2-Substituted piperazines as constrained amino acids. Application to the synthesis of potent, non carboxylic acid inhibitors of farnesyltransferase [1]

Full text of DOI:10.1021/jm9508090

© Copyright 1996 by the American Chemical Society
Volume 39, Number 7
March 29, 1996
Communications to the Editor
Sch em e 1. Synthesis of 2-Alkyl-4-acylpiperazine FTase
2-Su bstitu ted P ip er a zin es a s Con str a in ed
Inhibitorsa
Am in o Acid s. Ap p lica tion to th e
Syn th esis of P oten t, Non Ca r boxylic Acid
In h ibitor s of F a r n esyltr a n sfer a se
Theresa M. Williams,* Terrence M. Ciccarone,
Suzanne C. MacTough, Rhonda L. Bock,
Michael W. Conner,† J oseph P. Davide,‡
Kelly Hamilton,‡ Kenneth S. Koblan,‡
Nancy E. Kohl,‡ Astrid M. Kral,‡ Scott D. Mosser,‡
Charles A. Omer,‡ David L. Pompliano,‡
Elaine Rands,‡ Michael D. Schaber,‡ Daksha Shah,‡
Francine R. Wilson,‡ J ackson B. Gibbs,‡,§
Samuel L. Graham, George D. Hartman,
Allen I. Oliff,‡ and Robert L. Smith
a
(a) BnNHCH2CO2C2H5, DCC, CH2Cl2, 18 h (100%); (b) HCl,
CHCl3; NaHCO3, H2O (100%); (c) LiAlH4, THF, reflux, 15 h; Boc2O,
CH2Cl2, 2 h (89%); (d) H2 10% Pd/C, CH3OH, 16 h (100%); (e) 2,3-
dimethylbenzoic acid, EDC‚HCl, HOBT, DMF, 3 h (88%); (f) TFA,
CH2Cl2, 0.75 h; N-Boc-S(Tr)-L-cysteinal, NaBH(OAc)3, ClCH2CH2Cl,
0-20 °C, pH 6, 18 h (67%); (g) 4 equiv of Et3SiH, TFA, CH2Cl2,
0.75 h (55%).
Departments of Medicinal Chemistry, Cancer Research, and
Safety Assessment, Merck Research Laboratories,
West Point, Pennsylvania 19486, and Department of
Pharmacology, University of Pennsylvania School of
Medicine, Philadelphia, Pennsylvania 19104
animal models of cancer has been demonstrated by the
inhibition ras-dependent tumor growth in nude mice9
and by the regression of tumors in Ha-ras-transgenic
mice (Oncomouse).10 Current medicinal chemistry ef-
forts are focused on obtaining an inhibitor suitable for
drug development.
Received November 2, 1995
Mutations in the ras oncogene are present in many
human cancers, including 30-50% of colon and 90% of
pancreatic cancer.1,2 The Ras protein undergoes a series
of post-translational modifications, including S-farnes-
ylation of a cysteine residue located in the C-terminal
tetrapeptide, a region of the molecule referred to as the
“CaaX box” (C ) cysteine, a ) any aliphatic amino acid,
X ) a prenylation specificity residue).2 The enzyme
farnesyltransferase (FTase) utilizes farnesyl diphos-
phate (FPP) to farnesylate the cysteine thiol of CaaX
sequences, in which X is usually serine, methionine, or
glutamine.3-5 Since farnesylation of mutant Ras pro-
teins is required for cell transformation,6 inhibition of
FTase represents a pharmacological target for cancer
chemotherapy.7 FTase inhibitors have been shown to
inhibit protein farnesylation in cell culture and to
suppress ras-transformed cell growth without affecting
normal cell growth.8 Efficacy of an FTase inhibitor in
Tetrapeptides corresponding to the C-terminus of Ras
inhibited farnesylation of the full length protein by
acting as alternate substrates.3,11,12 Modifications to
either the a2 residue of the Ca1a2X box or to the
tetrapeptide backbone eliminated substrate activity
while retaining inhibitory activity.13-20 Two critical
binding elements present in these inhibitors were the
N-terminal thiol group and the C-terminal carboxylic
acid. Since FTase is an intracellular enzyme, the utility
of FTase inhibitors in treating cancer is highly depend-
ent on their ability to cross the cell membrane and
inhibit intracellular protein farnesylation. Although
potent inhibitors of FTase in vitro, a major limitation
of the carboxylic acids was poor cell membrane perme-
ability; an ester prodrug strategy was required in order
to obtain activity in cell culture.14,16,19,21,22 The limita-
tions of prodrugs prompted the design of inhibitors
which do not depend upon a carboxylic acid for in vitro
potency. For example, the pseudodipeptide amide 1a
† Department of Cancer Research, Merck Research Laboratories.
