Synthesis and NMR characterization of two novel anthracene-derived BIS-aminophosphonates. Basic hydrolysis of some aminophosphonate derivatives

Article abstract of DOI:10.1080/10426507.2011.638349

The synthesis of two novel bis-aminophosphonates bearing anthracene rings-bis[N-methyl(diethoxyphosphonyl)-1-(9-anthryl)]benzidine (3) and 4,4-bis[N-methyl(diethoxy-phosphonyl)-1-(9-anthryl)]diaminodiphenylmethane (4)-via the Kabachnik-Fields reaction is reported. The compounds have been characterized by elemental analysis, TLC, IR, NMR (¹H, ¹³C, ³¹P) and fluorescent spectra. The reaction leads to a mixture of the two possible forms (meso and racemic), with predominant formation of one of the diastereomers. The recrystallized compounds 3 and 4 consist of only one diastereomer. A racemization at the chiral centers and a cleavage of the C-P bond are observed in the alkaline hydrolysis of the new compound 4 and three previously described aminophosphonate derivatives 5-7. Supplemental materials are available for this article. Go to the publisher's online edition of Phosphorus, Sulfur, and Silicon and the Related Elements to view the free supplemental file.

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Synthesis and NMR Characterization
of Two Novel Anthracene-Derived BIS-
Aminophosphonates. Basic Hydrolysis of
Some Aminophosphonate Derivatives
a
a
a
a
I. Kraicheva , E. Vodenicharova , E. Tashev , T. Tosheva , I.
a
a
Tsacheva & K. Troev
a
Institute of Polymers, Bulgarian Academy of Sciences , Acad. G.
Bonchev Street, Sofia , Bulgaria
Accepted author version posted online: 04 Jan 2012.Published
online: 27 Mar 2012.
To cite this article: I. Kraicheva , E. Vodenicharova , E. Tashev , T. Tosheva , I. Tsacheva & K. Troev
(2012) Synthesis and NMR Characterization of Two Novel Anthracene-Derived BIS-Aminophosphonates.
Basic Hydrolysis of Some Aminophosphonate Derivatives, Phosphorus, Sulfur, and Silicon and the
Related Elements, 187:5, 660-667, DOI: 10.1080/10426507.2011.638349
To link to this article: http://dx.doi.org/10.1080/10426507.2011.638349
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Phosphorus, Sulfur, and Silicon, 187:660–667, 2012
Copyright ꢀ
Taylor & Francis Group, LLC
C
ISSN: 1042-6507 print / 1563-5325 online
DOI: 10.1080/10426507.2011.638349
SYNTHESIS AND NMR CHARACTERIZATION
OF TWO NOVEL ANTHRACENE-DERIVED
BIS-AMINOPHOSPHONATES. BASIC HYDROLYSIS
OF SOME AMINOPHOSPHONATE DERIVATIVES
I. Kraicheva, E. Vodenicharova, E. Tashev, T. Tosheva,
I. Tsacheva, and K. Troev
Institute of Polymers, Bulgarian Academy of Sciences, Acad. G. Bonchev Street,
Sofia, Bulgaria
GRAPHICAL ABSTRACT
OC H5
OC H
2 5
2
C H O
O
P
O
OC H
2 5
2
5
P
R
NH
NH
Abstract The synthesis of two novel bis-aminophosphonates bearing anthracene rings – bis[N-
ꢁ
methyl(diethoxyphosphonyl)-1-(9-anthryl)]benzidine (3) and 4,4 -bis[N-methyl(diethoxy-
phosphonyl)-1-(9-anthryl)]diaminodiphenylmethane (4) – via the Kabachnik–Fields reaction
is reported. The compounds have been characterized by elemental analysis, TLC, IR, NMR
1
13
31
(
H, C, P) and fluorescent spectra. The reaction leads to a mixture of the two possible
forms (meso and racemic), with predominant formation of one of the diastereomers. The
recrystallized compounds 3 and 4 consist of only one diastereomer. A racemization at the
chiral centers and a cleavage of the C-P bond are observed in the alkaline hydrolysis of
the new compound 4 and three previously described aminophosphonate derivatives 5–7.
Supplemental materials are available for this article. Go to the publisher’s online edition of
Phosphorus, Sulfur, and Silicon and the Related Elements to view the free supplemental file.
Keywords Aminophosphonic acids; NMR spectroscopy; basic hydrolysis
Received 20 September 2011; accepted 30 October 2011.
