Synthesis, Fourier transform infrared, 1D and 2D NMR spectral studies on the conformation of two new cholesteryl 4-alkoxyphenyl-4′ benzoates

Article abstract of DOI:10.1016/j.molstruc.2003.08.026

Two new cholesteryl 4-alkoxyphenyl-4′-benzoates (C_nH _2n+1OC₆H₄C₆H₄COOCh), where Ch represents cholesteryl moiety and n = 10 and 16) have been synthesized and their molecular orientation at ambient temperature were studied. The structure determination on these compounds was performed in solid state by infrared spectroscopy based on vibrational analysis wherein the cholesteryl-phenyl and phenyl-aliphatic carbon linkages were concluded. Their molecular structures were further ascertained through the ¹H and ¹³C NMR spectra along with two-dimensional COSY, NOESY, ROESY, ¹H-¹³C HMQC and HMBC. The long-range connectivity as concluded from the NOESY, ROESY and HMBC spectra together with the related data led to a postulation that the title compounds in the liquid state exist in the conformation whereby the cholesteryl moiety was not lying along the entire molecular long axis. The cholesteryl fragment was presumed to be bent at the ester linkage of O=C-O and the phenyl rings located between cholesteryl and alkoxy chain group are not coplanar.

Full text of DOI:10.1016/j.molstruc.2003.08.026

Journal of Molecular Structure 687 (2004) 57–64
www.elsevier.com/locate/molstruc
Synthesis, Fourier transform infrared, 1D and 2D NMR spectral studies on
the conformation of two new cholesteryl 4-alkoxyphenyl-40 benzoates
a,
a
b
a
*
Guan-Yeow Yeap , Sie-Tiong Ha , Masato M. Ito , Peng-Lim Boey ,
Wan Ahmad Kamil Mahmooda
aSchool of Chemical Sciences, Universiti Sains Malaysia, Minden 11800, Penang, Malaysia
bDepartment of Bioengineering, Faculty of Engineering, Soka University, Hachioji, Tokyo 192-8577, Japan
Received 26 June 2003; revised 18 August 2003; accepted 26 August 2003
Abstract
Two new cholesteryl 4-alkoxyphenyl-40-benzoates (CnH2nþ1OC6H4C6H4COOCh), where Ch represents cholesteryl moiety and n ¼ 10
and 16) have been synthesized and their molecular orientation at ambient temperature were studied. The structure determination on these
compounds was performed in solid state by infrared spectroscopy based on vibrational analysis wherein the cholesteryl–phenyl and phenyl–
aliphatic carbon linkages were concluded. Their molecular structures were further ascertained through the 1H and 13C NMR spectra along
with two-dimensional COSY, NOESY, ROESY, 1H–13C HMQC and HMBC. The long-range connectivity as concluded from the NOESY,
ROESY and HMBC spectra together with the related data led to a postulation that the title compounds in the liquid state exist in the
conformation whereby the cholesteryl moiety was not lying along the entire molecular long axis. The cholesteryl fragment was presumed to
be bent at the ester linkage of OyC–O and the phenyl rings located between cholesteryl and alkoxy chain group are not coplanar.
q 2003 Elsevier B.V. All rights reserved.
Keywords: Structure determination; Vibrational analysis; 1H NMR; 13C NMR; 2D NMR; Cholesteryl-4-alkoxyphenyl-40-benzoates
1. Introduction
and Ch represent a phenyl ring and cholesteryl moiety,
respectively) were made 82 years later by Dave and
coworker and their mesomorphic properties had also been
studied [14]. Later, Yakubov had performed a systematic
study of infrared spectra of ROACh in different phases and
found a number of correlations between spectra, structure
and mesomorphic characteristic of these compounds [15].
