Design and synthesis of an orally active matrix metalloproteinase inhibitor

Article abstract of DOI:10.1016/j.bmc.2006.05.040

A series of 4-(4-phenoxy)benzoylamino-4-methoxymethyloxymethyl butyric acid hydroxamates, which were derived from l-glutamic acid, were synthesized and evaluated as matrix metalloproteinase inhibitors. Most of the compounds listed in Tables 1-3 exhibited

Full text of DOI:10.1016/j.bmc.2006.05.040

Bioorganic & Medicinal Chemistry 14 (2006) 6383–6403
Design and synthesis of an orally active matrix
metalloproteinase inhibitor
Shingo Yamamoto, Shingo Nakatani,* Masahiro Ikura, Tsuneyuki Sugiura,
Yoshitaka Nishita, Satoshi Itadani, Koji Ogawa, Hiroyuki Ohno,
Kanji Takahashi, Hisao Nakai and Masaaki Toda
Minase Research Institute, Ono Pharmaceutical Co., Ltd, 3-1-1 Sakurai, Shimamoto, Mishima, Osaka 618-8585, Japan
Received 29 March 2006; revised 22 May 2006; accepted 23 May 2006
Available online 9 June 2006
Abstract—A series of 4-(4-phenoxy)benzoylamino-4-methoxymethyloxymethyl butyric acid hydroxamates, which were derived from
L-glutamic acid, were synthesized and evaluated as matrix metalloproteinase inhibitors. Most of the compounds listed in Tables 1–3
exhibited strong inhibitory activity against MMP-2 and MMP-9, as well as even stronger inhibitory activity against MMP-3, but
showed relatively weak inhibition of MMP-1. Structure–activity relationships are discussed.
Ó 2005 Elsevier Ltd. All rights reserved.
1. Introduction
Matrix metalloproteinase inhibitors (MMPIs) generally
consist of two basic features, a zinc chelating ligand
and a chemical moiety which binds the substrate recog-
nition cleft of the enzyme. Widely utilized zinc binding
moieties include: hydroxamic acid,3 thiol,4 carboxylic
acid5 phosphinic acid6, and other chelators.7 The struc-
ture with the substrate recognition site of MMPs has
been designed from substrate of MMPs or structural
information of MMP–inhibitor complex. Consequently,
a large number of synthetic MMPIs have been
reported.8
Matrix metalloproteinases (MMPs) are postulated to
regulate the homeostasis of a variety of tissues under
the control of tissue inhibitors of metalloproteinases
(TIMPs), which associate with and block the activity
of MMPs. An imbalance between MMPs and their nat-
ural inhibitors (TIMPs) is believed to contribute to the
manifestation of various pathological or physiological
states involving the degradation of extracellular matrix
(ECM) components, including osteoarthritis, rheuma-
toid arthritis, angiogenesis, cancer, pulmonary emphyse-
ma, corneal ulceration, rupture of atherosclerotic
plaque, aortic aneurysm, and periodontal disease. For
more than 30 years, MMPs have been heralded as prom-
ising targets for the treatment of such diseases.1
In our previous papers,we have reported on the discov-
ery of a series of L-glutamic acid-based MMP inhibi-
tors.9 We have also reported that several N-benzoyl
4-aminobutyric acid hydroxamate analogs 1a–d were
identified as MMP inhibitors with increased activity
against MMP-3.10 Among them, the N-(4-phenoxy)ben-
zoyl analogs exhibited relatively strong inhibitory activ-
ity against MMP-3 (stromelysin). In addition, we found
that N-benzoyl 4-aminobutyric acid hydroxamate
analogs with C2 or C4 substituents showed an increase
of inhibitory activity against MMP-3 (Fig. 1).10 Based
on this information, C2 and C4 substitutions of 1a were
investigated to identify MMP inhibitors with strong
inhibitory activity against MMP-3 as well as MMP-2
and MMP-9. We report here on the discovery of new
orally active and L-glutamic acid-based MMP inhibitors
that exhibit strong activity against MMP-3 in addition
to MMP-2 and MMP-9.
Nearly 20 members of this enzyme family, sharing sig-
nificant sequence homology, have been reported.2 They
can be subdivided into: (1) collagenases (MMP-1, -8,
-13, and -18); (2) gelatinases (MMP-2 and -9); (3) strom-
elysins (MMP-3, -10, and -11); and (4) membrane-type
MMPs (MT-MMPs) (MMP-14, -15, -16, and -17).
Keywords: MMP; Matrix metalloproteinase inhibitor; Hydroxamate
inhibitor; L-Glutamic acid.
*
Corresponding author. E-mail: s.nakatani@ono.co.jp
0968-0896/$ - see front matter Ó 2005 Elsevier Ltd. All rights reserved.
doi:10.1016/j.bmc.2006.05.040

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S. Yamamoto et al. / Bioorg. Med. Chem. 14 (2006) 6383–6403
corresponding carboxylic acids. Condensation of 29a–l
O
R
R
1
2
H
N
and 29n with O-protected hydroxylamine in the presence
of EDC followed by acidic deprotection resulted in 2–12
and 14, 15, respectively. Condensation of 29m with O-
benzylhydroxylamine followed by catalytic hydrogena-
tion produced 13.
HO
N
H
O
X
1
Synthesis of 16 and 19 is described in Scheme 2. Protec-
tion of the hydroxyl moiety of 24 as an ethoxymethyl
ether and tert-butyldimethylsilyl ether afforded 30a
and 30b, respectively. Stereoselective C2-methylation
of 30a,b provided 31a,b. Deprotection of 31a,b by cata-
lytic hydrogenation followed by N-acylation with
4-phenoxybenzoic acid resulted in 32a,b, respectively.
Alkaline hydrolysis of 32a,b provided the corresponding
carboxylic acids 33a,b, respectively. Condensation of
33a with O-benzylhydroxylamine followed by deprotec-
tion via catalytic hydrogenation gave 16. Condensation
of 33b with O-benzylhydroxylamine followed by depro-
tection with TBAF and catalytic hydrogenation resulted
in 19.
X
a
b
c
O
Cl
Cl
O
d
Synthesis of 17 and 18 is described in Scheme 3. Protec-
tion of the hydroxymethyl group of 3413 as a methoxy-
ethoxymethylether or pivaloyl ester by conventional
procedures gave 35a,b, respectively. Stereoselective C2-
alkylation of 35a,b by the usual procedure afforded
36a,b, respectively. Acidic deprotection of 36a,b fol-
lowed by N-acylation with 4-phenoxybenzoic acid led
to production of 37a,b, respectively. Catalytic hydroge-
nation of 37a,b gave carboxylic acids 38a,b, respectively.
Condensation of 38a,b with O-protected hydroxylamine
followed by acidic deprotection resulted in 17 and 18,
respectively.
(R , R = H)
1
2
R (C2-substituent); R = H
1
2
OH
Synthesis of 20 is described in Scheme 4. C-Acylation of
Meldrum’s acid with 39 produced 40, after which sodi-
um borohydride reduction afforded 41. Intramolecular
cyclization and decarboxylation of 41 gave a five-
membered lactam 42, after which alkaline hydrolysis fol-
lowed by esterification provided 43. Acidic deprotection
of 43 followed by N-acylation with 4-phenoxybenzoic
acid resulted in 44. Stereoselective C2-methylation fol-
lowed by alkaline hydrolysis provided 46, and condensa-
tion of 46 with O-protected hydroxylamine in the
presence of EDC followed by acidic deprotection result-
ed in 20.
R = H; R (C4-substituent)
1
2
O
OH
O
Figure 1. Structures with an increased inhibitory activity against
MMP-3.
2. Chemistry
Synthesis of 21 is described in Scheme 5. Acidic
deprotection of 30a followed by N-acylation with 4-
phenoxybenzoic acid afforded 47. Stereoselective C2-
ethylation of 47 by the usual C-alkylation procedure
provided 48. Alkaline hydrolysis of 48 led to the cor-
responding carboxylic acid 49, while condensation of
49 with O-benzylhydroxylamine in the presence of
EDC followed by deprotection in the usual manner
resulted in 21.
The test compounds listed in Tables 1–3 were synthe-
sized as outlined in Schemes 1–6.
Synthesis of 2–15 is described in Scheme 1. Protection of
the hydroxyl group of 2411 as a methoxymethyl ether
gave 25. Removal of the N-carbobenzyloxy group by a
catalytic hydrogenation followed by N-acylation with
a 4-phenoxybenzoic acid afforded 27. Stereoselective
C2-alkylation12 of 25 resulted in 26a–e. Catalytic hydro-
genation followed by N-acylation with 4-phenoxybenzo-
ic acid provided 28a–e. Stereoselective C2-alkylation of
27 with an appropriate electrophile afforded 28f–g and
i–m, while catalytic hydrogenation of 28f gave 28h.
Alkaline hydrolysis of 27 and 28a–m led to their
Synthesis of 22 and 23 is described in Scheme 6.
Acidic deprotection of 35a followed by N-acylation
with 4-phenoxybenzoic acid produced 50. Stereoselec-
tive C2-ethylation of 50 by the usual C-alkylation
procedure provided 52a, while stereoselective C2-ethy-

S. Yamamoto et al. / Bioorg. Med. Chem. 14 (2006) 6383–6403
6385
Table 1. Effect of the C2-substituent on the activity profiles of 4S-methoxymethyloxymethyl analogs
Me
O
O
R
O
H
N
HO
N
H
O
O
a,b
IC50 (lM)
Compound
R
MMP-1
MMP-2
MMP-9
MMP-3
2
3
H
Me
7.0
2.8
3.2
2.6
9.1
1.4
0.55
0.42
1.9
1.5
0.95
1.8
5.8
2.4
0.0035
0.0005
0.0011
0.0017
0.0035
0.0005
0.0007
0.0006
0.0004
0.0012
0.0037
0.0017
0.0014
0.0005
0.0013
0.0013
0.0006
0.0007
0.0020
0.0005
0.0003
0.0005
0.0008
0.0007
0.0015
0.0006
0.0031
0.0005
0.11
0.047
0.036
0.037
0.078
0.019
0.016
0.033
0.040
0.018
0.029
0.020
0.11
4
Et
n-Pr
5
6
i-Bu
Bn
7
8
2-Pyridylmethyl
3-Pyridylmethyl
4-Pyridylmethyl
Allyl
9
10
11
12
13
14
15
1-Naphthylmethyl
CH2CO2-t-Bu
OH
SPh
0.0094
a Concentration required for 50% inhibition of enzyme activity.
b IC50 values were determined in a single experimental run in duplicate.
Table 2. Effect of the C4-substituent on the activity profiles of 2S-methyl analogs
R
O
H
N
HO
N
H
O
O
a,c
IC50 (lM)
Compound
R
MMP-1
2.8
MMP-2
0.0005
0.0005
0.0012
MMP-9
0.0013
0.0008
0.0005
MMP-3
0.047
O
O
3
16
17
Me
Me
O
O
O
O
2.5
0.026
Me
2.6
0.038
O
O
18
19
NTb
4.5
0.0008
0.0007
0.0014
0.0008
0.065
0.036
O
OH
H
20
NT
0.071
0.11
6.4
a Concentration required for 50% inhibition of enzyme activity.
b Not tested.
c IC50 values were determined in a single experimental run in duplicate.
lation of 35b afforded 51. Acidic deprotection of 51
followed by N-acylation with 4-phenoxybenzoic acid
led to 52b. Catalytic hydrogenation of 52a,b provided
carboxylic acids 53a,b, respectively. Condensation
of 53a,b with O-benzylhydroxylamine followed by
catalytic hydrogenation resulted in 22 and 23,
respectively.
3. Results and discussion
The compounds listed in Tables 1–3 were tested for their
inhibitory potency against MMP-1 (human collage-
nase), MMP-2 (human gelatinase A), MMP-9 (human
gelatinase B), and MMP-3 (recombinant human
stromelysin).14

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S. Yamamoto et al. / Bioorg. Med. Chem. 14 (2006) 6383–6403
Table 3. Effect of the C4-substituent on the activity profiles of 2S-ethyl analogs
R
O
H
N
HO
N
H
O
O
a,b
Compound
R
IC50
(lM)
MMP-1
3.2
MMP-2
0.0011
MMP-9
0.0006
MMP-3
0.036
O
O
4
21
22
23
Me
O
O
O
O
O
Me
3.0
3.2
0.0005
0.0006
0.0011
0.0006
0.0006
0.005
0.029
0.032
0.040
Me
O
>10
O
a Concentration required for 50% inhibition of enzyme activity.
b IC50 values were determined in a single experimental run in duplicate.
Since the discovery of the N-(4-phenoxy)benzoyl analog
(1a) as a new chemical lead for MMP-3 inhibitors, fur-
ther optimization of 1a has been continued.
fold, and 6.9-fold more potent activity against MMP-1,
MMP-2, MMP-9, and MMP-3, respectively. In addition,
the 2S-pyridin-3-ylmethyl analog 9 exhibited 17-fold, 5.8-
fold, 2.6-fold, and 3.3-fold more potent activity against
MMP-1, MMP-2, MMP-9, and MMP-3, respectively.
Furthermore, the 2S-pyridin-4-ylmethyl analog 10
showed 3.7-fold, 8.8-fold, 1.6-fold, and 2.8-fold more po-
tent activity against MMP-1, MMP-2, MMP-9, and
MMP-3, respectively. Thus, basic pyridine moieties were
also found to be accepted as illustrated by 8 (2R), 9 (2S),
and 10 (2S). Introduction of a 2S-allyl residue into the C2
position of 2afforded 11, which also had increased activity
against all of the MMP isoforms. Its inhibitory spectrum
seemed to be close to that of 2S-benzyl analog 7. Introduc-
tion of a 2S-naphthalene-1-ylmethyl moiety at the C2 po-
sition of 2 afforded 12, which showed 7.8-fold and 3.8-fold
more potent activity against MMP-1 and MMP-3, respec-
tively, while it showed no change of activity against
MMP-2 and MMP-9. Introduction of a 2R-tert-butyloxy-
carbonylmethyl residue at the C2 position of 2 provided
13, with an increased activity against MMP-1, MMP-2,
MMP-9, and MMP-3. Introduction of heteroatoms such
as 2S-hydroxy and 2S-phenylthio residues at the C2 posi-
tion of 2 afforded 14 and 15. The 2S-hydroxy analog 14
exhibited equipotent, 2.5-fold more potent, and 2.4-fold
less potent activity against MMP-1, MMP-2, and
MMP-9 relative to 2, respectively, while it retained activ-
ity against MMP-3. The 2S-phenylthio analog 15 exhibit-
ed 2.9-fold, 7-fold, 2.6-fold, and 12-fold more potent
inhibition of MMP-1, MMP-2, MMP-9, and MMP-3,
respectively, relative to 2. Thus, all of these compounds
listed in Table 1 showed very strong inhibitory activity
against MMP-2 and MMP-9, while exhibiting moderate
to weak activity against MMP-1. With regard to inhibi-
tion of MMP-3, most of the 2S-analogs 3–7, 9–12, 15
and 2R-analogs 8, 13 exhibited more potent inhibitory
activity compared with 2. As a result, the 2S-methyl ana-
log 3 and the 2S-ethyl analog 4 were selected as the chem-
ical leads for further optimization because their synthesis
was relatively simple.
Introduction of the C4 substituents such as a methoxy-
methoxymethyl moiety into the N-benzoyl 4-aminobu-
tyric acid hydroxamate resulted in the increased
inhibition of MMP-3.10
Second, we focused on optimization of the C2 substituent,
as shown in Table 1. Introduction of a 2S-methyl residue
at the C2 position of 2 afforded 3, which was 2.5-fold more
potent, 7-fold more potent, and 2.3-fold more potent as
an inhibitor of MMP-1, MMP-2, and MMP-3, respective-
ly, while it showed the same activity against MMP-9. The
corresponding 2S-ethyl and 2S-propyl analogs 4 and 5
were also synthesized and evaluated. Compound 4 exhib-
ited 2.2-fold, 3.2-fold, 2.2-fold, and 3.1-fold more potent
inhibitory activity against MMP-1, MMP-2, MMP-9,
and MMP-3, respectively, relative to unsubstituted 2.
The 2S-propyl analog 5 showed nearly the same inhibito-
ry spectrum as that of 4 with regard to all the MMP iso-
forms. Thus, analogs 3–5 tended to show increased
activity against all of the MMP isoforms relative to
unsubstituted analog 2, while 3 retained its activity
against MMP-9. Introduction of a 2S-isobutyl residue
at the C2 position of 2 afforded 6, which showed nearly
equipotent activity against MMP-1, MMP-9, and
MMP-3, while it retained the same activity against
MMP-2. Introduction of a 2S-benzyl residue at the C2 po-
sition of 2 afforded 7, which showed 5-fold, 7-fold, 2.6-
fold, and 5.8-fold more potent inhibitory activity against
MMP-1, MMP-2, MMP-9, and MMP-3, respectively.
Thus, the 2S-benzyl analog 7 exhibited increased activity
against all the MMP isoforms, while 2S-isobutyl analog 6
tended to show less and/or unchanged activity. Introduc-
tion of 2R- or 2S-pyridinylmethyl residues at the C2 posi-
tion of 2 afforded 8–10, with an increase of inhibitory
activity against all of the MMP isoforms. The 2R-pyri-
din-2-ylmethyl analog 8 exhibited 13-fold, 5-fold, 4.3-

S. Yamamoto et al. / Bioorg. Med. Chem. 14 (2006) 6383–6403
6387
OMe
O
R2
R1
b
MeO2C
N Cbz
H
Cbz
MeO2C
N
H
26a-e
e
c 2-pyridylmethyl
d 4-pyridylmethyl
24 R = CH OH
-R :
2
a Me
b Bn
1
2
a
25 R = CH OCH OCH
1
2
2
3
c, d
c,d
OMe
OMe
O
O
O
O
R3
e
MeO2C
N
H
MeO2C
N
H
O
O
27
28a-g, i-m 28f
28h
c
f
f
OMe
O
OMe
O
O
O
R3
R3
H
N
g, h(29a-l and n)
or i, j (29m)
HO2C
N
H
HO
N
H
O
O
O
2-15
29a-n
-R
:
a
3
Me
Bn
n-Pr
h
3-pyridylmethyl
1-naphthylmethyl
OH
b
c
d
e
f
i
j
2-pyridylmethyl
4-pyridilmethyl
k
i-Bu
allyl
l
SPh
t
m
CH CO Bu
2
2
g
n
H
Et
Scheme 1. Synthesis of 2–15. Reagents and conditions: (a) MOMCl, iPr2NEt, CH2Cl2; (b) RBr or RI, LiHMDS, THF; (c) H2, Pd/C, MeOH; (d) 4-
phenoxybenzoic acid, EDC, HOBt, Et3N, DMF; (e) RBr or RI or PhSSPh or 2-sulfonyl oxaziridine, LiHMDS, THF; (f) NaOH aq, THF–MeOH; (g)
O-(2-methoxypropane-2-yl)hydroxylamine, EDC, HOBt, Et3N, DMF; (h) HCl, MeOH; (i) O-benzylhydroxylamine, EDC, HOBt, Et3N, DMF; (j)
H2, Pd/C, MeOH.
Then further optimization of the 2S-methyl analog 3
was conducted as described in Table 2. Replacement
of the 4S-methoxymethyloxymethyl residue of 3 with a
4S-ethoxymethyloxymethyl residue afforded 16, with
slightly more potent inhibitory activity against MMP-9
and MMP-3, while it retained the equipotent activity
against MMP-1 and MMP-2. Replacement of the 4S-
methoxymethyloxymethyl residue of 3 with a 4S-meth-
oxyethyloxymethyloxymethyl residue gave 17, which
showed 2.4-fold less potent and 2.6-fold more potent
inhibitory activity against MMP-2 and MMP-9,
respectively, while it retained the same activity against
MMP-1 and MMP-3. Replacement of the 4S-meth-
oxymethyloxymethyl residue of 3 with a pivaloyloxy-
methyl residue produced 18, which was slightly less
potent as an inhibitor of MMP-2 and MMP-3, while it
retained the same activity against MMP-9. Deprotection
of the methoxymethyl group of 3 afforded 19, which
showed nearly equipotent activity against MMP-1,
MMP-2, MMP-9, and MMP-3, respectively. Replace-
ment of the hydroxymethyl residue of 19 with a methyl
residue led to 20, which showed 101-fold less potent,
138-fold less potent, and 136-fold less potent inhibition
of MMP-2, MMP-9, and MMP-3, respectively. Based
on this information, an O-substitution in the 4S-substi-
tuent seems to be essential for potent activity. Thus,
most of the chemical modifications described above
resulted in a retention of the potent inhibitory activity
although 4S-methyl analog 20 resulted in a decrease of
the inhibitory activity relative to other analogs.

