Synthesis of conformationally locked l-deoxythreosyl phosphonate nucleosides built on a bicyclo[3.1.0]hexane template

Article abstract of DOI:10.1021/jo101475p

Two conformationally locked versions of l-deoxythreosyl phosphonate nucleosides (2 and 3) were synthesized to investigate the preference of HIV reverse transcriptase for a conformation displaying either a fully diaxial or fully diequatorial disposition of substituents. Synthesis of the enantiomeric 4-(6-amino-9H-purin-9-yl)bicyclo[3.1.0]hexan-2-ol carbocyclic nucleoside precursors (diaxially disposed) proceeded straightforwardly from commercially available (1R,4S)-4-hydroxy-2-cyclopent-2-enyl-1-yl acetate employing a hydroxyl-directed Simmons-Smith cyclopropanation that culminated with a Mitsunobu coupling of the purine base. For the more complicated 1-(6-amino-9H-purin-9-yl)bicyclo[3.1.0]hexan-3-ol carbocyclic nucleoside precursors (diequatorially disposed), the obligatory linear approach required the syntheses of key 1-aminobicyclo[3.1.0.]hexan-3-yl benzoate precursors that were assembled via the amide variant of the Kulinkovich reaction involving the intramolecular cyclopropanation of a substituted δ-vinylamide. Completion of the purine ring was achieved by conventional approaches but with much improved yields through the use of a microwave reactor. The syntheses of the phosphonates and the corresponding diphosphates were achieved by conventional means. None of the diphosphates, which were supposed to act as nucleoside triphosphate mimics, could compete with dATP even when present in a 10-fold excess. This article not subject to U.S. Copyright. Published 2010 by the American Chemical Society.

Full text of DOI:10.1021/jo101475p

pubs.acs.org/joc
Synthesis of Conformationally Locked L-Deoxythreosyl Phosphonate
Nucleosides Built on a Bicyclo[3.1.0]hexane Template
Hisao Saneyoshi,†,§ Jeffrey R. Deschamps,‡ and Victor E. Marquez*,†
†Chemical Biology Laboratory, Center for Cancer Research, National Cancer Institute at Frederick,
National Institutes of Health, Frederick, Maryland 21702, United States, and ‡Naval Research Laboratory,
Washington, D.C. 20375, United States. §Current address: Nano Medical Engineering Laboratory,
RIKEN Advanced Science Institute, 2-1 Hirosawa, Wako-Shi, Saitama, 351-0198, Japan
marquezv@mail.nih.gov
Received August 7, 2010
Two conformationally locked versions of L-deoxythreosyl phosphonate nucleosides (2 and 3) were
synthesized to investigate the preference of HIV reverse transcriptase for a conformation displaying
either a fully diaxial or fully diequatorial disposition of substituents. Synthesis of the enantiomeric
4-(6-amino-9H-purin-9-yl)bicyclo[3.1.0]hexan-2-ol carbocyclic nucleoside precursors (diaxially disposed)
proceeded straightforwardly from commercially available (1R,4S)-4-hydroxy-2-cyclopent-2-enyl-1-yl
acetate employing a hydroxyl-directed Simmons-Smith cyclopropanation that culminated with
a Mitsunobu coupling of the purine base. For the more complicated 1-(6-amino-9H-purin-9-yl)bicyclo-
[3.1.0]hexan-3-ol carbocyclic nucleoside precursors (diequatorially disposed), the obligatory linear
approach required the syntheses of key 1-aminobicyclo[3.1.0.]hexan-3-yl benzoate precursors that were
assembled via the amide variant of the Kulinkovich reaction involving the intramolecular cyclopropana-
tion of a substituted δ-vinylamide. Completion of the purine ring was achieved by conventional
approaches but with much improved yields through the use of a microwave reactor. The syntheses of
the phosphonates and the corresponding diphosphates were achieved by conventional means. None of the
diphosphates, which were supposed to act as nucleoside triphosphate mimics, could compete with dATP
even when present in a 10-fold excess.
Introduction
welcome finding since with the exception of acyclic phospho-
nate nucleosides, where the ribose is replaced by an alkolyalkyl
moiety2 and a couple of phosphonomethoxydihydrofuranyl
nucleosides bearing the nucleobases adenine and thymine,3
all phosphonate nucleosides built on furanose, pyranose, and
Five years ago, Herdewijn and co-workers reported the
synthesis of some L-deoxythreosyl phosphonate nucleosides,
among which those carrying the adenine (1a) and thymine
(1b) bases proved effective against HIV-1 and HIV-2 with
EC50 values of 2.53 and 6.59 μM, respectively.1 This was a
ꢀ
(2) Holy, A.; Votruba, I.; Merta, A.; Cerny, J.; Vesely, J.; Vlach, J.;
ꢀ
ꢀ
Sediva, K.; Rosenberg, I.; Otmar, M.; Hrebabecky, H.; Travnicek, M.;
Vonkac, V.; Snoeck, R.; De Clercq, E. Antiviral Res. 1990, 13, 295–311.
(3) Kim, C. U.; Luh, B. Y.; Martin, J. C. J. Org. Chem. 1991, 56, 2642–
2647.
(1) Wu, T.; Froeyen, M.; Kempeneers, V.; Pannecouque, C.; Wang, J.;
Busson, R.; De Clercq, E.; Herdewijn, P. J. Am. Chem. Soc. 2005, 127, 5056–
5065.
DOI: 10.1021/jo101475p
Published on Web 10/21/2010
J. Org. Chem. 2010, 75, 7659–7669 7659
This article not subject to U.S. Copyright. Published 2010 by the American Chemical Society

Saneyoshi et al.
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carbocyclic pseudosugars have failed to produce effective anti-
HIV compounds.
Modeling of the L-deoxythreosyladenine phosphonate nu-
cleoside (1a) inside the HIV reverse transcriptase (RT) domain
at the 30-end of the primer, paired with a thymidine nucleotide
in the template strand, revealed that the sugar ring was puck-
ered in the 30-endo conformation with the 10-(adenin-9-yl) and
30-O-(phosphonomethyl) groups in a quasi-diaxial orientation.1
A similar axial disposition of all the substituents in L-R-threo-
furanosyl nucleosides was also revealed by X-ray analysis and
such a conformation was in addition consistent with the
formation of stable duplexes in L-R-threofuranosyl-(30f20)-
oligonucleotides (TNAs).4
FIGURE 2. Structures of enantiomers of conformationally locked
nucleosides.
for their nucleoside and nucleotide substrates.5,6 Because the
additional bulk added by the bicyclic scaffold could be steri-
cally unfavorable at the active site of RT, we also synthesized
the optical enantiomers of each of the targets to allow the base
and the O-phosphonomethyl group to bind in a different
orientation and possibly avoid unfavorable steric contacts
(ent-2 and ent-3, Figure 2).
Results and Discussion
Synthesis. The synthesis of the first target phosphonate (2)
started from commercially available (1R,4S )-4-hydroxy-
2-cyclopent-2-enyl-1-yl acetate (4, Scheme 1), which is derived
from the enzymatic hydrolysis of prochiral cis-1,4-diacyl-
2-cyclopentendiols.7 An ensuing hydroxyl-directed Simmons-
Smith cyclopropanation provided the bicyclo[3.1.0]hexane
template 5 in excellent yield. Then, reaction of the free
secondary alcohol in 5 with pivalic acid under Mitsunobu
conditions afforded the inverted ester in (6), which as
reported in the literature8 was stable under conditions that
hydrolyzed the acetate moiety to give 7. The coupling 7 with
6-chloropurine under Mitsunobu conditions gave the desired
purine carbonucleoside 8 which after ammonolysis and
reductive elimination of the pivaloyl protecting group led
to the key conformationally locked threosyl nucleoside 9.
Employing the transient Jones silylation procedure,9 the
amino group in 9 was selectively protected with dimethoxy-
trityl chloride10 to give compound 10. Finally, the target
phosphonate 2 was assembled after reaction with diethyl
[(trifluoromethanesulfonyl)oxy]methanephosphonate11 fol-
lowed by deprotection with trimethylsilyl bromide.
For the synthesis of the antipode (ent-2), some changes
were implemented to improve yields and to reduce the
number of steps (Scheme 2). Beginning with the same inter-
mediate 5, we performed the Mitsunobu reaction with
the N(Boc2)-protected adenine,12 which resulted in a 24%
increase yield of the coupled product (12). Selective removal
of the acetate group was followed by a tandem oxidation-
reduction protocol to invert the configuration of the second-
ary alcohol. This was more efficient than the Mitsunobu
inversion used in Scheme 1. The obtained product (14) was
FIGURE 1. Structures of L-deoxythreosyl phosphonate nucleo-
sides (A) and conformationally locked versions (B).
