Reaction of N-acyl-α-triphenylphosphonio-α-amino acid esters with organic bases: Mechanism of the base-catalyzed nucleophilic substitution of the triphenylphosphonium group

Article abstract of DOI:10.1007/s007060200090

Reactions of N-acyl-α-triphenylphosphonio-α-amino acid methyl esters with organic bases (triethylamine or DBU) were investigated as the crucial step of the base-catalyzed displacement of the triphenylphosphonium group by nucleophiles. It was proved that N

Full text of DOI:10.1007/s007060200090

Monatshefte f u r Chemie 133, 1197±1204 ꢀ2002)
Reaction of N-Acyl-a-triphenylphosphonio-
a-amino Acid Esters with Organic Bases:
Mechanism of the Base-Catalyzed
Nucleophilic Substitution of the
Triphenylphosphonium Group
Ã
Roman Mazurkiewicz and Miroslawa Grymel
Institute of Organic Chemistry and Technology, Silesian Technical University,
PL-44100 Gliwice, Poland
Summary. Reactions of N-acyl-ꢀ-triphenylphosphonio-ꢀ-amino acid methyl esters with organic bases
ꢀtriethylamine or DBU) were investigated as the crucial step of the base-catalyzed displacement of the
triphenylphosphonium group by nucleophiles. It was proved that N-acyl-ꢀ-triphenylphosphoniogly-
cinates are transformed to an equilibrium mixture of the corresponding N-acyliminoacetates and
N-acyl-ꢀ-triphenylphosphoranylidene glycinates by bases. In the case of N-acyl-ꢀ-triphenylphospho-
nio-ꢀ-amino acid esters with quaternary ꢀ-carbon, the ꢀ-substituted homologues of the N-acyliminoa-
cetates were detected to be the only primary reaction product which, however, can undergo further
tautomerization to the corresponding ꢀ,ꢁ-dehydro-ꢀ-amino acid derivatives. In both these cases the
reaction of N-acyl-ꢀ-triphenylphosphonio-ꢀ-amino acid esters with nucleophiles proceeds via the addi-
tion of a nucleophile to the activated CˆN double bond of the N-acylimino intermediate.
Keywords. N-ꢀ-Triphenylphosphonioglycinates; Nucleophilic substitution; Synthetic equivalents of
ꢀ-amino acid ꢀ-cations; Glycine functionalization.
Introduction
Since the pioneering investigations of Ben-Ishai et al. [1] on the ®rst synthetic equiv-
alents of glycine ꢀ-cations, the important problem of synthesizing ꢀ-amino acids by a
new bond formation between the ꢀ-position of an ꢀ-amino acid electrophilic equiv-
alent and a nucleophile has attracted the attention of organic chemists. In the course
of the last twenty ®ve years many synthetic equivalents of ꢀ-amino acid ꢀ-cations
have been introduced [2, 3].
Recently, we have developed and reported convenient and effective syntheses
of N-acyl-ꢀ-triphenylphosphonio glycinates ꢀ2; [2]) and their ꢀ-alkyl substituted
analogues ꢀ4; [4]) from 4-triphenylphosphoranylidene-5ꢀ4H)-oxazolones 1 or 4-
alkyl-4-triphenylphosphonio-5ꢀ4H)-oxazolone iodides 3. We have also described
ÃCorresponding author. E-mail: romanm@zeus.polsl.gliwice.pl

1
198
R. Mazurkiewicz and M. Grymel
Scheme 1
a simple method for the displacement of the triphenylphosphonium group in these
compounds by a variety of oxygen, sulfur, nitrogen, and carbon nucleophiles [2±4]
in the presence of triethylamine or DBU, demonstrating that the ꢀ-triphenylphos-
phonio-ꢀ-amino acid derivatives 2 and 4 may be considered to be new interesting
synthetic equivalents of ꢀ-amino acid ꢀ-cations. The described transformations
enable an easy functionalization of the glycine ꢀ-position with nucleophiles or
even its double functionalization with electrophiles ꢀalkyl halides) and nucleo-
philes ꢀScheme 1). In the present paper we report our investigations on the mecha-
nism of the base-catalyzed displacement of the triphenylphosphonium group in
phosphonium salts 2 and 4 by nucleophiles.
