Synthesis and antiviral and cytostatic activities of carbocyclic nucleosides incorporating a modified cyclobutane ring. Part 1: Guanosine analogues

Article abstract of DOI:10.1002/(SICI)1521-4184(199910)332:10<348::AID-ARDP348>3.0.CO;2-H

Five new carbocyclic nucleosides were prepared by constructing a guanine (compounds 3,5) or 8-azaguanine (compounds 4, 6, and 7) base on the amino group of (1'S,3'R)-3-(3'-amino-2',2'-dimethylcyclobutyl)propan-1-ol (8), and their activities against a variety of viruses and tumor cell lines were determined. Only compounds 3 and 7 showed a detectable activity at subtoxic concentrations against some viruses tested.

Full text of DOI:10.1002/(SICI)1521-4184(199910)332:10<348::AID-ARDP348>3.0.CO;2-H

348
Caamaño and co-workers
Synthesis and Antiviral and Cytostatic Activities of Carbocyclic
Nucleosides Incorporating a Modified Cyclobutane Ring
Part 1: Guanosine Analogues
M. José Figueira, J. Manuel Blanco, Olga Caamaño*, Franco Fernández, Xerardo García-Mera, and Carmen López
Departamento de Química Orgánica, Facultad de Farmacia, Universidad de Santiago, E-15706 Santiago de Compostela, Spain
Graciela Andrei, Robert Snoeck, Elisabeth Padalko, Johan Neyts, Jan Balzarini, and Erik De Clercq
Rega Institute for Medical Research, Katholieke Universiteit Leuven, B-3000 Leuven, Belgium
Key Words: Synthesis; carbocyclic nucleosides; guanosine analogues; antiviral testing; cytostatic activity
droxymethyl group by carbons in normal nucleosides, cases
Summary
are known of 4′-homo-carbocyclic nucleosides showing sig-
[10]
nificant anti-HSV-1 activity
.
Five new carbocyclic nucleosides were prepared by constructing
a guanine (compounds 3, 5) or 8-azaguanine (compounds 4, 6, and
7) base on the amino group of (1′S,3′R)-3-(3′-amino-2′,2′-di-
methylcyclobutyl)propan-1-ol (8), and their activities against a
variety of viruses and tumor cell lines were determined. Only
compounds 3 and 7 showed a detectable activity at subtoxic
concentrations against some viruses tested.
Chemistry
Precursor amino alcohol 8 was prepared from nopinone (9)
by modification of the previously established synthetic
[11]
route
. Treatment of nopinone (9) with hydroxylamine-O-
sulfonic acid in acetic acid led to a crude product that was
chromatographed to afford lactam 10 (49% yield) and a small
amount of the isomeric lactam 11 (5% yield).
Although the hydrolysis of 10 required forcing conditions,
it produced amino acid hydrochloride salt in 99% yield,
which was converted into free 12 by ion-exchange chroma-
tography. In our modified approach, (Scheme 1) the carbox-
Introduction
There is growing interest in carbocyclic analogues of nu-
cleosides (CANs) owing to their potential antineoplastic and
antiviral properties . For example, oxetanocin analogues 1
[1]
ylic acid 12 was reduced directly, with LiAlH in refluxing
4
THF, rather than its methyl ester, thus obviating the use of
diazomethane for preparation of the latter. Customary work-
(Cyclobut-A) and 2 (Cyclobut-G) inhibit the replication of
herpes simplex virus type 1 and type 2, varicella-zoster virus,
up of the crude product gave amino alcohol 8 in 28% yield,
and human cytomegalovirus, and have some activity against
[12]
[2–6]
together with a small amount of amine 13 (12% yield)
.
human immunodeficiency virus
.
However, the yield of 8 could be improved by using an
alternative work-up in which the crude product was first
converted to the diacetyl derivative 14 (87%). This was then
hydrolyzed in refluxing 2N HCl (22 h) to afford 8 in 83%
yield.
The synthesis of CANs usually involves construction of a
natural or modified purine or pyrimidine base on an appro-
[7]
priate amino alcohol . We are currently engaged in a re-
search programme aimed at assessing the effects of structural
parameters of the amino alcohol moiety on the biological
[8]
activity of CANs . In this work we report the preparation
and biological evaluation of a series of guanosine analogues
with a dimethylcyclobutane ring, 3–7. These compounds are
structurally related to Cyclobut-G (2).
Antiviral and/or cytotoxic activity of nucleoside anti-
metabolites is usually shown after they have undergone phos-
phorylation, and this step seems to be essential for activation
of 2′,3′-didehydro-2′,3′-dideoxynucleosides, and their ana-
logues with regard to anti-HIV action . Although such
activities are not observed after elongation of the 4′-hy-
Scheme 1. a) H2NOSO3H, AcOH, reflux; b) 12N HCl, reflux; c) Dowex
50Wx8-200, 14M NH4OH; d) LiAlH4, THF, reflux; e) Ac2O, py., r.t.; f) 2N
HCl, reflux; g) Amberlite IRA-400 (OH).
