Monosaccharidic push-pull butadienes: Versatile synthetic intermediates

Article abstract of DOI:10.5560/ZNB.2014-3179

Monosaccharidic push-pull butadienes are interesting building blocks for the synthesis of various heterocyclic and natural products due to their biological prevalence and significant π-electron interactions between donor and acceptor groups. A series of 1,5-anhydro-3,4,6-tri-O-benzyl-2-deoxy-2- formyl-D-arabino-hex-1-enitol (2) and 1,5-anhydro-3,4-di-O-benzyl-2-deoxy-2- formyl-L-erythrohex-1-enitol (4) derived push-pull branched chain sugars have been synthesized by condensation with active methylene compounds using basic aluminum oxide (Al₂O₃) or anhydrous sodium acetate (NaOAc) at room temperature. The compounds have been fully characterized by spectroscopic techniques and elemental analyses.

Full text of DOI:10.5560/ZNB.2014-3179

Monosaccharidic Push-pull Butadienes: Versatile Synthetic
Intermediates
Ahmed Bari
Research Center, College of Pharmacy, King Saud University, P. O. Box: 2457, Riyadh, 11451,
Saudi Arabia
Reprint requests to Ahmed Bari. Tel: +966533977946. Fax: +96614676220.
E-mail: abari@ksu.edu.sa
Z. Naturforsch. 2014, 69b, 98 – 102 / DOI: 10.5560/ZNB.2014-3179
Received June 28, 2013
Monosaccharidic push-pull butadienes are interesting building blocks for the synthesis of various
heterocyclic and natural products due to their biological prevalence and significant π-electron in-
teractions between donor and acceptor groups. A series of 1,5-anhydro-3,4,6-tri-O-benzyl-2-deoxy-
2-formyl-D-arabino-hex-1-enitol (2) and 1,5-anhydro-3,4-di-O-benzyl-2-deoxy-2-formyl-L-erythro-
hex-1-enitol (4) derived push-pull branched chain sugars have been synthesized by condensation
with active methylene compounds using basic aluminum oxide (Al2O3) or anhydrous sodium ac-
etate (NaOAc) at room temperature. The compounds have been fully characterized by spectroscopic
techniques and elemental analyses.
Key words: Push-pull Butadiene, Nucleoside Analogs, Active Methylene Compounds,
Condensation, Formyl Glycal
Introduction
pound under Knoevenagel–Cope conditions afford
push-pull butadienes. Because of the biological po-
tential [15] of this family of compounds and in ac-
cord with our efforts on exploring new synthetic meth-
ods, now the transformations of benzyl-protected 2-
formylglucal and 2-formylarabinal [16] using Al2O3
and in another method anhydrous NaOAc, to obtain C-
2(3) branched-chain glycals with an integrated push-
pull butadiene structural unit are described (Scheme 1).
Sodium acetate and aluminum oxide were selected
because of their basic character and because they
give better yields than similar compounds [17].
1,5-anhydro-3,4,6-tri-O-benzyl-2-deoxy-2-formyl-D-
arabino-hex-1-enitol (2) and 1,5-Anhydro-3,4-di-O-
benzyl-2-deoxy-2-formyl-L-erythro-hex-1-enitol (4)
were treated with various active methylene compounds
(Table 1) to give the monosaccharidic butadienes 3a–e
and 5a–e as yellow syrups. For compounds 3a–e
a longer reaction time was required due to the lower
basicity when aluminum oxide was applied, but no
side products were observed in dichloromethane at
room temperature. Heating of the mixture at higher
Carbohydrates are involved in a wide variety of bio-
logical functions and consequently show enormous po-
tential as therapeutic agents for a number of cases rang-
ing from infectious diseases to cancer therapies [1 – 4].
Push-pull butadienes are the class of compounds in
which the electron-releasing and electron-withdrawing
groups are attached on either end of the butadiene
chain that enhances the conjugation in the system [5,
6]. In these types of systems, the C=C double bonds
usually become more polarized due to π-electron delo-
calization [7 – 9]. Several branched chain sugars have
been reported starting from hexose and pentose gly-
cals which were used as synthetic intermediates to syn-
thesize a variety of nucleoside analogs [10]. All these
sugars are suitable precursors for cyclization reactions
with various N-nucleophiles leading to different types
of heterocyclic and carbocyclic anellated monosaccha-
rides [11].
