Novel phosphanucleoside analogs of dideoxynucleosides

Article abstract of DOI:10.1016/j.tet.2017.07.020

The synthesis of modified nucleoside analogs is an attractive area of medicinal research. Here, we have developed a synthetic route leading to a new class of dideoxynucleoside analogs, the phosphanucleosides containing 1-hydroxymethylphospholane 1-oxide rings. The preparation of these compounds consisted of a multistep synthesis of phospholane scaffold using a ring-closing metathesis and stereoselective hydroboration reaction. Subsequent nucleobase construction afforded the phosphanucleosides bearing all four nucleobases. The racemic phosphanucleosides were easily resolved on reverse phase using N-acetyl-L-tryptophan as a derivatizing agent.

Full text of DOI:10.1016/j.tet.2017.07.020

Tetrahedron xxx (2017) 1e9
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Tetrahedron
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Novel phosphanucleoside analogs of dideoxynucleosides
**
*
ꢀ
ꢁ
ꢀ
ꢀꢀ
Ondrej Pav , Milos Budesínský, Ivan Rosenberg
IOCB Prague, Flemingovo nam. 2, 16610, Prague, Czech Republic
a r t i c l e i n f o
a b s t r a c t
Article history:
The synthesis of modified nucleoside analogs is an attractive area of medicinal research. Here, we have
developed a synthetic route leading to a new class of dideoxynucleoside analogs, the phosphanucleo-
sides containing 1-hydroxymethylphospholane 1-oxide rings. The preparation of these compounds
consisted of a multistep synthesis of phospholane scaffold using a ring-closing metathesis and stereo-
selective hydroboration reaction. Subsequent nucleobase construction afforded the phosphanucleosides
bearing all four nucleobases. The racemic phosphanucleosides were easily resolved on reverse phase
Received 27 March 2017
Received in revised form
16 June 2017
Accepted 11 July 2017
Available online xxx
using N-acetyl-L-tryptophan as a derivatizing agent.
Keywords:
© 2017 Published by Elsevier Ltd.
Phosphanucleoside
Nucleoside analog
Ring-closing metathesis
Stereoselective hydroboration
Chiral resolution
1. Introduction
phosphanucleoside analogs related to dideoxynucleosides. The
aimed phosphanucleoside analogs exhibit structural similarity
with furanose-based nucleosides, such as 20,3'-dideoxyinosine
(ddI) and 20,3'-dideoxycytidine (ddC), which were approved as in-
hibitors of HIV reverse transcriptase.14 The presence of the 1-oxide
group mimicking the 40-substituent also resembles the structure of
anti-HCV compounds.15,16
Moreover, we report N-acetyl-L-tryptophan as an efficient
derivatizing agent for the chiral resolution of racemates of the
prepared phosphanucleosides.
Nucleoside analogs have been screened in clinical trials for
almost five decades and have become cornerstones for the treat-
ment of various viral infections and cancers. The approval of several
new drugs over the past decade demonstrates wide interest in this
group of compounds, and demonstrates that these analogs still
possess strong therapeutic potentials.1 Moreover, the rapid evolu-
tion of drug resistance has recently become a serious issue.
Therefore, the search for novel compounds with antiviral and
antimicrobial activities is strongly required.
Sugar-modified nucleosides such as carba-,2,3 aza-,4,5 and thia-
nucleosides,6 in which the furanose oxygen is replaced by a carbon,
nitrogen, or sulfur atom, respectively, exhibit a variety of inter-
esting biological properties.7,8 Surprisingly, phosphanucleosides
have not received significant attention, and only a few types of
these compounds have been reported in the literature.9e12
Recently, we reported the first comprehensive study on the syn-
thesis of phosphanucleosides bearing all four nucleobases.13 These
compounds resembled the structure of 3-deoxynucleosides.
Encouraged by these results, and intending to extend the scope
of phosphanucleoside chemistry, we report here an original set of
2. Results and discussion
Since the publication of our first set of phosphanucleosides,13
we have significantly improved the synthesis of the key synthon
6 (Scheme 1). The higher yielding and more convenient synthetic
route utilized the ring-closing metathesis of diallyl(tritylox-
ymethyl)phosphine oxide (10). In the key step (10 / 6), only
1.5 mol% of Grubbs catalyst (1st generation) was used to achieve
nearly quantitative cyclization. Compound 10 was easily prepared
in three steps starting from diethyl phosphite (7) and allylmagne-
sium bromide followed by the reaction of the diallylphosphine
oxide (8) with formaldehyde, affording the hydroxymethyl deriv-
ative 9, which was then protected with a trityl group to obtain the
desired diallyl derivative 10.
* Corresponding author.
** Corresponding author.
Hydroboration of phospholene 6 with BH3*THF complex fol-
lowed by treatment with aqueous sodium perborate afforded a
mixture of trans and cis racemates 11a and 11b in an approximately
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E-mail addresses: ondrej.pav@uochb.cas.cz (O. Pav), ivan.rosenberg@uochb.cas.
cz (I. Rosenberg).
http://dx.doi.org/10.1016/j.tet.2017.07.020
0040-4020/© 2017 Published by Elsevier Ltd.
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2
Scheme 1. (i) NH4H2PO2, BSA, 110 ꢀC, 72 h; (ii) (COCl)2, DCM, r.t., 16 h; (iii) DIBAL, DCM, ꢁ78 ꢀC, 2 h; (iv) CH2O, TEA, EtOH, r.t., 16 h; (v) Tr-Cl, pyridine, 60 ꢀC, 36 h; (vi) allylMgBr,
Et2O, r.t., 4 h; (vii) Grubb's catalyst, 1st gen., DCM, 50 ꢀC, 6 h.
3:1 ratio (Scheme 2). The major product was identified as the trans
racemate 11a. This finding added the phosphine oxide group to the
list of already reported functional groups, such as ether, acetate and
hydroxy groups,17e19 which direct stereoselectivity of the hydro-
boration reaction. In our case, the phosphine oxide group directed
cis hydroboration. We attempted to improve the stereoselectivity of
hydroboration reaction using bulkier borane reagents such as 9-
BBN, catecholborane and pinacolborane. Unfortunately, we did
not observe formation of the product in any case.
Since we were not able to separate the mixture of hydroxy de-
rivatives 11a and 11b on silica gel, we carried out further trans-
formations with the mixture of diastereomers. The hydroxy group
was converted to the mesylate using methanesulfonyl chloride in
the presence of N-methylimidazole in DCM, and subsequently
treated with sodium azide in DMF to afford azides 13 and 14. At this
point, azido diastereomers were easily separated using chroma-
tography on silica gel. The substitution reaction was accompanied
by approximately 15% elimination. Azides 13 and 14 were hydro-
genated at atmospheric pressure in the presence of catalytic Pd/C to
provide the corresponding amines 15 and 16 as starting compounds
for nucleobase construction (Scheme 3).
derivative 26 was then converted into the cytosine derivative by
treatment with aqueous ammonia. Cleavage of the DMTr group
using 80% acetic acid afforded the free cytosine phosphanucleoside
27 (Scheme 4).
