α-Glucosidase inhibitory activities of phenolic acid amides with l-amino acid moiety

Article abstract of DOI:10.1039/c6ra08330g

α-Glucosidase inhibitors can effectively control postprandial hyperglycemia. In this study, a series of phenolic acids with the l-amino acid moiety were synthesized and their inhibitory activities against α-glucosidase from Saccharomyces cerevisiae (EC 3.

Full text of DOI:10.1039/c6ra08330g

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The α-Glucosidase Inhibitory Activities of Phenolic Acid Amides
with L-Amino Acid Moiety†‡
Bin Liu,§a Ji-Mei Ma,§a Hang-Wei Chen,a Zi-Long Li,a Lin-Hao Sun, a Zhen Zeng a and Hong Jiang*a
Abstract: α-glucosidase inhibitors can effectively control the postprandial hyperglycemia. In this paper, a series of phenolic
acid with L-amino acid moiety were synthesized and their inhibitory activities against α-glucosidase from Saccharomyces
cerevisiae (EC 3.2.1.20) were evaluated. The results suggested that all these compounds showed strong α-glucosidase
inhibitory activities. In particular, the N-(4-hydroxyl-phenylpropenoyl)-L-alanine (c2) and N-(4-hydroxyl-phenylpropenoyl)-
L-methionine (c8) exhibited much higher potency (IC50 values 0.04 mM) than the positive control acarbose (IC50 values 1.70
mM). Three-dimensional quantitative structure-activity relationship (3D-QSAR) model for comparative molecular field
analysis (CoMFA) was generated and the result showed that bulk groups and high electron density groups on the amino
acid residues were benefit to their activities, moreover, the substituents with low electron density and small steric
hindrance on the para position of the benzene ring were helpful to improve the activities. Kinetic analysis indicated that
compound (c2) acted as a mixed-type inhibitor with Ki value of 0.0124 mM. Docking analysis revealed that they could bind
to α-glucosidase at the catalytic site via hydrogen bonds and a π-π stacking.
Received 00th January 2016,
Accepted 00th January 20xx.
DOI: 10.1039/x0xx00000x
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sativum fruit etc.21 Researches demonstrated that the cocoa
extract or cocoa products could well control the glucose level in
diabetic-induced rats and genetically inherited diabetic rats.
1. Introduction
22, 23
Diabetes mellitus (DM) is a common chronic metabolic diseases
characterized by elevating plasma glucose levels.1,2 The type
Abbe Maleyki et al. (2008) revealed that the polyphenol extract
from cocoa had an effect on postprandial glucose control.24 Apart
from polyphenol, are there any other α-glucosidase inhibitors in
cocoa products? Exploring this problem would be valuble to
develop food-based glucose-lowering agents. Considering the
large family of phenolic acid amides with L-amino acid moiety
present in cocoa, we speculated that they may act as α-
glucosidase inhibitors and cause hypoglycemic effect induced by
cocoa. To validate this hypothesis, 42 such phenolic acid amides
were synthesized, and some of them have already been isolated
from cocoa or other natural products. Their α-glucosidase
inhibitory activities in vitro were investigated.
Ⅱ
diabetes mellitus (TIIDM) caused by insulin resistance accounts for
more than 90 percent DM,3 and has become a worldwide health
concern due to its constantly growing incidence and serious
complications.4,5 Currently glucose-lowering agents include
sulfonylureas, glinides, biguanides and α-glucosidase inhibitors.6-8
Among them, α-glucosidase inhibitors can effectively control the
postprandial hyperglycemia through inhibiting the catalytic
activity of α-glucosidase, a key enzyme catalyzes the final step in
the digestive process of carbohydrates.9,10 Sugar analogue α-
glucosidase inhibitors such as acarbose, miglitol and voglibose are
common used in clinic. However, most of them have
gastrointestinal side effects.11-13 Many natural non-glycosidic
compounds present in plants have been reported with good α-
glucosidase inhibition.14-16 This may provide a valuable approach
for the development of safe and effective α-glucosidase inhibitors.
Polyphenols are widespread in plants and exhibit various
medicinal properties.17,18 As an important kind of polyphenol,
phenolic acid amides with L-amino acid moiety are widely
distributed in plants such as cocoa (Theobroma cacao ),19,20
Angelica archanglica root, Sambucus nigra flowers, Coriandrum
2. Results and discussion
2.1. Chemistry
The synthetic method was illustrated in Fig. 1 and ferulic acid
derivative was exemplified. 42 kinds of N-phenylpropenoyl-L-
amino acids were synthesized. The structures were illustrated in
1
Table 1. All the synthesized compounds were confirmed by the H
NMR and MS techniques. All spectral data were in accordance
with the assumed structure.
2.2. The inhibitory activities against α-glucosidase and 3D QSAR
model development
All the synthesized compounds were evaluated for their inhibitory
activities against α-glucosidase. The IC50 values are summarized in
table 1. Some compounds had better activities than acarbose (IC50
value of 1.70 mM). Among them, compound c2, c3, and c8 showed
much more strong activities than acarbose with their IC50 values
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0.04, 0.07 and 0.04 mM, respectively, indicating much more active
than acarbose. Compounds a9, a13, a14, c9, c13, c14, which were
natural present in the cocoa beans, showed similar or better
activities than acarbose. This result indicated that the phenolic
acid amides in cocoa might play part roles on the hypoglycemic
effects of cocoa beans.
25
Fig. 1 The synthetic route of N-[4-hydroxy-3-methoxyl-(E)-cinnamoyl]-L-amino acid
Table.1 The in vitro α-glucosidase inhibition activities of compounds
Compound
a1
R
IC50 (mM )
34.43
23.07
31.50
17.76
22.16
2.16
Compound
b1
R
IC50 (mM )
3.53
Compound
c1
R
IC50 (mM )
0.72
0.04
0.07
0.27
0.40
0.21
0.30
0.04
0.68
3.42
1.42
0.23
0.12
0.13
Gly
Ala
Leu
Ile
Gly
Ala
Leu
Ile
Gly
Ala
Leu
Ile
a2
b2
9.63
c2
a3
b3
6.43
c3
a4
b4
10.60
15.29
29.42
1.17
c4
a5
Val
Pro
Phe
Met
Trp
Ser
Gln
Thr
Glu
Asp
b5
Val
Pro
Phe
Met
Trp
Ser
Gln
Thr
Glu
Asp
c5
Val
Pro
Phe
Met
Trp
Ser
Gln
Thr
Glu
Asp
a6
b6
c6
a7
2.13
b7
c7
a8
19.27
1.84
b8
11.16
3.95
c8
a9
b9
c9
a10
a11
a12
a13
a14
1.10
b10
b11
b12
b13
b14
1.20
c10
c11
c12
c13
c14
4.31
2.93
3.25
3.80
2.10
1.95
1.91
1.53
* IC 50 (acarbose) = 1.70 mM
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The statistical parameters of CoMFA were showed in Table 2. An yellow area), bulk groups decreased the inhibitory activities, thus
optimum number of principal components (ONC=10) was the activities of
b series compouds with methoxy on the
recommended based on the LOO cross-validated run with a q2 value para of benzene rings were weaker than that of c series. In the
of 0.561. The subsequent non-cross-validated correlation electrostatic fields, groups with high electron density (red areas on
coefficients r2 value was 0.977, greater than the value required for a the residual part of amino acids) increased the activities. For
good model. The CoMFA model contour map included 51.2% of the example, compounds with negative electron groups such as
electrostatic
field descriptor, and 48.8% of the contributing steric hydroxyl (a10, a12, b10 and b12), amino (a11 and b11), carboxyl
fi
eld, indicating a greater in
fl
uence of the electrostatic eld.In order (a13, a14, b13 and b14) on their amino acid side chains performed
fi
to validate the prediction capabilities of the 3D QSAR model better inhibitory activities among a and b series compounds.
further, predicted activity and the residuals between the Substituents with low electron density (blue) regions on the
experimental and the predicted activity of the training set and test benzene ring of cinnamic acid were expected to increase activities.
set were measured respectively (see supplement information Table Among the three series, the electron density of substituents on the
S1). The Linear regression analysis plot bwtween predicted pIC50 cinnamic acid had the following order: 4-hydroxy-3-methoxy>4-
agaainst observed pIC50 of traning set (Fig.2(A)) showed that the methoxy>4-hydroxy,and the 4-hydroxy substituted compounds (c
predicted pIC50 values were almost in accordance with the series) exhibited much stronger activities than a and b series. On
experimental values with a slop of 0.980. The predicted pIC50 the whole, the electrostatic field had more influence than steric
values of test set well suited the experiment data (Figure 2(B)). The
field on the activities.
result indicated that the CoMFA model had a good predictability.
