Studies on oxidative transformations of dinucleoside H-phosphonoselenoates

Article abstract of DOI:10.1135/cccc20060832

The utility of a new type of synthetic intermediates, H-phosphonoselenoate diesters, in the preparation of potentially biologically important nucleotide analogues containing the P-Se bond, was explored by converting dinucleoside H-phosphonoselenoates 1 in

Full text of DOI:10.1135/cccc20060832

832
Bollmark, Kullberg, Stawinski:
STUDIES ON OXIDATIVE TRANSFORMATIONS OF DINUCLEOSIDE
H-PHOSPHONOSELENOATES
a
a
a1,b,
Martin BOLLMARK , Martin KULLBERG and Jacek STAWINSKI
*
a
Department of Organic Chemistry, Arrhenius Laboratory, Stockholm University,
S-106 91 Stockholm, Sweden; e-mail: js@organ.su.se
Institute of Bioorganic Chemistry, Polish Academy of Sciences, 61-704 Poznan, Poland
1
b
Received March 1, 2006
Accepted April 14, 2006
Dedicated to Professor Antonín Holý on the occasion of his 70th birthday.
Th e utility of a n ew type of syn th etic in term ediates, H-ph osph on oselen oate diesters, in th e
preparation of poten tially biologically im portan t n ucleotide an alogues con tain in g th e P–Se
bon d, was explored by con vertin g din ucleoside H-ph osph on oselen oates 1 in to various ph os-
ph orus(V) derivatives un der oxidative con dition s.
Keyw ord s: H-Ph osph on oselen oates; H-Ph osph on ates; Oxidation s; Ph osph oroselen oth ioates;
Ph osph orodiselen oates; Ph osph orofluoridoselen oates; Oligon ucleotides; Din ucleotides.
Sin ce m ost syn th etically useful m eth ods for th e preparation of selen o-
ph osph ates rely on oxidative con version of P(III) to P(V) com poun ds usin g
electroph ilic selen ium 1–5, we search ed for an altern ative m eth odology
utilizin g as a startin g m aterial selen oph osph orus com poun ds at a lower oxi-
dation state. Th is would provide an altern ative way for preparin g selen o-
ph osph ate derivatives an d perm it syn th esis of n ovel selen oph osph ate
an alogues, n ot accessible by tradition al m eth ods.
For th is purpose we recen tly em barked on exploration of H-ph osph on o-
selen oates as a n ew type of syn th etic in term ediates an d developed efficien t
protocols for th e preparation of H-ph osph on oselen oate m on o- an d di-
esters6–8 (see also th e precedin g paper in th is issue9). We h oped th at a dis-
tin ctive feature of H-ph osph on oselen oates, i.e. th e presen ce of selen ium
boun d to a ph osph orus(III) atom , sh ould en able furth er oxidative tran sfor-
m ation s at th e ph osph orus cen ter in th ese com poun ds th at could be ex-
ploited in th e syn th esis of n ew ph osph ate an alogues.
Collect. Czech. Chem. Commun. 2006, Vol. 71, No. 6, pp. 832–841
© 2006 Institute of Organic Chemistry and Biochemistry
doi:10.1135/cccc20060832

Dinucleoside H-Phosphonoselenoates
833
In th is paper oxidative tran sform ation s of din ucleoside H-ph osph on o-
selen oate 1 to produce various n ucleotide an alogues con tain in g th e P–Se
bon d, are discussed.
RESULTS AND DISCUSSION
Sin ce H-ph osph on oselen oate diesters were in ten ded to be syn th etic in ter-
m ediates rath er th an target com poun ds, th eir oxidative tran sform ation s to
provide access to various selen ium -con tain in g ph osph ate an alogues were of
crucial practical im portan ce.