The results described above seem to indicate that the ability
of the base and the O-phosphonomethyl groups to maintain
their axial disposition is quite important for TNAs and for
the anti-HIV activity of 1a and 1b; however, as shown in
Figure 1A, the flexible nature of the 5-membered ring should
allow rapid equilibration to the all-equatorial conformation
which on steric grounds ought to be more stable. In order to
test the preference of HIV RTfor either diaxialordiequatorial
disposition of substituents, we constructed conformationally
rigid analogues of each conformer (2 and 3, Figure 1B) using
the bicyclo[3.1.0]hexane scaffold that we have successfully
employed to study the conformational preferences of enzymes
€
(4) Schoning, K.-U.; Scholz, P.; Guntha, S.; Wu, X.; Krishnamurthy, R.;
Eschenmoser, A. Science 2000, 290, 1347–1351.
(7) Laumen, K; Schneider, M. Tetrahedron Lett. 1984, 25, 5875–5878.
(8) Myers, A. G.; Hammond, M; Wu, Y. Tetrahedron Lett. 1996, 37,
3083–3086.
(9) Ti, G. S.; Gaffney, B. L.; Jones, R. A. J. Am. Chem. Soc. 1982, 104,
1316–1329.
(10) Sierzchala, A. B.; Dellinger, D. J.; Betley, J. R.; Wyrzkiewicz, T. K.;
Yamada, C. M.; Caruthers, M. H. J. Am. Chem. Soc. 2003, 125, 13427–
13441.
(11) Xu, Y.; Flavin, M. T.; Xu, Z. J. Org. Chem. 1996, 61, 7697–7701.
(12) (a) Dey, S; Garner, P. J. Org. Chem. 2000, 65, 7697–7699. (b) Yin, X;
Li, W; Schneller, S. W. Tetrahedron Lett. 2006, 47, 9187–9189.
(5) Marquez, V. E. The properties of Locked Methanocarba Nucleosides
in Biochemistry, Biotechnology and Medicine. In Modified Nucleosides in
Biochemistry, Biotechnology and Medicine; Herdewijn, P., Ed.; Wiley-VCH:
New York, 2008; Chapter 12, pp 307-341.
(6) Part of this work was presented as a poster at the XVIII International
Round Table for Nucleosides, Nucleotides and Nucleic Acids, Kyoto, Japan,
Sep 8-11, 2008: Saneyoshi, H.; Vu, B. C.; Hughes, S. H.; Boyer, P. L.;
Sarafianos, S. G.; Marquez, V. E. Nucleic Acids Symp. Ser. No. 52 2008, 623–
624.
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SCHEME 1
SCHEME 2
converted to the final target (ent-2) in the same manner
shown in Scheme 1.
rearrangement of the intermediate acyl azide to the isocya-
nate, which could be trapped with H2O to give the desired
bicyclic cyclopropylamine. Alternatively, a carbene inser-
tion protocol (B), also used by us in assembling the bicyclo-
[3.1.0]hexane system, was considered. However, the addi-
tional step of removing the carbonyl group adjacent to the
fused cyclopropane made this approach less attractive. A
more straightforward approach (C) based on the amide
variant of the Kulinkovich reaction,13 as developed by
For the syntheses of compounds 3 and ent-3, we consid-
ered three possible approaches to the key bicyclic cyclopro-
pylamine as described retrosynthetically in Scheme 3. The
first route considered (A) was based on a previous synthesis
of bicyclo[3.1.0]hexane nucleosides from our laboratory
using a 1,3-dipolar cycloaddition of diazomethane to a
hydroxyl-protected 4-hydroxycyclopent-1-enecarbonitrile
to give the cis-fused pyrazoline intermediate, which without
isolation was expected to undergo photolysis-induced ni-
trogen extrusion to the fused bicyclic system. Several steps
to the intermediate bicyclic amine were required, including
hydrolysis of the nitrile to the carboxylic acid and Curtius
(13) (a) Kunlinkovich, O. G.; Sviridov, S. V.; Vasilevskii, D. A.; Prityckaja,
T. S. Zh. Org. Khim. 1989, 25, 2244–2245. (b) Kunlinkovich, O. G.;
Sviridov, S. V.; Vasilevskii, D. A. Synthesis 1991, 3, 234. (c) For a compre-
hensive review, see: Kulinkovich, O. G.; de Meijere, A. Chem. Rev. 2000,
100, 2789–2834.
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SCHEME 3
SCHEME 4
Chaplinski and de Meijere,14 and later expanded in scope by
Lee and Cha15 to the intramolecular cyclopropanation of
substitued ω-vinylamides, was able to provide the desired
bicyclic cyclopropylamine in one step. This latter approach
was successfully accomplished as depicted in Scheme 4.
Through a copper bromide-promoted addition,16 (R)-epi-
chlorohydrin was reacted with vinylmagnesium bromide to
provide compound 16. The ensuing nucleophilic displacement
with KCN afforded the corresponding nitrile (17), which was
hydrolyzed to the acid. Without isolation, activation of the acid
with N-(3-dimethylaminopropyl)-N-ethylcarbodiimide (EDAC)
in the presence of hydroxybenzotriazole (HOBT) gave the
key δ-vinyldibenzylamide (18) upon reaction with diben-
zylamine (HNBn2). Reaction of 18 with chloromethyl
methyl ether produced the MOM-protected δ-vinyldibenzyl-
amide (19), and the subsequent room temperature intramo-
lecular cyclopropanation with stoichiometric amounts of
Ti(O-i-Pr)4 in the presence of i-PrMgCl in THF afforded a
1.5:1 mixture of diastereoisomers which after hydrolysis of
the MOM group (20 and 21) were separated by columan
chromatography. The required inversion of configuration
of the secondary alcohol was performed by a Mitsunobu
reaction with benzoic acid to give compound 22, and gen-
eration of the required amine (23) was achieved by catalytic
hydrogenation.
(14) Chaplinski, V.; de Meijere, A. Angew. Chem., Int. Ed. Engl. 1996, 35,
413–414.
(15) Lee, J.; Cha, J. K. J. Org. Chem. 1997, 62, 1584–1585.
(16) Burova, S. A.; McDonald, F. E. J. Am. Chem. Soc. 2004, 126, 2495–
2500.
From amine 23, the two-step construction of the purine
ring was efficiently achieved (81%) by reacting first with
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SCHEME 5
SCHEME 6
N-(4,6-dichloropyrimidin-5-yl)formamide17 in a microwave
reactor for 20 min and then immediately cyclizing the
transiently isolated intermediate;also in a microwave re-
actor for 120 min;in the presence of diethoxymethyl acetate
to give compound 25 (Scheme 5). Use of the microwave for
the construction of the purine ring was quite useful in terms of
shortening the reaction time, avoiding prolonged heating in an
oil bath, and improving the yields. Ammonolysis produced the
desired adenine ring and simultaneously hydrolyzed the ben-
zoyl ester-protecting group to give the carbocyclic nucleoside
26. In a similar fashion, as performed for compounds 2 and ent-
2, the amino group was selectively protected with dimethoxy-
trityl chloride and the final target phosphonate 3was assembled
(17) Harnden, M. R.; Wyatt, P. G.; Boyd, M. R.; Sutton, D. J. Med.
Chem. 1990, 33, 187–196.
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FIGURE 3. Displacement ellipsoid plot of (-)-9 (left) and (-)-26 (right) drawn at the 50% probability level showing, respectively, the axial
and equatorial orientation of the substituents. Note that (-)-26 crystallizes with two molecules in the asymmetric unit (one of which is
disordered) plus three water molecules. In this view, the disordered molecule of (-)-26 and the water are omitted for clarity.
TABLE 1. Optical Rotation Values for the Enantiomeric Phosphonates
diaxial compounds 2-DP and ent-2-DP, molecular modeling
showed severe steric clashes between the fused cyclopropane
ring and amino acids Y115 and M184, respectively.
phosphonate
optical rotation
diaxial phosphonate (2)
[R]20D = -13.5
[R]20D = þ13.5
[R]20D = -43.4
[R]21D = þ43.1
diaxial phosphonate (ent-2)
diequatorial phosphonate (3)
diequatorial phosphonate (ent-3)
Experimental Section
(1S,2R,4S,5R)-4-Hydroxybicyclo[3.1.0]hexan-2-yl Acetate (5).