Address correspondence to I. Kraicheva, Institute of Polymers, Bulgarian Academy of Sciences, Acad. G.
Bonchev Street, Block 103 A, 1113 Sofia, Bulgaria. E-mail: kraicheva@yahoo.com
6
60

ANTHRACENE-DERIVED BIS-AMINOPHOSPHONATES
661
INTRODUCTION
Aminophosphonic acid derivatives continuously attract attention because of their
versatile biological activity, which affords a great number of possibilities for medicinal and
pharmaceutical applications.1 Considerable efforts have been devoted to the synthesis
and investigation of the structure and biological properties of these important “phosphorus
–3
2
,4–7
analogues” of natural α-aminocarboxylic acids.
Aminophosphonates can mimic amino
acids quite effectively due to the close structural resemblance and can act as inhibitors and
regulators of metabolic processes.2 The diverse applications of the aminophosphonate
derivatives include the use as inhibitors of bone resorption, bone-seeking radiopharma-
ceuticals, haptens for the generation of catalytic antibodies, antibacterial, antiviral, and
antitumor agents.8
,8
–11
In search for new compounds with potential anticancer activity, the amino-
phosphonates offer some very important advantages: They possess a negligible
mammalian toxicity, a resistance to proteolytic enzyme hydrolysis, and give numerous
2
,12
opportunities for combining various pharmacophoric groups in their molecules.
Anthracene-bearing aminophosphonates deserve particular interest in the design of new
antitumor therapeuticals, considering the fact that the anthracene-derived planar structure is
1
3,14
the main pharmacophoric fragment of some cytostatic drugs.
Anthracene-based agents
act as inhibitors of tubulin polymerization and some of them have been reported to display
strong antiproliferative activity against several tumor cell lines, including multi-drug resis-
tant phenotypes.1
5–18
Anthracene crown compounds are used as fluorescent probes for the
19
solid phase transitions of phosphatidylcholines. The fluorescent properties of anthracene-
containing aminophosphonates are anticipated find valuable bioanalytical applications in
the study of the subcellular distribution and binding in normal and tumor cells.
Only few examples of anthracene-containing aminophosphonates are described in the
literature.2
0–22
Here we report on the synthesis and spectroscopic characterization of two
novel anthracene-containing bis-aminophosphonates with potential antitumor activity. Data
about the alkaline hydrolysis of one of the new compounds and other three aminophospho-
nate derivatives synthesized earlier6
,23,24
are also presented. The evaluation of the cytotoxic
potential of the novel bis-aminophosphonates is in progress.
RESULTS AND DISCUSSION
Two novel bis-aminophosphonates, containing anthracene rings–bis[N-methyl
ꢁ
(
diethoxy-phosphonyl)-1-(9-anthryl)]benzidine (3) and 4.4 -bis[N-methyl(diethoxyphos
phonyl)-1-(9-anthryl)]diaminodiphenylmethane (4)–were synthesized via the Kabachnik–
Fields reaction according to Scheme 1.
Products 3 and 4 were obtained as yellow fluorescent crystalline solids, soluble in
methanol, ethanol, chloroform, and benzene. Thin layer chromatography (TLC) gave one
spot for each of the compounds. The elemental analyses of the compounds are consistent
with their composition. The molecular structure of the bis-aminophosphonates was con-
firmed by IR and NMR spectroscopy. The IR spectra of 3 and 4 show absorption bands at
−
1
3
361–3310 and 1236–1225 cm , which are attributed to NH and P O stretching vibra-
1
tion, respectively. The H NMR spectra of the bis-aminophosphonates, recorded in CDCl3
solution, display the signal for the CHP proton as a doublet at 6.31 (3) ppm and 6.24 (4)
ppm. The signal for the NH proton of these compounds is observed as a broad singlet. The
methyl protons from the alkoxy groups give two triplets of doublets (3) or a triplet and a

662
I. KRAICHEVA ET AL.
Scheme 1 Synthesis of bis-aminophosphonates 3 and 4.
triplet of doublets (4) due to the nonequivalence of the two ester groups.25 Three multiplets
were observed for the methylene protons of the ethoxy groups in 3 and 4. The aromatic
protons of compounds 3 and 4 display multiplets in the expected region of the spectra. For
6
the proton H-10 of the anthracene ring, a doublet with JPH of 2.9 Hz (3) and of 2.8 Hz
(
4) is observed. The assignment of the signal is based on the analysis of the H,H-COSY
21
NMR spectra (for 3 and 4) and on literature data. Thus, a long-range phosphorus coupling
6
to the proton position 10 of the anthracene ring with JPH = 2.9 Hz has been reported
for a 9-anthryl-aminophosphonate.21 The signals of the anthracene protons in α-position in
3
compounds 3 and 4 appear as doublets. The values of the coupling constants JHH measured
from the spectra are also in accordance with the literature data. The protons in β-position
21
(
AnthH-β) of compounds 3 and 4 give poorly resolved multiplets.
