Discovery and Optimization of Chromeno[2,3-c]pyrrol-9(2H)-ones as Novel Selective and Orally Bioavailable Phosphodiesterase 5 Inhibitors for the Treatment of Pulmonary Arterial Hypertension

Article abstract of DOI:10.1021/acs.jmedchem.7b00523

Phosphodiesterase 5 (PDE5) inhibitors have been used as clinical agents to treat erectile dysfunction and pulmonary arterial hypertension (PAH). Herein, we detail the discovery of a novel series of chromeno[2,3-c]pyrrol-9(2H)-one derivatives as selective and orally bioavailable inhibitors against phosphodiesterase 5. Medicinal chemistry optimization resulted in 2, which exhibits a desirable inhibitory potency of 5.6 nM with remarkable selectivity as well as excellent pharmacokinetic properties and an oral bioavailability of 63.4%. In addition, oral administration of 2 at a dose of 5.0 mg/kg caused better pharmacodynamics effects on both mPAP (mean pulmonary artery pressure) and RVHI (index of right ventricle hypertrophy) than sildenafil citrate at a dose of 10.0 mg/kg. These activities along with its reasonable druglike properties, such as human liver microsomal stability, cytochrome inhibition, hERG inhibition, and pharmacological safety, indicate that 2 is a potential candidate for the treatment of PAH.

Full text of DOI:10.1021/acs.jmedchem.7b00523

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Article
Discovery and Optimization of Chromeno[2,3-c]pyrrol-9(2H)-ones
as Novel Selective and Orally Bioavailable Phosphodiesterase 5
Inhibitors for the Treatment of Pulmonary Arterial Hypertension
Deyan Wu, Tianhua Zhang, Yiping Chen, Yadan Huang, Haiju Geng, Yanfa Yu,
Chen Zhang, Zengwei Lai, Yinuo Wu, Xiaolei Guo, Jianwen Chen, and Hai-Bin Luo
J. Med. Chem., Just Accepted Manuscript • DOI: 10.1021/acs.jmedchem.7b00523 • Publication Date (Web): 07 Jul 2017
Downloaded from http://pubs.acs.org on July 8, 2017
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Discovery and Optimization of Chromeno[2,3-c]pyrrol-9(2H)-ones as
Novel Selective and Orally Bioavailable Phosphodiesterase 5 Inhibitors
for the Treatment of Pulmonary Arterial Hypertension
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a,#
a,#
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Deyan Wu , Tianhua Zhang , Yiping Chen , Yadan Huang , Haiju Geng , Yanfa Yu , Chen Zhang ,
a
a
c
a,
a, b,
Zengwei Lai , Yinuo Wu , Xiaolei Guo , Jianwen Chen *, HaiꢀBin Luo
*
a
School of Pharmaceutical Sciences, Sun YatꢀSen University, Guangzhou 510006, P. R. China
Collaborative Innovation Center of High Performance Computing, National University of Defense
b
Technology, Changsha 410073, China
c
Infinitus (China) Co. Ltd, Guangzhou 510663, China
ABSTRACT
Phosphodiesterase 5 (PDE5) inhibitors have been used as clinical agents to treat erectile dysfunction and
pulmonary arterial hypertension (PAH). Herein, we detail the discovery of a novel series of
chromeno[2,3ꢀc]pyrrolꢀ9(2H)ꢀone derivatives as selective and orally bioavailable inhibitors against
phosphodiesterase 5. Medicinal chemistry optimization resulted in 2, which exhibits a desirable
inhibitory potency of 5.6 nM with remarkable selectivity as well as excellent pharmacokinetic properties
and an oral bioavailability of 63.4%. In addition, oral administration of 2 at a dose of 5.0 mg/kg caused
better pharmacodynamics effects on both mPAP (mean pulmonary artery pressure) and RVHI (index of
right ventricle hypertrophy) than sildenafil citrate at a dose of 10.0 mg/kg. These activities along with its
reasonable drugꢀlike properties, such as human liver microsomal stability, cytochrome inhibition, hERG
inhibition, and pharmacological safety, indicate that 2 is a potential candidate for the treatment of PAH.
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INTRODUCTION
Pulmonary arterial hypertension (PAH) is a syndrome resulting from the restricted flow of blood
through the pulmonary arterial circulatory system, which leads to pathological increases in pulmonary
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vascular resistance (PVR) and ultimately rightꢀsided heart failure. In addition, PAH is a progressive
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, 4
and deadly disease with a poor prognosis and approximately 15% mortality within one year. Recently,
multiple pathogenic pathways have been implicated in the development of PAH, and three of these
pathways are important because they have been targeted by drugs (i.e., prostacyclin derivatives
(epoprostenol, treprostinil, and iloprost), endothelin receptor antagonists (bosentan, bitaxsentan, and
5, 6
ambrisentan), and phosphodiesterase 5 (PDE5) inhibitors (sildenafil and tadalafil)).
PDE5 is a cGMPꢀspecific enzyme that is primarily distributed in smooth muscle. PDE5 was initially
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, 8
discovered in bovine lung and rat platelets
and later found in several other tissues (i.e., corpus
9ꢀ13
cavernosum, heart, lung, liver, brain, platelets, prostate, urethra, bladder, and stomach). PDE5 plays
an important role in vascular relaxation mediated by the NO/cGMP pathway in vascular smooth muscle
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4, 15
cells.
Therefore, PDE5 is a prime target for the development of inhibitors to treat the diseases
16
associated with low cGMP levels. Currently, several PDE5 inhibitors have been approved to treat
several diseases, such as erectile dysfunction (sildenafil, vardenafil, tadalafil, avanafil, udenafil, and
1
7ꢀ21
12ꢀ13, 16, 22ꢀ28
mirodenafil)
and PAH (sildenafil and tadalafil).
Sildenafil was approved by the FDA in
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998 as the first oral drug for the treatment of erectile dysfunction. In addition, this drug was approved
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3, 16, 24ꢀ27
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for the treatment of PAH in 2005.
However, extensive studies have revealed several side effects
30
of sildenafil, such as vision disturbance and hearing loss . Therefore, the discovery of novel PDE5
inhibitors with new scaffolds continues to attract much attention in both academics and industry.
We previously discovered a series of 1ꢀaryl chromeno[2,3ꢀc]pyrrolꢀ9(2H)ꢀones as potent PDE5
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inhibitors, and the hit 3ꢀ(4ꢀhydroxybenzyl)ꢀ1ꢀ(thiophenꢀ2ꢀyl)chromeno[2,3ꢀc]pyrrolꢀ9(2H)ꢀone (1,
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Figure 1) exhibited considerable inhibitory affinity (IC50 = 17 nM) against PDE5. However, 1 has
relatively weak pharmacokinetic properties with an oral bioavailability of 4.9 %. Herein, we report the
medicinal chemistry optimization (Figure 2) of 1 to improve its binding affinity and oral bioavailability.
This optimization led to the discovery of 2 with higher inhibitory potency and significantly improved
pharmacokinetic properties with an oral bioavailability of 63.4%. The best compound 2 (Figure 1) has
an IC50 of 5.6 nM against PDE5 with remarkable selectivity across the PDE families, excellent
pharmacokinetic properties, and a marked pharmacodynamic profile against PAH in vivo. These
activities along with reasonable drugꢀlike properties, such as human/rat liver microsomal stability,
hERG inhibition, cytochrome inhibition, pharmacological safety, indicate that 2 is a potential candidate
for the treatment of PAH.
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CHEMISTRY
The targeted compounds were prepared by the synthetic routes reported in Schemes 1ꢀ5. Our initial
efforts focused on the syntheses of dihydrochromeno [2,3ꢀc]pyrrolesꢀ1ꢀcarboxylates and (1ꢀ
carbonyl)chromeno[2,3ꢀc] pyrrolꢀ9(2H)ꢀones (Schemes 1). Ethyl 4ꢀ(2ꢀhydroxyphenyl)ꢀ2,4ꢀ
dioxobutanoate (4) was synthesized by the reaction of 2’ꢀhydroxyacetophenone and diethyl oxalate in
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the presence of sodium hydride.
The key intermediate (3ꢀ(4ꢀ(tertꢀbutoxy)benzyl)ꢀ9ꢀoxoꢀ2,9ꢀ
dihydrochromeno[2,3ꢀc]pyrroleꢀ1ꢀcarboxylate (5)) was synthesized according to our previously reported
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procedure.
Compound 9 was the deprotected product, and compound 6 was the hydrolysate product.
Compound 8 was obtained using the transesterification reaction followed by deprotection from 5. In
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addition, compounds 10aꢀ10c were synthesized by the amidation reaction of 6 and amines, and
compounds 11aꢀ11c were the deprotected products from 10a-c, respectively.
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1ꢀAryl)chromeno[2,3ꢀc]pyrrolꢀ9(2H)ꢀones 17aꢀ17j and 21aꢀ21c were also synthesized according
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to our previously reported procedures (Schemes 2 and 3).
The key step of each route was the
synthesis of propaneꢀ1,3ꢀdiones 15aꢀ15j or 19aꢀ19b. As shown in Schemes 2, all the propaneꢀ1,3ꢀdiones
5aꢀ15j were synthesized by the reported procedure with a BakerꢀVenkataraman rearrangement.
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However, the propaneꢀ1,3ꢀdiones 19aꢀ19b were synthesized using a more effective procedure that was
similar to the synthesis of compound 4 (Schemes 3). To synthesize compound 23, carboxylic acid 6 was
used as the starting material. This material was treated with acethydrazide and HATU in the presence of
DIPEA to obtain intermediate 22 followed by treatment with POCl to afford 1,3,4ꢀoxadiazole 23
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(
Scheme 4). The syntheses of 1ꢀ(thiazolꢀ2ꢀyl)chromeno[2,3ꢀc]pyrrolꢀ9(2H)ꢀones 2 and 30 began with a
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published route to obtain the racemic amino acid chloride salts 28a-b, and then, the Fmoc group was
introduced with fluorenylmethoxycarbonyl chloride (FmocꢀCl) in dioxane/aqueous Na CO (Scheme
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5
).
The resulting Fmocꢀprotected amino acids were subsequently treated with 15j to obtain product 2
or 30 using the same procedure as that employed in the synthesis of 17.
RESULTS AND DISCUSSION
Rational Design of Novel PDE5 inhibitors to Improve Binding Affinities and Pharmacokinetic
Properties.
We previously discovered a series of (1ꢀaryl)chromeno[2,3ꢀc]pyrrolꢀ9(2H)ꢀones as novel PDE5
3
1
inhibitors, and the hit (1) had an IC50 of 17 nM against PDE5. However, 1 has relatively weak
pharmacokinetic properties with an oral bioavailability of less than 5%. To improve its inhibitory
potency and metabolic stability, structural optimization of compound 1 was necessary. Using structureꢀ
based design (Figure 2, molecular docking and molecular dynamics simulations), we replaced the
thiophene ring with a thiazole ring with the hope that it can form stronger bidentate Hꢀbond interactions
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between the inhibitors and crucial residue Q817, which was the key site for improving the binding
affinities. In addition, the replacement of the 4ꢀhydroxybenzyl group with other aromatic groups or
heterocycle groups may help to overcome its metabolic instability.
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To avoid interference of false positive compounds with our subsequent study, PAINS screening of
the designed compounds was performed using an online program (i.e., “PAINSꢀRemover”,
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http://www.cbligand.org/PAINS/), and all the compounds passed the filter.
Structure-activity Relationships (SARs) of Substituent Groups at the C1 Position of
Chromeno[2,3-c]pyrrol-1-carboxylates.
