moderate to good yield (Table 2, entries
1 and 6).
The olefin geometry was assigned on the basis of the chemical
1. Experimental
shift of the vinylic protons in the 1H NMR spectrum of the diiodide
1.1. General methods
q
IUPAC nomenclature: (2E/2Z)-5S,6R,7S,9-tetra-O-acetyl-4,8-anhydro-1,2,3-tri-
deoxy-1,2-diiodonon-2-enitol.
* Corresponding authors. Tel.: +66 43 754246; fax: +66 43 754246 (U.S.).
E-mail addresses: uthai.s@msu.ac.th (U. Sakee), R.Grigg@leeds.ac.uk (R. Grigg).
All reagents were commercially available and used without
purification. Flash column chromatography was performed using
0008-6215/$ - see front matter Ó 2009 Elsevier Ltd. All rights reserved.
doi:10.1016/j.carres.2009.06.021

U. Sakee et al. / Carbohydrate Research 344 (2009) 2096–2099
2097
Table 1
1.2. (2E)-5S,6R,7S,9-Tetra-O-acetyl-4,8-anhydro-1,2,3-trideoxy-
1,2-diiodonon-2-enitol (E-2) and (2Z)-5S,6R,7S,9-Tetra-O-acetyl-
4,8-anhydro-1,2,3-trideoxy-1,2-diiodonon-2-enitol (Z-2)
The reaction of b-C-galactose allene (1) with iodinea
OAc
OAc
OAc
O
OAc
I2
9
3
2
C
I
8
7
Iodine (0.754 g, 2.970 mmol) was added to a stirred solution of
the 1-C-(tetra-O-acetyl-b-D-galactopyranosyl)allene (1) (1.0 g,
O
C
6
AcO
AcO
5
I
4
1
AcO
AcO
2.7 mmol) in EtOH (200 mL).The resulting mixture was stirred
and heated under reflux for 3 h. The solvent was then removed,
the residue was dissolved in Et2O (100 mL), and the solution was
sequentially washed with satd sodium thiosulfate (100 mL), satd
NaHCO3 (100 mL), and satd brine (100 mL). The organic layer was
separated, dried (Na2SO4), and filtered, and the filtrate evaporated
under reduced pressure. Purification of the residue by flash column
chromatography, eluting with 2:1 hexane–Et2O, gave a 1:3.2 mix-
ture of E- and Z-2 as a pale-yellow gum (1.61 g, 2.59 mmol, 96%).
Gradient flash column chromatography of the mixture of E- and
Z-2 with 3:1 to 2:1 hexane–Et2O afforded partial separation of E-
and Z-2 with some fractions containing mixtures of E- and Z-2.
2
1
Entry
Solvent
Temperatureb (°C)
Timec (h)
Yieldd (%)
E/Ze
1
2
3
4
5
6
7
8
9
CH2Cl2
CH2Cl2
MeOH
MeOH
EtOH
rt
40
rt
70
48
24
24
3
20
25
30
40
92
22
96
97
81
1:2.3
1:1.7
1:1.9
1:2.3
1:1.9
1:1.5
1:3.2
1:1.7
1:4.1
80
3
MeC6H5
EtOH
EtOH
90
3
3
1.5
1.5
Reflux
Reflux
Reflux
CH3CN
a
Compound 1 (0.540 mmol), I2 (0.594 mmol), and 20 mL of solvent were used.
Oil bath temperature except where noted.
TLC monitoring to 100% completion.
b
c
1.2.1. Data for E-2
Pale-yellow gum; ½a D24
ꢁ
+238.5 (c 0.218, CHCl3); IR (film): 2971,
1H NMR
d
e
Isolated yield.
2121, 1737, 1615, 1423, 1366, 753, 600, 542 cmꢀ1
;
Ratios were determined by 1H NMR.
