Synthesis, structure, and antiproliferative activity of selenophenfurin, an inosine 5'-monophosphate dehydrogenase inhibitor analogue of selenazofurin

Article abstract of DOI:10.1021/jm960864o

The synthesis and biological activity of selenophenfurin (5-β-D- ribofuranosylselenophene-3-carboxamide, 1), the selenophene analogue of selenazofurin, are described. Glycosylation of ethyl selenophene-3- carboxylate (6) under stannic chloride-catalyzed conditions gave 2- and 5- glycosylated regioisomers, as a mixture of α- and β-anomers, and the β- 2,5-diglycosylated derivative. Deprotected ethyl 5-β-D- ribofuranosylselenophene-3-carboxylate (12β) was converted into selenophenfurin by ammonolysis. The structure of 12β was determined by ¹H- and ¹³C-NMR, crystallographic, and computational studies. Selenophenfurin proved to be antiproliferative against a number of leukemia, lymphoma, and solid tumor cell lines at concentrations similar to those of selenazofurin but was more potent than the thiophene and thiazole analogues thiophenfurin and tiazofurin. Incubation of K562 cells with selenophenfurin resulted in inhibition of IMP dehydrogenase (IMPDH) (76%) and an increase in IMP pools (14.5-fold) with a concurrent decrease in GTP levels (58%). The results obtained confirm the hypothesis that the presence of heteroatoms such as S or Se in the heterocycle in position 2 with respect to the glycosidic bond is essential for both cytotoxicity and IMP dehydrogenase inhibitory activity in this type of C-nucleosides.

Full text of DOI:10.1021/jm960864o

J . Med. Chem. 1997, 40, 1731-1737
1731
Syn th esis, Str u ctu r e, a n d An tip r olifer a tive Activity of Selen op h en fu r in , a n
In osin e 5′-Mon op h osp h a te Deh yd r ogen a se In h ibitor An a logu e of Selen a zofu r in
Palmarisa Franchetti,* Loredana Cappellacci, Ghassan Abu Sheikha, Hiremagalur N. J ayaram,‡
Vivek V. Gurudutt,‡ Thaw Sint,‡ Bryan P. Schneider,‡ William D. J ones,† Barry M. Goldstein,§ Graziella Perra,∇
Antonella De Montis,∇ Anna Giulia Loi,∇ Paolo La Colla,∇ and Mario Grifantini
Dipartimento di Scienze Chimiche, Universita` di Camerino, Via S. Agostino, 1, 62032 Camerino, Italy, Laboratory for
Experimental Oncology, Indiana University School of Medicine, Indianapolis, Indiana 46202, Department of Chemistry,
University of Rochester, Rochester, New York 14620, Department of Biophysics, University of Rochester Medical Center,
Rochester, New York 14642, and Dipartimento di Biologia Sperimentale, Universita` di Cagliari, 09124 Cagliari, Italy
Received December 23, 1996X
The synthesis and biological activity of selenophenfurin (5-â-D-ribofuranosylselenophene-3-
carboxamide, 1), the selenophene analogue of selenazofurin, are described. Glycosylation of
ethyl selenophene-3-carboxylate (6) under stannic chloride-catalyzed conditions gave 2- and
5-glycosylated regioisomers, as a mixture of R- and â-anomers, and the â-2,5-diglycosylated
derivative. Deprotected ethyl 5-â-D-ribofuranosylselenophene-3-carboxylate (12â) was converted
1
into selenophenfurin by ammonolysis. The structure of 12â was determined by H- and 13C-
NMR, crystallographic, and computational studies. Selenophenfurin proved to be antiprolif-
erative against a number of leukemia, lymphoma, and solid tumor cell lines at concentrations
similar to those of selenazofurin but was more potent than the thiophene and thiazole analogues
thiophenfurin and tiazofurin. Incubation of K562 cells with selenophenfurin resulted in
inhibition of IMP dehydrogenase (IMPDH) (76%) and an increase in IMP pools (14.5-fold) with
a concurrent decrease in GTP levels (58%). The results obtained confirm the hypothesis that
the presence of heteroatoms such as S or Se in the heterocycle in position 2 with respect to the
glycosidic bond is essential for both cytotoxicity and IMP dehydrogenase inhibitory activity in
this type of C-nucleosides.
Inosine 5′-monophosphate dehydrogenase (EC
1.1.1.205, IMPDH) catalyzes the conversion of IMP to
XMP utilizing NAD as a proton acceptor and is the rate-
limiting enzyme in the de novo purine biosynthetic
pathway leading to the formation of guanine nucle-
otides. The activity of IMPDH increases markedly in
proliferating cells,1,2 and inhibitors of the enzyme may
be useful as antitumor and immunosuppressive agents.
IMPDH inhibitors lead to an accumulation of the
intracellular levels of IMP, which can serve as a
phosphate donor for the phosphorylation of 2′,3′-
dideoxynucleosides. Thus, these inhibitors are able to
potentiate the anti-HIV activity of retroviral drugs such
as 2′,3′-dideoxyinosine (ddI).3,4 It has recently been
reported that IMPDH exists as two isoforms, type I and
type II, encoded by distinct genes.5a,b Type I is the
prevalent species expressed in normal cells, whereas the
type II isoform is upregulated and predominates in
neoplastic and fast replicating cells.6-8 Thus, selective
inhibition of type II IMPDH may provide improved
selectivity against cancer cells.
potent than tiazofurin in several antitumor screens and
in vitro studies.10 Both the antiproliferative and matu-
ration-inducing effects of these nucleoside analogues
appear to be due to inhibition of IMPDH, which induces
the shutdown of guanine nucleotide synthesis.11 In
sensitive cells, tiazo- and selenazofurin are converted
into analogues of the cofactor nicotinamide adenine
dinucleotide (NAD). These analogues, called TAD and
SAD, respectively, are excellent inhibitors of IMPDH.11
Crystal structures of tiazo- and selenazofurin dem-
onstrate close intramolecular contact between the thia-
zole S or selenazole Se heteroatom and the furanose ring
oxygen O1′.12 Molecular orbital calculations suggest
that these close contacts result from an attractive
electrostatic interaction between the positively charged
sulfur or selenium and the lone pair of electrons on the
furanose oxygen. This interaction would be expected
to constrain rotation about the C-glycosidic bond in the
active anabolites TAD and SAD, influencing the binding
of these dinucleotide inhibitors to the target enzyme.
