550
GERHARD K. E. SCRIBA AND DIDIER M. LAMBERT
neurotransmitter in the CNS while b-alanine acts as
an agonist at the strychnine-sensitive glycine
receptor (Marvizon et al 1986).
The present study was conducted to evaluate the
potential of prodrugs combining phenytoin and Z-
amino acids with regard to a synergism of the
compounds. The derivatives were synthesized by
5Á6 Hz); 13C NMR (50 MHz) CDCl3 d: 172Á2,
169Á1, 156Á3, 154Á6, 138Á5, 136Á6, 128Á9, 128Á8,
128Á6, 128Á2, 128Á1, 126Á8, 70Á4, 67Á2, 62Á4, 42Á5;
MS m=z: 473 (M ), 266, 237, 194, 180, 165, 107,
91.
3-(N-Benzyloxycarbonylamino)-[(2,4-dioxo-5,5-
diphenyl-3-imidazolidinyl)methoxy]propionic acid
ester (Z-b-alanine-phenytoin). Yield 2Á0 g, 58%;
esteri®cation of 3-hydroxymethylphenytoin,
a
phenytoin prodrug (Varia et al 1984), with Z-gly-
cine, the homologous Z-b-alanine and Z-GABA
and with Z-phenylalanine as an amino acid devoid
of CNS activity.
1
mp 49±50ꢀC, H NMR (200 MHz) CDCl3 d: 7Á65
(1H, s), 7Á38±7Á30 (15H, m), 5Á55 (2H, s), 5Á37 (1H,
t, J 6 Hz), 3Á34 (2H, dt, J 6, 5Á8 Hz), 2Á48 (2H,
t, J 5Á8 Hz); 13C NMR (50 MHz) CDCl3 d: 172Á3,
171Á1, 156Á3, 154Á6, 138Á6, 136Á5, 129Á3, 128Á9,
128Á8, 128Á5, 128Á1, 126Á8, 70Á4, 66Á8, 62Á1, 36Á4,
Materials and Methods
34Á2; MS m=z: 487 (M ), 266, 237, 194, 180, 120,
91.
General methods
4-(N-Benzyloxycarbonylamino)-[(2,4-dioxo-5,5-
diphenyl-3-imidazolidinyl)methoxy]butanoic acid
ester (Z-GABA-phenytoin). Yield 2Á7 g, 76%; mp
54±55ꢀC, 1H NMR (200 MHz) CDCl3 d: 8Á04 (1H),
7Á40±7Á30 (15H, m), 5Á51 (2H, s), 5Á08 (1H, s), 5Á03
(2H, s), 3Á12 (2H, t, J 7Á2 Hz), 2Á28 (2H, t,
J 7Á2 Hz), 1Á73 (2H, m); 13C NMR (50 MHz)
CDCl3 d: 172Á4, 171Á9, 156Á6, 154Á8, 138Á7, 136Á6,
128Á8, 128Á7, 128Á5, 128Á2, 127Á5, 126Á6, 70Á3, 66Á7,
Melting points were determined on a Ko¯er melting
point apparatus and are uncorrected. NMR spectra
were recorded on a Varian Gemini 200 (Varian
AG, Bremen, Germany). The chemical shifts are
reported as d (ppm) values relative to tetra-
methylsilane. Mass spectra were obtained on a
Varian MAT 44S (Varian AG, Bremen, Germany)
at 70 eV. Z-glycine, Z-phenylalanine and bis(2-
oxo-3-oxazolidinyl)phosphinic acid chloride were
obtained from Fluka (Deisenhofen, Germany). 3-
Hydroxymethylphenytoin (Varia et al 1984), Z-b-
alanine (Fiedler et al 1993) and Z-GABA (Blan-
kespoor et al 1984) were synthesized as described.
Methylene chloride was distilled over P2O5, trie-
thylamine was distilled over KOH.
62Á0, 40Á2, 31Á0, 24Á9; MS m=z: 501 (M ), 394,
266, 237, 194, 180, 91.
2-(N-Benzyloxycarbonylamino) -3-phenyl-[(2,4-
dioxo-5,5-diphenyl-3-imidazolidinyl)methoxy]pro-
pionic acid ester (Z-phenylalanine-phenytoin).
Yield 2Á0 g, 49%; mp 67±68ꢀC,1H NMR
(200 MHz) CDCl3 d: 8Á01 (1H, s), 7Á40±7Á02
(20H, m), 5Á63 (1H, d, J 10Á3 Hz), 5Á53 (1H, d,
J 10Á3 Hz), 5Á32 (1H, d, J 8Á3 Hz), 5Á06 (1H, d,
J 12 Hz), 4Á98 (1H, d, J 12 Hz), 4Á64 (1H, m),
3Á00 (2H, m); 13C NMR (50 MHz) CDCl3 d: 172Á1,
170Á4, 155Á6, 154Á6, 138Á6, 138Á5, 135Á3, 129Á3,
128Á9, 128Á7, 128Á6, 128Á5, 128Á1, 128Á0, 127Á9,
127Á1, 126Á8, 70Á4, 67Á0, 62Á6, 54Á7, 37Á9; MS
Prodrug synthesis
Two grams (7Á1 mmol) of 3-hydroxmethylpheny-
toin, 7Á1 mmol of the respective Z-amino acid, 1Á5 g
(15 mmol) of triethylamine and 1Á9 g (7Á5 mmol) of
bis(2-oxo-3-oxazolidinyl)phosphinic acid chloride
were stirred in 50 mL methylene chloride under
nitrogen at room temperature for 2 h. The mixture
was poured into ice-cold 0Á05 M HCl and extracted
twice with methylene chloride. The organic layer
was dried over Na2SO4 and evaporated under
reduced pressure. Column chromatography on
silica gel (Merck, Darmstadt, Germany) using
methylene chloride±methanol (100 : 1, v=v) as
eluent yielded amorphous solids.
m=z: 563 (M ), 413, 266, 237, 208, 194, 180,
160, 131, 91.
Prodrug hydrolysis
Hydrolysis was performed at 20Æ 0Á5ꢀC in 5% rat
plasma diluted with phosphate-buffered saline and
50 mM phosphate buffer, pH 7Á4 containing 30%
acetonitrile. Stock solutions of the compounds in
acetonitrile were added to the prewarmed incuba-
tion mixtures to give a ®nal concentration of 1 mM.
The reaction mixtures were vigorously stirred
during the kinetic run. Samples (100 mL) were
N-Benzyloxycarbonyl-[(2,4-dioxo-5,5-diphenyl-3-
imidazolidinyl)methoxy]acetic acid ester (Z-gly-
cine-phenytoin). Yield 2Á2 g, 65%; mp 62±
63ꢀC,1H NMR (200 MHz) CDCl3 d: 7Á66 (1H, s),
7Á38±7Á30 (15H, m), 5Á58 (2H, s), 5Á38 (1H, t,
J 5Á6 Hz), 5Á07 (2H, s), 3Á93 (2H, d, J