Opiate receptor ligands

Compounds of Formula 1 bind opioid receptors: ##STR1## wherein X and Y are each independently ##STR2##

DESCRIPTION 
1. Technical Field 
The invention relates generally to the field of medicinal chemistry, and 
specifically to compounds which bind to opioid receptors. 
2. Background of the Invention 
Opioid receptors are named for their binding affinity to morphine and other 
opium-derived compounds. The three classes of opioid receptor are 
designated p (morphine-like), .kappa.(ketazocine-like), and .delta.. 
##STR3## 
DISCLOSURE OF THE INVENTION 
One aspect of the invention is a compound of Formula 1 which binds to the 
opioid receptor: 
##STR4## 
wherein X and Y are each independently 
##STR5## 
where n and p are each independently 0, 1, or 2; m is 1 or 2, and R.sub.7 
is H, lower alkyl, hydroxy-lower alkyl, phenyl, or aryl-lower alkyl; 
R.sub.2 is lower alkyl, alkenyl, haloalkyl, haloalkenyi, or 
##STR6## 
where r is an integer from 1 to 8 inclusive; a, b, and c are each 
independently 1, 2, 3 or 4; 
Q.sub.1 and Q.sub.2 are each independently 
##STR7## 
where s, t, and u are each independently 0 to 6 inclusive, and R.sub.9 and 
R.sub.10 are each independently H, OH, lower alkyl, hydroxy-lower alkyl, 
aryl, or 
##STR8## 
where v and w are each independently 0-4 inclusive; 
R.sub.1, R.sub.3, R.sub.4, R.sub.5, R.sub.6 and R.sub.8 are each 
independently H, halo, OH, NH.sub.2, NO.sub.2, CN, SH, SO.sub.2, SO.sub.3, 
or --W--(CH.sub.2).sub.q --Z-R, where q is an integer from 1 to 6 
inclusive; R is H, lower alkyl, aryl, or benzyl, and W and Z are each 
independently a bond, --O--, --NR--, --S', --SO.sub.2 --, --SO.sub.3 --, 
##STR9## 
or two R.sub.1, R.sub.3, R.sub.4 or R.sub.8 together form a ring. 
Another aspect of the invention is the method of modulating opioid receptor 
activity, comprising contacting an opioid receptor with a compound of 
formula 1. 
Modes of Carrying Out The Invention 
A. Definitions 
The term "compound of formula 1" refers to compounds of the formula: 
##STR10## 
wherein X and Y are each independently 
##STR11## 
where n and p are each independently 0, 1, or 2; m is 1 or 2, and R.sub.7 
is H, lower alkyl, hydroxy-lower alkyl, phenyl, or aryl-lower alkyl; 
R.sub.2 is lower alkyl, alkenyl, haloalkyl, haloalkenyl, or 
##STR12## 
where r is an integer from 1 to 8 inclusive; a, b, and c are each 
independently 1, 2, 3 or 4; 
Q.sub.1 and Q2 are each independently 
##STR13## 
where s, t, and u are each independently 0 to 6 inclusive, and R.sub.9 and 
R.sub.10 are each independently H, OH, lower alkyl, hydroxy-lower alkyl, 
aryl, or 
##STR14## 
where v and w are each independently 0-4 inclusive; R.sub.1, R3, R.sub.4, 
R.sub.5, R.sub.6 and R.sub.8 are each independently H, halo, OH, NH.sub.2, 
NO.sub.2, CN, SH, SO.sub.2, SO.sub.3, or --W--(CH.sub.2).sub.q --Z--R, 
where q is an integer from 1 to 6 inclusive; R is H, lower alkyl, aryl, or 
benzyl, and W and Z are each independently a bond, --O--, --NR--, --S--, 
--SO.sub.2 --, --SO.sub.3 -- 
##STR15## 
or two R.sub.1, R.sub.3, R.sub.4 or R.sub.8 together form a ring (for 
example, two R.sub.1 s may form an alkylenedioxy ring, such as 
##STR16## 
A presently preferred subgenus of compounds of formula 1 is that wherein X 
and Y are each --CH.sub.2 --, and R.sub.2 is 3,4-methylenedioxybenzyl. 