6388
S. Yamamoto et al. / Bioorg. Med. Chem. 14 (2006) 6383–6403
OR
OR
d, e
a or b
c
24
Cbz
Cbz
MeO2C
N
H
MeO2C
N
H
30a R = EOM
30b R = TBS
31a R = EOM
31b R = TBS
OR
OR
O
O
g, h
f
HO2C
N
H
MeO2C
N
H
or g, i, h
O
O
32a R = EOM
32b R = TBS
33a R = EOM
33b R = TBS
OR
O
H
N
HO
N
H
O
O
16 R = EOM
19 R = H
Scheme 2. Synthesis of 16 and 19. Reagents and conditions: (a) EOMCl, iPr2NEt, CH2Cl2; (b) TBSCl, imidazole, DMF; (c) MeI, LiHMDS, THF;
(d) H2, Pd/C, MeOH; (e) 4-phenoxybenzoic acid, EDC, HOBt, Et3N, DMF; (f) NaOH aq, THF–MeOH; (g) O-benzylhydroxylamine, EDC,
HOBt, Et3N, DMF; (h) H2, Pd/C, MeOH; (i) TBAF, THF.
OR
OR
OH
a or b
c
BnO2C
NHBoc
BnO2C
NHBoc
BnO2C
NHBoc
34
35a R = MEM
35b R = Pivaloyl
36a R = MEM
36b R = Pivaloyl
OR
O
OR
O
d, e
f
BnO2C
N
H
HO2C
N
H
O
O
37a R = MEM
38a R = MEM
37b R = Pivaloyl
38b R = Pivaloyl
OR
O
H
N
g, h
HO
N
H
O
O
17 R = MEM
18 R = Pivaloyl
Scheme 3. Synthesis of 17 and 18. Reagents and conditions: (a) MEMCl, iPr2NEt, CH2Cl2; (b) PivCl, pyridine; (c) MeI, LiHMDS, THF; (d) TFA–
H2O, CH2Cl2; (e) 4-phenoxybenzoic acid, EDC, HOBt, Et3N, DMF; (f) H2, Pd/C, MeOH; (g) O-(2-methoxypropane-2-yl)hydroxylamine, EDC,
HOBt, Et3N, DMF; (h) HCl, MeOH.
Further optimization was also conducted for 2S-ethyl
analog 4. Chemical modification was again focused
on optimization of the 4S-methoxymethyloxymethyl
residue, as described in Table 3. Replacement of the
4S-methoxymethyloxymethyl residue of 4 with eth-
oxymethyloxymethyl or methoxyethyloxymethyloxy-
methyl residues afforded 21 and 22, respectively.
Compound 21 exhibited nearly equipotent inhibitory
activity against MMP-2 and MMP-9 compared with
4, while it retained its previous activity against
MMP-1 and MMP-9. Compound 22 demonstrated
nearly equipotent activity against MMP-2, while it
retained the previous level of activity against other
isoforms. Replacement of the 4S-methoxymethyloxy-
methyl residue with a pivaloyloxymethyl residue result-
ed in 23, with 8.3-fold less potent activity against
MMP-9, although it retained the previous level of
activity against MMP-2 and MMP-3.

S. Yamamoto et al. / Bioorg. Med. Chem. 14 (2006) 6383–6403
6389
O
O
O
O
O
O
O
a
b
c
O
O
NHBoc
NHBoc
HO2C
NHBoc
39
40
41
O
e, f
d
NBoc
MeO2C
N
H
MeO2C
NHBoc
O
O
42
43
44
O
O
g
h
MeO2C
N
H
HO2C
N
H
O
O
45
46
O
H
N
i, j
HO
N
H
O
O
20
Scheme 4. Synthesis of 20. Reagents and conditions: (a) Meldrum’s acid, DMAP, DCC, CH2Cl2; (b) NaBH4, AcOH, CH2Cl2; (c) toluene reflux;
(d) i—NaOH aq, acetone; ii—CH2N2, MeOH; (e) 4 N HCl/EtOAc; (f) 4-phenoxybenzoic acid, EDC, HOBt, Et3N, DMF; (g) MeI, LiHMDS, THF
(h) NaOH aq, MeOH; (i) O-(2-methoxypropane-2-yl)hydroxylamine, EDC, HOBt, Et3N, DMF; (j) HCl, MeOH.
O
O
O
O
O
O
a, b
c
30a
MeO2C
N
H
MeO2C
N
H
O
O
47
48
O
O
O
O
O
O
H
N
e, f
d
HO
N
H
HO2C
N
H
O
O
O
49
21
Scheme 5. Synthesis of 21. Reagents and conditions: (a) H2, Pd/C, MeOH; (b) 4-phenoxybenzoic acid, EDC, HOBt, Et3N, DMF; (c) EtI, LiHMDS,
THF; (d) NaOH aq, THF–MeOH; (e) O-benzylhydroxylamine, EDC, HOBt, Et3N, DMF; (f) H2, Pd/C, MeOH.
Our focus was placed on the compound 9 possessing
broad inhibitory spectrum. As shown in Figure 2, an
in vivo potential of 9 as a stromelysin inhibitor was eval-
uated based on its ability to inhibit stromelysin (MMP-
3)-induced proteoglycan release in the knee joints of
guinea pigs.17 Compound 9 showed dose-dependent
suppression of proteoglycan release from the knee joint
cartilage after oral dosing. This finding strongly suggests
that our inhibitors may have therapeutic potential for
diseases where MMPs are overexpressed.
In summary, optimization of the C2-substituent was
conducted in a series of 4-(4-phenoxy) benzoylamino-
4-methoxymethyloxymethyl butyric acid hydroxamates.
Most of the analogs listed in Table 1 exhibited strong
inhibitory activity against MMP-2 and MMP-9 in addi-
tion to increased inhibition of MMP-3, while showing
moderate to weak activity against MMP-1.
Further optimization of the 4S substituents of 3 and 4,
which were selected for their ease of synthesis and the

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S. Yamamoto et al. / Bioorg. Med. Chem. 14 (2006) 6383–6403
OR
O
BnO2C
N
H
a,b
c
O
50 R = MEM
35a, b
OR
O
OR
c
a, b
BnO2C
N
H
BnO2C
NHBoc
O
51 R = Pivaloyl
52a R = MEM
52b R = Pivaloyl
OR
O
OR
O
H
N
e, f
d
HO
N
H
HO2C
N
H
O
O
O
53a R = MEM
53b R = Pivaloyl
22 R = MEM
23 R = Pivaloyl
Scheme 6. Synthesis of 22 and 23. Reagents and conditions: (a) TFA–H2O, CH2Cl2; (b) 4-phenoxybenzoic acid, EDC, HOBt, Et3N, DMF; (c) EtI,
LiHMDS, THF; (d) H2, Pd/C, MeOH; (e) O-benzylhydroxylamine, EDC, HOBt, Et3N, DMF; (f) H2, Pd/C, MeOH.
coupling constants (J) in hertz (Hz). Fast atom bom-
bardment (FAB) and electron ionization (EI) mass
spectra were obtained with a JEOL JMS-DX303HF
or JMS-700 spectrometer. Atmospheric pressure chem-
ical ionization (APCI) mass spectra were determined by
a Hitachi M-1200 H spectrometer. Matrix-assisted laser
desorption ionization (MALDI) mass spectra obtained
on a PerSeptive Biosystems VoyagerTM Elite spectrome-
ter. IR spectra were measured using a Perkin-Elmer
FTIR 1760X or JASCO FTIR-430 spectrometer. Col-
umn chromatography was carried out using silica gel
[Merck silica gel 60 (0.063–0.200 mm), Wako Gel
C200, Fuji Silysia FL60D, or Fuji Silysia BW-235].
TLC was also performed on silica gel (Merck TLC
plate, silica gel 60 F254). The following abbreviations
for solvents and reagents are used: THF, tetrahydrofu-
ran; EtOAc, ethylacetate; MeOH, methanol; DMF,
N,N-dimethylformamide; CH2Cl2, dichloromethane;
CHCl3, chloroform; EDCÆHCl, 1-[3-(dimethylami-
no)propyl]-3-ethylcarbodiimide hydrochloride; HOBt,
1-hydroxybenzotriazole; HMPA, hexamethylphospho-
ramide; DMSO, dimethylsulfoxide; AcOH, acetic
acid; LiHMDS, lithium hexamethyldisilazane; FITC,
fluorescein isothiocyanate; MOCAc, 7-methoxycouma-
rin-4-acetyl; Dpa, N-3-(2,4-dinitrophenyl)-L-2,3-diami-
nopropionyl; Dnp, 2,4-dinitrophenyl.
200
150
100
50
n = 4
N.S.
(22%)
#
(51%)
##
(66%)
0
Sham
SLN
Control
3
10
30
Compound 9 (mg/Kg, p.o.)
Figure 2. Effect of compound
9
on stromelysin (SLN)-induced
proteoglycan release in the knee joints of guinea pigs. Each bar
represents means standard error of four animals. (##) p < 0.01,
significantly different from SLN control (Dunnett t test). (#) p < 0.05,
significantly different from SLN control (Dunnett t test). NS, not
significantly different from SLN control. The numbers in parentheses
represent the percent inhibition of proteoglycan release to SLN
control.
SAR study, was carried out as described in Tables 2 and 3,
respectively. Among the compounds tested, 16–18 were
also found to inhibit stromelysin (MMP-3)-induced pro-
teoglycan release in the knee joints of guinea pigs.
4.1. Methyl (4S)-4-{[(benzyloxy)carbonyl]amino}-5-
(methoxymethoxy)pentanoate (25)
4. Experimental
To a stirred solution of 24 (93.6 g, 333 mmol) and N,N-
(diisopropyl)ethylamine (170 mL, 999 mmol) in CH2Cl2
(170 mL) was added methoxymethyl chloride (38.0 mL,
500 mmol) cooling with an ice bath. The reaction mix-
ture was stirred at room temperature for 2 h, quenched
with aqueous NH4Cl, and extracted with CH2Cl2. The
organic layer was dried over MgSO4 and evaporated
to give a crude product, which was purified by silica
Analytical samples were homogeneous as confirmed by
thin-layer chromatography (TLC) and yielded spectro-
scopic data consistent with the assigned structures. All
1H NMR spectra were obtained with a Varian Gemini-
200 or MERCURY-300 spectrometer. The chemical
shift values are reported in parts per million (d) and

S. Yamamoto et al. / Bioorg. Med. Chem. 14 (2006) 6383–6403
6391
gel chromatography with EtOAc–n-hexane (1:1) as an
eluent to give 25 (83.5 g, 77%) as a white solid: TLC
Rf = 0.52 (EtOAc–n-hexane, 1:1); H NMR (CDCl3): d
7.40–7.26 (m, 5H), 5.10 (s, 2H), 5.03 (d, J = 9.3 Hz,
1H), 4.60 (s, 2H), 3.92–3.79 (m, 1H), 3.66 (s, 3H),
3.65–3.50 (m, 2H), 3.34 (s, 3H), 2.42 (t, J = 7.5 Hz,
2H), 2.00–1.80 (m, 2H).
4.2.6. Methyl (2S)-2-[(2S)-2-{[(benzyloxy)carbonyl]ami-
no}-3-(methoxymethoxy)propyl]-4-methylpent-4-enoate
(26e). Yield 73%; TLC Rf = 0.37 (EtOAc–n-hexane,
2:3); 1H NMR (CDCl3): d 7.40–7.23 (m, 5H), 5.09
(s, 2H), 4.91 (d, J = 9.2 Hz, 1H), 4.76 (s, 1H), 4.59
(s, 2H), 4.00–3.78 (m, 1H), 3.61–3.42 (m, 5H), 3.33 (s,
3H), 2.77–2.58 (m, 1H), 2.34 (dd, J = 13.8, 8.4 Hz,
1H), 2.19 (dd, J = 13.8 Hz and 6.6 Hz, 1H), 1.93 (dt,
J = 14.0 Hz and 9.8 Hz, 1H), 1.80–1.62 (m, 4H).
1
4.2. Preparation of 26
Compounds 26a–e were prepared from the compound
25 according to the general procedure described below.
4.3. Methyl (4S)-5-(methoxymethoxy)-4-[(4-phenoxy-
benzoyl)amino]pentanoate (27)
4.2.1. General procedure for preparation of 26 from 25.
To a stirred solution of LiHMDS (8.0 mmol, 1.0 M in
THF) in dry THF (15 mL) was added a solution of com-
pound 25 (3.6 mmol) in dry THF (10 mL) at ꢀ78 °C.
After stirring for 1 h, alkyl halide (11 mmol) was added
to the solution and stirred at ꢀ78 °C for 3 h. The reaction
mixture was quenched with aqueous NH4Cl and extract-
ed with EtOAc. The organic layer was washed with brine,
dried over Na2SO4, and evaporated. The resulting residue
was purified by silica gel chromatography with EtOAc–
n-hexane as an eluent to afford compound 26.
A solution of compound 25 (4.15 g, 12.8 mmol) in
MeOH (20 mL) was vigorously stirred in the presence
of 10% Pd/C (200 mg) under hydrogen atmosphere for
1 h. After removing the catalyst by filtration through a
pad of Celite, the reaction mixture was concentrated in
vacuo to afford
a crude amine: TLC Rf = 0.38
(CHCl3–MeOH, 9:1); 1H NMR (CDCl3): d 4.64 (s,
2H), 3.68 (s, 3H), 3.51 (dd, J = 9.6, 4.0 Hz, 1H), 3.31
(dd, J = 9.6 Hz and 7.2 Hz, 1H), 3.02–2.89 (m, 1H),
2.59–2.31 (m, 2H), 1.92–1.73 (m, 1H), 1.70–1.50 (m,
1H).
4.2.2. Methyl (2S,4S)-4-{[(benzyloxy)carbonyl]amino}-5-
(methoxymethoxy)-2-methylpentanoate (26a). Yield 67%;
TLC Rf = 0.46 (EtOAc–n-hexane, 1:1); 1H NMR
(CDCl3): d 7.35–7.32 (m, 5H), 5.08 (s, 2H), 4.50 (s,
2H), 3.85–3.98 (m, 1H), 3.61 (s, 3H), 3.54–3.52 (m,
2H), 3.32 (s, 3H), 2.96–2.58 (m, 1H), 1.98 (ddd,
J = 14.4 Hz, 10.5 Hz, and 7.2 Hz, 1H), 1.64 (m, 1H),
1.21 (d, J = 6.9 Hz, 3H).
A solution of the crude amine, EDCÆHCl (2.68 g,
14.0 mmol), HOBtÆH2O (2.11 g, 14.0 mmol), 4-phenoxy-
benzoic acid (2.73 g, 12.8 mmol), and triethylamine
(3.88 mL, 28.1 mmol) in DMF (30 mL) was stirred at
room temperature for 3 h. The reaction mixture was
diluted with EtOAc. The organic layer was washed with
aqueous NaHCO3, H2O, and brine, dried over Na2SO4
and evaporated. The resulting residue was triturated
with diethyl ether to afford compound 27 as a white
powder (4.47 g, 91%): TLC Rf = 0.67 (EtOAc–n-hexane,
4:1); 1H NMR (CDCl3): d 7.77 (d, J = 8.8 Hz, 2H), 7.43–
7.33 (m, 2H), 7.21–7.12 (m, 1H), 7.08–7.03 (m, 2H), 7.01
(d, J = 8.8 Hz, 2H), 6.63 (d, J = 8.8 Hz, 1H), 4.65 (s,
2H), 4.40–4.22 (m, 1H), 3.75 (dd, J = 10.4 Hz and
3.4 Hz, 1H), 3.63 (s, 3H), 3.61 (dd, J = 10.4 Hz and
4.0 Hz, 1H), 3.38 (s, 3H), 2.61–2.35 (m, 2H), 2.14–1.96
(m, 2H).
4.2.3. Methyl (2S,4S)-2-benzyl-4-{[(benzyloxy)carbon-
yl]amino}-5-(methoxymethoxy)pentanoate (26b). Yield
92%; TLC Rf = 0.48 (EtOAc–n-hexane, 2:3); H NMR
1
(CDCl3): d 7.42–7.30 (m, 5H), 7.25–7.08 (m, 5H), 5.09
(s, 2H), 4.92 (d, J = 10.0 Hz, 1H), 4.56 (s, 2H), 4.00–
3.80 (m, 1H), 3.58–3.40 (m, 5H), 3.29 (s, 3H), 2.98–
2.65 (m, 3H), 2.02–1.87 (m, 1H), 1.72 (dt, J = 14.4,
5.0 Hz, 1H).
4.2.4. Methyl (2R,4S)-4-{[(benzyloxy)carbonyl]amino}-5-
(methoxymethoxy)-2-(2-pyridinylmethyl)pentanoate (26c).
4.4. Preparation of compound 28
1
Yield 92%; TLC Rf = 0.14 (EtOAc–n-hexane, 1:1); H
Compounds 28a–e were prepared from the compounds
26a–e according to the same procedure as described
for the preparation of 27 from 25, respectively. Com-
pounds 28f,g and i–m were prepared from 27 according
to the general procedure for the preparation of 26 from
25. Preparation of compound 28h was described below.
NMR (CDCl3): d 8.52–8.48 (m, 1H), 7.56 (dt, J = 7.6,
2.2 Hz, 1H), 7.37–7.28 (m, 5H), 7.14–7.08 (m, 2H),
5.08 (s, 2H), 5.07–5.01 (m, 1H), 4.56 (s, 2H), 3.96–3.82
(m, 1H), 3.60–3.47 (m, 5H), 3.29 (s, 3H), 3.17–2.95
(m, 3H), 2.02 (dt, J = 14.0, 8.1 Hz, 1H), 1.77 (dt,
J = 14.0 Hz and 4.8 Hz, 1H).
4.4.1. Methyl (2S,4S)-5-(methoxymethoxy)-2-methyl-4-
[(4-phenoxybenzoyl)amino]pentanoate (28a). Yield 92%;
TLC Rf = 0.42 (EtOAc–n-hexane, 1:1); 1H NMR
(CDCl3): d 7.77–7.74 (m, 2H), 7.40–7.35 (m, 2H), 7.14
(t, J = 7.5 Hz, 1H), 7.05–6.98 (m, 4H), 6.43 (d,
J = 9.0 Hz, 1H), 4.64 (d, J = 6.9 Hz, 1H), 4.62 (d,
J = 6.9 Hz, 1H), 4.43–4.35 (m, 1H), 3.70 (dd,
J = 9.9 Hz and 3.3 Hz, 1H), 3.60 (dd, J = 9.9 Hz and
3.9 Hz, 1H), 3.55 (s, 3H), 2.63–2.50 (m, 1H), 2.18
(ddd, J = 14.4 Hz, 10.8 Hz and 7.8 Hz, 1H), 1.72–1.61
(m, 1H), 1.24 (d, J = 6.9 Hz, 3H).
4.2.5. Methyl (2S,4S)-4-{[(benzyloxy)carbonyl]amino}-5-
(methoxymethoxy)-2-(4-pyridinylmethyl)pentanoate (26d).
1
Yield 73%; TLC Rf = 0.26 (EtOAc–n-hexane, 9:1); H
NMR (CDCl3): d 8.49–8.44 (m, 2H), 7.40–7.28 (m,
5H), 7.10–7.00 (m, 2H), 5.14 (d, J = 12.2 Hz, 1H), 5.08
(d, J = 12.2 Hz, 1H), 4.99 (d, J = 8.8 Hz, 1H), 4.59 (s,
2H), 4.03–3.84 (m, 1H), 3.62–3.45 (m, 5H), 3.32 (s,
2H), 2.94–2.67 (m, 3H), 2.00 (ddd, J = 14.4 Hz, 9.8 Hz
and 6.2 Hz, 1H), 1.71 (ddd, J = 14.4 Hz, 6.2 Hz and
4.8 Hz, 1H).