13
1
C{ H} NMR spectra of the bis-aminophosphonates display the signal of the CHP
carbon atom as a doublet with a large coupling constant (153.1 Hz and 152.6 Hz for 3 and
4
, respectively) due to one-bond interaction of the carbon with phosphorus. For quaternary
ꢁ
carbon atoms (ArC-4,4 ) adjacent to the nitrogen atoms in 3 and 4 doublets are observed.
The signals show three-bond couplings to phosphorus of 13.2 Hz (3 and 4). The other
aromatic carbon atoms give singlets in the 13C NMR spectra. The methyl and methylene
carbon atoms of the nonequivalent alkoxy groups in compounds 3 and 4 display pairs of
doublets. A doublet is observed for the anthracene carbon atom in meso-position (AnthC-
5
1
0) with a coupling constant JPC of 4.5 Hz (3 and 4). Long-range phosphorus–carbon
coupling constants over up to seven bonds have been reported for similar conjugated planar
26,27
13
systems.
The C NMR spectra of 3 and 4 display singlets for other anthracene carbon
atoms. Each anthracene carbon atom in 3 and 4 gives a distinct signal due to the loss of
21
symmetry in the 9-anthryl unit of aminophosphonate derivatives.
The bis-aminophosphonates 3 and 4 possess two identical chiral centers and can exist
as two diastereomeric pairs: meso form (R,S) and racemic mixture of two enantiomers (R,R
and S,S). The 31P{ H} NMR spectra of crude products show the presence of two singlets
with very similar chemical shifts and with different intensities at 25.05 ppm and 24.95 ppm
1
(82.4% and 17.6%, respectively) for 3 and at 25.11 ppm and 25.06 ppm (83.3% and 16.7%,
respectively) for 4. This indicates the presence of the two possible diastereomers in each
of the non-recrystallized products. In the 31P{ H} NMR spectra of the purified samples of
1
3
and 4 only one signal appears at 25.06 ppm (3) and 24.57 ppm (4), which is assigned to

ANTHRACENE-DERIVED BIS-AMINOPHOSPHONATES
663
Figure 1 Fluorescence spectra of compounds 3 and 4 in methanol (λEx = 380 nm).
the major diastereomer formed in the reaction. Thus, the recrystallized compounds 3 and 4
consist of only one diastereomer.
The fluorescence emission spectra in methanol of the bis-aminophosphonates 3 and
4
were recorded. The fluorescence maxima appear in the region 444–608 nm both in the
spectra of compounds 3 and 4 (Figure 1).
The alkaline hydrolysis of the purified bis-aminophosphonate 4 was performed ac-
2
8–30
31
cording to the known procedure.
The reaction mixture was studied by P NMR
spectroscopy. The 31P { H} NMR spectra of the samples show two singlets at 24.45 ppm
and 24.36 ppm with decreasing intensities in the course of the reaction. These signals can
be assigned to the phosphorus of the CHP fragment in the two diastereomers of compound
1
4
. Thus, a diastereoisomerization of 4 occurs in alkaline medium similar to the case of
30
31
1
some bis-aminophosphonates reported earlier. The P{ H} NMR spectra reveal a singlet
1
1
at 4.42 ppm, which in the H coupled spectra appears as a doublet of triplets with JPH =
3
6
07.6 Hz and JPH = 8.4 Hz. The signal is due to the phosphorus atom of HP(O)(ONa)(OEt)
resulting from hydrolysis. This indicates that the alkaline hydrolysis of 4 leads to a cleavage
of the C-P bond and to the formation of the sodium salt of phosphonic acid monoethyl
31
1
ester. After 4 h from the beginning of the reaction, the P{ H}NMR spectra display an
additional signal of a very low intensity at 17.3 ppm. The signal is due to the presence of
a negligible amount (4%) of sodium salt of the monoester of compound 4 formed under
alkaline conditions. The more stable Schiff base precursor obtained as yellow precipitate
1
during the hydrolysis of 4 was isolated in 91% yield. Its H NMR spectrum was identical
ꢁ
ꢁ
with the spectrum of the Schiff base N,N -di(9-anthrylidene)-4,4 -diaminodiphenylmethane
synthesized by us as a model compound (see Experimental section). The hydrolysis of the
6
,23,24
aminophosphonate derivatives 5–7, synthesized previously,
was carried out under the
same conditions (Figure 2).

