Gram Scale Syntheses of (-)-Incarvillateine and Its Analogs. Discovery of Potent Analgesics for Neuropathic Pain

Article abstract of DOI:10.1021/acs.jmedchem.6b00132

(-)-Incarvillateine (INCA) is the major antinociceptive component of Incarvillea sinensis, which has been used to treat rheumatism and relieve pain in traditional Chinese medicine. We have developed a concise and general synthetic approach for INCA, which

Full text of DOI:10.1021/acs.jmedchem.6b00132

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Article
Gram Scale Syntheses of (-)-Incarvillateine and Its Analogs,
Discovery of Potent Analgesics for Neuropathic Pain
Bin Huang, Fengying Zhang, Gang Yu, Yan Song, Xintong
Wang, Meiliang Wang, Zehui Gong, Ruibin Su, and Yanxing Jia
J. Med. Chem., Just Accepted Manuscript • DOI: 10.1021/acs.jmedchem.6b00132 • Publication Date (Web): 29 Mar 2016
Downloaded from http://pubs.acs.org on March 29, 2016
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Gram Scale Syntheses of (ꢀ)ꢀIncarvillateine and Its
Analogs, Discovery of Potent Analgesics for
Neuropathic Pain
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§
Bin Huang,†,§ Fengying Zhang,†,§ Gang Yu,‡, Yan Song,† Xintong Wang,† Meiliang Wang,‡ Zehui
Gong,‡ Ruibin Su,‡ and Yanxing Jia*,†
†State Key Laboratory of Natural and Biomimetic Drugs, School of Pharmaceutical Sciences,
Peking University, 38 Xueyuan Road, Beijing 100191, China; State Key Laboratory of Drug
Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, 555 Zuchongzhi
Road, Shanghai 201203, China
‡State Key Laboratory of Toxicology and Medical Countermeasures, Beijing Key Laboratory of
Neuropsychopharmacology, Beijing Institute of Pharmacology and Toxicology, 27 Taiping
Road, Beijing 100850, China
ABSTRACT: (ꢀ)ꢀIncarvillateine (INCA) is the major antinociceptive component of Incarvillea
sinensis, which has been used to treat rheumatism and relieve pain in Traditional Chinese
Medicine. We have developed a concise and general synthetic approach for INCA, which
enabled gramꢀscale asymmetric syntheses of (ꢀ)ꢀINCA, (ꢀ)ꢀincarvilline, (ꢀ)ꢀisoincarvilline, and
six other INCA analogues. The synthesis of isoincarvilline was reported for the first time. Three
structurally simplified analogues of INCA were also synthesized. In vivo screening found that
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INCA and two structurally optimized analogues were efficacious in preventing the acetic acidꢀ
induced writhing response. Moreover, their analgesic efficacy was demonstrated in formalin
induced pain model. More importantly, administration of 20 or 40 mg/kg of INCA and two
structurally optimized analogues showed strong analgesic effects in spared nerve injury (SNI)
model, and their effective doses were lower than the current gold standard, Gabapentin (100
mg/kg in this model).
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■ INTRODUCTION: Pain is one of the most common discomforts sought for medical care,
among which neuropathic pain is usually difficult to treat because the underlying
pathophysiology is complex.1ꢀ5 The current clinically available analgesics for the treatment of
neuropathic pain mainly include the following drug classes: opioids, tricyclic antidepressants,
anticonvulsant agents, and nonsteroidal antiꢀinflammatory drugs (NSAIDs)/analgesics. However,
these drugs only provide 30ꢀ50% reduction in pain in about 50% of patients, and they have
significant side effects that also limit their use.6 Therefore, the search for new agents for the
treatment of neuropathic pain continues to be an active area of scientific research.4, 7ꢀ11
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Figure 1. Structures of incarvillateine and related alkaloids.
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Incarvillea sinensis, one of the main components of the Chinese herbal medicine “Tougucao”,
has been traditionally used to treat rheumatism and relieve pain. The search for the
pharmacological ingredients of this plant has resulted in the isolation of a number of novel
monoterpene alkaloids (Figure 1), such as incarvillateine (INCA) (1), incarvilline (2), and
incarvine C (3).12ꢀ19 INCA, the structurally more complex member of these alkaloids, is likely
generated via dimerization of incarvine C (3), a hydroxycinnamate derivative of incarvilline (2).
Isoincarvilline (4), also called 4ꢀepiꢀincarvilline, was isolated from Incarvillea mairei var.
grandiflora by Zhang and coworkers in 2009.20
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Analgesic activity studies of these alkaloids have shown that INCA possesses more potent
antinociceptive activity than morphine in the formalinꢀinduced pain model in mice.21ꢀ23
However, 2, 3, and related compounds isolated from the same plant exhibited no or weak
activity. Thus, INCA was considered as the major active component.22 Further studies on the
antinociceptive mechanism of INCA as selective receptor antagonists suggested that it might not
only interact with µꢀ and kꢀopioid receptors, but also with adenosine receptor. These results
indicate that its mechanism of action is different from that of morphine.21,23 Since INCA does not
belong to any reported structural groups that show efficacy against pathological pain, it and its
analogues have the potential to be developed as new analgesic drugs.
Structurally, these monoterpene alkaloids (1ꢀ3) share the common bicyclic piperidine moiety
bearing five contiguous stereocenters, which provide an intriguing synthetic challenge. Not
surprisingly, these alkaloids have attracted considerable attention from the synthetic community
and several total syntheses have been reported.24ꢀ30 However, either the long steps or the
expensive heavy metal catalysts limited the large scale preparation of INCA and its analogues.
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Although we have developed an enantioselective, concise total synthesis of incarvilline and
INCA in 2009, the low reproducibility and the use of at least 8 equiv of disiamylborane at the
hydroboration/oxidation step as well as this targetꢀoriented synthesis limited large scale
preparation of these natural products and analogues.26
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The previous structure–activity relationship (SAR) studies of 1 mainly focused on the αꢀ
truxillic acid moiety.22,31ꢀ34 A systematic description of the pharmacological profile, the exact
mechanism of action of INCA, and the detailed structure–activity relationship (SAR) of the
incarvilline unit part await to be revealed. Herein we report a concise, gram scale asymmetric
synthesis of 1, 2 and 4, which would be used to investigate the antinociceptive effects of (ꢀ)ꢀ
INCA and possible mechanisms underlying their antinociceptive effects.34 In addition, six
analogues were synthesized, which differed in the substituents of the piperidine nucleus. The C4ꢀ
methyl group of the piperidine nucleus was epimerized or replaced with a double bond to reveal
the role of C4ꢀsubstituent in the antinociceptive activity of INCA. The Nꢀmethyl group of the
piperidine nucleus was replaced with nꢀpropyl group, allyl group, nꢀbutyl group or Loop C to
study the effect of Nꢀsubstitution on the antinociceptive activity of INCA. Three structurally
simplified analogues, in which the incarvilline unit was replaced by piperidine structure, were
synthesized to investigate whether the fiveꢀmembered ring of the incarvilline unit is essential for
the antinociceptive activity of INCA.35,36 These compounds were screened by the acetic acid
abdominal constriction assay.37,38 The analgesic efficacies of INCA and analogues 15e and 15h
were further assessed in formalin induced pain model and in spared nerve injury (SNI)
model.39,40
■RESULTS AND DISCUSSION
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Chemistry. The total synthesis of natural product 1, 2, and 4 as well as the preparation of
incarvillateine’s analogues and simplified analogues are shown in Schemes 1ꢀ5.
Scheme 1. Retrosynthetic Analysis of Incarvilline, Isoincarvilline, Incarvillateine and Its
Analogues
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Our improved and more general route was depicted in Scheme 1. We envisioned that 1 and its
analogues, 2 and 4, could be accessed from the key common intermediate 5. 5 could be readily
manipulated from 6, which would be prepared from carvone by using a Favorskii rearrangement
as the key step.
As shown in Scheme 2, our synthesis of the common intermediate 5 commenced with the
known compound 7, which was readily prepared from commercially available monoterpene (R)ꢀ
(ꢀ)ꢀcarvone through selective allylic chlorination.41 Selective epoxidation of 7 followed by
opening the resulting epoxide, protection of the chlorohydrin provided the desired compound 9.