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S. Yamamoto et al. / Bioorg. Med. Chem. 14 (2006) 6383–6403
4.4.2. Methyl (2S,4S)-2-benzyl-5-(methoxymethoxy)-4-
[(4-phenoxybenzoyl)amino]pentanoate (28b). Yield 97%;
TLC Rf = 0.51 (EtOAc–n-hexane, 1:1); 1H NMR
(CDCl3): d 7.75 (d, J = 8.8 Hz, 2H), 7.42–7.34 (m,
2H), 7.28–7.10 (m, 3H), 7.08–6.95 (m, 3H), 6.44 (d,
J = 9.0 Hz, 1H), 4.62 (d, J = 7.2 Hz, 1H), 4.58 (d,
J = 7.2 Hz, 1H), 4.44–4.28 (m, 1H), 3.68 (dd,
J = 10.2 Hz and 3.2 Hz, 1H), 3.56 (dd, J = 10.2 Hz and
4.2 Hz, 1H), 3.40 (s, 3H), 3.29 (s, 3H), 3.00–2.70 (m,
3H), 2.15 (ddd, J = 14.4 Hz, 10.6 Hz and 8.8 Hz, 1H),
1.80 (dt, J = 14.4 Hz and 4.4 Hz, 1H).
(CDCl3): d 7.78–7.73 (m, 2H), 7.42–7.34 (m, 2H),
7.21–7.13 (m, 1H), 7.06 (m, 4H), 6.12 (d, J = 8.8 Hz,
1H), 4.63 (s, 2H), 4.43–4.28 (m, 1H), 3.70 (dd,
J = 13.2 Hz and 3.4 Hz, 1H), 3.58 (dd, J = 13.2 Hz and
4.0 Hz, 1H), 3.56 (s, 3H), 3.36 (s, 3H), 2.50 (m, 1H),
2.21–2.04 (m, 2H), 1.83–1.57 (m, 3H), 0.89 (t,
J = 7.2 Hz, 3H).
4.4.8. Methyl (2S,4S)-5-(methoxymethoxy)-4-[(4-pheno-
xybenzoyl)amino]-2-propylpentanoate (28h). A solution
of 28f (640 mg, 1.49 mmol) in MeOH (5.0 mL) was vig-
orously stirred in the presence of 10% Pd/C (60 mg) un-
der hydrogen atmosphere for 6 h. After removing the
catalyst by filtration through a pad of Celite, the reac-
tion mixture was evaporated. The resulting residue was
purified by silica gel chromatography with EtOAc–n-
hexane (1:4) as an eluent to afford 28h (79%): TLC
4.4.3. Methyl (2R,4S)-5-(methoxymethoxy)-4-[(4-pheno-
xybenzoyl)amino]-2-(2-pyridinylmethyl)pentanoate (28c).
1
Yield 79%; TLC Rf = 0.29 (EtOAc–n-hexane, 9:1); H
NMR (CDCl3):
d 8.55–8.44 (m, 1H), 7.77 (d,
J = 8.8 Hz, 2H), 7.58 (dt, J = 7.8 Hz and 1.8 Hz, 1H),
7.42–7.30 (m, 2H), 7.21–6.96 (m, 7H), 6.69 (d,
J = 8.8 Hz, 1H), 4.60 (s, 2H), 4.43–4.23 (m, 1H), 3.70
(dd, J = 10.0 Hz and 3.4 Hz, 1H), 3.59 (dd,
J = 10.0 Hz and 4.0 Hz, 1H), 3.49 (s, 3H), 3.33 (s, 3H),
3.20–2.96 (m, 3H), 2.29–2.10 (m, 1H), 1.87 (dt,
J = 13.8 Hz and 4.4 Hz, 1H).
1
Rf = 0.51 (EtOAc–n-hexane, 1:1); H NMR (CDCl3): d
7.76–7.73 (m, 2H), 7.40–7.26 (m, 2H), 7.19–7.14 (m,
1H), 7.05–6.98 (m, 4H), 6.56 (d, J = 8.4 Hz, 1H), 4.64
(d, J = 6.6 Hz, 1H), 4.62 (d, J = 6.6 Hz, 1H), 4.29–4.40
(m, 1H), 3.70 (dd, J = 9.9 Hz and 3.3 Hz, 1H), 3.57
(dd, J = 9.9 Hz and 3.9 Hz, 1H), 2.55–2.46 (m, 1H),
2.18–2.07 (m, 1H), 1.77 (dd, J = 14.2 Hz and 4.5 Hz,
1H), 1.65–1.48 (m, 2H), 1.36–1.23 (m, 2H), 0.89 (t,
J = 7.2 Hz, 3H).
4.4.4. Methyl (2S,4S)-5-(methoxymethoxy)-4-[(4-pheno-
xybenzoyl)amino]-2-(4-pyridinylmethyl)pentanoate (28d).
1
Yield 99%; TLC Rf = 0.15 (EtOAc–n-hexane, 9:1); H
NMR (CDCl3):
d
8.51–8.46 (m, 2H), 7.77 (d,
4.4.9. Methyl (2S,4S)-5-(methoxymethoxy)-4-[(4-phen-
oxybenzoyl)amino]-2-(3-pyridinylmethyl)pentanoate (28i).
J = 8.8 Hz, 2H), 7.43–7.33 (m, 2H), 7.21–6.97 (m, 7H),
6.52 (d, J = 8.8 Hz, 1H), 4.64 (d, J = 6.6 Hz, 1H), 4.62
(d, J = 6.6 Hz, 1H), 4.55–4.36 (m, 1H), 3.72 (dd,
J = 10.8 Hz and 3.4 Hz, 1H), 3.60 (dd, J = 10.8 Hz and
4.2 Hz, 1H), 3.43 (s, 3H), 3.36 (s, 3H), 3.02–2.74 (m,
3H), 2.17 (ddd, J = 14.2 Hz, 10.6 Hz and 7.6 Hz, 1H),
1.79 (ddd, J = 14.2 Hz, 5.4 Hz and 4.8 Hz, 1H).
1
Yield 84%; TLC Rf = 0.19 (EtOAc–n-hexane, 9:1); H
NMR (CDCl3): d 8.45 (dd, J = 4.8 Hz and 1.8 Hz,
1H), 8.43–8.40 (m, 1H), 7.76 (d, J = 8.8 Hz, 2H), 7.51
(dt, J = 7.8 Hz and 1.8 Hz, 1H), 7.44–7.33 (m, 2H),
7.25–7.13 (m, 2H), 7.09–7.03 (m, 2H), 7.01 (d,
J = 8.8 Hz, 1H), 6.50 (d, J = 9.2 Hz, 1H), 4.64 (d,
J = 7.8 Hz, 1H), 4.61 (d, J = 7.8 Hz, 1H), 4.55–5.36
(m, 1H), 3.71 (dd, J = 10.2 Hz and 3.0 Hz, 1H), 3.59
(dd, J = 10.2 Hz and 4.0 Hz, 1 H), 3.42 (s, 3H), 3.35 (s,
3H), 3.04–2.88 (m, 2H), 2.86–2.69 (m, 1H), 2.18 (ddd,
J = 14.0 Hz, 10.4 Hz and 7.8 Hz, 1H), 1.81 (dt,
J = 14.0 Hz and 5.0 Hz, 1H).
4.4.5. Methyl (2S,4S)-2-isobutyl-5-(methoxymethoxy)-4-
[(4-phenoxybenzoyl)amino]pentanoate (28e). Yield 81%;
TLC Rf = 0.67 (EtOAc–n-hexane, 1:1); 1H NMR
(CDCl3): d 7.76 (d, J = 8.8 Hz, 2H), 7.43–7.34 (m,
2H), 7.22–7.14 (m, 1H), 7.08–6.97 (m, 4H), 6.37 (d,
J = 9.2 Hz, 1H), 4.63 (s, 2H), 4.43–4.24 (m, 1H), 3.71
(dd, J = 10.0 Hz and 3.4 Hz, 1H), 3.58 (dd,
J = 10.0 Hz and 4.0 Hz, 1H), 3.49 (s, 3H), 3.37 (s, 3H),
2.65–2.49 (m, 1H), 2.00 (dt, J = 14.4 Hz and 10.4 Hz,
1H), 1.75 (dt, J = 14.4 Hz and 4.8 Hz, 1H), 1.66–1.44
(m, 2H), 1.42–1.28 (m, 1H), 0.89 (d, J = 6.6 Hz, 3H),
0.88 (d, J = 6.6 Hz, 3H).
4.4.10. Methyl (2S,4S)-5-(methoxymethoxy)-2-(1-naph-
thylmethyl)-4-[(4-phenoxybenzoyl)amino]pentanoate (28j).
1
Yield 95%; TLC Rf = 0.51 (EtOAc–n-hexane, 1:1); H
NMR (CDCl3): d 8.05–7.96 (m, 1H), 7.87–7.80 (m,
1H), 7.79–7.69 (m, 3H), 7.52–7.26 (m, 6H), 7.21–7.10
(m, 1H), 7.07–6.95 (m, 4H), 6.41 (d, J = 9.0 Hz, 1H),
4.57 (d, J = 8.0 Hz, 1H), 4.53 (d, J = 8.0 Hz, 1H),
4.46–4.25 (m, 1H), 3.64 (dd, J = 10.2 Hz and 3.4 Hz,
1H), 3.54 (dd, J = 10.2 Hz and 4.0 Hz, 1H), 3.41 (dd,
J = 13.8 Hz and 8.2 Hz, 1H), 3.35 (s, 3H), 3.26 (dd,
J = 13.8 Hz and 6.8 Hz, 1H), 3.24 (s, 3H), 3.08–2.88
(m, 1H), 2.27 (dt, J = 14.0 Hz and 9.8 Hz, 1H), 1.89
(dt, J = 14.0 Hz and 4.8 Hz, 1H).
4.4.6. Methyl (2S)-2-{(2S)-3-(methoxymethoxy)-2-[(4-
phenoxybenzoyl)amino]propyl}-4-pentenoate (28f). Yield
93%; TLC Rf = 0.54 (EtOAc–n-hexane, 1:1); H NMR
(CDCl3): d 7.76–7.73 (m, 2H), 7.40–7.34 (m, 2H),
7.18–7.14 (m, 1H), 7.04–6.69 (m, 4H), 6.44 (d,
J = 9.0 Hz, 1H), 5.79–5.65 (m, 1H), 5.09–5.02 (m, 2H),
4.65–4.60 (m, 2H), 4.41–4.30 (m, 1H), 3.69 (dd,
J = 10.2 Hz and 3.3 Hz, 1H), 3.57 (dd, J = 10.2 Hz and
3.9 Hz, 1H), 3.49 (s, 3H), 3.36 (s, 3H), 2.63–2.29 (m,
2H), 2.19–2.08 (m, 1H), 1.84–1.77 (m, 1H).
1
4.4.11. Methyl (2S,4S)-2-hydroxy-5-(methoxymethoxy)-
4-[(4-phenoxybenzoyl)amino]pentanoate (28k). Yield
52%; TLC Rf = 0.26 (EtOAc–n-hexane, 9:1); H NMR
1
(CDCl3): d 7.80–7.76 (m, 2H), 7.43–7.35 (m, 2H),
7.22–7.14 (m, 1H), 7.08–6.99 (m, 5H), 4.70 (d,
J = 6.6 Hz, 1H), 4.66 (d, J = 6.6 Hz, 1H), 4.55–4.44
(m, 1H), 4.45 (d, J = 4.4 Hz, 1H), 4.30 (ddd,
4.4.7. Methyl (2S,4S)-2-ethyl-5-(methoxymethoxy)-4-[(4-
phenoxybenzoyl)amino]pentanoate (28g). Yield 75%;
TLC Rf = 0.59 (EtOAc–n-hexane, 3:2); 1H NMR

