Sugar-modified conjugated diene analogues of adenosine and uridine: Synthesis, interaction with S-adenosyl-L-homocysteine hydrolase, and antiviral and cytostatic effects

Article abstract of DOI:10.1021/jm020064f

Moffatt oxidation of 2′,3′-O-isopropylideneuridine (1a) and treatment of the crude 5′-aldehyde with formylmethylene-stabilized Wittig reagent gave the vinylogously extended 7′-aldehyde 2a. Condensation of 2a with ethoxycarbonyl- or dibromomethylene phosph

Full text of DOI:10.1021/jm020064f

J . Med. Chem. 2002, 45, 2651-2658
2651
Su ga r -Mod ified Con ju ga ted Dien e An a logu es of Ad en osin e a n d Ur id in e:
Syn th esis, In ter a ction w ith S-Ad en osyl-L-h om ocystein e Hyd r ola se, a n d An tivir a l
a n d Cytosta tic Effects
Stanislaw F. Wnuk,*,† Bong-Oh Ro,†,‡ Carlos A. Valdez,† Elzbieta Lewandowska,†,§ Neida X. Valdez,†
Pablo R. Sacasa,† Dan Yin,| J insong Zhang,| Ronald T. Borchardt,| and Erik De Clercq
Department of Chemistry, Florida International University, Miami, Florida 33199, Department of Pharmaceutical Chemistry,
University of Kansas, Lawrence, Kansas 66047, and Rega Institute for Medical Research, Katholieke Universiteit of Leuven,
B-3000 Leuven, Belgium
Received February 7, 2002
Moffatt oxidation of 2′,3′-O-isopropylideneuridine (1a ) and treatment of the crude 5′-aldehyde
with formylmethylene-stabilized Wittig reagent gave the vinylogously extended 7′-aldehyde
2a . Condensation of 2a with ethoxycarbonyl- or dibromomethylene phosphorane reagents gave
the conjugated dienes 6a and 4a , respectively. Deacetonization gave diene ester 7a [5′(E),7′(E);
with s-trans conformation] and dibromodiene 5a [5′(E)], respectively. Analogously, 2′,3′-O-
isopropylideneadenosine (1b) was Wittig-extended into the conjugated dibromodiene 5b [5′(E)]
and dienoic ester 7b [5′(E),7′(E)]. Furthermore, palladium-catalyzed coupling of the vinyl 6′(E)-
stannanes 14 with (E) and (Z) ethyl 3-iodoacrylate gave stereodefined access to dienoic esters
7 (E,E) and 16 (E,Z). Incubation of AdoHcy hydrolase with 100 µM of 5b resulted in partial
inhibition of the enzyme without any apparent change in the enzyme’s nicotinamide adenine
dinucleoside (NAD+) content. In contrast, 7b and 16b produced time- and concentration-
dependent inactivation of S-adenosyl-L-homocysteine (AdoHcy) hydrolase producing significant
decreases in the enzyme’s NAD+ content. However, 7b and 16b upon incubation with AdoHcy
hydrolase were not metabolized suggesting that these compounds are type I mechanism-based
inhibitors. No specific antiviral activity was noted for 5a ,b, 7a ,b, and 16a ,b against any of the
viruses tested; dibromodiene 5b proved cytotoxic at a concentration g6.7 µM and cytostatic at
g11 µM, while dienoic esters 16a ,b showed activity against both varicella-zoster virus (at 10
µM, 16a ) and cytomegalovirus (at 10 µM, 16a ; 18 µM, 16b).
In tr od u ction
The enzyme S-adenosyl-L-homocysteine (AdoHcy) hy-
drolase (EC 3.3.1.1) effects hydrolytic cleavage of AdoHcy
to adenosine (Ado) and L-homocysteine (Hcy).1 The
cellular levels of AdoHcy and Hcy are critical since
AdoHcy is a potent feedback inhibitor of crucial trans-
methylation enzymes,1,2 and elevated plasma levels of
F igu r e 1.
Hcy in humans have been shown to be a risk factor in
activity of AdoHcy hydrolase.7 Addition of an enzyme-
coronary artery disease.3 A number of inhibitors that
sequestered water molecule across the 5′,6′-double bond
of B (Y ) F), followed by loss of bromide, was proposed
to generate the homoAdo 6′-carboxyl fluoride at the
function as substrates for the “3′-oxidative activity” of
AdoHcy hydrolase and convert the enzyme from its
active form [nicotinamide adenine dinucleotide (NAD+)]
active site of AdoHcy hydrolase.7b Nucleophilic attack
to its inactive form [reduced nicotinamide adenine
by proximal amino acid functionalities caused type II
dinucleotide (NADH), type I inhibition] have been
(covalent binding) inhibition. Addition of water across
prepared.1 Inhibitors that function as substrates for the
the 5′,6′-triple bond of haloacetylenes8 C followed by
tautomerization of the hydroxyvinyl intermediates was
“5′/6′-hydrolytic activity” include the vinyl fluorides
[9-(5-deoxy-5-fluoro-â-D-erythro-pent-4-enofuranosyl)ad-
postulated to generate similar reactive electrophiles at
enine],4 the homovinyl halides5 A (Figure 1), and the
the enzyme active site.8,9 The doubly homologated vinyl
oxime derivatives of adenosine 5′-aldehyde6 among
halides D and its acetylenic analogue with greater
conformational flexibility at C5′ relative to vinylogous
others, and they have been reviewed.1
The geminal (dihalohomovinyl)adenosines B were
designed as putative new substrates for the hydrolytic
B or acetylenic C derivatives were not substrate for the
hydrolytic activity of the AdoHcy hydrolase.10
* To whom correspondence should be addressed. Tel: 305-348-6195.
Covalent inhibition of AdoHcy hydrolase with 5′-
Fax: 305-348-3772. E-mail: wnuk@fiu.edu.
deoxy-5′-difluoromethylthioadenosine by the electro-
philic entity (thioformyl fluoride) liberated from the
substrate has been reported by Guillerm and co-
workers.11a,b They also developed a new series of the 5′-
thioadenosine analogues substituted at sulfur with
† Florida International University.
‡ Sabbatical leave from Chosun University, Kwangju City, Korea.
§ Faculty leave from the Department of Chemistry, University of
Agriculture, Poznan, Poland.
| University of Kansas.
Katholieke Universiteit of Leuven.
10.1021/jm020064f CCC: $22.00 © 2002 American Chemical Society
Published on Web 04/24/2002

2652 J ournal of Medicinal Chemistry, 2002, Vol. 45, No. 12
Wnuk et al.
Sch em e 1a
Sch em e 2a
a
Reagents: (a) Bu3SnH/AIBN/toluene/∆. (b) (E or Z) ethyl
3-iodopropenoate/Pd(PPh3)4/THF/∆. (c) TFA/H2O.
2′,3′-O-isopropylideneadenosine (1b) gave 7′-aldehyde
2b in lower yield (22%). Attempted deprotection (NH3/
MeOH, TFA/H2O) of 2c failed to give pure 3b (a
vinylogous extension of the potent inhibitor adenosine
5′-aldehyde6). Treatment of 2c with ethoxycarbonyl-
methylene Wittig reagent and successive deprotections
of the resulting 6c gave the diene 7b (E,E) with the
extended conjugation to an ethoxycarbonyl group at C8′
(42% overall from 2c). Condensation of the aldehyde 2c
with (dibromomethylene)triphenylphosphorane and sub-
sequent deprotections produced somehow unstable con-
jugated dibromodiene 5b in low yield after tedious
purifications. Therefore, the synthesis of 5b from sugar
precursors was investigated.
Selective hydrolysis of the 5,6-O-isopropylidene acetal
from 1,2;5,6-di-O-isopropylidene-R-D-allofuranose and
oxidative cleavage with periodic acid17 gave the deho-
mologated 5-aldehyde, which was treated with formyl-
methylene Wittig reagent to give the vinylogous alde-
hyde 8 as E-isomer (68% overall). Successive Wittig type
olefination with the dibromomethylene reagent gave 10
that was benzoylated to produce (dibromodiene)ribose
11 (53%; 36% total). Subjection of 3-O-benzoyl-1,2;5,6-
di-O-isopropylidene-R-D-allofuranose to this double Wit-
tig extension sequence gave 11 in higher yield (61%
total). The isopropylidene group was removed from 11
(TFA/H2O), and the product was acetylated to give the
anomeric acetates 12 (44%; R/â, ∼1:4). Coupling (SnCl4/
CH3CN)18 of the anomeric mixture of 12 and adenine
followed by deacylation gave the somehow unstable 8′,8′-
dibromodiene adenosine 5b.
a
Reagents: (a) DCC/DMSO/Cl2CHCO2H. (b) Ph3PdCHCHO/
CH2Cl2. (c) TFA/H2O. (d) NH3/MeOH. (e) CBr4/PPh3/(Zn)CH2Cl2.
(f) Ph3PdCHCO2Et/CH2Cl2. (g) BzCl/pyridine. (h) (i) TFA/H2O; (ii)
Ac2O/pyridine/DMAP. (i) Adenine/SnCl4/CH3CN.
allenyl and propynyl groups that are processed by
hydrolytic activity of the enzyme causing its irreversible
inactivation.11c The X-ray crystal structures of AdoHcy
hydrolase revealed an unusual dual role for a catalytic
water molecule at the active site.12
We now describe the syntheses of the first dibromo-
dienes and dienoic esters of the uracil and adenine
nucleosides; their antiviral, cytotoxic, and cytostatic
activities; and the interaction of adenine analogues with
AdoHcy hydrolase. The conjugated dienes derived from
adenosine were designed as putative substrates of the
hydrolytic activity of AdoHcy hydrolase. These deriva-
tives with extended conjugation to the furanosyl ring
should provide different stereochemical and conforma-
tional attributes for proper binding. Moreover, dienoic
esters having a carboxylate group at C9′ might approach
the binding site for the carboxylate function of AdoHcy
hydrolase (C10′).