Trans dideoxyphosphanucleosides 28e31, resembling a-nucle-
osides, were prepared using the same protocols as the cis de-
rivatives (Scheme 4).
The preparation of dideoxyphosphanucleosides using 1-
trityloxymethylphosphol-3-ene 1-oxide (6) as a starting precursor
afforded the desired compounds in excellent yields. Unfortunately,
the phosphanucleosides were afforded as racemic mixtures. To
address this issue, we examined several methods to resolve the
racemic mixtures on a preparative scale to obtain optically pure
enantiomers. As a proof of principle, we chose guanine derivative
25 as a model compound. First, we tried lipase-catalyzed separation
of the racemic phosphanucleotide as reported by Garcia et al.22
Unfortunately, neither the introduction nor the cleavage of the
levulinyl group led to the separation of the isomers. Therefore, we
derivatized phosphanucleoside 25 with several chiral reagents,
such as R-mandelic acid, BOC-
1,2:3,4-diisopropylidene- -galacturonic acid, and examined the
chiral resolution on both silica gel and reverse phase. The best re-
sults were obtained using 1,2:3,4-diisopropylidene- -galacturonic
acid and N-acetyl- -tryptophan. In both cases, we obtained sepa-
L-proline, N-Ac-L-tryptophan and
D
Uracil derivative 19 was prepared from the appropriate amine
15 using 4-nitrophenyl-3-ethoxyacryloylcarbamate 17 (Scheme
4).20 The reaction of the amine with the nitrophenyl carbamate
afforded the ureido derivative 18, which was subsequently trans-
formed into the uracil derivative via acid-catalyzed cyclization.
Adenine (24) and guanine (25) phosphanucleosides were syn-
thesized using 4,6-dichloro-5-formamidopyrimidine 20 and 2-
D
L
ration of the enantiomers on reverse phase. Since the ester with
galacturonic acid showed lability under the work-up and purifica-
tion conditions, we selected the tryptophan ester as a chiral reso-
lution group for preparative-scale separation. The Mitsunobu
reaction was employed to form the tryptophan phosphanucleoside
conjugates (Scheme 5). The diastereomers were easily separated on
C18 reverse phase using 0.1% acetic acid in water as a mobile phase,
separating the faster-eluting isomer 32 and slower-eluting isomer
33. Cleavage of the tryptophan ester group of the faster-eluting
amino-4,6-dichloro-5-formamidopyrimidine
21,
respectively
(Scheme 4).21 In the first step, the purine rings were formed in a
one-pot reaction under heating at 130 ꢀC. The 6-chloropurine de-
rivative 22 was converted into the adenine phosphanucleoside 24
by treatment with aqueous ammonia followed by treatment with
acetic acid to remove the trityl group. The 2-amino-6-chloropurine
derivative 23 was treated with hydrochloric acid in methanol to
afford guanine phosphanucleoside 25.
isomer 32 using aqueous ammonia afforded, after HPLC purifica-
20
tion, the pure enantiomer 25(þ) ([
a
]
D
¼ þ 52.6 (0.156; 20%
aqueous methanol)). Similarly, cleavage of the ester group of the
Cytosine derivative 27 was prepared from the appropriate
DMTr-protected uracil phosphanucleoside, which was treated with
2,4,6-triisopropylbenzenesulfonyl chloride in the presence of trie-
thylamine and N,N-dimethylaminopyridine in acetonitrile. TIPS
slower-eluting isomer 33 afforded the pure enantiomer 25(ꢁ)
20
([
a]
¼ - 52.3 (0.235; 20% aqueous methanol)). The applicability of
D
the tryptophan-based separation protocol on the phosphanucleo-
tides bearing adenine, uracil and cytosine nucleobases is shown in
Scheme 2. Proposed intermediate leading to a diastereoselective hydroboration.
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O. Pav et al. / Tetrahedron xxx (2017) 1e9
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Scheme 3. (i) a) BH3*THF, THF, r.t., 2 h; b) NaBO3*4H2O, THF/H2O, r.t., 16 h; (ii) MsCl, N-methylimidazole, DCM, r.t., 1 h; (iii) NaN3, DMF, 80 ꢀC, 16 h; (iv) H2, Pd/C, EtOH, r.t., 16 h.
Scheme 4. (i) Dioxane, r.t., 2 h; (ii) DOWEX Hþ, dioxane, 90 ꢀC, 4 h; (iii) DIPEA, n-BuOH, 130 ꢀC, 40 h; (iv) a) aq. NH3, acetonitrile, r.t., 5 days; b) 80% AcOH, 60 ꢀC, 16 h; (v) 1 M HCl,
MeOH 60 ꢀC, 16 h; (vi) a) DMTr-Cl, pyridine, r.t., 16 h; b) TIPS-Cl, TEA, DMAP, acetonitrile, r.t., 16 h; (vii) a) aq. NH3, acetonitrile, r.t., 16 h; b) 80% AcOH, r.t. 16 h; (viii) B¼U (i-ii); B¼A
(iii-iv); B¼G (iii,v); B¼C (vi-vii).
the SI. Despite an enormous effort, we were not able to determine
the absolute configuration of the pure enantiomers 25(þ) and
25(¡). Neither NMR study based on the measurements of the
tryptophan diastereomers 32 and 33 nor attempts to isolate a
crystal for X-ray measurements provided the desired results.
Although detailed analysis of most 1H NMR spectra was very
complicated since the spectra showed complex multiplets due to
many J(H,H), additional splitting by J(H,P) and partial overlap of
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Scheme 5. Chiral resolution of the phosphanucleoside racemate using N-acetyl-L-tryptophan. (i) N-acetyl-L-tryptophan, PPh3, DIAD, DMF, r.t., 2 h; (ii) aq. NH3, MeOH, r.t., 16 h.
some proton signals, we were able to determine all coupling con-
stants and conformations of phospholane rings in the case of the cis
and trans uracil derivatives 19 and 28. The stereochemical assign-
ments of the signals of the geminal protons in positions 2, 4 and 5
were achieved from the observed NOE contacts with the hydrox-
ymethyl group and uracil nucleobase. The results are shown in
Table 1 in the Experimental section.