Over a cooling bath at 0 °C, compound 4 (3 g, 21.1 mmol)
was dissolved in CH2Cl2 (100 mL) and treated with 1 M Et2Zn
(23.2 mL). After the mixture was stirred at 0 °C for 15 min, CH2I2
(3.8 mL, 46.8 mmol) and 1 M Et2Zn-hexane (23.2 mL) were
added. Fifteen minutes later, an additional amount of CH2I2
(3.8 mL, 46.8 mmol) was added. The reaction mixture was allowed
to reach room temperature, and after being stirred for 6 h, the
contents was poured onto a cold, aqueous solution of NH4Cl (200
mL). Following the extraction with CHCl3 (6 ꢀ 100 mL), the
organic layer was dried (MgSO4), filtered, and evaporated in
vacuo. The residue was purified by column chromatography on
silica gel with hexanes/EtOAc (100:0 f 50:50, v/v) as eluent to
give 5 (3.2 g, 97%) as a syrup: [R]22D=þ48.8° (c 1.55, CHCl3); 1H
NMR (CDCl3) δ 5.08 (td, J=8.3, 4.7 Hz, 1 H, H-2), 4.38 (td, J=
8.3, 4.7 Hz, 1 H, H-4), 2.42 (br s, 1 H, 3-OH), 2.29-2.22 (m, 1 H,
H-1), 2.00 (s, 3 H, CH3-COO), 1.70-1.57 (m, 2 H, H-3a, H-3b),
1.20-1.09 (m, 1 H, H-5), 0.91-0.88 (m, 1 H, H-6b), 0.52-0.47
(m, 1 H, H-6a); 13C NMR (CDCl3) δ 171.1, 73.3, 70.3, 33.1, 22.8,
21.3, 20.0, 2.4; FAB-MS m/z (relative intensity) 157.1 (MHþ,
after reaction with diethyl [(trifluoromethanesulfonyl)oxy]-
methanephosphonate followed by deprotection with trimethyl-
silyl bromide.
Starting from the enantiomeric amine 21 (Scheme 4), the
construction of the final target, ent-3, was achieved in a
manner similar to that depicted in Scheme 6.
Syntheses of Diphosphates. The diphosphates 2-DP, 3-DP,
and ent-3-DP were custom made from the corresponding
phosphonate acids by TriLink BioTechnologies, San Diego,
CA, following the procedure of Herdewijn et al.1 The char-
acteristics of the final products and the method of purification
can be found in the Experimental Section. Unfortunately, the
synthesis was unsuccessful in the case of ent-2-DP.
Structural Analysis. The optical rotation values (Table 1)
as well as the crystal structures of intermediates (-)-9 and
(-)-26 were in keeping with the structures proposed. The
crystal structures of the precursors also show clearly the all-
axial and all-equatorial disposition of substituents in (-)-9
and (-)-26, respectively (Figure 3). Although the glycosyl
bond in (-)-9 was clearly anti, the crystal structure of (-)-26
showed two conformations with the glycosyl bond in the anti
and syn orientations (only the syn conformation is shown).
Biological Activity. All phosphonates (2, ent-2, 3, and
ent-3) were inactive against HIV in cell culture. Furthermore,
both 2-DP and 3-DP incorporated into DNA only when they
were the exclusive A nucleotide available; however, neither
could compete with dATP even when present in a 10:1 excess.
Therefore, we conclude that the bicyclo[3.1.0]hexane tem-
plate mimicking a threosyl template is not recognized by
cellular kinases and the resulting triphosphate mimics may
have severe steric contacts with important amino acids at the
active site of HIV RT (vide infra). In the case of the fully
diequatorial compounds 3-DP and ent-3-DP, the presence
of the syn conformation, as inferred from the structure of
(-)-26, may explain their lack of recognition. For the fully
17.8). Anal. Calcd for C8H12O3 0.1H2O: C, 60.82; H, 7.78.
3
Found: C, 60.72; H, 7.89.
(1R,2R,4R,5S )-4-Acetoxybicyclo[3.1.0]hexan-2-yl Pivalate
(6). Compound 5(1.3 g, 8.33 mmol), pivalic acid (1.3 g, 12.7 mmol),
and PPh3 (4.4 g, 16.8 mmol) were dissolved in THF (80 mL).
The solution was cooled to 0 °C and treated with DIAD (3.2 mL,
16.5 mmol). The reaction mixture was allowed to reach room
temperature and was stirred for 30 min before evapora-
tion to dryness in vacuo. The residue was purified by column
chromatography on silica gel with hexane/EtOAc (100:0 f
75:15, v/v) as eluent to give 6 (1.90 g, 95%) as a syrup:
1
[R]22D= þ74.9 (c 0.72, CHCl3); H NMR (CDCl3) δ 5.44 (td,
J = 8.4, 4.7 Hz, 1 H, H-4), 5.11 (d, J = 5.3 Hz, 1 H, H-2),
2.06-2.00 (m, 4 H, CH3COO, H-3a,), 1.84-1.79 (m, 1 H, H-1),
1.54-1.44 (m, 2 H, H-3b, H-5), 1.17 (s, 9 H, (CH3)3COO),
0.63-0.58 (m, 1 H, H-6b), 0.54-0.51 (m, 1 H, H-6a); 13C NMR
(CDCl3) δ 178.0, 171.2, 75.4, 38.6, 32.9, 27.0, 21.7, 21.1, 19.3,
5.2; FAB-MS m/z (relative intensity) 279.1 (M þ Kþ,39.4).
Anal. Calcd for C13H20O4: C, 64.98; H, 8.39. Found: C, 65.20;
N, 8.48.
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(1R,2R,4R,5S )-4-Hydroxybicyclo[3.1.0]hexan-2-yl Pivalate (7).
Compound 6 (60 mg, 0.25 mmol) was dissolved in MeOH
(2.5 mL) and stirred with K2CO3 (35 mg, 0.25 mmol) at room
temperature for 2 h. After diluting with CHCl3 (15 mL), the
organic layer was washed with aqueous NH4Cl and brine, dried
(MgSO4), filtered, and evaporated in vacuo. The residue was then
purified by column chromatography on silica gel eluted with
hexane/EtOAc (2:1, v/v) as eluent to give 7 (46 mg, 92%) as a
syrup: [R]25D= þ88.3 (c 0.585, CHCl3); 1H NMR (CDCl3) δ 5.12
(d, J=5.2 Hz, 1 H, H-2), 4.80-4.75 (m, 1 H, H-4), 1.91 (ddd,
J=14.9, 7.8, 1.1 Hz, 1 H, H-3a), 1.71-1.65 (m, 1 H, H-5), 1.52-
1.48 (m, 1 H, H-1), 1.42-1.34 (m, 1 H, H-3b), 1.18 (s, 9 H, (CH3)3-
COO), 0.60-0.55 (m, 2 H, H-6a, H-6b); 13C NMR (CDCl3) δ
178.1, 76.4, 72.5, 38.6, 35.9, 27.0, 22.0, 21.4, 4.4; FAB-MS m/z
(relative intensity) 199.1 (MHþ, 13.2). Anal. Calcd for C11H18O3:C,
66.64; H, 9.15. Found: C, 66.50; H, 9.23.
(10R,20R,40S,50S)-4-(6-Chloro-9H-purin-9-yl)bicyclo[3.1.0]hexan-
2-yl Pivalate (8). PPh3 (778 mg, 2.9 mmol) was dissolved in THF
(10 mL) and treated with DIAD (577 μL, 2.9 mmol) at 0 °C. The
mixture was stirred for 20 min, and then compound 7 (255 mg,
1.3 mmol) and 6-chloropurine (319 mg, 2.1 mmol) dissolved in THF
(3 mL) were added. The mixture was stirred at room temperature for
2 h and evaporated in vacuo. The residue was purified by column
chromatography on silica gel with hexane/EtOAc (50:50, v/v) as
eluent to give 8 (223 mg, 55%) as a white solid: mp 237-238 °C;
