Methyl esters of 2-(N-hydroxycarbamimidoyl)benzoyl-substituted α-amino acids as promising building blocks in peptidomimetic synthesis: a comparative study

Article abstract of DOI:10.1007/s00706-018-2293-9

Abstract: An efficient and simple synthetic protocol for the synthesis of a number methyl esters of 2-(N-hydroxycarbamimidoyl)benzoyl-substituted (S)-α-amino acids via subsequent coupling and hydroxyamination of 2-cyanobenzamide derivatives has been developed. Comparative analysis of three pseudopeptide series based on 2-cyano- and 2-amidoxime-substituted benzoic acid and its pyridine and pyrazine counterparts has been provided and it has revealed a practical advantage of the benzoic acid derivatives due to their greater availability. The impact of the nitrogen atom in the aromatic ring on the trans/cis-amide equilibrium in the proline derivatives is discussed. Graphical abstract: [Figure not available: see fulltext.]

Full text of DOI:10.1007/s00706-018-2293-9

Monatshefte für Chemie - Chemical Monthly
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ORIGINAL PAPER
Methyl esters of 2-(N-hydroxycarbamimidoyl)benzoyl-substituted
a-amino acids as promising building blocks in peptidomimetic
synthesis: a comparative study
Volodymyr A. Tkachuk1 • Olga V. Hordiyenko1
Axelle Arrault
Irina V. Omelchenko2 • Volodomir V. Medviediev2 •
•
3
Received: 5 May 2018 / Accepted: 14 September 2018
Ó Springer-Verlag GmbH Austria, part of Springer Nature 2018
Abstract
An efficient and simple synthetic protocol for the synthesis of a number methyl esters of 2-(N-hydroxycarbamimi-
doyl)benzoyl-substituted (S)-a-amino acids via subsequent coupling and hydroxyamination of 2-cyanobenzamide
derivatives has been developed. Comparative analysis of three pseudopeptide series based on 2-cyano- and 2-amidoxime-
substituted benzoic acid and its pyridine and pyrazine counterparts has been provided and it has revealed a practical
advantage of the benzoic acid derivatives due to their greater availability. The impact of the nitrogen atom in the aromatic
ring on the trans/cis-amide equilibrium in the proline derivatives is discussed.
Graphical abstract
Keywords Amino acids Á Carboxylic acids Á Heterocycles Á Isomers Á Tautomerism Á X-ray structure determination
Introduction
effectively replace guanidine group of arginine in the
arginine mimetics for the treatment of blood-coagulation
disorders [6]. Since that time, a new application of ami-
doximes not only as precursors for the synthesis of bio-
logically active agents of amidine series, but also as
prodrugs—precursors of amidine active forms that enhance
oral bioavailability—has begun [7]. Amidoxime prodrugs
such as platelet aggregation inhibitor sibrafiban [8] and a
first oral direct thrombin inhibitor ximelagatran [9] have
been developed (Fig. 1).
Amidoximes have gained an increased attention in recent
decades because they have been shown to be reduced
in vivo to the amidines [1–5] which are known to
Electronic supplementary material The online version of this
article (https://doi.org/10.1007/s00706-018-2293-9) contains
supplementary material, which is available to authorized
users.
&
Olga V. Hordiyenko
olga.hordiyenko@gmail.com
Amidoximes are also known to behave as nitric oxide
donors (NO donors) because of their transformation by
enzymes into amides with a subsequent release of NO [10].
L-Indospicine is a natural product amino acid analogue of
L-arginine, and N-hydroxy-L-indospicine which is a carbon
isostere of N-hydroxy-L-arginine acts as one of the best
inhibitors of arginase [11–15] (Fig. 2).
1
2
3
Faculty of Chemistry, Taras Shevchenko National University
of Kyiv, Kiev, Ukraine
SSI ‘‘Institute for Single Crystals’’ National Academy of
Science of Ukraine, Kharkiv, Ukraine
Laboratoire de Chimie Physique Macromol e´ culaire, ENSIC,
Universit e´ de Lorraine, Nancy, France
123

V. A. Tkachuk et al.
Fig. 1 Amidoxime prodrugs
sibrafiban and ximelagatran
At the same time, simpler molecules, based on a readily
available 2-cyanobenzoic acid, were not studied. There-
fore, the present work is a continuation of our research on
the synthesis of the corresponding amino acid analogues
with cyano and amidoxime groups in benzene ring and
comparative studies on the synthesis and structure of these
three series of potential arginine and indospicine mimetics.
Fig. 2 L-Indospicine and its N-hydroxy derivative—carbon isosteres
of L-arginine and N-hydroxy-L-arginine; 2-(N-hydroxycarbamimi-
doyl)benzoic acid 1
Results and discussion
For the synthesis of the target amidoxime-containing
pseudopeptides, we employed the previously developed in
our group a simple strategy based on the coupling of
Cyanobenzoic acids serve as precursors of molecules
0
containing N -hydroxycarbamimidoyl (amidoxime) motif.
There are much data concerning synthesis and biological
0
2
-cyanonicotinic or 2-cyanopyrazinic acids with methyl
activity of 3- and 4-(N -hydroxycarbamimidoyl)benzamide
0
esters of L-a-amino acids followed by the conversion of the
cyano group into amidoxime one [52, 53].
derivatives [16–22], whereas the derivatives of 2-(N -hy-
droxycarbamimidoyl)benzoic acid (1) remain poorly stud-
ied. The acid
To prepare the starting acid 5, different approaches
known from the literature have been checked [54, 55]. The
route which was previously successfully used for the
preparation of pyridine- and pyrazine-containing cyano
acids includes ammonolysis of phthalic anhydride (2) with
the formation of phthalamic acid (3) [56], subsequent
dehydration and simultaneous esterification with methyl
chloroformate, and selective hydrolysis of methyl car-
boxylate 4 [55]. The approach via saponification of methyl
1 itself is unknown; thus, when
-amidinobenzoic acid was re-aminated with hydroxyl-
2
amine, heterocyclization resulted in 3-hydroxyimino-2,3-
dihydro-1H-isoindol-1-one [23]. However, few derivatives
of 1 were reported on their biological activity [24–26].
N-(2-Cyanobenzoyl)-substituted amino acids, namely
the derivatives of glycine and DL-phenylalanine, were
reported by Bergel and Stoke in 1957 [27] but no infor-
mation on their preparation was given. Later, some N-2-
cyanobenzoylated a-amino acid derivatives were prepared
by peptide coupling techniques [28–36]. Their structural
isomers 2-N-substituted 3-iminoisoindoline-1-ones are
available by alkylation of 3-amino-1H-isoindole-1-one
2
-cyanobenzoate (4) was proved to be the best method
which, with an improvement of acid preparation (up to
6% yield) and prolonged ester hydrolysis (up to 87%),
7
provided the highest yields of the target acid 5 (Scheme 1).
The conditions for each step were similar to that used for
pyridine and pyrazine acids, although the highest total
yield was achieved in the case of 2-cyanobenzoic acid (5).
Compared with alternative method of dehydration of
[
[
37, 38] or its condensation with a-amino acid derivatives
39–41], from substituted phthalamic acid [42] or
2
-iodobenzamides [43], and exhibited a wide range of
biological activities [37, 39, 42, 44, 45]. Despite the known
phthalamic acid (3) with Ac O [54], this method allows
2
transformation of unsubstituted and N-substituted
obtaining a pure final product 5 without phthalimide
impurities.
2
1
-cyanobenzamides into corresponding 3-iminoisoindolin-
-ones [46–51], the direct formation of compounds of this
Another method we attempted to develop was dehy-
dration of oxime of 2-formylbenzoic acid (6) [57] to cyano
acid 5 with acetic anhydride (Scheme 2). It was carried out
under conditions similar to those used in the preparation of
phthalamic acid (3) [54]. Since the yields were not high
enough (20–30%) and despite once it was possible to reach
series from amino acids derived 2-cyanobenzamides
remains unexplored.
Earlier, we have proposed a general approach to the
synthesis of pyridin(pyrazin)yl-2(3) containing amidoxime
pseudopeptides based on the coupling of 2(3)-cyanopy-
ridine(pyrazine)carboxylic acid with methyl esters of L-a-
amino acids followed by hydroxylamine treatment [52, 53].
95% yield of acid 5, this approach was found to be
ineffective.
1
23

Methyl esters of 2-(N-hydroxycarbamimidoyl)benzoyl-substituted a-amino acids…
Scheme 1
Scheme 2
It should be noted that with prolonged storage at
ambient temperature, the acid 5 undergoes slow hydrolysis
with a phthalimide formation. The purity control of the
compound 5 is best assessed by the presence/absence of
yields of esters 8/9 were significantly higher (90–95%) than
for pyridine (58–85% [52]) and pyrazine derivatives
(51–68% [53]).
The formation of the cyclic isomeric iminoisoindolones
9a–9h as minor products together with the desired
2-cyanobenzamides 8a–8h was detected by TLC of the
reaction mixture. The individual isomers were isolated by
column chromatography (gradient elution of ethyl acetate/
petroleum ether 0:100–60:40). Chromatographic separation
of crude Trp 8g/9g and Glu 8h/9h derivative mixtures
made it possible to obtain only 8 g and 8 h compounds in
an individual form.
phthalimide 4-7-H four-proton singlet at the 7.8 ppm
1
region in the H NMR spectrum in DMSO-d solution.
6
The acid 5 was coupled with a series of methyl esters of
L-a-amino acids with activating agent 1-ethyl-3-(dimethyl-
aminopropyl)carbodiimide hydrochloride (EDCI) in the
presence of hydroxybenzotriazole (HOBT) and TEA in
DCM medium according to a previously developed pro-
tocol [52]. A characteristic feature of this reaction is the
formation in most cases of a mixture of coupling products:
methyl 2-[[(2-cyanophenyl)carbonyl]amino]alkanoates 8
and their tautomers endo-N- substituted methyl 2-(1-imino-
The degree of tautomeric conversion of 2-cyanobenza-
mides 8a–8h into 9a–9h depends on the reaction time and
the branching of the amino acid side chain. The Gly
derivative 8a has been completely transformed into imi-
noisoindolone 9a in less than 1 day, and for the Leu
derivative 8d conversion to the corresponding cyclic iso-
mer 9d has been completed upon stirring the reaction
mixture at rt for 2 days.
3
-oxo-1,3-dihydro-2H-isoindol-2-yl)alkanoates 9 derived
from subsequent ring closure (Scheme 3, Table 1). This
result differs from the described amination of the methyl
esters of 2-cyanobenzoic or 2-cyanopyridine carboxylic
acids with amines or alkylhydrazines, which was accom-
panied by the formation of only cyclic products with an
amino residue at the exocyclic atom of nitrogen [38]. Total
An attempted coupling of 2-cyanobenzoic acid (5) with
methyl ester of alanine under microwave irradiation at
Scheme 3
123