Ch em istr y
Stille coupling19 between the nucleoside vinyl 6′(E)-
stannanes 14a or 14b [prepared5,20 by stannyldesul-
fonylation of the readily available 6′(E)-tosylvinyl homo-
nucleosides21 13] and the corresponding vinyl halides
was found to give stereodefined access to dienes. Thus,
Pd-catalyzed coupling of 14a or 14b with ethyl E-3-
iodopropenoate gave dienoic esters 6a or 6b as single
isomers (E,E; Scheme 2). On the other hand, cross
coupling of the 14a or 14b with ethyl Z-3-iodopropeno-
ate afforded dienes 15a and 15b (E,Z; 70% yield).
Coupling constant analysis in the 1H NMR spectra
(J 5′-6′ ) 15.3 Hz, J 6′-7′ ) 11.4 Hz, and J 7′-8′ ) 11.3 Hz)
were diagnostic15 for the 5′(E)/7′(Z) stereochemical as-
signment. The structure of dienes was also confirmed
by correlation spectroscopy (COSY) and HETCOR ex-
periments. Deprotection of 6a ,b and 15a ,b gave 7a ,b
and 16a ,b, respectively.
Moffatt oxidation13 of 2′,3′-O-isopropylideneuridine
(1a ) and treatment of the crude 5′-aldehyde with
formylmethylene-stabilized Wittig reagent gave the
vinylogously extended 7′-aldehyde 2a (61%; E isomer,
J 5′-6′ ) 15.8 Hz) as demonstrated14 for thymidine
analogues (Scheme 1). Condensation of 2a with ethoxy-
carbonylmethylene-stabilized Wittig reagent produced
conjugated diene 6a as a single product in 81% yield.
Deacetonization [trifluoroacetic acid (TFA)/H2O] and
crystallization gave dienoic ester 7a . The 1H nuclear
magnetic resonance (NMR) coupling constants for 6a
(J 5′-6′ ) 15.3 Hz, J 6′-7′ ) 10.3 Hz, and J 7′-8′ ) 15.4 Hz)
and 7a are indicative of 5′(E)/7′(E) stereochemical
assignments with an s-trans conformation and are in
harmony with the literature values for the conjugated
dienoic esters.15 Treatment of the 7′-aldehyde 2a with
generated in situ dibromomethylene phosphorane re-
agent (Ph3P/CBr4)16 gave the conjugated 8′,8′-dibromo-
diene 4a in 71% as a single isomer. Removal of the
isopropylidene group yielded 5a .
In a ctiva tion of S-Ad en osyl-L-h om ocystein e
Hyd r ola se
The 6-N-benzoyl-2′,3′-O-isopropylideneadenosine (1c)
was converted into the vinyl 7′-aldehyde 2c (48%) while
Incubation of AdoHcy hydrolase with 100 µM of
dibromodiene 5b resulted in partial inhibition of the

Adenosine and Uridine Conjugated Diene Analogues
J ournal of Medicinal Chemistry, 2002, Vol. 45, No. 12 2653
Ta ble 1. Inhibition of AdoHcy Hydrolase with 5b, 7b, and 16b
% enzyme
% NAD+
compds
activity remaininga
remainingb
5b
7b
16b
48 ( 1
3.6 ( 0.1
1.8 ( 0.6
93.1 ( 3.4
25.9 ( 3.4
36.2 ( 6.8
a
AdoHcy hydrolase (210 nM) was incubated with 100 µM 5b,
7b, and 16b in buffer A at 37 °C for 20 min, and the remaining
enzyme activity was assayed as described in the Experimental
b
Section. Data are the average of duplicate determinations. Ado-
Hcy hydrolase (5.8 µM) was incubated with 100 µM 5b, 7b, and
16b in buffer A at 37 °C for 20 min, and the NAD+/NADH content
was assayed as described in the Experimental Section.
enzyme activity without any apparent change in the
enzyme’s NAD+ content (Table 1). In addition, 5b itself
was not metabolized upon incubation with AdoHcy
hydrolase (data not shown). These results suggest that
5b is not a substrate for the enzyme’s hydrolytic or 3′-
oxidative activities. The compound appears to be a
competitive inhibitor of AdoHcy hydrolase with weak
inhibitory effects on the enzyme (Table 1).
Adenosine dienoic esters 7b and 16b were designed
as putative substrates for the hydrolytic activity of
AdoHcy hydrolase. Conceptually, enzyme-mediated ad-
dition of water might occur as a 1,2- or 1,4-process
across the conjugated dienes in 7b and 16b resulting
in the formation of metabolites, which should be detect-
able by high-performance liquid chromatography (HPLC).
To test this hypothesis, compounds 7b and 16b were
incubated with AdoHcy hydrolase and the incubation
buffer was analyzed by HPLC for the formation of any
metabolites of these compounds. No evidence for the
disappearance of 7b and 16b or the appearance of
metabolites was obtained (data not shown). These
results suggest that 7b and 16b are not substrates for
the enzyme’s hydrolytic activity.
Incubation of compounds 7b and 16b at 100 Μ with
AdoHcy hydrolase produced significant inhibition of the
enzyme activity and partial depletion of its NAD+
content (Table 1). Dienoic esters 7b and 16b produced
time- and concentration-dependent inactivation of
AdoHcy hydrolase (Figure 2A). The Ki and kinact values
for 7b and 16b (Table 2) were obtained using the Kitz
and Wilson equation22 {kobs ) kinact ‚ [I]/(Ki + [I])}
(Figure 2B). These results, which are similar to those
reported on doubly homologated dihalovinyl and acety-
lene analogues of adenosine,10 suggest that inactivation
of AdoHcy hydrolase by 7b and 16b involves a type I
mechanism (cofactor depletion). However, we cannot
totally rule out the possibility of a type II mechanism
(covalent modification) where the products arising from
the enzyme’s hydrolytic activity are tightly bound to the
enzyme and are not released into the solution.
F igu r e 2. Time course of inactivation on AdoHcy hydrolase
by 16b. (A) AdoHcy hydrolase (210 nM) was incubated with
16b (9, 0.1 Μ; b, 1 Μ; 2, 10 Μ; and 1, 100 Μ) in buffer A at
37 °C. At the times indicated, enzyme activity was determined
in the synthetic direction as described in the Experiemental
Section. (B) This shows a plot of kobs values, pseudo-first-order
rate constant calculated from the data shown in A vs the
concentration of 16b. These data were then fitted to the Kitz
and Wilson equation22 to estimate the Ki and kinact values for
16b.
Ta ble 2. Ki and kinact Values for the Inhibitory Effects of 7b
and 16b on AdoHcy Hydrolase
compds
Ki (µM)
kinact (min-1
)
7b
16b
10 ( 6
13.7 ( 14
0.7 ( 0.1
0.59 ( 0.1
(7a ), 175 ((33) (7b), 40 ((7.5) (16a ), and 160 ((10) µM
(16b), respectively.
An tivir a l, Cytotoxic, a n d Cytosta tic Activities
In human embryonic lung (HEL) cells, the compounds
showed minor activity against human cytomegalovirus
(CMV, strains AD-169 and Davis) and varicella-zoster
virus (VZV, strains YS, OKA, 07/1, and YS/R) at
subtoxic concentrations. The minimum cytotoxic con-
centrations were >120 Μ for 5a and 7a ,b and 45 µM
for 5b. The CC50 of 5b for HEL cells was 54 µM. E,Z-
Dienoic esters 16a ,b showed some activity against both
VZV [50% effective concentration (EC50): 10 µM, 16a ]
and CMV (EC50: 10 µM, 16a ; 18 µM, 16b ) albeit
Uridine 5a , 7a , or 16a and adenosine 5b, 7b, or 16b
diene analogues were examined for their antiviral,
cytotoxic, and cytostatic activity in a broad spectrum of
antiviral, cytotoxic, and cytostatic tests. When evaluated
against human immunodeficiency virus (HIV-1, IIIB
strain; HIV-2, ROD strain) in T-lymphocytic MT-4 cells,
no antiviral effects were noted with 5a ,b, 7a ,b, and
16a ,b at subtoxic concentrations. The 50% cytostatic
concentration (CC50) was 300 (5a ), 11 ((5.5) (5b), >370

2654 J ournal of Medicinal Chemistry, 2002, Vol. 45, No. 12
Wnuk et al.
distillation from CaH2 [except tetrahydrofuran (THF)/potas-
sium] under argon. Sonication was performed with a Branson
5200 ultrasonic bath.
concentrations that were at an average 5-fold below the
cytotoxicity threshold.
In human embryonic skin muscle (E6SM) cell cul-
tures, again, 5b was the most cytotoxic (minimum
concentration required to cause a microscopically de-
tectable alteration of normal cell morphology g6.7 µM).
For the other compounds, it was g40 µM. No activity
was noted against herpex simplex virus (HSV-1, KOS
strain; HSV-2, G strain), vaccinia virus, or vesicular
stomatitis virus at subtoxic concentrations.
