Transition state analogue inhibitors of protozoan nucleoside hydrolases

Article abstract of DOI:10.1016/S0968-0896(99)00210-2

Protozoan parasites are unable to synthesize purines de novo and must rely on purine salvage pathways for their requirements. Nucleoside hydrolases, which are not found in mammals, function as key enzymes in purine salvage in protozoa. Inhibition of these enzymes may disrupt purine supply and specific inhibitors are potential therapeutic agents for the control of protozoan infections. A series of 1,4-dideoxy-1,4-imino-D-ribitols bearing C- bonded aromatic substituents at C-1 have been synthesized, following carbanion additions to the imine 2, and tested as potential nucleoside hydrolase inhibitors. Nucleoside analogues 8, 11, 14, 17, 20, 24-26, 28 exhibit K(i) values in the range 0.2-22 μM against two representative isozymes of protozoan nucleoside hydrolases. (C) 1999 Elsevier Science Ltd.

Full text of DOI:10.1016/S0968-0896(99)00210-2

Bioorganic & Medicinal Chemistry 7 (1999) 2599±2606
Transition State Analogue Inhibitors of Protozoan Nucleoside
Hydrolases
Richard H. Furneaux, a Vern L. Schramm b and Peter C. Tyler a,*
aCarbohydrate Chemistry, Industrial Research Limited, PO Box 31310, Lower Hutt, New Zealand
bDepartment of Biochemistry, Albert Einstein College of Medicine, Bronx, NY 10461, USA
Received 27 May 1999; accepted 6 July 1999
AbstractÐProtozoan parasites are unable to synthesize purines de novo and must rely on purine salvage pathways for their
requirements. Nucleoside hydrolases, which are not found in mammals, function as key enzymes in purine salvage in protozoa.
Inhibition of these enzymes may disrupt purine supply and speci®c inhibitors are potential therapeutic agents for the control of
protozoan infections. A series of 1,4-dideoxy-1,4-imino-d-ribitols bearing C-bonded aromatic substituents at C-1 have been syn-
thesized, following carbanion additions to the imine 2, and tested as potential nucleoside hydrolase inhibitors. Nucleoside analo-
gues 8, 11, 14, 17, 20, 24±26, 28 exhibit Ki values in the range 0.2±22 mM against two representative isozymes of protozoan
nucleoside hydrolases. # 1999 Elsevier Science Ltd. All rights reserved.
from activation of the leaving group. The ribooxo-
carbenium ion is promoted by conformational distor-
tion of the sugar using protein contacts and a catalytic
site Ca2+ to permit both the ring oxygen and the 50-
hydroxymethyl oxygens' unshared electrons to partici-
pate in the cleavage of the sugar-base bonds. The `IAG
nucleoside hydrolase' from Trypanosoma brucei brucei is
representative of the second isozyme type which com-
prise purine-speci®c hydrolases.3,6,12 These enzymes
obtain a signi®cant part of their catalytic eciency from
protonation of the leaving group. Both classes of
hydrolase enzymes utilize mechanisms which involve
transition states appreciably stabilized by contributions
from the ribofuranose based oxocarbenium ion. This led
to the prediction that 1,4-dideoxy-1,4-imino-d-ribitol
derivatives 3, which will be partially N-protonated at pH
7 (pKa=6.5),13 would be good transition state analogue
inhibitors of the nucleoside hydrolases.
Introduction
Infections due to protozoan parasites are a continuing
health problem world-wide with more than two billion
people estimated to be infected by these organisms.
Approximately two million deaths per year, largely of
infants, result from malaria alone.1 Protozoan parasites
are devoid of the capacity for de novo purine biosynth-
esis and rely completely on salvage pathways for their
purine requirements.2 Nucleoside hydrolases provide a
pathway for obtaining purines by nucleoside salvage in
several protozoa whose pathways of purine salvage have
been characterized.3 These enzymes are not found in
mammals, but they are widely distributed in bacteria, yeast
and protozoa.4,5 Inhibitors for these enzymes have poten-
tial as antimicrobials in purine auxotrophs, especially the
protozoan parasites.
Two isozymes of protozoan nucleoside hydrolases have
been characterized.3,6±12 Nonspeci®c enzymes, the `IU-
nucleoside hydrolases'5 from Crithidia fasciculata and
Leishmania major are examples of the ®rst type. The
enzymes catalyze the hydrolysis of all commonly occur-
ring purine and pyrimidine nucleosides, and also p-
nitrophenyl b-d-ribofuranoside. Catalysis occurs by
promoting the formation of a ribofuranose-based oxo-
carbenium ion transition state with modest assistance
We have reported some preliminary investigations into
the synthesis14 and testing15 of iminoribitol derivatives 3
which revealed potent (nM) inhibitors, e.g. 4 and 5
(Scheme 1), of the IU nucleoside hydrolase, but none of
the compounds tested had Ki values better than 12 mM
against the IAG nucleoside hydrolase. Since this latter
class of enzyme has a higher catalytic eciency in those
parasites that have been studied,3,6,8 the discovery of
more ecient inhibitors of the IAG type of enzyme
could be of importance. We present here further
attempts at the design and synthesis of compounds to
act as inhibitors of nucleoside hydrolasesÐparticularly
Key words: Antibiotics; antiparasitics; enzyme inhibitors; nucleosides.
* Corresponding author. Fax: +64-4-569-0055; e-mail: p.tyler@-
irl.cri.nz
0968-0896/99/$ - see front matter # 1999 Elsevier Science Ltd. All rights reserved.
PII: S0968-0896(99)00210-2

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R. H. Furneaux et al. / Bioorg. Med. Chem. 7 (1999) 2599±2606
the IAG class of enzyme. Selected biological data are
given; a more detailed analysis is presented elsewhere.16
iminoribitol derivative 1 (Scheme 1).14,19 We have con-
tinued this approach in the synthesis of new analogues.
Compounds selected for synthesis and testing were
designed to have basic sites in the aryl residues available
for protonation by the enzyme, and to have `aglycons'
with greater similarities to those of the natural sub-
strates of the enzymes. These were expected to have
enhanced anity for the IAG nucleoside hydrolase as
this enzyme is believed to utilize two enzymatic general
acids to protonate the purine and thus facilitate the
nucleoside hydrolysis.6 Initially compounds 8, 11, 14, 17
and 20 (Scheme 2) were chosen for these reasons and
because they were synthetically accessible.