Gratefully, Favorskii rearrangement of 9 with NaOMe gave the desired cyclopentane 6 in 97%
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yield without affecting the allylic chloride.42 The nucleophilic displacement of allylic chloride in
compound 6 with NaN3 in DMF at 80 °C yielded the corresponding azide 10. Reduction of azide
10 under Staudinger conditions (Ph3P, THF, H2O), accompanied by spontaneously cyclization
provided the key common intermediate 5.43 It is noteworthy that 20 grams of 5 could be easily
prepared by using this approach.
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Scheme 2. Synthesis of the Common Intermediate 5
With grams of the key intermediate 5 in hand, the syntheses of 2, 4, and its analogues were
carried out as illustrated in Scheme 3. Catalytic hydrogenation of olefin 5 with Pd/C in methanol
afforded 11a in 59% yield, together with its C4ꢀepimer 11b in 38% yield. They could be readily
separated by column chromatography. Methylation of lactam 11a with MeI in the presence of
NaH gave 12a, which was subsequently reduced with LiAlH4. After the removal of the THP
protecting group under acidic conditions, 2 was obtained.
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Following the same synthetic route as described for 11a, the transformation of 11b to 4 and
compound 5 to 13e were smoothly achieved. The physical data of our synthesized 4 were
identical to that reported in the literature.20 It is worth noting that the total synthesis of (ꢀ)ꢀ
isoincarvilline was achieved for the first time. In order to investigate the effect of piperidine
nitrogen substitution, compounds 13aꢀd were synthesized following the same route as described
for 2.
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Scheme 3. Synthesis of 2, 4 and Five Analogues 13a-e
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Scheme 4. Synthesis of Incarvillateine and Its Analogues
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With rapid access to large quantities of 2, 4, and five analogues (13a-e), syntheses of INCA
and its analogues (15a-f) were carried out in accordance with our previously reported sequence:
coupling between tosylꢀprotected αꢀtruxillic acid and alcohol (2, 4, and 13a-e) followed by
removal of the tosyl protecting groups (Scheme 4).24,26
Scheme 5. Synthesis of Structurally Simplified Analogues 15g-i
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Subsequently, three structurally simplified analogues (15g-i) were prepared by the following
sequence: esterification, removal of the Boc groups, reductive amination and removal of the
tosyl groups as illustrated in Scheme 5.44
■ PRELIMINARY BIOLOGICAL EVALUATION AND STRUCTURE-ACTIVITY
RELATIONSHIP STUDY
The antinociceptive effects of INCA and its analogues on tonic pain were evaluated using the
acetic acid writhing test. 37,38 The classical NSAID Aspirin DLꢀlysine was used as a reference
drug. In this test, intraperitoneal (i.p.) injection of acetic acid induced significant nociceptive
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responses in vehicleꢀtreated mice. Administration of INCA and its analogues 30 min before
acetic acid injection, and their effects on the pain behavior at a dose of 20 mg/kg are summarized
in Table 1.
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Table 1. Inhibitory Activity of INCA and Analogues in the Writhing Test (N = 9-10)
Compounds
Doses (mg/kg)
Inhibitory rate (%)
100 (s.c.)
81.9
Aspirin-DL-Lysine
100 (i.p.)
20 (s.c.)
20 (i.p.)
20 (s.c.)
20 (s.c.)
20 (s.c.)
20 (i.p.)
20 (s.c.)
20 (i.p.)
20 (s.c.)
20 (s.c.)
20 (s.c.)
20 (s.c.)
85.4
69.2
78.5
48.2
70.6
13.1
88.1
77.8
89.4
65.1
41.2
75.7
22.4
1
15a
15b
15c
15d
15e
15f
15g
15h
15i
Subcutaneous (s.c.) and intraperitoneal (i.p.) administration of Aspirin DLꢀlysine (100 mg/kg)
produced 81.9% and 85.4% inhibition of pain, respectively. INCA (20 mg/kg, s.c.) and (20
mg/kg, i.p.) produced 69.2% and 78.5% inhibition of pain, respectively. The substitution groups
on the piperidine nitrogen exhibited significant influence on the pain inhibitory activity. 15a (20
mg/kg, s.c.) with nꢀpropyl group and 15c (20 mg/kg, s.c.) with nꢀbutyl group showed weak
analgesic activity, only produced 48.2% and 13.1% inhibition of pain, respectively. However,
15b (20 mg/kg, s.c.) with allyl group and 15d (20 mg/kg, i.p.) with Loop C group showed higher
analgesic activity than INCA, produced 70.6% and 88.1% inhibition of pain, respectively. The
C4ꢀsubstituents of the piperidine nucleus showed no significant effect on the analgesic activity.
Compound 15f (20 mg/kg, s.c.) with the C4ꢀepimer methyl group produced 65.1% inhibition of
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pain. Compound 15e (20 mg/kg, s.c.) and (20 mg/kg, i.p.), the most readily prepared compound
with the C4ꢀmethyl group replaced by a double bond, produced 77.8% and 89.4% inhibition of
pain, respectively. For structurally simplified compound 15g-i, the length of linker played an
important role in the analgesic effects. 15h (20 mg/kg, s.c.) showed slightly higher activity than
INCA at the same dose, produced 75.7% inhibition of pain. While 15g and 15i (20 mg/kg, s.c.)
showed lower activity than INCA, produced only 41.2% and 22.4% inhibition of pain,
respectively.
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In subsequent studies, INCA, chemically tractable compound 15e and structurally simplified
compound 15h, which has a lower molecular weight, less complex structure, and high water
solubility, were evaluated in formalinꢀinduced pain model and spared nerve injury (SNI)-induced
neuropathic model.
■FURTHER BIOLOGICAL EVALUATION
Effects of INCA, 15e and 15h on formalin-induced pain. The formalin test was designed to
evaluate the antinociceptive effects of selected compounds as a classic model of acute and
chronic pain.37,39 Fig. 2 shows the effect of INCA, 15e and 15h on the formalin induced pain
response during the first and second phases. These three compounds were administered 10 min
before formalin (1%, 20 ꢁL, intraplantar) challenge respectively. Compared to vehicle, INCA
reduced the display of nocifensive behavior in both Phase 1 and Phase 2 in a doseꢀdependent
manner. During phase 1, the licking or biting time was reduced from 156 ± 8 s in vehicleꢀtreated
mice to 101 ± 5 s (P < 0.001) and 51 ± 7 s (P < 0.001) in mice treated with 10 and 20 mg/kg
INCA, respectively. (Fig. 2A). In Phase 2 of high dose group (INCA, 20 mg/kg, i.p.), the time
was reduced from 159 ± 25 s to 1 ± 0 s, (P < 0.001); in mediate dose group (INCA, 10 mg/kg,
i.p.), the time was reduced to 67 ± 19 s, (P < 0.001) (Fig. 2A). While 15e only reduced
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nocifensive behavior in Phase 2 of mediate dose group (10 mg/kg, i.p.), the time was reduced
from 178 ± 19 s to 87 ± 18 s, (P< 0.01) (Fig. 2B). 15h also only reduced nocifensive behavior in
Phase 2 of mediate dose group (10 mg/kg, i.p.), the time was reduced from 159 ± 15 s to 95 ± 18
s, (P< 0.05) (Fig. 2C).
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Figure 2. Effect of INCA on formalinꢀinduced pain in ICR mice. Mice were administered
vehicle (Veh) INCA, 15e or 15h (5, 10, 20 mg/kg, i.p.) 10 min before an intraplantar injection of
formalin. The time spent licking or biting the injected paw was recorded in 0–10 min (first phase)
and 15–30 min (second phase). Data are expressed as the mean ± SEM, n = 9–11. *P<0.05,
**P<0.01, ***P<0.001, compared with Vehꢀtreated mice.
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Sham
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2.0
1.5
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Veh
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10 mg/kg INCA
20 mg/kg INCA
100 mg/kg Gaba
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9
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*
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***
0
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Time (min)
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100 mg/kg Gaba
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120 150 180
Time (min)
Figure 3. Antiꢀnociceptive effect of INCA (10, 20 mg/kg, i.p.), 15e, 15h (10, 20, 40 mg/kg,
i.p.) or gabapentin (100 mg/kg, i.p.) on SNI induced neuropathic pain response. Results were
expressed as mean ± SEM (n = 9ꢀ10), *P < 0.05, **P < 0.01, *** P < 0.001, compared with
vehicle (Veh) group, twoꢀway ANOVA followed by Bonferroni posttests.
