A.sub.4 B.sub.6 macrotricyclic enantioselective receptors for amino acid derivatives, and other compounds

The subject invention provides chiral receptor molecules having the structure: ##STR1## wherein A has the structure: ##STR2## and R.sub.1 and R.sub.2 are independently the same or different and are H, F, alkyl, aryl, etc.; X is CH.sub.2 or NH; Y is C.dbd.O or SO.sub.2 ; and n is 0 to about 3; which are useful for the purification of enantiomers of amino acid derivatives and other compounds. The subject invention also provides methods of preparing said receptor molecules.

BACKGROUND OF THE INVENTION 
This invention relates to the field of molecular recognition of small 
ligands. More particularly, the invention relates to compositions useful 
for the purification of enantiomers of amino acid derivatives and for the 
purification of certain compounds able to form hydrogen bonds, methods for 
preparing these compositions, and methods for using them. 
Standard approaches to the optical resolution and purification of organic 
and biological molecules include crystallization, distillation, 
extraction, and chromatography (Eliel, Stereochemistry of Carbon 
Compounds, New York: McGraw-Hill, 1962). Each methodology is based on a 
physical or chemical interaction of a molecule with an element of its 
environment, and may involve molecular sizing, electrostatics, 
hydrophobicity, sterics, or polarity. The efficiency of purification 
increases as the differences in interaction energy for all the species 
present in the mixture increase. The relevant interactions for 
cystallization are crystal lattice forces and solvation of the molecule; 
for distillation, the interaction is a liquid-gas phase transition; while 
for extraction and chromatography, the interaction is exchange between 
non-miscible phases. Common to all these classic methods is the limitation 
that as molecular structures become increasingly similar, the energy 
differentials for the relevant interaction diminish to the extent that 
high resolution is no longer feasible. A general approach to purification 
necessitates an enhanced capability for transcending this natural tendency 
toward shrinking energy differences. The ability to purify very similar or 
chiral molecules is of economic and practical importance to the developing 
fields of biotechnology, and should greatly accelerate the development of 
new pharmaceuticals and bioactive and other useful compounds. 
The ability to distinguish similar molecules is an important goal of 
research in the field of molecular recognition. Early efforts to bind 
molecules selectively involved naturally occurring host molecules, such as 
clathrates, cholic acid, and cyclodextrins (Diederich, Angew. Chem. Int. 
Ed. Eng., 27, 362 (1988); Breslow, Science (Washington, D.C.), 218, 532 
(1982)). The first example of a synthetic system specifically designed to 
undergo inclusion complexation was a cyclophane (Stetter & Roos, Chem. 
Ber., 88, 1390 (1955)). Synthetic crown ethers and cyclic polyamines were 
designed to complex metal ions selectively by adjusting ring size and 
number of heteroatoms (Pederson, Angew. Chem. Int. Ed. Eng., 16, 16 
(1972)). Macrobicyclic compounds have been prepared which show selectivity 
for trihydrobenzenes with certain substitution patterns (Ebmeyer and 
Vogtle, Angew. Chem. Int. Ed. Engl., 28, 79 (1989)). 
The use of chiral components in constructing host compounds has led to the 
development of molecules which are, in principle, capable of 
diasteroselective complexation with chiral guests. While several systems 
have exhibited some diastereoselectivity, numerous attempts to produce 
chiral hosts have not produced any known compounds of practical utility 
prior to the present invention. The earliest preparations of chiral crown 
amino ethers were applied to cation complexation, and not to chiral 
discrimination by diastereoselective complexation (Wudl & Gaeta, J. Chem. 
Soc., Chem. Commun., 107 (1972)). Chiral hosts based on 
biphenyl-macrocycles have shown promise (Kyba, et al., J. Amer. Chem. 
Soc., 100, 4555 (1978)). A recent example intended to distinguish 
enantiomers of amino acids and arylpropionic acids however appears from 
binding studies not to function as a host for nonpolar molecules (Rubin, 
et al., J. Org. Chem., 51, 3270 (1986)). 
High enantioselectivity has thus largely eluded prior workers in the field. 
A bilaterally symmetric host containing two diiodotyrosine moieties was 
one of the first to exhibit a measurable difference in binding energy with 
mirror image guest molecules (Sanderson, et al., J. Amer. Chem. Soc., 111, 
8314 (1989)); free energy differences ranged from -0.15 to 0.48 kcal/mole, 
with binding site saturations up to 67%. More recently, a related chiral 
host was made with pyridyl moieties replacing benzene rings in the 
macrocycle, which showed free energy differences up to about 1 kcal/mole 
and a range of binding saturations of approximately 40-80% (Liu, et al., 
J. Org. Chem., 55, 5184 (1990)). Chiral hosts in which the 
enantioselection energies exceed 1 kcal/mole have been virtually 
nonexistant prior to the present invention. 
Progress toward a completely chemoselective or enantioselective host has 
been limited, proceeding roughly in parallel with growing understanding of 
intermolecular interactions controlling binding affinity in natural 
receptors like enzymes and hormone receptors. The present invention 
provides a composition of matter which possesses enzyme-like 
enantioselectivity which is sufficiently high to offer practical utility 
in optical organic resolution and chemical purification of compounds. 
SUMMARY OF THE INVENTION 
The present invention relates to a composition of matter having the 
structure: 
##STR3## 
wherein each of A, B, C, X, Y, and Z is independently O, NH, 
N(CH.sub.2).sub.m CH.sub.3, N(C.dbd.O)(CH.sub.2).sub.m CH.sub.3, CH.sub.2, 
S, or Se; each of R.sub.1, R.sub.2, and R.sub.3 is independently phenyl, 
4-hydroxyphenyl, pyridyl, pyrrolyl, indolyl, naphthyl, thiophenyl, 
(C.dbd.O)(CH.sub.2).sub.p CH.sub.3, NH(C.dbd.O)(CH.sub.2).sub.p CH.sub.3, 
OH, COOH, NH.sub.2, or SH; and m, n, and p are integers between 0 and 5. 
The invention provides a process of obtaining a purified enantiomeric 
isomer of a compound of interest from a mixture of isomers of such 
compounds which comprises contacting the mixture of isomers with the 
composition under conditions such that the enantiomeric isomer binds to 
the composition to form a complex, separating the resulting complex from 
the mixture, treating the complex so as to separate the enantiomeric 
isomer from the composition, and recovering the purified enantiomeric 
isomer. 
The invention also provides a process of obtaining a purified organic 
compound of interest able to form hydrogen bonds from a mixture of organic 
compounds which comprises contacting the mixture with the composition 
under conditions such that the organic compound binds to the composition 
to form a complex, separating the resulting complex from the mixture, 
treating the complex so as to separate compound from the composition, and 
recovering the purified compound. 
The invention further provides a process of preparing the composition which 
comprises: (a) reacting a chiral multifunctional reagent containing at 
least one protecting group with a compound having the structure: 
##STR4## 
wherein each of A, B, C, X, Y, and Z is independently O, NH, 
N(CH.sub.2).sub.m CH.sub.3, N(C.dbd.O)(CH.sub.2).sub.m CH.sub.3, CH.sub.2, 
S, or Se, under conditions permitting formation of a compound having the 
structure: 
##STR5## 
wherein each of A, B, C, X, Y, and Z is independently O, NH, 
N(CH.sub.2).sub.m CH.sub.3, N(C.dbd.O)(CH.sub.2).sub.m CH.sub.3, CH.sub.2, 
S, or Se; each of R.sub.1, R.sub.2, and R.sub.3 is independently phenyl, 
4-hydroxyphenyl, pyridyl, pyrrolyl, indolyl, naphthyl, thiophenyl, 
(C.dbd.O)(CH.sub.2)pCH.sub.3, NH(C.dbd.O)(CH.sub.2).sub.p CH.sub.3, OH, 
COOH, NH.sub.2, or SH; and m, n, and p are integers between 0 and 5; 
(b) treating the compound formed in step (a) under suitable conditions so 
as to cleave one protecting group and form a compound having the 
structure: 
##STR6## 
wherein each of A, B, C, X, Y, and Z is independently O, NH, 
N(CH.sub.2).sub.m CH.sub.3, N(C.dbd.O)(CH.sub.2).sub.m CH.sub.3, CH.sub.2, 
S, or Se; each of R.sub.1, R.sub.2, and R.sub.3 is independently phenyl, 
4-hydroxyphenyl, pyridyl, pyrrolyl, indolyl, naphthyl, thiophenyl, 
(C.dbd.O)(CH.sub.2).sub.p CH.sub.3, NH(C.dbd.O)(CH.sub.2).sub.p CH.sub.3, 
OH, COOH, NH.sub.2, or SH; and m, n, and p are integers between 0 and 5; 
(c) treating the compound formed in step (b) with a condensing agent under 
conditions permitting multiple macrolactamization so as to thereby form 
the composition. 
The present invention further provides a composition of matter having the 
structure: 
##STR7## 
wherein A has the structure: 
##STR8## 
and R.sub.1 and R.sub.2 are independently the same or different and are H, 
F, a linear or branched chain alkyl, arylalkyl, alkoxyalkyl, aminoalkyl, 
alkylaminoalkyl, hydroxyalkyl, (cycloalkyl)alkyl, or acylalkyl group, or 
an aryl group, a linear or branched chain alkylaryl, pyridyl, thiophene, 
pyrrolyl, indolyl or naphthyl group; X is CH.sub.2 or NH; Y is C.dbd.O or 
SO.sub.2 ; and n is 0 to about 3. 
The present invention also provides a composition of matter having the 
structure: 
##STR9## 
wherein A has the structure: 
##STR10## 
and R.sub.1 is H, a linear or branched chain alkyl, arylalkyl, 
alkoxyalkyl, aminoalkyl, alkylaminoalkyl, hydroxyalkyl, (cycloalkyl)alkyl, 
or acylalkyl group, or an aryl group, a linear or branched chain 
alkylaryl, pyridyl, thiophene, pyrrolyl, indolyl or naphthyl group. 
The present invention also provides a composition of matter having the 
structure: 
##STR11## 
wherein R.sub.1, R.sub.2 and R.sub.3 are C.sub.6 H.sub.4 (OCH.sub.2 
CH.dbd.CH.sub.2); A, B and C are CH.sub.2 ; X, Y and Z are S; and n is 1.

DETAILED DESCRIPTION OF THE INVENTION 
The present invention provides a composition of matter having the 
structure: 
##STR12## 
wherein each of A, B, C, X, Y, and Z is independently O, NH, 
N(CH.sub.2).sub.m CH.sub.3, N(C.dbd.O)(CH.sub.2).sub.m CH.sub.3, CH.sub.2, 
S, or Se; each of R.sub.1, R.sub.2, and R.sub.3 is independently phenyl, 
4-hydroxyphenyl, pyridyl, pyrrolyl, indolyl, naphthyl, thiophenyl, 
(C.dbd.O)(CH.sub.2).sub.p CH.sub.3, NH(C.dbd.O)(CH.sub.2).sub.p CH.sub.3, 
OH, COOH, NH.sub.2, or SH; and m, n, and p are integers between 0 and 5. 
In one embodiment of the invention, X, Y, and Z are each O; in another 
embodiment, they are each S. In certain other embodiments, R.sub.1, 
R.sub.2, and R.sub.3 are each phenyl, or they are each 4-hydroxyphenyl. 
Additionally, in certain embodiments, n is desirably 1. 
The invention further provides a process of obtaining a purified 
enantiomeric isomer of a compound of interest from a mixture of isomers of 
such compounds which comprises contacting the mixture of isomers with the 
chiral host composition defined hereinabove under conditions such that the 
enantiomeric isomer binds to the composition to form a complex, separating 
the resulting complex from the mixture, treating the complex so as to 
separate the enantiomeric isomer from the composition, and recovering the 
purified enantiomeric isomer. In one embodiment, the process is used to 
purify enantiomers of amino acid derivatives, of which diamides are 
particularly effective. 
The invention also provides a process of obtaining a purified organic 
compound of interest from a mixture of organic compounds able to form 
hydrogen bonds, which comprises contacting the mixture with the chiral 
host composition defined hereinabove under conditions such that the 
organic compound binds to the composition to form a complex, separating 
the resulting complex from the mixture, treating the complex so as to 
separate the compound from the composition, and recovering the purified 
compound. In one embodiment, the process is used to purify derivatives of 
amino acids differing in side-chains. The process is particularly well 
suited to purify diamide derivatives of amino acids. 
One application of the composition is to bind it to a solid support such 
that a chromatographic adsorbent results which is specific for 
enantiomeric isomers of compounds of interest and other organic compounds 
of interest which differ only in side-chain substitution. Effective use of 
the composition bound to a solid support is made to obtain the 
enantiomeric isomers of an amino acid derivative in a purified form and to 
obtain a purified organic compound of interest able to form hydrogen bonds 
from a mixture of compounds. The compound to be purified by the 
composition is preferably a diamide. 
