Synthetic approaches to nuclease-resistant, nonnatural dinucleotides of anti-HIV integrase interest

Article abstract of DOI:10.1080/15257770500265703

□ New, nonnatural dinucleotide 5′-monophosphates with a surrogate isonucleoside component of L-related stereochemistry, have been synthesized. Structures of the target compounds were confirmed by multinuclear NMR spectra (¹H, ¹³C,

Full text of DOI:10.1080/15257770500265703

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Synthetic Approaches to Nuclease-Resistant,
Nonnatural Dinucleotides of Anti-Hiv Integrase Interest
Guochen Chi a & Vasu Nair a
a Department of Pharmaceutical and Biomedical Sciences and The Center for Drug
Discovery , University of Georgia , Athens, Georgia, USA
Published online: 16 Aug 2006.
To cite this article: Guochen Chi & Vasu Nair (2005) Synthetic Approaches to Nuclease-Resistant, Nonnatural
Dinucleotides of Anti-Hiv Integrase Interest, Nucleosides, Nucleotides and Nucleic Acids, 24:10-12, 1449-1468, DOI:
10.1080/15257770500265703
To link to this article: http://dx.doi.org/10.1080/15257770500265703
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Nucleosides, Nucleotides, and Nucleic Acids, 24:1449–1468, 2005
c
Copyright ꢀ Taylor & Francis Group, LLC
ISSN: 1525-7770 print/1532-2335 online
DOI: 10.1080/15257770500265703
SYNTHETIC APPROACHES TO NUCLEASE-RESISTANT,
NONNATURAL DINUCLEOTIDES OF ANTI-HIV
INTEGRASE INTEREST
ᮀ
Guochen Chi and Vasu Nair
Department of Pharmaceutical and Biomedical
Sciences and The Center for Drug Discovery, University of Georgia, Athens, Georgia, USA
New, nonnatural dinucleotide 5ꢀ-monophosphates with a surrogate isonucleoside component of
ᮀ
L-related stereochemistry, have been synthesized. Structures of the target compounds were confirmed
by multinuclear NMR spectra (1H, 13C, 31P, COSY), UV hypochromicity, FAB HRMS data and
X-ray crystallography. These compounds are totally resistant to cleavage by 3ꢀ- and 5ꢀ-exonucleases.
Dinucleotides of this study with a terminal L-isonucleoside component showed remarkable selectivity
for inhibition of the strand transfer step of HIV-1 integrase. To the best of our knowledge, these
compounds represent only the second example of this type of selectivity of inhibition of the strand
transfer step.
Keywords Synthesis; Phosphorylation; Exonuclease; Inhibitors; HIV integrase
INTRODUCTION
The retroviral enzyme, HIV integrase, is essential for the replication
of HIV. It incorporates HIV double helical DNA into host chromosomal
DNA.[1–7] The viral enzyme first catalyzes the enzymatic removal of two ter-
minal nucleotides at the 3ꢁ-end of each strand of viral DNA (3ꢁ-processing)
leaving recessed ends that terminate with xxCA-OH (Figure 1). In the next
steps (strand transfer, integration) nucleophilic attack of the terminal 3ꢁ-
OH of the tailored HIV DNA on a specific internucleotide phosphodiester
In honor and celebration of the life and career of Dr. John A. Montgomery.
Received 21 January 2005; accepted 10 March 2005.
The project described was supported by Grant Number RO1 AI43181 (to V.N.) from the National
Institutes of Health. Its contents are solely the responsibility of the authors and do not necessarily
represent the official views of the NIH. V. N. thanks the Georgia Research Alliance for an award
toward the purchase of the 500 MHz NMR spectrometer used in this project. We thank Dr. N. Neamati
for the anti-HIV integrase data. The HRMS data were determined at the Nebraska Center for Mass
Spectrometry.
Address correspondence to Vasu Nair, Department of Pharmaceutical and Biomedical Sciences,
University of Georgia, Athens, GA 30602. E-mail: vnair@rx.uga.edu
1449

1450
G. Chi and V. Nair
FIGURE 1 Processing of viral DNA prior to integration into host DNA.
functionality results in cleavage of host DNA and this is followed by integra-
tion of the tailored HIV DNA into host DNA.[1–3] The integration process
is essential for the replication of HIV and there is apparently no functional
equivalent of HIV integrase in human cells.
Some small oligonucleotides of natural origin are capable of interfering
with the integration process by competing with viral DNA for binding to HIV
integrase.[8] Protein-nucleotide interactions appear to be of importance in
other steps of the replication cycle of HIV such as the recognition and bind-
ing of Tat protein to HIV-1 TAR RNA.[9] However, small oligonucleotides of
natural origin are rapidly cleaved by cellular nuclease activity. In addition,
increasing nuclease resistance by chemical alteration of the internucleotide
phosphate bond results in decreased integrase activity.[8] A nonnatural din-
ucleotide with a conformationally unusual internucleotide phosphodiester
bond that joins a D-deoxynucleoside and an L-related isodeoxynucleoside
(pIsodApdC, Figure 2), previously synthesized by us,[10] exhibits resistance
to mammalian 3ꢁ- and 5ꢁ-exonucleases.[11] This compound is an inhibitor of
wild-type HIV-1 integrase, inhibiting both the 3ꢁ-processing and strand trans-
fer steps.[10] We report here some new results that suggest that changing the
FIGURE 2 Structure of pIsodApdC.

Dinucleotides of Anti-HIV Integrase Interest
1451
FIGURE 3 Structures of title nonnatural dinucleotides.
position of the surrogate nucleoside component of the dinucleotide (as in
compound 2b, Figure 3) can dramatically change the mode of inhibitory
activity from both key steps of integrase action to just the strand transfer
step. This article will describe the synthesis and anti-HIV integrase activity
of these compounds (Figure 3).
RESULTS AND DISCUSSION
The preparation of dinucleotides utilized protected isodeoxy- or isodi-
deoxy- nucleosides as starting materials. Thus, 6-N-benzoylisodeoxyadenosine
5[12] was 5ꢁ-protected using dimethoxytrityl chloride in pyridine and benzoy-
lated with benzoyl chloride to give intermediate 6 (Scheme 1). Addition of
concentrated ammonium hydroxide selectively removed one 6-N-benzoyl
SCHEME 1 Synthesis of protected isodeoxyadenosine 8.

1452
G. Chi and V. Nair
group in the tribenzoyl intermediate 6 but the benzoate group at the 3ꢁ-
position was not affected. Detritylation of the resulting compound 7 gave in-
termediate 8 (73% yield from 5). 6-N, 3ꢁ-O-dibenzoyl-2ꢁ-deoxyadenosine[13]
was prepared by a similar method from natural 2ꢁ-deoxyadenosine in 40%
yield.
Although 6-N-benzoyl-isodideoxyadenosine 15 (Scheme 2) can be syn-
thesized by deoxygenation and detritylation reactions from 6-N-benzoyl-5ꢁ-
O-DMTr-isodeoxyadenosine, synthesis of the latter from isodeoxyadenosine
was difficult on a gram scale because of the difficulty associated with pu-
rifying isodeoxyadenosine due to its relatively high polarity. An alternative
procedure was through the cyclic sulfate 9. Treatment of 9 with adenine and
DBU gave 10 which, when treated with HCl in methanol, removed both the
sulfate and silyl groups simultaneously to give isodeoxyadenosine.[14] Selec-
tive hydrolysis of the sulfate group was desirable as the protecting group at
the 5ꢁ-position was required for the next step. Maintaining silyl protection
at the 5ꢁ-position also simplified purification at this stage. Thus, after the
cyclic sulfate 9 and adenine were heated in the presence of DBU in anhy-
drous CH3CN for 2 h, the solvent was evaporated. The residue, in THF and
MeOH, was treated with 2 equivalents of concentrated sulfuric acid in THF
with 2 equivalents of water for 1.5 h.15 Under these conditions, the reaction
proceeded smoothly and the sulfate group was hydrolyzed selectively with-
out cleavage of the silyl protecting group. Compound 11 was easily purified
(64% yield from 9) and was converted to 12 (88% yield) by the conven-
tional method.[16] Compound 12 was deoxygenated[17,18] at the 3ꢁ-position
SCHEME 2 Synthesis of isodideoxyadenosine 15.