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INCA, 15e and 15h reduced spared nerve injury (SNI)-induced neuropathic pain. As
shown in Fig. 3, SNI surgery, which reflects neurotrauma in the clinic, induced significant
mechanical allodynia.37,40 Consistent with previous reports, the positive control gabapentin
reversed SNIꢀinduced decreases in mechanical withdrawal threshold.45 INCA [F(4,264) = 78.29,
p < 0.001], 15e [F(4,240) = 95.45, p < 0.001] and 15h [F(4,240) = 75.10, p < 0.001] also
produced significant antinociceptive effects, with potencies much higher than that of gabapentin.
Our previous study on the pharmacological effects of INCA in a set of experimental pain
models indicates that INCA is a novel analgesic for inflammatory and neuropathic pain with
limited effect on motor function. Further mechanism study indicates that its effects against
pathological pain are closely related to the activation of the adenosine receptor system.34 In this
report, we demonstrated that the two INCA analogues (15e, 15h) exhibited strong
antinociceptive action against neuropathic pain with potency much higher than that of reference
drug gabapentin. Therefore, INCA analogues could be promising leading candidates for the
development of analgesics.
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■CONCLUSIONS
We described an efficient synthetic route for the large scale synthesis of INCA and its
analogues. The first total synthesis of isoincarvilline was also achieved. The analgesic effects of
these compounds were initially evaluated in acetic acid writhing test. INCA, two structurally
optimized compounds 15e and 15h were further investigated. They exhibited potent analgesic
activity in two other pain models including formalin induced pain model and spared nerve injury
(SNI) model. Our results suggested that they could be developed as potent analgesics to treat
neuropathic pain.
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■EXPERIMENTAL SECTION
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(A). Chemistry. Nuclear magnetic resonance [1H and C NMR] spectra were determined on
Bruker AVIIIꢀ400 [1H NMR (400 MHz), 13C NMR (100 MHz)] or Bruker AVIIIꢀ600 [13C NMR
(150 MHz)] spectrometers. The following abbreviations are used for the multiplicities: s: singlet,
d: doublet, t: triplet, q: quartet, quint: quintet, m: multiplet, br d: broad doublet, br s: broad
singlet for proton spectra and carbon spectra. Coupling constants (J) are reported in Hertz (Hz).
Infrared spectra were recorded with a thin layer of the product on a KBr disk. Mass spectra were
recorded using a PE SCLEX QSTAR spectrometer.
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Bis((4R,4aS,6R,7S,7aR)-2,4,7-trimethyloctahydro-1H-cyclopenta[c]pyridin-6-yl)
(1R,2R,3S,4S)-2,4-bis(4-hydroxy-3-methoxyphenyl)cyclobutane-1,3-dicarboxylate (1). To a
solution of tosyl protected αꢀtruxillic acid (600 mg, 0.86 mmol) in THF (20 mL) at ꢀ78 °C was
successively added triethylamine (260 ꢁL, 1.9 mmol), pivaloyl chloride (230 ꢁL, 1.9 mmol)
under an argon atmosphere. After the reaction mixture was stirred at 0 °C for 1 h, the white solid
was filtered and washed with THF. The solution was evaporated to dryness and the flask was
charged with acetonitrile (10 mL), then 2 (311 mg, 1.7 mmol) and DMAP (30 mg, 0.2 mmol)
was added. The resulting solution was stirred for 3 d at room temperature. The mixture was
concentrated under reduced pressure. The residue was purified by FCC (CH2Cl2/MeOH/NH4OH,
150:10:1) to afford accompanied with DMAP. The mixture was further purified by a column
chromatography of Sephadex LHꢀ20 (CH2Cl2/MeOH, 1:1) to give pure tosyl protected 1. To a
solution of tosyl protected 1 (0.8 mmol) in THF (8 mL) at ꢀ40 °C, fresh prepared Na/Anthracene
(4.8 mL, 0.5 M in THF) was added dropwise. The reaction mixture was stirred at the same
temperature for 30 min. Then the reaction was quenched with sat. NaHCO3. The mixture was
extracted with CH2Cl2, and the combined organic layers were washed with brine, dried over
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Na2SO4, filtered, and concentrated under reduced pressure. The residue was purified by FCC
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(CH2Cl2/MeOH/NH4OH, typically 150:10:1) to afford compound 1 as a white solid (488 mg,
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80%). [α]D ꢀ14.8 (c 1.39, CHCl3); H NMR (400 MHz, CDCl3) δ 6.83ꢀ6.78 (m, 6H), 4.93ꢀ4.85 (m,
2H), 4.39ꢀ4.29 (m, 2H), 3.90ꢀ3.81 (m, 2H), 3.89 (s, 3H), 3.87 (s, 3H), 2.60ꢀ2.55 (m, 2H), 2.50ꢀ
2.45 (m, 2H), 2.19 (s, 6H), 2.13 (m, 1H), 2.02ꢀ1.92 (m, 3H), 1.87ꢀ1.81 (m, 3H), 1.77ꢀ1.64 (m,
2H), 1.63ꢀ1.54 (m, 3H), 1.44 (t, J = 12.0 Hz, 2H), 1.08 (dd, J = 13.6, 9.0 Hz, 1H), 0.81 (d, J =
7.6 Hz, 3H), 0.76 (d, J = 6.8 Hz, 3H), 0.72 (d, J = 6.8 Hz, 3H), 0.60 (d, J = 7.2 Hz, 3H), 0.58ꢀ
0.54 (m, 1H); 13C NMR (100 MHz, CDCl3) δ 171.9, 171.7, 146.73, 146.65, 145.3, 145.1, 130.7,
130.5, 120.4, 119.9, 114.6, 110.9, 110.8, 76.6, 76.4, 57.6, 57.5, 57.3, 57.2, 55.83, 55.78, 47.9,
47.3, 46.13, 46.09, 45.9, 45.8, 41.8, 41.2, 40.41, 40.37, 37.4, 37.3, 30.30, 30.26, 29.7, 29.2, 17.1,
16.9, 14.9, 14.4; HRMS (ESI) m/z calcd for C42H59N2O8 [M + H]+ 719.4266, found 719.4288.
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(4R,4aS,6R,7S,7aR)-2,4,7-Trimethyloctahydro-1H-cyclopenta[c]pyridin-6-ol (2). A stirred
solution of compound 5 (5.0 mmol) in THF (10 mL) was cooled to 0 °C under Ar. NaH (180 mg,
7.5 mmol) was added slowly in several portions, and alkylation reagent was added in one portion.
The reaction was warmed to room temperature and stirred until starting materials disappeared.
Then the reaction was quenched with sat. NH4Cl. The mixture was extracted with EtOAc, and
the combined organic layers were washed with brine, dried over Na2SO4, filtered, and
concentrated under reduced pressure to give a crude product, which was used in the next step
o
without further purification. To a solution of the above crude product in THF (25 mL) at 0 C,
LiAlH4 (380 mg, 10 mmol) was added in several portions. The reaction mixture was allowed to
warm to room temperature and stirred for 1 h and then quenched with few drops of NaOH (2.0
M in H2O). The reaction mixture was filtered through a pad of celite, and washed with EtOAc.
