Synthesis of aminopropyl phosphonate nucleosides with purine and pyrimidine bases

Article abstract of DOI:10.1135/cccc20060015

The synthesis and antiviral evaluation of new acyclic phosphonate nucleosides related to HPMPC (Cidofovir) has been described. These aminopropyl phosphonate nucleosides 1-3 have an amino function within either the acyclic chain (series 2 and 3) or as subs

Full text of DOI:10.1135/cccc20060015

Synthesis of Aminopropyl Phosphonate Nucleosides
15
SYNTHESIS OF AMINOPROPYL PHOSPHONATE NUCLEOSIDES WITH
PURINE AND PYRIMIDINE BASES
1
2
3
4,
Ding ZHOU , Irene M. LAGOJA , Arthur VAN AERSCHOT and Piet HERDEWIJN *
Laboratory of Medicinal Chemistry, Rega Institute, Minderbroedersstraat 10, B-3000 Leuven,
1
2
Belgium; e-mail: ding.zhou@rega.kuleuven.be, irene.lagoja@rega.kuleuven.be,
3
4
arthur.vanaerschot@rega.kuleuven.be, piet.herdewijn@rega.kuleuven.be
Received Jun e 9, 2005
Accepted Novem ber 14, 2005
Th e syn th esis an d an tiviral evaluation of n ew acyclic ph osph on ate n ucleosides related to
HPMPC (Cidofovir) h as been described. Th ese am in opropyl ph osph on ate n ucleosides 1–3
h ave an am in o fun ction with in eith er th e acyclic ch ain (series 2 an d 3) or as substituen t (se-
ries 1). Both purin e an d pyrim idin e n ucleotide an alogues h ave been syn th esized. In con trast
to HPMPC th e oxygen an alogue of 2c, on ly a weak an tih erpes virus activity could be dem -
on strated for 2b an d 2c.
Keyw ord s: Acyclic n ucleoside ph osph on ates; Acyclic n ucleotide an alogues; Am in opropyl
ph osph on ic acids; An tiviral activity; Mitsun obu reaction .
Replication of h um an im m un odeficien cy virus type 1 can be reduced in
HIV-in fected patien ts usin g a com bin ation of an tiviral drugs targeted at th e
reverse tran scriptase an d protease1. Un fortun ately, due to th e h igh m uta-
tion rate of HIV, th e treatm en t, even com bin ation th erapy, selects drug-
resistan t varian ts2.
Th e acyclic n ucleotide ph osph on ates (ANPs) are broad-spectrum an tiviral
agen ts with poten t an d selective an tiviral activity in vitro an d in vivo. Th ey
h ave sh own to be effective again st several DNA viruses an d retroviruses in -
cludin g HIV 3. Th ese com poun ds were design ed to circum ven t th e first
ph osph orylation step, n ecessary for th e activation of n orm al n ucleoside an -
alogues4. On ce in side th e cells, th ey are con verted in to active diph osph o-
rylated m etabolites, wh ich react with th e viral DNA polym erase (of h erpes
viruses) or act as ch ain term in ators in th e HIV reverse tran scriptase (RT) re-
action 5. (S)-9-[3-Hydroxy-2-(phosphonomethoxy)propyl]adenine, ((S)-HPMPA),
an acyclic n ucleotide an alogue reported by Holý an d De Clercq et al.6, is a
represen tative of th is class wh ich possesses broad-spectrum an tiviral activ-
ity. (S)-1-[3-Hydroxy-2-(ph osph on om eth oxy)propyl]cytosin e ((S)-HPMPC,
cidofovir) h as been approved for th e treatm en t of CMV-retin itis in AIDS pa-
tien ts.
Collect. Czech. Chem. Commun. 2006, Vol. 71, No. 1, pp. 15–34
© 2006 Institute of Organic Chemistry and Biochemistry
doi:10.1135/cccc20060015

16
Zhou, Lagoja, Van Aerschot, Herdewijn:
More recen tly, a series of purin e an d pyrim idin e N-[2-(ph osph on o-
m eth oxy)eth yl] derivatives bearin g am in om eth yl or azidom eth yl groups
were reported7–9. Am on g th em , 9-[3-am in o-2-(ph osph on om eth oxy)propyl]-
aden in e proved active again st varicella-zoster virus (VZV) an d cytom egalo-
virus (CMV). Followin g th is in terest, we describe h ere th e syn th esis an d
evaluation of th e wh ole series of acyclic n ucleotide an alogues, with th e n at-
ural purin e (A, G) an d pyrim idin e (U, C) bases, bearin g an am in o fun ction
in th e position 2 or 3 of th e acyclic sugar m oiety, as sh own in Ch art 1.
A
O
P
C
O
P
OH
OH
OH
OH
O
O
H
H
HO
HO
(S)-HPMPA
(S)-HPMPC
B
B
O
P
B
O
O
P
NH2
OH
H
N
H
N
HO
HO
OH
OH
HO
HO
O
P
H
H
H
1
HO
3
2
B = A, G, C, U
O
NH2
N
NH2
O
N
N
N
HN
N
N
HN
H2N
U =
A =
C =
G =
N
O
N
O
N
N
CHART 1
Com poun ds 1a–1d are (ph osph on om eth oxy)propyl an alogues with an
am in o substituen t in th e 2′-position . Th is am in o group form s an in tern al
salt with th e ph osph on ate fun ction , in fluen cin g th e polarity an d th e
con form ation al flexibility of th e m olecule. Com poun ds 2a–2d are th e
(ph osph on om eth yl)am in o con gen ers of HPMPA an d HPMPC. Th e th ird se-
ries 3a–3d h ave th e in verse fun ction ality com pared with th e first series
1a–1d , an d a secon dary am in o group in stead of a prim ary am in o fun ction .
Th e free secon dary h ydroxy group of 3a–3d an d th e prim ary h ydroxy
group of 2a–2d m igh t m im ic on e of th e h ydroxy groups of a ribose un it
(sh ould th is be im portan t for th e in teraction with m etabolic en zym es
an d/or with polym erases).
RESULTS AND DISCUSSION
Am in opropyl ph osph on ate n ucleosides can be prepared by two differen t
strategies. Eith er th ey are obtain ed by ph osph on oylation of th e acyclic
n ucleosides, as exem plified for am in opropyl ph osph on ic acids of type 2
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Synthesis of Aminopropyl Phosphonate Nucleosides
17
an d 3. Altern atively, th e aglycon is in troduced on an am in opropyl group,
already fun ction alized with a protected ph osph on om eth yl eth er group, as
exem plified for am in opropyl ph osph on ate n ucleosides of type 1. A possible
ch iral syn th esis was en visaged on ly if som e of th ese ph osph on ates would
display in terestin g an tiviral activity.
Synthesis of Aminopropyl Phosphonate Nucleosides 1a –1d
A possible reaction path way, startin g from racem ic 1,2-O-isopropyliden e-
glycerol (4) is outlin ed in Sch em e 1. Ben zoylation of 4 followed by h ydroly-
sis of th e isopropyliden e protectin g group derives (±)-2,3-dih ydroxypropyl
OBz
X
OBz
OH
d)
b)
MMTrO
e)
X
O
O
RO
8 X = OMs
9 X = N3
4 X = OH
6 R = H
a)
c)
5 X = OBz
7 R = MMTr
f)
Y
OCH2P(O)(Oi-Pr)2
OCH2P(O)(Oi-Pr)2
h)
i)
MMTrO
N3
B
N3
HO
N3
12
j)
k)
14b
15b
13b B = G
10 Y = OH
g)
13a B = A
13c B = U
13d B = C
11 Y = OCH2P(O)(Oi-Pr)2
l)
O
m)
OH
P
OH
O
OCH2P(O)(Oi-Pr)2
n)
a: B = A
B
NH2
B
NH2
b: B = G
c: B = U
d: B = C
16a-16d
1a-1d
SCHEME 1
Syn th esis of am in opropyl ph osph on ate n ucleosides 1a–1d
a) BzCl, Py (n ot isolated); b) TFA/H2O (3:1) (49%, both steps); c) MTrCl, Py; d) MsCl, Py (77%,
both steps); e) NaN3, DMF, 100 °C; f) 1 NaOH in MeOH (50%, 2 steps); g) NaH,
M
CF3SO3CH2PO(Oi-Pr)2, –20 °C; h ) 3% TFA in DCM (73%, 2 steps); i) 13a: Ph 3P, DIAD, aden in e,
THF (53%), 14b : Ph 3P, DIAD, 6-ch loro-2-am in opurin e THF (47%), 13c: Ph 3P, DIAD,
3-ben zoyluracil, THF, sat. NH3 in MeOH (69%, 2 steps); j) 15b: H2O, reflux (85%); k) 13b: TFA
in H2O (63%); l) MesCl, Et3N, MeCN, 26% NH4OH in H2O (60%, 2 steps); m ) H2S, Py, Et3N; n )
Me3SiBr, MeCN (1a: 49%, 1b: 44%, 1c: 51%, 1d : 48%, 2 steps)
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18
Zhou, Lagoja, Van Aerschot, Herdewijn:
ben zoate (6). Th e prim ary h ydroxy fun ction is selectively protected with a
m eth oxytrityl group to obtain 7. Reaction with m esyl ch loride givin g 8 in -
troduces a good leavin g group allowin g n ucleoph ilic substitution with so-
dium azide to yield 9. Th e followin g deben zoylation to 10, treatm en t with
(diisopropoxyph osph oryl)m eth yl trifluorom eth an esulfon ate yields th e
ph osph on ate 11, wh ich in turn can be con verted in to th e key in term ediate
of th is syn th etic path way: (±) diisopropyl [(2-azido-3-h ydroxypropoxy)-
m eth yl]ph osph on ate 12. Mitsun obu con dition s10 (triph en ylph osph in e,
diisopropyl azodicarboxylate (DIAD) in THF at room tem perature) were
used to in troduce th e n ucleobases on to th e ph osph on ate 12. Couplin g of
3-ben zoyluracil to 12, followed by deben zoylation yields th e 1-alkyluracil
derivative 13c in good yield (69%, both steps). However, n o product form a-
tion could be observed usin g cytosin e as n ucleobase. Th erefore, 13c was
sm ooth ly con verted to th e cytosin e derivative 13d by treatm en t with
NH4OH, followin g activation with m esitylen esulfon yl ch loride (MesCl) in
Et3N/aceton itrile (60%, both steps)11. An altern ative m eth od usin g activa-
tion with POCl3/triazole12 was less satisfactory. Mitsun obu con dition s were
applied to in troduce th e purin e bases. Reaction of 12 with aden in e yields
13a in 53% yield. Guan in e was n ot directly in troduced by th e Mitsun obu
couplin g due to th e form ation of an in separable m ixture of N7/N9 isom ers
(1:2). Th erefore, th e couplin g was accom plish ed with 2-am in o-6-ch loro-
purin e (N9 47%; N7/N9 1:4), yieldin g th e triph en ylph osph oran yliden e de-
rivative 14b, wh ich could be h ydrolyzed to th e 2-am in o-6-ch loropurin e
derivative 15b. Treatm en t th ereof with trifluoroacetic acid (TFA) fin ally af-
fords th e desired in term ediate 13b (Sch em e 2).