Results and Discussion
Our earlier studies [12 – 14] have shown that formyl temperature resulted in the formation of various side
glycals when reacted with an active methylene com- products and lower yields.
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A. Bari · Push-pull Butadienes: Versatile Synthetic Intermediates
99
a)
R2
R2
R1
R1
O
O
R3
R3
BnO
BnO
1'
2'
R5
3a−e, 5a−e
CHO
R4
b)
1
:
:
2
4
R
R
R2 H, R3
= = OBn
= CH2OBn,
1
H, R2
R3
H
=
=
= OBn,
Scheme 1. Reagents and conditions: a) CH2Cl2, CH2R4R5, Al2O3, r. t.; b) ethanol, CH2R4R5, anhydrous NaOAc, r. t.
Table 1. Monosaccharidic push-pull butadienes 3a–e and 5a– Table 2. Yields of compounds 3a–e and 5a–e using Al2O3
e (Bn = benzyl).
(method A; see Scheme 1) and NaOAc (method B).
Compound R1
R2
R3
R4
R5
Compound
Yield (%)
method A
method B
3a
3b
3c
3d
3e
5a
5b
5c
5d
5e
CH2OBn
CH2OBn
CH2OBn
CH2OBn
H
H
H
H
OBn CN
OBn COCH3
OBn COOCH3 COOCH3
OBn COCH3
OBn COCH3
CONH2
CONH2
3a
3b
3c
3d
3e
5a
5b
5c
5d
5e
46
44
51
46
51
46
43
40
49
45
47
54
60
59
59
55
53
55
57
58
CONHPh
p-ClCONHPh
CONH2
CH2OBn
H
H
H
H
H
H
OBn
OBn
OBn
OBn
OBn
H
H
H
H
H
CN
COCH3
COOCH3 COOCH3
COCH3
COCH3
CONH2
CONHPh
p-ClCONHPh
The IR and NMR spectra of compounds 3a–e tramolecular hydrogen bond N–H···O, while the other
showed the absence of signals for the formyl group and appears at around δ = 6 ppm.
the formation of a butadiene unit. The comparison with
The NMR spectra of 3a–e and 5a–e showed the ex-
the spectra of similar compounds [18] whose structures istence of only the E-isomers which was proved by
were analyzed by means of 2D experiments allowed gated decoupling (GD) spectra in which a large cou-
the assignment of all 13C NMR signals. The intense pling constant (J = 13 Hz) was found for the CN sub-
color of the compounds could be due to the ‘push-pull’ stituent and H-10 at the exocyclic butadiene unit of 3a.
property of the C-branched butadiene moiety which On the other hand there is a smaller value (J = 6.6 Hz)
causes characteristic alternating chemical shifts of sp2 for the coupling between H-10 and the attached car-
carbon atoms of C-1, C-2 and C-10 and C-20.
bonyl group, in accordance with the configuration re-
Moreover, similar results were obtained when an- ported by Peseke et al. for similar compounds [19].
hydrous sodium acetate was used as a base to prepare
compounds 5a–e. It is noteworthy that the yields were
better when anhydrous sodium acetate was used (Ta-
ble 2). The IR and NMR spectra of compounds 5a–e
showed the absence of signals for the formyl group.
According to the 13C NMR spectra, a CN group is
present in compound 5a, while a strong absorption in
the IR spectrum also confirms the presence of a nitrile
group. In the 1H NMR spectrum of compounds 3a, 3b,
5a, and 5b, two NH signals were found, one of which
Experimental Section
Organic solvents used were dried by standard methods.