[R]21D= þ9.9 (c 0.975, CHCl3); 1H NMR (CDCl3) δ 8.73 (s, 1 H,
H-2),8.56(s,1H,H-8),5.30(d,J=5.7 Hz, 1 H, H-20),5.24(d,J=7.0
Hz, 1 H, H-40), 2.34-2.27 (dt, J = 16.4, 6.4 Hz, 1 H, H-30b),
2.04-1.90 (m, 3 H, H-10, H-30a, H-50), 1.09 (s, 9 H, (CH3)3COO),
0.98-0.92 (m, 1 H, H-60b), 0.39-0.35 (m, 1 H, H-6a); 13C NMR
(CDCl3) δ 177.7, 151.7, 151.3, 150.9, 144.0, 131.6, 75.7, 55.4, 38.6,
37.5, 27.0, 23.6, 22.4, 7.0; FAB-MS m/z (relative intensity) 335.1
(MHþ, 100). Anal. Calcd for C16H19ClN4O2: C, 57.40; H, 5.72; N,
16.73. Found: C, 57.40; H, 5.78; N, 16.68.
(10R,20R,40S,50S)-4-(6-Amino-9H-purin-9-yl)bicyclo[3.1.0]hexan-
2-ol (9). Compound 8 (215 mg, 0.64 mmol) was dissolved in
dioxane-NH4OH (5 mL, 1:1, v/v) and heated in a microwave
reactor (100 °C) for 10 min. The solution was then diluted with
CHCl3 (20 mL) and washed with brine. The organic layer was dried
(MgSO4) and evaporated in vacuo. The residue was immediately
dissolved in CH2Cl2 (5 mL), and under argon it was treated with
1 M DIBAL-H in toluene (1.3 mL) at -78 °C. After being stirred for
60 min, the reaction was quenched with MeOH (1 mL) and
evaporated in vacuo. The residue was redissolved in CHCl3/MeOH
(20 mL, 9:1, v/v) and filtered through a pad of Celite. The solution
was evaporated in vacuo, and the residue was purified by column
chromatography on silica gel eluted with CHCl3-MeOH (90:10,
v/v, 0.5%Et3N). Finally, the compound was precipitated with Et2O
at -78 °C to give compound 9 (126 mg, 85%) as a white solid. An
analytical sample was recrystallized from EtOH: mp 209-210 °C;
[R]22D=-28.3 (c 0.605, MeOH); 1H NMR (CD3OD) δ8.54 (s, 1 H,
H-2),8.21(s,1H,H-8),5.03(d,J=7.4 Hz, 1 H, H-40),4.35(d,J=5.3
Hz, 1 H, H-20), 2.24-2.17 (m, 1 H, H-30b), 1.90-1.79 (m, 3 H, H-10,
H-30a, H-50), 0.82-0.76 (m, 1 H, H-60b), 0.28-0.24 (m, 1 H, H-60a);
13C NMR (CD3OD) δ 157.3, 153.3, 150.1, 142.6, 120.1, 74.0, 57.3,
40.4, 27.4, 23.7, 7.4; FAB-MS m/z (relative intensity) 232.1 (MHþ,
100). Anal. Calcd for C11H13N5O: C, 57.13; H, 5.67; N, 30.28.
Found: C, 56.95; H, 5.81; N, 30.34.
(10R,20R,40S,50S )-4-(6-(Bis(4-methoxyphenyl)(phenyl)methyl-
amino)-9H-purin-9-yl)bicyclo[3.1.0]hexan-2-ol (10). Compound
9 (357 mg, 1.5 mmol) was coevaporated three times with
anhydrous pyridine and finally dissolved in anhydrous pyridine
(10 mL). Under an argon atmosphere, the solution was treated
with (CH3)3SiCl (292 μL, 2.3 mmol), stirred at room temperature
for 5 min, and then treated with [(MeO)Ph]2PhCCl (DMTrCl,
604 mg, 1.8 mmol). After 18 h, the reaction was quenched with
aqueous NaHCO3 (1 mL) and evaporated in vacuo. The residue
was dissolved in CHCl3 (60 mL), washed with brine, dried
(MgSO4), and evaporated in vacuo. Purification by column chro-
matography on silica gel eluted with CHCl3/MeOH (99:1 f 98:2,
v/v, 0.5%Et3N) gave compound 10 (653 mg, 79%) as a white
foam: [R]22D= -41.0 (c 0.96, CHCl3); 1H NMR (CDCl3) δ 8.04
(s, 1 H, H-2), 7.90 (s, 1 H, H-8), 7.34-7.19 (m, 9 H, PhH), 6.97
(s, 1 H, (MeO)2TrNH), 6.80-6.77 (m, 4 H, PhH), 6.65 (br s, 1 H,
OH-20), 4.81 (d, 1 H, J = 8.2 Hz, H-40), 4.33 (br, 1 H, H-20),
2.39-2.30 (m, 1 H, H-30b), 2.00 (d, 1 H, J=16.2 Hz, H-30a), 1.86
(dt, 1 H, J=9.0, 4.6 Hz, H-10), 1.61 (dt, 1 H, J=8.7, 4.3 Hz, H-50),
0.81-0.75 (m, 1 H, H-60b), 0.05-0.01 (m, 1 H, H-60a); 13C NMR
(CDCl3) δ 158.2, 154.3, 151.2, 145.3, 140.7, 137.3, 130.0, 128.7,
127.8, 126.8, 113.1, 73.2, 70.6, 58.1, 55.2, 41.2, 27.9, 23.3, 7.7;
FAB-MS m/z (relative intensity) 534.2 (MHþ, 33.8). Anal. Calcd
for C32H31N5O3 0.3H2O: C, 71.30; H, 5.91; N, 12.99. Found: C,
3
71.16; H, 5.87; N, 12.98.
Diethyl ((10R,20R,40S,50S)-4-(6-(Bis(4-methoxyphenyl)(phenyl)-
methylamino)-9H-purin-9-yl)bicyclo[3.1.0]hexan-2-yloxy)methyl-
phosphonate (11). Compound 10 (59 mg, 0.10 mmol) was coevap-
orated four times with anhydrous toluene and dissolved in
anhydrous THF (0.5 mL) under argon. The solution was treated
with 1 M [(CH3)3Si]2NLi (LiHMDS, 133 μL) and stirred at room
temperature for 5 min before the addition of trifluoromethansul-
fonyl diethoxy methyl phosphonate10 (40 mg, 0.13 mmol) in
anhydrous THF (1 mL). After 25 min, the reaction was quenched
with aqueous NaHCO3 (1 mL) and diluted with CHCl3 (20 mL).
The mixture was washed with brine, dried (MgSO4), and evapo-
rated in vacuo. The residue was purified by column chromatog-
raphy on silica gel eluted with CHCl3/MeOH (98:2, v/v, 0.5%
Et3N) to give 11 (67 mg, 88%) as a syrup: [R]26D=-11.3 (c 0.75,
CHCl3); 1H NMR (CDCl3) δ 8.32 (s, 1 H, H-2), 8.07 (s, 1 H, H-8),
7.35-7.19 (9H, m, PhH), 6.88 (1H, br s, (MeO)2TrNH), 6.80-
6.77 (m, 4 H, PhH), 5.10 (distorted dd, 1 H, J=5.9, 1.7 Hz, H-40),
4.22-4.11 (m, 5 H, (CH3CH2O)2P, H-20), 3.85-3.72 (m, 8 H,
(MeO)2TrNH, PCH2O), 2.07-2.00 (m, 3 H, H-10, H-30a, H-30b),
1.73 (dt, 1 H, J=9.1, 3.9 Hz, H-50), 1.37-1.27 (m, 6 H, (CH3-
CH2O)2P), 0.78 (dt, 1 H, J=8.6, 6.2 Hz, H-60b), 0.19-0.15 (m, 1
H, H-60a); 13C NMR (CDCl3) δ 158.2, 154.0,. 151.8, 148.5, 145.5,
139.8, 137.5, 130.0, 128.7, 127.7, 126.6, 120.5, 113.0, 83.8 (JCP
=
11.0 Hz), 70.4, 62.4 (JCP=6.5 Hz), 62.1 (JCP=168.0 Hz), 55.2,
54.2, 36.6, 23.3, 23.0, 16.5 (JCP=4.2 Hz), 16.4 (JCP=4.2 Hz), 6.8;
APCI-MS m/z (relative intensity) 684.3 (MHþ, 18.2). Anal. Calcd
for C37H42N5O6P 0.4H2O:C, 64.32; H, 6.24;N, 10.14. Found: C,
3
64.27; H, 6.43; N, 9.99.
((10R,20R,40S,50S )-4-(6-Amino-9H-purin-9-yl)bicyclo[3.1.0]-
hexan-2-yloxy)methylphosphonic Acid Sodium Salt (2). Com-
pound 11 (40 mg, 58.5 μmol) was dissolved in CH3CN (1 mL)
under argon. The solution was treated with (CH3)3SiBr
(TMSBr, 38 μL, 0.29 mmol) and stirred for 2 days at room
temperature. After the solution was quenched with triethy-
lammonium bicarbonate (TEAB) buffer (3 mL), the CH3CN
was evaporated in vacuo. The aqueous buffer solution that
remained was washed three times with EtOAc and evaporated
in vacuo. The residue was purified by reversed-phase chroma-
tography (1.5 cm ꢀ4 cm) on a C-18 silica gel column eluted
with 0.1 M TEAB/CH3CN (100:0-90:10, v/v) and further
purified by reversed-phase HPLC using a similar column
eluted with 0.1 M TEAB/CH3CN (100:0 f 90:10, v/v). The
desired fractions were combined, coevaporated with EtOH,
and lyophilized. Finally, the compound was applied to a
Dowex (Naþ) column to give compound 2 (16 mg, 73%) as a
1
white solid: [R]20D =-13.5 (c 0.45, H2O); H NMR (D2O) δ
8.51 (s, 1 H, H-2), 8.14 (s, 1 H, H-8), 4.89 (distorted d, J=5.1 Hz,
1 H, H-40), 4.21 (distorted d, J=3.6 Hz, 1 H, H-20), 3.54 (dd,
J=13.0, 9.2 Hz, 1 H, PCHHO), 3.43 (dd, J=13.0, 8.9 Hz, 1 H,
PCHHO), 2.10-2.05 (m, 3 H, H-10, H-30a, H-30b), 1.81 (td,
J=8.5, 4.2 Hz, 1 H, H-50), 0.82 (dt, J=8.5, 6.0 Hz, 1 H, H-60b),
0.32-0.29 (m, 1 H, H-60a); 13C NMR (D2O) δ 154.3, 151.0,
147.8, 141.6, 117.7, 83.3 (JCP=11.8 Hz), 63.7 (JCP=157.3 Hz),
J. Org. Chem. Vol. 75, No. 22, 2010 7665

Saneyoshi et al.