[9]
Arch. Pharm. Pharm. Med. Chem.
© WILEY-VCH Verlag GmbH, D-69451 Weinheim, 1999
0365-6233/99/1010/0348 $17.50 +.50/0

Carbocyclic Nucleosides
349
vaccinia virus and vesicular stomatitis virus in human
embryonic skin-muscle fibroblasts (E SM); vesicular sto-
6
matitis virus, respiratory syncytial virus and Coxsackie B4
virus in human epithelial (HeLa) cells; parainfluenza virus
type 3, reovirus type 1, sindbis virus and punta toro virus
in African green monkey (Vero) kidney cells. Brivudine
and ribavirin as well as acyclovir, ganciclovir and/or (S)-
9-(2,3-dihydroxypropyl)adenine were used in parallel
tests as reference drugs.
– At compound concentrations up to 250 µg/mL: influenza
virus (strains H2N2 A2 Japan/305/57, B Hong Kong/5/72,
H3N2 (X31) in Madin-Darby canine kidney (MDCK)
cells. Ribavirin, rimantadine, and amantadine were used
in parallel tests as reference drugs.
– At compound concentrations up to 200 µg/mL: human
immunodeficiency virus (HIV) types 1 and 2 in T-lympho-
cyte (CEM/0) cells; cytotoxicity against host cells was
correspondingly evaluated.
– At compound concentrations up to 50 µg/mL: cytomega-
lovirus (CMV, strains AD-169 and DAVIS) and varicella-
zoster virus (VZV, strains OKA, YS, 07/1, and YS/R) in
human embryonic lung (HEL) cells. Cidofovir and ganci-
clovir orbrivudine and acyclovir were used in parallel tests
as reference drugs.
Scheme 2. a) 2-Amino-4,6-dichloropyrimidine, Et3N, n-butanol, reflux;
b) 4-chlorobenzenediazonium chloride, H2O, AcOH, NaOAc, r.t.; c) Zn,
AcOH, H2O, EtOH, reflux; d) CH(OEt)3,12N HCl, r.t.; e) NaNO2, AcOH,
H2O, r.t.; f) 0.33N NaOH, reflux; g) NH3, MeOH, 75 °C.
Results and Discussion
The great majority of the compounds did not show an
appreciable antiviral activity in these assays. However, the
compounds 3 and 7 showed some activity against vaccinia
virus, compound 3 (IC , 50 µg/mL) and compound 7 (IC ,
The synthesis of analogues 3–7 is detailed in Scheme 2; in
[13]
50
50
all cases, well established methods
were used to construct
60 µg/mL), TK HSV-1 (VMW 1837), compound 3 (IC ,
40 µg/mL) and compound 7 (IC , 70 µg/mL), and Coxsackie
B4 virus, compound 3 (IC , 60 µg/mL), at subtoxic concen-
50
a guanine or a modified guanine base on the amino group of
(1′S,3′R)-3-(3′-amino-2′,2′-dimethylcyclobutyl)propan-1-ol
(8). Briefly, 8 was condensed with 2-amino-4,6-dichlo-
ropyrimidine; the resulting pyrimidinylamino compound 15
was condensed with 4-chlorobenzenediazonium chloride to
afford the 5-(4-chlorophenyl-azo)pyrimidine 16, which was
reduced with zinc in acetic acid to give the triaminopyrimid-
ine 17.
Then 17 was cyclized, either in triethyl orthoformate, which
gave the 9-substituted 2-amino-6-chloropurine 3, or in so-
dium nitrite/acetic acid, which gave the 5-amino-7-chloro-
3H-1,2,3-triazolo[4,5-d]pyrimidine derivative 4 in good
yield. The guanosine analogue 5, and the corresponding
8-azaguanosine analogue 6, were obtained from 3 and 4,
respectively, by hydrolysis in dilute sodium hydroxide. The
2,6-diamino-8-azapurinyl compound 7 was obtained by treat-
ment of 4 with ammonia in a pressurized vessel.
50
50
trations. Activity found for some of the compounds tested
–
against TK viruses suggests that, as in the case of their lower
[8]
homologues , phosphorylation by a viral kinase is not a
previous requisite for their activity.
In connection with anti-HIV tests, a weak cytotoxic activity
against the host cells was detected for compounds 3 (CC ,
50
64 ± 4 µg/mL), 4 (CC , 82 ± 1 µg/mL), 6 (CC , 116 ±
50
50
2 µg/mL) and 7 (CC , 87 ± 4 µg/mL). Compounds 3–7 were
50
also tested for cytostatic activity against two tumor cell lines,
Table 1. Inhibitory effects of compounds 3–7 on the proliferation of murine
leukemia (L1210/0) cells and human T-lymphocyte (Molt4/C8) cells.