1-[5,6-Dideoxy-2,3-O-isopr opyliden e-â-D-r ibo-h ept-5(E)-
en od ia ld o-1,4-fu r a n osyl]u r a cil (2a ). A solution of 1a (2.84
g, 10 mmol) and dicyclohexylcarbodiimide (DCC; 7.21 g, 35
mmol) in dried Me2SO (25 mL) was cooled (∼5 °C) under argon,
Cl2CHCO2H (0.41 mL, 645 mg, 5 mmol) was added, and
stirring was continued for 90 min at ambient temperature. The
(triphenylphosphoranylidene)acetaldehyde (3.19 g, 10.5 mmol)
was then added in one portion, and the resulting solution was
stirred for 5 h. Oxalic acid dihydrate (3.15 g, 25 mmol) in
MeOH (20 mL) was added, and after 20 min, the reaction
mixture was concentrated (to ∼one-third volume), dicyclo-
hexylurea was filtered and washed with cold MeOH, and the
combined filtrates were evaporated (in vacuo). The residue was
partitioned (NaHCO3/H2O/CHCl3), and the organic layer was
washed (H2O, brine) and dried (MgSO4), and volatiles were
evaporated. Column chromatography of the residue (50 f 70%
Also, in HeLa cell cultures, no activity was noted with
any of the compounds against vesicular stomatitis virus,
respiratory syncytial virus, or Coxsackie B4 virus at a
concentration of g35 µM (minimum cytotoxic concentra-
tion for 5b) or g200 µM (5a , 7a ,b, and 16a ,b). In vero
cell cultures, again, 5b was cytotoxic at g35 mM (the
other compounds at g200 µM), and no specific activity
against parainfluenza virus type 3, reovirus type 1,
Sindbis virus, Coxsackie B4 virus, or Punta Toro virus
was noted at subtoxic concentrations.
1
EtOAc/hexane) gave 2a (1.88 g, 61%) as a syrup. H NMR: δ
1.32 and 1.53 (2 × s, 2 × 3, 2 × Me), 4.74 (“t”, J ) 4.8 Hz, 1,
H4′), 4.92 (dd, J ) 4.3, 6.2 Hz, 1, H3′), 5.13 (d, J ) 6.3 Hz, 1,
H2′), 5.56 (s, 1, H1′), 5.72 (d, J ) 7.9 Hz, H5), 6.22 (ddd, J )
1.5, 7.8, 15.8 Hz, 1, H6′), 6.93 (dd, J ) 5.7, 15.8 Hz, 1, H5′),
7.27 (d, J ) 8.0 Hz, 1, H6), 9.51 (d, J ) 7.8 Hz, 1, H7′), 10.40
(br s, 1, NH). 13C NMR: δ 25.56, 27.40, 84.81 and 85.06 (C2′
and C3′), 88.08 (C4′), 96.91 (C1′), 103.15 (C5), 115.05, 132.47
(C6′), 144.11 (C6), 150.75 (C2), 153.11 (C5′), 164.38 (C4), 193.91
(C7′). MS: m/z 309 (MH+).
Su m m a r y a n d Con clu sion s
The novel dibromodienes 5a ,b and dienoic esters 7a ,b
and 16a ,b with the extended conjugation to the ribose
ring were prepared from uridine and adenosine (or
hexofuranose precursors) using Wittig type homologa-
tions or Stille cross-coupling procedures. The adenosine
analogues 5b, 7b, and 16b, with two possible sites for
the hydrolytic interaction with the AdoHcy hydrolase
via a 1,2- or 1,4-process, were found to be type I
inhibitors of the enzyme. Dibromodiene 5b was found
to be a competitive inhibitor, whereas dienoic esters 7b
and 16b produced time- and concentration-dependent
inactivation of AdoHcy hydrolase with significant de-
creases in the enzyme’s NAD+ content. However, upon
incubation of 7b and 16b with AdoHcy hydrolase, no
metabolites of these dienes were detected suggesting
that they are not substrates for the enzyme’s hydrolytic
activity. However, we cannot totally rule out the pos-
sibility that metabolites are formed but they are tightly
bound to the enzyme and not released into the incuba-
tion media. No specific antiviral activity was observed
with any of the compounds at subtoxic concentrations.
Compound 5b emerged as the most cytotoxic (cytotox-
icity threshold: 6.7 µM).
6-N-Ben zoyl-9-[5,6-d id eoxy-2,3-O-isop r op ylid en e-â-D-
r ibo-h ep t-5(E)-en od ia ld o-1,4-fu r a n osyl]a d en in e (2c). Oxi-
dation of 1c13 (1.23 g, 3 mmol) and treatment of the crude 5′-
aldehyde with (triphenylphosphoranylidene)acetaldehyde (as
described for 2a ; column chromatography: CHCl3 f 2%
MeOH/CHCl3) gave 2c (625 mg, 48%). 1H NMR: δ 1.39 and
1.53 (2 × s, 2 × 3, 2 × Me), 4.93 (“t”, J ) 4.5 Hz, 1, H4′), 5.25
(dd, J ) 3.7, 6.1 Hz, 1, H3′), 5.55 (dd, J ) 1.2, 6.2 Hz, 1, H2′),
6.08 (ddd, J ) 1.5, 7.7, 15.8 Hz, 1, H6′), 6.22 (d, J ) 1.3 Hz, 1,
H1′), 6.83 (dd, J ) 5.4, 15.8 Hz, 1, H5′), 7.44-8.05 (m, 6, Harom
and NH), 8.11 (s, 1, H2), 8.71 (s, 1, H8), 9.43 (d, J ) 7.8 Hz, 1,
H7′). MS: m/z 436 (100, MH+).
Note. Subjection of 1b (307 mg, 1 mmol) to this sequence
and two column chromatographies (CHCl3 f 4% MeOH/CHCl3
and EtOAc f 2% MeOH/EtOAc) gave 2b (73 mg, 22%; ∼10%
1
contamination). H NMR: δ 9.46 (d, J ) 7.7 Hz, 1, H7′). MS:
m/z 332 (100, MH+).
Dep r otection of 2c. Attem p ted Syn th esis of 9-[5,6-
Did eoxy-â-D-r ibo-h ep t-5(E)-en od ia ld o-1,4-fu r a n osyl]a d -
en in e (3b). Treatment of 2c (44 mg, 1 mmol) with NH3/MeOH
and TFA/H2O (as described for 7b) followed by RP-HPLC
purification (as described for 5b) gave small quantities of 3b
(∼4 mg) contaminated (∼25%, 1H NMR) by byproducts. 1H
NMR (MeOH-d4): δ 6.36 (ddd, J ) 1.5, 7.8, 15.8 Hz, 1, H6′),
7.14 (dd, J ) 5.7, 15.8 Hz, 1, H5′), 9.60 (d, J ) 7.8 Hz, 1, H7′).
Exp er im en ta l Section
1-[8,8-Dibr om o-5,6,7,8-tetr adeoxy-2,3-O-isopr opyliden e-
â-D-r ibo-oct-5(E)-7-d ien ofu r a n osyl]u r a cil (4a ). The solu-
tion of 2a (308 mg, 1 mmol) in CH2Cl2 (10 mL) was added into
Uncorrected melting points were determined with a capil-
lary apparatus. UV spectra were measured with solutions in
1
MeOH. H (400 MHz) and 13C (100 MHz) NMR spectra were
a
stirring mixture containing (dibromomethylene)triphen-
ylphosphorane [generated in situ by stirring CBr4 (663 mg, 2
mmol) and Ph3P (1.05 g, 4 mmol) in dried CH2Cl2 (20 mL) for
15 min at ∼0 °C (ice-bath) under N2]. After 1 h (ice-bath was
removed after 10 min), the reaction mixture was partitioned
(NaHCO3/H2O/CHCl3). The organic layer was washed (H2O,
brine) and dried (MgSO4), and volatiles were evaporated.
Column chromatography of the residue (50 f 65% EtOAc/
hexane) gave 4a (329 mg, 71%). 1H NMR: δ 1.35 and 1.58
(2 × s, 2 × 3, 2 × Me), 4.62 (dd, J ) 4.1, 7.5 Hz, 1, H4′), 4.86
(dd, J ) 4.1, 6.1 Hz, 1, H3′), 5.13 (d, J ) 6.3 Hz, 1, H2′), 5.57
(s, 1, H1′), 5.77 (d, J ) 7.9 Hz, H5), 6.08 (dd, J ) 7.5, 15.4 Hz,
1, H5′), 6.34 (dd, J ) 10.2, 15.4 Hz, 1, H6′), 6.98 (d, J ) 10.2
Hz, H7′), 7.24 (d, J ) 8.0 Hz, 1, H6), 10.25 (br s, 1, NH). MS:
determined with solutions in CDCl3 unless otherwise specified.
Mass spectra (MS) were obtained with atmospheric pressure
chemical ionization (APCI) except when CI (CH4) is noted.
Merck kieselgel 60-F254 sheets were used for thin-layer chro-
matography (TLC), and products were detected with 254 nm
light or by development of color with Ce(SO4)2/(NH4)6Mo7O24
‚
4H2O/H2SO4/H2O. Merck kieselgel 60 (230-400 mesh) was
used for column chromatography. Preparative reversed-phase
(RP)-HPLC was performed with a Supelcosil LC-18S column
with a Perkin-Elmer LC 200 binary pump system (gradient
solvent systems are noted) or analytical reversed-phase column
(Vydac C18, 5 µm, 250 mm × 4.6 mm; Hesperia, CA) for
enzymatic assays. Elemental analyses were determined by
Galbraith Laboratories, Knoxville, TN. Reagent grade chemi-
cals were used, and solvents were dried by reflux over and
m/z 467 (27, MH+ [81Br2]), 465 (53, MH+ 81/79Br2]), 463 (27,
[
MH+ [79Br2]).

