New steroid α, β-unsaturated ketones as chiral components of induced cholesteric liquid crystal systems

Article abstract of DOI:10.1007/s11172-009-0137-9

New (E)-16-arylidene derivatives of 3β-hydroxyandrost-5-en-17-one and their acetates containing different substituents in the arylidene fragment were synthesized. The ability of the synthesized chiral compounds to induce helical supramolecular ordering (t

Full text of DOI:10.1007/s11172-009-0137-9

Russian Chemical Bulletin, International Edition, Vol. 58, No. 5, pp. 1072—1083, May, 2009
1072
New steroid α,βꢀunsaturated ketones as chiral components
of induced cholesteric liquid crystal systems
F. G. Yaremenko,a N. S. Pivnenko,b L. A. Kutulya,b Zh. A. Kondratyuk,a
N. B. Novikova,b and N. I. Shkolnikovab
a V. Ya. Danilevsky Institute of Problems of Endocrine Pathology,
Academy of Medical Sciences of Ukraine,
10 ul. Artema, 61002 Kharkov, Ukraine.
Eꢀmail: yaremenko_f@ukr.net
b NTK “Institute for Single Crystals,” National Academy of Sciences of Ukraine,
60 prosp. Lenina, 61001 Kharkov, Ukraine.
Eꢀmail: kutulya@isc.kharkov.com
New (E)ꢀ16ꢀarylidene derivatives of 3βꢀhydroxyandrostꢀ5ꢀenꢀ17ꢀone and their acetates
containing different substituents in the arylidene fragment were synthesized. The ability of the
synthesized chiral compounds to induce helical supramolecular ordering (their helical twisting
power) upon the introduction into the nematic liquid crystal (LC) 4ꢀcyanoꢀ4´ꢀpentylbiphenyl
(5CB) and into multicomponent mixtures E63 and LCꢀ1289 characterized by a wide mesophase
interval. The dependence of the helical twisting power of the studied chiral additives (CAd) on
their molecular structure was analyzed. The highest helical twisting power (44.6—67.1 μm–1
)
was revealed for the synthesized acetates. It was found that the composites based on LCꢀ1289
and E63 containing the studied CAd in very low concentrations (≤10—11 mol.%) have selective
light reflection in the visible spectral region. The helical twisting power of the studied
α,βꢀunsaturated ketones is determined by the combined influence of the anisotropy of polarizꢀ
ability of CAd molecules and specific features of their molecular shape.
Key words: 3βꢀhydroxyꢀ5ꢀandrostenꢀ17ꢀone (E)ꢀ16ꢀarylidene derivatives, steric structure,
liquid crystals, chiral additives, helical twisting power, selective light reflection.
It is known that chiral compounds based on natural
chiral additives to nematic 4ꢀnꢀbutoxyphenyl 4ꢀnꢀhexylꢀ
oxybenzoate (LC ZLI 1792, Merck, Germany). When
these CAd are introduced into the nematic LC, their heliꢀ
cal twisting power by the absolute value does not exceed
15 μm–1. The low helical twisting power (|βmol| = 4.4 μm–1)
was revealed for cholesterol nonanoate in the nematic
steroid structures (numerous cholesterol esters with
aliphatic and aromatic carboxylic acids) exhibit the
mesomorphic properties, forming the cholesteric (Chol)
and Chol and/or smectic A* (SmA*) mesophases.1,2 At
the same time, steroid compounds (both mesogenic and
possessing no intrinsic mesomorphic properties), being
introduced to the nematic mesophase, can induce the
formation of a helical supramolecular structure (see, e.g.,
Ref. 3). In materials science of liquid crystals (LC), the
chiral compounds with this ability were named chiral
additives (CAd). The helical twisting power (β) is a quanꢀ
titative characteristic of the efficiency of the CAd effect in
the LC systems.4,5 In the most part of cholesterol esters
this ability is manifested in the intrinsic mesophase, proꢀ
viding the formation of the supramolecular helix, whose
pitch corresponds to selective light reflection in the
visible spectral region.2 Particular cholesterol esters
CholOCOAlk (Alk = C15H31 and C16H33) were studied3 as
systems ZLIꢀ4792 and MLCꢀ6260 (Merck). The |βmol
|
value of the cholesterol derivatives containing the difluorꢀ
oxymethylene bridging group in the same LC systems is
still lower (<0.05 μm–1).6
The strong helical twisting power of the steroid comꢀ
pounds with the unusual molecular shape was reported.7
Molecules of compounds of this type, namely, diastereoꢀ
meric dimeric steroid derivatives of 2,6,9ꢀtrioxabicycloꢀ
[3.3.1]nonanes, contain the angular quasiꢀplanes.
In
one of the studied diastereoisomers (with the concave
surface, concave) these quasiꢀplanes form an angle of 65°,
and in the second (planar) diastereoisomer this angle is
165°. It was shown that the sizes and orientation of the
Dedicated to Professor S. V. Tsukerman (1909—1985) on his
100th birthday.
Molecular fragments of the nearly planar structure arranged
at a certain angle to each other are implied.
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 1044—1055, May, 2009.
1066ꢀ5285/09/5805ꢀ01072 © 2009 Springer Science+Business Media, Inc.

Liquid crystals based on 16ꢀarylideneandrostenꢀ17ꢀone Russ.Chem.Bull., Int.Ed., Vol. 58, No. 5, May, 2009
1073
Scheme 1
1
1
4
DEA is dehydroepiandrosterone; R = H (1), Ас (2); substituents R —R for all compounds studied are given in Table 1.
quasiꢀplanes affect considerably the helical twisting power
of the chiral compounds. It was also found that an inꢀ
crease in the size of the 3βꢀsubstituent enhances the twistꢀ
ing effect of the compounds (3ꢀH < 3ꢀMe < 3ꢀOBz).
At the same time, the studies of various nonꢀsteroid
CAd (see, e.g., Refs 5 and 8—14), including those conꢀ
taining the enone fragments,5,8—10,13 made it possible to
formulate some structural criteria that determine the abilꢀ
ity of chiral compounds to efficiently induce the helical
supramolecular ordering upon the introduction into the
nematic LC. It was revealed that an important role
belongs to the presence in CAd molecules of a highly
polarized πꢀelectronic system, including that fixed by the
saturated cycle of the sꢀcisꢀenone group or its enhydrazone
analog >С=С—C=N—N< (see Refs 8, 10, 12, 13, and 15).
Nevertheless, the role of various structural features of
chiral molecules as factors determining their helical twistꢀ
ing power in mesophases is studied incompletely. There
are contradictory data on the influence of orientation of
the alkyl substituent (for example, the Me group at the
chiral center8,10,13) on the twisting effect of the additives.
In order to study the factors affecting the helical twistꢀ
ing power of the CAd, we synthesized new chiral
α,βꢀunsaturated ketones, viz., 16ꢀarylidene derivatives of
3ꢀhydroxyandrostꢀ5ꢀenꢀ17ꢀone (1a—j) and their acetates
(2a—e) (Scheme 1, Table 1). The synthesized compounds
were studied as potential twisting additives to the LC
systems.
Interest in these compounds is due to a combination
in their molecules of the structural carrier of chirality
(steroid androstene skeleton) and the arylidene group with
the sꢀcisꢀenone fragment (fixed fiveꢀmembered ring). It
can be expected that the study of compounds with this
structure would allow one to extend concepts about the
influence of the steric structure of molecules of these CAd
on their helical twisting power in the mesophases. It is
of special interest to compare the effect of the size and
geometry of the aliphatic cycle fixing the configuration of
the cinnamoyl motive (the sixꢀmembered ring in the strucꢀ
tures based on 3Rꢀmethylcyclohexanone9,10,12,13 and
pꢀmenthanꢀ3ꢀones5,8 and the fiveꢀmembered ring in
unsaturated ketones studied in the present work). It is also
important to obtain information on the influence of the
orientation of methyl substituents relative to the basal
plane of the steroid ring on the efficiency of twisting in
the mesophase. The positive influence of the Me group
in the axial position on the twisting properties of the CAd
was observed for α,βꢀunsaturated ketones and pꢀmenthanꢀ
3ꢀone and pꢀmenthꢀ4ꢀenꢀ3ꢀone derivatives.5,8 At the same
time, the high helical twisting power of Zꢀisomers of
3Rꢀmethylcyclohexanone arylidene derivatives,16 which
exist in the “chair” conformation and containing the
methyl substituent in the equatorial position, was found.17
It can be expected that an information on the influꢀ
ence of the molecular polarizability of chiral additives
would be provided by the comparison of the helical twistꢀ
Table 1. Helical twisting power (βmol) of CAd 1 and 2 in the
nematic matrix 5CB
CAd R1
R2
R3
R4
H
β
mol/μm–1
1a
1b
1c
1d
1e
1f
1ga
1h
1i
H
H
H
H
H
H
H
H
H
OMe
OMe
H
OMe
OCHF2
OCHF2
OCHF2
Ph
OMe
OC9H19
OMe
H
OMe
OMe
OCHF2
OMe
H
OMe
CH2OMe
OEt
OMe
OMe
H
OMe
H
OMe
OMe
CH2OMe
OMe
OMe
–38.7 1.0
OMe –34.4 1.7
OMe –33.6 1.2
H
H
H
H
H
–34.2 0.9
–32.2 1.1
–29.0 1.1
–6.2 0.3
6.1 0.8b
OMe –20.3 0.3
H
H
1j
H
5.6 0.5b
2a
2b
2c
2d
2e
Ac
Ac
Ac
Ac
Ac
–60.8 1.9
OMe –60.9 1.6
–67.1 0.7
OMe –44.6 0.5
H
H
–48.1 0.5
–11.8 0.4
CholAc
a
Compound 1g contains no double bonds in the steroid
skeleton.
b The sign of β was not determined.
c
Cholesterol acetate.