3. Conclusions
In summary, we prepared a new class of analogs of dideox-
ynucleosides,
phosphanucleosides
containing
1-
hydroxymethylphospholane 1-oxide rings. A ring-closing metath-
esis of diallyltrityloxymethylphosphine oxide was employed to
improve the yield of the synthesis of 1-trityloxymethylphosphol-3-
ene 1-oxide. The stereoselective hydroboration reaction revealed
the phosphine oxide as a new cis-directing group. We have suc-
Two large vicinal J(H,H) couplings of H-3 in both isomers
(11.2e12.4 Hz) suggested the pseudoaxial position of H-3 and
pseudoequatorial orientation of uracil in both isomers. Such ar-
rangements appear in the conformations of envelope type 3E of
isomer 19 and 3E of isomer 28. These conformation types were
also supported by the observed long-range couplings of the
pseudoequatorial protons: J(2t, 4t) ¼ 2.0 Hz in 19 and J(2c,
4c) ¼ 1.7 Hz in 28. A molecular modeling and geometry optimi-
zation afforded preferred conformations that were slightly shifted
from the envelope to the twist forms: 3E to 4T3 in isomer 19
(maximum pucker tmax ¼ 39) and 3E to 4T3 in isomer 28
cessfully employed N-acetyl-L-tryptophan as an efficient deriva-
tizing agent for the chiral resolution of racemates of the prepared
phosphanucleosides. The prepared phosphanucleosides exhibited
no cytotoxicity. The syntheses of phosphonate and phosphate
prodrugs followed by antiviral and antimicrobial screenings are
currently under way.
4. Experimental section
(
tmax ¼ 44). The 3J(H,H) values derived from calculated torsion
Unless stated otherwise, all used solvents were anhydrous. Mass
spectra were recorded on a ZAB-EQ (VG Analytical) instrument
using FAB (ionization with Xe, accelerating voltage 8 kV; glycerol
and thioglycerol as matrices) and on LTQ Orbitrap XL (Thermo
Fisher Scientific) using ESI ionization. The NMR spectra were
measured on Bruker AVANCE-600 instrument (1H at 600.13 MHz
and 13C at 150.9 MHz) with a cryoprobe and Bruker AVANCE-500
instrument with a cryoprobe (31P at 202.4 MHz) in DMSO-d6 at
angles of protons were in very good agreement with experimental
3J(H,H) values. Theoretical envelope (3E and 3E) and twist (4T3 and
4T3) forms, and preferred calculated conformations of isomers 19
and 28 are shown in Fig. 1.
The prepared compounds were tested for their cytostatic ac-
tivity (HepG2, HL60, HeLa S3, and CCRF-CEM), but no significant
effects were observed.
Table 1
1H NMR data of compounds 19 and 28.a
Compound config. H-2c
H2-t
H-3
H-4c
H-4t
H-5c
H-5t
H-6a
H-6b
6-OH
19
cis
2.08 dt
1.99 dddd
4.93 tdd
1.88 qdd
2.135 ddddd 2.31 br td
1.68 dddd
3.90 dd
3.87 dd
5.54 br
2c,2t ¼ 14.6 2t,2c ¼ 14.6 3,4c ¼ 12.4 4c,3 ¼ 12.4
4t,P ¼ 31.6
5c,5t ¼ 14.9 5t,P ¼ 17.9
6a,6b ¼ 14.2 6b,6a ¼ 14.2
2c,3 ¼ 11.8
2c,P ¼ 11.0
2t,P ¼ 11.5
2t,3 ¼ 7.7
2t,4t ¼ 2.0
3,2c ¼ 11.8 4c,4t ¼ 12.4 4t,4c ¼ 12.4
5c,4c ¼ 7.4
5c,P ¼ 7.3
5c,4t ¼ 1.6
5t,5c ¼ 14.9 6a,P ¼ 3.7 6b,P ¼ 4.4
3,2t ¼ 7.7
3,4t ¼ 5.7
3,P < 1
4c,5t ¼ 12.4 4t,5t ¼ 7.9
5t,4c ¼ 12.4
5t,4t ¼ 7.9
4c,5c ¼ 7.4
4c,P ¼ 1.7
4t,3 ¼ 5.7
4t,2t ¼ 2.0
4t,5c ¼ 1.6
2.195 ddtd
4t,4c ¼ 15.8
28
trans
2.40 dddd
1.99 ddd
4.69 tddd
2.09 dddt
1.97 ddt
1.77 tdd
3.86 dt
3.82 ddd
5.63 dt
2c,2t ¼ 14.2 2t,P ¼ 19.0
3,4t ¼ 11.5 4c,P ¼ 20.2
5c,5t ¼ 14.8 5t,5c ¼ 14.8 6a,6b ¼ 14.0 6b,6a ¼ 14.0 OH,P ¼ 8.3
2c,3 ¼ 7.2
2c,P ¼ 4.6
2c,4c ¼ 1.7
2t,2c ¼ 14.2 3,2t ¼ 11.2 4c,4t ¼ 15.8 4t,3 ¼ 11.5
5c,4c ¼ 8.1
5c,4t ¼ 12.0 5t,4t ¼ 8.1
5c,P ¼ 7.9 5t,4c ¼ 2.1
5t,P ¼ 14.8
6a,OH ¼ 5.7
6a,P ¼ 5.7
6b,OH ¼ 5.7
6b,P ¼ 4.0
OH,6a ¼ 5.7
OH,6b ¼ 5.7
2t,3 ¼ 11.2
3,2c ¼ 7.2
3,4c ¼ 5.8
3,P ¼ 2.5
4c,5c ¼ 8.1
4c,3 ¼ 5.8
4c,5t ¼ 2.1
4c,2c ¼ 1.7
4t,5c ¼ 12.0
4t,5t ¼ 8.1
4t,P ¼ 4.2
a
Samples were measured in DMSO-d6 at 40 ꢀC. Coupling constants are given in italics.
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Fig. 1. Theoretical envelope (3E and 3E) and twist (4T3 and 4T3) forms, and preferred calculated conformations of isomers 19 (top) and 28 (bottom).
25 ꢀC. The 1H and 13C spectra were referenced to the solvent peak
(using dH(DMSO) ¼ 2.50 ppm; dC(DMSO) ¼ 39.7 ppm) and 31P
spectra to external H3PO4. Structural assignment of proton and
carbon signals was achieved combining 1D-1H and 13C-spectra
with homonuclear 2D-H,H-COSY, 2D-H,H-ROESYand heteronuclear
2D-H,C-HSQC and 2D-H,C-HMBC spectra. IR spectra were recorded
using KBr pellets on Nicolet 6700 (Thermo Electron Corp.).
H-3); 5.32 (m, 4H, H-4); 3.59 (m, 2H, P-CH2-O); 2.90 (m, 4H, H-2).