S. Yamamoto et al. / Bioorg. Med. Chem. 14 (2006) 6383–6403
6393
J = 10.6 Hz, 4.6 Hz and 2.6 Hz, 1H), 3.83 (dd,
J = 10.2 Hz and 3.4 Hz, 1H), 3.77 (s, 3H), 3.73 (dd,
J = 10.2 Hz and 3.4 Hz, 1H), 3.40 (s, 3H), 2.22 (ddd,
J = 14.2 Hz, 10.5 Hz and 2.8 Hz, 1H), 1.90 (ddd,
J = 14.2 Hz, 10.5 Hz and 3.6 Hz, 1H).
4.5.4. (2R,4S)-5-(Methoxymethoxy)-4-[(4-phenoxyben-
zoyl)amino]-2-(2-pyridinylmethyl)pentanoic acid (29c).
Yield 69%; TLC Rf = 0.43 (CHCl3–MeOH, 9:1); 1H
NMR (CDCl3): d 8.50–8.42 (m, 1H), 7.82–7.68 (m,
3H), 7.47–7.22 (m, 4H), 7.20–7.10 (m, 1H), 7.07–6.94
(m, 4H), 6.82 (d, J = 8.8 Hz, 1H), 4.60 (s, 2H), 4.50–
4.28 (m, 1H), 3.64 (dd, J = 10.2 Hz and 3.6 Hz, 1H),
3.55 (dd, J = 10.2 Hz and 4.4 Hz, 1H), 3.33 (s, 3H),
3.31 (dd, J = 16.2 Hz and 8.4 Hz, 1H), 3.18 (dd,
J = 16.2 Hz and 2.2 Hz, 1H), 2.98–2.82 (m, 1H), 2.40
(ddd, J = 14.2 Hz, 11.4 Hz and 6.0 Hz, 1H), 1.76 (ddd,
J = 14.2 Hz, 7.8 Hz and 3.8 Hz, 1H), 3.20–2.96 (m,
3H), 2.29–2.10 (m, 1H), 1.87 (dt, J = 13.8 Hz and
4.4 Hz, 1H).
4.4.12. Methyl (2S,4S)-5-(methoxymethoxy)-4-[(4-phen-
oxybenzoyl)amino]-2-(phenylthio)pentanoate (28l). Yield
35%; TLC Rf = 0.54 (EtOAc–n-hexane, 1:1); H NMR
1
(CDCl3): d 7.74–7.70 (m, 2H), 7.50–7.20 (m, 7H),
7.19–7.18 (m, 1H), 7.06–6.96 (m, 4H), 6.44 (d,
J = 8.8 Hz, 1H), 4.63 (d, J = 6.6 Hz, 1H), 4.59 (d,
J = 6.6 Hz, 1H), 4.65–4.48 (m, 1H), 3.79–3.56 (m, 3H),
3.44 (s, 3H), 3.34 (s, 3H), 2.40 (ddd, J = 14.5 Hz,
10.6 Hz and 8.8 Hz, 1H), 2.07 (ddd, J = 14.5 Hz,
5.6 Hz and 4.0 Hz, 1H).
4.5.5. (2S,4S)-5-(Methoxymethoxy)-4-[(4-phenoxyben-
zoyl)amino]-2-(4-pyridinylmethyl)pentanoic acid (29d).
Yield 69%; TLC Rf = 0.17 (CHCl3–MeOH, 9:1); 1H
NMR (CDCl3): d 12.28 (br s, 1H), 8.43 (d, J = 5.8 Hz,
2H), 8.24 (d, J = 9.2 Hz, 1H), 7.90 (d, J = 8.8 Hz, 2H),
7.50–7.38 (m, 2H), 7.24–7.14 (m, 3H), 7.13–6.99 (m,
4H), 4.62–4.48 (m, 2H), 4.43–4.23 (m, 1H), 3.60–3.43
(m, 2H), 3.24 (s, 3H), 2.94 (dd, J = 13.2 Hz and
4.8 Hz, 1H), 2.79 (dd, J = 13.2 Hz and 9.2 Hz, 1H),
2.70–2.56 (m, 1H), 1.92–1.64 (m, 2H).
4.4.13. 4-tert-Butyl 1-methyl (2R)-2-{(2S)-3-(methoxy-
methoxy)-2-[(4-phenoxybenzoyl)amino]propyl}succinate
(28m). Yield 100%; TLC Rf = 0.25 (EtOAc–n-hexane,
1:1); 1H NMR (CDCl3): d 7.76 (d, J = 8.7 Hz, 2H),
7.42–7.37 (m, 2 H), 7.21–7.13 (m, 1H), 7.08–7.01 (m,
2H), 7.00 (d, J = 8.7 Hz, 2H), 6.56 (d, J = 8.4 Hz, 1H),
4.63 (s, 2H), 4.42–4.30 (m, 2H), 3.75 (dd, J = 10.2 Hz
and 3.3 Hz, 1H), 3.64–3.58 (m, 4H), 3.36 (s, 3H), 2.90–
2.80 (m, 1H), 2.70–2.53 (m, 2H), 2.16 (ddd,
J = 13.8 Hz, 9.9 Hz and 7.2 Hz, 1H), 1.81 (ddd,
J = 13.8 Hz, 6.0 Hz and 4.8 Hz, 1H), 1.42 (s, 9H).
4.5.6. (2S,4S)-2-Isobutyl-5-(methoxymethoxy)-4-[(4-phe-
noxybenzoyl)amino]pentanoic acid (29e). Yield 92%;
TLC Rf = 0.36 (CHCl3–MeOH, 19:1); 1H NMR
(CDCl3): d 7.73 (d, J = 8.8 Hz, 2H), 7.42–7.30 (m,
2H), 7.21–7.11 (m, 1H), 7.07–7.02 (m, 2H), 6.97 (d,
J = 8.8 Hz, 2H), 6.56 (d, J = 9.2 Hz, 1H), 4.65 (d,
J = 7.8 Hz, 1H), 4.61 (d, J = 7.8 Hz, 1H), 4.48–4.30
(m, 1H), 3.74 (dd, J = 10.2 Hz and 3.0 Hz, 1H), 3.60
(dd, J = 10.2 Hz and 4.2 Hz, 1H), 3.36 (s, 3H), 2.63–
2.49 (m, 1H), 2.08 (dt, J = 14.2 Hz and 9.4 Hz, 1H),
1.75 (dt, J = 14.2 Hz and 5.4 Hz, 1H), 1.70–1.50 (m,
2H), 1.46–1.30 (m, 1H), 0.90 (d, J = 6.2 Hz, 6H).
4.5. Preparation of 29
The compounds 29a–n were prepared from the corre-
sponding methyl esters 27 and 28a–m, respectively,
according to the general procedure.
4.5.1. General procedure for preparation of 29. To a stir-
red solution of 28 (1.43 mmol) in THF (10 mL) and
MeOH (2 mL) was added 2 N NaOH (5 mL)at room tem-
perature and stirring was continued for 4 h. The reaction
mixture was neutralized with 1 N HCl and diluted with
EtOAc. The organic layer was washed with brine, dried
over Na2SO4, and evaporated to give compound 29.
4.5.7. (2S)-2-{(2S)-3-(Methoxymethoxy)-2-[(4-phenoxy-
benzoyl)amino]propyl}-4-pentenoic acid (29f). Yield
82%; TLC Rf = 0.49 (CHCl3–MeOH–AcOH, 100:5:1);
1H NMR (CD3OD): d 7.83–7.78 (m, 2H), 7.43–7.30
(m, 2H), 7.21–7.14 (m, 1H), 7.07–6.96 (m, 4H), 5.88–
5.68 (m, 1H), 5.13–4.99 (m, 2H), 4.62 (s, 2H), 4.43–
4.28 (m, 1H), 3.62 (dd, J = 10.0 Hz and 5.4 Hz, 1H),
3.56 (dd, J = 10.0 Hz and 5.4 Hz, 1H), 3.32 (s, 3H),
2.55–2.33 (m, 3H), 1.99–1.86 (m, 2H).
4.5.2. (2S,4S)-5-(Methoxymethoxy)-2-methyl-4-[(4-phe-
noxybenzoyl)amino]pentanoic acid (29a). Yield 100%;
1H NMR (CD3OD): d 7.83–7.79 (m, 2H), 7.43–7.36
(m, 2H), 7.22–7.14 (m, 1H), 7.07–6.96 (m, 4H), 4.62 (s,
2H), 4.42–4.30 (m, 1H), 3.59 (d, J = 5.8 Hz, 2H), 3.32
(s, 3H), 2.59–2.41 (m, 1H), 2.11–2.19 (m, 1H), 1.73
(ddd, J = 14.0 Hz, 7.8 Hz and 4.2 Hz, 1H), 1.22 (d,
J = 7.0 Hz, 3H).
4.5.8. (2S,4S)-2-Ethyl-5-(methoxymethoxy)-4-[(4-phen-
oxybenzoyl)amino]pentanoic acid (29g). Yield 100%;
TLC Rf = 0.50 (CHCl3–MeOH–AcOH–H2O, 100:10:1:1);
1H NMR (CD3OD): d 7.89–7.78 (m, 2H), 7.44–7.36
(m, 2H), 7.22–7.14 (m, 1H), 7.06–6.96 (m, 4H), 4.62 (s,
2H), 4.40–4.26 (m, 1H), 3.62 (dd, J = 8.3 Hz and
5.0 Hz, 1H), 3.56 (dd, J = 8.3 Hz and 5.6 Hz, 1H), 3.33
(s, 3H), 2.29–2.24 (m, 1H), 2.02–1.56 (m, 4H), 0.93 (t,
J = 7.2 Hz, 3H).
4.5.3. (2S,4S)-2-Benzyl-5-(methoxymethoxy)-4-[(4-phe-
noxybenzoyl)amino]pentanoic acid (29b). Yield 100%;
TLC Rf = 0.35 (CHCl3–MeOH, 19:1); 1H NMR
(CDCl3): d 7.72 (d, J = 8.8 Hz, 2H), 7.42–7.30 (m,
2H), 7.28–7.10 (m, 3H), 7.06–6.97 (m, 2H), 6.95 (d,
J = 8.8 Hz, 2H), 6.63 (d, J = 9.2 Hz, 1H), 4.59 (d,
J = 7.2 Hz, 1H), 4.57 (d, J = 7.2 Hz, 1H), 4.50–4.28
(m, 1H), 3.69 (dd, J = 10.2 Hz and 3.0 Hz, 1H), 3.56
(dd, J = 10.2 Hz and 3.6 Hz, 1H), 3.29 (s, 3H), 3.12–
2.68 (m, 3H), 2.20–2.00 (m, 1H), 1.80 (dt, J = 14.4 Hz
and 5.0 Hz, 1H).
4.5.9. (2S,4S)-5-(Methoxymethoxy)-4-[(4-phenoxyben-
zoyl)amino]-2-propylpentanoic acid (29h). Yield 100%;
TLC Rf = 0.43 (CHCl3–MeOH–AcOH, 100:10:1); 1H
NMR (CD3OD): d 7.83–7.79 (m, 2H), 7.44–7.36 (m,

6394
S. Yamamoto et al. / Bioorg. Med. Chem. 14 (2006) 6383–6403
2H), 7.22–7.14 (m, 1H), 7.07–6.97 (m, 4H), 4.62 (s, 2H),
4.46–4.27 (m, 1H), 3.62 (dd, J = 9.9 Hz and 5.4 Hz, 1H),
3.57 (dd, J = 9.9 Hz and 5.4 Hz, 1H), 3.33 (s, 3H), 2.51–
2.38 (m, 1H), 2.03–1.75 (m, 2H), 1.65–1.28 (m, 4H), 0.91
(t, J = 7.0 Hz, 3H).
4.35–4.21 (m, 1H), 3.62 (d, J = 5.4 Hz, 2H), 3.33 (s,
3H), 2.44–2.36 (m, 2H), 2.12–1.88 (m, 2H).
4.6. Preparation of compounds 2–15
Compounds 2–12 and 14, 15 were prepared from the
corresponding carboxylic acids 29a–l and 29n, respec-
tively, according to the general procedure. Preparation
of compound 13 was described below.
4.5.10. (2S,4S)-5-(Methoxymethoxy)-4-[(4-phenoxy-
benzoyl)amino]-2-(3-pyridinylmethyl)pentanoic
acid
(29i). Yield 90%; TLC Rf = 0.43 (CHCl3–MeOH, 9:1);
1H NMR (DMSO-d6): d 10.36 (s, 1H), 8.69 (s, 1H),
8.40–8.32 (m, 2H), 8.12 (d, J = 9.4 Hz, 1H), 7.91 (d,
J = 8.8 Hz, 2H), 7.54–7.38 (m, 3H), 7.29–7.17 (m, 2H),
7.12–7.06 (m, 2H), 7.03 (d, J = 8.8 Hz, 2H), 4.56 (s, 2H),
4.40–4.20 (m, 1H), 3.60–3.42 (m, 2H), 3.22 (s, 3H), 2.87
(dd, J = 13.6 Hz and 4.8 Hz, 1H), 2.75 (d, J = 13.6 Hz
and 9.6 Hz, 1H), 2.43–2.28 (m, 1H), 1.90–1.59 (m, 2H).
4.6.1. General procedure for preparation of 2–12, 14, and
15. A mixture of crude carboxylic acid 29 (0.51 mmol),
EDCÆHCl (1.5 mmol), HOBtÆH2O (1.5 mmol), and O-
(2-methoxypropane-2-yl)hydroxylamine (4.3 mmol) in
DMF (5 mL) was stirred at room temperature for 3 h.
The reaction mixture was diluted with EtOAc. The
organic layer was washed with aqueous NaHCO3,
H2O, and brine, dried over Na2SO4, and evaporated.
To a stirred solution of the resulting residue in MeOH
(10 mL) was added 2 N HCl (0.1 mL) at room tempera-
ture. After stirring for 15 min, the reaction mixture was
concentrated under reduced pressure to give a crude
hydroxamic acid, which was triturated with diethyl ether
to afford compounds 2–12, 14, and 15.
4.5.11. (2S,4S)-5-(Methoxymethoxy)-2-(1-naphthylmeth-
yl)-4-[(4-phenoxybenzoyl)amino]pentanoic acid (29j).
Yield 99%; TLC Rf = 0.33 (CHCl3–MeOH, 19:1); 1H
NMR (CDCl3): d 8.08–7.98 (m, 1H), 7.85–7.77 (m,
1H), 7.76–7.62 (m, 3H), 7.51–7.27 (m, 6H), 7.20–7.09
(m, 1H), 7.03–6.98 (m, 2H), 6.93 (d, J = 8.8 Hz, 2H),
6.58 (d, J = 8.8 Hz, 1H), 4.50 (d, J = 10.0 Hz, 1H),
4.48 (d, J = 10.0 Hz, 1H), 4.42–4.27 (m, 1H), 3.63 (dd,
J = 10.2 Hz and 3.0 Hz, 1H), 3.56–3.41 (m, 2H), 3.23
(dd, J = 13.8 Hz and 7.2 Hz, 1H), 3.15 (s, 3H), 3.10–
2.90 (m, 1H), 2.21 (dt, J = 14.4 Hz and 9.2 Hz, 1H),
1.87 (dt, J = 14.4 Hz and 4.8 Hz, 1H).
4.6.2. N-{(1S)-4-(Hydroxyamino)-1-[(methoxymethoxy)-
methyl]-4-oxobutyl}-4-phenoxybenzamide (2). Yield 83%;
TLC Rf = 0.36 (CHCl3–MeOH–H2O–AcOH, 100:10:1:1);
MS (MALDI, pos.) m/z 427 (M+K)+, 411 (M+Na)+,
389 (M+H)+; IR (KBr) 2878, 1632, 1588, 1550, 1489,
1316, 1251, 1172, 1150, 1103, 1039, 848, 752, 693
4.5.12. (2S,4S)-2-Hydroxy-5-(methoxymethoxy)-4-[(4-
phenoxybenzoyl)amino]pentanoic acid (29k). Yield
100%; TLC Rf = 0.29 (CHCl3–MeOH–AcOH–H2O,
1
cmꢀ1; H NMR (DMSO-d6): d 10.33 (s, 1H), 8.66 (s,
1H), 8.16 (d, J = 8.4 Hz, 1H), 7.87 (d, J = 8.8 Hz, 2H),
7.46–7.38 (m, 2H), 7.22–7.15 (m, 2H), 7.07–6.99 (m,
4H), 4.54 (s, 2H), 4.19–3.94 (m, 1H), 3.49–3.45 (m,
1
85:15:1:1); H NMR (CD3OD): d 7.86–7.80 (m, 2H),
7.44–7.36 (m, 2H), 7.22–7.15 (m, 1H), 7.08–6.97 (m,
4H), 4.63 (s, 1H), 4.57–4.45 (m, 1H), 4.20 (dd,
J = 10.2 Hz and 3.0 Hz, 1H), 3.67–3.64 (m, 2H), 3.33
(s, 3H), 2.22–2.08 (m, 1H), 1.97–1.83 (m, 1H).
2H), 3.22 (s, 3H), 2.07–1.57 (m, 4H); optical rotation
30
D
C20H25N2O6: 389.1709. Found: 389.1713.
½aꢁ ꢀ30.46 (c 0.24, DMF); HRMS (FAB) calcd for
4.5.13. (2S,4S)-5-(Methoxymethoxy)-4-[(4-phenoxy-
benzoyl)amino]-2-(phenylthio)pentanoic acid (29l). Yield
100%; TLC Rf = 0.27 (CHCl3–MeOH–AcOH, 100:5:1);
1H NMR (CD3OD): d 7.81–7.75 (m, 2H), 7.52–7.36
(m, 4H), 7.30–7.18 (m, 4H), 7.07–6.95 (m, 4H), 4.61 (s,
2H), 4.57–4.37 (m, 1H), 3.67–3.58 (m, 3H), 3.31 (s,
3H), 2.38–2.03 (m, 2H).
4.6.3. N-{(1S,3S)-4-(Hydroxyamino)-1-[(methoxymeth-
oxy)methyl]-3-methyl-4-oxobutyl}-4-phenoxybenzamide
(3). Yield 70%; TLC Rf = 0.49 (CHCl3–MeOH–H2O–
AcOH, 100:10:1:1); MS (MALDI, pos.) m/z 441
(M+K)+, 425 (M+Na)+; IR (KBr) 3248, 2933, 1637,
1588, 1543, 1489, 1244, 1170, 1110, 1039, 963, 918,
1
876, 753, 692 cmꢀ1; H NMR (DMSO-d6): d 10.38 (d,
J = 1.5 Hz, 1H), 8.66 (d, J = 1.5 Hz, 1H), 8.05 (d,
J = 8.4 Hz, 1H), 7.88 (d, J = 8.7 Hz, 2H), 7.45–7.40
(m, 2H), 7.22–7.17 (m, 1H), 7.08–7.01 (m, 4H), 4.55 (s,
2H), 4.21–4.08 (m, 1H), 3.52–3.44 (m, 2H), 3.22 (s,
4.5.14.
(2R,4S)-2-(2-tert-Butoxy-2-oxoethyl)-5-(meth-
oxymethoxy)-4-[(4-phenoxybenzoyl)amino]pentanoic acid
(29m). Yield 94%; TLC Rf = 0.47 (CHCl3–MeOH, 9:1);
1H NMR (CDCl3): d 7.75 (d, J = 8.8 Hz, 2H), 7.41–7.37
(m, 2H), 76.21–7.11 (m, 1H), 7.08–7.00 (m, 2H), 6.98 (d,
J = 8.8 Hz, 2H), 6.73 (d, J = 9.2 Hz, 1H), 4.62 (s, 2H),
4.48–4.31 (m, 1H), 3.77 (dd, J = 10.4 Hz and 3.0 Hz,
1H), 3.63 (dd, J = 10.4 Hz and 4.2 Hz, 1H), 3.36 (s,
3H), 2.97–2.78 (m, 1H), 2.77–2.56 (m, 2H), 2.17 (ddd,
J = 14.2 Hz, 9.8 Hz and 7.0 Hz, 1H), 1.82 (ddd,
J = 14.2 Hz, 7.0 Hz and 5.4 Hz, 1H), 1.42 (s, 9H).
3H), 2.25–2.09 (m, 1H), 1.67 (t, J = 7.2 Hz, 2H), 1.01
30
D
(d, J = 6.6 Hz, 3H); optical rotation ½aꢁ ꢀ4.56 (c 0.25,
DMF); HRMS (FAB) calcd for C21H27N2O6:
403.1869. Found: 403.1871.
4.6.4. N-{(1S,3S)-3-[(Hydroxyamino)carbonyl]-1-[(meth-
oxymethoxy)methyl]pentyl}-4-phenoxybenzamide
(4).
Yield 81%; TLC Rf = 0.62 (CHCl3–MeOH–AcOH,
100:5:1); MS (MALDI, pos.) m/z 467 (M+K)+, 451
(M+Na)+, 429 (M+H)+; IR (KBr) 3276, 2926, 1632,
1539, 1489, 1342, 1244, 1153, 1111, 1041, 960, 916,
4.5.15. (4S)-5-(Methoxymethoxy)-4-[(4-phenoxybenzoyl)-
amino]pentanoic acid (29n). Yield 99%; 1H NMR
(CDCl3): d 7.84–7.80 (m, 2H), 7.43–7.36 (m, 2H),
7.23–7.13 (m, 1H), 7.07–6.97 (m, 4H), 4.62 (s, 2H),
1
878, 754, 692 cmꢀ1; H NMR (DMSO-d6): d 10.43 (s,
1H), 8.66 (br s, 1H), 8.06 (d, J = 8.4 Hz, 1H), 7.89–