Adenosine and Uridine Conjugated Diene Analogues
J ournal of Medicinal Chemistry, 2002, Vol. 45, No. 12 2655
1-[8,8-Dib r om o-5,6,7,8-t et r a d eoxy-â-D-r ibo-oct -5(E)-7-
d ien ofu r a n osyl]u r a cil (5a ). A solution of 4a (46 mg, 0.1
mmol) in CF3CO2H/H2O (9:1, 3 mL) was stirred at ∼0 °C (ice-
bath) for 1 h. Volatiles were evaporated under oil-pump
vacuum (<10 °C), coevaporated with toluene (3×), and kept
under vacuum for 1 h. Column chromatography (EtOAc f 3%
MeOH/EtOAc) of the residue and crystallization (MeOH/
EtOAc) gave 5a (26 mg, 62%); mp 167-169 °C. UV: max 252
3, 2 × Me), 4.14 (q, J ) 7.2 Hz, 2, CH2), 4.79 (dd, J ) 3.4, 6.2
Hz, 1, H4′), 5.10 (dd, J ) 3.5, 6.1 Hz, 1, H3′), 5.56 (dd, J )
1.5, 6.2 Hz, 1, H2′), 5.80 (d, J ) 15.4 Hz, H8′), 6.10 (dd, J )
6.4, 15.3 Hz, 1, H5′), 6.19 (s, 1, H1′), 6.22 (dd, J ) 10.8, 15.4
Hz, 1, H6′), 7.10 (dd, J ) 10.3, 15.4 Hz, H7′), 7.48-8.03 (m, 5,
H
arom), 8.11 (s, 1, H2), 8.75 (s, 1, H8), 9.51 (br s, 1, NH). MS:
m/z 506 (100, MH+).
Eth yl 1,5,6,7,8-P en ta d eoxy-1-(u r a cil-1-yl)-â-D-r ibo-n on -
5(E),7(E)-d ien ofu r a n u r on a te (7a ). A solution of 6a (113 mg,
0.3 mmol) in CF3CO2H/H2O (9:1, 5 mL) was stirred at ∼0 °C
(ice-bath) for 1 h. Volatiles were evaporated under vacuum,
coevaporated with toluene (3 ×), and kept under vacuum for
1 h. Column chromatography (EtOAc f 3% MeOH/EtOAc) and
crystallization (MeOH) gave 7a (69 mg, 68%) as white needles;
mp 177-178 °C. UV: max 259 nm (ꢀ 37 300), min 223 nm (ꢀ
8500). 1H NMR (Me2SO-d6): δ 1.22 (t, J ) 7.1 Hz, 3, CH3),
3.88 (q, J ) 5.5 Hz, 1, H3′), 4.10 (q, J ) 5.0 Hz, 1, H2′), 4.13
(q, J ) 7.1 Hz, 2, CH2), 4.32 (t, J ) 5.7 Hz, 1, H4′), 5.42 (d,
J ) 6.0 Hz, 1, OH3′), 5.57 (d, J ) 5.4 Hz, 1, OH2′), 5.66 (d,
J ) 8.0 Hz, 1, H5), 5.77 (d, J ) 4.5 Hz, 1, H1′), 6.05 (d, J )
15.4 Hz, 1, H8′), 6.43 (dd, J ) 6.1, 15.3 Hz, 1, H5′), 6.50 (dd,
J ) 9.8, 15.3 Hz, 1, H6′), 7.26 (dd, J ) 9.9, 15.3 Hz, 1, H7′),
7.62 (d, J ) 8.1 Hz, 1, H6), 10.40 (br s, 1, NH). 13C NMR (Me2-
SO-d6): δ 14.50, 60.32, 73.08 and 73.92 (C2′ and C3′), 88.29
(C4′), 89.43 (C1′), 102.45 (C5), 122.21 (C8′), 129.67 (C6′), 140.48
(C5′), 141.39 (C6), 144.00 (C7′), 151.45 (C2), 164.00 (C4), 166.41
(C9′). MS: m/z 339 (MH+). Anal. [C15H18N2O7 (338.33)] C,
H, N.
1
nm (ꢀ 24 400), min 222 nm (ꢀ 7300). H NMR (Me2SO-d6): δ
3.88 (q, J ) 5.5 Hz, 1, H3′), 4.09 (q, J ) 4.8 Hz, 1, H2′), 4.28
(t, J ) 4.8 Hz, 1, H4′), 5.40 (d, J ) 6.1 Hz, 1, OH3′), 5.55 (d,
J ) 5.3 Hz, 1, OH2′), 5.67 (d, J ) 8.0 Hz, 1, H5), 5.76 (d, J )
4.2 Hz, 1, H1′), 6.24-6.27 (m, 2, H5′,6′), 7.29 (dd, J ) 4.9, 6.3
Hz, 1, H7′), 7.60 (d, J ) 8.1 Hz, 1, H6), 11.40 (br s, 1, NH). 13
C
NMR (Me2SO-d6): δ 72.86 (C3′), 73.69 (C2′), 83.17 (C4′), 89.54
(C1′), 92.03 (C8′), 102.37 (C5), 128.06 (C6′), 136.21 (C5′), 136.54
(C7′), 141.37 (C6), 150.88 (C2), 163.37 (C4). MS: m/z 427 (47,
MH+ [81Br2]), 425 (100, MH+ 81/79Br2]), 423 (48, MH+ [79Br2]).
[
Anal. [C12H12Br2N2O5 (424.05)] C, H.
Eth yl 1,5,6,7,8-P en tadeoxy-2,3-O-isopr opyliden e-1-(u r a-
cil-1-yl)-â-D-r ibo-n on -5(E),7(E)-d ien ofu r a n u r on a t e (6a ).
Meth od A. (Carbethoxymethylene)triphenylphosphorane (191
mg, 0.55 mmol) was added to a stirred solution of 2a (154 mg,
0.5 mmol) in dried CH2Cl2 (10 mL) at ambient temperature
under N2. After 14 h, the reaction mixture was partitioned
(NaHCO3/H2O/CH2Cl2), and the organic layer was washed
(brine) and dried (MgSO4), and volatiles were evaporated.
Column chromatography (50 f 60% EtOAc/hexane) gave 6a
1
(153 mg, 81%). H NMR: δ 1.32 (t, J ) 7.1 Hz, 3, CH3), 1.37
E t h yl 1-(Ad en in -9-yl)-1,5,6,7,8-p en t a d eoxy-â-D-r ibo-
n on -5(E),7(E)-d ien ofu r a n u r on a te (7b). (Step a). A solution
of 6c (126 mg, 0.25 mmol) in NH3/MeOH (10 mL) was stirred
overnight at ∼5 °C. Volatiles were evaporated, and the residue
was flash chromatographed (50 f 70% EtOAc/hexane) to give
6b (89 mg, 89%). (Step b). Treatment of 6b (60 mg, 0.15 mmol)
with TFA/H2O (as described for 5a ) and crystallization (MeOH)
gave 7b (40 mg, 72%; 64% total); mp 117-119 °C. UV: max
259, 257 nm (ꢀ 39 000, 39 100), min 258, 223 nm (ꢀ 38 700,
9600). 1H NMR (Me2SO-d6): δ 1.22 (t, J ) 7.1 Hz, 3, CH3),
4.14 (q, J ) 7.2 Hz, 2, CH2), 4.19 (q, J ) 5.1 Hz, 1, H3′), 4.45
(t, J ) 4.3 Hz, 1, H4′), 4.67 (q, J ) 5.3 Hz, 1, H2′), 5.52 (d,
J ) 5.7 Hz, 1, OH3′), 5.57 (d, J ) 5.6 Hz, 1, OH2′), 5.96 (d,
J ) 4.9 Hz, 1, H1′), 6.02 (d, J ) 15.3 Hz, 1, H8′), 6.46-6.51
(m, 2, H5′,6′), 7.28 (dd, J ) 10.1, 15.3 Hz, 1, H7′), 7.31 (br s,
2, NH2), 8.13 (s, 1, H2), 8.32 (s, 1, H8). 13C NMR (Me2SO-d6):
δ 14.40, 60.25, 73.02 and 74.12 (C2′ and C3′), 84.75 (C4′), 89.10
(C1′), 119.95 (C5), 121.90 (C8′), 129.25 (C6′), 140.10 (C5′),
140.70 (C8), 143.96 (C7′), 149.65 (C4), 152.94 (C2), 156.20 (C6),
166.70 (C9′). MS: m/z 362 (100, MH+). Anal. [C16H19N5O5‚H2O
(379.38)] C, H, N.
and 1.59 (2 × s, 2 × 3, 2 × Me), 4.22 (q, J ) 7.1 Hz, 2, CH2),
4.62 (dd, J ) 4.3, 7.0 Hz, 1, H4′), 4.84 (dd, J ) 4.4, 6.5 Hz, 1,
H3′), 5.11 (dd, J ) 1.3, 6.3 Hz, 1, H2′), 5.57 (d, J ) 1.1 Hz, 1,
H1′), 5.75 (d, J ) 8.0 Hz, H5), 5.90 (d, J ) 15.4 Hz, 1, H8′),
6.24 (dd, J ) 7.1, 15.3 Hz, 1, H5′), 6.38 (dd, J ) 10.3, 15.3 Hz,
1, H6′), 7.24 (d, J ) 7.9 Hz, 1, H6), 7.28 (dd, J ) 10.3, 15.4
Hz, H7′), 10.05 (br s, 1, NH). 13C NMR: δ 14.64, 25.65, 27.49,
60.85, 84.85 and 85.14 (C2′ and C3′), 88.73 (C4′), 95.82 (C1′),
103.07 (C5), 114.99, 123.34 (C8′), 130.86 (C6′), 138.44 (C5′),
143.33 and 143.44 (C6 and C7′), 150.50 (C2), 164.16 (C4),
167.05 (C9′). MS: m/z 379 (MH+).
