Synthesis and anticonvulsant activities of N-benzyl-2-acetamidopropionamide derivatives

Article abstract of DOI:10.1021/jm9508705

Studies have demonstrated that 2-substituted N-benzyl-2-acetamidoacetamides (2) are potent anticonvulsants. A recent investigation has led to the hypothesis that an important structural feature in 2 for maximal anticonvulsant activity is the placement of a small, substituted heteroatom moiety one atom from the C(2) site. This paper validates this hypothesis. Twelve derivatives of N-benzyl-2-acetamidopropionamide have been prepared in which six different heteroatom substituents (chloro, bromo, iodo, oxygen, nitrogen, and sulfur) were incorporated at the C(3) site. Highly potent activities were observed for the two oxygen-substituted derivatives, N-benzyl-2-acetamido-3-methoxypropionamide (18) and N-benzyl-2-acetamido-3-ethoxypropionamide (19). The ED₅₀ values in mice following intraperitoneal (ip) dosing for the maximal electroschock-induced seizure test for 18 and 19 were 8.3 and 17.3 mg/kg, respectively. These values compared favorably to the ED₅₀ value found for phenytoin (ED₅₀ = 6.5 mg/kg). Comparable activities were observed for 18 and 19 upon oral (po) administration to rats (18, ED₅₀ = 3.9 mg/kg; 19, ED₅₀ = 19 mg/kg; phenytoin, ED₅₀ = 23 mg/kg). Evaluation of the individual stereoisomers for 18 demonstrated that the principal anticonvulsant activity resided in the (R)-stereoisomer. The ED₅₀ value for (R)-18 was 4.5 mg/kg, and the ED₅₀ for (S)-18 exceeded 100 mg/kg. This difference in activity for the two stereochemical isomers surpassed comparable values for other members within this class of compounds. The protective indices (PI = TD₅₀/ED₅₀) (where TD₅₀ represents a neurotoxic dose impairing rotorod performance) for (R)-18 in mice (ip) and in rats (po) were 6.0 and > 130, respectively.

Full text of DOI:10.1021/jm9508705

J . Med. Chem. 1996, 39, 1907-1916
1907
Syn th esis a n d An ticon vu lsa n t Activities of N-Ben zyl-2-a ceta m id op r op ion a m id e
Der iva tives
Daeock Choi,† J ames P. Stables,‡ and Harold Kohn*,†
Department of Chemistry, University of Houston, Houston, Texas 77204-5641, and Epilepsy Branch,
National Institute of Neurological Disorders and Stroke, National Institutes of Health,
Federal Building, Room 114, Bethesda, Maryland 20892-9020
Received November 29, 1995X
Studies have demonstrated that 2-substituted N-benzyl-2-acetamidoacetamides (2) are potent
anticonvulsants. A recent investigation has led to the hypothesis that an important structural
feature in 2 for maximal anticonvulsant activity is the placement of a small, substituted
heteroatom moiety one atom from the C(2) site. This paper validates this hypothesis. Twelve
derivatives of N-benzyl-2-acetamidopropionamide have been prepared in which six different
heteroatom substituents (chloro, bromo, iodo, oxygen, nitrogen, and sulfur) were incorporated
at the C(3) site. Highly potent activities were observed for the two oxygen-substituted
derivatives, N-benzyl-2-acetamido-3-methoxypropionamide (18) and N-benzyl-2-acetamido-3-
ethoxypropionamide (19). The ED50 values in mice following intraperitoneal (ip) dosing for
the maximal electroschock-induced seizure test for 18 and 19 were 8.3 and 17.3 mg/kg,
respectively. These values compared favorably to the ED50 value found for phenytoin (ED50
)
6.5 mg/kg). Comparable activities were observed for 18 and 19 upon oral (po) administration
to rats (18, ED50 ) 3.9 mg/kg; 19, ED50 ) 19 mg/kg; phenytoin, ED50 ) 23 mg/kg). Evaluation
of the individual stereoisomers for 18 demonstrated that the principal anticonvulsant activity
resided in the (R)-stereoisomer. The ED50 value for (R)-18 was 4.5 mg/kg, and the ED50 for
(S)-18 exceeded 100 mg/kg. This difference in activity for the two stereochemical isomers
surpassed comparable values for other members within this class of compounds. The protective
indices (PI ) TD50/ED50) (where TD50 represents a neurotoxic dose impairing rotorod
performance) for (R)-18 in mice (ip) and in rats (po) were 6.0 and >130, respectively.
In tr od u ction
acetamidoacetamide derivatives,5 the decrease in activ-
ity of the 2-thien-3-yl (6) (ED50 ) 88 mg/kg) adduct
versus the isomeric 2-thien-2-yl (5) (ED50 ) 45 mg/kg)
compound, and the dramatic increase in activity for the
O-methylhydroxylamine (9) (ED50 ) 6.2 mg/kg) and
O,N-dimethylhydroxylamine (10) (ED50 ) 6.7 mg/kg)
derivatives versus the C(2) hydroxylamine compound
(8) (ED50 ≈ 100 mg/kg).6 Another critical aspect of the
structure-activity profile observed for N-benzyl-2-acet-
amidoacetamide derivatives (2) was the discovery that
in three different cases the (R)-stereoisomer was ap-
proximately 10 times more potent in the control of MES
seizures than the (S)-enantiomer.1,4,5,7 These differences
in activities were the greatest eudismic ratio10 reported
to date for MES-selective anticonvulsant agents.
Over the past 10 years we have reported on the
anticonvulsant properties of functionalized amino acid
derivatives that conform to the general structure 1.1-9
Systematic evaluation of over 100 derivatives has led
to our proposal that stringent steric and electronic
requirements exist for this novel class of compounds for
protection against maximal electroshock (MES)-induced
seizure. Our structure-activity studies indicated two
important trends. First, in cases where an aromatic
moiety was positioned at the C(2) site improved activity
was noted for those compounds that contained a small,
electron-rich R2 substituent.5,7 Second, enhanced pro-
tection against MES-induced seizures was observed for
C(2) cyclic and acyclic R2 groups that contained a
substituted heteroatom one atom from the C(2) site.6,7,9
Consistent with these contentions were the relative
activities (mice, ip) of 3 (ED50 ) 10 mg/kg) versus the
2-tetrahydrofuran-2-yl diastereomers (7) (ED50 ) 52-
90 mg/kg),7 the relative potencies of 2-furan-2-yl (3)
(ED50 ) 10 mg/kg), 2-pyrrol-2-yl (4) (ED50 ) 16 mg/kg),
and 2-thien-2-yl (5) (ED50 ) 45 mg/kg) N-benzyl-2-
† University of Houston.
Recently, we found that the three C(2) electron-
deficient heteroaromatic compounds (11-13) possessed
‡ NIH.
X Abstract published in Advance ACS Abstracts, April 1, 1996.
0022-2623/96/1839-1907$12.00/0 © 1996 American Chemical Society

1908 J ournal of Medicinal Chemistry, 1996, Vol. 39, No. 9
Choi et al.
Ta ble 1. Physical and Pharmacological Data in Mice for N-Benzyl-2-acetamidopropionamidesa
d
no.
R2
mpb
MESc ED50
TD50
PIe
5.9
14f
CH3
138-139
77 [1]
(67-89)
450 [0.5]
(420-500)
>100, <300
>100, <300
∼300
15
16
17
18
CH2Cl
CH2Br
CH2I
143-144
123-125
169-170
121-122
∼100
>30, <100
>30, <100
8.3 [0.5]
(7.9-9.8)
17 [0.25]
(15-19)
CH2OCH3
43 [0.25]
(38-47)
78 [0.25]
(64-90)
>30, <100
>100
5.2
4.6
19
CH2OCH2CH3
113-114
20
21
22
23
24
25
26
27
8
CH2OCH2CHdCH2
CH2NH2
76-77
>30, <100
>100
>100, <300
>100
>30, <100
>100, <300
>30, <100
>100, <300
∼100 [1]
6.2 [0.5]
(5.4-7.2)
6.7 [0.5]
(5.7-7.7)
6.5 [2]
119-120
107-108
90-91
CH2N(H)CH3
CH2N(H)CH2CH3
CH2N(CH3)2
CH2-morpholino
CH2SCH3
>100, <300
∼100
125-126
147-148
142-143
201-203
144-146 dec
95-97
>300
>300
>100, <300
g
CH2OH
N(H)OH
<300
h
-
9
N(H)OCH3
46 [0.5]g
(38-56)
51 [0.5]g
(40-60)
43 [0.5]
(36-48)
69 [0.5]
(63-73)
480 [0.25]
(410-570)
7.4
7.6
6.6
3.1
1.7
10
N(CH3)OCH3
phenytoini
165-167
(5.7-7.2)
22 [1]
(15-23)
290 [0.25]
(240-360)
phenobarbitalj
valproatei
a
The compounds were administered intraperitoneally. ED50 and TD50 values are in mg/kg. Numbers in parentheses are 95% confidence
intervals. A dose-response curve was generated for all compounds that displayed sufficient activity. The dose-effect data for these
compounds was obtained at the “time of peak effect” (indicated in hours in the brackets). The compounds were tested through the auspices
of the National Institute of Neurological and Communicative Disorders and Stroke at the National Institutes of Health, except for compounds
b
8-10 and 27 which were tested at the Eli Lilly Company (Indianapolis, IN). Melting points (°C) are uncorrected. c MES ) maximal
d
electroshock seizure test. Neurologic toxicity determined using the rotorod test unless otherwise noted. e PI ) protective index (TD50
/
ED50). f Reference 3. TD50 ) neurologic toxicity determined from horizontal screen test (ref 22). Test not conducted. Reference 11a.
g
h
i
j
Reference 11b.
outstanding anticonvulsant activities.9 This discovery
ran counter to our original projections of the beneficial
properties that accompany incorporation of an electron-
rich aromatic substituent at this site and challenged the
validity of this aspect of our structure-activity relation-
ship. In this paper we provide additional documenta-
tion that the key structural feature for maximal anti-
convulsant activity is the placement of a small, sub-
stituted heteroatom moiety one atom from the C(2) site.
Highlighting this report is the remarkable activity of
N-benzyl-2-acetamido-3-methoxypropionamide (18) (Table
1). In agreement with previous findings,1,4,5,7 we dem-
onstrate that the activity of this racemate resided pref-
erentially in the (R)-stereoisomer.
Ch em istr y
The preferred synthetic route developed for the
halogen (15-17) and the oxygen-substituted (18-20)
adducts is provided in Scheme 1. Beginning with
commercially available ethyl acetamidocyanoacetate
(28), addition of benzylamine gave 29,12 which upon
dissolution in acidic methanol furnished methyl ester
30.13 Reduction of 30 with NaBH4 and LiCl14 produced
27 in 58% overall yield from 28. Treatment of serine
derivative 27 with the appropriate halotrimethylsi-
lanes15 afforded 15-17 in moderate yields (20-74%).16
Attempts to prepare the corresponding fluoro derivative
(31) with fluorotrimethylsilane were not successful and
gave 32. Formation of 15 from 27 with chlorotrimeth-
ylsilane was surprising in light of previous literature
results.15,17 The generality and utility of this procedure
for the synthesis of â-halo amino acid derivatives for
peptide synthesis has been briefly evaluated.16 Syn-
thesis of ethers 18-20 was accomplished by coupling
27 with the appropriate alkyl iodide in the presence of
Ag2O.
