α-hydroxy-α-aminophosphinic acids: I. Synthesis of a new analog of phenylglycine and its enantiomers

Article abstract of DOI:10.1007/s11176-005-0267-1

Methods for synthesis of a new phosphinic analog of phenylglycine, (α-aminobenzyl)(hydroxy-methyl) phosphinic acid and its enantiomers are developed. 2005 Pleiades Publishing, Inc.

Full text of DOI:10.1007/s11176-005-0267-1

Russian Journal of General Chemistry, Vol. 75, No. 4, 2005, pp. 533 536. Translated from Zhurnal Obshchei Khimii, Vol. 75, No. 4, 2005,
pp. 571 574.
Original Russian Text Copyright
2005 by Rozhko, Ragulun.
-Hydroxy- -aminophosphinic Acids: I. Synthesis
of a New Analog of Phenylglycine and Its Enantiomers
L. F. Rozhko and V. V. Ragulun
Institute of Physiologically Active Compounds, Russian Academy of Sciences, Chernogolovka, Russia
Received December 10, 2003
Abstract Methods for synthesis of a new phosphinic analog of phenylglycine, ( -aminobenzyl)(hydroxy-
methyl)phosphinic acid and its enantiomers are developed.
Phosphinic acids containing
-hydroxy and
hydrogenation of [ -(benzylamino)benzyl]phosphinic
acid (IV) using ammonium formate as the source of
hydrogen [12, 13] [Scheme (1)].
-amino groups are phosphorus analogs of -amino
as well as -hydroxy acids. Replacement of the
carboxy group in an amino acid by phosphoryl usually
results in inhibition of enzymatic processes involving
the prototype natural amino acid [1, 2]. Appearance
in an -aminophosphoryl compound of an -hydroxy
group may affect the inhibiting properties of this
compound. -Hydroxy- -aminophosphinic acids can
be regarded, from the one side, as Kabachnik Fields
reaction products and, from the other, as products of
the Abramov reaction that is essentially reversible.
The ability of -hydroxyphosphoryl compounds to
reversible dissociation [3, 4] with formation of an
aminophosphonous component susceptible to oxida-
tion may significantly affect the ability of -hydroxy-
-aminophosphinic acids to inhibit natural enzymes
and alter not only the rate, but also direction of the
corresponding biochemical reactions.
Scheme 1.
OH
P
O
Ph
HO
AcNH2/PhCH(O)
P H
NHAc
HO
O
OH
II
III
HCl, reflux
PhCH2NH2/PhCH(O)
HCOONH4;
10% Pd/C
Diasorb (H+)
OH
O
HO
Ph
HO
Ph
N
P
P
NH2
O
OH
Ph
IV
I
Among -aminophosphoryl compounds, analogs
of phenylglycine, especially phosphonic [5, 6] and
phosphonous analogs [7, 8], are the most thoroughly
studied. These compounds exhibit diverse and sig-
nificant biologic activity [9, 10]. In this connection of
interest is the acidic phosphinic analog of phenyl-
glycine, containing an -hydroxymethyl fragment.
The enantiomers of I were prepared with the aid of
Penicillinamidase (PcAm) [14, 15] as the biocatalyst
for hydrolysis of N-phenylacetyl derivative V which,
in its turn, was obtained by the acylation of amino
acid I with phenylacetyl chloride according to a clas-
sical Schotten Baumann procedure [16] [Scheme (2)].
Here we present various methods for preparing a
new phosphinic analog of phenylglycine, ( -amino-
benzyl)(hydroxymethyl)phosphinic acid (I), and its
enantiomers.
The (S)-I enantiomer obtained by enzymatic hydr-
olysis was separated from unhydrolyzed acid (R)-V
by means ion-exchange chromatography [14, 15].
Acid hydrolysis usually does not touch bonds sur-
rounding chirality center in various phenylglycine
analogs [17 19]. Therefore, (R)-V hydrolyzed without
appreciable racemization and gave the optical antipode
(R)-I.
