Multitarget-directed benzylideneindanone derivatives: Anti-β-amyloid (Aβ) aggregation, antioxidant, metal chelation, and monoamine oxidase B (MAO-B) inhibition properties against Alzheimer's disease

Article abstract of DOI:10.1021/jm300978h

A novel series of benzylideneindanone derivatives were designed, synthesized, and evaluated as multitarget-directed ligands against Alzheimer's disease. The in vitro studies showed that most of the molecules exhibited a significant ability to inhibit self-induced β-amyloid (Aβ _1-42) aggregation (10.5-80.1%, 20 μM) and MAO-B activity (IC ₅₀ of 7.5-40.5 μM), to act as potential antioxidants (ORAC-FL value of 2.75-9.37), and to function as metal chelators. In particular, compound 41 had the greatest ability to inhibit Aβ_1-42 aggregation (80.1%), and MAO-B (IC₅₀ = 7.5 μM) was also an excellent antioxidant and metal chelator. Moreover, it is capable of inhibiting Cu(II)-induced Aβ_1-42 aggregation and disassembling the well-structured Aβ fibrils. These results indicated that compound 41 is an excellent multifunctional agent for the treatment of AD.

Full text of DOI:10.1021/jm300978h

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Article
Multi-target-directed Benzylidene-indanone derivatives: Anti-# Amyloid
(A#) aggregation, Antioxidant, Metal chelation and Monoamine
oxidase B (MAO-B) Inhibition Properties Against Alzheimer's disease
Ling Huang, Chuanjun Lu, Yang Sun, Fei Mao, Zonghua
Luo, Tao Su, Huailei Jiang, Wenjun Shan, and Xingshu Li
J. Med. Chem., Just Accepted Manuscript • Publication Date (Web): 14 Sep 2012
Downloaded from http://pubs.acs.org on September 17, 2012
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Journal of Medicinal Chemistry is published by the American Chemical Society. 1155
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Multiꢀtargetꢀdirected Benzylideneꢀindanone derivatives: Antiꢀβ
Amyloid (Aβ) aggregation, Antioxidant, Metal chelation and
Monoamine oxidase B (MAOꢀB) Inhibition Properties Against
Alzheimer's disease
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Ling Huang, Chuanjun Lu, Yang Sun, Fei Mao，Zonghua Luo，Tao Su, Huailei Jiang,
Wenjun Shan, Xingshu Li*
Institute of Drug Synthesis and Pharmaceutical Processing, School of Pharmaceutical
Sciences, Sun Yat-sen University, Guangzhou 510006, China
ABSTRACT
A novel series of benzylideneꢀindanone derivatives were designed, synthesised and
evaluated as multiꢀtargetꢀdirected ligands against Alzheimer's disease. The in vitro
studies showed that most of the molecules exhibited a significant ability to inhibit
selfꢀinduced Aβ aggregation (10.5ꢀ80.1%, 20 ꢁM) and MAOꢀB activity (IC50 of
7.5ꢀ40.5ꢁM), to act as potential antioxidants (ORACꢀFL value of 2.75ꢀ9.37), and to
function as metal chelators. In particular, compound 41, had the greatest ability to
inhibit Aβ aggregation (80.1%) and MAOꢀB (IC50=7.5ꢁM), was also an excellent
antioxidant and metal chelator. Moreover, it is capable of inhibiting Cu(II)ꢀinduced
Aβ aggregation and disassembling the wellꢀstructured Aβ fibrils. These results
indicated that compound 41 is an excellent multifunctional agent for the treatment of
AD.
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Introduction
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Alzheimer’ disease (AD) is a multifaceted, progressive neurodegenerative
disorder characterised by progressive cognitive decline and memory loss. Although
the etiology of AD is not fully known at present, several conditions have been
considered to play significant roles in the pathogenesis of AD. These include the
development of deposits of βꢀamyloid and τꢀprotein, oxidative stress, dyshomeostasis
of biometals, and low levels of acetylcholine (ACh).1 In particular, the production and
accumulation of oligomeric aggregates of Aβ in the brain are a central event in the
pathogenesis of AD according to the “amyloid hypothesis” as they are thought to be
able to initiate the pathogenic cascade, ultimately leading to neuronal loss and
dementia.2 Aβ can efficiently generate reactive oxygen species in the presence of
some transition metals and form stable dityrosine crossꢀlinked dimers, which are
generated by free radical attack under oxidative conditions.3 Oxidative damage is
present within the brain of AD patients, and it was shown to affect every class of
biological macromolecules, including nucleic acids, proteins, lipids, and
carbohydrates.4 It is also an event that precedes the appearance of other pathological
hallmarks of the disease, such as amyloid plaques and neurofibrillary tangles.5,6
Therefore, antioxidant protection is important during aging and especially in AD
patients as the endogenous antioxidant protection system declines rapidly.
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Monoamine oxidases A and B (MAOꢀA and MAOꢀB) are important
FADꢀdependent enzymes (flavoenzymes) responsible for the metabolism of
neurotransmitters such as dopamine, serotonin, adrenaline, and noradrenaline and for
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the inactivation of exogenous arylalkylamines.7 Thus, the inhibition of MAO
ꢀA/MAOꢀB increases, primarily in the CNS, the levels of such neurotransmitters,
which are decreased in AD patients compared to ageꢀmatched controls.8 Selegiline, a
selective MAOꢀB inhibitor, has been shown to significantly improve learning and
memory deficits in animal models associated with AD and to slow the disease
progression in AD patients.9 This evidence suggested that selective MAOꢀB inhibitors
seem to be an important treatment of AD.
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Recently, transition metals, including copper and zinc, have been found to directly
bind to amyloid plaques by spectroscopic studies.10,11 Moreover, studies suggested
that redoxꢀactive metal ions, such as Cu2+ and Fe2+, are involved in the production of
reactive oxygen species (ROS) and oxidative stress,12 which implies that these
biometals also play a central role in many critical aspects of AD. Thus, modulation of
such biometals in the brain has been proposed as a potential therapeutic strategy for
the treatment of AD.13
The multifaceted conditions of the AD state have encouraged active research in
the development of multiꢀtargetꢀdirected ligands (MTDLs) to act as agents for the
treatment of this disease.14,15,16,17 These drugs, which possess two or more
complementary biological activities, may represent an important clinical advance in
the future.
