4-Benzyloxy-γ-sultone derivatives: Discovery of a novel family of non-nucleoside inhibitors of human cytomegalovirus and varicella zoster virus

Article abstract of DOI:10.1021/jm8014662

We report the synthesis and antiviral activity of a new family of non-nucleoside antivirals, derived from the 4-keto-1,2-oxathiole-2,2-dioxide (β-keto-γ-sultone) heterocyclic system. Several 4- and 5-substituted-5H-1,2-oxathiole-2,2-dioxide derivatives were found to have a selective inhibitory activity against human cytomegalovirus (HCMV) and varicella zoster virus (VZV) replication in vitro, being inactive against a variety of other DNA and RNA viruses. A structure-activity relationship (SAR) study showed that the presence of a benzyl at the 5 position and a benzyloxy substituent at the 4 position are a prerequisite for anti-HCMV and VZV activity. The novel compounds do not show cross-resistance against a wide variety of mutant drug-resistant HCMV strains, pointing to a novel mechanism of antiviral action.

Full text of DOI:10.1021/jm8014662

1582
J. Med. Chem. 2009, 52, 1582–1591
4-Benzyloxy-γ-Sultone Derivatives: Discovery of a Novel Family of Non-Nucleoside Inhibitors of
Human Cytomegalovirus and Varicella Zoster Virus
Sonia De Castro,† Carlos Garc´ıa-Aparicio,† Graciela Andrei,‡ Robert Snoeck,‡ Jan Balzarini,‡ Mar´ıa-Jose´ Camarasa,† and
Sonsoles Vela´zquez*,†
Instituto de Qu´ımica Me´dica (CSIC), C/Juan de la CierVa 3, E-28006 Madrid, Spain, Rega Institute for Medical Research, K. U. LeuVen,
Minderbroedersstraat 10, B-3000 LeuVen, Belgium
ReceiVed NoVember 21, 2008
We report the synthesis and antiviral activity of a new family of non-nucleoside antivirals, derived from the
4-keto-1,2-oxathiole-2,2-dioxide (ꢀ-keto-γ-sultone) heterocyclic system. Several 4- and 5-substituted-5H-
1,2-oxathiole-2,2-dioxide derivatives were found to have a selective inhibitory activity against human
cytomegalovirus (HCMV) and varicella zoster virus (VZV) replication in vitro, being inactive against a
variety of other DNA and RNA viruses. A structure-activity relationship (SAR) study showed that the
presence of a benzyl at the 5 position and a benzyloxy substituent at the 4 position are a prerequisite for
anti-HCMV and VZV activity. The novel compounds do not show cross-resistance against a wide variety
of mutant drug-resistant HCMV strains, pointing to a novel mechanism of antiviral action.
Scheme 1a
Introduction
Herpes virus infections in humans are found worldwide and
are among the most frequent causes of viral infections in
immunocompetent as well as in immunocompromised patients.
Although generally benign in the immunocompetent host, human
cytomegalovirus (HCMVa) infection is associated with clinical
symptoms such as pneumonia, retinitis, and gastrointestinal
disease in the immunocompromised, as well as congenital birth
defects in neonates.1-3 Other herpesviruses such as varicella
zoster virus (VZV) are widespread among the human population,
and VZV is known to be responsible for a primary infection of
varicella (chicken pox) in young children.4,5 Reactivation of
latent VZV infection in the ganglia is associated with herpes
zoster (shingles), a highly debilitating illness characterized by
persistent neuropathic pain.6,7 There are currently five FDA-
approved drugs used for the treatment of HCMV infections,
namely ganciclovir or its prodrug valganciclovir, cidofovir,
foscarnet, and the antisense oligonucleotide fomivirsen, whereas
a Reagents and conditions: (i) 4.5 N HCl methanol, rt; (ii) BnBr, NaH,
THF, rt; (iii) BnBr, K2CO3, TEBAI, acetonitrile, rt.
the drug of choice for the treatment of VZV infections is
acyclovir.8,9 However, the currently available compounds suffer
from a number of limitations including poor oral bioavailability
and/or toxicity as well as the emergence of single and multiple
drug resistance.10,11 All of the licensed compounds (with the
exception of fomivirsen) are nucleoside-based antivirals that act
by targetting the viral DNA polymerase. There are a number
of nucleoside analogues in preclinical development (i.e., the (ꢀ-
L-ribofuranosyl)benzimidazole derivative maribavir or 1263-
W9412 and the (ꢀ-D-ribofuranosyl)benzimidazole derivatives
BDCRB and TCRB13) that act as “non-nucleoside inhibitors”
of HCMV by targetting processing, synthesis, and/or maturation
of viral DNA. The lipophilic alkyl furano pyrimidine dideoxy-
nucleosides act against HCMV by inhibiting an early event in
the HCMV infection process.14 Also, several non-nucleoside
analogues are described as HCMV (and VZV) inhibitors, such
as the 4-oxo-4,7-dihydrothieno[2,3-ꢀ]pyridines,15 4-hydrox-
yquinoline carboxamides,16 and 4-oxo-dihydroquinolines.17
These classes of compounds inhibit the viral DNA polymerases.
The non-nucleoside inhibitor BAY 38-4766 (tomeglovir) inhibits
HCMV by targetting HCMV DNA maturation via the UL89
and UL59 gene products.18,19 Current progress on the develop-
ment of human herpesvirus inhibitors have been recently
reviewed.20-25
* To whom correspondence should be addressed. Phone: (+34)-
912587458. Fax: (+34)-91 5644853. E-mail: iqmsv29@iqm.csic.es.
†
Instituto de Qu´ımica Me´dica (CSIC).
Rega Institute for Medical Research, K. U. Leuven.
‡
a Abbreviations: HCMV, human cytomegalovirus; VZV, Varicella zoster
virus; SAR, structure-activity relationship; BDCRB, 2-bromo-5,6-dichloro-
1-(ꢀ-D-ribofuranosy)benzimidazole; TCRB, 2,5,6-trichloro-1-(ꢀ-D-ribofura-
nosyl)benzimidazole; TEBAI, tetrabutylammonium iodide; HSV-1, herpes
simplex virus type 1; TK-, thymidine kinase-deficient; ACV, acyclovir;
HSV-2, herpes simplex virus type 2; HEL, human embrionic lung; MCC,
minimal cytotoxic concentration; GCV or DHPG, ganciclovir; PFA,
foscarnet; HPMPC, cidofovir; PMEDAP, 9-(2-phosphonylmethoxyethyl)-
2,6-diaminopurine; HPMPA, 9-(3-hydroxy-2-phosphonylmethoxypropyl)-
adenine; HPFC, High performance flash chromatography.
We previously reported26 studies on the reactivity toward
electrophiles and amines on simple model substrates of the
scarcely explored 4-amino-1,2-oxathiole-2,2-dioxide (ꢀ-amino-
γ-sultone) heterocyclic system 1 (Scheme 1). We found that
acid hydrolysis worked smoothly in this system, leading to the
10.1021/jm8014662 CCC: $40.75
2009 American Chemical Society
Published on Web 02/18/2009

4-Benzyloxy-γ-Sultone DeriVatiVes
Journal of Medicinal Chemistry, 2009, Vol. 52, No. 6 1583
Scheme 2a
ꢀ-keto-γ-sultone compound 2.26 Alternative reported methods
for the synthesis of the ꢀ-keto-γ-sultone heterocycle involved
cyclization of R-(carboxyethyl)alkyl alkanesulfonates.27 Alky-
lation of 2 with benzyl bromide in the presence of a base
(Scheme 1) gave the 4-benzyloxy sultone derivative 3. This
compound showed a very limited inhibitory activity against
HCMV (EC50 g 50 µM) and VZV (EC50 g 5 µM) replication
in cell culture, being inactive against a variety of other DNA
and RNA viruses. These results prompted us to explore the
biological potential of this readily available heterocyclic system.
We describe herein the results of this work that has led to the
discovery of an entirely new class of non-nucleoside inhibitors
of human cytomegalovirus (HCMV) and varicella zoster virus
(VZV). Structure-activity relationships (SAR) were focused
on the substituents at the C-4 and C-5 positions of the sultone
moiety. These studies showed that the presence of aromatic rings
at both positions are a prerequisite for anti-HCMV and VZV
activity. The synthesis, biological evaluation, and SAR studies
of this new family of compounds is reported.
