Synthesis of transition state analogue inhibitors for purine nucleoside phosphorylase and N-riboside hydrolases

Article abstract of DOI:10.1016/S0040-4020(00)00194-0

Syntheses of the 'Immucillins', potent aza-C-nucleoside inhibitors of purine nucleoside phosphorylase are reported as well as those of 5-deoxy-, 5- deoxyfluoro- and 2-deoxy- analogues and others having modified bases. (C) 2000 Elsevier Science Ltd.

Full text of DOI:10.1016/S0040-4020(00)00194-0

TETRAHEDRON
Pergamon
Tetrahedron 56 (2000) 3053±3062
Synthesis of Transition State Analogue Inhibitors for Purine
Nucleoside Phosphorylase and N-Riboside Hydrolases
Gary B. Evans,a Richard H. Furneaux,a Graeme J. Gainsford,a Vern L. Schrammb
and Peter C. Tylera,
*
aCarbohydrate Chemistry, Industrial Research Limited, P.O. Box 31310, Lower Hutt, New Zealand
bDepartment of Biochemistry, Albert Einstein College of Medicine of Yeshiva University, 1300 Morris Park Avenue, Bronx, NY 10461, USA
Received 18 November 1999; revised 17 February 2000; accepted 2 March 2000
AbstractÐSyntheses of the `Immucillins', potent aza-C-nucleoside inhibitors of purine nucleoside phosphorylase are reported as well as
those of 5-deoxy-, 5-deoxy¯uoro- and 2-deoxy- analogues and others having modi®ed bases. q 2000 Elsevier Science Ltd. All rights
reserved.
Introduction
completely on salvage pathways to recover these bases from
the host for DNA and RNA synthesis.9 In designing inhibi-
tors, it has to be born in mind that the nucleoside hydrolases
present in such protozoan parasites can vary in their
substrate speci®city and in their mechanisms of hydroly-
sis.10±13 For example, purine salvage in the trypanosome
Crithidia fasciculata involves two distinct nucleoside
hydrolases14,15 while a third nucleoside hydrolase has been
found in Trypanosoma brucei brucei.16 Nevertheless, the
apparently speci®c role for these enzymes in the protozoa
suggests they may be suitable targets for antibiotic design.
Nucleoside processing enzymes are ubiquitous and essential
to provide precursors for RNA and DNA synthesis and
energy metabolism. Examples of these enzymes include
purine nucleoside phosphorylase and a number of nucleo-
side N-riboside hydrolases and transferases.
A genetic de®ciency of purine nucleoside phosphorylase
(PNP) in humans results in the selective depletion of
T-cells.1,2 PNP is the only enzyme which degrades
20-deoxyguanosine in T-cells, and when not degraded,
20-deoxyguanosine is converted instead to 20-deoxyguano-
sine triphosphate (dGTP), which accumulates. High levels
of dGTP cause an allosteric inhibition of ribonucleotide
diphosphate reductase which prevents the normal DNA
replication required for clonal expansion of T-cell popu-
lations.3±5
The transition states characterised to date for reactions
promoted by PNP and nucleoside hydrolase enzymes have
similar features. Kinetic isotope effect studies on PNP from
calf spleen have been used to predict a transition state struc-
ture in which the enzyme stabilises a ribooxocarbenium ion
and also assists the purine to become a leaving group by
electron-withdrawing interactions.17 Nucleoside hydrolase
transition states also feature incipient ribooxocarbenium
ions, but the proportion of the activation energy derived
from protonation or other activation of the purine leaving
group varies depending upon the enzyme.8,12,13
Undesirable activation of T-cells is associated with a
number of human disease states including psoriasis,
rheumatoid arthritis, T-cell lymphomas, transplant tissue
rejection and possibly other autoimmune disorders. Conse-
quently PNP inhibition has become a target for drug
design.6,7
Nucleoside N-riboside hydrolases (nucleoside hydrolases)
are also of potential interest to the medicinal chemist.
These enzymes are found in protozoan parasites but are
not known to exist in mammalian cells.8 Protozoa have
lost the capacity for de novo purine biosynthesis and rely
Keywords: carbohydrate mimetics; enzyme inhibitors; nucleosides;
purines.
* Corresponding author. Fax: 164-4-5690055; e-mail: p.tyler@irl.cri.nz
From analysis of these results we predicted that 1,4-
dideoxy-1,4-imino-d-ribitol compounds 1, which will be
0040±4020/00/$ - see front matter q 2000 Elsevier Science Ltd. All rights reserved.
PII: S0040-4020(00)00194-0

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G. B. Evans et al. / Tetrahedron 56 (2000) 3053±3062
Table 1. Ki values (nM) for binding of compounds 2 and 3 with two PNP's and two nucleoside hydrolase isozymes
Compound
Human PNP
Ki (nM)
Bovine PNP
Ki (nM)
IAG nucleoside
hydrolase Ki (nM)
IU nucleoside
hydrolase Ki (nM)
2
3
0.072
0.029
0.023
0.030
24
110
42
84
largely protonated at pH 7 (pKaˆ6.5),18 will be potent
transition state analogue inhibitors of both PNP and nucleo-
side hydrolases. Preliminary studies on the synthesis and
biological activity of nucleoside hydrolase inhibitors 1
(Rˆsubstituted aromatic)13,19,20 led to the conclusion that
for more potent inhibition of these enzymes the R group
needed to better mimic the purine base of the substrate;
and the same was expected to be the case for PNP from
evaluation of the enzyme transition state by studies of the
kinetic isotope effects.17 Consequently we have synthesised
the iminoribitol C-glycosides 2 and 3 (the `Immucillins'),
which emerged as exceedingly potent inhibitors of both
bovine and human PNP as well as two nucleoside hydro-
lases with different substrate speci®cities, the IAG and IU
nucleoside hydrolases from Trypanosoma brucei brucei and
Crithidia fasciculata, respectively (Table 1).21,22 In
addition, the 50-phosphates of 2 and 3 are potent inhibitors
of phosphoribosyltransferases.23±25
this chemistry is not suitable for our purposes. Conceivably,
the target aza-C-nucleosides 2 and 3 could be prepared
using the methodology indicated in Scheme 1, i.e. by adding
a suitable lithiated 9-deazapurine derivative to the imine 5.
However, we decided that assembling the 9-deazapurines on
a preformed aza-C-glycoside offered a more established
route to the proposed inhibitors. Such an approach has
been successful in the synthesis of 9-deazainosine, 9-deaza-
guanosine and 9-deazaadenosine.29±31 A direct synthesis of
9-deazaguanosine by an acid-catalyzed reaction between
9-deazaguanine and 1-O-acetyl-2,3,5-tri-O-benzoyl-b-d-
ribofuranose has been described,32 and some aza-C-glyco-
sides have been prepared by employing Lewis acid cata-
lyzed conditions,33,34 but these approaches did not appear
appropriate for the synthesis of aza-C-nucleosides.
Addition of lithiated acetonitrile to imine 5 afforded the
cyanomethyl C-glycoside derivative
6
(RˆCH2CN).
Variable amounts of disubstituted acetonitrile were also
produced following deprotonation of the active methylene
moiety in 6 and subsequent addition of the derived anion to
imine 5. This could be minimised by conducting the reac-
tion under dilute conditions with an excess of the lithiated
acetonitrile. The iminoribitol nitrogen atom of 6 was
protected as the Boc carbamate to give 7 and treatment of
this with Bredereck's reagent afforded enamine 8. Mild acid
hydrolysis gave 9, which was allowed to react with ethyl
glycinate to give enamines 10. The NMR spectra of 8 and 9
indicated they were each single isomers whereas 10 was a
mixture of diastereoisomers. Protection of the enamine
nitrogen atom was required in order to effect a cyclisation
to the pyrrole, and when 10 was treated with excess benzyl
chloroformate and DBU the pyrrole 11 was produced
(Scheme 2). Hydrogenolysis of 11 readily afforded pyrrole
12, from which the two target compounds 2 and 3 were
derived (Scheme 3).
These Immucillins have considerable potential for the
control of T-cell proliferative disorders such as psoriasis,
rheumatoid arthritis, T-cell lymphomas and transplant tissue
rejection as well as antibiotics for protozoan parasite
infections such as malaria, trypanosomiasis and sleeping
sickness.
