An efficient green protocol for the preparation of acetoacetamides and application of the methodology to a one-pot synthesis of Biginelli dihydropyrimidines. Expansion of dihydropyrimidine topological chemical space

Article abstract of DOI:10.1039/c5ra14355a

The present study describes the preparation of N-aryl-(15) and N-alkyl-(17) acetoacetamides, in good to excellent yields, using both conventional and microwave heating, by reaction of amine derivatives (14 and 16) with 2,2,6-trimethyl-4H-1,3-dioxin-4-one (TMD, 12) in aqueous medium. The acetoacetamides were used to prepare novel Biginelli dihydropyrimidine derivatives. The introduction of the amino acid derivatives potentially allows for the exploration of new structural complexity and topologically diversifies the chemical space occupied by this versatile chemical scaffold.

Full text of DOI:10.1039/c5ra14355a

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An efficient green protocol for the preparation of acetoacetamidDeOsI: 1a0.n10d39/C5RA14355A
application of the methodology to a one-pot synthesis of Biginelli
dihydropyrimidines. Expansion of dihydropyrimidine topological
chemical space.
Fernando H. S. Gama, Rodrigo O.M.A de Souza and Simon J. Garden*
Instituto de Química, Universidade Federal do Rio de Janeiro,
Centro de Tecnologia, Bloco A,
Cidade Universitária, 21949-909 Rio de Janeiro-RJ, Brazil
Contact information: garden@iq.ufrj.br, Tel.: 55-21-3893-7135
Graphical Abstract
A one pot synthesis of Biginelli dihydropyrimidines. The novel use of the aminoacids
allows topological diversification of the chemical space.
Keywords: acetylketene; acetoacetanilides; acetoacetamides; reaction in/on water;
Biginelli dihydropyrimidines; chemical space.
Abstract: The present study describes the preparation of N-aryl- (15) and N-alkyl-
(17) acetoacetamides, in good to excellent yields, using both conventional and
microwave heating, by reaction of amine derivatives (14 and 16) with 2,2,6-trimethyl-
4H-1,3-dioxin-4-one (TMD, 12) in aqueous medium. The acetoacetamides were used

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DOI: 10.1039/C5RA14355A
to prepare novel Biginelli dihydropyrimidine derivatives. The introduction of the
aminoacid derivatives potentially allows for the exploration of new structural
complexity and topologically diversifies the chemical space occupied by this versatile
chemical scaffold.

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DOI: 10.1039/C5RA14355A
1. Introduction
Derivatives of 1,3-dicarbonyl compounds have a long history in synthetic
organic chemistry and are important substrates in multicomponent reactions.1 One of
these multi-component reactions is the Biginelli reaction,2 the mechanism of which
continues to generate debate as it is highly reaction condition dependent.3 Although
this reaction has been known since the late 19th century, the Biginelli reaction
continues to attract the interest of many research groups around the world as this class
of compounds presents many interesting pharmacological/biological activities
including: cardiovascular 4,3f, 4 chemical modulators of heat shock protein 70 5,5 anti-
tumor 6,6 antioxidant 7,7 anti-inflammatory,8 antitubercular 8,9 antifungal 9,10
antimicrobial 10,11 and antiviral 11 properties12 (Figure 1).
The Biginelli reaction is very versatile and it can be carried out with many
variations in all three components providing an extensive number of 3,4-
dihydropyrimidin-2(1H)-one (or -thione) derivatives, which are also referred to as
DHPMs (Figure 1).2, 3g, 13 Numerous synthetic methodologies have been devised that
have principally focused upon reaction efficiency as a function of catalyst and
reaction conditions2i and more recently it has been recognized that the DHPM
scaffold is a highly functionalized substrate that can be readily applied to post-
condensation transformations.2f, 2h
Additionally, in recent years great advances have been made with respect to
the asymmetric synthesis of DHPMs.14 Recent examples of enantioselective DHPM
synthesis include the use of chiral covalently modified nanocomposites,15 double
axially chiral bis-phosphorylimides,16 chiral amines,17 chiral phosphoric acids,18 and a
chiral ytterbium complex19 as asymmetric catalysts. The enantiomers of racemic
DHPMs have been resolved by chemical or chiral chromatographic resolution20 or by
enzymatic methods,21 recent examples include the use of aminoacid derivatives,22 or
chiral sulfoxides23 as chiral auxiliary and chromatographic separation of the
diastereoisomers. (S)-Monastrol 6 was obtained by enantioselective enzymatic
hydrolysis of the butanoyl phenol esters24 and racemic acetates were resolved with an
immobilized lipase from Candida Antarctica.25

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Figure 1: Structurally diverse examples of DHPMs prepared in the last century.
Among the many different examples of DHPMs, the exocyclic amide
derivatives are also important (figure 1 for examples) and over the last 10 years, the
use of acetoacetamides in Biginelli reactions has increased.3g, 9a, 26 However, these
DHPMs are limited to simple amine derivatives, such as hydrazides and anilides.
Subsequent modification of the C5 position (the exocyclic carboxylic acid derivative)
is limited.2f, 2h This limitation suggests that in order to explore new chemical space2f, 27
around the DHPM scaffold that it is important to investigate the synthesis and use of
novel, or little known, acylacetamide derivatives which may be directly incorporated
into the Biginelli reaction. Further, in order to explore new chemical space based
upon the DHPM scaffold it is necessary to introduce more complex and topologically
diversified building blocks.28 Additionally, bearing in mind that the DHPMs already
occupy a drug-like and biologically active chemical space then the new building
blocks, for DHPM synthesis, should also posses similar characteristics and a diverse
set of building blocks should be readily available. One interesting possibility, amongst
many other options, is the use of acylacetamides derived from aminoacids or
peptides.29

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Thus the present study aimed to develop an environmentally DObIe: 1n0i.1g0n39/C5RA14355A
methodology for the synthesis of acetoacetamides in water starting from aniline or
aminoacid derivatives and a stable precursor of acetylketene. The synthetic
methodology was applied to a one-pot, four reagents, synthesis of novel DHPM
derivatives. The introduction of the exocyclic aminoacid groups introduces a new
spatial and topological complexity to the structures of the DHPMs.
2. Results and Discussion
The 2,2,6-trimethyl-4H-1,3-dioxin-4-one (TMD – 12) is a stable equivalent of
diketene which can be used to directly generate acetylketene 13 at temperatures above
900C, via a pseudo-retro-Diels-Alder reaction, eliminating acetone, or it can be
chemically modified so as to permit the synthesis of acylketene derivatives.30 The
synthesis of amides from the reaction of 12 with amines or anilines has typically
involved refluxing the substrates in toluene or xylene.31 A few exceptions include
refluxing in THF in the presence of NaOAc for 24 hours,32 heating in a mixture of
biphenyl and diphenyl ether,33 microwave heating in: THF/DMA,34 DMF,35 or in the
absence of solvent;36 or by conventional heating in the presence of the amine,37 or by
the use of dichlorobenzene as solvent.38
Initially we had prepared acetoacetanilides 15 by refluxing 12 and 14 in
toluene. However, 15 required chromatographic separation from their dehydrated
dimers, 4-pyridones.39 Therefore we sought a more efficient and chemoselective
preparation of 5. Given that the rate of decomposition of 12 becomes appreciable
above 90oC40 we decided to investigate the use of water as a solvent for the reaction.
The use of water could potentially introduce a competing nucleophile (water) for the
acetylketene. However, Birney et al.41 have shown that amines are kinetically more
reactive than alcohols in trapping acetylketene 13. Even if water were to compete
with the added amine/aniline, the product would be acetoacetic acid. This would
decompose under the reaction conditions to give acetone and CO2 and therefore
would not contaminate the desired acetoacetamide products (15 and 17). Besides this,
any competition between the water and amines for 13 could be offset by the use of an
excess of acetylketene precursor. The use of water as a medium for conducting
organic reactions has resulted in the discovery of a number of benefits despite the
apparent contradiction of the lack of solubility of the hydrophobic organic
substrates.42

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TMD (12, 1 equiv.) was added in a single portion to a gently DbOoI: i1l0i.1n0g39/C5RA14355A
solution/emulsion of 14a in water that was vigorously stirred in an open flask. With
the passage of time it was clear that 12 and 14a were being consumed and that
acetone was evolved from the reaction. After heating the reaction mixture for 1.5
hours, TLC analysis of a sample of the aqueous solution extracted with EtOAc
revealed the exclusive formation of 15a. The aqueous solution was hot filtered
through a cotton plug to remove a small quantity of an immiscible, dark, oil. On
cooling of the solution large colourless plates of 15a readily formed. The product 15a
was isolated in 84% yield (table 1). Subsequently, an improved procedure that
generally resulted in still higher product yields was developed. This involved the use
of an excess of TMD (1.5 equiv.s) and refluxing the reaction for 2.5 hours.
Subsequently, the reaction was allowed to cool and a sub-stoichiometric quantity of
2M aqueous HCl (0.8 equiv.s) was added which had the benefit of solubilizing any
unreacted aniline/dark oil as well as promoting the crystallization of the product 15a.
The products were isolated by filtration and no further purification was necessary
when using this procedure. Additionally, the reaction of 12 and 14a in water under
microwave irradiation at a controlled temperature of 1500C during 3 minutes gave an
equally good yield of 15a. Nonetheless, the conventional heating methodology in
water was successfully applied to a variety of substituted anilines where the
substituents span the range of electronic effects (a notable exception was p-
nitroaniline that formed product but readily hydrolyzed under the reaction conditions)
and sterically encumbered 2,6-dimethylaniline 14m which gave an excellent yield of
15m. The products were isolated by filtration and found to be of sufficient purity for
spectroscopic analysis, thus requiring no further purification (table 1). Additionally
secondary alky- and benzyl- anilines (14o-q) could also be employed as substrates to
give good yields of the tertiary N-alkyl- or benzyl- acetoacetanilides (15o-q). These
products were oils and were separated from the reaction medium by extraction and
filtered through a short column of silica to give the final purified product for
spectroscopic characterization. The reaction of 14q was also conducted in refluxing
xylenes from which an equivalent yield to the reaction in water was obtained (table
1).

