Cytostatic 6-arylpurine nucleosides V.+ synthesis of 8-substituted 6-phenylpurine ribonucleosides

Article abstract of DOI:10.1135/cccc20030837

Regioselective Suzuki-Miyaura reaction of 8-bromo-6-iodo-9-(2,3,5-tri-O-acetyl-β-D-ribofuranosyl)purine with phenylboronic acid gave 8-bromo-6-phenylpurine derivative that was used for cross-coupling reactions (with PhB(OH)₂, Me₃Al, Et₃Al, BnZnCl) or nucleophilic substitutions (with NaOH, NaOMe, NH₃, NHMe₂ or thiourea). A series of 8-X-substituted 6-phenyl-9-(β-D-ribofuranosyl)purines (X = Ph, Me, Et, Bn, OH, OMe, NH₂, NMe₂, SH) was prepared in this way directly or after deprotection. None of the title nucleosides exhibited any considerable cytostatic activity.

Full text of DOI:10.1135/cccc20030837

Cytostatic 6-Arylpurine Nucleosides
837
CYTOSTATIC 6-ARYLPURINE NUCLEOSIDES V.+ SYNTHESIS OF
8-SUBSTITUTED 6-PHENYLPURINE RIBONUCLEOSIDES
1,
2
++
Michal HOCEK *, Dana HOCKOVÁ and Jan ŠTAMBASKÝ
Institute of Organic Chemistry and Biochemistry, Academy of Sciences of the Czech Republic,
1
2
CZ-16610 Prague 6, Czech Republic; e-mail: hocek@uochb.cas.cz, lasice@uochb.cas.cz
Received Decem ber 17, 2002
Accepted Jan uary 30, 2003
Dedicated to the memory of Professor Otakar Červinka.
Regioselective Suzuki–Miyaura reaction of 8-brom o-6-iodo-9-(2,3,5-tri-O-acetyl-β-D-ribo-
furan osyl)purin e with ph en ylboron ic acid gave 8-brom o-6-ph en ylpurin e derivative th at was
used for cross-couplin g reaction s (with Ph B(OH)2, Me3Al, Et3Al, Bn Zn Cl) or n ucleoph ilic
substitution s (with NaOH, NaOMe, NH3, NHMe2 or th iourea). A series of 8-X-substituted
6-ph en yl-9-(β-D-ribofuran osyl)purin es (X = Ph , Me, Et, Bn , OH, OMe, NH2, NMe2, SH) was
prepared in th is way directly or after deprotection . Non e of th e title n ucleosides exh ibited
an y con siderable cytostatic activity.
Keyw ord s: Purin es; Nucleosides; Cross-couplin g reaction s; Nucleoph ilic substitution s;
Suzuki–Miyaura reaction ; Halodeam in ation s; An tin eoplastic agen ts.
Recen tly, a sign ifican t cytostatic activity of 6-arylpurin e ribon ucleosides
h as been described1. Th e SAR studies revealed a crucial in fluen ce of th e
presen ce of th e β-D-ribofuran osyl m oiety in th e position N-9 an d th e effect
of substitution at th e purin e an d ben zen e rin gs on th eir biological activity.
Th us 6-(4-substituted ph en yl)purin e ribon ucleosides displayed sign ifican t
in vitro cytostatic activity (in h ibition of th e cell growth of L1210, HeLa S3
an d CCRF-CEM cell cultures, IC50 = 0.25–10 µm ol/l), wh ile th e 6-ph en yl-
purin e bases an d 2-am in o-6-ph en ylpurin e ribon ucleosides were en tirely in -
active in th ese assays. Later, also several 6-h etaryl an d 6-ben zylpurin e
ribon ucleosides were foun d to sh ow2 con siderable activity. In con trast,
sugar-m odified 6-arylpurin e n ucleosides3 (2′- or 5′-deoxyribosides an d
+ For part IV, see ref.6
++On leave from Departm en t of Organ ic Ch em istry, In stitute of Ch em ical Tech n ology, Prague.
Collect. Czech. Chem. Commun. (Vol. 68) (2003)
doi:10.1135/cccc20030837

838
Hocek, Hocková, Štambaský:
acyclon ucleosides) as well as 6-(h et)arylpurin e acyclic n ucleotide an a-
logues4,5 were devoid of an y cytostatic activity. Also in active were 2-sub-
stituted 6-ph en ylpurin e n ucleosides6. As an exten sion of th e SAR study of
th is class of com poun ds, we report h ere on th e syn th esis of 6-ph en ylpurin e
ribon ucleosides bearin g diverse substituen ts in th e position 8. Un like in po-
sition 2, a substituen t in position 8 does n ot in terfere with h ydro-
gen -bon din g to a com plem en tary n ucleobase, but in prin ciple could
m odulate a bin din g to an active site of th e target cellular system .
Our syn th etic strategy relied on regioselective Suzuki–Miyaura cross-
couplin g reaction s of dih alopurin es with ph en ylboron ic acid7–9 (for a com -
preh en sive review on cross-couplin gs in purin es, see ref.10). Wh ile th e
regioselectivity of th is reaction was already exten sively studied in
2,6-dih alopurin es6,8,11, in 6,8-dih alopurin es on ly regioselectivities of an alo-
gous Stille couplin gs with organ ostan n an es an d Negish i reaction s with
organ ozin c reagen ts were described12. 6,8-Dich loropurin es prefer th e reac-
tion in position 6, wh ile 8-brom o- or 8-iodo-6-ch loropurin es react preferen -
tially in position 8. Con siderin g th e regioselectivity rules, an acyl-protected
8-brom o-6-iodopurin e ribon ucleoside sh ould be a good startin g com poun d
for th is study: it sh ould be easily available from kn own 13 8-brom oaden o-
sin e an d th e Suzuki–Miyaura reaction sh ould proceed preferen tially in th e
position 6.
Our first goal was an efficien t larger-scale syn th esis of kn own 14,15
2′,3′,5′-tri-O-acetyl-8-brom oaden osin e (1) as a suitable precursor. In our
h an ds, th e publish ed procedures for th e brom in ation of 2′,3′,5′-tri-O-acetyl-
aden osin e m akin g use of Br2/dioxan e14 or N-brom oacetam ide/ch loroform 15
were n ot practical – both th ese reaction s led to com plex m ixtures from
wh ich th e required com poun d 1 was isolated by colum n ch rom atograph y
in low yields. Th erefore, we h ave prepared 8-brom oaden osin e by a kn own 13
efficien t brom in ation of aden osin e with brom in e in acetate buffer (pH 4).
Its subsequen t acetylation by acetic an h ydride in pyridin e followed by
treatm en t with eth an ol afforded th e desired crystallin e 1 in good yield
without using chrom atography. The protected 8-brom oadenosine 1 was easily
converted to 8-bromo-6-iodo-9-(2,3,5-tri-O-acetyl-β-D-ribofuranosyl)purin e (2)
by m ean s of iododeam in ation reaction usin g isopen tyl n itrite (i-Am ONO)
an d CH2I2 in 45% yield (an alogously to th e kn own 16 iododeam in ation of
acetylated aden osin e).
Th e n ext step was th e regioselective Suzuki–Miyaura cross-couplin g reac-
tion (for a review on th e use of th is reaction in purin es, see ref.17) of
dih alopurin e 2 with on e equivalen t of ph en ylboron ic acid. Un der stan dard
Collect. Czech. Chem. Commun. (Vol. 68) (2003)