Results and Discussion
Trying to explain the mechanism of the base-catalyzed displacement of the triphe-
nylphosphonium group of N-acyl-ꢀ-triphenylphosphonio-ꢀ-amino acid esters by
nucleophiles, we examined in detail their reaction with triethylamine or DBU in
ꢀ
CD CN at 25 C. We monitored changes of the composition of the reaction mix-
3
tures as a function of the reaction time using IR and NMR spectroscopy.
N-Acyl-ꢀ-triphenylphosphonioglycinates 2 have been obtained for the ®rst
time from ꢀ-bromoglycinates and triphenylphosphine by Kober and Steglich in
1983 [5]. They found that ethyl N-benzoyl-ꢀ-triphenylphosphonioglycinate bro-
mide is converted into diethyl 2,3-bis-ꢀbenzoylamino)-fumarate in the presence
of triethylamine. The authors did not examine the reaction of N-benzoyl-ꢀ-triphe-
nylphosphonioglycinate with nucleophiles. In order to explain the formation of
2
,3-bis-ꢀbezoylamino)-fumarate they assumed that N-benzoyl-ꢀ-triphenylphospho-
nioglycinate is converted to a mixture of the corresponding ylide ꢀethyl N-benzoyl-
-triphenylphosphoranylidene glycinate) and ethyl N-benzoyliminoacetate upon
ꢀ

Reaction of N-Acyl-ꢀ-triphenylphosphonio-ꢀ-amino Acid Esters with Bases
1199
action of triethylamine at the ®rst step of the reaction. The condensation of the
ylide with the N-benzoyliminoacetate results in 2,3-bis-ꢀbenzoylamino)-fumarate.
As we observed in our ®rst experiment, the treatment of methyl N-pivaloyl-
ꢀ
-triphenylphosphonioglycinate tetra¯uoroborate with triethylamine resulted in an
immediate disappearance of the starting ester. A detailed analysis of spectroscopic
data led to the conclusion that the reaction mixtures contained two new compounds
which were assigned tentatively as the corresponding ylide and N-acyliminoacetate
analogous to those proposed by Kober and Steglich [5]. In addition, the reaction
mixtures also contained triphenylphosphine, triethylamine tetra¯uoroborate, and
the previously isolated and identi®ed dimethyl 2,3-bis-ꢀpivaloylamino)-fumarate.
1
13
We were able to assign the most characteristic H and C NMR signals of the ylide
a and N-pivaloyliminoacetate 5a ꢀTable 1). Integration of the methoxy resonances
6
1
in the H NMR spectra allowed to estimate the concentration of the components of
the reaction mixture ꢀFig. 1). Evidently, 6 is formed as a result of the deprotonation
at the ꢀ-carbon, whereas deprotonation at the nitrogen and cleavage of triphenyl-
phosphine results in the formation of N-pivaloyliminoacetate 5.
