Design and Synthesis of A-Ring Simplified Pyripyropene A Analogues as Potent and Selective Synthetic SOAT2 Inhibitors

Article abstract of DOI:10.1002/cmdc.201700645

Currently, pyripyropene A, which is isolated from the culture broth of Aspergillus fumigatus FO-1289, is the only compound known to strongly and selectively inhibit the isozyme sterol O-acyltransferase 2 (SOAT2). To aid in the development of new cholester

Full text of DOI:10.1002/cmdc.201700645

Accepted Article
Title: Design and Synthesis of A-Ring Simplified Pyripyropene A
Analogs as Potent and Selective Synthetic SOAT2 Inhibitors
Authors: Masaki Ohtawa, Shiho Arima, Naoki Ichida, Tomiaki
Terayama, Hironao Ohno, Takaya Yamazaki, Taichi Ohshiro,
Noriko Sato, Satoshi Omura, Hiroshi Tomoda, and Tohru
Nagamitsu
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10.1002/cmdc.201700645
ChemMedChem
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Design and Synthesis of A-Ring Simplified Pyripyropene A
Analogs as Potent and Selective Synthetic SOAT2 Inhibitors
Masaki Ohtawa,[a,†] Shiho Arima,[a,†] Naoki Ichida,[a] Tomiaki Terayama,[a] Hironao Ohno,[a] Takaya
Yamazaki,[a] Taichi Ohshiro,[b] Noriko Sato,[c] Satoshi Omura,[d] Hiroshi Tomoda,[b] and Tohru
Nagamitsu*[a]
[a]
[b]
Dr. M. Ohtawa, S. Arima, N. Ichida, T. Terayama, H. Ohno, T. Yamazaki, Prof. T. Nagamitsu
Department of Synthetic Natural Products Chemistry, School of Pharmacy, Kitasato University, 5-9-1 Shirokane, Minato-ku, Tokyo 108-8641, Japan.
E-mail: nagamitsut@pharm.kitasato-u.ac.jp
Dr. T. Ohshiro, Prof. H. Tomoda
Department of Microbial Chemistry, School of Pharmacy, Kitasato University, 5-9-1 Shirokane, Minato-ku, Tokyo 108-8641, Japan.
E-mail: tomodah@pharm.kitasato-u.ac.jp
[c]
[d]
N. Sato
School of Pharmacy, Kitasato University, 5-9-1 Shirokane, Minato-ku, Tokyo 108-8641, Japan.
Prof. S. Omura
Kitasato Institute for Life Sciences and Graduate School of Infection Control Sciences, Kitasato University, 5-9-1 Shirokane, Minato-ku, Tokyo 108-8641,
Japan.
†
These authors contributed equally to this study.
Supporting information for this article is given via a link at the end of the document.
Abstract: Currently, pyripyropene A, which is isolated from the
culture broth of Aspergillus fumigatus FO-1289, is the only
compound known to strongly and selectively inhibit the isozyme
sterol O-acyltransferase 2 (SOAT2). To aid in the development of
new cholesterol-lowering or antiatherosclerotic agents, new A-ring
simplified pyripyropene A analogs were designed and synthesized
based on the total synthesis and the results of the structure–activity
relationship studies of pyripyropene A achieved by our group.
Among the analogs, two A-ring simplified pyripyropene A analogs
exhibited equally efficient SOAT2 inhibitory activity compared with
that of natural pyripyropene A. These new analogs are the most
potent and selective SOAT2 inhibitors to be used as synthetic
compounds and attractive seed compounds for the development of
enzyme assay using rat liver microsomes (Figure 1).[7]
Accordingly, approximately 200 derivatives have been
semisynthetically prepared from 1 for a first structure–activity
relationship (SAR) study. Certain derivatives have been reported
to be not only more potent than 1, but also active in decreasing
the absorption of cholesterol in vivo from the intestines of
hamsters.[8] Recent molecular biological studies have revealed
the presence of two isozymes, namely, SOAT1 and SOAT2.[9]
SOAT1 is ubiquitously expressed, and a high-level expression is
observed in sebaceous glands, steroidogenic tissues, and
macrophages, while SOAT2 is predominantly expressed in the
liver (hepatocytes) and intestine.[10] Hence, selective inhibitors
toward SOAT2 are expected to demonstrate potential as better
drug for dyslipidemia, including atherosclerotic disease and steatosis. drug candidates with fewer side effects as cholesterol-lowering
or antiatherosclerotic agents. A cell-based assay using SOAT1-
or SOAT2-expressing Chinese hamster ovary (CHO) cells has
been developed by our group, and the selectivity of microbial
Introduction
SOAT inhibitors previously discovered by our group has been
investigated.[11] Consequently, only 1 is confirmed to be a potent
Sterol O-acyltransferase (SOAT), which is also known as acyl-
and selective inhibitor toward SOAT2 among reported SOAT
inhibitors including our natural SOAT inhibitors. Moreover, the in
CoA: cholesterol acyltransferase (ACAT)[1] plays an important
role in the metabolism of cholesterol in mammals. Hence, a
vivo efficacy of
1
in atherosclerosis has been also
demonstrated.[12] PPPA derivatives synthesized previously have
been evaluated in this cell-based assay to investigate their
selective inhibition toward the SOAT isozymes.[11b] Compared to
1, several PPPA derivatives exhibited more potent SOAT2
inhibitory activity; however, unfortunately, the isozyme selectivity
for all of the synthesized PPPA derivatives was considerably
less than that of 1. Therefore, new PPPA derivatives (>200)[13]
are prepared in a semisynthetic manner, and the second SAR of
1 is elucidated (Figure 1). Finally, 7-O-p-cyanobenzoyl PPPA
derivative 2,[13a] 1,11-O-o-methylbenzylidene acetal derivative
3,[13c] and 1,11-O-o,o-dimethylbenzylidene acetal derivative 4,[13c]
which exhibited SOAT2 inhibitory activity and isozyme selectivity
greater than those of 1, have been developed (Figure 2 and
Table 1).
large number of synthetic SOAT inhibitors, such as ureas,
imidazoles, and amides, have been reported for the treatment of
hypercholesterolemia and atherosclerosis.[2] Among these
inhibitors, the development of avasimibe[3] and pactimibe[4] had
been expected; however, their clinical studies were unsuccessful.
To the best of our knowledge, thus far, no new cholesterol-
lowering or antiatherosclerotic agents from SOAT inhibitors have
emerged in the market.[5]
During the course of our screening for naturally derived SOAT
inhibitors with a chemical structure different from the synthetic
inhibitors developed in the 1990s, a number of new natural
products have been discovered.[6] Among these natural products,
the fungal metabolite pyripyropene A (PPPA, 1) has been
reported to be one of the most potent SOAT inhibitors in an
1
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10.1002/cmdc.201700645
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Essential
R'
Essential
O
O
N
O
O
N
For SOAT2 inhibitory activity
diacetyl ≥
o,o-dimethylbenzylidene acetal ≥
o-methylbenzylidene acetal ≥
benzylidene acetal
Essential
HO
HO
13
R
O
O
O
O
p-cyanophenyl ≥
p-halophenyl ≥
p-methoxyphenyl >
i-pentyl > phenyl = n-pentyl
> methyl >> others
>> others
H
H
1
7
AcO
H
OAc
R
R'O
For isozyme selectivity
o,o-dimethylbenzylidene acetal ≥
o-methylbenzylidene acetal ≥
benzylidene acetal ≥
diacetyl
H
11
AcO
R'O
Pyripyropene A (1)
>> others
Figure 1. Structure and summary of SAR of pyripyropene A (1).
PPPA, namely, A-ring simplified PPPA analogs, were focused
on. Hence, a new, efficient, synthetic route for 1 and their
analogs was required, and the stereocontrolled total synthesis of
1 was achieved by our group.[13d,15] Herein, we report the design,
synthesis, and biological evaluation of novel A-ring simplified
PPPA analogs by an extension of all our research results on
PPPA (1), which permit the discovery of the most potent and
selective SOAT2 inhibitors as synthetic compounds.[16] Recently,
Li and Nan et al. have reported similar results by the application
of our total synthesis, where a new analog exhibited more potent
and selective SOAT2 inhibitory activity compared with that
observed for 1.[17] In addition, we report the results from the
biological evaluation of the analog in our assay system.
O
H
O
N
O
H
O
N
HO
H
HO
H
O
O
O
OR
AcO
AcO
OR
H
O
Me
2
3
O
O
N
HO
O
H
O
Results and Discussion
Me
O
H
OR
H
R =
O
Figure 3 shows the designed A-ring simplified PPPA analogs for
the third SAR study of 1. In our total synthesis, (R)-carvone,
corresponding to the B-ring of 1 as the starting material, was
selected, and subsequent ring construction was achieved in
order of A, C, and D (by coupling with the E-ring). Hence, the
exclusion of the several steps for the construction of the A-ring
from the total synthesis possibly affords the designed A-ring
simplified PPPA analogs 5–9.
CN
Me
4
Figure 2. Synthetic PPPA derivatives 2–4 developed by our group as potent
and selective SOAT2 inhibitors.
Table 1. SOAT1 and SOAT2 inhibitory activities and isozyme selectivities of
pyripyropene A (PPPA, 1) and synthetic PPPA derivatives 2–4.
