Synthesis of 4-N-alkyl and ribose-modified AICAR analogues on solid support

Article abstract of DOI:10.1016/j.tet.2008.04.071

Herein, we report the solid-phase synthesis of several 5-aminoimidazole-4-(N-alkyl)carboxamide-1-ribosides (4-N-alkyl AICARs) and the corresponding 2′,3′-secoriboside derivatives. The method uses the N-1-dinitrophenyl-inosine 5′-bonded to a solid support.

Full text of DOI:10.1016/j.tet.2008.04.071

Tetrahedron 64 (2008) 6475–6481
Contents lists available at ScienceDirect
Tetrahedron
journal homepage: www.elsevier.com/locate/tet
Synthesis of 4-N-alkyl and ribose-modified AICAR analogues on solid support
,
c
Giorgia Oliviero a, Jussara Amato a, Nicola Borbone b, Stefano D’Errico a, Gennaro Piccialli a , Enrico Bucci ,
*
Vincenzo Piccialli d, Luciano Mayol b
a
`
`
Facolta di Scienze Biotecnologiche, Dipartimento di Chimica delle Sostanze Naturali, Universita di Napoli Federico II, via D. Montesano 49, 80131 Napoli, Italy
b
`
`
Facolta di Farmacia, Dipartimento di Chimica delle Sostanze Naturali, Universita di Napoli Federico II, via D. Montesano 49, 80131 Napoli, Italy
c Bioindustry Park del Canavese SpA, via Ribes 5, 10010 Colleretto Giacosa, Torino, Italy
d
`
`
Facolta di Scienze MM.FF.NN., Dipartimento di Chimica Organica e Biochimica, Universita di Napoli Federico II, via Cynthia 4, 80126 Napoli, Italy
a r t i c l e i n f o
a b s t r a c t
Article history:
Herein, we report the solid-phase synthesis of several 5-aminoimidazole-4-(N-alkyl)carboxamide-1-
ribosides (4-N-alkyl AICARs) and the corresponding 20,30-secoriboside derivatives. The method uses the
N-1-dinitrophenyl-inosine 50-bonded to a solid support. This inosine derivative has the C-2 of the purine
base strongly activated towards the attack of N-nucleophiles thus allowing the preparation of several N-1
alkylated inosine supports from which a small library of 4-N-alkyl AICAR derivatives has been synthe-
sized. A set of new 4-N-alkyl AICA-20,30-secoriboside derivatives have also been obtained in high yields
by solid-phase cleavage of the 20,30-ribose bond.
Received 15 November 2007
Received in revised form 2 April 2008
Accepted 17 April 2008
Available online 24 April 2008
Keywords:
AICAR
Nucleoside analogues
Solid-phase synthesis
Combinatorial chemistry
Ó 2008 Elsevier Ltd. All rights reserved.
1. Introduction
correlated with the pathogenesis of diabetic retinopathy.10 Fur-
thermore, the extracellular role of adenosine and other nucleosides
Nucleosides and their phosphorylated counterparts constitute
an important class of biomolecules possessing a pivotal role in
cellular metabolism and signal transmission. For example, they are
involved in nucleic acid replication and in a very wide number of
interactions with enzymes, structural proteins, and other biological
targets of therapeutic importance. Many nucleoside analogues are
currently used in therapy as antivirals1 and others are active
compounds exhibiting antineoplastic,2 antibiotic, and antifungal
properties.3 The research of new active nucleosides is still very
dynamic and promising; substances such as nelarabine,4 entecavir,5
clofarabine,6 and azacitidine7 are examples of anticancer and an-
tiviral drugs recently approved by U.S. FDA. Particular attention has
as endogenous cell function modulators indicates the adenosine
receptors as significant targets with wide therapeutic potential. In
this context, AICAR has been indicated as a promising prodrug,
which induces benefits in patients suffering from autism, cerebral
palsy, insomnia, schizophrenia, and other neuropsychiatric symp-
toms generally associated to chronic low levels of adenosine.11
However, AICAR has short half-life in the cell, it does not efficiently
cross the blood–brain barrier and is poorly adsorbed from the
gastrointestinal tract. Consequently, the production of new AICAR
derivatives is an appealing objective in the field of medicinal
chemistry. In recent years, the syntheses of a number of AICAR
derivatives, such as the 2-aryl,12 4-N-benzyl,13 4-substituted,14 5-
substituted,15 5-hydroxyl (Bredinin),16 triazolyl-riboside (Ribavi-
rin),17 20,30-secoriboside derivatives,18 have been reported in the
literature.
Recently, the production of large nucleoside analogue libraries
has emerged as an important synthetic goal to chase the high
efficiency and velocity of the current biological screenings. In this
frame, the solid-phase synthesis, associated with a combinatorial
approach, offers the advantage of combining the rapid synthesis
with an easily obtainable molecular diversity around a single core
scaffold.
recently been paid to 5-aminoimidazole-4-carboxamide-1-
D
b-
-ribofuranosyde (AICAR) since its 50-phosphorylated derivative
(ZMP), a key biosynthetic precursor of purine nucleotides, is an
activator of AMP-activated protein kinase (AMPK).8 A possible
therapeutic importance of its exploitation arises from the fact that
the AICAR-induced AMPK activation strongly inhibits the basal and
the insulin-stimulated glucose uptake, the lipogenesis, the glucose
oxidation, as well as the lactate production in fat cells.9 It has been
also found that the control of protein kinase C (PKC) activation is
In this paper, we report a new solid-phase synthetic strategy to
obtain AICAR analogue libraries. The methodology has been tested
in the synthesis of the two small AICAR libraries 10a–g and 15a–g
* Corresponding author. Tel.: þ39 081 678541; fax: þ39 081 678552.
E-mail address: picciall@unina.it (G. Piccialli).
0040-4020/$ – see front matter Ó 2008 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tet.2008.04.071

6476
G. Oliviero et al. / Tetrahedron 64 (2008) 6475–6481
O2N
O2N
O2N
O
O
O
HN
HN
N
O2N
R-HN
O2N
N
N
O2N
N
N
O
R-HN
HO
N
O
N
O
N
N
N
iv
R-NH2
O
MMT
O
MMT
i
HO
OH
HO
OH
HO
OH
5
4
6f-g
for 5f-g
ii, 80-85%
for 5a-e
i, 93-95%
iii 95%
or
O
O
N
O
O
R
R
R
N
H2N
HO
N
H
N
H
N
N
N
N
O
H2N
H2N
H2N
N
N
N
N
iv
O
O
O
v
O
MMT
O
MMT
HO
O
MMT
85-90%
HO
OH
OH
HO
OH
HO
OH
9a-g
8a-g
7
10a-g
(72-86% from 4)
75-80% for c-f
5-7% for a,b,g
vi
vi 75-80%
iv
O
O
O
O
R
R
R
R
N
N
H
H2N
N
N
H
H2N
N
N
N
N
N
N
N
N
N
N
O
O
O
O
iv
v
HO
MMT O
O
MMT
HO
80-88%
HO
OH
HO
13a-g
14: R = H (from 4)
OH
HO
OH
HO
OH
15a-g
11a-g
(80-95% from 4)
12a-g
(58-67% from 4)
16: R = H (from 14)
Scheme 1. (i) R–NH2 (38.0 equiv) in DMF, 8 h, 50 ꢀC; (ii) 1 M K2CO3 in DMF, 15 h, 50 ꢀC; (iii) EDA/DMF (1:1, w/w) 8 h, 50 ꢀC; (iv) 2% TFA solution in DCM; (v) 5 M NaOH in EtOH, 6 h,
reflux; (vi) NaIO4 (10 equiv) in DMF/H2O (1:1, v/v), 12 h, 60 ꢀC or Pb(OAc)4 (15 equiv), in DCM, 2 h, rt; resin washings and treatment with NaBH4 (20 equiv) in EtOH, 2 h, rt.