2.4. Kinetic analysis
To further explore the inhibitory characteristics of these
2.3. Interpretation of the inhibitory activity and 3D QSAR model
The steric and electrostatic contour map obtained via CoMFA compounds, compound c2 were chosen as a representative to study
model was showed in Fig. 3. In the steric eld, bulky groups (the the inhibition mode. The kinetic analysis was performed using
green area distributed on the amino acid residual chain, such as Lineweaver-Burk (Fig. 4(A)) and Dixon plots (Fig. 4(B)). Compounds
aromatic rings in compound a7, a9, b7 and b9) were responsible for c2 showed a mixed inhibitory type against -glucosidase from S.
fi
α
the high inhibitory activities, while compounds with small groups cerevisiae. The inhibitory constant (Ki) value was 0.0124 mM. The
(a1-a5 and a8, b1-b5 and b8) had much lower activities in the a and result indicated that the inhibitory type was different from
b series compounds. But on the para position of benzene rings (the acarbose, which was reported to be a competitive inhibitor. 26
Table 2 Statistical results of the CoMFA model (q2 was leave-one-out cross-validated correlation coefficient; ONC, optimum number of principal component;
r2, non-cross-validated correlation coefficients; SEE, standard error of the estimate; F, the ratio between explained and unexplained variance.)
LOO
ONC
NV
Relative contributor
q2
r2
SEE
F
Steric
Electrostatic
0.561
10
0.977
0.143
101.655
0.488
0.512
Fig. 2 Predicted versus observed pIC50 of the (A) training set and (B) test set
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Fig. 3 CoMFA contour map for α-glucosidase. Steric areas: bulk groups increase (green) or decrease (yellow) potency. Electrostatic areas: high electron
density (red) and low electron density (blue) regions are exp.ected to increase potency.
Fig. 4 Lineweaver−Burk (A) and Dixon (B) plots of α-glucosidase inhibition at different concentrations of pNPG and compound c2
2.5. Docking study
π π
- stacking between the benzene ring and Phe157 also
a
contributed to the binding. In all, as shown in Fig. 5(B) c2 had a
very similar locationto the native ligand maltose (Fig. 5(B)). Thus,
c2 could well block the active center and exert its inhibitory
actions. However, it was different in the case of compound a2 (Fig.
5(C)). The introduction of 3-methoxyl to the benzene ring caused
the reverse of the binding locations. Moreover the phenyl group
entered the pocket in a sideways because of the narrow pore of
the pocket. When the hydrophilic property of the amino acid
terminal was increased by introduction of a carboxyl to compound
a14 (Fig. 5(D)), it could enter the pocket in a perfect way by
binding to Asp214, Glu276, Asp349, Asp68, Arg212, Arg439 via
hydrogen bond. Therefore, the binding types were not totally the
same among these compounds, both the substituents on the
phenyl ring and amino acid residues had great influence on the
bonding position.
The Ramachandran plot (see supplement information Fig. S1)
analysis by PROCHECK con rmed the quality of the modeling 3D
fi
structure with 87.6% of residues lied in the most favored regions,
11.6% in the additional allowed regions, 0.2% in the generously
allowed regions respectively. Considering the inhibitory type was a
mixed one, blind docking was firstly conducted using c2 as ligand
model, interestingly, the binding sites were coincident with the
catalytic pocket of
(Fig. 5(A)).
α-glucosidase from Saccharomyces cerevisiae
As showed in Fig. 5 (A), amino acids terminal of the compound
c2 are oriented towards the core of the suit. And c2 had a close
interaction with the active sites Asp214 of the pocket. In the
meantime, the hydroxyl group on the benzene ring of c2
interacted with the residues of Asp349 and Arg 439. Furthermore,
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Fig. 5 Docking model predicted structural details of compound c2 (A and B), a2(C), a14 (D) Green: target inhibitors; Yellow: native ligand
maltose; Blue: Bonding residues of inhibitors.
stirring, two more equivalent of sodium hydroxide solid (20 mmol)
was added to the reaction mixture. The mixture was stirred for an
additional 3-4 h at room temperature. The acetone was then
4 Experimental
4.1. General
evaporated. The residual aqueous phase was adjust to pH 2 with
aqueous hydrochloric acid and then extracted with ethyl acetate(20
mL×3). The combined organic phase was washed with water, dried
over MgSO4 and concentrated to afford the crude product, which
was purified by column chromatography on silica gel (ethyl
acetate/petroleum ether 1:2 (v/v)) to get the finnal product. The
spectra data and physical properties of the compounds were
showed as following:
α
-Glucosidase (EC 3.2.1.20) from Saccharomyces cerevisiae was
purchased from Sigma. The -Nitrophenyl- -Dglucopyranoside
NPG), phenolic acids and amino acids were purchased from
p
α
(
p
Aladdin Co. Ltd (Shanghai, China) and all the chemicals were of
analytical reagent grade. Melting points (m.p) were measured on a
Taike digital micro melting point apparatus X-4 (Beijing, China), 1H
NMR spectroscopy was obtained using Bruker AM spectrometers
on600 MHz or 400Hz in DMSO. MS (ESI) spectra were recorded on
Agilent 6100 Single Quad spectrometer.
N
-[4-hydroxy-3-methoxy-(
yellow solid (1.63 g, 65% yield); mp 224-226
d6-DMSO) 12.56 (s, 1H, -COOH), 9.44 (s, 1H, -OH), 8.23 (t, J=5.9Hz,
1H, -NH), 7.34 (d, = 15.7 Hz, 1H, Ph-CH=CH), 7.15 (d, = 1.8 Hz, 1H,
Ph-H), 7.01 (dd, = 8.2, 1.8 Hz, 1H, Ph-H), 6.79 (d, = 8.1 Hz, 1H, Ph-
H), 6.54 (d, = 15.7 Hz, 1H, -CH=CH-), 3.87 (d, = 5.9 Hz, 2H, -CH2),
3.81 (s, 3H, -CH3); MS m/z 252.2 [M+H]+.
-[4-hydroxy-3-methoxy-(
yellow amorphous solid (1.59 g, 60% yield); mp 95-97
(400 MHz, d6-DMSO)
(d, = 7.4 Hz, 1H, -NH), 7.33 (d,
= 1.7 Hz, 1H, Ph-H), 7.00 (dd,
E
)-cinnamoyl]-L-glycine acid a1, a light
°
C; 1H NMR (400 MHz,
4.2. Syntheses of N-phenylpropenoyl-L-amino acids
δ
The synthetic method was based on the reported method with
modifications27. The experiment procedure was as following using
ferulic acid derivative as example : (
was added to aqueous solution (15 mL) of sodium hydroxide (64
mmol) below 15 C. After the solid dissolved completely, acetic
anhydride (26 mmol ) was added dropwise to the solution in an ice
bath. After stirring for 30 min at room temperature, the reaction
mixture was acidified to pH 1.0 with hydrochloric acid (2 mol/L) to
precipitate. The suspension was filtered. The filtered cake was
washed three times with water and dried in vacuum. The solid was
used in the next step without further purification. Thionyl chloride
(2 mmol) and a catalytic amount of DMF were added to the
suspension of the above acetylated phenylpropenoic acid derivative
in 20 mL chloroform. The mixture was heated for 7-8 h at 55 ºC.
