Design of two alternative routes for the synthesis of naftifine and analogues as potential antifungal agents

Article abstract of DOI:10.3390/molecules23030520

Two practical and efficient approaches have been implemented as alternative procedures for the synthesis of naftifine and novel diversely substituted analogues 16 and 20 in good to excellent yields, mediated by Mannich-type reactions as the key step of the processes. In these approaches, theγ-aminoalcohols 15 and 19 were obtained as the key intermediates and their subsequent dehydration catalyzed either by Br?nsted acids like H₂SO₄ and HCl or Lewis acid like AlCl₃, respectively, led to naftifine, along with the target allylamines 16 and 20. The antifungal assay results showed that intermediates 18 (bearing both a β-aminoketo- and N-methyl functionalities in their structures) and products 20 were the most active. Particularly, structures 18b, 18c, and the allylamine 20c showed the lowest MIC values, in the 0.5-7.8 μg/mL range, against the dermatophytes Trichophyton rubrum and Trichophyton mentagrophytes. Interesting enough, compound 18b bearing a 4-Br as the substituent of the phenyl ring, also displayed high activity against Candida albicans and Cryptococcus neoformans with MIC₈₀ = 7.8 μg/mL, being fungicide rather than fungistatic with a relevant MFC value = 15.6 μg/mL against C. neoformans.

Full text of DOI:10.3390/molecules23030520

molecules
Article
Design of Two Alternative Routes for the
Synthesis of Naftifine and Analogues as
Potential Antifungal Agents
Rodrigo Abonia 1,*, Alexander Garay 1, Juan C. Castillo 1,2 ID , Braulio Insuasty 1,
Jairo Quiroga 1 ID , Manuel Nogueras 3 ID , Justo Cobo 3 ID , Estefanía Butassi 4
and Susana Zacchino 4
ID
1
Grupo de Investigación de Compuestos Heterocíclicos (GICH), Departamento de Química,
Universidad del Valle, A. A. 25360 Cali, Colombia; talero22@hotmail.co (A.G.);
juan.castillo06@uptc.edu.co (J.C.C.); braulio.insuasty@correounivalle.edu.co (B.I.);
jairo.quiroga@correounivalle.edu.co (J.Q.)
2
Escuela de Ciencias Químicas, Facultad de Ciencias, Universidad Pedagógica y Tecnológica
de Colombia UPTC, Avenida Central del Norte, A. A. 150003 Tunja, Colombia
Department of Inorganic and Organic Chemistry, Universidad de Jaén, 23071 Jaén, Spain;
3
mmontiel@ujaen.es (M.N.); jcobo@ujaen.es (J.C.)
Área de Farmacognosia, Facultad de Ciencias Bioquímicas y Farmacéuticas,
4
Universidad Nacional de Rosario, Suipacha 531, CP 2000 Rosario, Argentina;
fefabutassi@hotmail.com (E.B.); szaabgil@citynet.net.ar (S.Z.)
*
Correspondence: rodrigo.abonia@correounivalle.edu.co; Tel.: +57-2-339-3248
Received: 30 January 2018; Accepted: 21 February 2018; Published: 26 February 2018
Abstract: Two practical and efficient approaches have been implemented as alternative procedures
for the synthesis of naftifine and novel diversely substituted analogues 16 and 20 in good to
excellent yields, mediated by Mannich-type reactions as the key step of the processes. In these
approaches, the
γ-aminoalcohols 15 and 19 were obtained as the key intermediates and their
subsequent dehydration catalyzed either by Brønsted acids like H2SO4 and HCl or Lewis acid
like AlCl3, respectively, led to naftifine, along with the target allylamines 16 and 20. The antifungal
assay results showed that intermediates 18 (bearing both a
in their structures) and products 20 were the most active. Particularly, structures 18b, 18c, and the
allylamine 20c showed the lowest MIC values, in the 0.5–7.8 g/mL range, against the dermatophytes
β-aminoketo- and N-methyl functionalities
µ
Trichophyton rubrum and Trichophyton mentagrophytes. Interesting enough, compound 18b bearing
a 4-Br as the substituent of the phenyl ring, also displayed high activity against Candida albicans
and Cryptococcus neoformans with MIC80 = 7.8
µg/mL, being fungicide rather than fungistatic with
a relevant MFC value = 15.6 µg/mL against C. neoformans.
Keywords: benzylamines; propiophenone salts; γ-aminoalcohols; Mannich-type reaction; allyamines;
naftifine analogues; antifungal activity
1. Introduction
Allylamines represent one of the most important primary units in organic chemistry [
important synthetic precursors for -aminoacids [ ], alkaloids [ ] and carbohydrate derivatives [
Among the synthetic allylamines of biological importance, it is worth mentioning cinnarizine (
used for the treatment of vertigo and related cerebral disorders [ ], abamine ( ), an important
tool to elucidate the mechanisms that regulate the levels of abscisic acid (ABA) in plants and
animals [ ], terbinafine (brand name Lamisil) and naftifine (brand name Naftin) that are effective
antifungal agents. Naftifine is a topical allylamine that is effective against a broad spectrum of
1
]. They are
].
),
β
2
3
4
1
5
2
6
Molecules 2018, 23, 520; doi:10.3390/molecules23030520
www.mdpi.com/journal/molecules

Molecules 2018, 23, 520
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dermatophyte fungi of the Trichophyton and Microsporum spp., and has also shown good activity
against Candida and Aspergillus spp. Terbinafine represents the most effective of this chemical class
of antimycotic compounds. Terbinafine proved to be highly active against dermatophytes and
Sporothrix schenckii and also exerts good activity against several yeasts [7–9] (Figure 1).
Figure 1. Some allylamines with important biological activities.
Since naftifine was discovered, different synthetic routes have been developed to obtain it and
some of its analogues. Among them, Stütz et al. obtained naftifine in 94% yield via a cinnamyl Schiff´s
base (Scheme 1, entry 1) [10], Petasis et al. obtained it in 82% yield via a trans-2-phenylvinylboronic acid
coupling reaction (Scheme 1, entry 2) [11], and Correia et al. synthesized it in 68% yield via a Heck-type
reaction (Scheme 1, entry 3) [12].
Scheme 1. Some previous synthetic approaches for the synthesis of naftifine.

Molecules 2018, 23, 520
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Despite the good performance of the allylamines as antifungal agents, there have been some
cases in which they have failed in the treatment of patients who have shown antifungal resistance
toward some of these drugs [13,14]. These findings suggest the need of looking for new methods and
synthesis of new potential antifungal agents inspired in naftifine that can be used as alternatives to the
existing ones.
As part of our current program on the synthetic utilization of benzylamine derivatives [15–17],
herein we wish to report our results on the synthesis of naftifine and analogues through two alternative
synthetic strategies mediated in both cases by Mannich-type reactions.
2. Results and Discussion
2.1. Chemistry
In view of the above, we envisioned that our previous results on the synthesis of
γ-aminoalcohols
type 15 and 19 18 19], could be exploited as alternative approaches for the synthesis of naftifine
[
,
and analogues mediated by Mannich-type reactions. In this direction, two straightforward
strategies, shown in Schemes 2 and 3, were proposed. Strategy 1 consisted on the synthesis of
γ
-aminoalcohols 15 via a three-component Mannich-type reaction between secondary amines 13
,
(see Figure 2), formaldehyde and activated alkenes 14. Subsequently, a dehydration of 15 should afford
the expected allylamines 16, as shown in Scheme 2. It is remarkable that from Strategy 1, products 16
could be formed by a combination of both Mannich- and aza-Prins-type reactions in a one pot sequence
if acid is used as catalyst since Step 1. It is worth mentioning that, the N-vinylpyrrolidin-2-one 14a
and 2,3-dihydrofuran 14b were chosen in this strategy along with styrene 14c as activated alkenes,
due to the fact that these two heterocyclic rings can be found forming part of the structures of synthetic
compounds with outstanding antifungal activities [20–23]. For that reason we supposed that the
presence of these heterocycles instead of the phenyl ring in the naftifine analogues (i.e., X = heterocycle
in 16), along with the allylamine moiety in the same structure could produce enhanced effects in the
antifungal assays.
Scheme 2. Designed alternative route for the synthesis of naftifine-analogues 16 by combination of
a three-component Mannich- and aza-Prins-reactions.

Molecules 2018, 23, 520
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The proposed Strategy 2 consisted in the synthesis of
corresponding
γ
-aminoalcohols 19 via reduction of their
β
-aminoketones 18. The subsequent dehydration of 19 should also afford a second
family of allylamines 20, as shown in Scheme 3.
Scheme 3. Designed alternative route for the synthesis of naftifine and analogues 20 from
a reduction/dehydration strategy.
Prior to starting, it is worth mentioning that the non-commercial secondary amines 13a–f
(Figure 2), were synthesized from their corresponding primary amines and different aryl aldehydes
via a reductive amination reaction [15–17].
Figure 2. Set of secondary amines 13 used for the synthesis of the intermediate γ-aminoalcohols 15.
Initially, with the aim of obtaining the allylamines 16, described in Scheme 2, an acid-catalyzed
one-pot approach was planned in order to obtain products 16 directly in a one-step sequence (involving
an in situ dehydration), without isolation of their corresponding
γ-aminoalcohol intermediates
15 (i.e., from a combination of both Mannich- and aza-Prins-type reactions). Thus, as a model
reaction, a mixture of amine 13a (1.0 mmol), formaldehyde (1.5 mmol) and alkene 14a (1.0 mmol)
in acetonitrile (ACN) was treated with a catalytic amount of conc. H2SO4 at room temperature
for 24 h. The thin-layer chromatography (TLC) analysis showed the formation of a complex mixture
of products. Then, the reaction mixture was neutralized with NaOH and their components were
separated by column chromatography affording the expected allylamine 16a in only 11% yield along