Results and Discussion
A facile synthesis of some (1S)-1-aryl-1,4-dideoxy-1,4-
imino-d-ribitols has been claimed17 following the addi-
tion of organometallic C-nucleophiles to 2,3,5-tri-O-
substituted-d-ribofuranose derivatives, oxidation of the
C-1 and C-4 hydroxy groups in the products, and then
reductive amination of the resultant 1,4-dicarbonyl
compounds. While further investigations con®rmed that
these products had the required 1,4-dideoxy-1,4-imino-
pentitol structures, they also revealed that they had the
all-cis b-l-lyxo-con®guration18 and were thus unsuitable
for use in the current work.
The precursors of compounds 8, 11, 14 and 17, i.e. 7, 10,
13 and 16, respectively, were made by additions of
lithiated aryls produced from the corresponding aryl
bromides 6, 9, 12 and 15 to the imine 2 (Scheme 2). The
p-cyanophenyl precursor 19 was derived from the known
p-bromo-analogue 19a14 [made from p-dibromobenzene
(18) and 2] by treatment with palladium acetate and
Our previous syntheses of (1S)-1-aryl-1,4-dideoxy-1,4-
imino-d-ribitols (3) utilized additions of organometallic
species to the imine 2 which was generated from the
Scheme 1. General route to the (1S)-1-aryl-iminoribitols.
Scheme 2. Synthesis of the (1S)-1-aryl-iminoribitols.

R. H. Furneaux et al. / Bioorg. Med. Chem. 7 (1999) 2599±2606
2601
potassium cyanide. The preparations of the aryllithium
reagents, their additions to imine 2 and the deprotection
of the products to give the required 8, 11, 14, 17 and 20
are detailed in the Experimental section. The stereo-
chemistry at C-1 of the products obtained by additions
to imine 2 is inferred by analogy with that of the com-
pound produced by use of phenylmagnesium bromide
with this imine. NMR NOE interactions between H-1
and H-4 and between phenyl protons and H-2 estab-
lished the b-(S)-stereochemistry.19
Consequently we decided to synthesize iminoribitol
derivatives with `aglycons' that resemble more closely
the substrate bases inosine, adenosine and guanosine.
Since the iminoribitol 2 cannot usefully be linked
directly through the vinylic position to N-9 of a purine
as the resulting aminal would be expected to be too
susceptible to hydrolysis, the methylene-bridged com-
pounds 24±26, and also 28, were selected as targets. For
the preparation of the ®rst three of these the alcohol 23,
made by addition of lithiated 1,3-dithiane to imine 2 to
give 21 followed by N-protection to 22, hydrolysis of the
dithiane and reduction of the derived aldehyde (Scheme
3) was the key compound. Conversion of the alcohol 23
to the tri¯ate or mesylate ester and displacement of the
sulfonyloxy leaving groups with 6-chloropurine, ade-
nine or 6-chloroguanine, followed by de-O-protection
and hydrolysis of the halides, gave the nucleoside ana-
logues 24±26. Similar homonucleosides,20 and homo-
azasugars (2,5-dideoxy-2,5-diiminohexitols)21 have been
reported previously.
When tested against the two classes of nucleoside hydro-
lases (Table 1) compounds 8, 11, 14, 17 and 20 proved to
be inferior to 4 and 5 against the IU hydrolase and, apart
from the 4-cyanophenyl derivative 20, not clearly better
against the purine speci®c IAG hydrolase.
Table 1. Inhibition of nucleoside hydrolases by (1S)-aryl-imino-d-
ribitolsa
Compound
IU nucleoside
hydrolase Ki (mM)
IAG nucleoside
hydrolase Ki (mM)
The methylene-bridged analogue 28 was prepared via
the protected derivative 27 by use of 2 and lithiated 6-
methylnicotinamide (Scheme 4).
4
5
8
11
14
17
20
0.028
0.03
0.21
0.94
0.43
5.0
115
12
>2
>30
>50
>2
3.4
When tested for inhibition of the IU and IAG nucleo-
side hydrolases (Table 2) each compound generally
showed similar inhibitory properties against both the
isozyme representatives, the IU and IAG hydrolases,
but with much less potency against the former than did
4 and 5. However, improved inhibition against the IAG
0.92
a
Inhibition constants for 4, 5, 11 and 14 have been reported.15,16
The remainder are reported here for the ®rst time.
Scheme 3. General route to the (1S)-1-aryl-iminoribitols. Reagents: (a) (tBuO)2CO, CH2Cl2; (b) (CF3CO2)2Hg, CaCO3, MeCN±H2O; (c) NaBH4;
(d) RSO2Cl, base; (e) 6-chloropurine or 6-chloroguanine; (f) CF3CO2H±H2O.
Scheme 4. Synthesis of nicotinamide-based analogue 28.

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R. H. Furneaux et al. / Bioorg. Med. Chem. 7 (1999) 2599±2606
1
Table 2. Inhibition of nucleoside hydrolases by homo-aza-C-nucleo-
sidesa
as a syrup (1.9 g, 2.8 mmol, 53%); H NMR d 7.1±6.6
(19H, m, Ar), 4.36, 4.34 (8H, 2s, ArCH2), 3.84, 3.83
(12H, 2s, OCH3); 13C NMR d 158.72, 158.68, 144.78
and 142.25 (C), 130.52 (CH), 129.76, 129.68, 125.1,
124.8, 123.53 and 115.07 (C), 113.63 and 113.57 (CH),
55.24 (CH2), 52.95 and 52.7 (CH3); HRMS (MH+)
calcd for C38H40 79BrN2O4: 667.2171; found: 667.2156.
Compound
IU nucleoside
hydrolase Ki (mM)
IAG nucleoside
hydrolase Ki (mM)
24
25
26
28
5.4
21
22
5.2
3.6
13
5
2.3
5-Bromo-2,3-bis[di-(4-methoxybenzyl)amino]pyridine (9).