V. A. Tkachuk et al.
Table 1 Coupling of
-cyanobenzoic acid (5) with
a
Yield /% 8A:9B
Entry
AA
Products
Py [52] A:B
Pz [53] A:B
2
methyl esters of (S)-a-amino
acids and the comparison with
coupling of 2-cyanopyridine
and 2-cyanopyrazine series
d
– :58
1
2
3
4
5
6
7
8
9
a
Gly
Ala
Val
Leu
Met
Phe
Trp
Glu
Pro
8a:9a
8b:9b
8c:9c
8d:9d
8e:9e
8f:9f
8g:9g
8h:9h
8i
74:15
80:9
85:6
91:4
83:7
86:3
–
15:58
37:34
9:76
–
d
– :76
d
– :83
23:28
–
–
–
3:65
–
b
92:0
c
84:0
–
–
95
74
49
Yield after column chromatography separation
b 1
Only one compound 8g was isolated, 9g was detected by TLC and H NMR in the crude product
c 1
Only one compound 8h was isolated, 9h was detected by TLC and H NMR in the crude product
d
The open form A was not isolated
5
0 °C shortened the processing time to 5–10 min. How-
replacing the phenylene ring by a more electron-deficient
pyridine and an even greater degree of pyrazine nucleus
results in a significant shift of the NH signals to a low field.
One of the reasons that causes such shifts can be the
E configuration of the substituents at C=N bond and syn
orientation of the NH atom to the aromatic ring of the
iminoisoindolones 9. The NH proton that is oriented
towards the aromatic ring and located in the same plane is
influenced by the anisotropic effect of the aromatic ring
current so that its signal is found at much lower field
(8.56–8.65 ppm). The same deshielding effect additionally
can be caused by nitrogen atoms of the pyridine and pyr-
azine rings of corresponding analogues. Significant differ-
ences in the shifts of the carbon atoms signals which
belong to the open A and cyclic form B were observed in
ever, in this case, in spite of the rapid conversion of acid 5
into the final mixture consisting of amide 8b and imi-
noisoindolone 9b in approximately a 1:1 ratio, formation of
phthalimide as a by-product was more intensive according
to TLC.
The electronic nature of the aromatic ring significantly
affects the tautomeric ratio of two forms 8A/9B. If in the
case of cyanobenzamides the open form 8A much more
predominates, then for the compounds of the series of p-
deficient pyridine, the cyclic form of iminoisoindolone
B was much more prevalent, and only the cyclic ester was
isolated for the Gly, Phe, and Trp derivatives [52]. A
similar situation was observed in the pyrazine series: for
Ala, the cyclic form B content was slightly larger (23:28),
whereas in the case of Phe it predominated almost com-
pletely (3:65) [53]. Evidently, the presence of an electron-
negative nitrogen atom in the b-position to the cyano group
leads to its activation to the nucleophilic attack by the
nitrogen atom of the amide fragment to afford pyrrolidine
ring closure.
1
3
the C NMR spectra. The signal of the CN group of the
amides of 8 was manifested at about d = 118 ppm, and in
the spectra of iminoisoindolones 9 a signal of about
160 ppm appeared instead of it, which can correspond to
the carbon atom of the N–C=N chain. Carbon which was
bound to the CN group and resonated in a region of
110–112 ppm shifted to a lower field of 130–132 ppm.
The bond configuration is determined by X-ray
diffraction of the cyclic Gly 9a and Ala 9b derivatives
(Fig. 3). It is the same as C=N bond E configuration of the
pyridine series [52].
The assignment of isomers, as in the case of aza ana-
logues, has been made based on the chemical shifts of the
1
NH protons signals in their H NMR spectra in CDCl
3
(
Table 2). In the spectra of iminoisoindolones 9a–9f, there
are broadened single-proton NH signals of reduced inten-
sity at d = 8.40–8.90 ppm, while the signals of amide
CONH group protons of 8a–8f appear in the form of
doublets or broadened singlets at 6.60–7.20 ppm. For
pyridine derivatives, the open form reveals NH signals in
the region of 7.01–7.15 ppm, whereas for pyrazine amides,
at 8.20–8.26 ppm. Similarly, cyclic aza isomers exhibit
signals of NH protons in the region of 9.29–9.37 ppm
The 9a compound was previously studied by single-
crystal X-ray diffraction analysis at 200 K [43]; cell
parameters are close to the current experimental data at
298 K. The distribution of electron density in N(2)=C(7)–
N(1)–C(8)=O(1) fragment is rather similar in 9a and 9b,
revealing minor p-conjugation. However, the N(2)=C(7)
˚
and N(1)–C(8) bonds in 9a (1.263(5) and 1.388(5) A) are
little longer than corresponding bonds in 9b (1.255(2) and
(
pyridine) and 9.46–9.51 ppm (pyrazine) that are shifted
downfield compared to benzene species 9a–9f
8.56–8.65 ppm). The conclusion that can be drawn is that
˚
1.372(2) A). The H atom at N(2) has syn orientation with
(
respect to the benzene ring in both compounds. Both N(1)
1
23

Methyl esters of 2-(N-hydroxycarbamimidoyl)benzoyl-substituted a-amino acids…
Table 2 Comparison of d (NH) chemical shift values (CDCl
3
) in the open A and cyclic B forms
AA, R
3
Open form A, d (NH)/ppm (CDCl )
Ala, R=Me
Phe, R=Bn
6.88
6.64
7.15
8.26
8.20
[a]
–
3
Cyclic form B, d (NH)/ppm (CDCl )
Ala, R=Me
Phe, R=Bn
8.56
8.65
9.34
9.29
9.51
9.46
[
b]
[
[
a]
Was not isolated
1
Was observed in a crude H NMR spectrum but was not isolated
b]
Fig. 3 Molecular structure of 9a and 9b according to X-ray diffraction study with the atom numbering used in the crystallographic analysis.
Atoms are shown as 50% thermal ellipsoids
atoms are planar (sum of the valence angles centred on
N(1) is 359.3(9)° and 360.0(6)° in 9a and 9b, respectively).
The carboxylic substituent at N(1) reveals –sc orientation
in 9a but –ac orientation in 9b with respect to the C(7)–
N(1) endocyclic bond (the C(7)–N(1)–C(9)–C(10) torsion
angle is - 80.9° in 9a while the corresponding C(7)–N(1)–
C(9)–C(11) torsion angle is -125.7° in 9b). In the crystal,
both compounds form chains along the [101] crystallo-
graphic direction in 9a and [100] in 9b, due to the N–
approach after the start of our research. They were isolated
as a sole product from the reaction of 2-iodobenzamides
derived from amino acid methyl/ethyl esters and benzyl
cyanide in the presence of potassium phosphate and cop-
per(I) iodide catalyst [43]. More stringent reaction condi-
tions (heating in DMSO at 100 °C for 11–25 h) probably
contributed to the formation of only one tautomer of imi-
noisoindolone 9.
L-Proline derivative 8i for which the ring closure is not
possible was isolated in 95% yield which significantly
exceeds the yields of ProOMe transformations with
cyanopyridine (74%, DCM, rt, [52]) and cyanopyrazine
acids (49%, THF, 0°C, [53]) (Scheme 4).
0
0
H…O intermolecular hydrogen bonds (N(2)–H(2)…O(2)
0
˚
0
(
x ? 0.5, 1 - y, z ? 0.5, H…O 2.32 A, N–H…O 157°)
0
0
˚
in 9a; N(2)–H(2)…O(1) (x - 1, y, z, H…O 2.33 A, N–
0
H…O 178°) in 9b.
It should be noted that iminoisoindolones 9a–9g were
obtained recently by another more complicated synthetic
1
13
Its H and C NMR spectra exhibit the double set of
signals of all atoms due to trans,cis-amide isomerism.
123

V. A. Tkachuk et al.
Scheme 4
1 13
According to H, C NMR, HSQC, NOESY spectra of 8i,
Table 3 Synthesis of amidoxime derivatives 10a–10i
the approximate ratio of the rotamers is estimated. Cross-
peaks corresponding to the spatial interaction between the
proton at C6 position of the benzene ring and the proton at
C5 position of the pyrrolidine unit indicate that the major
product is the trans-isomer (& 77%), and the minor is cis-
isomer (& 23%), accordingly. This isomeric trans,cis ratio
is similar to that of 77:23 ratio of the pyridine analogue
a
Yield /%
Entry
AA
R
Product
[
52], whereas pyrazine counterpart exhibits in solution the
1
2
3
4
5
6
7
8
9
a
Gly
Ala
Val
Leu
Met
Phe
Trp
Glu
Pro
H
10a
10b
10c
10d
10e
10f
10g
10h
10i
72
75
83
89
82
88
93
81
92
cis-amide conformation in much higher content when both
forms are nearly equally populated: trans/cis—54:46 due
to additional 4-N atom that involved in noncovalent
intramolecular n ? p* interaction with Cco of the pyrro-
lidine ring [53].
Me
i-Pr
i-Bu
(CH
Bn
2 2 3
) SCH
The N(2) atom of pyrrolidine ring in 8i is planar [sum of
the valence angles centred on N(2) is 359.4(6)°] due to the
conjugation in amide fragment N(2)–C(8)=O(1) (Fig. 4).
The pyrrolidine ring adopts not envelope but twist con-
formation. Atoms C(10) and C(11) are disordered over two
mirror symmetrical twist conformations (deviations of the
CH
2
-3-indolyl
(CH
2
)
2
CO
2
H
Yield after column chromatography purification
˚
˚
atoms are ? 0.32 A and - 0.29 A for C(10A) and C(11A),
0.34 and ? 0.15 for C(10B) and C(11B), respectively).
axial orientation (the C(9)–N(2)–C(12)–C(13) torsion
angle is 116.2(2)°) and its carboxylic fragment is turned to
the N(2)–C(12) endocyclic bond [the N(2)–C(12)–C(13)–
O(2) torsion angle is 153.3(2)°]. The aryl ring of the sub-
stituent at the N(2) atom is located in cis-conformation to
the N(2)–C(12) endocyclic bond and is rotated with respect
to the plane of the amide fragment (the C(12)–N(2)–C(8)–
C(1) and N(2)–C(8)–C(1)–C(2) torsion angles are
-
The carboxymethyl substituent at C(12) atom is located in
-
9.0(3)° and - 62.5(2)°, respectively).
In the crystal phase, molecules of 8i are organized in 3D
structure due to non-specific and weak C–H…p interac-
0
tions (H(10D)…C(5) - x, 0.5 ? y, - 1.5 - z. H…C’
˚
.73 A, sum of the van der Waals radii is 2.87 A [58]).
˚
2
Further, amidoximes 10a–10i were obtained in good
yields from corresponding methyl esters 8a–8i and 9a–9h
Table 3). Similar to aza-analogues [52, 53], the pyrro-
(
lidine cycle of iminoisoindolones 9a–9f, taken in an indi-
vidual form under the reaction conditions is opened with
the formation of the desired amidoximes 10a–10h.
Therefore, upon treatment with hydroxylamine of the crude
amides 8a–8h, which contained an impurity of the
Fig. 4 Molecular structure of cis-8i according to X-ray diffraction
study with the atom numbering used in the crystallographic analysis.
Atoms are shown as 40% thermal ellipsoids
1
23