Molecules 2018, 23, 520
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with unreacted starting amine 13a and pyrrolidin-2-one (the acid-catalyzed degradation product
from 14a) [24] (Scheme 4).
Scheme 4. Attempts for acid-catalyzed synthesis of allylamine 16a via a one-step sequence.
In an attempt to improve the yield of product 16a the reaction was repeated with other both
stronger (HCl) and milder protic acids (i.e., oxalic, acetic and formic), but unfortunately, with the same
behavior and low product yield (Scheme 4). Similar results were obtained when 14a was replaced
by 2,3-dihydrofuran as activated alkene. In a further experiment, the same model reaction depicted
in Scheme 4 was performed, but using styrene instead of alkene 14a in the presence of H2SO4. After
purification and characterization of the product, we were delighted to confirm that naftifine was
obtained in an acceptable 65% yield. The higher stability of styrene in acidic medium in comparison
with alkene 14a and 2,3-dihydrofuran (both structures decomposes in such conditions), permitted
the selective formation of naftifine in a one-pot procedure (by combination of both Mannich- and
aza-Prins-type reactions), as initially was planned in Strategy 1 (Scheme 2).
Due to the above drawbacks of the acid-catalyzed one-step reaction, when 14a and
2,3-dihydrofuran were used as activated alkenes, we decided to move the process to a two-step
sequence involving the isolation of the
Step 1 of Strategy 1 depicted in Scheme 2, a set of
γ
-aminoalcohol intermediates 15 (Scheme 2). Starting with
-aminoalcohols 15a (Figure 3), was obtained by
γ
–k
following our previously established catalyst-free three-component methodology [19]. Thus, a mixture
of secondary amines 13 (1.0 mmol, Figure 2), polyformaldehyde (1.5 mmol) and the corresponding
activated alkene 14 (1.0 mmol) was stirred at room temperature in ACN to afford the corresponding
γ-aminoalcohols 15 in good yields (Figure 3).
Figure 3. Set of γ-aminoalcohols 15 obtained via a three-component Mannich-type reaction.
Subsequently, after several failed attempts to optimize the dehydration reaction mediated by
different Brønsted-Lowry acids (Scheme 2, Step 2), the expected allylamines 16 were obtained by

Molecules 2018, 23, 520
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subjecting the corresponding
γ
-aminoalcohols 15 (1.0 mmol) to reflux in 1,4-dioxane as the solvent
in the presence of AlCl3 (1.0 mmol) as Lewis acid catalyst. After neutralization with triethylamine
(TEA) and purification, the expected compounds 16 were obtained in in acceptable to excellent yields
(Scheme 2, Step 2). Scheme 5 depicts the structures of the new allylamines 16 obtained from Strategy 1
(Scheme 2), in a two-step sequence.
R
R
R
N
N
N
H
X
OH
ACN
rt
AlCl3
p-dioxane
- H2O
CH2O (aq)
+
+
14
X
X
13
16
15
Scheme 5. New allylamines 16 obtained by dehydration of the
Naftifine was obtained from Strategy 1 in a one-pot fashion starting from styrene and catalyzed by
sulfuric acid.
γ
-aminoalcohols 15 catalyzed by AlCl3.
a
Regarding Strategy 2, depicted in Scheme 3, we could optimize steps 1 and 2 to obtain satisfactory
yields of the expected -aminoalcohols 19 20 (Figure 4) in a one-pot reaction by treating amines 13
(1.0 mmol) with propiophenone salts 17a (1.0 mmol) in a mixture of 1,4-dioxane/TEA at reflux.
γ
–
–
f
Compounds 17 were obtained from a Mannich reaction between the corresponding acetophenones,
dimethylamine hydrochloride and polyformaldehyde in ethanol at reflux [25]. After removing the
solvent, the obtained crude products (corresponding to the
β-aminoketones 18), were reduced by
treatment with NaBH4 in MeOH affording the expected
yields (Figure 4).
γ
-aminoalcohols 19 20 in good to excellent
–
Once we obtained the set of aminoalcohols 19
trials leading to the expected naftifine and its analogues 21
analogues 21 22 were obtained in good to excellent yields by refluxing 19
–
20 (Figure 4), we attempted a couple of
22. Thus, the expected naftifine and
20 in 5N HCl (Step 3),
–
–
–
followed by neutralization with NaOH and purification. Scheme 6 depicts the structures of the
new allylamines 21–22. It is remarkable that naftifine was obtained using Strategy 2 in a very good
yield (90%). This value is comparable with the 94% yield obtained previously by Stütz et al., and higher
than those obtained through either Petasis or Correia´s methodologies, as shown in Scheme 1. A further
advantage of our Strategy 2 is the easy availability of the starting materials used, the simplicity of the
processes involved and a major structural diversity in comparison with previous reports.

Molecules 2018, 23, 520
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Finally, structures for all the new compounds obtained from strategies 1 and 2 were fully assigned
by IR, NMR, elemental analysis and mass spectra, (see also Supplementary Materials).
Figure 4. Set of
γ-aminoalcohols 19–20 obtained via a one-pot SN/reduction sequence from amines 13f
and 13h and propiophenone salts 17a–f.
Scheme 6. Naftifine and analogues 21–22 obtained by dehydration of the γ-aminoalcohols 19–20
catalyzed by 5N HCl.
2.2. Antifungal Activity Studies
Minimum inhibitory concentrations (MIC) of compounds 15
and Laboratory Standards Institute (CLSI) microbroth dilution methods M27-A3 for yeasts and
M38-A2 for filamentous fungi [26 27], against a panel of eight fungal clinically relevant species
comprising two yeasts (Candida albicans and Cryptococcus neoformans), three Aspergillus spp. (A. niger,
–22 were determined with the Clinical
,

Molecules 2018, 23, 520
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A. fumigatus, and A. flavus) and three dermatophytes (Trichophyton rubrum, T. mentagrophytes and
Microsporum gypseum). Compounds were tested at serial two-fold dilutions from 250 to 0.5 g/mL.
Compounds with MICs > 250 g/mL were considered inactive; between 250–125 g/mL low active,
and in the range 62.5–20 µg/mL, moderately active. MICs below 20 g/mL was considered as
22, some conclusions
µ
µ
µ
µ
indicative of high activity. From the obtained MIC values of compounds 15
–
can be drawn:
(i) In general, the series of precursors 15 and products 16 were significantly less active than the
series of precursors 18–20 and products 21–22.
(ii) Almost all compounds 15
against A. flavus, A. niger and M. gypseum (data not shown).
(iii) Compounds 15 22 identified with the letters and
(31.2–250 µg/mL) activities against the rest of the fungal panel (data not shown).
–22 showed either very low to moderate activities or were inactive
–
a
d–k showed moderate to low
(iv) Among compounds 18
–
22, the structures 18b
,
18c and 21c displayed outstanding activities
g/mL), (Table 1), while 19b was moderately
against one or more dermatophytes (0.5–7.8
µ
active (MICs = 31.2–62.5 µg/mL) against four of the fungi tested (i.e., C. neoformans, M. gypseum,
T. rubrum and T. mentagrophytes), being the only compound of the series showing activity
against M. gypseum. It is worth to take into account that the most active compounds within
18–
22 possess a CH3 group as R substituent although with variations in the substituent R1 of the
phenyl ring. This finding is in accordance with the required features found by Stütz et al. for the
allylamines to display antifungal activity [10].
(v) Compound 18b was the most active of the whole series, showing activity not only against
dermatophytes but also against Candida spp., S. cerevisiae, C. neoformans and A. flavus
(MICs between 7.8 to 15.6
bearing 4-Br and 3,4-methylenedioxy R1 substituents, the
activities, suggesting that the ketone group play an important role in the antifungal activity of
these structures. Instead, among the -aminoalcohols 19 20, only 19b showed moderate activity
against dermatophytes and C. neoformans, while its corresponding allylamine 21b displayed very
low activities (MICs = 125–250 g/mL) against the whole fungal panel. It is remarkable that
allylamine 21c displayed the most outstanding activities against T. rubrum and T. mentagrophytes
µg/mL). From these results it is clear that within the compounds
β-aminoketones 18 displayed the best
γ
–
µ
(MICs = 0.5–1.0
future research.
µg/mL) constituting this datum a finding that deserves great attention for
It is worth taking into account that compound 18b displayed high activity against all yeasts
as well as A. fumigatus. This finding constitutes an interesting result, since previous studies of
naftifine-analogues reported no activity against this fungal species [10,28].
In order to have a look into the potential usefulness of 18b against clinically relevant yeasts,
we investigated the fungal inhibition percentages displayed by 18b against C. albicans and C. neoformans
at concentrations obtained by two fold-dilutions from 250 to 3.9 µg/mL. In addition, the inhibition
percentages of 19b and 21b were also determined for comparative purposes against the two clinically
important fungal species. With these data, two graphs showing inhibition % (Y axis) vs. concentration
(X axis), were constructed (Figure 5). The selection of these two fungal species for deepening the
studies of the antifungal behavior of 18b, was due to their clinical relevance. C. neoformans is the
main cause of cryptococcal meningoencephalitis among HIV patients with impaired defenses that
many times led to disease relapse and death [29,30]. In turn, C. albicans is the fourth leading cause
of nosocomial bloodstream infection (BSI) in intensive care units, causing fatal invasive candidiasis
in a high percentage of patients [31]. For these reasons, new compounds that show new potential
anticandidal or anti-cryptococcal drugs are highly welcome.

Molecules 2018, 23, 520
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Table 1. MIC values (µg/mL) of allylamine derivatives 18, 19 and 21 acting against human opportunistic pathogenic fungi. MIC/MFC values are recorded in µg/mL.
Compound
b
R
R1
Ca
Sc
Cn
Afu
Afl
An
Mg
Tr
Tm
CH3
CH3
4-Br
3,4-OCH2O
15.6/62.5
125/125
15.6/31.3
125/125
7.8/15.6
31.25/62.5
7.8/15.6
31.3/62.5
250/250
250/250
250/>250
250/>250
>250/>250
>250/>250
3.9/3.9
7.8/15.6
2.0/2.0
7.8/15.6
18
c
b
c
CH3
CH3
4-Br
3,4-OCH2O
125/250
>250
125/250
>250
62.5/125
>250
250/>250
>250
250/>250
>250
250/>250
>250
62.5/125
250/250
31.2/62.5
250/250
31.2/62.5
250/250
19
b
CH3
CH3
4-Br
3,4-OCH2O
250
125/>250
>250
250/250
>250
125/250
>250
250/>250
>250
250/>250
>250
250/>250
125/>250
125/>250
125/>250
1.0/1.8
125/>250
0.5/1.0
21
c
Amphotericin B
Terbinafine
1.0/1.0
-
1.0/1.0
-
1.0/2.0
-
2.0/2.0
-
2.0/2.0
-
2.0/2.0
-
0.5/0.5
0.5/0.5
0.5/0.5
0.008/0.015
0.004/0.008
0.004/0.015
Ca: Candida albicans ATCC 10231, Sc: Saccharomyces cerevisiae ATCC 9763, Cn: Cryptococcus neoformans ATCC 32264, An: Aspergillus niger ATCC 9029, Afl: Aspergillus flavus ATCC 9170, Afu:
Aspergillus fumigatus ATCC 26934, Mg: Microsporum gypseum CCC 115, Tr: Trichophyton rubrum CCC 113, Tm: Trichophyton mentagrophytes ATCC 9972.