JOCArticle
55.4, 35.2, 22.5, 21.6, 5.9; 31P NMR (D2O) δ 15.8; FAB-MS
m/z (relative intensity) 324.2 (MH-, 100); HRMS (FAB) calc
for (C12H15N5O4P-) 324.0867 (MH-), found 324.0850.
(10S,20R,40R,50R)-4-(6-(Bis(tert-butoxycarbonyl)amino)-9H-
purin-9-yl)bicyclo[3.1.0]hexan-2-yl Acetate (12). Compound
5 (400 mg, 2.5 mmol), N-(Boc)2adenine (1.29 g, 3.8 mmol),
and PPh3 (1.01 g, 3.8 mmol) were dissolved in THF (25 mL).
After being cooled to 0 °C, the solution was treated with DIAD
(786 μL, 3.8 mmol) and stirred at the same temperature for
30 min. The reaction mixture was evaporated in vacuo, and the
crude residue was purified by column chromatography on
silica gel eluted with hexane/EtOAc (100:0 f 60:40%, v/v) to
give compound 12 (953 mg, 79%) as a syrup: [R]21D= 40.8
(c 1.39, CHCl3); 1H NMR (CDCl3) δ 8.85 (s, 1 H, H-2), 8.18 (s,
1 H, H-8), 5.62 (td, J=8.5, 4.7 Hz, 1 H, H-20), 5.22 (d, J=7.0
Hz, 1 H, H-40), 2.27 (dd, J=15.3, 8.2 Hz, 1 H, H-30b), 2.19-
2.14 (m, 1 H, H-10), 2.06 (s, 3 H, CH3CO), 1.96-1.88 (m, 1 H,
H-30a), 1.77-1.73 (1 m, 1 H, H-50), 1.46 (s, 18 H, (CH3)3COCO ꢀ
2), 0.91-0.82 (m, 2 H, H-60a, H-60b); 13C NMR (CDCl3) δ 171.0,
152.8, 152.0, 150.5, 150.4, 142.4, 129.0, 83.8, 74.8, 55.4, 34.2, 27.8,
22.0, 21.0, 20.8, 6.1; FAB-MS m/z (relative intensity) 474.3 (MHþ,
65.9). Anal. Calcd for C23H31N5O6 1.4H2O: C, 55.39; H, 6.83; N,
14.04. Found: C, 55.63; H, 6.59; N, 13.63.
(CH3)3COCO ꢀ 2), 0.84-0.79 (m, 1 H, H-60b), 0.13 (dt, J=5.9, 3.9
Hz, 1 H, H-60a); 13C NMR (CDCl3) δ 152.5, 151.2, 150.5, 150.2,
145.8, 129.4, 83.8, 73.1, 56.9, 40.3, 27.8, 27.2, 23.1, 7.4; FAB-MS
m/z (relative intensity) 432.3 (MHþ, 65.9). Anal. Calcd for C21H29-
N5O5: C, 58.45; H, 6.77; N, 16.23. Found: C, 58.60; H, 6.82;
N, 16.24.
Diethyl ((10S,20S,40R,50R)-4-(6-(Bis(tert-butoxycarbonyl)amino)-
9H-purin-9-yl)bicyclo[3.1.0]hexan-2-yloxy)methylphosphonate (15).
Compound 14 (150 mg, 0.35 mmol) was coevaporated three times
with anhydrous toluene and dissolved in THF (3.5 mL). After being
cooled to -78 °C, the solution was treated with 1 M [(CH3)3Si]2NLi
(LiHMDS in THF, 383 μL) followed by the addition of diethoxy-
phosphonomethyl trifluoromethanesulfonate (115 mg, 0.38 mmol)
in THF (1 mL). The solution was stirred at -78 °C for 20 min,
quenched by addition of aqueous NH4Cl (1 mL), and further
diluted with EtOAc (50 mL). The organic solution was washed
with brine, dried (MgSO4), filtered, and evaporated in vacuo. The
residue was purified by column chromatography on silica gel eluted
with hexane/EtOAc (100:0 f 0:100, v/v), CHCl3-MeOH (98:2,
v/v) to give 15 (176 mg, 87%) as a syrup: [R]20D=9.8 (c1.2, CHCl3);
1HNMR(CDCl3, 400 MHz) δ8.82 (s, 1 H, H-2), 8.68 (s, 1 H, H-8),
5.25 (d, J=7.0 Hz, 1 H, H-40), 4.22-4.08 (m, 5 H, (CH3CH2O)2P,
H-20), 3.81 (dd, J=13.8, 9.3 Hz, 1 H, PCHHO), 3.72 (dd, J=13.8,
8.9 Hz, 1 H, PCHHO), 2.18-2.11 (m, 1 H, H-30b), 2.07-2.02 (m,
2 H, H-10, H-30a), 1.71 (dt, J=8.4, 4.4 Hz, 1 H, H-50), 1.44 (s, 18 H,
(CH3)3COCO ꢀ 2), 1.33 (t, J=7.1 Hz, 3 H, (CH3CH2O)2P), 1.28 (t,
J = 7.1 Hz, 3 H, (CH3CH2O)2P), 0.87-0.81 (m, 1 H, H-60b),
0.23-0.19 (m, 1 H, H-60a); 13C NMR (CDCl3, 100 MHz) δ 153.1,
151.5, 150.5, 149.8, 144.9, 128.6, 83.7 (JCP=11.3 Hz), 83.5, 62.5
(JCP=5.0 Hz), 62.4 (JCP=4.9 Hz), 62.1 (JCP=168.3 Hz), 54.6, 36.7,
27.7, 23.3, 23.1, 16.41 (JCP=3.5 Hz), 16.35 (JCP=3.5 Hz), 6.8; FAB-
MS m/z (relative intensity) 582.3 (MHþ, 83.4). Anal. Calcd for
C26H40N5O8P: C, 53.69; H, 6.93; N, 12.04. Found: C, 53.56; H,
7.32; N, 11.65.
(10S,20R,40R,50R)-4-(6-(Bis(tert-butoxycarbonyl)amino)-9H-
purin-9-yl)bicyclo[3.1.0]hexan-2-ol (13). Compound 12 (872 mg,
1.8 mmol) was dissolved in MeOH (20 mL) and treated with
K2CO3 (254 mg, 1.8 mmol). After the solution was stirred at
room temperature for 2 h, CHCl3 (150 mL) was added, and the
organic layer was washed with brine and aqueous NH4Cl,
dried (MgSO4), filtered, and evaporated in vacuo. The crude
material was purified by column chromatography on silica gel
eluted with hexane/EtOAc (100:0 f 0:100%, v/v) to give com-
pound 13 (722 mg, 91%) as a white foam: [R]21D= 26.7 (c 2.06,
1
CHCl3); H NMR (CDCl3) δ 8.84 (s, 1 H, H-2), 8.19 (s, 1 H,
H-8), 5.20 (d, J=6.8 Hz, 1 H, H-40), 4.94-4.99 (m, 1 H, H-20),
2.27 (br, 1 H, OH-20), 2.10 (dd, J=15.1, 7.9 Hz, 1 H, H-30b),
1.95 td, J=8.6, 4.6 Hz, 1 H, H-10), 1.78 (ddd, J=15.4, 8.7,
7.1 Hz, 1 H, H-30a), 1.67 (td, J=8.6, 4.4 Hz, 1 H, H-50), 1.45 (s,
18 H, (CH3)3COCO ꢀ 2), 0.87 (td, J=5.9, 3.8 Hz, 1 H, H-60b),
0.84-0.78 (m, 1 H, H-60a); 13C NMR (CDCl3) δ 152.8, 151.9,
150.6, 150.2, 142.7, 129.0, 83.8, 72.0, 56.1, 36.9, 27.8, 23.3,
21.8, 5.2; FAB-MS m/z (relative intensity) 432.3 (MHþ,
((10S,20S,40R,50R)-4-(6-Amino-9H-purin-9-yl)bicyclo[3.1.0]-
hexan-2-yloxy)methylphosphonic Acid Sodium Salt (ent-2). Follow-
ing the same procedure as for compound 2, ent-2 was obtained in
72% yield: [R]20D=13.5 (c 0.450, H2O). The 1H NMR, 13C NMR,
and mass spectral data were identical to 2.
