Synthesis and biological evaluation of novel urea, thiourea and squaramide diastereomers possessing sugar backbone

Article abstract of DOI:10.1016/j.carres.2020.107991

A series of novel chiral 14 urea, thiourea and squaramide stereoisomers possessing carbohydrate backbones as well as amide functional groups was synthesized and characterized by their, ¹H NMR, ¹³C NMR, FT-IR, HRMS, optical rotation, and melting points. Their antiproliferative activities were investigated against HeLa and PC3 cell lines. The compounds 9, 11 and 12 showed better activities at 25 μM against PC3 cell line with respect to the standard 5-fluorouracil (5-FU). Especially, the compounds 9 and 11 showed higher activities than the standard 5-FU even at low concentration (5 μM) against HeLa cell line. IC₅₀ results also confirm these activities. The compounds 9, 10 and 11 have the IC₅₀ values of 1.10 μM, 1.51 μM and 1.02 μM, respectively while 5-FU has 2.51 μM. Moreover, their cytotoxicity tests have proven that their viabilities were in between 50% and 100%.

Full text of DOI:10.1016/j.carres.2020.107991

CarbohydrateResearch492(2020)107991
Contents lists available at ScienceDirect
Carbohydrate Research
journal homepage: www.elsevier.com/locate/carres
Synthesis and biological evaluation of novel urea, thiourea and squaramide
diastereomers possessing sugar backbone
Özer Işılara, Adnan Buluta,∗∗, Ayse Sahin Yaglioglub, İbrahim Demirtaşb, Esra Aratc,
Mustafa Türkd
a Department of Chemistry, Kırıkkale University, 71450, Yahşihan, Kırıkkale, Turkey
b Department of Chemistry, Çankırı Karatekin University, 18200, Çankırı, Turkey
c Scientific and Technological Research Application and Research Center, Kırıkkale University, 71450, Yahşihan, Kırıkkale, Turkey
d Department of Bioengineering, Kırıkkale University, 71450, Yahşihan, Kırıkkale, Turkey
A R T I C L E I N F O
A B S T R A C T
Keywords:
A series of novel chiral 14 urea, thiourea and squaramide stereoisomers possessing carbohydrate backbones as
well as amide functional groups was synthesized and characterized by their, 1H NMR, 13C NMR, FT-IR, HRMS,
optical rotation, and melting points. Their antiproliferative activities were investigated against HeLa and PC3
cell lines. The compounds 9, 11 and 12 showed better activities at 25 μM against PC3 cell line with respect to the
standard 5-fluorouracil (5-FU). Especially, the compounds 9 and 11 showed higher activities than the standard
5-FU even at low concentration (5 μM) against HeLa cell line. IC50 results also confirm these activities. The
compounds 9, 10 and 11 have the IC50 values of 1.10 μM, 1.51 μM and 1.02 μM, respectively while 5-FU has
2.51 μM. Moreover, their cytotoxicity tests have proven that their viabilities were in between 50% and 100%.
Sugar
Urea
Thiourea
Squaramide
Antiproliferative activity
Cytotoxicity
1. Introduction
observed in the use of the pure enantiomer L-dopa [11]. The timolol can
be given as another classical example for different pharmaceutical be-
Cancer is a major global public health problem. In addition, the
incidence and mortality rates of cancer continue to increase. It has been
reported that there will be an estimated 18.1 million new cancer cases
and 9.6 million cancer deaths in 2018 [1]. Cervix cancer is the most
common cancer worldwide among women. Among men, prostate
cancer was the second most common cancer type diagnosed with 15.0%
[2].
haviours of enantiomers as drugs. While (S) isomer becomes effective
for hypertension by decreasing intraocular pressure in the treatment of
glaucoma, (R) isomer is considerably less potent [12,13]. With all the
explanations given above, it is clear that pharmaceutical consequences
of chirality might not be interpreted correctly without taking stereo-
chemistry into consideration.
All the compounds 9–22 that we have in the present study include
Brønsted acidic hydrogens which are bound to nitrogen atoms. It is well
known that the inhibitory effect of nitrogen-bound acidic hydrogen (i.e.
amide hydrogen) [14]. Hence, new molecules containing amide are
important to drug industry due to their biological activities (Fig. 1). It
has been reported that there are many applications of functional amides
in biological activities such as fungicidal [15], herbicidal [16], in-
secticidal [17], anticancer [18], and antibacterial [19]. Some cholic
acid-aryl amide derivatives were tested against three human cancer cell
lines (HT29, MDAMB231, U87MG) and a human normal cell line
(HEK293T). Good promising results were obtained as follows: 1.35 μM,
1.41 μM and 4.52 μM against the breast cancer cell line compared to
Cisplatin (7.21 μM) [20]. Furthermore, a number of several bile acid
derivatives were synthesized and screened towards MCF-7, MDA-MB-
231, PC3, HeLa and HT-29 with high activities (IC50 < 5 μM) [21].
Over the past decades, sugar derivatives have been much attraction
for the cytotoxic studies [3–8]. Their unique chiral structures are giving
valuable contributions to the drugs. Thus, new derivatives of sugars as
drugs are important stereoisomers. Apart from their role as drugs, new
sugar synthesis can be considered as “chiral pool” in asymmetric re-
action methods since the starting compound can be used in large scale
[9]. Another advantage, particularly for drug industry, is that reactions
can be achieved without the use of a chiral catalyst.
It was reported that 53% of the drugs which used in market have at
least one chiral centre whereas in clinical use, 27% of the total are in
single enantiomer form [10]. It is conceivable that chiral drug com-
pounds can display different biological and pharmacological activities
from their enantiomers or racemate forms. For instance, the use of D,L-
dopa can cause granulocytopenia, yet this adverse effect has not been
∗ Corresponding author.
E-mail address: adnnblt@kku.edu.tr (A. Bulut).
https://doi.org/10.1016/j.carres.2020.107991
Received 7 November 2019; Received in revised form 22 March 2020; Accepted 23 March 2020
Availableonline29March2020
0008-6215/©2020ElsevierLtd.Allrightsreserved.

Ö. Işılar, et al.
CarbohydrateResearch492(2020)107991
Fig. 2. a) Free nucleophilic attack in allo-sugar. b) Forbidden nucleophilic at-
tack in gluco-sugar.
Fig. 1. The structures of some amide drugs.
2. Results and discussion
2.1. Chemistry
The synthesis of the target compounds 9–22 can be divided into two
parts as follows: First, synthesis of amino sugars, secondly; synthesis of
urea, thiourea and squaramide derivatives. In the first part, the tosy-
lated sugar 2 was prepared in the usual manner in which p-toluene-
sulfonyl chloride and the sugars 1 having free hydroxyl group is reacted
in the presence of 4-dimethylaminopyridine (DMAP) with catalytic
amount (Scheme 1). Next, the azido derivative 3 was obtained by nu-
cleophilic displacement azide ion with the tosyl group of 2. It is note-
worthy that the displacement reaction between the azide ion and tosyl
group of 2 changed the stereochemistry at C-3 position of 2. Thus, allo-
tosyl derivative 2 gave the gluco-azido derivative 3 (Scheme 1). How-
ever, the synthesis of 3-azido-3-deoxy-1,2:5,6-di-O-isopropylidene-α-D-
allofuranose failed when the same protocol was followed. The hindrance
of the replacement reaction on C3-OTs arises from the repulsions be-
tween the endooxygens of the isopropylidene group to the bicyclic
system and the nucleophilic azide ion (Fig. 2) [22].