Cytostatic 6-Arylpurine Nucleosides
839
an h ydrous con dition s in toluen e usin g K2CO3 as a base an d Pd(PPh 3)4 as
catalyst, th is reaction afforded regioselectively th e 8-brom o-6-ph en ylpurin e
n ucleoside 3 in 56% yield (27% of un reacted startin g com poun d 2 was re-
covered). An alogous cross-couplin g of 2 with 3.6 equivalen ts of ph en yl-
boron ic acid gave th e 6,8-diph en ylpurin e 4a in a good yield of 83%
(Sch em e 1).
NH2
NH2
N
N
N
N
Br
N
N
N
O
N
O
HO
AcO
OH OH
1. Ac2O,
pyridine
2. EtOH
OAc OAc
Br2, dioxane, Na2HPO4
or
NBA, CHCl3
(complex mixtures of products)
PhB(OH)2
K2CO3
Pd(PPh3)4
NH2
I
i-AmONO,
CH2I2
N
N
N
N
N
N
N
N
N
Br
Br
Br
N
O
N
O
N
O
AcO
AcO
AcO
OAc OAc
OAc OAc
OAc OAc
3
2
1
cross-coupling
i)
Pd(PPh3)4
SN
X
ii)
N
NaOMe
AcO
N
N
N
N
R
N
N
N
R
X
N
N
O
N
O
N
O
HO
HO
OH OH
OH OH
OAc OAc
4,5
R
5
6
6
X
4
a phenyl
b methyl
c ethyl
a OCH3
b OH
c NH2
d N(CH3)2
e SH
d benzyl
i) (a) PhB(OH)2, (b) Me3Al, (c) Et3Al, (d) BnZnCl;
ii) (a) NaOMe, (b) NaOH, (c) NH3/MeOH, (d) Me2NH/EtOH; (e) 1. thiourea, 2. NaOMe
SCHEME 1
Collect. Czech. Chem. Commun. (Vol. 68) (2003)

840
Hocek, Hocková, Štambaský:
Th e 8-brom o-6-ph en ylpurin e 3 was used as a key in term ediate for furth er
derivatization s in position 8 (for som e recen t exam ples of cross-couplin g re-
action s in position 8, see ref.18). Cross-couplin g reaction s of 3 with
trim eth ylalum in ium 19 an d trieth ylalum in ium gave rise to th e 8-m eth yl-
an d 8-eth ylpurin es 4b (70% yield) an d 4c (55% yield), respectively. Sim i-
larly, th e reaction of 3 with ben zylzin c ch loride2 gave th e 8-ben zyl-
6-ph en ylpurin e 4d in 52% yield. Treatm en t of th e protected 6,8-disubsti-
tuted purines 4a–4d with catalytic am ount of sodium m ethoxide in m ethanol
gave free ribon ucleosides 5a–5d in th e yields of 58–83% after crystalliza-
tion .
Nucleoph ilic substitution s of th e 8-brom o-6-ph en ylpurin e 3 were an -
oth er possible approach for th e derivatization as th e brom in e in position 8
of purin e is very reactive20–22. Surprisin gly, even th e treatm en t of th e
8-brom opurin e 3 with catalytic am oun t of sodium m eth oxide in m eth an ol
at am bien t tem perature (origin ally m ean t to sim ply deprotect th e
brom opurin e n ucleoside) led to com plete displacem en t of th e brom in e to
give th e 8-m eth oxy-6-ph en ylpurin e ribon ucleoside 6a in 84% yield. Th is
h igh reactivity of 8-brom o-6-ph en ylpurin e is in con trast to th at of 2-h alo-
6-ph en ylpurin e n ucleosides th at were deprotected6 un der th e sam e con di-
tion s with out an y n ucleoph ilic substitution of th e h alogen e (Cl, Br or I) in
position 2. An alogously, treatm en t of com poun d 3 with aqueous NaOH
gave th e 8-h ydroxypurin e n ucleoside 6b in 65% yield (th is sim ple reaction
turn ed out to be m ore efficien t th an stan dard use of sodium acetate in ace-
tic acid20, wh ich led to com plex m ixture). Reaction of com poun d 3 with
saturated m eth an olic am m on ia at am bien t tem perature gave a m ixture of
th e desired 8-am in o-6-ph en ylpurin e n ucleoside 6c (54%) an d 8-m eth oxy-
purin e 6a as side-product (15%). Th is very h igh reactivity is in con trast to
th at of 2′,3′,5′-tri-O-acetyl-8-brom oaden osin e, wh ich was deprotected15 by
m eth an olic am m on ia with out an y substitution of th e brom in e. Eth an olic
dim eth ylam in e (an alogously to ref.21) also reacted with 3 at am bien t tem -
perature to give th e 8-dim eth ylam in o derivative 6d in 77% yield. In all th e
above n ucleoph ilic substitution s, th e acetyl protective groups were cleaved
sim ultan eously to give directly th e free ribon ucleosides 6a–6d . Treatm en t
of 3 with thiourea (analogously to ref.22) gave 6-phenyl-8-sulfanyl-9-(2,3,5-tri-
O-acetyl-β-D-ribofuran osyl)purin e th at was deprotected to th e free
n ucleoside 6e by NaOMe in m eth an ol. Som e of th e fin al free n ucleosides
could n ot be crystallized directly from th e crude products an d h ad to be pu-
rified by preparative HPLC.
All com poun ds were com pletely ch aracterized by NMR an d m ass spectra.
Assign m en t of th e sign als was based on COSY, HMBC an d HMQC experi-
Collect. Czech. Chem. Commun. (Vol. 68) (2003)

