Construction of a series of intermediates in the β-oxidation pathway from THA to EPA via DHA in free acid form

Article abstract of DOI:10.1016/j.bmc.2018.07.004

β-Oxidation of most fatty acids occurs in the mitochondria. However, β-oxidation for ω-3 polyunsaturated fatty acids (PUFAs) is distinct from abundant fatty acids and occurs in the peroxisomes. Since little is known about peroxisomal β-oxidation, here we report the synthesis of proposed intermediates of ω-3 PUFA β-oxidation steps in free fatty acid form having a conjugated double bond, a β-hydroxyl group, a β-olefin and a β-carbonyl group. These fatty acids can serve as authentic samples for biological experiments.

Full text of DOI:10.1016/j.bmc.2018.07.004

Bioorganic&MedicinalChemistryxxx(xxxx)xxx–xxx
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Bioorganic & Medicinal Chemistry
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Construction of a series of intermediates in the β-oxidation pathway from
THA to EPA via DHA in free acid form
Satoshi Kanamori, Hiroaki Ishida, Keiko Yamamoto, Toshimasa Itoh⁎
Laboratory of Drug Design and Medicinal Chemistry, Showa Pharmaceutical University, 3-3165 Higashi-Tamagawagakuen, Machida, Tokyo 194-8543, Japan
A B S T R A C T
β-Oxidation of most fatty acids occurs in the mitochondria. However, β-oxidation for ω-3 polyunsaturated fatty acids (PUFAs) is distinct from abundant fatty acids
and occurs in the peroxisomes. Since little is known about peroxisomal β-oxidation, here we report the synthesis of proposed intermediates of ω-3 PUFA β-oxidation
steps in free fatty acid form having a conjugated double bond, a β-hydroxyl group, a β-olefin and a β-carbonyl group. These fatty acids can serve as authentic samples
for biological experiments.
1. Introduction
shunt or in the retroconversion of EPA in mammals. However, these
intermediates can be proposed on the basis of two other pathways.
Reaction mechanisms in the mitochondrial β-oxidation pathway are
well known in other unsaturated fatty acids and the metabolic pathway
of DHA to EPA in yeast is known.11 It is thought that oxidation in
Eicosapentaenoic acid (EPA, C20:5n-3) and docosahexaenoic acid
(DHA, C22:6n-3) are representative ω-3 polyunsaturated fatty acids
(PUFAs) (Fig. 1).
These PUFAs and their oxidized metabolites are important research
subjects in nutrition, metabolomics, molecular biology, cell biology,
and medicine,1–5 etc. The oxidation of EPA and DHA is catalyzed by
lipoxygenase, cyclooxygenase6 or cytochrome P4507 for the synthesis
of chemical mediators such as leukotrienes, prostaglandins, pro-
resolvins mediators and neuroprotectins.6–10 Additionally, β-oxidation
is fundamental for life, maintaining homeostasis by producing energy.
In mammals, β-oxidation takes place in mitochondria, with some ex-
ceptions.
mammals also passes through a similar pathway. The proposed
pathway is shown in Scheme 2. THA-CoA is dehydrogenated to afford
α,β-unsaturated-THA-CoA (1-CoA). The conjugated olefin is hydrated
to afford β-hydroxy compound 2-CoA. Next, the β-hydroxyl group of 2-
CoA is further oxidized to afford β-keto compound 3-CoA, and the α-
carbon of the β-keto ester is cleaved to generate DHA-CoA. The retro-
conversion pathway to EPA contains additional reactions because this
pathway occurs via the highly conjugated compound 4-CoA. DHA-CoA
is dehydrogenated to afford 4-CoA. The highly conjugated 4-CoA is
then reduced to 5-CoA. The deconjugated 5-CoA is converted to con-
jugated ester 6-CoA and hydration of the conjugated olefin affords 7-
CoA. The β-hydroxyl group is further oxidized to afford 8-CoA, in which
the α -carbon of the β-keto ester is then cleaved to generate EPA-CoA.
Herein, we report the syntheses of seven PUFAs in their free fatty
acid forms (Fig. 2), which are predicted to be peroxisomal β-oxidation
intermediates from THA to EPA via DHA in mammals. In this paper, we
β-Oxidation for ω-3 PUFAs occurs in peroxisomes for the synthesis
of DHA and its retroconversion to EPA (Scheme 1).11
Although ω-3 PUFAs have recently been trending in lipid research,
reports of peroxisomal β-oxidation are far fewer than those of mi-
tochondrial β-oxidation. Scheme 1 shows the synthetic pathway for
EPA and DHA by peroxisomal β-oxidation. EPA-CoA is converted to
docosapentaenoyl-CoA (DPA-CoA, C22:5n-3) by elongase. Due to the
lack of Δ4-desaturase in mammals,12 there is an indirect route for the
synthesis of DHA, the so called Sprecher’s shunt.13,14 In this route, DPA-
CoA, C22:5n-3 is converted to tetracosahexaenoyl-CoA (THA-CoA,
C24:6n-3) by elongase and Δ6-desaturase, and then acetyl-CoA is
cleaved off by β-oxidation to afford DHA-CoA. EPA-CoA is then bio-
synthesized by β-oxidation of DHA-CoA. In the liver, there has been a
report that the rate of retroconversion of DHA to EPA is 20% in a study
using tritium labeled DHA.15
Fig. 1. Structures of representative ω-3 PUFAs.
No β-oxidation intermediates have been reported via Sprecher’s
⁎
Corresponding author.
E-mail address: titoh@ac.shoyaku.ac.jp (T. Itoh).
https://doi.org/10.1016/j.bmc.2018.07.004
Received 8 June 2018; Received in revised form 30 June 2018; Accepted 3 July 2018
0968-0896/©2018ElsevierLtd.Allrightsreserved.
Pleasecitethisarticleas:Kanamori,S.,Bioorganic&MedicinalChemistry(2018),https://doi.org/10.1016/j.bmc.2018.07.004

S. Kanamori et al.
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show several synthetic approaches for obtaining the complete perox-
14 was achieved in 43% yield over 2 steps (Scheme 4).
isomal β-oxidation intermediates of ω-3 PUFAs.
Using Dess-Martin periodinane, aldehydes 16 (97%) and 18 (83%)
were prepared from alcohols 15 and 17, respectively (Figs. S1 and S2).
Wittig reactions were performed with ylide 9 using LHMDS as a
base in THF with and without HMPA (Scheme 5). Ester 19 was obtained
in 28% yield from 9 and aldehyde 16. In the presence of HMPA, the
yield was only slightly increased (30%). In the case of 20 from 9 and
18, the yield of the Wittig reaction was 22% without HMPA, but 53% in
the presence of HMPA. Esters 19 and 20 were treated with 5% KO-
H-iPrOH/H2O to give target DHA isomer 5 in 97% yield and 6 in
quantitative yield, respectively.
2. Results and discussion
Since the synthesis of skipped Z olefins requires sensitive reactions
and multiple steps, we planned to use EPA and DHA esters, which are
abundant resources and easy to obtain.
2.1. Synthesis of β-olefinic acids
Ester 21 was obtained by coupling of ylide 14 and (E)-ethyl-4-ox-
obut-2-enate (28% yield). In addition, since three Wittig reactions
proceeded with multiple byproduct, we couldn’t isolate E isomers for
19, 20 and 21.
We synthesized isomers of DHA 5 and 6 and docosaheptaenoic acid
4 as follows. In our previous study, phosphorous ylide 9 was synthe-
sized via iodolactonization and glycol cleavage using EPA as the
starting material (Scheme 3).16
It should be noted that 1,4-adducts were obtained when MeOH was
used as the solvent in the hydrolysis of conjugated PUFA esters, thus
iPrOH was used as the solvent.17 Accordingly, highly conjugated ester
21 was treated with 5% KOH-iPrOH/H2O to provide docosaheptaenoic
acid (4) in 35% yield. When the reaction was monitored by TLC, same
products appeared, which were thought to contain 1,4- or 1,6-conjugate
In order to synthesize 4, we first synthesized phosphorous ylide 14
from DHA as the key intermediate. Iodolactonization of DHA afforded
lactone 10.16 Lactone 10 was treated with KOH-MeOH aq. to afford glycol
11 and subsequent glycol cleavage was accomplished by NaIO4 and
NaBH4 to give alcohol 12 in 33% yield for the 3 steps. After bromination
of alcohol 12 (quant), followed by treatment with PPh3, synthesis of ylide
Sprecher’s shunt
retroconversion
Scheme 1. Biosynthetic pathway of EPA and DHA.
Scheme 2. β-Oxidation of THA to EPA via DHA.
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Fig. 2. Structures of the target compounds.
Scheme 3. Preparation of phosphorus ylide 9 via iodolactonization.
Scheme 4. Preparation of phosphorus ylide 14 via iodolactonization.
Scheme 5. Synthesis of DHA isomer 5 and 6.
Scheme 6. Synthesis of docosaheptaenoic acid (4).
adducts. We thought that the conjugation reactions could be suppressed
by using tBuOH, which is bulkier than iPrOH. As expected, using tBuOH
as a solvent, we succeeded in improving the yield to 50% (Scheme 6).
2.2. Racemic synthesis of β-hydroxyl acids 2 and 7
We planned to synthesize β-hydroxyl acids 2 and 7 in racemic form
in order to provide standard samples for the asymmetric synthesis and
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Scheme 7. Synthesis of ( )-β-hydroxyl acid 2.
Scheme 8. Synthesis of ( )-β-hydroxyl acid 7.
for the synthesis of achiral β-keto acids. The β-hydroxyl group was
constructed using the Reformatsky reaction,18 as follows. Aldehyde 22,
prepared from DHA ethyl ester, was treated with Zn and ethyl bro-
moacetate to give ( )-23 in 90% yield. Treatment of ( )-β-hydroxyl
ester 23 with 5% KOH-MeOH/H2O gave ( )-2 in 90% yield (Scheme
7).
Table 1
Results of ligand screening for asymmetric β-boration.
Likewise, β-hydroxyl ester ( )-25 was produced from aldehyde
2419 derived from EPA ethyl ester (65% yield) and then treated with
5% KOH-MeOH/H2O to obtain ( )-7 in 96% yield (Scheme 8).
