2′-deoxy cyclic adenosine 5′-diphosphate ribose derivatives: Importance of the 2′-hydroxyl motif for the antagonistic activity of 8-substituted cADPR derivatives

Article abstract of DOI:10.1021/jm7010386

The structural features needed for antagonism at the cyclic ADP-ribose (cADPR) receptor are unclear. Chemoenzymatic syntheses of novel 8-substituted 2′-deoxy-cADPR analogues, including 8-bromo-2′-deoxy-cADPR 7, 8-amino-2′-deoxy-cADPR 8, 8-O-methyl-2′-deoxy-cADPR 9, 8-phenyl-2′-deoxy-cADPR 10 and its ribose counterpart 8-phenyl-cADPR 5 are reported, including improved syntheses of established antagonists 8-amino-cADPR 2 and 8-bromo-cADPR 3. Aplysia californica ADP-ribosyl cyclase tolerates even the bulky 8-phenyl-nicotinamide adenine 5′-dinucleotide as a substrate. Structure-activity relationships of 8-substituted cADPR analogues in both Jurkat T-lymphocytes and sea urchin egg homogenate (SUH) were investigated. 2′-OH Deletion decreased antagonistic activity (at least for the 8-amino series), showing it to be an important motif. Some 8-substituted 2′-deoxy analogues showed agonist activity at higher concentrations, among which 8-bromo-2′-deoxy-cADPR 7 was, unexpectedly, a weak but almost full agonist in SUH and was membrane-permeant in whole eggs. Classical antagonists 2 and 3 also showed previously unobserved agonist activity at higher concentrations in both systems. The 2′-OH group, without effect on the Ca ²⁺-mobilizing ability of cADPR itself, is an important motif for the antagonistic activities of 8-substituted cADPR analogues.

Full text of DOI:10.1021/jm7010386

J. Med. Chem. 2008, 51, 1623–1636
1623
2′-Deoxy Cyclic Adenosine 5′-Diphosphate Ribose Derivatives: Importance of the 2′-Hydroxyl
Motif for the Antagonistic Activity of 8-Substituted cADPR Derivatives
Bo Zhang,† Gerd K. Wagner,† Karin Weber,‡ Clive Garnham,§ Anthony J. Morgan,§ Antony Galione,§ Andreas H. Guse,‡ and
Barry V. L. Potter*,†
Wolfson Laboratory of Medicinal Chemistry, UniVersity of Bath, Department of Pharmacy and Pharmacology, ClaVerton Down, Bath,
BA2 7AY, United Kingdom, The Calcium Signaling Group, Institute of Biochemistry and Molecular Biology I: Cellular Signal Transduction, Center of
Experimental Medicine, UniVersity Medical Center Hamburg-Eppendorf, Martinistrasse 52, D-20246 Hamburg, Germany, and Department of
Pharmacology, UniVersity of Oxford, Mansfield Road, Oxford OX1 3QT, United Kingdom
ReceiVed August 21, 2007
The structural features needed for antagonism at the cyclic ADP-ribose (cADPR) receptor are unclear.
Chemoenzymatic syntheses of novel 8-substituted 2′-deoxy-cADPR analogues, including 8-bromo-2′-deoxy-
cADPR 7, 8-amino-2′-deoxy-cADPR 8, 8-O-methyl-2′-deoxy-cADPR 9, 8-phenyl-2′-deoxy-cADPR 10 and
its ribose counterpart 8-phenyl-cADPR 5 are reported, including improved syntheses of established antagonists
8-amino-cADPR 2 and 8-bromo-cADPR 3. Aplysia californica ADP-ribosyl cyclase tolerates even the bulky
8-phenyl-nicotinamide adenine 5′-dinucleotide as a substrate. Structure-activity relationships of 8-substituted
cADPR analogues in both Jurkat T-lymphocytes and sea urchin egg homogenate (SUH) were investigated.
2′-OH Deletion decreased antagonistic activity (at least for the 8-amino series), showing it to be an important
motif. Some 8-substituted 2′-deoxy analogues showed agonist activity at higher concentrations, among which
8-bromo-2′-deoxy-cADPR 7 was, unexpectedly, a weak but almost full agonist in SUH and was membrane-
permeant in whole eggs. Classical antagonists 2 and 3 also showed previously unobserved agonist activity
at higher concentrations in both systems. The 2′-OH group, without effect on the Ca2+-mobilizing ability
of cADPR itself, is an important motif for the antagonistic activities of 8-substituted cADPR analogues.
Introduction
Although such 8-substituted cADPR analogues have been
extensively studied, one central question remains unanswered:
which structural features control the agonistic/antagonistic
activities?
Cyclic adenosine 5′-diphosphate ribose 1 (cADPR;a Figure
1) was first discovered by Lee et al.1 as a Ca2+-mobilizing
metabolite of nicotinamide adenine dinucleotide (NAD+).
cADPR is a potent second messenger,2 and its Ca2+ release is
regulated independently of the well-established inositol tris-
phosphate/Ca2+ channel,1,3 most likely by the ryanodine receptor
(RyR).4 Since its discovery, some useful cADPR derivatives
have been synthesized and biologically studied. Among these
analogues, 8-substituted derivatives, such as 8-amino-cADPR
2 and 8-bromo-cADPR 3 are antagonists of cADPR/Ca2+
signaling, and these two 8-substituted derivatives have been
widely used as biological tools in studies of cADPR-mediated
Ca2+ release.5 8-Amino-cADPR 2, as the most potent competi-
tive antagonist, has been employed in numerous studies in a
variety of biological systems, including sea urchin egg fertiliza-
tion,6 T cell activation,7 and smooth muscle8 and cardiac
myocytes.9 8-Bromo-cADPR 3, although not as potent as 2,
has also been a valuable pharmacological tool, particularly
because it has proven to be cell-permeant.10 The related 7-deaza
8-bromo-cADPR has found several biological applications as a
more attractive agent, because it is not only membrane-permeant
but also more potent in blocking Ca2+ release and more resistant
to both chemical and enzymatically-induced hydrolysis.10–13
The early finding that 8-substitution of cADPR converts
cADPR from an agonist into an antagonist seemed to indicate
that 8-substitution alone could be responsible for this activity.
This idea, however, was subsequently found not to be correct.
Shuto et al.14a reported that some 8-substituted cyclic adenosine
diphosphocarbocyclic ribose (cADPcR) analogues are agonists
rather than antagonists of Ca2+ release in sea urchin egg
homogenate, suggesting that the oxygen atom of the “northern”
ribose (Figure 1)b may also be an important structural feature,
contributing to the antagonistic activity of 8-substituted cADPR
analogues. Such a substitution in the “southern” ribose also
generated an agonist.14b A small group of N1-cyclized 8-sub-
stituted cyclic inosine 5′-diphosphoribose (cIDPR) analogues
were also synthesized in our laboratory.15,16 Some of the
compounds acted as potent agonists in Jurkat T lymphocytes,
suggesting that the 6-amino group of the adenine may also play
a part in the antagonistic effect of 8-substituted cADPR
analogues. These results indicate that the agonistic/antagonistic
activity of 8-substituted cADPR derivatives is clearly not only
governed by 8-substitution. Most likely, there is a global
cooperative conformational effect that governs the whole
process, and this can be coordinated by several structural
features. We demonstrated that modification of the 3′-hydroxyl
of the southern ribose by methylation could also induce
antagonism, at least in sea urchin homogenate.17 A recent
conformational study18 focused on the idea that antagonism by
* To whom correspondence should be addressed. Telephone: ++44-
1225-386639. Fax: ++44-1225-386114. E-mail: b.v.l.potter@bath.ac.uk.
†
University of Bath.
University Medical Center Hamburg-Eppendorf.
University of Oxford.
‡
§
a Abbreviations: cADPR, cyclic adenosine 5′-diphosphate ribose;
cADPcR, cyclic adenosine diphosphocarbocyclic ribose; cIDPR, cyclic
inosine 5′-diphosphoribose; NAD+, nicotinamide adenine dinucleotide;
TEAB, triethylammonium bicarbonate; ꢀ-NMN+, ꢀ-nicotinamide 5′-
mononucleotide; CDI, carbonyldiimidazole; TEP, triethyl phosphate; TMP,
trimethylphosphate; ADPRC, ADP-ribosyl cyclase.
b The two sugars of cADPR and analogues can be distinguished by a
“southern” and “northern” nomenclature and also adopting prime and
double-prime notation for the sugar carbons, depending upon their linkage
to either N9 or N1 of the adenine, respectively.
10.1021/jm7010386 CCC: $40.75
2008 American Chemical Society
Published on Web 02/28/2008

1624 Journal of Medicinal Chemistry, 2008, Vol. 51, No. 6
Zhang et al.
potency.5 To further explore this idea, we also synthesized
8-phenyl-2′-deoxy-cADPR 10 and its ribose counterpart 8-phen-
yl-cADPR 5. Derivatives with a bulky phenyl group at the 8
position were expected to illuminate the relation between
agonistic/antagonistic activity, potency, and the size of the
substituents in this position. In addition, we investigated the
effect of these substitutions upon the cyclization of the corre-
sponding NAD+ analogues using the ADP-ribosyl cyclase from
Aplysia californica.
Chemistry
Figure 1. cADPR structure and its numbering system.
To date, cADPR analogues have been synthesized either by
total chemical synthesis14,19 or a chemoenzymatic method.15–17
Both of the two approaches have their advantages but also
drawbacks. The major drawback of the chemoenzymatic method
is the selectivity of the Aplysia cyclase, which, although
generally promiscuous, cannot always catalyze the transforma-
tion of a NAD+ analogue into the active N1-cyclized product.
Hydrolysis or N7 cyclization is the result for some NAD+
analogues. The total synthetic approach works efficiently for
producing carbocyclic cADPcR and other analogues, but just
to produce a single analogue, the synthetic route is rather long
and difficult.
The earliest reported synthesis of 8-substituted cADPR
analogues was through the chemoenzymatic approach, demon-
strating the high substrate tolerance of the Aplysia cyclase.23
As we showed earlier that 2′-deoxy-NAD+ is also recognized
as a substrate by this enzyme,17 we sought to adopt this method
in the present study for the preparation of 8-substituted 2′-deoxy-
cADPR analogues by incubation of the corresponding NAD+
derivatives with Aplysia ADP ribosyl cyclase. The required
NAD+ analogues can be synthesized by coupling the relevant
nucleotides with nicotinamide 5′-mononucleotide (ꢀ-NMN+).
Of the cADPR analogues targeted in this study (Figure 2),
the 8-bromo-substituted analogues are the most convenient to
synthesize, because bromination of nucleotides has been widely
reported in many publications and can be achieved in one step
in high yield. On the basis of this consideration, Wagner et al.16
reported a rapid synthetic route toward a limited number of
8-substituted N1-cIDPR derivatives. This approach was centered
on the cyclic inosine 5′-diphosphate ribose (cIDPR) analogue
8-bromo-cIDPR, from which syntheses of other cIDPR ana-
logues were achieved by replacement of bromine with other
nucleophiles or by a Suzuki cross-coupling reaction. However,
this approach relies heavily on the excellent and unusual stability
of N1-cIDPR analogues and is therefore not applicable in our
case, because cADPR analogues are known to undergo rapid
hydrolysis at the N1-C1′′ linkage at raised temperatures. The
8-bromo-NAD+ analogues are also not ideal for any chemical
reactions, because the NAD+ molecules are prone to lose the
nicotinamide moiety even at ambient temperature. 8-Bromo-
nucleotides 12 and 13 are stable under basic conditions and even
at elevated temperatures, allowing us to follow the above
strategy by employing 12 and 13 as the initial building blocks,
from which 8-azido-, 8-amino-, 8-O-methyl-, and 8-phenyl-
substituted nucleotides were synthesized in one or two steps
(Scheme 1).
Figure 2. Structures of the cADPR analogues discussed in the text.
such a 3′-hydroxyl-methylated cADPR analogue might be
related to an altered “backbone” conformation, but the evidence
was not sufficient to establish this idea. More importantly, it is
not known what conformation cADPR analogues may adopt
when they actually bind to their receptor. Other work19,20
explored radical structural modifications of the northern ribose
in particular, but only agonistic activities were observed.
Modification of the pyrophosphate system led to potent agonist
activity for a triphosphate analogue of cADPR,21 and phospho-
nate analogues showed decreased agonist activity.22 The above
results illustrate that the global structural features that control
the agonistic/antagonistic activity of 8-substituted cADPR
derivatives are far from clear and thus encouraged us to pursue
further structure-activity relationship (SAR) studies on this class
of molecule.
Among southern ribose-modified analogues, 2′-deoxy-cADPR
was first synthesized by Ashamu et al.17 and is almost as potent
as cADPR in mediating Ca2+ release from cADPR-sensitive
stores in sea urchin egg homogenates, indicating that 2′-OH
deletion has no or little effect on the agonistic activity of
cADPR, at least in the invertebrate assay system. It was not
demonstrated, however, whether such a deletion might also
potentially affect antagonistic activity. Because deletion of the
2′-OH group also decreases hydrophilicity, this modification
might be expected to improve membrane permeability in
8-substituted compounds, which would be highly desirable for
pharmacological intervention.
To improve our understanding of SAR in this class of
8-substituted cADPR analogues, we have designed, synthesized,
and biologically evaluated a group of as yet unexplored
8-substituted 2′-deoxy-cADPR derivatives (Figure 2). This series
of new cADPR analogues includes 8-bromo-2′-deoxy-cADPR
7 and 8-amino-2′-deoxy-cADPR 8, the 2′-OH deleted version
of the well-established antagonists 2 and 3, and 8-O-methyl-
2′-deoxy-cADPR 9, whose parent compound 8-O-methyl-
cADPR 4 was also exploited previously as an antagonist in T
lymphocytes.12 It was suggested that substitution with a large
group at the 8 position might result in a decrease in antagonistic
The starting building blocks, 8-bromo-AMP analogues 12 and
13, were synthesized using the protocol of Ikehara et al.24,25
Purification using reverse-phase chromatography gave 12 and
13 as their triethylammonium salts in 85 and 55% yield,
respectively. Nair et al.26 reported that treatment of 8-bromo-
2′-deoxyadenosine with NaN3 gave the desired 8-azido-2′-
deoxyadenosine in good yield. Application of this reaction to