Attempts to isolate the ylide 6a and N-acyliminoacetate 5a from the reaction
mixture by column chromatography failed, probably because of the instability of
these compounds. Nevertheless, we were able to prove the formation of the ylides
6a, b by trapping them in a Wittig reaction with methyl tri¯uoropyruvate. The yield
of the Wittig reaction product 10a was much higher than expected from the highest
detected concentration of 6a in the reaction mixture. On the other hand, extraordinary
1 13
Table 1. H and C NMR data of 5a, 6a, 7a, 8a, and 9a ꢀCD CN)
3
1
13
H NMR ꢀꢂ=ppm)
C NMR ꢀꢂ=ppm, J=Hz)
1
CR R
2
R
E
CONH COOMe CˆP NˆC OMe
ꢀC
6 5
H )
3
Pˆ
R
Other
C
1
C
2
C
3
C
4
3 3
CMe CMe
b
), 166.1 163.2
b
5
a
a
t-Bu ±
t-Bu ±
±
±
3.03 ꢀs, 3H, OCH
.80 ꢀs, 9H, t-Bu)
6.65 ꢀs, 1H, NH),
3
a
±
183.6 49.4
±
±
±
±
38.88 27.77
±
±
0
6
180.7 171.3
48.2
±
50.4 127.3 134.9 129.5 133.1 38.80 27.66
90.9 9.8 12.2 0.5
3
0
.44 ꢀs, 3H, OCH
3
),
c
34.9
156.2
.79 ꢀs, 9H, t-Bu)
d
7
a
a
t-Bu ±
±
±
3.71 ꢀs, 6H, OCH
3
), 178.2 164.8
a
±
±
±
53.1
±
±
±
±
±
±
±
±
39.84 27.36 125.4 ꢀ>Cˆ)
41.3 27.1 21.3 ꢀMe)
1.20 ꢀs, 18H, t-Bu)
b
), 157.3 163.0
b
8
t-Bu Me
3.79 ꢀs, 3H, OCH
3
193.3 53.7
2.18 ꢀs, 3H, CH
3
),
1
.17 ꢀs, 9H, t-Bu)
d
9
a
t-Bu ± CH
2
8.07 ꢀs, 1H, NH),
177.8 165.4
±
±
53.5
±
±
±
±
40.3 27.5 132.9 ꢀCˆCH
108.1 ꢀCˆCH
2
)
)
6
5
3
1
.40 ꢀs, 1H, ˆCH
2
),
),
),
.75 ꢀs, 1H, ˆCH
2
2
.80 ꢀs, 3H, OCH
3
.21 ꢀs, 9H, t-Bu)
a
b
The signal of the NH group is hidden under the signals of triphenylphosphine; assignments may be interchanged; signals of
c
d
the ylide Ph P group are hidden under the signals of triphenylphosphine; signals identi®ed and assigned by comparison with
3
the spectrum of the isolated compound

1
200
R. Mazurkiewicz and M. Grymel
Fig. 1. Conversion of N-pivaloyl-ꢀ-triphenylphosphonioglycinate 2a to the corresponding ꢀ-triphe-
nylphosphoranylidene glycinate 6a, iminoacetate 5a, and their condensation product 7a under the
in¯uence of Et N ꢀcf. Scheme 2; R ˆ t-Bu)
3
high yields of products of the triphenylphosphonium group displacement were
obtained, multiples of the amount that would follow from the highest estimated
concentration of N-pivaloyliminoacetate 5a in the reaction mixture [2±4]. These
two results clearly indicated an equilibrium between N-acyliminoacetate and ylide.
1
The results of an analogous reaction with DBU were very similar, although both H
13
and C NMR spectra of the reaction mixture were dif®cult to interpret because of the
overlapping signals of the protonated DBU.
To the best of our knowledge, N-acyl-ꢀ-triphenylphosphonio-ꢀ-amino acid
esters with quaternary ꢀ-carbon are hitherto unknown compounds. Using the meth-
odology described above, we investigated the reaction of N-pivaloyl-ꢀ-triphenyl-
phosphonioalanine methyl ester with triethylamine. Again triethylamine causes the
disappearance of the ester in less than two minutes. However, as expected, ꢀ-ꢀN-
pivaloylimino)-propionate 8a was detected to be the only primary reaction product.
If esters 8 possess a hydrogen at the ꢁ-position, they can undergo a slow tautomer-
ization to the corresponding ꢀ,ꢁ-dehydro-ꢀ-amino acid derivative 9 which can be
isolated in good yields ꢀ57±65%). The tautomerization can be monitored conve-
1
13
niently by IR as well as H and C NMR spectroscopy.
Possible mechanisms of the nucleophilic displacement of the triphenylphos-
phonium group in N-acyl-ꢀ-triphenylphosphonio-ꢀ-amino acid esters with tertiary
or quaternary ꢀ-carbons are presented in Schemes 2 and 3. We assume that in both
these cases the crucial step of the reaction consists in the addition of a nucleophile
to the activated CˆN double bond of the N-acylimino intermediate 5 or 8. There-
fore, the investigated mechanism can be described as an elimination-nucleophilic
addition process. N-Acyliminoacetates 5 have been considered to be unstable reac-
tive intermediates in reactions of N-acyl-ꢀ-chloroglycinates or N-acyl-ꢀ-bromo-
glycinates with nucleophiles initiated by triethylamine [6] or diazomethane [7] so
far in the literature.