Dinucleotides of Anti-HIV Integrase Interest
1453
by conversion of the 3ꢁ-hydroxyl group to its imidazole thiocarbonyl ester
(compound 13) which was treated with tributyltin hydride and AIBN in re-
fluxing toluene to give 14 in 63% yield. Desilylation with fluoride ions gave
intermediate 15 (77% yield).
Isodeoxycytidine 19 (Scheme 3), another key intermediate, cannot
be synthesized from the direct reaction of the sulfate 9 and cytosine,
because O-alkylation and not N-alkylation of cytosine is the predominant
reaction. However, it was synthesized from isodeoxyuridine 16 as previously
described.[19] Thus, the dibenzoyl derivative 17 of isodeoxyuridine was con-
verted to its corresponding 4-O-triisopropylbenzenesulfonyl derivative 18.
Ammonolysis of this intermediate and subsequent deprotection of the ben-
zoyl group with methanolic ammonia afforded isodeoxycytidine 19, which
was fully characterized through its 4-N-benzoyl derivative 20 (76% yield
from 16). Compound 20 can be tailored for coupling by its conversion to
21 in three steps (5ꢁ-O-tritylation, benzoylation and detritylation, 73% yield).
The dinucleotides were synthesized by the phosphoramidite method
(Scheme 4).[20] Thus, for example, the free 5ꢁ-hydroxyl group of isonucle-
oside 21 was condensed with the reagent, 2-cyanoethyl tetraisopropylphos-
phorodiamidite, in the presence of 1H-tetrazole to give the intermediate
22 which was directly coupled with nucleoside 23.[12] Subsequent oxidation
with iodine and detritylation provided the phosphotriester 3a (62% yield
from 21). 5ꢁ-Phosphorylation of 3a was performed using bis(2-cyanoethyl)
N, N-diisopropyl-phosphoramidite and 1-H-tetrazole. Compound 4a was ob-
tained in 85% yield after oxidation with iodine. The other protected din-
ucleotides, 3b-g and 4b-g, were synthesized using a similar approach as for
3a and 4a (Figure 4). For example, coupling isonucleoside 8 or 15 with 6-
N-benzoyl-5ꢁ-O-DMTr-deoxyadenosine afforded 3c or 3d, respectively. Com-
pound 4h was synthesized from 3g in 63% yield (Scheme 5).
SCHEME 3 Synthesis of protected isodeoxycytidine 21.

1454
G. Chi and V. Nair
SCHEME 4 Synthetic route to nonnatural dinucleotide 2a.
The protected dinucleotides, 3a-g and 4a-h (Scheme 4 and Figure 4),
were deprotected using concentrated ammonium hydroxide at room tem-
perature for 24 h. The benzoyl group and the 2-cyanoethyl group were si-
multaneously removed. Purification was performed by HPLC using a C-18
column with elution involving MeOH and 10 mM aqueous AcOH. The
residual acetic acid was removed completely by coevaporation several times
with water. Lyophilization produced the target compounds as white spongy
solids. The yields of the target compounds 1 and 2 (Figure 3) were in the
range of 58–89% for the deprotection step. The compounds were character-
ized by their 1H, 13C and 31P NMR spectra, HRMS data, single-crystal X-ray
crystallography[21] and quantitative UV spectral data.

Dinucleotides of Anti-HIV Integrase Interest
1455
FIGURE 4 Structures of fully protected nonnatural dinucleotides.
Integrase inhibition assays were conducted with purified recombinant
HIV-1 integrase (wild type) using a 21-mer oligonucleotide substrate.[22]
The data (Table 1) clearly showed that compounds 2b-d have strand transfer
inhibitory activity against wild-type HIV-1 integrase but do not exhibit
inhibition of the 3ꢁ-processing step. This is in sharp contrast to compound
pIsodApdC (Figure 2, L-related, D-stereochemistry) which showed strong
inhibition of both key steps of the integrase mechanism of action.[10,23]
The major structural difference between dinucleotide, pIsodApdC, and
TABLE 1 Anti-HIV-1 Integrase (Wild-type) Inhibition Data for
Dinucleotides[22]
3ꢀ-Processing
IC50
Strand transfer
Compounds
,
M
I
,
M
C
50
pIsodApdC (Figure 2)[10]
pIsodApd5MeC[10]
pIsodApIsodC (2a)
pdApIsodC (2b)
pdApIsodA (2c)
pdApIsoddA (2d)
pIsodApdA (2e)
pIsodApU (2f)
19
60
25
50
1000
65
1000
1000
1000
1000
1000
1000
1000
405
41
114
1000
1000
1000
58
pIsodApC (2g)
pdCpIsodT (25)a
pdCpIsodU (26)a
164
43
aSynthesized as described for compounds of the series 1 and 2
(see experimental for data).
Preliminary data on a few of the compounds were reported in the
communication cited in Chi et al.[23]

1456
G. Chi and V. Nair
SCHEME 5 Synthetic route to nonnatural dinucleotide 2h.
its counterpart 2b (or the related compound 2c) is the position and
accompanying stereochemistry of the surrogate isonucleoside component.
The inhibition of integrase by pIsodApdC (Figure 2) is likely the result of
base recognition and binding by the viral enzyme. Thus, it is remarkable that
this apparently small structural and accompanying stereochemical change
in the counterpart of the compound of Figure 3 (i.e., compounds 2b, 2c) can
produce such a major impact on the mode of inhibition of integrase. Related
results were also observed with pdCpIsodT and pdCpIsodU (Table 1).
The only other reported selective inhibitor of strand transfer is a class of
diketo containing compounds,[24–26] and, to the best of our knowledge,
the compounds described here represent the second examples. Also, in
comparing integrase activities of 2g (pIsodApC) with pIsodApdC (Figure 2),
it should be noted that the presence of 2ꢁ-OH in the cytidine moiety
of 2g resulted in complete loss of the activity. The other counterpart
of the anti-HIV integrase active compound, pIsodApdC (Figure 2), one
with two L-related isonucleoside components, pIsodApIsodC, 2a, was also
not an inhibitor. Finally, the internucleotide phosphodiester linkage of all
dinucleotides with isonucleoside components were resistant to cleavage by
mammalian 3ꢁ- and 5ꢁ-exonucleases.[11]

