A novel synthetic approach to phosphorylated peptidomimetics

Article abstract of DOI:10.1002/hc.21093

It has been shown that the derivatives of diethyl 5-amino-2- phthalimidoalkyl-1,3-oxazol-4-ylphosphonates can be employed in the synthesis of phosphorylated peptidomimetics containing the phosphonoglycine residue. The reaction of diethyl 5-alkylamino-2-aminoalkyl-1,3-oxazol-4-ylphosphonates with unsaturated azlactones was utilized to obtain phosphorylated peptidomimetics with dehydroamino acid moieties. The double bond in the latter was reduced with zinc in acetic acid to provide the corresponding saturated peptidomimetics containing a diethoxyphosphoryl group in the side chain.

Full text of DOI:10.1002/hc.21093

Heteroatom Chemistry
Volume 24, Number 4, 2013
A Novel Synthetic Approach to
Phosphorylated Peptidomimetics
Olena I. Lukashuk, Kostyantyn M. Kondratyuk,
Alexandr V. Golovchenko, Vladimir S. Brovarets,
and Valery P. Kukhar
Institute of Bioorganic Chemistry and Petrochemistry, National Academy of Sciences of Ukraine,
Kiev-94 02660, Ukraine
Received 7 December 2012; revised 4 April 2013
Phosphopeptide mimetic molecules can be
ABSTRACT: It has been shown that the derivatives
structurally divided into two types: one containing
of diethyl 5-amino-2-phthalimidoalkyl-1,3-oxazol-4-
the peptide chain with a terminal phosphono group
ylphosphonates can be employed in the synthe-
and the other with a nonterminal phosphorylated
sis of phosphorylated peptidomimetics contain-
amino acid residue. The latter type has been much
ing the phosphonoglycine residue. The reaction
less studied, since phosphoamino acid residues are
of diethyl 5-alkylamino-2-aminoalkyl-1,3-oxazol-4-
difficult to introduce at certain internal positions
ylphosphonates with unsaturated azlactones was uti-
of polypeptides. Peptidomimetics of this kind were
lized to obtain phosphorylated peptidomimetics with
applied to the synthesis of natural peptide com-
dehydroamino acid moieties. The double bond in the
pounds such as desoxy-biphenomycin B [5], the
latter was reduced with zinc in acetic acid to provide
vanadium- and iron-containing clam blood pigments
the corresponding saturated peptidomimetics contain-
( )-tunichrome An-1 [6], and tunichromes Mm-1
ing a diethoxyphosphoryl group in the side chain.
and Mm-2 [7] as well as the alkaloids hexaacetyl-
ꢀC
2013 Wiley Periodicals, Inc. Heteroatom Chem.
celenamide A [8, 9] and clionamide [10]. Moreover,
some of these compounds are efficient glutathione
transferase inhibitors [11,12], thus adding to the bi-
ological significance of phosphopeptide mimetics.
Peptidomimetics containing α,β-dehydroamino
acid residues are equally important compounds
from the fundamental and application point of view.
They were employed in retrosynthetic routes to
natural substances [13]. Members of this class, as
for instance, the cyclopeptide phytotoxin tentoxin,
the antitumor drugs cytoxin, and kahalalide F, and
fungicide pseudomycin, are also quite notable for
their biological activity. It is significant that the in-
troduction of α,β-dehydroamino acid residues into
synthetic counterparts of bioactive natural peptides
makes them more resistant to cleaving enzymes [14].
Currently, several synthetic methods exist
to obtain peptides with the phosphonoglycine
residue. One of them involves the reaction
24:289–297, 2013; View this article online at wiley-
onlinelibrary.com. DOI 10.1002/hc.21093
INTRODUCTION
Phosphorylated peptides containing a phosphono-
glycine moiety have received considerable attention
of organic and bioorganic chemists [1,2]. This is due
to the fact that compounds of peptide nature con-
taining aminoalkylphosphonic acid residues have
been found in biological systems [3]. On the other
hand, phosphopeptides are known to efficiently in-
hibit enzymes [4].
Correspondence to: Vladimir S. Brovarets; e-mail: brovarets@
bpci.kiev.ua.
ꢀC
2013 Wiley Periodicals, Inc.
289

290 Lukashuk et al.
Δ
SCHEME 1
between the metallated derivatives of diethyl
isocyanomethylphosphonates and methyl α-
isocyanatocarboxylates at −70◦С [15]. Another
approach is based on the reaction of glyoxylic acid
derivatives with N-benzylurethane, which leads to
N-benzyloxycarbonyl-2-ethoxyglycine derivatives.
These products, when treated with phosphorus
trichloride and triethyl phosphite, afford the
tion mixture at 50–60◦С for 3–4 h has been found
to be the optimum condition for phthalimide depro-
tection. This convenient synthetic approach enables
smooth formation of compounds 3a–e and easy sep-
aration of the phthalazide produced in the reaction.
We also adapted our method to access more
complex structures 6 and 7 as shown in Scheme 2. It
seemed reasonable to obtain them from unsaturated
azlactones readily cleavage by N-nucleophiles to pro-
vide dehydroamino acids [22–26]. However, the in-
teraction of azlactone 4 with 2-aminoalkyloxazoles
5 in glacial acetic acid does not proceed smoothly
and products 6 could not be isolated from the reac-
tion mixture. When this reaction was performed in
boiling dioxane, peptidomimetics 6 and imidazolone
derivatives 7 were formed in a ratio independent of
the reaction time. In this case, compounds 7a,b were
isolated in a pure state (Table 1). When toluene was
heated at 65◦C, compounds 6 were solely formed and
imidazolones 7 were not even detected by LS/MS.