(Scheme 1) where the nucleosides are modified on the 4-carbox-
amide residue or both at the 4-carboxamide and the ribose moiety,
respectively.
conditions, N-1 alkyl-inosines react at the C-2 of the purine system
to give 4-N-alkyl AICAR derivatives by pyrimidine ring cleavage and
concomitant extrusion of the C-2 carbon itself.21 Therefore, we
decided to extend this process to the solid-phase chemistry aiming
at two main targets: (i) to efficiently prepare a set of 4-N-alkyl
AICAR derivatives (10a–g) as well as the corresponding precursor
solid supports (9a–g) from N-1 alkyl-inosine supports 8a–g; (ii) to
combine the set of AICAR derivatives with a ribose modification
(20,30-secoribosyl derivatives) thus producing the new kind of
products 15a–g, as well as the related solid supports 13a–g, which
are in turn potentially useful for further AICAR derivatization/
modification.
2. Results and discussion
Our synthetic approach uses as starting material the recently
proposed N-1-dinitrophenyl-inosine solid support 4 synthesized as
depicted in Scheme 2. Support 4 reacting with R–NH2 nucleophiles
is converted into N-1 alkyl-inosine solid supports 8a–g from which
the AICAR libraries 10a–g and 15a–g could be obtained (Scheme 1).
In a previous paper, we utilized support 4 to prepare small libraries
of N-1 alkyl-inosines and their corresponding 20,30-secoriboside
derivatives.19 We also demonstrated that when 4 reacts with eth-
ylenediamine (EDA), the AICAR support 7 can be obtained in an
almost quantitative yield.19,20 It is well known that, under alkaline
Support 4 was obtained by binding 1-(2,4-dinitrophenyl)-
inosine
3 (Scheme 2) to the commercially available poly-
styrenemonomethoxytrityl chloride (MMTCl) resin by 50-O-trityl
ether linkage. Inosine derivative 3 was synthesized by the reaction
O2N
O2N
O
O
O
N
HN
O
N
N
N
N
O2N
O2N
HO
N
N
N
O
N
O
N
N
MMTCl
O
i
HO
O
MMT
iii
O
HO
OH
R1O
OR1
4
2 : R1-R1 = Acetonide
3 : R1 = H
1
ii
Scheme 2. (i) DNCB (2.2 equiv), K2CO3 (2.0 equiv), 2 h, 80 ꢀC; (ii) HCOOH/H2O (6:4, v/v), 4 h, rt; (iii) 3 (1.5 equiv) in pyridine (1.5 mL/250 mg of resin), DMAP (0.2 equiv), 24 h rt.

G. Oliviero et al. / Tetrahedron 64 (2008) 6475–6481
6477
Table 1
Reactions on the support 4
analyses and purifications indicated that the above reactions,
leading to 15c–f, proceeded with 75–80% yields, whereas complex
reaction mixtures were obtained for supports 13a,b,g leading to
very low quantities of the corresponding products 15a,b,g (5–7%
Entry
R–NH2
6, 11, Yielda (%)
10, 15, Yielda (%)
a
6 (NI), 11 (95)
6 (NI), 11 (95)
10 (81), 15 (60)
10 (83), 15 (67)
NH2
NH2
HO
HO
yields). These results suggest that the presence of the 4-N-(u-
b
hydroxyalkyl) portion on the AICAR supports 9a,b,g leads to large
side reactions when the products were reacted with sodium met-
aperiodate. In the case of AICAR support 7, the reaction furnished
support 14 from which the AICA-20,30-secoriboside 1618 could be
obtained in 70% overall yield (from 4) after the usual TFA treatment.
This prompted us to test the alternative pathway where the C2–C3
scission of the ribose moiety, with formation of 20,30-secoribosides
12a–g, was accomplished prior to the pyrimidine ring degradation.
Following this route, ribose cleavage of 8a–g furnished 12a–g in
good reaction yields (75–80%, from 8), which in turn were con-
verted into the pyrimidine-degraded supports 13a–g from which
the products 15a–g were obtained as described above (80–88%
yields from 12). The success of this pathway demonstrated that the
presence of a 20,30-secoribosyl moiety does not interfere with the
alkaline degradation of the purine ring leading to the AICA het-
erocyclic system. Though a 75–80% yield for the ribose cleavage
could seem acceptable, we considered this result not completely
satisfactory for a solid-phase reaction supporting a combinatorial
synthetic strategy. In fact, the above reaction causes a reduction in
the overall yield and purity of the derivatives 15a–g (60–70% yields
from 4). In order to further improve the yield of the C2–C3 bond
cleavage in ribose, lead tetraacetate (LTA)23 was used in DCM or
DMF. Though the process was accomplished at several LTA/8a–g
ratios and varying the reaction time, no significant improvement of
the 20,30-secoribosyl derivatives 12a–g was obtained after the usual
NaBH4 treatment (60–65% yields). However, it is to be noted that in
both oxidative cleavage procedures (i.e., sodium metaperiodate or
LTA) the predominant side products resulted to be the corre-
sponding unreacted inosines 11a–g.
3
c
6 (NI), 11 (93)
6 (NI), 11 (95)
10 (84), 15 (63)
10 (86), 15 (69)
NH2
NH2
d
e
f
6 (NI), 11 (94)
6 (90), 11 (85)
10 (83), 15 (62)
10 (76), 15 (59)
NH2
NH2
NH2
HO
g
6 (85), 11 (80)
10 (72), 15 (58)
O
O
NI: not isolated.
a
Starting from support 4.
of the commercially available 20-30-O-isopropylidene inosine 2 with
2,4-dinitrochlorobenzene (DNCB), followed by 20-30 deprotection
by aqueous formic acid treatment as previously described.19 The
reaction of the MMTCl resin (1.3 mequiv g-1) with 3 in the presence
of 4-(N,N-dimethylamino)pyridine (DMAP), in anhydrous pyridine,
afforded support 4 in almost quantitative yield. Reaction of 4 with
several N-nucleophiles (R–NH2, Table 1) furnished the N-1 alkyl-
inosine supports 8a–g. In the above reactions, the R–NH2 nucleo-
philes react with the strongly activated purine C-2 atom to give the
open intermediates 5 possessing an N-alkyl formamidine group.