The filtrate was dried over Na2SO4 and concentrated under reduced pressure to give a crude
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product, which was used in the next step without further purification. To a solution of the above
crude product in MeOH (10 mL) at room temperature, HCl (0.8 mL, 12.0 M in H2O) was added
dropwise. The reaction mixture was stirred at the same temperature for 4 h. Then the mixture
was concentrated under reduced pressure. The residue was diluted with NaOH (0.2 M in H2O),
extracted with CH2Cl2, and the combined organic layers were washed with brine, dried over
Na2SO4, filtered, and concentrated under reduced pressure. The residue was purified by FCC
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(CH2Cl2/MeOH/NH4OH = 150:10:1) to afford 2 as a white solid (820 mg, 90%). [α]D ꢀ8.9 (c 0.75,
CHCl3); 1H NMR (400 MHz, CDCl3) δ 4.30 (m, 1H), 2.66 (ddd, J = 11.4, 6.0, 1.2 Hz, 1H), 2.50
(ddd, J = 11.4 , 4.2, 1.2 Hz, 1H), 2.39 (dt, J = 12.5, 6.6 Hz, 1H), 2.28 (brs, 1 H), 2.22 (s, 3H),
2.06 (m, 1H), 1.89 (m, 1 H), 1.82 (dd, J = 13.2, 6.6 Hz, 1H), 1.79 (dd, J = 13.2, 6.6 Hz, 1H), 1.65
(t, J = 11.4 Hz, 1H), 1.54 (t, J = 11.4 Hz, 1H), 1.48 (dd, J = 13.2, 7.4 Hz, 1H), 1.01 (d, J = 7.4 Hz,
3H), 0.85 (d, J = 6.6 Hz, 3H); 13C NMR (100 MHz, CDCl3) δ 73.4, 58.1 (C×2), 46.3, 45.9, 42.3,
37.5, 32.7, 30.6, 17.4, 14.2; HRMS (ESI) calcd for C11H22NO [M + H]+ 184.1701, found
184.1692.
(4S,4aS,6R,7S,7aR)-2,4,7-Trimethyloctahydro-1H-cyclopenta[c]pyridin-6-ol
(4).
Compound 4 (81% yield) was prepared in a manner similar to that described for the synthesis of
3
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2. [α]D ꢀ74.8 (c 2.0, CHCl3); [lit. , [α]D ꢀ77.3 (c 0.2335, CHCl3); H NMR (400 MHz, CDCl3) δ
4.19 (td, J = 6.6, 2.4 Hz, 1H), 2.81 (d, J = 12.0 Hz, 1H), 2.65 (d, J = 12.0 Hz, 1H), 2.22 (s, 3H),
2.08 (dd, J = 12.0, 4.4 Hz, 1H), 2.04 (m, 1H), 1.92 (dd, J = 14.6, 6.6 Hz, 1H), 1.77 (dd, J = 11.2,
5.2 Hz, 1H), 1.72 (ddd, J = 14.6, 8.0, 2.4 Hz, 1H), 1.51ꢀ1.41 (m, 2H), 1.36 (m, 1H), 0.98 (d, J =
6.8 Hz, 3H), 0.80 (d, J = 6.4 Hz, 3H); 13C NMR (100 MHz, CDCl3) δ 74.9, 63.4, 55.4, 46.8, 43.6,
42.1, 39.4, 38.8, 34.5, 17.7, 11.8; HRMS (ESI) calcd for C11H22NO [M + H]+ 184.1701, found
184.1704.
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(4aR,6R,7S,7aR)-7-Methyl-4-methylene-6-((tetrahydro-2H-pyran-2-yl)oxy)octahydro-1H-
cyclopenta[c]pyridin-1-one (5). PPh3 (22.5 g, 85.5 mmol) and H2O (14.1 mL, 777 mmol) was
added to a solution of the above crude product in THF (450 mL). The reaction mixture was
heated to reflux and stirred for 12 h and then concentrated under reduced pressure. The residue
was purified by FCC (CH2Cl2/EtOAc = 2:1 to CH2Cl2/MeOH = 20:1) to afford compound 5 as a
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white solid (18.6 g, 90%). H NMR (400 MHz, CDCl3, 1:1 mixture of epimeric acetals, data for
both epimeric acetals given) δ 6.69 (brs, 2H), 4.89 (brs, 3H), 4.86 (s, 1H), 4.73 (m, 1H), 4.58 (m,
1H), 4.12 (m, 1H), 4.03 (m, 1H), 3.90ꢀ3.84 (m, 4H), 3.71 (m, 1H), 3.67 (m, 1H), 3.51ꢀ3.47 (m,
2H), 3.28 (dd, J = 18.4, 9.6 Hz, 1H), 3.19 (dd, J = 18.4, 9.6 Hz, 1H), 2.57 (t, J = 9.6 Hz, 1H),
2.52 (t, J = 9.6 Hz, 1H), 2.24 (m, 2H), 2.17 (ddd, J = 13.6, 8.2, 2.0 Hz, 1H), 2.07 (dd, J = 13.6,
7.8 Hz, 1H), 1.94 (m, 1H), 1.85ꢀ1.76 (m, 3H), 1.74ꢀ1.65 (m, 2H), 1.62ꢀ1.51 (m, 8H), 1.29 (d, J =
13
6.8 Hz, 3H), 1.18 (d, J = 6.8 Hz, 3H); C NMR (100 MHz, CDCl3, 1:1 mixture of epimeric
acetals, data for both epimeric acetals given) δ 175.8, 175.6, 143.0, 142.8, 110.2 (C×2), 110.1,
94.4, 81.2, 77.2 (C×2), 62.8, 61.4, 49.3, 45.4, 45.3, 44.1, 43.8, 40.7 (C×2), 38.9, 36.4, 30.8, 30.6,
25.4, 25.3, 19.4, 18.8, 14.2, 14.1.
Methyl(1R,2S,3R,5R)-5-(3-chloroprop-1-en-2-yl)-2-methyl-3-((tetrahydro-2H-pyran-2-
yl)oxy)cyclopentane-1-carboxylate (6). To a stirred solution of compound 9 (25.8 g, 80.4 mmol)
o
in Et2O (300 mL) at 0 C, NaOMe (20.1 mL, 6 M in MeOH, 120.6 mmol) was added dropwise.
The reaction was kept for 1 h at the same temperature. Then the reaction was quenched with sat.
NH4Cl and extracted with EtOAc, and the combined organic layers were washed with brine,
dried over Na2SO4, filtered, and concentrated under reduced pressure. The residue was purified
by FCC (PE/EtOAc = 20:1) to afford compound 6 (24.6 g, 97%) as a colorless oil. 1H NMR (400
MHz, CDCl3, 1:1 mixture of epimeric acetals, data for both epimeric acetals given) δ 5.20 (s,
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1H), 5.19 (s, 1H), 4.96 (s, 1H), 4.95 (s, 1H), 4.65 (m, 1H), 4.57 (m, 1H), 4.20 (t, J = 4.0 Hz, 1H),
4.09 (t, J = 4.0 Hz, 1H), 4.04 (d, J = 12.0 Hz, 2H), 4.00 (d, J = 12.0 Hz, 2H), 3.63 (m, 1H), 3.53
(brs, 6H), 3.46 (m, 2H), 3.38 (dt, J = 10.8, 6.8 Hz, 1H), 3.28 (dt, J = 10.8, 6.8 Hz, 1H), 2.84 (dd,
J = 10.0, 8.0 Hz, 1H), 2.80 (dd, J = 10.0, 8.0 Hz, 1H), 2.60ꢀ2.50 (m, 2H), 1.98ꢀ1.91 (m, 2H),
1.83ꢀ1.73 (m, 3H), 1.68ꢀ1.60 (m, 3H), 1.57ꢀ1.45 (m, 9H), 1.08 (d, J = 7.0 Hz, 3H), 0.98 (d, J =
7.0 Hz, 3H); 13C NMR (100 MHz, CDCl3, 1:1 mixture of epimeric acetals, data for both epimeric
acetals given) δ 174.5 (C×2), 145.6, 145.5, 115.0, 114.7, 100.2, 94.7, 81.4, 76.6, 62.6, 61.7, 53.5
(C×2), 51.2 (C×2), 48.4, 48.3, 42.4, 42.2, 42.04, 41.98, 38.9, 36.1, 30.9, 30.7, 25.5, 25.4, 19.7,
19.1, 14.0, 13.9.