Tri-O-benzyl-D-glucal, L-arabinose, anhydrous sodium ac-
etate, active methylene compounds, and basic aluminum ox-
ide were purchased from Aldrich and were used as ob-
tained. IR spectra were recorded with a Perkin Elmer BX
FT-IR spectrometer. 1H and 13C NMR spectra were recorded
on a Bruker instrument at 500.133 and 125.76 MHz, re-
spectively, at 293 K in CDCl3. The mass spectra were ob-
is significantly downfield (δ = 8 ppm) due to an in- tained on a Micromass LCT mass spectrometer. The elemen-
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100
A. Bari · Push-pull Butadienes: Versatile Synthetic Intermediates
tal analyses for C, H and N were done on a Perkin-Elmer 1,5-Anhydro-3,4,6-tri-O-benzyl-2-[(E)-2-acetyl-2-amino-
CHN-2440 analyzer (C, H, N) and were in full agreement carbonyl-vinyl]-2-deoxy-D-arabino-hex-1-enitol (3b)
with the proposed compositions. Thin-layer chromatography
Rf = 0.62 (toluene-ethyl acetate, 8 : 2), yellowish syrup. –
(TLC) was performed with fluorescent silica gel HF254 plates
(Merck) viewed under UV 254 and 265 nm light and char-
ring with 10% sulfuric acid in ethanol. Merck silica gel 60
(230 – 400 mesh) was used for column chromatography sep-
1H NMR (500.133 MHz, CDCl3): δ = 2.05 (s, 3H, CH3),
3.45 (dd, 1H, J6a,6b = 10.5 Hz, J5,6a = 5.5, H-6a), 3.57
(dd, 1H, J5,6b = 7.4 Hz, H-6b), 3.87 (t, 1H, H-4), 4.32 (d,
1H, J = 10.7 Hz, CHHPh), 4.30 (m, 2H, CH2Ph), 4.51 (q,
2H, J = 12.1 Hz, CH2Ph), 4.52 (d, 1H, J3,4 = 2.4 Hz, H-
arations.
3), 4.66 (m, 1H, H-5), 4.67 (d, 1H, J = 10.7 Hz, CHHPh),
5.95 (br, 1H, NH), 6.92 (s, 1H, H-1), 7.02 – 7.32 (m, 16H,
Ph, H-10), 8.28 (br, 1H, NH). – 13C NMR (125.76 MHz,
CDCl3): δ = 30.1, 67.6, 67.9, 70.3, 70.5, 71.3, 73.3, 74.6,
78.4, 111.7, 113.6, 126.5 – 128.5 (o-, m-, p-Ph), 132.5, 136.1,
137.1, 137.2, 155.2 (C-10), 157.9, 160.3 (C-1), 166.1 (C=O),
163.6 (C=O). – IR (film): v = 3310, 3180 (NH2), 1680, 1700
(C=O) cm−1. – MS (CI, isobutane): m/z(%) = 528 (21)
[M+H]+, 420 (43) [M–OCH2Ph]+, 313 (17). – C32H33NO6
(527.23): calcd. C 72.85, H 6.30, N 2.65; found C 72.82, H
6.27, N 2.63.
General procedure for the preparation of compounds 3a–e
and 5a–e
Method A
To a vigorously stirred solution of formyl glucal (2) or
arabinal (4) (1.0 mmol) in CH2Cl2 (10 mL) was added the
active methylene compound (1.1 mmol) followed by Al2O3
(3 equiv. by wt). The resulting mixture was then stirred for
5 h for completion of the reaction, the progress of the reac-
tion being monitored by TLC. The solid was filtered off, and
the filtrate was evaporated to afford the crude product which
was purified by column chromatography to give the desired
compound.
1,5-Anhydro-3,4,6-tri-O-benzyl-2-[(E)-2,2-methoxy-
carbonyl-vinyl]-2-deoxy-D-arabino-hex-1-enitol (3c)
Rf = 0.57 (toluene-ethyl acetate, 8 : 2), yellowish syrup.
Method B
–
1H NMR (500.133 MHz, CDCl3): δ = 2.03 (s, 6H, 2 ×
To a vigorously stirred solution of formyl glucal (2) or
arabinal (4) (1.0 mmol) in ethanol (10 mL) was added an ac-
tive methylene compound (1.1 mmol) followed by anhydrous
sodium acetate (1.2 mmol). The resulting mixture was then
stirred for 3 h for completion of the reaction, the progress
of the reaction being monitored by TLC. The solvent was
evaporated to afford the crude product which was purified by
column chromatography to give the desired compound.
