Design and synthesis of a novel series of HIV-1 protease inhibitors

Article abstract of DOI:10.1016/S0968-0896(99)00163-7

The synthesis and the SAR study of novel pseudo symmetric inhibitors of HIV-1 protease are described. Michael addition of amino acid derivatives to vinyl ketones was utilized to derive a potent (nM) series of HIV-1 protease inhibitors.

Full text of DOI:10.1016/S0968-0896(99)00163-7

Bioorganic & Medicinal Chemistry 7 (1999) 2105±2114
Design and Synthesis of a Novel Series of HIV-1 Protease
Inhibitors
Eiji Takashiro, a,* Yuji Nakamura, a Shuichi Miyamoto, a Yuji Ozawa, b
Akiko Sugiyama b and Katsumi Fujimoto a
aExploratory Chemistry Research Laboratories, Sankyo Co. Ltd., 1-2-58 Hiromachi, Shinagawa-ku, Tokyo, 147-8710, Japan
bBiological Research Laboratories, Sankyo Co. Ltd., 1-2-58 Hiromachi, Shinagawa-ku, Tokyo 140-8710, Japan
Received 20 April 1999; accepted 8 June 1999
AbstractÐThe synthesis and the SAR study of novel pseudo symmetric inhibitors of HIV-1 protease are described. Michael addi-
tion of amino acid derivatives to vinyl ketones was utilized to derive a potent (nM) series of HIV-1 protease inhibitors. # 1999
Elsevier Science Ltd. All rights reserved.
Introduction
Therefore, inhibitors with a new skeleton are always
required. Our strategy is shown below (Fig. 1).
Replication of the HIV virus requires processing of the
proteins encoded by the gag and gag-pol genes by a
virally encoded aspartyl protease (HIV-1 protease).1±3
As such, inhibition of HIV-1 protease (HIV-1PR) o€ers
an attractive target for the treatment of acquired
immunode®ciency syndrome (AIDS).4±9 Progress in the
treatment of AIDS leading to an e€ective therapy has
been slow, but recent results with new AIDS drugs,
notably the HIV-1 PR inhibitors, allow for cautious
optimism. Four HIV PR inhibitors, namely saquinavir,
ritonavir, indinavir and nel®navir, have been approved
for clinical use by the FDA.10
A, vinyl ketones, were synthesized from a-amino acids
by known procedure.17±20 B, amines, were commercially
available. Here A was used as Michael acceptors and B
was employed as donors. After joining A and B, a hy-
droxyl group, which would interact with HIV PR
aspartate groups, was introduced by reduction. We
demonstrated that inhibitors with a 3-hydroxy-2-
methylbenzoyl group at the P2 site were very potent.16
In this study, the 3-hydroxy-2-methylbenzoyl group21±23
was incorporated into our novel backbone as the P2
group.
AHPBA (3(S)-amino-2(S)-hydroxy-4-phenylbutanoic acid)
is one of the promising peptide-mimic isosters in the
design of HIV-1 PR inhibitors. Kiso11±13 and our
group14±16 independently discovered that AHPBA-
derived inhibitors showed potent inhibitory activity
against HIV-1 PR. In these compounds, AHPBA and
proline derivatives were linked via amide bonds. To
reduce the peptide-like characteristics, we concentrated
our e€orts on connecting the two components without
using peptide bonds.5,12,15,16
Results and Discussion
Chemistry and structure±activity relationship
First we chose vinyl ketone 1-a, derived from Boc-phe-
nylalanine,17±19 as a Michael acceptor and benzyl-
methylamine (2) as the donor (Scheme 1).
Michael addition of 2 to 1-a gave ketone 3. Because 3
was unstable, in situ reduction was required. Although
there remained the important problem of stereocontrol,
reduction with NaBH4 a€orded the expected (R)-alco-
hol 4 as the major product in ca. 3:1 ratio.17 Most of the
reducing agents tested, such as diisobutylaluminum hy-
dride (DIBAL-H) gave complex mixtures and use of l-
Selectride1 a€orded undesirable (S)-alcohol (epi-4) as
the major product.24 Treatment of 4 and epi-4 with NaH
Recent reports indicated that HIV-1 does develop resis-
tance to some protease inhibitors. Di€erent HIV-1 pro-
tease inhibitors are expected to produce distinctly di€erent
patterns of resistance.5,10 To overcome drug resistance, a
combined use of di€erent protease inhibitors is needed.
* Corresponding author.
0968-0896/99/$ - see front matter # 1999 Elsevier Science Ltd. All rights reserved.
PII: S0968-0896(99)00163-7

2106
E. Takashiro et al. / Bioorg. Med. Chem. 7 (1999) 2105±2114
in DMF gave the oxazolidinones. The con®gurations of
the hydroxyl groups in 4 and epi-4 were assigned by
NMR analysis of the oxazolidinones.25±27 The NOE was
observed only in the cis oxazolidinone, derived from the
R-epimer 4 (Fig. 2).
Among these compounds, 11 and 13 were potent. In our
previous paper,16 we reported that compounds with an
ortho-methyl group at the P2 benzene ring were good
inhibitors. Here, 13, with an ortho-methyl group, was
also potent. The repulsion between the substituent and
sulfonamide plane may have been the cause of favorable
interaction at the S2 pocket.34,35
The hydroxyl group in 4 was protected to give an ace-
tate 5. Hydrogenolysis of the benzyl group in 5 gave a
secondary amine, which was then sulfonated under
usual conditions to give 6. Boc groups in 6 were
removed by 4 N-HCl/1,4-dioxane to give a primary
amine, which was then coupled with 3-hydroxy-2-
methylbenzoic acid,28 followed by removal of the acetyl
group to give 7. Compounds 8±13 were also synthesized
by this method.
The resulting compounds had one carbon extended to
the hydroxyethylamine isoster of VX-478.29±33 HIV-1
PR inhibitory activity of the sulfonamide bearing com-
pounds is shown in Table 1.
Figure 2. Stereochemical assignments of the oxazolidinones.
Figure 1. Design of inhibitors with novel backbones.
Scheme 1. Synthesis of sulfonamide bearing compounds. (a)/EtOH; (b) NaBH4/EtOH (36%, 2 steps); (c) Ac2O, Et3N, DMAP (cat.)/CH2Cl2 (81%);
(d) H2, Pd-C, AcOH/EtOH; (e) p-toluenesulfonyl chloride, Et3N/CH2Cl2 (41%, 2 steps); (f) 4 N HCl/1,4-dioxane; (g) 3-hydroxy-2-methylbenzoic
.
acid, EDCl HCl, HOBt, Et3N/DMF; (h) 1 N NaOHaq./MeOH 45%, 3 steps).

E. Takashiro et al. / Bioorg. Med. Chem. 7 (1999) 2105±2114
2107
Our strategy proved to be e€ective by the above results.
We next turned our attention to changing the Michael
donors from benzyl amines to amino acid derivatives,
which means inhibitors with two amino acid units became
our targets.36±40 Scheme 2 describes our initial attempt.
Table 1. HIV-1 PR inhibitor activity of sulfonamide bearing com-
pounds
(S)-phenylglycine tert-butylamide 14 attacked the con-
jugated double bond of 1-a to a€ord the corresponding
ketone. This ketone was reduced with NaBH4 in situ and
treatment of the crude alcohol with Ac2O and NEt3 pro-
duced N- and O- diacylated compound. Saponi®cation
with aqueous NaOH gave 15. Although 15 was assayed as
a diastereomixture, it showed good inhibitory activity
(IC50=500 nM). This result encouraged us to investigate
detailed structure±activity relationship with regards to
inhibitors with two amino acid units. We next adopted a
3-hydroxy-2-methylbenzamide as the P2 moiety instead of
a Boc group.16,21±23 The preparation of the representative
compound 18 is outlined in Scheme 3.
No
R1
H
R2
Ar
IC50 (nM)
1300
7
Me
8
H
H
Et
isopropyl
isopropyl
Et
1600
1500
2500
900
For linkage of vinylketone 1-a and 16, the above
method was also employed to a€ord 17 (64%, 3 steps).
The Boc group in 17 was removed under acidic condi-
tions (4 N-HCl/1,4-dioxane), which was then coupled
with 3-hydroxy-2-methylbenzoic acid using 1-(3-di-
9
10
11
12
13
Me
H
.
methylaminopropyl)-3-ethylcarbodiimide hydrochloride
.
(EDCI HCl) and 1-hydroxybenzotriazole (HOBt).
Hydrolysis in alkaline condition gave 18 in 43% yield (3
steps). Chromatographic separation of the diaster-
eomers was carried out in this step.41 Compounds 19±39
were also prepared in this way.
H
hydroxyethyl
Et
6500
800
H
The inhibitory activity of these compounds is shown in
Table 2.
Scheme 2. Preparation of compound having two amino acid units. (a) Et3N/EtOH; (b) NaBH4/EtOH; (c) Ac2O, Et3N, DMAP/CH2Cl2 (78%, 3
steps); (d) 1 N NaOHaq./MeOH (89%).
Scheme 3. Preparation of pseudo symmetric compounds containing 3-hydroxy-2-methylbenzamide. (a) Et3N/EtOH; (b) NaBH4/EtOH; (c) Ac2O,
.