Molecules 2018, 23, 520
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120
100
80
60
40
20
0
120
100
80
60
40
20
0
18b
19b
21b
18b
19b
21b
0
3.9
7.8
15.6
31.2
62.5
125
250
0
3.9
7.8
15.6
31.2
62.5
125
250
Concentration (g/mL)
Concentration (g/mL)
(A)
(B)
Figure 5. Comparative antifungal activities of compounds 18b
substituent but differing in their functional groups (i.e., 18b is a
and 21b an allylamine). ( ) against C. albicans; ( ) against C. neoformans. Amphotericin B (Amp B)
g/mL against C. albicans and at 0.5 g/mL against C. neoformans. Curves
,
β
19b
,
21b possessing the same R1
-ketoamine; 19b a γ-aminoalcohol
A
B
inhibits 100% growth at 1.0
of Amp B are not included.
µ
µ
In Figure 5A,B the higher percentage of inhibition of C. albicans and C. neoformans by 18b in
comparison with 19b and 21b can be clearly observed, suggesting that the -aminoketo structure plays
an important role in the anti-yeast activity of this naftifine-analogue. As an example, while 18b showed
80% inhibition of C. albicans at 7.8 g/mL, 19b and 21b inhibited less than 10% and similar results
β
µ
can be observed against C. neoformans. Table 2 shows the inhibition percentages values displayed by
the above three compounds used to construct Figure 5.
From Table 2 and Figure 5, it is clear that compound 18b is the most active, being fungicidal rather
than fungistatic with a MFC = 15.6
Instead, 19b is fungicide at high concentrations (125 and 250
fungicide up to 250 g/mL. In addition, the MIC80 of 18b against both fungi is 7.8
µ
g/mL against C. neoformans and 62.5
g/mL, respectively) and 21b was no
g/mL (Table 2),
µg/mL against C. albicans.
µ
µ
µ
a relevant low value that positions 18b as a good candidate for future research. As it is clearly stated in
the CLSI document M27A2 for yeasts, application of a less stringent endpoint such as MIC80 (allowing
some turbidity above the MIC), has improved inter-laboratory agreement and also discriminates
between putatively susceptible and resistant isolates [32].

Molecules 2018, 23, 520
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Table 2. The inhibition percentages values and Minimum Inhibitory Concentrations (MIC100, MIC80 and MIC50) and Minimum Fungicidal Concentration (MFC) of
the naftifine-analogues 18b, 19b and 21b against C. albicans (Ca) and C. neoformans (Cn).
MFC
(µg/mL)
Concentrations of the Compounds (µg/mL)
MIC (µg/mL)
Fungus
Compound
250
125
62.5
31.2
15.6
7.8
3.9
MIC100
MIC80
MIC50
MFC
Ca
100
100
100
100
100
87.4 ± 1.7
28.8 ± 2.6
15.6
7.8
7.8
62.5
18b
19b
21b
Cn
Ca
Cn
Ca
Cn
100
100
100
100
100
100
100
98.9 ± 3.6
7.7 ± 1.6
8.37 ± 1.3
5.6 ± 1.2
19.3 ± 1.2
39.3 ± 3.7
7.8
125
7.8
62.5
31.2
62.5
>250
7.8
15.6
250
86.8 ± 1.3
100
54.3 ± 2.2
87.3 ± 1.6
52.4 ± 2.1
48.8 ± 1.8
20.7 ± 3.2
20.2 ± 1.3
14.9 ± 1.6
35.1 ± 0.0
4.5 ± 0.7
31.2
31.2
31.2
31.2
100
100
0
1.9 ± 1.5
0
62.5
250
125
95.4 ± 8.3
58.1 ± 2.7
83.2 ± 10.2
52.5 ± 4.2
74.9 ± 5.7
49.4 ± 2.3
>250
>250
>250
Ca
100
100
100
100
100
100
100
100
100
100
100
100
100
100
1.0
1.2
0.5
0.5
0.2
0.2
1.0
1.2
Amphotericin B
Cn

Molecules 2018, 23, 520
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3. Materials and Methods
3.1. General Information
Melting points were determined on a Büchi melting point B-450 apparatus (Instrumart,
South Burlington, VT, USA) and are uncorrected. FTIR spectra were recorded on a Shimadzu FTIR
1
8400 spectrophotometer (Scientific Instruments Inc., Seattle, WA, USA) in KBr disks and films. H- and
13C-NMR spectra were recorded on a Bruker Avance 400 spectrophotometer (Bruker BioSpin GmbH,
Rheinstetten, Germany) operating at 400 MHz and 100 MHz, respectively, and using CDCl3 as
solvent and tetramethylsilane as internal standard. DEPT spectra were used for the assignment
of carbon signals. Mass spectra were run on a Shimadzu-GCMS 2010-DI-2010 spectrometer
(
Scientific Instruments Inc., Columbia, SC, USA) (equipped with a direct inlet probe) operating
at 70 eV. Microanalyses were performed on a Thermo-Finnigan Flash EA1112 CHN elemental
analyzer (Thermo Fischer Scientific Inc., Madison, WI, USA), and the values are within 0.4% of
±
the theoretical values. Silica gel aluminum plates (Merck 60 F254) were used for analytical TLC.
The starting chemicals were purchased from (Sigma-Aldrich, San Luis, MO, USA) and Merck Millipore
(Billerica, MA, USA) analytical or reagent grade and were used without further purification, unless
otherwise noted. All starting materials were weighed and handled in air at room temperature.
The reactions were monitored by TLC visualized by a (254/365 nm) UVGL-25 compact UV Lamp (UVP,
Upland, CA, USA) and/or with vanillin-H2SO4 in EtOH. Column chromatography was performed on
silica gel (230–400 mesh, Merck). Non-commercially available secondary amines 13a
13e and 13f were prepared using known procedures [15–17,19,33,34].
, 13b, 13c, 13d,
3.2. Synthesis
3.2.1. General Procedure for the Synthesis of Secondary Amines 13a–e
A mixture of primary amine (1.0 mmol) and the appropriate aldehyde (1.0 mmol) was heated
◦
in an oil bath at 120 C for 20–45 min. After a complete disappearance of the starting materials,
as monitored by TLC, the mixture was allowed to cool to ambient temperature and dissolved in
methanol (4–5 mL). Then, solid NaBH4 (2.0 mmol) was added portionwise with stirring over a period
of 5 min. The stirring was continued at ambient temperature for 30 min further. After the reaction was
complete (monitored by TLC), the volume of the reaction mixture was reduced to 1 mL under reduced
pressure, and water (5 mL) was added. The aqueous solution was extracted with EtOAc (2
and the combined organic layers were dried with anhydrous Na2SO4. The mixture was filtered and the
×
5 mL),
solvent was removed under reduced pressure. All amines 13 were used without further purification.
3.2.2. General Procedure for the Synthesis of γ-Aminoalcohols 15
A mixture of secondary amine 13 (~200 mg, 1.0 mmol), polyformaldehyde (1.5 mmol) and the
activated alkene 14 (1.1 mmol) was dissolved in ACN (2 mL). The solution was stirred at room
temperature for 3 days until the starting secondary amine 13 was no longer detected by TLC (revealed
with an ethanolic solution of vanillin-sulfuric acid or iodine). After the excess of solvent was removed
under reduced pressure, the oily material obtained was purified by column chromatography on
silica gel, using EtOAc:hexane (2:1 v/v) as eluent. When the same reaction was performed starting from
N-methyl-1-(naphthalen-1-yl)methanamine 13a, polyformaldehyde and styrene in the presence of
conc. H2SO4 (1 drop) as catalyst, during 24 h, afforded directly naftifine as the main reaction product.
3.2.3. General Procedure for the Synthesis of Allylamines 16
A mixture of the γ-aminoalcohol 15 (200 mg, 1.0 mmol), AlCl3 (1.0 mmol) and ACN (4 mL) was
stirred at reflux during 2–3 h. After reaction finished (TLC control), TEA (0.5 mL) was added at
room temperature. The solvent was removed under reduced pressure, water (5 mL) was added and the
aqueous solution was extracted with EtOAc (3
×
5 mL). The combined organic layers were dried with