Methyl esters of 2-(N-hydroxycarbamimidoyl)benzoyl-substituted a-amino acids…
Scheme 5
orientation of the H(1) atom at O(1) with respect to NH2
group is due to the intramolecular attractive contact
˚
H(2A)…O(1) 2.23 A (sum of van der Waals radii [58] is
˚
2.46 A). The ester fragment of the substituent at the car-
bamide group is located in ac-conformation to the C(8)–
N(3) bond and its carboxylic group is turned to the N(3)–
C(9) bond (the C(8)–N(3)–C(9)–C(13) and N(3)–C(9)–
C(13)–O(4) torsion angles are 131.8(2)° and 32.6(2)°,
respectively). The isopropyl group is turned in such a way
that the N(3)–C(9)–C(10)–H10 torsion angle is 45°
(Table 1, SI).
Fig. 5 Molecular structure of 10c according to X-ray diffraction
study with the atom numbering used in the crystallographic analysis.
Atoms are shown as 50% thermal ellipsoids
corresponding iminoisoindolones 9a–9h, their complete
conversion to the final amidoximes 10a–10h was observed.
The treatment with hydroxylamine hydrochloride and Et N
3
was carried out in MeOH at 0 °C followed by stirring at
ambient temperature for 1.5–8 h. The crude products were
purified by silica gel flash column chromatography to
afford amidoximes 10a–10i in 72–93% yield which
exceeded the yields for pyridine (67–79% [52]) and pyr-
azine analogues (63–84% [53]).
Like the starting Pro CN-derivative 8i, amidoxime 10i is
a mixture of cis- and trans-amide conformers, since two
sets of signals with approximately the same trans/cis ratio
of 75:25 belonging to individual isomers were observed in
1
13
the H and C NMR spectra (Scheme 5). As in the cases of
pyrazine Pro derivative [53], the general tendency to adopt
trans-conformation is observed (Table 4).
This conclusion was proved by X-ray diffraction data of
1
amidoxime 10c (Fig. 5). Compounds 10a–10i in their H
As a by-product in these conversions, 1H-isoindole-
1,3(2H)-dione oxime (11) was isolated in each case
(Scheme 6). According to TLC, it was formed in an
insignificant amount already in the reaction mixture.
However, its content increased during the extraction of
amidoximes from the reaction mixture with EtOAc and
their further chromatographic purification, which led to
decreasing the yields of compounds 10a–10i. The higher
the amount of oxime 11 monitored by TLC, the less
branched was the amino acid side chain: Gly [ Ala [
Pro [ Met [ Val [ Leu [ Phe [ Trp. The gradual for-
mation of oxime precipitate 11 occurred even with pro-
longed exposure to solutions of purified 10a–10i in EtOAc
at room temperature, and when they were heated. In the
solid state, compounds 10a–10i, in particular those con-
taining the less branched amino acid side chains—Gly, Ala
and Pro—partially decomposed, and much more when the
substances were contaminated with residual solvent.
Transformation of glycine derivative 10a into oxime 11
was completed in 56 h upon stirring its methanolic solution
at rt (TLC).
NMR spectra in DMSO-d exhibit characteristic chemical
6
shifts: sharp two-proton singlet of amidoxime NH group at
2
d = 5–6 ppm, OH signal at 9–10 ppm, and signal of amide
1
3
CONH of 10a–10 h at 8–9 ppm. In addition, in the
C
NMR spectra, the signals due to CN group disappeared,
instead, a new signals at d = 151–154 ppm that originated
from carbon atoms of N–C=NOH group were observed.
The IR spectra of amidoximes 10a–10i exhibited broad
-
1
absorption bands at 3000–3500 cm , due to NH, NH , and
2
OH groups, sharp bands at 1720–1750 (C=O) and
-
1
1
620–1640 (C–N) cm
and the lack of characteristic
1
-
cyano group band at 2223–2230 cm
.
The vicinal amide and N-hydroxycarbamimidoyl groups
are rotated with respect to the plane of benzene ring (angles
between planes are 47.3° and 61.8°, respectively; Fig. 5).
Both N(2) and N(3) atoms adopt planar configuration (sum
of the valence angles centred on these atoms are 355(7)°
and 360.0(3)°, respectively). The bond lengths in N-hy-
droxycarbamimidoyl fragment differ negligibly from the
˚
corresponding mean values (N(1)–O(1) 1.430(2) A and
N(2)–C(7) 1.350(2) are elongated against the mean values
Oxime 11 was first obtained by the reaction of
hydroxylamine with ethyl 2-cyanobenzoate [60], and later
˚
of 1.415 A and 1.340 A, respectively [59]). The anti
˚
123

V. A. Tkachuk et al.
Table 4 Trans/cis-distribution in Pro pseudopeptides 8i, 10i with those obtained from 2-cyanonicotinic and 2-cyanopyrazinic acids
a
Yield /%
a
Yield /%
Cyano derivative
Trans/cis ratio
Oxime derivative
Trans/cis ratio
9
5
77/23
92
75/25
8
7
77/23
70
68/32
4
9
54/46
93
74/26
Taken from [53]
a
Isolated yield
Scheme 6
from unsubstituted 3-aminoisoindol-1-one by heating with
hydroxylamine hydrochloride in methanol [47]. Therefore,
we investigated the reaction of bulk tert-butyl
that during the initial stage of the reaction, the intermediate
esters that have not been isolated were probably seen as
additional spots on TLC. An attempt to convert diethyl-
amide of 2-cyanobenzoic acid 13 into the corresponding
amidoxime also failed, leading exclusively to compound 11
in 2 days.
2
-cyanobenzoate 12 with hydroxylamine (Scheme 7). The
pyrrolidine ring closure leading to oxime 11 also occurred
although in this case the reaction was completed within
more than 1 day at room temperature. It should be noted
1
23

Methyl esters of 2-(N-hydroxycarbamimidoyl)benzoyl-substituted a-amino acids…
Scheme 7
Scheme 8
2
5 1
Taking these facts into account, it can be assumed that
the ease of formation of the cyclic amidoxime 11 from
amides 10 can be determined not only by steric hindrance,
but electronic effects as well, in particular by the presence
of an N-(methyl alkanoate) group that prevents cyclization.
To investigate the possibility of the pyrrolidine ring
opening of 3-N-aryl-substituted analogues of isoindolones
were quantitatively isolated. Probably, the steric hindrance
created by the bulk aryl residue prevents the 3-C atom of
the isoindole nucleus of compounds 16a–16d from attack
by hydroxylamine.
Conclusion
9
, N-aryl imines 16a–16d were synthesized by (Z,E)-3-
arylimino-2,3-dihydro-1H-isoindol-1-ones 15a, 15b
61, 62] alkylation according to the known protocol [38]
Scheme 8). Like unsubstituted at the exocyclic nitrogen
Comparative analysis of pseudopeptides based on 2-cyano-
and 2-amidoxime-substituted benzoic acid and its pyridine
and pyrazine counterparts revealed that the developed
approach allows to obtain the desired compounds in high
yields and benefits from operational simplicity and avail-
ability of starting materials. These compounds can be used
as pseudopeptide building blocks, in particular, amid-
oximes as precursors of amidines in L-arginine and L-in-
dospicine mimetics.
[
(
isoindolones 9a–9 h, their N-arylated analogues 16a–16d
exist as E-isomers of the substituents at C=N bond [61].
This conclusion was reached based on the observation that
the 4-H proton signals are considerably shifted upfield
because of the shielding effect of N-aromatic ring
[
61, 63–65]. However, attempts to transform them into the
corresponding N-arylamidoximes upon treatment with
hydroxylamine under the above-described conditions were
unsuccessful. Furthermore, the heating of the reaction
mixture at 50 °C for several hours did not afford the
desired product. In each case, only the starting compounds
In the series of cyano-pseudopeptides, 2-cyano group of
benzoic acid under employed conditions exhibits lower
reactivity towards pyrrolidine ring closure reaction with
amide unit in contrast to its aza analogues. NMR studies of
a series of proline-containing peptides reveal a pronounced
123