We offer a one-pot synthesis of acid I from (hydr-
oxymethyl)phosphonous acid (II) and acetamide in
acetic anhydride by a modified Kabachnik Fields re-
action [11] without isolation of [ -(acetylamino)-
benzyl]phosphinic acid (III) [Scheme (1)]. Besides, as
an alternative approach, we propose the synthesis of
amino acid I by the Kabachnik Fields reaction with
benzylamine as the amino component, followed by
The absolute configuration of the enantiomers of
the phosphonic analog of phenylglycine is known [20],
and it is unlikely that the presence of a hydroxymethyl
1070-3632/05/7504-0533 2005 Pleiades Publishing, Inc.

534
ROZHKO, RAGULUN
acetonitrile to distilled water. The column was preli-
Scheme 2.
minarily calibrated with phenylacetic acid. The enzy-
matic reactions were performed with immobilized
PcAm (activity 103 U/g).
H
N
O
Ph
PhCH2C(O)Cl
O
P
(R,S)-I
Synthesis of ( -aminobenzyl)(hydroxymethyl)-
phosphinic acid (I). a. To a solution of 20.5 g of
(hydroxymethyl)phosphonous acid and 12.6 g of acet-
amide in 20 ml of acetic anhydride, 21.7 g of benz-
aldehyde was added. The resulting mixture was slow-
ly heated with stirring to 70 C, after which the mix-
ture spontaneously warmed up to 120 C. The boiling
reaction mixture was stirred for 5 h. The 31P NMR
spectrum of the reaction mixture showed a singlet at
45 ppm assignable to [ -(acetylamino)benzyl]phos-
phinic acid (III). After cooling, the reaction mixture
was evaporated in a vacuum. The oily residue was
diluted with 150 ml of conc. HCl, and the mixture
was refluxed for 7 h, cooled, concentrated to ca. 70 ml,
and washed with benzene (2 20 ml) and ether (2
20 ml). The aqueous phase was evaporated in a
vacuum, and the residue was subjected to cation-ex-
change chromatography (eluent H2O 0.5 N HCl).
Fractions with a positive ninhydrin test were collected
and evaporated in a vacuum. The residue was dis-
solved in aqueous ethanol and treated with excess
propylene oxide to obtain 17.8 g of acid I. Yield
42.1% [per (hydroxymethyl)phosphonous acid], mp
228 230 C. Additional crystallization from aqueous
ethanol gave an analytically pure sample of acid I.
Ph
HO
OH
(R,S)-V
OH
P
H
OH
OH
.
...
...
1) PcAm,
2) Dowex-50WX(H+)
H
NH2
O
(S)-I
OH
P
OH
P
H
H
OH
HCl
.
...
...
Ph
Ph
.
...
...
Ph
NH
O
NH2
O
(S)-I
O
(R)-V
fragment on phosphorus may radically alter the con-
figuration of the stereogenic -carbon atom.
To conclude, methods for synthesis of a new phos-
phinic analog of phenylglycine (racemate) and an
enzymatic method of separation of the amino acid into
optical antipodes are offered.
EXPERIMENTAL
The H and 31P NMR spectra were recorded on a
1
1
Yield 15.8 g (37%), mp 235 238 C. H NMR spec-
Bruker DPX-200 Fourier spectrometer against internal
TMS and external 85% H3PO4. The optical rotation
was measured on Perkin Elmer 421 and Polamat A
polarimeters. The melting points were measured on a
Boetius-PHMK device or in a heating block in an
open capillary. Thin-layer chromatography was
carried out on Silufol plates (eluent chloroform
acetone, 5:1) and on glass plates (Merck) with a UV-
254 silica gel layer (0.2 mm); development in UV
light or iodine vapor. In addition, Alufol (Kavalier)
plates (neutral alumina on aluminum, eluent isobu-
tanol acetic acid water, 5:1:1, or pyridine acetic
acid water isobutanol, 1:3:5:5) was used. The
plates were sprayed with ninhydrin, and amino acids
were detected at 100 C. The starting hydroxymethyl-
phosphonous acid was prepared according to the
procedure described in [21]. Ion-exchange chromato-
graphy was carried out on Dowex 50WX8-200 (H+)
(Lancaster), KU-2-8-U (H+) (IKhT), and Diasorb-
Sulfo (H+) (BioKhimMak) cation-exchange resins.