(500 MHz, CDCl3): d 6.4 (1H, d, J 6.4, 3-H), 5.42–5.44 (1H, m, 7-
H), 5.3 (1H, dd, J 10.7 and 6.0, 5-H), 5.17 (1H, dd, J 10.7 and 3.0,
6-H), 4.8 (1H, app t, J 6.0 and 5.95, 4-H), 4.56 and 4.37 (2H,
2 ꢂ d, J 10.25, 1-H), 4.0–4.2 (3H, m, 8-H and 2 ꢂ 9-H), 2.1, 2.08,
2.03 and 2.01 (12H, 4 ꢂ s, 4 ꢂ OCOMe); 13C NMR (75 MHz, CDCl3):
d 169.2, 169.1, 169.0, 168.8, 134.2, 129.2, 107.4, 69.7, 68.0, 67.0,
66.4, 65.7, 60.2, 20.9, 19.8, 19.7, 19.6; ESIMS (positive-ion): m/z
Silica Gel 60 (230–400 mesh). Optical rotations were measured on
an AA-100 polarimeter at room temperature and are given in
10ꢀ1 deg cm2 gꢀ1. Accurate molecular masses were recorded on a
Bruker micrOTOF instrument. Infrared spectra were recorded using
a Perkin–Elmer FTIR spectrometer. The IR samples were prepared
as thin films by evaporation of a solution of the compound in
CH2Cl2 onto a germanium plate. Nuclear magnetic resonance spec-
tra were determined at 500 MHz (1H) and at 75 MHz (13C) on Bru-
ker spectrometers. Chemical shift values are quoted in parts per
million (ppm) downfield from TMS, and coupling constants are in
hertz. Chemical shift multiplicities are reported as s = singlet,
d = doublet, dd = doublet of doublets, t = triplet, q = quartet,
m = multiplet, br = broad, and br s = broad singlet, app. t = apparent
625 (MH+, 100); HRMS: calcd for C17H22I2NaO9 (M
646.9245; found: 646.9255.
+ Na):
1.2.2. Data for Z-2
Pale-yellow gum; ½a D24
ꢁ
+253.5 (c 0.493, CHCl3); IR (film): 2971,
1H NMR
2121, 1737, 1615, 1423, 1366, 753, 600, 542 cmꢀ1
;
(500 MHz, CDCl3): d 6.36 (1H, d, J 7.7, 3-H), 5.42–5.46 (1H, m, 7-
H), 5.36 (1H, dd, J 10.25 and 6.0, 5-H), 5.18 (1H, dd, J 10.25 and
3.0, 6-H), 4.78 (1H, app. t, J 6.85 and 6.4, 4-H), 4.50 and 4.45 (2H,
triplet. 1-C-(tetra-O-acetyl-b-
D-galactopyranosyl)allene (1) was
prepared according to a literature method.6
I
OAc
OAc
OAc
OAc
OAc
O
OAc
O
OAc
O
OAc
O
I
I
I
-
I
+
I
I
C
C
C
AcO
AcO
AcO
AcO
I
I
I
AcO
AcO
AcO
AcO
1
E-2
Z-2
3
Scheme 1. Proposed E/Z isomerization mechanism.
5.8
H1a
H1b
OAc
OAc
OAc
6.3
OAc
I
H3
H3
I
O
O
I
AcO
AcO
8.5
5.1
6.3
I
10.6
H
AcO
AcO
H
H4
H4
Z-2
E-2
Figure 1. NOE data for E-2 and Z-2.