Scheme 2. Synthesis of urea and thiourea based sugars 9–12.
Moreover, the squaramide derivatives 14–22 were obtained by the
reaction of 3,4-dimethoxy-3-cyclobutene-1,2-dione and the corre-
sponding amines (sugar amines or aromatic amines) [24]. (Scheme 3).
All the analyses (presented in experimental and supplementary data
sections) for the characterization of the newly synthesized novel urea,
thiourea, and squaramides are in good agreement with the expected
structures.
In the last step of this part, the amino sugar 4 was obtained by
reduction of the azido sugar 3 with LiAlH4 as pointed out in the lit-
erature [22]. Similar synthetic methodology was followed for the
synthesis of the amino sugar 8 as given in Scheme 1.
In the second part, the amino sugars 4 and 8 were readily converted
into the urea and thiourea derivatives 9, 10, 11, and 12 respectively in
high yields (Scheme 2) [23].
2.2. Antiproliferative activity results against HeLa and PC3 cells
Antiproliferative activities of the compounds 9–22 and 5-
Scheme 1. Synthesis of sugar amines 4–8.
2

Ö. Işılar, et al.
CarbohydrateResearch492(2020)107991
Scheme 3. Synthesis of squaramide based sugars 13–22.
results compared to the urea and thiourea derivatives 9–12.
Table 1
IC50 values of compounds 9–22 and 5-FU.
The antiproliferative activities of the compounds 9–22 and 5-FU
were determined to have increased depending on concentration against
the HeLa cell line (Fig. 3). At all doses, 9 and 11 were determined to
have higher activities than 5-FU against HeLa cell. The compound 10
was observed to have higher activity than 5-FU at 100, 50 and 25 μM
concentrations but not at 5 μM. In other words, the compound 10
showed a cell selective activity against HeLa cells at high concentra-
tions, although it had a satisfactory IC50 value (IC50 = 1.51 μM). In-
terestingly the only active squaramide derivative against HeLa cell was
21 which showed moderate activity compared with 5-FU at all doses
(Fig. 3). It should not be neglected that the compound 21 also had a
satisfactory IC50 value (Table 1).
Entry
Compound
HeLa (μM)
PC3 (μM)
1
9
1.10
11.84
45.42
14.47
17.14
53.68
nda
2
10
11
12
13
14
15
16
17
18
19
20
21
22
5-FU
1.51
3
1.02
4
13.22
58.39
50.74
51.36
41.26
nda
5
6
7
nda
8
59.01
67.95
64.84
27.13
49.05
nda
9
10
11
12
13
14
15
nda
24.04
19.37
4.02
In the case of PC3 cell line, similar antiproliferative activities were
detected for the compounds 9–22 as in the HeLa cell line (Fig. 4). In
other words, while the urea and thiourea derivatives 9–12 except 10
gave good results compared to the standard, the squaramides 13–22
showed moderate activities. As can be seen in Fig. 4, urea or thiourea
derivatives 9–12 gave high activities at 100 μM, 50 μM and 25 μM
concentrations compared to the 5-FU standard. Unfortunately, they are
almost inactive at 5 μM in PC3 cell line.
16.59
2.51
16.20
3.10
a
Not detected.
Florouracil (5-FU) against HeLa and PC3 cells were investigated at four
different concentrations (100, 50, 25 and 5 μM). IC50 values of com-
pounds 9–22 against HeLa and PC3 cells are given in Table 1.
As can be seen in Table 1, IC50 inhibition activities proved that the
compounds 9 (IC50 = 1.10 μM), 10 (IC50 = 1.51 μM) and 11
(IC50 = 1.02 μM) gave more promising results than the standard 5-FU
More specifically, the urea and thiourea derivatives 9–12 containing
3,5-bis(trifluorophenyl) and sugar groups showed fairly good activity
against HeLa and PC3 cell lines compared to squaramide derivatives
13–20 which bear the same sugars (4 or 8) but different aromatics
(phenyl or naphthyl).
(IC50
=
2.51 μM) against HeLa cell line. Compound 21
(IC50 = 4.02 μM) showed moderate activity compare with against HeLa
cell line. On the other hand, compound 9 (IC50 = 11.84 μM), 11
(IC50 = 14.47 μM), 22 (IC50 = 16.20 μM) and 12 (IC50 = 17.14 μM)
have moderate activity in comparison with the 5-FU against PC3 cancer
cell line. Another result that we have seen in Table 1 is that 10
squaramide derivatives 13–22 except 21 did not show satisfactory
2.3. Cytotoxicity results against L929 fibroblast cell
The aforementioned results prompted us to test the compounds
9–12 in the cytotoxicity test namely MTT in L929 cell line. The cell
viability was found to above 50% when different concentrations of
3

Ö. Işılar, et al.
CarbohydrateResearch492(2020)107991
Fig. 3. Antiproliferative activity of 9–22 and 5-FU against HeLa cells line × Data are presented as mean
SD (n = 6). Statistically significant difference
(p < 0.01) was observed between treatments (ANOVA, Duncan).
samples 9–12 were applied in L929 fibroblast cell. As can be seen, the
cell viability changed in the range of 53.01%–61.72% for all studied
compounds, when at the highest concentration (0.2 mg/mL) of the
compounds (Table 2). On the other hand, while the compounds 9–11
inhibited cancer cells (HeLa and PC3) at a concentration of 1 μM, no
toxic effects were observed in healthy cells (L929). Therefore, it can be
said that the synthesized compounds 9–12 can be tested as a cancer
drug after additional tests.
purification or flash column. Their antiproliferative activities were
tested against HeLa and PC3 cancer cell lines in vitro. As far as we are
aware, antiproliferative screening for chiral urea, thiourea, and squar-
amide possessing sugar backbones has not been reported in the relevant
literature yet, even though many stable examples of urea, thiourea, and
squaramide as biological active compounds have been demonstrated
before. In the preliminary studies, it was determined that the com-
pounds 9–22 have dose-dependent activities against two cancer cell
lines. Moreover, the results also indicated that the compounds 9–12
that including urea or thiourea have higher or comparable activities
than the standard 5-FU against HeLa and PC3 cancer cell lines. In ad-
dition, the compound 10 was determined to exhibit cell-selective ac-
tivity against HeLa cells.
3. Conclusions
Good to excellent yields of chiral ureas, thioureas and squaramides
9–22 bearing two Brønsted acidic hydrogens were obtained after simple
Fig. 4. Antiproliferative activity of 9–22 and 5-FU against PC3 cells line × Data are presented as mean
SD (n = 6). Statistically significant difference (p < 0.01)
was observed between treatments (ANOVA, Duncan).
4

Ö. Işılar, et al.
CarbohydrateResearch492(2020)107991
Table 2
Viability values of L929 fibroblast cells. L929 fibroblast cells were seeded in a concentration of 5 × 103 cells and incubated for 24 h. All the experiments were
repeated 3 times. The viability of L929 fibroblast cells were given as absorbance vs. concentration.