V. A. Tkachuk et al.
effect of the aromatic ring nature upon the cis-to-trans ratio
of the adjacent amide bond in solution. 2-Cyano-substi-
tuted benzoic and nicotinic acid amides exhibit a prefer-
ence of the proline residue for the trans form, whereas
method using spherical harmonics, implemented in the
SCALE3 ABSPACK scaling algorithm of the CrysAlisPro
program package [66]. Structures were solved by direct
2
methods and refined against F within anisotropic
2
-cyanopyrazine counterpart adopts the cis-amide confor-
approximation for all non-hydrogen atoms using the
OLEX2 [67] program package with SHELXT and
SHELXL modules [68]. 9a structure was refined as a twin
with twinning matrix (0.124, 0, - 0.876, 0, - 1, 0,
-1.124, 0, - 0.124) using HKLF5 instruction [refined
BASF parameter is 0.362(8)]. In 8i, the C10 and C11 atoms
of pyrrolidine ring were disordered over two symmetrical
twist conformations with relative component ratio of
0.59:0.41. The C(10A)–C(11A) and C(10B)–C(11B) bonds
mation in much higher content of 46% when both forms are
nearly equally populated in solution. Thus, the hypothesis
that the presence of the extra nitrogen atom of pyrazine
ring favours the cis-conformation for cyano derivatives was
confirmed. The conversion of cyano group into amidoxime
unit revealed almost the same isomeric ratio with a pref-
erence of the proline residue for the trans form of the entire
three types of amidoxime pseudopeptides.
˚
were restrained to have fixed length of 1.52(1) A, and all
neighbouring bonds C(9)–C(10A,B) and C(12)–C(11A,B)
were restrained to be approximately of the same length to
˚
within 0.01 A. All H atoms were placed in idealized
Experimental
Melting points were determined on a Boetius microscope
hot plate apparatus. Elemental analyses (C, H, N, S) were
conducted using the Vario Micro Cube; their results were
found to be in good agreement (± 0.3%) with the calcu-
lated values.
positions and constrained to ride on their parent atoms with
Uiso = 1.2Ueq (1.5 Ueq for OH and CH groups) except the
3
H atoms at N(2) atoms in 9b and 10c that were refined
isotropically. Details of the data collection and processing,
structure solving and refinement are summarized in
Table 2 (SI). CCDCs 1836420–1836423 contain the sup-
plementary crystallographic data for this paper. These data
can be obtained free of charge from the Cambridge Crys-
tallographic Data Centre via www.ccdc.cam.ac.uk/data_
request/cif.
LC/MS spectra were recorded using a system that con-
sisted of a high-performance liquid chromatograph (Agi-
lent 1100 Series) equipped with a diode-matrix and mass-
selective detector (Agilent LC/MSD SL); ionization
method: chemical ionization under atmospheric pressure
(
APCI). IR spectra were recorded with a PerkinElmer
2
-Carbamoylbenzoic acid (3) [56] A suspension of 10.0 g
1
Spectrum BX FTIR Spectrometer with KBr pellets. H and
3
phthalic anhydride (2, 67.5 mmol) in 50 cm 28% NH OH
1
3
4
C NMR spectra were measured on a Bruker Avance 300
was stirred at 50 °C until the reagent was dissolved. After
cooling to 0 °C, the precipitated product was separated off.
To the filtrate 50 cm acetone was added and the additional
model spectrometer operating at 300 and 75 MHz, and
Bruker Avance 400 model spectrometer at 400 and
3
1
00 MHz, respectively, in CDCl and DMSO-d at 20 °C
3
6
1 13
amount of precipitate was obtained. The combined pre-
3
cipitates were dissolved in 50 cm water and re-precipita-
with tetramethylsilane as an internal reference. H and
C
chemical shifts (d) are given in parts per million (ppm)
relative to the residual solvent peak. HMBS spectra were
recorded on a Bruker Avance 300 model spectrometer at
tion was performed with addition of 10 M HCl (dropwise
to pH 3) while cooling. The precipitate was filtered off,
washed with acetone and dried to afford 8.49 g (76%) acid
3
00 and 75 MHz. HSQC and NOESY spectra were
recorded on a Bruker Avance 500 spectrometer at 500 and
25 MHz. Coupling constants J were directly taken from
3
as a colourless crystalline powder. M.p.: 144–145 °C
([49] 145 °C);
1
the spectra and are not averaged. TLC analyses were car-
ried out on silica gel-coated aluminium sheets (Merck) and
spots were visualized with UV light. Preparative column
chromatography was carried out using silica gel 60,
Methyl 2-cyanobenzoate (4) [55] To a stirred suspension
of 3.52 g compound 3 (21.3 mmol) in 50 cm DCM at
3
3
3
0 °C 6.23 cm TEA (44.7 mmol) and 3.62 cm methyl
chloroformate (46.8 mmol) were added. After stirring at
room temperature overnight, the reaction mixture was
4
0–63 lm.
3
concentrated under reduce pressure, diluted with 100 cm
3
DCM, washed with 3 9 100 cm H O and 100 cm brine,
3
Crystal structure determination
2
dried over anhydrous MgSO , and concentrated under
4
3
Diffraction data for crystals of 8i, 9a, 9b, and 10c were
collected on an Xcalibur-3 diffractometer (MoKa radia-
tion, k = 0.71073 A, CCD-detector, graphite monochro-
mator, x-scanning) at room temperature. Empirical
absorption correction was provided with a multi-scan
reduced pressure. The residue was washed with 100 cm
petroleum ether and dried to afford 3.38 g (98%) com-
˚
pound 4 as a colourless crystal. M.p.: 47–49 °C (Ref. [49]
47 °C); H and C NMR spectra were found to be iden-
tical with the ones described in [49].
1
13
1
23

Methyl esters of 2-(N-hydroxycarbamimidoyl)benzoyl-substituted a-amino acids…
2
methyl 2-cyanobenzoate 4 (20.4 mmol), 60 cm MeOH,
-Cyanobenzoic acid (5) [55] The mixture of 3.29 g
J = 7.5 Hz, J = 7.5 Hz, 1H, 5-H ), 7.75 (d, J = 7.5 Hz,
1 2 Ar
13
3
1H, 3-H ), 7.81 (d, J = 7.5 Hz, 1H, 6-H ) ppm;
C
Ar
Ar
3
and 22 cm 1 M NaOH was stirred overnight, and then
NMR (75 MHz CDCl ,): d = 18.4, 49.1, 52.8, 111.0,
3
concentrated in vacuo. The residue was diluted with
117.5, 128.7, 131.4, 133.0, 134.3, 138.0, 164.7, 173.2 ppm;
IR (KBr): mꢀ = 3298, 2933, 2225 (CN), 1742, 1645, 1591,
1536 cm ; LC/MS: m/z (%) = 233 (100, [M?H] ).
3
00 cm H O and 100 cm DCM, and then acidified with
3
1
2
3
2 cm 1 M HCl under cooling. The resulting precipitate
-1
?
2
3
was collected, washed with 100 cm H O, 100 cm pet-
3
2
Methyl (2S)-2-[[(2-cyanophenyl)carbonyl]amino]-3-methyl-
butanoate (8c, C H N O ) It was prepared according to
General procedure A (1.105 g, 85%). The product was
roleum ether and dried to afford 2.60 g (87%)
1
4 16 2 3
2
2
-cyanobenzoic acid 5 as a white crystalline powder. M.p.:
13
1
28–230 °C ([54] 227–228 °C). H and C NMR spectra
isolated by column chromatography (gradient elution of
were found to be identical with the ones described in [69].
EA/PE 0:100–60:40, R = 0.53) as a white powder. M.p.:
f
1
7
7–78 °C; H NMR (300 MHz, CDCl ): d = 1.02 (d,
3
General procedure A for the synthesis
of compounds 8a–8i and 9a–9h
J = 6.9 Hz, 3H, CHCH ), 1.07 (d, J = 6.9 Hz, 3H,
3
CHCH ), 2.28–2.38 (m, 1H, CHCH ), 3.79 (s, 3H, CH O),
3
3
3
4
.81 (dd, J = 8.4 Hz, J = 8.7 Hz, 1H, C H), 6.77 (d,
1 2 a
To a suspension of 0.735 g 2-cyanobenzoic acid (5,
5
J = 7.5 Hz, 1H, NH), 7.59 (dd, J = 7.5 Hz, J = 7.8 Hz,
1
3
mmol) in 50 cm DCM 1.4 cm TEA (10 mmol), methyl
3
2
Jm = 1.2 Hz, 1H, 4-H ), 7.68 (dd, J = 7.8 Hz,
Ar
ester L-a-amino acid hydrochloride (5 mmol), and 0.675 g
HOBt (5 mmol) were added. The mixture was stirred at
J2 = 7.5 Hz, Jm = 1.2 Hz, 1H, 5-H ), 7.78 (d,
Ar
J = 7.8 Hz, 1H, 3-H ), 7.83 (d, J = 7.8 Hz, 1H, 6-H )
Ar
Ar
0 °C and 0.970 g EDCI (5.05 mmol) was added. Then, the
mixture was stirred at room temperature overnight. The
1
3
ppm; C NMR (75 MHz, CDCl ): d = 18.6, 19.7, 32.2,
3
5
1
1
3.0, 58.7, 111.2, 118.2, 129.6, 131.9, 133.6, 134.8, 138.8,
65.7, 172.8 ppm; IR (KBr): mꢀ = 3271, 2952, 2223 (CN),
731, 1644, 1591, 1540 cm ; LC/MS: m/z (%) = 261
precipitate was filtered off and the filtrate was evaporated
under reduced pressure. The residue was diluted with
3
0 cm DCM, washed with solution of 0.1 N HCl
-
1
5
?
(100, [M?H] ).
3
3
(
3 9 25 cm ), 15 cm brine, then dried over MgSO and
4
concentrated under reduced pressure. The residue was
purified by flash column chromatography (gradient elution
of ethyl acetate/petroleum ether 0:100–70:30) to afford the
desired products as separate fractions of 9a–9h, then 8a–8i.
Methyl (2S)-2-[[(2-cyanophenyl)carbonyl]amino]-4-methyl-
pentanoate (8d, C H N O ) It was prepared according to
General procedure A (1.248 g, 91%). The product was
1
5 18 2 3
isolated by column chromatography (gradient elution of
EA/PE 0:100–60:40, R = 0.53) as a white powder. M.p.:
f
Methyl
2-[[(2-cyanophenyl)carbonyl]amino]acetate
1
9
1–92 °C; H NMR (300 MHz, CDCl ): d = 0.99 and 1.01
3
(
procedure A (0.807 g, 74%). The product was isolated by
8a, C H N O ) It was prepared according to General
1
1 13 3 4
(2d, J = 6.6 and 7.2 Hz, 6H, 2CH ), 1.68–1.86 [m, 3H,
3
CH ? CH(CH ) ], 3.79 (s, 3H, CH O), 4.85–4.92 (m, 1H,
2
3 2
3
column chromatography (gradient elution of EA/PE 0:100–
1
C H), 6.64 (d, J = 6.9 Hz, 1H, NH), 7.59 (dd,
a
7
0:30, R = 0.32) as a white powder. M.p.: 112–113 °C; H
f
J1 = 7.5 Hz, J2 = 7.5 Hz, 1H, 4-H ), 7.66 (dd,
Ar
NMR (300 MHz, CDCl ): d = 3.74 (s, 3H, CH O), 4.21 (d,
J = 5.1 Hz, 2H, CH ), 7.13 (br s, 1H, NH), 7.56 (dd,
2
3
3
J = 7.8 Hz, J = 7.5 Hz, 1H, 5-H ), 7.77 (d, J = 7.8 Hz,
Ar
1
2
13
1
H, 3-H ), 7.84 (d, J = 7.8 Hz, 1H, 6-H ) ppm;
Ar
C
Ar
J = 7.8 Hz, J = 7.8 Hz, 4-H ), 7.64 (dd, J = 7.8 Hz,
1 Ar
2
1
NMR (100 MHz CDCl ,): d = 22.0, 22.9, 25.0, 41.5, 51.6,
3
J = 7.8 Hz, 5-H ), 7.72 (d, J = 7.8 Hz, 1H, 3-H ), 7.78
2
Ar
Ar
5
1
1
2.6, 110.8, 117.5, 128.7, 131.3, 132.9, 134.2, 137.8,
65.0, 173.3 ppm; IR (KBr): mꢀ = 3288, 2954, 2227 (CN),
738, 1641, 1535 cm ; LC/MS: m/z (%) = 275 (100,
1
3
(
d, J = 7.8 Hz, 1H, 6-H ) ppm; C NMR (75 MHz,
Ar
CDCl ): d = 42.4, 53.1, 111.6, 118.0, 129.0, 131.9, 133.4,
3
-1
1
34.9, 138.1, 166.0, 170.5 ppm; IR (KBr): mꢀ = 3269, 2227
CN), 1749, 1648, 1538 cm ; LC/MS: m/z (%) = 219
?
[M?H] ).
-
1
(
?
100, [M ?H] ).
(
Methyl (2S)-2-[[(2-cyanophenyl)carbonyl]amino]-4-(methyl-
sulfanyl)butanoate (8e, C H N O S) It was prepared
according to General procedure A (1.212 g, 83%). The
1
4 16 2 3
Methyl (2S)-2-[[(2-cyanophenyl)carbonyl]amino]propanoate
8b, C H N O ) It was prepared according to General
procedure A (0.928 g, 80%). The product was isolated by
(
1
2 12 2 3
product was isolated by column chromatography (gradient
elution of EA/PE 0:100–60:40, R = 0.38) as a yellowish
f
column chromatography (gradient elution of EA/PE 0:100–
1
1
white powder. M.p.: 90–91 °C; H NMR (300 MHz,
6
0:40, R = 0.31) as a white powder. M.p.: 96–97 °C; H
f
CDCl ): d = 2.09 (s, 3H, CH S), 2.10–2.15 (m, 1H,
3
3
NMR (300 MHz, CDCl ): d = 1.56 (d, J = 7.2 Hz, 3H,
3
CHCH ), 2.26–2.31 (m, 1H, CHCH ), 2.58–2.61 (m, 2H,
2
2
CH ), 3.79 (s, 3H, CH O), 4.82 (pseudo quintet,
3
3
CH S), 3.77 (s, 3H, CH O), 4.90–4.95 (m, 1H, CH), 7.15
2
3
J = 7.2 Hz, 1H, C H), 6.88 (br s, 1H, NH), 7.58 (dd,
a
13
br s, 1H, NH), 7.57–7.82 (m, 4H, 3-6-H ) ppm; C NMR
(
Ar
J1 = 7.5 Hz, J2 = 7.5 Hz, 1H, 4-H ), 7.66 (dd,
Ar
123