2′-Deoxy cADPR DeriVatiVes
Journal of Medicinal Chemistry, 2008, Vol. 51, No. 6 1625
Scheme 1. Syntheses of 8-Substituted Nucleotides from the Bromo Analoguesa
a Reagents and conditions: (a) NaN3, H2O/DMF (20%, v/v), 80 °C, (b) 1,4-dithiol-(D,L)-threitol, 0.05 M TEAB buffer (pH 8), room temperature, (c)
NaOMe, MeOH, refluxing, and (d) Pd(PPh3)4, phenylboronic acid, Na2CO3, 2:1 MilliQ/MeCN, 80 °C. Compounds 12-18 are in their triethylammonium
salt form.
Scheme 2. Synthesis of 8-O-Methyl-2′-deoxy-AMPa
nucleosides are more likely to undergo hydrolysis in acidic
conditions than their ribose counterparts.29 This is probably due
to the reason that, under acidic conditions, a 2′-deoxy-nucleoside
may form a more stable oxonium intermediate at the ribosyl
C-1′ position, thus facilitating a rapid hydrolysis. Because of
the lack of acid stability, phosphorylation of 20 using the
conventional POCl3/TEP method30 is problematic, because this
method requires an aqueous workup, which will result in an
acidic solution. It was indeed found that the 8-substituted 2′-
deoxy-AMP that formed in the phosphorylation reaction de-
a Reagents and conditions: (a) NaOMe, MeOH, refluxing and (b) POCl3,
TMP, -20 °C. Compound 16 is in the triethylammonium form.
graded rapidly during the aqueous workup (data not shown).
Different buffer solutions were attempted in the aqueous workup
the 8-bromonucleotide 13 in our case, however, was found not
to be successful because the starting material 13 formed a
stage, including TEAB buffer and H2O/pyridine, but all failed.
sodium salt upon treatment with NaN3, which precipitated from
We later found that quenching the phosphorylation reaction by
the reaction medium (DMF), thus blocking the progress of the
the addition of ice, followed immediately by neutralization with
reaction. To solve this problem, a H2O/DMF mixture was used.
a solution of NaOH could effectively decrease the degradation
The sodium salt that formed was successfully solubilized in this
of the product. Thus, purification using reverse-phase chroma-
polar solvent system, and the reaction was complete after heating
tography combined with ion-exchange chromatography gave the
overnight. The reaction process could not be monitored by
desired compound 16 in its triethylammonium form, albeit not
HPLC because 14 has the same retention time as the starting
bromo compound 13 in our solvent system. Instead, the reaction
in high yield.
Verlinde et al. demonstrated that 8-phenyl-adenosine could
be produced via the Stille-type cross-coupling reaction of a
protected 8-bromo-adenosine.31 A Suzuki cross-coupling reac-
tion was also recently reported,32,33 facilitating the synthesis of
8-phenyl-nucleosides from the corresponding unprotected 8-bro-
mo-nucleosides. In general, the Suzuki-type coupling reactions
are easier to handle than the Stille type because they work under
moist or even aqueous solutions and they tolerate the presence
of some unprotected functional groups, e.g., the hydroxyl group
on the nucleoside ribose. Wagner et al.16 reported a synthesis
of 8-phenyl-cIDPR from 8-bromo-cIDPR by adaptation of the
Suzuki cross-coupling reaction, demonstrating the wider ap-
plication of this reaction to stable nucleotide-type compounds.
In the light of this result, it was expected that Suzuki-Miyaura
conditions would be compatible with the use of unprotected
nucleotides, such as 8-bromo-AMP 12, and two examples for
the Suzuki-Miyaura reaction of unprotected nucleotides have
indeed been reported during the course of this study.34,35
Compound 12 dissolved in a MilliQ water/MeCN mixture was
treated with Na2CO3, phenylboronic acid, and the palladium
catalyst Pd(PPh3)4 under an argon atmosphere at 80 °C for 3 h
(Scheme 1). HPLC analysis indicated that most of the starting
material had been consumed and that a new product had formed
was monitored by changes in the maximum UV absorption
(UVmax). A clear shift from 262 to 282 nm was noticed,
indicating the formation of 14.27 Reduction of azido 14 into
amino 15 was achieved using a dithiothreitol (DTT)-mediated
reduction.27,28 The DTT-mediated reduction is normally per-
formed in aqueous solution at near neutral pH and room
temperature. This reaction is thus ideal for reducing polar and
unstable molecules, for example, the 8-azido-nucleotides in our
case. Treatment of 14 with DTT in TEAB buffer in the dark
overnight and purification using reverse-phase chromatography
gave 15 in 39% isolated yield based on bromo compound 13.
A shift of UVmax from 281 to 274 nm was noticed in this
experiment consistent with the observation of Armstrong et al.27
Attempts to produce 8-methoxy-2′-deoxy-AMP 16 by treatment
of 13 with NaOMe failed, because the addition of NaOMe
transformed 13 into its sodium salt, which was not soluble in
the reaction solvent MeOH. The addition of water to the reaction
system was not feasible, because this reaction requires anhydrous
conditions. 8-OMe-2′-deoxy-adenosine 20, however, could be
synthesized by treatment of 8-bromo-2′-deoxy-adenosine 19 with
NaOMe in over 90% yield26 (Scheme 2). This encouraged us
to perform a phosphorylation reaction on this compound to
pursue a synthesis of the desired 16. It is known that 2′-deoxy-

1626 Journal of Medicinal Chemistry, 2008, Vol. 51, No. 6
Zhang et al.
Scheme 3. Syntheses of 8-Substituted 2′-Deoxy-NAD+ Analogues Using the CDI Methoda
a Reagents and conditions: (a) CDI, TEA, room temperature, anhydrous DMF and (b) anhydrous DMF, 2 days. Compounds 21-23 are in the
triethylammonium form.
Scheme 4. Syntheses of NAD+ Analogues Using a Lewis-Acid-Mediated Condensationa
a Reagents and conditions: (a) PPh3, dipyridyl disulfide, morpholine, DMSO, room temperature and (b) MnCl2/formamide (0.2 M), MgSO4, ꢀ-NMN+,
room temperature. Compounds 29-32 are in their triethylammonium form.
with a retention time of 12.10 min. Purification using reverse-
phase chromatography gave the desired 8-phenyl-AMP 17 in
55% yield as its triethylammonium salt, showing a multiplet
(integration 5H) at the aromatic region of its 1H NMR spectrum,
representing the phenyl group. It was also noticed that the UVmax
of the phenyl compound migrated to ca. 276 nm, consistent with
the report by Wagner et al.16 8-Phenyl-2′-deoxy-AMP 18 was
synthesized in the same manner. In this case, an excess of
phenylboronic acid (4 equiv) and Pd(PPh3)4 was added in two
stages to the reaction to drive it to completion. RP-HPLC
indicated that the starting material had been nearly 100%
consumed and that a new compound at 13.7 min was seen as
the sole product. Purification using reverse-phase media,
however, gave a mixture of the desired compound 18 as its
triethylammonium salt (92% yield by 1H NMR) and remaining
phenylboronic acid, suggesting that the RP system might not
work efficiently to separate these two compounds, which have
close polarities. The mixture was not further purified but was
directly used in the next step to produce the corresponding
morpholidate (as shown in Scheme 4). It was found that the
impurity phenylboronic acid was easily removed at the mor-
pholidate step, because it possibly formed a morpholinium salt
that dissolved in acetone and was therefore removed in the
filtrate together with other reagents, such as triphenylphosphine
or dipyridyl disulfide.
The 8-substituted 2′-deoxy-NAD+ analogues were first
synthesized by a carbonyldiimidazole (CDI)-mediated conden-
sation between the above 2′-deoxy nucleotides and ꢀ-NMN+.
An active species b was formed in this reaction as shown in
Scheme 3.36,37 In general, ꢀ-NMN+ a was first treated with
triethylamine (TEA) and then with an excess of CDI in
anhydrous DMF to provide the activated intermediate b,
showing a characteristic singlet at ca. -9.0 ppm in the 31P NMR
spectrum. After the remaining CDI had been quenched by the
addition of methanol, the intermediate was treated with the
relevant nucleotide in anhydrous DMF to form the desired
NAD+ analogue. 8-Bromo-2′-deoxy-AMP 13 was thus treated
with the intermediate b in anhydrous DMF for 2 days.
Purification of product using ion-exchange chromatography gave
the desired 8-bromo-2′-deoxy-NAD+ 21 in 31% yield as its
triethylammonium salt, showing a triplet at 6.38 ppm and a
doublet at 5.98 ppm in the 1HNMR spectrum, representing the
H-1′ and H-1′′ anomeric protons, respectively. In the 31P NMR
spectrum, two doublets were seen at -11.17 and -10.53 ppm,
indicating the formation of the pyrophosphate bond. 8-Amino-
2′-deoxy-NAD+ 22 and 8-O-methyl-2′-deoxy-NAD+ 23 were
synthesized in the same manner. Purification using ion-exchange
chromatography gave compounds 22 and 23 both in ca. 40%
isolated yield.