We present here the ®rst report of the synthesis of 2 and 3 as
well as some close analogues. The full biological properties
of these compounds are reported elsewhere.21,22
Results and Discussion
Our previous syntheses of compounds belonging to set 1
utilised additions of organometallic species to the imine 5
(Scheme 1), which is generated from the iminoribitol
derivative 4.19,26 Others have claimed an alternative facile
synthesis of some (1S)-aryl-1,4-dideoxy-1,4-imino-d-ribitols
by the addition of organometallic compounds to a 2,3,5-tri-
O-protected-d-ribofuranose derivative followed by oxi-
dation of the 1,4-diol product and then reductive amination
of the resultant 1,4-dicarbonyl compound to give (1S)-aryl-
1,4-dideoxy-1,4-imino-d-ribitol compounds.27 However,
further investigations have revealed that these compounds
have, in fact, the l-lyxo stereochemistry28 and consequently
Treatment of 12 with formamidine acetate generated the
deazapurine aza-C-glycoside 13, which was deprotected
with TFA to give the target deazainosine analogue 2 (74%
yield from 11). Alternatively, treatment of 12 with benzoyl
isothiocyanate followed by methyl iodide and DBU
afforded the isothiourea 14, which when allowed to react
with ammonia in methanol in a sealed tube at 1008C gave 15
along with lesser amounts of 16. Again, deprotection was
Scheme 1.

G. B. Evans et al. / Tetrahedron 56 (2000) 3053±3062
3055
Scheme 2. Reagents: (i) (Boc)2O, CH2Cl2; (ii) tBuOCH(NMe2)2, DMF, 708C; (iii) THF, HOAc, H2O; (iv) H2NCH2CO2Et´HCl, NaOAc, MeOH; (v) ClCO2Bn,
DBU, CH2Cl2, re¯ux; (vi) H2, Pd/C, EtOH.
effected with TFA to give the deazaguanosine analogue 3
(32% yield from 11).
derivative 19 (Scheme 4). Hydrogenolysis of this material
gave the 50-deoxy compound 20 with the pyrrole moiety
N-deprotected. This was then converted into the
50-deoxy-9-deaza-inosine and -guanosine analogues 21
and 22 by use of the methods employed to prepare 2
and 3.
We were also interested in probing the structure±activity
relationships of these novel and potent inhibitors of nucleo-
side metabolism. In the ®rst instance we focussed on the
50-position of the aza-C-nucleosides with the intention of
preparing 50-deoxy and 50-deoxy¯uoro analogues.
However, attempts to effect various SN1- or SN2-like reac-
tions at C-50 of 17 or its 50-O-mesylate derivative were
unsuccessful with the deazapurine moiety appearing to
participate in the reaction. In consequence, the protected
pyrrole 11 was used to prepare 50-deoxy analogues. Desilyl-
ation of 11 and mesylation of the resulting alcohol 18
followed by displacement of the 50-sulfonyloxy group
with bromide ions afforded the 50-bromo-50-deoxy
When alcohol 18 was treated with DAST a mixture of
products, which did not contain ¯uorine was formed and
appeared to result from participation of the pyrrole moiety.
However, when alcohol 23 obtained by desilylation of 7 was
allowed to react with DAST, the 5-deoxy-5-¯uoro deriva-
tive 24 was produced. The acetonitrile component of 24 was
then elaborated, as outlined in Schemes 2 and 3, for the
synthesis of 2 to produce the 50-deoxy¯uoro-9-deazainosine
analogue 25 (Scheme 5).
Scheme 3. Reagents: (i) H2NCHyNH.HOAc, EtOH, re¯ux; (ii) TFA; (iii) BzNCS, CH2Cl2; (iv) DBU, MeI, CH2Cl2; (v) NH3, MeOH, 1008C.

3056
G. B. Evans et al. / Tetrahedron 56 (2000) 3053±3062
Scheme 4. Reagents: (i) Bu4NF; (ii) MsCl, DMAP, Et3N; (iii) Bu4NBr; (iv) H2, Pd/C, Et3N, EtOH; (v) H2NCHyNH.HOAc, EtOH, re¯ux; (vi) TFA; (vii)
BzNCS, CH2Cl2; (viii) DBU, MeI, CH2Cl2; (ix) NH3, MeOH, 1008C.
The 20-deoxy analogues of 2 and 3 were also required for
structure±activity studies as transition state analogue
inhibitors, particularly because PNP accepts purine 20-deoxy-
nucleosides as substrates.35 As a result of the dif®culties
encountered when attempting modi®cations at C-5 when
the deazapurine moiety was present, we chose to deoxy-
genate at C-2 prior to formation of the deazapurine. This
was achieved by deprotection of 6 (RˆCH2CN) to afford 26
followed by reprotection to give 27 and then 28 (Scheme 6);
deoxygenation was effected by radical reduction of the
imidazolethiocarbamate 29 resulting in 30. Elaboration of
the deazapurine moieties was carried out as described above
for the synthesis of 2 and 3 (Schemes 2 and 3) affording 32
and 33.
Scheme 5. Reagents: (i) Bu4NF; (ii) DAST, CH2Cl2; (iii) reagents (ii)±(vi)
in Scheme 2, then (i) and (ii) in Scheme 3.
Scheme 6. Reagents: (i) TFA; (ii) (Boc)2O; (iii) O[(iPr)2SiCl]2, imidazole, DMF; (iv) (Imidazolyl)2CyS; (v) Bu3SnH; (vi) reagents (ii)±(v) in Scheme 2; (vii)
reagents (i) and (ii) in Scheme 3; (viii) Bu4NF; (ix) H2, Pd/c; (x) reagents (iii)±(v) and (ii) in Scheme 3.

G. B. Evans et al. / Tetrahedron 56 (2000) 3053±3062
3057
Scheme 7. Reagents: (i) H2NCH2CN, NaOAc, MeOH; (ii) DBU, BnOCOCl, CH2Cl2; (iii) H2, Pd/C, EtOH; (iv) H2NCHyNH, EtOH; (v) aq. TFA; (vi) aq. H2O2,
DMSO.
1
D2O was the solvent acetone (d H, 2.20; 13C, 33.2) was
used as internal reference. High resolution accurate mass
determinations were performed by Hort Research Ltd on a
VG70-250S double focusing, magnetic sector mass spectro-
meter under chemical ionisation conditions using isobutane
or ammonia as the ionising gas, or under high-resolution
FAB conditions in a glycerol or nitrobenzyl alcohol matrix.
Melting points were determined on a Reichert hot stage
microscope and are uncorrected. Optical rotations were
determined with a Perkin±Elmer 241 automatic polarimeter
and are given in units of 1021deg cm2 g21. Aluminium-
backed silica gel sheets (Merck or Reidel de Haen) were
Fig. 1. ORTEP diagram of (1R)-1-(9-deazahypoxanthin-9-yl)-1,2,4-
used for thin layer chromatography. Column chroma-
trideoxy-1,4-imino-d-erythro-pentitol hydrochloride (32´HCl)
tography was performed on silica gel (230±400 mesh,
Merck). Chromatography solvents were distilled prior to use.
The 9-deazaadenosine analogue 35 was prepared by way of
7-O-tert-Butyldimethylsilyl-2,3,6-trideoxy-3,6-imino-4,5-
O-isopropylidene-d-allo-heptononitrile (6, RˆCH2CN).
A solution of the iminoribitol compound 419 (2.0 g,
7.0 mmol) in pentane (40 mL) was stirred with N-chloro-
succinimide (1.2 g, 9.0 mmol) for 1 h. The solids and
solvent were removed, the residue was dissolved in dry
THF (40 mL) and the solution was cooled to 2788C.