The invention further provides a process of preparing the composition, 
which comprises: 
(a) reacting a chiral multifunctional reagent containing at least one 
protecting group with a compound having the structure: 
##STR13## 
wherein each of A, B, C, X, Y, and Z is independently O, NH, 
N(CH.sub.2).sub.m CH.sub.3, N(C.dbd.O)(CH.sub.2).sub.m CH.sub.3, CH.sub.2, 
S, or Se, under conditions permitting formation of a compound having the 
structure: 
##STR14## 
wherein each of A, B, C, X, Y, and Z is independently O, NH, 
N(CH.sub.2).sub.m CH.sub.3, N(C.dbd.O)(CH.sub.2).sub.m CH.sub.3, CH.sub.2, 
S, or Se; each of R.sub.1, R.sub.2, and R.sub.3 is independently phenyl, 
4-hydroxyphenyl, pyridyl, pyrrolyl, indolyl, naphthyl, thiophenyl, 
(C.dbd.O)(CH.sub.2).sub.p CH.sub.3, NH(C.dbd.O)(CH.sub.2).sub.p CH.sub.3, 
OH, COOH, NH.sub.2, or SH; and m, n, and p are integers between 0 and 5; 
(b) treating the compound formed in step (a) under suitable conditions to 
cleave one protecting group to form a compound having the structure: 
##STR15## 
wherein each of A, B, C, X, Y, and Z is independently O, NH, 
N(CH.sub.2).sub.m CH.sub.3, N(C.dbd.O)(CH.sub.2).sub.m CH.sub.3, CH.sub.2, 
S, or Se; each of R.sub.1, R.sub.2, and R.sub.3 is independently phenyl, 
4-hydroxyphenyl, pyridyl, pyrrolyl, indolyl, naphthyl, thiophenyl, 
(C.dbd.O)(CH.sub.2).sub.p CH.sub.3, NH(C.dbd.O)(CH.sub.2).sub.p CH.sub.3, 
OH, COOH, NH.sub.2, or SH; and m, n, and p are integers between 0 and 5; 
(c) treating the compound formed in step (b) with a condensing agent under 
conditions permitting multiple macrolactamization, thereby forming the 
desired composition. 
The preparation of the composition strategically exploits its C.sub.3 
symmetry. The synthesis of the composition could proceed in a manner 
analogous to the detailed experimental examples given hereinbelow for 
embodiments in which X, Y, and Z are S, and R.sub.1, R.sub.2, R.sub.3 are 
4-hydroxyphenyl, except that if there is only one protecting group in the 
chiral multifunctional reagent of step (a), then none of the side-group 
protection reactions would pertain. 
The coupling of step (a) above can be carried out by several alternative 
methods of forming amide bonds. One approach is to contact the achiral 
tetraaromatic triamino triester above shown with the p-nitrophenyl active 
ester of the chiral multifunctional reagent, made from p-nitrophenol, 
N-hydroxybenzotriazole, and N,N-dicyclohexylcarbodiimide. The reaction may 
be performed in the presence of aprotic dipolar solvents, such as 
N,N-dimethylformamide, tetrahydrofuran, or dimethylsulfoxide, diluted with 
a miscible cosolvent, such as dichloromethane, to the extent required to 
achieve solubility of all reactants, at temperatures from about 0.degree. 
to 100.degree. C., preferably from 0.degree. to 30.degree. C. The 
preparation of the starting material for step (a) can be obtained by 
trialkylation of 1,3,5-trimercaptobenzene or phloroglucinol with 
N-protected methyl 3-(aminomethyl)-5-(bromomethyl)benzoate, followed by 
cleavage of the N-protecting group. In one embodiment of the invention, 
the chiral multifunctional reagent containing at least one protecting 
group in step (a) is an amino acid containing an N-protecting group. In 
certain embodiments, the amino acid is L-phenylalanine or L-tyrosine. The 
N-protecting group is preferably chosen such that it may be removed in 
process step (b) by an acid, for example, trifluoroacetic acid. In 
general, process step (b) involves the removal of three protecting groups 
on the tetraaromatic intermediate. This reaction could be effected by any 
method corresponding to the lability of the protecting group. A large 
variety of protecting groups are available for the purpose, including 
t-butyloxycarbonyl (BOC), benzyloxycarbonyl, 2-bromobenzyloxycarbonyl, and 
p-toluensulfonyl. While a preferred method is to use acid-sensitive BOC 
groups, other effective protecting groups also removable by acid include 
biphenylisopropyloxycarbonyl (Bpoc) and adamantyloxycarbonyl (Adoc), Still 
other protecting groups may be selected such that alternative methods of 
removal are feasible according to the invention, including photolytic, 
reductive, electrochemical, and mild base conditions. This flexibility 
allows a wide range of chiral multifunctional reagents to be used to 
prepare the composition. 
Prior to condensation process (c), the protecting ester group (for example, 
methyl) on each of the three aromatic moieties could be cleaved to give 
the carboxylic acid by (i) transesterification with trimethylsilylethanol, 
followed by (ii) fluoride-induced silane elimination. The condensing agent 
in step (c) could comprise a reagent generated (i) from an agent selected 
from a group comprising pentafluorophenol, hydroxybenzotriazole, 
4-nitrophenol, 2-nitrophenol, pentachlorophenol, hydroxysuccinimide, and 
hydroxypiperidine and (ii) from an agent selected from a group consisting 
of N,N-dicyclohexyldiimide, diisopropylcarbodiimide, and 
carbonyldiimidazole. Other condensing methods may also serve the purpose, 
including Woodward's reagent K, mixed anhydrides, 
triphenylphosphine/2,2'-dipyridyl sulfide, ketenimines, and 
acyloxyphosphonium salts. In a preferred embodiment, the condensing agent 
is the combination of N,N-dicyclohexylcarbodiimide and pentafluorophenol. 
If the multifunctional chiral reagent of step (a) contains an alcohol 
function, the process of steps (b) and (c) could be simply adapted to 
generate three ester linkages after multiple macrolactonization. Other 
modifications in the multifunctional chiral reagent of step (a) could be 
readily envisioned to form such alternative linkages as thioesters, 
thionoesters, and phosphoramides. 
The protecting groups which may be present on side-group functionalities 
could be cleaved by a method corresponding to their lability. In one 
embodiment, R.sub.1, R.sub.2, and R.sub.3 are 4-hydroxyphenyl which should 
be made by coupling with the suitably protected multifunctional chiral 
reagent Boc-L-tyrosine (Tyr). The protecting group on the Tyr is 
preferably an allyl ether. The processes described provided the 
embodiments of the composition, wherein R.sub.1, R.sub.2, and R.sub.3 are 
phenyl, in 30% overall yield for the trithia receptor and 7% yield for the 
trioxa receptor, respectively referred to hereinafter as 1 and 2. 
Preparation of the tyrosine trithia macrocycle is described in Examples 1 
to 16, which serve as an enabling model illustrative for all embodiments 
of the composition. 
The present invention also provides a composition of matter hereinafter 
denoted 9 having the structure: 
##STR16## 
wherein A has the structure: 
##STR17## 
and R.sub.1 and R.sub.2 are independently the same or different and are H, 
F, a linear or branched chain alkyl, arylalkyl, alkoxyalkyl, aminoalkyl, 
alkylaminoalkyl, hydroxyalkyl, (cycloalkyl)alkyl, or acylalkyl group, or 
an aryl group, a linear or branched chain alkylaryl, pyridyl, thiophene, 
pyrrolyl, indolyl or naphthyl group; X is CH.sub.2 or NH; Y is C.dbd.O or 
SO.sub.2 ; and n is 0 to about 3. In one embodiment, the present invention 
provides a composition wherein X is NH. 
In another embodiment, the invention provides a composition wherein X is 
CH.sub.2, Y is C.dbd.O and n is 1. In another embodiment, the invention 
provides a composition wherein R.sub.1 and R.sub.2 are H. 
The present invention also provides a composition of matter (hereinafter 
referred to as 10) having the structure: 
##STR18## 
wherein A has the structure: 
##STR19## 
and R.sub.1 is H, a linear or branched chain alkyl, arylalkyl, 
alkoxyalkyl, aminoalkyl, alkylaminoalkyl, hydroxyalkyl, (cycloalkyl)alkyl, 
or acylalkyl group, or an aryl group, a linear or branched chain 
alkylaryl, pyridyl, thiophene, pyrrolyl, indolyl or naphthyl group. In one 
embodiment, the invention provides a composition wherein R.sub.1 is a 
phenyl group. In another embodiment, the invention provides a composition 
wherein R.sub.1 is a benzyloxymethyl group. 
The present invention further provides a composition of matter (hereinafter 
referred to as 2A) having the structure: 
##STR20## 
wherein R.sub.1, R.sub.2 and R.sub.3 are C.sub.6 H.sub.4 (OCH.sub.2 
CH.dbd.CH.sub.2); A, B and C are CH.sub.2 ; X, Y and Z are S; and n is 1. 
The present invention also provides a compound which comprises the 
compositions of matter 9, 10, or 2A, bound to a solid support. 
The present invention further provides a complex which comprises the 
compositions 9, 10, or 2A, bound to a derivative of an amino acid. In one 
embodiment, the invention provides a composition wherein the derivative is 
an amide. 
The present invention provides a process of obtaining a purified 
enantiomeric isomer of a compound of interest from a mixture of isomers of 
such compounds which comprises contacting the mixture of isomers with the 
compositions 9, 10, or 2A, under conditions such that the enantiomeric 
isomer binds to the compositon to form a complex, separating the resulting 
complex from the mixture, treating the complex so as to separate the 
enantiomeric isomer from the composition, and recovering the purified 
enantiomeric isomer. 
The present invention further provides a process of obtaining a purified 
organic compound of interest from a mixture of organic compounds able to 
form hydrogen bonds, which comprises contacting the mixture with the 
compositions 9, 10, or 2A, under conditions such that the organic compound 
binds to the composition to form a complex, separating the resulting 
complex from the mixture, treating the complex so as to separate the 
organic compound from the composition, and recovering the purified 
compound. In one embodiment, the invention provides a process wherein the 
purified organic compound is an amino acid derivative. 
The present invention also provides a process of preparing the composition 
having the structure: 
##STR21## 
wherein A has the structure: 
##STR22## 
wherein R.sub.1 and R.sub.2 are H and n is 1 which comprises: (a) 
condensing a compound having the structure: 
##STR23## 
with a compound having the structure: 
##STR24## 
under suitable conditions to produce a compound having the structure: 
##STR25## 
(b) hydrolyzing the compound formed by step (a) under suitable conditions 
to form an acid compound having the structure: 
##STR26## 
(c) treating the compound formed in step (b) under suitable conditions so 
as to activate the acid compound to form a compound having the structure: 
##STR27## 
(d) reacting the compound formed in step (c) under suitable conditions 
with a compound having the structure: 
##STR28## 
to form a compound having the structure: 
##STR29## 
(e) saponifying the compound formed by step (d) under suitable conditions 
to form a diacid having the structure: 
##STR30## 
(f) activating the diacid formed in step (e) under suitable conditions to 
form a compound having the structure: 
##STR31## 
(g) deprotecting the compound formed in step (f) under suitable conditions 
to form a diamino diacid having the structure: 
##STR32## 
(h) dimerizing the diamino diacid formed in step (g) under suitable 
conditions to form the composition having the structure: 
##STR33## 
wherein A has the structure: 
##STR34## 
and R.sub.1 and R.sub.2 are H and n is 1. 
In condensing step (a) it is to be understood that esters other than methyl 
esters may be used in an equivalent manner for the purposes of the 
process. Other useful esters include ethyl, propyl, phenol, and benzyl 
esters. The condensing agent in step (a) could comprise a reagent 
generated (i) from an agent selected from a group comprising 
pentafluorophenol, hydroxybenzotriazole, 4-nitrophenol, 2-nitrophenol, 
pentachlorophenol, hydroxysuccinimide, and hydroxypiperidine and (ii) from 
an agent selected from a group consisting of N,N-dicyclohexyldiimide, 
diisopropylcarbodiimide, and carbonyldiimidazole. Other condensing methods 
may also serve the purpose, including Woodward's reagent K, mixed 
anhydrides, triphenylphosphine/2,2'-dipyridyl sulfide, ketenimines, and 
acyloxyphosphonium salts. Hydrolyzing step (b) may be performed using base 
or acid catalysis, though preferably base catalysis. Favorable results 
obtain using sodium hydroxide. Treating step (c) is effected by a wide 
variety of procedures, including reaction of pentafluorophenol with DCC or 
1-(3-(dimethylamino)propyl)-3-ethylcarbodiimide hydrochloride (EDC). 
Reacting step (d) is performed in the presence of a nonnucleophilic base 
such as triethylamine. Good solvents for the purpose include dimethyl 
acetamide or dimethyl formamide. Saponifying step (e) is carried out using 
a base, such as sodium hydroxide. Other bases which effect the step 
include lithium hydroxide, potassium hydroxide, and tetramethylammonium 
hydroxide. Activating step (f) is effectively performed using an 
activating agent such as pentafluorophenol. Other agents include 
hydroxybenzotriazole, 4-nitrophenol, 2-nitrophenol, pentachlorophenol, 
hydroxysuccinimide, and hydroxypiperidine. Deprotecting step (g) is 
carried out preferrably under mildly acidic conditions. Useful acids 
include trifluoroacetic, trichloroacetic acid and hydrochloric acid in 
dioxane solution. Scavengers such as anisole help prevent untoward 
alkylation reactions. Dimerizing step (h) may be effectively performed in 
the presence of a mild nonnucleophilic base, such as diisopropylethylamine 
or triethylamine in a dipolar nonaqueous solvent, such as tetrahydrofuran. 
The present invention also provides a process of preparing the composition 
having the structure: 
##STR35## 
wherein A is a 1,3,5-trisubstituted phenyl moiety and R.sub.1 and R.sub.2 
are H and n is 1 which comprises: reacting a compound having the 
structure: 
##STR36## 
with a compound having the structure: 
##STR37## 
under suitable conditions to form a compound: 
##STR38## 
wherein A has the structure: 
##STR39## 
and R.sub.1 and R.sub.2 are H and n is 1. 
