PREFERENTIAL HYDROLYSIS OF KYNURENINE PEPTIDES
2 9 9
A n a l . Calcd. for C16H13N10 5: C, 64.21; H, 4.38;
N, 4.68. Found: C, 64.17; H, 4.33; N, 4.64.
In order to confirm the complete reduction of the
keto group, a sample was hydrolyzed in HC1 6 N at 110
ß-Benzoyl-propionyl-glycine ethyl ester. — To a so- for 20 hrs and then chromatographed on Whatman n. 1
lution of 2.94 g (21 mmoles) of glycine ethyl ester
hydrochloride with 21 mmoles of triethylamine in 100
ml of anhydrous chloroform, 5.98 g (20 mmoles) of
yS-benzoyl-propionyl-p-nitrophenyl ester were added,
and the mixture was stirred for 48 hrs. After removing
the precipitate of the triethylammonium salt and alka-
line and acidic washings, the solvent was removed
in vacuo and the residue crystallized from methanol-
ethyl ether. The yield was 3.94 g (35%), mp 78°.
paper sheet (solvent mixture n-butyl alcohol-water-ace-
tic acid, 40:50:3). Ninhydrin reaction revealed only
two spots: glycine, Rf = 0.3 and y-phenyl-y-hvdroxy-pro-
pyl-amine, Rf 0.67, whereas /J-amino-propiophenone (Rf
0.53) did not appear on the chromatogram.
Glycyl-y-phenyl-y-hydroxy-propylamide hydrochloride.
— A solution of carbobenzoxy-glycyl-}'-phenl-y-hydroxy-
propylamide (1.7 g) in 60 ml of methanol and few
drops of acetic acid, was hydrogenated in the presence
of 0.3 g of 10% palladium on chorcoal for 6 hrs. The
filtrate was evaporated in vacuo after removal of cata-
lyst, and the residual oil added of equimolecular
amount of dry HC1, crystallized from ethanol-ethyl
A n a l . Calcd for C14H170 4N: C, 63.86; H, 6.51:
N, 5.32. Found: C, 63.90; H, 6.37; N, 5,26.
y-Phenyl-y-hydroxybutyryl-glycine ethyl ester. — To
a solution of 1.32 g (5 mmoles) of /?-benzoyl-propionvl-
glycine ethyl ester and 1.5 g oxalic acid in 10 ml of ether. The yield was 4 g (83%), mp 100°; single nin-
hydrin positive spot (Rfi 0.75, /?f2 0.50).
50% methanol, 1.85 g (50 mmoles) of NaBH4 were
added slowly under vigorous stirring. When a negative
acetone-test (2,4-dinitropheyl hydrazine) was observed
(about 30 minutes), few drops of conc. HC1 were added
to destroy the excess of NaBH4 . The reaction mixture,
diluted with water and freed from methanol under re-
duced pressure, was extracted with ethyl acetate. After
washing with water, the ethyl acetate solution was eva-
porated to dryness and the residue crystallized from
benzene-ligroine. The yield was 1.19 g (90%), mp 113°.
A n a l . Calcd. for C11H170 2N2C1: C, 54.10; H, 6.97;
N, 11.48. Found: C, 54.00; H, 6.93; N, 11.40.
a-Amino-ß-benzoyl-propionic acid. — It was pre-
pared according to
f
r a S e r and
r
a
P h
a
e l from benzoyl-
acrylic acid 18. This product was utilized for the suc-
cessive synthesis, in addition, in order to control the
retention volume of its reduction product, a-amino-/i-
benzoyl-propionic acid was also reduced with NaBH4 .
The obtained compound y-phenyl-homoserine, which is
the substance formed during hydrolysis of y-phenyl-
homoseryl peptides, emerged from the column in two
distinct peaks.
In fact the possibility to obtain, from benzoyl-acrylic
acid and ammonia, a mixture of a-amino-/?-benzoyl-pro-
pionic and /?-amino-/?-benzoyl-propionic acids was al-
ready discussed by several authors 18, 21, 22. On the aim
to overcome such a doubt we devised a new unambigous
route of synthesis for a-amino-/?-benzoyl-propionic acid.
A solution of 60 ml of anhydrous methanol, 0.6 g of
Na, 5.7 g (26.2 mmoles) of diethyl acetaminomalonate
and 4.9 g (24.6 mmoles) of phenacylbromide was
heated at reflux for 6 hrs. After removal of the solvent
in vacuo, the residual oil was extracted with chloro-
form; the solution was concentrated to dryness and the
residue hydrolyzed with a mixture of 50 ml of conc.
HC1 and 20 ml of glacial acetic acid for 6 hrs at 90“.
The reaction mixture, diluted with 300 ml of water,
was extracted for 24 hrs in a liquid-liquid apparatus
with ethyl ether. The ethereal extract left a residue
(3 g) that dissolved in 100 ml of water and brought to
pH 7 with NaOH solution, was applied to a 3 x 30 cm
column of strong cationic resin Amberlite IR 120(H®).
The first 500 ml water washings were discharged and
the column was then eluted with 2 / of 0.2 N HC1 which
yielded 1.2 g of a crystalline compound identified as
glycine hydrochloride by its chromatographic be-
haviour and analytical data. The column was finally
A n a l . Calcd. for C14H 190 4N: C, 63.36; H, 7.22;
N, 5.28. Found: C, 63.41; H, 7.30; N, 5.33.
Carbobenzoxy-glycyl-ß-benzoyl-ethylamide. — To a
solution of 1.85 g (10 mmoles) of /?-aminopropiophe-
none hydrochloride and 10 mmoles of triethylamine in
60 ml anhydrous chloroform, 3.33 g (11 mmoles) of
carbobenzoxy-glycine-p-nitrophenyl ester were added.
After 48 hrs at room temperature the solution was
washed with 1 N HC1 and 5% NaHC03 , dried over
anhydrous Na2S 04 , concentrated to small volume and
cooled at 0°. The white crystalline product was col-
lected by filtration and dried in vacuo. The yield was
3.06 g (90%), mp 116 —117°, single ninhydrin posi-
tive spot (Rfx 0.90; Rf2 0.75).
A n a l . Calcd. for
C, 67.04; H, 5.93;
N, 8.23. Found: C, 67.10; H, 5.95; N, 8.13.
Carbobenzoxy-glycyl-y-phenyl-y-hydroxy-propylamide.
— To a solution of 1.70 g (9 mmoles) of carbobenz-
oxy-glycyl-/3-benzoyl-ethylamide and 1.5 g of oxalic
acid in 10 ml of 50% methanol, 1.85 g (50 mmoles) of
NaBH4 were added slowly under vigorous stirring.
After 30 minutes (negative acetone test) a few drops of
conc. HC1 were added, the mixture was diluted with
water and cooled. The collected precipitate was washed
with water and dried. The yield was 1.30 g (76%) mp
133°.
A n a l . Calcd. for C19H*>.,04N2: C, 66.64; H, 6.49;
N, 8.18. Found: C, 66.57; H, 6.44; N, 8.06.
21 J. B o u g a u l t , Ann. Chim. analyt. IS, 491 [1908],
22 J. B o u g a u l t and P. c h a B r i e r , c . R. hebd. Seances Acad.
Sei. 226, 1378 [1948].
Unauthenticated
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