Products 6a–e are isolated as thick oils and crys-
tallize within 1–2 weeks. The 1Н NMR signals from
the methylene group of compounds 6a and 6b are
observed as a doublet at 4.53 and 4.56 ppm, re-
spectively, whereas compounds 6c–e show the corre-
sponding resonances as multiplets at 3.72–3.76 and
2.89–2.92 ppm.
corresponding
N-benzyloxycarbonyl-substituted
phosphorylated glycines, which, on debenzylation
with hydrogen on palladium, are applied to peptide
synthesis [16] (see, for instance, the preparation of
mucronine B [17] and chlamydocin [18]).
Here, we present a novel synthetic pathway
to phosphorylated peptidomimetics containing the
phosphonoglycine moiety; it includes, as a main
step, acid-assisted oxazole ring cleavage.
RESULTS AND DISCUSSION
As shown previously, the derivatives of diethyl 5-
amino-1,3-oxazol-4-ylphosphonates decompose hy-
drolytically in an acidic environment to yield phos-
phonoglycine amides [19, 20]. We have performed
analogous conversions using easily available phthal-
imido derivatives of 5-alkylamino-2-aminoalkyl-1,3-
oxazol-4-ylphosphonic acids 1 [21] (see Scheme 1).
On heating compounds 1a–f in 70% aqueous
acetic acid, the oxazole ring smoothly cleaves to
form phthalimide-protected phosphopeptide mimet-
ics 2a–f in high yields (see Table 1). Compounds 2a–f
appear as white crystals soluble in methylene chlo-
ride and hexane. Their 1H NMR spectra show a char-
acteristic signal from the methine proton of the NH–
CH–P moiety as a doublet of doublets at 5.11–5.59
Imidazolones 7a,b are colorless crystalline
solids. Their methylene protons give rise to a sin-
1
glet Н resonance at 4.94–4.96 ppm. The IR spectra
of compounds 7a and 7b show no absorption bands
at 3100–3500 cm−1 characteristic of the NH group
vibrations.
On heating oxazoles 6a–d or 7a in 70% aque-
ous acetic acid, the oxazole ring opens to give, in
79–94% yields, phosphorylated peptidomimetics 8a–
d or 9, which need no further purification (see
Table 1). The oxazole ring cleavage in the conver-
sions 6a–d → 8a–d and 7a → 9 is easy to moni-
2
3
ppm with JHP = 17.5–20.4 Hz and JHН = 7.3–9.5
Hz. The signals from the NH group of compounds
2a–e appear at 7.01–7.83 ppm as a broad doublet
with 3JHН = 7.3–9.6 Hz (see Table 2).
On treating phthalimido derivatives 2a–e of hy-
drazine hydrate in ethanol, phosphopeptide mimet-
ics 3a–e result (see Table 1). Incubating the reac-
1
tor by Н NMR spectroscopy. Indeed, compounds
8a–d and 9 exhibit a characteristic signal from the
Heteroatom Chemistry DOI 10.1002/hc

A Novel Synthetic Approach to Phosphorylated Peptidomimetics 291
TABLE 1 Physical and Analytical Data of Compounds 2, 3, 6–9, 11
Elemental Analysis, Found (Calcd) (%)
Compound
(Product)
Melting
Molecular Formula
(Weight)
Point (◦C) Yield (%)a
C
H
N
P
2a
2b
2c
2d
2e
2f
191–192
185–187
197–198
176–178
195–196
195–197
oil
oil
oil
oil
oil
69–71
79–80
83–85
75–77
65–66
183–185
176–178
86–87
94–96
93–95
77–78
98–100
80–82
82–83
95
93
88
96
90
95
75
76
78
C21H28N3O7P (465.44) 54.30 (54.19) 6.17 (6.06) 9.19 (9.03)
C20H26N3O8P (467.41) 51.59 (51.39) 5.80 (5.61) 9.01 (8.99) `6.52 (6.63)
6.53 (6.65)
C
23H26N3O7P (487.44) 56.52 (56.67) 5.55 (5.38) 8.68 (8.62)
6.34 (6.46)
6.40 (6.43)
6.32 (6.43)
6.08 (6.18)
C22H30N3O7P (479.47) 55.22 (55.11) 6.55 (6.31) 8.83 (8.76)
C21H28N3O8P (481.44) 52.43 (52.39) 5.98 (5.86) 8.77 (8.73)
C24H28N3O7P (501.47) 57.56 (57.48) 5.75 (5.63) 8.46 (8.38)
3a
3b
3c
3d
3e
6a
6b
6c
6d
6e
7a
7b
8a
8b
8c
8d
9
C13H26N3O5P (335.34) 46.55 (46.56) 7.92 (7.81) 12.60 (12.53) 9.16 (9.24)
C12H24N3O5P (337.31) 42.75 (42.73) 7.19 (7.17) 12.49 (12.46) 9.14 (9.18)
C15H24N3O5P (357.34) 50.44 (50.42) 6.89 (6.77) 11.89 (11.76) 8.57 (8.67)
C14H28N3O5P (349.36) 48.23 (48.13) 8.25 (8.08) 12.06 (12.03) 8.75 (8.87)
C13H26N3O6P (351.34) 44.52 (44.44) 7.49 (7.46) 11.99 (11.96) 8.71 (8.82)
77
78
86(93)
83(95)
92(95)
85(92)
79(90)
10
11
88
87
88
79
94
64
53
C
30H37N4O6P (580.61) 62.18 (62.06) 6.55 (6.42) 9.68 (9.65)
5.21 (5.33)
5.30 (5.32)
5.13 (5.21)
5.14 (5.19)
4.96 (5.02)
5.47 (5.51)
5.48 (5.49)
5.11 (5.17)
5.06 (5.16)
5.03 (5.06)
5.01 (5.04)
5.22 (5.33)
5.11 (5.16)
5.00 (5.04)
C29H35N4O7P (582.59) 59.85 (59.79) 6.11 (6.06) 9.71 (9.62)
C31H39N4O6P (594.64) 62.75 (62.61) 6.50 (6.61) 9.49 (9.42)
C30H37N4O7P (596.611) 60.40 (60.39) 6.39 (6.25) 9.48 (9.39)
C
C
33H37N4O6P (616.64) 64.32 (64.28) 6.13 (6.05) 9.14 (9.09)
30H35N4O5P (562.60) 64.09 (64.04) 6.35 (6.27) 10.07 (9.96)
C29H33N4O6P (564.57) 62.76 (61.69) 5.75 (5.89) 10.02 (9.92)
C30H39N4O7P (598.63) 60.25 (60.19) 6.63 (6.57) 9.39 (9.36)
C
29H37N4O7P (600.60) 57.99 (57.99) 6.36 (6.21) 9.46 (9.33)
C31H41N4O7P (612.65) 60.86 (60.77) 6.89 (6.75) 9.19 (9.14)
C
C
31H41N4O7P (612.65) 58.68 (58.62) 6.52 (6.40) 9.20 (9.12)
30H37N4O6P (580.61) 62.10 (62.06) 6.48 (6.42) 9.72 (9.65)
11a
11b
C30H41N4O7P (600.64) 60.02 (59.99) 6.98 (6.88) 9.39 (9.33)
31H43N4O7P (614.67) 60.15 (60.07) 7.15 (7.05) 9.18 (9.11)
C
aA value in brackets is yield by method B (see Experimental).