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As shown in the previous study , the C1 position must retain a Hꢀbond receptor to form the Hꢀ
bond interactions between the inhibitors and residue Q817. Therefore, our initial investigations of the
SARs of chromeno[2,3ꢀc]pyrrolꢀ9(2H)ꢀone derivatives were carried out by substituting the C1 position
with carboxylates or amides. The inhibitory activities of these substituted compounds (8 with a
carboxylic methyl ether and 11aꢀ11c with an amide group) against PDE5 are shown in Table 1.
However, all the compounds exhibited weaker PDE5 inhibitory activities than compound 1, indicating
that carboxylate substitution at this position is unfavorable for the formation of Hꢀbond interactions and
the subpocket is more favorable for holding an aromatic ring than an alkyl substituent.
SARs of Substituent Groups at the C1 Position of (1-Aryl)chromeno[2,3-c]pyrrol-9(2H)-ones.
Based on these results, we decided to change the aromatic rings at the C1 position, and the results
of these substituted compounds against PDE5 are summarized in Table 2. Compounds 17a-17i and 21a-
2
1c have a sixꢀmembered aromatic ring, and compounds 17j and 23 bear a fiveꢀmembered aromatic ring
at position C1. The introduction of sixꢀmembered aromatic rings at position C1 resulted in weaker
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inhibitions than those with fiveꢀmembered aromatic rings (1 and 17j). The derivatives with a sixꢀ
membered aromatic ring (17a and 17i) have better IC values of 20.5 nM and 16.4 nM, respectively.
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Finally, compound 17j bearing a thiazolꢀ2ꢀyl group enhanced the inhibition with an IC of 5.4 nM,
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suggesting that a thiazolꢀ2ꢀyl group at this position was favorable for the formation of Hꢀbond
interactions with residue Q817 in the substrate binding pocket. Therefore, the thiazolꢀ2ꢀyl group was
selected as the best substituent group at position C1 because it may increase the inhibitory affinities and
improve the solubility.
SARs of Substituent Groups at the C3 Position.
Among the studied compounds, 17j exhibited the best potency with an IC of 5.4 nM against the
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PDE5A catalytic domain. However, this compound has a 4ꢀhydroxybenzyl group at the C3 position,
which could be easily oxidized. Enhancement of the stability of functional groups is an efficient
approach for increasing the metabolic stability and improving the pharmacokinetic properties of a
molecule. Further investigation (Table 3) revealed that the compound with a benzo[d][1,3]dioxolꢀ5ꢀ
ylmethyl group at the C3 position (2) has a similar inhibitory potency (IC = 5.6 nM) against PDE5.
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However, other modifications, such as replacement of a 4ꢀhydroxybenzyl group with a 4ꢀ(tertꢀ
butoxy)benzyl group (16j) or a 4ꢀ(trifluoromethyl)benzyl group (30), failed to improve their binding
affinities. Finally, compounds 17j and 2 were selected as the best inhibitors for subsequent study.
Significant Improvement of the Pharmacokinetic Properties of Compound 2 over 1
Due to the relatively higher inhibitory affinities of the two compounds (17j and 2), both compounds
were subjected to preliminary pharmacokinetic assessment in vivo to choose the best one for screening
of the selectivity across PDE families and the pharmacodynamics evaluation. As a result, compound 2
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exhibited excellent pharmacokinetic properties, and its pharmacokinetic data are summarized in Table 4.
In addition, the results for 17j (its oral bioavailability < 10%) are summarized in Table S4. After oral
administration of a 5 mg/kg dose of 2 to rats, pharmacokinetic analysis revealed that 2 had a Cmax of 368
ng/mL, t1/2 of 5.17 h, and oral bioavailability of 63.4% (Table 4). Its oral bioavailability was remarkably
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higher than that of sildenafil (23%) or sildenafil citrate (41%) , which demonstrated that 2 is suitable
for use in subsequent pharmacodynamic tests.
Binding of 2 to the PDE5 Catalytic Domain
The binding pattern of PDE5 in complex with 2 after 20 ns molecular dynamics (MD) simulations
provided insight into the activity data (Figure 3). Compound 2 formed two Hꢀbond interactions (2.7 Å
and 3.1 Å) with invariant residue Q817 and aromatic π−π stacking interactions against residue F820,
which are two characteristic interactions of inhibitors with various PDE families. Surprisingly, this
compound possessed an additional Hꢀbond of 2.8 Å with residue Y79 in the active site of PDE5, which
was not observed in the binding pattern between sildenafil and PDE5. Therefore, the new scaffold and
different binding pattern of compound 2 provide a good example of the rational design of PDE5
inhibitors.
Remarkable Selectivity of Compound 2 across PDE Families
The selectivity of compound 2 across PDE families was also measured (Table 5). Its inhibitions
towards PDE1B, PDE3A, PDE7A1, and PDE9A2 were very weak (IC > 10000 nM). Its IC values
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against PDE8A1, PDE4D2, PDE2A, PDE10A, and PDE6A were 1111ꢀfold, 494ꢀfold, 65ꢀfold, 27ꢀfold,
and 10ꢀfold higher, respectively, than that against PDE5A1, which demonstrated that 2 exhibited
remarkable selectivity over other PDEs in vitro. For the sildenafil reference compound, its IC value
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against PDE6A was 5ꢀfold higher than that against PDE5A1, which is comparable to the literature
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Reasonable drug-like properties of compound 2.
Based on its pharmacokinetic profile with an oral bioavailability of 63.4% and t1/2 of 5.17 h after
oral administration, compound 2 was further subjected to preliminary drugꢀlike evaluations, such as
human/rat liver microsomal stability, cytochrome inhibition, hERG inhibition, and pharmacological
safety.
Human/rat liver microsomal stability. Human and rat liver microsomes are extensively used in the
pharmaceutical industry for in vitro drug metabolism assays and evaluating the ADME properties of
drugs in development. Herein, we examined compound 2 using a standard microsomal stability assay
with comparison to the midazolam control compound (Sigma Aldrich). The results indicate that 2 was
stable in the human and rat liver microsomes based on a t1/2 of 56.0 and 24.7 min, respectively, and Eh
(hepatic extraction ratio) of 54% and 65% (Table 6), respectively, which is significantly better than
those for the positive control (midazolam, t1/2 of approximately 2.7 and 2.4 min, respectively, and E of
h
approximately 96% and 95%, respectively).
Cytochrome inhibition. Cytochrome P450s (CYPs) are the major enzymes involved in the metabolism
of various xenobiotics. Among the various CYP isoenzymes, several human hepatic CYP enzymes play
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a dominant role in the metabolism of drugs and other xenobiotics.
activities of compound 2 against seven human hepatic CYP enzymes (Table 7) were tested. Therefore, 2
has an IC of 7.6 ꢁM against CYP1A2, and its IC values for the other six CYPs (CYP2B6, CYP2C8,
In this study, the inhibitory
50
50
CYP2C9, CYP2C19, CYP2D6, and CYP3A4) were uniformly more than 20 ꢁM. The results suggest
that 2 exhibited a very weak inhibitory effect on these CYP isoenzymes except CYP1A2. Therefore,
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compound 2 is unlikely to exhibit significant pharmacokinetic interactions with drugs that are
metabolized by the seven major CYP isoforms.
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hERG inhibition. hERG (human etherꢀaꢀgoꢀgo related gene) forms the major portion of one of the ion
channel proteins that conducts potassium ions out of the muscle cells of the heart, and this current is
critical in correctly timing the return to the resting state of the cell membrane during the cardiac action
potential, which has made hERG inhibition an important antitarget that must be avoided during drug
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development. In our study, compound 2 inhibited hERG with an IC of more than 10 ꢁM using an
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automated patch clamp electrophysiology measurement in CHOꢀhERG cells. The results suggest that 2
exhibited a weak inhibitory effect on hERG, which indicates that further development of compound 2 is
appropriate.
Pharmacological Safety. The favorable pharmacokinetic profile of 2 along with its highly desirable
inhibitory potency against PDE5 and remarkable selectivity across PDEs warranted its use in in vitro
safety studies. First, the maximum tolerated dose of 2 was determined for acute toxicity in mice.
Twentyꢀfour mice were randomly divided into three groups and given single oral doses of 0 mg/kg,
1
000 mg/kg, or 1500 mg/kg 2 on the first day. The animals treated with 2 did not exhibit any poisoning
symptoms or mortality immediately or during the postꢀtreatment period of two weeks. In addition, no
abnormal behaviors or significant changes in the water/food consumption and body weight were
observed during the period of the experiments. Therefore, inhibitor 2 was well tolerated up to a dose of
1500 mg/kg with no acute toxicity. Second, the maximum tolerated dose of 2 for shortꢀterm (2ꢀweek)
toxicity in rats was also determined. Twentyꢀfour SD rats were randomly divided into four groups and
given daily oral doses of 0 mg/kg, 30 mg/kg, 100 mg/kg or 300 mg/kg 2. Our results demonstrated that
the compound did not cause any adverse effect on the body weight or any other signs of overt toxicity at
daily doses up to 300 mg/kg for two weeks.
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Pharmacodynamics Profile against PAH in Rats.
Effects on mPAP (mean pulmonary artery pressure) and RVHI (index of right ventricle
hypertrophy). The pharmacodynamics effects of compound 2 against PAH in vivo are shown in Figure
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. A significant increase of mPAP was detected in the model group compared to that in the control
group (p<0.01), and the RVHI of the model group was significantly higher than that of the control group
(p<0.01), which suggests that it successfully induced the rats with PAH 3 weeks after monocrotaline
(MCT) injection successfully. Therefore, the mPAPs (18.65 mmHg and 22.13 mmHg) of the groups
treated with compound 2 at a dose of 5.0 mg/kg and sildenafil citrate at a dose of 10.0 mg/kg
significantly decreased (p<0.01) compared to that of the model group (32.74 mmHg). For the RVHI,
similar trends were also observed. At a dose of 5.0 mg/kg, compound 2 exhibited better effects on both
mPAP and RVHI than sildenafil citrate at a dose of 10.0 mg/kg.
Effects on the thickness of the small pulmonary arteries in rats with PAH. The effects of
compound 2 on the thickness of the small pulmonary arteries are shown in Figure 5. The model group
had significantly thicker small pulmonary arteries than the other groups (p<0.05, p<0.01). The wall
thickness percentage of the external diameter (WT %) of the model group increased significantly
(p<0.05, p<0.01). As shown in Figure 5, compound 2 and the reference compound (sildenafil citrate)
exhibited a marked reduction compared to that of the model group and performed well.
CONCLUSION
In summary, a series of chromeno[2,3ꢀc]pyrrolꢀ9(2H)ꢀone derivatives as novel PDE5 inhibitors
starting from compound 1 were successfully designed and synthesized using a structureꢀbased discovery
strategy. In total, twentyꢀone derivatives of chromeno[2,3ꢀc]pyrrolꢀ9(2H)ꢀones were discovered,
resulting in ten compounds with IC values ranging from 1 to 100 nM and two compounds with IC <
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0 nM. Compound 2 exhibited an IC of 5.6 nM with remarkable selectivity over other PDEs. After
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oral administration of a 5 mg/kg dose of 2 to rats, the pharmacokinetic analysis revealed that 2 had a
Cmax of 368 ng/mL, t1/2 of 5.17 h, and oral bioavailability of 63.4%. Furthermore, its IC50 value(s)
against CYP1A2 and six other CYPs (CYP2B6, CYP2C8, CYP2C9, CYP2C19, CYP2D6, and CYP3A4)
were 7.6 ꢁM and uniformly > 20 ꢁM, respectively. In addition, 2 was essentially inactive at hERG with
an IC of >10 ꢁM. In addition, 2 was well tolerated up to a dose of 1500 mg/kg with no acute toxicity
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and up to a daily dose of 300 mg/kg. Moreover, 2 did not exhibit shortꢀterm (2ꢀweek) toxicity. These
activities led to the selection of 2 as a potential candidate for treatment of PAH.