(R)-3-Hydroxyhex-5-enenitrile (17). Compound 1616 (10 g,
82.9 mmol) was dissolved in MeOH (100 mL) and treated with
KCN (5.9 g, 90.6 mmol). After being stirred and heated for 24 h
at 70 °C, the solvent was removed in vacuo and the residue was
dissolved in EtOAc (250 mL) and washed with aqueous NH4Cl
and brine. The organic solution was dried (MgSO4), filtered, and
evaporated in vacuo. The residue was purified by column chro-
matography on silica gel eluted with hexane/EtOAc (100:0 f
70:30, v/v) to give 17 (7.7 g, 84%) as an oil: [R]21D=-6.8 (c 0.8,
92.9%). Anal. Calcd for C21H29N5O5 0.4H2O: C, 57.49; H,
3
6.85; N, 15.96. Found: C, 57.49; H, 6.84; N, 15.87.
(10S,20S,40R,50R)-4-(6-(Bis(tert-butoxycarbonyl)amino)-9H-
purin-9-yl)bicyclo[3.1.0]hexan-2-ol (14). Compound 13 (110 mg,
0.25 mmol) was dissolved in CH2Cl2 (2.5 mL) under argon. After
being cooled to 0 °C, the solution was treated with the Dess-
Martin periodinane reagent (162 mg, 0.37 mmol) and stirring
continued for 5 h allowing the reaction to reach room temperature.
EtOAc (30 mL) was added, and the combined organic solution was
washed with cold, aqueous NaHCO3, cold 10% aqueous Na2S2O3,
and brine. After drying (MgSO4), the filtrate was evaporated in
vacuo. The residue coevaporated two times with anhydrous
toluene and once with anhydrous THF. Finally, under argon
at -78 °C, the residue was treated with 1 M L-selectride in THF
(280 μL, 0.280 mmol) for 10 min and quenched with acetone
(1 mL) followed by aqueous NH4Cl (3 mL). The mixture was
extracted with EtOAc (30 mL), and the organic extract was washed
with brine, dried (MgSO4), filtered and evaporated in vacuo. The
crude material was purified by column chromatography on silica
gel eluted with hexane/EtOAc (100:0 f 0:100%, v/v) to give
compound 14 (103 mg, 94%) as a white solid: mp 173 °C-174
°C; [R]21D= 52.7° (c 1.14, CHCl3); 1H NMR (CDCl3) δ 8.84 (s, 1
H, H-2), 8.53 (s, 1 H, H-8), 5.07 (d, J=8.0 Hz, 1 H, H-40), 4.43 (d,
J=5.5 Hz, 1 H, H-20), 4.36 (br s, 1 H, OH-20), 2.27-2.35 (m, 1 H,
H-30b), 1.98 (d, J=16.3 Hz, 1 H, H-30a), 1.91 (dt, J=8.9, 4.5 Hz,
1 H, H-10), 1.68 (dt, J=8.4, 4.2 Hz, 1 H, H-50), 1.46 (s, 18 H,
1
CHCl3); IR (neat) 2251 cm-1; H NMR (CDCl3, 400 MHz) δ
5.83-5.73 (m, 1 H, H-5), 5.18-5.23 (m, 2 H, H-6a, H-6b), 3.97
(td, J=12.1, 5.4 Hz, 1 H, H-3), 2.55 (dd, J=16.7, 5.1 Hz, 1 H,
H-2b), 2.47 (dd, J=16.7, 6.3 Hz, 1 H, H-2a), 2.45-2.31 (m, 3 H,
OH-3, H-4a, H-4b); 13C NMR (CDCl3, 100 MHz) δ 132.4,
119.9, 117.4, 66.7, 40.8, 21.2. Anal. Calcd for C6H9NO 0.1H2O:
3
C, 63.81; H, 8.21; N, 12.40. Found: C, 63.87; H, 8.10; N, 12.32.
(R)-N,N-Dibenzyl-3-hydroxyhex-5-enamide (18). Compound
17 (3.0 g, 27.0 mmol) was dissolved in a mixture of 25% aqueous
NaOH (50 mL) and MeOH (50 mL). The solution was stirred for
24 h at 90 °C, cooled to room temperature, and neutralized with
concentrated HCl. The solution was extracted with EtOAc (2 ꢀ
200 mL), and the organic phase was dried (MgSO4), filtered, and
evaporated in vacuo. The residue was dissolved in anhydrous DMF
(140 mL) and treated with dibenzylamine (Bn2NH, 6.4 mL, 32.4
mmol), hydroxybenzotriazole (HOBT, 4.4 g, 32.6 mmol), and N-(3-
dimethylaminopropyl)-N-ethylcarbodiimide hydrochloride (10.4 g,
54.2 mmol) at 0 °C. After room temperature was reached, stirring
was continued for 16 h before all the volatiles were removed in
vacuo. The residue was dissolved in EtOAc (250 mL), washed with
7666 J. Org. Chem. Vol. 75, No. 22, 2010

Saneyoshi et al.
JOCArticle
brine, dried (MgSO4), filtered, and evaporated in vacuo. The crude
product obtained was purified by column chromatography on silica
gel eluted with hexane/EtOAc (100:0 f 70:30, v/v) to give 18 (5.4 g,
65%) as a solid: mp 57-58 °C; [R]20D=-43.4 (c 0.45, CHCl3); 1H
NMR (CDCl3, 400 MHz) δ 7.40-7.13 (m, 10 H, PhH), 5.87-5.77
(m, 1 H, H-5), 5.12-5.05 (m, 2 H, H-6a, H-6b), 4.67 (d, J=14.2 Hz,
1 H, PhCHH), 4.53 (1H, d, J=14.8 Hz, 1 H, PhCHH), 4.38 (AB q,
J=17.0 Hz, 2 H, PhCH2), 4.21-4.15 (m, 1 H, H-3), 2.60 (dd, J=
16.4, 2.6 Hz, 1 H, H-2b), 2.43 (dd, J=16.4, 9.3 Hz, 1 H, H-2a),
2.31-2.38 (m, 1 H, H-4b), 2.27-2.20 (m, 1 H, H-4a); 13C NMR
(CDCl3, 100 MHz) δ 173.0, 136.7, 135.8, 134.3, 128.9, 128.5, 128.0,
127.6, 127.4, 126.3, 117.4, 67.7, 49.7, 47.9, 40.7, 38.5; FAB-MS m/z
(relative intensity) 310.2 (MHþ, 83.2(. Anal. Calcd for C20H23NO2:
C, 77.64; H, 7.49; N, 4.53. Found: C, 77.59; H, 7.34; N, 4.56.
(R)-N,N-Dibenzyl-3-(methoxymethoxy)hex-5-enamide (19).
Under a blanket of argon and over a cooling bath at 0 °C,
compound 18 (560 mg, 1.8 mmol) was dissolved in CH2Cl2
(5 mL) and treated with diisopropylethylamine (617 μL, 4.5
mmol) and methyl chloromethyl ether (MOMCl, 150 μL, 2.0
mmol). The mixture was allowed to reach room temperature
and stirred for 16 h. The reaction was diluted with Et2O
(100 mL) and washed with brine and aqueous NaHCO3. The ether
layer was dried (MgSO4), filtered, and evaporated in vacuo.
The residue was purified by column chromatography on silica
gel eluted with hexane/EtOAc (100:0 f 75:25, v/v) to give 19
(629 mg, 99%) as an oil: [R]22D=5.3 (c 0.65, CHCl3); 1H NMR
(CDCl3, 400 MHz) δ 7.38-7.16 (m, 10 H, PhH), 5.87-5.77 (m,
1 H, H-50), 5.10-5.01 (m, 2 H, H-60a, H-60b), 4.74-4.65 (m,
3 H, PhCH2, OCHHOCH3), 4.57-4.39 (m, 3 H, PhCH2,
OCHHOCH3), 4.33-4.27 (m, 1 H, H-3), 2.71 (dd, J = 15.4,
7.5 Hz, 1 H, H-2b), 2.48 (dd, J = 15.4, 5.2 Hz, 1 H, H-2a),
2.47-2.37 (m, 2 H, H-4a, H-4b); 13C NMR (CDCl3, 100 MHz) δ
171.4, 137.3, 136.5, 134.1, 128.9, 128.5, 128.2, 127.6, 127.3, 126.5,
117.7, 96.4, 75.0, 55.6, 50.0, 48.2, 39.4, 38.2; FAB-MS m/z (rela-
tive intensity) 354.2 (MHþ, 22.2). Anal. Calcd for C22H27NO3: C,
74.76; H, 7.70; N, 3.96. Found: C, 74.58; H, 7.64; N, 3.92.