The reacting step may be effectively performed as a one-pot procedure in 
the presence of a mild nonnucleophilic base such as diisopropylethylamine. 
Useful solvents include dipolar nonaqueous solvents such as dimethyl 
formamide and tetrahydrofuran. The reaction may be carried out over a 
range of temperatures from -25.degree. C. to 60.degree. C., but preferably 
at 0.degree.-10.degree. C. 
The present invention also provides a process of preparing the composition 
having the structure: 
##STR40## 
which comprises: (a) reacting a compound having the structure: 
##STR41## 
with ammonia under suitable conditions to form a compound having the 
structure: 
##STR42## 
(b) reacting the compound formed by step (a) with an acylating agent under 
suitable conditions to form a plurally acylated compound having the 
structure: 
##STR43## 
(c) reacting the plurally acylated compound formed by step (b) with a 
compound having the structure: 
##STR44## 
under suitable conditions to form an alkylated amide having the 
structure: 
##STR45## 
(d) reacting the alkylated amide formed by step (c) with 
benzene-1,3,5-trithiol under suitable conditions to form a sulfide having 
the structure: 
##STR46## 
(e) deprotecting the sulfide formed by step (d) under suitable conditions 
to form a free amine ester having the structure: 
##STR47## 
(f) re-acylating the free amine ester formed by step (e) under suitable 
conditions to form an acylamine ester having the structure: 
##STR48## 
(g) saponifying the acylamine ester formed by step (f) under suitable 
conditions to form an acylamine acid having the structure: 
##STR49## 
(h) activating the acylamine acid formed by step (g) under suitable 
conditions to form an acylamine activated ester having the structure: 
##STR50## 
(i) de-protecting the acylamine activated ester formed by step (h) under 
suitable conditions to form a free amine activated ester having the 
structure: 
##STR51## 
and (j) cyclizing the free amine activated ester formed by step (i) under 
suitable conditions to form the composition. 
Reacting step (a) may be carried out in the presence of a miscible 
co-solvent such as methanol, and occurs in high yield when performed at 
ambient temperatures. Reacting step (b) may be carried out using a variety 
of acylating agents in the presence of nonnucleophilic base and 
4-dimethylaminopyridine catalyst. Common agents include t-Boc-Cl and 
Amyloxycarbonyl chloride. Reacting step (c) is efficiently performed using 
sodium hexamethyldisilylazide in tetrahydrofuran solution. Preferred 
temperatures range from -80.degree. C. to -70.degree. C. A dry ice bath 
providing a temperature of -78.degree. C. is convenient for this purpose. 
Reacting step (d) is readily effected in the presence of a nonnucleophilic 
base such as diisopropylethylamine in a dipolar nonaqueous solvent such as 
tetrahydrofuran. Deprotecting step (e) occurs well by using a mild acid, 
such as trifluoacetic acid in the presence of a scavenger such as anisole. 
Reacylating step (f) is carried out using a variety of acylating agents. 
t-Boc.sub.2 O is a preferred acylating agent for the purposes of the 
synthesis. Saponifying step (g) may be carried out using such bases as 
lithium hydroxide and sodium hydroxide. Lithium hydroxide is a preferred 
base. Activating step (h) is carried out using pentafluorophenol in the 
presence of various condensing agents, including DCC and EDC. 
De-protecting step (i) may be performed using a mild acid such as 
trifluoroacetic acid and a scavenger. Cyclizing step (j) is performed 
using a dropwise addition technique and a nonnucleophilic base such as 
diisopropylethylamine in a dipolar nonaqueous solvent such as dimethyl 
acetamide or dimethyl formamide. 
Receptors 1 and 2 are capable of high binding selectivity among simple 
amino acid derivatives (Table I). With Boc-protected, N-methylamide acid 
derivatives, enantioselectivity ranges from 1.7 to 3.0 kcal/mole with the 
L isomer always being bound preferentially (entries 1/2, 5/6, 7/8, 9/10, 
12/13). 
Side-chain functionality can also be distinguished by the chiral receptors 
(Table I; entries 1-8 vs 9, 10 and 12, 13). The side-chain hydroxyls of 
serine and threonine contribute about 2 kcal/mole to association energies 
and effectively distinguish these amino acids from Ala, Val, and Leu. Such 
hydroxylated L-amino acids bind better than O-benzyl-L-serine (entry 11) 
by about 3 kcal/mole. Nuclear magnetic resonance data suggest that the 
operative mode of complexation involves close proximity of the C-terminal 
group of the amino acid derivatives to all four aromatic rings in the 
host. Entries 14-17 (Table I) suggest that other binding modes may apply 
to amino acid derivatives having small N-terminal functionalities such as 
acetyl. 
The chiral host compounds may be utilized in any manner suitable for the 
intended purpose. For example, the host may be covalently bound to a 
polymer by modification of the synthetic method described above by 
replacing phloroglucinol or a similar starting material with one which has 
the additional substitution of an alkyl, aryl, or aralkyl, linker 
containing a reactive moiety at its terminus, comprising a halide, amine, 
carboxylate, alcohol, or thiol, if necessary in suitably protected form. 
The resulting chiral polymer may serve as an adsorbent for use as a 
convenient extractive reagent, in which the polymer may be combined with a 
mixture of racemic amino acid derivatives or a mixture of compounds 
related by differing side-chain substitution in a range of polar or 
nonpolar solvents. After sufficient agitation at a temperature suitable 
for promoting binding of one component in the mixture, ranging from 
-90.degree. to 180.degree. C. preferably from 0.degree. to 35.degree. C., 
the polymeric complex is then separated by gravity or suction filtration, 
centrifugation, or sedimentation and decanting. The desired enantiomeric 
derivative or related compound may be obtained by washing the polymer with 
a suitable buffer, solvent, or mixture of solvents at a temperature 
suitable for releasing the derivative from the polymeric host. The chiral 
polymer may also serve as an adsorbent in a chromatographic column, in 
which the mixture of enantiomers or related compounds may bind with 
different affinities, and then be eluted after washing with a suitable 
buffer, solvent, or mixture of solvents. The adsorbent is preferably 
prepared using finer meshes (&gt;400 U.S. mesh) of chloromethylated 0.5-2.0% 
divinyl-benzene cross-linked polystyrene and either aminoethyl, 
hydroxyethyl, or carboxyethyl derivatives of phloroglucinol or 
benzenetrithiol, according to the described procedure. Any polymeric resin 
selected from the group consisting of polyacrylamide, phenolformaldehyde 
polymers, polymethacrylate, carbohydrates, aluminates, and silicates may 
serve as the solid medium. 
While not wishing to be bound by a particular theory of action, the high 
selectivity in the binding of various substrates to a host molecule as 
observed while practicing the present invention could result from high 
conformational homogeneity and substantial host/guest contact. Monte Carlo 
conformational searching using the MacroModel/AMBER force field, in which 
Phe is modeled by Ala, predicts that the chiral receptors have similar 
conformations with C3 symmetry. The Phe's are folded into turns around the 
periphery of a large binding cavity with dimensions (.about.6 .ANG. 
diameter) similar to those of .alpha.-cyclodextrin. Some variability 
remains in the central ring Ar--X--CH.sub.2 --Ar' torsion angles, with 
little effect on the shape and nature of the binding cavity. Experimental 
evidence supporting the predicted structure includes NH--CH.sub.a coupling 
constants (J 1=8.1 Hz; J 2=8.0 Hz) and N--H infrared bands (free and 
hydrogen-bonded: 3434, 3321) cm.sup.-1) in dilute CDCl.sub.3 solution. The 
chiral host on forming a bound complex undergoes only minor conformational 
change, according to simulated annealing calculations. Specific contacts 
which may be responsible for the selective binding interactions in the 
complex could include three N--H/O.dbd.C hydrogen bonds, according to 
molecular mechanics modelling. 
The chiral hosts of the present invention bind diamides of certain amino 
acids with high selectivity which is dependent upon the nature of the 
amino acid side chain (2.about.kcal/mol for serine vs alanine) and the 
identity of the N-alkyl substituent (&gt;3 kcal/mol for methyl vs 
tert-butyl). These synthetic hosts are among the most enantioselective 
known, and bind certain derivatives of L-amino acids with selectivities as 
high as 3 kcal/mol. No other composition has been available to the art 
which achieves binding energy differentials of the magnitude herein 
disclosed for diastereoselective complexation of amino acid derivatives. 
The following Experimental Details are set forth to aid in an understanding 
of the invention, and are not intended, and should not be construed, to 
limit in any way the invention set forth in the claims which follow 
thereafter. 
TABLE I 
__________________________________________________________________________ 
.DELTA.G's of Association (kcal/mole) of 1 and 2 with Amino Acid 
Derivatives 
-.DELTA.G.sup.a 
Saturation.sup.b % 
.DELTA..DELTA.G.sup.c 
Entry 
Peptide substrate 
1 2 1 2 1 2 
__________________________________________________________________________ 
1 N--Boc--D--Ala--NHMe 
1.7 
2.1 
53 70 
2 N--Boc--L--Ala--NHMe 
3.9 
3.8 
93 90 2.2 
1.7 
3 N--Boc--L--Ala--NHBn 
1.4 51 
4 N--Boc--L--Ala--NHtBu 
.sup. nc.sup.d 
5 N--Boc--D--Val--NHMe 
1.5 
1.5 
51 54 
6 N--Boc--L--Val--NHMe 
4.4 
4.0 
79 74 2.9 
2.5 
7 N--Boc--D--Leu--NHMe 
1.5 
1.6 
64 60 
8 N--Boc--L--Leu--NHMe 
4.1 
3.8 
88 78 2.6 
2.2 
9 N--Boc--D--Ser--NHMe 
3.8 
4.4 
86 94 
10 N--Boc--L--Ser--NHMe 
&gt;6.1 
&gt;6.2 
95 96 &gt;2.3 
&gt;1.8 
11 N--Boc--L--Ser(OBn)--NHMe 
3.1 83 
12 N--Boc--D--Thr--NHMe 
3.2 
3.6 
84 90 
13 N--Boc--L--Thr--NHMe 
&gt;6.2 
1 g.sup.e 
&gt;95 &gt;3.0 
14 N--Ac--D--Ala--NHMe 
2.7 90 
15 N--Ac--L--Ala--NHMe 
3.9 94 1.2 
16 N--Ac--D--Ala--NHtBu 
2.0 59 
17 N--Ac--L--Ala--NHtBu 
3.0 85 1.0 
__________________________________________________________________________ 
.sup.a Measured by NMR titration at 25 C. with 1 or 2 at 0.5 mM 
concentration in CDCl.sub.3. 
.sup.b Extent of extrapolated saturation at end of titration. 
.sup.c Enantioselectivity, .DELTA.G(D) - .DELTA.G(L). 
.sup.d No complexation detected. 
.sup.e Too large to measure accurately. 
Experimental Details 
EXAMPLE 1 
Preparation of methyl-3,5-dimethyl-benzoate: 
A solution of 3,5-dimethyl benzoic acid (25 g, 0.17 mol) in methanol (250 
ml) was treated with sulfuric acid (1 ml, cat. amount) and heated to 
reflux. After 10 hours, the solution was cooled to room temperature, 
concentrated to approximately 1/2 volume and poured into 200 ml of crushed 
ice. The mixture was extracted twice with 200 ml portions of diethyl 
ether. The organic phase was extracted with saturated aqueous sodium 
carbonate, dried over magnesium sulfate, and concentrated under reduced 
pressure. The resulting solid was recrystallized from hexanes to yield the 
product (24.5 g, 90% yield) as volatile white plates. 
mp=32.degree.-35.degree. C. (lit. mp=35.degree.-36.degree. C.) 
EXAMPLE 2 
Preparation of methyl-3,5-bis(bromomethyl)-benzoate: 
A solution of methyl-3,5-dimethyl-benzoate (16.8 g, 0.10 mol) in carbon 
tetrachloride (150 ml) was treated with N-bromosuccinimide (35.6 g, 0.20 
mmol), and benzoyl peroxide (500 mg, cat. amount), and heated to reflux. 