Observation of close S/Se‚‚‚O contacts in analogues TAD
and SAD bound to alcohol dehydrogenase supports this
hypothesis.13
Selenazofurin (2-â-D-ribofuranosylselenazole-4-car-
boxamide, NSC 340847), the selenium analogue of
tiazofurin, is a widely studied agent with a diverse array
of biological effects. These include potent antitumor and
antiviral activity, as well as efficacy as a maturation-
inducing agent.9a-d Selenazofurin is 5-10-fold more
Recently we synthesized thiophenfurin (5-â-D-ribo-
furanosylthiophene-3-carboxamide, TPF), a C-nucleo-
side isostere of tiazofurin, in which the thiazole ring is
replaced by a thiophene heterocycle.14 Like tiazofurin,
thiophenfurin was found to be active as an antitumor
agent both in vitro and in vivo and to inhibit IMPDH.
These studies supported the hypothesis that the pres-
ence of S in the heterocycle in position 2 with respect
to the glycosidic bond is essential for cytotoxicity and
IMPDH inhibition, whereas the N atom of the thiazole
* Author to whom correspondence should be addressed at Universita`
di Camerino. Tel: (+39)737-40336. Fax: (+39)737-637345. E-mail:
grima@camserv.unicam.it.
‡ Indiana University School of Medicine.
† University of Rochester.
§ University of Rochester Medical Center.
∇ Universita` di Cagliari.
X Abstract published in Advance ACS Abstracts, April 1, 1997.
S0022-2623(96)00864-3 CCC: $14.00 © 1997 American Chemical Society

1732 J ournal of Medicinal Chemistry, 1997, Vol. 40, No. 11
Franchetti et al.
Sch em e 1a
a
(a) SnCl4/ClCH2CH2Cl; (b) EtONa, EtOH; (c) 30% NH4OH.
Sch em e 2a
ring of tiazofurin is not. Ab initio computations sug-
gested that, as found in tiazofurin, an electrostatic
interaction between the positively charged thiophene
sulfur and the furanose oxygen stabilizes the conforma-
tion in which the thiophene sulfur is cis to the furanose
oxygen, with a marginally close nonbonded S‚‚‚O contact
of 3.04 Å.14
a
(a) Hg(OCOCH3)2, H+, I2; (b) Zn/AcOH; (c) (CH3)3SiCN,
(Ph3P)4Pd(0), Et3N; (d) HCl; (e) SOCl2, EtOH.
The ethyl selenophene-3-carboxylate (6) was obtained
by reacting the 3-carboxylic acid 5 with SOCl2 and
ethanol. Acid 5 is a known compound which has been
prepared in different ways;15a,b however, we found it
more convenient to carry out its synthesis by the method
reported in Scheme 2. Tetraiodoselenophene (2), pre-
pared by reaction with mercuric acetate in glacial acetic
acid and then with iodine,16 was treated with zinc
powder and acetic acid (80%) under reflux to give
3-iodoselenophene (3). Compound 3 was converted into
nitrile 4 by cyanation with trimethylsilyl cyanide in
This finding prompted us to extend the study of
structure-activity relationships in this type of C-
nucleosides to selenophenfurin (5-â-D-ribofuranosylse-
lenophene-3-carboxamide, 1), the selenophene analogue
of selenazofurin.
Ch em istr y
The synthesis of selenophenfurin (1) was carried out
as outlined in Scheme 1, by direct C-glycosylation of
ethyl selenophene-3-carboxylate (6) under Friedel-
Crafts conditions, as described for thiophenfurin.14

Synthesis and Activity of Selenophenfurin
J ournal of Medicinal Chemistry, 1997, Vol. 40, No. 11 1733
anhydrous triethylamine in the presence of tetrakis-
(triphenylphosphine)palladium(0); hydrolysis of 4 with
hydrochloric acid under reflux gave the acid 5.
The reaction of 6 with 1,2,3,5-tetra-O-acetyl-â-D-
ribofuranose (7) in 1,2-dichloroethane in the presence
of SnCl4 gave 2- and 5-glycosylated regioisomers as a
mixture of R- and â-anomers (8R,â, 9R,â, 42%) and the
2,5-bis(â-D-ribofuranosyl) derivative 10 (11%). The
mixture of anomers 8R,â and isomer 9â was separated
from 9R and 10 by chromatography.
The mixture of 8R,â and 9â was treated with a
catalytic amount of sodium ethoxide in ethanol to give
deblocked ethyl esters 11R,â and 12â which were
separated by column chromatography. Starting from
9R and 10, the esters 12R and 13 were obtained in a
similar way. The glycosylation position was determined
by 1H-NMR and proton-proton nuclear Overhauser
effect (NOE) difference spectroscopy. The 1H-NMR
spectrum of 11â showed that the signal of the H-2
proton of selenophene had disappeared, indicating that
the glycosylation position was at C-2. On the other
F igu r e 1. Molecular structure of 12â. Non-hydrogen atoms
are represented by thermal ellipsoids at the 50% probability
level. The dotted line indicates the 3.12 Å nonbonded Se‚‚‚O
contact.
1
hand, the H-NMR spectra of compounds 12R,â lacked
the signal of the H-5 proton, supporting C-5 glycosyla-
tion. The structures of compounds 12R,â were further
supported by NOE experiments. In fact, when the H-1′
signal of these compounds was irradiated, a NOE effect
was observed at H-4, confirming that the ribosyl moiety
resides at C-5. The anomeric configuration was also
assigned on the basis of NOE experiments. In fact,
selective irradiation of the anomeric signal of 11â and
12â increased the intensity of the H-4′ signal (1.5% and
2.3%, respectively), while no intensity enhancement of
the H-3′ signal was observed; this indicates that H-1′
and H-4′ are located on the same face of the ribosyl
ring.17 The anomeric configuration was further sup-
ported by studies of 13C-NMR data. Thus, the finding
that C-1′ in 12â resonates upfield of C-1′ in 12R is in
accord with the previous observation of anomeric chemi-
cal shifts in thiophenfurin.14
F igu r e 2. Energy vs C-glycosidic torsion angle ø in a sele-
nophenfurin model fragment. The fragment is illustrated at
top ø ) 0° conformation. Numbers adjacent to the selenium
and oxygen are natural bond orbital point charges. Rotation
about ø is indicated by the arrow. Curves were obtained with
the furanose moiety constrained in either a 3′-endo or 2′-endo
pucker. Points on each curve were obtained at the RHF/3-
21G(*)//3-21G(*) level.
lenium remains cis to the furanose oxygen, with a
nonbonded close Se‚‚‚O contact of 3.12 Å.