Entry
Ligand
mol%
2 steps yield (%)
ee of 25 (%)a
1
2
3
4
5
6
7
8
9
(R)-(S)-Josiphos
(R)-Segphos
(R,R)-Quinoxaline
(R,R)-Trost ligand
(S)-Bis(oxazoline)
MacMillan’s cat
Cinchonidine
No
10
10
10
10
10
10
10
0
37
60
7
62
84
56
16
16
34
–
–
–
0
2.3. Asymmetric synthesis of β-hydroxyl acids 2 and 7
We planned to perform the asymmetric synthesis of 2 and 720 as in
the peroxisomal β-oxidation. However, the stereochemistry of the hy-
droxylation reaction in the metabolic pathway of DHA and THA has not
yet been clarified. Furthermore, there are no examples to introduce a
hydroxyl group stereoselectively to the β-position of a fatty acid.
Therefore, the asymmetric synthesis was conducted with reference to
the β-boration reaction, which is an asymmetric reaction applied to
non-aromatic substrates.21 The stereoselectivity was introduced with β-
boration by 1,4-addition to the α,β-unsaturated ester 20, and the de-
sired compound was obtained by a two-step reaction in which the β-
hydroxyl form was obtained by oxidation using Bpin with retention of
configuration (Scheme 9).
Screening results of the ligands (Fig. S1) for this reaction are shown
in Table 1. The reaction with josiphos catalyst was the best to achieve
stereoselectivity in (R)-25 at 84% ee (entry 1). Other ligands were
moderate or poor in selectivity (entries 2–7). This result was sufficient
to determine the absolute configuration of 7. In order to confirm that
the reaction occurred by contribution of this phosphine ligand, we
21
Trace
Trace
Trace
42
PPh3
10
a
Determined by chiral HPLC.
carried out two reactions with no ligand and with PPh3 (entry 8, 9). It
was found that the phosphine ligand was necessary for the reaction
progress.
We determined the absolute configuration by applying the new
Mosher method (Fig. 3, Fig. S3),22 and the enantiomeric excess of 25
was measured by HPLC using a chiral column (Fig. S2). As expected
from the literature, the R form was obtained.
Next, we attempted the asymmetric β-boration of α,β-unsaturated
methyl ester 2923 (Scheme 10). Treatment of 29 with B2pin2, (R)-(S)-
josiphos, NaOtBu and MeOH gave 30 in 64% yield, which was oxidized
Scheme 9. Enantioselective synthesis of (R)-β-hydroxyl acid 7 using asymmetric β-boration.
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Fig. 3. Determination of absolute configuration.
to afford (R)-31 in 95% yield and 83% ee as determined by 1H NMR
analysis (Fig. S3).
Table 2
Optical yield of product (% ee).
We investigated the effect of the esters on the resulting en-
antiomeric excess by comparing methyl and ethyl esters of 1 and 6
under the conditions of entry 1, Table 1. When the ethyl ester of 6 was
used as a substrate (20), the optical yield was 84% ee. With the methyl
ester as a substrate (34), the optical yield was 9% ee (Fig. S4, Table 2).
In contrast, when the ethyl ester of 1 was used as a substrate (38), the
optical yield was almost a racemic mixture (3% ee), but with methyl
ester 29 as a substrate, the optical yield was 87% ee. (Fig. S5, Table 2).
The reason for this selectivity is unclear as yet. This experiment is the
first successful application of asymmetric synthesis using an un-
saturated fatty acid as a substrate.
Substrate
R = Me
9a)
R = Et
84b)
83a)
3a)
Determined by 1H NMR using diastereomer of MTPA ester.
Determined by chiral HPLC using 25. It is because peaks of diastereomers
a)
b)
of MTPA ester were overlapped in 1H NMR chart.
the yield was improved (from 32% to 72%). In addition, we found that
these β-keto acids were unstable and should be treated at less than
35 °C, otherwise a decarboxylated product was produced, which was
observed by 1H NMR.
2.4. Synthesis of β-keto acids 3 and 8
We then attempted the synthesis of β-keto acids 3 and 8. The first
synthetic strategy for target β-keto acid 3 is shown in Scheme 11. The
hydroxyl group of ester 23 was oxidized by Swern oxidation to obtain
β-keto ester 42 in 47% yield. Hydrolysis of ester 42 under various
conditions using LiOH or Lipase PS did not proceed.
For the second approach, we hydrolyzed the β-hydroxyl ester to the
acid and examined the oxidation reaction of the β-hydroxyl group.
Compound 3 could not be obtained under any conditions (Dess–Martin,
Jones, Parikh-Doering oxidations). It was considered that the β-keto
carboxylic acid was unstable under these conditions. Therefore, we
protected the β-keto group of 42 by an acetal to afford 43 in 50% yield
(Scheme 12). Treatment of acetal-protected ester 43 with 5% KOH-
MeOH/H2O gave 44 (87% yield). Acetal 44 was deprotected under mild
conditions using CBr4 and PPh3 to obtain 3 in 67% yield.24
In the synthesis of β-keto acid 8 (Scheme 13), 47 was prepared by
the same synthetic route. However, the yield of 8 was only 32% in the
deprotection step due to the difficulty of separating it from triphenyl-
phosphine oxide. Thus, we attempted to use tris(2-carboxyethyl)phos-
phine hydrochloride (TCEP·HCl), which is a water-soluble phosphine
reagent used in molecular biology as a reducing agent. As a result, the
phosphine oxide of TCEP was removed by a simple extraction step and
3. Conclusion
We achieved the construction of proposed intermediates in the β-
oxidation pathway from THA to EPA via DHA. First, we synthesized
three β-olefinic acids. At the hydrolysis step, we found that bulky
tBuOH solvent suppressed byproducts, which resulted in increased
yields. Second, asymmetric syntheses of β-hydroxyl acids were
achieved by asymmetric β-boration-oxidation reactions. These synth-
eses are the first examples of the β-boration applied to unsaturated fatty
acids. Third, we synthesized β-keto acids, which were found to be un-
stable. To solve this problem, the β-keto carboxyl group was protected,
the ester moiety was hydrolyzed, and then the acetal group was de-
protected with CBr4 and PPh3. Furthermore, the yield was improved
using a water-soluble phosphine, TCEP.
These intermediates are potential β-oxidized metabolites in per-
oxisomes. We expect these compounds to be valuable in leading to the
elucidation of mechanisms in vivo. Moreover, information on diseases
that cause abnormalities in the involved enzymes, such as peroxisome
disease, may be obtained. Since these synthetic intermediates have
Scheme 10. Enantioselective synthesis of (R)-β-hydroxyl acid 2 using asymmetric β-boration.
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Scheme 11. Attempted from 23 to 3.
Scheme 12. Synthesis of β-keto acid 3.
Scheme 13. Synthesis of β-keto acid 8.
their own characteristics, e.g., conjugated double bonds, β-hydroxyl
groups, β-olefins, β-carbonyls, their biological activities may be dif-
ferent.
4.2. Synthesis
4.2.1. (3Z,6Z,9Z,12Z,15Z)-Octadeca-3,6,9,12,15-pentaen-1-ol (12)
A solution of 10 (4.00 g, 8.81 mmol) in 5% KOH/MeOH–H2O (19:1,
20 mL) was stirred at 60 °C for 3 h. The reaction mixture was acidified
with 1 N aqueous HCl and then extracted with ethyl acetate. The or-
ganic layer was washed with water, dried, and evaporated. The crude
product in THF/H2O (2:1, 24 mL) was added NaIO4 (4.67 g,
13.21 mmol) and the mixture was stirred at 0 °C for 1 h. The mixture
was extracted with ethyl acetate. The organic layer was washed with
water, dried, and evaporated. The residue was solved in MeOH (20 mL)
and treated with NaBH4 (1.65 g, 43.70 mmol) at 0 °C for 2 h. The re-
action was quenched with water at 0 °C and then extracted with ethyl
acetate. The organic layer was washed with water, dried over MgSO4,
and evaporated. The residue was chromatographed on silica gel (100 g,
8% ethyl acetate–hexane) to give 12 (1.27 g, 33%, 3 steps). 1H NMR
(300 MHz, CDCl3) δ 0.98 (3H, t, J = 7.5 Hz, H-15), 2.08 (2H, q,
J = 7.5 Hz, H-17), 2.36 (2H, q, J = 7.0 Hz, H-2), 2.80–2.88 (8H, m, H-
5, 8, 11, 14), 3.65 (2H, m, H-1), 5.24–5.62 (10H, m, H-3, 4, 6, 7, 9, 10,
12, 13, 15, 16). 13C NMR (150 MHz, CDCl3) δ 14.3, 20.6, 25.6 (2 car-
bons), 25.7, 25.8, 30.8, 62.2, 125.7, 127.0, 127.9, 128.0 (2 carbons),
128.3 (2 carbons), 128.6, 131.1, 132.1. IR (neat) 3012, 2962, 2931,
1668, 1440, 1394, 1267, 1049.
4. Experimental procedures
4.1. General experimental procedures
All reagents were purchased from commercial sources and were
used without further purification. Organic solvents were dried by
standard methods. All air and moisture sensitive reactions were carried
out under nitrogen atmosphere. Unless otherwise stated, NMR spectra
were recorded at 300, 400 or 600 MHz for 1H NMR and 75, 100 or
150 MHz for 13C NMR in CDCl3 solution with TMS as an internal
standard and the chemical shifts are given in δ values. High resolution
mass spectra were obtained using JEOL AccuTOF LC-plus JMS-T100LP
spectrometer. IR spectra were recorded on a Shimadzu FTIR-8400S
spectrometer or a JASCO FT/IR-420 spectrometer, and data are given in
cm−1. Optical rotations were measured on a JASCO P-2200 polari-
meter, using a sodium lamp (589 nm).