Oxidation to Phosphoroselenoates
Oxidation in volvin g iodin e in th e presen ce of water, wh ich results in re-
placem en t of th e P–H bon d with a P–O bon d, is a stan dard procedure in
H-ph osph on ate ch em istry10 to con vert P(III) in to P(V) com poun ds. An
an alogous oxidation of H-ph osph on oselen oate diesters sh ould yield th e
correspon din g ph osph oroselen oate derivatives; h owever, th e problem is
th at ph osph oroselen oate diesters are kn own to un dergo deselen ization in
th e presen ce of iodin e an d water, givin g rise to ph osph ate diesters5.
In deed, it was foun d th at un der stan dard oxidation con dition s used for
H-ph osph on ate diesters (2 equivalen ts of iodin e in pyridin e con tain in g 2%
water)10, H-ph osph on oselen oates 1 un derwen t rapid (<1 m in ) an d quan tita-
tive con version to th e correspon din g din ucleoside ph osph ate with com -
plete selen ium rem oval. Usin g an equim olar am oun t of iodin e, th e expect-
1
ed ph osph oroselen oate 2 (δP 51.9 an d 51.7 ppm , JPSe = 824 an d 823 Hz)
was form ed as a m ajor product (31P NMR spectroscopy), but still deselen -
ization to th e correspon din g ph osph ate diester occurred to ca. 20%. Sim ilar
results were obtain ed wh en iodin e was replaced by N-iodosuccin im ide or
wh en oxidation was carried out in aceton itrile in th e presen ce of lim ited
am oun ts of a base an d water.
By perform in g th e reaction with iodin e un der an h ydrous con dition s, we
h oped to gen erate th e in term ediate iodoph osph oroselen ote (an alogously to
iodoph osph oroth ioate11) th at was expected to be less pron e to deselen izat-
ion . Un fortun ately, th is reaction produced a com plex m ixture of products
as in dicated by 31P NMR spectra.
Due to th e h igh reactivity of th e P–H bon d in H-ph osph on oselen oates 1
on on e h an d, an d h igh propen sity of selen ium in ph osph oroselen oate
diesters 2 toward oxidation , on th e oth er, we th ough t th at tetrach loro-
m eth an e12 in th e presen ce of a weak base sh ould secure rapid oxidation of 1
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834
Bollmark, Kullberg, Stawinski:
with out affectin g th e selen ium in product 2. It was rewardin g to fin d out
th at, in deed, treatm en t of H-ph osph on oselen oate 1 in pyridin e con tain in g
2% water with 10 equivalen ts of CCl4 effected rapid (<5 m in ) an d clean
oxidation to din ucleoside ph osph oroselen oate 2 (Sch em e 1). Un der th e an -
h ydrous reaction con dition s, th e in term ediacy of th e correspon din g ph os-
ph oroselen och loridates (δP 62.7 an d 64.2 ppm ) in th is reaction could be
establish ed by 31P NMR spectroscopy.
SCHEME 1
Havin g in m in d th e possibility of a pyridin e-m ediated ligan d-exch an ge
process in H-ph osph on oselen oate diesters (an alogously to H-ph osph on o-
th ioate diesters13), we in vestigated also oth er reaction con dition s for th e
oxidation of 1, n am ely, by usin g CCl4 (10 equivalen ts) in aceton itrile con -
tain in g lim ited am oun t of pyridin e (20 equivalen ts) an d water (50 equiva-
len ts). Usin g th is protocol, th e oxidation of H-ph osph on oselen oate 1 was
com plete with in 10 m in with out detectable (31P NMR spectroscopy) side
products form ation (deselen ization or ligan ds exch an ge). In a separate ex-
perim en t we also foun d th at th e produced ph osph oroselen oate diester 2
was resistan t to oxidation with CCl4 even upon prolon ged reaction tim e
(few h ours).