Remaining thionyl chloride and solvent were removed by
evaporation to give a pale yellow oily liquid.
A solution of the above acyl chlorides (10 mmol) in 20 mL
acetone and 10 mL hydroxide sodium (10 mmol) solution were add
dropwise simultaneously to a solution of sodium salts of L-amino
acid in 10 mL acetone and water (1:1) in ice bath. Followed by 2 h of
J
J
J
J
E)-ferulic acid (10 mmol each)
J
J
º
N
E
)-cinnamoyl]-L-alanine acid a2,
a
°
C; 1H NMR
δ
12.84 (s, 1H, -COOH), 9.45 (s, 1H, -OH), 8.23
= 15.7 Hz, 1H, Ph-CH=CH-), 7.13 (d,
J
J
J
J
= 8.2, 1.7 Hz, 1H, Ph-H), 6.79 (d,
J
J
=
=
8.1 Hz, 1H, Ph-H), 6.52 (d,
J = 15.7 Hz, 1H, Ph-CH=CH-), 4.32 (q,
7.8 Hz, 1H, -CH-), 3.80(s, 3H, -OCH3), 1.31 (d, J = 7.3 Hz, 3H, -CH3);
MS m/z 266.2 [M+H]+.
N
-[4-hydroxy-3-methoxy-(
yellow amorphous solid (1.68 g, 55% yield); mp 96-98
(400 MHz, d6-DMSO) 12.56 (s, 1H, -COOH), 9.45 (s, 1H, -OH), 8.18
(d, = 8.1 Hz, 1H, -NH), 7.33 (d, = 15.7 Hz, 1H, Ph-CH=CH), 7.13 (d,
= 1.6 Hz, 1H, Ph-H), 6.99 (dd, = 8.2, 1.7 Hz, 1H, Ph-H), 6.79 (d,
= 15.7 Hz, 1H, -CH=CH), 4.34 (dt, = 8.9,
E
)-cinnamoyl]-L-leucine acid a3, a light
°
C; 1H NMR
δ
J
J
J
J
J =
8.1 Hz, 1H, Ph-H), 6.53 (d,
J
J
5.6 Hz, 1H, -CH-), 3.81 (s, 3H, -OCH3), 1.75
–
1.61 (m, 1H, -CH-), 1.61
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– 1.48 (m, 2H, -CH2-), 0.91 (d, J = 6.5 Hz, 3H, -CH3-), 0.86 (d, J = 6.5
N-[4-hydroxy-3-methoxy-(E)-cinnamoyl]-L-glutamine acid a11, a
Hz, 3H, -CH3-). Ms m/z 308.4 [M+H]+.
white amorphous solid (1.61 g, 50% yield); mp 96-99 °C; 1H NMR
(400 MHz, d6-DMSO) δ 12.40 (s, 1H, -COOH), 9.46 (s, 1H, Ph-OH),
N-[4-hydroxy-3-methoxy-(E)-cinnamoyl]-L-isoleucine acid a4,
a
white amorphous solid (1.53 g, 50% yield); mp 94-97 °C; 1H NMR 8.21 (d, J = 7.9 Hz, 1H, -NH), 7.33 (d, J = 15.7 Hz, 1H, Ph-CH=CH-),
(400 MHz, d6-DMSO) δ 12.58 (s, 1H, -COOH), 9.45 (s, 1H, -OH), 8.05 7.13 (d, J = 1.7 Hz, 1H, Ph-H), 7.00 (dd, J = 8.2, 1.7 Hz, 1H, Ph-H),
(d, J = 8.5 Hz, 1H, -NH), 7.33 (d, J = 15.7 Hz, 1H, Ar-CH=CH), 7.13 (d, J 6.80 (d, J = 8.1 Hz, 1H, Ph-H), 6.53 (d, J = 15.7 Hz, 1H, Ph-CH=CH-),
= 1.6 Hz, 1H, Ar-H), 6.99 (dd, J = 8.2, 1.6 Hz, 1H, Ar-H), 6.81 (t, J =
12.4 Hz, 1H, Ar-H), 6.67 (d, J = 15.7 Hz, 1H -CH=CH), 4.32 (dd, J = 8.4,
5.9 Hz, 1H, -NH-CH-), 3.81 (s, 3H, -OCH3), 1.82 (dd, J = 7.5, 5.6 Hz, 1H,
-CH-), 1.44 – 1.16 (m, 2H, -CH2), 0.92 – 0.85 (m, 6H, -(CH3)2); MS m/z
308.4 [M+H]+.
4.33 (td, J = 8.7, 5.1 Hz, 1H，-CH-), 3.81 (s, 3H, -OCH3-), 2.41 – 2.20
(m, 2H, -CH2-), 2.09 – 1.93 (m, 1H, -CH2-), 1.94 – 1.75 (m, 1H, -CH2-);
MS m/z 324.3 [M+H]+.
N-[4-hydroxy-3-methoxy-(E)-cinnamoyl]-L-threonine acid a12, a
1
white solid (1.36 g, 46% yield); mp 192-194 °C; H NMR (400 MHz,
N-[4-hydroxy-3-methoxy-(E)-cinnamoyl]-L-valine acid a5, a white
amorphous solid (1.61 g, 55% yield); mp 90-92 °C; 1H NMR (400
MHz, d6-DMSO) δ 12.53 (s, 1H, -COOH), 9.45 (s, 1H, -OH), 8.03 (d, J =
8.6 Hz, 1H, -NH), 7.32 (d, J = 15.7 Hz, 1H, Ph-CH=CH-), 7.13 (d, J = 1.7
Hz, 1H, Ph-H), 6.99 (dd, J = 8.2, 1.7 Hz, 1H, Ph-H), 6.79 (d, J = 8.1 Hz,
1H, Ph-H), 6.68 (d, J = 15.7 Hz, 1H, Ph-CH=CH-), 4.28 (dd, J = 8.5, 5.6
Hz, 1H, -NH-CH-), 3.81 (s, 3H, -OCH3), 2.14 – 2.06 (m, 1H, -CH-),
0.97-0.85 (m, 6H, -CH(CH3)2); MS m/z 294.3 [M+H]+.
d6-DMSO) δ 12.92 (s, 1H, -COOH), 9.44 (s, 1H, Ph-OH), 7.77 (d, J =
8.7 Hz, 1H, -NH ), 7.31 (d, J = 15.7 Hz, 1H, Ph-CH=CH-), 7.17 (d, J =
1.6 Hz, 1H, Ph-H), 7.00 (dd, J = 8.2, 1.6 Hz, 1H, Ph-H), 6.81 (d, J=8.1
Hz, 1H, Ph-H), 6.80 (d, 1H, Ph-CH=CH-), 4.33 (dd, J = 8.7, 3.1 Hz, 1H,
-CH-), 4.16 (dd, J = 6.3, 3.2 Hz, 1H, -CH-), 3.81 (s, 4H, -OCH3), 1.07 (d,
J = 6.3 Hz, 3H, -CH3); MS m/z 296.3 [M+H]+.