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4.2.2. ((3Z,6Z,9Z,12Z,15Z)-Octadeca-3,6,9,12,15-pentaen-1-yl)
triphenylphosphonium bromide (14)
127.8, 128.0, 128.1, 128.2 (2 carbons), 128.3, 128.5, 129.2, 132.0,
134.0, 172.5. HRMS (ESI+ caled. for C23H34O2Na [M+Na]+
)
To a solution of 12 (101 mg, 0.387 mmol) in CH2Cl2 (3 mL) were
added PPh3 (305 mg, 1.16 mmol) and CBr4 (385 mg, 1.16 mmol) and
the mixture was stirred at room temperature for 1 h. The reaction
mixture was evaporated. The residue was chromatographed on silica
gel (100 g, 100% hexane) to give 1-brominated 13. To a solution of the
crude material (0.20 g, 0.63 mmol) in CH3CN (3.0 mL) was added PPh3
(0.49 g, 1.89 mmol) and the mixture was stirred at 80 °C for 24 h in a
sealed tube. The reaction mixture was evaporated and the residue was
chromatographed on silica gel (70 g, 10% MeOH–CH2Cl2) to give 14
(150 mg, 43% in 2 steps). 1H NMR (300 MHz, CDCl3) δ 0.96 (3H, t,
J = 7.4 Hz, H-15), 2.17–2.80 (8H, m, H-5, 8, 11, 14), 3.91 (2H, m, H-1),
5.25–5.40 (10H, m, H-3, 4, 6, 7, 9, 10, 12, 13), 5.64 (1H, m, H-13),
7.70–7.90 (15H, m, Ph). 13C NMR (75 MHz, CDCl3) δ 14.2, 20.4 (2
carbons), 20.5 (2 carbons), 22.6, 23.3, 25.5 (4 carbons), 117.8, 118.9,
126.6, 126.8, 126.9, 127.3, 127.7 (2 carbons), 128.4, 128.5, 128.7,
130.1, 130.3 (2 carbons), 130.5 (2 carbons), 132.1, 133.7 (2 carbons),
365.24565, found 365.24733. IR (neat) 3012, 2962, 2929, 2376, 2312,
1743, 1542, 1508, 1433, 1259, 1193, 1166, 968, 705 cm−1
.
4.2.6. (3E,7Z,10Z,13Z,16Z,19Z)-Docosa-3,7,10,13,16,19-hexaenoic acid
(5)
A solution of 19 (29 mg, 0.085 mmol) in 5% KOH/iPrOH–H2O (1:1,
0.8 mL) was stirred at 60 °C for 30 min. The reaction mixture was
acidified with 1 N aqueous HCl and then extracted 3 times with ethyl
acetate, dried over MgSO4, and evaporated to give 5 (27.3 mg, 97%). 1H
NMR (300 MHz, CDCl3) δ 0.97 (3H, t, J = 7.5 Hz, H-22), 2.03–2.17
(6H, m, H-5, 6, 21), 2.84 (8H, m, H-9, 12, 15, 18), 3.07–3.15 (2H, m, H-
2), 5.38 (10H, m, H-7, 8, 10, 11, 13, 14, 16, 17, 19, 20), 5.56 (2H, m, H-
3, 4). 13C NMR (150 MHz, CDCl3) δ 14.3, 20.6, 25.5, 25.6 (3 carbons),
25.7, 26.8, 29.7, 32.4, 37.5, 121.3, 127.0, 127.9, 128.1, 128.2, 128.3,
128.6, 129.2, 132.1, 134.7, 176.9. HRMS (ESI+) calcd. for C22H32NaO2
[M+Na]+ 351.2300, found 351.23158. IR (neat) 3012, 2962, 2929,
133.8 (2 carbons), 134.9 (2 carbons), 135.0 (2 carbons). HRMS (ESI+
)
2376, 2312, 1743, 1508, 1433, 1259, 1166, 968, 705 cm−1
.
caled. for C36H43BrP [M+H]+ 587.22653, found 587.22743. IR (neat)
3564, 3521, 3502, 3461, 3440, 3421, 3404, 3373, 3305, 3286, 3247,
4.2.7. Ethyl (2E,7Z,10Z,13Z,16Z,19Z)-docosa-2,7,10,13,16,19-hexaenoate
(20)
1699, 1436, 1101, 989, 744, 719, 688, 649, 617, 599 cm−1
.
To a solution of phosphonium bromide 9 (205.4 mg, 0.386 mmol)
and HMPA (100 µL, 1.158 mmol) in THF (0.5 mL) at −78 °C under
argon was added LHMDS (0.463 mL of a 1.0 M solution in hexane,
0.463 mmol). The mixture was added slowly a solution of 18 (131.4 mg,
0.772 mmol) in THF (0.7 mL). The reaction mixture was allowed to
warm to 0 °C for 2 h. The reaction was quenched by addition of satu-
rated aqueous NH4Cl, and the mixture was diluted with ethyl acetate.
The mixture was extracted 3 times with ethyl acetate. The organic layer
was washed with water and brine, dried over MgSO4, and evaporated.
The residue was chromatographed on silica gel (60 g, 3% ethyl acet-
ate–hexane) to give 20 (73.2 mg, 53%). 1H NMR (300 MHz, CDCl3) δ
0.97 (3H, t, J = 7.5 Hz, H-22), 1.29 (3H, t, J = 7.1 Hz, COO–CH2–CH3),
1.52 (2H, m, H-5), 2.10 (4H, m, H-6, 21), 2.68 (2H, m, H-4), 2.85 (8H,
m, H-9, 12, 15, 18), 4.18 (2H, q, J = 7.1 Hz, COO–CH2–CH3), 5.38
(10H, m, H-7, 8, 10, 11, 13, 14, 16, 17, 19, 20), 5.83 (1H, td, J = 1.5,
15.6 Hz, H-2), 6.90–7.02 (1H, td, J = 6.9, 15.6 Hz, H-3). 1H NMR
(300 MHz, benzene‑d6) δ 0.91 (3H, t, J = 7.5 Hz, H-22), 1.00 (3H, t,
J = 7.1 Hz, COO–CH2–CH3), 1.21 (2H, m, H-5), 1.85 (4H, m, H-6, 4),
2.01 (2H, m, H-21), 2.73–2.95 (8H, m, H-9, 12, 15, 18), 4.06 (2H, q,
J = 7.0 Hz, COO–CH2–CH3), 5.25 (1H, ttd, J = 1.5, 7.1, 10.7 Hz, H-7),
5.31–5.54 (9H, m, H-8, 10, 11, 13, 14, 16, 17, 19, 20), 5.57 (1H, td,
J = 1.5, 15.5 Hz, H-2), 7.04 (1H, td, J = 6.9, 15.6 Hz, H-3). 13C NMR
(75 MHz, CDCl3) δ 14.2, 20.5, 25.5, 25.6 (3 carbons), 26.6, 27.9, 31.6,
60.1, 121.5, 127.0, 127.8, 128.0, 128.1, 128.2, 128.5 (2 carbons),
4.2.3. Methyl (E)-7-oxohept-3-enoate (16)
To a solution of 15 (393 mg, 2.48 mmol) in CH2Cl2 (50 mL) was
added Dess–Martin Periodinane (1.58 g, 3.72 mmol), NaHCO3 (3.96 g,
47.12 mmol) at room temperature. The mixture was stirred at that
temperature for 1 h and the reaction was quenched with sat NaHCO3
and sat Na2S2O3. The reaction mixture was extracted 3 times with
CH2Cl2, and the organic layer was washed with brine, dried over
MgSO4, and evaporated. The residue was chromatographed on silica gel
(15 g, 40% ethyl acetate–hexane) to give 16 (377 mg, 97%). 1H NMR
(300 MHz, CDCl3) δ 2.40 (2H, m), 2.55 (2H, m), 3.08 (2H, m), 3.68 (3H,
s), 5.60 (2H, m), 9.77 (1H, t, J = 1.5 Hz).
4.2.4. Ethyl (E)-7-oxohept-2-enoate (18)
To a solution of 17 (1.02 g, 5.96 mmol) in CH2Cl2 (50 mL) was
added Dess–Martin Periodinane (3.79 g, 8.94 mmol), NaHCO3 (9.52 g,
113.2 mmol) at room temperature. The mixture was stirred at that
temperature for 1 h and the reaction was quenched with sat NaHCO3
and sat Na2S2O3. The mixture was extracted 3 times with CH2Cl2, and
the organic layer was washed with brine, dried over MgSO4, and eva-
porated. The residue was chromatographed on silica gel (50 g, 30%
ethyl acetate–hexane) to give 18 (849 mg, 83%). 1H NMR (300 MHz,
CDCl3) δ: 1.29 (3H, t, J = 7.1 Hz), 1.81 (2H, m), 2.24 (2H, m), 2.49
(2H, dt, J = 1.2, 7.2 Hz), 4.19 (2H, q, J = 7.1 Hz), 5.84 (1H, td, J = 1.5,
15.6 Hz), 6.86–6.97 (1H, td, J = 6.9, 15.6 Hz), 9.78 (1H, t, J = 1.3 Hz).
129.2 132.1, 133.2.0, 148.9, 166.6. HRMS (ESI+
24H36O2Na [M+Na]+ 379.26130, found 379.26025. IR (neat) 3608,
3566, 3544, 3523, 3012, 2923, 2852, 23474, 1745, 1722, 1500, 1338,
1338, 1186, 1041, 979 cm−1
) caled. for
C
4.2.5. Methyl (3E,7Z,10Z,13Z,16Z,19Z)-docosa-3,7,10,13,16,19-hexaenoate
(19)
.