Indanones and their derivatives are important bioactive molecules that have been
studied to determine their biological activities within disease states, including
Alzheimer’s disease and cancer. For example, gallic acidꢀbased indanone (1, Fig. 1)
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derivatives and some imidazolylꢀsubstituted 2ꢀbenzylidene indanone derivatives were
recently studied as inhibitors for cancer treatment.18 Indanocine (2, Fig. 1) and its
analogues were developed to combat drugꢀresistant malignancies.19 Donepezil
hydrochloride (3, Fig. 1), which acts as an AChE inhibitor, was approved by the FDA
for the treatment of mild to moderate Alzheimer’s disease.20
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Previously, we reported the design, synthesis and evaluation of 9ꢀO and 9ꢀN
substituted berberine derivatives as dual or multifunctional agents for the treatment of
Alzheimer’s disease.21,22 In this paper, we report the study of the design, synthesis,
and evaluation of a novel series of indanone derivatives that were found to show
potentially applicable biological activities, including the inhibition of selfꢀinduced Aβ
aggregation, inhibition of MAOꢀB activity, antioxidant properties and metal chelation.
Results and Discussion
Chemistry
The synthetic route of key intermediates 7ꢀ9 and 11ꢀ18 is shown in Scheme 1. The
protection of hydroxy groups at the phenyl ring of 4ꢀ6 provided the THPꢀprotected
aromatic aldehyde derivatives 7ꢀ9. The substitution of the fluorine atom of 4ꢀfluoro
benzaldehyde with a series of amines in the presence of TBAB gave intermediates
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11ꢀ16. In compounds 17ꢀ18, the aldehydes with a substituted amino group at the
4ꢀposition were converted to 11ꢀ12 by aminomethylation with formaldehyde and
formic acid in reflux.
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Scheme 1. Synthesis of the aromatic aldehyde intermediates 7ꢀ9 and 11ꢀ18. Reagents
and conditions: (a) 3,4ꢀ2HꢀDihydropyran, PPTS, DCM, rt; (b) R3NR4, TBAB, K2CO3,
DMSO, 90 ; (c) 37% HCHO, HCOOH, reflux.
According to Scheme 2, 20 was synthesised by the reaction of
5,6ꢀdimethoxyꢀ1ꢀindanone with boron tribromide in dichloromethane, which then
reacted with iodomethane in the presence of lithium carbonate to provide
6ꢀhydroxyꢀ5ꢀmethoxylꢀ1ꢀindanone, 21. The reaction of compound 21 with
3,4ꢀ2Hꢀdihydropyran afforded the THPꢀprotected indanone derivative 22. The target
compounds 23ꢀ24, without the hydroxy group on indanone or aldehyde segment, were
obtained
by
direct
condensation
of
the
commercially
available
5,6ꢀdimethoxyꢀ1ꢀindanone (19) and the appropriate aldehydes in ethanolic KOH
solution. Condensation of 5,6ꢀdihydroxyꢀ1ꢀindanone (20) and corresponding amine,
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catalysed by TsOH, gave compounds 38ꢀ41. Finally, compounds 25ꢀ37 were obtained
by the condensation of THPꢀprotected indanone (22) with the appropriate
benzaldehyde in ethanolic KOH solution, followed by removal of the THP protection.
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Scheme 2. Synthesis of target compounds 23ꢀ41. Reagents and conditions: (a) BBr3,
DCM, ꢀ78oC; (b) Li2CO3, MeI, DMF, 55oC;(c) 3,4ꢀ2HꢀDihydropyran ,PPTS, DCM, rt;
(d) appropriate benzaldehyde, 4%KOH, EtOH, rt; (e) (i) appropriate benzaldehyde,
4%KOH, EtOH, rt; (ii) 2M HCl, EA/butanoneꢀ2, reflux. (f) appropriate benzaldehyde,
TsOH, reflux.
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Inhibition of selfꢀmediated Aβ1–42 aggregation
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The ability of the indanone derivatives to inhibit Aβ1ꢀ42 aggregation was assessed
using the thioflavin T (ThT) fluorescence assay23 with curcumin as standard. The
results summarised in Table 1 showed that most indanone derivatives exhibited
moderateꢀtoꢀgood potencies compared to that of curcumin. The optimal Aβ1ꢀ42
aggregation inhibition potency (80.1%) was provided by compound 41 that features
two hydroxy groups at the 5ꢀ and 6ꢀpositions of the indanone moiety (A ring) and one
methyl(propyl)amino substitution at the 4ꢀposition of the aldehyde (B ring). These
substituted groups seem to play an important role in the inhibition of Aβ aggregation.
As indicated in Table 1, compound 23, with four methoxy groups on the A and B
ring, gave the lowest inhibitive activity (10.5%). Deꢀmethylation in different position
in part led to a slight increase of the inhibitory activity for several compounds
(14.2ꢀ28.4%). It is interesting that most of the substituted amino groups at the
4ꢀposition of the B ring (R4) generally gave better results of the inhibitive activity
23.7ꢀ80.1%), with the exception of compounds 32 and 34 (NHEt, 10.5%, NHcycꢀHex,
16.8%). Compound 24, featuring two hydroxy groups at 5ꢀ and 6ꢀposition of the A
ring and one diethylamino group at the 4ꢀposition of B ring, gave 23.7% inhibition
activity. On the other hand, compound 30, with a hydroxy at 6ꢀposition of A ring, led
to 33.8% inhibition. These results imply that the methoxy group is not favourable for
inhibition activity. Fixation of the A ring with a 5ꢀmethoxyꢀ6ꢀhydroxy substitution of
the amino groups also led to changes in measured inhibitory activity (compound 31,
diethylamino group at the 4ꢀposition of the B ring, 40.7%; compound 33,
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propylamino group, 38.4%, and others). Compounds 38ꢀ41, with two hydroxy groups
on the A ring, gave 61.4% ꢀ 80.1% inhibitory activity, which suggested that the two
hydroxy groups at the 5ꢀ and 6ꢀpositions of the A ring seem to be beneficial to their
activity.
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Table 1. Inhibition of Aβ1–42 aggregation and Oxygen Radical Absorbance Capacity
(ORAC, Trolox Equivalents) by Curcumin and benzylideneꢀindanone derivatives
23ꢀ41.
Comp.