Treatment of 12â with ammonium hydroxide (30%)
gave selenophenfurin (1). In a similar way, ethyl esters
11â, 12R, and 13 were converted to the amides 14â, 15,
and 16. The glycosylation position on compound 13 was
Ab initio computations at the RHF/3-21G(*)//3-21G-
(*) level suggest that the Se‚‚‚O contact observed in
selenophenfurin is stabilized by an electrostatic interac-
tion between a positively charged selenophene selenium
and negatively charged furanose oxygen. Donation of
mobile selenium valence electrons to the conjugated
system of the selenophene ring results in a positive
charge on the heteroatom. This effect is similar to that
identified for thiophenfurin, tiazofurin, selenazofurin,
and their analogues.12,14 Calculation of energy vs C-
glycosidic torsion angle ø for a selenophenfurin model
fragment (Figure 2) yields a similar curve to that
obtained for thiophenfurin.14 The energy shows a global
minimum at a C-glycosidic torsion angle of ∼20° for the
2′-endo sugar conformation, with a slightly higher
minimum at ø ∼ 0° for the 3′-endo sugar conformation.
As with thiophenfurin,14 this result suggests that the
minimum energy value of ø for selenophenfurin is lower
than that observed in the crystal structure of the
carboxylate intermediate.
1
established to be at C-2 and C-5 on the basis of the H-
NMR spectrum, which showed that the H-2 and H-5
signals were lacking. The anomeric configuration was
established to be â, based on the observation that, in
1
the H- and 13C-NMR spectra, the chemical shift pat-
terns were similar to those reported for the correspond-
ing thiophene derivative.14
Cr ysta llogr a p h ic a n d Com p u ta tion a l Stu d ies
The crystal structure of the selenophenfurin carboxy-
late intermediate 12â (ethyl 5-â-D-ribofuranosylsele-
nophene-3-carboxylate) was determined, as crystals of
the parent compound could not be obtained. The
molecular structure of 12â is isomorphous to that of the
corresponding thiophene analogue14 and also shares
several features observed in the structures of related
thiazole and selenazole nucleosides12 (Figure 1). The
selenophene ring is planar, with the ethyl carboxylate
substituent at C-3 coplanar to the heterocycle. The
C-glycosidic torsion angle is 46.3°, close to that seen for
thiophenfurin (46.5°) but higher than that observed in
selenazofurin (30.5°).12 However, the selenophene se-
Biologica l Activity
Effect of Selen op h en fu r in on th e P r olifer a tion
of Mu r in e a n d Hu m a n Tu m or Cell Lin es. The
antiproliferative activity of selenophenfurin was tested
in vitro against a panel of leukemia, lymphoma, and

1734 J ournal of Medicinal Chemistry, 1997, Vol. 40, No. 11
Franchetti et al.
Ta ble 2. Effects of Selenophenfurin, Selenazofurin,
Ta ble 1. Antiproliferative Activity of Selenophenfurin,
Selenazofurin, Thiophenfurin, and Tiazofurin
Thiophenfurin, and Tiazofurin (10 µM) on IMPDH Activity of
K562 Cells in Culture
a
IC50 (µM)
IMPDH activity
selenophen- selenazo- thiophen-
tiazo-
furin
(nmol of XMP formed/
h/mg of protein)
inhibition
(%)a
cell lines
furin
furin
furin
compd
control
selenophenfurin
selenazofurin
thiophenfurin
tiazofurin
Leukemia/Lymphoma
5.04 ( 0.14
1.06 ( 0.28
1.01 ( 0.12
2.62 ( 0.19
2.07 ( 0.15
0
76
80
52
59
L1210b
0.3
0.5
0.5
1.2
1.5
1.6
1.2
0.6
1.7
2.3
5.8
6.4
8.7
3.5
2.9
2.9
2.5
5.7
7.5
8.2
10
K562c
0.45
0.7
0.9
0.9
0.3
0.3
Wil2-NSd
CCRF-SBe
Rajif
CCRF-CEMg
MOLT-4g
a
Significantly different from control values (p < 0.05).
5.2
Ta ble 3. Effects of Selenophenfurin, Selenazofurin,
Thiophenfurin, and Tiazofurin (10 µM) on Ribonucleotide
Levels of K562 Cells in Culture
Carcinoma
CHO-K1h
HT-29i
HeLaj
2.9
3.5
6.4
9.9
1.2
0.6
7.7
7.9
13.8
2.3
55
40
90
79
17
6.4
100
100
% of controla
ACHNk
5637l
>100
nucleo-
tide
control
(nmol/g)
selenophen- selenazo- thiophen- tiazo-
24
furin
furin
furin
furin
a
Compound concentration required to reduce cell viability by
50%. b L1210, murine lymphocytic leukemia. c K562, human eryth-
IMP
GMP
GDP
GTP
40.5 ( 5.6
51.1 ( 2.4
58.1 ( 4.4
442.9 ( 12.5
1464
0
61
1043
0
59
703
0
66
60
1033
0
89
d
roid leukemia. Wil2-NS, human splenic lymphoblastoid cells.
e CCRF-SB, human acute B-lymphoblastic leukemia. f Raji, human
42
50
55
g
Burkitt lymphoma. CCRF-CEM and MOLT-4, human acute
h
a
T-lymphoblastic leukemias. CHO-K1, Chinese hamster ovary.
Significantly different from saline control (p < 0.05). K562
cells in culture (1 × 107) were incubated with saline (control),
selenophenfurin, selenazofurin, thiophenfurin, or tiazofurin for 2
h at 37 °C. Cells were extracted with trichloroacetic acid and
neutralized with tri-n-octylamine, and an aliquot was analyzed
by HPLC.
i
j
HT-29, human colon adenocarcinoma. HeLa, human cervix
carcinoma. k ACHN, human renal adenocarcinoma. l 5637, human
bladder carcinoma.
solid tumors cell lines, mostly derived from human
tumors. Selenazofurin, tiazofurin, and thiophenfurin
were used as reference drugs (Table 1).
Con clu sion s
Against liquid and solid tumor cell lines, no significant
differences could be seen in both potency and spectrum
of antiproliferative activity between selenophenfurin
and selenazofurin. However, the test compound showed
a potency superior to that of thiophenfurin and tiazo-
furin, particularly against solid tumor cell lines.
As observed for thiophenfurin, structure-activity
relationships show that the glycosylation position and
the anomeric configuration are determinants for the
antiproliferative activity of selenophenfurin. In fact, the
2-glycosylated isomers 14â and the R-anomer 15 were
inactive (data not shown).