——————————————————————————————
IC50 (g/mL)a)
Compounds
L1210/0
Molt4/C8
——————————————————————————————
3
4
5
6
7
87.5 ± 1.5
106 ± 14
>200
49.4 ± 15.6
72.5 ± 6.9
Biological Evaluation
The new carbocyclic nucleosides 3–7 were evaluated for
their antiviral activity in a wide variety of assay systems:
>200
178 ± 31
96.8 ± 11.7
88.2 ± 5.3
89.2 ± 1.1
– At compound concentrations up to 400 µg/mL: herpes
simplex virus type 1 (strain KOS), herpes simplex virus
——————————————————————————————
a
–
50% Inhibitory concentration, or concentration required to inhibit cell
type 2 (strain G), thymidine kinase-deficient (TK ) herpes
simplex virus type 1 (strains B 2006 and VMW 1837),
proliferation during the linear growth phase by 50%
Arch. Pharm. Pharm. Med. Chem. 332, 348–352 (1999)

350
Caamaño and co-workers
from a dropping funnel of water (12 mL) and 1N NaOH (6 mL). After a
further 30 min stirring the solvents were evaporated and the resulting residue
was dried by successive dissolution-evaporation cycles using absolute etha-
nol (25 mL) and then toluene (2 × 25 mL). The residue was stirred in Ac2O
(1.62 mL) and pyridine (1.62 mL) at room temperature for 20 h, and then the
solvent was evaporated, the oil remaining was dissolved in CH2Cl2 (75 mL),
washed with saturated NaHCO3, and then H2O, and dried over anhydrous
Na2SO4. Concentration of this solution gave 14 (0.58 g, 87%) as an oil. An
analytical sample was obtained by bulb-bulb distillation in a Kugelrohr
apparatus (oven temp. 130–135 °C/0.01 Torr) (ref.[11] 133–135 °C).
and except for compound 5, showed some weak inhibition of
cell proliferation (Table 1).
Acknowledgements
The authors thank the Spanish Ministry of Education and Science (MEC-
DGICYT, PB94-0617) and the Xunta of Galicia (XUGA 20307B94) for
financial support of this work. Work at the Rega Institute was supported by
the “Geconcerteerde Onderzoeksacties” (No.95/5), the Belgian “Fonds voor
Wetenschappelijk Onderzoeck” (No. G.0180.95) and the Biomedical Re-
search Programme of the European Commission.
(1′S,3′R)-3-(3′-Amino-2′,2′-dimethylcyclobutyl)propan-1-ol (8)
A solution of 14 (0.56 g, 2.32 mmol) in 2 N HCl (60 mL) was heated under
reflux for 22 h. The solvent was evaporated and the solid remaining was dried
by three dissolution-evaporation cycles, using absolute ethanol (20 mL) and
then toluene (2 × 20 mL) to form the corresponding azeotropes. The white
solid obtained was the hydrochoride of 8 (0.47 g). Mp 160–164 °C (ref.[11]
mp 162–164 °C).
The solid 8HCl was dissolved in MeOH (40 mL) and passed through a
column packed with Amberlite IRA-400 resin in OH- form (16 mL). Con-
centration of the basic eluate under reduced pressure gave 8 (0.32 g, 83%) as
a colorless oil that spontaneously crystallized. An analytical sample was
obtained by recrystallization of this material from EtOH/Et2O. Mp 79–81 °C
(ref.[11] mp 79–81 °C).
Experimental Part
Silica gel (230 mesh) was purchased from Merck. All other chemicals used
were of reagent grade and were obtained from Aldrich Chemical Co. Melting
points were measured on a Reichert Kofler thermopan and are uncorrected.
Na-D line polarimetry was carried out at 25 °C in a Perkin-Elmer 241
polarimeter. Infrared spectra were recorded in a Perkin-Elmer FT-IR 1640
spectrometer. 1H NMR and 13C NMR spectra were recorded in a Bruker
AMX 300 spectrometer, at 300 and 75 MHz, respectively. Microanalyses
were performed by a Perkin-Elmer 240B Elemental Analyser. Biological
assays on antiviral and cytotoxic activities and/or cytostatic activity against
tumor cell lines were carried out using standard testing protocols [14]
.