Results and Discussion
Chemistry. The known ꢀ-keto-γ-sultone intermediate 2 was
prepared, as previously described by our group,26 by acid
hydrolysis of the enamine derivative 1 with 4.5 N HCl in
methanol (Scheme 1). Alkylation of intermediate 2 with benzyl
bromide in the presence of a base to give 3 was explored under
different reaction conditions. Thus, when 2 was reacted, at room
temperature, with 2 equiv of benzyl bromide in dry THF in the
presence of 2 equiv of NaH, the 4-O-benzyl derivative 3 was
isolated in 40% yield, together with unreacted starting material
(27%), after 24 h. Increasing amounts of benzyl bromide (3
equiv) and base (3 equiv) slightly improved the yield of 3 (53%
vs 40%). However, reaction of 2 with benzyl bromide (1 equiv)
in acetonitrile under phase-transfer-catalyzed conditions,28
K2CO3 (1.5 equiv) as base, and tetrabutylammonium iodide
(TEBAI) as catalyst, afforded the desired compound 3 in 70%
yield, after 3 h. Thus, under these alkylation conditions, the
yield of 3 was significantly improved by using lower amounts
of base and benzyl bromide and shorter reaction times.
a Reagents and conditions: (i) TMSCN, BF3 ·Et2O, dichloromethane, rt;
(ii) MsCl, dichloromethane, TEA, 0 °C; (iii) Cs2CO3, acetonitrile, rt; (iv)
4.5 N HCl methanol, rt; (v) BnBr, K2CO3, TEBAI, acetonitrile, rt.
the inhibitory potency against HCMV and VZV. Thus, replace-
ment of the 5-ethyl group of compound 8b by alkyl groups of
different length (compounds 8d,e) and by branched-alkyl groups
(compounds 8f,g) was next undertaken. The synthesis of
compounds 8d-g (Scheme 2) was carried out by following a
similar four-step procedure to that described for the synthesis
of 8a-c, starting from the appropriate commercially available
ketones 4d-g in good yields. Similarly, compound 8h (the
conformationally restricted analogue of 8b) was prepared from
the commercially available ꢀ-tetralone 4h (Scheme 2). Substitu-
tion of the 5-ethyl group of 8b by other alkyl groups resulted
in inactive compounds as will be mentioned below.
Initial structure-activity relationship studies on this sultone
template were focused on the C-5 substituents (Scheme 2). The
number and position of benzyl groups at the 5 position was
first explored. Compounds 8a-c were prepared from the
corresponding ꢀ-keto-γ-sultone derivatives 7a-c. The synthesis
of intermediates 7a-c was carried out by starting from the
appropriate commercially available ketones 4a-c following a
four-step procedure involving cyanohydrin formation, mesyla-
tion, base-cyclization, and hydrolysis as previously described.26
Thus, treatment of 4a-c with trimethylsilyl cyanide in the
presence of equimolecular amounts of BF3 ·Et2O afforded the
corresponding cyanohydrines, which upon treatment with mesyl
chloride in the presence of triethylamine, as base, yielded the
desired alkyl sulfonate derivatives 5a-c in 63%, 74%, and 73%
yields, respectively. Reaction of 5a-c with Cs2CO3 gave the
desired ꢀ-amino-γ-sultone derivatives 6a-c in moderate to good
yields (52-81%). Acid hydrolysis (4.5 N HCl in methanol) of
compounds 6a-c proceeded also in good yields to provide the
ꢀ-keto-γ-sultone derivatives 7a-c. These keto compounds
(7a-c) were then treated with benzyl bromide under the
optimized phase-transfer-catalyzed alkylation conditions de-
scribed above, to afford the target 4-benzyloxy derivatives 8a-c
in 31%, 53%, and 57% yields, respectively. Antiviral studies
indicated that the presence of both a benzyl and an ethyl group
at the 5-position of the sultone moiety (compound 8b) improved
Further structural modifications were focused on the 4-ben-
zyloxy substituent of 8b while the 5-benzyl and 5-ethyl
substituents were maintained (Scheme 3). To determine the role
of the phenyl group at the 4 position in the biological activity,
a first series of 4-substituted alkyloxy sultone derivatives was
prepared in which the phenyl group was absent (compound 9)
or replaced by a variety of groups of different nature (com-
pounds 10-15). Other aromatic substituents such as diphenyl-
methyl at this position were also introduced (compound 16).
Compounds 9-16 were prepared from the keto precursor 7b,
following the optimized alkylation procedure described above
for the synthesis of compound 3. Thus, treatment of 7b with
the corresponding alkyl bromides in the presence of K2CO3 (1.5
equiv) as base and TEBAI as catalyst afforded, exclusively, the
4-O-alkylated derivatives 9, 12-16 (Scheme 3) in moderate to
good yields (32-67%). However, in the reaction of 7b with
allyl bromide, the 4-O-allylated derivative 10 together with the
C,O-diallylated compound 11 were isolated in 70% and 12%
yield, respectively. All of these compounds were inactive against
HCMV and VZV replication, which indicated a key role for a
phenyl group at the 4 position.
Modifications of the length and nature of the methylene spacer
between the phenyl group and the oxygen attached to the
4-position of the sultone moiety of compound 8b were next
carried out (Scheme 3). Thus, methylene spacers of different

1584 Journal of Medicinal Chemistry, 2009, Vol. 52, No. 6
De Castro et al.
Scheme 3a
a Reagents and conditions: (i) RBr, K2CO3, TEBAI, acetonitrile, 40 °C; (ii) PhCOCl or p-CH3PhSO2Cl, NaH 60%, THF, rt.
length (compounds 17-20) or spacers of different nature
(compounds 21, 22) were explored. Treatment of 7b with
phenylethyl bromide, 3-phenylpropyl bromide, 4-phenylbutyl
bromide, or 6-phenyl hexyl bromide under the optimized phase-
transfer-catalyzed conditions (K2CO3, TEBAI), as described
above, gave compounds 17-20 in moderate to good yields
(40-76%). The 4-O-acyl derivatives 21 and 22, in which the
methylene spacer of compound 8b was replaced by a -CO-
or by a -SO2- spacer, were synthesized in moderate yields
(41% and 30% yields, respectively) by reaction of the keto
intermediate 7b with benzoyl chloride or p-toluensulfonyl
chloride in dry THF in the presence of NaH.
Finally, a variety of substituents of different electronic and
steric properties were incorporated at the phenyl ring of the
4-benzyloxy moiety of compound 8b to determine the role of
such substitution on HCMV and VZV inhibition. The target
compounds 23-33 (Scheme 3) were prepared in moderate to
good yields (40-81%) by reaction of 7b, with the appropriate
commercially available substituted benzyl bromides following
the optimized alkylation procedure described above for com-
pound 3.
Antiviral Activity. Compounds 8b, 17, 26, and 28 lacked
inhibitory activity against a wide variety of viruses, including
parainfluenza-3 virus, reovirus-3, Sindbis virus, Coxackie virus
B4, Punta Toro virus in Vero cell cultures, and vesicular
stomatitis virus, Coxsackie virus B4 and respiratory syncitial
virus in HeLa cell cultures, and herpes simplex virus type 1
(HSV-1) (KOS) and a thymidine kinase-deficient (TK-) acy-
clovir-resistant (ACVr) strain, HSV-2, vaccinia virus, and
vesicular stomatitis in HEL cell cultures. However, they showed
antiviral activity against human cytomegalovirus (HCMV) and
varicella zoster virus (VZV). Therefore, a variety of novel 4-
and 5-substituted-γ-sultone derivatives and the 4-keto-γ-sultone
intermediate 2 were evaluated against HCMV and VZV strains
in human embryonic lung (HEL) cells,30 and the results were
compared to those obtained for the reference compounds
ganciclovir, cidofovir, acyclovir, and brivudin (Tables 1 and
2). Several of the compounds showed pronounced anti-HCMV
and anti-VZV activity. Dual anti-HCMV and anti-VZV activity
has been also recently described for a series of bicyclic
furanopyrimidine deoxynucleosides,31,32 1-acylazetidine deriva-
tives,33 and substituted imidazo[1,2-a]pyridine derivatives.34
The following structure-activity relationships were observed.
The substituents at the C-5 position on 4-benzyloxy-γ-sultone
derivatives had a pronounced influence on antiviral activity
(Table 1). As shown in Table 1, the 5-dibenzyl-substituted
derivative 3 weakly blocked HCMV- or VZV-induced plaque
formation with an EC50 value of g50 µM or g5 µM,
respectively, and a minimal cytotoxic concentration (MCC) or
50% cytostatic concentration (CC50) values of g200. Interest-
ingly, replacement of one of the benzyl groups by an ethyl group
(compound 8b) markedly enhanced the antiviral activity against
both HCMV strains (EC50 ) 13 and 9.3 µM) and VZV strains
(EC50 ) 6.4 and 5.6 µM) while retaining a relatively low
cytotoxicity (MCC g 50). Thus, the therapeutic index (ratio
CC50/EC50 g 5-10) of compound 8b was improved compared
to that of the 5-dibenzyl-substituted derivative 3 (ratio CC50/
EC50 e 4). Substitution of both benzyl groups by ethyl groups
(compound 8c) led to a marked decrease in antiviral activity.
Replacement of the 5-ethyl group of compound 8b by alkyl
groups of different length (compounds 8d,e) or by branched-
alkyl groups (compounds 8f,g) annihilated the antiviral activity.
Also, the conformationally restricted analogue of 8b (compound
8h) was inactive. From these results, it appears that the
concomitant presence of a benzyl and an ethyl group at the C-5
position is required for antiviral activity.