13C NMR (150.9 MHz, CD3OD):
d
¼ 142.48 (ArC); 128.48 (ArC);
127.72 (ArC); 127.27 (ArC); 126.22 (d); 120.35 (d); 88.80 (d, >C<);
57.58 (d, P-CH2-O); 31.26 (d, C-2). 31P NMR (202.3 MHz, CD3OD):
d
¼ 48.95.
4.2. 1-Trityloxymethylphosphol-3-ene 1-oxide (6)
4.1. Diallyl(trityloxymethyl)phosphine oxide (10)
Grubbs catalyst, 1st generation (2.1 g; 2.6 mmol) was added
portionwise (0.3 g every one hour, for 6 h) under argon at 50 ꢀC to a
stirred solution of diallyl(trityloxymethyl)phosphine oxide (10)
(71.2 g; 176.9 mmol) in DCM (1 L). The crude product was evapo-
rated and purified by chromatography on silica gel (elution with
gradient of 0e10% ethanol in chloroform). The obtained dark foam
was treated with charcoal in ethanol at reflux. Charcoal was
filtered off and the solvent evaporated to afford 1-
trityloxymethylphosphol-3-ene 1-oxide 6 as a white foam. Yield
61.1 g (92%).
Diethyl phosphite 7 (31 mL; 242 mmol) in diethyl ether
(200 mL) was added dropwise under argon at 4 ꢀC to a stirred so-
lution of allylmagnesium bromide (800 mL; 800 mmol) in diethyl
ether (400 mL). The reaction mixture was stirred for an additional
30 min at 4 ꢀC and then for 4 h under argon at r.t. After that, the
mixture was poured onto a cooled aqueous solution of potassium
carbonate (166 g; 1.2 mol; 1 L). The mixture was filtered through
cellite, the solids were washed with ethanol and the filtrate was
evaporated. The crude product was dissolved in ethanol (1 L) and
the solution was filtered, evaporated and coevaporated with
ethanol (3 ꢂ 200 mL). The crude diallylphosphine oxide 8 was used
without further purification. 31P NMR (202.3 MHz, CD3OD):
IR nmax (KBr) 3086, 3054, 1618, 1491, 1447, 1156, 1090, 1033, 958,
844, 709, 632.
HRMS (FAB) calcd for C24H24O2P (M þ H)þ 375.1514, found
375.1514. 1H NMR (600.1 MHz, CDCl3):
d
¼ 7.39 (m, 6H, ortho-ArH);
d
¼ 38.30.
7.31 (m, 6H, meta-ArH); 7.26 (m, 3H, para-ArH); 5.93 (dm,
J(P,H) ¼ 28.6 Hz, SJ(H,H) ¼ 5.3 Hz, 2H, H-3 and H-4); 3.64 (d,
J(P,H) ¼ 8.2 Hz, 2H, P-CH2-O); 2.65 (bdd, J(H,H) ¼ 17.7 Hz,
J(P,H) ¼ 6.4 Hz, 2H, H-2a and H-5a); 2.52 (bdd, J(H,H) ¼ 17.7 Hz,
J(P,H) ¼ 15.0 Hz, 2H, H-2b and H-5b). 13C NMR (150.9 MHz, CDCl3):
Triethylamine (34 mL; 242 mmol) was added to a solution of
diallylphosphine oxide 8 and formaldehyde (36 mL of 13.3 M so-
lution in water; 484 mmol) in ethanol (1 L). The reaction mixture
was stirred for 16 h at r.t. and evaporated. The crude product was
treated with chloroform (1 L) and anhydrous sodium sulfate was
added. The solution was filtered, evaporated and coevaporated with
pyridine (3 ꢂ 200 mL). The crude diallyl(hydroxymethyl)phosphine
oxide 9 was used without further purification. 31P NMR (202.3 MHz,
d
¼ 142.58 (3C, ipso-ArC); 128.57 (6C, ortho-ArC); 128.03 (6C, meta-
ArC); 127.44 (3C, para-ArC); 127.36 (d, J(P,C) ¼ 11.0 Hz, C-3 and C-4);
84.45 (d, J(P,C) ¼ 12.3 Hz, >C<); 59.86 (d, J(P,C) ¼ 81.4 Hz, P-CH2-O);
30.13 (d, J(P,C) ¼ 65.1 Hz, C-2 and C-5). 31P NMR (202.3 MHz, CDCl3):
CD3OD):
d
¼ 50.28.
d
¼ 66.90.
Trityl chloride (89.4 g; 315 mmol) was added to a solution of
diallyl(hydroxymethyl)phosphine oxide 9 in pyridine (1 L). The
reaction mixture was stirred for 36 h at 60 ꢀC, quenched by the
addition of methanol (50 mL) and evaporated. The residue was
dissolved in chloroform (1 L) and extracted with saturated solution
of sodium hydrogencarbonate (3 ꢂ 200 mL). The organic layer was
dried over anhydrous sodium sulfate and evaporated. Diallyl(-
trityloxymethyl)phosphine oxide 10 was purified by chromatog-
raphy on silica gel (elution with gradient of 0e10% ethanol in
chloroform) to yield 71.2 g (73%) of white foam.
4.3. (3S,1S and 3R,1R) 3-Azido-1-trityloxymethylphospholane 1-
oxide (13) and (3S,1R and 3R,1S) 3-azido-1-
trityloxymethylphospholane 1-oxide (14)
A solution of borane*THF complex (30 mL of 1 M solution in
THF; 30 mmol) was added to
a
solution of 1-
trityloxymethylphosphol-3-ene 1-oxide 6 (9.4 g; 25 mmol) in THF
(250 mL). The reaction mixture was stirred for 2 h at r.t. After that,
an aqueous solution of sodium perborate tetrahydrate (4.6 g;
30 mmol; 500 mL) was added and the mixture was stirred for
IR nmax (KBr) 3082, 3062, 1175, 1598, 1492, 1443, 1153, 1085,
1034, 950, 919, 706, 631.
16
h at r.t. The mixture was extracted with chloroform
HRMS (FAB) calcd for C26H28O2P (M þ H)þ 403.1827, found
(3 ꢂ 200 mL). The organic layer was dried over anhydrous sodium
403.1824. 1H NMR (600.1 MHz, CD3OD):
ArH); 7.47 (m, 6H, meta-ArH); 7.42 (m, 3H, para-ArH); 5.82 (m, 2H,
d
¼ 7.57 (m, 6H, ortho-
sulfate and evaporated. The reaction afforded 3-hydroxy-1-
trityloxymethylphospholane 1-oxide as
a
mixture of two
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diastereomers in an approximately 1:3 ratio (HPLC faster eluting
isomer 11b/HPLC slower eluting isomer 11a; gradient from 0.1 M
TEAA in water/MeOH (1:1) to MeOH in 15 min). The mixture of
diastereomers was used without further purification or separation.