Lithium tetramethylpiperidide (25 mL, 0.4 M in THF) was
added dropwise and the resulting solution was then added
via cannula to one of lithiated acetonitrile [prepared by the
dropwise addition of acetonitrile (2.08 mL, 40 mmol) to a
solution of butyllithium (29.8 mL, 41.8 mmol) in dry THF
(50 mL) at 2788C, followed by stirring for 45 min and then
addition of tetramethylpiperidine (0.67 mL, 4 mmol)] at
2788C. The reaction mixture was stirred for 10 min then
quenched carefully with acetic acid (4 mL) and partitioned
between water and chloroform. The organic phase was
dried, concentrated, and chromatographed to afford nitrile
6 (RˆCH2CN) (0.83 g, 2.5 mmol, 36%) as a syrup. 1H NMR
d 4.47 (1H, dd, J4,5ˆ6.6, J5,6ˆ3.8 Hz, H-5), 4.30 (1H, dd,
the pyrrole 34 and condensation with formamidine acetate.
Hydrolysis of the cyano group of 34 afforded the corre-
sponding amide and hence 36, a monocyclic analogue of
the deazahypoxanthine derivative 2 (Scheme 7).
An X-ray diffraction analysis of 32´HCl (Fig. 1) con®rmed
its structure providing proof that the product derived by the
addition of lithioacetonitrile to imine 5 [i.e. 6 (RˆCH2CN)]
possessed the required b-stereochemistry. The independent
molecules are bound into a three dimensional lattice by at
least six hydrogen bonds which involve N-1, O-5 as parent
donors to one Cl2, N-10 as a donor to another Cl2 and O-60,
N-30 and O-3 acting as acceptors. The ®ve-membered ring
(N-1,C-1±C-4) adopts an envelope conformation [f
66(1)8]36 with the `¯ap atom' C-2 0.67(1) A from the
Ê
plane of the other four. The fused ®ve- and six-membered
0
C-1 0.06(1) and 0.09(1) A, respectively, from the plane.
Ê
rings are coplanar (mean deviation 0.012 A) with O-6 and
Ê
There are no signi®cant deviations from the expected
bond lengths and angles.
0
J3,4ˆ4.6 Hz, H-4), 3.74 (1H, dd, J6,7ˆ3.9, J7,7 ˆ10.2 Hz,
0
0
H-7), 3.66 (1H, dd, J6,7 ˆ5.2 Hz, H-7 ), 3.40 (1H, m,
0
H-3), 3.30 (1H, m, H-6), 2.68, 2.58 (2H, 2 dd, J2,2 ˆ16.7,
Experimental
0
0
0
J2,3ˆ5.3, J2 ,3 ˆ6.9 Hz, H-2,2 ), 1.51, 1.32 (6H, 2s, CCH3),
0.91 [9H, s, C(CH3)3], 0.08 (6H, s, SiCH3). 13C NMR d
117.5 (C-1), 113.7 (C), 84.5 (C-4), 82.3 (C-5), 65.4 (C-6),
64.5 (C-7), 60.7 (C-3), 27.2, 25.0 [C(CH3)2], 25.8 [C(CH3)3],
22.4 (C-2), 18.2 [C(CH3)3], 25.5, 25.6 (SiCH3). HRMS
(MH1) calcd for C16H31N2O3Si: 327.2104; found: 327.2091.
General
NMR spectra were recorded on a Bruker AC-300 instrument
at 300 MHz (1H) or 75 MHz (13C). Normally, spectra were
measured in CDCl3 with Me4Si as internal reference; when

3058
G. B. Evans et al. / Tetrahedron 56 (2000) 3053±3062
N-tert-Butoxycarbonyl-7-O-tert-butyldimethylsilyl-2,3,6-
trideoxy-3,6-imino-4,5-O-isopropylidene-d-allo-heptono-
nitrile (7). A solution of 6 (RˆCH2CN) (0.80 g, 2.45 mmol)
in CH2Cl2 (20 mL) containing di-tert-butyl dicarbonate
(0.59 g, 2.7 mmol) was stirred at room temperature for
16 h. The solution was concentrated and the residue
chromatographed to afford the Boc derivative 7 (0.89 g,
SiCH3). 13C NMR d 161.9, 151.1, 147.3, 135.7 (C), 125.3
(C-50), 117.4, 111.9, 105.5 (C), 83.9, 82.7 (C-2,3), 80.5
[OC(CH3)3], 69.6, 67.1 (C-1,4), 69.1 (ArCH2), 63.4, 59.7
(C-5, CH2CH3), 28.3 [OC(CH3)3], 27.7, 25.6 [C(CH3)2],
26.1 [SiC(CH3)3],18.5 [SiC(CH3)], 14.5 (CH2CH3). HRMS
(M1) calcd for C34H51N3O9Si: 673.3395; found: 673.3432.
1
2.09 mmol, 85%) as a syrup. H NMR d 4.68±4.51 (2H,
(1S)-N-tert-Butoxycarbonyl-5-O-tert-butyldimethylsilyl-
1-(9-deazahypoxanthin-9-yl)-1,4-dideoxy-1,4-imino-2,3-
O-isopropylidene-d-ribitol (13). A solution of 11 (1.84 g,
2.73 mmol) in ethanol (30 mL) was stirred with 10% Pd/C
(0.1 g) in an atmosphere of hydrogen for 3 h. The solids and
solvent were removed and the residual 12 was dissolved in
ethanol (40 mL) containing formamidine acetate (1.40 g,
13.4 mmol) and the solution was heated under re¯ux for
16 h. The solvent was removed and chromatography of
the residue gave the deazahypoxanthine derivative 13
m, H-4,5), 4.16±3.71 (4H, m, H-3,6,7,70), 2.95±2.66 (2H,
m, H-2,20), 1.48 [9H, s, OC(CH3)3], 1.46, 1.34 [6H, 2s,
C(CH3)2], 0.91 [9H, s, SiC(CH3)3], 0.09, 0.08 (6H, 2s,
SiCH3). 13C NMR d 117.2 (C-1), 112.1 (C), 84.0 and
82.9, 81.8 and 81.1 (C-4,5),37 66.2 and 65.9, 61.7 and 61.4
(C-3,6), 63.2 and 62.9 (C-7), 28.2 [OC(CH3)3], 27.1, 25.1
[C(CH3)2], 25.9 [SiC(CH3)3], 21.3 and 20.5 (C-2), 18.3
[SiC(CH3)], 25.5 (SiCH3). HRMS (MH1) calcd for
C21H39N2O5Si: 427.2628; found: 427.2606.
1
(1.3 g, 2.5 mmol, 91%) as a syrup. H NMR d 8.22 (1H,
(1S)-1-(3-Amino-N-benzyloxycarbonyl-2-ethoxycarbonyl-
pyrrol-4-yl)-N-tert-butoxycarbonyl-5-O-tert-butyldimethyl-
silyl-1,4-dideoxy-1,4-imino-2,3-O-isopropylidene-d-ribitol
(11). tert-Butoxy-bis(N,N-dimethylamino)methane (1.5 mL,
7.28 mmol) was added to a solution of 7 (0.88 g, 2.07 mmol)
in DMF (5 mL) and the mixture was heated at 65±708C for
1 h. Toluene (20 mL) was added and the solution was
washed (£3) with water, dried and concentrated to dryness.
The residue of crude 8 was dissolved in THF/acetic acid/
water (1:1:1 v/v/v, 40 mL) at room temperature and after
1.5 h, chloroform (50 mL) was added and the mixture was
washed with water (£2), aqueous sodium bicarbonate, dried
and evaporated to dryness. Chromatography of the residue
gave the hept-1-enitol derivative 9 (0.68 g, 1.5 mmol, 72%)
as a syrup. 1H NMR d 7.13 (1H, d, Jˆ12.6 Hz, H-1), 4.92,
4.83 (2H, 2d, J4,5ˆ5.7 Hz, H-4,5), 4.77 (1H, s, H-3), 4.02
(1H, m, H-6), 3.73±3.51 (2H, m, H-7,70), 1.49 [9H, s,
OC(CH3)3], 1.46, 1.34 [6H, 2s, C(CH3)2], 0.91 [9H, s,
SiC(CH3)3], 0.10 (6H, s, SiCH3). 13C NMR d 162.7 (C-1),
118.8, 112.1, 90.2 and 83.2 (C), 82.7, 82.1 (C-4,5), 66.2
(C-6), 62.4 (C-7), 59.1 (C-3), 28.3 [OC(CH3)3], 27.1, 25.1
[C(CH3)2], 26.0 [SiC(CH3)3],18.4 [SiC(CH3)3], 25.3 (SiCH3).
bs, H-20), 7.33 (1H, bs, H-80), 5.35 (1H, bs, H-1), 5.20 (1H,
bs, H-2 or 3), 4.86 (1H, d, Jˆ5.6 Hz, H-2 or 3), 4.11 (1H, bs,
H-4), 3.72 (2H, bs, H-5a,5b), 1.55, 1.35 [6H, 2s, C(CH3)2],
1.46 [9H, bs, OC(CH3)3], 0.91[9H, s, SiC(CH3)3], 0.09 (6H,
s, CH3). 13C NMR d 155.5, 154.6 and 143.2 (C), 141.1 and
127.8 (CH), 118.2, 117.2 and 111.9 (C), 84.6 and 82.7
(C-2,3), 80.2 [OC(CH3)3], 66.5 (C-4), 62.8 (C-5), 61.5 (C-1),
28.5[OC(CH3)3], 27.5, 25.5 [C(CH3)2], 25.9 [SiC(CH3)3],18.3
[SiC(CH3)], 25.3 Si(CH3). HRMS (MH1) calcd for
C25H41N4O6Si: 521.2795; found: 521.2780.