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Table 1: Reactions of 12 with 14 conducted in water to give 15.
Product; yield (%) b,c
Lit. yield (%) [ref]
14 a
15
a All R = H
b R3 = Cl
(15a) 84,b 94,c 90 d
(15b) 77 b
(15c) 77,b 97 c
(15d) 78 b
(15e) 91 b
(15f) 74 b
(15g) 48,b 94 c
(15h) 75,b 80 c
(15i) 65,b 95 c
(15j) 76 b
70 e 31p ; 67 e 31f
52 e 31p
73 e 31f
31 h 31e
---
c R3 = OMe
d R3 = Me
e R3 = COOH
f R3 = Br
100 f 43
62 g 44
---
63 h 45
93 e 31p
94 e 31g
90 i 46
g R3 = F
h R1 = OMe; R3 = NO2
i R2 = Cl; R3 = OMe
j R2 = OMe
k R1 = OMe
l R2 = CF3
(15k) 64 b
(15l) 46,b 60 c
(15m) 49,b 97 c
(15n) 85 c
(15o) 74 c
(15p) 80 c
m R1;R4 = Me
n R2;R4 = OMe
o R5 = Me
---
97 e 31g, 47
85 e 48
90 j 49
35 j 49
p R5 = Et
q R5 = Bn
(15q) 60,c 64 e
a
b
all groups R=H unless otherwise indicated; Yield of crystallized product when using one equivalent
c
of TMD in relation to the aniline (reaction time 1.5 hours); Yield of crystallized product when using
d
1.5 equivalents of TMD in relation to the aniline (reaction time 2.5 hours); Yield of crystallized
e
product after microwave heating for 3 min at 1500C in water; aniline and TMD in refluxing xylenes
f
g
for 30 mins to 2h; using diketene in refluxing benzene for 10h; anilines and ethyl acetoacetate in
h
i
refluxing toluene for 10h; anilines and diketene in refluxing toluene for 10h; using diketene at room
j
temperature in HOAc solution with a quantity of HgSO4 as catalyst overnight; diketene added to
preheated aniline (90oC) in the absence of solvent for 1h.
In order to validate the efficiency of the aqueous methodology developed in
this study, the reaction of 12 with aniline was performed on a 0.10 mol scale.
Differently from the previous experiments 12 (0.15 mol) was added from a dropping
funnel over a period of 5 minutes to a gently boiling, rapidly stirred,

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solution/emulsion of aniline in a reduced volume of water (150 mL). The reaction
mixture was refluxed for 2.5 hours. The addition of TMD was purposefully regulated
so as to avoid the possibility of a very vigorous initial reaction due to the thermal
elimination of acetone as a consequence of the scale of the reaction and because of the
decreased volume of water in relation to the increased quantity of 14a. After the
heating period, the lightly coloured hot aqueous solution was quickly filtered through
a cotton wool plug in a preheated sintered glass funnel with the aid of an applied
vacuum. This resulted in the elimination of a small quantity of a dark immiscible oil.
The residue was washed with a small quantity of hot water and to the cooling filtrate
was added 3N HCl (0.9 equivalents/14a). This resulted in the precipitation of the
product 15a. On complete cooling the colourless crystals were isolated by filtration
and washed with water. After air drying a 93% yield of 15a (m.p. 81-3oC) was
obtained.
The successful application of the aqueous reaction methodology for the
preparation of 15 was extended to the use of aminoacid derivatives 16. Aminoacid
acetoacetamide derivatives 17 have been prepared by the reaction between diketene or
cyclobutane-1,3-dione under basic conditions in aqueous medium, and subsequently
used as building blocks in organic synthesis.31c, 50 One example of this strategy is the
synthesis of tetramic acids 20 (Scheme 1).50a, 50e, 50f
Scheme 1: Synthesis of a tetramic acid from an acetoacetylaminoacid derivative.
Thus, initially a mixture of two equivalents of 12 and L-tryptophan (16a) were
refluxed in water in the presence of a sub-stoichiometric quantity of K2CO3 (80
mol%) in order to neutralize the carboxylic acid group. After refluxing for 2 hours the
mixture was acidified (pH ~ 1) and extracted with EtOAc. The crude material was
purified by silica gel column chromatography eluting with CH2Cl2/EtOAc 50%, and
resulted in the desired product in quantitative yield of 17a. The same reaction
performed under microwave irradiation at a controlled temperature of 1500C during 5
minutes resulted in a 90% yield of 17a after the same isolation methodology.
Following these results, we tested the reactivity of other aminoacids and a few
aminoesters using the same synthetic method (no K2CO3 used in the latter case). In

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most cases the respective acetoacetamides were obtained in moderate to eDxOcIe: 1l0le.1n0V3ti9e/wCA5rRticAl1e4O3n5li5nAe
yields (17a-n) (Table 2). In general, conventional heating gave better yields of
products although the microwave heating method was not optimized. However, the
latter method provides good to excellent yields after only 5 minutes of heating.
Table 2: Acetoacetamide derivatives from L-amino acids and esters.
a,b
Product; yield (%)
a,b
Product; yield (%)
Reagent (16)
Reagent (16)
(17)
[Lit. Yield %]
(17)
a L-tryptophan
b L-leucine
c L-valine
(17a) 100,a 90b
(17b) 100,a 93b
(17c) 85,a 84b [50 50a
(17d) 75,a 86b
l
]
(17l) 77,a 40b
d L-methionine
e L-
(17e) 92,a 92b
(17f) 90,a 75b
m
phenylalanine
f L-
phenylglycine
g L-tyrosine
h L-cysteine
i Methyl L-
tryptophan
j Methyl L-
phenylalanine
k Methyl L-
phenylglycine
(17g) 72,a 45b
(17h) 42,a 50b
(17m) 76a
(17i) 100,a 70b [70 51
]
n
(17j) 84,a 65b [80 50b
]
(17n) 84a
(17k) 60,a 53b [60 31c
]
a
b
Yield for conventional heating in water, 2h reaction time; Yield for Microwave heating, 5 min.
reaction time.
With the successful preparation of 15 and 17 by the aqueous medium protocol,
it was envisaged that a one-pot process involving four different reagents for the
synthesis of Biginelli DHPMs, 12, 14 or 16, urea (2) and benzaldehyde derivatives
(1), could be developed. The one-pot methodology would in principle be more
efficient as it would eliminate manipulation and purification steps. Thus the one-pot
reaction was conducted in the following manner: firstly 15 or 17 were prepared as
previously described, the water was removed under reduced pressure, and secondly,

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to the residue were added 1, 2, and ethanol, along with a catalytic quantity of formic
acid. The reactions were refluxed overnight and after cooling the crude Biginelli
products 18 or 19 had precipitated. Precipitation was completed by the addition of
water and the products were isolated by filtration. Compounds 18 and 19 were
purified by recrystallization from EtOH. The Biginelli products 18 and 19 were
obtained with good to excellent yields (Tables 3 and 4). As expected all the
dihydropyrimidines 18 obtained from the acetoacetanilides 15 were racemic products,
whereas the reactions that employed 17 resulted in the formation of a pair of
diastereoisomers of 19. The diastereoselectivity obtained when using 17 was very
minor or non-existent (Scheme 2; Table 4).
Scheme 2: One-pot synthesis of dihydropyrimidine derivatives 18 and 19.

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Table 3: Dihydropyrimidine derivatives 18 from a one-pot, four reagents, DpOrIo: 1c0e.1s0Vs3i9e/wCA5rRticAl1e4O3n5li5nAe
using anilines.
Product; yield (%) a,b
[Lit. Yield (%)]
(18a)
Product; yield (%) a,b
[Lit. Yield (%)]
(18f)
Reagents
Reagents
12; 14a; 2; 1a
[Y= CH2(O2)]
12; 14d; 2; 1c
(Y = p-CN)
86
65
(18g)
(18b)
12; 14a; 2; 1d
(Y = p-NO2)
12; 14d; 2; 1a
[Y= CH2(O2)]
82 (64 9a
)
74
(18h)
(18c)
12; 14a; 2; 1b
(Y = p-OMe)
12; 14d; 2; 1d
(Y = p-NO2)
81 (93 26b
)
80
(18d)
(18i)
12; 14a; 2; 1e
(Y = 3-OMe 4-
OH)
12; 14d; 2; 1b
(Y = p-OMe)
67
86
(18j)
(18e)
12; 14d; 2; 1e
(Y = 3-OMe 4-
OH)
12; 14a; 2; 1c
(Y = p-CN)
64
64

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Table 4: Dihydropyrimidine derivatives 19 from a one-pot, four reagents, DpOrIo: 1c0e.1s0Vs3i9e/wCA5rRticAl1e4O3n5li5nAe
using aminoacid derivatives.
Reagents
Product; yield (%) a,b
Reagents
Product; yield (%) a,b
(19g)
(19a)
12; 16f; 2; 1a
[Y= CH2(O2)]
12; 16a; 2; 1c
(Y = p-CN)
dr 1.2:1
dr 1.5:1
25
74
83
(19b)
(19h)
12; 16a; 2; 1b
(Y = p-OMe)
dr 1:1
12; 16f; 2; 1b
(Y = p-OMe)
dr 1.2:1
50
(19i)
(19c)
12; 16b; 2; 1c
(Y = p-CN)
dr 1:1
12; 16e; 2; 1a
[Y= CH2(O2)]
dr 1.5:1
54
74
50
(19j)
(19d)
12; 16b; 2; 1b
(Y = p-OMe)
dr 1:1
12; 16f; 2; 1c
(Y = p-CN)
dr 2.3:1
53
(19k)
(19e)
12; 16b; 2; 1a
[Y= CH2(O2)]
dr 1:1
12; 16g; 2; 1a
[Y= CH2(O2)]
dr 1:1
62
70
(19f)
12; 16f; 2; 1c
(Y = p-CN)
dr 1.3:1
85

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3. Conclusion
Acetoacetamide derivatives 15 and 17 were successfully prepared with good
to excellent yields by the reaction of 12, a precursor for acetylketene 13 generation,
with anilines 14 and aminoacid derivatives 16 by refluxing the reagents in water. The
preparation of 17 in aqueous medium was also investigated by comparing
conventional heating with microwave heating. The benefit of the latter method being
the reduced reaction time, 5 minutes compared with 2 hours. The reaction conditions
reported in the present study allow for the “large” scale preparation of
acetoacetamides without the need for the use of organic solvents. A one-pot, four
reagents, process for the synthesis of Biginelli DHPMs was developed that employed
an aqueous methodology for the preparation of 15 and 17 whereby these
intermediates were subsequently used without purification in the three component
reaction employing 1 and 2 to give good to excellent yields of 18 and 19 after
recrystallization. The one-pot methodology for the synthesis of 18 or 19 from 12, 14
or 16, 1 and 2 increases the efficiency of the preparation of 18 or 19 by eliminating
manipulation and purification of the intermediates 15 and 17. The introduction of the
exocyclic aminoacid groups introduces a new spatial complexity to the structures of
the DHPMs and therefore the novel Biginelli products are being screened for
pharmacological activity.
4. Experimental
All chemicals and solvents (analytical grade) were received from commercial
sources and used without further purification. Analytical thin layer chromatography
(TLC) was performed on pre-coated silica gel 60 F254 aluminum plates (Merck) with
visualization under UV light – 254 and 366 nm. Melting points were determined with
a Mel. Temp. II apparatus and are uncorrected. IR spectra were measured on a Nicolet
505 Magma FT-IR spectrometer. High resolution mass spectra (HRMS) were
1
recorded on a Q-TOF instrument (micromass, Manchester, UK). H and 13C NMR
spectra were recorded at 200 MHz on a Bruker DPX instrument using CDCl3 and or
DMSO-d6 as solvents. The chemical shifts were referenced to the residual non-
deuterated solvent signals or relative to TMS as internal standard. Coupling constants
J are given in Hertz and their multiplicities have the standard designations.