V. A. Tkachuk et al.
(
75 MHz, CDCl ): d = 16.1, 30.6, 31.9, 53.0, 53.3, 111.4,
18.0, 129.2, 131.9, 133.4, 134.7, 138.3, 165.6, 172.6 ppm;
52.5, 53.2, 53.4, 111.6, 118.0, 129.1, 132.0, 133.4, 134.9,
138.3, 165.7, 172.5, 174.1 ppm; IR (KBr): mꢀ = 3459, 3317,
2230 (CN), 1753, 1737, 1686, 1645, 1594, 1578,
3
1
IR (KBr): mꢀ = 3473, 3429, 3313, 2958, 2919, 2228 (CN),
1
-
753, 1645, 1593, 1578, 1535 cm ; LC/MS: m/z
1
-1
?
1530 cm ; LC/MS: m/z (%) = 305 (95, [M?H] ).
Methyl cis/trans-(2S)-1-[(2-cyanophenyl)carbonyl]pyrro-
lidine-2-carboxylate (8i, C H N O ) It was prepared
?
%) = 293 (100, [M?H] ).
(
Methyl (2S)-2-[[(2-cyanophenyl)carbonyl]amino]-3-phenyl-
propanoate (8f, C H N O ) It was prepared according to
General procedure A (1.324 g, 86%). The product was
1
4 14 2 3
according to General procedure A (1.226 g, 95%). The
18 16 2 3
product was isolated by column chromatography (gradient
isolated by column chromatography (gradient elution of
elution of EA/PE 0:100–70:30, R = 0.34) as colourless
f
1
EA/PE 0:100–60:40, R = 0.47) as a white powder. M.p.:
f
crystals. M.p.: 87–88 °C; H NMR (500 MHz, CDCl ):
3
1
1
26–127 °C; H NMR (300 MHz, CDCl ): d = 3.23–3.40
d = 1.89–2.14 (m, 4H, CH ), 2.29–2.37 (m, 1.3H, CH ),
3
2
2
(
m, 2H, CH ), 3.80 (s, 3H, CH O), 5.09–5.15 (m, 1H,
3.36–3.40 (m, 1H, CH C H-Protrans), 3.45–3.49 (m, 1H,
2 a
2
3
C H), 6.64 (d, J = 6.3 Hz, 1H, NH), 7.18 (d,
a
CH C H-Protrans), 3.53 (s, 0.87H, OCH3cis), 3.76 (s, 3H,
2 a
J = 6.6 Hz,1H, H ), 7.25–7.32 (m, 5H, H ), 7.57–7.66
Ar Ph
OCH3trans), 3.80–3.83 (m, 0.62H, CH C H-Pro ), 4.23–
2 a cis
(
m, 3H, 3-5-H ), 7.79 (d, J = 7.5 Hz, 1H, 6-H ) ppm;
Ar
4.25 (m, 0.29H, C H-Pro ), 4.68–4.71 (m, 1H, C H-
a cis a
Ar
1
3
C NMR (75 MHz CDCl ): d = 38.3, 53.2, 54.6, 111.7,
Protrans), 7.40 (d, J = 7.5 Hz, 0.29H, H-Ar ), 7.46–7.71
cis
3
1
3
1
17.9, 127.9, 128.9, 129.3 (2C -3, 5), 130.0 (2C -2, 6),
Ph Ph
(m, 5H, 3-6-H ) ppm; C NMR (125 MHz, CDCl ): d
Ar
3
1
31.9, 133.4, 135.0, 136.2, 138.3, 165.3, 172.2 ppm; IR
trans(cis) = (22.8) 25.0, 29.5 (31.4), (46.7) 49.0, 52.5
(52.6), 58.0 (60.9), (110.02) 110.04, (116.8) 116.9, 127.65
(127.68), (129.9) 130.0, (132.9) 133.0, (133.1) 133.3, 140.4
(
KBr): mꢀ = 3303, 2227 (CN), 1739, 1676, 1639, 1590,
-
573, 1525 cm ; LC/MS: m/z (%) = 309 (100, [M?H] ).
1
?
1
(
140.6), 166.2 (166.6), (172.0) 172.1 ppm; IR (KBr):
-
Methyl (2S)-2-[[(2-cyanophenyl)carbonyl]amino]-3-(1H-in-
dol-3-yl)propanoate (8g, C H N O ) It was prepared
according to General procedure A (1.596 g, 92%). The
1
;
mꢀ = 2953, 2227 (CN), 1735, 1624, 1591, 1490, 1414 cm
LC/MS: m/z (%) = 259 (100, [M?H] ).
2
0
17
3
3
?
product was isolated by column chromatography (gradient
Methyl 2-(1-imino-3-oxo-1,3-dihydro-2H-isoindol-2-yl)ac-
etate (9a) It was prepared according to General procedure
A (0.164 g, 15%). The product was isolated by column
chromatography (gradient elution of EA/PE 0:100–70:30,
elution of EA/PE 0:100–60:40, R = 0.28) as a white
f
1
powder. M.p.: 131–132 °C; H NMR (300 MHz, CDCl ):
3
d = 3.37–3.52 (m, 2H, CH ), 3.71 (s, 3H, CH O), 5.09–
2
3
1
13
5
.15 (m, 1H, C H), 6.88 (d, J = 4.5 Hz, 1H, CONH),
a
R = 0.51) as colourless crystals. H NMR and C NMR
f
7
.03–7.07 (m, 2H, H ), 7.13 (dd, J1 = 7.8 Hz,
Ar
spectra were found to be identical with the ones described
J = 7.2 Hz, 1H, H ), 7.32 (d, J = 7.8 Hz, 1H, HInd(2)),
Ar
in Ref. [43]; IR (KBr): mꢀ = 3449, 3287, 1741, 1728, 1662,
1621, 1472, 1437 cm ; LC/MS: m/z (%) = 219 (100,
2
-
1
7
7
.43–7.47 (m, 3H, H ), 7.53 (d, J = 7.8 Hz, 1H, HInd),
Ar
?
[M ?H] ).
.65 (dd, J = 4.5 Hz, J = 6.3 Hz, 1H, H ), 8.74 (s, 1H,
Ar
1
2
1
3
NHInd) ppm; C NMR (75 MHz, CDCl ,): d = 27.9, 53.1,
3
Methyl
(2S)-2-(1-imino-3-oxo-1,3-dihydro-2H-isoindol-2-
5
1
1
1
4.4, 109.7, 111.5, 112.1, 118.1, 118.9, 120.0, 122.6,
24.0, 128.1, 128.6, 131.7, 133.2, 134.8, 136.8, 138.1,
65.6, 172.6 ppm; IR (KBr): mꢀ = 3407, 3361, 2228 (CN),
yl)propanoate (9b) It was prepared according to General
procedure A (0.105 g, 9%). The product was isolated by
column chromatography (gradient elution of EA/PE 0:100–
-
1
739 (C=O), 1659 (C–N), 1623, 1593, 1574, 1530 cm
?
;
1
13
6
0:40, R = 0.52) as a colourless crystals. H NMR and
f
C
LC/MS: m/z (%) = 348 (100, [M?H] ).
NMR spectra were found to be identical with the ones
described in Ref. [43]; IR (KBr): mꢀ = 3279, 2915, 1735,
1717, 1652, 1420 cm ; LC/MS: m/z (%) = 233 (100,
Dimethyl (2S)-2-[[(2-cyanophenyl)carbonyl]amino]pentane-
dioate (8h, C H N O ) It was prepared according to
General procedure A (1.277 g, 84%). The product was
-
1
15 16 3 5
?
[M?H] ).
isolated by column chromatography (gradient elution of
Methyl (2S)-2-(1-imino-3-oxo-1,3-dihydro-2H-isoindol-2-yl)-
EA/PE 0:100–60:40, R = 0.39) as a white powder. M.p.:
f
3-methylbutanoate (9c) It was prepared according to
1
8
1
2
4–85 °C; H NMR (300 MHz, CDCl ): d = 2.08–2.21 (m,
3
General procedure A (0.078 g, 6%). The product was iso-
H, CHCH ), 2.27–2.39 (m, 1H, CHCH ), 2.43-2.60 (m,
2
2
lated by column chromatography (gradient elution of EA/
1
PE 0:100–60:40, R = 0.67) as a white powder. H NMR
H, CH CO), 3.65 (s, 3H, CH O CCH ), 3.77 (s, 3H,
2
3
2
2
f
CH O CCH), 4.79-4.86 (m, 1H, C H), 7.18 (d,
3
2
a
13
and C NMR spectra were found to be identical with the
J = 6.9 Hz, 1H, NH), 7.58 (dd, J = 7.5 Hz, J = 7.8 Hz,
1
2
ones described in Ref. [43]. IR (KBr): mꢀ = 3437, 3403,
1
7
6
H, 4-H ), 7.66 (dd, J = 7.5 Hz, J = 7.5 Hz, 1H, 5-H ),
Ar 1 2 Ar
3
292, 2965, 1772, 1741, 1728, 1687, 1660, 1470, 1415,
.75 (d, J = 7.5 Hz, 1H, 3-H ), 7.77 (d, J = 7.8 Hz, 1H,
Ar
-1
390 cm ; LC/MS: m/z (%) = 261 (100, [M?H] ).
?
1
1
3
-H ) ppm; C NMR (75 MHz, CDCl ): d = 27.6, 30.7,
Ar
3
1
23