(1S)-1-(9-Deazahypoxanthin-9-yl)-1,4-dideoxy-1,4-imino-
d-ribitol hydrochloride (2´HCl). Compound 13 (0.475 g,
0.91 mmol) in tri¯uoroacetic acid (20 mL) was allowed to
stand at room temperature overnight. The solution was
concentrated, and the residue, dissolved in water, was
washed with chloroform (£2) and the water was evaporated.
The residue was dissolved in aqueous methanol (1:1) and
treated with Amberlyst A21 base resin until the solution had
pH ,7. The solids and solvent were removed and the resi-
due was dissolved in water, treated with excess aqueous HCl
and then lyophilised. Trituration of the residue with ethanol
gave the salt 2´HCl as a white crystalline solid (0.225 g,
0.74 mmol, 81%). Recrystallised from 90% ethanol it had
mp .3008C (with darkening) [a]Dˆ20.50 (cˆ1.6, H2O).
IR (cm21) 3400±2750, 1708, 1632, 1560, 1478, 1190, 1022.
1H NMR (D2O with DCl) d 9.04 (1H, s, H-20), 8.00 (1H, s,
H-80), 5.00 (1H, d, J1,2ˆ9 Hz, H-1), 4.71 (1H, dd,
J2,3ˆ5.4 Hz, H-2), 4.44 (1H, dd, J3,4ˆ3.2 Hz, H-3), 3.96
(m, H-5a,5b), 3.90 (1H, m H-4). 13C NMR d 155.4 (C),
148.0 (C-80), 135.0 (C), 133.5 (C-20), 121.4 and 107.5
(C), 76.7 (C-2), 73.3 (C-3), 68.8 (C-4), 61.4 (C-5), 58.1
(C-1). HRMS (M1) calcd for C11H14N4O4: 266.1015;
found: 266.1004.
Ethyl glycinate hydrochloride (5.0 g, 35.8 mmol) and
sodium acetate (6.0 g, 73 mmol) were added to a stirred
solution of 9 (3.82 g, 8.4 mmol) in methanol (80 mL).
Stirring was continued at room temperature for 16 h and
the solvent was removed. Chromatography of the residue
gave N-tert-butoxycarbonyl-7-O-tert-butyldimethylsilyl-2-
cyano-1,2,3,6-tetradeoxy-1-N-(ethoxycarbonylmethylamino)-
3,6-imino-4,5-O-isopropylidene-d-allo-hept-1-enitol (10)
(3.46 g, 6.42 mmol) as a mixture of isomers. A solution of
this material (3.46 g, 6.42 mmol) in dry CH2Cl2 (80 mL)
containing 1,8-diazabicyclo[5.4.0]undec-7-ene (18 mL,
116 mmol) and benzyl chloroformate (8.8 mL, 43 mmol)
was heated under re¯ux for 4 h, cooled and washed with
dilute aqueous HCl, aqueous sodium bicarbonate, dried and
concentrated. Chromatography of the residue afforded
(1S)-1-(9-Deazaguanin-9-yl)-1,4-dideoxy-1,4-imino-d-
ribitol hydrochloride (3´HCl). A solution of 11 (0.158 g,
0.235 mmol) in ethanol (5 mL) was stirred with 10% Pd/C
(0.02 g) in an atmosphere of hydrogen for 3 h. The solids
and solvent were removed and to a solution of the residual
pyrrole derivative 12 (0.12 g) in CH2Cl2 (10 mL) at 08C was
added a solution (0.8 mL) of benzoyl isothiocyanate in
dichloromethane (0.38 mL in 10 mL). After 0.5 h, the
solution was warmed to room temperature and 1,8-diaza-
bicyclo[5.4.0]undec-7-ene (80 mL) and methyl iodide
1
pyrrole derivative 11 (3.68 g, 5.47 mmol, 65% from 9). H
NMR (d6-Benzene) d 7.23±7.00 (5H, m, Ar), 5.16 and 5.10
(1H, d, Jˆ12.2 Hz, ArCH2), 4.94 (1H, s, H-1), 4.65 and 4.53
(1H, d, J2,3ˆ5.3 Hz, H-2,3), 4.35 (1H, bs), 4.09 (2H, dd,
Jˆ7.1 Hz, CH2CH3), 3.59±3.41 (2H, m), 1.43, 1.17 [6H,
2s, C(CH3)2], 1.35 [9H, s, OC(CH3)3], 0.95 (3H, t,
CH2CH3), 0.87 [9H, s, SiC(CH3)3], 20.03, 20.05 (6H, 2s,

G. B. Evans et al. / Tetrahedron 56 (2000) 3053±3062
3059
(100 mL) were added. After another 0.5 h the reaction
solution was chromatographed directly on silica gel
affording (1S)-1-[3-(N-benzoyl-S-methylisothiocarbamoyl)-
imino-2-ethoxycarbonylpyrrol-4-yl]-N-tert-butoxycarbonyl-
5-O-tert-butyldimethylsilyl-1,4-dideoxy-1,4-imino-2,3-O-
isopropylidene-d-ribitol (14) (0.16 g, 0.223 mmol). A
solution of this material (0.20 g, 0.279 mmol) in methanol
saturated with ammonia (20 mL) was heated in a sealed tube
at 958C for 16 h. The solvent was removed and chroma-
tography of the residue afforded (1S)-1-(9-deazaguanin-9-
yl)-N-tert-butoxycarbonyl-1,4-dideoxy-1,4-imino-2,3-O-
isopropylidene-d-ribitol (15) (0.064 g, 0.12 mmol), which
was dissolved in tri¯uoroacetic acid (3 mL) and allowed
to stand at room temperature for 16 h. The solvent was
removed and a solution of the residue in aqueous methanol
(10 mL) (1:1 v/v) was treated with Amberlyst A21 base
resin until the solution was pH,7. The solids and solvent
were removed and a solution of the residue in water was
treated with excess HCl and then concentrated to dryness.
Trituration with ethanol gave 3´HCl (0.024 g, 0.075 mmol,
32% from 11) as a white solid, which darkened at ca. 2608C
but did not melt below 3008C [a]Dˆ20.62 (cˆ1.0, H2O).