S. Yamamoto et al. / Bioorg. Med. Chem. 14 (2006) 6383–6403
6395
7.85 (m, 2H), 7.47–7.38 (m, 2H), 7.23–7.15 (m, 1H),
7.09–6.99 (m, 4H), 5.73–5.60 (m, 1H), 5.05–4.92 (m,
2H), 4.54 (s, 2H), 4.19–4.05 (m, 1H), 3.52 (dd,
J = 10.1 Hz and 5.2Hz, 1H), 3.44 (dd, J = 10.1 Hz and
1295, 1242, 1170, 1148, 1109, 1038, 915, 876, 754,
1
693 cmꢀ1; H NMR (DMSO-d6): d 10.44 (s, 1H), 8.69
(s, 1H), 8.46–8.40 (m, 1H), 8.06 (d, J = 8.4 Hz, 1H),
7.88 (d, J = 8.8 Hz, 2H), 7.65 (td, J = 7.8 Hz and
1.8 Hz, 1H), 7.49–7.38 (m, 2H), 7.23–7.13 (m, 3H),
7.11–7.04 (m, 2H), 7.02 (d, J = 8.8 Hz, 2H), 4.52 (s,
2H), 4.23–4.06 (m, 1H), 3.49 (d, J = 5.4 Hz, 2H), 3.20
(s, 3H), 2.96 (dd, J = 13.8 Hz and 8.4 Hz, 1H), 2.85
5.2 Hz, 1H), 3.22 (s, 3H), 2.20–2.17 (m, 3H), 1.82–1.59
30
D
(m, 2H); optical rotation ½aꢁ ꢀ33.75 (c 0.40, DMF);
HRMS (FAB) calcd for C22H29N2O6: 417.2026. Found:
417.2028.
(dd, J = 13.8 Hz and 6.6 Hz, 1H), 2.78–2.58 (m, 1H),
30
D
4.6.5. N-{(1S,3S)-3-[(Hydroxyamino)carbonyl]-1-[(meth-
oxymethoxy)methyl]hexyl}-4-phenoxybenzamide (5).
Yield 89%; TLC Rf = 0.60 (CHCl3–MeOH–H2O–
AcOH, 100:10:1:1); MS (MALDI, pos.) m/z 469
(M+K)+, 453 (M+Na)+, 431 (M+H)+; IR (KBr) 3281,
2953, 1636, 1589, 1542, 1489, 1320, 1245, 1169, 1115,
1.77 (t, J = 7.0 Hz, 2H); optical rotation ½aꢁ ꢀ42.43 (c
0.14, DMF); HRMS (FAB) calcd for C26H30N3O6:
480.2135. Found: 480.2135.
4.6.9. N-[(1S,3S)-4-(Hydroxyamino)-1-[(methoxymeth-
oxy)methyl]-4-oxo-3-(3-pyridinylmethyl)butyl]-4-phen-
oxybenzamide (9). Yield 42%; TLC Rf = 0.43 (CHCl3–
MeOH, 9:1); MS (APCI, neg. 40 V) m/z 478 (MꢀH)ꢀ;
IR (KBr) 3224, 2930, 1638, 1587, 1542, 1489, 1307,
1242, 1170, 1109, 1038, 915, 876, 796, 754, 713,
1
1042, 916, 876, 753, 693 cmꢀ1; H NMR (DMSO-d6):
d 10.40 (s, 1H), 8.69 (d, J = 1.4 Hz, 1H), 8.02 (d,
J = 8.4 Hz, 1H), 7.86 (d, J = 8.8 Hz, 2H), 7.46–7.37
(m, 2H), 7.23–7.15 (m, 1H), 7.08–6.98 (m, 4H), 4.54 (s,
2H), 4.16–4.00 (m, 1H), 3.48–3.44 (m, 2H), 3.21 (s,
3H), 2.14–1.99 (m, 1H), 1.78–1.58 (m, 2H), 1.45–1.28
693 cmꢀ1; H NMR (DMSO-d6): d 10.36 (s, 1H), 8.69
1
(s, 1H), 8.40–8.32 (m, 2H), 8.12 (d, J = 9.4 Hz, 1H),
7.91 (d, J = 8.8 Hz, 2H), 7.54–7.38 (m, 3H), 7.29–7.17
(m, 2H), 7.12–7.06 (m, 2H), 7.03 (d, J = 8.8 Hz, 2H),
4.56 (s, 2H), 4.40–4.20 (m, 1H), 3.60–3.42 (m, 2H),
3.22 (s, 3H), 2.87 (dd, J = 13.6 Hz and 4.8 Hz, 1H),
(m, 2H), 1.27–1.07 (m, 2H), 0.80 (t, J = 7.2 Hz, 3H);
30
D
optical rotation ½aꢁ ꢀ22.88 (c 0.20, DMF); HRMS
(FAB) calcd for C23H31N2O6: 431.2182. Found:
431.2184.
2.75 (dd, J = 13.6 Hz and 9.6 Hz, 1H), 2.43–2.28 (m,
30
D
4.6.6. N-{(1S,3S)-3-[(Hydroxyamino)carbonyl]-1-[(meth-
oxymethoxy)methyl]-5-methylhexyl}-4-phenoxybenza-
mide (6). Yield 80%; TLC Rf = 0.36 (CHCl3–MeOH,
19:1); MS (MALDI, pos.) m/z 483 (M+K)+, 467
(M+Na)+, 445 (M+H)+; IR (KBr) 3237, 2954, 1636,
1588, 1542, 1489, 1243, 1170, 1110, 1038, 919, 876,
1H), 1.90–1.59 (m, 2H); optical rotation ½aꢁ ꢀ43.36 (c
0.14, DMF); HRMS (FAB) calcd for C26H30N3O6:
480.2135. Found: 480.2138.
4.6.10. N-[(1S,3S)-4-(Hydroxyamino)-1-[(methoxymeth-
oxy)methyl]-4-oxo-3-(4-pyridinylmethyl)butyl]-4-phen-
oxybenzamide (10). Yield 73%; TLC Rf = 0.27 (CHCl3–
MeOH, 9:1); MS (MALDI, pos.) m/z 502 (M+Na)+, 480
(M+H)+; IR (KBr) 3275, 2928, 1636, 1609, 1588, 1542,
1489, 1304, 1245, 1170, 1109, 1038, 915, 850, 752, 692,
796, 753, 693, 493 cmꢀ1 1H NMR (DMSO-d6): d
;
10.46 (s, 1H), 8.72 (s, 1H), 8.00 (d, J = 8.4 Hz, 1H),
7.88 (d, J = 8.8 Hz, 2H), 7.48–7.38 (m, 2H), 7.23–7.16
(m, 1H), 7.10–7.03 (m, 2H), 7.01 (d, J = 8.8 Hz, 2H),
4.56 (s, 2H), 4.22–4.01 (m, 1H), 3.60–3.40 (m, 2H),
3.24 (s, 3H), 2.25–2.08 (m, 1H), 1.78–1.60 (m, 2H),
1.58–1.32 (m, 2H), 1.28–1.07 (m, 1H), 0.82 (d,
626, 542 cmꢀ1 1H NMR (DMSO-d6): d 10.44–10.30
;
(br s, 1H), 8.75–8.62 (br s, 1H), 8.40 (d, J = 6.0 Hz,
2H), 8.13 (d, J = 8.4 Hz, 1H), 7.91 (d, J = 8.7 Hz, 2H),
7.48–7.38 (m, 2H), 7.22–7.18 (m, 1H), 7.13 (d,
J = 6.0 Hz, 2H), 7.06 (d, J = 7.8 Hz, 2H), 7.02 (d,
J = 8.7 Hz, 2H), 4.55 (s, 2H), 4.34–4.21 (m, 1H), 3.58–
3.42 (m, 2H), 3.22 (s, 3H), 2.91–2.71 (m, 2H), 2.46–
J = 6.0 Hz, 3H), 0.80 (d, J = 6.0 Hz, 3H); optical rota-
30
D
for C24H33N2O6: 445.2339. Found: 445.2339.
tion ½aꢁ ꢀ26.99 (c 0.395, DMF); HRMS (FAB) calcd
4.6.7. N-{(1S,3S)-3-Benzyl-4-(hydroxyamino)-1-[(meth-
oxymethoxy)methyl]-4-oxobutyl}-4-phenoxybenzamide
(7). Yield 65%; TLC Rf = 0.39 (CHCl3–MeOH, 19:1); MS
(MALDI, pos.) m/z 517 (M+K)+, 501 (M+Na)+, 479
(M+H)+; IR (KBr) 3292, 2937, 1631, 1588, 1536, 1489,
1455, 1334, 1243, 1171, 1148, 1101, 1038, 965, 912, 878,
2.32 (m, 1H), 1.85–1.61 (m, 2H); optical rotation
½aꢁ ꢀ40.66 (c 0.355, DMF); HRMS (FAB) calcd for
30
D
C26H30N3O6: 480.2135. Found: 480.2130.
4.6.11. N-{(1S,3S)-3-[(Hydroxyamino)carbonyl]-1-[(meth-
oxymethoxy)methyl]-5-hexen-1-yl}-4-phenoxybenzamide
(11). Yield 81%; TLC Rf = 0.62 (CHCl3–MeOH–AcOH,
100:5:1); MS (MALDI, pos.) m/z 467 (M+K)+, 451
(M+Na)+, 429 (M+H)+; IR (KBr) 3276, 2926, 1632,
1539, 1489, 1342, 1244, 1153, 1111, 1041, 960, 916,
1
848, 798, 767, 754, 735, 694 cmꢀ1; H NMR (DMSO-
d6): d 10.36 (s, 1H), 8.09 (d, J = 8.6 Hz, 1H), 7.91 (d,
J = 8.8 Hz, 2H), 7.50–7.38 (m, 2H), 7.30–7.08 (m, 8H),
7.03 (d, J = 8.8 Hz, 2H), 4.54 (s, 2H), 4.36–4.18 (m, 1H),
3.58–3.40 (m, 2H), 3.20 (s, 3H), 2.84–2.65 (m, 2H),
1
878, 754, 692 cmꢀ1; H NMR (DMSO-d6): d 10.43 (s,
2.45–2.30 (m, 1H), 1.88–1.58 (m, 2H); optical rotation
½aꢁ ꢀ42.67 (c 0.76, DMF); HRMS (FAB) calcd for
1H), 8.66 (br s, 1H), 8.06 (d, J = 8.4 Hz, 1H), 7.89–
7.85 (m, 2H), 7.47–7.38 (m, 2H), 7.23–7.15 (m, 1H),
7.09–6.99 (m, 4H), 5.73–5.60 (m, 1H), 5.05–4.92 (m,
2H), 4.54 (s, 2H), 4.19–4.05 (m, 1H), 3.52 (dd,
J = 10.1 Hz and 5.2 Hz, 1H), 3.44 (dd, J = 10.1 Hz and
30
D
C27H31N2O6: 479.2182. Found: 479.2184.
4.6.8. N-[(1S,3R)-4-(Hydroxyamino)-1-[(methoxymeth-
oxy)methyl]-4-oxo-3-(2-pyridinylmethyl)butyl]-4-phen-
oxybenzamide (8). Yield 29%; TLC Rf = 0.20 (CHCl3–
MeOH, 19:1); MS (APCI, neg. 40 V) m/z 478 (MꢀH)ꢀ;
IR (KBr) 3223, 2932, 1638, 1588, 1542, 1489, 1436,
5.2 Hz, 1H), 3.22 (s, 3H), 2.20–2.17 (m, 3H), 1.82–1.59
30
D
(m, 2H); optical rotation ½aꢁ ꢀ33.75 (c 0.40, DMF);
HRMS (FAB) calcd for C23H29N2O6: 429.2026. Found:
429.2030.

6396
S. Yamamoto et al. / Bioorg. Med. Chem. 14 (2006) 6383–6403
4.6.12. N-[(1S,3S)-4-(Hydroxyamino)-1-[(methoxymeth-
oxy)methyl]-3-(1-naphthylmethyl)-4-oxobutyl]-4-phenoxy-
benzamide (12). Yield 85%; TLC Rf = 0.36 (CHCl3–
MeOH, 19:1); MS (MALDI, pos.) m/z 567 (M+K)+,
551 (M+Na)+, 529 (M+H)+; IR (KBr) 3223, 2931,
1638, 1587, 1539, 1488, 1395, 1242, 1170, 1108, 1036,
4.6.15. N-[(1S,3S)-4-(Hydroxyamino)-1-[(methoxymeth-
oxy)methyl]-4-oxo-3-(phenylthio)butyl]-4-phenoxybenza-
mide (15). Yield 64%; TLC Rf = 0.27 (CHCl3–MeOH–
AcOH, 100:5:1); MS (MALDI, pos.) m/z 535
(M+K)+, 519 (M+Na)+, 497 (M+H)+; IR (KBr)
3293, 1631, 1531, 1488, 1331, 1243, 1171, 1104,
1
918, 876, 780, 753, 692 cmꢀ1; H NMR (DMSO-d6): d
1039, 913, 873, 847, 799, 755, 695 cmꢀ1 1H NMR
;
10.26 (s, 1H), 8.63 (s, 1H), 8.16 (d, J = 8.4 Hz, 1H),
8.04–7.82 (m, 4H), 7.80–7.70 (m, 1H), 7.52–7.16 (m,
7H), 7.14–6.96 (m, 4H), 4.52 (s, 2H), 4.50–4.28 (m,
1H), 3.61–3.40 (m, 2H), 3.25–3.02 (m, 5H), 2.69–2.52
(DMSO-d6): d 10.69 (s, 1H), 8.97 (s, 1H), 8.17 (d,
J = 8.0 Hz, 1H), 7.86 (d, J = 8.8 Hz, 2H), 7.47–7.39
(m, 4H), 7.34–7.16 (m, 4H), 7.08–6.99 (m, 4H),
4.53 (s, 2H), 4.38–4.25 (m, 1H), 3.62–3.35 (m,
(m, 1H), 2.00–1.78 (m, 2H); optical rotation
½aꢁ ꢀ66.46 (c 0.305, DMF); HRMS (FAB) calcd for
3H), 3.19 (s, 3H), 2.02 (t, J = 6.8 Hz, 2H); optical
30
D
C31H33N2O6: 529.2339. Found: 529.2341.
30
D
rotation ½aꢁ ꢀ92.93 (c 0.215, DMF); HRMS
(FAB) calcd for C26H29N2O6S: 497.1746. Found:
497.1747.
4.6.13. tert-Butyl (3R,5S)-3-[(hydroxyamino)carbonyl]-6-
(methoxymethoxy)-5-[(4-phenoxybenzoyl)amino]hexano-
ate (13). A mixture of 29m (595 mg, 1.20 mmol),
EDCÆHCl (348 mg, 1.83 mmol), HOBtÆH2O (274 mg,
1.83 mmol), O-benzylhydroxylamine hydrochloride
(690 mg, 3.22 mmol), and triethylamine (506 lL,
1.83 mmol) in DMF (30 mL) was stirred at room temper-
ature for 3 h. The reaction mixture was diluted with
EtOAc. The organic layer was washed with aqueous
NaHCO3, H2O, then brine, dried over Na2SO4, and evap-
orated. The resulting residue was triturated with diethyl
ether to afford O-benzylhydroxamic acid (469 mg, 65%).
The O-benzylhydroxamic acid (458 mg, 0.77 mmol) was
dissolved in MeOH (10 mL), and vigorously stirred in
the presence of 10% Pd/C (50 mg) under hydrogen atmo-
sphere for 1 h. After removing the catalyst by filtration
through a pad of Celite, the reaction mixture was evapo-
rated. The resulting residue was triturated with diethyl
ether to afford compound 13 (352 mg, 91%).
4.7. Methyl (4S)-4-{[(benzyloxy)carbonyl]amino}-
5-(ethoxymethoxy)pentanoate (30a)
Compound 30a was prepared from 24 in 69% yield
according to the same procedure as described for the
preparation of 25 from 24.
TLC Rf = 0.59 (EtOAc–n-hexane, 1:1); MS (MALDI,
pos.) m/z 378 (M+K)+, 362 (M+Na)+, 340 (M+H)+;
1H NMR (CDCl3): d 7.37–7.28 (m, 5H), 5.10 (s, 2H),
5.05 (d, J = 9.0 Hz, 1H), 4.65 (s, 2H), 3.90–3.78 (m,
1H), 3.65 (s, 3H), 3.61–3.52 (m, 4H), 2.41 (t,
J = 7.6 Hz, 2H), 1.94–1.84 (m, 2H), 1.20 (t, J = 7.1 Hz,
3H).
4.8. Methyl (4S)-4-{[(benzyloxy)carbonyl]amino}-5-
{[tert-butyl(dimethyl)silyl]oxy}pentanoate (30b)
To a stirred solution of 24 (13.5 g, 48.0mmol) in DMF
(48 mL) were added imidazole (7.20 g, 106 mmol) and
TBSCl (15.2 g, 101 mmol) at 0 °C. After stirring at room
temperature for 30 min, the reaction mixture was diluted
with EtOAc. The organic layer was washed with 1 N
HCl, H2O, aqueous NaHCO3, H2O, and brine, dried
over Na2SO4, and evaporated. The resulting residue
was purified by silica gel chromatography with
EtOAc–n-hexane (1:10) as an eluent to give 30b
(14.0 g, 74%): TLC Rf = 0.29 (EtOAc–n-hexane, 1:4);
1H NMR (CDCl3): d 7.41–7.32 (m, 5H), 5.09 (s, 2H),
4.93 (d, J = 8.8 Hz, 1H), 3.80–3.69 (m, 6H), 2.39 (t,
J = 7.2 Hz, 2H), 2.04–1.78 (m, 2H), 0.87 (s, 9H), 0.03
(s, 6H).
TLC Rf = 0.54 (CHCl3–MeOH, 9:1); MS (MALDI,
pos.) m/z 541 (M+K)+, 525 (M+Na)+, 503 (M+H)+;
IR (KBr) 3298, 2932, 1729, 1637, 1589, 1543, 1490,
1368, 1321, 1247, 1200, 1157, 1120, 1040, 957, 917,
1
877, 847, 792, 754, 693 cmꢀ1; H NMR (DMSO-d6): d
10.47 (s, 1H), 8.75 (s, 1H), 8.05 (d, J = 8.4 Hz, 1H),
7.88 (d, J = 8.7 Hz, 2H), 7.47–7.40 (m, 2H), 7.23–7.17
(m, 1H), 7.10–7.04 (m, 2H), 7.03 (d, J = 8.7 Hz, 2H),
4.55 (s, 2H), 4.20–4.03 (m, 1H), 3.57–3.43 (m, 2H),
3.23 (s, 3H), 2.55–2.34 (m, 3H), 1.74–1.66 (m, 2H),
30
D
1.36 (s, 9H); optical rotation ½aꢁ ꢀ15.80 (c 0.30,
DMF); HRMS (FAB) calcd for C26H35N2O8:
503.2393. Found: 503.2398.
4.6.14.
N-{(1S,3S)-3-Hydroxy-4-(hydroxyamino)-1-
4.9. Methyl (2S,4S)-4-{[(benzyloxy)carbonyl]amino}-5-
(ethoxymethoxy)-2-methylpentanoate (31a)
[(methoxymethoxy)methyl]-4-oxobutyl}-4-phenoxybenz-
amide (14). Yield 74%; TLC Rf = 0.57 (CHCl3–MeOH–
AcOH, 85:15:1); MS (MALDI, pos.) m/z 443 (M+K)+,
427 (M+Na)+, 405 (M+H)+; IR (KBr) 3298, 1626,
1551, 1491, 1335, 1248, 1156, 1113, 1041, 923, 849,
Compound 31a was prepared from 30a in 65% yield
according to the general procedure as described for the
preparation of 26 from 25.
753, 695, 642 cmꢀ1; H NMR (DMSO-d6): d 10.44 (s,
1
1H), 8.69 (br s, 1H), 8.19 (d, J = 8.4 Hz, 1H), 8.89 (d,
J = 8.8 Hz, 2H), 7.48–7.38 (m, 2H), 7.22–7.16 (m, 1H),
7.09–7.01 (m, 4H), 5.36 (br s, 1H), 4.55 (s, 2H), 4.41–
4.24 (m, 1H), 3.87 (dd, J = 9.8 Hz and 2.6 Hz, 1H),
TLC Rf = 0.46 (EtOAc–n-hexane, 1:1); MS (MALDI,
pos.) m/z 392 (M+K)+, 376 (M+Na)+; 1H NMR
(CDCl3): d 7.39–7.30 (m, 5H), 5.10 (s, 2H), 4.92 (d,
J = 9.8 Hz, 1H), 4.65 (s, 2H), 4.01–3.82 (m, 1H), 3.62
(s, 3H), 3.59–2.84 (m, 4H), 2.53 (sextet, J = 7.1 Hz,
1H), 2.70–1.90 (m, 1H), 1.66–1.53 (m, 1H), 1.26–1.16
(m, 6H).
3.56–3.42 (m, 2H), 3.22 (s, 3H), 1.96–1.66 (m, 2H); opti-
30
D
calcd for C20H25N2O7: 405.1662. Found: 405.1663.
cal rotation ½aꢁ ꢀ53.02 (c 0.235, DMF); HRMS (FAB)