First, the synthesis of 5, which is the simplest analog in this
paper, was performed according to our total synthesis (Scheme
1). The regioselective hydrogenation of (R)-(-)-carvone[18]
afforded 11, which was subjected to b-epoxide formation. First,
acetoxybromination under the conditions employed previously
by our group (NBA and AgOAc)[15] was performed to smoothly
afford 12a; however, second methanolysis and epoxide
formation did not afford desired product 13, in addition to
substrate decomposition. After the screening of the
transformation, the bromohydrin was prepared by treatment with
NBS and 1 N HClO4,[19] followed by epoxide formation via the
exposure to DBU, furnishing desired b-epoxide 13 in 55% yield
over three steps from (R)-(-)-carvone. The Wittig olefination of
13, instead of Peterson olefination employed in our total
synthesis,[15] and subsequent acidic work-up led to the opening
of the epoxide, furnishing the corresponding g-hydroxy-a,b-
unsaturated aldehyde in 95% yield;
IC50 (µM)
Compounds
SOAT1
SOAT2
SI[a]
Pyripyropene A (1)
>80.00
4.16
0.0700
0.0009
>1000
4622
2
3
4
>72.80
>71.20
0.0118
0.0072
>6161
>9916
[a] Selectivity index (SI): IC50(SOAT1) / IC50(SOAT2)
Furthermore, compared to 1, these PPPA derivatives,
particularly 3, exhibited more potent in vivo efficacy.[14]
As described above, the attractive lead compounds for the
development of drugs for dyslipidemia were successfully
obtained. Next, the third SAR studies of 1 were planned, where
new analogs that were not derived from chemically natural
2
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Our total synthesis
This study
E
O
O
N
D
Construction
of D-ring
by coupling
with E-ring
13
HO
C
Construction
of A-ring
Construction
of C-ring
3
O
O
O
2
1
O
O
4 H
B
6
A
7
B
O
10
H
11
Construction
of C-ring
Construction
O
of D-ring
by coupling
with E-ring
O
Exclusion of
the construction
of A-ring
(R)-Carvone
Pyripyropene A (1)
O
H
O
N
O
H
O
N
O
O
N
HO
HO
H
HO
3
O
O
O
O
O
O
4
O
O
O
H
1
7
10
H
H
11
CN
5
6
7
O
O
N
O
H
O
N
N
O
H
O
HO
HO
HO
H
O
O
O
O
O
O
O
O
O
O
O
10
1
H
O
O
1
1
7
7
7
O
O
10
10
11
H
11
H
11
O
O
CN
CN
O
O
8
9
10
Figure 3. The developed synthetic strategy for the new target A-ring simplified PPPA analogs 5–10 for the third SAR study of PPPA (1).
this aldehyde was protected as a TBS ether to afford aldehyde
14 in 76% yield. The treatment of 14 with a corresponding
Grignard reagent derived from iodide 15[20] followed by the
Dess–Martin oxidation afforded diketo ester equivalent 16 in
68% in two steps. The methanolysis of 16 and the heating of the
corresponding diketo methyl ester with DBU at 100 °C furnished
an inseparable diastereomixture (3ꢀ:ꢀ1 at C5) of dihydro-g-pyrone
17 by the intramolecular oxa-conjugate addition of the resulting
conjugated enol in 80% yield over two steps.[21] The enolization
of 17 by treatment with LHMDS, g-acylation with nicotinoyl
chloride, and intramolecular cyclization for the formation of g-
pyrone in one pot afforded 18 in 66% yield as an inseparable
3ꢀ:ꢀ1 diastereomixture. The deprotection of the TBS ether under
acidic conditions and acetylation furnished desired ketoacetate
19 and its C5 epimer 20 in isolated yields of 53% and 14%,
respectively, over 2 steps. Finally, the reduction of the keto
group of 19 with NaBH4 afforded interesting results; reduction
with NaBH4 and NaBH4–CeCl3 (Luche conditions[22]) afforded
desired b-alcohol 5 and its C13 epimer 21 in 93% and 74%
yields, respectively, the stereochemistry of which was confirmed
by NOE and ROESY experiments. In addition, the reduction of
20 was attempted. The reaction with NaBH4–CeCl3 afforded b-
alcohol 22 in 88% yield; however, the reduction using only
NaBH4 led to decomposition without any reduced products. The
reason why stereochemistry observed with the presence or
absence of CeCl3 differs is still unclear; however, similar results
using other substrates have been reported previously by the
Krief[23] and Jean[24] groups, and the Krief group has provided a
promising hypothesis for these results. During the reduction of
19 in the presence of CeCl3, some CeCl3-containing species
would be located at the less-hindered a-face of the 13-ketone,
which blocked the nucleophilic attack from the a-face. Hence,
the subsequent attack of the hydride would be forced from the
original hindered b-face, affording a-alcohol 21. Conversely, the
reaction of 19 in the absence of CeCl3 would be reduced by the
hydride from the less-hindered a-face, affording b-alcohol 5.
During the reduction of 20, the CeCl3-containing species would
be located at the less-hindered b-face (convex face) of the 13-
ketone of 20, and the attack of the hydride would be forced from
the original hindered a-face (concave face), affording b-alcohol
22. The corresponding a-alcohol, which was obtained by the
reduction of 20 with NaBH4, possibly decomposed owing to its
unstability.
Next, A-ring simplified PPPA analogs 6 and 7 were also
synthesized (Scheme 2). The double methylation[25] of known
ketone 11, which was obtained by the regioselective
hydrogenation
of
(R)-(-)-carvone,
afforded
23.
The
acetoxybromination of a,b-unsaturated ketone 23 under the
conditions previously reported by our group (NBA and AgOAc)[15]
smoothly proceeded to furnish the corresponding bromoacetate,
which was subjected to methanolysis to afford b-epoxide 24 in
62% yield over five steps. The Peterson olefination of 24
3
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O
O
O
O
b
d
c
a
X
Br
O
OR
e
11
12a R = Ac
12b R = H
13
(R)-(–)-Carvone
O
O
O
OMe
O
O
O
O
H
5
O
g
f
h
H
OTBS
OTBS
OTBS
14
16
17
O
O
N
O
O
N
O
O
N
O
O
O
i
j
13
13
+
5R
5S
O
O
O
H
H
H
OTBS
OAc
19
OAc
18
20
k
m
93%
l
74%
88%
O
O
O
I
15
O
O
N
O
H
O
N
O
O
N
4.6%
H
HO
H
HO
HO
NOE
13R
13R
5S
13S
5R
5R
8.5%
O
O
O
H
ROESY
H
H
H
OAc
OAc
OAc
H
H
2.4%
2.4%
5
21
22
Scheme 1. Synthesis of A-ring simplified PPPA analogs 5, 21, and 22. Reagents and conditions: a) PtO2, H2, neat, rt; b) NBA, AgOAc, AcOH, rt; c) K2CO3, MeOH,
rt; d) NBS, 1N HClO4, H2O-dioxane, 0 °C; e) DBU, rt, 55% over three steps; f) 1. MeOCH2PPh3Cl, t-BuOK, THF, then aq. HCO2H, rt, 95%, 2. TBSCl, imidazole,
DMAP, DMF, 50 °C, 76%; g) 1. 15, i-PrMgCl, THF, –30 °C, 2. DMP, CH2Cl2, 0 °C, 68% over two steps; h) 1. MeOH, toluene, 90 °C, 2. DBU, toluene, 100 °C, 80%
over two steps (dr = 3:1); i) LHMDS, nicotinoyl chloride hydrochloride, THF, –78 °C to rt, 66% (dr = 3:1); j) 1. AcCl, MeOH, rt, 2. Ac2O, Et3N, DMAP, CH2Cl2, rt,
53% over two steps for 19, 14% over two steps for 20; k) NaBH4, MeOH, 0 °C, 93%; l) NaBH4, CeCl3, MeOH, 0 °C, 74%; m) NaBH4, CeCl3, MeOH, 0 °C, 88%.
followed by the hydrolysis and TBS protection of the resulting
secondary alcohol afforded a,b-unsaturated aldehyde 25. In this
case, instead of Peterson olefination as shown in Scheme 1, the
Wittig reaction gave no reaction. This result would be caused by
the steric hindrance at the a-positions of the carbonyl group and
is in agreement with that reported previously.[15] Diketo ester
equivalent 26 was obtained in 44% yield over 4 steps by
coupling between aldehyde 25 and the corresponding Grignard
reagent derived from iodide 15 followed by the Dess–Martin
oxidation. The methanolysis of 26 followed by treatment with
DBU in toluene at 100°C stereoselectively afforded dihydro-g-
pyrone 27 by the intramolecular oxa-conjugate addition in 69%
yield over 2 steps without any other stereoisomer unlike the
synthesis of 19 shown in Scheme 1. The stereochemistries of 27
were confirmed by NOESY. This result is in agreement with that
obtained in the total synthesis of 1 reported previously by our
group.[15] The stereoselective a-protonation at C5 of the resulting
enolate after the intramolecular oxa-conjugate addition can be
completely controlled by two key sterically demanding groups on
the b-face, originating from the C4 and C6-axial methyl groups,
respectively. Compound 28 bearing the pyridyl-a-pyrone moiety
was synthesized in 44% yield by the coupling of the
corresponding enolate derived from 27 with nicotinoyl chloride.
Finally, the deprotection of the TBS group in 28 was conducted
under acidic conditions, followed by acylation (acetyl or p-
cyanobenzoyl) and the stereoselective Luche reduction to
furnish A-ring simplified PPPA analogs 6 and 7 in 73% and 44%,
respectively, over three steps. Notably, the final Luche reduction
in Scheme 2 and the total synthesis of 1 reported previously by
our group exhibited the same stereoselectivity, but that of the
Luche reduction of 19 in Scheme 1 was reversed. In the former
case, the presence of the two axial methyl groups at C4 and C6
would completely block the reduction from the extremely
hindered b-face, leading to the sole formation of the b-hydroxy
group, which was reduced from the less-hindered a-face. The
latter would lead to the opposite stereoselectivity in the Luche
reduction because of the decrease in the steric hindrance by the
absence of the C4-axial methyl group.