664
I. KRAICHEVA ET AL.
Figure 2 Aminophosphonate derivatives 5–7.
The reaction of the anthracene-derived aminophosphonate 5 and of the furan-
containing bis-aminophosphonate 7 afforded a quantitative yield of the corresponding
Schiff base precursor, while the aminophosphonate 6 gave a mixture consisting of the
Schiff base and the unchanged starting product. Thus, in all compounds 4–7, a cleavage
of the P-C bond in alkaline medium was established. The lower stability of 4, 5, and 7
is probably due to the presence of an anthracene- and furan-containing substituent at the
CHP group. Data for the influence of some substituents in aminophosphonate derivatives
2
8,29
on their alkaline hydrolysis have been reported.
CONCLUSION
Two novel anthracene-derived bis-aminophosphonates 3 and 4 were synthesized via
the Kabachnik–Fields reaction. The compounds were characterized by elemental analysis,
1
13
31
TLC, IR, NMR ( H, C, and P), and fluorescent spectra. The reaction of diethyl phosphite,
9
ꢁ
-anthracenecarboxaldehyde, and diamines (benzidine and 4,4 -diaminodiphenylmethane,
respectively) leads to a mixture of the two possible diastereomers (meso and racemic forms)
with the predominant formation of one of them (82% and 83% for compounds 3 and 4,
respectively). The 31P NMR study reveals that the purified samples of compounds 3 and
4
consist of only one diastereoisomer. In alkaline medium, the hydrolysis of the new bis-
aminophosphonate 4 and of other three aminophosphonate derivatives 5–7, synthesized
earlier, proceeds with a cleavage of the P-C bond and formation of the sodium salt of
phosphonic acid monoethyl ester. The corresponding Schiff base precursor was isolated in
high yield as a result of the hydrolysis of 4, 5, and 7. The alkaline hydrolysis of 6 leads
to a mixture of the Schiff base precursor and the unchanged aminophosphonate. The lower
stability of 4, 5, and 7 is probably due to the presence of an anthracene- and furan-containing
substituent at the CHP fragment of these aminophosphonate derivatives.
EXPERIMENTAL
Diethyl phosphite (Fluka) was purified by vacuum distillation. 9-anthracenecarbox
ꢁ
aldehyde, benzidine and 4,4 -diaminodiphenylmethane were purchased from Fluka. All
solvents were freshly distilled prior to use. The melting points of the compounds were
determined on a Kofler microscope and are uncorrected. IR spectra were obtained with

ANTHRACENE-DERIVED BIS-AMINOPHOSPHONATES
13
665
1
1
an IRAffinity-1 spectrophotometer. H, C{ H}, and 2D NMR spectra in CDCl3 were
1
13
recorded with a Bruker DRX-250 spectrometer at r.t. H and C chemical shifts are re-
31
ferred to tetramethylsilane (TMS) as an internal standard. P NMR spectra in CDCl3
31
were obtained with a Bruker DRX-250 spectrometer. P chemical shifts are given with
respect to 85% H3PO4 as an external standard. The thin layer chromatography was
performed on a Merk Silica gel 60 F254 at r.t. The samples were applied as methano-
lic solutions and the chromatograms were developed in ascending order in the elut-
ing system – diethyl ether:hexane:methanol = 6:4:1. The spots were detected under
UV light. Fluorescent spectra were recorded with a Jasko fluorimeter 6600. [N-methyl-
23
(
diethoxyphosphonyl)-1-(9-anthryl)]-p-toluidine 5 was prepared as described previously.
p-[N-methyl(diethoxyphosphonyl)-(4-dimethylaminophenyl)]toluidine 6 was synthesized
6
ꢁ
applying the procedure reported earlier. 4,4 -Bis[N-methyl(diethoxyphosphonyl)-1-(2-
furyl)]diamino-diphenylmethane 7 was obtained according to the procedure described by
2
4
ꢁ
ꢁ
ꢁ
us. The Schiff base N,N -bis(9-anthrylidene)-4,4 -diaminodiphenylmethane was synthe-
sized from 9-anthracene-carboxaldehyde and 4,4 -diaminodiphenylmethane; m.p.: 228–
◦
1
2
30 C; Rf = 0.90. H NMR (CDCl3): δ = 9.70 (s, 2H, CH = N), 8.75 (m, 4H, Anth-H),
8
56 (s, 2H, Anth-H-10), 8.05 (m, 4H, Anth-H), 7.55 (m, 8H, Anth-H), 7.41 (m, 8H, Ar-
H), 4.16 (s, 2H, CH2). The hydrolysis was performed following the procedure described
2
8–30
previously.
