592 Bull. Chem. Soc. Jpn. Vol. 80, No. 3 (2007)
Dehydroabietic Acid Esters as Chiral Dopants
ꢁ1
ꢅ
ꢅ
¼
the product as a white solid (99.0 mg, 0.315 mmol, 75.7%): mp
34
to induced helical structure (HTP 9 mm , MHTP 4{5
¼
62–62.8 ꢄC, ½ꢂꢆD þ54:4ꢄ (c 1.0, MeOH) (lit.: mp 63–64.5 ꢄC,
mmꢁ1 molꢁ1 kg). Although the relation between the ester struc-
ture and HTP seems complex, it is similar to that of the chro-
man derivatives, which also contain a carboxyl group on a qua-
ternary asymmetric carbon.7
20
½ꢂꢆD þ61ꢄ);19 1H NMR (200 MHz, CDCl3) ꢆ 7.16 (d, J ¼ 8:30
Hz, 1H), 6.99 (d, J ¼ 8:30 Hz, 1H), 6.88 (s, 1H), 3.66 (s, 3H),
2.97–2.70 (m, 3H), 2.43–2.11 (m, 2H), 1.97–1.35 (m, 10H), 1.27
(s, 3H), 1.22 (d, J ¼ 6:84 Hz, 6H); 13C NMR (100 MHz, CDCl3) ꢆ
16.48, 18.56, 21.69, 23.96 (2C), 25.08, 29.98, 33.45, 36.63, 36.93,
37.98, 44.84, 47.65, 51.87, 123.88, 124.11, 126.86, 134.68,
145.70, 146.91, 179.12; IR (KBr) 2930, 1718, 1496, 1251, 1176,
Experimental
Infrared spectra were recorded on a JASCO FT/IR 400 spec-
trometer. Melting temperatures were determined on Mel-Temp
melting point apparatus (Laboratory Devices, MA) and were re-
ported uncorrected. The measurement of 1H NMR spectra was
performed on Bruker AC300P and AC200, DPX400 spectrome-
ters, and EI-MS spectra were recorded on a JEOL DX303 spec-
trometer (Molecular Analysis and Life Science (MALS) Center,
Saitama University). Specific rotations were measured with a
JASCO DIP-370 polarimeter. The computations were performed
with MM2 (CAChe ver. 7.5)15 and MOPAC 2002 (AM1 &
PM3, CAChe ver. 7.5).10
822 cmꢁ1
.
ꢀ
Synthesis of Hexyl Dehydroabietate (3 ). General proce-
dure: A 30-mL, two-necked, round-bottom flask, equipped with
a magnetic stirring bar and a reflux condenser protected from
moisture by a CaCl2 drying tube, was charged with dehydroabietic
ꢀ
acid 1 (217 mg, 0.723 mmol). Thionyl chloride (2 mL) was added
in one portion, and the reaction mixture was heated at reflux for
3 h. Excess thionyl chloride was removed under reduced pressure.
The flask was flushed with nitrogen, and dry tetrahydrofuran
(THF, 2 mL), dry pyridine (500 mL), and then 1-hexanol (80.5 mg,
0.780 mmol) were added. After stirring at rt for 48 h, the salt was
removed by filtration, and the filtrate was concentrated under
reduced pressure to dryness. The residue was dissolved in ether,
and the solution was poured into a separatory funnel and washed
with water (15 mL ꢃ 2). The organic layer was dried over anhyd.
NaSO4. The solution was concentrated under reduced pressure to
dryness, and the residue was purified by chromatography (silica
gel, hexane:ethyl acetate = 4:1). The eluent was removed to ob-
ꢀ
Dehydroabietic Acid (DAA) (1 ). Dehydroabietic acid was
kindly supplied by Arakawa Chemical Industries Ltd. and purified
to >99% purity according to the literature:16 mp 170–171.5 ꢄC,
30
20
½ꢂꢆD þ61:8ꢄ (c 1.0, MeOH) (lit.: mp 170–171.5 ꢄC, ½ꢂꢆD þ62:5ꢄ,
c 2.0, 95% EtOH).7,12
Measurement of HTP and Handedness of the Induced
Chirality. The LC sample was prepared by adding 1 wt % of a
chiral dopant into the achiral host LC mixture ZLI-1132 (Merck).
The helical pitch of the chiral nematic phases were measured us-
ing wedge-shaped samples, contained between a convex lens and
a plane glass plate (Cano-wedge cell, tan ꢄ ¼ 0:0083, 0.0140,
0.0194, 0.0288, E. H. C. Ind., Ltd.,) by means of the resulting
Cano lines.11 All solvents were used as received except for dry
tetrahydrofuran and dry pyridine used in the synthesis of most
of the DAA esters.