Et3N, DMAP/CH2Cl2 (64%, 3 steps); (d) 4 N HCl/1,4-dioxane; (e) 3-hydroxy-2-methylbenzoic acid, EDCl HCl, HOBt, Et3N/DMF (h) 1 N NaO-
Haq./MeOH (43%, 3 steps).

2108
E. Takashiro et al. / Bioorg. Med. Chem. 7 (1999) 2105±2114
Table 2. HIV-1 PR inhibitory activity of 3-hydroxy-2-methylbenza-
mide bearing compounds
Table 3. HIV-1 PR inhibitor activity of compounds with various
amide groups
No
R
IC50 (nM)
90
No
R1
R2
IC50 (nM) No
R1
Ac
R2
IC50 (nM)
18
18
19
20
Ac
H
90
16900
26200
4300
25
26
3600
380
31
2200
1500
32*
33*
34*
35*
36*
37
Me
27*
Ac
2500
21* Bn
1800
22
H
1800
28
29
Ac
Ac
>100,000
3800
1100
23* Ac
800
1600
100,000
5000
24
H
6000
30
Ac
1500
*Tested as a diastereomixture.
*Tested as a diastereomixture.
It is clearly shown that the nitrogen atom at the C-4
position should be acylated for good inhibition. A basic
nitrogen would not have the same e€ect (18 versus 19
versus 20 versus 21) (22 versus 23) (18 versus 26). Oxy-
gen atoms in the sulfonamides in 11 or 13 and in the
acyl group of 18 may form hydrogen bonds to the
structural water. The structural water acts as a bridge to
Ile50 and Ile500.
Table 4. HIV-1 PR inhibitory activity of compounds with various Ar
groups
Compared with 18, inhibitors with a larger aromatic
ring or a substituted benzene ring as R2 groups, were
not good inhibitors (18 versus 30) (18 versus 27 versus
28 versus 29). It is likely that these substitutents disturb
the hydrophobic interaction at this site. Comparing 18
and 25, l-amino acid was apparently favorable. To
develop more active compounds, our attention was then
focused on changing the tert-butyl amide group to other
groups (Table 3).
No
Ar
IC50 (nM)
18
38
39
90
29
41
Figure 3. Proposed enzyme-inhibitor interaction.

E. Takashiro et al. / Bioorg. Med. Chem. 7 (1999) 2105±2114
2109
Unfortunately, no potent compounds appeared among
the inhibitors we synthesized. This result stimulated us
to change the P1 aromatic moiety (Table 4).
(1 N, 65 mL) at 0ꢀC and stirred for 20 min at this tem-
perature. The reaction mixture was poured into ice-cold
aqueous HCl (3 N) and extracted with EtOAc. The organic
extracts were washed (saturated aqueous NaHCO3), dried
(Na2SO4) and concentrated in vacuo. The residue was
puri®ed by ¯ash column chromatography (hexane:
EtOAc=75:25) to give 1-b (3.4 g) in 34% yield (2 steps).
As shown in Table 4, inhibitors with larger aromatic
rings were more potent than those with a phenyl group.
Their superior potency suggested that there may be extra
room in the S1 hydrophobic pocket. Figure 3 represents
the proposed enzyme±inhibitor interaction.
Mp 94ꢀC; 1H NMR (CDCl3) d 1.42 (s, 9H), 3.04 (dd, 1H,
J1=13.8, J2=6.3 Hz), 3.21 (dd, 1H, J1=13.8, J2=6.3
Hz), 4.91 (ddd, 1H, J1=J2=J3=6.3 Hz), 5.27 (d, 1H,
J=6.3 Hz), 5.88 (d, 1H, J=10.2 Hz), 6.39 (d, 1H,
J=17.4 Hz), 6.49 (dd, 1H, J1=17.4, J2=10.2 Hz), 7.17±
7.19 (m, 2H), 7.33±7.38 (m, 1H), 7.41±7.45 (m, 2H),
7.46±7.56 (m, 2H), 7.57±7.61 (m, 2H); IR (KBr) 3360,
2986, 1704, 1683, 1612, 1508, 1404, 1301, 1250, 1168,
831, 733 cm 1; [a]d25 +77.6ꢀ (c 1.13, CHCl3). Anal. calcd
for C22H25NO3: C, 75.19; H, 7.17; N, 3.99. Found: C,
75.24; H, 7.39; N., 3.77; mass m/z 352 [M+H]+.
Since they are composed of two b-arylalanine portions,
the potent inhibitors 18, 38 and 39 seem to have pseudo
symmetry. It is presumed that the high potency of these
compounds was due to this structural feature.
Conclusion
HIV-1 protease inhibitors with a novel backbone have
been designed. We developed an ecient method for the
construction of a-amino alcohol using Michael addition
of amine to a,b-unsaturated ketone followed by reduction
of the ketone moiety. The resulting pseudo-symmetric
structure served as a peptide-mimic isoster where two
amino acid analogues were connected without an amide
bond. Further work for investigating more active com-
pounds and determining the structure of the protease/
inhibitor complex is now in progress.
[1(S)-(2-Naphthyl)-methyl-2-oxo-but-3-enyl]-carbamic
acid tert-butyl ester (1-c). Mp 77ꢀC; H NMR (CDCl3)
1
d 1.42 (s, 9H), 3.19 (dd, 1H, J1=14.2, J2=5.6 Hz), 3.34
(d, 1H, J1=14.2, J2=6.2 Hz), 5.26±5.29 (m, 1H), 5.84
(d, 1H, J=11.6 Hz), 6.36 (d, 1H, J=17.5 Hz), 6.48 (dd,
1H, J1=17.5, J2=11.6 Hz), 7.26±7.28 (m, 1H), 7.44±
7.49 (m, 2H), 7.58 (s, 1H), 7.77±7.87 (m, 3H); IR (KBr)
1
3350, 1688, 1512, 1404, 1370, 1248, 1168, 823 cm
;
[a]2d5 +82.6ꢀ (c 0.232, CHCl3). Anal. calcd for
.
C20H23NO3 1/5H2O: C, 73.03; H, 7.17; N, 4.26. Found:
C, 73.35; H, 7.55; N, 3.78; mass m/z 326 [M+H]+.
Experimental
All experiments dealing with air- and moisture- sensitive
compounds were conducted under an atmosphere of dry
N2. Melting points (mp) were determined with a
Yanaco melting point apparatus and are not corrected.
Infrared (IR) spectra were measured with a Nic 5SXC
FT±IR spectrophotometer. 1H NMR spectra were
recorded on a JEOL JNM-GX 270 FT±NMR or a
VARIAN Mercury 400 spectrometer. Chemical shifts
were expressed in d ppm from the internal standard tet-
ramethylsilane (TMS). Splitting patterns are indicated as
follows: s, singlet; d, doublet; t, triplet; m, multiplet; br,
broad peak. EI- and FAB±MS were taken on a JEOL
JMS-D 300 mass spectrometer and relevant data are
tabulated as m/z. Column chromatography was carried
out using SK-34 (Kishida, 70±-230 mesh). Preparative
thin-layer chromatography (PTLC) was performed using
60 F254 plates (Merck art. 5744). Optical rotations ([a]d)
were measured on a Jasco DIP-360 polarimeter.
[1(S)-Benzyl-4-(benzyl-methyl-amino)-2(R)-hydroxy-butyl]
-carbamic acid tert-butyl ester (4). A solution of 1-a (383
mg, 1.39 mmol) and benzylmethylamine (354 mg, 2.92
mmol) in EtOH (5 mL) was stirred for 2 h at room tem-
perature. After cooling to 0ꢀC, NaBH4 (50.4 mg, 1.33
mmol) was added to the reaction mixture and stirred for
1 h at this temperature. The reaction was stopped by
adding CH3CO2H and the mixture was continuously
stirred for 5 min. To this mixture was added saturated
aqueous NaHCO3 and the products were extracted with
EtOAc. The combined organic extracts were washed
(brine), dried (Na2SO4) and concentrated in vacuo. Pur-
i®cation by PTLC (hexane:EtOAc:acetone=4:5:1)
a€orded 4 (200 mg, 36.1%) as a colorless crystalline and
epi-4 (78.9 mg, 14.2%) as a colorless oil.
ꢀ
1
Mp 82 C; H NMR (CDCl3) d 1.33 (s, 9H), 1.55±1.59
(m, 1H), 1.71±1.79 (m, 1H), 2.22 (s, 3H), 2.60 (dd, 1H,
J1=12.6, J2=3.7 Hz), 2.73 (dd, 1H, J1=12.6, J2=2.5
Hz), 2.83±2.88 (m, 1H), 3.01 (dd, 1H, J1=14.0, J2=4.0
Hz), 3.41 (d, 1H, J=12.8 Hz), 3.65 (d, 2H, J=12.8 Hz),
3.80 (br, 1H), 4.53 (d, 1H, J=8.9 Hz), 7.17±7.36 (m,
[1(S)-(Biphenyl-4-yl)-methyl-2-oxo-but-3-enyl]-carbamic
acid tert-butyl ester (1-b). A solution of Boc-(4-phenyl)-
Phe-OH (8 g, 21 mmol), N, O-dimethylhydroxyl-
.