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4.1a Preparation of N-aryl acetoacetamides (15) - Aqueous method.
In a round bottom flask, aniline (5 mmol) and distilled water (15 mL) were
agitated and heated to reflux. Upon reflux, TMD (8 mmol) was added and the reflux
was maintained for 1.5 hours. Upon completion of the reaction as determined by
TLC, the reaction mixture was allowed to cool and aqueous 2M HCl (2 mL) was
added resulting in the precipitation of a solid. The solid was isolated by filtration and
recrystallized from water.
When the product was an oil, it was extracted from the diluted reaction
medium with EtOAc and the crude material was purified by silica gel column
chromatography eluting with CH2Cl2 followed by a CH2Cl2/EtOAc gradient up to
50% EtOAc.
4.1b Preparation of N-alkyl acetoacetamides (17) – Conventional heating
In a round bottom flask, L-amino acids (5 mmol) were suspended in distilled
water (10 mL). Into this suspension K2CO3 (80mol% - 4mmol) was added and the
mixture heated to reflux. Upon reflux, TMD (10 mmol) was added and reflux was
maintained for 2 hours. Upon completion of the reaction as determined by TLC, the
reaction mixture was allowed to cool and the mixture was acidified with aqueous 6M
HCl (pH ~ 1) and extracted with AcOEt. The organic fractions were united, dried
over anhydrous Na2SO4, filtered and evaporated under reduce pressure. The crude
product was filtered through a short silica gel column eluting with AcOEt.
4.1c Preparation of N-alkyl acetoacetamides (17) – MW heating
To a microwave reactor vial were added: L-amino acid (1 mmol), distilled
water (4 mL), K2CO3 (80mol% - 0.8mmol) and TMD (2 mmol). The microwave
heating parameters were: Temp.: As fast as possible, until 1500C; time duration: 5
min; Pressure: 9.0 Bar (Monowave 300). Upon completion of the reaction as
determined by TLC, the reaction mixture was allowed to cool and the mixture was
acidified with aqueous 6M HCl (pH ~ 1) and extracted with AcOEt. The organic
fractions were united, dried over anhydrous Na2SO4, filtered and evaporated under
reduce pressure. The crude product was purified by filtration through a short silica gel
column using AcOEt as eluent.

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4.2 Physical and Spectroscopic data for the reported compounds.
4.2.1 N-(Phenyl)-3-oxobutanamide (15a) Colorless crystals, mp. 82-30C IR (cm-1):
3298, 3255, 3197, 3137, 2953, 2924, 1725, 1713, 1662, 1600, 1553, 1542, 1498,
1446, 1409, 1362, 1341, 1315, 1167, 905, 755, 692, 526, 505.1H NMR (200 MHz,
CDCl3): 2.28 (s, 3H), 3.55 (s, 2H), 7.05-7.12 (t, J = 8.0 Hz, 1H), 7.25-7.33 (t, J =
8.0 Hz, 2H), 7.49-7.53 (d, J = 8.0 Hz, 2H), 9.11 (s, 1H). 13C NMR (50 MHz,
CDCl3):  31.2, 49.8, 120.2, 124.5, 128.9, 137.5, 163.5, 205.1.
4.2.2 N-(4-Chlorophenyl)-3-oxobutanamide (15b) Colorless crystals, mp. 130-10C
IR (cm-1): 3289, 3252, 3189, 3125, 3070, 1712, 1659, 1607, 1554, 1492, 1417, 1399,
1
1361, 1343, 1314, 1161, 1092, 1015, 834, 816, 764, 671, 508, 436. H NMR (200
MHz, DMSO-d6):  2.19 (s, 3H), 3.54 (s, 2H), 7.32-7.36 (d, J = 8.0 Hz, 2H), 7.56-
7.60 (d, J = 8.0 Hz, 2H), 10.20 (s, 1H). 13C NMR (50 MHz, DMSO-d6):  30.2, 52.3,
120.7, 127.0, 128.7, 137.8, 165.2, 202.7.
4.2.3 N-(4-Methoxyphenyl)-3-oxobutanamide (15c) Colorless crystals, mp. 114-50C
IR (cm-1): 3282, 3252, 3196, 3137, 3077, 3003, 2960, 2836, 1716, 1655, 1608, 1561,
1
1513, 1421, 1360, 1250, 1161, 1036, 840, 789, 615, 522, 455. H NMR (200 MHz,
CDCl3):  2.29 (s, 3H), 3.54 (s, 2H), 3.76 (s, 3H), 6.80-6.85 (d, J = 10.0 Hz, 2H),
13
7.39-7.44 (d, J = 10.0 Hz, 2H), 8.99 (s, 1H). C NMR (50 MHz, CDCl3):  31.1,
49.8, 55.4, 114.1, 121.9, 130.6, 156.6, 163.4, 205.1.
4.2.4 N-(4-Methylphenyl)-3-oxobutanamide (15d) Colorless crystals, mp. 87-90C
IR (cm-1): 3294, 3255, 3192, 3129, 2958, 2918, 1714, 1658, 1606, 1556, 1513, 1418,
1
1359, 1343, 1316, 1162, 834, 818, 786, 510, 500. H NMR (200 MHz, CDCl3): 
2.29 (s, 6H, 2CH3), 3.54 (s, 2H), 7.08-7.12 (d, J = 8.0 Hz, 2H), 7.38-7.42 (d, J = 8Hz,
2H), 9.03 (s, 1H). 13C NMR (50 MHz, CDCl3):  20.8, 31.1, 49.9, 120.2, 129.4,
134.2, 134.9, 163.4, 205.1.
4.2.5 4-(3-Oxobutanamido)benzoic acid (15e) Pale yellow crystals, mp. 204-60C.
IR (cm-1): 3305, 2996, 2887, 2665, 2549, 1678, 1600, 1514, 1406, 1319, 1277, 1160,
1
852, 769, 540, 503. H NMR (200 MHz, DMSO-d6):  2.20 (s, 3H), 3.60 (s, 2H),

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6.73-6.88 (d, J = 10.0 Hz, 2H), 7.87-7.92 (d, J = 10.0 Hz, 2H), 10.39 (s, 1H).
C
DOI: 10.1039/C5RA14355A
NMR (50 MHz, DMSO-d6):  30.2, 52.4, 118.3, 125.3, 130.4, 142.8, 167.2, 202.6.
+
HRMS (m/z + H+): Obs.: 222.0766; Calc.: 222.0838 (C11H12NO4 ).
4.2.6 N-(4-Bromophenyl)-3-oxobutanamide (15f) Brown crystals, mp. 136-70C IR
(cm-1): 3288, 3250, 3185, 3120, 3067, 1716, 1658, 1605, 1552, 1489, 1417, 1395,
1
1360, 1341, 1313, 1239, 1160, 1075, 1011, 832, 816, 760, 654, 536, 505. H NMR
(200 MHz, CDCl3):  2.31 (s, 3H), 3.57 (s, 2H), 7.42 (s, 4H), 9.24 (s, 1H). 13C NMR
(50 MHz, CDCl3):  31.3, 49.4, 117.1, 121.7, 131.9, 136.5, 163.4, 205.3. HRMS
(m/z + H+): Obs.: 255.9973 / 257.9973; Calc.: 256.0092 / 258.0034 (C10H11NO2Br+).
4.2.7 N-(4-Fluorophenyl)-3-oxobutanamide (15g) Colorless crystals, mp. 98-90C
IR (cm-1): 3257, 3212, 3153, 3070, 2925, 1721, 1667, 1621, 1569, 1553, 1509, 1414,
1
1360, 1339, 1314, 1237, 1215, 1167, 839, 799, 518, 501, 465. H NMR (200 MHz,
CDCl3):  2.30 (s, 3H), 3.56 (s, 2H), 6.94-7.03 (t, J = 8.0 Hz, 2H), 7.44-7.51 (dd, J =
13
8.0 Hz, 2H), 9.16 (s, 1H). C NMR (50 MHz, CDCl3):  31.2, 49.5, 115.4, 115.8,
121.9, 122.0, 133.5, 133.5, 157.1, 162.0, 163.5, 205.2.
4.2.8 N-(2-Methoxy-4-nitrophenyl)-3-oxobutanamide (15h) Yellow crystals, mp.
113-40C IR (cm-1): 3273, 3106, 3080, 1712, 1690, 1616, 1590, 1538, 1509, 1486,
1413, 1343, 1277, 1259, 1222, 1099, 1023, 883, 800, 746, 553. 1H NMR (200 MHz,
DMSO-d6):  2.18 (s, 3H), 3.78 (s, 2H), 3.98 (s, 3H), 7.80 (s, 1H), 7.85-7.90 (d, J =
10.0 Hz, 1H), 8.39-8.44 (d, J = 10.0 Hz, 2H), 9.92 (s, 1H). 13C NMR (50 MHz,
DMSO-d6):  30.2, 51.8, 56.5, 105.9, 116.9, 119.2, 134.0, 142.7, 148.4, 166.3, 203.3.
+
HRMS (m/z + H+): Obs.: 253.0824; Calc.: 253.0884 (C11H13N2O5 ).
4.2.9 N-(3-Chloro-4-methoxyphenyl)-3-oxobutanamide (15i) Purple crystals, mp.
106-70C. IR (cm-1): 3288, 3253, 3124, 2917, 2844, 1720, 1661, 1595, 1539, 1502,
1
1443, 1399, 1287, 1258, 1215, 1158, 1061, 1025, 871, 820, 731, 689, 537, 498. H
NMR (200 MHz, CDCl3):  2.30 (s, 3H), 3.56 (s, 2H), 3.85 (s, 3H), 6.82-6.86 (d, J =
13
8.0 Hz, 1H), 7.33-7.37 (d, J = 8.0 Hz, 1H), 7.59 (s, 1H), 9.11 (s, 1H). C NMR (50
MHz, CDCl3):  31.2, 49.4, 56.3, 112.2, 119.8, 122.4, 122.7, 131.0, 152.0, 163.5,