It was also observed that the benzyloxy moiety at the 4
position of 8b was essential or preferable for its antiviral activity

4-Benzyloxy-γ-Sultone DeriVatiVes
Journal of Medicinal Chemistry, 2009, Vol. 52, No. 6 1585
Table 1. Activity of 5-Substituted 4-Benzyloxy-γ-sultone Derivatives 3, 8a-h, and 4-Keto γ-Sultone Intermediate 2 against Human Cytomegalovirus
(HCMV) and Varicella Zoster Virus (VZV) in HEL Cell Cultures
a Effective concentration required to inhibit by 50% the HCMV-induced cytopathicity in human embryonic lung (HEL) fibroblast cell cultures at 7 days
post infection, as described in refs 14 and 30, virus input was 100 plaque-forming units (PFU). b Effective concentration required to reduce VZV plaque
formation after 5 days in HEL cell cultures by 50%, as compared to untreated controls. c Compound concentration required to cause a microscopically
visible alteration of normal cell morphology. d Cytotoxic concentration required to reduce cell growth by 50%.
because the 4-keto-γ-sultone intermediate 2 displayed no (for
HCMV) or less (2-fold) activity (for VZV) (Table 1). Thus,
the next phase of SAR investigations focused on modifications
at the 4-benzyloxy substituent of 8b (Table 2). Substitution of
the phenyl group at the 4 position by other groups of different
nature (compounds 9-16) invariably annihilated the activity
against HCMV or markedly weakened the activity against VZV.
Regarding the length and nature of the methylene spacer
between the phenyl group and the oxygen attached to the
4-position, compounds 17 and 18, bearing an ethyl and a propyl
spacer, respectively, retained the potency of the methylene
analogue 8b against HCMV and VZV but with a slightly

1586 Journal of Medicinal Chemistry, 2009, Vol. 52, No. 6
De Castro et al.
Table 2. Activity of 4-Substituted γ-Sultone Derivatives 9-34 against Human Cytomegalovirus (HCMV) and Varicella Zoster Virus (VZV) in HEL
Cell Cultures
EC50 (µΜ)
anti-HCMV activitya
anti-VZV activityb
cytotoxicity (µM)
d
compd
R
AD-169
Davis
OKA (TK+)
07/1 (TK-)
MCCc
CC50
9
10
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
CH3
>400
>400
>80
>80
>400
>200
>400
6.9
>400
>400
>80
168
>16
59
199
>400
20
>80
5.7
>3.2
6.2
285
>16
52
199
>400
7.0
>80
7.5
6.5
>20
8.4
>400
80
400
>200
>200
112
>200
>200
>200
>200
48
133
99
<200
>200
109
CH2CHdCH2
CH2CHdC(CH3)2
CH2CN
CH2CO2CH3
CH2Chx
CHPh2
(CH2)2Ph
(CH2)3Ph
(CH2)4Ph
235
>400
>400
g200
g80
g20
g20
g20
g20
>400
400
g80
g16
>50
g50
80
>200
g16
g400
g20
g20
g20
g80
>400
>150
>200
>150
>400
>200
>400
9.3
9.0
8.7
7.8
6.4
>3.2
<3.2
>400
>80
>400
12
(CH2)6Ph
COPh
8.7
179
>400
>400
SO2Ph(4-CH3)
CH2Ph (4-NO2)
CH2Ph (4-CF3)
CH2Ph (4-F)
CH2Ph (4-Cl)
CH2Ph (4-Br)
CH2Ph (4-OCH3)
CH2Ph (4-CH3)
CH2Ph (4-t-Bu)
CH2Ph (2-Cl)
CH2Ph (3-Cl)
CH2Ph(3,4-diCl)
>80
>80
8
7
9.7
6
142
>80
>80
80
54
<200
7.7
6.7
99
15
10.4
10
8.6 (YS strain 10.4)
7.6 (YS strain 10)
8.3
120
8.6 (YS-R strain 9.3)
>50
<200
171
5.7
6.3
106
5.9
7.3e
10
6.7
>3.2
32
200
>200
7.2
5.9
6.4
41.5
20e
g5e
>4
8
6.4e
>200
>4
>16
6.5
>80
2.3
8.7 (YS strain >5)
7.3
>3.2
37
38
50
36.7
33
7.2
>80
4.6
0.5
34f
92
134
74
733
600
ganciclovir
cidofovir
acyclovir
brivudin
0.3
1.1
0.015
74
g150
a Effective concentration required to inhibit by 50% the HCMV-induced cytopathicity in human embryonic lung (HEL) fibroblast cell cultures at 7 days
post infection, as described in refs 14 and 30. Virus input was 100 plaque-forming units (PFU). b Effective concentration required to reduce VZV plaque
formation after 5 days in HEL cell cultures by 50%, as compared to untreated controls. c Compound concentration required to cause a microscopically
visible alteration of normal cell morphology. d Cytotoxic concentration required to reduce cell growth by 50%. e No complete inhibition at higher drug
concentration. f The synthesis of compound 34 has been described in ref 26.
increased cytostatic activity. Longer methylene linkers (i.e., n
> 3, compounds 19 and 20) showed further increased cytotox-
icity (MCC values for these compounds were in the same range
as their EC50 values). Substitution of the methylene spacer of
8b by a carbonyl or sulfoxide group (compounds 21 and 22)
resulted in inactive compounds.
3-position or disubstitution at the 3- and 4-positions were present
(compounds 32 and 33).
Compound 26 was also evaluated against a panel of mutant
HCMV strains that had been selected for resistance against a
wide variety of anti-HCMV compounds including DHPG
(ganciclovir), PFA (foscarnet), (S)-HPMPC (cidofovir), PMEDAP,
(S)-HPMPA, and ACV (acyclovir). Interestingly, 26 kept full
antiviral sensitivity against all strains evaluated (Table 3).
Similar observations were made for compound 24, suggesting
that the novel compounds most likely act through another
antiviral target than the currently existing antiviral compounds
(Table 3). It is, however, unclear which stage in the infection
cycle of HCMV and VZV the compounds are targetting. (Cross)-
resistance studies against mutant HCMV strains that are resistant
to the currently existing benzimidazoles and non-nucleoside
inhibitors may reveal whether the compounds share a similar
or a different mechanism of antiviral action.
Finally, the influence of substitutions on the 4-benzyloxy
aromatic ring on the antiviral activity and cytotoxicity was
examined. Among the 4-substituted derivatives, the tested
compounds can be classified in three groups: a group of
(virtually) inactive compounds (23 and 28 with a NO2 or a OCH3
group), a group of active compounds, with an EC50 between 6
and 15 µM, bearing electron-withdrawing substituents such as
CF3 or F (compounds 24 and 25) or alkyl groups (29 and 30
with a CH3 or a t-Bu) that were more cytotoxic than the
unsubstituted derivative 8b, and the 4-chloro and 4-bromo
derivatives 26 and 27 that show antiviral activity at ca. 6-10
µM with relatively low cytotoxicity. Thus, the selectivity indices
(ratio CC50 to EC50) for compounds 26 and 27 were similar to
that of the unsubstituted analogue 8b. On the other hand, an
increased toxicity was noticed when a chlorine atom at the
Conclusions
In conclusion, we report on the discovery of a new family of
non-nucleoside anti-HCMV and anti-VZV agents based upon

4-Benzyloxy-γ-Sultone DeriVatiVes
Journal of Medicinal Chemistry, 2009, Vol. 52, No. 6 1587
Table 3. Anti-HCMV Activity of 26 against Drug-Resistant HCMV Strainsa
wild-type HCMV
mutant HCMV (AD169) virus strains
AD/DHPGR
clone 4
AD/PFAR
clone C
AD/HPMPCR
clone 5
AD/PMEDAPR
clone 4
AD/HPMPAR
clone 2
AD/ACVR
clone 1
compd
Davis
AD169
26
GCV
(DHPG)
11 ( 0.71
0.66 ( 0.34
11 ( 1.3
0.7 ( 0.39
11 ( 2.1
4.3 ( 1.5
9.6 ( 0.64
2.6 ( 0.85
11 ( 8.2
4.0 ( 2.0
12 ( 5.6
3.5 ( 3.1
9.9 ( 0.98
1.2 ( 0.75
11 ( 1.8
0.69 ( 0.26
foscarnet
(PFA)
11 ( 0.71
13 ( 4.2
20 ( 9.2
95 ( 6.6
11 ( 4.1
63 ( 24
13 ( 0.75
35 ( 21
cidofovir
(HPMPC)
0.069 ( 0.026
0.076 ( 0.028
0.74 ( 0.85
0.045 ( 0.007
1.0 ( 0.76
0.092 ( 0.075
0.55 ( 0.29
0.095 ( 0.022
PMEDAP
HPMPA
acyclovir
(ACV)
7.7 ( 0.35
0.2 ( 0
7.5 ( 3.5
8.4 ( 2.7
0.17 ( 0.11
15 ( 6.5
1.9 ( 0.99
2.1 ( 1.5
4.3 ( 0.87
25 ( 13
0.036 ( 0.006
176 ( 34
3.5 ( 1.8
2.1 ( 1.7
7.6 ( 2.2
37 ( 12
0.12 ( 0.097
125 ( 106
0.82 ( 0.040
1.9 ( 1.4
1.0 ( 0.87
>50
0.080 ( 0.014
200 ( 0
a 50% Effective concentration or compound concentration required to inhibit virus-induced cytopathicity by 50%.