Bis[N-methyl(diethoxyphosphonyl)-1-(9-anthryl)]benzidine (3)
Benzidine (1.08 g, 5.87 mmol) and diethyl phosphite (1.62 g, 11.74 mmol) were
placed in a flask, equipped with magnetic stirrer, thermometer, and reflux condenser and
stirred at r.t. 9-anthracenecarboxaldehyde (2.42 g, 11.75 mmol) dissolved in dry benzene
(15 mL) was added to the reaction mixture. The mixture was refluxed for 12 h with stirring.
The yellow precipitate obtained was recrystallized from ethanol. Yield: 2.75 g (56%); m.p.:
◦
2
38–240 C; Rf = 0.52. Anal. Calcd. for C50H50N2O6P2: C, 71.77%; H, 5.98%; N, 3.35%.
−
1
Found: C, 71.52%; H, 5.69%; N, 3.21%. IR (neat), v˜ (cm ): 3310 (νNH); 1225 (νP O);
1
1
(
159, 1016 (νPOEt). Flurescence spectrum: Ex 380 nm, λmax = 444 nm, 518 nm. H NMR
3
3
CDCl3): δ = 9.01 (d, JHH = 9.0 Hz, 2H, AnthH-α), 8.45 (d, JHH = 9.1 Hz, 2H, AnthH-α),
6
3
8
.40 (d, JPH = 2.9 Hz, 2H, AnthH-10), 8.03 (d, JHH = 8.4 Hz, 2H, AnthH-α), 7.94 (d,
3
ꢁ
ꢁ
JHH = 8.3, 2H, AnthH-α), 7.51 (m, 8H, AnthH-β), 6.97 (m, 4H, ArH-2,6,2 ,6 ), 6.44 (m,
ꢁ
ꢁ
2
4
3
7
H, ArH, 3,5,3 ,5 ), 6.31 (d, JPH = 27.0, 2H, CHP), 4.54 (br s, 2H, NH), 4.21, 3.70 and
3
4
3
.25 (3 m, 8H, OCH2), 1.33 (td, JHH = 7.1 Hz, JPH = 0.3 Hz, 6H, CH3), 0.63 (td, JHH =
.1 Hz, JPH = 0.6 Hz, 6H, CH3). C{ H} NMR (CDCl3): δ = 145.5 (d, JPC = 13.2 Hz,
4
13
1
3
ꢁ
5
ArC-4,4 ), 129.8 (AnthC-α), 129.1 (AnthC-α), 128.9 (d, JPC = 4.5 Hz, AnthC-10), 126.8
ꢁ ꢁ
(
ArC-2,6,2 ,6 ), 126.6 (AnthC-β), 126.4 (AnthC-α), 125.9 (AnthC-β), 125.1 (AnthC-β),
ꢁ
ꢁ
2
1
6
1
24.7 (AnthC-β), 122.6 (AnthC-α), 113.6 (ArC-3,5,3 ,5 ), 63.3 (d, JPC = 7.1 Hz, OCH2),
2 1 3
3.0 (d, JPC = 7.0 Hz, OCH2), 55.0 (d, JPC = 153.1, CHP), 16.5 (d, JPC = 5.9 Hz, CH3),
3
31
1
5.7 (d, JPC = 5.7 Hz, CH3). P{ H} NMR (CDCl3): δ = 25.06 ppm.
ꢀ
4
,4 -Bis[N-methyl(diethoxyphosphonyl)-1-(9-anthryl)]
diaminodiphenylmethane (4)
ꢁ
Compound 4 was prepared from 4,4 -diaminodiphenylmethane (1.24 g, 6.26 mmol),
diethyl phosphite (1.73 g, 12.54 mmol), and 9-anthracenecarboxaldehyde (2.58 g, 12.52
mmol) following the procedure given for compound 3.