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DOI: 10.1039/C5RA14355A
205.2. HRMS (m/z + H ): Obs.: 242.0584 / 244.0584; Calc.: 242.0657 / 244.0599
(C11H13NO3Cl+).
4.2.10 N-(3-Methoxyphenyl)-3-oxobutanamide (15j) The product was extracted
with EtOAc and the crude material was purified by silica gel column chromatography
eluting with CH2Cl2 followed by a CH2Cl2/EtOAc gradient up to 10 % EtOAc. Pale
brown oil. IR (cm-1): 3312, 3147, 2960, 2836, 1720, 1667, 1598, 1546, 1454, 1423,
1
1290, 1256, 1206, 1158, 1044, 856, 774, 689, 522, 457. H NMR (200 MHz,
CDCl3):  2.30 (s, 3H), 3.56 (s, 2H), 3.78 (s, 3H), 6.66-6.69 (d, J = 6.0 Hz, 1H), 7.00-
13
7.08 (t, J = 8.0 Hz, 1H), 7.16-7.20 (d, J = 8.0 Hz, 2H), 9.13 (s, 1H). C NMR (50
MHz, CDCl3):  31.2, 49.8, 55.3, 105.9, 110.4, 112.3, 129.7, 138.6, 160.1, 163.5,
+
205.2. HRMS (m/z + H+): Obs.: 208.0938; Calc.: 208.0974 (C11H14NO3 ).
4.2.11 N-(2-Methoxyphenyl)-3-oxobutanamide (15k) Beige solid, mp. 85-70C IR
(cm-1): 3280, 2971, 2842, 1710, 1676, 1598, 1542, 1488, 1459, 1438, 1365, 1289,
1
1251, 1221, 1174, 1119, 1045, 1022, 760, 731, 594, 509, 494. H NMR (200 MHz,
CDCl3):  2.31 (s, 3H), 3.58 (s, 2H), 3.89 (s, 3H), 6.85-7.04 (m, 3H), 8.28-8.32 (d, J
13
= 8.0 Hz, 1H), 9.22 (s, 1H). C NMR (50 MHz, CDCl3):  31.0, 50.8, 55.8, 110.1,
120.1, 120.9, 124.1, 127.3, 148.3, 163.2, 204.3. HRMS (m/z + H+): Obs.: 230.0765;
Calc.: 230.0793 (C11H13NO3Na).
4.2.12 N-(3-Trifluoromethylphenyl)-3-oxobutanamide (15l) Pale yellow solid, mp.
107-90C IR (cm-1): 3306, 3100, 2960, 2929, 1715, 1664, 1616, 1567, 1496, 1424,
1364, 1334, 1316, 1188, 1161, 1116, 1072, 898, 882, 802, 741, 701, 661, 634, 528,
519, 459. 1H NMR (200 MHz, CDCl3):  2.32 (s, 3H), 3.60 (s, 2H), 7.33-7.46 (dd, J
= 8.0 Hz, 2H), 7.69-7.73 (d, J = 8.0 Hz, 2H), 7.85 (s, 1H), 9.43 (s, 1H). 13C NMR (50
MHz, CDCl3):  31.3, 49.3, 116.8, 121.0, 123.1, 126.5, 129.5, 131.7, 138.0, 163.8,
+
205.3. HRMS (m/z + H+): Obs.: 246.0742; Calc.: 246.0807 (C11H11F3NO2 ).
4.2.13 N-(2,6-Dimethylphenyl)-3-oxobutanamide (15m) Colourless crystals, mp.
134-50C. IR (cm-1): 3215, 3180, 3035, 2965, 1713, 1669, 1643, 1451, 1475, 1413,
1330, 1179, 1166, 760, 717, 515. 1H NMR (200 MHz, CDCl3):  2.19 (s, 6H, 2CH3),
13
2.31 (s, 3H), 3.59 (s, 2H), 7.05 (s, 3H), 8.46 (s, 1H). C NMR (50 MHz, CDCl3): 

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18.3, 31.0, 49.4, 127.3, 128.1, 133.6, 135.1, 163.9, 204.8. HRMS (m/z + H D):OI:O10b.1s0.3:9/C5RA14355A
+
206.1179; Calc.: 206.1181 (C12H16NO2 ).
4.2.14 N-(2,5-Dimethoxyphenyl)-3-oxobutanamide (15n) Colourless crystals, mp.
71-3oC IR (cm-1): 3062, 3030, 2922, 1721, 1633, 1636, 1600, 1485, 1454, 1358,
1
1289, 1207, 1083, 1013, 828, 776, 728, 701, 577. H NMR (200 MHz, CDCl3): 
2.31 (s, 3H), 3.58 (s, 2H), 3.76 (s, 3H), 3.85 (s, 3H), 6.54 – 6.60 (dd, J = 2.0/4.0 Hz,
1H), 6.77 – 6.81 (d, J = 8.0 Hz, 1H), 8.04 – 8.05 (d, J = 2.0 Hz, 1H), 9.59 (s, 1H).
13C NMR (200 MHz, CDCl3):  30.9, 50.7, 55.7, 56.3, 106.4, 108.7, 110.9, 128.0,
142.5, 153.7, 163.3, 204.1.
4.2.15 N-methyl-3-oxo-N-phenylbutanamide (15o) The product was extracted with
EtOAc and the crude material was purified by silica gel column chromatography
eluting with CH2Cl2 followed by a CH2Cl2/EtOAc gradient up to 50 % EtOAc. Pale
brown oil. IR (cm-1): 3062, 3040, 2925, 1721, 1656, 1595, 1497, 1379, 1343, 1301,
1124, 924, 776, 702, 561, 540. The product was observed to be a mixture of keto and
1
enol tautomers. H NMR (200 MHz, CDCl3):  1.79 (s, 1H), 2.08 (s, 3H), 3.29 (s,
6H), 4.68 (s, 0.3H), 7.17 – 7.21 (d, J = 8.0 Hz, 2H), 7.35 – 7.42 (m, J = 8.0 Hz, 3H),
13
14.25 (s, 0.3H). C NMR (200 MHz, CDCl3):  21.6, 30.2, 36.3, 37.2, 49.8, 88.8,
127.2, 127.3, 127.5, 128.2, 129.6, 129.9, 143.3, 143.5, 166.6, 171.8, 202.2.
4.2.16 N-ethyl-3-oxo-N-phenylbutanamide (15p) The product was extracted with
EtOAc and the crude material was purified by silica gel column chromatography
eluting with CH2Cl2 followed by a CH2Cl2/EtOAc gradient up to 50 % EtOAc. Pale
brown oil. IR (cm-1): 3063, 3041, 2973, 2934, 1720, 1667, 1662, 1595, 1496, 1416,
1261, 1180, 862, 799, 771, 703. The product was observed to be a mixture of keto and
enol tautomers. 1H NMR (200 MHz, CDCl3):  1.09 – 1.16 (t, J = 8.0 Hz, 3H), 1.77
(s, 1H), 2.07 (s, 4H), 3.23 (s, 2H), 3.71 – 3.82 (q, J = 8.0 Hz, 2.9H), 4.56 (s, 0.2H),
7.13 – 7.17 (d, J = 8.0 Hz, 2H), 7.38 – 7.42 (m, J = 8.0 Hz, 3H), 14.33 (s, 0.3H). 13C
NMR (200 MHz, CDCl3):  12.9, 13.2, 21.6, 30.2, 44.0, 50.2, 89.1, 127.7, 128.3,
128.4, 129.5, 129.8, 141.7, 141.8, 166.1, 171.4, 202.2.

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DOI: 10.1039/C5RA14355A
4.2.17 N-benzyl-3-oxo-N-phenylbutanamide (15q) The product was extracted with
EtOAc and the crude material was purified by silica gel column chromatography
eluting with CH2Cl2 followed by a CH2Cl2/EtOAc gradient up to 50 % EtOAc. Pale
brown oil. IR (cm-1): 3063, 3031, 2925, 1721, 1655, 1637, 1595, 1496, 1359, 1276,
1212, 1157, 1082, 1018, 923, 780, 734, 700, 562, 537. The product was observed to
1
be a mixture of keto and enol tautomers. H NMR (200 MHz, CDCl3):  1.83 (s,
1H), 2.11 (s, 3H), 3.33 (s. 2H), 4.67 (s, 0.4H), 4.94 (s, 3H), 6.98 – 7.02 (m, J = 8.0
Hz, 3H), 7.27 – 7.35 (m, 7H), 14.33 (s, 0.3H). 13C NMR (200 MHz, CDCl3):  21.6,
30.3, 50.1, 52.9, 88.9, 127.3, 127.4, 127.7, 128.3, 128.4, 128.7, 129.4, 129.6, 136.9,
137.4, 141.8, 166.6, 202.1.
4.2.18 (3-oxobutanoyl)-L-tryptophan (17a) Colourless crystal. m.p. 163-5oC. IR
(cm-1): 3392, 3345, 2915, 1724, 1710, 1620, 1530, 1358, 1274, 1216, 1198, 739, 620.
1H NMR (200 MHz, DMSO d6) δ 10.85 (s, 1H), 8.44 (d, J = 7.8 Hz, 1H), 7.53 (d, J
= 7.4 Hz, 1H), 7.34 (d, J = 7.9 Hz, 1H), 7.15 (d, J = 2.1 Hz, 1H), 7.03 (dd, J = 10.5,
7.8 Hz, 2H), 4.57 – 4.46 (m, 1H), 3.32 (s, 2H), 3.11 (dd, J = 18.0, 6.7 Hz, 2H), 2.04
13
(s, 3H). C NMR (50 MHz, DMSO d6) δ 203.1, 173.3, 166.3, 136.2, 127.3, 123.8,
121.1, 118.6, 118.3, 111.5, 109.8, 53.2, 51.1, 29.8, 27.2. [α]D = + 17.0 (c 0.1 EtOH).
HRMS (m/z - H+) calc.: 287.1037. Obs.: 287.1040.
4.2.19 (3-oxobutanoyl)-L-leucine (17b) Colourless crystal. m.p. 122-3oC. IR (cm-1):
1
3308, 2958, 2875, 2611, 2480, 1724, 1701, 1616, 1560, 1276, 1248, 1154, 1127. H
NMR (200 MHz, CDCl3) δ 7.46 (d, J = 7.8 Hz, 1H), 4.57 – 4.41 (m, 1H), 3.40 (s,
2H), 2.20 (s, 3H), 1.70 – 1.48 (m, 3H), 0.87 (dd, J = 5.7, 2.5 Hz, 6H). 13C NMR (50
MHz, CDCl3) δ 203.7, 174.5, 165.9, 50.8, 49.8, 40.9, 30.4, 24.6, 22.7, 21.6. [α]D = -
22.0 (c 0.1 EtOH). HRMS (m/z - H+) calc.: 214.1085. Obs: 214.1087.
4.2.20 (3-oxobutanoyl)-L-valine (17c) Colourless crystal. m.p. 121-2oC. IR (cm-1):
1
3316, 2926, 2470, 1724, 1698, 1620, 1560, 1250, 1183, 696. H NMR (200 MHz,
CDCl3) δ 7.54 (d, J = 8.5 Hz, 1H), 4.14 (dd, J = 8.5, 4.9 Hz, 1H), 3.18 (s, 2H), 1.99 –
1.82 (m, 4H), 0.66 (dd, J = 6.4, 3.4 Hz, 6H). 13C NMR (50 MHz, CDCl3) δ 202.91,
172.66, 165.70, 56.66, 49.96, 30.01, 29.66, 18.43, 17.10. [α]D = - 5 (c 0.1 EtOH).
HRMS (m/z - H+) calc.: 200.0928. Obs.: 200.0933.

