Development of a practical and efficient synthesis of SIPI-4884, a HMG CoA reductase inhibitor for the treatment of hypercholesterolemia

Article abstract of DOI:10.1021/op400060z

An improved process of the novel HMG CoA reductase inhibitor SIPI-4884 has been developed for early preclinical pharmacology and safety studies, and it was made up with an efficient nine-step and scalable process. Significant improvements in the nucleophi

Full text of DOI:10.1021/op400060z

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Full Paper
Development of a Practical and Efficient Synthesis of SIPI-4884, a HMG
CoA Reductase Inhibitor for the Treatment of Hypercholesterolemia
Qun Hao, Jing Pan, Yongjia Li, Zhengyan Cai, and Weicheng Zhou
Org. Process Res. Dev., Just Accepted Manuscript • DOI: 10.1021/op400060z • Publication Date (Web): 24 May 2013
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Development of a Practical and Efficient Synthesis
of SIPI-4884, a HMG CoA Reductase Inhibitor for
the Treatment of Hypercholesterolemia
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Qun Hao, Jing Pan, Yongjia Li, Zhengyan Cai, Weicheng Zhou*
State Key Lab of New Drug & Pharmaceutical Process, Shanghai Key Lab of Anti-Infectives,
Shanghai Institute of Pharmaceutical Industry, State Institute of Pharmaceutical Industry,
Shanghai 200437, China
ABSTRACT: An improved process of the novel HMG CoA reductase inhibitor SIPI-4884 has
been developed for early preclinical pharmacology and safety studies and it was made up with an
efficient nine-step and scalable process. Significant improvements in the nucleophilic
substitution, reduction, Witting-Horner reaction and preparation of calcium salt were
demonstrated. The overall yield was improved to 17.2%.
INTRODUCTION
Hypercholesterolemia is a well-known risk factor for atherosclerotic diseases, especially for
coronary heart disease.1 Currently, the most common method of treating hypercholesteromia is
the use of 3-hydroxy-3-methyl glutaryl-coenzyme A (HMG-CoA) reductase inhibitors, also
known as statins, including lovastatin, simvastatin, pravastatin, fluvastatin, atorvastatin,
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rosuvastatin and pitavastatin. Their mechanism of action is based on the reversible and
competitive inhibition of HMG-CoA reductase which is the rate-limiting enzyme of cholesterol
biosynthesis in the liver and nonhepatic tissues, ultimately resulting in up-regulation of the low
density lipoprotein (LDL) receptor in liver, clearing of LDL particles from the blood stream and
decreased levels of circulating cholesterol.2
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Figure 1: Structure of SIPI-4884
Our efforts in this area resulted in the identification of Calcium
(3R,5S,6E)-7-[6,7,8-trifluoro-4-(4-fluoro-phenylthio)-quinoline-3-yl]-3,5-dihydroxy-hept-6-enoa
te (SIPI-4884, 1) as a novel HMG CoA reductase inhibitor for the treatment of
hypercholesterolemia.3 Herein we describe the original synthesis used to prepare SIPI-4884 and
the optimization of the reaction conditions for this synthesis to support scale-up from laboratory
to pilot plant campaign and future preclinical pharmacology and safety studies.
RESULTS AND DISCUSSION
The synthesis utilized for the optimization and scale-up campaign is shown in Scheme 1,
wherein three key building blocks, ethyl 6,7,8-trifluoro-4-hydroxy-quinoline-3-carboxylate (2),
4-fluoro-thiophenol,
and
tert-butyl
(3R,5S)-6-oxo-3,5-dihydroxy-3,5-O-isopropylidene-hexanoate (8), are combined in an nine-step
sequence. The optimization focuses on three modest yield steps, including the second step
(nucleophilic substitution), third step (reduction) and sixth step (Witting-Horner reaction). In
addition, the other steps also require development.
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Scheme 1. Synthesis routes of 1
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Synthesis route in the first laboratory campaign
The optimized synthesis route
2.1 Preparation of ethyl 4-chloro-6,7,8-trifluoroquinoline-3-carboxylate (3)
This step in the preliminary procedure used excess phosphorylchloride about 10 equivalents
(equiv) as both chlorination reagent and solvent. The process was improved with toluene as
solvent and the amount of POCl3 was decreased to 1.5 equiv. The isolation yield was 80% after
recrystallization.
