Design and synthesis of 2(5H)-furanone liquid-crystal compounds based on natural molecules and biphenyl derivatives

Article abstract of DOI:10.1007/s11164-012-0721-8

Starting from natural molecules, for example l-menthol and amino acids, a series of 2(5H)-furanone liquid-crystal compounds were designed, and synthesized by esterification of N-[5-menthoxy-2(5H)-furanonyl] amino acids with biphenyl-4-ol or biphenyl-4,4′-diol in the presence of dehydrating agents. The structures of all the novel compounds were confirmed by FTIR, ¹H NMR, and mass spectroscopy, and by elemental analysis. The liquid-crystal properties of the target compounds were characterized by differential scanning calorimetry (DSC), X-ray diffraction (XRD), and polarization optical microscopy (POM). The DSC and XRD results showed that some compounds containing short alkyl chains or with the phenyl far from the amino in the amino acid unit formed a mesomorphic phase. Products obtained from biphenyl-4,4′-diol were more likely to form a mesomorphic phase. However, POM revealed no optical texture. These investigations provide, for the first time, a basis for application of 2(5H)-furanones in liquid crystals by combination of different functional units, including biphenyl, l-menthol, and amino acids.

Full text of DOI:10.1007/s11164-012-0721-8

Res Chem Intermed (2013) 39:1865–1876
DOI 10.1007/s11164-012-0721-8
Design and synthesis of 2(5H)-furanone liquid-crystal
compounds based on natural molecules and biphenyl
derivatives
•
•
•
Shi-He Luo Jin-Feng Xiong Zhao-Yang Wang
Guang-Zhen Mo
Received: 25 June 2012 / Accepted: 7 July 2012 / Published online: 21 July 2012
Ó Springer Science+Business Media B.V. 2012
Abstract Starting from natural molecules, for example L-menthol and amino acids,
a series of 2(5H)-furanone liquid-crystal compounds were designed, and synthesized
by esterification of N-[5-menthoxy-2(5H)-furanonyl] amino acids with biphenyl-4-ol
or biphenyl-4,40-diol in the presence of dehydrating agents. The structures of all the
novel compounds were confirmed by FTIR, 1H NMR, and mass spectroscopy, and by
elemental analysis. The liquid-crystal properties of the target compounds were
characterized by differential scanning calorimetry (DSC), X-ray diffraction (XRD),
and polarization optical microscopy (POM). The DSC and XRD results showed that
some compounds containing short alkyl chains or with the phenyl far from the amino
in the amino acid unit formed a mesomorphic phase. Products obtained from biphenyl-
4,40-diol were more likely to form a mesomorphic phase. However, POM revealed no
optical texture. These investigations provide, for the first time, a basis for application
of 2(5H)-furanones in liquid crystals by combination of different functional units,
including biphenyl, L-menthol, and amino acids.
Keywords 2(5H)-Furanone ꢀ Liquid crystal ꢀ Biphenyl ester ꢀ Synthesis ꢀ
Amino acid ꢀ L-Menthol
Introduction
Because oftheir unique photoelectric performance, for example goodoptical properties,
reflection choice for polarized light, circular dichroism, ferroelectricity, and
Electronic supplementary material The online version of this article (doi:10.1007/s11164-012-
0721-8) contains supplementary material, which is available to authorized users.
S.-H. Luo ꢀ J.-F. Xiong ꢀ Z.-Y. Wang (&) ꢀ G.-Z. Mo
School of Chemistry and Environment, South China Normal University,
Guangzhou 510006, People’s Republic of China
e-mail: wangwangzhaoyang@tom.com; wangzy@scnu.edu.cn
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S.-H. Luo et al.
piezoelectricity, chiral liquid-crystal materials have potential applications in many
fields, including non-linear optics, snap switches, and microelectronics [1–4]. The
number ofreports onthe synthesis ofchiral liquidcrystalsfromdifferent chiralmoieties,
for example menthyl [5–9] and amino acid units [10–12], is therefore increasing.
Biphenyl liquid crystals have been widely used in photoelectric display materials
and other applications, because of their many advantages, e.g., good physical and
chemical stability, wide temperature range, appropriate low viscosity, fast response,
and low driver voltage [13–20]. Thus, introducing chiral menthyl into biphenyl
liquid-crystal materials has become a new topic of research [7, 9, 21, 22]. There
have, however, been no reports of the design and synthesis of biphenyl liquid
crystals containing both chiral menthyl and amino acid units.
It has been found that 2(5H)-furanone derivatives can be used in liquid-crystal
research [23]. Herein, to further expand the applications of 3,4-dihalo-2(5H)-
furanone [24–26], on the basis of synthesis of N-[5-menthoxy-2(5H)-furanonyl]
amino acids [26–29], a series of novel liquid-crystal compounds 5 were designed,
and synthesized by esterification of biphenyl-4,40-diol or biphenyl-4-ol with N-[5-
menthoxy-2(5H)-furanonyl] amino acids 4 (Scheme 1). The structures and liquid
crystal properties of the target compounds 5a–5p were systematically characterized
1
by FTIR, H NMR, mass spectroscopy, DSC, XRD, and POM.
Results and discussion
Synthesis of the target compounds by esterification
For esterification of phenols with low activity, the traditional process involves
acylation of carboxylic acids then dehydrohalogenation. This produces large
amounts of the corrosive gases sulfur dioxide and hydrogen chloride. Esterification
via dehydrating condensation between carboxylic acids and phenols effectively
avoids production of corrosive gases, and the by-product H2O does not cause
R'
Br
Br
2
14
11
Br
4 3
Br
HO
15
13
7
COOH
RHN
n
1. L-Menthol, H+
Br2
H
10
6
H
O
CHO
O
O
5
O
9
12
2. Recrystallization
(petroleum ether)
H2O
8
O
KOH, EtOH, r.t.