Molecules 2018, 23, 520
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anhydrous Na2SO4, the mixture was filtered and the solvent was removed under reduced pressure.
Finally, the crudes were purified by column chromatography on silica gel using CHCl3:MeOH (40:1 v/v
)
as eluent.
(E)-1-(3-(Benzyl(naphthalen-1-ylmethyl)amino)prop-1-en-1-yl)pyrrolidin-2-one (16a). Following the strategy
1 for the formation of allylamines, the reaction of γ-aminoalcohol 15a (200 mg, 0.52 mmol) and AlCl3
(69 mg, 0.52 mmol) in 4.0 mL of ACN afforded product 16a as a yellow oil. Yield: 92% (177 mg). FT-IR
1
(film): 3058, 3030, 2925, 2798, 1702, 1660, 1408, 1364, 1334, 1119 cm−1. H-NMR
δ (ppm): 8.28–8.21
(m, 1H), 7.89–7.82 (m, 1H), 7.77 (d, J = 8.0 Hz, 1H), 7.56 (d, J = 6.8 Hz 1H), 7.53–7.46 (m, 2H), 7.46–7.41
(m, 1H), 7.37–7.28 (m, 4H), 7.27–7.21 (m, 1H), 7.02 (d, J = 14.4 Hz, 1H), 5.00 (dt, J = 7.2, 14.4 Hz, 1H),
4.04 (s, 2H), 3.66 (s, 2H), 3.41 (t, J = 7.2 Hz, 2H), 3.19 (d, J = 6.8 Hz, 2H), 2.46 (t, J = 8.2 Hz, 2H), 2.06 (tt,
J = 7.6, 7.6 Hz, 2H). 13C-NMR
δ (ppm): 173.0 (C=O), 139.7 (Cq), 135.2 (Cq), 133.8 (Cq), 132.4 (Cq), 129.0,
128.3, 128.1, 127.7, 127.3, 126.8, 126.2, 125.5, 125.5, 125.2, 124.8, 108.8, 58.4, 56.6, 54.1, 45.2, 31.2, 17.3.
Anal. Calcd. for C25H26N2O: C, 81.05; H, 7.07; N, 7.56. Found: C, 80.82; H, 7.25; N, 7.32.
(E)-1-(3-((4-Chlorobenzyl)(naphthalen-1-ylmethyl)amino)prop-1-en-1-yl)pyrrolidin-2-one (16b). Following
the strategy 1 for the formation of allylamines, the reaction of
and AlCl3 (68 mg, 0.51 mmol) in 4.0 mL of ACN afforded product 16b as a yellow oil. Yield: 85%
(176 mg). FT-IR (film): 3046, 2925, 2882, 2803, 1702, 1660, 1488, 1408, 1298, 1089 cm−1 1H-NMR
(ppm): 8.25–8.20 (m, 1H), 7.87–7.83 (m, 1H), 7.77 (d, J = 8.4 Hz, 1H), 7.54–7.46 (m, 3H), 7.44–7.39
γ-aminoalcohol 15b (215 mg, 0.51 mmol)
.
δ
(m, 1H), 7.24 (s, 4H), 7.01 (d, J = 14.4 Hz, 1H), 4.96 (dt, J = 7.2, 14.4 Hz, 1H), 4.00 (s, 2H), 3.58 (s, 2H),
3.43 (t, J = 7.2 Hz, 2H), 3.15 (d, J = 6.8 Hz, 2H), 2.48 (t, J = 8.4 Hz, 2H), 2.09 (tt, J = 8.0, 8.0 Hz, 2H).
13C-NMR
δ (ppm): 173.0 (C=O), 138.3 (Cq), 134.9 (Cq), 133.8 (Cq), 132.4 (Cq), 132.3 (Cq), 130.2, 128.4,
128.2, 127.8, 127.3, 126.3, 125.5, 125.5, 125.2, 124.7, 108.4, 57.6, 56.8, 54.3, 45.2, 31.2, 17.4. Anal. Calcd.
for C25H25ClN2O: C, 74.15; H, 6.22; N, 6.92. Found: C, 74.02; H, 6.50; N, 7.05.
(E)-1-(3-((Benzo[d][1,3]dioxol-5-ylmethyl)(naphthalen-1-ylmethyl)amino)prop-1-en-1-yl)pyrrolidin-2-one (16c).
Following the strategy 1 for the formation of allylamines, the reaction of γ-aminoalcohol 15c (216 mg,
0.50 mmol) and AlCl3 (68 mg, 0.51 mmol) in 4.0 mL of ACN afforded product 16c as a yellow oil.
Yield: 77% (159 mg). FT-IR (film): 3045, 2977, 2922, 2884, 2802, 1701, 1660, 1487, 1441, 1409, 1364, 1298,
1
1243, 1113, 1038 cm−1. H-NMR
δ
(ppm): 8.30–8.24 (m, 1H), 7.88–7.82 (m, 1H), 7.77 (d, J = 8.4 Hz, 1H),
7.57–7.46 (m, 3H), 7.43 (t, J = 7.6 Hz, 1H), 7.03 (d, J = 14.4 Hz, 1H), 6.86 (s, 1H), 6.80–6.71 (m, 2H), 5.92
(s, 2H, OCH2O), 5.00 (dt, J = 7.2, 14.4 Hz, 1H), 4.00 (s, 2H), 3.53 (s, 2H), 3.42 (t, J = 7.2 Hz, 2H), 3.16 (d,
J = 6.8 Hz, 2H), 2.46 (t, J = 8.0 Hz, 2H), 2.05 (tt, J = 7.6, 7.6 Hz, 2H). 13C-NMR
δ (ppm): 172.9 (C=O),
147.4 (Cq), 146.3 (Cq), 135.1 (Cq), 133.7 (Cq), 133.5 (Cq), 132.3 (Cq), 128.2, 127.6, 127.2, 126.1, 125.4
(2 × CH), 125.1, 124.7, 121.9, 109.2, 108.5, 107.7, 100.7, 57.9, 56.4, 53.8, 45.1, 31.1, 17.2. Anal. Calcd. for
C26H26N2O3: C, 75.34; H, 6.32; N, 6.76. Found: C, 75.48; H, 6.21; N, 6.83.
(E)-1-(3-((Naphthalen-1-ylmethyl)(napthalen-2-ylmethyl)amino)prop-1-en-1-yl)pyrrolidin-2-one
(16d).
Following the strategy 1 for the formation of allylamines, the reaction of -aminoalcohol 15d (237 mg,
γ
0.54 mmol) and AlCl3 (73 mg, 0.55 mmol) in 4.0 mL of ACN afforded product 16d as a yellow oil.
Yield: 68% (154 mg). FT-IR (film): 3045, 2927, 2882, 2800, 1701, 1660, 1509, 1409, 1363, 1299, 1261, 1224,
1
1115 cm−1. H-NMR
δ (ppm): 8.02 (d, J = 8.4 Hz, 2H), 7.83 (d, J = 8.0 Hz, 2H), 7.77 (d, J = 8.4 Hz,
2H), 7.51 (d, J = 6.8 Hz, 2H), 7.47–7.38 (m, 4H), 7.28–7.22 (m, 2H), 7.06 (d, J = 14.4 Hz, 1H), 5.04 (dt,
J = 7.2, 14.4 Hz, 1H), 4.04 (s, 4H), 3.42 (t, J = 7.2 Hz, 2H), 3.22 (d, J = 7.2 Hz, 2H), 2.47 (t, J = 8.0 Hz,
2H), 2.07 (tt, J = 7.6, 7.6 Hz, 2H). 13C-NMR
δ (ppm): 172.9 (C=O), 135.1 (Cq), 133.8 (Cq), 132.5 (Cq),
128.2, 127.9 (2 × CH), 126.4, 125.4, 125.3, 125.2, 125.1, 108.4, 57.2, 54.6, 45.2, 31.1, 17.4. Anal. Calcd.
For C29H28N2O: C, 82.82; H, 6.71; N, 6.66. Found: C, 82.90; H, 6.85; N, 6.48.
(E)-1-(3-((Naphthalen-1-ylmethyl)(3,4,5-trimethoxybenzyl)amino)prop-1-en-1-yl)pyrrolidin-2-one
(16e).
Following the strategy 1 for the formation of allylamines, the reaction of -aminoalcohol 15e (239 mg,
γ
0.50 mmol) and AlCl3 (68 mg, 0.51 mmol) in 4.0 mL of ACN afforded product 16e as a yellow oil.
Yield: 69% (159 mg). FT-IR (film): 3042, 2298, 2936, 2831, 1700, 1660, 1591, 1505, 1461, 1414, 1230, 1125,