of this residue in dry dichloromethane, Et3N (4 mL, 28 mmol) was
added. The mixture was cooled to -30 °C, and methanesulfonyl
chloride (0.92 mL, 12 mmol) was slowly added. The mixture was
stirred at -20 °C for 1 h and at 0 °C for an additional hour. Volatiles
were removed and the residue was dissolved in ethyl acetate (10
mL) and washed successively with water (1 × 10 mL) and brine
(2 × 10 mL). The organic phase was filtered, dried (Na2SO4), and
evaporated to dryness. The final residue was purified by flash
column chromatography (hexane/ethyl acetate, 10:1) to give the
target products 5a-h.
the easily available ꢀ-keto-γ-sultone template. We have shown
that substituents at the 4 and 5 positions of the γ-sultone moiety
strongly influence the activity/toxicity of these compounds. The
presence of a benzyl group at the 5 position and a benzyloxy
substituent at the 4 position are a prerequisite for anti-HCMV
and VZV activity. From the synthesized compounds, the
4-chloro and 4-bromobenzyloxy sultone derivatives 26 and 27
and the unsubstituted analogue 8b ranked among the most potent
and selective inhibitors against HCMV and VZV. All com-
pounds showed similar activity against TK+ and nucleoside
drug-resistant TK- VZV strains, thus indicating a mechanism
of action independent of the virus-encoded thymidine kinase
as expected from their non-nucleoside structure. Also, com-
pounds 24 and 26 were equally inhibitory against a wide variety
of drug-resistant HCMV strains, suggesting another antiviral
target than that of the currently existing compounds. These
compounds rank among the few classes of non-nucleoside
inhibitors with dual anti-HCMV and VZV activity described
so far.
(()-1-Diphenylmethyl-2-(methanesulfonyloxy)propionitrile (5a).
1,1-Diphenyl-2-propanone (0.84 g, 4 mmol) was treated with
trimethylsilyl cyanide for 2 h and then with methanesulfonyl
chloride for 2 h to give 0.80 g (63%) of 5a as a white amorphous
1
solid. H NMR [300 MHz, (CD3)2CO] δ: 1.95 (s, 3H, CH3), 3.17
(s, 3H, CH3SO2), 4.66 (s, 1H, CH), 7.31, 7.62 (2m, 5H, Ph). MS
(ES+) m/z 316.2 [M + 1]+. Anal. (C17H17NO3S): C, H, N, S.
(()-2-Benzyl-2-(methanesulfonyloxy)butyronitrile(5b).261-Phen-
yl-2-butanone 1b (0.30 g, 2 mmol) was treated with trimethylsilyl
cyanide for 2 h and then with methanesulfonyl chloride for 2 h to
give 0.37 g (74%) of 5b as a white amorphous solid. IR (film):
2536 cm-1. MS (ES+) m/z 254.6 [M + 1]+.
(()-2-Ethyl-2-(methanesulfonyloxy)butyronitrile (5c).29 3-Pen-
tanone (0.34 g, 4 mmol) was reacted with trimethylsilyl cyanide
for 3 h. The mixture was reacted with methanesulfonyl chloride
for 2 h to give 0.52 g (73%) of 5c as a white amorphous solid. MS
(ES+) m/z 192.3 [M + 1]+.
Experimental Section
Chemical Procedures. Melting points were determined in a
Reichert-Jung Thermovar hot-stage microscope equipped with a
polarizer. IR spectra were obtained on a Perkin-Elmer Spectrum
One spectrophotometer. The purity of the compounds was ascer-
tained through combustion analysis. Microanalyses were obtained
a Heraeus CHN-O-RAPID instrument. The analytical results are
within (0.4% of the theoretical values. Mass spectra were measured
on a quadropole mass spectrometer equipped with an electrospray
source (Hewlett-Packard, LC/MC HP 1100). 1H NMR and 13C
NMR spectra were recorded with a Bruker 300 Avance and a Varian
XL-500 spectrometer operating at 300 and 500 MHz and at 75 and
125 MHz, respectively, with Me4Si as the internal standard.
Analytical thin-layer chromatography (TLC) was performed on
silica gel 60 F254 (Merck). Separations on silica gel were performed
by preparative centrifugal circular thin-layer chromatography
(CCTLC) on a Chromatotron (Kiesegel 60 PF254 gypsum-based
(Merck), layer thickness of 1 mm, flow rate of 5 mL/min). Flash
column chromatography was performed with silica gel 60 (230-400
mesh)(Merck). Liquid chromatography was performed using a force
flow (flash chromatography) HPFC Horizon system (Biotage) with
Flash 25 M cartridges (KP-Sil Silica, 60 Å, 40-63 µM). Triethy-
lamine, dichloromethane, and acetonitrile were dried by refluxing
over calcium hydride. Tetrahydrofurane was dried by refluxing over
sodium.
(()-2-Benzyl-2-(methanesulfonyloxy)propionitrile (5d). 1-Phen-
yl-2-propanone (0.74 g, 4 mmol) was treated with trimethylsilyl
cyanide for 2 h. The mixture was reacted with methanesulfonyl
chloride for 2 h to afford compound 5d (0.80 g, 63%) as a white
amorphous solid. MS (ES+) m/z 240.7 [M + 1]+. Anal.
(C11H13NO3S): C, H, N, S.
(()-2-Benzyl-2-(methanesulfonyloxy)pentanenitrile (5e). 1-Phen-
yl-2-pentanone (0.64 g, 4 mmol) was reacted with trimethylsilyl
cyanide for 2 h. Reaction of the mixture with methanesulfonyl
chloride for 2 h gave 0.54 g (51%) of 5e as a white amorphous
solid. MS (ES+) m/z 268.7 [M + 1]+. Anal. (C13H17NO3S): C, H,
N, S.
(()-2-Benzyl-3-methyl-2-(methanesulfonyloxy)butyronitrile
(5f). 1-Phenyl-3-methyl-2-butanone (0.64 g, 4 mmol) was treated
with trimethylsilyl cyanide for 2 h and then with methanesulfonyl
chloride for 2 h to yield compound 5f (0.76 g, 72%) as a white
amorphous solid. MS (ES+) m/z 268.9 [M + 1]+. Anal.
(C13H17NO3S): C, H, N, S.
(()-1-Benzyl-5-methyl-2-(methanesulfonyloxy)pentaneni-
trile (5g). 1-Phenyl-4-methyl-2-pentanone (0.70 g, 4 mmol) was
treated with trimethylsilyl cyanide for 2 h and then with methane-
sulfonyl chloride for 2 h to give 0.72 g (65%) of 5g as a white
amorphous solid. MS (ES+) m/z 282.4 [M + 1]+. Anal.
(C14H19NO3S): C, H, N, S.
Synthesis of Compounds 5a-h: General Procedure. To a
solution of the corresponding ketone 4a-h (4 mmol) in dichlo-
romethane (10 mL), trimethylsilyl cyanide (0.80 mL, 6 mmol) and
boron trifluoride diethyl etherate (20 mL, 4 mmol) were added.
The mixture was stirred at room temperature for 1-24 h. Volatiles
were removed and the residue was dissolved in ethyl acetate (20
mL) and washed with brine (2 × 10 mL). The organic layer was
dried (Na2SO4), filtered, and evaporated to dryness. To a solution
(()-2-Cyano-2-(methanesulfonyloxy)-1,2,3,4-tetrahydronaph-
thalene (5h). ꢀ-Tetralone (0.52 mL, 4 mmol) was reacted with
trimethylsilyl cyanide for 2 h and then with methanesulfonyl
chloride for 1 h to afford compound 5h (0.50 g, 50%) as a white

1588 Journal of Medicinal Chemistry, 2009, Vol. 52, No. 6
De Castro et al.
amorphous solid. MS (ES+) m/z 252.5 [M + 1]+. Anal.
(C12H13NO3S): C, H, N, S.
(()-5-Diphenylmethyl-5-methyl-4-oxo-1,2-oxathiolane-2,2-
dioxide (7a). Compound 6a (0.32 g, 1 mmol) was reacted with
4.5 N HCl in methanol to give 0.17 g (54%) of 7a as a white solid;
Synthesis of Compounds 6a-h: General Procedure. A
suspension of the corresponding cyanomesylate 5a-h (2 mmol)
in dry acetonitrile (6 mL) was treated with cesium carbonate (0.98
g, 3.0 mmol) and the mixture was stirred at room temperature for
2-7 h. Solvent was removed and the residue was dissolved in ethyl
acetate (20 mL) and washed, successively, with water (10 mL) and
brine (2 × 10 mL). The organic layer was dried (Na2SO4), filtered,
and evaporated to dryness. The residue was purified by flash column
chromatography (hexane/ethyl acetate, 3:1) to give the final products
6a-h.
1
mp (ethanol/water) 143-144 °C. H NMR [300 MHz, CDCl3] δ:
1.67 (s, 3H, CH3), 2.59, 3.59 (AB system, 2H, J ) -16.8 Hz, H-3),
4.29 (s, 1H, CH), 7.29, 7.54 (2m, 8H, 2Ph). 13C NMR [75 MHz,
CDCl3] δ: 22.3 (CH3), 52.8 (CH), 58.4 (C-3), 100.3 (C-5), 127.7,
127.9, 129.0, 129.3, 129.8, 137.2, 137.3 (2Ph), 201.2 (C-4). MS
(ES+) m/z 317.0 [M + 1]+, 334.0 [M + H2O]+, 338.9 [M + Na]+,
655.0 [2M + Na]+. Anal. (C17H16O4S): C, H, S.