The term "peptoid" refers to monomers other than the twenty conventional 
amino acids and the common nucleotides and nucleosides (i.e., the DNA 
bases dA, dC, dG, and dT, and the RNA bases A, C, G, and U). The terms 
"amide peptoid" and nonconventional amino acid" refer to peptoids which 
are linked together through amide (peptide) bonds. Amide polypeptoid bonds 
may include substituents on the amide nitrogen atom. Presently preferred 
peptoids include those wherein the side chain (the residue attached to the 
backbone N) is selected from the following: 2-hydroxyethyl, 
3-hydroxypropyl, 2-(4-hydroxyphenyl)ethyl, 2-phenethyl, 2,2-diphenylethyl, 
1-naphthylmethyl, 4-(phenyl)phenyl, methyl, 2-methylpropyl, 
2-methoxyethyl, pentyl, 1-ethylpropyl, cyClohexyl, 
(1-tetrahydrofuryl)methyl, 4-(phenoxy)phenyl, 3,4-methylenedioxybenzyl, 
3,4-dimethoxybenzyl, 2-aminoethyl, 2-(N-morpholino)ethyl, 2-carboxyethyl, 
2-(2-(2oaminoethoxy)ethoxy)ethyl, 2-methoxypyrid-5-yl, adamantyl, 
1-hydroxy-1-phenylprop-2-yl, 4oethenylphenyl, 4-biphenyl, 3-biphenyl, 
4-butylphenyl, 4-cyclohexylphenyl, 4-iodophenyl, 2,2-diphenylethyl, 
4-trifluoromethylbenzyl, 2-(4-chlorophenyl)ethyl, 
2-(cyclohex-1-enyl)ethyl, 2-phenoxyethyl, 2-phenethylamino, 
2-(4-sulfonamidophenyl)ethyl, 3,4-dihydroxyphenethyl, 4-nitrophenethyl, 
2-(4-hydroxyphenyl)-2-hydroxyethyl, 2-(4-aminophenyl)ethyl, and 
6,7-dimethoxytetrahydroisoquinolinyl. 
N-substituted glycine monomers are named Nxxx, where xxx is the multiletter 
abbreviation for the amino acid that has the corresponding side chain. An 
"h" immediately following the N indicates that the monomer is a homolog, 
having an additional --CH.sub.2 -- between the nitrogen atom and the rest 
of the side chain (e.g., Nhhis has imidazolylethyl rather than 
imidazolyhnethyl as its side chain). An "m" following the N indicates an 
.alpha.-methyl residue (i.e., an N-substituted alanine instead of an 
N-substituted glycine): a "p" indicates an .alpha.-phenyl residue. A "p" 
following the N indicates that the backbone is .beta.-alanine 
(3-aminopropanoic acid) rather than glycine. A "z" following the N 
indicates that the submonomer used is a hydrazine derivative, resulting in 
an N--N bond between the side chain and the backbone: 
__________________________________________________________________________ 
Nala = N-methylglycine (sarcosine); 
Nasp = N-(carboxymethyl)glycine; 
Nglu = N-(2-carboxyethyl)glycine; 
Nphe = N-benzylglycine; 
Nhhis = N-(imidazolylethyl)glycine; 
Nile = N-(1-methylpropyl)glycine; 
Nlys = N-(4-aminobutyl)glycine; 
Nleu = N-(2-methylpropyl)glycine; 
Nmet = N-(2-methylthioethyl)glycine; 
Nhser = N-(hydroxyethyl)glycine; 
Nasn = N-(carbamylmethyl)glycine; 
Ngln = N-(2-carbamylmethyl)glycine; 
Nval = N-(1-methylethyl)glycine; 
Narg = N-(3-guanidinopropyl)glycine; 
Nhtrp = N-(3-indolylethyl)glycine; 
Nhtyr = N-(p-hydroxyphenethyl)glycine; 
Nthr = N-(1-hydroxyethyl)glycine; 
Ncys = N-(thiomethyl)glycine; 
Norn = N-(3-aminopropyl)glycine; 
Nhphe = N-(2-phenethyl)glycine; 
Ncpro = N-cyclopropylglycine; 
Ncbut = N-cyclobutyglycine; 
Nchex = N-cyclohexylglycine; Nchep = N-cycloheptylglycine; 
Ncoct = N-cyclooctylglycine; Ncdec = N-cyclodecylglycine; 
Ncund = N-cycloundecylglycine; 
Ncdod = N-cyclododecylglycine; 
Nbhm = N-(2,2-diphenylethyl)glycine; 
Nbhe = N-(3,3-diphenylpropyl)glycine; 
Nbiph = N-(4-phenyl)phenylglycine; 
Npop = N-(4-phenoxyphenyl)glycine; 
Nmhphe = N-(2-phenethyl)alanine; 
Nphphe = N-(2-phenethyl)beta-alanine; 
Nphtyr = N-(p-hydroxyphenethyl)beta-alanine; 
Npbiph = N-(4-phenyl)phenylbeta-alanine; 
Nnbhm = N-(N-(2,2-diphenylethyl)carbamylmethyl)glycine; 
Nnbhe = N-(N-(3,3-diphenylpropyl)carbamylmethyl)glycine; 
Nbmc = 1-carboxy-1-(2,2-diphenylethylamino)cyclopropane; 
Naeg = N-(2-aminoethyl)glycine; 
Nzhphe = N-(2-phenethylamino)glycine 
[or 2-phenethylhydrazopropanoic acid]; 
Nzhtyr = N-(p-hydroxyphenethylamino)glycine; 
Noco = N-(3,4-methylenedioxyphenethyl)glycine; 
Npen = N-pentylglycine; Nmdb = N-(3,4-methylenedioxybenzyl)glycine; 
Nddb = N-(3,4-dimethoxybenzyl)glycine; 
Nedb = N-(3,4-ethylenedioxybenzyl)glycine; 
Ntmb = N-(3,4,5-trimethoxybenzyl)glycine; 
Nbha = N-(2,2-diphenylethyl)alanine; 
Nvbhm = 4-(N-(2,2-diphenyl)ethyl)aminobut-2-enamide; and 
Nbvp = N-(3,3-diphenylprop-2-enyl)glycine. 
