2
A. ÖZDEMIR ET AL.
O
OH
OH
O
O
Lactobacillus fermentum P1
O
O
O
O
+
D-optimal experimental design-based
optimization
1
(S)-2
(R)-2
Figure 1. Asymmetric bioreduction of 1-(benzo[d][1,3]dioxol-5-yl)ethanone (1) by Lactobacillus fermentum P1 using the D-optimal experimental design-based opti-
mization strategy.
have piperonyl rings, have been presented to have some Bellingham þ Stanley, ADP 220, polarimetry was used to meas-
[
11]
activities, such as anticancer and antiviral.
Moreover, syn- ure specific rotation. Reducing the ketone 1 with NaBH in
4
thetic molecules bearing piperonyl rings, such as anticonvul- MeOH synthesized a reference sample of the racemic alcohol.
sant, anticancer, antiamoebic, and antiproliferative, have NMR spectra were noted on 400 MHz spectrometer in CDCl3
[
12–15]
enarmous biological activity.
Synthesis of various com- using TMS as internal standard. (S)-1-(1,3-Benzodioxol-5-yl)e-
[17]
1
pounds with piperonyl rings has been reported. However,
there are not many studies involving the asymmetric reduc-
tion of prochiral ketones containing the piperonyl ring to
chiral secondary alcohols using chemical or biocatalysts.
Asymmetric reduction of piperonyl methyl ketone (1) in the
presence of the chemical catalyst paracyclophane-ruthenium,
R)-1-(1,3-benzodioxal-5-yl)ethanol ((R)-2) was obtained in
4% yield and 90% enantiomeric excess (ee).
is only one research study in the current literature, including
asymmetric reduction of 1 using a biocatalyst, and in this
study, the synthesis of (R)-2 was performed with 99% ee
and 89% yield, and the classical optimization technique was
thanol (S)-2:
Colorless oil, yield 91%, H NMR (400 MHz,
CDCl ) d ¼ 6.89-6.75 (m, 3H), 5.94 (s, 2H), 4.81 (q, J¼ 6.4 Hz,
3
1
3
1
(
1
(
H), 1.82 (bs, 1H, (OH)), 1.45 (d, J¼ 6.4 Hz, 3H); C NMR
100 MHz, CDCl ) d ¼ 148.0, 147,1, 140.2, 118.9, 108.3, 106.3,
3
20
D
01.1, 70.5, 25.4; [a]
¼ ꢁ46.4 (c 1.0, CHCl ), ee >99%;
3
20
[17]
lit[a]D ¼ þ46.5 (c 1.0, CHCl , %99 ee for R enantiomer)
;
3
(
9
HPLC, Chiralcel OD column, n-hexane/i-PrOH, 95:5, flow rate
of 1.0mL/min, 210nm, t (S) 17.7, t (R) 18.9min. The HPLC
[
16]
So far, there
R
R
condition of substrate 1: Chiralcel OD column, n-hexane/i-
[
17]
used.
Generally, each parameter is tested independently
Conditions of bacterial strain and culture condition
in the classical optimization technique. Also, mathematical
model methods can be used to optimize reaction conditions.
It has been shown that the mathematical model methods are
preferable over the conventional optimization methods with
respect to reaching results quickly, easy optimization, multi-
factor interactions, cheaper, and the use of statistical evalu-
In this study, Lactobacillus fermentum P1 as a biocatalyst
was used for the bioreduction, and this strain was previously
[21]
isolated from fermented product koumiss.
The isolation,
drying, and storage conditions of the bacteria were carried
[17]
out previously reported in the literature.
[
18]
ation.
Examples of successful application of mathematical
methods with different substrates and biocatalysts have been
reported in the literature.
This study offers an optimization technique with a D-
optimal experimental design for the production of the corre-
sponding chiral alcohol by reducing the prochiral ketone
[
19,20]
General procedure for the synthesis of
(
S)-1-(1,3-Benzodioxol-5-yl)ethanol
Lactobacillus fermentum P1 (25 mg) was added to a suspen-
sion of freshly MRS broth (100 mL). The mixture was stirred
1
-(benzo [d] [1,3] dioxol-5-yl) ethanone (1) using the
ꢀ
in an orbital shaker (193 rpm) at 26.5 C for 2 hours. Note
freeze-dried whole-cell of L. fermentum P1 as a safe Lactic
Acid Bacteria (LAB) to obtain high conversion and ee
that the pH of the reaction medium was arranged to 6.20
using 1 M HCl. Also, the mixture was stirred for a further 2 h
under the same conditions. Further, 1 mmol substrate 1 was
(Figure 1). To the best of our knowledge, this is the first
paper to find the optimum reaction conditions to the asym-
metric bioreduction of 1-(benzo[d][1,3]dioxol-5-yl)ethanone
ꢀ
included in the mixture and stirred at 193 rpm, at 26.5 C for
30 h, and culture supernatant was obtained. Filtrates were
(1) while using the proposed optimization method.
removed with CH Cl (3 ꢂ 125 mL) from the culture super-
2
2
natant. The extracts were dried over Na SO and then a vac-
2
4
uum was used to evaporate them. Then, the crude product
was cleansed by column chromatography with hexane: ethyl
acetate (90:10) solvent mixture and characterized by NMR
analysis. Next, the product was specified for the absolute con-
figuration by comparing their optical rotational values from
the literature. Conversion of the substrate was determined by
Materials and methods
General
All solvents, chemicals, and culture medium (MRS) were
obtained from commercial suppliers in high purity. The reac-
tions were controlled by TLC using hexane: ethyl acetate
(
90:10) as mobile phase. (S)-2 was cleansed by column chro- filtering a small amount of crude product through a small col-
matography charged with silica-gel using hexane: ethyl acetate umn having silica gel. Further, the obtained product was ana-
90:10) solvent mixture. Enantiomeric excess was determined lyzed on a chiral OD column and compared the ketone peak
from a chiral HPLC analysis on an Agilent 1260 system with the alcohol peaks. The ee was calculated by HPLC ana-
equipped by using UV and chiral detector. lysis using a chiral OD column.
(