2.2 Preparation of ethyl 4-(4-fluoro-phenylthio)-6,7,8-trifluoroquinoline-3-carboxylate (4)
It was known that in general, the nucleophilic reaction was carried out in a polar aprotic
solvent in the presence of base4. The substitution of compound 3 with 4-fluoro-thiophenol was
conducted in N,N-dimethylformamide (DMF) with Et3N in the preliminary test and it was found
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that the main product was 4,7-disubstituted quinoline 13 (Table 1, entry 1). If the reaction
temperature was decreased to -15℃, the desired product 4 was obtained in very low yield after
7
8
9
column chromatography (Table 1, entry 2). Then with the low-polar solvent tetrahydrofuran
(THF) as solvent, a variety of bases including inorganic and organic, were screened, the product
was contaminated with byproduct 13. After column chromatography, product 4 was obtained
(Table 1, entries 3-8).
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When the reaction was carried out in DMF or dimethyl sulfoxide (DMSO) without base, no
desired product was found and the main spot was identified as the starting material 3 by thin
layer chromatography (TLC) (Table 1, entries 9-10). Surprisingly, the reaction went quite well in
a non-polar solvent dichloromethane in the absence of base, no resulting in formation of
compound 13, although a little of starting material 3 remained after nineteen hours reflux. We
reasoned that, because of the presence of HCl generated, it was difficult to drive the substitution
to completion without using any bases. Thus the distillation of about half of the solvent, which
took HCl away, was conducted after nineteen hours, and the reaction was continued for another
hour under reflux to complete the reaction with high yield 86% after recrystallization (Table 2,
entry 11).
The scale-up with 5.4 kg of compound 3 gave the better result (yield 91%, Table 1, entry 12).
During the distillation, the reaction went to the end without additional reflux.
Table 1. Screening of bases and solvents for the monosubstitution
entry solvent
base
Et3N
Et3N
Et3N
Time (h) yield (%)a
Temp (℃)
1
2
3
DMF
DMF
THF
20
1
1
4
70 b
30
-15
-15
38
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THF
THF
THF
THF
THF
DMF
4-Methylmorpholine -15
4
1
1
1
1
2
45
55
40
51
pyridine
K2CO3
Na2CO3
NaHCO3
—
-15
-15
-15
-15
-15
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c
c
10
DMSO
CH2Cl2
CH2Cl2
-15
2
—
—
—
11
reflux
reflux
19+1
19
86
91
12d
a Isolated yield
b yield of ethyl 4,7-di(4-fluoro-phenylthio)-6,8-difluoroquinoline-3-carboxylate (13)
c No desired product was found, the main spot was compound 3 by TLC.
d scale-up with 5.4 kg
2.3 Preparation of 4-(4-fluoro-phenylthio)-6,7,8-trifluoro-quinoline-3-methanol (5)
Several reducing agents were screened for the reduction of compound 4 and the results were
shown in Table 2. No product was found with LiAlH4 or NaBH4 (Table 2, entries 1-2). When
diisobutyl aluminium hydride (DIBALH, 4 equiv) was served, the yield of 5 was 52% after
purification by chromatography (Table 2, entry 3), meanwhile one over-reductive byproduct 14
was found (Table 4). It prompted us to reduce the amount of DIBALH. Finally, slight excess (2.2
equiv) was proved to be suitable (Table 2, entry 5) to avoid the impurity 14 with the yield 83%
after recrystallization by toluene and heptane.
Table 2. Screening of reducing agent for the reduction
entry Reducing agent
LiAlH4
Equiv of reductant yield (%)
a
1
0.5
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d
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NaBH4
1~4
DIBALH
DIBALH
DIBALH
DIBALH
4.0
2.5
2.2
2.1
52b
74b
83c
76c
46c
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ZnCl2/ KBH4(1:2) 1.25
a the reaction was complicated, so the product was not isolated
b Isolated yield after column chromatography
c Isolated yield after recrystallization
d The starting material remain
On the other hand, modest yield (46%) was received by using ZnCl2/KBH4 (1.25 equiv, Table
2, entry 7). Although the yield was lower than in DIBALH condition, ZnCl2/KBH4 provided an
alternative method to minimize the total cost (since the reagents were much cheaper than
DIBALH) and to avoid the potential risk related with DIBALH.
2.4 Preparation of
4-(4-fluoro-phenylthio)-6,7,8-trifluoro-3-(diphenyl-oxo-phosphonyl-methyl)-quinoline (7)
Bromination of compound 5 with PBr3 in dichloromethane gave
3-bromomethyl-4-(4-fluoro-phenylthio)-6,7,8-trifluoro-quinoline (6) in 90% yield, which was
used to the next step without any purification.