(1S,3R,5S)-1-(Dibenzylamino)bicyclo[3.1.0]hexan-3-ol (20) and
(1R,3R,5R)-1-(Dibenzylamino)bicyclo[3.1.0]hexan-3-ol (21). Com-
pound 19 (500 mg, 1.4 mmol) was dissolved in THF (5 mL) and
treated with Ti(O-i-Pr)4 (405 μL, 1.4 mmol) followed by 2 M
i-PrMgCl/THF (2.8 mL, 5.6 mmol) at room temperature. After
1 h, the reaction was quenched with aqueous NH4Cl (1 mL) and
diluted with EtOAc (100 mL). The entire mixture was filtered
through a Celite pad and washed with aqueous NaHCO3 and
brine. The organic phase was dried (MgSO4), filtered, and evapo-
rated in vacuo. The residue was dissolved in 3% HCl/MeOH (20
mL) and stirred at 60 °C for 4 h. After all of the volatiles were
removed in vacuo, the residue was diluted with EtOAc (200 mL)
and neutralized with aqueous NaHCO3 (5 mL). The organic phase
was washed with brine, dried (MgSO4), filtered, and evaporated in
vacuo. The crude product was purified by column chromatogra-
phy on silica gel eluted with hexane/EtOAc (100:0 f 80:20, v/v) to
give 20 (195 mg, 47%) as a white solid, mp 120-121 °C, and isomer
21 (127 mg, 31%) also as a white solid.
(m, 1 H, H-3), 3.76 (d, J=13.4 Hz, 2 H, PhCH2), 3.68 (d, J=
13.4 Hz, 2 H, PhCH2), 2.12 (dd, J=12.0, 7.2 Hz, 1 H, H-2b), 1.98
(ddd, J=12.0, 8.0, 1.6 Hz, 1 H, H-2a), 1.85 (dd, J=12.3, 7.1 Hz,
1 H, H-4b), 1.31 (ddd, J=12.8, 8.4, 4.8 Hz, 1 H, H-4a), 1.26 (d,
J=5.3 Hz, 1 H, OH), 0.87 (dt, J=9.0, 4.6 Hz, 1 H, H-5), 0.40 (ddd,
J=8.7, 4.9, 1.1 Hz, 1 H, H-6b), 0.18 (pseudo t, J ≈ 4.7 Hz, 1 H,
H-6a); 13C NMR (CDCl3, 100 MHz) δ 140.1, 129.0, 127.9, 126.7,
70.8, 56.9, 49.3, 36.2, 32.9, 24.4, 18.3; FAB-MS m/z (relative
intensity) 294.2 (MHþ, 28.2). Anal. Calcd for C20H23NO: C,
81.87; H, 7.90; N, 4.77. Found: C, 81.84; H, 7.87; N, 4.84.
(1S,3S,5S )-1-(Dibenzylamino)bicyclo[3.1.0]hexan-3-yl Benzo-
ate (22). A mixture of compound 20 (403 mg, 1.4 mmol), benzoic
acid (418 mg, 3.4 mmol), and PPh3 (898 mg, 3.42 mmol) was
dissolvedinTHF(14mL). After beingcooledto0°C, the solution
was treatedwithDIAD(700 μL, 3.4mmol) andstirred for 30 min.
The solventwas evaporatedinvacuo, andthe residue was purified
by column chromatography on silica gel eluted with hexane/
EtOAc (100:0 f 90:10, v/v) to give 22 (514 mg, 94%) as a
1
white solid: mp 88-89 °C; [R]20D=-42.7 (c 0.71, CHCl3); H
NMR (CDCl3, 400 MHz) δ 8.06-8.04 (m, 2 H, PhH), 7.60-7.21
(m, 13 H, PhH), 4.90 (quintet, J=7.7 Hz, 1 H, H-3), 3.79 (d, J=
13.3 Hz, 2 H, PhCH2), 3.71 (d, J=13.3, Hz, PhCH2), 2.37 (dd,
J=12.4, 7.5 Hz, 1 H, H-2b), 2.20 (ddd, J=12.3, 7.8, 1.6 Hz, 1 H,
H-2a), 2.04 (dd, J=12.6, 7.4 Hz, 1 H, H-4b), 1.66 (ddd, J=12.8,
8.2, 4.9 Hz, 1 H, H-4a), 0.97 (dt, J=9.0, 4.6 Hz, 1 H, H-5), 0.51
(distorted dd, J=8.6, 4.8 Hz, 1 H, H-6b), 0.31 (t, J=4.8 Hz, 1 H,
H-6a); 13C NMR (CDCl3, 100 MHz) δ 166.2, 140.0, 132.9, 130.4,
129.5, 129.0, 128.3, 128.0, 126.8, 73.9, 57.0, 49.4, 33.0, 30.0, 24.0,
18.9; FAB-MS m/z (relative intensity) 398.2 (MHþ, 38.2). Anal.
Calcd for C27H27NO2: C, 81.58; H, 6.85; N, 3.52. Found: C,
81.50; H, 6.91; N, 3.43.
(1S,3S,5S )-1-Aminobicyclo[3.1.0]hexan-3-yl Benzoate Hydro-
chloride (23). Compound 22 (320 mg, 0.8 mmol) was dissolved in
EtOAc-MeOH (8 mL, 1:1, v/v) and treated with 2 M HCl/Et2O
(1.2 mL, 2.4 mmol) under argon. After the addition of 10 wt %
Pd/C (500 mg), the argon atmosphere was replaced with H2 gas
and the mixture was stirred at room temperature for 20 h. The
mixture was filtered through Celite, and the filtrate was evapo-
rated in vacuo to give compound 23 (198 mg, 97%) as a brown
solid: mp 212 °C dec; [R]21D=-11.4 (c 0.45, MeOH); 1H NMR
(CD3OD, 400 MHz) δ 8.02-7.98 (m, 2 H, PhH), 7.62-7.44 (m, 3
H, PhH), 4.99 (quintet, J=7.7 Hz, 1 H, H-3), 2.76 (dd, J=12.3,
7.3 Hz, 1 H, H-2b), 2.36 (dd, J = 12.9, 7.4 Hz, 1 H, H-4b),
2.27-2.14 (m, 2 H, H-2a, H-4a), 1.84 (dt, J=9.4, 4.7 Hz, 1 H,
H-5), 1.08 (pseudo t, J ≈ 7.8 Hz, 1 H, H-6b), 0.87 (distorted dd,
J=6.6, 4.7 Hz, 1 H, H-6a); 13C NMR (CD3OD, 100 MHz) δ
167.3, 134.5, 131.0, 130.5, 129.6, 73.7, 39.6, 36.8, 33.7, 21.2, 14.5;
FAB-MS m/z (relative intensity) 218.2 (MHþ, 100). Anal. Calcd
for C13H16ClNO2 0.5H2O: C, 59.43; H, 6.52; N, 5.33. Found: C,
3
59.45; H, 6.35; N, 5.40.