(1′S,3′R)-3-[3′-(2-Amino-6-chloropyrimidin-4-yl)amino-2′,2′-dimethyl-
cyclobutylpropan-1-ol (15)
(1R)-7,7-Dimethyl-2-azabicyclo[4.1.1]octan-3-one (10) and (1R)-7,7-di-
methyl-3-azabicyclo[4.1.1]octan-2-one (11)
Freshly prepared 8 (3.34 g, 21.27 mmol), 2-amino-4,6-dichloropyrimidine
(5.26 g, 32.07 mmol), triethylamine (18 mL), and n-butanol (88 mL) were
heated under reflux in an argon atmosphere for 71 h. After evaporation of the
volatile solvents, the residue was pre-adsorbed on silica gel, packed on top
of a silica gel column (300 g), and chromatographed with 20:1
CH2Cl2/MeOH as eluant. The fractions containing product were concen-
trated to a syrup that crystallized spontaneously, affording 15 (5.53 g, 92%)
as a white crystalline solid: Mp 48–49 °C. IR (KBr) cm–1: 3322, 2936, 1582,
1459, 1367, 1245, 1158, 1055. 1H NMR (DMSO-d6) δ: 0.90 and 1.17 (2 s,
3H+3H, >C(CH3)2), 1.21–1.38 (m, 3H), 1.40–1.55 (m, 3H), 1.65–1.76 (m,
1H), 1.87 (br s, 1H, D2O exch., OH), 2.39 (dt, 1H, J = 7.67, 10.65 Hz, C3′-H),
3.62 (t, 2H, J = 6.26 Hz, OCH2), 4.94 (br s, 3H, D2O exch., NH2 + NH), 5.77
(s, 1H, pyrimidine C5-H). Anal. C13H21ClN4O: C, H, N.
A mixture of 9 (10 g, 72.35 mmol), glacial AcOH (260 mL) and hydroxy-
lamine-O-sulfonic acid (12.68 g, 112.15 mmol) was stirred at 90 °C for 5 h.
Once this mixture had cooled, H2O (260 mL) was added and the organic layer
was separated, washed with 10% NaHCO3 and then brine, and dried over
anhydrous Na2SO4. This solution was concentrated to a brown oil (8.06 g),
which was column chromatographed on silica gel with 2:3 hexane/EtOAc as
eluent. First to elute from the chromatography column was 10 (5.38 g, 49%),
which was isolated as a white solid [11]. Next eluted 11 (0.60 g, 5%), which
was also isolated as a white solid.
Compound 11. An analytical sample of 11 was obtained by recrystalliza-
25
tion from cyclohexane. Mp 69–71 °C. [α]D 48.22 (c 0.62, MeOH). IR
(KBr) cm–1: 3286, 2925, 1644, 1472, 1359, 1142, 782. 1H NMR (CDCl3) δ:
1.04 and 1.35 (2 s, 3H+3H, >C(CH3)2), 1.78–1.91 (m, 1H), 2.15–2.29 (m,
2H), 2.24 (d, 1H, J = 12.41 Hz), 2.39 (dt, 1H, J = 7.48, 12.41 Hz,), 2.64 (dddd,
1H, J = 1.03, 2.18, 4.47, 6.41 Hz), 3.12 (dddd, 1H, J = 1.76, 6.22, 6.84, 14.14
(1′S,3′R)-3-{3′-[2-Amino-6-chloro-5-(4-chlorophenylazo)pyrimidin-
4-ylamino-2′,2′-dimethylcyclobutyl}propan-1-ol (16)
Hz), 3.73 (dt, 1H, J = 4.48, 13.43 Hz,), 6.23 (br s, 1H, D2O exch., NH). 13
C
NMR (CDCl3) δ: 20.00 (CH2), 20.76 (CH3), 26.80 (CH2), 29.31 (CH3), 39.68
(CH2), 40.37 (C), 41.55 (CH), 53.57 (CH), 178.24 (C). Anal. C9H15NO: C,
H, N.
4-Chlorobenzenediazonium chloride was prepared by mixing 4-chlo-
roaniline (2.84 g, 22.27 mmol), 3 N HCl (44 mL) and NaNO2 (1.70 g,
24.64 mmol) in cold H2O (18 mL). This solution was added to a mixture of
15 (5.53 g, 19.57 mmol), AcOH (109 mL), H2O (89 mL), and NaOAc3 H2O
(35.50 g), and stirred overnight at room temperature. The yellow precipitate
was filtered out and washed with cold H2O until the washings were neutral,
and then air-dried under a fume hood to yield 16 (6.93 g, 84 %). An analytical
sample was obtained by recrystallization of the crude product from acetone.
