Convergent solution-phase combinatorial synthesis with multiplication of diversity through rigid biaryl and diarylacetylene couplings

Article abstract of DOI:10.1021/jo990639p

The solution-phase synthesis of iminodiacetic acid diamide libraries linked to aryl iodides and their Pd-catalyzed dimerization are detailed. Mixtures containing 64 980 components are synthesized in only 4 steps from N- BOC-iminodiacetic acid anhydride (1) and 21 readily available starting materials, demonstrating the multiplication of diversity achievable by the convergent assembly of building blocks. Both biaryl formation and sequential Stille couplings with bis(tributylstannyl)-acetylene are utilized to dimerize the functionalized iminodiacetic acid diamide precursors resulting in product libraries with two sets of binding groups separated by variable length rigid linkers suitable for probing protein-protein interactions. Deconvolution libraries synthesized alongside the full mixtures allow for identification of active components.

Full text of DOI:10.1021/jo990639p

7094
J . Org. Chem. 1999, 64, 7094-7100
Con ver gen t Solu tion -P h a se Com bin a tor ia l Syn th esis w ith
Mu ltip lica tion of Diver sity th r ou gh Rigid Bia r yl a n d
Dia r yla cetylen e Cou p lin gs
Dale L. Boger,* Weiqin J iang, and J oel Goldberg
Department of Chemistry and the Skaggs Institute for Chemical Biology, The Scripps Research Institute,
10550 North Torrey Pines Road, La J olla, California 92037
Received April 16, 1999
The solution-phase synthesis of iminodiacetic acid diamide libraries linked to aryl iodides and their
Pd-catalyzed dimerization are detailed. Mixtures containing 64 980 components are synthesized
in only 4 steps from N-BOC-iminodiacetic acid anhydride (1) and 21 readily available starting
materials, demonstrating the multiplication of diversity achievable by the convergent assembly of
building blocks. Both biaryl formation and sequential Stille couplings with bis(tributylstannyl)-
acetylene are utilized to dimerize the functionalized iminodiacetic acid diamide precursors resulting
in product libraries with two sets of binding groups separated by variable length rigid linkers
suitable for probing protein-protein interactions. Deconvolution libraries synthesized alongside
the full mixtures allow for identification of active components.
In tr od u ction
solution-phase techniques (Figure 1).12 Recently we dis-
closed an example of the convergent combination of a
small number of monomers that is especially suited for
the discovery of receptor antagonists and their deriviti-
zation into potential receptor dimerization agonists.13
Mixture libraries containing 476 775 and 114 783 975
components were prepared by the dimerization of func-
tionalized iminodiacetic acid diamides via the olefin
metathesis reaction. Deconvolution of these mixtures can
be accomplished by the complementary techniques of
positional scanning14 and deletion synthesis deconvolu-
tion.13
Complementary to our development of the olefin me-
tathesis reaction to simultaneously join iminodiacetic
acid derivatives and randomize the length of the linking
tether, we have explored other methods of such conver-
gent library synthesis. Herein we report the palladium-
catalyzed dimerization of iodoarene-appended iminodi-
acetic acid diamide libraries (Figure 2). As in the olefin
metathesis studies, these libraries were designed to
contain binding groups of appreciable size to allow
sufficient contact with target protein surfaces. In this
investigation we explored dimerization methods which
result in a rigid core from which the pendent binding
groups are directed toward the target proteins. This may
Ligand-induced receptor and protein dimerization or
oligomerization has emerged as a general mechanism for
signal transduction1 and important members of many
receptor superfamilies are activated by such a process.2-5
Many of these receptors and proteins appear to bind their
ligands using only a small cluster of residues for a
majority of the binding interaction.6,7 This has led to the
expectation that small molecules may be capable of
inducing their dimerization and activation, and recently
peptide,7,8 as well as nonpeptide,9 agonists promoting
receptor homodimerization have been identified through
the random screening of compound libraries. Our interest
in combinatorial chemistry rested on its potential to
provide candidate leads for promoting receptor activation
by dimerization. This, coupled with the potential of
utilizing a single approach for the discovery of antago-
nists and their conversion to agonists, is an important
element underlying our continued development10,11 of
(1) Hinterding, K.; Alonso-Diaz, D.; Waldmann, H. Angew. Chem.,
Int. Ed. Engl. 1998, 37, 688. Klemm, J . D.; Schreiber, S. L.; Crabtree,
G. R. Annu. Rev. Imunol. 1998, 16, 569. Heldin, C.-H. Cell 1995, 80,
213.
(2) Ullrich, A.; Schlessinger, J . Cell 1990, 61, 203.
