Synthesis and anticonvulsant activities of (R)-N-(4′-substituted) benzyl 2-acetamido-3-methoxypropionamides

Article abstract of DOI:10.1021/jm901563p

The structure-activity relationship (SAR) for the N-benzyl group in the clinical antiepileptic agent (R)-lacosamide [(R)-N-benzyl 2-acetamido-3- methoxypropionamide, (R)-3] has been explored. Forty-three compounds were prepared and then evaluated at the National Institute of Neurological Disorders and Stroke Anticonvulsant Screening Program for seizure protection in the maximal electroshock (MES) and subcutaneous Metrazol models. Comparing activities for two series of substituted aryl regioisomers (2′, 3′, 4′) showed that 4′-modified derivatives had the highest activity. Significantly, structural latitude existed at the 4′-site. The SAR indicated that nonbulky 4′-substituted (R)-3 derivatives exhibited superb activity, independent of their electronic properties. Activities in the MES test of several compounds were comparable with or exceeded that of (R)-3 and surpassed the activities observed for the traditional antiepileptic agents phenytoin, phenobarbital, and valproate. 2009 American Chemical Society.

Full text of DOI:10.1021/jm901563p

1288 J. Med. Chem. 2010, 53, 1288–1305
DOI: 10.1021/jm901563p
Synthesis and Anticonvulsant Activities of (R)-N-(40-Substituted)benzyl
2-Acetamido-3-methoxypropionamides
†
†
†
†
ꢀ †
ꢀ
Christophe Salome, Elise Salome-Grosjean, Ki Duk Park, Pierre Morieux, Robert Swendiman,
Erica DeMarco,† James P. Stables,‡ and Harold Kohn*,†,§
†Division of Medicinal Chemistry and Natural Products, University of North Carolina Eshelman School of Pharmacy, University of North
Carolina, Chapel Hill, North Carolina 27599-7568, ‡Epilepsy Branch, National Institute of Neurological Disorders and Stroke, National Institutes
of Health, 6001 Executive Boulevard, Suite 2106, Rockville, Maryland 20892, and Department of Chemistry, University of North Carolina,
§
Chapel Hill, North Carolina 27599-3290
Received October 21, 2009
The structure-activity relationship (SAR) for the N-benzyl group in the clinical antiepileptic agent (R)-
lacosamide [(R)-N-benzyl 2-acetamido-3-methoxypropionamide, (R)-3] has been explored. Forty-three
compounds were prepared and then evaluated at the National Institute of Neurological Disorders and
Stroke Anticonvulsant Screening Program for seizure protection in the maximal electroshock (MES)
and subcutaneous Metrazol models. Comparing activities for two series of substituted aryl regioisomers
(20, 30, 40) showed that 40-modified derivatives had the highest activity. Significantly, structural latitude
existed at the 40-site. The SAR indicated that nonbulky 40-substituted (R)-3 derivatives exhibited superb
activity, independent of their electronic properties. Activities in the MES test of several compounds were
comparable with or exceeded that of (R)-3 and surpassed the activities observed for the traditional
antiepileptic agents phenytoin, phenobarbital, and valproate.
the newlysynthesizedmolecules wasevaluatedforactivityand
toxicity in a series of in vivo animal models. Reports from our
investigations have led other researchers to further pursue the
pharmacological benefits of FAAs.19 Most sites in 1 (e.g., R1,
R2, and R3) have been modified. We learned that acetyl
[CH3C(O)] exhibited the highest anticonvulsant activity in
an induced rodent seizure model [maximal electroshock
(MES)] for R1. The MES test is a well-established, commonly
used animal model for identifying new drug candidates having
potential human efficacy to treat generalized and partial
seizures that are secondarily generalized. We also determined
that the optimal R3 substituent was a benzyl (PhCH2)-type
moiety. Finally, isoelectronic substitution of the amide car-
bonyl (site a) with a thiocarbonyl group, insertion of an alkyl
unit or deletion of the chiral center in 1 (site b), and replace-
ment of the amide hydrogen with an alkyl group (site c)
reduced anticonvulsant activity.9-18
Epilepsy, a major neurological disorder that affects all
populations,1 describes the types of recurrent seizures pro-
duced by paroxysmal, excessive, synchronous neuronal dis-
charges in the brain.2,3 In the United States alone, more than
2 million people suffer from epilepsy and its sequelae; 340000
are children.4 For many of these individuals, the disabilities
and associated neuropsychological and behavioral factors
adversely affect their quality of life. The lifestyle restrictions
and the large expense for treatment, lost productivity, and
rehabilitation result in a huge cost to society.4
The treatment mainstayfor patientswithepileptic disorders
has been the long-term and consistent administration of
anticonvulsant drugs.5,6 Unfortunately, current medications
are ineffective for approximately one-third of these patients.7
Many continue to have seizures, while others experience
disturbing side effects (e.g., drowsiness, dizziness, nausea,
and liver damage).8 Thus, there is a need for more efficacious
drugs that function by different pharmacological pathways.
In 1985, we discovered a novel class of anticonvulsant
agents, termed functionalized amino acids (FAAs,a 1).9 We
subsequently synthesized more than 250 FAAs.10-18 Each of
*To whom correspondence should be addressed: Division of Medic-
inal Chemistry and Natural Products, UNC Eshelman School of
Pharmacy, University of North Carolina, Chapel Hill, NC 27599-
7568, and Department of Chemistry, University of North Carolina,
Chapel Hill, NC 27599-3290. E-mail: hkohn@email.unc.edu. Tele-
phone: (919) 843-8112. Fax: (919) 966-0204.
a Abbreviations: FAA, functionalized amino acid; MES, maximal
electroshock seizure; SAR, structure-activity relationship; AB, affinity
bait; CR, chemical reporter; IBCF, isobutyl chloroformate; NMM, N-
methylmorpholine; DMTMM, 4-(4,6-dimethoxy-1,3,5-triazin-2-yl)-4-
methylmorpholinium chloride; NINDS, National Institute of Neurolo-
gical Disorders and Stroke; ASP, Anticonvulsant Screening Program;
The stringent structural requirements for 1 (R1, R3, sites
a-c) led us to focus on molecular template 2. We observed
impressive anticonvulsant activities in both mice and rats for
smaller R2 groups (e.g., 2-furanyl, 2-pyrrolyl, 1-pyrazolyl, 2-
oxazolyl, 2-thiazolyl, 2-pyridyl, 2-pyrimidyl, 2-pyrazinyl, O-
methylhydroxylamino, and N,O-dimethylhydroxylamino)
that contained a substituted heteroatom, that is, one atom
removed from the C(2) chiral atom.13-16,18 These compounds
exhibited activity in the MES-induced seizure test (mice, ip)
that were comparable with or exceeded that of the standard
ip, intraperitoneally; po, orally; ED50, effective dose (50%); TD50
,
neurological impairment (toxicity, 50%); PI, protective index; scMet,
subcutaneous Metrazol.
r
pubs.acs.org/jmc
Published on Web 12/30/2009
2009 American Chemical Society

Article
Journal of Medicinal Chemistry, 2010, Vol. 53, No. 3 1289
Table 1. Effect of Site of N-Benzyl Substitution on the Anticonvulsant Activities of (R)-N-(4-Substituted)benzyl 2-Acetamido-3-methoxypropionamide
Derivativesa
mice (ip)b
Tox,e TD50
rats (po)c
Tox,g TD50
aryl
site
no.
(R)-3h
(R)-4
R4
mp (°C)
MES,d ED50
PIf
MES,d ED50
PIf
H
143-144 4.5 [0.5] (3.7-5.5)
173-175 >10, <30 [0.5]
150-151 6.9 [0.25] (6.1-8.0)
144-145 4.2 [0.5] (3.5-5.1)
130-131 >30, <100 [0.25]
147-148 >10, <30 [0.5]
134-135 3.6 [0.25] (3.0-4.3)
9.5 [2] (8.1-10)
27 [0.25] (26-28)
>100, <300 [0.5]
46 [0.25] (40-55)
28 [0.25] (22-34)
>100, <300 [0.5]
>30, <100 [0.5]
13 [0.25] (9.2-19)
66 [2] (53-72)
6.0 3.9 [2] (2.6-6.2)
11 [0.25] (9.5-13)
6.7 6.9 [0.5] (4.3-9.9)
6.7 2.6 [2] (1.9-3.6)
23 [0.25] (16-35)
>500 [0.5]
>30 [0.5]
>400
>130
F
20
30
40
20
30
40
>2.7
(R)-5h
F
>58
>48
>22
(R)-6h
(R)-7
(R)-8
F
>125, <250
>500
OCF3
OCF3
OCF3
(R)-9
3.6 1.7 [0.5] (1.4-2.2)
6.9 30 [4] (22-39)
3.2 9.1 [5] (7.6-12)
63 [0.5] (47-76)
j
37
>100
phenytoini
phenobarbitali
valproatei
22 [1] (15-23)
69 [0.5] (63-73)
61 [0.5] (44-96)
6.7
0.6
270 [0.25] (250-340) 430 [0.25] (370-450) 1.6 490 [0.5] (350-730) 280 [0.5] (190-350)
a The compounds were tested through the auspices of the NINDS ASP. b The compounds were administered intraperitoneally. ED50 and TD50 values
are in milligrams per kilogram. c The compounds were administered orally. ED50 and TD50 values are in milligrams per kilogram. d MES, maximal
electroshock seizure test. e TD50 value determined from the rotorod test. f PI, protective index (TD50/ED50). g Tox, behavioral toxicity. h From ref 18.
i From ref 34. j No ataxia observed up to 3000 mg/kg.
antiepileptic agent phenytoin (MES ED50 = 9.5 mg/kg) in the
MES-induced seizure test.20
diminished anticonvulsant profiles.15,26,27 When the 40-sub-
stituted 2 compounds were compared with the 30-substituted
isomers, the 40-substituted derivatives provided significantly
greater seizure protection as defined in the rodent MES
seizure model.18,26 To confirm this finding, we prepared
two different series of compounds in which we placed
the N-benzyl amide substituent at either the 40- or 30-site
(Table 1). In addition, we prepared the 20-regioisomer. The
fluoro [(R)-4-(R)-6] and the trifluoromethoxy [(R)-7-(R)-9]
substituents were selected for this study. In both series,
the order of favorable anticonvulsant activity in the MES
test (mice, ip) was as follows: 40 > 30 > 20 (see Pharmaco-
logical Activity). Accordingly, we focused our SAR study on
the 40-position in (R)-3.
Table 2 lists the prepared N-(40-substituted)benzyl (R)-3
derivatives [(R)-6 and (R)-9-(R)-39]. The first set of com-
pounds contained a hydrocarbon group attached at the 40-
benzyl site. We determined the effect of the structural size of
the N-benzyl 40-substituent on (R)-3 anticonvulsant activity
by preparing alkyl derivatives (R)-10-(R)-14. Next, the
effect of a two-carbon hydrocarbon substituent at the
40-site shape was evaluated by systematically changing it
from tetrahedral (sp3) [(R)-11] to planar (sp2) [(R)-21] to
linear (sp) [(R)-2324]. Then, to gauge the importance of
size, electronic effects, hydrophobic interactions, and hydro-
gen bonding interactions on anticonvulsant activity, we
synthesized 40-substituted hydrocarbon derivatives (R)-15-
(R)-20, (R)-22, and (R)-24-(R)-27 in which additional
groups were appended to the hydrocarbon moiety. A second
set of compounds prepared were N-(40-substituted)benzyl
(R)-3 analogues, (R)-6, (R)-9, and (R)-28-(R)-39, that
contained a substituent directly attached to the N-benzyl
moiety that either could withdraw or could donate elec-
trons to the aromatic ring. Here, we synthesized the
cyano [(R)-28], aldehyde [(R)-29], carboxylic acid [(R)-30],
methyl ester [(R)-31], nitrogen-substituted [(R)-32-(R)-34],
oxygen-containing [(R)-9 and (R)-35], halogen-substituted
[(R)-6 and (R)-36-(R)-38], and sulfamide [(R)-39] (R)-3
analogues.
A single 1 structure-activity relationship (SAR) feature
dominated all others. We demonstrated that the principal
anticonvulsant activity of the test candidate resided in the D-
amino acid configuration.11-13,18 The potency ratio of the
more active to the less active isomer21 ranged from 10 to >22.
These differences are among the highest, if not the highest,
reported for MES-selective anticonvulsants.
(R)-Lacosamide[(R)-3,(R)-N-benzyl 2-acetamido-3-methoxy-
propionamide18] emerged as the lead compound, 1, and has
been successfully marketed in the United States and Europe for
the adjunctive treatment of partial-onset seizures in adults.22
Whole animal pharmacology studies have revealed a distinctive
profile for (R)-3 and other 2s.11-18,23 Accordingly, we have
used agents containing “affinity bait” (AB) and “chemical repor-
ter” (CR) groups to initiate a chemical biology-based study
to search the brain proteome for (R)-3 binding targets.24
The AB moiety is designed to irreversibly react with the target,
and the CR group permits protein detection and capture.
In an effort to facilitate these studies, we have determined
the SAR for the C(2) side chain oxygen substituent in (R)-325
that identifes the structural parameters for the AB and CR
moieties at this site. We report herein that substitution at the
N-benzyl 40-position in (R)-3 provided compounds that exhibit
superb anticonvulsant activities and safety profiles. This finding
was surprising since preliminary studies with other 2s suggested
that substitutions made at this specific site were not very promising
candidates.15,26,27
Results and Discussion
Choice of Compounds. Earlier studies of 2 indicated
that substituting an N-benzyl group led to compounds with

1290 Journal of Medicinal Chemistry, 2010, Vol. 53, No. 3
Salomeꢀ et al.
Table 2. Selected Physical and Pharmacological Data for (R)-N-(4-Substituted)benzyl 2-Acetamido-3-methoxypropionamide Derivativesa
mice (ip)b
Tox,e TD50
rats (po)c
Tox,g TD50
>500 [0.5]
8.1 [0.25] (5.6-10) >500
no.
(R)-3h
R4
mp (°C)
MES,d ED50
PIf
MES,d ED50
PIf
H
CH3
143-144 4.5 [0.5] (3.7-5.5)
128-129 11 [0.25] (7.3-15)
132-133 >10, <30 [0.5]
126-127 8.5 [0.25] (6.4-10)
27 [0.25] (26-28)
31 [0.25] (22-38)
>30, <100 [0.5]
13 [0.5] (12-15)
>100, <300 [0.5]
>100, <300 [0.5]
>300 [0.5]
6.0 3.9 [2] (2.6-6.2)
3
>130
>62
>14
(R)-10
(R)-11
(R)-12
(R)-13
(R)-14
(R)-15
(R)-16
(R)-17
(R)-18
(R)-19
(R)-20
(R)-21
(R)-22
(R)-23i
(R)-24
(R)-25
(R)-26
(R)-27
(R)-28
(R)-29
(R)-30
(R)-31
(R)-32
(R)-33
(R)-34
(R)-35
(R)-9
CH2CH3
18 [0.25] (13-22)
>250
(CH2)2CH3
CH(CH3)2
C(CH3)3
1.5 <30 [0.25-0.5]
>30 [0.25-4.0]
>30 [0.25-4.0]
>30 [0.25-4.0]
>30 [0.25-4.0]
95-97
125-126 >100, <300 [0.5]
>300 [0.5]
CH2NH-t-Boc 153-154 >300 [0.5]
>10, <30 [0.5]
>30 [0.25-4.0]
CH2NH2 HCl >210
3
>300 [0.5]
CH2OCH3
CF3
119-120 73 [0.25] (62-88)
160-161 >10, <30 [0.5]
180 [0.25] (160-210)
>100, <300 [0.5]
>300 [0.5]
2.3 45 [0.5] (29-76)
4.9 [1] (2.7-7.6)
>500 [0.25-4.0]
>280
>11
>57
(CH2)3OH
(CH2)3OCH3
CHdCH2
C6H5
118
>300 [0.5]
105-107 20 [0.25] (18-23)
62 [0.25] (57-74)
148-149 3.5 [0.25] (2.8-4.6) 16 [0.25] (11-19)
3.1 16 [0.5] (8.8-25)
4.6 7.6 [0.5] (2.9-12)
>500 [0.5-4.0]
>150, <225
>32
>20
>25
>74
178-180 8.0 [0.5] (5.3-12)
161-162 >3, <10 [0.5]
178-180 >10, <30 [0.5]
11 [0.5]
2.0 [0.5] (0.8-3.4) 49 [0.5] (34-77)
3.4 [0.5] (2.0-6.1) >250
CtCH
CtC-CH3
CtC-C(CH3)3 120-121 >300
CtC-Si(CH3)3 126-127 >3 [0.5]
CtCCH2OCH3 141-142 10 [0.25] (7.7-12)
>10, <30 [0.5]
>30, <100 [0.5]
>30, <100 [0.5]
>3, <10 [0.5]
15 [0.25] (13-17)
1.5 18 [1] (8.6-33)
>3.3 >30
100 [0.5] (86-120)
>30
5.5
CN
168-169 150 [1.0] (140-170) >500
C(H)O
CO2H
CO2CH3
NH2
132-133 >300
>300
197-198 >300 [0.5]
167-168 >100, <300
151-152 >300 [0.5]
>300 [0.5]
>300 [0.5]
>300 [0.5]
>100, <300 [0.5]
46
N(H)C(O)CF3 202-204 >300 [0.5]
>30
>30
N3
OCH3
OCF3
149-150 8.4 [0.25] (5.7-12)
146-147 >30, <100 [0.5]
5.5 3.9 [0.5] (2.5-6.2) >250
>64
>18
37
>100, <300 [0.5]
28 [0.5] (21-35)
>500 [0.25-4.0]
134-135 3.6 [0.25] (3.0-4.3) 13 [0.25] (9.2-19)
144-145 4.2 [0.25] (3.5-5.1) 28 [0.25] (22-34)
3.6 1.7 [0.5] (1.4-2.2) 63 [0.5] (48-76)
(R)-6h
F
Cl
6.7 2.6 [2] (1.9-3.6)
>125, <250
>48
>200
61
(R)-36
(R)-37
(R)-38
(R)-39
phenytoin j
phenobarbital j
valproate j
155
5.0 [0.25] (4.4-5.6) 28 [0.25] (22-33)
5.6 1.0 [0.5] (0.4-1.8) >200
3.5 4.9 [0.5] (3.0-7.2) 300 [0.25] (220-350)
2.6 12 [0.25] (7.0-19) >500 [0.25-4.0]
Br
I
SO2NH2
159-161 8.7 [0.25] (7.2-10)
159-160 16 [0.25] (14-18)
177-179 >300 [0.5]
9.5 [2] (8.1-10)
30 [0.25] (24-36)
41 [0.25] (28-58)
>300 [0.5]
>43
66 [2] (53-72)
69 [0.5] (63-73)
270 [0.25] (250-340) 430 [0.25] (370-450)
6.9 30 [4] (22-39)
3.2 9.1 [5] (7.6-12)
k
>100
22 [1] (15-23)
61 [0.5] (44-96)
6.7
0.6
1.6 490 [0.5] (350-730) 280 [0.5] (190-350)
a The compounds were tested through the auspices of the NINDS ASP. b The compounds were administered intraperitoneally. ED50 and TD50 values
are in milligrams per kilogram. c The compounds were administered orally. ED50 and TD50 values are in milligrams per kilogram. d MES, maximal
electroshock seizure test. e TD50 value determined from the rotorod test. f PI, protective index (TD50/ED50). g Tox, behavioral toxicity. h From ref 18.
i From ref 24. j From ref 34. k No ataxia observed up to 3000 mg/kg.
Finally, for eight N-(40-substituted)benzyl (R)-3 deriva-
tives, we prepared the corresponding (S)-stereoisomer
(Table 3). Structural characterization of the (S)-derivatives
[(S)-11, (S)-21, (S)-23, (S)-26, (S)-28, (S)-29, (S)-34, and (S)-
38] confirmed that the syntheses routinely gave stereospecific
products. Determining their pharmacological evaluation
permitted us to verify that the principal activity for the
N-(40-substituted)benzyl 2-acetamido-3-methoxypropiona-
mides resided in the (R)-stereoisomer (D-configuration).
Chemistry. Synthesis of (R)-4-(R)-39 followed a standard
protocol (Scheme 1). Beginning with either N-t-Boc (40)- or
N-Cbz (41)-protected D-serine, the acid was coupled with the
N-(40-substituted)benzylamine 42, using either the mixed
anhydride [isobutyl chloroformate (IBCF) and N-methyl-
morpholine (NMM)]28a or the 4-(4,6-dimethoxy-1,3,5-tria-
zin-2-yl)-4-methylmorpholinium chloride (DMTMM)28b
procedure to give amide 43 or 44, respectively. The 40-
substituted benzyl amine was either commercially available
or synthesized using previously reported methods (see the
Supporting Information). We observed that amide coupling
proceeded with no racemization of the C(2) chiral center.
After purification, methylation of the serine hydroxy group
with CH3I and Ag2O provided the optically pure ethers
45 and 46. Removing the N-protecting group (i.e., acid,
H2/Pd-C) followed by acetylation (acetyl chloride, Et3N)
gave the desired N-(40-substituted)benzyl (R)-3 derivative 47,
in most cases.
For the (R)-stereoisomers of 12, 15, 19, 20, 23-27, 29, 30,
and 32-34, additional steps were required to generate the
sought-after compound. 40-Iodo derivative (R)-38 served as a
precursor to (R)-12 and (R)-23-(R)-27 (Scheme 2). Using
Sonogashira coupling conditions [CuI, PdCl2(PPh3)2, and