Dinucleotides of Anti-HIV Integrase Interest
1457
EXPERIMENTAL SECTION
General
1H, 13C, and 31P NMR spectra were recorded on Varian Mercury Plus
400 MHz or Varian Inova 500 MHz NMR spectrometers. High-resolution ESI
or FAB mass spectral data were obtained through the Nebraska Center for
Mass Spectrometry. UV spectra were recorded on a Varian Cary 3 UV-visible
spectrometer. Column chromatographic separations were carried out using
230–400 mesh silica gel. HPLC separations were performed on a Beckman
Gold HPLC using a Waters C18 column (300 × 30 mm). The solvent system
was methanol and 10 mM aqueous HOAc with a flow rate of 5 mL/min
(linear gradient from 0 to 8–25% methanol, depending on the polarity of
the compound and then 8–25% methanol).
6-N, 3 -O-Dibenzoyl-1 -deoxy-2 -isoadenosine (8). A suspension of 6-
N-benzoyl-1ꢁ-deoxy-2ꢁ-isoadenosine 5[12] (2.13 g, 6 mmol) in anhydrous
pyridine (60 mL) was treated with DMTrCl (4.07 g, 12 mmol). After 2 h,
BzCl (2.79 mL, 24 mmol) was added gradually under ice-bath temperatures.
The mixture was stirred overnight at room temperature, cooled in an
ice bath, and then treated with water (5 mL). After 5 min, concentrated
ammonium hydroxide (10 mL) was added (the concentration of NH4OH
in the mixture was about 2 M). After stirring at rt for 30 min, the pyridine
was evaporated under vacuum and co-evaporated with toluene (2 × 40 mL).
The residue was dissolved in CH2Cl2 (200 mL), washed with brine (80
mL) and saturated aqueous NaHCO3 (80 mL). The methylene chloride
layer was dried, filtered, and concentrated. The residue in CH2Cl2 (10
mL) was treated with 3% CF3COOH in CH2Cl2 (60 mL) under ice-bath
temperatures and then stirred at room temperature for 30 min. Additional
CH2Cl2 (100 mL) was added and the solution was washed with saturated
aqueous NaHCO3 (60 mL × 2). The methylene chloride layer was dried,
filtered, concentrated and purified on a silica gel column (CH2Cl2:CH3OH,
30:1). The product (2.01 g) was obtained as a white solid (yield 73.0%).
1HNMR (DMSO-d6): 11.20 (s, 1H), 8.73 (s, 1H), 8.61 (s, 1H), 8.02 (m, 4H),
7.53–7.71 (m, 6H), 5.64 (dd, 1H, J = 5.0, 3.0), 5.46 (m, 1H), 5.17 (t, 1H, J =
5.5, OH), 4.41 (dd, 1H, J = 10.5, 4.0), 4.34 (dd, 1H, J = 10.5, 6.0), 4.15 (m,
1H), 3.80 (m, 2H). 13CNMR (DMSO-d6): 166.1, 165.7, 152.7, 151.9, 150.7,
143.6, 134.3, 133.9, 132.9, 130.0, 129.4, 129.3, 129.0, 125.8, 84.9, 79.6, 70.9,
60.8, 60.7. FAB-HRMS: [M+H]+ calcd. for C24H22N5O5 460.1621, found
460.1606.
5 -O-(t-Butyldiphenylsilyl)-1 -deoxy-2 -isoadenosine (11). To a suspen-
sion of adenine (1.35 g, 10 mmol) in anhydrous CH3CN (100 mL), DBU
(1.60 g, 10.5 mmol) was added and the suspension was stirred at room tem-

1458
G. Chi and V. Nair
perature for 0.5 h. A solution of cyclic sulfate 9 (4.35 g, 10 mmol) in CH3CN
(100 mL) was added and the reaction mixture was then heated at 75◦C for
2 h. The solvent was then evaporated and the residue in THF (150 mL) and
CH3OH (10 mL) was treated with sulfuric acid solution in THF (20 mL,
1 mmol H2SO4/1 mmol H2O in 1 mL THF) at 0◦C and the reaction mix-
ture was stirred at room temperature for 1.5 h. Triethylamine (6.07 g, 60
mmol) was added to neutralize the acid and the solvent was removed and
the residue was purified on a silica gel column (CH2Cl2:CH3OH, 25:1) to
1
give 11 (3.12 g, 63.7%). HNMR (CDCl3): 8.20 (s, 1H), 7.80 (s, 1H), 7.65
(m, 4H), 7.32–7.41 (m, 6H), 6.40 (s, 2H, NH2), 4.91 (m, 1H), 4.66 (dd, 1H,
J = 5.5, 5.0), 4.45 (dd, 1H, J = 9.5, 6.5), 4.31 (dd, 1H, J = 9.5, 6.0), 4.05
(m, 1H), 3.93 (dd, 1H, J = 11.5, 3.5), 3.88 (dd, 1H, J = 11.5, 4.5), 1.01
(s, 9H). 13CNMR (CDCl3): 155.9, 152.7, 149.9, 138.7, 135.8, 133.3, 130.0,
127.9, 119.6, 85.4, 77.0, 69.9, 63.9, 63.3, 27.0, 19.5. ESI-MS: [M+H]+ 490.
6-N-Benzoyl-5 -O-(t-butyldiphenylsilyl)-1 -deoxy-2 -isoadenosine (12)
was synthesized in 87.5% yield from 11 by known methods.16 1HNMR
(CDCl3): 9.21 (br, 1H), 8.67 (s, 1H), 8.05 (s, 1H), 7.98 (m, 2H), 7.32–7.67
(m, 13H), 5.37 (br, 1H, OH), 5.03 (m, 1H), 4.80 (t, 1H, J = 6.0), 4.43
(dd, 1H, J = 9.5, 6.5), 4.30 (dd, 1H, J = 9.5, 6.0), 4.04 (m, 1H), 3.96 (dd,
1H, J = 11.0, 3.0), 3.90 (dd, 1H, J = 11.0, 4.0), 1.02 (s, 9H). 13CNMR
(CDCl3): 165.0, 152.5, 151.9, 149.6, 141.5, 135.7, 133.7, 133.3, 133.2, 133.1,
130.1, 130.0, 129.1, 128.1, 128.0, 127.9, 122.6, 85.1, 76.8, 70.0, 63.8, 63.2,
27.1, 19.5. ESI-MS: [M+H]+ 594.
6-N-Benzoyl-1 , 3 -Dideoxy-2 -isoadenosine (15). A solution of 6-N-
benzoyl-5ꢁ-O-tert-butyl-diphenylsilyl-1ꢁ-deoxy-2ꢁ-isoadenosine 12 (1.78 g, 3.0
mmol) and 1,1ꢁ-thiocarbonyl-diimidazole (802 mg, 4.5 mmol) in dry 1,2-di-
chloroethane (20 mL) was stirred under reflux for 4h. The solvent was evap-
orated and the residue was purified on a silica gel column (CHCl3:CH3OH,
50:1) to give 1.90 g (2.70 mmol, 90%) of 13. To a refluxing solution of
13 in anhydrous toluene (20 mL), a nitrogen-purged solution of tributyltin
hydride (1.21 mL, 4.5 mmol) and 2, 2ꢁ-azobis(2-methylpropionitrile) (394
mg, 2.4 mmol) in anhydrous toluene (15 mL) was added dropwise over a
period of 15 min. The reaction mixture was stirred at reflux for 2 h and then
the solvent was evaporated under reduced pressure. The resulting residue
was purified on a silica gel column (CHCl3:CH3OH, 50:1) to afford 1.10 g
(1.90 mmol) of 14. Compound 14 was dissolved in THF (15 mL). Acetic
acid (0.22 mL, 3.8 mmol) and TBAF solution in THF (3.8 mL, 3.8 mmol)
were added under ice-bath temperatures. The resulting mixture was stirred
at room temperature for 3 h. The solvent was removed and the residue was
purified on a silica gel column (CHCl3:CH3OH, 40:1) to give 0.50 g of 15
1
as an amorphous solid (total yield from 12 was 49.1%). HNMR (CDCl3):