(()-5-Benzyl-5-ethyl-4-oxo-1,2-oxathiolane-2,2-dioxide (7b).26
Compound 6b (0.10 g, 0.39 mmol) was reacted with 4.5 N HCl in
methanol (2 mL, 9 mmol) for 14 h to afford 7b (0.08 g, 76%) as
a white solid; mp (ethanol/water) 103-104 °C (mp lit.26 102-104
(()-4-Amino-5-diphenylmethyl-5-methyl-5H-1,2-oxathiole-
2,2-dioxide (6a). Compound 5a (0.62 mL, 2 mmol) was treated
with cesium carbonate for 4 h to give compound 6a (0.32 g, 52%)
°C). IR (film): 1769 cm-1
.
5,5-Diethyl-4-oxo-1,2-oxathiolane-2,2-dioxide (7c).29 Com-
pound 6c (0.18 g, 1 mmol) was reacted with 4.5 N HCl in methanol
to yield compound 7c (0.14 g, 77%) as a viscous colorless oil. MS
(ES+) m/z 193.0 [M + 1]+, 215.0 [M + Na]+.
1
as a white solid; mp (ethanol/water) 233-234 °C. H NMR [300
MHz, (CD3)2CO] δ: 1.65 (s, 3H, CH3), 4.68 (s, 1H, CH), 5.27 (s,
1H, H-3), 6.28 (bs, 2H, NH2), 7.30, 7.61 (2m, 10H, 2Ph). 13C NMR
[75 MHz, (CD3)2CO ]δ: 24.2 (CH3), 55.6 (CH), 87.0 (C-3), 90.0
(C-5), 126.1, 126.3, 127.2, 127.7, 128.8, 129.1, 139.1, 138.5 (2Ph),
158.3 (C-4). MS (ES+) m/z 316.0 [M + 1]+, 333.0 [M + H2O]+,
338.0 [M + Na]+, 631.2 [2M + 1]+, 653.3 [2M + Na]+. Anal.
(C17H17NO3S): C, H, N, S.
(()-5-Benzyl-5-methyl-4-oxo-1,2-oxathiolane-2,2-dioxide (7d).
Compound 6d (0.24 g, 1 mmol) was reacted with 4.5 N HCl in
methanol to give compound 7d (0.21 g, 88%) as a viscous colorless
oil. MS (ES+) m/z 241.1 [M + 1]+, 236.0 [M + Na]+, 529.3 [2M
+ Na]+. Anal. (C11H12O4S): C, H, S.
(()-4-Amino-5-benzyl-5-ethyl-5H-1,2-oxathiole-2,2-dioxide (6b).26
Compound 5b (0.25 g, 1 mmol) was reacted with cesium carbonate
(0.49 g, 1.5 mmol) for 2 h to give 6b (0.20 g, 81%) as a white
solid; mp (toluene) 164-166 °C (lit.26 165-166 °C). IR (film):
(()-5-Benzyl-5-propyl-4-oxo-1,2-oxathiolane-2,2-dioxide (7e).
Compound 6e (0.26 g, 1 mmol) was reacted with 4.5 N HCl in
methanol to afford 0.22 g (81%) of 7e as a white solid; mp (ethanol/
water) 90-91 °C. MS (ES+) m/z 269.0 [M + 1]+, 291.0 [M +
Na]+, 559.2 [2M + Na]+. Anal. (C13H16O4S): C, H, S.
(()-5-Benzyl-5-isopropyl-4-oxo-1,2-oxathiolane-2,2-dioxide (7f).
Compound 6f (0.36 g, 1 mmol) was reacted with 4.5 N HCl in
methanol to give 0.11 g (81%) of 7f as a white solid; mp (ethanol/
water) 88-89 °C. MS (ES+) m/z 269.0 [M + 1]+, 291.0 [M +
Na]+, 559.2 [2M + Na]+. Anal. (C13H16O4S): C, H, S.
(()-5-Benzyl-5-isobutyl-4-oxo-1,2-oxathiolane-2,2-dioxide (7g).
Compound 6g (0.28 g, 1 mmol) was treated with 4.5 N HCl in
methanol to afford compound 7g (0.21 g, 73%) as a white solid;
mp (ethanol/water) 118-119 °C. MS (ES+) m/z 283.0 [M + 1]+,
300.0 [M + H2O]+, 305.0 [M + Na]+, 587.3 [2M + Na]+. Anal.
(C14H18O4S): C, H, S.
(()-1,2,3,4-Tetrahydronaphthalene-2-spiro-5′-(4′-oxo-1′,2′-ox-
athiolane-2′,2′-dioxide) (7h). Compound 6h (0.36 g, 1 mmol) was
reacted with 4.5 N HCl in methanol to give 0.15 g (58%) of 7h as
a viscous colorless oil. MS (ES+) m/z 253.1 [M + 1]+, 270.0 [M
+ H2O]+, 275.0 [M + Na]+, 527.0 [2M + Na]+. Anal. (C12H12O4S):
C, H, S.
Alkylation of ꢀ-Keto-γ-sultone Derivatives: General Proce-
dure. A mixture of the corresponding ketone 2, 7a-h (1 equiv),
K2CO3 (1.5 equiv), and tetrabuthylamonium iodine (0.1 equiv) in
dry acetonitrile (5 mL) was stirred at room temperature for 15 min.
Then, the appropriate alkylbromide (1-6 equiv) was added and
the mixture was stirred at 40 °C for 3-24 h. The solvent was
evaporated to dryness and the residue was purified by flash column
chromatography or by HPFC on a Horizon system to give the target
compounds.
3503, 3408 cm-1
.
4-Amino-5,5-diethyl-5H-1,2-oxathiole-2,2-dioxide (6c).29
A
solution of 5c (0.36 g, 2 mmol) in dry acetonitrile was treated with
cesium carbonate for 2 h to give 0.24 g (70%) of 6c as a white
solid; mp (ethanol/water) 163-164 °C (lit.29 162-164 °C).
(()-4-Amino-5-benzyl-5-methyl-5H-1,2-oxathiole-2,2-diox-
ide (6d). Compound 5d (0.64 g, 2 mmol) was reacted with cesium
carbonate for 3 h to give 0.36 g (76%) of 6d as a white solid; mp
(ethanol/water) 199-200 °C. MS (ES+) m/z 240.1 [M + 1]+, 257.0
[M + H2O]+, 262.0 [M + Na]+, 479.2 [2M + 1]+, 501.2 [2M +
Na]+. Anal. (C11H13NO3S): C, H, N, S.
(()-4-Amino-5-benzyl-5-propyl-5H-1,2-oxathiole-2,2-diox-
ide (6e). Compound 5e (0.54 mL, 2 mmol) was reacted with cesium
carbonate for 2 h to afford compound 6e (0.26 g, 50%) as a white
solid; mp (ethanol/water) 180-181 °C. Anal. (C13H17NO3S): C,
H, N, S.
(()-4-Amino-5-benzyl-5-isopropyl-5H-1,2-oxathiole-2,2-di-
oxide (6f). A solution of 5f (0.54 g, 2 mmol) was treated with
cesium carbonate for 3 h to give 0.32 g (62%) of 6f as a white
solid;mp (ethanol/water) 185-186 °C. MS (ES+) m/z 268.0 [M +
1]+, 285.0 [M + H2O]+, 290.0 [M + Na]+, 535.2 [2M + 1]+, 557.3
[2M + Na]+. Anal. (C13H17NO3S):C, H, N, S.
(()-4-Amino-5-benzyl-5-isobutyl-5H-1,2-oxathiole-2,2-diox-
ide (6g). Compound 5g (0.56 g, 2 mmol) was reacted with cesium
carbonate for 3 h to yield 0.36 g (66%) of 6g as a white solid; mp
(ethanol/water) 201-202 °C. MS (ES+) m/z 282.0 [M + 1]+, 299.2
[M + H2O]+, 304.0 [M + Na]+, 563.2 [2M + 1]+, 585.3 [2M +
Na]+. Anal. (C14H19NO3S): C, H, N, S.
(()-1,2,3,4-Tetrahydronaphthalene-2-spiro-5′-(4′-amino-5′H-
1′,2′-oxathiole-2′,2′-dioxide) (6h). A solution of 5h (0.50 g, 2
mmol) in dry acetonitrile was treated with cesium carbonate for
7 h to give 0.36 g (70%) of 6h as a white solid; mp (ethanol/water)
194-195 °C. MS (ES+) m/z 252.1 [M + 1]+, 269.0 [M + H2O]+,
274.0 [M + Na]+, 503.12 [M + 1]+, 525.0 [2M + Na]+. Anal.
(C12H13NO3S): C, H, N, S.