(3) Moutoussamy, S.; Kelly, P. A.; Finidori, J . Eur. J . Biochem. 1998,
255, 1.
(4) Massague, J .; Attisano, L.; Wrana, J . L. Trends Cell Biol. 1994,
4, 172. Lemmon, M. A.; Schlessinger, J . Trends Biochem. Sci. 1994,
19, 459.
(5) Smith, C. A.; Farrah, T.; Goodwin, R. G. Cell 1994, 76, 959.
(6) Wells, J . A. Science 1996, 273, 449. Reineke, U.; Schneider-
Mergener, J . Angew. Chem., Int. Ed. Engl. 1998, 37, 769.
(7) Livnah, O.; Stura, E. A.; J ohnson, D. L.; Middleton, S. A.;
Mulcahy, L. S.; Wrighton, N. C.; Dower, W. J .; J olliffe, L. K.; Wilson,
I. A. Science 1996, 273, 464.
(8) Cwirla, S. E.; Balasubramanian, P.; Duffin, D. J .; Wagstrom, C.
R.; Gates, C. M.; Singer, S. C.; Davis, A. M.; Tansik, R. L.; Mattheakis,
L. C.; Boytos, C. M.; Schatz, P. J .; Baccanari, D. P.; Wrighton, N. C.;
Barrett, R. W.; Dower, W. J . Science, 1997, 276, 1696. Kimura, T.;
Kaburaki, H.; Miyamoto, S.; Katayama, J .; Watanabe, Y. J . Biochem.
1997, 122, 1046,
(10) Cheng, S.; Comer, D. D.; Williams, J . P.; Myers, P. L.; Boger,
D. L. J . Am. Chem. Soc. 1996, 118, 2567. Boger, D. L.; Tarby, C. M.;
Myers, P. L.; Caporale, L. H. J . Am. Chem. Soc. 1996, 118, 2109.
Cheng, S.; Tarby, C. M.; Comer, D. D.; Williams, J . P.; Caporale, L.
H.; Myers, P. L.; Boger, D. L. Bioorg. Med. Chem. 1996, 4, 727. Boger,
D. L.; Ducray, P.; Chai, W.; J iang, W.; Goldberg, J . Bioorg. Med. Chem.
Lett. 1998, 8, 2339. Boger, D. L.; Ozer, R. S.; Andersson, C.-M. Bioorg.
Med. Chem. Lett. 1997, 7, 1903. Boger, D. L.; Chai, W. Tetrahedron
1998, 54, 3955. Boger, D. L.; Chai, W.; Ozer, R. S.; Andersson, C.-M.
Bioorg. Med. Chem. Lett. 1997, 7, 463.
(11) Boger, D. L.; Goldberg, J .; J iang, W.; Chai, W.; Ducray, P.; Lee,
J . K.; Ozer, R. S.; Andersson, C.-M. Bioorg. Med. Chem. 1998, 6, 1347.
(12) For a recent review on solution-phase combinatorial chemistry,
see: Merritt, A. T. Comb. Chem. High Throughput Screening 1998, 1,
57.
(9) Tian, S.-S.; Lamb, P.; King, A. G.; Miller, S. G.; Kessler, L.;
Luengo, J . I.; Averill, L.; J ohnson, R. K.; Gleason, J . G.; Pelus, L. M.;
Dillon, S. B.; Rosen, J . Science 1998, 281, 257. Kimura, T.; Kaburaki,
H.; Tsujino, T.; Ikeda, Y.; Kato, H.; Watanabe, Y. FEBS Lett. 1998,
428, 250.
(13) Boger, D. L.; Chai, W.; J ing, Q. J . Am. Chem. Soc. 1998, 120,
7220.
(14) Dooley, C. T.; Houghten, R. A. Life Sci. 1993, 52, 1509. Pinilla,
C.; Appel, J . R.; Blanc, P.; Houghten, R. A. Biotechniques 1992, 13,
901.
10.1021/jo990639p CCC: $18.00 © 1999 American Chemical Society
Published on Web 08/21/1999

Convergent Solution-Phase Combinatorial Synthesis
J . Org. Chem., Vol. 64, No. 19, 1999 7095
Sch em e 1
F igu r e 1.
(re)orientation of the membrane bound target proteins.15
Two palladium-catalyzed dimerization protocols are de-
scribed which link functionalized iodoarene precursors,
biaryl formation by direct homocoupling, and diaryl-
acetylene formation by sequential Stille couplings with
bis(tributylstannyl)acetylene.