ESI-MS calcd for C24H26NO3P (M þ H)þ 393.2, found 393.2.
Methanesulfonyl chloride (3.9 mL; 50 mmol) was added to a
solution of a mixture of 3-hydroxy-1-trityloxymethylphospholane
1-oxide 11a and 11b and N-methylimidazole (4.4 mL; 55 mmol) in
DCM (250 mL). The reaction mixture was stirred for 1 h at r.t. The
solution was diluted with chloroform (500 mL) and extracted with
a saturated solution of sodium chloride (3 ꢂ 200 mL). The organic
layer was dried over anhydrous sodium sulfate, evaporated and
coevaporated with toluene. The crude mixture of mesyl de-
rivatives 12a and 12b was used without further purification or
separation.
Sodium azide (7.6 g; 125 mmol) was added to a solution of a
mixture of 3-mesyloxy-1-trityloxymethylphospholane 1-oxide 12a
and 12b in DMF (250 mL). The reaction mixture was stirred for
16 h at 80 ꢀC and evaporated. The residue was dissolved in chlo-
roform (500 mL) and extracted with a saturated solution of sodium
hydrogencarbonate (3 ꢂ 200 mL). The organic layer was dried over
anhydrous sodium sulfate and evaporated. The diastereomers were
separated by chromatography on silica gel. First chromatography
(elution with gradient of 0e50% aceton in toluene) afforded faster
eluting trans racemate 14 (1.7 g; 16%; white foam). Second subse-
quent chromatography (elution with gradient 5e10% ethanol in
chloroform) afforded slower eluting cis racemate 13 (4.5 g; 43%;
white foam).
14:
IR nmax (KBr) 3087, 3058, 2933, 2847, 2099, 1597, 1491, 1449,
1154, 1088, 1033, 840, 707, 632.
HRMS (FAB) calcd for C24H25N3O2P (M þ H)þ 418.1684, found
418.1683.
NMR data see Tables 2 and 3.
4.4. (3S,1S and 3R,1R) 3-Amino-1-trityloxymethylphospholane 1-
oxide (15)
Azido derivative 13 (4.5 g; 10.8 mmol) and 10% Pd/C catalyst
(0.5 g) were suspended in ethanol (100 mL). The mixture was hy-
drogenated at atmospheric pressure for 16 h at r.t. The reaction
mixture was filtered through a layer of Celite and the solvent was
evaporated. The crude amino derivative 15 was used without
further purification (yellow oil).
ESI-MS calcd for C24H27NO2P (M þ H)þ 392.2, found 392.4.
4.5. (3S,1R and 3R,1S) 3-Amino-1-trityloxymethylphospholane 1-
oxide (16)
Azido derivative 14 (1.7 g; 4.0 mmol) and 10% Pd/C catalyst
(0.25 g) were suspended in ethanol (50 mL). The mixture was hy-
drogenated at atmospheric pressure for 16 h at r.t. The reaction
mixture was filtered through a layer of Celite and the solvent was
evaporated. The crude amino derivative 16 was used without
further purification (yellow oil).
ESI-MS calcd for C24H27NO2P (M þ H)þ 392.2, found 392.1.
13:
IR nmax (KBr) 3086, 3058, 2917, 2835, 2100, 1491, 1449, 1154,
1088, 1033, 707, 632.
4.6. (3S,1S and 3R,1R) 1-Hydroxymethyl-3-(uracil-1-yl)
phospholane 1-oxide (19)
HRMS (FAB) calcd for C24H25N3O2P (M þ H)þ 418.1684, found
418.1684.
4-Nitrophenyl-3-ethoxyacryloylcarbamate (0.7 g; 2.8 mmol)
Table 2
13C and 31P NMR data of compounds 13, 14, 19, 24, 25 and 27e33 in DMSO-d6.[a]
Compound
config.[b]
Phospholane ring
Base
C-2
C-3
C-4
C-5
C-6
P
C-2
C-4
C-5
C-6
C-8
13[c]
14[d]
19
cis
30.43
62.5
30.87
63.1
27.60
59.8
29.35
60.1
29.71
59.9
27.87
60.0
29.78
69.4
31.25
60.2
31.24
60.1
30.02
59.6
30.49
64.2
30.39
64.0
59.47
13.0
59.70
10.9
54.16
17.3
53.32
16.2
52.52
16.0
54.92
16.6
53.66
17.0
53.13
15.4
52.66
15.4
54.32
16.2
52.11
18.4
52.26
18.6
29.80
4.6
29.77
5.2
28.99
~0
30.34
~0
30.38
~0
29.18
~0
28.59
~0
30.20
~0
30.48
~0
28.96
~0
29.39
2.2
29.64
<2
23.76
61.2
23.20
61.4
25.00
56.8
25.04
57.0
25.11
57.0
25.18
56.9
22.47
57.4
22.70
57.7
22.65
57.7
22.61
57.6
25.68
59.9
25.75
59.6
62.01
79.5
61.15
79.7
59.88
78.1
59.62
78.2
59.75
78.2
59.90
77.7
59.25
79.2
59.24
79.1
59.19
79.2
59.37
78.7
61.64
74.8
61.23
75.1
62.00
e
e
e
e
e
trans
cis
62.74
60.22
61.11
61.68
60.85
62.72
63.01
62.85
62.77
56.93
57.20
e
e
e
e
e
150.99
152.48
153.64
155.62
151.00
152.43
153.56
155.54
153.62
153.57
163.29
149.48
151.17
165.48
163.27
149.41
156.95
165.39
151.08
151.09
101.85
119.37
116.99
94.15
141.91
156.23
157.00
142.43
142.20
156.24
151.02
142.53
156.95
156.93
e
24
cis
139.29
135.14
e
25
cis
27
cis
28
trans
trans
trans
trans
cis
101.78
119.27
117.09
94.05
e
29
139.46
135.94
e
30
31
32[e]
33[f]
117.03
117.06
135.20
135.29
cis
[a]
The J(C,P) values are given in italics.
[b] Configuration of base relative to CH2OH group.
Additional carbon atoms: [c] OTr: 88.09 d, J(C,P)¼11.8 (>C<), 142.86 (3x C-ipso), 128.48 (6x C-ortho), 128.29 (6x C-meta), 127.58 (3x C-para); [d] OTr: 88.18 d, J(C,P)¼11.4 (>C<),
142.86 (3x C-ipso), 128.51 (6x C-ortho), 128.35 (6x C-meta), 127.62 (3x C-para); [e] Trp-NAc: 172.07 (C¼O), 53.50 (C
a
), 27.11 (C
b
), 123.36 C2), 109.47 (C3), 118.10 (C4), 118.65
[f]
(C5), 121.17 (C6), 111.63 (C7), 136.30 (C8), 127.17 (C9), 169.81 (N-CO), 22.36 (CH3); Trp-NAc: 172.08 (C¼O), 53.58 (C
a
), 27.15 (Cb
), 124.02 C2), 109.43 (C3), 118.08 (C4),
118.62 (C5), 121.19 (C6), 111.65 (C7), 136.33 (C8), 127.14 (C9), 169.94 (N-CO), 22.34 (CH3).