Meth od B. Ethyl (E)-3-iodopropenoate23 (49 µL, 80 mg, 0.35
mmol) was added to 14a 20 (160 mg, 0.29 mmol) and Pd(PPh3)4
(15 mg, 0.013 mmol) in dried THF (7 mL), and the solution
was gently heated (oil bath, 70 °C) for about 2.5 h. Volatiles
were evaporated, and the residue was partitioned (NaHCO3/
H2O/CH2Cl2). The organic layer was washed (diluted Na2S2O3,
brine), dried (MgSO4), evaporated, and column-chromato-
graphed (55 f 70% EtOAc/hexane or CH2Cl2 f 3% MeOH/
CH2Cl2) to give 6a (82 mg, 75%).
Note. Care has to be taken to avoid unnecessary heating
and prolonged reaction time. The coupling reactions were
usually ceased when TLC showed ∼90-95% consumption of
vinyl stannanes 14 in order to avoid/minimize isomerization
of dienes.
3-O-Ben zoyl-5,6-dideoxy-2,3-O-isopr opyliden e-r-D-r ibo-
h ep t-5(E)-en od ia ld o-1,4-fu r a n ose (9). Treatment of 3-O-
benzoyl-1,2;5,6-di-O-isopropylidene-R-D-allofuranose8a (3 g, 8.25
mmol) with H5IO6 (crude 5-aldehyde was dissolved in EtOAc
and washed with NaHCO3/H2O) and Ph3PdCHCHO (2 h; as
1
described for 10, step a) gave 9 (2.1 g, 80%). H NMR: δ 1.21
E t h yl 1-(Ad en in -9-yl)-1,5,6,7,8-p en t a d eoxy-2,3-O-iso-
p r op ylid en e-â-D-r ibo-n on -5(E),7(E)-d ien ofu r a n u r on a t e
(6b). Treatment of 14b5 (55 mg, 0.093 mmol) with ethyl (E)-
3-iodopropenoate23 (14 µL, 25 mg, 0.11 mmol) (as described
and 1.50 (2 × s, 2 × 3, 2 × Me), 4.75 (dd, J ) 4.8, 9.4 Hz, 1,
H3), 4.88 (ddd, J ) 1.3, 4.9, 9.0 Hz, 1, H4), 4.94 (t, J ) 4.1 Hz,
1, H2), 5.85 (d, J ) 3.6 Hz, 1, H1), 6.33 (ddd, J ) 1.3, 7.7, 15.8
Hz, 1, H6), 6.80 (dd, J ) 4.9, 15.7 Hz, 1, H5), 7.36 (t)/7.49 (t)/
7.97 (d, 5, Harom), 9.50 (d, J ) 7.8 Hz, H7). 13C NMR: δ 26.81
and 26.94 (CMe2), 76.50 (C2), 76.57 (C3), 78.76 (C4), 104.83
(C1), 113.7 (CMe2), 128.90/129.24/130.88/133.98 (Bz), 132.90
(C6), 150.94 (C5), 165.80 (Bz), 193.23 (C7). HRMS (CI): m/z
319.1173 (100, MH+ [C17H19O6] ) 319.1182).
1
for 6a , method B) gave 6b (27 mg, 73%). H NMR: δ 1.28 (t,
J ) 7.1 Hz, 3, CH3), 1.41 and 1.63 (2 × s, 2 × 3, 2 × Me), 4.19
(q, J ) 7.1 Hz, 2, CH2), 4.78 (dd, J ) 3.4, 6.2 Hz, 1, H4′), 5.12
(dd, J ) 3.5, 6.1 Hz, 1, H3′), 5.56 (br d, J ) 6.2 Hz, 1, H2′),
5.80 (d, J ) 15.4 Hz, 1, H8′), 5.88 (br s, 2, NH2), 6.11 (s, 1,
H1′), 6.17 (dd, J ) 6.4, 15.4 Hz, 1, H5′), 6.25 (dd, J ) 10.5,
15.3 Hz, 1, H6′), 7.13 (dd, J ) 10.5, 15.4 Hz, 1, H7′), 7.89 (s, 1,
H2), 8.37 (s, 1, H8). MS: m/z 402 (MH+). Depending on the
experiment, diene 6b was contaminated by isomer 15b (5-
8,8-Dibr om o-5,6,7,8-tetr a d eoxy-1,2-O-isop r op ylid en e-
r-D-r ibo-oct-5(E)-7-d ien ofu r a n ose (10). (Step a). H5IO6
(2.19 g, 9.6 mmol) was added to a solution of 1,2;5,6-di-O-
isopropylidene-R-D-allofuranose8a (2 g, 7.68 mmol) in dried
EtOAc (80 mL) at ambient temperature, and stirring was
continued for 2 h (TLC showed conversion into more polar
5-aldehyde). The mixture was filtered, the filter cake was
washed (EtOAc), and the combined filtrate was evaporated.
The residue was dissolved in dried CH2Cl2 (50 mL), (triphen-
ylphosphoranylidene)acetaldehyde (2.33 g, 7.68 mmol) was
1
20%; H NMR).
Eth yl 1-(6-N-Ben zoyla d en in -9-yl)-1,5,6,7,8-p en ta d eoxy-
2,3-O-isop r op ylid en e-â-D-r ibo-n on -5(E),7(E)-d ien ofu r a n -
u r on a te (6c). Treatment of 2c (287 mg, 0.66 mmol) with
(carbethoxymethylene)triphenylphosphorane (243 mg, 0.7 mmol)
(as described for 6a , method A) gave 6c (216 mg, 65%). 1H
NMR: δ 1.25 (t, J ) 7.1 Hz, 3, CH3), 1.39 and 1.62 (2 × s, 2 ×

2656 J ournal of Medicinal Chemistry, 2002, Vol. 45, No. 12
Wnuk et al.
then added in one portion, and the resulting solution was
stirred at ambient temperature overnight. The solution was
washed (NaHCO3/H2O, brine) and dried (MgSO4), and volatiles
were evaporated. Chromatography (50 f 70% EtOAc/hexane)
of the residue gave 5,6-dideoxy-2,3-O-isopropylidene-R-D-ribo-
hept-5-enodialdo-1,4-furanose (8; 1.12 g, 68%). 1H NMR: δ 6.34
(ddd, J ) 1.5, 8.0, 15.7 Hz, 1, H6), 6.83 (dd, J ) 4.5, 15.8 Hz,
1, H5), 9.51 (d, J 7-6 ) 8.0 Hz, 1, H7). (Step b). The solution of
the above material (8; 1.12 g, 5.2 mmol) in CH2Cl2 (25 mL)
was added via syringe into a mixture containing (dibromo-
methylene)triphenylphosphorane [generated in situ by stirring
CBr4 (3.02 mg, 9.1 mmol), Ph3P (2.39 g, 9.1 mmol), and
activated Zn (dust; 595 mg, 9.1 mmol) in dried CH2Cl2 (50 mL)
for 6 h at ambient temperature under N2; sonication was
applied intermittently for a total of 30 min.]. After 12 h, the
reaction mixture was partitioned (NaHCO3/H2O//CHCl3), and
the organic layer was washed (H2O, brine) and dried (MgSO4),
and volatiles were evaporated. Column chromatography of the
residue (40 f 60% EtOAc/hexane) gave 10 (1.37 g, 71%; 48%
overall yield) as white crystals; mp 134-136 °C (dec). 1H
NMR: δ 1.29 and 1.50 (2 × s, 2 × 3, 2 × Me), 2.41 (d, J ) 10.8
Hz, 1, OH3), 3.63 (ddd, J ) 5.0, 8.9, 10.6 Hz, 1, H3), 4.14 (t,
J ) 7.6 Hz, 1, H4), 4.51 (t, J ) 4.5 Hz, 1, H2), 5.78 (d, J ) 3.8
Hz, 1, H1), 5.84 (dd, J ) 6.3, 15.5 Hz, 1, H5), 6.36 (ddd, J )
1.1, 10.4, 15.4 Hz, 1, H6), 6.90 (d, J ) 10.4 Hz, H7). 13C NMR:
δ 26.41 and 26.52 (CMe2), 76.01 (C3), 78.32 (C2), 80.04 (C4),
92.57 (C8), 103.73 (C1), 112.73 (CMe2), 129.42 (C6), 132.61
CH3CN (25 mL), and stirring was continued for 18 h at
ambient temperature. Volatiles were evaporated, and the
residue was partitioned (NaHCO3/H2O//CHCl3). The organic
layer was washed (brine), dried (MgSO4), evaporated, and
chromatographed (EtOAc f 1% MeOH/EtOAc) to give 2′-O-
acetyl-3′O-benzoyl-5b [120 mg, 51%; contaminated (∼15%, 1H
NMR)]. (c) Deprotection. A solution of the above material (120
mg) in NH3/MeOH (10 mL) was stirred for 5 h at ∼5 °C.
Volatiles were evaporated, and the residue was chromato-
graphed (EtOAc f 8% MeOH/EtOAc) and crystallized (MeOH)
to give 5b [19 mg, 11% (steps b and c)] as white crystals; mp
104-107 °C (soften), 172-174 °C (dec). UV: max 253 nm (ꢀ
1
28 000), min 225 nm (ꢀ 10 300). H NMR (Me2SO-d6): δ 4.19
(q, J ) 5.2 Hz, 1, H3′), 4.41 (t, J ) 5.3 Hz, 1, H4′), 4.69 (q,
J ) 5.1 Hz, 1, H2′), 5.45 (d, J ) 5.8 Hz, 1, OH3′), 5.58 (d, J )
5.6 Hz, 1, OH2′), 5.94 (d, J ) 4.8 Hz, 1, H1′), 6.25 (dd, J ) 9.3,
15.4 Hz, 1, H6′), 6.32 (dd, J ) 5.8, 15.3 Hz, 1, H5′), 7.29 (br s,
2, NH2), 7.30 (d, J ) 9.2 Hz, 1 H7′), 8.16 (s, 1, H2), 8.27 (s, 1,
H8). MS: m/z 450 (49, MH+ [81Br2]), 448 (100, MH+ 81/79Br2]),
[
446 (50, MH+ [79Br2]). Anal. [C13H13Br2N5O3‚CH3OH (479.14)]
C, H, N. RP-HPLC purification (preparative LC-18S column,
20 f 50% CH3CN/H2O for 70 min at 2.5 mL/min) of the mother
liquor gave an additional 5b (14 mg, 8%; 19% total; tR 66 min).