1074
Russ.Chem.Bull., Int.Ed., Vol. 58, No. 5, May, 2009
Yaremenko et al.
ing power of the compounds with the double bond in
cyclohexane ring B of the steroid skeleton and without it.
Finally, the variation of the character of substituents and
their positions in the benzene ring changing the shape of
the additive molecules would make it possible to monitor
the effect of this very important factor on the properties of
the LC systems including the CAd under study.
ton =СНβ (δ 7.37—7.82) is also identified in this region.
In addition, the spectrum of each synthesized compound
exhibits signals belonging to the corresponding substituꢀ
ents R2, R3, or R4 in the benzene ring.
The signals of the protons ОН, MeСОО, H(3),
H(4), H(6), H(14), and H(15) and the groups 18ꢀMe and
19ꢀMe were identified on the basis of analysis of their
multiplicity and comparison with the literature data
for similar compounds.20 The modification of the cycloꢀ
pentane ring by the cinnamoyl fragment insignificantly
affects the signals of other protons of the steroid skeleton
of the compounds under study.
Steric structures of androstꢀ5ꢀenꢀ17ꢀone 16ꢀarylidene
derivatives. Specific features of the steric structure of the
studied 16ꢀarylidene derivatives were characterized on the
basis of the results of their AM1 simulation and 1Н NMR
spectra. The results of simulation of structure 1g of the
5αꢀandrostane series compared to the corresponding
Δ5ꢀderivative 1f indicate the substantial difference in the
conformations of their rings B. In the case of compound
1g with the saturated skeleton including rings A—C, all
the three cycles have the “chair” conformation with
approximately the same ensocyclic torsion angles
(ϕ = 55.0—58.3°) close to those in the unsubstituted
cyclohexane molecule, namely, 55.9° (see Ref. 21) and
54.5° (see Ref. 22), and lying almost in one plane.
The helical twisting power of CAd 1 and 2 was studied
in solutions of nematic 4ꢀcyanoꢀ4´ꢀpentylbiphenyl (5CB)
at relatively low concentrations (0.01—0.02 mole fracꢀ
tions) with the purpose of revealing the fundamental reguꢀ
larities of the influence of the molecular structure on the
efficiency of the twisting effect of CAd. In addition, in the
case of the CAd with the maximum |βmol| values, the search
for possibilities of preparation of LC compositions selecꢀ
tively reflecting light in the visible spectral region at modꢀ
erate concentrations (~10 mol.%) of additives is practiꢀ
cally significant. For this study we chose the multicomꢀ
ponent mixtures LC E63 (Merck) and LCꢀ1289 (Moscow
Scientific Industrial Joint Enterprise “NIOPIK”) characꢀ
terized by a wide temperature mesomorphic interval.
According to the existing concepts (see, e.g., Refs 5,
8, 10, and 11), the most important molecular factors
determining the efficiency of formation of the supramoꢀ
lecular helix in the mesophase upon the introduction of
the CAd are the molecular polarizability (its anisotropy
and chirality) and the shape of the additive molecules.
The theoretical simulation in the framework of the
semiempirical AM1 method18 was performed to elucidate
the molecular shape of the CAd of the studied type. It was
shown for a series of chiral carbocyclic compounds (see,
e.g., Ref. 17) that the simulation results are adequate to
the experimental data.
Results and Discussion
Synthesis and identification of 3βꢀhydroxyandrostꢀ
5ꢀenꢀ17ꢀone 16ꢀarylidene derivatives. New α,βꢀunsaturꢀ
ated ketones 1 containing the hydroxy substituent at the
3βꢀcarbon atom were synthesized by the condensation of
3βꢀhydroxyandrostꢀ5ꢀenꢀ17ꢀone (DEA) with aromatic
aldehydes in an alkaline medium by analogy to the earlier
described procedure19 (see Scheme 1). The correspondꢀ
ing 3βꢀacetoxy derivatives 2 were synthesized by the acetyꢀ
lation of hydroxy compounds 1 with acetic anhydride in
pyridine.
According to the simulation results, if the molecules
of the studied compounds contain the С(5)=С(6) double
bond, sixꢀmembered cycle В takes the “halfꢀchair”
conformation with the substantially flattened fragment
С(10)С(5)С(6)С(7) (structure 1f). The appreciable change
in the geometry compared to saturated structure 1g
follows from the simulation results for ring A as well
(decrease in the torsion angles in the region adjacent to
the cyclohexene fragment). The presence of the С(5)=С(6)
double bond affects the geometry of cycle С to relatively
The individual character of the synthesized compounds
and their composition were confirmed by the results of
HPLC and mass spectrometry. Their structure follows
1
from the Н NMR and IR spectra. The structures of the
obtained compounds contain the arylidene group, which
1
is manifested by the presence in the Н NMR spectra of
multiplets of aromatic protons at 6.46—7.77 ppm correꢀ
sponding to the character of substitution in the benzene
ring. The characteristic singlet signal of the arylidene proꢀ

Liquid crystals based on 16ꢀarylideneandrostenꢀ17ꢀone Russ.Chem.Bull., Int.Ed., Vol. 58, No. 5, May, 2009
1075
Table 2. Energy characteristics (ΔE/kcal mol–1) and selected
torsion angles (ϕen, ϕAr/deg) for probable conformers of comꢀ
pounds 1 and 2 according to the AM1 calculations
lesser extent. In addition, the change in the geometry of
ring B induces a noticeable turn of cycle С relative to
cycle A (by 12—14°) in structure 1f. This imparts someꢀ
what twisted shape to the system of rings of the steroid
skeleton, which makes a certain contribution to its
chirality. A similar situation is observed in the structure of
the estrone 16ꢀbenzylidene derivative (according to the
results of our simulation, the turn angle of cycle С relative
to benzene ring А is 8°). The results of the Xꢀray diffracꢀ
tion study of this compound indicate some turn of ring С
relative to cycle А.23
As a whole, the steric structure of the fragment of the
CAd under study, including the cyclohexane (A and C)
and cyclohexene (B) rings in the consecutive trans—transꢀ
fusion, and the equatorial 3βꢀorientation of the hydroxy
group are analogous to those for cholesterol and its esters
(see, e.g., Xꢀray diffraction data24). This threeꢀring sysꢀ
tem along with annelated fiveꢀmembered ring D has the
anisotropic quasiꢀplate shape with the angular methyl
groups 18ꢀMe and 19ꢀMe. The presence of the highly
polarized double bond С(5)=С(6) in this fragment
undoubtedly favors the dispersion attraction between the
CAd and surrounding molecules of the nematic solvent.
The cinnamoyl group in the studied CAd has the
Еꢀconfiguration according to the NOESY results for
ketone 1i. The multiplet of orthoꢀprotons with the center
at δ 7.6 is characterized by the correlation peak with the
signals of protons at the C(15) atom, which makes it
possible to assign the compounds studied to Еꢀisomers.
No higherꢀfield signal of the arylidene proton, which
is characteristic of the Zꢀisomers and appears usually at
6.3—6.5 ppm,17,25,26 is observed in the spectra of these
compounds. Evidently, according to the earlier estabꢀ
lished regularities (see, e.g., Ref. 17), the Zꢀisomers of the
studied α,βꢀunsaturated ketones are characterized by conꢀ
siderably higher energies due to the substantial steric strain
between the O atom of the carbonyl group and the
aryl group.
CAd ΔE
ϕ
ϕ
CAd ΔE
ϕ
ϕ
Ar
en
Ar
en
1a 0.81
0
1b 0.88
0
2.01
2.06
1c 0.55
0
1.68
1.16
1d 0.74
0
1i 0.70
0
7.0
3.5
10.3
3.7
6.7
8.9
10.2
3.0
5.7
8.7
7.8
4.0
9.8
4.7
6.6
8.8
51.6
–33.6
48.9
–29.9
62.2
–54.6
51.3
–35.2
65.0
–57.4
51.1
–31.7
46.4
–27.8
62.6
–56.3
2a 0.78
8.5
4.0
10.3
4.2
5.8
8.9
8.2
4.5
9.8
4.2
6.4
8.7
8.1
4.7
52.8
–32.0
50.7
–31.7
65.1
–59.2
51.1
–29.9
47.6
–29.0
62.7
–56.1
54.4
0
2b 0.55
0
1.67
0.98
2c 0.73
0
2d 0.69
0
1.92
1.65
2e 0.68
0
–30.0
1.90
1.63
position of this ring and at the C(15) atom. In the general
case, according to the simulation results, for the orthoꢀ
and metaꢀsubstituted compounds the rotation of the
aromatic ring gives four alternative rotamers differed by
values of the torsion angle ϕAr. These structures differ
from each other, on the one hand, by the remote or
approached arrangement of substituents R3 and R4 relaꢀ
tive to the steroid skeleton (Fig. 1, а and b or Fig. 1, c and
d, respectively) and, on the other hand, by their arrangeꢀ
ment “above” (see Fig. 1, a, d) or “under” the skeleton
(see Fig. 1, b, c). The mutual transformations of these
rotamers affect the random molecular shape of the CAd
and its anisometry depending on the number of size of the
orthoꢀ and paraꢀsubstituents.
By analogy to some other chiral α,βꢀunsaturated
ketones (see, e.g., Ref. 27), for the compounds with
R4 = H, using CAd 1a, 1d, 1f and 2a, 2c, 2e (see Table 2)
as examples, we consider two main types of rotamers at
the arylidene group: with the negative value of the torsion
angle ϕAr (type А) and with the positive ϕAr value (type B).
The rotamers of the first type in which the ϕAr angle varies
from –33.6° to –29.9° are energetically more favorable.
For energetically less favorable rotamers of type В the
positive ϕAr angle ranges from 51.1° to 56.3°. It is regularly
that rotamers A have the more flattened enone group
(ϕen = 3.5—4.7°). Flatter rotamers А are energetically
more preferential due to more favorable (compared to
rotamers B) possibilities of double bond conjugation with
the aryl group.
In the studied compounds, the sꢀcisꢀenone group is
fixed by fiveꢀmembered ring D. This exocyclic enone
group is only somewhat twisted relative to the ordinary
bond C(16)—C(17): according to the simulation results,
the torsion angle О=С(17)—С(16)=С(20) (ϕen) is 4—10°
(Table 2). Nevertheless, this twisting can be very imporꢀ
tant for inducing the helical supramolecular structure in
the mesophase due to its stereospecific character: the sign
of this torsion angle (plus) is unambiguously determined
by the configuration of the rigid steroid skeleton and
remains unchanged upon the variation of substituents R2,
R3, and R4 in the aryl group.
The steric structure of the arylidene fragment of the
studied compounds is characterized, on the one hand, by
the degree of acoplanarity of the benzene ring and double
bond (torsion angle ϕAr, see Table 2), and on the other
hand, by steric strain between the H atoms in the orthoꢀ
The energy differences of the rotamers are more conꢀ
siderable in the presence of the methoxy substituent in the
orthoꢀposition of the benzene ring (R4 = OMe) of the
studied ketones (see Table 2, compounds 1b, 1c, 1i, 2b,
and 2d). It is characteristic that the rotamers with higher