Develop m en ta l Stu d ies. Initial efforts focused on the
preparation of a modest library to validate the approach
and allow for optimization of the reaction conditions
(Scheme 1). N-BOC-iminodiacetic acid anhydride (1),
formed in situ from the readily available dicarboxylic
acid, was the starting point for the library synthesis.10,11
Functionalization with phenethylamine provided mono-
amide 2 in 90% yield, and subsequent coupling (PyBOP)
of the remaining carboxylic acid with 4-methoxyphen-
ethylamine provided 3 in 92% yield. Simple liquid-liquid
extractions provided pure products for both steps. The
third functionalization of the iminodiacetic acid template
involved the coupling to an iodoarene suitable for Pd-
catalyzed dimerization. Variability in the chain-length
connecting the iminodiacetic acid template to the dimer-
ization center was included to allow the binding groups
to span a variety of distances. Both meta and para
substitution of the iodobenzamides were also chosen to
increase the diversity of reaction products. N-BOC depro-
tection of 3 (HCl-dioxane) and PyBrOP coupling of the
crude HCl salt with the 10 iodoarene-linked carboxylic
acids C1-C10 (Figure 3) provided the dimerization
precursors 4-13 (48-84%). Regardless of the conversion,
unreacted starting materials or reaction byproducts were
easily removed by acidic and basic liquid-liquid extrac-
tions providing pure products.
F igu r e 2. Dimerization via biaryl and diarylacetylene rigid
linkages which position target binding groups R1 and R2.
be an especially important property for receptor dimer-
ization agonist libraries considering recent studies which
suggest receptor activation is achievable only by a precise
(15) Livnah, O.; Stura, E. A.; Middleton, S. A.; J ohnson, D. L.;
J olliffe, L. K.; Wilson, I. A. Science 1999, 283, 987. Remy, I.; Wilson,
I. A.; Michnick, S. W. Science 1999, 283, 990. Ballinger, M. D.; Wells,
J . A. Nature Struct. Biol. 1998, 5, 938. Livnah, O.; J ohnson, D. L.;
Stura, E.; Farrell, F. X.; Barbone, F. P.; You, Y.; Liu, K. D.; Goldsmith,
M. A.; He, W.; Krause, C. D.; Pestka, S.; J olliffe, L. K.; Wilson, I. A.
Nature Struct. Biol. 1998, 5, 993. Syed, R.; Reid, S. W.; Li, C.;
Cheetham, J . C.; Aoki, K. H.; Liu, N.; Zhan, H.; Osslund, T. D.; Chirino,
A. J .; Zhang, J .; Finer-Moore, J .; Elliott, S.; Sitney, K.; Katz, B. A.;
Matthews, D. J .; Wendoloski, J . J .; Egrie, J .; Stroud, R. M. Nature
1998, 395, 511.
With the model iodoarene precursors in hand, their
symmetrical and unsymmetrical dimerizations were
investigated16 (Scheme 2). Initial experiments with the
Stille coupling reaction between the iodoarenes (4-13)

7096 J . Org. Chem., Vol. 64, No. 19, 1999
Boger et al.
Sch em e 2
F igu r e 3. The 21 building blocks used to assemble both the
biaryl and diarylacetylene libraries.
and bis(tributylstannyl)acetylene17 suggested that the
reactivities of the iodobenzamide derivatives were nearly
identical regardless of the amide substitution (chain
length) or site of substitution (meta or para). Optimum
conditions were found to be reaction with bis(tributyl-
stannyl)acetylene (0.5 equiv) and Pd(Ph3)4 (0.05 equiv)
in dioxane at 100 °C for 4 h. Addition of a few crystals of
BHT were found to improve the reaction yields which
ranged from 40 to 68% for the homodimerizations 4-13
f 14-23. Other additives such as LiCl17 used in similar
couplings were found to have no effect on these reactions.
The iodides were completely consumed under these
conditions, and no reduction or other byproducts (e.g.,
biaryl formation) were observable. The lack of these
byproducts from 14 and 19 was further demonstrated by
an independent synthesis of the biaryl products 25 and
30 and the reduction product 36 (Scheme 3). Comparison
Sch em e 3
1
of these products by H NMR spectroscopy and TLC to
that of the crude Stille product confirmed their absence.
Consequently, purification mainly involved the removal
of catalyst and tin byproducts. This was accomplished
by eluting the reaction mixtures from a short column of
SiO2. All impurities were found to be removable by this
method, providing compounds judged clean by NMR
spectroscopy.
Unsymmetrical couplings were first examined by re-
acting an equimolar mixture of the 5 m-iodobenzamide
(16) The corresponding aryl bromides were also tested and found
to be either too unreactive or lead to unacceptable amounts of reduction
byproduct in both the Stille and biaryl coupling reactions.