Methyl esters of 2-(N-hydroxycarbamimidoyl)benzoyl-substituted a-amino acids…
1
Methyl (2S)-2-(1-imino-3-oxo-1,3-dihydro-2H-isoindol-2-yl)-
-methylpentanoate (9d) It was prepared according to
General procedure A (0.055 g, 4%). The product was iso-
powder. M.p.: 126–128 °C; H NMR (400 MHz, DMSO-
d ): d = 3.67 (s, 3H, CH O), 3.95 (d, J = 5.2 Hz, 2H,
4
6
3
CH ), 5.64 (s, 2H, NH ), 7.46–7.48 (m, 4H, 3-6-H ), 8.62
2 2 Ar
3
(br m, 1H, NH), 9.52 (s, 1H, OH) ppm; C NMR
1
lated by column chromatography (gradient elution of EA/
PE 0:100–60:40, R = 0.72) as a colourless viscous sub-
f
(100 MHz, DMSO-d ): d = 41.6, 52.3, 128.3, 129.1, 129.5,
6
1
13
stance. H NMR and C NMR spectra were found to be
identical with the ones described in Ref. [43]; IR (KBr):
mꢀ = 3547, 3464, 3371, 3289, 2958, 2875, 1732, 1652, 1472,
129.9, 132.8, 136.5, 152.1, 169.6, 170.8 ppm; IR (KBr):
1
-
mꢀ = 3416, 3362, 1738, 1631, 1539 cm ; LC/MS: m/z
(%) = 252 (100, [M?H] ).
?
-
1
?
1
416 cm ; LC/MS: m/z (%) = 275 (100, [M?H] ).
Methyl (2S)-2-(1-imino-3-oxo-1,3-dihydro-2H-isoindol-2-yl)-
-(methylsulfanyl)butanoate (9e) It was prepared
Methyl (2S)-2-[[[2-(N’-hydroxycarbamimidoyl)phenyl]car-
bonyl]amino]propanoate (10b, C H N O ) It was pre-
pared according to General procedure B (0.994 g, 75%).
1
2 15 3 4
4
according to General procedure A (0.102 g, 7%). The
The product was isolated by column chromatography
product was isolated by column chromatography (gradient
(gradient elution of EA/PE 0:100–90:10, R = 0.31) as a
f
1
elution of EA/PE 0:100–60:40, R = 0.56) as a yellowish
f
white powder. M.p.:134–136 °C; H NMR (300 MHz,
1
13
powder. M.p.: 79–80 °C; H NMR and C NMR spectra
were found to be identical with the ones described in Ref.
DMSO-d ): d = 1.34 (d, J = 7.2 Hz, 3H, CH ), 3.66 (s,
6
3
3H, CH O), 4.37–4.47 (pseudo quintet, J = 7.2 Hz, 1H,
3
[
43]; IR (KBr): mꢀ = 3450, 3294, 2914, 1772, 1743, 1733,
C H), 5.66 (s, 2H, NH ), 7.45–7.48 (m, 4H, 3-6-H ), 8.51
a
2
Ar
-
661, 1444, 1415 cm ; LC/MS: m/z (%) = 293 (100,
1
13
(d, J = 6.9 Hz, NH), 9.51 (s, 1H, OH) ppm; C NMR
1
?
[
M?H] ).
Methyl (2S)-2-(1-imino-3-oxo-1,3-dihydro-2H-isoindol-2-yl)-
-phenylpropanoate (9f) It was prepared according to
(100 MHz, DMSO-d ): d = 17.5, 48.6, 52.6, 128.5, 129.2,
6
129.6, 130.0, 133.0, 136.5, 152.2, 168.8, 173.7 ppm; IR
(
KBr): mꢀ = 3486, 3439, 3332, 3208, 3034, 2940, 2888,
3
-
733, 1638, 1601, 1586, 1563 cm ; LC/MS: m/z
1
1
General procedure A (0.046 g, 3%). The product was iso-
?
%) = 266 (100, [M?H] ).
(
lated by column chromatography (gradient elution of EA/
PE 0:100–60:40, R = 0.66) as a yellowish viscous sub-
f
Methyl (2S)-2-[[[2-(N’-hydroxycarbamimidoyl)phenyl]car-
bonyl]amino]-3-methylbutanoate (10c, C H N O ) It
was prepared according to General procedure B (1.216 g,
1 13
stance. H NMR and C NMR spectra were found to be
1
4 19 3 4
identical with the ones described in Ref. [43]; LC/MS: m/z
?
%) = 309 (100, [M ? H] ).
(
83%). The product was isolated by column chromatogra-
phy (gradient elution of EA/PE 0:100–90:10, R = 0.50) as
f
1
General procedure B for the synthesis
of compounds 10a–10i
colourless crystals. M.p.: 121–122 °C;
H
NMR
(300 MHz, CDCl ): d = 0.95 (d, J = 6.9 Hz, 3H, CH ),
3
3
0.99 (d, J = 6.9 Hz, 3H, CH ), 2.15–2.26 (m, 1H,
3
To
a
stirred solution of 0.520 g hydroxylamine
3
CH(CH ) ), 3.74 (s, 3H, CH O), 4.67 (dd, J = 8.4 Hz,
3 2 3 1
3
hydrochloride (7.5 mmol) in 20 cm methanol 1.05 cm
J = 8.4 Hz, C H), 5.07 (s, 2H, NH ), 7.21 (d, J = 8.4 Hz,
2
a
2
TEA (7.5 mmol) was added at 0 °C. After 15 min appro-
priate 2-cyanobenzamide 8 (5 mmol) was added to this
solution. The reaction mixture was stirred from 0 °C to
ambient temperature until the TLC showed the absence of
starting material. After that the clear solution was con-
1H, NH), 7.43–7.47 (m, 3H, 3-5-H ), 7.64–7.66 (m, 1H, 6-
Ar
1
3
H ) ppm; C NMR (75 MHz, CDCl ): d = 18.7, 19.6,
Ar
3
31.9, 52.9, 58.8, 129.5, 130.1, 130.5, 131.0, 131.2, 136.1,
153.7, 169.2, 173.0 ppm; IR (KBr): mꢀ = 3439, 3325, 2956,
1732, 1623, 1598, 1541 cm ; LC/MS: m/z (%) = 294
-
1
3
?
(100, [M?H] ).
centrated to * 5 cm under reduced pressure at ambient
temperature, diluted with 15 cm brine and then extracted
3
Methyl (2S)-2-[[[2-(N’-hydroxycarbamimidoyl)phenyl]car-
bonyl]amino]-4-methylpentanoate (10d, C H N O ) It
was prepared according to General procedure B (1.366 g,
3
with 5 9 25 cm ethyl acetate. The combined parts of the
1
5 21 3 4
extract were dried over MgSO and concentrated under
4
reduced pressure at ambient temperature. The residue was
then purified by column chromatography (ethyl acetate/
petroleum ether 7:3) to afford the desired product as a
white solid.
89%). The product was isolated by column chromatogra-
phy (gradient elution of EA/PE 0:100–90:10, R = 0.53) as
f
1
a white powder. M.p.: 129–130 °C; H NMR (300 MHz,
DMSO-d ): d = 0.90 (2d, J = 6.9 Hz, 6H, 2CH ), 1.56-
6
3
Methyl 2-[[[2-(N’-hydroxycarbamimidoyl)phenyl]carbonyl]-
amino]acetate (10a, C H N O ) It was prepared
according to General procedure B (0.791 g, 72%). The
1.76 (m, 3H, CH(CH ) ? CH ), 3.66 (s, 3H, CH O), 4.38-
3 2 2 3
4.46 (m, 1H, C H), 5.64 (s, 2H, NH ), 7.46 (s, 4H, 3-6-
2
1
1
13
3
4
a
H ), 8.50 (d, J = 7.5 Hz, 1H, NH), 9.50 (s, 1H, OH) ppm;
Ar
1
3
product was isolated by column chromatography (gradient
C NMR (100 MHz, DMSO-d ): d = 21.9, 23.4, 24.6,
6
elution of EA/PE 0:100–90:10, R = 0.27) as a white
f
40.3, 51.3, 52.4, 128.6, 129.1, 129.7, 130.0, 132.8, 136.2,
123