2′-Deoxy cADPR DeriVatiVes
Journal of Medicinal Chemistry, 2008, Vol. 51, No. 6 1627
Lee et al.38 reported that NAD+ analogues could be synthe-
sized by a Lewis-acid-mediated condensation between activated
phosphoromorpholidates and ꢀ-NMN+. This method has been
successfully used recently to synthesize 8-substituted NHD+
analogues in high yield.15,16 8-Bromo-2′-deoxy-AMP morpholi-
date 24 was produced from compound 13 (triethylammonium
salt) by treatment with PPh3, morpholine, and dipyridyl disulfide
(Scheme 4).39 Workup of this reaction gave the desired 24 as a
yellow solid in 72% yield, showing a characteristic singlet at
8.20 ppm in the 31P NMR spectrum, representing the formation
of morpholidate. The successful synthesis of 24 suggested that
the Lewis-acid-mediated condensation could also be used to
produce 2′-deoxy-NAD+ analogues. Thus, morpholidates 25-28
(Scheme 4) were synthesized and then condensed with ꢀ-NMN+
in the presence of Lewis acid (MnCl2) in formamide. Purification
using reverse-phase chromatography gave the desired dinucle-
otides, 8-bromo-NAD+ 29, 8-amino-NAD+ 30, 8-phenyl-NAD+
31, and 8-phenyl-2′-deoxy-NAD+ 32 as their triethylammonium
salts.
Table 1. Conformational Analysis of 8-Substituted cADPR/
2′-Deoxy-cADPR Analoguesa
R
compound C2′-endo (%) (10J1′,2′
)
H-2′ (ppm)
∆
H-2′
syn/anti
2
3
5
7
8
9
10
56
53
60
5.36
5.35
5.56
3.20 (H-2′a)
3.19 (H-2′a)
3.19 (H-2′a)
3.46 (H-2′a)
0.92
0.91
1.12
0.40
0.39
0.39
0.66
syn
syn
syn
syn
syn
syn
syn
62–67
66–69
64–68
70
a
∆H-2′ values represent the difference between the chemical shift of H-2′
of the above cyclic compounds and H-2′ of AMP or 2′-deoxy-AMP. H-2′
chemical shifts for AMP and 2′-deoxy-AMP are 4.62 and 2.80 (H-2′a),
respectively. Inset shows key descriptors of nucleoside and nucleotide
conformation.
8-Substituted NAD+ analogues 21–23 and 29-32 were then
incubated with Aplysia ADP-ribosyl cyclase. Purification of
products using ion-exchange chromatography gave the desired
8-substituted cADPR analogues 2, 3, 5, and 7–10 (Figure 2) as
the triethylammonium salts. The cyclic structures of these
determined the preferred conformation of the southern ribose
for all of the new 8-substituted cADPR/2′-deoxy-cADPR
analogues. The results from our analysis are summarized in
Table 1. We find that, while the substituent in position 8 has
some influence on the conformation of the southern ribose
(compare, e.g., 8-amino cADPR 2, 8-bromo cADPR 3, and
8-phenyl cADPR 5), the 2′-deoxy cADPR analogues in this
series generally adopt the C2′-endo conformation to a higher
percentage than their ribose counterparts, irrespective of the
nature of the substituent in position 8 (2 versus 8, 3 versus 7,
and 5 versus 10). This slight difference regarding the conforma-
tion of the southern ribose in 2′-deoxyribo and ribo nucleotides
has also been observed for analogues unsubstituted at position
8, e.g., 2′-deoxy AMP (63–68% C2′-endo) and AMP (52% C2′-
endo).
1
cADPR analogues were confirmed by the H NMR spectrum:
(1) the aromatic peaks at 8–9 ppm representing nicotinamide
had disappeared, indicating the cleavage of the nicotinamide
moiety in this reaction; (2) two doublets were observed at ca.
6.0 ppm, representing both the H-1′ and H-1″, demonstrating
that these two riboses were connected to the purine base by a
glycosyl bond. The enzymatic reaction was monitored by ion-
pair HPLC. It was found that the above NAD+ analogues were
turned over by the Aplysia cyclase at a roughly similar rate to
that of NAD+ itself. The fact that 8-phenyl-NAD+ and 8-phenyl-
2′-deoxy-NAD+ were also quickly converted by the Aplysia
cyclase into the corresponding cyclic compounds further
indicates, perhaps somewhat surprisingly, that the enzyme has
excellent tolerance toward even very large substituents at the 8
position. Direct chemical modification of an already cyclized
precursor was required to achieve a similar end in the cIDPR
series,15 and a similarly bulky 8-S-phenyl cADPcR derivative
was earlier synthesized by a total synthetic route and, at high
concentrations, appeared to act as a competitive antagonist.14
In cADPR, the adenine base is oriented in the syn conforma-
tion both in the crystal structure, with a torsion angle ꢁ of 64
((1)° about the glycosidic bond,43 and in solution.18,42 The
chemical shift of the H-2′ signal has been identified as an
indicator for the position of the syn/anti equilibrium in nucleo-
sides and nucleotides, and a significant downfield shift of the
H-2′ signal is regarded as indicative of the predominance of
the syn conformer.44,45 In cADPR, H-2′ experiences a downfield
shift of 0.59 ppm compared to AMP, a nucleotide that exists
predominantly in the anti form.44 We observed a similar
Conformational Analysis. To identify the bioactive confor-
mations of the new cADPR analogues, knowledge of their
solution structures is required. We have extracted information
about the conformation of important partial structures for all
8-substituted cADPR/2′-deoxy-cADPR analogues from their 1H
NMR spectra in D2O. Of particular interest in the context of
this study were potential conformational changes in the southern
ribose, resulting from structural modification of positions 2′ and
8. In solution, the furanose in nucleosides and nucleotides
generally exists in a conformational equilibrium between the
C2′-endo (S type) and C3′-endo (N type) form (Table 1). In
addition, the nucleobase can be oriented toward (syn) or away
from (anti) the ribose ring, depending upon the torsion angle ꢁ
about the glycosidic bond. It is apparent that these local
conformational changes also affect the global conformation and
overall shape of the molecule.
1
downfield shift for the H-2′ signal in the H NMR spectra of
all of the new 8-substituted cADPR/2′-deoxy-cADPR analogues
compared to AMP or 2′-deoxy-AMP (Table 1). These results
confirm that all of the new cADPR analogues adopt a global
conformation characterized by the syn orientation of the
nucleobase, similar to that of cADPR itself. This finding is not
unexpected. Linear dinucleotides with bulky substituents at
position 8 frequently adopt the syn conformation, because of
the nonbonded repulsion between the substituent in position 8
and the ribose ring,46,47 and the conformational constraints
imposed by the macrocycle in cADPR and similar molecules
strongly disfavor the anti conformation.
While both 2′-deoxy and ribo analogues in the present series
seem to share the same global conformation, we did find,
however, that values for ∆H-2′ were generally lower for the 2′-
deoxy analogues than for the ribo derivatives. This suggests
that, although the syn conformation is preferred in both classes
For nucleosides and nucleotides, the magnitude of the
H1′-H2′ coupling constant is directly correlated to the ratio of
the C2′-endo/C3′-endo conformers.40–42 Altona et al. have
shown that the percentage of the C2′-endo population can be
40
estimated by taking 10J1′2′
.
Using Altona’s approach, we

1628 Journal of Medicinal Chemistry, 2008, Vol. 51, No. 6
Zhang et al.
weak antagonists of Ca2+ release, as are 8-bromo-2′-deoxy
cADPR 7 and 8-bromo cADPR 3. On the other hand, in the
case of the 8-amino congeners (8 versus 2), removal of the 2′-
OH group does result in a 30-fold reduction in potency (8, IC50
value of approximately 6 µM; 2, IC50 value of approximately
0.2 µM; Figure 3A). None of the cADPR analogues antagonized
Ca2+ release induced by Ins(1,4,5)P3 (inset in Figure 3A).
These results suggest that there is a role for the 2′-hydroxyl
group in antagonizing cADPR-induced calcium release in T cells
and that this role seems to be modulated by the nature of the
substituent in position 8. Both 8-amino compounds 2 and 8
preferentially adopt a C2′-endo conformation at the southern
ribose and a syn conformation about the N9-glycosyl linkage
(see above and Table 1). This probably indicates that the
different antagonistic activity of compounds 2 and 8 is not
caused by a different global conformation or a different
conformation of the southern ribose. There is, however, the
possibility that subtle conformational differences between the 8-
substituted 2′-deoxy cADPR analogues and their ribose coun-
terparts, e.g., in the torsion angle ꢁ, may explain the differential
biological effects seen for compounds 2 and 8. Alternatively,
these differential biological effects may result from differential
hydrogen-bonding patterns, and this possibility will be discussed
in more detail below.
Ca2+ Release Agonism in Jurkat T Cells. At 100 µM
concentration, all of the analogues tested in this series
(including the well-documented antagonists 8-bromo and
8-amino-cADPR23,6–10) stimulate Ca2+ release in Jurkat T
cells, albeit less strongly than the parent cADPR (Figure 3B).
It is noteworthy that this is the first report of the agonistic
properties of these analogues at higher concentrations. In
previous studies, these compounds had been used mostly at
concentrations of 10 µM and below, possibly because of their
limited availability, which may explain why their agonistic
effects had not previously been observed (for discussion Vide
infra).
The most potent agonists in the present study belong to the
2′-deoxyribo series (e.g., 7-deaza-2′-deoxy cADPR 11, 8-amino-
2′-deoxy cADPR 8, and 8-methoxy-2′-deoxy cADPR 9),
although the 2′-deoxyribo analogues are not generally more
potent than the ribo analogues. In those cases that allow a direct
comparison between the 2′-deoxyribo and ribo series (8-phenyl,
8-bromo, and 8-amino), little difference in activity was observed
for the 8-phenyl (10 versus 5) and 8-bromo (7 versus 3) pairs,
respectively, while the 8-amino pair of compounds once again
defies this trend. At a 100 µM concentration, 8-amino-2′-deoxy
cADPR 8 stimulates Ca2+ release more potently than 8-amino
cADPR 2 (Figure 3B). It was noticed that analogues with a
large phenyl substitutent at position 8 could also induce Ca2+
release, suggesting that the binding site of the receptor is
relatively tolerant to the size of a substitutent at this position.
This may suggest that cADPR could be attached to a tether at
this position while still retaining binding affinity, and such a
ligand could be used in, e.g., an affinity chromatography column
to detect and purify the cADPR receptor, etc.
Figure 3. Effects of cADPR analogues on Ca2+ release in permeabi-
lized Jurkat T cells. (A) Antagonist activities of 8-amino-cADPR (IC50
value of approximately 0.2 µM), 8-amino-2′-deoxy-cADPR (IC50 value
of approximately 6 µM), 8-O-methyl-2′-deoxy-cADPR (IC50 value of
approximately 8 µM), and 8-bromo-cADPR (IC50 value of ap-
proximately 10 µM) toward Ca2+ release induced by 30 µM cADPR
in permeabilized Jurkat T cells. The ryanodine receptor antagonist
ruthenium red blocked approximately 70% of Ca2+ release evoked by
cADPR. The inset shows the effect of 100 µM of the cADPR analogues
on Ca2+ release induced by InsP3 (4 µM). (B) Ca2+ release activity of
the 8-substituted cADPR analogues in permeabilized Jurkat T cells.
Jurkat T cells were permeabilized, and [Ca2+] was determined using
fura2 fluorescence as described in the Experimental Section.
of compounds, the torsion angle ꢁ of the 2′-deoxy analogues
may be slightly different from the ribose compounds.
Biological Results
Ca2+ Release Antagonism in Jurkat T Cells. First, we
investigated the effect of the new cADPR analogues on cADPR-
mediated Ca2+ release in permeabilized T Jurkat cells. Under
these conditions, the known antagonist 8-amino cADPR 223
inhibits Ca2+ release with an IC50 value of approximately 0.2
µM (Figure 3A). By comparison, all other analogues in this
series, including all of the new 2′-deoxy derivatives, displayed
decreased potency (e.g., 8-amino-2′-deoxy cADPR 8, IC50 value
of approximately 6 µM; 8-methoxy-2′-deoxy cADPR 9, IC50
value of approximately 8 µM; Figure 3A). Interestingly, in the
case of the 8-phenyl (10 versus 5) and the 8-bromo (7 versus
3) derivatives, there is little difference between the 2′-deoxyribo
and the ribo congeners with regard to their inhibitory activity.
Both 8-phenyl-2′-deoxy cADPR 10 and 8-phenyl cADPR 5 are
When these results are taken together, they may suggest an
important role for hydrogen bonding in determining the bioac-
tivity of cADPR and its analogues. Only in those cases where
hydrogen bonding is possible between hydrogen donors at
position 8 and the cADPR receptor have we found a clear
difference in bioactivity for the 2′-deoxyribo and ribo analogues
(8-amino-2′-deoxy cADPR 8 versus 8-amino cADPR 2), at least
in T cells. In those cases, where no such hydrogen bonding is
possible (8-phenyl and 8-bromo) differences in bioactivity