(1S)-1-(9-Deazahypoxanthin-9-yl)-1,4,5-trideoxy-1,4-
imino-d-ribitol hydrochloride (21´HCl). A solution of 19
(0.27 g, 0.43 mmol) in ethanol (10 mL) containing triethyl-
amine (0.186 mL, 1.37 mmol) was stirred under hydrogen
with 20% Pd(OH)2/C (0.10 g) for 16 h. The solids and
solvent were removed and chromatography of the residue
afforded 20 (0.153 g, 0.37 mmol, 86%) as a syrup. 1H NMR
d 6.47 (1H, bs, H-50), 5.03 (1H, s), 4.98 (2H, bs, NH2), 4.84,
4.49 (2H, 2d, Jˆ5.5 Hz), 4.30 (2H, q, Jˆ7.1 Hz, CH2CH3),
4.14 (1H, m), 1.49, 1.34 (3H each, 2s, CCH3), 1.45 [9H, s,
OC(CH3)3], 1.34 (3H, t, CH2CH3), 1.15 (3H, d, Jˆ7.1 Hz,
H-5). 13C NMR d 154.9 (C), 119.6 (CH), 113.0, 111.9 and
106.5 (C), 86.2 and 84.3 (CH), 80.1 (C), 60.8 (CH), 59.5
(CH2), 59.1 (CH), 28.4 [C(CH3)3], 27.4, 25.6, 19.9 and 14.7
(CH3). Treatment of 20 (0.075 g, 0.18 mmol) with forma-
midine acetate, tri¯uoroacetic acid and then hydrochloric
acid as described above in the preparation of 2´HCl led to
1
21´HCl (0.033 g, 0.11 mmol, 61%) as a solid. H NMR
500 MHz, D2O, d 8.82 (1H, s, H-20), 7.93 (1H, s, H-80),
4.96 (1H, d, J1,2ˆ8.5 Hz, H-1), 4.82 (1H, dd, J2,3ˆ5.1 Hz,
H-2), 4.30 (1H, t, H-3), 3.87 (1H, dq, J3,4ˆ4.1, J4,5ˆ7.3 Hz,
H-4), 1.53 (3H, d, H-5abc). 13C NMR d 155.6 (C), 147.1
(C-20), 137.4 (C), 132.6 (C-80), 121.0 and 108.2 (C), 76.5
(C-3), 75.6 (C-2), 63.1 (C-4), 58.2 (C-1), 18.1 (C-5). HRMS
(M1) calcd for C11H15N4O3: 251.1144; found: 251.1131.
1
IR (cm21) 3400±2750, 1709, 1570, 1400, 1125, 1080. H
NMR (D2O with DCl) d 7.71 (1H, s, H-80), 4.86 (1H, d,
J1,2ˆ9.1 Hz, H-1), 4.65 (1H, dd, J2,3ˆ5.0 Hz, H-2), 4.40
(1H, dd, J3,4ˆ3.2 Hz, H-3), 3.94 (2H, m, H-5a,5b), 3.87
(1H, m, H-4). 13C NMR d 156.6, 153.6 and 136.0 (C),
132.1 (C-80), 115.0 and 105.4 (C), 76.4 (C-2), 73.4 (C-3),
68.6 (C-4), 61.5 (C-5), 58.2 (C-1). HRMS (M1) calcd for
C11H16N5O4: 282.1202; found: 282.1204.
(1S)-1-(9-Deazaguanin-9-yl)-1,4,5-trideoxy-1,4-imino-d-
ribitol hydrochloride (22´HCl). Treatment of 20 (0.075 g,
0.18 mmol) sequentially with benzoyl isothiocyanate,
methyl iodide and DBU, ammonia in methanol, tri¯uoro-
acetic acid and then hydrochloric acid as described above in
the preparation of 3´HCl afforded 22´HCl (0.016 g,
(1S)-1-[3-Amino-N-benzyloxycarbonyl-2-ethoxycarbonyl-
pyrrol-4-yl]-5-bromo-N-tert-butoxycarbony1-1,4,5-tri-
deoxy-1,4-imino-2,3-O-isopropylidene-d-ribitol (19). Tetra-
butylammonium ¯uoride (2.0 mL, 1 M in THF) was added
to a solution of 11 (1.06 g, 1.58 mmol) in THF (10 mL).
After 1 h toluene (30 mL) was added and the solution was
washed with water (£2) and processed normally. Chroma-
tography of the crude product afforded (1S)-1-[3-amino-N-
benzyloxycarbonyl-2-ethoxycarbonylpyrrol-4-yl]-N-tert-
butoxycarbony1-1,4-dideoxy-1,4-imino-2,3-O-isopropyl-
idene-d-ribitol (18) (0.734 g, 1.31 mmol). 4-N,N-Dimethyl-
1
0.053 mmol, 29%) as a solid. H NMR (D2O) d 7.69 (1H,
s, H-80), 4.82 (1H, d, J1,2ˆ8.8 Hz, H-1), 4.24 (1H, t,
Jˆ4.3 Hz, H-3), 3.82 (1H, m, H-4), 1.50 (3H, d, J4,5ˆ
7.1 Hz, H-5). The resonance for H-2 was beneath the
HOD peak at d 4.6. 13C NMR d 156.5, 153.5 and 135.8
(C), 131.7 (C-8), 114.9 and 105.6 (C), 76.7 and 75.7
(C-2,3), 63.4 and 58.1 (C-1,4), 18.4 (C-5). HRMS (M1)
calcd for C11H16N5O3: 266.1253; found: 266.1249.
N-tert-Butoxycarbonyl-2,3,6,7-tetradeoxy-7-¯uoro-3,6-
imino-4,5-O-isopropylidene-d-allo-heptononitrile (24). A
solution of the silylated nitrile 7 (1.7 g, 4.0 mmol) in THF
(10 mL) was treated with tetrabutylammonium ¯uoride
(6 mL, 1 M in THF) for 1 h. The solution was concentrated
to dryness and chromatography of the residue afforded
alcohol 23 (1.15 g, 3.68 mmol). Diethylaminosulfur tri-
¯uoride (0.46 mL, 3.5 mmol) was added to this material
(0.84 g, 2.69 mmol) in CH2Cl2 (20 mL). After 6 h, methanol
(1 mL) was added and the solution was concentrated to
dryness. Chromatography of the residue gave ¯uoro-
aminopyridine
(0.02 g,
0.16 mmol),
triethylamine
(0.45 mL, 6.0 mmol) and then methanesulfonyl chloride
(0.10 mL, 1.29 mmol) were added to 18 (0.45 g, 0.80
mmol) in CH2Cl2 (10 mL). After 1 h, the solution was
processed and the crude product in toluene (10 mL) con-
taining tetrabutylammonium bromide (1.55 g, 4.8 mmol)
was heated at 1008C for 2 h. The cooled solution was
washed with water, dried and concentrated to dryness.
Chromatography of the residue afforded the bromide 19
1
(0.277 g, 0.44 mmol, 28% from 11) as a syrup. H NMR
1
d 7.36 (5H, m, Ar), 7.00 (1H, d, Jˆ0.8 Hz, H-50), 5.54 (2H,
bs, NH2), 5.34, 5.30 (2H, 2d, Jˆ12.3 Hz, ArCH2), 5.00 (1H,
bs), 4.85±4.78 (2H, m), 4.26 (1H, m), 4.19 (2H, q,
Jˆ7.1 Hz, CH2CH3), 3.40 (1H, m), 3.04 (1H, m), 1.50,
1.36 (6H, 2s, CCH3), 1.45 [9H, s, C(CH3)3], 1.22 (3H, t,
Jˆ7.1 Hz, CH2CH3). 13C NMR d 161.6, 154.9, 150.5,
146.2 and 134.9 (C), 128.7, 128.4 and 124.6 (CH), 116.6,
112.5 and 105.1 (C), 83.7 and 83.1 (CH), 81.7 (C), 69.3
(CH2), 66.3 (CH), 60.0 (CH2), 58.8 (CH), 32.0 (CH2), 28.3
[C(CH3)3], 27.3 and 25.4 [C(CH3)2], 14.4 (CH2CH3). HRMS
(MH1) calcd for C28H37BrN3O8: 622.1764; found: 622.1752.
compound 24 (0.36 g, 1.15 mmol, 42%) as a syrup. H
NMR d 4.77 (1H, d, Jˆ5.8 Hz), 4.65±4.06 (5H, m),
2.86±2.60 (2H, m), 1.49 [12H, s, C(CH3)3), CH3], 1.34
(3H, s, CH3). 13C NMR d 153.4, 116.9 and 112.6 (C),
83.1(d, JC,Fˆ170 Hz, C-7), 83.9, 82.8 and 81.2, 80.5
(C-4,5), 64.4, 61.4(C-3,6), 28.2 [C(CH3)3], 27.0 and 24.5
(CH3), 21.2 and 20.5 (C-2).37 HRMS (MH1) calcd for
C15H24FN2O4: 315.1720; found: 315.1695.
