Anti-AIDS agents 72. Bioisosteres (7-carbon-DCKs) of the potent anti-HIV lead DCK

Article abstract of DOI:10.1016/j.bmcl.2007.05.026

Three 9,10-di-O-(-)-camphanoyl-7,8,9,10-tetrahydro-benzo[h]chromen-2-one (7-carbon-DCK) analogs (3a-c) were synthesized and evaluated for inhibition of HIV-1 replication in H9 lymphocytes. All three new carbon bioisosteres of the anti-HIV lead DCK showed anti-HIV activity. Compound 3a had an EC₅₀ value of 0.068 μM, which was comparable to that of DCK in the same assay. The preliminary results indicated that 7-carbon-DCK analogs merit attention as potential HIV-1 inhibitors for further development into clinical trials candidates.

Full text of DOI:10.1016/j.bmcl.2007.05.026

Bioorganic & Medicinal Chemistry Letters 17 (2007) 4316–4319
Anti-AIDS agents 72. Bioisosteres (7-carbon-DCKs)
of the potent anti-HIV lead DCK
Yang Wang,a Shao-Xu Huang,a Peng Xia,a,* Yi Xia,b Zheng-Yu Yang,b
Nicole Kilgore,c Susan L. Morris-Natschkeb and Kuo-Hsiung Leeb,*
aDepartment of Medicinal Chemistry, School of Pharmacy, Fudan University, Shanghai 200032, China
bNatural Products Research Laboratories, School of Pharmacy, University of North Carolina, Chapel Hill, NC 27599-7360, USA
cPanacos Pharmaceuticals, Inc., 209 Perry Parkway, Suite 7, Gaithersburg, MD 20877, USA
Received 28 March 2007; revised 4 May 2007; accepted 9 May 2007
Available online 16 May 2007
Abstract—Three 9,10-di-O-(ꢀ)-camphanoyl-7,8,9,10-tetrahydro-benzo[h]chromen-2-one (7-carbon-DCK) analogs (3a–c) were syn-
thesized and evaluated for inhibition of HIV-1 replication in H9 lymphocytes. All three new carbon bioisosteres of the anti-HIV lead
DCK showed anti-HIV activity. Compound 3a had an EC50 value of 0.068 lM, which was comparable to that of DCK in the same
assay. The preliminary results indicated that 7-carbon-DCK analogs merit attention as potential HIV-1 inhibitors for further devel-
opment into clinical trials candidates.
ꢀ 2007 Elsevier Ltd. All rights reserved.
30,40-Di-O-(ꢀ)-camphanoyl-(+)-cis-khellactone (DCK,
1) demonstrated extremely potent inhibitory activity
against HIV-1 replication in H9 lymphocytic cells with
an EC50 value of 2.56 · 10ꢀ4 lM and a therapeutic in-
dex (TI) of 1.37 · 105 in our prior research.1 In subse-
quent structural modification studies, numerous DCK
derivatives were synthesized and at least 20 DCK ana-
logs have shown promising inhibitory activity against
HIV-1 replication in H9 lymphocytes.2 Among them,
3-methyl, 4-methyl, and 5-methyl substituted DCKs
were much more potent than DCK and AZT in the same
assay with EC50 and TI values ranging from 5.25 · 10ꢀ5
to 2.39 · 10ꢀ7 lM and 2.15 · 106 to 3.97 · 108, respec-
tively.3 In addition, a preliminary mechanistic study
showed that 3-hydroxymethyl-4-methyl DCK inhibits
HIV reverse transcriptase (RT) via a different mecha-
nism of action from those of current clinical anti-HIV/
AIDS drugs.4 It was also found that DCK analogs are
strongly synergistic with approved drugs such as AZT
and act at a point in the virus life cycle immediately fol-
lowing the target for AZT and nevirapine.4 In our recent
research on structural modification of 4-methyl DCK
(2), the ring oxygen atom in the A or C ring of DCK
was replaced by a sulfur atom, and these sulfur-contain-
ing analogs also exhibited potent inhibitory effects on
HIV-1 replication in H9 lymphocytes.5,6 Moreover,
gem-dimethyl substitution at the 8-position was found
to be preferable to larger alkyl substituents or hydrogen
atoms.7 In a continuing effort to identify the pharmaco-
phores in this class of potent anti-HIV agents, we
designed a new series of DCK analogs, namely 7-car-
bon-DCK derivatives (3a–c). In these compounds, a
methylene group replaces the oxygen in the C ring of
DCK. Thus, these analogs are bioisosteres of DCK,
and the effect of the 7-oxygen atom on the anti-HIV
activity of DCK-type compounds can be further ex-
plored. In addition, to help determine the possible impact
of the 8,8-dimethyl groups, both unsubstituted (3a and
3b) and dimethylated (3c) analogs were prepared. Here-
in, we report the synthesis of compounds 3a–c and their
preliminary anti-HIV bioassay results (Fig. 1).
The synthesis of 3a and 3b was accomplished by a seven-
step sequence, as illustrated in Scheme 1. The key interme-
diates 7,8-dihydro-benzo[h]chromen-2-one (10a) and its
4-methyl analog (10b) were prepared according to the
procedure reported in our prior work.8 Sharpless asym-
metric dihydroxylation (AD) of 10a and 10b afforded
dihydroxy derivatives 11a and 11b in moderate yield
(45–49%).9 Finally, 7-carbon-DCK analogs 3a and 3b
Keywords: Anti-HIV activity; DCK; Bioisostere.
*
Corresponding authors. Tel.: +86 21 54237563 (P.X.); tel.: +1 919
962 0066; fax: +1 919 966 3893 (K.-H.L.); e-mail addresses:
pxia@shmu.edu.cn; khlee@unc.edu
0960-894X/$ - see front matter ꢀ 2007 Elsevier Ltd. All rights reserved.
doi:10.1016/j.bmcl.2007.05.026