1076
Russ.Chem.Bull., Int.Ed., Vol. 58, No. 5, May, 2009
Yaremenko et al.
a
b
c
d
C
O
H
Fig. 1. Steric structures of rotamers of the arylidene fragment of compound 1c: a, methoxy groups are apart and arranged above the
steroid skeleton; b, methoxy groups are apart and oriented down from the steroid skeleton; c, methoxy groups are brought together and
oriented down from the steroid skeleton; d, methoxy groups are brought together and oriented up from the steroid skeleton.

Liquid crystals based on 16ꢀarylideneandrostenꢀ17ꢀone Russ.Chem.Bull., Int.Ed., Vol. 58, No. 5, May, 2009
1077
both positive and negative ϕAr angles (|ϕAr| = 45—55°)
possess higher energies compared to those of the energetiꢀ
cally more favorable (by 1.5—2.0 kcal mol–1) rotamers.
Therefore, the fraction of these rotamers in an equilibꢀ
rium system is smaller and, in some cases, negligible (for
instance, for compound 1b). As follows from the simulaꢀ
tion results, the lowerꢀenergy rotamers correspond to the
situation when the methoxy group of R4 is apart from
the main skeleton (see Fig. 1, a, b). In these rotamers, the
transverse molecular axis is “displaced” relative to
the fundamental molecular axis of the steroid skeleton
and forms with the latter an obtuse angle (125°—130°
according to the simulation results). This orientation of
the orthoꢀmethoxy group (and similar for metaꢀsubstituꢀ
ent R3) increases the anisotropy of the CAd molecules
and the anisotropy of their polarizability, which exerts the
most appreciable effect in the case of 3βꢀacetoxyꢀsubstiꢀ
tuted compounds 2.
supramolecular twisting in the mesophase was revealed
for a wide series of biaryl structures with the helical nature
of chirality.28—31
The absolute values of the helical twisting power (β) for
compounds 1 and 2 (see Table 1) vary in the very wide
range: from very low values (CAd 1g, 1h, and 1j) to the
values higher more than an order of magnitude (2a—с).
When analyzing the relationship between the helical
twisting power of the CAd and their steric structure, we
based our considerations, as in the earlier studies,13,16,17
on the concepts on the decisive influence on the properꢀ
ties of the induced cholesteric mesophases of the balance
of the forces of anisotropic intermolecular attraction and
specific steric repulsion between the molecules of the CAd
and nematic solvent. The former factor is defined by the
characteristics of molecular polarizability of the CAd, first
of all, by its anisotropy (anisotropic component of the
dispersion attraction between molecules of the compoꢀ
nents). As for the specific steric repulsion in nematic—
CAd systems, it is determined (when the same nematic is
used) by the molecular shape of the CAd.
Compared to cholesterol esters, the very high helical
twisting power of the most part of the synthesized comꢀ
pounds containing the 3βꢀhydroxy substituents (1a—1f)
and first of all the 3βꢀacetoxy substituents (2a—e, see
Table 1) are the result of the replacement of the isooctyl
radical by the conjugated cinnamoyl group O=C—C=С—Ar
and related polarization and steric features of the molꢀ
ecules. Undoubtedly, this group substantially enhances
the polarizability of molecules, including its important
component along the fundamental molecular axis.
The polarizability of the steroid skeleton of the studied
CAd and efficiency of their intermolecular dispersion
interaction with the nematic depend to a considerable
extent on the presence of the С(5)=С(6) double bond.
The absence of this double bond in molecule 1g decreases
substantially the dispersion component of intermolecular
attraction in the nematic—CAd system and, as a conseꢀ
quence, sharply decreases the helical twisting power of
CAd 1g compared to that of compound 1f. However, it
should be noted that cholesterol ester molecules also conꢀ
tain the С(5)=С(6) double bond and, nevertheless, they
exhibit very weak twisting properties (for the β values for
cholesterol acetate obtained by us using the method simiꢀ
lar to that used in the studies of CAd 1 and 2, see Table 1).
Obviously, in the case of cholesterol acetate, the polarizꢀ
ability effect mainly caused by the С(5)=С(6) bond is
insufficient to provide the necessary dispersion attraction
between molecules of CAd and nematic 5CB. In the sysꢀ
tems under study, this attraction is achieved due to the
combined effect of the easily polarized double bond
С(5)=С(6) and arylidene group with readily polarized
alkyloxy groups (see Table 1). At the same time, one
should take into account a possible influence of the more
pronounced chirality of the skeleton of the studied
The rotameric state of trimethoxyꢀsubstituted arylidene
derivatives 1i and 2d (see table 2) does not substantially
differ from that for the dimethoxy derivatives containing
оꢀMeO group.
The rotamers at the arylidene group are sterically
…
hindered due to the shortened nonvalent contact Нo H(15)
1
(2.14—2.23 Å). Nevertheless, in the experimental H
NMR spectra of the compounds both with R4 = OMe and
unsubstituted in the orthoꢀposition, the retarded rotation
of the benzene ring is not observed, at least at temperaꢀ
tures close to ambient.
It is doubtless that the rotamer differences for the
arylidene group of the studied unsaturated ketones conꢀ
tribute to the degree of anisotropy of these chiral molꢀ
ecules, i.e., determine their random molecular shape to a
substantial extent.
Structure and helical twisting power of the unsaturated
ketones under study. All studied compounds 1 and 2
induce the left cholesteric helix in the mesophase 5CB
(the β values are negative, see Table 1). This direction of
induced twisting in the mesophase correlates with the
above mentioned stereospecific character of twisting of
the enone group in the CAd molecules, namely, with the
positive sign of the torsion angle ϕen, which is unambiguꢀ
ously determined by the configuration of the rigid steroid
skeleton. This feature of the structure of the studied molꢀ
ecules defines, most likely, the steric peculiarities of their
intermolecular dispersion interaction with the surroundꢀ
ing molecules of the nematic and, finally, defines the
direction of twisting (sign) of the induced cholesteric
helix. It should be mentioned that the same sign of the
corresponding torsion angle was obtained for the efficient
CAd of the series of leftꢀtwisting 2ꢀarylideneꢀpꢀmenthanꢀ
3ꢀones using simulation and by the data of Xꢀray diffracꢀ
tion experiments.5
A similar ratio between the intramolecular twisting of
the πꢀsystem of the CAd and the direction of induced