N-[4-hydroxy-3-methoxy-(E)-cinnamoyl]-L-glutamic acid a13,
a
light yellow amorphous solid (1.97 g, 61%); mp 108-110 °C; 1H NMR
(600 MHz, d6-DMSO) δ 12.41 (s, 2H, -COOH), 9.46 (s, 1H), 8.22 (d, J =
7.9 Hz, 1H, -NH), 7.33 (d, J = 15.7 Hz, 1H, Ph-CH=CH-), 7.14 (d, J = 1.8
Hz, 1H, Ph-H), 7.00 (dd, J = 8.2, 1.8 Hz, 1H, Ph-H), 6.79 (d, J = 8.1 Hz,
1H, Ph-H), 6.53 (d, J = 15.7 Hz, 1H, Ph-CH=CH-), 4.37 – 4.28 (m, 1H, -
CH-), 3.81 (s, 3H, -OCH3), 2.38 – 2.22 (m, 2H, -CH2-), 2.06 – 1.97 (m,
1H, -CH2-), 1.85 – 1.178(m, 1H, -CH2-).; MS m/z 324.2 [M+H]+.
N-[4-hydroxy-3-methoxy-(E)-cinnamoyl]-L-proline acid a6,
a
1
white solid (1.90 g, 65% yield); mp 171-173 °C; H NMR (400 MHz,
d6-DMSO) δ 12.39 (s, 1H, -COOH), 9.46 (s, 1H, -OH), 7.38 (d, J = 15.4
Hz, 1H, Ph-CH=CH-), 7.29 (d, J = 1.6 Hz, 1H, Ph-H), 7.10 (d, J = 8.2 1H,
Ph-H), 6.81 (d, J = 15.8 Hz, 1H, Ph-CH=CH-), 6.78 (d, J = 8.3 Hz, 1H,
Ph-H), 4.33 (dd, J = 8.7, 3.9 Hz, 1H, -N-CH-), 3.82 (s, 3H, -OCH3), 3.77
– 3.61 (m, 1H, -CH2-), 2.22 – 1.81 (m, 3H, -CH2-, -CH2-); MS m/z
292.4 [M+H]+.
N-[4-hydroxy-3-methoxy-(E)-cinnamoyl]-L-aspartic acid a14,
a
yel-low solid (1.76 g, 57% yield); mp 187-189 °C; 1H NMR (400 MHz,
d6-DMSO) δ 12.49 (s, 2H, -COOH), 9.45 (s, 1H, -OH), 8.22 (d, J = 8.0
Hz, 1H, -NH), 7.33 (d, J = 15.7 Hz, 1H, Ph-CH=CH-), 7.14 (d, J = 1.6 Hz,
1H, Ph-H), 6.99 (dd, J = 8.2, 1.6 Hz, 1H, Ph-H), 6.79 (d, J = 8.1 Hz,
1H,Ph-H), 6.58 (d, J = 15.7 Hz, 1H, Ph-CH=CH-), 4.66 (dd, J = 13.3, 7.2
Hz, 1H, -CH-), 3.81 (s, 3H, -OCH3), 2.70 (qd, J = 16.6, 6.3 Hz, 2H, -CH2-
); MS m/z 310.3 [M+H]+.
N-[4-hydroxy-3-methoxy-(E)-cinnamoyl]-L-phenylalanine acid a7,
1
a white amorphous solid (2.11 g, 62% yield); mp 82-85 °C; H NMR
(400 MHz, d6-DMSO) δ 12.67 (s, 1H, -COOH ), 9.45 (s, 2H, -OH), 8.23
(d, J = 8.1 Hz, 2H, -NH), 7.24 (m, 6H, Ph-H, Ph-CH=CH-), 7.11 (d, J =
1.7 Hz, 1H, Ph-H), 6.98 (dd, J = 8.2, 1.7 Hz, 1H, Ph-H), 6.78 (d, J = 8.1
Hz, 1H, Ph-H), 6.52 (d, J = 15.7 Hz, 1H, Ph-CH=CH- ), 4.56 (td, J = 9.1,
4.8 Hz, 1H), 3.80 (s, 3H, -OCH3 ), 3.11 (dd, J = 13.9, 4.8 Hz, 1H, -CH2-
), 2.92 (dd, J = 13.9, 9.5 Hz, 1H, -CH2-); MS m/z 342.3 [M+H]+.
N-[4-hydroxy-3-methoxy-(E)-cinnamoyl]-L-methionine acid a8, a
yellow amorphous solid (1.85 g, 57% yield); mp 92-94 °C; 1H NMR
(400 MHz, d6-DMSO) δ 9.47 (s, 1H, -OH), 8.27 (d, J = 7.9 Hz, 1H, -
NH), 7.37 (d, J = 15.7 Hz, 1H, Ph-CH=CH-), 7.15 (d, J = 1.6 Hz, 1H, Ph-
H), 7.02 (dd, J = 8.2, 1.6 Hz, 1H, Ph-H), 6.81 (d, J = 8.1 Hz, 1H, Ph-H),
6.55 (d, J = 15.7 Hz, 1H, Ph-CH=CH-), 4.46 (td, J = 8.7, 4.6 Hz, 1H, -
CH-), 3.82 (s, 3H, -OCH3), 2.66 – 2.31 (m, 2H, -CH2-CH2-), 2.10 – 1.98
(m, 5H, -CH2-CH2-S-CH3); MS m/z 326.3 [M+H]+.
N-[4-hydroxy-3-methoxy-(E)-cinnamoyl]-L-tryptophane acid a9, a
white solid(1.93 g, 51% yield); mp 85-87 °C;1H NMR (400 MHz, d6-
DMSO) δ 10.83(s, 1H, -OH), 9.44 (s, 1H, -NH), 8.18 (d, J = 7.9 Hz, 1H,
-NH), 7.54 (d, J = 7.8 Hz, 1H, Ar-H), 7.32 (dd, J = 15.6, 11.9 Hz, 2H,
Ph-CH=CH-, Ar-H), 7.16 (d, J = 2.1 Hz, 1H, Ph--H), 7.12 (d, J = 1.6 Hz,
1H, Ar-H), 7.07 (t, J = 7.2 Hz, 1H, Ar-H), 7.02 – 6.94 (m, 2H, Ar-H, Ph-
H), 6.79 (d, J = 8.1 Hz, 1H, Ph-H), 6.56 (d, J = 15.7 Hz, 1H, Ph-CH=CH-
), 4.63 (td, J = 8.3, 5.0 Hz, 1H, -CH-), 3.80 (s, 3H, -OCH3), 3.23 (dd, J =
14.7, 4.9 Hz, 1H, -CH2-), 3.07 (dd, J = 14.7, 8.7 Hz, 1H, -CH2-); MS m/z
381.3 [M+1]+.
N-[4-methoxy-(E)-cinnamoyl]-L-glycine acid b1,
a white solid
(1.90 g, 81% yield); mp 165-167 °C; 1H NMR (600 MHz, d6-DMSO) δ
12.58 (s, 1H，-COOH), 8.32 (t, J = 5.9 Hz, 1H, -NH), 7.53 (d, J = 8.6
Hz, 2H, Ph-H), 7.40 (d, J = 15.8 Hz, 1H, Ph-CH=CH-), 6.98 (d, J = 8.6
Hz, 2H, Ph-H), 6.57 (d, J =15.8 Hz, 1H, Ph-CH=CH-), 3.88 (d, J = 5.9
Hz, 2H, -CH2-), 3.78 (s, 3H, -OCH3); MS m/z 236.3 [M+H]+.
