Design and synthesis of non-peptide Ras CAAX mimetics as potent farnesyltransferase inhibitors

Article abstract of DOI:10.1021/jm950414g

Cysteine farnesylation of the ras oncogene product Ras is required for its transforming activity and is catalyzed by farnesyltransferase (FTase). The Ras carboxyl terminal tetrapeptide CAAX (C is cysteine, A is any aliphatic amino acid, X is methionine or serine) is the minimum sequence for FTase recognition. We report here the design, synthesis, and biological characterization of Ras CAAX non-peptide mimetics in which the cysteine is linked through a reduced pseudopeptide bond to 4-amino-3'-carboxybiphenyl. These non-peptide mimetics are potent inhibitors of FTase (IC₅₀ = 40 nM for the most potent inhibitor) and are highly selective for FTase over GGTase I (geranylgeranyltransferase I). They are not substrates for farnesylation, do not have peptidic features, and have no hydrolyzable bonds. Structure- activity studies reveal the importance of the position of the carboxylic acid on the aryl ring as well as the reduction of the cysteine amide bond. Substitution at the 2-position of 4-amino-3'-carboxybiphenyl increases inhibitory potency, while the removal of the carboxylic acid results in a 10- fold loss of inhibitory activity.

Full text of DOI:10.1021/jm950414g

J . Med. Chem. 1996, 39, 217-223
217
Design a n d Syn th esis of Non -P ep tid e Ra s CAAX Mim etics a s P oten t
F a r n esyltr a n sfer a se In h ibitor s
Yimin Qian,† Andreas Vogt,‡ Sa¨ıd M. Sebti,*,‡ and Andrew D. Hamilton*,†
Department of Chemistry, Faculty of Arts and Science, and Department of Pharmacology, School of Medicine,
University of Pittsburgh, Pittsburgh, Pennsylvania 15260
Received J une 7, 1995X
Cysteine farnesylation of the ras oncogene product Ras is required for its transforming activity
and is catalyzed by farnesyltransferase (FTase). The Ras carboxyl terminal tetrapeptide CAAX
(C is cysteine, A is any aliphatic amino acid, X is methionine or serine) is the minimum sequence
for FTase recognition. We report here the design, synthesis, and biological characterization of
Ras CAAX non-peptide mimetics in which the cysteine is linked through a reduced pseudopep-
tide bond to 4-amino-3′-carboxybiphenyl. These non-peptide mimetics are potent inhibitors of
FTase (IC50 ) 40 nM for the most potent inhibitor) and are highly selective for FTase over
GGTase I (geranylgeranyltransferase I). They are not substrates for farnesylation, do not have
peptidic features, and have no hydrolyzable bonds. Structure-activity studies reveal the
importance of the position of the carboxylic acid on the aryl ring as well as the reduction of the
cysteine amide bond. Substitution at the 2-position of 4-amino-3′-carboxybiphenyl increases
inhibitory potency, while the removal of the carboxylic acid results in a 10-fold loss of inhibitory
activity.
In tr od u ction
Although Ras and other cellular proteins are farne-
sylated, most prenylated proteins are geranylgerany-
lated.11 At least two classes of enzymes catalyzing the
addition of a geranylgeranyl group to proteins have been
identified in mammalian cells. One is geranylgeranyl-
transferase type-I (GGTase I), which modifies proteins
with a carboxyl terminal sequence CAAX where X is
leucine or isoleucine.12 The other is geranylgeranyl-
transferase type-II (GGTase II), which catalyzes the
modification of proteins with the carboxyl terminal
sequences CC or CXC (C is cysteine).13 As protein
geranylgeranylation is more prevalent than farnesyla-
tion, inhibitors with selectivity for FTase over GGTase
are expected to exhibit fewer side effects.
The discovery that CAAX tetrapeptides can potently
inhibit FTase in vitro has played a key role in the design
of FTase inhibitors.14 However, these tetrapeptides are
totally inactive in whole cells due to poor cellular uptake
and metabolic instability. We15 and others16 have
previously reported CAAX peptidomimetics and
pseudopeptides as FTase inhibitors. Although these
peptidomimetics showed potent FTase inhibition, they
still retained several peptide characteristics, such as one
or more amide bonds and an unchanged methionine
residue. A highly desirable goal in this area has been
to construct inhibitors without peptidic features. In this
paper, we report the design, synthesis and biological
activity of a series of non-peptide CAAX mimetics.
The mammalian ras genes encode a family of 21 kDa,
guanine nucleotide binding proteins called Ras.1 Ras
uses an on/off cycle between its GTP (active) and a GDP
(inactive) bound state to regulate the transduction of
biological information from the plasma membrane to the
nucleus. Ras serves as a relay between growth factor
receptor tyrosine kinases and the serine/thereonine
kinase network that triggers MAP (mitogen-activated
protein) kinase and causes proliferation and differentia-
tion.2 Single amino acid substitutions at positions 12,
13, or 61 lock Ras in its GTP-bound form and result in
uncontrolled growth. These mutations are found in 50%
of colon and 95% of pancreatic human carcinomas.3
Thus, blocking oncogenic Ras may provide new targets
for drug design in cancer chemotherapy.4, 10
The crucial role played by Ras in signal transduction
is absolutely dependent on its plasma membrane as-
sociation.4,5 Ras is synthesized as a cytosolic precursor
and is post-translationally modified by a lipid in order
to anchor itself in the membrane.6 The first and
obligatory step in this modification is the attachment
of a farnesyl group to the cysteine residue of the Ras
carboxyl terminal sequence CAAX, a reaction catalyzed
by farnesyltransferase (FTase).7 This farnesylation
reaction is followed by peptidase removal of the AAX
tripeptide and carboxymethylation of the remaining
farnesylated cysteine.8 FTase is a heterodimeric met-
alloenzyme composed of R and â subunits with molec-
ular weights of 49 and 46 kDa, respectively.9 Since
farnesylation is the required step for Ras membrane
localization and subsequent transforming activity, in-
hibition of FTase provides an attractive strategy for
developing new anti-cancer drugs.10
Design
A tetrapeptide such as Cys-Val-Ile-Met (1) can inhibit
FTase in vitro (IC50 ) 200 nM) but has no effect on
whole cells due presumably to poor membrane perme-
ability and sensitivity to proteolysis. In order to en-
hance cellular uptake and improve stability toward
proteases, we replaced the central two amino acids in
Cys-Val-Ile-Met by 3-(aminomethyl)benzoic acid and
4-aminobenzoic acid.15 These spacers provided a hy-
drophobic link between cysteine and methionine resi-
dues. The most potent inhibitor in this series, Cys-4-
* To whom correspondence should be addressed.