The phosphorylation of compound 6 was performed in reflux toluene with diphenyl
ethoxyphosphine (1.5 equiv). The yield of 7 was 95%.
2.5 Preparation of tert-Butyl (3R,5S,6E)-7-[4-(4-fluoro-phenylthio)-6,7,8-trifluoro-quinoline
-3-yl]-3,5-dihydroxy-3,5-O-isopropylidene-6-heptenoate (9)
In order to construct the E-olefine by the Wittig-Horner reaction of compound 7 with tert-butyl
(3R,5S)-6-oxo-3,5-dihydroxy-3,5-O-isopropylidene-hexanoate (8), a series of conditions were
tested and the data were shown in Table 3, from which lithium tetramethylpiperidine in THF was
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identified as the preferred base (Table 3, entry 1) although K2CO3 in DMF also produced an
acceptable yield (entry 6).
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Table 3. Screening of bases (1.5 equiv) and solvents for the Wittig-Horner reaction
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entry solvent
base
E:Z
yield a (%)
1
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8
THF
n-BuLi +tetramethylpiperidine 95:5 66
b
THF
n-BuLi
77:23
THF
n-BuLi+4-butylaniline
n-BuLi+HMDS
NaH
89:11 55
79:21 b
89:11 40
95:5 59
THF
THF
DMF
2-Me THF
K2CO3
n-BuLi +tetramethylpiperidine 90:10 60
b
b
CH3OCH(CH3)3 n-BuLi +tetramethylpiperidine
—
—
—
—
9
CH2Cl2
THF
n-BuLi +tetramethylpiperidine
10
n-BuLi +tetramethylpiperidinec 95:5 82f
a Isolated yield of E-form after silica gel chromatography (petroleum ether : EtOAc, 6 : 1)
b Unreacted
c 1.1 equiv of the base was used.
f Yield of E-form after crystallization.
After identifying the base and solvent, experiments on the stoichiometry of lithium
tetramethylpiperidine showed that 1.1 equiv of the base was optimal with a yield of 82% (Table
3, entry 10).
2.6 Preparation of calcium salt 1
In the first laboratory campaign, compound 9 was converted to lactone 10 by F3CCOOH
(TFA), the lactone 10 in THF was hydrolyzed to the corresponding carboxylate sodium salt at 0
℃ by saponification with NaOH aqueous solution, then HCl solution was added to adjust pH
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7-8, the solution was concentrated under reduced pressure to evaporate THF at 40℃, and CaCl2
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9
aq solution was added to generate calcium salt 1. In the process, especially during the
evaporation of THF, it was found that the product was contaminated with the Z-isomer.
Sometimes this impurity contributed 3-5 percentages determined by HPLC. This impelled us to
explore another method. In the optimized process, the deprotection of compound 9 with
hydrochloric acid instead of highly corrosive TFA generated a new intermediate tert-butyl
(3R,5S,6E)-7-[6,7,8-trifluoro-4-(4-fluoro-phenylthio)-quinoline-3-yl]-3,5-dihydroxy-hept-6-enoa
te (11, Scheme 1). Two choices were attempted to obtain the final product: acidic deprotection
from 9 to generated 11 first, and then basic hydrolysis from 11 and generation of calcium salt
were conducted in one pot. Alternatively, deprotection and hydrolysis were carried out in one pot,
then acidified to form the carboxylic acid 12, which was transferred to the calcium salt 1
(Scheme 1). The experiments showed that the purity of either 11 or 12 must be more than 98% in
order to assure the calcium salt 1 as an active pharmaceutical ingredient (API) with purity more
than 99%. The efforts of controlling the quality of 11 were unsatisfactory. The purity of 11
reached above 98% after recrystallization by ethanol, but the yield was 43%. The main
impurities were identified as the lactone 10 and carboxylic acid 12.
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So the second choice was adopted. Acid 12 was prepared from the acidic deprotection
followed by basic hydrolysis from 9 and recrystallized by ethanol with high purity (99%). The
calcium salt 1 was generated via the sodium salt from 12. An extensive screen of solvents for
recrystallization of the final product was made, it was found that calcium salt 1 was
recrystallized in 10% aqueous acetone with suitable solid form properties for downstream
processing and the purity of more than 99% by HPLC.