Effects of Selen op h en fu r in on IMP DH Activity
a n d In tr a cellu la r Nu cleotid e Levels. Selenophen-
furin and its parent compounds were also tested for
inhibitory properties against IMPDH from human my-
elogenous leukemia K562 cells in culture, as previously
reported.14 IMPDH activity was performed by enzyme
kinetic studies and is expressed as nmol of XMP formed/
mg of protein/h. For these studies, K562 cells were
exposed to 10 µM each of the inhibitors or saline for 2
h at 37 °C. The results indicate that IMPDH activity
was strongly inhibited (76%) by the action of seleno-
phenfurin with a potency similar to that of selenazo-
furin (80% inhibition) and greater than that of thiophen-
furin and tiazofurin (Table 2).
Since inhibition of IMPDH results in perturbation of
nucleotide pools, we examined the influence of sele-
nophenfurin on the ribonucleotide concentration in
K562 cells. The results provided in Table 3 show an
increase in IMP levels (14.6-fold) with a concurrent
decrease in guanylate concentration. Among the four
compounds, selenophenfurin was found to have the
highest activity in enhancing the IMP level and de-
creasing the guanine nucleotide pools. Except for the
guanylates, no other purine and pyrimidine nucleotide
concentrations were perturbed.
This research shows that selenophenfurin is a C-
nucleoside endowed with remarkable activity against
a variety of tumor cell lines in culture. Its potency
against human leukemic and solid tumor cell lines
suggests that this agent might be useful against tumors
in man. Replacement of the nitrogen atom by the CH
group in the selenazole ring of selenazofurin does not
affect the biological activity. This confirms the finding
for the sulfur analogue tiazofurin that the nitrogen atom
in the heterocycle is not essential for activity.
Overall, these and previous results14,18 suggest that
the major determinant for the antitumor and IMPDH
inhibitory activity of this type of C-nucleosides is the
presence of a sulfur or selenium heteroatom in position
2 on the base. This placement permits an attractive
electrostatic interaction between the heteroatom and the
furanose oxygen, potentially constraining rotation about
the C-glycosidic bond. This constraint may enhance
anabolism of the parent compound to the NAD analogue
or stabilize binding of the NAD analogue to the target
enzyme.
Exp er im en ta l Section
Melting points were determined on a Buchi apparatus and
are uncorrected. Elemental analyses were determined on a
EA 1108 CHNS-O (Fisons Instruments) analyzer. Ultraviolet
spectra were recorded on an HP 8452 A diode array spectro-
photometer driven by an Olivetti M 24. Thin layer chroma-
tography (TLC) was run on silica gel 60 F254 and RP-18 plates;
silica gel 60 (70-230 and 230-400 mesh; Merck) for column
chromatography was used. Nuclear magnetic resonance 1H
and 13C spectra were determined at 300 and 75 MHz, respec-
tively, with a Varian VXR-300 spectrometer. The chemical
shift values are expressed in δ values (parts per million)
relative to tetramethylsilane as an internal standard. All
exchangeable protons were confirmed by addition of D2O.
Stationary NOE experiments were run on degassed solutions
at 25 °C. A presaturation delay of 1 s was used, during which
the decoupler low power was set at 20 dB attenuation.

Synthesis and Activity of Selenophenfurin
J ournal of Medicinal Chemistry, 1997, Vol. 40, No. 11 1735
Tiazofurin and selenazofurin were obtained through the Drug
Synthesis & Chemistry Branch, Developmental Therapeutics
Program, Division of Cancer Treatment, National Cancer
Institute (Bethesda, MD).
(t, J ) 7.1 Hz, 3H, OCH2CH3), 2.00-2.10 (3s, 9H, OCOCH3),
4.10-4.35 (m, 5H, H-5′, H-4′, OCH2CH3), 5.38 (dd, J ) 4.5,
7.0 Hz, 1H, H-3′), 5.50 (t, J ) 3.8 Hz, 1H, H-2′), 5.65 (d, J )
3.0 Hz, 1H, H-1′), 7.62 (s, 1H, H-4), 9.03 (s, 1H, H-2). Anal.
(C18H22O9Se) C, H.
Tetr a iod oselen op h en e (2). To a mixture of selenophene
(48 g, 0.366 mol), acetic acid (1.8 L), and mercury acetate (466.5
g, 1.464 mol) heated at 95 °C was added iodine (373.08 g, 1.47
mol) portionwise under stirring. The heating was continued
for 30 min. After cooling at room temperature, the mixture
was diluted with water (2.7 L), stirred for 20 min, and then
stored for 15 h at 4 °C. The solid formed was filtered, washed
with water, and added to a water solution (3.6 L) of KI (358.8
g). The mixture was stirred for 2 h at room temperature, and
the solid was filtered, washed with water, and recrystallized
from DMF/H2O to give 2 (226.4 g, 97.4%) as a white solid: mp
205-210 °C (lit.16 mp 208 °C). 13C-NMR (Me2SO-d6): δ 92.5
(C-3, C-4), 110.58 (C-2, C-5). Anal. (C4I4Se) C.
3-Iod oselen op h en e (3). To a stirred mixture of 2 (226 g,
0.356 mol) and acetic acid (80% solution in water, 4.5 L) was
added portionwise zinc powder (122.4 g, 1.87 mol). The
mixture was heated under reflux for 2 h, cooled at room
temperature, and filtered. The aqueous phase was neutralized
with a saturated solution of NaHCO3 and extracted with ethyl
ether (400 mL × 3). The combined organic phases were dried
over anhydrous Na2SO4 and evaporated to dryness to give an
oily residue which was purified by distillation: bp 83 °C/1.5
mmHg (lit.16 bp 56 °C/1 mmHg); 50.3 g, 55%.
Selen op h en e-3-ca r bon itr ile (4). Tetrakis(triphenylphos-
phine)palladium(0) (4.39 g, 3.8 mmol) was added under
nitrogen atmosphere to a stirred solution containing 3 (50 g,
0.195 mol) and trimethylsilyl cyanide (38.9 mL, 0.292 mol) in
anhydrous triethylamine (388 mL, 2.78 mol). The reaction
mixture was heated under reflux for 30 min. After cooling to
room temperature, the mixture was partitioned between water
and benzene. The organic phase was separated, dried over
anhydrous Na2SO4, and evaporated to dryness under vacuum
to give an oily residue which was purified by distillation: bp
80 °C/1 mmHg (lit.15 bp 90-91 °C/10 mmHg); 21.55 g, 71%.