.
amine hydrochloride (3.5 g, 35 mmol), EDCI HCl (6 g,
31 mmol) and NEt3 (3.5 g, 35 mmol) in CH2Cl2 (60 mL)
was stirred for 10 h at room temperature. The reaction
mixture was diluted with CH2Cl2, washed (brine) and
dried (Na2SO4). After removal of the solvent in vacuo,
the residue (6 g) was used in the next step.
5H) ; IR (CHCl3) 3358, 2980, 1739, 1686, 1525, 1496,
1
1454, 1367, 1247, 1171, 1044, 1018, 861, 741, 699 cm
[a]d25 10.5ꢀ (c 1.35, CHCl3); mass m/z 399 [M+H]+.
;
[1(S)-Benzyl-4-(benzyl-methyl-amino)-2(S)-hydroxy-butyl]-
1
carbamic acid tert-butyl ester (epi-4). H NMR (CDCl3) d
1.22±1.31 (m, 1H), 1.40 (s, 9H), 1.83±1.92 (m, 1H), 2.19 (m,
3H), 2.45±2.50 (m, 1H), 2.72±2.78 (m, 1H), 2.88 (d, 2H,
J=7.6 Hz), 3.35 (d, 1H, J=12.8 Hz), 3.63±3.70 (m, 2H),
To the solution of the above crude product (6 g) in THF
(100 mL) was added a solution of vinyl magnesium bromide

2110
E. Takashiro et al. / Bioorg. Med. Chem. 7 (1999) 2105±2114
3.73 (d, 1H, J=10.4 Hz), 5.09 (d, 1H, J=9.5 Hz), 7.17±7.44
(m, 5H); IR (CHCl3) 2985, 1730, 1375, 1254, 1046, 940
cm 1;[a]d25 +0.89ꢀ (c0.71, CHCl3); mass m/z 399 [M+H]+.
NEt3 (52 mg, 0.514 mmol) in DMF (4 mL) was stirred
for 1 day at room temperature. The reaction was quen-
ched with H2O and the mixture was extracted with
EtOAc. The organic extracts were washed (H2O), dried
(Na2SO4) and concentrated in vacuo. The residue was
used in the next step without further puri®cation.
[1(S)-Benzyl-4-(benzyl-methyl-amino)-2(R)-acetoxy-butyl]-
carbamic acid tert-butyl ester (5). A solution of 4 (66.4
mg, 0.167 mmol), Ac2O (96.5 mg, 0.944 mmol), NEt3
(94.1 mg, 0.930 mmol) and a catalytic amount of
DMAP in CH2Cl2 (3 mL) was stirred for 4 h at room
temperature. The reaction was quenched with brine and
the mixture was extracted (EtOAc) and dried (Na2SO4).
After removal of the solvent in vacuo, the residue was
puri®ed by PTLC (hexane:EtOAc=5:5) to a€ord 5
(59.5 mg) in 81% yield.
The solution of the above crude product and aqueous
NaOH (1 N, 0.3 mL) in MeOH (3 mL) was stirred for 30
min at room temperature. Brine was added and this reac-
tion mixture was extracted with EtOAc. After removal of
the solvent in vacuo, the residue was puri®ed by PTLC
(hexane:EtOAc=4:6) to a€ord 7 in 45% yield (3 steps).
Mp 78ꢀC; H NMR (CDCl3) d 1.61±2.11 (m, 2H), 1.98
1
ꢀ
1
Mp 61 C; H NMR (CDCl3) d 1.33 (s, 9H), 1.77±1.89
(m, 2H), 1.99 (s, 3H), 2.21 (s, 3H), 2.49 (dd, 2H,
J1=J2=7.1 Hz), 2.66 (dd, 1H, J1=14.0, J2=9.1 Hz),
2.86 (dd, 1H, J1=14.0, J2=5.5 Hz), 3.52±3.59 (m, 2H),
4.10±4.15 (m, 1H), 4.93 (d, 1H, J=3.5 Hz), 5.08 (d, 1H,
J=8.7 Hz) 5.36 (br, 1H), 7.16±7.48 (m, 5H); IR
(CHCl3) 3444, 2980, 1711, 1498, 1455, 1368, 1252, 1167,
1046, 1025, 873 cm 1; mass m/z 441 [M+H]+.
(s, 3H), 2.44 (s, 3H), 2.66±2.91 (m, 3H), 2.76 (s, 3H),
3.02±3.16 (m, 2H), 3.40±3.54 (m, 1H), 3.96±4.16 (m,
1H), 4.35±4.49 (m, 1H), 6.02 (d, 1H, J=8.6 Hz), 6.58 (d,
1H, J=7.8 Hz), 6.76 (d, 1H, J=7.8 Hz), 6.95 (t, 1H, 7.8
Hz), 7.19±7.35 (m, 7H), 7.59±7.70 (m, 2H); IR (KBr)
3350, 2925, 1638, 1585, 1528, 1456, 1333, 1158, 1088,
949, 722 cm 1; mass m/z 497 [M+H]+.
N-[1(S)-Benzyl-4-(ethyl-p-toluenesulfonyl-amino)-2(R)-
hydroxy-butyl]-3-hydroxy-2-methylbenzamide (8). Mp
73ꢀC; 1H NMR (CDCl3) d 1.26 (t, 3H, J=7.1 Hz), 1.63±
1.97 (m, 3H), 2.00 (s, 3H), 2.42 (s, 3H), 2.81 (dd, 1H,
J1=14.1, J2=10.4 Hz), 3.00±3.34 (m, 4H), 3.42±3.66
(m, 1H), 3.86±4.06 (m, 2H), 4.35±4.48 (m, 1H), 5.57 (s,
1H), 5.97 (d, 1H, J=7.8 Hz), 6.58 (d, 1H, J=7.8 Hz),
6.77 (d, 1H, J=7.8 Hz), 6.97 (d, 1H, J=7.8 Hz), 7.16±
7.44 (m, 6H), 7.60±7.71 (m, 2H); IR (KBr) 3349, 2930,
1638, 1585, 1527, 1496, 1466, 1330, 1285, 1153, 1089,
911, 730, 700 cm 1; mass m/z 511 [M+H]+.
{1(S)-Benzyl-2(R)-acetoxy-4-[methyl-(p-toluenesulfonyl)-
amino]-butyl}-carbamic acid tert-butyl ester (6). A sus-
pension of 5 (290 mg, 0.658 mmol), AcOH (62.5 mg, 1.04
mmol) and 10% Pd±C (40 mg) in EtOH (5 mL) was stir-
red under H2 (1 atm) at room temperature for 1 day.
After changing the atmosphere to N2, the mixture was
diluted with EtOAc. The mixture was ®ltered through a
Celite pad (washed with EtOAc), and the mixture was
washed (saturated aqueous NaHCO3), dried (Na2SO4)
and concentraed in vacuo. The residue (105 mg) was used
in the next step without further puri®cation.
N-[1(S)-Benzyl-4-(isopropyl-p-toluenesulfonyl-amino)-2
To the stirred solution of the above crude amine (105
mg) and NEt3 (64.1 mg, 0.633 mmol) in CH2Cl2 (4 mL)
was added p-toluenesulfonyl chloride (80.4 mg, 0.422
mmol) at 0ꢀC and stirred for 3 h at this temperature.
The reaction was stopped by adding saturated aqueous
NaHCO3 and the mixture was extracted with EtOAc.
The combined organic extracts were washed (brine),
dried (Na2SO4) and concentrated in vacuo. The residue
was puri®ed with PTLC (hexane:EtOAc=6:4) to give 6
(62.2 mg) in 41.0% yield (2 steps).
(R)-hydroxy-butyl]-3-hydroxy-2-methylbenzamide
(9).
Mp 66ꢀC; H NMR (CDCl3) d 0.96 (d, 3H, J=6.7 Hz),
1.11 (d, 3H, J=6.7 Hz), 1.74±1.98 (m, 2H), 2.05 (s, 3H),
2.42 (s, 3H), 2.83 (dd, 1H, J1=14.3, J2=10.3 Hz), 3.02±
3.20 (m, 1H), 3.22±3.48 (m, 2H), 3.77±4.17 (m, 3H), 4.33±
4.46 (m, 1H), 5.50 (s, 1H), 5.93 (d, 1H, J=7.3 Hz), 6.58 (d,
1H, J=7.3 Hz), 6.78 (d, 1H, J=7.3 Hz), 6.96 (t, 1H, J=7.8
Hz), 7.16±7.35 (m, 7H), 7.61±7.72 (m, 2H); IR (KBr) 3347,
2975, 2928, 1638, 1532, 1467, 1455, 1327, 1285, 1149, 1119,
1088, 870, 731, 700 cm 1; mass m/z 525 [M+H]+.
1
1H NMR (CDCl3) d 1.32 (s, 9H), 1.79±1.97 (m, 2H),
2.09 (s, 3H), 2.43 (s, 3H), 2.54±2.79 (m, 1H), 2.69 (s, 3H)
2.81±3.19 (m, 3H), 3.98±4.16 (m, 1H), 4.55±4.70 (m,
1H), 4.83±5.00 (m, 1H), 7.17±7.33 (m, 7H), 7.62±7.67
(m, 2H); mass m/z 505 [M+H]+.
N-[1(S)-Benzyl-4-(isopropyl-p-toluenesulfonyl-amino)-2
(R)-hydroxy-butyl]-3-hydroxy-2,5-dimethylbenzamide (10).