CH3), 3.41 (dd, 1H, J6a,6b = 10.7, J5,6a = 5.5 Hz, H-6a),
3.55 (dd, 1H, J5,6b = 7.4 Hz, H-6b), 3.85 (t, 1H, H-4), 4.30
(d, 1H, J = 10.4 Hz, CHHPh), 4.33 (m, 2H, CH2Ph), 4.53
(q, 2H, J = 12.2 Hz, CH2Ph), 4.50 (d, 1H, J3,4 = 2.4 Hz, H-
3), 4.64 (ddd, 1H, H-5), 4.65 (d, 1H, J = 10.4 Hz, CHHPh),
6.90 (s, 1H, H-1), 7.05 – 7.30 (m, 16H, Ph, H-10). – 13C NMR
(125.76 MHz, CDCl3): δ = 14.1, 14.3, 67.4, 67.8, 70.5, 70.6,
71.1, 73.2, 74.4, 78.5, 94.7, 111.5, 113.2, 126.4 – 128.7 (o-,
m-, p-Ph), 136.1, 137.2, 137.4, 154.2 (C-10), 157.7, 160.3 (C-
1), 163.7 (C=O), 163.8 (C=O). – IR (film): v = 1722, 1725
(C=O) cm−1. – MS (CI, isobutane): m/z(%) = 559 (17)
[M+H]+, 451 (23) [M–OCH2Ph]+, 343 (10). – C33H34O8
(558.23): calcd. C 70.95, H 6.13; found C 70.92, H 6.17.
1,5-Anhydro-3,4,6-tri-O-benzyl-2-[(E)-2-cyano-2-amino-
carbonyl-vinyl]-2-deoxy-D-arabino-hex-1-enitol (3a)
Rf = 0.58 (toluene-ethyl acetate, 8 : 2), yellowish syrup. –
1H NMR (500.133 MHz, CDCl3): δ = 3.40 (dd, 1H, J6a,6b
=
10.8, J5,6a = 5.5 Hz, H-6a), 3.59 (dd, 1H, J5,6b = 7.5 Hz, H-
6b), 3.89 (t, 1H, H-4), 4.30 (d, 1H, J = 10.9 Hz, CHHPh),
4.32 (m, 2H, CH2Ph), 4.50 (q, 2H, J = 11.9 Hz, CH2Ph),
4.55 (d, 1H, J3,4 = 2.4 Hz, H-3), 4.67 (m, 1H, H-5), 4.67 (d,
1H, J = 10.9 Hz, CHHPh), 6.05 (br, 1H, NH), (6.95 (s, 1H,
1,5-Anhydro-3,4,6-tri-O-benzyl-2-[(E)-2-acetyl-
2-N-(phenylamino)carbonyl-vinyl]-2-deoxy-D-arabino-
hex-1-enitol (3d)
Rf = 0.52 (toluene-ethyl acetate, 7 : 3, yellowish syrup.
H-1), 7.02 – 7.35 (m, 16H, Ph, H-10), 8.24 (br, 1H, NH). – – 1H NMR (500.133 MHz, CDCl3): δ = 2.06 (s, 3H, CH3),
13C NMR (125.76 MHz, CDCl3): δ = 67.5, 67.9, 70.1, 70.3, 3.42 (dd, 1H, J6a,6b = 10.9, J5,6a = 5.5 Hz, H-6a), 3.60 (dd,
71.5, 73.1, 74.4, 78.1, 90.7, 111.9, 113.5, 127 – 128.5 (o-, m-, 1H, J5,6b = 7.4 Hz, H-6b), 3.87 (t, 1H, H-4), 4.31 (d, 1H,
p-Ph), 136.2, 136.9, 137.1, 157.6, 157.8 (C-10), 160.6 (C- J = 11.2 Hz, CHHPh), 4.31 (m, 2H, CH2Ph), 4.49 (q, 2H,
1), 166.3 (C=O). – IR (film): v = 3319, 3187 (NH2), 2224 J = 12.1 Hz, CH2Ph), 4.53 (d, 1H, J3,4 = 2.4 Hz, H-3), 4.65
(CN), 1710 (C=O) cm−1. – MS (CI, isobutane): m/z(%) = (ddd, 1H, J4,5 = 5.5 Hz, H-5), 4.66 (d, 1H, J = 11.2 Hz,
511 (27) [M+H]+, 403 (30) [M–OCH2Ph]+, 297 (19). – CHHPh), 6.93 (s, 1H, H-1), 7.05 – 7.31 (m, 17H, Ph, H-
C31H30N2O5 (510.22): calcd. C 72.92, H 5.92, N 5.49; found 10), 7.40 (m, 3H, Ph), 10.2 (br, 1H, NH). – 13C NMR
C 72.87, H 5.90, N 5.45.