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4.2.21 (3-oxobutanoyl)-L-methionine (17d) Brown oil. IR (cm-1): 3320, 2923, 2483,
1
1920, 1721, 1698, 1626, 1557, 1440, 1258, 1183, 711. H NMR (200 MHz, CDCl3)
δ 7.83 (d, J = 7.5 Hz, 1H), 4.67 (dd, J = 12.4, 7.2 Hz, 1H), 3.52 (s, 2H), 2.56 (t, J =
7.2 Hz, 2H), 2.27 (s, 3H), 2.23 – 2.15 (m, 1H), 2.09 (s, 3H), 2.06 – 1.96 (m, 1H). 13C
NMR (50 MHz, CDCl3) δ 204.4, 174.2, 167.0, 51.7, 49.4, 31.0, 30.8, 29.9, 15.3. [α]D
= + 29.0 (c 0.1 EtOH). HRMS (m/z - H+) calc.: 232.0649. Obs.: 232.0649.
4.2.22 (3-oxobutanoyl)-L-phenylalanine (17e) Colourless crystal. m.p. 110-120C.
1
IR (cm-1): 3415, 2944, 1728, 1640, 1531, 1426, 1219, 1162, 1109, 748. H NMR
(200 MHz, CDCl3 + DMSO d6) δ 7.46 (d, J = 5.3 Hz, 1H), 7.16 – 7.00 (m, 5H), 4.62
(td, J = 7.4, 5.4 Hz, 1H), 3.20 (s, 2H), 2.97 (dt, J = 13.9, 7.7 Hz, 2H), 1.99 (s, 3H).
13C NMR (50 MHz, CDCl3 + DMSO) δ 202.9, 172.6, 165.4 136.1, 129.0, 127.9,
126.3, 53.0, 50.1, 37.1, 29.9. [α]D = + 8.0 (c 0.1 EtOH). HRMS (m/z - H+) calc.:
248.0928. Obs.: 248.0929.
4.2.23 (3-oxobutanoyl)-L-phenylglycine (17f) Colourless crystal. m.p. 133-50C. IR
1
(cm-1): 3390, 2963, 1717, 1625, 1544, 1261, 1099, 1026, 800, 721, 658. H NMR
(200 MHz, CDCl3 + DMSO d6) δ 8.33 (d, J = 6.6 Hz, 1H), 7.38 – 7.31 (m, 2H), 7.30
13
– 7.19 (m, 3H), 5.42 (d, J = 7.2 Hz, 1H), 3.39 (s, 2H), 2.14 (s, 3H). C NMR (50
MHz, CDCl3 + DMSO) δ 202.8, 171.4, 165.2, 136.4, 128.0, 127.5, 126.8 77.6, 76.4,
56.1, 49.9, 29.8. [α]D = - 169.0 (c 0.1 EtOH). HRMS (m/z - H+) calc.: 234.0772.
Obs.: 234.0771.
4.2.24 (3-oxobutanoyl)-L-tyrosine (17g) Colourless crystal. m.p. 186-70C. IR (cm-
1
1): 3360, 2964, 2627, 1708, 1627, 1543, 1157, 1252, 1229, 818. H NMR (200 MHz,
CDCl3 + DMSO d6) δ 7.55 (d, J = 7.8 Hz, 1H), 6.62 (d, J = 8.4 Hz, 2H), 6.31 (d, J =
8.4 Hz, 2H), 4.22 (dd, J = 7.6, 5.5 Hz, 1H), 2.97 (s, 2H), 2.58 (ddd, J = 21.4, 14.0, 6.3
Hz, 2H), 1.74 (s, 3H). 13C NMR (50 MHz, CDCl3 + DMSO d6) δ 202.2, 172.1,
165.2, 155.1, 129.3, 126.2, 114.4, 52.9, 49.9, 35.7, 29.1. [α]D = + 49.0 (c 0.1 EtOH).
HRMS (m/z - H+) calc.: 264.0877. Obs.: 264.0880.
4.2.25 (3-oxobutanoyl)-L-cisteine (17h) Yellow crystal. m.p. 126-80C. IR (cm-1):
3385, 2554, 1716, 1625, 1534, 1359, 1228, 1200, 1165. 1H NMR (200 MHz, CDCl3

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+ DMSO d6) δ 7.75 (d, J = 7.3 Hz, 1H), 4.61 (dt, J = 7.4, 4.5 Hz, 1H), 3.33 D(Os,I: 210H.10)3,9/C5RA14355A
2.84 (ddd, J = 8.9, 4.5, 2.8 Hz, 2H), 2.10 (s, 3H), 1.49 (t, J = 8.9 Hz, 1H). 13C NMR
(50 MHz, CDCl3 + DMSO d6) δ 203.1, 171.2, 165.8, 53.7, 50.2, 30.2, 26.2. [α]D = +
8.0 (c 0.1 EtOH). HRMS (m/z - H+) calc.: 204.0336. Obs.: 204.0336.
4.2.26 methyl (3-oxobutanoyl)-L-tryptophanate (17i) Pale brown oil. IR (cm-1):
3270, 2952, 1752, 1709, 1655, 1548, 1437, 1224, 1209. 1H NMR (200 MHz, CDCl3)
δ 8.48 (s, 1H), 7.53 (d, J = 7.5 Hz, 1H), 7.40 – 7.28 (m, 2H), 7.14 (td, J = 13.7, 6.7
Hz, 2H), 7.03 (d, J = 2.1 Hz, 1H), 4.92 (dd, J = 13.2, 5.7 Hz, 1H), 3.69 (s, 3H), 3.32
13
(d, J = 5.7 Hz, 2H), 3.28 (s, 2H), 2.11 (s, 3H). C NMR (50 MHz, CDCl3) δ 203.8,
172.2, 165.6, 136.1, 127.4, 123.1, 122.1, 119.5, 118.4, 111.3, 109.5, 52.9, 52.3, 49.6,
30.6, 27.5. [α]D = + 10.0 (c 0.1 EtOH). HRMS (m/z - H+) calc.: 301.1194. Obs.:
301.1201.
4.2.27 methyl (3-oxobutanoyl)-L-phenylalaninate (17j) Pale yellow oil. IR (cm-1):
1
3288, 1755, 1720, 1638, 1354, 1210, 1175. H NMR (200 MHz, CDCl3) δ 7.35 –
7.26 (m, 3H), 7.19 – 7.10 (m, 2H), 4.88 (dt, J = 6.8, 5.8 Hz, 1H), 3.73 (s, 3H), 3.39 (s,
2H), 3.13 (qd, J = 13.9, 6.2 Hz, 2H), 2.22 (s, 3H). 13C NMR (50 MHz, CDCl3) δ
203.6, 171.6, 165.3, 135.8, 129.2, 128.5, 127.1, 53.4, 52.3, 49.6, 37.8, 30.7. [α]D = +
4.0 (c 0.1 EtOH). HRMS (m/z - H+) calc.: 286.1050. Obs.: 286.1052.
4.2.28 methyl (3-oxobutanoyl)-L-phenylglycine (17k) Pale yellow oil. IR (cm-1):
1
3289, 3038, 2955, 1753, 1726, 1640, 1534, 1354, 1216, 1173, 1156. H NMR (200
MHz, CDCl3) δ 7.95 (d, J = 6.1 Hz, 1H), 7.41 – 7.31 (m, 5H), 5.56 (d, J = 7.1 Hz,
13
1H), 3.72 (s, 3H), 3.44 (s, 2H), 2.24 (s, 3H). C NMR (50 MHz, CDCl3) δ 203.8,
170.9, 165.1, 136.0, 128.9, 128.6, 127.2, 56.6, 52.7, 49.4, 30.8. [α]D = -21.0 (c 0.1
EtOH). HRMS (m/z + Na+) calc.: 272.0898. Obs.: 272.0893.
4.2.29 methyl (S)-2-(3-oxobutanoyl)-2,3,4,9-tetrahydro-1H-pyrido[3,4-b]indole-3-
carboxylate (17l) Pale brown oil. IR (cm-1): 3288, 1755, 1720, 1638, 1354, 1210,
1175. Although the tertiary acetoacetamide derivative is stable on silica gel, it was
1
observed to streak on elution on silica TLC plates. H NMR analysis of this
compound suggested the presence of multiple conformers due to the rigid amide bond
that does not freely rotate on the NMR timescale at room temperature, and tautomers

