R. Skerlj et al. / Bioorg. Med. Chem. Lett. 21 (2011) 262–266
265
when the aminomethyl group was adjacent to the oxygen atom of
the oxazole 3l the compound was inactive with an IC50 of 2.83
whereas substitution adjacent to the nitrogen atom 3m resulted in
a potent compound with an IC50 of 0.0072 M. On the other hand
substitution of the aminomethyl group at the 2-position 3n had a
deleterious impact on potency with an IC50 of 20 M. Incorporation
of the imidazole 3k resulted in an inactive compound that was
also cytotoxic to MT-4 cells. As was the case with the previous
series the effects on SDF-1 induced Ca2+ flux tracked with the
anti-HIV-1 activity.
replication. These compounds displayed good pharmacokinetics
in rat and dog but because of the large anti-HIV-1 fold shift in po-
lM
tency in the presence of
advanced.
a-AGP these compounds were not further
l
l
Supplementary data
Supplementary data (experimental procedures and character-
ization data for the synthesis of compounds 2e–2i) associated with
this article can be found, in the online version, at doi:10.1016/
The methodology used to prepare the compounds in Table 2
was similar to that utilized in Scheme 1. The key step in many of
these examples was the generation of the bromomethyl (3a–b,
3d–e) or aldehyde moiety (3c, 3f–n) of the heterocycle which
was then coupled with tert-butyl 2-((5,6,7,8-tetrahydroquinolin-
8-ylamino)methyl)-1H-benzo[d]imidazole-1-carboxylate5 via N-
alkylation or reductive amination. In most of the reductive amina-
tion examples the amine was masked by use of the phthalimide
group. For example, the furan 3h was synthesized by mono protec-
tion of furan-3,4-diyldimethanol 7 as the TBDMS ether followed by
Mitsunobu reaction of the alcohol with phthalimide to install the
requisite protected amine, acid mediated cleavage of the silyl ether
to give the alcohol and finally TPAP oxidation to afford the alde-
hyde 8 (Scheme 2). Reductive amination with the fully elaborated
secondary amine5 in the presence of NaBH(OAc)3, following an
acidic workup to remove any complexed boron species, and depro-
tection of the phthalimide with hydrazine furnished 3h as the free-
base. In the N-alkylation examples the bromomethyl moiety was
readily accessed from commercially available starting materials.
For instance, as exemplified by the synthesis of 3e, 4-methylthi-
ophene-3-carbonitrile 9 was readily converted to the correspond-
ing bromide using NBS in the presence of AIBN which then
underwent N- alkylation with the secondary amine to give com-
pound 10. Reduction of the nitrile to the primary amine using H2
in the presence of Raney Ni followed by deprotection afforded
compound 3e (Scheme 3).
References and notes
1. Montaner, J. S.; Hogg, R.; Wood, E.; Kerr, T.; Tyndall, M.; Levy, A. R.; Harrigan, P.
R. Lancet 2006, 368, 531.
2. Gulick, R. M.; Lalezari, J.; Goodrich, J.; Clumeck, N.; DeJesus, E.; Horban, A.;
Nadler, J.; Clotet, B.; Karlsson, A.; Wohlfeiler, M.; Montana, J. B.; McHale, M.;
Sullivan, J.; Ridgway, C.; Felstead, S.; Dunne, M. W.; van der Ryst, E.; Mayer, H.
N. Eng. J. Med. 2008, 359, 1429.
3. De Clercq, E.; Yamamoto, N.; Pauwels, R.; Balzarini, J.; Witvrouw, M.; De Vreese,
K.; Debyser, Z.; Rosenwirth, B.; Peichl, P.; Datema, R. Antimicrob. Agents
Chemother. 1994, 38, 668.
4. (a) Hendrix, C. W.; Collier, A. C.; Lederman, M. M.; Schols, D.; Pollard, R. B.;
Brown, S.; Jackson, J. B.; Coombs, R. W.; Glesby, M. J.; Flexner, C. W.; Bridger, G.