Selen op h en e-3-ca r boxylic Acid (5).15 A mixture of 4 (21
g, 0.134 mol) and concentrated HCl (500 mL) was heated under
reflux for 1 h. After cooling at room temperature the precipi-
tated solid was collected and recrystallized from water to give
5 (15.8 g, 67%) as a white solid.
Eth yl Selen op h en e-3-ca r boxyla te (6). A mixture of 5
(15 g, 85.69 mmol) and SOCl2 (30 mL, 0.41 mol) was heated
at 100 °C for 45 min. After evaporation, to the oily residue
cooled at 0 °C was added anhydrous ethanol (20 mL), and the
mixture was stirred at room temperature for 5 h. After
evaporation in vacuo, the ester 6 was obtained as a yellow oil
(17.4 g, 100%). TLC (CHCl3): Rf ) 0.72. 1H-NMR (Me2SO-
d6): δ 1.30 (t, J ) 7.1 Hz, 3H, OCH2CH3), 4.25 (q, J ) 7.1 Hz,
2H, OCH2CH3), 7.7 (dd, J ) 1.3, 5.4 Hz, 1H, H-4), 8.22 (dd, J
) 2.5, 5.5 Hz, 1H, H-5), 9.05 (dd, J ) 1.3, 2.5 Hz, 1H, H-2).
Anal. (C7H8O2Se) C, H.
Evaporation of the last fraction gave 10 as a colorless oil
(6.6 g, 11%). TLC (CHCl3): Rf ) 0.37. 1H-NMR (DMSO-d6):
δ 1.30 (t, J ) 7.1 Hz, 3H, OCH2CH3), 2.0-2.10 (m, 18H,
OCOCH3), 4.15-4.45 (m, 8H, H-4′a, H-4′b, 2H-5′a, 2H-5′b,
OCH2CH3), 5.20 (m, 3H, H-2′a, H-3′a, H-3′b), 5.40 (m, 1H,
H-2′b), 5.81 (d, J ) 3.3 Hz, 1H, H-1′b), 6.01 (d, J ) 3.3 Hz,
1H, H-1′a), 7.63 (s, 1H, H-4). Anal. (C29H36O16Se) C, H.
Eth yl 2-â-D-Ribofu r a n osylselen op h en e-3-ca r boxyla te
(11â), Eth yl 2-r-D-Ribofu r a n osylselen op h en e-3-ca r boxy-
la te (11R), a n d Eth yl 5-â-D-Ribofu r a n osylselen op h en e-
3-ca r boxyla te (12â). The oily mixture of 8â,R and 9â (13 g)
was treated with sodium ethoxide in ethanol (273 mL, 15.12
mmol) for 1 h at room temperature. To the reaction mixture
was added 0.55 g of Dowex 50w × 8 resin (H+) (washed with
ethanol), and the suspension was stirred for 1 h. The resin
was filtered off, washed with ethanol, and discarded. The
filtrate was evaporated to dryness, and the residue was
chromatographed on a silica gel column with CHCl3-MeOH
(96:4) as eluent to give 11â as a white solid (0.57 g, 6%): mp
65-67 °C. TLC (CHCl3-MeOH, 96:4): Rf ) 0.35. 1H-NMR
(DMSO-d6): δ 1.30 (t, J ) 7.1 Hz, 3H, OCH2CH3), 3.6 (m, 2H,
H-5′), 3.76 (m, 1H, H-4′), 3.82 (m, 2H, H-2′, H-3′), 4.25 (q, J )
7.1 Hz, 2H, OCH2CH3), 4.82 (t, J ) 5.4 Hz, 1H, OH), 4.94 (d,
J ) 5.5 Hz, 1H, OH), 5.02 (d, J ) 5.3 Hz, OH), 5.52 (d, J ) 3.5
Hz, 1H, H-1′), 7.60 (d, J ) 5.8 Hz, 1H, H-4), 8.04 (d, J ) 5.8
Hz, 1H, H-5). Anal. (C12H16O6Se) C, H.
Evaporation of the following fraction gave 11R (0.187 g, 2%)
as a colorless oil. TLC (CHCl3-MeOH, 96:4): Rf ) 0.3. 1H-
NMR (DMSO-d6): δ 1.30 (t, J ) 7.1 Hz, 3H, OCH2CH3), 3.50,
3.60 (2m, 2H, H-5′), 3.75 (m, 1H, H-4′), 3.82 (m, 1H, H-3′), 3.96
(m, 1H, H-2′), 4.25 (q, J ) 7.1 Hz, 2H, OCH2CH3), 4.85 (t, J )
5.4 Hz, 1H, OH), 5.0 (m, 1H, OH), 5.20 (d, J ) 7.3 Hz, 1H,
OH), 5.55 (dd, J ) 5.4, 5.1 Hz, 1H, H-1′), 7.60 (d, J ) 5.8 Hz,
1H, H-4), 8.02 (d, J ) 5.8 Hz, 1H, H-5). Anal. (C12H16O6Se)
C, H.
Evaporation of the last fraction gave 12â (4.7 g, 50%) as
white needles (crystallized from CHCl3): mp 115-116 °C. TLC
(CHCl3-MeOH, 96:4): Rf ) 0.26. 1H-NMR (DMSO-d6): δ 1.30
(t, J ) 7.1 Hz, 3H, OCH2CH3), 3.50 (t, J ) 5.0 Hz, 2H, H-5′),
3.70 (m, 1H, H-4′), 3.82 (q, J ) 4.5 Hz, 1H, H-3′), 3.92 (m, 1H,
H-2′), 4.22 (q, J ) 7.1 Hz, 2H, OCH2CH3), 4.80 (d, J ) 6.9 Hz,
1H, OH), 4.85 (t, J ) 5.4 Hz, 1H, OH), 5.05 (d, J ) 4.6 Hz,
1H, OH), 5.20 (d, J ) 7.2 Hz, 1H, H-1′), 7.52 (d, J ) 1.4 Hz,
1H, H-4), 8.9 (d, J ) 1.4 Hz, 1H, H-5). 13C-NMR (Me2SO-d6):
δ 14.6 (CH3CH2), 60.8 (CH3CH2), 62.4 (C-5′), 72.0 (C-3′), 78.7
(C-2′), 81.1 (C-1′), 86.0 (C-4′), 125.3 (C-4), 135.0 (C-5), 140.1
(C-2), 153.9 (C-3), 163.0 (CdO). Anal. (C12H16O6Se) C, H.