Selection of Com p ou n d s
The compounds examined in this study are deriva-
tives of N-benzyl-2-acetamidopropionamide2 (14) in
which a heteroatom substituent has been attached at
the C(3) position (Table 1). Groups placed at this site
included halogen (15-17), oxygen (18-20), nitrogen
(21-25), and sulfur (26) moieties. In all cases, the
initially prepared compounds were racemates. Serving
as key reference compounds were the methyl (alanyl)2
(14), hydroxymethyl (serinyl) (27), and the three C(2)-
hydroxylamine6 (8-10) derivatives along with the proven
antiepileptic agents phenytoin,11a phenobarbital,11b and
valproate.11a
2-Acetamidoacrylic acid (33) served as the starting
material for the remaining compounds in our initial
series. Compound 33 was first converted to N-benzyl-
amide 34 and then treated with both amine and sulfur
nucleophiles in protic solvents to give 21-26.18,19 The
utility of N-benzyl-2-acetamido-3-chloropropionamide

N-Benzyl-2-acetamidopropionamide Derivatives
J ournal of Medicinal Chemistry, 1996, Vol. 39, No. 9 1909
Ta ble 2. Pharmacological Evaluation of Functionalized
(R,S)-N-Benzyl-2-acetamidopropionamide Derivatives upon
Oral Administration to Ratsa
Sch em e 1. Preparation of
N-Benzyl-2-acetamidopropionamide Derivatives
no.
MES,b ED50
Tox,c TD50
PId
e
14
18
19
48 [1]
(32-72)
3.8 [2]
(2.9-5.5)
19 [0.5]
(14-24)
23 [2]
(21-25)
9.1 [5]
(7.6-12)
400 [0.5]
(330-440)
-
>21
390 [1]
100
>26
>22
(320-520)
f
-
f
phenytoing
-
phenobarbitalh
valproateg
61 [0.5]
(44-96)
860 [0.5]
(720-1100)
6.7
2.2
a
ED50 and TD50 values are in mg/kg. Numbers in parentheses
are 95% confidence intervals. The dose effect data was obtained
at the “time of peak effect” (indicated in hours in the brackets).
b
MES ) maximal electroshock seizure test. c Tox ) neurologic
d
toxicity (the rotorod test). PI ) protective index (TD50/MES ED50).
e No ataxia observed up to 1000 mg/kg. f No attaxia observed up
g
h
to 500 mg/kg. Reference 11a. Reference 11b.
of the hydrochloride salts of the optically pure serine
methyl esters 36 with benzylamine gave benzylamide
37, which was then acylated with acetic anhydride to
provide 27. Three criteria were used to assess the
enantiopurity of 27. These were melting point, optical
rotation, and the detection of only a single acetyl methyl
1
signal in the H NMR spectrum of 27 upon addition of
a saturated solution of (R)-(-)-mandelic acid.20 NMR
analysis indicated that conversion of 36 to 27 proceeded
to give an approximate 2:1 mixture of the enantiomers.
Accordingly, 27 was repeatedly recrystallized until
optically pure and then alkylated with MeI and Ag2O
to give the desired ether 18 without racemization.
The pronounced anticonvulsant activity observed for
(R)-18 led us to devise an alternative, more expeditious
synthetic route for this compound (Scheme 3). Begin-
ning with D-serine ((R)-35), treatment with acetic
anhydride in acetic acid gave the N-acylated derivative
38, which was converted to N-benzylamide (R)-27 using
the mixed anhydride coupling procedure.21 NMR and
optical measurements indicated that both steps pro-
ceeded without racemization. Alkylation of (R)-27 with
MeI and Ag2O gave (R)-N-benzyl-2-acetamido-3-meth-
oxypropionamide ((R)-18) in 30% overall yield. The
success of this protocol permitted the rapid synthesis
of derivatives of (R)-18 in which the substitution pattern
on the benzylamide group was altered (Table 3). Ac-
cordingly, treatment of (R)-38 with 3-fluorobenzylamine
and 4-fluorobenzylamine provided (R)-39 and (R)-40,
respectively, which were then converted to the methyl
ethers (R)-41 and (R)-42, respectively, with MeI and
Ag2O.
(15) was also briefly examined for the synthesis of
N-benzyl-3-substituted-2-acetamidopropionamide de-
rivatives. Treatment of 15 with KOH or NaH provided
the elimination product 34, while addition of sodium
methanethiolate to 15 in MeOH gave the substitution
product 26 in 89% yield. Information concerning the
mechanism of this transformation was obtained by
rerunning this reaction in CD3OD. Under these condi-
tions the C(2) methine site was fully deuterated (NMR
analysis, data not shown). This finding coupled with
the observation that only 15% C(2)H f C(2)D exchange
occurred upon dissolution of 26 in basic CH3OD indi-
cated that conversion of 15 to 26 proceeded through 34,
rather than by direct SN2 displacement of the chloride
group in 15.
P h a r m a cologica l Eva lu a tion
The anticonvulsant activities for 2-acetamido-N-ben-
zylpropionamide derivatives 15-26 were determined
using the procedure described by Kupferberg,22 and
these results compared to 8-10,6 14,2 27, and the
clinically proven antiepileptic agents phenytoin,11a
phenobarbital,11b and valproate.11a All compounds were
administered intraperitoneally (ip) to mice. Table 1 lists
the results obtained from the initial mouse identification
and quantitation screening studies. They include the
ED50 values for racemates 15-26 that are protective
The pharmacological activity observed for N-benzyl-
2-acetamido-3-methoxypropionamide (18) warranted
our preparation of the individual (R)- and (S)-enanti-
omers (Table 2). The original preparative route devel-
oped took advantage of the commercial availability of
both D- and L-serine derivatives (Scheme 2). Treatment

1910 J ournal of Medicinal Chemistry, 1996, Vol. 39, No. 9
Sch em e 2. Preparation of Enantiopure 18
Choi et al.
Sch em e 3. Improved Procedure for the Preparation of
Enantiopure (R)-18 and Related Compounds
respect to heteroatom substituent was observed for the
C(2) aromatic compounds 3 (ED50 ) 10 mg/kg), 4 (ED50
) 16 mg/kg), and 5 (ED50 ) 45 mg/kg).5 The compara-
tively low activity observed for amines 21-25 has been
tentatively attributed, in part, to the basicity of this
substituent. This difference in activity was reminiscent
of the decreased activity observed for the C(2) imidazole
derivative 43 (ED50 >100 mg/kg) versus the less basic,
isomeric C(2) pyrazole adduct 44 (ED50 ) 17 mg/kg).7
in blocking hind limb extension induced in the MES test.
Also contained in Table 1 are the median doses for
neurological impairment (TD50) using either the ro-
torod23 or the horizontal screen24 (HS) test. In most
cases, the TD50s were only determined for those com-
pounds that had good activity in the MES test. The
protective index (PI ) TD50/ED50) for these adducts,
where appropriate, is also shown in Table 1.
Inspection of the composite data in Table 1 provided
strong support for our current structure-activity rela-
tionship for this class of anticonvulsants. Highlighted
were the beneficial value accrued by the placement of a
heteroatom one atom from the C(2) site, the need for
the heteroatom to be substituted, and the stringent
steric requirements that limit the size of the C(2)
substituent. Six different heteroatoms (O, N, S, Cl, Br,
and I) were incorporated in N-benzyl-2-acetamidopro-
pionamide (14). Of these, the oxygen-substituted de-
rivatives 18-20 proved to be the most effective for the
control of MES-induced seizures. The anticonvulsant
Support for our suggestion that increased anticon-
vulsant protection accompanied substitution of the
heteroatom moiety was provided by the comparison of
the ED50 values for methyl ether 18 (ED50 ) 8.3 mg/
kg) and ethyl ether 19 (ED50 ) 17 mg/kg) versus alcohol
27 (ED50 >100, <300 mg/kg). This dramatic increase
in protection in the MES test paralleled the previous
findings observed for the C(2) O-methylhydroxylamines
9 (ED50 ) 6.2 mg/kg) and 10 (ED50 ) 6.7 mg/kg) versus
the parent compound 8 (ED50 ≈ 100 mg/kg).6
The effect of size of the C(2) substituent on pharma-
cological activity could be discerned by the progressive
decrease in protection from MES-induced seizures ob-
served in the O-alkyl series (18-20) and the N,N-di-
substituted derivatives 24 and 25. In both sets of com-
pounds we observed a drop in anticonvulsant activity
as the size of the groups attached to the heteroatom
increased. Comparable patterns were reported for func-
tionalized C(2) aromatic amino acid derivatives (e.g., 3,
ED50 ) 10 mg/kg versus 45, ED50 >100, <300 mg/kg;5
46, ED50 ) 32 mg/kg versus 47, ED50 >300 mg/kg5).
The pharmacological activities of racemic 18 and 19
warranted their further evaluation. Table 2 lists the
MES ED50, TD50, and PI value for these compounds
upon oral administration (po) to rats with similar data
activities of both 18 (ED50 ) 8.3 mg/kg) and 19 (ED50
)
17 mg/kg) exceeded that of 14 (ED50 ) 77 mg/kg).
Moreover, the MES ED50 values and protective indices
of racemic 18 and 19 were comparable to those reported
for phenytoin11a (ED50 ) 6.5 mg/kg) and phenobarbital11b
(ED50 ) 22 mg/kg), respectively. A similar trend with

N-Benzyl-2-acetamidopropionamide Derivatives
J ournal of Medicinal Chemistry, 1996, Vol. 39, No. 9 1911
Ta ble 3. Selected Physical and Pharmacological Data for Functionalized N-Benzyl-2-acetamidopropionamide Stereoisomers
mice (ip)b
Tox,d TD50
rat (po)f
no.
R2
CH3
Ar
mpa
MES,c ED50
PIe
5.9
MES,c ED50
Tox,d TD50
PIe
h
(R,S)-14
Ph
Ph
Ph
Ph
Ph
139-141
77 [1]g
(67-89)
450 [0.5]
(420-500)
210 [0.5]
(150-260)
840 [0.5]
(690-950)
43 [0.25]
(38-47)
27 [0.25]
(26-28)
>300
48 [1]
(32-72)
28 [4]
-
>21
h
(R)-14
(S)-14
CH3
139-141
139-142
121-122
143-144
55 [0.5]i
3.9
1.5
5.2
6.0
-
>36
(50-60)
(22-35)
j
j
CH3
550 [0.5]
(460-740)
8.3 [0.5]
(7.9-9.8)
4.5 [0.5]
(3.7-5.5)
>100, <300
>100, <300
53 [2]
-
-
(R,S)-18
(R)-18
CH2OCH3
CH2OCH3
3.8 [2]
(2.9-5.5)
3.9 [0.5]
(2.6-6.2)
>30
390 [1]
(320-510)
>500 [0.5]
100
>130
(S)-18
(R,S)-27
(R)-27
CH2OCH3
CH2OH
CH2OH
Ph
Ph
Ph
143-144
201-203
148-149
>30
j
j
>300
>500 [2]
-
-
-
j
j
>9.4
6.7
-
(38-67)
(R)-41
(R)-42
CH2OCH3
CH2OCH3
Ph(m-F)
Ph(p-F)
150-151
144-145
6.9 [0.25]
(6.1-8.0)
4.2 [0.5]
(3.5-5.1)
46 [0.25]
(40-55)
28 [0.25]
(22-34)
6.9 [0.5]
(4.3-9.9)
2.6 [2]
>400 [0.5]
>58
6.7
>125, <250
(1.9-3.6)
a
Melting points (°C) are uncorrected. b The compounds were administered intraperitoneally. ED50 and TD50 values are in mg/kg. Numbers
in parentheses are 95% confidence intervals. The dose effect data was obtained at the “time of peak effect” (indicated in hours in the
d
brackets). c MES ) maximal electroshock seizure test. Tox ) neurologic toxicity determined from rotorod test. e PI ) protective index
g
h
i
j
(TD50/MES ED50). f The compounds were administered orally. Reference 3. No ataxia observed up to 1000 mg/kg. Reference 4. Data
not available.
for racemic 14 and some of the current clinically used
antiepileptic agents.11 Both 18 and 19 provided en-
hanced protection against MES-induced seizures versus
14. These results gave further proof that the placement
of a small, substituted heteroatom moiety one atom from
the C(2) site in this series of compounds leads to
improved anticonvulsant activities. Significantly, the
MES ED50 values for 18 (ED50 ) 3.8 mg/kg) and 19
(ED50 ) 19 mg/kg) were better than those reported for
phenytoin (ED50 ) 23 mg/kg). Moreover, the PI value
for 18 was 100.