To a solution of phosphonium bromide 9 (104.6 mg, 0.196 mmol)
and HMPA (47.7 µL, 0.274 mmol) in THF (0.2 mL) at −78 °C under
argon was added LHMDS (0.235 mL of a 1.0 M solution in hexane,
0.235 mmol). The mixture was added slowly to a solution of 18
(91.8 mg, 0.588 mmol) in THF (0.2 mL). The reaction mixture was al-
lowed to warm to 0 °C for 1.5 h. The reaction mixture was quenched by
addition of saturated aqueous NH4Cl, and the mixture was diluted with
ethyl acetate. The mixture was extracted 3 times with ethyl acetate. The
organic layer was washed with water and brine, dried over MgSO4, and
evaporated. The residue was chromatographed on silica gel (5 g, 5%
ethyl acetate–hexane) to give 19 (20 mg, 30%). 1H NMR (300 MHz,
CDCl3) δ 0.97 (3H, t, J = 7.5 Hz, H-22), 2.03–2.17 (6H, m, H-5, 6, 21),
2.85 (8H, m, H-9, 12, 15, 18), 3.03–3.11 (2H, m, H-2), 3.68 (3H, s, O-
Me), 5.30 (1H, ttd, 1.4, 7.0, 10.7 Hz, H-7), 5.38 (9H, m, H-8, 10, 11, 13,
14, 16, 17, 19, 20), 5.56 (2H, m, H-3, 4). 13C NMR (75 MHz, CDCl3) δ
14.2, 20.5, 25.5, 25.6 (3 carbons), 26.8, 32.4, 37.8, 51.7, 122.0, 127.0,
4.2.8. (2E,7Z,10Z,13Z,16Z,19Z)-Docosa-2,7,10,13,16,19-hexaenoic acid
(6)
A solution of 20 (50.5 mg, 0.137 mmol) in 5% KOH/iPrOH–H2O
(19:1, 3 mL) was stirred at room temperature for 17 h. The reaction
mixture was acidified with 1 N aqueous HCl and then extracted 3 times
with ethyl acetate. The organic layer was washed with water and brine,
dried over MgSO4, and evaporated, and evaporated to give 6 (49.9 mg,
quant.). 1H NMR (300 MHz, CDCl3) δ 0.97 (3H, t, J = 7.5 Hz, H-22),
1.55 (2H, m, H-5), 2.09 (4H, m, H-21), 2.08 (4H, m, H-6, 21), 2.85 (8H,
m, H-9, 12, 15, 18), 5.38 (10H, m, H-7, 8, 10, 11, 13, 14, 16, 17, 19,
20), 5.77 (1H, td, J = 1.5, 15.5 Hz, H-2), 6.23 (1H, td, J = 6.9, 15.6 Hz,
H-3). 13C NMR (150 MHz, CDCl3) δ 14.3, 20.6, 25.5, 25.6 (2 carbons),
25.7, 26.7, 27.8, 31.8, 120.8, 127.0, 127.9, 128.1, 128.2 (2 carbons),
128.3, 128.6, 128.7, 129.1, 132.0, 152.0, 171.8. HRMS (ESI+) caled.
for C22H32O2Na [M+Na]+ 351.2300, found 351.22826. IR (neat)
7

S. Kanamori et al.
Bioorganic&MedicinalChemistryxxx(xxxx)xxx–xxx
3012, 2962, 2927, 2873, 2854, 1697, 1681, 1649, 1452, 1417, 1396,
(19:1, 47 mL) was stirred at 60 °C for 30 min. The reaction mixture was
acidified with 1 N aqueous HCl and then extracted 3 times with ethyl
acetate. The organic layer was washed with water, dried over MgSO4,
and evaporated. The residue was chromatographed on silica gel (30 g,
40% ethyl acetate–hexane) to give ( )-2 (1.56 g, 90%). 1H NMR
(300 MHz, CDCl3) δ 0.97 (3H, t, J = 7.5 Hz, H-24), 1.58 (2H, m, H-2),
2.08 (2H, m, H-23), 2.22 (2H, m, H-5), 2.44–2.62 (2H, m, H-4), 2.83
(10H, m, H-8, 11, 14, 17, 20), 4.05 (1H, m, H-3), 5.37 (12H, m, H-6, 7,
9, 10, 12, 13, 15, 16, 18, 19, 21, 22). 13C NMR (75 MHz, CDCl3) δ 14.2,
20.5, 21.0, 23.2, 25.5, 25.6 (3 carbons), 36.2, 67.4, 127.0, 127.8, 128.0,
128.1 (3 carbons), 128.2 (3 carbons), 128.5, 128.7, 129.0, 132.0,
177.7. HRMS (ESI+) caled. for C22H34O3Na [M+Na]+ 369.24056,
found 369.24117. IR (neat) 3346, 3012, 2964, 2931, 1712, 1402, 1217,
1311, 1286, 1228, 979, 929, 705 cm−1
.
4.2.9. Ethyl
(2E,4Z,7Z,10Z,13Z,16Z,19Z)-docosa-2,4,7,10,13,16,19-
heptaenoate (21)
To a solution of phosphonium bromide 14 (1.29 g, 2.21 mol), (E)-
Ethyl 4-oxobut-2-enoate (0.80 mL, 6.63 mmol) in THF (15 mL) was
added LHMDS (1.0 M in THF, 6.63 mL, 6.63 mmol) at −78 °C. The re-
action mixture was allowed to warm to 0 °C for 1 h, and the reaction
was quenched with water. The mixture was extracted 3 times with ethyl
acetate. The organic layer was washed with water and brine, dried over
MgSO4, and evaporated. The residue was chromatographed on silica gel
(200 g, 3% ethyl acetate–hexane) to give 21 (222 mg, 28%). 1H NMR
(300 MHz, CDCl3) δ 0.97 (3H, t, J = 7.5 Hz, H-22), 1.30 (3H, t,
J = 7.2 Hz, COO–CH2–CH3), 2.07 (2H, m, H-21), 2.71–3.13 (10H, m, H-
9, 12, 15, 18), 4.18 (2H, q, J = 7.1 Hz, COO–CH2–CH3), 5.38 (10H, m,
H-7, 8, 10, 11, 13, 14, 16, 17, 19, 20), 5.79 (1H, tq, J = 0.7, 10.6 Hz, H-
5), 5.89 (1H, d, J = 15.2 Hz, H-2), 6.14 (1H, t, J = 11.4 Hz, H-4),
7.58–7.67 (1H, ddd, J = 0.98, 11.6, 15.2 Hz, H-3). 13C NMR (75 MHz,
CDCl3) δ 14.2, 14.3, 20.5, 25.5, 25.6 (3 carbons), 26.5, 60.3, 121.8,
126.5, 126.6, 127.7, 127.8, 127.9, 128.3 (3 carbons), 128.5 (2 car-
bons), 129.4, 138.6, 138.95, 167.1 HRMS (ESI+) caled. for C24H34O2Na
[M+Na]+ 377.24565, found 377.24167. IR (neat) 3012, 2964, 1714,
1068, 973, 757, cm−1
.
4.2.13. Ethyl (7Z,10Z,13Z,16Z,19Z)-3-hydroxydocosa-7,10,13,16,19-
pentaenoate (( )-25)
To a solution of aldehyde 24 (1.24 g, 4.36 mmol) in benzene
(8.6 mL) was added Zn (2.56 g, 39.25 mmol), ethyl bromoacetate
(4.37 mL, 26.2 mmol). The reaction was stirred at 110 °C for 30 min.
The mixture was diluted with ethyl acetate and filtered through Celite,
evaporated. The residue was chromatographed on silica gel (100 g, 5%
ethyl acetate–hexane) to give
(
)-25 (1.07 g, 65%). 1H NMR
1433, 1365, 1265, 1163, 1118, 1039, 993, 869, 696 cm−1
.
(300 MHz, CDCl3) δ 0.97 (3H, t, J = 7.5 Hz, H-22), 1.28 (3H, t,
J = 7.1 Hz, COO–CH2–CH3), 1.49 (4H, m, H-4, 5), 2.08 (4H, m, H-6,
21), 2.35–2.53 (2H, m, H-2) 2.85 (8H, m, H-9, 12, 15, 18), 4.00–4.11
(1H, br, H-3), 4.18 (2H, q, J = 7.1 Hz, COO–CH2–CH3), 5.38 (10H, m,
H-7, 8, 10, 11, 13, 14, 16, 17, 19, 20). 13C NMR (75 MHz, CDCl3) δ 14.1,
14.2, 20.5, 25.4, 25.5, 25.6 (3 carbons), 27.0, 36.0, 41.2, 60.6, 67.9,
127.0, 127.8, 128.0, 128.1 (2 carbons), 128.2, 128.3, 128.5, 129.7,
4.2.10. (2E,4Z,7Z,10Z,13Z,16Z,19Z)-Docosa-2,4,7,10,13,16,19-
heptaenoic acid (4)
A solution of 21 (16.3 mg, 0.046 mmol) in 5% KOH/tBuOH–H2O
(1:1, 1 mL) was stirred at room temperature for 23 h. The reaction
mixture was acidified with 1 N aqueous HCl and then extracted 3 times
with ethyl acetate. The organic layer was washed with water and brine
over MgSO4, dried, and evaporated. The residue was chromatographed
on silica gel (5 g, 30% ethyl acetate–hexane) to give 4 (7.5 mg, 50%).
1H NMR (300 MHz, CDCl3) δ 0.97 (3H, t, J = 7.5 Hz, H-22), 2.07 (2H,
m, H-21), 2.85 (8H, m, H-9, 12, 15, 18), 3.10 (2H, t, H-6), 5.38 (10H, m,
H-7, 8, 10, 11, 13, 14, 16, 17, 19, 20), 5.76–5.97 (2H, m, H-2, 5), 6.18
(1H, t, J = 11.0 Hz, H-4), 7.58–7.67 (1H, ddd, J = 1.0, 11.7, 15.3 Hz,
H-3). 13C NMR (75 MHz, CDCl3) δ 14.2, 20.5, 25.5, 26.6 (3 carbons),
26.6, 120.7, 126.2, 126.4, 127.0, 127.6, 127.8, 127.9, 128.3, 128.5 (2
carbons), 129.6, 132.0, 140.0, 141.2, 171.9. HRMS (ESI+) caled. for
132.0, 173.0. HRMS (ESI+
)
caled. for C24H38O3Na [M+Na]+
397.27186, found 397.27144. IR (neat) 3523, 3012, 2960, 2925, 2854,
2380, 2312, 2017, 1743, 1722, 1542, 1508, 1396, 1338, 1271, 1178,
1093, 1029 cm−1
.
4.2.14. (7Z,10Z,13Z,16Z,19Z)-3-Hydroxydocosa-7,10,13,16,19-
pentaenoic acid (( )-7)
A solution of ( )-25 (80 mg, 0.213 mmol) in 5% KOH/MeOH–H2O
(19:1, 20 mL) was stirred at 60 °C for 20 min. The reaction mixture was
acidified with 1 N aqueous HCl and then extracted with ethyl acetate.