Meth od B. Treatment of 2c (287 mg, 0.66 mmol) with
PhP3dCBr2 (as described for 4a ) gave contaminated (∼15%,
1H NMR) 4c (86 mg, 22%). Debenzoylation with NH3/MeOH
followed by treatment with TFA/H2O (as described for 7b) and
RP-HPLC purification gave 5b (15 mg, 5% overall from 2c).
Compound 5b was stable when kept at ∼5 °C for weeks.
However, significant decomposition (∼10-15%, 1H NMR) was
observed after 4 months.
(C5), 135.96 (C7). HRMS (CI): m/z 371.9217 (50, M+ [C11H14
-
81Br2O4] ) 371.9220), 369.9254 (100, M+ 81/79Br2] ) 369.9239),
[
367.9276 (49, M+ [79Br2] ) 367.9259). Anal. [C11H14Br2O4
(370.04)] C, H.
3-O-Ben zoyl-8,8-d ibr om o-5,6,7,8-tetr a d eoxy-1,2-O-iso-
pr opyliden e-r-D-r ibo-oct-5(E),7-dien ofu r an ose (11). Meth -
od A. Treatment of the 9 (318 mg, 1 mmol) with Ph3PdCBr2
(1.75 mmol; as described for 10, step b; column chromatogra-
phy: 20 f 35% EtOAc/hexane) gave 11 (360 mg, 76%). 1H
NMR: δ 1.30 and 1.58 (2 × s, 2 × 3, 2 × Me), 4.70-4.74 (m,
2, H3,4), 4.92-4.96 (m, 1, H2), 5.88 (d, J ) 3.5 Hz, 1, H1),
5.91 (dd, J ) 5.6, 15.5 Hz, 1, H5), 6.36 (dd, J ) 10.2, 15.5 Hz,
1, H6), 6.92 (d, J ) 10.2 Hz, H7), 7.41 (t)/7.55 (t)/8.02 (d, 5,
Eth yl 1,5,6,7,8-P en tadeoxy-2,3-O-isopr opyliden e-1-(u r a-
cil-1-yl)-â-D-r ibo-n on -5(E),7(Z)-d ien ofu r a n u r on a te (15a ).
Treatment of 14a 20 (114 mg, 0.2 mmol) with ethyl (Z)-3-
iodopropenoate23 (31 µL, 54 mg, 0.24 mmol) (as described for
6a , method B) gave 15a (60 mg, 79%). 1H NMR: δ 1.22 (t,
J ) 7.1 Hz, 3, CH3), 1.37 and 1.59 (2 × s, 2 × 3, 2 × Me), 4.20
(q, J ) 7.1 Hz, 2, CH2), 4.70 (dd, J ) 4.1, 7.1 Hz, 1, H4′), 4.85
(dd, J ) 4.2, 6.1 Hz, 1, H3′), 5.10 (br d, J ) 5.0 Hz, 1, H2′),
5.62 (s, 1, H1′), 5.74 (d, J ) 11.9 Hz, 1, H8′), 5.76 (d, J ) 8.4
Hz, 1, H5), 6.15 (dd, J ) 7.3, 15.5 Hz, 1, H5′), 6.59 (t, J ) 11.3
Hz, 1, H7′), 7.24 (d, J ) 8.1 Hz, 1, H6), 7.28 (dd, J ) 10.6,
15.4 Hz, 1, H6′), 9.42 (br s, 1, NH). MS: m/z 379 (MH+).
H
arom). 13C NMR: δ 27.01 and 27.10 (CMe2), 76.89 (C3), 77.72
(C2/4), 93.55 (C8), 104.54 (C1), 113.51 (CMe2), 128.81/129.53/
130.26/133.89 (Bz), 130.50 (C6), 132.68 (C5), 136.23 (C7),
171.48 (Bz). HRMS (CI): m/z 476.9560 (49, MH+ [C18H19
-
E t h yl 1-(Ad en in -9-yl)-1,5,6,7,8-p en t a d eoxy-2,3-O-iso-
p r op ylid en e-â-D-r ibo-n on -5(E),7(Z)-d ien ofu r a n u r on a t e
(15b). Treatment of 14b5 (135 mg, 0.23 mmol) with ethyl (Z)-
3-iodopropenoate23 (35 µL, 62 mg, 0.27 mmol) (as described
81Br2O5] ) 476.9563), 474.9595 (100, MH+
[
81/79Br2] ) 474.9580),
472.9575 (49, MH+ [79Br2] ) 472.9599).
Meth od B. BzCl (0.23 mL, 280 mg, 2.0 mmol) was added
to a solution of 10 (500 mg, 1.35 mmol) in dried pyridine (5
mL) at 0 °C, and the mixture was stirred for 4 h at ambient
temperature under N2. NaHCO3/H2O (1 mL) was added,
volatiles were evaporated in vacuo, and the residue was
partitioned (EtOAc//NaHCO3/H2O). The organic layer was
washed (1 M HCl/H2O, NaHCO3/H2O, brine), dried (Na2SO4),
and evaporated, and the residue was column chromatographed
(15 f 30% EtOAc/hexane) to give 11 (474 mg, 74%).
1
for 6a , method B) gave 15b (72 mg, 78%). H NMR: δ 1.27 (t,
J ) 7.1 Hz, 3, CH3), 1.42 and 1.64 (2 × s, 2 × 3, 2 × Me), 4.18
(q, J ) 7.2 Hz, 2, CH2), 4.85 (br d, J ) 7.1 Hz, 1, H4′), 5.10-
5.14 (m, 1, H3′), 5.57 (br d, J ) 6.2 Hz, 1, H2′), 5.62 (br s, 2,
NH2), 5.67 (d, J ) 11.7 Hz, 1, H8′), 6.06 (dd, J ) 7.2, 15.0 Hz,
1, H5′), 6.14 (s, 1, H1′), 6.45 (t, J ) 11.2 Hz, 1, H7′), 7.53 (dd,
J ) 11.4, 15.3 Hz, 1, H6′), 7.91 (s, 1, H2), 8.37 (s, 1, H8). 13C
NMR: δ 14.64, 25.81, 27.52, 60.56, 84.70 and 85.11 (C2′ and
C3′), 88.08 (C4′), 91.09 (C1′), 114.95, 119.83 (C8′), 120.75 (C5),
129.30 (C6′), 138.88 (C8), 140.47 (C5′), 143.06 (C7′), 149.82
(C4), 153.55 (C2), 155.83 (C6), 166.34 (C9′). MS: m/z 402 (100,
MH+).
9-[8,8-Dib r om o-5,6,7,8-t et r a d eoxy-â-D-r ibo-oct -5(E),7-
d ien ofu r a n osyl]a d en in e (5b). Meth od A. (a) Acetolysis. A
solution of 11 (474 mg, 1 mmol) in CF3CO2H/H2O (9:1, 6 mL)
was stirred at ∼0 °C (ice-bath) for 1 h. Volatiles were
evaporated (<10 °C), coevaporated with toluene (3×), and kept
under vacuum for 1 h. Pyridine (5 mL), DMAP (3 mg), and
Ac2O (0.47 mL, 510 mg, 5 mmol) were added, and the mixture
was stirred at ∼5 °C overnight. Volatiles were evaporated, the
residue was dissolved (EtOAc), and the solution was washed
(dilute HCl/H2O, saturated NaHCO3/H2O, brine), dried (Na2-
SO4), and evaporated. Chromatography (15 f 25% EtOAc/
hexanes) of the residue resulted in partial separation of the
Eth yl 1,5,6,7,8-P en ta d eoxy-1-(u r a cil-1-yl)-â-D-r ibo-n on -
5(E),7(Z)-d ien ofu r a n u r on a te (16a ). Treatment of 15a (57
mg, 0.15 mmol) with TFA/H2O (as described for 7a ) gave 16a
(31 mg, 61%), which failed to crystallize; mp 167-169 °C (white
solid from CH3CN). UV: max 262 nm (ꢀ 39 800), min 223 nm
1
(ꢀ 8100). H NMR (Me2SO-d6): δ 1.21 (t, J ) 7.1 Hz, 3, CH3),
3.91 (q, J ) 5.7 Hz, 1, H3′), 4.08-4.14 (m, 3, H2′ and CH2),
4.35 (t, J ) 5.6 Hz, 1, H4′), 5.39 (d, J ) 6.0 Hz, 1, OH3′), 5.53
(d, J ) 5.4 Hz, 1, OH2′), 5.65 (d, J ) 8.0 Hz, 1, H5), 5.75 (d,
J ) 11.2 Hz, 1, H8′), 5.78 (d, J ) 4.4 Hz, 1, H1′), 6.33 (dd, J )
6.6, 15.3 Hz, 1, H5′), 6.76 (t, J ) 11.4 Hz, 1, H7′), 7.44 (dd,
J ) 11.4, 15.4 Hz, 1, H6′), 7.62 (d, J ) 8.1 Hz, 1, H6), 11.40
(br s, 1, NH). 13C NMR (Me2SO-d6): δ 14.96, 60.58, 73.59 and
74.45 (C2′ and C3′), 83.82 (C4′), 90.14 (C1′), 102.90 (C5), 118.96
(C8′), 127.88 (C6′), 141.75 and 141.96 (C5′ and C6), 144.48
1
anomers of 12 (228 mg, 44%; â/R, ∼4:1). H NMR: δ 6.18 (s,
0.75, H1), 6.57 (d, J ) 4.4 Hz, 0.25, H1). HRMS (FAB): m/z
542.9289 (52, MNa+ [C19H1881Br2O7Na] ) 542.9276), 540.9297
(100, MNa+
[
81/79Br2] ) 540.9297), 538.9318 (49, MNa+
[79Br2] ) 538.9317). (b) Coupling. SnCl4 (0.118 mL, 260 mg,
1.0 mmol) was added dropwise to a suspension of adenine (84
mg, 0.6 mmol) and anomeric 12 (207 mg, 0.4 mmol) in dried

Adenosine and Uridine Conjugated Diene Analogues
J ournal of Medicinal Chemistry, 2002, Vol. 45, No. 12 2657
(3) (a) Malinow, M. R. Plasma Homocysteine and Arterial Occlusive
Disease: A Mini-review. Clin. Chem. 1995, 41, 173-176. (b)
Nehler, M. R.; Taylor, L. M.; Porter, J . M. Homocysteine as a
Risk Factor for Artherosclerosis: A review. Cardiovasc. Surg.