Cl
Cl
O
N
N
N
a)
b)
c)
N
R-OH 12
R-OH 10
N
HN
H2N
Ph3P
N
R
N
R
N
R
N
N
H2N
N
N
14b
18b
15b
19b
13b
12, 13b, 14b, 15b: R = (i-PrO)2(O)PCH2
O
10, 18b, 19b: R = MMTrO
N3
N3
a) 2-NH2-6-Cl-purine, Ph3P, DIAD; b) THF, H2O, reflux; c) TFA, H2O
SCHEME 2
Detailed path way for th e syn th esis of 13b an d 19b
a) 2-NH2-6-Cl-purin e, Ph 3P, DIAD, THF; b) THF, H2O, reflux; c) TFA, H2O
Collect. Czech. Chem. Commun. 2006, Vol. 71, No. 1, pp. 15–34

Synthesis of Aminopropyl Phosphonate Nucleosides
19
As h ydrogen ation was precluded in view of th e trityl m oiety, reduction of
th e azide fun ction was accom plish ed usin g H2S in pyridin e to obtain
16a–16d . Th e desired am in opropyl ph osph on ate n ucleosides 1a–1d were
obtain ed by deprotection of th e ph osph on ate esters usin g brom otrim eth yl-
silan e.
Synthesis of Aminopropyl Phosphonate Nucleosides 2a –2d
In itially, th e sam e strategy, i.e. in troduction of th e n ucleobases to th e ph os-
ph on oylated acyclic precursor, was applied to obtain am in opropyl ph os-
ph on ate n ucleosides 2. However, th e reaction failed, due to th e favoured
form ation of an aziridin e by-product un der Mitsun obu con dition s. To cir-
cum ven t th is problem , th e base was in troduced prior to th e ph osph on ate
m oiety (Sch em e 3).
Startin g from in term ediate 10, th e n ucleobases were in troduced un der
Mitsun obu con dition s (17a, 19b, 19c). In th e case of aden in e, th e 6-am in o
fun ction h ad to be protected with a ben zoyl group to give 19a, before in -
B
B
d)
a)
10
MMTrO
NH2
MMTrO
b)
N3
20a-20c
17a B: A
19a B = ABz
c)
18b
19b B: 2-NH2-6-Cl-purine
e)
B
19c B: U
B
g)
HO
2a-2d
NHCH2P(O)(OH)2
MMTrO
NHCH2P(O)(Oi-Pr)2
21a B = ABz
21b B = 2-NH2-6-Cl-purine
21c B = U
a: B = A; b: B = G; c: B = U; d: B = C
f)
21d B = C
SCHEME 3
Syn th esis of am in opropyl ph osph on ate n ucleosides 2a–2d
a) 17a: A, Ph 3P, DIAD, THF (45%), 18b: 2-am in o-6-ch loropurin e, Ph 3P, DIAD, THF (45%), 19c:
UBz, Ph 3P, DIAD, THF, NH3/MeOH (46%); b) BzCl, Py, 0 °C (85%); c) H2O, THF, reflux (82%);
d) Ph 3P, THF, H2O, reflux (20a: 94%, 20b: 91%, 20c: 88%); e) CF3SO3CH2P(O) (Oi-Pr)2, Et3N,
THF (n ot isolated except 21c (85%)); f) MesCl, Py, 26% NH4OH (n ot isolated); g) 2a:
NH3/MeOH, Me3SiBr, DMF (45%, 3 steps), 2b: 75% TFA, Me3SiBr, DMF (42%, 3 steps), 2c:
Me3SiBr, MeCN (68%), 2d : Me3SiBr, MeCN (40%, 2 steps)
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20
Zhou, Lagoja, Van Aerschot, Herdewijn:
troduction of th e ph osph on ate m oiety, wh ereas protection of th e less reac-
tive 2-am in o fun ction of 2-am in o-6-ch loropurin e is n ot n eeded. Followin g
reduction of th e azide fun ction to obtain 20a–20c, th e in troduction of th e
ph osph on ate m oiety an d subsequen t deprotection to yield th e required
am in opropyl ph osph on ate n ucleosides 2a–2c could be ach ieved with out
isolation an d purification of th e in term ediates. An alogously to th e proce-
dure described in Sch em e 1, th e cytosin e derivative 2d was prepared by
con version of uracil an alogue 21c, followed by deprotection .
Synthesis of Aminopropyl Phosphonate Nucleosides 3a –3d
A syn th etic path way yieldin g am in opropyl ph osph on ate n ucleosides of
type 3 is outlin ed in Sch em e 4. Again , th e syn th esis starts from racem ic iso-
propyliden eglycerol 4. Followin g activation with a tosyl group, n ucleo-
R
N3
N3
e)
c)
O
O
RO
OH
RO
OH
1 R = OH
22 R = OTs
23 R = N3
24 R = H
26 R = H
a)
b)
d)
k)
f)
25 R = MMTr
27 R = Ms
g)
NHCH2P(O)(Oi-Pr)2
N3
NHR
OTBDMS
i)
B1
B
OH
B1
h)
OTBDMS
29a R = ABz
32a-32d
30a-30d R = H
31a-31d R = CH2P(O)(Oi-Pr)2
28a R = A
j)
29b R = 2-NH2-6-Cl-purine
l)
29c R = U
O
h)
OH
28d R = C
29d R = CBz
P
OH
NH
a: B1 = ABz; b: B1 = 2-NH2-6-Cl-purine;
c: B1 = U; d: B1 = CBz
a: B = A
B
OH
b: B = G
c: B = U
d: B = C
3a-3d
SCHEME 4
Syn th esis of am in opropyl ph osph on ate n ucleosides 3a–3d
a) TsCl, Py (94%); b) NaN3, DMF, 100 °C; c) TFA, H2O (3:1) (33%, 2 steps); d) MTrCl, Py;
e) TBDMSCl, im idazole, DMF, 4% TsOH in MeOH, CH2Cl2 (1:2) (37%, 3 steps); f) MsCl, Py
(81%); g) 29a: LiH, aden in e, THF, 100 °C (47%), BzCl, Py, NH3/MeOH (82%), 29b: Cs2CO3,
2-am in o-6-ch loropurin e, DMF, 90 °C (38%), 29c: K2CO3, NaI, uracil, DMF, 90 °C (43%), 28d :
Cs2CO3, cytosin e, DMF, 90 °C (45%); h ) BzCl, Py (85%); i) Ph 3P, THF, H2O, reflux (30a: 80%,
30b: 90%, 30c: 91%, 30d : 81%); j) Et3N, CF3SO3CH2P(O)(Oi-Pr)2, THF; k) 31a: NH3/MeOH, 1 M
TBAF in THF, 31b: 75% TFA in H2O, 1 M TBAF in THF, 31c: 1 M TBAF in THF, 31d : NH3/MeOH,
1 M TBAF in THF; l) Me3SiBr, MeCN (3 steps: 3a: 24%, 3b: 23%, 3c: 41%, 3d : 24%)
Collect. Czech. Chem. Commun. 2006, Vol. 71, No. 1, pp. 15–34

Synthesis of Aminopropyl Phosphonate Nucleosides
21
ph ilic substitution to in troduce an azido fun ction is carried out. Com poun d
23 is subsequen tly h ydrolyzed to 24. Protection of th e secon dary alcoh ol
fun ction to obtain 26 was ach ieved usin g a m eth oxytrityl group for in ter-
m ediate protection of th e prim ary h ydroxy group. To avoid reduction of
th e azido fun ction to an am in o fun ction un der Mitsun obu con dition s, th e
classical m eth od of couplin g purin e an d pyrim idin e bases by n ucleoph ilic
substitution of alkyl sulfon ates was applied13. Followin g th e reaction with
m esyl ch loride to 27, th e pyrim idin e an d purin e bases could be in troduced
to obtain 28a, 29b, 29c an d 28d . In th e case of aden in e an d cytosin e, th e
exocyclic am in o group was protected by ben zoylation to obtain 29a an d
29d , respectively. Durin g th e couplin g reaction of cytosin e to obtain 28d
(45%), th e O-alkylated an alogue (less polar) was form ed as a by-product.
Th e in troduction of 2-am in o-6-ch loropurin e to yield 29b was accom plish ed
with m oderate yield (38%). However, th e required N9 isom er was obtain ed
alm ost exclusively. Havin g in h an d th e in term ediates 29a–29d , reduction
of th e azide to an am in o fun ction followed by alkylation with (diiso-
propoxyph osph oryl)m eth yl trifluorom eth an esulfon ate yielded com poun ds
31a–31d . Con version of th e 2-am in o-6-ch loropurin e to guan in e, as well as
deprotection of th e aden in e an d cytosin e base followed by h ydrolysis of th e
silyl m oiety, afforded th e in term ediates 32a–32d . Treatm en t with brom o-
trim eth ylsilan e yielded th e desired am in opropyl ph osph on ic acids 3a–3d .
All ph osph on ates 1, 2 an d 3 were exch an ged to th eir disodium salts. Purity
of th e differen t an alogues was verified by an alytic RP-HPLC with Bu4NHSO4
as th e ion pairin g agen t (n ot sh own ).
BIOLOGICAL RESULTS
All acyclic n ucleoside ph osph on ates 1–3, in th eir sodium form , were evalu-
ated in vitro for cytotoxicity an d for th eir activity again st a variety of viruses
in cludin g HIV-1, HIV-2, HSV-1, HSV-2, th ym idin e kin ase (TK)-deficien t
HSV-1/TK– an d vaccin ia virus (VV), varicella-zoster virus (VZV TK– an d TK+)
an d cytom egalovirus (CMV) replication in HEL cells. Brivudin , Ribavirin ,
Acyclovir, Gan ciclovir were used as referen ce drugs. Com poun ds 1–3 did
n ot sh ow cytotoxicity an d are in active again st HIV-1 an d HIV-2. Margin al
biological activity on ly could be observed for som e of th e am in opropyl
ph osph on ate derivatives 2 an d 3 (Table I).
Collect. Czech. Chem. Commun. 2006, Vol. 71, No. 1, pp. 15–34

22
Zhou, Lagoja, Van Aerschot, Herdewijn:
TABLE I
Sum m ary of biological activities foun d for am in opropyl ph osph on ate n ucleosides 1–3
HSV, µg/m l CMV, µg/m l
VZV, µM
Com -
poun d
HSV-1 HSV-2
TK+
VZV
TK–
VZV
b
AD-169
strain
MCCa
MCC
MCC
CC50
CC50
(F)
(Lyon s)
2b
2c
3c
48
80
n .a
48
>400
>400
>400
72
23
>100
>100
100
>50
>50
>50
45
>100
>100
>100
>50
>50
>50
n .a
n .a
n .a
>20
n .a
>20
n .a
n .a
a
Min im um cytotoxic con cen tration th at causes a m icroscopically detectable alteration of
b
cell m orph ology; cytotoxic con cen tration required to reduce cell growth by 50%; n .a., n ot
active at th e h igh est con cen tration tested.
CONCLUSION
Th e syn th esis of am in opropyl ph osph on ate n ucleosides 1–3 h as been de-
scribed. Com poun ds of type 2 an d 3 are obtain ed by ph osph on oylation of
th e acyclic n ucleosides. Th e aglycon is in troduced on th e am in opropyl
group already fun ction alized with a protected ph osph on om eth yl eth er
group in th e case of am in opropyl ph osph on ate n ucleosides 1. Com poun ds
2a–2d are th e (ph osph on om eth yl)am in o con gen ers of HPMPA an d HPMPC.