‡ Department of Safety Assessment, Merck Research Laboratories.
§ Department of Pharmacology, University of Pennsylvania School
of Medicine.
0022-2623/96/1839-1345$12.00/0 © 1996 American Chemical Society

1346 J ournal of Medicinal Chemistry, 1996, Vol. 39, No. 7
Communications to the Editor
Ta ble 1. FTase Inhibition and Selectivity of Piperazines in Vitro and Inhibition of Ras Processing in Cell Culture
IC50 (nM)
IC50 (µM)
compd
R
Ar
FTasea
GGTase Ib
NDd
160 ( 40 (2)
360 (1)
Ras processingc
5a
5b
5c
5d
5e
5f
n-C4H9
n-C4H9
n-C4H9
phenyl
24 ( 4 (2)
1 ( 1 (3)
5 ( 2 (2)
ND
0.5
0.5
10
5
0.5
0.5
1-naphthyl
2,3-dimethylphenyl
2,3-dimethylphenyl
2,3-dimethylphenyl
1-naphthyl
H
C2H5
160 ( 30 (2)
68 ( 10 (2)
3 ( 2 (5)
2800 (1)
ND
CH3OCH2CH2
c-Pr-OCH2CH2
10000 ( 1000e (2)
3900e (1)
5g
1-naphthyl
1 ( 2 (2)
a
Concentration of compound required to inhibit 50% of FTase-catalyzed incorporation of [3H]FPP into recombinant human Ha-Ras
protein. Assay results are reported ( SEM for the number of determinations in parentheses and were obtained using the protocol described
b
in ref 11. Inhibition of bovine type-I GGTase, except where noted. c Inhibition of post-translational processing of Ras protein in RAT1
d
cells transformed with viral Ha-ras. Assay conditions are described in ref 34. Not determined. e Inhibition of human recombinant GGTase
I.
Sch em e 2. Synthesis of (2-Alkoxyethyl)piperazine
(IC50 of 23 nM) was designed to mimic the Ca1a2 portion
Intermediatea
of the Ca1a2X box.23 Unfortunately, assays in cell
culture with 1a and related compounds were largely
hampered by nonmechanism-based cytotoxicity. We
therefore concentrated our efforts upon improving the
potency and tolerability of the non carboxylic acid
inhibitors.
Ch em istr y. 2-Alkylpiperazines were synthesized
essentially according to the procedure described for the
synthesis of enantiomerically pure 2-methylpipera-
zine.24 For example, N-Boc-norleucine 2 was coupled
to ethyl N-benzylglycinate, followed by N-deprotection
and cyclization to the diketopiperazine 3 (Scheme 1).
LAH reduction then furnished the N-benzylpiperazine.
The N-benzyl protecting group was removed by catalytic
a
hydrogenation, and the free amine was acylated with
2,3-dimethylbenzoic acid to give 4. Reductive alkylation
with (S)-N-Boc-S-trityl cysteine aldehyde was best ac-
complished under conditions described for the reductive
alkylation of weakly basic amines.25 Simultaneous
removal of the N-Boc and S-trityl protecting groups with
Et3SiH and TFA furnished (2-amino-3-mercaptopropyl)-
piperazine 5c. Compounds 5a ,b,e were synthesized in
similar fashion from the appropriate amino acids.
Compound 5d was prepared from comercially available
tert-butyl 1-piperazinecarboxylate.