(1S)-1-(9-Deazahypoxanthin-9-yl)-1,4,5-trideoxy-5-¯uoro-
1,4-imino-d-ribitol hydrochloride (25´HCl). Treatment of

3060
G. B. Evans et al. / Tetrahedron 56 (2000) 3053±3062
24 (0.36 g, 1.15 mmol) sequentially with tert-butoxybis-
(dimethylamino)methane, aq. acetic acid, ethyl glycinate,
DBU and benzyl chloroformate, hydrogen and Pd/C, for-
mamidine acetate, tri¯uoroacetic acid and then hydrochloric
acid as described above in the preparation of 2´HCl from 7
afforded the ¯uorinated deazahypoxanthine compound
17.2, 17.1, 17.0 and 16.9 [CH(CH3)2], 13.2, 13.1, 12.7 and
12.6 [CH(CH3)2]. HRMS (MH1) calcd for C24H47N2O6Si2:
515.2973; found: 515.2999.
N-tert-Butoxycarbonyl-2,3,6-trideoxy-4-O-[imidazole-
(thiocarbonyl)]-3,6-imino-5,7-O-(1,1,3,3-tetraisopropyl-
disiloxa-1,3-diyl)-d-allo-heptononitrile (29). A solution of
28 (1.5 g, 2.9 mmol) in toluene (20 mL) containing thiocar-
bonyldiimidazole (90%, 0.9 g, 4.5 mmol) was stirred at
908C for 2 h. The solution was concentrated and chromato-
1
25´HCl (0.027 g, 0.089 mmol, 8%) as a solid. H NMR
(D2O) d 8.57 (1H, s, H-20), 7.86 (1H, s, H-80), 5.04 (1H,
d, J1,2ˆ8.3 Hz, H-1), 4.90 (2H, d, JH,Fˆ45.1 Hz, H-5a,5b),
4.60 (1H, t, Jˆ4.5 Hz, H-3), 4.10 (1H, dd, J3,4ˆ3.2 Hz,
13
1
J4,Fˆ28.8 Hz, H-4). C NMR d 156.2 (C), 146.8 (C-20),
graphed to afford ester 29 (1.8 g, 99%) as an oil. H NMR
140.4 (C), 132.6 (C-80), 121.2 and 108.4 (C), 83.0
(CDCl3) 8.33, 7.62, 7.06 (3H, 3s, Im), 5.90 (1H, d,
Jˆ4.6 Hz, H-4), 4.91 (1H, dd, Jˆ7.9, 4.6 Hz, H-5), 4.30±
4.22 (3H, m, H-3,7,70), 3.75 (1H, brs, H-6), 2.82 (2H, m,
H-2,20), 1.49 [9H, s, C(CH3)3], 1.09±0.94 [28H, m,
CH(CH3)2]. 13C NMR d 183.2 (CyS), 154.9 (CyO),
136.8, 131.1 and 118.0 (Im), 117.1 (C-1), 83.3 (C-4), 82.1
[C(CH3)3], 76.0 (C-5), 63.8 (C-6), 59.2 (C-3), 28.3 [C(CH3)3],
21.7 (C-2), 17.4, 17.2, 17.1 and 16.8 [CH(CH3)2], 13.2,
13.1, 12.7, 12.6 [CH(CH3)2]. HRMS (MH1) calcd for
C28H49N4O6SSi2: 625.2911; found: 625.2850.
(JC,Fˆ169 Hz, C-5), 76.1 (C-2), 72.7 (C-3), 66.4 (JC,F
ˆ
17.9 Hz, C-4), 59.0 (C-1). HRMS (M1) calcd for
C11H14FN4O3: 269.1050; found: 269.1051.
2,3,6-Trideoxy-3,6-imino-d-allo-heptononitrile (26). A
solution of 6 (RˆCH2CN) (1.93 g, 5.9 mmol) in tri¯uoro-
acetic acid (20 mL) was allowed to stand at room tempera-
ture overnight. The reaction mixture was concentrated in
vacuo and a solution of the residue in water (50 mL) was
washed with chloroform (2£50 mL) and the aqueous layer
concentrated to afford the unprotected 26 as the tri¯uoro-
N-tert-Butoxycarbonyl-2,3,4,6-tetradeoxy-3,6-imino-5,7-
O-(1,1,3,3-tetraisopropyldisiloxa-1,3-diyl)-d-ribo-hepto-
nonitrile (30). To a solution of 29 (1.8 g, 2.9 mmol) in
toluene (50 mL), tri-n-butyltin hydride (1.0 mL) was
added and the mixture was heated at 808C for 3 h, cooled,
concentrated and the residue was chromatographed to afford
the deoxy compound 30 (0.74 g, 1.48 mmol, 51%) as an oil.
1H NMR (CDCl3) 4.72 (1H, dd, Jˆ12.0, 7.1 Hz, H-5), 4.20
(2H, 2 dd, Jˆ11.1, 4.0 Hz, H-7,70), 3.80 (1H, brs, H-3), 3.66
(1H, m, H-6), 2.63±2.59 (2H, m, H-2,20), 2.20±2.17 (2H, m,
H-4,40), 1.47 [9H, s, (C(CH3)3], 1.08±1.00 [28H, m,
CH(CH3)2]. 13C NMR d 154.9 (CO), 117.6 (C-1), 81.0
[C(CH3)3], 73.1 (C-5), 67.5 (C-6), 64.5 (C-7), 59.2 (C-3),
28.3 [C(CH3)3], 21.7 (C-2), 17.4, 17.2, 17.1, 16.8
[CH(CH3)2], 13.2, 13.1, 12.7, 12.6 [(CH(CH3)2]. HRMS
(MH1) calcd for C24H47N2O5Si2: 499.3024; found:
499.3024.
1
acetic acid salt (1.0 g, 3.5 mmol, 59%). H NMR (D2O) d
3.89 (1H, t, Jˆ5.3 Hz, H-5), 3.78 (1H, t, J3,4ˆ6.3 Hz, H-4),
3.56 (1H, dd, Jˆ11.8, 5.6 Hz, H-7a), 3.54 (1H, dd, Jˆ11.8,
5.6 Hz, H-7b), 3.34 (1H, q, Jˆ7.0 Hz, H-3), 3.18 (1H, q,
0
Jˆ5.1 Hz, H-6), 2.72 (2H, dd, J2,2 ˆ17.3 Hz, J2,3ˆ7.1 Hz,
J2 ,3ˆ5.3 Hz, H-2,20). 13C NMR d 121.4 (CN), 77.1 (C-4),
0
74.3 (C-5), 67.2 (C-6), 64.2 (C-7), 60.4 (C-3), 23.1 (C-2).
HRMS (M1) calcd for C7H12N2O3: 172.0848; found:
172.0839.
N-tert-Butoxycarbonyl-2,3,6-trideoxy-3,6-imino-d-allo-
heptononitrile (27). A solution of crude 26 (1.0 g,
3.5 mmol) in methanol (20 mL) containing di-tert-butyl
dicarbonate (2.09 g, 9.6 mmol) was adjusted to neutral pH
by the addition of triethylamine, stirred at room temperature
for 16 h and concentrated in vacuo. Chromatography of the
residue afforded carbamate 27 (0.80 g, 2.9 mmol, 83%) as
1
an oil. H NMR (CDCl3) 4.18±4.11 (2H, m, H-4,5), 3.80±
(1R)-1-[3-Amino-1-N-benzyloxycarbonyl-2-ethoxycarbonyl-
pyrrol-4-yl]-N-tert-butoxycarbonyl-1,2,4-trideoxy-1,4-
imino-3,5-O-(1,1,3,3-tetraisopropyldisiloxa-1,3-diyl)-d-
erythro-pentitol (31). To a solution of 30 (0.74 g, 1.5 mmol)
in DMF (10 mL), tert-butoxy-bis(dimethylamino)methane
(1.5 mL, excess) was added and the solution heated at
65±708C for 1 h. Toluene (50 mL) was then added and the
solution was washed with water (3£20 mL), dried and
concentrated to dryness. The residue was dissolved in
THF/acetic acid/water (1:1:1 v/v/v, 40 mL) at room
temperature. After 1.5 h, chloroform (50 mL) was added
and the mixture was washed with water (2£20 mL), aqueous
sodium bicarbonate, and then dried and evaporated to
dryness. Chromatography of the residue afforded the
analogue of enol 9 (0.68 g, 94%) as an oil. To this material
in methanol (10 mL) were added ethyl glycinate hydro-
chloride (0.90 g, 6.5 mmol) and sodium acetate (1.0 g,
12.2 mmol). The mixture was stirred at room temperature
for 16 h and concentrated to dryness. Chromatography of
the residue gave the analogue of enamine 10 (0.80 g, 100%)
as a diastereomeric mixture. A solution of this material in
dry CH2Cl2 (20 mL) containing 1,8-diazabicyclo[5.4.0]-
undec-7-ene (3.6 mL, 24 mmol) and benzyl chloroformate
3.45 (4H, m, H-3,6,7,70), 2.80±2.46 (2H, m, H-2,20), 1.47
[9H, s, C(CH3)3]. 13C NMR d 74.0 (C-4), 71.5 (C-5), 66.1
(C-6), 62.7 (C-7), 58.9 and 58.3 (C-3), 28.2 [C(CH3)3], 21.1
(C-2).37 HRMS (MH1) calcd for C12H20N2O5: 272.1372;
found: 272.1379.