Molecules 2018, 23, 520
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1
1009 cm−1. H-NMR
δ
(ppm): 8.36–8.31 (m, 1H), 7.87–7.81 (m, 1H), 7.76 (d, J = 8.4 Hz, 1H), 7.52–7.37
(m, 4H), 7.05 (d, J = 14.4 Hz, 1H), 6.49 (s, 2H), 4.99 (dt, J = 7.2, 14.4 Hz, 1H), 4.03 (s, 2H), 3.80 (s, 3H),
3.76 (s, 6H), 3.54 (s, 2H), 3.43 (t, J = 7.2 Hz, 2H), 3.22 (d, J = 6.8 Hz, 2H), 2.47 (t, J = 8.2 Hz, 2H), 2.08
(tt, J = 8.0, 8.0 Hz, 2H). 13C-NMR
δ (ppm): 173.0 (C=O), 152.9 (Cq), 136.5 (Cq), 135.8 (Cq), 135.2 (Cq),
133.9 (Cq), 132.4 (Cq), 128.4, 127.9, 127.5, 126.3, 125.4, 125.3, 125.1, 125.0, 108.3, 105.5, 60.7, 58.1, 57.1,
55.9, 54.5, 45.1, 31.1, 17.3. Anal. Calcd. For C28H32N2O4: C, 73.02; H, 7.00; N, 6.08. Found: C, 73.15;
H, 6.89; N, 6.23.
(E)-1-(3-Benzyl(3,4,5-trimethoxybenzyl)amino)prop-1-en-1-yl)pyrrolidin-2-one (16f). Following the strategy
1 for the formation of allylamines, the reaction of
(77 mg, 0.58 mmol) in 4.0 mL of ACN afforded product 16f as a yellow oil. Yield: 66% (149 mg).
FT-IR (film): 2942, 2838, 1704, 1659, 1594, 1166, 1124, 1034, 1009 cm–1. 1H-NMR
(ppm): 7.37 (d,
γ-aminoalcohol 15f (236 mg, 0.55 mmol) and AlCl3
δ
J = 6.8 Hz, 2H), 7.32 (t, J = 7.5 Hz, 2H), 7.24 (td, J = 1.9, 7.2 Hz, 1H), 7.04 (d, J = 14.5 Hz, 1H), 6.62
(s, 2H), 4.95 (dt, J = 7.0, 14.3 Hz, 1H), 3.87 (s, 6H), 3.83 (s, 3H), 3.59 (s, 2H), 3.53 (s, 2H), 3.46 (t, J = 7.2
Hz, 2H), 3.14 (dd, J = 1.8, 6.8 Hz, 2H), 2.48 (t, J = 8.2 Hz, 2H), 2.13–2.05 (m, 2H). 13C-NMR
δ (ppm):
173.0 (C=O), 153.1 (Cq), 139.6 (Cq), 136.7 (Cq), 135.5 (Cq), 128.7, 128.2, 126.8, 126.2, 108.6, 105.4, 60.8,
58.1, 57.9, 56.1, 53.9, 45.2, 31.2, 17.4. MS (70 eV, EI): m/z (%) 409 [M-1]+ (5), 300 (12), 124 (100), 181 (39),
91 (45) [PhCH2]+. Anal. Calcd. For C24H30N2O4: C, 70.22; H, 7.37; N, 6.82. Found: C, 70.35; H, 7.23;
N, 6.93.
(E)-1-(3-Methyl(naphthalen-1-ylmethyl)amino)prop-1-en-1-yl)pyrrolidin-2-one (16g). Following the strategy
1 for the formation of allylamines, the reaction of
(80 mg, 0.60 mmol) in 4.0 mL of ACN afforded product 16g as a yellow oil. Yield: 89% (149 mg).
FT-IR (film): 3045, 2976, 2942, 2878, 2785, 1701, 1660, 1406, 1337 cm−1 1H-NMR
(ppm): 8.28 (d,
J = 8.3 Hz, 1H), 7.86 (d, J = 8.0 Hz, 1H), 7.79 (dd, J = 1.4, 7.7 Hz, 1H), 7.57–7.51 (m, 1H), 7.51–7.46
m, 1H), 7.46–7.39 (m, 2H), 7.08 (d, J = 14.4 Hz, 1H), 5.06 (dt, J = 7.2, 14.4 Hz, 1H), 3.91 (s, 2H), 3.50
(t, J = 7.2 Hz, 2H), 3.18 (d, J = 7.3 Hz, 2H), 2.49 (t, J = 8.4 Hz, 2H), 2.25 (s, 3H), 2.08 (tt, J = 7.6, 7.6 Hz,
2H). 13C-NMR
(ppm): 173.0 (C=O), 134.8 (Cq), 133.8 (Cq), 132.3 (Cq), 128.3, 127.8, 127.3, 126.1, 125.7,
γ-aminoalcohol 15g (178 mg, 0.57 mmol) and AlCl3
.
δ
(
δ
125.4, 125.0, 124.4, 108.7, 59.8, 58.0, 45.1, 42.2, 31.1, 17.3. Anal. Calcd. For C19H22N2O: C, 77.52; H, 7.53;
N, 9.52. Found: C, 77.67; H, 7.64; N, 9.41.
(E)-1-(3-(Dibenzylamino)prop-1-enyl)pyrrolidin-2-one (16h). Following the strategy 1 for the formation of
allylamines, the reaction of γ-aminoalcohol 15h (172 mg, 0.51 mmol) and AlCl3 (69 mg, 0.52 mmol) in
4.0 mL of ACN afforded product 16h as a yellow oil. Yield: 94% (154 mg) (lit. [19], yellow oil).
(E)-1-(3-(Benzyl(methyl)amino)prop-1-enyl)pyrrolidin-2-one (16i). Following the strategy 1 for the
formation of allylamines, the reaction of γ-aminoalcohol 15i (134 mg, 0.51 mmol) and AlCl3 (69 mg,
0.52 mmol) in 4.0 mL of ACN afforded product 16i as a yellow oil. Yield: 64% (80 mg). FT-IR (film):
1
2927, 2885, 1701, 1665, 1589 cm−1. H-NMR
δ
(ppm): 7.31–7.22 (m, 5H), 7.01 (d, J = 14.6 Hz, 1H), 5.01
(dt, J = 7.2, 14.8 Hz, 1H), 3.51 (t, J = 7.8 Hz, 2H), 3.49 (s, 2H), 3.06 (d, J = 7.3 Hz, 2H), 2.48 (t, J = 8.2 Hz
,
2H), 2.18 (s, 3H), 2.15–2.07 (m, 2H). 13C-NMR
δ
(ppm): 173.1 (C=O), 138.9 (Cq), 129.1, 128.2, 127.0, 126.3,
108.7, 61.7, 57.5, 45.2, 41.9, 31.2, 17.4. MS (70 eV, EI): m/z (%) 243 [M-1]+ (7), 153 (63), 124 (100), 120 (26),
91 (56) [PhCH2]+, 69 (21). Anal. Calcd. For C15H20N2O: C, 73.74; H, 8.25; N, 11.47. Found: C, 73.85
H, 8.12; N, 11.62.
;
N-(4-Chlorobenzyl)-1-(4,5-dihydrofuran-3-yl)-N-(naphthalen-1-ylmethyl)methanamine (16k). Following the
strategy 1 for the formation of allylamines, the reaction of -aminoalcohol 15k (217 mg, 0.57 mmol)
γ
and AlCl3 (80 mg, 0.60 mmol) in 4.0 mL of ACN afforded product 16k as a yellow oil. Yield: 62%
1
(128 mg). FT-IR (film): 3045, 2921, 2888, 2853, 2799, 1663, 1489, 1090 cm-1. H-NMR
δ
(ppm): 8.26–8.21
(m, 1H), 7.90–7.85 (m, 1H), 7.79 (d, J = 8.0 Hz, 1H), 7.57 (d, J = 6.8 Hz, 1H), 7.53–7.48 (m, 2H), 7.47–7.42
(m, 1H), 7.28–7.26 (m, 4H), 6.29 (s, 1H), 4.35 (t, J = 9.4, Hz, 2H), 4.02 (s, 2H), 3.59 (s, 2H), 3.12 (s, 2H), 2.62
(t, J = 9.0 Hz, 2H). 13C-NMR
δ (ppm): 143.0, 138.2 (Cq), 135.0 (Cq), 133.8 (Cq), 132.4 (Cq), 132.3 (Cq),

Molecules 2018, 23, 520
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130.1, 128.4, 128.2, 127.7, 126.9, 125.5, 125.4, 125.2, 124.4, 112.3 (Cq), 70.3, 57.6, 56.7, 50.2, 31.8. Anal.
Calcd. For C23H22ClNO: C, 75.92; H, 6.09; N, 3.85. Found: C, 76.05; H, 5.99; N, 4.01.
3.2.4. General Procedure for the Synthesis of the γ-Aminoalcohols 19 and 20
(i) Synthesis of the β-aminoketones 18. A mixture of amine 13 (500 mg, 1.0 mmol) and the suitable
3-(N,N-dimethylamino)propiophenone hydrochloride 17 (1.0 mmol) was dissolved in a mixture
of 1,4-dioxane (5 mL) and TEA (1 mL). The solution was stirred at reflux for 0.5–2 h until the
starting materials were not further detected by TLC. After cooling, the solvent was removed under
reduced pressure and the crude was extracted from an aqueous solution with EtOAc (2
The combined organic layers were dried with anhydrous Na2SO4 and the solvent was removed under
×
5 mL).
reduced pressure. Ketones 18 were used without further purification for the reduction step.
(ii) Synthesis of the γ-aminoalcohols 19 and 20. Residue of the β-aminoketone 18 was re-dissolved in
methanol (5 mL) and subjected to reduction by following a similar procedure than the above described
for the synthesis of the starting secondary amines 13. After reaction was completed (TLC control),
the crude was purified by column chromatography on silica gel, using a mixture of CH2Cl2:MeOH
(20:1) as eluent.
3-(Methyl(naphthalen-1-ylmethyl)amino)propan-1-one (18a). Following the general procedure for the
formation of
β-aminoketones, the reaction of N-methyl-1-(naphthalen-1-yl)methanamine (13g,
453 mg, 3.01 mmol) and 1-(phenyl)-3-(N,N-dimethylamino)propan-1-one hydrochloride (17a, 750 mg,
3.51 mmol) in a mixture of 1,4-dioxane (5.0 mL) and TEA (1.0 mL) afforded compound 18a as an orange
solid (168 mg, 21% yield). M.p. = 88–90 ◦C (amorphous) (lit. [10], 55%).
1-(4-Bromophenyl)-3-(methyl(naphthalen-1-ylmethyl)amino)propan-1-one
(
18b).
Following the
general procedure for the formation of
β-aminoketones, the reaction of N-methyl-1-
(naphthalen-1-yl)methanamine 13g (515 mg,
3.01 mmol) and 1-(4-bromophenyl)-3-
(N,N-dimethylamino)propan-1-one hydrochloride (17b, 875 mg, 2.99 mmol) in a mixture of
1,4-dioxane (5.0 mL) and TEA (1.0 mL) afforded compound 18b as a yellow solid (518 mg, 45% yield).
◦
M.p. = 55–57 C (amorphous). FTIR (KBr): 3060, 2947, 2840, 2794, 1685 (C=O), 1584, 1069 cm−1
.
1H-NMR
(m, 4H), 7.41–7.37 (m, 2H), 3.94 (s, 2H), 3.11 (t, J = 7.2 Hz, 2H), 2.96 (t, J = 7.2 Hz, 2H), 2.33 (s, 3H).
13C-NMR
(ppm): 198.4 (C=O), 135.4 (Cq), 134.4 (Cq), 133.8 (Cq), 132.3 (Cq), 131.6, 129.4, 128.3, 128.0,
δ (ppm): 8.23–8.19 (m, 1H), 7.87–7.83 (m, 1H), 7.80–7.75 (m, 1H), 7.68–7.64 (m, 2H), 7.51–7.45
δ
127.9 (Cq), 127.3, 125.7, 125.5, 124.9, 124.6, 61.0, 52.7, 42.3, 37.0. Anal. Calcd. For C21H20BrNO: C, 65.98;
H, 5.27; N, 3.66. Found: C, 66.12; H, 5.35; N, 3.73.
1-(Benzo[d][1,3]dioxol-5-yl)-3-(methyl(naphthalen-1-ylmethyl)amino)propan-1-one (18c).
Following
the general procedure for the formation of -aminoketones, the reaction of N-methyl-1-
β
(naphthalen-1-yl)methanamine (13g, 527 mg, 3.08 mmol) and 1-(benzo[d][1,3]dioxol-5-yl)-3-
(N,N-dimethylamino)- propan-1-one hydrochloride (17c, 799 mg, 3.10 mmol) in a mixture of
1,4-dioxane (5.0 mL) and TEA (1.0 mL) afforded compound 18c as a yellow solid (567 mg, 53% yield).
M.p. = 91–92 ◦C (amorphous). FTIR (KBr): 3045, 2981, 2950, 2904, 2795, 2764, 1669 (C=O), 1601, 1503,
1256, 1036 cm−1
7.51–7.36 (m, 6H), 6.77 (d, J = 8.0 Hz, 1H), 6.03 (s, 2H, OCH2O), 3.95 (s, 2H), 3.11 (t, J = 7.2 Hz, 2H),
2.96 (t, J = 7.2 Hz, 2H), 2.30 (s, 3H). 13C-NMR
(ppm): 197.6 (C=O), 151.5 (Cq), 148.0 (Cq), 134.6 (C),
. δ (ppm): 8.27–8.22 (m, 1H), 7.86–7.82 (m, 1H), 7.77 (d, J = 6.8 Hz, 1H),
1H-NMR
δ
133.8 (Cq), 132.4 (Cq), 131.8 (Cq), 128.3, 127.9, 127.4, 125.7, 125.5, 125.0, 124.7, 124.2, 107.8, 107.7, 101.7
(OCH2O), 61.0, 53.2, 42.2, 36.7. Anal. Calcd. For C22H21NO3: C, 76.06; H, 6.09; N, 4.03. Found: C, 76.21;
H, 6.25; N, 3.86.
3-(Methyl(naphthalen-1-ylmethyl)amino)-1-(3,4,5-trimethoxyphenyl)propan-1-one (18d).
the general procedure for the formation of -aminoketones, the reaction of N-methyl-1-
(naphthalen-1-yl)methanamine 13g 498 mg, 2.91 mmol) and 3-(N,N-dimethylamino)-1-
Following
β
(
,