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O. Pav et al. / Tetrahedron xxx (2017) 1e9
7
Table 3
Proton chemical shifts of compounds 13, 14, 19, 24, 25 and 27e33 in DMSO-d6.
Compound
config.[a]
Phospholane ring
Base
H-2c
H2-t
H-3
H-4c
H-4t
H-5c
H-5t
H-6a
H-6b
6-OH
13[b]
14[c]
19
cis
trans
cis
2.06
2.15
2.06
1.92
1.72
1.98
4.34
4.21
4.92
1.67
1.87
1.87
2.18
1.95
2.12
1.95
1.90
2.30
1.68
1.72
1.68
3.44
3.435
3.895
3.44
3.435
3.86
e
e
e
e
5.60
11.29 bs (NH), 5.62 d (H-5),
7.63 d (H-6)
24
25
27
28
29
30
cis
cis
cis
trans
trans
trans
trans
cis
2.45
~2.23
2.02
2.39
2.64
2.57
2.36
2.14
2.26
2.27
~2.23
1.94
1.99
2.42
2.34
1.93
2.28
2.20
5.08
4.82
4.94
4.69
4.82
4.59
4.73
4.81
4.79
2.23
2.08
1.85
2.07
2.31
2.23
2.03
2.35
2.22
2.42
2.37
2.065
2.17
2.53
2.40
2.12
2.04
1.93
2.39
2.38
2.30
1.96
2.08
2.02
1.96
2.17
2.125
1.78
1.71
1.65
1.77
1.83
1.80
1.75
1.76
1.74
3.95
3.92
3.89
3.86
3.92
3.90
3.85
4.57
4.62
3.91
3.89
3.85
3.81
3.88
3.84
3.80
4.50
4.41
5.64
5.61
5.58
5.63
5.68
5.66
5.59
e
8.20 s (H-8), 8.14 s (H-2), 7.22 bs (NH2)
10.62 bs (NH), 7.77 s (H-8), 6.47 bs (NH2)
7.565 d (H-6), 7.09 b, 7.03 b (NH2), 5.705 d (H-5)
11.29 (NH), 7.88 d (H-6), 5.58 d (H-5)
8.32 s (H-8), 8.14 s (H-2), 7.21 bs (NH2)
10.56 s (NH), 7.92 s (H-8), 6.47 bs (NH2),
7.77 d (H-6), 7.08 b, 6.96 b (NH2), 5.69 d (H-5)
10.63 bs (NH], 7.77 s (H-8), 6.45 bs (NH2)
10.62 bs (NH], 7.74 s (H-8), 6.43 bs (NH2)
31
32[d]
33[e]
cis
e
[a]
Configuration of base - relative to CH2OH group.
Additional protons: [b] OTr: 7.41 m (6x ortho-ArH), 7.37 m (6x meta-ArH), 7.30 m (3x para-ArH); [c] OTr: 7.39 m (6x ortho-ArH), 7.38 m (6x meta-ArH), 7.30 m (3x para-ArH); [d]
Trp-NAc: 1.81 s (Ac), 8.46 d (NH), 4.55 ddd (H ), 3.18 dd (H 1), 3.08 dd (H
2), 10.88 d (NH1), 7.20 d (H2), 7.48 dq (H4), 6.96 ddd (H5), 7.05 ddd (H6), 7.32 dt (H7); [e] Trp-NAc:
1.82 s (Ac), 8.50 d (NH), 4.56 ddd (H ), 3.17 dd (H 1), 3.07 dd (H 2), 10.88 d (NH1), 7.20 d (H2), 7.48 dq (H4), 6.94 ddd (H5), 7.04 ddd (H6), 7.31 dt (H7).
a
b
b
a
b
b
was added to a solution of 3-amino-1-trityloxymethylphospholane
1-oxide 15 (1.1 g; 2.8 mmol) in dioxane (50 mL). The reaction
mixture was stirred for 4 h at r.t. After that, Dowex 50 (Hþ form, 5 g)
was added and the suspension was stirred for 2 h at 90 ꢀC. The resin
was filtered off and washed with dioxane (100 mL). The product
was released from the resin with water (100 mL), evaporated, pu-
rified by preparative HPLC (elution with gradient of 0e10% meth-
anol in water) and freeze-dried from water to yield 0.47 g (69%) of
white lyofilisate.
found 268.0963.
NMR data see Tables 2 and 3.
4.8. (3S,1S and 3R,1R) 3-(Guanin-9-yl)-1-
hydroxymethylphospholane 1-oxide (25)
2-Amino-4,6-dichloro-5-formamidopyrimidine 21 (1.1 g;
5.7 mmol) and DIPEA (2.6 mL; 15.2 mmol) were added to a solution
of 3-amino-1-trityloxymethylphospholane 1-oxide 15 (1.5 g;
3.8 mmol) in n-butanol (50 mL). The reaction mixture was stirred
for 40 h at 130 ꢀC and evaporated. 3-(2-Amino-6-chloropurine-9-
yl)-1-trityloxymethylphospholane 1-oxide 23 was purified by
chromatography on silica gel (first isocratic wash with 50% acetone/
toluene, second elution with gradient of 0e10% ethanol in chloro-
form). ESI-MS calcd for C29H28ClN5O2P (M þ H)þ 544.2, 546.2 found
544.1, 546.1.
IR nmax (KBr) 3283, 2992, 2810, 1680, 1623, 1462, 1423, 1386,
1267, 1147, 1050, 779, 763.
HRMS (FAB) calcd for C9H14N2O4P (M þ H)þ 245.0691, found
245.0692.
NMR data see Tables 1e3.
4.7. (3S,1S and 3R,1R) 3-(Adenin-9-yl)-1-
After that, the residue was treated 16 h at 60 ꢀC with concen-
trated hydrochloric acid/methanol 1/10 (25 mL), diluted with water
(100 mL) and treated with Dowex 50 (Hþ form,10 g). The resin was
filtered off and washed with methanol (100 mL) and water
(100 mL). The product was released from the resin with 5% aqueous
ammonia (100 mL), evaporated, purified by preparative HPLC
(elution with gradient of 0e20% methanol in water) and freeze-
dried from water to yield 0.56 g (52%) of white lyofilisate.