Reaction of N-Acyl-ꢀ-triphenylphosphonio-ꢀ-amino Acid Esters with Bases
1201
Scheme 2
Scheme 3
N-Acyl-ꢀ-triphenylphosphonio-ꢀ-amino acid esters with tertiary and quater-
nary ꢀ-carbons behave in a different way if no nucleophilic agent is present in
the reaction mixture or if it is of low reactivity. In the ®rst case, the ylide acts as a
nucleophile; its slow condensation with N-acyliminoacetate yields the dimer 7
ꢀ
Scheme 2). In the second case, as already mentioned, the corresponding N-acyl-
imino intermediate can undergo a slow tautomerization to the ꢀ,ꢁ-dehydro-ꢀ-
amino acid derivative 9, provided that it bears a hydrogen atom at the ꢁ-position
ꢀ
Scheme 3).

1
202
R. Mazurkiewicz and M. Grymel
Experimental
Melting points, determined in capillary tubes, are uncorrected. IR spectra were recorded on a Zeiss
1
Specord M 80 spectrophotometer; the measurements were carried out using 0.075 mm cells. H, C,
13
3
and P NMR spectra were recorded in CDCl or CD CN on a Varian Unity Inova-300 spectrometer
1
3
3
1
13
operating at 300, 75.5, and 121.4MHz; chemical shifts are quoted relative to internal TMS ꢀ H, C) or
31
external H PO ꢀ P). Kieselgel 60 ꢀMerck, 0.063±0.200 mm) was used for column chromatography.
3
4
Elemental analyses ꢀC, H, N, P) proved to be in satisfactory agreement ꢀÆ 0.4%) with the calculated
values.
Methyl N-pivaloyl-ꢀ-triphenylphosphonioglycinate iodide and methyl N-benzoyl-ꢀ-triphenylphos-
phonioglycinate iodide ꢀ2a and 2b) as well as 2-t-butyl-4-methyl-4-triphenylphosphonio-5ꢀ4H)-oxa-
zolone iodide and 2-benzoyl-4-methyl-4-triphenylphosphonio-5ꢀ4H)-oxazolone iodide ꢀ3a and 3b)
were synthesized as previously described [2, 4].
N-Pivaloyl-ꢀ-triphenylphosphonioalanine methyl ester iodide ꢀ4a; C H INO P)
2
7
31
3
3
A solution of 5.4 g 3a ꢀ10 mmol) in 20 cm MeOH was stirred at 20 C for 2.5 h. The excess of MeOH
ꢀ
3
was evaporated, and the crude product was dissolved in 15cm CH CN and precipitated with 30cm
3
3
diethyl ether to give 4.8g ꢀ84%) of crystalline product.
1
ꢀ
‡
3
M.p.: 132.5±134 C; H NMR: ꢂ ˆ 8.72 ꢀd, 1H, J ˆ 4.9 Hz, NH), 7.85±7.52 ꢀm, 15H, Ph P ), 3.83
‡
13
s, 3H, OMe), 2.27 ꢀd, 3H, J ˆ 19.0 Hz, CH ±C±P Ph ), 0.94 ꢀs, 9H, t-Bu) ppm; C NMR: ꢂ ˆ 170.1
‡
ꢀ
ꢀ
3
3
d, J ˆ 0.5 Hz, CONH), 66.1 ꢀd, J ˆ 60.2Hz, C ±P ), 180.3 ꢀd, J ˆ 12.2Hz, COOMe), 54.1 ꢀOMe),
ꢀ
1
20.1 ꢀd, J ˆ 80.5Hz, Ph P, C ), 135.5 ꢀd, J ˆ 9.1 Hz, Ph P, C ), 129.5 ꢀd, J ˆ 12.4Hz, Ph P, C ), 134.2
3
1
3
2
3
3
31
ꢀ
d, J ˆ 0.5 Hz, Ph P, C ), 38.4 ꢀCMe ), 27.1 ꢀCMe ), 28.3 ꢀMe) ppm; P NMR: ꢂ ˆ 51.0 ppm; IR:
3
4
3
3
À 1
ꢃ ˆ 3230 m, 1764 s, 1732 s, 1660s, 1512 s cm
.