The final group of compounds evaluated were the
individual (R)- and (S)-stereoisomers of 18 and the (R)-
stereoisomers of 27, 41, and 42 (Table 3). A distin-
guishing feature previously determined for this class of
anticonvulsant agents was the marked differences in
activity observed for the two enantiomers that com-
prised the racemate.1,4,5,7 For example, in mice (ip) the
(R)-stereoisomer of N-benzyl-2-acetamidopropionamide
((R)-14) was 10 times more effective in the control of
MES-induced seizures than the corresponding (S)-
isomer, (S)-14. Comparable differences in potencies
were observed for the stereoisomers of 3 and 46. Con-
sistent with these findings, we observed that the anti-
convulsant activity for 18 resided in the (R)-stereoiso-
mer. The eudismic ratio determined in the MES test
in mice (ip) was >22 and surpassed comparable values
found for 3, 14, and 46. Similarly, we noted a signifi-
cant improvement in anticonvulsant activity of (R)-27
(ED50 ) 53 mg/kg) versus the corresponding racemate
(R,S)-27 (ED50 >100, <300 mg/kg). Included in this
survey were the two monofluorinated derivatives (R)-
41 and (R)-42. These compounds were prepared be-
cause we previously observed improvements in the PI
values for select monofluorinated N-benzyl derivatives
of 3 and 14.3,7 In keeping with this trend, both (R)-41
(PI ) 6.7) and (R)-42 (PI ) 6.7) exhibited modest im-
provements in their PI values versus (R)-18 (PI ) 6.0).
extended to derivatives of N-benzyl-2-acetamidopropi-
onamide (14) in which a heteroatom moiety has been
positioned one atom from the C(2) site. Highly potent
activities against MES-induced seizures were observed
for both N-benzyl-2-acetamido-3-methoxypropionamide
(18) and N-benzyl-2-acetamido-3-ethoxypropionamide
(19). Evaluation of the individual stereoisomers of 18
demonstrated that the anticonvulsant activity resided
in the (R)-stereoisomer. The potency of (R)-18 in mice
(ip) exceeded the value previously reported for pheny-
toin. The findings that the anticonvulsant properties
of 18 and 19 surpassed that of 14 provided further
evidence that placement of small, substituted heteroa-
tom groups one atom from the C(2) site in the function-
alized amino acid derivatives leads to improved phar-
macological activity.
Exp er im en ta l Section
Gen er a l Meth od s. Melting points were determined with
a Thomas-Hoover melting point apparatus and are uncor-
rected. Infrared spectra (IR) were run on Perkin-Elmer 1330
and 283 and Mattson Genesis spectrometers and were cali-
brated against the 1601 cm-1 band of polystyrene. Absorption
values are expressed in wavenumbers (cm-1). Proton (1H
NMR) and carbon (13C NMR) nuclear magnetic resonance
spectra were taken on Nicolet NT-300 and General Electric
QE-300 NMR instruments. Chemical shifts (δ) are in parts
per million (ppm) relative to Me4Si, and coupling constants (J
values) are in hertz. All chemical ionization mass spectral
investigations were conducted at the University of Texas at
Austin by Dr. M. Moini on a Finnigan MAT TSQ-70 instru-
ment. Microanalyses were provided by Atlantic Microlab, Inc.
(Norcross, GA). Ethyl R-acetamidocyanoacetate (28) was
obtained from Aldrich Chemical Co. (Milwaukee, WI). Thin-
layer chromatography was performed on precoated silica gel
GHLF microscope slides (2.5 × 10 cm; Analtech No. 21521).
Syn th esis of Meth yl r-Aceta m id o-N-ben zylm a lon a m a -
te13 (30). To a methanolic suspension (800 mL) of 29 (28.5 g,
123.1 mmol) was added p-toluenesulfonic acid (24.0 g, 126.2
mmol). The mixture was heated at reflux (12 h). The resulting
suspension was concentrated in vacuo. The residue was
dissolved in a 3:2 mixture of EtOAc and H2O (3 L). The
organic layer was separated and the aqueous layer extracted
with EtOAc (2 L). The organic layers were combined, dried
(Na2SO4), and evaporated in vacuo. The residue was recrys-
Con clu sion s
The structure-anticonvulsant activity relationship
for functionalized amino acid derivatives has been

1912 J ournal of Medicinal Chemistry, 1996, Vol. 39, No. 9
Choi et al.
tallized (1:1 EtOAc/hexanes), and washed with Et2O (1 L) to
give 21.2 g (65%) of 30: mp 158-159 °C (lit.13 mp 158-159
°C); Rf 0.36 (6% MeOH-CHCl3); IR (KBr) 2920, 1750, 1630,
1370, 890, 790 cm-1; 1H NMR (DMSO-d6) δ 1.90 (s, C(O)CH3),
3.66 (s, OCH3), 4.30 (t, J ) 6.3 Hz, CH2), 5.14 (d, J ) 7.8 Hz,
CH), 7.21-7.32 (m, 5 PhH), 8.61 (d, J ) 7.8 Hz, NH), 8.96 (t,
J ) 6.3 Hz, NH); 13C NMR (DMSO-d6) 22.1 (C(O)CH3), 42.3
(CH2), 52.4 (CH), 56.5 (OCH3), 126.8 (C4′), 127.0 (2C2′ or 2C3′),
128.2 (2C2′ or 2C3′), 138.7 (C1′), 165.4 (C(O)CH3 or C(O)OCH3),
168.3 (C(O)CH3 or C(O)OCH3), 169.6 (C(O)NH) ppm; MS (+CI)
265 (M+ + 1, 22), 264 (100). Anal. (C13H16N2O4).
Syn th esis of N-Ben zyl-2-a ceta m id o-3-iod op r op ion a -
m id e (17). To an CH3CN suspension (100 mL) of 27 (1.18 g,
5.0 mmol) was added iodotrimethylsilane (0.84 mL, 6.0 mmol)
under N2. The reaction mixture was heated at reflux (1 h),
and then the solvent was removed in vacuo. The residue was
dissolved in a 1:1 mixture of H2O and CHCl3. The organic
layer was separated, washed with a saturated aqueous NaH-
CO3 solution, dried (Na2SO4), and evaporated in vacuo. The
crude product was triturated with EtOAc (20 mL) to give 0.35
g (20%) of 17 as a white solid: mp 169-170 °C dec; Rf 0.65
(10% MeOH-CHCl3); IR (KBr) 3287, 3067, 2928, 1645, 1551,
1
1455, 1376, 742, 698 cm-1; H NMR (CDCl3) δ 2.05 (s, C(O)-
Syn t h esis of N-Ben zyl-2-a cet a m id oh yd r a cr yla m id e
(27). To an anhydrous THF solution (400 mL) of 30 (14.4 g,
54.5 mmol) was successively added dry LiCl (4.62 g, 109 mmol),
NaBH4 (4.13 g, 109 mmol), and EtOH (200 mL). The reaction
mixture was stirred at room temperature (5 h). The suspen-
sion was concentrated in vacuo. After continuous extraction
(12 h) of the product using CHCl3 (1000 mL) and H2O (250
mL), the organic layer was collected, dried (Na2SO4), and
removed in vacuo to give a crude white solid. The crude
product was triturated with Et2O (500 mL) to give 11.45 g
(89%) of 27: mp 201-203 °C; Rf 0.40 (10% MeOH-CHCl3);
IR (KBr) 3287, 3085, 2969, 2859, 1648, 1552, 1456, 1055, 697
CH3), 4.38-4.51 (m, CH2I), 4.48 (d, J ) 5.7 Hz, NHCH2), 4.63-
4.70 (m, CH), 6.52 (br d, J ) 7.2 Hz, NH), 6.87 (br s, NH),
7.30-7.35 (m, 5 PhH); 13C NMR (CDCl3) 4.8 (CH2I), 22.8 (C(O)-
CH3), 43.4 (CH2N), 53.3 (CH), 127.3 (C4′), 127.4 (2C2′ or 2C3′),
128.3 (2C2′ or 2C3′), 136.9 (C1′), 168.4 (C(O)CH3 or C(O)NH),
169.8 (C(O)CH3 or C(O)NH) ppm; MS (+CI) (rel intensity) 220
(20), 219 (100); Mr (+CI) 347.025 81 [M+ + 1] (calcd for C12H16
IN2O2 347.025 65). Anal. (C12H15IN2O2‚0.33H2O) C, H, N.
-
Syn th esis of Dih yd r ooxa zole 32. To an CH3CN solution
(5 mL) of 27 (47 mg, 0.2 mmol) was added fluorotrimethylsi-
lane (0.92 µL, 1 mmol) at -78 °C. The reaction solution was
warmed to room temperature and stirred (1 d). The solvent
was removed under reduced pressure, and then the product
was isolated by preparative TLC (10% MeOH-CHCl3) to give
20 mg (46%) of 32: mp 129-130 °C; IR (KBr) 3287, 3084, 3067,
1
cm-1; H NMR (DMSO-d6) δ 1.88 (s, C(O)CH3), 3.59 (dd, J )
5.7 Hz, 5.7 Hz, CH2O), 4.19-4.35 (m, CH2NH, CH), 4.92 (t, J
) 5.7 Hz, OH), 7.10-7.40 (m, 5 PhH), 7.94 (d, J ) 5.7 Hz,
NH), 8.38 (t, J ) 5.7 Hz, NH); 13C NMR (DMSO-d6) 22.2 (C(O)-
CH3), 41.6 (CH2N), 54.9 (CH), 61.3 (CH2OH), 126.2 (C4′), 126.5
(2C2′ or 2C3′), 127.7 (2C2′ or 2C3′), 138.9 (C1′), 169.1 (C(O)CH3
or C(O)NH), 169.9 (C(O)CH3 or C(O)NH) ppm; MS (+CI) (rel
intensity) 237 (M+ + 1, 100), 219 (9); Mr (+CI) 237.123 88 [M+
+ 1] (calcd for C12H17N2O3 237.123 92). Anal. (C12H16N2O3)
C, H, N.