Sulfurization to Phosphoroselenothioates
Syn th esis of ph osph oroselen oth ioate diesters by oxidation of precursor
H-ph osph on oselen oate 1 with sulfur, was in vestigated. Sulfurization of
H-ph osph on ate14–16 or H-ph osph on oth ioate17,18 diesters with elem en tal
sulfur in pyridin e is a com m on procedure for con vertin g P(III) com poun ds
to various ph osph oroth ioate derivatives. Th is reaction , wh en carried out
with H-ph osph on oselen oates 1 in aceton itrile con tain in g pyridin e (20 equi-
valen ts) in th e presen ce of sulfur (3 equivalen ts) was, as expected, un even t-
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Dinucleoside H-Phosphonoselenoates
835
ful an d afforded th e correspon din g din ucleoside ph osph oroselen oth ioates 3
1
(δP 98.1 an d 98.5, JPSe = 759 an d 761 Hz) quan titatively with in 10 m in
(Sch em e 2).
SCHEME 2
Sulfurization of H-ph osph on oselen oates 1 on a preparative scale was
carried out with elem en tal sulfur (3 equivalen ts) in aceton itrile con tain in g
pyridin e (20 equivalen ts) an d th e correspon din g din ucleoside ph osph oro-
selen oth ioates 3 were obtain ed after ch rom atograph y on silica gel in 95%
yield. Th e reaction was also carried out on separate diastereom ers of 1.
31P NMR spectroscopy revealed th at sulfurization of th ese H-ph osph on o-
selen oate diesters was com pletely stereospecific producin g from a faster
m ovin g diastereom er of 1 (δP 74.8 ppm ), a diastereom er of 3 with ch em ical
shift δP 98.1 ppm , and from a slower m oving diastereom er of 1 (δP 76.7 ppm ),
a diastereom er of 3 reson atin g at δP 98.5 ppm . Sim ilarly to oth er sul-
furization reaction of P(III) com poun ds19–21, form ation of ph osph oro-
selen oth ioates 3 occurred m ost likely with reten tion of con figuration at th e
ph osph orus cen tre.
Selenization to Phosphorodiselenoates
Th ere are two available approach es to th e syn th esis of dialkyl ph osph oro-
diselen oates. On e of th em in volves treatm en t of th e appropriate alcoh ol
with ph osph orus pen taselen ide22 to produce sym m etrical diselen oate
diesters, an d th e oth er on e is based on reaction of N-ph en ylph osph oro-
am idoselen oates with sodium h ydride an d carbon diselen ide23
.
Neith er of th ese procedures h as been applied to th e syn th esis of n ucleo-
side ph osph orodiselen oate diesters, probably because of h arsh reaction con -
dition s or difficulties in obtain in g appropriate startin g m aterials. Th is
m igh t explain wh y th e syn th esis of n ucleoside ph osph orodiselen oate h as
n ot been yet described in th e literature.
Collect. Czech. Chem. Commun. 2006, Vol. 71, No. 6, pp. 832–841

836
Bollmark, Kullberg, Stawinski:
We foun d th at by usin g 3H-1,2-ben zoth iaselen ol-3-on e (BTSe)5, a sele-
n ium tran sferrin g reagen t soluble in organ ic solven ts, it was possible to
clean ly con vert H-ph osph on oselen oate 1 in to th e correspon din g diselen o-
ph osph ate 4 (δP 85.5 ppm ) th at could be isolated in 85% yield (Sch em e 3).
Gen eration of H-ph osph on oselen oate diester 1 in situ, followed by th e
addition of BTSe (1.5. equivalen ts) allowed preparation of diselen oate 4
with out prior isolation of th e H-ph osph on oselen oate diesters. Usin g ele-
m en tal selen ium in stead of BTSe for th e selen ization step, gave in ferior
results.