S. Yamamoto et al. / Bioorg. Med. Chem. 14 (2006) 6383–6403
6397
4.10. Methyl (2S,4S)-4-{[(benzyloxy)carbonyl]amino}-5-
{[tert-butyl(dimethyl)silyl]oxy}-2-methylpentanoate (31b)
4.14. (2S,4S)-5-{[tert-Butyl(dimethyl)silyl]oxy}-2-methyl-
4-[(4-phenoxybenzoyl)amino]pentanoic acid (33b)
Compound 31b was prepared from 30b in 52% yield
according to the general procedure as described for the
preparation of 26 from 25.
Compound 33b was prepared from 32b in 100% yield
according to the general procedure for the preparation
of 29 from 27 or 28a–m.
TLC Rf = 0.64 (EtOAc–n-hexane, 1:2); 1H NMR
(CDCl3): d 7.38–7.31 (m, 5H), 5.08 (s, 2H), 4.82 (d,
J = 9.3 Hz, 1H), 3.82–3.71 (m, 1H), 3.62 (s, 3H), 3.62–
3.55 (m, 2H), 2.51 (sextet, J = 7.2 Hz, 1H), 1.98–1.84
(m, 1H), 1.62–1.54 (m, 1H), 1.20 (d, J = 6.9 Hz, 3H),
0.88 (s, 9H), 0.03 (s, 6H).
1H NMR (CDCl3): d 11.67 (s, 1H), 8.01 (d, J = 8.8 Hz,
1H), 7.84 (d, J = 8.8 Hz, 2H), 7.40 (t, J = 7.7 Hz, 2H),
7.17 (t, J = 7.7 Hz, 1H), 7.04 (d, J = 7.7 Hz, 2H), 6.99
(d, J = 8.8 Hz, 2H), 4.12–3.95 (m, 1H), 3.81–3.71 (m,
1H), 3.62–3.48 (m, 1H), 2.39–2.26 (m, 1H), 1.96–1.58
(m, 2H), 1.04 (d, J = 6.8 Hz, 3H), 0.82 (s, 9H), 0.01 (s,
6H).
4.11. Methyl (2S,4S)-5-(ethoxymethoxy)-2-methyl-4-[(4-
phenoxybenzoyl)amino]pentanoate (32a)
4.15. N-[(1S,3S)-1-[(Ethoxymethoxy)methyl]-4-(hydroxy-
amino)-3-methyl-4-oxobutyl]-4-phenoxybenzamide (16)
Compound 32a was prepared from 31a in 37% yield
according to the same procedure as described for the
preparation of 27 from 25.
Compound 16 was prepared from 33a in 85% yield
according to the same procedure as described for the
preparation of 13 from 29m.
TLC Rf = 0.32 (EtOAc–n-hexane, 1:1); 1H NMR
(CDCl3): d 7.77 (d, J = 8.8 Hz, 2H), 7.38 (m, 2H), 7.18
(m, 1H), 7.05 (d, J = 7.7 Hz, 2H), 7.01 (d, J = 8.8 Hz,
2H), 6.46 (d, J = 8.8 Hz, 1H), 4.71 (d, J = 6.9 Hz, 1H),
4.69 (d, J = 6.9 Hz, 1H), 4.40 (m, 1H), 3.72 (dd,
J = 10.2 Hz and 3.3 Hz, 1H), 3.65–3.56 (m, 2H), 3.55
(s, 3H), 2.57 (m, 1H), 2.19 (ddd, J = 14.3 Hz, 10.9 Hz
and 7.7 Hz, 1H), 1.69 (ddd, J = 14.3 Hz, 6.3 Hz and
4.1 Hz, 1H), 1.25 (d, J = 6.9 Hz, 3H), 1.21 (t,
J = 7.1 Hz, 3H).
TLC
Rf = 0.40
(CHCl3–MeOH–AcOH–H2O,
100:10:1:1); MS (APCI, neg. 40 V) m/z 415 (MꢀH)ꢀ;
IR (KBr) 3288, 1636, 1589, 1540, 1489, 1357, 1314,
1242, 1199, 1170, 1121, 1041, 967, 876, 843, 753,
692 cmꢀ1 1H NMR (DMSO-d6): d 10.37 (br, 1H),
;
8.66 (br, 1H), 8.03 (d, J = 8.8 Hz, 1H), 7.87 (d,
J = 8.8 Hz, 2H), 7.43 (dd, J = 7.4 Hz and 8.5 Hz,
2H), 7.20 (t, J = 7.4 Hz, 1H), 7.06 (d, J = 8.5 Hz,
2H), 7.02 (d, J = 8.8 Hz, 2H), 4.59 (s, 2H), 4.14 (m,
1H), 3.50–3.45 (m, 4H), 3.32 (s, 2H), 2.17 (m, 1H),
1.66 (m, 2H), 1.09 (t, J = 7.1 Hz, 3H), 1.01 (d,
30
D
4.12. Methyl (2S,4S)-5-{[tert-butyl(dimethyl)silyl]oxy}-2-
methyl-4-[(4-phenoxybenzoyl)amino]pentanoate (32b)
J = 6.9 Hz, 3H); optical rotation ½aꢁ ꢀ5.46 (c 0.49,
DMF); HRMS (FAB) calcd for C22H29N2O6:
417.2026. Found: 417.2039.
Compound 32b was prepared from 31b in 56% yield
according to the same procedure as described for the
preparation of 27 from 25.
4.16. N-[(1S,3S)-4-(Hydroxyamino)-1-(hydroxymethyl)-
3-methyl-4-oxobutyl]-4-phenoxybenzamide (19)
1H NMR (CDCl3): d 7.73 (d, J = 8.7 Hz, 2H), 7.38 (t,
J = 7.7 Hz, 2H), 7.18 (t, J = 7.7 Hz, 1H), 7.05 (d,
J = 7.7 Hz, 2H), 7.00 (d, J = 8.7 Hz, 2H), 6.26 (d,
J = 9.0 Hz, 1H), 4.31–4.21 (m, 1H), 3.69 (d,
J = 3.6 Hz, 2H), 3.57 (s, 3H), 2.54 (m, 1H), 2.19–2.08
(m, 1H), 1.72–1.63 (m, 1H), 1.25 (d, J = 6.9 Hz, 3H),
0.90 (s, 9H), 0.06 (s, 6H).
To a stirred solution of compound 33b (437 mg,
0.96 mmol) in DMF (10 mL) were added O-ben-
zylhydroxylamine hydrochloride (183 mg, 1.15 mmol),
EDCÆHCl (550 mg, 2.88 mmol), HOBtÆH2O (440 mg,
2.88 mmol), and triethylamine (0.4 mL, 2.88 mmol) at
0 °C. After stirring at room temperature for 2.5 h, the
reaction mixture was diluted with EtOAc. The organic
layer was washed with 1 N HCl, H2O, aqueous NaH-
CO3, H2O, and brine, dried over Na2SO4, and evapo-
rated. To a stirred solution of the resulting residue in
THF (5 mL) was added tetrabutylammonium fluoride
(3 mL) at 0 °C. After stirring at room temperature
for 1 h, the reaction mixture was diluted with EtOAc.
The organic layer was washed with 1 N HCl, H2O,
aqueous NaHCO3, H2O, and brine, dried over
Na2SO4, and evaporated to afford O-benzylhydroxamic
acid, a solution of which in MeOH (6.0 mL) was vigor-
ously stirred in the presence of 5% Pd/C (90 mg) under
hydrogen atmosphere for 45 min. After removing the
catalyst by filtration through a pad of Celite, the reac-
tion mixture was evaporated. The resulting residue was
washed with diethyl ether to afford compound 19
(299 mg, 87%).
4.13. (2S,4S)-5-(Ethoxymethoxy)-2-methyl-4-[(4-phen-
oxybenzoyl)amino]pentanoic acid (33a)
Compound 33a was prepared from 32a in 100% yield
according to the general procedure for the preparation
of 29 from 27 or 28a–m.
TLC Rf = 0.46 (CH2Cl2–MeOH, 9:1); MS (APCI, neg.
1
20 V) m/z 400 (MꢀH)ꢀ; H NMR (CDCl3): d 12.04 (s,
1H), 8.12 (d, J = 8.4 Hz, 1H), 7.85 (d, J = 8.7 Hz, 2H),
7.40 (t, J = 7.6 Hz, 2H), 7.17 (t, J = 7.6 Hz, 1H), 7.04
(d, J = 7.6 Hz, 2H), 7.00 (d, J = 8.7 Hz, 2H), 4.57 (s,
2H), 4.24–4.13 (m, 1H), 3.52–3.42 (m, 4H), 2.37–2.26
(m, 1H), 1.93–1.84 (m, 1H), 1.62–1.53 (m, 1H), 1.10–
1.01 (m, 6H).

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S. Yamamoto et al. / Bioorg. Med. Chem. 14 (2006) 6383–6403
TLC Rf = 0.14 (CHCl3–MeOH, 9:1); MS (MALDI,
pos.) m/z 381 (M+Na)+, 359 (M+H)+; IR (KBr)
3290, 3095, 2964, 2875, 1636, 1588, 1550, 1503,
1489, 1359, 1322, 1247, 1199, 1171, 1085, 1048,
1H NMR (CDCl3): d 7.36–7.30 (m, 5H), 5.15 (d,
J = 12.6 Hz, 1H), 5.09 (d, J = 12.6 Hz, 1H), 4.43 (d,
J = 10.0 Hz, 1H), 4.07–4.00 (m, 2H), 2.68–2.44 (m,
1H), 1.96–1.80 (m, 1H), 1.62–1.49 (m, 1H), 1.42 (s,
9H), 1.23 (d, J = 6.8 Hz, 3H), 1.20 (s, 9H).
1033, 950, 877, 842, 752, 691, 659, 483 cmꢀ1 1H
;
NMR (DMSO-d6): d 10.33 (s, 1H), 8.62 (s, 1H),
7.89–7.83 (m, 3 H), 7.41 (t, J = 7.6 Hz, 2H), 7.17 (t,
J = 7.6 Hz, 1H), 7.04 (d, J = 7.6 Hz, 2H), 7.00 (d,
J = 8.7 Hz, 2H), 4.68 (t, J = 5.7 Hz, 1H), 4.02–3.91
(m, 1H), 3.45–3.28 (m, 2H), 2.21–2.08 (m, 1H),
4.21. Benzyl (2S,4S)-5-[(2-methoxyethoxy)methoxy]-2-
methyl-4-[(4-phenoxybenzoyl)amino]pentanoate (37a)
To a stirred solution of compound 36a (1.0 g, 2.4 mmol)
in CH2Cl2 (10 mL) were added TFA–H2O (10:1) at 0 °C.
After stirring at 0 °C for 30 min, the reaction mixture
was diluted with toluene and evaporated. To a stirred
solution of the resulting residue in DMF (10 mL) was
added EDCÆHCl (1.4 g, 7.2 mmol), HOBtÆH2O (1.1 g,
7.2 mmol), 4-phenoxybenzoic acid (670 mg, 3.1 mmol),
and triethylamine (1.0 mL, 7.2 mmol) at 0 °C. The reac-
tion mixture was diluted with EtOAc. The organic layer
was washed with aqueous NaHCO3, H2O, and brine,
dried over Na2SO4, and evaporated. The resulting resi-
due was purified by silica gel chromatography with
EtOAc–n-hexane (1:1) as an eluent to afford compound
37a (1.1 g, 85%).
1.72–1.55 (m, 2H), 0.98 (t, J = 6.6 Hz, 3H); optical
30
D
calcd for C19H23N2O5: 359.1607. Found: 359.1611.
rotation ½aꢁ ꢀ15.2 (c 0.17, DMF); HRMS (FAB)
4.17. Benzyl (4S)-4-[(tert-butoxycarbonyl)amino]-5-[(2-
methoxyethoxy)methoxy]pentanoate (35a)
Compound 35a was prepared from 34 in 100% yield
according to the same procedure as described for the
preparation of 25 from 24.
TLC Rf = 0.40 (EtOAc–n-hexane, 1:1); 1H NMR
(CDCl3): d 7.40–7.28 (m, 5H), 5.12 (s, 2H), 4.88–4.78
(m, 1H), 4.70 (s, 2H), 3.83–3.48 (m, 7H), 3.38 (s, 3H),
2.45 (t, J = 7.8 Hz, 2H), 1.98–1.75 (m, 2H), 1.43 (s, 9H).
TLC Rf = 0.24 (EtOAc–n-hexane, 1:1); 1H NMR
(CDCl3): d 7.76 (d, J = 8.7 Hz, 2H), 7.40–7.23 (m,
7H), 7.17 (t, J = 7.4 Hz, 1H), 7.02 (d, J = 8.7 Hz,
2H), 6.98 (d, J = 8.7 Hz, 2H), 6.57 (d, J = 9.0 Hz,
1H), 5.06 (d, J = 12.3 Hz, 1H), 4.92 (d, J = 12.3 Hz,
1H), 4.73 (d, J = 10.5 Hz, 1H), 4.71 (d, J = 10.5 Hz,
1H), 4.47–4.37 (m, 1H), 3.78–3.59 (m, 4H), 3.51 (t,
J = 4.7 Hz, 2H), 3.27 (s, 3H), 2.60 (m, 1H), 2.26–
2.15 (m, 1H), 1.74–1.65 (m, 1H), 1.26 (d, J = 7.2 Hz,
3H).
4.18. Benzyl (4S)-4-[(tert-butoxycarbonyl)amino]-5-[(2,2-
dimethylpropanoyl)oxy]pentanoate (35b)
To a stirred solution of compound 34 (3.0 g, 9.29 mmol)
in pyridine (9 mL) was added pivaloyl chloride (2.2 g,
18.6 mmol) at 0 °C. After stirring at room temperature
for 1 h, the reaction mixture was diluted with EtOAc.
The organic layer was washed with 1 N HCl, H2O, aque-
ous NaHCO3, H2O, and brine, dried over Na2SO4, and
evaporated. The resulting residue was purified by silica
gel chromatography with EtOAc–n-hexane (1:6) as an
eluent to afford compound 35b (2.7 g, 72%).
4.22. Benzyl (2S,4S)-5-[(2,2-dimethylpropanoyl)oxy]-2-
methyl-4-[(4-phenoxybenzoyl)amino]pentanoate (37b)
Compound 37b was prepared from 36b in 84% yield
according to the same procedure as described for the
preparation of 37a from 36a.
TLC Rf = 0.36 (EtOAc–n-hexane, 1:4); 1H NMR
(CDCl3): d 7.39–7.32 (m, 5H), 5.12 (s, 2H), 4.52 (d,
J = 9.3 Hz, 1H), 4.16–3.98 (m, 2H), 3.96–3.87 (m, 1H),
2.47 (t, J = 7.7 Hz, 2H), 1.95–1.83 (m, 1H), 1.79–1.66
(m, 1H), 1.42 (s, 9H), 1.20 (s, 9H).
TLC Rf = 0.50 (toluene–EtOAc, 4:1); 1H NMR
(CDCl3): d 7.71 (d, J = 9.0 Hz, 2H), 7.43–7.14 (m,
8H), 7.07–6.96 (m, 4H), 6.19 (d, J = 9.0 Hz, 1H), 5.05
(d, J = 12.2 Hz, 1H), 4.92 (d, J = 12.2 Hz, 1H), 4.62–
4.45 (m, 1H), 4.25 (dd, J = 11.4 Hz and 5.8 Hz, 1H),
4.09 (dd, J = 11.4 Hz and 5.8 Hz, 1H), 2.61 (m, 1H),
2.16–1.95 (m, 1H), 1.73–1.60 (m, 1H), 1.27 (d,
J = 6.9 Hz, 3H), 1.18 (s, 9H).
4.19. Benzyl (2S,4S)-4-[(tert-butoxycarbonyl)amino]-5-
[(2-methoxyethoxy)methoxy]-2-methylpentanoate (36a)
Compound 36a was prepared from 35a according to the
general procedure for the preparation of 26 from 25.
TLC Rf = 0.22 (EtOAc–n-hexane, 1:2); 1H NMR
(CDCl3): d 7.39–7.34 (m, 5H), 5.16 (d, J = 12.5 Hz, 2H),
5.08 (d, J = 12.5 Hz, 1H), 4.74–4.69 (m, 2H), 3.91–3.78
(m, 1H), 3.70–3.65 (m, 2H), 3.54 (t, J = 4.7 Hz, 4H),
3.38 (s, 3H), 2.58 (m, 1H), 2.02–1.89 (m, 1H), 1.65–1.56
(m, 1H), 1.42 (s, 9H), 1.22 (d, J = 7.2 Hz, 3H).
4.23. (2S,4S)-5-[(2-Methoxyethoxy)methoxy]-2-methyl-
4-[(4-phenoxybenzoyl)amino]pentanoic acid (38a)
A solution of 37a (1.06 g, 2.03 mmol) in MeOH
(20 mL) was vigorously stirred in the presence of 5%
Pd/C (300 mg) under hydrogen atmosphere for
40 min. After removing the catalyst by filtration
through a pad of Celite, the reaction mixture was con-
centrated in vacuo to afford 38a:1H NMR (DMSO-d6):
d 12.07 (br s, 1H), 8.11 (d, J = 8.7 Hz, 1H), 7.85 (d,
J = 8.7 Hz, 2H), 7.40 (t, J = 7.5 Hz, 2H), 7.17 (t,
J = 7.5 Hz, 1H), 7.06–6.97 (m, 4H), 4.60 (s, 2H),
4.20. (2S,4S)-4-[(tert-Butoxycarbonyl)amino]-5-[(2,2-
dimethylpropanoyl)oxy]-2-methylpentanoate (36b)
Compound 36b was prepared from 35b according to the
general procedure for the preparation of 26 from 25.