In this paper, we report another expansion of cholesteryl
benzoates whereby we synthesized cholesteryl 4-alkoxy-
phenyl-40-benzoates (CnH2nþ1OC6H4C6H4COOCh or
ROABCh), a new liquid crystals compound which consists
of two phenyl rings (A and B) compared to one ring in
ROACh. The conformation of the compounds thus obtained
were elucidated by Fourier transformed infrared and NMR
techniques including the two-dimensional multinuclear
Cholesterol is one of the well-known natural products
since it is commercially available as an economic natural
product and possesses multiple chiral carbon atoms which
are prerequisites for chiral recognition [1–4]. Its derivatives
exist in several unique aggregates such as liquid crystals,
organic gels and monolayers [5–9]. Many of the cholesterol
derivatives possessed cholesteric mesophases since the
existence of cholesteryl fragment in the molecular structure
is one of the requirements towards the formation of
mesophase [4,10–12].
In 1888, the Australian botanists Reinitzer had discov-
ered the first thermotropic liquid crystalline material known
as cholesteryl benzoates, whereby the molecular structure
consists of an aromatic ring linked to the cholesteryl
fragment at the ester linkage of COO [13]. The expansion of
cholesteryl benzoates known as cholesteryl 4-n-alkoxy-
benzoates (CnH2nþ1OC6H4COOCh or ROACh, where A
1
correlation spectroscopy. The partial H and complete 13C
NMR assignments were performed for the first time to
provide full account of NMR analysis for the conformation
of ROABCh in the solution state. Hereafter, 10OABCh and
16OABCh denote ROABCh with the integer representing
the number of carbon atom, n ¼ 10 and 16, respectively.
*
Corresponding author. Fax: þ60-4657-4854.
E-mail address: gyyeap@usm.my (G.-Y. Yeap).
0022-2860/$ - see front matter q 2003 Elsevier B.V. All rights reserved.
doi:10.1016/j.molstruc.2003.08.026

58
G.-Y. Yeap et al. / Journal of Molecular Structure 687 (2004) 57–64
Fig. 1. Synthesis and atomic labeling scheme for 10OABCh. Reagents and conditions; (i) C10H21Br, KOH, KI, CH3OH, inert atmospheres, reflux for 12 h (ii)
dilute HCl; (iii) SOCl2, (iv) cholesterol, pyridine, CH2Cl2, inert atmospheres, reflux for 6 h.
2. Experimental
acid was prepared by alkylation of 4-hydroxybiphenyl-40-
carboxylic acid. The white solid thus obtained was acidified
with dilute hydrochloric acid. 4-n-Hexadecyloxy-40-biphe-
nylcarboxylic acid was synthesized with the similar method
with 1-bromohexadecane.
4-Hydroxybiphenyl-40-carboxylic acid was obtained
from TCI Chemical Company (Japan). Whilst cholesterol
was purchased from Acros Organics (USA), 1-bromodecane
and 1-bromohexadecane were obtained from Aldrich
Chemical Company (USA).
2.2. Synthesis of cholesteryl 4-decyloxyphenyl-40-benzoates
(10OABCh)
2.1. Synthesis of 4-n-decyloxy-40-biphenylcarboxylic acid
Cholesteryl 4-decyloxyphenyl-40-benzoates was syn-
thesized in the modified reaction described by Gray [16].