Eth yl 5-r-D-Ribofu r a n osylselen op h en e-3-ca r boxyla te
(12R). Compound 12R was obtained from 9R (2 g, 4.33 mmol)
as described for 11â, as a colorless oil (1.14 g, 79%), after
chromatography on a silica gel column eluting with CHCl3-
MeOH (94:6). TLC (CHCl3-MeOH, 96:4): Rf ) 0.10. 1H-NMR
(DMSO-d6): δ 1.30 (t, J ) 7.1 Hz, 3H, OCH2CH3), 3.45 (m,
1H, H-5′), 3.60 (m, 1H, H-5′), 3.80 (m, 1H, H-4′), 3.97 (m, 1H,
H-3′), 4.18 (m, 1H, H-2′), 4.22 (q, J ) 7.1 Hz, 2H, OCH2CH3),
4.70 (t, J ) 5.7 Hz, 1H, OH), 4.95 (m, 1H, OH), 5.2 (d, J ) 2.5
Hz, 1H, H-1′), 5.28 (d, J ) 3.7 Hz, 1H, OH), 7.60 (s, 1H, H-4),
9.0 (s, 1H, H-2). 13C-NMR (DMSO-d6): δ 14.4 (CH3CH2), 60.5
(CH3CH2), 61.7 (C-5′), 72.7 (C-2′, C-3′), 79.2 (C-1′), 82.2 (C-4′),
127.3 (C-4), 133.7 (C-5), 142.1 (C-2), 149.4 (C-3), 163.1 (CdO).
Anal. (C12H16O6Se) C, H.
E t h yl 2-(2,3,5-Tr i-O-a cet yl-â-D-r ib ofu r a n osyl)selen o-
p h en e-3-ca r boxyla te (8â), Eth yl 2-(2,3,5-Tr i-O-a cetyl-r-
D-r ibofu r a n osyl)selen op h en e-3-ca r boxyla te (8R), Eth yl
5-(2,3,5-Tr i-O-a cet yl-â-D-r ib ofu r a n osyl)selen op h en e-3-
ca r boxyla te (9â), Eth yl 5-(2,3,5-Tr i-O-a cetyl-r-D-r ibofu r a -
n osyl)selen op h en e-3-ca r boxyla te (9R), a n d Eth yl 2,5-
Bis(2,3,5-t r i-O-a cet yl-â-D-r ib ofu r a n osyl)selen op h en e-3-
ca r boxyla te (10). To a stirred solution of ethyl selenophene-
3-carboxylate (6) (17 g, 83.7 mmol) in dry 1,2-dichloroethane
(160 mL) were added 1,2,3,5-tetra-O-acetyl-â-D-ribofuranose
(7) (26.6 g, 83.7 mmol) and SnCl4 (8.3 mL), and the mixture
reacted at room temperature for 18 h. The reaction mixture
was diluted with H2O, neutralized with NaHCO3, and ex-
tracted with CH2Cl2 (100 mL × 3). The combined CH2Cl2
extracts were dried over anhydrous Na2SO4 and evaporated
to dryness. The obtained residue was chromatographed on a
silica gel column eluting with CHCl3-n-hexane (80:20). Three
main fractions were separated. From the fast eluate, a
mixture of 8â,R and 9â was obtained as a colorless oil (13.9 g,
36%). TLC (CHCl3-n-hexane, 80:20): Rf ) 0.36.
Eth yl 2,5-Di-â-D-r ibofu r a n osylselen op h en e-3-ca r boxy-
la te (13). Compound 13 was prepared from 10 (3.8 g, 5.55
mmol) by the above method. The reaction residue was purified
by flash chromatography using CHCl3-MeOH (90:10) to give
13 as a foam (2.17 g, 56%). TLC (CHCl3-MeOH, 90:10): Rf
) 0.15. 1H-NMR (DMSO-d6): δ 1.30 (t, J ) 7.1 Hz, 3H,
OCH2CH3), 3.48 (t, J ) 5.1 Hz, 2H, H-5′b), 3.58 (m, 2H, H-5′a),
3.70-3.90 (m, 6H, H-4′a, H-4′b, H-3′a, H-3′b, H-2′a, H-2′b),
4.25 (q, J ) 7.1 Hz, 2H, OCH2CH3), 4.70 (d, J ) 7.2 Hz, 1H,
H-1′b), 4.82 (t, J ) 5.3 Hz, 1H, OH), 4.95 (d, J ) 4.7 Hz, 1H,
Evaporation of the following fraction gave 9R as an oil (2.32
g, 6%). TLC (CHCl3): Rf ) 0.43. 1H-NMR (DMSO-d6): δ 1.30

1736 J ournal of Medicinal Chemistry, 1997, Vol. 40, No. 11
Franchetti et al.
OH), 5.0 (d, J ) 4.8 Hz, 1H, OH), 5.16 (d, J ) 7.2, 1H, OH),
5.54 (d, J ) 3.7 Hz, 1H, H-1′a), 7.46 (s, 1H, H-4). Anal.
(C17H24O10Se) C, H.
carboxylate substituent. Similar values were observed in the
thiophene analogue.
Com p u ta tion a l Stu d y. Energy as a function of C-glyco-
sidic torsion angle ø was computed for a selenophenfurin model
fragment using methods similar to those described for thiophen-
furin.14 Ab initio calculations were performed using the
Gaussian 94 system of programs and internal basis sets.20
The selenophenfurin model fragment contained a sele-
nophene heterocycle with the carboxamide substituent omit-
ted. The heterocycle was connected via a C-glycosidic bond
to a 2′-hydroxyfuranose ring. By analogy to selenazofurin, ø
was defined by atoms O1′-C1′-C2-Se1. A value of ø ) 0°
refers to the conformation in which the furanose oxygen is cis
planar to the selenophene selenium. A positive value of ø
indicates a counterclockwise rotation of the C2-O1/Se bond
relative to the C1′-O1′ bond when viewed down the C-
glycosidic bond from C2 to C1′.
2-â-D-Ribofu r a n osylselen op h en e-3-ca r boxa m id e (14â).