The successive fast ring re-closure, favored by the loss of 2,4-dini-
troaniline as leaving group, led to N-1-alkyl-inosines 8a–e (93–95%
yields). We observed that in the case of sterically hindered amines
(entries f and g), the reaction stopped at intermediate products 5,
which, after detachment from the support, could be isolated and
characterized (6f and g). As previously demonstrated, treatment
with carbonate in DMF (at 50 ꢀC) converted these open-pyrimidine
species 5 in the N-1-alkyl-inosine supports 8f and g (80–85% yields)
by the six-membered ring re-closure.22 Reaction yields obtained for
8a–g were evaluated quantifying the N-1-alkyl-inosines 11a–g
released from a weighted amount of supports 8a–g by treatment
with 2% (v/v) TFA in DCM taking into account that the starting
support 4 had a nucleoside functionalization of 1.26 mequiv g-1. The
corresponding 4-N-alkyl AICAR supports 9a–g were then obtained
by cleavage of the pyrimidine ring in supports 8a–g by NaOH
treatment (5 M in EtOH, reflux, 85–90% reaction yields). TFA
treatment of supports 9a–g released the crude AICAR derivatives
10a–g, which were purified by HPLC. The overall yield (starting
from support 4) of the pure obtained nucleosides 10 and 11 are
reported in Table 1. The structures and the purity of the products
were confirmed by 1H NMR spectroscopy and ESIMS data. In
a typical reaction starting from 20 mg of solid support 4, and con-
sidering an average molecular weight of 320 g molꢁ1, 6–7 mg of
each crude AICAR derivatives 10a–g could be obtained in 70–85%
purity.
2.1. Biological results
All compounds were tested for their effect on cellular pro-
liferation using a human breast cancer cell line (MCF-7). The pro-
liferative effects were evaluated in the absence of 5% fetal calf
serum (FCS), while the anti-proliferative effects were evaluated in
the absence of serum. The proliferation was evaluated by a standard
colorimetric procedure (MTT test)24 after 24 and 48 h in triplicate
using 1 mM of each compound dissolved in water or in 10% ethanol
to improve solubility. The toxicity of the 10:90 ethanol/water so-
lution was tested separately. No significant effect on proliferation
was observed for any compound tested. Further experiments using
different conditions and cell lines are currently undergoing.
3. Conclusions
In conclusion, we have successfully utilized the N-1-dini-
trophenyl-inosine solid support 4, where the nucleoside is an-
chored to an MMT-polystyrene resin by the 50-ribose position, to
synthesize small libraries of inosine and AICAR derivatives. The
following solid-phase reactions have been carried out on this
support and its derivatives: (i) the N-1 alkylation of purine by
reaction of 4 with a variety of amines (90–95% yields); (ii) the
alkaline cleavage of the N-1 alkyl-inosine base leading to AICAR
derivatives (85–90% yields); (iii) the 20,30-oxidative cleavage of the
ribose moiety (75–80% yields). The proposed synthetic pathways
allowed the preparation of small libraries of the N-1 alkyl-inosines
11a–g, 4-N-alkyl AICAR derivatives 10a–g, and the corresponding
20,30-secoriboside derivatives 15a–g. It is to be noted that the
reported solid-phase reactions proceed with yields comparable
to, or higher than, those obtainable from the corresponding
Next, we explored the possibility of performing the 20,30-oxi-
dative cleavage of the ribose moiety in supports 9a–g. In a first
attempt, we employed the previously tested19 reaction conditions,
namely sodium metaperiodate followed by borohydride reduction
of the di-aldehyde products. In a typical reaction, the supports 9a–g
were left in contact with a solution of NaIO4 (10 equiv excess) in
DMF/H2O and shaken for 12 h at 60 ꢀC. The resulting supports, after
washing, were treated with NaBH4 in EtOH and shaken for 2.0 h at
room temperature to give supports 13a–g that were analyzed by
detaching the nucleosidic material by TFA treatment. The HPLC

6478
G. Oliviero et al. / Tetrahedron 64 (2008) 6475–6481
procedures in solution. Furthermore, the proposed solid-phase
procedures furnished a new group of solid supports bearing ino-
sine derivatives (8a–g, 12a–g) or AICAR derivatives (9a–g, 13a–g),
which can be utilized in a combinatorial manner to achieve
a number of further derivatizations/conjugations both on the
imidazolyl residue and/or on the ribose or 20,30-secoribose moiety.
evaporated to dryness to furnish 3 (1.13 g, 99%) as a pale yellow
amorphous solid that constituted a 1:1 mixture of atropisomers
at the N(1)–phenyl bond. The product was used without further
purification; mp 210–212 ꢀC; nmax (neat) 3402, 3098, 1704, 1546,
1343, 1217 cmꢁ1; 1H NMR dH (CD3OD) 9.05 (s, 1H, H-3 DNP), 8.82–
8.72 (m, 1H, H-5 DNP), 8.49, 8.52 (2s, 2H, H-2 and H-8), 8.08–7.98
(m, 1H, H-6 DNP), 6.14–6.06 (m, 1H, H-10), 4.70–4.60 (m, 1H, H-20),
4.40–4.32 (m, 1H, H-30), 4.19–4.12 (m, 1H, H-40), 3.94–3.74 (m, 2H,
4. Experimental
4.1. General
H-50a,b); UV (H2O) lmax 246 nm,
3
¼20,100; HRESIMS calcd for
C
16H14N6NaO9: 457.0720, found: 457.0715 (MþNa)þ.
4-Methoxytrityl chloride resin (1% divinylbenzene, 200–400
mesh, 1.3 mmol g-1 substitution) was purchased from CBL Patras,
Greece. Anhydrous solvents were used for reactions. All the other
reagents were obtained from commercial sources and were used
without further purification. The reactions on solid phase were
performed using glass columns (10 mm diameter, 100 mm length)
with fused-in sintered glass-disc PO (bore of plug 2.5 mm), which
were shaken on an orbital shaker, or round bottom flask, when
reactions were performed at high temperatures. Mps were de-
termined on a Reichert Thermovar apparatus. IR spectra were
collected on a Jasco FT-IR-430 spectrometer. The 1H NMR spectra
were performed on a Varian Mercury Plus 400 MHz using CD3OD
and CDCl3 as solvents; chemical shifts were reported in parts per
4.3. General procedure for the scaffold synthesis
4.3.1. Loading of 3 on solid support
1-(2,4-Dinitrophenyl)inosine (3) (1.13 g, 2.60 mmol) was evap-
orated with dry pyridine (3ꢂ1.5 mL) and then coupled with the
MMTCl resin (1.30 g, 1.69 mmol), and swollen with dry pyridine
(8 mL) in the presence of DMAP (0.35 mmol, 42.0 mg) for 24 h at
room temperature. The resin was filtered and washed with CH2Cl2
(3ꢂ5 mL), CH2Cl2/MeOH (1:1, v/v, 3ꢂ5 mL), and MeOH (3ꢂ5 mL),
and finally dried in vacuo. The reaction yield was evaluated by
cleavage of the nucleoside from the solid support by treatment with
2% (v/v) TFA in DCM (8 min, rt) followed by quantitative UV ex-
periment (3, lmax¼246 nm, ¼20,100, H2O). The solid support 4 was
3
million (
7.26. RP-HPLC analyses of crude products were carried out on a
Jasco UP-2075 Plus pump using a 5
m, 4.8ꢂ150 mm C-18 reverse-
d
) relative to residual solvent signals: CD2HOD 3.31, CHCl3
obtained in almost quantitative yield (1.26 mmol g -1, 97%).