4-n-Decyloxy-40-biphenylcarboxylic acid was converted to
The compounds were prepared according to the scheme
as shown in Fig. 1. 4-n-Decyloxy-40-biphenylcarboxylic
Table 1
Acquisition parameters used in the NMR measurements
Parameters
Types of Bruker programs
1H NMR
13C NMR
2D COSY
2D NOESY
2D ROESY
2D HMQC
2D HMBC
SF
400.1 MHz
12 ppm
100.6 MHz
200 ppm
400.1 MHz
10 ppm
400.1 MHz
14 ppm
400.1 MHz
12 ppm
F1 ¼ 100:6 MHz
F2 ¼ 400:1 MHz
F1 ¼ 200 ppm
F2 ¼ 12 ppm
8.3 ms (908
flip angle)
0.1 s
F1 ¼ 100:6 MHz
F2 ¼ 400:1 MHz
F1 ¼ 200 ppm
F2 ¼ 12 ppm
8.3 ms (908
flip angle)
0.4 s
SW
PW
8.3 ms (308
flip angle)
4.0 s
20.0 ms (908
flip angle)
1.3 s
8.3 ms (908
flip angle)
0.2 s
8.3 ms (908
flip angle)
0.2 s
8.3 ms (908
flip angle)
0.2 s
AQ
D1
NS
TD
1.0 s
2.0 s
2.0 s
1.5 s
1.5 s
1.0 s
1.0 s
16
6699
24
24
24
20
24
65536
65536
F1 ¼ 256
F1 ¼ 400
F1 ¼ 400
F1 ¼ 512
F1 ¼ 512
F2 ¼ 2048
F2 ¼ 2048
F2 ¼ 2048
F2 ¼ 1024
F2 ¼ 4096
Abbreviations: F1; 13C channel; F2; 1H channel (except 2D COSY, NOESY and ROESY, where F1 and F2 are 1H channels); SF, spectrometer frequency;
SW, spectral width; PW, pulse width; AQ, acquisition time; D1, relaxation delay; NS, number of scan; TD, number of data points.

G.-Y. Yeap et al. / Journal of Molecular Structure 687 (2004) 57–64
59
Fig. 2. FTIR spectra of 10OABCh and 16OABCh sandwiched between zinc selenide windows and measured within frequency range 4000–650 cm21
.
its acid chloride using excess thionyl chloride. The acid
chloride produced was then esterified with cholesterol in the
presence of pyridine as the base. The esterification reaction
was performed under inert atmospheres. Cholesteryl 4-
hexadecyloxyphenyl-40-benzoates (16OABCh) was pre-
pared with the similar method. The labeling of atomic
positions in 10OABCh (Fig. 1) was numbered in a
sequential manner for discussion purpose in the later part
of spectroscopic techniques.
first in the solid state by using the infrared spectral analysis
which was further studied by advanced NMR techniques
wherein the compounds were present in solution.
3.1. IR spectroscopy
The IR spectra of the title compounds and the selected
data were shown in Fig. 2 and Table 2, respectively. It is
clearly shown from the figure and data that the title
compounds were well isolated wherein the terminal
phenolic hydroxy group (OH) attached at one end of the
biphenyl moiety was substituted by OR, where RyCnH2nþ1
and n ¼ 10 and 16. The presence of these alkyl groups can
be supported by the appearance of diagnostic bands within
the frequency range 2926–2852 cm21 as reported by
Wiberley and his coworkers [18]. The bands with strong
intensities observed at 1706 and 1703 cm21 in the IR
spectra of 10OABCh and 16OABCh, respectively, can be
ascribed to the carbonyl CyO as that present in the ester
The purification of both compounds was carried out by
using column chromatography over silica gel 60 with a
mixture of chloroform: n-hexane (1:1) as the eluent.
2.3. FT-IR measurements
The FT-IR spectra of 10OABCh and 16OABCh were
recorded by using Perkin Elmer 2000-FTIR spectropho-
tometer in the frequency range 4000–650 cm21. All solid
samples were sandwiched between two zinc selenide
windows prior to measurement at ambient temperature.
Table 2
Frequencies (cm21) and relative intensities of the assigned bands of
2.4. NMR measurements
10OABCh and 16OABCh
NMR spectra were recorded in CDCl3 at 298 K on a
Bruker 400 MHz Ultrashielde equipped with a 5 mm BBI
inverse gradient probe. Chemical shifts were referenced to
internal TMS. The concentration of solute molecules was
25 mg in 0.8 ml CDCl3. Standard Bruker pulse programs
[17] were used throughout the entire experiment. The
spectroscopic details were summarized in Table 1.