After 3 hours, the mixture was cooled to room temperature and filtered 
through a sintered glass funnel. The filtrate was concentrated under 
reduced pressure and recrystallized from diethyl ether/hexanes (1:1) to 
yield the product (18.0 g, 55% yield) as a granular white solid. mp 
64.degree.-70.degree. C. (lit. mp 65.degree.-69.degree. C.); TLC (20% 
ethyl acetate/hexanes): R.sub.f =0.65 (UV active, CAM stain) 
EXAMPLE 3 
Preparation of methyl-3-bromomethyl-5-bis(Boc)aminomethyl-benzoate: 
A mixture of sodium hydride (3.6 g, 90 mmol) and N,N-dimethylformamide (150 
ml) was cooled to 0.degree. C. and treated with solid 
di-tert-butyliminodicarboxylate (17.4 g, 76.0 mmol) with vigorous 
stirring. The mixture was stirred at 0.degree. C. for 15 minutes, the ice 
bath was removed and a solution of methyl-3,5-bis(bromomethyl)-benzoate 
(23.6 g, 73.2 mmol) in N,N-dimethylformamide was added dropwise over 30 
minutes. After 12 hours the mixture was poured into 100 ml 1/4 saturated 
aqueous ammonium chloride and extracted with the three 100 ml portion of 
hexanes. The organic layer was dried over magnesium sulfate, concentrated 
under reduced pressure and chromatographed using a gradient of 10-20% 
ethyl acetate/hexanes to yield the product (22.0 g, 66% yield). TLC (20% 
ethyl acetate/hexanes): R.sub.f =0.55 (UV active, CAM stain) 
EXAMPLE 4 
Preparation of 
benzene-1,3,5-tris)methyl-3'-thiomethyl-5'-bis(Boc)aminomethyl-benzoate]; 
A solution of benzene-1,3,5-trithiol (900 mg, 5.16 mmol) in tetrahydrofuran 
(60 ml) was treated with N,N-diisopropylethylamine (3.1 ml, 17.67 mmol) 
with vigorous stirring. The mixture was allowed to stir until all solids 
had dissolved and was treated with solution of 
methyl-3-bromomethyl-5-bis(Boc)aminomethyl-benzoate (8.1 g, 17.67 mmol) in 
tetrahydrofuran. After 24 hours the mixture was poured into 100 ml 
saturated aqueous ammonium chloride and extracted with three 100 ml 
portions of diethyl ether. The organic phase was dried over magnesium 
sulfate, concentrated under reduced pressure, and the resulting oil was 
chromatographed using a gradient of 20-40% ethyl acetate/hexanes to yield 
the product (5.10 g, 76% yield) as a colorless oil. TLC (40% ethyl 
acetate/hexanes): R.sub.f =0.65 (UV active, Cl.sub.2 /TDM stain) 
EXAMPLE 5 
Preparation of 
benzene-1,3,5-tris[methyl-3'-thiomethyl-5'-aminomethyl-benzoate 
hydrochloride salt]: 
A solution of 
benzene-1,2,3,5-tris[methyl-3'-thiomethyl-5'-bis(Boc)aminomethyl-benzoate 
hydrochloride](4.8 g, 3.67 mmol) in absolute methanol (25 ml) was treated 
with 25 ml "10% methanolic HCl" (a mixture of 2.5 ml acetyl chloride and 
22.5 ml absolute methanol) and allowed to stir at room temperature for 3 
hours. All volatiles were removed under reduced pressure and the resulting 
white powder was dried under high vacuum. The product (3.00 g, quant. 
yield) was used without additional purification. 
EXAMPLE 6 
Preparation of N-.alpha.-Boc-L-tyrosine methyl ester: A solution of 
L-tyrosine methyl ester hydrochloride (10.0 g, 43.2 mmol) in 
N,N-dimethylformamide (100 ml) was cooled to 0.degree. C. and treated with 
solid di-tert-butyl dicarbonate (13.0 g, 65 mmol) and triethylamine (6.6 
ml, 47.5 mmol). After one hour the ice bath was remove and the solution 
was allowed to warm to room temperature. After 4 hours the solution was 
poured into 200 ml ethyl acetate, extracted with 100 ml 1.0M aqueous 
hydrochloric acid, 200 ml saturated aqueous sodium bicarbonate, 200 ml 
saturated aqueous sodium chloride, dried over magnesium sulfate, and 
concentrated under reduced pressure. The crude product (12.56 g, 98% 
yield) was used without additional purification. 
EXAMPLE 7 
Preparation of N-.alpha.-BOC-L-tyrosine-O-allyl ether methyl ester: 
A solution of N-.alpha.-BOC-L-tyrosine methyl ester (12.5 g, 42.3 mmol) in 
N,N-dimethylformamide (100 ml) was treated with allyl bromide (4.5 ml, 
51.8 mmol), tetra-n-butylammonium iodide (1.5 g, 4.3 mmol) and potassium 
carbonate (12 g, 86.4 mmol) and allowed to stir overnight. After 14 hours 
the mixture was poured into 200 ml ethyl acetate and extracted with 100 ml 
1.0M aqueous citric acid, 100 ml saturated aqueous sodium bicarbonate, 
saturated aqueous sodium chloride, dried over magnesium sulfate and 
concentrated under reduced pressure. The resulting oil was chromatographed 
using a gradient of 20-40% ethyl acetate/hexanes to yield the product 
(14.0 g, 99% yield) a colorless oil. TLC (40% ethyl acetate/hexanes): 
R.sub.f =0.40 (UV active, Cl.sub.2 /TDM stain) 
EXAMPLE 8 
Preparation of N-.alpha.-BOC-L-tyrosine-O-allyl ether: 
A solution of N-.alpha.-BOC-L-tyrosine-O-allyl ether methyl ester (14.0 g, 
41.7 mmol) in a mixture of tetrahydrofuran (100 ml) and water (10 ml) was 
treated with lithium hydroxide (10.0 g, 260 mmol) and allowed to stir at 
room temperature. After 6 hours all of the starting material had been 
consumed, as determined by thin layer chromatography, and the reaction 
mixture was diluted with 200 ml ethyl acetate and acidified to pH 2 with 
1.0M aqueous potassium hydrogen sulfate. The organic phase was dried over 
magnesium sulfate and concentrated under reduced pressure to yield the 
product (13.4 g, quant. yield). The product was used without additional 
purification. 
EXAMPLE 9 
Preparation of N-.alpha.-BOC-L-tyrosine-O-allyl ether-p-nitrophenyl ester: 
A solution of N-.alpha.-BOC-L-tyrosine-O-allyl ether (13.4 g, 41.7 mmol) in 
chloroform (100 ml) was cooled to 0.degree. C. and was treated with 
p-nitrophenol (17 g, 128 mmol), N-hydroxybenzotriazole (3.0 g, 21.3 mmol) 
and N,N'-dicyclohexylcarbodiimide (10.5 g, 51.2 mmol). The mixture was 
allowed to stir overnight at room temperature. After 15 hours the solution 
was filtered to remove N,N'-dicyclohexylurea, concentrated under reduced 
pressure and chromatographed using 100% chloroform to yield the product 
(13.7 g, 74% yield) as a yellow oil which solidified upon standing. TLC 
(100% chloroform): R.sub.f =0.30 (UV active, ninhydrin stain) 
EXAMPLE 10 
Preparation of 
benzene-1,3,5-tris[methyl-3'-thiomethyl-5'-aminomethyl-(N-.alpha.-BOC-L-ty 
rosine-amide-O-allyl-ether)benzoate]: 
A solution of 
benzene-1,3,5-tris[methyl-3'-thiomethyl-5'-aminomethyl-benzoate 
hydrochloride salt] (2.33 g, 2.86 mmol) in N,N-dimethylformamide (30 ml) 
was treated with N,N-diisopropylethylamine (1.9 ml, 10.87 mmol) with 
vigorous stirring until all solids had dissolved. The solution was cooled 
to 0.degree. C. and treated with solid 
N-.alpha.-BOC-L-tyrosine-O-allyl-ether-p-nitrophenyl ester (2(0 (4.3 g, 
9.72 mmol). After one hour the ice bath was removed and the mixture was 
mixed with silica gel (13 g) and all volatiles were removed under reduced 
pressure. The preabsorbed reaction mixture was placed directly onto a 
chromatography column containing silica gel equilibrated with 40% ethyl 
acetate/hexanes. The column was eluted with 40% ethyl acetate/hexanes to 
remove unreacted p-nitrophenyl ester and most of the p-nitrophenol. The 
product was then eluted with 10% methanol/chloroform to yield a fine 
yellow powder slightly contaminated with p-nitrophenol. The mixture was 
redissolved in methylene chloride and extracted with two 200 ml portions 
of 0.5M aqueous sodium hydroxide. The organic phase was dried over 
magnesium sulfate and concentrated under reduced pressure to yield to 
product (4.41 g, 96% yield) as a pale yellow powder. TLC (8% 
acetone/methylene chloride): R.sub.f =0.45 (UV active, Cl.sub.2 /TDM 
stain) 
EXAMPLE 11 
Preparation of 
benzene-1,3,5-tris[2'-(trimethyl)silylethyl-3'-thiomethyl-5'-aminomethyl-( 
N-.alpha.-Boc-L-tyrosine-amide-O-allyl-ether)-benzoate]: 
A suspension of 
benzene-1,3,5-tris[methyl-3'-thiomethyl-5'-aminomethyl-(N-.alpha.-BOC-L-ty 
rosine-amide-O-allyl-ether)benzoate] (4.3 g, 2.66 mmol) in 
2-(-trimethyl)silylethanol (10 ml, 70 mmol) and toluene (10 ml) was 
thoroughly purged with argon and treated with titanium ethoxide (0.050 ml, 
catalytic amount) and heated to reflux. After 6 hours the mixture was 
cooled to room temperature, filtered through a pad of Celite (diatomaceous 
earth) and concentrated under reduced pressure. The resulting oil was 
chromatographed using a gradient of 100% methylene chloride-5% 
methanol/methylene chloride to yield the product (4.2 g, 84% yield) as a 
pale yellow powder. TLC (8% acetone/methylene chloride): R.sub.f =0.85 (UV 
active, Cl.sub.2 /TDM stain). 
EXAMPLE 12 
Preparation of 
benzene-1,3,5-tris[3'-thiomethyl-5'-aminomethyl-(N-.alpha.-BOC-L-tyrosine- 
amide-O-allyl-ether)-benzoic acid]: 
A solution of 
benzene-1.3.5-tris[2'-(trimethyl)silylethyl-3'-thiomethyl-5'-aminomethyl-) 
N-.alpha.-BOC-L-tyrosine-amide-O-allyl-ether)-benzoate] (4.2 g, 2.24 mmol) 
in tetrahydrofuran (75 ml) was treated with tetra-n-butylammonium fluoride 
(1.0M solution in tetrahydrofuran) (10.08 ml, 10.08 mmol). After 4 hours 
the solution was diluted with 100 ml ethyl acetate and acidified to pH 2 
with 1.0M aqueous potassium hydrogen sulfate. The organic layer was dried 
over magnesium sulfate and concentrated under reduced pressure to yield 
the product (3.50 g, quant. yield). The product was used without 
additional purification. TLC (10% methanol/chloroform): R.sub.f =0.15 (UV 
active, Cl.sub.2 /TDM stain). 
EXAMPLE 13 
PreparatiOn of 
benzene-1,3,5-tris[pentafluorophenyl-3'-thiomethyl-5'-aminomethyl-(N-.alph 
a.-BOC-L-tyrosine-amide-O-allyl-ether)-benzoate]: 
A solution of 
benzene-1,3,5-tris[3'-thiomethyl-5'-aminomethyl-(N-.alpha.-BOC-L-tyrosine- 
amide-O-allyl-ether)-benzoic acid] (3.50 g, 2,24 mmol) in tetrahydrofuran 
(50 ml) was treated with pentafluorophenol (3.7 g, 20.16 mmol), and was 
allowed to stir at room temperature. After 3 hours the reaction mixture 
was concentrated under reduced pressure and the resulting oil was 
chromatographed using a gradient of 100% methylene chloride-10% 
acetone/methylene chloride to yield the product (2.60 g, 56% yield) as a 
white powder. 
TLC (5% acetone/methylene chloride): R.sub.f =0.45 (UV active, CAM stain) 
EXAMPLE 14 
Preparation of 
benzene-1,3,5-tris[{pentafluorophenyl-3'-thiomethyl-5'-aminomethyl-(L-tyro 
sine-amide-O-allyl-ether)-benzoate}-trifluoroacetate salt]: 
A solution of 
benzene-1,3,5-tris[pentafluorophenyl-3'-thiomethyl-5'-aminomethyl-(N-.alph 
a.-BOC-L-tyrosine-amide-O-allyl-ether)-benzoate] (2.5 g, 1.21 mmol) in 
methylene chloride (100 ml) was treated with anisole (10.0 ml, 93.0 mmol) 
and trifluoroacetic acid (50.0 ml). After 3 hours the mixture was 
concentrate under reduced pressure, resuspended in toluene and 
concentrated again. Finally, the product was triturated three times in 
diethyl ether to yield the product (1.90 g, quant. yield) as a white 
powder. The product was used without additional purification. 
EXAMPLE 15 
Preparation of L-tyrosine macrocycle tris-allyl ether: 
benzoate}-trifluoroacetate salt] (1.47 g, 1.21 mmol) in 
N,N-dimethylacetamide (25 ml) was added via syringe pump (33 hours) to a 
stirring solution of N,N-diisopropylethylamine (30.0 ml, 180 mmol) in 
tetrahydrofuran (500 ml). Twelve hours after the addition had been 
completed, the reaction mixture was diluted with an equal volume of ethyl 
acetate, extracted with two 200 ml portions of 5% aqueous hydrochloric 
acid, two 200 ml portions of saturated aqueous sodium bicarbonate, and 100 
ml saturated aqueous sodium chloride. The organic phase was dried over 
magnesium sulfate, concentrated under reduced pressure and chromatographed 
using a gradient of 100% chloroform--5% methanol/chloroform to yield the 
product (892 mg, 65% yield) as a pale yellow powder. TLC (25% acetone 
methylene chloride): R.sub.f =0.45 (UV active, CAM stain). 
EXAMPLE 16 
Preparation of the L-tyrosine macrocycle 1: 
A solution of the L-tyrosine macrocycle tris-allyl ether (50 mg, 0.041 
mmol) in tetrahydrofuran (15 ml) was treated with 
5,5-dimethyl-cyclohexan-1,3-dione (100 mg, 0.71 mmol) and 
tetrakis-(triphenylphosphine)palladium (10.0 mg, cat. amount) and allowed 
to stir at room temperature. After 4 hours the solution was diluted with 
50 ml ethyl acetate and extracted with three 20 ml portions of saturated 
aqueous sodium bicarbonate and 20 ml saturated aqueous sodium chloride. 
The organic phase was dried over magnesium sulfate and concentrated under 
pressure. The resulting solid was chromatographed using 10% 
methanol/chloroform to yield the product (1; 40.0 mg, 89% yield) as a pale 
yellow powder. TLC (10% methanol/chloroform): R.sub.f =0.20 (UV active, 
CAM stain). 