Ferric chloride (0.2g, 1.2 mmol) and activated charcoal
(0.3 g) were added to a suspension of 2-amino-5-bromo-3-
nitropyridine (1.0g, 4.6 mmol) in methanol (40 mL) and
the mixture was heated under re¯ux. Hydrazine hydrate
(1.0 mL) was added and re¯ux was continued for 3 h. The
mixture was cooled, ®ltered and the ®ltrate was evapo-
rated to give a white solid (0.94g). Sodium hydride (60%,
1.7 g, 42mmol) was added to a stirred solution of this
material in DMF (20 mL), followed by 4-methoxybenzyl
chloride (5.8 mL, 32mmol), and the mixture was stirred at
room temperature for 16h and quenched by the addition
of ethanol (5 mL). Chloroform (50 mL) was added and the
solution was washed with water (Â2) and processed to
give a crude residue which, after chromatography, a€or-
ded 9 as a syrup (3.52 g, 5.3 mmol, 87%); 1H NMR d 7.95
(1H, d, J=2.1 Hz, Ar), 7.04±6.75 (17H, m, Ar), 4.59, 4.22
a
Inhibition constants are from ref 16.
nucleoside hydrolase was observedÐparticularly with
24, 26 and 28.
Conclusion
A number of (1S)-1-(purin-9-yl)methyl and -aryl-1,4-
dideoxy-1,4-imino-d-ribitols have been synthesized and
tested against two representative protozoan nucleoside
hydrolases. Compounds 20, 24, 26 and 28 bind as well
as substrate (Ki values 2±5 mM) to the IAG nucleoside
hydrolase. It is not obvious why 20 and 28 are the most
potent inhibitors of the IAG nucleoside hydrolase,
however both have aglycones that contain sites to
accept hydrogen bonds from the enzymatic general
acids. Investigations are continuing to ®nd inhibitors of
equivalent potency to those already discovered for the
IU enzyme.
(4H each, 2s, ArCH2), 3.77, 3.76 (6H each, 2s, OCH3); 13
C
NMR d 158.9, 158.6 and 152.5 (C), 140.8 (CH), 137.9 (C),
131.2, 130.6, 130.4 and 130.1 (CH), 128.6 (C), 113.74 and
113.69 (CH), 111.7 (C), 55.2 (CH3), 51.8 and 50.6 (CH2);
HRMS (MH+) calcd for C37H3979BrN3O4: 668.2124;
found: 668.2136.
Experimental
4-Bromo-N-(tert-butoxycarbonyl)-1-naphthylamine (12).
A solution of 4-bromo-1-naphthylamine (1.0 g, 4.5 mmol)
in 1,2-dichloroethane (20 mL) containing N,N-diisopro-
pylethylamine (1.57 mL, 9.0 mmol) and di-tert-butyl
dicarbonate (1.5 g, 6.9 mmol) was heated under re¯ux.
After 4 h, more di-tert-butyl dicarbonate (4.0 g,
18.3mmol) was added and re¯uxing was continued for
16h. The solution was washed with HCl (2 M), aqueous
NaHCO3 and processed normally. The solid residue was
triturated with petroleum ether to give 12 (1.16 g,
3.6 mmol, 80%). Recrystallized from petroleum ether it
NMR spectra were recorded on a Bruker AC-300
instrument at 300 MHz (1H) or 75 MHz (13C) in CDCl3
unless otherwise stated with TMS as internal reference.
In D2O acetone was used as internal reference. High-
resolution accurate mass determinations were per-
formed by Hort Research Limited on a VG70-250S
double focussing magnetic sector mass spectrometer
under chemical ionization conditions using isobutane or
ammonia as the ionizing gas, or under high-resolution
FAB conditions in a glycerol or nitrobenzyl alcohol
matrix. Elemental analyses were performed by the
Campbell Laboratory, Otago University. Melting
points (mp) were determined on a Reichert hot stage
microscope and are uncorrected. Aluminum-backed
silica gel sheets (Merck or Reidel de Haen) were used
for thin layer chromatography. Column chromato-
graphy was performed on silica gel (230±400 mesh,
Merck). Chromatography solvents were distilled prior
to use. The imine 2 was prepared as described14 and was
used directly without isolation.
had mp 138±140ꢀC; H NMR d 8.14 (1H, dd, J=7.3,
1
1.8 Hz, Ar), 7.75 (1H, dd, J=7.7, 2.0 Hz, Ar), 7.64 (2H, m,
Ar), 7.44 (2H, m, Ar), 6.74 (1H, s, NH), 1.44 (9H, s, CH3);
13C NMR d 153.4, 133.1 and 132.4 (C), 129.9, 128.2,
127.4, 126.9 and 121.0 (CH), 119.2, 118.2 and 81.2 (C),
28.5 [C(CH3)3]. Anal. calcd for C15H16BrNO2: C, 55.92;
H, 5.01; Br, 24.80; N, 4.35. Found: C, 56.22; H, 4.79; Br,
24.77; N, 4.54.
4-Bromo-(N-tert-butoxycarbonyl)benzylamine (15). Di-
tert-butyl dicarbonate (6.0 g, 27.5mmol) and N,N-diiso-
propylethylamine (4.8 mL, 27.6 mmol) were added to a
stirred suspension of 4-bromobenzylamine hydrochloride
(5.1 g, 22.9mmol) in dichloromethane (40 mL). After 2 h
the solution was washed with HCl (2 M), aq NaHCO3 and
processed normally to give a syrup. Trituration with pet-
roleum ether a€orded crystalline 15 (3.3g, 11.5mmol,
50%). Recrystallized from petroleum ether it had mp 92±
93ꢀC; 1H NMR d 7.44, 7.14 (2H, 2d, J=8.4Hz, Ar), 4.87
(1H, bs, NH), 4.25 (2H, d, J=5.9 Hz, CH2); 13C NMR d
4-Bromo-1,2-bis[di-(4-methoxybenzyl)amino]benzene (6).