methine proton of the NH–CH–P moiety as a doublet
of doublets at 5.43–5.54 ppm. The methylene proton
resonances of the glycine residue in products 8a,b
are shifted upfield and appear as a multiplet at 4.15–
4.16 ppm. The α- and β-methylene protons of the
β-alanine moiety in compounds 8c,d are nonequiv-
alent and give rise to two groups of multiplets at
3.64–3.75 and 2.50–2.60 ppm, respectively. For im-
idazolone derivative 9, the methylene proton reso-
nances of the glycine residue are also shifted upfield
to 4.47 ppm.
glets are observed at 18.3 and 18.4 ppm for com-
pound 11a and at 18.5 and 18.8 ppm for 11b. In the
corresponding 1Н NMR spectra, the methine proton
of the NHCHP moiety manifests itself by a multi-
plet at 5.46 and 5.49 ppm for compounds 11a and
11b, respectively, thus also suggesting the oxazole
ring cleavage and the second chiral center forma-
tion. The methine proton of the NHСНСН2 moiety
gives rise to a multiplet at 4.70 ppm for compound
11a and to two multiplets at 5.01 and 4.87 ppm for
11b.
Several methods are available for the dou-
ble bond reduction in α,β-dehydroamino acids
[12, 27–29] but none concerning the case when
their residues are incorporated into phosphopep-
tide mimetics. To obtain reduced analogues of com-
pounds 8, we attempted, unsuccessfully, their direct
hydrogenation with zinc in an AcOH:HCl (10:3) mix-
ture. In contrast, oxazoles 6a,c were thus reduced
directly to peptidomimetics 11a,b in good yields
(53%–64%), without isolation of intermediate prod-
ucts 10a,b (Scheme 3 and Table 1).
To conclude, we have developed a novel
synthetic route to peptidomimetics with a di-
ethoxyphosphoryl group in the side chain. The
method that is based on acid-assisted oxazole ring
cleavage in 5-alkylamino-2-aminoalkyl-1,3-oxazol-
4-ylphosphonic acid derivatives affords, in high
yields and without laborious purification, new com-
pounds of the peptide nature containing the phos-
phonoglycine moiety. A combined azlactone/oxazole
strategy of the peptide synthesis has enabled the
preparation of phosphorylated peptidomimetics
with dehydroamino acid residues. Under the appro-
priate conditions chosen for C C bond reduction,
the latter products have been converted to their sat-
urated analogues.
Compounds 11a,b containing two asymmetric
carbon atoms are isolated as 1:1 diastereomeric mix-
tures. This is demonstrated well by their 31P NMR
spectra in which two separate equally intense sin-
Heteroatom Chemistry DOI 10.1002/hc

292 Lukashuk et al.
TABLE 2 Spectroscopic Data of Compounds 2, 3, 6–9, 11
31P NMR
(CDCl3/H3PO4)
(ppm)
Mass-Spectrum:
m/z, [M]+ (ret.