Entry
Concentration (mg/mL)
% Cell viability
9
10
11
12
1
0.2
53.01
55.08
57.00
75.38
80.84
86.73
100
1.2
1
60.64
66.47
68.88
81.94
83.49
85.44
1.4
0.7
2
57.60
61.47
68.28
86.72
88.23
94.77
0,5
1,2
1
61.72
70.31
83.26
91.52
93.39
101.96
1
2
0.1
3.5
2
3
0.05
0,7
2.3
2.5
4
4
0.025
0.0125
0.00625
1.2
1.8
3
1,5
1,4
0,7
0.7
1.5
2
5
6
Control
0.7
4. Experimental
4.1.3. 3-Amino-3-deoxy-1,2:5,6-di-O-isoproylidene-α-D-glucofuranose (4)
0.5 g (1.75 mmol) 3 was dissolved in 15 mL dry THF at −10 °C
under a nitrogen atmosphere. The reaction mixture was stirred for
15 min. Subsequently, 0.27 g LiAlH4 (7.00 mmol) was added, which
was then stirred for 4 h. Next, the mixture was hydrolysed with satu-
rated NH4Cl and extracted with CH2Cl2. The organic phase was dried
with MgSO4 and concentrated under reduced pressure. 0.34 g product
was obtained as light yellow oil (74% yield). 1H NMR (400 MHz, CDCl3)
δ 5.79 (d, J = 3.5 Hz, 1H, H-1), 4.30 (d, J = 3.5 Hz, 1H, H-2),
4.17–4.08 (m, 1H, H-3), 4.05 (dd, J = 8.3, 6.1 Hz, 1H, H-4), 3.90 (ddd,
J = 13.2, 8.6, 4.1 Hz, 2H, H-5, H-6a), 3.44 (d, J = 3.3 Hz, 1H, H-6b),
1.41 (s, 3H, -CH3), 1.33 (s, 3H, -CH3), 1.27 (s, 3H, -CH3), 1.22 (s, 3H,
-CH3); 13C NMR (101 MHz, CDCl3) δ 111.1 (C(CH3)2), 108.9 (C(CH3)2),
104.8 (C-1), 86.3 (C-4), 81.3 (C-2), 72.7 (C-5), 67.8 (C-3), 57.1 (C-6),
26.6 (-CH3), 26.6 (-CH3), 25.9 (-CH3), 25.1 (-CH3).
4.1. Chemistry (General methods)
All chemicals and solvents were purchased from Sigma-Aldrich. TLC
analyses were performed on 250 μm Silica Gel 60 F254 plates. Column
chromatography was performed using 230–400-mesh silica gel. 1H and
13C NMR spectra were recorded on a Bruker Spectrospin Avance
DPX400 spectrometer at 400 and 100 MHz, respectively. FT-IR spectra
were obtained by Bruker Platinum ATR-IR instruments. Optical rota-
tions were measured on a Rudolph Research Analytical Autopol III
Polarimeter. High-resolution mass spectra (HRMS) were obtained on an
Agilent 6224 (TOF-ESI) LC/MS spectrometer. Melting points were de-
termined with a Stuart SMP50 apparatus.
4.1.1. 1,2:5,6-Di-O-isopropylidene-3-O-tosyl-α-D-allofuranose (2)
4.1.4. 1,2:3,4-Di-O-isopropylidene-6-O-tosyl-α-D-galactopyranose (6)
0.52 g (1,99 mmol) 1,2:3,4-di-O-isopropylidene-α-D-galactopyranose
was dissolved in 2.0 mL pyridine. To this solution, catalytic amount
DMAP and 0.46 g (2.41 mmol) p-toluenesulfonyl chloride were added
and stirred for 24 h. The reaction was monitored with TLC (Hexane/
Ethyl acetate, 10:1). When TLC indicated the disappearance of the
starting materials, it was poured into ice-crash and extracted with
CHCl3. The solvent was removed under reduced pressure and the re-
sidue was purified by silica gel using Hexane/Ethyl acetate, (10:1) as
eluent. 0.74 g product was obtained as white solid (90% yield). 1H NMR
(400 MHz, CDCl3) δ 7.80 (d, J = 8.3 Hz, 2H, Ar-H), 7.33 (d, J = 8.0 Hz,
2H, Ar-H), 5.45 (d, J = 4.9 Hz, 1H, H-1), 4.59 (dd, J = 7.9, 2.5 Hz, 1H,
H-3), 4.29 (dd, J = 5.0, 2.5 Hz, 1H, H-2), 4.23–4.16 (m, 2H, H-4, H-5),
4.13–4.00 (m, 2H, H-6a, H-6b), 2.43 (s, 3H, Ar-CH3), 1.49 (s, 3H, -CH3),
1.34 (s, 3H, -CH3), 1.31 (s, 3H, -CH3), 1.27 (s, 3H, -CH3); 13C NMR
(101 MHz, CDCl3) δ 144.8 (C-SO3), 132.9 (C-Ar) 129.7 (C-Ar), 128.1 (C-
Ar), 109.5 (C(CH3)2), 108.9 (C(CH3)2), 96.1 (C-1) 70.5 (C-4) 70.4 (C-3),
70.3 (C-2), 68.2 (C-6), 65.9 (C-5), 25.9 (-CH3), 25.8 (-CH3), 24.9 (-CH3),
24.3 (-CH3), 21.6 (Ar-CH3).
The synthesis procedure was adapted which has been previously
reported by Richardson [22]. 1.0
g (3.8 mmol) 1,2:5,6-di-O-iso-
propylidene-α-D-allofuranose was dissolved in 4.3 mL pyridine. To this
solution, catalytic amount DMAP and 0.73 g (3.8 mmol) of p-toluene-
sulfonyl chloride were added and stirred for 2 days at room tempera-
ture. When TLC (Hexane/Ethyl acetate, 10:1) indicated the dis-
appearance of the starting materials, it was poured into ice. Next, it was
extracted with CHCl3 and purified with Hexane/Ethyl acetate (10:1)
system. Finally, the amount of product was 1.399 g (57% yield). White
solid: mp 175 °C; 1H NMR (400 MHz, CDCl3): δ 7.80 (d, J = 8.3 Hz, 2H,
Ar-H), 7.28 (d, J = 8.2 Hz, 2H, Ar-H), 5.69 (d, J = 3.1 Hz, 1H, H-1),
4.58 (m, 2H, H-4, H-5), 4.19 - 4.02 (m, 2H, H-2, H-3), 3.86 (dd, J = 8.5,
6.7 Hz, 1H, H-6a), 3.71 (dd, J = 8.5–6.5 Hz, 1H, H-6b), 2.38 (s, 3H, Ar-
CH3), 1.46 (s, 3H, -CH3), 1.25 (s, 3H, -CH3), 1.22 (s, 3H, -CH3), 1.21 (s,
3H, -CH3). 13C NMR (101 MHz, CDCl3) δ 145.2 (C-SO3), 133.2 (C-Ar),
129.7 (C-Ar), 128.4 (C-Ar), 113.6 (C(CH3)2), 109.9 (C(CH3)2), 103.8 (C-
1), 77.9 (C-4), 77.0 (C-2), 76.6 (C-5), 74.7, (C-3), 65.2 (C-6), 26.7
(-CH3), 26.6 (-CH3), 26.1 (-CH3), 25.1 (-CH3), 21.7 (Ar-CH3).