N-Benzoyl-ꢀ-triphenylphosphonioalanine methyl ester iodide ꢀ4b; C H INO P)
2
9
27
3
3
A solution of 5.6 g 3b ꢀ10 mmol) in 20cm MeOH was stirred at 20 C for 1 h. The excess of MeOH
ꢀ
3
was evaporated, and the crude product was dissolved in 13cm CH CN and precipitated with 26cm
3
3
diethyl ether to give 3.9g ꢀ66%) of the crystalline product.
1
ꢀ
‡
3
M.p.: 144±145 C; H NMR: ꢂ ˆ 9.53 ꢀd, 1H, J ˆ 3.1 Hz, NH), 7.92±7.29 ꢀm, 20H, Ph, Ph P ),
‡
13
.85 ꢀs, 3H, OMe), 2.36 ꢀd, 3H, J ˆ 19.0 Hz, CH ±C±P Ph ) ppm; C NMR: ꢂ ˆ 168.5 ꢀd,
‡
3
3
3
J ˆ 0.5 Hz, CONH), 66.7 ꢀd, J ˆ 58.1Hz, C ±P ), 169.9 ꢀd, J ˆ 12.2Hz, COOMe), 54.2 ꢀOMe),
ꢀ
1
1
5
19.8 ꢀd, J ˆ 81.2 Hz, Ph P, C ), 135.5 ꢀd, J ˆ 8.8 Hz, Ph P, C ), 129.6 ꢀd, J ˆ 12.4 Hz, Ph P, C ),
3
1
3
2
3
3
31
34.4 ꢀd, J ˆ 0.5 Hz, Ph P, C ), 132.7, 129.9, 128.7, 128.1 ꢀPh), 28.2 ꢀMe) ppm; P NMR: ꢂ ˆ
3
4
À 1
1.8ppm; IR: ꢃ ˆ 3168m, 1773 s, 1729 s, 1662 s, 1520s cm
.
Reactions of N-acyl-ꢀ-triphenylphosphonio-ꢀ-amino acid esters with triethylamine or DBU
To a stirred suspension of 1 mmol N-acyl-ꢀ-triphenylphosphonio-ꢀ-amino acid ester 2 or 4 in 4 cm
3
3
CD CN, 0.17 cm triethylamine ꢀ1.25 mmol) or 0.19cm DBU ꢀ1.25 mmol) were added at 25 C. The
3
ꢀ
3
composition of the reaction mixtures as a function of time was monitored by IR and NMR spectroscopy.
Dimethyl 2,3-bis-*acylamino)-fumarates 7; general procedure
3
To a stirred suspension of 1 mmol methyl N-acyl-ꢀ-triphenylohosphonioglycinate iodide in 4 cm
3
CH Cl , 0.17 cm triethylamine ꢀ1.25 mmol) were added at room temperature. After 3 h the solvent
2
2
was evaporated, and the residue was puri®ed by column chromatography ꢀethyl acetate:benzeneˆ 1:5).
The crude product was recrystallized from benzene:hexaneˆ 3:1.

Reaction of N-Acyl-ꢀ-triphenylphosphonio-ꢀ-amino Acid Esters with Bases
Dimethyl 2,3-bis-*pivaloylamino)-fumarate ꢀ7a; C H N O )
1203
1
6 26 2 6
ꢀ
1
Yield: 89%; m.p.: 164±166 C; H NMR: ꢂ ˆ 8.72 ꢀs, 2H, NH), 3.84 ꢀs, 6H, OMe), 1.26 ꢀs, 18H, t-Bu)
1
3
ppm; C NMR: ꢂ ˆ 176.5 ꢀCONH), 163.3 ꢀCOOMe), 121.5 ꢀˆC±), 52.0 ꢀOMe), 38.6 ꢀCMe ), 26.2
3
À 1
ꢀ
CMe ) ppm; IR: ꢃ ˆ 3540 m, 1742 vs, 1684 vs, 1630s cm
.