IR nmax (KBr) 3301, 3136, 2747, 1687, 1533, 1479, 1174, 1150, 1053,
780, 727, 638.
hydroxymethylphospholane 1-oxide (24)
4,6-Dichloro-5-formamidopyrimidine 20 (0.6 g; 3.3 mmol) and
DIPEA (1.8 mL; 10.4 mmol) were added to a solution of 3-amino-1-
trityloxymethylphospholane 1-oxide 15 (1.0 g; 2.6 mmol) in 1-
butanol (25 mL). The reaction mixture was stirred for 40 h at
130 ꢀC and evaporated. The residue was treated 5 days at r.t. with
aqueous ammonia/acetonitrile 1/1 (25 mL) and evaporated. The
crude adenine derivative was treated at 60 ꢀC for 16 h with 80%
acetic acid in water (100 mL), diluted with water (100 mL) and
treated with Dowex 50 (Hþ form, 10 g). The resin was filtered off
and washed with methanol (100 mL) and water (100 mL). The
product was released from the resin with 5% aqueous ammonia
(100 mL), evaporated, purified by preparative HPLC (elution with
gradient of 0e20% methanol in water) and freeze-dried from
water to yield 0.36 g (52%) of white lyofilisate.
HRMS (FAB) calcd for C10H15N5O3P (M þ H)þ 284.0913, found
284.0912.
NMR data see Tables 2 and 3.
4.9. (3S,1S and 3R,1R) 3-(Cytosin-1-yl)-1-
hydroxymethylphospholane 1-oxide (27)
IR nmax (KBr) 3426, 3328, 3181, 1641, 1601, 1572, 1502, 1475, 1414,
1330, 1157, 1051, 798, 723, 646.
Dimethoxytrityl chloride (0.3 g; 0.9 mmol) was added to a
mixture of 3-(uracil-1-yl)-1-hydroxymethylphospholane 1-oxide
HRMS (FAB) calcd for
C
10H15N5O2P (M
þ
H)þ 268.0963,
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O. Pav et al. / Tetrahedron xxx (2017) 1e9
8
19 (0.2 g; 0.8 mmol) and TEA (0.3 mL; 2.2 mmol) in pyridine
(10 mL). The reaction mixture was stirred for 16 h at r.t., quenched
by the addition of methanol (1 mL) and evaporated. The residue
was dissolved in chloroform (500 mL) and extracted with a satu-
rated solution of sodium hydrogencarbonate (3 ꢂ 200 mL). The
organic layer was dried over anhydrous sodium sulfate and evap-
orated. The crude dimethoxytrityl derivative was used without
further purification. ESI-MS calcd for C30H32N2O6P (M þ H)þ 547.2
found 547.2.
2,4,6-Triisopropylbenzenesulfonyl chloride (0.3 g; 1.2 mmol)
was added to a mixture of DMT derivative, TEA (0.3 mL; 2.2 mmol)
and DMAP (0.1 g; 0.8 mmol) in acetonitrile (10 mL). The reaction
mixture was stirred for 16 h at r.t. After that, 10 mL of aqueous
ammonia was added. The reaction mixture was stirred for 16 h at
r.t. and evaporated. The crude cytosine derivative was dissolved in
aqueous 50% methanol (100 mL) and treated with Dowex 50 (Hþ
form, 10 g). The resin was filtered off and washed with methanol
(100 mL) and water (100 mL). The product was released from the
resin with 5% aqueous ammonia (100 mL), evaporated, purified by
preparative HPLC (elution with gradient of 0e10% methanol in
water) and freeze-dried from water to yield 0.12 g (61%) of white
lyofilisate.
1425, 1335, 1310, 1212, 1174, 1146, 1081, 796, 730, 644.
HRMS (FAB) calcd for C10H15N5O2P (M þ H)þ 268.0963, found
268.0962.
NMR data see Tables 2 and 3.
4.12. (3S,1R and 3R,1S) 3-(Guanin-9-yl)-1-
hydroxymethylphospholane 1-oxide (30)
2-Amino-4,6-dichloro-5-formamidopyrimidine 21 (1.1 g;
5.7 mmol) and DIPEA (2.6 mL; 15.2 mmol) were added to a solution
of 3-amino-1-trityloxymethylphospholane 1-oxide 16 (1.5 g;
3.8 mmol) in n-butanol (50 mL). The reaction mixture was stirred
for 40 h at 130 ꢀC and evaporated. 3-(2-Amino-6-chloropurine-9-
yl)-1-hydroxymethylphospholane 1-oxide was purified by chro-
matography on silica gel (first isocratic wash with 50% acetone/
toluene, second elution with gradient of 0e10% ethanol in chloro-
form). ESI-MS calcd for C29H28ClN5O2P (M þ H)þ 544.2, 546.2 found
544.2, 546.2.
After that, the residue was treated 16 h at 60 ꢀC with concen-
trated hydrochloric acid/methanol 1/10 (25 mL), diluted with water
(100 mL) and treated with Dowex 50 (Hþ form, 10 g). The resin was
filtered off and washed with methanol (100 mL) and water
(100 mL). The product was washed off of the resin with 5% aqueous
ammonia (100 mL), evaporated, purified by preparative HPLC
(elution with gradient of 0e20% methanol in water) and freeze-
dried from water to yield 0.63 g (58%) of white lyofilisate.
IR nmax (KBr) 3433, 2926, 1686, 1534, 1483, 1172, 1149, 1046, 781,
728, 638.
IR nmax (KBr) 3338, 3161, 1665, 1644, 1628, 1527, 1488, 1152, 1140,
1049, 1044, 787.
HRMS (FAB) calcd for C9H15N3O3P (M þ H)þ 244.0851, found
244.0850.
NMR data see Tables 2 and 3.
4.10. (3S,1R and 3R,1S) 1-Hydroxymethyl-3-(uracil-1-yl)
phospholane 1-oxide (28)
HRMS (FAB) calcd for C10H15N5O3P (M þ H)þ 284.0913, found
284.0913.
NMR data see Tables 2 and 3.
4-Nitrophenyl-3-ethoxyacryloylcarbamate (0.7 g; 2.8 mmol)
was added to a solution of 3-amino-1-trityloxymethylphospholane
1-oxide 16 (1.1 g; 2.8 mmol) in dioxane (50 mL). The reaction
mixture was stirred for 4 h at r.t. After that, Dowex 50 (Hþ form, 5 g)
was added and the suspension was stirred for 2 h at 90 ꢀC. The resin
was filtered off and washed with dioxane (100 mL). The product
was washed off of the resin with water (100 mL), evaporated, pu-
rified by preparative HPLC (elution with gradient of 0e10% meth-
anol in water) and freeze-dried from water to yield 0.51 g (75%) of
white lyofilisate.