(h) 1-Naphthoic acid, EDC‚HCl, HOBT, DMF (90%); (i) CH3I,
NaH, DMF, 0 °C, 1 h (85%); (j) C2H5OCHCH2, Hg(O2CCH3)2, 20
°C, 18 h; (k) CH2I2, (C2H5)2Zn, Et2O, 30 °C, 1 h (34%, two steps).
The benzyl ester of N-Boc-L-aspartic acid (6) was
converted to the (2-hydroxyethyl)piperazine 7 following
steps a-d in Scheme 1 and subsequent coupling to
1-naphthoic acid (Scheme 2). O-Alkylation of 7 with
methyl iodide in the presence of sodium hydride fur-
nished methyl ether 8. Alcohol 7 was also converted to
the vinyl ether with mercuric acetate in ethyl vinyl
ether; the vinyl ether was subsequently reacted with
diiodomethane and diethylzinc to give cyclopropylether
9.26 Both 8 and 9 were further elaborated to 5f and 5g,
respectively, according to steps f and g, Scheme 1.
Resu lts a n d Discu ssion . It is well established that
the introduction of conformational constraints into
peptides can dramatically affect receptor binding affin-
ity.27 Pseudodipeptide FTase inhibitors 1a ,b have ac-
cess to a plethora of conformations, and structural
information relating to their binding conformation(s)
was not available. We hypothesized that in a compound
such as 1b (IC50 ) 900 nM23), replacing the aliphatic
amino acid with piperazine would be one way of
stabilizing and testing an approximately extended
conformation. Appropriate substitution on the pipera-
zine ring might also exploit the hydrophobic a1 binding
site occupied by Ca1a2X analogs. In subsequent studies,
a series of N-acylpiperazines emerged as the most active
compounds from among a number of piperazine-con-
strained analogs. For example, N-acylpiperazine 5a
was found to be 40-fold more potent than 1b (Table 1).
Variation of the N-acyl substituent led to further
improvements in potency, e.g. 1-naphthoylpiperazine
5b, which had an IC50 of 1 nM. To further ascertain
the importance of conformational constraint upon activ-
ity, the ring-opened analog 10 was synthesized and
found to be 650-fold less active than the constrained
analog 5c. Shortening or eliminating the C-2 piperazine
alkyl substituent (5d ,e) led to a decrease in activity,
consistent with this group occupying a lipophilic a1
binding pocket. Inverting the stereochemistry of the
butyl group in 5c led to a 2-fold decrease in potency
(data not shown).

Communications to the Editor
J ournal of Medicinal Chemistry, 1996, Vol. 39, No. 7 1347
Ta ble 2. Effect of FTase Inhibitors on the Anchorage
Independent Growth of ras- and raf-Transformed Cells in Soft
Agar
soft agar MICa (µM)
compd
ras
raf
>10
>50
NDc,d
CTEb (µM)
5b
5f
5g
10
10
2.5
10
g100
25
The piperazines 5 were not substrates of FTase.
Kinetic analysis of 5c binding to FTase revealed a
competitive mode of inhibition with respect to the Ras
substrate (Ki ) 1 nM). The closely related prenyl
transferase geranylgeranyltransferase I (GGTase I)
recognizes CaaX sequences wherein X is leucine.11,28,29
It is interesting to note that piperazines 5 selectively
inhibited FTase compared to GGTase, despite the lack
of a structural element corresponding to the specificity-
determining X residue (Table 1). This phenomenon has
also been observed in two other series of FTase inhibi-
tors.23,30 Simple alkyl-substituted piperazines such as
5b exhibited up to 160-fold selectivity for inhibition of
FTase.
a
Minimum inhibitory concentration (MIC) required to achieve
a reduction in size and number of colonies of RAT1 v-ras- or RAT1
v-raf-transformed cells in soft agar relative to vehicle-treated
b
control. Assay conditions are described in ref 21. Highest
nontoxic concentration in cultured RAT1 cells assessed by viable
staining with MTT.31 c Not determined. No inhibition of colony
d
formation was observed in a v-mos-transformed control cell line
at 2.5 µM, the highest concentration tested.