On ly in th is series m argin al activity again st HSV an d VZV could be dem on -
strated. Replacem en t of th e oxygen atom in th e acyclic ch ain of HPMPC
with a n itrogen fun ction results in a large reduction in biological activity.
EXPERIMENTAL
For all reaction s, an alytical grade solven ts were used. All m oisture-sen sitive reaction s were
carried out in oven -dried glassware (100 °C) un der n itrogen atm osph ere. 1H NMR was deter-
m in ed usin g a Varian Un ity 500 MHz spectrom eter with tetram eth ylsilan e (TMS) as in tern al
stan dard. A 200 MHz Varian Gem in i apparatus was used for 13C NMR determ in ation in
DMSO-d6 (39.6 ppm ) or CDCl3 (76.9 ppm ) an d usin g th e solven t peak as referen ce. Ch em i-
cal sh ifts (δ) are given in ppm , couplin g con stan ts (J) in Hz. Wh ere n eeded COSY an d DEPT
were used to assign proton an d carbon reson an ces. Exact m ass m easurem en ts were per-
form ed on a quadrupole tim e-of-fligh t m ass spectrom eter (Q-Tof-2, Microm ass, Man ch ester,
U.K.) equipped with a stan dard electrospray-ion ization (ESI) in terface; sam ples were in fused
in i-PrOH/H2O 1:1 at 3 µl/m in . TLC was perform ed with TLC alum in um sh eets (Merck, Silica
gel 60 F254). Th e spots were exam in ed with UV ligh t, or sprayed with sulfuric acid/
an isaldeh yde or 1% potassium perm an gan ate solution . Colum n ch rom atograph y was per-
form ed on ICN silica gel 60–200 60A. Th e n am es of th e com poun ds were m ade in accord
with IUPAC rules.
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Synthesis of Aminopropyl Phosphonate Nucleosides
23
Th e syn th esis of th e en an tiom erically pure com poun ds 22–27, 29a h as been publish ed re-
cen tly, startin g from (S)-1,2-O-isopropyliden eglycerol14. Th e racem ic con gen ers used h ere
were prepared in an alogous fash ion .
(±)-2,3-Dih ydroxypropyl Ben zoate (6)
Un der ice-coolin g, ben zoyl ch loride (20.00 m l, 0.17 m m ol) was added slowly to a solution
of 1,2-O-isopropyliden eglycerol 4 (15.00 g, 0.11 m ol) in dry pyridin e (100 m l). Th e reaction
was th en allowed to warm to room tem perature an d stirred for 5 h . After th e solven t was
evaporated, th e residual oil was co-evaporated with toluen e (2 × 20 m l), dissolved in CH2Cl2
(40 m l) an d wash ed with saturated aqueous NaHCO3 (2 × 25 m l). Th e organ ic layer was
dried over an h ydrous Na2SO4 an d con cen trated. Th e residue was treated with 75% TFA in
water (50 m l) for 4 h , con cen trated in vacuo an d purified by colum n ch rom atograph y
(CH2Cl2/MeOH 95:5 to 92:8). Yield 10.91 g (49%); RF 0.60 (CH2Cl2/MeOH 90:10). 1H NMR
(DMSO-d6): 3.58–3.61 (d, 2 H, H-3′, J3′,2′ = 5.8), 3.90–3.97 (m , 1 H, H-2′), 4.24–4.33 (dd, 1 H,
H-1′A, J1′A,2′ = 6.0, Jgem = 11.2), 4.36–4.44 (dd, 1 H, H-1′B, J1′B,2′ = 4.4, Jgem = 11.2), 7.43–7.63
(m , 3 H, 3,4,5-H-Ar), 7.80–8.04 (d, 2 H, 2,6-H-Ar, J = 8.4). 13C NMR (CDCl3): 63.2 (C-3′),
66.7 (C-2′), 70.0 (C-1′), 129.0 (C-3,5-Ar), 129.8 (C-2,6-Ar), 133.6 (C-4-Ar), 166.5 (C=O).
ES-MS calculated for C10H13O4 [M + H]+: 197.0814; foun d: 197.0809.
(±)-2-(Mesyloxy)-3-[(4-m eth oxytrityl)oxy]propyl Ben zoate (8)
Com poun d 6 (10.00 g, 51.0 m m ol) was co-evaporated with dry pyridin e (2 × 20 m l) an d dis-
solved in pyridin e (40 m l). MTrCl (17.30 g, 56.1 m m ol) was added an d th e reaction m ixture
was stirred for 5 h . Mesyl ch loride (6.41 g, 56.1 m m ol) was added an d stirrin g was con tin -
ued for an addition al 2 h . Th e reaction was quen ch ed by th e addition of saturated aqueous
NaHCO3 (30 m l) an d extracted with CH2Cl2 (4 × 30 m l). Th e organ ic layer was dried over
an h ydrous Na2SO4 an d con cen trated in vacuo. Th e residue was purified by colum n ch rom a-
tograph y (CH2Cl2). Yield 21.43 g (77%); RF 0.54 (CH2Cl2). 1H NMR (CDCl3): 3.04 (s, 3 H,
CH3), 3.45–3.53 (dd, 1 H, H-3′A, J3′A,2′ = 5.6, Jgem =11.4), 3.55–3.62 (dd, 1 H, H-3′B, J3′B,2′
=
4.4, Jgem = 11.4), 3.80 (s, 3 H, CH3), 4.59–4.62 (m , 2 H, H-1′), 5.09–5.19 (m , 1 H, H-2′),
6.84–6.92 (d, 2 H, H-MTr), 7.31–7.64 (m , 15 H, H-MTr, 3,4,5-H-Bz), 8.00–8.05 (d, 2 H,
2,6-H-Ar). 13C NMR (CDCl3): 38.5 (CH3 Ms), 55.0 (O-CH3), 62.4 (C-3′), 63.3 (C-1′), 78.4
(C-2′), 87.0 (C-MTr), 113.1 (C-MTr), 127.1, 127.8, 128.0, 128.2, 128.4, 129.3, 129.8, 130.4
(C-MTr), 129.6 (C-3,5-Bz), 130.2 (C-2,6-Bz), 133.3 (C-4-Bz), 134.6, 143.6, 158.7 (C-MTr),
165.9 (C=O). ES-MS calculated for C31H30NaO7S [M + Na]+: 569.1609; foun d: 569.1605.
(±)-2-Azido-3-[(4-m eth oxytrityl)oxy]propan -1-ol (10)
A m ixture of com poun d 8 (21.00 g, 38.5 m m ol) an d NaN3 (3.74 g, 54.9 m m ol) was dissolved
in DMF (30 m l) an d stirred at 100 °C overn igh t. Th e reaction was con cen trated un der re-
duced pressure. Th e residue was dissolved in CH2Cl2 (20 m l) an d wash ed with water (2 ×
20 m l). Th e organ ic layer was dried over an h ydrous Na2SO4 an d con cen trated. Th e residual
oil was treated with 1 M NaOH in MeOH (40 m l) overn igh t. After con cen tratin g th e m ixture,
th e residue was dissolved in H2O (20 m l) an d extracted with CH2Cl2 (2 × 30 m l). Th e or-
gan ic layer was dried over an h ydrous Na2SO4, con cen trated an d purified by colum n ch rom a-
tograph y (CH2Cl2/MeOH 99:1). Yield 7.44 g (50%); RF 0.25 (CH2Cl2/MeOH 99:1). 1H NMR
(CDCl3): 3.29–3.32 (m , 2 H, H-3′), 3.58–3.70 (m , 3 H, H-2′, H-1′), 3.80 (s, 3 H, CH3),
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24
Zhou, Lagoja, Van Aerschot, Herdewijn:
6.82–6.87 (d, 2 H, H-MTr), 7.23–7.54 (m , 12 H, H-MTr). 13C NMR (CDCl3): 55.2 (CH3), 62.8
(C-3′), 63.3 (C-2′), 63.5 (C-1′), 87.1 (C-MTr), 113.3 (C-MTr), 127.1, 128.0, 128.4, 130.4,
135.1, 144.0, 158.8 (C-MTr). ES-MS calculated for C23H23N3NaO3 [M + Na]+: 412.1637;
foun d: 412.1643.
(±) Diisopropyl [(2-Azido-3-h ydroxypropoxy)m eth yl]ph osph on ate (12)
A m ixture of 10 (3.40 g, 8.7 m m ol) an d CF3SO3CH2P(O)(Oi-Pr)2 (3.90 g, 10.4 m m ol) was dis-
solved in THF (30 m l) an d cooled to –30 °C. NaH (0.34 g, 11.2 m m ol) was added un der stir-
rin g, th e reaction m ixture was allowed to warm to 0 °C. Stirrin g at 0 °C was con tin ued for
1 h . Followin g addition of MeOH, th e solven t was evaporated, th e residue was dissolved in
CH2Cl2 (30 m l) an d extracted with saturated aqueous NaHCO3 (2 × 30 m l). Th e organ ic
layer was dried over an h ydrous Na2SO4, con cen trated an d th e residue was treated with 3%
TFA in CH2Cl2 (25 m l) over a period of 2 h . Th en a saturated aqueous NaHCO3 solution
(25 m l) was added an d th e m ixture was extracted with CH2Cl2 (2 × 30 m l). Th e organ ic
layer was dried over an h ydrous Na2SO4 an d con cen trated in vacuo. Th e residue was purified
by colum n ch rom atograph y (EtOAc, eth yl acetate). Yield 2.02 g (73%); RF 0.20 (EtOAc).
1H NMR (CDCl3): 1.31–1.34 (d, 12 H, 4 × CH3), 3.55–3.88 (m , 7 H, H-3′, H-2′, H-1′,
O-CH2-P), 4.68–4.78 (m , 2 H, 2 × O-CH-(CH3)2). 13C NMR (CDCl3): 23.8 (4 × CH3), 61.3
(C-2′), 61.9 (C-3′), 64.3, 67.6 (O-CH2-P), 71.5 (d, 2 × O-CH-(CH3)2, JC,P = 5.2), 72.0 (d, C-1′,
J1′,P = 5.2). FAB-MS calculated for C10H22N3NaO5P [M + Na]+: 318.3; foun d: 318.0.
Syn th esis of Com poun ds 13 an d 14b by Mitsun obu Reaction . Gen eral Procedure
A m ixture of 12 (0.60 g, 2.03 m m ol), a n ucleobase [a aden in e (0.56 g, 4.06 m m ol),
b 2-am in o-6-ch loropurin e (0.69 g, 4.07 m m ol), c 3-ben zoyluracil (0.68 g, 3.05 m m ol)] an d
triph en ylph osph in e (for a, b 1.07 g, 4.07 m m ol, for c 0.81 g, 3.05 m m ol) were dissolved in
dry THF (10 m l) an d cooled to 0 °C in an ice bath . Th en DIAD (for a, b, c 0.51 g, 2.54 m m ol)
in THF (2 m l) was added dropwise over 30 m in . Th e reaction was allowed to warm to room
tem perature an d stirrin g was con tin ued overn igh t. Th e reaction m ixture was con cen trated;
th e residue was dissolved in CH2Cl2 (20 m l) an d wash ed with water (2 × 15 m l). Th e organ ic
layer was dried over an h ydrous Na2SO4 an d th e solven t was evaporated. Th e residue was pu-
rified by colum n ch rom atograph y.