Sodium hydride (60%, 1.72g, 43mmol) was added to a
stirred solution of 1,2-diamino-4-bromobenzene22 (1.0 g,
5.3 mmol) in DMF (20 mL) followed by 4-methoxybenzyl
chloride (5.8 mL, 32mmol). The mixture was stirred at
room temperature for 2 days and then quenched with eth-
anol (5 mL). Chloroform (50 mL) was added and the
solution was washed with water (Â2) and processed to give
a crude residue which, after chromatography, a€orded 6

R. H. Furneaux et al. / Bioorg. Med. Chem. 7 (1999) 2599±2606
2603
155.8 and 138.1 (C), 131.7 and 129.1 (CH), 121.1 (C), 44.1
(CH2), 28.4 [C(CH3)]3. Anal. calcd for C12H16BrNO2: C,
50.37; H, 5.64; Br, 27.92; N, 4.89. Found: C, 50.53; H,
5.69; Br, 27.94; N, 5.11.
dd, J=3.0, 7.4 Hz, Ar), 7.71 (1H, d, J=7.9 Hz, Ar), 7.62
(1H, d, J=7.9 Hz, Ar), 7.44 (2H, m, aromatic), 6.78 (1H,
s, NH), 4.82 (1H, d, J1,2=4.4Hz, H-1), 4.44 (1H, dd,
J2,3=6.9 Hz, H-2), 4.38 (1H, dd, J3,4=5.0, Hz, H-3), 3.84
0
(1H, dd, J4,5=3.08, J5,5 =10.1 Hz, H-5), 3.68 (1H, dd,
0
J4,5 =6.3 Hz, H-5 ), 3.37 (1H, m, H-4), 1.56, 1.22 [6H, 2s,
(1S)-5-O-tert-Butyldimethylsilyl-1,4-dideoxy-1,4-imino-
2,3-O-isopropylidene-1-{3,4-bis[di-(4-methoxybenzyl)ami-
C(CH3)2], 1.46 [9H, s, C(CH3)3], 0.83 [9H, s, C(CH3)3],
0.05, 0.04 [6H, 2s, Si(CH3)2]; 13C NMR d 153.7, 134.1,
132.5, 132.2 and 127.1 (C), 126.1, 125.8, 124.9, 123.2,
121.1 and 118.7 (CH), 113.8 (C), 87.0 (C-2), 81.6 (C-3),
80.6 (C), 65.7 (C-4), 64.5 (C-5), 64.2 (C-1), 28.4 [C(CH3)3],
27.7 and 25.5 [C(CH3)2], 26.0 [C(CH3)3], 18.4 [C(CH3)3],
5.2 and 5.3 [Si(CH3)2]; HRMS (MH+) calcd for
C29H45N2O5Si: 529.3098. Found: 529.3110.
no]phenyl}-D-ribitol (7).
A solution of 6 (0.92 g,
1.38mmol) in ether (15 mL) and THF (5 mL) was cooled
to 40ꢀC and butyllithium (0.96 mL, 1.25mmol) was
added. The solution was cooled further to 78ꢀC and a
cold ( 78ꢀC) solution of imine 2,14 prepared from 1
(0.175g, 0.61mmol), was added by cannula. After 0.5 h,
water was added, the mixture was extracted with chloro-
form and processed normally. Chromatography a€orded
7 as a syrup (0.183g, 0.21mmol, 34%); 1H NMR d 6.95±
6.67 (19H, m, Ar), 4.39±4.16 (10H, m, H-2,3, N-CH2),
3.96 (1H, d, J=4.8 Hz, H-1), 3.79±3.65 (2H, m, H-5,50),
3.683, 3.679 (6H, 2s, OCH3), 3.18 (1H, m, H-4), 1.49 and
1.26 [6H, 2s, C(CH3)2], 0.81 [9H, s, C(CH3)3], 0.05, 0.04
[6H, 2s, Si(CH3)2]; 13C NMR d 158.6, 143.5, 142.8 and
134.8 (C), 130.6, 130.5, 122.0, 120.5 and 120.4 (CH), 114.0
(C), 113.5 and 113.4 (CH), 87.8 (C-2), 81.8 (C-3), 67.8 (C-
1), 65.7 (C-4), 63.6 (C-5), 55.2 (OCH3), 53.3 and 53.2
(NCH2O) 27.6 and 25.5 [C(CH3)2], 26.0 [C(CH3)3], 18.4
[C(CH3)3], 5.3 [Si(CH3)2]; HRMS (MH+) calcd for
C52H68N3O7Si: 874.4827. Found: 874.4852.
(1S)-1-[N-(4-tert-Butoxycarbonylamino)methyl]phenyl-5-
O-tert-butyldimethylsilyl-1,4-dideoxy-1,4-imino-2,3-O-
isopropylidene-D-ribitol (16). Butyllithium (2.6 mL,
3.9 mmol) was added to a solution of 15 (0.64 g, 2.2 mmol)
in THF (10 mL) at 78ꢀC and after 0.5 h a solution of
imine 2,14 prepared from 1 (0.16 g, 0.56 mmol), was added
by cannula to the resulting suspension. After 0.5 h, water
was added, the mixture was extracted with chloroform and
processed normally. Chromatography a€orded 16
(0.055 g, 0.11mmol, 20%); 1H NMR d 7.37, 7.25 (4H, 2d,
J=8.2 Hz, Ar), 4.85 (1H, bs, NH), 4.49 (1H, dd, J2,3=7.0,
J3,4=4.7 Hz, H-3), 4.40 (1H, dd, J1,2=5.3 Hz, H-2), 4.29
(2H, d, J=5.7 Hz, CH2), 4.17 (1H, d, H-1), 3.87 (1H, dd,
0
0
(1S)-5-O-tert-Butyldimethylsilyl-1,4-dideoxy-1,4-imino-
2,3-O-isopropylidene-1-{2,3-bis[di-(4-methoxybenzyl)-
amino]-5-pyridyl}-D-ribitol (10). A solution of 9 (1.2 g,
1.8 mmol) in ether (30 mL) was cooled to 40ꢀC and
butyllithium (1.35 mL, 1.75mmol) was added dropwise.