__________________________________________________________________________ 
The term "alkyl" as used herein refers to saturated hydrocarbon radicals 
containing from 1 to 30 carbon atoms, inclusive. Alkyl radicals may be 
straight, branched, or cyclic. Exemplary alkyl radicals include n-pentyl, 
n-hexyl, n-octyl, n-dodecyl, 2-dodecyl, 4-octadecyl, 
3,5-diethylcyclohexyl, duryl, and the like. The term "lower alkyl" as used 
herein refers to straight, branched, and cyclic chain hydrocarbon radicals 
having from 1 to 8 carbon atoms, such as methyl, ethyl, propyl, isopropyl, 
n-butyl, s-butyl, t-butyl, n-pentyl, n-hexyl, cyclopentyl, cyclohexyl, 
2-methylcyclopentyl, cyclopentylacetyl, and the like. "Alkoxy" refers to 
radicals of the formula --OR, where R is alkyl as defined above: "lower 
alkoxy" refers to alkoxy radicals wherein R is lower alkyl. "Hydroxy-lower 
alkyl" refers to radicals of the formula HO--R--, where R is lower 
alkylene of 1 to 8 carbons, and may be straight, branched, or cyclic. 
"Hydroxy-lower alkoxy" refers to radicals of the formula HO--R--O--, where 
R is lower alkylene of 1 to 8 carbons, and may be straight, branched, or 
cyclic. "Lower alkoxy-lower alkyl" refers to groups of the formula R.sub.a 
O--R.sub.b --, where R.sub.a and R.sub.b are each independently lower 
alkyl. "Lower alkoxy-lower alkoxy" refers to groups of the formula R.sub.a 
O--R.sub.b O--, where R.sub.a and R.sub.b are each independently lower 
alkyl. 
"Alkenyl" refers to hydrocarbon radicals of 2-20 carbon atoms having one or 
more double bonds. Alkenyl radicals may be straight, branched, or cyclic. 
Exemplary alkenyl radicals include 1-pentenyl, 3-hexenyl, 1,4-octadienyl, 
3,5-diethylcyclohexenyl, and the like. "Lower alkenyl" refers to alkenyl 
radicals having 2-8 carbon atoms. 
The term "alkynyl" refers to hydrocarbon radicals of 2-20 carbon atoms 
having one or more triple bonds. Alkynyl radicals may be straight, 
branched, or cyclic. Exemplary alkynyl radicals include 1-pentynyl, 
3-hexynyl, octa-2-yn-6-enyl, 3,5-diethylcyclohexynyl, and the like. "Lower 
alkynyl" refers to alkynyl radicals having 2-8 carbon atoms. 
The term "haloalkyl" refers to an alkyl radical substituted with one or 
more halogen atoms. Exemplary haloalkyl radicals include trifluoromethyl, 
2,2,2-trifluoroethyl, -chlorocyclohexyl, 2-bromo-3-chlorocyclohexyl, 
2,3-dibromobutyl, and the like. 
The term "haloalkenyl" refers to an alkenyl radical substituted with one or 
more halogen atoms. Exemplary haloalkenyl radicals include 
3-chloroprop-2-enyl, 4,4-dichlorobut-2-enyl, 
5-bromo-3-methylcyclohex-2-enyl, and the like. 
"Aryl" refers to aromatic hydrocarbons having up to 14 carbon atoms, 
preferably phenyl or naphthyl. "Aryl-lower alkyl" refers to radicals of 
the form Ar--R--, where Ar is aryl and R is lower alkyl. "Aryloxy" refers 
to radicals of the form Ar--O--, where Ar is aryl. "Aryloxy-lower alkyl" 
refers to radicals of the form ArO--R--, where Ar is aryl and R is lower 
alkyl. 
The term "acyl" refers to a radical of the formula RCO--, in which R is H, 
alkyl as defined above, phenyl, benzyl or naphthyl. Exemplary acyl groups 
include acetyl, propionyl, formyl, t-butoxycarbonyl, benzoyl, and the 
like. "Lower acyl" refers to radicals wherein R is lower alkyl. 
The term "halo" refers to a halogen radical, such as F, Cl, Br, or I. 
The term "treatment" as used herein refers to reducing or alleviating 
symptoms in a subject, preventing symptoms from worsening or progressing, 
inhibition or elimination of the causative agent, or prevention of the 
infection or disorder in a subject who is free therefrom. Thus, for 
example, treatment of opiate addiction in a patient may be reduction of 
opiate effect (blockade), or the prevention of relapse in a patient who 
has been cured. 