O
1
1
2
3
5d: n=1, R=CH3, R'=H, R''=H
HO
5e
: n=1, R=H, R'=CH2Ph, R''=H
: n=1, R=H, R'=Ph, R''=H
R'
R'
5f
5g: n=3, R=R'=H, R''=H
COOH
Br
COO
n
n
5h
: n=1, R=R'=H, R''=H
RN
H
Br
RN
H
H
5i
: n=1, R=H, R'=CH2CH(CH3)2, R''=OH
5j: n=1, R=H, R'=CH(CH3)2, R''=OH
R''
H
O
O
5k
: n=5, R=R'=H, R''=OH
EDAC HCl
HOBt, DCM, r.t.
O
M*O
O
5l
M*O
: n=1, R=CH3, R'=H, R''=OH
R''
4
5a-5p
5m: n=1, R=H, R'=CH2Ph, R''=OH
(
)
M*=Menthyl
5a: n=1, R=H, R'=CH2CH(CH3)2, R''=H 5n
: n=1, R=H, R'=Ph, R''=OH
5o: n=3, R=R'=H, R''=OH
5p: n=1, R=R'=H, R''=OH
5b
5c
: n=1, R=H, R'=CH(CH3)2, R''=H
: n=5, R=H, R'=H, R''=H
Scheme 1 Synthetic route to compounds 5a–5p
123

Design and synthesis of 2(5H)-furanone liquid crystals
1867
environmental pollution [30]. Therefore, we chose the latter esterification method
for synthesis of the target compounds 5 in this work.
First, we selected N,N0-dicyclohexylcarbodiimide (DCC) as dehydrating agent
and N,N-dimethylaminopyridine (DMAP) as catalyst. The crude products were very
difficult to purify, especially removal of the by-product 1,3-dicyclohexylurea. Also,
an expensive coupling reagent, 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide
hydrochloride (EDACꢀHCl) [31, 32], was used in the presence of catalytic amount
of N-hydroxybenzotriazole (HOBt) [33].
Even so, because of the low activity of the phenols used for esterification, yields
of products were generally low (16–25 %). Yields were lower when using biphenyl-
4,40-diol as reactant than when using biphenyl-4-ol. Perhaps, because of the
existence of two hydroxyl groups in biphenyl-4,40-diol, simultaneous esterification
of both hydroxyl groups as a competitive side-reaction led to the lower yield.
In the literature, when the more effective dehydrating agent EDACꢀHCl was used
in the synthesis of some biphenyl esters liquid crystals, yields were only 13–22 %
[31], also indicating yields are not high.
Structure characterization of the new compounds
In the IR spectra, stretching absorption of the N–H groups was observed in the
region 3,400–3,200 cm-1, except for 5d and 5l. Stretching absorption bands of
saturated C–H groups were observed in the region 2,960–2,920 cm-1. A strong
C=O stretching band appeared at 1,760–1,710 cm-1, and the C=C stretching band
occurred in the 1,650–1,620 cm-1 region. Benzene ring skeletal stretching occurred
in the region 1,600–1,450 cm-1
.
1
In H NMR, there was a singlet at 5.71–6.80 ppm from the 5-H of the 2(5H)-
furanone. Furthermore, there were a series of peaks at 6.90–7.60 ppm from the
biphenyl groups. These results, combined with those from mass spectroscopy and
elemental analysis, confirmed the structures of all the newly synthesized compounds
were as expected.
Liquid crystal characterization of target compounds
The liquid crystal properties of the target compounds were characterized by DSC,
XRD, and POM. Using the DSC curve of compound 5c as representative, there are
two endothermic peaks on the heating curve (Fig. 1), indicative of a series of phase
transformations. The transition temperatures and enthalpies of different compounds
are summarized in Table 1.
It was found that with decreasing alkyl chain length in the amino acid units, the
2(5H)-furanone compounds (e.g., 5k and 5p) were more likely to occur as the
mesomorphic phase. For 2(5H)-furanones containing an amino acid unit with a
benzene ring structure, the temperature range for compounds with the phenyl being
far from the amino in the amino acid unit (e.g., 5e and 5m) is obviously larger than
for the others. Compounds prepared from biphenyl-4,40-diol were also more likely
to occur as the mesomorphic phase (e.g., 5n vs. 5f, 5p vs. 5h).
123

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S.-H. Luo et al.