Synthesis of Compounds 7a-h: General Procedure. A solu-
tion of the appropriate ꢀ-amino-γ-sultone derivative 6a-h (1.1
mmol) in 4.5 N HCl in methanol (1.6 mL, 7.2 mmol) was stirred
at room temperature for 16 h. Then, a solution of 1 N NaOH in
methanol was added until pH ∼ 6, salts were filtered, and the
solvent was evaporated. The final residue was purified by flash
column chromatography (hexane/ethyl acetate, 1:5) to give the final
products 7a-h.
4-Benzyloxy-5,5-dibenzyl-5H-1,2-oxathiole-2,2-dioxide (3). Com-
pound 226 (0.17 g, 0.55 mmol) was treated with benzyl bromide
(63 µL, 0.55 mmol) for 3 h. Purification of the residue by flash
column chromatography (hexane/ethyl acetate, 6:1) gave com-
pound 3 (0.15 g, 70%) as a white solid; mp (ethanol/water)
1
122-123 °C. H NMR [300 MHz, CDCl3] δ: 3.04, 3.16 (AB
system, 2H, J ) -14.3 Hz, CH2Ph), 4.77 (s, 2H, CH2O), 5.49
(s, 1H, H-3), 7.26-7.43 (m, 15H, 3Ph). 13C NMR [75 MHz,
CDCl3] δ: 42.4 (2 CH2), 74.7 (CH2O), 92.4 (C-5), 96.2 (C-3),
128.2, 127.4, 128.5, 129.0, 130.7, 133.3, 133.2 (Ph). MS (ES+)
m/z 407.1 [M + 1]+, 424.1 [M + H2O]+, 853.3 [2M + Na]+.
Anal. (C24H22O4S): C, H, S.
Method B. A solution of 226 (0.12 g, 0. 39 mmol) and a sodium
hydride 60% dispersion in mineral oil (0.03 g, 1.17 mmol) in dry
THF (2 mL), previously degassed under an argon atmosphere, was
stirred at room temperature for 15 min. Then, benzyl bromide (135

4-Benzyloxy-γ-Sultone DeriVatiVes
Journal of Medicinal Chemistry, 2009, Vol. 52, No. 6 1589
µL, 1.17 mmol) was added and the mixture was stirred at room
temperature for 24 h. The reaction was quenched with acetic acid
until the pH of the mixture was ∼7, and ethyl acetate was added
(5 mL). The resulting mixture was washed with water (2 × 5 mL)
and brine (2 × 5 mL). The combined organic layers were dried
(Na2SO4), filtered, and evaporated to dryness. The residue was
purified by CCTLC on a Chromatotron (hexane/ethyl acetate, 3:1)
to give 3 (0.06 g, 53%) as a white solid; mp (ethanol/water)
123-124 °C.
solid; mp (ethanol/water) 220-221 °C. MS (ES+) m/z 343.0 [M +
1]+, 360.1 [M + H2O]+, 365.0 [M + Na]+, 707.2 [2M + Na]+.
Anal. (C19H18O4S): C, H, S.
(()-5-Benzyl-5-ethyl-4-methoxy-5H-1,2-oxathiole-2,2-diox-
ide (9). Compound 7b26 (0.10 g, 0.39 mmol) was treated with
methyl iodide (24 µL, 0.39 mmol) for 3 h. Purification of the final
residue by HPFC on a Horizon system (hexane/ethyl acetate, 3:1)
gave compound 9 (0.07 g, 63%) as a white solid; mp (ethanol/
1
water) 103-104 °C. H NMR [300 MHz, (CD3)2CO] δ: 0.92 (m,
(()-4-Benzyloxy-5-diphenylmethyl-5-methyl-5H-1,2-oxathi-
ole-2,2-dioxide (8a). Compound 7a (0.17 g, 0.55 mmol) was reacted
with benzyl bromide (63 µL, 0.55 mmol) for 5 h. The residue was
purified by flash column chromatography (hexane/ethyl acetate, 6:1)
to give 0.07 g (31%) of 8a as a white solid; mp (ethanol/water):
3H, CH3CH2), 1.87 (m, 2H, CH3CH2), 3.17 (s, 2H, CH2Ph), 3.97
(s, 3H, CH3O), 6.25 (s, 1H, H-3), 7.32 (m, 4H, Ph). 13C NMR [75
MHz, CDCl3] δ: 7.6 (CH3CH2), 29.2 (CH3CH2), 43.2 (CH2Ph), 59.6
(CH3O), 93.7 (C-5), 95.6 (C-3), 127.5, 128.3, 130.8, 133.6 (Ph),
168.7 (C-4). MS (ES+) m/z 269.0 [M + 1]+, 291.0 [M + Na]+,
559.2 [2M + Na]+. Anal. (C13H16O4S): C, H, S.
1
146-147 °C. H NMR [300 MHz, CDCl3] δ: 1.72 (s, 3H, CH3),
4.30 (s, 1H, CH), 4.75, 4.91 (AB system, 2H, J ) -10.9 Hz,
CH2Ph), 5.62 (s, 1H, H-3), 7.29-7.62 (m, 15H, 3Ph). 13C NMR
[75 MHz, CDCl3] δ: 24.5 (CH3), 57.3 (CH), 75.0 (CH2O), 92.4,
95.3 (C-3, C-5), 127.5, 127.7, 128.5, 128.9, 129.2, 129.6, 129.8,
133.4, 138.2, 138.5 (3Ph), 168.9 (C-4). MS (ES+) m/z 407.0 [M +
1]+, 424.2 [M + H2O]+, 429.0 [M + Na]+, 835.2 [2M + Na]+.
Anal. (C24H22O4S): C, H, S.
(()-5-Benzyl-4-benzyloxy-5-ethyl-5H-1,2-oxathiole-2,2-diox-
ide (8b). 7b26 (0.10 g, 0.39 mmol) was reacted with benzyl bromide
(45 µL, 0.39 mmol) for 3 h. The residue was purified by CCTLC
on a Chromatotron (hexane/ethyl acetate, 3:1) to give 8b (0.09 g,
70%) as a white solid; mp (ethanol/water) 107-109 °C. MS (ES+)
m/z 345.1 [M + 1]+, 362.2 [M + H2O]+, 367.1 [M + Na]+, 711.2
[2M + Na]+. Anal. (C19H20O4S): C, H, S.
4-Benzyloxy-5,5-diethyl-5H-1,2-oxathiole-2,2-dioxide (8c). A
solution of 7c (0.10 g, 0.55 mmol) in dry acetonitrile was treated
with benzyl bromide (63 µL, 0.55 mmol) for 3 h. After the workup,
the residue was purified by flash column chromatography (hexane/
ethyl acetate, 6:1) to give 0.08 g (57%) of 8c as a white solid; mp
(ethanol/water) 95-98 °C. MS (ES+) m/z 283.0 [M + 1]+, 305.0
[M + Na]+, 587.0 [2M + Na]+. Anal. (C14H18O4S): C, H, S.
(()-5-Benzyl-4-benzyloxy-5-methyl-5H-1,2-oxathiole-2,2-di-
oxide (8d). A solution of 7d (0.13 g, 0.55 mmol) in dry acetonitrile
was treated with benzyl bromide (63 µL, 0.55 mmol) for 3 h. After
the workup, the residue was purified by flash column chromatog-
raphy (hexane/ethyl acetate, 6:1) to give 0.09 g (52%) of 8d as a
white solid; mp (ethanol/water) 139-140 °C. MS (ES+) m/z 331.0
[M + 1]+, 348.0 [M + H2O]+, 353.0 [M + Na]+, 683.3 [2M +
Na]+. Anal. (C18H18O4S): C, H, S.
(()-5-Benzyl-4-benzyloxy-5-propyl-5H-1,2-oxathiole-2,2-di-
oxide (8e). Compound 7e (0.15 g, 0.55 mmol) was treated with
benzyl bromide (63 µL, 0.55 mmol) for 3 h. The final residue was
purified by flash column chromatography (hexane/ethyl acetate, 6:1)
to give 0.10 g (54%) of 8e as a white solid; mp (ethanol/water)
105-107 °C. MS (ES+) m/z 359.0 [M + 1]+, 376.3 [M + H2O]+,
381.0 [M + Na]+, 739.2 [2M + Na]+. Anal. (C20H22O4S): C, H, S.
(()-5-Benzyl-4-benzyloxy-5-isopropyl-5H-1,2-oxathiole-2,2-
dioxide (8f). A solution of 7f (0.15 g, 0.55 mmol) in dry acetonitrile
was treated with benzyl bromide (63 µL, 0.55 mmol) for 4 h. After
the workup, the residue was purified by flash column chromatog-
raphy (hexane/ethyl acetate, 6:1) to give 0.12 g (63%) of 8f as a
white solid; mp (ethanol/water) 114-115 °C. MS (ES+) m/z 359.0
[M + 1]+, 376.3 [M + H2O]+, 381.0 [M + Na]+, 739.2 [2M +
Na]+. Anal. (C20H22O4S): C, H, S.