4.13. (3S,1R and 3R,1S) 3-(Cytosin-1-yl)-1-
hydroxymethylphospholane 1-oxide (31)
Dimethoxytrityl chloride (0.3 g; 0.9 mmol) was added to a
mixture of 3-(uracil-1-yl)-1-hydroxymethylphospholane 1-oxide
28 (0.2 g; 0.8 mmol) and TEA (0.3 mL; 2.2 mmol) in pyridine
(10 mL). The reaction mixture was stirred for 16 h at r.t., quenched
by the addition of methanol (1 mL) and evaporated. The residue
was dissolved in chloroform (500 mL) and extracted with satu-
rated solution of sodium hydrogencarbonate (3 ꢂ 200 mL). The
organic layer was dried over anhydrous sodium sulfate and
evaporated. The crude dimethoxytrityl derivative was used
IR nmax (KBr) 3426, 3090, 2886, 2798, 1681, 1622, 1465, 1387,
1271, 1148, 1053, 765.
HRMS (FAB) calcd for C9H14N2O4P (M þ H)þ 245.0691, found
245.0690.
NMR data see Tables 1e3.
without further purification. ESI-MS calcd for
C30H32N2O6P
(M þ H)þ 547.2 found 547.2.
4.11. (3S,1R and 3R,1S) 3-(Adenin-9-yl)-1-
hydroxymethylphospholane 1-oxide (29)
2,4,6-Triisopropylbenzenesulfonyl chloride (0.3 g; 1.2 mmol)
was added to a mixture of DMT derivative, TEA (0.3 mL; 2.2 mmol)
and DMAP (0.1 g; 0.8 mmol) in acetonitrile (10 mL). The reaction
mixture was stirred for 16 h at r.t. After that, 10 mL of aqueous
ammonia was added. The reaction mixture was stirred for 16 h at
r.t. and evaporated. The crude cytosine derivative was dissolved in
50% methanol in water (100 mL) and treated with Dowex 50 (Hþ
form, 10 g). The resin was filtered off and washed with methanol
(100 mL) and water (100 mL). The product was released from the
resin with 5% aqueous ammonia (100 mL), evaporated, purified by
preparative HPLC (elution with gradient of 0e10% methanol in
water) and freeze-dried from water to yield 0.13 g (68%) of white
lyofilisate.
4,6-Dichloro-5-formamidopyrimidine 20 (0.6 g; 3.3 mmol) and
DIPEA (1.8 mL; 10.4 mmol) were added to a solution of 3-amino-1-
trityloxymethylphospholane 1-oxide 16 (1.0 g; 2.6 mmol) in n-
butanol (25 mL). The reaction mixture was stirred for 40 h at 130 ꢀC
and evaporated. The residue was treated 5 days at r.t. with aqueous
ammonia/acetonitrile 1/1 (25 mL) and evaporated. The crude
adenine derivative was treated at 60 ꢀC for 16 h with 80% acetic acid
in water (100 mL), diluted with water (100 mL) and treated with
Dowex 50 (Hþ form, 5 g). The resin was filtered off and washed with
methanol (100 mL) and water (100 mL). The product was washed
off of the resin with 5% aqueous ammonia (100 mL), evaporated,
purified by preparative HPLC (elution with gradient of 0e20%
methanol in water) and freeze-dried from water to yield 0.37 g
(54%) of white lyofilisate.
IR nmax (KBr) 3334, 3185, 1646, 1610, 1580, 1528, 1489, 1147, 1043,
787.
HRMS (FAB) calcd for C9H15N3O3P (M þ H)þ 244.0851, found
244.0850.
IR nmax (KBr) 3316, 3153, 2925, 2855, 1650, 1605, 1574, 1485,
NMR data see Tables 2 and 3.
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O. Pav et al. / Tetrahedron xxx (2017) 1e9
9
4.14. General procedure for the resolution of phospholane
racemates
NMR data were identical to those of racemic compound 25.
HRMS (FAB) calcd for C10H15N5O3P (M þ H)þ 284.0913, found
284.0913.
20
4.14.1. 1-(N-Acetyl-
L
-tryptophanyloxymethyl)-3-(guanin-9-yl)
[a
]
¼ - 52.3 (0.235; 20% methanol/water).
D
phospholane 1-oxide 32 and 33
DIAD (0.32 mL; 1.6 mmol) was added to a mixture of racemic 3-
(guanin-1-yl)-1-hydroxymethylphospholane 1-oxide 25 (0.22 g;
Acknowledgments
0.8 mmol), triphenylphoshine (0.4 g; 1.6 mmol) and N-acetyl-L-
This work was supported by the Czech Science Foundation
[Grants 17-12703S and 13-26526S] and Ministry of Health of the
Czech Republic [15-31604A (all rights reserved)] under the IOCB
research project RVO:61388963.
tryptophan (0.4 g; 1.6 mmol) in DMF (10 mL). The reaction mixture
was stirred for 2 h at r.t., quenched by the addition of methanol
(1 mL) and evaporated. The tryptophan diastereomers were sepa-
rated by chromatography on reverse phase (elution with gradient of
methanol in 0.1% acetic acid/water; Luna 5
mM C18 100 Å,
Appendix A. Supplementary data
250 ꢂ 21.20 mm, Phenomenex) as faster eluting isomer 32 (0.11 g;
27%; white foam) and slower eluting isomer 33 (0.1 g; 24%; white
foam).
Supplementary data related to this article can be found at http://
dx.doi.org/10.1016/j.tet.2017.07.020.
Faster eluting isomer 32: HRMS (FAB) calcd for C23H27N7O5P
(M þ H)þ 512.1811, found 512.1811.
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Slower eluting isomer 33: HRMS (FAB) calcd for C23H27N7O5P
(M þ H)þ 512.1811, found 512.1812.
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((þ)-25)
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[
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¼ þ 52.6 (0.156; 20% methanol/water).
D
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((ꢁ)-25)
Slower eluting 1-(N-acetyl-L-tryptophanyloxymethyl)-3-(gua-
nin-9-yl)phospholane 1-oxide 33 (0.10 g; 0.20 mmol) was treated
16 h at r.t. with aqueous ammonia/methanol 1/2 (5 mL) and
evaporated. The product was purified by preparative HPLC (elution
with gradient of 0e20% methanol in water) and freeze-dried from
water to yield 49 mg (86%) of white lyofilisate.
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ꢁ
Please cite this article in press as: Pav O, et al., Novel phosphanucleoside analogs of dideoxynucleosides, Tetrahedron (2017), http://dx.doi.org/
10.1016/j.tet.2017.07.020