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(R)-5-(3-Chloroprop-1-en-2-yl)-2-methylcyclohex-2-en-1-one (7). To
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agitation stirred solution of (R)ꢀcarvone (15.0 g, 0.1 mmol) in CH2Cl2 (300 mL) at 0 C,
CeCl3·7H2O (37.0 g, 0.1 mmol) in water (100 mL) was added in one portion, and a solution of
NaClO (150 mL, 8% in H2O) was added dropwise during 3 h. Then the reaction was diluted with
water (150 mL). The mixture was extracted with CH2Cl2, and the combined organic layers were
washed with sat. Na2S2O3, brine, dried over Na2SO4, filtered, and concentrated under reduced
pressure. The residue was purified by FCC (PE/EtOAc = 40:1) to afford compound 7 (11.0 g,
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60%) as a faint yellow oil. [α]D ꢀ36.6 (c 2.0, CHCl3); H NMR (400 MHz, CDCl3) δ 6.73 (m, 1H),
5.23 (s, 1H), 5.03 (s, 1H), 4.06 (s, 2H), 2.94 (m, 1H), 2.63 (ddd, J = 16.0, 3.6, 1.6 Hz, 1H); 2.53
(m, 1H), 2.36 (dd, J = 16.0, 13.2 Hz, 1H); 2.30 (m, 1H); 1.76 (m, 3H); 13C NMR δ 198.7, 146.5,
143.9, 135.5, 115.0, 46.8, 42.9, 37.7, 31.3, 15.6; HRMS (ESI) calcd for C10H14OCl [M + H]+
185.0733, found 185.0733.
(1R,4R,6R)-4-(3-Chloroprop-1-en-2-yl)-1-methyl-7-oxabicyclo[4.1.0]heptan-2-one (8). To
a stirred solution of compound 7 (21.3 g, 114.0 mmol) in MeOH (216 mL) at 0 oC, H2O2 (36 mL,
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35% in H2O) and NaOH (28.5 mL, 2.0M in H2O) was added dropwise. The reaction was allowed
to warm to room temperature and kept for 3 h. Then the mixture was diluted with water and
extracted with CH2Cl2, and the combined organic layers were washed with sat. Na2S2O3, brine,
dried over Na2SO4, filtered, and concentrated under reduced pressure to give compound 8 as a
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faint yellow oil (20.7 g, 90%). [α]D +64.8 (c 1.0, CHCl3); H NMR (400 MHz, CDCl3) δ 5.23 (s,
1H), 5.01 (s, 1H), 4.05 (s, 2H), 3.47 (d, J = 3.0 Hz, 1H), 3.01 (m, 1H), 2.69 (ddd, J = 17.6, 4.4,
0.8 Hz, 1H), 2.47 (dt, J = 14.8, 3.0 Hz, 1H), 2.06 (dd, J = 17.6, 11.4 Hz, 1H), 1.96 (dd, J = 14.8,
13
11.4 Hz, 1H), 1.42 (s, 3H); C NMR δ 204.7, 146.7, 115.2, 61.0, 58.9, 47.0, 42.0, 31.2, 29.1,
15.2.
(2S,3R,5R)-2-Chloro-5-(3-chloroprop-1-en-2-yl)-2-methyl-3-((tetrahydro-2H-pyran-2-
yl)oxy)cyclohexan-1-one (9). To a stirred solution of compound 8 (21.3 g, 106.5 mmol) in THF
(540 mL) at 0 oC, LiCl (46.8 g, 110.8 mmol) was added in one portion and TFA (23.7 mL, 319.5
mmol) was added dropwise. The reaction mixture was stirred for 2 h and then quenched with sat.
NaHCO3. The mixture was extracted with EtOAc and the combined organic layers were washed
with brine, dried over Na2SO4, filtered and concentrated under reduced pressure. The residue was
purified by FCC (PE/EtOAc = 10:1) to afford a faint yellow oil. DHP (34.2 mL, 375.6 mmol)
was added to a solution of the above mentioned faint yellow oil in CH2Cl2 (126 mL) at room
temperature, PPTS (2.67 g, 10.65 mmol) was added dropwise. The reaction was kept at room
temperature for 24 h and then quenched with sat. NaHCO3. The mixture was extracted with
EtOAc and the combined organic layers were washed with brine, dried over Na2SO4, filtered and
concentrated under reduced pressure. The residue was purified by FCC (PE/EtOAc = 50:1) to
1
afford compound 9 as a colorless oil (26.3 g, 77%). H NMR (400 MHz, CDCl3, 1:1 mixture of
epimeric acetals, data for both epimeric acetals given) δ 5.29 (s, 1H), 5.27 (s, 1H), 5.11 (s, 1H),
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5.09 (s, 1H), 4.78 (m, 1H), 4.74 (m, 1H), 4.26 (m, 1H), 4.13ꢀ4.04 (m, 5H), 3.88ꢀ3.79 (m, 2H),
3.58ꢀ3.50 (m, 2H), 3.15 (m, 1H), 3.08ꢀ3.00 (m, 2H), 2.93 (m, 1H), 2.51ꢀ2.41 (m, 1H), 2.33 (m,
1H), 2.22ꢀ2.11 (m, 2H), 1.80ꢀ1.50 (m, 14H), 1.74 (s, 3H), 1.62 (s, 3H).
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Methyl
(1R,2S,3R,5R)-5-(3-azidoprop-1-en-2-yl)-2-methyl-3-((tetrahydro-2H-pyran-2-
yl)oxy)cyclopentane-1-carboxylate (10). To a stirred solution of compound 6 (24.6 g, 77.7
o
mmol) in DMF (390 mL) at 70 C, NaN3 (10.2 g, 155.7 mmol) was added in one portion. The
reaction was kept for 15 h at the same temperature. Then the mixture was concentrated under
reduced pressure. The residue was diluted with water, extracted with EtOAc, and the combined
organic layers were washed with brine, dried over Na2SO4, filtered, and concentrated under
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reduced pressure to give compound 10. H NMR (400 MHz, CDCl3, 1:1 mixture of epimeric
acetals, data for both epimeric acetals given) δ 5.12 (s, 1H), 5.11 (s, 1H), 5.01 (s, 1H), 5.00 (s,
1H), 4.67 (m, 1H), 4.58 (m, 1H), 4.23 (m, 1H), 4.11 (m, 1H), 3.89ꢀ3.83 (m, 2H), 3.81 (d, J =
14.2 Hz, 2H), 3.69 (d, J = 14.2 Hz, 2H), 3.58 (s, 3H), 3.57 (s, 3H), 3.50 (m, 2H), 3.23 (dt, J =
10.8, 6.8 Hz, 1H), 3.15 (dt, J = 10.8, 6.8 Hz, 1H), 2.86 (dd, J = 10.2, 8.2 Hz, 1H), 2.81 (dd, J =
10.2, 8.2 Hz, 1H), 2.64ꢀ2.51 (m, 2H), 2.09ꢀ1.94 (m, 3H), 1.86ꢀ1.76 (m, 3H), 1.73ꢀ1.62 (m, 2H),
1.61ꢀ1.45 (m, 8H), 1.11 (d, J = 7.0 Hz, 3H), 1.01 (d, J = 7.0 Hz, 3H).
(4R,4aS,6R,7S,7aR)-4,7-Dimethyl-6-((tetrahydro-2H-pyran-2-yl)oxy)octahydro-1H-
cyclopenta[c]pyridin-1-one (11a), and (4S,4aS,6R,7S,7aR)-4,7-Dimethyl-6-((tetrahydro-2H-
pyran-2-yl)oxy)octahydro-1H-cyclopenta[c]pyridin-1-one (11b). To a stirred solution of
compound 5 (11.4 g, 43 mmol) in MeOH (120 mL), 10% Pd/C (2.2 g, 2.2 mmol) was added in
one portion, the reaction mixture was purged with H2, and stirred at room temperature under an
atmosphere of H2 (4 atm) for 15 h. Then the reaction mixture was filtered through a pad of Celite,
and washed with EtOAc. The filtrate was then washed with brine, dried over Na2SO4 and
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concentrated under reduced pressure. The residue was purified by FCC (CH2Cl2/EtOAc = 2:1) to
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afford two white solid 11a (6.8 g, 59%) and 11b (4.4 g, 38%). Compound 11a: H NMR (400
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MHz, CDCl3, 1:1 mixture of epimeric acetals, data for both epimeric acetals given) δ 6.62 (brs,
2H), 4.69 (m, 1H), 4.56 (m, 1H), 4.09 (m, 1H), 4.00 (m, 1H), 3.90ꢀ3.83 (m, 2H), 3.50ꢀ3.45 (m,
2H), 3.06ꢀ2.98 (m, 3H), 2.70 (m, 1H), 2.60 (m, 1H), 2.44 (m, 2H), 2.15ꢀ2.01 (m, 5H), 1.89ꢀ1.75
(m, 4H), 1.73ꢀ1.64 (m, 2H), 1.59ꢀ1.48 (m, 9H), 1.38 (m, 1H), 1.27 (d, J = 6.8 Hz, 3H), 1.14 (d, J
= 6.8 Hz, 3H), 0.89 (d, J = 6.8 Hz, 3H), 0.88 (d, J = 6.8 Hz, 3H); HRMS (ESI) calcd for
C15H26NO3 [M + H]+ 268.1913, found 268.1907. Compound 11b: 1H NMR (400 MHz, CDCl3,
1.3:1 mixture of epimeric acetals, data for both epimeric acetals given) δ 5.87 (brs, 1.6H), 4.72
(m, 1H), 4.58 (m, 0.8H), 4.06 (m, 1H), 3.97ꢀ3.95 (m, 0.8H), 3.93ꢀ3.86 (m, 1.9H), 3.52ꢀ3.48 (m,
1.9H), 3.20ꢀ3.15 (m, 1.7H), 2.95 (m, 1.7H), 2.53 (t, J = 10.2 Hz, 1H), 2.48 (t, J = 10.2 Hz, 0.8H),
2.27ꢀ2.07 (m, 5.7H), 1.85ꢀ1.78 (m, 1.9H), 1.75ꢀ1.68 (m, 2.7H), 1.59ꢀ1.48 (m, 10H), 1.34 (d, J =
6.8 Hz, 3H), 1.23 (d, J = 6.8 Hz, 2.5H), 0.98 (d, J = 6.8 Hz, 5.4H); HRMS (ESI) calcd for
C15H26NO3 [M + H]+ 268.1913, found 268.1913.