time, min)
Compound
IR (KBr) (cm−1
)
1H NMR (CDCl3/TMS) (ppm)
2a
3285,1727, 1677,
1638, 1254,
1026, 955
1.32 (m, 6Н, 2ОСН2СН3), 1.61–1.64 (m, 6Н,
3СН2 piperidine), 3.54 (m, 1Н, 1/2CH2
piperidine), 3.60 (m, 3Н, CH2 piperidine,
1/2CH2 piperidine), 4.16 (m, 4Н,
17.2
465 (0.86)
2ОСН2СН3), 4.48 (s, 2H, CH2), 5.55 (dd,
1Н, СН, 2JHP = 17.5 Hz, 3JHН = 8.3 Hz),
7.56 (d, 1Н, NH, 3JHН = 8.3 Hz), 7.75–7.89
(m, 4Н, arom)
2b
3331,1725–1656,
253,1025,961
1.32 (m, 6Н, 2ОСН2СН3), 3.53 (m, 2Н, CH2
morpholine), 3,66 (m, 2Н, CH2 morpholine),
3.76 (m, 4Н, CH2 morpholine), 4.17 (m, 4Н,
2ОСН2СН3), 4.48 (s, 2Н, СН2), 5.52 (dd,
1Н, NH, 2JHP = 18.3 Hz, 3JHН = 8.6 Hz),
7.75–7.88 (m, 4Н, arom), 7.83 (d, 1Н, NH,
3JHН = 8.6 Hz)
17.0
467 (0.80)
2c
2d
3256, 1717, 1634,
1266, 1017, 977
1.25 (m, 6Н, 2ОСН2СН3), 4.13 (m, 4Н,
2ОСН2СН3), 4.44–4.50 (m, 4Н, СН2
glycine, СН2 benzylamine), 5.11 (dd, 1Н,
СН, 2JHP = 19.1 Hz, 3JHН = 7.3 Hz), 7.01 (d,
1Н, NH, 3JHН = 7.3 Hz), 7.16 (br s, 1Н, NH),
7.23–7.86 (m, 9Н, arom)
19.2
17.6
487 (0.79)
479 (0.83)
3403, 1717, 1644,
1245, 1023
1.29 (m, 6Н, 2ОСН2СН3), 1.62–1.66 (m, 6Н,
3СН2 piperidine), 2.73 (m, 2Н, СН2), 3.51
(m, 1Н, 1/2CH2 piperidine), 3.57 (m, 2Н, CH2
piperidine), 3.72 (m, 1Н, 1/2CH2 piperidine),
4.02 (m, 2Н, СН2), 4.11 (m, 4Н,
2ОСН2СН3), 5.59 (dd, 1Н, NH, 2JHP = 18.3
Hz, 3JHН = 8.6 Hz), 7.31 (d, 1Н, NH, 3JHН
8.6 Hz), 7.72–7.84 (m, 4Н, arom)
=
2e
2f
3401, 1720, 1651,
1245, 1026
1.28 (m, 6Н, 2ОСН2СН3), 2.73 (m, 2Н, СН2),
3.56 (m, 2Н, NCH2 morpholine), 3.66 (m,
1Н, 1/2CH2, morpholine), 3.75 (m, 5Н,
17.6
19.4
481 (0.88)
501 (0.86)
1/2CH2 morpholine, 2СН2 morpholine), 4.00
(m, 2Н, СН2), 4.12 (m, 4Н, 2ОСН2СН3),
5.57 (dd, 1Н, СН, 2JHP = 19.4 Hz, 3JHН
=
9.6 Hz), 7.63 (d, 1Н, NH, 3JHН = 9.6 Hz),
7.72–7.83 (m, 4Н, arom)
3288, 1721,1670,
1234, 102, 983
1.19–1.24 (m, 6Н, 2ОСН2СН3), 2.71 (m, 2Н,
СН2), 3.98 (m, 4Н, 2ОСН2СН3), 4.13 (m,
2Н, СН2), 4.40 (dd, 1Н, СН, 2JHH = 14.8 Hz,
3JHH = 5.6 Hz), 4.47 (dd, 1Н, СН, 2JHН
=
14.8 Hz, 3JHН = 5.8 Hz), 5.16 (dd, 1Н, СН,
3JHP = 20.4 Hz, 3JHН = 8.2 Hz), 7.10 (d, 1Н,
NH, 3JHН = 8.2 Hz), 7.26–7.28 (m, 5Н,
arom), 7.37 (m, 1Н, NH), 7.68–7.78 (m, 4Н,
arom)
3a
3b
3298, 1638, 233,
1049, 947
1.34 (m, 6Н, 2ОСН2СН3), 1.59–1.66 (m, 6Н,
3СН2 piperidine), 1.97 (br s, 2Н, NH2), 3.42
(s, 2Н, СН2), 3.60 (m, 3Н, CH2, 1/2CH2
piperidine), 3.68 (m, 1Н, 1/2CH2 piperidine),
4.18 (m, 4Н, 2ОСН2СН3), 5.56 (dd, 1Н, СН,
2JHP = 17.1 Hz, 3JHН = 7.3 Hz), 8.13 (d, 1Н,
NH, 3JHН = 7.3 Hz)
18.1
17.3
335 (0.70)
3329, 1649, 1241,
1026, 965
1.33 (m, 6Н, 2ОСН2СН3), 3.04 (br s, 2Н, NH2),
3.44 (s, 2Н, СН2), 3.54–3.81 (m, 8Н, 4СН2
morpholine), 4.18 (m, 4Н, 2ОСН2СН3), 5.53
(dd, 1Н, СН, 2JHP = 17.2 Hz, 3JHН = 6.2 Hz),
8.13 (d, 1Н, NH, 3JHН = 6.2 Hz)
337 (0.49)
(Continued)
Heteroatom Chemistry DOI 10.1002/hc

A Novel Synthetic Approach to Phosphorylated Peptidomimetics 293
TABLE 2 Continued
31P NMR
(CDCl3/H3PO4)
(ppm)
Mass-Spectrum:
m/z, [M]+ (ret.