(125.76 MHz, CDCl3): δ = 29.4, 67.4, 67.8, 70.3, 70.5, 71.6,
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73.3, 74.6, 78.3, 82.2, 111.7, 113.7, 127.2 – 129.5 (o-, m-, p- 11.9 Hz, CH2Ph), 5.0 (dd, 2H, J = 10.7 Hz, CH2Ph), 5.15
Ph), 136.3, 136.7, 137.3, 152.7 (C-10), 157.7, 160.4 (C-1), (m, 1H, J3,4 = 4.2 Hz, H-3), 6.01 (br, 1H, NH), 7.12 (s, 1H,
167.3 (C=O), 198.1 (C=O). – IR (film): v = 3315, (NH), H-1), 7.13 – 7.27 (m, 10 H, Ph), 7.55 (s, 1H, H-10), 8.24 (br,
1690, 1698 (C=O) cm−1. – MS (CI, isobutane): m/z(%) = 1H, NH). – 13C NMR (125.76 MHz, CDCl3): δ = 64.2, 66.5,
604 (17) [M+H]+, 390 (41) [M–2 × OCH2Ph]+, 299 (29). – 71.9, 72.3, 74.1, 92.5, 116.6, 127.6, 127.7, 128.2, 128.3,
C38H37NO6 (603.26): calcd. C 75.60, H 6.18, N 2.32; found 128.4, 128.7 (Ph), 137.2, 138.5 (i-Ph), 155.3 (C-10), 162.3
C 75.63, H 6.16, N 2.35.
(C-1), 164.1 (C=O), 166.3 (C=O). – IR (film): v = 3334
(NH), 1690, 1705 (C=O) cm−1. – MS (CI, isobutane):
m/z(%) = 408 (19) [M+H]+, 300 (23) [M–OCH2Ph]+, 193
(36). – C24H25NO5 (407.17): calcd. C 70.74, H 6.18, N 3.44;
found C 70.73, H 6.16, N 3.45.
1,5-Anhydro-3,4,6-tri-O-benzyl-2-[(E)-2-acetyl-
2-N-(p-chlorophenyl)-carboxamide-vinyl]-2-deoxy-
D-arabino-hex-1-enitol (3e)
Rf = 0.52 (toluene-ethyl acetate, 8:2), yellowish syrup. –
1H NMR (500.133 MHz, CDCl3): δ = 2.09 (s, 3H, CH3),
3.41 (dd, 1H, J6a,6b = 10.8, J5,6a = 5.4 Hz, H-6a), 3.57 (dd,
1H, J5,6b = 7.5 Hz, H-6b), 3.90 (t, 1H, H-4), 4.33 (d, 1H, J =
1,5-Anhydro-3,4-di-O-benzyl-2-[(E)-2,2-methoxycarbonyl-
vinyl]-2-deoxy-L-erythro-hex-1-enitol (5c)
Rf = 0.52 (toluene-ethyl acetate, 8:2), yellowish syrup. –
11.2 Hz, CHHPh), 4.33 (m, 2H, CH2Ph), 4.50 (q, 2H, J = 1H NMR (500.133 MHz, CDCl3): δ = 3.80 (quintet (AB),
11.9 Hz, CH2Ph), 4.53 (d, 1H, J3,4 = 2.5 Hz, H-3), 4.67 (ddd, 1H, H-4), 4.13 (dddd, 1H, J5a,5b = 10.7 Hz, H-5a), 4.31 (dd,
1H, H-5), 4.66 (d, 1H, J = 11.2 Hz, CHHPh), 6.97 (s, 1H, H- 1H, H-5b), 4.66 (dd, 2H, J = 11.9 Hz, CH2Ph), 5.05 (dd, 2H,
1), 7.07 – 7.33 (m, 18H, Ph, H-10), 7.39 (m, 2H, Ph), 10.5 (br, J = 10.5 Hz, CH2Ph), 5.14 (dd, 1H, J3,4 = 4.0 Hz, H-3), 7.12
1H, NH). – 13C NMR (125.76 MHz, CDCl3): δ = 29.5, 67.5, (s, 1H, H-1), 7.15 – 7.28 (m, 10 H, Ph), 7.57 (s, 1H, H-10). –