To assay the effect of piperazine FTase inhibitors in
an animal tumor model, 5f was evaluated for its ability
to block tumor growth in nude mice. The growth of
tumors arising from Ha-ras-transfected RAT1 cells
subcutaneously implanted in nude mice was signifi-
cantly inhibited by treatment with 5f. A dose of 45 mpk
ip once daily for 5 days or po twice daily for 10-16 days
resulted in 47% and 49% reductions in tumor weight,
respectively, when compared to the vehicle-treated
control group. Sections of tumor tissue taken at time
of necropsy from untreated mice exhibited microscopic
characteristics of an aggressive sarcoma. These sections
showed a high degree of cellularity, with many mitotic
figures indicative of rapidly proliferating tissue. In
contrast, sections of tumor tissue from treated animals
were distinctly less cellular and contained few or no
mitotic figures. Thus 5f not only inhibited tumor
growth but also altered the histological appearance of
the remaining tumor tissue. A similar effect has also
been reported in animal studies of a prodrug CaaX
peptidomimetic FTase inhibitor.33 In contrast, the
growth of tumors derived from a v-mos transformed
RAT1 control cell line was not affected by similar ip
administration of 5f, thus confirming the specificity for
ras-transformed cell growth inhibition observed in soft
agar.
Con clu sion . A series of piperazines 5 were designed
as constrained analogs of dipeptide amide FTase inhi-
bitors 1. This conformational constraint increased
potency by 40-fold and resulted in compounds with
nanomolar IC50 values vs FTase. A key feature of these
inhibitors is that a carboxylic acid is not required for
high inhibition potency. Suppression of Ras processing
in cell culture demonstrated the ability of piperazines
5 to inhibit intracellular protein farnesylation. Selective
inhibition of colony formation of ras-transformed cells
in soft agar reversed one of the key phenotypic changes
associated with cancer cells. The piperazine 5f signifi-
cantly inhibited ras-dependent tumor growth in nude
mice. On the basis of these results, piperazine FTase
inhibitors represent a promising class of potential
cancer chemotherapeutics.
In an assay where Ha-ras-transformed cells were
incubated with these inhibitors for 24 h and then lysed,
denaturing gel electrophoresis of immunoprecipitated
Ras protein showed inhibition of Ras processing (far-
nesylation). The most active compounds in this assay
had IC50s of ∼0.5 µM (Table 1). A second cell assay
measured the competence of these compounds in inhib-
iting transformed cell growth. Both the size and
number of colonies of ras-transformed RAT1 cells were
reduced in soft agar in the presence of 10 µM 5b (Table
2). Furthermore, growth inhibition was selective for
ras-transformed cells. The raf oncogene transforms
cells in a farnesylation- and ras-independent manner,
and the growth of these cells was not sensitive to 5b up
to a concentration of 10 µM. Growth inhibition was also
not the result of cellular toxicity, as determined by
viable staining with the dye MTT31 (Table 2). An
important goal was to inhibit cancer cell growth without
engendering toxicity to normal cells, as assessed by
comparison of the minimun inhibitory concentration
(MIC) and the cytotoxic endpoint (CTE, concentration
compatible with g90% cell survival). Unfortunately, the
cytotoxicity profile of piperazine 5b was similar to that
of the dipeptide amides 1. In both series of compounds,
toxicity was not mechanism related, since the CTE did
not correlate with FTase inhibitory potency. Cytotox-
icity in cytolytic lymphocytes had previously been
reported for a series of dipeptide ester substrates of
dipeptidyl peptidase-1.32 Cell toxicity was greatest
when the dipeptide was comprised of hydrophobic
residues, but was absent in analogs incorporating a
hydrophilic residue such as serine. Application of these
findings to the current series of FTase inhibitors led to
the synthesis of compounds with polar functional groups
in the piperazine C-2 substituent. While the serine-
derived piperazines were no longer cytotoxic, they were
also less active FTase inhibitors. Gratifyingly, however,
the ethers 5f and 5g were potent inhibitors both in vitro
and in cell culture and exhibited at least a 10-fold
difference in concentration between the CTE and MIC
in cell culture (Tables 1 and 2). These compounds
additionally exhibited an increased selectivity (>3000-
fold) for FTase inhibition vs GGTase I inhibition.