time, min)
Compound
IR (KBr) (cm−1
)
1H NMR (CDCl3/TMS) (ppm)
3c
3309, 1675, 1247,
1025, 977
1.29 (m, 6Н, 2ОСН2СН3), 2.40 (br s, 2Н, NH2),
3.44 (s, 2Н, СН2), 4.08 (m, 2Н, ОСН2СН3),
4.20 (m, 2Н, ОСН2СН3), 4.44 (dd, 1Н, СН,
2JHН = 15.3 Hz, 3JHН = 5.2 Hz), 4.54 (dd,
1Н, СН, 2JHН = 15.3 Hz, 3JHН = 6.4 Hz),
5.18 (dd, 1Н, 2JHP = 20.5 Hz, 3JHН = 8.3
Hz), 7.32 (m, 6Н, arom; NH), 8.03 (d, 1Н,
NH, 3JHН = 8.3 Hz)
17.1
357 (0.68)
3d
3301, 1663, 1242,
1028, 963
1.31 (m, 6Н, 2ОСН2СН3), 1.57–1.64 (m, 6Н,
3СН2 piperidine), 2.61 (m, 2Н, СН2), 3.13
(m, 2Н, СН2), 3.56 (m, 4Н, 2CH2 piperidine),
4.15 (m, 4Н, 2ОСН2СН3), 5.48 (dd, 1Н, СН,
2JHP = 17.2 Hz, 3JHН = 6.8 Hz), 8.01 (d, 1Н,
NH, 3JHН = 6.8 Hz), 8.17 (br s, 2Н, NH2)
1.31 (m, 6Н, 2ОСН2СН3), 2.64 (m, 2Н, СН2),
3.14 (m, 2Н, СН2), 3.52–3.76 (m, 8Н, 4СН2
morpholine), 4.16 (m, 4Н, 2ОСН2СН3), 5.48
(m, 1Н, СН), 6.28 (br s, 2Н, NH2), 8.18 (m,
1Н, NH)
18.5
349 (0.67)
3e
6a
3291, 1652, 1231,
1026, 966
18.2
14.2
351 (0.65)
3250,
1652,1625,1578,
1278, 1024,966
1.30 (m, 6Н, 2ОСН2СН3), 1.63 (m, 6Н, 3СН2
piperidine), 2.33 (s, 3Н, СН3), 3.48 (m, 4Н,
2CH2 piperidine), 4.08 (m, 4Н, 2ОСН2СН3),
4.53 (d, 2Н, СН2, 3JHН = 6.2 Hz), 7.13–7.90
(m, 9Н, arom), 7.30 (s, 1Н, СН), 7.38 (br s,
1Н, NH), 8.20 (br s, 1Н, NH)
–
6b
6c
6d
6e
3258, 1662, 1578,
1151, 1271,
1024, 967
1.31 (m, 6Н, 2ОСН2СН3), 2.34 (s, 3Н, СН3),
3.58 (m, 4Н, 2CH2 morpholine), 3.78 (m, 4Н,
2CH2 morpholine), 4.10 (m, 4Н,
13.0
14.1
13.4
14.5
–
–
–
–
2ОСН2СН3), 4.56 (d, 2Н, СН2, 3JHН = 5.2
Hz), 7.05 (br s, 1Н, NH), 7.15–7.87 (m, 9Н,
arom), 7.24 (s, 1Н, СН), 7.94 (br s, 1Н, NH)
1.27 (m, 6Н, 2ОСН2СН3), 1.63 (m, 6Н, 3СН2
piperidine), 2.33 (s, 3Н, СН3), 2.89 (m, 2Н,
СН2), 3.46 (m, 4Н, 2CH2 piperidine), 3.75
(m, 2Н, СН2), 4.05 (m, 4Н, 2ОСН2СН3),
7.10–7.91 (m, 11Н, arom, СН, NH), 8.20 (br
s, 1Н, NH)
3246, 1626, 1578,
1283, 1025, 966
3255, 1604, 1579,
1275, 1025, 967
1.27 (m, 6Н, 2ОСН2СН3), 2.32 (s, 3Н, СН3),
2.90 (m, 2Н, СН2), 3.53 (m, 4Н, 2CH2
morpholine), 3.72 (m, 2Н, СН2), 3.77 (m,
4Н, 2CH2 morpholine), 7.02 (br s, 1Н, NH),
7.12–7.88 (m, 10Н, arom, СН), 8.16 (br s,
1Н, NH)
1.25 m, (6Н, 2ОСН2СН3), 2.34 (s, 3Н, СН3),
2.92 (m, 2Н, СН2), 3.76 (m, 2Н, СН2), 4.02
(m, 4Н, 2ОСН2СН3), 4.47 (d, 2Н, СН2, 3JHН
= 5.7 Hz), 6.32 (t, 1Н, NH, 3JHН = 5.7 Hz),
6.97–7.86 (m, 17Н, arom, СН, 2NH), 7.56
(br s, 1Н, NH)
3249, 1637, 1281,
1024, 967
7a
7b
1720, 1643, 1255,
1036, 965
1.32 (m, 6Н, 2ОСН2СН3), 1.61 (m, 6Н, 3СН2
piperidine), 2.42 (s, 3Н, СН3), 3.46 (m, 4Н,
2CH2 piperidine), 4.07 (m, 4Н, 2ОСН2СН3),
4.94 (s, 2Н, СН2), 7.28–8.16 (m, 10Н, arom,
СН)
1.33 (m, 6Н, 2ОСН2СН3), 2.42 (s, 3Н, СН3),
3.53 (m, 4Н, 2CH2 morpholine), 3.76 (m, 4Н,
2CH2 morpholine), 4.10 (m, 4Н,
13.5
12.3
–
–
1716, 1629, 1261,
1029, 966
2ОСН2СН3), 4.96 (s, 2Н, СН2), 7.28–8.15
(m, 10Н, arom, СН)
(Continued)
Heteroatom Chemistry DOI 10.1002/hc

294 Lukashuk et al.
TABLE 2 Continued
31P NMR
(CDCl3/H3PO4)
(ppm)
Mass-Spectrum:
m/z, [M]+ (ret.