J.; Badel, K.; MacFarland, R. T.; Henson, G. W.; Calandra, G. J. Acquir. Immune
Defic. Syndr. 2004, 37, 1253; (b) Franzen, S.; Bridger, G.; Whitcomb, J. M.; Toma,
L.; Stawiski, E.; Parkin, N.; Petropoulos, C. J.; Huang, W. Antimicrob. Agents
Chemother. 2008, 52, 2608.
5. Skerlj, R. T.; Bridger, G. J.; Kaller, A.; McEachern, E. J.; Crawford, J.; Zhou, Y.;
Atsma, B.; Langille, J.; Nan, S.; Veale, D.; Wilson, T.; Harwig, C.; Hatse, S.;
Princen, K.; De Clercq, E.; Schols, D. J. Med. Chem. 2010, 53, 3376.
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Kaufman, J. L.; Maziarz, R. T.; Hosing, C.; Fruehauf, S.; Horwitz, M.; Cooper, D.;
Bridger, G.; Calandra, G. Blood 2009, 113, 5720.
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Nademanee, A.; McCarty, J.; Bridger, G.; Calandra, G. J. Clin. Oncol. 2009, 27,
4767.
10. Bridger, G. J.; Skerlj, R. T.; Hernandez-Abad, P. E.; Bogucki, D. E.; Wang, Z.; Zhou,
Y.; Nan, S.; Boehringer, E. M.; Wilson, T.; Crawford, J.; Metz, M.; Hatse, S.;
Princen, K.; De Clercq, E.; Schols, D. J. Med. Chem. 2010, 53, 1250.
11. (a) Gudmundsson, K. S.; Sebahar, P. R.; Richardson, L. D.; Miller, J. F.; Turner, E.
M.; Catalano, J. G.; Spaltenstein, A.; Lawrence, W.; Thomson, M.; Jenkinson, S.
Bioorg. Med. Chem. Lett. 2009, 19, 5048; (b) Gudmundsson, K. S.; Boggs, S. D.;
Catalano, J. G.; Svolto, A.; Spaltenstein, A.; Thomson, M.; Wheelan, P.;
Jenkinson, S. Bioorg. Med. Chem. Lett. 2009, 19, 6399; (c) Miller, J. F.; Turner,
E. M.; Gudmundsson, K. S.; Jenkinson, S.; Splatenstein, A.; Thomson, M.;
Wheelan, P. Bioorg. Med. Chem. Lett. 2010, 20, 2125; (d) Catalano, J. G.;
Gudmundsson, K. S.; Svolto, A.; Boggs, S. D.; Miller, J. F.; Spaltenstein, A.;
Thomson, M.; Wheelan, P.; Minick, D. J.; Phelps, D. E.; Jenkinson, S. Bioorg. Med.
Chem. Lett. 2010, 20, 2186; (e) Miller, J. F.; Gudmundsson, K. S.; Richardson, L.
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Based on ADME considerations representative compounds from
the pyridine 3a, thiophene 3e and furan 3h series were prepared
(Table 3) as the (S)-enantiomer using methodology previously re-
ported16 since AMD070 and related (S)-enantiomers5 had shown
a marked increase in potency. This observation was corroborated,
for example, the IC50 of (S)-3a, 3e, and 3h was 4.2, 1.0, and
0.3 nM, respectively, a 5-, 103-, and 35-fold increase in potency
over the corresponding racemates (Tables 2 and 3). The IC50 was
also evaluated for X4 HIV-1 infection in PBMC and was found to
be twofold higher for compounds 3a and 3e (IC50 of 9.9 and
2.0 nM) and 10-fold higher for compound 3h (IC50 of 4.1 nM) con-
sistent with other compounds when comparing inhibition of infec-
tion in the MT-4 CD4+ T cell line and in PBMC. However, in the
12. Klement, I.; Lennick, K.; Tucker, C. E.; Knochel, P. Tetrahedron Lett. 1993, 34,
4623.