† Department of Chemistry.
‡ Department of Pharmacology.
X Abstract published in Advance ACS Abstracts, December 1, 1995.
0022-2623/96/1839-0217$12.00/0 © 1996 American Chemical Society

218 J ournal of Medicinal Chemistry, 1996, Vol. 39, No. 1
Qian et al.
more, the hydrophobic biphenyl residue in 4 mimics the
side chains of tripeptide Val-Ile-Met in 1 which provide
a large hydrophobic area.
Syn th esis
The basic approach used for the preparation of these
compounds is illustrated in Scheme 1 with the synthesis
of compound 4. 1-Bromo-4-nitrobenzene was coupled
to (3-methylphenyl)boronic acid17 through a modified
Suzuki18 coupling to afford compound 14.19 Compound
14 was oxidized to carboxylic acid 15 which was
converted to the acid chloride and reacted with lithium
tert-butoxide20 to give the tert-butyl ester 16. Reduction
of 16 by hydrogenation and subsequent reductive ami-
nation21 of the resulting amine with N-Boc-S-tritylcys-
teinal 1716d,22 gave the fully protected derivative 18,
which was deprotected by trifluoroacetic acid in the
presence of triethylsilane.23 Compound 4 was purified
by reverse phase HPLC and isolated as its trifluoroac-
etate salt by lyophilization.
F igu r e 1. Structures of compounds 3-10.
aminobenzoyl-Met 2 (IC50 ) 150 nM), retained significant
Our previous results had shown that linking cysteine
and methionine through a 3-(aminomethyl)benzoic acid
spacer led to moderate inhibition of FTase.15a In an
attempt to reproduce the same distance dependence in
the biphenyl series we have prepared compounds 11 and
12.
structural similarity to the original CAAX sequence,
particularly with respect to the two amide bonds and
the key cysteine and methionine residues. Our goal in
this work was to replace one part of this structure, the
methionine residue, by an extended hydrophobic sub-
unit. To this end we designed a series of 4-amino-3′-
carboxybiphenyl derivatives as mimics of the Val-Ile-
Met tripeptide but with restricted conformational
flexibility. We also reduced the cysteine amide bond to
provide completely non-peptidic Ras CAAX mimetics.
The structures of the primary CAAX mimetics in this
study are shown in Figure 1.
Although the structures of these designed non-peptide
CAAX mimetics are significantly different from that of
the tetrapeptide Cys-Val-Ile-Met, the functional groups
of free amine, thiol, and carboxylic acid are retained.
Our early reported results suggested that an extended
rather than a turn conformation of tetrapeptide 1 might
be responsible for its inhibitory activity.15 Therefore,
we calculated an energy-minimized conformation of
compound 4 by using the AMBER force field within the
MacroModel program in the absence of solvent and
compared it with the extended conformation of tet-
rapeptide 1. Molecular modeling (Figure 2) shows that
the designed non-peptide mimetic 4 has the functional
groups arranged very similarly to those of the tetrapep-
tide 1 (SH to COOH distance about 10.5 Å). Further-
The synthesis of 11 and 12 is described in Scheme 2.
Compound 19 was made from 3-methyl-3′-carboxybi-
phenyl (itself formed from aryl-aryl coupling of methyl
3-bromobenzoate with (3-methylphenyl)boronic acid fol-
lowed by a sponification) via the same method as
compound 16. Bromination of 19 followed by reaction
with sodium azide gave 20 which was catalytically
hydrogenated to give the corresponding amine. Reac-
tion of Boc-trityl-protected cysteine with this amine
through the mixed anhydride method gave 21, while
compound 22 was made by reductive amination with
Boc-trityl-protected cysteinal.
Biologica l Eva lu a tion
The ability of these synthetic compounds to inhibit
FTase and GGTase I in vitro was investigated by using
partially purified FTase and GGTase I from human
Burkitt lymphoma (Daudi) cells.24 Enzymes were in-
cubated with [3H]FPP and recombinant H-Ras-CVLS
F igu r e 2. Energy-minimized structures of CVIM and 4 in extended conformations.

Potent Farnesyltransferase Inhibitors
J ournal of Medicinal Chemistry, 1996, Vol. 39, No. 1 219
Sch em e 1. Representative Synthesis of FTase Inhibitorsa
a
Reagents: (a) Pd(OAc)2; (b) KMnO4, pyridine/H2O; (c) (1) (COCl)2, (2) tert-butyl alcohol, n-BuLi; (d) (1) H2, Pd/C, (2) N-Boc-S-
tritylcysteinal 17, (3) NaB(CN)H3; (e) TFA, Et3SiH.
Sch em e 2. Synthesis of Compounds 11 and 12a
a
Reagents: (a) (1) NBS, (2) NaN3; (b) (1) H2, Pd/BaSO4, (2) N-Boc-S-tritylcysteine, isobutyl chloroformate, Et3N; (c) TFA, Et3SiH; (d)
(1) H2, Pd/BaSO4, (2) N-Boc-S-tritylcysteinal, NaB(CN)H3.
(FTase) or [3H]GGPP and H-Ras-CVLL (GGTase I) in
the presence of different concentrations of inhibitors.
After incubation for 30 min at 37 °C, the reaction was
stopped and filtered on glass fiber filters to separate free
from incorporated label, as described earlier.9 The
activity of the inhibitors is reported in Table 1 as IC50
values, the concentration at which FTase or GGTase I
activity was inhibited by 50%. Some of the inhibitors
were further characterized for their ability to serve as
substrates for farnesylation by thin layer chromatog-
raphy.24
where no methionine residue is present and the tri-
peptide AAX is completely replaced by a simple hydro-
phobic moiety. The most potent inhibitor in the CAAX
series is Cys-Ile-Phe-Met14 with an IC50 value of 30 nM.
Peptidomimetic inhibitor 10 is as potent as CIFM
despite the large difference between their structures.
These results confirm our hydrophobic strategy for AAX
replacement.
As seen in Table 1, the precise positioning of the free
carboxylate is important for potent inhibition. Com-
pounds 3, 4, and 5 differ only in their positioning of the
carboxylic acid on the phenyl ring. Inhibitor 4 has the
carboxylic acid positioned in correspondence with the
dipeptide mimetic 2, while this positioning in 3 and 5
The published sequence dependence studies on FTase
have shown a strong preference for methionine in the
terminal position of CAAX. Here we describe inhibitors

220 J ournal of Medicinal Chemistry, 1996, Vol. 39, No. 1
Qian et al.