m
4.3.2. Treatment of solid support 4 with N-nucleophiles a–g
(products 8a–g and 11a–g)
phase column eluted with a linear gradient of CH3CN in 0.1 M TEAB
(pH 7.0, from 0 to 60% in 60 min, flow 1.0 mL min-1) equipped with
a Jasco UV-2075 Plus UV detector. The UV spectra were recorded on
a Jasco V-530 UV spectrophotometer. Mass spectra were recorded
on an Applied Biosystems API 2000 mass spectrometer using
electron spray ionization (ESI) technique in positive mode. The
High Resolution MS were recorded on a Bruker APEX II FT-ICR mass
spectrometer using electron spray ionization (ESI) technique in
positive mode. Column chromatography was performed on silica
gel (Merck, Kieselgel 60, 0.063–0.200 mm). Analytic TLC detections
were performed using F254 silica gel plates (0.2 mm, Merck). TLC
spots were detected under UV light (254 nm).
Solid support 4 (100 mg, 0.13 mmol), previously swollen in
DMF, was left in contact with amines a–g (5.0 mmol) in DMF
(1.5 mL) under shaking for 8 h at 50 ꢀC. The reaction of 4 with
amines a–e furnished, after usual washings, supports 8a–e. In the
case of amines f and g, after detachment from the support as
described above, intermediates 6f and g could be obtained, after
HPLC purification, in 90 and 85% yields, respectively. Alternatively,
supports 5f–g were treated with a 1 M solution of K2CO3 in DMF
(15 h, 50 ꢀC) thus giving supports 8f and g. After filtration and
washings with DMF (3ꢂ5 mL), DMF/MeOH (1:1, v/v, 3ꢂ5 mL), and
MeOH (3ꢂ5 mL), supports 8a–g were dried under reduced pres-
sure. The yields of N-1-alkyl-inosines 11a–g (80–95%, from 4, Table
1) were calculated by quantifying the products obtained by HPLC
purification of the crude nucleoside material released from
a weighted amount of resin (as described above) and taking into
account that the starting support 4 had a 1.26 mol g-1 nucleoside
functionalization.
4.2. Synthesis
4.2.1. 1-(2,4-Dinitrophenyl)-20,30-O-isopropylideninosine (2)
A
mixture of 20,30-O-isopropylideninosine (1) (1.00 g,
3.24 mmol), 2,4-dinitrochlorobenzene (820 mg, 4.05 mmol), and
K2CO3 (560 mg, 4.05 mmol) was suspended in anhydrous DMF
(5 mL) and stirred at 80 ꢀC for 3 h. The reaction was monitored by
TLC (CHCl3/MeOH, 95:5). After cooling, the mixture was filtered and
the solid was washed with CHCl3. The filtrates and washings,
collected and evaporated to dryness, were purified on a silica gel
column eluted with increasing amounts of MeOH in CHCl3 (from 0 to
5%) to give 2 as a pale yellow amorphous solid consisting of a 1:1
mixture of atropisomers at the N(1)–phenyl bond (1.20 g, 80%); mp
235–237 ꢀC; nmax (CHCl3) 3417, 3106,1710,1538,1348 cmꢁ1; 1H NMR
dH (CDCl3) 9.04 (br s,1H, H-3 DNP), 8.72–8.62 (m,1H, H-5 DNP), 8.11,
4.3.3. Formation of 4-N-alkyl AICAR derivatives 10a–g
Supports 8a–g (100 mg, 0.10–0.12 mmol) were treated with
NaOH (5 M in EtOH) for 6 h at reflux. After filtration and washings
with EtOH (3ꢂ5 mL), EtOH/H2O (1:1, v/v, 3ꢂ5 mL), H2O (3ꢂ5 mL),
and MeOH (3ꢂ5 mL), supports 9a–g were dried under reduced
pressure. The reaction yields (8/9, 80–90%) and the overall yields
of 4-N-alkyl AICAR derivatives 10a–g (72–86% from 4) were eval-
uated on isolated products after HPLC purification of the material
released from a weighted amount of resin, as described above. 1H
NMR spectra (see later) confirmed the purity of the products.
´
8.14 (2s, 2H, H-2 and H-8), 7.81–7.72 (m,1H, H-6 DNP), 6.07–5.96 (m,
1H, H-10), 5.22–5.11 (m,1H, H-20), 5.10–5.02 (br s,1H, H-30), 4.53 (br s,
1H, H-40), 4.02–3.75 (m, 2H, H-50a,b), 2.90 (br s, 1H, OH, exchange
with D2O), 1.64, 1.39 (2s, 6H, 2CH3); UV (MeOH) lmax 246 nm,
4.3.4. Formation of 4-N-alkyl AICA-20,30-secoriboside derivatives
15c–f (pathway 9/13/15)
3
¼20,200; HRESIMS calcd for C19H18N6NaO9: 497.1033, found:
Supports 9c–f (100 mg, 0.09–0.11 mmol) were left in contact
with a solution of NaIO4 (235 mg, 1.1 mmol) in DMF/H2O (1.5 mL,
1:1, v/v) and shaken for 12 h at 60 ꢀC. The resulting supports, after
washings with DMF (3ꢂ5 mL), DMF/H2O (1:1, v/v, 3ꢂ5 mL), H2O
(3ꢂ5 mL), and then with EtOH (3ꢂ5 mL), were treated with NaBH4
(2.2 mmol) in EtOH (1.5 mL) and shaken for 2.0 h at room
temperature. After filtration and washings with EtOH (3ꢂ5 mL),
497.1056 (MþNa)þ.
4.2.2. 1-(2,4-Dinitrophenyl)inosine (3)
Compound 2 (1.20 g, 2.60 mmol) was dissolved in HCOOH/H2O
(6:4, v/v, 16 mL) and left at room temperature for 4 h. The reaction
was monitored by TLC (CHCl3/MeOH, 6:4). The mixture was

G. Oliviero et al. / Tetrahedron 64 (2008) 6475–6481
6479
EtOH/H2O (1:1, v/v, 3ꢂ5 mL), H2O (3ꢂ5 mL), and MeOH (3ꢂ5 mL),
supports 13c–f were dried under reduced pressure. Reaction yields
(9/13, 75–80%, Table 1) were evaluated by HPLC analysis and
purification of the crude 4-N-alkyl AICA-20,30-secoriboside de-
rivatives 15c–f released from a weighted amount of resin, as de-
scribed above. The same reactions, performed on 9a,b,e furnished
very low quantities of the corresponding 15a,b,e.