666
I. KRAICHEVA ET AL.
◦
Yield: 2.71 g, (51%); m.p.: 183–185 C; Rf = 0.54. Anal. Cacld. for C51H52N2O6P2:
C, 72.00%; H, 6.12%; N, 3.29%. Found: C, 71.83%; H, 6.01%; N, 3.12%. IR (neat), v˜
−
1
(
cm ): 3361 (νNH); 1236 (νP O); 1161, 1041 (νPOEt). Flurescence spectrum: Ex 380 nm,
1
3
λmax = 444 nm, 455 nm, 533 nm, 608 nm. H NMR (CDCl3): δ = 8.99 (d, JHH =
.0 Hz, 2H, AnthH-α), 8.40 (d, JHH = 8.5 Hz, 2H, AnthH-α), 8.39 (d, JPH = 2.8 Hz, 2H,
3
6
9
3
3
AnthH-10), 8.01 (d, JHH = 8.2 Hz, 2H, AnthH-α), 7.93 (d, JHH = 8.3 Hz, 2H, AnthH-α),
ꢁ ꢁ ꢁ ꢁ
.49 (m, 8H, AnthH-β), 6.61 (m, 4H, ArH-2,6,2 ,6 ), 6.33 (m, 4H, ArH, 3,5,3 ,5 ), 6.24 (d,
7
2
JPH = 27.2 Hz, 2H, CHP), 4.37 (br s, 2H, NH), 4.17 and 3.69 (2 m, 6H, OCH2), 3.43
3
3
(
7
s, 2H, CH2), 3.24 (m, 2H, OCH2), 1.32 (t, JHH = 7.1 Hz, 6H, CH3), 0.63 (td, JHH =
4
13
1
3
.1 Hz, JPH = 0.5 Hz, 6H, CH3). C{ H} NMR (CDCl3): δ = 145.1 (d, JPC = 13.2 Hz,
ꢁ
ꢁ
ꢁ
5
ArC-4,4 ), 129.7 (AnthC-α), 129.2 (ArC-2,6,2 ,6 ), 129.0 (AnthC-α), 128.8 (d, JPC =
4
.5 Hz, AnthC-10), 126.8 (AnthC-β), 126.5 (AnthC-α), 125.7 (AnthC-β), 125.0 (AnthC-
ꢁ
ꢁ
2
β), 124.6 (AnthC-β), 122.6 (AnthC-α), 113.3 (ArC-3,5,3 ,5 ), 63.3 (d, JPC = 7.0 Hz,
2
1
OCH2), 62.9 (d, JPC = 7.0 Hz, OCH2), 53.0 (d, JPC = 152.6 Hz, CHP), 39.8 (CH2),
3
3
31
1
1
2
6.5 (d, JPC = 5.9 Hz, CH3), 15.7 (d, JPC = 5.7 Hz, CH3). P{ H} NMR (CDCl3): δ =
4.57 ppm.
Alkaline Hydrolysis of Compound 4
Compound 4 (0.54 g, 0.63 mmol) dissolved in dry ethanol (50 mL) was placed in a
flask, provided with mechanical stirrer and reflux condenser. NaOH (0.17 g, 4.25 mmol)
was added to the stirred solution and the mixture was heated to reflux for 16 h. Samples of
the solution were analyzed by 3 P NMR spectroscopy after every 2 h during the reaction.
The yellow precipitate obtained was filtered, washed with ethanol, dried, and analyzed
1
1
◦
1
by H NMR spectroscopy. Yield: 0.33 g, (91%); m.p.: 226–228 C; Rf = 0.90. H NMR
(
CDCl3): δ = 9.63 (s, 2H, CH = N), 8.67 (m, 4H, AnthH), 8.48 (s, 2H, AnthH-10), 7.97
(
m, 4H, AnthH), 7.46 (m, 8H, AnthH), 7.33 (m, 8H, ArH), 4.07 (s, 2H, CH2). To precipitate
the excess of the base, carbon dioxide was passed through the solution, the Na2CO3 formed
was filtered off and the resulting solution was evaporated in vacuo.
Hydrolysis of the aminophosphonates 5 and 6 and of the bis-aminophosphonate 7 in
alkaline medium was performed according to the procedure given for compound 4.
ACKNOWLEDGMENTS
Thanks are due to Bulgarian National Science Fund of Ministry of Education and
Science for financial support: contract DTK-02/34 (2009).
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2
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