Mp 222–223.5 °C. IR (KBr) cm–1: 3187, 2934, 1638, 1568, 1475, 1369,
1059, 835, 782. 1H NMR (DMSO-d6) δ: 0.97 and 1.12 (2 s, 3H+3H,
>C(CH3)2), 1.24–1.41 (m, 4H), 1.47–1.57 (m, 1H), 1.64–1.69 (m, 1H),
2.29–2.37 (m, 1H), 3.34–3.37 (m, 2H), 4.23–4.31 (m, 1H), 4.37 (t, 1H, D2O
exch., J = 5.06 Hz, OH), 7.46 (s, 1H, D2O exch., NHH), 7.56 (d, 2H, J = 8.64
Hz, C3-H + C5-H of 4-ClC6H4), 7.64 (s, 1H, D2O exch., NHH), 7.71 (d, 2H,
J = 8.64 Hz, C2-H + C6-H of 4-ClC6H4), 10.36 (d, 1H, D2O exch., J = 8.06
Hz, NH). 13C NMR (DMSO-d6) δ: 16.67 (CH3), 26.32 (CH2), 29.22 (CH3),
31.09 (CH2), 32.05 (CH2), 43.23 (C), 50.67 (CH), 61.02 (CH2), 118.63 (C),
122.95 (CH), 129.70 (CH), 133.58 (C), 150.85 (C), 154.64 (C), 161.32 (C),
165.07(C) . Anal. C19H24Cl2N6O: C, H, N.
(1′S,3′R)-3-(3′-Amino-2′,2′-dimethylcyclobutyl)propanoic Acid (12)
Amino acid hydrochloride salt 12 HCl was prepared from 10 [11]. A
.
.
solution of 12 HCl (0.65 g, 3.13 mmol) in water (27 mL) was deposited on
top of a column of Dowex 50wX8-200 (11 mL of resin, 20 mL of water) and
the column was eluted with water until the eluate had pH 6, and then with
14 M NH4OH (100 mL). Concentration of the ammoniacal eluate under
reduced pressure gave 12 (0.51 g, 95%). An analytical sample was prepared
by recrystallization from an H2O/acetone solvent pair. Mp 235–237 °C. IR
(KBr) cm–1: 2962, 2227, 1637, 1558, 1508, 1457, 1390, 781, 520. 1H NMR
(D2O) δ: 0.87 and 0.93 (2 s, 3H+3H, >C(CH3)2), 1.30–1.53 (m, 3H),
1.58–1.66 (m, 1H), 1.88–1.93 (m, 2H), 2.14 (dt, 1H, J = 7.58, 10.91 Hz,
C1′-H), 3.15 (dd, 1H, J = 7.79, 9.50 Hz, C3′-H). 13C NMR (D2O) δ: 14.97
(CH3), 26.33 (CH2), 27.76 (CH3), 28.64 (CH2), 35.81 (CH2), 39.22 (CH),
41.16 (C), 51.26 (CH), 183.70 (C). Anal. C9H17NO2: C, H, N.
(1′S,3′R)-3-(3′-Acetylamino-2′,2′-dimethylcyclobutyl)propyl Acetate (14)
(1′S,3′R)-3-[3′-(2,5-Diamino-6-chloropyrimidin-4-yl)amino-2′,2′-dimethyl-
cyclobutyl]propan-1-ol (17)
Amino acid 12 (0.50 g, 2.92 mmol) was added in two portions to a cooled
(0 °C) suspension of LiAlH4 (0.28 g, 7.30 mmol) in dry THF (7.50 mL)
stirring under argon. The suspension was heated under reflux for 7 h and then
stirred vigorously, cooled to 0 °C and quenched by slow, successive addition
A mixture of 16 (7.07 g, 16.71 mmol), zinc dust (11.66 g), AcOH
(5.73 mL), H2O (250 mL), and EtOH (250 mL) was heated under reflux in
an argon atmosphere for 7 h. The zinc was filtered off, and the solvents were
Arch. Pharm. Pharm. Med. Chem. 332, 348–352 (1999)

Carbocyclic Nucleosides
351
D2O exch., C1-H). 13C NMR (DMSO-d6) δ: 16.12 (CH2), 26.33 (CH3), 28.15
(CH3), 29.41 (CH2), 31.18 (CH), 39.02 (CH2), 44.19 (C), 53.94 (CH2), 61.16
(CH), 117.52 (C), 136.53 (C), 152.06 (C), 153.58 (C), 156.97 (C). Anal.
C14H21N5O2: C, H, N.
evaporated to leave a solid residue (15.22 g), which was pre-adsorbed on
silica gel, packed on top of a silica gel column (340 g), and chromatographed
with 9:1 CH2Cl2/MeOH as eluant. The fractions containing product were
concentrated to a pink solid (4.3 g, 86%). An analytical sample was obtained
by recrystallization of the crude product from H2O. Mp 128–130 °C. IR
(KBr) cm–1: 3509, 3308, 2929, 1574, 1500, 1437, 1248, 1055, 863. 1H NMR
(CDCl3) δ: 0.89 and 1.17 (2 s, 3H+3H, >C(CH3)2), 1.22–1.55 (m, 5H, one
of them D2O exch., OH), 1.63–1.77 (m, 2H), 2.38 (dt, 1H, J = 7.68, 10.61
Hz, C1′-H), 2.70 (s, 2H, D2O exch., NH2), 3.63 (t, 2H, J = 6.22 Hz, OCH2),
4.08 (dt, 1H, J = 8.05, 9.71 Hz, C3′-H), 4.59 (s, 2H, D2O exch., NH2), 5.40
(d, 1H, D2O exch., J = 7.91 Hz, NH). 13C NMR (CDCl3) δ: 16.15 (CH3),
26.63 (CH2), 29.57 (CH3), 31.27 (CH2), 32.24 (CH2), 39.51 (CH), 43.95 (C),
51.61 (CH), 63.21 (CH2), 111.38 (C), 148.71 (C), 158.01 (C), 159.22 (C).