(17) For the use of bis(tributylstannyl)acetylene to synthesize dia-
rylalkynes, see: Cummins, C. H. Tetrahedron Lett. 1994, 35, 857.

Convergent Solution-Phase Combinatorial Synthesis
J . Org. Chem., Vol. 64, No. 19, 1999 7097
synthesis (individual homocouplings of 4-13, Scheme 2)
worked effectively with the best conditions being 10%
Pd/C (0.1 equiv) and Et3N (2.0 equiv) in DMF at 100 °C,
for 18 h. All starting materials were consumed, and the
product biaryls were isolated in moderate to good yields
for both the meta- and para-substituted iodobenzamides.
A small amount of reduction byproduct (e.g., 36) was
observed even under these optimized conditions; however,
conducting the reactions highly concentrated (0.2 M) kept
this to a minimum (<10%). The biaryl products (25-34)
were found to be chromatographically similar to one
another and distinct from any reaction byproducts (in-
cluding reduction products). Therefore, they could be
similarly purified by eluting the crude product mixture
from a short column of SiO2.20
Unsymmetrical and mixture biaryl couplings were
examined first by dimerizing a mixture of the 5 m-
iodobenzamide derivatives 4 and 6-9. The eluted product
mixture contained all 15 predicted dimeric products (75%
yield) demonstrated by MS analysis of the product
mixture (Figure 4b). The p-iodobenzamide derivatives 5
and 10-13 were similarly reacted with analogous results.
Mixed meta and para couplings were tested by subjecting
a mixture of 9 and 12 to the 10% Pd/C, Et3N, DMF
conditions in which a statistical 1:1:2 distribution of the
two homo- and hetero-coupled and products (29, 33, and
35) were formed in 60% yield.
Syn t h esis of F u ll Mixt u r e a n d Decon volu t ion
Libr a r ies. With optimized conditions for both the ho-
mocoupling and Stille coupling reactions in hand, the
synthesis of biaryl and diarylacetylene full matrix librar-
ies was conducted (Scheme 4, Figure 3). Following the
synthetic protocols used with the model substrates, two
libraries containing 64 980 members each were as-
sembled in a total of five steps. Functionalization of 1
with a mixture of six amines (A1-A6) provided 37 in 74%
yield (Scheme 4). PyBOP coupling of the remaining
carboxylic acid group with 6 amines (B1-B6) provided
36 compound mixture 38 (65%). This mixture was depro-
tected (HCl-dioxane) and coupled with the 10 iodoarene
carboxylic acids (C1-C10) providing mixture 39 (360
components, 67%). After each coupling reaction in this
sequence, the product mixtures were purified by acid and/
or base extractions which effectively removed any unre-
acted starting materials or reaction byproducts without
affecting the integrity of the product mixtures. The
iodoarene mixture 39 was then subjected to each of our
two palladium-catalyzed dimerization strategies. The
reaction and purification conditions employed were the
same as described for the smaller mixture models. The
direct coupling was found to proceed in 90% yield based
on the average product molecular weight, and the Stille
coupling with bis(tributylstannyl)acetylene was in 76%
yield resulting in iminodiacetic acid diamide dimer
libraries with rigid biaryl and diarylacetylene cores. Each
product library contains 64 980 components (360 ho-
modimers and 64 620 heterodimers).
F igu r e 4. ESMS of the dimerization sublibraries synthesized
from the couplings of a mixture of 4 and 6-9 by either (a)
Stille coupling with bis(tributylstannyl)acetylene, Pd(Ph3)4 or
(b) homocoupling with 10% Pd/C, Et3N. Each product mixture
consists of 15 components with 14 distinct molecular weights.
derivatives 4 and 6-9 in a single reaction vessel using
the same reaction and purification conditions optimized
for the individual compounds. The purified product
mixture contained all 15 dimeric products18 (63% yield)
as confirmed by MS analysis of the product mixture
(Figure 4a). Similarly a mixture of the p-iodobenzamide
derivatives 10-13 were reacted providing the expected
mixture of 9 products in comparable yield. The meta and
para mixture couplings were investigated by reacting 7
and 12 in which a statistical 1:1:2 distribution of the two
homo- and hetero-coupled products (16, 22, and 24) were
observed, the mixture yield being 42%.
We have previously reported the synthesis of biaryl
libraries by the Pd/C-catalyzed homocoupling of substi-
tuted iodoarenes.19 This was extended to the same
iodoarene-linked iminodiacetic acid diamides used in the
Stille coupling reactions. The test reactions for biaryl
At the same time that the full mixture libraries were
constructed, positional scanning14 and deletion synthe-
sis13 deconvolution libraries were assembled (see Table
1). These sublibraries are designed to be synthesized and
screened alongside the parent mixtures to allow identi-
fication of active components. For either process, decon-
(18) A statistical dimerization of n components results in a mixture
of n(n + 1)/2 products.