1H, H-8), 6.00 (d, 1H, J¼5.0 Hz, H-10), 4.64–4.60 (m, 1H, H-20), 4.34–
4.29 (m, 1H, H-30), 4.20 (t, 2H, J¼4.0 Hz, CH2N), 4.15–4.11 (m, 1H,
H-40), 3.86 (dd, 1H, J¼12.2, 2.6 Hz, H-50a), 3.75 (dd, 1H, J¼12.2,
2.6 Hz, H-50b), 3.60 (t, 2H, J¼6.3 Hz, CH2O), 2.03–1.94 (m, 2H,
CH2CH2N); UV (MeOH) lmax 249 nm,
3
¼9900; HRESIMS calcd for
C
13H19N4O6: 327.1305, found: 327.1291 (MþH)þ.
4.4.4. 1-(5-Hydroxypentyl)inosine (11b)
Amorphous solid, mp over 250 ꢀC (decomp.); nmax (neat) 3375,
2929, 1679, 1427, 1240 cmꢁ1 1H NMR dH (CD3OD) 8.40 (br s, 1H,
4.3.5. Formation of 4-N-alkyl AICA-20,30-secoriboside derivatives
15a–g (pathway 8/12/13/15)
;
Supports 8a–g (100 mg, 0.10–0.12 mmol) were left in contact
with a solution of NaIO4 (235 mg, 1.1 mmol) in DMF/H2O (1.5 mL,
1:1, v/v) and shaken for 12 h at 60 ꢀC. The resulting supports, after
washings with DMF (3ꢂ5 mL), DMF/H2O (1:1, v/v, 3ꢂ5 mL), H2O
(3ꢂ5 mL), and then with EtOH (3ꢂ5 mL), were treated with NaBH4
(2.2 mmol) in EtOH (1.5 mL) and shaken for 2.0 h at room tem-
perature. After filtration and washings with EtOH (3ꢂ5 mL), EtOH/
H2O (1:1, v/v, 3ꢂ5 mL), H2O (3ꢂ5 mL), and MeOH (3ꢂ5 mL), sup-
ports 12a–g were dried under reduced pressure. Reaction yields
(8/12, 75–80%) were evaluated by HPLC analysis and purification
of the crude 1-N-alkyl-inosine-20,30-secoriboside derivatives re-
leased from a weighted amount of resin, as described above.19
Alternatively, supports 8a–g (100 mg, 0.10–0.12 mmol) were left
into contact with a solution of LTA (235 mg, 1.1 mmol) in DCM
(1.5 mL) and shaken for 24 h at room temperature. The resulting
supports, after usual washings, were treated with NaBH4 (2.2 mmol)
in EtOH (1.5 mL) as described above, thus obtaining supports 12a–g
in 60–65% reaction yield (8/12) calculated by HPLC on the re-
leased material. Then, supports 12a–g were treated with 5 M NaOH
in EtOH as described above for the reaction 8/9 thus giving sup-
ports 13a–g. The TFA treatment of 13a–g furnished 15a–g (80–88%
from 12a–g), which were purified by HPLC as described above for
10a–g. The overall yields of pure 15a–g (from 4) resulted to be in
the range 58–67% (Table 1). 1H NMR spectra (see later) confirmed
the purity of the products.
H-2), 8.35 (s,1H, H-8), 6.02 (d,1H, J¼5.5 Hz, H-10), 4.64–4.60 (m,1H,
H-20), 4.33–4.29 (m, 1H, H-30), 4.14–4.08 (m, 3H, H-40, CH2N), 3.87
(dd, 1H, J¼12.1, 2.6 Hz, H-50a), 3.75 (dd, 1H, J¼12.1, 2.6 Hz, H-50b),
3.60 (t, 2H, J¼6.2 Hz, CH2O), 1.85–1.77 (m, 2H, CH2), 1.61–1.56 (m,
2H, CH2), 1.48–1.38 (m, 2H, CH2); UV (MeOH) lmax 249 nm,
3
¼10,000; HRESIMS calcd for C15H22N4NaO6: 377.1437, found:
377.1453 (MþNa)þ.
4.4.5. 1-Propylinosine (11c)
Amorphous solid, mp 185–187 ꢀC; nmax (neat) 3324, 3302, 1702,
1240 cmꢁ1 1H NMR dH (CD3OD) 8.43 (br s, 1H, H-2), 8.35 (s, 1H,
;
H-8), 6.01 (d, 1H, J¼5.5 Hz, H-10), 4.64–4.60 (m, 1H, H-20), 4.34–4.31
(m, 1H, H-30), 4.18–4.11 (m, 1H, H-40), 4.07 (t, 2H, J¼7.3 Hz, CH2N),
3.87 (dd, 1H, J¼12.5, 2.6 Hz, H-50a), 3.75 (dd, 1H, J¼12.5, 2.6 Hz,
H-50b), 1.83–178 (m, 2H, CH2CH3), 0.98 (t, 3H, J¼7.0 Hz); UV (MeOH)
lmax 252 nm,
3
¼9700; HRESIMS calcd for C13H18N4NaO5: 333.1175,
found: 333.1207 (MþNa)þ.
4.4.6. 1-Butylinosine (11d)
Amorphous solid, mp 170–172 ꢀC; nmax (neat) 3334, 3296, 1693,
1384, 1232 cmꢁ1 1H NMR dH (CD3OD) 8.41 (br s, 1H, H-2), 8.36 (s,
;
1H, H-8), 6.02 (d, 1H, J¼5.5 Hz, H-10), 4.64–4.60 (m, 1H, H-20), 4.34–
4.30 (m, 1H, H-30), 4.14–4.08 (m, 3H, H-40, CH2N), 3.87 (dd, 1H,
J¼12.1, 2.6 Hz, H-50a), 3.75 (dd, 1H, J¼12.1, 2.6 Hz, H-50b), 1.80–1.71
(m, 2H, CH2), 1.45–1.35 (m, 2H, CH2), 0.98 (t, 3H, J¼7.7 Hz, CH3); UV
(MeOH) lmax 252 nm,
3
¼9800; HRESIMS calcd for C14H21N4O5:
4.4. Synthesized scaffolds
325.1512, found: 325.1490 (MþH)þ.