Ack n ow led gm en t. We thank Dr. G. M. Smith, Mr.
K. D. Anderson, Ms. P. A. Ciecko, and Mr. M. M. Zrada
for elemental analyses and Dr. H. G. Ramjit and Mr.
A. B. Coddington for mass spectra for the reported
compounds. We are also grateful to Ms. J . Kaysen for
manuscript preparation. We would also like to acknowl-
edge Dr. Warren Nichols for helpful discussion.

1348 J ournal of Medicinal Chemistry, 1996, Vol. 39, No. 7
Communications to the Editor
(19) Wai, J . S.; Bamberger, D. L.; Fisher, T. E.; Graham, S. L.; Smith,
R. L.; Gibbs, J . B.; Mosser, S. D.; Oliff, A. I.; Pompliano, D. L.;
Rands, E.; Kohl, N. E. Synthesis and biological activity of Ras
farnesyl-protein transferase inhibitors. Tetrapeptide analogs
with aminomethyl and carbon linkages. Biorg. Med. Chem. 1994,
2, 939-947.
(20) Vogt, A.; Yimin, Q.; Blaskovich, M. A.; Fossum, R. D.; Hamilton,
A. D.; Sebti, S. M. A non-peptide mimic of Ras-CaaX: Selective
inhibition of farnesyltransferase and Ras processing. J . Biol.
Chem. 1995, 270, 660-664.
(21) Kohl, N. E.; Mosser, S. D.; deSolms, S. J .; Giuliani, E. A.;
Pompliano, D. L.; Graham, S. L.; Smith, R. L.; Scolnick, E. M.;
Oliff, A. I.; Gibbs, J . B. Selective inhibition of ras-dependent
transformation by a farnesyltransferase inhibitor. Science 1993,
260, 1934-1937.
(22) Qian, Y.; Blaskovich, M. A.; Seong, C. M.; Vogt, A.; Hamilton,
A. D.; Sebti, S. M. Peptidomimetic inhibitors of p21ras farnesyl-
transferase: hydrophobic functionalization leads to disruption
of p21ras membrane association in whole cells. Bioorg. Med.
Chem. Lett. 1994, 4, 2579-2584.
(23) deSolms, S. J .; Deana, A. A.; Giuliani, E. A.; Graham, S. L.; Kohl,
N. E.; Mosser, S. D.; Oliff, A. I.; Pompliano, D. L.; Rands, E.;
Scholz, T. H.; Wiggins, J . M.; Gibbs, J . B.; Smith, R. L.
Pseudopeptide inhibitors of Ras farnesyl-protein transferase. J .
Med. Chem. 1995, 38, 3967-3971.
(24) Kiely, J . S.; Priebe, S. R. An improved synthesis of (R) and (S)-
2-methylpiperazine. Org. Prep. Proc. Int. 1990, 22, 761-768.
(25) Abdel-Magid, A. F.; Maryanoff, C. A.; Carson, K. G. Reductive
amination of aldehydes and ketones by using sodium triacetoxy-
borohydride. Tetrahedron Lett. 1990, 31, 5595-5598.
(26) Furukawa, J .; Kawadata, N.; Nishimura, J . Synthesis of cyclo-
propanes by the reaction of olefins with dialkylzinc and meth-
ylene iodide. Tetrahedron 1968, 24, 53-58.
(27) For leading references, see: (a) Hirschmann, R. Medicinal
chemistry in the golden age of biology: lessons from steriod and
peptide research. Angew. Chem. Int. Ed. Engl. 1991, 30, 1278-
1301. (b) Hruby, V. J .; Al-Obeidi, F.; Kazmierski, W. Emerging
approaches in the molecular design of receptor-selective peptide
ligands: conformational, topographical and dynamic consider-
ations. Biochem. J . 1990, 268, 249-262.
(28) Casey, P. J .; Thissen, J . A.; Moomaw, J . F. Enzymatic modifica-
tion of proteins with a geranylgeranyl isoprenoid. Proc. Natl.