EXAMPLE 17 
Preparation of a receptor bound to a solid support: 
A solid phase peptide reaction vessel was charged with Merrifield resin 
(chloromethylated polystyrene crosslinked with 2% divinylbenzene; 100 mg, 
0.100 meq), the macrocyclic tris-phenol made according to Example 16 
(110.0 mg, 0.100 mmol), potassium carbonate (14 mg, 0.100 mmol), and 
N,N-dimethylformamide (2 ml). The mixture was placed on a rotary agitator 
for four days. The reaction mixture was washed successively with 5.times.5 
ml portions of methylene chloride, methanol, deionized water, methanol, 
and methylene chloride. The resulting solid was dried under high vacuum 
and weighed to dermine the amount of alkylation. The coupled resin weighed 
116.3 mg (approximately 15% based on chloromethyl groups). The organic 
washes were diluted with 100 ml ethyl acetate and extracted with 50 ml 
portions of 1M aqueous potassium hydrogen sulfate, saturated aqueous 
sodium bicarbonate, and saturated aqueous sodium chloride. The organic 
phase was dried over magnesium sulfate, concentrated under reduced 
pressure, and chromatographed using 10% methanol/chloroform to recover 
unreacted tris-phenol (40.1 mg). The infrared spectrum shows type I, II, 
and III amide bands (1650, 1510, and 1230 cm.sup.-1). 
EXAMPLE 18 
Method of resolution of N-.alpha.-Boc-DL-valine methylamide: The 
resin-bound tyrosine receptor (50 mg) prepared in Example 17 was placed in 
a solid-phase peptide synthesis reaction vessel (a cylinderical glass 
container with a ground glass joint (standard taper 14/20) on top, a 
coarse glass frit, and a stopcock at the bottom; treated with 
dichlorodimethylsilane to reduce adhesion to the glass surface) was 
pre-swelled by washing 5 times with 50 ml portions of chloroform and 
forcing excess solvent out with a stream of argon. A solution of 10 mM 
N-.alpha.-BOC-DL-valine methylamide (57.6 mg) was dissolved in 
perdeuterobenzene, and incubated with the resin-bound host for five 
minutes. The resin was washed with acetone (5 times 50 ml). The collected 
washings were concentrated under reduced pressure to afford 14.5 mg of 
resolved N-.alpha.-BOC-valine methylamide. The extent of enantiomeric 
enrichment was determined as follows. The BOC group was removed by 
treatment with a large excess of anhydrous methanolic HCl. On 
neutralization with triethylamine, the resulting amine was reacted with 
N-.alpha.-BOC-L-alanine p-nitrophenyl ester to give 
N-.alpha.-BOC-L-alanylvaline methylamide (19.0 mg, 97.2%) after 
chromatography. NMR integration and comparison with authentic DL 
diastereomeric compounds revealed an 85:15 mixture of diastereomers, i.e., 
70% enantiomeric enrichment. The resin could be regenerated by washing 
five times with 50 ml portions of methanol, dried under a stream of argon, 
and re-swelled with chloroform. 
EXAMPLE 19 
Synthesis of an O-allyl tyrosyl C.sub.3 -Symmetric receptor: 
N-Boc-O-Allyl-L-tyrosine amide 3. 
Di-tert-butyl dicarbonate (13.0 g, 59.6 mmol) was added to a solution of 
L-tyrosine methyl ester hydrochloride (10.0 g, 43.2 mmol) and i-Pr.sub.2 
NEt (6.6 mL, 38.0 mmol) in DMF (100 mL). The reaction mixture was poured 
into 1M aq KHSO.sub.4 after 8 h and extracted with ethyl acetate 
(3.times.). The combined extracts were washed with aq NaHCO.sub.3 and 
brine. Drying and evaporation afforded a yellow oil which was dissolved in 
DMF (100 mL). Potassium carbonate (12.0 g, 86 mmol), allyl bromide (4.5 
mL, 51.8 mmol), and n-Bu.sub.4 -NI (1.5 g, 4.3 mmol) were added. The 
reaction mixture was stirred for 16 h, poured into 1M aq KHSO.sub.4, and 
extracted with ethyl acetate (3.times.). The combined organic layers were 
washed with aq NaHCO.sub.3 and brine. Drying and solvent removal afforded 
N-Boc-O-allyl-L-tyrosine methyl ester as a yellow oil. 
Ammonia (20 mL) was condensed into a solution of N-Boc-O-allyl-L-tyrosine 
methyl ester in CH.sub.3 OH (60 mL) at -78 .degree. C. in a high pressure 
glass reaction vessel. The vessel was sealed and slowly warmed to rt. 
After 2 days, the vessel was cooled to -78 .degree. C. and opened. Argon 
was bubbled through the solution while it was allowed to warm slowly to 
rt. After 1 h, the solution was transferred to a round-bottom flask and 
all volatiles were removed. The light brown solid residue was washed with 
hexane/ethyl acetate (2:1) to yield the N-Boc-O-allyl-L-tyrosine amide 3 
(13.0 g, 94%) as a white solid: mp 145.degree. C.; R.sub.f 0.28 (diethyl 
ether); .sup.1 H NMR (CDCl.sub.3) .delta.1.40 (9H, s), 2.97 (1H, dd, 
J=7.2, 13.6 Hz), 3.05 (1H, dd, J=6.4, 13.6 Hz), 4.30 (1H, m), 4.51 (d, 
J=5.2 Hz), 5.06 (1H, m), 5.29 (1H, dd, J=1.4, 10.8 Hz), 5.38 (1H, dd, 
J=1.2, 19.2 Hz), 5.40 (1H, bs), 5.78 (1H, bs), 6.04 (1H, m), 6.86 (2H, d, 
J=8.4 Hz), 7.13 (2H, d, J=8.4 Hz); .sup.13 C NMR (CDCl.sub.3) .delta.27.9, 
37.3, 55.2, 68.5, 77.2, 114.6, 117.3, 128.4, 130.0, 132.9, 148.8, 157.3, 
173.7; IR (KBr) 3677, 3390, 3195, 1678, 1661, 1515, 1248, 1168 cm.sup.-1 ; 
HRMS calcd for C.sub.17 H.sub.24 N.sub.2 O.sub.4 320.1736; found 320.1741. 
N-Boc-O-Allyl-L-tyrosine N,N-di-Boc-amide 4. 
To a solution of 3 (3.0 g, 9.38 mmol) in CH.sub.2 Cl.sub.2 at rt was added 
i-Pr.sub.2 -NEt (6.52 mL, 37.5 mmol), DMAP (192 mg, 1.56 mmol), and 
di-tert-butyl dicarbonate (5.12 g, 23.5 mmol). After 2 h the reaction 
mixture was washed with 1M aq KHSO.sub.4 and 1M aq NaHCO.sub.3. Drying, 
concentration, filtration through a pad (10 g) of silica gel with 30% 
ether in pentane and evaporation afforded crude 4 (4.39 g, 90%) as a pale 
yellow oil. Trituration with hexane gave 4 as a white amorphous solid: mp 
87.degree. C.; R.sub.f 0.55 (50% ether/hexane); .sup.1 H NMR (CDCl.sub.3) 
.delta.1.36 (9H, s), 1.53 (18H, s), 2.76 (1H, dd, J=6.8, 14.0 Hz), 3.13 
(1H, dd, J=4.8, 14.0 Hz), 4.51 (d, J=5.2 Hz), 5.05 (1H, d, J=9.6 Hz), 5.26 
(1H, dd, J=1.6, 10.0 Hz), 5.41 (1H, dd, J=1.6, 18.0 Hz), 5.57 (1H, dd, 
J=4.8, 6.8 Hz), 6.05 (1H, m), 6.84 (2H, d, J=8.4 Hz), 7.12 (2H, d, J=8.4 
Hz); .sup.13 C NMR (CDCl.sub.3) .delta.27.6, 28.3, 38.3, 54.8, 68.8, 79.6, 
85.2, 114.6, 117.5, 128.1, 130.7, 133.4, 149.2, 155.0, 157.8, 174.7; IR 
(KBr) 2979, 2361, 1788, 1728, 1609, 1511, 1458, 1368, 1316, 1224, 1144, 
1011 cm.sup.-1 ; HRMS (M+1) calcd for C.sub.27 H.sub.43 N.sub.2 O.sub.8 
521.2863, found 521.2854. Anal. Calcd for C.sub.26 H.sub.42 N.sub.2 
O.sub.8 : C,62.05; H,8.10; N,5.36. Found: C,62.29; H,7.70; N,5.38. 
Boc-Amidomethyl methyl (bromomethyl)benzoate 5. 
NaN(TMS).sub.2 (1M THF; 4.75 mL, 4.75 mmol) was added dropwise to a 
solution of 4 (2.50 g, 4.81 mmol) in THF (40 mL) at -78 .degree. C. Methyl 
3,5-bis(bromomethyl)benzoate (1.86 g, 5.77 mmol) and n-Bu.sub.4 NI (431 
mg, 1.17 mmol) were added after 5 min, and the reaction mixture was warmed 
to 10.degree.-15.degree. C. After 45 min the reaction mixture was diluted 
with ether (40 mL) and washed with aq NH.sub.4 Cl. The aqueous phase was 
extracted with ether (2.times.) and the extracts were washed with brine. 
Drying, concentration, and flash chromatography (10-20% ethyl 
acetate/hexane) afforded 5 (2.96 g, 82%) as a white foam; R.sub.f 0.45 
(50% ether/hexane); .sup.1 H NMR (CDCl.sub.3) .delta.1.33 (9H, s), 1.42 
(18H, s), 3.09 (1H, dd, J=8.4, 14.0 Hz), 3.44 (1H, dd, J=6.4, 14.0 Hz), 
3.89 (3H, s), 4.45 (2H, s), 4.51 (d, J=5.2 Hz), 4.56 (1H, J=15.2 Hz), 4.95 
(1H, dd, J=15.2 Hz), 5.29 (1H, d, J=10.8 Hz), 5.41 (1H, d, J=17.6 Hz), 
5.72 (1H, dd, J=6.0, 8.4 Hz), 6.05 (1H, m), 6.81 (2H, d, J=8.4 Hz), 7.18 
(2H, d, J=8.4 Hz), 7.50 (1H, s), 7.90 (1H, s), 7.92 (1H, s); .sup.13 C NMR 
(d.sub.6 -DMSO) .delta.27.2, 27.3, 33.2, 35.0, 48.0, 52.2, 61.5, 68.1, 
82.0, 83.1, 114.3, 117.1, 120.9, 128.0, 128.7, 130.1, 130.5, 133.8, 133.8, 
139.0, 139,3. 151.9, 151.9, 156.8, 165.6, 173.6; IR (film) 3286, 2979, 
2933, 1787, 1752, 1710, 1611, 1511, 1481, 1458, 1368, 1302, 1238, 1142, 
1027, 999, 923 cm.sup.-1 ; HRMS (M+1) calcd for C.sub.37 H.sub.50 O.sub.10 
N.sub.2 Br 763.2637, found 763.2755. 
Nona-Boc Trisulfide 6. 
Compound 5 (2.0 g, 2.63 mmol) was added to a suspension of 
benzene-1,3,5-trithiol.sup.6 (140 mg, 0.80 mmol) and i-Pr.sub.2 NEt (610 
.mu.L, 35.1 mmol) in THF (20 mL) at rt. The reaction mixture was quenched 
with aq NH.sub.4 Cl after 6 h and extracted with ether (2.times.). After a 
brine wash and concentration, flash chromatography (5-3:1:1 
pentane:benzene:diethyl ether) gave 6 (1.38 g, 78%) as a solid white foam: 
mp 80.degree. C.; R.sub.f 0.35 (33% hexane/diethyl ether); .sup.1 H NMR 
(CDCl.sub.3) .delta.1.31 (27H, s), 1.40 (54H, s), 3.13 (3H, dd, J=8.4, 
13.2 Hz), 3.44 (3H, dd, J=6.0, 13.2 Hz), 3.86 (9H, s), 4.08 (6H, s), 4.50 
(6H, d, J=5.2 Hz), 4.54 (3H, d, J=15.2), 4.98 (3H, J=15.2 Hz), 5.27 (3H, 
J=9.6 Hz), 5.40 (3H, d, J=15.2 Hz), 5.71 (3H, dd, J=6.0, 8.4 Hz), 6.03 
(3H, m), 6.82 (6H, d, J=8.4 Hz), 7.02 (3H, s), 7.19 (6H, d, J=8.4 Hz), 
7.51 (3H, s), 7.86 (6H, s); .sup.13 C NMR (d.sub.6 -DMSO) .delta.27.2, 
27.3, 35.0, 35.7, 48.0, 52.0, 61.4, 81.9, 83.0, 114.3, 117.1, 120.9, 
124.2, 127.1, 128.5, 129.8, 130.5, 132.6, 133.8, 137.6, 138.0, 138.9, 
151.3, 151.8, 156.8, 165.6, 173.6; IR (film) 3420, 2979, 1791, 1733, 1653, 
1636, 1609, 1558, 1511, 1474, 1457, 1436, 1368, 1314, 1219, 1145, 1011, 
960, 926, 850, 772, cm.sup.-1. Anal. Calcd for C.sub.117 H.sub.150 N.sub.6 
O.sub.30 S.sub.3 : C,63.40; H,6.82; N,3.79. Found: C,62.87; H,6.80; 
N,3.68. 
Tri-Boc Trisulfide 7. 
