4
Tetrahedron
(S) as well as substrate tolerance toward bulky alcohols such as
1H, OH), 4.66 (dd, J = 6.0, 7.6 Hz, 1H, CH), 7.25–7.34 (m, 5 H,
ACCEPTED MANUSCRIPT
6a. They proposed that their variant has a cavity to accommodate
the phenyl group, which is responsible for the inversion of the
enantiopreference. However, this (S)-selective variant showed
low enantioselectivity for those substrates with small (1-2a) or
medium-sized (4a) substituents. Ema and co-workers reported
that a double mutant of BCL (Ile287Phe/Ile290Ala) could also
resolve bulky secondary substrates such as 6a.23, 24
Ph).
1
1-Phenyl-1-pentanol, rac-4a. Colorless oil (3.8 g, 83%). H
NMR (400 MHz, CDCl3): δ 0.88-0.90 (t, J=7.0, 3H, CH3), 1.25-
1.39 (m, 4H, CH2CH2), 1.70-1.81 (m, 2H, CHCH2), 1.86 (d,
J=2.4, 1H, OH), 4.63-4.67 (m, 1H, CH), 7.25-7.34 (m, 5H, Ph).
1
1-Phenyl-1-hexanol, rac-5a. Colorless oil, (1.2 g, 85%). H
NMR (400 MHz, CDCl3) δ 0.87 (t, J=7.0, 3H, CH3), 1.29–1.43
(m, 6H, (CH2)3CH3), 1.66–1.82 (m, 2H, CHCH2), 1.83 (br s, 1H,
OH), 4.64-4.68 (m, 1H, CH), 7.25–7.35 (m, 5H, Ph).
Here we reported that the two enzymes improved their
substrate scope by simply using them in liquid CO2. With this
interesting finding, it is promising that liquid CO2 could
positively improve the catalytic properties of other classes of
enzyme.
1
1-Phenyl-1-heptanol, rac-6a. Colorless oil (1.5 g, 90%). H
NMR (400 MHz, CDCl3) δ 0.87 (t, J = 6.8 Hz, 3H, CH3), 1.23–
1.43 (m, 8H, (CH2)4CH3), 1.66–1.84 (m, 2H, CHCH2), 1.86 (br s,
1H, OH), 4.66 (t, J = 6.6 Hz, 1H, CH), 7.25–7.35 (m, 5H, Ph).
4. Experimental
1
4.1. General
1-Phenyl-1-dodecanol, rac-7a. Clear crystal (2.8 g, 90%). H
NMR (400 MHz, CDCl3) δ 0.88 (t, 3H, J = 7.0 Hz, CH3), 1.25–
1.41 (m, 18H, (CH2)9CH3), 1.67–1.82 (m, 2H, CHCH2), 1.83 (d,
J=3.2, 1H, OH), 4.64-4.68 (m, 1H, CH), 7.24–7.36 (m, 5H, Ph).
Novozym 435 (CAL-B) was purchased from MIK Pharm Co.,
Ltd. (Japan), Amano Lipase PS-C was kindly donated by Amano
Enzymes, Inc. (Japan). Chemicals were purchased from Nacalai
Tesque, Inc., Wako Pure Chemical Industries, Ltd., Tokyo
Chemical Industry Co. Ltd., or Aldrich Chemical Co. and used
without further purification unless otherwise mentioned. Organic
solvents were dried over molsieve 4Å. Vinyl acetate was freshly
distilled and dried over molsieve 4Å before used.
α-Cyclopropylbenzyl alcohol, rac-8a. Colorless oil (1.9 g,
80%). 1H NMR (400 MHz, CDCl3) δ 0.37-0.65 (m, 4H, CH2CH2),
1.20-1.23 (m, 1H, CH(CH2)2), 1.97 (s, 1H, OH), 4.02 (d, 1H, J =
8.4 Hz, CH), 7.27-7.45 (m, 5H, Ph).
2-Methyl-1-phenyl-1-propanol, rac-9a. Colorless oil (2.9 g,
1
GC analysis was performed on a Shimadzu GC-2010 Plus
equipped with FID detector and a CP-Chirasil DEX CB column
(Varian, 25 m × 0.32 mm, 0.25 µm film thickness) or a DB-17
column (J&W Scientific; 25 m × 0.25 mm, 0.25 µm film
thickness) using He carrier gas (5 ml/min, head pressure: 274 kPa,
72%). H NMR (400 MHz, CDCl3) δ 0.79 (d, J = 6.8 Hz, 3H,
CH3), 1.00 (d, J = 6.4 Hz, 3H, CH3), 1,86 (s, 1H, OH), 1.96 (octet,
J = 6.8 Hz, 1H, CHCH3CH3), 4.35 (dd, J=3.2, 6,8 Hz, 1H,
CHOH), 7.24-7.35 (m, 5H, Ph).
o
injector: 180 C, detector: 180 oC,). TLC was carried out on
4.3. General procedure for preparation of racemic acetates (3-
9b) as authentic sample for chiral GC analysis
Kiesegel 60F254 (Merck) sheets; spots were visualized by UV
light (254 nm) or developed by treatment with 5% ethanolic
phosphomolybdic acid solution and heating of the dried plates.