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(4R,4aS,6R,7S,7aR)-4,7-Dimethyl-2-propyloctahydro-1H-cyclopenta[c]pyridin-6-ol (13a).
Compound 13a (56% yield) was prepared in a manner similar to that described for the synthesis
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of 2. [α]D ꢀ2.0 (c 1.0, CHCl3); H NMR (400 MHz, CDCl3) δ 4.29 (m, 1H), 2.74 (m, 1H), 2.58
(m, 1H), 2.42 (m, 1H), 2.26 (t, J = 7.6 Hz, 2H), 2.08 (m, 1H), 1.91 (m, 1H), 1.85ꢀ1.77 (m, 2H),
1.68 (t, J = 11.6 Hz, 1H), 1.61ꢀ1.47 (m, 4H), 1.01 (d, J = 7.2 Hz, 3H), 0.88 (t, J = 7.2 Hz, 3H),
0.85 (d, J = 4.0 Hz, 3H); 13C NMR (100 MHz, CDCl3) δ 73.5, 60.7, 55.8, 45.4, 42.4, 38.1, 32.8,
30.1, 19.7, 17.4, 14.1, 11.9; HRMS (ESI) calcd for C13H26NO [M + H]+ 212.2009, found
212.2006.
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(4R,4aS,6R,7S,7aR)-2-Allyl-4,7-dimethyloctahydro-1H-cyclopenta[c]pyridin-6-ol (13b).
Compound 13b (92% yield) was prepared in a manner similar to that described for the synthesis
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of 2. [α]D +7.2 (c 1.0, CHCl3); H NMR (400 MHz, CDCl3) δ 5.88 (m, 1H), 5.18 (d, J = 12.0 Hz,
1H), 5.14 (d, J = 4.0 Hz, 1H), 4.29 (t, J = 6.4 Hz, 1H), 2.97 (d, J = 6.8 Hz, 2H), 2.75 (dd, J =
11.6, 6.0 Hz, 1H), 2.60 (dd, J = 11.6, 4.0 Hz, 1H), 2.42 (m, 1H), 2.08 (m, 1H), 1.90 (m, 1H),
1.84ꢀ1.76 (m, 2H), 1.69 (t, J = 11.6 Hz, 1H), 1.58 (t, J = 11.6 Hz, 1H), 1.50 (dd, J = 13.6, 3.6 Hz,
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1H), 1.01 (d, J = 7.2 Hz, 3H), 0.85 (d, J = 7.2 Hz, 3H); C NMR (100 MHz, CDCl3) δ 134.5,
118.5, 73.4, 61.8, 55.64, 55.59, 45.5, 42.4, 38.0, 32.7, 30.3, 17.4, 14.1; HRMS (ESI) calcd for
C13H24NO [M + H]+ 210.1852, found 210.1848.
(4R,4aS,6R,7S,7aR)-2-Butyl-4,7-dimethyloctahydro-1H-cyclopenta[c]pyridin-6-ol (13c).
Compound 13c (90% yield) was prepared in a manner similar to that described for the synthesis
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of 2. [α]D ꢀ10.2 (c 2.0, CHCl3); H NMR (400 MHz, CDCl3) δ 4.28 (dt, J = 6.4, 1.6 Hz, 1H), 2.74
(ddd, J = 11.2, 5.6, 1.6 Hz, 1H ), 2.58 (ddd, J = 11.2, 4.4, 1.6 Hz, 1H), 2.42 (td, J = 12.8, 6.4 Hz,
1H), 2.29 (dd, J = 8.8, 6.8 Hz, 2H), 2.07 (m, 1H), 1.90 (m, 1H), 1.79 (td, J = 12.8, 6.4 Hz, 2H),
1.68 (t, J = 11.2 Hz, 1H), 1.55 (t, J = 11.6 Hz, 1H), 1.52ꢀ1.44 (m, 3H), 1.34ꢀ1.22 (m, 3H), 1.01
(d, J = 7.6 Hz, 3H), 0.91 (t, J = 7.6 Hz, 3H), 0.87 (d, J = 6.8 Hz, 3H); 13C NMR (100 MHz,
CDCl3) δ 72.9, 58.0, 55.0, 54.9, 44.6, 42.3, 37.6, 32.5, 29.4, 27.7, 20.5, 17.2, 14.0, 13.8; HRMS
(ESI) calcd for C14H28NO [M+H]+ 226.2171, found 226.2167.
(4R,4aS,6R,7S,7aR)-2-(Cyclopropylmethyl)-4,7-dimethyloctahydro-1H-
cyclopenta[c]pyridin-6-ol (13d). Compound 13d (88% yield) was prepared in a manner similar
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to that described for the synthesis of 2. [α]D ꢀ8.7 (c 2.0, CHCl3); H NMR (400 MHz, CDCl3) δ
4.29 (t, J = 6.2 Hz, 1H), 2.86 (ddd, J = 11.4, 6.0, 1.2 Hz, 1H ), 2.70 (ddd, J = 11.4, 4.2, 1.2 Hz,
1H), 2.42 (qd, J = 13.0, 6.2 Hz, 1H), 2.19 (d, J = 6.4 Hz, 2H), 2.08 (m, 1H), 1.91 (m, 1H), 1.83
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(dd, J = 13.2, 6.6 Hz, 1H), 1.80 (dd, J = 13.0, 6.6 Hz, 1H), 1.67 (t, J = 11.6 Hz, 1H), 1.57 (t, J =
11.6 Hz, 1H), 1.48 (dd, J = 13.2, 7.4 Hz, 1H), 1.01 (d, J = 7.4 Hz, 3H), 0.86 (d, J = 7.0 Hz, 3H),
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0.84 (m, 1H), 0.50 (m, 2H), 0.08 (m, 2H); C NMR (100 MHz, CDCl3) δ 73.5, 64.0, 56.11,
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56.06, 45.7, 42.4, 38.1, 32.7, 30.4, 17.6, 14.2, 8.2, 4.05, 4.02; HRMS (ESI) calcd for C14H26NO
[M + H]+ 224.2009, found 224.2008.
(4aR,6R,7S,7aR)-2,7-Dimethyl-4-methyleneoctahydro-1H-cyclopenta[c]pyridin-6-ol (13e).
Compound 13e (81% yield) was prepared in a manner similar to that described for the synthesis
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of 2. H NMR (400 MHz, CDCl3) δ 4.85 (s, 1H), 4.81 (s, 1H), 4.22 (m, 1H), 3.00 (d, J=12.4 Hz,
1H), 2.78 (q, J = 6.6 Hz, 1H), 2.72 (d, J = 12.4 Hz, 1H), 2.44 (dd, J = 11.6, 4.4 Hz, 1H), 2.37 (dd,
J = 11.6, 4.8 Hz, 1H), 2.24 (dt, J = 13.8, 6.4 Hz, 1H), 2.24 (s, 3H), 1.93ꢀ1.82 (m, 2H), 1.69 (ddd,
J = 13.8, 7.6, 2.8 Hz, 1H), 1.68 (brs, 1H), 0.98 (d, J = 6.6 Hz, 3H); 13C NMR (100 MHz, CDCl3)
δ 145.9, 109.6, 74.1, 61.4, 56.8, 46.3, 45.0, 40.4, 40.2, 38.4, 12.6.