N-tert-Butoxycarbonyl-2,3,6-trideoxy-3,6-imino-5,7-O-
(1,1,3,3-tetraisopropyldisiloxa-1,3-diyl)-d-allo heptono-
nitrile (28). 1,3-Dichloro-1,1,3,3-tetraisopropyldisiloxane
(0.9 mL, 2.8 mmol) was added dropwise to a solution of
27 (0.8 g, 2.9 mmol) and imidazole (0.70 g, 10.3 mmol) in
DMF (10 mL) at 08C. The resulting solution was allowed to
warm to room temperature, diluted with toluene (150 mL),
washed with water (3£25 mL), dried and concentrated.
Chromatography of the resulting residue afforded the
1
disilyloxy derivative 28 (1.4 g, 2.7 mmol, 96%) an oil. H
NMR d 4.62 (1H, dd, Jˆ6.5, 4.8 Hz, H-5), 4.23 (1H, dd,
Jˆ11.4, 3.8 Hz, H-4), 4.00 (3H, m, H-3,7,70), 3.65 (1H, m,
H-6), 2.99, 2.66 (2H, 2brs,H-2,20), 1.46 (9H, s, [C(CH3)3],
1.07±1.01 [28H, m, CH(CH3)2]. 13C NMR d 154.9 (CO),
117.3 (C-1), 81.2 [C(CH3)3], 73.8 (C-4), 73.8 (C-5), 63.5
(C-6), 63.5 (C-7), 60.8 (C-3), 28.2 [C(CH3)3], 21.4 (C-2),

G. B. Evans et al. / Tetrahedron 56 (2000) 3053±3062
3061
(1.7 mL, 11.9 mmol) was heated under re¯ux overnight,
cooled and washed with dilute aqueous HCl, aqueous
sodium bicarbonate, dried and concentrated. Chroma-
tography of the residue afforded pyrrole derivative 31
(0.70 g, 94 mmol, 62% from 30) as an oil. 1H NMR
(CDCl3) 7.40±7.35 (5H, m, Ar), 7.04 (1H, s, H-50), 5.82
(2H, brs, NH2), 5.29 (2H, d, Jˆ1.4 Hz, CH2Ar), 4.97 (1H,
brd, Jˆ8.3 Hz, H-3), 4.82 (1H, m, H-4), 4.22 (2H, q,
Jˆ7.1 Hz, CH2CH3), 4.01 (1H, dd, Jˆ11.1, 4.4 Hz, H-5a),
3.70 (1H, td, Jˆ9.3, 4.4 Hz, H-5b), 3.49 (1H, m, H-1),
2.47±2.19 (2H, m, H-2), 1.46 [9H, s,C(CH3)3], 1.04±0.98
[28H, m, CH(CH3)2]. 13C NMR d 161.6, 154.9, 150.3, 147.2
and 134.9 (C), 128.5, 128.3 and 125.4 (CH), 118.7, 104.6
(C), 81.0 [C(CH3)3], 74.8 (C-3), 69.0 (CH2Ar), 66.3 (C-4),
65.3 (C-5), 59.7 (CH2CH3), 50.8 (C-1), 38.4 (C-2), 28.3
[C(CH3)3], 17.5, 17.4, 17.2, 17.0 [CH(CH3)2], 13.4, 13.2,
13.0, 12.5 [CH(CH3)2]. HRMS (M1) calcd for
C37H59N3O9Si2: 745.3790; found: 745.3748.
15 (0.30 g, 56%) as an oil. A solution of this material in
tri¯uoroacetic acid (5 mL) was allowed to stand at room
temperature for 16 h. The solvent was removed and the
residue was dissolved in THF, treated with tetrabutylammo-
nium ¯uoride trihydrate (200 mg) and stirred for 1 h. The
solvent was removed and the residue was dissolved in
methanol (5.0 mL) and acetyl chloride (0.75 mL) was
added dropwise and the mixture allowed to stand at room
temperature for 16 h when ether (25 mL) was added and the
resulting crystals were removed to afford the deoxynucleo-
side analogue 33 as the solid hydrochloride salt (89 mg,
0.30 mmol, 30% from 31), which did not melt below
1
3008C. H NMR (D2O) d 7.63 (s, H-80). 5.14 (1H, dd,
Jˆ12.2, 6.3 Hz, H-1), 4.55 (1H, brt, Jˆ2.9 Hz, H-3), 3.88
(m, 3H, H-4,5a,5b), 2.63 (1H ddd, Jˆ14.1, 12.3, 5.7 Hz,
H-2a),), 2.69 (1H dd, Jˆ14.3, 6.3 Hz, H-2b). 13C NMR d
153.9, 150.9 and 132.4 (C), 129.8 (C-80), 112.3 and 104.4
(C), 71.4 (C-3), 69.0 (C-4), 59.3 (C-5), 53.2 (C-1), 38.6
(C-2). HRMS (M1) calcd for C11H16N5O3: 266.1253;
found: 266.1262.
(1R)-1-(9-Deazahypoxanthin-9-yl)-1,2,4-trideoxy-1,4-
imino-d-erythro-pentitol hydrochloride (32´HCl).
A
solution of 31 (0.28 g, 0.38 mmol) in ethanol (10 mL) was
stirred with formamidine acetate (0.50 g, 4.8 mmol) under
re¯ux for 8 h. The solvent was removed and chroma-
tography of the residue gave (1R)-N-tert-butoxycarbonyl-
1,2,4-trideoxy-1-(9-deazahypoxanthin-9-yl)-1,4-imino-
3,5-O-(1,1,3,3-tetraisopropyldisiloxa-1,3-diyl)-d-erythro-
pentitol (120 mg, 53%). A solution of this material in
tri¯uoroacetic acid (2 mL) was allowed to stand at room
temperature overnight then concentrated and a solution of
the residue in water was washed (£2) with chloroform and
then evaporated. The residue was dissolved in THF and
treated with tetrabutylammonium ¯uoride trihydrate
(200 mg) and stirred for 1 h. The solvent was evaporated
and chromatography gave a residue which was redissolved
in methanolic HCl, the resulting precipitate was ®ltered to
afford the salt 32´HCl as a white solid (37 mg, 0.15 mmol,
34% from 31) which darkened but did not melt below
(1S)-1-(9-Deazaadenin-9-yl)-1,4-dideoxy-1,4-imino-d-
ribitol hydrochloride (35´HCl). Enol 9 (0.20 g, 0.44
mmol) was treated as described above in the conversion
of 9 into 2 via 11 and 13, except that aminoacetonitrile
hydrochloride was used in place of ethyl glycinate, to
give, by way of 34, the hydrochloride 35 (0.039 g,
1
0.13 mmol, 29%) as a solid. H NMR (D2O) d 8.45 (1H,
s, H-20), 8.06 (1H, s, H-80), 5.02 (1H, d, J1,2ˆ8.8 Hz, H-1),
4.80 (1H, dd, J2,3ˆ4.9 Hz, H-2), 4.47 (1H, dd, Jˆ3.5,
4.8 Hz, H-3), 3.98 (2H, m, H-5a,5b), 3.93 (1H, m, H-4).
13C NMR d 152.1 (C), 146.2 (C-20), 140.7 (C), 135.3
(C-80), 115.4 and 107.7 (C), 76.0 (C-2), 73.1 (C-3), 68.4
(C-4), 61.3 (C-5), 58.3 (C-1). HRMS (M1) calcd for
C11H16N5O3: 266.1253; found: 266.1264.