Ta ble 1. In Vitro Activity of CAAX Mimetic Inhibitors of
FTase
enzyme active site and the methoxy group, correspond-
ing to the valine or isoleucine binding pocket with
CVIM. It is also possible that the increased potency is
due to the restricted flexibility of the biphenyl.
inhibitors FTase IC50 (nM) GGTase I IC50 (nM) substrate
3
4
5
6
7
8
9
10
11
12
543 (3)a
114 (10)
4 575 (4)
13 500 (2)
1 070 (3)
710 (3)
917 (3)
40 (6)
100 000 (2)
11 000 (1)
140 000 (2)a
100 000 (6)
>100 000 (2)
100 000 (2)
>100 000 (3)
>100 000 (3)
>100 000 (3)
43 600 (5)
ndb
no
no
nd
no
no
no
nd
no
nd
In contrast to our dipeptide mimetic in which cysteine
and methionine were linked through 3-(aminomethyl)-
benzoic acid,15 the biphenyl derivatives of compound 11
and 12 have extremely poor activity toward FTase even
though they keep the similar distance dependence when
compared with compound 4. This result suggested that
the pharmacophore of (R)-1,2-diamino-3-mercaptopro-
pane must be linked to a well-defined hydrophobic
residue in order to obtain a potent inhibition activity.
As reported by others, the incorporation of an aro-
matic amino acid into the A2 position of CA1A2X (such
as CIFM) prevents the tetrapeptide from serving as a
substrate for farnesylation.14a Table 1 shows that the
designed non-peptide CAAX mimetics (such as com-
pound 4) are not substrates for farnesylation. This lack
of farnesylation by FTase may be due to the inhibitor
binding to the enzyme in a conformation that does not
permit farnesyl transfer to the thiol group.
>100 000 (3)
35 000 (2)
a
The number inside the bracket stands for experimental times.
nd stands for not determined.
b
is either closer to or farther from the N-terminus. The
effect of this changing position on inhibition potency is
significant (5-fold difference between 4 and 3, 40-fold
difference between 4 and 5). This result is consistent
with our early reported study in which cysteine and
methionine residues are linked through 4-aminobenzoic
acid or 3-aminobenzoic acid.15b
We next investigated the influence of different sub-
stituents at the 3′-position of compound 4 on FTase
inhibitory potency. Methylation of the carboxylic acid,
as in 9, or replacement of the carboxylic acid by methyl
or hydrogen, as in 8 and 7, resulted in inhibitors with
10-fold less activity (around 1 µM) than 4. This suggests
that in the active site of the enzyme there is a positively
charged residue which interacts with the negatively
charged carboxylate from the inhibitor. However, this
electrostatic interaction requires the carboxylate at the
3′-position of the aromatic ring. The different activity
between 7 and 5 (4-fold) suggested that the 4′-position
of the aromatic ring is close to a hydrophobic region in
the enzyme.
Since GGTase I is an enzyme closely related to FTase,
and geranylgeranylation is a more common protein
prenylation reaction than farnesylation,11 it is critical
for FTase inhibitors to be selective. The results from
Table 1 showed that our compounds are poor inhibitors
of GGTase I. The selectivity for FTase over GGTase I
with compound 10 is about 1100-fold. In the tetrapep-
tide CAAX series, the X position directs farnesylation
or geranylgeranylation. Despite removing all features
of the CAAX C-terminal residue (Met or Ser) from our
peptidomimetics, the high selectivity against GGTase I
is retained. This suggests there is a larger difference
than previously thought between the active site of FTase
and that of GGTase I.
Probably the most striking result comes from reduc-
tion of the amide bond. For tetrapeptide CIFM, it has
been shown by others that reduction of the N-terminal
peptide bond results in loss of selectivity for FTase over
GGTase I, while the reduction of the C-terminal peptide
bond leads to a reduction in FTase inhibitory potency.16d
Here we observe an increase in selectivity for FTase over
GGTase I when the cysteine amide bond is reduced in
our biphenyl-derived inhibitors (compare 4 to 6). We
also show that the C-terminal amide bond is not
necessary for potent inhibition activity since there is no
amide bond in compound 10. In our earlier paper,24
reduction of the cysteine amide bond of compound 2 was
shown to have little effect on the activity. Here we
observed a 100-fold difference in inhibition activity
between 4 and 6. One reason for this enhanced activity
on reduction of the amide bond is the increased flex-
ibility of the (R)-2-amino-3-mercaptopropyl unit and the
consequent accessibility of alternative binding confor-
mations.
Con clu sion s
We have synthesized true non-peptide Ras CAAX
mimetics which have no amide bonds and lack any
peptidic features of the tripeptide AAX. These mimetics
are potent inhibitors of FTase and are highly selective
against GGTase I. The structure-activity relationship
showed that a key feature for FTase recognition is the
separation of a (R)-1,2-diamino-3-mercaptopropyl group
and a carboxylic acid by a hydrophobic scaffold. The
rigidity of our scaffold provides important information
about the active site of FTase. These Ras CAAX
mimetics have several desirable features for further
drug design. They have small molecular weights, lack
peptidic features, are highly potent and specific, and are
not metabolically inactivated. We are currently inves-
tigating their ability to antagonize oncogenic Ras sig-
naling and their antitumor efficacy in animal models
with human tumor xenografts.
Exp er im en ta l Section
We then focused on increasing hydrophobicity and
restricting conformational flexibility of the biphenyl
spacer by placing substituents at the 2-position of the
aryl ring. The substitution of hydrogen by a methoxy
group at the 2-position of the left hand aromatic ring
increased the inhibitory activity by 3-fold. Thus, 2-meth-
oxy-4-[N-[2(R)-amino-3-mercaptopropyl]amino]-3′-car-
boxybiphenyl has the most potent activity (IC50 ) 20-
60 nM in six independent experiments). This suggested
there might be a hydrophobic interaction between the
1H and 13C NMR spectrum were recorded on a Bruker AM-
300 spectrometer. Chemical shifts were reported in δ (ppm)
relative to tetramethylsilane. All coupling constants were
described in hertz. Elemental analyses were performed by
Atlantic Microlab Inc., GA. Optical rotations were measured
on
a Perkin-Elmer 241 polarimeter. Concentrations are
expressed in g/mL. Flash column chromatography was per-
formed on silica gel (40-63 µm) under a pressure of about 4
psi. Solvents were obtained from commercial suppliers and
purified as follows: tetrahydrofuran and ether were distilled

Potent Farnesyltransferase Inhibitors
J ournal of Medicinal Chemistry, 1996, Vol. 39, No. 1 221
from sodium benzophenone ketyl; methylene chloride was
distilled over lithium aluminum hydride. Preparative HPLC
was performed using a Waters 600 E controller and a Waters
490 E Multi-Wavelength UV detector with a 25 × 10 cm Delta-
Pak C-18 300 Å cartridge column inside a Waters 25 × 10 cm
Radial Compression Module. Analytical HPLC was performed
using a Rainin HP controller and a Rainin UV-C detector with
a Rainin 250 × 4.6 mm 5 µm Microsorb C-18 column. High-
resolution mass spectra (HRMS) and low-resolution mass
spectra (LRMS) were performed on a Varian MAT CH-5 and
VG 7070 mass spectrometer. The purity of all the synthesized
inhibitors was more than 98% as indicated by analytical
HPLC.