2.7 Impurity Control5
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Detection, identification, and control of impurities in the API are of primary importance during
the development of any drug candidate. Table 4 summarizes several impurities that have been
identified during the development process. 5-oxo product (19) was a main impurity detected in
the API stored more than 2 years, inferring the formation owing to oxidation. The
diastereoisomers were not found in API. All the impurities can be controlled effectively in the
process.
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Table 4. Impurity summary and control strategy
Structure
Common Name
Control Strategy
Comments
4,7-disubstituted Specified in 3 at Well controlled by the
product 13
NMT
0.1%, reaction
controlled
crystallization
monosubstituted
product
in
of
over-reductive
product 14
Controlled
crystallization
specifying
0.5% of 5.
in Reduce the amount of
by reducing agent
NMT
lactone 10
Hydrolysis in the This impurity was found
process in deprotection step.
ethyl ester 16
Hydrolysis in the This impurity was found
process
in crystallization of 12 by
ethanol and may be
converted to the final
product in the following
step..
Z-isomer 17
Specified in API at Most
NMT
controlled
Z-olefine
0.1%, controlled
in crystallization
was
by
after
crystallization of 1
Wittig-Horner reaction
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Enantiomer 18
Specified in API at
NMT
0.1%,
in
controlled
7
8
crystallization of 1
9
Diastereoisomer Specified in API at Diastereoisomers was not
10
11
12
13
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NMT 0.1%. detected in API.
19
5-oxo product 15 Specified in API at Generated by oxidation in
NMT
controlled
0.2%, the air.
in
The API must be storaged
in the absence of air.
crystallization of 1.
CONCLUSION
In summary, an efficient nine-step and scalable process was developed for the preparation of
SIPI-4884 (1). Significant improvements in the nucleophilic substitution, reduction,
Witting-Horner reaction and preparation of calcium salt were demonstrated. The reaction of 3
with 4-fluro-thiophenol was carried out in CH2Cl2 without base, the formation of disubstituted
by-product 13 was avoided and the yield of compound 4 was increased to 91% after
recrystallization. The reduction with DIBALH gave a yield of 83%, and the method by
ZnCl2/KBH4 might be cheaper and safer. The final product 1 was synthesized from carboxylic
acid 12, recrystallized by acetone-ethanol (8:1), and the yield and purity (HPLC>99%) were
much better than the result from other ways. The overall yield was improved to 17.2% (from
compound 2). A total 1.2 kg of API was produced for preclinical studies, utilizing the route
shown in Scheme 1.
EXPERIMENTAL SECTION
Melting points were determined on a capillary melting point apparatus and were uncorrected.
Nuclear magnetic resonance (NMR) spectra were recorded on a Varian INOVA-400
spectrometer with chemical shifts (δ) and coupling constants (J) given in ppm and Hz
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respectively relative to TMS as an internal standard. Mass spectra were recorded by an Q-TOF
Mass Spectrometer using electrospray ionization (ESI). Optical rotations were measured with a
Rudolph Autopol IV. Solvents and reagents were used without any pretreatment. Achiral HPLC
analyses were carried out on an Agilent 1100 series using Welch column (4.6 × 250 mm, 5µm)
with THF-methanol-buffer (0.02 M ammonium acetate, adjusted to pH 4.5 with acetic acid)
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o
13-48-39 as the mobile phase, 0.8 mL/min at 30 C with detection at 255 nm. HPLC retention
times: 2 = 6.85 min, 17 = 19.87 min, 15 = 20.37 min, 1 = 21.42 min, 19 = 23.31 min, 3 = 27.09
min, 5 = 29.06 min, 7 = 34.43 min, 16 = 43.19 min, 4 = 53.13 min. Achiral HPLC analyses of
compound 9 and 11 were carried out on an Agilent 1100 series using Welch column (4.6 × 250
mm, 5µm) with THF - buffer (0.02 M ammonium acetate, adjusted to pH 4.5 with acetic acid)
52-48 as the mobile phase, 1 mL/min at 30 oC with detection at 255 nm. HPLC retention times: 1
= 3.49 min, 9 = 7.84 min, 11 = 16.66 min. Chiral HPLC analyses were carried out on an Agilent
1100 series using CHIRALCEL AS-H column (4.6
×
250 mm, 5µm) with
o
hexane-ethanol-trifluoroacetic acid (80-20-0.1) as the mobile phase, 0.8 mL/min at 30 C with
detection at 255 nm. HPLC retention times: 18 = 6.81 min, 1 = 9.73 min. HPLC purity is
reported by area %.