Cytostatic 6-Arylpurine Nucleosides
841
m en ts, as well as on an alogy with our previous results1–7. In m ost cases, th e
presen ce of th e substituen t in position 8 caused an up-field sh ift of th e
H-1′. Som e of th e fin al free n ucleosides appeared to be quite h ygroscopic.
In com poun ds 6b an d 6e, th ere is a possibility of tautom erism of
8-h ydroxy- or 8-sulfan ylpurin e to 7H-purin -8(9H)-on e or -th ion e,
respectively. We h ave n ot studied th is ph en om en on th orough ly but, as th e
13C NMR spectral pattern s were sim ilar to th e recen tly described an alogous
8-substituted aden in es20,22, we suppose th at also h ere th e 8-(th i)oxo-
tautom ers prevail.
In con clusion , th e 8-substituted 6-ph en ylpurin e ribon ucleosides were
prepared by regioselective Suzuki–Miyaura cross-couplin g reaction of
8-brom o-6-iodopurin e n ucleoside 2 with ph en ylboron ic acid, followed by
an oth er cross-couplin g or n ucleoph ilic substitution an d/or deprotection .
Th e title n ucleoside an alogues 5a–5d , 6a–6e were tested for th eir cytostatic
activity (in h ibition of cell growth of th e followin g cell cultures: m ouse leu-
kem ia L1210 cells (ATCC CCL 219), h um an prom yelocytic leukem ia HL60
cells (ATCC CCL 240), h um an cervix carcin om a HeLaS3 cells (ATCC CCL
2.2) an d h um an T lym ph oblastoid CCRF-CEM cell lin e (ATCC CCL 119)).
In con trast to th e sign ifican t in vitro activity of th e correspon din g
8-un substituted 6-ph en ylpurin e ribon ucleosides in th ese cell lin es, n on e of
th e 8-substituted 6-ph en ylpurin e n ucleosides exerted an y con siderable ac-
tivity in an y of th ese assays23.
EXPERIMENTAL
Un less oth erwise stated, solven ts were evaporated at 40 °C/2 kPa an d com poun ds were dried
at 60 °C/2 kPa. Meltin g poin ts were determ in ed on a Kofler block an d are un corrected. Opti-
cal rotation s were m easured at 25 °C on a Autopol IV (Rudolph Research An alytical)
polarim eter, [α]D values are given in 10–1 deg cm 2 g–1. NMR spectra were m easured on a
Bruker AMX-3 400 (400 MHz for 1H an d 100.6 MHz for 13C n uclei), a Bruker DRX 500 (500
MHz for 1H an d 125.8 MHz for 13C). Ch em ical sh ifts are given in ppm (δ-scale), couplin g
con stan ts (J) in Hz. TMS was used as in tern al stan dard. Mass spectra were m easured on a
ZAB-EQ (VG An alytical) spectrom eter usin g FAB (ion ization by Xe, acceleratin g voltage 8 kV,
glycerol m atrix). Toluen e was degassed in vacuo an d stored over m olecular sieves un der ar-
gon . DMF was distilled from P2O5, degassed in vacuo an d stored over m olecular sieves un der
argon . THF was refluxed with Na an d ben zoph en on e un der argon an d fresh ly distilled prior
to use. Preparative HPLC separation s (ca 70 m g batch es of m ixtures) were perform ed on a
colum n (20
× 100 m m ) packed with 7 µm C18 reversed ph ase (W aters Delta 600
ch rom atograph ) usin g a lin ear gradien t MeOH/H2O (1:4 to 9:1) as eluen t. Preparative TLC
was carried out on 40 × 17 × 0.4 cm loose layers of silica gel con tain in g a UV in dicator.
Cytostatic activity tests were perform ed as described in ref.1 8-Brom oaden osin e was prepared
accordin g to ref.13
Collect. Czech. Chem. Commun. (Vol. 68) (2003)

842
Hocek, Hocková, Štambaský:
8-Brom o-2′,3′,5′-tri-O-acetyladen osin e (1)
Acetic an h ydride (33 m l, 350 m m ol) was added to a stirred solution of 8-brom oaden osin e
(9 g, 26 m m ol) in pyridin e (200 m l) at 0 °C. Th e stirred m ixture was slowly allowed to reach
am bien t tem perature an d th e stirrin g was con tun ued overn igh t. EtOH (10 m l) was added
an d th e m ixture was stirred for an oth er 1 h . Th en th e solven ts were evaporated in vacuo an d
th e residue was co-distilled with EtOH (2 × 100 m l) an d toluen e (2 × 100 m l). Th e residue
was re-crystallized from EtOH/toluen e (1:1) to give 7.1 g (58%) of com poun d 1; m .p.
188–189 °C (ref.15 187–188 °C).
8-Brom o-6-iodo-9-(2,3,5-tri-O-acetyl-β-D-ribofuran osyl)purin e (2)
A m ixture of com poun d 1 (8 g, 17 m m ol), CH2I2 (23.2 m l, 288 m m ol), i-Am ONO (24 m l,
178 m m ol) an d aceton itrile (130 m l) was refluxed for 8 h . Th en th e solven ts were evapo-
rated in vacuo, th e residue was dissloved in ch loroform (200 m l) an d wash ed with 10% aque-
ous Na2S2O3 (2 × 150 m l) an d H2O (150 m l). Th e organ ic ph ase was evaporated an d th e
residue was ch rom atograph ed on a silica gel colum n (250 g, eth yl acetate/h exan es 1:3 to
3:1) to give th e crude product wh ich was recrystallized from CH2Cl2/h eptan e to yield 2
(4.4 g, 45%) as yellowish solid; m .p. 149–151 °C, [α]D –0.3 (c 0.4, DMF). FAB MS, m/z (rel.%):
585/583 (50) [M + H], 327/325 (40), 92 (100). 1H NMR (CDCl3, 500 MHz): 2.03, 2.10 an d
2.16 (3 × s, 3 × 3 H, CH3CO); 4.31 (dd, 1 H, J = 12.0 an d 5.8, H-5′a); 4.39–4.47 (m , 1 H,
H-4′); 4.49 (dd, 1 H, J = 12.0 an d 3.6, H-5′b); 5.86 (t, 1 H, J = 5.9, H-3′); 6.12 (d, 1 H, J = 4.5,
H-1′); 6.32 (dd, 1 H, J = 5.9 an d 4.5, H-2′); 8.62 (s, 1 H, H-2). 13C NMR (CDCl3, 125.8 MHz):
20.35, 20.48 an d 20.62 (CH3); 62.73 (CH2-5′); 70.23 (CH-3′); 71.81 (CH-2′); 80.25 (CH-4′);
89.11 (CH-1′); 120.71 (C-5); 133.31, 139.39 an d 148.32 (C-4, C-6 an d C-8); 151.89 (CH-2);
169.34, 169.47 an d 170.38 (CO). HR MS (FAB), calculated for C16H1781BrIN4O7 [M + H]:
584.9305; foun d: 584.9326. For C16H16BrIN4O7 (583.1) calculated: 32.96% C, 2.77% H,
13.70% Br, 21.76% I, 9.61% N; foun d: 33.16% C, 2.87% H, 13.75% Br, 21.39% I, 9.29% N.
8-Brom o-6-ph en yl-9-(2,3,5-tri-O-acetyl-β-D-ribofuran osyl)purin e (3)
Toluen e (20 m l) was added to an argon -purged flask con tain in g 2 (1.162, 2 m m ol),
ph en ylboron ic acid (270 m m ol, 2.2 m m ol), K2CO3 (400 m g, 2.9 m m ol) an d Pd(PPh 3)4
(58 m g, 0.05 m m ol). Th e m ixture was stirred at 100 °C un der argon for 8 h . Th en th e sol-
ven t was evaporated in vacuo an d th e residue was ch rom atograph ed on a silica gel colum n
(100 g, eth yl acetate/h exan es 1:3 to 3:1) to give th e product 3 (600 m g, 56%) followed by
un reacted startin g com poun d (320 m g, 27%). Com poun d 3 was isolated as a colorless foam .
FAB MS, m/z (rel.%): 535/533 (15) [M + H], 377/375 (100). 1H NMR (CDCl3, 500 MHz): 2.05,
2.12 an d 2.18 (3 × s, 3 × 3 H, CH3CO); 4.36 (dd, 1 H, J = 12.0 an d 5.7, H-5′a); 4.42–4.46 (m ,
1 H, H-4′); 4.54 (dd, 1 H, J = 12.0 an d 2.8, H-5′b); 5.98 (t, 1 H, J = 5.9, H-3′); 6.21 (d, 1 H, J =
4.0, H-1′); 6.42 (t, 1 H, J = 5.0, H-2′); 7.54–7.56 (m , 3 H, H-arom .); 8.70 (d, 2 H, J = 7.3,
H-arom .); 8.98 (s, 1 H, H-2). 13C NMR (CDCl3, 125.8 MHz): 20.41, 20.51 an d 20.65 (CH3);
62.87 (CH2-5′); 70.34 (CH-3′); 72.03 (CH-2′); 80.11 (CH-4′); 88.81 (CH-1′); 128.73, 129.74
an d 131.34 (CH-arom .); 131.52, 132.61 an d 134.84 (C-5, C-6 an d C-i-arom .); 152.36 (CH-2);
152.84 an d 154.20 (C-4 an d C-8); 169.41, 169.54 an d 170.52 (CO). HR MS (FAB), calculated
for C22H2281BrN4O7 [M + H]: 535.0651; foun d: 535.0647.
Collect. Czech. Chem. Commun. (Vol. 68) (2003)