1997, 559-567. (c) Nygard, O.; Nordrehaung, J . E.; Refsum, H.;
Ueland, P. M.; Faratad, M.; Vollset, S. E. Plasma Homocysteine
Levels and Mortality in Patients with Coronary Artery Disease.
N. Engl. J . Med. 1997, 337, 230-236. (d) Refsum, H.; Ueland,
P. M.; Nygard, O.; Vollset, S. E. Homocysteine and Cardiovas-
cular Disease. Annu. Rev. Med. 1998, 49, 31-62.
(4) (a) McCarthy, J . R.; J arvi, E. T.; Matthews, D. P.; Edwards, M.
L.; Prakash, N. J .; Bowlin, T. L.; Mehdi, S.; Sunkara, P. S.; Bey,
P. 4′,5′-Unsaturated 5′-Fluoroadenosine Nucleosides: Potent
Mechanism-Based Inhibitors of S-Adenosyl-L-homocysteine Hy-
drolase. J . Am. Chem. Soc. 1989, 111, 1127-1128. (b) Yuan, C.-
S.; Yeh, J .; Liu, S.; Borchardt, R. T. Mechanism of Inactivation
of S-Adenosyl-L-homocysteine Hydrolase by Fluorine-containing
Adenosine Analogues. J . Biol. Chem. 1993, 268, 17030-17037.
(5) Wnuk, S. F.; Yuan, C.-S.; Borchardt, R. T.; Balzarini, J .; De
Clercq, E.; Robins, M. J . Nucleic Acid Related Compounds. 84.
Synthesis of 6′(E and Z)-Halohomovinyl Derivatives of Adeno-
sine, Inactivation of S-Adenosyl-L-homocysteine Hydrolase, and
Correlation of Anticancer and Antiviral Potencies with Enzyme
Inhibition. J . Med. Chem. 1994, 37, 3579-3587.
(6) (a) Wnuk, S. F.; Yuan, C.-S.; Borchardt, R. T.; Balzarini, J .; De
Clercq, E.; Robins, M. J . Anticancer and Antiviral Effects and
Inactivation of S-Adenosyl-L-homocysteine Hydrolase with 5′-
Carboxaldehydes and Oximes Synthesized from Adenosine and
Sugar-Modified Analogues. J . Med. Chem. 1997, 40, 1608-1618.
(b) Huang, H.; Yuan, C.-S.; Wnuk, S. F.; Robins, M. J .; Borchardt,
R. T. The Mechanism of Inactivation of Human Placental
S-Adenosylhomocysteine Hydrolase by (E)-4′,5′-Didehydro-5′-
methoxyadenosine (DMAO) and Adenosine 5′-carboxaldehyde
Oxime (ACAO). Arch. Biochem. Biophys. 1997, 343, 109-117.
(7) (a) Wnuk, S. F.; Mao, Y.; Yuan, C.-S.; Borchardt, R. T.; Andrei,
J .; Balzarini, J .; De Clercq, E.; Robins, M. J . Discovery of Type
II (Covalent) Inactivation of S-Adenosyl-L-homocysteine Hydro-
lase. Synthesis and Evaluation of Dihalohomovinyl Nucleoside
Analogues Derived from Adenosine. J . Med. Chem. 1998,
41, 3078-3083. (b) Yuan, C.-S.; Wnuk, S. F.; Robins, M. J .;
Borchardt, R. T. A Novel Mechanism-Based Inhibitor (6′-Bromo-
5′,6′-didehydro-6′-deoxy-6′-fluorohomoadenosine) That Covalent-
ly Modifies Human Placental S-Adenosylhomocysteine Hydro-
lase. J . Biol. Chem. 1998, 273, 18191-18197.
(8) (a) Robins, M. J .; Wnuk, S. F.; Yang, X.; Yuan, C.-S.; Borchardt,
R. T.; Balzarini, J .; De Clercq, E. Inactivation of S-Adenosyl-L-
homocysteine Hydrolase and Antiviral Activitiy with 5′,5′,6′,6′-
Tetradehydro-6′-Deoxy-6′-Halohomoadenosine Analogues (4′-
Haloacetylene Analogues Derived from Adenosine). J . Med.
Chem. 1998, 41, 3857-3864. (b) Yang, X.; Yin, D.; Wnuk, S. F.;
Robins, M. J .; Borchardt, R. T. Mechanism of Inactivation of
Human S-Adenosyl-L-homocysteine Hydrolase by 5′,5′,6′,6′-
Tetrahydro-6′-Deoxy-6′-Halohomoadenosines. Biochemistry 2000,
39, 15234-15241.
(C7′), 151.45 (C2), 163.92 (C4), 166.87 (C9′). MS: m/z 339
(MH+). Anal. [C15H18N2O7 (338.33)] C, H, N.
E t h yl 1-(Ad en in -9-yl)-1,5,6,7,8-p en t a d eoxy-â-D-r ibo-
n on -5(E),7(Z)-d ien ofu r a n u r on a te (16b). Treatment of 15b
(55 mg, 0.14 mmol) with TFA/H2O (as described for 7a ) gave
16b (35 mg, 71%); mp 158-160 °C (MeOH). UV: max 261 nm
1
(ꢀ 37 500), min 225 nm (ꢀ 7000). H NMR (Me2SO-d6): δ 1.17
(t, J ) 7.1 Hz, 3, CH3), 4.09 (q, J ) 7.1 Hz, 2, CH2), 4.20 (q,
J ) 5.3 Hz, 1, H3′), 4.47 (t, J ) 5.6 Hz, 1, H4′), 4.66 (q, J )
5.1 Hz, 1, H2′), 5.48 (d, J ) 5.5 Hz, 1, OH3′), 5.62 (d, J ) 5.5
Hz, 1, OH2′), 5.73 (d, J ) 11.3 Hz, 1, H8′), 5.96 (d, J ) 4.7 Hz,
1, H1′), 6.40 (dd, J ) 6.7, 15.3 Hz, 1, H5′), 6.77 (t, J ) 11.4
Hz, 1, H7′), 7.32 (br s, 2, NH2), 7.43 (dd, J ) 11.4, 15.3 Hz, 1,
H6′), 8.16 (s, 1, H2), 8.33 (s, 1, H8). 13C NMR (Me2SO-d6): δ
14.92, 60.53, 73.86 and 74.92 (C2′ and C3′), 84.37 (C4′), 88.69
(C1′), 118.75 (C8′), 119.90 (C5), 127.71 (C6′), 140.57 (C8),
142.24 (C5′), 144.59 (C7′), 150.21 (C4), 153.56 (C2), 156.96 (C6),
166.23 (C9′). MS: m/z 362 (100, MH+). Anal. [C16H19N5O5
(361.35)] C, H, N.
In a ctiva tion of Ad oHcy Hyd r ola se. Human AdoHcy
hydrolase (2.5 µg) was incubated with 100 µM 5b, 7b, and 16b
in potassium phosphate buffer (250 µL; 50 mM, pH 7.2,
containing 1 mM EDTA; buffer A) at 37 °C for 20 min. The
remaining enzyme activity was assayed in the synthetic
direction as described.8b The enzyme was incubated with 1 mM
Ado and 1 mM Hcy in buffer A at 37 °C for 1 min followed by
addition of 10 µL of 5 M HClO4 to terminate the reaction. The
reaction product, AdoHcy, was quantitatively measured using
RP-HPLC with the detector monitoring at 258 nm.
Various concentrations of 7b and 16b were incubated with
AdoHcy hydrolase (2.5 µg) in buffer A at 37 °C for different
times (0-20 min). Remaining enzyme activities were deter-
mined as described above. These data were then used to
calculate Ki and kinact values by fitting to the Kitz and Wilson
equation:22 kobs ) kinact ‚ [I]/(Ki + [I]).
Deter m in a tion of th e NAD+ Con ten t of Ad oHcy Hy-
d r ola se a fter In cu ba tion w ith In h ibitor s 5b, 7b, a n d 16b.
AdoHcy hydrolase (5.8 µM) was incubated with 100 µM
inhibitor in buffer A at 37 °C for 20 min. The cofactors were
then released from the enzyme by the addition of 10 µL of 5 N
HClO4. The concentration of NAD+ was analyzed by RP-HPLC
(C18 column, flow rate of 1 mL/min with a linear gradient of
2-98% solvent B over 25 min). Solvent A was 25 mM
phosphate, pH 3.2, 10 mM heptane sulfonic acid, and solvent
B was acetonitrile. The NAD+ content was monitored at
258 nm.
An tivir a l, Cytotoxic, a n d Cytosta tic Activity Assa ys.