N-[4-methoxy-(E)-cinnamoyl]-L-alanine acid b2, a white solid
(1.99 g, 80% yield); mp 162-164 °C; 1H NMR (600 MHz, d6-DMSO) δ
12.57 (s, 1H, -COOH), 8.32 (d, J = 7.3 Hz, 1H, -NH), 7.51 (d, J = 8.7 Hz,
2H, Ph-H ), 7.38 (d, J = 15.8 Hz, 1H, Ph-CH=CH-), 6.98 (d, J = 8.7 Hz,
2H, Ph-H), 6.56 (d, J = 15.8 Hz, 1H, Ph-CH=CH- ), 4.32 (t, J = 7.3 Hz,
1H, -CH-), 3.78 (s, 3H, -OCH3), 1.32 (d, J = 7.3 Hz, 3H, -CH3);MS m/z
250.1 [M+H]+.
N-[4-methoxy-(E)-cinnamoyl]-L-leucine acid b3,
a white am-
1
orphous solid (2.15 g, 74% yield); mp 85-87 °C; H NMR (600 MHz,
d6-DMSO) δ 12.57 (s, 1H, -COOH), 8.25 (d, J = 8.1 Hz, 1H, -NH), 7.51
(d, J = 8.8 Hz, 2H, Ph-H), 7.38 (d, J = 15.8 Hz, 1H, Ph-CH=CH-), 7.03 –
6.93 (m, 2H, Ph-H ), 6.57 (d, J = 15.8 Hz, 1H, Ph-CH=CH-), 4.36 (ddd,
J = 9.8, 8.1, 5.2 Hz, 1H, NH-CH-), 3.79 (s, 1H, -OCH3), 1.71 – 1.62 (m,
1H, -CH-), 1.62 – 1.50 (m, 2H, -CH2-), 0.91 (d, J = 6.6 Hz, 3H, -CH3),
0.87 (d, J = 6.5 Hz, 3H, -CH3); MS m/z 292.3 [M+H]+.
N-[4-hydroxy-3-methoxy-(E)-cinnamoyl]-L-serine acid a10, a light
1
yellow solid (1.32 g, 47% yield); mp 184-187 °C; H NMR (400 MHz,
N-[4-methoxy-(E)-cinnamoyl]-L-isoleucine acid b4, a white am-
orphous solid (2.03g, 70% yield); mp 83-85 °C; 1H NMR (600 MHz,
d6-DMSO) δ 12.61 (s, 1H, -COOH), 8.12 (d, J = 8.3 Hz, 1H, -NH), 7.51
(d, J = 7.9 Hz, 2H, Ph-H), 7.37 (d, J = 15.7 Hz, 1H, Ph-CH=CH-), 6.98
(d, J = 8.0 Hz, 2H, Ph-H), 6.70 (d, J = 15.7 Hz, 1H, Ph-CH=CH-), 4.32 (t,
J = 6.9 Hz, 1H, -CH-), 3.79 (s, 3H, -OCH3), 1.83 (m, 1H, -CH-), 1.45 –
1.42 (m, 1H, -CH2-), 1.26 – 1.98(m, 1H, -CH2-), 0.89 – 0.85 (m, 6H, -
CH3); MS m/z 292.3 [M+H]+.
d6-DMSO) δ 12.51 (s, 1H, -COOH) 9.44 (s, 1H, Ph-OH), 8.04 (d, J = 8.0
Hz, 1H, -NH), 7.32 (d, J = 15.7 Hz, 1H, Ph-CH=CH-), 7.15 (d, J = 1.7 Hz,
1H, Ph-H), 7.00 (dd, J = 8.2, 1.7 Hz, 1H, Ph-H), 6.79 (d, J = 8.1 Hz, 1H,
Ph-H), 6.69 (d, J = 15.7 Hz, 1H, Ph-CH=CH-), 5.06 (s, 1H, -OH), 4.42 –
4.39 (m, 1H, -CH-), 3.75 (dd, J = 10.8, 5.0 Hz, 1H, -CH2), 3.66 (dd, J =
10.8, 4.1 Hz, 1H, -CH2). MS m/z 282.3 [M+H]+.
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N-[4-methoxy-(E)-cinnamoyl]-L-valine acid b5,
a
white 4.35 (dd, J = 8.8, 3.1 Hz, 1H, -NH-CH), 4.23 – 4.12 (m, 1H, -CH), 3.79
amorphous solid (1.52 g, 55% yield); mp 70-73 °C; 1H NMR (600 (s, 3H, -OCH3), 1.08 (d, J = 6.4 Hz, 3H, -CH3); MS m/z 254.2 [M+H]+.
MHz, d6-DMSO) δ 12.62 (s, 1H, -COOH), 8.11 (d, J = 8.6 Hz, 1H, -NH),
N-[4-methoxy-(E)-cinnamoyl]-L- glutamic acid b13, a white
7.51 (d, J = 8.3 Hz, 2H, Ph-H), 7.38 (d, J = 15.7 Hz, 1H, Ph-CH=CH-), amorphous solid (1.68 g, 55% yield); mp 85-87 °C; 1H NMR (600
6.99 (d, J = 8.3 Hz, 2H, Ph-H), 6.72 (d, J = 15.8 Hz, 1H, Ph-CH=CH-), MHz, DMSO) δ 12.44 (s, 1H), 8.30 (d, J = 7.9 Hz, 1H), 8.30 (d, J = 7.9
4.29 (dd, J = 8.3, 5.9 Hz, 1H, -CH-), 3.79 (s, 3H, -OCH3), 2.10 (dd, J = Hz, 1H), 7.58 – 7.47 (m, 1H), 7.39 (d, J = 15.8 Hz, 1H), 6.99 (d, J = 8.8
13.2, 6.6 Hz, 1H, -CH(CH3)2), 0.92 (dd, J = 6.5, 4.0 Hz, 6H, -CH(CH3)2); Hz, 1H), 6.58 (d, J = 15.8 Hz, 1H), 4.35 (td, J = 8.9, 5.1 Hz, 1H), 3.79
MS m/z 278.2 [M+H]+.
(s, 2H), 2.42 – 2.22 (m, 1H), 2.11 – 1.99 (m, 1H), 1.83 (dtd, J = 14.7,
N-[4-methoxy-(E)-cinnamoyl]-L-proline acid b6, a white solid 8.9, 6.0 Hz, 1H); MS m/z 308.3 [M+H]+.
1
(1.81 g, 66% yield); mp 197-199 °C; H NMR (600 MHz, d6-DMSO) δ
N-[4-methoxy-(E)-cinnamoyl]-L-aspartic acid b14, a white solid
1
12.51 (s, 1H, -COOH), 7.66 (d, J = 7.9 Hz, 2H, Ph-H), 7.43 (d, J = 15.4 (1.81 g, 62% yield); mp 160-163 °C; H NMR (600 MHz, d6-DMSO) δ
HZ, 1H, Ph-CH=CH-), 6.97 (d, J = 8.0 Hz, 2H, Ph-H), 6.87 (d, J = 15.5 12.60 (s, 2H,-COOH), 8.34 (d, J = 8.0 Hz, 1H,-NH-), 7.53 (d, J = 8.7 Hz,
Hz, 1H, Ph-CH=CH-), 4.34 (dd, J = 8.6, 3.7 Hz, 1H, -CH-), 3.79 (s, 3H, - 2H, Ph-H), 7.39 (d, J = 15.8 Hz, 1H, Ph-CH=CH-), 6.98 (d, J = 8.8 Hz,
OCH3), 3.77 – 3.67 (m, 2H, -NH-CH2-), 2.32 – 2.06 (m, 1H, NH-CH2- 2H, Ph-H), 6.60 (d, J = 15.8 Hz, 1H, Ph-CH=CH-), 4.66 (m, 1H , -NH-
CH2-), 2.01 – 1.79 (m, 3H, NH-CH2-CH2-); MS m/z 276.2 [M+H]+.