Cytostatic 6-Arylpurine Nucleosides
843
6,8-Diph en yl-9-(2,3,5-tri-O-acetyl-β-D-ribofuran osyl)purin e (4a)
Toluen e (10 m l) was added to an argon -purged flask con tain in g 2 (290, 0.5 m m ol),
ph en ylboron ic acid (224 m m ol, 1.8 m m ol), K2CO3 (200 m g, 1.5 m m ol) an d Pd(PPh 3)4
(29 m g, 0.025 m m ol). Th e m ixture was stirred at 100 °C un der argon for 8 h . Th en th e sol-
ven t was evaporated in vacuo an d th e residue was ch rom atograph ed on a silica gel colum n
(100 g, eth yl acetate/h exan es 1:3 to 3:1) to give th e product 4a (220 m g, 83%) as a colorless
foam . FAB MS, m/z (rel.%): 531 (15) [M + H], 273 (100). 1H NMR (CDCl3, 400 MHz): 2.02,
2.07 an d 2.12 (3 × s, 3 × 3 H, CH3CO); 4.36–4.42 (m , 2 H) an d 4.54–4.60 (m , 1 H, H-4′ an d
H-5′); 6.06–6.08 (m , 2 H, H-1′ an d H-3′); 6.56–6.58 (m , 1 H, H-2′); 7.49–7.61 (m , 6 H,
H-arom .); 7.88–7.89 (m , 2 H, H-arom .); 8.83 (d, 2 H, J = 6.7, H-arom .); 9.03 (s, 1 H, H-2).
13C NMR (CDCl3, 100.6 MHz): 20.36, 20.49 an d 20.69 (CH3); 62.90 (CH2-5′); 70.56 (CH-3′);
72.05 (CH-2′); 79.93 (CH-4′); 87.98 (CH-1′); 127.94, 128.62, 129.00, 129.87, 129.98 an d
130.97 (CH-arom .); 128.83 an d 131.22 (C-5 an d C-i-arom .); 152.02 (CH-2); 153.33, 154.66
an d 155.33 (C-4, C-6 an d C-8); 169.30, 169.48 an d 170.63 (CO). HR MS (FAB), calculated for
C
28H27N4O7 [M + H]: 531.1880; foun d: 531.1862.
8-Meth yl-6-ph en yl-9-(2,3,5-tri-O-acetyl-β-D-ribofuran osyl)purin e (4b)
Trim eth ylalum in ium (2 M solution in toluen e, 1.5 m l, 3 m m ol) was added dropwise to a
stirred solution of 3 (356 m g, 0.66 m m ol) an d Pd(PPh 3)4 (58 m g, 0.05 m m ol) in THF (15 m l)
un der argon atm osph ere at room tem perature. Th e m ixture was th en stirred at 80 °C for 7 h
an d allowed to stan d at room tem perature overn igh t. Th en th e m ixture was poured in to a
m ixture of crush ed ice (200 m l) an d NaHCO3 (1 g) an d extracted in to ch loroform (2 ×
100 m l). Th e organ ic layers were dried with MgSO4 an d evaporated. Th e residue was
ch rom atograph ed on a colum n (100 g, eth yl acetate/h exan es 1:3 to 3:1) to give th e product
4b (220 m g, 70%) as a colorless foam . FAB MS, m/z (rel.%): 469 (32) [M + H], 211 (100). 1H
NMR (CDCl3, 500 MHz): 2.04, 2.11 an d 2.18 (3 × s, 3 × 3 H, CH3CO); 2.77 (s, 3 H, CH3);
4.36 (dd, 1 H, J = 12.0 an d 5.5, H-5′a); 4.41–4.45 (m , 1 H, H-4′); 4.54 (dd, 1 H, J = 12.0 an d
3.1, H-5′b); 5.98 (t, 1 H, J = 6.0, H-3′); 6.07 (d, 1 H, J = 4.4, H-1′); 6.31 (dd, 1 H, J = 4.4 an d
6.0, H-2′); 7.50–7.58 (m , 3 H, H-arom .); 8.72 (d, 2 H, J = 7.3, H-arom .); 8.95 (s, 1 H, H-2).
13C NMR (CDCl3, 125.8 MHz): 14.84, 20.47, 20.54 an d 20.64 (CH3); 63.00 (CH2-5′); 70.45
(CH-3′); 72.48 (CH-2′); 79.90 (CH-4′); 87.05 (CH-1′); 128.64, 129.62 an d 130.74 (CH-arom .);
130.48 an d 135.65 (C-5 an d C-i-arom .); 151.65 (CH-2); 153.21, 153.56 an d 153.65 (C-4, C-6
an d C-8); 169.57 an d 170.48 (CO). HR MS (FAB), calculated for C23H25N4O7 [M + H]:
469.1723; foun d: 469.1717.
8-Eth yl-6-ph en yl-9-(2,3,5-tri-O-acetyl-β-D-ribofuran osyl)purin e (4c)
Th is com poun d was prepared in th e sam e m an n er as 4b startin g from 3 (270 m g, 0.5 m m ol),
Et3Al (0.9 M solution in h exan e, 2 m l, 1.8 m m ol), Pd(PPh 3)4 (29 m g, 0.025 m m ol) an d THF
(10 m l). Yield 135 m g (55%). Colorless foam . FAB MS, m/z (rel.%): 483 (10) [M + H], 225
(100). 1H NMR (CDCl3, 400 MHz): 1.51 (t, 3 H, J = 7.4, CH3CH2); 2.03, 2.09 an d 2.16 (3 × s,
3 × 3 H, CH3CO); 3.03 (q, 2 H, J = 7.4, CH2CH3); 4.34–4.43 (m , 2 H, H-5′a an d H-4′); 4.53
(dd, 1 H, J = 11.4 an d 2.4, H-5′b); 5.97 (t, 1 H, J = 5.6, H-3′); 6.05 (d, 1 H, J = 4.3, H-1′); 6.38
(dd, 1 H, J = 4.3 an d 5.6, H-2′); 7.49–7.57 (m , 3 H, H-arom .); 8.76 (d, 2 H, J = 7.3, H-arom .);
8.93 (s, 1 H, H-2). 13C NMR (CDCl3, 100.6 MHz): 11.59 (CH3CH2); 20.43, 20.53 an d 20.63
(CH3); 21.55 (CH3CH2); 62.98 (CH2-5′); 70.55 (CH-3′); 72.31 (CH-2′); 79.96 (CH-4′); 86.77
Collect. Czech. Chem. Commun. (Vol. 68) (2003)