The antiviral, cytotoxic, and cytostatic activity assays were
performed according to well-established procedures.24
(9) Parry, R. J .; Muscate, A.; Askonas, L. J . 9-(5′,6′-Dideoxy-â-D-
ribo-hex-5′-ynofuranosyl)adenine, a Novel Irreversible Inhibitor
of S-Adenosylhomocysteine Hydrolase. Biochemistry 1991, 30,
9988-9997.
(10) Wnuk, S. F.; Valdez, C. A.; Khan, J .; Moutinho, P.; Robins, M.
J .; Yang, X.; Borchardt, R. T.; Balzarini, J .; De Clercq, E. Doubly
Homologated Dihalovinyl and Acetylene Analogues of Adenosine.
Synthesis, Interaction with S-Adenosyl-L-homocysteine Hydro-
lase, and Antiviral and Cytostatic Effects. J . Med. Chem. 2000,
43, 1180-1186.
Ack n ow led gm en t. This work was supported by an
award from the American Heart Association, Florida/
Puerto Rico Affiliate. We also thank Chosun University
(B.-O.R.) and the United States Public Health Service
(R.T.B., Grant GM-29332) for support.
Refer en ces
(11) (a) Muzard, M.; Guillerm, D.; Vandenplas, C.; Guillerm, G. 5′-
Deoxy-5′-difluoromethylthioadenosine. A potent enzyme-acti-
vated acylating agent of S-adenosyl-L-homocysteine hydrolase.
Bioorg. Med. Chem. Lett. 1997, 7, 1037-1040. (b) Muzard, M.;
Guillerm, D.; Vandenplas, C.; Guillerm, G. The mechanism of
inactivation of S-adenosylhomocysteine hydrolase by fluorinated
analogues of 5′-methylthioadenosine adenosine. J . Enzyme Inhib.
1998, 13, 443-456. (c) Guillerm, G.; Guillerm, D.; Vandenplas-
Witkowski, C.; Roginaux, H.; Carte, N.; Leize, E.; Van Dorsse-
laer, A.; De Clercq, E.; Lambert, C. Synthesis, Mechanism of
Action and Antiviral Activity of a New Series of Covalent
Mechanism-Based Inhibitors of S-adenosyl-L-homocysteine Hy-
drolase. J . Med. Chem. 2001, 44, 2743-2752.
(12) (a) Turner, M. A.; Yuan, C.-S.; Borchardt, R. T.; Hershfield, M.
S.; Smith, G. D.; Howell, P. L. Structure Determination of
Selenomethionyl S-Adenosylhomocysteine Hydrolase using data
at a single wavelength. Nat. Struct. Biol. 1998, 5, 369-376. (b)
Hu, Y.; Komoto, J .; Huang, Y.; Gomi, T.; Ogawa, H.; Takata, Y.;
Fujioka, M.; Takusagawa, F. Crystal Structure of S-Adenosyl-
homocysteine Hydrolase from Rat Liver. Biochemistry 1999, 38,
8323-8333.
(1) (a) Yuan, C.-S.; Liu, S.; Wnuk, S. F.; Robins, M. J .; Borchardt,
R. T. Design and Synthesis of S-Adenosylhomocysteine Hydro-
lase Inhibitors as Broad-Spectrum Antiviral Agents. In Advances
in Antiviral Drug Design; De Clercq, E., Ed; J AI Press: Green-
wich, 1996; Vol. 2, pp 41-88. (b) Yuan, C.-S.; Saso, Y.; Lazarides,
E.; Borchardt, R. T.; Robins, M. J . Recent Advances in S-
Adenosyl-L-homocysteine Hydrolase Inhibitors and their Poten-
tial Clinical Applications. Exp. Opin. Ther. Patents 1999, 9,
1197-1206. (c) Yin, D.; Yang, X.; Borchardt, R. T. Mechanism-
Based S-Adenosyl-L-homocysteine Hydrolase Inhibitors in the
Search for Broad-Spectrum Antiviral Agents. In Biomedical
Chemistry: Applying Principles to the Understanding and
Treatment of Disease; Torrence, P. F., Ed.; J ohn Wiley & Sons:
New York, 2000; pp 41-71. (d) Wnuk, S. F. Targeting “Hydro-
lytic” Activity of the S-Adenosyl-L-homocysteine Hydrolase. Mini-
Rev. Med. Chem. 2001, 1, 307-316.
(2) (a) Ueland, P. M. Pharmacological and Biochemical Aspects of
S-Adenosylhomocysteine and S-Adenosylhomocysteine Hydro-
lase. Pharmacol. Rev. 1982, 34, 223-253. (b) Chiang, P. K.
Biological Effects of Inhibitors of S-Adenosylhomocysteine Hy-
drolase. Pharmacol. Ther. 1998, 77, 115-134.

2658 J ournal of Medicinal Chemistry, 2002, Vol. 45, No. 12
Wnuk et al.
(13) Ranganathan, R. S.; J ones, G. H.; Moffatt, J . G. Novel Analogues
of Nucleoside 3′,5′-Cyclic Phosphates. I. 5′-Mono- and Dimethyl
Analogues of Adenosine 3′,5′-Cyclic Phosphate. J . Org. Chem.
1974, 39, 290-298.
synthesis. In Chemistry of Tin, 2nd ed.; Smith, P. J ., Ed.;
Chapman & Hall: London, 1998; pp 290-387.
(20) (a) Wnuk, S. F.; Robins, M. J . Nucleic Acid Related Compounds.
78. Stereocontrolled syntheses of 6′(E and Z)-halovinyl analogues
from uridine-derived vinyl sulfones via vinyltin intermediates.
Can. J . Chem. 1993, 71, 192-198.
(14) J ones, R. J .; Swaminathan, S.; Milligan, J . F.; Wadwani, S.;
Froehler, B. C.; Matteucci, M. D. Oligonucleotides Containing a
Covalent Conformationally Restricted Phosphodiester Analogue
for High-Affinity Triple Helix Formation: The Riboacetal In-
ternucleotide Linkage. J . Am. Chem. Soc. 1993, 115, 9816-9817.
(15) (a) Sakai, T.; Seko, K.; Tsuji, A.; Utaka, M.; Takeda, A. New
Synthesis of a-Benzoyloxy Aldehydes. Application to the Ste-
reoselective Synthesis of Conjugated (E,E)-Dienoic Esters. J .
Org. Chem. 1982, 47, 1101-1106. (b) Ma, D.; Lu, X. A Conve-
nient Stereoselective Synthesis of Conjugated dienoic esters and
amides. Tetrahedron 1990, 46, 3189-3198. (c) Crisp, G. T.;
Glink, P. T. Elaboration of the Side Chain of a-Amino Acids by
Palladium Catalysed Stille Coupling. Tetrahedron 1994, 50,
3213-3234.
(16) Corey, E. J .; Fuchs, P. L. A Synthetic Method for Formyl-
Ethynyl Conversion (RCHO f RC t CH or RC t CR′).
Tetrahedron Lett. 1972, 3769-3772.
(17) Xie, M.; Berges, D. A.; Robins, M. J . Efficient “Dehomologation”
of Di-O-isopropylidenehexofuranose Derivatives to Give O-
Isopropylidenepentofuranoses by Sequential Treatment with
Periodic Acid in Ethyl Acetate and Sodium Borohydride. J . Org.
Chem. 1996, 61, 5178-5179.
(21) (a) Wnuk, S. F.; Robins, M. J . Nucleic Acid Related Compounds.
63. Synthesis of 5′-deoxy-5′-methyleneadenosine and related
Wittig-extended nucleosides. Can. J . Chem. 1991, 69, 334-338.
(b) Wnuk, S. F.; Dalley, N. K.; Robins, M. J . Nucleic Acid Related
Compounds. 67. Synthesis of 5′-amino and 5′-methylthio chain-
extended nucleosides from uridine. Can. J . Chem. 1991, 69,
2104-2111.
(22) Kitz, R.; Wilson, I. B. Esters of Methanesulfonic Acid as
Irreversible Inhibitors of Acetylcholinesterase. J . Biol. Chem.
1962, 237, 3245-3249.
(23) Takeuchi, R.; Tanabe, K.; Tanaka, S. Stereodivergent Synthesis
of (E)- and (Z)-2-Alken-4-yn-1-ols from 2-Propynoic Acid:
A
Practical Route via 2-Alken-4-ynoates. J . Org. Chem. 2000, 65,
1558-1561.
(24) (a) De Clercq, E.; Descamps, J .; Verhelst, G.; Walker, R. T.;
J ones, A. S.; Torrence, P. F.; Shugar, D. Comparative Efficacy
of Different Antiherpes Drugs against Different Strains of
Herpes Simplex Virus. J . Infect. Dis. 1980, 141, 563-574. (b)
De Clercq, E. Antiviral and Antimetabolic Activities of
Neplanocins. Antimicrob. Agents Chemother. 1985, 28, 309-321.
(c) Pauwels, R.; Balzarini, J .; Baba, M.; Snoeck, R.; Schols, D.;
Herdewijn, P.; Desmyter, J .; De Clercq, E. Rapid and Automated
Tetrazolium-based Colorimetric Assays for the Detection of anti-
HIV Compounds. J . Virol. Methods 1988, 20, 309-321.
(18) Saneyoshi, M.; Satoh, E. Synthetic Nucleosides and Nucleotides.
XIII. Stannic Chloride Catalyzed Ribosylation of Several 6-Sub-
stituted Purines. Chem. Pharm. Bull. 1979, 27, 2518-2521.
(19) (a) Mitchell, T. N. Palladium-catalysed Reaction of Organotin
Compounds. Synthesis 1992, 803-815. (b) J ousseaume, B.;
Pereyre, M. The uses of organotin compounds in organic
J M020064F