CH), 3.79 (s, 3H, -OCH3), 2.75 (dd, J = 16.6, 5.4 Hz, 1H, -CH2), 2.66
N-[4-methoxy-(E)-cinnamoyl]-L-phenylalanine acid b7, a white (dd, J = 16.6, 7.2 Hz, 1H,-CH2); MS m/z 294.3 [M+H]+.
solid (2.43g, 75% yield); mp 161-165 °C; 1H NMR (600 MHz, d6-
N-[4-hydroxy-(E)-cinnamoyl]-L-glycine acid c1, a white solid (1.65
1
DMSO) δ 12.76 (s, 1H, -COOH), 8.31 (d, J = 8.1 Hz, 1H, -NH), 7.49 (d, g, 75% yield); mp 232-233 °C; H NMR (600 MHz, d6-DMSO) δ 12.49
J = 8.4 Hz, 2H, Ph-H), 7.33 (d, J = 15.8 Hz, 1H, Ph-CH=CH-), 7.30 – (s, 1H, -COOH), 10.00 (s, 1H, -OH), 8.26 (t, J = 5.9 Hz, 1H , -NH), 7.41
7.24 (m, 4H, Ph-H), 7.20 (dd, J = 10.8, 4.1 Hz, 1H , Ph-H), 6.97 (d, J = (d, J = 8.6 Hz, 2H, Ph-H ), 7.34 (d, J = 15.7 Hz, 1H, Ph-CH=CH-), 6.79
8.4 Hz, 2H, Ph-H), 6.55 (d, J = 15.8 Hz, 1H, Ph-CH=CH-), 4.57 (td, J = (d, J = 8.6 Hz, 2H, Ph-H), 6.50 (d, J = 15.8 Hz, 1H, Ph-CH=CH-), 3.86
8.7, 5.0 Hz, 1H,-CH-), 3.78 (s, 3H,-OCH3), 3.12 (dd, J = 13.9, 4.7 Hz, (d, J = 5.9 Hz, 2H, -CH2-); MS m/z 222.3 [M+H]+.
1H, -CH2), 2.99 – 2.85 (m, 1H, -CH2-); MS m/z 326.3 [M+H]+.
N-[4-hydroxy-(E)-cinnamoyl]-L-alanine acid c2, a white solid (1.59,
N-[4-methoxy-(E)-cinnamoyl]-L-methionine acid b8, a white solid 68% yield); mp 205-206 °C; 1H NMR (600 MHz, d6-DMSO) δ 12.55 (s,
1
(1.91 g, 62% yield); mp 149-152 °C; H NMR (600 MHz, d6-DMSO) δ 1H, -COOH), 9.85 (s, 1H, -OH), 8.27 (d, J = 7.4 Hz, 1H, -NH), 7.39 (d, J
12.71 (s, 1H, -COOH), 8.33 (d, J = 7.9 Hz, 1H, -NH), 7.52 (d, J = 8.7 Hz, = 8.6 Hz, 2H, Ph-H), 7.33 (d, J = 15.7 Hz, 1H, Ph-CH=CH-), 6.79 (d, J =
2H, Ph-H), 7.39 (d, J = 15.8 Hz, 1H, Ph-CH=CH-), 6.99 (d, J = 8.7 Hz, 8.6 Hz, 2H, Ph-H), 6.48 (d, J = 15.8 Hz, 1H, Ph-CH=CH-), 4.31 (m, 1H,-
2H, Ph-H), 6.57 (d, J = 15.8 Hz, 1H, Ph-CH=CH-), 4.50 – 4.38 (m, 1H, - CH-), 1.31 (d, J = 7.3 Hz, 3H, -CH3); MS m/z 236.1 [M+H]+.
CH-), 3.79 (s, 3H, -OCH3), 2.51 – 2.49 (m, 2H, -CH2-S-), 2.05 (s, 3H, -
N-[4-hydroxy-(E)-cinnamoyl]-L-leucine acid c3, a white solid (1.77
g, 64% yield); mp 182-184 °C; H NMR (600 MHz, d6-DMSO) δ 12.54
1
CH3), 2.03 – 1.90 (m, 2H, -CH2-); MS m/z 310.2 [M+H]+.
N-[4-methoxy-(E)-cinnamoyl]-L-tryptophane acid b9,
a light (s, 1H, -COOH), 9.85 (s, 1H, -OH), 8.21 (d, J = 8.1 Hz, 1H, -NH), 7.39
yellow amorphous solid (2.00 g, 55%); mp 70-72°C; 1H NMR (600 (d, J = 8.6 Hz, 2H, Ph-H), 7.33 (d, J = 15.7 Hz, 1H, Ph-CH=CH-), 6.80
MHz, d6-DMSO) δ 12.71 (s, 1H, -COOH), 10.85 (d, J = 1.4 Hz, 1H, -NH (d, J = 8.6 Hz, 2H, Ph-H), 6.49 (d, J = 15.8 Hz, 1H, Ph-CH=CH-), 4.34
-), 8.29 (d, J = 7.9 Hz, 1H, -NH-COOH ), 7.55 (d, J = 7.9 Hz, 1H, Ar-H), (ddd, J = 9.8, 8.1, 5.2 Hz, 1H, -NH-CH-), 1.73 – 1.59 (m, 1H, -CH-),
7.49 (d, J = 8.8 Hz, 2H, Ph-H), 7.34 (d, J = 15.7, 1H, Ph-CH=CH-), 7.32 1.62 – 1.44 (m, 2H, -CH2), 0.91 (d, J = 6.6 Hz, 3H, -CH3), 0.86 (d, J =
(d, J=8.0 Hz, 1H, Ar-H )7.16 (d, J = 2.2 Hz, 1H, Ar-H), 7.10 – 7.02 (m, 6.5 Hz, 3H, -CH3); MS m/z 278.3 [M+H]+.
1H, Ar-H), 7.01 – 6.93 (m, 3H, Ar-H, 2Ph-H), 6.59 (d, J = 15.8 Hz, 1H ,
N-[4-hydroxy-(E)-cinnamoyl]-L-isoleucine acid c4, a white am-
Ph-CH=CH-), 4.62 (td, J = 8.3, 5.0 Hz, 1H, -CH-), 3.78 (s, 3H, -OCH3), orphous solid (1.66 g, 60% yield); mp 108-110 °C; 1H NMR (600 MHz,
3.23 (dd, J = 14.7, 4.9 Hz, 1H, -CH2-), 3.07 (dd, J = 14.7, 8.8 Hz, 1H, - d6-DMSO) δ 12.61 (s, 1H, -COOH), 9.85 (s, 1H, -OH), 8.10 (d, J = 8.5
CH2-); MS m/z 365.2 [M+H]+.
Hz, 1H, -NH), 7.39 (d, J = 8.6 Hz, 2H, Ph-H), 7.33 (d, J = 15.7 Hz, 1H,
N-[4-methoxy-(E)-cinnamoyl]-L-serine acid b10, a white solid Ph-CH=CH-), 6.80 (d, J = 8.6 Hz, 2H, Ph-H), 6.63 (d, J = 15.7 Hz, 1H,
1
(1.59 g, 60% yield); mp 183-184 °C; H NMR (600 MHz, d6-DMSO) δ Ph-CH=CH-), 4.31 (dd, J = 8.5, 6.0 Hz, 1H, NH-CH-), 1.90 – 1.75 (m,
12.66 (s, 1H, -COOH), 8.17 (d, J = 8.0 Hz, 1H, -NH -), 7.52 (d, J = 8.7 1H, -CH-), 1.46 – 1.40 (m, 1H, -CH2-), 1.25 – 1.15 (m, 1H, -CH2-),
Hz, 2H, Ph-H), 7.38 (d, J = 15.8 Hz, 1H , Ph-CH=CH-), 6.98 (d, J = 8.8 0.89 (d, J = 6.84, 3H, -CH3) 0.86 (t, J = 7.38, 3H, -CH3); MS m/z 278.2
Hz, 2H, Ph-H), 6.73 (d, J = 15.8 Hz, 1H, Ph-CH=CH-), 4.50 – 4.36 (m, [M+H]+.