Article
Journal of Medicinal Chemistry, 2010, Vol. 53, No. 3 1291
Table 3. Effect of C(2) (S)-Stereochemistry on the Anticonvulsant Activities of (4-Substituted)benzyl Analogues of N-Benzyl 2-Acetamido-
3-methoxypropionamide Derivativesa
mice (ip)b
Tox,e TD50
rats (po)c
Tox,g TD50
no.
(S)-3h
(S)-11
R4
mp (°C)
MES,d ED50
PIf
MES,d ED50
>30
PIf
H
143-144 >100, <300
132-133 >100, <300 [0.5]
140-142 >100, <300 [0.5]
159-160 >300
>300
>30
>30 [0.25-4]
CH2CH3
CHdCH2
CtCH
>100, <300 [0.5]
>300
>300
>30 [0.25-4]
(S)-21
(S)-23i
(S)-26
CtC- Si(CH3)3 126-127 >30, <100 [0.5]
>100, <300 [0.5]
>300 [0.5]
>300
>30
>30
>30
>30
(S)-28
(S)-29
(S)-34
CN
C(H)O
N3
168-169 >100, <300 [0.5]
132-133 >300
149-150 >100, <300
159-160 >100, <300 [0.5]
9.5 [2] (8.1-10)
>300
>300
>30
>30
>30
>30
(S)-38
I
phenytoinj
phenobarbitalj
valproatej
66 [2] (53-72)
69 [0.5] (63-73)
6.9 30 [4] (22-39)
3.2 9.1 [5] (7.6-12)
k
>100
22 [1] (15-23)
61 [0.5] (44-96)
6.7
0.6
270 [0.25] (250-340) 430 [0.25] (370-450) 1.6 490 [0.5] (350-730) 280 [0.5] (190-350)
a The compounds were tested through the auspices of the NINDS ASP. b The compounds were administered intraperitoneally. ED50 and TD50 values
are in milligrams per kilogram. c The compounds were administered orally. ED50 and TD50 values are in milligrams per kilogram. d MES, maximal
electroshock seizure test. e TD50 value determined from the rotorod test. f PI, protective index (TD50/ED50). g Tox, behavioral toxicity. h From ref 18.
i From ref 24. j From ref 34. k No ataxia observed up to 3000 mg/kg.
Scheme 1. General Procedure for the Preparation of (R)- and (S)-N-(40-Substituted)benzyl 2-Acetamido-3-methoxypropionamide
Derivatives
Scheme 2. Sonogashira Coupling of Compound 38 To Give Derivatives 12 and 23-27
alkyne],29 (R)-38 was treated with 1-propyne, 3,3-dimethyl-
but-1-yne, trimethylsilylacetylene, and 3-methoxyprop-1-yne
to give alkynes (R)-24-(R)-27, respectively. In most cases,
the Pd-based impurities were removed from the coupled

1292 Journal of Medicinal Chemistry, 2010, Vol. 53, No. 3
Salomeꢀ et al.
Scheme 3. Catalytic Reduction Procedures for Preparing Compounds 20, 32, and 33
Scheme 4. Preparation of Compounds (R)-34 and (S)-34
Scheme 5. Deprotection Procedures Used To Prepare Compounds 15, 29, and 30
products with a scavenger resin (PhosPhonics, catalog no.
SPM32). Treating (R)-26 with TBAF gave the parent acet-
ylene (R)-23, while hydrogenation (PtO2) of (R)-24 gave
(R)-12. Catalytic reduction (PtO2, H2) of (R)-27 provided
(R)-20 (Scheme 3). Similarly, the 40-nitro derivative (R)-4826
served as a precursor to the aniline derivative (R)-32,
and trifluoroacetamide (R)-33. Catalytic reduction (PtO2,
H2) of (R)-48 gave (R)-32, which was then treated with
ethyl trifluorothioacetate30 to yield (R)-33. Synthesis of azide
(R)-34 began with (R)-serine [(R)-49] (Scheme 4). Acetylation
followed by mixed anhydride coupling28a with 4-aminobenzyl-
amine (50) gave (R)-51. The aniline derivative (R)-51 was
directly converted to the azide (R)-52 by sequential addition
of tert-butyl nitrite and trimethylsilyl azide,31 which was
then treated with CH3I and Ag2O to give (R)-34. We used
different deprotection methods to prepare (R)-15, (R)-29,
and (R)-30 (Scheme 5). Compound (R)-15 was prepared
from (R)-16 upon treatment with HCl in dioxane. Similarly,
deprotection (HCl in a THF/H2O mixture) of acetal (R)-53
gave (R)-29. Finally, methyl ester (R)-31 was converted to

Article
Journal of Medicinal Chemistry, 2010, Vol. 53, No. 3 1293
Scheme 6. Preparation of Compound (R)-19
acid (R)-30 with LiOH, followed by workup without race-
mization. We employed a different method to prepare (R)-19
(Scheme 6). For this compound, we prepared optically pure
(R)-5825 and then coupled (DMTMM28b) it with benzyl-
amine 57.
The (S)-3 analogues listed in Table 3 were prepared
using the same methods employed for the corresponding
(R)-stereoisomers.
provided any protection at the doses (typically 300 mg/kg)
and times (0.5 and 4 h) tested (data not shown). The absence
of seizure protection in this assay is a hallmark of FAA
activity and this class of compounds.9-18
Table 1 provides the comparative anticonvulsant activities
for N-benzyl 2-acetamido-3-methoxypropionamide deriva-
tives in which we systematically placed either a fluoro or
a trifluoromethoxy group at the 20-, 30-, and 40-positions
of the N-benzylamide moiety. We prepared only the (R)-
stereoisomer for these studies since previous investigations
showed that the principal anticonvulsant activity resided in
this stereoisomer.11-13,18 In Table 3, we present additional
data consistent with this finding. In the two series of com-
pounds listed in Table 1, the 40-isomers [(R)-6 and (R)-9]
were more active than the corresponding 30-regioisomers
[(R)-5 and (R)-8)], a result in agreement with earlier FAA
studies.18,26 Previously, our laboratory had not prepared any
N-(20-substituted)benzylamide 2s. Thus, it was important for
us to determine the effect on anticonvulsant activity of
substitution at this site. Using the trifluoromethoxy series
as an example, the ED50 values for the 20-isomer [(R)-7],
30-isomer [(R)-8], and 40-isomer [(R)-9] in mice were 30-100,
10-30, and 3.6 mg/kg, respectively. A similar trend was
observed for the 40-fluoro regioisomers (R)-4-(R)-6. These
findings led us to focus our SAR studies on N-(40-substitu-
ted)benzyl (R)-3 derivatives.
Table 2 reports the observed anticonvulsant activities for
32 N-(40-substituted)benzyl (R)-3 analogues. Listed first
are the 40-modified alkyl (R)-3 analogues, (R)-10-(R)-14,
in which the size of the 40-alkyl group progressively in-
creases. The MES seizure protection values in mice for the
40-substituted methyl [(R)-10, 11 mg/kg], ethyl [(R)-11,
10-30 mg/kg], and propyl [(R)-12, 8.5 mg/kg] derivatives
were only slightly lower than that of the parent compound
(R)-3 (4.5 mg/kg).18 A similar finding was observed in the
model but using the Sprague-Dawley rat. This finding
was surprising since earlier results suggested that substitu-
ents placed at the 40-position of the N-benzyl amide moiety in
(R)-3 resulted in a significant loss of MES seizure protec-
tion upon administration to mice.15,26,27 For example, we
reported previously that the MES ED50 values for the 40-NO2
[(R)-48] and 40-NCS [(R)-59] analogues were 100-300 and
24 mg/kg, respectively.26 However, when the n-propyl
moiety in (R)-12 was changed to the isopropyl group to give
(R)-13 (for mice, MES ED50 = 10-30 mg/kg; for rats, MES
ED50 > 30 mg/kg) and then to a tert-butyl moiety to provide
Three criteria were used to assess the enantiopurity of
(R)-4-(R)-39 and (S)-11, (S)-21, (S)-23, (S)-26, (S)-28,
(S)-29, (S)-34, and (S)-38. These were melting point, optical
rotation, and the detection of only a single acetyl methyl
1
and O-methyl signal in the H NMR spectrum for each
compound when a saturated solution of (R)-(-)-mandelic
acid was added.32
We report in the Experimental Section the details
(synthetic procedure and characterization) for the final step
for all compounds evaluated in the seizure models. In the
Supporting Information, we provide a synthetic scheme for
each compound tested, and for all the synthetic compounds
prepared in this study the experimental procedures that were
utilized and their physical and spectroscopic properties.
Pharmacological Activity. Compounds (R)-4-(R)-39, (S)-
11, (S)-21, (S)-23, (S)-26, (S)-28, (S)-29, (S)-34, and (S)-38
were tested for anticonvulsant activity at the National
Institute of Neurological Disorders and Stroke’s (NINDS)
Anticonvulsant Screening Program (ASP) using the proce-
dures described by Stables and Kupferberg.33 The pharma-
cological data from the MES test are summarized in
Tables 1-3, along with similar results obtained for (R)-3
and the clinical antiepileptic agents phenytoin,34 valproate,34
and phenobarbital.34 All compounds were administered
intraperitoneally (ip) to mice and orally (po) to rats. The
tables list the values that were determined to be protective in
blocking hind limb extension induced in the MES seizure
model from the rodent identification studies. For com-
pounds that exhibited significant activity, we report the
effective dose (50%) (ED50) values obtained in quantitative
screening evaluations. Also provided are the median doses
for neurological impairment (50%) (TD50) in mice, using the
rotorod test,35 and the behavioral toxicity effects observed in
rats. TD50 values were determined for those compounds
exhibiting significant activity in the MES test. The protective
index (PI = TD50/ED50) values for these analogues are also
listed. Although all of the compounds were evaluated in
the subcutaneous Metrazol (scMet) seizure model, none

1294 Journal of Medicinal Chemistry, 2010, Vol. 53, No. 3
Salomeꢀ et al.
(R)-14 (for mice, MES ED50 = 100-300 mg/kg; for rats,
MES ED50>30 mg/kg), we saw a progressive loss of anti-
convulsant activity. These findings indicated that inclu-
sion of bulky groups at the 40-position interfered with drug
function. Conversely, nonbulky hydrophobic groups re-
tained excellent activity in both species.
ED50 = 3-10 mg/kg and in rats MES ED50 =3.4 mg/kg;
for (R)-27 in mice MES ED50 = 10 mg/kg and in rats
MES ED50 = 18 mg/kg]. When the trimethylsilylacetylenic
derivative (R)-26 was evaluated in the MES seizure model,
significant toxicity was observed at a 3 mg/kg dose, thereby
preventing us from assessing the trimethylsilyl group’s im-
pact on anticonvulsant activity. The pronounced anticon-
vulsant activity of the 40-phenyl analogue (R)-22 (for mice,
MES ED50 = 3-10 mg/kg; for rats, MES ED50=2.0 mg/kg)
was surprising given that the lowest-energy conformer for
biphenyl in the gaseous state is twisted, and the dihedral
angle between the two phenyl rings is close to 44°.36 The
progressive loss of activity observed as we proceeded from
(R)-12 to (R)-14 suggested that increases in the three-dimen-
sional steric size of the 40-site would result in a loss in acti-
vity, and thus, the attachment of the 40-phenyl group to give
(R)-22 would lead to a reduction in anticonvulsant activity.
The excellent seizure protection of (R)-22 can be rationalized by
the low barrier for rotation around the central biphenyl bond
(estimated to be 1.4 kcal/mol).37 Accordingly, the energy
penalty for a near-planar arrangement could be compensated
by beneficial drug-receptor interactions (e.g., hydrophobic,
aromatic interactions).
The final set of 40-modified (R)-3 analogues was the largest
and comprised 14 derivatives, each of which contained a
functional group directly attached to the N-benzyl moiety
[(R)-6, (R)-9, and (R)-28-(R)-39]. This group of compounds
together with the alkyl [(R)-10-(R)-12], trifluoromethyl
[(R)-18], ethenyl [(R)-21], alkynyl [(R)-23, (R)-24, and
(R)-27], and aryl [(R)-22] derivatives documented that at-
tachment of functional groups at the 40-site can provide
strong seizure protection. Testing results demonstrated a
highly significant anticonvulsant effect for the 40-azido [(R)-
34], 40-trifluoromethoxy [(R)-9], 40-F [(R)-6], and 40-Cl [(R)-
36] derivatives in mice (MES ED50 = 3.6-8.4 mg/kg) as well
as in the rat (MES ED50 = 1.0-3.9 mg/kg). These values
were either comparable with or exceeded that of (R)-3 (for
mice, MES ED50 = 4.5 mg/kg; for rats, MES ED50 = 3.9
mg/kg).18 As a group, all the 40-halogen-substituted (R)-3
derivatives [(R)-6 and (R)-36-(R)-38] exhibited pronounced
activity. In addition, the smaller halogens (F and Cl)
exhibited slightly better seizure protection than the larger
halogen derivatives (Br and I). We noticed a significant
loss of seizure protection in mice when proceeding from
40-ethynyl derivative (R)-23 (MES ED50 = 3-10 mg/kg)
to the 40-cyano analogue (R)-28 (MES ED50=150 mg/kg).
This finding was surprising given their similar size. Finally,
attaching a 40-substituent that could either ionize at physio-
logical pH values or donate a hydrogen bond {i.e., 40-CO2H
[(R)-30], 40-NH2 [(R)-32], 40-NHC(O)CF3 [(R)-33], and
40-SO2NH2 [(R)-39]} provided compounds that were in-
active in the MES test (mice) at the highest doses utilized
(300 mg/kg).
Next, we evaluated six modified 40-alkyl (R)-3 derivatives,
(R)-15-(R)-20, that contained a functional group(s) attached
to the 40-substituted alkyl side chain. Incorporating an amino
[(R)-15], a carbamate [(R)-16], or an alcohol [(R)-19] moiety
into the alkyl side chain resulted in compounds with no
anticonvulsant activity in mice at 300 mg/kg. Inclusion of a
methoxy group to give (R)-17 (for mice, MES ED50 =73mg/kg;
for rats, MES ED50 =45 mg/kg) and (R)-20 (for mice, MES
ED50 = 20 mg/kg; for rats, MES ED50 = 16 mg/kg) gave
compounds that provided significant seizure protection. None-
theless, the activity of (R)-17 was noticeably lower than that of its
isosteric propyl analogue (R)-12 (for mice, MES ED50 = 8.5
mg/kg; for rats, MES ED50 = <30 mg/kg). Finally, the 40-
trifluoromethyl derivative (R)-18 exhibited significant activity in
mice (MES ED50=10-30 mg/kg) and exceptional anticonvul-
sant activity in rats (MES ED50 = 4.9 mg/kg). The activity of
(R)-18 in the rat closely matched that found for (R)-3 (MES
ED50 = 3.9 mg/kg), was slightly better than that of the 40-methyl
derivative (R)-10 (MES ED50 =8.1 mg/kg), and exceeded the
values reported for the established anticonvulsants phenytoin,20
phenobarbital,34 and valproate.20 Taken together, these findings
show that additional attachment of specific functional groups (i.
e., alcohol, amino, or carbamate) to the 40-alkyl substituent led to
compounds with reduced anticonvulsant activities.
The next set of compounds listed in Table 2 were the 40-
ethenyl [(R)-21], 40-phenyl [(R)-22], and 40-alkynyl [(R)-23-
(R)-27] (R)-3 derivatives. In this series, the spatial disposition
of the 40-group was changed from the tetrahedral (sp3)
arrangement found in (R)-10-(R)-14 to either a trigonal
(sp2) or a linear (sp) arrangement. Superb activities in the
primary models were observed for the nonbulky derivatives
(R)-21-(R)-24 and (R)-27. The MES ED50 values in mice
ranged from 3 to 10 mg/kg. Similarly, (R)-21 (MES ED50
=
7.6 mg/kg) and (R)-23 (ED50 = 3.4 mg/kg) exhibited ex-
cellent seizure protection in the rat. Comparing the anti-
convulsant activities for the 40-substituted ethyl [(R)-11],
ethenyl [(R)-21], and ethynyl [(R)-23] derivatives, we ob-
served a modest improvement in anticonvulsant activities in
both mice and rats as we progressively decreased the spatial
size of the 40-group. This finding is consistent with the
pattern observed for the alkyl derivatives (R)-10-(R)-14.
The effect of the steric size of the 40-group on anticonvulsant
activity was further reinforced by the activities of (R)-25
and (R)-27. Attachment of a tert-butyl to the terminal end of
the 40-ethynyl group in (R)-23 to give (R)-25 led to a
precipitous drop in anticonvulsant activity in mice (MES
ED50 > 300 mg/kg), while adding the straight chain meth-
oxymethylene unit to (R)-23 to give (R)-27 did not appreci-
ably affect anticonvulsant activity [for (R)-23 in mice MES
The anticonvulsant activity observed for 40-chloro deriva-
tive (R)-36 in rats (MES ED50 = 1 mg/kg) made this
compound the most potent 2 prepared to date; it was nearly
4 times more active than (R)-3. Using the methodology
advanced by Topliss,38 we explored whether the improved
activity of (R)-36 over (R)-3 was due to an electronic effect
provided by the 40-chloro substituent. Accordingly, we pre-
pared the 30,40-dichloro derivative (R)-60. When (R)-60
was evaluated in mice, protection in the MES-induced
seizure test was between 30 and 100 mg/kg, demonstrating
that this derivative was considerably less active than (R)-36.