SCHEME 3
Conversion to Phosphorofluoridoselenoates
Wh en din ucleoside H-ph osph on oselen oate 1 in ch loroform was treated
with tetrach lorom eth an e (10 equivalen ts) an d trieth ylam in e (TEA, 4 equiv-
alen ts) a com plete con version to th e correspon din g ch loroph osph oro-
selen oate (δP 63.7 an d 62.8 ppm ; see Sch em e 4) occurred with in 5 m in . Th e
subsequen t addition of trieth ylam in e trish ydrofluoride (TAF)24 furn ish ed
SCHEME 4
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Dinucleoside H-Phosphonoselenoates
837
clean an d in stan tan eous form ation of din ucleoside ph osph orofluorido-
1
selen oate 5 (δP 66.7 an d 65.8 ppm , JPF = 1147 an d 1159 Hz).
Th e above tran sform ation was virtually quan titative an d th e produced
ph osph orofluoridoselen oate 5 was stable en ough to be isolated in pure
state by colum n ch rom atograph y on silica gel in 80% yield.
Thiobenzylation of H-Phosphonoselenoates
Th e con version of H-ph osph on ate or H-ph osph on oth ioate diesters to th e
correspon din g S-ben zyl triesters can be accom plish ed via sulfurization , fol-
lowed by S-ben zylation , or oxidation followed by S-ben zylation , respec-
tively. Th is syn th etic approach is, h owever, n ot an option in th e case of H-
ph osph on oselen oate diesters, sin ce th e ph osph oroselen oth ioate in term edi-
ate was expected to be preferen tially alkylated on th e selen ium atom 25
.
We foun d, h owever, th at N-(2,4-dich loroben zyl)th iosuccin im ide26, a re-
agen t developed by van Boom et al., can effect syn th esis of th e th ioselen o
ph osph otriester 6 in on e step usin g th e correspon din g H-ph osph on o-
selen oate diester as a startin g m aterial.
To th is en d, din ucleoside H-ph osph on oselen oate 1 (gen erated in situ
from th e correspon din g n ucleoside H-ph osph on oselen oate m on oesters an d
a suitably protected n ucleoside) in m eth ylen e ch loride was treated with
N-(2,4-dich loroben zyl)th iosuccin im ide (2 equivalen ts). Th e reaction was
clean an d produced with in 25 m in 6 (δP 105.0 an d 104.4 ppm ) as th e sole
n ucleotidic product (Sch em e 5).
SCHEME 5
Collect. Czech. Chem. Commun. 2006, Vol. 71, No. 6, pp. 832–841

838
Bollmark, Kullberg, Stawinski:
In aceton itrile–pyridin e (4:1, v/v) th e oxidative th ioben zylation of 1 with
N-(2,4-dich loroben zyl)th iosuccin im ide was even faster (5 m in ), an d, after
work-up, th e triester 6 was isolated in 85% yield. Com poun d 6 h as been
previously prepared by Mich alski et al. em ployin g a protocol th at in volved
an in term ediate din ucleoside S-dich loroben zyl ph osph ite, followed by its
oxidation with elem en tal selen ium 27
.
In con clusion , by preparin g n ew kin ds of n ucleotide an alogues we dem -
on strated th e usefuln ess of H-ph osph on oselen oate diesters in th e syn th esis
of n ucleotide an alogues bearin g th e P–Se bon d. Th e added value of th e de-
scribed procedures is th at th ey can be perform ed with sim ilar efficien cy
both on isolated an d on in situ produced din ucleoside H-ph osph on o-
selen oates. Easy access to H-ph osph on oselen oates sh ould expan d an d com -
plem en t syn th etic m eth ods of th e preparation of biologically im portan t
ph osph ate an alogues based on th e H-ph osph on ate an d H-ph osph on o-
th ioate m eth odology developed in th is Laboratory28–30
.