residue was purified by flash column chromatography (1.5:1
) hexane:ethyl acetate) to give a white foam (7.40 g, 91%):
mp 59-60 °C dec; 1H NMR (CDCl3) δ 7.41 (m, 6H), 7.20-7.31
(m, 9H), 5.13 (d, J ) 8.9 Hz, 1H), 4.76 (br s, 1H), 3.64 (s, 3H),
3.15 (s, 3H), 2.56 (dd, J ) 4.7 and 12.1 Hz, 1H), 2.39 (dd, J )
7.8 and 12.1 Hz, 1H), 1.43 (s, 9H); 13C NMR (CDCl3) δ 170.7,
154.9, 144.2, 129.3, 127.6, 126.4, 79.3, 66.4, 61.2, 49.5, 33.8,
31.8, 28.1. This carboxamide (2.02 g, 4.0 mmol) was dissolved
in 30 mL of ether and cooled to -10 °C. Lithium aluminum
hydride (167 mg, 4.40 mmol) was added, and the mixture was
stirred for 15 min under nitrogen. Then 40 mL of 0.5 N HCl
was added, and the solution was extracted with ether. The
ether layer was washed with 0.5 N HCl and dried. The
evaporation of solvents gave a white foam (1.80 g) which was
used for further reaction without purification. The 1H NMR
spectrum of this compound was complex. The percentage of
the aldehyde was about 65-70%, which was calculated ac-
cording to the integration of the sharp singlet (δ 9.17) and the
trityl peak (δ 7.40, m, 6H; 7.28, m, 9H). Lowering the
temperature to -45 °C did not improve the aldehyde percent-
age.
4-Nitr o-3′-m eth ylbip h en yl (14). To a mixture of 4-ni-
trobenzene (3.0 g, 14.8 mmol) and (3-methylphenyl)boronic
acid (2.06 g, 15.1 mmol) in 35 mL of acetone and 40 mL of
water was added K2CO3‚1.5H2O (5.93 g, 37.5 mmol) and Pd-
(OAc)2 (101 mg, 0.50 mmol). The deep black mixture was
refluxed for 6 h and then cooled. The mixture was extracted
with ether, and the organic layer was passed through a layer
of Celite. The pale yellow solution was dried and evaporated
to dryness. The residue was recrystallized from hot methanol
4-[N-[2(R)-[(ter t-Bu toxyca r bon yl)a m in o]-3-[(tr ip h en yl-
m et h yl)t h io]p r op yl]a m in o]-3′-(ter t-b u t oxyca r b on yl)b i-
p h en yl (18). Compound 16 (768 mg, 2.56 mmol) was dis-
solved in THF. A catalytic amount of 10% Pd on activated
carbon (78 mg) was added. The mixture was hydrogenated
(40 psi) for 30 min. The black mixture was passed through a
thin layer of Celite, and the pale yellow solution was evapo-
rated. The residue was dissolved in 10 mL of methanol. To
this solution was added 0.5 mL of acetic acid and a solution of
the same equivalents of aldehyde 17 (according to the 1H NMR
determination) in 6 mL of methanol. Sodium cyanoborohy-
dride (241 mg, 3.84 mmol, 1.5 equiv) was added, and the
mixture was stirred overnight. After evaporation of solvents,
the residue was extracted with ethyl acetate and concentrated
sodium bicarbonate. The organic layer was dried and evapo-
rated. The residue was purified by flash column chromatog-
raphy (3.5:1 ) hexane:THF) to give a white foam (1.09 g,
1
to give pale yellow crystals (2.68 g, 85%): mp 59-60 °C; H
NMR (CDCl3) δ 8.26 (d, J ) 8.7 Hz, 2H), 7.70 (d, J ) 8.7 Hz,
2H), 7.41 (m, 3H), 7.26 (d, J ) 7.1 Hz, 1H), 2.43 (s, 1H); 13C
NMR (CDCl3) δ 147.6, 146.8, 138.8, 138.6, 129.6, 128.9, 128.0,
127.6, 124.4, 123.9, 21.4; LRMS (EI) for C13H11NO2 213 (M+,
intensity 100); HRMS (EI) calcd 213.0789, obsd 213.0778.
4-Nitr o-3′-ca r boxybip h en yl (15). Compound 14 (2.31 g,
10 mmol) was suspended in a mixture of 10 mL of pyridine
and 20 mL of water. The mixture was heated to reflux, and
then KMnO4 (7.9 g, 50 mmol) was added in portions. This
mixture was refluxed for 1 h and then stirred at room
temperature for 4 h. The hot mixture was filtered, and the
black solid was washed with hot water. The filtrate was
acidified with 6 N HCl. The precipitate was collected and dried
(2.16 g, 89%): mp 265 °C dec; 1H NMR (DMSO-d6) δ 11.1-
11.4 (br s, COOH), 8.32 (d, J ) 8.7 Hz, 2H), 8.27 (s, 1H), 8.02
(m, 4H), 7.66 (t, J ) 7.8 Hz, 1H); 13C NMR (DMSO-d6) δ 167.1,
148.9, 145.6, 138.2, 131.8, 131.5, 129.6 (br), 127.9, 124.2 (br);
LRMS (EI) for C13H9O4N 243 (M+, 100), 152 (60); HRMS (EI)
calcd 243.0531, obsd 243.0544. Anal. (C13H9NO4) C, H, N.