Anal. C13H22ClN5O: C, H, N.
(1′R,3′S)-5-Amino-6,7-dihydro-3-[3′-(3-hydroxypropyl)-2′,2′-dimethyl-
cyclobutyl]-3H-1,2,3-triazolo[4,5-d]pyrimidin-7-one (6)
A mixture of 4 (0.36 g, 1.16 mmol) and 0.33 N NaOH (14.5 mL) was
heated under reflux for 3 h, whereupon its pH was adjusted to 3 with 6 N
HCl. A gelatinous precipitate that had been formed was filtered off, washed
with cold water, and then dried in vacuo over P2O5 to afford 6 (0.18 g, 52%)
as an off-white solid. Recrystallization of this material from H2O afforded
25
an analytical sample with mp 261–263 °C. [α]D 97.40 (c 0.50, MeOH). IR
(KBr) cm–1: 3286, 2926, 1716, 1639, 1602, 1573, 1458, 1365, 1305, 786,
680. 1H NMR (DMSO-d6) δ: 0.65 and 1.22 (2 s, 3H+3H, >C(CH3)2),
1.27–1.47 (m, 4H), 1.81–1.92 (m, 1H, C3′-H), 2.42 (dt, 1H, J = 7.9, 10.76
Hz, C4′-H), 2.63 (virtual c, 1H, J = 10.48 Hz, C4′-H), 3.34-3.39 (m, 2H,
OCH2), 4.39 (t, 1H, D2O exch., J = 4.96 Hz, OH), 4.52 (dd, 1H, J = 8.25,
9.69 Hz, C1′-H), 6.83 (s, 2H, D2O exch., NH2), 10.89 (s, 1H, D2O exch.,
NH). 13C NMR (DMSO-d6): δ: 16.11 (CH2), 26.24 (CH3), 27.27 (CH3),
29.10 (CH2), 30.59 (CH), 39.58 (CH2), 44.49 (C), 56.77 (CH2), 60.88 (CH),
124.43 (C), 151.61 (C), 155.16 (C), 156.18 (C). Anal. C13H20N6O2: C, H,
N.
(1′S,3′R)-3-[3′-(2-Amino-6-chloro-9H-purin-9-yl)-2′,2′-dimethylcyclo-
butyl]propan-1-ol (3)
A mixture of 17 (1.50 g, 5.00 mmol), triethyl orthoformate (28.85 mL) and
12 N HCl (1.35 mL) was stirred overnight. The resulting suspension was
evaporated to dryness in vacuo, and the residue was treated with 0.5 N HCl
(39 mL) for 4 h at room temperature, whereupon the mixture was adjusted
to pH 8 with 0.5 N NaOH and the solvents were evaporated. The crude
product (4.62 g) was triturated in CHCl3 (10 mL), undissolved NaCl was
filtered off, and the CHCl3 was evaporated. The pale yellow residue (1.36 g)
was chromatographed on silica gel (35 g) using 20:1 CHCl3/MeOH as eluant,
and 3 (0.81 g, 52%) was isolated as a white solid. An analytical sample was
obtained by recrystallization of this material from EtOH/H2O. Mp 161–
(1′S,3′R)-3-[3′-(5,7-Diamino-3H-1,2,3-triazolo[4,5-d]pyrimidin-3-yl)-
2′,2′-dimethylcyclobutyl]propan-1-ol (7)
25
163 °C. [α ]D 139.65 (c 0.58, MeOH). IR (KBr) cm–1: 3328, 2933, 1612,
1562, 1465, 1403, 1239, 1058, 914. 1H NMR (DMSO-d6) δ: 0.67 and 1.23
(2 s, 3H+3H, >C(CH3)2), 1.29–1.41 (m, 4H), 1.83–1.85 (m, 1H), 2.35–2.42
(m, 2H), 3.34–3.40 (m, 2H), 4.36–4.42 (m, 2H, one of them D2O exch., OH
+ C3′-H), 6.83 (s, 2H, D2O exch., NH2), 8.26 (s, 1H, C8-H). 13C NMR
(DMSO-d6) δ: 16.11 (CH2), 26.31 (CH3), 27.99 (CH3), 29.35 (CH2), 31.16
(CH), 38.91 (CH2), 44.35 (C), 54.33 (CH2), 61.13 (CH), 123.91 (C), 142.57
(C), 149.57 (C), 154.81 (C), 160.06 (C). Anal. C14H20ClN5O: C, H, N.