Dinucleotides of Anti-HIV Integrase Interest
1459
9.57 (br, 1H), 8.76 (s, 1H), 8.50 (s, 1H), 8.00 (d, 2H, J = 7.5), 7.58 (m,
1H), 7.47 (t, 2H, J = 7.5), 5.38 (m, 1H), 4.19 (d, 1H, J = 10.5), 4.11 (m,
1H), 4.03 (dd, 1H, J = 10.5, 5.5), 3.99 (dd, 1H, J = 12.5, 2.0), 3.62 (dd,
1H, J = 12.5, 3.0), 2.65 (m, 1H), 2.30 (m, 1H). 13CNMR (CDCl3): 165.0,
152.4, 151.5, 149.5, 141.7, 138.7, 132.6, 128.7, 127.9, 122.5, 79.8, 73.2, 62.5,
54.9, 33.8. FAB-HRMS: [M+H]+ calcd. For C17H18N5O3P 340.1410, found
340.1401.
1 -Deoxy-2 -isocytidine (19) was prepared from the dibenzoyl deriva-
tive of its uracil counterpart 1ꢁ-deoxy-2ꢁ-isouridine using the literature
method.[14,19]
4-N-Benzoyl-1 -deoxy-2 -isocytidine (20) was synthesized in 86.5% yield
from 1ꢁ-deoxy-2ꢁ-isocytidine by the standard method.[16] 1HNMR (DMSO-
d6): 11.21 (s, 1H), 8.16 (d, 1H, J = 7.0), 7.99 (d, 2H, J = 7.5), 7.49–7.63
(m, 3H), 7.32 (d, 1H, J = 7.0), 5.71 (d, 1H, J = 5.5), 4.90 (m, 2H), 4.17 (m,
1H), 4.07 (dd, 1H, J = 10.0, 6.5), 3.96 (dd, 1H, J = 10.0, 3.5), 3.59–3.65 (m,
2H), 3.53 (m, 1H). 13CNMR (DMSO-d6): 167.7, 163.0, 155.6, 147.7, 133.6,
133.2, 128.94, 128.9, 96.7, 86.8, 76.4, 70.2, 65.3, 60.9. ESI-HRMS: [M+H]+
calcd. for C16H18N3O5 332.1246, found 332.1260.
4-N, 3 -O-Dibenzoyl-1 -deoxy-2 -isocytidine (21) was synthesized in
73.0% yield from 20 by a similar method to that for 8, but without the addi-
tion of concentrated ammonia solution. 1HNMR (DMSO-d6): 11.26 (s, 1H),
8.24 (d, 1H, J = 7.5), 8.00 (m, 4H), 7.49–7.71 (m, 6H), 7.36 (d, 1H, J =
7.5), 5.47 (dd, 1H, J = 5.5, 3.5), 5.21 (m, 1H), 5.09 (t, 1H, J = 5.5), 4.22
(m, 2H), 4.05 (m, 1H), 3.73 (m, 2H). 13CNMR (DMSO-d6): 167.8, 165.7,
163.4, 155.4, 148.2, 134.3, 133.6, 133.2, 129.9, 129.5, 129.3, 128.9, 96.8, 85.1,
79.4, 70.2, 63.9, 60.7. ESI-HRMS: [M+H]+ calcd. for C23H22N3O6 436.1509,
found 436.1511.
6-N-Benzoyl-P-(2-cyanoethyl)-1 -deoxy-2 -isoadenylyl-(3 →5 )-4-N, 3 -
O-Dibenzoyl-1 -deoxy-2 -isocytidine (3a). To a suspension of 21 (261 mg,
0.60 mmol) and 1H-tetrazole (63 mg, 0.90 mmol) in dry CH2Cl2 (5 mL),
2-cyanoethyl N, N, Nꢁ,Nꢁ-tetraisopropylphosphoro-diamidite (271 mg, 0.90
mmol) was added. After stirring for 2 h, 1H-tetrazole (63 mg, 0.90 mmol)
and 23[12] (513 mg, 0.78 mmol) were added. The reaction mixture was
stirred for 4 h and then iodine (460 mg, 1.81 mmol) in THF-H2O-pyridine
(66:33:1, 4.6 mL) was added. After 10 min, the mixture was poured into
CH2Cl2 (100 mL) and washed with 0.2 M sodium sulfite (30 mL × 2). The
organic layer was dried, filtered, and concentrated. The residue in 5 mL of
dichloromethane was stirred with 2% dichloroacetic acid in CH2Cl2 (20 mL)
for 20 min. The reaction mixture was poured into CH2Cl2 (100 mL) and

1460
G. Chi and V. Nair
washed with saturated aqueous sodium bicarbonate (50 mL). The organic
layer was dried, filtered, and concentrated. The residue was purified over
silica gel column (CH2Cl2:CH3OH, 25:1) to give 3a (340 mg, 62.5%) as an
1
amorphous solid. H NMR (CDCl3): 9.30 (br, 2H), 8.70 and 8.68 (s and s,
1H), 8.45 and 8.44 (s and s, 1H), 7.77–8.02 (m, 7H), 7.38–7.60 (m, 10H),
5.32–5.58 (m, 3H), 5.14 (m, 1H), 3.98–4.58 (m, 12H), 2.76 (m, 2H). 31P
NMR (CDCl3): −1.57, −2.28. ESI-HRMS: [M+H]+ calcd. for C43H41N9O12P
906.2612, found 906.2627.
Compounds 3b-g (data given below) were synthesized using a similar
procedure to that described above for 3a.
6-N-Benzoyl-P-(2-cyanoethyl)-2 -deoxyadenylyl-(3 →5 )-4-N, 3 -O-Di-
benzoyl-1 -deoxy-2 -isocytidine (3b) (68.0% yield). 1HNMR (CDCl3): 9.35
and 9.21 (br and br, 2H), 8.69 and 8.57 (s and s, 1H), 8.32 and 8.30 (s and
s, 1H), 7.85–8.02 (m, 7H), 7.39–7.62 (m, 10H), 6.49 (m, 1H), 5.95 (m, 1H,
OH), 5.61 (m, 1H), 5.26–5.40 (m, 2H), 4.21–4.70 (m, 8H), 3.75–3.99 (m,
2H), 3.10 (m, 1H), 2.60–2.91 (m, 3H). 31PNMR (CDCl3): −1.64, −2.28. ESI-
HRMS: [M+Na]+ calcd. for C43H40N9NaO12P 928.2432, found 928.2442.
6-N-Benzoyl-P-(2-cyanoethyl)-2 -deoxyadenylyl-(3 →5 )-6-N, 3 -O-Di-
benzoyl-1 -deoxy-2 -isoadenosine (3c) (48.7% yield). 1HNMR (CDCl3): 9.03
(br, 2H), 8.80, 8.77, 8.74, and 8.71 (s, s, s and s, 2H), 8.43 and 8.41 (s and s,
1H), 8.21 and 8.16 (s and s, 1H), 7.96–8.07 (m, 6H), 7.42–7.66 (m, 9H), 6.51
and 6.26 (m and m, 1H), 5.68 and 5.64 (m and m, 1H), 5.51–5.55 (m, 1H),
5.37 and 5.30 (m and m, 1H), 4.25–4.70 (m, 8H), 3.80–4.00 (m, 2H), 3.07–
3.23 (m, 1H), 2.59–2.94 (m, 3H). 31PNMR (CDCl3): −2.18, −2.39. FAB-
HRMS: [M+H]+ calcd. for C44H41N11O11P 930.2725, found 930.2690.
6-N-Benzoyl-P-(2-cyanoethyl)-2 -deoxyadenylyl-(3 →5 )-6-N-benzoyl-1 ,
3 -dideoxy-2 -isoadenosine (3d) (58.0% yield). 1HNMR (CDCl3): 8.79,
8.77, 8.76 and 8.73 (s, s, s and s, 2H), 8.42, 8.38, 8.25, and 8.19 (s, s, s
and s, 2H), 8.03 (m, 4H), 7.47-7.65 (m, 6H), 6.52 and 6.40 (m and m, 1H),
5.45 (m, 1H), 5.39 and 5.36 (t and t, 1H, J = 5.5 and 5.5), 4.44–4.55 (m,
2H), 4.27–4.38 (m, 5H), 4.17 (m, 1H), 3.98 (m, 1H), 3.88 (m, 1H), 3.22 and
3.15 (m and m, 1H), 2.64–2.87 (m, 4H), 2.23 (m, 1H). 31PNMR (CDCl3):
−1.29, −1.50. FAB-HRMS: [M+H]+ calcd. For C37H37N11O9P 810.2513,
found 810.2505.
6-N-Benzoyl-P-(2-cyanoethyl)-1 -deoxy-2 -isoadenylyl-(3 →5 )-6-N, 3 -O-
Dibenzoyl-2 -deoxyadenosine (3e) (69.9% yield). 1HNMR (CDCl3): 9.38
(br, 2H), 8.73, 8.69, 8.63 and 8.61 (s, s, s and s, 2H), 8.39, 8.38, 8.37 and
8.34 (s, s, s and s, 2H), 8.00–8.03 (m, 6H), 7.44–7.62 (m, 9H), 6.55 and