4.1.2. 3-Azido-3-deoxy-1,2:5,6-di-O-isopropylidene-α-D-glucofuranose (3)
The synthesis procedure was adapted which has been previously
reported by Nayak [30]. 0.45 g (1.08 mmol) 2 was dissolved in 10 mL
DMF (N,N-dimethylformamide). To this solution, 1.156 g (17.79 mmol)
NaN3 was added. The mixture was refluxed at 153 °C for 4 h. Next,
20 mL of distilled water was added to the mixture. The reaction mixture
was extracted with 50 mL CHCl3. Then, organic phase was concentrated
under reduced pressure. 0.25 g product was obtained as light yellow oil
(83% yield). 1H NMR (400 MHz, CDCl3) δ 5.86 (d, J = 3.6 Hz, 1H, H-
1), 4.62 (d, J = 3.6 Hz, 1H, H-2), 4.29–4.20 (m, 1H, H-4), 4.18–4.06
(m, 3H, H-3, H-5, H-6a), 3.98 (dd, J = 8.7, 4.8 Hz, 1H, H-6b), 1.51 (s,
4.1.5. 6-Azido-6-deoxy-1,2:3,4-di-O-isopropylidene-α-D-galactopyranose
(7)
0.7 g (1.69 mmol) 6 was dissolved in 14 mL DMF. To this solution,
0.44 g (6.76 mmol) NaN3 was added. The mixture was refluxed for 4 h.
Then, the reaction mixture allowed to cool to room temperature and
25 mL distilled water was added. The solution was extracted with
CH2Cl2 and concentrated in vacuo. The crude product was purified by
column chromatography on silica gel using Hexane/Ethyl acetate (7:1).
0.4 g product was obtained as light yellow oil (83% yield). 1H NMR
(400 MHz, CDCl3) δ 5.48 (d, J = 5.0 Hz, 1H, H-1), 4.56 (dd, J = 7.9,
2.5 Hz, 1H, H-3), 4.27 (dd, J = 5.0, 2.5 Hz, 1H, H-2), 4.13 (dd, J = 7.9,
1.9 Hz, 1H, H-4), 3.85 (ddd, J = 7.5, 5.3, 1.8 Hz, 1H, H-5), 3.45 (dd,
J = 12.7, 7.9 Hz, 1H, H-6a), 3.29 (dd, J = 12.7, 5.3 Hz, 1H, H-6b), 1.48
(s, 3H, -CH3), 1.39 (s, 3H, -CH3), 1.28 (s, 3H, -CH3), 1.27 (s, 3H, -CH3);
13C NMR (101 MHz, CDCl3) δ 109.6 (C(CH3)2), 108.8 (C(CH3)2), 96.3
3H, -CH3), 1.44 (s, 3H, -CH3), 1.37 (s, 3H, -CH3), 1.32 (s, 3H, -CH3); 13
C
NMR (101 MHz, CDCl3) δ 112.3 (C(CH3)2), 109.6 (C(CH3)2), 105.0 (C-
1), 83.4 (C-4), 80.5 (C-2), 73.0 (C-5), 67.6 (C-3), 66.4 (C-6), 26.9
(-CH3), 26.6 (-CH3), 26.2 (-CH3), 25.1 (-CH3).
5

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CarbohydrateResearch492(2020)107991
(C-1), 71.2 (C-4), 70.8 (C-3), 70.4 (C-2), 66.9 (C-6), 50.7 (C-5), 26.0
(-CH3), 25.9 (-CH3), 24.9 (-CH3), 24.4 (-CH3).
4.2.3. 3-[3,5-Bis(trifluoromethylphenyl)-urido]-3-deoxy-1,2:5,6-di-O-
isopropylidene-α-D-glucofuranoside (11)
Following the general procedure from 4 (1.0 mmol) and 3,5-bis
(trifluoromethyl)phenyl isocyanate (1.1 mmol) the compound 11 was
4.1.6. 6-Amino-6-deoxy-1,2:3,4-di-O-isopropylidene-α-D-galactopyranose
(8)
obtained (283.2 mg, 55%). Light yellow solid: mp 89.4–92.6 °C; [ ]2D5
=
–12.25 (c 0.01, CH2Cl2); FT-IR (neat): 3289, 2989, 1624, 1528, 1472,
1377, 1276, 1170, 1128, 1072, 1016, 884, 681; 1H NMR (400 MHz,
CDCl3) δ 8.88 (s, 1H, Urea N-H), 7.82 (s, 2H, Ar-H), 7.60 (s, 1H, Ar-H),
5.83 (s, 1H, Urea N-H), 4.77 (d, J = 3.7 Hz, 1H, H-1), 4.09 (m, 6H, H-2,
H-3, H-4, H-5, H-6a, H-6b), 1.56–1.23 (m, 12H, -CH3); 13C NMR
(101 MHz, CDCl3) δ 171.7 (C=O), 124.3 (C-Ar), 123.3 (C-Ar), 118.8 (C-
Ar), 112.5 (C(CH3)2), 110.6 (C(CH3)2), 104.4 (C-1), 84.3 (C-2), 72.8 (C-
4), 67.3 (C-5), 61.2 (C-6), 60.6 (C-3), 26.3 (-CH3), 26.0 (-CH3), 25.0
(-CH3), 21.0 (-CH3).
0.38 g (1.33 mmol) 7 was dissolved in dry THF at −10 °C under a
nitrogen atmosphere. Subsequently, 0.20 g LiAlH4 (5.32 mmol) was
added. Then, the reaction mixture allowed to cool to room temperature
and stirred overnight. The solution was cooled to 0 °C and 1 M NaOH
solution was added until gas evolution was ceased. Then the solution
was extracted with CHCl3 (20 mL) and removal of the solvent in vacuo
afforded 0.29 g amino sugar 8 as light yellow oil (85% yield). 1H NMR
(400 MHz, CDCl3) δ 5.55 (d, J = 5.1 Hz, 1H, H-1), 4.60 (dd, J = 7.9,
2.3 Hz, 1H, H-3), 4.32 (dd, J = 5.1, 2.3 Hz, 1H, H-2), 4.23 (dd, J = 7.9,
1.9 Hz, 1H, H-4), 3.73–3.67 (m, 1H, H-5), 2.96 (dd, J = 13.2, 7.8 Hz,
1H, H-6a), 2.84 (dd, J = 13.2, 4.9 Hz, 1H, H-6b), 1.54 (s, 3H, -CH3),
1.45 (s, 3H, -CH3), 1.34 (s, 3H, -CH3), 1.34 (s, 3H, -CH3); 13C NMR
(101 MHz, CDCl3) δ 109.1 (C(CH3)2), 108.3 (C(CH3)2), 96.3 (C-1), 71.7
(C-4), 70.7 (C-3), 70.6 (C-2), 69.4 (C-6), 42.3 (C-5), 26.0 (-CH3), 25.9
(-CH3), 24.9 (-CH3), 24.3 (-CH3).