2′-Deoxy cADPR DeriVatiVes
Journal of Medicinal Chemistry, 2008, Vol. 51, No. 6 1629
between the 2′-deoxyribo and ribo analogues are negligible. This
trend holds for both agonistic and antagonistic behavior. At 100
µM, 8-amino-2′-deoxy cADPR 8 is a more potent agonist
(partial agonist) of cADPR-mediated Ca2+ release than 8-amino
cADPR 2. Conversely, at 1 µM concentration, 8-amino cADPR
2 is a much more potent antagonist than 2′-deoxy-8-amino
cADPR 8. Furthermore, the 2′-hydroxy group may be involved
in direct interactions with the receptor, e.g., as a hydrogen-
bonding acceptor, similar to what has been suggested for the
3′-hydroxy group.17 In sea urchin homogenates, it was found
that 3′-OMe-cADPR blocked the cADPR-induced Ca2+ release
in a concentration-dependent manner, while 3′-deoxy-cADPR
was inactive, suggesting the 3′-OH as an important motif for
binding to the receptor.17 The amino substitutent at position 8
together with the 2′-hydroxyl group may be cooperative in
interacting with the receptor by hydrogen bonding, and impor-
tantly, both groups are probably required for the outstanding
antagonistic activity of 2. Thus, the deletion of the 2′-OH
consequently results in the breakdown of the cooperative
hydrogen bonding, and this probably explains the differential
bioactivities for analogues 2 and 8.
Removing the 2′-hydroxyl group and the resulting breakdown
of any intermolecular hydrogen bond at this position may further
affect Ca2+-release activities. However, in the T-cell system,
7-deaza-2′-deoxy-cADPR 1111b (Figure 3B), similar to its ribose
counterpart 7-deaza-cADPR,48 acted as a partial agonist,
consistent with the previous conclusion that, for inducing
calcium release, a 2′-hydroxyl group is not crucial. The fact
that compound 11 does not exhibit any antagonistic activity
further demonstrated that substitution at the 8-position is indeed
one of the key requirements for antagonistic activity.
Ca2+ Release in Sea Urchin Egg Homogenates (SUH).
Many cADPR analogues were investigated in the invertebrate
sea urchin egg homogenate (SUH) system, suggesting that the
SUH system may be more suitable to test our 8-substituted 2′-
deoxy-cADPR analogues. Thus, 8-amino-2′-deoxy-cADPR 8
and the ribose derivative 2 were evaluated in the SUH system
(Figure 4). In agreement with observations in T cells,
8was found to be a weaker antagonist, but it was only 2 times
less potent than its ribose counterpart 2. In comparison to the
results in T cells, the effect of 2′-OH deletion in this case was
less significant. Nevertheless, this combined with the results in
T cells could lead to the conclusion that the 2′-OH group is
indeed an important motif for the antagonistic activity, at least
for the 8-amino-cADPR derivatives. Removal of the 2′-OH
group will result in a decrease of antagonistic activity in both
SUH and T-cell systems. Compounds 2 and 8 in SUH were
both found to be agonists at high concentrations as observed in
T cells (Figure 4), and their potencies for mobilizing Ca2+ are
shown in Table 2.
As shown in the concentration–response curve (Figure 4),
the plateau for 8 could not be defined, suggesting that this
compound, unlike the ribose analogue 2, is possibly a full
agonist. Indeed, when 8-bromo-2′-deoxy-cADPR 7 was evalu-
ated for Ca2+-releasing activity in SUH, it was found, surpris-
ingly, that 7 is a weak but almost full agonist (Figure 5A). It
was also noticed that 7, similar to cADPR itself, cross-
desensitized the Ca2+ release by 500 nM cADPR (Figure 5A).
The interesting activity of 7 seems to corroborate our observation
that, in T cells, 2′-OH deletion of the 8-substituted cADPR
analogues may result in better partial agonists. Because 8-bromo-
cADPR 3 is known to be cell-permeant, it is thus expected that
compound 7 may also have this property. Incubation of
8-bromo-2′-deoxy-cADPR 7 with intact sea urchin eggs pre-
Figure 4. Comparison of the biological activities of 8-amino-cADPR
and 8-amino-2′-deoxy-cADPR. (A) 8-NH2-2′-deoxy cADPR 8, (B)
8-NH2-cADPR 2, and (C) comparison of 8-NH2-2′-deoxy cADPR 8
and 8-NH2-cADPR 2.
loaded with the Ca2+ dye rhod dextran revealed that 7 is indeed
cell-permeant (Figure 5B); the Ca2+ response is relatively small,
oscillatory, and cortical compared to that elicited by sperm but

1630 Journal of Medicinal Chemistry, 2008, Vol. 51, No. 6
Zhang et al.
Table 2. Comparison of the Agonistic and Antagonistic Potency of
Compound 2 with 8
compound
EC50
IC50
8-amino-cADPR 2
89 µM (69–116)
0.105 µM
(0.088–0.126)
0.22 µM
8-amino-2′-deoxy-cADPR 8 >89 µM (plateau not
defined, constraining
(0.16–0.3)
to 100% gives
89 µM (73–108)
significant (interestingly, this is similar to the small oscillatory
responses to 5 mM caffeine; data not shown). This result for 7
in intact cells is thus rather promising, and it suggests that further
structural modification on this compound could potentially lead
to a potent membrane-permeable agonist, which would be a
useful tool in the armamentarium to study the role of cADPR
in Ca2+ release from intracellular stores (Vide infra). While there
have been useful membrane-permeant antagonists available for
some time, there is as yet no highly potent membrane-permeant
agonist. A few other agents to date have shown promise in this
regard, such as 2′′,3′′-dideoxydidehydro-cADPcR.42 This com-
pound however only works efficiently in the T lymphocyte but
not in the SUH system. Zhang et al.19,20 reported that replace-
ment of the ribose moiety with an ether bridge could lead to
promising membrane-permeant agents, but these compounds are
still only weak agonists. 8-bromo-N1-cIDPR was also found to
be a cell-permeant agonist in T-lymphocytes, but the agonistic
effect was also weak.49
Observation of Ca2+ release activity for analogues, particu-
larly for the classical antagonists 2 and 3, at higher concentration
in both the Jurkat T cell and SUH systems (Figure 4 and Table
2) is surprising and has not been previously noted. These data
may indicate two sites of action of differing affinity, e.g., a lower
affinity nucleotide-binding site distinct from the high-affinity
cADPR one. There are precedents for low-affinity nucleotide-
binding sites, which cause Ca2+ release both at RyR,50 the lower
affinity site leading to activation of the channel, and also for
the inositol trisphosphate receptor51 that could potentially be
involved here. This site could be nonselective, e.g., an ATP-
binding site.52 While this interpretation is necessarily only
speculative at present, our data should stimulate further experi-
ments to explore this effect.
Figure 5. (A) Ca2+ mobilization induced by cADPR and 8-bromo-
2′-deoxy-cADPR in sea urchin egg homogenate. 8-Bromo-2′-deoxy-
cADPR 7 shows weak but almost full agonistic activity (green line)
and cross-desensitizes the Ca2+ mobilization by cADPR (black line).
The agonistic result is compared to cADPR (blue and red lines). (B)
Agonistic effect of 8-bromo-2′-deoxy-cADPR in intact sea urchin eggs.
The figure shows the Ca2+ release in response to the indicating
concentrations of the 8-bromo-2′-deoxy-cADPR 7 in sea urchin eggs
microinjected with the Ca2+ dye rhod dextran (10 µM intracellular
concentration). The image is F/F0, where blue is low Ca2+ and red is
Conclusions
We have synthesized a group of 8-substituted cADPR/2′-
deoxy-cADPR analogues using chemoenzymatic methodology.
Biological evaluation of these 8-substituted cADPR/2′-deoxy-
cADPR analogues revealed that, at least for the 8-amino series,
2′-OH deletion resulted in a decrease of the antagonistic activity
in both T cells and in sea urchin egg homogenates. This suggests
that the 2′-OH group, although it has no effect on the Ca2+
-
high Ca2+
.
mobilizing ability of cADPR itself, is an important motif for
the antagonistic activities of 8-substituted cADPR analogues.
2′-OH deletion may also result in an increase in the agonistic
effects of the 8-substituted cADPR analogues as shown by our
studies in both T cells and sea urchin egg systems. A biological
study of 8-bromo-2′-deoxy cADPR 7 in intact sea urchin eggs
reveals that 7 is not only essentially a full agonist but is also
cell-permeant, indicating that 7 might be a potential lead
compound toward the design of a potent membrane-permeable
cADPR receptor agonist. For the first time, agonist activity at
higher concentrations was observed in two diverse systems for
the classical cADPR receptor antagonists 8-bromo-cADPR and
8-amino-cADPR, raising the possibility that, in both systems,
there could be a lower affinity nucleotide-binding site that could
contribute to Ca2+ mobilization, possibly distinct from the high-
affinity cADPR site.
Experimental Section
General Procedure. All reagents and solvents were of com-
mercial quality and were used directly unless otherwise described.
A. californica ADP-ribosyl cyclase was purchased from Sigma-
Aldrich Company Ltd., Gillingham, U.K. Triethylamine was dried
over potassium hydroxide, distilled, and kept over potassium
hydroxide under argon for use in the CDI-coupling reactions.
Morpholine was distilled and stored over potassium hydroxide, and