V. A. Tkachuk et al.
-
1736, 1642, 1599, 1524 cm ; LC/MS: m/z (%) = 381
1
1
52.3, 168.8, 173.4 ppm; IR (KBr): mꢀ = 3457, 3399, 3335,
-
953, 1719, 1642, 1518 cm ; LC/MS: m/z (%) = 308
1
?
(100, [M?H] ).
2
?
100, [M?H] ).
(
Dimethyl (2S)-2-[[[2-(N’-hydroxycarbamimidoyl)phenyl]car-
bonyl]amino]pentanedioate (10h, C H N O ) It was
prepared according to General procedure B (1.365 g, 81%).
Methyl (2S)-2-[[[2-(N’-hydroxycarbamimidoyl)phenyl]car-
1
5 19 3 6
bonyl]amino]-4-(methylsulfanyl)butanoate (10e, C H N
4 19 3-
1
O4S) It was prepared according to General procedure B
1.333 g, 82%). The product was isolated by column
The product was isolated by column chromatography
(
(gradient elution of EA/PE 0:100–90:10, R = 0.45) as a
f
1
chromatography (gradient elution of EA/PE 0:100–90:10,
1
white powder. M.p.: 97–99 °C; H NMR (300 MHz,
R = 0.43) as a pale yellow powder. M.p.: 88–90 °C; H
CD CN): d = 1.92–2.02 (m, 1H, CHCH ), 2.12–2.23 (m,
f
3
2
NMR [300 MHz, (CD ) CO]: d = 2.05–2.20 (m, 5H,
1H, CHCH ), 2.48–2.51 (m, 2H, CH CO), 3.65 (s, 3H,
2 2
3
2
CH S, CHCH ), 2.62–2.68 (m, 2H, CH S), 3.71 (s, 3H,
2
CH CO CH ), 3.72 (s, 3H, C CO CH ), 4.54–4.62 (m, 1H,
2 2 3 a 2 3
3
2
CH O), 4.70–4.78 (m, 1H, C H), 5.60 (s, 2H, NH ), 7.45–
a
C H), 5.26 (s, 2H, NH ), 7.47–7.56 (m, 5H, 3-6-H
a 2 Ar-
3
2
1
3
7
.49 (m, 3H, 3-5-H ), 7.60–7.63 (m, 1H, 6-H ), 8.01 (d,
Ar
? NH) ppm; C NMR (75 MHz, CD CN): d = 27.7,
Ar
3
1
J = 7.8 Hz, 1H, NH), 9.01 (br s, 1H, OH) ppm; C NMR
3
30.8, 52.4, 53.06, 53.12, 129.3, 130.3, 130.4, 131.1, 132.5,
136.7, 153.7, 169.7, 173.1, 174.5 ppm; IR (KBr):
mꢀ = 3464, 3390, 3321, 1735, 1716, 1642, 1599, 1578,
(
75 MHz, (CD ) CO): d = 15.3, 30.8, 32.3, 52.6, 52.8,
3
2
1
1
1
29.6, 129.9, 130.3, 130.7, 132.9, 136.6, 153.5, 169.1,
73.0 ppm; IR (KBr): mꢀ = 3473, 3440, 3365, 3314, 3265,
736, 1637, 1601, 1579, 1550, 1438, 1382; LC/MS: m/z
-
1
?
1535 cm ; LC/MS: m/z (%) = 338 (100, [M?H] ).
Methyl cis/trans-(2S)-1-[[2-(N’-hydroxycarbamimidoyl)-
phenyl]carbonyl]pyrrolidine-2-carboxylate (10i, C H N -
?
(
%) = 326 (100, [M?H] ).
1
4 17 3
Methyl (2S)-2-[[[2-(N’-hydroxycarbamimidoyl)phenyl]car-
bonyl]amino]-3-phenylpropanoate (10f, C H N O ) It
was prepared according to General procedure B (1.500 g,
O4) It was prepared according to the General procedure B
(1.339 g, 92%). The product was isolated by column
chromatography (gradient elution of EA/PE 0:100–90:10,
1
8 19 3 4
1
8
8%). The product was isolated by column chromatogra-
Rf = 0.23) as a colourless viscous substance. H NMR
phy (gradient elution of EA/PE 0:100–90:10, R = 0.49) as
f
(300 MHz, CDCl ): d = 1.80–2.01 (m, 3.2H, H-Pro), 2.22–
2.29 (m, 1.1H, H-Pro), 3.21–3.31 (m, 1.5H, NCH -Pro),
2
3
1
a white powder. M.p.: 119–121 °C; H NMR (300 MHz,
CDCl ) d = 3.12–3.26 (m, 2H, CH ), 3.72 (s, 3H, CH O),
3.47 (s, 0.8H, CH O) 3.68–3.74 (m, 2.8H, CH O ? H-
3
3
2
3
3
4
.96 (s, 2H, NH ), 5.01–5.08 (m, 1H, C H), 7.17–7.57 (m,
2
Pro), 4.17–4.20 (m, 0.23H, C H), 4.57–4.62 (m, 0.77H,
a
a
1
0H, HAr ? NH) ppm; C NMR (100 MHz, DMSO-d6):
3
1
C H), 5.17 (s, 2H, NH ), 7.20–7.56 (m, 4.3H, H -3-6)
a 2 Ar
1
3
d = 37.4, 52.5, 54.7, 127.1, 128.5, 128.9 (C -3 ? C -5),
ppm; C NMR (75 MHz, CDCl ): d = (23.4) 25.3, 30.1
Ph
Ph
3
1
29.1, 129.7 (C -5 ? C -2 ? C -6), 130.0, 132.8,
Ph
(31.5), (46.9) 49.5, (52.8) 52.9, 59.2 (61.4), 127.5 (127.6),
Ar
Ph
1
36.1, 137.7, 152.3, 168.8, 172.3 ppm; IR (KBr):
-
(129.1) 129.2, (129.9) 130.0, 130.1, 130.3, (136.3) 136.4,
1
mꢀ = 3432, 3285, 1748, 1624, 1591, 1552 cm ; LC/MS: m/
z (%) = 342 (100, [M?H] ).
(152.7) 152.9, 170.2 (170.5), 173.1 ppm; IR (KBr):
-1
?
mꢀ = 3339, 2952, 1733, 1613, 1595, 1499, 1451, 1420 cm
LC/MS: m/z (%) = 292 (100, [M?H] ).
;
?
Methyl (2S)-2-[[[2-(N’-hydroxycarbamimidoyl)phenyl]car-
bonyl]amino]-3-(1H-indol-3-yl)propanoate (10g, C H N
0 20 4-
2
General procedure C for the synthesis of 3-
O4) It was prepared according to General procedure B
1.767 g, 93%). The product was isolated by column
(arylimino)-2,3-dihydro-1H-isoindol-1-ones 15a,
(
15b [61]
chromatography (gradient elution of EA/PE 0:100–90:10,
R = 0.34) as a yellowish white powder. M.p.: 108–110 °C;
f
To the solution of 0.292 g 3-imino-2,3-dihydro-1H-isoin-
3
dol-1-one (14, 2 mmol) in a mixture of 10 cm ethanol and
1
H NMR (300 MHz, DMSO-d ): d = 3.15–3.24 (m, 2H,
6
CH ), 3.61 (s, 3H, CH O), 4.66–4.73 (m, 1H, C H), 5.66
3
2
a
3
.4 cm acetic acid appropriate amount of arylamine
0
(
s, 2H, NH ) 7.02 (dd, J = 7.2 Hz, J = 7.5 Hz, 1H, C
2 1 2 6-
(6.5 mmol) was added and reaction mixture was heated
HInd), 7.10 (dd, J = 7.2 Hz, J = 7.5 Hz, 1H, C HInd), 7.27
2
1
5
under reflux until the TLC showed the absence of starting
(
s, 1H, C H ), 7.37 (d, J = 7.8 Hz, 1H, C HInd), 7.41–
a Ind 7
compound 14. The obtained orange or yellow solution was
3
cooled and poured into 20 cm water to give an ochre or
7
.48 (m, 4H, 4-7-H), 7.55 (d, J = 7.8 Hz, 1H, C HInd),
4
8
.58 (d, J = 7.5 Hz, 1H, CONH), 9.57 (s, 1H, OH), 10.84
yellow precipitate. This substance was filtered by suction,
3
washed with distilled water (3 9 5 cm ) and dried in the
1
3
s, 1H, NHInd) ppm; C NMR (75 MHz, DMSO-d6):
(
d = 27.1, 51.9, 53.7, 109.4, 111.5, 118.1, 118.4, 121.0,
air. After recrystallization from ethanol the obtained pro-
1
1
23.9, 127.1, 128.1, 128.6, 129.2, 129.5, 132.3, 135.7,
36.1, 151.8, 168.2, 172.2 ppm; IR (KBr): mꢀ = 3375, 3059,
duct 15 was used in the next step.
1
23