Fig. 1 DSC curve obtained from the representative target compound 5c
Table 1 Transition
Compounds Transition temperature,
temperatures and enthalpies of
target compounds 5
T (°C) (enthalpies, DH (J g-1))
Heating
Cooling
5a
5b
5c
5d
5e
5f
Cr 121.3 (0.6) I
Oil
–
Oil
Cr 95.8 (22.3) Sm 120.6 (13.6) I I 101.1 (-3.3) Cr
Cr 126.8 (25.6) I
I 76.9 (-1.7) Cr
I 33.1 (-0.3) Cr
I 76.7 (-8.2) Cr
–
Cr 32.3 (0.4) Sm 124.0 (0.5) I
Cr 126.1 (5.8) I
5g
5h
5i
Cr 142.8 (32.8) I
Cr 124.6 (2.4) I
I 124.4 (-0.1) Cr
I 34.2 (-0.7) Cr
I 66.4 (-0.3) Cr
I 33.7 (-0.3) Cr
–
–
5j
Cr 73.0 (6.0) Sm 116.3 (0.1) I
Cr 39.9 (0.2) Sm 119.3 (1.7) I
Cr 108.0 (0.6) I
5k
5l
5m
5n
5o
5p
Cr 48.3 (0.2) Sm 126.2 (1.2) I
Cr 32.3 (0.5) Sm 124.9 (4.9) I
Cr 74.0 (1.2) I
I 75.7 (-1.2) Cr
I 24.6 (-0.3) Cr
–
Cr 30.4 (0.7) Sm 124.1 (1.0) I
–
Using 5c as a representative liquid-crystal 2(5H)-furanone compound, the liquid
crystal properties were further confirmed by use of XRD. The XRD spectrum of
compound 5c at room temperature is shown in Fig. 2. Generally, for liquid
crystalline molecules with a smectic phase, nematic phase, or cholesteric phase,
there is a significantly diffraction peak near 20°, but only the smectic phase liquid
crystal has another diffraction peak near 6°. Therefore, the XRD result shows that
the compound 5c may occur as the smectic phase [34, 35].
However, characterization by use of POM revealed no significant phase texture
among the 16 new compounds. This may be because of the narrow temperature
123

Design and synthesis of 2(5H)-furanone liquid crystals
1869
Fig. 2 XRD spectrum of 2(5H)-furanone compound 5c
range. Also, these results, combined with those from DSC, revealed that the
enthalpy values for changes between phases of different morphology were relatively
small (Table 1), which may be another reason for the lack of significant phase
texture.
Experimental
General
Infrared spectra were recorded on a Bruker Vector 33 FT-IR instrument by the
liquid film method in the absorption range 4,000–400 cm-1. 1H NMR spectra were
obtained in CDCl3 on a Varian DRX-400 MHz spectrometer with tetramethylsilane
(TMS) as internal standard. Elemental analysis was performed with a Thermo
Flashea TM 112 elemental analyzer. Mass spectra (MS) were recorded on a Thermo
LCQ DECA XP MAX mass spectrometer.
Differential scanning calorimetry was performed with Perkin–Elmer DSC7
thermal analyzer at a heating rate of 10 °C min-1 under a nitrogen atmosphere
(flow velocity 20 mL min-1). X-ray diffraction was recorded on a Bruker D8
Advance X-ray diffractometer using CuKa radiation with a wavelength of
1.5418 9 10-10 m, and scanning range 2h = 5–50° at a scanning speed of 0.03°
at 5 s per step. Optical texture was recorded on a Nikon Eclipse polarization optical
microscope equipped with a heating and cooling stage.
All reagents and solvents were commercially available and used as received.
Using furfural, natural menthol, and amino acid as starting materials, the
intermediate N-[5-menthoxy-2(5H)-furanonyl] amino acids 4a–4h were prepared
in accordance with the literature [26–29].
Typical procedure for synthesis of target compounds 5a–5p
A flame-dried 50-mL round-bottomed flask was charged with 4 (0.24 mmol),
EDACꢀHCl (0.6 mmol), and HOBt (0.7 mmol) in dried CH2Cl2 (20 mL) The
123

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S.-H. Luo et al.
reaction mixture was stirred for 0.5 h in an ice-water bath, then biphenyl-4-ol or
biphenyl-4,40-diol (0.2 mmol, in 5 mL dried CH2Cl2) was added. The reaction was
stirred for 72 h at room temperature. The resulting mixture was washed with water
(20 mL 9 2). The organic layer was dried with magnesium sulfate, and concen-
trated under vacuum to give a crude product, which was purified by column
chromatography on silica gel, with gradient elution with mixtures of petroleum
ether and ethyl acetate, to afford samples of 5a–5p for analysis.
Biphenyl-4-yl 2-((S)-4-bromo-2-((1R,2S,5R)-2-isopropyl-5-methylcyclohexyloxy)-
5-oxo-2,5-dihydrofuran-3-ylamino)-4-methylpentanoate (5a)
White viscous solid, yield 21 %; 1H NMR (400 MHz, CDCl3, TMS) d: 0.85 (3H, d,
J = 6.8 Hz, CH3-12), 0.91–0.98 (7H, m, CH-13, CH3-14, CH3-15), 1.05–1.09 (6H,
m, CH3-20, CH3-21), 1.11–1.20 (2H, m, CH2-9), 1.33–1.43 (2H, m, CH-8, CH-11),
1.55–1.73 (5H, m, CH2-10, CH2-18, CH-19), 2.17–2.27 (2H, m, CH2-7), 3.53–3.66
(1H, m, CH-6), 4.82–5.07 (2H, m, NH, CH-17), 5.76 (1H, s, CH-5), 7.19 (2H, d,
J = 7.2 Hz, ArH-24,26), 7.35–7.39 (1H, m, ArH-34), 7.43–7.47 (2H, m, ArH-
31,33), 7.57 (2H, d, J = 7.6 Hz, ArH-30,32), 7.62 (2H, d, J = 8.0 Hz, ArH-25,27);
IR (film) m: 3379, 3036, 2955, 2928, 2870, 1759, 1651, 1609, 1497, 1470, 1246,
1199, 957, 829, 745, 521; ESI-MS m/z (%): 622 ([M ? Na]?, 100.0); Anal. Calcd
for C32H40BrNO5: C 64.21, H 6.74, N 2.34, Found: C 64.11, H 6.70, N 2.43.