2′-Deoxy cADPR DeriVatiVes
Journal of Medicinal Chemistry, 2008, Vol. 51, No. 6 1631
MnCl2/formamide (0.2 M) was dried over molecular sieves (4 Å)
for over 4 days. H2O was of MilliQ quality. 1H, 13C, and 31P NMR
spectra were collected in DMSO or D2O, on either a JEOL Delta
at 270 MHz (1H), 68 MHz (13C), or 109 MHz (31P) or a Varian
Mercury-vx machine at 400 MHz (1H) or 100 MHz (13C).
Abbreviations for splitting patterns are described below: s (singlet),
d (doublet), t (triplet), m (multiplet), etc. UV spectra were collected
on either a Perkin-Elmer Lambda EZ 201 or a Lambda 3B
spectrophotometer. Low-resolution FAB- mass spectra were re-
corded on a Micromass Autospec instrument on samples in a
m-nitrobenzyl alcohol matrix at the Mass Spectrometry Centre,
University of Bath. Accurate mass was recorded either by the Mass
Spectrometry Centre at the University of Bath or from the EPSRC
National Mass Spectrometry Service Centre at the University of
Swansea. HPLC analysis was carried out on a Waters 2695 Alliance
module equipped with a photodiode array detector, a Hichrom
Guard column, and a Phenomenex Synergi 4 µm MAX-RP 80A
column (150 × 4.6 mm). Phosphate buffer [45% (v/v), pH 6.4] in
MeOH containing 0.17% (m/v) of cetrimide was used as the solvent
system, and samples were eluted at 1 mL/min and monitored at
254 nm. All nucleotides were purified on a Pharmacia Biotech
Gradifrac system with a P-1 pump and a UV optical unit (280 nm).
The following purification methods were employed: (a) synthetic
phosphates were loaded on the Q Sepharose ion-pair column
(saturated with MilliQ water) and were eluted with a gradient of
0–50% 1 M TEAB (pH 7.1–7.6) against MilliQ water, and (b)
compound was loaded on a LiChroprep RP-18 column which was
saturated with 0.05 M TEAB buffer (pH 6.0–6.4) and eluted with
a gradient of 0–30% MeCN against 0.05 M TEAB buffer. Cyclic
products were quantified using an Ames phosphate assay,53 from
which the extinction coefficients were calculated and used to
precisely quantify the concentration of biological solutions.
Determination of Ca2+ Release in Permeabilized T Cells.
Jurkat T cells were permeabilized by saponin, and experiments were
performed as described in an earlier report.54 Briefly, cells were
incubated with saponin in an intracellular buffer (20 mM HEPES,
110 mM KCl, 2 mM MgCl2, 5 mM KH2PO4, and 10 mM NaCl at
pH 7.2) in the absence of extracellular Ca2+. Then, saponin was
removed by repeated wash procedures, and the cells were finally
resuspended in intracellular buffer. The cells were then kept on
ice for 2 h to allow for resealing of intracellular stores. At the start
of each individual experiment, the stores of permeabilized cells
were reloaded with Ca2+ upon the addition of ATP and an ATP-
regenerating system consisting of creatine phosphate and creatine
kinase.55 [Ca2+] was determined fluorimetrically by fura2/free acid
added to the suspension. Changes in fura2 fluorescence were
measured using a Hitachi F-2000 spectrofluorometer (alternating
excitation at 340 and 380 nm and emission at 495 nm). When the
Ca2+ stores were refilled, test compounds were added. Usually,
the quality of the permeabilized cell preparation was controlled by
its responsiveness to Ins(1,4,5)P3 and cADPR on each day. Each
experiment was calibrated using excess CaCl2 and EGTA/Tris to
obtain the maximal and minimal fura2 ratios.
Evaluation of cADPR Analogues in Intact Sea Urchin Eggs.
To intact sea urchin eggs microinjected with Ca2+ dye rhod dextran
(∼10 µM final) was added 100 and 400 µM 2′-deoxy-8-bromo-
cADPR. The Ca2+ response was monitored at excitation (543 nm)
and emission (>560 nm) on a Zeiss LSM510 confocal microscope.
8-Bromo-2′-deoxy-adenosine 5′-Monophosphate (13). Com-
pound 13 was synthesized by adaptation of a literature method.25
A suspension of 2′-deoxy-AMP disodium salt (100 mg, 0.27 mmol)
in NaOAc/AcOH buffer (4 mL, 0.9 M, pH 4.05) was heated strongly
with a heat gun for 2 min. The resulting solution was cooled to
room temperature, and a solution of bromine in MilliQ water (3.5
mL, 1.3% v/v) was added dropwise over 20 min. The reaction
mixture was then stirred at room temperature in the dark for 2 h,
after which another portion of a bromine water solution (1 mL)
was added. The reaction mixture was stirred for a further hour.
The reaction was then quenched by dropwise addition of a saturated
solution of NaHSO3 until the color of the solution became just
yellowish, and the pH was adjusted to 7 with NaOH (5 M). The
crude product was purified by a reverse-phase system and eluted
with a linear gradient of 0–30% acetonitrile against 0.05 M TEAB
buffer. The appropriate fractions were collected, and the solvent
was removed in Vacuo. Excess TEAB was co-evaporated with
MeOH (3×), generating the title compound 13 as a yellow solid in
the triethylammonium form (0.15 mmol, 55%). HPLC: 7.87 min
1
at 254 nm. UV (H2O) λmax: 265.2 nm. H NMR (D2O, 270 MHz)
δ: 8.06 (s, 1H, H-2), 6.43 (t, J1′,2′a ) J1′,2′b ) 7.2 Hz, 1H, H-1′),
4.73 (m, 1H, H-3′), 4.12 (m, 1H, H-4′), 4.06 (m, 2H, H-5′), 3.26
(m, 1H, H-2′a), and 2.43 (m, 1H, H-2′b). 31P NMR (D2O, 109 MHz)
δ: 1.50 (s). m/z (FAB-): 407.8 [(M - H)-, 95%], 409.8 [(M -
H)-, 95%].
8-Bromo-2′-deoxy-adenosine 5′-Monophosphate Morpholi-
date (24). To a solution of 8-bromo-2′-deoxy-AMP triethylammo-
nium salt (39 mg, 69 µmol) in dry DMSO (0.6 mL) was added in
sequence dipyridyl disulfide (180 mg, 0.82 mmol), morpholine (0.1
mL, 1.15 mmol), and triphenylphosphine (214 mg, 0.82 mmol).
The resulting yellow solution was stirred at room temperature for
3.5 h and was quenched by dropwise addition of a solution of
sodium iodide (0.1 M, 20 mL). The resulting sodium salt precipitate
was filtered, washed with acetone, and dried in Vacuo to give the
title compound 26 as a sticky solid (50 µmol, 72%). 1H NMR (D2O,
270 MHz) δ: 8.02 (s, 1H, H-2), 6.50 (dd, J1′,2′a ) 7.4 Hz, J1′,2′b
)
7.2 Hz, 1H, H-1′), 4.15 (m, 1H, H-3′), 4.00 (m, 3H, H-4′ and H-5′),
3.38 (m, 5H, 2 × CH2O and H-2′a), 2.72 (m, 4H, 2 × CH2N), and
2.48 (m, 1H, H-2′b). 31P NMR (D2O, 109 MHz) δ: 8.20 (s). HRMS
Calcd for [M - H]- C14H1979BrN6O6P- (FAB-), 477.0287; found,
477.0279. Calcd for C14H1981BrN6O6P-, 479.0267; found, 479.0290.
8-Bromo-2′-deoxy-nicotinamide Adenine Dinucleotide (21,
8-Br-2′-deoxy-NAD+). To a suspension of ꢀ-NMN+ (50 mg, 149
µmol) in dry DMF (0.4 mL) was added freshly distilled triethyl-
amine (22 µL) and carbonyldiimidazole (CDI, 100 mg, 0.61 mmol)
under a nitrogen atmosphere. The reaction mixture was stirred at
room temperature for 3 h. A 31P NMR spectrum indicated that all
starting ꢀ-NMN+ had been consumed, and a new peak at -9 ppm
was formed. The reaction was stopped by addition of dry methanol
(few drops), and the solution was stirred at room temperature for
a further 10 min. The reaction solution was then concentrated to
dryness in Vacuo and was co-evaporated with dry DMF 3 times to
remove any residual methanol. To the resulting yellow residue was
added 8-bromo-2′-deoxy-AMP triethylammonium salt (40 mg, 71
µmol, dried over P2O5 in Vacuo for 2 days) and DMF (0.4 mL).
The clear yellow solution was stirred at room temperature for 3
days (HPLC analysis indicated that over 80% of the starting material
was reacted). DMF was removed in Vacuo, and the residue was
purified by the Q-Sepharose system. The appropriate fractions were
pooled and evaporated, and excess TEAB was removed by co-
evaporating with MeOH to afford the title compound 21 as a glassy
solid in the triethylammonium form (22 µmol, 31%). HPLC: 3.37
Evaluation of cADPR Analogues in Sea Urchin Egg Homo-
genates. Sea urchin eggs from Lytechinus pictus (Marinus, Long
Beach, CA) were obtained by intracoelomic injection of 0.5 M KCl,
shed into artificial seawater (435 mM NaCl, 40 mM MgCl2, 15
mM MgSO4, 11 mM CaCl2, 10 mM KCl, 2.5 mM NaHCO3, and
20 mM Tris at pH 8), dejellied by passing through 90 µm nylon
mesh, and then washed twice by centrifugation. Homogenates of
sea urchin eggs were prepared as described.1 Briefly, eggs were
disrupted in an intracellular-like medium consisting of 250 mM
potassium gluconate, 250 mM N-methylglucamine, 20 mM HEPES,
and 1 mM MgCl2 at pH 7.2, supplemented with 1 mM ATP, 10
units/mL creatine kinase, and 10 mM phosphocreatine and protease
inhibitors. Ca2+ concentrations were measured with fluo-3 (3 µM)
at 17 °C, using 500 µL of continuously stirred homogenate in a
fluorimeter (Perkin-Elmer LS-50B) at 506 nm excitation and 526
nm emission.
1
min at 254 nm. UV (H2O) λmax: 265.2 nm. H NMR (D2O, 400
MHz) δ: 9.29 (s, 1H, HN-2), 9.09 (d, J6,5 ) 6.2 Hz, 1H, HN-6),
8.82 (d, J4,5 ) 8.2 Hz, 1H, HN-4), 8.18 (dd, J5,4 ) 8.2 Hz, J5,6
)
6.2 Hz, 1H, HN-5), 8.10 (s, 1H, H-2), 6.38 (dd, J1′,2′a ) 7.4 Hz,