Article
Journal of Medicinal Chemistry, 2010, Vol. 53, No. 3 1295
Table 4. Evaluation of Selected (R)-N-(4-Substituted)benzyl 2-Acetamido-3-methoxypropionamide Derivatives in the Rat Hippocampal Kindled
Seizure Model Assaya
preliminary hippocampal kindling test (rat)
seizure score
after-discharge duration (s)
hippocampal kindled rat (0.25 h) (ip)
ED50 (mg/kg) (interval)
no.
(R)-17
(R)-20
R4
predrug
drug
predrug
drug
CH2OCH3
(CH2)3OCH3
CHdCH2
5
0
2
0
0
0
0
0
3
40-69
21-40
27-43
29-65
25-160
17-36
33-53
42-72
12
21
0-11
0
87 (58-130)
NDd
4-5
4-5
4
(R)-21
(R)-34
NDd
N3
Cl
I
6 (3-9)
(R)-36
(R)-38
(R)-3b,c
phenytoinc
phenobarbitalc
valproatec
4-5
5
2
NDd
0-4
0
12 (7.5-18)
14 (9.1-18)
34 (21-45)
20 (14-28)
210 (150-280)
H
5
4-5
51
a The compounds were tested through the auspices of the NINDS ASP. b From ref 23. c NINDS ASP internal control data. d Not determined.
Following the Topliss methodology, we compared the activ-
ity of (R)-36 (MES ED50 =5 mg/kg) with those of 40-CF3
[(R)-18; MES ED50 = 10-30 mg/kg], 40-Br [(R)-37; MES
ED50=8.7 mg/kg], 40-I [(R)-38; MES ED50=16 mg/kg], 20,
40-dichloro [(R)-61; MES ED50 = 30-100 mg/kg], and 40-
NO2 [(R)-48; MES ED50=100-300 mg/kg26] (R)-3 deriva-
tives in mice and found that (R)-36 was the most potent.
Collectively, these findings suggest that the improved acti-
vity observed for (R)-36 over (R)-3 is not due to electronic
effects provided by the 40-chloro substituent.38
(R)-34, (R)-36, and (R)-38 led to a significant decrease in
seizures (Racine score proceeding from 5 to 0-2) and a
marked corresponding reduction in the after-discharge dura-
tion. The ED50 values for (R)-34 and (R)-38 in the hippo-
campal kindled test (rat, ip) were calculated to be 6 and 12
mg/kg, respectively, surpassing the ED50 value for (R)-3
(14 mg/kg) and those of the standard antiepileptic drugs
phenytoin, phenobarbital, and valproate.23,41
Conclusions
The SAR for the N-benzyl group in the clinically available
antiepileptic agent (R)-3 has been explored. We prepared and
characterized 43 compounds, which were evaluated at the
NINDS ASP for seizure protection in MES and scMet rodent
models. Significant anticonvulsant protection against MES-
induced seizures was observed for many of these compounds.
Comparison of the protective actions for two series of sub-
stituted aryl regioisomers (20, 30, 40) demonstrated that the
40-modified derivatives exhibited the highest level of seizure
protection. It was determined that some degree of structural
latitude existed at this site. The SAR indicated that nonbulky
40-substituted (R)-3 derivatives exhibited superb activity in-
dependent of their electronic properties. The anticonvulsant
activities of (R)-6, (R)-9, (R)-21-(R)-23, (R)-34, (R)-36, and
(R)-37wereeithercomparable withor exceeded thatof (R)-318
in rodent MES tests, and they surpassed the activities ob-
served for the traditional antiepileptic agents phenytoin,34
phenobarbital,34 and valproate.34
This study complements an earlier report that explored
the effect of structural replacement of the C(2)-methoxy
group in (R)-3 on anticonvulsant activity.25 In this investi-
gation, we similarly observed that small, nonbulky 3-alkoxy
groups provided the greatest seizure protection. Taken
together, the SAR results provide clues concerning the
topography and binding properties of the receptor binding
site(s) that elicit (R)-3 function. Furthermore, the finding
that structural modifications can be made at the C(2)
methoxy side chain and at the 40-benzyl amide site in (R)-3
without a loss of significant anticonvulsant activity sets the
stage for the construction of AB&CR agents24 designed to
interrogate the brain proteome for drug binding sites.
Finally, we evaluated eight (S)-N-(40-substituted)benzyl 2-
acetamido-3-methoxypropionamide derivatives (Table 3).
Included in this set were 40-substituents [i.e., I, CH2CH3,
C(H)CH2, CCH, and N3] that exhibited superb anticonvul-
sant activities when incorporated in the (R)-enantiomer.
Most (S)-stereoisomers exhibited very little seizure protec-
tion in the MES test in mice with activities either between
100 and 300 mg/kg or greater than 300 mg/kg. Only (S)-26
displayed protection, but it was modest (MES ED50
=
30-100 mg/kg). Our inability to determine the anticonvul-
sant activity for (R)-26 prevented us from further exploring
the pharmacological basis for this finding. The minimal
anticonvulsant activities observed for these (S)-stereo-
isomers when compared with those of their N-(40-substitu-
ted)benzyl (R)-3 counterparts were in agreement with pre-
vious findings for chiral 2s.11-13,18
Several of the more active N-(40-substituted)benzyl (R)-3
derivatives were also evaluated in the rapid hippocampal
kindled rat model39 (Table 4). This assay is considered a
model of partial complex seizures, which are the most
common type of seizures in humans. They also represent
the subgroup of patients with the highest proportion of
drug resistance.40 Administration of (R)-17, (R)-20, (R)-21,

1296 Journal of Medicinal Chemistry, 2010, Vol. 53, No. 3
Salomeꢀ et al.
Identification of the (R)-3 receptor sites will advance future
antiepileptic drug discovery efforts.
washed with a saturated NaHCO3 solution, dried (Na2SO4), and
concentrated in vacuo. The residue was recrystallized with
EtOAc and/or purified by column chromatography on SiO2.
Preparation of (R)-N-(20-Fluoro)benzyl 2-Acetamido-3-methoxy-
propionamide [(R)-4].TFA (10 mL) was added to a CH2Cl2 solution
(200 mL) of (R)-N-(20-fluoro)benzyl 2-N-(tert-butoxycarbonyl)-
amino-3-methoxypropionamide (2.90 g, 8.9 mmol), and the solu-
tion was stirred at room temperature (1 h). A saturated aqueous
NaHCO3 solution was added until the pH reached ∼9. The layers
were separated, and the aqueous layer was washed with CH2Cl2
(2 ꢀ 100 mL). The organic layers were combined, dried (MgSO4),
and concentrated in vacuo.
Using method D, triethylamine (3.7 mL, 26.7 mmol) and
acetyl chloride (1.3 mL, 17.8 mmol) gave 1.12 g (88%) of (R)-4 as
a white solid after purification by flash column chromatography
on silica gel with an EtOAc/MeOH mixture (10/0 to 9/1) as the
eluant: Rf = 0.52 (EtOAc); mp 173-175 °C; [R]25.2D -23.0° (c
1.0, CHCl3); IR (nujol) 3289, 2925, 2858, 1638, 1550, 1457, 1376,
1237, 1135, 977, 842, 754, 610 cm-1; 1H NMR (CDCl3) δ 2.00 [s,
CH3C(O)], 3.35 (s, OCH3), 3.43 (dd, J = 7.2, 9.0 Hz, CHH0O),
3.76 (dd, J = 4.5, 9.0 Hz, CHH0O), 4.46-4.63 (m, CH2NH,
CH), 4.84-4.91 (br s, NHCH2), 6.64 [d, J = 7.2 Hz, NHC-
(O)CH3], 7.00-7.13 (m, 2 ArH), 7.23-7.32 (m, 2 ArH); addition
of an excess of (R)-(-)-mandelic acid to a CDCl3 solution of
(R)-4 gave only one signal for the acetyl methyl and one signal
for the ether methyl protons; 13C NMR (CDCl3) δ 23.0
[CH3C(O)], 37.4 (d, J = 4.0 Hz, NHCH2), 52.4 (CHCH2),
58.9 (OCH3), 71.8 (CH2OCH3), 115.1 (d, J = 21.0 Hz, C3),
124.2 (d, J = 3.4 Hz, C5), 124.8 (d, J = 14.5 Hz, C4 or C6), 129.1
(d, J = 8.2 Hz, C6 or C4), 129.6-129.7 (br d, C1), 160.8 (d, J =
244.7 Hz, CF), 170.1, 170.4 [2 C(O)]; HRMS (M þ Csþ) (ESIþ)
401.0278 [M þ Csþ] (calcd for C13H17FN2O3Csþ 401.0274).
Anal. (C13H17FN2O3): C, H, F, N.
Experimental Section
General Methods. Melting points were determined in open
capillary tubes using a Thomas-Hoover melting point apparatus
and are uncorrected. Infrared spectra (IR) were recorded on an
ATI Mattson Genesis FT-IR spectrometer. Absorption values
are expressed in wavenumbers (cm-1). Optical rotations were
obtained on a Jasco P-1030 polarimeter at the sodium D line
(589 nm) using a 1 dm path length cell. NMR spectra were
recorded at 300 or 400 MHz (1H) and 75 or 100 MHz (13C) using
TMS as an internal standard. Chemical shifts (δ) are reported in
parts per million from tetramethylsilane. Low-resolution mass
spectra were recorded with a BioToF-II-Bruker Daltonics
spectrometer by M. Crowe and S. Habibi at the University
of North Carolina Department of Chemistry. The high-resolu-
tion mass spectra were recorded on a Bruker Apex-Q 12
Telsa FTICR spectrometer by M. Crowe and S. Habibi. Micro-
analyses were performed by Atlantic Microlab, Inc. (Norcross,
GA). Reactions were monitored by analytical thin-layer
chromatography (TLC) plates (Aldrich, catalog no. Z12272-6,
or Dynamic Adsorbents Inc., catalog no. 84111) and analyzed
with 254 nm light. The reaction mixtures were purified by
MPLC (CombiFlash Rf) with self-packed columns (silica gel
from Dynamic Adsorbents Inc., catalog no. 02826-25) or by
flash column chromatography using silica gel (Dynamic Adsor-
bents Inc., catalog no. 02826-25). All chemicals and solvents
were reagent grade and used as obtained from commercial
sources without further purification. THF was distilled from
blue sodium benzophenone ketyl. Yields reported are for pur-
ified products and were not optimized. All compounds were
checked by TLC, 1H and 13C NMR, MS, and elemental
analyses. The analytical results are within 0.40% of the theore-
tical value. The TLC, NMR, and analytical data confirmed the
purity of the products was g95%.
Preparation of (R)-N-(20-Trifluoromethoxy)benzyl 2-Acetamido-
3-methoxypropionamide [(R)-7]. An EtOH solution (200 mL)
of (R)-N-(20-trifluoromethoxy)benzyl 2-N-(benzyloxycarbonyl)-
amino-3-methoxypropionamide (3.40 g, 8.0 mmol) was treated
with H2 (1 atm) in the presence of 10% Pd/C (340 mg) at room
temperature (16 h). The mixture was carefully filtered through a
bed of Celite. The pad was washed with MeOH and CH2Cl2, and
the washings were collected and evaporated in vacuo.
General Procedure for the Mixed Anhydride Coupling Reac-
tion (Method A). To a cooled THF solution (-78 °C, dry ice/
acetone bath) of acid (R)/(S)-43 or 44 ([C] ∼ 0.1 M) were added
NMM (1.0-1.2 equiv), followed by stirring for 2 min, IBCF
(1.0-1.2 equiv), followed by stirring for 5 min, and then the
desired benzylamine (1.0-1.2 equiv). Upon addition, the reac-
tion mixture was allowed to warm to room temperature and
further stirred (2-3 h). The salts were filtered and rinsed with
THF, and the filtrate was concentrated in vacuo. The residue
obtained was purified by flash chromatography and/or by
recrystallization from EtOAc when necessary.
Using method D, triethylamine (3.3 mL, 24.0 mmol) and
acetyl chloride (1.2 mL, 16.0 mmol) gave 3.50 g (88%) of (R)-7 as
a white solid after purification by flash column chromatography
on silica gel with an EtOAc/MeOH mixture (10/0 to 9/1) as the
eluant: Rf = 0.36 (EtOAc); mp 130-131 °C; [R]24.8 -15.1°
D
(c 1.0, CHCl3); IR (nujol) 2919, 2858, 1640, 1547, 1458, 1272,
1
1203, 1164, 767, 712, 606 cm-1; H NMR (CDCl3) δ 1.98 [s,
General Procedure for the Preparation of 3-Methoxy-2-ami-
dopropionamide Derivatives (Method B). To a CH3CN solution
of alcohol ([C] ∼ 0.05-0.5 M) were successively added Ag2O
(5 equiv) and MeI (10 equiv) at room temperature. The reaction
mixture was maintained at room temperature (2-4 days) and
filtered through Celite, and the solvent was evaporated in vacuo.
The residue was purified by column chromatography on SiO2.
General Procedure for the Preparation of Cbz Deprotection
(Method C). An EtOH or MeOH solution ([C] ∼ 0.01-0.2 M) of
(R)- or (S)-46 was treated with H2 (1 atm) in the presence of 10%
Pd/C [10-20% (w/w)] at room temperature (16 h). The mixture
was carefully filtered through a bed of Celite. The pad was
washed with MeOH and CH2Cl2, and the washings were
collected and evaporated in vacuo. The compounds were used
without further purification.
General Procedure for N-Acetylation (Method D). The 2-
aminopropionamide residue was dissolved in CH2Cl2
(0.05-0.3 M); triethylamine (1.2-6 equiv) and acetyl chloride
(1.2-3 equiv) were carefully added at 0 °C, and the resulting
solution was stirred at room temperature (2-4 h). An aqueous
10% citric acid solution was added, and the reaction mixture
was extracted with CH2Cl2. The organic layers were combined,
CH3C(O)], 3.35 (s, OCH3), 3.45 (br dd, J = 7.2, 9.3 Hz,
CHH0O), 3.76 (dd, J = 4.2, 9.3 Hz, CHH0O), 4.46-4.63 (m,
CH2NH, CH), 6.71 [br d, J = 6.3 Hz, NHC(O)CH3], 7.22-7.40
(m, CH2NH, 4 ArH); addition of excess (R)-(-)-mandelic acid
to a CDCl3 solution of (R)-7 gave only one signal for the acetyl
methyl and one signal for the ether methyl protons; 13C NMR
(CDCl3) δ 22.9 [CH3C(O)], 38.1 (CH2NH), 52.4 (CHCH2), 58.9
(OCH3), 71.7 (CH2OCH3), 120.4 (1 ArC), 120.5 (q, J=256.1 Hz,
OCF3), 127.0, 128.8, 129.7, 130.3, 147.1 (5 ArC), 170.2, 170.4 [2
C(O)]; HRMS (M þ Naþ) (ESIþ) 357.1038 [M þ Naþ] (calcd for
C14H17F3N2O4Naþ 357.1038). Anal. (C14H17F3N2O4): C, H, F, N.
Preparation of (R)-N-(30-Trifluoromethoxy)benzyl 2-Acetamido-
3-methoxypropionamide [(R)-8]. An EtOH solution (200 mL) of
(R)-N-(30-trifluoromethoxy)benzyl 2-N-(benzyloxycarbonyl)-
amino-3-methoxypropionamide (1.80 g, 4.2 mmol) was treated
with H2 (1 atm) in the presence of 10% Pd/C (180 mg) at room
temperature (16 h). The mixture was carefully filtered through a
bed of Celite, and the filtrate was evaporated in vacuo to yield a
yellow oil.
Using method D, triethylamine (0.7 mL, 5.0 mmol) and acetyl
chloride (0.35 mL, 5.0 mmol) gave 750 mg (54%) of (R)-8 as a
white solid after recrystallization with EtOAc: Rf = 0.33