Ethyl 4-chloro-6,7,8-trifluoro-quinoline-3-carboxylate (3). A suspension of ethyl
4-hydroxyl-6,7,8-trifluoroquinoline-3-carboxylate 2 (10.0 kg, 36.87 mol) in toluene (50 L) was
stirred while phosphorylchloride (8.49 kg, 55.35mol) was added at room temperature. After
addition, it was heated under refluxing for 2 h and became a clear solution. After concentrated
under reduced pressure, the residue was treated with ice water (20 L) and Na2CO3 (4.17 kg) to
adjust pH 8, then the solid was filtrated, and washed with water (3 × 8 L) and heptane (4 L) to
o
afford a off-white solid after drying at 80 C for 5 h. The obtained solid was charged into ethyl
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acetate (20 L) and heated to reflux for 20 min. The clear solution was cooled to 0-10 C, stirred
5
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for 5 h and the precipitated solid was filtrated and washed with ethyl acetate (3 L), then dried at
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60 ℃ for 10 h to furnish title compound 3 as a white acicular crystal (8.67 kg, 81.2% yield), mp:
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116-119 C, 1H-NMR (400MHz, CDCl3)
δ (ppm): 9.21(s, 1H), 8.01-7.96(m, 1H), 4.51(q,
J=7.2, 2H), 1.46(t, J=7.2, 3H), MS (ESI+) : m/z, 290.10 ([M+H]+).
Ethyl 4-(4-fluoro-phenylthio)-6,7,8-trifluoro-quinoline-3-carboxylate
(4).
Ethyl
4-chloro-6,7,8-trifluoro-quinoline-3-carboxylate 3 (5.4 kg, 18.7 mol) and 4-fluorophenthiol (2.5
kg, 19.2 mol) was dissolved in CH2Cl2 (50.0 L) at room temperature and the mixture was heated
to reflux for 19 h. Then the solution was concentrated to dryness, toluene (13 L) and heptane (8.7
L) were added to the residue, and the mixture was heated to reflux to give a solution. It was
cooled to 10 oC over 10 h. The solid was isolated by filtration, washed with a mixture of toluene
(3 L) and heptane (3 L), then washed twice with water (5 L) , washed twice with heptane, and
then dried for 10 h at 60 oC to afford the product 4 as a yellow solid (6.5 kg, 91.0%), mp
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131-133℃. H-NMR (400MHz, CDCl3) δ (ppm): 9.04 (s, 1H), 8.05-8.00 (m, 1H), 7.24-7.20(m,
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2H), 6.99-6.94(m, 2H), 4.30(q, 2H, J=7.2), 1.32(t, 3H, J=7.2), C NMR (100MHz, CDCl3) δ
(ppm): 165.2, 163.5, 161.0, 152.2, 149.6, 149.3, 147.3, 144.8, 142.7, 140.1, 137.2, 132.1, 130.7,
129.3, 124.6, 116.7, 107.0, 62.3, 13.9 (CDCl3), 77.3, 77.0, 76.7. MS (ESI+) : m/z, 382.05
([M+H]+).
4-(4-Fluoro-phenylthio)-6,7,8-trifluoro-quinoline-3-methanol (5). (DIBALH method) A
suspension of 4 (1500 g, 3.94 mol) in a mixture of toluene (6000 mL) was stirred at -5 oC while
the solution of DIBALH in toluene (1 M, 8.67 L, 8.67 mol) was added during 4 h under an
atmosphere of nitrogen. The solution was stirred at 0 oC for 3 h, then it was slowly poured into a
mixture of ice water (10L) and EtOAc (7.5 L), 6 M HCl (3.1 L) was added to adjust pH 4-5. The
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organic phase was separated, and the aqueous phase was extracted with ethyl acetate twice
(2×2.5 L). The combined organic phase was washed with water (3×2.5 L), dried over anhydrous
Na2SO4, filtered and washed with EtOAc (2 L), concentrated under reduced pressure to dryness.
The residue was crystallized with toluene (8100 mL) and heptane (5400 mL), and stirred at room
temperature for 10 h, and the solids were isolated by filtration, washed with 2 L of toluene and
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heptane (3:5), and dried at 60 oC for 10 h to give the title compound 5 as a yellow solid (1335 g,
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83.2% yield). mp：149-151 C。1H NMR(400 MHz, CDCl3)
δ (ppm): 9.14 (s, 1H), 8.00-7.95
(m, 1H), 7.07-7.03 (m, 2H), 6.95-6.91 (m, 2H), 5.04 (s, 2H), 2.26 (br, 1H), 13C NMR (100MHz,
CDCl3) δ (ppm): 190.1, 163.2, 160.7, 152.2, 150.7, 149.7, 147.2, 144.7, 141.9, 139.4, 139.3,
138.8, 136.1, 132.5, 131.3, 130.4, 129.4, 128.8, 125.6, 117.0, 116.7, 116.4, 109.5, 106.4, 62.6,
61.6, 44.6 (CDCl3), 77.3, 77.0, 76.7. MS (ESI+) : m/z, 340.20 ([M+H]+).