4
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O
O
O
O
a
c
b
O
11
23
24
(R)-(–)-Carvone
O
O
O
OMe
O
H
O
O
O
H
O
e
d
f
H
H
OTBS
OTBS
OTBS
H
25
26
27
NOESY
O
O
N
O
O
N
HO
H
O
O
O
g
h
4
6
ROESY for 6
H
H
OTBS
OR
H
28
6
7
R = Ac
R = p-cyanobenzoyl
Scheme 2. Synthesis of the A-ring simplified PPPA analogs 6 and 7. Reagents and conditions: a) PtO2, H2, neat, rt; b) 1. LDA, MeI, THF, 0 °C to rt, 2. LDA, MeI,
THF, 0 °C to rt; c) NBA, AgOAc, AcOH, rt, 2. K2CO3, MeOH, rt, 62% over five steps; d) 1) TMSCH2OMe, s-BuLi, t-BuOK, THF, –78 °C to rt, 2. TBSCl, imidazole,
DMAP, DMF, 60 °C; e) 1. 15, i-PrMgCl, THF, –30 °C to rt, 2. DMP, CH2Cl2, rt, 44% over four steps; f) 1. MeOH, toluene, 90 °C, 2. DBU, toluene, 100 °C, 69%
over two steps; g) LHMDS, nicotinoyl chloride hydrochloride, THF, –78 °C to rt, 44%; h) 1. AcCl, MeOH, THF, 0 °C, 2. Ac2O, Et3N, DMAP, CH2Cl2, rt or p-
cyanobenzoic acid, EDCI, DMAP, CH2Cl2, rt, 3. NaBH4, CeCl3, MeOH, –78 °C to 0 °C, 73% over three steps for 6, 44% over three steps for 7.
Finally, A-ring simplified PPPA analogs 8, 9, and 10 were
synthesized (Schemes 3 and 4). First, 8 was synthesized
starting with the chlorination[26] of known 6,6-dimethylcarvone
(29).[25] The hydrolysis[27] of the resulting allyl chloride
afforded allyl alcohol 30 in 92% yield (Scheme 3). Next, the
regioselective hydroboration followed by oxidation[28] of 30
was performed under various conditions; however, either a
reaction did not proceed or substrate decomposition was
observed. Hence, the titanocene-catalyzed reductive
epoxide-opening reaction[28,29] by the TBS protection of a
hydroxy group afforded 31 as a diastereomixture (ca. 3ꢀ:ꢀ2) in
high yield over 2 steps. The reductive epoxide-opening
reaction in the presence of water as the hydride source[30] of
31 afforded the desired primary alcohol in 72% yield, which
was protected as a TBS ether to afford 32 in 93% yield. The
subsequent conversion of 32 to 8 was carried out according
to our total synthesis.[15] The acetoxybromination of 32 and
methanolysis furnished b-epoxide 33 in 60% yield over two
steps, which was subjected to the Peterson olefination, TBS
protection, the coupling of the resulting aldehyde 34 with 15,
and the Dess–Martin oxidation, furnishing 35 in 42% yield
over 4 steps. The methanolysis of 35 and stereoselective
cyclization afforded dihydro-g-pyrone 36 in 66% yield over 2
steps. The subsequent construction of the pyridyl-g-pyrone
moiety afforded 37 in 34% yield. Finally, the deprotection of
the TBS ether, acetylation, and Luche reduction afforded A-
ring simplified PPPA analog 8 in 51% yield over 3 steps.
A-ring simplified PPPA analogs 9 and 10 were derived from
37 (Scheme 4). Desilylation under acidic conditions, silylene
acetal formation of 1,3-diol in the resulting triol, and p-
cyanobenzoylation at C7 afforded 38, which was converted
into the desired 9 by desilylation, acetylation, and the Luche
reduction in a total yield of 38% over 6 steps from 37. In
addition, another analog 10 was similarly synthesized from 37
(total yield of 25% over 4 steps) by desilylation, acetalization
with o-tolualdehyde, p-cyanobenzoylation of C7 hydroxy
group of the resulting acetal 39, and the Luche reduction.
New A-ring simplified PPPA analogs 5–10, 21, and 22 were
synthesized according to our total synthesis.[15] Moreover, A-
ring simplified PPPA analog 40, which exhibited more potent
and selective SOAT2 inhibitory activity compared with that of
1, was synthesized according to the report by Li and Nan et
al.[17,21] (Figure 4). Table 2 summarizes the SOAT inhibitory
activities and isozyme selectivities of all compounds.
The SOAT2 inhibitory activities and isozyme selectivities of 5,
8, 21, and 22 disappeared, while those of 6 considerably
decreased in comparison with those of 1. These new analogs
lack A-ring. Therefore, pyripyropene A (1), bearing a rigid
steroid-like skeleton, exhibits
a potent inhibitory activity
because the three acetoxy groups are located in the suitable
position when binding to SOAT2.[31] In contrast, among
analogs 7, 9, and 10, bearing the p-cyanobenzoyl group,
analogs 7 and 10 exhibited the same SOAT2 inhibitory
activity compared with that of 1; however, that of analog 9
slightly decreased. These new analogs also lack A-ring;
however, since they bear the p-cyanobenzoyl group at C7
(and the o-methylbenzylideneacetal at C1 and 11 for 10) in
common with the most potent and selective PPPA derivative
2-4, the SOAT2 inhibitory activity may be maintained.
Therefore, their substituents proved to be considerably
effective for binding to SOAT2. Unfortunately, the isozyme
selectivities of analogs 7 and 10, exhibiting a potent SOAT2
inhibitory activity, were less than that of 1. With regard to
isozyme selectivity, the rigid steroid-like skeleton of 1 might
be better than the A-ring simplified PPPA analogs. However,
notably, the analogs 7 and 10 have the highest SI values
among all synthetic SOAT inhibitors reported till date.
5
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O
O
O
O
a
b
c
O
HO
TBSO
29
30
31
(R)-(–)-Carvone
O
H
O
O
e
d
O
f
TBSO
OTBS
TBSO
TBSO
TBSO
TBSO
TBSO
32
33
34
O
O
O
H
OMe
O
O
O
g
i
h
O
TBSO
TBSO
OTBS
TBSO
OTBS
TBSO
35
36
O
O
N
O
O
N
HO
O
H
j
O
O
ROESY
H
H
TBSO
TBSO
OTBS
AcO
AcO
OAc
H
37
8
Scheme 3. Synthesis of A-ring simplified PPPA analog 8. Reagents and conditions: a) ref. 40; b) 1. t-BuOCl, silica gel, hexane, –30 °C to rt, 92%, 2. Cu2O, p-
TsOH, DMSO, H2O, rt, 92%; c) 1. mCPBA, CH2Cl2, 0 °C to rt, 99%, 2. TBSCl, imidazole, CH2Cl2, rt, 95%; d) 1. Cp2TiCl2, Mn, H2O, THF, rt, 72%, 2. TBSCl,
imidazole, CH2Cl2, rt, 93%; e) 1. NBA, AgOAc, AcOH, rt, 2. K2CO3, MeOH, rt, 60% over two steps; f) 1. TMSCH2OMe, s-BuLi, t-BuOK, THF, –78 °C to 0 °C, 2.
TBSCl, Et3N, DMAP, DMF, 50 °C; g) 1. 15, i-PrMgCl, THF, –30 °C to rt, 2. DMP, CH2Cl2, 0 °C, 42% over four steps; h) 1. MeOH, toluene, 90 °C, 2. DBU, toluene,
100 °C, 66% over two steps; i) LHMDS, nicotinoyl chloride hydrochloride, THF, –78 °C to rt, 34%; j) 1. AcCl, MeOH, 0 °C, 2. Ac2O, Et3N, DMAP, MeCN, 0 °C to rt,
3. NaBH4, CeCl3·7H2O, MeOH, 0 °C, 51% over three steps.
O
H
O
N
O
H
O
N
HO
H
O
a
b
O
O
O
O
O
O
7
O
AcO
AcO
H
H
t-Bu
Si
O
CN
CN
t-Bu
9
38
37
ROESY
O
O
N
O
O
N
HO
H
c
d
O
O
O
O
H
H
O
H
H
O
O
O
O
H
OH
H
H
H
H
H
CN
10
39
Scheme 4. Synthesis of A-ring simplified PPPA analogs 9 and 10. Reagents and conditions: a) 1. AcCl, MeOH, 0 °C to rt, 2. (t-Bu)2Si(OTf)2, 2,6-lutidine, DMF,
0 °C, 3. p-cyanobenzoic acid, EDCI, DMAP, CH2Cl2, rt; b) 1. Et3N·3HF, THF, rt, 2. Ac2O, Et3N, DMAP, MeCN, 0 °C to rt, 3. NaBH4, CeCl3·7H2O, MeOH, 0 °C,
38% over six steps; c) 1. AcCl, MeOH, 0 °C, 2. o-tolualdehyde, PPTS, DMF, 0 °C to rt; d) 1. p-cyanobenzoic acid, EDCI, DMAP, DMF, rt, 2. NaBH4, CeCl3·7H2O,
MeOH, 0 °C, 25% over four steps.
6
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10.1002/cmdc.201700645
ChemMedChem
FULL PAPER
selectivity as synthetic compounds. Currently, the further
optimization of A-ring simplified PPPA analogs and in vivo tests
are underway in our laboratory.
O
H
O
N
O
HO
H
steps
O
Experimental Section
AcO
OAc
(S)-Carvone
AcO
Chemistry
40
Figure 4. Structure of the A-ring simplified PPPA analog 40 reported by Li and
Nan et al. as a potent and selective SOAT2 inhibitor.[17]
General: All reactions were performed in flame-dried glassware under
nitrogen using standard techniques for handling air-sensitive materials.
Commercial reagents were used without further purification unless
otherwise noted. Organic solvents were distilled and dried over 3 or 4 Å
molecular sieves (MS). Cold baths were prepared under the following
conditions: 0 °C, wet ice/water; −78 °C, dry ice/acetone. Purification by
flash column chromatography was performed over silica gel 60N
(spherical, neutral, particle size of 40–50 µm). Thin-layer chromatography
(TLC) was performed on 0.25 mm Merck silica gel 60 F254 plates, and
the effluents were visualized by UV (254 nm) as well as using
phosphomolybdic acid and p-anisaldehyde TLC stains. Yields
corresponded to chromatographically and spectroscopically pure
compounds unless otherwise noted. 1H and 13C NMR spectra were
recorded using an internal deuterium lock on 400-MR, VNMRS-400, and
UNITY-400 spectrometers (Agilent Technologies, Waldbronn, Germany).