2098
U. Sakee et al. / Carbohydrate Research 344 (2009) 2096–2099
Table 2
The reaction of diiodide 2 with primary amines under different reaction conditionsa
OAc
OAc
OAc
OAc
9
NH2
I
3
2
C
I
7
8
O
O
C
R
base
6
AcO
+
AcO
5
NH
I
4
1
AcO
AcO
R
4a, R = H
5a, R = H
2
5b, R = Ph
4b, R = Ph
Entry
Nucleophile
Base (mol equiv)
Solvent
Temperature (°C)
Timeb (h)
Product, yieldc (%)
E:Z
1
2
3
4
5
6
7
4a
4a
4a
4b
4b
4b
4a
Et3N (1.1)
Et3N (2)
CH2Cl2
CH2Cl2
CH2Cl2
CH2Cl2
THF
rt
rt
40
rt
rt
Reflux
Reflux
24
24
12
24
24
24
24
5a (45)
5a (27)
5a (22)
5b (53)
5b (25)
5b (79)
5a (25)
1:1.25
1:1.25
1:1.2
1:1.3
1:1.5
Et3N (1.1)
Et3N (1.1)
Et3N (1.1)
K2CO3 (5)
K2CO3 (5)
CH2Cl2
CH2Cl2
1:2.16
1:1.5
a
Compound 2 (1: 1.9-E/Z-mixture) (0.33 mmol), nucleophile (1.1 mol equiv), and 5 mL of solvent were used.
Reaction monitored by TLC.
Isolated yield.
b
c
5. 2
H1a
H1b
AcO
AcO
5. 5
OAc
OAc
I
H3
NH
H3
O
O
NH
H
AcO
AcO
11.1 11.2
9. 2
I
6. 2
AcO
AcO
H
H4
H4
E-5a
Z-5a
Figure 2. NOE data for E-5a and Z-5a.
2 ꢂ d, J 10.25, 1-H), 4.05–4.15 (2H, m, 2 ꢂ 9-H), 4.02 (1H, app t, J
6.0 and 5.1), 2.1, 2.06 and 2.03 (12H, 4 ꢂ s, 4 ꢂ OCOMe); 13C
NMR (75 MHz, CDCl3): d 170.9, 170.56, 170.52, 170.2, 130.6, 76.6,
69.9, 69.0, 67.8, 67.5, 62.0, 21.2, 21.1, 21.0; ESIMS (positive-ion):
m/z 625 (MH+, 100); HRMS: calcd for C17H22I2NaO9 (M+Na):
646.9245; found: 646.9255.
0.705 mmol) under reflux for 24 h. Purification of the residue by
gradient elution flash column chromatography with 1:1 to 1:2 hex-
ane–EtOAc afforded E-5a (0.096 g, 0.160 mmol, 25%) and Z-5a
(0.208 g, 0.346 mmol, 54%) as pale-yellow gums.
1.3.1.1. Data for E-5a.
½
a 2D4
ꢁ
ꢀ190.7 (c 1.206, CHCl3); IR (film):
3473, 2970, 1739, 1624, 1489, 1434, 1365, 1217, 701, 538 cmꢀ1
;
1.3. General procedure for the reaction of 2 with primary
amines
1H NMR (500 MHz, CDCl3): d 7.32–7.33 (5H, m, Ar-H),6.6 (1H, d, J
6.8, 3-H), 5.41–5.42 (1H, m, 7-H), 5.2–5.26 (2H, m, 5-H and 6-H),
4.9 (1H, app t, J 6.3 and 6.2, 4-H), 4.4.0–4.1 (3H, m, 8-H and
2 ꢂ 9-H), 3.7 and 3.6 (2H, 2d, J 12.9, NCH2Ph), 3.5 and 3.4(2H, 2d,
J 14.8, 2 ꢂ 1-H), 2.1, 2.06, 2.01 and 1.96 (12H, 4 ꢂ s, 4 ꢂ OCOMe);
13C NMR (75 MHz, CDCl3): d 170.7, 170.6, 170.5, 170.2, 139.2,
135.4, 128.9, 128.7, 127.1, 117.5, 70.9, 69.2, 68.4, 68.1, 67.5, 62.1,
54.2, 52.1, 21.6, 21.2; ESIMS (positive-ion): m/z 604 (MH+, 100);
HRMS: calcd for C24H31INO9 (M+H): 604.1049; found: 604.1070.
