A novel synthetic route for the anti-HIV drug MC-1220 and its analogues

Full text of DOI:10.1002/cmdc.201000244

DOI: 10.1002/cmdc.201000244
A Novel Synthetic Route for the Anti-HIV Drug MC-1220 and its Analogues
Yasser M. Loksha,[a] Daniel Globisch,[a] Roberta Loddo,[b] Gabriella Collu,[b] Paolo La Colla,[b] and
Erik B. Pedersen*[a]
The human immunodeficiency virus type 1 (HIV-1) is the etio-
logical agent of acquired immunodeficiency syndrome (AIDS).
The viral reverse transcriptase (RT) of HIV-1 is one of the most
promising targets for inhibition of HIV-1 replication; it can be
inhibited by two classes of drugs that belong either to the nu-
cleoside reverse transcriptase inhibitors (NRTIs) or to the non-
nucleoside reverse transcriptase inhibitors (NNRTIs).[1–6]
The HIV pandemic continues to spread throughout the
world, particularly affecting populations in developing coun-
tries. Efforts to limit this scourge need to be maximally imple-
mented. Women now account for the majority of HIV-infected
people worldwide, indicating the need for products that allow
women the option of self-protection from HIV transmission
without the knowledge of their sexual partners. The concepts
of vaginal microbicides are a potentially promising strategy to
prevent the spread of HIV. Microbicides are self-administered,
prophylactic products designed to protect against sexually
transmitted pathogens, including HIV-1. A special subgroup of
NNRTIs, the dihydroalkoxybenzyloxopyrimidines (DABOs), have
a proven capacity to irreversibly block HIV-1 replication.[7–10]
This property correlates with their ability to bind HIV-1 RT with
high affinity. One of the most important lead compounds of
this series of tight-binding NNRTIs is MC-1220, which is used in
racemic form.[11,12] The synthesis of
moiety at C6 from a readily available pyrimidine precursor. As
starting material we chose 4,6-dichloro-N,N,5-trimethylpyrimi-
din-2-amine (1)[14] due to the proper C2 substitution and the
activated C6 position. Because compound 1 is not commercial-
ly available, it was necessary to start from diethyl methylmalo-
nate and N,N-dimethylguanidine sulfate using sodium methox-
ide as a base to give 2-(dimethylamino)-5-methylpyrimidine-
4,6-diol.[14] The diol was held at reflux in phosphorus oxychlor-
ide to give the starting compound 1. Treatment of compound
1 with the sodium salt of the appropriate arylmethyl cyanides
(2,6-difluorobenzyl cyanide, 3,5-dimethylbenzyl cyanide, and
2,4,6-trimethylbenzyl cyanide) afforded the corresponding 2-[6-
chloro-2-(dimethylamino)-5-methylpyrimidin-4-yl]-2-(aryl)aceto-
nitriles 2a–c in high yields (86–98%). Nucleophilic substitution
of compound 1 under the same conditions as mentioned
above, followed by oxidation with a stream of oxygen bubbled
through the reaction mixture for 3 h, afforded the 4-aryl-6-
chloro-N,N-5-trimethylpyrimidin-2-amines 4a,b in 52 and 99%
yields, respectively. All five compounds were subsequently hy-
drolyzed, and in the case of 2a–c, also decarboxylated with
7m hydrochloric acid and acetic acid to furnish the corre-
sponding
6-aryl-2-(dimethylamino)-5-methylpyrimidin-4(3H)-
ones 3a–c in 82–89% yield, and 6-aryl-2-(dimethylamino)-5-
methylpyrimidin-4(3H)-ones 5a,b in 80 and 94% yields, respec-
tively, as new MC-1220 analogues (Scheme 1).
MC-1220 and its analogues was
previously published by Mai
et al.[11] and Bartolini et al.[12] by
condensation of the corresponding
b-keto esters with guanidine sul-
fate derivatives. The b-keto esters,
however, were prepared through
multistep reactions.[11] Recently,
Radi et al. reported the synthesis
of arylmethyl-functionalized (S)-DABOs and related analogues
from C6-protected formyl pyrimidinone.[13] Herein we describe
a new and efficient synthetic route to racemic MC-1220 which
can also be used for the preparation of its analogues.
The key step in our new synthetic route to MC-1220 and its
analogues is an efficient procedure to introduce the arylmethyl
Scheme 1. Reagents and conditions: a) NaH, DMF, room temperature, 1 h;
b) 7m HCl, AcOH, reflux, 40 h; c) 1) NaH, DMF, room temperature, 2 h, 2) O2,
room temperature, 4 h.