R1
R2
R3
R4
Inhibition of Aβ1ꢀ42 ORACb
aggregation(%)a
Curcumin
23
ꢀ
ꢀ
ꢀ
ꢀ
52.1±2.7
10.5±0.4
23.7±0.7
28.4±0.9
16.3±0.5
19.5±1.0
24.0±1.3
14.2±0.7
33.8±1.3
40.7±1.6
2.57±0.17
0.65±0.04
7.85±0.68
4.83±0.31
9.37±0.59
4.55±0.26
3.55±0.20
6.58±0.55
7.90±0.52
3.96±0.33
OMe OMe OMe OMe
24.HCl
25
OMe OMe
OMe OH
OMe OH
OMe OH
OMe OH
OMe OH
OMe OH
OMe OH
H
H
H
N(Me)2
OMe
OH
26
27
OMe OMe
OH OMe
OMe OH
28
29
30.HCl
31.HCl
H
H
N(Me)2
N(Et)2
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32.HCl
OMe OH
OMe OH
OMe OH
OMe OH
OMe OH
OMe OH
H
H
H
H
H
H
H
H
H
H
NHEt
NHPr
10.5±0.3
38.4±1.1
16.8±0.5
38.0±1.5
42.1±2.0
50.0±2.4
61.4±1.9
67.0±3.8
74.4±2.9
80.1±4.0
4.75±0.39
4.14±0.40
3.60±0.25
2.75±0.11
5.34±0.23
5.11±0.38
5.63±0.44
5.41±0.26
5.87±0.41
5.60±0.59
33.HCl
34.HCl
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35.HCl
N(Pr)2
NMeEt
NMePr
N(Me)2
N(Et)2
NMeEt
NMePr
36.HCl
37.HCl
38.TsOH
39.TsOH
40.TsOH
41.TsOH
OH
OH
OH
OH
OH
OH
OH
OH
aThe ThioflavinꢀT fluorescence method was used. Values are expressed as the mean ± SD from at
least two independent measurements. All values were obtained at the concentration of 20 ꢂM of
the tested compounds.
bThe mean ± SD of the three independent experiments, data are expressed as ꢂ mol of trolox
equivalent/ꢂ mol of tested compound
Effects on abundance of Aβ fibrils by compound 41
To complement the ThT binding assay, Aβ1–42 aggregation was also monitored by
transmission electron microscopy (TEM) (Figure 2.). The results showed that the
sample of Aβ1–42 alone had aggregated into amyloid fibrils after 24 h incubation,
while only small bulk aggregates were visible and no characteristic fibrils were
observed in the sample of Aβ1–42 in presence of 41. The TEM results were well
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consistent with the results of ThT measurements, which strongly proved that 41 can
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inhibit the Aβ1–42 fibrils formation.
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Aβ (0h)
Aβ+ 41 (24h)
Aβ alone (24h)
Figure 2. TEM images of Aβ1–42(20ꢂM) in the presence and absence of 20ꢂM compound 41 after
24 h of aggregation.
Antiꢀoxidant activity in vitro
The antioxidant activity of the benzylideneꢀindanone derivatives were determined
by an oxygen radical absorbance capacity assay that uses fluorescein (ORACꢀFL),
according to the method originally described by Ou et al. 24,25 and further modified by
Dávalos et al.26 Trolox, a vitamin E analogue, was used as a standard, and the
antioxidant activity was expressed as Trolox equivalents (ꢁmol of Trolox/ꢁmol of
tested compound). As shown in Table 1, most of the target compounds demonstrated
good to excellent antioxidant activity with ORACꢀFL values of 2.60–9.37 Trolox
equivalents. Upon comparison of the ORACꢀFL values of compound 23 with that of
the other compounds, it is apparent that the free hydroxy or amino substituents are
crucial to the radical scavenging ability.
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Inhibition of MAOs in vitro
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To further study the multipotent biological profile of the target compounds, the
inhibitory activity against MAOꢀA and MAOꢀB (recombinant human enzyme) was
determined and compared with that of Ladostigil, which was an MAOꢀB inhibitor
approved to carry out phase II clinical trial by FDA. As shown in Table 2, most of the
indanone derivatives were effective in inhibiting MAOꢀB in the micromolar range.
Compound 41, the most potent MAOꢀB inhibitors, with the IC50 of 7.50ꢂM, is about
5ꢀfold more potent than ladostigil. However, when the hydroxy groups at the 5ꢀ
position of the A ring replaced by methoxy group (compound 37), the inhibitory
activity to both MAOꢀA (4.3% at 50ꢂM) and MAOꢀB (IC50=40.5ꢂM) decreased
dramatically, which indicated that the hydroxy groups at the 5ꢀ position of A ring is
critical to the activity.
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Table 2. Inhibitory activity of typical molecules with human recombinant MAO
isoforms and selectivity indices (SI)
Comp.
R1
R2
R3
R4
IC50(ꢂM)a
MAOꢀB
SIb
MAOꢀA
19.3%c
14.4% c
31.HCl
36.HCl
OMe OH
OMe OH
H
H
N(Et)2
18.55±1.1
28.7±1.7
ꢀ
ꢀ
NMeEt
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37.HCl
OMe OH
H
H
H
H
H
ꢀ
NMePr
4.3% c
40.5±3.0
10.90±0.8
7.71±0.5
10.7±0.3
7.50±0.9
ꢀ
38.TsOH
39.TsOH
40.TsOH
41.TsOH
clorgyline
ladostigil
selegiline
rasagiline
OH
OH
OH
OH
ꢀ
OH
OH
OH
OH
ꢀ
N(Me)2
38.5±2.4
41.4±3.1
35.2±0.9
37.7±2.2
3.53
N(Et)2
5.36
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NMeEt
3.29
NMePr
5.03
ꢀ
ꢀ
ꢀ
ꢀ
4.1±0.2nM n.t.
ꢀ
ꢀ
ꢀ
ꢀ
n.t.
37.1±3.1
ꢀ
ꢀ
ꢀ
ꢀ
70.2±3.8
0.7d
18.5±2.1nM 37945
ꢀ
ꢀ
ꢀ
0.014d
50
aAll IC50 values shown in this Table are the mean ±SEM from three experiments.
bhMAOꢀB selectivity index = IC50 (hMAOꢀA)/IC50(hMAOꢀB).
cThe inhibition rate of compounds to MAOꢀA at 50ꢂM.
d Reference 27
Docking study of compound 41 to MAOꢀB
In order to evaluate the binding modes of this class of indanone derivatives with
respect to human MAOꢀB， docking simulations were carried out using the
CDOCKER program in the Discovery studio 2.1 software based on the Xꢀray crystal
structure of human MAOꢀB (PDB entry 2Z5X). Based on the in vitro inhibition
results, we selected compound 41, the highest MAOꢀB inhibitor, as a typical ligand
for the evaluation. As shown in Figure 3 and 4, the indanone moiety of compound 41
close to the FAD cofactor, adopting parallel πꢀπ interactions with Tyr398 (4.45 Å).