Bis((4R,4aS,6R,7S,7aR)-4,7-dimethyl-2-propyloctahydro-1H-cyclopenta[c]pyridin-6-yl)
(1R,2R,3S,4S)-2,4-bis(4-hydroxy-3-methoxyphenyl)cyclobutane-1,3-dicarboxylate
(15a).
Compound 15a (84% yield) was prepared in a manner similar to that described for the synthesis
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of 1. [α]D ꢀ46.8 (c 0.5, CHCl3); H NMR (400 MHz, CDCl3) δ 6.80ꢀ6.76 (m, 6H), 4.88 (dd, J =
14.6, 7.2 Hz, 1H), 4.79 (dd, J = 14.6, 7.0 Hz, 1H), 4.35 (dd, J = 10.2, 7.4 Hz, 1H), 4.30 (dd, J =
10.2, 7.4 Hz, 1H), 3.86 (s, 3H), 3.85 (s, 3H), 3.84 (m, 2H), 2.66 (m, 2H), 2.54 (m, 2H), 2.29ꢀ2.16
(m, 4H), 2.11 (m, 1H), 1.96 (m, 3H), 1.83 (m, 3H), 1.76ꢀ1.67 (m, 2H), 1.64ꢀ1.56 (m, 3H), 1.53ꢀ
1.42 (m, 4H), 1.04 (dd, J = 13.6, 8.2 Hz, 1H), 0.83 (t, J = 7.4 Hz, 6H), 0.79 (d, J = 7.4 Hz, 3H),
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0.74 (d, J = 6.8 Hz, 3H), 0.58 (d, J = 7.2 Hz, 3H), 0.66ꢀ0.46 (m, 1H); C NMR (100 MHz,
CDCl3) δ 171.9, 171.7, 146.7, 146.6, 145.2, 145.0, 130.7, 130.5, 120.4, 119.9, 114.49, 114.45,
110.9, 110.8, 76.6, 76.4, 60.7 (C×2), 55.8, 55.7, 55.5 (C×2), 55.2, 55.1, 47.9, 47.3, 45.63, 45.58,
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41.8, 41.2, 40.52, 40.49, 37.92, 37.86, 30.0, 29.9, 29.8, 29.3, 19.53,19.50, 17.1, 16.9, 14.8, 14.4,
12.0 (C×2); HRMS (ESI) calcd for C46H67N2O8 [M + H]+ 775.4892, found 775.4899.
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Bis((4R,4aS,6R,7S,7aR)-2-allyl-4,7-dimethyloctahydro-1H-cyclopenta[c]pyridin-6-yl)
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(1R,2R,3S,4S)-2,4-bis(4-hydroxy-3-methoxyphenyl)cyclobutane-1,3-dicarboxylate
(15b).
Compound 15b (84% yield) was prepared in a manner similar to that described for the synthesis
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of 1. [α]D ꢀ36.8 (c 0.2, CHCl3); H NMR (400 MHz, CDCl3) δ 6.80ꢀ6.77 (m, 6H), 5.83 (dd, J =
16.6, 7.2 Hz, 1H), 5.79 (dd, J = 16.4, 7.0 Hz, 1H), 5.13 (d, J = 12.8 Hz, 2H), 5.10 (d, J = 4.6 Hz,
2H), 4.88 (m, 2H), 4.36 (dd, J = 10.4, 7.8 Hz, 1H), 4.31 (dd, J = 10.4, 7.8 Hz, 1H), 3.88 (s, 3H),
3.86 (s, 3H), 3.84 (m, 2H), 2.96ꢀ2.85 (m, 4H), 2.64 (dd, J = 11.2, 5.6 Hz, 2H), 2.56ꢀ2.48 (m,
2H), 2.13 (m, 1H), 2.13ꢀ1.88 (m, 3H), 1.85ꢀ1.76 (m, 3H), 1.74ꢀ1.66 (m, 2H), 1.66ꢀ1.55 (m, 3H),
1.50ꢀ1.40 (m, 2H), 1.05 (dd, J = 13.8, 8.4 Hz, 1H), 0.79 (d, J = 7.0 Hz, 3H), 0.75 (d, J = 6.6 Hz,
3H), 0.70 (d, J = 6.4 Hz, 3H), 0.59 (d, J = 7.2 Hz, 3H), 0.60ꢀ0.47 (m, 1H); 13C NMR (100 MHz,
CDCl3) δ 171.9, 171.7, 146.54, 146.48, 145.0, 144.9, 134.8 (C×2), 130.9, 130.7, 120.4, 120.0,
118.1 (C×2), 114.4 (C×2), 110.8, 110.7, 76.7, 76.4, 61.9 (C×2), 55.84, 55.79, 55.43, 55.41, 55.1,
55.0, 47.9, 47.3, 45.9, 45.8, 41.8, 41.2, 40.5, 40.4, 37.94, 37.90, 30.3, 30.2, 29.9, 29.3, 17.2, 17.0,
14.8, 14.4; HRMS (ESI) calcd for C46H63N2O8 [M + H]+ 771.4579, found 771.4578.
Bis((4R,4aS,6R,7S,7aR)-2-butyl-4,7-dimethyloctahydro-1H-cyclopenta[c]pyridin-6-yl)
(1R,2R,3S,4S)-2,4-bis(4-hydroxy-3-methoxyphenyl)cyclobutane-1,3-dicarboxylate
(15c).
Compound 15c (84% yield) was prepared in a manner similar to that described for the synthesis
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of 1. [α]D ꢀ4.4 (c 1.0, CHCl3); H NMR (400 MHz, CDCl3) δ 6.87ꢀ6.78 (m, 6H), 5.72 (brs, 2H),
4.94ꢀ4.84 (m, 2H), 4.39ꢀ4.29 (m, 2H), 3.91 (s, 3H), 3.89 (s, 3H), 3.87ꢀ3.80 (m, 2H), 2.62 (m, 2H),
2.51 (m, 2H), 2.23 (m, 4H), 2.14 (m, 1H), 1.97 (m, 3H), 1.87ꢀ1.78 (m, 3H), 1.76ꢀ1.52 (m, 5H),
1.43 (m, 5H), 1.31ꢀ1.22 (m, 5H), 1.06 (m, 1H), 0.88 (t, J = 7.2 Hz, 6H), 0.81 (d, J = 7.2 Hz, 3H),
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0.75 (d, J = 6.8 Hz, 3H), 0.70 (d, J = 6.8 Hz, 3H), 0.60 (d, J = 7.2 Hz, 3H), 0.58ꢀ0.53 (m, 1H);
13C NMR (100 MHz, CDCl3) δ 171.9, 171.7, 146.7, 146.6, 145.2, 145.0, 130.7, 130.5, 120.4,
119.9, 114.5 (C×2), 110.8, 110.7, 76.7, 76.4, 58.6 (C×2), 55.8, 55.7, 55.6 (C×2), 55.3, 55.1, 47.9,
47.3, 45.7, 45.6, 41.7, 41.2, 40.5 (C×2), 37.92, 37.87, 30.02, 29.96, 29.8, 29.3, 28.5, 28.4, 20.8
(C×2), 17.1, 16.9, 14.8, 14.4, 13.9 (C×2); HRMS (ESI) calcd for C48H71N2O8 [M + H]+ 803.5210,
found 803.5203.