Biphenyl-4-yl 2-((S)-4-bromo-2-((R,2S,5R)-2-isopropyl-5-methylcyclohexyloxy)-
5-oxo-2,5-dihydrofuran-3-ylamino)-3-methylbutanoate (5b)
White viscous solid, yield 24 %; 1H NMR (400 MHz, CDCl3, TMS) d: 0.87 (3H, d,
J = 6.8 Hz, CH3-12), 0.95–1.09 (13H, m, CH-13, CH3-14, CH3-15, CH3-19, CH3-
20), 1.15–1.25 (2H, m, CH2-9), 1.37–1.43 (2H, m, CH-8, CH-11), 1.65–1.76 (3H, m,
CH2-10, CH-18), 2.21–2.25 (2H, m, CH2-7), 3.59–3.76 (1H, m, CH-6), 4.086 (1H, d,
J = 6.8 Hz, CH-17), 5.55 (1H, s, NH), 5.74 (1H, s, CH-5), 7.13–7.18 (2H, m, ArH-
23,25), 7.32–7.37 (3H, m, ArH-30,32, 33), 7.52–7.56 (4H, m, ArH-24,26,29,31); IR
(film) m: 3356, 2955, 2855, 1732, 1655, 1543, 1508, 1486, 1261, 1123, 1018, 799,
745, 575; ESI-MS m/z (%): 638 ([M ? CH3OH ? Na]?, 10.3); Anal. Calcd for
C31H38BrNO5: C 63.70, H 6.55, N 2.40, Found: C 63.63, H 6.50, N 2.30.
Biphenyl-4-yl 6-((S)-4-bromo-2-((R,2S,5R)-2-isopropyl-5-methylcyclohexyloxy)-
5-oxo-2,5-dihydrofuran-3-ylamino)hexanoate (5c)
1
Yellowish viscous solid, yield 24 %; H NMR (400 MHz, CDCl3, TMS) d: 0.81
(3H, d, J = 6.4 Hz, CH3-12), 0.86–0.99 (7H, m, CH-13, CH3-14, CH3-15),
1.02–1.20 (2H, m, CH2-9), 1.25–1.43 (4H, m, CH-8, CH-11, CH2-18), 1.46–1.57
(2H, m, CH2-19), 1.62–1.73 (4H, m, CH2-10, CH2-17), 2.14–2.26 (2H, m, CH2-7),
2.63 (2H, t, J = 6.4 Hz, CH2-20), 3.41–3.68 (3H, m, CH-6, CH2-16), 4.84 (1H, s,
NH), 5.73 (1H, s, CH-5), 7.15 (2H, d, J = 7.6 Hz, ArH-23,25), 7.32–7.39 (1H, m,
ArH-33), 7.42–7.46 (2H, m, ArH-30, 32), 7.55–7.60 (4H, m, ArH-24,26,29,31); IR
(Film) m: 3244, 3032, 2951, 2928, 2870, 1755, 1647, 1516, 1485, 1454, 1203, 1130,
123

Design and synthesis of 2(5H)-furanone liquid crystals
1871
937, 848, 748, 698; ESI-MS m/z (%): 622 ([M ? Na]?, 100.0); Anal. Calcd for
C32H40BrNO5: C 64.21, H 6.74, N 2.34, Found: C 64.11, H 6.64, N 2.30.
Biphenyl-4-yl 2-(((S)-4-bromo-2-((R,2S,5R)-2-isopropyl-5-methylcyclohexyloxy)-
5-oxo-2,5-dihydrofuran-3-yl)(methyl)amino)acetate (5d)
White viscous solid, yield 25 %; 1H NMR (400 MHz, CDCl3, TMS) d: 0.79 (3H, d,
J = 6.8 Hz, CH3-12), 0.89–0.96 (7H, m, CH-13, CH3-14, CH3-15), 0.98–1.18 (2H,
m, CH2-9), 1.28–1.43 (2H, m, CH-8, CH-11), 1.63–1.71 (2H, m, CH2-10), 2.18–2.27
(2H, m, CH2-7), 3.27 (3H, s, CH3-17), 3.59–3.66 (1H, ddd, J1 = 4.4 Hz,
J2 = 4.4 Hz, J3 = 4.4 Hz, CH-6), 4.40–4.45 (2H, m, CH2-18), 5.90 (1H, s, CH-
5), 7.21 (2H, d, J = 8.8 Hz, ArH-21,22), 7.34–7.39 (1H, m, ArH-31), 7.43–7.47
(2H, m, ArH-29,30), 7.57 (2H, d, J = 7.2 Hz, ArH-27,28), 7.62 (2H, d, J = 8.8 Hz,
ArH-23,24); IR (film) m: 3032, 2955, 2870, 1759, 1628, 1516, 1485, 1454, 1204,
1115, 957, 845, 745, 698; ESI-MS m/z (%): 578 ([M ? Na]?, 100.0); Anal. Calcd
for Calcd for C29H34BrNO5: C 62.59, H 6.16, N 2.52, Found: C 62.50, H 6.10, N
2.59.