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There were two hydrogen bonds between indanon moiety and FAD cofactor
(FADꢀNH…41ꢀO11；41ꢀOH…FADꢀO), which could explain the critical function of
hydroxy groups at the 5ꢀ position of A ring. Meanwhile, the benzene amine group
interact with many hydrophilic acids, such as Phe168, Pro 115, Ser200, Leu 187,
ILe199, Thr 131 and so on.
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Figure 3: Predicted positions of 41 into hMAOꢀB catalytic sites. Compound 41 and The FAD
cofactor were depicted using stick and space fill representation respectively.
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Figure 4: Representation of compound 41 docked into the binding site of MAOꢀB highlighting
the protein residues that form the main interactions with the inhibitor. Hydrogenꢀbonding
interaction between ligand and residues are shown with the green line.
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Metal binding properties of compound 41
The chelation ability of compound 41 toward biometals such as Cu( ), Fe( ) and
Zn( ) was studied by UVꢀvis spectrometry (Figure 5). When adding CuSO4, the
maximum absorption at 437nm exhibited a red shift to 451nm, which indicated the
formation of 41ꢀCu( ). However, with the addition of FeSO4 and ZnCl2, there was no
significant shift. Interestingly, after adding FeSO4, the absorption at 437 nm decreased
obviously, which indicated that there was a possible interaction between 41 and
Fe( ).
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To determine the stoichiometry of the complex 41ꢀCu( ), the molar ratio method
was used by preparing solutions of compound 41 with ascending amounts of CuSO4.
The UV spectra were performed to obtain the absorbance of the complex of CuSO4
and 41 at different concentrations at 451nm. According to the Figure 6, the
absorbance linearly increased at first. When the mole fraction of Cu( ) to 41 was
more then 0.8, the absorbance tended to be stable. Therefore, two straight lines were
drawn with the intersection point at a mole fraction of 0.8, revealing a 1:1
stoichiometry for complex 41ꢀCu( ).
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0.9
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Figure 6: Determination of the stoichiometry of complex 41ꢀCu(II) by molar ration method.
Effects on metalꢀinduced Aβ1–42 aggregation by compound 41
In order to investigate the effects of 41 on Cu(II)ꢀinduced Aβ aggregation, we
carried out two individual studies (Figure 7 and Figure 8): inhibition activity of
metalꢀinduced Aβ1–42 aggregation by compound 41 and disaggregation effects of 41 on
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Cu(II)ꢀinduced Aβ1–42 aggregates. ThT binding assay and transmission electron
microscopy (TEM) were be used to identify the degree of Aβ aggregation.
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Aβ+Cu(II)+41
Aβ+Cu(II)
Aβ alone
0
50
100
150
Figure 7: Visualization of Aβ species from inhibition experiments. Top: Scheme of the inhibition
experiment . Bottom: ( A ) the results of ThT binding assay; (B)TEM images of samples.
Figure 8: Visualization of Aβ species from disaggregation experiments. Top: Scheme of the
disaggregation experiment . Bottom: TEM images of samples.
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As shown in Figure 7, Cu(II) could accelerate the aggregation of Aβ. However,
the rate of Aβ aggregation slowed down when adding 41 to the samples, which
suggested that 41 could inhibited Cu(II)ꢀinduced Aβ aggregation noticeably through
chelating with Cu(II). The results of TME are consistent with ThT binding assay
results. For the disaggregation studies (Figure 8), 41 (50 ꢁM) was added to Aβ fibrils
generated by reacting Aβ (50 ꢁM) with 1 equiv of Cu(II) (50 ꢁM) for 24 h at 37°C
with constant agitation. The TME figures illustrated that much fewer Aβ aggregates
were observed after adding 41, which indicated that 41 is able to alter the structure of
metalꢀtriggered Aβ aggregates affording their disaggregation. In short, based on these
TEM results, we can conclude that compound 41 is capable of inhibiting
Cu(II)ꢀinduced Aβ aggregation and disassembling the wellꢀstructured Aβ fibrils.
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Conclusion
In conclusion, most benzylideneꢀindanone derivatives exhibited multifunctional
activity as potential antiꢀAD drugs, which include significant ability to inhibit
selfꢀinduced Aβ aggregation and MAOꢀB activity, to act as antioxidants and
bioꢀmetal chelators. Among the synthesised compounds, compound 41,
5,6ꢀdihydroxyꢀ2ꢀ(4ꢀ(methyl(propyl)amino)benzylidene)ꢀ2,3ꢀdihydroꢀ1Hꢀindenꢀ1ꢀone
4ꢀmethylbenzenesulfonate, gave the greatest inhibitory potency towards selfꢀinduced
Aβ aggregation (80.1%, 20 ꢂM), which was proved by TEM. Meanwhile, this
compound was also an excellent antioxidant (ORACꢀFL value of 5.60) and MAOꢀB
inhibitor (IC50=7.5ꢁM). UVꢀvis spectrometry and TME results confirmed that
compound 41 is not only a good bioꢀmetal chelator by inhibiting Cu(II)ꢀinduced Aβ
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aggregation, but also could disassemble the wellꢀstructured Aβ fibrils. Such
multifunctional properties highlight compound 41 as interesting candidate for further
studies directed to the development of novel drugs in the treatment of AD.
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Experimental Section
General Information. The 1H NMR and 13C NMR spectra were recorded using TMS
as the internal standard on a Bruker BioSpin GmbH spectrometer at 400.132 MHz and
100.614 MHz, respectively. Coupling constants are given in Hz. MS spectra were
recorded on an Agilent LCꢀMS 6120 instrument with an ESI and APCI mass selective
detector. Highꢀresolution mass spectra were obtained using
a
Shimadzu
LCMSꢀITꢀTOF mass spectrometer. Flash column chromatography was performed
using silica gel (200–300 mesh) purchased from Qingdao Haiyang Chemical Co. Ltd
or alumina from Sinopharm Chemical Reagent Co. Ltd. All the reactions were
monitored by thin layer chromatography using silica gel. The purity of compounds
23ꢀ41 (higher than 95%) was confirmed through HPLC (Agilent technologies 1200
series system, TCꢀC18 column (4.6×250 mm, 5ꢂm), eluted with methanol/water
(0.1% TFA), 75:25, at a flow rate of 0.5 mL/min).
General procedure for the preparation of 7ꢀ9
To the solution of 4, 5 or 6 (1mmol) and PPTS (1.5mmol) in DCM (10ml),
3,4ꢀ2Hꢀdihydropyran (1.5mol) was added. The mixture was stirred for 10h and
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concentrated in vacuum. The crude residue was purified by flash chromatography on a
5
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silica gel to furnish the oil products 7ꢀ9.