Molecules 2018, 23, 520
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(3,4,5-trimethoxy- phenyl)propan-1-one hydrochloride (17d, 896 mg, 2.95 mmol) in a mixture
of 1,4-dioxane (5.0 mL) and TEA (1.0 mL) afforded compound 18d as a yellow solid (572 mg, 50%
yield). M.p. = 94 ◦C (amorphous). FTIR (KBr): 3045, 2940, 2835, 2794, 1676 (C=O), 1584, 1504, 1459,
1
1412, 1336, 1126, 1003 cm−1. H NMR
δ (ppm): 8.25–8.20 (m, 1H), 7.85–7.80 (m, 1H), 7.76 (d, J = 7.6 Hz,
1H), 7.76 (d, J = 7.6 Hz, 1H), 7.49–7.35 (m, 4H), 7.12 (s, 2H), 3.96 (s, 2H), 3.91 (s, 3H), 3.84 (s, 6H), 3.13 (t,
J = 7.2 Hz, 2H), 2.98 (t, J = 7.2 Hz, 2H), 2.34 (s, 3H). 13C-NMR
δ
(ppm): 198.2 (C=O), 152.9 (Cq), 142.4
(Cq), 134.5 (Cq), 133.8 (Cq), 132.3 (Cq), 132.1 (Cq), 128.3, 127.9, 127.3, 125.7, 125.5, 125.0, 124.6, 105.4,
61.1, 60.8 (OCH3), 56.1 (OCH3), 53.2, 42.4, 36.9. Anal. Calcd. For C24H27NO4: C, 73.26; H, 6.92; N, 3.56.
Found: C, 73.41; H, 6.87; N, 3.67.
(
±
)-3-(N-Methyl-N-((naphthalen-5-yl)methyl)amino)-1-phenylpropan-1-ol (19a). Following the general
procedure for the formation of -aminoalcohols, the reaction of -aminoketone 18a (394 mg, 1.30 mmol)
γ
β
and NaBH4 (98 mg, 2.60 mmol) in 5.0 mL of MeOH afforded compound 19a as a yellow solid. Yield: 93%
(369 mg). M.p. = 75–76 ◦C (lit. [18], 76–77 ◦C).
(
±
)-1-(4-Bromophenyl)-3-(methyl(naphthalen-1-ylmethyl)amino)propan-1-ol (19b). Following the general
procedure for the formation of -aminoalcohols, the reaction of -aminoketone 18b (510 mg, 1.34 mmol)
and NaBH4 (101 mg, 2.68 mmol) in 5.0 mL of MeOH afforded compound 19b as a yellow oil.
γ
β
Yield: 83% (427 mg). FTIR (film): 3374, 3046, 2948, 2801, 1593, 1509, 1485, 1463, 1072, 1048, 1009 cm−1
.
1H-NMR δ (ppm): 8.18 (d, J = 8.8 Hz, 1H), 7.91 (d, J = 8.0 Hz, 1H), 7.85 (d, J = 8.0 Hz, 1H), 7.63–7.58
(m, 1H), 7.56–7.51 (m, 1H), 7.46–7.38 (m, 2H), 7.31 (d, J = 8.4 Hz, 2H), 6.95 (d, J = 8.4 Hz, 2H), 6.19 (br s,
1H, OH), 4.74 (dd, J = 3.2, 7.6 Hz, 1H), 4.03 (d, J = 12.8 Hz, 1H), 3.86 (d, J = 12.8 Hz, 1H), 2.80–2.72
(m, 1H), 2.69–2.62 (m, 1H), 2.40 (s, 3H), 1.96–1.88 (m, 1H), 1.86–1.75 (m, 1H). 13C-NMR
δ (ppm):
143.8 (Cq), 133.9 (Cq), 133.3 (Cq), 132.3 (Cq), 131.0, 128.6, 128.4, 128.1, 127.2, 126.3, 125.9, 125.1, 123.9,
120.3 (Cq), 74.5, 61.2, 55.6, 42.2, 34.3. Anal. Calcd. For C21H22BrNO: C, 65.63; H, 5.77; N, 3.64. Found:
C, 65.70; H, 5.86; N, 3.58.
(
±
)-1-(Benzo[d][1,3]dioxol-5-yl)-3-(methyl(naphthalen-1-ylmethyl)amino)propan-1-ol (19c). Following the
general procedure for the formation of -aminoalcohols, the reaction of -aminoketone 18c (495 mg,
γ
β
1.42 mmol) and NaBH4 (108 mg, 2.85 mmol) in 5.0 mL of MeOH afforded compound 19c as a white
solid. Yield: 93% (461 mg). M.p. = 96–98 ◦C. FT-IR (KBr): 3373, 3045, 2948, 2886, 2841, 2800, 1599,
1
1503, 1486, 1441, 1241, 1039 cm−1. H-NMR
δ
(ppm): 8.21 (d, J = 8.4 Hz, 1H), 7.90 (d, J = 8.0 Hz, 1H),
7.86–7.81 (m, 1H), 7.64–7.58 (m, 1H), 7.55–7.50 (m, 1H), 7.47–7.41 (m, 2H), 6.74 (d, J = 1.2 Hz, 1H), 6.68
(d, J = 8.0 Hz, 1H), 6.61 (dd, J = 1.2, 7.8 Hz, 1H), 5.98 (br s, 1H, OH), 5.91 (s, 2H), 4.72 (dd, J = 5.6, 5.6 Hz,
1H), 3.99 (d, J = 12.8 Hz, 1H), 3.93 (d, J = 12.8 Hz, 1H), 2.86–2.78 (m, 1H), 2.70–2.63 (m, 1H), 2.37 (s, 3H),
1.90–1.84 (m, 2H). 13C-NMR
δ (ppm): 147.4 (Cq), 147.4 (Cq), 146.2 (Cq), 139.0 (Cq), 133.9 (Cq), 133.4
(Cq), 132.3 (Cq), 128.6, 128.4, 127.9, 126.3, 125.8, 125.1, 123.9, 118.6, 107.8, 106.2, 100.7, 75.1, 61.1, 56.2,
42.1, 34.8. Anal. Calcd. For C22H23NO3: C, 75.62; H, 6.63; N, 4.01. Found: C, 75.70; H, 6.75; N, 4.15.
(
±
)-3-(Methyl(naphthalen-1-ylmethyl)amino)-1-(3,4,5-trimethoxyphenyl)propan-1-ol (19d). Following the
general procedure for the formation of -aminoalcohols, the reaction of -aminoketone 18d (520 mg,
γ
β
1.32 mmol) and NaBH4 (100 mg, 2.64 mmol) in 5.0 mL of MeOH afforded compound 19d as a yellow
oil. Yield: 90% (470 mg). FT-IR (film): 3414, 3050, 2940, 2834, 1592, 1506, 1461, 1417, 1232, 1182, 1126,
1
1009 cm−1. H-NMR
δ
(ppm): 8.22 (d, J = 8.4 Hz, 1H), 7.88 (d, J = 8.0 Hz, 1H), 7.82 (dd, J = 1.8, 7.0 Hz,
1H), 7.61–7.56 (m, 1H), 7.54–7.42 (m, 3H), 6.56 (s, 2H), 6.07 (br s, 1H, OH), 4.72 (dd, J = 2.4, 9.0 Hz, 1H),
4.01 (d, J = 13.0 Hz, 1H), 3.96 (d, J = 13.0 Hz, 1H), 3.83 (s, 9H), 2.99–2.90 (m, 1H), 2.74–2.65 (m, 1H),
2.36 (s, 3H), 2.01–1.88 (m, 1H), 1.87–1.79 (m, 1H). 13C-NMR
δ (ppm): 153.0 (Cq), 140.7 (Cq), 136.7 (Cq),
133.8 (Cq), 133.4 (Cq), 132.2 (Cq), 128.6, 128.30, 127.8, 126.2, 125.7, 125.1, 123.8, 102.4, 75.5, 61.0, 60.7,
56.9, 56.0, 43.0, 35.0. Anal. Calcd. For C24H29NO4: C, 72.89; H, 7.39; N, 3.54. Found: C, 72.95; H, 7.50;
N, 3.42.
(
±
)-1,10-(1,4-Phenylene)bis(3-(methyl(naphthalen-1-ylmethyl)amino)propan-1-ol (19e). Following the
general procedure for the formation of -aminoalcohols, the reaction of -aminoketone 18e (481 mg,
γ
β