1078
Russ.Chem.Bull., Int.Ed., Vol. 58, No. 5, May, 2009
Yaremenko et al.
androstene derivatives due to the aboveꢀmentioned feaꢀ
tures of their geometry compared to CAd 1g.
containing the extended nonyloxy substituent in the
paraꢀposition of the benzene ring.
An important role of anisotropy of polarizability of the
studied CAd in providing a strong helical twisting power
is indicated by the fact that the |β| values of CAd 2 conꢀ
taining the acetoxy group at the 3βꢀcarbon atom approxiꢀ
mately twofold exceed those for hydroxy analogs 1 (cf. the
data for compounds 1a and 2a, 1c and 2b, 1d and 2c, 1f
and 2e). It is poorly probable that this effect is caused by
the selfꢀassociation of the hydroxyꢀcontaining CAd due
to the formation of intermolecular hydrogen bonds
>C=O...HO— and, as a consequence, by some disordering
of the additive in the nematic medium.32 This selfꢀassoꢀ
ciation of CAd is hindered, on the one hand, by the low
acidity of the alcoholic hydroxyl and, on the other hand,
weak protonꢀwithdrawing properties of the carbonyl
group included into the strained aliphatic fiveꢀmembered
cycle.33 When the β value is measured by the Granjean—
Cano method, the CAd concentration is rather low
(0.01—0.02 mole fractions), which also decreases the
probability of selfꢀassociation. The intermolecular assoꢀ
ciation of the hydroxyꢀsubstituted CAd with the nematic
cyanoꢀcontaining solvent can be considered also poorly
probable because of the very weak basic properties of the
nitrile group.34
It was found that compound 1h containing the bipheꢀ
nyl substituent possesses a very weak helical twisting
power. This fact seems important for understanding of the
role of the anisotropy of CAd polarizability during the
induction of the supramolecular helix in the mesophase.
In the earlier studied CAd series,8,35,36 including those
belonging to the class of α,βꢀunsaturated ketones,8,34 the
introduction of an additional benzene ring into the conꢀ
jugated molecular chain is accompanied by a considerꢀ
able increase in |β|. In the series of 1R,4Rꢀ2ꢀarylideneꢀ
pꢀmenthanꢀ3ꢀones, the effect of the biphenyl group
exceeds the influence of both the strong electronꢀdonatꢀ
ing dimethylamino group and the strong electronꢀwithꢀ
drawing nitro group introduced into the benzene ring.8 It
can be assumed that the unexpectedly weak helical twistꢀ
ing power of the CAd containing the biphenyl group in
the series of compounds 1 compared to other known
molecular systems is explained by the influence of the
molecular shape prevailing on the polarizability effect.
For compounds 1 two molecular axes can be considered,
which define the shape of the molecules arranged at an
angle to each other. This angle depends substantially on
the substitution pattern in the phenyl group. In the case of
phenylꢀsubstituted CAd 1h, its value estimated by us by
the AM1 simulation is ~105°—107°. This fact along with
the presence of the extended transverse biphenyl fragꢀ
ment substantially decreases anisotropy of both the shape
and polarizability of molecules and negatively affects the
efficiency of inducing the helicoidal structure. A similar
situation can be assumed for weakly twisting CAd 1j
An analysis of the relationship between the helical
twisting power of CAd 1 and 2 and the character of substiꢀ
tution in their benzene ring suggests that strong twisting is
favored by the presence of the alkoxy substituent R3 in the
metaꢀposition combined with the methoxy group R4 and
3βꢀacetoxy group (CAd 2a—c, see Table 1).
In both series of 1 and 2, the trimethoxyꢀsubstituted
CAd exhibit a lower helical twisting power than the subꢀ
stituted CAd (cf. the data for compounds 1i and 1a—c, 2d
and 2a,b). This can be a consequence of the randomly
stronger (in the first case) turn out of the aryl group relaꢀ
tive to its axis, which decreases the molecular anisometry
(effect of changing the molecular shape) and anisotropy
of polarizability (polarization effect).
The replacement of the methoxy group in molecules
of CAd 1a, as well as of acetate 2a, by the difluoromethoxy
group is accompanied by the noticeable decrease in |β|
(cf. the data for compounds 1a and 1f, 2a and 2e). This is
possibly reasoned by the electronꢀacceptor effect of the
OCHF2 group characterized by the constant δp = 0.18,37
due to which the electron density on the benzene rings of
CAd 1f and 2e is lower than that in molecules of the
methoxyꢀsubstituted analogs. The corresponding decrease
in the contribution to the polarizability of the arylidene
fragment and studied molecular systems as a whole can
weaken the dispersion attraction between molecules of 1f
(or 2e) and the nematic solvent compared to that in the
case of CAd 1a (or 2a).
The experimental data suggest that the geometry of
the saturated cycle that fixes the sꢀcisꢀenone group
(cyclopentane ring D) in the molecular systems under
study exerts no decisive effect on the helical twisting
power of the CAd. Note for comparison that although the
3R,6Rꢀ3ꢀmethylꢀ6ꢀisopropylcyclohexanone (pꢀmenthanꢀ
one) 2ꢀarylidene derivatives containing the sꢀcisꢀenone
group fixed by the cyclohexane ring exhibit a weaker twisting
effect than acetates 2, they can be attributed, nevertheless,
to well twisting CAd. For the pꢀmethoxyꢀsubstituted comꢀ
pound of this series in 5CB, |βmol| = 27.8 0.4 μm–1,38 while
|βmol| increases to 40.1 2.4 μm–1 upon the introduction
of an additional benzene ring to the arylidene fragment.15
LC systems selectively reflecting light in the visible specꢀ
tral region. The typical spectral characteristics for the LC
systems selectively reflecting light are presented in Fig. 2.
This property is most pronounced for the composites based
on liquid crystals Е63 and LCꢀ1289 containing CAd 2a—c
with the high helical twisting power. The results of meaꢀ
surements in LCꢀ1289 with the known molar composiꢀ
tion are most appropriate for the establishment of the
correlation of this property with the molecular structure
of the CAd. Therefore, the spectral characteristics and the
data on the helical twisting power in this nematic correꢀ
late in Table 3 with the molar and weight concentrations

Liquid crystals based on 16ꢀarylideneandrostenꢀ17ꢀone Russ.Chem.Bull., Int.Ed., Vol. 58, No. 5, May, 2009
1079
Table 3. Characteristics of LC composites nematic—CAd
capable of selective light reflection in the visible spectral
region
of the CAd, whereas those in E63 correlate with the weight
concentrations only. It is seen from the data in Table 3
that the studied CAd 2a,b in LCꢀ1289 exhibit selective
light reflection in the visible green range (λmax = 511—
525 nm) at the concentrations 5.8—6.2 mol.% (9.5—
10.3 wt.%). Selective light reflection of the LC composition
including compound 2b (5.6 mol.%, 9.7 wt.%) is someꢀ
what shifted to the shortꢀwavelength region, which correꢀ
sponds to the higher helical twisting power of this CAd.
The |βmol| values of the studied steroid α,βꢀunsaturated
ketones 2a—c noticeably exceed the corresponding value
for the known CAd, viz., 2ꢀ(4ꢀphenylbenzylidene)ꢀpꢀ
menthanꢀ3ꢀone (PBM). Possibly, this difference is caused
by the fact that the quasiꢀplate fragment of the studied
molecules including four aliphatic rings contains two anꢀ
gular Me groups. This structural feature of compounds 1
and 2 along with the presence of the cinnamoyl fragment
provides the balance of forces of dispersion attraction and
specific steric repulsion favorable for helix ordering.
Thus, the study of the new type of chiral α,βꢀunsaturꢀ
ated ketones made it possible to create the series of LC
CAd
С (wt.%)
Тi
Тred
λ
max/nm
P
β (Тred)
[С (mol.%)] /°С
/К
(color)
/μm
at 298 К
Nematic LCꢀ1289*
2a
2b
9.5 [5.8]
9.7 [5.9]
47
40.6
525
(green)
482
(greenishꢀ
blue)
0.364 47.4
(28.9)
0.328 51.7
(31.5)
47
40.6
2c
10.3 [6.2] 45.5
39
511
(green)
571
(yellowishꢀ
green)
0.356 45.3
(27.2)
0.365 35.6
(31.7)
PBM
8.6 [7.7] 57.5 50.9
Nematic E63**
54 47.5
1e
2a
13.1
9.1
660
(red)
498
0.432 17.7
0.360 30.6
75.5 68.5
(greenishꢀ
blue)
681
(red)
618
(red)
509
(green)
580
2b
7.2
8
71
71
86
79
50
64
64
0.460 30.1
0.422 29.3
0.376 27.0
0.429 23.5
0.329 24.9
I (rel. units)
1.2
2b
1
3
a
4
2
2c
9.9
9.9
12.2
79
2e
72
0.8
0.4
0
(yellow)
530
PBM
43.5
(green)
* The composition of LCꢀ1289: 38% 4ꢀcyanoꢀ4´ꢀnꢀpentylꢀ, 8%
4ꢀcyanoꢀ4´ꢀnꢀpropoxyꢀ, and 15% 4ꢀcyanoꢀ4´ꢀnꢀoctylbiphenyls,
30% 4ꢀethoxyphenyl 4ꢀnꢀbutylcyclohexanecarboxylate,
9% 4ꢀcyanodiphenyl transꢀ4ꢀbutylcyclohexanecarboxylate.
LCꢀ1289 is characterized by the following phase transitions:
Cryst (–20) → N (62) → Iso (Cryst, N, and Iso are the crystalꢀ
line, nematic, and isotropic phases, respectively). Here and for
nematic E63 the temperatures (°С) of the phase transitions
Cryst → N and N → Iso are given in parentheses.
450
500
550
600
650 λ/nm
I (rel. units)
** The nematic E63 includes diphenyl and terphenyl cyano
derivatives and has the phase transitions: Cryst (8) → N (83) → Iso.
the exact content of the components LC E63 is unknown.
b
3
4
1
0.8
0.6
0.2
2
composites capable of selective light reflection in the
visible spectral region from the red to blueꢀgreen color.
In addition, the studies of the synthesized compounds
extended the concepts about the structural factors affectꢀ
ing the helical twisting power in the mesophase. As disꢀ
cussed above, these factors are the presence of the polarꢀ
ized double bond in the steroid skeleton, the presence of
the polarized arylidene fragment containing the alkoxy
substituents, whose positions in the benzene ring substanꢀ
tially affect the molecular shape (its anisotropic characꢀ
teristics), and the presence of the acetoxy group and related
450 500 550 600 650 700 750
λ/nm
Fig. 2. Selective light reflection spectra of chiral nematic mixꢀ
tures: a, LCꢀ1289—2с (5.9 mol.%) at T = 28.5 (1), 37.5 (2), 40.5
(3), and 44.5 °С (4); b, E63—2f (9.9 wt.%) at T = 28.5 (1), 36.5
(2), 41.5 (3), and 47 °С (4).