Biphenyl-4-yl 2-((S)-4-bromo-2-((R,2S,5R)-2-isopropyl-5-methylcyclohexyloxy)-
5-oxo-2,5-dihydrofuran-3-ylamino)-3-phenylpropanoate (5e)
Yellowish viscous solid, yield 22 %; 1H NMR (400 MHz, CDCl3, TMS) d:
0.68–0.79 (3H, m, CH3-12), 0.84–0.95 (7H, m, CH-13, CH3-14, CH3-15), 1.00–1.14
(2H, m, CH2-9), 1.25–1.37 (2H, m, CH-8, CH-11), 1.62–1.68 (2H, m, CH2-10),
1.92–2.26 (2H, m, CH2-7), 3.32–3.42 (2H, m, CH2-18), 3.44–3.51 (1H, ddd,
J1 = 4.0 Hz, J2 = 3.6 Hz, J3 = 4.0 Hz, CH-6), 5.21–5.70 (3H, m, CH-5, NH, CH-
17), 7.10 (2H, d, J = 8.0 Hz, ArH-27,28), 7.25 (2H, d, J = 4.2 Hz, ArH-20,24),
7.34–7.39 (3H, m, ArH-21,22,23), 7.41–7.49 (3H, m, ArH-35,36,37), 7.56 (2H, d,
J = 7.6 Hz, ArH-33,34), 7.61 (2H, d, J = 8.0 Hz, ArH-29,30); IR (Film) m: 3236,
3101, 2955, 2924, 2866, 1732, 1651, 1454, 1242, 1122, 937, 849, 748, 536; ESI-MS
m/z (%): 656 ([M ? Na]?, 100.0); Anal. Calcd for Calcd for C35H38BrNO5: C
66.45, H 6.05, N 2.21; Found: C 66.40, H 6.00, N 2.11.
Biphenyl-4-yl 2-((S)-4-bromo-2-((R,2S,5R)-2-isopropyl-5-methylcyclohexyloxy)-
5-oxo-2,5-dihydrofuran-3-ylamino)-2-phenylacetate (5f)
White viscous solid, yield 22 %; 1H NMR (400 MHz, CDCl3, TMS) d: 0.85 (3H, d,
J = 6.8 Hz, CH3-12), 0.88–0.99 (7H, m, CH-13, CH3-14, CH3-15), 1.02–1.16 (2H,
m, CH2-9), 1.28–1.34 (2H, m, CH-8, CH-11), 1.63–1.71 (2H, m, CH2-10), 1.99–2.29
(2H, m, CH2-7), 3.57–3.67 (1H, m, CH-6), 5.35 (1H, s, CH-17), 5.76 (1H, s, CH-5),
5.81 (1H, s, NH), 6.91 (2H, d, J = 8.4 Hz, ArH-26,27), 7.06 (2H, d, J = 8.0 Hz,
ArH-19,23), 7.35–7.44 (3H, m, ArH-20,21,22), 7.47–7.53 (5H, m, ArH-
32,33,34,35,36), 7.56 (2H, d, J = 8.4 Hz, ArH-28,29); IR (Film) m: 3302, 3040,
2955, 2824, 2855, 1751, 1647, 1609, 1501, 1462, 1250, 1199, 1034, 818, 725, 644;
ESI-MS m/z (%): 618 ([M ? H]?, 10.4); Anal. Calcd for Calcd for C34H36BrNO5:
C 66.02, H 5.87, N 2.26, Found: C 66.00, H 5.77, N 2.16.
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S.-H. Luo et al.
Biphenyl-4-yl 4-((S)-4-bromo-2-((R,2S,5R)-2-isopropyl-5-methylcyclohexyloxy)-5-
oxo-2,5-dihydrofuran-3-ylamino)butanoate (5g)
1
Yellowish viscous solid, yield 25 %; H NMR (400 MHz, CDCl3, TMS) d: 0.80
(3H, d, J = 6.8 Hz, CH3-12), 0.85–0.95 (7H, m, CH-13, CH3-14, CH3-15),
0.96–1.15 (2H, m, CH2-9), 1.28–1.38 (2H, m, CH-8, CH-11), 1.62–1.68 (2H, m,
CH2-10), 2.06–2.13 (2H, m, CH2-18), 2.14–2.29 (2H, m, CH2-7), 2.70–2.75 (2H, m,
CH2-19), 3.54–3.60 (1H, ddd, J1 = 4.4 Hz, J2 = 4.0 Hz, J3 = 4.4 Hz, CH-6),
3.62–3.71 (2H, m, CH2-17), 5.05 (1H, s, NH), 5.75 (1H, s, CH-5), 7.15 (2H, d,
J = 8.8 Hz, ArH-22,23), 7.34–7.38 (1H, m, ArH-32), 7.43–7.47 (2H, m, ArH-
30,31), 7.56 (2H, d, J = 7.2 Hz, ArH-28,29), 7.60 (2H, d, J = 8.8 Hz, ArH-24,25);
IR (film) m: 3321, 3032, 2955, 2924, 2870, 1755, 1643, 1516, 1485, 1454, 1203,
1138, 949, 849, 745, 698; ESI-MS m/z (%): 592 ([M ? Na]?, 100.0); Anal. Calcd
for Calcd for C30H36BrNO5: C 63.16, H 6.36, N 2.46, Found: C 63.06, H 6.30, N
2.33.