Trifluoroacetic acid (75 mL) and anisole (19 mL) were added via syringe to 
a solution of 6 (11.4 g, 5.15 mmol) in CH.sub.2 Cl.sub.2 (150 mL) at rt. 
After 18 h, concentration gave a light pink residue which was triturated 
with ether to yield a white powder (low resolution mass spectrophotometric 
data; m/z=1316). That material was dissolved in DMF (80 mL) containing 
K.sub.2 CO.sub.3 (3.78 g, 31 mmol), i-Pr.sub.2 NEt (5.4 mL, 31 mmol), and 
di-tert-butyl dicarbonate (5.61 g, 25.75 mmol). After 17 h, the reaction 
mixture was poured into ethyl acetate (1000 mL) and washed with 1M aq 
KHSO.sub.4, NaHCO.sub.3, and brine. Drying, concentration, and trituration 
with ether afforded 7 (7.07 g, 85%) as a white powder: mp 138.degree. C.; 
R.sub.f 0.39 (10% acetone/CH.sub.2 Cl.sub.2); .sup.1 H NMR (d.sub.6 -DMSO) 
.delta.1.29 (27H, s), 2.67 (3H, dd, J=10.4, 14.0 Hz), 2.86 (3H, dd, J=4.4, 
14.0 Hz), 3.76 (9H, s), 4.10 (3H, m), 4.27 (12H, m), 4.45 (6H, d, J=5.2 
Hz), 5.20 (3H, d, J=10.4 Hz), 5.33 (3H, J=17.6 Hz), 6.04 (3H, m), 6.77 
(6H, d, J=8.4 Hz), 7.10 (3H, s), 7.11 (6H, d, J=8.4 Hz), 7.51 (3H, s), 
7.73 (3H, s), 7.81 (3H, s), 8.50 (3H, m); .sup.13 C NMR (d.sub.6 -DMSO) 
.delta.27.2, 30.8, 35.8, 36.6, 41.7, 52.1, 56.2, 68.0, 78.0, 114.2, 117.2, 
123.7, 127.0, 128.1, 129.8, 130.1, 132.6, 133.8, 137.7, 140.6, 155.3, 
156.6, 162.3, 165.9, 172.0,; IR (KBr) 3310, 2926, 1720, 1511, 1437, 1367, 
1310, 1242, 1167, 1024 cm.sup.-1. Anal. Calcd for C.sub.87 H.sub. 
102N.sub.6 O.sub.18 S.sub.3 : C,64.66; H,6.36; N,5.20. Found: C,64.07; 
H,6.50; N,5.02. 
Pentafluorophenyl Ester of 7. 
A solution of 1M aq LiOH (15 mL, 15 mmol) was added to 7 (500 mg, 0.309 
mmol) in THF/EtOH/H.sub.2 O (6:3:2, 100 mL). The reaction mixture was 
poured into 1M aq KHSO.sub.4 after 8 h and extracted with ethyl acetate 
(3.times.). After the extracts were washed with brine and dried, solvent 
removal afforded the crude acid as a light brown powder which was washed 
with ether. 
Pentafluorophenol (600 mg, 3.26 mmol) and 
1-(3-(dimethylamino)propyl)-3-ethylcarbodiimide hydrochloride (320 mg, 
1.69 mmol) were added to a stirred solution of the crude acid (470 mg) in 
THF (7.0 mL). After 4 h of stirring, concentration gave a brown residue 
from which the tris(pentafluorophneyl ester) (435 mg, 68%) was isolated by 
flash chromatography (0-10% acetone/CH.sub.2 Cl.sub.2) as an amorphous 
white solid: mp 158.degree. C.; R.sub.f 0.24 (5% acetone/CH.sub.2 
Cl.sub.2); .sup.1 H NMR (CDCl.sub.3) .delta.1.35 (27H, s), 2.98 (6H, d, 
J=7.2 Hz), 4.02 (6H, s), 4.35 (6H, d, J=4.4 Hz), 4.44 (6H, ddd, J=1.6, 
1.8, 5.6 Hz), 5.25 (3H, dd, J=1.6, 10.4 Hz), 5.36 (3H, dd, J=1.6, 17.2 
Hz), 5.99 (3H, dddd, J=1.6, 1.8, 10.4, 17.2 Hz), 6.76 (6H, d, J=8.4 Hz), 
6.98 (3H, s), 7.05 (6H, d, J=8.4 Hz), 7.34 (3H, s), 7.90 (3H, s), 7.99 
(3H, s); .sup.13 C NMR (CDCl.sub.3) .delta.29.5, 32.3, 39.0, 39.3, 44.1, 
57.5, 70.1, 81.7, 116.1, 119.0, 128.9, 129.9, 130.1, 131.4, 131.6, 134.5, 
135.7, 138.7, 140.0, 140.9, 141.0, 157.0, 158.9, 163.3, 173.5; IR (KBr) 
3371, 2979, 1686, 1615, 1517, 1444, 1368, 1224, 1166 cm.sup.-1. Anal. 
Calcd for C.sub.102 H.sub.93 F.sub.15 O.sub.18 S.sub.3 : C, 59.13; H,4.52; 
N,4.06. Found: C,58.53; H,4.52; N,4.06. 
Tyrosine Macrocycle 2A. 
Anisole (12 mL) and trifluoroacetic acid (60 mL) were added via syringe to 
a stirring solution of the above tris(pentafluorophenyl ester) (3.16 g, 
1.52 mmol) in CH.sub.2 --Cl.sub.2 (125 mL). After 6 h, the reaction 
mixture was concentrated. The resulting pink oil was triturated with ether 
to yield the tris-TFA amine salt as a white powder (3.20 g). 
A solution of the above tris-TFA amine salt (1.50 g, 0.710 mmol) in 
N,N-dimethylacetamide (25 mL) was added dropwise over 36 h to a rapidly 
stirred solution of i-Pr.sub.2 NEt (30 mL, 172 mmol) in THF (1200 mL) at 
rt. After the solution was stirred for an additional 12 h, 800 mL of THF 
was removed and the remaining solution was diluted with ethyl acetate (400 
mL). The solution was then washed with 0.5M aq HCl (2.times.), aq 
NaHCO.sub.3 (2.times.), and brine. Drying, concentration, and flash 
chromatography (10-50% acetone in CH.sub.2 Cl.sub.2) afforded 2A as an 
amorphous white solid (680 mg, 78%): mp 200.degree. C.; R.sub.f 0.38 (20% 
acetone/CH.sub.2 Cl.sub.2); .sup.1 H NMR (CDCl.sub.3) .delta.3.09 (3H, dd, 
J=7.2, 14.0 Hz), 3.24 (3H, dd, J=7.2, 14.0 Hz), 3.78 (3H, d, J=15.2 Hz), 
4.03 (3H, dd, J=4.2, 14.2 Hz), 4.11 (3H, d, J=15.2 Hz), 4.38 (3H, dd, 
J=6.8, 14.2 Hz), 4.53 (6H, d, J=5.2 Hz), 4.80 (3H, dd, J=7.2, 15.6 Hz), 
5.28 (3H, dd, J=1.2, 9.6 Hz), 5.41 (3H, dd, J=1.2, 17.2 Hz), 6.04 (3H, m), 
6.65 (3H, d, J=8.0 Hz), 6.68 (3H, s), 6.83 (3H, bs), 6.92 (6H, d, J=8.4 
Hz), 7.08 (3H, s), 7.21 (6H, d, J=8.4 Hz), 7.44 (3H, s), 7.55 (3H, s); 
.sup.13 C NMR (CDCl.sub.3) .delta.32.3, 35.8, 37.6, 45.0, 56.1, 70.2, 
116.3, 119.1, 127.3, 129.7, 130.3, 131.5, 131.6, 131.8, 134.2, 134.5, 
134.7, 137.9, 140.0, 141.0, 158.9, 168.6, 172.4; IR (KBr) 3310, 2926, 
1654, 1510, 1457, 1242, 1178, 1113, 1019, 926, 824 cm.sup.-1 ; HRMS calcd 
for C.sub.69 H.sub.66 N.sub.6 O.sub.9 S.sub.3 1219.4130, found 1219.4093. 
EXAMPLE 20 
Determination of Optical Purity of 5. 
K.sub.2 CO.sub.3 (20 mg, 0.145 mmol) was added to a stirred solution of 3 
(100 mg, 0.131 mmol) in CH.sub.3 OH (2 mL). After 30 min, the reaction 
mixture was filtered, diluted with ether (10 mL), and washed with aq 
NH.sub.4 Cl and brine. Concentration followed by flash chromatography (20% 
diethyl ether/pentane) afforded N-Boc-O-allyltyrosine methyl ester (40.0 
mg, 92%). 
The above methyl ester was dissolved in CH.sub.3 OH (5.0 mL) and acetyl 
chloride (1.0 mL, 13.5 mmol) was carefully added by pipette. After 3 h, 
all volatiles were removed and the resulting white solid was taken up in 
diethyl ether which was washed with 0.5M aq LiOH and brine. Drying and 
solvent removal afforded O-allyl-tyrosine methyl ester as a waxy solid 
(26.8 mg, 95%). 
O-Allyltyrosine methyl ester (20 mg, 0.084 mmol) was added to a stirred 
solution of (S)-(-)-methoxy(trifluoromethyl)phenyl-acetic acid (28.0 mg, 
0.120 mmol) and DCC (40 mg, 0.20 mmol) in CH.sub.2 Cl.sub.2 (0.50 mL). 
After 3 h the reaction mixture was diluted with CH.sub.2 Cl.sub.2 (10.0 
mL), filtered, and washed with 0.5M aq NaOH. Drying and solvent removal 
afforded the crude (S)-(-)-methoxy-(trifluoromethyl)phenyl-acetamide as a 
waxy oil containing DCC and N,N-dicyclohexylurea: R.sub.f 0.55 (50% 
ether/hexane); .sup.1 H NMR (CDCl.sub.3) .delta.3.05 (1H, dd, J=6.4, 14.4 
Hz), 3.13 (1H, dd, J=5.4, 14.4 Hz), 3.24 (3H, s), 3.74 (3H, s), 4.52 (2H, 
d, J=5.2 Hz), 4.87 (1H, ddd, J=5.4, 6.0, 6.4 Hz), 5.29 (1H, d, J=10.4 Hz), 
5.41 (1H, d, J=17.6 Hz), 6.06 (1H, m), 6.83 (2H, d, J=8.4 Hz), 7.05 (2H, 
d, J=8.4 Hz), 7.28 (1H, d, J=6.0 Hz), 7.39 (3H, m), 7.52 (2H, m); .sup.13 
C NMR (CDCl.sub.3) .delta.28.9, 37.0, 52.5, 53.4, 53.7, 55.0, 69.0, 77.9, 
115.2, 117.8, 127.8, 128.1, 128.7, 129.8, 130.4, 133.4, 158.0, 166.2, 
171.9,; IR (film) 3411, 3140, 2953, 2851, 1745, 1696, 1511, 1244, 1233, 
1224, 1178 cm.sup.-1 ; HRMS (M+1) calcd for C.sub.23 H.sub.25 F.sub.3 
NO.sub.5 452.1685, found 452.1685. 
O-Allyltyrosine methyl ester (20 mg, 0.084 mmol) was added to a stirring 
solution of (RS)-(.+-.)-methoxy(trifluoromethyl)-phenylacetic acid (28.0 
mg, 0.120 mmol) and DCC as described in the preceding paragraph to yield 
an authentic mixture of diastereomeric MTPA amides: R.sub.f 0.55 and 0.57 
(50% ether/hexane); .sup.1 HNMR (CDCl.sub.3) .delta.2.95-3.15 (2H, m), 
3.24/3.46 (3H, s), 3.74/3.76 (3H, s), 4.50 (2H, m), 4.80-5.0 (1H, m), 5.26 
(1H, d, J=10.4 Hz), 5.38 (1H, d, J=17.4 Hz), 6.03 (1H, m), 6.71/6.83 (2H, 
d, J=8.4 Hz), 6.77/7.05 (2H, d, J=8.4 Hz), 7.28 (1H, m), 7.39 (3H, m), 
7.50 (2H, m); .sup.13 C NMR (CDCl.sub.3) .delta.28.9, 36.62, 37.0, 52.2, 
52.5, 53.4, 53.7, 54.6, 69.0, 77.9, 114.6, 114.7, 117.4, 117.5, 127.1, 
127.7, 128.2, 128.3, 129.1, 129.3, 129.9, 130.0, 133.0, 158.0, 166.2, 
171.9; IR (film) 3411, 3140, 2953, 2851, 1745, 1696, 1511, 1244, 1233, 
1224, 1178 cm.sup.-1 ; HRMS (M+1) calcd for C.sub.23 H.sub.25 F.sub.3 
NO.sub.5 452.1685, found 452.1695. 
EXAMPLE 21 
One-step synthesis of 9. 