time, min)
Compound
IR (KBr) (cm−1
)
1H NMR (CDCl3/TMS) (ppm)
8a
3402, 1644, 1249,
1023, 976
1.29 (m, 6Н, 2ОСН2СН3), 1.55–1.63 (m, 6Н,
3СН2 piperidine), 2.33 (s, 3Н, СН3), 3.54 (m,
4Н, 2CH2 piperidine), 4.15 (m, 6Н,
17.5
17.0
18.3
–
–
–
2ОСН2СН3, СН2), 5.54 (dd, 1Н, СН, 2JHP
=
17.6 Hz, 3JHН = 8.3 Hz), 7.13–7.94 (m, 11Н,
arom, 2NH), 8.21 (s, 1Н, NH)
8b
8c
3283, 1651, 1252,
1026, 975
1.31 (m, 6Н, 2ОСН2СН3), 2.34 (s, 3Н, СН3),
3.48–3.76 (m, 8Н, 4СН2 morpholine), 4.16
(m, 6Н, 2ОСН2СН3, СН2), 5.49 (dd, 1Н,
СН, 2JHP = 16.4 Hz, 3JHН = 7.5 Hz),
7.16–7.91 (m, 12Н, arom, СН, 2NH), 8.01 (s,
1Н, NH)
1.20 (m, 6Н, 2ОСН2СН3), 1.54–1.65 (m, 6Н,
3СН2 piperidine), 2.32 (s, 3Н, СН3), 2.50 (m,
1Н, СН), 2.60 (m, 1Н, СН), 3.53 (m, 4Н,
2CH2 piperidine), 3.64 (m, 1Н, СН), 3.71 (m,
1Н, СН), 4.08 (m, 4Н, 2ОСН2СН3), 5.45
(dd, 1Н, СН, 2JHP = 17.6 Hz, 3JHН = 8.3 Hz),
7.11–7.95 (m, 12Н, С6Н5, С6Н4, СН, 2NH),
8.55 (br s, 1Н, NH)
3250, 1627,1260,
1025, 966
8d
9
3286, 1649, 1250,
1025, 974
1.26 (m, 6Н, 2ОСН2СН3), 2.33 (s, 3Н, СН3),
2.58 (m, 2Н, СН2), 3.49–3.75 (m, 10Н,
4СН2 morpholine, СН2), 4.09 (m, 4Н,
2ОСН2СН3), 5.43 (dd, 1Н, СН, 2JHP = 17.7
Hz, 3JHН = 8.0 Hz), 7.04–7.93 (m, 12Н,
arom, СН, 2NH), 8.23 (br s, 1Н, NH)
1.29 (m, 6Н, 2ОСН2СН3), 1.66 (m, 6Н, 3СН2
piperidine), 2.41 (s, 3Н, СН3), 3.56 (m, 4Н,
2CH2 piperidine), 4.13 (m, 4Н, 2ОСН2СН3),
17.0
17.2
–
–
–
3291, 1721, 1676,
1642, 1262,
1023, 968
4.47 (s, 2Н, СН2), 5.50 (dd 1Н, СН, 2JHP
=
16.6 Hz, 3JHН = 8.0 Hz), 7.25–8.15 (m, 9Н,
arom), 7.39 (d, 1Н, NH, 3JHН = 8.0 Hz)
1.21 (m, 6H, 2ОСН2СН3), 1.44, 1.59 (m, 6Н,
3СН2 piperidine), 2.22 (s, 3Н, СН3), 2.98,
3.09 (m, 2Н, СН2), 3.48 (m, 4Н, 2CH2
piperidine), 3.85 (m, 2Н, СН2 glycine), 4.04
(m, 4Н, 2ОСН2СН3), 4.70 (m, 1Н, СН), 5.46
(m, 1Н, СНР), 7.05–7.82 (m, 9Н, arom),
8.39 (m, 1Н, NH), 8.44 (m, 1Н, NH), 8.60 (m,
1Н, NH).
11a
3332, 1643, 1235,
1019
18.3
18.4
11ba
3328, 1655, 1243,
1022
1.29 (m, 6H, 2ОСН2СН3), 1.62 (m, 6H, 3CH2
piperidine), 2.29 (s, 3Н, СН3), 2.33, 2.52 (m,
2Н, NHCH2CH2), 3.10–3.31 (m, 4Н, СН2,
1H, 1/2NHCH2CH2CO), 3.46–3.78 (m, 5Н,
2CH2- piperidine, 1Н, 1/2NHCH2CH2CO),
4.14 (m, 4Н, 2OCH2CH3), 4.87, 5.01 (m, 1Н,
СН), 5.49 (m, 1Н, СНР), 7.07- 7.72 (m, 12Н,
arom, 3NH).
18.5
18.8
–
a1H and 31Р NMR spectra were recorded in DMSO-d6.
EXPERIMENTAL
spectra were recorded on a Vertex 70 spectropho-
1
tometer in KBr tablets. The H, 31P, and 13C NMR
All starting materials were purchased from Acros,
Merck, and Fluka. Solvents were purified according
to the standard procedures. The progress of reac-
tions was monitored by TLC (Silicagel ALUGRAMꢀR
SIL G/UV254 by MACHEREY-NAGEL, Germany). IR
spectra were measured on a spectrometer Bruker
Avance DRX-500 (Germany; 500, 202, and 125 MHz,
respectively) in CDCl3 solution. Chemical shifts are
reported relative to internal Si(CH3)4 (1H, 13C) or
external 85% H3PO4 (31P).
Heteroatom Chemistry DOI 10.1002/hc

A Novel Synthetic Approach to Phosphorylated Peptidomimetics 295
Δ
SCHEME 2
SCHEME 3
LC/MS spectra were registered using a liquid
solvent A and 0.1% aqueous trifluoroacetic acid
as solvent B; the eluent flow rate was 3 mL/min,
and the injection volume was 1 μL; the elu-
tion was monitored simultaneously with three
UV detectors, at 215, 254, and 285 nm; ana-
lytes were ionized by atmospheric pressure chem-
ical ionization; the scan range was m/z 80–
chromatography/mass spectrometric system con-
sisting of an Agilent 1100 series high-performance
liquid chromatograph equipped with a diode ma-
trix and an Agilent LC/MSD SL mass-selective de-
tector. LC/MS analysis was performed on a 4.6 ×
15 mm Zorbax SB-C18 column (Agilent Technolo-
gies, Santa Clara, CA), with 1.8 μm particle size
(PN 821975-932); an acetonitrile:water (95:5) mix-
ture with 0.1% trifluoroacetic acid was used as
1000. Melting points were measured with
a
Fisher-Johns apparatus (Thermo Fisher Scientific,
Dubuque, IA).