Molecules 2018, 23, 520
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0.91 mmol) and NaBH4 (69 mg, 1.82 mmol) in 5.0 mL of MeOH afforded compound 19e as a yellow oil.
Yield: 80% (388 mg). FT-IR (film): 3363, 3048, 2948, 2841, 2800, 1463, 1129, 1076, 1049, 1021 cm−1
1H-NMR
(ppm): 8.21 (d, J = 8.0 Hz, 2H), 7.88 (d, J = 8.0 Hz, 2H), 7.85–7.79 (m, 2H), 7.63–7.56 (m, 2H),
.
δ
7.54–7.48 (m, 2H), 7.46–7.39 (m, 4H), 7.06 (s, 2H), 7.05 (s, 2H), 5.89 (br s, 2H, OH), 4.80–4.74 (m, 2H),
3.99 (d, J = 13.1 Hz, 1H), 3.99 (d, J = 12.8 Hz, 1H), 3.92 (d, J = 13.1 Hz, 1H), 3.92 (d, J = 12.8 Hz, 1H),
2.85–2.76 (m, 2H), 2.69–2.61 (m, 2H), 2.36 (s, 6H), 1.93–1.85 (m, 4H). 13C-NMR
δ (ppm): 143.3 (Cq),
133.9 (Cq), 133.5 (Cq), 132.3 (Cq), 128.6, 128.3, 127.9, 126.3, 125.8, 125.2, 125.1, 124.0, 75.0, 61.1, 56.3,
42.1, 34.7. Anal. Calcd. For C36H40N2O2: C, 81.17; H, 7.57; N, 5.26. Found: C, 81.26; H, 7.65; N, 5.01.
(
±
)-3-Benzyl(2-hydroxyethyl)amino)-1-phenylpropan-1-ol (20a). Following the general procedure for the
formation of -aminoalcohols, the reaction of -aminoketone 23a (521 mg, 1.84 mmol) and NaBH4
γ
β
(139 mg, 3.68 mmol) in 5.0 mL of MeOH afforded compound 20a as a yellow oil. Yield: 94% (494 mg).
1
FT-IR (film): 3396, 2943, 2827, 1603, 1129, 1059, 1031 cm−1. H-NMR
δ
(ppm): 7.39–7.22 (m, 10H), 4.84
(dd, J = 3.5, 8.8 Hz, 1H), 3.81 (d, J = 13.3 Hz, 1H), 3.75–3.64 (m, 2H), 3.55 (d, J = 13.1 Hz, 1H), 2.86 (ddd,
J = 4.5, 8.8, 13.2 Hz, 1H), 2.79–2.69 (m, 3H), 2.61 (ddd, J = 4.4, 5.7, 13.3 Hz, 1H), 1.89–1.82 (m, 2H), OH
is absent. 13C-NMR
δ (ppm): 144.6 (Cq), 137.9 (Cq), 129.3, 128.6, 128.3, 127.5, 127.2, 125.6, 74.9, 59.9,
59.6, 56.2, 52.8, 35.3. Anal. Calcd. For C18H23NO2: C, 72.76; H, 8.12; N, 4.91. Found: C, 72.85; H, 8.01;
N, 5.06.
(
±
)-2-Benzyl(2-hydroxyethyl)amino)-1-(4-methoxyphenyl)propan-1-ol (20f).
Following the general
procedure for the formation of -aminoalcohols, the reaction of -aminoketone 23f (530 mg, 1.69 mmol)
γ
β
and NaBH4 (128 mg, 3.38 mmol) in 5.0 mL of MeOH afforded compound 20f as a yellow solid. Yield:
1
87% (464 mg). M.p. = 68–69 ◦C. FT-IR (KBr): 3375, 2949, 2835, 1611, 1176, 1130, 1034 cm−1. H-NMR
δ
(ppm): 7.37–7.29 (m, 5H), 7.23 (d, J = 8.8 Hz, 2H), 6.85 (d, J = 8.5 Hz, 2H), 5.52 (br s, 1H, OH), 4.78 (dd,
J = 3.3, 8.6 Hz, 1H), 3.80 (s, 3H), 3.80 (d, J = 13.1 Hz, 1H), 3.73–3.63 (m, 2H), 3.54 (d, J = 13.1 Hz, 1H),
2.87–2.67 (m, 4H), 2.59 (ddd, J = 5.1, 5.1, 13.1 Hz, 1H), 1.98–1.88 (m, 1H), 1.77–1.85 (m, 1H). 13C-NMR
δ
(ppm): 158.7 (Cq), 137.9 (Cq), 136.8 (Cq), 129.2, 128.5, 127.4, 126.7, 113.6, 74.4, 59.8, 59.5, 56.1, 55.2,
52.7, 35.2. Anal. Calcd. For C19H25NO3: C, 72.35; H, 7.99; N, 4.44. Found: C, 72.51; H, 8.10; N, 4.60.
3.2.5. General Procedure for the Synthesis of Allylamines 21 and 22
A mixture of the
reflux during 2–3 h. After reaction finished (TLC control), the mixture was neutralized with 5N NaOH
until pH = 8. Then, solution was extracted with EtOAc (3 5 mL), the combined organic layers were
γ-aminoalcohol 19 and 20 (300 mg) and 5N HCl solution (5 mL) was stirred at
×
dried with anhydrous Na2SO4 and the solvent was removed under reduced pressure. Crudes were
purified by column chromatography on silica gel, using a mixture of CHCl3:MeOH (40:1) as eluent.
(E)-N-Methyl-N-(naphthalen-1-ylmethyl)-3-phenylprop-2-en-1-amine (21a), naftifine. Following the
strategy 2 for the formation of allylamines, the reaction of γ-aminoalcohol 19a (310 mg, 1.01 mmol)
and 5N HCl solution (5.0 mL) afforded compound 21a as a yellow oil (lit. [10] 94%, lit. [11] 82%,
lit. [12], 68%). Yield: 90% (310 mg). FT-IR (film): 3028, 2943, 2835, 2786, 1596, 1509, 1451, 1362, 1127,
1
1013 cm−1. H-NMR
δ
(ppm): 8.36 (d, J = 8.4 Hz, 1H), 7.90 (d, J = 7.6 Hz, 1H), 7.83 (d, J = 8.0 Hz, 1H),
7.62–7.43 (m, 6H), 7.37 (t, J = 7.2 Hz, 2H), 7.32–7.25 (m, 1H), 6.63 (d, J = 15.6 Hz, 1H), 6.43 (td, J = 6.4,
15.6 Hz, 1H), 4.01 (s, 2H), 3.34 (d, J = 6.0 Hz, 2H), 2.34 (s, 3H). 13C-NMR
δ
(ppm): 137.1 (Cq), 134.8 (Cq),
133.9 (Cq), 132.7, 132.5 (Cq), 128.5, 128.4, 127.9, 127.5, 127.4, 127.3, 126.3, 125.8, 125.5, 125.1, 124.6, 60.3,
60.1, 42.4. Anal. Calcd. For C21H21N: C, 87.76; H, 7.37; N, 4.87. Found: C, 87.83; H, 7.45; N, 4.95.
(E)-3-(4-Bromophenyl)-N-methyl-N-(naphthalen-1-ylmethyl)prop-2-en-1-amine (21b).
Following the
strategy 2 for the formation of allylamines, the reaction of -aminoalcohol 19b (301 mg, 0.78 mmol)
γ
and 5N HCl solution (5.0 mL) afforded compound 21b as a yellow solid. Yield: 81% (231 mg).
M.p. = 55–57 ◦C (lit. [35], 84%).

Molecules 2018, 23, 520
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(E)-3-(Benzo[d][1,3]dioxol-5-yl)-N-methyl-N-(naphthalen-1-ylmethyl)prop-2-en-1-amine (21c). Following the
strategy 2 for the formation of allylamines, the reaction of -aminoalcohol 19c (325 mg, 0.93 mmol)
γ
and 5N HCl solution (5.0 mL) afforded compound 21c as a yellow oil. Yield: 90% (277 mg). FT-IR
1
(film): 3040, 2979, 2943, 2885, 2835, 2783, 1600, 1487, 1443, 1249, 1039 cm−1. H-NMR
δ
(ppm): 8.33
(d, J = 8.0 Hz, 1H), 7.88 (d, J = 7.6 Hz, 1H), 7.80 (d, J = 7.6 Hz, 1H), 7.58–7.41 (m, 4H), 6.98 (d, J = 1.2 Hz
1H), 6.84 (dd, J = 1.2, 8.0 Hz, 1H), 6.78 (d, J = 8.0 Hz, 1H), 6.51 (d, J = 16.0 Hz, 1H), 6.22 (td, J = 6.8,
15.6 Hz, 1H), 5.98 (s, 2H, OCH2O), 3.96 (s, 2H), 3.28 (d, J = 6.0 Hz, 2H), 2.30 (s, 3H). 13C-NMR
(ppm):
,
δ
148.0 (Cq), 147.0 (Cq), 134.9 (Cq), 133.9 (Cq), 132.5 (Cq), 132.2, 131.6 (Cq), 128.4, 127.9, 127.4, 125.8,
125.7, 125.5, 125.1, 124.6, 120.8, 108.2, 105.7, 101.0, 60.3, 60.0, 42.4. Anal. Calcd. For C22H21NO2: C,
79.73; H, 6.39; N, 4.23. Found: C, 79.90; H, 6.45; N, 4.05.
(E)-N-Methyl-N-(naphthalen-1-ylmethyl)-3-(3,4,5-trimethoxyphenyl)prop-2-en-1-amine (21d). Following the
strategy 2 for the formation of allylamines, the reaction of γ-aminoalcohol 19d (314 mg, 0.79 mmol)
and 5N HCl solution (5.0 mL) afforded compound 21d as a yellow oil. Yield: 70% (209 mg). FT-IR
1
(film): 3041, 2938, 2834, 2786, 1581, 1505, 1457, 1416, 1331, 1239, 1126, 1011 cm−1. H-NMR
δ
(ppm):
8.33 (d, J = 8.4 Hz, 1H), 7.88 (d, J = 7.6 Hz, 1H), 7.80 (d, J = 7.6 Hz, 1H), 7.59–7.41 (m, 4H), 6.64 (s, 2H),
6.52 (d, J = 15.6 Hz, 1H), 6.29 (td, J = 6.8, 15.6 Hz, 1H), 3.98 (s, 2H), 3.89 (s, 6H), 3.87 (s, 3H), 3.30 (d,
J = 6.4 Hz, 2H), 2.32 (s, 3H). 13C-NMR
δ (ppm): 153.2 (Cq), 137.6 (Cq), 134.7 (Cq), 133.8 (Cq), 132.8 (Cq),
132.4 (Cq), 132.4, 128.4, 127.9, 127.4, 127.2, 125.8, 125.5, 125.1, 124.5, 103.3, 60.8, 60.3, 60.2, 56.0, 42.5.
Anal. Calcd. For C24H27NO3: C, 76.36; H, 7.21; N, 3.71. Found: C, 76.45; H, 7.10; N, 3.86.
(E)-N-Methyl-3-(4-((E)-3-(methyl(naphthalen-1-ylmethyl)amino)prop-1-en-1-yl)phenyl)-N-(naphthalen-2-
ylmethyl)prop-2-en-1-amine (21e). Following the strategy 2 for the formation of allylamines, the reaction
of
a yellow oil. Yield: 78% (213 mg). FT-IR (film): 3042, 2943, 2834, 2785, 1596, 1509, 1456, 1013 cm−1
1H-NMR
(ppm): 8.36 (d, J = 8.4 Hz, 2H), 7.90 (d, J = 8.4 Hz, 2H), 7.83 (d, J = 8.0 Hz, 2H), 7.61–7.44
(m, 8H), 7.39 (s, 4H), 6.61 (d, J = 16.0 Hz, 2H), 6.42 (td, J = 6.8, 16.0 Hz, 2H), 3.33 (d, J = 6.8 Hz, 4H), 4.00
(s, 4H), 2.33 (s, 6H). 13C-NMR
(ppm): 136.2 (Cq), 134.8 (Cq), 133.9 (Cq), 132.5 (Cq), 132.3, 128.4, 127.9,
127.4 ( 2C), 126.5, 125.8, 125.5, 125.1, 124.6, 60.4, 60.1, 42.4. Anal. Calcd. For C36H36N2: C, 87.05;
γ-aminoalcohol 19e (295 mg, 0.55 mmol) and 5N HCl solution (5.0 mL) afforded compound 21e as
.
δ
δ
×
H, 7.31; N, 5.64. Found: C, 87.22; H, 7.44; N, 5.45.
(E)-2-(Benzyl(cinnamyl)amino)ethan-1-ol (22a). Following the strategy 2 for the formation of allylamines,
the reaction of
compound 22a as a yellow oil. Yield: 70% (217 mg). FT-IR (film): 3424, 2944, 2880, 1599, 1580, 1127,
1053, 1028 cm−1 1H-NMR
(ppm): 7.42–7.25 (m, 10H), 6.55 (d, J = 16.0 Hz, 1H), 6.29 (td, J = 6.8,
16.0 Hz, 1H), 3.73 (s, 2H), 3.65 (t, J = 5.4 Hz, 2H), 3.34 (dd, J = 1.0, 6.8 Hz, 2H), 2.76 (t, J = 5.4 Hz, 2H),
2.43 (br s, 1H, OH). 13C-NMR
(ppm): 138.7 (Cq), 136.8 (Cq), 133.2, 129.0, 128.5, 128.4, 127.5, 127.2,
γ-aminoalcohol 20a (331 mg, 1.16 mmol) and 5N HCl solution (5.0 mL) afforded
.
δ
δ
126.5, 126.3, 58.6, 58.2, 56.0, 54.8. Anal. Calcd. For C18H21NO: C, 80.86; H, 7.92; N, 5.24. Found: C,
80.97; H, 8.04; N, 5.33.
(E)-2-(Benzyl(3-(4-methoxyphenyl)allyl)amino)ethan-1-ol (22f). Following the strategy 2 for the formation
of allylamines, the reaction of γ-aminoalcohol 20f (319 mg, 1.01 mmol) and 5N HCl solution (5.0 mL)
afforded compound 22f as a colorless oil. Yield: 68% (204 mg) (lit. [36], yellow oil).
3.3. Antifungal Evaluation
3.3.1. Microorganisms and Media
For the antifungal evaluation, standardized strains from the American Type Culture Collection
(ATCC), Rockville, MD, USA, and CEREMIC (CCC), Centro de Referencia en Micología, Facultad
de Ciencias Bioquímicas y Farmacéuticas, Suipacha 531-(2000)-Rosario, Argentina, were used:
C. albicans ATCC 10231, S. cerevisiae ATCC 9763, C. neoformans ATCC 32264, Aspergillus flavus
ATCC 9170, Aspergillus fumigatus ATTC 26934, Aspergillus niger ATCC 9029, Trichophyton rubrum