EXPERIMENTAL SECTION
Syntheses. All starting materials and reagents were purchased from commercial suppliers (Sigmaꢀ
Aldrich, Adamas, Energy, Bide, ShuYa, J&K, and Meryer) and used directly without further
®
purification. Chemical HG/T2354ꢀ92 silica gel (200ꢀ300 mesh, Haiyang ) was used for chromatography,
®
and silica gel plates with fluorescence F254 (0.25 mm, Huanghai ) were used for thinꢀlayer
chromatography (TLC) analysis. Reactions that required anhydrous conditions were performed under
1
13
argon or a calcium chloride tube. The H NMR and C NMR spectra were recorded at room temperature
on a Bruker AVANCE III 400 instrument with tetramethylsilane (TMS) as an internal standard. The
following abbreviations are used: s (singlet), d (doublet), dd (two doublets), ddd (three doublets), t
(triplet), q (quartet), br s (broad singlet) and m (multiplet). The coupling constants are reported in Hz.
The lowꢀ and highꢀresolution mass spectra (LRMS and HRMS) were recorded on a MATꢀ95
spectrometer. The purity of the compounds was determined by reverseꢀphase highꢀperformance liquid
chromatography (HPLC) analysis and confirmed to be more than 95%. HPLC instrument: SHIMADZU
LCꢀ20AT (column: Hypersil BDS C , 5.0 ꢁm, 4.6 × 150 mm (Elite); Detector: SPDꢀ20A UV/VIS
1
8
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detector, UV detection at 254 nm; Elution, MeOH in water (80%, v/v); T = 25°C; and flow rate = 1.0
mL/min.
Ethyl 4ꢀ(2ꢀhydroxyphenyl)ꢀ2,4ꢀdioxobutanoate (4). To a solution of 2’ꢀhydroxyacetophenone (3) (2.72 g,
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0.0 mmol) in toluene (80 mL) at 0°C was added sodium hydride (4.0 g, 100 mmol). The mixture was
stirred at room temperature for 15 min and diethyl oxalate (4.0 mL, 30.0 mmol) was added and the
mixture was stirred at 60°C for 2 h. After the solution had cooled to room temperature it was poured into
a mixture of ice and water and acidified by the addition of 2 N aqueous HCl. The resulting solution was
extracted with portions of ethyl acetate (2×100 mL). The combined organic extracts were dried over
anhydrous sodium sulfate, and concentrated to give a crude, which was purified by silica gel column
chromatography (petroleum ether/EtOAc, 3:1) to get the product 4 (3.2 g) as a yellow solid. Yield: 68%;
+
+
MS (ESI) m/z calcd C H O [M+H] 237.1, found 237.1.
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5
Ethyl 3ꢀ(4ꢀ(tertꢀbutoxy)benzyl)ꢀ9ꢀoxoꢀ2,9ꢀdihydrochromeno[2,3ꢀc]pyrroleꢀ1ꢀcarboxylate (5). To a
solution of 4 (3.2 g, 13.6 mmol), FmocꢀOꢀtertꢀbutylꢀLꢀtyrosine (11.2 g, 24.4 mmol), 4ꢀdimethylpyridine
(663 mg, 5.4 mmol) in pyridine (50 mL) was added DCC (5.6 g, 27.2 mmol). The mixture was stirred at
room temperature for 3 h until the start material disappeared as monitored by TLC. The reaction
temperature was raised to 50°C for 6 h. After the reaction mixture was evaporated under vacuum, the
residue was diluted with ethyl acetate (150 mL) and filtered to remove the side product DCU. The
filtrate was evaporated and purified by silica gel column chromatography (petroleum ether/EtOAc, 5:1)
1
to afford 5 (4.0 g) as a yellow solid. Yield: 70%; H NMR (400 MHz, CDCl ) δ 9.97 (br s, 1H), 8.38 (dd,
3
J = 8.0, 1.4 Hz, 1H), 7.69 – 7.59 (m, 1H), 7.41 (d, J = 8.3 Hz, 1H), 7.31 (t, J = 7.5 Hz, 1H), 7.14 (d, J =
8
1
.4 Hz, 2H), 6.95 (d, J = 8.4 Hz, 2H), 4.45 (q, J = 7.1 Hz, 2H), 4.21 (s, 2H), 1.47 (t, J = 7.1 Hz, 3H),
.33 (s, 9H).
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ꢀ(4ꢀ(tertꢀButoxy)benzyl)ꢀ9ꢀoxoꢀ2,9ꢀdihydrochromeno[2,3ꢀc]pyrroleꢀ1ꢀcarboxylic acid (6). To a solution
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of 5 (2.0 g, 4.8 mmol) in THF (40 mL) and water (160 mL) was added Potassium hydroxide (4.0 g, 71.6
mmol). The mixture was stirred at 60°C for 12 h. After the solution had cooled to room temperature it
was evaporated to remove most of the solvent and acidified by the addition of 4 N aqueous HCl. The
resulting solution was extracted with portions of ethyl acetate (3×100 mL). The combined organic
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extracts were dried over anhydrous sodium sulfate, and concentrated to afford the product 6 as a yellow
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solid, which was used directly in the next step without further purification. H NMR (400 MHz, CDCl )
3
δ 9.05 (br s, 1H), 8.32 (d, J = 7.7 Hz, 1H), 7.62 (t, J = 7.6 Hz, 1H), 7.39 (d, J = 8.3 Hz, 1H), 7.30 ꢀ 7.25
(m, 1H), 7.12 (d, J = 8.0 Hz, 2H), 6.92 (d, J = 7.9 Hz, 2H), 4.14 (s, 2H), 1.32 (s, 9H).
Methyl 3ꢀ(4ꢀ(tertꢀbutoxy)benzyl)ꢀ9ꢀoxoꢀ2,9ꢀdihydrochromeno[2,3ꢀc]pyrroleꢀ1ꢀcarboxylate (7). To a
solution of 5 (210 mg, 0.5 mmol) in methanol (100mL) was added lithium hydroxide hydrate (63 mg,
1
.5 mmol). The mixture was stirred at room temperature for 12 h. Then it was evaporated to remove
most of the solvent and acidified by the addition of 2 N aqueous HCl. The resulting solution was
extracted with portions of ethyl acetate (2×30 mL). The combined organic extracts were dried over
anhydrous sodium sulfate, and concentrated to afford the product 7 (202 mg) as a yellow solid. Yield:
1
100%; H NMR (400 MHz, CDCl ) δ 13.29 (br s, 1H), 8.16 (dd, J = 8.0, 1.6 Hz, 1H), 7.75 (ddd, J = 8.6,
3
7
.1, 1.7 Hz, 1H), 7.53 (d, J = 7.9 Hz, 1H), 7.44 – 7.34 (m, 1H), 7.20 (d, J = 8.5 Hz, 2H), 6.91 (d, J = 8.5
Hz, 2H), 4.15 (s, 2H), 3.86 (s, 3H), 1.25 (s, 9H).
Methyl 3ꢀ(4ꢀhydroxybenzyl)ꢀ9ꢀoxoꢀ2,9ꢀdihydrochromeno[2,3ꢀc]pyrroleꢀ1ꢀcarboxylate (8). To a solution
of 7 (101 mg, 0.25 mmol) in dichloromethane (3.0 mL) was added trifluoroacetic acid (1.0 mL). The
mixture was stirred at room temperature for 2 h. Then it was diluted with dichloromethane (50 mL) and
washed with saturated aqueous sodium bicarbonate and water. The organic layer was dried over
anhydrous sodium sulfate, and purified by silica gel column chromatography (petroleum ether/EtOAc,
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:1) to afford the product 8 (77 mg) as a yellow solid. Yield: 88%; purity: 99%; H NMR (400 MHz,
DMSO – d ) δ 13.27 (br, 1H), 9.25 (s, 1H), 8.16 (d, J = 7.9 Hz, 1H), 7.75 (t, J = 7.7 Hz, 1H), 7.54 (d, J
6
=
8.3 Hz, 1H), 7.38 (t, J = 7.5 Hz, 1H), 7.10 (d, J = 8.3 Hz, 2H), 6.68 (d, J = 8.4 Hz, 2H), 4.06 (s, 2H),
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.86 (s, 3H); C NMR (101 MHz, DMSO – d ) δ 172.89, 160.44, 156.31, 156.05, 142.90, 134.71,
6
129.64×2, 129.24, 126.94, 123.88, 122.91, 120.54, 118.26, 115.72×2, 113.75, 112.50, 52.12, 28.99.
Ethyl 3ꢀ(4ꢀhydroxybenzyl)ꢀ9ꢀoxoꢀ2,9ꢀdihydrochromeno[2,3ꢀc]pyrroleꢀ1ꢀcarboxylate (9). To a solution
of 5 (105 mg, 0.25 mmol) in dichloromethane (3.0 mL) was added trifluoroacetic acid (1.0 mL). The
mixture was stirred at room temperature for 2 h. Then it was diluted with dichloromethane (50 mL) and
washed with saturated aqueous sodium bicarbonate and water. The organic layer was dried over
anhydrous sodium sulfate, and purified by silica gel column chromatography (petroleum ether/EtOAc,
1
2:1) to afford the product 9 (85 mg) as a yellow solid. Yield 92%; purity: 99%; H NMR (400 MHz,
DMSO – d ) δ 13.20 (br, 1H), 9.26 (s, 1H), 8.16 (d, J = 7.9 Hz, 1H), 7.74 (t, J = 7.7 Hz, 1H), 7.53 (d, J
6
=
8.4 Hz, 1H), 7.38 (t, J = 7.5 Hz, 1H), 7.10 (d, J = 8.0 Hz, 2H), 6.68 (d, J = 8.0 Hz, 2H), 4.33 (q, J =
13
7
.0 Hz, 2H), 4.07 (s, 2H), 1.36 (t, J = 7.0 Hz, 3H); C NMR (101 MHz, DMSO – d ) δ 172.88, 160.04,
6
1
56.31, 156.05, 142.88, 134.66, 129.63×2, 129.28, 126.98, 123.85, 122.95, 120.32, 118.24, 115.72×2,
+
+
114.17, 112.44, 60.80, 28.97, 14.82; HRMS (ESI) m/z calcd C H NO [M+H] 364.1179, found
2
1
18
5
3
64.1184.
General Procedure for Synthesis of Compounds 10a-10c. To a solution of 6 (0.6 mmol) in
dichloromethane (8.0 mL) was added amines (0.9 mmol), triethylamine (125 ꢁL, 0.9 mmol) and HATU
(
459 mg, 1.2 mmol). The mixture was stirred at room temperature for 12 h. Then it was concentrated to
give a crude, which was purified by silica gel column chromatography (petroleum ether/EtOAc, 5:1) to
get the product as a white solid.
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ꢀ(4ꢀ(tertꢀButoxy)benzyl)ꢀ1ꢀ(morpholineꢀ4ꢀcarbonyl)chromeno[2,3ꢀc]pyrrolꢀ9(2H)ꢀone (10a). Yield:
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8
9
1
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5
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6
1
4
1%; H NMR (400 MHz, Acetone – d ) δ 11.81 (br s, 1H), 8.24 (dd, J = 7.9, 1.5 Hz, 1H), 7.74 (ddd, J
6
=
8.8, 7.1, 1.8 Hz, 1H), 7.51 (dd, J = 8.4, 0.7 Hz, 1H), 7.36 (ddd, J = 8.1, 7.1, 1.0 Hz, 1H), 7.23 (d, J =
0
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.6 Hz, 2H), 6.90 (d, J = 8.5 Hz, 2H), 4.21 (s, 2H), 3.70 (s, 8H), 1.28 (s, 9H).