Acad. Sci. U.S.A. 1991, 88, 8631-8635.
(29) Yokoyama, K.; Goodwin, G. W.; Ghomashchi, F.; Glomset, J . A.;
Gelb, M. H. A protein geranylgeranyl- transferase from bovine
brain: implications for protein prenylation specificity. Proc. Natl.
Acad. Sci. U.S.A. 1991, 88, 5302-5306.
(30) Sebti, S. M.; Vogt, A.; Qian, Y.; Blaskovich, M. A.; Fossum, R.
D.; Hamilton, A. D. A non-peptide mimetic of Ras-CAAX:
selective inhibition of farnesyltransferase and Ras processing.
J . Biol. Chem. 1995, 270, 660-664.
(31) Mossman, T. Rapid colorimetric assay for cellular growth and
survival: application to proliferation and cytotoxicity assays. J .
Immun. Methods 1983, 65, 55-63.
(32) Thiele, D. L.; Lipsky, P. E. The action of leucyl-leucyl methyl
ester on cytotoxic lymphocytes requires uptake by a novel
dipeptide-specific facilitated transport system and dipeptidyl
peptidase I-mediated conversion to membranolytic products. J .
Exp. Med. 1990, 172, 183-194.
(33) Kohl, N. E.; Conner, M. W.; Gibbs, J . B.; Graham, S. L.;
Hartman, G. D.; Oliff, A. I. Development of inhibitors of protein
farnesylation as potential chemotherapeutic agents. J . Cell
Biochem. 1995, Suppl. 22, 145-150.
(34) Gibbs, J . B.; Pompliano, D. L.; Mosser, S. D.; Rands, E.; Lingham,
R. B.; Singh, S. B.; Scolnik, E. M.; Kohl, N. E.; Oliff, A. I.
Selective inhibition of farnesyl-protein transferase blocks Ras
processing in vivo. J . Biol. Chem. 1993, 268, 7617-7620.
Refer en ces
(1) Rodenhuis, S. Ras and human tumors. Semin. Cancer Biol. 1992,
3, 241-247.
(2) Casey, P. J .; Solski, P. A.; Der, C. J .; Buss, J . E. p21 ras is
modified by a farnesyl isoprenoid. Proc. Natl. Acad. Sci. U.S.A.
1989, 86, 8323-8327.
(3) Reiss, Y.; Goldstein, J . L.; Seabra, M. C.; Casey, P. J .; Brown,
M. S. Inhibition of purified p21ras farnesyl:protein transferase
by Cys-AAX tetrapeptides. Cell 1990, 62, 81-88.
(4) Schaber, M. D.; Moores, S. L.; Marshall, M. S.; Friedman, P. A.;
Dixon, R. A. F.; Gibbs, J . B. Polyisoprenylation of Ras in vitro
by a farnesyl-protein transferase. J . Biol. Chem. 1990, 265,
14701-14704.
(5) Manne, V.; Roberts, D.; Tobin, A.; O’Rourke, E.; DeVirgilio, M.;
Meyers, C.; Ahmed, N.; Kurz, B.; Resh, M.; Kung, H.-F.;
Barbacid, M. Identification and preliminary characterization of
protein-cysteine farnesyltransferase. Proc. Natl. Acad. Sci.
U.S.A. 1990, 87, 7541-7545.
(6) Kato, K.; Cox, A. D.; Hisaka, M. M.; Graham, S. M.; Buss, J . E.;
Der, C. J . Isoprenoid addition to Ras protein is the critical
modification for its membrane association and transforming
activity. Proc. Natl. Acad. Sci. U.S.A. 1992, 89, 6403-6407.
(7) Gibbs, J . B. Ras C-terminal processing enzymes- new drug
targets. Cell 1991, 65, 1-4.
(8) Gibbs, J . B.; Oliff, A. I.; Kohl, N. Farnesyltransferase inhibi-
tors: Ras research yields a potential cancer therapeutic. Cell
1994, 77, 175-178.