The organic layer was washed with water, dried over MgSO4, and
evaporated, and evaporated to give ( )-7 (71.7 mg, 97%). 1H NMR
(300 MHz, CDCl3) δ 0.97 (3H, t, J = 7.5 Hz, H-22), 1.52 (4H, m, H-4,
5), 2.08 (4H, m, H-6, 21), 2.43–2.61 (2H, m, H-2), 2.85 (8H, m, H-9, 12,
15, 18), 4.00–4.11 (1H, br, H-3), 5.38 (10H, m, H-7, 8, 10, 11, 13, 14,
16, 17, 19, 20). 13C NMR (150 MHz, CDCl3) δ 14.3, 20.6, 25.6 (2 car-
bons), 25.7 (2 carbons), 27.0, 36.0, 40.9, 67.8, 127.0, 127.9, 128.1 (2
C
22H30NaO2 [M+Na]+ 349.21435, found 349.21199. IR (neat) 3012,
2962, 2929, 2873, 2873, 2856, 2358, 2339, 1693, 1679, 1633, 1421,
1284, 1122, 995, 964, 873, 669 cm−1
.
4.2.11. Ethyl (6Z,9Z,12Z,15Z,18Z,21Z)-3-hydroxytetracosa-6,9,12,15,18,21-
hexaenoate (( )-23)
To a solution of aldehyde 22 (1.61 g, 5.16 mmol) in benzene
(10 mL) was added Zn (0.6 g, 8.92 mmol), ethyl bromoacetate (0.66 mL,
6.192 mmol), and I2 (224.3 mg, 1.54 mmol). The reaction was stirred at
room temperature for 1 h. The mixture was diluted with ethyl acetate
and filtered through Celite, evaporated. The residue was chromato-
graphed on silica gel (30 g, 3% ethyl acetate–hexane) to give ( )-23
(1.86 g, 90%). 1H NMR (300 MHz, CDCl3) δ 0.97 (3H, t, J = 7.5 Hz, H-
22), 1.28 (3H, t, J = 7.1 Hz, COO–CH2–CH3), 1.54 (4H, m, H-4, 5), 2.08
(4H, m, H-23), 2.21 (2H, m, H-4), 2.35–2.54 (2H, m, H-2), 2.85 (10H,
m, H-8, 11, 14, 17, 20), 4.00–4.11 (1H, br, H-3), 4.18 (2H, q, J = 7.1 Hz
COO–CH2–CH3), 5.38 (12H, m, H-6, 7, 9, 10, 12, 13, 15, 16, 18, 19, 21,
22). 13C NMR (100 MHz, CDCl3) δ 14.2, 14.3, 23.2, 25.5, 25.6, 25.7 (3
carbons), 36.1, 41.2, 60.7, 67.4, 126.9, 127.8, 128.0, 128.2 (4 carbons),
128.3 (2 carbons), 128.6 (2 carbons), 129.3, 132.0, 173.0. HRMS (ESI)
caled. for C26H40O3Na [M+Na]+ 423.28751, found 423.28498. IR
carbons), 128.3 (4 carbons), 128.6, 129.6, 132.1, 177.0. HRMS (ESI+
)
caled. for C22H34O3Na [M+Na]+ 369.24056, found 369.24117. IR
(neat) 3575, 3460, 3012, 2935, 2306, 1749, 1672, 1658, 1641, 1539,
1577, 1402, 1269, 1188, 1041, 719, 680, 649 cm−1
.
4.2.15. Ethyl
(R,7Z,10Z,13Z,16Z,19Z)-3-(4,4,5,5-tetramethyl-1,3,2-
dioxaborolan-2-yl)docosa-7,10,13,16,19-pentaenoate (26)
THF (0.50 mL) was added under nitrogen to CuCl (0.55 mg,
5.6 μmol, 2 mol%), NaOtBu (0.8 mg, 8.4 μmol), and (R)-(S)-josiphos li-
gand (12.8 mg,0.028 mmol). The reaction mixture was stirred for
30 min at 0 °C, then bis(pinacolato)diboron (78 mg, 0.38 mmol) in THF
(0.20 mL) were added. The reaction mixture was stirred for 10 min.
Then 20 (100 mg, 0.28 mmol) in THF (0.5 mL) and subseqently MeOH
(22 µL, 0.56 mmol) were added. The reaction was stirred at 0 °C for 1 h.
The mixture was diluted with ethyl acetate and filtered through Celite,
evaporated. The residue was chromatographed on silica gel (4 g, 5%
ethyl acetate–hexane) to give 26 (67.2 mg, 49%). 1H NMR (300 MHz,
CDCl3) δ 0.97 (3H, t, J = 7.5 Hz, H-22), 1.28 (15H, m, COO–CH2–CH3,
B(pin)), 1.36 (5H, m, H-3, 4, 5), 2.08 (4H, m, H-6, 21), 2.85 (8H, m, H-
(neat) 3010, 2964, 2931, 1731, 1712, 1238, 1176, 1026, 723 cm−1
.
4.2.12. (6Z,9Z,12Z,15Z,18Z,21Z)-3-Hydroxytetracosa-6,9,12,15,18,21-
hexaenoic acid (( )-2)
A solution of ( )-23 (1.86 g, 4.63 mmol) in 5% KOH/MeOH–H2O
8

S. Kanamori et al.
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9, 12, 15, 18), 4.18 (2H, q, J = 7.2 Hz, COO–CH2–CH3), 5.38 (10H, m,
H-7, 8, 10, 11, 13, 14, 16, 17, 19, 20). 13C NMR (75 MHz, CDCl3) δ 14.3,
20.5, 24.6 (2 carbons), 24.8 (2 carbons), 25.5, 25.6 (3 carbons), 27.4,
28.8, 30.2, 35.8, 60.1, 83.1, 127.0, 127.7, 127.9 (3 carbons), 128.1 (4
carbons), 128.5 (2 carbons), 130.1, 132.0, 173.9. HRMS (ESI+) caled.
for C30H49B1O4Na [M+Na]+ 507.36216, found 507.36604. IR (neat)
3012, 2975, 2930, 1733, 1387, 1318, 1267, 1143, 1036, 968, 857,
4.2.19. Ethyl (R,7Z,10Z,13Z,16Z,19Z)-3-(((R)-3,3,3-trifluoro-2-methoxy-2-
phenylpropanoyl)oxy)docosa-7,10,13,16,19-pentaenoate (28)
To a solution of alcohol 25 (14.8 mg, 0.036 mmol) in CH2Cl2
(0.37 μL) were added triethylamine (20.5 μL, 0.147 mmol), DMAP
(22.5 mg, 0.184 mmol), and (S)-methoxy(trifluoromethyl)phenylacetyl
chloride (13.8 μL, 0.073 mmol) at 0 °C. The solution was stirred at room
temperature for 1.5 h. The reaction mixture was poured into ice and
water, and extracted 3 times with ether. The organic layer was washed
with water, dried over MgSO4, and evaporated. The residue was chro-
matographed on silica gel (6 g, 10% ethyl acetate-hexane) to give (R)-
MTPA ester 28 (12 mg, 55%). 1H NMR (300 MHz, CDCl3) δ 0.97 (3H, t,
J = 7.5 Hz, H-22), 1.09–1.29 (5H, m, H-4, COO–CH2–CH3), 1.56 (2H,
m, H-5), 1.87–2.07 (4H, m, H-6, 21), 2.43–2.65 (2H, t, J = 6.8 Hz, H-2),
2.83 (8H, m, H-9, 12, 15, 18), 3.54 (3H, s, MTPA-OMe), 3.66 (1H, s, H-
1), 5.22–5.44 (10H, m, H-7, 8, 10, 11, 13, 14, 16, 17, 19, 20), 5.49 (1H,
m, H-3), 7.39 (3H, m, MTPA-Ph), 7.53 (2H, m, MTPA-Ph). 13C NMR
(75 MHz, CDCl3) δ 14.0, 14.2, 20.5, 24.5, 25.5, 25.6 (4 carbons), 26.6,
29.6, 33.1, 38.8, 55.4, 60.9, 73.1, 127.0, 127.3 (2 carbons), 127.8,
128.0, 128.1, 128.2 (2 carbons), 128.3 (2 carbons), 128.5 (2 carbons),
129.1 (2 carbons), 129.5, 132.0, 165.8, 169.9. HRMS (ESI+) caled. for
205 cm−1. [α]D +7.1 (c 0.17, CHCl3).
23
4.2.16. Ethyl (R,7Z,10Z,13Z,16Z,19Z)-3-Hydroxydocosa-7,10,13,16,19-
pentaenoate ((R)-25)
A solution of 26 (40.3 mg, 0.08 mmol) in THF/H2O (1:1, 1.6 mL)
was added NaBO3·4H2O (104.8 mg, 0.68 mmol). The reaction was
stirred at room temperature for 3 h. The organic layer was washed with
water and brine, dried over MgSO4, and evaporated. The residue was
chromatographed on silica gel (5 g, 5% ethyl acetate–hexane) to give
(R)-25 (25.5 mg, 77%, 84% ee). 1H NMR (300 MHz, CDCl3) δ 0.97 (3H,
t, J = 7.5 Hz, H-22), 1.28 (3H, t, J = 7.1 Hz, COO–CH2–CH3), 1.49 (4H,
m, H-4, 5), 2.08 (4H, m, H-6, 21), 2.35–2.53 (2H, m, H-2) 2.85 (8H, m,
H-9, 12, 15, 18), 4.00–4.11 (1H, br, H-3), 4.18 (2H, q, J = 7.1 Hz,
COO–CH2–CH3), 5.38 (10H, m, H-7, 8, 10, 11, 13, 14, 16, 17, 19, 20).
13C NMR (75 MHz, CDCl3) δ 14.1, 14.2, 20.5, 25.4, 25.5, 25.6 (3 car-
bons), 27.0, 36.0, 41.2, 60.6, 67.9, 127.0, 127.8, 128.0, 128.1 (2 car-
bons), 128.2, 128.3, 128.5, 129.8, 132.0, 173.1. HRMS (ESI+) caled.
for C24H38O3Na [M+Na]+ 397.27186, found 397.26758. IR (neat)
3011, 2963, 2931, 2865, 2362, 2325, 1734, 1716 cm−1. [α]D23 +4.5 (c
0.12, CHCl3).
C
34H45F3O5Na [M+Na]+ 613.31168, found 613.30870. IR (neat)
3014, 2959, 2930, 2852, 2357, 1748, 1452, 1268, 1169, 1122, 1019,
716 cm−1
.