To an ice cold solution of (-)-(1R,2R)-diaminocyclohexane (24 mg, 0.211 
mmol) and iPrNEt.sub.2 (0.11 mL, 0.417 mmol) in THF (100 mL) and 
dimethylacetamide (10 mL) was added 1,3,5-benzenetricarbonyl trichloride 
(36 mg, 0.139 mmol) as a single portion with stirring. After 2 hours at 
0.degree. C., the mixture was allowed to warm to room temperature and 
stirred for an additional 12 hours. All volatiles were then removed at 
reduced pressure and the residue was purified by flash chromatography on 
silica gel using methylene chloride:methanol=97:3 to give, as the most 
mobile compound, an amorphous white solid (9; 5.8 mg, 13%) .sup.1 H NMR 
(CDCl.sub.3) .delta.8.58 (s, 1H), 8.47 (s, 1H), 8.19 (s, 1H), 7.80 (d, 1H, 
J=6.84 Hz), 7.51 (m, 1H), 7.11 (m, 1H), 4.31 (m, 1H), 4.09 (m, 1H), 3.71 
(m, 1H), 2.33 (m, 1H), 2.17 (m, 1H), 2.08 (m, 1H), 1.94 (m, 1H), 1.70-1.03 
(m, 8H); .sup.13 C NMR (CDCl.sub.3) .delta.169.2, 166.4, 165,3, 135.1, 
134.8, 133.8, 130.2, 129.6, 128.1, 57.5, 54.7, 52.4, 32.6, 31.7, 31.2, 
25.0, 24.7, 24.1; IR (neat) 3336, 2937, 1644, 1537, 1322 cm.sup.-1 ; MS 
(FAB)m/z 1309 (M+). HRMS (FAB) calcd for C.sub.72 H.sub.85 O.sub.12 
N.sub.12 1309.6410, found 1309.6311. 
Results and Discussion 
Unlike most synthetic host molecules (Notable exceptions: Petti, M. A.; 
Shepodd, T. J.; Barrans, R. E.; Dougherty, D. A. J. Am. Chem. Soc. 1988 
110, 6825. Mock, W. L.; Shih, N.-Y. J. Am. Chem. Soc. 1989, 111, 2697. 
Sherman, J. C.; Cram, D. J. J. Am. Chem. Soc. 1989, 111, 4527. Jeong, 
K.-S.; Muehldorf, A. V.; Rebek, J. J. Am. Chem, Soc. 1990, 112, 6144. 
Hong, J.-I.; Namgoong, S. K.; Bernardi, A.; Still, W. C. J. Am. Chem. Soc. 
1991, 113, 5111. Webb, T. H.; Suh, H.; Wilcox, C. S. J. Am. Chem. Soc. 
1991, 113, 5111. Webb, T. H.; Suh, H.; Wilcox, C. S. J. Am. Chem. Soc. 
1991, 113, 8554. Tanner, M. E.; Knobler, C. B.; Cram, D. J. J. Org. Chem. 
1992, 57, 40) biological receptors are conformationally well defined and 
large enough to almost fully encapsulate the substrates which they often 
bind with exquisite selectivity. Constructing analogous synthetic 
receptors is challenging because such structures seem to require complex 
atomic networks to form large binding sites and position binding 
functionality. 
A practical synthesis of a highly enantioselective, C.sub.3 -symmetric host 
molecule 2A has been developed. The basic strategy is a significant 
improvement over the relatively lengthy previous synthesis and involves 
direct addition of a Boc-tyrosine amide anion derivative 4 to methyl 
3,5-bis(bromomethyl)-benzoate to give an advanced intermediate 5. The 
final step, a triple macrolactamization, closes three 19-membered rings 
simultaneously to produce the bridged macrotricyclic receptor in 70-80% 
yield. 
The C.sub.3 -symmetric receptor 1A (Hong, J.-L. I.; Namgoong, S. K.; 
Bernardi, A.; Still, W. C. J. Am. Chem. Soc. 1991, 113, 5111) described 
hereinabove is one of the most enantioselective synthetic receptors yet 
reported and binds N-Boc-N'-methylamide derivatives of simple amino acids 
with enantioselectivity ranging from 2 to 3 kcal/mol (90-99% ee) (Other 
enantioselective hosts for neutral molecules: Canceill, J.; Lacombe, L.; 
Collet, A.; J. Am. Chem. Soc. 1985, 107, 6993. Pirkle, W. H.; Pochapsky, 
T. C. J. Am. Chemo Soc. 1987, 109, 5957. Sanderson, P. E. J.; Kilburn, J. 
D.; Still, W. C. J. Am. Chem. Soc. 1989, 111, 8314. Castro, P. P.; 
Georgiadis, T. M.; Diederich, F. J. Org. Chem, 1989, 54, 5384. Liu, R.; 
Sanderson, P. E. J.; Still, W. C. J. Org. Chem. 1990, 55, 5184. Jeong, 
K.-S.; Muehldorf, A. V.; Rebek, J. J. Am. Chem. Soc. 1980, 112, 6144. 
Webb, T. H.; Suh, H.; Wilcox, C. S. J. Am. Chem. Soc. 1991, 113, 8554). 
Such highly enantioselective receptors could have practical applications 
as resolving agents. A practical synthesis is provided hereinabove of 
O-allyl tyrosyl receptor 2A, a derivative of 1A which could be covalently 
bound to a solid support. 
For a derivative of 1A which could be bound to a solid support, the O-allyl 
derivative 2A is appropriate. Such otherwise stable ethers can be 
deprotected (Kunz, H.; Unverzagt, C. Angew. Chem., Int. Ed. Engl. 1984, 
23, 436) with transition metals to free phenols or attached (Tambute, A.; 
Begos, A.; Lienne, M.; Macaudiere, P.; Caude, M.; Rosset, R.; New J. Chem. 
1989, 13, 625) directly to a support using free radical chemistry. The 
present synthesis avoids the problematic di-tert-butyl iminodicarboxylate 
anion coupling and addition of nitrogen and amino acid in separate steps. 
Instead, a more convergent route is provided in which an N-anionic amino 
acid fragment would be added to bis(bromomethyl)benzoate in a single step. 
Use of a Boc-stabilized amide ion made from N-Boc-O-allyltyrosine amide is 
summarized in FIG. 1, and proved more reactive to acylation than was the 
primary amide. Thus, the major product with 1 equiv of Boc.sub.2 O/DMAP, 
the tri-Boc material could be isolated in 95% yield. 
As shown in FIG. 1, the desired Boc-stabilized amide anion could 
nevertheless be obtained and the planned coupling achieved. Thus starting 
with commercially available O-allyl-N-Boc-tyrosine methyl ester 3, 
NH.sub.3 was used to prepare the corresponding primary amide which then 
formed the tri-Boc derivative 4. 
On treatment of 4 with sodium hexamethyldisilylazide in THF at -78.degree. 
C., a rapid deprotonation and Boc-migration occurred, leading to the 
Boc-stabilized amide anion shown below. While this anion was stable enough 
to be alkylated with benzylic bromides at low temperatures, warming it to 
15.degree. C. caused elimination of tert-butoxide leading to 8. For 
preparation of 2A, 1.2 equiv of 3,5-bis-(bromomethyl)benzoate were used 
with Bu.sub.4 NI catalysis and obtained 5 in 82% yield. 
Although the alkylation proceeded smoothly, 5 might be acidic enough to 
have racemized under the basic conditions of the alkylation. To test for 
such racemization, a sample of 5 was treated with K.sub.2 CO.sub.3 in 
methanol and then HCl in methanol. The first treatment converted (Flynn, 
D. A.; Zelle, R. E.; Grieco, P. A. J. Org. Chem. 1983, 48, 2824) the 
C-terminal Boc-amide to methyl ester while the second removed the two 
N-terminal Boc groups, yielding O-allyltyrosine methyl ester. This 
material was then coupled using DCC to 
(S)-.alpha.-methoxy-.alpha.-(trifluoromethyl)phenylacetic acid (Mosher's 
acid) to provide the corresponding amide. .sup.1 H and .sup.13 C NMR 
comparison of this material with corresponding amides from authentic D- 
and L-O-allyltyrosine methyl ester showed that very little (&lt;5%) 
racemization had occurred. Under the conditions of an .sup.1 H NMR 
experiment, as little as 2% of the epimerized D-tyrosine derivative could 
have been detected. 
The benzylic bromide 5 was then used to triply alkylate 
sym-trimercaptobenzene (Bellavita, V. Chim. Ital. 1932, 62, 655) using 
Hunig's base (i-Pr.sub.2 NEt) providing C.sub.3 -symmetric 6 in 78% yield. 
The remainder of the synthesis involved a triple macrolactamization via an 
activated benzoic acid ester. However, the Boc-substituted amide was quite 
labile toward acid and base, and conversion of the methyl ester to acid 
was difficult in its presence. Furthermore, the problematic Boc could not 
be removed from the C-terminal amide without simultaneously deprotecting 
the tyrosyl amine. An effective solution to the problem was to remove all 
Boc protecting groups with TFA and then restore Boc protection of the free 
amines with Boc.sub.2 O to obtain 7 in 86% yield over both steps. 
The three methyl esters of 7 were hydrolyzed using aqueous lithium 
hydroxide and then the resulting acids were esterfied to pentafluorophenol 
using 1-(3-(dimethylamino)propyl)-3-ethylcarbodiimide in THF. Flash 
chromatography (Still, W. C.; Kahn, M.; Mitra, A. J. Org. Chem., 1978, 43, 
2923) provided the activated tris(pentafluorophenyl ester) in 68% yield. 
After removing the remaining Boc protecting groups using trifluoroacetic 
acid, the crude trifluoroacetate salt in N,N-dimethylacetamide was added 
via syringe pump to a large volume of dry THF containing excess Hunig's 
base. The addition was carried out at room temperature over 36 h using a 
syringe pump and the final concentration of reactant was .about.0.5 mM. 
This triple macrolactamization was suitable for reactions of this type and 
provided 2A in 78% yield after silica gel chromatography. 
II 
A practical synthesis of the C.sub.3 -symmetric receptor 2A is provided 
which proceeds in an overall yield of 27% and requires no high resolution 
chromatographic separations. Solution-phase binding experiments in 
CDCl.sub.3 showed that 2A bound N-Boc-N'-methylamides of amino acids with 
the same high enantioselectivities as found with 1A. Receptor 2A is useful 
in solid-phase resolution of protected amino acids. 
Also described herein is an example of a large synthetic receptor which has 
only minimal structural complexity, but has binding selectivities 
approaching those of biological receptors. This receptor 9 is an A.sub.4 
B.sub.6 cyclooligomer of trimesic acid (A) and (R,R)-diaminocyclohexane 
(B). It binds amino acid residues in peptide chains with very high 
selectivities for chirality (up to 99+% ee) and side-chain identity (up to 
3+ kcal/mol). 
In designing 9, minimal receptor flexibility was achieved by using 
fragments having few opportunities for conformational isomerism and by 
joining them with planar amide bonds. Because one of the fragments (A) has 
three joining points, the neutral, nonpolymeric condensation products of A 
and B are bridged polycyclics. Among the ways in which A and B can be 
combined, structure 9 is appealing because of its well-defined binding 
cavity and appropriately positioned hydrogen-bonding groups. 
9 was made by first preparing an amide-linked Boc-B-A-B-A-B-Boc oligomer 
having the two internal carboxylates activated as pentafluorophenyl 
esters. When this material was deprotected (TFA, anisole) and slowly added 
to iPr.sub.2 NEt/THF, it dimerized to 9 in 39% yield. Alternatively, 9 
could be prepared in a single step (13% yield) by simply mixing 
commercially available A acid trichloride and B at 3 mM concentration with 
iPr.sub.2 NEt in dry THF. 
.sup.1 H NMR titrations in CDCl.sub.3 showed that 9 formed 1:1 complexes 
with certain peptides and that N-Ac-L-Val-NHtBu was particularly well 
bound. To predict the structure of the most stable complex, a 5000-step 
MacroModel/SUMM conformational search (Goodman, J. M.; Still, W. C. J. 
Comput. Chem. 1991, 12, 1110) was carried out using AMBER.sup.*3 and GB/SA 
chloroform (Still, W. C.; Tempczyk, A.; Hawley, R. C.; Hendrickson, T. J. 
Am. Chem. Soc. 1990 112, 6127. CHCl.sub.3 parameter set: Hollinger, F.; 
Still, W. C., unpublished results). The most stable structure found is a 
complex held together by four intermolecular hydrogen bonds forming a 
structure resembling a peptidic three-strand .beta.-sheet. 
A related pair of intramolecular hydrogen bonds (between B's) closes the 
unbound end of 9 to produce a deep cavity which fully encapsulates the 
side chain (R) of a bound L-peptide. With L-valine, this structure places 
the side-chain isopropyl near the face of the four aromatic rings (A) of 
9. It is incompatible with the .sup.1 H NMR of the corresponding L-valine 
methylamide complex, which shows a 2.5 ppm upfield shift for the 
side-chain methyls and an .about.1 ppm downfield shift of only one of the 
three different types of host NH's. 
The picture which emerges from association energy measurements (Table II) 
is also in accord with the binding mode described supra which projects 
L-amino acid side chains into the central cavity of the receptor. 
TABLE II 
__________________________________________________________________________ 
Binding Energies (Kcal/mol) of Receptor 9 and Peptides.sup.a 
entry 
peptide -.DELTA.G(L) 
-.DELTA.(D) 
.DELTA..DELTA..sub.G.sup.b (% 
__________________________________________________________________________ 
ee) 
1 N--Ac--Gly--NHMe 1.9 
2 N--Ac--Ala--NHMe 3.5 2.2 1.3 (80) 
3 N--Ac--Val--NHMe 5.0 2.4 2.6 (97) 
4 N--Ac--Ile--NHMe 4.3 2.4 1.9 (92) 
5 N--Ac--Leu--NHMe 3.4 2.4 1.0 (68) 
6 N--Ac--Pgly.sup.c --NHMe 
5.9 2.9 3.0 (&gt;99) 
7 N--Ac--Phe--NHMe .sup. NC.sup.d 
2.0 &gt; -2.0 
(.93) 
8 N--Oc.sup.e --Tyr--NHMe 
.sup. NC.sup.d 
9 N--Ac--Ser--NHMe 3.5 3.4 0.1 (8) 
10 N--Ac--HSer.sup.f --NHMe 
5.1 3.7 1.4 (83) 
11 N--Ac--Thr--NHMe 3.5 2.9 0.6 (46) 
12 N--Boc--Val--NHMe 
2.8 1.7 1.1 (70) 
13 N--Boc--Val--NH.sub.2 
4.9 3.7 1.2 (76) 
14 N--Boc--Gly--Val--NHMe 
6.2 3.2 3.0 (&gt;99) 
15 N--Boc--Gly--Val--Gly--NHBn 
&gt;7.2 4.6 &gt;2.6 (&gt;97) 
__________________________________________________________________________ 
.sup.a By NMR titration at 25.degree. C. of 0.5 mM 9 in CDCl.sub.3 (each 
binding energy is the average of two to five independent measurements on 
different protons, and the average of two to five independent measurement 
on different protons, and the largest deviation from the average is 
.ltoreq.0.2 kcal/mol). 