1080
Russ.Chem.Bull., Int.Ed., Vol. 58, No. 5, May, 2009
Yaremenko et al.
1Н NMR (CDCl3, 500 MHz), δ: 7.39 (br.s, 1 H, =CHβ); 7.18
(d, 1 H, J = 8.5 Hz); 7.07 (br.s, 1 H); 6.92 (d, 1 H, J = 8.5 Hz);
5.40 (dd, 1 H, C(6)H, J = 4.4, 2.0 Hz); 3.93 (s, 3 H); 3.92 (s, 3
H); 3.54 (m, 1 H, C(3)H); 2.89 (dd, 1 H, J = 15.9, 5.8 Hz); 2.43
(td, 1 H, J = 14.1, 2.7 Hz); 2.36—2.17 (m, 3 H); 1.10—1.67 (m,
6 H); 1.62—1.34 (m, 5 H); 1.15—1.05 (m, 2 H); 1.08 (s, 3 H);
0.99 (m, 3 H). MS, m/z (Irel (%)): 436 [M]+ (100), 213 (10), 177
(14), 176 (58), 161 (12), 151 (22), 105 (14), 91 (18).
increase in the molecular anisometry and anisotropy of
polarizability. The quasiꢀplate shape of the steroid skelꢀ
eton is also important, and its substantial influence is
enhanced (compared to that of cholesterol esters) by the
action of a combination of other aforementioned strucꢀ
tural peculiarities of the CAd under study.
It is most likely that the angular methyl groups affect
the stereospecific repulsion between molecules of the
additive and nematic, although it is impossible to separate
the contribution of this type of interaction, because necesꢀ
sary authentic compounds for comparison are lacking.
It should be mentioned that the effect of each particuꢀ
lar factor taken separately can be insufficient for providꢀ
ing the high efficiency of twisting typical of the most part
of the studied CAd. However, their combined effect makes
it possible to achieve good results.
16Еꢀ(2,4ꢀDimethoxybenzylidene)ꢀ3ꢀβꢀhydroxyandrostꢀ5ꢀenꢀ
17ꢀone (1b). The yield was 40%, m.p. 175—179 °С (from
MeOH), [α]D20 +34.9 (c 1.0, СНCl3). Found (%): С, 77.15; Н,
8.47. C28H36O4. Calculated (%): С, 77.03; Н, 8.31. IR (KBr),
1
ν/cm–1: 3432 (ОН); 1712 (С=О); 1625 sh (С=C). Н NMR
(CDCl3, 500 MHz), δ: 7.82 (br.s, 1 H, =CHβ); 7.47 (d, 4 H,
J = 8.5 Hz); 6.53 (dd, 1 H, J = 8.5, 2.2 Hz); 6.46 (d, 1 H,
J = 2.2 Hz); 5.39 (dd, 1 H, C(6)H, J = 4.4, 2.0 Hz); 3.85 (s,
6 H); 3.53 (m, 1 H, C(3)H); 2.78 (dd, 1 H, J = 15.9, 6.5 Hz);
2.40 (td, 1 H, J = 14.1, 2.7 Hz); 2.35—2.15 (m, 3 H); 1.99—1.75
(m, 4 H); 1.73—1.48 (m, 5 H); 1.42—1.30 (m, 2 H); 1.13—1.01
(m, 2 H); 1.07 (s, 3 H); 0.98 (m, 3 H). MS, m/z (Irel (%)): 436
[M]+ (71), 406 (33), 405 (100), 177 (17), 176 (32), 161 (49),
151 (30).
Experimental
1H NMR spectra were recorded on Varian Mercury VXꢀ200
(200 MHz) and Bruker DRXꢀ500 (500.13 MHz) spectrometers
in CDCl3 and DMSOꢀd6. Chemical shifts are given relative
to Me4Si.
16Еꢀ(2,3ꢀDimethoxybenzylidene)ꢀ3ꢀβꢀhydroxyandrostꢀ5ꢀenꢀ
17ꢀone (1c). The yield was 80%, m.p. 158—160 °С (from
20
MeOH), [α]D +8.8 (c 1.0, СНCl3). Found (%): С, 77.23;
Н, 8.38. C28H36O4. Calculated (%): С, 77.03; Н, 8.31. IR (KBr),
ν/cm–1: 3420 (ОН); 1712 (С=О); 1624 (С=C). 1Н NMR
(CDCl , 500 MHz), δ: 7.78 (br.s, 1 H, =CHβ); 7.13 (d, 4 H,
J = 8.53Hz); 7.09 (t, 1 H, J = 8.5 Hz); 6.94 (d, 1 H, J = 8.5 Hz);
5.38 (dd, 1 H, C(6)H, J = 4.4, 2.0 Hz); 3.88 (s, 3 H); 3.84 (s,
3 H); 3.53 (m, 1 H, C(3)H); 2.80 (dd, 1 H, J = 15.9, 6.5 Hz);
2.41 (td, 1 H, J = 14.1, 2.7 Hz); 2.34—2.14 (m, 3 H); 1.99 (dm,
1 H, J = 12.8 Hz); 1.89—1.48 (m, 8 H); 1.43—1.30 (m, 2 H);
1.13—1.02 (m, 2 H); 1.07 (s, 3 H); 0.99 (m, 3 H). MS, m/z
(Irel (%)): 436 [M]+ (12), 407 (12), 406 (68), 405 (100), 161 (59),
105 (10), 91 (14).
The completeness of the reaction was monitored by TLC on
Silufol UVꢀ254 plates in a chloroform—methanol (3 : 1) system,
developing with iodine vapors or UV irradiation. Quantitative
chromatographic analysis was carried out on a Bischoff
highꢀperformance liquid chromatograph with a UV detector
(λ = 254 nm), using a column 2.0Ѕ250 mm packed with Prontosil
120ꢀ5ꢀC18ꢀH (5 μm), MeCH—H2O (87 : 13) as eluent, and a
flow rate of 0.25 mL min–1. According to the HPLC data, the
content of the major substance was at least 96%. Mass spectra
with direct inlet were measured on a Varian 1200L GCꢀMS
instrument (the energy of ionizing electrons was 70 eV), and the
m/z values for I > 10% are presented.
IR spectra were recorded in KBr pellets on a Specord
IRꢀ85 instrument. Specific rotation was determined on a
Perkin—Elmerꢀ343 polarimeter in chloroform and expressed in
(deg mL) (g dm)–1, and the solution concentration was expressed
in g (100 mL)–1. Melting points were measured on a Boetius
heating stage in the polarized light and were not corrected; the
double values possibly indicate liquidꢀcrystalline transformations.
Substituted benzaldehydes were commercially available
(Aldrich) and used as received. Dehydroepiandrosterone (DEA)
(Acros) was additionally recrystallized from methanol and,
according to the HPLC data, it contained at least 98% of the
major substance.
3ꢀβꢀHydroxyꢀ16Еꢀ(4ꢀmethoxyꢀ3ꢀmethoxymethylbenzylidene)ꢀ
androstꢀ5ꢀenꢀ17ꢀone (1d). The yield was 89%, m.p. 94—97 °С
20
(from MeOH), [α]D –19.9 (c 1.0, СНCl3). Found (%):
С, 77.18; Н, 8.28. C29H38O4. Calculated (%): С, 77.29; Н, 8.49.
IR (KBr), ν/cm–1: 3492 (ОН); 1716 (С=О); 1624 (С=C).
1Н NMR (DMSOꢀd6, 200 MHz), δ: 7.54 (d, 1 Н, J = 8.8 Hz);
7.53 (br.s, 1 Н, =CHβ); 7.23 (br.s, 1 H); 7.06 (d, 1 H, J = 8.8 Hz);
5.30 (d, 1 H, C(6)H, J = 4.0 Hz); 4.40 (s, 2 H); 3.82 (s, 3 H);
3.34 (m, 1 Н, C(3)H); 3.31 (s, 3 Н); 2.75 (dd, 1 H, J = 17.0,
7.0 Hz); 2.14 (m, 3 Н); 1.9—1.2 (m, 11 Н); 1.0—1.09 (m, 2 Н);
0.98 (s, 3 H); 0.86 (s, 3 H). MS, m/z (Irel (%)): 450 [M]+ (100),
213 (15), 190 (31), 159 (17), 135 (15), 91 (11).
16Еꢀ(4ꢀDifluoromethoxyꢀ3ꢀethoxybenzylidene)ꢀ3ꢀβꢀhydroxyꢀ
androstꢀ5ꢀenꢀ17ꢀone (1e). The yield was 90%, m.p. 100—102 °С
(from MeOH). Found (%): С, 71.76; Н, 7.28. C29H36F2O4.
Calculated (%): С, 71.58; Н, 7.46. IR (KBr), ν/cm–1: 3456
(ОН); 1716 (С=О); 1628 (С=C). 1Н NMR (CDCl3, 500 MHz),
δ: 7.37 (br.s, 1 H, =CHβ); 7.19 (d, 1 H, J = 8.5 Hz); 7.13 (d,
1 H, J = 8.5 Hz); 7.09 (br.s, 1 H); 6.62 (t, 1 H, J = 74.8 Hz);
5.40 (dd, 1 H, C(6)H, J = 4.3, 1.9 Hz); 4.12 (q, 2 H); 3.54 (m,
1 H, C(3)H); 2.86 (dd, 1 H, J = 15.9, 5.5 Hz); 2.42 (td, 1 H,
J = 13.9, 2.7 Hz); 2.36—2.16 (m, 3 H); 1.99 (dm, 1 H, J = 12.8 Hz);
1.90—1.65 (m, 5 H); 1.63—1.33 (m, 5 H); 1.47 (t, 3 H, J = 6.9 Hz);
1.15—1.05 (m, 2 H); 1.08 (s, 3 H); 0.98 (m, 3 H). MS, m/z
(Irel (%)): 486 [M]+ (100), 227 (11), 226 (60), 213 (21), 201
3ꢀβꢀHydroxyꢀ16Еꢀarylideneandrostꢀ5ꢀenꢀ17ꢀones 1 (general
procedure). The corresponding benzaldehyde (1.92 mmol) and
KOH (0.1 g) were added to a solution of DEA (0.50 g, 1.73 mmol)
in alcohol (10 mL). The reaction mixture was refluxed for 3 h.
A precipitate of the product was filtered off and crystallized
from methanol (15 mL).
16Еꢀ(3,4ꢀDimethoxybenzylidene)ꢀ3ꢀβꢀhydroxyandrostꢀ5ꢀenꢀ
17ꢀone (1а). The yield was 0.48 g (72%), m.p. 192—193 °С
(from MeOH) (cf. Ref. 39: m.p. 270—272 °С; cf. Ref. 40: m.p.
20
150—153 °С), [α]D –13.5 (c 1.0, СНCl3). Found (%):
С, 77.10; Н, 8.42. C28H36O4. Calculated (%): С, 77.03; Н, 8.31.
IR (KBr), ν/cm–1: 3536 (ОН); 1716 (С=О); 1620 (С=C).