1632 Journal of Medicinal Chemistry, 2008, Vol. 51, No. 6
Zhang et al.
J1′,2′b ) 7.2 Hz, 1H, H-1′), 5.98 (d, J1′′,2′′ ) 4.7 Hz, 1H, H-1′′),
4.42–4.15 (m, 9H, H-ribose), 3.33 (m, 1H, H-2′a), and 2.40 (m,
1H, H-2′b). 31P NMR (D2O, 109 MHz) δ: –11.17 (d, JPP ) 18.7
Hz), -10.52 (d, JPP ) 18.7 Hz). m/z (FAB-): 725.0, 727.0 [(M)-,
resulting yellow residue was co-evaporated with DMF (3 × 2 mL)
to remove any remaining methanol. The residue was dissolved in
dry DMF (0.4 mL), to which was added 8-amino-2′-deoxy AMP
(40 mg, 80 µmol), and the mixture was stirred at room temperature
for 2 days. DMF was removed in Vacuo, and the residue was
purified on a Q-Sepharose ion-exchange column, eluted with a
gradient of 0–50% 1 M TEAB against MilliQ water. The title
compound was produced in its triethylammonium form (31 µmol,
60%]. HRMS Calcd for [M + H]+ C21H2779BrN7O13P2+ (FAB+),
81
726.0325; found, 726.0325. Calcd for [M + H]+ C21H26
-
+
BrN7O13P2 (FAB+), 728.0305; found, 728.0348.
Cyclic 8-Bromo-2′-deoxy-adenosine 5′-Diphosphate Ribose
(7, 8-Br-2′-deoxy-cADPR). A solution of 8-bromo-2′-deoxy NAD+
21 (19 mg, 22 µmol) in HEPES buffer (25 mM, pH 7.4, 76 mL)
was incubated with Aplysia cyclase (115 µL) at room temperature
for 40 min, after which HPLC analysis of the solution indicated
the completion of the reaction (a new peak was produced at ca.
7.78 min). The reaction solution was diluted with MilliQ water
(conductivity < 200 µS/cm) and purified by Q-Sepharose ion-
exchange chromatography, and the product eluted with a gradient
of 0–50% 1 M TEAB buffer against MilliQ water. The fractions
containing the title compound were collected and evaporated in
Vacuo. The resulting white residue was co-evaporated with MeOH
(3×) to give the title compound 7 in its triethylammonium form
1
39%). HPLC: 2.95 min at 254 nm. UV (H2O) λmax: 269.9 nm. H
NMR (D2O, 270 MHz) δ: 9.29 (s, 1H, HN-2), 9.17 (d, J6,5 ) 5.9
Hz, 1H, HN-6), 8.77 (d, J4,5 ) 7.9 Hz, 1H, HN-4), 8.20 (dd, J5,4
)
7.9 Hz and J5,6 ) 5.9 Hz, 1H, HN-5), 7.94 (s, 1H, H-2), 6.23 (dd,
J1′,2′a ) 8.1 Hz and J1′,2′b ) 7.1 Hz, 1H, H-1′), 6.08 (d, J1′′,2′′ ) 4.5
Hz, 1H, H-1′′), 4.73–4.15 (m, 9H, H-ribose), 2.72 (m, 1H, H-2′a),
and 2.23 (m, 1H, H-2′b). 31P NMR (D2O, 109 MHz) δ: -10.68
(m). m/z (FAB+): 663.1 [(M + H)+, 65%]. HRMS Calcd. for [M
+
+ H]+ C21H29N8O13P2 (FAB+), 663.1329; found, 663.1321.
Cyclic 8-Amino-2′-deoxy-adenosine 5′-Diphosphate Ribose
(8, 8-NH2-2′-deoxy-cADPR). A solution of 8-amino-2′-deoxy-
NAD+ (4 mg, 4.8 µmol) and Aplysia cyclase (20 µL) in HEPES
buffer (25 mM, pH 7.4, 12 mL) was stirred at room temperature
for 1 h after which HPLC analysis suggested the formation of a
cyclic compound. The reaction mixture was purified as described
for 7 to give the title compound 8 as a glassy solid in the
triethylammonium form (3.7 µmol, 77%). HPLC: 3.88 min at 254
nm. UV (H2O, pH 5.0) λmax: 277.0 nm (ꢀ/13 400 dm3 mol-1 cm-1).
(19 µmol, 86%). HPLC: 7.78 min at 254 nm. UV (H2O, pH 5.2)
1
λ
max: 265.2 nm (ꢀ/11 300 dm3 mol-1 cm-1). H NMR (D2O, 400
MHz) δ: 8.96 (s, 1H, H-2), 6.55 (dd, J1′,2′a ) 6.7 Hz and J1′,2′b
)
6.2 Hz, 1H, H-1′), 6.11 (d, J1′′,2′′ ) 4.0 Hz, 1H, H-1′′), 4.99 (m,
1H, H-3′), 4.67 (m, 1H, H-2′′), 4.61 (m, 1H, H-4′′), 4.35 (m, 1H,
H-3′′), 4.25 (m, 2H, H-5′′a and H-5′a), 4.11 (m, 1H, H-4′), 3.88
(m, 1H, H-5′′b), 3.79 (m, 1H, H-5′b), 3.20 (m, 1H, H-2′a), and
2.54 (m, 1H, H-2′b). 31P NMR (D2O, 109 MHz) δ: –10.10 (d, JPP
) 14.0 Hz), -10.58 (d, JPP ) 14.0 Hz). m/z (FAB+): 604.0 [(M +
H)+, 80%], 606.0 [(M + H)+, 80%]. HRMS Calcd for [M + H]+
1H NMR (400 MHz, D2O) δ: 8.60 (s, 1H, H-2), 6.06 (dd, J1′,2′a
)
6.9 Hz and J1′,2′b ) 6.6 Hz, 1H, H-1′), 5.89 (d, J1′′,2′′ ) 4.1 Hz, 1H,
H-1′′), 4.69 (m, 1H, H-3′), 4.55 (m, 2H, H-2′′ and H-4′′), 4.25 (m,
1H, H-5′′a), 4.18 (m, 2H, H-3′′ and H-5′a), 4.02 (m, 1H, H-4′),
3.92 (m, 1H, H-5′′b), 3.81 (m, 1H, H-5′b), 3.19 (m, 1H, H-2′a),
+
C15H2179BrN5O12P2 (FAB+), 603.9845; found, 603.9838. Calcd
+
for [M + H]+ C15H2181BrN5O12P2 (FAB+), 605.9825; found,
and 2.35 (m, 1H, H-2′b). 13P NMR (D2O, 109 MHz) δ: -10.09
605.9840.
+
(m) and -10.56 (m). HRMS Calcd for [M + H]+ C15H23N6O12P2
,
8-Amino-2′-deoxy-adenosine 5′-Monophosphate (15, 8-NH2-
2′-deoxy-AMP). To a solution of sodium azide (34 mg, 0.52 mmol)
in DMF (5 mL) was added 8-Br-2′-deoxy-AMP (60 mg, 107 µmol)
and H2O (1 mL). After heating at 80 °C in the dark overnight, the
resulting yellow solution was evaporated in Vacuo and purified by
reverse-phase column chromatography. The appropriate fractions
were collected and concentrated, and the excess TEAB was removed
by co-evaporating with MeOH (3×) to give the 8-azido compound
541.0849 (ES+); found, 541.0826.
8-Methoxy-2′-deoxy-adenosine (20)..26 To a solution of 8-bromo-
2′-deoxy adenosine (267 mg, 0.81 mmol) in dry methanol (11 mL)
was added sodium methoxide (114 mg, 2.11 mmol) under an argon
atmosphere. The resulting yellow suspension was heated to reflux
for 24 h. The reaction solution was evaporated in Vacuo, and the
resulting yellow residue was purified by flash column chromatog-
raphy, eluted with DCM/methanol (8:1). The title compound was
produced as a yellow solid (216 mg, 95%). 1H NMR (DMSO, 270
1
14. UV (H2O) λmax: 281.8 nm. H NMR (D2O, 270 MHz) δ: 7.97
(s, 1H, H-2), 6.23 (dd, J1′,2′a ) 6.8 Hz and J1′,2′b ) 6.7 Hz, 1H,
H-1′), 4.66 (m, 1H, H-3′), 4.06–3.98 (m, 3H, H-4′ and H-5′), 3.00
(m, 1H, H-2′a), and 2.31 (m, 1H, H-2′b). 31P NMR (D2O, 109 MHz)
δ: 1.29 (s). m/z (FAB+): 373.0 [(M + H)+, 65%]. HRMS Calcd.
for C10H14N8O6P+ [M + H]+, 373.0774; found, 373.0790. To a
solution of 8-azido-2′-deoxy-AMP 14 in TEAB buffer (pH 8.0, 0.05
M, 7.5 mL) was added 1, 4-dithiol-(D,L)-threitol (20 mg, 129.9
µmol), and the reaction solution was stirred at room temperature
in the dark overnight. HPLC analysis indicated that a new peak
was formed at 8.4 min with a UV(max) at 274 nm. The crude product
was purified by the reverse-phase system, and excess TEAB was
removed by co-evaporating with MeOH. Title compound 15 was
obtained as a glassy solid (42 µmol, 39% over two steps). HPLC:
MHz) δ: 8.00 (s, 1H, H-2), 6.92 (brs, 2H, NH2), 6.15 (dd, J1′,2a′
)
6.4 Hz and J1′,2b′ ) 5.6 Hz, 1H, H-1′), 5.24 (m, 2H, 3′-OH and
5′-OH), 4.38 (m, 1H, H-3′), 4.08 (s, 3H, CH3O), 3.81 (m, 1H, H-4′),
3.50 (m, 2H, H-5′), 2.97 (m, 1H, H-2′a), and 2.08 (m, 1H, H-2′b).
m/z (FAB+): 282.1 [(M + H)+, 98%]. HRMS Calcd. for [M +
+
H]+ C11H16N5O4 (ES+), 282.1202; found, 282.1199.
8-Methoxy-2′-deoxy-adenosine 5′-Monophosphate (16). A
suspension of 8-methoxy-2′-deoxy-adenosine (165 mg, 0.59 mmol,
dried in Vacuo at 110 °C) in trimethylphosphate (2.0 mL) was
heated strongly with a heat gun. The resulting clear solution was
cooled to -20 °C, to which was added POCl3 (0.16 mL) under an
argon atmosphere. The reaction mixture was stirred for further 2 h,
quenched by addition of ice (10 mL), and neutralized immediately
with NaOH (5 M). It was extracted with cold ethyl acetate (5 × 20
mL), and the aqueous layers were pooled, dried, and purified on
reverse-phase column, eluted with a gradient of 0–30% MeCN
against 0.05 M TEAB. The fractions containing the desired
compound were pooled, evaporated, and co-evaporated with MeOH
to afford the crude 8-methoxy-2′-deoxy-AMP as a glassy solid. It
was further purified on Q-Sepharose ion-exchange chromatography
giving the pure title compound in its triethylammonium salt (60
1
8.41 min at 254 nm. UV (H2O) λmax: 274.7 nm. H NMR (D2O,
270 MHz) δ: 7.94 (s, 1H, H-2), 6.33 (dd, J1′,2′a ) 8.1 Hz and J1′,2′b
) 5.4 Hz, 1H, H-1′), 4.66 (m, 1H, H-3′), 4.19 (m, 1H, H-4′), 4.12
(m, 2H, H-5′), 2.69 (m, 1H, H-2′a), and 2.25 (m, 1H, H-2′b). 31P
NMR (D2O, 109 MHz) δ: 1.55 (s). m/z (FAB+): 346.9 [(M + H)+,
12%]. HRMS Calcd. for [M + H]+C10H16N6O6P+ (FAB+),
347.0869; found, 347.0881.
8-Amino-2′-deoxy-nicotinamide Adenine Dinucleotide (22,
8-NH2-2′-deoxy-NAD+). To a suspension of ꢀ-NMN+ (60 mg, 180
µmol) in DMF (400 µL) was added TEA (30 µL) and CDI (100
mg). This reaction mixture was stirred under argon atmosphere at
room temperature for 3 h, after which a 31P NMR spectrum of the
reaction mixture indicated that all starting ꢀ-NMN+ was consumed
and a new singlet was formed (ca. -9.0 ppm). A few drops of
methanol were added, and the reaction mixture was stirred at room
temperature for a further 10 min and evaporated in Vacuo. The
1
mg, 20%). HPLC: 6.21 min. UV (H2O) λmax: 259.3 nm. H NMR
(D2O, 270 MHz) δ: 8.03 (s, 1H, H-2), 6.34 (appt, J1′,2′a ) J1′,2′b
)
7.2 Hz, 1H, H-1′), 4.67 (m, 1H, H-3′), 4.17 (s, 3H, OMe), 4.14
(m, 1H, H-4′), 4.02 (m, 2H, H-5′), 3.07 (m, 1H, H-2′a), and 2.38
(m, 1H, H-2′b). 31P NMR (D2O, 109 MHz) δ: 1.33 (s). m/z (FAB-):
359.1 [(M - H)-, 70%]. HRMS Calcd for [M - H]– C11H15N5O7P-
(FAB-), 360.0709; found, 360.0652.