Dinucleotides of Anti-HIV Integrase Interest
1461
6.47 (m and m, 1H), 5.72 and 5.68 (m and m, 1H), 5.35 (m, 1H), 5.18
and 5.09 (m and m, 1H), 4.22–4.51 (m, 7H), 4.03 (m, 1H), 3.80–3.91 (m,
2H), 3.08–3.15 (m, 1H), 2.71–2.81 (m, 3H). 31PNMR (CDCl3): −2.57. FAB-
HRMS: [M+H]+ calcd. for C44H41N11O11P 930.2725, found 930.2716.
6-N-Benzoyl-P-(2-cyanoethyl)-1 -deoxy-2 -isoadenylyl-(3 →5 )-3-N,
2 -O, 3 -O-Tribenzoyl Uridine (3f) (68.1% yield). 1HNMR (CDCl3): 9.15
(br, 1H), 8.78 and 8.75 (s and s, 1H), 8.47 and 8.42 (s and s, 1H), 7.88–8.00
(m, 8H), 7.26–7.81 (m, 13H), 6.05–6.10 (m, 1H), 5.94 (m, 1H), 5.77 (m,
1H), 5.61 (m, 1H), 5.51 (m, 1H), 5.29 (m, 1H), 4.46–4.55 (m, 2H), 4.32–
4.40 (m, 4H), 4.25 (m, 1H), 4.15 (m, 1H), 3.97–4.06 (m, 2H), 2.79 (t, 2H,
J = 6.0). 31PNMR (CDCl3): −1.23, −2.16. FAB-HRMS: [M+H]+ calcd. for
C50H44N8O15P 1027.2664, found 1027.2633.
6-N-Benzoyl-P-(2-cyanoethyl)-1 -deoxy-2 -isoadenylyl(3 →5 )-4 -N,
2 -O, 3 -O-Tribenzoyl Cytidine (3g) (66.5% yield). 1HNMR (CDCl3): 9.22
(br, 2H), 8,72, 8.68, 8.66, and 8.50 (s, s, s and s, 2H), 7.73–7.98 (m, 9H),
7.28–7.58 (m, 13H), 5.77–6.04 (m, 3H), 5.50 (m, 1H), 5.42 and 5.30 (m
and m, 1H), 4.28–4.67 (m, 7H), 4.17 (m, 1H), 3.96–4.09 (m, 2H), 2.73–
2.88 (m, 2H). 31PNMR (CDCl3): −1.67, −2.64. FAB-HRMS: [M+H]+ calcd.
for C50H45N9O14P 1026.2824, found 1026.2809.
6-N-Benzoyl-5 -O-[di(2-cyanoethoxy)phosphinyl]-P-(2-cyanoethyl)-1 -
deoxy-2 -isoadenylyl-(3 →5 )-4-N, 3 -O-Dibenzoyl-1 -deoxy-2 -isocytidine
(4a). To a solution of 3a (272 mg, 0.30 mmol) and 1H-tetrazole(42 mg,
0.60 mmol) in CH2Cl2 (5 mL), di(2-cyanolethyl) N, N-diisopropylphosphor-
amidite (163 mg, 0.60 mmol) was added. The resulting mixture was stirred
at room temperature for 4 h. Iodine (300 mg, 1.18 mmol) in THF-H2O-
pyridine (66:33:1, 3.0 mL) was added. After 10 min, the mixture was poured
into CH2Cl2 (100 mL) and washed with 0.2 M sodium sulfite (30 mL × 2).
The organic layer was dried, filtered and concentrated. The residue was
purified on a silica gel column (CH2Cl2:CH3OH, 20:1) to give 4a (279 mg,
1
85.1%) as an amorphous solid. HNMR (CDCl3): 9.11 (br, 2H), 8.74 and
8.72 (s and s, 1H), 8.36 and 8.32 (s and s, 1H), 7.85–8.03 (m, 7H), 7.39–7.63
(m, 10H), 5.43–5.60 (m, 2H), 5.16–5.31 (m, 2H), 4.07–4.65 (m, 16H), 2.67–
2.85 (m, 6H). 31PNMR (CDCl3): −0.70, −1.75, −1.85, −2.27. ESI-HRMS:
[M+H]+ calcd. for C49H48N11O15P2 1092.2807, found 1092.2798.
Compounds 4b-g were synthesized using a similar procedure to that
described for 4a.
6-N-Benzoyl-5 -O-[di(2-cyanoethoxy)phosphinyl]-P-(2-cyanoethyl)-2 -
deoxyadenylyl-(3 →5 )-4-N, 3 -O-Dibenzoyl-1 -deoxy-2 -isocytidine (4b)
(90.3% yield). 1HNMR (CDCl3): 9.00 (br, 2H), 8.76 and 8.72 (s and s,

1462
G. Chi and V. Nair
1H), 8.30 and 8.24 (s and s, 1H), 7.88–8.06 (m, 7H), 7.45–7.64 (m, 10H),
6.57 (m, 1H), 5.65 (m, 1H), 5.21–5.46 (m, 2H), 4.16–4.70 (m, 14H), 3.27
(m, 1H), 2.70–2.90 (m, 7H). 31PNMR (CDCl3): −0.89, −1.87, −1.92, −2.03.
ESI-HRMS: [M+Na]+ calcd. for C49H47N11NaO15P2 1114.2626, found
1114.2605.
6-N-Benzoyl-5 -O-[di(2-cyanoethoxy)phosphinyl]-P-(2-cyanoethyl)-2 -
deoxyadenylyl-(3 →5 )-6-N, 3 -O-Dibenzoyl-1 -deoxy-2 -isoadenosine (4c)
(93.1% yield). 1HNMR (CDCl3): 9.27 and 9.04 (br, 2H), 8.78, 8.76, 8.74,
and 8.69 (s, s, s and s, 2H), 8.43 and 8.40 (s and s, 1H), 8.27 and 8.22 (s
and s, 1H), 7.97–8.07 (m, 6H), 7.45–7.65 (m, 9H), 6.60 and 6.45 (m and m,
1H), 5.68 (m, 1H), 5.54 (m, 1H), 5.42 and 5.35 (m and m, 1H), 4.22–4.71
(m, 14H), 3.14–3.26 (m, 1H), 2.70–2.92 (m, 7H). 31PNMR (CDCl3): −2.13,
−2.39, −2.45, −2.50. FAB-HRMS: [M+H]+ calcd. for C50H48N13O14P2
1116.2919, found 1116.2865.
6-N-Benzoyl-5 -O-[di(2-cyanoethoxy)phosphinyl]-P-(2-cyanoethyl)-2 -
deoxyadenylyl-(3 →5 )-6-N-benzoyl-1 , 3 -Dideoxy-2 -isoadenosine (4d)
(60.3% yield). 1HNMR (CDCl3): 8.79, 8.77, and 8.73 (s, s and s, 2H),
8.45, 8.44, 8.31, and 8.27 (s, s, s and s, 2H), 8.03 (m, 4H), 7.49–7.63 (m,
6H), 6.60 and 6.50 (t and t, 1H, J = 6.5), 5.44 (s, br, 2H), 4.15–4.58 (m,
14H), 3.25 and 3.18 (m and m, 1H), 2.78–2.90 (m, 8H), 2.24 (m, 1H).
31PNMR (CDCl3): −1.32, −1.35, −1.57. FAB-HRMS: [M+H]+ calcd. For
C43H44N13O12P2 996.2708, found 996.2666.
6-N-Benzoyl-5 -O-[di(2-cyanoethoxy)phosphinyl]-P-(2-cyanoethyl)-1 -
deoxy-2 -isoadenylyl-(3 →5 )-6-N, 3 -O-Dibenzoyl-2 -deoxyadenosine (4e)
(83.6% yield). 1HNMR (CDCl3): 9.20 (br, 2H), 8.79, 8.76, 8.74, and 8.68 (s,
s, s and s, 2H), 8.43, 8.40, 8.33, and 8.24 (s, s, s and s, 2H), 7.99–8.07 (m, 6H),
7.45–7.64 (m, 9H), 6.61 and 6.54 (m and m, 1H), 5.69–5.76 (m, 1H), 5.45
(m, 1H), 5.19–5.26 (m, 1H), 4.29–4.51 (m, 14H), 3.06–3.18 (m, 1H), 2.67–
2.85 (m, 7H). 31PNMR (CDCl3): −2.31, −2.37, −2.41, −2.56. FAB-HRMS:
[M+H]+ calcd. for C50H48N13O14P2 1116.2919, found 1116.2895.
6-N-Benzoyl-5 -O-[di(2-cyanoethoxy)phosphinyl]-P-(2-cyanoethyl)-1 -
deoxy-2 -isoadenylyl-(3 →5 )-3-N, 2 -O, 3 -O-Tribenzoyluridine (4f) (84.9%
yield). 1HNMR (CDCl3): 9.21 (br, 1H), 8.82 and 8.79 (s and s, 1H), 8.45
and 8.40 (s and s, 1H), 7.84–8.02 (m, 8H), 7.27–7.73 (m, 13H), 6.24 and 6.17
(d and d, 1H, J = 5.6 and 6.0), 5.99 and 5.94 (d and d, 1H, J = 8.4 and 8.8),
5.82 (m, 1H), 5.53–5.67 (m, 2H), 5.29 (m, 1H), 4.28–4.59 (m, 14H), 2.75–
2.85 (m, 6H). 31PNMR (CDCl3): −1.02, −1.15, −1.94. FAB-HRMS: [M+H]+
calcd. for C56H51N10O18P2 1213.2858, found 1213.2812.