(19) Boger, D. L.; Goldberg, J .; Andersson, C.-M. J . Org. Chem. 1999,
64, 2422.
(20) The product biaryls can also be purified by size exclusion
chromatography using Bio-Beads S-X8 resin, THF eluent.

7098 J . Org. Chem., Vol. 64, No. 19, 1999
Boger et al.
Ta ble 1. Yield s (Ca lcu la ted by th e Aver a ge P r od u ct
Molecu la r Weigh t) for th e Syn th esis of Sca n n in g a n d
Deletion Decon volu tion Mixtu r e Libr a r iesa
Sch em e 4
volution of each library requires only 22 additional
mixture syntheses. Each of the positional scanning
sublibraries contains a single substitution at one location
but the full mixtures at the other positions. For example,
the mixture 40 sca n A1 is the diarylalkyne product
containing only A1 in the first substitution position (R1-
NH2), combined with B1-B6 and C1-C10. The deletion
synthesis deconvolution libraries are synthesized in a
similar fashion, but in this case a single building block
is omitted at one location and the full mixtures are used
at the other positions. For example, 40 d eleteA1 is the
diarylalkyne product containing only A2-A6 in the first
substitution position (R2NH2), combined with B1-B6 and
C1-C10. Both of these deconvolution libraries are syn-
thesized by the same synthetic procedure as the parent
library (Scheme 4, Figure 3).
a
See text for an explanation of the structures and codes.
Stille coupling with bis(tributylstannyl)acetylene (diaryl-
alkyne formation) resulting in product libraries contain-
ing 64 980 components. Both deletion synthesis decon-
volution and positional scanning sublibraries, synthe-
sized alongside the parent mixtures, allow for rapid
identification of active components. The examination of
these libraries in receptor dimerization and other protein-
protein interaction screens is in progress, and the results
will be disclosed in due course.
Exp er im en ta l Section
Con clu sion s
N-((ter t-Bu tyloxy)ca r bon yl)-N′-(2-(4-m eth oxyp h en yl)-
eth yl)-N′′-(2-(p h en yl)eth yl)im in od ia cetic Acid Dia m id e
(3). Monoamide 211 (0.41 g, 1.3 mmol) was dissolved in DMF
(5.0 mL) and added to a flask containing i-Pr2NEt (0.33 g, 2.6
The combinatorial dimerization of iodoarene-linked
iminodiacetic carboxamide libraries was conducted by
both Pd-catalyzed homocoupling (biaryl formation) and

Convergent Solution-Phase Combinatorial Synthesis
J . Org. Chem., Vol. 64, No. 19, 1999 7099
(1.5 mL) and treated with m-iodobenzoic acid (C1, 41.9 mg,
0.169 mmol), PyBrOP (79 mg, 0.169 mmol), and i-Pr2NEt (88
µL, 0.507 mmol). After 18 h of stirring at 25 °C, the reaction
mixture was diluted with EtOAc (50 mL) and washed with
10% aqueous HCl (3 × 50 mL), saturated aqueous NaHCO3
(50 mL), and saturated aqueous NaCl (50 mL). Drying (Na2-
SO4) and concentration provided 4 as a white foam (63 mg,
68%): 1H NMR (CDCl3, 250 MHz) δ 7.75 (m, 2H), 7.28 (m,
6H), 7.18 (m, 2H), 7.10 (m, 1H), 6.85 (m, 2H), 3.86 (br s, 4H),
3.76 (s, 3H), 3.61 (m, 4H), 2.85 (m, 4H); IR (film) νmax 3274,
3062, 2932, 2834, 1651, 1558, 1512, 1454, 1398, 1372, 1331,
1301, 1247, 1196, 1178, 1033, 1009, 958, 914, 803, 750, 735,
700 cm-1; FABHRMS (NBA-CsI) m/z 732.0359 (M + Cs+,
C
28H30N3O4I requires 732.0335).
Characterization data for 5-13 may be found in Supporting
Information.