Assignments
Compound
10OABCh
16OABCh
nC–H stretching
2926 vs
2852 s
1706 s
1467 m
1286 m
1256 w
828 m
2923 vs
2852 s
1703 s
1469 m
1287 m
1257 w
830 w
nCyO
a
nCH2
nC29–C28–O
nC36–O
narom(1,4)
b
3. Results and discussion
Abbreviations: v, very; s, strong; m, medium; w, weak.
Methylene groups in cholesteryl fragment.
1,4-Disubstituted aromatic ring.
a
The molecular structure associated with the title
compounds 10OABCh and 16OABCh was investigated
b

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G.-Y. Yeap et al. / Journal of Molecular Structure 687 (2004) 57–64
Table 3
1H NMR chemical shifts (ppm) and coupling constants (Hz) of 10OABCh and 16OABCh in CDCl3
Atom
Chemical shift (ppm)
Cholesterola
10OABCh
16OABCh
H4
2.19–2.33, m
2.49–2.51, d, J ¼ 7:7
4.88–4.91, m
2.49–2.51, d, J ¼ 7:7
4.86–4.94, m
H3
3.47–3.57, m
H6
5.36, d
5.45–5.46, d, J ¼ 3:8
4.01–4.04, t, J ¼ 6:6
6.99–7.03, dd, J ¼ 4:5; 8.7
7.57–7.59, d, J ¼ 8:6
7.62–7.64, d, J ¼ 8:6
8.09–8.11, dd, J ¼ 2:6; 8.7
5.45–5.46, d, J ¼ 4:0
4.01–4.04, t, J ¼ 6:6
6.99–7.02, dd, J ¼ 3:6; 8.7
7.56–7.58, d, J ¼ 8:6
7.62–7.64, d, J ¼ 8:8
8.08–8.11, dd, J ¼ 2:5; 8.5
H41
–
–
–
–
–
H35&H37
H34&H38b
H31&H39b
H30&H40
TMS as internal standard; d, doublet; dd, double doublets; t, triplet; m, multiplet.
Reported by Bhacca et al. [26].
a
b
The peaks ascribed to the pairs of (i) H31&H39 and (ii) H34&H38 are doublets wherein only one J coupling constant was observable in each (i) and (ii).
bond between the biphenyl moiety and cholesterol fragment
(Fig. 1). Another band with medium intensities observed for
the title compounds at 1467–1469 cm21 can be due to the
methylene groups of cholesterol fragment [19]. A strong
band occurred at 1286 and 1287 cm21 in the IR spectra of
10OABCh and 16OABCh, respectively, can be attributed to
the stretching of C29–C28–O. This observation resembles
that reported by Smith et al. [20]. In addition to this band,
there is another band occurring at 1256–1257 cm21 with
weak intensities indicating the stretching of C36–O in ether
bond [20,21]. The 1,4-disubstitued aromatic ring attached to
the cholesteryl fragment can also be assigned from the
diagnostic band observed at 828 and 830 cm21 in the
respective IR spectra of 10OABCh and 16OABCh. These
bands fall within the frequency range as reported by
Landgrebe [22].
Whilst the type of 13C nuclei was determined by DEPT, the
13C assignments were deduced from HMQC experiments.
The remaining signals owing to the quaternary carbons were
derived from HMBC correlations (Table 6). HMBC
experiment was also used to determine the multiple bonds
1H–13C correlations.