The term "preparation" refers to a sample to be tested for the presence of 
opioid receptor. Preparations may be whole tissues, tissue homogenates, 
host cells (e.g., recombinant host cells), biopsy samples, blood and/or 
blood fractions, lymph, and the like. 
B. General Method 
Compounds of the invention are easily synthesized by standard chemical 
methods. The presently-preferred method of synthesis is the "submonomer" 
technique described by R. Zuckermann et al., J Am Chem Soc (1992) 
114:10646-7, incorporated herein by reference. Briefly, an activated 
solid-phase synthesis resin is treated to remove any protecting or capping 
groups, then acylated with an acetic acid derivative having a good leaving 
group (e.g., bromoacetic acid) under standard conditions. The leaving 
group is then displaced in an S.sub.N 2 displacement reaction using an 
amine corresponding to the desired side chain, producing a secondary 
amine. The resulting secondary amine is then acylated with an acetic acid 
derivative, and the cycle repeated for each desired sidechain. Compounds 
in which R.sub.7 is a residue other than H are synthesized by employing an 
acetic acid derivative incorporating the desired residue. Thus, where 
R.sub.7 is methyl one would employ 2-bromopropanoic acid. 
For example, to synthesize the compound Nhtyr-Nbiph-Nhphe, the acylated 
resin is treated with phenethylamine (to provide the homo-Phe side chain), 
acylated with bromoacetic acid, the bromine displaced with 4-aminobiphenyl 
(to provide the 4-(phenyl)phenyl side chain), acylated with bromoacetic 
acid, and the bromine displaced with 4-hydroxyphenethylamine (to provide 
the homo-Tyr side chain). The last amine may be further acylated or 
alkylated to reduce the basicity of the compound. The compound is then 
cleaved from the resin using standard methods, providing either an acid or 
an amide, depending upon the cleavage conditions. In either case, the 
terminal carbonyl function may be converted to an amide, acid, aldehyde, 
alcohol, amine or other group as desired. The final compound is typically 
purified by chromatography. If desired, simple acid addition salts and/or 
esters may be prepared using standard techniques. 
Compounds of the invention may also be prepared by traditional 
solution-phase synthesis, beginning with an ester of bromoacetic acid, and 
proceeding as described above. Alternatively, one may synthesize compounds 
in the N.fwdarw.C direction in the solution phase, using complete monomers 
(rather than "submonomers"). For example, Fmoc-protected Nhtyr (with Fmoc 
protecting the amine) may be condensed with Nbiph-tBu ester with 
N,N-diisopropylcarbodiimide (DIC) in DIEA/CH.sub.2 Cl.sub.2 to forIn 
(Fmoc)Nhtyr-Nbiph-tBu. The tBu ester is then removed with trifluoroacetic 
acid (TFA) and scavengers, and the compound condensed with Nhtyr-tBu ester 
to form (Fmoc)Nhtyr-Nbiph-Nhtyr-tBu. The compound is then deprotected 
using TFA, scavengers, and pyrrolidine to provide Nhtyr-Nbiph-Nhtyr. 
Alternatively, one may use tBOC-protected Nhtyr, and employ methyl esters 
of Nbiph and Nhtyr, cleaving the esters with NaOH rather than TFA with 
scavengers. It may be necessary to isolate intermediate stage compounds, 
e.g., by chromatography or fractional crystallization. 
The reactants employed in synthesis of the compounds are generally 
commercially available. Other reactants (e.g., less-common substituted 
amines) may be prepared by standard chemical means from amines that are 
commercially available. 
Compounds of the invention may be assayed for activity using standard 
protocols. For example, one may employ the protocol demonstrated in the 
Examples below to determine binding of compounds of the invention to any 
desired receptor subtype (e.g., using different sources of tissue). 
Compounds which exhibit strong binding to receptors will exert either 
agonistic or (more usually) antagonistic activity, which may be determined 
by means of appropriate tissue-based or in vivo assays known in the art. 
Compounds within the scope of the invention may easily be assayed for 
activity by standard receptor-binding assays. 
The compounds of the invention may be administered by a variety of methods, 
such as intravenously, orally, intramuscularly, intraperitoneally, 
bronchially, intranasally, and so forth. The preferred route of 
administration will depend upon the nature of the compound and the 
condition to be treated. Compounds may be administered orally if well 
absorbed and not substantially degraded upon ingestion (compounds of the 
invention are generally resistant to proteases). The compounds may be 
administered as pharmaceutical compositions in combination with a 
pharmaceutically acceptable excipient. Such compositions may be aqueous 
solutions, emulsions, creams, ointments, suspensions, gels, liposomal 
suspensions, and the like. Thus, suitable excipients include water, 
saline, Ringer's solution, dextrose solution, and solutions of ethanol, 
glucose, sucrose, dextran, mannose, mannitol, sorbitol, polyethylene 
glycol (PEG), phosphate, acetate, gelatin, collagen, Carbopol.RTM., 
vegetable oils, and the like. One may additionally include suitable 
preservatives, stabilizers, antioxidants, antimicrobials, and buffering 
agents, for example, BHA, BHT, citric acid, ascorbic acid, tetracycline, 
and the like. Cream or ointment bases useful in formulation include 
lanolin, Silvadene.RTM. (Marion), Aquaphor.RTM. (Duke Laboratories), and 
the like. Other topical formulations include aerosols, bandages, 
sustainedrelease patches, and the like. Alternatively, one may incorporate 
or encapsulate the compound in a suitable polymer matrix or membrane, thus 
providing a sustained-release delivery device suitable for implantation 
near the site to be treated locally. Other devices include indwelling 
catheters and devices such as the Alzet.RTM. minipump. Further, one may 
provide the compound in solid form, especially as a lyophilized powder. 