Mp 53ꢀC; H NMR (CDCl3) d 0.97 (d, 3H, J=8.8 Hz),
1
1.12 (d, 3H, J=6.7 Hz), 1.71±1.96 (m, 1H), 1.99 (s, 3H),
2.17 (s, 3H), 2.42 (s, 3H), 2.82 (dd, 1H, J1=14.3,
J2=10.5 Hz), 3.13 (dd, 1H, J1=14.3, J2=4.9 Hz), 3.22±
3.47 (m, 2H), 3.86±4.17 (m, 3H), 4.30±4.45 (m, 1H), 5.26
(s, 1H), 5.86 (d, 1H, J=7.1 Hz), 6.34 (s, 1H), 6.59 (s,
1H), 7.19±7.38 (m, 7H), 7.59±7.74 (m, 2H); IR (KBr)
3347, 2975, 2926, 1640, 1527, 1496, 1454, 1327, 1149,
1088, 867, 700 cm 1; mass m/z 539 [M+H]+.
N-[1(S)-Benzyl-4-(methyl-p-toluenesulfonyl-amino)-2(R)-
hydroxy-butyl]-3-hydroxy-2-methylbenzamide (7).
A
solution of 6 (61.5 mg, 0.122 mmol) in 1,4-dioxane (4
mL, contained 4 N HCl) was stirred for 2 h at room
temperature. After removal of the solvent in vacuo the
residue was used in the next step.
N-{1(S)-Benzyl-4-[ethyl-(p-methoxy)-benzenesulfonyl-
amino]-2(R)-hydroxy-butyl}-3-hydroxy-2-methylbenza-
mide (11). Mp 52 C; H NMR (CDCl3) d 1.10 (t, 1H,
J=7.2 Hz), 1.61±1.92 (m, 3H), 1.99 (s, 3H), 2.82 (dd,
The suspension of the above crude product, EDCI (58.8
mg, 0.307 mmol), HOBt (21.2 mg, 0.157 mmol), 3-hy-
droxy-2-methylbenzoic acid (45 mg, 0.296 mmol) and
ꢀ
1

E. Takashiro et al. / Bioorg. Med. Chem. 7 (1999) 2105±2114
2111
1H, J1=14.3, J2=10.4 Hz), 3.01±3.35 (m, 4H), 3.45±
3.59 (m, 1H), 3.86 (s, 3H), 3.96±4.09 (m, 1H), 4.31±4.48
(m, 1H), 6.00 (d, 1H, J=7.9 Hz), 6.57 (d, 1H, J=7.9
Hz), 6.76 (d, 1H, J=7.9 Hz), 6.87±6.99 (m, 3H), 7.20±
7.34 (m, 6H), 7.66±7.71 (m, 2H); IR (KBr) 3348, 2937,
1638, 1597, 1526, 1465, 1329, 1260, 1150, 1091, 1026,
911, 835, 804, 702 cm 1; mass m/z 527 [M+H]+.
for 3 h at room temperature. To this mixture was added
brine. Then the mixture was extracted (EtOAc), dried
(Na2SO4) and concentrated in vacuo. The residue was
puri®ed by PTLC (hexane:EtOAc=3:7) to a€ord 15
(33.4 mg) in 89% yield.
Mp 73ꢀC; 1H NMR (CDCl3) d 1.29 (s, 9H), 1.35 (s, 9H),
2.22 (s, 3H), 2.71±2.84 (m, 4H), 3.37±3.74 (m, 4H),
4.55±4.65 (m, 1H), 5.29±5.39 (m, 1H), 5.60±5.70 (m,
N-[1(S)-Benzyl-4-(hydroxyethyl-p-toluenesulfonyl-amino)-
2(R)-hydroxy-butyl]-3-hydroxy-2-methylbenzamide (12).
1H), 5.75±5.84 (m, 1H), 7.13±7.49 (m, 10H); IR (KBr)
1
Mp 69ꢀC; H NMR (CDCl3) d 1.60±1.91 (m, 5H), 1.99
3319, 2973, 1683, 1626, 1496, 1365, 1032, 743, 700 cm
.
1
.
(s, 3H), 2.43 (s, 3H), 2.28 (dd, 1H, J1=14.5, J2=10.7
Hz), 3.01±3.20 (m, 3H), 3.22±3.33 (m, 1H), 3.45±3.67
(m, 1H), 3.72±3.88 (m, 2H), 4.08±4.23 (m, 1H), 4.31±
4.41 (m, 1H), 6.11 (d, 1H, J=7.7 Hz), 6.58 (d, 1H,
J=7.7 Hz), 6.76 (d, 1H, J=7.7 Hz), 6.94 (t, 1H, J=7.7
Hz), 7.19±7.66 (m, 7H), 7.67±7.71 (m, 2H); IR (KBr)
3352, 2927, 1637, 1585, 1528, 1455, 1332, 1285, 1156,
1088, 911, 732, 700 cm 1; mass m/z 527 [M+H]+.
Anal. calcd for C30H43N3O5 1/2H2O: C, 67.39; H, 8.29;
N, 7.86. Found: C, 67.19; H, 8.21; N., 8.07; mass m/z
526 [M+H]+.
{4-[Acetyl-(1(S)-tert-butylcarbamoyl-2-phenyl-ethyl)-
amino]-1(S)-benzyl-2(R,S)-acetoxy-butyl}-carbamic acid
tert - butyl ester (17). A solution of H-Phe-NH-tert-
.
butyl hydrochloride 16 (1.15 g, 4.44 mmol), 1-a (1.04 g,
3.78 mmol) and NEt3 (1.16 g, 11.5 mmol) in EtOH (15
mL) was stirred for 3 h at room temperature. To this
mixture was added NaBH4 (212 mg, 5.6 mmol) at 0ꢀC
and stirred for 2 h at this temperature. The reaction was
stopped by adding CH3CO2H (0.5 mL) and diluted with
EtOAc. The mixture was washed with saturated aqu-
eous NaHCO3 and concentrated in vacuo. The residue
was diluted with EtOAc, washed (brine), dried
(Na2SO4) and concentrated in vacuo. The residue was
used in the next step without further puri®cation.
N-{1(S)-Benzyl-4-[ethyl-(2,4,6-trimethyl)-benzenesulfonyl-
amino]-2(R)-hydroxy-butyl}-3-hydroxy-2-methylbenza-
ꢀ
1
mide (13). Mp 61 C; H NMR (CDCl3) d 1.02 (t, 3H,
J=7.2 Hz), 1.68±1.89 (m, 1H), 1.96 (s, 3H), 2.27 (s, 3H),
2.59 (s, 6H), 2.74 (dd, 1H, J1=14.4, J2=10.6 Hz), 2.97±
3.10 (m, 1H), 3.11±3.32 (m, 3H), 3.38±3.45 (m, 1H),
3.50±3.60 (m, 1H), 3.82±3.88 (m, 2H), 4.14±4.37 (m,
1H), 5.95 (d, 1H, J=7.2 Hz), 6.26 (s, 1H), 6.51 (d, 1H,
J=7.6 Hz), 6.83 (d, 1H, J=8.0 Hz), 6.88±6.99 (m, 2H),
7.19±7.40 (m, 6H); IR (KBr) 3342, 2972, 2938, 1638,
1523, 1467, 1382, 1307, 1286, 1146, 1056, 906, 734, 701
cm 1; mass m/z 539 [M+H]+.
The solution of the above crude product, Ac2O (1.59 g,
15.5 mmol), NEt3 (1.61 g, 15.9 mmol) and catalytic
amount of DMAP in CH2Cl2 (10 mL) was stirred for 12
h. The reaction mixture was quenched with brine and
extracted with EtOAc. After removal of the solvent in
vacuo, the residue was puri®ed by ¯ash column chro-
matography (hexane:EtOAc:Acetone=5:4:1) to a€ord
17 (1.4 g) in 64% yield (3 steps) as a diastereomixture
(colorless oil).
{4-[Acetyl-(1(S)-tert-butylcarbamoyl-1-pheny-methyl)-
amino]-1(S)-benzyl-2(R,S)-hydroxy-butyl}-carbamic acid
tert - butyl ester (15). A solution of 1-a (141 mg, 0.512
mmol), NEt3 (130 mg, 1.28 mmol) and (S)-phenylglycine
.
tert-butyl amide hydrochloride 14 (100 mg, 0.413 mmol)
in EtOH (4 mL) was stirred for 3 h at room temperature.
The reaction mixture was cooled to 0ꢀC and to this was
added NaBH4 (22.8 mg, 0.603 mmol). It was then stirred
for 2 h at this temperature. The reaction was stopped by
adding of CH3CO2H and stirred for another 5 min. The
mixture was diluted with EtOAc and washed with satu-
rated aqueous NaHCO3. The organic extracts were dried
(Na2SO4) and concentrated in vacuo. The residue (276
mg) was used in the next step without further puri®cation.
Mp 51ꢀC; 1H NMR (CDCl3) d 1.27 (s, 9H), 1.33 (s, 9H),
1.75±1.85 (m, 2H), 2.04 (s, 3H), 2.10 (s, 3H), 2.56±2.86 (m,
2H), 3.03±3.31 (m, 4H), 4.06±4.08 (m, 1H), 4.39±4.65 (m,
1H), 4.74±4.85 (m, 2H), 6.27±6.43 (m, 1H), 7.14±7.40 (m,
10H); IR (KBr) 3325, 2973, 1740, 1712, 1631, 1526, 1366,
1
1170, 1024, 749, 700 cm
.