Biphenyl-4-yl 2-((S)-4-bromo-2-((R,2S,5R)-2-isopropyl-5-methylcyclohexyloxy)-
5-oxo-2,5-dihydrofuran-3-ylamino)acetate (5h)
1
Yellowish viscous solid, yield 24 %; H NMR (400 MHz, CDCl3, TMS) d: 0.85
(3H, d, J = 6.8 Hz, CH3-12), 0.87–0.89 (1H, m, CH-13), 0.92 (3H, d, J = 6.8 Hz,
CH3-14), 0.96 (3H, d, J = 6.8 Hz, CH3-15), 1.01–1.16 (2H, m, CH2-9), 1.28–1.37
(2H, m, CH-8, CH-11), 1.66–1.70 (2H, m, CH2-10), 2.14–2.24 (2H, m, CH2-7),
3.54–3.61 (1H, ddd, J1 = 4.0 Hz, J2 = 3.6 Hz, J3 = 4.0 Hz, CH-6), 4.32–4.35
(2H, m, CH2-17), 5.31 (1H, s, NH), 5.73 (1H, s, CH-5), 6.91 (2H, d, J = 8.4 Hz,
ArH-20,21), 7.30–7.44 (3H, m, ArH-28,29,30), 7.48 (2H, d, J = 8.4 Hz, ArH-
26,27), 7.54 (2H, d, J = 7.2 Hz, ArH-22,23); IR (Film) m: 3391, 3009, 2959, 2920,
2851, 1728, 1647, 1520, 1466, 1261, 1096, 1022, 864, 799, 698; ESI-MS m/z (%):
580 ([M ? K]?, 100.0); Anal. Calcd for C28H32BrNO5: C 62.00 H 5.95, N 2.58,
Found: C 62.10 H 5.85, N 2.50.
40-Hydroxybiphenyl-4-yl 2-((S)-4-bromo-2-((R,2S,5R)-2-isopropyl-
5-methylcyclohexyloxy)-5-oxo-2,5-dihydrofuran-3-ylamino)-4-methyl-pentanoate (5i)
White viscous solid, yield 18 %; 1H NMR (400 MHz, CDCl3, TMS) d: 0.84 (3H, d,
J = 7.2 Hz, CH3-12), 0.88–0.95 (7H, m, CH-13, CH3-14, CH3-15), 1.04–1.09 (2H,
m, CH2-9), 1.28–1.34 (8H, m, CH-8, CH-11, CH3-20, CH3-21), 1.62–1.69 (3H, m,
CH2-10, CH-19), 1.76–1.84 (2H, m, CH2-18), 2.00–2.13 (2H, m, CH2-7), 3.54–3.61
(1H, ddd, J1 = 4.0 Hz, J2 = 4.4 Hz, J3 = 3.6 Hz, CH-6), 4.84–4.97 (1H, b, NH),
5.33–5.43 (1H, m, CH-17), 5.71 (1H, s, CH-5), 6.88 (2H, d, J = 8.4 Hz, ArH-
31,33), 7.07–7.16 (2H, m, ArH-24,26), 7.36 (1H, s, OH), 7.41 (2H, d, J = 8.4 Hz,
ArH-30,32), 7.48–7.57 (2H, m, ArH-25,27); IR (Film) m: 3337, 3063, 2955, 2925,
2855, 1751, 1663, 1616, 1493, 1458, 1265, 1130, 945, 826, 694; ESI-MS m/z (%):
648 ([M ? H ? CH3OH]?, 15.4); Anal. Calcd for C32H40BrNO6: C 62.54, H 6.56,
N 2.28, Found: C 62.50, H 6.50, N 2.19.
123

Design and synthesis of 2(5H)-furanone liquid crystals
1873
40-Hydroxybiphenyl-4-yl 2-((S)-4-bromo-2-((R,2S,5R)-2-isopropyl-5-
methylcyclohexyloxy)-5-oxo-2,5-dihydrofuran-3-ylamino)-3-methyl-butanoate (5j)
White viscous solid, yield 18 %; 1H NMR (400 MHz, CDCl3, TMS) d: 0.87 (3H, d,
J = 7.2 Hz, CH3-12), 0.90 (3H, d, J = 6.8 Hz, CH3-14), 0.93 (3H, d, J = 6.8 Hz,
CH3-15), 0.95–1.03 (1H, m, CH-13), 1.05 (3H, d, J = 6.8 Hz, CH3-19), 1.08 (3H, d,
J = 6.8 Hz, CH3-20), 1.11–1.26 (2H, m, CH2-9), 1.33–1.42 (2H, m, CH-8, CH-11),
1.62–1.66 (2H, m, CH2-10), 1.68–1.70 (1H, m, CH-18), 2.20–2.33 (2H, m, CH2-7),
3.55–3.62 (1H, ddd, J1 = 4.0 Hz, J2 = 4.0 Hz, J3 = 4.0 Hz, CH-6), 4.74 (1H, b,
NH), 5.56 (1H, d, J = 8.8 Hz, CH-17), 5.74 (1H, s, CH-5), 7.12–7.17 (2H, m, ArH-
30,32), 7.31–7.36 (4H, m, ArH-23,25,29,31), 7.56 (2H, d, J = 7.6 Hz, ArH-24,26),
8.10 (1H, s, OH); IR (Film) m: 3322, 3063, 2959, 2928, 2870, 1744, 1647, 1601,
1547, 1501, 1443, 1260, 1134, 957, 825, 694; ESI-MS m/z (%): 634
([M ? H ? CH3OH]?, 48.0); Anal. Calcd for C31H38BrNO6: C 62.00, H 6.38, N
2.33, Found: C 62.10, H 6.28, N 2.30.
