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N-Formylphenylalanine Ethyl Esters by Hydrogenolysis of Ethyl 5-Aryl-2-oxazoline-4-carboxylates.

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three times with benzene (3 x 50 ml), and concentrated under
vacuum. On treatment of the residue with light petroleum
(b.p. S&7OoC), a crystalline precipitate of (4b) (9.4 g) appeared. Concentration of the light petroleum solution afforded a further crop of crystals (2.8 g) [m.p. 74-75 OC; I R
spectrum (KBr): 2170 cm-1 (vNC), 3380 cm-1 (vOH)]. A solution of (4b) ( 5 g) in dioxane (20 ml) was added dropwise (ice cooling) to a mixture of 2 N hydrochloric acid (50ml)
and dioxane (SO ml). After two hours’ stirring, work-up a t
room temperature yielded l-formylamino-2-phenyl-2-propanol (3.3 g).
Received: April 9, 1970
[ Z 197 IE]
German version: Angew. Chem. 82, 482 (1970)
[*] Dr. A. Niirrenbach and Dr. W. A. Boll
Badische Anilin- und Soda-Fabrik AG
67 Ludwigshafen (Germany)
Prof. Dr. U. Schollkopf and Dr. F. Gerhart
Organisch-Chemisches Institut der Universitat
34 Gottingen, Windausweg 2 (Germany)
[ l ] Syntheses with a-Metalated Isocyanides. Part 6. - Part 5:
D . Hoppe and U . Schollkopf, Angew. Chem. 82, 290 (1970);
Angew. Chem. internat. Edit. 9, 300 (1970).
[2] U.Schollkopf and F. Gerhart, Angew. Chem. 80,842 (1968);
Angew. Chem. internat. Edit. 7, 805 (1968).
[3] D. S. Mafteson and R . A . Bailey, J . Amer. chern. SOC.YO,
3761 (1968).
141 In this connection, see also F . Gerharf and U. Schollkopf,
Tetrahedron Letters 1968, 6231; Th. Kauffmann, E. Koppelmann, and H . Berg, Angew. Chem. 82, 138 (1970); Angew.
Chem. internat. Edit. 9, 163 (1970).
[ S ] On addition of ethanol, methanol, or water, Az-oxazolines
are obtained, which are also formed on treatment of ( 4 ) with
alkali.
Ar-CHy
(C)
C~HS
p-CHa-Cdb
P-CH3OC6H4
(4
CsHs
lbi
H
H
H
CH,
3
2
12
30
Organisch-Chernisches Institut der Universitat
34 Gottingen, Windausweg (Germany)
[l] Syntheses with or-Metalated Isocyanides, Part 7. - Part 6:
W. A. Boll, F. Gerhart, A . Niirrenbach, and U. Schollkopf,
Angew. Chem. 82, 482 (1970); Angew. Chem. internat. Edit. Y,
458 (1970).
[ 2 ] D . Hoppe and U . Schollkopf, Angew. Chem. 82, 290 (1970);
Angew. Chem. internat. Edit. 9, 300 (1970).
[3] The 2-oxazoline must be free from cyanide ions and isocyanide since these poison the catalyst.
Hydrogen Fluoride-Potassium Hydrogen
Phosphite (1/1), an Unusual Lattice Compound[**l
By Hans Falius, Dietrich Mootz, and Horst Altenburg[*l
KF
NHCHO
I
-COzC,H5
R1
7
I
(a)
[*] Prof. Dr. U. Schollkopf and Dip1.-Chem. D. Hoppe
~
Phenylalanine and its derivatives (e.g. tyrosine, thyroxine,
dopa, methyl-dopa, etc.) have attracted a great deal of
attention because of their biological activity. We have found
that N-formylphenylalanine ethyl esters (2), R1 = H, and
the a-methyl compounds (2),R* = CH3, can be prepared by
hydrogenolysis of 5-aryl-2-oxazoline-4-carboxylates( I ) [21
with e . g . palladium/activated charcoal in ethanol. Compounds (2) can be converted into phenylalanines by heating
with 20 % hydrochloric acid, while brief heating with potassium hydroxide in ethanol affords N-formylphenylalanines.