EXPERIMENTAL
Materials an d Meth ods
Pyridin e, 2,6-lutidin e, aceton itrile, an d trieth ylam in e (TEA) were refluxed with CaH2 an d
th en distilled an d stored over 4Å m olecular sieves or CaH2 (TEA). Din ucleoside H-ph os-
ph on oselen oate diester 1 was prepared via con den sation of 5′-O-(4,4′-dim eth ytrityl)th ym id-
in e 3′-H-ph osph on oselen oate m on oester6–8 with 3′-O-(4,4′-dim eth ytrityl)th ym idin e as
described in th e precedin g paper in th is issue. TLC an alyses were carried out on Merck plates
precoated with silica gel 60 F254 usin g th e followin g eluen ts: toluen e–m eth an ol (9:1, v/v;
system A); ch loroform –m eth an ol (9:1, v/v; system B). 1H, 13C, 19F an d 31P NMR spectra were
m easured in CDCl3; ch em ical sh ifts (δ scale) are given in ppm , couplin g con stan ts (J) in Hz.
31P NMR experim en ts were carried out in 10-m m tubes usin g ph osph orus com poun d 1
(0.05 m m ol) in a solven t (2 m l). H3PO4 (2%) in D2O was used as extern al stan dard (coaxial
in n er tube). Th e values of th e ch em ical sh ifts for th e in term ediates produced in situ in som e
experim en ts varied (±1 ppm ) depen din g on th e reaction con dition s.
Trieth ylam m on ium 5′-O-(4,4′-Dim eth oxytrityl)th ym idin -3′-yl
3′-O-(4,4-Dim eth oxytrityl)th ym idin -5′-yl Ph osph oroselen oate (2)
5′-O-(4,4′-Dim eth oxytrityl)th ym idin -3′-yl 3′-O-(4,4′-dim eth oxytrityl)th ym idin -5′-yl H-ph os-
ph on oselen oate (1; 0.1 m m ol) was treated with CCl4 (1 m m ol) in MeCN con tain in g pyri-
din e (2 m m ol) an d water (50 m m ol) for 10 m in . TEA (0.5 m m ol) was added, th e reaction
m ixture was con cen trated an d separated on a silica gel colum n usin g CH2Cl2 con tain in g a
gradien t of m eth an ol (0–5%) an d trieth ylam in e (0.1%). Ph osph oroselen oate 2 was isolated
as a wh ite solid in 95% yield (purity > 98% by 1H NMR). 31P NMR: 49.51 an d 49.26 (1JPSe
=
818 an d 820). 1H NMR: 7.72 (s, 1 H); 7.67 (s, 1 H); 7.59 (s, 1 H); 7.53 (s, 1 H); 7.27 (m ,
40 H); 6.80 (m , 16 H); 6.47 (m , 1 H); 6.36 (m , 1 H); 6.17 (dd, 3J = 8.79 an d 5.86, 2 H); 5.36
(m , 2 H); 4.30 (m , 2 H); 3.95 (m , 4 H); 3.77 (s, 6 H); 3.76 (s, 6 H); 3.74 (s, 6 H); 3.71 (s, 6 H);
Collect. Czech. Chem. Commun. 2006, Vol. 71, No. 6, pp. 832–841

Dinucleoside H-Phosphonoselenoates
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3.65 (m , 2 H); 3.32 (m , 4 H); 3.12 (q, 3J = 7.22, 12 H); 2.63 (m , 2 H); 2.23 (m , 2 H); 1.87 (m ,
4 H); 1.83 (s, 6 H); 1.29 (m , 24 H). 13C NMR: 164.34, 164.09, 158.92, 150.86, 150.70,
145.35, 145.28, 144.63, 137.38, 136.56, 136.50, 135.77, 135.49, 130.47, 130.44, 130.38,
128.51, 128.19, 127.29, 114.29, 113.54, 111.52, 111.39, 111.14, 87.47, 87.42, 87.36, 86.87,
74.63, 62.72, 55.48, 45.00, 39.02, 34.03, 32.13, 29.89, 29.71, 29.56, 29.36, 29.16, 22.89,
14.33, 12.66, 11.79, 8.81
Trieth ylam m on ium 5′-O-(4,4′-Dim eth oxytrityl)th ym idin -3′-yl
3′-O-(4,4′-Dim eth oxytrityl)th ym idin -5′-yl Ph osph oroselen oth ioate (3)
5′-O-(4,4′-Dim eth oxytrityl)th ym idin -3′-yl 3′-O-(4,4′-dim eth oxytrityl)th ym idin -5′-yl H-ph os-
ph on oselen oate (1; 0.1 m m ol) was treated with sulfur (0.3 m m ol) in MeCN con tain in g pyri-
din e (2 m m ol) for 10 m in . Th e reaction m ixture was treated with TEA (0.5 m m ol),
con cen trated an d purified on a silica gel colum n usin g CH2Cl2 con tain in g a gradien t of
m eth an ol (0–5%) an d trieth ylam in e (0.1%). Th e product was isolated as a wh ite solid in
95% yields (purity > 98% by 1H NMR).