4-Nitr o-3′-(ter t-bu toxyca r bon yl)bip h en yl (16). To a
solution of 15 (1.215 g, 5 mmol) in 30 mL of methylene chloride
was added oxalyl chloride (0.65 mL, 7.45 mmol) and one drop
of DMF. The mixture was stirred until no further bubbling
was observed. The clear solution was evaporated to dryness
to give the crude acid chloride. To another flask containing
7.0 mL of tert-butyl alcohol was added n-BuLi (1.8 M in
hexane, 2.8 mL, 5.04 mmol) under a water bath. The turbid
solution was stirred for 5 min at room temperature, and then
the above acid chloride in 20 mL of THF was added through
a dropping funnel. The mixture was stirred overnight before
the solvents were evaporated. The residue was dissolved into
methylene chloride and washed with 0.5 N NaOH. The
organic layer was dried over MgSO4 and evaporated. The
residue was recrystallized from methanol to give pale yellow
crystals (851 mg, 57%): mp 110.5-111.0 °C; 1H NMR (CDCl3)
δ 8.32 (d, J ) 7.8 Hz, 2H), 8.24 (s, 1H), 8.06 (d, J ) 7.7 Hz,
1H), 7.77 (m, 3H), 7.56 (t, J ) 7.7 Hz, 1H), 1.63 (s, 9H); 13C
NMR (CDCl3) δ 165.1, 147.1, 146.5, 138.7, 132.8, 131.0, 129.6,
129.0, 128.2, 127.8, 124.0, 81.4, 28.0; LRMS (EI) for C17H17O4N
299 (M+, 20), 243 (70), 266 (30), 152 (25); HRMS (EI) calcd
299.1157, obsd 299.1192. Anal. (C17H17NO4) C, H, N.
61%): mp 75.0-76.0 °C dec; [R]25 ) -2.13 (c ) 0.01, CH3-
D
1
COOC2H5); H NMR (CDCl3) δ 8.14 (s, 1H), 7.86 (d, J ) 7.7
Hz, 1H), 7.66 (d, J ) 7.8 Hz, 1H), 7.40 (m, 9H), 7.22-7.30 (m,
9H), 6.61 (d, J ) 8.5 Hz, 2H), 4.58 (d, J ) 7.1 Hz, 1H), 3.83
(br m, 2H, Cys R proton and the amine), 3.12 (br m, 2H, CH2N),
2.48 (br m, 2H, CH2S), 1.60 (s, 9H), 1.44 (s, 9H); 13C NMR
(CDCl3) δ 165.9, 155.6, 147.5, 144.4, 141.2, 132.3, 130.1, 129.5,
129.2, 128.5, 128.0, 127.9, 127.1, 126.8, 112.9, 80.9, 79.7, 67.0,
49.4, 47.1, 34.3, 28.3, 28.2 (expect 14 aromatic C, observed 13).
Anal. (C44H48N2O4S‚1.2H2O) C, H, N, S.
4-[N-[2(R)-Am in o-3-m er ca p top r op yl]a m in o]-3′-ca r box-
ybip h en yl (4). Compound 18 (600 mg, 0.85 mmol) was
dissolved in 2 mL of TFA and 2 mL of methylene chloride.
Triethylsilane was added dropwise to the deep brown mixture
until the brown color had disappeared. The mixture was then
kept at room temperature for 1 h. Then solvents were
evaporated, and the residue was dried under vacuum. The
solid was triturated with 30 mL of ether and 3 mL of 3 N HCl
in ether. The white precipitate was filtered and washed with
ether to obtain a crude product (270 mg, 84%). This crude
product was dissolved into 30 mL of dilute HCl solution (0.01
N) and was lyophilized. Analytical HPLC showed the purity
to be 95%: mp 105-106 °C dec; [R]25 ) +13.16 (c ) 0.01 in
D
1
methanol); H NMR (CD3OD) δ 8.18 (s, 1H), 7.89 (d, J ) 7.7
Hz, 1H), 7.78 (d, J ) 7.3 Hz, 1H), 7.49 (m, 3H), 6.82 (d, 8.5
Hz, 2H), 3.56 (m, 2H, CHN and CH2N), 3.42 (dd, J ) 8.9 and
15.2 Hz, 1H, CH2N), 2.94 (dd, J ) 4.9 and 14.6 Hz, 1H, CH2S),
2.83 (dd, J ) 5.6 and 14.6 Hz, 1H, CH2S); 13C NMR (D2O and
CD3OD) δ 171.1, 147.1, 141.4, 131.9, 130.9, 130.1, 128.8, 128.5,
127.0, 115.2, 53.2, 45.4, 25.0; LRMS (FAB, glycerol) for
C16H18N2O2S (M + 1) 303. Anal. (C16H18N2O2S‚2HCl) C, H,
N, S. Further purification by preparative HPLC (Waters C-18,
40% acetonitrile, 60% water, 0.1% TFA, 40 min gradient) gave
product 4 (120 mg) with a purity over 99.9%.
N-Boc-S-tr itylcystein a l (17). To a solution of N-Boc-S-
tritylcysteine (7.44 g, 16 mmol) in 85 mL of methylene chloride
was added triethylamine (2.22 ml, 16 mmoL) and N,O-
dimethylhydroxylamine hydrochloride (1.57 g, 16.1 mmol).
This mixture was cooled in an ice bath, and 1-(3-(dimethyl-
amino)propyl)-3-ethylcarbodiimide hydrochloride (EDCI, 3.08
g, 16.0 mmol) and HOBT (2.17 g, 16 mmol) were added. The
mixture was stirred at 0 °C for 1 h and at room temperature
for a further 10 h. The mixture was extracted with methylene
chloride and 0.5 N HCl. The organic layer was washed
consecutively with 0.5 N HCl, concentrated NaHCO3, and
brine. The organic layer was dried and evaporated. The
3-Meth yl-3′-(ter t-bu toxyca r bon yl)bip h en yl (19). The
coupling of (3-methylphenyl)boronic acid with 3-bromobenzoic
acid methyl ester gave a 3-methyl-3′-(methoxycarbonyl)biphen-
yl (79% yield), which was then hydrolyzed to give a 3-methyl-

222 J ournal of Medicinal Chemistry, 1996, Vol. 39, No. 1
Qian et al.
3′-carboxybiphenyl (97% yield). Compound 19 (an oil) was
prepared from this acid using the same method as for the
preparation of compound 16 (65% yield): 1H NMR (CDCl3) δ
8.21 (s, 1H), 7.95 (d, J ) 7.8 Hz, 1H), 7.73 (d, J ) 6.6 Hz, 1H),
7.46 (m, 3H), 7.35 (t, J ) 7.5 Hz, 1H), 7.20 (d, J ) 7.4 Hz,
1H), 2.43 (s, 3H), 1.62 (s, 9H); 13C NMR (CDCl3) δ 165.6, 141.3,
140.2, 138.3, 132.4, 140.0, 128.7, 128.5, 128.3, 128.0, 127.9,
124.2, 81.0, 28.1, 21.4; LRMS (EI) for C18H20O2 268 (M+, 35),
212 (100), 195 (20); HRMS (EI) calcd 268.1463, obsd 268.1458.