Y. Wang et al. / Bioorg. Med. Chem. Lett. 17 (2007) 4316–4319
4317
Figure 1. Structures of DCK (1), 4-methyl DCK (2), and 7-carbon-DCK analogs (3a–c).
Scheme 1. Synthesis of 3a and 3b. Reagents and conditions: (i) Raney Ni-Al alloy, 1% aq KOH/water, 90 ꢁC, 2 h; (ii) L-Malic acid, H2SO4, HOAc,
140 ꢁC, 6 h (R = H); CH3COCH2COOC2H5, POCl3, 100 ꢁC, 18 h (R = CH3); (iii) CrO3, HOAc, rt, 3 days; (iv) NaBH4, CH3OH, 1 h; (v) 2% H2SO4,
reflux, 6–16 h; (vi) AD-mix-a (K2OsO4 Æ 2H2O, K3Fe(CN)6, (DHQ)2PHAL, K2CO3), t-butanol/H2O 1:1, rt, 2–3 days; (vii) (S)-camphanic chloride,
pyridine, DMAP, CH2Cl2, rt, 24 h.
were obtained in 62% and 82% yields, respectively, by
acylation of 11a and 11b with (S)-(ꢀ)-camphanic chloride
in CH2Cl2 at room temperature with pyridine as acid
scavenger.
ing from 15. Physical and spectral data for 3a–c were
consistent with their chemical structures.12
The anti-HIV activities of compounds 3a-c were evalu-
ated in H9 lymphocytes, with AZT as the reference com-
pound. The bioassay data are shown in Table 1 and
indicated that all three compounds inhibited HIV repli-
cation and had reasonable therapeutic index (TI) values.
Compounds 3a and 3b had significant EC50 values of
0.068 and 0.083 lM, respectively. Thus, the presence
of the C-4 methyl in these 7-carbon DCK analogs did
not lead to increased potency, in contrast to results with
DCK and 4-methyl DCK. Although an absence of gem-
dimethylation was detrimental in the 7-oxy DCK series,7
it was hard to make a definitive conclusion in the 7-car-
bon DCK series (comparison of 3c with 3b) due to sol-
ubility problems with 3c. However, the 7-carbon analog
3b was more potent and had a higher TI than the corre-
As shown in Scheme 2, the preparation of 3c followed a
slightly different synthetic route with 5-methoxy-1-tetr-
alone (12) as starting material. Dimethylation of 12 with
CH3I in the presence of t-BuOK afforded 2,2-dimethyl-
5-methoxy-1-tetralone (13) in 91% yield.10 Reduction of
dimethylated tetralone 13 with H2 catalyzed with 10%
Pd-C gave 1,2,3,4-tetrahydro-5-methoxy-2,2-dimethyl-
naphthalene (14) quantitatively.11 Demethylation of 14
with BBr3 resulted in the formation of phenol derivative
15 in 98% yield.11 The remaining synthetic steps fol-
lowed those detailed above for 3a and 3b from phenol
5. The target compound 3c was thus obtained in an
overall yield of 5% via a six-step reaction sequence start-