(±) Diisopropyl {[3-(6-amino-9H-purin-9-yl)-2-azidopropoxy]methyl}phosphonate (13a): Yield
0.44 g (53%); RF 0.28 (CH2Cl2/MeOH 95: 5). 1H NMR (CDCl3): 1.30, 1.33 (d, 12 H, 4 × CH3),
3.61–4.43 (m , 7 H, H-3′, H-2′, H-1′, O-CH2-P), 4.67–4.83 (m , 2 H, 2 × O-CH-(CH3)2), 6.54 (s,
2 H, NH2), 7.88 (s, 1 H, H-2), 8.30 (s, 1 H, H-8). 13C NMR (CDCl3): 22.5 (4 × CH3), 43.8
(C-1′), 59.8 (C-2′), 64.6, 67.9 (O-CH2-P), 69.8–69.9 (d, 2 × O-CH-(CH3)2, JC,P = 6.1), 71.1–71.4
(d, C-3′, J3′,P = 10.7), 119.3 (C-5), 141.0 (C-8), 150.0 (C-4), 153.1 (C-2), 155.9 (C-6). ES-MS
calculated for C15H26N8O4P [M + H]+: 413.1814; foun d: 413.1819.
(±) Diisopropyl {[3-(2-amino-6-oxo-1,6-dihydro-9H-purin-9-yl)-2-azidopropoxy]methyl}phosphonate
(13b ): Th e ph osph oran yliden e derivative (14b ) (0.60 g, 0.85 m m ol) obtain ed after
Mitsun obu reaction [yield 0.68 g (47%); RF 0.40 (CH2Cl2/MeOH 95:5); FAB-MS [M + H]+:
707.1] was dissolved in THF (10 m l), water (3 m l) was added an d th e m ixture was h eated
un der reflux for two days. Th e solven t was rem oved in vacuo an d th e residue 15b was puri-
fied by colum n ch rom atograph y (CH2Cl2/MeOH 95:5) [yield 0.32
g (85%); RF 0.50
(CH2Cl2/MeOH 95:5); FAB-MS [M + H]+: 447.1]. Com poun d 15b (0.30 g, 0.75 m m ol) was
treated furth er with 75% TFA in water (10 m l) at room tem perature overn igh t. Th e solven t
Collect. Czech. Chem. Commun. 2006, Vol. 71, No. 1, pp. 15–34

Synthesis of Aminopropyl Phosphonate Nucleosides
25
was evaporated an d th e residue 13b was purified by colum n ch rom atograph y (CH2Cl2/
MeOH 9:1). Yield 0.20 g (63%); RF 0.45 (CH2Cl2/MeOH 9:1). 1H NMR (CDCl3): 1.20, 1.23 (d,
12 H, 4 × CH3), 3.47–4.16 (m , 7 H, H-3′, H-2′, H-1′, O-CH2-P), 4.51–4.63 (m , 2 H, 2 ×
O-CH-(CH3)2), 6.52 (s, 2 H, NH2), 7.71 (s, 1 H, H-8), 10.67 (s, 1 H, NH). 13C NMR (CDCl3):
23.6 (4 × CH3), 43.0 (C-1′), 59.7 (C-2′), 63.4, 66.6 (O-CH2-P), 70.1–70.2 (d, 2 × O-CH-(CH3)2,
JC,P = 6.1), 72.1–72.3 (d, C-1′, J1′,P = 10.7), 116.6 (C-5), 137.6 (C-8), 151.8 (C-2), 153.7 (C-4),
156.9 (C-6). ES-MS calculated for C15H26N8O5P [M + H]+: 429.1764; foun d: 429.1760.
(±) Diisopropyl {[2-azido-3-(2,4-dioxo-1,2,3,4-tetrahydropyrimidin-1-yl)propoxy]methyl}phosphonate
(13c): Yield 0.69 g (69%); RF 0.22 (EtOAc). 1H NMR (CDCl3): 1.31, 1.34 (d, 12 H, 4 × CH3),
3.56–4.05 (m , 7 H, H-3′, H-2′, H-1′, O-CH2-P), 4.70–4.80 (m , 2 H, 2 × O-CH-(CH3)2),
5.68–5.72 (d, 1 H, H-5, J5,6 = 8.0 ), 7.27–7.31 (d, 1 H, H-6, J5,6 = 8.0), 10.2 (br, 1 H, NH).
13C NMR (CDCl3): 22.5 (4 × CH3), 47.7 (C-1′), 57.9 (C-2′), 63.1, 66.5 (O-CH2-P), 69.9–70.0
(d, 2 × O-CH-(CH3)2, JC,P = 6.1), 71.0–71.2 (d, C-1′, J1′,P = 10.7), 100.8 (C-5), 144.0 (C-6),
149.8 (C-2), 162.8 (C-4). ES-MS calculated for C14H25N5O6P [M + H]+: 390.1543; foun d:
390.1548.
(±) Diisopropyl {[3-(4-amino-2-oxopyrimidin-1(2H)-yl)-2-azidopropoxy]methyl}phosphonate
(13d ): Et3N (350 µl) was added dropwise to a solution of 13c (0.30 g, 0.77 m m ol) an d
m esitylen esulfon yl ch loride (0.51 g, 2.31 m m ol) in MeCN (10 m l) at 0 °C un der n itrogen .
After stirrin g at room tem perature for 2 h , 26% NH4OH in water (5 m l) was added an d th e
m ixture was stirred for an oth er 3 h . Th e resultin g m ixture was extracted with eth yl acetate
(2 × 15 m l). Th e organ ic layer was wash ed with water (15 m l), dried over an h ydrous Na2SO4
an d con cen trated un der h igh vacuum . Th e residue was purified by colum n ch rom atograph y
(CH2Cl2/MeOH 9:1). Yield 0.18 g (60%); RF 0.48 (CH2Cl2/MeOH 9:1). 1H NMR (CDCl3):
1.33, 1.36 (d, 12 H, 4 × CH3), 3.43–4.10 (m , 7 H, H-3′, H-2′, H-1′, O-CH2-P), 4.68–4.82 (m ,
2 H, 2 × O-CH-(CH3)2), 5.89–5.93 (d, 1 H, H-5, J5,6 = 6.8 ), 7.26–7.30 (d, 1 H, H-6, J5,6 = 6.8).
13C NMR (CDCl3): 23.9 (4 × CH3), 50.4 (C-1′), 59.6 (C-2′), 64.5, 67.8 (O-CH2-P), 71.2–71.4
(d, 2 × O-CH-(CH3)2, JC,P = 7.6), 72.8–73.0 (d, C-1′, J1′,P = 10.7), 95.0 (C-5), 146.0 (C-6),
156.7 (C-2), 166.6 (C-4). ES-MS calculated for C14H26N6O5P [M + H]+: 389.1702; foun d:
389.1704.
Syn th esis of Am in opropyl Ph osph on ate Nucleosides 1. Gen eral Procedure
Un der ice-coolin g, H2S gas was bubbled th rough a solution of com poun d 13a–13d (a 0.21 g,
0.51 m m ol; b 0.13 g, 0.30 m m ol; c 0.25 g, 0.64 m m ol; d 0.15 g, 0.39 m m ol) in pyridin e/
trieth ylam in e 4:1 (10 m l) for 20 m in , followed by stirrin g for an oth er 1 h . Th e solven t was
evaporated an d th e residue was co-evaporated with toluen e (2 × 10 m l). Th e residue
(16a–16d ) was dissolved in MeCN (10 m l) an d Me3SiBr (0.24 g, 15.3 m m ol) was added.
Stirrin g was con tin ued overn igh t. Th e reaction m ixture was con cen trated an d was purified
by colum n ch rom atograph y (CH2Cl2/MeOH 9:1, CH2Cl2/MeOH/H2O 5:4:1). All com poun ds
1a–1d were an alysed as disodium salts.
(±)-{[2-Amino-3-(6-amino-9H-purin-9-yl)propoxy]methyl}phosphonic acid (1a): Yield 75 m g
(49%); RF 0.24 (MeOH). 1H NMR (D2O): 3.45–3.79 (m , 5 H, CH2-P, H-1′, H-2′), 4.42 (m , 2 H,
H-3′), 7.95 (s, 1 H, H-2), 8.02 (s, 1 H, H-8). 13C NMR (D2O): 45.5 (C-1′), 52.3 (C-2′), 69.9,
72.9 (CH2-P), 72.8–72.1 (d, C-3′, JC-3′,P = 11.2), 120.2 (C-5), 144.5 (C-8), 150.9 (C-4), 154.6
(C-2), 157.3 (C-6). ES-MS calculated for C9H14N6O4P [M – H]–: 301.0814; foun d: 301.0809.
(±)-{[2-Amino-3-(2-amino-6-oxo-1,6-dihydro-9H-purin-9-yl)propoxy]methyl}phosphonic acid
(1b): Yield 42 m g (44%); RF 0.33 (CH2Cl2/MeOH/H2O 5:4:1). 1H NMR (D2O): 3.47–3.60 (m ,
Collect. Czech. Chem. Commun. 2006, Vol. 71, No. 1, pp. 15–34

26
Zhou, Lagoja, Van Aerschot, Herdewijn:
5 H, CH2-P, H-1′, H-2′), 4.19 (m , 2 H, H-3′), 7.71 (s, 1 H, H-8). 13C NMR (D2O): 46.8 (C-1′),
52.3 (C-2′), 70.1, 73.0 (CH2-P), 73.8–74.1 (d, C-3′, JC-3′,P = 12.2), 118.0 (C-5), 142.2 (C-8),
153.9 (C-4), 156.4 (C-2), 161.6 (C-6). ES-MS calculated for C9H14N6O5P [M – H]–: 317.0763;
foun d: 317.0770.
(±)-{[2-Amino-3-(2,4-dioxo-1,2,3,4-tetrahydropyrimidin-1-yl)propoxy]methyl}phosphonic acid
(1c): Yield 90 m g (51%); RF 0.32 (CH2Cl2/MeOH/H2O 5:4:1). 1H NMR (D2O): 3.44–3.48 (d,
2 H, CH2-P, JH,P = 8.8), 3.56–3.71 (m , 3 H, H-1′, H-2′), 3.91–4.12 (m , 2 H, H-3′), 5.78–5.82 (d,
1 H, H-5, J5,6 = 7.8), 7.60–7.64 (d, 1 H, H-6, J5,6 = 7.8). 13C NMR (D2O): 50.6 (C-1′), 51.8
(C-2′), 69.9, 72.9 (CH2-P), 72.0–72.2 (d, C-3′, JC-3′,P = 12.2), 104.3 (C-5), 149.5 (C-6), 155.2
(C-2), 169.5 (C-4). ES-MS calculated for C8H13N3O6P [M – H]–: 278.0542; foun d: 278.0547.
(±)-{[2-Amino-3-(4-amino-2-oxopyrimidin-1(2H)-yl)propoxy]methyl}phosphonic acid (1d ): Yield
52 m g (48%); RF 0.25 (CH2Cl2/MeOH/H2O 5:4:1). 1H NMR (D2O): 3.43–3.73 (m , 5 H, CH2-P,
H-1′, H-2′), 3.90–4.13 (m , 2 H, H-3′), 5.92–5.96 (d, 1 H, H-5, J5,6 = 7.2), 7.53–7.56 (d, 1 H,
H-6, J5,6 = 7.2). 13C NMR (D2O): 51.2 (C-2′), 52.1 (C-1′), 69.9, 72.9 (CH2-P, J = 151),
72.3–72.5 (d, C-3′, JC,P = 13.7), 98.4 (C-5), 149.3 (C-6), 160.8 (C-2), 168.9 (C-4). ES-MS calcu-
lated for C8H14N4O5P [M – H]–: 277.0702; foun d: 277.0703.