3ꢀ(4ꢀ(tertꢀButoxy)benzyl)ꢀ1ꢀ(4ꢀisopropylpiperazineꢀ1ꢀcarbonyl)chromeno[2,3ꢀc]pyrrolꢀ9(2H)ꢀone (10b).
1
Yield: 39%; H NMR (400 MHz, CDCl ) δ 10.88 (br s, 1H), 8.25 (dd, J = 8.0, 1.4 Hz, 1H), 7.65 (ddd, J
3
=
8.6, 7.2, 1.7 Hz, 1H), 7.42 (d, J = 8.0 Hz, 1H), 7.33 – 7.28 (m, 1H), 7.09 (d, J = 8.4 Hz, 2H), 6.81 (d, J
= 8.4 Hz, 2H), 4.10 (d, J = 9.8 Hz, 2H), 3.84 (s, 4H), 3.13 – 3.05 (m, 1H), 2.96 (s, 4H), 1.24 (s, 9H),
1
.21 (d, J = 6.5 Hz, 6H).
3
ꢀ(4ꢀ(tertꢀButoxy)benzyl)ꢀ1ꢀ(4ꢀcyclopropylpiperazineꢀ1ꢀcarbonyl)chromeno[2,3ꢀc]pyrrolꢀ9(2H)ꢀone
1
(10c). Yield: 44%; H NMR (400 MHz, CDCl ) δ 12.00 (br s, 1H), 8.29 (dd, J = 8.0, 1.6 Hz, 1H), 7.62
3
(
ddd, J = 8.6, 7.2, 1.7 Hz, 1H), 7.38 (d, J = 8.0 Hz, 1H), 7.33 – 7.27 (m, 1H), 6.97 (d, J = 8.4 Hz, 2H),
6
.69 (d, J = 8.4 Hz, 2H), 3.99 (s, 2H), 3.76 (d, J = 26.1 Hz, 4H), 2.71 (d, J = 15.9 Hz, 4H), 1.78 (s, 1H),
.21 (d, J = 28.6 Hz, 9H), 0.55 – 0.35 (m, 4H).
1
General Procedure for Synthesis of Compounds 11a-11c. To a solution of 10 (0.25 mmol) in
dichloromethane (3.0 mL) was added trifluoroacetic acid (1.0 mL). The mixture was stirred at room
temperature for 2 h. Then it was diluted with dichloromethane (50 mL) and washed with saturated
aqueous sodium bicarbonate and water. The organic layer was dried over anhydrous sodium sulfate, and
purified by silica gel column chromatography (petroleum ether/EtOAc, 2:1) to afford the product 11 as a
yellow solid.
3
ꢀ(4ꢀHydroxybenzyl)ꢀ1ꢀ(morpholineꢀ4ꢀcarbonyl)chromeno[2,3ꢀc]pyrrolꢀ9(2H)ꢀone (11a). Yield: 87%;
1
purity
＞
99%; H NMR (400 MHz, DMSO – d ) δ 12.83 (br s, 1H), 9.26 (s, 1H), 8.15 (d, J = 7.6 Hz, 1H),
6
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.74 (t, J = 7.4 Hz, 1H), 7.53 (d, J = 8.3 Hz, 1H), 7.36 (t, J = 7.4 Hz, 1H), 7.10 (d, J = 8.3 Hz, 2H), 6.70
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(
d, J = 8.4 Hz, 2H), 4.01 (s, 2H), 3.67 (s, 4H), 3.58 (s, 2H), 3.48 (s, 2H); C NMR (101 MHz, DMSO –
d6) δ 174.16, 161.52, 156.68, 156.29, 140.55, 134.78, 129.68×2, 129.65, 126.69, 123.52, 122.28, 118.51,
18.30, 116.13, 115.72×2, 109.38, 66.70, 66.54, 47.69, 42.85, 29.06; HRMS (ESI) m/z calcd
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+
+
C H N O [M+H] 405.1445, found 405.1437.
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3ꢀ(4ꢀHydroxybenzyl)ꢀ1ꢀ(4ꢀisopropylpiperazineꢀ1ꢀcarbonyl)chromeno[2,3ꢀc]pyrrolꢀ9(2H)ꢀone
(11b).
1
Yield: 91%; purity: 98%; H NMR (400 MHz, DMSO – d ) δ 12.74 (br s, 1H), 9.22 (s, 1H), 8.14 (dd, J
6
=
7.9, 1.6 Hz, 1H), 7.74 (ddd, J = 8.7, 7.1, 1.8 Hz, 1H), 7.52 (d, J = 7.8 Hz, 1H), 7.40 – 7.30 (m, 1H),
7.10 (d, J = 8.5 Hz, 2H), 6.69 (d, J = 8.5 Hz, 2H), 4.00 (s, 2H), 3.65 (s, 2H), 3.43 (s, 2H), 3.18 (d, J =
13
5
1
.2 Hz, 1H), 2.68 (s, 1H), 2.38 (s, 3H), 0.97 (d, J = 6.3 Hz, 6H); C NMR (101 MHz, DMSO – d ) δ
6
74.02, 161.21, 156.70, 156.27, 140.46, 134.68, 129.68, 129.64×2, 126.66, 123.46, 122.32, 119.08,
118.26, 115.71×3, 109.29, 54.23, 49.12, 48.95, 48.47, 47.44, 29.08, 18.51×2; HRMS (ESI) m/z calcd
+
+
C H N O [M+H] 446.2074, found 446.2065.
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ꢀ(4ꢀCyclopropylpiperazineꢀ1ꢀcarbonyl)ꢀ3ꢀ(4ꢀhydroxybenzyl)chromeno[2,3ꢀc]pyrrolꢀ9(2H)ꢀone (11c).
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Yield: 91%; purity: 99%; H NMR (400 MHz, DMSO – d ) δ 12.76 (br s, 1H), 9.22 (s, 1H), 8.13 (dd, J
6
=
7.9, 1.6 Hz, 1H), 7.74 (ddd, J = 8.7, 7.1, 1.7 Hz, 1H), 7.53 (d, J = 8.4 Hz, 1H), 7.41 – 7.29 (m, 1H),
7.10 (d, J = 8.5 Hz, 2H), 6.69 (d, J = 8.5 Hz, 2H), 4.00 (s, 2H), 3.63 (s, 2H), 3.41 (s, 2H), 2.60 (s, 2H),
1
3
2
.48 (s, 2H), 1.71 – 1.59 (m, 1H), 0.51 – 0.27 (m, 4H); C NMR (101 MHz, DMSO – d ) δ 174.05,
6
1
61.33, 156.72, 156.28, 140.49, 134.71, 129.68, 129.65×2, 126.67, 123.48, 122.34, 119.03, 118.27,
115.75, 115.72×2, 109.32, 53.40, 52.96, 47.05, 46.45, 38.39, 29.09, 6.22×2; HRMS (ESI) m/z calcd
+
+
C H N O [M+H] 444.1918, found 444.1909.
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General Procedure for Synthesis of Compounds 13a-13j. The acids 12a-j (12.0 mmol) were
dissolved in thionyl chloride (5.0 mL), respectively. The mixture was then heated at reflux for 12 h.
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After cooling to room temperature, the solution was evaporated under vacuum to afford the carbonyl
chlorides 13a-j as a yellow oil, which was used directly in the next step without further purification.
General Procedure for Synthesis of Compounds 14a-b, 14e, 14g, and 14h.To a solution of 2’ꢀ
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hydroxyacetophenone (1.36 g, 10.0 mmol) and pyridine (4.0 mL, 50 mmol) in dichloromethane (30 mL)
was added dropwise of 13a (or 13b, 13e, 13g, 13h; from the previous step) in dichloromethane (10 mL)
at 0°C, respectively. The mixture was stirred at room temperature for 2 h. Then the reaction mixture was
diluted with dichloromethane (60 mL) and washed with 3 M aqueous HCl and water. The organic layer
was dried over anhydrous sodium sulfate, and concentrated to give a crude, which was purified by silica
gel column chromatography (petroleum ether/EtOAc, 8:1) to get the product as a yellow solid.
1
2ꢀAcetylphenyl picolinate (14a). Yield: 64%; H NMR (400 MHz, CDCl ) δ 8.87 (d, J = 4.0 Hz, 1H),
3
8
8
2
1
.32 (d, J = 7.8 Hz, 1H), 8.00 – 7.87 (m, 2H), 7.64 – 7.57 (m, 2H), 7.41 (t, J = 7.6 Hz, 1H), 7.32 (d, J =
.1 Hz, 1H), 2.60 (s, 3H).
1
ꢀacetylphenyl pyrimidineꢀ4ꢀcarboxylate (14b). Yield: 58%; H NMR (400 MHz, CDCl ) δ 9.53 (d, J =
3
.4 Hz, 1H), 9.11 (d, J = 5.0 Hz, 1H), 8.21 (dd, J = 5.0, 1.4 Hz, 1H), 7.94 (dd, J = 7.8, 1.6 Hz, 1H), 7.66
(ddd, J = 8.1, 7.5, 1.7 Hz, 1H), 7.45 (td, J = 7.7, 1.2 Hz, 1H), 7.32 (dd, J = 8.1, 1.0 Hz, 1H), 2.60 (s, 3H).
1
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ꢀAcetylphenylꢀ4ꢀchloropicolinate (14e). Yield: 98%; H NMR (400 MHz, CDCl ) δ 8.74 (d, J = 5.1 Hz,
3
1
H), 8.29 (s, 1H), 7.90 (d, J = 7.8 Hz, 1H), 7.66 – 7.52 (m, 2H), 7.41 (t, J = 7.6 Hz, 1H), 7.27 (d, J = 5.6
Hz, 1H), 2.58 (s, 3H).
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ꢀacetylphenyl 2ꢀchloronicotinate (14g). Yield: 95%; H NMR (400 MHz, CDCl ) δ 8.61 (dd, J = 4.8,
3
2
.0 Hz, 1H), 8.54 (dd, J = 7.7, 2.0 Hz, 1H), 7.91 (dd, J = 7.8, 1.6 Hz, 1H), 7.64 (td, J = 7.8, 1.6 Hz, 1H),
7.48 – 7.40 (m, 2H), 7.30 (dd, J = 8.4, 1.3 Hz, 1H), 2.60 (s, 3H).
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ꢀAcetylphenylꢀ3ꢀchloroisonicotinate (14h). Yield: 51%; H NMR (400 MHz, CDCl ) δ 8.82 (s, 1H),
3
.72 (d, J = 4.8 Hz, 1H), 8.03 (d, J = 4.9 Hz, 1H), 7.93 (d, J = 7.8 Hz, 1H), 7.66 (s, 1H), 7.45 (s, 1H),
.29 (s, 1H), 2.61 (s, 3H).
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General Procedure for Synthesis of Compounds 14c-d, 14f, and 14i-j. To a solution of 2’ꢀ
hydroxyacetophenone (1.63 g, 12.0 mmol) and pyridine (2.88 mL, 36 mmol) in dichloromethane (30 mL)
was added dropwise of 13c (or 13d, 13f, 13i-j; from the previous step) in dichloromethane (10 mL) at
0°C, respectively. The mixture was then stirred at 0°C for 1h and stirred at room temperature for 2 h.