Article
Journal of Medicinal Chemistry, 2010, Vol. 53, No. 3 1297
(EtOAc); mp 147-148 °C; [R]25.0 -12.1° (c 1.0, CHCl3); IR
for the acetyl methyl and one signal for the ether methyl pro-
tons; 13C NMR (CDCl3) δ 21.0 (PhCH3), 23.1 [CH3C(O)], 43.3
(CH2NH), 52.4(CHCH2), 59.0 (OCH3), 71.7 (CH2OCH3), 127.4,
129.3, 134.8, 137.1 (4 ArC), 169.9, 170.3 [2 C(O)]; HRMS (M þ
Hþ) (ESIþ) 265.1552 [M þ Hþ] (calcd for C14H20N2O3Hþ
265.1552). Anal. (C14H20N2O3): C, H, N.
Preparation of (R)-N-(40-Ethyl)benzyl 2-Acetamido-3-methoxy-
propionamide [(R)-11]. A MeOH solution (250 mL) of (R)-N-(40-
ethyl)benzyl 2-N-(benzyloxycarbonyl)amino-3-methoxypropion-
amide (1.20 g, 3.0 mmol) was treated with H2 (1 atm) in the presence
of 10% Pd/C (120 mg) at room temperature (3 days). The mixture
was carefully filtered through a bed of Celite. The pad was washed
with MeOH and CH2Cl2, and the washings were collected and
evaporated in vacuo to yield a yellow solid.
Using method D, triethylamine (0.5 mL, 3.5 mmol) and acetyl
chloride (250 μL, 3.5 mmol) gave (R)-11 as a white solid after
recrystallization with EtOAc: mp 132-133 °C; IR (nujol) 3413,
3305, 3057, 2968, 2932, 1693, 1528, 1266, 1116 cm-1; 1H NMR
(CDCl3) δ 1.22 (t, J = 7.5 Hz, CH3CH2), 2.02 [s, CH3C(O)], 2.63
(q, J = 7.5 Hz, CH3CH2), 3.37 (s, OCH3), 3.43 (dd, J = 7.2, 9.0
Hz, CHH0O), 3.79 (dd, J = 4.2, 9.0 Hz, CHH0O), 4.43 (d, J =
6.0 Hz, CH2NH), 4.50-4.58 (m CH), 6.47 [br d, J = 6.9 Hz,
NHC(O)CH3], 6.71-6.82 (br t, CH2NH), 7.15-7.18 (m, 4
ArH); addition of excess (R)-(-)-mandelic acid to a CDCl3
solution of (R)-11 gave only one signal for the acetyl methyl and
one signal for the ether methyl protons; 13C NMR (CDCl3) δ
15.5 (CH2CH3), 23.1 [CH3C(O)], 28.5 (CH2CH3), 43.3
(CH2NH), 52.4 (CHCH2), 59.0 (OCH3), 71.7 (CH2OCH3),
127.5, 128.1, 135.0, 143.5 (4 ArC), 169.8, 170.3 [2 C(O)]; HRMS
(M þ Hþ) (ESIþ) 279.1708 [M þ Hþ] (calcd for C15H22N2O3Hþ
279.1705). Anal. (C15H22N2O3): C, H, N.
Preparation of (S)-N-(40-Ethyl)benzyl 2-Acetamido-3-methoxy-
propionamide [(S)-11]. A MeOH solution (250 mL) of (S)-N-(40-
ethyl)benzyl 2-N-(benzyloxycarbonyl)amino-3-methoxypropion-
amide (1.20 g, 3.0 mmol) was treated with H2 (1 atm) in the
presence of 10% Pd/C (120 mg) at room temperature (3 days). The
mixture was carefully filtered through a bed of Celite. The pad was
washed with MeOH and CH2Cl2, and the washings were collected
and evaporated in vacuo to yield a yellow solid.
Using method D, triethylamine (0.5 mL, 3.5 mmol) and acetyl
chloride (250 μL, 3.5 mmol) gave (S)-11 as a white solid after
recrystallization with EtOAc: mp 132-133 °C; IR (nujol) 3286,
2932, 2928, 1637, 1554, 1458, 1375, 1311, 1197, 1102, 1051, 909,
821, 724 cm-1; 1H NMR (CDCl3) δ 1.22 (t, J = 7.5 Hz, CH3-
CH2), 2.02 [s, CH3C(O)], 2.62 (q, J = 7.5 Hz, CH3CH2), 3.37 (s,
OCH3), 3.43 (dd, J = 7.2, 9.0 Hz, CHH0O), 3.79 (dd, J = 4.5, 9.0
Hz, CHH0O), 4.43 (d, J = 5.7 Hz, CH2NH), 4.43-4.58 (m, CH),
6.48 [br d, J = 6.3 Hz, NHC(O)CH3], 6.71-6.82 (br t, CH2NH),
7.15-7.18 (m, 4 ArH); addition of excess (R)-(-)-mandelic acid
to a CDCl3 solution of (S)-11 gave only one signal for the acetyl
methyl and one signal for the ether methyl protons; 13C NMR
(CDCl3) δ 15.8 (CH2CH3), 23.4 [CH3C(O)], 28.7 (CH2CH3),
43.5 (CH2NH), 52.6 (CHCH2), 59.3 (OCH3), 72.0 (CH2OCH3),
127.7, 128.4, 135.2, 143.8 (4 ArC), 170.1, 170.5 [2 C(O)]; HRMS
(M þ Hþ) (ESIþ) 279.1708 [M þ Hþ] (calcd for C15H22N2O3Hþ
279.1705). Anal. (C15H22N2O3): C, H, N.
Preparation of (R)-N-(40-Propyl)benzyl 2-Acetamido-3-methoxy-
propionamide [(R)-12]. PtO2 (100 mg) was added to an EtOH
solution of (R)-24 (700 mg, 2.25 mmol), and the mixture was stirred
at room temprerature under H2 (1 atm) for 24 h. The reaction
mixture was filtered through a pad of Celite, and the pad was
washed successively with EtOH and CH2Cl2. The filtrate was
concentrated under vacuum, and the residue was purified by flash
chromatography on silica gel with an EtOAc/hexane mixture
(8/2 to 10/0) as the eluant to yield (R)-12 (560 mg, 79%) as a white
solid: Rf = 0.37 (EtOAc); mp 126-127 °C; [R]25.4D -27.2° (c 0.5,
CHCl3); IR (nujol) 3439, 3374, 3140, 2949, 2859, 1637, 1548, 1457,
1374, 1305, 1137, 1098, 972, 832, 725 cm-1; 1H NMR (CDCl3) δ
0.93 (t, J = 7.5 Hz, CH3CH2), 1.57-1.64 (m, CH2CH2CH3), 2.04
[s, CH3C(O)], 2.57 (t, J = 7.8 Hz, CH2CH2CH3), 3.34-3.45 (m,
D
(nujol) 3287, 3041, 2859, 2355, 1637, 1552, 1456, 1377, 1272,
1214, 1150, 715, 610 cm-1; 1H NMR (CDCl3) δ 2.04 [s, CH3C-
(O)], 3.39 (s, OCH3), 3.44 (dd, J = 7.6, 9.0 Hz, CHH0O), 3.83
(dd, J = 4.2, 9.0 Hz, CHH0O), 4.43-4.60 (m, CH2NH, CH),
6.38-6.46 [br d, NHC(O)CH3], 6.82-6.91 (br t, CH2NH),
7.11-7.15 (m, 2 ArH), 7.19 (d, J = 7.8 Hz, 1 ArH), 7.36 (dt, J =
1.9, 7.8 Hz, 1 ArH); addition of excess (R)-(-)-mandelic acid to
a CDCl3 solution of (R)-8 gave only one signal for the acetyl
methyl and one signal for the ether methyl protons; 13C NMR
(CDCl3) δ 23.1 [CH3C(O)], 42.8 (CH2NH), 52.5 (CHCH2),
59.0 (OCH3), 71.6 (CH2OCH3), 120.4 (q, J = 255.6 Hz, OCF3),
119.7, 119.8, 125.6, 130.0, 140.4 (5 ArC), 149.5 (COCF3), 170.2,
170.4 [2 C(O)]; LRMS (M þ Naþ) (ESIþ) 357.1 [M þ Naþ]
(calcd for C14H17F3N2O4 Naþ 357.1). Anal. (C14H17F3N2O4):
C, H, F, N.
Preparation of (R)-N-(40-Trifluoromethoxy)benzyl 2-Acetamido-
3-methoxypropionamide [(R)-9]. An EtOH solution (400 mL)
of (R)-N-(40-trifluoromethoxy)benzyl 2-N-(benzyloxycarbonyl)-
amino-3-methoxypropionamide (3.90 g, 9.2 mmol) was treated
with H2 (1 atm) in the presence of 10% Pd/C (390 mg) at room
temperature (16 h). The mixture was carefully filtered through a
bed of Celite, and the filtrate was evaporated in vacuo to yield a
brown oil: 1H NMR (CDCl3) δ 1.44-1.95 (br s, NH2), 3.38
(s, OCH3), 3.50-3.67 (br m, CH2, CH), 4.46 (d, J = 5.7 Hz,
NCH2), 7.17 (d, J = 8.0 Hz, 2 ArH), 7.31 (d, J = 8.0 Hz, 2 ArH),
7.80-8.00 [br s, NHC(O)].
Using method D, triethylamine (1.5 mL, 11.0 mmol) and
acetyl chloride (0.78 mL, 11.0 mmol) gave 2.50 g (83%) of (R)-9
as a white solid after recrystallization with EtOAc: Rf = 0.49
(EtOAc); mp 134-135 °C; [R]24.9 -17.6° (c 0.5, CHCl3); IR
D
(nujol) 3279, 3088, 2958, 2858, 1638, 1553, 1456, 1377, 1285,
1221, 1148, 988, 918, 841, 725 cm-1; 1H NMR (CDCl3) δ 2.04
[s, CH3C(O)], 3.39 (s, OCH3), 3.44 (dd, J=7.5, 9.0 Hz, CHH0O),
3.82 (dd, J = 4.2, 9.0 Hz, CHH0O), 4.44-4.52 (m, CH2NH),
4.52-4.59 (m, CH), 6.41 [br d, J = 6.6 Hz, NHC(O)CH3], 6.78-
6.89 (br t, CH2NH), 7.18 (d, J = 8.1 Hz, 2 ArH), 7.29 (d, J = 8.1
Hz, 2 ArH); addition of excess (R)-(-)-mandelic acid to a CDCl3
solution of (R)-9 gave only one signal for the acetyl methyl and
one signal for the ether methyl protons; 13C NMR (CDCl3) δ
23.1 [CH3C(O)], 42.7 (CH2NH), 52.5 (CHCH2), 59.1 (OCH3),
71.7 (CH2OCH3), 120.4 (q, J = 255.5 Hz, CF3), 121.2, 128.7,
136.7 (3 ArC), 148.4 (d, J = 1.7 Hz, COCF3), 170.1, 170.4
[2 C(O)]; HRMS (M þ Hþ) (ESIþ) 335.1219 [M þ Hþ] (calcd
for C14H17F3N2O4Hþ 335.1218). Anal. (C14H17F3N2O4): C,
H, F, N.
Preparation of (R)-N-(40-Methyl)benzyl 2-Acetamido-3-methoxy-
propionamide [(R)-10]. An EtOH solution (250 mL) of (R)-N-
(40-methyl)benzyl
2-N-(benzyloxycarbonyl)amino-3-methoxy-
propionamide (3.20 g, 9.0 mmol) was treated with H2 (1 atm) in
the presence of 10% Pd/C (320 mg) at room temperature (16 h).
The mixture was carefully filtered through a bed of Celite, and
1
the filtrate was evaporated in vacuo to yield a colorless oil: H
NMR (CDCl3) δ 1.60-1.65 (br s, NH2), 2.33 (s, PhCH3), 3.37
(s, OCH3), 3.56-3.67 (m, CH2, CH), 4.34-4.43 (m, HNCH2),
7.10-7.79 (m, 4 ArH), 7.70-7.77 [br s, NHC(O)]; 13C NMR
(CDCl3) δ 21.0 (PhCH3), 42.9 (CH2NH), 54.8 (CH), 58.8
(OCH3), 74.5 (CH2), 127.6, 129.3, 135.3, 137.0 (4 ArC), 172.5
[C(O)].
Using method D, triethylamine (1.5 mL, 10.8 mmol) and
acetyl chloride (766 μL, 10.8 mmol) gave 1.70 g (72%) of (R)-10
as a white solid after two recrystallizations with EtOAc: Rf =
0.50 (EtOAc); mp 128-129 °C; [R]25D -22.4° (c 1.0, CHCl3); IR
(nujol) 3285, 3062, 1637, 1548, 1458, 1375, 1311, 1105, 915, 808,
724 cm-1; 1H NMR (CDCl3) δ 1.98 [s, CH3C(O)], 2.32 (PhCH3),
3.35 (s, OCH3), 3.45 (dd, J = 6.9, 9.3 Hz, CHH0O), 3.75 (dd, J =
4.2, 9.3 Hz, CHH0O), 4.36-4.43 (m, CH2NH), 4.57-4.62
(m, CH), 6.71 [br d, J=6.9 Hz, NHC(O)CH3], 6.98-7.04 (br t,
CH2NH), 7.09-7.16 (m, 4 ArH); addition of excess (R)-(-)-
mandelic acid to a CDCl3 solution of (R)-10 gave only one signal

1298 Journal of Medicinal Chemistry, 2010, Vol. 53, No. 3
Salomeꢀ et al.
CHH0O, OCH3), 3.81 (dd, J = 4.2, 9.0 Hz, CHH0O), 4.44 (d, J =
5.7 Hz, CH2NH), 4.50-4.57 (m, CH), 6.38-6.46 (br m, CHNH),
6.63-6.73 (br m, CH2NH), 7.12-7.19 (m, 4 ArH); addition of
excess (R)-(-)-mandelic acid to a CDCl3 solution of (R)-12 gave
only one signal for the acetyl methyl and one signal for the ether
methyl protons; 13C NMR (CDCl3) δ 13.8 (CH2CH3), 23.1 [CH3-
C(O)], 24.5 (CH2CH3), 37.6 (CH2CH2CH3), 43.3 (CH2NH), 52.4
(CHCH2), 59.0 (OCH3), 71.8 (CH2OCH3), 123.4, 128.7, 135.0,
142.0 (4 ArC), 169.9, 170.3 [2 C(O)]; HRMS (M þ Hþ) (ESIþ)
293.1865 [M þ Hþ] (calcd for C16H24N2O3Hþ 293.1865). Anal.
(C16H24N2O3): C, H, N.
one signal for the acetyl methyl and one signal for the ether
methyl protons; 13C NMR (CDCl3) δ 23.1 [CH3C(O)], 31.3
[C(CH3)3], 34.4 [C(CH3)3], 43.2 (CH2NH), 52.4 (CHCH2), 59.0
(OCH3), 71.8 (CH2OCH3), 125.5, 127.2, 134.7, 150.4 (4 ArC),
169.9, 170.3 [2 C(O)]; HRMS (M þ Hþ) (ESIþ) 307.2022 [M þ
Hþ] (calcd for C17H26N2O3Hþ 307.2021). Anal. (C17H26N2O3):
C, H, N.
Preparation of (R)-N-(40-Aminomethyl)benzyl 2-Acetamido-3-meth-
oxypropionamide Hydrochloride [(R)-15]. A saturated HCl solution in
dioxane (11.25 mL, 45.0 mL) was added to (R)-16 (1.70 g, 4.5 mmol)
at 0 °C, and the solution was stirred at room temperature (4 h). The
reaction solution was concentrated in vacuo and dried (30 min). The
residue was triturated with Et2O, and the white solid was filtered to
yield (R)-15 (1.20 g, quantitative): Rf = 0.00 (EtOAc); mp >210 °C;
[R]26.2D -1.6° (c1.0, DMSO); IR (nujol) 3124, 2919, 2860, 1635, 1639,
1457, 1374, 1281, 1195, 1121, 974, 728 cm-1; 1H NMR (DMSO-d6) δ
1.87 [s, CH3C(O)], 3.25 (s, OCH3), 3.44-3.56 (m, CH2OCH3), 3.97
(q, J = 5.7 Hz, CH2NH3Cl), 4.28 (d, J = 6.0 Hz, CH2NH),
4.36-4.50 (m, CH), 7.26 (d, J = 7.9 Hz, 2 ArH), 7.43 (d, J = 7.9
Hz, 2 ArH), 8.15 [br d, J = 7.8 Hz, NHC(O)CH3], 8.38-8.55
(br m, NH3Cl), 8.58 (br t, J = 6.0 Hz, CH2NH); 13C NMR
(DMSO-d6) δ 22.5 [CH3C(O)], 41.6, 41.8 (2 CH2NH), 52.6
(CHCH2), 58.1 (OCH3), 72.0 (CH2OCH3), 127.0, 128.7, 132.2,
139.6 (4 ArC), 169.3, 169.7 [2 C(O)]; HRMS (M þ Hþ) (ESIþ)
280.1661 [M þ Hþ] (calcd for C14H21N3O3Hþ 280.1661). Anal.
Preparation of (R)-N-(40-Isopropyl)benzyl 2-Acetamido-3-meth-
oxypropionamide [(R)-13]. An EtOH solution (250 mL) of (R)-N-
(40-isopropyl)benzyl 2-N-(benzyloxycarbonyl)amino-3-methoxy-
propionamide (1.80 g, 4.7 mmol) was treated with H2 (1 atm) in
the presence of 10% Pd/C (180 mg) at room temperature (16 h).
The mixture was carefully filtered through a bed of Celite, and the
1
filtrate was evaporated in vacuo to yield a brown oil: H NMR
(CDCl3) δ 1.24 [d, J=6.9 Hz, CH(CH3)2], 2.89 [sept, J = 6.9 Hz,
CH(CH3)2], 3.38 (s, OCH3), 3.59-3.66 (m, CH2, CH), 4.35-4.49
(m, HNCH2), 7.16 (m, 4 ArH), 7.69-7.82 [br s, NHC(O)]; 13C
NMR (CDCl3) δ 23.9 [CH(CH3)2], 33.8 [CH(CH3)2], 42.9
(CH2NH), 54.8 (CHCH2), 58.8 (OCH3), 74.5 (CH2), 126.7,
127.7, 135.6, 148.1 (4 ArC), 172.5 [C(O)].
Using method D, triethylamine (0.79 mL, 5.6 mmol) and
acetyl chloride (0.40 mL, 5.6 mmol) gave 2.40 g (62%) of (R)-13
as a white solid after purification by flash column chromato-
graphy on silica gel with an EtOAc/hexane mixture (80/20 to
100/0) as the eluant: Rf = 0.39 (80/20 EtOAc/hexanes); mp
(C14H22ClN3O3 0.49HCl): C, H, N.
3
Preparation of (R)-N-[40-(tert-Butoxycarbonyl)aminomethyl]-
benzyl 2-Acetamido-3-methoxypropionamide [(R)-16]. An EtOH
solution (400 mL) of (R)-N-[40-(tert-butoxycarbonyl)aminomethyl]-
benzyl 2-N-(benzyloxycarbonyl)amino-3-methoxypropionamide
(5.30 g, 11.2 mmol) was treated with H2 (1 atm) in the presence
of 10% Pd/C (530 mg) at room temperature (24 h); then
an additional 470 mg of Pd/C was added, and the mixture
was allowed to stir at room temperature (12 h). The mixture
was carefully filtered through a bed of Celite, and the filtrate was
evaporated in vacuo to yield a brown oil.
95-97 °C; [R]27.0 -10.5° (c 0.5, CHCl3); IR (nujol) 3289,
D
2921, 2858, 1635, 1550, 1457, 1376, 1312, 1193, 1101, 1048,
1
913, 811, 723 cm-1; H NMR (CDCl3) δ 1.24 [d, J=6.9 Hz,
CH(CH3)2], 2.03 [s, CH3C(O)], 2.90 [sept, J = 6.9 Hz, CH-
(CH3)2], 3.38 (s, OCH3), 3.43 (dd, J=7.8, 9.0 Hz, CHH0O), 3.81
(dd, J =4.2, 9.0 Hz, CHH0O), 4.44 (d, J=5.7 Hz, CH2NH),
4.50-4.56 (m, CH), 6.44 [br d, J=6.3 Hz, NHC(O)CH3], 6.65-
6.74 (br t, CH2NH), 7.19 (s, 4 ArH); addition of excess (R)-(-)-
mandelic acid to a CDCl3 solution of (R)-13 gave only one signal
for the acetyl methyl and one signal for the ether methyl pro-
tons; 13C NMR (CDCl3) δ 23.2 [CH3C(O)], 24.0 [CH(CH3)2],
33.8 [CH(CH3)2], 43.3 (CH2NH), 52.4 (CHCH2), 59.0 (OCH3),
71.7 (CH2OCH3), 126.7, 127.5, 135.1, 148.2 (4 ArC), 169.9,
170.3 [2 C(O)]; LRMS (M þ Naþ) (ESIþ) 315.2 [M þ Hþ] (calcd
for C16H22N2O3Naþ 315.2). Anal. (C16H22N2O3): C, H, N.
Preparation of (R)-N-(40-tert-Butyl)benzyl 2-Acetamido-3-meth-
oxypropionamide [(R)-14]. An EtOH solution (250 mL) of (R)-N-
(40-tert-butyl)benzyl 2-N-(benzyloxycarbonyl)amino-3-methoxy-
propionamide (4.00 g, 10.0 mmol) was treated with H2 (1 atm)
in the presence of 10% Pd/C (400 mg) at room temperature (16 h).
The mixture was carefully filtered through a bed of Celite, and the
Using method D, triethylamine (1.9 mL, 13.5 mmol) and
acetyl chloride (0.96 mL, 13.5 mmol) gave 2.50 g (60%) of (R)-16
as a white solid after recrystallization with EtOAc: Rf = 0.47
(EtOAc); mp 153-154 °C; [R]24.9 -15.9° (c 1.0, CHCl3); IR
D
(nujol) 3318, 2919, 2861, 1675, 1639, 1530, 1458, 1374, 1260,
1
1167, 1127, 1057, 835, 724 cm-1; H NMR (CDCl3) δ 1.45 [s,
C(CH3)3], 2.01 [s, CH3C(O)], 3.37 (s, OCH3), 3.44 (dd, J = 7.2,
9.0 Hz, CHH0O), 3.79 (dd, J = 4.2, 9.0 Hz, CHH0O), 4.28 (d,
J = 5.7 Hz, CH2NH), 4.43 (d, J = 5.7 Hz, CH2NH), 4.51-4.57
(m, CH), 4.86-4.95 (br s, t-BocNH), 6.49-6.57 [br d, NHC-
(O)CH3], 6.83-6.93 (br m, CH2NH), 7.17-7.26 (m, 4 ArH);
addition of excess (R)-(-)-mandelic acid to a CDCl3 solution of
(R)-16 gave only one signal for the acetyl methyl and one signal
for the ether methyl protons; 13C NMR (CDCl3) δ 23.1 [CH3-
C(O)], 28.4 [C(CH3)3], 43.2, 44.3 (2 CH2NH), 52.4 (CHCH2),
59.0 (OCH3), 71.7 (CH2OCH3), 79.5 [C(CH3)3], 127.7, 136.9,
138.3 (3 ArC), 155.9 [NC(O)O], 170.0, 170.4 [2 C(O)]; one signal
was not detected and is believed to overlap with nearby peaks;
HRMS (M þ Hþ) (ESIþ) 380.2186 [M þ Hþ] (calcd for C19H29-
N3O5Hþ 380.2185). Anal. (C19H29N3O5): C, H, N.
Preparation of (R)-N-(40-Methoxymethyl)benzyl 2-Acetamido-
3-methoxypropionamide [(R)-17]. A MeOH solution (400 mL) of
(R)-N-(40-methoxymethyl)benzyl 2-N-(benzyloxycarbonyl)amino-
3-methoxypropionamide (3.50 g, 9.1 mmol) was treated with H2
(1 atm) in the presence of 10% Pd/C (350 mg) at room temperature
(16 h). The mixture was carefully filtered through a bed of Celite, and
the filtrate was evaporated in vacuo to yield a colorless oil.
1
filtrate was evaporated in vacuo to yield a brown oil: H NMR
(CDCl3) δ 1.31 [s, C(CH3)3], 1.58-1.62 (br s, NH2), 3.38 (s,
OCH3), 3.59-3.66 (m, CH2, CH), 4.36-4.49 (m, HNCH2), 7.21
(d, J = 8.4 Hz, 2 ArH), 7.36 (d, J = 8.4 Hz, 2 ArH), 7.69-7.81 [br
s, NHC(O)]; 13C NMR (CDCl3) δ 31.3 [C(CH3)3], 34.5 [C(CH3)3],
42.8 (CH2NH), 54.9 (CH), 58.8 (OCH3), 74.5 (CH2), 125.5, 127.4,
135.2, 150.3 (4 ArC), 172.5 [C(O)]; HRMS (M þ Hþ) (ESIþ)
265.1916 [M þ Hþ] (calcd for C15H24N2O2Hþ 265.1916).
Using method D, triethylamine (1.7 mL, 12.0 mmol) and
acetyl chloride (856 μL, 12.0 mmol) gave 1.70 g (55%) of (R)-14
as a white solid after recrystallization with EtOAc: Rf =0.73
(EtOAc); mp 125-126 °C; [R]26.8 -26.0° (c 1.0, CHCl3);
D
IR (nujol) 3280, 2920, 2860, 1636, 1544, 1456, 1374, 1301,
1247, 1197, 1119, 966, 815, 725 cm-1 1H NMR (CDCl3) δ
;
Using method D, triethylamine(1.5 mL, 10.9 mmol) and acetyl
chloride (772 μL, 10.9 mmol) gave 1.50 g (56%) of (R)-17 as a
white solid after trituration with EtOAc: Rf = 0.35 (EtOAc); mp
119-120 °C; [R]25D -25.4° (c 0.5, CHCl3); IR (nujol) 3266, 3069,
2935, 2863, 1635, 1550, 1458, 1457, 1382, 1282, 1226, 1194, 1125,
948, 836, 792, 726 cm-1; 1H NMR (CDCl3) δ 2.03 [s, CH3C(O)],
3.37, 3.38 (2 s, 2 OCH3), 3.43 (dd, J = 7.5, 9.1, CHH0O), 3.80 (dd,
1.30 [s, C(CH3)3], 1.99 [s, CH3C(O)], 3.37 (s, OCH3), 3.46 (dd,
J=7.2, 9.0 Hz, CHH0O), 3.77 (dd, J=4.2, 9.0 Hz, CHH0O),
4.36-4.44 (m, CH2NH), 4.56-4.62 (m, CH), 6.63 [br d, J=6.6
Hz, NHC(O)CH3], 6.89-6.98 (br t, CH2NH), 7.18 (d, J=8.1
Hz, 2 ArH), 7.35 (d, J = 8.1 Hz, 2 ArH); addition of excess
(R)-(-)-mandelic acid to a CDCl3 solution of (R)-14 gave only