1
1648, 1551, 1055, 742, 697 cm-1; H NMR (DMSO-d6) δ 1.93
(s, CH3), 4.21-4.38 (m, NHCH2, OCH2CH), 4.55-4.61 (m, CH),
7.22-7.33 (m, 5 PhH), 8.43 (t, J ) 5.7 Hz, NH); 13C NMR (CD3-
OD) 13.6 (CH3), 44.1 (NHCH2), 69.7 (CH), 71.9 (OCH2CH),
128.3 (C4′), 128.6 (2C2′ or 2C3′), 129.6 (2C2′ or 2C3′), 139.6 (C1′),
170.7 (C(N)O or C(O)), 173.7 (C(N)O or C(O)) ppm; MS (+CI)
(rel intensity) 219 (M+ + 1, 100), 141 (41); Mr (+CI) 219.112 64
[M+ + 1] (calcd for C12H15N2O2 219.113 35).
Syn th esis of N-Ben zyl-2-a ceta m id o-3-ch lor op r op ion a -
m id e (15). To an CH3CN suspension (300 mL) of 27 (3.54 g,
15.0 mmol) was added chlorotrimethylsilane (4.76 mL, 37.5
mmol) under N2. The reaction mixture was heated at reflux
(8 h), and then the solvent was removed under reduced
pressure. The residue was dissolved in a 1:1 mixture of CHCl3
and H2O (200 mL). The organic layer was separated, and the
aqueous layer was extracted with CHCl3 (200 mL). The
organic layers were combined, dried (Na2SO4), and evaporated
in vacuo. The white residue was triturated with Et2O (150
mL) to give 2.83 g (74%) of 15 as a white solid: mp 143-144
°C; Rf 0.55 (10% MeOH-CHCl3); IR (KBr) 3291, 3061, 3038,
2951, 2930, 1631, 1536, 1370, 753, 695 cm-1; 1H NMR (CDCl3)
δ 2.06 (s, C(O)CH3), 3.72 (dd, J ) 6.3, 11.1 Hz, CHH′Cl), 3.94
(dd, J ) 6.3, 11.1 Hz, CHH′Cl), 4.48 (d, J ) 5.7 Hz, NHCH 2),
4.72-4.81 (m, CH), 6.36 (br d, J ) 6.3 Hz, NH), 6.49 (br s,
NH), 7.22-7.35 (m, 5 PhH); 13C NMR (DMSO-d6) 22.5 (C(O)-
CH3), 42.2 (CH2N or CH2Cl), 44.6 (CH2N or CH2Cl), 53.9 (CH),
126.7 (C4′), 127.0 (2C2′ or 2C3′), 128.2 (2C2′ or 2C3′), 138.4 (C1′),
168.4 (C(O)CH3 or C(O)NH), 169.5 (C(O)CH3 or C(O)NH) ppm;
MS (+CI) (rel intensity) 257 (M+ + 1, 28), 255 (M+ + 1, 81),
Syn th esis of N-Ben zyl-2-a ceta m id o-3-m eth oxyp r op i-
on a m id e (18). To an CH3CN solution (500 mL) of 27 (2.36 g,
10 mmol) were successively added Ag2O (11.59 g, 50.0 mmol)
and CH3I (6.23 mL, 100 mmol) at room temperature, and then
the reaction mixture was stirred at room temperature (4 d).
The insoluble salts were filtered, and the solvent was removed
in vacuo to give a white solid. The residue was triturated with
Et2O (50 mL) to give 2.10 g (84%) of 18: mp 121-122 °C; Rf
0.47 (10% MeOH-CHCl3); IR (KBr) 3290, 3087, 2924, 2878,
2820, 1637, 1548, 1139, 695 cm-1; 1H NMR (CDCl3) δ 2.04 (s,
C(O)CH3), 3.38 (s, OCH3), 3.43 (dd, J ) 7.8, 9.0 Hz, CHH′OCH3),
3.82 (dd, J ) 4.2, 9.0 Hz, CHH′OCH3), 4.48 (d, J ) 6.0 Hz,
NHCH2), 4.51-4.57 (m, CH), 6.43 (br d, J ) 5.4 Hz, NH), 6.74
(br s, NH), 7.25-7.37 (m, 5 PhH); 13C NMR (CDCl3) 23.2 (C(O)-
CH3), 43.5 (CH2N), 52.4 (CH), 59.1 (OCH3), 71.7 (CH2OCH3),
127.4 (C4′ and 2C2′ or 2C3′), 128.7 (2C2′ or 2C3′), 137.8 (C1′),
170.0 (C(O)CH3 or C(O)NH), 170.3 (C(O)CH3 or C(O)NH) ppm;
MS (+CI) (rel intensity) 251 (M+ + 1, 100), 219 (100); Mr (+CI)
251.139 39 [M+ + 1] (calcd for C13H19N2O3 251.139 57). Anal.
(C13H18N2O3) C, H, N.
220 (100); Mr (+CI) 255.090 85 [M+ + 1] (calcd for C12H16
ClN2O2 255.090 03). Anal. (C12H15ClN2O2) C, H, N.
-
Syn th esis of N-Ben zyl-2-a ceta m id o-3-br om op r op ion a -
m id e (16). To an CH3CN suspension (250 mL) of 27 (2.36 g,
10 mmol) was added bromotrimethylsilane (3.30 mL, 25 mmol)
under N2. The reaction mixture was heated at reflux (2 h),
and then the solvent was removed in vacuo. The product was
purified by flash column chromatography on SiO2 gel (EtOAc)
to give 1.25 g of 16. The crude product was triturated with
Et2O (250 mL) to give 1.09 g (34%) of the desired product: mp
123-125 °C; Rf 0.50 (EtOAc); IR (KBr) 3287, 3067, 2928, 1645,
Syn th esis of N-Ben zyl-2-a ceta m id o-3-eth oxyp r op ion a -
m id e (19). Using the preceding procedure and 27 (2.36 g, 10
mmol), Ag2O (11.59 g, 50 mmol), and EtI (12.0 mL, 150 mmol)
gave crude 19 after stirring at room temperature (18 h). The
insoluble salts were filtered, and the solvent was removed in
vacuo. The residue was dissolved in MeOH (50 mL), treated
with charcoal, and dried (MgSO4). The solvent was evaporated
under reduced pressure and triturated with Et2O (100 mL) to
give 0.60 g (23%) of 19 as a white solid: mp 113-114 °C; Rf
0.60 (5% MeOH-CHCl3); IR (KBr) 3307, 3277, 3064, 2975,
1
1551, 1455, 1376, 742, 698 cm-1; H NMR (CDCl3) δ 2.04 (s,
C(O)CH3), 3.59 (dd, J ) 4.8, 10.5 Hz, CHH′Br), 3.74 (dd, J )
4.8, 10.5 Hz, CHH′Br), 4.47 (d, J ) 5.7 Hz, NHCH2), 4.79-
4.83 (m, CH), 6.42 (br d, J ) 6.6 Hz, NH), 6.47 (br s, NH),
7.29-7.37 (m, 5 PhH); 13C NMR (CDCl3) 23.1 (C(O)CH3), 32.2
(CH2Br), 43.8 (CH2N), 53.6 (CH), 127.6 (C4′), 127.7 (2C2′ or
2C3′), 128.7 (2C2′ or 2C3′), 137.4 (C1′), 168.6 (C(O)CH3 or C(O)-
NH), 170.4 (C(O)CH3 or C(O)NH) ppm; MS (+CI) (rel inten-
sity) 301 (M+ + 1, 5), 299 (M+ + 1, 5), 220 (72), 219 (100); Mr
(+CI) 299.039 22 [M+ + 1] (calcd for C12H16BrN2O2 299.039 51).
Anal. (C12H15BrN2O2‚0.67H2O) C, H, N.
1
2861, 1630, 1549, 1392, 1119, 1103, 731, 707 cm-1; H NMR
(DMSO-d6) δ 1.09 (t, J ) 6.9 Hz, OCH2CH3), 1.87 (s, C(O)-
CH3), 3.43 (q, J ) 6.9 Hz, OCH2CH3), 3.48-3.57 (m, CH2OCH2-
CH3), 4.25-4.35 (m, NHCH2), 4.44-4.50 (m, CH), 7.10-7.35
(m, 5 PhH), 8.08 (d, J ) 7.8 Hz, NH), 8.50 (t, J ) 5.7 Hz, NH);
13C NMR (DMSO-d6) 15.0 (OCH2CH3), 22.6 (C(O)CH3), 42.0
(CH2N), 52.9 (CH), 65.8 (OCH2CH3), 126.7 (C4′), 126.9 (2C2′
or 2C3′), 128.2 (2C2′ or 2C3′), 139.3 (C1′), 169.5 (C(O)CH3 or
C(O)NH), 169.9 (C(O)CH3 or C(O)NH) ppm; MS (+CI) (rel

N-Benzyl-2-acetamidopropionamide Derivatives
J ournal of Medicinal Chemistry, 1996, Vol. 39, No. 9 1913
intensity) 265 (M+ + 1, 100), 219 (22); Mr (+CI) 265.155 04
[M+ + 1] (calcd for C14H21N2O3, 265.155 21). Anal. (C14H20N2O3)
C, H, N.
J ) 8.4, 11.7 Hz, CHH′N(H)CH3), 3.14 (dd, J ) 3.3, 11.7 Hz,
CHH′N(H)CH3), 4.30-4.34 (m, CH), 4.33-4.51 (m, NHCH2),
6.87 (br d, J ) 3.9 Hz, NH), 7.24-7.35 (m, 5 PhH), 8.25 (br s,
NH); 13C NMR (CDCl3) 23.0 (C(O)CH3), 36.1 (N(H)CH3), 43.2
(CH2NH), 52.7 (CH), 52.8 (CH2N(H)CH3), 127.2 (C4′ or 2C2′
or 2C3′), 127.3 (C4′ or 2C2′ or 2C3′), 128.5 (C4′ or 2C2′ or 2C3′),
138.1 (C1′), 170.5 (C(O)CH3 or C(O)NH), 171.2 (C(O)CH3 or
C(O)NH) ppm; MS (+CI) (rel intensity) 250 (M+ + 1, 100); Mr
(+CI) 250.156 82 [M+ + 1] (calcd for C13H20N3O2 250.155 52).
Anal. (C13H19N3O2) C, H, N.