3
Dimethyl 2,3-bis-*benzoylamino)-fumarate ꢀ7b; C H N O )
20 18 2 6
ꢀ
1
Yield: 85%; m.p.: 185±187 C; H NMR: ꢂ ˆ 9.60 ꢀs, 2H, NH), 7.96±7.48 ꢀm, 10H, Ph), 3.90 ꢀs, 6H,
13
OMe) ppm; C NMR: ꢂ ˆ 165.5 ꢀCONH), 164.2 ꢀCOOMe), 122.6 ꢀˆ C±), 53.2 ꢀOMe), 132.8, 132.4,
À 1
1
28.8, 127.6 ꢀPh) ppm; IR: ꢃ ˆ 3540 m, 1741vs, 1676vs, 1632s cm
.
Wittig reaction of methyl N-acyl-ꢀ-triphenylphosphonioglycinate iodides
with methyltri¯uoropyruvate in the presence of triethylamine
To a stirred suspension of 1 mmol methyl N-pivaloyl-ꢀ-triphenylphosphonioglycinate tetra¯uoroborate
3
or N-benzoyl-ꢀ-triphenylphosphonioglycinate iodide in 2.5 cm CH CN, a solution of 0.17 cm methyl
3
3
3
tri¯uoropyruvate ꢀ1.5mmol) in 1.5 cm CH CN and 0.17cm triethylamine ꢀ1.25 mmol) was added
3
3
at room temperature. After 6 h the solvent was evaporated, and the residue was puri®ed by column
chromatography ꢀethyl acetate:benzene ˆ 1:5). The crude product was recrystallized from a mixture of
benzene and hexane.
2
-Pivaloylamino-3-tri¯uormethylbutendioic acid dimethyl ester ꢀ10a; C H F NO )
12 16 3 5
ꢀ
1
Yield: 95%; m.p.: 79±81 C; H NMR: ꢂ ˆ 11.90 ꢀs, 1H, NH), 3.93 ꢀs, 3H, OMe), 3.89 ꢀs, 3H, OMe),
1
3
1
.29 ꢀs, 9H, t-Bu) ppm; C NMR: ꢂ ˆ 176.6 ꢀCONH), 167.0 ꢀCOOMe), 162.4 ꢀˆCꢀCO)OMe), 147.5
ꢀ
q, JC±F ˆ 3.4 Hz, NHCˆC), 122.5 ꢀq, J ˆ 269.8 Hz, CF ), 99.0 ꢀq, J ˆ 33.2Hz, CF Cˆ), 53.4
C±F
3
C±F
3
ꢀ
OMe), 53.0 ꢀOMe), 40.0 ꢀCMe ), 27.0 ꢀCMe ) ppm; IR: ꢃ ˆ 3230 m, 1755vs, 1721 s, 1682s,
3
3
À 1
.
1
605 vscm
2
-Benzoylamino-3-tri¯uormethylbutendioic acid dimethyl ester ꢀ10b; C H F NO )
14 12 3 5
ꢀ
1
Yield: 46%; m.p.: 101.5±103.5 C; H NMR: ꢂ ˆ 12.60 ꢀs, 1H, NH), 8.00±7.42 ꢀm, 5H, Ph), 4.00
1
3
ꢀ
s, 3H, OMe), 3.93 ꢀs, 3H, OMe) ppm; C NMR: ꢂ ˆ 164.1 ꢀCONH), 167.3 ꢀCOOMe), 133.8, 131.3,
1
2
1
29.2, 128.1 ꢀPh), 162.2 ꢀˆCꢀCO)OMe), 147.6 ꢀq, J ˆ 3.4 Hz, NHCˆC), 122.5 ꢀq, J
ˆ
C±F
C±F
70.0Hz, CF ), 99.6 ꢀq, J ˆ 33.4Hz, CF Cˆ), 53.6 ꢀOMe), 53.1 ꢀOMe) ppm; IR: ꢃ ˆ 3600br,
3
C±F
3
À 1
758 vs, 1711 s, 1682 s, 1609 vs cm
.