After 0.5 h, the solution was cooled to 78ꢀC and a solu-
tion of imine 214 prepared from 1 (0.16g, 0.56mmol) was
added by cannula. After 0.5 h, water was added, the mix-
ture was extracted with chloroform and processed nor-
mally. Chromatography a€orded 10 (0.23 g, 0.26mmol,
46%); 1H NMR d 7.89 (1H, d, J=1.7Hz, Ar), 6.99±6.65
(17H, m, Ar), 4.55 (4H, 2dd, N-CH2), 4.35 (1H, dd,
J=4.9, 7.0 Hz, H-3), 4.21±4.09 (5H, m, H-2, N-CH2), 3.97
(1H, d, J=8.5 Hz, H-1), 3.76 (2H, m, H-5,50), 3.69, 3.68
(6H, 2s, OCH3), 3.21 (1H, dd, J=4.9, 8.8 Hz, H-4), 1.50,
1.26 [6H, 2s, C(CH3)2], 0.81 [9H, s, C(CH3)3], 0.06, 0.04
[6H, 2s, Si(CH3)2]; 13C NMR d 158.5, 158.3 and 153.5 (C),
138.6 (CH), 136.7 and 130.9 (C), 130.4 and 130.0 (CH),
129.0 (C), 127.4 (CH), 113.9 (C), 113.4 and 113.3 (CH),
87.2 (C-3), 81.5 (C-2), 65.5 (C-4), 65.3 (C-1), 63.6 (C-5),
55.04 and 55.0 (CH3), 52.0 and 50.5 (CH2), 27.4 and 25.2
J4,5=3.7, J5,5 =10.2 Hz, H-5), 3.76 (1H, dd, J4,5 =5.3 Hz,
H-50), 3.34 (1H, dd, H-4), 1.58, 1.33 [6H, 2s, C(CH3)2], 1.46
[9H, s, C(CH3)3], 0.91 [9H, s, C(CH3)3], 0.08 [6H, Si(CH3)2];
13C NMR d 155.8, 140.6 and 138.1 (C), 127.7 and 126.8
(CH), 114.1 (C), 87.6 (C-2), 81.8 (C-3), 67.7 (C-1), 65.6
(C-4), 63.8 (C-5), 44.4 (CH2), 28.4 and 25.9 [C(CH3)3],
27.5 and 25.4 [C(CH3)2], 18.3 [C(CH3)3], 5.4 [Si(CH3)2].
(1S)-1-(3,4-Diaminophenyl)-1,4-dideoxy-1,4-imino-D-ribi-
tol (8). A solution of 7 (0.175g, 0.20mmol) in tri-
¯uoroacetic acid (10 mL) was allowed to stand at room
temperature for 24h and then evaporated to dryness. A
solution of the residue in water was extracted (Â2) with
chloroform and the aqueous phase was concentrated to
dryness. The residue in water was eluted through a col-
umn of Amberlyst A26 base resin. Evaporation of the
1
eluant a€orded 8 (0.018g, 0.075 mmol, 37%); H NMR
(D2O) d 6.94±6.76 (3H, m, Ar), 4.11±3.93 (2H, m, H-2,3),
3.90 (1H, d, J1,2=7.1 Hz, H-1), 3.79 (2H, m, H-5,50), 3.25±
3.17 (1H, m, H-4); 13C NMR d 137.1 and 134.6 (C), 122.1,
120.4 and 119.0 (CH), 79.2 and 74.9 (C-2,3), 67.9 and 67.4
(C-1,4), 64.7 (C-5); HRMS (MH+) calcd for C11H18N3O3:
240.1348. Found: 240.1342.
[C(CH3)2], 25.8 [C(CH3)3], 18.1 [C(CH3)3],
5.5
[Si(CH3)2]; HRMS (MH+) calcd for C51H67N4O7Si:
875.4779. Found: 875.4784.
(1S)-1-(2,3-Diamino-5-pyridyl)-1,4-dideoxy-1,4-imino-D-
ribitol (11). Acidic deprotection of 10 (0.14 g,
0.16 mmol) was carried out as described above in the
(1S)-1-[(N-tert-Butoxycarbonylamino)naphthalen-4-yl]-5-
O-tert-butyldimethylsilyl-1,4-dideoxy-1,4-imino-2,3-O-
isopropylidene-D-ribitol (13). Butyllithium (2.95 mL,
4.6 mmol) was added to a solution of 12 (0.84 g, 2.6 mmol)
in THF (5mL) at 78ꢀC. After 2 h, a solution of imine
2,14 prepared from 1 (0.175g, 0.61mmol), was added by
cannula. After 0.5 h, water was added, the mixture was
extracted with chloroform and processed normally.
Chromatography a€orded 13 (0.213 g, 0.40mmol, 66%);
1H NMR d 8.28 (1H, dd, J=2.1, 6.7 Hz, Ar), 7.81 (1H,
1
formation of 8 to give 11 (0.02 g, 0.08 mmol, 50%); H
NMR (D2O) d 7.54, 7.12 (2H, 2d, J=1.8 Hz, Ar), 4.04±
3.98 (2H, m, H-2,3), 3.87 (1H, d, J1,2=7.4 Hz, H-1),
3.72 (2H, 2d, J4,5=5.4 Hz, H-5,50), 3.17 (1H, dd,
J3,4=9.0 Hz, H-4); 13C NMR d 151.6 (C), 139.2 (CH),
132.2 and 129.8 (C), 125.0 (CH), 78.8 and 74.9 (C-2,3),
67.6 (C-4), 65.5 (C-1), 65.1 (C-5); HRMS (MH+) calcd
for C10H17N4O3: 241.1301. Found: 241.1307.

2604
R. H. Furneaux et al. / Bioorg. Med. Chem. 7 (1999) 2599±2606
(1S)-(1-Aminonaphthalen-4-yl)-1,4-dideoxy-1,4-imino-D-
ribitol (14). Acidic deprotection of 13 (0.21 g, 0.40mmol)
was carried out as described above in the formation of 8 to
give 14 (0.03 g, 0.11mmol, 28%); 1H NMR (MeOH-d4) d
8.16 (1H, d, J=8.4 Hz, Ar), 8.05 (1H, d, J=8.5 Hz, Ar),
7.67±7.44 (3H, m, Ar), 6.85 (1H, d, J=7.9Hz, Ar), 5.06
(1H, d, J1,2=6.8Hz, H-1), 4.43 (1H, dd, J2,3=5.3 Hz, H-
2), 4.19 (1H, t, H-3), 3.82 (2H, d, H-5,50), 3.51 (1H, dd,
J=4.3, 8.7 Hz, H-4); 13C NMR d 145.9 and 134.4 (C),
127.5, 126.3 and 125.5 (CH), 125.4 (C), 124.2 and 123.5
(CH), 122.7 (C), 109.7 (CH), 76.8 (C-2), 73.4 (C-3), 66.3
(C-4), 62.7 (C-1), 61.5 (C-5); HRMS (MH+) calcd for
C15H18N2O3: 274.1317. Found: 274.1312.
6-O-tert-Butyldimethylsilyl-2,5-dideoxy-2,5-imino-3,4-O-
isopropylidene-D-allose propane-1,3-diyl dithioacetal (21).