[a] Dr. Y. M. Loksha, D. Globisch, Prof. E. B. Pedersen
Nucleic Acid Center, Department of Physics and Chemistry, University of
Southern Denmark, Campusvej 55, 5230 Odense M (Denmark)
Fax: (+45)66158780
Following the synthetic route shown in Scheme 2, we found
it interesting to synthesize the MC-1220 analogues with a
chloro substituent in the pyrimidine ring at C4. Reaction of
4a,b with methylmagnesium bromide afforded the tertiary al-
cohols 6a,b, which were dehydrated into the vinyl compounds
7a,b in high yields using phosphorus pentoxide or phosphorus
oxychloride, respectively. For a direct conversion of the carbon-
yl group in compound 4b into a vinyl moiety, a Tebbe olefina-
E-mail: ebp@ifk.sdu.dk
[b] Dr. R. Loddo, Dr. G. Collu, Prof. P. La Colla
Dipartimento di Scienze e Tecnologie Biomediche, Sezione di Microbiologia
e Virologia Generale e Biotecnologie Microbiche, Universitꢀ di Cagliari Insti-
tution, Cittadella Universitaria, 09042 Monserrato (Italy)
Supporting information for this article is available on the WWW under
http://dx.doi.org/10.1002/cmdc.201000244: Full experimental details for
the synthesis of compounds outlined in Schemes 1–3 and spectral data.
ChemMedChem 2010, 5, 1847 – 1849
ꢀ 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
1847

MED
Scheme 3. Reagents and conditions: a) 7m HCl, AcOH, reflux, 42 h; b) 10%
Pd/C, EtOH, 3.5 bar H2, 5 h; c) MeI, NaH, DMF, room temperature, 2 h.
Scheme 2. Reagents and conditions: a) 1) MeMgBr, Et2O, 208C, 14 h, 2) sat.
NH4Cl; b) P2O5, CH2Cl2, room temperature, 20 h, or POCl3, CH2Cl2, reflux, 20 h;
c) TiCl4, Mg, THF, CH2Cl2, 08C, 20 min; d) 10% Pd/C, EtOH, 3.5 bar H2, room
temperature, 4 h.
be explained by a rapid keto–enol tautomerism in the pyrimi-
dinone ring. Only compound 12a (MC-1220) was soluble in
deuterated chloroform, and in this solvent carbon signals of
C2, C4, C5, and C6 could be detected by 13C NMR spectroscopy.
tion (methylenation)[15–19] was applied by using a titanium
methylene complex. The desired product 7b was isolated after
column chromatography as the minor product in only 7%
yield, while the major product was confirmed to be [6-chloro-
2-(dimethylamino)-5-methylpyrimidin-4-yl]-(3,5-dimethylphe-
nyl)methanol (8) in 27% yield.
1
However, elemental microanalysis, H NMR spectroscopy, EIMS,
and HRMS confirmed the proposed structures.
Table 1 lists the data for the inhibitory activities of the syn-
thesized compounds against wild-type HIV-1 (strain HTLV-IIIB)
Reduction of 7b using 10%
Table 1. Cytotoxicity and anti-HIV-1 activity of synthesized compounds 3a–c, 5a,b, 11 a,b, 12a (MC-1220),
12b, and 13a,b.
Pd/C and H2 furnished 4-chloro-
6-[1-(3,5-dimethylphenyl)ethyl]-
N,N,5-trimethylpyrimidin-2-amine
(9) in 5% yield and 4-[1-(3,5-di-
methylphenyl)ethyl]-N,N,5-trime-
thylpyrimidin-2-amine (10) in
13% yield.
Compd
CC50 [mm][a]
SI[b]
EC50 [mm][c]
Y181C
wild-type
EFVR
K103N+Y181C
3a
3b
3c
5a
5b
11 a
11 b
12a
12b
13a
13b
>100
>100
>100
>100
8Æ0.1
>100
>100
>100
44Æ0.2
46
>1428
>200
>250
>333
–
>500
>40
>10000
488
0.07
>100
>100
>100
>100
>8
>100
>100
>100
>44
ꢀ100
ꢀ100
>100
>100
>100
>8
>100
ꢀ100
90Æ10
>44
0.5Æ0.1
0.4Æ0.1
0.3Æ0.1
21Æ6
>100
94
>8
The synthetic route to MC-
1220 is outlined in Scheme 3.