S. Yamamoto et al. / Bioorg. Med. Chem. 14 (2006) 6383–6403
6399
4.26–4.11 (m, 1H), 3.55–3.38 (m, 6H), 3.19 (s, 3H),
2.38–2.24 (m, 1H), 1.92–1.81 (m, 1H), 1.61–1.52 (m,
1H), 1.05 (d, J = 6.9 Hz, 3H).
4.27. tert-Butyl [(1R)-2-(2,2-dimethyl-4,6-dioxo-1,3-di-
oxan-5-yl)-1-methyl-2-oxoethyl]carbamate (40), tert-bu-
tyl [(1R)-2-(2,2-dimethyl-4,6-dioxo-1,3-dioxan-5-yl)-1-
methylethyl]carbamate (41), and tert-butyl (2R)-2-meth-
yl-5-oxo-1-pyrrolidinecarboxylate (42)
4.24. (2S,4S)-5-[(2,2-Dimethylpropanoyl)oxy]-2-methyl-
4-[(4-phenoxybenzoyl)amino]pentanoic acid (38b)
To a stirred solution of compound 39 (5.0 g, 26.5 mmol)
in CH2Cl2 (150 mL) were added 4-dimethylaminopyri-
dine (8.1 g, 66.3 mmol), Meldrums’ acid (7.6 g,
53 mmol), and N,N0-dicyclohexylcarbodiimide (10.9 g,
53 mmol) in CH2Cl2 (150 mL). After stirring at room
temperature for 24 h, the solution was filtered, and then
washed with 5% KHSO4, and brine, dried over Na2SO4,
and filtered. To a stirred solution of the filtrate were
added AcOH (16.6 mL, 291 mmol) and NaBH4 (2.5 g,
66 mmol) at 0 °C. After stirring for 1.5 h at 0 °C, the
reaction mixture was diluted with CH2Cl2. The organic
layer was washed with H2O, and brine, dried over
Na2SO4, and evaporated. The resulting residue was
purified by silica gel chromatography with CH2Cl2–
MeOH (9:1) as an eluent to afford compound 41. A solu-
tion of compound 41 (1.74 g) in toluene was stirred at
110 °C for 5 h. The reaction mixture was diluted with
EtOAc. The organic layer was washed with aqueous
NaHCO3, H2O, and brine, dried over Na2SO4, and
evaporated. The resulting residue was purified by silica
gel chromatography with EtOAc–n-hexane (3:17) as an
eluent to afford compound 42 (1.32 g, 25%).
Compound 38b was prepared from 37b in 86% yield
according to the same procedure as described for the
preparation of 38a from 37a.
1H NMR (DMSO-d6): d 12.11 (br s, 1H), 8.15 (d,
J = 8.7 Hz, 1H), 7.81 (d, J = 8.7 Hz, 2H), 7.41 (t,
J = 7.7 Hz, 2H), 7.17 (t, J = 7.7 Hz, 1H), 7.04 (d,
J = 7.7 Hz, 2H), 7.01 (d, J = 8.7 Hz, 2H), 4.36–4.25
(m, 1H), 4.08–3.94 (m, 2H), 2.38–2.23 (m, 1H),
1.93–1.82 (m, 1H), 1.55–1.45 (m, 1H), 1.17–1.05 (m,
12H).
4.25. N-[(1S,3S)-4-(Hydroxyamino)-1-{[(2-methoxyeth-
oxy)methoxy]methyl}-3-methyl-4-oxobutyl]-4-phenoxy-
benzamide (17)
Compound 17 was prepared from 38a in 69% yield
according to the general procedure for the preparation
of 2–15 from 29a–n, respectively.
TLC Rf = 0.43 (CHCl3–MeOH, 9:1); MS (APCI, neg.
40 V) m/z 445 (MꢀH)ꢀ; IR (KBr) 3274, 3067, 2917,
1634, 1541, 1490, 1341, 1316, 1249, 1198, 1168,
1115, 1062, 1042, 954, 921, 870, 849, 754, 692, 489
TLC Rf = 0.53 (EtOAc–n-hexane, 1:1); 1H NMR
(CDCl3): d 4.29–4.19 (m, 1H), 2.60 (ddd, J = 16.3 Hz,
11.1 Hz and 9.0 Hz, 1H), 2.42 (ddd, J = 17.4 Hz,
9.0 Hz and 3.0 Hz, 1H), 2.23–2.09 (m, 1H), 1.68–1.58
(m, 1H), 1.52 (s, 9H), 1.31 (d, J = 6.6 Hz, 3H).
cmꢀ1 1H NMR (DMSO-d6): d 10.35 (s, 1H), 8.64
;
(s, 1H), 8.01 (d, J = 8.7 Hz, 1H), 7.85 (d,
J = 8.7 Hz, 2H), 7.41 (t, J = 7.7 Hz, 2H), 7.17 (t,
J = 7.7 Hz, 1H), 7.04 (d, J = 7.7 Hz, 2H), 7.00 (d,
J = 8.7 Hz, 2H), 4.59 (s, 2H), 4.18–4.06 (m, 1H),
3.55–3.37 (m, 6H), 3.19 (s, 3H), 2.15 (sextet,
4.28. Methyl (4R)-4-[(tert-butoxycarbonyl)amino]pent-
anoate (43)
J = 7.1 Hz, 1H), 1.68–1.60 (2m, 2H), 0.99 (d,
30
D
J = 6.6 Hz, 3H); optical rotation ½aꢁ ꢀ5.0 (c 0.46,
To a stirred solution of compound 42 (785 mg,
3.90 mmol) in acetone (5.0 mL) was added 1 N NaOH
(2 mL) at room temperature. After stirring for 3 h, the
reaction mixture was quenched with 1 N HCl and dilut-
ed with EtOAc. The organic layer was washed with
brine, dried over Na2SO4, and evaporated to afford a
crude product. To a stirred solution of the crude prod-
uct in MeOH (3 mL) was added CH2N2 (3 mL) and stir-
ring was continued for 5 min. The reaction mixture was
evaporated. The resulting residue was purified by silica
gel chromatography with EtOAc–n-hexane (3:17) as an
eluent to afford compound 43 (784 mg, 87%).
DMF); HRMS (FAB) calcd for C23H31N2O7:
447.2131. Found: 447.2132.
4.26. (2S,4S)-5-(Hydroxyamino)-4-methyl-5-oxo-2-[(4-
phenoxybenzoyl)amino]pentyl pivalate (18)
Compound 18 was prepared from 38b in 77% yield
according to the general procedure for the preparation
of 2–15 from 29a–n, respectively.
TLC Rf = 0.52 (CHCl3–MeOH, 9:1); MS (MALDI,
pos.) m/z 481 (M+K)+, 465 (M+Na)+, 443 (M+H)+;
IR (KBr) 3290, 3067, 2973, 2873, 1733, 1637, 1589,
1541, 1489, 1398, 1365, 1284, 1245, 1200, 1167,
1110, 1034, 1024, 1011, 988, 968, 953, 876, 849,
TLC Rf = 0.31 (EtOAc–n-hexane, 15:85); 1H NMR
(CDCl3): d 4.38–4.28 (m, 1H), 3.67 (s, 3H), 2.39–2.34
(m, 2H), 1.84–1.61 (m, 2H), 1.42 (s, 9H), 1.13 (d,
J = 6.6 Hz, 3H).
752, 691, 597, 492 cmꢀ1 1H NMR (DMSO-d6): d
;
10.38 (s, 1H), 8.07 (d, J = 9.0 Hz, 1H), 7.82 (d,
J = 8.7 Hz, 2H), 7.41 (t, J = 7.7 Hz, 2H), 7.18 (t,
J = 7.7 Hz, 1H), 7.07–6.99 (m, 4H), 4.30–4.18 (m,
1H), 4.07–3.94 (m, 2H), 2.20–2.11 (m, 1H), 1.73–
4.29. Methyl (4R)-4-[(4-phenoxybenzoyl)amino]pentano-
ate (44)
1.49 (m, 2H), 1.06 (s, 9H), 0.99 (d, J = 6.6 Hz, 3H);
To a stirred solution of compound 43 (650 mg,
2.8 mmol) in EtOAc (2 mL) was added 4 N HCl–EtOAc
(6 mL) at 0 °C. After stirring at room temperature for
1 h, the reaction mixture was concentrated in vacuo to
30
D
optical rotation ½aꢁ +4.0 (c 0.45, DMF); HRMS
(FAB) calcd for C24H31N2O6: 443.2182. Found:
443.2185.

6400
S. Yamamoto et al. / Bioorg. Med. Chem. 14 (2006) 6383–6403
afford a crude amine. To a stirred solution of the crude
amine in DMF (6 mL) were added EDCÆHCl (810 mg,
4.2 mmol), HOBtÆH2O (862 mg, 5.6 mmol), 4-phenoxy-
benzoic acid (722 mg, 3.4 mmol), and triethylamine
(0.6 mL, 4.2 mmol) at 0 °C. The reaction mixture was
diluted with EtOAc. The organic layer was washed with
aqueous NaHCO3, H2O, and brine, dried over Na2SO4,
and evaporated. The resulting residue was purified by
silica gel chromatography with EtOAc–toluene (1:19)
as an eluent to afford compound 44 (696 mg, 76%).
TLC Rf = 0.38 (EtOAc–n-hexane, 1:1); 1H NMR
(CDCl3): d 7.78–7.31 (m, 2H), 7.41–7.33 (m, 2H),
7.20–7.12 (m, 1H), 7.06–6.97 (m, 4H), 6.65 (d,
J = 8.8 Hz, 1H), 4.69 (s, 2H), 4.40–4.22 (m, 1H), 3.75
(dd, J = 10.2 Hz and 3.2 Hz, 1H), 3.65–3.55 (m, 3H),
3.63 (s, 3H), 2.51–2.41 (m, 2H), 2.07–1.95 (m, 2H),
1.20 (t, J = 7.0 Hz, 3H).
4.33. Methyl (2S,4S)-5-(ethoxymethoxy)-2-ethyl-4-[(4-
phenoxybenzoyl)amino]pentanoate (48)
TLC Rf = 0.25 (EtOAc–n-hexane, 1:1); 1H NMR
(CDCl3): d 7.76–7.72 (m, 2H), 7.41–7.33 (m, 2H),
7.20–7.12 (m, 1H), 7.06–6.97 (m, 4H), 6.21 (d,
J = 8.8 Hz, 1H), 4.26–4.10 (m, 1H), 2.51–2.38 (m, 2H),
1.95–1.84 (m, 2H), 1.26 (d, J = 6.6 Hz, 3H).
Compound 48 was prepared from 47 in 100% yield
according to the general procedure for the preparation
of 26 from 25.
TLC Rf = 0.53 (EtOAc–n-hexane, 1:1); 1H NMR
(CDCl3): d 7.78–7.73 (m, 2H), 7.41–7.33 (m, 2H),
7.20–7.13 (m, 1H), 7.06–6.97 (m, 1H), 6.42 (d,
J = 8.8 Hz, 1H), 4.70 (d, J = 6.6 Hz, 1H), 4.60 (d,
J = 6.6 Hz, 1H), 4.42–4.28 (m, 1H), 3.72 (dd,
J = 10.3 Hz and 3.4 Hz, 1H), 3.62–3.57 (m, 1H), 3.60
(q, J = 6.6 Hz, 2H), 3.50 (s, 3H), 2.50–2.36 (m, 1H),
2.19–2.02 (m, 1H), 1.76 (ddd, J = 14.4 Hz, 4.4 Hz and
4.4 Hz, 1H), 1.70–1.56 (m, 2H), 1.19 (t, J = 7.0 Hz,
3H), 0.89 (t, J = 7.8 Hz, 3H).
4.30. Methyl (2S,4R)-2-methyl-4-[(4-phenoxybenzoyl)-
amino]pentanoate (45)
Compound 45 was prepared from 44 in 84% yield
according to the general procedure for the preparation
of 26 from 25.
TLC Rf = 0.50 (EtOAc–n-hexane, 1:1); 1H NMR
(CDCl3): d 7.75–7.72 (m, 2H), 7.40–7.34 (m, 2H),
7.19–7.14 (m, 1H), 7.05–6.98 (m, 4H), 5.97 (d,
J = 8.4 Hz, 1H), 4.35–4.20 (m, 1H), 3.55 (s, 3H), 2.61–
2.49 (m, 1H), 2.00 (ddd, J = 14.2 Hz, 10.6 Hz and
8.1 Hz, 1H), 1.65–1.56 (m, 1H), 1.24 (d, J = 6.3 Hz,
3H), 1.22 (d, J = 7.2 Hz, 3H).
4.34. (2S,4S)-5-(Ethoxymethoxy)-2-ethyl-4-[(4-phenoxy-
benzoyl)amino]pentanoic acid (49)
Compound 49 was prepared from 48 in 100% yield
according to the general procedure for the preparation
of 29 from 27 or 28a–m.
4.31. (2S,4R)-2-Methyl-4-[(4-phenoxybenzoyl)amino]-
pentanoic acid (46) and N-[(1R,3S)-4-(hydroxyamino)-
1,3-dimethyl-4-oxobutyl]-4-phenoxybenzamide (20)
TLC
Rf = 0.44
(CHCl3–MeOH–AcOH–H2O,
100:10:1:1); 1H NMR (CD3OD): d 7.83–7.78 (m,
2H), 7.43–7.36 (m, 2H), 7.22–7.15 (m, 1H), 7.07–
6.96 (m, 4H), 4.67 (s, 2H), 4.39–4.23 (m, 1H),
3.65–3.52 (m, 4H), 2.43–2.29 (m, 1H), 2.04–1.66
(m, 4H), 1.51 (t, J = 7.2 Hz, 3H), 0.92 (t,
J = 7.2 Hz, 3H).
Compound 46 was prepared from 45 in 100% yield
according to the general procedure for preparation of
29. Compound 46: TLC Rf = 0.48 (CHCl3–MeOH–
AcOH, 100:5:1). Compound 20 was prepared from 46
in 89% yield (in two steps) according to the general pro-
cedure for the preparation of 2–15 from 29a–n.
4.35. N-{(1S,3S)-1-[(Ethoxymethoxy)methyl]-3-[(hydroxy-
amino)carbonyl]pentyl}-4-phenoxybenzamide (21)
Compound 20: TLC Rf = 0.26 (CHCl3–MeOH–AcOH,
100:5:1); MS (MALDI, pos.) m/z 365 (M+Na)+, 343
(M+H)+; IR (KBr) 3282, 2969, 1632, 1589, 1541, 1489,
Compound 21 was prepared from 49 in 85% yield
according to the general procedure for the preparation
of 2–15 from 29a–n.
1354, 1246, 1169, 1015, 967, 870, 752, 692 cmꢀ1 1H
;
NMR (DMSO-d6): d 10.39 (s, 1H), 8.68 (d, J = 1.6 Hz,
1H), 8.03 (d, J = 8.4 Hz, 1H), 7.88–7.84 (m, 2H), 7.47–
7.39 (m, 2H), 7.23–7.15 (m, 1H), 7.08–6.99 (m, 4H),
4.08–3.92 (m, 1H), 2.21–2.07 (m, 1H), 1.75 (ddd,
J = 13.8 Hz, 7.7 Hz and 6.6 Hz, 1H), 1.46 (ddd,
J = 13.8 Hz, 7.7 Hz and 6.6 Hz, 1H), 1.11 (d,
TLC Rf = 0.33 (CHCl3–MeOH–AcOH, 100:5:1); MS
(MALDI, pos.) m/z 469 (M+K)+, 453 (M+Na)+,
431 (M+H)+; IR (KBr) 3276, 2928, 1634, 1589,
1542, 1489, 1244, 1171, 1116, 1046, 843, 753,
693 cmꢀ1 1H NMR (DMSO-d6): d 10.40 (s, 1H),
;
J = 6.6 Hz, 3H), 1.01 (d, J = 6.6 Hz, 3H); optical rota-
30
D
for C19H23N2O4: 343.1658. Found: 343.1663.
8.70 (d, J = 0.8 Hz, 1H), 8.02 (d, J = 8.4 Hz, 1H),
7.86 (d, J = 8.8 Hz, 2H), 7.46–7.38 (m, 2H), 7.23–
7.15 (m, 1H), 7.08–6.99 (m, 4H), 4.59 (s, 2H),
4.19–4.01 (m, 1H), 3.52–3.42 (m, 2H), 3.47 (q,
J = 7.0 Hz, 2H), 2.05–1.92 (m, 1H), 1.79–1.32 (m,
tion ½aꢁ +19.84 (c 0.25, DMF); HRMS (FAB) calcd
4.32. Methyl (4S)-5-(ethoxymethoxy)-4-[(4-phenoxy-
benzoyl)amino]pentanoate (47)
4H), 1.07 (t, J = 7.2 Hz, 3H), 0.76 (t, J = 7.0 Hz,
30
D
3H); optical rotation ½aꢁ ꢀ22.10 (c 0.20, DMF);
Compound 47 was prepared from 30a in 100% yield
according to the same procedure as described for the
preparation of 27 from 25.
HRMS (FAB) calcd for C23H31N2O6: 431.2182.
Found: 431.2183.