Lyophilized formulations typically contain stabilizing and bulking agents, 
for example human serum albumin, sucrose, mannitol, and the like. A 
thorough discussion of pharmaceutically acceptable excipients is available 
in Remington's Pharmaceutical Sciences (Mack Pub. Co.). 
Compounds of the invention may be used to detect the presence of opiate 
receptor in tissues, cells, body fluids, and the like, exploiting the fact 
that compounds of the invention bind to opiate receptor. In general, a 
sample is obtained, and is contacted with a compound of the invention 
under physiological conditions. The sample is then rinsed, and examined 
for binding of the compound. Examination may be facilitated by using 
labeled compound (e.g., radiolabeled with .sup.3 H, .sup.13 C, .sup.125 I, 
and the like). This assay may be useful, inter alia, for examining 
expression of opiate receptor in recombinant host cells, and for studying 
pathological distributions of opiate receptor. 
C. Examples 
The examples presented below are provided as a further guide to the 
practitioner of ordinary skill in the art, and are not to be construed as 
limiting the invention in any way.

EXAMPLE 1 
(Preparation of Compounds) 
Compounds of the invention are prepared as follows: 
A.) General Synthesis of Compounds 
Oligomer synthesis was performed on a Rink amide polystyrene resin (0.61 
mmol/g, 1% crosslinked, 100-200 mesh). N,N-Dimethylformamide (DMF), 
dimethylsulfoxide (DMSO), methylene chloride, glacial acetic acid and 
trifluoroacetic acid (TFA) were obtained from commercial suppliers and 
used without further purification. Piperidine, bromoacetic acid, 
N,N-diisopropylcarbodiimide (DIC), 4-aminobiphenyl, tyramine, 
3,4-methylenedioxybenzylamine, 2,2-diphenethylamine, and other reagents 
were obtained from Aldrich and used without further purification. 
All reactions were performed at room temperature in a 2.0 L vessel equipped 
with a 10 cm coarse glass frit. Agitation of the resin-reagent slurry was 
performed at every step by rotary shaking at 200 rpm. Filtration of the 
resin-reagent slurry was achieved by the application of vacuum. 
A 2.0 L vessel was charged with Rink amide resin (100 g, 0.061 mol). The 
resin was briefly swelled in DMF (1.5 L) with gentle agitation and 
drained. The 9-fluorenyhnethoxycarbonyl (Fmoc) group was then removed by 
treatment with 20% piperidine/DMF (1.7 L, 1.times.5 rain, followed by 
1.times.20 rain). The resin was then washed with DMF (6.times.1.7 L). The 
remainder of the compound was synthesized by performing three cycles of 
acylation with bromoacetic acid and displacement with an amine. 
General acylation conditions (0.061 mol resin) 
Resin-bound amines were bromoacetylated by in situ activation with DIC. To 
the oligomer-resin was added a DMF solution of bromoacetic acid (0.67 M, 
900 mL) followed by DIC (neat, 93 mL, 0.60 tool). The reaction mixture was 
agitated for 30 min at room temperature. The mixture was drained and the 
reaction was repeated once. The resin was washed with DMF (3.times.1.7 L). 
General displacement conditions (0.61 mol) 
Resin-bound bromoacetamides were displaced by the addition of the amine as 
a solution in DMSO (1-2 M, 1.0 L). The reaction mixture was agitated at 
room temperature for 2 hours. The reaction mixture was drained and the 
resin was washed with DMF (3.times.1.7 L). Reagents were used at 2.0 M 
concentration, except tyramine and. phenethylhydrazine (used at 1.0 M). 
General Cleavage and Purification 
After completion of the synthesis the resin was washed with CH.sub.2 
Cl.sub.2 (3.times.1.7 L) and air-dried for 5 minutes. The full length 
trimer was cleaved from the resin (0.061 mol) by treatment with 95% TFA/5% 
water (1.5 L) at room temperature for 15 minutes. The resin was then 
washed with 95% TFA/5% water (1.times.1.0 L) and CH.sub.2 Cl.sub.2 (1 
.times.1 L). The filtrates were pooled and the solvent removed by rotary 
evaporation. The residue was dissolved in glacial acetic acid (150 mL) and 
lyophilized. 