trum (D2O + DCl), , ppm: 3.37 d (2H, JHP 6.5 Hz);
4.25 d (1H, JHP 11.0 Hz); 7.38 m (5H). 31P NMR
spectrum (D2O + DCl), P, ppm: 34.5. Found, %: C
43.75, 43.63; H 6.47, 6.48; P 14.19, 14.16. C8H12
NO3P H2O. Calculated, %: C 43.84; H 6.44; P 14.31.
b. 1. Synthesis of [ -(Benzylamino)benzyl]-
(hydroxymethyl)phosphinic acid (IV). A solution of
2.1 g of (hydroxymethyl)phosphonous acid and 2.4 ml
of benzylamine in 8 ml of dry toluene was heated
with vigorous stirring to 50 C, and 2.2 ml of benz-
aldehyde was added slowly to the solution over the
course of 15 min. The reaction mixture warmed up to
80 C and was stirred at that temperature for 2 h, after
which it was evaporated in a vacuum. The residue was
treated with 20 ml of 2 N HCl, insoluble particles
were filtered off, and the filtrate was evaporated in a
vacuum. The residue was dissolved in aqueous
ethanol ( 1:5) and treated with excess propylene
oxide. Additional crystallization from aqueous ethanol
gave 4.5 g of acid IV. Yield 70% [per (hydroxy-
methyl)phosphonous acid]. 1H NMR spectrum (D2O +
DCl), , ppm: 3.22 d.d (2H, CH2O, JHP 7.0 Hz, JHH
6.7 Hz); 3.45 d (1H, CH2Ph, JHH 13.3 Hz), 3.97 d (1H,
CHP, JHP 10.7 Hz), 6.70 m (2H, 2Ph), 6.90 m (8H,
Enzymatic hydrolysis was followed and quantit-
ative analysis of the mixture was carried out by means
of HPLC on a Gilson chromatograph with a UV-Vis
118 detector at 254 nm, column Diasorb 130 C16/T
(4 250 mm, sorbent particle size 5 m), eluent
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 75 No. 4 2005

-HYDROXY- -AMINOPHOSPHINIC ACIDS: I.
535
2Ph). 31P NMR spectrum (D2O + DCl), P, ppm:
33.8. Found, %: C 51.94, 52.03; H 7.07, 6.98; P 8.88,
8.76. C15H18NO3P H2O. Calculated, %: C 52.17;
H 7.01; P 8.97.
in a vacuum to ca. 20 ml and then passed through a
cation-exchange column (H+) (3 30 cm), eluent water.
1. Fractions with a negative ninhydrin test were
collected and evaporated in a vacuum. The residue
was crystallized from ether to give 2.9 g (61.7%) of
2. Hydrogenation of [ -(benzylamino)benzyl]-
(hydroxymethyl)phosphinic acid (IV). To a solution
of 5 g of acid IV in 30 ml of ethanol, 1.8 g of ammo-
nium formate and 1 g of 10% Pd/C were added. The
resulting mixture was stirred for 15 h at room tempe-
rature, the catalyst was removed by filtration through
a Celite bed, and the filtrate was evaporated in a
vacuum. The residue was dissolved in a minimum of
water and passed through a strongly acidic cation-ex-
change resin to remove ammonium ions. Fractions
with a positive ninhydrin test were combined and
evaporated in a vacuum. The residue was crystallized
from aqueous ethanol to give 1.9 g of acid I. Yield
64.5% [per acid IV, total yield 45.5% per phospho-
1
acid (R)-V, mp 131-134 C. The H and 31P NMR
spectra of the sample were identical to those of
(R,S)-V. Found, %: C 59.36, 59.13; H 5.64, 5.67;
P 9.38, 9.35. C16H18NO4P 0.25H2O. Calculated, %:
25
546
C 59.35, H 5.76, P 9.57. [ ]
19.3 (c 1.0, EtOH).