Article
Journal of Medicinal Chemistry, 2010, Vol. 53, No. 3 1299
J = 4.2, 9.1 Hz, CHH0O), 4.41-4.49 (m, CH2OCH3, CH2NH),
4.51-4.58 (m, CH), 6.42-6.52 [br d, NHC(O)CH3], 6.75-6.84
(br t, CH2NH), 7.24 (d, J = 7.9 Hz, 2 ArH), 7.30 (d, J = 7.9 Hz, 2
ArH); addition of excess (R)-(-)-mandelic acid to a CDCl3 solu-
tion of (R)-17 gave only one signal for the acetyl methyl and
one signal for the ether methyl protons; 13C NMR (CDCl3) δ 23.2
[CH3C(O)], 43.3 (CH2NH), 52.5 (CHCH2), 58.1 (OCH3), 59.1
(OCH3), 71.8 (CH2OCH3), 74.3 (CH2OMe), 127.5, 128.1, 137.3,
137.5 (4 ArC), 170.0, 170.3 [2 C(O)]; HRMS (M þ Hþ) (ESIþ)
295.1658 [M þ Hþ] (calcd for C15H22N2O4Hþ 295.1658). Anal.
(C15H22N2O4): C, H, N.
Preparation of (R)-N-(40-Trifluoromethyl)benzyl 2-Acetamido-
3-methoxypropionamide [(R)-18]. An EtOH solution (250 mL)
of (R)-N-(40-trifluoromethyl)benzyl 2-N-(benzyloxycarbonyl)-
amino-3-methoxypropionamide (1.20 g, 3.0 mmol) was treated
with H2 (1 atm) in the presence of 10% Pd/C (120 mg) at room
temperature (16 h). The mixture was carefully filtered through a
bed of Celite. The pad was washed with MeOH and CH2Cl2, and
the washings were collected and evaporated in vacuo to yield a
yellow solid: 1H NMR (CDCl3) δ 1.62-1.67 (br d, NH2), 3.39
(s, OCH3), 3.58-3.72 (m, CH2, CH), 4.52 (d, J = 6.0 Hz,
HNCH2), 7.39 (d, J=8.2 Hz, 2 ArH), 7.58 (d, J=8.2 Hz, 2
ArH), 7.88-7.89 [br s, NHC(O)].
mL) of (R)-27 (1.00 g, 3.1 mmol) was treated with H2 (1 atm) in
the presence of 10% PtO2 (50 mg) at room temperature (16 h).
The mixture was carefully filtered through a bed of Celite.
The filtrate was concentrated in vacuo, and the residue was
purified by flash chromatography on silica gel with EtOAc as
the eluant to yield (R)-20 (510 mg, 51%) as a white solid: Rf =
0.27 (EtOAc); mp 105-107 °C; [R]25 3.0° (c 0.5, DMSO); IR
D
(nujol) 3283, 3085, 1638, 1550, 1457, 1379, 1299, 1122, 979, 725,
1
605 cm-1; H NMR (CDCl3) δ 1.81-1.92 (m, CH2), 2.03 [s,
CH3C(O)], 2.67 (t, J = 7.8 Hz, CH2Ph), 3.33-3.46 (m, CHH0O,
CH2O, 2 OCH3), 3.80 (dd, J = 4.0, 9.1 Hz, CHH0O), 4.44 (d, J =
5.7 Hz, CH2NH), 4.50-4.57 (m, CH), 6.45 [br d, J = 6.6 Hz,
NHC(O)CH3], 6.70-6.75 (br t, CH2NH), 7.15-7.20 (m, 4 ArH);
addition of excess (R)-(-)-mandelic acid to a CDCl3 solution of
(R)-20 gave only one signal for the acetyl methyl and one signal for
the ether methyl protons; 13C NMR (CDCl3) δ 23.2 [CH3C(O)],
31.2, 31.9 (2 CH2), 43.3 (CH2NH), 52.4 (CHCH2), 58.6, 59.1 (2
OCH3), 71.7, 71.9 (2 CH2OMe), 127.5, 128.8, 135.3, 141.4 (4 ArC),
169.9, 170.2 [2 C(O)]; HRMS (M þ Naþ) (ESIþ) 345.1784 [M þ
Naþ] (calcd for C17H26N2O4Naþ 345.1790). Anal. (C17H26N2O4):
C, H, N.
Preparation of (R)-N-(40-Vinyl)benzyl 2-Acetamido-3-methoxy-
propionamide [(R)-21]. pTSA (769 mg, 4.04 mmol) was added to a
CH2Cl2 (6 mL) solution of (R)-N-(40-vinyl)benzyl 2-N-(tert-
butoxycarbonyl)amino-3-methoxypropionamide (900 mg, 2.7
mmol). The reaction mixture was stirred at room temperature
(24 h), and then triethylamine (2.3 mL, 16.2 mmol) followed
by acetyl chloride (574 μL, 8.1 mmol) was added at 0 °C. The
solution was stirred at room temperature (30 min). Aqueous 10%
citric acid was added, and then the organic layer was separated.
The aqueous layer was extracted with CH2Cl2 (2 ꢀ 30 mL). The
organic layers were combined, washed with aqueous saturated
NaHCO3 and H2O, dried (MgSO4), and concentrated in vacuo.
The residue was purified by column chromatography (SiO2;
EtOAc) to yield 700 mg (77%) of white solid: Rf = 0.49 (5/5
EtOAc/acetone); mp 148-149 °C; [R]26D 3.5° (c 1.0, DMSO); IR
(nujol)3281, 3093, 1638, 1552, 1456, 1381, 1298, 1246, 1125, 1043,
Using method D, triethylamine (0.5 mL, 3.5 mmol) and acetyl
chloride (250 μL, 3.5 mmol) gave 495 mg (55%) of (R)-18 as a
white solidafter recrystallization with EtOAc:Rf = 0.45 (EtOAc);
mp 160-161 °C; [R]26.7 2.6° (c 0.5, DMSO); IR (nujol) 3393,
D
3278, 3145, 2923, 2834, 2723, 2673, 1638, 1552, 1456, 1374, 1157,
1111, 965, 840, 726 cm-1; 1H NMR (CDCl3) δ 2.05 [s, CH3C(O)],
3.40 (s, OCH3), 3.45 (dd, J = 7.8, 9.3 Hz, CHH0O), 3.83 (dd, J =
4.2, 9.3 Hz, CHH0O), 4.50-4.61 (m, CH2NH, CH), 6.37-6.44 [br
d, NHC(O)CH3], 6.85-6.94 (br t, CH2NH), 7.38 (d, J = 8.2 Hz,
2 ArH), 7.58 (d, J = 8.2 Hz, 2 ArH); addition of excess (R)-(-)-
mandelic acid to a CDCl3 solution of (R)-18 gave only one signal
for the acetyl methyl and one signal for the ether methyl protons;
13C NMR (CDCl3) δ 23.1 [CH3C(O)], 42.9 (CH2NH), 52.5
(CHCH2), 59.1 (OCH3), 71.6 (CH2OCH3), 124.0 (q, J = 270.4
Hz, CF3), 125.6 (q, J = 3.4 Hz, C3), 127.5 (C2), 129.7 (q, J = 31.9
Hz, C4), 142.0 (C1), 170.3, 170.5 [2 C(O)]; HRMS (M þ Hþ)
(ESIþ) 319.1270 [M þ Hþ] (calcd for C14H17F3N2O3Hþ
307.1269). Anal. (C14H17F3N2O3): C, H, F, N.
986, 917, 825, 722, 604 cm-1 1H NMR (CDCl3) δ 2.03 [s,
;
CH3C(O)], 3.38 (s, OCH3), 3.43 (dd, J = 7.2, 9.0 Hz, CHH0O),
3.80 (dd, J = 4.2, 9.0 Hz, CHH0O), 4.43-4.52 (m, CH2NH),
4.53-4.58 (m, CH), 5.24 (d, Jcis = 10.8 Hz, CHdCHH0), 5.75 (d,
Preparation of (R)-N-[40-(3-Hydroxypropyl)]benzyl 2-Acetamido-
3-methoxypropionamide [(R)-19].4-(3-Hydroxypropyl)benzylamine
(600 mg, 3.6 mmol) was added to a THF (33 mL) solution of the
(R)-2-acetamido-3-methoxypropionoic acid [(R)-58]25 (532 mg, 3.3
mmol), and the mixture was stirred at room temperature (5 min).
DMTMM28b (1.10 g, 4.0 mmol) was added, and the reaction
mixture was stirred at room temperature (16 h). The white pre-
cipitate was filtered, and the filtrate was concentrated in vacuo. The
residue was purified by flash column chromatography on silica gel
with EtOAc to an EtOAc/acetone mixture (5/5) as the eluant to yield
after recrystallization with EtOAc a white solid (560 mg, 55%):
Rf = 0.26 (8/2 EtOAc/acetone); mp 118 °C; [R]26.9D -25.0° (c 0.5,
CHCl3); IR (nujol mull) 3339, 3279, 2951, 2862, 1630, 1552, 1456,
1376, 1304, 1195, 1140, 1097, 1038, 909, 820, 724 cm-1; 1H NMR
(CDCl3) δ 1.34-1.45 (br m, OH), 1.83-1.93 (br m, CH2-
CH2CH2), 2.03 [s, CH3C(O)], 2.70 (t, J = 7.8 Hz, CH2Ar), 3.38
(s, OCH3), 3.43 (dd, J=7.5, 9.0 Hz, CHH0O), 3.63-3.72 (br m,
CH2OH), 3.80 (dd, J=3.9, 9.0 Hz, CHH0O), 4.44 (d, J=6.0 Hz,
CH2NH), 6.41-6.50 [br d, CH3C(O)NH], 6.69-6.79 (m, NH),
7.12-7.23 (m, 4 ArH); addition of excess (R)-(-)-mandelic acid to
a CDCl3 solution of (R)-19 gave only one signal for the acetyl
methyl and one signal for the ether methyl protons; 13C NMR
(CDCl3) δ 23.0 [CH3C(O)], 31.7, 34.2 (2 CH2), 43.2 (NCH2),
52.6 (CHCH2), 59.0 (OCH3), 61.9 (CH2OH), 72.1 (CH2O), 127.5,
128.7, 135.3, 141.2 (4 ArC), 170.1, 170.6 [2 C(O)]; HRMS (M þ
Hþ) (ESIþ) 309.1815 [M þ Hþ] (calcd for C16H24N2O4Hþ
319.1814). Anal. (C16H24N2O4): C, H, N.
J
trans=17.7 Hz, CHdCHH0), 6.46 [br d, J=6.6 Hz, NHC(O)-
CH3], 6.70 (dd, Jcis=10.8 Hz, Jtrans=17.7 Hz, CHdCH2), 6.75-
6.82 (br m, CH2NH), 7.24 (d, J = 8.1 Hz, 2 ArH), 7.35 (d, J = 8.1
Hz, 2 ArH); addition of excess (R)-(-)-mandelic acid to a CDCl3
solution of (R)-21 gave only one signal for the acetyl methyl
and one signal for the ether methyl protons; 13C NMR (CDCl3) δ
23.3 [CH3C(O)], 43.4 (CH2NH), 52.6 (CHCH2), 59.2 (OCH3),
72.0 (CH2OCH3), 114.1 (CHdCH2), 126.7, 127.8, 136.6, 137.0,
137.6 (4 ArC, CHdCH2), 170.2, 170.6 [2 C(O)]; HRMS
(M þ Kþ) (ESIþ) 315.1115 [M þ Kþ] (calcd for C15H20N2O3Kþ
315.1111). Anal. (C15H20N2O3): C, H, N.
Preparation of (S)-N-(40-Vinyl)benzyl 2-Acetamido-3-methoxy-
propionamide [(S)-21]. Employing the same procedure utilized for
(R)-N-(40-vinyl)benzyl 2-acetamido-3-methoxypropionamide and
using (S)-N-(40-vinyl)benzyl 2-N-(tert-butoxycarbonyl)amino-
3-methoxypropionamide (900 mg, 2.7 mmol), triethylamine (2.3
mL, 16.2 mmol), and acetyl chloride (574 μL, 8.1 mmol) gave 690
mg (76%) of (S)-21 after silica gel column chromatography: Rf=
0.45 (1/9 MeOH/EtOAc); mp 140-142 °C; [R]26 -3.1° (c 1.0,
D
DMSO); IR (nujol) 3284, 3087, 1640, 1548, 1457, 1378, 1298, 1244,
1198, 1127, 1046, 985, 912, 826, 721 cm-1; 1H NMR (CDCl3) δ
2.02 [s, CH3C(O)], 3.38 (s, OCH3), 3.44 (dd, J = 7.5, 9.0, Hz,
CHH0O), 3.80 (dd, J = 4.2, 9.0 Hz, CHH0O), 4.39-4.48 (m,
CH2NH), 4.53-4.59 (m, CH), 5.24 (d, Jcis=11.1 Hz, CHdCHH0),
5.75 (d, Jtrans =17.4 Hz, CHdCHH0), 6.48 [br d, J = 6.6 Hz,
NHC(O)CH3], 6.70 (dd, Jcis = 11.1 Hz, Jtrans = 17.4 Hz,
CHdCH2), 6.82-6.85 (br m, CH2NH), 7.22 (d, J = 8.1 Hz, 2
ArH), 7.34 (d, J = 8.1 Hz, 2 ArH); addition of excess (R)-(-)-
mandelic acid to a CDCl3 solution of (S)-21 gave only one signal
Preparation of (R)-N-[40-(3-Methoxypropyl)]benzyl 2-Aceta-
mido-3-methoxypropionamide [(R)-20]. An EtOH solution (30