(1S)-1-(3-Amino-2-carboxamidopyrrol-4-yl)-1,4-dideoxy-
1,4-imino-d-ribitol (36). Hydrogen peroxide (0.5 mL) was
added dropwise to a solution of 34 (90 mg, 0.14 mmol) and
potassium carbonate (50 mg) in DMSO (1.0 mL) and stirred
for 10 min. The mixture was diluted with water (50 mL),
extracted with ethyl acetate (3£20 mL), and the combined
organic layers were dried, concentrated and chromato-
graphed to give a product (20 mg) which was dissolved in
tri¯uoroacetic acid (1 mL) and the solution was allowed to
stand at room temperature for 16 h. The solvent was
removed and the residue in water (20 mL) was washed
with CH2Cl2 (2£5 mL). The aqueous layer was evaporated
and chromatography afforded the pyrrole C-nucleoside 36
(10 mg, 0.04 mmol, 28%) as an oil. 1H NMR (D2O) d 6.98
(1H, s, H-50), 4.26±4.12 (3H, m, H-1,2,3), 3.78 (2H, d,
Jˆ5.1 Hz, H-5a,5b), 3.39 (1H, d, J1,2ˆ4.8 Hz, H-4). 13C
NMR D2O d 168.7, 141.0 and 126.2 (C), 124.1 (C-50),
113.2 (C), 77.6 (C-2), 74.4 (C-3), 67.7 and 59.3 (C-1,4),
64.0 (C-5). HRMS (MH1) calcd for C10H17N4O4:
257.1250; found: 257.1253.
1
3008C. H NMR (D2O) d 8.65 (1H, s, H-20), 7.80, (1H, s,
H-80), 5.26 (1H, dd, Jˆ12.1, 6.4 Hz, H-1), 4.57 (1H, m
H-3), 3.87 (3H, m, H-4, H-5a,5b), 2.60 (1H, ddd, Jˆ14.3,
12.2, 5.7 Hz, H-2a), 2.69 (1H, dd, Jˆ14.3, 6.4 Hz, H-2b).
13C NMR d 153.7 (C), 144.6 (C-20), 135.9 (C), 130.4 (C-80),
118.6 and 107.6 (C), 71.5 (C-3), 69.1 (C-4), 59.3 (C-5), 53.4
(C-1), 38.8 (C-2). HRMS (M1) calcd for C11H15N4O3:
251.1144; found: 251.1143.
(1R)-1-(9-Deazaguanin-9-yl)-1,2,4-trideoxy-1,4-imino-d-
erythro-pentitol hydrochloride (33´HCl). A solution of 31
(0.78 g, 1 mmol) in ethanol (10 mL) was stirred with 10%
Pd/C (100 mg) in an atmosphere of hydrogen for 1.5 h. The
solids and solvent were removed to afford a residue (0.62 g)
which was dissolved in dichloromethane (10 mL) at 08C and
a solution (4.8 mL) of benzoyl isothiocyanate in dichloro-
methane (0.30 mL in 10 mL) was added. After 0.5 h, the
solution was warmed to room temperature and 1,8-diaza-
bicyclo[5.4.0]undec-7-ene (320 mL) and methyl iodide
(700 mL) were added. After another 0.5 h the reaction
solution was chromatographed directly affording the
analogue of 14 (0.67 g, 91%). A solution of this material
in methanol saturated with ammonia (20 mL) was heated in
a sealed tube at 1058C for 16 h. The solvent was removed
and chromatography of the residue afforded the analogue of
X-Ray single crystal analysis data
Compound 32´HCl, C11H14N4O3´HCl, had monoclinic space
group P21 (4),38 aˆ6.3458(14), bˆ6.3655(14), cˆ
Ê
Ê 3
15.129(3) A; bˆ96.11(3)8; Vˆ607.6(2) A ; Zˆ2; Dcˆ
1.562 g cm23
;
Tˆ158(2) K;
l
(MoKa)ˆ0.71073 A;
Ê

3062
G. B. Evans et al. / Tetrahedron 56 (2000) 3053±3062
mˆ0.326 mm21. Data were collected on a Siemens P4
diffractometer with SMART CCD detector on a crystal of
poor quality (fractured) 0.80£0.29£0.04 mm; 34068 re¯ec-
tions were collected in a triclinic cell and converted on
solution to a ®nal monoclinic cell [4293 re¯ections merged
to 1609 unique re¯ections (6.46,2u,52.78) of which 1578
had I.2s(I)]. The absorption (SADABS) ratio of mini-
mum:maximum transmission was 1.0:0.280. The structure
was solved by direct methods39 and re®ned on F2 using all
data40 to give R1, wR2ˆ0.092, 0.246. The absolute con®g-
uration was not determined. All hydrogens atoms were
included but not re®ned in calculated positions (0.84±
Â
14. Parkin, D. W.; Horenstein, B. A.; Abdulah, D. R.; Estupinan,
B.; Schramm, V. L. J. Biol. Chem. 1991, 266, 20658±20665.
Â
15. Estupinan, B.; Schramm, V. L. J. Biol. Chem. 1994, 269,
23068±23073.
16. Parkin, D. W. J. Biol. Chem. 1996, 271, 21713±21719.
17. Kline, P. C.; Schramm, V. L. Biochemistry 1993, 32, 13212±
13219.
18. Horenstein, B. A.; Schramm, V. L. Biochemistry 1993, 32,
7089±7097.
19. Furneaux, R. H.; Limberg, G.; Tyler, P. C.; Schramm, V. L.
Tetrahedron 1997, 53, 2915±2930.
20. Furneaux, R. H.; Tyler, P. C.; Schramm, V. L. Bioorg. Med.
Chem. 1999, 7, 2599±2606.
40
Ê
1.0 A as de®ned ) with constrained thermal isotropic para-
meters (1.2 times parent C, O or N equivalent values).
Protonation at N-1 was established by the stereochemistry
and distances of hydrogen bond contacts. Possible rotational
disorder of the hydrogen atom on O-3 could not be
modelled. The ®nal maximum shift/error was 0.00,
21. Miles, R. W.; Tyler, P. C.; Furneaux, R. H.; Bagdassarian,
C. K.; Schramm, V. L. Biochemistry 1998, 37, 8615±8621.
22. Miles, R. W.; Tyler, P. C.; Evans, G. B.; Furneaux, R. H.;
Parkin, D. W.; Schramm, V. L. Biochemistry 1999, 38, 13147±
13154.
and the ®nal difference map excursions were around
Ê 23
23. Li, C. M.; Tyler, P. C.; Furneaux, R. H.; Kicska, G.; Xu, Y.;
Grubmeyer, C.; Girven, M. E.; Schramm, V. L. Nature Struct. Biol.
1999, 6, 582±587.
11.88 (near O-3) and 20.52 e A
.
24. Shi, W.; Li, C. M.; Tyler, P. C.; Furneaux, R. H.; Grubmeyer,
C.; Schramm, V. L.; Almo, S. C. Nature Struct. Biol. 1999, 6, 588±
593.
Acknowledgements
The authors thank 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.
25. Shi, W.; Li, C. M.; Tyler, P. C.; Furneaux, R. H.; Cahill, S. M.;
Girvin, M. E.; Grubmeyer, C.; Schramm, V. L.; Almo, S. C.
Biochemistry 1999, 38, 9872±9880.
26. Horenstein, B. A.; Zabinski, R. F.; Schramm, V. L. Tetrahedron
Lett. 1993, 34, 7213±7216.
27. Yokoyama, M.; Akiba, T.; Ochiai, Y.; Momotake, A.; Togo,
H. J. Org. Chem. 1996, 61, 6079±6082.
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