Butyllithium (19.6 mL, 27.4 mmol) was added to a solu-
tion of 1,3-dithiane (3.63 g, 30.2 mmol) in THF (50 mL) at
20ꢀC and after 0.5 h the solution was cooled to 78ꢀC
and added by cannula to a solution of imine 2,14 prepared
from 1 (2.5 g, 8.7 mmol). After 0.5 h, water was added, the
mixture was extracted with chloroform and processed
normally. Chromatography a€orded 21 as a syrup (2.72 g,
6.7 mmol, 77%); 1H NMR d 4.50 (1H, dd, J2,3=4.8,
J3,4=7.0 Hz, H-3), 4.34 (1H, dd, J4,5=4.5 Hz, H-4), 4.06
(1H, d, J=7.0Hz, H-1), 3.69 (1H, dd, J5,6=3.9,
0
0
0
J6,6 =10.3 Hz, H-6), 3.60 (1H, dd, J5,6 =4.9Hz, H-6 ),
3.17 (1H, m, H-5), 2.87±2.71 (4H, m, SCH2), 2.05, 1.86
(2H, 2m, CH2), 1.45, 1.27 [6H, 2s, C(CH3)2], 0.83 [9H, s,
C(CH3)3], 0.05 [6H, Si(CH3)2]; 13C NMR d 113.5 (C), 83.4
(C-3), 81.7 (C-4), 67.0 (C-2), 65.3 (C-5), 63.7 (C-6), 49.8
(C-1), 29.3 and 29.0 (SCH2), 27.3 and 25.3 [C(CH3)2], 25.8
[C(CH3)3 and CH2], 18.1 [C(CH3)3], 5.5 and 5.6
[Si(CH3)2]; HRMS (MH+) calcd for C18H36NO3S2Si:
406.1906. Found: 406.1898.
(1S)-1-(4-Aminomethyl)phenyl-1,4-dideoxy-1,4-imino-D-
ribitol (17). Acidic deprotection of 16 (0.055 g,
0.11 mmol) was carried out as described above in the
1
formation of 8 to give 17 (0.025 g, 0.10 mmol, 90%); H
NMR (D2O) d 7.50 (4H, m, Ar), 4.09 (5H, br s, H-1,2,3,
ArCH2), 3.80 (2H, m, H-5,50), 3.25 (1H, m, H-4); 13C
NMR (142.4 and 138.4ꢀC), 131.3 and 130.5 (CH), 79.3
and 74.8 (C-2,3), 67.8 (C-1), 67.5 (C-4), 64.9 (C-5), 46.0
(ArCH2); HRMS (MH+) calcd for C12H19N2O3:
239.1396. Found: 239.1370.
N-tert-Butoxycarbonyl-6-O-tert-butyldimethylsilyl-2,5-di-
deoxy-2,5-imino-3,4-O-isopropylidene-D-allose propane-
1,3-diyl dithioacetal (22). A solution of 21 (1.0 g,
2.47 mmol) in dichloromethane (20 mL) containing di-
tert-butyl dicarbonate (0.81 g, 3.71 mmol) was stirred at
room temperature for 2 days, and then concentrated to
dryness. Chromatography a€orded 22 as a syrup
(1S)-5-O-tert-Butyldimethylsilyl-1-(4-cyanophenyl)-1,4-
dideoxy-1,4-imino-2,3-O-isopropylidene-D-ribitol (19).
Argon was bubbled through a solution of (1S)-1-(4-bromo-
phenyl)-5-O-tert-butyldimethylsilyl-1,4-dideoxy-1,4-imino-
2,3-O-isopropylidene-d-ribitol14 (19a, 0.68 g, 1.54 mmol) in
HMPA (10 mL) containing palladium acetate (0.070 g,
0.31 mmol) and potassium cyanide (0.50 g, 7.7 mmol) for
0.5 h, and then the solution was heated at 75ꢀC under
argon for 3 h. Toluene was added and the mixture was
washed with NaHCO3 (aq), water and processed normally
to give, following chromatography, 19 as a syrup (0.351 g,
0.90 mmol, 58%); 1H NMR d 7.62, 7.55 (4H, 2d,
J=8.3 Hz, Ar), 4.46 (1H, dd, J2,3=6.9, J3,4=4.2 Hz, H-3),
4.34 (1H, t, H-2), 4.23 (1H, d, J1,2=5.4 Hz, H-1), 3.84
1
(1.17 g, 2.32 mmol, 94%); H NMR d 4.79, 4.65 (2H,
2m, H-3,4), 4.37±4.14 (2H, m, H-1,2), 4.03 (1H, m, H-
5), 3.80±3.58 (2H, m, H-6,60), 3.12±2.70 (4H, m, SCH2),
2.11±1.90 (2H, m, CH2), 1.47 [12H, s, CH3, C(CH3)3],
1.33 (3H, s, CH3), 0.90 [9H, s, C(CH3)3], 0.08 [6H,
Si(CH3)2]; 13C NMR d 154.8 and 111.6 (C), 82.6 and
81.7 (C-3,4), 80.1 (C), 66.6 (C-2), 66.4 (C-5), 63.1 (C-6),
46.7 (C-1), 28.2 [C(CH3)3], 27.3 and 25.4 (CH2), 27.1
and 25.2 [C(CH3)2], 25.8 [C(CH3)3], 18.2 [C(CH3)3],
5.4 and 5.5 [Si(CH3)2]; HRMS (MH+) calcd for
C23H44NO5S2Si: 506.2430. Found: 506.2427.
0
(1H, dd, J4,5=4.0, J5,5 =10.2 Hz, H-5), 3.72 (1H, dd,
0
0
J4,5 =6.0 Hz, H-5 ), 3.41 (1H, m, H-4), 1.59, 1.33 (6H, 2s,
CH3), 0.90 [9H, s, C(CH3)3], 0.08 [6H, Si(CH3)2]; 13C
NMR d 147.2 (C), 132.2 and 127.1 (CH), 118.8, 114.1 and
111.0 (C), 87.1 (C-2), 81.7 (C-3), 67.5 (C-1), 65.3 (C-4),
64.4 (C-5), 27.4 and 25.3 [C(CH3)2], 25.8 [C(CH3)3], 18.2
[C(CH3)3], 5.5 [Si(CH3)2]; HRMS (MH+) calcd for
C21H33N2O3Si: 389.2260. Found: 389.2223.