4.2.20. Methyl (R,6Z,9Z,12Z,15Z,18Z,21Z)-3-(4,4,5,5-tetramethyl-1,3,2-
dioxaborolan-2-yl)tetracosa-6,9,12,15,18,21-hexaenoate (30)
THF (0.5 mL) was added under nitrogen to CuCl (0.53 mg,
5.43 μmol), NaOtBu (0.78 mg, 8.14 μmol), and (R)-(S)-josiphos ligand
(17.3 mg, 0.027 mmol). The reaction mixture was stirred for 30 min at
0 °C, then bis(pinacolato)diboron (75 mg, 0.29 mmol) in THF (0.5 mL)
were added. The reaction mixture was stirred for 10 min. Then, 29
(100.1 mg, 0.27 mmol) in THF (0.5 mL) and subsequently MeOH
(0.54 mmol, 21 μL) were added. The reaction was stirred at 0 °C for
1.5 h. The reaction mixture is evaporated. The residue was chromato-
graphed on silica gel (10 g, 5% ethyl acetate–hexane) to give 30
(86.6 mg, 64%). 1H NMR (300 MHz, CDCl3) δ 0.97 (3H, t, J = 7.5 Hz,
H-24), 1.24 (12H, d, J = 2.6 Hz, B-pin), 1.37 (2H, m, H-2), 1.53 (1H, m,
H-3), 2.08 (4H, m, H-5, 23), 2.44 (2H, m, H-4), 2.82 (10H, m, H-8, 11,
14, 17, 20), 3.65 (3H, s, H-1), 5.35 (12H, m, H-6, 7, 9, 10, 12, 13, 15,
16, 18, 19, 21, 22). 13C NMR (75 MHz, CDCl3) δ 14.2, 20.5, 24.7 (3
carbons), 25.5, 25.6 (4 carbons), 26.4, 30.5, 35.4, 51.4, 83.1, 127.0,
127.8, 127.9 (4 carbons), 128.1 (4 carbons), 128.5 (3 carbons), 129.9,
4.2.17. (R,7Z,10Z,13Z,16Z,19Z)-3-hydroxydocosa-7,10,13,16,19-
pentaenoic acid (R)-7
A solution of (R)-25 (49.7 mg, 0.124 mmol) in 5% KOH/CH3OH–H2O
(19:1, 3 mL) was stirred at room temperature for 18 h. The reaction mix-
ture was acidified with 1 N aqueous HCl and then extracted 3 times with
ethyl acetate. The organic layer was washed with water, dried over
MgSO4, and evaporated to give (R)-7 (26.3 mg, 63%). 1H NMR (300 MHz,
CDCl3) δ 0.97 (3H, t, J = 7.5 Hz, H-22), 1.49 (4H, m, H-4, 5), 2.08 (4H, m,
H-6, 21), 2.35–2.53 (2H, m, H-2), 2.85 (8H, m, H-9, 12, 15, 18), 4.00–4.11
(1H, br, H-3), 5.38 (10H, m, H-7, 8, 10, 11, 13, 14, 16, 17, 19, 20). 13C
NMR (100 MHz, CDCl3) δ 14.2, 20.5, 23.3, 25.5 (2 carbons), 25.6 (2
carbons), 26.9, 36.0, 40.8, 67.7, 126.9, 127.8, 128.0 (2 carbons), 128.2 (3
carbons), 128.5, 129.5, 132.0, 176.9. HRMS (ESI+) caled. for C22H34O3Na
[M+Na]+ 369.24056, found 369.24117. IR (neat) 3011, 2967, 2927,
2851, 1717 cm−1. [α]D +2.5 (c 0.11, CHCl3).
24
)
132.0, 174.2. HRMS (ESI+ caled. for C31H49BNaO4 [M+Na]+
4.2.18. Ethyl (R,7Z,10Z,13Z,16Z,19Z)-3-(((S)-3,3,3-trifluoro-2-methoxy-
2-phenylpropanoyl)oxy)docosa-7,10,13,16,19-pentaenoate (27)
519.36216, found 519.36251. IR (neat) 3012, 2962, 2931, 2931, 2873,
1731, 1433, 1265, 1197, 1174, 1068, 918, 705 cm−1. [α]D +6.7 (c
24
To a solution of alcohol 25 (15.2 mg, 0.0379 mmol) in CH2Cl2
(0.38 mL) were added triethylamine (21 μL, 0.151 mmol), DMAP
(23 mg, 0.189 mmol), and (R)-methoxy(trifluoromethyl)phenylacetyl
chloride (14 μL, 0.075 mmol) at 0 °C. The solution was stirred at room
temperature for 2 h. The reaction mixture was poured into ice and
water, and extracted 3 times with ether. The organic layer was washed
with water, dried over MgSO4, and evaporated. The residue was chro-
matographed on silica gel (1 g, 5% ethyl acetate-hexane) to give (S)-
MTPA ester 27 (17 mg, 78%). 1H NMR (300 MHz, CDCl3) δ 0.97 (3H, t,
J = 7.5 Hz, H-22), 1.19 (3H, t, J = 7.1 Hz, COO–CH2–CH3), 1.42 (2H,
m, H-5), 1.72 (2H, m, H-4), 2.07 (4H, m, H-6, 21), 2.71 (2H, t,
J = 6.8 Hz, H-4), 2.83 (8H, m, H-9, 12, 15, 18), 3.54 (3H, s, MTPA-
OMe), 3.66 (1H, s, H-1), 5.22–5.44 (10H, m, H- 7, 8, 10, 11, 13, 14, 16,
17, 19, 20), 5.49 (1H, m, H-3), 7.39 (3H, m, MTPA-Ph), 7.53 (2H, m,
MTPA-Ph). 13C NMR (75 MHz, CDCl3) δ 14.0, 14.2, 20.5, 24.9, 25.5,
25.6 (3 carbons), 26.7, 33.2, 38.6, 55.3, 60.8, 73.3, 73.3, 127.0, 127.4
(3 carbons), 127.8, 128.0, 128.1 (2 carbons), 128.2, 128.3 (3 carbons),
128.5, 128.6, 129.1, 129.5, 132.0, 165.8, 169.7. HRMS (ESI+) caled.
for C34H45F3O5Na [M+Na]+ 613.30784, found 613.31168. IR (neat)
0.11, CHCl3).
4.2.21. Methyl (R,6Z,9Z,12Z,15Z,18Z,21Z)-3-hydroxytetracosa-6,9,12,15,
18,21-hexaenoate ((R)-31)
A solution of 30 (66.9 mg, 0.13 mmol) in THF/H2O (2:1, 2.6 mL)
was added NaBO3·4H2O (246.9 mg, 1.60 mmol). The organic layer was
washed with water and brine, dried over MgSO4, and evaporated. The
residue was chromatographed on silica gel (5 g, 15% ethyl acet-
ate–hexane) to give (R)-31 (49 mg, 95%). 1H NMR (300 MHz, CDCl3) δ
0.98 (3H, t, J = 7.5 Hz, H-24), 1.56 (2H, m, H-4), 2.08 (2H, m, H-23),
2.22 (2H, m, H-5), 2.47 (2H, m, H-2), 2.85 (10H, m, H-8, 11, 14, 17,
20), 3.72 (3H, s, COO–CH3), 4.02 (1H, m, H-3), 5.37 (12H, m, H-6, 7, 9,
10, 12, 13, 15, 16, 18, 19, 21, 22). 13C NMR (75 MHz, CDCl3) δ 14.2,
20.5, 23.3, 25.5, 25.6 (4 carbons), 36.2, 41.1, 51.7, 67.4, 127.0, 127.8,
128.1 (3 carbons), 128.2 (3 carbons), 128.5, 128.6, 129.2, 132.0,
173.3. HRMS (ESI+
) calcd. for C25H38NaO3 409.27186, found
409.27157. IR (neat) 3012, 2962, 2931, 2873, 1735, 1438, 1390, 1301,
1263, 1197, 1174, 1068, 927, 688 cm−1. [α]D +1.2 (c 0.19, CHCl3).
24
3012, 2935, 2360, 1748, 1453, 1268, 1169, 1122, 1019, 716 cm−1
.
9