1H NMR spectra were recorded at 400 MHz on a Bruker biospin
AVANCE III 400 spectrometer in CDCl3. The optical rotations
were measured with 10 cm path-length cells on a JASCO P-2200
Polarimeter.
In a typical reaction, acetic anhydride (500 µL, 5.3 mmol),
pyridine (200 µL) and triethylamine (4.0 mmol) were added
subsequently to a stirred solution of 1-phenylpentanol rac-4a
(492 mg, 3.0 mmol) in dichloromethane (2 mL) at room
temperature. The reaction was stirred for 24 h – 52 h at room
temperature, monitored by TLC. Dichloromethane (10 mL) was
added and the mixture was quenched with an addition of 1M aq.
HCl (2 mL). The aqueous layer was extracted with
dichloromethane (2 x 10 mL). The combined organic extracts
were neutralized and washed with saturated aq. NaHCO3 (5 mL)
and brine (10 mL), then dried over MgSO4 and filtered. The
organic solvent was concentrated under reduced pressure and the
residue was purified by silica gel column chromatography
(hexane/ethyl acetate, 3:1) to give corresponding acetate rac-4b.
The 1H NMR spectra of acetates 3b,24 4b,24 5b,24 6b,24 7b,26 8b,28
9b29 were all in agreement with those reported in the literature.
The experimental apparatus for dense CO2 reactions in the
batch reactor consisted of a CO2 gas cylinder, liquid CO2 pump
(Jasco, PU-2080-CO2), manometer (Taiatsu Techno, Osaka, 25
MPa or 35 MPa), stop valve (Swagelok, SS2NBS4), magnetic
stir (Koike, HE-16GA), thermostatic bath (Iuchi, TR1),
recirculation chiller (Eyela, CCA-1111), and 10 mL stainless
steel pressure-resistant vessel (Taiatsu Techno, Osaka, TVS-N2
type).
4.2. General procedure for preparation of racemic alcohols (3-
9a)
1
1-Phenylbutyl acetate, rac-3b. Colorless oil (0.4 g, 88%). H
For a typical reaction, NaBH4 (1.0 g, 26.8 mmol) was added to
a stirred solution of 1-pentanophenone (4.4 g, 26.8 mmol) in dry
methanol (30 mL). The exotherm was controlled by an ice bath.
The suspension was stirred at room temperature for 4 h,
monitored by TLC. After the reaction was quenched by an
addition of water (20 mL), the methanol was removed under
vacuum and the residue was extracted with ethyl acetate (3 x 30
mL). The combined organic phases were washed with brine (20
mL), dried over MgSO4 and then filtered. The organic solvent
was evaporated under reduced pressure and the residue was
purified by silica gel column chromatography (hexane/ethyl
acetate, 3:1) to give rac-4a (3.8 g, 83%). The 1H NMR spectra of
alcohols 3a,24 4a,24 5a,24 6a,24 7a,25 8a,26 9a,27 were all in
agreement with those reported in the literature.
NMR (400 MHz, CDCl3) δ 0.91 (t, J = 7.4 Hz, 3H, CH2CH3),
1.19–1.40 (m, 2H, CH2CH3), 1.69–1.78 (m, 1H, CHCH2), 1.85–
1.94 (m, 1H, CHCH2), 2.06 (s, 3H, COCH3), 5.74 (dd, J = 6.4,
7.6 Hz, 1H, CH), 7.25–7.36 (m, 5H, Ph).
1
1-Phenylpentyl acetate, rac-4b. Colorless oil (0.2 g, 80%). H
NMR (400 MHz, CDCl3) δ 0.87 (t, J 7.2 Hz, 3H, CH2CH3), 1.15–
1.37 (m, 4H, (CH2)2CH3), 1.72–1.78 (m, 1H, CHCH2), 1.86–1.94
(m, 1H, CHCH2), 2.06 (s, 3H, COCH3), 5.72 (dd, J 6.6, 7.4 Hz,
1H, CH), 7.25–7.33 (m, 5H, Ph).
1
1-Phenylhexyl acetate, rac-5b. Colorless oil (0.1 g, 89%). H
NMR (CDCl3, 400 MHz) δ 0.84-0.88 (m, 3H, CH2CH3), 1.24–
1.31 (m, 6H, (CH2)3CH3), 1.76–1.79 (m, 1H, CHCH2), 1.86–1.90
(m, 1H, CHCH2), 2.06 (s, 3H, COCH3), 5.72 (dd, 1H, J = 6.2, 7.8
Hz, CH), 7.27–7.35 (m, 5H, Ph).
1-Phenyl-1-butanol, rac-3a. Colorless oil (2.2 g, 87%). 1H
NMR (400 MHz, CDCl3) δ 0.93 (t, J=7.4 Hz, 3H, CH3), 1.26–
1.47 (m, 2 H, CH2CH3), 1.63–1.83 (m, 2H, CHCH2), 1.92 (br s,
1
1-Phenylheptyl acetate, rac-6b. Colorless oil (0.2 g, 81%). H
NMR (400 MHz, CDCl3) δ 0.86 (t, J = 7.0 Hz, 3H, CH2CH3),
1.21–1.31 (m, 8H, (CH2)4CH3), 1.75–1.79 (m, 1H, CHCH2),