Syn th esis of N-Ben zyl-2-a ceta m id o-3-(a llyloxy)p r op i-
on a m id e (20). Utilizing the procedure employed for 18 and
using 27 (2.36 g, 10 mmol), Ag2O (11.59 g, 50 mmol), and allyl
iodide (9.1 mL, 100 mmol) gave crude 20 after stirring at 45
°C (6 d). The insoluble salts were removed in vacuo to give
an oily residue. The residue was purified by flash column
chromatography on SiO2 gel (3% MeOH-CHCl3). After re-
moval of the solvent the residue was dried in vacuo and then
triturated with a 1:1 mixture of Et2O/hexanes (40 mL) to give
1.20 g (44%) of 20: mp 76-77 °C; Rf 0.57 (5% MeOH-CHCl3);
Syn th esis of N-Ben zyl-2-a ceta m id o-3-(N-eth yla m in o)-
p r op ion a m id e (23). Utilizing the procedure for 21 and using
34 (1.53 g, 7 mmol) and EtNH2 (6.31 g, 140 mmol) gave crude
23 after stirring at room temperature (18 h). The resulting
residue was triturated with Et2O (50 mL) to give 1.70 g (92%)
of 23 as a white solid: mp 90-91 °C; Rf 0.32 (10% MeOH-
CHCl3); IR (KBr) 3271, 3103, 2961, 1680, 1628, 1567, 1543,
IR (KBr) 3288, 3090, 3064, 2859, 1635, 1541, 1108, 696 cm-1
;
1H NMR (DMSO-d6) δ 1.86 (s, C(O)CH3), 3.49-3.58 (m,
CHCH2O), 3.94 (d, J ) 5.1 Hz, OCH2CHCH2), 4.21-4.34 (m,
NHCH2), 4.44-4.51 (m, CH), 5.12-5.27 (m, OCH2CHCH2),
5.77-5.91 (m, OCH2CHCH2), 7.20-7.31 (m, 5 PhH), 8.09 (d,
J ) 7.5 Hz, NH), 8.50 (t, J ) 5.4 Hz, NH); 13C NMR (DMSO-
d6) 22.5 (C(O)CH3), 42.0 (CH2NH), 52.8 (CH), 69.8 (CHCH2O),
71.1 (OCH2CHCH2), 116.6 (OCH2CHCH2), 126.6 (C4′), 126.9
(2C2′ or 2C3′), 128.1 (2C2′ or 2C3′), 134.9 (OCH2CHCH2), 139.2
(C1′), 169.4 (C(O)CH3 or C(O)NH), 169.5 (C(O)CH3 or C(O)-
NH) ppm; MS (+CI) (rel intensity) 277 (M+ + 1, 100), 219 (19);
Mr (+CI) 277.155 74 [M+ + 1] (calcd for C15H21N2O3 277.155 22).
Anal. (C15H20N2O3) C, H, N.
1
745, 696 cm-1; H NMR (CDCl3) δ 1.03 (t, J ) 7.2 Hz, N(H)-
CH2CH3), 2.01 (s, C(O)CH3), 2.50-2.72 (m, CHH′N(H)CH2CH3
and N(H)CH 2CH3), 3.16-3.21 (m, CHH ′N(H)CH2CH3),
4.31-4.37 (m, CH), 4.35-4.51 (m, N(H)CH2), 6.94 (br d, J )
5.4 Hz, NH), 7.24-7.35 (m, 5 PhH), 8.43 (br s, NH); 13C NMR
(CDCl3) 15.0 (N(H)CH2CH3), 22.9 (C(O)CH3), 43.2 (N(H)CH2-
CH3 or CH2NH), 43.7 (N(H)CH2CH3 or CH2NH), 50.5 (CH or
CH2N(H)CH2CH3), 51.8 (CH or CH2N(H)CH2CH3), 127.1 (C4′),
127.2 (2C2′ or 2C3′), 128.4 (2C2′ or 2C3′), 138.1 (C1′), 170.4 (C(O)-
CH3 or C(O)NH), 171.2 (C(O)CH3 or C(O)NH) ppm; MS (+CI)
Syn th esis of N-Ben zyl-2-a ceta m id oa cr yla m id e (34). To
a THF solution (300 mL) containing 33 (3.70 g, 28.6 mmol)
were successively added 4-methylmorpholine (3.5 mL, 31.5
mmol), isobutyl chloroformate (4.1 mL, 31.5 mmol), and
benzylamine (3.4 mL, 31.5 mmol) at room temperature. The
reaction mixture was stirred at room temperature (1 h), then
the insoluble salts were filtered, and the solvent was removed
in vacuo. The product was purified by flash column chroma-
tography on SiO2 gel (5% MeOH-CHCl3) to give 4.50 g (72%)
of 34 as a white solid: mp 124-125 °C; Rf 0.58 (5% MeOH-
(rel intensity) 264 (M+ + 1, 100); Mr (+CI) 264.171 77 [M+
+
1] (calcd for C14H22N3O2 264.171 20). Anal. (C14H21N3O2) C,
H, N.
Syn t h esis of N-Ben zyl-2-a cet a m id o-3-(N,N-d im et h -
yla m in o)p r op ion a m id e (24). Utilizing the procedure for 21
and using 34 (1.53 g, 7 mmol) and N,N-dimethylamine (7.0 g,
155.6 mmol) gave crude 24 after stirring at room temperature
(24 h). The residue was triturated with Et2O (100 mL) to give
a white solid, and the solid was filtered to give 1.70 g (92%) of
24: mp 125-126 °C; Rf 0.60 (10% MeOH-CHCl3); IR (KBr)
3250, 3096, 3050, 2942, 2827, 1632, 1573, 1553, 1457, 1428,
1
CHCl3); IR (KBr) 3345, 1685, 1655, 1632, 1499, 878 cm-1; H
NMR (DMSO-d6) δ 1.80 (s, C(O)CH3), 4.16 (d, J ) 5.5 Hz, CH2),
5.23 (s, CHH′), 5.81 (s, CHH′), 7.03-7.14 (m, 5 PhH), 8.70 (d,
J ) 5.5 Hz, NH), 8.92 (s, NH); 13C NMR (DMSO-d6) 24.0
(C(O)CH3), 42.6 (CH2NH), 103.4 (CH2), 126.9 (C4′), 127.3 (2C2′
or 2C3′), 128.4 (2C2′ or 2C3′), 136.3 (C), 139.4 (C1′), 164.3 (C(O)-
CH3 or C(O)NH), 169.5 (C(O)CH3 or C(O)NH) ppm; MS (+CI)
(rel intensity) 219 (M+ + 1, 100), 177 (55); Mr (+CI) 219.112 52
[M+ + 1] (calcd for C12H15N2O2, 219.113 35). Anal. (C12H14N2O2)
C, H, N.
1275, 1246, 1044, 739 cm-1 1H NMR (DMSO-d6) δ 1.83 (s,
;
C(O)CH3), 2.15 (s, N(CH3)2), 2.32-2.49 (m, CH2N(CH3)2),
4.25-4.28 (m, NHCH2), 4.36-4.44 (m, CH), 7.20-7.37 (m, 5
PhH), 7.99 (br d, J ) 7.8 Hz, NH), 8.55 (br t, J ) 5.4 Hz, NH);
13C NMR (CDCl3) 23.1 (C(O)CH3), 43.3 (CH2NH), 45.0 (N(CH3)2),
49.7 (CH), 60.5 (CH2N(CH3)2), 127.2 (C4′ or 2C2′ or 2C3′), 127.3
(C4′ or 2C2′ or 2C3′), 128.6 (C4′ or 2C2′ or 2C3′), 138.3 (C1′),
170.3 (C(O)CH3 or C(O)NH), 171.3 (C(O)CH3 or C(O)NH) ppm;
MS (+CI) (rel intensity) 264 (M+ + 1, 100); Mr (+CI) 264.171 72
[M+ + 1] (calcd for C14H22N3O2 264.171 20). Anal. (C14H21N3O2)
C, H, N.
Syn th esis of N-Ben zyl-2-a ceta m id o-3-a m in op r op ion a -
m id e (21). NH3 (2.40 g, 141 mmol) was passed into a stirred
methanolic solution (50 mL) of 34 (1.53 g, 7 mmol). The
reaction solution was stirred at room temperature (10 d), and
then the solvent was removed in vacuo. The resulting residue
was purified by flash column chromatography on SiO2 gel (30%
MeOH-CHCl3) and then further purified by recrystallization
from EtOAc to give 0.37 g (22%) of 21 as a white solid: mp
119-120 °C; Rf 0.52 (30% MeOH-CHCl3); IR (KBr) 3348,
3288, 3244, 3206, 3059, 2931, 1655, 1590, 1545, 1305, 1273,
Syn th esis of N-Ben zyl-2-a ceta m id o-3-m or p h olin op r o-
p ion a m id e (25). A morpholine (7.85 mL, 90 mmol) solution
of 34 (1.31 g, 6 mmol) was stirred at room temperature (4 d).
The excess morpholine was removed in vacuo, and the result-
ing residue was triturated with Et2O (50 mL) to give a white
solid. The solid was purified by flash column chromatography
on SiO2 gel (5% MeOH-CHCl3) and then further purified by
recrystallization from EtOAc to give 1.30 g (72%) of 25: mp
147-148 °C; Rf 0.31 (5% MeOH-CHCl3); IR (KBr) 3295, 3244,
3086, 2968, 2859, 2819, 1648, 1562, 1543, 1275, 1114, 863, 734
1179, 939, 695 cm-1 1H NMR (CDCl3) δ 2.04 (s, C(O)CH3),
;
2.70 (dd, J ) 8.1, 12.0 Hz, CHH′NH2), 3.36 (dd, J ) 2.4, 12.0
Hz, CHH′NH2), 4.28-4.34 (m, CH), 4.45 (d, J ) 6.0 Hz,
NHCH2), 6.85 (br d, J ) 5.1 Hz, NH), 7.25-7.36 (m, 5 PhH),
7.91 (br s, NH); 13C NMR (CDCl3) 22.6 (C(O)CH3), 43.0 (CH2-
NH2 or CH2Ph), 43.5 (CH2Ph or CH2NH), 54.2 (CH), 127.0
(C4′), 127.1 (2C2′ or 2C3′), 128.3 (2C2′ or 2C3′), 137.8 (C1′), 170.7
(C(O)CH3 or C(O)NH), 170.8 (C(O)CH3 or C(O)NH) ppm; MS
(+CI) (rel intensity) 236 (M+ + 1, 100), 219 (27), 218 (76); Mr
(+CI) 236.140 07 [M+ + 1] (calcd for C12H18N3O2, 236.139 90).
Anal. (C12H17N3O2) C, H, N.
cm-1 1H NMR (CDCl3) δ 2.03 (s, C(O)CH3), 2.29-2.42 (m,
;
CHH′N(CHH′CH2)2O), 2.71-2.79 (m, CHH′N(CHH′CH2)2O),
3.45-3.56 (m, N(CH2CH2)2O), 4.31 (dd, J ) 4.2, 14.4 Hz,
NHCHH′), 4.34-4.39 (m, CH), 4.58 (dd, J ) 6.3, 14.4 Hz,
NHCHH′), 6.58 (br d, J ) 3.3 Hz, NH), 7.26-7.37 (m, 5 PhH),
8.33 (br s, NH); 13C NMR (CDCl3) 23.1 (C(O)CH3), 43.6 (CH2-
NH), 48.9 (N(CH2CH2)O), 53.3 (CH), 59.7 (CH2N(CH2CH2)O),
66.8 (N(CH2CH2)O), 127.6 (C4′ or 2C2′ or 2C3′), 127.7 (C4′ or
2C2′ or 2C3′), 128.8 (C4′ or 2C2′ or 2C3′), 137.9 (C1′), 170.2
(C(O)CH3 or C(O)NH), 170.8 (C(O)CH3 or C(O)NH) ppm;
MS (+CI) (rel intensity) 306 (M+ + 1, 100); Mr (+CI) 306.181 68
[M+ + 1] (calcd for C16H24N3O3 306.181 77). Anal. (C16H23N3O3‚
0.25H2O) C, H, N.
Syn th esis of N-Ben zyl-2-a ceta m id o-3-(N-m eth yla m i-
n o)p r op ion a m id e (22). Using the preceding procedure and
34 (1.53 g, 7 mmol) and a methanolic solution of MeNH2 (2
M, 70 mL, 140 mmol) gave crude 22 after stirring at room
temperature (18 h). The resulting residue was triturated with
Et2O (50 mL) to give 1.61 g (93%) of 22 as a white solid: mp
107-108 °C; Rf 0.46 (30% MeOH-CHCl3); IR (KBr) 3376,
Syn th esis of N-Ben zyl-2-a ceta m id o-3-(m eth ylth io)p r o-
p ion a m id e (26). To a stirred methanolic solution (150 mL)
of 34 (2.18 g, 10 mmol) was added NaSMe (2.10 g, 30 mmol).