Methyl ꢀ-*N-acylamino)-acrylates 9; general procedure
To a stirred suspension of 1 mmol methyl N-acylamino-ꢀ-triphenylphosphoniopropionate iodide in
3
3
4
cm CH CN, 5 mg hydroquinone and 0.17cm triethylamine ꢀ1.25 mmol) were added at room
3
temperature. After 2 h the solvent was evaporated, and the residue was puri®ed by column chroma-
tography ꢀethyl acetate:benzeneˆ 1:5).
Methyl ꢀ-*N-pivaloylamino)-acrylate ꢀ9a; C H NO )
9
15
3
1
Yield: 57%; resin; H NMR: ꢂ ˆ 8.07 ꢀs, 1H, NH), 6.62 ꢀs, 1H, ˆCH ), 5.87 ꢀs, 1H, ˆCH ), 3.86
2
2
1
3
ꢀ
s, 3H, OCH ), 1.27 ꢀs, 9H, t-Bu) ppm; C NMR: ꢂ ˆ 177.3 ꢀCONH), 165.0 ꢀCOOMe), 131.0
3
ꢀ
>CˆCH ), 108.3 ꢀ>CˆCH ), 53.0 ꢀOMe), 39.9 ꢀCMe ), 27.4 ꢀCMe ) ppm; IR: ꢃ ˆ 3420 m,
2
2
3
3
À 1
.
1
724 s, 1682vs, 1640 m cm

1
204
R. Mazurkiewicz and M. Grymel: N-Acyl-ꢀ-triphenylphosphonio-ꢀ-amino Acid Esters
Methyl ꢀ-*N-benzoylamino)-acrylate ꢀ9b; C H NO )
1
1
11
3
1
Yield: 65%; resin; H NMR: ꢂ ˆ 8.56 ꢀs, br, 1H, NH), 7.85±7.45 ꢀm, 5H, Ph), 6.80 ꢀd, 1H, J ˆ 1.5 Hz,
1
3
ˆ
CH ), 6.00 ꢀd, 1H, J ˆ 1.5 Hz, ˆCH ), 3.89 ꢀs, 3H, OCH ) ppm; C NMR: ꢂ ˆ 165.8, 164.8 ꢀCONH
2
2
3
and COOMe), 134.3 132.1, 128.8, 127.0 ꢀPh), 132.1 ꢀ>CˆCH ), 109.0 ꢀ>CˆCH ), 53.1 ꢀOMe)
2
2
À 1
ppm; IR: ꢃ ˆ 3410m, 1720 s, 1680 vs cm
.
Acknowledgements
Financial help by the Polish State Committee for Scienti®c Research ꢀGrant No 3T09A 11416) is
gratefully acknowledged.
References
[
1] Zoller U, Ben-Ishai D ꢀ1975) Tetrahedron 31: 863; Ben-Ishai D, Sataty I, Bernstein Z ꢀ1976) ibid
2: 1571
3
[2] Mazurkiewicz R, Grymel M ꢀ1999) Monatsh Chem 130: 597
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[4] Mazurkiewicz R, Grymel M, Brachaczek A, Heczko K ꢀ1998) XVIIIth European Colloquium on
Heterocyclic Chemistry, Rouen, France, B-33; Mazurkiewicz R, Pierwocha A, Grymel M ꢀ1998)
ibid, B-34
[
[
5] Kober R, Steglich W ꢀ1983) Liebigs Ann Chem 599
6] Kober R, Papadopoulos K, Miltz W, Enders D, Steglich W ꢀ1985) Tetrahedron 41: 1693; Munster
P, Steglich W ꢀ1987) Synthesis 3: 223; Bretschneider T, Miltz W, Munster W, Steglich W ꢀ1988)
Tetrahedron 44: 5403
[7] Bernstein Z, Ben-Ishai D ꢀ1977) Tetrahedron 33: 881
Received October 31, 2001. Accepted *revised) December 17, 2001