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9
General procedure for the preparation of 11ꢀ16
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The mixture of 4ꢀfluorobenzaldehyde (10, 2mmol), TBAB (1mmol), K2CO3 (2mmol)
and the appropriate amine (10mmol) in DMSO was heated at 90 for 20h. After
cooled to room temperature, the mixture was diluted with 50ml water, and then
extracted with ethyl acetate (50ml x 3). The combined organic phase was washed by
water (10ml), brine (10ml), dried over Na2SO4, filtered and concentrated in vacuum to
give the crude product which was purified by flash chromatography on a silica gel to
furnish the oil products 11ꢀ16.
General procedure for the preparation of 17ꢀ18
The mixture of 11ꢀ12 (1mmol), formaldehyde (5mmol) and formic acid (3mmol) was
refluxed for 3h and concentrated in vacuum. The crude product was purified by flash
chromatography on a silica gel to furnish the oil products 17ꢀ18.
5,6ꢀdihydroxyꢀ2,3ꢀdihydroꢀ1Hꢀindenꢀ1ꢀone (20)
BBr3 (6mmol) was added slowly to the mixture of 5,6ꢀdimethoxyꢀ1ꢀindanone (19,
2mmol) in 20ml DCM at ꢀ78 . After 3h, the mixture was cooled to room temperature,
stirred for 1h and then water (50ml) was added to provide a red solid, which was
filtered and dried to yield 20.
6ꢀhydroxyꢀ5ꢀmethoxyꢀ2,3ꢀdihydroꢀ1Hꢀindenꢀ1ꢀone (21)
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Li2CO3 (2mmol) and MeI (2.5mmol) were added to a solution of 20 (2mmol) in 15 ml
DMF. The mixture was stirred at 55 for 3h and cooled to room temperature. Ethyl
acetate (150 mL) was added to the mixture and the organic phase was washed by
water (50ml x 3), brine (10ml), dried over Na2SO4, filtered and concentrated in
vacuum to furnish a yellow solid 21.
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5ꢀmethoxyꢀ6ꢀ(tetrahydroꢀ2Hꢀpyranꢀ2ꢀyloxy)ꢀ2,3ꢀdihydroꢀ1Hꢀindenꢀ1ꢀone (22)
3,4ꢀ2Hꢀdihydropyran (1.5mol) was added to a solution of 20 (1mmol) and PPTS
(1.5mmol) in DCM (10ml). The mixture was stirred for 10h, and concentrated in
vacuum. The crude product was purified by flash chromatography on a silica gel to
furnish the oil products 22.
General procedure for the preparation of 23ꢀ24
5ml 4% KOH was added to a solution of 5,6ꢀdimethoxyꢀ1ꢀindanone (19) (384mg,
2mmol) with the appropriate benzaldehyde (2mmol) in 5ml EtOH. After stirred at
room temperature for 2ꢀ5 h, the solid was filtered, washed with water, and crystallized
from methanol.
2ꢀ(3,4ꢀdimethoxybenzylidene)ꢀ5,6ꢀdimethoxyꢀ2,3ꢀdihydroꢀ1Hꢀindenꢀ1ꢀone (23)
5,6ꢀdimethoxyꢀ1ꢀindanone (19) was treated with 3,4ꢀdimethoxybenzaldehyde
according to general procedure to give the desired product 23 as a yellow solid, 83%
1
yield. Mp=195.6ꢀ196.3 ; H NMR (400 MHz, CDCl3) δ 7.54 (s, 1H), 7.34 (s, 1H),
7.30 – 7.25 (m, 1H), 7.17 (d, J = 1.7 Hz, 1H), 6.99 (s, 1H), 6.94 (d, J = 8.4 Hz, 1H),
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4.00 (s, 2H), 3.97 – 3.93 (m, 12H); 13C NMR (101 MHz, CDCl3) δ 194.37, 155.26,
149.64, 144.52, 133.36, 132.52, 131.26, 128.63, 124.37, 113.34, 111.32, 107.21,
105.10, 56.26, 55.97, 32.06; LCMS (APCI) m/z [(M+H)]+ = 341.4; HRMS (ESI) m/z
calcd for C20H20O5, 341.1384. found, 341.1378; Purity: 95.1% (by HPLC).
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2ꢀ(4ꢀ(dimethylamino)benzylidene)ꢀ5,6ꢀdimethoxyꢀ2,3ꢀdihydroꢀ1Hꢀindenꢀ1ꢀone
(24)
5,6ꢀdimethoxyꢀ1ꢀindanone (19) was treated with 4ꢀ(dimethylamino)benzaldehyd
according to general procedure to give the desired product 24 as a yellow solid, 85%
1
yield. Mp=205.0ꢀ205.9 ; H NMR (400 MHz, CDCl3) δ 7.57 (m, 3H), 7.34 (s, 1H),
6.97 (s, 1H), 6.73 (d, J = 8.8 Hz, 2H), 3.99 (s, 3H), 3.94 (s, 3H), 3.90 (s, 2H), 3.04 (s,
13
6H). C NMR (101 MHz, CDCl3) δ 193.29, 154.81, 150.98, 149.45, 144.36, 133.35,
132.45, 131.71, 130.67, 123.44, 111.96, 107.23, 105.04, 56.21, 56.14, 40.08, 32.37;
LCMS (APCI) m/z [(M+H)]+ = 324.4; HRMS (ESI) m/z calcd for C20H21NO3,
324.1594. found, 324.1588; Purity: 99.7% (by HPLC).
General procedure for the preparation of 25ꢀ37
To a solution of the THP protected indanone (22) (261mg, 1mmol) in EtOH (3ml), the
appropriate benzaldehyde (1mmol) and 3ml of 4% KOH were added. After stirred at
room temperature for 2ꢀ5h, the produced light yellow solid was filtered. The solid was
dissolved in 10ml EA/butanone (1:1), and treated with 5ml 2M HCl. The mixture was
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refluxed for 2h and then concentrated in vacuum. The solid residue was washed with
water, and crystallized from methanol.