S. Yamamoto et al. / Bioorg. Med. Chem. 14 (2006) 6383–6403
6401
4.36. Benzyl (4S)-5-[(2-methoxyethoxy)methoxy]-4-[(4-
phenoxybenzoyl)amino]pentanoate (50)
4.40. (2S,4S)-2-Ethyl-5-[(2-methoxyethoxy)methoxy]-4-
[(4-phenoxybenzoyl)amino]pentanoic acid (53a)
Compound 50 was prepared from 35a in 100% yield
according to the same procedure as described for the
preparation of 37a from 36a.
Compound 53a was prepared from 52a in 94% yield
according to the same procedure as described for the
preparation of 38a from 37a.
TLC Rf = 0.53 (EtOAc–n-hexane, 1:1); 1H NMR
(CDCl3): d 7.78 (d, J = 8.8 Hz, 2H), 7.42–7.26 (m 7H),
7.22–7.14 (m, 1H), 7.06–6.96 (m, 4H), 6.75 (d,
J = 8.8 Hz, 2H), 5.16–5.00 (m, 2H), 4.78–4.68 (m, 2H),
4.42–4.23 (m, 1H), 3.80 (dd, J = 10.6, 3.6 Hz, 1H),
3.75–3.58 (m, 3H), 3.56–3.48 (m, 2H), 3.33 (s, 3H),
2.61–2.40 (m, 2H), 2.12–1.97 (m, 2H).
TLC Rf = 0.27 (CHCl3–MeOH, 19:1); 1H NMR
(CDCl3): d 7.76 (d, J = 8.8 Hz, 2H), 7.42–7.31 (m,
2H), 7.21–7.12 (m, 1H), 7.06–7.00 (m, 2H), 6.97 (d,
J = 8.8 Hz, 2H), 6.69 (d, J = 9.0 Hz, 1H), 4.74 (d,
J = 7.0 Hz, 2H), 4.70 (d, J = 7.0 Hz, 1H), 4.47–4.29
(m, 1H), 3.80 (dd, J = 10.2 Hz and 3.4 Hz, 1H), 3.74–
3.67 (m, 2H), 3.62 (dd, J = 10.2 Hz and 3.6 Hz, 1H),
3.57–3.50 (m, 2H), 3.35 (s, 3H), 2.54–2.36 (m, 1H),
2.09 (dt, J = 14.4 Hz and 9.2 Hz, 1H), 1.80 (dt,
J = 14.4 Hz and 5.4 Hz, 1H), 1.76–1.58 (m, 2H), 0.94
(t, J = 7.4 Hz, 3H).
4.37. Benzyl (2S,4S)-4-[(tert-butoxycarbonyl)amino]-5-
[(2,2-dimethylpropanoyl)oxy]-2-ethylpentanoate (51)
Compound 51 was prepared from 35b in 55% yield
according to the general procedure for the preparation
of 26 from 25.
4.41. (2S,4S)-5-[(2,2-Dimethylpropanoyl)oxy]-2-ethyl-4-
[(4-phenoxybenzoyl)amino]pentanoic acid (53b)
TLC Rf = 0.58 (toluene–EtOAc, 4:1); 1H NMR
(CDCl3): d 7.40–7.32 (m, 5H), 5.21 (d, J = 12.5 Hz,
1H), 5.06 (d, J = 12.5 Hz, 1H), 4.43 (d, J = 8.8 Hz,
1H), 4.09–3.91 (m, 3H), 2.51–2.36 (m, 1H), 1.87–1.57
(m, 4H), 1.42 (s, 9H), 1.19 (s, 9H), 0.87 (t, J = 7.3 Hz,
3H).
Compound 53b was prepared from 52b in 100% yield
according to the same procedure as described for the
preparation of 38a from 37a.
1H NMR (DMSO-d6): d 12.13 (br s, 1H), 8.14 (d,
J = 8.7 Hz, 1H), 7.80 (d, J = 8.7 Hz, 2H), 7.41 (t,
J = 7.7 Hz, 2H), 7.17 (t, J = 7.7 Hz, 2H), 7.04 (d,
J = 7.7 Hz, 2H), 7.00 (d, J = 8.7 Hz, 2H), 4.32–4.20
(m, 1H), 4.08–3.94 (m, 2H), 2.26–2.17 (m, 1H), 1.83–
1.72 (m, 1H), 1.66–1.43 (m, 2H), 1.06 (s, 9H), 0.80 (t,
J = 7.5 Hz, 3H).
4.38. Benzyl (2S,4S)-2-ethyl-5-[(2-methoxyethoxy)meth-
oxy]-4-[(4-phenoxybenzoyl)amino]pentanoate (52a)
Compound 52a was prepared from 50 in 96% yield
according to the general procedure for the preparation
of 26 from 25.
4.42. N-((1S,3S)-3-[(Hydroxyamino)carbonyl]-1-{[(2-
methoxyethoxy)methoxy]methyl}pentyl)-4-phenoxy-
benzamide (22)
TLC Rf = 0.39 (EtOAc–n-hexane, 1:1); 1H NMR
(CDCl3): d 7.76 (d, J = 9.0 Hz, 2H), 7.41–7.13 (m,
8H), 7.02 (d, J = 8.4 Hz, 2H), 6.98 (d, J = 9.0 Hz, 2H),
6.52 (d, J = 8.7 Hz, 1H), 5.05 (d, J = 12.6 Hz, 1H),
4.84 (d, J = 12.6 Hz, 2H), 4.73 (d, J = 6.9 Hz, 1H),
4.70 (d, J = 6.9 Hz, 1H), 4.43–4.31 (m, 1H), 3.75 (dd,
J = 10.2 Hz and 3.6 Hz, 1H), 3.72–3.66 (m, 2H), 3.60
(dd, J = 10.2 Hz and 3.9 Hz, 1H), 3.54–3.49 (m, 2H),
3.34 (s, 3H), 2.53–2.40 (m, 1H), 2.14 (ddd,
J = 14.4 Hz, 10.2 Hz and 8.7 Hz, 1H), 1.78 (dt,
J = 14.4 Hz and 4.8 Hz, 1H), 1.72–1.60 (m, 2H), 0.87
(t, J = 7.5 Hz, 3H).
Compound 22 was prepared from 53a in 88% yield
according to the same procedure as described for the
preparation of 13 from 29m.
TLC Rf = 0.43 (CHCl3–MeOH, 9:1); MS (APCI, neg.
40 V) m/z 445 (MꢀH)ꢀ; IR (KBr) 3274, 3067, 2917,
1634, 1541, 1490, 1341, 1316, 1249, 1198, 1168,
1115, 1062, 1042, 954, 921, 870, 849, 754, 692,
489 cmꢀ1 1H NMR (DMSO-d6): d 10.35 (s, 1H),
;
8.64 (s, 1H), 8.01 (d, J = 8.7 Hz, 1H), 7.85 (d,
J = 8.7 Hz, 2H), 7.41 (t, J = 7.7 Hz, 2H), 7.17 (t,
J = 7.7 Hz, 1H), 7.04 (d, J = 7.7 Hz, 2H), 7.00 (d,
J = 8.7 Hz, 2H), 4.59 (s, 2H), 4.18–4.06 (m, 1H),
3.55–3.37 (m, 6H), 3.19 (s, 3H), 2.15 (sextet,
4.39. Benzyl (2S,4S)-5-[(2,2-Dimethylpropanoyl)oxy]-2-
ethyl-4-[(4-phenoxybenzoyl)amino]pentanoate (52b)
Compound 52b was prepared from 51 in 58% yield
according to the same procedure as described for the
preparation of 37a from 36a.
J = 7.1 Hz, 1H), 1.68–1.60 (m, 2H), 0.99 (d,
30
D
J = 6.6 Hz, 3H); optical rotation ½aꢁ ꢀ5.0 (c 0.46,
DMF); HRMS (FAB) calcd for C24H33N2O7:
461.2288. Found: 461.2301.
1H NMR (CDCl3): d 7.70 (d, J = 9.0 Hz, 2H), 7.40–7.17
(m, 8H), 7.20 (d, J = 7.8 Hz, 2H), 6.98 (d, J = 9.0 Hz,
2H), 6.17 (d, J = 9.0 Hz, 1H), 5.05 (d, J = 12.3 Hz,
1H), 4.82 (d, J = 12.3 Hz, 1H), 4.56–4.44 (m, 1H),
4.28–4.22 (m, 1H), 4.13–4.06 (m, 1H), 2.53–2.44 (m,
1H), 2.09–1.97 (m, 1H), 1.78–1.63 (m, 3H), 1.19 (s,
9H), 0.88 (t, J = 7.5 Hz, 3H).
4.43. (2S,4S)-4-[(Hydroxyamino)carbonyl]-2-[(4-phenoxy-
benzoyl)amino]hexyl pivalate (23)
Compound 23 was prepared from 53b in 73% yield
according to the same procedure as described for the
preparation of 13 from 29m.

6402
S. Yamamoto et al. / Bioorg. Med. Chem. 14 (2006) 6383–6403
TLC Rf = 0.69 (CHCl3–MeOH, 9:1); MS (MALDI,
pos.) m/z 495 (M+K)+, 479 (M+Na)+, 457 (M+H)+;
IR (KBr) 3262, 3069, 2967, 2932, 2875, 1733, 1638,
1589, 1543, 1489, 1459, 1397, 1364, 1284, 1245, 1151,
1109, 1034, 975, 902, 876, 848, 751, 691, 595,
the injection of SLN, the animals were sacrificed under
anesthesia, and then the knee joints were opened and
washed with 500 lL of saline containing 0.38% sodium
citrate. Next, the proteoglycan content of the washings
was measured as a marker of cartilage destruction.18
Briefly, the washings were treated with papain (Wor-
thington Biochemical, NJ, USA). After the addition of
dimethyl-methylene blue solution, the absorbance was
measured at 540 nm and the proteoglycan content was
calculated from the standard curve for chondroitin sul-
fate. Each group consisted of four animals. These exper-
iments were carried out in accordance with the
Guidelines for Animal Experiments of ONO Pharma-
ceutical Co., Ltd. (Osaka, Japan).
1
492 cmꢀ1; H NMR (DMSO-d6): d 10.41 (s, 1H), 8.71
(s, 1H), 8.07 (d, J = 8.7 Hz, 1H), 7.81 (d, J = 8.6 Hz,
2H), 7.41 (t, J = 7.6 Hz, 2H), 7.17 (t, J = 7.6 Hz, 1H),
7.04 (d, J = 7.6 Hz, 2H), 7.00 (d, J = 8.6 Hz, 2H),
4.25–4.13 (m, 1H), 4.08–3.94 (m, 2H), 2.03–1.91 (m,
1H), 1.63 (t, J = 6.9 Hz, 2H), 1.48–1.36 (m, 2H), 1.06
(s, 9H), 0.75 (t, J = 7.5 Hz, 3H); optical rotation
30
D
C25H33N2O6: 457.2339. Found: 457.2336.
½aꢁ ꢀ9.4 (c 0.15, DMF); HRMS (FAB) calcd for
5. Biological assay
5.1. MMP-1 assay
References and notes
1. (a) Mandal, M.; Mandal, A.; Das, S.; Chakraborti, T.;
Chakraborti, S. Mol. Cell. Biochem. 2003, 252, 305–329;
(b) Matter, H.; Schudok, M. Curr. Opin. Drug Discovery
Dev. 2004, 7, 513–535.
Commercially available assay kits (Yagai, Yamagata
City, Japan) were used. The solutions provided in the
kits were used unless otherwise stated. A 98 lL portion
of enzyme solution (0.5 U/mL) and 2 lL of inhibitor
solution (DMSO) were incubated with 100 lL of
0.5 mg/mL FITC-labeled type I collagen solution at
37 °C for 3 h. After incubation with 300 L of quenching
solution on ice for 30 min, the reaction mixture was cen-
trifuged at 2000g for 15 min. Supernatant was used for
measurement of fluorescence by RF5300-PC. Excitation
and emission wavelengths were 495 and 520 nm,
respectively.
2. (a) Supuran, C. T.; Scozzafava, A. In Proteinase and
Peptidase Inhibition: Recent Potential Targets for Drug
Development; Smith, H. J., Simons, C., Eds.; Taylor and
Francis: London, New York, 2002; pp 35–61; (b) Woess-
ner, J. F.; Nagase, H. In Matrix Metalloproteinases and
TIMPs; Oxford University Press, 2000; pp 1–223.
3. Levy, D. E.; Lapierre, F.; Liang, W.; Ye, W.; Lange, C.
W.; Li, X.; Grobelny, D.; Casabonne, M.; Tyrrell, D.;
Holme, K.; Nadzan, A.; Galardy, R. E. J. Med. Chem.
1998, 41, 199–223.
4. Hughes, I.; Harper, G. P.; Karran, E. H.; Markwell, R. E.;
Miles-Williams, A. J. Bioorg. Med. Chem. Lett. 1995, 5,
3039–3042.
5.2. MMP-2 and MMP-9 assays15
5. Pikul, S.; Ohler, N. E.; Ciszewski, G.; Laufersweiler, M.
C.; Almstead, N. G.; De, B.; Natchus, M. G.; Hsieh, L. C.;
Janusz, M. J.; Peng, S. X.; Branch, T. M.; King, S. L.;
Taiwo, Y. O.; Mieling, G. E. J. Med. Chem. 2001, 44,
2499–2502.
A mixture of 130 lL of MOCAc-Pro-Leu-Gly-Leu-
Dpa-Ala-Arg-NH2 (final concentration: 15 lM) and
20 lL of inhibitor solution was incubated at 37 °C for
5 min. Enzyme solution (50 lL) was added, and the
reaction was performed at 37 °C for 10 min. Its fluores-
cence was measured by fmax. Excitation and emission
wavelengths were 320 and 390 nm, respectively.
6. Reiter, L. A.; Rizzi, J. P.; Pandit, J.; Lasut, M. J.;
McGahee, S. M.; Parikh, V. D.; Blake, J. F.; Danley, D.
E.; Laird, E. R.; Lopez-Anaya, A.; Lopresti-Morrow, L.
L.; Mansour, M. N.; Martinelli, G. J.; Mitchell, P. G.;
Owens, B. S.; Pauly, T. A.; Reeves, L. M.; Schulte, G. K.;
Yocum, S. A. Bioorg. Med. Chem. Lett. 1999, 9, 127–132.
7. Jacobsen, E. J.; Mitchell, M. A.; Hendges, S. K.; Belonga,
K. L.; Skaletzky, L. L.; Stelzer, L. S.; Lindberg, T. J.;
Fritzen, E. L.; Schostarez, H. J.; O’Sullivan, T. J.;
Maggiora, L. L.; Stuchly, C. W.; Laborde, A. L.; Kubicek,
M. F.; Poorman, R. A.; Beck, J. M.; Miller, H. R.;
Petzold, G. L.; Scott, P. S.; Truesdell, S. E.; Wallace, T.
L.; Wilks, J. W.; Fisher, C.; Goodman, L. V.; Kaytes, P.
S.; Ledbetter, S. R.; Powers, E. A.; Vogeli, G.; Mott, J. E.;
Trepod, C. M.; Staples, D. J.; Baldwin, E. T.; Finzel, B. C.
J. Med. Chem. 1999, 42, 1525–1536.
5.3. MMP-3 assay16
A mixture of 190 lL of MOCAc-Arg-Pro-Lys-Pro-Val-
Glu-Nva-Trp-Arg-Lys(Dnp)–NH2 (final concentra-
tion:15 lM) and 10 lL of inhibitor solution was incu-
bated at 37 °C for 5 min. Enzyme solution (50 lL) was
added, and the reaction was performed at 37 °C for
10 min. Its fluorescence was measured by fmax. Excita-
tion and emission wavelengths were 320 and 390 nm,
respectively.
8. (a) Whittaker, M.; Floyd, C. D.; Brown, P.; Gearing, A. J.
H. Chem. Rev. 1999, 99, 2735–2776; (b) Skiles, J. W.;
Gonnella, N. C.; Jeng, A. Y. Curr. Med. Chem. 2004, 11,
2911–2977.
9. Takahashi, K.; Ikura, M.; Habashita, H.; Nishizaki, M.;
Sugiura, T.; Yamamoto, S.; Nakatani, S.; Ogawa, K.;
Ohno, H.; Nakai, H.; Toda, M. Bioorg. Med. Chem. 2005,
13, 4527–4543.
5.4. In vivo assay17
Compound 9 was orally administered to male Hartley
guinea pigs (SLC, Shizuoka, Japan), weighing 221–
375 g, at 60 min before the intra-articular injection of re-
combinant human stromelysin (SLN). (Sufficient en-
zyme was injected so that proteoglycan release was
increased 6-fold relative to the control). Carboxymethyl
cellulose (0.5%) was used as the solvent. Two hours after
10. (a) Ikura, M.; Nakatani, S.; Yamamoto, S.; Sugiura, T.;
Ogawa, K.; Ohno, H.; Takahashi, K.; Nakai, H.; Toda,
M. Bioorg. Med. Chem. 2006, 14, 4241–4252; (b)

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Nishita, Y.; Itadani, S.; Ogawa, K.; Ohno, H.; Takahashi,
K.; Nakai, H.; Toda, M. Bioorg. Med. Chem., in press.
11. Kokotos, G. Synthesis 1990, 299–301.
phorbol-myristate-acetate and IL-1 beta. MMP-9 was
purchased from Yagai (Yamagata City, Japan).
15. Knight, C. G.; Willenbrock, F.; Murphy, G. A. FEBS
Lett. 1992, 296, 263–266.
12. (a) Hanessian, S.; Schaum, R. Tetrahedron Lett. 1997, 38,
163–166; (b) Hanessian, S.; Schaum, R. Tetrahedron Lett.
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1993, 34, 6513–6516; (b) Stanfield, C. F.; Parker, J. E.;
Kanellis, P. J. Org. Chem. 1981, 46, 4797–4798; (c)
Falorni, M.; Porcheddu, A.; Taddei, M. Tetrahedron Lett.
1999, 40, 4395–4396.
16. Nagase, H.; Fields, C. G.; Fields, G. B. J. Biol. Chem.
1994, 269, 20952–20957.
17. MacPherson, L. J.; Bayburt, E. K.; Capparelli, M. P.;
Carroll, B. J.; Goldstein, R.; Justice, M. R.; Zhu, L.; Hu, S.;
Melton, R. A.; Fryer, L.; Goldberg, R. L.; Doughty, J. R.;
Spirito, S.; Blancuzzi, V.; Wilson, D.; O’Byrne, E. M.;
Ganu, V.; Parker, D. T. J. Med. Chem. 1997, 40, 2525–2532.
18. Schrier, D. J.; Flory, C. M.; Finkel, M.; Kuchera, S. L.;
Lesch, M. E.; Jacobson, P. B. Arthritis Rheum. 1996, 39,
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14. MMP-1 and MMP-2 were purified from the culture
medium of human dermal fibroblasts stimulated with