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due to the acidic methylene unit of the 1,3-dicarbonyl system. HRMS [2M+Na ]
DOI: 10.1039/C5RA14355A
calc.: 651.2425. Obs.: 651.2446.
4.2.30 methyl Nα-(4-methoxybenzyl)-Nα-(3-oxobutanoyl)-L-tryptophanate (17m)
Pale brown oil. IR (cm-1): 3400, 1740, 1633, 1613, 1248, 1177, 748. Although the
tertiary acetoacetamide derivative is stable on silica gel, it was observed to streak on
1
elution on silica TLC plates. H NMR analysis of this compound suggested the
presence of multiple conformers due to the rigid amide bond that does not freely
rotate on the NMR timescale at room temperature, and tautomers due to the acidic
methylene unit of the 1,3-dicarbonyl system.
4.2.31 methyl (S)-2-(N-(4-methoxybenzyl)-3-oxobutanamido)-2-phenylacetate
(17n) Pale brown oil. IR (cm-1): 3400, 1740, 1635, 1612, 1247, 1179, 752. Although
the tertiary acetoacetamide derivative is stable on silica gel, it was observed to streak
1
on elution on silica TLC plates. H NMR analysis of this compound suggested the
presence of multiple conformers due to the rigid amide bond that does not freely
rotate on the NMR timescale at room temperature, and tautomers due to the acidic
methylene unit of the 1,3-dicarbonyl system.
4.3 Preparation of dihydropyrimidines (18 / 19) from acetoacetanilides (15) or
acetoacetamides (17).
In a round bottom flask, the 1,3 dicarbonyl derivatives 15 or 17 (1mmol) were
prepared as previously described. After the reflux period the water was removed
under reduced pressure to give the crude products that were subsequently dissolved in
EtOH (5 mL). Urea 2 (2.5 mmol) and a benzaldehyde derivative 1 (1mmol), followed
by formic acid (10 drops), were added and the mixture was heated to reflux overnight.
Upon completion of the reaction as determined by TLC, the mixture was diluted with
ice cold water and the solid was removed by filtration under reduce pressure. The
dihydropyrimidine products were recrystallized from ethanol.
4.3.1
4-(benzo[d][1,3]dioxol-5-yl)-6-methyl-2-oxo-N-phenyl-1,2,3,4-tetrahydro
pyrimidine-5-carboxamide (18a) White solid. m.p. 276-70C IR (cm-1): 3377, 3114,
1
2951, 1710, 1680, 1625, 1597, 779. H NMR (200 MHz, DMSO) δ 9.52 (s, 1H),
8.70 (s, 1H), 7.64 – 7.45 (m, 3H), 7.24 (t, J = 7.5 Hz, 2H), 7.00 (t, J = 7.2 Hz, 1H),

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DOI: 10.1039/C5RA14355A
6.89 – 6.64 (m, 3H), 5.97 (s, 2H), 5.32 (s, 1H), 2.05 (s, 3H). C NMR (50 MHz,
DMSO) δ 165.3, 152.4, 147.3, 146.4, 139.2, 138.4, 138.3, 128.5, 123.1, 119.6, 108.0,
106.8, 105.4, 100.9, 54.8, 17.0. HRMS (m/z + H+) calc.: 352.1292. Obs.: 352.1153.
4.3.2 4-(benzo[d][1,3]dioxol-5-yl)-6-methyl-2-oxo-N-(p-tolyl)-1,2,3,4-tetrahydro
pyrimidine-5-carboxamide (18b) White solid. m.p. 272-50C IR (cm-1): 3369, 3263,
1
1716, 1678, 1248, 1038, 789. H NMR (200 MHz, DMSO) δ 9.44 (s, 1H), 8.67 (s,
1H), 7.50 (s, 1H), 7.42 (d, J = 8.4 Hz, 2H), 7.05 (d, J = 8.3 Hz, 2H), 6.89 – 6.68 (m,
13
3H), 5.96 (s, 2H), 5.30 (s, 1H), 2.22 (s, 3H), 2.03 (s, 3H). C NMR (50 MHz,
DMSO) δ 165.1, 152.5, 147.3, 146.5, 138.3, 138.1, 136.7, 132.1, 128.9, 119.6, 119.6,
108.0, 106.8, 105.5, 100.9, 54.9, 20.4, 17.0. HRMS (m/z + H+) calc.: 338.1499. Obs.:
338.1505.
4.3.3
4-(4-methoxyphenyl)-6-methyl-2-oxo-N-phenyl-1,2,3,4-tetrahydro
pyrimidine-5-carboxamide (18c) White solid. m.p. 238-400C IR (cm-1): 3403, 3277,
1
1708, 1673, 1246, 1175, 754. H NMR (200 MHz, DMSO) δ 9.52 (s, 1H), 8.69 (s,
1H), 7.64 – 7.45 (m, 3H), 7.36 – 7.14 (m, 4H), 6.99 (t, J = 7.3 Hz, 1H), 6.87 (d, J =
8.5 Hz, 2H), 5.37 (s, 1H), 3.70 (s, 3H), 2.04 (s, 3H). 13C NMR (50 MHz, DMSO) δ
165.4, 158.6, 152.6, 139.2, 138.2, 136.5, 128.5, 127.6, 123.1, 119.6, 113.8, 105.7,
55.1, 54.6, 17.0. HRMS (m/z + H+) calc.: 366.1448. Obs.: 366.1454.
4.3.4
4-(4-methoxyphenyl)-6-methyl-2-oxo-N-(p-tolyl)-1,2,3,4-tetrahydro
pyrimidine-5-carboxamide (18d) White solid. m.p. 233-40C IR (cm-1): 3404, 3279,
1
1709, 1673, 1627, 1246, 1174, 755. H NMR (200 MHz, DMSO) δ 9.43 (s, 1H),
8.66 (s, 1H), 7.49 (s, 1H), 7.42 (d, J = 8.3 Hz, 2H), 7.19 (d, J = 8.6 Hz, 2H), 7.04 (d, J
= 8.3 Hz, 2H), 6.87 (d, J = 8.6 Hz, 2H), 5.34 (s, 1H), 3.70 (s, 3H), 2.21 (s, 3H), 2.03
(s, 3H). 13C NMR (50 MHz, DMSO) δ 165.2, 158.6, 152.6, 137.9, 136.7, 136.5,
132.0, 128.9, 127.6, 119.7, 113.8, 105.8, 55.1, 54.6, 20.4, 17.0. HRMS (m/z + H+)
calc.: 352.1656. Obs.: 352.1593.
4.3.5 4-(4-cyanophenyl)-6-methyl-2-oxo-N-phenyl-1,2,3,4-tetrahydropyrimidine-
5-carboxamide (18e) White solid. m.p. 273-40C IR (cm-1): 3307, 1727, 1664, 1623,
1242, 1190, 746. 1H NMR (200 MHz, DMSO) δ 9.60 (s, 1H), 8.85 (s, 1H), 7.82 (d, J
= 7.9 Hz, 2H), 7.70 (s, 1H), 7.59 – 7.40 (m, 4H), 7.25 (t, J = 7.6 Hz, 2H), 7.00 (t, J =

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DOI: 10.1039/C5RA14355A
7.1 Hz, 1H), 5.45 (s, 1H), 2.05 (s, 3H). C NMR (50 MHz, DMSO) δ 165.1, 152.4,
149.5, 139.2, 139.0, 132.6, 128.5, 127.3, 123.2, 119.7, 110.1, 104.5, 54.9, 17.1.
HRMS (m/z + H+) calc.: 336.1346. Obs.: 336.1330.
4.3.6
4-(4-cyanophenyl)-6-methyl-2-oxo-N-(p-tolyl)-1,2,3,4-tetrahydro-
pyrimidine-5-carboxamide (18f) White solid. m.p. 2850C IR (cm-1): 3303, 1728,
1
1664, 1623, 1243, 770. H NMR (200 MHz, DMSO) δ 9.53 (s, 1H), 8.83 (s, 1H),
7.82 (d, J = 8.2 Hz, 2H), 7.69 (s, 1H), 7.51 – 7.34 (m, 4H), 7.05 (d, J = 8.3 Hz, 2H),
5.43 (s, 1H), 2.22 (s, 3H), 2.03 (s, 3H). 13C NMR (50 MHz, DMSO) δ 164.9, 152.5,
149.5, 139.0, 136.5, 132.6, 132.2, 128.9, 127.3, 119.7, 118.8, 110.1, 104.6, 54.9, 20.4,
17.1. HRMS (m/z + H+) calc.: 347.1503. Obs.: 347.1564.
4.3.7 6-methyl-4-(4-nitrophenyl)-2-oxo-N-phenyl-1,2,3,4-tetrahydropyrimidine-5-
carboxamide (18g) White solid. m.p. 278-90C IR (cm-1): 3375, 3268, 1727, 1667,
1
1623, 1239, 1150, 747. H NMR (200 MHz, DMSO) δ 9.63 (s, 1H), 8.89 (s, 1H),
8.22 (d, J = 8.7 Hz, 2H), 7.75 (s, 1H), 7.60 – 7.45 (m, 4H), 7.24 (t, J = 7.8 Hz, 2H),
7.00 (t, J = 7.3 Hz, 1H), 5.51 (s, 1H), 2.06 (s, 3H). 13C NMR (50 MHz, DMSO) δ
165.1, 152.4, 151.5, 146.8, 139.3, 139.0, 128.5, 127.6, 123.8, 123.3, 119.7, 104.5,
54.8, 17.1. HRMS (m/z + H+) calc.: 353.1244. Obs.: 353.1250.
4.3.8 6-methyl-4-(4-nitrophenyl)-2-oxo-N-(p-tolyl)-1,2,3,4-tetrahydropyrimidine-
5-carboxamide (18h) White solid. m.p. 276-70C IR (cm-1): 3375, 3253, 1725, 1667,
1
1623, 1234, 1107, 771. H NMR (200 MHz, DMSO) δ 9.55 (s, 1H), 8.85 (s, 1H),
8.21 (d, J = 8.7 Hz, 2H), 7.73 (s, 1H), 7.52 (d, J = 8.7 Hz, 2H), 7.40 (d, J = 8.3 Hz,
2H), 7.04 (d, J = 8.2 Hz, 2H), 5.48 (s, 1H), 2.21 (s, 3H), 2.04 (s, 3H). 13C NMR (50
MHz, DMSO) δ 164.9, 152.4, 151.5, 146.8, 139.1, 136.5, 132.3, 129.0, 127.7, 123.9,
119.8, 104.6, 54.8, 20.4, 17.1. HRMS (m/z + H+) calc.: 367.1401. Obs.: 367.1355.
4.3.9
4-(4-hydroxy-3-methoxyphenyl)-6-methyl-2-oxo-N-phenyl-1,2,3,4-tetra-
hydropyrimidine-5-carboxamide (18i) White solid. m.p. 255-70C IR (cm-1): 3403,
1
3277, 1708, 1673, 1630, 1246, 1175, 754. H NMR (200 MHz, DMSO) δ 9.50 (s,
1H), 8.90 (s, 1H), 8.64 (s, 1H), 7.54 (d, J = 7.7 Hz, 2H), 7.46 (s, 1H), 7.24 (t, J = 7.8
Hz, 2H), 6.99 (t, J = 7.3 Hz, 1H), 6.82 (s, 1H), 6.70 (s, 2H), 5.33 (s, 1H), 3.67 (s, 3H),
2.03 (s, 3H). 13C NMR (50 MHz, DMSO) δ 165.5, 152.6, 147.4, 145.9, 139.2, 137.9,