1300 Journal of Medicinal Chemistry, 2010, Vol. 53, No. 3
Salomeꢀ et al.
for the acetyl methyl and one signal for the ether methyl protons;
13C NMR (CDCl3) δ 23.4 [CH3C(O)], 43.5 (CH2NH), 52.6
(CHCH2), 59.3 (OCH3), 71.9 (CH2OCH3), 114.2 (CHdCH2),
126.7, 127.8, 136.5, 137.1, 137.6 (4 ArC, CHdCH2), 170.2, 170.5
[2 C(O)]; HRMS (M þ Kþ) (ESIþ) [M þ Kþ] 315.1114 (calcd
Hz, 2 ArH), 7.42 (d, J = 8.4 Hz, 2 ArH), 8.11 [br d, J = 7.8 Hz,
NHC(O)CH3], 8.52 (br t, J = 6.0 Hz, CH2NH); addition of
excess (R)-(-)-mandelic acid to a CDCl3 solution of (S)-23 gave
only one signal for the acetyl methyl and one signal for the ether
methyl protons; 13C NMR (CDCl3) δ 23.2 [CH3C(O)], 43.2
(CH2NH), 52.5 (CHCH2), 59.1 (OCH3), 71.7 (CH2OCH3), 77.3
(CtC), 83.3 (CtC), 121.2, 127.3, 132.4, 138.8 (4 ArC), 170.1,
170.4 [2 C(O)]; the HMQC experiment showed a correlation
for C15H20N2O3Kþ 315.1111). Anal. (C15H20N2O3 0.10H2O):
3
C, H, N.
Preparation of (R)-N-(Biphenyl-4-yl)methyl 2-Acetamido-3-meth-
oxypropionamide [(R)-22]. Using method D, triethylamine (0.79
mL, 5.7 mmol), acetyl chloride (561 μL, 2.8 mmol), and (R)-
N-(biphenyl-4-yl)methyl 2-amino-3-methoxypropionamide hydro-
chloride (600 mg, 1.9 mmol) gave 380 mg (55%) of (R)-N-(biphenyl-
4-yl)methyl 2-acetamido-3-methoxypropionamide as a white solid
after purification by flash column chromatography on silica gel with
an EtOAc/MeOH mixture (100/0 to 80/20) as the eluant and
recrystallization with EtOAc: Rf = 0.20 (EtOAc); mp 178-180
°C; [R]26.9D -8.8° (c 0.5, CHCl3); IR (nujol) 3293, 3087, 2870, 1642,
1547, 1457, 1376, 1298, 1127, 727 cm-1;1H NMR (CDCl3) δ2.04 [s,
CH3C(O)], 3.40 (s, OCH3), 3.45 (dd, J = 7.5, 9.2 Hz, CHH0O), 3.83
(dd, J = 3.9, 9.2 Hz, CHH0O), 4.50-4.61 (m, CH2NH, CH), 6.45
[br d, J = 5.7 Hz, NHC(O)CH3], 6.76-6.84 (br t, CH2NH),
7.31-7.38 (m, 3 ArH), 7.41-7.48 (m, 2 ArH), 7.55-7.60 (m,
4 ArH); addition of excess (R)-(-)-mandelic acid to a CDCl3
solution of (R)-22 gave only one signal for the acetyl methyl and
one signal for the ether methyl protons; 13C NMR (CDCl3) δ 23.2
[CH3C(O)], 43.2 (CH2NH), 52.4 (CHCH2), 59.1 (OCH3), 71.6
(CH2OCH3), 127.0, 127.3, 127.4, 127.8, 128.8, 136.9, 140.5 (7 ArC),
170.0, 170.3 [2 C(O)]; one signal was not detected and is believed to
overlap with nearby peaks; HRMS (M þ Hþ) (ESIþ) 327.1709
[M þ Hþ] (calcd for C19H22N2O3Hþ 327.1708). Anal. (C19H22-
1
between the δ 3.07 signal in the H NMR spectrum and the δ
77.3 peak in the 13C NMR spectrum; 13C NMR (DMSO-d6) δ
22.3 [CH3C(O)], 41.6 (CH2NH), 52.4 (CHCH2), 58.0 (OCH3),
71.8 (CH2OCH3), 80.2 (CtC), 83.2 (CtC), 119.8, 126.9, 131.3,
140.2 (4 ArC), 169.2, 169.6 [2 C(O)]; the HMQC experiment
showed a correlation between the δ 4.14 signal in the 1H NMR
spectrum and the δ 80.2 peak in the 13C NMR spectrum; HRMS
(M þ Naþ) (ESIþ) 297.1212 [M þ Naþ] (calcd for C15H18N2-
O3Naþ 297.1215). Anal. (C15H18N2O3 0.25H2O): C, H, N.
3
Preparation of (R)-N-[40-(Prop-1-ynyl)]benzyl 2-Acetamido-3-meth-
oxypropionamide [(R)-24]. To an anhydrous triethylamine solution
(0.1 M, 2.66 mL) of (R)-38 (100 mg, 0.266 mmol) were sequentially
added dichlorobis(triphenylphosphine)palladium(II) (19 mg, 0.026
mmol) and CuI (2.5 mg, 0.013 mmol) in a flame-dried Schlenk tube
under Ar. The mixture was cooled to -78 °C, and then the reaction
vessel was evacuated and propyne bubbled into the triethylamine
solution until the solution reached ∼1 atm. The mixture was stirred at
room temperature (16 h). The mixture was cooled to -78 °C and re-
evacuated. A balloon of propyne was bubbled into the mixture, and
the reaction mixture was stirred at room temperature (24 h). The
reaction mixture was concentrated in vacuo, and the residue was
purified by flash chromatography on silica gel with an EtOAc/hexane
mixture (5/5 to 10/0) as the eluant to yield (R)-24 (70 mg, 92%) as a
white solid. The desired product (60 mg) was purified with 340 mg
of resin scavenger (PhosPhonics, catalog no. SPM32) to remove
the traces of palladium to yield 50 mg (66%) of (R)-N-[40-(prop-1-
ynyl)]benzyl 2-acetamido-3-methoxypropionamide: Rf = 0.37 (Et-
OAc); mp 178-180 °C; [R]24.3D -18.0° (c 0.5, CHCl3); IR (nujol)
3474, 3273, 2960, 2856, 1683, 1550, 1457, 1375, 1299, 1125, 978, 811,
724 cm-1; 1H NMR (CDCl3) δ 2.04 [s, CH3C(O)], 2.05 (s, CH3),
3.38-3.45 (m, CHH0O, OCH3), 3.81(dd, J= 4.2, 9.3 Hz, CHH0O),
4.39-4.50 (m, CH2NH), 4.51-4.57 (m, CH), 6.39-6.45 [br d,
NHC(O)CH3], 6.71-6.79 (br t, CH2NH), 7.17 (d, J = 8.1 Hz, 2
ArH), 7.35 (d, J = 8.1 Hz, 2 ArH); addition of excess (R)-(-)-
mandelic acid to a CDCl3 solution of (R)-24 gave only one signal for
the acetyl methyl and one signal for the ether methyl protons; 13C
NMR (CDCl3) δ 4.33 (CH3), 23.2 [CH3C(O)], 43.3 (CH2NH), 52.4
(CHCH2), 59.1 (OCH3), 71.7 (CH2OCH3), 79.4 (CtC), 86.1
(CtC), 123.2, 127.3, 131.8, 137.3 (4 ArC), 170.0, 170.3 [2 C(O)];
HRMS (M þ Hþ) (ESIþ) 311.1372 [M þ Hþ] (calcd for
N2O3 0.1H2O): C, H, N.
3
Preparation of (R)-N-(40-Ethynyl)benzyl 2-Acetamido-3-meth-
oxypropionamide [(R)-23]. A 1 M THF solution of TBAF (8.7
mL, 8.66 mmol) was added to a THF (60 mL) solution of (R)-26
(1.50 g, 4.33 mmol), and then the solution was stirred at room
temperature (4 h). CH2Cl2 and an aqueous 10% citric acid solution
were added, and the organic layer was separated. The aqueous
layer was extracted with CH2Cl2 (2 ꢀ 30 mL). The organic layers
were combined, dried (MgSO4), and concentrated in vacuo. The
residue was purified by flash chromatography on silica gel with
EtOAc as the eluant to yield (R)-23 (0.81 g, 68%) as a white solid:
Rf = 0.41 (EtOAc); mp 161-162 °C; [R]24D 4.2° (c 0.5, DMSO);
IR (nujol) 3290, 1634, 1544, 1458, 1375, 1311, 1240, 1197, 1104,
1041, 714 cm-1; 1H NMR (CDCl3) δ 2.02 [s, CH3C(O)], 3.07 (s,
CtCH), 3.37 (s, OCH3), 3.45 (dd, J = 7.2, 9.3 Hz, CHH0O), 3.77
(dd, J = 4.5, 9.3 Hz, CHH0O), 4.36-4.49 (m, CH2NH), 4.56-4.63
(m, CH), 6.60 [br d, J = 6.9 Hz, NHC(O)CH3], 7.01-7.10 (br t,
CH2NH), 7.20 (d, J = 8.2 Hz, 2 ArH), 7.44 (d, J = 8.2 Hz, 2 ArH);
addition of excess (R)-(-)-mandelic acid to a CDCl3 solution of
(R)-23 gave only one signal for the acetyl methyl and one signal for
the ether methyl protons; 13C NMR (CDCl3) δ 23.1 [CH3C(O)],
43.1 (CH2NH), 52.5 (CHCH2), 59.0 (OCH3), 71.7 (CH2OCH3),
77.3 (CtC), 82.2 (CtC), 121.2, 127.3, 132.4, 138.7 (4 ArC),
170.1, 170.4 [2 C(O)]; HRMS (M þ Naþ) (ESIþ) 297.1210
[M þ Naþ] (calcd for C15H18N2O3Naþ 297.1215). Anal. (C15H18-
N2O3): C, H, N.
C16H20N2O3Hþ 311.1372). Anal. (C16H20N2O3 0.2H2O): C, H, N.
3
Preparation of (R)-N-[40-(3,3-Dimethylbut-1-ynyl)]benzyl 2-Acet-
amido-3-methoxypropionamide [(R)-25]. To an anhydrous THF (10
mL) solution of (R)-38 (376 mg, 1.0 mmol) were sequentially added
triethylamine (280 μL, 2.0 mmol), 3,3-dimethylbut-1-yne (182 μL,
1.5 mmol), dichlorobis(triphenylphosphine)palladium(II) (35 mg,
0.05 mmol), and CuI (19 mg, 0.1 mmol) under Ar. The mixture was
stirred at room temperature (4 h), and then Et2O (10 mL) was
added and the precipitate filtered through a Celite pad. The filtrate
was concentrated in vacuo, and the residue was purified by flash
chromatography on silica gel with an EtOAc/MeOH mixture (9/1)
as the eluant to yield (R)-25 (220 mg, 66%) as a brown solid: Rf =
Preparation of (S)-N-(40-Ethynyl)benzyl 2-Acetamido-3-meth-
oxypropionamide [(S)-23]. Employing the preceding procedure
and using (S)-26 (50 mg, 0.145 mmol) and TBAF (290 μL, 0.290
mmol) gave 753 mg (91%) of (S)-23 as a white solid: Rf = 0.41
(EtOAc); mp 159-160 °C; [R]24 -4.4° (c 0.5, DMSO); IR
0.22 (EtOAc); mp 120-121 °C; [R]25 4.8° (c 1.0, DMSO); IR
D
D
(nujol) 3289, 2728, 1635, 1544, 1458, 1375, 1304, 1234, 975, 724
cm-1; 1H NMR (CDCl3) δ 2.03 [s, CH3C(O)], 3.07 (s, CtCH),
3.38 (s, OCH3), 3.44 (dd, J = 7.5, 9.0 Hz, CHH0O), 3.80 (dd, J =
4.2, 9.0 Hz, CHH0O), 4.41-4.51 (m, CH2NH), 4.52-4.57 (m,
CH), 6.46 [br d, J = 5.4 Hz, NHC(O)CH3], 6.80-6.92 (br t,
CH2NH), 7.21 (d, J = 8.4 Hz, 2 ArH), 7.45 (d, J = 8.4 Hz, 2
ArH); 1H NMR (DMSO-d6) δ 1.87 [s, CH3C(O)], 3.25 (s,
OCH3), 3.44-3.55 (m, CHH0, CHH0), 4.14 (s, CtCH), 4.29
(d, J = 6.0 Hz, CH2NH), 4.43-4.48 (m, CH), 7.25 (d, J = 8.4
(nujol) 3287, 2727, 2364, 1641, 1547, 1458, 1375, 1297, 1132, 972,
1
816, 724 cm-1; H NMR (CDCl3) δ 1.31 [s, (CH3)3C], 2.00 [s,
CH3C(O)], 3.35(s, OCH3), 3.42 (dd, J=7.5, 9.0Hz, CHH0O), 3.76
(dd, J = 4.2, 9.0 Hz, CHH0O), 4.33-4.50 (m, CH2NH), 4.50-4.61
(m, CH), 6.60 [d, J = 6.3 Hz, NHC(O)CH3], 6.91-6.99 (br t, CH2-
NH), 7.14 (d, J = 8.1 Hz, 2 ArH), 7.33 (d, J = 8.1 Hz, 2 ArH);
addition of excess (R)-(-)-mandelic acid to a CDCl3 solution of
(R)-25 gave only one signal for the acetyl methyl and one signal
for the ether methyl protons; 13C NMR (CDCl3) δ 23.2

Article
Journal of Medicinal Chemistry, 2010, Vol. 53, No. 3 1301
[CH3C(O)], 27.9 [C(CH3)3], 31.0 [C(CH3)3], 43.3 (CH2NH), 52.5
(CHCH2), 59.1 (OCH3), 71.8 (CH2OCH3), 78.6 (CtC), 98.8
(CtC), 123.3, 127.2, 131.8, 137.1 (4 ArC), 170.2, 170.6 [2 C(O)];
HRMS (M þ Hþ) (ESIþ) 331.2019 [M þ Hþ] (calcd for C19-
9.0 Hz, CHH0O), 4.32 (s, CtCCH2OCH3), 4.38-4.52 (m, CH2-
NH), 4.54-4.61 (m, CH), 6.52 [d, J = 6.6 Hz, NHC(O)CH3],
6.91-6.99 (br t, CH2NH), 7.19 (d, J=7.9 Hz, 2 ArH), 7.41 (d, J=
7.9 Hz, 2 ArH); addition of excess (R)-(-)-mandelic acid to a
CDCl3 solution of (R)-27 gave only one signal for the acetyl
methyl and one signal for the ether methyl protons; 13C NMR
(CDCl3) δ 23.2 [CH3C(O)], 43.2 (CH2NH), 52.5 (CHCH2), 57.7
(CtCCH2OCH3), 59.1 (OCH3), 60.4 (CtCCH2OCH3), 71.7
(CH2OCH3), 85.2 (CtC), 86.0 (CtC), 121.8, 127.3, 132.1,
138.4 (4 ArC), 170.4 [br, 2 C(O)]; HRMS (M þ Hþ) (ESIþ)
319.1652 [M þ Hþ] (calcd for C17H22N2O4Hþ 319.1658). Anal.
H26N2O3Hþ 331.2029). Anal. (C19H26N2O3 0.2H2O): C, H, N.
3
Preparation of (R)-N-[40-(Trimethylsilyl)ethynyl]benzyl 2-Acet-
amido-3-methoxypropionamide [(R)-26]. To an anhydrous THF
(70 mL) solution of (R)-38 (2.40 g, 6.38 mmol) were sequentially
added triethylamine (1.8 mL, 12.76 mmol), trimethylsilylacetylene
(1.35 mL, 9.57 mmol), dichlorobis(triphenylphosphine)palladium-
(II) (224 mg, 0.319 mmol), and CuI (121 mg, 0.638 mmol) under
Ar. The mixture was stirred at room temperature (4 h), and then
Et2O was added and the precipitate filtered through a Celite pad.
The filtrate was concentrated in vacuo, and the residue was purified
by flash chromatography on silica gel with an EtOAc/MeOH
mixture (9/1) as the eluant to yield (R)-26 (1.50 g, 68%). The
desired product (1.50 g) was purified with 7.50 g of resin scavenger
(PhosPhonics, catalog no. SPM32) to remove the traces of palla-
dium to yield 1.20 g (55%) of (R)-26 as a brown solid: Rf = 0.41
(EtOAc); mp 126-127 °C; [R]24D 6.1° (c 1.0, DMSO); IR (nujol)
3285, 2157, 1641, 1546, 1457, 1375, 1302, 1248, 1130, 975, 862, 723
cm-1; 1H NMR (CDCl3) δ 0.24 [s, (CH3)3Si], 1.99 [s, CH3C(O)],
3.35 (s, OCH3), 3.45 (dd, J=7.2, 9.0 Hz, CHH0O), 3.75 (dd, J=4.2,
9.0 Hz, CHH0O), 4.33-4.47 (m, CH2NH), 4.57-4.62 (m, CH),
6.66 [br d, J=6.9 Hz, NHC(O)CH3], 7.07-7.13 (br t, CH2NH),
7.17 (d, J=7.9 Hz, 2 ArH), 7.40 (d, J = 7.9 Hz, 2 ArH); addition of
excess (R)-(-)-mandelic acid to a CDCl3 solution of (R)-26 gave
only one signal for the acetyl methyl and one signal for the ether
methyl protons; 13C NMR (CDCl3) δ -0.1 [(CH3)3Si], 23.2
[CH3C(O)], 43.2 (CH2NH), 52.4 (CHCH2), 59.1 (OCH3), 71.6
(CH2OCH3), 94.4 (CtC), 104.7 (CtC), 122.4, 127.2, 132.3, 138.3
(4 ArC), 170.0, 170.3 [2 C(O)]; HRMS (M þ Naþ) (ESIþ)
369.1605 [M þ Naþ] (calcd for C18H26N2O3SiNaþ 369.1610).
Anal. (C18H26N2O3Si): C, H, N.
(C17H22N2O4 0.33H2O): C, H, N.
3
Preparation of (R)-N-(40-Cyano)benzyl 2-Acetamido-3-meth-
oxypropionamide [(R)-28]. A MeOH solution (150 mL) of (R)-
N-(40-cyano)benzyl 2-N-(benzyloxycarbonyl)amino-3-methoxy-
propionamide (1.80 g, 4.8 mmol) was treated with H2 (1 atm) in
the presence of 10% Pd/C (250 mg) at room temperature
(36 h). The mixture was carefully filtered through a bed of Celite,
and the filtrate was evaporated in vacuo to yield a colorless oil.
Using method D, triethylamine (810 μL, 5.8 mmol) and acetyl
chloride (410 μL, 5.8 mmol) gave 320 mg (42%) of (R)-28 as a
white solid after trituration with EtOAc: Rf = 0.54 (9/1 EtOAc/
MeOH); mp 168-169 °C; [R]24D 4.9° (c 1.0, DMSO); IR (nujol)
3273, 2725, 2226, 1635, 1547, 1458, 1374, 1309, 1191, 1093, 907,
727 cm-1 1H NMR (DMSO-d6) δ 1.87 [s, CH3C(O)], 3.26
;
(s, OCH3), 3.45-3.57 (m, CH2OCH3), 4.36 (d, J = 6.0 Hz, CH2-
NH), 4.43-4.49 (m, CH), 7.34(d, J =8.6 Hz, 2 ArH), 7.42(d, J=
8.6 Hz, 2 ArH), 8.14 [d, J = 7.8 Hz, NHC(O)CH3], 8.61 (t, J =
6.0 Hz, CH2NH); addition of excess (R)-(-)-mandelic acid to a
CDCl3 solution of (R)-28 gave only one signal for the acetyl
methyl and one signal for the ether methyl protons; 13C NMR
(DMSO-d6) δ 22.4 [CH3C(O)], 41.7 (CH2NH), 52.6 (CHCH2),
58.1 (OCH3), 71.9 (CH2OMe), 109.3 (CCN), 118.8 (CN), 127.6,
132.1, 145.3 (3 ArC), 169.4, 170.0 [2 C(O)]; HRMS (M þ Naþ)
(ESIþ) 298.1163 [M þ Naþ] (calcd for C14H17N3O3Naþ 298.1168).
Preparation of (S)-N-[40-(Trimethylsilyl)ethynyl]benzyl 2-Ace-
tamido-3-methoxypropionamide [(S)-26]. Employing the preced-
ing procedure and using (S)-38 (2.40 g, 6.38 mmol), triethyl-
amine (1.8 mL, 12.76 mmol), CuI (121 mg, 0.638 mmol), dichloro-
bis(triphenylphosphine)palladium(II) (224 mg, 0.319 mmol), and
trimethylsilylacetylene (1.35 mL, 9.57 mmol) gave 1.97 g (91%) of
Anal. (C14H17N3O3 0.25H2O): C, H, N.
3
Preparation of (S)-N-(40-Cyano)benzyl 2-Acetamido-3-meth-
oxypropionamide [(S)-28]. Employing the preceding procedure
and using (S)-N-(40-cyano)benzyl 2-N-(benzyloxycarbonyl)-
amino-3-methoxypropionamide (1.20 g, 3.2 mmol), 10% Pd/C
(250 mg), triethylamine (540 μL, 3.8 mmol), and acetyl chloride
(273 μL, 3.8 mmol) gave 620 mg (70%) of (S)-28 as a white solid
after trituration with EtOAc: Rf = 0.54 (9/1 EtOAc/MeOH);
mp 168-169 °C; [R]25D -4.9° (c 1.0, DMSO); IR (nujol) 3271,
2726, 2228, 1630, 1552, 1458, 1374, 1312, 1194, 1095, 908, 729
cm-1; 1H NMR (CDCl3) δ 2.04 [s, CH3C(O)], 3.40 (s, OCH3),
3.45 (dd, J=7.2, 9.6 Hz, CHH0O), 3.81 (dd, J=3.9, 9.6 Hz,
CHH0O), 4.49-4.61 (m, CH2NH, CH), 6.48 [br d, J=5.7 Hz,
NHC(O)CH3], 7.06-7.08 (br m, CH2NH), 7.34 (d, J=8.4 Hz, 2
ArH), 7.36 (d, J=8.4 Hz, 2 ArH); addition of excess (R)-(-)-
mandelic acid to a CDCl3 solution of (S)-28 gave only one signal
for the acetyl methyl and one signal for the ether methyl protons;
13C NMR (CDCl3) δ 23.1 [CH3C(O)], 43.0 (CH2NH), 52.5
(CHCH2), 59.1 (OCH3), 71.5 (CH2OCH3), 111.2 (CCN), 118.6
(CN), 127.8, 132.4, 143.5 (3 ArC), 170.3, 170.4 [2 C(O)]; HRMS
(M þ Naþ) (ESIþ) 298.1163 [M þ Naþ] (calcd for C14H17-
N3O3Naþ 298.1168). Anal. (C14H17N3O3): C, H, N.
(S)-26 as a brown solid: Rf = 0.41 (EtOAc); mp 126-127 °C; [R]24
D
-6.2° (c 1.0, DMSO); IR (nujol) 3285, 2727, 2157, 1641, 1546,
1457, 1374, 1304, 1250, 1137, 862, 725 cm-1; 1H NMR (DMSO-d6)
δ 0.22 [s, (CH3)3Si], 1.87 [s, CH3C(O)], 3.25 (s, OCH3), 3.44-3.55
(m, CHH0O, CHH0O), 4.29 (d, J = 5.7 Hz, CH2NH), 4.43-4.51
(m, CH), 7.24 (d, J=8.2 Hz, 2 ArH), 7.40 (d, J=8.2 Hz, 2 ArH),
8.10 [br d, J = 8.1 Hz, NHC(O)CH3], 8.53 (br t, J = 6.0 Hz,
CH2NH); addition of excess (R)-(-)-mandelic acid to a CDCl3
solution of (S)-26 gave only one signal for the acetyl methyl and one
signal for the ether methyl protons; 13C NMR (DMSO-d6) δ -0.2
[(CH3)3Si], 22.4 [CH3C(O)], 41.7 (CH2NH), 52.6 (CHCH2), 58.1
(OCH3), 71.9 (CH2OCH3), 93.6(CtC), 105.1 (CtC), 120.0, 127.1,
131.4, 140.4 (4 ArC), 169.3, 169.8 [2 C(O)]; HRMS (M þ Naþ)
(ESIþ) 369.1603 [M þ Naþ] (calcd for C18H26N2O3SiNaþ
369.0161). Anal. (C18H26N2O3Si): C, H, N.
Preparation of (R)-N-[40-(3-Methoxyprop-1-ynyl)]benzyl 2-Acet-
amido-3-methoxypropionamide [(R)-27]. To an anhydrous THF (10
mL) solution of (R)-38 (376 mg, 1.0 mmol) were sequentially added
triethylamine (280 μL, 2.0 mmol), 3-methoxyprop-1-yne (125 μL,
1.5 mmol), dichlorobis(triphenylphosphine)palladium(II) (70 mg,
0.1 mmol), and CuI (38 mg, 0.2 mmol) under Ar. The mixture was
stirred at room temperature (4 h), and then Et2O (10 mL) was
added and the precipitate filtered through a Celite pad. The filtrate
was concentrated in vacuo, and the residue was purified by flash
chromatography on silica gel with an EtOAc/MeOH mixture (9/1)
as the eluant to yield (R)-27 (260 mg, 82%) as a beige solid: Rf =
Preparation of (R)-N-(40-Formyl)benzyl 2-Acetamido-3-meth-
oxypropionamide [(R)-29]. (R)-N-[40-(1,3-Dioxolan-2-yl)]benzyl
2-acetamido-3-methoxypropionamide (1.62 g, 5.0 mmol) was
dissolved in a 2:1 THF/H2O mixture (30 mL), and 2 M HCl
(10 drops) was added. The reaction mixture was stirred at room
temperature overnight and diluted with H2O (20 mL). The
solution was neutralized with the dropwise addition of a satu-
rated aqueous NaHCO3 solution at 0 °C. The THF was removed
in vacuo, and the remaining aqueous layer was extracted with
CHCl3 (5 ꢀ 25 mL). The organic layers were combined, dried
(Na2SO4), and concentrated in vacuo, and the residue was
recrystallized from EtOAc to give 930 mg (66%) of (R)-29 as a
white solid. The mother liquor was concentrated and purified
0.27 (EtOAc); mp 141-142 °C; [R]27 4.4° (c 1.0, DMSO); IR
D
(nujol) 3278, 3096, 1640, 1554, 1458, 1370, 1304, 1257, 1192, 1099,
966, 903, 810, 732 cm-1; 1H NMR (CDCl3) δ 2.02 [s, CH3C(O)],
3.37 (s, OCH3), 3.45-3.47 (m, CHH0O, OCH3), 3.78 (dd, J = 4.2,