Then the reaction mixture was diluted with dichloromethane (60 mL) and washed with 3 M aqueous
HCl and water. The organic layer was dried over anhydrous sodium sulfate, and concentrated to get the
product as a yellow solid, which was used directly in the next step without further purification.
General Procedure for Synthesis of Compounds 15a-15j. Procedure A. To a solution of 14 (6.0
mmol) in THF (50 mL) was added potassium tertꢀbutoxide (875 mg, 7.8 mmol). The mixture was stirred
at room temperature for 12 h under argon. Then it was quenched with water (50 mL) and acidified with
2
N aqueous HCl to pH = 6.0. The mixture was evaporated under vaccum to remove the THF. Then the
solid was filtered and washed with hexane to get the product 15 as a yellow solid, which was used
directly in the next step without further purification.
Procedure B. To a solution of 14 (3.0 mmol) in pyridine (20 mL) was added potassium hydroxide (202
mg, 3.6 mmol). The mixture was stirred at 60°C for 8 h under argon. Then it was diluted with water
(
200 mL) and acidified with 4 N aqueous HCl. The resulting solution was extracted with portions of
ethyl acetate (3×40 mL). The combined organic extracts were dried over anhydrous sodium sulfate, and
concentrated to give a crude, which was purified silica gel column chromatography (petroleum
ether/EtOAc, 6:1 to 2:1) to get the product 15 as a yellow solid.
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ꢀ(2ꢀHydroxyphenyl)ꢀ3ꢀ(pyridinꢀ2ꢀyl)propaneꢀ1,3ꢀdione (15a). Procedure A. Yield: 16%; H NMR
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(
400 MHz, CDCl ) δ 15.18 (br s, 1H), 12.14 (s, 1H), 8.73 (ddd, J = 4.7, 1.7, 0.9 Hz, 1H), 8.14 – 8.09 (m,
3
1
–
H), 7.97 (dd, J = 8.1, 1.6 Hz, 1H), 7.89 (td, J = 7.8, 1.8 Hz, 1H), 7.62 (s, 1H), 7.54 – 7.49 (m, 1H), 7.49
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7.43 (m, 1H), 7.03 (dd, J = 8.4, 1.0 Hz, 1H), 6.96 (ddd, J = 8.2, 7.2, 1.1 Hz, 1H).
1
1ꢀ(2ꢀHydroxyphenyl)ꢀ3ꢀ(pyrimidinꢀ4ꢀyl)propaneꢀ1,3ꢀdione (15b). Procedure A. Yield: 51%; H NMR
(400 MHz, CDCl ) δ 14.70 (br s, 1H), 12.00 (s, 1H), 9.34 (s, 1H), 9.00 (d, J = 5.0 Hz, 1H), 8.01 (d, J =
3
5
.1 Hz, 1H), 7.96 (d, J = 7.9 Hz, 1H), 7.70 (s, 1H), 7.55 (t, J = 7.8 Hz, 1H), 7.05 (d, J = 8.4 Hz, 1H),
6.99 (t, J = 7.6 Hz, 1H).
ꢀ(2ꢀHydroxyphenyl)ꢀ3ꢀ(pyridinꢀ3ꢀyl)propaneꢀ1,3ꢀdione (15c). Procedure A. Yield: 61%; H NMR
400 MHz, CDCl ) δ 15.18 (br s, 1H), 12.14 (s, 1H), 8.73 (ddd, J = 4.7, 1.7, 0.9 Hz, 1H), 8.14 – 8.09 (m,
1
1
(
3
1H), 7.97 (dd, J = 8.1, 1.6 Hz, 1H), 7.89 (td, J = 7.8, 1.8 Hz, 1H), 7.62 (s, 1H), 7.54 – 7.49 (m, 1H), 7.49
–
7.43 (m, 1H), 7.03 (dd, J = 8.4, 1.0 Hz, 1H), 6.96 (ddd, J = 8.2, 7.2, 1.1 Hz, 1H).
1
1
ꢀ(2ꢀHydroxyphenyl)ꢀ3ꢀ(pyridinꢀ4ꢀyl)propaneꢀ1,3ꢀdione (15d). Procedure B. Yield: 74%; H NMR
(400 MHz, CDCl ) δ 15.14 (br s, 1H), 11.94 (s, 1H), 8.83 (s, 2H), 7.83 (s, 3H), 7.54 (t, J = 7.7 Hz, 1H),
3
7
.06 (d, J = 8.4 Hz, 1H), 6.98 (t, J = 7.6 Hz, 1H), 6.94 (s, 1H).
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1ꢀ(4ꢀChloropyridinꢀ2ꢀyl)ꢀ3ꢀ(2ꢀhydroxyphenyl)propaneꢀ1,3ꢀdione (15e). Procedure A. Yield: 14%; H
NMR (400 MHz, CDCl ) δ 8.67 (d, J = 5.1 Hz, 1H), 8.29 (d, J = 8.4 Hz, 1H), 8.13 (s, 1H), 7.77 (t, J =
3
7
.4 Hz, 1H ), 7.64 (d, J = 8.1 Hz, 1H), 7.50 – 7.46 (m, 3H).
1
1ꢀ(5ꢀChloropyridinꢀ2ꢀyl)ꢀ3ꢀ(2ꢀhydroxyphenyl)propaneꢀ1,3ꢀdione (15f). Procedure B. Yield: 14%; H
NMR (400 MHz, CDCl ) δ 15.13 (br s, 1H), 12.09 (s, 1H), 8.66 (s, 1H), 8.06 (d, J = 8.3 Hz, 1H), 7.94 (d,
3
J = 8.0 Hz, 1H), 7.85 (d, J = 8.1 Hz, 1H), 7.57 (s, 1H), 7.51 (t, J = 7.4 Hz, 1H), 7.03 (d, J = 8.5 Hz, 1H),
6
.97 (t, J = 7.4 Hz, 1H).
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ꢀ(2ꢀChloropyridinꢀ3ꢀyl)ꢀ3ꢀ(2ꢀhydroxyphenyl)propaneꢀ1,3ꢀdione (15g). Procedure A. Yield: 36%; H
NMR (400 MHz, CDCl ) δ 15.19 (br s, 1H), 11.91 (s, 1H), 8.54 (dd, J = 4.8, 2.0 Hz, 1H), 8.11 (dd, J =
3
7
.7, 2.0 Hz, 1H), 7.74 (dd, J = 8.1, 1.6 Hz, 1H), 7.52 (ddd, J = 8.6, 7.3, 1.6 Hz, 1H), 7.42 (dd, J = 7.7,
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.8 Hz, 1H), 7.05 (dd, J = 8.4, 1.0 Hz, 1H), 6.99 – 6.91 (m, 2H).
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1ꢀ(3ꢀChloropyridinꢀ4ꢀyl)ꢀ3ꢀ(2ꢀhydroxyphenyl)propaneꢀ1,3ꢀdione (15h). Procedure B. Yield: 76%; H
NMR (400 MHz, CDCl ) δ 15.04 (br s, 1H), 11.87 (s, 1H), 8.77 (s, 1H), 8.66 (s, 1H), 7.72 (d, J = 7.8 Hz,
3
1
H), 7.65 (d, J = 4.6 Hz, 1H), 7.53 (t, J = 7.6 Hz, 1H), 7.05 (d, J = 8.4 Hz, 1H), 6.96 (t, J = 7.5 Hz, 1H),
6.92 (s, 1H).
ꢀ(2ꢀFluorophenyl)ꢀ3ꢀ(2ꢀhydroxyphenyl)propaneꢀ1,3ꢀdione (15i). Procedure A. Yield: 23%; H NMR
400 MHz, CDCl ) δ 8.07 (td, J = 7.6, 1.8 Hz, 1H), 7.89 (dtd, J = 19.1, 7.5, 1.8 Hz, 1H), 7.67 – 7.56 (m,
1
1
(
3
2H), 7.53 – 7.43 (m, 1H), 7.28 – 7.16 (m, 3H), 7.14 – 7.03 (m, 1H).
ꢀ(2ꢀHydroxyphenyl)ꢀ3ꢀ(thiazolꢀ2ꢀyl)propaneꢀ1,3ꢀdione (15j). Procedure A. Yield: 31%; H NMR (400
MHz, CDCl ) δ 15.16 (br s, 1H), 11.89 (s, 1H), 8.05 (d, J = 3.0 Hz, 1H), 7.90 (dd, J = 8.1, 1.6 Hz, 1H),
1
1
3
7
.69 (d, J = 3.1 Hz, 1H), 7.52 (ddd, J = 8.6, 7.3, 1.5 Hz, 1H), 7.37 (s, 1H), 7.03 (dt, J = 8.4, 1.5 Hz, 1H),
6
.99 – 6.93 (m, 1H).
General Procedure for Synthesis of Compounds 16a-16j. To a solution of 15 (1.0 mmol), FmocꢀOꢀ
tertꢀbutylꢀLꢀtyrosine (827 mg, 1.8 mmol), 4ꢀdimethylpyridine (49 mg, 0.4 mmol) in pyridine (10 mL)
was added DCC (412 mg, 2.0 mmol). The mixture was stirred at room temperature for 3 h until the start
material disappeared as monitored by TLC. The reaction temperature was raised to 50°C for 6 h, and a
major yellow spot could be observed by TLC. After the reaction mixture was evaporated under vacuum,
the residue was diluted with ethyl acetate (40 mL) and filtered to remove the side product DCU. The
filtrate was evaporated and purified by silica gel column chromatography (petroleum ether/EtOAc, 5:1)
to afford 16 as a yellow solid.
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ꢀ(4ꢀ(tertꢀButoxy)benzyl)ꢀ1ꢀ(pyridinꢀ2ꢀyl)chromeno[2,3ꢀc]pyrrolꢀ9(2H)ꢀone (16a). Yield: 30%;
H
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NMR (400 MHz, CDCl ) δ 9.42 (d, J = 7.8 Hz, 1H), 8.48 (d, J = 4.1 Hz, 1H), 8.41 (dd, J = 7.9, 1.6 Hz,
3
1
1
H), 7.81 (td, J = 7.8, 1.8 Hz, 1H), 7.69 – 7.63 (m, 1H), 7.42 (d, J = 8.4 Hz, 1H), 7.34 (d, J = 8.0 Hz,
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H), 7.20 (d, J = 8.4 Hz, 2H), 7.19 – 7.15 (m, 1H), 6.98 (d, J = 8.5 Hz, 2H), 4.24 (s, 2H), 1.35 (s, 9H).
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3ꢀ(4ꢀ(tertꢀButoxy)benzyl)ꢀ1ꢀ(pyrimidinꢀ4ꢀyl)chromeno[2,3ꢀc]pyrrolꢀ9(2H)ꢀone (16b). Yield: 54%; H
NMR (400 MHz, CDCl ) δ 10.36 (br s, 1H), 9.35 (dd, J = 5.4, 1.3 Hz, 1H), 9.04 (d, J = 1.2 Hz, 1H),
3
8
.77 (d, J = 5.4 Hz, 1H), 8.40 (dd, J = 8.0, 1.7 Hz, 1H), 7.70 (t, J = 6.9 Hz, 1H), 7.46 (d, J = 8.5 Hz,
1H), 7.37 (t, J = 7.5 Hz, 1H), 7.21 (d, J = 8.4 Hz, 2H), 7.01 (d, J = 8.4 Hz, 2H), 4.27 (s, 2H), 1.37 (s,
9
H).