All NMR signals were reported in ppm relative to the internal reference
standard provided by chloroform (i.e., 7.26 or 77.0 ppm for 1H and 13C
spectra, respectively). Multiplicity data were presented as follows: s =
singlet, d = doublet, t = triplet, q = quartet, m = multiplet, br = broad, dd =
doublet of doublets, and dt = doublet of triplets. Coupling constants (J)
were reported in hertz. Infrared spectra were recorded on an FT/IR460-
plus infrared spectrometer (JASCO, Tokyo, Japan). Absorption data were
expressed in wavenumbers (cm−1). Optical rotation was recorded on a
JASCO DIP-1000 polarimeter (JASCO, Tokyo, Japan) and reported as
follows: [a]TD, concentration (g/100 mL), and solvent. High-resolution
mass spectra were recorded on a JEOL JMS-700 MStation, JEOL JMS-
AX505HA, and JEOL JMS-T100LP systems (JEOL, Tokyo, Japan)
equipped with FAB, EI, and ESI high-resolution mass spectrometers.
Table 2. SOAT1 and SOAT2 inhibitory activities and isozyme selectivities of
A-ring simplified PPPA analogs 5–10, 21, 22, and 40.
IC50 (µM)
Compounds
SOAT1
SOAT2
SI[a]
Pyripyropene A (1)
>80.0
>23.5
>23.5
>23.5
>22.0
8.0
0.07
>23.50
>23.50
>23.50
3.40
>1000.0
—
5
21
22
6
—
—
6.5
7
0.07
114.3
—
8
>17.4
>15.1
9.8
>17.40
0.86
9
17.6
89.1
—
10
40
0.11
>18.4
>18.40
[a] Selectivity index (SI): IC50(SOAT1) / IC50(SOAT2)
(1S,4R,6S)-4-Isopropyl-1-methyl-7-oxabicyclo[4.1.0]heptan-2-one
(13): Colorless solid; [a]27 –9.2 (c 1.0, CHCl3); IR (KBr) 1711, 1215 cm–
D
1
;
1H-NMR (400 MHz, CDCl3) d 3.43 (d, 1H, J = 4.8 Hz), 2.56 (t, 1H, J =
Conversely, A-ring simplified PPPA analog 40 reported by Li and
Nan et al. as a potent and selective SOAT2 inhibitor did not
exhibit any SOAT2 inhibitory activity and isozyme selectivity in
our assay system, which not only is different from that used in
their study but also is the most accurate assay system used
currently for measuring the SOAT2 inhibitory activity and
13.2 Hz), 2.11-2.03 (m, 2H), 1.89-1.81 (m, 2H), 1.55-1.48 (m, 1H), 1.39
(s, 3H), 0.90 (d, 3H, J = 6.8 Hz), 0.87 (d, 3H, J = 6.8 Hz); 13C-NMR (100
MHz, CDCl3) d 209.7, 65.7, 59.9, 44.8, 39.4, 32.8, 27.3, 19.5, 19.3, 15.1;
EI-HRMS calcd for C10H16O2 168.1150 (M＋), found 168.1148 (M＋).
(3S,5S)-3-((tert-Butyldimethylsilyl)oxy)-5-isopropyl-2-
isozyme selectivity.[21] The new analogs
7 and 10 were
methylcyclohex-1-enecarbaldehyde (14): Colorless solid; [a]27 +53.5
D
(c 1.0, CHCl3); IR (KBr) 3054, 2959, 1710, 1680, 1423, 1265 cm–1 1H-
;
considered to be not only the most potent and selective
synthetic SOAT2 inhibitor but also attractive seed compounds
for the discovery of drugs for dyslipidemia, including
atherosclerosis and steatosis.
NMR (400 MHz, CDCl3) d 10.15 (s, 1H), 4.27 (br s, 1H), 2.41-2.35 (m,
1H), 2.14 (s, 3H), 2.04-1.96 (m, 1H), 1.78-1.68 (m, 1H), 1.61-1.49 (m,
1H), 1.33-1.24 (m, 1H), 1.26 (dd, 1H, J = 10.0, 11.2 Hz), 0.92 (s, 9H)
0.90 (dd, 6H, J = 1.8, 6.6 Hz), 0.12 (d, 6H, J = 4.2 Hz); 13C-NMR (100
MHz, CDCl3) d 192.5, 157.2, 134.3, 73.7, 38.2, 36.7, 32.5, 26.4, 26.1,
20.0, 19.5, 18.4, 13.7, –3.6, –4.6; FAB-HRMS (m-NBA) calcd for
C17H32NaO2Si 319.2069 (M+Na＋), found 319.2064 (M+Na＋).
Conclusions
In conclusion, novel A-ring simplified PPPA analogs were
designed, synthesized, and evaluated in terms of their SOAT2
inhibitory activities and isozyme selectivities. Designed analogs
were prepared by the application of the total synthesis of PPPA
reported by our group[15] except for several steps associated with
the A-ring construction. Among the analogs, the synthesized A-
ring simplified pyripyropene A analogs 7 and 10 exhibited the
same efficacy for the SOAT2 inhibitory activity compared with
that of natural pyripyropene A and extremely high isozyme
5-((3S,5S)-3-((tert-Butyldimethylsilyl)oxy)-5-isopropyl-2-
methylcyclohex-1-enecarbonyl)-2,2,6-trimethyl-4H-1,3-dioxin-4-one
(16): Colorless oil; [a]27D +26.6 (c 1.0, CHCl3); IR (KBr) 3120, 2958, 1734,
1658, 1571, 1463, 1390, 1352, 1260, 1216, 1076 cm–1 1H-NMR (400
;
MHz, CDCl3) d 4.21 (br s, 1H), 2.27 (s, 3H), 2.15-2.08 (m, 1H), 1.96-1.90
(m, 2H), 1.70 (br s, 9H), 1.53-1.46 (m, 2H), 1.34-1.28 (m, 1H), 0.87 (br s,
15H), 0.06 (s, 6H); 13C-NMR (100 MHz, CDCl3) d 196.8, 175.4, 158.8,
138.5, 136.1, 109.8, 106.6, 73.0, 39.1, 36.7, 32.4, 31.3, 31.1, 26.2, 25.8,
25.7, 20.2, 19.9, 19.7, 18.5, 16.5, –3.7, –4.5; ESI-HRMS (TFA-Na) calcd
for C24H40NaO5Si, 459.2543 (M+Na＋), found 459.2526 (M+Na＋).
7
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10.1002/cmdc.201700645
ChemMedChem
FULL PAPER
(4aR,6S,8S,8aS)-Methyl-8-((tert-butyldimethylsilyl)oxy)-6-isopropyl-
2,8a-dimethyl-4-oxo-4a,5,6,7,8,8a-hexahydro-4H-chromene-3-
(5aS,6S,8S,9aS,10S)-10-Hydroxy-8-isopropyl-5a-methyl-1-oxo-3-
(pyridin-3-yl)-1,5a,6,7,8,9,9a,10-octahydropyrano[4,3-b]chromen-6-yl
carboxylate (17): As a 3ꢀ:ꢀ1 diastereomixture; colorless oil; [a]27 +31.7
acetate (21): Colorless solid; [a]27 +27.1 (c 1.0, CHCl3); IR (KBr) 2928,
D
D
(c 1.0, CHCl3); IR (KBr) 2957, 2932, 1707, 1679, 1587, 1464, 1437, 1391,
1362, 1257, 1216, 1114 cm–1; 1H-NMR (400 MHz, CDCl3) d 3.87-3.82 (m,
1H), 3.79 (s, 3H), 2.47 (dd, 1H, J = 16.0, 4.0 Hz), 2.22 (s, 3H), 2.15-2.07
(m, 1H), 1.77-1.71 (m, 1H), 1.57-1.47 (m, 2H), 1.30-1.25 (m, 1H), 1.19 (s,
3H), 1.00-0.84 (m, 16H), 0.11 (d, 6H, J = 9.2 Hz); 13C-NMR (100 MHz,
CDCl3) d 189.4, 175.3, 166.0, 110.3, 87.5, 76.3, 69.0, 52.2, 50.1, 40.6,
36.1, 32.4, 25.4, 23.6, 20.6, 19.7, 19.4, 17.9, 9.8, –4.8, –5.3; ESI-HRMS
(TFA-Na) calcd for C22H38NaO5Si, 433.2386 (M+Na＋), found 433.2403
(M+Na＋).
2859, 1715, 1261 cm–1; 1H-NMR (400 MHz, CDCl3) d 9.01 (d, 1H, J = 2.4
Hz), 8.69 (dd, 1H, J = 1.6, 4.8 Hz), 8.10 (ddd, 1H, J = 1.6, 2.4, 8.0 Hz),
7.40 (ddd, 1H, J = 0.8, 5.2, 8.0 Hz), 6.49 (s, 1H), 5.06 (dd, 1H, J = 4.8,
12.0 Hz), 4.45 (d, 1H, J = 10.0 Hz), 2.33-2.27 (m, 1H), 2.18 (s, 3H), 2.01-
1.95 (m, 1H), 1.86 (ddd, 1H, J = 3.6, 10.0, 12.4 Hz), 1.59-1.43 (m, 2H),
1.33-1.27 (m, 1H), 1.28 (s, 3H), 1.37-1.20 (m, 1H), 1.02-0.87 (m, 1H),
0.93 (d, 3H, J = 6.7 Hz), 0.91 (d, 3H, J = 6.7 Hz); 13C-NMR (100 MHz,
CDCl3) d 170.6, 164.0, 163.4, 157.6, 151.2, 146.8, 133.7, 121.0, 100.0,
83.9, 64.5, 63.6, 45.0, 40.9, 32.4, 30.0, 28.9, 23.0, 21.7, 20.2, 20.1, 14.5,
12.3; ESI-HRMS (TFA-Na) calcd for C23H27NNaO6 436.1736 (M+Na＋),
found 436.1734 (M+Na＋).