B.) Synthesis of Nbhm-Nmdb-Nhtyr (CHIR-4531) 
The compound Nbhm-Nmdb-Nhtyr (Nbhm=N-benzhydryhnethylglycine; 
Nmdb=N-(3,4-methylenedioxybenzyl)glycine; and 
Nhtyr=N-4-hydroxyphenethylglycine) was synthesized as described in part A) 
above, using 4-hydroxyphenethylamine as the first amine added, 
3,4-methylenedioxybenzylamine as the second amine added, and 
benzhydryhnethylamine as the third amine added. 
##STR17## 
After completion of the synthesis the resin was washed with CH.sub.2 
Cl.sub.2 (3.times.1.7 L) and air dried for 5 minutes. The full length 
trimer was cleaved from the resin (0.061 mol) by treatment with 95% TFA/5% 
water (1.5 L) at room temperature for 15 minutes. The resin was then 
washed with 95% TFA/5% water (1.times.1.0 L) and CH.sub.2 Cl.sub.2 (1 
.times.1 L). The filtrates were pooled and the solvent removed by rotary 
evaporation. The residue was dissolved in glacial acetic acid (150 mL) and 
lyophilized to afford the crude product (CHIR4531, depicted above). The 
purity of the crude product was determined by reverse-phase HPLC. The 
product was characterized by FAB-mass spectrometry. 
C.) Synthesis of Backbone Variants 
Proceeding as described in part A) above, but substituting 3-bromopropanoic 
acid, 2-bromopropanoic acid, and 2-phenyl-3-bromopropanoic acid for 
bromoacetic acid at some positions, compounds wherein X and/or Y are other 
than --CH.sub.2 -- are prepared. 
D.) Synthesis of Additional Compounds 
Other compounds are prepared proceeding as in part A above, but 
substituting for 2,2-diphenethylamine the following compounds: 
2,2-diphenylpropylamine, 3,3-diphenylpropylamine, tritylamine, 
benzhydrylamine, 2-phenethylamine, 2-phenethylhydrazine; 
2-hydroxy-2,2-diphenethylamine, 2-(4-t-butyl)phenethylamine, 
2-phenylpropylamine, 2-(4-methyl)phenethylamine, 
2-(4-ethyl)phenethylamine, (naphth-1-yl)(phenyl)methylamine, 
(4-methylphenyl)(phenyl)methylamine, (4-chlorophenyl)(phenyl)methylamine, 
2-(2-chlorophenyl)ethylamine, 1-phenyl-2-methylprop-2-ylamine, 
1-phenyl-prop-2-ylamine, 2-(4-chlorophenyl)ethylamine, 
2-(3-chlorophenyl)ethylamine, 2-(3-fluorophenyl)ethylamine, and 
1-(4-chlorophenyl)-2-methylprop-2-ylamine. 
The following reactants are substituted for 3,4-methylenedioxybenzylamine: 
3,4-methylenedioxybenzhydrazide, 3,4-methylenedioxyphenethylamine, 
3,4-methylenedioxybenzylthiosemicarbazide, 
1-(3,4-methylenedioxyphenyl)prop-2-ylamine, veratrylamine, 
3,4-methylenedioxyaniline, 6-amino-3,4-methylenedioxyacetophenone, 
1,2-dimnino-4,5-methylenedioxybenzene, 3-methyoxy-4-hydroxybenzylamine, 
6,7-methylenedioxynaphthylamine, 3-methyoxy-2-hydroxybenzylamine, 
2,3-dimethoxybenzylamine, 3,4,5-trimethoxybenzylamine, 
4-methoxybenzhydrylamine, 2,4-dimethoxybenzylamine, 
2,4,6-trimethoxybenzylamine, 2-ethoxybenzylamine, 
1-(3,4-dimethoxyphenyl)-2-phenethylamine, 4-(4-methoxyphenyl)phenylamine, 
2-(3-chlorophenoxy)ethylamine, 2-amino-4,5-dimethoxybenzamide, 
3-methoxyphenethylamine, 4-amino-2-methylnaphthol, 
3-hydroxybenzylhydrazine, lauryamine, decylamine, nonylamine, octylamine, 
1,12-diaminododecane, 1,10-diaminododecane, 1,9-diaminododecane, 
1,8-diaminododecane, 1,1,3,3-tetramethylbutylamine, 
2-amino-3-methylbutane, 2-octylamine, isobutylamine, 1,3-diaminopropane, 
1,1-dimethylpropylamine, 1,4-dimethylheptylamine, 2,2-dimethylpropylamine, 
1,2-diaminopropane, 2-aminopropane, pentylamine, 1,5-diaminopentane, 
1,5-diamino-2-methylpentane, 2-aminohexane, hexylamine, 2-aminopentane, 
butylamine, 2-amino-5-methylhexane, 3-aminoheptane, 1,6-hexanediamine, 
1,3-dimethylbutylamine, 4-methylbutylamine, 2-methylbutylamine, 
1-ethylpropylamine, 1,4-diaminobutane, 2-ethylhexylamine, 2-aminoheptane, 
heptylamine, 1,7-diaminoheptane, 3-amino-2,4-dimethylpentane, 
1,2-diaminobutane, 2-aminobutane, propylamine, 1,5-dimethylhexylamine, 
1,6-diamino-2,4,4-trimethylhexane, stearylamine, pahnitylamine, 
pentadecylamine, tetradecylamine, and tridecylamine. 