A mixture of 1.0 g of acid (R)-V and 10 l of 6 N
HCl was refluxed for 10 h and then evaporated. The
residue was partitioned between 20 ml of water and
5 ml of ether. The aqueous phase was washed with
ether (2 10 ml) and evaporated in a vacuum. The
residue was treated with excess propylene oxide in
aqueous ethanol ( 1:7) to obtain 0.53 g of acid (R)-I.
Yield 84.0% per (R)-V and 51.6% per (R,S)-V. mp
190 195 C (softening) and 233 235 C (melting with
1
nous acid II]. mp 233 235 C. The H and 31P NMR
spectra (D2O + DCl) were identical to those of the
amino acid prepared by procedure a.
1
decomposition). The H and 31P NMR spectra of the
sample were identical to those of (R,S)-I. Found, %:
C 47.37; 47.65; H 5.95, 6.22; P 15.12, 15.31.
C8H12NO3P. Calculated,%: C 47.77; H 6.01; P 15.40.
Synthesis of (R,S)-(hydroxymethyl)[ -[(phe-
nylacetyl)amino]benzyl]phosphinic acid (V). To a
vigorously stirred solution of 17.8 g of racemic amino-
phosphinic acid I in 70 ml of water, 14.0 ml of phenyl-
acetyl chloride was added dropwise at 0 5 C and pH
9 maintained with 50% aqueous KOH. The reaction
mixture was then acidified to pH 5 and extracted with
ether (2 30 ml). The aqueous phase was acidified to
pH 2 and extracted with ethyl acetate (3 50 ml). The
extract was dried over MgSO4 and evaporated in a va-
cuum. The residue was crystallized from ether and
recrystallized from a hexane acetone mixture to iso-
late an analytically pure acid V. Yield 17.8 g
25
546
25
546
[ ]
+4.1 (c 1.0, 6N HCl); [ ]
+8.2 (c 1.0,
H2O).
2. Fractions with a positive ninhydrin test were
collected (eluent 0.5 N HCl) and evaporated. The re-
sidue was treated with excess propylene oxide in
aqueous ethanol ( 1:7) to obtain 1.7 g of acid (S)-I.
Yield 57.4% per (R,S)-V. mp 170 174 C (softening),
1
221 224 C (melting with decomposition). H and 31P
NMR spectra in D2O were identical to those of (R,S)-
I. Found, %: C 43.59, 43.75; H 6.39, 6.27; P 13.97,
13.81. C8H12NO3P H2O. Calculated, %: C 43.84, H
1
[63% per (R,S)-I]. mp 115 117 C. H NMR spec-
25
546
25
546
6.44, P 14.13. [ ]
4.0 (c 1.0 6N HCl); [ ]
trum (CD3OD), , ppm: 3.66 m (4H, CH2OH +
CH2Ph); 5.5O d (1H, CH, JHP 14 Hz), 7.30 m (10H,
2 Ph). 31P NMR spectrum (CD3OD), P, ppm: 41.6.
Found,%: C 59.28, 59.03; H 5.66, 5.78; P 9.31, 9.46.
C16H18NO4P H2O. Calculated, %: C 59.35, H 5.76,
P 9.57.
8.3 (c 1.0, H2O).
ACKNOWLEDGMENTS
The work was supported by the Research and De-
velopment Department, Nippon Chemical Industrial
Co. (agreem. no. 98-99/add. no. 2). The authors
express their gratitude to G.D. Shishko for elemental
analysis of new compounds.
Enzymatic synthesis of (R)-I and (S)-I. Racemic
acid IV was dissolved in 80 ml of water at pH 7.5
(maintained with 1 N KOH), and preliminary prepared
PcAm ( 5 g) was added to the solution. The resulting
mixture was stirred at room temperature (20 25 C).