2′-Deoxy cADPR DeriVatiVes
Journal of Medicinal Chemistry, 2008, Vol. 51, No. 6 1633
8-Methoxy-2′-deoxy-nicotinamide Adenine Dinucleotide (23,
8-OMe-2′-deoxy-NAD+). To a suspension of ꢀ-NMN+ (60 mg,
180 µmol) in DMF (400 µL) was added TEA (30 µL) and CDI
(100 mg). This reaction mixture was stirred under argon atmosphere
at room temperature for 3 h. A few drops of methanol were added,
and the reaction mixture was stirred at room temperature for a
further 10 min and evaporated under reduced vacuum. The resulting
yellow residue was co-evaporated with DMF (3 × 2 mL) to remove
any remaining methanol. The residue was dissolved in dry DMF
(0.4 mL), to which was added 8-methoxy-2′-deoxy-AMP (40 mg,
77 µmol), and the mixture was stirred at room temperature for 2
days. DMF was removed in Vacuo, and the residue was purified
on Q-Sepharose ion-exchange column. The product eluted with a
gradient of 0–50% 1 M TEAB against MilliQ water. The appropri-
ate fractions were pooled, evaporated in Vacuo, and co-evaporated
with MeOH (3×) to generate the desired dinucleotide in its
triethylammonium form (31 µmol, 40%). HPLC: 2.92 min. UV
quenched by dropwise addition of a solution of sodium iodide in
acetone (0.1 M, 15 mL), and the resulting yellow precipitate was
filtered, washed with acetone, and dried in Vacuo. The title
compound 27 was obtained as a yellow solid (70 µmol, 74%). UV
1
(H2O) λmax: 273.5 nm. H NMR (D2O, 270 MHz) δ: 8.17 (s, 1H,
H-2), 7.53 (m, 5H, ArH), 5.79 (d, 1H, J1′,2′ ) 4.9 Hz, H-1′), 5.21
(m, 1H, H-2′), 4.52 (m, 1H, H-3′), 4.06 (m, 3H, H-4′ and H-5′),
3.42 (m, 4H, 2 × CH2O), and 2.83 (m, 4H, 2 × CH2N). 31P NMR
(D2O, 109 MHz) δ: 8.29 (s). HRMS Calcd. for [M + H]+
C20H26N6O6P+ (ES+), 493.1601; found, 493.1596.
8-Phenyl-nicotinamide Adenine Dinucleotide (31, 8-Ph-
NAD+). A suspension of 8-phenyl-AMP morpholidate (28 mg, 57
µmol), ꢀ-NMN+ (23 mg, 68 µmol), and MgSO4 (13 mg, 108 µmol)
in a solution of MnCl2 in formamide (0.2 M, 0.42 mL) was stirred
at room temperature for 48 h. Precipitation of the product occurred
by dropwise addition of MeCN (2 mL); it was filtered and treated
with Chelex resin to remove any residual Mn2+. The crude
compound was purified on a reverse-phase column, eluted with a
0–30% gradient of MeCN/0.05 M TEAB. The fractions containing
the product was pooled and evaporated in Vacuo, and excess TEAB
was co-evaporated with MeOH (5×) to afford the desired dinucle-
otide as a glassy solid in its triethylammonium form (38 µmol,
1
(H2O) λmax: 259.3 nm. H NMR (D2O, 400 MHz) δ: 9.15 (s, 1H,
HN-2), 8.96 (d, J6,5 ) 6.3 Hz, 1H, HN-6), 8.62 (d, J4,5 ) 8.0 Hz,
1H, HN-4), 8.02 (dd, J5,4 ) 8.0 Hz and J5,6 ) 6.3 Hz, 1H, HN-5),
7.84 (s, 1H, H-2), 6.09 (dd, J1′,2′a ) 7.2 Hz and J1′,2′b ) 6.9 Hz,
1H, H-1′), 5.88 (d, J1′′,2′′ ) 5.0 Hz, 1H, H-1′′), 4.50 (m, 1H, H-3′),
4.37 (m, 1H, H-4′′), 4.28 (m, 2H, H-2′′ and H-3′′), 4.18–3.94 (m,
5H, H-ribose), 4.02 (s, 3H, CH3O), 2.88 (m, 1H, H-2′a), and 2.22
1
66%). HPLC: 4.53 min at 254 nm. UV (H2O) λmax: 273.5 nm. H
NMR (D2O, 400 MHz) δ: 9.21 (s, 1H, HN-2), 9.05 (d, J6,5 ) 6.4
(m, 1H, H-2′b). 31P NMR (D2O, 109 MHz) δ: -10.53 (d, Jpp
)
Hz, 1H, HN-6), 8.67 (d, J4,5 ) 8.1 Hz, 1H, HN-4), 8.15 (dd, J5,4
)
17.1 Hz) and -11.03 (d, Jpp ) 17.1 Hz). m/z (FAB-): 675.9 [(M
- H)-, 40%]. HRMS Calcd. for [M + H]+ C22H30N7O14P2+ (ES+),
678.1326; found, 678.1321.
8.1 Hz and J5,6 ) 6.4 Hz, 1H, HN-5), 8.13 (s, 1H, H-2), 7.62–7.46
(m, 5H, Ar-H), 5.91 (d, J1′′,2′′ ) 5.0 Hz, 1H, H-1′′), 5.78 (d, J1′,2′
)
5.9 Hz, 1H, H-1′), 5.13 (m, 1H, H-2′), 4.40 (m, 1H, H-3′), 4.34
(m, 1H, H-2′′), and 4.38–4.13 (m, 7H, H-ribose). 31P NMR (D2O,
109 MHz) δ: -11.50 (m). m/z (FAB-): 738.1 [(M - H)-, 100%].
Cyclic 8-Methoxy-2′-deoxy-adenosine 5′-Diphosphate Ri-
bose (9, 8-OMe-2′-deoxy-cADPR). 8-Methoxy-2′-deoxy-NAD+ (5
mg, 5.9 µmol) and Aplysia cyclase (22 µL) were incubated in
HEPES buffer (15 mL, pH 7.4, 25 mM) until HPLC analysis
indicated that the starting dinucleotide was completely consumed.
The reaction mixture was diluted with MilliQ and purified as
described for 7 to give the title compound as a glassy solid (5.6
µmol, 95%). HPLC: 3.90 min at 254 nm. UV (H2O) λmax: 259.3
nm (ꢀ/11 500 dm3 mol-1 cm-1). 1H NMR (D2O, 400 MHz) δ:
-
HRMS Calcd. for [M - H]– C27H30N7O14P2 (FAB-), 738.1326;
found, 738.1329.
Cyclic 8-Phenyl-adenosine 5′-Diphosphate Ribose (5, 8-Ph-
cADPR). To a solution of 8-phenyl-NAD+ (5 mg, 5.5 µmol) in
HEPES buffer (25 mM, pH 7.4, 13 mL) was added Aplysia cyclase
(19.5 µL). The resulting clear solution was stirred at room
temperature for 1 h, and the product was purified as described for
7. The desired compound 5 was obtained as a glassy solid in its
triethylammonium form (3.8 µmol, 69%). HPLC: 9.95 min at 254
8.79 (s, 1H, H-2), 6.28 (dd, J1′,2′b ) 6.8 Hz and J1′,2′ ) 6.4 Hz,
a
1H, H-1′), 5.99 (d, J1′′,2′′ ) 4.2 Hz, 1H, H-1′′), 4.83 (m, 1H, H-3′),
4.69 (m, 1H, H-2′′, overlap with HOD signal), 4.62 (m, 1H, H-4′′),
4.35 (m, 1H, H-3′′), 4.26 (m, 2H, H-5′a and H-5′′a), 4.09 (m and
s, 4H, H-4′ and OCH3), 4.01 (m, 1H, H-5″b), 3.86 (m, 1H, H-5′b),
3.19 (m, 1H, H-2′a), and 2.38 (m, 1H, H-2′b). 31P NMR (D2O,
109 MHz) δ: -10.82 (m), -11.46 (m). m/z (FAB-): 553.8 [(M -
H)-, 100%]. HRMS Calcd for [M - H]– C16H22N5O13P2- (FAB-),
554.0689; found, 554.0698.
1
nm. UV (H2O) λmax: 275.8 nm (ꢀ/20 264 dm3 mol-1 cm-1). H
NMR (D2O, 400 MHz) δ: 9.07 (s, 1H, H-2), 7.77–7.62 (m, 5H,
Ar-H), 6.20 (d, J1′′,2′′ ) 4.2 Hz, 1H, H-1′′), 6.07 (d, J1′,2′ ) 6.0 Hz,
1H, H-1′), 5.56 (dd, J2′,1′ ) 6.0 Hz and J2′,3′ ) 5.3 Hz, 1H, H-2′),
4.77 (m, 3H, H-4′′, H-2′′, and H-3′), 4.48 (m, 3H, H-3′′, H-5′′a,
and H-5′a), 4.29 (m, 1H, H-4′), and 4.13 (m, 2H, H-5′′b and H-5′b).
31P NMR (D2O, 109 MHz) δ: -10.09 (brs) and -10.84 (brs). m/z
(FAB-): 616.0 [(M - H)-, 100%]. HRMS Calcd for [M - H]-
8-Phenyl-adenosine 5′-Monophosphate (17, 8-Ph-AMP). To
a stirred solution of 8-bromo-AMP triethylammonium salt (140 mg,
0.24 mmol), phenylboronic acid (40 mg, 0.33 mmol), and sodium
carbonate (76 mg, 0.72 mmol) in 2:1 MilliQ/MeCN (4.1 mL,
degassed) was added Pd(PPh3)4 (40 mg, 35 µmol) under an argon
atmosphere. The resulting yellow suspension was vigorously stirred
at 80 °C for 3 h. The reaction mixture was filtered, and the filtrate
was purified using reverse-phase chromatography. The product
eluted with a gradient of 0–30% MeCN against 0.05 M TEAB
buffer. The appropriate fractions were collected and evaporated,
and the resulting residue was co-evaporated with MeOH (3×) to
give the title compound 17 in triethylammonium salt (77 mg, 55%).
HPLC: 12.10 min. UV (H2O) λmax: 275.8 nm. 1H NMR (D2O, 270
MHz) δ: 8.21 (s, 1H, H-2), 7.66 (m, 2H, ArH), 7.56 (m, 3H, ArH),
5.85 (d, J1′,2′ ) 6.2 Hz, 1H, H-1′), 5.16 (appt, J2′,1′ ) J2′,3′ ) 6.2
Hz, 1H, H-2′), 4.35 (m, 1H, H-3′), and 4.21 (m, 3H, H-4′ and H-5′).
31P NMR (D2O, 109 MHz) δ: 1.59 (s). HRMS: Calcd for [M +
H]+ C16H19N5O7P+ (ES+), 424.1022; found, 424.1019.
-
C21H24N5O13P2 (FAB-), 616.0846; found, 616.0856.
8-Phenyl-2′-deoxy-adenosine 5′-Monophosphate Morpholi-
date (28). To a stirred solution of 8-Br-2′-deoxy-adenosine 5′-
monophosphate (190 mg, 0.34 mmol), phenylboronic acid (80 mg,
0.65 mmol) and Na2CO3 (220 mg, 2.07 mmol) in aqueous MeCN
(33%, 5 mL, degassed) was added Pd(PPh3)4 (70 mg, 60 µmol)
under an argon atmosphere. The resulting yellow suspension was
vigorously stirred at 80 °C for 3 h, after which further portions of
phenylboronic acid (80 mg, 0.65 mmol) and Pd(PPh3)4 (70 mg, 60
µmol) were added. The resulting suspension was stirred at 80 °C
for a further 2 h and purified as described for 17, giving crude
8-phenyl-2′-deoxy AMP 18 as a glassy solid in its triethylammo-
nium form (92% based on 1H NMR). HPLC: 13.71 min at 254
1
nm. UV (H2O) λmax: 275.8 nm. H NMR (CD3OD, 270 MHz) δ:
8.22 (s, 1H), 7.77 (m, 2H), 7.53 (m, 3H), 6.25 (appt, J1′,2′a ) J1′,2′b
) 6.8 Hz, 1H), 4.79 (m, 1H), 4.11 (m, 3H), 3.62 (m, 1H), and
2.20 (m, 1H). m/z (ES-): 406.18 [(M - H)-, 100%]. HRMS Calcd
for [M + H]+ C16H19N5O6P+ (ES+), 408.1073; found, 408.1071.
To a solution of 18 in dry DMSO (0.6 mL) was added dipyridyl
disulfide (190 mg, 862 µmol), morpholine (0.25 mL, 2.86 mmol),
and triphenylphosphine (220 mg, 839 µmol). The resulting green
solution was stirred at room temperature for 3 h and quenched with
a solution of NaI in acetone (0.1 M, 20 mL). The resulting
precipitate was filtered, washed with acetone, and dried in Vacuo
8-Phenyl-adenosine 5′-Monophosphate Morpholidate (27). To
a solution of 8-phenyl-AMP triethylammonium salt (55 mg, 95
µmol) in dry DMSO (0.4 mL) was added triphenylphosphine (113
mg, 431 µmol), morpholine (100 µL, 1.14 mmol), and dipyridyl
disulfide (95 mg, 431 µmol). The resulting yellow solution was
stirred at room temperature for 2 h, and HPLC analysis indicated
that all starting 8-phenyl-AMP was consumed. The reaction was