844
Hocek, Hocková, Štambaský:
(CH-1′); 128.58, 129.72 an d 130.71 (CH-arom .); 135.75 (C-i-arom .); 151.57 (CH-2); 153.35,
153.54 an d 157.91 (C-4, C-6 an d C-8); 169.46, 169.52 an d 170.50 (CO). HR MS (FAB), calcu-
lated for C24H27N4O7 [M + H]: 483.1880; foun d: 483.1868.
8-Ben zyl-6-ph en yl-9-(2,3,5-tri-O-acetyl-β-D-ribofuran osyl)purin e (4d )
THF (10 m l) was added to an argon -purged flask con tain in g th e 3 (420 m g, 0.8 m m ol) an d
Pd(PPh 3)4 (59 m g, 0.05 m m ol). Th e m ixture was stirred at am bien t tem perature for 10 m in
an d, after dissolution of th e solids, a solution of ben zylzin c ch loride (Rieke® organ ozin c re-
agen t, 0.5 M solution in THF, 5 m l, 2.5 m m ol) was added dropwise at am bien t tem perature
(with in 10 m in ). Th e stirrin g at am bien t tem perature was con tin ued for 15 m in followed by
stirrin g at 60 °C for 8 h . Th en th e reaction m ixture was allowed to stan d overn igh t at am bi-
en t tem perature an d poured in to saturated aqueous NH4Cl (10 m l). To th is m ixture, satu-
rated aqueous Na2EDTA (10 m l) was added an d th e m ixture was stirred for 10 m in . Th en th e
reaction m ixture was extracted with eth yl acetate (3 × 20 m l) an d th e collected organ ic lay-
ers were wash ed with saturated aqueous Na2EDTA (20 m l) an d brin e (20 m l), dried with an -
h ydrous MgSO4 an d evaporated in vacuo. Colum n ch rom atograph y of th e residue on silica
gel (50 g, eth yl acetate/h exan es 1:3 to 3:1) afforded, after evaporation an d dryin g, th e prod-
uct 4d as am orph ous solid (223 m g, 52%). FAB MS, m/z (rel.%): 545 (30) [M + H], 287 (100).
1H NMR (CDCl3, 500 MHz): 1.85, 2.05 an d 2.10 (3 × s, 3 × 3 H, CH3CO); 4.31–4.61 (m , 5 H,
H-4′, H-5′ an d CH2Ph ); 5.94–5.97 (m , 2 H, H-1′ an d H-3′); 6.24 (dd, 1 H, J = 4.4 an d 5.7,
H-2′); 7.25–7.25 (m , 5 H, H-arom .); 7.52–7.63 (m , 3 H, H-arom .); 8.77 (d, J = 7.1, H-arom .);
9.05 (s, 1 H, H-2). 13C NMR (CDCl3, 125.8 MHz): 20.20, 20.44 an d 20.66 (CH3); 34.83
(CH2Ph ); 63.03 (CH2-5′); 70.31 (CH-3′); 72.01 (CH-2′); 79.76 (CH-4′); 87.11 (CH-1′); 127.30,
128.42, 128.64, 128.95, 129.78 an d 130.85 (CH-arom .); 135.35 an d 135.65 (C-5 an d
C-i-arom .); 151.93 (CH-2); 153.24, 154.18 an d 154.75 (C-4, C-6 an d C-8); 168.89, 169.34
an d 170.53 (CO). HR MS (FAB), calculated for C24H27N4O7 [M + H]: 545.2036; foun d:
545.2068.
Deprotection of Nucleosides 4a–4d . Gen eral Procedure
A 1 M m eth an olic MeONa (100 µl, 0.1 m m ol) was added to a solution of a protected
n ucleoside 4a–4d (0.25–0.5 m m ol) in MeOH (20 m l) an d th e m ixture was stirred at am bien t
tem perature overn igh t. Th e solven t was evaporated an d th e residue was ch rom atograph ed
on
a colum n (silica gel 50 g, eth yl acetate/MeOH 9:1). Th e crude products were
recrystallized from EtOH (96% aq.)/toluen e/h eptan e to give free n ucleosides 5a–5d .
6,8-Diphenyl-9-(β-D-ribofuranosyl)purine (5a). Wh ite solid; yield 83%; m .p. 112–116 °C; [α]D
–31.3 (c 0.5, DMF). FAB MS, m/z (rel.%): 405 (10) [M + H], 273 (100). 1H NMR (DMSO-d6,
400 MHz): 3.58–3.65 (m , 1 H, H-5′a); 3.74–3.80 (m , 1 H, H-5′b); 3.94–3.98 (m , 1 H, H-4′);
4.27–4.30 (m , 1 H, H-3′); 5.11 (dd, 1 H, J = 6.9 an d 5.2, H-2′); 5.22 (d, 1 H, J = 4.6, 3′-OH);
5.36 (t, 1 H, J = 5.8, 5′-OH); 5.50 (d, 1 H, J = 6.1, 2′-OH); 5.88 (d, 1 H, J = 6.5, H-1′);
7.56–7.70 (m , 6 H, H-arom .); 7.89–7.92 (m , 2 H, H-arom .); 8.86 (d, 2 H, J = 7.6, H-arom .);
9.04 (s, 1 H, H-2). 13C NMR (DMSO-d6, 100.6 MHz): 61.91 (CH2-5′); 70.52 an d 70.62 (CH-2′
an d CH-3′); 86.27 (CH-4′); 89.41 (CH-1′); 128.71, 128.86, 129.43, 129.86, 131.02 an d 131.17
(CH-arom .); 130.69 an d 135.21 (C-5 an d C-i-arom .); 151.39 (CH-2); 152.91, 153.22 an d
156.15 (C-4, C-6 an d C-8). HR MS (FAB), calculated for C22H21N4O4 [M + H]: 405.1563;
foun d: 405.1530. For C22H20N4O4 (404.4) calculated: 65.34% C, 4.98% H, 13.85% N; foun d:
65.23% C, 5.31% H, 13.56% N.
Collect. Czech. Chem. Commun. (Vol. 68) (2003)