67.7, 70.1, 70.4, 71.3, 73.6, 74.5, 78.4, 81.1, 111.5, 112.9, 13C NMR (125.76 MHz, CDCl3): δ = 14.1, 14.2, 66.5, 71.9,
127.2 – 129.2 (o-, m-, p-Ph), 136.2, 136.6, 137.5, 152.9 (C- 72.3, 74.1, 92.5, 113.1, 116.4, 127.5, 127.4, 128.6, 128.3,
10), 157.6, 160.1 (C-1), 167.4 (C=O), 198.5 (C=O). – IR 128.4, 128.5 (Ph), 137.2, 138.3 (i-Ph), 153.6 (C-10), 162.4
(film): v = 3238, 3365 (NH), 1692, 1705 (C=O) cm−1. – MS (C-1), 163.2 (C=O), 163.4 (C=O). – IR (film): v = 1725,
(CI, isobutane): m/z(%) = 638 (21) [M+H]+, 425 (15) [M– 1728 (C=O) cm−1. – MS (CI, isobutane): m/z(%) = 439
2 × OCH2Ph]+, 271 (42). – C38H36ClNO6 (637.22): calcd. (18) [M+H]+, 224 (15) [M–2 × OCH2Ph]+. – C25H26O7
C 71.52, H 5.69, N 2.19; found C 71.56, H 5.71, N 2.18.
(438.17): calcd. C 68.48, H 5.98; found C 68.47, H 5.96.
1,5-Anhydro-3,4-di-O-benzyl-2-[(E)-2-cyano-2-amino-
carbonyl-vinyl]-2-deoxy-L-erythro-hex-1-enitol (5a)
1,5-Anhydro-3,4-di-O-benzyl-2-[(E)-2-acetyl-
2-N-(phenylamino)carbonyl-vinyl]-2-deoxy-L-erythro-
hex-1-enitol (5d)
Rf = 0.52 (toluene-ethyl acetate, 7:3), yellowish syrup. –
1H NMR (500.133 MHz, CDCl3): δ = 3.81 (quintet (AB),
Rf = 0.55 (toluene-ethyl acetate, 8:2), yellowish syrup. –
1H, H-4), 4.15 (dddd, 1H, J5a,5b = 10.6 Hz, H-5a), 4.32 (dd, 1H NMR (500.133 MHz, CDCl3): δ = 3.78 (quintet (AB),
1H, H-5b), 4.66 (dd, 2H, J = 11.9 Hz, CH2Ph), 5.02 (dd, 1H, H-4), 4.12 (dddd, 1H, J5a,5b = 10.5 Hz, H-5a), 4.33 (dd,
2H, J = 10.5 Hz, CH2Ph), 5.16 (m, 1H, J3,4 = 3.8 Hz, H- 1H, H-5b), 4.65 (dd, 2H, J = 12.2 Hz, CH2Ph), 5.02 (dd, 2H,
3), 6.08 (br, 1H, NH), 7.10 (s, 1H, H-1), 7.15 – 7.30 (m, 10 J = 10.5 Hz, CH2Ph), 5.15 (m, 1H, J3,4 = 3.7 Hz, H-3), 7.13
H, Ph), 7.58 (s, 1H, H-10), 8.35 (br, 1H, NH). – 13C NMR (s, 1H, H-1), 7.15 – 7.27 (m, 12 H, Ph), 7.35 (m, 3H, Ph), 7.57
(125.76 MHz, CDCl3): δ = 64.2, 66.5, 71.9, 72.3, 74.1, (s, 1H, H-10), 10.3 (br, 1H, NH). – 13C NMR (125.76 MHz,
92.5, 113.1, 116.6, 127.6, 127.7, 128.2, 128.3, 128.4, 128.7 CDCl3): δ = 29.6, 64.4, 66.3, 71.5, 72.1, 74.3, 94.7, 112.8,
(Ph), 137.2, 138.5 (i-Ph), 157.4 (C-10), 162.3 (C-1), 167.5 116.3, 127.6, 127.8, 127.9, 128.1, 128.4, 128.5, 128.7, 128.9,