(ZnCl2/ KBH4 method) KBH4 (352.1 g, 6.52 mol), anhydrous ZnCl2 (445.0 g, 3.26 mol) and
THF (7 L) were charged into reactor at room temperature and stirred for 2 h. Compound 4 (1000
g, 2.63 mol) in toluene (10.5 L) were added to the above suspension. And then it was heated to
reflux for 3.5 h and cooled to room temperature. Some solid was removed by filtration. Ice water
(5 L) and EtOAc (5 L) was added to the filtrate, 6 M HCl (1750 mL) was added to adjusted pH
1. The organic phase was separated, the aqueous layer was extracted with EtOAc (2 ×2 L). The
combined organic phase was washed with saturated aqueous sodium hydrogen carbonate (5 L)
and water (2× 5 L), dried over anhydrous Na2SO4, filtered, washed with EtOAc (1 L) and
concentrated to dryness. After crystallization in toluene (3 L) and heptane (5 L), a yellow solid 5
(414.6 g, 46.6% yield) was given. mp: 148-150 ℃.
4-(4-fluoro-phenylthio)-6,7,8-trifluoro-3-(diphenyl-oxo-phosphonyl-methyl)-quinoline (7).
A solution of PBr3 (173 mL, 1.8 mol) in CH2Cl2 (2 L) was added to the mixture of 5 (520 g, 1.53
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mol) in CH2Cl2 (3 L) at 0 oC. The resulting mixture was stirred at room temperature for 2 h. The
solution was concentrated under vacuum to an oil, and then saturated Na2CO3 aqueous solution
was slowly added to adjust pH 7-8.6 The solids were filtrated, washed with water (3 ×1 L), and
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next reaction without any purification. H NMR (400 MHz, CDCl3)
δ (ppm): 9.04 (s, 1H),
8.00-7.90 (m, 1H), 7.13-7.10 (m, 2H), 6.98-6.93 (m, 2H), 4.91 (s, 2H), 13C NMR (100MHz,
CDCl3) δ (ppm): 163.3, 160.8, 152.2, 150.0, 147.5, 144.9, 142.4, 140.2, 136.8, 130.7, 129.3,
125.6, 117.1, 107.1, 32.5, 28.2 (CDCl3), 77.3, 77.0, 76.7. MS (ESI+) : m/z, 402.55 ([M+H]+).
6 (530 g, 1.32 mol) and diphenyl ethoxyphosphine (455.4 g, 1.98mol) were dissolved in
toluene (2650 mL). The solution was refluxed for 2 h during which time the precipitated solid
developed. The slurry was cooled to room temperature, heptane (1.3 L) was added and stirred for
5 h. The solid was isolated by filtration and washed with toluene (2×500 mL). After drying at 80
oC for 10 h, the desired product 7 as a white solid (655.7 g, 95.1% yield) was afforded, mp:
244-245 oC, 1H NMR(400 MHz, CDCl3)
δ (ppm): 8.83 (s, 1H), 7.76-7.73 (m, 5H), 7.54-7.50 (m,
2H), 7.46-7.41 (m, 4H), 6.91-6.83 (m, 4H), 4.28 (d, 2H, J=13.6 Hz), 13C NMR (100MHz,
CDCl3) δ (ppm): 162.8, 160.4, 152.1, 151.9, 149.5, 147.5, 144.8, 141.6, 140.7, 139.1, 163.0,
132.3, 132.0, 131.2, 131.1, 130.2, 129.7, 128.8, 125.5, 125.4, 116.8, 116.6, 107.1, 106.9, 35.5,
34.9 (CDCl3), 77.3, 77.0, 76.7. MS (ESI+) : m/z, 340.20 ([M+H]+).
.tert-Butyl
(3R,5S,6E)-7-[4-(4-fluoro-phenylthio)-6,7,8-trifluoro-quinoline
-3-yl]-3,5-dihydroxy-3,5-O-isopropylidene-6-heptenoate (9). 287.1 ml (0.84 mol) of 2.93 M
hexane solution of n-BuLi was added to a solution of 2,2,6,6-tetramethylpiperidine (129.4 g,
o
0.92 mol) in THF (4 L) at 0 C and the solution stirred for 1 h under an atmosphere of nitrogen.