The handedness of an induced helix was determined by the
contact method with the mixture of the achiral host LC and CN
(2 wt %), which is known to cause left handedness.1a
Crystal Structure Analysis of DAA (1 ). Data collection
was performed on a Bruker SMART CCD system (MALS Center)
1
tain a colorless oil (103 mg, 0.268 mmol, 34.4%). H NMR (300
MHz, CDCl3) ꢆ 7.17 (d, J ¼ 8:27 Hz, 1H), 7.00 (d, J ¼ 8:27 Hz,
1H), 6.88 (s, 1H), 4.01–3.99 (m, 2H), 2.95–2.70 (m, 3H), 2.42–
2.15 (m, 2H), 1.94–1.10 (m, 27H), 0.877 (t, J ¼ 6:80 Hz, 3H);
13C NMR (100 MHz, CDCl3) ꢆ 14.08, 16.33, 18.15, 22.96, 23.64,
23.95 (2C), 25.97, 26.09, 28.91, 30.35, 31.56, 33.58, 36.51, 37.05,
37.79, 43.69, 46.51, 60.89, 123.49, 125.04, 128.78, 132.56,
146.91, 153.05, 177.29; IR (neat) 2932, 1724, 1497, 1460, 1244,
32
1173, 822 cmꢁ1; ½ꢂꢆD þ26:9ꢄ (c 1.0, MeOH).
ꢀ
ꢀ
scribed in the general procedure, 4 (114 mg, 0.277 mmol) was
Synthesis of Octyl Dehydroabietate (4 ). Prepared as de-
ꢀ
obtained as colorless oil in 34.4% yield from 1 (241 mg, 0.803
ꢀ
mmol) and 1-octanol (105 mg, 0.808 mmol). H NMR (300 MHz,
with graphite monochromated Mo Kꢂ radiation (ꢅ ¼ 0:71069
1
˚
A) at 123 K. The linear absorption coefficient, (ꢁ), for Mo Kꢂ
was 0.071 mmꢁ1. The crystal structure was solved by a direct
method with SIR9717 and refined by full-matrix least-squares us-
ing SHLEXL9718 to a final reliability value of 0.0572. The non-hy-
drogen atoms were refined anisotropically while the hydrogen
atoms were located at geometrically calculated positions.
CDCl3) ꢆ 7.17 (d, J ¼ 8:07 Hz, 1H), 7.00 (d, J ¼ 8:07 Hz, 1H),
6.89 (s, 1H), 4.20–3.95 (m, 2H), 3.00–2.78 (m, 3H), 2.40–2.20
(m, 2H), 1.94–1.10 (m, 31H), 0.878 (t, J ¼ 6:60 Hz, 3H); IR (neat)
32
2925, 1723, 1497, 1467, 1245, 1174, 822 cmꢁ1; ½ꢂꢆD þ35:8ꢄ (c
1.0, EtOH). Found: C, 81.34; H, 11.03%. Calcd for C28H44O2:
C, 81.49; H, 10.74%.
Crystallographic data for DAA have been deposited with
Cambridge Crystallographic Data Centre: Deposition number
CCDC-299433 for DAA. Copies of the data can be obtained free
(or from the CCDC, 12, Union Road, Cambridge, CB2 1EZ,
UK; Fax: +44 1223 36033; e-mail: deposit@ccdc.cam.ac.uk).
ꢀ
general procedure, 5 (162 mg, 0.368 mmol) was obtained as col-
Synthesis of Decyl Dehydroabietate (5 ). Following the
ꢀ
ꢀ
orless oil in 32.7% yield from 1 (338 mg, 1.13 mmol) and 1-dec-
anol (179 mg, 1.13 mmol). 1H NMR (300 MHz, CDCl3) ꢆ 7.17 (d,
J ¼ 8:09 Hz, 1H), 7.00 (d, J ¼ 8:09 Hz, 1H), 6.88 (s, 1H), 4.20–
3.95 (m, 2H), 2.92–2.70 (m, 3H), 2.39–2.20 (m, 2H), 1.82–1.69
(m, 6H), 1.65–1.55 (m, 1H), 1.40–1.15 (m, 28H), 0.878 (t, J ¼
6:62 Hz, 3H); IR (neat) 2926, 1724, 1497, 1460, 1245, 1173,
ꢀ
Synthesis of Methyl Dehydroabietate (2 ). A 50-mL round-
bottom flask, equipped with a magnetic stirring bar and a reflux
condenser topped by a CaCl2 drying tube, was charged with dehy-
32
ꢀ
droabietic acid 1 (125 mg, 0.417 mmol). Methanol (20 mL) and
822 cmꢁ1; ½ꢂꢆD þ30:5ꢄ (c 1.0, EtOH). Found: C, 81.37; H,
conc. H2SO4 (5 drops) was added, and the reaction mixture was
heated under reflux for 24 h. The reaction mixture was concentrat-
ed under reduced pressure and diluted with ether (15 mL). The
mixture was washed with sat. NaHCO3 aq, water, brine, and dried
over anhyd. NaSO4. The solution was concentrated to dryness,
and the residue was purified by chromatography (silica gel, hex-
ane:ethyl acetate = 20:1). The eluent was concentrated to obtain
10.91%. Calcd for C30H48O2: C, 81.76; H, 10.97%.
Synthesis of Phenyl Dehydroabietate (6 ). Following the
ꢀ
general procedure, 6 (155 mg, 0.412 mmol) was obtained as a
ꢀ
ꢀ
colorless oil in 43.4% yield from 1 (269 mg, 0.897 mmol) and
phenol (89.3 mg, 0.949 mmol). 1H NMR (300 MHz, CDCl3) ꢆ
7.50–7.31 (m, 3H), 7.25–7.13 (m, 3H), 7.00 (d, J ¼ 8:09 Hz, 1H),
6.88 (s, 1H), 2.92–2.70 (m, 3H), 2.39–2.20 (m, 2H), 1.95–1.75 (m,