1H, -CH-), 3.79 (s, 3H ,-OCH3), 3.76 (dd, J = 10.9, 5.0 Hz, 1H, -CH2-),
3.67 (dd, J = 10.9, 4.0 Hz, 1H, -CH2-), 2.55 – 2.43 (m, 1H, -OH); MS solid (1.23 g, 47% yield); mp 108-107 °C; 1H NMR (600 MHz, d6-
m/z 266.3 [M+H]+.
DMSO) δ 12.61 (s, 1H, -COOH), 9.85 (s, 1H, -OH), 8.08 (d, J = 8.6 Hz,
N-[4-hydroxy-(E)-cinnamoyl]-L-valine acid c5, a white amorphous
N-[4-methoxy-(E)-cinnamoyl]-L-glutamine acid b11, a white solid 1H, -NH), 7.40 (d, J = 8.6 Hz, 2H, Ph-H), 7.33 (d, J = 15.7 Hz, 1H, Ph-
1
(1.74 g, 57% yield); mp 165-168 °C; H NMR (600 MHz, d6-DMSO) δ CH=CH-), 6.80 (d, J = 8.6 Hz, 2H, Ph-H), 6.65 (d, J = 15.7 Hz, 1H, Ph-
12.79 (s, 1H,-COOH), 8.28 (d, J = 6.6 Hz, 1H, -NH-), 7.51 (d, J = 8.6 CH=CH-), 4.28 (dd, J = 8.6, 5.7 Hz, 1H, -NH-CH-), 2.10 (dd, J = 12.8,
Hz, 2H, Ph-H), 7.37 (d, J = 15.9 Hz, 1H, Ph-CH=CH), 7.35(s, 1H, -NH2), 6.7 Hz, 1H, -CH-), 0.91 (d, J = 4.0 Hz, 3H,-CH3), 0.90 (d, J = 3.9 Hz,
6.98 (d, J = 8.6 Hz, 2H, Ph-H), 6.79 (s, 1H , -NH2), 6.65 (d, J = 15.8 Hz, 3H,-CH3); MS m/z 264.2 [M+H]+.
1H, Ph-CH=CH-), 4.27 (m, 1H, -CH-), 3.79 (s, 3H , -OCH3), 2.23 – 2.11
(m, 2H, -CH2-), 2.01 (m, 1H, -CH2-), 1.81 (m, 1H, -CH2-); MS m/z 61% yield); mp 235-236 °C; 1H NMR (600 MHz, d6-DMSO) δ 12.61 (s,
307.3 [M+H]+.
1H, -COOH), 9.85 (s, 1H, , -OH), 8.08 (d, J = 8.6 Hz, 1H, -NH), 7.39 (d,
N-[4-hydroxy-(E)-cinnamoyl]-L-proline acid, a white solid (1.59 g,
N-[4-methoxy-(E)-cinnamoyl]-L-threonine acid b12, a white solid J = 8.6 Hz, 2H, Ph-H), 7.33 (d, J = 15.7 Hz, 1H, Ph-CH=CH-), 6.80 (d, J
1
(1.08 g, 43% yield); mp 153-156 °C; H NMR (600 MHz, d6-DMSO) δ = 8.6 Hz, 2H, Ph-H), 6.64 (d, J = 15.7 Hz, 1H, Ph-CH=CH-), 4.28 (dd, J
12.57 (s, 1H,-COOH), 7.93 (d, J = 8.8 Hz, 1H,-NH -), 7.52 (d, J = 8.7 = 8.6, 5.7 Hz, 1H, -N-CH-), 2.09 (dd, J = 12.8, 6.7 Hz, 1H, -CH2-), 0.91
Hz, 2H, Ph-H), 7.37 (d, J = 15.7 Hz, 1H, Ph-CH=CH-), 6.98 (d, J = 8.7 (dd, J = 6.8, 4.0 Hz, 5H, -CH2-); MS m/z 262.2 [M+H]+
Hz, 2H, Ph-H), 6.83(d, J = 15.8 Hz, 1H, Ph-CH=CH-), 4.99 (s, 1H,-OH),
N-[4-hydroxy-(E)-cinnamoyl]-L-phenylalanine acid c7, a white
solid (2.14, 69% yield ); mp 235-236 °C; 1H NMR (600 MHz, d6-
8 |RSC Adv.
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DMSO) δ 12.77 (s, 1H, -COOH), 9.87 (s, 1H, -OH), 8.30 (d, J = 8.1 Hz, 4.65 (td, J = 7.4, 5.6 Hz, 1H, -CH-), 2.74 (dd, J = 16.6, 5.5 Hz, 1H, -
1H, -NH), 7.38 (d, J = 8.6 Hz, 2H, Ph-H), 7.32 – 7.23 (m, 5H, Ph- CH2-), 2.65 (dd, J = 16.6, 7.2 Hz, 1H, -CH2-); MS m/z 280.2 [M+H]+
CH=CH-, Ph-H), 7.21 – 7.18 (m, 1H, Ph-H), 6.80 (d, J = 8.6 Hz, 2H, Ph-
H), 6.49 (d, J = 15.8 Hz, 1H, Ph-CH=CH-), 4.57 (ddd, J = 9.5, 8.3, 4.8 4.3. The inhibitory activity against α-glucosidase
Hz, 1H, -CH-), 3.11 (dd, J = 13.9, 4.8 Hz, 1H, -CH2-), 2.92 (dd, J = 13.9,
The α-glucosidase inhibitory activities were evaluated by the
9.6 Hz, 1H, -CH2-); MS m/z 312.3 [M+H]+.
reported method.28 500 ꢀL aqueous solution of sodium salt of the
N-[4-hydroxy-(E)-cinnamoyl]-L-methionine acid c8, a white solid
test sample was incubated at 37 ºC for 15 min with 100 ꢀL α-
glucosidase (0.5 U/mL in 100 mM solution of sodium phosphate
buffer) in 500 ꢀL phosphate buffer (pH 6.8). 0.5 mL of pNPG (2.5
mM) was then added and incubated for another 15 min. The
reaction was terminated by the addition of 1 mL of 1M sodium
carbonate solution. The inhibitory activities were quantified by
measuring the absorbance at 405 nm. Acarbose was used as
positive control. The inhibition of the test sample was calculated
1
(1.68 g, 57% yield); mp 169-172 °C; H NMR (600 MHz, d6-DMSO) δ
12.66 (s, 1H, -COOH), 9.86 (s, 1H, -OH), 8.28 (d, J = 7.9 Hz, 1H, -NH),
7.40 (d, J = 8.6 Hz, 2H, Ph-H), 7.34 (d, J = 15.7 Hz, 1H, Ph-CH=CH-),
6.80 (d, J = 8.6 Hz, 2H, Ph-H), 6.49 (d, J = 15.8 Hz, 1H, Ph-CH=CH-),
4.45 – 4.41 (m, 1H, -CH-), 2.54 – 2.50 (m, 2H, -CH2-), 2.05 (s, 3H, -
CH3), 2.02 – 1.88 (m, 2H, -CH2-); MS m/z 296.2 [M+H]+.