4.4.1. 5-[(Cyclohexylamino)methyleneamino]-1-(
b
-
D
-ribo-
4.4.7. 1-Benzylinosine (11e)
furanosyl)imidazole-4[N-(2,4-dinitrophenyl)]carboxamide (6f)
Amorphous solid, mp over 250 ꢀC (decomp.); nmax (neat) 3423,
3302, 2917, 1656, 1204, 1111 cmꢁ1; 1H NMR dH (CDCl3) 12.36 (s, 1H,
NH, exchange with D2O), 9.18–9.13 (m, 2H, H-6 and H-3 DNP), 8.70
(br s, 1H, H-2), 8.48 (dd, 1H, J¼9.8, 2.4 Hz, H-5 DNP), 7.47 (s, 1H,
CH]N), 5.78 (br s, 1H, H-10), 4.62–4.59 (m, 1H, H-20), 4.38–4.41 (m,
2H, H-30, H-40), 3.94–3.87 (m, 2H, 2H-50), 3.45 (br s, 1H, CHN), 2.20–
Amorphous solid, mp 217–220 ꢀC (lit.25 219–222 ꢀC); nmax (neat)
3383, 3298, 1698, 1490, 1212 cmꢁ1; 1H NMR dH (CD3OD) 8.44, 8.33
(2s, 2H, H-2, H-8), 7.32–7.26 (m, 5H, Ph), 6.00 (d,1H, J¼5.9 Hz, H-10),
5.29 (s, 2H, CH2Ph), 4.69–4.63 (m, 1H, H-20), 4.33–4.30 (m,1H, H-30),
4.13–4.09 (m,1H, H-40), 3.87 (dd,1H, J¼12.5, 2.9 Hz, H-50a), 3.75 (dd,
1H, J¼12.5, 2.9 Hz, H-50b); UV (MeOH) lmax 249 nm,
¼10,100;
3
HRESIMS calcd for
C17H18N4NaO5: 381.1175, found: 381.1173
1.20 (m, 10H, 5CH2); UV (MeOH) lmax 275 nm,
3
¼13,300; HRESIMS
(MþNa)þ.
calcd for C22H27N7NaO9: 556.1768, found: 556.1779 (MþNa)þ.
4.4.8. 1-Cyclohexylinosine (11f)
4.4.2. 5-[(1R,2S,3R,4R)-2,3-Dihydroxy-4-((hydroxymethyl)-
Amorphous solid, mp 188–191 ꢀC; nmax (neat) 3344, 3286, 1706,
cyclopentyl)aminomethyleneamino]-1-(
b
-D-ribofuranosyl)imid-
1368, 1238 cmꢁ1 1H NMR dH (CD3OD) 8.37, 8.32 (2s, 2H, H-2,
;
azole-4[N-(2,4-dinitrophenyl)]carboxamide (6g)
H-8), 6.00 (d, 1H, J¼5.9 Hz, H-10), 4.64–4.60 (m, 1H, H-20), 4.34–4.30
(m, 1H, H-30), 4.22–4.19 (m, 1H, CHN), 4.11–4.10 (m, 1H, H-40),
3.85 (dd, 1H, J¼12.0, 2.9 Hz, H-50a), 3.72 (dd, 1H, J¼12.0, 2.9 Hz,
H-50b), 2.00–1.30 (m, 10H, 5CH2); UV (MeOH) lmax 246 nm,
Amorphous solid, mp over 250 ꢀC (decomp.); nmax (neat) 3430,
3320, 2904, 1668, 1264, 1128 cmꢁ1; 1H NMR dH (CDCl3) 9.20 (d, 1H,
H-5 DNP), 9.03 (s, 1H, H-3 DNP), 8.64 (s, 1H, H-2), 8.42 (d, 1H, H-6
DNP), 7.73 (s, 1H, CHN), 6.03 (d, 1H, H-10), 4.63–4.60 (m, 1H, H-20),
4.40–4.36 (m, 2H, H-30, H-20), 4.22–4.18 (m, 2H, H-40, H-30), 3.76–
3.72 (m, 2H, CH2O), 3.62–3.59 (m, 2H, CH2O), 3.23–3.20 (m, 1H,
H-100), 2.02–1.98 (m, 2H, H-400, H-500a), 1.62–1.59 (m, 1H, H-500b), 1.18
3
¼9800; HRESIMS calcd for C16H23N4O5: 351.1668, found: 351.1699
(MþH)þ.
4.4.9. 1-[(1R,2S,3R,4R)-2,3-(Isopropylidenedioxy)-4-
(s, 3H, CH3), 1.31 (s, 3H, CH3); UV (CHCl3) lmax 276 nm,
3
¼12,900;
(hydroxymethyl)cyclopentyl]inosine (11g)
HRESIMS calcd for C25H31N7NaO12: 644.1928, found: 644.1945
Amorphous solid, mp over 250 ꢀC (decomp.); nmax (neat) 3380,
3298, 1685, 1703, 1430, 1210; 1H NMR dH (CD3OD) 8.40 (br s, 1H,
H-2), 8.36 (s, 1H, H-8), 6.04 (d, 1H, J¼5.4 Hz, H-10), 5.23–5.19 (m, 1H,
H-200), 4.73–4.70 (m, 1H, H-300), 4.60–4.58 (m, 2H, H-100, H-20),
4.33–4.29 (m, 1H, H-30), 4.10–4.09 (m, 1H, H-40), 3.75–3.83 (m, 4H,
H-50a,b, H-600a,b), 2.40–2.12 (m, 3H, H-400, H-500a,b), 1.16 (s, 3H, CH3),
(MþNa)þ.
4.4.3. 1-(3-Hydroxypropyl)inosine (11a)
Amorphous solid, mp 215–218 ꢀC; nmax (neat) 3390, 2930, 1700,
1450, 1232 cmꢁ1 1H NMR dH (CD3OD) 8.41 (br s, 1H, H-2), 8.34 (s,
;

6480
G. Oliviero et al. / Tetrahedron 64 (2008) 6475–6481
1.30 (s, 3H, CH3); UV (MeOH) lmax 253 nm,
3
¼9500; HRESIMS calcd
4.4.16. 5-Amino-1-(b-D-ribofuranosyl)imidazole-4-
[N-((1R,2S,3R,4R)-2,3-isopropylidenedioxy)-4-
(hydroxymethyl)cyclopentyl]carboxamide (10g)
for C19H26N4NaO8: 461.1648, found: 461.1620 (MþNa)þ.
4.4.10. 5-Amino-1-(
b
-
D
-ribofuranosyl)imidazole-4-
Amorphous solid, mp over 250 ꢀC (decomp.); nmax (neat) 3349,
3325, 1706, 1217, 1122 cmꢁ1; 1H NMR dH (CD3OD) 7.37 (br s, 1H, H-
2), 5.57 (d, 1H, J¼5.5 Hz, H-10), 5.19–5.15 (m, 1H, H-200), 4.55–4.40
(m, 3H, H-20, H-100, H-300), 4.26–4.22 (m, 1H, H-30), 4.13–4.09 (m, 1H,
H-40), 3.80–3.68 (m, 4H, H-50a,b, H-600a,b), 2.30–2.10 (m, 3H, H-400,
H-500a,b), 1.18 (s, 3H, CH3), 1.31 (s, 3H, CH3); UV (MeOH) lmax 268 nm,
[N-(3-hydroxypropyl)]carboxamide (10a)
Amorphous solid, mp over 250 ꢀC (decomp.); nmax (neat) 3402,
3322, 1678, 1220 cmꢁ1 1H NMR dH (CD3OD) 7.31 (s, 1H, H-2), 5.54
;
(d, 1H, J¼6.6 Hz, H-10), 4.50–4.45 (m, 1H, H-20), 4.24–4.20 (m, 1H,
H-30), 4.06–4.03 (m, 1H, H-40), 3.79 (dd, 1H, J¼12.1, 2.6 Hz, H-50a),
3.74 (dd, 1H, J¼12.1, 2.6 Hz, H-50b), 3.63 (t, 2H, J¼6.2 Hz, CH2O),
3.31 (2H, CH2N, partly covered by solvent signal), 1.81–1.74 (m, 2H,
3
¼10,500; HRESIMS calcd for C18H28N4NaO8: 451.1805, found:
451.1812 (MþNa)þ.