3.2.1. 1H spectral assignment
The signal corresponding to the proton attached with C3
in cholesterol was shifted to lower field
(d ¼ 4:88–4:91 ppm) upon replacement of OH by OCOR0
in 10OABCh where R0 is C6H4C6H4C10H21 (Table 3). The
COSY, NOESY and ROESY experiments were sub-
sequently used to determine the positions of the protons at
C4 and C6 wherein the proton at C3 was correlated with the
protons at C4 but not with the protons at C6. A typical
COSY spectrum resulted from the observed 1H–1H
connectivities in 10OABCh is shown in Fig. 3. It is
known that the protons at C-4 were far from H6 but
surprisingly the information from all 2D homonuclear
experiments (Table 5) seemed to indicate these protons (H4
and H6) were coupled with each other. The long-range
The infrared spectral investigation with the understand-
ing associated with the chemical stabilities exhibited by the
cholesterol fragment and the alkoxy bonding in the biphenyl
group in ambient temperature have led to a conclusion that
the alkoxylated biphenyl which carried the long alkyl
carbon chain of carbon number 10 and 16 have resulted in
the formation of elongated cholesteryl 4-alkoxyphenyl-40-
benzoates. Their molecular structure can best be represented
as that shown in Fig. 1.
4
coupling J of both protons showed J ¼ 3:8 Hz.
The peaks which appeared within d ¼ 6:99–8:11 ppm
in the 1H NMR spectrum of 10OABCh indicate the
presence of aryl group. The protons associated with the
aryl group were further identified by the NOESY and
ROESY experiments. Through these techniques, the H35
atom and its equivalent H37 atom were distinguished from
both H30 and H40 atoms. Similarly, the methylene
protons at C41 were found to be correlated with H35 (or
H37) but not with H30 (or H40) (Table 5). This
observation was further supported by the presence of
3.2. NMR spectroscopy
In order to further analyze the conformation in the
1
solution state, the conventional 1D H NMR, 13C NMR,
DEPT along with 2D COSY, NOESY, ROESY, HMQC and
HMBC were used to further substantiate the molecular
structures of the title compounds. Whilst the selected 1D 1H
NMR data and the relevant coupling constants for
cholesterol, 10OABCh and 16OABCh are shown in Table
3, the 13C chemical shift are summarized in Table 4. 1H–1H
1
double doublets (dd) shown by H35 (or H37) in the H
NMR (Table 3) which can be ascribed to the coupling
with H34 (or H38) and the methylene protons at C41
(Table 5). After distinguishing the H35 (or H37) from H30
(or H40), H31 (or H39) could easily be assigned since it
only showed correlation with H30, which is identical with
1
1
COSY, H–1H NOESY and H–1H ROESY maps used to
establish the relative disposition of the protons and the
observed homonuclear cross peaks are tabulated in Table 5.

G.-Y. Yeap et al. / Journal of Molecular Structure 687 (2004) 57–64
Table 5
61
H40. Fig. 4 shows the selected NOE and ROE relation-
1H–1H correlations from 2D COSY, NOESY and ROESY on 10OABCh
ships as observed from the NOESY and ROESY spectra.
Similar characteristics shown by 16OABCh are also
favourable for the assignments of H and C atoms.
and 16OABCh
Compounds
10OABCh
Atom H
COSY
NOESY
ROESY
3.2.2. 13C spectral assignment
4
3, 6
3, 6
3, 6
The 13C NMR signals were identified by DEPT before
being assigned by the analysis of the HMQC spectrum for
41
–
35 or 37
4
35 or 37
4
3
4
6
4
4
4
35 or 37
34 or 38
31 or 39
30 or 40
34 or 38
35 or 37
30 or 40
31 or 39
34 or 38, 41
35 or 37
30 or 40
31 or 39
34 or 38, 41
35 or 37
30 or 40
31 or 39
Table 4
13C NMR chemical shifts (ppm) of cholesterol, 10OABCh and 16OABCh
in CDCl3
Carbon no.