(5aS,6S,8S,9aR)-6-((tert-Butyldimethylsilyl)oxy)-8-isopropyl-5a-
methyl-3-(pyridin-3-yl)-5a,6,7,8,9,9a-hexahydropyrano[4,3-
b]chromene-1,10-dione (18): As a 3ꢀ:ꢀ1 diastereomixture; colorless oil;
[a]27D +11.1 (c 1.0, CHCl3); IR (KBr) 3055, 2982, 2307, 1758, 1429, 1265
cm–1; 1H-NMR (400 MHz, CDCl3) d 9.06 (d, 1H, J = 2.4 Hz), 8.75 (dd, 1H,
J = 1.6, 4.8 Hz), 8.19 (dt, 1H, J = 2.0, 8.0 Hz), 7.46 (ddd, 1H, J = 2.0, 4.8,
8.0 Hz), 6.43 (s, 1H), 3.97 (dd, 1H, J = 5.3, 11.2 Hz), 2.63 (dd, 1H, J =
4.0, 12.0 Hz), 2.20 (dd, 1H, J = 2.0, 14.0 Hz), 1.81 (dt, 1H, J = 2.4, 13.2
Hz), 1.56 (dd, 1H, J = 6.8, 12.4 Hz), 1.48-1.40 (m, 1H), 1.30 (s, 3H),
1.22-1.21 (m, 1H), 1.11-1.05 (m, 1H), 0.96 (s, 9H), 0.92 (d, 3H, J = 6.8
Hz), 0.91 (d, 3H, J = 6.8 Hz), 0.19 (s, 3H), 0.15 (s, 3H); 13C-NMR (100
MHz, CDCl3) d 188.0, 173.5, 162.7, 157.0, 152.8, 147.8, 134.1, 127.0,
134.1, 127.0, 124.1, 98.3, 89.9, 76.1, 51.6, 40.4, 36.0, 32.3, 30.0, 26.1,
24.3, 20.1, 19.0, 11.1, –4.1, –4.2; ESI-HRMS (TFA-Na) calcd for
C27H37NNaO5Si 506.2339 (M+Na＋), found 506.2345 (M+Na＋).
(5aS,6S,8S,9aR,10R)-10-Hydroxy-8-isopropyl-5a-methyl-1-oxo-3-
(pyridin-3-yl)-1,5a,6,7,8,9,9a,10-octahydropyrano[4,3-b]chromen-6-yl
acetate (22): Colorless solid; [a]27 +18.5 (c 0.1, CHCl3); IR (KBr) 2927,
D
1715, 1572, 1432, 1223, 1094 cm–1 1H-NMR (400 MHz, CDCl3) d 9.02-
;
9.00 (m, 1H), 8.70-8.68 (m, 1H), 8.16 (d, 1H, J = 8.0 Hz), 7.46 (dd, 1H, J
= 4.8, 7.2 Hz), 6.42 (s, 1H), 5.04 (dd, 1H, J = 5.2, 12.0 Hz), 4.77 (d, 1H, J
= 9.6 Hz), 2.21-2.14 (m, 2H), 2.09 (s, 3H), 1.91-1.85 (m, 1H), 1.59-1.35
(m, 3H), 1.54 (s, 3H), 1.33-1.22 (m, 1H), 0.94 (d, 3H, J = 6.8 Hz), 0.92 (d,
3H, J = 6.8 Hz); 13C-NMR (100 MHz, CDCl3) d 170.5, 164.1, 162.9, 156.9,
150.7, 146.3, 134.4, 102.6, 100.2, 84.4, 70.8, 68.5, 60.1, 44.6, 37.0, 32.5,
30.0, 27.4, 21.6, 21.0, 20.5, 20.2, 20.1; ESI-HRMS (TFA-Na) calcd for
C23H28NO6 414.1917 (MH＋), found 414.1910 (MH＋).
(1S,4S,6S)-4-Isopropyl-1,3,3-trimethyl-7-oxabicyclo[4.1.0]heptan-2-
(5aS,6S,8S,9aR)-6-(Acetoxy)-8-isopropyl-5a-methyl-3-(phenyl)-
one (24): Yellow oil; [a]27 –102.7 (c 1.0, CHCl3); IR (KBr) 1743, 1075
D
5a,6,7,8,9,9a-hexahydropyrano[4,3-b]chromene-1,10-dione
Yellow solid; [a]27D +10.2 (c 1.0, CHCl3); IR (KBr) 2930, 1757, 1628, 1536.
1431, 1262 cm–1 1H-NMR (300 MHz, CDCl3) d 9.06 (dd, 1H, J = 0.6, 2.1
(19):
cm–1; 1H-NMR (400 MHz, CDCl3) d 3.42 (d, 1H, J = 4.8 Hz), 2.15 (dd, 1H,
J = 10.4, 15.6 Hz), 2.02 (ddd, 1H, J = 4.8, 6.4, 15.6 Hz), 1.96-1.89 (m,
1H), 1.58-1.53 (m, 1H), 1.38 (s, 3H), 1.16 (s, 3H), 1.12 (s, 3H), 0.93 (d,
3H, J = 6.8 Hz), 0.87 (d, 3H, J = 6.8 Hz); 13C-NMR (100 MHz, CDCl3) d
210.5, 63.3, 57.1, 49.9, 47.5, 27.6, 24.8, 24.4, 20.9, 20.8, 18.9, 16.7; EI-
HRMS calcd for C12H20O2 196.1463 (M＋), found 196.1451 (M＋).
;
Hz), 8.74 (dd, 1H, J = 1.8, 4.8 Hz), 8.18 (ddd, 1H, J = 1.8, 2.1, 8.4 Hz),
7.44 (dd, 1H, J = 0.6, 8.4 Hz), 6.54 (s, 1H), 5.26 (dd, 1H, J = 5.1, 11.7
Hz), 2.75 (dd, 1H, J = 3.6, 12.3 Hz), 2.27 (ddd, 1H, J = 3.9, 5.7, 14.4 Hz),
2.19 (s, 3H), 2.06-1.98 (m, 1H), 1.64-1.53 (m, 1H), 1.39 (s, 3H), 1.40-
1.29 (m, 1H), 1.18-1.05 (m, 1H), 0.87-0.81 (m, 1H), 0.92 (d, 6H, J = 6.3
Hz); 13C-NMR (100 MHz, CDCl3) d 187.0, 173.2, 170.5, 162.9, 156.9,
153.0, 147.9, 134.1, 126.9, 124.1, 100.5, 98.5, 87.4, 76.1, 51.6, 40.4,
32.3, 32.0, 24.5, 21.6, 20.2, 20.0, 12.0; ESI-HRMS (TFA-Na) calcd for
C23H25NNaO6 434.1580 (M+Na＋), found 434.1565 (M+Na＋).
5-((3S,5S)-3-((tert-Butyldimethylsilyl)oxy)-5-isopropyl-2,6,6-
trimethylcyclohex-1-ene-1-carbonyl)-2,2,6-trimethyl-4H-1,3-dioxin-4-
one (26): Yellow oil; [a]27 +27.7 (c 1.0, CHCl3); IR (KBr) 2957, 2858,
D
1744, 1656, 1545, 1468, 1377, 1346, 1253, 1198 cm–1 1H-NMR (300
;
MHz, CDCl3) d 4.15 (t, 1H, J = 14.7 Hz), 2.45 (s, 3H), 1.98-1.89 (m, 1H),
1.79-1.71 (m, 1H), 1.70 (s, 3H), 1.69 (s, 3H), 1.60-1.55 (m, 2H), 1.55 (s,
3H), 1.13 (s, 3H), 0.95 (s, 3H), 0.93 (d, 3H, J = 6.9 Hz), 0.89 (s, 9H), 0.84
(d, 3H, J = 6.9 Hz), 0.10 (s, 3H), 0.07 (s, 3H); 13C-NMR (75 MHz, CDCl3)
d 197.6, 179.1, 158.2, 143.4, 132.4, 110.3, 105.8, 77.4, 72.6, 47.3, 39.5,
29.7, 26.0, 25.6, 25.3, 25.3, 25.2, 24.8, 24.6, 23.7, 21.8, 18.8, 18.3, 16.5,
–3.8, –4.7; ESI-HRMS (TFA-Na) calcd for C26H44NaO5Si 487.2856
(M+Na＋), found 487.2841 (M+Na＋).
(5aS,6S,8S,9aS)-6-(Acetoxy)-8-isopropyl-5a-methyl-3-(phenyl)-
5a,6,7,8,9,9a-hexahydropyrano[4,3-b]chromene-1,10-dione
Yellow solid; [a]27D +63.5 (c 1.0, CHCl3); IR (KBr) 2930, 1757, 1628, 1536,
1431, 1262 cm–1 1H-NMR (300 MHz, CDCl3) d 9.08-9.06 (m, 1H), 8.75-
(20):
;
8.72 (m, 1H), 8.22 (dd, 1H, J = 1.5, 7.2 Hz), 7.65 (dd, 1H, J = 5.1, 6.9 Hz),
6.41 (s, 1H), 5.38 (dd, 1H, J = 5.1, 11.7 Hz), 2.94 (dd, 1H, J = 3.0, 4.2
Hz), 2.67 (dd, 1H, J = 2.1, 13.2 Hz), 2.09 (s, 3H), 1.91-1.85 (m, 1H), 1.67
(s, 3H), 1.54-1.35 (m, 2H), 1.35-1.09 (m, 2H), 0.90 (d, 6H, J = 5.1 Hz);
13C-NMR (75 MHz, CDCl3) d 186.7, 173.6, 170.3, 162.8, 157.0, 152.4,
147.5, 134.6, 129.1, 124.3, 100.2, 98.7, 88.0, 70.0, 51.6, 37.7, 33.0, 32.4,
30.0, 25.7, 21.6, 21.4, 20.7; ESI-HRMS (TFA-Na) calcd for C23H25NNaO6
434.1588 (M+Na＋), found 434.1565 (M+Na＋).