The reaction solution was stirred at room temperature (3 h).
1
3290, 3207, 2940, 2816, 1648, 1572, 1537, 753, 696 cm-1; H
NMR (CDCl3) δ 2.01 (s, C(O)CH3), 2.40 (s, NHCH3), 2.53 (dd,

1914 J ournal of Medicinal Chemistry, 1996, Vol. 39, No. 9
Choi et al.
The solvent was removed under reduced pressure, and the
residue was dissolved in a 4:1 mixture of CHCl3 and H2O (250
mL). The organic layer was dried (Na2SO4) and evaporated
in vacuo. The white residue was triturated with Et2O (200
mL) to give 2.30 g (86%) of 26: mp 142-143 °C; Rf 0.41 (10%
MeOH-CHCl3); IR (KBr) 3274, 3090, 3059, 2918, 1642, 1545,
1371, 695 cm-1; 1H NMR (CDCl3) δ 2.02 (s, C(O)CH3), 2.15 (s,
SCH3), 2.78 (dd, J ) 7.8, 13.8 Hz, CHH′SCH3), 2.90 (dd, J )
5.4, 13.8 Hz, CHH′SCH3), 4.46 (d, J ) 5.7 Hz, NHCH2), 4.52-
4.57 (m, CH), 6.56 (br d, J ) 6.6 Hz, NH), 6.93 (br s, NH),
7.26-7.36 (m, 5 PhH); 13C NMR (CDCl3) 15.8 (SCH3), 23.0
(C(O)CH3), 36.3 (CH2SCH3), 43.6 (CH2NH), 52.2 (CH), 127.4
(C4′), 127.6 (2C2′ or 2C3′), 128.6 (2C2′ or 2C3′), 137.5 (C1′), 170.3
(C(O)CH3 or C(O)NH), 170.4 (C(O)CH3 or C(O)NH) ppm; MS
(+CI) (rel intensity) 267 (M+ + 1, 100), 219 (6); Mr (+CI)
267.116 26 [M+ + 1] (calcd for C13H19N2O2S 267.116 73). Anal.
(C13H18N2O2S) C, H, N.
5 PhH), 7.96 (d, J ) 7.8 Hz, NH), 8.39 (t, J ) 5.7 Hz, NH),
addition of excess (R)-(-)-mandelic acid to a CDCl3 solution
of (S)-27 gave only one signal for the acetyl methyl protons;
13C NMR (DMSO-d6) 22.7 (C(O)CH3), 42.0 (CH2NH), 55.3 (CH),
61.7 (CH2OH), 126.6 (C4′), 126.9 (2C2′ or 2C3′), 128.1 (2C2′ or
2C3′), 139.4 (C1′), 169.4 (C(O)CH3 or C(O)NH), 170.2 (C(O)-
CH3 or C(O)NH) ppm; MS (+CI) (rel intensity) 237 (M+ + 1,
100), 219 (33); Mr (+CI) 237.124 03 [M+ + 1] (calcd for
C12H17N2O3 237.123 92). Anal. (C12H16N2O3) C, H, N.
Syn t h esis of (R)-N-Ben zyl-2-a cet a m id oh yd r a cr yl-
a m id e ((R)-27). Using the preceding procedure and enriched
(R)-37 (10.00 g, 51.5 mmol) and Ac2O (5.8 mL, 61.8 mmol) gave
7.60 g (62%) of enriched (R)-27 as a white solid. The reaction
product was recrystallized (2×) using EtOH to give 3.50 g
(29%) of (R)-27: mp 148-149 °C; [R]23 (c ) 1, MeOH) )
D
+22.4°; Rf 0.40 (10% MeOH-CHCl3); IR (KBr) 3295, 3090,
2964, 1642, 1533, 1376, 1281, 1051, 705 cm-1 1H NMR
;
Syn th esis of (S)-en r ich ed N-Ben zyl-2-a m in oh yd r a cr yl-
a m id e ((S)-37). To a stirred methanolic solution (250 mL) of
L-serine methyl ester hydrochloride ((S)-36) (20.00 g, 128
mmol) was added benzylamine (55.9 mL, 512 mmol), and then
the reaction solution was heated at reflux (18 h). The solvent
was removed under reduced pressure, the insoluble salts were
filtered, and the excess benzylamine was removed under high
vacuum (Kugelrohr). The residue was dissolved in H2O (100
mL), and the product was extracted with CHCl3 (8 × 200 mL).
The organic layers were combined and dried (Na2SO4), and
the solvent was removed under reduced pressure. The residue
was triturated with Et2O (150 mL) and filtered to give 8.50 g
(DMSO-d6) δ 1.86 (s, C(O)CH3), 3.57 (dd, J ) 5.7, 5.7 Hz, CH2-
OH), 4.25-4.31 (m, CH), 4.27 (d, J ) 5.7 Hz, NHCH2), 4.92
(t, J ) 5.7 Hz, CH2OH), 7.18-7.32 (m, 5 PhH), 7.94 (d, J )
7.8 Hz, NH), 8.38 (t, J ) 5.7 Hz, NH), addition of excess (R)-
(-)-mandelic acid to a CDCl3
solution of (R)-27 gave only one
signal for the acetyl methyl protons; 13C NMR (DMSO-d6) 22.7
(C(O)CH3), 42.0 (CH2NH), 55.6 (CH), 61.8 (CH2OH), 126.7
(C4′), 127.0 (2C2′ or 2C3′), 128.2 (2C2′ or 2C3′), 139.4 (C1′), 169.5
(C(O)CH3 or C(O)NH), 170.3 (C(O)CH3 or C(O)NH) ppm; MS
(+CI) (rel intensity) 237 (M+
+ 1, 100), 219 (8); Mr (+CI)
237.123 88 [M+
+ 1] (calcd for C12H17N2O3 237.123 92). Anal.
(C12H16N2O3) C, H, N.
(34%) of the product as a white solid: mp 76-80 °C; [R]23 (c
Syn th esis of (S)-N-Ben zyl-2-a ceta m id o-3-m eth oxyp r o-
p ion a m id e ((S)-18). To a stirred CH3CN solution (300 mL)
of (S)-27 (1.65 g, 7 mmol) were successively added Ag2O (8.11
g, 35 mmol) and MeI (4.4 mL, 70 mmol) at room temperature.
The reaction mixture was stirred at room temperature (4 d).
The insoluble salts were filtered, and the solvents were
removed in vacuo to give a white solid. The residue was
triturated with Et2O (100 mL) to give 1.40 g (80%) of (S)-18:
D
1
) 1, MeOH) ) +1.3°; Rf 0.30 (10% MeOH-CHCl3); H NMR
(DMSO-d6) δ 1.84 (br s, NH2), 3.23 (t, J ) 5.4 Hz, CH), 3.39-
3.55 (m, CH2OH), 4.28 (d, J ) 5.7 Hz, NHCH2), 4.76 (t, J )
5.4 Hz, CH2OH), 7.18-7.32 (m, 5 PhH), 8.33 (t, J ) 5.7 Hz,
NH); 13C NMR (DMSO-d6) 41.8 (NHCH2), 57.0 (CH), 64.3
(CH2OH), 126.6 (C4′), 127.0 (2C2′ or 2C3′), 128.2 (2C2′ or 2C3′),
139.5 (C1′), 179.3 (C(O)NH) ppm; MS (+CI) (rel intensity) 195
(M+ + 1, 100), 117 (30); Mr (+CI) 195.113 48 [M+ + 1] (calcd
for C10H15N2O2 195.113 35).
mp 143-144 °C; [R]23 (c ) 1, MeOH) ) -16.8°; Rf 0.47 (10%
D
MeOH-CHCl3); IR (KBr) 3289, 3086, 2923, 2876, 2806, 1636,
1
1547, 1138, 695 cm-1; H NMR (CDCl3) δ 2.04 (s, C(O)CH3),
Syn t h esis of (R)-en r ich ed N-Ben zyl-2-a m in oh yd r a c-
r yla m id e ((R)-37). HCl (8.00 g, 219.4 mmol) was passed into
MeOH (250 mL), and then D-serine ((R)-35) (20.00 g, 190.3
mmol) was added. The reaction solution was heated at reflux
(18 h), then benzylamine (81.6 mL, 761 mmol) was added, and
then the reaction mixture was heated for additional 18 h. The
solvent was removed under reduced pressure, the insoluble
salts were filtered, and the excess benzylamine was removed
under high vacuum (Kugelrohr). The residue was dissolved
in H2O (100 mL), and the product was extracted with CHCl3
(8 × 200 mL). The organic layers were combined and dried
(Na2SO4), and the solvent was removed under reduced pres-
sure. The residue was triturated with Et2O (150 mL) and
filtered to give 10.0 g (27%) of the product as a white solid:
3.38 (s, OCH3), 3.43 (dd, J ) 7.8, 9.0 Hz, CHH′OCH3), 3.82
(dd, J ) 4.2, 9.0 Hz, CHH′OCH3), 4.48 (d, J ) 6.0 Hz, CH2),
4.51-4.57 (m, CH), 6.44 (br d, J ) 5.4 Hz, NH), 6.75 (br s,
NH), 7.25-7.37 (m, 5 PhH), addition of excess (R)-(-)-mandelic
acid to a CDCl3 solution of (S)-18 gave only one signal for the
acetyl methyl and ether methyl protons; 13C NMR (CDCl3) 23.2
(C(O)CH3), 43.6 (CH2NH), 52.4 (CH), 59.1 (OCH3), 71.7 (CH2-
OCH3), 127.4 (C4′), 127.5 (2C2′ or 2C3′), 128.7 (2C2′ or 2C3′),
137.8 (C1′), 170.0 (C(O)CH3 or C(O)NH), 170.3 (C(O)CH3 or
C(O)NH) ppm; MS (+CI) (rel intensity) 251 (M+ + 1, 100), 117
(100); Mr (+CI) 251.140 50 [M+ + 1] (calcd for C13H19N2O3
251.139 57). Anal. (C13H18N2O3) C, H, N.
Syn th esis of (R)-N-Ben zyl-2-a ceta m id o-3-m eth oxyp r o-
p ion a m id e ((R)-18). Using the preceding procedure and (R)-
27 (2.36 g, 10 mmol), Ag2O (11.59 g, 50 mmol), and MeI (6.2
mL, 100 mmol) gave 2.20 g (88%) of (R)-18 after stirring at
mp 74-78 °C; [R]23 (c ) 1, MeOH) ) -1.6°; Rf 0.30 (10%
D
1
MeOH-CHCl3); H NMR (DMSO-d6) δ 1.87 (br s, NH2), 3.23
(t, J ) 5.4 Hz, CH), 3.39-3.55 (m, CH2OH), 4.28 (d, J ) 5.7
Hz, NHCH2), 4.76 (t, J ) 5.4 Hz, CH2OH), 7.18-7.32 (m, 5
PhH), 8.34 (t, J ) 5.7 Hz, NH); 13C NMR (DMSO-d6) 41.8
(NHCH2), 56.9 (CH), 64.3 (CH2OH), 126.6 (C4′), 127.0 (2C2′
or 2C3′), 128.1 (2C2′ or 2C3′), 139.5 (C1′), 173.3 (C(O)NH) ppm;
MS (+CI) (rel intensity) 195 (M+ + 1, 53), 117 (100); Mr (+CI)
195.113 56 [M+ + 1] (calcd for C10H15N2O2 195.113 35).