N-tert-Butoxycarbonyl-6-O-tert-butyldimethylsilyl-2,5-di-
deoxy-2,5-imino-3,4-O-isopropylidene-D-allitol (23). Cal-
cium carbonate (3.4 g) was added to a stirred solution of
22 (0.34 g, 0.67 mmol) in 5% aqueous MeCN (15 mL)
followed by mercury(II) tri¯uoroacetate (3.47 g,
8.1 mmol) and the mixture was stirred for 4 h. Chloro-
form (50 mL) was added and the mixture was ®ltered
through Celite, washed with aqueous NaHCO3 and
processed to give a syrup which was dissolved in ethanol
and sodium borohydride (0.1 g, 2.6 mmol) was added.
After 1 h the solution was partitioned between chloro-
form and water and the organic layer was processed
normally to give, after chromatography, 23 as a syrup
(1S)-1-(4-Cyanophenyl)-1,4-dideoxy-1,4-imino-D-ribitol
(20). A solution of 19 (0.22 g, 0.57 mmol) in THF:
water:tri¯uoroacetic acid (15 mL, 10:4:1 v/v/v) was
heated under re¯ux for 3 h and then concentrated to
dryness. The residue in water was extracted (Â2) with
chloroform, concentrated to dryness, then redissolved in
water and the solution was treated with Amberlyst A21
base resin to neutral pH. Lyophilization a€orded 20
1
(0.194 g, 0.46 mmol, 69%); H NMR d 4.77±4.32 (3H,
m), 4.14 (1H, m), 4.07±3.58 (5H, m), 1.47, 1.38 (6H, 2s,
CH3), 1.45, 0.89 [9H, s, C(CH3)3], 0.08 (6H, s, CH3); 13
C
1
(0.12 g, 0.51 mmol, 89%); H NMR (D2O) d 7.73, 7.55
(4H, 2d, J=8.2 Hz, Ar), 4.13 (1H, d, J1,2=7.3 Hz, H-1),
4.04 (2H, m, H-2,3), 3.72 (2H, m, H-5,50), 3.27 (1H, dd,
J=5.8, 9.6 Hz, H-4); 13C NMR d 147.5 (C), 135.5 and
130.7 (CH), 122.3 and 113.3 (C), 79.1 and 74.6 (C-2,3),
67.6 and 67.5 (C-1,4), 64.7 (C-5); HRMS (MH+) calcd
for C12H15N2O3: 235.1083. Found: 235.1080.
NMR d 111.4 (C), 81.9 and 81.6 (CH), 81.4 and 80.8
(CH), 80.5 and 80.1 (C), 66.5 (CH), 66.2 and 65.7 (CH),
64.6 and 63.7 (CH2), 63.5 and 62.9 (CH2), 28.2
[C(CH3)3], 27.4 and 25.4 [C(CH3)2], 25.8 [C(CH3)3], 18.4
[C(CH3)3], 5.7 [Si(CH3)2]; HRMS (MH+) calcd for
C20H40NO6Si: 418.2625. Found: 418.2610.

R. H. Furneaux et al. / Bioorg. Med. Chem. 7 (1999) 2599±2606
2605
1,2,5-Trideoxy-1-(hypoxanthin-9-yl)-2,5-imino-D-allitol
(24). To a solution of 23 (0.05 g, 0.12mmol) and 2,6-di-
tert-butyl-4-methylpyridine (0.123g, 0.6 mmol) in CH2Cl2
(3mL) at 0ꢀC was added tri¯uoromethanesulfonic anhy-
dride (0.040mL, 0.24mmol). After 0.5 h the solution was
washed with HCl (2 M), aqueous NaHCO3 and processed
normally. 6-Chloropurine (0.074 g, 0.48 mmol) and
potassium carbonate (0.066g, 0.48mmol) were added to a
solution of the crude product in DMF (3 mL) and the
mixture was stirred at room temperature for 0.5 h.
Chloroform (10 mL) was added, the solution was washed
(Â2) with water and processed normally to give, after
chromatography, N-tert-butoxycarbonyl-6-O-tert-butyl-
dimethylsilyl-1-(6-chloropurin-9-yl)-1,2,5-trideoxy-2,5-
imino-3,4-O-isopropylidene-d-allitol (0.035g, 0.063 mmol,
52%). This material was dissolved in tri¯uoroacetic acid
(3mL) and the solution was allowed to stand for 6 h.
Water (1 mL) was added and the solution was left at
room temperature for 16h and then concentrated to
dryness. The residue was dissolved in water and extracted
(Â2) with chloroform and the aqueous phase was con-
centrated to dryness. The residue in water was treated
with Amberlyst A21 base resin until the solution was
neutral, and then the solids and solvent were removed to
6-chloroguanine was used in place of adenine. This a€or-
1
ded 26 as a solid (0.025 g, 0.084 mmol, 35%); H NMR
(D2O) d 7.80 (1H, s, Ar), 4.48 (2H, m, H-1,10), 4.05 (2H,
m, H-3,4), 3.92±3.70 (3H, m, H-2,6,60), 3.58 (1H, m, H-
5); 13C NMR d 142.9 (CH), 74.6 and 73.6 (C-3,4), 67.9
and 64.1 (C-2,5), 62.3 (C-6), 46.3 (C-1); HRMS (MH+)
calcd for C11H17N6O4: 297.1311. Found: 297.1331.
6-O-tert-Butyldimethylsilyl-1-(5-carboxamido-2-pyridyl)-
1,2,5-trideoxy-2,5-imino-3,4-O-isopropylidene-D-allitol
(27).