66.29; H, 8.10; N, 6.67; mass m/z 582 [M+H]+.
.
Anal. calcd for
C33H47N3O6 H2O: C, 66.09; H, 8.23; N, 7.01. Found: C,
The solution of the above crude product (276 mg),
Ac2O (124 mg, 1.21 mmol), NEt3 (131 mg, 1.29 mmol)
and a catalytic amount of DMAP in CH2Cl2 (3 mL) was
stirred for 1 day. The reaction was quenched with brine
and the mixture was extracted with EtOAc and dried
(Na2SO4). After removal of the solvent in vacuo, the
residue was puri®ed by PTLC (hexane:EtOAc=4:6) to
give diacetate (182 mg) in 78% yield.1H NMR (CDCl3)
d 1.10±1.57 (m, 2H), 1.33 (s, 9H), 1.37 (s, 9H), 2.00 (s,
3H), 2.20 (s, 3H), 2.53±2.72 (m, 2H), 3.22±3.46 (m, 3H),
3.95±4.03 (m, 1H), 4.50±4.68 (m, 1H), 5.34±5.94 (m,
2H), 7.08±7.48 (m, 10H); mass m/z 568 [M+H]+.
{4-[Acetyl-(1(S)-tert-butylcarbamoyl-2-phenyl-ethyl)-
amino]-1(S)-benzyl-2(R)-hydroxy-butyl}-3-hydroxy-2-
methylbenzamide (18). A solution of 17 (308 mg, 0.529
mmol) in 1,4-dioxane (5 mL, contained 4 N HCl) was
stirred for 2 h at room temperature. After removal of the
solvent in vacuo, the residue was used in the next step.
.
The solution of the above crude product, EDCI Cl (223
mg, 1.16 mmol), HOBt (70 mg, 0.46 mmol), 3-hydroxy-
2-methylbenzoic acid (158 mg, 1.04 mmol) and NEt3
(113 mg, 1.12 mmol) in DMF (8 mL) was stirred for 1
day. The reaction was stopped by the addition of brine
and the mixture was extracted with EtOAc. The com-
bined organic extracts were washed (brine), dried
The solution of the above diacetate (44 mg) and aqu-
eous NaOH (1 N, 0.3 mL) in MeOH (4 mL) was stirred

2112
E. Takashiro et al. / Bioorg. Med. Chem. 7 (1999) 2105±2114
(Na2SO4) and concentrated in vacuo. The residue was
used in the next step without further puri®cation.
{4-[Acetyl-(1(S)-tert-butylcarbamoyl-1-pheny-methy)]-
amino}-1(S)-benzyl-2(R,S)-hydroxy-butyl}-3-hydroxy-2-
ꢀ
1
methylbenzamide (23). Mp 51 C; H NMR (CDCl3) d
1.31 (s, 9H), 1.70±1.89 (m, 1H), 1.91 (s, 3H), 1.93±2.17
(m, 2H), 2.20 (s, 3H), 2.47±2.94 (m, 3H), 3.56±3.63 (m,
2H), 4.09±4.27 (m, 1H), 5.82 (d, 1H, J=13.8 Hz), 6.02±
6.17 (m, 1H), 6.44±6.52 (m, 1H), 6.75±6.77 (m, 1H),
The solution of the above crude product and aqueous
NaOH (1 N, 1.5 mL) in MeOH (4 mL) was stirred for 3
h at room temperature. To this mixture was added 5%
aqueous KHSO4 and extracted with EtOAc. The
organic extracts were washed with brine, dried
(Na2SO4) and concentrated in vacuo. The residue was
puri®ed by PTLC (EtOAc:acetone=8:2) to a€ord 18
(130 mg) in 43% yield (3 steps).
6.85±6.91 (m, 1H), 7.10±7.54 (m, 10H); IR (KBr) 3309,
1
1633, 1520, 1454, 1365, 1283, 1223, 1080, 701 cm
mass m/z 560 [M+H]+.
;
{4 - [(1(S) - tert - Butylcarbamoyl - 1 - tert - butyl - methy)] -
amino}-1(S)-benzyl-2(R)-hydroxy-butyl}-3-hydroxy-2-
ꢀ
1
Mp 55 C; H NMR (CDCl3) d 1.26 (s, 9H), 1.42 (br,
1H), 1.65±1.69 (m, 1H), 1.93 (d, 1H, J=8.7 Hz), 1.98 (s,
3H), 2.11 (s, 3H), 2.73 (dd, 1H, J1=14.0, J2=10.7 Hz),
2.95 (dd, 1H, J1=14.1, J2=4.5 Hz), 3.21 (d, 2H, J=7.7
Hz), 3.40±3.46 (m, 2H), 3.63±3.73 (m, 1H), 4.15±4.19
(m, 1H), 4.64±4.66 (m, 1H), 6.00 (d, 1H, J=7.7 Hz),
6.49 (d, 1H, J=8.4 Hz), 6.81 (d, 1H, J=8.2 Hz), 6.91 (t,
1H, J=7.8 Hz), 7.13±7.32 (m, 12H); IR (KBr) 3308,
2965, 2930, 1635, 1522, 1454, 1365, 1283, 1223, 1175,
1079, 834, 701 cm 1; mass m/z 574 [M+H]+.
methylbenzamide (24). Mp 47ꢀC; H NMR (CDCl3) d
1
1.00 (s, 9H), 1.04±1.36 (m, 2H), 1.37 (s, 9H), 1.64±1.68
(m, 1H), 1.94 (s, 3H), 2.79±2.88 (m, 2H), 3.14 (dd, 1H,
J1=14.6, J2=4.0 Hz), 3.87 (d, 1H, J=5.5 Hz), 4.40±
4.45 (m, 1H), 5.93±6.00 (m, 2H), 6.55 (d, 1H, J=7.8
Hz), 6.77 (d, 1H, J=7.8 Hz), 6.93 (d, 1H, J=7.8 Hz),
7.19±7.33 (m, 8H); IR (KBr) 3308, 2962, 1644, 1522,
1455, 1365, 1283, 1224, 1081, 700 cm 1; mass m/z 498
[M+H]+.
{4-[(1(S)-tert-Butylcarbamoyl-2-phenyl-ethyl)-amino]-1(S)-
benzyl-2(R,S)-hydroxy-butyl}-3-hydroxy-2-methylbenz-
amide (19). H NMR (CDCl3) d 1.20 (s, 9H), 1.68±1.76
{4-[Acetyl-(1(R)-tert-butylcarbamoyl-2-phenyl-ethyl)-
amino]-1(S)-benzyl-2(R)-hydrꢀoxy-butyl}-3-hydroxy-2-
1
1
methylbenzamide (25). Mp 98 C; H NMR (CDCl3) d
(m, 1H), 1.94 (d, 1H, J=2.9 Hz), 2.29 (s, 3H), 2.43±3.00
(m, 7H), 3.17±3.45 (m, 1H), 3.66±3.79 (m, 1H), 4.23±
4.31 (m, 1H), 6.49±6.62 (m, 1H), 6.71±6.79 (m, 1H),
6.92±7.00 (m, 1H), 7.19±7.33 (m, 13H); mass m/z 532
[M+H]+.
1.25 (s, 9H), 1.40±1.75 (m, 2H), 1.91 (s, 3H), 2.07 (s,
3H), 2.65±2.79 (m, 1H), 2.89±3.01 (m, 1H), 3.06±3.74
(m, 6H), 4.16±4.27 (m, 1H), 6.34 (d, 1H, J=8.6 Hz),
6.48 (d, 1H, J=7.5 Hz), 6.76 (t, 1H, J=7.7 Hz), 6.84 (t,
1H, J=7.7 Hz), 7.10±7.38 (m, 12H); IR (KBr) 3306,
2966, 1635, 1526, 1454, 1365, 1284, 1223, 1175, 1080,
750, 701 cm 1; mass m/z 574 [M+H]+.
{4-[Methy-(1(S)-tert-butylcarbamoyl-2-phenyl-ethyl)-
amino]-1(S)-benzyl-2(R)-hydroxy-butyl}-3-hydroxy-2-
methylbenzamide (20). Mp 75ꢀC; H NMR (CDCl3) d
{4-[Propionyl-(1(S)-tert-butylcarbamoyl-2-phenyl-ethyl)-
amino]-1(S)-benzyl-2(R)-hydroxy-butyl}-3-hydroxy-2-
1
1.19 (s, 9H), 1.72±1.86 (m, 1H), 1.90 (s, 3H), 2.46 (s,
3H), 2.47±2.58 (m, 2H), 2.70±3.00 (m, 4H), 3.04±3.20
(m, 3H), 3.62±3.79 (m, 1H), 3.87±3.90 (m, 1H), 4.26±
4.37 (m, 1H), 6.03 (d, 1H, J=9.2 Hz), 6.51 (d, 1H,
J=7.4 Hz), 6.65±6.80 (m, 1H), 6.87±7.07 (m, 1H), 7.14±
7.75 (m, 12H); IR (KBr) 3296, 2965, 2858, 1739, 1643,
1521, 1455, 1285, 1223, 1032, 749, 700 cm 1; mass m/z
546 [M+H]+.
methylbenzamide (26). Mp 98ꢀC; H NMR (CDCl3) d
1
1.11 (dd, 3H, J1=14.4, J2=7.3 Hz), 1.26 (s, 9H), 1.98 (s,
3H), 2.28±2.42 (m, 2H), 2.73±3.00 (m, 2H), 3.01±3.23 (m,
2H), 3.41±3.75 (m, 3H), 4.21±4.32 (m, 1H), 4.69±4.73
(m, 1H), 5.84±6.08 (m, 1H), 6.50±6.62 (m, 1H), 6.77±
6.83 (m, 1H), 6.93±6.99 (m, 1H), 7.14±7.34 (m, 13H); IR
(KBr) 3315, 2966, 1637, 1527, 1455, 1365, 1283, 1222,
1071, 750, 701cm 1; mass m/z 588 [M+H]+.