Molecules 2018, 23, 520
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CCC 113, Trichophyton mentagrophytes ATCC 9972, and Microsporum gypseum CCC 115. Strains
◦
were grown on Sabouraud-chloramphenicol agar slants for 48 h at 30 C, maintained on slopes
of Sabouraud-dextrose agar (SDA, Oxoid, Cambridge, UK), and subcultured every 15 days to prevent
pleomorphic transformations. Inocula of cell or spore suspensions were obtained according to reported
procedures [26,27] and adjusted to 1–5 × 103 cells/spores with colony forming units (CFU)/mL.
3.3.2. Antifungal Susceptibility Testing
Minimum inhibitory concentration (MIC) of each compound was determined by using broth
microdilution techniques according to the guidelines of the Clinical and Laboratory Standards
Institute for yeasts (M27-A3) [26] and for filamentous fungi (including dermatophytes) (M38-A2) [27].
MIC values were determined in RPMI-1640 (Sigma-Aldrich) buffered to pH 7.0 with MOPS. Microtiter
◦
◦
trays were incubated at 35 C for yeasts and Aspergillus spp. and at 28–30 C for dermatophyte
strains in a moist, dark chamber, and MICs were visually recorded at 48 h for yeasts, and at a time
according to the control fungus growth, for the rest of fungi. For the assay, stock solutions of pure
compounds were two-fold diluted with RPMI from 250 to 1.0
3.9, 2.0, 1.0 and 0.5 g/mL) (final volume = 100 L) and a final DMSO concentration
of 100 L of inoculum suspension was added to each well with the exception of the sterility control
µg/mL (=250, 125, 62.5, 31.3, 15.6, 7.8,
µ
µ
≤
1%. A volume
µ
where sterile water was added to the well instead. Terbinafine (obtained from the commercial drug
Lamisil from Novartis Co., Basel, Switzerland) and amphotericin B were used as positive controls.
Endpoints were defined as the lowest concentration of drug resulting in total inhibition (MIC100) of
visual growth compared to the growth in the control wells containing no antifungal drug. In addition
to MIC determinations, the evaluation of Minimum Fungicide Concentration (MFC) of each compound
against the fungal panel was accomplished by subculturing a sample of media from MIC tubes showing
no growth, onto drug-free agar plates.
3.3.3. Fungal Growth Inhibition Percentage Determination
Yeasts broth microdilution technique M27-A3 of CLSI [26] was performed in 96-well microplates.
For the assay, compound test wells (CTWs) were prepared with stock solutions of each compound
in DMSO (maximum concentration
250–3.9 An inoculum suspension (100
g/mL−1
in the well = 200 L). A growth control well (GCW) (containing medium, inoculum, and the
≤
1%), diluted with RPMI-1640, to final concentrations of
µ
.
µL) was added to each well (final volume
µ
same amount of DMSO used in a CTW, but compound-free) and sterility control well (SCW)
(sample, medium, and sterile water instead of inoculum) were included for each fungus tested.
Microtiter trays were incubated in a moist, dark chamber at 30 ◦C for 48 h for both yeasts.
Microplates were read in a VERSA Max microplate reader (Molecular Devices, Sunnyvale, CA,
USA). Amphotericin B was used as positive control. Tests were performed in triplicate. Reduction
of growth for each compound concentration was calculated as follows: % of inhibition = 100
−
(OD405 CTW − OD405 SCW)/(OD405 GCW − OD405 SCW). The means
±
SD (standard deviations)
were used for constructing the dose-response curves representing % inhibition vs. concentration of
each compound. Dose-response curves were constructed with SigmaPlot 11.0 software.
3.3.4. MIC100, MIC80 and MIC50 Determinations
Three endpoints were defined from the dose-response curves. Minimum Inhibitory concentration
(MIC) resulting in total fungal growth inhibition was named MIC100, while MIC80 and MIC50 were
defined as the minimum concentration that inhibits 80% or 50% of the fungal growth, respectively.
4. Conclusions
In summary, we have developed two efficient and straightforward approaches for the synthesis
of naftifine and diversely substituted analogues 16 and 20 mediated by a Mannich-type reaction
in at least one step of each approach. Strategy 1 involved a two-step (both Mannich- and

Molecules 2018, 23, 520
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aza-Prins- combined reactions) sequence, mediated by an uncatalyzed three-component Mannich-type
reaction leading to -aminoalcohols 15 as the key intermediates for allylamines 16. Particularly,
γ
we were able to obtain naftifine in a one-pot fashion through Strategy 1 starting from styrene. Although
naftifine was isolated in a relatively lower yield than in previous approaches, remarkably, this strategy
represents the first direct method for the synthesis of this antifungal compound. Strategy 2 consisted
in a three-step sequence involving a one-pot synthesis of the
intermediates for allylamines 21 and 22. In general, naftifine and the target products 16
γ
-aminoalcohols 19 and 20 as the key
21 and 22 were
,
obtained in good to excellent yields after their corresponding dehydration processes catalyzed whether
by Brønsted or Lewis acids like H2SO4, HCl and AlCl3, respectively. The synthesized compounds
were tested for antifungal properties against a panel of clinically important fungi. Most compounds
were inactive against Aspergillus spp., while showed relevant activities against the dermatophytes
T. rubrum and T. mentagrophytes. The most active compounds 18b and 18c possessed a
structure, and among them, compounds 18b 18c and 21c were 4-Br (18b) or 3,4-methylenedioxy
(18c and 21c) substituted in their R1 groups. Interesting enough, 18b displayed high activities also
against yeasts, with a MIC80 against C. neoformans and C. albicans of 7.8 g/mL. This is a relevant low
β-aminoketo
,
µ
value that positions 18b as a good hit candidate for future research. In addition, 18b is fungicide rather
than fungistatic with MFC value of 15.6 µg/mL against C. neoformans.
1
Supplementary Materials: The supplementary materials are available online. Copies of H- and 13C-NMR
spectra for allylamines 16, 21 and 22 and naftifine are available online.
Acknowledgments: Authors thank COLCIENCIAS, Universidad del Valle-Project No. CI-7812, the Spanish
“Consejería de Innovación, Ciencia y Empresa, Junta de Andalucía” and “Centro de Instrumentación
Científico-Técnico de la Universidad de Jaén” for financial support. SZ and EB acknowledge ANPCyT for
funds PICT2014-1170 and CONICET for the fellowship to EB.
Author Contributions: R.A. designed the experiments; A.G. and J.C.C. performed the experiments; R.A., A.G.,
J.C.C., B.I., J.Q., M.N and J.C. analyzed the synthetic results, all spectral data and wrote the manuscript; E.B. and
S.Z. performed the antifungal evaluation, analyzed the antifungal results and helped to write the manuscript.
All authors read and approved the final manuscript.
Conflicts of Interest: The authors declare no conflict of interest.
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Sample Availability: Samples of the compounds are not available from the authors.
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