N-[4-hydroxy-(E)-cinnamoyl]-L-tryptophane acid c9, a white solid
(1.75 g, 50% yield); mp 171-173 °C;1H NMR (600 MHz, d6-DMSO) δ
according to the following equation:
12.68 (s, 1H, -COOH), 10.85 (d, J = 1.4 Hz, 1H, -OH), 9.85 (s, 1H, -
Asample − Abackground


NH), 8.25 (d, J = 7.9 Hz, 1H, -CO-NH-), 7.56 (d, J = 7.9 Hz, 1H, Ar-H),
7.38 (d, J = 8.6 Hz, 2H, Ph-H), 7.33 (d, J = 8.1 Hz, 1H, Ar-H), 7.30 (d, J
= 15.7 Hz, 1H, Ph-CH=CH-), 7.16 (d, J = 2.2 Hz, 1H, Ar-H), 7.11 – 7.03
(m, 1H, Ar-H), 7.02 – 6.93 (m, 1H, Ar-H), 6.79 (d, J = 8.6 Hz, 2H, Ph-
H), 6.52 (d, J = 15.7 Hz, 1H, Ph-CH=CH-), 4.62 (td, J = 8.3, 5.1 Hz, 1H,
-CH-), 3.23 (dd, J = 14.7, 4.9 Hz, 1H, -CH2-), 3.07 (dd, J = 14.7, 8.8 Hz,
1H, -CH2-);MS m/z 351.2 [M+H]+.



a(%) = 1−
×100%


Ablank

Where a(%) is the percentage of inhibition of the tested sample or
acarbose, Asample is the tested absorbance after reaction, Abackground
is the initial absorbance of the test sample. Ablank is the absorbance
of enzyme solution with pNPG.
Lineweaver–Burk plot analysis was performed to determine the
mode of inhibition of α-glucosidase. The reaction was carried out
with an increasing concentration of inhibitors and varying
concentrations of pNPG as the substrate. All the data were analyzed
using a computer program for nonlinear regressions (OriginPro 8.0).
N-[4-hydroxy-(E)-cinnamoyl]-L-serine acid c10, a light yellow solid
1
(1.12 g, 45% yield); mp 185-189 °C; H NMR (600 MHz, d6-DMSO) δ
12.62 (s, 1H, -COOH), 9.85 (s, 1H, Ph-OH), 8.12 (d, J = 8.0 Hz, 1H,
NH-), 7.40 (d, J = 8.6 Hz, 2H, Ph-H), 7.33 (d, J = 15.7 Hz, 1H, Ph-
CH=CH-), 6.80 (d, J = 8.6 Hz, 2H, Ph-H), 6.64 (d, J = 15.7 Hz, 1H, Ph-
CH=CH-), 5.04 (s, 1H, -OH), 4.41 (dt, J = 8.2, 4.7 Hz, 1H, -CH-), 3.75
(dd, J = 10.9, 5.1 Hz, 1H,-CH2-), 3.66 (dd, J = 10.9, 4.2 Hz, 1H, -CH2-);
MS m/z 252.3 [M+H]+.
4.4. 3D QSAR model development and validation.
N-[4-hydroxy-(E)-cinnamoyl]-L-glutamine acid c11, a white solid
(1.54 g, 53% yield); mp 196-198 °C; H NMR (600 MHz, d6-DMSO) δ
The QSAR study was performed in SYBYL 7.3. In our study, 85% of
the synthesized compounds and their pIC50 (-logIC50) was selected
for training set to develop the 3D QSAR model and other 15% for
test set to evaluate the model, based on their molecular properties
(see supporting information Table S1). Prior to the form of the
model, compound c1 was selected as the template molecule and
optimized to get the low energy conformation. The other molecules
were optimized and superimposed based on the template using
Database Alignment. Least-Squares Analysis (LSA) method was used
to obtain the CoMFA model. The model was validated using test set
correlation and Leave-one-out (LOO) cross validation.
1
12.59 (s, 1H, -COOH), 9.89 (s, 1H, Ph-OH), 8.27 (d, J = 7.7 Hz, 1H,
NH-), 7.39 (d, J = 8.6 Hz, 2H, Ph-H), 7.33 (d, J = 15.7 Hz, 1H, Ph-
CH=CH-), 7.31(s, 1H, -NH2), 6.79 (d, J = 8.1 Hz, 2H, Ph-H), 6.78(s, 1H,
-NH2), 6.50 (d, J = 15.8 Hz, 1H, Ph-CH=CH-), 4.28 (td, J = 8.8, 5.0 Hz,
1H, -CH-), 2.16 – 2.13 (m, 2H, -CH2-), 2.10 – 1.90 (m, 1H, -CH2-), 1.79
(m, 1H, -CH2-); MS m/z 293.2 [M+H]+.
N-[4-hydroxy-(E)-cinnamoyl]-L-threonine acid c12, a white solid
1
(1.08 g, 41% yield); mp 201-204 °C; H NMR (600 MHz, d6-DMSO) δ
12.54 (s, 1H, -COOH), 9.84 (s, 1H, Ph-OH), 7.89 (d, J = 8.8 Hz, 1H,-
NH), 7.41 (d, J = 8.6 Hz, 2H, Ph-H), 7.33 (d, J = 15.7 Hz, 1H, Ph-
CH=CH), 6.80 (d, J = 8.6 Hz, 2H, Ph-H), 6.75 (d, J = 15.7 Hz, 1H, Ph-
CH=CH), 4.97 (s, 1H, -OH), 4.35 (dd, J = 8.8, 3.2 Hz, 1H, -CH), 4.18
(qd, J = 6.3, 3.3 Hz, 1H, -CH-), 1.08 (d, J = 6.4 Hz, 3H, -CH3); MS m/z
266.2 [M+H]+.
N-[4-hydroxy-(E)-cinnamoyl]-L-glutamate acid c13, a white amo-
rphous solid (1.63 g, 56%); mp 201-204 °C; 1H NMR (600 MHz,
DMSO) δ 12.41 (s, 1H, -COOH), 9.86 (s, 1H, -OH), 8.24 (d, J = 7.9 Hz,
1H, -NH), 7.40 (d, J = 8.6 Hz, 1H, Ph-H), 7.34 (d, J = 15.7 Hz, 1H, Ph-
CH=CH), 6.80 (d, J = 8.6 Hz, 1H, Ph-H), 6.49 (d, J = 15.8 Hz, 1H, Ph-
CH=CH), 4.58 – 4.11 (m, 1H, -CH-), 2.37 – 2.24 (m, 2H, -CH2-), 2.07 –
1.97 (m, 1H, -CH2-), 1.82 – 1.184( m, 1H, -CH2-); MS m/z 294.3
[M+H]+
4.5. Docking studies
The crystal 3D structure of α-glucosidase from S. Cerevisiae was
predicted by homology modeling. The amino acid sequence and the
active sites were retrieved from UniProt protein resource data bank
29
with the accessing code P53341 (http://www.uniprot.org).
Similarity search and homology modeling were conducted in SWISS
MODEL
server
(http://www.swissmodel.expasy.org).
The
crystallographic structure of S. cerevisiae isomaltase (PDB code
3AXH) was selected as the template with a 72.51% sequence
identity with the target protein. The final structure generated from
homology modeling was evaluated using PROCHECK. The docking
study was run by Surflex-dock in SYBYL 7.3, and the results were
visualized using PyMol.
N-[4-hydroxy-(E)-cinnamoyl]-L- asparagic acid c14, a white solid
1
(1.72 g, 62% yield); mp 214-216 °C; H NMR (600 MHz, d6-DMSO) δ
12.59 (s, 2H, -COOH), 9.87 (s, 1H, -OH), 8.30 (d, J = 8.0 Hz, 1H, -NH),
7.41 (d, J = 8.6 Hz, 2H, Ph-H), 7.34 (d, J = 15.7 Hz, 1H, -Ph-CH2=CH2),
6.79 (t, J = 5.6 Hz, 2H, Ph-H), 6.52 (d, J = 15.7 Hz, 1H, Ph-CH2=CH2-),
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Research Artcle
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A table of contents entry
The phenolic acid amides with LꢀAmino acid moiety showed excellent inhibitory activities on
αꢀglucosidase.