A 1:1.9 mixture of E- and Z-2 (0.33 mmol) was dissolved in
CH2Cl2 (5 mL), and K2CO3 (5.0 mol equiv) or Et3N (1.1 mol equiv),
and amine (1.1 mol equiv) were added. The resulting mixture
was stirred and heated under reflux for 24 h, cooled, poured into
water, and extracted with CH2Cl2 (2 ꢂ 20 mL). The organic layer
was separated and washed with water (2 ꢂ 50 mL), dried (Na2SO4),
and filtered, and the filtrate was evaporated. Purification of the res-
idue by flash column chromatography afforded the product.
1.3.1.2. Data for Z-5a.
½
a 2D4
+107.2 (c 1.212, CHCl3); IR (film):
ꢁ
3473, 2970, 1739, 1624, 1489, 1434, 1365, 1217, 701, 538 cmꢀ1
;
1.3.1. (2E)-5S,6R,7S,9-Tetra-O-acetyl-4,8-anhydro-1-(benzylamino)-
1,2,3-trideoxy-2-iodonon-2-enitol (E-5a) and (2Z)-5S,6R,7S,9-
tetra-O-acetyl-4,8-anhydro-1-(benzylamino)-1,2,3-trideoxy-2-
iodonon-2-enitol (Z-5a)
Compounds E-5a and Z-5a were prepared by the general proce-
dure from 1:1.9-E/Z-2 (0.400 g, 0.641 mmol) in CH2Cl2 (7 mL),
K2CO3 (0.442 g, 3.205 mmol), and benzylamine (4a) (0.075 g,
1H NMR (500 MHz, CDCl3): d 7.34–7.35 (5H, m, Ar-H), 6.2 (1H, d,
J 7.7, 3-H), 5.44 (1H, dd, J 3.3 and 1.6, 7-H), 5.41 (1H, dd, J 10.3
and 5.9, 5-H), 5.2 (1H, dd, J 10.3 and 3.3, 6-H), 4.78 (1H, dd, J 7.7
and 5.9, 4-H), 4.0–4.2 (3H, m, 6-H and 2 ꢂ 9-H), 3.7 and 3.68
(2H, 2d, J,13.0, 2 ꢂ 1-H), 3.57 and 3.53 (2H, 2d, J 15.5, NCH2Ph),
2.1, 2.04 and 2.02 (12H, 4 ꢂ s, 4 ꢂ OCOMe); 13C NMR (75 MHz,
CDCl3): d 170.9, 170.6, 170.5, 170.2, 139.7, 129.0, 128.7, 128.2,

U. Sakee et al. / Carbohydrate Research 344 (2009) 2096–2099
2099
127.7, 119.5, 76.5, 69.7, 69.0, 67.9, 67.6, 62.1, 61.0, 51.4, 21.3, 21.2,
21.1, 21.0; ESIMS (positive-ion): m/z 604 (MH+, 100); HRMS: calcd
for C24H31INO9 (M+H): 604.1049; found: 604.1070.
(4H, app t, J 7.7 and 6.8, Ar-H), 7.4–7.45 (4H, m, 4 ꢂ Ar-H), 7.34
(1H, t, J 7.25, Ar-H), 6.25 (1H, d, J 7.7, 3-H), 5.43–5.45 (1H, m, 7-
H), 5.41 (1H, dd, J 10.3 and 5.95, 5-H), 5.2 (1H, dd, J 10.3 and 3.0,
6-H), 4.95 (1H, app t, J 6.8 and 6.4, 4-H), 4.05–4.17 (3H, m, 8-H
and 2 ꢂ 9-H), 3.75 and 3.72 (2H, 2d, J 13.25, 2 ꢂ 1-H), 3.59 and
3.55 (2H, 2d, J 15.8, NCH2Ar), 2.17, 2.15, 2.03 and 2.02 (12H,
4 ꢂ s, 4 ꢂ OCOMe); 13C NMR (75 MHz, CDCl3): d 170.4, 170.1,
170.0, 169.7, 140.8, 140.2, 138.4, 128.7, 127.9, 127.3, 127.2,
127.0, 119.1, 76.1, 69.3, 68.5, 68.3, 67.5, 67.2, 61.7, 60.5, 50.7,
20.9, 20.8, 20.7, 20.6; ESIMS (positive-ion): m/z 680 (MH+, 100);
HRMS: calcd for C30H35INO9 (M+H): 680.1351; found: 680.1365.