3-Azid o-3′-(ter t-bu toxyca r bon yl)bip h en yl (20). Com-
pound 19 (2.18 g, 8.13 mmol) and N-bromosuccinimide (1.70
g, 9.50 mmol) was suspended in 60 mL of CCl4. Dibenzoyl
peroxide (20 mg) was added, and the mixture was refluxed
for 1.5 h. After the solid was removed, the filtrate was washed
with concentrated sodium bicarbonate and dried over sodium
sulfate. 1H NMR showed the crude material contained 70%
of monobrominated and 30% of dibrominated product. This
material was dissolved in 20 mL of DMSO, and sodium azide
(3.70 g, 57 mmol) was added. The mixture was heated to 80
°C for 4 h before being poured into a mixture of methylene
chloride and water. The organic layer was dried and evapo-
rated. The residue was purified by flash column chromatog-
raphy (5% of ethyl acetate in hexane) to give 20 (2.14 g, 78%,
two steps) as a colorless oil: 1H NMR (CDCl3) δ 8.22 (s, 1H),
8.00 (d, J ) 7.7 Hz, 1H), 7.76 (d, J ) 8.2 Hz, 1H), 7.58 (m,
2H), 7.50 (m, 2H), 7.33 (d, J ) 7.6 Hz, 1H), 4.43 (s, 2H), 1.62
(s, 9H); 13C NMR (CDCl3) δ 165.2, 140.5, 140.3, 135.8, 132.3,
130.7, 129.1, 128.5, 128.2, 127.8, 127.1, 126.7, 126.6, 80.9, 54.3,
27.8.
cyanoborohydride (193 mg, 1.50 equiv) was added to the above
solution, and the mixture was stirred at room temperature
overnight. After workup, the crude residue was purified by
flash column chromatography (1:1 ) ethyl acetate:hexane) to
give a white foam (602 mg, 41%): mp 66-68 °C dec; 1H NMR
(CDCl3) δ 8.21 (s, 1H), 7.96 (d, J ) 7.7 Hz, 1H), 7.73 (d, J )
8.0 Hz, 1H), 7.37-7.51 (m, 10H), 7.15-7.31 (m, 10H), 4.69 (br
d, 1H), 3.75 (br s, 3H, PhCH2N and Cys R H), 2.68 (dd, J )
6.0 and 12.3 Hz, 1H, CH2S), 2.56 (dd, J ) 5.5 and 12.3 Hz,
1H, CH2S), 2.47 (m, 1H, CH2N), 2.35 (m, 1H, CH2N), 1.62 (s,
9H), 1.42 (s, 9H), 1.12 (br s, 1H, NH).
3-[[N-[2(R)-Am in o-3-m er ca p top r op yl]a m in o]m eth yl]-
3′-ca r boxybip h en yl (12). Compound 22 (480 mg, 0.672
mmol) was dissolved in a mixture of 2 mL of methylene
chloride and 2 mL of trifluoroacetic acid. Several drops of
triethylsilane were added until the deep brown color had
disappeared. This mixture was kept at room temperature for
1.5 h, then the solvents were evaporated, and the residue was
dried under vacuum. The solid residue was dissolved in 1 mL
of acetic acid and 2 mL of HCl (1.7 M) in acetic acid. Finally
5 mL of HCl (3 M) in ether and 10 mL of ether were added.
The white precipitate was washed with dry ether and dried
to give a hydrochloride salt (215 mg, 81%): 1H NMR (D2O) δ
8.16 (s, 1H), 7.94 (d, J ) 7.7 Hz, 1H), 7.85 (d, J ) 7.7 Hz, 1H),
7.70 (s, 2H), 7.55 (t, J ) 7.8 Hz, 2H), 7.46 (d, J ) 7.5 Hz, 1H),
4.36 (s, 2H, PhCH2), 3.81 (m, 1H, Cys R H), 3.57 (dd, J ) 5.7
and 13.7 Hz, 1H, CH2N), 3.44 (dd, J ) 6.5 and 13.7 Hz, 1H,
CH2N), 2.97 (dd, J ) 5.3 and 15.1 Hz, 1H, CH2S), 2.86 (dd, J
) 5.9 and 15.1 Hz, 1H, CH2S).
2-Met h oxy-4-n it r o-3′-(ter t-b u t oxyca r b on yl)b ip h en yl
(23). The coupling of 1-bromo-2-methoxy-4-nitrobenzene with
(3-methylphenyl)boronic acid followed by oxidation gave the
2-methoxy-4-nitro-3′-carboxybiphenyl. The reaction of the acid
chloride with lithium tert-butoxide gave 23 (three steps,
35%): mp 88.0-88.5 °C; 1H NMR (CDCl3) δ 8.13 (s, 1H), 8.00
(d, J ) 7.7 Hz, 1H), 7.89 (d, J ) 8.3 Hz, 1H), 7.81 (s, 1H), 7.69
N-Boc-S-t r it ylcyst ein yl-3-(a m in om et h yl)-3′-(ter t-b u -
toxyca r bon yl)bip h en yl (21). Compound 20 (0.75 g, 2.43
mmol) was dissolved in 30 mL of methanol. A catalytic
amount of 5% palladium on barium sulfate (0.30 g) was added.
The mixture was hydrogenated at 1 atm for 5 h. The catalyst
was removed by filtration, and the methanol was evaporated.
This residue was dissolved in 40 mL of methylene chloride.
N-Boc-S-tritylcysteine (1.12 g, 2.43 mmol) was added at 0 °C
followed by EDCI (1 equiv) and HOBT (1 equiv). The mixture
was stirred for 24 h. After workup and evaporation of solvents,
the residue was purified by flash column chromatography
(hexane:ethyl acetate ) 3.2:1) to give 21 (570 mg, 44%): mp
84-86 °C; 1H NMR (CDCl3) δ 8.17 (s, 1H), 7.95 (d, J ) 7.7 Hz,
1H), 7.70 (d, J ) 7.7 Hz, 1H), 7.50-7.30 (m, 9H), 7.30-7.10
(m, 11H), 6.44 (br, 1H), 4.86 (br, 1H), 4.45 (d, J ) 4.0 Hz, 2H,
CH2Ph), 3.87 (br, 1H, Cys R H), 2.75 (dd, J ) 7.2 and 12.8 Hz,
1H, CH2S), 2.55 (dd, J ) 5.3 and 12.8 Hz, 1H, CH2S), 1.62 (s,
9H), 1.36 (s, 9H). Anal. (C45H48N2O5S) C, H, N, S.
Cyst ein yl-3-(a m in om et h yl)-3′-ca r b oxyb ip h en yl (11).