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Then compound 7 (400 g, 0.76 mol) was added and stirred for 1 h at 0 C, the solution of
tert-butyl (3R,5S)-6-oxo-3,5-dihydroxy-3,5-O-isopropylidene-hexanoate (8) (258 g, 0.92 mol) in
THF (400 ml) was added to the reaction solution and stirred for 3 h at room temperature. The
solution was quenched with ice water (4 L), EtOAc (4 L) was added and the organic layer was
separated. The aqueous phase was extracted with EtOAc (2×1.2 L), the combined organic layer
was washed with water (3×1.2 L) and dried over sodium sulfate. The organic solvent was
removed via rotary evaporation, and then ethanol (1200 mL) and heptane (2400 mL) was added
and heated to reflux for 1 h, after which the solution was filtered hot. The filtrate was allowed to
cool to room temperature. The resulting slurry was stirred for 10 h and the solids were isolated
by filtration, washed with mixture of ethanol (150 mL) and heptane (300 mL), and dried at 60 oC
for 15 h to give the product 9 as a off-white solid (354.4 g, 82.3% yield), mp：133-135℃, [α]2D0
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=8.3 (c 1, CH2Cl2)。HPLC purity (area %)：99.42%。1H NMR (400 MHz, CDCl3) δ (ppm):
9.08 (s, 1H), 8.08-8.03 (m, 1H), 7.25 (d, 1H, J=16.0), 7.08-7.05 (m, 2H), 6.94-6.90 (m, 2H), 6.32
(dd, 1H, J=16.0, 5.4)，4.57-4.53 (m, 1H), 4.32-4.28 (m, 1H), 2.49-2.28(m, 2H), 1.67-1.21 (m,
17H), 13C NMR (100MHz, CDCl3) δ (ppm): 150.0, 163.1, 160.6, 152.3, 149.8, 149.3, 147.5,
144.9, 141.8, 139.2, 138.1, 131.1, 130.9, 129.9, 125.9, 125.7, 116.7, 116.5, 116.4, 106.7, 106.4,
99.1, 80.7, 69.4, 65.9, 42.5, 36.4, 30.0, 28.1, 19.6 (CDCl3), 77.3, 77.0, 76.7. MS (ESI+) : m/z,
564.20 ([M+H]+).
(3R,5S,6E)-7-[4-(4-fluoro-phenylthio)-6,7,8-trifluoro-quinoline
-3-yl]-3,5-dihydroxy-6-heptenoic acid (12). To a solution of compound 9 (350g, 0.62 mol) in
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THF (3.5L) was added dropwise 6 M HCl solution (700 mL) at 20-30 C, and stirred for 3 h.
NaOH (252 g, 6.3 mol) in water (800 mL) was added dropwise to the solution at 0 oC and stirred
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for 1 h. 6 M HCl solution (300 ml) was added to the reaction mixture at 0-5 C, EtOAc (3.5 L)
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was added and the organic layer was separated, the aqueous phase was extracted with EtOAc
(2×1 L). The organic layer was combined, washed with saturated NaCl aqueous solution (1 L),
water (2×1L) and dried over sodium sulfate, the solution was concentrated to dryness. Ethanol
(3.5 L) was added to the residue and heated to reflux for 1 h, after which the clear solution was
cooled at room temperature. The resulting slurry was stirred at room temperature for 10 h, and
the solid was isolated by filtration, washed with ethanol (300 mL), and dried in a vacuum oven at
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60 C for 15 h to afford the product 12 as a light yellow solid (244.1 g, 84.1% yield), mp :
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172-174 C, [α]2D0=30.4 (c 1, THF), HPLC purity (area %): 99.27%. H NMR(400 MHz,
DMSO-d6) δ (ppm) : 9.30 (s, 1H), 8.12-8.07 (m, 1H), 7.22-7.11 (m, 2H), 7.09-7.08 (m, 2H), 7.28
(d, 1H, J=15.6), 6.76 (dd, 1H, J=15.8, 5.2), 5.09-5.08 (m, 1H), 4.71 (m, 1H), 4.38 (m, 1H),
4.01-4.00 (m, 1H), 2.42-2.25 (m, 2H), 1.70-1.57 (m, 2H), 13C NMR (100MHz, DMSO-d6) δ
(ppm): 193.0, 162.6, 160.1, 151.4, 150.1, 148.9, 147.0, 144.4, 141.6, 140.9, 138.4, 136.2, 136.0,