{4-[Benzyl-(1(S)-tert-butylcarbamoyl-2-phenyl-ethyl)-
amino]-1(S)-benzyl-2(R,S)-hydroxy-butyl}-3-hydroxy-2-
{4-[Acetyl-(1(S)-tert-butylcarbamoyl-2-(p-chloro)-phenyl-
ethyl) - amino] - 1(S) - benzyl - 2(R,S) - hydroxy - butyl} - 3 -
methylbenzamide (21). Mp 75ꢀC; H NMR (CDCl3) d
1
hydroxy-2-methylbenzamide (27). Mp 91ꢀC; H NMR
1
1.19 (s, 9H), 1.63±1.80 (m, 2H), 1.90 (s, 3H), 2.86±3.34
(m, 7H), 3.54±3.79 (m, 2H), 3.90±4.15 (m, 2H), 4.77 (br,
1H), 5.99±6.02 (m, 1H), 6.45±6.51 (m, 1H), 6.73±6.78
(m, 1H), 6.88±6.91 (m, 1H), 7.15±7.53 (m, 15H) ; IR
(CD3OD) d 1.26 (s, 9H), 1.65±1.90 (m, 1H), 1.97 (s, 3H),
2.12 (s, 3H), 2.36±2.50 (m, 2H), 2.56±2.70 (m, 1H),
2.83±3.29 (m, 3H), 3.47±3.76 (m, 4H), 4.16±4.45 (m,
1H), 6.56 (d, 1H, J=7.5 Hz), 6.75 (d, 1H, J=7.1 Hz),
6.90±6.96 (m, 1H), 7.02±7.75 (m, 12H); IR (KBr) 3306,
2965, 2932, 1739, 1631, 1527, 1455, 1283, 1225, 1170,
1015, 701 cm 1; mass m/z 609 [M+H]+.
(KBr) 3309, 2962, 1645, 1585, 1518, 1454, 1284, 1076,
1
.
745, 700 cm . Anal. calcd for C39H47N3O4 H2O: C,
73.21; H, 7.72; N, 6.57. Found: C, 73.60; H, 7.58; N,
6.40.; mass m/z 622 [M+H]+.
{4-[(1(S)-tert-Butylcarbamoyl-1-pheny-methyl)-amino]-
1(S)-benzyl-2(R)-hydroxy-butyl}-3-hydroxy-2-methylbenz-
{4- [Acetyl - (1(S) -tert - butylcarbamoyl - 2-(p- hydroxy) -
phenyl-ethyl)-amino]-1(S)-benzyl-2(R)-hydroxy-butyl}-3-
ꢀ
ꢀ
1
1
amide (22). Mp 48 C; H NMR (CDCl3) d 1.24 (s, 9H),
1.85±2.05 (m, 3H), 2.65±2.73 (m, 2H), 3.22±3.74 (m,
4H), 4.77±4.93 (m, 4H), 6.51±7.05 (m, 4H), 7.18±7.89
(m, 11H); IR (KBr) 3311, 1739, 1633, 1584, 1530, 1455,
1283, 1080, 701 cm 1; mass m/z 519 [M+H]+.
hydroxy-2-methylbenzamide (28). Mp 109 C; H NMR
(CDCl3) d 1.26 (s, 9H), 1.58±1.91 (m, 2H), 2.02 (s, 3H),
2.26 (s, 3H), 2.49±2.65 (m, 3H), 2.83±3.16 (m, 4H),
3.24±3.36 (m, 1H), 3.62±3.79 (m, 3H), 4.60±4.77 (m,
1H), 4.89±4.92 (m, 1H), 5.96 (d, 1H, J=9.3 Hz), 6.53±

E. Takashiro et al. / Bioorg. Med. Chem. 7 (1999) 2105±2114
2113
9.78 (m, 3H), 6.84±7.00 (m, 3H), 7.12±7.44 (m, 9H); IR
(KBr) 3301, 2965, 2931, 1740, 1643, 1517, 1455, 1367,
1227, 1032, 834, 751, 701 cm 1; mass m/z 632 [M+H]+.
N, 6.47. Found: C, 70.20; H, 6.85; N, 6.24; mass m/z
622 [M+H]+.
{4-[Acetyl-(1(S)-(m-methyl)-benzylcarbamoyl-2-phenyl-
ethyl) - amino] - 1(S) - benzyl - 2(R,S) - hydroxy - butyl} - 3 -
{4-[Acetyl-(1(S)-tert-butylcarbamoyl-2-(p-benzyloxy)-phenyl-
ethyl)-amino]-1(S)-benzyl-2(R)-hydroxy-butyl}-3-hydroxy-2-
ꢀ
1
hydroxy-2-methylbenzamide (34). Mp 111 C; H NMR
(CDCl3) d 1.70±1.98 (m, 2H), 1.94 (s, 3H), 2.08 (s, 3H),
2.23 (s, 3H), 2.60 (dd, 1H, J1=14.4, J2=10.6 Hz), 2.81
(dd, 1H, J1=14.4, J2=4.3 Hz), 2.92±2.98 (m, 1H), 3.25±
3.64 (m, 5H), 4.09±4.38 (m, 3H), 4.74 (br, 1H), 5.92 (d,
1H, J=7.2 Hz), 6.46 (t, 1H, J=7.2 Hz), 6.69±6.77 (m,
1H), 6.81±7.00 (m, 3H), 7.03±7.47 (m, 13H); IR (KBr)
3297, 2927, 1638, 1525, 1455, 1284, 1173, 1075, 834,
749, 700 cm 1; mass m/z 622 [M+H]+.
methylbenzamide (29). Mp 104ꢀC; H NMR (CDCl3) d
1
1.26 (s, 9H), 1.52±1.99 (m, 2H), 2.02 (s, 3H), 2.14 (s,
3H), 2.57±3.16 (m, 5H), 3.44±3.48 (m, 1H), 3.66±3.74 (m,
2H), 4.24 (br, 1H), 4.62 (br, 1H), 4.97 (s, 2H), 5.71±5.86
(m, 1H), 6.51±6.58 (m, 1H), 6.70±6.80 (m, 2H), 6.85±
6.97 (m, 2H), 7.05±7.14 (m, 2H), 7.16±7.40 (m, 11H); IR
(KBr) 3304, 2964, 2931, 1739, 1625, 1512, 1454, 1364,
1283, 1120, 1080, 832, 699 cm 1, Anal. calcd for
.
C41H49N3O6 3/2H2O: C, 69.67; H, 7.41; N, 5.94. Found:
C, 69.87; H, 7.06; N, 5.67; mass m/z 680 [M+H]+.
{4-[Acetyl-(1(S)-(p-methyl)-benzylcarbamoyl-2-phenyl-
ethyl) - amino] - 1(S) - benzyl - 2(R,S) - hydroxy - butyl} - 3 -
1
{4-[Acetyl-(1(S)-tert-butylcarbamoyl-2-(ꢀ-naphtyl)-ethyl)-
amino]-1(S)-benzyl-2(R)-hydroxy-butyl}-3-hydroxy-2-
hydroxy-2-methylbenzamide (35). Mp 126ꢀC; H NMR
(CDCl3) d 1.64±1.88 (m, 2H), 1.94 (s, 3H), 2.11 (s, 3H),
2.33 (s, 3H), 2.57±2.67 (m, 1H), 2.75±2.86 (m, 1H),
3.20±3.75 (m, 5H), 4.11±4.37 (m, 4H), 4.80 (br, 1H),
6.07 (d, 1H, J=8.3 Hz), 6.48 (dd, 1H, J1=11.6, J2=7.6
Hz), 6.75 (t, 1H, J=9.3 Hz), 6.89 (dd, 1H, J1=15.0,
J2=7.6 Hz), 7.00±7.09 (m, 5H), 7.12±7.43 (m, 11H); IR
(KBr) 3296, 1640, 1584, 1536, 1454, 1284, 1174, 1074,
1032, 747, 700 cm 1; mass m/z 622 [M+H]+.
methylbenzamide (30). Mp 45ꢀC; H NMR (CDCl3) d
1
1.26 (s, 9H), 1.41±1.92 (m, 2H), 1.92 (s 3H), 2.08 (s, 3H),
2.56±2.74 (m, 3H), 3.36±3.70 (m, 6H), 4.80 (br, 1H),
5.90 (br, 1H), 6.43 (br, 1H), 6.83 (br, 1H), 7.09±7.43 (m,
10H), 7.51±7.84 (m, 5H); IR (KBr) 3307, 2965, 1635,
1
1522, 1455, 1365, 1284, 1223, 1174, 1080, 748, 701 cm
.