CH2); UV (MeOH) lmax 268 nm,
3¼10,700; HRESIMS calcd for
C
12H20N4NaO6: 339.1280, found: 339.1302 (MþNa)þ.
4.4.17. 5-Amino-1-[1-(1,3-dihydroxypropan-2-yloxy)-2-hydroxy-
ethyl]imidazole-4-[N-(3-hydroxypropyl)]carboxamide (15a)
4.4.11. 5-Amino-1-(
[N-(5-hydroxypentyl)]carboxamide (10b)
b
-
D
-ribofuranosyl)imidazole-4-
Amorphous solid, mp over 250 ꢀC (decomp.); nmax (neat) 3378,
3327,1698,1220 cmꢁ1; 1H NMR dH (CD3OD) 7.34 (s,1H, H-2), 5.60 (t,
1H, J¼5.7 Hz, H-10), 3.87–3.83 (m, 2H, CH2O), 3.75–3.64 (m, 2H,
CH2O), 3.61–3.49 (m, 5H, CH, 2CH2O), 3.31 (2H, CH2N, partly cov-
ered by solvent signal), 1.80–1.75 (m, 2H, CH2); UV (MeOH) lmax
Amorphous solid, mp over 250 ꢀC (decomp.); nmax (neat) 3409,
3338, 2934, 1623, 1255 cmꢁ1; 1H NMR dH (CD3OD) 7.38 (s, 1H, H-2),
5.56 (d, 1H, J¼6.2 Hz, H-10), 4.50–4.46 (m, 1H, H-20), 4.23–4.19 (m,
1H, H-30), 4.08–4.05 (m,1H, H-40), 3.77–3.72 (m, 2H, H-50a,b), 3.55 (t,
2H, J¼6.2 Hz, CH2O), 3.31 (2H, CH2N, partly covered by solvent
signal),1.62–1.55 (m, 4H, 2CH2), 1.48–1.42 (m, 2H, CH2); UV (MeOH)
268 nm,
3
¼10,200; HRESIMS calcd for C12H22N4NaO6: 341.1437,
found: 341.1445 (MþNa)þ.
lmax 268 nm,
3
¼10,900; HRESIMS calcd for C14H24N4NaO6:
4.4.18. 5-Amino-1-[1-(1,3-dihydroxypropan-2-yloxy)-2-hydroxy-
ethyl]imidazole-4-[N-(5-hydroxypentyl)]carboxamide (15b)
367.1594, found: 367.1586 (MþNa)þ.
Amorphous solid, mp over 250 ꢀC (decomp.); nmax (neat) 3370,
3323, 1702, 1210 cmꢁ1; 1H NMR dH (CD3OD) 7.35 (s,1H, H-2), 5.62 (t,
1H, J¼5.9 Hz, H-10), 3.95–3.85 (m, 2H, CH2O), 3.78–3.64 (m, 2H,
CH2O), 3.60–3.50 (m, 5H, CH, 2CH2O), 3.32 (2H, CH2N, partly cov-
ered by solvent signal), 1.64–1.54 (m, 4H, 2CH2), 1.48–1.38 (m, 2H,
4.4.12. 5-Amino-1-(b-D-ribofuranosyl)imidazole-4-
(N-propyl)carboxamide (10c)
Amorphous solid, mp 202–205 ꢀC; nmax (neat) 3330, 2980, 1702,
1210, 1166 cmꢁ1; 1H NMR dH (CD3OD) 7.36 (s, 1H, H-2), 5.54 (d, 1H,
J¼6.6 Hz, H-10), 4.50–4.45 (m, 1H, H-20), 4.24–4.20 (m, 1H, H-30),
4.09–4.06 (m, 1H, H-40), 3.79 (dd, 1H, J¼11.7, 2.6 Hz, H-50a), 3.74 (dd,
1H, J¼11.7, 2.6 Hz, H-50b), 3.31 (2H, CH2N, partly covered by solvent
signal), 1.63–1.57 (m, 2H, CH2CH3), 0.98 (t, 3H, J¼7.3 Hz, CH3); UV
CH2); UV (MeOH) lmax 268 nm,
C
3
¼10,100; HRESIMS calcd for
14H26N4NaO6: 369.1750, found: 369.1756 (MþNa)þ.
4.4.19. 5-Amino-1-[1-(1,3-dihydroxypropan-2-yloxy)-2-hydroxy-
ethyl]imidazole-4-(N-propyl)carboxamide (15c)
(MeOH) lmax 267 nm,
3¼10,400; HRESIMS calcd for C12H20N4NaO5:
323.1331, found: 323.1324 (MþNa)þ.
Amorphous solid, mp 225–229 ꢀC; nmax (neat) 3384, 3332, 1705,
1264, 1176 cmꢁ1; 1H NMR dH (CD3OD) 7.36 (s, 1H, H-2), 5.62 (t, 1H,
J¼3.3 Hz, H-10), 3.90–3.83 (m, 2H, CH2O), 3.78–3.62 (m, 2H, CH2O),
3.61–3.49 (m, 3H, CH, CH2O), 3.30 (2H, CH2N, partly covered by
solvent signal), 1.65–1.56 (m, 2H, CH2), 0.96 (t, 3H, J¼7.2 Hz, CH3);
4.4.13. 5-Amino-1-(b-D-ribofuranosyl)imidazole-4-
(N-butyl)carboxamide (10d)
Amorphous solid, mp 222–225 ꢀC; nmax (neat) 3398, 3347, 1702,
1239, 1120 cmꢁ1
;
1H NMR dH (CD3OD) 7.32 (s, 1H, H-2), 5.52 (d,
UV (MeOH) lmax 267 nm,
C
3
¼10,300; HRESIMS calcd for
1H, J¼5.5 Hz, H-10), 4.50–4.46 (m, 1H, H-20), 4.20–4.16 (m, 1H,
H-30), 4.13–4.10 (m, 1H, H-40), 3.79 (dd, 1H, J¼12.5, 2.9 Hz, H-50a),
3.74 (dd, 1H, J¼12.5, 2.9 Hz, H-50b), 3.31 (2H, CH2N, partly covered
by solvent signal), 1.60–1.51 (m, 2H, CH2), 1.45–1.36 (m, 2H, CH2),
12H22N4NaO5: 325.1488, found: 325.1480 (MþNa)þ.