Compound 21 (150 mg) was deprotected using the same
method as for the preparation of compound 4. Final purifica-
tion by preparative HPLC gave 11 as a white solid (42 mg,
46%): mp 88-89 °C dec; 1H NMR (CD3OD) δ 8.26 (s, 1H), 8.01
(d, J ) 7.7 Hz, 1H), 7.86 (d, J ) 7.7 Hz, 1H), 7.64 (s, 1H), 7.56
(m, 2H), 7.46 (t, J ) 7.6 Hz, 1H), 7.35 (d, J ) 7.6 Hz, 1H),
4.53 (s, 2H), 4.00 (t, J ) 5.2 Hz, 1H, Cys R H), 3.06 (dd, J )
14.6 and 5.2 Hz, 1H, CH2S), 2.97 (dd, J ) 14.6 and 6.8 Hz,
1H, CH2S); LRMS (EI) for C17H18N2O3S 331 (M + 1, 8), 281
(100), 226 (75). Anal. (C17H18N2O3S‚HCl‚0.6H2O) C, H, N.
3-[[N -[2(R )-[(t er t -B u t o x y c a r b o n y l)a m in o ]-3-[(t r i-
p h en ylm eth yl)th io]p r op yl]a m in o]m eth yl]-3′-(ter t-bu tox-
yca r bon yl)bip h en yl (22). The azide 20 (900 mg, 2.91 mmol)
was dissolved in 20 mL of methanol. A catalytic amount of
5% Pd on barium sulfate (90 mg) was added. This mixture
was hydrogenated at 1 atm overnight. The catalyst was
removed, and the methanol was evaporated. The remaining
residue was dissolved in a mixture of 0.5 N HCl (20 mL) and
ether (20 mL). The aqueous phase was neutralized with 1 N
NaOH and extracted into methylene chloride. After the
evaporation of solvents, a viscous oil was obtained (600 mg,
73%): 1H NMR (CDCl3) δ 8.22 (s, 1H), 7.97 (d, J ) 7.8 Hz,
1H), 7.75 (d, J ) 7.7 Hz, 1H), 7.57 (s, 1H), 7.50 (m, 2H), 7.43
(t, J ) 7.7 Hz, 1H), 7.33 (d, J ) 7.4 Hz, 1H), 3.96 (s, 2H), 1.62
(s, 9H), 1.46 (br s, 2H, NH2). This amine (581 mg, 2.05 mmol)
was dissolved in 10 mL of methanol and 0.5 mL of acetic acid
before N-Boc-S-tritylcysteinal (1 equiv, according to 1H NMR
determination of the aldehyde percentage) was added. Sodium
(d, J ) 7.7 Hz, 1H), 7.48 (m, 2H), 3.90 (s, 3H), 1.60 (s, 9H); 13
C
NMR (CDCl3) δ 165.2, 156.7, 148.0, 136.3, 136.2, 133.2, 132.0,
130.8, 130.1, 129.0, 127.9, 115.8, 106.0, 81.1, 55.9, 27.9; LRMS
(EI) for C18H19NO5 329 (M+, 30), 273 (100).
2-Meth oxy-4-[N-[2(R)-[N-(ter t-bu toxyca r bon yl)a m in o]-
3-[(tr ip h en ylm eth yl)th io]p r op yl]a m in o]-3′-(ter t-bu toxy-
ca r bon yl)bip h en yl (24). Compound 24 was prepared using
the same method as for the preparation of compound 18 (yield
63%): mp 76.0-77.0 °C dec; [R]25 ) -11.25 (c ) 0.01, CH3-
D
1
COOC2H5); H NMR (CDCl3) δ 8.09 (s, 1H), 7.86 (d, J ) 7.0
Hz, 1H), 7.65 (d, J ) 7.0 Hz, 1H), 7.37 (t, J ) 7.7 Hz, 1H),
7.43 (m, 6H), 7.21-7.32 (m, 9H), 7.11 (d, J ) 8.1 Hz, 1H), 6.21
(s, 1H), 6.18 (d, J ) 8.1 Hz, 1H), 4.58 (d, J ) 6.1 Hz, 1H), 3.86
(br s, 1H), 3.76 (s and m, 4H), 3.14 (br d, J ) 4.9 Hz, 2H), 2.49
(br d, J ) 5.1 Hz, 2H), 1.59 (s, 9H), 1.43 (s, 9H); 13C NMR
(CDCl3) δ 165.9, 157.3, 155.5, 148.8, 144.3, 138.9, 133.3, 131.5,
131.2, 130.0, 129.4, 127.8, 127.5, 126.7, 118.7, 104.7, 96.2, 80.5,
79.4, 66.8, 55.2, 49.3, 47.0, 34.1, 28.2, 28.1. Anal. (C45H50N2O5S)
C, H, N, S.
2-Meth oxy-4-[N-[2(R)-am in o-3-m er captopr opyl]am in o]-
3′-ca r boxybip h en yl (10). Compound 10 was obtained from
the deprotection of compound 24: mp 120-121 °C dec [R]25
D
) +12.62 (c ) 0.01, in methanol); 1H NMR (CD3OD) δ 8.09 (s,
1H), 7.89 (d, J ) 7.8 Hz, 1H), 7.67 (d, J ) 7.8 Hz, 1H), 7.43 (t,
J ) 7.7 Hz, 1H), 7.20 (d, J ) 8.1 Hz, 1H), 6.56 (s, 1H), 6.53 (d,
J ) 8.1 Hz, 1H), 3.81 (s, 3H), 3.60 (m, 2H, Cys R H and CH2N),
3.48 (m, 1H, CH2N), 2.96 (dd, J ) 4.9 and 13.7 Hz, 1H, CH2S),
2.86 (dd, J ) 5.4 and 13.7 Hz, 1H, CH2S); 13C NMR (D2O and
CD3OD) δ 171.1, 158.2, 149.3, 139.7, 135.1, 132.2, 131.1, 130.4,
129.4, 128.4, 120.5, 106.2 (broad, due to deuterium exchange),
98.8, 56.3, 53.4, 45.1, 24.9; LRMS (EI) for C17H20N2O3S 332
(M+). Anal. (C17H20N2O3S‚1.2HCl‚H2O) C, H, N, S.