.
Anal. calcd for C38H45N3O5 3/2H2O: C, 70.13; H, 7.43;
N, 6.46. Found: C, 70.26; H, 7.09; N, 6.08; mass m/z
624 [M+H]+.
{4-[Acetyl-(1(S)-cyclohexylcarbamoyl-2-phenyl-ethyl)-
amino]-1(S)-benzyl-2(R)-hydroxy-butyl}-3-hydroxy-2-
1
{4-[Acetyl-(1(S)-ethylcarbamoyl-2-phenyl-ethyl)-amino]-1(S)-
benzyl-2(R)-hydroxy-butyl}-3-hydroxy-2-methylbenzamide
(31). Mp 175ꢀC; 1H NMR (CDCl3) d 1.05 (t, 3H,
J=7.2 Hz), 1.62±1.82 (m, 2H), 1.98 (s, 3H), 2.11 (s, 3H),
2.73 (dd, 1H, J1=14.2, J2=10.6 Hz), 2.94 (dd, 1H,
J1=14.5, J2=4.7 Hz), 3.12±3.35 (m, 4H), 3.37±3.49 (m,
2H), 3.60±3.69 (m, 1H), 4.23±4.28 (m, 1H), 4.62±4.69
(m, 1H), 5.98 (d, 1H, J=7.8 Hz), 6.51 (t, 1H, J=7.6
Hz), 6.80 (d, 1H, J=7.6 Hz), 6.92 (t, 1H, J=7.6 Hz),
7.04±7.38 (m, 12H); IR (KBr) 3308, 2930, 1639, 1536,
1454, 1375, 1284, 1174, 1032, 750, 701 cm 1; mass m/z
546 [M+H]+.
methylbenzamide (36). Mp 112ꢀC; H NMR (CDCl3) d
1.00±1.95 (m, 12H), 1.99 (s, 3H), 2.15 (s, 3H), 2.73±2.81
(m, 1H), 2.92±3.04 (m, 1H), 3.22±3.30 (m, 2H), 3.41±
3.57 (m, 1H), 3.63±3.76 (m, 2H), 4.12±4.35 (m, 1H),
4.56±4.74 (m, 1H), 6.13 (d, 1H, J=8.2 Hz), 6.54 (dd,
1H, J1=11.8, J2=7.5 Hz), 6.81 (t, 1H, J=9.3 Hz), 6.95
(dd, 1H, J1=13.2, J2=7.8 Hz), 7.17±7.41 (m, 13H); IR
(KBr) 3291, 2932, 1637, 1531, 1453, 1284, 1175, 750,
1
.
700 cm . Anal. calcd for C36H45N3O5 H2O: C, 69.93;
H, 7.67; N, 6.80. Found: C, 70.19; H, 7.42; N, 6.49;
mass m/z 600 [M+H]+.
{4-[Acetyl-(1(S)-pyrrolidylcarbonyl-2-phenyl-ethyl)-amino]-
1(S)-benzyl-2(R)-hydroxy-butyl}-3-hydroxy-2-methylbenz-
{4-[Acetyl-(1(S)-benzylcarbamoyl-2-phenyl-ethyl)-amino]-
1(S)-benzyl-2(R,S)-hydroxy-butyl}-3-hydroxy-2-methylbenz-
amide (37). Mp 115ꢀC; H NMR (CDCl3) d 1.50±2.12
1
amide (32). Mp 58ꢀC; H NMR (CDCl3) d 1.24±1.30
(m, 6H), 1.97 (s, 3H), 2.10 (s, 3H), 2.75±3.11 (m, 5H),
3.16±3.79 (m, 4H), 4.02±4.15 (m, 1H), 4.31±4.79 (m,
3H), 5.16±5.59 (m, 1H), 6.52 (t, 1H, J=7.8 Hz), 6.79 (d,
1H, J=7.6 Hz), 6.87 (t, 1H, J=7.6 Hz), 7.13±7.72 (m,
1
(m 1H), 1.70±1.96 (m, 1H), 2.01 (s, 3H), 2.13 (s, 3H),
2.56±2.70 (m, 1H), 2.80±2.99 (m, 2H), 3.24±3.75 (m,
5H), 4.19±4.44 (m, 3H), 4.70±4.81 (m, 1H), 5.60±5.89
(m, 2H), 6.53 (dd, 1H, J1=14.0, J2=7.3 Hz), 6.79 (dd,
1H, J1=11.9, J2=7.9 Hz), 6.93±7.00 (m, 1H), 7.04±7.42
(m, 15H); IR (KBr) 3291, 1636, 1527, 1454, 1284, 1175,
1079, 1030, 749 cm 1; mass m/z 608 [M+H]+.
11H); IR (KBr) 3303, 2931, 2877, 1628, 1453, 1283,
1
1081, 1032, 751, 701 cm
.
C, 68.12; H, 7.08; N, 7.24; mass m/z 594 [M+Na]+.
.
C34H41N3O5 3/2H2O: C, 68.21; H, 7.41; N, 7.01. Found:
Anal. calcd for
{4-[Acetyl-(1(S)-(o-methyl)-benzylcarbamoyl-2-phenyl-
ethyl) - amino] - 1(S) - benzyl - 2(R,S) - hydroxy - butyl} - 3 -
{4-[Acetyl-(1(S)-tert-butylcarbamoyl-2-phenyl-ethyl)-amino]-
1(S)-(4-phenyl)-benzyl-2(R)-hydroxy-butyl}-3-hydroxy-2-
hydroxy-2-methylbenzamide (33). Mp 55ꢀC; H NMR
methyl-benzamide (38). Mp 106ꢀC; H NMR (CDCl3) d
1
1
(CDCl3) d 1.50±1.90 (m, 1H), 1.92 (s, 3H), 2.04 (s, 3H),
2.15 (s, 3H), 2.57 (dd, 1H, J1=14.1, J2=10.5 Hz), 2.75±
2.82 (m, 1H), 3.23±3.63 (m, 6H), 4.08±4.39 (m, 4H), 4.76
(br, 1H), 6.00 (d, 1H, J=7.9 Hz), 6.21±6.70 (m, 1H),
1.26 (s, 9H), 1.33±1.49 (m, 1H), 1.66±1.79 (m, 1H), 1.99
(s, 3H), 2.11 (s, 3H), 2.75±2.86 (m, 1H), 2.94±3.10 (m,
1H), 3.21 (d, 2H, J=7.8 Hz), 3.40±3.47 (m, 2H), 3.61±
3.68 (m, 1H), 3.72±3.78 (m, 1H), 4.22 (br, 1H), 4.66 (br,
1H), 6.08 (d, 1H, J=7.9 Hz), 6.79 (d, 1H, J=7.3 Hz),
6.89 (t, 1H, J=7.8 Hz), 7.13±7.35 (m, 11H), 7.38±7.44
(m, 2H), 7.47±7.57 (m, 4H); IR (KBr) 3309, 2965, 1631,
6.71±7.00 (m, 2H), 7.04±7.45 (m, 15H); IR (KBr) 3296,
1
1638, 1527, 1455, 1284, 1175, 1074, 745, 701 cm
.
.
Anal. calcd for C38H43N3O5 3/2H2O: C, 70.24; H, 7.29;

2114
E. Takashiro et al. / Bioorg. Med. Chem. 7 (1999) 2105±2114
1
1521, 1454, 1365, 1283, 1223, 1077, 1039, 762, 699 cm
.
Yu, B.; Erickson, J. W. Bioorg. Med. Chem. Lett. 1995, 5,
1707.
22. Kempf, D. J.; Flentge, C. A.; Wideburg, N. E.; Saldivar,
A.; Vasavanonda, S.; Norbeck, D. W. Bioorg. Med. Chem.
Lett. 1995, 5, 2725.
.
Anal. calcd for C40H47N3O5 3/2H2O: C, 70.98; H, 7.44;
N, 6.21. Found : C, 71.24; H, 7.09; N, 5.95; mass m/z
650 [M+H]+.
23. Kalish, V. J.; Tatlock, J. H.; Davies II, J. F.; Kaldor, S. W.;
Dressmen, B. A.; Reich, S.; Pino, M.; Nyugen, D.; Appelt, K.;
Musick, L.; Wu, B.-W. Bioorg. Med. Chem. Lett. 1995, 5, 727.
24. For the reduction of a-amino ketones, see: Dondoni, A.,
Perrone, D. Synthesis 1993, 1162 and references cited therein.
25. For the assignment of the absolute stereochemistry based
on the vicinal coupling, see: Futagawa, S.; Inui, T.; Shiba, T.
Bull. Chem. Soc. Jpn. 1973, 46, 3308.
26. Rich, D. H.; Sun, E. T. O. J. Med. Chem. 1980, 23, 27.
27. Cardillo, G.; Orena, M.; Sandri, S.; Tomasini, C. Tetra-
hedron 1985, 41, 163.
28. Houbion, J. A.; Miles, J. A.; Paton, J. A. Org. Prep. Proc.
Int. 1979, 11, 27.