Gen er a l P r oced u r e for th e Syn th esis of In d ivid u a l
Dia r yla cetylen es, P r ep a r a tion of 14. Iodide 4 (14.4 mg,
0.024 mmol), bis(tributylstannyl)acetylene (7.24 mg, 0.012
mmol), and tetrakis(triphenylphosphine)palladium (1.38 mg,
0.0012 mmol) were dissolved in dioxane (0.2 mL). Three
crystals of BHT (2,6-di-tert-butyl-4-methylphenol) were added,
and the reaction mixture was stirred at 100 °C for 5 h. The
solvent was evaporated and chromatography (SiO2, 50% EtOH/
EtOAc) afforded 14 as a colorless oil (7.0 mg, 60%): 1H NMR
(CDCl3, 250 MHz) δ 7.90-6.95 (m, 22H), 6.75 (m, 4H), 3.90-
3.40 (m, 22H), 3.20-2.60 (m, 8H); IR (film) νmax 3274, 3064,
2933, 1652, 1558, 1539, 1512, 1456, 1398, 1301, 1246, 1178,
1112, 1087, 1033, 957, 806, 750, 699 cm-1; FABHRMS (NBA-
CsI) m/z 1101.3583 (M + Cs+, C58H60N6O8 requires 1101.3527).
Characterization data for 15-23 may be found in Support-
ing Information.
Syn th esis of a 15-Com p on en t Dia r yla cetylen e Su bli-
br a r y. An equimolar solution of m-iodobenzamides 4 and 6-9
(0.004 mmol each, 0.020 mmol total) in 0.4 mL dioxane was
treated with bis(tributylstannyl)acetylene (6.0 mg, 0.010
mmol), Pd(PPh3)4 (11.4 mg, 0.0010 mmol), and three crystals
of BHT and stirred at 100 °C for 5 h. The solvent was
evaporated and chromatography (SiO2, 5-50% EtOH/EtOAc)
1
afforded the sublibrary as a yellow oil (7.2 mg, 63%). The H
NMR spectrum was consistent with the desired product
mixture, and the mass spectrum exhibited all predicted
molecular ions (15 components which have 14 unique molec-
ular weights): ESMS (M + Na+) m/z 991, 1048, 1076, 1104,
1105, 1133, 1161, 1174, 1189, 1217, 1231, 1259, 1287, 1357.
The mixture Stille coupling of p-iodobenzamides 10-13
under identical conditions afforded the expected 10-component
product mixture (9 unique molecular weights) in 47% yield:
ESMS (M + Na+ or M + H+) m/z 1107, 1134, 1162, 1190, 1218,
1231, 1260, 1290, 1335.
F igu r e 5. Comparison of the 1H NMR (CDCl3) spectra of 3,
8, 17, and 28.
Mixtu r e Stille Cou p lin g betw een Meta a n d P a r a
Su bstr a tes (7 a n d 12). A solution of iodobenzamides 7 (4.0
mg, 5.85 µmol) and 12 (4.5 mg, 6.32 µmol) in dioxane (0.3 mL)
was treated with bis(tributylstannyl)acetylene (3.7 mg, 6.1
µmol), Pd(PPh3)4 (0.7 mg, 0.61 µmol), and three crystals of
BHT, and stirred at 100 °C for 5 h. The solvent was evaporated
and chromatography (SiO2, 5-50% EtOH/EtOAc) afforded the
product mixture as a yellow oil (3.0 mg, 42%). The 1H NMR
spectrum was consistent with a 1:1:2 mixture of products 16,
22, and 24, and MS analysis confirmed the presence of all three
molecular ions: ESMS (M + Na+) m/z 1161, 1189, 1218.
mmol) and 4-methoxyphenethylamine (0.21 g, 1.42 mmol).
PyBOP (0.74 g, 1.42 mmol) was added, and the reaction
mixture was stirred for 16 h at 25 °C and then poured into a
separatory funnel containing 50 mL of 10% aqueous HCl and
extracted into EtOAc (3 × 50 mL). The combined organic
phases were washed with 10% aqueous HCl (2 × 50 mL),
saturated aqueous NaHCO3 (2 × 50 mL), and saturated
aqueous NaCl (50 mL), dried (Na2SO4), and concentrated to
provide 0.55 g (94%) of 3 as a colorless oil (see Figure 5 for a
1
comparison of H NMR spectra): 1H NMR (CDCl3, 250 MHz)
δ 7.29-7.08 (m, 7H), 6.81 (d, 2H, J ) 8.5 Hz), 3.74 (m, 7H),
3.50 (m, 4H), 2.80 (m, 4H), 1.38 (s, 9H); IR (film) νmax 3243,
3066, 2974, 2932, 1700, 1652, 1558, 1513, 1456, 1394, 1367,
1247, 1175, 1140, 1033, 960, 894, 846, 751, 700 cm-1; FAB-
HRMS (NBA-NaI) m/z 470.2651 (M + H+, C26H35N3O5 re-
quires 470.2655).