134.9, 131.0, 130.1, 125.8, 123.3, 117.0, 116.8, 106.7, 68.9, 65.4, 56.3, 44.4, 42.7, 18.6 (CDCl3),
140.3-39.1. MS (ESI+): m/z, 468.10 ([M+H]+)
Calcium
(3R,5S,6E)-7-[6,7,8-trifluoro-4-(4-fluoro-phenylthio)-quinoline-3-yl]-3,5-dihydroxy-hept-6-e
noate (1). NaOH aqueous solution (21.6 g, 0.54 mol, 1.2 L ) was added to the slurry of
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carboxylic acid 12 (240 g, 0.51 mol) in water7 (2.4 L) at 0-10 C for 3 h to give the clear
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solution. 1 M HCl solution (ca. 30 mL) was added dropwise below 10 C and calcium chloride
aqueous solution (31.2 g, 0.28 mol, 200 mL) was slowly added to the sodium salt solution. After
stirring for 1 h, the precipitate was filtrated and then slurried with water (2 L) for 30 min,
filtrated again and washed with water (1 L). The resulting solid was dried in a vacuum oven at 60
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oC for 15 h to afford the crude product 1. Crude 1 (245 g) was suspended in a mixture of acetone
(1960 mL) and water (245 mL). When the mixture was heated to reflux to give solution,
activated charcoal (12 g) was added. After stirring 20 min, the hot solution was filtrated, washing
with acetone (200 ml). The filtered solution was cooled to 20 oC. The resulting slurry was stirred
for 24 h, then the solid was isolated by filtration, washed twice with a mixture of acetone (160
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mL) and water (20 mL).The solid was dried in a vacuum oven at 60 C for 15 h to afford the
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calcium salt 1 as a white solid (210.7 g, 84.3% yield), mp : 170 C decomposed, [α]2D0=26.4 (c 1,
DMF), HPLC purity (area %): 99.06%.IR (thin film): cm-1 3344.1, 2919.5, 1508.1, 1489.0,
1
1562.9, 1094.5, 829.4, 1231.9, 1395.5, 969.9. H NMR (400 MHz, DMSO-d6) δ (ppm): 9.25 (s,
1H), 8.06-8.02 (m, 1H), 7.27-7.07 (m, 5H), 6.77 (dd, 1H, J=16.4, 5.2), 4.42-4.44 (m, 1H),
3.96-3.94 (m, 1H), 2.24-2.06 (m, 2H), 1.66-1.52 (m, 2H), MS (ESI+) : m/z, 973.10 ([M+H]+),
Anal. Calcd For C44H32F8N2O8S2Ca: C, 53.3; H, 3.43; N, 2.82. Found: C, 53.01; H, 3.31; N 2.66
.
AUTHOR INFORMATION
Corresponding Author
*E-mail: profzhouwc@yahoo.com.cn
Notes
The authors declare no competing financial interest.
ACKNOWLEDMENTS
This work was supported by The National Basic Research Program (973 Program,
2012CB724501).
REFERENCES
(1) Grundy, S.M. Intern. Med. 1997, 241, 295-306.
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(2) Endo, A. J. Lipid. Res. 1992, 33, 1569-1582.
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(3) (a) Cai, Z.; Zhou, W.; Sun, L. Bioorg. Med. Chem. 2007, 15, 7809-7829. (b) Hao, Q.; Cai,
Z.; Pan, J.; Li, Y.; Xia, Y.; Min, Y.; Sheng,Y.; Zhou, W. Chem. Biol. Drug. Des. 2011, 78,
730-733. (c) Zhao, S.; Zhou, W.; Liu, J. Bioorg. Med. Chem. 2007, 17, 7915-7923.
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(4) Zhao, S.; Zhou, W. Syn. Commun. 2011, 41, 20-32.
(5) The synthesis of impurities see: (a) Hao, Q.; Cai, Z.; Pan, J.; Li, Y.; Zhou, W. Chin. J.
Pharm. 2010, 41, 884-890. The determination of the related substances see: (b) Li, Y.; Zhang, S.;
Hao, Q.; Cai, Z.; Zhou, W. Chin. J. Pharm. 2012, 43, 281-285.
(6) The HBr salt was generated after concentration, Na2CO3 solution was added to affor the
free base.
(7) The water used in this step is deionized water.
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