A solution of 4 (0.24 g, 0.77 mmol) in MeOH (10 mL) was cooled to
–60 °C in a reaction bomb. Liquid ammonia was passed into the solution and
the bomb was sealed and then heated at 75 °C for 48 h. Evaporation of the
ammonia and MeOH afforded crude 7 (0.21 g) as brown crystals, which were
recrystallized from H2O to afford pure 7 (0.17 g, 76%). Mp 174–176 °C.
[α]D 120.94 (c 0.64, MeOH). IR (KBr) cm–1: 3338, 3200, 2937, 1657,
25
1593, 1494, 1421, 1355, 1049. 1H NMR (DMSO-d6) δ: 0.65 and 1.23 (2 s,
3H+3H, >C(CH3)2), 1.28–1.48 (m, 4H), 1.81–1.90 (m, 1H, C1′-H), 2.42 (dt,
1H, J = 7.90, 10.74 Hz, C4′-H), 2.70 (virtual q, 1H, J = 10.49 Hz, C4′-H),
3.39 (dd, 2H, J = 5.62, 10.88 Hz, OCH2, on addition of D2O, this signal
simplifies to a triplet), 4.39 (t, 1H, D2O exch., J = 5.16 Hz, OH), 4.55 (dd,
1H, J = 8.22, 9.87 Hz, C3′-H), 6.31 (s, 2H, D2O exch., NH2), 7.50 (br s, 2H,
D2O exch., NH2). 13C NMR (DMSO-d6) δ: 16.24 (CH2), 26.25 (CH3), 27.34
(CH3), 29.21 (CH2), 30.87 (CH), 38.89 (CH2), 44,49 (C), 56.33 (CH2), 60.83
(CH), 120.50 (C), 152.01 (C), 156.19 (C), 162.77 (C). Anal. C13H21N7O: C,
H, N.
(1′S,3′R)-3-[3′-(5-Amino-7-chloro-3H-1,2,3-triazolo[4,5-d]pyrimidin-
3-yl)-2′,2′-dimethylcyclobutyl]propan-1-ol (4)
A cooled solution of 17 (2 g, 6.67 mmol) in AcOH (10.64 mL) and H2O
(53 mL) was treated with NaNO2 (0.60 g, 8.69 mmol) in H2O (35 mL) and
stirred for 2 h at 0 °C and then 2 h at room temperature. The resulting solution
was evaporated to dryness, and the solid residue (2.88 g) was chromatogra-
phed on silica gel (170 g) with 6:1 CHCl3/MeOH as eluant. Compound 4
(1.27 g, 61%) was isolated as a pale yellow solid that after recrystallization
25
from 1:1 hexane/EtOAc, had mp 106–108 °C. [α ]D 86.47 (c 0.51, MeOH).
IR (KBr) cm–1: 3320, 3204, 2939, 1647, 1606, 1564, 1515, 1450, 1430, 1391,
1245, 1192, 1004. 1H NMR (CDCl3) δ: 0.76 and 1.30 (2 s, 3H+3H,
>C(CH3)2), 1.39–1.63 (m, 5H, one of them D2O exch., OH), 1.91–2.04 (m,
1H, C4′-H), 2.55 (dt, 1H, J = 7.84, 11.21 Hz, C4′-H), 2.92 (virtual q, 1H, J
= 10.66 Hz, C1′-H), 3.67–3.70 (m, 2H, OCH2), 4.69 (dd, 1H, J = 8.13, 10.00
Hz, C3′-H), 5.43 (s, 2H, D2O exch., NH2). 13C NMR (CDCl3) δ: 16.64 (CH2),
26.48 (CH3), 27.77 (CH3), 29.44 (CH2), 31.07 (CH), 39.75 (CH2), 45.53 (C),
58.33 (CH2), 63.16 (CH), 130.13 (C), 152.65 (C), 154.28 (C), 161.00 (C).
Anal. C13H19ClN6O: C, H, N.
References and Notes
[1] V. E. Marquez, Adv. Antiviral Drug Des. E. De Clercq, , Ed. JAI Press
Inc., Greenwich, CT, USA 1996; Vol. 2, pp. 89–146.
[2] D. W. Norbeck, E. Kern, S. Hayashi, W. Rosenbrook, H. Sham, T.
Herrin, J. J. Plattner, J. Erickson, J. Clement, R. Swanson, N.
Shipkowitz, D. Hardy, K. Marsh, G. Arnett, W. Shannon., S. Broder,
H. Mitsuya J. Med. Chem. 1990, 33, 1281–1285.
[3] D. F. Smee, B. B. Barnett, R. W. Sidwell, E. J. Reist, A. Holy Antivir.
Res. 1995, 26, 1–9.