Liquid crystals based on 16ꢀarylideneandrostenꢀ17ꢀone Russ.Chem.Bull., Int.Ed., Vol. 58, No. 5, May, 2009
1081
(11), 198 (14), 178 (12), 159 (11), 131 (15), 119 (10), 107 (13),
105 (25), 102 (20), 93 (14), 91 (28), 81 (12).
J = 8.5 Hz); 7.27 (br.s, 1 H, =CHβ); 7.01 (d, 2 H, J = 8.0 Hz);
5.33 (m, 1 H, C(6)H); 4.62 (d, 1 H, J = 5.0 Hz); 4.00 (t, 2 H,
J = 5.7 Hz); 3.25 (m, 1 H, C(3)H); 2.77 (dd, 1 H, J = 15.8,
5.7 Hz); 2.10—2.20 (m, 3 H); 1.80—1.60 (m, 7 H); 1.50—1.20
(m, 18 Н); 1.10—0.90 (m, 2 Н); 1.02 (s, 3 H); 0.88 (s, 3 H);
0.86 (t, 3 Н, J = 7.5 Hz). MS, m/z (Irel (%)): 518 [M]+ (100),
520 (10), 519 (44), 518 (100), 327 (10), 258 (17), 233 (21),
231 (19), 213 (40), 211 (10), 201 (11), 133 (21), 132 (40),
131(22), 107 (34), 105 (13), 91 (10).
3ꢀβꢀAcetoxyꢀ16Еꢀ(arylidene)androstꢀ5ꢀenꢀ17ꢀones (general
procedure). Acetic anhydride (4 mL, 42.3 mmol) was added to
hydroxy derivative 1 (0.68 mmol) in pyridine (2 mL). The
reaction mixture was stirred for several hours (TLC monitoring).
After the reaction completed, the solution was poured to iceꢀ
cold water acidified with HCl. A precipitate of the acetate was
filtered off and crystallized from methanol (10 mL).
16Еꢀ(4ꢀDifluoromethoxyꢀ3ꢀmethoxybenzylidene)ꢀ3ꢀβꢀhydroxyꢀ
androstꢀ5ꢀenꢀ17ꢀone (1f). The yield was 61%, m.p. 118—120 °С
(from MeOH). Found (%): С, 71.32; Н, 7.07. C28H34F2O4.
Calculated (%): С, 71.17; Н, 7.25. IR (KBr), ν/cm–1: 3380
(ОН); 1720 (С=О); 1632 (С=C). 1Н NMR (CDCl3, 500 MHz),
δ: 7.38 (br.s, 1 H, =CHβ); 7.20 (d, 1 H, J = 8.5 Hz); 7.15 (d,
1 H, J = 8.5 Hz); 7.10 (br.s, 1 H); 6.59 (t, 1 H, J = 74.8 Hz);
5.40 (dd, 1 H, C(6)H, J = 4.3, 1.9 Hz); 3.91 (s, 3 H); 3.54 (m,
1 H, C(3)H); 2.87 (dd, 1 H, J = 15.8, 5.7 Hz); 2.43 (td, 1 H,
J = 14.0, 2.6 Hz); 2.36—2.16 (m, 3 H); 2,00—1.66 (m, 6 H);
1.63—1.34 (m, 5 H); 1.15—1.05 (m, 2 H); 1.08 (s, 3 H); 0.99
(m, 3 H). MS, m/z (Irel (%)): 472 [M]+ (100), 281 (11), 231
(29), 213 (36), 212 (81), 187 (15).
16Еꢀ(4ꢀDifluoromethoxyꢀ3ꢀmethoxybenzylidene)ꢀ3ꢀβꢀhydroxyꢀ
5αꢀandrostanꢀ17ꢀone (1g). For the synthesis of this derivative,
epiandrosterone obtained by an earlier described procedure41
was used instead of DEA. The yield was 85%, m.p. 118—120 °С
(from MeOH). Found (%): С, 70.69; Н, 7.48. C28H36F2O4.
Calculated (%): С, 70.86; Н, 7.65. IR (KBr), ν/cm–1: 3268
(ОН); 1720 (С=О); 1632 (С=C). 1Н NMR (DMSOꢀd6, 200
MHz), δ: 7.38 (br.s, 1 Н, =CHβ); 7.33—7.23 (m, 3 Н); 7.13 (t,
1 H, J = 74.4 Hz); 4.42 (d, 1 H, J =5.0 Hz); 3.88 (s, 3 H); 2.78
(dd, 1 H, J = 17.4, 7 Hz); 1.95—0.70 (m, 3 Н); 1.8—1.5 (m,
6 Н); 1.4—1.0 (m, 10 Н); 0.88 (s, 3 H); 0.81 (s, 3 H). MS, m/z
(Irel (%)): 474 [M]+ (35), 287 (13), 215 (14), 213 (20), 212 (100),
187 (15), 107 (17), 105 (14), 95 (11), 93 (14), 91 (17), 81 (14).
3ꢀβꢀHydroxyꢀ16Еꢀ(4ꢀphenylbenzylidene)androstꢀ5ꢀenꢀ
17ꢀone (1h). The yield was 58%, m.p. 244—246 °С (from MeOH).
Found (%): С, 84.77; Н, 8.14. C32H36O2. Calculated (%):
С, 84.91; Н, 8.02. IR (KBr), ν/cm–1: 3420 (ОН); 1712 (С=О);
1628 (С=C). 1Н NMR (DMSOꢀd6, 500 MHz), δ: 7.77 (d, 2 H,
J = 8.5 Hz); 7.72 (d, 4 H, J = 8.5 Hz); 7.48 (t, 2 H, J = 8.5 Hz);
7.39 (t, 1 H, J = 8.5 Hz); 7.34 (s, 1 H, =CHβ); 5.32 (dd, 1 H,
C(6)H, J = 4.4, 2.0 Hz); 4.62 (d, 1 H, OH, J = 3.7 Hz); 3.27
(m, 1 H, C(3)H); 2.84 (dd, 1 H, J = 15.9, 5.8 Hz); 2.55 (t, 1 H,
J = 14.1 Hz); 2.20—2.09 (m, 3 H); 1.82—1.63 (m, 6 H); 1.50
(qd, 1 H, J = 12.7, 3.9 Hz); 1.41—1.28 (m, 3 H); 1.02—0.96
(m, 2 H); 1.01 (s, 3 H); 0.90 (m, 3 H). MS, m/z (Irel (%)):
452 [M]+ (65), 261 (14), 231 (14), 229 (11), 213 (25), 193 (23),
192 (100), 191 (39), 178 (16), 167 (41), 165 (17), 145 (11),
131 (13), 119 (12), 115 (14), 107 (14), 105 (28), 95 (11), 93 (18),
91 (41), 81 (22).
3ꢀβꢀHydroxyꢀ16Еꢀ(2,3,4ꢀtrimethoxybenzylidene)androstꢀ
5ꢀenꢀ17ꢀone (1i). The yield was 75%, m.p. 186—188 °С (from
MeOH). Found (%): С, 74.49; Н, 8.02. C29H38O5. Calcuꢀ
lated (%): С, 74.65; Н, 8.20. IR (KBr), ν/cm–1: 3492 (ОН);
1716 (С=О); 1624 (С=C). 1Н NMR (CDCl3, 200 MHz), δ:
7.72 (br.s, 1 H, =CHβ); 7.27 (d, 1 H, J = 8.5 Hz); 6.72 (d, 1 H,
J = 8.5 Hz); 5.38 (dd, 1 H, C(6)H, J = 4.2, 2.1 Hz); 3.91 (s,
3 H); 3.90 (s, 3 H); 3.87 (s, 3 H); 3.53 (m, 1 H, C(3)H); 2.78
(dd, 1 H, J = 15.8, 5.6 Hz); 2.39 (td, 1 H, J = 14.0, 2.6 Hz);
2.32—1.26 (m, 14 H); 1.16—1.03 (m, 2 H); 1.07 (s, 3 H); 0.97
(m, 3 H). MS, m/z (Irel (%)): 466 [M]+ (7), 436 (30), 435 (100),
191 (28), 181 (11).
3ꢀβꢀAcetoxyꢀ16Еꢀ(3,4ꢀdimethoxybenzylidene)androstꢀ5ꢀenꢀ
17ꢀone (2a). The yield was 0.24 g (91%), m.p. 142—144 °С and
178—180 °С (from MeOH) (cf. Ref. 39: m.p. 142—144 °С).
Found (%): С, 75.43; Н, 8.09. C30H38O5. Calculated (%): С,
75.28; Н, 8.00. IR (KBr), ν/cm–1: 1730, 1724, 1708 (С=О);
1
1624 (С=C). Н NMR (CDCl3, 500 MHz), δ: 7.39 (br.s, 1 H,
=CHβ); 7.18 (d, 1 H, J = 8.5 Hz); 7.07 (br.s, 1 H); 6.92 (d, 1 H,
J = 8.5 Hz); 5.43 (dd, 1 H, C(6)H, J = 4.2, 2.1 Hz); 4.61 (m,
1 H, C(3)H); 3.93 (s, 3 H); 3.91 (s, 3 H); 2.89 (dd, 1 H,
J = 15.9, 5.7 Hz); 2.43 (td, 1 H, J = 14.1, 2.5 Hz); 2.38—2.31
(m, 3 H); 2.18 (dm, 1 H, J = 17.0 Hz); 2.04 (s, 3 H); 1.98 (d.m,
1 H, J = 12.5 Hz); 1.92—1.53 (m, 8 H); 1.45—1.35 (m, 2 H);
1.20—1.07 (m, 2 H); 1.09 (s, 3 H); 0.98 (m, 3 H). MS, m/z
(Irel (%)): 478 [M]+ (30), 419 (13), 418 (42), 214 (15), 213 (87),
211 (13), 205 (14), 177 (35), 176 (100), 161 (25), 151 (47), 105 (12).
3ꢀβꢀAcetoxyꢀ16Еꢀ(2,3ꢀdimethoxybenzylidene)androstꢀ5ꢀenꢀ
17ꢀone (2b). The yield was 82%, m.p. 132—135 °С и 150—152 °С
(from MeOH). Found (%): С, 75.12; Н, 7.93. C30H38O5.
Calculated (%): С, 75.28; Н, 8.00. IR (KBr), ν/cm–1: 1731,
1709 (С=О); 1624 (С=C). 1Н NMR (DMSOꢀd6, 200 MHz), δ:
7.56 (br.s, 1 H, =CHβ); 7.2—7.1 (m, 3 Н); 5.38 (d, 1 H, C(6)H,
J = 3.4 Hz); 4.44 (m, 1 H, C(3)H); 3.83 (s, 3 H); 3.74 (s, 3 H);
2.73 (dd, 1 H, J = 16.2, 5.8 Hz); 2.30 (d, 2 H, J = 7.8 Hz); 2.12
(m, 1 H); 1.9—1.3 (m, 11 Н); 1.1—1.0 (m, 2 Н); 1.03 (s, 3 H);
0.89 (s, 3 H). MS, m/z (Irel (%)): 478 [M]+ (4), 448 (21), 447
(57), 388 (27), 387 (100), 161 (23), 91 (13).
3ꢀβꢀAcetoxyꢀ16Еꢀ(4ꢀmethoxyꢀ3ꢀmethoxymethylbenzylidene)ꢀ
androstꢀ5ꢀenꢀ17ꢀone (2c). The yield was 84%, m.p. 89—92 °С
(from MeOH). Found (%): С, 75.49; Н, 8.02. C31H40O5.
Calculated (%): С, 75.57; Н, 8.18. IR (KBr), ν/cm–1: 1732,
1716 (С=О); 1624 (С=C). 1Н NMR (DMSOꢀd6, 300 MHz), δ:
7.57 (d, 1 Н, J = 8.1 Hz); 7.55 (br.s, 1 Н, =CHβ); 7.26 (br.s,
1 H); 7.09 (d, 1 H, J = 8.1 Hz); 5.41 (d, 1 H, C(6)H, J = 4.2 Hz);
4.46 (m, 1 H, C(3)H); 4.41 (s, 2 Н); 3.83 (s, 3 H); 3.33 (s, 3 H);
2.77 (dd, 1 H, J = 15.9, 6.3 Hz); 2.30 (d, 2 H, J = 7.5 Hz); 2.13
(m, 1 H, J = 15.9 Hz); 1.99 (s, 3 Н); 1.9—1.5 (m, 8 Н); 1.30
(m, 2 Н); 1.06 (m, 2 Н); 1.03 (s, 3 H); 0.88 (s, 3 H). MS, m/z
(Irel (%)): 492 [M]+ (18), 433 (12), 432 (40), 400 (17), 229 (13),
228 (13), 227 (11), 214 (19), 213 (100), 211 (32), 209 (14),
199 (11), 197 (13), 191 (10), 190 (62), 189 (11), 187 (12),
186 (16), 175 (14), 173 (21), 171 (13), 165 (18), 161 (21),
160 (25), 159 (45), 157 (16), 145 (18), 143 (13), 135 (30),
131 (13), 129 (16), 128 (13), 115 (12), 105 (19), 91 (20), 81 (19).
3ꢀβꢀAcetoxyꢀ16Еꢀ(2,3,4ꢀtrimethoxybenzylidene)androstꢀ
5ꢀenꢀ17ꢀone (2d). The yield was 70%, m.p. 186—188 °С (from
3ꢀβꢀHydroxyꢀ16Еꢀ(4ꢀnonyloxybenzylidene)androstꢀ5ꢀenꢀ17ꢀ
one (1j). The yield was 87%, m.p. 98—100 °С (from MeOH).
Found (%): С, 81.16; Н, 9.59. C35H50O3. Calculated (%):
С, 81.03; Н, 9.71. IR (KBr), ν/cm–1: 3408 (ОН); 1728 (С=О);
1600 (С=C). 1Н NMR (DMSOꢀd6, 500 MHz), δ: 7.59 (d, 2 H,