Gen er a l P r oced u r e for th e Th ir d Diver sifica tion ,
In d ivid u a l Com p on en ts. P r ep a r a tion of N-(3-iod oben -
zoyl)-N′-(2-p h en yleth yl)-N′′-(2-(4-m eth oxyp h en yl)eth yl)-
im in od ia cetic Acid Dia m id e (4). The BOC derivative 3 (71
mg, 0.15 mmol) was stirred in 4 N HCl-dioxane (1.0 mL) for
2 h. Solvent and excess acid were removed under a stream of
N2, and the remaining crude HCl salt was dissolved in DMF
Gen er a l P r oced u r e for th e Syn th esis of In d ivid u a l
Bia r yls, P r ep a r a tion of 30. Iodide 5 (10.6 mg, 17.7 mmol)
was mixed with 10% Pd/C (1.8 mg, 1.77 mmol) and Et3N (3.2
µL, 25.8 mmol) in DMF (90 µL, 0.2 M) and stirred at 100 °C
for 18 h. The solvent was evaporated and chromatography
(SiO2, 5-50% EtOH/EtOAc) afforded 30 as a pale yellow foam
(5.4 mg, 64%): 1H NMR (CDCl3, 250 MHz) δ 7.48 (m, 4H),
7.38 (m, 4H), 7.25 (m, 10H), 7.18 (m, 4H), 6.86 (m, 4H), 3.89
(m, 8H), 3.75 (m, 6H), 3.55 (m, 8H), 2.85 (m, 8H); IR (film)
νmax 3281, 3063, 2930, 1650, 1565, 1512, 1454, 1400, 1301,
1246, 1178, 1087, 1032, 1000, 910, 834, 730, 699 cm-1
;
FABHRMS (NBA-CsI) m/z 1077.3488 (M + Cs+, C56H60N6O8
requires 1077.3527).

7100 J . Org. Chem., Vol. 64, No. 19, 1999
Boger et al.
Characterization data for 25-29 and 31-34 may be found
in Supporting Information.
monoamide solution and stirred at 25 °C for 16 h. The reaction
mixture was poured into 50 mL of 10% aqueous HCl and
extracted into EtOAc (50 mL). The organic phase was washed
with 10% aqueous HCl (2 × 50 mL), saturated aqueous
NaHCO3 (2 × 50 mL), and saturated aqueous NaCl (50 mL),
dried (Na2SO4), and concentrated to provide 62.5 mg (90%) of
38 as a viscous oil.
P r oced u r e for th e Th ir d Diver sifica tion , Syn th esis of
Mixtu r e 39. Mixture 38 (42.4 mg, 0.0795 mmol) was stirred
in 4 N HCl-dioxane (0.1 mL) for 2 h, and then solvent and
excess acid were removed in vacuo. A stock solution was
prepared by diluting a mixture of 0.5 mmol of each iodoarene
carboxylic acid (C1-C10) to 5.00 mL in DMF. This stock
solution (0.079 mL, 0.0079 mmol of each acid) was added to a
DMF solution (0.8 mL) of the crude amine hydrochloride salts,
treated with PyBrOP (37.1 mg, 0.079 mmol) and i-Pr2NEt (14
µL, 0.16 mmol), and stirred for 18 h at 25 °C. The reaction
mixture was diluted with EtOAc (50 mL) and washed with
10% aqueous HCl (3 × 50 mL), saturated aqueous NaHCO3
(50 mL), and saturated aqueous NaCl (50 mL). Drying (Na2-
SO4) and concentration provided 51.1 mg (81%) of 39 as pale
yellow oil.
Syn t h esis of a 64 980-Com p on en t Dia r yla cet ylen e
Libr a r y, 40. Mixture 39 (35.0 mg, 0.044 mmol), bis(tributyl-
stannyl)acetylene (11.7 µL, 0.022 mmol), and Pd(PPh3)4 (2.5
mg, 0.0022 mmol) were dissolved in 1.1 mL of dioxane. Three
crystals of BHT were added, and the reaction mixture was
stirred at 100 °C for 5 h. The solvent was evaporated and
chromatography (5-50% EtOH/EtOAc) afforded 24.3 mg (81%,
based on average molecular weight) of 52 as a pale yellow oil.
Syn th esis of a 64 980-Com p ou n d Bia r yl Libr a r y, 41.
Mixture 39 (6.4 mg, 8.11 µmol), 10% Pd/C (0.9 mg, 0.811 µmol),
and Et3N (1.4 µL, 16.2 µmol) were added to DMF (0.04 mL),
and the reaction mixture was stirred at 100 °C for 18 h. The
solvent was evaporated and chromatography (5-50% EtOH/
EtOAc) afforded 4.8 mg (64%, based on average molecular
weight) of 41 as a pale yellow oil.