Hz
Received: March 13, 1970
[ Z 178 IE]
German version: Angew. Chem. 82,483 (1970)
Publication delayed at authors’ request
H F + KH[PHO3I
By Ulrich Schollkopf and Dieter Hoppel*]
-
A solution of ethyl 5-phenyl-2-oxazoline-4-carboxylate
12,31
(5.0 g, 23 mmoles) in dry ethanol (SO ml) is shaken a t room
temperature with 0.25 g of palladium/activated charcoal
(10 % palladium, Merck) under hydrogen (normal pressure);
in 3 hours 510 ml (22 mmoles) of hydrogen is taken up.
After flushing with nitrogen, filtration, and evaporation of
solvent there remains 5 g (99 %) of (2a) [NMR spectrum
(CCl4): CH2. T = 7.0 (d, J = 7 Hz); CH, T = 5.2 (m). IR
spectrum (film): 3320 cm-1 (vNH); 1740 and 1680 cm-1
(VC0)l.
Studies on phosphorofluoridous acid have led to the discovery
of the adduct H F . KH[PH03] ( I ) , which is stable only in the
solid state. It may be readily prepared by the following two
methods:
N-Formylphenylalanine Ethyl Esters
by Hydrogenolysis of Ethyl
5-Aryl-2-oxazoline-4-carboxylates
111
04N
Ar f t C 0 2 C z H ,
H
R’
N- Forniylphenylalanine ethyl ester (2a)
99
9s
9s
99
Cleavage of the C-0 bond in ( I ) , R1 = CH3, (2OoC, atmospheric pressure, proceeds ten times slower than in ( I ) ,
R1 = H; furthermore, substitution in the nucleus, e.g. by
methoxy groups, lowers the rate of hydrogenolysis. In these
cases it is advisable to carry out the hydrogenation at higher
temperatures o r under pressure.
Angew. Chem. internat. Edit. f Vol. 9 (1970)f No. 6
H . KHLPHOJ
F
+ H ~ [ P H O ~ ] ~ (1)
( I ) is obtained as large colorless monoclinic crystals; dfo =
2.139 gcm-3, m.p. 9 6 ° C . Unit cell: a = 6.692, 6 = 11.040,
c = 7.841 A; p = 127.88 O ; space group P21/c with Z = 4.
In the absence of moisture the crystals are stable at room
temperature; when kept in glass vessels, however, local
attack of the glass surface occurs. In aqueous solution, which
shows a strong acid reaction, the compound exhibits only the
reactions of its constituent ions; it cannot be reisolated
from this solution. The N M R spectra (in methanol and in
water) show only one fluorine signal alongside the resonances
characteristic of phosphorous acid. The adduct is therefore
not a hydrate of potassium phosphorofluoridite K[PHOzF] .
HzO, as was previously assumed. Its IR spectrum closely
resembles that of KH[PH03].
The properties of “phosphorofluoridous hydrate” described
by Heinz and ROhner[11 suggest that it is also a n adduct of
composition H F . Hz[PHO3], for phosphorofluoridous acid
is stable and the vPF frequency (about 884 cm-1 in the acid)
was not observed in the spectrum of this “acid hydrate”.
Unlike phosphorofluoridous acid 121, compound ( I ) is immediately oxidized completely to phosphate by iodine in
hydrogen carbonate solution. On alkalimetric titration it is
neutralized by two equivalents of alkali in two stages. When
( I ) is heated in a vacuum it loses H 2 0 and HF, loss of
weight setting in a t 115 OC, to give a mixture containing a
little K[PHOzF] and much KZ[P2H2051.
Preparation :
1. Equimolar amounts of Hz[PH03] and K F are vigorously
ground together, the mixture first becoming sticky and then
liquid. The syrupy liquid is extracted with hot methanol,
filtered, and allowed to cool; yield 30 %.
459
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hydrogenolysis, carboxylated, oxazoline, esters, ethyl, aryl, formylphenylalanine
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