1634 Journal of Medicinal Chemistry, 2008, Vol. 51, No. 6
Zhang et al.
to afford the desired morpholidate as a yellow solid in 75% yield
over both steps. Compound 28 was used in the next step without
further purification. 1H NMR (D2O, 270 MHz) δ: 8.21 (s, 1H, H-2),
7.68 (m, 5H, ArH), 6.26 (appt, J1′,2′a ) J1′,2′b ) 7.4 Hz, 1H, H-1′),
4.73 (m, 1H, H-3′, overlap with HOD peak), 3.98 (m, 3H, H-4′
and H-5′), 3.35 (m, 5H, 2 × CH2O, H-2′a), 2.76 (m, 4H, 2 ×
CH2N), and 2.27 (m, 1H, H-2′b). 31P NMR (D2O, 109 MHz) δ:
8.10 (s). m/z (ES-): 475.18 [(M - H)-, 100%]. HRMS Calcd for
[M - H]- C20H24N6O6P- (ES-), 475.1495; found, 475.1493.
8-Phenyl-2′-deoxy-nicotinamide Adenine Dinucleotide (32,
8-Ph-2′-deoxy-NAD+). To a mixture of 8-Ph-2′-deoxy-AMP
morpholidate (30 mg, 63 µmol), ꢀ-NMN+ (25 mg, 75 µmol), and
MgSO4 (14 mg, 117 µmol) was added a solution of MnCl2 in
formamide (0.2 M, 460 µL). The resulting suspension was stirred
at room temperature and monitored by HPLC. After 48 h, the
reaction was quenched by the addition of MeCN (2 mL) and the
yellow precipitate was filtered, washed with MeCN, and treated
addition of MeCN (2 mL). The resulting yellow precipitate was
filtered, washed with MeCN, and treated with Chelex to remove
any residual Mn2+. The crude product was purified on a reverse-
phase column, eluted with a gradient of 0–30% MeCN against 0.05
M TEAB buffer. The appropriate fractions were pooled, evaporated
in Vacuo, and co-evaporated with MeOH (3×) to give 8-Br-NAD+
29 as a triethylammonium salt. 1H NMR (D2O, 270 MHz) δ: 9.27
(s, 1H, HN-2), 9.09 (d, J6,5 ) 5.4 Hz, 1H, HN-6), 8.79 (d, J4,5 ) 8.1
Hz, 1H, HN-4), 8.28 (m, 1H, HN-5), 8.07 (s, 1H, H-2), 5.96 (d,
J1′,2′′ ) 3.4 Hz, 1H, H-1′′), 5.93 (d, J1′,2′ ) 5.5 Hz, 1H, H-1′), 5.17
(m, 1H, H-2′), and 4.57–4.24 (m, 9H, H-ribose). 31P NMR (D2O,
109 MHz): -10.46 (brs). m/z (ES-): 739.57 [(M - H)-, 100%,
79Br], 741.45 (81Br). Compound 29 in HEPES buffer (25 mM,
pH7.4, 106 mL) was incubated with Aplysia ADP ribosyl cyclase
(127 µL) at room temperature for 1 h and then purified according
to previously described conditions for 7. The title compound 3 was
formed as a triethylammonium salt in 49% yield over two steps.
HPLC: 8.39 at 254 min. UV (H2O) λmax: 265.2 nm. 1H NMR (D2O,
400 MHz) δ: 8.89 (s, 1H, H-2), 6.02 (d, J1′,2′ ) 5.3 Hz, 1H, H-1′),
5.99 (d, J1′′,2′′ ) 4.0 Hz, 1H, H-1′′), 5.35 (dd, J2′,1′ ) 5.3 Hz, J2′,3′
) 5.0 Hz, 1H, H-2′), 4.62 (m, 3H, H-2″, H-3′, and H-4′′), 4.25 (m,
4H, H-3′′, H-5′a, H-5′′a, and H-4′), 4.00 (m, 1H, H-5′′b), and 3.86
(m, 1H, H-5′b). 31P NMR (D2O, 109 MHz) δ: -9.81 (brs), -10.75
with Chelex resin (sodium form) to remove any residual Mn2+
.
The crude product was further purified on a reverse-phase column,
giving the title compound 32 as a glassy solid in its triethylam-
monium form (38 µmol, 60%). HPLC: 4.62 min. UV (H2O) λmax
:
1
275.8 nm. H NMR (D2O, 400 MHz) δ: 9.11 (s, 1H, HN-2), 8.94
(d, J6,5 ) 6.1 Hz, 1H, HN-6), 8.57 (d, J4,5 ) 8.4 Hz, 1H, HN-4),
8.05 (dd, 1H, J5,4 ) 8.4 Hz and J5,6 ) 6.1 Hz, HN-5), 8.03 (s, 1H,
H-2), 7.42 (m, 5H, ArH), 6.09 (dd, J1′,2′b ) 7.5 Hz and J1′,2′a ) 6.8
Hz, 1H, H-1′), 5.80 (d, J1′′,2′′ ) 4.7 Hz, 1H, H-1′′), 4.56 (m, 1H,
H-3′), 4.24 (m, 1H, H-2′′), 4.24–3.96 (m, 7H, H-ribose), 2.89 (m,
1H, H-2′a), and 2.02 (m, 1H, H-2′b). 31P NMR (D2O, 109 MHz)
δ: -11.43 (brs) and -11.76 (brs). m/z (ES-): 599.94 [(M -
nicotinamide)-, 100%], 721.94 [(M - H)-, 20%]. HMRS Calcd
for [M - H]- C27H30N7O13P2- (ES-), 722.1377; found, 722.1382.
Cyclic 8-Phenyl-2′-deoxy-adenosine 5′-Diphosphate Ribose
(10, 8-Ph-2′-deoxy-cADPR). To a solution of 8-phenyl-2′-deoxy-
NAD+ (24 mg, 27 µmol) in HEPES buffer (110 mL, pH 7.4, 25
mM) was added Aplysia ADP ribosyl cyclase (150 µL). The
resulting clear solution was stirred at room temperature for 1 h
and was purified on Q-Sepharose ion-exchange column to give the
desired compound 10 in its triethylammonium form (16 µmol,
60%). HPLC: 12.72 min at 254 nm. UV (H2O) λmax: 277 nm (ꢀ/
-
(brs). HRMS Calcd for [M - H]- C15H1979BrN5O13P2 (ES-),
617.9638; found, 617.9641.
8-Amino-adenosine 5′-Monophosphate Morpholidate (26). To
a solution of 8-amino AMP triethylammonium salt (110 mg, 0.21
mmol) in dry DMSO (0.6 mL) was added a sequence of triph-
enylphosphine (200 mg, 0.76 mmol), morpholine (0.13 mL, 1.49
mmol), and dipyridyl disulfide (168 mg, 0.76 mmol). The resulting
solution was stirred at room temperature for 3.5 h and purified as
described for 25, giving the desired morpholidate 26 as a yellow
solid (141 µmol, 67%). HPLC: single peak at 2.70 min at 254 nm.
1H NMR (D2O, 270 MHz) δ: 7.89 (s, 1H, H-2), 5.92 (d, J1′,2′
)
7.2 Hz, 1H, H-1′), 4.73 (m, 1H, H-2′), 4.42 (m, 1H, H-3′), 4.26
(m, 1H, H-4′), 4.03 (m, 2H, H-5′), 3.58 (m, 4H, 2 × CH2O), and
2.96 (m, 1H, 2 × CH2N). 31P NMR (D2O, 109 MHz) δ: 7.90 (s).
m/z (ES-): 430.48 [(M - H)-, 100%]. HRMS Calcd for [M -
H]- C14H21N7O7P- (ES-), 430.1240; found, 430.1249.
1
21 349 dm3 mol-1 cm-1). H NMR (D2O, 400 MHz) δ: 9.02 (s,
Cyclic 8-Amino-adenosine 5′-Diphosphate Ribose (2, 8-NH2-
cADPR). 8-Amino-cADPR was earlier reported by Lee et al.23 To
a mixture of 8-amino-AMP morpholidate (60 mg, 139 µmol),
ꢀ-NMN+ (58 mg, 174 µmol), and MgSO4 (38 mg, 317 µmol) was
added a solution of MnCl2 in formamide (0.2 M, 1.25 mL). The
resulting suspension was stirred at room temperature for 2 days
and purified as described for 29 to form 8-amino-NAD+ 30 as a
triethylammonium salt. 1H NMR (D2O, 400 MHz) δ: 9.29 (s, 1H,
HN-2), 9.16 (d, J6,5 ) 6.3 Hz, 1H, HN-6), 8.76 (d, J4,5 ) 8.2 Hz,
1H, HN-4), 8.16 (dd, J5,4 ) 8.2 Hz and J5,6 ) 6.3 Hz, 1H, HN-5),
7.96 (s, 1H, H-2), 6.08 (d, J1′′,2′′ ) 5.1 Hz, 1H, H-1′′), 5.84 (d, J1′,2′
) 7.1 Hz, 1H, H-1′), 4.66 (m, 1H, H-2′), 4.43 (m, 1H, H-4′′), and
4.42–4.23 (m, 8H, ribose-H). 31P NMR (D2O, 109 MHz) δ: -10.42
(d, JPP ) 17.1 Hz) and -11.24 (d, JPP ) 17.1 Hz). HRMS Calcd
for [M - H]- C21H27N8O14P2- (ES-), 677.1122; found, 677.1122.
Compound 30 and Aplysia cyclase (256 µL) in HEPES buffer (25
mM, pH 7.4, 166 mL) was incubated at room temperature for 40
min. The reaction mixture was purified as described for 7 to afford
2 as a glassy solid in the triethylammonium form in 38% yield
over two steps. HPLC: 4.39 min at 254 nm. UV (H2O) λmax: 275.8
1H, H-2), 7.67 (m, 5H, ArH), 6.41 (appt, J1′2′a ) J1′2′b ) 7.0 Hz,
1H, H-1′), 6.15 (d, J1′′,2′′ ) 3.9 Hz, 1H, H-1′′), 4.94 (m, 1H, H-3′),
4.77 (m, 2H, H-2′′ and H-4′′), 4.49 (m, 2H, H-3′′ and H-5′a), 4.39,
(m, 1H, H-5′′a), 4.19 (m, 1H, H-4′), 4.14 (m, 1H, H-5′′b), 4.06
(m, 1H, H-5′b), 3.46 (m, 1H, H-2′a), and 2.46 (m, 1H, H-2′b). 31
P
NMR (D2O, 109 MHz) δ: -9.95 (d, JPP ) 16.4 Hz) and -10.85
(d, JPP ) 16.4 Hz). m/z (ES-): 600.06 [(M - H)-, 100%]. HRMS
-
Calcd [M - H]- C21H24N5O12P2 (ES-), 600.0897; found,
600.0902.
8-Bromo-adenosine 5′-Monophosphate Morpholidate (25). To
a solution of 8-bromo-AMP 12 (126 mg, 220 µmol) in DMSO (0.6
mL) was added triphenylphosphine (200 mg, 763 µmol), morpholine
(130 µL, 1.49 mmol), and dipyridyl disulfide (168 mg, 763 µmol).
The resulting yellow solution was stirred at room temperature for
3 h and quenched with a solution of sodium iodide in acetone (0.1
M, 20 mL). The resulting precipitate was filtered, washed with
acetone, and dried under reduced pressure to afford the desired
morpholidate 25 as a yellow solid (187 µmol, 85%). 1H NMR (D2O,
270 MHz) δ: 8.08 (s, 1H, H-2), 6.00 (d, J1′,2′ ) 4.7 Hz, 1H, H-1′),
5.29 (m, 1H, H-2′), 4.70 (m, 1H, H-3′), 4.16 (m, 1H, H-4′), 3.95
(m, 2H, H-5′), 3.39 (m, 4H, 2 × CH2O), and 2.75 (m, 4H, 2 ×
CH2N). 31P NMR (D2O, 109 MHz) δ: 8.26 (s). m/z (ES-): 493.37
[(M - H)-, 100%], 495.25 [(M - H)-, 100%]. HRMS Calcd for
[M - H]– C14H1979BrN6O7P- (ES-), 493.0236; found, 493.0240.
Cyclic 8-Bromo-adenosine 5′-Diphosphate Ribose (3, 8-Br-
cADPR). 8-Bromo-cADPR was synthesized and biologically
studied by Lee et al.23 To a mixture of 8-bromo-AMP morpholidate
(73 µmol), ꢀ-NMN+ (31 mg, 92 µmol), and MgSO4 (18 mg, 150
µmol) was added a solution of MnCl2 in formamide (0.2 M, 0.56
mL) under a nitrogen atmosphere. The reaction mixture was then
stirred at room temperature for 2 days and quenched by dropwise
1
nm. H NMR (D2O, 400 MHz) δ: 8.72 (s, 1H, H-2), 6.01 (d, J1′′,
2′′ ) 4.0 Hz, 1H, H-1′′), 5.80 (d, J1′,2′ ) 5.6 Hz, 1H, H-1′), 5.36
(dd, J2′,1′ ) 5.6 Hz and J2′,3′ ) 4.8 Hz, 1H, H-2′), 4.65 (m, 3H,
H-3′, H-4′′, and H-2′′), 4.38 (m, 1H, H-3′′), 4.29 (m, 2H, H-5′a
and H-5′′a), 4.22 (m, 1H, H-4′), 4.04 (m, 1H, H-5′′b), and 3.94
(m, 1H, H-5′b). 31P NMR (D2O, 109 MHz) δ: –9.87 (d, JPP
)
11.6 Hz) and -10.21 (d, JPP ) 11.6 Hz). HRMS Calcd for [M -
-
H]- C15H21N6O13P2 (FAB-), 555.0642; found, 555.0645.
Acknowledgment. We thank Dr. C. Moreau for practical
advice on this work, Dr. T. J. Woodman for collecting NMR
data, and Ms. Alison Smith for collecting LCMS data. We

2′-Deoxy cADPR DeriVatiVes
Journal of Medicinal Chemistry, 2008, Vol. 51, No. 6 1635
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acknowledge Project Grant support (55709 to B.V.L.P.), a
Biomedical Research Collaboration Grant (068065 to A.H.G.
and B.V.L.P.) from the Wellcome Trust, and grant support from
Deutsche Forschungsgemeinschaft (GU 360/9-1 and 9-2 to
A.H.G.). Thanks are also expressed to the EPSRC National Mass
Spectrometry Service at Swansea for support.
Supporting Information Available: Table (HPLC %) to show
the degree of purity, HPLC traces for all key pyrophosphate
1
compounds, H NMR spectra for compounds 2, 3, 5, and 7-10,
and 13C data for all compounds. This material is available free of
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