40-Hydroxybiphenyl-4-yl 6-((S)-4-bromo-2-((R,2S,5R)-2-isopropyl-5-
methylcyclohexyloxy)-5-oxo-2,5-dihydrofuran-3-ylamino)hexanoate (5k)
White viscous solid, yield 17 %; 1H NMR (400 MHz, CDCl3, TMS) d: 0.82 (3H, d,
J = 7.6 Hz, CH3-12), 0.84–0.95 (7H, m, CH-13, CH3-14, CH3-15), 0.98–1.13 (2H,
m, CH2-9), 1.33–1.38 (4H, m, CH-8, CH-11, CH2-18), 1.57–1.65 (4H, m, CH2-17,
CH2-19), 1.67–1.73 (2H, m, CH2-10), 1.99–2.03 (2H, m, CH2-7), 2.23 (2H, t,
J = 7.6 Hz, CH2-20), 3.42–3.70 (3H, m, CH-6, CH2-16), 5.30–5.39 (2H, m, NH,
CH-5), 7.13 (2H, d, J = 8.4 Hz, ArH-30,32), 7.35–7.45 (4H, m, ArH-23,25,29,31),
7.53 (2H, d, J = 8.4 Hz, ArH-24,26), 7.86 (1H, s, OH); IR (Film) m: 3352, 3062,
2951, 2924, 2855, 1744, 1643, 1497, 1454, 1211, 1188, 964, 822, 529; ESI-MS m/
z (%): 613 ([M ? H]?, 10.0); Anal. Calcd for C32H40BrNO6: C 62.00; H 6.38, N
2.33, O 15.98, Found: C 62.00, H 6.24, N 2.40.
40-Hydroxybiphenyl-4-yl 2-(((S)-4-bromo-2-((R,2S,5R)-2-isopropyl-
5-methylcyclohexyloxy)-5-oxo-2,5-dihydrofuran-3-yl)(methyl)amino)acetate (5l)
White viscous solid, yield 16 %; 1H NMR (400 MHz, CDCl3, TMS) d: 0.72 (3H, d,
J = 6.8 Hz, CH3-12), 0.78–0.93 (7H, m, CH-13, CH3-14, CH3-15), 0.96–1.09 (2H,
m, CH2-9), 1.23–1.34 (2H, m, CH-8, CH-11), 1.56–1.61 (2H, m, CH2-10), 2.11–2.17
(2H, m, CH2-7), 3.18 (3H, s, CH3-17), 3.51–3.57 (1H, ddd, J1 = 4.4 Hz,
J2 = 4.4 Hz, J3 = 4.0 Hz, CH-6), 4.34–4.80 (2H, m, CH2-18), 5.82 (1H, s, CH-
5), 6.86 (1H, d, J = 8.4 Hz, ArH-29,30), 7.08 (2H, d, J = 8.4 Hz, ArH-21,22), 7.34
(2H, d, J = 8.0 Hz, ArH-27,28), 7.46 (2H, d, J = 8.0 Hz, ArH-23,24), 7.94 (1H, s,
OH); IR (Film) m: 3352, 3032, 2955, 2924, 2870, 1759, 1624, 1497, 1454, 1261,
1169, 957, 826, 521; ESI-MS m/z (%): 596 ([M ? Na]? 50.0); Anal. Calcd for
C29H34BrNO6: C 60.84, H 5.99, N 2.45, Found: C 60.80, H 5.90, N 2.47.
123

1874
S.-H. Luo et al.
40-Hydroxybiphenyl-4-yl 2-((S)-4-bromo-2-((R,2S,5R)-2-isopropyl-5-
methylcyclohexyloxy)-5-oxo-2,5-dihydrofuran-3-ylamino)-3-phenyl-propanoate
(5m)
White viscous solid, yield 20 %; 1H NMR (400 MHz, CDCl3, TMS) d: 0.81 (3H, d,
J = 6.8 Hz, CH3-12), 0.83–0.94 (7H, m, CH-13, CH3-14, CH3-15), 0.96–1.14 (2H,
m, CH2-9), 1.26–1.30 (2H, m, CH-8, CH-11), 1.68–1.70 (2H, m, CH2-10), 2.05–2.26
(2H, m, CH2-7), 3.37–3.69 (3H, m, CH-6, CH2-18), 5.19–5.26 (1H, m, CH-17), 5.31
(1H, s, CH-5), 5.35 (1H, s, NH), 6.90 (2H, d, J = 8.4 Hz, ArH-35,36), 7.00 (1H, s,
OH), 7.13 (2H, d, J = 8.4 Hz, ArH-27,28), 7.28–7.37 (3H, m, ArH-20,22,24),
7.38–7.43 (2H, m, ArH-21,23), 7.45 (2H, d, J = 8.4 Hz, ArH-33,34), 7.53 (2H, d,
J = 8.4 Hz, ArH-29,30); IR (Film) m: 3445, 3051, 2959, 2924, 2855, 1750, 1651,
1620, 1497, 1265, 1088, 972, 783, 745, 702, 571; ESI-MS m/z (%): 650 ([M ? H]?,
55.1); Anal. Calcd for C35H38BrNO6: C 64.81, H 5.91, N 2.16, Found: C 64.80, H
5.99, N 2.21.