Chemical shift (ppm)
16OABCh
4
3, 6
3
6
Cholesterol
10OABCh
16OABCh
41
–
35 or 37
4
35 or 37
–
3
4
6
4
–
4
1
37.67
32.02
72.13
42.68
141.17
122.07
32.30
32.30
50.54
36.89
21.49
40.19
42.72
57.17
24.69
28.64
56.57
12.26
19.80
36.20
19.13
36.60
24.25
39.92
28.41
22.97
23.22
37.47
29.97
37.47
29.96
35 or 37
34 or 38
31 or 39
30 or 40
34 or 38
35 or 37
30 or 40
31 or 39
34 or 38, 41
35 or 37
30 or 40
31 or 39
34 or 38, 41
35 or 37
30 or 40
31 or 39
2
3
74.92
74.92
4
38.67
38.67
5
140.13
123.16
32.35
140.12
123.16
32.35
6
7
8
32.31
32.31
9
50.47
50.47
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
32
33
36
30, 40
34, 38
31, 39
35, 37
41
Xa
37.07
37.08
21.46
21.46
40.16
40.16
Table 6
2D 1H–13C HMQC and HMBC correlations for 10OABCh and 16OABCh
42.74
42.74
57.12
57.11
24.71
24.71
Compounds Atom HMQC HMBC [J(C,H)]
28.65
28.65
56.56
56.56
1J
2J
3J
4J
Ja
12.27
12.28
19.80
19.80
10OABCh H4
C4
C3, C5 C2, C6, C10 C1
–
36.21
36.22
H41b C41
–
C36
–
–
–
19.13
19.14
H3
H6
C3
C6
–
–
–
36.60
36.60
C7
C36
C36
C33
C33
C32
C32
–
C8, C10
–
C1
C36
C6
C6
–
24.25
24.25
H35 C35
H37 C37
H34 C34
H38 C38
H31 C31
H39 C39
H30 C30
H40 C40
C32
39.93
39.93
–
C32
28.43
28.43
C36
C36
C33
C33
C28
C28
C31 or C39
C31 or C39
C34 or C38
C34 or C38
C33
22.97
22.97
–
23.23
23.23
–
166.38
129.33
132.66
145.52
159.81
130.46
128.71
126.75
115.33
68.56
166.22
129.32
132.65
145.51
159.81
130.46
128.70
126.75
115.33
68.55
–
–
–
C33
–
16OABCh H4
C4
C3, C5 C2, C6, C10 C1
–
–
H41a C41
–
C36
–
–
H3
H6
C3
C6
–
–
–
C7
C36
C36
C33
C33
C32
C32
–
C8, C10
–
C1
–
H35 C35
H37 C37
H34 C34
H38 C38
H31 C31
H39 C39
H30 C30
H40 C40
C32
C6
C6
–
–
C32
23.08, 26.35,
26.45, 29.66,
29.72, 29.74,
29.81, 29.99
23.10, 26.35,
26.45, 28.33,
29.48, 29.67,
29.74, 29.78,
29.81, 29.99,
30.01, 30.07,
30.11, 32.34
14.53
C36
C36
C29
C29
C28
C28
C31 or C39
C31 or C39
C34 or C38
C34 or C38
C33
–
–
–
–
–
C33
–
Yb
14.52
a
Intramolecular interaction.
b
Correlate with methylene in the alkyl chain but cannot determine their
real positions because 13C chemical shift for the methylene chain cannot be
TMS used as internal standard.
a
10OABCh: X ¼ C42–C49; 16OABCh: X ¼ C42–C55.
10OABCh: Y ¼ C50; 16OABCh: Y ¼ C56.
b
distinguished.

62
G.-Y. Yeap et al. / Journal of Molecular Structure 687 (2004) 57–64
1
Fig. 3. H–1H connectivities in the COSY spectrum of 10OABCh.
the protonated carbons on the basis of the additivity rules
and substituent effects [23,24]. A HMQC spectrum for
10OABCh is shown in Fig. 5. The assignments for these
carbon nuclei were supported by HMBC cross peaks as
that exhibited in the HMBC spectrum of 10OABCh
(Fig. 6). In order to substantiate the carbon assignments on
the cholesterol fragment, efforts were also made through
a comparison with the signals inferred from the NMR
spectrum of unreacted cholesterol [25].