(()-4-Allyloxy-5-benzyl-5-ethyl-5H-1,2-oxathiole-2,2-diox-
ide and (()-3-Allyl-4-allyloxy-5-benzyl-5-ethyl-5H-1,2-oxathiole-
2,2-dioxide (10 and 11). Compound 7b26 (0.10 g, 0.39 mmol) was
reacted with allyl bromide (51 µL, 0.58 mmol) for 4 h. The final
residue was purified by HPFC on a Horizon system (hexane/ethyl
acetate, 3:1). The faster running fractions afforded 11 (0.02 g, 12%)
as a viscous colorless oil. MS (ES+) m/z 335.0 [M + 1]+, 353.0
[M + H2O]+, 691.0 [2M + Na]+. Anal. (C18H22O4S): C, H, S.
The slowest moving fractions afforded 0.08 g (72%) of 10 as a
viscous colorless oil. MS (ES+) m/z 295.0 [M + 1]+, 312.3 [M +
H2O]+, 317.0 [M + Na]+, 611.2 [2M + Na]+. Anal. (C15H18O4S).
C, H, S.
(()-5-Benzyl-5-ethyl-4-dimethylallyloxy-5H-1,2-oxathiole-2,2-
dioxide (12). A solution of 7b26 (0.10 g, 0.39 mmol) was treated
with dimethylallyl bromide (68 µL, 0.39 mmol) for 3 h. After the
workup, the residue was purified by HPFC on a Horizon system
(hexane/ethyl acetate, 3:1) to give 0.03 g (32%) of 12 as a viscous
colorless oil. MS (ES+) m/z 323.3 [M + 1]+, 340.3 [M + H2O]+,
345.2 [M + Na]+, 667.5 [2M + Na]+. Anal. (C17H22O4S): C, H, S.
(()-5-Benzyl-4-cyanomethyloxy-3-ethyl-5H-1,2-oxathiole-2,2-
dioxide (13). Compound 7b26 (0.10 g, 0.39 mmol) was treated with
bromoacetonitrile (27 µL, 0.39 mmol) for 3 h. Purification of the
final residue by HPFC on a Horizon system (hexane/ethyl acetate,
3:1), gave compound 13 (0.07 g, 60%) as a white solid; mp (ethanol/
water) 111-114 °C. MS (ES+) m/z 294.2 [M + 1]+, 311.2 [M +
H2O]+, 316.0 [M + Na]+, 609.2 [2M + Na]+. Anal. (C14H15NO4S):
C, H, S.
(()-5-Benzyl-5-ethyl-4-methoxycarbonylmethoxy-5H-1,2-ox-
athiole-2,2-dioxide (14). Compound 7b26 (0.10 g, 0.39 mmol) was
reacted with methyl bromoacetate (37 µL, 0.39 mmol) for 3 h. The
final residue was purified by HPFC on a Horizon system (hexane/
ethyl acetate, 3:1), to give 0.085 g (67%) of 14 as a white solid;
mp (ethanol/water) 145-146 °C. MS (ES+) m/z 327.0 [M + 1]+,
344.0 [M + H2O]+, 349.0 [M + Na]+, 675.3 [2M + Na]+. Anal.
(C15H18O6S): C, H, S.
(()-5-Benzyl-4-cyclohexylmethoxy-5-ethyl-5H-1,2-oxathiole-
2,2-dioxide (15). A solution of 7b26 (0.10 g, 0.39 mmol) was treated
with bromomethylcyclohexane (55 µL, 0.39 mmol) for 3 h. After
the workup, the residue was purified by HPFC on a Horizon system
(hexane/ethyl acetate, 3:1), to give 0.048 g (35%) of 15 as a white
solid; mp (ethanol/water) 110-111 °C. MS (ES+) m/z 351.2 [M +
1]+, 368.3 [M + H2O]+, 373.3 [M + Na]+, 723.5 [2M + Na]+.
Anal. (C19H26O4S): C, H, S.
(()-5-Benzyl-4-diphenylmethoxy-5-ethyl-5H-1,2-oxathiole-
2,2-dioxide (16). A solution of 7b26 (0.10 g, 0.39 mmol) was treated
with diphenylbromomethane (0.096 g, 0.39 mmol) for 3 h. The
residue was purified by HPFC on a Horizon system (hexane/ethyl
acetate, 3:1), to give 0.064 g (39%) of 16 as a white solid; mp
(ethanol/water) 173-174 °C. MS (ES+) m/z 421.0 [M + 1]+, 438.1
[M + H2O]+, 443.0 [M + Na]+, 863.3 [2M + Na]+. Anal.
(C25H24O4S): C, H, S.
(()-5-Benzyl-5-ethyl-4-(2′-phenylethoxy)-5H-1,2-oxathiole-
2,2-dioxide (17). Compound 7b26 (0.10 g, 0.39 mmol) was treated
with 2-phenylethyl bromide (46 µL, 0.39 mmol) for 5 h. Purification
of the final residue by HPFC on a Horizon system (hexane/ethyl
acetate, 3:1), gave compound 17 (0.072 g, 52%) as a white solid;
(()-5-Benzyl-4-benzyloxy-5-isobutyl-5H-1,2-oxathiole-2,2-
dioxide (8g). Compound 7g (0.15 g, 0.55 mmol) was treated with
benzyl bromide (63 µL, 0.55 mmol) for 3 h. Purification of the
final residue by flash column chromatography (hexane/ethyl acetate,
6:1) gave 8g (0.09 g, 45%) as a white solid; mp (ethanol/water)
114-115 °C. MS (ES+) m/z 373.3 [M + 1]+, 390.2 [M + H2O]+,
395.2 [M + Na]+, 767.5 [2M + Na]+. Anal. (C21H24O4S): C, H, S.
(()-1,2,3,4-Tetrahydronaphthalene-2-spiro-5′-(4′-benzyloxy-
5′H-1′,2′-oxathiole-2′,2′-dioxide) (8h). Compound 7h (0.14 g, 0.55
mmol) was reacted with benzyl bromide (63 µL, 0.55 mmol) for
4 h. The final residue was purified by flash column chromatography
(hexane/ethyl acetate, 6:1) to give 0.08 g (44%) of 8h as a white

1590 Journal of Medicinal Chemistry, 2009, Vol. 52, No. 6
De Castro et al.
mp (ethanol/water) 56-57 °C. MS (ES+) m/z 359.2 [M + 1]+, 376.3
[M + H2O]+, 381.0 [M + Na]+, 739.2 [2M + Na]+. Anal.
(C20H22O4S): C, H, S.
solid; mp (ethanol/water) 114-115 °C. MS (ES+) m/z 363.0 [M +
1]+, 385.0 [M + Na]+, 747.2 [2M + Na]+. Anal. (C19H19FO4S):
C, H, S.
(()-5-Benzyl-5-ethyl-4-(3′-phenylpropoxy)-5H-1,2-oxathiole-
2,2-dioxide (18). Compound 7b26 (0.10 g, 0.39 mmol) was reacted
with 3-phenylpropyl bromide (59 µL, 0.39 mmol) for 5 h. The final
residue was purified by HPFC on a Horizon system (hexane/ethyl
acetate, 3:1) to give 0.058 g (40%) of 18 as a viscous colorless oil.
MS (ES+) m/z 373.3 [M + 1]+, 395.2 [M + Na]+, 767.3 [2M +
Na]+. Anal. (C21H24O4S): C, H, S.
(()-5-Benzyl-5-ethyl-4-(4′-chlorobenzyloxy)-5H-1,2-oxathiole-
2,2-dioxide (26). Via the procedure described for 23, a solution of
7b26 (0.10 g, 0.39 mmol) was treated with 4-chlorobenzyl bromide
(0.08 g, 0.39 mmol) for 3 h to give 0.068 g (47%) of 26 as a white
solid; mp (ethanol/water) 75-77 °C. MS (ES+) m/z 379.1 [M +
1]+, 396.1 [M + H2O]+, 401.1 [M + Na]+, 779.2 [2M + Na]+.
Anal. (C19H19ClO4S): C, H, S.
(()-5-Benzyl-5-ethyl-4-(4′-phenylbutoxy)-5H-1,2-oxathiole-
2,2-dioxide (19). 7b26 (0.10 g, 0.39 mmol) was treated with
4-phenylbutyl bromide (83 µL, 0.39 mmol) for 5 h. Purification of
the residue by HPFC on a Horizon system (hexane/ethyl acetate,
3:1) gave compound 19 (0.114 g, 76%) as a viscous colorless oil.
MS (ES+) m/z 387.2 [M + 1]+, 404.2 [M + H2O]+, 795.5 [2M +
Na]+. Anal. (C22H26O4S): C, H, S.
(()-5-Benzyl-5-ethyl-4-(4′-bromobenzyloxy)-5H-1,2-oxathiole-
2,2-dioxide (27). The procedure described for 23 was followed
with 7b26 (0.10 g, 0.39 mmol) and 4-bromobenzyl bromide
(0.097 g, 0.39 mmol) for 3 h to give 0.086 g (52%) of 27 as a
white solid; mp (ethanol/water): 118-120 °C. MS (ES+) m/z
423.0 [M + 1]+, 445.0 [M + Na]+, 867.0 [2M + Na]+. Anal.
(C19H19BrO4S): C, H, S.