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135.2, 128.5, 123.1, 119.6, 118.6, 115.3, 110.9, 105.7, 55.6, 54.8, 17.0. HRMS (m/Vziew Article Online
DOI: 10.1039/C5RA14355A
+ H+) calc.: 354.1448. Obs.: 354.1440.
4.3.10 4-(4-hydroxy-3-methoxyphenyl)-6-methyl-2-oxo-N-(p-tolyl)-1,2,3,4-tetra-
hydropyrimidine-5-carboxamide (18j) White solid. m.p. 257-80C IR (cm-1): 3309,
1
3228, 1694, 1667, 1621, 1254, 1155, 808. H NMR (200 MHz, DMSO) δ 9.42 (s,
1H), 8.91 (s, 1H), 8.60 (s, 1H), 7.50 – 7.34 (m, 3H), 7.04 (d, J = 8.3 Hz, 2H), 6.82 (s,
1H), 6.70 (s, 2H), 5.31 (s, 1H), 3.67 (s, 3H), 2.21 (s, 3H), 2.02 (s, 3H). 13C NMR (50
MHz, DMSO) δ 165.4, 152.6, 147.4, 145.9, 137.6, 136.7, 135.3, 132.1, 128.9, 119.7,
118.6, 115.3, 110.9, 105.8, 55.6, 54.9, 20.4, 17.0. HRMS (m/z + H+) calc.: 368.1605.
Obs.: 368.1610.
4.3.11
(4-(4-cyanophenyl)-6-methyl-2-oxo-1,2,3,4-tetrahydropyrimidine-5-
carbonyl)-L-tryptophan (19a) White solid. m.p. > 2500C (dec.) IR (cm-1): 3293,
2230, 1698, 1667, 1608, 1515, 1458, 1239, 745. 1H NMR (200 MHz, DMSO – d6) δ
10.22 (s, 1H), 8.42 (s, 1H), 7.51 – 7.36 (m, 2H), 7.32 – 7.19 (m, 4H), 7.11 – 6.89 (m,
5H), 5.22 (s, 1H), 4.59 (br, 1H), 3.31 – 3.07 (m, 2H), 1.85;1.89 (s, 3H). 13C NMR (50
MHz, DMSO – d6) δ 174.0, 166.3, 166.0, 148.4, 148.2, 139.6, 139.1, 136.1, 132.6,
132.0, 131.9, 127.2, 127.1, 126.7, 123.4, 123.1, 121.0, 118.5, 118.1, 111.2, 110.3,
109.5, 109.2, 103.9, 103.6, 54.9, 53.1, 26.8, 16.8. HRMS (m/z + Na+) calc.:
466.1485. Obs.: 466.1474.
4.3.12
(4-(4-methoxyphenyl)-6-methyl-2-oxo-1,2,3,4-tetrahydropyrimidine-5-
carbonyl)-L-tryptophan (19b) White solid. m.p. > 2500C (dec.) IV (cm-1): 3289,
1
3116, 1718, 1667, 1617, 1510, 1245. H NMR (200 MHz, DMSO-d6) δ 10.14 –
10.10 (d, 2H), 8.34 (s, 2H), 7.46 – 7.23 (m, 4H), 7.05 – 6.77 (m, 12H), 6.73 – 6.60
(m, 4H), 6.52 (d, J = 8.6 Hz, 2H), 5.38 (s, 2H), 5.06 (s, 1H), 5.01 (s, 1H), 4.72 – 4.61
(m, 1H), 4.61 – 4.47 (m, 1H), 3.65 (s, 3H), 3.63 (s, 3H), 3.22 – 3.01 (m, 4H), 1.95 (s,
3H), 1.92 (s, 3H). 13C NMR (50 MHz, CDCl3/ DMSO-d6) δ 174.0, 173.5, 166.4,
166.2, 160.6, 158.7, 158.5, 153.2, 153.1, 139.5, 138.5, 136.1, 136.0, 135.4, 135.1,
127.5, 127.3, 127.1, 123.3, 123.2, 120.9, 118.4, 118.1, 113.7, 113.6, 111.1, 109.3,
109.0, 104.6, 104.2, 54.9, 52.9, 52.5, 26.8, 16.9. HRMS (m/z + Na+) calc.: 471.1638.
Obs.: 471.1643.

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4.3.13
(4-(4-cyanophenyl)-6-methyl-2-oxo-1,2,3,4-tetrahydropyrimidine-5V-iew Article Online
DOI: 10.1039/C5RA14355A
carbonyl)-L-leucine (19c) White solid. m.p. > 2500C (dec.) IR (cm-1): 3411, 3246,
1
2962, 2234, 1705, 1640, 1497, 1243. H NMR (200 MHz, DMSO – d6) δ 8.57 (s,
1H), 8.49 (s, 1H), 7.64 – 7.32 (m, 12H), 5.43 (s, 1H), 5.33 (s, 1H), 4.28 – 4.20 (m,
1H), 4.17 – 4.09 (m, 1H), 2.03 (s, 3H), 2.01 (s, 3H), 1.49 – 1.31 (m, 4H), 1.23 – 0.95
(m, 2H), 0.79 – 0.70 (m, 6H), 0.70 – 0.60 (m, 6H). 13C NMR (50 MHz, CDCl3/
DMSO-d6) δ 174.4, 174.3, 166.7, 166.5, 152.9, 152.8, 149.1, 139.3, 136.8, 132.0,
131.9, 127.6, 127.3, 118.5, 110.3, 104.5, 103.6, 55.4, 54.7, 50.7, 50.1, 24.4, 24.1,
22.8, 20.9, 20.8, 17.0, 16.7.
4.3.14
(4-(4-methoxyphenyl)-6-methyl-2-oxo-1,2,3,4-tetrahydropyrimidine-5-
carbonyl)-L-leucine (19d) White solid. m.p. > 2500C (dec.) IR (cm-1): 3414, 3248,
1
2957, 1705, 1643, 1613, 1514, 1498, 1243. H NMR (200 MHz, DMSO-d6) δ 8.43
(s, 1H), 8.31 (s, 1H), 7.21 – 7.02 (m, 8H), 6.74 (d, J = 8.73 Hz, 4H), 5.26 (s, 1H), 5.19
(s, 1H), 4.35 – 4.22 (m, 1H), 4.22 – 4.11 (m, 1H), 3.68 (s, 6H), 2.06 (s, 3H), 2.01 (s,
3H), 1.48 – 1.31 (m, 4H), 1.28 – 1.04 (m, 2H), 0.76 – 0.67 (m, 6H), 0.67 – 0.59 (m,
6H). 13C NMR (50 MHz, DMSO-d6) δ 174.56, 174.38, 166.78, 166.63, 158.68,
158.65, 153.07, 152.96, 139.38, 135.84, 135.58, 127.67, 113.57, 113.40, 105.74,
104.15, 55.29, 54.93, 54.89, 54.64, 50.53, 50.04, 24.20, 23.97, 22.83, 20.98, 20.93,
17.02, 16.65. HRMS (m/z + Na+) calc.: 398.1686. Obs.: 398.1686.
4.3.15 (4-(benzo[d][1,3]dioxol-5-yl)-6-methyl-2-oxo-1,2,3,4-tetrahydropyrimidine-
5-carbonyl)-L-leucine (19e) White solid. m.p. > 2500C (dec.) IR (cm-1): 3412, 3247,
2959, 1705, 1644, 1491, 1449, 1248, 1240. 1H NMR (200 MHz, DMSO-d6 + CDCl3)
δ 8.44 (s, 1H), 8.32 (s, 1H), 7.19 (s, 3H), 7.06 (s, 1H), 6.81 – 6.62 (m, 6H), 5.86 (s,
4H), 5.23 (s, 1H), 5.16 (s, 1H), 4.29 (dd, J = 14.6, 8.5 Hz, 1H), 4.20 – 4.08 (m, 1H),
2.05 (s, 3H), 2.00 (s, 3H), 1.46 – 1.31 (m, 4H), 1.25 – 0.94 (m, 2H), 0.78 – 0.70 (m,
6H), 0.69 – 0.62 (m, J = 6.2 Hz, 6H). 13C NMR (50 MHz, CDCl3 + DMSO-d6) δ
174.5, 174.4, 166.7, 166.6, 152.9, 152.8, 147.4, 147.3, 146.6, 146.5, 139.4, 137.7,
135.7, 119.8, 119.7, 107.7, 107.5, 107.1, 107.0, 105.6, 104.1, 100.7, 55.6, 54.9, 50.6,
50.0, 24.2, 24.0, 22.9, 20.9, 17.0, 16.6. HRMS (m/z + Na+) calc.: 412.1479. Obs.:
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4.3.16
2-(4-(4-cyanophenyl)-6-methyl-2-oxo-1,2,3,4-tetrahydropyrimidine-5V-iew Article Online
DOI: 10.1039/C5RA14355A
carboxamido)-2-phenylacetic acid (19f) White solid. m.p. > 2500C (dec.) IR (cm-1):
1
3412, 3247, 2959, 1705, 1644, 1491, 1449, 1248, 1240. H NMR (200 MHz,
DMSO-d6) δ 8.79 (s, 1H), 8.73 (s, 1H), 8.38 – 8.29 (m, 1H), 7.76 (d, J = 7.6 Hz, 2H),
7.68 (s, 1H), 7.64 (s, 1H), 7.46 – 7.34 (m, 2H), 7.37 – 7.22 (m, 5H), 5.38 (s, 1H), 5.32
13
(s, 1H), 2.05 (s, 3H). C NMR (50 MHz, DMSO-d6) δ 172.0, 171.9, 166.1, 166.0,
152.6, 149.5, 149.4, 140.0, 138.7, 137.1, 132.4, 128.3, 128.3, 127.8, 127.7, 127.4,
127.4, 118.8, 110.0, 103.6, 103.2, 56.5, 54.9, 54.5, 17.0, 16.9. HRMS (m/z + Na+)
calc.: 413.1220. Obs.: 413.1222.
4.3.17
2-(4-(benzo[d][1,3]dioxol-5-yl)-6-methyl-2-oxo-1,2,3,4-tetrahydro-
pyrimidine-5-carboxamido)-2-phenylacetic acid (19g) White solid. m.p. > 2500C
1
(dec.) IR (cm-1): 3240, 2956, 1715, 1657, 1613, 1524, 1483, 1238, 1041. H NMR
(200 MHz, DMSO-d6) δ 8.65 (s, 1H), 8.57 (s, 1H), 8.21 – 8.25 (d, J = 6.6 Hz, 1H),
8.08 – 8.11 (d, J = 7.4 Hz, 1H), 7.49 (s, 1H), 7.42 (s, 1H), 7.29 (s, 5H), 6.92 – 6.57
13
(m, 3H), 5.97 (s, 2H), 5.32 (d, J = 6.4 Hz, 1H), 5.20 (s, 1H), 2.06 (s, 3H). C NMR
(50 MHz, DMSO-d6) δ 172.0, 171.8, 166.2, 166.1, 152.5, 147.2, 146.3, 139.8, 138.3,
138.2, 138.0, 137.2, 137.1, 128.2, 127.6, 119.6, 119.5, 107.8, 107.0, 106.9, 104.4,
103.8, 100.8, 56.4, 54.7, 54.4, 16.9, 16.8. HRMS (m/z + Na+) calc.: 432.1166. Obs.:
432.1171.
4.3.18 2-(4-(4-methoxyphenyl)-6-methyl-2-oxo-1,2,3,4-tetrahydropyrimidine-5-
carboxamido)-2-phenylacetic acid (19h) White solid. m.p. > 2500C (dec.) IR (cm-
1
1): 3281, 2929, 2837, 1716, 1659, 1616, 1512, 1279, 1243, 1176. H NMR (200
MHz, DMSO-d6 + CDCl3) δ 8.63 (s, 1H), 8.55 (s, 1H), 7.95 – 7.91 (d, J = 6.6 Hz,
1H), 7.80 – 7.76 (d, J = 7.1 Hz, 1H), 7.44 (s, 1H), 7.38 (s, 1H), 7.30 – 7.11 (m, 7H),
6.79 (d, J = 8.0 Hz, 2H), 5.32 (d, J = 6.9 Hz, 1H), 5.25 (s, 1H), 3.72 (s, 3H), 2.07 (s,
13
3H). C NMR (50 MHz, DMSO-d6 + CDCl3) δ 171.9, 171.7, 166.1, 165.8, 158.5,
158.4, 152.6, 152.5, 140.0, 138.0, 137.2, 137.1, 136.2, 128.0, 127.5, 127.4, 113.5,
113.4, 104.4, 103.6, 56.2, 54.8, 54.5, 54.3, 16.9, 16.8. HRMS (m/z + Na+) calc.:
418.1373. Obs.: 418.1392.
4.3.19 (4-(benzo[d][1,3]dioxol-5-yl)-6-methyl-2-oxo-1,2,3,4-tetrahydropyrimidine-
5-carbonyl)-L-phenylalanine (19i) White solid. m.p. > 2500C (dec.) IR (cm-1):