4318
Y. Wang et al. / Bioorg. Med. Chem. Lett. 17 (2007) 4316–4319
Scheme 2. Synthesis of 3c. Reagents and conditions: (i) t-BuOK/THF, reflux, 5 h, CH3I, 0.5 h; (ii) H2, Pd-C, CH3SO3H, HOAc, CH3COOC2H5,
C2H5OH, rt, 36 h; (iii) BBr3/CH2Cl2, ꢀ78 ꢁC; (iv) CH3COCH2COOC2H5, POCl3, benzene, reflux, 24 h, 66.0%; (v) CrO3, HOAc, rt, 30 h (yield:
17 = 39.0%, 18 = 19.9%); (vi) NaBH4, CH3OH, 0.5 h (yield: 70.3%); (vii) 2% H2SO4, 120–130 ꢁC, 5 h (yield: 95.0%); (viii) AD-mix-a (K2OsO4 Æ 2H2O,
K3Fe(CN)6, (DHQ)2PHAL, K2CO3), t-butanol/H2O 1:1, CH3SO2NH2, rt, 32 h (yield: 75.5%); (ix) (S)-camphanic chloride, Et3N, DMAP, CH2Cl2,
rt, 4 h (yield: 81.2%).
Table 1. Anti-HIV data of compounds 3a–c in acutely infected H9
lymphocytes
20272010 and 20672022) awarded to P. Xia and Y.
Wang, respectively, a research grant (20020246069)
for Ph.D. program from the National Education
Administration of China awarded to P. Xia, and Grant
AI-33066 from the National Institute of Allergies and
Infectious Diseases awarded to K.H. Lee.
a
b
Compound
IC50 (lM)
EC50 (lM)
TIc
3a
3b
57.2
54.4
0.068
0.083
<0.39
0.049
0.0059
0.0137
841
659
3cd
>39.4
>16.1
>38.9
500
>100
>328
>6600
36,520
DCKe
4-Me DCKe
AZT
Supplementary data
a Concentration that inhibits uninfected H9 cell growth by 50%.
b Concentration that inhibits viral replication by 50%.
c TI, therapeutic index IC50/EC50
.
Supplementary data associated with this article can be
found, in the online version, at doi:10.1016/j.bmcl.
2007.05.026.
d More precise data could not be determined due to solubility
problems.
e The data for DCK and 4-methyl DCK were cited from Ref. 8. EC50
and TI values for DCK and 4-methyl DCK were 2.56 · 10ꢀ4 lM,
1.83 · 10ꢀ6 lM, and 1.37 · 105, 6.89 · 107, respectively, in previous
screenings, using a different methodology, and publications.1
References and notes
sponding demethylated 7-oxy DCK derivative, 20,20-
dihydro-4-methyl DCK (EC50 = 6.9 lM, TI > 6).7 Com-
pound 3b was also more potent against HIV replication
but was more cytotoxic than the analogous 7-thio ana-
log (EC50 = 0.141 lM, TI = 1,110).6
1. Huang, L.; Kashiwada, Y.; Cosentino, L. M.; Fan, S.;
Chen, C. H.; McPhail, A. T.; Fujioka, T.; Mihashi, K.;
Lee, K. H. J. Med. Chem. 1994, 37, 3947.
2. Yu, D.; Suzuki, M.; Xie, L.; Morris-Natschke, S. L.; Lee,
K. H. Med. Res. Rev. 2003, 23, 322.
3. Xie, L.; Takeuchi, Y.; Cosentino, L. M.; Lee, K. H.
J. Med. Chem. 1999, 42, 2662.
Further structural modification and biological screening
are in progress as these promising bioassay results dem-
onstrate that 7-carbon-DCK analogs merit attention as
potential HIV-1 inhibitors.
4. Xie, L.; Yu, D.; Wild, C.; Allaway, G.; Turpin, J.; Smith,
P. C.; Lee, K. H. J. Med. Chem. 2004, 47, 756.
5. Xia, P.; Yin, Z. J.; Chen, Y.; Zhang, Q.; Zhang, B. N.;
Xia, Y.; Yang, Z. Y.; Kilgore, N.; Wild, C.; Morris-
Natschke, S. L.; Lee, K. H. Bioorg. Med. Chem. Lett.
2004, 14, 3341.
6. Chen, Y.; Zhang, Q.; Zhang, B. N.; Xia, P.; Xia,
Y.; Yang, Z. Y.; Kilgore, N.; Wild, C.; Morris-
Natschke, S. L.; Lee, K. H. Bioorg. Med. Chem.
2004, 12, 6383.
Acknowledgments
This research was supported by grants from the Na-
tional Natural Science Foundation of China (Nos.