Inspection from 13C NMR data (Table 4) showed that
the signals corresponding to C2, C3 and C4 in
cholesterol were shifted upon replacement of OH by
OCOR0 in 10OABCh. This phenomenon resembles that
observed for the H3 atom in the 1H NMR. Whilst
Fig. 4. Selected NOE and ROE relationships and intramolecular interaction via HMBC for 10OABCh.

G.-Y. Yeap et al. / Journal of Molecular Structure 687 (2004) 57–64
63
Fig. 5. One bond CH correlations in the HMQC spectrum of 10OABCh.
the chemical shifts for C2 and C4 were observed at the
high field, C-3 signal was shifted to opposite field. Only
these carbons were shifted drastically because they are
located near the OH group in cholesterol. 16OABCh
shows similar shift pattern as those discussed for
10OABCh.
All the 13C chemical shifts sequence for both title
compounds was unchanged in CDCl3 under ambient
Fig. 6. Long-range CH correlations in the HMBC spectrum of 10OABCh.

64
G.-Y. Yeap et al. / Journal of Molecular Structure 687 (2004) 57–64
temperature. The signals due to the carbonyl, aromatic and
aliphatic carbons were observed in these spectra. The
difference between these two compounds was that there are
six more signals in the 13C spectrum of 16OABCh in
comparison with that in 10OABCh.
the spectroscopic data for 16OABCh which is present in
solution at ambient temperature.
Acknowledgements
As for 10OABCh, the HMQC spectrum (Fig. 5)
confirmed the attachments of different aromatic hydrogens
onto the respective carbons as that discussed in the earlier
part on the 1H–1H homonuclear correlations. From this
figure, the carbon atoms occurred at different chemical
shifts can be assigned. The signals owing to the C35 (or
C37), C34 (or C38), C31 (or C39) and C30 (or C40) atoms
were observed at d ¼ 115:33; 128.71, 126.75 and
130.46 ppm, respectively. A cross peak due to the coupling
between the proton at C4 and a carbon C5 located at
d ¼ 140:13 ppm can be observed. The one-bond 13C–1H
connectivities were well observed for C4, C41, C3 and C6
which cross peaks appeared at d ¼ 38:67; 68.56, 74.92 and
123.16 ppm, respectively.
Authors thank the Universiti Sains Malaysia and the
Malaysian Government for financing this project through
FRGS Grant No. 304/PKIMIA/670032 and IRPA Grant No.
305/PKIMIA/610947.
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[4] P.J. Collings, M. Hird, Introduction to Liquid Crystals and Physics,
Taylor and Francis, USA, 1998, pp. 10–112.
The aromatic quaternary carbons in 10OABCh were
established throughout the connectivities between the
carbon and its neighbouring proton by using a long-range
correlations HMBC experiment (Fig. 6). Thus, the long-
range cross peaks of H30 (or H40) with C28
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(d ¼ 166:38 ppm),
H31
(or
H39)
with
C29
(d ¼ 129:33 ppm) and the methylene protons at C41 with
C36 (d ¼ 159:81 ppm) suggest strongly the positions of
these atoms. The C32 and C33 carbons were assigned via
correlations with H31 (or H39) and H34 (or H38),
respectively. 16OABCh shows similar characteristics as
those discussed for 10OABCh.
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The signal attributed to C36 correlated to H6 proton. On
the basis of this analysis, the long-range connectivity
through intramolecular interaction between C6 and H37
proton was established even though the C6 atom is far away
from H37. One of the probabilities of having this kind of
interaction is to bring together the atoms into close
proximity. As shown in Fig. 6, the C37, C38, C39 and
C40 are likely to be brought near each other by folding up at
the OyC–O linkage. The observation of non-interaction
between H31 (or H39) and H34 (or H38) as inferred from
2D homonuclear experiments (Table 5) indicates that
biphenyl moeities are not coplanar and this phenomenon
has further supported the molecular structure of 10OABCh
as elucidated from the NOE and ROE relationships and
intramolecular interaction via HMBC for this compound
(Fig. 4). Similar feature can also be inferred from
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