Treatment of compound 11â (0.5 g, 1.08 mmol) with 30%
ammonium hydroxide (15 mL) for 8 h at room temperature
and evaporation to dryness afforded a product which was
purified by chromatography on a silica gel column eluting with
CHCl3-MeOH (80:20). Evaporation of the homogeneous frac-
tions gave 90 mg (27.5%) of 14â as a white foam. TLC
(CHCl3-MeOH, 80:20): Rf ) 0.46. 1H-NMR (DMSO-d6): δ 3.5
(t, J ) 4.9 Hz, 2H, H-5′), 3.68 (t, J ) 5.9 Hz, 1H, H-4′), 3.82
(dd, J ) 4.7 Hz, 8.1 Hz, 1H, H-3′), 3.9 (br s, 1H, H-2′), 4.8 (t,
J ) 5.2 Hz, 1H, OH), 4.9 (br s, 1H, OH), 5.38 (d, J ) 7.0 Hz,
1H, H-1′), 5.9 (br s, 1H, OH), 7.48 (br s, 1H, NH), 7.52 (d, J )
5.8 Hz, 1H, H-4), 7.82 (br s, 1H, NH), 8.0 (d, J ) 5.8 Hz, 1H,
H-5). Anal. (C10H13NO5Se) C, H. N.
5-â-D-R ib ofu r a n osylselen op h en e-3-ca r b oxa m id e (1).
The title compound was obtained from 12â (4 g, 11.93 mmol)
(reaction time 9 h) by the above method. After chromato-
graphic purification of the reaction mixture (CHCl3-MeOH-
NH4OH, 70:29:1), 1 was obtained as a white foam (2.15 g, 58%).
TLC (CHCl3-MeOH, 70:30): Rf ) 0.31. UV (MeOH) λmax 210
nm (ꢀ 35 300), 240 (ꢀ 10 500). 1H-NMR (Me2SO-d6): δ 3.50 (t,
J ) 5.1 Hz, 2H, H-5′), 3.72 (m, 1H, H-4′), 3.80-3.95 (m, 2H,
H-3′, H-2′), 4.76 (d, J ) 6.6 Hz, 1H, H-1′), 4.8 (t, J ) 5.5 Hz,
1H, OH), 5.0 (d, J ) 3.5 Hz, 1H, OH), 5.18 (d, J ) 7.0 Hz, 1H,
OH), 7.12 (br s, 1H, NH), 7.58 (s, 1H, H-4), 7.70 (br s, 1H,
NH), 8.70 (s, 1H, H-2). Anal. (C10H13NO5Se) C, H, N.
5-r-D-Ribofu r a n osylselen op h en e-3-ca r boxa m id e (15).
Compound 15 was prepared from 12R (1 g, 2.98 mmol)
(reaction time 9 h) by the above method. The reaction residue
was chromatographed on a silica gel column with CHCl3-
MeOH (90:10) to give 15 as a foam (0.486 g, 53%). TLC
(CHCl3-MeOH, 90:10): Rf ) 0.07. 1H-NMR (Me2SO-d6): δ
3.46 (m, 2H, H-5′), 3.65 (t, J ) 6.0 Hz, 1H, H-4′), 3.81 (m, 1H,
H-3′), 3.90 (m, 1H, H-2′), 4.75 (d, J ) 7.0 Hz, 1H, H-1′), 4.80-
5.30 (br s, 3H, OH), 7.1 (br s, 1H, NH), 7.57 (s, 1H, H-4), 7.70
(br s, 1H, NH), 8.68 (s, 1H, H-2). Anal. (C10H13NO5Se) C, H,
N.
Energy profiles for the selenophenfurin model compound
were obtained with the furanose ring fixed in both 3′-endo and
2′-endo puckers. The slightly lower global energy minimum
for the 2′-endo conformer was normalized to 0 kcal/mol.
Energies for each conformer were obtained for values of ø
between ø ) -180° and 180°. In each case, the value of ø was
incremented in 20° steps and fixed. All remaining geometry
variables describing the fragment were then optimized, with
the exception of the furanose torsion angles. The starting
geometry at each value of ø was the optimized geometry
obtained at the previous value. All geometry optimizations
used the analytical gradient method.20,21 Optimized geom-
etries and associated SCF energies were obtained using the
3-21G* basis set. Thus, each point in Figure 2 represents a
calculation at the RHF/3-21G*//3-21G* level.20,21 Point charges
were obtained from the selenophenfurin fragment using the
natural population analysis method incorporated in Gaussian
94.20,22 Charges were obtained from optimized geometries at
the RHF level of theory using a 3-21G* basis set.20,21
An tip r olifer a tive Assa ys. The cells used are as follows:
L1210, murine lymphocytic leukemia cells; K562, human
myelogenous leukemia cells; Wil2-NS, human splenic B-
lymphoblastoid cells; CCRF-SB, human acute B-lymphoblastic
cells; Raji, human lymphoblast-like cells from
a Burkitt
2,5-Di-â-D-r ib ofu r a n osylselen op h en e-3-ca r b oxa m id e
(16). Compound 16 was obtained from 13 (1.7 g, 3.65 mmol)
by the above method and purified by chromatography on a
silica gel column (CHCl3-MeOH, 80:20) as a foam (0.8 g, 50%).
TLC (CHCl3-MeOH-NH4OH, 60:30:10): Rf ) 0.29. 1H-NMR
(Me2SO-d6): δ 3.40 (m, 4H, 2H-5′a, 2H-5′b), 3.60-3.90 (3m,
6H, H-4′a, H-4′b, H-3′a, H-3′b, H-2′a, H-2′b), 4.65 (d, J ) 7.0,
1H, H-1′b), 4.70-5.12 (3 br s, 6H, OH), 5.33 (d, J ) 7.3 Hz,
1H, H-1′a), 7.37 (s, 1H, H-4), 7.40 (br s, 1H, NH), 7.80 (br s,
1H, NH). Anal. (C15H21NO9Se) C, H, N.
lymphoma; CCRF-CEM and MOLT-4, human acute T-lym-
phoblastic leukemias; CHO-K1, Chinese hamster ovary cells;
HT-29, human colon adenocarcinoma; HeLa, human cervix
carcinoma; ACHN, human renal adenocarcinoma; 5637, hu-
man bladder carcinoma. Cell cultures were grown in their
specific media supplemented with 10% FCS and antibiotics
and incubated at 37 °C in a humidified, 5% CO2 atmosphere.
Exponentially growing leukemia and lymphoma cells were
resuspended at a density of 1 × 105 cells/mL, in growth
medium, and cultured with various concentrations of the
compounds. Cell viability was determined after 96 h at 37 °C
by the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bro-
mide (MTT) method.23 Activity against solid tumor-derived
cells was evaluated in exponentially growing cultures seeded
at 5 × 104 cells/mL and allowed to adhere for 16 h to culture
plates before addition of the drugs. Cell viability was deter-
mined by the MTT method 4 days later.