1302 Journal of Medicinal Chemistry, 2010, Vol. 53, No. 3
Salomeꢀ et al.
by flash chromatography (5/95 MeOH/CHCl3) to yield 336 mg
of product (24%) [total yield, 1.27 g (90%)]: Rf = 0.40 (5/95
MeOH/CHCl3); mp 132-133 °C; [R]25D 10.4° (c 1.0, CHCl3); IR
2-N-(benzyloxycarbonyl)amino-3-methoxypropionamide (1.28
g, 3.2 mmol) in anhydrous MeOH (35 mL). The mixture was
hydrogenated (45 psi, 24 h) and then filtered through Celite. The
filtrate was evaporated in vacuo, leaving a mixture (0.80 g) of a
white solid and an oil of the desired amine (TLC analysis using
ninhydrin indicated the presence of a primary amine).
(nujol) 3288, 1687, 1642, 1549, 1458, 1375 cm-1 1H NMR
;
(CDCl3) δ 1.96 [s, CH3C(O)], 3.36 (s, OCH3), 3.53 (dd, J =
6.0, 9.3 Hz, CHH0O), 3.75 (dd J = 4.8, 9.3 Hz, CHH0O), 4.38-
4.58 (m, NHCH2), 4.71 (app dt, J = 5.4, 6.0 Hz, CH), 7.03 (d,
J=7.8 Hz, NHCH2), 7.38 (d, J=8.4 Hz, 2 ArH), 7.68 [t, J=5.4
Hz, NHC(O)CH3], 7.77 (d, J = 8.4 Hz, 2 ArH), 9.93 [s, C(O)H];
addition of excess (R)-(-)-mandelic acid to a CDCl3 solution of
(R)-29 gave only one signal for the methoxy protons and the
acetyl peak protons, and addition of excess (R)-(-)-mandelic
acid to a CDCl3 solution of (S)-29 and (R)-29 (1/2 ratio) gave
two signals for the acetyl methyl protons [δ 2.037 (S) and 2.023
(R) (Δppm = 0.014)] and two signals for the methoxy protons
[δ 3.346 (S) and 3.377 (R) (Δppm = 0.031)]; 13C NMR (CDCl3)
δ 23.0 [CH3C(O)], 43.1 (NHCH2), 52.8 (CHCH2), 59.1 (OCH3),
72.0 (CH2OCH3), 127.7, 130.0, 135.5, 145.3 (4 ArC), 170.5,
170.7 [2 C(O)], 192.0 [C(O)H]; HRMS [M þ Naþ] (ESIþ)
301.1158 [M þ Naþ] (calcd for C14H18N2O4Naþ 301.1164).
Anal. (C14H18N2O4): C, H, N.
Using method D, triethylamine (1.25 mL, 9 mmol) and acetyl
chloride (0.32 mL, 4.5 mmol) gave 0.43 g of a white solid (47%)
after recrystallization with EtOAc: Rf = 0.62 (9/1 CHCl3/
MeOH); mp 167-168 °C; [R]25 -11.4° (c 2.2, CHCl3); IR
D
(nujol) 3279, 2927, 1712, 1639, 1550, 1457 cm-1 1H NMR
;
(CDCl3) δ 2.04 [s, CH3C(O)], 3.39 (s, CH3O), 3.45 (dd, J =
7.5, 9.0 Hz, CHH0O), 3.82 (dd, J = 4.2, 9.0 Hz, CHH0O), 3.91 [s,
CH3OC(O)], 4.51-4.55 (m, CH, CH2NH), 6.45 [d, J = 6.6 Hz,
NHC(O)CH3], 6.85-6.95 (br m, NHCH2), 7.32 (d, J = 8.4 Hz, 2
ArH), 8.00 (d, J = 8.4 Hz, 2 ArH); addition of excess (R)-(-)-
mandelic acid to a CDCl3 solution of (R)-31 gave only one signal
for the acetyl methyl protons and one signal for the ether methyl
protons; 13C NMR (75 MHz, CDCl3) δ 23.3 [CH3C(O)], 43.3
(CH2NH), 52.3 [CH3OC(O)], 52.7 (CH), 59.2 (CH3OCH2), 72.0
(CH2OCH3), 127.3, 129.4, 130.1, 143.4 (4 ArC), 167.0 [OC(O)],
170.4, 170.6 [2 C(O)]; HRMS (ESI) 309.1451 [M þ Hþ] (calcd
for C15H20N2O5Hþ 309.1450). Anal. (C15H20N2O5): C, H, N.
Preparation of (R)-N-(40-Amino)benzyl 2-Acetamido-3-meth-
oxypropionamide [(R)-32].7 A MeOH solution (150 mL) of (R)-
N-(40-nitro)benzyl 2-acetamido-3-methoxypropionamide (2.00
g, 6.8 mmol) was treated with H2 (1 atm) in the presence of PtO2
(160 mg) at room temperature (16 h). The mixture was carefully
filtered through a bed of Celite, and the filtrate was evaporated
in vacuo to yield a colorless oil that was triturated with EtOAc
to give 1.67 g of (R)-32 as a white solid (90%): Rf=0.39 (9/1
CHCl3/MeOH); mp 151-152 °C (lit.7 mp 183-184 °C); 1H
NMR (CDCl3) δ 2.02 [s, CH3C(O)], 3.36 (s, OCH3), 3.42 (dd,
J=7.8, 9.3 Hz, CHH0O), 3.78 (dd, J=4.5, 9.3 Hz, CHH0O), 4.34
(d, J = 5.4 Hz, CH2NH), 4.48-4.55 (m, CH), 6.48 [br d, J = 6.0
Hz, NHC(O)CH3], 6.60-6.67 (m, CH2NH, 2 ArH), 7.05 (d, J =
8.1 Hz, 2 ArH); addition of excess (R)-(-)-mandelic acid to a
CDCl3 solution of (R)-32 gave only one signal for the acetyl
methyl and one signal for the ether methyl protons.
Preparation of (S)-N-(40-Formyl)benzyl 2-Acetamido-3-meth-
oxypropionamide [(S)-29]. Using the preceding procedure, (S)-
N-[40-(1,3-dioxolan-2-yl)]benzyl 2-acetamido-3-methoxypropi-
onamide (1.65 g, 5.1 mmol) gave 900 mg (63%) of (S)-29
after recrystallization from EtOAc and another 268 mg (19%)
after flash chromatography [total yield, 1.17 g (82%)]: Rf = 0.40
(5/95 MeOH/CHCl3); mp 132-133 °C; [R]25 -10.4° (c 1.0,
D
CHCl3); IR (nujol) 3288, 3073, 1687, 1637, 1551, 1458, 1375
cm-1; 1H NMR (CDCl3) δ 2.04 [s, CH3C(O)], 3.40 (s, OCH3),
3.46 (dd, J =7.5, 9.6 Hz, CHH0O), 3.83 (dd J =4.2, 9.6 Hz,
CHH0O), 4.48-4.64 (m, NHCH2, CH), 6.45 [d, J = 6.6 Hz,
NHC(O)CH3], 6.99-7.15 (m, NHCH2), 7.42 (d, J=8.1 Hz, 2
ArH), 7.85 (d, J= 8.1 Hz, 2 ArH), 9.99 [s, C(O)H]; addition
of excess (R)-(-)-mandelic acid to a CDCl3 solution of (S)-29
gave only one signal for the acetyl peak protons and the meth-
oxy protons, and addition of excess (R)-(-)-mandelic acid to
a CDCl3 solution of (S)-29 and (R)-29 (1/2 ratio) gave two
signals for the acetyl methyl protons [δ 2.037 (S) and 2.023 (R)
(Δppm =0.014)] and two signals for the methoxy protons [δ
3.317 (S) and 3.351 (R) (Δppm = 0.034)]; 13C NMR (CDCl3) δ
23.4 [CH3C(O)], 43.4 (NHCH2), 52.7 (CH), 59.4 (OCH3), 71.7
(CH2OCH3), 128.0, 130.3, 135.9, 145.2 (4 ArC), 170.5, 170.6 [2
C(O)], 192.0 [C(O)H]; HRMS [M þ Naþ] (ESIþ) 301.1161 [M þ
Naþ] (calcd for C14H18N2O4Naþ 301.1164). Anal. (C14H18-
N2O4): C, H, N.
Preparation of (R)-N-[40-(2,2,2-Trifluoroacetamido)]benzyl 2-Acet-
amido-3-methoxypropionamide [(R)-33]. (S)-Ethyl trifluoroacetate
(2.99 g, 18.9 mmol) was added to a MeOH (10 mL) solution of
(R)-32 (1.00 g, 3.8 mmol) at room temperature, and then the
reaction mixture was maintained at this temperature (3 h). Addition
of EtOAc (10 mL) led to the precipitation of (R)-33 as a white solid
(600 mg) after filtration. The filtrate was concentrated in vacuum and
the residue purified by flash chromatography on silica gel with EtOAc
as the eluant to yield an additional 350 mg of (R)-33 as a white solid.
The solids were combined to produce 950 mg (70%) of (R)-33: Rf =
Preparation of (R)-N-(40-Carboxy)benzyl 2-Acetamido-3-
methoxypropionamide [(R)-30]. To a solution of (R)-31 (0.75 g,
2.6 mmol) in a THF/H2O mixture (1/1, 50 mL) at 0 °C was added
0.24 (EtOAc); mp 202-204 °C; [R]26 -1.2° (c 0.5, DMSO); IR
LiOH H2O (66 mg, 2.8 mmol). The resulting solution was
D
3
(nujol) 3389, 3282, 1721, 1653, 1536, 1459, 1375, 1294, 1249, 1206,
1150, 1066, 974, 896, 838, 727, 653 cm-1; 1H NMR (DMSO-d6) δ
1.87 [s, CH3C(O)], 3.25 (s, OCH3), 3.45-3.55 (m, CHH0O), 4.27 (d,
J = 5.8 Hz, CH2NH), 4.44-4.50 (m, CH), 7.27 (d, J = 8.7 Hz, 2
ArH), 7.58 (d, J = 8.7 Hz, 2 ArH), 8.11 [d, J = 7.8 Hz, CH3C-
stirred (36 h). The solvent was removed in vacuo, washed with
Et2O (4 ꢀ 100 mL), acidified to a pH of ∼2 (1 N HCl), extracted
with EtOAc (8 ꢀ 50 mL), dried (MgSO4), filtered, and concen-
trated in vacuo to yield 472 mg of a white powder (66%): Rf =
0.51 (9/1 CHCl3/MeOH); mp 197-198 °C; [R]25 6.0° (c 0.8,
D
(O)NH], 8.51 (t, J = 5.8 Hz, CH2NH), 11.23 [s, CF3C(O)NH]; 13
C
MeOH); IR (nujol) 3163, 2923, 2856, 1692, 1637, 1533, 1457,
1376, 1291, 1122, 939 cm-1; 1H NMR (CD3OD) δ 2.03 [s, CH3-
C(O)], 3.37 (s, OCH3), 3.60 (dd, J = 5.1, 9.7 Hz, CHH0O), 3.72
(dd, J=5.1, 9.7 Hz, CHH0O), 4.48 (d, J=6.0 Hz, CH2NH), 4.53
(t, J = 9.7 Hz, CH), 7.39 (d, J = 8.3 Hz, 2 ArH), 7.97 (d, J = 8.3
Hz, 2 ArH), 8.57-8.66 (br t, NHCH2); one amide proton
and the carboxylic acid proton were not observed; 13C NMR
(75 MHz, CD3OD) δ 21.4 [CH3C(O)], 42.7 (CH2NH), 54.2
(CH), 58.2 (CH3O), 72.0 (CH2OCH3), 127.1, 129.6, 129.8,
144.3 (4 ArC), 168.8 [HOC(O)], 171.6, 172.6 [2 C(O)]; LRMS
(ESI) 295.1 [MþHþ] (calcd for C14H18N2O5Hþ 295.1). Anal.
(C14H18N2O5): C, H, N.
NMR (DMSO-d6) δ 22.4 [CH3C(O)], 41.5 (CH2NH), 52.6 (CH),
58.1 (OCH3), 71.9 (CH2OCH3), 115.7 (q, J = 284.6 Hz, CF3), 120.1,
127.4, 134.7, 136.7 (4 ArC), 154.3 [q, J = 37.5 Hz, HNC(O)CF3],
169.3, 169.7 [2 C(O)]; HRMS (M þ Hþ) (ESIþ) 362.1321 [M þ Hþ]
(calcd for C15H18F3N3O4Hþ 362.1328). Anal. (C15H18F3N3O4):
C, H, F, N.
Preparation of (R)-N-(40-Azido)benzyl 2-Acetamido-3-meth-
oxypropionamide [(R)-34]. Ag2O (4.85 g, 20.9 mmol) was added
to a CH3CN solution (100 mL) of (R)-N-(40-azido)benzyl 2-
acetamido-3-hydroxypropionamide (1.16 g, 4.2 mmol) and
CH3I (2.61 mL, 41.9 mmol) at room temperature under Ar.
The reaction mixture was stirred at room temperature in the
dark (5 days) and filtered, and the filtrate was concentrated in
vacuo. The solid was purified by flash column chromatography
Preparation of (R)-N-[40-(Methyloxycarbonyl)]benzyl 2-Acet-
amido-3-methoxypropionamide [(R)-31]. Pd/C (10%, 400 mg)
was added to a solution of (R)-N-[40-(methyloxycarbonyl)]benzyl