29. For sulfonamide bearing compounds, see: Kim, E. E.;
Baker, C. T.; Dwyer, M. D.; Murcko, M. A.; Rao, B. G.;
Tung, R. D.; Navia, M. A. J. Am. Chem. Soc. 1995, 117, 1181.
30. Vazquez, M. L.; Bryant, M. L.; Clare, M. C.; DeCres-
cenzo, G. A.; Doherty, E. M.; Freskos, J. N.; Getman, D. P.;
Houseman, K. A.; Julien, J. A.; Kocan, G. P.; Mueller, R. A.;
Shieh, H.-S.; Stallings, W. C.; Stegeman, R. A.; Talley, J. J. J.
Med. Chem. 1995, 38, 581.
31. Baker, C. T.; Salituro, F. G.; Court, J. J.; Deininger, D.
D.; Kim, E. E.; Li, B.; Novak, P. M.; Rao, B. G.; Pazhani-
samy, S.; Schairer, W. C.; Tung, R. D. Bioorg. Med. Chem.
Lett. 1998, 8, 3631.
32. Salituro, F. G.; Baker, C. T.; Court, J. J.; Deininger, D.
D.; Kim, E. E.; Li, B.; Novak, P. M.; Rao, B. G.; Pazhani-
samy, S.; Porter, M. D.; Schairer, W. C.; Tung, R. D. Bioorg.
Med. Chem. Lett. 1998, 8, 3637.
33. For the chemistry of hydroxyethylamine, see: Shiabata, N.;
Katoh, T.; Terashima, S. Tetrahedron Lett. 1997, 38, 619 and
references cited therein.
{4-[Acetyl-(1(S)-tert-butylcarbamoyl-2-phenyl-ethyl)-amino]-
1(S)-ꢀ-napthylmethy-2(R)-hydroxy-butyl}-3-hydroxy-2-
methyl-benzamide (39). Mp 115ꢀC; H NMR (CDCl3) d
1
1.25 (s, 9H), 1.43±1.52 (m,1H), 1.70±1.79 (m, 1H), 1.91
(s, 3H), 2.10 (s, 3H), 2.90±3.00 (m, 2H), 3.08±3.14 (m,
2H), 3.21 (d, 2H, J=7.6 Hz), 3.35±3.48 (m, 2H), 3.67±
3.76 (m, 1H), 4.24 (br, 1H), 4.68 (br, 1H), 6.08 (d, 1H,
J=7.8 Hz), 6.46 (d, 1H, J=7.5 Hz), 6.70±6.89 (m, 3H),
7.11±7.26 (m, 5H), 7.33±7.46 (m, 3H), 7.63±7.82 (m,
4H); IR (KBr) 3308, 2964, 1634, 1523, 1454, 1365, 1284,
1
1223, 1079, 750, 701 cm
.
C, 69.74; H, 7.10; N, 6.00.; mass m/z 624 [M+H]+.
.
C38H45N3O5 2H2O: C, 69.17; H, 7.49; N, 6.37. Found :
Anal. calcd for
References and Notes
1. Mitsuya, H.; Yarchoan, R.; Broder, S. Science 1990, 249, 1533.
2. Yarchoan, R.; Mitsuya, H.; Broder, S. Trends in Pharmacol.
Sci. 1993, 14, 196 and references cited therein.
3. Hellen, C. U. T.; Krausslich, H-G.; Wimmer, E. Biochem-
istry 1989, 28, 9881.
4. For excellent reviews on HIV-1 protease inhibitors, see: Wlo-
dawer, A.; Erickson, J. W. Annu. Rev. Biochem. 1993, 62, 543.
5. West, M. L.; Fairlie, D. P. Trends in Pharmacol. Sci. 1995, 16,
67.
6. Meek, T. D. J. Enzyme Inhibition 1992, 6, 65.
7. Barry, M.; Gibbons, S.; Back, D.; Mulcahy, F. Clin. Phar-
macokinet. 1997, 32, 194.
8. Lunney, E. A. Med. Chem. Res. 1998, 8, 352.
9. Patick, A. K.; Potts, K. E. Clinic. Microb. Rev. 1998, 11, 614.
10. Boden, D.; Markowitz, M. Antimicrob. Agents Chemother.
1998, 42, 2775.
11. Mimoto, T.; Imai, J.; Tanaka, S.; Hattori, N.; Takahashi,
O.; Kisanuki, S.; Nagano, Y.; Shintani, M.; Hayashi, H.;
Sakikawa, H.; Akaji, K.; Kiso, Y. Chem. Pharm. Bull. 1991,
39, 2465.
34. Kaldor et al. reported that o-methyl-N-methylbenzamide
exhibited a preference for an orientation in which the amide
carbonyl and benzene ring were not coplanar. In this case, the
ortho-methyl group might a€ected the conformation of sulfo-
namide, see: Kaldor, S. W.; Hammond, M.; Dressmen, B. A.;
Fritz, J. E.; Crowell, T. A.; Hermann, R. A. Bioorg. Med.
Chem. Lett. 1994, 4, 1385.
35. For the conformation of N,N-dialkyl-benzenesulfona-
mides, see: 29 and references cited therein.
36. For acyclic symmetric inhibitors, see: Housur, M. V., Bhat,
T. N., Kempf, D. J., Baldwin, E. T., Liu, B., Gulnik, S.,
Wideburg, N. E., Norbeck. D. W., Appelt, K., Erickson, J. W.
J. Am. Chem. Soc. 1994, 116, 847.
12. Mimoto, T.; Imai, J.; Tanaka, S.; Hattori, N.; Kisanuki,
S.; Akaji, K.; Kiso, Y. Chem. Pharm. Bull. 1991, 39, 3088.
13. Mimoto, T.; Imai, J.; Kisanuki, S.; Enomoto, H.; Hattori,
N.; Akaji, K.; Kiso, Y. Chem. Pharm. Bull. 1992, 40, 2251.
14. Sakurai, M.; Higashida, S.; Sugano, M.; Komai, T.; Yagi,
R.; Ozawa, Y.; Handa, H.; Nishigaki, T.; Yabe, Y. Bioorg.
Med. Chem. 1994, 2, 807.
15. Komai, T.; Higashida, S.; Sakurai, M.; Nitta, T.; Kasuya,
A.; Miyamoto, S.; Yagi, R.; Ozawa, Y.; Handa, H.; Mohri,
H.; Yasuoka, A.; Oka, S.; Nishigaki, T.; Kimura, S.; Shimada,
K.; Yabe, Y. Bioorg. Med. Chem. 1996, 4, 1365.
16. Takashiro, E.; Watanabe, T.; Nitta, T.; Kasuya, A.;
Miyamoto, S.; Ozawa, Y.; Yagi, R.; Nishigaki, T.; Shibayama,
T.; Nakagawa, A.; Iwamoto, A.; Yabe, Y. Bioorg. Med. Chem.
1998, 6, 595.
17. Spaltenstein, A.; Leban, J. J.; Huang, J. J.; Reinhardt, K. R;
Viveros, O. H.; Sigafoos, J.; Crouch, R. Tetrahedron. Lett.
1996, 37, 1343.
18. Kim, B. M.; Guare, J. P.; Hani®n, C. M.; Arford-Bickersta€,
D. J.; Vacca, J. P.; Ball, R. G. Tetrahedron. Lett. 1994, 35, 5153.
19. Ohba, T.; Ikeda, E.; Takei, H. Bioorg. Med. Chem. Lett.
1996, 6, 1875.
37. Greer, J.; Erickson; J. W.; Baldwin, J. J.; Varney, M. D. J.
Med. Chem. 1994, 37, 1035.
38. For carbohydrate based symmetric inhibitors, see: Zuc-
carello, G.; Bouzide, A.; Kvarnstrom, I.; Niklasson, G.;
Svensson, S. C. T.; Brisander, M.; Danielsson, H.; Nillroth,
U.; Karlen, A.; Hallberg, A.; Classon, B.; Samuelsson, B. J
Org. Chem. 1998, 63, 4898.
39. Alterman, M.; Bjorsne, M.; Muhlman, A.; Classon, B.;
Kvarnstrom, I.; Danielson, H.; Markgren, P-O.; Nillroth, U.;
Unge, T.; Hallberg, A.; Samuelsson, B. J Med. Chem. 1998,
41, 3782.
40. For cyclic compounds with C2 symmetric structure, see:
Rodgers, J. D.; Lam, P. Y.-S.; Johnson, B. L.; Wang, H.; Ko,
S. S.; Seitz, S. P.; Trainor, G. L.; Anderson, P. S.; Kalbe, R.
M.; Bacheler, L. T.; Cordova, B.; Garber, S.; Reid, C.;
Wright, M. R.; Chang, C.-H.; Erickson-Viitanen, S. Chemistry
& Biology 1998, 5, 597 and references cited therein.
41. Compounds 19, 21, 23, 27, 32, 33, 34, 35 and 36 could not be
separated by PTLC. They were assayed as diastereomixtures.
20. Hanson, G. J.; Lindberg, T. J. Org. Chem. 1985, 50, 5399.
21. For the studies of P2 benzamides, see: Randad, R. S.;
Lubkowska, L. L.; Bhat, T. N.; Munshi, S. M.; Gulnik, S. V.;