4.2.4. 6-[3,5-Bis(trifluoromethylphenyl)-urido]-6-deoxy-1,2:3,4-di-O-
isopropylidene-α-D-galactopyranoside (12)
Following the general procedure from 8 (1.0 mmol) and 3,5-bis
(trifluoromethyl)phenyl isocyanate (1.1 mmol) the compound 12 was
obtained (444.3 mg, 86%). Light yellow solid: mp 159.3–162.1 °C;
[ ]2D5
=
14.11 (c 0.01, CH2Cl2); FT-IR (neat): 3357, 2989, 2938, 1701,
1553, 1471, 1386, 1275, 1169, 1126, 1108, 1063, 987, 878; 1H NMR
(400 MHz, CDCl3) δ 7.58 (s, 2H, Ar-H), 7.50 (s, 1H, Urea N-H), 7.23 (s,
1H, Ar-H), 6.35 (s, 1H, Urea N-H), 5.56 (d, J = 4.8 Hz, 1H, H-1), 4.61
(dd, J = 7.8, 2.0 Hz, 1H, H-3), 4.43–4.30 (m, 2H, H-2, H-5), 4.20 (d,
J = 7.9 Hz, 1H, H-4), 3.61–3.45 (m, 1H, H-6a), 3.20–3.03 (m, 1H, H-
6b), 1.55 (s, 3H, -CH3), 1.41–1.24 (m, 9H, -CH3); 13C NMR (101 MHz,
CDCl3) δ 155.2 (C=O), 140.7 (C-Ar), 132.1 (-CF3), 124.4 (C-Ar), 121.7
(C-Ar), 118.0 (C-Ar), 110.2 (C(CH3)2), 109.8 (C(CH3)2), 96.5 (C-1),
71.5 (C-4), 70.7 (C-3), 66.7 (C-2), 40.9 (C-6), 31.6 (C-5), 25.9 (-CH3),
25.7 (-CH3), 25.0 (-CH3), 24.5 (-CH3); HRMS (ESI), m/z calcd. for
4.2. General procedure for the synthesis of urea and thiourea based
compounds
A solution of sugar amine (4 or 8) (1.0 mmol) in dry THF (5 mL) was
treated with 3,5-bis(trifluoromethyl)phenyl isocyanate (1.1 mmol) or
3,5-bis(trifluoromethyl)phenyl isothiocyanate (1.1 mmol) at room
temperature. The mixture was stirred overnight. The solvent was re-
moved in vacuum and remaining solid was purified by column chro-
matography.
C
21H25F6N2O6 [M + H]+ 515.1617, found: 515.1619.
4.2.1. 3-[3,5-Bis(trifluoromethylphenyl)-thiourido]-3-deoxy-1,2:5,6-di-O-
isopropylidene-α-D-glucofuranoside (9)
4.3. General procedure for the synthesis of squaramide based compounds
Following the general procedure from 4 (1.0 mmol) and 3,5-bis
(trifluoromethyl)phenyl isothiocyanate (1.1 mmol) the compound 9
was obtained (387.6 mg, 72%). Light yellow solid: mp 67.1–70.4 °C;
To a solution of 3,4-dimethoxy-3-cyclobutene-1,2-dione (1.0 mmol)
in methanol (3 mL), 1.0 mmol sugar amine (4 or 8) was added at room
temperature in one portion. After 6 h aromatic amine or sugar amine
(1.0 mmol) was dissolved in methanol (2 mL) and added to the reaction
mixture in one portion. After 24 h, the product was purified by filtra-
tion.
[ ]2D5
=
–10.49 (c 0.01, CH2Cl2); FT-IR (neat): 3355, 2989, 2963, 2937,
1701, 1537, 1472, 1382, 1276, 1214, 1170, 1128, 1069, 1015, 882; 1
H
NMR (400 MHz, CDCl3) δ 8.87 (s, 1H, Thiourea N-H), 7.81 (s, 2H, Ar-
H), 7.60 (s, 1H, Ar-H), 5.87 (s, 1H, Thiourea N-H), 4.77 (d, J = 3.7 Hz,
1H, H-1), 4.47–3.67 (m, 6H, H-2,3,4,5,6a,6b), 1.59–1.21 (m, 12H,
-CH3); 13C NMR (101 MHz, CDCl3) δ 131.9 (C-Ar), 123.6 (C-Ar), 118.6
(C(CH3)2), 109.8 (C(CH3)2), 109.7 (C-1), 71.5 (C-2), 70.7 (C-4), 70.6
(C-5), 47.2 (C-6), 45.0 (C-3), 25.9 (-CH3), 25.8 (-CH3), 24.9 (-CH3), 24.3
4.3.1. 3,4-Bis-(3-amino-3-deoxy-1,2:5,6-di-O-isopropylidene-α-D-
glucofuranose)cyclobut-3-ene-1,2-dione (13)
Following the general procedure from 4 (2.0 mmol) the compound
13 was obtained (250.7 mg, 42%). White solid: mp ≥ 250 °C; [ ]2D5
=
(-CH3); HRMS (ESI), m/z calcd. for C21H25F6N2O5S [M
+
H]+
–18.70 (c 0.01, DMSO); FT-IR (neat): 3148, 3055, 2938, 1805, 1653,
1556, 1458, 1374, 1211, 1162, 1077, 1044, 1024, 867, 836; 1H NMR
(400 MHz, DMSO) δ 7.51 (s, 2H, Amide-NH), 5.93 (d, J = 3.5 Hz, 2H,
H-1), 4.64 (m, 4H, H-2, H-3), 4.24–3.96 (m, 6H, H-4, H-5, H-6a), 3.86
(dd, J = 7.8, 4.1 Hz, 2H, H-6b), 1.44 (s, 6H, -CH3), 1.32 (s, 6H, -CH3),
1.26 (s, 6H, -CH3), 1.24 (s, 6H, -CH3); 13C NMR (101 MHz, DMSO) δ
183.1 (C=O), 167.3 (C=C), 111.4 (C(CH3)2), 108.8 (C(CH3)2), 104.0
(C-1), 84.1 (C-4), 78.7 (C-2), 71.9 (C-5), 66.5 (C-3), 58.7 (C-6), 26.7
(-CH3), 26.2 (-CH3), 25.9 (-CH3), 25.2 (-CH3); HRMS (ESI), m/z calcd.
for C28H41N2O12 [M + H]+ 597.2659, found: 597.2629.
531.1388, found: 531.1192.
4.2.2. 6-[3,5-Bis(trifluoromethylphenyl)-thiourido]-6-deoxy-1,2:3,4-di-O-
isopropylidene-α-D-galactopyranoside (10)
Following the general procedure from 8 (1.0 mmol) and 3,5-bis
(trifluoromethyl)phenyl isothiocyanate (1.1 mmol) the compound 10
was obtained (470.0 mg, 88%). Light yellow solid: mp 171.6–174.2 °C;
[ ]2D5
=
–39.41 (c 0.005, CH2Cl2); FT-IR (neat): 3303, 3101, 2986, 2932,
2861, 1548, 1468, 1384, 1274, 1210, 1168, 1128, 1061, 991, 882; 1H
NMR (400 MHz, CDCl3) δ 8.39 (s, 1H, Thiourea N-H), 7.73 (s, 2H, Ar-
H), 7.49 (s, 1H, Ar-H), 7.36 (s, 1H, Thiourea N-H), 5.51 (d, J = 5.0 Hz,
1H, H-1), 4.58–4.45 (m, 2H, H-3, H-5), 4.33 (dd, J = 5.0, 2.5 Hz, 1H,
H-2), 4.24 (dd, J = 7.9, 1.7 Hz, 1H, H-4), 4.08 (s, 1H, H-6a), 3.50–3.33
(m, 1H, H-6b), 1.47 (s, 3H, -CH3), 1.36–1.26 (m, 9H, -CH3); 13C NMR
(101 MHz, CDCl3) δ 181.7 (C=O), 131.3 (-CF3), 123.2 (C-Ar), 122.6 (C-
Ar), 120.5 (C-Ar), 117.7 (C-Ar), 108.8 (C(CH3)2), 108.7 (C(CH3)2), 95.5
(C-1), 70.5 (C-4), 69.7 (C-3), 69.6 (C-2), 44.1 (C-6), 28.7 (C-5), 24.9
(-CH3), 24.8 (-CH3), 23.9 (-CH3), 23.3 (-CH3); HRMS (ESI), m/z calcd.
for C21H25F6N2O5S [M + H]+ 531.1388, found: 531.1436.