(4aR,6S,8S,8aS) -Methyl-8-((tert-butyldimethylsilyl)oxy)-6-isopropyl-
2,5,5,8a-tetramethyl-4-oxo-4a,5,6,7,8,8a-hexahydro-4H-chromene-3-
carboxylate (27): Yellow oil; [a]27 +19.9 (c 0.1, CHCl3); IR (KBr) 2371,
D
1745, 1060 cm–1 1H-NMR (400 MHz, CDCl3) d 3.82 (dd, 1H, J = 4.8,
;
11.6 Hz), 3.78 (s, 3H), 2.39 (s, 1H), 2.13 (s, 3H), 2.02-1.97 (m, 1H), 1.52
(ddd, 1H, J = 3.2, 4.8, 13.7 Hz), 1.39-1.29 (m, 1H), 1.31 (s, 3H), 1.25 (s,
3H), 1.04-1.00 (m, 1H), 1.03 (s, 3H), 0.91 (s, 9H), 0.90 (d, 3H, J = 6.8 Hz),
0.79 (d, 3H, J = 6.8 Hz), 0.10 (s, 3H), 0.10 (s, 3H); 13C-NMR (100 MHz,
CDCl3) d 189.3, 174.0, 166.6, 111.5, 87.9, 77.2, 58.9, 52.0, 51.3, 37.8,
29.4, 28.9, 25.9, 25.2, 24.6, 20.6, 19.0, 18.3, 16.9, 13.5, –4.4; ESI-HRMS
(TFA-Na) calcd for C24H42NaO5Si 461.2699 (M+Na＋), found 461.2697
(M+Na＋).
(5aS,6S,8S,9aS,10R)-10-Hydroxy-8-isopropyl-5a-methyl-1-oxo-3-
(pyridin-3-yl)-1,5a,6,7,8,9,9a,10-octahydropyrano[4,3-b]chromen-6-yl
acetate (5): Colorless solid; [a]27 +17.8 (c 1.0, CHCl3); IR (KBr) 3055,
D
2929, 1708, 1428, 1264 cm–1; 1H-NMR (300 MHz, CDCl3) d 9.03 (d, 1H, J
= 4.8 Hz), 8.70 (d, 1H, J = 4.5 Hz), 8.15 (d, 1H, J = 5.1 Hz), 7.44 (dd, 1H,
J = 3.0, 4.8 Hz), 6.50 (s, 1H), 5.02 (dd, 1H, J = 4.8, 11.7 Hz), 4.64 (d, 1H,
J = 4.2 Hz), 2.21 (s, 3H), 2.01-1.95 (m, 1H), 1.90-1.81 (m, 2H), 1.65-1.42
(m, 3H), 1.50 (s, 3H), 1.37-1.29 (m, 1H), 0.94 (d, 3H, J = 6.6 Hz), 0.93 (d,
3H, J = 6.6 Hz); 13C-NMR (75 MHz, CDCl3) d 170.8, 164.4, 163.4, 157.7,
151.9, 147.2, 133.4, 103.6, 99.9, 83.0, 62.0, 43.7, 41.4, 32.6, 30.1, 27.8,
23.0, 21.7, 20.2, 20.1, 14.5, 13.0; ESI-HRMS (TFA-Na) calcd for
C23H27NNaO6 436.1736 (M+Na＋), found 436.1723 (M+Na＋).
(5aS,6S,8S,9aR)-6-((tert-Butyldimethylsilyl)oxy)-8-isopropyl-5a,9,9-
trimethyl-3-(pyridin-3-yl)-5a,6,7,8,9,9a-hexahydro-1H,10H-
pyrano[4,3-b]chromene-1,10-dione (28): Yellow oil; [a]27 +43.1 (c 1.0,
D
CHCl3); IR (KBr) 2965, 1743, 1262, 1075 cm–1 1H-NMR (400 MHz,
;
CDCl3) d 9.04 (s, 1H), 8.74 (d, 1H, J = 6.0 Hz), 8.17 (d, 1H, J = 13.2 Hz),
8
This article is protected by copyright. All rights reserved.

10.1002/cmdc.201700645
ChemMedChem
FULL PAPER
7.46-7.42 (m, 1H), 6.38 (s, 1H), 3.94 (dd, 1H, J = 4.8, 11.7 Hz), 2.55 (s,
1H), 2.06-1.99 (m, 1H), 1.62-1.56 (m, 2H), 1.30 (s, 3H), 1.24 (s, 3H), 1.11
(s, 3H), 1.11-1.06 (m, 1H), 0.95 (s, 9H), 0.93 (d, 3H, J = 6.8 Hz), 0.82 (d,
3H, J = 6.8 Hz), 0.18 (s, 3H), 0.15 (s, 3H); 13C-NMR (100 MHz, CDCl3) d
187.5, 172.4, 161.9, 157.1, 151.9, 146.9, 134.5, 100.9, 98.1, 90.8, 90.5,
77.4, 76.9, 60.4, 51.1, 38.2, 29.8, 29.4, 28.8, 25.9, 25.2, 24.6, 22.8, 18.9,
18.3, 16.8, 14.2, –4.2, –4.3; ESI-HRMS (TFA-Na) [M+Na]+ calcd for
C29H41NNaO5 534.2652 (M+Na＋), found 534.2658 (M+Na＋).
(1S,4S,6S)-1,3,3-Trimethyl-4-(2,2,3,3,9,9,10,10-octamethyl-4,8-dioxa-
3,9-disilaundecan-6-yl)-7-oxabicyclo[4.1.0]heptan-2-one
(33):
Colorless solid; [a]27 –33.8 (c 1.0, CHCl3); IR (KBr) 1701, 1470, 1406,
D
1389, 1362, 1255, 1216, 1091, 1007 cm–1 1H-NMR (400 MHz, CDCl3) d
;
3.60 (m, 4H), 3.38 (ddd, 1H, J = 1.2, 1.5, 3.0 Hz), 2.17 (m, 2H), 1.89 (m,
1H), 1.74 (m, 1H), 1.38 (s, 3H) 1.17 (s, 3H), 1.11 (s, 3H), 0.88 (m, 18H),
0.04 (m, 12H); 13C-NMR (100 MHz, CDCl3) d 210.4, 63.7, 63.4, 61.2,
57.2, 47.3, 43.3, 43.2, 26.1, 24.8, 22.5, 18.4, 16.8, –5.2, –5.3; ESI-HRMS
(TFA-Na) calcd for C24H48NaO4Si2 479.2989 (M+Na＋), found 479.2967
(M+Na＋).
(5aS,6S,8S,9aS,10R)-10-Hydroxy-8-isopropyl-5a,9,9-trimethyl-1-oxo-
3-(pyridin-3-yl)-5a,6,8,9,9a,10-hexahydro-1H,7H-pyrano[4,3-
b]chromen-6-yl acetate (6): Colorless solid; [a]27 +58.3 (c 1.0, CHCl3);
5-((3S,5S)-3-((tert-Butyldimethylsilyl)oxy)-2,6,6-trimethyl-5-
(2,2,3,3,9,9,10,10-octamethyl-4,8-dioxa-3,9-disilaundecan-6-
yl)cyclohex-1-enecarbonyl)-2,2,6-trimethyl-4H-1,3-dioxin-4-one (35):
D
IR (KBr) 3433, 2361, 1638, 1241, 1041 cm–1 1H-NMR (400 MHz, CDCl3)
;
d 9.03 (s, 1H), 8.70 (s, 1H), 8.13 (d, 1H, J = 8.4 Hz), 7.44 (brs, 1H), 6.47
(s, 1H), 5.05 (d, 1H, J = 4.0 Hz), 5.00 (dd, 1H, J = 4.8, 12.0 Hz), 2.82 (brs,
1H), 2.18 (s, 3H), 2.06-1.99 (m, 1H), 1.79 (ddd, 1H, J = 13.2, 4.8, 3.2 Hz),
1.67 (s, 3H), 1.54 (m, 2H), 1.32 (m, 1H), 1.28 (s, 3H), 1.23 (s, 3H), 0.96
(d, 3H, J = 6.8 Hz), 0.85 (d, 3H, J = 6.8 Hz); 13C-NMR (75 MHz, CDCl3) d
170.5, 161.7, 126.5, 105.0, 102.2, 84.3, 78.0, 77.4, 60.6, 53.0, 51.5, 39.8,
29.9, 27.8, 26.3, 25.6, 25.4, 21.6, 19.1, 19.1, 15.9, 15.8; ESI-HRMS
(TFA-Na) calcd for C25H31NNaO6 464.2049 (M+Na＋ ), found 464.2048
(M+Na＋).
Yellow oil; [a]27 –11.0 (c 1.0, CHCl3); IR (KBr) 3020, 2956, 2930, 1739,
D
1649, 1538, 1471, 1380, 1349, 1255, 1216 cm–1 1H-NMR (400 MHz,
;
CDCl3) d 4.12 (ddd, 1H, J = 2.7, 6.0, 6.6 Hz), 3.61 (m, 4H), 2.44 (s, 3H),
1.92 (m, 2H), 1.75 (m, 1H), 1.70 (s, 3H), 1.69 (s, 3H), 1.62 (m, 1H), 1.52
(d, 3H, J = 9.2 Hz) 1.15 (s, 3H), 0.97 (s, 3H), 0.89 (m, 27H), 0.04 (m,
18H); 13C-NMR (100 MHz, CDCl3) d 197.7, 178.9, 158.0, 143.3, 132.4,
110.3, 105.8, 72.2, 64.6, 61.0, 41.8, 41.5, 39.0, 30.7, 26.2, 26.1, 26.0,
25.5, 25.4, 25.1, 24.3, 23.6, 21.8, 18.5, 18.4, 18.2, 16.5, –3.8, –4.8, –5.3;
ESI-HRMS (TFA-Na) [M+Na]+ calcd for C38H72NaO7Si3 747.4484 (M+Na
＋), found 747.4481 (M+Na＋).