Syn th esis of Com poun ds 19a–19c by Mitsun obu Reaction . Gen eral Procedure
Com poun d 10 (1.50 g, 3.86 m ol),
a n ucleobase [a aden in e (1.05 g, 7.71 m m ol),
b 2-am in o-6-ch loropurin e (1.31 g, 7.63 m m ol), c 3-ben zoyluracil (1.30 g, 5.78 m m ol)] an d
triph en ylph osph in e (2.02 g, 7.71 m m ol) were dissolved in dry THF (10 m l) an d cooled to
0 °C. DIAD (1.53 m l, 7.71 m m ol) in THF (1 m l) was added dropwise over 30 m in . Th e reac-
tion was allowed to warm to room tem perature an d stirrin g was con tin ued overn igh t. Th e
reaction m ixture was con cen trated; th e residue was dissolved in CH2Cl2 (30 m l) an d wash ed
with water (2 × 20 m l). Th e organ ic layer was dried over an h ydrous Na2SO4, th e solven t was
evaporated an d th e residue was purified by colum n ch rom atograph y.
(±)-N-(9-{2-Azido-3-[(4-methoxytrityl)oxy]propyl}-9H-purin-6-yl)benzamide (19a): Followin g
th e Mitsun obu reaction , 17a was obtain ed [yield 0.88 g (45%); RF 0.21 (CH2Cl2/MeOH 95:5);
ES-MS [M + H]+: 507.2257]. Un der ice-coolin g, ben zoyl ch loride (4.43 m l, 4.73 m m ol) was
added to a solution of com poun d 17a (0.80 g, 1.58 m m ol) in pyridin e (15 m l). Th e reaction
was stirred for 1 h an d allowed to warm to room tem perature. After stirrin g overn igh t, th e
reaction was quen ch ed with m eth an ol an d th e solven t was evaporated. Th e residue was
cooled to 0 °C an d treated with saturated NH3 in MeOH (20 m l) for 60 m in . Followin g evap-
oration of th e solven t, th e rem ain in g m ixture was dissolved in CH2Cl2 (20 m l) an d wash ed
with saturated aqueous NaHCO3 (2 × 10 m l). Th e organ ic layer was dried over an h ydrous
Na2SO4, evaporated an d purified by colum n ch rom atograph y to obtain 19a (CH2Cl2/MeOH
97:3). Yield 0.89 g (85%); RF 0.81 (CH2Cl2/MeOH 95:5). 1H NMR (CDCl3): 3.25–3.33 (dd,
1 H, H-1′A, J1′A,2′ = 6.0, Jgem = 10.0), 3.41–3.48 (dd, 1 H, H-1′B, J1′B,2′ = 4.0, Jgem = 10.0), 3.79
(s, 3 H, O-CH3), 3.96–4.03 (m , 1 H, H-2′), 4.12–4.23 (dd, 1 H, H-3′A, J3′A,2′ = 8.2, Jgem = 12.2),
4.28–4.37 (dd, 1 H, H-3′B, J3′B,2′ = 4.2, Jgem = 12.2), 6.83–6.87 (d, 2 H, H-Ar), 7.20–7.64 (m ,
15 H, H-Ar), 7.97–8.05 (m , 3 H, H-Ar), 7.98 (s, 1 H, H-2), 8.75 (s, 1 H, H-8), 9.19 (br, 1 H,
NH). 13C NMR (CDCl3): 44.5 (C-1′), 55.1 (O-CH3), 60.7 (C-2′), 63.7 (C-3′), 87.3 (C-MTr),
122.8 (C-5), 113.3, 127.2, 127.9, 128.2, 128.8, 130.3, 132.8, 133.7, 134.7, 143.5 (C-Ar), 143.7
(C-8), 149.6 (C-4), 152.7 (C-2), 155.9 (C-6), 158.8 (C-Ar), 164.7 (C=O). ES-MS calculated for
C
35H36N8O3 [M + H]+: 661.2910; foun d: 661.2520.
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Synthesis of Aminopropyl Phosphonate Nucleosides
27
(±)-9-{2-Azido-3-[(4-methoxytrityl)oxy]propyl}-6-chloro-9H-purin-2-amine (19b): Followin g th e
Mitsun obu reaction , 18b was obtain ed [yield 1.39 g (45%); RF 0.67 (CH2Cl2/MeOH 94:6);
FAB-MS [M + H]+: 801.2]. To a solution of com poun d 18b (0.90 m g, 1.25 m m ol) in THF
(20 m l), water (5 m l) was added an d th e m ixture was refluxed for two days. Th e solven t was
rem oved un der vacuum an d th e residue 19b was purified by colum n ch rom atograph y
(CH2Cl2/MeOH 95:5). Yield 0.56 g (82%); RF 0.65 (CH2Cl2/MeOH 95:5). 1H NMR (CDCl3):
3.20–3.28 (dd, 1 H, H-1′A, J1′A,2′ = 6.0, Jgem = 10.2), 3.32–3.40 (dd, 1 H, H-1′B, J1′B,2′ = 4.0,
Jgem = 10.2), 3.78 (s, 3 H, O-CH3), 3.88–3.97 (m , 1 H, H-2′), 4.04–4.09 (dd, 1 H, H-3′A,
J3′A,2′ = 4.0, Jgem = 12.0), 4.28–4.37 (dd, 1 H, H-3′B, J3′B,2′ = 5.2, Jgem = 12.0), 5.37 (s, 2 H,
NH2), 6.81–6.88 (d, 2 H, H-Ar), 7.19–7.35 (m , 8 H, H-Ar), 7.43–7.48 (d, 2 H, H-Ar), 7.69 (s,
1 H, H-8). 13C NMR (CDCl3): 44.0 (C-1′), 55.2 (O-CH3), 60.4 (C-2′), 63.5 (C-3′), 87.2
(C-MTr), 124.9 (C-5), 113.2, 127.2, 127.9, 128.2, 130.2, 134.6 (C-Ar), 142.6 (C-8), 143.7
(C-Ar), 151.3 (C-2), 153.7 (C-4), 158.8 (C-Ar), 159.1 (C-6). ES-MS calculated for
C
28H26ClN8O2P [M + H]+: 541.1862; foun d: 541.1868.
(±)-1-{2-Azido-3-[(4-methoxytrityl)oxy]propyl}pyrimidine-2,4(1H,3H)-dione (19c): Yield 1.76 g
(46%); RF 0.40 (CH2Cl2/MeOH 99:1). 1H NMR (CDCl3): 3.15–3.23 (dd, 1 H, H-1′A, J1′A,2′
=
5.68, Jgem = 10.7), 3.36–3.45 (dd, 1 H, H-1′B, J1′B,2′ = 3.7, Jgem = 10.4), 3.41–3.52 (dd, 1 H,
H-3′A, J3′A,2′ = 8.24, Jgem = 13.1), 3.79 (s, 3 H, O-CH3), 3.84–3.93 (m , 1 H, H-2′), 3.97–4.05
(dd, 1 H, H-3′B, J3′B,2′ = 4.2, Jgem = 13.1), 5.58–5.62 (d, 1 H, H-5, J5,6 = 7.6), 6.83–6.87 (d,
2 H, H-Ar), 7.07–7.11 (d, 1 H, H-6, J5,6 = 7.6 ), 7.27–7.56 (m , 8 H, H-Ar), 7.80–7.85 (d, 4 H,
H-Ar), 10.04 (br, 1 H, NH). 13C NMR (CDCl3): 49.0 (C-1′), 55.2 (O-CH3), 60.1 (C-2′), 63.2
(C-3′), 87.1 (C-MTr), 102.0 (C-5), 113.2, 127.3, 128.0, 128.6, 130.3, 134.7, 143.7 (C-Ar),
145.2 (C-6), 151.0 (C-4), 158.8 (C-Ar), 164.1 (C-2). ES-MS calculated for C27H24N5O4 [M –
H]–: 482.1828; foun d: 482.1831.
Reduction to Com poun ds 20a–20c. Gen eral Procedure
Triph en ylph osph in e (0.39 g, 1.5 m m ol) was added to a solution of 19a (0.61 g, 1.0 m m ol),
19b (0.53 g, 1.0 m m ol) an d 19c (0.49 g, 1.0 m m ol), respectively, in dry THF (10 m l). Th e
reaction was stirred overn igh t. Th en water (10 m l) was added an d th e reaction was refluxed
for an oth er 3 h . Th e reaction m ixture was con cen trated to a sm all volum e an d purified by
colum n ch rom atograph y.
(±)-N-(9-{2-Amino-3-[(4-methoxytrityl)oxy]propyl}-9H-purin-6-yl)benzamide (20a): Yield 0.55 g
(94%); RF 0.31 (CH2Cl2/MeOH 95:5). 1H NMR (CDCl3): 3.15–3.17 (m , 2 H, H-1′), 3.31–3.40
(m , 1 H, H-2′), 3.79 (s, 3 H, O-CH3), 4.16-4.26 (dd, 1 H, H-3′A, J3′A,2′ = 7.6, Jgem = 14.0),
4.18–4.28 (dd, 1 H, H-3′B, J3′B,2′ = 4.4, Jgem = 14.0), 6.82–6.86 (d, 2 H, H-Ar), 7.27–7.61 (m ,
15 H, H-Ar), 7.97 (s, 1 H, H-2), 8.00–8.06 (d, 2 H, H-Ar), 8.77 (s, 1 H, H-8). 13C NMR
(CDCl3): 47.9 (C-1′), 51.3 (C-2′), 55.2 (O-CH3), 65.7 (C-3′), 86.6 (C-MTr), 113.3, 127.1, 128.0,
128.2, 128.9, 130.3, 132.7, 133.8, 135.1 (C-Ar), 143.9 (C-8), 144.1 (C-Ar), 149.4 (C-4), 152.5
(C-2), 158.8 (C-Ar), 164.7 (C=O). ES-MS calculated for C35H33N6O3 [M + H]+: 585.2614;
foun d: 585.2601.
(±)-9-{2-Amino-3-[(4-methoxytrityl)oxy]propyl}-6-chloro-9H-purin-2-amine (20b): Yield 0.47 g
(91%); RF 0.73 (CH2Cl2/MeOH 95:5). 1H NMR (CDCl3): 3.08–3.11 (m , 2 H, H-1′), 3.31–3.40
(m , 1 H, H-2′), 3.79 (s, 3 H, O-CH3), 3.98–4.08 (dd, 1 H, H-3′A, J3′A,2′ = 7.0, Jgem = 14.0),
4.18–4.28 (dd, 1 H, H-3′B, J3′B,2′ = 5.2, Jgem = 14.0), 5.14 (s, 2 H, NH2), 6.80–6.85 (d, 2 H,
H-Ar), 7.19–7.34 (m , 15 H, H-Ar), 7.40–7.45 (m , 4 H, H-Ar), 7.70 (s, 1 H, H-8). 13C NMR
(CDCl3): 47.6 (C-1′), 51.1 (C-2′), 55.2 (O-CH3), 65.6 (C-3′), 86.6 (C-MTr), 125.2 (C-5), 113.3,
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28
Zhou, Lagoja, Van Aerschot, Herdewijn:
127.1, 127.9, 128.3, 130.3, 135.1 (C-Ar), 143.2 (C-8), 144.3 (C-Ar), 151.3 (C-2), 154.2 (C-4),
158.8 (C-Ar), 159.0 (C-6). ES-MS calculated for C28H28ClN6O2 [M + H]+: 515.1962; foun d:
515.1958.