4.3.2. 3-(3-Amino-3-deoxy-1,2:5,6-di-O-isopropylidene-α-D-
glucofuranose)-4-(R)-((1-phenylethyl)amino)cyclobut-3-ene-1,2-dione
(14)
Following the general procedure from 4 (1.0 mmol) and (R)-(+)-α-
Methylbenzylamine (1.0 mmol) the compound 14 was obtained
(247.8 mg, 54%). White solid: mp 248 °C (decomposed); [ ]2D5
=
35.55 (c
0.01, DMSO); FT-IR (neat): 3149, 2982, 2935, 1799, 1647, 1549, 1452,
1373, 1210, 1163, 1073, 1014, 841; 1H NMR (400 MHz, DMSO) δ 7.71
(s, 1H, Amide-NH), 7.49 (s, 1H, Amide-NH), 7.44–7.35 (m, 4H, Ar-H),
6

Ö. Işılar, et al.
CarbohydrateResearch492(2020)107991
7.34–7.25 (m, 1H, Ar-H), 5.89 (d, J = 3.4 Hz, 1H, H-1), 5.19 (s, 1H, H-
2), 4.71–4.53 (m, 2H, H-3, H-4), 4.21–3.94 (m, 3H, H-5, H-6a, H-6b),
3.84 (s, 1H, -NHCH), 1.55 (d, J = 6.9 Hz, 3H, -CH3), 1.43 (s, 3H, -CH3),
1.32 (s, 3H, -CH3), 1.24 (s, 6H, -CH3); 13C NMR (101 MHz, DMSO) δ
182.9 (C=O), 182.4 (C=O), 167.1 (C=C), 166.9 (C=C), 128.7 (C-Ar),
127.4 (C-Ar), 126.0 (C-Ar), 111.3 (C-Ar), 108.7 (C(CH3)2), 104.0
(C(CH3)2), 84.1 (C-1), 72.0 (C-2), 70.0 (C-4), 66.6 (C-5), 60.2 (C-6),
58.7 (C-3), 52.7 (-NHCH), 31.3 (-CH3), 26.6 (-CH3), 26.3 (-CH3), 25.9
(-CH3), 25.2 (-CH3); HRMS (ESI), m/z calcd. for C24H31N2O7 [M + H]+
459.2131, found: 459.2114.
132.3 (C-Ar), 128.4 (C-Ar), 127.8 (C-Ar), 127.5 (C-Ar), 126.4 (C-Ar),
126.0 (C-Ar), 124.5 (C-Ar), 124.2 (C-Ar), 111.4 (C-Ar), 108.7
(C(CH3)2), 104.0 (C(CH3)2), 84.1 (C-1), 71.9 (C-2), 66.6 (C-4), 58.7 (C-
5), 54.9 (C-6), 52.9 (C-3), 52.8 (-NHCH), 26.6 (-CH3), 26.3 (-CH3), 25.9
(-CH3), 25.1 (-CH3), 22.8 (-CH3); HRMS (ESI), m/z calcd. for
C28H33N2O7 [M + H]+ 509.2287, found: 509.2280.
4.3.6. 3,4-Bis-(6-amino-6-deoxy-1,2:3,4-di-O-isopropylidene-α-D-galacto-
pyranose)cyclobut-3-ene-1,2-dione (18)
Following the general procedure from 8 (2.0 mmol) the compound
18 was obtained (365.2 mg, 59%). White solid: mp ≥ 250 °C; [ ]2D5
=
4.3.3. 3-(3-Amino-3-deoxy-1,2:5,6-di-O-isopropylidene-α-D-glucofura-
nose)-4-(S)-((1-phenylethyl)amino)cyclobut-3-ene-1,2-dione (15)
Following the general procedure from 4 (1.0 mmol) and (S)-(−)-α-
Methylbenzylamine (1.0 mmol) the compound 15 was obtained
–19.09 (c 0.01, DMSO); FT-IR (neat): 3148, 2938, 1806, 1653, 1556,
1457, 1264, 1211, 1162, 1076, 1044, 1024, 883, 867; 1H NMR
(400 MHz, DMSO) δ 7.56 (s, 2H, Amide-NH), 5.48 (d, J = 4.9 Hz, 1H,
H-1), 4.63 (dd, J = 7.8, 2.2 Hz, 2H, H-3), 4.37 (dd, J = 4.9, 2.3 Hz, 2H,
H-5), 4.22 (d, J = 8.1 Hz, 2H, H-2), 3.86 (s, 2H, H-4), 3.69–3.61 (m,
2H, H-6a), 3.58–3.47 (m, 2H, H-6b), 1.39 (s, 3H, -CH3), 1.37 (s, 3H,
-CH3), 1.30 (s, 3H, -CH3), 1.27 (s, 3H, -CH3); 13C NMR (101 MHz,
(303 mg, 66%). White solid: mp ≥ 250 °C; [ ]2D5
=
–37.36 (c 0.01,
DMSO); FT-IR (neat): 3150, 3030, 2980, 2934, 1794, 1645, 1550, 1467,
1373, 1210, 1164, 1076, 1025, 836; 1H NMR (400 MHz, DMSO) δ 7.72
(s, 1H, Amide-NH), 7.48 (s, 1H, Amide-NH), 7.42–7.34 (m, 4H, Ar-H),
7.32–7.26 (m, 1H, Ar-H), 5.92 (d, J = 3.6 Hz, 1H, H-1), 5.19 (s, 1H, H-
2), 4.76–4.53 (m, 2H, H-3, H-4), 4.21–3.96 (m, 3H, H-5, H-6a, H-6b),
3.89–3.73 (m, 1H, -NHCH), 1.54 (d, J = 6.9 Hz, 3H, -CH3), 1.44 (s, 3H,
-CH3), 1.28 (s, 3H, -CH3), 1.26 (s, 3H, -CH3), 1.17 (s, 3H, -CH3); 13C
NMR (101 MHz, DMSO) δ 182.9 (C=O), 182.4 (C=O), 167.2 (C=C),
167.0 (C=C), 128.7 (C-Ar), 127.4 (C-Ar), 125.9 (C-Ar), 111.4 (C-Ar),
108.7 (C(CH3)2, 104.0 (C(CH3)2, 84.1 (C-1), 71.9 (C-2), 66.6 (C-5), 58.7
(C-6), 52.7 (-NHCH), 26.6 (-CH3), 26.3 (-CH3), 25.9 (-CH3), 25.1 (-CH3);
HRMS (ESI), m/z calcd. for C24H31N2O7 [M + H]+ 459.2131, found:
459.2107.
DMSO)
δ 182.8 (C=O), 168.1 (C=C), 108.6 (C(CH3)2), 108.0
(C(CH3)2), 95.6 (C-1), 70.3 (C-4), 70.1 (C-3), 69.7 (C-2), 67.3 (C-6),
43.5 (C-5), 25.9 (-CH3), 25.6 (-CH3), 24.9 (-CH3), 24.3 (-CH3); HRMS
(ESI), m/z calcd. for C28H40N2O12Na [M + Na]+ 619.2478, found:
619.2525.