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ꢀ(4ꢀ(tertꢀButoxy)benzyl)ꢀ1ꢀ(pyridinꢀ3ꢀyl)chromeno[2,3ꢀc]pyrrolꢀ9(2H)ꢀone (16c). Yield: 56%;
H
NMR (400 MHz, CDCl ) δ 10.42 (br s, 1H), 8.90 (d, J = 1.7 Hz, 1H), 8.65 – 8.55 (m, 1H), 8.34 (dd, J =
3
8
0
4
3
.0, 1.7 Hz, 1H), 8.28 (dd, J = 4.8, 1.6 Hz, 1H), 7.65 (ddd, J = 8.6, 7.1, 1.7 Hz, 1H), 7.41 (dd, J = 8.4,
.7 Hz, 1H), 7.33 – 7.29 (m, 1H), 7.28 – 7.24 (m, 1H), 7.16 (d, J = 8.5 Hz, 2H), 6.94 (d, J = 8.5 Hz, 2H),
.21 (s, 2H), 1.33 (s, 9H).
1
ꢀ(4ꢀ(tertꢀButoxy)benzyl)ꢀ1ꢀ(pyridinꢀ4ꢀyl)chromeno[2,3ꢀc]pyrrolꢀ9(2H)ꢀone (16d). Yield: 55%;
H
NMR (400 MHz, CDCl ) δ 8.65 (d, J = 4.9 Hz, 2H), 8.38 (d, J = 8.0 Hz, 1H), 7.93 (d, J = 4.7 Hz, 2H),
3
7
.67 (d, J = 7.8 Hz, 1H), 7.44 (d, J = 8.5 Hz, 1H), 7.34 (d, J = 7.8 Hz, 1H), 7.20 (d, J = 7.7 Hz, 2H), 7.01
(d, J = 8.0 Hz, 2H), 4.27 (s, 2H), 1.37 (s, 9H).
3ꢀ(4ꢀ(tertꢀButoxy)benzyl)ꢀ1ꢀ(4ꢀchloropyridinꢀ2ꢀyl)chromeno[2,3ꢀc]pyrrolꢀ9(2H)ꢀone (16e). Yield: 50%;
1
H NMR (400 MHz, CDCl ) δ 10.37 (br s, 1H), 9.57 (d, J = 1.8 Hz, 1H), 8.42 (dd, J = 8.0, 1.6 Hz, 1H),
3
8
.32 (d, J = 5.3 Hz, 1H), 7.66 (ddd, J = 8.6, 7.1, 1.7 Hz, 1H), 7.42 (d, J = 7.7 Hz, 1H), 7.34 (ddd, J =
.1, 7.2, 1.0 Hz, 1H), 7.23 – 7.10 (m, 3H), 6.96 (d, J = 8.5 Hz, 2H), 4.21 (s, 2H), 1.34 (s, 9H).
8
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ꢀ(4ꢀ(tertꢀButoxy)benzyl)ꢀ1ꢀ(5ꢀchloropyridinꢀ2ꢀyl)chromeno[2,3ꢀc]pyrrolꢀ9(2H)ꢀone (16f). Yield: 45%;
1
H NMR (400 MHz, CDCl ) δ 10.15 (br s, 1H), 9.43 (d, J = 8.7 Hz, 1H), 8.41 (s, 1H), 8.38 (d, J = 7.8
3
Hz, 1H), 7.76 (d, J = 8.6 Hz, 1H), 7.66 (t, J = 7.7 Hz, 1H), 7.42 (d, J = 8.5 Hz, 1H), 7.33 (t, J = 7.7 Hz,
0
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H), 7.20 (d, J = 7.7 Hz, 2H), 6.98 (d, J = 7.9 Hz, 2H), 4.24 (s, 2H), 1.36 (s, 9H).
3ꢀ(4ꢀ(tertꢀButoxy)benzyl)ꢀ1ꢀ(2ꢀchloropyridinꢀ3ꢀyl)chromeno[2,3ꢀc]pyrrolꢀ9(2H)ꢀone (16g). Yield: 48%;
1
H NMR (400 MHz, CDCl ) δ 9.43 (s, 1H), 8.37 (dd, J = 7.8, 1.9 Hz, 1H), 8.31 – 8.24 (m, 2H), 7.65
3
(ddd, J = 8.7, 7.1, 1.7 Hz, 1H), 7.43 (d, J = 8.4 Hz, 1H), 7.35 – 7.29 (m, 2H), 7.21 (d, J = 8.5 Hz, 2H),
6.99 (d, J = 8.5 Hz, 2H), 4.24 (s, 2H), 1.35 (s, 9H).
3
ꢀ(4ꢀ(tertꢀButoxy)benzyl)ꢀ1ꢀ(3ꢀchloropyridinꢀ4ꢀyl)chromeno[2,3ꢀc]pyrrolꢀ9(2H)ꢀone (16h). Yield: 85%;
1
H NMR (400 MHz, CDCl ) δ 9.29 (s, 1H), 8.60 (s, 1H), 8.56 (d, J = 4.2 Hz, 1H), 8.34 (d, J = 8.1 Hz,
3
1H), 8.20 (d, J = 4.8 Hz, 1H), 7.69 (t, J = 7.7 Hz, 1H), 7.46 (d, J = 8.3 Hz, 1H), 7.34 (t, J = 7.4 Hz, 1H),
7
.23 (d, J = 7.8 Hz, 2H), 7.03 (d, J = 7.5 Hz, 2H), 4.27 (s, 2H), 1.37 (s, 9H).
1
3
ꢀ(4ꢀ(tertꢀButoxy)benzyl)ꢀ1ꢀ(2ꢀfluorophenyl)chromeno[2,3ꢀc]pyrrolꢀ9(2H)ꢀone (16i). Yield: 53%; H
NMR (400 MHz, CDCl ) δ 9.07 (s, 1H), 8.77 – 8.65 (m, 1H), 8.37 (dd, J = 8.0, 1.6 Hz, 1H), 7.68 – 7.62
3
(
m, 1H), 7.47 – 7.39 (m, 2H), 7.34 – 7.31 (m, 2H), 7.21 (d, J = 8.6 Hz, 2H), 7.15 – 7.09 (m, 1H), 7.00
(d, J = 8.5 Hz, 2H), 4.24 (s, 2H), 1.37 (s, 9H).
ꢀ(4ꢀ(tertꢀButoxy)benzyl)ꢀ1ꢀ(thiazolꢀ2ꢀyl)chromeno[2,3ꢀc]pyrrolꢀ9(2H)ꢀone (16j). Yield: 49%; H NMR
400 MHz, CDCl ) δ 10.76 (br s, 1H), 8.40 (dd, J = 8.0, 1.7 Hz, 1H), 7.74 (d, J = 3.2 Hz, 1H), 7.66 (ddd,
1
3
(
3
J = 8.6, 7.2, 1.7 Hz, 1H), 7.42 (d, J = 8.3 Hz, 1H), 7.37 (d, J = 3.2 Hz, 1H), 7.34 (t, J = 7.5 Hz, 1H), 6.99
t, J = 12.4 Hz, 2H), 6.85 (d, J = 7.9 Hz, 2H), 4.11 (s, 2H), 1.25 (s, 9H).
(
General Procedure for Synthesis of Compounds 17a-17j. To a solution of 16 (0.25 mmol) in
dichloromethane (3.0 mL) was added trifluoroacetic acid (1.0 mL). The mixture was stirred at room
temperature for 2 h. Then it was diluted with dichloromethane (50 mL) and washed with saturated
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Journal of Medicinal Chemistry
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aqueous sodium bicarbonate and water. The organic layer was dried over anhydrous sodium sulfate, and
purified by silica gel column chromatography (petroleum ether/EtOAc, 3:1 to 1:1) to afford the product
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7 as a yellow solid.
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ꢀ(4ꢀHydroxybenzyl)ꢀ1ꢀ(pyridinꢀ2ꢀyl)chromeno[2,3ꢀc]pyrrolꢀ9(2H)ꢀone (17a). Yield: 63%; purity: 98%;
1
H NMR (400 MHz, Acetone – d ) δ 11.66 (br s, 1H), 9.41 (d, J = 8.1 Hz, 1H), 8.60 – 8.44 (m, 1H),
6
8
.32 (dd, J = 7.9, 1.5 Hz, 1H), 8.14 (br, 1H), 7.86 (td, J = 8.0, 1.8 Hz, 1H), 7.72 (ddd, J = 8.7, 7.1, 1.7
Hz, 1H), 7.49 (d, J = 8.4 Hz, 1H), 7.41 – 7.30 (m, 1H), 7.25 – 7.20 (m, 3H), 6.77 (d, J = 8.5 Hz, 2H),
1
3
4.26 (s, 2H); C NMR (101 MHz, Acetone – d ) δ 174.73, 156.58, 155.94, 148.81, 148.71, 142.88,
6
1
1
37.06, 133.87, 130.12, 129.41×3, 126.87, 122.75, 122.65, 122.30, 122.14, 117.47, 115.58, 115.28,
+
3
+
09.10, 99.99, 28.62. HRMS (ESI) m/z calcd C H N O [M+H] 369.1234, found 369.1241.
23 17
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3ꢀ(4ꢀHydroxybenzyl)ꢀ1ꢀ(pyrimidinꢀ4ꢀyl)chromeno[2,3ꢀc]pyrrolꢀ9(2H)ꢀone (17b). Yield: 84%; purity:
1
9
9%; H NMR (400 MHz, DMSO – d ) δ 13.26 (br s, 1H), 9.20 (s, 1H), 9.18 (d, J = 11.7 Hz, 1H), 8.83
6
(d, J = 5.3 Hz, 1H), 8.23 (d, J = 7.5 Hz, 1H), 7.77 (t, J = 7.3 Hz, 1H), 7.55 (d, J = 8.2 Hz, 1H), 7.39 (t, J
1
3
=
7.4 Hz, 1H), 7.16 (d, J = 8.1 Hz, 2H), 6.69 (d, J = 8.2 Hz, 2H), 4.14 (s, 2H); C NMR (101 MHz,
DMSO – d ) δ 174.33, 157.98×2, 155.77×2, 154.44, 143.04, 134.49, 129.20×2, 129.12, 126.52, 123.34,
6
+
121.90, 119.25, 117.70, 117.61, 115.20×2, 110.93, 99.49, 28.39. HRMS (ESI) m/z calcd C H N O
3
2
2
16
3
+
[
M+H] 370.1186, found 370.1190.
3
ꢀ(4ꢀHydroxybenzyl)ꢀ1ꢀ(pyridinꢀ3ꢀyl)chromeno[2,3ꢀc]pyrrolꢀ9(2H)ꢀone (17c). Yield: 93%; purity: 95%;
1
H NMR (400 MHz, DMSO – d ) δ 12.53 (br s, 1H), 9.22 – 9.21 (m, 2H), 8.53 (dd, J = 4.8, 1.6 Hz, 1H),
6
8
.46 (ddd, J = 8.1, 2.3, 1.7 Hz, 1H), 8.18 (dd, J = 7.9, 1.6 Hz, 1H), 7.72 (ddd, J = 8.6, 7.1, 1.8 Hz, 1H),
.57 – 7.44 (m, 2H), 7.35 (t, J = 8.0 Hz, 1H), 7.13 (d, J = 8.5 Hz, 2H), 6.72 (d, J = 8.5 Hz, 2H), 4.08 (s,
7
2
1
3
H); C NMR (101 MHz, DMSO – d ) δ 174.71, 156.56, 156.27, 148.85, 148.58, 142.24, 135.33,
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34.59, 129.86, 129.53×2, 127.48, 126.87, 124.18, 123.58, 123.34, 122.31, 118.02, 115.75×2, 115.39,
+
+
08.55, 29.03. HRMS (ESI) m/z calcd C H N O [M+H] 369.1234, found 369.1244.