(5aS,6S,8S,9aS,10R)-10-Hydroxy-8-isopropyl-5a,9,9-trimethyl-1-oxo-
3-(pyridin-3-yl)-5a,6,8,9,9a,10-hexahydro-1H,7H-pyrano[4,3-
b]chromen-6-yl 4-cyanobenzoate (7): Colorless solid; [a]27 +88.3 (c
(4aR,6S,8S,8aS)-Methyl-8-((tert-butyldimethylsilyl)oxy)-2,5,5,8a-
tetramethyl-6-(2,2,3,3,9,9,10,10-octamethyl-4,8-dioxa-3,9-
disilaundecan-6-yl)-4-oxo-4a,5,6,7,8,8a-hexahydro-4H-chromene-3-
D
0.1, CHCl3); IR (KBr) 3433, 3020, 2341, 1637, 1216 cm–1 1H-NMR (400
;
MHz, CDCl3) d 8.99 (brs, 1H), 8.68 (brs, 1H), 8.23 (d, 2H, J = 8.4 Hz),
8.14 (brs, 1H), 7.80 (d, 2H, J = 8.4 Hz), 7.45 (brs, 1H), 6.41 (s, 1H), 5.28
(dd, 1H, J = 5.0, 12.2 Hz), 5.09 (d, 1H, J = 3.6 Hz), 2.85 (brs, 1H, 2.10-
2.04 (m, 1H), 1.92 (ddd, 1H, J = 3.2, 4.8, 13.0 Hz), 1.82 (s, 3H), 1.70 (m,
1H), 1.63 (d, 1H, J = 4.0 Hz), 1.28 (s, 3H), 1.25 (m, 4H), 0.98 (d, 3H, J =
6.8 Hz), 0.86 (d, 3H, J = 6.4 Hz); 13C-NMR (100 MHz, CDCl3) d 164.3,
163.8, 162.0, 134.3, 132.5, 130.5, 118.1, 116.8, 103.9, 100.2, 83.8, 79.8,
77.4, 77.3, 60.8, 53.1, 51.6, 39.7, 31.8, 31.1, 29.9, 27.7, 26.3, 25.6, 25.4,
22.9, 22.8, 19.1, 19.0, 16.1, 14.4; ESI-HRMS (TFA-Na) calcd for
C31H32N2NaO6 551.2158 (M+Na＋), found 511.2171 (M+Na＋).
carboxylate (36): Yellow oil; [a]27 –3.3 (c 1.0, CHCl3); IR (KBr) 3021,
D
2955, 2931, 1636, 1390, 1256, 1215, 1103 cm–1 1H-NMR (300 MHz,
;
CDCl3) d 3.79 (ddd, 4H, J = 4.5, 4.8, 6.6 Hz), 3.60 (m, 3H), 3.45 (dd, 1H,
J = 8.4, 9.9 Hz), 2.43 (s, 1H), 2.14 (s, 3H), 1.82 (d, 1H, J = 3.0 Hz), 1.69
(m, 1H), 1.50 (d, 1H, J = 13.5 Hz), 1.37 (d, 1H, J = 11.4 Hz), 1.32 (s, 3H),
1.06 (s, 3H), 0.92 (s, 3H), 0.88 (m, 27H), 0.04 (m, 18H).; 13C-NMR (100
MHz, CDCl3) d 189.3, 174.0, 166.6, 111.5, 87.8, 64.5, 61.2, 58.7, 52.1,
45.1, 40.7, 37.3, 30.4, 28.7, 26.2, 26.1, 25.9, 20.6, 18.5, 18.3, 16.8, 13.7,
–4.4, –5.2, –5.3; ESI-HRMS (TFA-Na) calcd for C36H70NaO7Si3 721.4327
(M+Na＋), found 721.4349 (M+Na＋).
(S)-5-(3-Hydroxyprop-1-en-2-yl)-2,6,6-trimethylcyclohex-2-enone
(30): Yellow oil; [a]27 +176.1 (c 1.0, CHCl3); IR (KBr) 3609, 3020, 1701,
(5aS,6S,8S,9aR)-6-((tert-Butyldimethylsilyl)oxy)-5a,9,9-trimethyl-8-
(2,2,3,3,9,9,10,10-octamethyl-4,8-dioxa-3,9-disilaundecan-6-yl)-3-
(pyridin-2-yl)-5a,6,7,8,9,9a-hexahydropyrano[4,3-b]chromene-1,10-
D
1666, 1522, 1423, 1216 cm–1; 1H-NMR (400 MHz, CDCl3) d 6.62 (m, 1H),
5.27 (s, 1H), 5.00 (s, 1H), 4.05 (m, 2H), 2.53 (m, 1H), 2.44 (m, 2H), 1.79
(m, 3H), 1.11 (s, 3H), 1.04 (s, 3H); 13C-NMR (100 MHz, CDCl3) d 204.4,
149.0, 142.6, 133.6, 112.0, 66.6, 47.1, 44.8, 29.7, 23.8, 19.8, 16.4; EI-
HRMS calcd for C12H18O2 194.1307 (M＋), found 194.1306 (M＋).
dione (37): Yellow oil; [a]27 +21.9 (c 1.0, CHCl3); IR (KBr) 3025, 2955,
D
2931, 2858, 1756, 1630, 1543, 1479, 1442, 1422, 1257, 1094 cm–1 1H-
;
NMR (300 MHz, CDCl3) d 9.05 (s, 1H), 8.76 (s, 1H), 8.22 (d, 1H, J = 8.1
Hz), 7.50 (m, 1H), 6.39 (s, 1H), 3.79 (ddd, 4H, J = 5.1, 5.7, 8.7 Hz), 3.50
(m, 1H), 2.60 (s, 1H), 1.84 (m, 1H), 1.71 (m, 1H), 1.56 (m, 1H), 1.42 (m,
1H), 1.44 (s, 3H), 1.15 (s, 3H), 0.97 (s, 3H), 0.91 (m, 27H), 0.04 (m,
18H); 13C-NMR (100 MHz, CDCl3) d 187.4, 172.4, 162.3, 157.2, 152.5,
147.5, 134.1, 126.9, 124.0, 100.9, 97.8, 90.4, 64.5, 61.2, 60.3, 45.0, 40.7,
37.8, 30.5, 28.6, 26.2, 26.1, 26.0, 18.6, 18.4, 16.7, 14.4, –4.2, –5.2, –5.3;
ESI-HRMS (TFA-Na) calcd for C41H70NO7Si3 772.4460 (MH＋ ), found
772.4446 (MH＋).
(R)-5-((R)-2-(((tert-Butyldimethylsilyl)oxy)methyl)oxiran-2-yl)-2,6,6-
trimethylcyclohex-2-enone (31): As a 1ꢀ:ꢀ1 diastereomixture; Yellow oil;
[a]27D –48.0 (c 1.0, CHCl3); IR (KBr) 1633, 1106 cm–1; 1H-NMR (300 MHz,
CDCl3) d 6.58 (t, 1H, J = 2.4 Hz), 3.60 (m, 2H), 2.94 (d, 1H, J = 5.4 Hz),
2.61 (m, 1H), 2.61 (d, 1H, J = 2.7 Hz), 2.44 (m, 1H), 1.93 (dd, 1H, J = 5.1,
6.0 Hz), 1.76 (s, 3H), 1.21 (s, 3H), 1.19 (s, 3H), 0.86 (m, 9H), 0.01 (m,
6H); 13C-NMR (100 MHz, CDCl3) d 203.7, 203.2, 141.9, 141.7, 133.9,
133.5, 64.3, 63.1, 61.3, 61.0, 52.7, 50.1, 49.3, 47.9, 44.6, 44.2, 26.5,
26.4, 26.1, 26.0, 25.8, 21.6, 21.3, 18.5, 18.4, 16.6, 16.5, –5.3, –5.4; ESI-
HRMS (TFA-Na) calcd for C18H32NaO3Si 347.2018 (M+Na ＋ ), found
347.2021 (M+Na＋).
2-((5aS,6S,8S,9aS,10R)-6-Acetoxy-10-hydroxy-5a,9,9-trimethyl-1-
oxo-3-(pyridin-2-yl)-1,5a,6,7,8,9,9a,10-octahydropyrano[4,3-
b]chromen-8-yl)propane-1,3-diyl diacetate (8): Colorless solid; [a]27
–
D
145.2 (c 0.1, CHCl3); IR (KBr) 3445, 2930, 2360, 2340, 1735, 1697, 1643,
1584, 1373, 1250, 1041 cm–1 1H-NMR (400 MHz, CDCl3) d 9.04 (s, 1H),
;
(S)-2,6,6-Trimethyl-5-(2,2,3,3,9,9,10,10-octamethyl-4,8-dioxa-3,9-
disilaundecan-6-yl)cyclohex-2-enone (32): Colorless oil; [a]27D –31.9 (c
1.0, CHCl3); IR (KBr) 3020, 2955, 2930, 2360, 2340, 1660, 1470, 1255,
8.71 (s, 1H), 8.20 (m, 1H), 7.50 (m, 1H), 6.50 (d, 1H, J = 4.8 Hz), 5.05 (d,
1H, J = 4.0 Hz), 4.94 (m, 1H), 4.19 (m, 2H), 3.97 (m, 2H), 2.29 (m, 1H),
2.16 (m, 3H), 2.12 (m, 2H), 2.08 (m, 1H), 2.08 (m, 6H), 1.97 (m, 1H),
1.58 (s, 3H), 1.34 (s, 3H), 1.25 (s, 3H); 13C-NMR (100 MHz, CDCl3) d
211.2, 157.7, 155.4, 154.3, 154.0, 153.4, 152.2, 136.0, 121.1, 113.7,
111.3, 69.6, 68.3, 60.0, 56.6, 42.2, 37.6, 33.6, 33.5, 33.4, 33.2, 21.8,
18.3, 18.1, 18.0, 16.3, 12.2, 12.0; ESI-HRMS (TFA-Na) calcd for
C29H35NNaO10 580.2159 (M+Na＋), found 580.2137 (M+Na＋).