4.3.7. 6-Amino-6-deoxy-3-(1,2:3,4-di-O-isopropylidene-α-D-galactopyranose)-
4-(R)-(1-phenylethyl)amino)cyclobut-3-ene-1,2-dione (19)
Following the general procedure from 8 (1.0 mmol) and (R)-(+)-α-
Methylbenzylamine (1.0 mmol) the compound 19 was obtained
(321.3 mg, 70%). White solid: mp 248 °C (decomposed); [ ]2D5
=
–31.27
4.3.4. 3-(3-Amino-3-deoxy-1,2:5,6-di-O-isopropylidene-α-D-glucofura-
nose)-4-(R)-((1-(naphthalen-2-yl)ethyl)amino)cyclobut-3-ene-1,2-dione
(16)
(c 0.01, DMSO); FT-IR (neat): 3151, 3032, 2975, 2932, 1795, 1645,
1541, 1453, 1374, 1209, 1075, 1002, 905; 1H NMR (400 MHz, DMSO)
δ 7.86 (s, 1H, Amide-NH), 7.40–7.36 (m, 5H, Ar-H), 7.30 (s, 1H, Amide-
NH), 5.48 (d, J = 5.0 Hz, 1H, H-1), 5.21 (s, 1H, H-3), 4.62 (dd, J = 7.8,
2.2 Hz, 1H, H-5), 4.37 (dd, J = 4.9, 2.3 Hz, 1H, H-2), 4.22 (d,
J = 7.6 Hz, 1H, H-4), 3.86 (s, 1H, H-6a), 3.67 (s, 1H, H-6b), 3.53 (s, 1H,
-NHCH), 1.57–1.49 (m, 3H, -CH3), 1.39 (s, 3H, -CH3), 1.35 (s, 3H,
-CH3), 1.29 (s, 3H, -CH3), 1.27 (s, 3H, -CH3); 13C NMR (101 MHz,
DMSO) δ 182.6 (C=O), 182.4 (C=O), 167.9 (C=C), 167.0 (C=C),
143.5 (C-Ar), 128.6 (C-Ar), 127.3 (C-Ar), 126.0 (C-Ar), 108.5
(C(CH3)2), 108.0 (C(CH3)2), 95.6 (C-1), 70.4 (C-4), 70.1 (C-3), 69.7 (C-
2), 67.3 (C-6), 52.6 (-NHCH), 43.6 (C-5), 25.9 (-CH3), 25.6 (-CH3), 24.9
(-CH3), 24.3 (-CH3), 23.0 (-CH3); HRMS (ESI), m/z calcd. for
C24H31N2O7 [M + H]+ 459.2131, found: 459.2159.
Following the general procedure from 4 (1.0 mmol) and (R)-(+)-1-
(2-Naphthyl)ethylamine (1.0 mmol) the compound 16 was obtained
(162.8 mg, 32%). White solid: mp 238 °C (decomposed); [ ]2D5
=
+31.28
(c 0.02, DMSO); FT-IR (neat): 3150, 3054, 2980, 2936, 1801, 1645,
1553, 1470, 1381, 1212, 1163, 1074, 1018, 858, 819; 1H NMR
(400 MHz, DMSO) δ 7.99–7.87 (m, 5H, Amide-NH, Ar-H), 7.55–7.45
(m, 4H, Ar-H), 5.89 (d, J = 2.8 Hz, 1H, H-1), 5.38 (s, 1H, H-2),
4.76–4.53 (m, 2H, H-3, H-4), 4.28–3.94 (m, 3H, H-5, H-6a, H-6b), 3.84
(s, 1H, -NHCH), 1.70–1.59 (m, 3H, -CH3), 1.43 (s, 3H, -CH3), 1.32 (s,
3H, -CH3), 1.24 (s, 6H, -CH3); 13C NMR (101 MHz, DMSO) δ 183.0
(C=O), 182.4 (C=O), 167.2 (C=C), 167.0 (C=C), 132.8 (C-Ar), 132.3
(C-Ar), 128.4 (C-Ar), 127.8 (C-Ar), 127.5 (C-Ar), 126.4 (C-Ar), 126.1
(C-Ar), 124.5 (C-Ar), 124.3 (C-Ar), 108.7 (C(CH3)2), 104.0 (C(CH3)2),
84.1 (C-1), 78.7 (C-2), 71.9 (C-4), 66.6 (C-5), 58.7 (C-6), 54.9 (C-3),
52.8 (-NHCH), 26.6 (-CH3), 26.3 (-CH3), 25.9 (-CH3), 25.1 (-CH3), 22.8
(-CH3); HRMS (ESI), m/z calcd. for C28H33N2O7 [M + H]+ 509.2287,
found: 509.2268.
4.3.8. 6-Amino-6-deoxy-3-(1,2:3,4-di-O-isopropylidene-α-D-galacto-
pyranose)-4-(S)-((1-phenylethyl)amino)cyclobut-3-ene-1,2-dione (20)
Following the general procedure from 8 (1.0 mmol) and (S)-(−)-α-
Methylbenzylamine (1.0 mmol) the compound 20 was obtained
(312.2 mg, 68%). White solid: mp ≥ 250 °C; [ ]2D5
=
–73.47 (c 0.01,
DMSO); FT-IR (neat): 3150, 3032, 2974, 2932, 1793, 1644, 1543, 1488,
1454, 1209, 1149, 1051, 913, 835; 1H NMR (400 MHz, DMSO) δ 7.86
(s, 1H, Amide-NH), 7.42–7.34 (m, 5H, Ar-H), 7.32–7.25 (m, 1H, Amide-
NH), 5.46 (d, J = 4.9 Hz, 1H, H-1), 5.21 (s, 1H, H-3), 4.63 (dd, J = 7.8,
2.3 Hz, 1H, H-5), 4.37 (dd, J = 5.0, 2.4 Hz, 1H, H-2), 4.22 (d,
J = 7.5 Hz, 1H, H-4), 3.84 (s, 1H, H-6a), 3.65 (dd, J = 12.1, 6.2 Hz,
1H, H-6b), 3.54 (s, 1H, -NHCH), 1.55–1.50 (m, 3H, -CH3), 1.37 (s, 3H,
-CH3), 1.35 (s, 3H, -CH3), 1.30 (s, 3H, -CH3), 1.26 (s, 3H, -CH3); 13C
NMR (101 MHz, DMSO) δ 182.6 (C=O), 182.2 (C=O), 168.0 (C=C),
166.9 (C=O), 143.6 (C-Ar), 128.6 (C-Ar), 127.3 (C-Ar), 125.9 (C-Ar),
108.6 (C(CH3)2), 108.0 (C(CH3)2), 95.6 (C-1), 70.4 (C-4), 70.1 (C-3),
69.7 (C-2), 67.4 (C-6), 52.7 (-NHCH), 43.6 (C-5), 25.9 (-CH3), 25.6
(-CH3), 24.8 (-CH3), 24.3 (-CH3), 22.9 (-CH3); HRMS (ESI), m/z calcd.
for C24H31N2O7 [M + H]+ 459.2131, found: 459.2159.