Cytostatic 6-Arylpurine Nucleosides
845
8-Methyl-6-phenyl-9-(β-D-ribofuranosyl)purine (5b). Wh ite solid; yield 71%; m .p. 149–151 °C;
[α]D –64.3 (c 0.5, DMF). FAB MS, m/z (rel.%): 343 (70) [M + H], 211 (100). 1H NMR
(DMSO-d6, 500 MHz): 2.76 (s, 1 H, CH3); 3.56–3.62 (m , 1 H, H-5′a); 3.73 (dd, 1 H, J = 4.5
an d 12.0, H-5′b); 3.98–4.02 (brm , 1 H, H-4′); 4.24–4.27 (m , 1 H, H-3′); 4.97–5.02 (m , 1 H,
H-2′); 5.18 (dd, 1 H, J = 4.8 an d 7.0, 5′-OH); 5.29 (d, 1 H, J = 4.8, 3′-OH); 5.44 (d, 1 H, J =
6.5, 2′-OH); 5.98 (d, 1 H, J = 6.6, H-1′); 7.56–7.62 (m , 3 H, H-arom .); 8.79–8.82 (m , 2 H,
H-arom .); 8.92 (s, 1 H, H-2). 13C NMR (DMSO-d6, 125.8 MHz): 15.49 (CH3); 62.21 (CH2-5′);
70.88 an d 71.98 (CH-2′ an d CH-3′); 86.55 (CH-4′); 88.87 (CH-1′); 129.10, 129.73 an d 131.40
(CH-arom .); 130.53 (C-5); 135.79 (C-i-arom .); 151.28 (CH-2); 151.82, 153.72 an d 155.77
(C-4, C-6 an d C-8). HR MS (FAB), calculated for C17H19N4O4 [M + H]: 343.1406; foun d:
343.1437. For C17H18N4O4 (342.3) calculated: 59.64% C, 5.30% H, 16.37% N; foun d: 59.35% C,
5.45% H, 16.05% N.
8-Ethyl-6-phenyl-9-(β-D-ribofuranosyl)purine (5c). Yellowish h ygroscopic solid; yield 68%;
m .p. 133–136 °C; [α]D –52.3 (c 0.4, DMF). FAB MS, m/z (rel.%): 357 (15) [M + H], 225 (100).
1H NMR (DMSO-d6, 400 MHz): 1.41 (t, 3 H, J = 7.1, CH3CH2); 3.09 (q, 2 H, J = 7.1,
CH3CH2); 3.55–3.62 (m , 1 H, H-5′a); 3.70–3.76 (m , 1 H, H-5′b); 4.02 (br, 1 H, H-4′); 4.27 (br,
1 H, H-3′); 5.06 (br, 1 H, H-2′); 5.17, 5.26 an d 5.43 (3 × brs, 3 × 1 H, OH); 5.96 (d, 1 H, J =
6.4, H-1′); 7.58–7.5 (m , 3 H, H-arom .); 8.80–8.84 (m , 2 H, H-arom .); 8.92 (s, 1 H, H-2). 13C
NMR (DMSO-d6, 100.6 MHz): 11.68 (CH3CH2); 21.20 (CH3CH2); 61.87 (CH2-5′); 70.56
(CH-3′); 71.35 (CH-2′); 86.20 (CH-4′); 88.33 (CH-1′); 126.62, 129.30 an d 130.91 (CH-arom .);
130.19 (C-5); 135.38 (C-i-arom .); 150.78 (CH-2); 151.60, 153.25 an d 159.49 (C-4, C-6 an d
C-8). HR MS (FAB), calculated for C18H21N4O4 [M + H]: 357.1563; foun d: 357.1516. For
C
18H20N4O4·2H2O (392.4) calculated: 55.09% C, 6.16% H, 14.28% N; foun d: 54.80% C,
6.32% H, 13.89% N.
8-Benzyl-6-phenyl-9-(β-D-ribofuranosyl)purine (5d). Yellowish solid; yield 58%; m .p. 160–162 °C;
[α]D –117.7 (c 0.5, DMF). FAB MS, m/z (rel.%): 419 (8) [M + H], 287 (100). 1H NMR
(DMSO-d6, 400 MHz): 3.56–3.62 (m , 1 H, H-5′a); 3.73 (dd, 1 H, J = 4.4 an d 12.0, H-5′b);
3.95–3.98 (m , 1 H, H-4′); 4.24–4.29 (m , 1 H, H-3′); 4.53 (s, 2 H, CH2Ph ); 4.99 (dd, 1 H, J =
6.3 an d 5.7, H-2′); 5.19 (dd, 1 H, J = 4.7 an d 7.5, 5′-OH); 5.26 (d, 1 H, J = 4.8, 3′-OH); 5.37
(d, 1 H, J = 6.7, 2′-OH); 6.02 (d, 1 H, J = 6.6, H-1′); 7.34–7.36 an d 7.57–7.61 (m , 8 H,
H-arom .); 8.78–8.81 (m , 2 H, H-arom .); 8.95 (s, 1 H, H-2). 13C NMR (DMSO-d6, 100.6 MHz):
33.50 (CH2Ph ); 61.77 (CH2-5′); 70.44 (CH-3′); 71.75 (CH-2′); 86.28 (CH-4′); 88.75 (CH-1′);
126.82, 128.62, 128.99, 129.35, 129.87 an d 131.02 (CH-arom .); 130.31 (C-5); 135.28 an d
135.88 (C-i-arom .); 151.03 (CH-2); 152.06, 153.07 an d 156.49 (C-4, C-6 an d C-8). HR MS
(FAB), calculated for C23H23N4O4 [M + H]: 419.1719; foun d: 419.1724. For C23H22N4O4
(418.4) calculated: 66.02% C, 5.30% H, 13.39% N; foun d: 66.34% C, 5.52% H, 13.07% N.
8-Meth oxy-6-ph en yl-9-(β-D-ribofuran osyl)purin e (6a)
Th is com poun d was obtain ed by treatm en t of 3 (190 m g, 0.36 m m ol) with 1 M m eth an olic
NaOMe (100 µl, 0.1 m m ol) in m eth an ol (10 m l) after an alogous work-up as in th e above
gen eral procedure. Wh ite solid; yield 84%; m .p. 102–104 °C; [α]D –39.4 (c 0.5, DMF). FAB
MS, m/z (rel.%): 359 (60) [M + H], 227 (100). 1H NMR (DMSO-d6, 500 MHz): 3.50–3.55 (brm ,
1 H, H-5′a); 3.64–3.69 (brm , 1 H, H-5′b); 3.91–3.95 (brm , 1 H, H-4′); 4.21–4.24 (brm , 1 H,
H-3′); 4.28 (s, 3 H, OCH3); 4.95–5.03 (m , 2 H, H-2′ an d 5′-OH); 5.21 (d, 1 H, J = 4.6, 3′-OH);
5.44 (d, 1 H, J = 5.6, 2′-OH); 5.89 (d, 1 H, J = 6.0, H-1′); 7.54–7.60 (m , 3 H, H-arom .);
7.72–7.74 (m , 2 H, H-arom .); 8.82 (s, 1 H, H-2). 13C NMR (DMSO-d6, 125.8 MHz): 58.02
Collect. Czech. Chem. Commun. (Vol. 68) (2003)