1082
Russ.Chem.Bull., Int.Ed., Vol. 58, No. 5, May, 2009
Yaremenko et al.
MeOH). Found (%): С, 73.28; Н, 7.82. C31H40O6. Calcuꢀ
lated (%): С, 73.20; Н, 7.93. IR (KBr), ν/cm–1: 1728, 1712
(С=О); 1628 (С=C). 1Н NMR (CDCl3, 200 MHz), δ: 7.72
(br.s, 1 H, =CHβ); 7.26 (d, 1 H, J = 8.5 Hz); 6.71 (d, 1 H,
J = 8.5 Hz); 5.41 (dd, 1 H, C(6)H, J = 4.2, 2.1 Hz); 4.60 (m,
1 H, C(3)H); 3.90 (s, 3 H); 3.89 (s, 3 H); 3.87 (s, 3 H); 2.78
(dd, 1 H, J = 15.8, 5.6 Hz); 2.39 (td, 1 H, J = 14.0, 2.6 Hz);
2.37—2.12 (m, 3 H); 2.03 (s, 3 H); 1.94—1.52 (m, 9 H);
1.46—1.29 (m, 2 H); 1.22—1.04 (m, 2 H); 1.07 (s, 3 H); 0.97
(m, 3 H). MS, m/z (Irel (%)): 508 [M]+ (10), 478 (37), 477
(100), 418 (16), 417 (52), 191 (47), 181 (25), 105 (10).
3ꢀβꢀAcetoxyꢀ16Еꢀ(4ꢀdifluoromethoxyꢀ3ꢀmethoxybenzylidene)ꢀ
androstꢀ5ꢀenꢀ17ꢀone (2e). The yield was 74%, m.p. 129—131 °С
(from MeOH). Found (%): С, 70.21; Н, 7.23. C30H36F2O5.
Calculated (%): С, 70.02; Н, 7.05. IR (KBr), ν/cm–1: 1777,
1711 (С=О); 1628 (С=C). 1Н NMR (CDCl3, 500 MHz), δ:
7.38 (br.s, 1 H, =CHβ); 7.20 (d, 1 H, J = 8.5 Hz); 7.14 (d, 1 H,
J = 8.5 Hz); 7.10 (br.s, 1 H); 6.59 (t, 1 H, J = 74.8 Hz); 5.42
(dd, 1 H, C(6)H, J = 4.2, 2.1 Hz); 4.61 (m, 1 H, C(3)H);
3.91 (s, 6 H); 2.87 (dd, 1 H, J = 15.9, 5.7 Hz); 2.43 (td, 1 H,
J = 14.0, 2.6 Hz); 2.39—2.29 (m, 2 H); 2.18 (dm, 1 H, J = 16.9 Hz);
2.04 (s, 3 H); 1.99 (dm, 1 H, J = 12.5 Hz); 1.91—1.53 (m, 8 H);
1.45—1.34 (m, 2 H); 1.20—1.06 (m, 2 H); 1.09 (s, 3 H); 0.98
(m, 3 H). MS, m/z (Irel (%)): 515 [M]+ (4), 455 (32), 454 (100),
214 (16), 213 (85), 212 (81), 187 (18), 145 (12), 107 (11), 105
(27), 91 (24), 81 (17).
References
1. Liquid Crystal Database, Version 3.1, LCI Publisher GmbH,
University of Gamburg (Germany), 1998.
2. V. G. Tishchenko, R. M. Cherkashina, L. N. Lisetskii, A. P.
Makhotilo, A. G. Kleopov, S. V. Shevchuk, in Obzornaya
informatsiya. Monokristally i osobo chistye veshchestva.
Kholestericheskie zhidkie kristally. Poluchenie, issledovanie,
primenenie [Review Information. Single Crystals and Specially
Pure Substances. Cholesteric Liquid Crystals: Preparation.
Investigation, Application], NIITEKhIM, Moscow, 1980,
67 pp. (in Russian).
3. V. Vill, F. Fischer, J. Thiem, Z. Naturforsch., 1988, 43a,
1119.
4. G. S. Chilaya, Fizicheskie svoistva i primenenie zhidkikh
kristallov s indutsirovannoi spiralґnoi strukturoi [Physical
Properties and Application of Liquid Crystals with Induced
Helical Structure], Metsniereba, Tbilisi, 1985, 88 pp. (in
Russian).
5. L. A. Kutulya, Proc. SPIE, 1997, 3488, 84.
6. P. Kirscha, T. Mergnerb, J. Fluorine Chem., 2006, 127, 146.
7. J. J. Park, S. Sternhell, S. C. Vonwiller, J. Org. Chem., 1998,
63, 6749.
8. L. A. Kutulya, in Funktsionalґnye materialy dlya nauki i
tekhniki [Functional Materials for Science and Technology],
Ed. V. P. Seminozhenko, Institute of Single Crystals,
National Academy of Sciences of Ukraine, Kharkov, 2001,
p. 381 (in Russian).
9. J. Lub, W. ten Hoeve, W. P. M. Nijssen, L. Diaz, R. T.
Wegh, Liq. Cryst., 2002, 29, 995.
10. L. A. Kutulya, A. I. Krivoshei, N. S. Pivnenko, N. I.
Shkolґnikova, Zh. Strukt. Khim., 2004, 45, 419 [J. Struct.
Chem. (Engl. Transl.), 2004, 45, 395].
Simulation of possible conformers of the studied structures
and the full optimization of their geometric parameters were
performed by the AM1 method accomplished in the MOPAC
6.0 program package. The starting structures for the optimization
were obtained using the program of model construction in
HyperChem 5.
Determination of the sign of the helical twisting power of
the CAd under study was carried out as described earlier.33 The
absolute values of the helical twisting power β induced by CAd
in the nematic solvent 5CB was determined using the ratio33
11. S. Superchi, M. I. Donnoli, G. Proni, G. P. Spada,
C. Rosini, J. Org. Chem., 1999, 64, 4762.
12. A. I. Krivoshey, L. A. Kutulya, V. V. Vashchenko, M. N.
Pivnenko, N. S. Pivnenko, A. S. Tolochko, V. I. Kulishov,
N. I. Shkolnikova, Proc. SPIE, 2003, 5257, 13.
β = (PTred•C•r)–1
,
(1)
13. A. I. Krivoshey, L. A. Kutulya, N. I. Shkolnikova, N. S.
Pivnenko, Proc. SPIE, 2004, 5507, 249.
where P is the pitch of the induced helix at the reduced temperaꢀ
ture (Tred), C is the CAd concentration expressed in mole fracꢀ
tions, r is the enantiomeric purity of the additive, which is equal
to 1 for the most part of natural products obtained by modificaꢀ
tion; Tred = 0.98•Ti (Ti is the isotropic transition temperature).
Selective light reflection spectra of the LC composites in the
nematics E63 and LCꢀ1289 were recorded on a Perkin—Elmer
Lambda 35 UV/VIS spectrometer. The planarꢀoriented LC
samples with a layer thickness of 10 μm were used. The helical
pitch (P) in the N*ꢀsystems was determined by the formula
14. I. M. Gella, N. S. Pivnenko, L. A. Kutulya, T. G. Drushlyak,
A. Yu. Kulikov, N. B. Novikova, Izv. Akad. Nauk, Ser. Khim.,
2005, 2331 [Russ. Chem. Bull., Int. Ed., 2005, 54, 2406].
15. T. G. Drushlyak, V. V. Abakumov, L. A. Kutulya, I. M.
Gella, S. V. Shishkina, N. S. Pivnenko, N. I. Shkolnikova,
O. V. Shishkin, Proc. XIV Intern. Symp. “Advanced Display
Technologies,” 2006, 103.
16. A. Krivoshey, N. Shkolnikova, N. Pivnenko, L. Kutulya,
Mol. Cryst. Liq. Cryst., 2006, 449, 21.
17. A. I. Krivoshei, N. S. Pivnenko, S. V. Shishkina, A. V. Turov,
L. A. Kutulya, O. V. Shishkin, Izv. Akad. Nauk, Ser. Khim.,
2006, 962 [Russ. Chem. Bull., Int. Ed., 2006, 55, 999].
18. M. J. P. Dewar, E. G. Zoebisch, E. F. Healy, J. J. P. Stewart,
J. Am. Chem. Soc., 1985, 107, 3902.
19. US Pat. 3163641; Сhem. Аbstrs, 1963, 62, 44124.
20. A. J. Pell, J. Keeler, J. Magn. Reson., 2007, 189, 293.
21. Obshchaya organicheskaya khimiya, 1, Stereokhimiya, ugleꢀ
vodorody, galogensoderzhashchie soedineniya [General Organic
Chemistry, 1, Stereochemistry, Hydrocarbons, HalogenꢀContainꢀ
ing Compounds], Ed. N. K. Kochetkov, Khimiya, Moscow,
1981, Section 2.1.5.1 (transl. from English).
P = λmax/n,
where n is the average refractive index of LC: n = 1.586 (see
Ref. 42) and 1.5 for E63 and LCꢀ1289, respectively.
The authors are grateful to Merck KGaA (Darmstadt,
Germany) for kindly presented nematic E63 and to the
Moscow Scientific Industrial Joint Enterprise “NIOPIK”
for kindly presented nematic LCꢀ1289.