Reaction progress was controlled by means HPLC by
the amount of phenylacetic acid in the solution. After
the reaction was complete, the enzyme was filtered
off, and the filtrate was extracted with ether (2
20 ml), acidified to pH 5, and extracted again with
ether (2 20 ml). The aqueous layer was concentrated
REFERENCES
1. Collinsova, M. and Jiracek, J., Curr. Med. Chem.,
2000, vol. 7, no. 6, p. 629.
2. Cherkasov, R.A. and Galkin, V.I., Usp. Khim., 1998,
vol. 67, no. 10, p. 940.
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 75 No. 4 2005

536
ROZHKO, RAGULUN
3. Baylis, E.K., Tetrahedron Lett., 1995, vol. 36, no. 51,
13. Miller, D.J., Hammond, S.M., Anderluzzi, D., and
Bugg, T.D.H., J. Chem. Soc., Perkin Trans. 1, 1998,
no. 1. p. 131.
p. 9389.
4. Gancarz, R., Gancarz, I., and Walkowjak, U., Phos-
phorus, Sulfur, Silicon Relat. Elem., 1995, vol. 104,
no. 1, p. 45.
14. Solodenko, V.A., Kasheva, N.A., Kukhar, V.P., Koz-
lova, E.V., Mironenko, D.A., and Svedas, V.-K.,
Tetrahedron, 1991, vol. 47, no. 24, p. 3989.
5. Hammerschmidt, F. and Hanbauer, M., J. Org. Chem.,
2000, vol. 65, no. 19, p. 6121.
15. Rozhko, L.F., Klochkov, S.G., Ragulin, V.V., and
Tsvetkov, E.N., Zh. Obshch. Khim., 1999, vol. 69,
no. 7, p. 1134.
6. Roos, G.H. and Balasubramaniam, S., Synth. Com-
mun., 1998, vol. 28, no. 20, p. 3877.
7. Boyd, E.A., Chan, W.C., and Loh, V.M., Tetrahedron
Lett., 1996, vol. 37, no. 10, p. 1647.
16. Schotten, C., Ber., 1884, vol. 17, p. 2544; Bau-
mann, E., Ber., 1886, vol. 19, p. 3218.
8. Mucha, A., Kafarski, P., Plenat, F., and Cristau, H.-J.,
Phosphorus, Sulfur, Silicon Relat. Elem., 1995,
vol. 105, nos. 1 4, p. 87.
17. Smith, A.B., Yager, K.M., and Taylor, C.M., J. Am.
Chem. Soc., 1995, vol. 117, no. 44, p. 10879.
18. Hamilton, R., Walker, B., and Walker, B.J., Tetra-
hedron Lett., 1995, vol. 36, no. 25, p. 4451.
9. Kafarski, P., Lejczak, B., Tyka, R., Koba, L., Plisz-
czak, E., and Wieczonek, P., J. Plant Growth Regul.,
1995, vol. 14, no. 4, p. 199.
19. Mikolajszyk, M., Lyzwa, P., and Drabowicz, J., Tetra-
hedron: Asymmetry, 1997, vol. 8, no. 24, p. 3991.
10. Zon, J., Amrhein, N., and Gancarz, R., Phytochemist-
ry, 2002, vol. 59, no. 1, p. 9.
20. Glowiak, T., Sawka-Dobrowolska, W., Kovalik, J.,
Mastalerz, P., Soroka, M., and Zon, J., Tetrahedron
Lett., 1977, vol. 45, no. 13, p. 3965.
11. Oleksyszyn, J. and Gruszecka, E., Tetrahedron Lett.,
1981, vol. 22, no. 36, p. 3537.
12. Yiotakis, A., Vassiliou, S., Jiracek, J., and Dive, V.,
21. Uhing, E.H., Rattenbury, K., and Toy, A.D.F., J. Am.
Chem. Soc., 1961, vol. 83, no. 5, p. 2299.
J. Org. Chem., 1996, vol. 61, no. 19, p. 6601.
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 75 No. 4 2005