1216, 1088 cm–1 1H-NMR (400 MHz, CDCl3) d 6.59 (dd, 1H, J = 0.9, 1.8
;
Hz), 3.55 (m, 4H), 2.35 (m, 2H), 2.06 (m, 1H), 1.85 (m, 1H), 1.72 (s, 3H),
1.16 (s, 3H), 1.02 (s, 3H), 0.86 (m, 18H), 0.01 (m, 12H); 13C-NMR (100
MHz, CDCl3) d 205.0, 143.7, 133.4, 63.8, 61.4, 45.6, 43.4, 42.9, 26.1,
24.8, 23.9, 20.5, 18.4, 16.6, –5.3, –5.4; ESI-HRMS (TFA-Na) calcd for
C24H48NaO3Si2 463.3040 (M+Na＋), found 463.3061 (M+Na＋).
9
This article is protected by copyright. All rights reserved.

10.1002/cmdc.201700645
ChemMedChem
FULL PAPER
2-((5aS,6S,8S,9aS,10R)-6-((4-Cyanobenzoyl)oxy)-10-hydroxy-5a,9,9-
trimethyl-1-oxo-3-(pyridin-3-yl)-5a,6,8,9,9a,10-hexahydro-1H,7H-
pyrano[4,3-b]chromen-8-yl)propane-1,3-diyl diacetate (9): Colorless
solid; [a]27D +97.2 (c 0.1, CHCl3); IR (neat) 3421, 3021, 2965, 1724, 1643,
Acknowledgements
This research was partially supported by a Grant-in-Aid for
Scientific Research (C) from the Ministry of Education, Culture,
Sports, Science and Technology (MEXT) of Japan (TN:
22590011 and MO: 25460152), Takeda Science Foundation
(MO), and Kitasato University research grant for young
researchers (MO). The authors would like to thank Dr. K. Nagai
(Kitasato University) for kindly measuring MS spectra.
1581, 1276, 1229, 1103, 1040 cm–1 1H-NMR (400 MHz, CDCl3) d 8.97
;
(brs, 1H), 8.67 (brs, 1H), 8.19 (d, 1H, J = 8.4 Hz), 8.06 (d, 1H, J = 8.0 Hz),
7.80 (d, 2H, J = 8.4 Hz), 7.38 (dd, 1H, J = 4.8, 8.0 Hz), 6.39 (s, 1H), 5.21
(dd, 1H, J = 4.4, 11.2 Hz), 5.08 (d, 1H, J = 4.0 Hz), 4.23-4.18 (m, 2H),
4.02 (dd, 1H, J = 6.4, 11.2 Hz), 3.93 (t, 1H, J = 10.0 Hz), 2.98 (brs, 1H),
2.35-2.31 (m, 1H), 2.10 (s, 3H), 2.06 (s, 3H), 1.82 (s, 3H), 1.77-1.65 (m,
3H), 1.37 (s, 3H), 1.27 (s, 3H), 1.27-1.23 (m, 1H); 13C-NMR (100 MHz,
CDCl3) d 171.1, 164.0, 163.8, 161.8, 157.4, 151.5, 146.7, 133.9, 133.0,
132.4, 130.2, 123.6, 117.9, 116.8, 103.2, 99.1, 83.6, 82.8, 78.9, 65.6,
62.4 60.5, 52.5, 46.1, 39.1, 34.9, 27.1, 26.7, 24.8, 20.9, 18.5, 15.9, 15.0;
ESI-HRMS (TFA-Na) calcd for C35H36N2NaO10 667.2259 (M+Na＋), found
667.2268 (M+Na＋).
Conflict of interest
The authors declare no conflict of interest.
(5aS,6S,8S,9aS,10R)-10-Hydroxy-5a,9,9-trimethyl-1-oxo-3-(pyridin-3-
yl)-8-(2-(o-tolyl)-1,3-dioxan-5-yl)-1,5a,6,7,8,9,9a,10-
Keywords: A-ring simplified PPPA analog • pyripyropene A •
SAR study • SOAT2 • Total synthesis
octahydropyrano[4,3-b]chromen-6-yl-4-cyanobenzoate
(10):
Colorless solid; [a]27 –105.6 (c 0.1, CHCl3); IR (KBr) 3448, 2360, 2341,
D
1643, 1277, 1086 cm–1 1H-NMR (400 MHz, CD3OD) d 9.08 (brs, 1H),
;
References:
8.69 (s, 1H), 8.31 (d, 1H, J = 8.0 Hz), 8.23 (d, 2H, J = 8.0 Hz), 7.90 (d,
2H, J = 8.8 Hz), 7.58 (brs, 1H), 7.48 (dd, 1H, J = 1.6, 7.6 Hz), 7.19-7.08
(m, 3H), 6.77 (s, 1H), 5.55 (s, 1H), 5.22 (dd, 1H, J = 4.8, 12.0 Hz), 5.04
(d, 1H, J = 3.6 Hz), 4.27-4.23 (m, 1H), 4.00-3.96 (m, 1H), 3.81 (dd, 1H, J
= 11.2, 18.8 Hz), 3.78 (dd, 1H, J = 11.2, 18.8 Hz), 2.42-2.32 (m, 1H),
2.31 (s, 3H), 2.12-2.06 (m, 1H), 1.86 (s, 3H), 1.80 (dd, 1H, J = 13.2, 25.6
Hz), 1.71 (d, 1H, J = 3.6 Hz), 1.40 (s, 3H), 1.32 (s, 3H), 1.27-1.22 (m,
1H); 13C-NMR (100 MHz, CDCl3) d 164.3, 163.6, 161.7, 135.9, 135.7,
133.9, 132.6, 130.5, 130.4, 129.0, 126.1, 125.7, 117.9, 117.0, 103.8,
100.0, 82.9, 79.0, 72.0, 70.7, 60.5, 52.6, 45.7, 39.4, 32.8, 32.0, 29.8,
29.7, 29.5, 27.3, 27.2, 22.8, 19.0, 18.8, 16.0, 14.2; ESI-HRMS (TFA-Na)
calcd for C39H39N2O8 663.2706 (MH＋), found 663.2713 (MH＋).
[1]
The older name for this enzyme is acyl-CoA: cholesterol
acyltransferase or ACAT, but this acronym is also used for the enzyme
acetyl-CoA acetyltransferase, so to avoid confusion we use SOAT to
designate the cholesterol esterifying enzyme.
[2]
[3]
B. D. Roth, Drug Discov. Today, 1998, 3, 19–25.
J. C. Tardif, J. Gregoire, P. L. L’Allier, T. J. Anderson, O. Bertrand,
F.Reeves, L. M. Title, F. Alfonso, E. Schampaert, A. Hassan, R. McLain,
M. L. Pressler, R. Ibrahim, J. Lesperance, J. Blue, T. Heinonen, J.
Rodes-Cabau, Circulation, 2004, 110, 3372–3377.
[4]
S. E. Nissen, E. M. Tuzcu, H. B. Brewer, I. Sipahi, S. J. Nicholls, P.
Ganz, P. Schoenhagen, D. D. Waters, C. J. Pepine, T. D. Crowe, M. H.
Davidson, J. E. Deanfield, L. M. Winsniewski, J. J. Hanyok, L. M.
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were maintained at 37 °C in 5% CO2 in Ham’s F-12 medium
supplemented with MEM vitamins, Geneticin (300 µg/mL), and 10% heat-
inactivated fetal bovine serum (hereafter referred to as medium A).
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Assay for the Synthesis of Neutral Lipids in SOAT1- and SOAT2-
CHO Cells: The assay for the synthesis of neutral lipids ([14C]cholesteryl
ester (CE),
14C]oleic acid in SOAT1- or SOAT2-CHO cells was carried out by our
[ [
14C]triglyceride (TG), and 14C]phospholipid (PL)) from
[
established method.[11b] Briefly, SOAT1- or SOAT2-CHO cells (1.25 × 105
cells in 250 µL of medium A) were cultured in a 48-well plastic microplate
in the culture medium described above and allowed to recover overnight
at 37 °C in 5% CO2. The assays were carried out with cells that were at
least 80% confluent. Following the overnight recovery, a test sample (2.5
µL; 0, 0.01, 0.1, and 1 mg/mL in MeOH) and [1-14C]oleic acid (5 µL of a
10% EtOH/PBS solution, 1 nmol, 1.85 KBq) were added to each culture.
After 6 h incubation at 37 °C in 5% CO2, the medium was removed, and
the cells in each well were washed twice with PBS. The cells were lysed
by the addition of 0.25 mL of 10 mM Tris-HCl (pH 7.5) containing 0.1%
(w/v) sodium dodecyl sulfate, and the cellular lipids were extracted by the
method reported by Bligh and Dyer.[32] After concentrating the organic
solvent, the total lipids were separated on a TLC plate (silica gel F254,
0.5 mm thickness, Merck, Darmstadt, Germany) and analyzed with an
FLA7000 analyzer (Fuji Film). In this cell-based assay, [14C]CE was
produced by the reaction of SOAT1 or SOAT2. SOAT inhibitory activity
(%) is defined as ([1-14C]CE-drug/[14C]CE-control) × 100. The IC50 value
defined as the drug concentration causing 50% inhibition of the biological
activity is calculated from duplicate experiments (n = 3).
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10
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10.1002/cmdc.201700645
ChemMedChem
FULL PAPER
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11
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FULL PAPER
Entry for the Table of Contents
O
O
N
HO
H
O
O
O
O
H
O
O
Pyripyropene A
O
O
H
O
N
O
O
N
HO
H
HO
O
O
7
O
O
O
O
H
H
O
H
CN
O
CN
H
10
New A-ring simplified pyripyropene A analogs
The most potent and selective synthetic SOAT2 inhibitors
New A-ring simplified pyripyropene A analogs were synthesized by application of our total synthesis. Among the analogs, two
analogs 7 and 10 exhibited the same efficacy for the SOAT2 inhibitory activity compared with that of natural pyripyropene A and
extremely high isozyme selectivity as synthetic compounds. The analogs 7 and 10 were considered to be the most potent and
selective synthetic SOAT2 inhibitor.
12
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