Compounds 6a,b were hydro-
lyzed under strong acidic condi-
tions to afford 2-(dimethyl-
amino)-6-(1-arylvinyl)-5-methyl-
pyrimidin-4(3H)-ones 11 a,b in 70
and 89% yields, respectively. The
products were reduced to MC-
1220 (12a) and 2-(dimethyl-
amino)-6-[1-(3,5-dimethylphenyl)-
ethyl]-5-methylpyrimidin-4(3H)-
one (12b). To study the struc-
ture–activity relationship of the
>8
0.2Æ0.05
2.5Æ0.2
44Æ6
17Æ2
0.01Æ0.003
0.09Æ0.01
0.7Æ0.2
3.5Æ0.1
–
–
>46
>100
>46
>100
>46
>100
>46
>100
>100
[a] Compound dose required to effect 50% protection of MT-4 cells from HIV-1-induced cytopathogenicity, as
determined by the MTT method; ’>’ indicates that the CC50 value was not reached at the highest concentra-
tion tested. [b] Selectivity index: ratio CC50/EC50; EC50 and CC50 values are expressed as the mean of at least two
separate experiments. [c] Compound dose required to decrease the viability of mock-infected cells by 50%, as
determined by the MTT method.
pyrimidine ring, compounds 12a,b were methylated by treat-
ment of their sodium salts with methyl iodide to afford the
corresponding methoxy derivatives 13a,b in 86 and 91%
yields, respectively.
and strains carrying the clinically relevant mutations that
appear in the presence of NNRTIs: Y181C (strain N119), double
mutant Y181C+K103N (strain A17), and the triple mutant
K103R+V179D+P225H (EFVR; efavirenz resistant strain) in MT-
4 cells.
The newly synthesized compounds were confirmed by com-
parison of NMR data.[11–14] The carbon signals C2, C4, C5, and
C6 could not be observed in 13C NMR spectra of compounds
3a–c, 5a,b, 11 a,b, and 12a,b, especially when NMR spectra
were processed using deuterated DMSO as a solvent. This can
As is apparent from the results listed in Table 1, the majority
of the novel compounds were non-cytotoxic toward MT-4 cells
at doses as high as 100 mm (the highest concentration tested);
however, compound 5b was surprisingly cytotoxic relative to
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[1] D. Jochmans, Virus Res. 2008, 134, 171–185.
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newly synthesized compounds were more active than the lead
compound MC-1220. In general, members of the 2,6-difluoro-
phenyl series (3a, 5a, 11 a, 12a) were more active than both
other series. When the arylalkyl group in compounds 3a,b was
replaced by an aroyl group in compounds 5a,b or a vinyl
group as in compound 11 a,b, the activity against HIV-1 was
decreased. In the case of the methoxy compounds 13a,b, the
lack of a hydrogen at the N3 position in the pyrimidine ring
may explain the complete loss of activity. Interestingly, the
new compound 12b was found to exhibit activity against the
Y181C mutant in the micromolar range (EC50 =3.5 mm). This
compound could be a new lead for further screening efforts.
Unfortunately, none of the other new compounds were found
to exhibit activity against the Y181C mutant.
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In summary, we present a new, rapid, and easy route for the
synthesis of the lead compound MC-1220 (12a) and its ana-
logue 12b by reduction in only four steps to give total respec-
tive yields of 29 and 43%. The key step in this route involves
reduction of the vinyl group in compounds 11 a,b. The inter-
mediates from this route, which are readily available in large
quantities, are also suitable for synthesizing new analogues of
MC-1220 for broad medicinal screening campaigns. Although
anti-HIV-1 activities were observed for the novel MC-1220 ana-
logues, in all cases, they were lower than that of the lead com-
pound MC-1220.
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Acknowledgements
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[22] The information in this document is provided as is, and no guarantee
or warranty is given that the information is fit for any particular pur-
pose. The user thereof uses the information as its sole risk and liability.
This work received funding from the European Community’s Sixth
Framework Programme under contract number LSHP-CT-2004-
503162 (Selection and development of microbicides for mucosal
use to prevent sexual HIV transmission/acquisition).[22]
Received: June 9, 2010
Keywords: antiviral agents · Grignard reaction · HIV · MC-
1220 · NNRTIs · pyrimidines
Revised: July 12, 2010
Published online on August 16, 2010
ChemMedChem 2010, 5, 1847 – 1849
ꢀ 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemmedchem.org
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