Syn t h esis of (S)-N-Ben zyl-2-a cet a m id oh yd r a cr yl-
a m id e ((S)-27). To a stirred CH2Cl2 suspension (100 mL) of
enriched (S)-37 (8.50 g, 43.7 mmol) was added Ac2O (5.0 mL,
52.4 mmol), and then the reaction suspension was stirred at
room temperature (1 h). The solvent was removed under
reduced pressure to give a white solid. The product was
triturated with Et2O (250 mL) to give 8.50 g (82%) of enriched
(S)-27 as a white solid. The reaction product was recrystal-
lized (3×) using EtOH to give 1.89 g (18%) of (S)-27: mp 147-
room temperature (4 d): mp 143-144 °C; [R]23
D (c ) 1, MeOH)
) +16.4°; Rf 0.47 (10% MeOH-CHCl3); IR (KBr) 3289, 3086,
2923, 2876, 2819, 1636, 1547, 1138, 695 cm-1; 1H NMR (CDCl3)
δ 2.04 (s, C(O)CH3), 3.38 (s, OCH3), 3.43 (dd, J ) 7.8, 9.0 Hz,
CHH′OCH3), 3.82 (dd, J ) 4.2, 9.0 Hz, CHH′OCH3), 4.48 (d, J
) 6.0 Hz, NHCH2), 4.51-4.57 (m, CH), 6.44 (br d, J ) 5.4 Hz,
NH), 6.75 (br s, NH), 7.25-7.37 (m, 5 PhH), addition of excess
(R)-(-)-mandelic acid to a CDCl3 solution of (R)-18 gave only
one signal for the acetyl methyl and ether methyl protons; 13
C
NMR (CDCl3) 23.2 (C(O)CH3), 43.5 (CH2NH), 52.4 (CH), 59.1
(OCH3), 71.7 (CH2OCH3), 127.4 (C4′), 127.5 (2C2′ or 2C3′),
128.7 (2C2′ or 2C3′), 137.9 (C1′), 169.9 (C(O)CH3 or C(O)NH),
170.3 (C(O)CH3 or C(O)NH) ppm; MS (+CI) (rel intensity) 251
(M+ + 1, 100), 219 (6); Mr (+CI) 251.139 76 [M+ + 1] (calcd
for C13H19N2O3 251.139 57). Anal. (C13H18N2O3) C, H, N.
Im p r oved Syn th esis of (S)-N-Ben zyl-2-a ceta m id oh y-
d r a cr yla m id e ((S)-27). To a stirred AcOH (20 mL) suspen-
sion of L-serine ((S)-35) (2.63 g, 25 mmol) was added Ac2O (2.5
mL, 26.3 mmol), and then the reaction suspension was stirred
at room temperature (24 h). The AcOH was removed in vacuo
148 °C; [R]23 (c ) 1, MeOH) ) -22.0°; Rf 0.40 (10% MeOH-
D
CHCl3); IR (KBr) 3289, 3088, 2965, 2855, 1642, 1570, 1551,
1053, 698 cm-1; 1H NMR (DMSO-d6) δ 1.86 (s, C(O)CH3), 3.57
(dd, J ) 5.7, 5.7 Hz, CH2OH), 4.26-4.31 (m, CH), 4.27 (d, J )
5.7 Hz, NHCH2), 4.94 (t, J ) 5.7 Hz, CH2OH), 7.18-7.32 (m,

N-Benzyl-2-acetamidopropionamide Derivatives
J ournal of Medicinal Chemistry, 1996, Vol. 39, No. 9 1915
to give an oily residue, and then THF (150 mL) was added to
the residue. The THF suspension was cooled to -78 °C under
N2, and 4-methylmorpholine (5.5 mL, 50 mmol) was added.
After stirring (2 min), isobutyl chloroformate (6.5 mL, 50
mmol) was added leading to the precipitation of white solid.
The reaction was allowed to proceed for an additional 2 min,
and then benzylamine (5.5 mL, 50 mmol) was added at -78
°C. The reaction mixture was allowed to stir at room tem-
perature (30 min), and then the 4-methylmorpholine hydro-
chloride salt was filtered. The organic layer was concentrated
in vacuo. The product was purified by flash column chroma-
tography on SiO2 gel (10% MeOH-CHCl3) to give 2.20 g (37%)
of (S)-27 as a white solid: mp 146-147 °C; [R]23D (c ) 1, MeOH)
[M+ + 1] (calcd for C12H16FN2O3 255.114 50). Anal. (C12H15
FN2O3‚0.2H2O) C, H, N.
-
Im p r oved Syn th esis of (S)-N-Ben zyl-2-a ceta m id o-3-
m eth oxyp r op ion a m id e ((S)-18). To a stirred CH3CN solu-
tion (300 mL) of (S)-27 (1.18 g, 5 mmol) were successively
added Ag2O (5.80 g, 25 mmol) and MeI (3.1 mL, 10 mmol) at
room temperature. The reaction mixture was stirred at room
temperature (4 d). The insoluble salts were filtered, and the
solvent was removed in vacuo to give a white solid. The white
solid was triturated with Et2O (100 mL) to give 1.00 g (80%)
of (S)-18: mp 143-144 °C; [R]23 (c ) 1, MeOH) ) -16.4°; 1H
D
NMR (CDCl3) δ 2.03 (s, C(O)CH3), 3.38 (s, OCH3), 3.43 (dd, J
) 7.5, 9.0 Hz, CHH′OCH3), 3.81 (dd, J ) 4.2, 9.0 Hz,
CHH′OCH3), 4.47 (d, J ) 5.7 Hz, NHCH2), 4.52-4.59 (m, CH),
6.48 (br d, J ) 6.0 Hz, NH), 6.81 (br s, NH), 7.25-7.37 (m, 5
PhH), addition of excess (R)-(-)-mandelic acid to a CDCl3
solution of (S)-18 gave only one signal for the acetyl methyl
and ether methyl protons.
1
) -21.5°; H NMR (DMSO-d6) δ 1.86 (s, C(O)CH3), 3.57 (dd,
J ) 5.1 Hz, 5.1 Hz, CH2O), 4.25-4.32 (m, CH2NH, CH), 4.91
(t, J ) 5.1 Hz, OH), 7.20-7.33 (m, 5 PhH), 7.93 (d, J ) 8.1
Hz, NH), 8.37 (t, J ) 5.7 Hz, NH), addition of excess (R)-
(-)-mandelic acid to a CDCl3 solution of (S)-27 gave only one
signal for the acetyl methyl protons.
Im p r oved Syn th esis of (R)-N-Ben zyl-2-a ceta m id o-3-
m eth oxyp r op ion a m id e ((R)-18). Using the preceding pro-
cedure and (R)-27 (1.42 g, 6 mmol), Ag2O (6.95 g, 30 mmol),
and MeI (3.7 mL, 60 mmol) gave 1.30 g (87%) of (R)-18 after
Im p r oved Syn th esis of (R)-N-Ben zyl-2-a ceta m id oh y-
d r a cr yla m id e ((R)-27). Using the preceding procedure and
D-serine ((R)-35) (5.26 g, 50 mmol), Ac2O (4.7 mL, 50 mmol),
4-methylmorpholine (11.0 mL, 100 mmol), isobutyl chlorofor-
mate (13.0 mL, 100 mmol), and benzylamine (10.4 mL, 100
mmol) gave 3.89 g (33%) of (R)-27 as a white solid after
stirring at room temperature (4 d): mp 143-144 °C; [R]23 (c
D
1
) 1, MeOH) ) +16.0°; H NMR (CDCl3) δ 2.04 (s, C(O)CH3),
3.38 (s, OCH3), 3.44 (dd, J ) 7.5, 9.0 Hz, CHH′OCH3), 3.81
(dd, J ) 4.2, 9.0 Hz, CHH′OCH3), 4.48 (d, J ) 5.7 Hz, NHCH2),
4.52-4.58 (m, CH), 6.46 (br d, J ) 5.7 Hz, NH), 6.78 (br s,
NH), 7.25-7.37 (m, 5 PhH), addition of excess (R)-(-)-mandelic
acid to a CDCl3 solution of (R)-18 gave only one signal for the
acetyl methyl and ether methyl protons.
purification: mp 147-148 °C; [R]23 (c ) 1, MeOH) ) +21.7°;
D
1H NMR (DMSO-d6) δ 1.86 (s, C(O)CH3), 3.57 (dd, J ) 5.1, 5.1
Hz, CH2O), 4.27-4.31 (m, CH2NH, CH), 4.90 (t, J ) 5.1 Hz,
OH), 7.20-7.31 (m, 5 PhH), 7.93 (d, J ) 8.1 Hz, NH), 8.37 (t,
J ) 6.0 Hz, NH), addition of excess (R)-(-)-mandelic acid to a
CDCl3 solution of (R)-27 gave only one signal for the acetyl
methyl protons.
Syn t h esis of (R)-N-(3-F lu or ob en zyl)-2-a cet a m id o-3-
m eth oxyp r op ion a m id e ((R)-41). Utilizing the improved
procedure for (S)-18 and using (R)-39 (2.54 g, 10 mmol), Ag2O
(11.59 g, 50 mmol), and MeI (6.2 mL, 100 mmol) gave crude
(R)-41 after stirring at room temperature (2 d). The product
was further purified by flash column chromatography on SiO2
gel (10% MeOH-CHCl3) to give 2.00 g (75%) of (R)-41: mp
Syn th esis of (R)-N-(3-F lu or oben zyl)-2-a ceta m id oh y-
d r a cr yla m id e ((R)-39). Utilizing the improved procedure for
(S)-27 and D-serine ((R)-35) (5.26 g, 50 mmol), Ac2O (5.7 mL,
60 mmol), 4-methylmorpholine (11.0 mL, 100 mmol), isobutyl
chloroformate (13.0 mL, 100 mmol), and 3-fluorobenzylamine
(11.8 mL, 100 mmol) gave 4.20 g (33%) of (R)-39 as a white
solid after purification: mp 137-138 °C; [R]23D (c ) 1, MeOH)
) +20.8°; Rf 0.32 (10% MeOH-CHCl3); IR (KBr) 3282, 3101,
2944, 1636, 1542, 1252, 1050, 779, 690 cm-1; 1H NMR (DMSO-
d6) δ 1.87 (s, C(O)CH3), 3.56-3.63 (m, CH2OH), 4.29 (d, J )
6.0 Hz, CH2NH), 4.25-4.30 (m, CH), 4.95 (t, J ) 5.4 Hz,
CH2OH), 7.00-7.09 (m, 3 ArH), 7.29-7.30 (m, 1 ArH), 7.97
(d, J ) 8.1 Hz, NH), 8.44 (t, J ) 6.0 Hz, NH), addition of excess
(R)-(-)-mandelic acid to a CDCl3 solution of (R)-39 gave only
one signal for the acetyl methyl protons; 13C NMR (DMSO-d6)
22.7 (C(O)CH3), 41.6 (CH2N), 53.4 (CH), 61.7 (CH2OH), 113.3
(d, J CF ) 20.0 Hz, C2′ or C4′), 113.6 (d, J CF ) 20.7 Hz, C2′ or
150-151 °C; [R]23 (c ) 1, MeOH) ) +16.5°; Rf 0.50 (10%
D
MeOH-CHCl3); IR (KBr) 3287, 3072, 2928, 2883, 1634, 1548,
1
1256, 1142, 785 cm-1; H NMR (CDCl3) δ 2.05 (s, C(O)CH3),
3.40 (s, OCH3), 3.44-3.47 (m, CHH′OCH3), 3.81-3.85 (m,
CHH′OCH3), 4.41-4.50 (m, NHCH2), 4.53-4.59 (m, CH), 6.42
(br s, NH), 6.81 (br s, NH), 6.93-7.05 (m, 3 PhH), 7.26-7.31
(m, 1 PhH), addition of excess (R)-(-)-mandelic acid to a CDCl3
solution of (R)-41 gave only one signal for the acetyl methyl
protons and ether methyl protons; 13C NMR (DMSO-d6) 22.8
(C(O)CH3), 42.7 (CH2N), 52.6 (CH), 58.9 (OCH3), 72.0 (CH2-
OCH3), 114.0 (d, J CF ) 21.5 Hz, C2′ and C4′), 122.7 (C6′), 129.9
(d, J CF ) 7.7 Hz, C5′), 140.6 (d, J CF ) 6.8 Hz, C1′), 162.9 (d, J CF
) 244.4 Hz, C3′), 170.2 (C(O)CH3 or C(O)NH), 170.5 (C(O)-
CH3 or C(O)NH) ppm; MS (+CI) (rel intensity) 269 (M+ + 1,
100); Mr (+CI) 269.129 31 [M+ + 1] (calcd for C13H18FN2O3
269.130 15). Anal. (C13H17FN2O3) C, H, N.