(()-5-Benzyl-5-ethyl-4-(6′-phenylhexyloxy)-5H-1,2-oxathiole-
2,2-dioxide (20). 7b26 (0.10 g, 0.39 mmol) was treated with
6-phenylhexyl bromide (0.094 g, 0.39 mmol) for 4 h. The residue
was purified by HPFC on a Horizon system (hexane/ethyl acetate,
3:1) to give 0.09 g (56%) of 20 as a viscous colorless oil. MS
(ES+) m/z 415.3 [M + 1]+, 437.3 [M + Na]+, 851.5 [2M + Na]+.
Anal. (C24H30O4S): C, H, S.
(()-5-Benzyl-5-ethyl-4-(4′-methoxybenzyloxy)-5H-1,2-oxathi-
ole-2,2-dioxide (28). Following the procedure described for 23, 7b26
(0.10 g, 0.39 mmol) was reacted with 4-methoxybenzyl bromide
(53 µL, 0.39 mmol) for 6 h to give compound 28 (0.058 g, 40%)
as a white solid; mp (ethanol/water) 80-81 °C. MS (ES+) m/z 375.0
[M + 1]+, 392.2 [M + H2O]+, 397.0 [M + Na]+, 771.3 [2M +
Na]+. Anal. (C20H22O5S). C, H, S.
(()-5-Benzyl-4-benzoyloxy-5-ethyl-5H-1,2-oxathiole-2,2-di-
oxide (21). A solution of 7b26 (0.10 g, 0.39 mmol) and a sodium
hydride 60% dispersion in mineral oil (0.028 g, 1.14 mmol) in dry
THF (5 mL) was stirred at room temperature for 10 min. Then,
benzoyl chloride (136 µL, 1.17 mmol) was added and the mixture
was stirred at room temperature for 5 h. The reaction was quenched
with acetic acid to pH ∼ 7, and ethyl acetate was added (5 mL).
The reaction mixture was successively washed with water (2 × 5
mL) and brine (2 × 5 mL). The combined organic layers were
dried (Na2SO4), filtered, and evaporated to dryness. The residue
was purified by HPFC on a Horizon system (hexane/ethyl acetate,
3:1) to give 21 (0.057 g, 41%) as a white solid; mp (ethanol/water)
139-140 °C. MS (ES+) m/z 359.0 [M + 1]+, 381.0 [M + Na]+,
739.2 [2M + Na]+. Anal. (C19H18O5S): C, H, S.
(()-5-Benzyl-5-ethyl-4-(4′-methylbenzyloxy)-5H-1,2-oxathiole-
2,2-dioxide (29). According to procedure described for 23, 7b26
(0.10 g, 0.39 mmol) was reacted with 4-methylbenzyl bromide
(0.072 g, 0.39 mmol) for 3 h to yield 0.059 g (42%) of 29 as a
viscous colorless oil. MS (ES+) m/z 359.0 [M + 1]+, 376.0 [M +
H2O]+, 381.0 [M + Na]+, 739.0 [2M + Na]+. Anal. (C20H22O4S):
C, H, S.
(()-5-Benzyl-5-ethyl-4-(4′-tert-butylbenzyloxy)-5H-1,2-oxathi-
ole-2,2-dioxide (30). The procedure described for 23 was followed
with 7b26 (0.10 g, 0.39 mmol) and 4-tert-butylbenzyl bromide (72
µL, 0.39 mmol) for 3 h to give 0.126 g (81%) of 30 as a viscous
colorless oil. MS (ES+) m/z 401.2 [M + 1]+, 418.0 [M + H2O]+,
491.2 [M + 2Na]+, 823.3 [2M + Na]+, 423.0 [M + Na]+. Anal.
(C23H28O4S): C, H, S.
(()-5-Benzyl-5-ethyl-4-(2′-chlorobenzyloxy)-5H-1,2-oxathiole-
2,2-dioxide (31). Following the procedure described for 23, 7b26
(0.10 g, 0.39 mmol) was treated with 2-chlorophenyl bromide (51
µL, 0.39 mmol) for 3 h to afford compound 31 (0.064 g, 60%) as
a white solid; mp (ethanol/water) 102-104 °C. MS (ES+) m/z 379.0
[M + 1]+, 779.2 [2M + Na]+. Anal. (C19H19ClO4S): C, H, S.
(()-5-Benzyl-5-ethyl-4-(3′-chlorobenzyloxy)-5H-1,2-oxathiole-
2,2-dioxide (32). The procedure described for 23 was followed with
7b26 (0.10 g, 0.39 mmol) and 3-chlorobenzyl bromide (51 µL, 0.39
mmol) for 3 h to give 0.098 g (66%) of 32 as a viscous colorless
oil. MS (ES+) m/z 379.0 [M + 1]+, 396.0 [M + H2O]+, 401.0 [M
+ Na]+, 779.0 [2M + Na]+. Anal. (C19H19ClO4S): C, H, S.
The slowest moving fractions afforded 0.05 g (50%) of unreacted
starting material.
(()-5-Benzyl-5-ethyl-4-(p-toluensulfonyloxy)-5H-1,2-oxathi-
ole-2,2-dioxide (22). Via the procedure describe for 21, compound
7b26 (0.10 g, 0.39 mmol) was reacted with p-toluensulfonyl chloride
(0.074 g, 0.39 mmol) and sodium hydride for 24 h. After the
workup, the residue was purified by flash column chromatography
(hexane/ethyl acetate, 3:1) to give 0.046 g (30%) of 22 as a white
solid; mp (ethanol/water) 89-90 °C. MS (ES+) m/z 409.2 [M +
1]+, 426.2 [M + H2O]+, 431.2 [M + Na]+, 839.3 [2M + Na]+.
Anal. (C19H20O6S2): C, H, S.
The slowest moving band afforded 0.057 g (57%) of unreacted
starting material.
(()-5-Benzyl-5-ethyl-4-(4′-nitrobenzyloxy)-5H-1,2-oxathiole-
2,2-dioxide (23). Via the general alkylation procedure, a solution
of 7b26 (0.10 g, 0.39 mmol) was treated with 4-nitrobenzyl bromide
(0.067 g, 0.39 mmol) for 5 h. After the workup, the residue was
purified by HPFC on a Horizon system (hexane/ethyl acetate, 3:1),
to give 0.094 g (62%) of 23 as a white solid; mp (ethanol/water)
115-118 °C. MS (ES+) m/z 390.0 [M + 1]+, 407.0 [M + H2O]+,
412.0 [M + Na]+, 801.0 [2M + Na]+. Anal. (C19H19NO6S): C, H,
N, S.
(()-5-Benzyl-5-ethyl-4-(4′-trifluorobenzyloxy)-5H-1,2-oxathi-
ole-2,2-dioxide (24). According to the procedure described for 23,
7b26 (0.10 g, 0.39 mmol) was reacted with 4-trifluoromethylbenzyl
bromide (0.093 g, 0.39 mmol) for 3 h to give 0.10 g (65%) of 24
as a white solid; mp (ethanol/water) 82-84 °C. MS (ES+) m/z 413.0
[M + 1]+, 430.0 [M + H2O]+, 434.9 [M + Na]+, 846.8 [2M +
Na]+. Anal. (C20H19F3O4S): C, H, S.
(()-5-Benzyl-5-ethyl-4-(3′,4′-dichlorobenzyloxy)-5H-1,2-ox-
athiole-2,2-dioxide (33). Via the procedure described for 23, a
solution of 7b26 (0.10 g, 0.39 mmol) was treated with 3,4-
dichlorobenzyl bromide (0.094 g, 0.39 mmol) for 4 h to yield 0.069
g (43%) of 33 as a white solid; mp (ethanol/water) 115-116 °C.
MS (ES+) m/z 413.2 [M + 1]+, 435.1 [M + Na]+, 848.9 [2M +
Na]+. Anal. (C19H18Cl2O4S): C, H, S.
Antiviral Assays. HCMV. Confluent human embryonic lung
(HEL) fibroblasts were grown in 96-well microtiter plates and
infected with the human cytomegalovirus (HCMV) strains Davis
and AD-169 at 100 PFU per well. Also, a variety of relevant drug-
resistant HCMV strains, mutated in the DNA polymerase gene, were
included in the infection and sensitivity studies. After a 2 h
incubation period, residual virus was removed and the infected cells
were further incubated with medium containing different concentra-
tions of the test compounds (in duplicate). After incubation for 7
days at 37 °C, virus-induced cytopathogenicity was monitored
microscopically after ethanol fixation and staining with Giemsa.
Antiviral activity was expressed as the EC50 or compound concen-
tration required to reduce virus-induced cytopathogenicity by 50%.
(()-5-Benzyl-5-ethyl-4-(4′-fluorobenzyloxy)-5H-1,2-oxathiole-
2,2-dioxide (25). The procedure described for 23 was followed with
7b26 (0.10 g, 0.39 mmol) and 4-fluorobenzyl bromide (49 µL, 0.39
mmol) for 3 h to give compound 25 (0.078 g, 54%) as a white

4-Benzyloxy-γ-Sultone DeriVatiVes
Journal of Medicinal Chemistry, 2009, Vol. 52, No. 6 1591
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Acknowledgment. We thank Lies Van den Heurck, Anita
Camps, and Steven Carmans for excellent technical assistance.
We also thank the Spanish MEC/MCINN (project SAF2006-
12713-C02), the European Commission [project HPAW-CT-
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