(±)-1-{2-Amino-3-[(4-methoxytrityl)oxy]propyl}pyrimidine-2,4(1H,3H)-dione (20c): Yield 0.41 g
(88%); RF 0.35 (CH2Cl2/MeOH 95:5). 1H NMR (CDCl3): 3.10–3.30 (m , 3 H, H-1′, H-2′),
3.60–3.67 (dd, 1 H, H-3′A, J3′A,2′ = 6.96, Jgem = 13.6), 3.79 (s, 3 H, O-CH3), 3.84–3.94 (dd,
1 H, H-3′B, J3′B,2′ = 5.40, Jgem = 13.6), 5.43–5.48 (d, 1 H, H-5, J5,6 = 8.0), 6.81–6.86 (d, 2 H,
H-Ar), 6.99–7.03 (d, 1 H, H-6, J5,6 = 8.0 ), 7.15–7.51 (m , 12 H, H-Ar). 13C NMR (CDCl3): 5.06
(C-1′), 52.0 (C-2′), 55.2 (O-CH3), 64.9 (C-3′), 86.4 (C-MTr), 101.5 (C-5), 113.2, 127.2, 128.0,
128.3, 130.3, 135.1, 143.7 (C-Ar), 145.5 (C-6), 151.3 (C-4), 158.8 (C-Ar), 163.9 (C-2). ES-MS
calculated for C27H27N3NaO4 [M + Na]+: 480.1899; foun d: 480.1917.
Syn th esis of Am in opropyl Ph osph on ate Nucleosides 2a, 2b
Com poun d 20a (0.53 g, 0.91 m m ol) or 20b (0.18 g, 0.35 m m ol) was dissolved in THF
(10 m l) an d cooled to 0 °C in an ice bath . Th en Et3N (2 m l) was added dropwise followed by
th e addition of CF3SO3CH2P(O)(Oi-Pr)2 (for a 0.45 g, 1.36 m m ol, for b 0.22 g, 0.64 m m ol).
Stirrin g was con tin ued at 0 °C for 5 h an d MeOH was added. Th e m ixture was con cen trated,
dissolved in CH2Cl2 (15 m l) an d wash ed with saturated aqueous NaHCO3 (2 × 10 m l). Th e
organ ic layer was dried over an h ydrous Na2SO4 an d con cen trated. In th e syn th esis of 2a,
th e residue was treated with saturated NH3 in MeOH (10 m l) at room tem perature overn igh t
an d th e reaction was con cen trated an d co-evaporated with MeCN (3 × 5 m l), wh ereas in
th at of 2b, th e m ixture was treated with 75% TFA in water (10 m l) for two days followed
by con cen tration an d co-evaporation with toluen e (3 × 10 m l). In both cases, th e obtain ed
residue was dissolved in DMF (10 m l) an d Me3SiBr (for a 0.29 g, 1.89 m m ol, for b 0.16 g,
1.05 m m ol) was added. Th e reaction was stirred for 3 days, con cen trated an d purified by
colum n ch rom atograph y (CH2Cl2/MeOH 9:1, CH2Cl2/MeOH/H2O 5:4:1). Com poun ds 2a, 2b
were an alysed as disodium salts.
(±)-({[2-(6-Amino-9H-purin-9-yl)-1-(hydroxymethyl)ethyl]amino}methyl)phosphonic acid (2a):
Yield 0.12 g (45%); RF 0.50 (MeOH + 1% EtN3). 1H NMR (D2O): 2.98–3.05 (d, 2 H, CH2-P,
JH,P = 12.6), 3.53–3.86 (m , 3 H, H-1′, H-2′), 4.46–4.49 (m , 2 H, H-3′), 8.01 (s, 2 H, H-2), 8.03
(s, 1 H, H-8). 13C NMR (D2O): 44.1, 46.7 (CH2-P, JC,P = 131.2), 51.0 (C-1′), 59.0 (C-3′),
61.0–61.1 (d, C-2′, JC-2′,P = 6.1), 120.1 (C-5), 144.5 (C-8), 151.0 (C-4), 154.7 (C-2), 157.4
(C-6). ES-MS calculated for C9H14N6O4P [M – H]–: 301.0814; foun d: 301.0807.
(±)-({[2-(2-Amino-6-oxo-1,6-dihydro-9H-purin-9-yl)-1-(hydroxymethyl)ethyl]amino}methyl)-
phosphonic acid (2b): Yield 46 m g (42%); RF 0.25 (MeOH). 1H NMR (D2O): 2.59–2.65 (d, 2 H,
CH2-P, JH,P = 12.0), 3.11 (m , 1 H, H-2′), 3.38–3.60 (m , 2 H, H-1′), 4.09 (m , 2 H, H-3′), 7.70 (s,
1 H, H-8). 13C NMR (D2O): 46.1 (C-1′), 47.4, 48.5 (CH2-P, JC,P = 131.2), 51.6 (C-3′),
62.0–62.4 (d, C-2′, JC-2′,P = 6.1), 119.7 (C-5), 142.2 (C-8), 154.6 (C-4), 161.5 (C-2), 167.2
(C-6). ES-MS calculated for C9H14N6O5P [M – H]–: 317.0763; foun d: 317.0764.
(±) Diisopropyl {[(2-(2,4-Dioxo-1,2,3,4-tetrah ydropyrim idin -1-yl)-
1-{[(4-m eth oxytrityl)oxy]m eth yl}eth yl)am in o]m eth yl}ph osph on ate (21c)
Com poun d 20c (1.00 g, 2.07 m m ol) was dissolved in THF (20 m l) an d cooled to 0 °C. EtN3
(3 m l) was added dropwise followed by th e addition of CF3SO3CH2P(O)(Oi-Pr)2 (1.02 g,
3.10 m m ol). Stirrin g was con tin ued at 0 °C for 5 h . MeOH was added, th e m ixture was con -
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Synthesis of Aminopropyl Phosphonate Nucleosides
29
cen trated, dissolved in CH2Cl2 (25 m l) an d wash ed with saturated aqueous NaHCO3 (2 ×
15 m l). Th e organ ic layer was dried over an h ydrous Na2SO4, con cen trated an d th e residue
was purified by colum n ch rom atograph y (CH2Cl2/MeOH 95:5). Yield 1.12 g (85%); RF 0.35
(CH2Cl2/MeOH 96:4). 1H NMR (CDCl3): 1.33, 1.36 (d, 12 H, 4 × CH3), 2.71–3.31 (m , 5 H,
H-1′, H-3′, H-2′), 3.79 (s, 3 H, O-CH3), 3.85–3.98 (m , 2 H, NH-CH2-P), 4.65–4.84 (m , 2 H,
O-CH-(CH3)2), 5.43–5.47 (d, 1 H, H-5, J5,6 = 7.6), 6.82–6.87 (d, 2 H, H-MTr), 7.12–1.16 (d,
1 H, H-6, J5,6 = 7.6), 7.19–7.47 (m , 12 H, H-Ar), 9.19 (br, 1 H, NH). 13C NMR (CDCl3): 23.9
(CH3), 42.1, 45.2 (NH-CH2-P), 49.9 (C-1′), 55.1 (O-CH3), 57.7–58.0 (d, C-2′, JC-3′,P = 16.7),
60.3 (C-3′), 68.9–69.1 (d, 2 × O-CH-(CH3)2, JC,P = 6.1), 86.5 (C-MTr), 101.1 (C-5), 113.2,
127.1, 127.9, 128.2, 130.2, 134.9, 143.9, 145.9 (C-Ar), 150.1 (C-6), 158.8 (C-2), 163.9 (C-4).
ES-MS calculated for C34H42N3NaO7P [M + Na]+: 658.2658; foun d: 658.2651.
(±)-({[2-(2,4-Dioxo-1,2,3,4-tetrah ydropyrim idin -1-yl)-
1-(h ydroxym eth yl)eth yl]am in o}m eth yl)ph osph on ic Acid (2c)
Me3SiBr (0.22 g, 1.42 m m ol) was added to a solution of 21c (0.30 g, 0.47 m m ol) in MeCN
(10 m l). Stirrin g was con tin ued overn igh t an d th e m ixture was con cen trated an d purified by
colum n ch rom atograph y (CH2Cl2/MeOH 9:1, CH2Cl2/MeOH/H2O 5:4:1). 2c was an alysed as
disodium salt. Yield 88 m g (68%); RF 0.42 (CH2Cl2/MeOH/H2O 5:4:1). 1H NMR (D2O):
3.03–3.08 (d, 2 H, CH2-P, JH,P = 10.2), 3.58–3.74 (m , 2 H, H-1′), 3.90 (m , 1 H, H-2′), 4.12 (m ,
2 H, H-3′), 5.78–5.82 (d, 1 H, H-5, J5,6 = 7.8), 7.59–7.63 (d, 1 H, H-6, J5,6 = 7.8). 13C NMR
(D2O): 43.9, 46.5 (CH2-P, JC,P = 128.2), 49.0 (C-1′), 58.8 (C-3′), 61.9 (C-2′), 104.4 (C-5), 149.4
(C-6), 155.0 (C-2), 168.9 (C-4). ES-MS calculated for C8H13N3O6P [M – H]–: 278.0542; foun d:
278.0552.
(±)-({[2-(4-Am in o-2-oxopyrim idin -1(2H)-yl)-
1-(h ydroxym eth yl)eth yl]am in o}m eth yl)ph osph on ic Acid (2d )
Com poun d 21c (0.50 g, 0.79 m m ol) was co-evaporated with dry pyridin e (2 × 10 m l) an d
dissolved in dry pyridin e (10 m l). Mesitylen esulfon yl ch loride (0.52 g, 2.36 m m ol) was
added. Stirrin g was con tin ued for 4 h , after wh ich 26% NH4OH in water (5 m l) was added
an d th e m ixture was stirred overn igh t. Th e reaction m ixture was con cen trated, dissolved in
CH2Cl2 (15 m l) an d wash ed with saturated aqueous NaHCO3 (2 × 10 m l). Th e organ ic layer
was dried over an h ydrous Na2SO4 an d con cen trated. Th e residue was co-evaporated with tol-
uen e (2 × 10 m l) an d dissolved in MeCN (10 m l). Me3SiBr (0.36 g, 2.36 m m ol) was added
an d stirrin g was con tin ued overn igh t. Th e m ixture was con cen trated an d furth er purified by
colum n ch rom atograph y (CH2Cl2/MeOH 9:1, CH2Cl2/MeOH/H2O 5:4:1). 2d was an alysed as
disodium salt. Yield 87 m g (40%); RF 0.32 (CH2Cl2/MeOH/H2O 5:4:1). 1H NMR (D2O): 2.96
(d, 2 H, CH2-P), 3.61–3.84 (m , 3 H, H-1′, H-2′), 4.05 (m , 2 H, H-3′), 5.95–5.99 (d, 1 H, H-5,
J5,6 = 7.1), 7.55–7.58 (d, 1 H, H-6, J5,6 = 7.1). 13C NMR (D2O): 44.7, 47.3 (CH2-P, JC,P
=
131.2), 50.8 (C-1′), 59.6 (C-3′), 61.3 (C-2′), 98.3 (C-5), 149.4 (C-6), 161.1 (C-2), 168.9 (C-4).