S. Kanamori et al.
Bioorganic&MedicinalChemistryxxx(xxxx)xxx–xxx
4.2.22. (R,6Z,9Z,12Z,15Z,18Z,21Z)-3-Hydroxytetracosa-
6,9,12,15,18,21-hexaenoic acid ((R)-2)
4.2.25. Ethyl (6Z,9Z,12Z,15Z,18Z,21Z)-3-oxotetracosa-6,9,12,15,18,21-
hexaenoate (42)
A solution of (R)-31 (13.0 mg, 0.033 mmol) in 5% KOH/MeOH–H2O
(19:1, 0.5 mL) was stirred at room temperature for 1.5 h. The reaction
mixture was acidified with 1 N aqueous HCl and then extracted 3 times
with ethyl acetate. The organic layer was washed with water, dried over
MgSO4, and evaporated. The residue was chromatographed on silica gel
(3 g, 40% ethyl acetate–hexane) to give (R)-2 (8.4 mg, 67%). 1H NMR
(300 MHz, CDCl3) δ 0.97 (3H, t, J = 7.5 Hz, H-24), 1.58 (2H, m, H-2),
2.08 (2H, m, H-23), 2.22 (2H, m, H-5), 2.54 (2H, m, H-4), 2.83 (10H, m,
H-8, 11, 14, 17, 20), 4.05 (1H, m, H-3), 5.37 (12H, m, H-6, 7, 9, 10, 12,
13, 15, 16, 18, 19, 21, 22) 13C NMR (100 MHz, CDCl3) δ 14.2, 20.5,
21.0, 23.2, 25.5, 25.6 (3 carbons), 36.1, 67.3, 126.9, 127.8, 128.0,
128.1 (3 carbons), 128.2 (3 carbons), 128.5, 128.8, 129.0, 132.0,
177.0. HRMS (ESI−) caled. for C24H35O3 [M−H]− 371.25862, found
371.25712. IR (neat) 3012, 2962, 2929, 2358, 2341, 1712, 1392, 1263,
To a solution of (COCl)2 (2.0 M in CH2Cl2, 6.3 mL, 12.64 mmol) in
CH2Cl2 (3 mL) was added a solution of DMSO (1.8 mL, 25.29 mmol) in
CH2Cl2 (3 mL) at −78 °C and the mixture was stirred at −78 °C for
10 min. A solution of 23 (3.38 g, 8.43 mmol) in CH2Cl2 (4 mL) was
added and the mixture was stirred at that temperature for 15 min. Et3N
(6.9 mL, 50.58 mmol) was added to the reaction mixture at −78 °C, and
then the mixture was allowed to warm to 0 °C. The reaction was
quenched with water and the mixture was extracted 3 times with ethyl
acetate. The organic layer was washed with water and brine, dried over
MgSO4, and evaporated. The residue was chromatographed on silica gel
(80 g, 5% ethyl acetate–hexane) to give 42 (1.58 g, 47%). 1H NMR
(300 MHz, CDCl3) δ 0.97 (3H, t, J = 7.5 Hz, H-24), 1.28 (3H, t,
J = 7.2 Hz, COO–CH2–CH3), 2.08 (2H, m, H-23), 2.37 (2H, m, H-5),
2.61 (2H, t, J = 7.2 Hz, H-4), 2.83 (10H, m, H-8, 11, 14, 17, 20), 3.43
(2H, s, H-3), 4.20 (2H, q, J = 7.2 Hz, COO–CH2–CH3), 5.38 (12H, m, H-
6, 7, 9, 10, 12, 13, 15, 16, 18, 19, 21, 22) 13C NMR (75 MHz, CDCl3) δ
14.1, 14.2, 20.5, 21.3, 25.5 (2 carbons), 25.6 (3 carbons), 42.7, 49.4,
61.3, 127.0, 127.8 (2 carbons), 128.0 (2 carbons), 128.1, 128.2 (3
carbons), 128.5, 129.3, 132.0, 167.1, 202.0. HRMS (FAB+) caled. for
C26H39O3 [M+H]+ 399.2899, found 399.2912. IR (neat) 3012, 2964,
2931, 1745, 1716, 1647, 1436, 1367, 1313, 1232, 1195, 1149, 1039,
684 cm−1. [α]D −6.7 (c 0.14, CHCl3).
24
4.2.23. Methyl
(R,6Z,9Z,12Z,15Z,18Z,21Z)-3-(((S)-3,3,3-trifluoro-2-
methoxy-2-phenylpropanoyl)oxy)tetracosa-6,9,12,15,18,21-hexaenoate
(32)
To
a solution of alcohol 31 (10.1 mg, 0.026 mol) in CH2Cl2
(0.26 mL) were added triethylamine (14 μL, 0.10 mmol), DMAP
(15.8 mg, 0.13 mmol), and (R)-methoxy(trifluoromethyl)phenylacetyl
chloride (9.7 μL, 0.052 mmol) at 0 °C. The solution was stirred at room
temperature for 5 h. The reaction mixture was poured into ice and
water, and extracted 3 times with ether. The organic layer was washed
with water, dried over MgSO4, and evaporated. The residue was chro-
matographed on silica gel (5 g, 10% ethyl acetate ethyl acetate-hexane)
to give (S)-MTPA ester 32 (13.7 mg, 87%). 1H NMR (300 MHz, CDCl3) δ
0.97 (3H, t, J = 7.5 Hz, H-24), 1.72 (2H, m, H-2), 2.04 (4H, m, H-5, 23),
2.71 (2H, t, J = 6.8 Hz, H-4), 2.83 (10H, m, H-8, 11, 14, 17, 20), 3.54
(3H, s, MTPA-OMe), 3.66 (1H, s, H-1), 5.39 (12H, m, H-6, 7, 9, 10, 12,
13, 15, 16, 18, 19, 21, 22), 5.49 (1H, m, H-3), 7.39 (3H, m, MTPA-Ph),
7.53 (2H, m, MTPA-Ph). 13C NMR (75 MHz, CHCl3) δ 14.2, 20.8, 22.8,
25.7, 25.8 (2 carbons), 33.8, 38.7, 52.1, 55.6, 72.9, 127.0, 127.3, 127.8,
127.9, 128.0 (2 carbons), 128.3 (4 carbons), 128.5 (4 carbons), 128.6,
128.8, 129.1, 129.6, 132.0, 132.2, 165.9, 170.3. HRMS (ESI+) calcd.
for C35H45F3NaO5 625.31168, found 625.31173. IR (neat) 3012, 2960,
2931, 2850, 1747, 1450, 1438, 1390, 1271, 1184, 1168, 1122, 1080,
927, 707 cm−1
.
4.2.26. Ethyl
2-(2-((3Z,6Z,9Z,12Z,15Z,18Z)-henicosa-3,6,9,12,15,18-
hexaen-1-yl)-1,3-dioxolan-2-yl)acetate (43)
To a solution of 42 (104.0 mg, 0.26 mmol) in benzene (10 mL) was
added ethylene glycol (278 µL, 2.6 mmol) and p-TsOH·H2O (4.4 mg,
0.013 mmol). The reaction was stirred at 110 °C for 24 h. The reaction
was quenched with water and the mixture was extracted 3 times with
ethyl acetate. The organic layer was washed with water and brine, dried
over MgSO4, and evaporated. The residue was chromatographed on
silica gel (20 g, 40% ethyl acetate–hexane) to give 43 (57.6 mg, 50%).
1H NMR (300 MHz, CDCl3) δ 0.97 (3H, t, J = 7.5 Hz, H-24), 1.27 (3H, t,
J = 7.2 Hz, COO–CH2–CH3), 1.88 (2H, m, H-4), 2.08 (2H, m, H-23),
2.19 (2H, m, H-5), 2.66 (2H, s, H-2), 2.83 (10H, m, H-8, 11, 14, 17, 20),
3.98 (4H, m, acetal-CH2), 4.15 (1H, m, COO–CH2–CH3), 5.37 (12H, m,
H-6, 7, 9, 10, 12, 13, 15, 16, 18, 19, 21, 22). 13C NMR (75 MHz, CDCl3)
δ 14.1, 14.2, 20.5, 21.4, 25.5 (2 carbons), 25.6 (3 carbons), 37.4, 42.7,
60.5, 65.1 (2 carbons), 109.1, 127.0, 127.8, 128.0 (2 carbons), 128.1 (2
carbons), 128.2 (2 carbons), 128.3, 128.5, 129.3, 132.0, 169.4. HRMS
(FAB+) caled. for C28H43O4 [M+H]+ 443.3161, found 443.3154. IR
(neat) 3012, 2964, 2931, 2894, 1735, 1442, 1390, 1369, 1265, 1218,
1018, 715, 696 cm−1
.
4.2.24. Methyl
(R,6Z,9Z,12Z,15Z,18Z,21Z)-3-(((R)-3,3,3-trifluoro-2-
methoxy-2-phenylpropanoyl)oxy)tetracosa-6,9,12,15,18,21-hexaenoate
(33)
1110, 1095, 1039, 948, 711 cm−1
.
To a solution of alcohol 31 (9.8 mg, 0.025 mmol) in CH2Cl2
(0.25 mL) were added triethylamine (14.0 μL, 0.10 mmol), DMAP
(15.4 mg, 0.12 mmol), and (S)-methoxy(trifluoromethyl)phenylacetyl
chloride (37 μL, 0.20 mmol) at 0 °C. The solution was stirred at room
temperature for 4 h. The reaction mixture was poured into ice and
water, and extracted 3 times with ether. The organic layer was washed
with water, dried over MgSO4, and evaporated. The residue was chro-
matographed on silica gel (5 g, 5% ethyl acetate-hexane to give (R)-
MTPA ester 33 (9.8 mg, 64%). 1H NMR (300 MHz, CDCl3) δ 0.97 (3H, t,
J = 7.5 Hz, H-24), 1.80 (2H, m, H-2), 2.10 (4H, m, H-5, 23), 2.64 (2H, t,
J = 6.8 Hz, H-4), 2.80 (10H, m, H-8, 11, 14, 17, 20), 3.53 (3H, s, MTPA-
OMe), 3.59 (1H, s, H-1), 5.37 (12H, m, H-6, 7, 9, 10, 12, 13, 15, 16, 18,
19, 21, 22), 5.49 (1H, m, H-3), 7.40 (3H, m, MTPA-Ph), 7.53 (2H, m,
MTPA-Ph). 13C NMR (75 MHz, CDCl3) δ 14.2, 20.5, 22.9, 25.6 (5 car-
bons), 33.6, 38.3, 51.8, 55.3, 73.0, 127.0, 127.4 (2 carbons), 127.8 (2
carbons), 127.9, 128.3 (2 carbons), 128.0 (2 carbons), 128.3 (4 car-
bons), 128.5, 129.2, 129.5, 132.0, 165.8, 170.1. HRMS (ESI+) calcd. for
4.2.27. 2-(2-((3Z,6Z,9Z,12Z,15Z,18Z)-Henicosa-3,6,9,12,15,18-hexaen-
1-yl)-1,3-dioxolan-2-yl)acetic acid (44)
A solution of 43 (57.6 mg, 1.36 mmol) in 5% KOH/MeOH–H2O
(19:1, 1.36 mL) was stirred at 60 °C for 1 h. The reaction mixture was
acidified with 1 N aqueous HCl and then extracted 3 times with ethyl
acetate. The organic layer was washed with water, dried over MgSO4,
and evaporated. The residue was chromatographed on silica gel (6 g,
50% ethyl acetate–hexane) to give 44 (48.8 mg, 87%). 1H NMR
(300 MHz, CDCl3) δ 0.97 (3H, t, J = 7.5 Hz, H-22), 1.87 (2H, t,
J = 5.0 Hz, H-2), 2.08 (2H, m, H-21), 2.19 (2H, m, H-3), 2.72 (2H, s, H-
1), 2.83 (10H, m, H-6, 9, 12, 15, 18), 4.04 (4H, m, acetal-CH2), 5.37
(12H, m, H-4, 5, 7, 8, 10, 11, 13, 14, 16, 17, 19, 20). 13C NMR (75 MHz,
CDCl3) δ 14.2, 20.5, 21.4, 25.5 (2 carbons), 25.6 (4 carbons), 37.2,
42.3, 65.1 (2 carbons), 108.9, 127.0, 127.8, 128.1, 128.2 (4carbons),
128.3, 128.5, 129.0, 132.0, 173.2. HRMS (ESI+) calcd. for C26H38NaO4
[M+Na]+ 437.26678, found 437.26869. IR (neat) 3012, 2964, 2931,
2360, 2341, 1712, 1436, 1394, 1267, 1222, 1118, 1047, 948,
C
35H45F3NaO5 625.31168, found 625.31038. IR (neat) 3012, 2958,
2925, 2850, 1749, 1438, 1269, 1168, 1122, 1016, 717 cm−1
.