Diastereoisom er obtain ed from faster m ovin g H-ph osph on oselen oate diester (RP)-1:
31P NMR: 98.11 (1JPSe = 759). 1H NMR: 7.80, 7.56, 7.29 (m , 20 H); 6.81 (m , 8 H); 6.54 (t, J =
7.42, 1 H); 6.35 (dd, J = 8.2 an d 5.7, 1 H); 5.45 (m , 1 H); 4.42 (m , 1 H); 4.22 (m , 1 H); 3.76
(s, 6 H); 3.74 (s, 3 H); 3.73 (s, 3 H); 3.65 (m , 1 H); 3.39 (m , 2 H); 3.12 (q, J = 7.22, 6 H); 2.54
(m , 1 H); 2.28 (m , 1 H); 1.98 (m , 4 H); 1.35 (s, 3 H); 1.29 (t, J = 7.22, 9 H); 1.25 (s, 3 H).
13C NMR: 164.38, 164.20, 158.90, 158.86, 150.95, 150.58, 145.33, 144.67, 139.49, 136.94,
136.59, 136.52, 136.00, 135.80, 135.57, 130.51, 130.46, 130.42, 128.59, 128.44, 128.22,
127.23, 114.29, 113.61, 113.49, 111.61, 111.35, 87.46, 87.20, 85.16, 84.93, 77.50, 75.69,
69.38, 66.48, 63.80, 55.48, 46.35, 39.45, 34.03, 32.13, 29.87, 29.71, 29.56, 29.36, 29.16,
22.89, 22.89, 12.69, 11.79, 8.90.
Diastereoisom er obtain ed from slower m ovin g H-ph osph on oselen oate diester (SP)-1:
31P NMR: 98.48 (1JPSe = 761). 1H NMR: 7.80, 7.57, 7.30 (m , 20 H); 6.82 (m , 8 H); 6.53 (t, J =
6.93, 1 H); 6.16 (m , 1 H); 5.45 (m , 1 H); 4.36 (m , 1 H); 3.96 (m , 1 H); 3.77 (s, 6 H); 3.74 (s,
3 H); 3.73 (s, 3 H); 3.65 (m , 1 H); 3.32 (m , 2 H); 3.09 (q, J = 7.22, 6 H); 2.58 (m , 1 H); 2.30
(m , 1 H); 1.94 (m , 2 H); 1.70 (m , 2 H); 1.28 (m , 15 H). 13C NMR: 164.24, 164.07, 158.94,
158.86, 150.89, 145.34, 144.67, 137.38, 136.55, 136.49, 135.81, 135.58, 130.48, 130.32,
128.60, 128.51, 128.44, 128.21, 127.32, 114.29, 113.62, 113.55, 113.53, 111.20, 111.16,
87.44, 87.21, 86.85, 85.14, 84.96, 75.68, 74.57, 63.82, 62.76, 55.48, 46.22, 39.45, 38.96,
34.03, 32.14, 29.89, 29.72, 29.57, 29.37, 29.17, 22.92, 12.67, 11.79, 8.97.