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DOI: 10.1039/C5RA14355A
3412, 3247, 2959, 1705, 1644, 1491, 1449, 1248, 1240. H NMR (200 MHz,
DMSO-d6) δ 8.58 (s, 1H), 8.55 (s, 1H), 7.86 – 7.82 (d, J = 7.99 Hz, 1H), 7.79 – 7.75
(d, J = 7.66 Hz, 1H), 7.49 (s, 1H), 7.44 (s, 1H), 7.26 – 7.04 (m, 5H), 6.85 – 6.40 (m,
3H), 5.97 (s, 2H), 5.13 (s, 1H), 5.03 (s, 1H), 4.47 (s, 1H), 4.30 (s, 1H), 3.12 – 2.80 (m,
2H), 1.87 (s, 3H). 13C NMR (50 MHz, DMSO-d6) δ 173.4, 173.1, 166.7, 166.4,
152.8, 147.2, 146.3, 139.0, 138.1, 138.0, 137.8, 128.9, 128.1, 128.0, 126.2, 119.4,
119.2, 107.9, 106.8, 106.6, 104.8, 104.4, 100.8, 54.4, 54.1, 53.3, 36.3, 36.0, 16.7,
16.6. HRMS (m/z + Na+) calc.: 446.1323. Obs.: 446.1329.
4.3.20
(4-(4-cyanophenyl)-6-methyl-2-oxo-1,2,3,4-tetrahydropyrimidine-5-
carbonyl)-L-phenylalanine (19j) White solid. m.p. > 2500C (dec.) IR (cm-1): 3291,
1
3240, 2232, 1716, 1666, 1618, 1532, 1244, 756. H NMR (200 MHz, DMSO-d6) δ
8.67 (s, 1H), 8.03 – 7.99 (d, J = 7.8 Hz, 1H), 7.91 – 7.88 (d, J = 7.5 Hz, 1H), 7.77 –
7.55 (m, 3H), 7.34 (d, J = 7.9 Hz, 1H), 7.26 – 7.05 (m, 6H), 5.28 (s, 1H), 5.18 (s, 1H),
13
4.47 (s, 1H), 4.34 (s, 1H), 3.12 – 2.83 (m, 2H), 1.85 (s, 3H). C NMR (50 MHz,
DMSO-d6) δ 173.4, 173.2, 166.6, 166.3, 152.7, 149.3, 139.4, 138.4, 138.1, 137.8,
132.3, 128.9, 128.8, 128.2, 128.0, 127.2, 126.9, 126.3, 126.2, 118.8, 109.8, 109.8,
103.9, 103.6, 54.5, 54.3, 53.4, 36.1, 35.9, 16.7. HRMS (m/z + Na+) calc.: 427.1377.
Obs.: 427.1380.
4.3.21 (4-(benzo[d][1,3]dioxol-5-yl)-6-methyl-2-oxo-1,2,3,4-tetrahydropyrimidine-
5-carbonyl)-L-tyrosine (19k) White solid. m.p. > 2500C (dec.) IR (cm-1): 3412,
1
3247, 2959, 1705, 1644, 1491, 1449, 1248, 1240. H NMR (200 MHz, DMSO-d6) δ
9.19 (s, 1H), 8.57 (s, 1H), 8.55 (s, 1H), 7.78 – 7.74 (d, J = 7.4Hz, 1H), 7.66 – 7.63 (d,
J = 7.3Hz, 1H), 7.48 (s, 1H), 7.44 (s,1H), 6.99 – 6.79 (m, 3H), 6.72 – 6.51 (m, 4H),
5.97 (s, 2H), 5.13 (s, 1H), 5.03 (s, 1H), 4.27 (s, 1H), 4.21 (s, 1H), 2.96 – 2.69 (m, 2H),
13
1.89 (s, 3H). C NMR (50 MHz, DMSO-d6) δ 173.5, 173.2, 166.7, 166.4, 155.8,
152.8, 147.2, 146.3, 139.0, 138.2, 137.8, 129.9, 128.1, 127.8, 119.5, 119.3, 114.9,
114.9, 107.9, 107.8, 106.8, 106.6, 104.8, 104.5, 100.8, 54.8, 54.4, 54.2, 53.8, 35.5,
35.3, 16.8, 16.7. HRMS (m/z + Na+) calc.: 462.1272. Obs.: 462.1279.

Page 29 of 34
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DOI: 10.1039/C5RA14355A
5. Acknowledgements
The authors thank FAPERJ, CNPq and CAPES for financial assistance. We thank
Prof. Marcos Eberlin (Instituto de Química, UNICAMP) and the IPPN-UFRJ facility
for HRMS analysis.
6. Supporting information available
Copies of 1H, 13C NMR and HRMS spectra.
7. References
(1) (a) Simon, C.; Constantieux, T.; Rodriguez, J. Eur. J. Org. Chem. 2004, 4957; (b)
Ramon, D. J.; Yus, M. Angew. Chem., Int. Ed. 2005, 44, 1602; (c) Pellissier, H.
Tetrahedron 2006, 62, 1619; (d) Tejedor, D.; Garcia-Tellado, F. Chem. Soc. Rev.
2007, 36, 484; (e) Shestopalov, A. M.; Shestopalov, A. A.; Rodinovskaya, L. A.
Synthesis-Stuttgart 2008, 1; (f) Ivanov, A. S. Chem. Soc. Rev. 2008, 37, 789; (g)
Kumaravel, K.; Vasuki, G. Curr. Org. Chem. 2009, 13, 1820; (h) Caddick, S.;
Fitzmaurice, R. Tetrahedron 2009, 65, 3325; (i) Biggs-Houck, J. E.; Younai, A.;
Shaw, J. T. Curr. Opin. Chem. Biol. 2010, 14, 371; (j) Domling, A.; Wang, W.;
Wang, K. Chem. Rev. 2012, 112, 3083; (k) Bonne, D.; Constantieux, T.; Coquerel, Y.;
Rodriguez, J. Chem.-Eur. J. 2013, 19, 2218.
(2) (a) Biginelli, P. Gazz. Chim. Ital 1889, 19; (b) Biginelli, P. Ber. 1891, 24; (c)
Kappe, C. O.; Roschger, P. J. Heterocycl. Chem. 1989, 26, 55; (d) Kappe, C. O.
Tetrahedron 1993, 49, 6937; (e) Kappe, C. O. Eur. J. Med. Chem. 2000, 35, 1043; (f)
Dallinger, D.; Kappe, C. O. Pure Appl. Chem. 2005, 77, 155; (g) Wan, J.-P.; Liu, Y.
Synthesis 2010, 3943; (h) Matache, M.; Dobrota, C.; Bogdan, N. D.; Funeriu, D. P.
Curr. Org. Synth. 2011, 8, 356; (i) Suresh; Sandhu, J. S. Arkivoc 2012, 66.
(3) (a) Folkers, K.; Johnson, T. B. J. Am. Chem. Soc. 1933, 55, 3784; (b) Sweet, F.;
Fissekis, J. D. J. Am. Chem. Soc. 1973, 95, 8741; (c) Kappe, C. O. J. Org. Chem.
1997, 62, 7201; (d) Cepanec, I.; Litvic, M.; Filipan-Litvic, M.; Gruengold, I.
Tetrahedron 2007, 63, 11822; (e) Ma, J. G.; Zhang, J. M.; Jiang, H. H.; Ma, W. Y.;
Zhou, J. H. Chin. Chem. Lett. 2008, 19, 375; (f) Kolosov, M. A.; Orlov, V. D.;
Beloborodov, D. A.; Dotsenko, V. V. Mol. Diversity 2009, 13, 5; (g) De Souza, R.; da
Penha, E. T.; Milagre, H. M. S.; Garden, S. J.; Esteves, P. M.; Eberlin, M. N.;