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6ꢀhydroxyꢀ5ꢀmethoxyꢀ2ꢀ(4ꢀmethoxybenzylidene)ꢀ2,3ꢀdihydroꢀ1Hꢀindenꢀ1ꢀone
(25)
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Intermediate 22 was treated with 4ꢀmethoxybenzaldehyde according to general
procedure to give the desired product 25 as a yellow solid, yield 77%. Mp=
1
227.0ꢀ227.6 ; H NMR (400 MHz, DMSOꢀd6) δ 9.48 (s, 1H), 7.70 (d, J = 8.7 Hz,
2H), 7.36 (s, 1H), 7.16 (s, 1H), 7.12 – 6.99 (m, 3H), 3.93 (s, 2H), 3.91 (s, 3H), 3.83 (s,
3H); 13C NMR (101 MHz, DMSOꢀd6) δ 191.96, 160.25, 154.39, 146.89, 143.32,
133.60, 132.25, 130.77, 130.36, 127.70, 114.49, 108.22, 108.05, 55.85, 55.30, 31.46;
LCMS (APCI) m/z [(MꢀH)]ꢀ = 295.3; HRMS (ESI) m/z calcd for C18H16O4, 297.1121.
found, 297.1119; Purity: 95.2% (by HPLC).
6ꢀhydroxyꢀ2ꢀ(4ꢀhydroxybenzylidene)ꢀ5ꢀmethoxyꢀ2,3ꢀdihydroꢀ1Hꢀindenꢀ1ꢀone
(26)
Intermediate 22 was treated with compounds 7 according to general procedure to give
1
the desired product 26 as a yellow solid, yield 65%. Mp= 278.8ꢀ279.5 ; H NMR
(400 MHz, DMSOꢀd6) δ 10.07 (s, 1H), 9.52 (s, 1H), 7.58 (d, J = 8.6 Hz, 2H), 7.31 (s,
1H), 7.14 (s, 1H), 7.06 (d, J = 2.4 Hz, 1H), 6.92 – 6.79 (m, 2H), 3.89 (s, 5H).13C
NMR (101 MHz, DMSOꢀd6) δ 191.99, 158.75, 154.18, 146.69, 143.23, 132.51,
131.25, 130.44, 126.23, 115.92, 115.82, 108.20, 107.93, 99.39, 55.82, 31.51. LCMS
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(APCI) m/z [(MꢀH)]ꢀ =281.3; HRMS (ESI) m/z calcd for C17H14O4, 283.0965. found,
283.0964; Purity: 98.9% (by HPLC).
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2ꢀ(3,4ꢀdimethoxybenzylidene)ꢀ6ꢀhydroxyꢀ5ꢀmethoxyꢀ2,3ꢀdihydroꢀ1Hꢀindenꢀ1ꢀone
(27)
Intermediate 22 was treated with 3,4ꢀdimethoxybenzaldehyde according to general
procedure to give the desired product 27 as a yellow solid, yield 63%. Mp=
1
177.8ꢀ178.4 ; H NMR (400 MHz, DMSOꢀd6) δ 7.35 (s, 1H), 7.30 (d, J = 7.0 Hz,
2H), 7.17 (s, 1H), 7.06 (d, J = 10.9 Hz, 2H), 3.96 (s, 2H), 3.90 (s, 3H), 3.84 (s, 3H),
3.82 (s, 3H); 13C NMR (101 MHz, DMSOꢀd6) δ 192.44, 150.60, 149.26, 143.86,
134.17, 131.72, 130.85, 128.40, 124.88, 113.83, 112.36, 108.75, 56.36, 56.05, 55.95,
31.87; LCMS (APCI) m/z [(MꢀH)]ꢀ =325.4; HRMS (ESI) m/z calcd for C19H18O5,
327.1227. found, 327.1224; Purity: 98.7% (by HPLC).
6ꢀhydroxyꢀ2ꢀ(3ꢀhydroxyꢀ4ꢀmethoxybenzylidene)ꢀ5ꢀmethoxyꢀ2,3ꢀdihydroꢀ1Hꢀinde
nꢀ1ꢀone (28)
Intermediate 22 was treated with compounds 8 according to general procedure to give
1
the desired product 28 as a yellow solid, yield 62%. Mp= 216.2ꢀ218.2 ; H NMR
(400 MHz, DMSOꢀd6) δ 7.30 (d, J = 13.3 Hz, 2H), 7.23 – 7.11 (m, 2H), 7.07 (s, 1H),
6.88 (d, J = 7.8 Hz, 1H), 3.92 (s, 2H), 3.88 (s, 3H), 3.85 (s, 3H); 13C NMR (101 MHz,
DMSOꢀd6) δ 191.97, 154.22, 148.38, 147.70, 146.76, 143.23, 132.74, 131.62, 130.44,
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126.65, 124.71, 115.80, 114.13, 108.22, 107.99, 55.86, 55.58, 31.43; LCMS (APCI)
m/z [(MꢀH)]ꢀ = 311.3; HRMS (ESI) m/z calcd for C18H16O5, 313.1071. found,
313.1070; Purity: 98.9% (by HPLC).
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6ꢀhydroxyꢀ2ꢀ(4ꢀhydroxyꢀ3ꢀmethoxybenzylidene)ꢀ5ꢀmethoxyꢀ2,3ꢀdihydroꢀ1Hꢀinde
nꢀ1ꢀone (29)
Intermediate 22 was treated with compounds 9 according to general procedure to give
1
the desired product 29 as a yellow solid, yield 60%. Mp= 222.9ꢀ223.5 ; H NMR
(400 MHz, DMSOꢀd6) δ 7.25 (s, 1H), 7.23 – 7.11 (m, 3H), 7.07 (s, 1H), 7.01 (d, J =
8.3 Hz, 1H), 3.89 (s, 3H), 3.87 (s, 2H), 3.82 (s, 3H); 13C NMR (101 MHz, DMSOꢀd6)
δ 191.93, 154.30, 149.15, 146.81, 146.51, 143.22, 133.40, 131.25, 130.39, 127.97,
123.33, 116.75, 112.17, 108.21, 108.00, 55.83, 55.58, 31.48; LCMS (APCI) m/z
[(MꢀH)]ꢀ = 311.3; HRMS (ESI) m/z calcd for C18H16O5, 313.1071. found, 313.1074;
Purity: 98.5% (by HPLC).
2ꢀ(4ꢀ(dimethylamino)benzylidene)ꢀ6ꢀhydroxyꢀ5ꢀmethoxyꢀ2,3ꢀdihydroꢀ1Hꢀindenꢀ1
ꢀone hydrochloride (30.HCl)
Intermediate 22 was treated with 4ꢀ(dimethylamino)benzaldehyde according to
general procedure to give the desired product 30 as a yellow solid, yield 65%. Mp=
1
217.8ꢀ219.0 ; H NMR (400 MHz, DMSOꢀd6) δ 9.46 (s, 1H), 7.56 (d, J = 8.9 Hz,
2H), 7.30 (s, 1H), 7.15 (s, 1H), 7.05 (d, J = 2.3 Hz, 1H), 6.78 (d, J = 8.9 Hz, 2H), 3.89
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(s, 3H), 3.86 (s, 2H), 2.99 (s, 6H); 13C NMR (101 MHz, DMSOꢀd6) δ 191.84, 153.88,
150.88, 146.60, 142.83, 132.21, 131.96, 130.81, 130.62, 122.44, 111.96, 108.24,
107.90, 99.48, 55.81, 31.70; LCMS (APCI) m/z [(MꢀH)]ꢀ = 308.4; HRMS (ESI) m/z
calcd for C19H19NO3, 310.1438. found, 310.1440; Purity: 96.2% (by HPLC).