Syn th esis of a 15 Com p on en t Bia r yl Libr a r y. An
equimolar solution of m-iodobenzamides 4, 6-9 (0.005 mmol
each, 0.025 mmol total) in DMF (0.13 mL) was treated with
10% Pd/C (2.6 mg, 0.0025 mmol) and Et3N (4.4 µL, 0.038 mmol)
and stirred at 100 °C for 5 h. The solvent was evaporated and
chromatography (SiO2, 5-50% EtOH/EtOAc) afforded the
1
library as a yellow oil (10.5 mg, 75%). The H NMR spectrum
was consistent with the desired product mixture, and the mass
spectrum exhibited all predicted molecular ions (15 compo-
nents which have 14 unique molecular weights): ESMS (M +
Cl-) m/z 980, 1036, 1065, 1093, 1094, 1122, 1150, 1163, 1178,
1206, 1220, 1248, 1276, 1346.
The mixture biaryl coupling of p-iodobenzamides 5 and 10-
13 under identical conditions afforded the expected 15-
component product mixture in 78% yield: ESMS (M + Na+)
m/z 966, 1024, 1053, 1081, 1082, 1110, 1138, 1151, 1166, 1194,
1209, 1236, 1264, 1335.
Mixtu r e Bia r yl Cou p lin g betw een Meta a n d P a r a
Su bstr a tes (9 a n d 12). A solution of iodobenzamides 9 (3.7
mg, 4.7 µmol) and 12 (3.4 mg, 4.7 µmol) was treated with 10%
Pd/C (1.0 mg, 0.94 µmol) and Et3N (1.7 µL, 14.1 µmol) and
stirred in DMF (0.05 mL) at 100 °C for 5 h. The solvent was
evaporated and chromatography (SiO2, 5-50% EtOH/EtOAc)
afforded the product mixture as a yellow oil (3.5 mg, 60%).
1
The H NMR spectrum was consistent with a 1:1:2 mixture of
products 20, 33, and 35, and MS analysis confirmed the
presence of all three molecular ions: ESMS (M - H)- m/z 1170,
1240, 1310.
F u ll Libr a r y Syn th esis: P r oced u r e for th e F ir st Di-
ver sifica tion , Syn th esis of Mixtu r e 37. A mixture of
N-(tert-butyloxy)carbonyl)iminodiacetic acid (0.5 g, 2.14 mmol)
and EDCI (0.413 g, 2.14 mmol) in DMF (5.0 mL) was stirred
for 1 h at 25 °C. A stock solution was prepared by diluting a
mixture of 0.5 mmol of each amine (A1-A6) to 3.0 mL in DMF.
This stock solution (2.14 mL, 0.356 mmol of each amine) was
added to the anhydride solution. The reaction mixture was
stirred for 18 h at 25 °C before it was poured into 50 mL of
10% aqueous HCl. The mixture was extracted with EtOAc (3
× 50 mL), the combined organic phases were washed with 10%
aqueous HCl (2 × 50 mL) and saturated aqueous NaCl (50
mL) dried (Na2SO4), and the solvent was removed in vacuo to
afford 0.66 g (78%) of 37 as a viscous oil, whose 1H NMR
spectrum included all peaks observable with authentic indi-
vidual materials.
P r oced u r e for th e Secon d Diver sifica tion , Syn th esis
of Mixtu r e 38. Monoamide mixture 37 (51.2 mg, 0.13 mmol)
was dissolved in DMF (1.3 mL) and treated with i-Pr2NEt
(0.045 mL, 0.26 mmol). A stock solution was prepared by
diluting a mixture of 0.5 mmol of each amine (B1-B6) to 3.0
mL in DMF. This stock solution (0.13 mL, 0.0217 mmol of each
amine) and PyBOP (67.6 mg, 0.13 mmol) were added to the
Ack n ow led gm en t. This work was supported by the
National Institutes of Health (CA78045), The R. W.
J ohnson Pharmaceutical Research Institute, and the
award of a predoctoral fellowship (J .G., NDSEG, 1995-
1998).
Su p p or tin g In for m a tion Ava ila ble: Experimental pro-
cedures and characterization of C2-C5 and C7-C10, char-
acterization of 5-13, 15-23, 25-29, and 31-34, general
procedures for the synthesis of the scanning and deletion
deconvolution sublibraries, and 1H NMR spectra of C2-C5,
C7-C10, 4-23, 25-34 and 36. This material is available free
of charge via the Internet at http://pubs.acs.org.
J O990639P