C4′), 122.9 (C6′), 130.1 (d, J CF ) 8.2 Hz, C5′), 142.6 (d, J CF
)
7.0 Hz, C1′), 162.3 (d, J CF ) 241.4 Hz, C3′), 169.6 (C(O)CH3 or
C(O)NH), 170.5 (C(O)CH3 or C(O)NH) ppm; MS (+CI) (rel
intensity) 255 (M+ + 1, 100); Mr (+CI) 255.113 54 [M+ + 1]
(calcd for C12H16FN2O3 255.114 50). Anal. (C12H15FN2O3) C,
H, N.
Syn t h esis of (R)-N-(4-F lu or ob en zyl)-2-a cet a m id o-3-
m eth oxyp r op ion a m id e ((R)-42). Utilizing the improved
procedure for (S)-18 and using (R)-40 (2.54 g, 10 mmol),
Ag2O (11.59 g, 50 mmol), and MeI (6.2 mL, 100 mmol) gave
crude (R)-42 after stirring at room temperature (7 d). The
product was further purified by flash column chromatogra-
phy (10% MeOH-CHCl3) to give 2.00 g (75%) of (R)-42: mp
Syn th esis of (R)-N-(4-F lu or oben zyl)-2-a ceta m id oh y-
d r a cr yla m id e ((R)-40). Utilizing the improved procedure for
(S)-27 and D-serine ((R)-35) (5.26 g, 50 mmol), Ac2O (5.7 mL,
60 mmol), 4-methylmorpholine (11.0 mL, 100 mmol), isobutyl
chloroformate (13.0 mL, 100 mmol), and 4-fluorobenzylamine
(11.8 mL, 100 mmol) gave 4.08 g (32%) of (R)-40 as a white
solid after purification: mp 169-170 °C; [R]23D (c ) 1, MeOH)
) +17.6°; Rf 0.31 (10% MeOH-CHCl3); IR (KBr) 3289, 3101,
3071, 2936, 1632, 1565, 1543, 1508, 1214, 1053, 814 cm-1; 1H
NMR (DMSO-d6) δ 1.86 (s, C(O)CH3), 3.56 (t, J ) 5.4 Hz, CH2-
OH), 4.25 (d, J ) 6.0 Hz, CH2NH), 4.25-4.29 (m, CH), 4.91
(t, J ) 5.4 Hz, CH2OH), 7.08-7.14 (m, 2C2′H), 7.25-7.29 (m,
2C3′H), 7.93 (d, J ) 7.8 Hz, NH), 8.39 (d, J ) 6.0 Hz, NH),
addition of excess (R)-(-)-mandelic acid to a CDCl3 solution
of (R)-40 gave only one signal for the acetyl methyl protons;
13C NMR (DMSO-d6) 22.7 (C(O)CH3), 41.3 (CH2N), 55.3 (CH),
144-145 °C; [R]23 (c ) 1, MeOH) ) +12.0°; Rf 0.52 (10%
D
MeOH-CHCl3); IR (KBr) 3281, 3102, 3072, 2959, 1632, 1547,
1513, 1223, 1100 cm-1; 1H NMR (CDCl3) δ 2.04 (s, C(O)CH3),
3.38 (s, OCH3), 3.39-3.46 (m, CHH′OCH3), 3.80-3.84 (m,
CHH′OCH3), 4.44 (br d, J ) 5.4 Hz, CH2NH), 4.48-4.56 (m,
CH), 6.42 (br s, NH), 6.76 (br s, NH), 6.99-7.05 (m, 2 PhH),
7.21-7.31 (m, 2 PhH), addition of excess (R)-(-)-mandelic acid
to a CDCl3 solution of (R)-42 gave only one signal for the acetyl
methyl protons and ether methyl protons; 13C NMR (CDCl3)
22.9 (C(O)CH3), 42.6 (CH2N), 52.5 (CH), 58.9 (OCH3), 72.0
(CH2OCH3), 115.3 (d, J CF ) 22.0 Hz, 2C3′), 129.0 (d, J CF ) 6.9
Hz, 2C2′), 133.7 (C1′), 161.9 (d, J CF ) 245.3 Hz, C4′), 170.1-
(C(O)CH3 or C(O)NH), 170.4 (C(O)CH3 or C(O)NH) ppm; MS
(+CI) (rel intensity) 269 (M+ + 1, 100); Mr (+CI) 269.129 66
61.7 (CH2OH), 114.8 (d, J CF ) 21.8 Hz, 2C3′), 128.9 (d, J CF
)
8.0 Hz, 2C2′), 135.6 (C1′), 161.1 (d, J CF ) 240.1 Hz, C4′), 169.4
(C(O)CH3 or C(O)NH), 170.3 (C(O)CH3 or C(O)NH) ppm; MS
(+CI) (rel intensity) 255 (M+ + 1, 100); Mr (+CI) 255.113 60
[M+ + 1] (calcd for C13H18FN2O3 269.130 15). Anal. (C13H17
FN2O3) C, H, N.
-

1916 J ournal of Medicinal Chemistry, 1996, Vol. 39, No. 9
Choi et al.
(8) Kohn, H.; Sawhney, K. N.; Robertson, D. W.; Leander, J . D.
Anticonvulsant Properties of N-Substituted R,R-Diamino Acid
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Activities of R-Acetamido-N-benzylacetamide Derivatives Con-
taining an Electron-deficient R-Heteroaromatic Substituent. J .
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P h a r m a cology. Compounds were screened under the
auspices of the National Institutes of Health for anticonvulsant
activity in both male albino Carthworth Farms No. 1 mice (ip
route) and male albino Sprague Dawley rats (oral (po) route).
All of the compounds were administered in suspensions of 0.5%
(w/v) of methylcellulose in water. The volumes are 0.01 mL/g
of body weight and 0.04 mL/10 g of body weight for mice and
rats, respectively. Activity was established using the electrical
(maximal electroshock or MES) test.25 In the MES test, a drop
of electrolyte solution with anesthetic (0.5% butacaine hemisul-
fate in 0.9% sodium chloride) was used in the eyes of the
animals prior to positioning the corneal electrodes and delivery
of current. A 60-cycle alternating current was administered
for 0.2 s in both species, 50 mA in mice and 150 mA in rats.26
Protection endpoints were defined as the abolition of the hind
limb tonic extensor component of the induced seizure. In mice,
effects of compounds on forced spontaneous motor activity were
determined using the rotorod test. The inability of animals
to maintain their balance for 1 min on a 1 in. diameter knurled
rod rotating at 6 rpm in three successive trials demonstrated
motor impairment. Normally under these conditions, a mouse
can maintain its balance indefinitely. In rats, motor impair-
ment is assessed by observing for overt evidence of ataxia,
abnormal gait and stance, and/or loss of placing response and
muscle tone. In the mouse identification screening study all
compounds were given at three dose levels (30, 100, and 300
mg/kg) and two time periods (0.5 and 4 h). Typically, in the
MES seizures test one animal was used at 30 and 300 mg/kg,
and three animals at 100 mg/kg. In the rotorod toxicity test
four animals were used at 30 and 300 mg/kg, and eight
animals at 100 mg/kg (Tables 1 and 3).
The quantitative determination of the median effective
(ED50) and toxic doses (TD50) were conducted at previously
calculated times of peak effect. Groups of at least eight
animals were tested using different doses of test compound
until at least two points were determined between 100 and
0% protection and minimal motor impairment. The dose of
candidate substance required to produce the defined endpoint
in 50% of the animals in each test, and the 95% confidence
interval were calculated by a computer program based on
methods described by Finney.27
(18) For a preliminary account of this transformation, see: Choi, D.;
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, Nâ Chemodifferentiated R, â-Diaminopro-
Preparation of a NR
pionic Ester through Michael Addition onto a Dehydroalanine
Derivative. J . Org. Chem. 1986, 51, 249-251. (b) Gulzar, M. S.;
Morris, K. B.; Gani, D. Control of the Regioselectivity of
N-Nucleophile Addition to N-Carbonyl Protected Dehydro-
alanines: a Model for the Ammonia-lyase Enzymes. J . Chem.
Soc., Chem. Commun. 1995, 1061-1062.
Ack n ow led gm en t. We thank Dr. Harvey Kupfer-
berg and the Anticonvulsant Screening Project (ASP)
of the National Institute of Neurological and Com-
munication Disorders and Stroke at the National In-
stitutes of Health for kindly performing the pharmaco-
logical studies and Dr. J . David Leander (Eli Lilly Co.,
Indianapolis, IN) for conducting the earlier pharmaco-
logical evaluation of 8-10 and 27. Funds for this
project were provided in part by the State of Texas
Advanced Technology Program.
(20) For comparable procedures for resolving stereoisomers, see: (a)
Weisman, G. R. In Asymmetric SynthesissAnalytical Methods;
Morrison, J . D., Ed.; Academic Press: New York, 1983; Vol. 1,
pp 153-171. (b) Dyllick-Brenzinger, R.; Roberts, J . D. Chiral
Recognition by 15N NMR Spectroscopy. 8-Benzyl-5,6,7,8-tetrahy-
droquinoline. J . Am. Chem. Soc. 1980, 102, 1166-1167. (c)
Parker, D.; Taylor, R. J . Direct 1H NMR Assay of the Enantio-
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O-Acetyl Mandelic Acid as a Chiral Solvating Agent. Tetrahedron
1987, 43, 5431-5456.
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(24) Coughenor, L. L.; McLean, R. R.; Parker, R. R. A New Device
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(26) Woodbury, L. A.; Davenport, V. D. Design and Use of a New
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