ES-MS calculated for C8H14N4O5P [M – H]–: 277.0702; foun d: 277.0705.
(±)-9-(3-Azido-2-{[tert-butyl(dim eth yl)silyl]oxy}propyl)-6-ch loro-9H-purin -2-am in e (29b)
A m ixture of com poun d 27 (0.50 g, 1.62 m m ol), 2-am in o-6-ch loropurin e (0.36 g, 2.11 m m ol)
an d cesium carbon ate (0.79 g, 2.43 m m ol) in dry DMF (20 m l) was gen tly h eated to 95 °C
un der n itrogen atm osph ere for 5 h , after wh ich th e reaction m ixture was cooled to room
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30
Zhou, Lagoja, Van Aerschot, Herdewijn:
tem perature an d filtered. Th e solven t of th e filtrate was rem oved un der reduced pressure.
Th e residue was purified by colum n ch rom atograph y (CH2Cl2/MeOH 99:1). Yield 0.23 g
(38%); RF 0.67 (CH2Cl2/MeOH 97:3). 1H NMR (CDCl3): –0.23, –0.01 (s, 6 H, 2 × Si-CH3), 0.84
(s, 9 H, 3 × CH3), 3.15–3.47 (m , 2 H, H-3′), 4.10–4.15 (m , 3 H, H-1′,2′), 5.43 (s, 2 H, NH2),
7.75 (s, 1 H, H-8). 13C NMR (CDCl3): –5.6, –5.1 (2 × Si-CH3), 17.6 (Si-C), 25.5 (3 × C-CH3),
46.9 (C-1′), 53.9 (C-3′), 69.2 (C-2′), 124.9 (C-5), 143.7 (C-8), 151.3 (C-2), 154.0 (C-4), 159.3
(C-6). ES-MS calculated for C14H24ClN8OSi [M + H]+: 383.1530; foun d: 383.1536.
(±)-1-(3-Azido-2-{[tert-butyl(dim eth yl)silyl]oxy}propyl)pyrim idin e-2,4(1H,3H)-dion e (29c)
A m ixture of 27 (0.80 g, 2.58 m m ol), uracil (0.35 g, 3.11 m m ol), NaI (0.47 g, 3.11 m m ol)
an d potassium carbon ate (0.79 g, 2.43 m m ol) in dry DMF (20 m l) was gen tly h eated to
90 °C un der n itrogen atm osph ere overn igh t an d th en allowed to cool to room tem perature.
Followin g filtration , th e solven t was rem oved un der reduced pressure. Th e residue was dis-
solved in EtOAc (20 m l) an d wash ed with saturated NaHCO3 (2 × 10 m l). Th e organ ic layer
was dried over an h ydrous Na2SO4, con cen trated an d furth er purified by colum n ch rom atog-
raph y (CH2Cl2/MeOH 98:2). Yield 0.36 g (43%); RF 0.49 (CH2Cl2/MeOH 97:3). 1H NMR
(CDCl3): –0.12, 0.10 (2 × s, 6 H, 2 × Si-CH3), 0.90 (s, 9 H, 3 × CH3), 3.15–3.22 (dd, 1 H,
H-3′A, J3′A,2′ = 3.6, Jgem = 13.2), 3.40–3.48 (dd, 1 H, H-3′B, J3′B,2′ = 4.0, Jgem = 13.2), 3.53–3.64
(dd, 1 H, H-1′A, J1′A,2′ = 8.0, Jgem = 13.6), 3.91–4.00 (dd, 1 H, H-1′B, J1′B,2′ = 3.8, Jgem = 13.6),
4.12–4.22 (m , 1 H, H-2′), 5.67–5.71 (d, 1 H, H-5, J5,6 = 8.0), 7.18–7.22 (d, 1 H, H-6, J5,6
=
8.0). 13C NMR (CDCl3): –5.1, –4.9 (2 × Si-CH3), 17.7 (Si-C), 25.6 (3 × C-CH3), 52.6 (C-1′),
54.2 (C-3′), 68.8 (C-2′), 101.6 (C-5), 146.3 (C-6), 151.0 (C-2), 164.0 (C-4). ES-MS calculated
for C13H24N5O3Si [M + H]+: 326.1648; foun d: 326.1645.
(±)-N-[1-(3-Azido-2-{[tert-butyl(dim eth yl)silyl]oxy}propyl)-2-oxo-
1,2-dih ydropyrim idin -4-yl]ben zam ide (29d )
A m ixture of 27 (0.50 m g, 1.62 m m ol), cytosin e (0.23 m g, 2.10 m m ol) an d cesium carbon ate
(1.06 g, 3.24 m m ol) in dry DMF (20 m l) was gen tly h eated to 90 °C un der n itrogen atm o-
sph ere overn igh t, th en allowed to cool to room tem perature an d filtered. Th e solven t was
rem oved un der reduced pressure. Th e residue 28d was purified by colum n ch rom atograph y
(CH2Cl2/MeOH 95:5, CH2Cl2/MeOH 9:1) [yield 0.24 g (45%); RF 0.52 (CH2Cl2/MeOH 9:1);
ES-MS [M + H]+: 325.1814]. To a solution of com poun d 28d (0.22 g, 0.68 m m ol) in pyridin e
(5 m l) ben zoyl ch loride (0.24 m l, 2.04 m m ol) was added. After stirrin g for 3 h , th e reaction
was quen ch ed with water (1 m l) an d th e reaction m ixture was evaporated un der reduced
pressure. Th e residue was dissolved in eth yl acetate (10 m l) an d wash ed with water (3 ×
10 m l). Th e organ ic layer was dried over an h ydrous Na2SO4 an d con cen trated an d th e resi-
due was purified by colum n ch rom atograph y (CH2Cl2/MeOH 98:2). Yield 0.25 g (85%);
RF 0.42 (CH2Cl2/MeOH 98:2). 1H NMR (CDCl3): –0.13, 0.07 (2 × s, 6 H, 2 × Si-CH3), 0.89 (s,
9 H, 3 × CH3), 3.15–3.23 (dd, 1 H, H-3′A, J3′A,2′ = 3.2, Jgem = 13.2), 3.46–3.55 (dd, 1 H, H-3′B,
J3′B,2′ = 3.8, Jgem = 13.2), 3.64–3.74 (dd, 1 H, H-1′A, J1′A,2′ = 8.2, Jgem = 13.0), 4.17–4.25 (dd,
1 H, H-1′B, J1′B,2′ = 3.0, Jgem = 13.2), 4.31–4.38 (m , 1 H, H-2′), 7.40–7.68 (m , 4 H, H-Ar, H-5),
7.80–7.84 (d, 1 H, H-6, J5,6 = 7.2), 7.94–7.97 (d, 1 H, H-Ar). 13C NMR (CDCl3): –5.5, –5.0 (2 ×
Si-CH3), 17.7 (Si-C), 25.7 (3 × C-CH3), 54.5 (C-1′), 54.7 (C-3′), 68.2 (C-2′), 96.3 (C-5), 127.8,
129.0, 131.9, 133.2 (C-Ar), 150.7 (C-6), 156.0 (C-2), 162.8 (C-4). ES-MS calculated for
C
20H29N6O3Si [M + H]+: 429.2070; foun d: 429.2075.
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Synthesis of Aminopropyl Phosphonate Nucleosides
31
Reduction to Com poun ds 30a–30d . Gen eral Procedure
To a solution of com poun d 29a (0.50 g, 1.11 m m ol), 29b (0.22 g, 0.58 m m ol), 29c (0.35 g,
1.07 m m ol) an d 29d (0.20 g, 0.47 m m ol), respectively, in dry THF (15 m l) triph en yl-
ph osph in e (0.58 g, 2.22 m m ol) (for b an d d 0.29 g, 1.11 m m ol) was added an d th e m ixture
was stirred overn igh t. Th en water was added an d th e reaction was stirred for an oth er 10 h .
Th e reaction m ixture was con cen trated to a sm all volum e an d purified by colum n ch rom a-
tograph y (CH2Cl2/MeOH 9:1).
(±)-N-[9-(3-Amino-2-{[tert-butyl(dimethyl)silyl]oxy}propyl)-9H-purin-6-yl]benzamide (30a): Yield
0.47 g (80%); RF 0.25 (CH2Cl2/MeOH 9:1). 1H NMR (DMSO-d6): –0.43, –0.10 (2 × s, 6 H, 2 ×
Si-CH3), 0.73 (s, 9 H, 3 × CH3), 2.55–2.69 (m , 2 H, H-3′), 3.36 (s, br, NH2), 4.05 (m , 1 H,
H-2′), 4.26 (m , 2 H, H-1′), 7.51–7.68 (m , 3 H, 3,4,5 H-Bz), 8.03–8.07 (d, 2 H, 2,6 H-Bz, J =
7.0), 8.36 (s, 1 H, H-8), 8.37 (s, 1 H, H-2). 13C NMR (DMSO-d6): –5.2, –4.4 (2 × Si-CH3), 18.0
(Si-C), 26.1 (3 × CH3), 45.6 (C-3′), 48.5 (C-1′), 72.2 (C-2′), 125.2 (C-5), 129.1 (3,5CH-Bz),
129.4 (2,6CH-Bz), 133.4 (4CH-Bz), 134.1 (1C-Bz), 146.3 (C-8), 150.5 (C-4), 152.2 (C-2), 153.4
(C-6), 166.8 (C=O). ES-MS calculated for C21H29N8O2Si [M + H]+: 427.2278; foun d: 427.2279.
(±)-9-(3-Amino-2-{[tert-butyl(dimethyl)silyl]oxy}propyl)-6-chloro-9H-purin-2-amine (30b): Yield
0.19 g (90%); RF 0.18 (CH2Cl2/MeOH 95:5). 1H NMR (CDCl3): –0.16, –0.00 (2 × s, 6 H, 2 ×
Si-CH3), 0.86 (s, 9 H, 3 × CH3), 1.81 (s, 2 H, NH2), 2.64–2.68 (m , 2 H, H-3′), 4.02–4.26 (m ,
3 H, H-2′, H-1′), 5.34 (s, 2 H, NH2), 7.80 (s, 1 H, H-8). 13C NMR (CDCl3): –5.3, –4.9 (2 ×
Si-CH3), 17.8 (Si-C), 25.6 (3 × CH3), 44.6 (C-3′), 46.6 (C-1′), 71.3 (C-2′), 143.8 (C-8), 151.4
(C-2), 154.1 (C-4), 159.2 (C-6). ES-MS calculated for C14H26ClN6OPSi [M + H]+: 357.16262;
foun d: 357.1629.