684 cm−1
.
10

S. Kanamori et al.
Bioorganic&MedicinalChemistryxxx(xxxx)xxx–xxx
4.2.28. (6Z,9Z,12Z,15Z,18Z,21Z)-3-Oxotetracosa-6,9,12,15,18,21-
hexaenoic acid (3)
acidified with 1 N aqueous HCl and then extracted 3 times with ethyl
acetate. The organic layer was washed with water, dried over MgSO4,
and evaporated to give 47 (43.7 mg, 96%). 1H NMR (300 MHz, CDCl3) δ
0.97 (3H, t, J = 7.5 Hz, H-22), 1.49 (2H, m, H-5) 1.83 (2H, m, H-4),
2.08 (4H, m, H-6, 21), 2.70 (2H, s, H-3), 2.83 (8H, m, H-9, 12, 15, 18),
4.04 (4H, m, acetal-CH2), 5.37 (10H, m, H-7, 8, 10, 11, 13, 14, 16, 17,
19, 20). 13C NMR (150 MHz, CDCl3) δ 14.3, 20.6, 23.5, 25.6 (2 car-
bons), 25.7 (2 carbons), 37.1, 42.2, 65.2 (2 carbons), 109.2, 127.0,
127.9, 128.2, 128.3 (4 carbons), 128.4, 128.6, 129.6, 132.1, 173.3.
HRMS (ESI+) caled. for C24H36NaO4 [M+Na]+ 411.25113, found
411.25184. IR (neat) 3012, 2960, 2923, 2358, 2341, 1737, 1714, 1699,
A solution of 44 (56 mg, 0.135 mmol) in acetone (1 mL) added PPh3
(71.2 mg, 0.27 mmol), CBr4 (89.7 mg, 0.27 mmol). The mixture was
extracted 3 times with ethyl acetate. The organic layer was washed with
water and brine over MgSO4, dried, and evaporated. The residue was
chromatographed on silica gel (20 g, 50% ethyl acetate–hexane) to give
3 (33.7 mg, 67%). 1H NMR (300 MHz, CDCl3) δ 0.98 (3H, t, J = 7.5 Hz,
H-23), 2.08 (2H, m, H-22), 2.40 (2H, m, H-4), 2.65 (2H, t, J = 7.4 Hz,
H-5), 2.85 (10H, m, H-7, 10, 13, 16, 19), 3.54 (2H, s, H-3), 5.37 (12H,
m, H-5, 6, 8, 9, 11, 12, 14, 15, 17, 18, 20, 21). 13C NMR (75 MHz,
CDCl3) δ 14.2, 20.5, 21.2, 21.6, 25.5 (2 carbons), 25.6 (3 carbons),
43.4, 29.9, 127.0, 127.3, 127.8, 128.0 (2 carbons), 128.2, 128.3, 128.5,
129.0, 129.7, 132.0, 208.3. HRMS (ESI−) calcd. for C24H33O3 [M−H]−
369.24297, found 369.24544. IR (neat) 3012, 2964, 2931, 1716, 1433,
1224, 1041, 948, 719, 680, 649 cm−1
.
4.2.32. (7Z,10Z,13Z,16Z,19Z)-3-Oxodocosa-7,10,13,16,19-pentaenoic
acid (8)
1357, 1265, 1159, 1068, 927, 711 cm−1
.
A solution of 47 (16 mg, 0.41 mmol) in acetone (0.41 mL) was
added CBr4 (27 mg, 0.082 mmol), TCEP· HCl (23.5 mg, 0.082 mmol).
The reaction mixture was stirred for 12 days at room temperature. The
reaction was quenched with water and the mixture was extracted
3 times with ethyl acetate. The organic layer was washed with water
and brine, dried over MgSO4, and evaporated. The residue was chro-
matographed on silica gel (5 g, 40% ethyl acetate–hexane) to give 8
(10.3 mg, 72%). 1H NMR (300 MHz, CDCl3) δ 0.97 (3H, t, J = 7.5 Hz,
H-22), 2.08 (4H, m, H-6, 21), 1.71 (2H, m, H-5), 2.37 (2H, m, H-5),
2.57 (2H, t, J = 7.3 Hz, H-4), 2.83 (8H, m, H-9, 12, 15, 18), 3.52 (2H, s,
H-2), 5.37 (10H, m, H-7, 8, 10, 11, 13, 14, 16, 17, 19, 20). 13C NMR
(150 MHz, CDCl3) δ 14.3, 20.6, 23.6, 25.6 (3 carbons), 26.5, 29.7, 43.0,
127.0, 127.9, 128.1 (2 carbons), 128.2, 128.3, 128.6, 128.7, 129.2,
132.1, 132.2, 167.7, 208.9. HRMS (ESI−) caled. for C22H31O3 [M−H]−
343.22732, found 343.22701. IR (neat) 2923, 2852, 2374, 2318, 1745,
4.2.29. Ethyl (7Z,10Z,13Z,16Z,19Z)-3-oxodocosa-7,10,13,16,19-pentaenoate
(45)
To a solution of (COCl)2 (2.0 M in CH2Cl2 1.25 mL, 2.50 mmol) in
CH2Cl2 (5 mL) was added a solution of DMSO (0.43 mL, 5.0 mmol) in
CH2Cl2 (2 mL) at −78 °C and the mixture was stirred at −78 °C for
10 min. A solution of 25 (781 mg, 2.08 mmol) in CH2Cl2 (4 mL) was
added and the mixture was stirred at that temperature for 10 min. Et3N
(1.45 mL, 10.4 mmol) was added to the reaction mixture at −78 °C, and
then the mixture was allowed to warm to 0 °C. The reaction was
quenched with water and the mixture was extracted 3 times with ethyl
acetate. The organic layer was washed with water and brine, dried over
MgSO4, and evaporated. The residue was chromatographed on silica gel
(100 g, 5% ethyl acetate–hexane) to give 45 (291 mg, 31%). 1H NMR
(300 MHz, CDCl3) δ 0.97 (3H, t, J = 7.5 Hz, H-22), 1.28 (3H, t,
J = 7.2 Hz, COO–CH2–CH3), 2.08 (4H, m, H-6, 21), 2.61 (2H, t,
J = 7.2 Hz, H-4), 2.83 (8H, m, H-9, 12, 15, 18), 3.43 (2H, s, H-3), 4.20
(2H, q, J = 7.1 Hz, COO–CH2–CH3), 5.37 (10H, m, H-7, 8, 10, 11, 13,
14, 16, 17, 19, 20). 13C NMR (75 MHz, CDCl3) δ 14.1 (2 carbons), 20.5,
23.2, 25.5, 25.6 (3 carbons), 26.3, 42.2, 49.3, 61.3, 127.0, 127.8, 128.0,
128.1 (2 carbons), 128.2, 128.5, 1 28.9 (2 carbons), 132.0, 167.2,
202.6. HRMS (ESI+) caled. for C24H36O3Na [M+Na]+ 395.25621,
found 395.25447. IR (neat) 3010, 2923, 2852, 2378, 2312, 1743, 1714,
1710, 1687, 1639, 1542, 1500, 1396, 1338 cm−1
.
Declaration of interest
Conflicts of interest: none.
Acknowledgements
This work was financially supported by the Platform for Drug
Discovery, Informatics, and Structural Life Science from the Japan
Agency for Medical Research and Development (AMED), and was also
supported by the MEXT-Supported Program for the Strategic Research
Foundation at Private Universities (2013–2017).
1527, 1508, 1488, 1423, 1338, 1232, 1176, 1031 cm−1
.
4.2.30. Ethyl 2-(2-((4Z,7Z,10Z,13Z,16Z)-nonadeca-4,7,10,13,16-
pentaen-1-yl)-1,3-dioxolan-2-yl)acetate (46)
To a solution of 45 (197 mg, 0.53 mmol) in benzene (15 mL) was
added ethylene glycol (658 µL, 10.6 mmol) and p-TsOH·H2O (45.6 mg,
0.26 mmol). The reaction was stirred at 110 °C for 13 h. The reaction
was quenched with water and the mixture was extracted 3 times with
ethyl acetate. The organic layer was washed with water and brine, dried
over MgSO4, and evaporated. The residue was chromatographed on
silica gel (50 g, 5% ethyl acetate–hexane) to give 46 (72 mg, 32%). 1H
NMR (300 MHz, CDCl3) δ 0.97 (3H, t, J = 7.5 Hz, H-22), 1.27 (3H, t,
J = 7.2 Hz, COO–CH2–CH3), 1.49 (2H, m, H-5) 1.83 (2H, m, H-4), 2.08
(4H, m, H-6, 21), 2.66 (2H, s, H-3), 2.83 (8H, m, H-9, 12, 15, 18), 3.98
(4H, m, acetal-CH2), 4.15 (1H, q, J = 7.1, 7.2 Hz, COO–CH2–CH3), 5.37
(10H, m, H-7, 8, 10, 11, 13, 14, 16, 17, 19, 20). 13C NMR (150 MHz,
CDCl3) δ 14.2, 14.3, 20.6, 23.5, 25.5, 25.6 (3 carbons), 27.2, 37.3, 42.7,
60.5, 65.1, 65.2, 109.4, 127.0, 127.9, 128.0, 128.1, 128.2 (2 carbons),
128.4, 128.6, 129.9, 132.0, 169.5. HRMS (ESI+) caled. for C26H40O4Na
[M+Na]+ 439.28243, found 439.28553. IR (neat) 3724, 3624, 2875,
2349, 2306, 1737, 1731, 1714, 1645, 1622, 1608, 1195, 1039, 948,
A. Supplementary data
Supplementary data associated with this article can be found, in the
online version, at https://doi.org/10.1016/j.bmc.2018.07.004.
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