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Bis((4R,4aS,6R,7S,7aR)-2-(cyclopropylmethyl)-4,7-dimethyloctahydro-1H-
cyclopenta[c]pyridin-6-yl) (1R,2R,3S,4S)-2,4-bis(4-hydroxy-3-ethoxyphenyl)cyclobutane-
1,3-dicarboxylate (15d). Compound 15d (75% yield) was prepared in a manner similar to that
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described for the synthesis of 1. [α]D ꢀ5.2 (c 1.0, CHCl3); H NMR (400 MHz, CDCl3) δ 6.80ꢀ
6.77 (m, 6H), 4.88 (m, 2H), 4.33 (m, 2H), 3.87 (s, 3H), 3.86 (s, 3H), 3.83 (m, 2H), 2.82 (m, 2H),
2.69 (m, 2H), 2.28ꢀ2.09 (m, 5H), 2.07ꢀ1.94 (m, 3H), 1.90ꢀ1.82 (m, 3H), 1.77ꢀ1.47 (m, 7H), 1.04
(m, 1H), 0.84 (m, 2H), 0.80 (d, J = 7.2 Hz, 3H), 0.76 (d, J = 6.8 Hz, 3H), 0.72 (d, J = 6.8 Hz,
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3H), 0.60 (d, J = 7.2 Hz, 3H), 0.56 (m, 1H), 0.47 (m, 4H), 0.06 (m, 4H); C NMR (100 MHz,
CDCl3) δ 172.0, 171.7, 146.7, 146.6, 145.2, 145.1, 130.7, 130.6, 120.4, 119.9, 114.52, 114.48,
110.8, 110.7, 76.6, 76.4, 63.7 (C×2), 55.83, 55.76, 55.4 (C×2), 55.1, 54.9, 47.9, 47.3, 45.6 (C×2),
41.8, 41.2, 40.55, 40.52, 37.9, 37.8, 30.0, 29.9, 29.8, 29.3, 17.2, 17.0, 14.9, 14.4, 7.83, 7.80, 4.4,
4.1, 4.0, 3.9; HRMS (ESI) calcd for C46H67N2O8 [M + H]+ 799.4892, found 799.4892.
Bis((4aR,6R,7S,7aR)-2,7-dimethyl-4-methyleneoctahydro-1H-cyclopenta[c]pyridin-6-yl)
(1R,2R,3S,4S)-2,4-bis(4-hydroxy-3-methoxyphenyl)cyclobutane-1,3-dicarboxylate
(15e).
Compound 15e (75% yield) was prepared in a manner similar to that described for the synthesis
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of 1. [α]D ꢀ45.6 (c 1.0, CHCl3); H NMR (400 MHz, CDCl3) δ 6.84ꢀ6.78 (m, 6H), 5.68 (brs, 2H),
4.86 (m, 2H), 4.82 (s, 1H), 4.81 (s, 1H), 4.80 (m, 2H), 4.38ꢀ4.29 (m, 2H), 3.88 (s, 3H), 3.86 (s,
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3H), 3.81 (m, 2H), 2.94 (d, J = 12.2 Hz, 2H), 2.68 (t, J = 12.0 Hz, 2H), 2.55 (m, 1H), 2.39ꢀ2.26
(m, 5H), 2.20 (brs, 6H), 2.11 (dt, J = 14.4, 6.2 Hz, 1H), 1.90 (dd, J = 14.4, 6.2 Hz, 1H), 1.86 (dd,
J = 14.4, 7.8 Hz, 1H), 1.82ꢀ1.66 (m, 3H), 1.31 (dd, J = 14.4, 8.0 Hz, 1H), 0.82 (m, 1H), 0.79 (d, J
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= 6.8 Hz, 3H), 0.51 (d, J = 5.6 Hz, 3H); C NMR (100 MHz, CDCl3) δ 171.8, 171.7, 146.55,
146.47, 145.02, 144.96, 144.81, 144.75, 130.9, 130.8, 120.5, 120.0, 114.4 (C×2), 110.8, 110.6,
110.2, 110.1, 77.7, 77.4, 61.0 (C×2), 56.14, 56.08, 55.9 (C×2), 48.0, 47.4, 46.0 (C×2), 45.2
(C×2), 41.7, 41.3, 40.0 (C×2), 38.70, 38.66, 35.7, 35.1, 12.8, 12.3; HRMS (ESI) calcd for
C42H55N2O8 [M + H]+ 715.3953, found 715.3953.
Bis((4S,4aS,6R,7S,7aR)-2,4,7-trimethyloctahydro-1H-cyclopenta[c]pyridin-6-yl)
(1R,2R,3S,4S)-2,4-bis(4-hydroxy-3-methoxyphenyl)cyclobutane-1,3-dicarboxylate
(15f).
Compound 15f (84% yield) was prepared in a manner similar to that described for the synthesis
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of 1. [α]D ꢀ72.8 (c 1.0, CHCl3); H NMR (400 MHz, CDCl3) δ 6.75ꢀ6.70 (m, 6H), 4.77 (m, 1H),
4.65 (m, 1H), 4.29 (m, 2H), 3.85 (s, 3H), 3.83 (s, 3H), 3.79ꢀ3.71 (m, 2H), 2.76 (t, J = 12.8 Hz,
2H), 2.59 (t, J = 12.2 Hz, 2H), 2.15 (s, 3H), 2.14 (s, 3H), 2.02 (dd, J = 12.0, 4.6 Hz, 2H), 1.97
(dd, J = 12.0, 4.6 Hz, 2H), 1.74 (dd, J = 14.8, 6.2 Hz, 1H), 1.60 (m, 1H), 1.49ꢀ1.20 (m, 9H), 1.04
(m, 1H), 0.76 (d, J = 6.4 Hz, 3H), 0.70 (d, J = 5.2 Hz, 3H), 0.66 (d, J = 6.4 Hz, 3H), 0.48 (d, J =
13
6.6 Hz, 3H); C NMR (100 MHz, CDCl3) δ 171.8, 171.7, 146.8, 146.5, 145.3, 145.1, 130.6
(C×2), 120.3, 120.1, 114.8, 114.5, 110.84, 110.77, 79.0, 78.6, 63.04, 62.97, 55.72, 55.66, 54.8,
54.6, 47.8, 47.5, 46.6, 46.5, 44.1, 44.0, 41.70, 41.66, 41.4, 41.2, 37.3 (C×2), 37.0, 36.5, 34.2,
34.0, 17.54, 17.51, 11.8, 11.3; HRMS (ESI) calcd for C42H59N2O8 [M + H]+ 719.4266, found
719.4262.
General Procedures for the Synthesis of 15g, 15h, 15i.
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Journal of Medicinal Chemistry
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To a stirred solution of tosylꢀprotected αꢀtruxillic acid (418 mg, 0.6 mmol) and compound 13f,
13g, 13h (1.2 mmol) in CH2Cl2 (4 mL) at room temperature, DMAP (147 mg, 1.2 mmol) and
EDCI (691 mg, 3.6 mmol) was added. The reaction was stirred at the same temperature
overnight. Then the mixture was diluted with sat. NaHCO3 and extracted with EtOAc, and the
combined organic layers were washed with brine, dried over Na2SO4, filtered, and concentrated
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under reduced pressure. The residue was purified by FCC (PE/EtOAc = 1.5:1) to afford both Boc
and tosyl protected intermediate.
To a stirred solution of the so obtained intermediate (1.08 mmol) in CH2Cl2 (11 mL) at room
temperature, TFA (3.7 mL) was added dropwise. The reaction was stirred at the same
temperature for 15 min. Then the mixture was quenched with sat. NaHCO3 and extracted with
CH2Cl2, and the combined organic layers were washed with brine, dried over Na2SO4, filtered,
and concentrated under reduced pressure to give a crude product, which was used in the next step
without further purification.
To a stirred solution of the so obtained crude product (1.0 mmol) in CH3CN (10 mL) at 0 °C,
NaCNBH3 (754 mg, 12.0 mmol) and formaldehyde (2.5 mL) was successively added. The
reaction was stirred at the same temperature for 8 h. Then the mixture was quenched with AcOH
(3.0 mL), adjusted pH to 11ꢀ12 with NaOH (10% in water) and extracted with CH2Cl2, and the
combined organic layers were washed with brine, dried over K2CO3, filtered, and concentrated
under reduced pressure. The residue was purified by FCC (CH2Cl2/MeOH/NH4OH, typically
15:1:0.1) to afford tosyl protected intermediate.
To a solution of tosyl protected 15g, 15h, 15i (0.9 mmol) in THF (9 mL) at ꢀ40 °C, fresh
prepared Na/Anthracene (5.4 mL, 0.5 M in THF) was added dropwise. The reaction mixture was
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