(±)-1-(3-Amino-2-{[tert-butyl(dimethyl)silyl]oxy}propyl)pyrimidine-2,4(1H,3H)-dione (30c): Yield
0.29 g (91%); RF 0.18 (CH2Cl2/MeOH 95:5). 1H NMR (CDCl3): –0.16, –0.00 (2 × s, 6 H, 2 ×
Si-CH3), 0.86 (s, 9 H, 3 × CH3), 2.71–2.80 (dd, 1 H, H-3′A, J3′A,2′ = 3.8, Jgem = 13.0), 2.84–2.93
(dd, 1 H, H-3′B, J3′B,2′ = 5.2, Jgem = 13.0), 3.75–4.14 (m , 2 H, H-1′), 4.32 (m , 1 H, H-2′),
5.68–5.72 (d, 1 H, H-5, J5,6 = 8.0 ), 7.27–7.30 (d, 1 H, H-5, J5,6 = 8.0 ). 13C NMR (CDCl3):
–5.2, –4.9 (2 × Si-CH3), 17.7 (Si-C), 25.7 (3 × CH3), 44.7 (C-3′), 51.9 (C-1′), 70.6 (C-2′), 101.2
(C-5), 146.5 (C-6), 151.3 (C-2), 164.1 (C-4). ES-MS calculated for C13H26N3O3Si [M + H]+:
300.1743; foun d: 300.1748.
(±)-N-[1-(3-Amino-2-{[tert-butyl(dimethyl)silyl]oxy}propyl)-2-oxo-1,2-dihydropyrimidin-4-yl]-
benzamide (30d ): Yield 0.15 g (81%); RF 0.49 (CH2Cl2/MeOH 9:1). 1H NMR (CDCl3): 0.04,
0.10 (2 × s, 6 H, 2 × Si-CH3), 0.90 (s, 9 H, 3 × CH3), 2.71–2.80 (m , 2 H, H-3′), 3.85–3.94 (m ,
2 H, H-1′), 4.13–4.20 (m , 1 H, H-2′), 7.47–7.61 (m , 4 H, H-Ar, H-5), 7.61–7.71 (d, 1 H, H-6,
J5,6 = 7.0), 7.93–7.96 (d, 1 H, H-Ar). 13C NMR (CDCl3): –5.3, –4.9 (2 × Si-CH3), 17.8 (Si-C),
25.6 (3 × C-CH3), 44.8 (C-3′), 54.0 (C-1′), 70.1 (C-2′), 96.1 (C-5), 127.7, 129.0, 131.9, 133.1
(C-Ar), 150.9 (C-6), 156.2 (C-2), 162.6 (C-4). ES-MS calculated for C20H31N4O3Si [M + H]+:
403.2165; foun d: 403.2138.
Syn th esis of Am in opropyl Ph osph on ate Nucleosides 31. Gen eral Procedure
To a solution of 30a (0.35 g, 0.82 m m ol) or 30b (0.18 g, 0.51 m m ol) or 30c (0.29 g,
0.95 m m ol) or 30d (0.15 m g, 0.35 m m ol), Et3N (10 µl) un der coolin g an d
CF3SO3CH2P(O)(Oi-Pr)2 (for a 0.40 g, 1.23 m m ol, for b 0.25 g, 0.76 m m ol, for c 0.47 g,
1.42 m m ol, for d 0.22 m g, 0.67 m m ol) in THF (10 m l) were added. Stirrin g was con tin ued
for 30 m in an d th e in term ediates 31a–31d were obtain ed.
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32
Zhou, Lagoja, Van Aerschot, Herdewijn:
In th e case of 31a an d 31d , th e solven t was rem oved un der h igh vacuum , th e residue was
dissolved in CH2Cl2 (10 m l) an d wash ed with H2O (2 × 10 m l). Th e organ ic layer was dried
over an h ydrous Na2SO4, con cen trated an d th e residue was treated with saturated NH3 in
MeOH (10 m l) overn igh t. Th e solven t was rem oved to obtain th e residue to be treated with
tetrabutylam m on ium fluoride (TBAF, vide in fra).
In th e case of 31b, th e residue was treated with 75% TFA in aqueous solution (10 m l) for
two days. Th en saturated aqueous NaHCO3 (15 m l) was added to quen ch th e reaction . Th e
m ixture was extracted with CH2Cl2 (2 × 10 m l). Th e organ ic layer was dried over an h ydrous
Na2SO4 an d con cen trated to obtain th e residue of 32b to be treated with TBAF (vide in fra).
In th e case of 31c, th e residue was dissolved in CH2Cl2 (10 m l) an d wash ed with H2O (2 ×
20 m l). Th e organ ic layer was dried an d con cen trated to be treated furth er with TBAF.
Gen eral Deprotection Procedure
Th e respective residues 31 were co-evaporated with THF (2 × 10 m l) an d th en treated with
1
M TBAF in THF (10 m l) overn igh t to obtain 32a–32d . Th e solven t was rem oved an d th e
residue was co-evaporated with toluen e (2 × 10 m l) an d dissolved in MeCN (10 m l). Me3SiBr
(for a, d 0.38 g, 2.46 m m ol, for b 0.23 g, 1.53 m m ol, for c 0.44 g, 2.86 m m ol) was added
an d th e reaction m ixture was stirred at room tem perature for two days. Th e solven t was
evaporated an d th e residue was purified by colum n ch rom atograph y (CH2Cl2/MeOH 9:1,
CH2Cl2/MeOH/H2O 5:4:1). All com poun ds 3a–3d were an alysed as disodium salts.
(±)-({[3-(6-Amino-9H-purin-9-yl)-2-hydroxypropyl]amino}methyl)phosphonic acid (3a): Yield
70 m g (24%); RF 0.50 (CH2Cl2/MeOH/H2O 5:4:1). 1H NMR (D2O): 2.92–2.98 (d, 2 H, CH2-P,
JH,P = 11.6), 3.13–3.37 (m , 2 H, H-1′), 4.10–4.39 (m , 3 H, H-3′, H-2′), 8.08 (2 × s, 2 H, H-2,
H-8). 13C NMR (D2O): 48.1, 49.1 (CH2-P), 51.6 (C-1′), 54.1 (C-3′), 68.1 (C-2′), 121.0 (C-5),
145.5 (C-8), 151.7 (C-4), 155.2 (C-2), 158.1 (C-6). ES-MS calculated for C9H14N6O4P [M –
H]–: 301.0814; foun d: 301.0813.
(±)-({[3-(2-Amino-6-oxo-1,6-dihydro-9H-purin-9-yl)-2-hydroxypropyl]amino}methyl)phosphonic
acid (3b): Yield 38 m g (23%); RF 0.30 (CH2Cl2/MeOH/H2O 5:4:1). 1H NMR (D2O): 2.96–3.04
(d, 2 H, CH2-P, JH,P = 11.6), 3.18 (m , 2 H, H-1′), 4.18 (m , 2 H, H-3′), 4.34 (m , 1 H, H-2′), 7.71
(s, 1 H, H-8). 13C NMR (D2O): 47.0, 49.6 (CH2-P, JC,P = 128.2), 47.9 (C-1′), 52.7–52.9 (d, C-3′,
JC-3′,P = 6.1), 67.3 (C-2′), 117.4 (C-5), 142.5 (C-8), 153.9 (C-4), 155.3 (C-2). ES-MS calculated
for C9H14N6O5P [M – H]–: 317.0763; foun d: 317.0667.
(±)-({[3-(2,4-Dioxo-1,2,3,4-tetrahydropyrimidin-1-yl)-2-hydroxypropyl]amino}methyl)phosphonic
acid (3c): Yield 115 m g (41%); RF 0.46 (CH2Cl2/MeOH/H2O 5:4:1). 1H NMR (D2O): 2.91–2.99
(d, 2 H, CH2-P, JH,P = 11.6), 3.07–3.37 (m , 2 H, H-1′), 3.65–3.76 (dd, 1 H, H-3′A, J3A′,2′ = 8.4,
Jgem = 14.4), 3.98–4.06 (dd, 1 H, H-3′B, J3B′,2′ = 3.2, Jgem = 14.4), 4.26 (m , 1 H, H-2′),
5.77–5.81 (d, 1 H, H-5, J5,6 = 7.6), 7.56–7.60 (d, 1 H, H-6, J5,6 = 7.6). 13C NMR (D2O): 46.6,
49.1 (CH2-P, JC,P = 126.7), 53.3–53.4 (d, C-3′, JC-3′,P = 4.6), 53.8 (C-1′), 67.0 (C-2′), 103.6
(C-5), 150.4 (C-6), 154.8 (C-2), 169.4 (C-4). ES-MS calculated for C8H13N3O6P [M – H]–:
278.0542; foun d: 278.0547.
(±)-({[3-(4-Amino-2-oxopyrimidin-1(2H)-yl)-2-hydroxypropyl]amino}methyl)phosphonic acid
(3d ): Yield 23 m g (24%); RF 0.33 (CH2Cl2/MeOH/H2O 5:4:1). 1H NMR (D2O): 2.91–2.97 (d,
2 H, CH2-P, JH,P = 11.6), 3.04–3.27 (m , 2 H, H-1′), 3.57–3.68 (dd, 1 H, H-3′A, J3A′,2′ = 9.3,
Jgem = 14.0), 3.98–4.06 (dd, 1 H, H-3′B, J3B′,2′ = 3.0, Jgem = 14.0), 4.23 (m , 1 H, H-2′),
5.93–5.96 (d, 1 H, H-5, J5,6 = 7.3), 7.50–7.54 (d, 1 H, H-6, J5,6 = 7.3). 13C NMR (D2O): 46.8,
49.3 (CH2-P, JC,P = 128.2), 53.5–53.6 (d, C-3′, JC-3′,P = 6.1), 55.1 (C-1′), 67.3 (C-2′), 97.7 (C-5),
Collect. Czech. Chem. Commun. 2006, Vol. 71, No. 1, pp. 15–34

Synthesis of Aminopropyl Phosphonate Nucleosides
33
149.9 (C-6), 160.7 (C-2), 168.9 (C-4). ES-MS calculated for C8H14N4O5 [M – H]–: 277.0702;
foun d: 277.0702.
Preparation of Disodium Salts of Am in opropyl Ph osph on ate Nucleosides 1–3.
Gen eral Procedure
All ph osph on ates 1a–1d , 2a–2d , 3a–3d were purified by ion exch an ge ch rom atograph y
(Seph adex-DEAE A-25 resin ). A gradien t of trieth ylam m on ium bicarbon ate (TEAB)/water
(0.01 M TEAB to 0.5 M TEAB in 1 h , 0.5 M TEAB in 30 m in ) was used. Th e ph osph on ic acids
were obtain ed as gum s, th ey were dissolved in water, passed th rough a colum n of Dowex
50WX8 (Na+) resin an d eluted with water to afford th e sodium salts as wh ite solids.
HPLC An alysis of Disodium Salts of Am in opropyl Ph osph on ate Nucleosides 1–3
Th e ph osph on ates 1a, 1b, 1c, 2a, 2d , 3a, 3b, 3d were an alysed by reversed-ph ase an alytic
HPLC on an Alltim a HP C18 HL 5µ colum n with 50 m M NH4H2PO4 an d 10 m M Bu4NHSO4
buffered at pH 5.0. Th e derivatives 1d , 2b, 2c, 3c proved still too polar for th is colum n , but
could be an alysed on a platin um EPS C18 100A 5µ colum n with a pH 6.0 buffer of 25 m M
NH4H2PO4 an d 10 m M Bu4NHSO4. Both th e colum n s were run at 0.65 cm 3/m in .
The authors thank Prof. J. Rozenski for Mass Analysis, Prof. R. Busson for NMR spectra and
Prof. E. De Clercq, Prof. C. Pannecouque and Prof. J. Neyts for antiviral screening. This work was
supported by the interfaculty council for development cooperation scholarships program of K.U.
Leuven. I. M. Lagoja is a research associate of the FW O (Fonds W etenschappelijk Onderzoek)
Vlaanderen.
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