.sup.b Enantioselectivity favoring L. 
.sup.c PGly, phenylglycine. 
.sup.d NC, no complex observed. 
.sup.e Oc, octanoyl. 
.sup.f HSer, homoserine. 
Thus peptide derivatives are bound with high selectivity for the 
L-configuration except when side chains are large (entries 7 and 8). 
Valine and phenylglycine side chains appear to fit the binding cavity 
quite well, but substantial reductions in binding occur when even single 
methylenes are added (entries 3 vs 4 and 5 and 6 vs 7 and 8). Removal of 
side-chain bulk from a near-optimal side chain (iPR) also diminishes 
binding. Thus stepwise truncation of side-chain iPR to Me to H costs 1.5 
kcal/mol per step with L-amino acids. The effect is less significant with 
D-amino acids, which the model suggests to have side chains projecting 
away from the binding site and into solvent. Finally, the large binding 
energies in entries 14 and 15 suggest that 9 can interact associatively 
with as many as three residues, a feat that appears unique among synthetic 
receptors. Presumably, the terminal residues of such peptides are able to 
form additional hydrogen bonds to the outlying amides of the host (NHCO 
and CONH in the schematic). 
Thus it is possible to assemble a large, conformationally well-defined 
receptor with remarkable binding properties starting from a few 
conformationally restricted subunits and well-known synthetic operations. 
There are doubtless many other such readily accessible heterooligomeric 
assemblies which have structural and binding properties analogous to those 
associated with macromolecular receptors. 
III 
The A.sub.4 B.sub.6 macrotricycle described herein is remarkable for 
several reasons. First, it self-assembles in a single step from two 
commercially available materials, benzene-1,3,5-tricarbonyl trichloride 
and the diamine (1R2R)-diaminocyclohexane. Though the yield of this 
extraordinary reaction is only 13%, the receptor is readily isolated 
because it is the most chromatographically mobile of the product formed. 
Second, A.sub.4 B.sub.6 is a highly selective receptor for neutral 
peptides. For example, it binds derivatives of L amino acids with 
enantioselectivities as high as 99% ee and can also distinguish between 
peptides based on the steric requirements of their sidechains. In some 
cases, this sidechain selectivity can be quite large and exceed 3 kcal/mol 
even when the peptides being compared differ only by a single methylene 
(e.g. phenylglycine vs phenylalanine). In the A.sub.4 B.sub.6 receptor, 
the conformationally rigid building blocks used minimize its flexibility. 
The synthesis and properties of two related A.sub.4 B.sub.6 cyclooligomers 
which are constructed from more conformationally flexible acyclic diamines 
(1R,2R)-1,2-diphenylethylenediamine (hereinafter B1) and 
(2R,3R)-2,3-diaminobutane-1,4-diol (hereinafter B2). The binding 
properties in this series of receptors are sensitive to the structure of 
the components used to assemble them, but rigid cyclic building blocks 
need not be used to obtain high binding selectivity. 
To prepare the receptors, a simple one-step coupling was performed on the 
amines and the triacid chloride as described for A.sub.4 B.sub.6. With B1, 
the A.sub.4 B1.sub.6 receptor was obtained in 10% yield when the coupling 
was carried out at a concentration corresponding to 6 nM in receptor. 
Synthesis of A.sub.4 B1.sub.6 : To an ice cold solution of 
(1R,2R)-diphenylethylenediamine (66 mg, 0.31 mmol) and IPr.sub.2 NEt (0.16 
mL, 0.63 mmol) in THF (100 mL) and dimethylacetamide (10 mL) was added 
1,3,5-benzenetricarbonyl trichloride (55 mg, 0.21 mmol) as a single 
portion with stirring. After 2 hours at 0.degree. C., the mixture was 
allowed to warm to room temperature and then to stand for an additional 12 
hours. Volatile materials were removed at reduced pressure and the crude 
product was purified by flash chromatography on silica gel (3% methanol in 
methylene chloride). A.sub.4 B1.sub.6 was the most mobile compound 
chromatographically and was isolated as an amorphous white solid (9.8 mg, 
10%); TLC (5% MeOH in CH.sub.2 Cl.sub.2) R.sub.f =0.71; .sup.1 H NMR 
(CDCl.sub.3) .delta.9.03 (d, 1H, J=5.2 Hz), 8.57 (d, 1H, J=9.2 Hz), 8.47 
(s, 1H), 8.27 (s, 1H), 7.70 (s, 1H), 7.46-7.12 (m, 15H), 6.81 (m, 1H), 
5.60 (m, 2H), 5.38 (dd, 1H, J=10.7, 6.9 Hz); .sup.13 C NMR (CDCl.sub.3) 
.delta.168.7, 165.8, 164.7, 141.8-128.5 (m), 64.7, 62.8, 60.0; IR (neat) 
3345, 2933, 1652, 1538, 1321 cm.sup.-1 ; MS(FAB) m/z 1899 (M+1). 
With B2, a more dilute 1 mM concentration was used to prepare A.sub.4 
B2.sub.6 in 7% yield. Both products were readily isolated as the most 
mobile reaction product on silica gel and were identified by mass 
spectroscopy and by their symmetry as revealed by .sup.13 C and .sup.1 H 
NMR. 
Binding energies were measured by titrating 0.5 mM solutions of receptor in 
CDCl.sub.3 with various N-acetyl amino acid methylamides and monitoring 
the receptor protons by 400 MHz NMR. In general, signals which showed the 
largest shifts upon binding were certain aromatic (H--C) and amide (H--N) 
protons. The binding energies found are given in Table III and all 
represent averages of at least two different binding measurements. 
Scatchard treatment of binding data indicated 1:1 complexes in all cases. 
TABLE III 
__________________________________________________________________________ 
Peptide-Binding Properties of Macrotricyclic Receptors in CDCl.sub.3. 
A.sub.4 B.sub.6 
A.sub.4 B1.sub.6 
A.sub.4 B2.sub.6 
Peptide Substrate.sup.a 
-.DELTA.G.sup.b 
.DELTA..DELTA.G.sup.c 
-.DELTA.G.sup.b 
.DELTA..DELTA.G.sup.c 
-.DELTA.G.sup.b 
.DELTA..DELTA.G.sup.c 
__________________________________________________________________________ 
GLY .sup. 1.9.sup.d 
1.4 1.5 
L--ALA 3.5 1.3 (80% ee) 
4.1 1.8 (90% ee) 
3.7 1.7 (89% ee) 
D--ALA 2.2 2.3 2.0 
L--VAL 5.0 2.8 (98% ee) 
4.5 2.4 (98% ee) 
3.8 1.5 (84% ee) 
D--VAL 2.4 2.1 2.3 
L--ILE 4.3 1.9 (92% ee) 
4.2 2.2 (95% ee) 
2.6 0.4 (32% ee) 
D--ILE 2.4 2.0 2.2 
L--LEU 3.4 1.0 (68% ee) 
3.6 1.5 (84% ee) 
2.5 0.3 (24% ee) 
D--LEU 2.4 2.1 2.2 
L--PHE NC -- NC -- NC -- 
D--PHE 2.0 1.5 1.4 
L--Phenylglycine 
5.9 3.0 (&gt;99% ee) 
5.7 3.9 (&gt;99% ee) 
3.4 1.6 (87% ee) 
D--Phenylglycine 
2.9 1.8 1.8 
L--Ethylglycine 
5.7 3.3 (&gt;99% ee) 
5.5 3.4 (&gt;99% ee) 
5.5 3.3 (&gt;99% ee) 
D--Ethylglycine 
2.4 2.1 2.2 
L--Propylglycine 
6.0 3.5 (&gt;99% ee) 
5.7 3.5 (&gt;99% ee) 
4.8 2.5 (97% ee) 
D--Propylglycine 
2.5 2.2 2.3 
L--Butylglycine 
3.9 1.4 (82% ee) 
3.8 1.8 (87% ee) 
2.5 0.2 (16% ee) 
D--Butylglycine 
2.5 2.2 2.3 
__________________________________________________________________________ 
.sup.a All peptides are Nacetyl, methylamides; 
.sup.b binding energy (kcal/mol); 
.sup.c enantioselectvity (kcal/mol); 
NC = no complexation observed. 
The binding results obtained with all three receptors support the general 
picture of the complex shown in FIG. 2. In the diagram, `+` and `-` 
represent receptor hydrogen bond donors (H--N) and acceptors (O.dbd.C), 
respectively. These functionalities presumably not only bind the peptidic 
substrate by hydrogen bonds but also associate to close the other end of 
the receptor to create a conical binding cavity which can encapsulate the 
sidechain (R) of a bound L amino acid. 
The binding data in Table III reveals a number of notable trends. First, 
all receptors bind all D amino acid substrates with roughly the same 
binding energy (2.0-2.5 kcal.mol). Thus the high enantioselectivities 
observed originate from especially favorable binding to L peptide 
substrates, not by destabilization of binding to D substrates. Second, 
both the A.sub.4 B.sub.6 receptor and the A.sub.4 B1.sub.6 analog have 
similar binding selectivities despite the construction of the latter from 
an acyclic diamine. Indeed, A.sub.4 B1.sub.6 binds six of the eight 
substrates studied with higher enantioselectivity than does A.sub.4 
B.sub.6. 
Both A.sub.4 B.sub.6 and A.sub.4 B1.sub.6 show surprisingly high 
selectivity among L amino acids which are distinguished only by the size 
and shape of their unfunctionalized, hydrocarbon sidechains. Amino acids 
having branched sidechains bind well only when the branch occurs at the 
substrate .beta.-carbon. Thus valine and isoleucine (R=i-Pr, s-Bu) bind 
well but leucine (R=i-Bu) does not. The receptors also distinguish 
substrates by sidechain length. Thus while alanine and butylglycine (R=Me, 
n-Bu) are rather poorly bound, ethylglycine and propylglycine (R=Et, n-Pr) 
are among the best substrates. All three receptors distinguish 
phenylglycine and phenylalanine by &gt;3 kcal/mol. These observations are 
compatible with the conical-cavity model which favors substrates having 
more steric bulk near the enlarged, open end of the binding cavity. 
Substrates with sidechains that are either too small to fill the cavity or 
too long to be accommodated are poorly bound. While binding selectivity 
based on steric effects is known (For example see: F. Diederich, K. Dick 
and D. Griebel, J. Am. Chem. Soc., 108, 2273 (1986); W. L. Mock and N.-Y. 
Shih, J. Am. Chem. Soc., 110, 4706 (1988); M. A. Petti, T. J. Shepodd, R. 
E. Barrans and D. A. Dougherty, J. Am. Chem. Soc., 110, 6825 (1988); D. J. 
Cram, M. E. Tanner, S. J. Kelpert and C. B. Knobler, J. Am. Chem. Soc., 
113, 8909 (1991); K. Naemura, K. Ueno, S. Takeuchi, Y. Tobe, T. Kaneda and 
Y. Sakata, J. Am. Chem. Soc., 115, 8475 (1993); L. Garle, B. Lozach, J.-P. 
Dutasta and A. Collet, J. Am. Chem. Soc., 115, 11652 (1993)), the subtle 
differences in sidechain bulk which these receptors are able to 
distinguish energetically by 1-2 kcal/mol is unusual with synthetic 
receptors. The key to such high steric selectivity appears to coincide 
with the receptor's ability to fully encapsulate the chemical substructure 
being distinguished. 
Like A.sub.4 B.sub.6 and A.sub.4 B1.sub.6 which bind L-peptides based on 
the steric requirements of their sidechains, receptor A.sub.4 B2.sub.6 
also distinguishes peptide sidechains sterically but with different 
selectivity. In particular, A.sub.4 B2.sub.6 selects for L-peptides whose 
sidechains are small and compact; thus alanine, valine and ethylglycine 
are well-bound while isoleucine, leucine, phenylglycine, propylglycine and 
butylglycine are more weakly bound relative to the other receptors. Thus 
A.sub.4 B2.sub.6 appears to have a smaller binding cavity, a property 
which may follow from cavity occupancy by benzyloxymethyl substituents or 
from partial cavity collapse due to the flexible nature of the B2 
fragment. 
These findings suggest that the highly selective binding found with the 
A.sub.4 B.sub.6 receptor may be general to cyclooligomeric molecules of 
this class and that binding selectivity can be altered by starting with 
different amine and acid chloride fragments. It may be noted that these 
receptors incorporate diamine fragments in two different structural 
environments: the upper and lower macrocycles include four equivalent 
amines B while two other B's link those macrocycles together. By varying 
these distinct B fragments independently, even more receptor diversity can 
be generated.