The following reactants are substituted for tyramine: phenethylamine, 
benzylamine, 3,4-methylenedioxyphenethylamine, 
3-tfifluoromethylphenethylamine, 2-chlorophenethylamine, 
3-chlorophenethylamine, phenylpropylamine, 4-chlorophenethylamine, 
2,4-dichlorophenethylamine, 3-bromophenethylamine, 4-iodophenethylamine, 
3-hydroxyphenethylamine, 4-hydroxyphenethylamine, 
2,4-dihydroxyphenethylamine, 2-methylphenethylamine, 
3-methylphenethylamine, 4-methylphenethylamine, 
2,4-dimethylphenethylamine, 2,4,6-trimethylphenethylamine, 
3-ethylphenethylamine, 4-ethylphenethylamine, 4-hexylphenethylamine, 
3-nitrophenethylamine, 2-aminophenethylamine, 4-aminophenethylamine, 
2,4-diaminophenethylamine, 2-methoxyphenethylamine, 
3-methoxyphenethylamine, 4-methoxyphenethylamine, 
2,4-dimethoxyphenethylamine, 2,4,6-trimethoxyphenethylamine, 
3,4-dimethoxyphenethylamine, 2-ethoxyphenethylamine, 
3-ethoxyphenethylamine, 4-ethoxyphenethylamine, 3-propoxyphenethylamine, 
4-butoxyphenethylamine, 4-t-butoxyphenethylamine, 
3-methoxymethylphenethylamine, 4-methoxymethylphenethylamine, 
3-(2-methoxyethyl)phenethylamine, 4-(2-methoxyethyl)phenethylamine, 
4-(2hydroxyethyl)phenethylamine, 4-(3-hydroxypropyl)phenethylamine, 
4-(2-hydroxyethoxy)phenethylamine, 4-phenylphenethylamine, 
4-(2-chlorophenyl)phenethylamine, 4-(2-aminophenyl)phenethylamine, 
3-(2,4,6-trimethylphenyl)phenethylamine, 4-phenoxyphenethylamine, 
4-(3-chlorophenoxy)phenethylamine, 4-(4-aminophenoxy)phenethylamine, 
3-benzylphenethylamine, 4-phenethylphenethylamine, 3-acetylphenethylamine, 
4-acetylphenethylamine, 4-(2-phenoxyethyl)phenethylamine, and 
3-benzyloxyphenethylamine. 
The compounds corresponding to the above-listed substitutions are prepared 
following the procedure set forth in part A) above. 
EXAMPLE 2 
(Activity In Vitro) 
Compounds were screened in vitro using the following assay: 
High-affinity ligands for the .mu.-specific opiate receptor were identified 
from a diverse peptoid library by testing the pools of compounds in 
solution-phase radioligand competition assays, and tracing the binding 
activity to individual compounds by iterative resynthesis and screening of 
smaller sub-pools. 
Rat forebrains were homogenized and washed in 50 mM Tris, pH 7.5 containing 
20 mM NaCl, 5 mM EGTA, 2 mM MgCl.sub.2, 21 .mu.g/mL aprotinin, 0.5 mg/L 
leupeptin, 0.7 mg/L pepstatin, 0.2 Mm PMSF. 50 .mu.L of membrane (10 mg/mL 
protein) were dispensed into 1 mL of 50 mM Tris, pH 7.5, 1 nM [.sup.3 
H]-DAMGO and the peptoid mixture. All assays were performed at 100 nM per 
peptoid. 
Nonspecific binding was determined as [.sup.3 H]-DAMGO bound in the 
presence of 1 .mu.M naloxone. Incubation was for 1 hr at room temperature. 
Unbound radioactivity was removed by rinsing the membranes on Whatman GF/B 
glass fiber filters. Each filter was washed 3 times with 3 mL of 50 mM 
Tris, pH 7.5, 4.degree. C. Filters were soaked overnight in 5 mL of 
Beckman ReadySafe scintillation cocktail and then counted for one minute 
in a Wallac 1409 liquid scintillation counter. Assays were performed in 
duplicate. 
Compound CHIR-4531 (Nbhm-Nmdb-Nhtyr) exhibited a K.sub.i =7 nM. Compound 
CHIR-4534 (Nbhm-Npen-Nhtyr) exhibited a K.sub.i =30 nM. Compound CHIR-4537 
(Nbhm-Nddb-Nhtyr) exhibited a K.sub.i =45 nM. 