Dinucleotides of Anti-HIV Integrase Interest
1463
6-N-Benzoyl-5 -O-[di(2-cyanoethoxy)phosphinyl]-P-(2-cyanoethyl)-1 -
deoxy-2 -isoadenylyl-(3 →5 )-4 -N, 2 -O, 3 -O-Tribenzoylcytidine (4g)
(84.6% yield). 1HNMR (CDCl3): 9.80 (br, 1H), 9.20 (br, 1H), 8.78 and
8.73 (s and s, 1H), 8.32 and 8.27 (s and s, 1H), 7.88–8.10 (m, 9H), 7.31–
7.72 (m, 13H), 6.10 (m, 1H), 5.76–5.92 (m, 2H), 5.49 (m, 1H), 5.33 and
5.12 (m and m, 1H), 4.27–4.73 (m, 14H), 2.75–2.93 (m, 6H). 31PNMR
(CDCl3): −1.38, −1.42, −1.50, −2.71. FAB-HRMS: [M+H]+ calcd. for
C56H52N11O17P2 1212.3018, found 1212.2981.
6-N-Benzoyl-5 -O-[(2-cyanoethoxy)(ethoxy)phosphinyl]-P-(2-cyanoeth-
yl)-1 -deoxy-2 -isoadenylyl-(3 →5 )-4-N, 2 , 3 -Tribenzoylcytidine (4h). To
a solution of 3a (190 mg, 0.185 mmol) and 2-cyanoethyl N, N, Nꢁ, Nꢁ-tetraiso-
propylphosphorodiamidite (112 mg, 0.370 mmol) in CH2Cl2 (8 mL), 1H-
tetrazole solution in acetonitrile (0.83 mL, 0.370 mmol) was added. The
reaction mixture was stirred at room temperature for 2 h. Then ethanol (22
µl, 0.37 mmol) and 1H-tetrazole solution in acetonitrile (0.83 mL, 0.370
mmol) were added. After 3 h, iodine (180 mg, 0.71 mmol) in THF-H2O-
pyridine (66:33:1, 1.8 mL) was added. After 10 min, the mixture was poured
into CH2Cl2 (100 mL), washed with 0.2 M sodium sulfite (30 mL × 2),
dried, filtered, and concentrated. The residue was purified by on a silica gel
column (CHCl3:CH3OH, 30:1) to give 4h (140 mg, 63.7%) as an amorphous
solid. 1HNMR (CDCl3): 10.1 and 9.68 (br and br, 1H), 9.20 (br, 1H), 8.73 (s,
1H), 8.23 and 8.20 (s and s, 1H), 7.28–8.04 (m, 22H), 6.04 and 5.99 (t and
t, 1H, J = 6.5 and 6.5), 5.59–5.80 (m, 2H), 5.45 (m, 1H), 5.11 and 5.05 (s
and s, 1H), 4.32–4.63 (m, 11H), 4.14 (m, 3H), 2.67–2.83 (m, 4H), 1.28 (m,
3H). 31PNMR (CDCl3): −0.68, −1.23, −2.87, −3.12. FAB-HRMS: [M+H]+
calcd. for C55H53N10O17P2 1187.3065, found 1187.3087.
General Procedure for Deprotection Reaction
The protected dinucleotide (100–200 mg) in concentrated ammonium
hydroxide (8 mL) was capped and stirred at room temperature for 24 h.
Then the reaction solution was evaporated to dryness and the residue was
dissolved in water (50 mL) and washed with ether (30 mL). The aqueous
layer was concentrated and purified by HPLC to give the product as a white
spongy solid after lyophilization.
1 -Deoxy-2 -isoadenylyl-(3 →5 )-1 -deoxy-2 -isocytidine (1a) (75.4%
yield). 1HNMR (D2O): 8.13 (s, 1H), 8.02 (s, 1H), 7.22 (d, 1H, J = 7.5),
5.65 (d, 1H, J = 7.5), 5.08 (m, 1H), 4.81 (m, 1H), 4.68 (m, 1H), 4.24 (dd,
1H, J = 10.5, 7.5), 4.10 (dd, 1H, J = 10.5, 5.0), 3.96 (m, 2H), 3.81–3.87
(m, 2H), 3.63–3.77 (m, 4H), 3.47 (s, br, 1H). 13CNMR (D2O): 165.2, 157.4,
155.3, 152.3, 148.8, 142.9, 140.5, 118.5, 96.0, 84.3, 83.7, 78.5, 76.0, 70.0,