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2ꢀ(4ꢀ(diethylamino)benzylidene)ꢀ6ꢀhydroxyꢀ5ꢀmethoxyꢀ2,3ꢀdihydroꢀ1Hꢀindenꢀ1ꢀo
ne hydrochloride (31.HCl)
Intermediate 22 was treated with 4ꢀ(diethylamino)benzaldehyde according to general
procedure to give the desired product 31 as a yellow solid, yield 83%. Mp=
150.6ꢀ151.2 ; 1H NMR (400 MHz, DMSOꢀd6) δ 7.70 (s, 2H), 7.34 (s, 1H), 7.21ꢀ7.18
(m, 2H), 7.14 (s, 1H), 7.08 (s, 1H), 3.91 (s, 2H), 3.89 (s, 3H), 3.49 – 3.47 (m, 4H),
1.08 (t, J = 6.9 Hz, 6H); 13C NMR (101 MHz, DMSOꢀd6) δ 191.82, 154.37, 146.86,
143.26, 132.24, 130.43, 108.21, 108.05, 55.87, 47.54, 31.50, 11.19; LCMS (APCI)
m/z [(MꢀH)]ꢀ = 336.4; HRMS (ESI) m/z calcd for C21H23NO3, 338.1751. found,
338.1751; Purity: 99.5% (by HPLC).
2ꢀ(4ꢀ(ethylamino)benzylidene)ꢀ6ꢀhydroxyꢀ5ꢀmethoxyꢀ2,3ꢀdihydroꢀ1Hꢀindenꢀ1ꢀon
e hydrochloride (32.HCl)
Intermediate 22 was treated with 4ꢀ(ethylamino)benzaldehyde according to general
procedure to give the desired product 32 as a yellow solid, yield 72%. Mp=
1
237.0ꢀ237.7 ; H NMR (400 MHz, DMSOꢀd6) δ 7.61 (d, J = 8.3 Hz, 2H), 7.31 (s,
1H), 7.14 (s, 1H), 7.08 (s, 1H), 6.95 (d, J = 7.7 Hz, 2H), 3.90ꢀ3.85 (m, 5H), 3.19ꢀ3.10
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(m, 2H), 1.21 (t, J = 7.1 Hz, 3H); 13C NMR (101 MHz, DMSOꢀd6) δ 191.74, 154.34,
146.95, 143.13, 132.01, 130.47, 108.17, 108.10, 55.85, 31.52, 12.48; LCMS (APCI)
m/z [(MꢀH)]ꢀ = 308.4; HRMS (ESI) m/z calcd for C19H19NO3, 310.1438. found,
310.1431; Purity: 99.8% (by HPLC).
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6ꢀhydroxyꢀ5ꢀmethoxyꢀ2ꢀ(4ꢀ(propylamino)benzylidene)ꢀ2,3ꢀdihydroꢀ1Hꢀindenꢀ1ꢀo
ne hydrochloride (33.HCl)
Intermediate 22 was treated with 4ꢀ(propylamino)benzaldehyde according to general
procedure to give the desired product 33 as a yellow solid, yield 75%. Mp=
1
222.1ꢀ222.9 ; H NMR (400 MHz, DMSOꢀd6) δ 7.58 (d, J = 8.2 Hz, 2H), 7.30 (s,
1H), 7.14 (s, 1H), 7.09 (s, 1H), 6.91 (d, J = 7.6 Hz, 2H), 3.90 (s, 3H), 3.89 (s, 2H),
3.10 (t, J = 7.1 Hz, 2H), 1.61 (dd, J = 14.2, 7.2 Hz, 2H), 0.95 (t, J = 7.3 Hz, 3H); 13C
NMR (101 MHz, DMSOꢀd6) δ 191.75, 154.25, 146.91, 143.04, 132.08, 130.98,
130.53, 108.18, 108.09, 55.87, 31.56, 20.50, 11.23; LCMS (APCI) m/z [(MꢀH)]ꢀ =
322.4; HRMS (ESI) m/z calcd for C20H21NO3, 324.1594. found, 324.1596; Purity:
99.3% (by HPLC).
2ꢀ(4ꢀ(cyclohexylamino)benzylidene)ꢀ6ꢀhydroxyꢀ5ꢀmethoxyꢀ2,3ꢀdihydroꢀ1Hꢀinden
ꢀ1ꢀone hydrochloride (34.HCl)
Intermediate 22 was treated with 4ꢀ(cyclohexylamino)benzaldehyde according to
general procedure to give the desired product 34 as a yellow solid, yield 77%. Mp=
1
250.4ꢀ251.0 ; H NMR (400 MHz, DMSOꢀd6) δ 9.57 (s, 1H), 7.46 (d, J = 8.5 Hz,
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2H), 7.26 (s, 1H), 7.15 (t, J = 13.5 Hz, 2H), 6.67 (d, J = 8.5 Hz, 2H), 6.27 (d, J = 7.9
Hz, 1H), 3.89 (s, 3H), 3.85 (s, 2H), 1.92 (d, J = 9.9 Hz, 2H), 1.73 (d, J = 13.0 Hz,
2H), 1.60 (d, J = 12.0 Hz, 1H), 1.51 – 0.91 (m, 6H); 13C NMR (101 MHz, DMSOꢀd6)
δ 191.79, 154.21, 149.21, 146.69, 142.41, 132.51, 132.51, 130.94, 129.61, 122.11,
112.61, 112.22, 108.20, 108.02, 99.22, 55.69, 50.12, 32.39, 32.13, 31.85, 25.32,
24.40, 24.25; LCMS (APCI) m/z [(MꢀH)]ꢀ =362.4; HRMS (ESI) m/z calcd for
C23H25NO3, 364.1907. found, 364.1900; Purity: 95.5% (by HPLC).