(1′R,3′S)-2-Amino-6,9-dihydro-9-[3′-(3-hydroxypropyl)-2′,2′-dimethyl-
cyclobutyl]-1H-purin-6-one (5)
[4] G. Yamanaka, A. V. Tuomari, M. Hagen, B. McGeever-Rubin, B. J.
Terry, M. Haffey, G.S . Bisacchi, A. K. Field, Mol. Pharmacol. 1991,
40, 446–453.
Compound 3 (0.30 g, 0.97 mmol) was heated under reflux for 5 h in 0.33 N
NaOH (20 mL), and then the solvent was evaporated. The resulting pale
yellow foam (0.71 g) was chromatographed on silica gel (30 g), and eluted
with 5:1 CHCl3/MeOH. Compound 5 (0.20 g, 71%) was isolated as white
[5] H. R. Yang, R. L. Drain, C. A. Franco, J. M. Clark, Antivir. Res. 1996,
29, 233–241.
25
solid that, after recrystallization from H2O, had mp 303–305 °C. [α]D
107.72 (c 0.61, MeOH). IR (KBr) cm–1: 3386, 2932, 1705, 1636, 1601, 1560,
1474, 1361. 1H NMR (DMSO-d6) δ: 0.66 and 1.19 (2 s, 3H+3H, >C(CH3)2),
1.24–1.42 (m, 4H), 1.76–1.81 (m, 1H, C3′-H), 2.26–2.33 (m, 2H), 3.31–3.41
(m, 2H, OCH2), 4.24–4.30 (m, 1H, C1′-H), 4.39 (t, 1H, D2O exch., J = 5.12
Hz, OH), 6.32 (s, 2H, D2O exch., NH2), 7.70 (s, 1H, C8-H), 10.50 (s, 1H,
[6] D. J. Tenney, G. Yamanaka, S. M. Voss, C. W. Cianci, A. V. Tuomari,
A. K. Sheaffer, M. Alam, R. J. Colonno, Antimicrob. Agents
Chemother. 1997, 41, 2680–2685.
[7] L. Agrafoglio, E. Suhas, A. Farese, R. Condom, R. Challand, R. A. Earl,
R. Guedj, Tetrahedron 1994, 50, 10611–10670.
Arch. Pharm. Pharm. Med. Chem. 332, 348–352 (1999)

352
Caamaño and co-workers
[12] (1R)-7,7-Dimethyl-2-azabicyclo[4.1.1]octane (13). IR (film) cm–1
[8] J. E. R. Borges, F. Fernández, X. García, A. R. Hergueta, C. López, G.
Andrei, R. Snoeck, M. Witvrouw, J. Balzarini, E. De Clercq, Nucleo-
sides & Nucleotides 1998, 17, 1237–1253.
:
3352, 2950, 1558, 1464, 1364, 1319, 1015. 1H NMR (CDCl3) δ: 0.93
and 1.07 (2 s, 3H+3H, >C(CH3)2), 1.10–1.36 (m, 2H), 1.42–1.58 (m,
2H one of then D2O exch., NH), 1.75–1.86 (m, 1H), 1.93–2.05 (m, 2H),
2.57 (t, 2H, J = 7.30 Hz), 3.50 (dd, 1H, J = 6.25, 10.84 Hz), 3.58 (ddd,
1H, J = 3.57, 7.79, 10.82 Hz). 13C NMR (CDCl3) δ: 16.90 (CH2), 26.93
(CH3), 31.38 (CH3), 34.96 (CH2), 39.95 (C), 40.52 (CH2), 40.98 (CH),
44.93 (CH2), 64.04 (CH). Anal. C9H17N: C, H, N.
[9] a) J. Balzarini, P. Herdewijin, E. De Clercq, J. Biol. Chem. 1989, 264,
6127–6133; b) L. L. Bondoc Jr., W. M. Shannon, J. A. Secrist III, R.
Vince, A. Friedland, Biochemistry 1990, 29, 9839–9843; c) W. P.
Parker, S. C. Shaddix, B. J. Bowdon, L. M. Rose, R. Vince, W. M.
Shannon, L. L. Bennet Jr., Antimicrob. Agents Chemother. 1993, 37,
1004–1009.
[13] R. Vince, M. Hua J. Med. Chem. 1990, 33, 17–21.
[10] a) L. B. Akella, R. Vince, Tetrahedron 1996, 52, 8407–8412; b) Ref.
[14] E. De Clercq, In In vitro and ex vivo test systems to rationalize drug
design and delivery, D. Crommelin, P. Couvreur, D. Duchêne Eds.;
Editions de Santé, Paris, France, 1994, pp 108–125.
8.
[11] J. M. Blanco, O. Caamaño, F. Fernández, G. Gómez, I. Nieto Synthesis
1996, 281–284.
Received: April 26, 1999 [FP390]
Arch. Pharm. Pharm. Med. Chem. 332, 348–352 (1999)