Trieth ylam m on ium 5′-O-(4,4′-Dim eth oxytrityl)th ym idin e-3′-yl
3′-O-(4,4′-Dim eth oxytrityl)th ym idin e-5′-yl Ph osph orodiselen oate (4)
Th is com poun d was obtain ed by selen ization of H-ph osph on oselen oate 1 (0.1 m m ol; pro-
duced in situ in aceton itrile–pyridin e (4:1, v/v) as described above) with 3H-1,2-ben zoth ia-
selen ol-3-on e5 (1.5 equiv.) in th e presen ce of trieth ylam in e (3 equiv.) for 5 m in , followed by
ch rom atograph y on silica gel usin g gradien t of m eth an ol (0–3%) in dich lorom eth an e con -
tain in g trieth ylam in e (0.1%). Yield 76%, wh ite foam (trieth ylam m on ium salt, purity > 98%
by 1H NMR). FAB HRMS [M]+, foun d 1323.2131; C62H62N4Na2O14PSe2 requires 1323.2126.
1
31P NMR: 85.50 (m ultiplet, JPSe = 751). 1H NMR (selected sign als): 6.50 (m , 1 H, Hb1′); 6.30
(m , 1 H, Ha1′); 5.52 (dd, 1 H, Ha3′); 4.39 (d, 1 H, Hb3′); 4.21 (s, 1 H, Ha4′); 3.78–3.65 (14 H,
Collect. Czech. Chem. Commun. 2006, Vol. 71, No. 6, pp. 832–841

840
Bollmark, Kullberg, Stawinski:
4 × O-CH3 an d Hb5′); 3.44 an d 3.26 (2 m , 2 H, Ha5′); 2.54 an d 2.25 (2 m , 2 H, Ha2′); 1.93
(m , 2 H, Hb2′); 1.92 an d 1.28 (2 s, 6 H, 2 × C5-CH3). 13C NMR (selected sign als): 84.91 (2 C,
Cb1′ an d Ca4′), 84.84 (Cb4′), 84.64 (Ca1′), 77.48 (Ca3′), 75.53 (Cb3′), 66.54 (d, Cb5′), 63.59
(Ca5′), 12.52 an d 11.50 (2 × C5-CH3).
5′-O-(4,4′-Dim eth oxytrityl)th ym idin e-3′-yl 3′-O-(4,4′-Dim eth oxytrityl)th ym idin e-5′-yl
Ph osph orofluoridoselen oate (5)
Th is com poun d was obtain ed by treatm en t of H-ph osph on oselen oate 1 (0.1 m m ol) an d
trieth ylam in e trih ydrofluoride (1 equiv.) in ch loroform (2 m l) with CCl4 (10 equiv.) an d
trieth ylam in e (4 equiv.) for 5 m in . Ch rom atograph y on silica gel usin g toluen e–eth yl acetate
furn ish ed 5 as ca. 1:1 m ixture of diastereom ers. Yield 80%, wh ite powder after lyoph iliz-
ation (purity > 98% by 1H NMR). FAB HRMS [M]+, foun d 1239.3051; C62H62FN4NaO14PSe re-
1
1
quires 1239.3047. 31P NMR (m ixture of diastereom ers): 68.00 (m ultiplet, JPSe = 1059, JPF
=
1148) an d 67.00 (m ultiplet, JPSe = 1064, JPF = 1160). 19F NMR (m ixture of diastereom ers):
1
1
–31.0 (2JFSe = 146, JFP = 1150) an d –31.5 (2JFSe = 147, JFP = 1162). 1H NMR (m ixture of
diastereom ers, selected sign als): 6.36 (m , 2 H, Ha1′ an d Hb1′); 5.44 (m , 1 H, Ha3′); 4.28 (m ,
1 H, Hb3′); 4.21 an d 4.11 (2 m , 1 H, Ha4′); 4.06, 3.93 an d 3.65 (3 m , 2 H, Hb5′); 3.95 (m ,
1 H, Hb4′); 3.44 an d 3.42 (2 m , 2 H, Ha5′); 2.44, 2.08 an d 1.75 (3 m , 4 H, Ha2′ an d Hb2′);
1.86, 1.84, 1.47 an d 1.45 (4 s, 6 H, 2 × C5-CH3). 13C NMR (m ixture of diastereom ers,
selected sign als): 85.71 an d 85.49 (C1′), 84.67 (d, J = 5, Ca4′), 84.49 (C1′ an d Ca4′), 83.77
(m , Cb4′), 82.31 an d 82.12 (Ca3′), 74.07 (Cb3′), 69.64 (m , Cb5′), 63.41 an d 63.34 (Ca5′),
39.32 (C2′), 38.92 (m , C2′), 12.66, 12.59, 11.94 an d 11.88 (2 × C5-CH3).