Y. Wang et al. / Bioorg. Med. Chem. Lett. 17 (2007) 4316–4319
4319
7. Zhang, Q.; Chen, Y.; Xia, P.; Xia, Y.; Yang, Z. Y.; Yu, D.
L.; Morris-Natschke, S. L.; Lee, K. H. Bioorg. Med.
Chem. Lett. 2004, 14, 5855.
8. Wang, Y.; Huang, S. X.; Xia, P. Synth. Commun. 2005, 35,
3141.
9. Sharpless, K. B.; Amberg, W.; Bennani, Y. L.; Crispino,
G. A.; Hartung, J.; Jeong, K. S.; Kwong, H. L.;
Morikawa, K.; Wang, Z. M.; Xu, D.; Zhang, X. L.
J. Org. Chem. 1992, 57, 2768.
10. Gabriel Garcia, J.; Enas, J. D.; Fronczek, F. R.;
VanBrocklin, H. F. J. Org. Chem. 1994, 59, 8299.
11. Bayston, D. J.; Fraser, J. L.; Ashton, M. R.; Baxter, A. D.;
Polywka, M. E. C.; Moses, E. J. Org. Chem. 1998, 63, 3137.
12. Physical and spectral data for 3a–c:
MS: calcd for C33H36O10Na+ 615.2201, found 615.2191.
9,10-Di-O-(ꢀ)-camphanoyl-4-methyl-7,8,9,10-tetrahydro-
benzo [h] chromen-2-one (3b). Mp 159–161 ꢁC; 1H NMR
(CDCl3, 300 MHz) d 0.96–1.12 (m, 18H, camphanoyl
CH3), 1.61–2.56 (m, 10H, 8-H, camphanoyl CH2), 2.42 (s,
3H, 4-CH3), 3.00–3.20 (m, 2H, 7-H), 5.31–5.38 (m, 1H, 9-
H), 6.24 (s, 1H, 3-H), 6.83 (d, J = 2.7 Hz, 1H, 10-H), 7.12
(d, J = 8.1 Hz, 1H, 6-H), 7.55 (d, J = 8.1 Hz, 1H, 5-H).
ESI-MS m/z (%): 606.30 (M+, 19). HR-MS: calcd for
C34H38O10Na+ 629.2357, found 629.2367.
9,10-Di-O-(ꢀ)-camphanoyl-4,8,8-trimethyl-7,8,9,10-tetra-
hydro-benzo [h] chromen-2-one (3c). Mp 148–150 ꢁC; 1H
NMR (CDCl3, 300 MHz) d 0.92–1.30 (m, 24H, campha-
noyl CH3, 8-CH3), 1.61–1.76 (m, 2H, camphanoyl CH2),
1.86–1.98 (m, 2H, camphanoyl CH2), 2.11–2.28 (m, 2H,
camphanoyl CH2), 2.45 (s, 3H, 4-CH3), 2.50–2.61 (m, 2H,
camphanoyl CH2), 2.82–3.02 (m, 2H, 7-H), 5.35 (d,
J = 5.1 Hz, 1H, 9-H), 6.25 (s, 1H, 3-H), 6.76 (d,
J = 5.1 Hz, 1H, 10-H), 7.11 (d, J = 8.4 Hz, 1H, 6-H),
7.59 (d, J = 8.1 Hz, 1H, 5-H). ESI-MS m/z (%): 657.30
(M+Na+, 100). HR-MS: calcd for C36H42O10Na+
657.2670, found 657.2690.
9,10-Di-O-(ꢀ)-camphanoyl-7,8,9,10-tetrahydro-benzo [h]
chromen-2-one (3a). Mp 120–122 ꢁC; 1H NMR (CDCl3,
300 MHz) d 0.94–1.13 (m, 18H, camphanoyl CH3), 1.61–
2.56 (m, 10H, 8-H, camphanoyl CH2), 3.07–3.17 (m, 2H,
7-H), 5.31–5.40 (m, 1H, 9-H), 6.38 (d, J = 9.3 Hz, 1H, 3-
H), 6.82 (d, J = 2.7 Hz, 1H, 10-H), 7.12 (d, J = 8.1 Hz, 1H,
6-H), 7.44 (d, J = 8.1 Hz, 1H, 5-H), 7.67 (d, J = 9.6 Hz,
1H, 4-H). ESI-MS m/z (%): 615.25 (M+Na+, 100). HR-