1.3.2. (2E)-5S,6R,7S,9-Tetra-O-acetyl-4,8-anhydro-1-[(biphenyl-
4-ylmethyl)amino]-1,2,3-trideoxy-2-iodonon-2-enitol (E-5b) and
(2Z)-5S,6R,7S,9-tetra-O-acetyl-4,8-anhydro-1-[(biphenyl-4-yl-
methyl)amino]-1,2,3-trideoxy-2-iodonon-2-enitol (Z-5b)
Compounds E/Z 5b were prepared by the general procedure
from 1:1.9-E/Z-2 (0.400 g, 0.641 mmol) in CH2Cl2 (7 mL), Et3N
(0.071 g, 0.705 mmol) and 1-biphenyl-4-ylmethanamine (4b)
(0.128 g, 0.705 mmol) at room temperature for 24 h. Workup, fol-
lowed by gradient elution flash column chromatography with 1:1
to 1:2 hexane–EtOAc, afforded E-5b (0.088 g, 0.147 mmol, 23%)
and Z-5b (0.116 g, 0.192 mmol, 30%) as pale-yellow gums.
Acknowledgments
We thank the EU for a Marie Curie fellowship (MIF1-CT-2005-
514549), PERCH-CIC, Faculty of Science, Mahasarakham University
for the research fellowship, and Leeds University for support.
1.3.2.1. Data for E-5b.
3474, 3003, 2970, 1742, 1488, 1435, 1366, 1228, 1217, 1084,
1053, 911, 765, 700, 530 cmꢀ1 1H NMR (500 MHz, CDCl3): d 7.5
½
a 2D4
ꢁ
ꢀ110.7 (c 0.659, CHCl3); IR (film):
;
References
and 7.6 (4H, 2d, J 7.7, Ar-H), 7.3–7.45 (5H, m, Ar-H), 6.6 (1H, d, J
6.8, 3-H), 5.4–5.45 (1H, m, 7-H), 5.26 (1H, dd, J 10.6 and 5.6, 5-
H), 5.2 (1H, dd, J 10.3 and 3, 6-H), 4.95 (1H, app t, J 6.4 and 6.0,
4-H), 4.0–4.1 (3H, m, 8-H and 2 ꢂ 9-H), 3.76 and 3.68 (2H, 2d, J
13.25, 2 ꢂ 1-H), 3.5 and 3.4 (2H, 2d, J 14.6, NCH2Ar), 2.1, 2.07, 2.0
and 1.97 (12H, 4 ꢂ s, 4 ꢂ OCOMe); 13C NMR (75 MHz, CDCl3): d
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54.3, 51.8, 21.3, 21.2, 21.0; ESIMS (positive-ion): m/z 680 (MH+,
100); HRMS: calcd for C30H35INO9 (M+H): 680.1351; found:
680.1365.
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Tetrahedron Lett. 1993, 34, 1867–1870; (c) Davies, I. W.; Shaw, R. W.; Wisedale,
R.; Gallagher, T. J. Chem. Soc., Perkin Trans. 1 1994, 3557–3561; (d) Friesen, R. W.;
Bayly, C. I.; Fogg, J. A. J. Org. Chem. 1995, 60, 448–451.
1.3.2.2. Data for (Z-5b).
3474, 3003, 2970, 1742, 1488, 1435, 1366, 1228, 1217, 1084,
1053, 911, 765, 700, 530 cmꢀ1 1H NMR (500 MHz, CDCl3): d 7.6
½
a 2D4
+234.9 (c 0.166, CHCl3); IR (film):
ꢁ
;