A solution of lithium tetramethylpiperidide
(LiTMP) in THF (10.5 mL, 9.6 mmol) was added to a sus-
pension of 6-methylnicotinamide (0.218g, 1.6 mmol) in
THF (15 mL) at 78ꢀC and the mixture was stirred at
30ꢀꢀC for 0.5 h. The resulting solution was cooled to
78 C and a solution of imine 2,14 prepared from 1 (0.23 g,
0.80mmol), was added by cannula. After 0.5 h, water was
added, the mixture was extracted with chloroform and
processed normally. Chromatography a€orded 27 as a
syrup (0.227g, 0.54mmol, 67%); 1H NMR d 8.90 (1H, d,
J=1.8Hz, Ar), 8.03 (1H, dd, J=2.1, 8.0 Hz, Ar), 7.25 (1H,
d, J=7.6Hz, Ar), 6.51 (2H, s, NH2), 4.38 (1H, dd,
J3,4=6.9, J4,5=4.5 Hz, H-4), 4.27 (1H, dd, J2,3=5.2Hz,
0
H-3), 3.71 (1H, dd, J5,6=4.0, J6,6 =10.3 Hz, H-6), 3.63
1
0
0
give 24 as a solid (0.009g, 0.032 mmol, 51%); H NMR
(1H, dd, J5,6 =4.9 Hz, H-6 ), 3.48 (1H, m, H-2), 3.21±3.12
(D2O) d 8.19, 8.17 (2H, 2s, Ar), 4.51 (1H, dd, J=14.5,
5.4 Hz, H-1), 4.39 (1H, dd, J=7.5Hz, H-10), 3.90 (2H, m,
H-3,4), 3.69±3.54 (3H, m, H-2,6,60), 3.16 (1H, dd, J=9.0,
4.6 Hz, H-5); 13C NMR d 161.5 and 152.0 (C), 148.7 and
145.3 (CH), 126.2 (C), 76.2 and 74.6 (C-3,4), 67.1 (C-5),
64.6 (C-6), 64.2 (C-2), 49.1 (C-1); HRMS (MH+) calcd for
C11H16N5O4: 282.1202. Found: 282.1196.
(2H, m, H-1, H-5), 2.92 (1H, dd, J=8.3, 14.2 Hz, H-10),
1.45, 1.26 [6H, 2s, C(CH3)2], 0.82 [9H, s, C(CH3)3], 0.05
[6H, Si(CH3)2]; 13C NMR d 167.7 and 162.7 (C), 148.1 and
135.8 CH), 127.0 (C), 123.3 (CH), 113.8 (C), 85.1 (C-3),
82.0 (C-4), 65.4 (C-5), 63.9 (C-2), 63.6 (C-6), 41.9 (C-1),
27.4 and 25.4 [C(CH3)2], 25.8 [C(CH3)3], 18.2 [C(CH3)3],
5.4,
C21H36N3O4Si: 422.2475. Found: 422.2503.
5.5 [Si(CH3)2]; HRMS (MH+) calcd for
1-(Adenin-9-yl)-1,2,5-trideoxy-2,5-imino-D-allitol (25).
Methanesulfonyl chloride (0.037mL, 0.48mmol) was
added to a solution of 23 (0.10 g, 0.24mmol) and N,N-
diisopropylethylamine (0.21 mL, 1.2 mmol) in CH2Cl2
(5mL) and after 1 h the solution was washed with HCl (2
M), aqueous NaHCO3 and processed normally. Adenine
(0.13 g, 0.96mmol) and potassium carbonate (0.132g,
0.96mmol) were added to a solution of the crude residue
in DMF (4mL) and the mixture was stirred at 100ꢀC for
6 h. Chloroform (15 mL) was added and the mixture was
washed (Â4) with water, and processed normally to give,
after chromatography, 1-(adenin-9-yl)-N-tert-butoxy-
carbonyl-6-O-tert-butyldimethylsilyl-1,2,5-trideoxy-2,5-
imino-3,4-O-isopropylidene-d-allitol (0.054g, 0.10mmol,
41%). This material was dissolved in tri¯uoroacetic acid
(3mL) and allowed to stand for 16h. It was processed as
described above for 24 to give 25 as a solid (0.02 g,
1-(5-Carboxamido-2-pyridyl)-1,2,5-trideoxy-2,5-imino-D-
allitol (28). Compound 27 (0.11g, 0.26mmol) was depro-
tected in tri¯uoroacetic acid and processed further as
described above in the preparation of 24 to give28as a solid
(0.053 g, 0.20 mmol; 77%); 1H NMR (D2O) d 8.86 (1H, s,
Ar), 8.18 (1H, dd, J=2.2, 8.1 Hz, Ar), 7.53 (1H, d,
J=8.1 Hz, Ar), 4.00 (1H, t, J=5.5 Hz, H-4), 3.88 (1H, t,
J=6.5 Hz, H-3), 3.74 (2H, m, H-6,60), 3.48 (1H, m, H-2),
0
0
3.28, 3.07 (2Â1H, dd, J1,1 =14.0, J1,2=5.4, J1 ,2=8.5 Hz,
H-1,10), 3.18 (1H, m, H-5); 13C NMR d 173.2 and 164.3 (C),
150.4, 139.6 (CH), 130.0 (C), 126.9 (CH), 77.4 (C-3), 74.2
(C-4), 67.0 (C-5), 64.8 (C-2), 63.9 (C-6), 42.4 (C-1); HRMS
(MH+) calcd for C12H18N3O4: 268.1297. Found: 268.1283.
Acknowledgements
1
0.071 mmol, 71%); H NMR (D2O) d 8.16, 8.14 (2H, 2s,
Ar), 4.45 (1H, dd, J=5.7, 14.5Hz, H-1), 4.32 (1H, dd,
J=7.3Hz, H-10), 3.91 (2H, m, H-3,4), 3.68 (1H, dd,
The authors thank Dr. Robert W. Miles for the unpub-
lished data of Tables 1 and 2, Dr. Herbert Wong for an
excellent NMR service and Professor Robin Ferrier for
assisting with the preparation of the manuscript. This
work was supported by research grants from the
National Institutes of Health, USA, and the Foundation
for Research Science and Technology, New Zealand.
0
J5,6=4.9, J6,6 =11.6 Hz, H-6), 3.61 (1H, dd,
0
0
J5,6 =5.6Hz, H-6 ), 3.52 (1H, m, H-2), 3.15 (1H, m, H-
5); 13C NMR d 158.1 (C), 155.1 (CH), 151.7 (C), 145.2
(CH), 120.9 (C), 76.3 and 74.7 (C-3,4), 66.7 (C-5), 64.8
(C-6), 64.1 (C-2), 49.0 (C-1); HRMS (MH+) calcd for
C11H17N6O3: 281.1362. Found: 281.1374.
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The alcohol 23 (0.10 g, 0.24 mmol) was treated as
described above in the preparation of 25 except that
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