13. A mixture of 5-cyano-2-methyl-benzoic acid methyl ester (see Ref. 12 for
preparation) (894 mg, 5.10 mmol), NBS (1.00 g, 5.62 mmol), and AIBN (125 mg,
0.761 mmol) in CCl4 (20 mL) was heated at reflux for 3 days then allowed to
cool to room temperature. The mixture was filtered, concentrated and the
crude purified by column chromatography on silica gel (5% EtOAc/hexanes) to
afford methyl 4-(bromomethyl)-3-cyanobenzoate 5a as a yellow solid (800 mg,
62%). 1H NMR (CDCl3) d 3.99 (s, 3H), 4.96 (s, 2H), 7.61 (d, 1H, J = 8.1 Hz), 7.77
(dd, 1H, J = 8.1, 1.8 Hz), 8.27 (d, 1H, J = 1.8 Hz).
14. A mixture of tert-butyl 2-((5,6,7,8-tetrahydroquinolin-8-ylamino)methyl)-1H-
benzo[d]imidazole-1-carboxylate (253 mg, 0.668 mmol), 5a (170 mg,
0.669 mmol), KI (6 mg, 0.04 mmol), and DIPEA (0.17 mL, 0.98 mmol) in
CH3CN (6.7 mL) was heated at 60 °C for 18 h. Saturated NaHCO3 (aq) (15 mL)
was added, the mixture was extracted with CH2Cl2 (3 Â 15 mL) and the organic
extracts were dried (MgSO4) and concentrated. The crude was purified by
column chromatography on silica gel (500:5:1 CH2Cl2/MeOH/NH4OH) to give
presence of 1 mg/mL of a-acid glycoprotein (AGP) there was a large
17–28-fold shift in anti-HIV-1 activity. Additional evidence that
these compounds are interacting with CXCR4 was provided by
the competitive binding with 125I-SDF-1 in CD4+CXCR4+ T cells
with the IC50 ranging from 20 to 89 nM (Table 3).
Due to the ease of handling these compounds were prepared as
their hydrochloride salts and evaluated in rat and dog pharmacoki-
netics (Table 4). The oral bioavailability of the thiophene com-
pound (S)-3e was poor in both species while the furan
compound (S)-3h showed moderate oral bioavailability (F = 17%
in rat and 27% in dog). In contrast, the pyridine compound (S)-3a
had excellent oral bioavailability in dog (F = 84%) and moderate
in rat (F = 22%).
tert-butyl
2-(((2-cyano-4-(methoxycarbonyl)benzyl)(5,6,7,8-
tetrahydroquinolin-8-yl)amino)methyl)-1H-benzo[d]imidazole-1-carboxylate
6 as a yellow foam (360 mg, 98%). 1H NMR (CDCl3) d 1.74 (m, 10H), 1.99 (m,
2H), 2.29 (m, 1H), 2.74 (m, 2H), 3.86 (s, 3H), 4.22 (d, 1H, J = 17 Hz), 4.33 (m,
1H), 4.36 (d, 1H, J = 17 Hz), 4.59 (d, 1H, J = 14 Hz), 4.65 (d, 1H, J = 14 Hz), 6.98
(dd, 1H, J = 8.0, 4.7 Hz), 7.25 (m, 3H), 7.33 (dd, 1H, J = 8.1, 1.8 Hz), 7.50 (m, 1H),
7.68 (m, 2H), 8.11 (d, 1H, J = 8.1 Hz), 8.41 (m, 1H).
In conclusion we identified a novel series of orally bioavailable
heterocyclic aminomethyl compounds of the chemokine receptor
CXCR4 based on inhibition of SDF-1 induced calcium signaling
and 125I-SDF-1 binding that retained potent inhibition of HIV-1