4.3.5. 3-(3-Amino-3-deoxy-1,2:5,6-di-O-isopropylidene-α-D-glucofura-
nose)-4-(S)-((1-(naphthalen-2-yl)ethyl)amino)cyclobut-3-ene-1,2-dione
(17)
Following the general procedure from 4 (1.0 mmol) and (S)-(−)-1-
(2-Naphthyl)ethylamine (1.0 mmol) the compound 17 was obtained
(247.8 mg, 54%). White solid: mp 241 °C (decomposed); [ ]2D5
=
–34.45
(c 0.01, DMSO); FT-IR (neat): 3152, 3055, 2981, 2935, 1800, 1647,
1556, 1471, 1381, 1212, 1165, 1075, 1018, 855, 819; 1H NMR
(400 MHz, DMSO) δ 7.96 (s, 1H, Amide-NH), 7.94–7.89 (m, 3H, Ar-H),
7.87 (s, 1H, Amide-NH), 7.54–7.50 (m, 4H, Ar-H), 5.92 (d, J = 3.0 Hz,
1H, H-1), 5.37 (s, 1H, H-2), 4.72–4.53 (m, 2H, H-3, H-4), 4.17–3.98 (m,
3H, H-5, H-6a, H-6b), 3.85–3.79 (m, 1H, -NHCH), 1.63 (t, J = 7.1 Hz,
3H, -CH3), 1.44 (s, 3H, -CH3), 1.26 (s, 6H, -CH3), 1.13 (s, 3H, -CH3); 13
C
NMR (101 MHz, DMSO) δ 182.5 (C=O), 167.2 (C=C), 132.8 (C-Ar),
7

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CarbohydrateResearch492(2020)107991
4.3.9. 6-Amino-6-deoxy-3-(1,2:3,4-di-O-isopropylidene-α-D-galacto-
pyranose)-4-(R)-((1-(naphthalen-2-yl)ethyl)amino)cyclobut-3-ene-1,2-
dione (21)
and 0.0625 mg/mL) were placed into the wells. Following 24 h in-
cubation under the same conditions, 3,(4,5-dimethylthiazol-2-yl)-2,5-
diphenyltetrazolium bromide (MTT) test was used for detecting of the
cytotoxicity. MTT reagent (50 μL) was added into each well. Upon in-
cubation for an additional 2 h, then MTT solvent (isopropanol) 100 μL
was added into each well, the plates were immediately read in an Elisa
Microplate Reader (BioTek, USA) at 570 nm wavelength and the per-
centage of cell viability of each group was calculated according to the
definition of control cell viability as 100%.
Following the general procedure from 8 (1.0 mmol) and (R)-(+)-1-
(2-Naphthyl)ethylamine (1.0 mmol) the compound 21 was obtained
(377.0 mg, 71%). White solid: mp 248 °C (decomposed); [ ]2D5
=
+19.71
(c 0.01, DMSO); FT-IR (neat): 3180, 2978, 2931, 1803, 1649, 1564,
1488, 1374, 1211, 1168, 1071, 1003, 903, 858; 1H NMR (400 MHz,
DMSO) δ 8.05–7.81 (m, 4H, Ar-H), 7.86 (s, 1H, Amide-NH) 7.60–7.49
(m, 3H, Ar-H), 7.44 (s, 1H, Amide-NH), 5.48 (d, J = 4.9 Hz, 1H, H-1),
5.39 (s, 1H, H-3), 4.61 (d, J = 7.1 Hz, 1H, H-5), 4.36 (d, J = 2.6 Hz,
1H, H-2), 4.22 (s, 1H, H-4), 3.86 (s, 1H, H-6a), 3.69 (s, 1H, H-6b), 3.54
(s, 1H, -NHCH), 1.64 (d, J = 6.8 Hz, 3H, -CH3), 1.38 (s, 3H, -CH3), 1.34
(s, 3H, -CH3), 1.27 (s, 6H, -CH3); 13C NMR (101 MHz, DMSO) δ 182.6
(C=O), 168.0 (C=C), 167.0 (C=C), 141.0 (C-Ar), 132.8 (C-Ar), 132.2
(C-Ar), 128.4 (C-Ar), 127.8 (C-Ar), 127.5 (C-Ar), 126.3 (C-Ar), 126.0
(C-Ar), 124.6 (C-Ar), 124.2 (C-Ar), 108.5 (C(CH3)2), 108.0 (C(CH3)2),
95.6 (C-1), 70.4 (C-4), 70.1 (C-3), 69.7 (C-2), 67.4 (C-6), 52.7 (-NHCH),
43.6 (C-5), 25.9 (-CH3), 25.6 (-CH3), 24.8 (-CH3), 24.3 (-CH3), 22.9
(-CH3); HRMS (ESI), m/z calcd. for C28H32N2O7Na [M + Na]+
531.2107, found: 531.2133.
Declaration of competing interest
The authors declare that they have no known competing financial
interests or personal relationships that could have appeared to influ-
ence the work reported in this paper.
Acknowledgment
This work was supported by Scientific Research Projects
Coordination Unit of Kırıkkale University. Project number: 2017/060.
Appendix A. Supplementary data
4.3.10. 6-Amino-6-deoxy-3-(1,2:3,4-di-O-isopropylidene-α-D-
galactopyranose)-4-(S)-((1-(naphthalen-2-yl)ethyl)amino)cyclobut-3-ene-
1,2-dione (22)
Supplementary data to this article can be found online at https://
doi.org/10.1016/j.carres.2020.107991.
Following the general procedure from 8 (1.0 mmol) and (S)-(−)-1-
(2-Naphthyl)ethylamine (1.0 mmol) the compound 22 was obtained
References
(351.2 mg, 69%). White solid: mp 235 °C (decomposed); [ ]2D5
=
–35.11
(c 0.01, DMSO); FT-IR (neat): 3161, 3056, 2974, 2931, 1798, 1646,
1552, 1472, 1380, 1212, 1182, 1072, 1003, 855, 818; 1H NMR
(400 MHz, DMSO) δ 7.98–7.89 (m, 4H, Ar-H), 7.85 (s, 1H, Amide-NH),
7.56–7.50 (m, 3H, Ar-H), 7.49 (s, 1H, Amide-NH), 5.48 (d, J = 4.9 Hz,
1H, H-1), 5.40 (s, 1H, H-3), 4.62 (dd, J = 7.8, 1.8 Hz, 1H, H-5), 4.37
(dd, J = 4.9, 2.4 Hz, 1H, H-2), 4.23 (d, J = 7.4 Hz, 1H, H-4), 3.85 (s,
1H, H-6a), 3.74–3.64 (m, 1H, H-6b), 3.57 (s, 1H, -NHCH), 1.63 (d,
J = 6.8 Hz, 3H, -CH3), 1.37 (s, 3H, -CH3), 1.31 (s, 3H, -CH3), 1.30 (s,
3H, -CH3), 1.25 (s, 3H, -CH3); 13C NMR (101 MHz, DMSO) δ 182.7
(C=O), 182.5 (C=O), 168.1 (C=C), 167.2 (C=C), 141.1 (C-Ar), 132.8
(C-Ar), 132.2 (C-Ar), 128.3 (C-Ar), 127.8 (C-Ar), 127.5 (C-Ar), 126.3
(C-Ar), 126.0 (C-Ar), 124.5 (C-Ar), 124.0 (C-Ar), 108.6 (C(CH3)2),
108.0 (C(CH3)2), 95.6 (C-1), 70.4 (C-4), 70.1 (C-3), 69.7 (C-2), 67.5 (C-
6), 52.7 (-NHCH), 43.6 (C-5), 25.9 (-CH3), 25.5 (-CH3), 24.8 (-CH3),
24.3 (-CH3), 23.0 (-CH3); HRMS (ESI), m/z calcd. for C28H33N2O7 [M +
H]+ 509.2287, found: 509.2298.
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