40-Hydroxybiphenyl-4-yl 2-((S)-4-bromo-2-((R,2S,5R)-2-isopropyl-
5-methylcyclohexyloxy)-5-oxo-2,5-dihydrofuran-3-ylamino)-2-phenylacetate (5n)
1
White viscous solid, yield 20 %; H NMR (400 MHz, CDCl3, TMS) d: 0.84–0.86
(3H, m, CH3-12), 0.88–0.96 (7H, m, CH-13, CH3-14, CH3-15), 1.03–1.09 (2H, m,
CH2-9), 1.25–1.41 (2H, m, CH-8, CH-11), 1.68–1.73 (2H, m, CH2-10), 2.05–2.23
(2H, m, CH2-7), 3.56–3.62 (1H, m, CH-6), 4.96 (1H, s, CH-17), 5.30–5.43 (2H, m,
NH, CH-5), 6.64 (1H, s, OH), 6.90 (2H, d, J = 6.0 Hz, ArH-34,35), 7.13 (2H, d,
J = 6.8 Hz, ArH-26,27), 7.28–7.42 (5H, m, ArH-19,20,21,22,23), 7.44 (2H, d,
J = 6.4 Hz, ArH-32,33), 7.53 (2H, d, J = 6.4 Hz, ArH-28,29); IR (Film) m: 3372,
3032, 2955, 2932, 2870, 1728, 1651, 1621, 1501, 1454, 1277, 1126, 953, 822, 745,
698, 517; ESI-MS m/z (%): 636 ([M ? H]?, 15.0); Anal. Calcd for C34H36BrNO6:
C 64.35, H 5.72, N 2.21, Found: C 64.30, H 5.70, N, 2.28.
40-Hydroxybiphenyl-4-yl 4-((S)-4-bromo-2-((R,2S,5R)-2-isopropyl-
5-methylcyclohexyloxy)-5-oxo-2,5-dihydrofuran-3-ylamino)butanoate (5o)
White viscous solid, yield 16 %; 1H NMR (400 MHz, CDCl3, TMS) d: 0.79 (3H, d,
J = 7.2 Hz, CH3-12), 0.84–0.95 (7H, m, CH-13, CH3-14, CH3-15), 0.96–1.14 (2H,
m, CH2-9), 1.28–1.37 (2H, m, CH-8, CH-11), 1.63–1.68 (2H, m, CH2-10), 2.02–2.10
(2H, m, CH2-18), 2.12–2.25 (2H, m, CH2-7), 2.71 (2H, t, J = 6.4 Hz, CH2-19),
3.53–3.61 (1H, ddd, J1 = 4.4 Hz, J2 = 4.0 Hz, J3 = 4.4 Hz, CH-6), 3.63–3.71
(2H, m, CH2-17), 5.07 (1H, s, NH), 5.75 (2H, s, CH-5, OH), 6.90 (2H, d,
J = 8.4 Hz, ArH-30,31), 7.11 (2H, t, J = 8.8 Hz, ArH-22,23), 7.42 (2H, d,
J = 8.4 Hz, ArH-28,29), 7.52 (2H, d, J = 8.4 Hz, ArH-24,25); IR (Film) m: 3325,
3030, 2955, 2928, 2870, 1744, 1643, 1524, 1497, 1447, 1204, 1165, 949, 829, 521;
ESI-MS m/z (%): 608 ([M ? Na]?, 85.1); Anal. Calcd for C30H36BrNO6: C 61.43,
H 6.19, N 2.39, Found: C 61.40, H 6.15, N 2.35.
123

Design and synthesis of 2(5H)-furanone liquid crystals
1875
40-Hydroxybiphenyl-4-yl 2-((S)-4-bromo-2-((R,2S,5R)-2-isopropyl-
5-methylcyclohexyloxy)-5-oxo-2,5-dihydrofuran-3-ylamino)acetate (5p)
White viscous solid, yield 18 %;1H NMR (400 MHz, CDCl3, TMS) d: 0.85 (3H, d,
J = 6.8 Hz, CH3-12), 0.87–0.90 (1H, m, CH-13), 0.92 (3H, d, J = 6.8 Hz, CH3-
14), 0.96 (3H, d, J = 6.8 Hz, CH3-15), 1.01–1.16 (2H, m, CH2-9), 1.28–1.38 (2H,
m, CH-8, CH-11), 1.66–1.70 (2H, m, CH2-10), 2.14–2.24 (2H, m, CH2-7), 3.54–3.61
(1H, ddd, J1 = 4.0 Hz, J2 = 3.6 Hz, J3 = 4.0 Hz, CH-6), 4.32–4.35 (2H, m, CH2-
17), 5.31 (1H, s, NH), 5.73 (1H, s, CH-5), 6.91 (2H, d, J = 8.4 Hz, ArH-28,29),
7.30–7.44 (3H, m, ArH-20,21), 7.48 (2H, d, J = 8.4 Hz, ArH-26,27), 7.54 (2H, d,
J = 7.2 Hz, ArH-22,23); IR (Film) m: 3352, 3306, 3071, 3040, 2955, 2924, 2855,
1752, 1644, 1609, 1462, 1250, 1130, 966, 818, 513; ESI-MS m/z (%): 557
([M ? H]?, 100.0); Anal. Calcd for C28H32BrNO6: C 60.22, H 5.78, N 2.51, Found:
C 60.20, H 5.79, N 2.57.
Conclusion
In summary, a series of N-[5-menthoxy-2(5H)-furanonyl] amino acid biphenyl
esters have been designed and synthesized. Although no optical texture was
observed by POM, DSC and XRD results indicated that some of the compounds
were mesomorphic phase liquid-crystals. There are only a few reports on 2(5H)-
furanones liquid-crystal materials [23]. Thus, this preliminary research provides a
basis for further application of furanone compounds in liquid-crystal materials.
Acknowledgments We are grateful to the National Natural Science Foundation of China (no.
20772035), the Third Talents Special Funds of Guangdong Higher Education (no. Guangdong-Finance-
Education (2011)431), and the Natural Science Foundation of Guangdong Province (no.
S2011010001556) for financial support.
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