1464
G. Chi and V. Nair
69.9, 64.1, 64.0, 61.1, 60.3. 31PNMR (D2O): −0.10. FAB-HRMS: [M+H]+
calcd. For C19H26N8O9P 541.1560, found 541.1552. UV (H2O): λmax 264(ε
19,300).
2 -Deoxyadenylyl-(3 →5 )-1 -deoxy-2 -isocytidine (1b) (83.9% yield).
1HNMR (D2O): 8.11 (s, 1H), 7.96 (s, 1H), 7.64 (d, 1H, J = 7.5), 6.21 (dd,
1H, J = 7.5, 6.5), 5.90 (d, 1H, J = 7.5), 4.74 (m, 2H), 4.26 (dd, 1H, J =
6.0, 3.0), 4.13 (q, 1H, J = 3.5), 4.07 (dd, 1H, J = 11.0, 6.5), 3.97–4.00 (m,
2H), 3.89–3.94 (m, 1H), 3.80 (m, 1H), 3.66 (dd, 1H, J = 12.5, 3.0), 3.61
(dd, 1H, J = 12.5, 4.5), 2.64 (m, 1H), 2.52 (m, 1H). 13CNMR (D2O): 160.9,
154.0, 151.6, 150.4, 148.1, 145.5, 141.1, 118.8, 95.5, 86.7, 85.0, 84.1, 76.0,
75.8, 69.2, 65.1, 64.1, 61.6, 38.4. 31PNMR (D2O): 0.17. ESI-HRMS: [M+H]+
calcd. For C19H26N8O9P 541.1560, found 541.1575. UV (H2O): λmax 262(ε
19,000).
2 -Deoxyadenylyl-(3 →5 )-1 -deoxy-2 -isoadenosine (1c) (85.6% yield).
1HNMR (D2O): 8.11 (s, 1H), 8.09 (s, 1H), 7.95 (s, 1H), 7.90 (s, 1H), 6.10 (t,
1H, J = 6.5), 4.86 (m, 1H), 4.70 (m, 1H), 4.43 (dd, 1H, J = 10.5, 4.0), 4.20
(m, 2H), 4.04 (m, 1H), 3.95–4.02 (m, 2H), 3.91 (m, 1H), 3.62 (dd, 1H, J =
13.0, 3.0), 3.55 (dd, 1H, J = 13.0, 4.5), 2.52 (m, 1H), 2.43 (m, 1H). 13CNMR
(D2O): 152.8, 152.1, 148.6, 148.4, 148.0, 147.8, 141.5 (two carbons), 118.7,
117.9, 86.3, 84.6, 83.8, 76.1, 75.2, 69.9, 63.9, 62.5, 61.3, 38.1. 31PNMR (D2O):
−0.41. FAB-HRMS: [M+H]+ calcd. for C20H26N10O8P 565.1673, found
565.1663. UV (H2O): λmax 259(ε 26,300).
1 -Deoxy-2 -isoadenylyl-(3 →5 )-2 -deoxyadenosine (1e) (89.8% yield).
1HNMR (D2O): 8.09 (s, 1H), 8.07 (s, 1H), 7.99 (s, 1H), 7.87 (s, 1H), 6.09
(t, 1H, J = 6.5), 5.01 (m, 1H), 4.51 (m, 1H), 4.42 (m, 1H), 4.15 (dd, 1H,
J = 11.0, 6.0), 4.05 (dd, 1H, J = 11.0, 3.0), 3.94–3.98 (m, 2H), 3.88–3.92
(m, 2H), 3.81 (dd, 1H, J = 12.5, 2.5), 3.70 (dd, 1H, J = 12.5, 5.0), 2.41 (m,
1H), 2.29 (m, 1H). 13CNMR (D2O): 152.8, 151.8, 149.2, 148.0, 147.8 (two
carbons), 141.5, 140.4, 117.9, 117.6, 85.8, 85.6, 83.6, 79.6, 70.8, 70.4, 65.0,
61.6, 60.2, 39.5. 31PNMR (D2O): −1.43. FAB-HRMS: [M+H]+ calcd. for
C20H26N10O8P 565.1673, found 565.1649. UV (H2O): λmax 259(ε 23,600).
1 -Deoxy-2 -isoadenylyl-(3 →5 )-uridine (1f) (81.8% yield). 1HNMR
(D2O): 8.24 (s, 1H), 8.21 (s, 1H), 7.23 (d, 1H, J = 8.0), 5.49 (d, 1H,
J = 4.0), 5.44 (d, 1H, J = 8.0), 5.22 (m, 1H), 4.57 (m, 1H), 4.23 (dd,
1H, J = 11.0, 6.5), 4.11 (dd, 1H, J = 11.0, 3.5), 3.92–3.99 (m, 4H), 3.82–
3.87 (m, 3H), 3.76 (dd, 1H, J = 12.0, 5.0). 13CNMR (D2O): 165.6, 151.2,
150.5, 148.4, 145.7, 142.6, 140.5, 117.9, 102.2, 88.1, 85.4, 82.3, 79.8, 73.6,
70.6, 69.0, 64.1, 61.9, 59.8. 31PNMR (D2O): −0.32. FAB-HRMS: [M+H]+
calcd. for C19H25N7O11P 558.1350, found 558.1336. UV (H2O): λmax 261(ε
20,300).

Dinucleotides of Anti-HIV Integrase Interest
1465
1 -Deoxy-2 -isoadenylyl-(3 →5 )-cytidine (1g) (89.9% yield). 1HNMR
(D2O): 8.16 (s, 1H), 8.03 (s, 1H), 7.31 (d, 1H, J = 8.0), 5.59 (d, 1H, J =
8.0), 5.44 (d, 1H, J = 3.0), 5.15 (m, 1H), 4.69 (m, 1H), 4.22 (dd, 1H, J =
10.0, 7.0), 4.07 (dd, 1H, J = 10.0, 3.5), 3.83–3.98 (m, 7H), 3.78 (dd, 1H, J =
12.5, 4.5). 13CNMR (D2O): 161.6, 153.5, 151.6, 149.9, 148.5, 141.7, 141.6,
118.4, 95.1, 89.4, 85.2, 81.8, 79.6, 74.3, 70.6, 68.2, 63.5, 61.8, 60.1. 31PNMR
(D2O): −0.42. FAB-HRMS: [M+H]+ calcd. for C19H26N8O10P 557.1510,
found 557.1498. UV (H2O): λmax 263(ε 20,200).
5 -O-Phosphoryl-1 -deoxy-2 -isoadenylyl-(3 →5 )-1 -deoxy-2 -isocyti-
dine (2a) (61.7% yield). 1HNMR (D2O): 8.34 (s, 1H), 8.24 (s, 1H), 7.46 (d,
1H, J = 7.5), 5.98 (d, 1H, J = 7.5), 5.20 (m, 1H), 4.78 (m, 1H), 4.63 (m,
1H, partly hid in water peak), 4.25 (dd, 1H, J = 10.0, 6.5), 4.18 (dd, 1H, J =
10.0, 4.0), 4.14 (dd, 1H, J = 5.5, 2.5), 4.05–4.09 (m, 2H), 4.00 (m, 1H), 3.90
(dd, 1H, J = 11.5, 6.0), 3.78–3.83 (m, 3H), 3.58 (m, 1H). 13CNMR (D2O):
159.2, 150.6, 149.2, 148.7, 146.0, 145.4, 143.0, 118.3, 95.1, 84.3, 83.8, 79.4,
75.9, 70.6, 69.0, 64.8, 64.0, 63.9, 61.9. 31PNMR (D2O): 0.96, −0.33. FAB-
HRMS: [M+H]+ calcd. for C19H27N8O12P2 621.1224, found 621.1234. UV
(H2O): λmax 265(ε 19,700).
5 -O-Phosphoryl-2 -deoxyadenylyl-(3 →5 )-1 -deoxy-2 -isocytidine (2b)
(58.8% yield). 1HNMR (D2O): 8.40 (s, 1H), 8.20 (s, 1H), 7.74 (d, 1H, J =
7.5), 6.37 (t, 1H, J = 6.5), 6.04 (d, 1H, J = 7.5), 4.82 (m, 1H), 4.73 (m,
1H), 4.28 (m, 2H), 3.98–4.09 (m, 3H), 3.89-3.93 (m, 3H), 3.81 (m, 1H),
2.71 (m, 1H), 2.61 (m, 1H). 13CNMR (D2O): 159.2, 150.5, 149.2, 148.3,
146.4, 145.5, 142.4, 118.5, 95.2, 85.5, 84.7, 84.3, 75.98, 75.92, 69.0, 65.1, 64.8,
64.1, 38.8. 31PNMR (D2O): 0.94, −0.030. FAB-HRMS: [M+H]+ calcd. for
C19H27N8O12P2 621.1224, found 621.1217. UV (H2O): λmax 262(ε 19,900).
5 -O-Phosphoryl-2 -deoxyadenylyl-(3 →5 )-1 -deoxy-2 -isoadenosine
(2c) (69.4% yield). 1HNMR (D2O): 8.37 (s, 1H), 8.26 (s, 1H), 8.19 (s, 1H),
8.16 (s, 1H), 6.29 (t, 1H, J = 7.0), 4.98 (m, 1H), 4.80 (s, br, 1H), 4.47 (m,
1H), 4.21–4.28 (m, 3H), 3.90–4.04 (m, 5H), 2.66 (m, 1H), 2.58 (m, 1H).
13CNMR (D2O): 150.2, 150.1, 148.5, 148.0, 145.1, 144.8, 142.8, 142.4, 118.4,
118.1, 85.3, 84.6, 84.0, 76.1, 75.8, 69.8, 64.6, 64.1, 62.8, 38.7. 31PNMR (D2O):
0.065, −0.75. FAB-HRMS: [M+H]+ calcd. for C20H27N10O11P2 645.1336,
found 645.1325. UV (H2O): λmax 259(ε 26,400).
5 -O-Phosphoryl-2 -deoxyadenylyl-(3 →5 )-1 , 3 -Dideoxy-2 -isoadeno-
sine (2d) (72.5% yield). 1HNMR (D2O): 8.39 (s, 1H), 8.34 (s, 1H), 8.19
(s, 1H), 8.16 (s, 1H), 6.30 (t, 1H, J = 6.5), 5.21 (m, 1H), 4.82 (s, br,
1H), 4.27 (s, br, 1H), 4.21 (s, br, 1H), 4.14 (d, 1H, J = 10.5), 4.04 (m,
1H), 3.98 (dd, 1H, J = 10.5, 5.5), 3.86–3.92 (m, 3H), 2.67 (m, 2H), 2.58