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ꢀ(4ꢀHydroxybenzyl)ꢀ1ꢀ(pyridinꢀ4ꢀyl)chromeno[2,3ꢀc]pyrrolꢀ9(2H)ꢀone (17d). Yield: 92%; purity: 98%;
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H NMR (400 MHz, DMSO – d ) δ 12.73 (s, 1H), 9.23 (s, 1H), 8.63 (d, J = 4.7 Hz, 2H), 8.31 – 8.11 (m,
6
3H), 7.75 (t, J = 7.6 Hz, 1H), 7.52 (d, J = 8.3 Hz, 1H), 7.37 (t, J = 7.5 Hz, 1H), 7.11 (d, J = 7.7 Hz, 2H),
1
3
6
.70 (d, J = 7.6 Hz, 2H), 4.11 (s, 2H); C NMR (101 MHz, DMSO – d ) δ 174.73, 156.27, 149.91×2,
6
1
42.92, 138.32, 134.80, 129.59, 129.54×3, 126.99, 123.87, 123.58, 122.36, 121.36, 118.06, 117.05,
+
+
115.75×3, 109.64, 28.99. HRMS (ESI) m/z calcd C H N O [M+H] 369.1234, found 369.1240.
23
17
2
3
1
ꢀ(4ꢀChloropyridinꢀ2ꢀyl)ꢀ3ꢀ(4ꢀhydroxybenzyl)chromeno[2,3ꢀc]pyrrolꢀ9(2H)ꢀone (17e). Yield: 75%;
1
purity＞99%; H NMR (400 MHz, DMSO – d ) δ 12.95 (br s, 1H), 9.45 (d, J = 1.6 Hz, 1H), 9.18 (s,
6
1
H), 8.58 (d, J = 5.0, 1H), 8.24 (dd, J = 8.0, 1.6 Hz, 1H), 7.75 (ddd, J = 8.6, 7.1, 1.7 Hz, 1H), 7.52 (d, J
7.8 Hz, 1H), 7.42 (dd, J = 5.3, 2.0 Hz, 1H), 7.38 (t, J = 7.0 Hz, 1H), 7.15 (d, J = 8.5 Hz, 2H), 6.69 (d,
=
1
3
J = 8.6 Hz, 2H), 4.12 (s, 2H); C NMR (101 MHz, DMSO – d ) δ 174.52, 155.84, 155.70, 150.15,
6
1
1
4
1
50.10, 143.75, 142.29, 134.35, 129.45, 129.18×2, 126.58, 123.74, 123.13, 121.84, 121.41, 117.58,
+
+
17.17, 115.16×3, 109.07, 28.30. HRMS (ESI) m/z calcd C H ClN O [M+H] 403.0844, found
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03.0850.
ꢀ(5ꢀChloropyridinꢀ2ꢀyl)ꢀ3ꢀ(4ꢀhydroxybenzyl)chromeno[2,3ꢀc]pyrrolꢀ9(2H)ꢀone (17f). Yield: 74%;
1
purity: 99%; H NMR (400 MHz, DMSO – d ) δ 12.88 (s, 1H), 9.26 (d, J = 8.6 Hz, 1H), 9.19 (s, 1H),
6
8
.63 (s, 1H), 8.21 (d, J = 7.7 Hz, 1H), 8.03 (d, J = 8.7 Hz, 1H), 7.74 (t, J = 7.6 Hz, 1H), 7.52 (d, J = 8.4
1
3
Hz, 1H), 7.37 (t, J = 7.4 Hz, 1H), 7.14 (d, J = 8.0 Hz, 2H), 6.68 (d, J = 8.0 Hz, 2H), 4.11 (s, 2H); C
NMR (101 MHz, DMSO – d ) δ 174.40, 155.87, 155.68, 147.23, 147.21, 142.17, 136.88, 134.29,
6
1
2
29.52, 129.16×2, 128.90, 126.50, 124.01, 123.14, 123.06, 121.88, 117.57, 116.74, 115.15×2, 108.81,
+
3
+
8.31. HRMS (ESI) m/z calcd C H ClN O [M+H] 403.0844, found 403.0851.
23 16
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ꢀ(2ꢀChloropyridinꢀ3ꢀyl)ꢀ3ꢀ(4ꢀhydroxybenzyl)chromeno[2,3ꢀc]pyrrolꢀ9(2H)ꢀone (17g). Yield: 76%;
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purity: 99%; H NMR (400 MHz, DMSO – d ) δ 12.48 (br s, 1H), 9.24 (s, 1H), 8.48 (dd, J = 4.8, 1.9 Hz,
6
1
H), 8.08 (dd, J = 8.0, 1.6 Hz, 1H), 8.04 (dd, J = 7.6, 1.9 Hz, 1H), 7.73 (ddd, J = 8.7, 7.1, 1.8 Hz, 1H),
.61 – 7.47 (m, 2H), 7.39 – 7.27 (m, 1H), 7.12 (d, J = 8.5 Hz, 2H), 6.71 (d, J = 8.5 Hz, 2H), 4.06 (s,
0
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2H); C NMR (101 MHz, DMSO – d ) δ 174.31, 156.94, 156.27, 150.14, 149.64, 142.52, 141.18,
6
1
1
34.58, 129.82, 129.55×2, 127.83, 126.50, 123.35, 122.95, 122.30, 121.38, 118.24, 115.75×2, 114.61,
ꢀ
ꢀ
09.56, 29.13. HRMS (ESI) m/z calcd C H ClN O [MꢀH] 401.0698, found 401.0707.
2
3
14
2
3
1ꢀ(3ꢀChloropyridinꢀ4ꢀyl)ꢀ3ꢀ(4ꢀhydroxybenzyl)chromeno[2,3ꢀc]pyrrolꢀ9(2H)ꢀone (17h). Yield: 55%;
1
purity: 99%; H NMR (400 MHz, DMSO – d ) δ 12.58 (br s, 1H), 9.23 (s, 1H), 8.75 (s, 1H), 8.59 (d, J =
6
5
.0 Hz, 1H), 8.09 (dd, J = 7.9, 1.6 Hz, 1H), 7.79 – 7.70 (m, 1H), 7.63 (d, J = 5.0 Hz, 1H), 7.53 (d, J =
13
8.4 Hz, 1H), 7.35 (t, J = 7.5 Hz, 1H), 7.12 (d, J = 8.5 Hz, 2H), 6.71 (d, J = 8.5 Hz, 2H), 4.08 (s, 2H); C
NMR (101 MHz, DMSO – d ) δ 174.25, 156.85, 156.29, 149.67, 147.87, 141.53, 138.20, 134.70,
6
1
2
1
30.81, 129.66, 129.57×2, 127.39, 126.56, 123.48, 122.31, 120.05, 118.28, 115.86, 115.77×2, 109.92,
ꢀ
ꢀ
9.16. HRMS (ESI) m/z calcd C H ClN O [MꢀH] 401.0698, found 401.0709.
2
3
14
2
3
ꢀ(2ꢀFluorophenyl)ꢀ3ꢀ(4ꢀhydroxybenzyl)chromeno[2,3ꢀc]pyrrolꢀ9(2H)ꢀone (17i). Yield: 91%; purity:
1
98%; H NMR (400 MHz, DMSO – d ) δ 12.35 (br s, 1H), 9.22 (s, 1H), 8.10 (dd, J = 7.9, 1.6 Hz, 1H),
6
7
6
.73 (ddd, J = 15.9, 8.2, 1.7 Hz, 2H), 7.58 – 7.39 (m, 2H), 7.35 – 7.28 (m, 3H), 7.12 (d, J = 8.5 Hz, 2H),
1
3
.70 (d, J = 8.5 Hz, 2H), 4.06 (s, 2H); C NMR (101 MHz, DMSO – d ) δ 174.27, 156.78, 156.22,
6
141.42, 134.42, 132.80, 130.51, 130.03, 129.54×2, 126.61, 124.41, 124.38, 123.24, 122.45, 120.41,
+
+
1
3
18.13, 116.13, 115.91, 115.71×2, 114.55, 108.94, 29.10; HRMS (ESI) m/z calcd C H FNO [M+H]
24 17 3
86.1187, found 386.1195.
ꢀ(4ꢀHydroxybenzyl)ꢀ1ꢀ(thiazolꢀ2ꢀyl)chromeno[2,3ꢀc]pyrrolꢀ9(2H)ꢀone (17j). Yield: 91%; purity: 95%;
3
1
H NMR (400 MHz, DMSO – d ) δ 13.05 (br s, 1H), 9.20 (s, 1H), 8.20 (dd, J = 7.9, 1.5 Hz, 1H), 7.93
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(
d, J = 3.2 Hz, 1H), 7.79 – 7.65 (m, 2H), 7.53 (d, J = 8.3 Hz, 1H), 7.38 (t, J = 7.5 Hz, 1H), 7.14 (d, J =
13
8
.4 Hz, 2H), 6.69 (d, J = 8.5 Hz, 2H), 4.09 (s, 2H); C NMR (101 MHz, DMSO – d ) δ 174.19, 156.89,
6
1
56.29, 155.72, 142.30, 141.11, 134.42, 129.36, 129.15×2, 126.15, 123.19, 121.71, 120.40, 119.71,
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8
9
0
1
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9
0
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9
0
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8
9
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+
+
1
17.80, 116.51, 115.17×2, 108.64, 28.38; HRMS (ESI) m/z calcd C H N O S [M+H] 375.0798,
21 15 2 3
found 375.0804.
General Procedure for Synthesis of Compounds 19a-19b. To a solution of 2’ꢀhydroxyacetophenone
3) (272 mg, 2.0 mmol) in toluene (10 mL) at 0°C was added sodium hydride (60% in mineral oil, 400
(
mg, 10.0 mmol). The mixture was stirred at room temperature for 15 min and 18 (2.0 mmol) was added
and the mixture was stirred at 60°C for 2 h. After the solution had cooled to room temperature it was
poured into a mixture of ice and water and acidified by the addition of 2 N aqueous HCl. The resulting
solution was extracted with portions of ethyl acetate (2×50 mL). The combined organic extracts were
dried over anhydrous sodium sulfate, and concentrated to give a crude, which was purified by silica gel
column chromatography (petroleum ether/EtOAc, 6:1 to 2:1) to get the product 19 as a yellow solid.
1
1
ꢀ(2ꢀHydroxyphenyl)ꢀ3ꢀ(pꢀtolyl)propaneꢀ1,3ꢀdione (19a). Yield: 37%; H NMR (400 MHz, CDCl ) δ
3
1
5.18 (br s, 1H), 12.14 (s, 1H), 8.73 (ddd, J = 4.7, 1.7, 0.9 Hz, 1H), 8.14 – 8.09 (m, 1H), 7.97 (dd, J =
8.1, 1.6 Hz, 1H), 7.89 (td, J = 7.8, 1.8 Hz, 1H), 7.62 (s, 1H), 7.54 – 7.49 (m, 1H), 7.49 – 7.43 (m, 1H),
7
.03 (dd, J = 8.4, 1.0 Hz, 1H), 6.96 (ddd, J = 8.2, 7.2, 1.1 Hz, 1H).
ꢀ(2ꢀHydroxyphenyl)ꢀ3ꢀ(2ꢀmethoxypyridinꢀ3ꢀyl)propaneꢀ1,3ꢀdione (19b). Yield: 24%; H NMR (400
1
1
MHz, CDCl ) δ 15.47 (br s, 1H), 12.12 (s, 1H), 8.34 (dd, J = 7.7, 1.9 Hz, 1H), 8.29 (dd, J = 4.8, 1.9 Hz,
3
1
H), 7.75 (dd, J = 8.1, 1.3 Hz, 1H), 7.50 – 7.44 (m, 1H), 7.42 (s, 1H), 7.05 (dd, J = 7.6, 4.9 Hz, 1H),
.00 (d, J = 8.1 Hz, 1H), 6.94 (t, J = 7.2 Hz, 1H), 4.14 (s, 3H).