Methyl esters of 2-(N-hydroxycarbamimidoyl)benzoyl-substituted a-amino acids…
1
1H, 6-H), 7.85 (d, J = 7.5 Hz, 1H, 7-H) ppm; C NMR
3
(
3Z,E)-3-[(2-Methylphenyl)imino]-2,3-dihydro-1H-isoindol-1-
one (15a, C H N O) It was prepared according to the
(75 MHz, CDCl ): d = 18.2, 40.4, 52.9, 119.7, 124.1,
15
12
2
3
General procedure C (0.42 g, 89%, Z/E = 83:17). The
124.9, 125.5, 127.2, 128.4, 130.4, 131.3, 132.6, 132.7,
product was isolated after recrystallization in ethanol as
1
133.7, 147.3, 150.4, 167.6, 168.9 ppm; IR (KBr):
-1
yellow crystals. M.p.: 154–155 °C; H NMR (300 MHz,
mꢀ = 3404, 2951, 1736, 1673, 1413, 1215 cm ; LC/MS: m/
z (%) = 309 (100, [M?H] ).
?
CDCl ): d = 2.16 (s, 0.52H, CH3,E), 2.23 (s, 2.48H, CH3,Z),
3
0
6
.60 (d, J = 7.8 Hz, 0.17H, 4-H ), 6.88–6.90 (m, 1H, 3 -
E
Methyl 2-[(1E)-1-[(2-methylphenyl)imino]-3-oxo-1,3-dihy-
dro-2H-isoindol-2-yl]propanoate (16b, C H N O ) It was
prepared according to General procedure D (0.193 g,
0
0
H ), 7.09–7.29 (m, 3H, 4 -6 H ), 7.37 (dd, J = 7.8 Hz,
tol
tol
1
1
9 18 2 3
J = 7.5 Hz, 0.17H, 5-H ) 7.48 (bs, 1H, NH), 7.59 (dd,
2 E
J = 7.5 Hz, J = 7.8 Hz, 0.17H, 6-H ), 7.68–7.80 (m,
1
2
E
80%). The product was isolated by column chromatogra-
1
.66H, 5,6-H ), 7.87–7.90 (m, 1H, 7-HZ?E), 8.10 (d,
Z
phy (EtOAc/petroleum ether 1:1) as an orange viscous
1
substance. TLC: R = 0.78; H NMR (300 MHz, CDCl ):
1
.83H, J = 7.8 Hz, 4-H ) ppm; C NMR (100 MHz,
3
0
Z
f
3
CDCl ): d = 17.8 (17.9) (CH ), 119.7, 122.5, 123.5,
3
3
d = 1.78 (d, J = 7.2 Hz, 3H, CH C ), 2.10 (s, 3H, CH -
3
a
3
(
123.7), (124.6), 125.0, (125.3), 126.8, (128.2), 129.6,
C ), 3.76 (s, 3H, CH O), 5.29 (q, J = 7.2 Hz, 1H, C H),
Ar
3
a
(
130.9), 131.0, 131.5, 132.3, (132.4), (133.2), 133.6, 135.9,
6.63 (d, J = 7.5 Hz, 1H, 4-H), 6.82 (d, J = 7.5 Hz, 1H,
1
1
45.5, 148.4, 168.2 ppm; IR (KBr): mꢀ = 3220, 3053, 1736,
675, 1475, 1348, 1307 cm ; LC/MS: m/z (%) = 237
H ), 7.11 (dd, J = 7.2 Hz, J = 7.5 Hz, 1H, H ), 7.20
Ar
-
1
1
2
Ar
(dd, J1 = 7.5 Hz, J2 = 7.8 Hz, 1H, H ), 7.25 (d,
Ar
?
(
100, [M?H] ).
J = 7.5 Hz, 1H, H ), 7.32 (dd, J = 7.5 Hz, J = 7.5 Hz,
1
Ar
2
(
3Z,E)-3-[(4-Chlorophenyl)imino]-2,3-dihydro-1H-isoindol-1-
1H, 5-H), 7.54 (dd, J = 7.5 Hz, J = 7.5 Hz, 1H, 6-H),
1 2
1
7.87 (d, J = 7.5 Hz, 1H, 7-H) ppm; C NMR (75 MHz,
3
one (15b) It was prepared according to the General pro-
cedure C (0.47 g, 91%). The product was isolated after
recrystallization in ethanol as yellow silky needles. M.p.:
CDCl ): d = 15.8, 18.4, 48.6, 53.1, 119.8, 124.2, 125.0,
3
125.6, 127.3, 128.4, 130.4, 131.4, 132.7, 132.8, 133.7,
147.6, 149.9, 167.5, 171.5 ppm; IR (KBr): mꢀ = 3398, 2995,
2949, 1750, 1670, 1393, 1226 cm ; LC/MS: m/z
1
13
219–220 °C; H NMR and C NMR spectra were found to
be identical with the ones described in [62].
-
1
?
(
%) = 323 (100, [M?H] ).
Methyl [(1E)-1-[(4-chlorophenyl)imino]-3-oxo-1,3-dihydro-
H-isoindol-2-yl]acetate (16c, C H ClN O ) It was pre-
General procedure D for the synthesis
of compounds 16a–16d [38]
2
1
7
13
2 3
pared according to General procedure D (0.225 g, 93%).
To a solution of appropriate amount of 3-(arylimino)-2,3-
3
dihydro-1H-isoindol-1-one 15 (0.75 mmol) in 10 cm dry
The product was isolated by column chromatography
(
EtOAc/petroleum ether 1:1) as yellow crystals. M.p.: 111–
1
acetone methyl 2-bromoalkanoate (1.12 mmol), 0.186 g
potassium iodide (1.12 mmol), and 0.207 g anhydrous
potassium carbonate (1.5 mmol) were added. The obtained
mixture was stirred at room temperature until the TLC
showed the absence of starting isoindolone 15
1
12 °C; R = 0.73; H NMR (300 MHz, CDCl ): d = 3.77
f
3
(s, 3H, CH O), 4.63 (s, 2H, CH ), 6.77 (d, J = 7.8 Hz, 1H,
3 2
0 0
-H), 6.90 (d, J = 8.7 Hz, 2H, 2 -H ? 6 -H), 7.33–7.41
4
0 0
m, 3H, 3 -H ? 5 -H ? 5-H), 7.57 (dd, J = 7.5 Hz,
1
(
J = 7.5 Hz, 1H, 6-H), 7.88 (d, J = 7.5 Hz, 1H, 7-H) ppm;
2
(
* 2–3 days). After that inorganic salts were filtered off
1
3
C NMR (75 MHz, CDCl ): d = 40.5, 53.1, 122.0, 124.5,
3
3
and washed with 5 cm acetone. The filtrate was concen-
trated under reduced pressure and the crude product was
purified by column chromatography (EtOAc/petroleum
ether 1:1) to afford the desired compound 16.
1
1
1
26.1, 130.1, 130.2 (2C), 130.3, 133.0, 133.6, 147.4, 151.2,
67.7, 168.9 ppm; IR (KBr): mꢀ = 3394, 2941, 1759, 1731,
669, 1420, 1211 cm ; LC/MS: m/z (%) = 329 (100,
-
1
?
[
M?H] ).
Methyl 2-[(1E)-1-[(4-chlorophenyl)imino]-3-oxo-1,3-dihydro-
H-isoindol-2-yl]propanoate (16d, C H ClN O ) It was
Methyl [(1E)-1-[(2-methylphenyl)imino]-3-oxo-1,3-dihydro-
2H-isoindol-2-yl]acetate (16a, C H N O ) It was pre-
18 16 2 3
pared according to General procedure D (0.195 g, 84%).
2
1
8
15
2 3
prepared according to General procedure D (203 mg,
9%). The product was isolated by column chromatogra-
phy (EtOAc/petroleum ether 1:1) as yellow crystals. M.p.:
The product was isolated by column chromatography
7
(
EtOAc/petroleum ether 1:1) as a orange viscous susb-
1
tance. TLC: R = 0.72; H NMR (300 MHz, CDCl3):
f
1
1
83–184 °C; TLC: R = 0.75; H NMR (300 MHz,
f
d = 2.06 (s, 3H, CH –C ), 3.74 (s, 3H, CH O), 4.67 (s,
3
Ar
3
CDCl ): d = 1.75 (d, J = 7.2 Hz, 3H, CH C ), 3.76 (s,
3
3 a
2
H, CH ), 6.63 (d, J = 7.8 Hz, 1H, 4-H), 6.83 (d,
2
3
H, CH O), 5.24 (q, J = 7.2 Hz, 1H, C H), 6.77 (d,
3 a
J = 7.5 Hz, 1H, H ), 7.08 (dd, J = 7.2 Hz, J = 7.2 Hz,
Ar
1
2
0
0
J = 7.5 Hz, 1H, 4-H), 6.90 (d, J = 8.4 Hz, 2H, 2 -H, 6 -
0
1
H, H ), 7.17 (dd, J = 7.5 Hz, J = 7.5 Hz, 1H, HAr),
Ar 1 2
0
H), 7.35-7.41 (m, 3H, 3 -H ? 5 -H ? 5-H), 7.57 (dd,
J = 7.5 Hz, J = 7.5 Hz, 1H, 6-H), 7.88 (d, J = 7.5 Hz,
7
.22 (d, J = 7.5 Hz, 1H, H ), 7.30 (dd, J = 7.5 Hz,
Ar
1
1
2
J = 7.5 Hz, 1H, 5-H), 7.51 (dd, J = 7.5 Hz, J = 7.5 Hz,
2
1
2
123

V. A. Tkachuk et al.
1
3
1
4
1
H, 7-H) ppm; C NMR (75 MHz, CDCl ): d = 15.7,
25. Oyama H, Umeda T (1989) Production of benzenecarboxyimi-
damido derivative by electrolytic reaction. JPH01215994 (A),
Aug 29, 1989; (1989) Chem Abstr 112:188007
3
8.6, 53.0, 121.8, 124.3, 125.9, 129.9, 130.0 (2C), 130.1,
32.8, 133.4, 147.3, 150.5, 167.3, 171.3 ppm; IR (KBr):
2
6. Oyama H, Umeda T, Niitsuma S, Shibata T, Wada T (1989)
Benzenecarboximidamide derivative and agricultural and horti-
cultural fungicide. JPS6434954, Feb 6, 1989; (1989) Chem Abstr
mꢀ = 3422, 2977, 2940, 2739, 2677, 2492, 1685, 1475,
-
398 cm ; LC/MS: m/z (%) = 343 (100, [M?H] ).
1
?
1
1
7. Bergel F, Stock (1957) J Proc Chem Soc 60
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11:194316
2
2
Acknowledgements VAT and OVH are grateful to the Universit e´ de
Lorraine for financial support.
(
A1), May 28, 1998; (1998) Chem Abstr 129:40984
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