1466
G. Chi and V. Nair
(m, 1H), 2.11 (m, 1H). 13CNMR (D2O): 150.4, 150.1, 148.4, 148.2, 145.3,
144.8, 142.9, 142.4, 118.5, 118.1, 85.5, 84.7, 78.3, 75.9, 72.3, 65.9, 64.8,
55.7, 38.9, 33.6. 31PNMR (D2O): 1.00, 0.25. FAB-HRMS: [M+H]+ calcd. For
C20H27N10O10P2 629.1387, found 629.1412. UV (H2O): λmax 259(ε 24,500).
5 -O-Phosphoryl-1 -deoxy-2 -isoadenylyl-(3 →5 )-2 -deoxyadenosine
(2e) (69.2% yield). 1HNMR (D2O): 8.28 (s, 1H), 8.23 (s, 1H), 8.19 (s,
1H), 8.05 (s, 1H), 6.20 (t, 1H, J = 7.0), 5.09 (m, 1H), 4.50 (m, 2H), 3.92–
4.20 (m, 8H), 2.57 (m, 1H), 2.34 (m, 1H). 13CNMR (D2O): 150.5, 149.8,
148.0, 147.8, 146.2, 145.0, 142.6, 141.9, 117.4, 117.1, 86.3, 84.9, 84.2, 79.9,
71.5, 70.9, 65.3, 63.6, 61.6, 39.2. 31PNMR (D2O): 0.49, −1.43. FAB-HRMS:
[M+H]+ calcd. for C20H27N10O11P2 645.1336, found 645.1333. UV (H2O):
λmax 259(ε 23,500).
5 -O-Phosphoryl-1 -deoxy-2 -isoadenylyl-(3 →5 )-uridine (2f) (60.0%
yield). 1HNMR (D2O): 8.28 (s, 1H), 8.23 (s, 1H), 7.26 (d, 1H, J = 8.0),
5.53 (d, 1H, J = 4.4), 5.50 (d, 1H, J = 8.0), 5.24 (m, 1H), 4.24 (dd, 1H,
J = 10.4, 6.4), 4.07–4.16 (m, 4H), 3.84–3.99 (m, 5H), one proton hid in
water peak. 13CNMR (D2O): 151.3, 149.6, 148.4, 144.4, 143.1, 140.6, 117.9,
102.4, 88.2, 83.9, 82.5, 79.7, 73.6, 70.8, 69.1, 64.3, 63.8, 61.8, one carbon not
observable. 31PNMR (D2O): 1.09, −0.59. FAB-HRMS: [M+H]+ calcd. for
C19H26N7O14P2 638.1013, found 638.0983. UV (H2O): λmax 261(ε 21,000).
5 -O-Phosphoryl-1 -deoxy-2 -isoadenylyl-(3 →5 )-cytidine (2g) (68.0%
yield). 1HNMR (D2O): 8.28 (s, 1H), 8.23 (s, 1H), 7.50 (d, 1H, J = 8.0),
5.96 (d, 1H, J = 8.0), 5.49 (d, 1H, J = 4.5), 5.24 (m, 1H), 4.52 (m, 1H), 4.26
(dd, 1H, J = 11.0, 6.0), 3.87–4.20 (m, 9H). 13CNMR (D2O): 159.3, 150.7,
148.6, 148.5, 146.3, 142.5, 117.7, 95.4, 89.1, 84.8, 82.8, 80.4, 74.1, 71.1, 69.0,
64.2, 63.7, 61.7, one carbon not observable. 31PNMR (D2O): 0.86, −0.44.
FAB-HRMS: [M+H]+ calcd. for C19H27N8O13P2 637.1173, found 637.1170.
UV (H2O): λmax 264(ε 19,800).
5 -O-Ethoxyphosphonyl-1 -deoxy-2 -isoadenylyl-(3 →5 )-cytidine (2h)
(66.0% yield). 1HNMR (D2O): 8.27 (s, 1H), 8.24 (s, 1H), 7.56 (d, 1H, J =
7.5), 5.93 (d, 1H, J = 7.5), 5.51 (d, 1H, J = 4.0), 5.24 (m, 1H), 4.52 (m,
1H), 4.26 (dd, 1H, J = 11.0, 6.0), 4.21 (dd, 1H, J = 11.0, 3.0), 3.99–4.16 (m,
6H), 3.88–3.95 (m, 2H), 3.81 (m, 2H), 1.10 (t, 3H, J = 7.0). 13CNMR (D2O):
159.2, 150.4, 148.54, 148.48, 145.9, 142.8, 142.7, 117.8, 95.3, 89.2, 84.7, 82.9,
80.3, 74.1, 71.0, 69.0, 64.2, 64.1, 62.7, 61.8, 15.8. 31PNMR (D2O): 0.95,
−0.52. FAB-HRMS: [M+H]+ calcd. for C21H31N8O13P2 665.1486, found
665.1460. UV (H2O): λmax 264(ε 18,000).

Dinucleotides of Anti-HIV Integrase Interest
1467
5 -O-Phosphoryl-2 -deoxycytidylyl-(3 →5 )-1 -deoxy-2 -isothymidine
(25). 1HNMR (D2O): 7.98 (d, 1H, J = 8.0), 7.37 (s, 1H), 6.07 (m, 2H),
4.80 (m, 1H), 4.69 (m, 1H), 4.26 (m, 1H), 4.24 (dd, 1H, J = 6.5, 4.0),
4.07 (dd, 1H, J = 10.5, 7.0), 3.88–4.02 (m, 5H), 3.79 (m, 1H), 2.48 (m,
1H), 2.19 (m, 1H), 1.71 (s, 3H). 13CNMR (D2O): 166.4, 159.0, 152.2, 148.1,
144.2, 139.2, 111.5, 94.9, 86.6, 85.2, 83.2, 75.7, 75.6, 69.1, 64.6, 64.2, 63.3,
38.8, 11.5. 31PNMR (D2O): 0.58, 0.002. FAB-HRMS: [M+H]+ calcd. for
C19H28N5O14P2 612.1108, found 612.1090. UV (H2O): λmax 274(ε 20,300).
5 -O-Phosphoryl-2 -deoxycytidylyl-(3 →5 )-1 -deoxy-2 -isouridine (26).
1HNMR (D2O): 7.99 (d, 1H, J = 8.0), 7.56 (d, 1H, J = 8.0), 6.10 (m, 2H),
5.71 (d, 1H, J = 8.0), 4.78 (m, 1H), 4.69 (m, 1H), 4.27 (m, 1H), 4.24 (dd,
1H, J = 6.0, 4.0), 4.09 (dd, 1H, J = 11.0, 7.0), 3.87-4.01 (m, 5H), 3.81
(m, 1H), 2.49 (m, 1H), 2.21 (m, 1H). 13CNMR (D2O): 166.2, 159.1, 152.1,
148.2, 144.2, 143.7, 102.2, 95.0, 86.6, 85.3, 83.5, 75.7, 75.6, 69.0, 64.6, 64.2,
63.8, 38.8. 31PNMR (D2O): −0.20, −0.81. FAB-HRMS: [M+H]+ calcd. for
C18H26N5O14P2 598.0952, found 598.0930. UV (H2O): λmax 271(ε 19,000).
X-Ray Crystallographic Data
Crystallographic data (excluding structure factors) for compound 2g
described in this article have been deposited with the Cambridge Crystallo-
graphic Data Centre as supplementary publication number CCDC 254123.
Copies of the data can be obtained, free of charge, on application to the
CCDC (deposit@ccdc.cam.ac.uk).
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