______________________________________ 
% Inhibition 
CHIR Compound K.sub.i at 100 nM 
______________________________________ 
4531 Nbhm-Nmdb-Nhtyr 
7 nM 
4534 Nbhm-Npen-Nhtyr 
30 nM 
4537 Nbhm-Nddb-Nhtyr 
45 nM 
4622 Nbhe-Nmdb-Nhtyr 
78% 
4626 Nbhm-Ntrnb-Nhtyr 
86% 
4627 Nbhm-Nphe-Nhtyr 
90% 
4628 Nbhm-Nphe-Nhphe 
77% 
5052 Nbha-Nmdb-Nhtyr 
73% 
5045 Nvbhm-Nmdb-Nhtyr 
58% 
5062 Nbvp-Nmdb-Nhtyr 
65% 
______________________________________ 
EXAMPLE 3 
(Assay In vivo) 
Compounds of the invention are tested in vivo as follows: Male Swiss (ICR) 
mice (25-30 g) and male Sprague Dawley albino rats (100-125 g) are housed 
in groups of 5, and allowed food and water ad libitum until the beginning 
of the experiment. 
A. Mouse stretch test: This procedure is a general, non-specific test for 
detecting antinociceptive activity in a wide variety of pharmacological 
agents. Each mouse (n=10) is administered either vehicle or test compound 
(0.1 mg/Kg to 300 mg/Kg) subcutaneously. After 5 rain, dilute acetic acid 
(0.6%) is injected i.p. (0.25 mL/25 g). Each animal is then observed after 
an additional 5 min, and the number of abdominal twists/hind leg stretches 
displayed by each mouse is counted for a 5 min. test period. Percent 
inhibition of response is calculated from 100.times.(mean number of 
stretches in vehicle group - mean number of stretches per mouse)/(mean 
number of stretches in vehicle group). The dose of compound causing 50% 
antinociception (at 95% confidence limits) is calculated by regression 
analysis. 
Oral studies are performed with different mice. Test compound (or vehicle) 
is administered orally, followed by acetic acid injection 25-55 min after 
administration. 
Antagonism studies are performed by first obtaining a dose-response crowe 
for s.c. morphine and vehicle. Mice are administered test compound s.c., 
(0.1 mg/Kg to 300 mg/Kg) followed 5 rain later by morphine in one of 4 
doses s.c. (determined according to standard experimental protocol). 
Morphine antagonism is demonstrated if the morphine dose-response curve is 
displaced to the right. 
B. Rat Formalin Test: Dilute formalin provides a continuous (tonic) 
background of pain that may be neurochemically and neurophysiologically 
different from the transient (phasic) pain associated with hot plate and 
tail-flick tests. 
Rats (n=8) are acclimated to individual Plexiglas observation chambers for 
at least 1 hr prior to testing. Each animal is then injected with 5% 
formalin (50 .mu.L) or saline (50 .mu.L) s.c. into the dorsal surface of 
the right hind paw. The rats display two spontaneous behaviors indicative 
of pain: flinching/shaking of the paw and/or hindquarters, and licking or 
biting of the injected paw. Flinching is the most reliable behavior to 
score in rats. The behavior is monitored between 0-10 rain (early/acute 
phase) and 20-35 min (late/tonic phase) following injection. 
Four doses of test compound are injected s.c. (0.1 mg/Kg to 300 mg/Kg). The 
pretreatment time is chosen so that peak antinociceptive activity 
coincides with the late/tonic phase of response. Results are expressed as 
mean % antagonism of formalin-induced flinching, and are calculated for 
individual, drug-treated formalin-injected rats. 
C. Neuroadaptation of Rats: This protocol provides information on how rats 
react to multiple doses of test compounds, and on eventual challenge with 
naloxone, a standard antagonist of opioid receptors. 
Four groups of 6 rats are injected s.c. with either vehicle or test 
compound at 8:00 AM, 4:00 PM, and midnight over 5 days. On the fifth day, 
only the morning injection is administered. The initial dosages are: day 
1=1 mg/Kg, day 2=2 mg/Kg, days 3-5=4 mg/Kg. Naloxone (3 mg/Kg, s.c.) or 
saline is administered 4 hr after the final injection of test compound. 
On day 4, the rats are acclimated to Plexiglas observation cages in a 
constant temperature room (20.degree. C.). The animals are trained to have 
their weights and rectal temperature taken. On day 5, this procedure is 
repeated before noting baseline readings, and challenging with naloxone or 
saline. Behaviors are monitored for 30 min before and after challenge with 
naloxone or saline. After the final weighing and temperature reading, 1 hr 
post challenge, each animal is euthanized with solid CO.sub.2. 
Behavioral changes in the 4 groups of rats (vehicle-saline, 
vehicle-naloxone, compound-naloxone, compound-saline) are assessed by a 
point-scoring technique (with weighted signs): Cowan et al., J Pharmacol 
Exp Ther (1988) 246:950.