846
Hocek, Hocková, Štambaský:
(OCH3); 61.87 (CH2-5′); 70.49 an d 70.71 (CH-2′ an d CH-3′); 85.67 (CH-4′); 86.73 (CH-1′);
128.22 (C-5); 128.60, 128.88 an d 130.55 (CH-arom .); 135.43 (C-i-arom .); 150.04 (CH-2);
148.72, 152.71 an d 158.21 (C-4, C-6 an d C-8). For C17H18N4O5·1/2H2O (367.4) calculated:
55.58% C, 5.21% H, 15.25% N; foun d: 55.50% C, 5.10% H, 14.96% N.
8-Hydroxy-6-ph en yl-9-(β-D-ribofuran osyl)purin e (6b)
A solution of brom o derivative 3 (350 m g, 0.66 m m ol) in 0.5 M sodium h ydroxide (10 m l)
was stirred at room tem perature for 2 days. Th e m ixture was n eutralized by addition of 0.5
M
acetic acid an d evaporated in vacuo. Th e residue was subjected to preparative TLC (7%
MeOH/EtOAc). After crystallization from water/m eth an ol th e product was obtain ed as wh ite
solid (160 m g, 65%); m .p. 233–235 °C; [α]D –37.3 (c 0.6, DMF). FAB MS, m/z (rel.%): 345
(30) [M + H], 213 (100). 1H NMR (DMSO-d6, 500 MHz): 3.48–3.53 (m , 1 H, H-5′a); 3.66 (dd,
1 H, J = 4.7 an d 11.8, H-5′b); 3.88–3.91 (m , 1 H, H-4′); 4.21–4.24 (m , 1 H, H-3′); 4.87 (dd,
1 H, J = 5.0 an d 6.8, 5′-OH); 4.99 (dd, 1 H, J = 5.8 an d 5.9, H-2′); 5.13 (d, 1 H, J = 5.0,
3′-OH); 5.32 (d, 1 H, J = 5.8, 2′-OH); 5.82 (d, 1 H, J = 5.9, H-1′); 7.52–7.57 an d 7.97–7.99 (m ,
6 H, H-arom . an d OH); 8.69 (s, 1 H, H-2). 13C NMR (DMSO-d6, 100.6 MHz): 62.11 (CH2-5′);
69.94 (CH-2′); 70.63 (CH-3′); 85.25 (CH-4′); 85.80 (CH-1′); 118.24 (C-5); 128.16, 128.76 an d
130.10 (CH-arom .); 134.66 (C-i-arom .); 141.77 (C-6); 150.12 (CH-2); 150.23 (C-4); 152.97
(C-8). For C16H16N4O5·3/2H2O (366.4) calculated: 51.75% C, 5.16% H, 15.09% N; foun d:
52.20% C, 5.24% H, 14.70% N.
8-Am in o-6-ph en yl-9-(β-D-ribofuran osyl)purin e (6c)
Brom o derivative 3 (600 m g, 1.13 m m ol) was dissolved in m eth an olic am m on ia (25 m l) an d
stirred at room tem perature overn igh t. Th e m ixture was evaporated in vacuo an d th e residue
was separated by preparative HPLC to obtain desired am in o derivative 6c (220 m g, 54%) fol-
lowed by 8-m eth oxy derivative 6a (60 m g, 15%) as a side product. Com poun d 6c: wh ite
am orph ous solid; [α]D –41.6 (c 0.6, DMF). FAB MS, m/z (rel.%): 344 (90) [M + H], 212 (100).
1H NMR (DMSO-d6, 400 MHz): 3.67–3.70 (m , 2 H, H-5′); 4.02–4.04 (m , 1 H, H-4′); 4.15–4.19
(m , 1 H, H-3′); 4.71 (dd, 1 H, J = 6.3 an d 7.4, H-2′); 5.18 (d, 1 H, J = 4.0, 3′-OH); 5.35 (d, 1 H,
J = 6.3, 2′-OH); 5.67 (t, 1 H, J = 4.7, 5′-OH); 6.09 (d, 1 H, J = 7.4, H-1′); 7.50–7.55 (m , 3 H,
H-arom .); 8.58 (s, 1 H, H-2); 8.71–8.75 (m , 2 H, H-arom .). 13C NMR (DMSO-d6, 100.6 MHz):
61.49 (CH2-5′); 70.56 (CH-2′); 70.92 (CH-3′); 85.78 (CH-4′); 86.47 (CH-1′); 128.26, 128.49
an d 129.47 (CH-arom .); 131.14 (C-5); 136.41 (C-i-arom .); 144.34 (C-6); 147.41 (CH-2);
154.00 an d 155.31 (C-4 an d C-8). HR MS (FAB), calculated for C16H18N5O4 [M + H]:
344.1359; foun d: 344.1320. For C16H17N5O4·1/2MeOH (359.4) calculated: 55.15% C, 5.33% H,
19.49% N; foun d: 55.12% C, 5.37% H, 19.28% N.
8-Dim eth ylam in o-6-ph en yl-9-(β-D-ribofuran osyl)purin e (6d )
Brom o derivative 3 (260 m g g, 0.52 m m ol) was dissolved in a 33% solution of dim eth yl-
am in e in eth an ol (5 m l). Th e reaction m ixture was stirred at room tem perature for 2 days
an d evaporated in vacuo. Th e residue was purified by preparative HPLC an d after crystalliza-
tion from water/eth an ol th e product was obtain ed as wh ite solid (150 m g, 77%); m .p.
173–174 °C; [α]D –56.8 (c 0.9, DMF). FAB MS, m/z (rel.%): 372 (15) [M + H], 240 (100). 1H NMR
(DMSO-d6, 400 MHz): 3.11 (s, 6 H, CH3); 3.54–3.61 (m , 1 H, H-5′a); 3.73 (dd, 1 H, J = 4.8
an d 11.8, H-5′b); 3.93–3.97 (m , 1 H, H-4′); 4.24–4.28 (m , 1 H, H-3′); 5.07 (dd, 1 H, J = 4.8
Collect. Czech. Chem. Commun. (Vol. 68) (2003)