Heteroatom Chemistry DOI 10.1002/hc

296 Lukashuk et al.
N-(Phthalimidoacetyl)
Diethyl 5-alkylamino-2-{N-[N-benzoyl-(4-
methylbenzylidene)glycyl]aminomethyl}-1,3-
oxazol-4-yl-phos-phonates 6a,b and Diethyl
5-alkylamino-2-[4,5-dihydro-4-(4-
methylbenzylidene)-5-oxo-2-phe-ny-limidazol-1-
ylmethyl]-1,3-oxazol-4-ylphosphonates
7a,b
diethoxyphosphorylglycine alkylamides 2a–c
A solution of one of compounds 1a–c (0.01 mol)
in an AcOH:H2O (5:1) mixture (50 mL) was heated
at 75оС in a water bath for 7 h, followed by the
evaporation of the reaction mixture to dryness un-
der reduced pressure. To remove AcOH completely,
the residue was treated with a 5% Na2CO3 so-
lution (20 mL) and extracted with CH2Cl2 (3×50
mL). The extract was dried over MgSO4 and evap-
orated to dryness under reduced pressure. The
resulting product was analyzed without further
purification.
Method A. To a solution of one of compounds 5a,b
(0.015 mol) in anhydrous dioxane (50 mL), azlactone
4 (2.6 g, 0.01 mol) was added and the mixture was
heated at reflux for 5–6 h under TLC control. The
solvent was evaporated in vacuo, the residue was
dissolved in toluene (20 mL), and the solution was
diluted with 70–100С petroleum ether. The mixture
was allowed to stand at 5–10◦С for 2–3 h and de-
canted. The oily residue was concentrated under re-
duced pressure and treated with 50% aqueous EtOH
to crystallize 7a or 7b. The toluene/petroleum ether
solution was evaporated in vacuo to give pure final
product 6a or 6b.
Method B. To a solution of one of compounds
5a,b (0.015 mol) in anhydrous toluene (50 mL),
azlactone 4 (2.6 g, 0.01 mol) was added and the mix-
ture was heated at 60–65◦С for 5–6 h under TLC
control. The solvent was evaporated in vacuo to give
a pure product 6a or 6b.
2a. 13C NMR: δ = 16.3, 24.3, 25.5, 26.0, 40.3; 44.0,
48.5, 63.8, 123.6, 132.1, 134.1, 163.5, 165.5, 167.7.
2b. 13C NMR: δ = 16.3, 40.2, 46.9, 47.2, 48.4, 64.1,
66.5, 123.6, 132.1, 134.2, 164.2, 165.9, 167.7.
2c. 13C NMR: δ = 16.2, 40.3, 44.0, 50.1, 51.2, 64.4,
123.5, 127.4, 127.5, 128.6, 132.1, 134.1, 137.6,
164.5, 166.2, 167.6.
N-(β-Phthalimidopropionyl) diethoxyphosphoryl-
glycine alkylamides 2d–f were obtained from cor-
responding oxazoles 1d–f similarly to compounds
2a–c.
6a. 13C NMR: δ = 16.3, 21.8, 23.9, 25.4, 37.8, 49.4,
62.22, 99.8, 100.2, 127.8, 130.9, 128.3, 128.5, 129.7,
132.0, 132.5, 133.2, 139.0, 142.4, 149.2, 150.3,
161.1, 161.9, 163.0, 167.8.
2e. 13C NMR: δ = 16.3, 34.2, 34.3, 47.0, 47.1, 48.00,
66.5, 63.8, 123.3, 132.1, 134.0, 164.4, 168.0, 169.1.
2f. 13C NMR: δ = 16.2, 34.2, 34.3, 43.8, 49.9, 51.0,
64.1, 123.2, 132.1, 134.1, 127.3, 127.5, 128.5, 137.7,
164.9, 168.0, 169.8.
Diethyl 5-alkylamino-2-{N-[N-benzoyl-(4-methyl-
benzylidene)glycyl]aminoethyl}-1,3-oxazol-4-yl-phos-
phonates 6c–e were obtained from corresponding
compounds 5c–e similarly to compounds 6a,b.
N-Glycyldiethoxyphosphorylglycine alkylamides
3a–c
6c. 13C NMR: δ = 16.3, 21.4, 24.0, 25.4, 27.7, 36.7,
49.5, 61.2, 98.6, 100.7, 127.7, 128.5, 128.5, 128.7,
129.2, 129.4, 131.0, 132.1, 133.2, 152.3, 152.4,
161.6, 161.9, 162.0, 165.9, 166.3.
To a solution of one of compounds 2a–c (0.01 mol)
in EtOH (50 mL), hydrazine hydrate (0.012 mol,
1.2 mL) was added and the mixture was heated at
50–55оС for 1–2 h under TLC control (Eluent sys-
tem - CH2Cl2:CH3OH as 95:5). The resulting white
precipitate was filtered off, and the filtrate was
evaporated to dryness under reduced pressure. The
residue was dissolved in CH2Cl2 (20 mL), and the
insoluble phthalazide was filtered off, followed by
the evaporation of the filtrate to dryness under re-
duced pressure. The products appeared as thick
oils.
6d. 13C NMR: δ = 16.3, 21.3, 27.6, 36.8, 48.4, 62.2,
66.2, 66.3, 62.33, 101.1, 101.2, 127.8, 128.4, 128.5,
128.9, 129.3, 130.9, 131.9, 132.9, 139.0, 153.0,
153.2, 162.4; 166.4, 166.7.
N-{N-[N-Benzoyl-(4-methylbenzylidene)glycyl]
glycyl} diethoxyphosphorylglycine alkylamides 8a,b
were obtained from corresponding compounds 6a,b
similarly to compounds 2a–c.
N-(β-Alanyl)diethoxyphosphorylglycine
alky-
8a. 13C NMR: δ = 16.4, 21.4, 43.0, 46.8, 47.3, 48.6,
64.1, 66.5, 127.7, 127.9, 128.8, 129.0, 128.9, 129.3,
129.6, 130.8, 132.4, 132.9, 139.4, 164.1, 164.2,
165.9, 168.4.
lamides 3d,e were obtained from correspond-
ing compounds 2d,e similarly to compounds
3a–c.