4.4.20. 5-Amino-1-[1-(1,3-dihydroxypropan-2-yloxy)-2-
hydroxyethyl]imidazole-4-(N-butyl)carboxamide (15d)
0.96 (t, 3H, J¼7.3 Hz, CH3); UV (MeOH) lmax 267 nm,
3
¼10,300;
Amorphous solid, mp 218–222 ꢀC; nmax (neat) 3398, 3340, 1702,
1241, 1160 cmꢁ1; 1H NMR dH (CD3OD) 7.34 (s, 1H, H-2), 5.60 (t, 1H,
J¼3.3 Hz, H-10), 3.91–3.84 (m, 2H, CH2O), 3.79–3.65 (m, 2H, CH2O),
3.61–3.49 (m, 3H, CH, CH2O), 3.31 (2H, CH2N, partly covered by
solvent signal), 1.60–1.51 (m, 2H, CH2), 1.46–1.32 (m, 2H, CH2), 0.96
HRESIMS calcd for
C13H22N4NaO5: 337.1488, found: 337.1480
(MþNa)þ.
4.4.14. 5-Amino-1-(b-D-ribofuranosyl)imidazole-4-
(N-benzyl)carboxamide (10e)
(t, 3H, J¼7.2 Hz, CH3); UV (MeOH) lmax 267 nm, ¼10,300; HRESIMS
3
Amorphous solid, mp 170–173 ꢀC (lit.25 171–172 ꢀC); nmax (neat)
calcd for C13H24N4NaO5: 339.1644, found: 339.1640 (MþNa)þ.
3334, 3256, 1456, 1696, 1198 cmꢁ1 1H NMR dH (CD3OD) 7.38–7.30
;
(m, 6H, Ph, H-2), 5.55 (d, 1H, J¼6.6 Hz, H-10), 4.54–4.48 (s, 3H,
CH2Ph, H-20), 4.19–4.16 (m, 1H, H-30), 4.08–4.05 (m, 1H, H-40), 3.79
(dd,1H, J¼12.1, 2.9 Hz, H-50a), 3.74 (dd,1H, J¼12.1, 2.9 Hz, H-50b); UV
4.4.21. 5-Amino-1-[1-(1,3-dihydroxypropan-2-yloxy)-2-
hydroxyethyl]imidazole-4-(N-benzyl)carboxamide (15e)
Amorphous solid, mp over 250 ꢀC (decomp.); nmax (neat) 3367,
3331, 1705, 1264, 1176 cmꢁ1; 1H NMR dH (CD3OD) 7.36–7.28 (m, 6H,
Ph, H-2), 5.60 (t, 1H, J¼5.6 Hz, H-10), 4.51 (s, 2H, CH2Ph), 3.96–3.84
(m, 2H, CH2O), 3.78–3.64 (m, 2H, CH2O), 3.61–3.49 (m, 3H, CH,
(MeOH) lmax 270 nm,
3
¼11,400; HRESIMS calcd for C16H20N4NaO5:
371.1331, found: 371.1325 (MþNa)þ.
4.4.15. 5-Amino-1-(
(N-cyclohexyl)carboxamide (10f)
Amorphous solid, mp 210–212 ꢀC; nmax (neat) 3320, 3295, 1689,
1197, 1172 cmꢁ1; 1H NMR dH (CD3OD) 7.35 (s, 1H, H-2), 5.54 (d, 1H,
J¼7.0 Hz, H-10), 4.50–4.45 (m, 1H, H-20), 4.24–4.19 (m, 1H, H-30),
4.07–4.04 (m, 1H, H-40), 3.82–3.72 (m, 3H, H-50a,b, CHN), 2.00–1.30
b
-
D
-ribofuranosyl)imidazole-4-
CH2O); UV (MeOH) lmax 270 nm,
C
3
¼11,200; HRESIMS calcd for
16H22N4NaO5: 373.1488, found: 373.1476 (MþNa)þ.
4.4.22. 5-Amino-1-[1-(1,3-dihydroxypropan-2-yloxy)-2-
hydroxyethyl]imidazole-4-(N-cyclohexyl)carboxamide (15f)
Amorphous solid, mp 210–213 ꢀC; nmax (neat) 3367, 3302, 1708,
(m, 10H, 5CH2); UV (MeOH) lmax 267 nm,
3¼10,800; HRESIMS calcd
1164 cmꢁ1 1H NMR dH (CD3OD) 7.33 (s, 1H, H-2), 5.59 (t, 1H,
;
for C15H24N4NaO5: 363.1644, found: 363.1635 (MþNa)þ.
J¼5.5 Hz, H-10), 3.94–3.84 (m, 2H, CH2O), 3.80–3.65 (m, 3H, CH2O,

G. Oliviero et al. / Tetrahedron 64 (2008) 6475–6481
6481
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CHN), 3.61–3.49 (m, 3H, CH, CH2O), 2.00–1.30 (m, 10H, 5CH2); UV
(MeOH) lmax 267 nm,
3
¼10,800; HRESIMS calcd for C15H26N4NaO5:
365.1801, found: 365.1810 (MþNa)þ.
4.4.23. 5-Amino-1-[1-(1,3-dihydroxypropan-2-yloxy)-2-hydroxy-
ethyl]imidazole-4-[N-((1R,2S,3R,4R)-2,3-isopropylidenedioxy)-
4-(hydroxymethyl)cyclopentyl]carboxamide (15g)
Amorphous solid, mp over 250 ꢀC (decomp.); nmax (neat) 3404,
3387, 1693, 1287, 1193 cmꢁ1; 1H NMR dH (CD3OD) 7.25 (s, 1H, H-2),
5.60(t,1H, J¼4.7 Hz, H-10), 5.20–5.17(m,1H, H-200), 4.56–5.50 (m, 2H,
H-100, H-300), 3.93–3.86 (m, 2H, CH2O), 3.80–3.67 (m, 2H, CH2O), 3.61–
3.49 (m, 5H, CH, 2CH2O), 2.36–2.10 (m, 3H, H-400, H-500a,b),1.32 (s, 3H,
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psychopharmacol. Biol. Psychiatry 2006, 30, 617–629.
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13. Ulrich,S.M.;Sallee, N.A.;Shokat, K.M.Bioorg.Med.Chem.Lett. 2002,12, 3223–3227.
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CH3),1.20 (s, 3H, CH3); UV (MeOH) lmax 268 nm,
3
¼10,200; HRESIMS
calcd for C18H30N4NaO8: 453.1961, found: 453.1969 (MþNa)þ.
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This work is supported by Bioindustry Park del Canavese SpA,
Torino, Italy in the context of the project iTECHPLAT -M. 3.4 A,
DOCUP Piemonte Region 2000/2006. The authors are grateful to the
‘Centro di Servizi Interdipartimentale di Analisi Strumentale
(CSIAS)’ for supplying the NMR facilities.
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