Liquid crystals based on 16ꢀarylideneandrostenꢀ17ꢀone Russ.Chem.Bull., Int.Ed., Vol. 58, No. 5, May, 2009
1083
22. A. N. Vereshchagin, V. E. Kataev, A. A. Bredikhin, A. P.
Timosheva, G. I. Kovylyaeva, E. Kh. Kazakova, in Konforꢀ
matsionnyi analiz uglevodorodov i ikh proizvodnykh [Conforꢀ
mational Analysis of Hydrocarbons and Their Derivatives],
Ed. B. A. Arbuzov, Nauka, Moscow, 1990, p. 241 (in Russian).
23. G. M. Allan, H. R. Lawrence, J. Cornet, C. Bubert, D. S.
Fischer, N. Vicker, A. Smith, H. J. Tutill, A. Purohit, J. M.
Day, M. F. Mahon, M. J. Reed, B. V. L. Potter, J. Med.
Chem., 2006, 49, 1325.
24. L. A. Kutulya, R. M. Cherkashina, V. G. Tishchenko,
Yu. N. Surov, A. G. Polishchuk, Zh. Obshch. Khim. [J. Gen.
Chem. USSR], 1983, 53, 1655 (in Russian).
25. A. Hassner, T. C. Mead, Tetrahedron, 1964, 20, 2201.
26. Р. Baas, H. Cerfontain, Tetrahedron, 1977, 33, 1509.
27. N. S. Pivnenko, A. I. Krivoshey, L. A. Kutulya, Magn. Reson.
Chem., 2003, 41, 517.
33. F. G. Yaremenko, V. D. Orlov, O. A. Tsiguleva, T. V.
Khandrimailova, Zh. Obshch. Khim. [J. Gen. Chem. USSR],
1979, 49, 434 (in Russian).
34. O. Ya. Neiland, Organicheskaya khimiya [Organic Chemiꢀ
stry], Vysshaya Shkola, Moscow, 1990, 751 pp. (in Russian).
35. L. A. Kutulya, G. P. Semenkova, S. N. Yarmolenko, A. P.
Fedoryako, I. E. Novikova, L. D. Patsenker
, Kristallografiya
[Crystallography], 1993, 38, 183 (in Russian).
36. L. A. Kutulya, I. B. Nemchenok, T. V. Khandrimailova,
Kristallografiya [Crystallography], 1990, 35, 1234 (in Russian).
37. L. M. Yagupolґskii, Aromaticheskie soedineniya s ftorsoderzhaꢀ
shchimi zamestitelyami [Aromatic Compounds with Fluorineꢀ
Containing Substituents], Naukova Dumka, Kiev, 1988, 320 pp.
(in Russian).
38. L. Kutulya, V. Vashchenko, G. Semenkova, N. Shkolnikova,
T. Drushlyak, J. Goodby, Mol. Cryst. Liq. Cryst., 2001, 361, 125.
39. S. Dubey, D. P. Jindal, P. Piplani, Ind. J. Chem., 2005, 44B,
2126.
28. G. Gottarelli, G. P. Spada, Mol. Cryst. Liq. Cryst., 1985,
123, 377.
29. G. Proni, G. P. Spada, P. Lustenberger, R. Welti,
F. Diederich, J. Org. Chem, 2000, 65, 5522.
40. S. Sano, Y. Inoue, K. Ishigaki, M. Takatani, M. Kaji, T.
Okamoto, Mem. Fac. Agr. Kinki Univ., 1996, 29, 53; Сhem.
Аbstrs, 1996, 125, 168437.
41. M. I. Merlani, L. Sh. Amiranashvili, N. I. Menґshova, E. P.
Kemertelidze, Khim. Prirod. Soedin. [Chem. Nat. Compd],
2007, 81 (in Russian).
30. G. Gottarelli, G. P. Spada, in Topics in Stereochemistry, 24,
MaterialsꢀChirality, Eds M. M. Green, R. J. M. Nolte,
E. W. Meijer, John Wiley & Sons, New York, 2003, p. 425.
31. M. Bandini, S. Casolari, P. G. Cozzi, G. Proni, E. Schmohel,
G. P. Spada, E. Tagliavini, A. UmaniꢀRonchi, Eur. J. Org.
Chem., 2000, 491.
42. Liquid Crystal Mixtures for Electroꢀoptic Displays, Merck,
1994.
32. N. I. Shkolnikova, Ph. D. (Chem.) Thesis, Institute of
Single Crystals, National Academy of Sciences of Ukraine,
Kharkov, 2003, 139 pp. (in Russian).
Received August 12, 2008;
in revised form December 10, 2008