7
General Procedure for Synthesis of Compounds 20a-20b. To a solution of 19 (1.0 mmol), FmocꢀOꢀ
tertꢀbutylꢀLꢀtyrosine (827 mg, 1.8 mmol), 4ꢀdimethylpyridine (49 mg, 0.4 mmol) in pyridine (10 mL)
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was added DCC (412 mg, 2.0 mmol). The mixture was stirred at room temperature for 3 h until the start
material disappeared as monitored by TLC. The reaction temperature was raised to 50°C for 6 h, and a
major yellow spot could be observed by TLC. After the reaction mixture was evaporated under vacuum,
the residue was diluted with ethyl acetate (40 mL) and filtered to remove the side product DCU. The
filtrate was evaporated and purified by silica gel column chromatography (petroleum ether/EtOAc, 5:1)
4
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9
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0
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9
0
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8
9
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to afford 20 as a yellow solid.
1
3
ꢀ(4ꢀ(tertꢀbutoxy)benzyl)ꢀ1ꢀ(pꢀtolyl)chromeno[2,3ꢀc]pyrrolꢀ9(2H)ꢀone (20a). Yield: 16%; H NMR (400
MHz, CDCl ) δ 8.49 (s, 1H), 8.35 (dd, J = 7.9, 1.7 Hz, 1H), 7.81 (d, J = 8.2 Hz, 2H), 7.63 (ddd, J = 8.7,
3
7
.1, 1.7 Hz, 1H), 7.39 (d, J = 8.4 Hz, 1H), 7.33 – 7.29 (m, 1H), 7.24 (d, J = 8.0 Hz, 2H), 7.19 (d, J = 8.5
Hz, 2H), 6.98 (d, J = 8.5 Hz, 2H), 4.21 (s, 2H), 2.39 (s, 3H), 1.36 (s, 9H).
3ꢀ(4ꢀ(tertꢀButoxy)benzyl)ꢀ1ꢀ(2ꢀmethoxypyridinꢀ3ꢀyl)chromeno[2,3ꢀc]pyrrolꢀ9(2H)ꢀone (20b). Yield:
1
6
1
7
2
5%; H NMR (400 MHz, CDCl ) δ 10.37 (br s, 1H), 9.59 (dd, J = 7.7, 1.8 Hz, 1H), 8.38 (dd, J = 8.0,
3
.7 Hz, 1H), 8.08 (dd, J = 4.8, 1.8 Hz, 1H), 7.69 – 7.60 (m, 1H), 7.41 (d, J = 8.4 Hz, 1H), 7.32 (d, J =
.2 Hz, 1H), 7.24 (d, J = 8.4 Hz, 2H), 7.11 (dd, J = 7.7, 4.8 Hz, 1H), 7.04 (d, J = 8.4 Hz, 2H), 4.23 (s,
H), 3.97 (s, 3H), 1.38 (s, 9H).
General Procedure for Synthesis of Compounds 21a-21b. To a solution of 20 (0.25 mmol) in
dichloromethane (3.0 mL) was added trifluoroacetic acid (1.0 mL). The mixture was stirred at room
temperature for 2 h. Then it was diluted with dichloromethane (50 mL) and washed with saturated
aqueous sodium bicarbonate and water. The organic layer was dried over anhydrous sodium sulfate, and
purified by silica gel column chromatography (petroleum ether/EtOAc, 3:1 to 1:1) to afford the product
2
1a/21b as a yellow solid.
ꢀ(4ꢀhydroxybenzyl)ꢀ1ꢀ(pꢀtolyl)chromeno[2,3ꢀc]pyrrolꢀ9(2H)ꢀone (21a). Yield: 92%; purity: 98%; H
1
3
NMR (400 MHz, DMSO – d ) δ 12.24 (br s, 1H), 9.20 (s, 1H), 8.17 (dd, J = 7.9, 1.6 Hz, 1H), 8.01 (d, J
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=
8.2 Hz, 2H), 7.70 (ddd, J = 8.6, 7.2, 1.7 Hz, 1H), 7.47 (d, J = 7.9 Hz, 1H), 7.35 – 7.30 (m, 1H), 7.27
1
3
(d, J = 8.1 Hz, 2H), 7.11 (d, J = 8.5 Hz, 2H), 6.70 (d, J = 8.5 Hz, 2H), 4.06 (s, 2H), 2.36 (s, 3H); C
NMR (101 MHz, DMSO – d ) δ 174.52, 156.47, 156.18, 141.91, 137.54, 134.35, 130.18, 129.48×2,
6
0
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2
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29.18×2, 128.70, 128.11×2, 128.08, 126.92, 123.15, 122.53, 117.88, 115.69×2, 113.79, 107.56, 28.94,
+
+
21.34; HRMS (ESI) m/z calcd C H NO [M+H] 382.1438, found 382.1448.
2
5
20
3
3
ꢀ(4ꢀHydroxybenzyl)ꢀ1ꢀ(2ꢀmethoxypyridinꢀ3ꢀyl)chromeno[2,3ꢀc]pyrrolꢀ9(2H)ꢀone (21b). Yield: 88%;
1
purity: 99%; H NMR (400 MHz, DMSO – d ) δ 12.10 (br s, 1H), 9.23 (s, 1H), 8.19 (dd, J = 6.0, 4.3
6
Hz, 2H), 8.11 (d, J = 7.9 Hz, 1H), 7.71 (t, J = 7.8 Hz, 1H), 7.50 (d, J = 8.3 Hz, 1H), 7.32 (t, J = 7.5 Hz,
13
1
H), 7.13 – 7.08 (m, 3H), 6.70 (d, J = 8.4 Hz, 2H), 4.06 (s, 2H), 3.90 (s, 3H); C NMR (101 MHz,
DMSO – d ) δ 174.34, 160.52, 156.64, 156.20, 146.53, 141.37, 140.94, 134.43, 130.06, 129.56×2,
6
126.70, 123.24, 122.38, 121.96, 118.07, 117.12, 115.68×2, 114.72, 113.86, 108.70, 53.95, 28.98; HRMS
+
+
(ESI) m/z calcd C H N NaO [M+Na] 421.1159, found 421.1150.
24 18 2 4
3
ꢀ(4ꢀHydroxybenzyl)ꢀ1ꢀ(2ꢀhydroxypyridinꢀ3ꢀyl)chromeno[2,3ꢀc]pyrrolꢀ9(2H)ꢀone (21c). To a solution
of 21b (100 mg, 0.25 mmol) in dichloromethane (10 mL) at ꢀ20°C was added boron tribromide (72 ꢁL,
.75 mmol). The mixture was stirred at ꢀ20°C for 2h and quenched with ice water (10 mL). The solution
0
was then extracted with portions of dichloromethane (3×20 mL), dried over anhydrous sodium sulfate,
and evaporated to afford a residue, which was purified by silica gel column chromatography (petroleum
1
ether/EtOAc, 1:3) to get the product 21c (44 mg) as a yellow solid. Yield: 46%; H NMR (400 MHz,
DMSO – d ) δ 13.27 (s, 1H), 12.32 (br s, 1H), 9.73 (dd, J = 7.4, 1.9 Hz, 1H), 9.24 (s, 1H), 8.22 (dd, J =
6
7
.9, 1.6 Hz, 1H), 7.74 (ddd, J = 8.7, 7.1, 1.7 Hz, 1H), 7.59 – 7.46 (m, 2H), 7.43 – 7.30 (m, 1H), 7.11 (d,
1
3
J = 8.5 Hz, 2H), 6.71 (d, J = 8.5 Hz, 2H), 6.55 (dd, J = 7.3, 6.3 Hz, 1H), 4.12 (s, 2H); C NMR (101
MHz, DMSO – d ) δ 173.87, 161.56, 155.86, 155.74, 141.65, 138.64, 134.00, 133.81, 129.25×2, 128.84,
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26.57, 125.61, 122.89, 121.95, 118.68, 117.33, 115.38×2, 112.11, 106.68, 103.81, 28.45; HRMS (ESI)
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5
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9
1
1
1
1
1
1
1
1
1
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2
2
2
2
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+
+
m/z calcd C H N NaO [M+Na] 407.1002, found 407.0991.
23 16
2
4
N'ꢀacetylꢀ3ꢀ(4ꢀ(tertꢀbutoxy)benzyl)ꢀ9ꢀoxoꢀ2,9ꢀdihydrochromeno[2,3ꢀc]pyrroleꢀ1ꢀcarbohydrazide (22).
To a solution of 6 (250 mg, 0.6 mmol) in dichloromethane (8.0 mL) was added acethydrazide (67 mg,
0.9 mmol), triethylamine (125 ꢁL, 0.9 mmol) and HATU (459 mg, 1.2 mmol). The mixture was stirred
at room temperature for 12 h. Then it was concentrated to give a crude, which was purified by silica gel
0
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9
0
column chromatography (petroleum ether/EtOAc, 5:1 to 3:1) to get the product 22 (169 mg) as a white
1
solid. Yield: 63%; H NMR (400 MHz, DMSO – d ) δ 13.44 (br s, 1H), 12.25 (s, 1H), 10.32 (s, 1H),
6
8
.25 (dd, J = 8.0, 1.4 Hz, 1H), 7.84 (t, J = 7.0 Hz, 1H), 7.61 (d, J = 8.4 Hz, 1H), 7.45 (t, J = 7.6 Hz, 1H),
.21 (d, J = 8.4 Hz, 2H), 6.90 (d, J = 8.4 Hz, 2H), 4.17 (s, 2H), 1.96 (s, 3H), 1.25 (s, 9H).
7
3ꢀ(4ꢀhydroxybenzyl)ꢀ1ꢀ(5ꢀmethylꢀ1,3,4ꢀoxadiazolꢀ2ꢀyl)chromeno[2,3ꢀc]pyrrolꢀ9(2H)ꢀone
(23).
Compound 22 (140mg, 0.31 mmol) was dissolved in phosphorus oxychloride (3.0 mL) and the mixture
was stirred at 60°C for 30 min. After the reaction mixture had cooled to room temperature it was poured
into a mixture of ice and water. The resulting solution was extracted with portions of ethyl acetate (3×20
mL). The combined organic extracts were dried over anhydrous sodium sulfate, and concentrated to give
a crude, which was purified by silica gel column chromatography (petroleum ether/EtOAc, 3:1 to 1:1) to
1
get the product 23 (67 mg) as a yellow solid. Yield: 58%; purity: 98%; H NMR (400 MHz, DMSO –
d6) δ 13.49 (br s, 1H), 9.25 (s, 1H), 8.17 (d, J = 7.9 Hz, 1H), 7.77 (t, J = 7.0 Hz, 1H), 7.56 (d, J = 8.3 Hz,
1H), 7.39 (t, J = 7.5 Hz, 1H), 7.12 (d, J = 8.3 Hz, 2H), 6.69 (d, J = 8.4 Hz, 2H), 4.08 (s, 2H), 2.61 (s,
13
3
1
H); C NMR (101 MHz, DMSO – d ) δ 173.40, 163.90, 158.98, 156.53, 156.34, 142.25, 134.97,
6
29.67×2, 129.37, 126.74, 123.88, 122.46, 119.66, 118.38, 115.75×2, 111.16, 108.08, 31.17, 11.17;
+
+
HRMS (ESI) m/z calcd C H N NaO [M+H] 396.0955, found 396.0946.
2
1
15
3
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