Cysten yl-4-a m in o-3′-ca r boxybip h en yl (6). Compound 6
was purified through preparative HPLC. Purity was shown
1
over 99%: mp 120.0-121.0 °C; H NMR (CD3OD) δ 8.25 (s,
1H), 7.98 (d, J ) 7.6 Hz, 1H), 7.84 (d, J ) 7.7 Hz, 1H), 7.74 (d,
J ) 7.0 Hz, 2H), 7.54 (t, J ) 7.7 Hz, 1H), 7.66 (d, J ) 8.6 Hz,
2H), 4.16 (q, J ) 5.0 Hz, 1H), 3.19 (dd, J ) 5.20 and 14.8 Hz,
1H), 3.07 (dd, J ) 7.7 and 14.7 Hz, 1H); 13C NMR (CD3OD) δ
169.8, 166.7, 141.9, 138.7, 137.8, 132.6, 132.2, 130.2, 129.5,

Potent Farnesyltransferase Inhibitors
J ournal of Medicinal Chemistry, 1996, Vol. 39, No. 1 223
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128.8, 128.5, 121.6, 56.9, 26.4; LRMS (EI) for C16H16O3N2S 316
(M+, 25), 213 (100); HRMS (EI) calcd 316.0882, obsd 316.0867.
Anal. (C16H16N2O3S‚CF3COOH‚H2O) C, H, N.
4-[N-[2(R)-Am in o-3-m er ca p top r op yl]a m in o]-2′-ca r box-
ybip h en yl (3): mp 129-130 °C dec; [R]25D ) +12.58 (c ) 0.01,
1
(10) Gibbs, J . B. Ras C-Terminal Processing Enzymes-New Drug
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CH3OH); H NMR (CD3OD) δ 7.73 (d, J ) 7.6 Hz, 1H), 7.50
(d, J ) 7.6 Hz, 1H), 7.35 (m, 2H), 7.21 (d, J ) 8.5 Hz, 2H),
6.86 (d, J ) 8.5 Hz, 2H), 3.58 (m, 2H), 3.46 (m, 1H), 2.97 (dd,
J ) 4.8 and 14.6 Hz, 1H), 2.86 (dd, J ) 5.4 and 14.6 Hz, 1H);
13C NMR (D2O and CD3OD) δ 174.3, 146.3, 141.9, 132.8, 132.7,
131.4, 130.6, 130.2, 127.9, 115.3, 52.9, 45.8, 25.0; LRMS (FAB,
glycerol) for C16H18N2O2S (M+1) 303. Anal. (C16H18N2O2S‚
1.6HCl) C, H, N, S.
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isoprenoids is determined by the COOH-terminal amino acid.
Proc. Natl. Acad. Sci. U.S.A. 1991, 88, 8934-8938.
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M. A.; Saleem, M.; Seong, C. M.; Wathen, S. P.; Hamilton, A.
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Seong, C. M.; Vogt, A.; Hamilton, A. D.; Sebti, S. M. Peptido-
mimetic Inhibitors of p21ras Farnesyltransferase: Hydrophobic
Functionalization Leads to Disruption of p21ras Membrane
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2579-2584.
4-[N-[2(R)-Am in o-3-m er ca p top r op yl]a m in o]-4′-ca r box-
ybip h en yl (5): mp 260 °C dec; [R]25D ) +12.20 (c ) 0.01, CH3-
1
OH); H NMR (CD3OD) δ 8.03 (d, J ) 8.5 Hz, 2H), 7.66 (d, J
) 8.4 Hz, 2H), 7.56 (d, J ) 8.4 Hz, 2H), 6.85 (d, J ) 8.5 Hz,
2H), 3.57 (m, 2H), 3.45 (m, 1H), 2.98 (dd, J ) 4.8 and 14.5 Hz,
1H), 2.85 (dd, J ) 5.7 and 14.5 Hz, 1H); 13C NMR (D2O and
CD3OD) δ 169.8, 146.4, 146.1, 133.6, 131.4, 129.8, 129.4, 127.1,
117.0, 53.3, 47.2, 25.5; LRMS (EI) for C16H18O2N2S 302 (M+,
15), 285 (15), 226 (100), 213 (50); HRMS (EI) calcd 302.1088,
obsd 302.1089. Anal. (C16H18N2O2S‚2HCl) C, H, N.
4-[N-[2(R)-Am in o-3-m er ca p t op r op yl]a m in o]b ip h en yl
(7): mp 216 °C dec; [R]25 ) +13.27 (c ) 0.01, CH3OH); 1H
D
NMR (CD3OD) δ 7.54 (m, 4H), 7.39 (m, 2H), 7.26 (m, 1H), 6.82
(br s, 2H), 3.56 (br m, 2H), 3.45 (m, 1H), 2.98 (m, 1H), 2.87
(m, 1H); 13C NMR (CD3OD) δ 144.8, 141.8, 135.7, 129.9, 129.1,
127.8, 127.4, 117.4, 53.2, 47.6, 25.5; LRMS (EI) for C15H18N2S
258 (M+, 15), 182 (100); HRMS (EI) calcd 258.1190, obsd
258.1183. Anal. (C15H18N2S‚1.6HCl) C, H, N, S.
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4-[N-[2(R)-Am in o-3-m er ca p top r op yl]a m in o]-3′-m eth yl-
bip h en yl (8): H NMR (CD3OD) δ 7.50 (d, J ) 8.2 Hz, 2H),
7.35 (m, 2H), 7.27 (t, J ) 7.6 Hz, 1H), 7.08 (d, J ) 7.3 Hz,
1H), 6.95 (d, J ) 8.2 Hz, 2H), 3.60 (m, 2H), 3.46 (m, 1H), 2.99
(dd, J ) 4.9 and 14.6 Hz, 1H), 2.88 (dd, J ) 5.5 and 14.6 Hz,
1H), 2.37 (s, 3H); LRMS (EI) for C16H20N2S 272 (M+, 15), 196
(100); HRMS (EI) calcd 272.1341, obsd 272.1347.
4-[N-[2(R)-Am in o-3-m er ca p t op r op yl]a m in o]-3′-m et h -
oxyca r bon ylbip h en yl (9): mp 86-89 °C dec; 1H NMR (CD3-
OD) δ 8.18 (s, 1H), 7.90 (d, J ) 7.7 Hz, 1H), 7.79 (d, J ) 6.6
Hz, 1H), 7.55 (d, J ) 8.6 Hz, 2H), 7.49 (t, J ) 7.7 Hz, 1H),
7.01 (d, J ) 8.6 Hz, 2H), 3.92 (s, 3H), 3.54-3.65 (m, 2H), 3.44-
3.52 (m, 1H), 2.97 (dd, J ) 4.7 and 14.7 Hz, 1H), 2.88 (dd, J )
5.5 and 14.7 Hz, 1H); LRMS (EI) for C17H20O2N2S 316 (M+,
15), 299 (20), 240 (100); HRMS (EI) calcd 316.1240, obsd
316.1239. Anal. (C17H20N2O2S‚2HCl) C, H, N, S.
1
Ack n ow led gm en t. This work was supported by a
grant from the National Institutes of Health (CA67771).
We thank the Andrew Mellon Foundation for a predoc-
toral fellowship to Y.Q.
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