Cr ysta llogr a p h ic Stu d y. Small colorless needle-shaped
crystals of the carboxylate precursor of selenophenfurin [ethyl
5-â-D-ribofuranosylselenophene-3-carboxylate, C12H16O6Se (12â)]
were obtained from chloroform. Crystals are orthorhombic,
space group P212121′ with cell dimensions a ) 4.934(1) Å, b )
12.760(3) Å, and c ) 21.764 Å, Z ) 4, and are isomorphous
with those of the thiophene analogue.14 Diffraction data were
collected at 223(2) K on a Siemens SMART CCD detector
system using graphite monochromatized Mo KR radiation from
a sealed-tube source. A total of 8695 reflections were mea-
sured to θ ) 28.3° and averaged to yield 3262 unique
reflections. The structure was solved by routine application
of direct methods and refined to R ) 3.8% (Rw2 ) 9.4%) for all
data using the SHELXTL package.19 The structure is isomor-
phous to that of the thiophene analogue.14 All non-hydrogen
atoms were refined with anisotropic temperature factors using
full-matrix least-squares techniques. Thiophene and ribose
methylene protons were added in idealized positions and
refined using a “riding” model.19 Initial positions of hydroxyl
and methyl protons were determined from maxima in differ-
ence map values over the loci of possible hydrogen positions
and their torsion angles subsequently refined.19 Isotropic
temperature factors for hydrogens were set at either 1.2 or
1.5 times the value of the equivalent isotropic factor of the
bound carbon or oxygen.19 High thermal parameters in the
ethyl carbons suggested some disorder in this portion of the
Cell growth at each drug concentration is expressed as
percentage of untreated controls, and the concentration result-
ing in 50% growth inhibition (IC50) was determined by linear
regression analysis.
IMP Deh yd r ogen a se Assa y. K562 cells (1 × 106 cells/
mL; 10 mL) in logarithmic phase of growth were incubated
with saline or indicated concentrations of the agents for 2 h
at 37 °C. The cells were then harvested by centrifugation,
washed once with cold phosphate-buffered saline, and lyzed
in buffer containing 50 mM Tris-HCl, pH 7.4, 150 mM NaCl,
10 mM MgCl2, 0.5% NP-40, and 2 µg/mL aprotinin. The lysate
was kept for 20 min on ice and centrifuged at 13000g for 20
min, and the supernatant was used as a source of IMPDH.
The enzyme activity was measured according to the pub-
lished methodology.24 Briefly, 5 µL aliquots of 0.5 M KCl
containing 20 mM allopurinol were dispensed into the apex
of Eppendorf tubes and dried at room temperature (25 °C).
For the conduct of the assay, in a total volume of 10 µL, tubes

Synthesis and Activity of Selenophenfurin
J ournal of Medicinal Chemistry, 1997, Vol. 40, No. 11 1737
W.; Srivastava, P. C.; Robins, R. K. Broad-spectrum antiviral
activity of 2-â-D-ribofuranosylselenazole-4-carboxamide, a new
antiviral agent. Antimicrob. Agents Chemother. 1983, 24, 353-
361. (d) Goldstein, B. M.; Leary, J . F.; Farley, B. A.; Marquez,
V. E.; Rowley, P. T. Induction of HL60 Cell Differentiation by
Tiazofurin and Its Analogues: Characterization and Efficacy.
Blood 1991, 78, 593-598.
contained 5 µL of the substrate mixture containing 286 µM
[2,8-3H]IMP (200 µCi/mL) and 1 mM NAD. The reaction was
initiated by the addition of a 5 µL aliquot of enzyme extract.
After 30 min at 37 °C, the reaction was terminated by heating
for 1 min at 95 °C. Tubes were centrifuged at 13000g for 0.5
min, 5 µL of 100% KOH was deposited on the underside of
the cap, and the tubes were closed and incubated at room
temperature overnight (16 h). The caps containing the droplet
were cut, and the radioactivity was determined by scintillation
spectrometry. IMP dehydrogenase activity is expressed as
nmol of XMP formed/mg of protein/h.
Deter m in a tion of th e Con cen tr a tion of In tr a cellu la r
Ribon u cleotid es. Cells in culture were treated with saline
or agents for 2 h at 37 °C; cells were harvested by centrifuga-
tion and washed once with cold saline. Cells were extracted
with cold 10% trichloroacetic acid and centrifuged for 0.5 min;
the supernatant was immediately neutralized with 0.5 M tri-
n-octylamine in freon. An aliquot of the neutralized extract
was analyzed on HPLC using a Partisil 10-SAX column as
described.25
(10) J ayaram, H. N.; Dion, R. L.; Glazer, R. I.; J ohns, D. G.; Robins,
R. K.; Srivastava, P. C.; Cooney, D. A. Initial studies on the
Mechanism of Action of a New Oncolytic Thiazole Nucleoside,
2-â-D-Ribofuranosylthiazole-4-carboxamide. Biochem. Pharma-
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Marquez, V. E.; Kelley, J . A.; Robins, R. K.; Cooney, D. A.; J ohns,
D. G. Conversion of 2-â-D-ribofuranosylselenazole-4-carboxamide
to an analogue of NAD with potent IMP dehydrogenase-
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of inosinate dehydrogenase by metabolites of 2-â-D-Ribofura-
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1982, 107, 862-868.
(12) Burling, F. T.; Goldstein, B. M. Computational Studies of
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(13) Li, H.; Hallows, W. A.; Punzi, J . S.; Marquez, V. E.; Carrell, H.
L.; Pankiewicz, K. W.; Watanabe, K. A.; Goldstein, B. M.
Crystallographic Studies of Two Alcohol Dehydrogenase-bound
Analogues of Thiazole-4-Carboxamide Adenine Dinucleotide
(TAD), the Active Anabolite of the Antitumor Agent Tiazofurin.
Biochemistry 1994, 33, 23-32.
Ack n ow led gm en t. This work was supported by the
CNR and by grants (94-0356 and 94-0359) from the
Ministry of Health ISS AIDS Project 1996, Italy.
Su p p or tin g In for m a tion Ava ila ble: Coordinates, ther-
mal parameters, bond lengths and angles, and crystal and
refinement data for selenophenfurin-3-carboxylate (12â) (6
pages); table of observed and calculated structure factors (8
pages). Ordering information is given on any current mast-
head page.
(14) Franchetti, P.; Cappellacci, L.; Grifantini, M.; Barzi, A.; Nocen-
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and Interactions with Inosine Monophosphate Dehydrogenase.
J . Med. Chem. 1995, 38, 3829-3837.
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(17) Rosemeyer, H.; Toth, G.; Seela, F. Assignment of Anomeric
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(19) Sheldrixk, G. SHELXTL Version 5 reference manual; Siemens
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