(C=O), 198.3 (C=O). – IR (film): v = 3319 (NH), 2225 129.1, 129.5 (o-, m-, p-Ph), 137.3, 138.5 (i-Ph), 152.4 (C-10),
(CN), 1700 (C=O) cm−1. – MS (CI, isobutane): m/z(%) = 162.5 (C-1), 167.2 (C=O), 197.7 (C=O). – IR (film): v =
391 (11) [M+H]+, 284 (15) [M–OCH2Ph]+, 177 (40). – 3340 (NH), 1694, 1698 (C=O) cm−1. – MS (CI, isobutane):
C23H22N2O4 (390.16): calcd. C 70.75, H 5.68, N 7.17; found m/z(%) = 484 (31) [M+H]+, 376 (19) [M–OCH2Ph]+, 257
C 70.72, H 5.71, N 7.19.
(53). – C30H29NO5 (483.20): calcd. C 70.75, H 5.68, N 7.17;
found C 70.72, H 5.71, N 7.19.
1,5-Anhydro-3,4-di-O-benzyl-2-[(E)-2-acetyl-2-amino-
carbonyl-vinyl]-2-deoxy-L-erythro-hex-1-enitol (5b)
1,5-Anhydro-3,4-di-O-benzyl-2-[(E)-2-acetyl-
2-N-(p-chlorophenyl)-carboxamide-vinyl]-2-deoxy-
L-erythro-hex-1-enitol (5e)
Rf = 0.52 (toluene-ethyl acetate, 8:2), yellowish syrup. –
1H NMR (500.133 MHz, CDCl3): δ = 2.08 (s, 3H, CH3),
3.80 (quintet (AB), 1H, H-4), 4.13 (dddd, 1H, J5a,5b
=
Rf = 0.57 (toluene-ethyl acetate, 7:3), yellowish syrup. –
10.4 Hz, H-5a), 4.30 (dd, 1H, H-5b), 4.66 (dd, 2H, J = 1H NMR (500.133 MHz, CDCl3): δ = 3.76 (quintet (AB),
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102
A. Bari · Push-pull Butadienes: Versatile Synthetic Intermediates
1H, H-4), 4.11 (dddd, 1H, J5a,5b = 10.5 Hz, H-5a), 4.30 (dd, 3340 (NH), 1690, 1705 (C=O) cm−1. – MS (CI, isobutane):
1H, H-5b), 4.63 (dd, 2H, J = 12.0 Hz, CH2Ph), 5.04 (dd, 2H, m/z(%) = 482 (37) [M–Cl]+, 410 (13) [M–OCH2Ph]+, 376
J = 10.4 Hz, CH2Ph), 5.15 (m, 1H, J3,4 = 4.2 Hz, H-3), 7.15 (45). – C30H28ClNO5 (517.17): calcd. C 69.56, H 5.45, N
(s, 1H, H-1), 7.12 – 7.29 (m, 10 H, Ph), 7.37 (m, 3H, Ph), 7.53 2.70; found C 69.56, H 5.42, N 2.73.
(s, 1H, H-10), 10.41 (br, 1H, NH). – 13C NMR (125.76 MHz,
Acknowledgement
CDCl3): δ = 29.5, 64.2, 66.1, 71.3, 71.9, 74.1, 94.5, 112.7,
The author would like to thank the Research Center,
College of Pharmacy and Deanship of Scientific Research,
King Saud University for supporting this study.
116.5, 127.4, 127.7, 127.8, 128.1, 128.3, 128.5, 128.6, 128.9,
129.5 (o-, m-, p-Ph), 137.1, 138.3 (i-Ph), 152.8 (C-10), 162.3
(C-1), 167.3 (C=O), 197.8 (C=O). – IR (film): v = 3210,
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