1
1
S-(2,4-Dich loroben zyl)-5′-O-(4,4′-dim eth oxytrityl)th ym idin e-3′-yl
3′-O-(4,4′-Dim eth oxytrityl)th ym idin e-5′-yl Ph osph oroselen oth ioate (6)
Th is com poun d was obtain ed by treatm en t of H-ph osph on oselen oate 1 (0.1 m m ol; pro-
duced in situ in aceton itrile–pyridin e (4:1, v/v) as described above) with N-(2,4-dich loro-
ben zyl)th iosuccin im ide26 (1.5 equiv.) for 5 m in , followed by ch rom atograph y on silica gel
usin g toluen e–eth yl acetate. Yield 85%, wh ite foam (ca. 1:1 m ixture of diastereom ers, pu-
rity > 98% by 1H NMR). FAB HRMS [M]+, foun d 1411.2543; C69H67Cl2N4O14PSSeNa requires
1
1411.2552. 31P NMR (m ixture of diastereom ers): 100.5 (m ultiplet, JPSe = 924) an d 98.50
1
(m ultiplet, JPSe = 921). 1H NMR (m ixture of diastereom ers, selected sign als): 6.30–6.40 (m ,
2 H, Ha1′ an d Hb1′); 5.36–5.47 (m , 1 H, Ha3′); 4,27 an d 4.23 (2 m , 1 H, Hb3′); 4.11 an d 4.02
3
(2 d, JPH = 15, 2 H, S-CH2); 4.09 (m , 1 H, Ha4′); 3.89 an d 3.92 (2 m , 1 H, Hb4′); 3.8–3.6 (m ,
2 H, Hb5′); 3.35 (m , 2 H, Ha5′); 2.33, 1.97 an d 1.63 (3 m , 2 H, Ha1′ an d Hb1′); 1.85, 1.47 an d
1.44 (3 s, 6 H, 2 × C5-CH3). 13C NMR (m ixture of diastereom ers, selected sign als): 85.58 an d
85.36 (C1′), 84.95 (d, J = 4.6, Ca4′), 84.47 an d 84.43 (C1′), 84.03 (d, J = 5.5, Ca4′), 83.86 an d
83.80 (2 d, J = 9.5, Cb4′), 80.49 an d 80.31 (2 d, J = 5.4, Ca3′), 74.50 an d 74.26 (Cb3′), 68.25
an d 67.91 (2 d, J = 7, Cb5′), 63.34 an d 63.13 (Ca5′), 39.24–38.86 (m , Ca2′ an d Cb2′), 37.26
an d 36.61 (2 d, J = 2.5 an d 4, S-C), 12.68, 12.63, 11.88 an d 11.81 (2 × C5-CH3).
Financial support from the Swedish Research Council is gratefully acknowledged.
Collect. Czech. Chem. Commun. 2006, Vol. 71, No. 6, pp. 832–841

Dinucleoside H-Phosphonoselenoates
841
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