(9) Kohl, N. E.; Wilson, F. R.; Mosser, S. D.; Giuliani, E. A.; deSolms,
S. J .; Conner, M. W.; Anthony, N. J .; Holtz, W. J .; Gomez, R. P.;
Lee, T.-J .; Smith, R. L.; Graham, S. L.; Hartman, G. D.; Gibbs,
J . B.; Oliff, A. Protein farnesyltransferase inhibitors block the
growth of ras-dependent tumors in nude mice. Proc. Natl. Acad.
Sci. U.S.A. 1994, 91, 9141-9145.
(10) Kohl, N. E.; Omer, C. A.; Conner, M. W.; Anthony, N. J .; Davide,
J . P.; deSolms, S. J .; Giuliani, E. A.; Gomez, R. P.; Graham, S.
L.; Hamilton, K.; Handt, L. K.; Hartman, G. D.; Koblan, K. S.;
Kral, A. M.; Miller, P. J .; Mosser, S. D.; O’Neill, T. J .; Shaber,
M. D.; Gibbs, J . B.; Oliff, A. Inhibition of farnesyltransferase
induces regression of mammary and salivary carcinomas in ras
transgenic mice. Nature Med. 1995, 1, 792-797.
(11) Moores, S. L.; Schaber, M. D.; Mosser, S. D.; Rands, E.; O’Hara,
M. B.; Garsky, V. M.; Marshall, M. S.; Pompliano, D. L.; Gibbs,
J . B. Sequence dependence of protein isoprenylation. J . Biol.
Chem. 1991, 166, 14603-14610.
(12) Reiss, Y.; Stradley, S. J .; Gierasch, L. M.; Brown, M. S. Sequence
requirement for peptide recognition by rat brain p21ras protein
farnesyltransferase. Proc. Natl. Acad. Sci. U.S.A. 1991, 88, 732-
736.
(13) Goldstein, J . L.; Brown, M. S.; Stradley, S. J .; Reiss, Y.; Gierasch,
L. M. Nonfarnesylated tetrapeptide inhibitors of protein farne-
syltransferase. J . Biol. Chem. 1991, 266, 15575-15578.
(14) J ames, G. L.; Goldstein, J . L.; Brown, M. S.; Rawson, T. E.;
Somers, T. C.; McDowell, R. S.; Crowley, C. W.; Lucas, B. K.;
Levinson, A. D.; Marsters, J . C., J r. Benzodiazepine peptido-
mimetics: potent inhibitors of Ras farnesylation in animal cells.
Science 1993, 260, 1937-1942.
(15) Nigam, M.; Seong, C.-M.; Qian, Y.; Hamilton, A. D.; Sebti, S.
M. Potent inhibition of human tumor p21ras farnesyltransferase
by A1A2-lacking p21ras CA1A2X peptidomimetics. J . Biol. Chem.
1993, 268, 20695-20698.
(16) Graham, S. L.; deSolms, S. J .; Giuliani, E. A.; Kohl, N. E.;
Mosser, S. D.; Oliff, A. I.; Pompliano, D. L.; Rands, E.; Breslin,
M. J .; Deana, A. A.; Garsky, V. M.; Scholz, T. H.; Gibbs, J . B.;
Smith, R. L. Pseudopeptide inhibitors of Ras farnesyl-protein
transferase. J . Med. Chem. 1994, 37, 725-732.
(17) Leftheris, K.; Kline, T.; Natarajan, S.; DeVirgilio, M. K.; Cho,
Y. H.; Pluscec, J .; Ricca, C.; Robinson, S.; Seizinger, B. R.;
Manne, V.; Meyers, C. A. Peptide based p21 Ras farnesyl
transferase inhibitors: systematic modification of the tetrapep-
tide CA1A2X motif. Biorg. Med. Chem. Lett. 1994, 4, 887-892.
(18) Qian, Y.; Blaskovich, M. A.; Saleem, M.; Seong, C.-M.; Wathen,
S. P.; Hamilton, A. D.; Sebti, S. M. Design and structural
requirements of potent peptidomimetic inhibitors of p21ras
farnesyltransferase. J . Biol. Chem. 1994, 269, 12410-12413.
J M9508090