Article
Journal of Medicinal Chemistry, 2010, Vol. 53, No. 3 1303
on silica gel (1/9 MeOH/CHCl3) to yield 0.98 g (80%) of (R)-34
as a white solid: Rf = 0.50 (1/9 MeOH/CHCl3); mp 149-150 °C;
[R]26D -15.2° (c 1.0, MeOH); IR (nujol) 3285, 2931, 2113, 1635,
1560, 1456 cm-1; 1H NMR (CDCl3) δ 2.03 [s, CH3C(O)], 3.38
(s, OCH3), 3.44 (dd, J = 7.5, 9.3 Hz, CHH0O), 3.80 (dd, J = 4.2,
9.3 Hz, CHH0O), 4.40 (1/2ABq, J = 6.2, 15.0 Hz, CHH0Ar), 4.46
(1/2ABq, J = 6.2, 15.0 Hz, CHH0Ar), 4.52-4.58 (m, CH), 6.48
[br d, J = 6.3 Hz, NHC(O)CH3], 6.82-6.85 (br m, CH2NH),
6.96-7.01 (m, 2 ArH), 7.23-7.28 (m, 2 ArH); addition of excess
(R)-(-)-mandelic acid to a CDCl3 solution of (R)-34 gave only a
single signal for the acetyl methyl protons and the ether methyl
protons, and addition of excess (R)-(-)-mandelic acid to a
CDCl3 solution of (R)-34 and (S)-34 (1/2 ratio) gave two
signals for the acetyl methyl protons [δ 1.995 (R) and 2.010 (S)
(Δppm = 0.015)] and two signals for the ether methyl protons [δ
3.302 (S) and 3.342 (R) (Δppm = 0.040)]; 13C NMR (CDCl3) δ
23.4 [CH3C(O)], 43.1 (CH2NH), 52.7 (CH), 59.3 (OCH3), 71.8
(CH2OCH3), 119.5, 129.1, 134.9, 139.5 (4 ArC), 170.2, 170.5
[2 C(O)]; HRMS (M þ Hþ) (ESIþ) 292.1406 [M þ Hþ] (calcd for
C13H17N5O3Hþ 292.1410). Anal. (C13H17N5O3): C, H, N.
Preparation of (S)-N-(40-Azido)benzyl 2-Acetamido-3-meth-
oxypropionamide [(S)-34]. Utilizing the preceding procedure,
(S)-N-(40-azido)benzyl 2-acetamido-3-hydroxypropionamide
(2.40 g, 8.7 mmol), Ag2O (10.04 g, 43.3 mmol), and MeI (5.40
mL, 86.6 mmol) gave crude (S)-N-(40-azido)benzyl 2-acetami-
do-3-methoxypropionamide after 4 days. The product was
purified by column chromatography (SiO2; 1/9 MeOH/CHCl3)
to yield 2.05 g (81%) of (S)-34 as a white solid: Rf = 0.50 (1/9
MeOH/CHCl3); mp 149-150 °C; [R]26D 15.4° (c 1.0, MeOH); IR
159.0 (4 ArC), 169.8, 170.3 [2 C(O)]; HRMS (M þ Naþ) (ESIþ)
303.1320 [M þ Naþ] (calcd for C14H20N2O4Naþ 303.1321). Anal.
(C14H20N2O4): C, H, N.
Preparation of (R)-N-(40-Chloro)benzyl 2-Acetamido-3-meth-
oxypropionamide [(R)-36]. A saturated HCl solution in dioxane
(1 mmol/2 mL, 24.0 mL) was added to (R)-N-(40-chloro)benzyl 2-
N-(tert-butoxycarbonyl)amino-3-methoxypropionamide (4.10 g,
12.0 mmol) at 0 °C, and the solution was stirred at room tempera-
ture (2 h). The reaction solution was concentrated in vacuo and
dried (30 min).
Using method D, triethylamine (5.0 mL, 36.0 mmol) and
acetyl chloride (1.3 mL, 18.0 mmol) gave 3.10 g (80%) of (R)-36
as a white solid after recrystallization with EtOAc: Rf = 0.42
(EtOAc); mp 155 °C; [R]27.0D -20.5° (c 1.0, CHCl3); IR (nujol)
3288, 3277, 3162, 2900, 1634, 1556, 1457, 1375, 1306, 1259, 1193,
1137, 1098, 1045, 964, 909, 801, 732 cm-1; 1H NMR (CDCl3) δ
2.01 [s, CH3C(O)], 3.37 (s, OCH3), 3.43 (dd, J = 7.8, 9.2 Hz,
CHH0O), 3.78 (dd, J = 4.2, 9.2 Hz, CHH0O), 4.34-4.49 (m,
CH2NH), 4.54-4.61 (m, CH), 6.54 [br d, J = 6.6 Hz, NHC-
(O)CH3], 6.94-7.03 (br t, CH2NH), 7.19 (d, J = 8.8 Hz, 2 ArH),
7.29 (d, J = 8.8 Hz, 2 ArH); addition of excess (R)-(-)-mandelic
acid to a CDCl3 solution of (R)-36 gave only one signal for the
acetyl methyl and one signal for the ether methyl protons; 13C
NMR (CDCl3) δ 23.1 [CH3C(O)], 42.8 (CH2NH), 52.5
(CHCH2), 59.1 (OCH3), 71.7 (CH2OCH3), 128.7, 133.2, 136.4
(3 ArC), 170.1, 170.4 [2 C(O)]; one signal was not detected and is
believed to overlap with nearby peaks; HRMS (M þ Hþ) (ESIþ)
285.1006 [M þ Hþ] (calcd for C13H17ClN2O3Hþ 285.1006).
Anal. (C13H17ClN2O3): C, H, Cl, N.
Preparation of (R)-N-(40-Bromo)benzyl 2-Acetamido-3-meth-
oxypropionamide [(R)-37]. Using method D, (R)-N-(40-bro-
mo)benzyl 2-amino-3-methoxypropionamide hydrochloride
(1.00 g, 3.1 mmol), triethylamine (1.3 mL, 9.3 mmol), and acetyl
chloride (0.3 mL, 3.7 mmol) gave 690 mg (68%) of (R)-37 as
a white solid after recrystallization with EtOAc: Rf = 0.08 (7/3
EtOAc/hexanes); mp 159-161 °C; [R]25D -15.9° (c 1.0, CHCl3);
IR (nujol mull) 3272, 3093, 2919, 2860, 1634, 1555, 1457, 1375,
1306, 1254, 1197, 1135, 1046, 964, 907, 795, 740, 606, 550,
468 cm-1; 1H NMR (CDCl3) δ 2.04 [CH3C(O)], 3.39 (s, OCH3),
3.43 (dd, J=7.5, 9.0 Hz, CHH0O), 3.81 (dd, J=4.2, 9.0 Hz,
CHH0O), 4.37-4.48 (m, CH2NH), 4.51-4.57 (m, CH), 6.40-
6.42 [br d, NHC(O)CH3], 6.76-6.84 (br t, CH2NH), 7.14 (d, J =
8.6 Hz, 2 ArH), 7.45 (d, J = 8.6 Hz, 2 ArH); addition of excess
(R)-(-)-mandelic acid to a CDCl3 solution of (R)-37 gave only
one signal for the acetyl methyl protons and one signal for the
ether methyl protons; 13C NMR (CDCl3) δ 23.1 [CH3C(O)],
42.8 (CH2NH), 52.4 (CH), 59.1 (OCH3), 71.6 (CH2OCH3),
121.3, 129.1, 131.7, 137.0 (4 ArC), 170.1, 170.4 [2 C(O)]; LRMS
(ESIþ) 351.0 [M þ Na]þ (100%), 353.0 [M þ 2 þ Na]þ (100%)
(calcd for C13H17BrN2O3Naþ 351.0 [M þ Na]þ). Anal.
(C13H17BrN2O3): C, H, Br, N.
(nujol) 3285, 2927, 2112, 1635, 1565, 1457 cm-1 1H NMR
;
(CDCl3) δ 2.03 [s, CH3C(O)], 3.38 (s, OCH3), 3.43 (dd, J =
7.5, 9.0 Hz, CHH0O), 3.81 (dd, J = 4.2, 9.0 Hz, CHH0O), 4.40
(1/2ABq, J = 6.0, 15.0 Hz, CHH0Ar), 4.46 (1/2ABq, J = 6.0,
15.0 Hz, CHH0Ar), 4.51-4.57 (m, CH), 6.43 [br d, J = 6.3 Hz,
NHC(O)CH3], 6.78-6.83 (br m, NHCH2), 6.96-7.01 (m, 2
ArH), 7.23-7.27 (m, 2 ArH); addition of excess (R)-(-)-man-
delic acid to a CDCl3 solution of (S)-34 gave only a single signal
for the acetyl methyl protons and the ether methyl protons, and
addition of excess (R)-(-)-mandelic acid to a CDCl3 solution of
(R)-34 and (S)-34 (1/2 ratio) gave two signals for the acetyl
methyl protons [δ 1.995 (R) and 2.010 (S) (Δppm = 0.015)] and
the ether methyl protons [δ 3.302 (S) and 3.342 (R) (Δppm =
0.040)]; 13C NMR (CDCl3) δ 23.3 [CH3C(O)], 43.1 (CH2NH),
52.7 (CH), 59.2 (OCH3), 72.0 (CH2OCH3), 119.4, 129.1, 135.0,
139.4 (4 ArC), 170.3, 170.6 [2 C(O)]; HRMS (M þ Hþ) (ESIþ)
292.1405 [M þ Hþ] (calcd for C13H17N5O3Hþ 292.1410). Anal.
(C13H17N5O3): C, H, N.
Preparation of (R)-N-(40-Methoxy)benzyl 2-Acetamido-3-
methoxypropionamide [(R)-35]. A MeOH solution (300 mL) of
(R)-N-(40-methoxy)benzyl 2-N-(benzyloxycarbonyl)amino-3-
methoxypropionamide (2.40 g, 6.4 mmol) was treated with
H2 (1 atm) in the presence of 10% Pd/C (480 mg) at room
temperature (16 h). The mixture was carefully filtered through a
bed of Celite, and the filtrate was evaporated in vacuo to yield a
colorless oil.
Preparation of (R)-N-(40-Iodo)benzyl 2-Acetamido-3-methox-
ypropionamide [(R)-38]. A saturated HCl solution in dioxane
(1 mmol/2 mL, 25.0 mL) was added to (R)-N-(40-iodo)benzyl 2-
N-(tert-butoxycarbonyl)amino-3-methoxypropionamide (5.50
g, 12.7 mmol) at 0 °C, and the solution was stirred at room
temperature (2 h). The reaction solution was concentrated in
vacuo and dried (30 min).
Using method D, triethylamine (1.1 mL, 7.74 mmol) and
acetyl chloride (550 μL, 7.74 mmol) gave 900 mg (70%) of (R)-35
as a white solid after trituration in EtOAc: Rf = 0.82 (EtOAc);
mp 146-147 °C; [R]25D -26.0° (c 0.5, CHCl3); IR (nujol) 3283,
2861, 1642, 1520, 1458, 1377, 1299, 1255, 1176, 1127, 1031, 978,
Using method D, triethylamine (10.7 mL, 76.0 mmol) and
acetyl chloride (2.7 mL, 38.0 mmol) gave 3.40 g (71%) of (R)-38
as a white solid after recrystallization with EtOAc: Rf = 0.76 (5/
5 acetone/EtOAc); mp 159-160 °C; [R]25D 3.3° (c 1.0, DMSO);
719 cm-1 1H NMR (CDCl3) δ 2.02 [s, CH3C(O)], 3.37 (s,
;
OCH3), 3.43 (dd, J = 7.8, 9.3 Hz, CHH0O), 3.76-3.81 (m,
CH3OC6H4, CHH0O), 4.39 (d, J = 6.0 Hz, CH2NH), 4.50-
4.57 (m, CH), 6.49 [br d, J = 6.0 Hz, NHC(O)CH3], 6.71-6.82
(br t, CH2NH), 6.86 (d, J = 8.4 Hz, 2 ArH), 7.18 (d, J = 8.4 Hz,
2 ArH); addition of excess (R)-(-)-mandelic acid to a CDCl3
solution of (R)-35 gave only one signal for the acetyl methyl
and one signal for the ether methyl protons; 13C NMR (CDCl3)
δ 23.2 [CH3C(O)], 43.0 (CH2NH), 52.4 (CH), 55.3 (C6H4-
OCH3), 59.0 (OCH3), 71.7 (CH2OCH3), 114.1, 128.8, 129.9,
IR (nujol) 3279, 1636, 1552, 1457, 1375, 1305, 1139, 725 cm-1
;
1H NMR (CDCl3) δ 2.02 [s, CH3C(O)], 3.38 (s, OCH3), 3.44 (dd,
J=7.2, 9.0 Hz, CHH0O), 3.79 (dd, J=4.2, 9.0 Hz, CHH0O),
4.38-4.41 (m, CH2NH), 4.52-4.59 (m, CH), 6.46 [br d, J=6.6
Hz, NHC(O)CH3], 6.85-6.93 (br t, CH2NH), 7.00 (d, J=8.4
Hz, 2 ArH), 7.64 (d, J = 8.4 Hz, 2 ArH); addition of excess (R)-
(-)-mandelic acid to a CDCl3 solution of (R)-38 gave only one
signal for the acetyl methyl and one signal for the ether methyl

1304 Journal of Medicinal Chemistry, 2010, Vol. 53, No. 3
Salomeꢀ et al.
protons; 13C NMR (CDCl3) δ 23.1 [CH3C(O)], 42.9 (CH2NH),
52.4 (CH), 59.1 (OCH3), 71.6 (CH2OCH3), 92.7 (CI), 129.3, 137.7,
139.1 (3 ArC), 170.1, 170.3 [2 C(O)]; HRMS (M þ Naþ) (ESIþ)
399.0177 [M þ Naþ] (calcd for C13H17IN2O3Naþ 399.0182). Anal.
(C13H17IN2O3): C, H, I, N.
recrystallization with EtOAc: Rf = 0.26 (EtOAc); mp 149 °C;
[R]23.7D -11.0° (c 1.0, CHCl3); IR (nujol) 3477, 3399, 3276, 2919,
2854, 2725, 2363, 1637, 1552, 1458, 1376, 1304, 1251, 1135, 1102,
1
1050, 974, 821, 724, 606, 505 cm-1; H NMR (CDCl3) δ 2.04
[CH3C(O)], 3.37-3.43 (m, OCH3, CHH0O), 3.80 (dd, J = 4.1,
9.2 Hz, CHH0O), 4.43-4.57 (m, CH2NH, CH), 6.36-6.40 [br
d, NHC(O)CH3], 6.90-7.02 (br t, CH2NH), 7.22 (dd, J = 2.1,
8.3 Hz, 1 ArH), 7.30 (d, J = 8.3 Hz, 1 ArH), 7.39 (d, J = 2.1 Hz,
1 ArH); addition of excess (R)-(-)-mandelic acid to a CDCl3
solution of (R)-61 gave only one signal for the acetyl methyl protons
and one signal for the ether methyl protons; 13C NMR (CDCl3)
δ 23.1 [CH3C(O)], 40.9 (CH2NH), 52.4 (CH), 59.0 (OCH3), 71.7
(CH2OCH3), 127.2, 129.2, 130.3, 133.8, 133.9 (5 ArC), 170.2,
170.4 [2 C(O)]; one signal was not detected and is believed to
overlap with nearby peaks; LRMS (ESIþ) 341.08 [M þ Naþ]
(100%), 343.08 [M þ 2 þ Naþ] (66%), 345.07 [M þ 4 þ Naþ]
(13%) (calcd for C13H16Cl2N2O3Naþ 341.04). Anal. (C13H16Cl2-
N2O3): C, H, Cl, N.
Pharmacology. Compounds were screened under the auspices
of the National Institutes of Health’s Anticonvulsant Screening
Program (ASP). Experiments were performed in male rodents
[albino Carworth Farms No. 1 mice (intraperitoneal route, ip)
or albino Spague-Dawley rats (oral route, po)]. Housing, hand-
ling, and feeding were in full accordance with recommendations
contained in the Guide for the Care and Use of Laboratory
Animals. Anticonvulsant activity was established using the
MES test,33,42 the scMet test,33 and the rapid hippocampal
kindled rat model39 using previously reported methods.26
Preparation of (S)-N-(40-Iodo)benzyl 2-Acetamido-3-methoxy-
propionamide [(S)-38]. Employing the preceding procedure and
using (S)-2-N-(40-iodo)benzyl 2-N-(tert-butoxycarbonyl)amino-
3-methoxypropionamide (3.70 g, 8.5 mmol), a saturated dioxane
solution of HCl (1 mmol/2 mL, 17.0 mL), triethylamine (3.6 mL,
25.6 mmol), and acetyl chloride (906 μL, 12.3 mmol) gave 2.43 g
(76%) of (S)-38 as a white solid after recrystallization with
EtOAc: Rf=0.76 (5/5 acetone/EtOAc); mp 159-160 °C; [R]24
D
-3.2° (c 1.0, DMSO); IR (nujol) 3278, 1636, 1552, 1458, 1375,
1
1305, 1138, 725 cm-1; H NMR (CDCl3) δ 2.02 [s, CH3C(O)],
3.38 (s, OCH3), 3.43 (dd, J=7.2, 9.0 Hz, CHH0O), 3.79 (dd, J =
4.2, 9.0 Hz, CHH0O), 4.38-4.42 (m, CH2NH), 4.53-4.59 (m,
CH), 6.47 [br d, J = 6.0 Hz, NHC(O)CH3], 6.85-6.93 (br t, CH2-
NH), 7.00 (d, J = 8.4 Hz, 2 ArH), 7.64 (d, J = 8.4 Hz, 2 ArH);
addition of excess (R)-(-)-mandelic acid to a CDCl3 solution of
(S)-38 gave only one signal for the acetyl methyl and one signal
for the ether methyl protons; 13C NMR (DMSO-d6) δ 22.4 [CH3-
C(O)], 41.4 (CH2NH), 52.5 (CH), 58.1 (OCH3), 71.9(CH2OCH3),
92.2 (CI), 129.3, 136.8, 139.1 (3 ArC), 169.3, 169.7 [2 C(O)];
HRMS (M þ Naþ) (ESIþ) 399.0177 [M þ Naþ] (calcd for C13-
H17IN2O3Naþ 399.0182). Anal. (C13H17IN2O3): C, H, I, N.
Preparation of (R)-N-(40-Sulfamoyl)benzyl 2-Acetamido-3-meth-
oxypropionamide [(R)-39]. Using method A, (R)-2-acetamido-3-
methoxypropionoic acid25 (1.00 g, 6.2 mmol), NMM (1.5 mL, 13.7
mmol), IBCF (1.0 mL, 7.9 mmol), and methyl 4-(aminomethyl)
benzenesulfonamide hydrochloride (2.07 g, 9.3 mmol) gave 1.25 g
(61%) of (R)-39 as a white solid after purification by column
chromatography (1/7 MeOH/CHCl3) and recrystallization (MeOH/
CHCl3): Rf = 0.35 (1/7 MeOH/CHCl3); mp 177-179 °C; [R]25
Acknowledgment. We thank the NINDS and the ASP at
the National Institutes of Health with Drs. Tracy Chen and
Jeffrey Jiang for kindly performing the pharmacological
studies via the ASP’s contract site at the University of Utah
with Drs. H. Wolfe, H. S. White, and K. Wilcox. Funds for
this study were generously provided by Grants R01NS054112
(H.K.) and F31NS060358 (P.M.) from the National Institute
of Neurological Disorders and Stroke and by the Korean
Research Foundation Grant funded by the Korean Govern-
ment (MOEHRD) (Grant KRF-2006-352-C00042 to K.D.P.).
The content is solely the responsibility of the authors and
does not necessarily represent the official views of the
National Institute of Neurological Disorders and Stroke or
the National Institutes of Health. H.K. has a royalty-stake
position in (R)-3.
10.7° (c 1.0, MeOH); IR (nujol) 3293, 2935, 1623, 1557, 1459 cm-D1
;
1H NMR (DMSO-d6) δ1.87 [s, CH3(O)], 3.26 (s, OCH3), 3.46-3.56
(m,CH2OCH3),4.34(d,J=6.1Hz,CH2NH), 4.43-4.50 (m, CH),
7.31 (s, NH2), 7.41 (d, J = 8.6 Hz, 2 ArH), 7.75 (d, J = 8.6 Hz,
2 ArH), 8.13 [d, J = 7.8 Hz, NHC(O)CH3], 8.59 (t, J = 6.1 Hz,
NHCH2); 13C NMR (DMSO-d6) δ 22.5 [CH3(O)], 41.7
(CH2NH), 52.7 (CH), 58.2 (OCH3), 72.0 (CH2OCH3), 125.5,
127.2, 142.5, 143.5 (4 ArC), 169.5, 169.9 [2 C(O)]; HRMS (M þ
Hþ) (ESIþ) 330.1117 [M þ Hþ] (calcd for C13H19N3O5SHþ
330.1124). Anal. (C13H19N3O5S): C, H, N, S.
Preparation of (R)-N-(30,40-Dichloro)benzyl 2-Acetamido-3-meth-
oxypropionamide [(R)-60]. Using method D, (R)-N-(30,40-dichlor-
o)benzyl 2-amino-3-methoxypropionamide hydrochloride (3.50 g,
11.2 mmol), triethylamine (4.6 mL, 33.5 mmol), and acetyl chloride
(0.95 mL, 13.4 mmol) gave 1.60 g (45%) of (R)-60 as a white solid
after recrystallization with EtOAc: Rf = 0.16 (7/3 EtOAc/hexanes);
mp 165 °C; [R]24.9D -10.5° (c 1.0, CHCl3); IR (nujol) 3292, 3096,
2927, 2859, 1636, 1555, 1459, 1379, 1256, 1135, 1034, 815, 724, 604,
491 cm-1; 1H NMR (CDCl3) δ 2.05 [CH3C(O)], 3.41 (s, OCH3),
3.45 (dd, J = 7.5, 9.3 Hz, CHH0O), 3.82 (dd, J = 4.1, 9.3 Hz,
CHH0O), 4.39-4.49 (m, CH2NH), 4.52-4.59 (m, CH), 6.39-6.41
[br d, NHC(O)CH3], 6.80-6.90 (br t, CH2NH), 7.10 (dd, J = 2.1,
8.1 Hz, 1 ArH), 7.36 (d, J = 2.1 Hz, 1 ArH), 7.40 (d, J = 8.1 Hz,
1 ArH); addition of excess (R)-(-)-mandelic acid to a CDCl3
solution of (R)-60 gave only one signal for the acetyl methyl protons
and one signal for the ether methyl protons; 13C NMR (CDCl3) δ
23.1 [CH3C(O)], 42.2 (CH2NH), 52.6 (CH), 59.1 (OCH3), 71.7
(CH2OCH3), 126.6, 129.1, 130.5, 131.3, 132.6, 138.3 (6 ArC), 170.2,
170.4 [2 C(O)]; LRMS (ESIþ) 341.05 [M þ Naþ] (100%), 343.05
[M þ 2 þ Naþ] (64%), 345.05 [M þ 4 þ Naþ] (11%) (calcd for
C13H16Cl2N2O3Naþ 341.04). Anal. (C13H16Cl2N2O3): C, H, Cl, N.
Preparation of (R)-N-(20,40-Dichloro)benzyl 2-Acetamido-3-meth-
oxypropionamide [(R)-61]. Using method D, (R)-N-(20,40-dichlor-
o)benzyl 2-amino-3-methoxypropionamide hydrochloride (2.70 g,
7.2 mmol), triethylamine (3.0 mL, 21.5 mmol), and acetyl chloride
(0.6 mL, 8.6 mmol) gave 1.45 g (63%) of (R)-61 as a white solid after
Supporting Information Available: Synthetic procedures for
the intermediates leading to the preparation of (R)-4, (R)-7-31,
(R)-33-39, (R)-60, and (R)-61 and (S)-11, (S)-21, (S)-23, (S)-26,
1
(S)-28, (S)-29, (S)-34, and (S)-38, elemental analyses, and H
and 13C NMR spectra of compounds evaluated in this study.
This material is available free of charge via the Internet at http://
pubs.acs.org.
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