Cytostatic 6-Arylpurine Nucleosides
847
an d 7.1, 5′-OH); 5.20 (d, 1 H, J = 4.9, 3′-OH); 5.25–5.30 (m , 1 H, H-2′); 5.42 (d, 1 H, J = 6.2,
2′-OH); 5.77 (d, 1 H, J = 6.7, H-1′); 7.50–7.60 (m , 3 H, H-arom .); 8.74 (s, 1 H, H-2); 8.77 (d,
2 H, J = 7.3, H-arom .). 13C NMR (DMSO-d6, 100.6 MHz): 41.83 (CH3); 62.01 (CH2-5′); 70.03
(CH-2′); 70.59 (CH-3′); 85.84 (CH-4′); 88.94 (CH-1′); 128.46, 128.83 an d 130.19 (CH-arom .);
130.32 (C-5); 135.82 (C-i-arom .); 148.91 (CH-2); 147.63, 153.99 an d 159.90 (C-4, C-6 an d
C-8). For C18H21N5O5·1/3H2O (377.4) calculated: 57.29% C, 5.79% H, 18.56% N; foun d:
57.30% C, 5.80% H, 18.41% N.
6-Ph en yl-8-sulfan yl-9-(2,3,5-tri-O-acetyl-β-D-ribofuran osyl)purin e
Brom o derivative 3 (360 m g, 0.68 m m ol) an d th iourea (760 m g, 10 m m ol) were dissolved in
eth an ol (10 m l) an d th e reaction m ixture was stirred at 100 °C for 7 h . After coolin g to
room tem perature, th e wh ite solid precipitate was filtered off an d wash ed with eth an ol to
obtain crude product (220 m g, 67%) wh ich was used for th e n ext step with out furth er puri-
fication . FAB MS, m/z (rel.%): 487 (25) [M + H], 229 (100). 1H NMR (CDCl3, 400 MHz): 2.00,
2.08 an d 2.12 (3 × s, 3 × 3 H, CH3CO); 4.23 (dd, 1 H, J = 12.0 an d 5.7, H-5′a); 4.34–4.38 (m ,
1 H, H-4′); 4.46 (dd, 1 H, J = 12.0 an d 3.5, H-5′b); 5.83 (t, 1 H, J = 6.2, H-3′); 6.29 (dd, 1 H, J =
6.2 an d 4.4, H-2′); 6.68 (d, 1 H, J = 4.4, H-1′); 7.56–7.59 (m , 3 H, H-arom .); 8.03–8.06 (m ,
2 H, H-arom .); 8.88 (s, 1 H, H-2); 13.84 (brs, 1 H, SH). 13C NMR (CDCl3, 100.6 MHz): 20.19,
20.31 an d 20.45 (CH3); 62.46 (CH2-5′); 69.65 an d 70.73 (CH-2′ an d CH-3′); 78.89 (CH-4′);
86.18 (CH-1′); 120.50 (C-5); 128.74, 128.77 an d 130.69 (CH-arom .); 134.00 (C-i-arom .);
144.51 (C-6); 151.05 (C-4); 151.38 (CH-2); 169.33, 169.34, 169.98 an d 172.10 (3 × CO an d
C-8).
6-Ph en yl-9-(β-D-ribofuran osyl)-8-sulfan ylpurin e (6e)
A 1 M m eth an olic MeONa (500 µl, 0.5 m m ol) was added to a m ixture of crude 6-ph en yl-
8-sulfan yl-9-(2,3,5-tri-O-acetyl-β-D-ribofuran osyl)purin e (150 m g, 0.3 m m ol) an d m eth an ol
(10 m l). Th e resultin g solution was stirred at room tem perature for 1 h an d th en its pH ad-
justed to 6 by addition of 1 M acetic acid. Solven ts were evaporated an d th e residue was
ch rom atograph ed on preparative TLC (7% MeOH/EtOAc). Th e crude product was crystallized
from water/m eth an ol to give th e title com poun d 6e as wh ite solid (80 m g, 72%); m .p.
262–263 °C; [α ]D –40.3 (c 0.5, DMF). FAB MS, m/z (rel.%): 361 (50) [M + H], 263 (100).
1H NMR (DMSO-d6, 500 MHz): 3.56 (dd, 1 H, J = 5.2 an d 11.7, H-5′b); 3.72 (dd, 1 H, J = 4.3
an d 11.7, H-5′b); 3.89–3.94 (m , 1 H, H-4′); 4.33–4.37 (m , 1 H, H-3′); 4.88 (brs, 1 H, 5′-OH);
5.13 (brs, 2 H, H-2′ an d 3′-OH); 5.31 (brs, 1 H, 2′-OH); 6.48 (d, 1 H, J = 5.6, H-1′); 7.56–7.58
an d 8.02–8.05 (m , 5 H, H-arom .); 8.83 (s, 1 H, H-2); 13.73 (s, 1 H, SH). 13C NMR (DMSO-d6,
100.6 MHz): 62.02 (CH2-5′); 70.34 an d 70.52 (CH-2′ an d CH-3′); 85.34 (CH-4′); 88.90
(CH-1′); 120.50 (C-5); 128.73, 128.74 an d 130.62 (CH-arom .); 134.09 (C-i-arom .); 144.20
(C-6); 151.13 (CH-2); 151.33 (C-4); 172.88 (C-8). For C16H16N4O4S·1/3H2O (366.4) calcu-
lated: 52.45% C, 4.58% H, 15.29% N; foun d: 52.51% C, 4.59% H, 14.98% N.
This work is a part of a research project Z4 055 905, supported by the Grant Agency of the Acad-
emy of Sciences of the Czech Republic (grant No. B4055201) and by Sumika Fine Chemicals Co Ltd.
(Osaka, Japan). The cytostatic activity was studied by Dr I. Votruba from the Institute of Organic
Chemistry and Biochemistry and NMR spectra were measured and interpreted by Dr H. Dvořáková
from the Institute of Chemical Technology, Prague. The contribution of these colleagues is gratefully
Collect. Czech. Chem. Commun. (Vol. 68) (2003)

848
Hocek, Hocková, Štambaský:
acknowledged. The authors’ thanks are also due to Ms K. Havlíčková for excellent technical assistance
and to the staff of the mass spectrometry and analytical departments of the Institute.
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