Heteroatom Chemistry DOI 10.1002/hc

A Novel Synthetic Approach to Phosphorylated Peptidomimetics 297
[6] Horenstein, B.; Nakanishi, K. J Am Chem Soc 1989,
111, 6242–6247.
[7] Kim, D.; Li, Y.; Horenstein, B.; Nakanishi, K. Tetra-
hedron Lett 1990, 31, 7119–7122.
[8] Schmidt, U.; Wild, I. Angew Chem 1984, 96, 996–997.
[9] Schmidt, U.; Wild, I. Liebigs Ann Chem 1985, 9,
1882–1894.
[10] Schmidt, U.; Lieberknecht, A.; Griesser, H.; Bo¨kens,
H. Liebigs Ann Chem 1985, 4, 785–793.
[11] Kunze, T.; Heps, S. Biochem Pharm 2000, 59, 973–
981.
N-{N-[N-Benzoyl-(4-methylbenzylidene)glycyl]-β-
alanyl}diethoxyphosphorylglycine alkylamides 8c,d
were obtained from corresponding compounds 6c,d
similarly to compounds 8a,b.
N-[4,5-Dihydro-4-(4-methylbenzylidene)-5-oxo-2-
phenylimidazol-1-ylacetyl]diethoxyphosphorylglycine
piperidide 9 was obtained from compound 7a simi-
larly to compounds 2a–c.
N-{N-[N-Benzoyl-(4-methylbenzyl)
glycyl]glycyl}
[12] Kazmaier, V.; Amino Acids, Peptides and Proteins
in Organic Chemistry; Hunghes A., Ed.; Wiley-VCH:
Weinheim, Germany, 2009, 3–34.
diethoxyphosphorylglycine piperidide 11a
To a stirred and cooled (5–10◦C) solution of com-
pound 6a (0.58 g, 0.001 mol) in an AcOH:HCl (10:3)
mixture (13 mL), powdered Zn (2g) was added in
25-mg portions during 5–10 min, followed by stir-
ring the reaction mixture at 5–10◦С for another
10 min under TLC control. The resulting precip-
itate was filtered off and washed with anhydrous
AcOH. After evaporation of the solvent in vacuo,
the product was purified by recrystallization from
CH3CN.
[13] Saavedna, C.; Boto, A.; Hernandes, R. Org Lett, 2012,
14, 3788–3791.
[14] Kunze, T. Arch Pharm 1996, 329, 503–509.
[15] Ko¨hler, B.; Sho¨llkopf, U. Liebigs Ann Chem 1987, 3,
267–269.
[16] Schmidt, U.; Lieberknecht, A.; Wild, J. Synth Com-
mun 1984, 1, 53–60.
[17] Schmidt, U.; Schanbacher, U. Angew Chem 1983, 95,
150–151.
[18] Schmidt, U.; Beuttler, T.; Lieberknechtt, A.; Criesser,
H. Tetrahedron Lett 1983, 24, 3573–3576.
[19] Ro¨hr, G.; Schnell, M.; Ko¨ckritz, A. Synthesis 1992,
10, 1031–1034.
[20] Kondratyuk, K. M.; Lukashuk, E. I.; Golovchenko,
A. V.; Rusanov, E. V.; Brovarets, V. S. Zh Obshch
Khim 2012, 82, 556–565.
[21] Kondratyuk, K. M.; Lukashuk, E. I.; Golovchenko,
A. V.; Brovarets, V. S. Tetrahedron (in press).
[22] Greenstein, I. P.; Winitz, M. Chemistry of the Amino
Acids; Wiley: New York, 1961, 2, p. 823.
[23] Gross, E.; Meienhoter, I. The Peptides; Academic
Press: New York, 1979, 1, p. 2.
N-{N-[N-Benzoyl-(4-methylbenzyl)glycyl]-β-
alanyl}diethoxyphosphorylglycine piperidide 11b was
obtained from compound 6c similarly to compound
11a.
REFERENCES
[1] Kukhar, V.; Hudson, H. Aminophosphonic
and Aminophosphinic acids; Wiley: New York,
1999.
[2] Hugles, A. Amino Acids, Peptides and Proteins in Or-
ganic Chemistry; Wiley-VCH: Weinheim, Germany,
2009.
[24] Phelps, D. I.; Godreau, P. V.; Nicholas, E. S. J Chem
Soc, Perkin Trans 2, 1981, 1, 140–142.
[25] Tripathy, P. K.; Mukerjee, A. K. Synthesis 1985, 3,
285–288.
[26] Abdallah, M. A.; Zayed, M. E.; Shawali, A. S. Indian
J Chem, Sect B: Org Chem Med Chem 2001, 40, 3,
187–190.
[3] Kafarski, P.; Lejezak, B. Curr Med Chem 2001, 1,
301–312.
[27] Bergel, F.; Stock, I. A. J Chem Soc 1957, 4563–4567.
[28] Lisichkina, I. N.; Vinogradova, A. I.; Bachurina, I.
B.; Kurkovska, L. N.; Belikov, V. M. Izv Akad Nauk
SSSR, Ser Khim 1994, 5, 884–886.
[29] Davies, J. S.; Eaton, M. C.; Ibrahim, M. N. J Hetero-
cyclic Chem 1980, 17, 1813–1814.
[4] Lejezak, B.; Kafarski, P. Top Heterocyclic Chem
2009, 20, 31–64.
[5] Berwe, M.; Winfried, J.; Kru¨ger, J.; Cancho-Crande,
Y.; Lampe, T.; Michels, M.; Paulsen, H.; Rad-
datz, S.; Weigand, S. Org Proc Res Dev 2011, 15,
1348–1357.
Heteroatom Chemistry DOI 10.1002/hc