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2ꢀ(4ꢀ(dipropylamino)benzylidene)ꢀ6ꢀhydroxyꢀ5ꢀmethoxyꢀ2,3ꢀdihydroꢀ1Hꢀindenꢀ1
ꢀone hydrochloride (35.HCl)
Intermediate 22 was treated with 4ꢀ(dipropylamino)benzaldehyde according to
general procedure to give the desired product 35 as a yellow solid, yield 80%. Mp=
1
122.9ꢀ123.0 ; H NMR (400 MHz, DMSOꢀd6) δ 7.60 (s, 2H), 7.30 (s, 1H), 7.13 (s,
1H), 7.07 (s, 1H), 7.00 – 6.79 (m, 2H), 3.89 (s, 3H), 3.88 (s, 2H), 3.34 (t, J = 7.5 Hz,
4H), 1.67 – 1.36 (m, 4H), 0.88 (t, J = 7.3 Hz, 6H); 13C NMR (101 MHz, DMSOꢀd6) δ
191.73, 154.20, 146.91, 142.95, 132.24, 130.62, 108.19, 108.09, 55.85, 54.85, 31.57,
19.28, 10.92; LCMS (APCI) m/z [(MꢀH)]ꢀ = 364.5; HRMS (ESI) m/z calcd for
C23H27NO3, 366.2064. found, 366.2078; Purity: 98.9% (by HPLC).
2ꢀ(4ꢀ(ethyl(methyl)amino)benzylidene)ꢀ6ꢀhydroxyꢀ5ꢀmethoxyꢀ2,3ꢀdihydroꢀ1Hꢀin
denꢀ1ꢀone hydrochloride (36.HCl)
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Intermediate 22 was treated with 4ꢀ(ethyl(methyl)amino)benzaldehyde according to
general procedure to give the desired product 36 as a yellow solid, yield 77%. Mp=
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193.7ꢀ194.4 ; H NMR (400 MHz, DMSOꢀd6) δ 7.61 (d, J = 8.4 Hz, 2H), 7.32 (s,
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1H), 7.15 (s, 1H), 7.07 (s, 1H), 6.93 (s, 2H), 3.92 – 3.87 (m, 5H), 3.49 (dd, J = 13.9,
6.8 Hz, 2H), 2.99 (s, 3H), 1.08 (t, J = 6.9 Hz, 3H); 13C NMR (101 MHz, DMSOꢀd6) δ
191.74, 154.30, 146.94, 143.07, 132.14, 130.76, 130.54, 108.21, 108.10, 55.86, 31.54,
10.64; LCMS (APCI) m/z [(MꢀH)]ꢀ = 322.4; HRMS (ESI) m/z calcd for C20H21NO3,
324.1594. found, 324.1582; Purity: 98.9% (by HPLC).
6ꢀhydroxyꢀ5ꢀmethoxyꢀ2ꢀ(4ꢀ(methyl(propyl)amino)benzylidene)ꢀ2,3ꢀdihydroꢀ1Hꢀi
ndenꢀ1ꢀone hydrochloride (37.HCl)
Intermediate 22 was treated with 4ꢀ(methyl(propyl)amino)benzaldehyde according to
general procedure to give the desired product 37 as a yellow solid, yield 77%. Mp=
1
133.1ꢀ133.8 ; H NMR (400 MHz, DMSOꢀd6) δ 7.57 (d, J = 8.7 Hz, 2H), 7.30 (s,
1H), 7.15 (s, 1H), 7.06 (s, 1H), 6.81 (d, J = 8.2 Hz, 2H), 3.90 (s, 3H), 3.88 (s, 2H),
3.40 – 3.34 (m, 2H), 2.99 (s, 3H), 1.56 (dd, J = 14.5, 7.4 Hz, 2H), 0.89 (t, J = 7.3 Hz,
3H). 13C NMR (101 MHz, DMSOꢀd6) δ 192.12, 153.84, 147.28, 142.71, 132.24,
130.59, 108.22, 108.06, 55.83, 31.62, 19.20, 11.02; LCMS (APCI) m/z [(MꢀH)]ꢀ =
336.4; HRMS (ESI) m/z calcd for C21H23NO3, 338.1751. found, 338.1760; Purity:
98.3% (by HPLC).
General procedure for the preparation of 38ꢀ41
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TsOH (380mg, 2mmol) was added to a suspension of 5,6ꢀdihydroxy indanone (20)
(2mmol) and the appropriate benzaldehyde (2mmol) in 10 ml toluene. After refluxed
for 10h, the solution was cooled to room temperature. The solid was filtered off,
washed with water, and crystallized from methanol.
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2ꢀ(4ꢀ(dimethylamino)benzylidene)ꢀ5,6ꢀdihydroxyꢀ2,3ꢀdihydroꢀ1Hꢀindenꢀ1ꢀone
4ꢀmethylbenzenesulfonate (38)
5,6ꢀdihydroxy indanone (20) was treated with 4ꢀ(dimethylamino)benzaldehyde
according to general procedure to give the desired product 38 as a yellow solid, yield
1
71%. Mp= 247.6ꢀ248.1 ; H NMR (400 MHz, DMSOꢀd6) δ 7.56 – 7.50 (m, 4H),
7.27 (s, 1H), 7.13 (d, J = 7.7 Hz, 2H), 7.04 (s, 1H), 6.94 (s, 1H), 6.78 (d, J = 8.9 Hz,
2H), 3.81(s, 2H), 2.99 (s, 6H), 2.28 (s, 3H); 13C NMR (101 MHz, DMSOꢀd6) δ
191.58, 152.67, 150.80, 145.76, 143.01, 135.74, 132.07, 131.36, 131.07, 130.55,
129.90, 128.97, 125.35, 122.65, 111.97, 111.68, 108.44, 41.59, 31.42, 20.50; LCMS
(APCI) m/z [(MꢀH)]ꢀ = 294.3; HRMS (ESI) m/z calcd for C18H17NO3, 296.1281.
found, 296.1276; Purity: 99.7% (by HPLC).
2ꢀ(4ꢀ(diethylamino)benzylidene)ꢀ5,6ꢀdihydroxyꢀ2,3ꢀdihydroꢀ1Hꢀindenꢀ1ꢀone
4ꢀmethylbenzenesulfonate (39)
5,6ꢀdihydroxy indanone (20) was treated with 4ꢀ(diethylamino)benzaldehyde
according to general procedure to give the desired product 39 as a yellow solid, yield
1
67%. Mp= 240.1ꢀ240.7 ; H NMR (400 MHz, DMSOꢀd6) δ 10.03 (s, 1H), 9.43 (s,
1H), 7.53 ꢀ 7.48 (m, 4H), 7.25 (s, 1H), 7.14 (d, J = 7.6 Hz, 2H), 7.05 (s, 1H), 6.94 (s,
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