(10S,30S,50S )-1-(6-Chloro-9H-purin-9-yl)bicyclo[3.1.0]hexan-
3-yl Benzoate (25). A solution of compound 23 (100 mg, 0.39
mmol) and N-(4,6-dichloropyrimidin-5-yl)formimidic acid
(79 mg, 0.41 mmol) in 1,4-dioxane (2 mL) was treated with
i-Pr2NEt (217 μL, 1.6 mmol) and heated in a microwave reactor
at 100 °C for 20 min. The mixture was evaporated in vacuo, and
the residue was extracted with EtOAc (50 mL), washed with
brine, dried (MgSO4), filtered, and evaporated in vacuo. The
crude 24 was then dissolved in diethoxymethyl acetate (2 mL)
and heated in a microwave reactor at 120 °C for 120 min. After
the volatiles were removed in vacuo, the residue was purified by
column chromatography on silica gel eluted with hexane/
EtOAc (100:0 f 60:40, v/v) to give 25 (113 mg, 81%) as a white
solid: 92-93 °C; [R]21D = -35.4 (c 0.30, CHCl3); 1H NMR
(CDCl3, 400 MHz) δ 8.78 (s, 1 H, H-2), 8.19 (1s, 1 H, H-8),
8.04-8.01 (m, 2 H, PhH), 7.58-7.41 (m, 3 H, PhH), 5.11
(quintet, J=7.8 Hz, 1 H, H-30), 2.94 (dd, J=12.5, 7.2 Hz, 1
H, H-20b), 2.59-2.46 (m, 3 H, H-20a, H-40a, H-40b), 2.17-2.13
Isomer 20: [R]20D=-18.4 (c 0.20, CHCl3); 1H NMR (CDCl3,
400 MHz) δ 7.31-7.18 (10H, m, PhH), 4.35 (distorted t, J=
6.4 Hz, 1 H, H-3), 3.77 (d, J=13.4 Hz, 2 H, PhCH2), 3.62 (d, J=
13.4 Hz, 2 H, PhCH2), 2.40 (ddd, J=13.8, 6.9, 2.2 Hz, 1 H,
H-2a), 2.48 (dt, J=14.0, 5.7 Hz, 1 H, H-4a), 1.66 (d, J=13.9 Hz,
1 H, H-2b), 1.36 (d, J=14.1 Hz, 1 H, H-4b), 1.10 (d, J=2.8 Hz,
1 H, OH), 0.91-0.86 (dt, J=9.2, 4.8 Hz, 1 H, H-5), 0.74 (pseudo
t, J ≈ 4.40 Hz, 1 H, H-6b), 0.68-0.64 (m, 1 H, H-6a); 13C NMR
(CDCl3, 100 MHz) δ 140.2, 129.0, 127.9, 126.7, 72.8, 56.9, 52.0,
37.8, 34.3, 26.4, 21.1; FAB-MS m/z (relative intensity) 294.2
(MHþ, 50.2). Anal. Calcd for C20H23NO: C, 81.87; H, 7.90; N,
4.77. Found: C, 81.70; H, 7.89; N, 4.78.
Isomer 21: mp 93 °C; [R]20D=2.4 (c 0.555, CHCl3); 1H NMR
(CDCl3, 400 MHz) δ 7.52-7.19 (m, 10 H, PhH), 3.93-3.84
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Saneyoshi et al.
JOCArticle
(m, 1 H, H-50), 1.35 (m, 1 H, H-60b), 1.24 (dd, J=6.5, 5.1 Hz,
1 H, H-60a); 13C NMR (CDCl3, 100 MHz) δ 166.0, 152.2, 152.4,
151.2, 145.6, 133.2, 131.9, 129.6, 128.4, 72.4, 40.8, 38.2, 32.9,
21.9, 16.6; FAB-MS m/z (relative intensity) 355.1 (MHþ, 100).
Anal. Calcd for C18H15ClN4O2: C, 60.94; H, 4.26; N, 15.79.
Found: C, 60.91; H, 4.35; N, 15.83.
(m, 6 H, (CH3CH2O)2P), 1.26-1.21 (m, 1 H, H-60a), 1.02(pseudo
t, 1 H, J ≈ 5.5 Hz, H-60b); 13C NMR (CDCl3, 100 MHz) δ 158.2,
154.1, 152.4, 149.7, 145.4, 139.9, 137.5, 130.0, 128.7, 127.8, 126.7,
121.0, 113.0, 80.0 (JCP=12.7 Hz), 70.5, 63.1 (JCP=168.2), 62.5
(JCP=2.5 Hz), 62.4(JCP=2.5 Hz), 55.1, 40.3, 38.8, 33.1, 16.8, 16.4
(JCP =5.6 Hz); FAB-MS m/z (relative intensity) 684.3 (MHþ,
(10S,30S,50S )-1-(6-Amino-9H-purin-9-yl)bicyclo[3.1.0]hexan-
3-ol (26). Compound 25 (80 mg, 0.23 mmol) was dissolved in
mixture of dioxane and 28% NH4OH (4 mL, 1:1, v/v) and heated
in a microwave reactor at 100 °C for 40 min. After the volatiles
were removed in vacuo, the residue was purified by column
chromatography on silica gel eluted with EtOAc-CHCl3-
MeOH (100:0:0 f 0:90:10, v/v) to give 26 (50 mg, 96%) as a
white solid. An analytical sample was recrystallized from EtOH:
mp 191 °C; [R]20D=-53.6 (c 0.415, MeOH); 1H NMR (CD3OD,
400 MHz) δ 8.23(s, 1 H, H-2), 8.17 (s, 1 H, H-8), 4.05 (quintet, J=
7.3 Hz, 1 H, H-30), 2.62 (dd, J = 12.7, 6.7 Hz, 1 H, H-20b),
2.24-2.09 (m, 3 H, H-20a, H-40a, H-40b), 2.03-1.99 (m, 1 H,
H-50), 1.27-1.22 (m, 1 H, H-60b), 1.10 (pseudo t, J ≈ 5.6 Hz, 1 H,
H-60a); 13C NMR (CD3OD, 100 MHz) δ 157.4, 153.7, 151.4,
143.0, 120.4, 71.7, 42.5, 42.2, 37.0, 23.3, 18.0; FAB-MS m/z (rela-
20.6). Anal. Calcd for C11H13N5O 0.7H2O: C, 63.82; H, 6.28; N,
3
10.06. Found: C, 63.82; H, 6.24; N, 9.87.
((10S,30S,50S )-1-(6-Amino-9H-purin-9-yl)bicyclo[3.1.0]hexan-
3-yloxy)methylphosphonic Acid Sodium Salt (3). Compound 28
(43 mg, 63 μmol) was dissolved in CH3CN (1 mL) and treated
with trimethylsilyl bromide (41 μL, 0.32 mmol) under argon.
The mixture was stirred at room temperature for 2 days and
quenched with triethylammonium bicarbonate buffer (TEAB,
3 mL). The CH3CN in the mixture was evaporated in vacuo, and
the residue was washed with EtOAc. The aqueous phase was
evaporated in vacuo and coevaporated with EtOH, and the
crude obtained was purified with a C-18 column (1.5 cm ꢀ 4 cm)
eluted with 0.1 M TEAB-CH3CN (100:0 f 90:10). The pro-
duct-containing fractions were coevaporated with EtOH and
lyophilized. The compound was then passed through a DOW-
EX (Naþ) column to give compound 3 (16 mg, 70%) as the
sodium salt: [R]20D = -43.4 (c 0.51, H2O); 1H NMR (D2O,
400 MHz) δ 8.24 (s, 1 H, H-2), 8.23 (s, 1 H, H-8), 3.96 (quintet, 1 H,
J=7.6 Hz, H-30), 3.60-3.51 (m, 2 H, PCH2O), 2.80 (dd, 1 H, J=
1 H, 12.2, 6.9 Hz, H-20a), 2.34 (dd, J=12.6, 7.1 Hz, 1 H, H-40a),
2.23-2.01 (m, 3 H, H-20b, H-40b, H-50), 1.31 (distorted dd, 1 H,
J=8.5, 6.5Hz, H-60a), 1.10(pseudot, 1 H, J ≈ 5.6Hz, H-60b); 13C
NMR (D2O, 100 MHz) δ 154.8, 151.8, 149.0, 142.5, 118.0, 79.1
(JCP=11.9 Hz), 65.4 (JCP=155.5 Hz), 39.8, 37.7, 32.2, 21.1, 15.3;
31P NMR (D2O, 100 MHz) δ 14.9; FAB-MS m/z (relative inten-
sity) 324.1 (MH-, 100); HRMS (FAB) calc for (C12H15N5O4P)
324.0867 (MH-), found 324.0851.
tive intensity) 232.1 (MHþ, 18.2). Anal. Calcd for C11H13N5O
3
0.7H2O: C, 54.18; H, 5.95; N, 28.72. Found: C, 54.16; H, 5.89;
N, 28.88.
(10S,30S,50S)-1-(6-(Bis(4-methoxyphenyl)(phenyl)methylamino)-
9H-purin-9-yl)bicyclo[3.1.0]hexan-3-ol (27). Compound 26 (150
mg, 0.65 mmol) was coevaporated four times with pyridine, dried
in vacuo overnight and dissolved in anhydrous pyridine (3.2 mL).
The solution was treated with (CH3)3SiCl (247 μL, 1.9 mmol), and
after 30 min of stirring it was treated with 4,40-dimethoxytrityl
chloride (242 mg, 0.68 mmol). After 1 day, the reaction was
quenched with H2O (1 mL) and evaporated in vacuo. The residue
was extracted with EtOAc (50 mL) and washed with brine, aqueous
NaHCO3, and brine. The organic phase was dried (MgSO4),
filtered, and evaporated in vacuo, and the residue was purified by
column chromatography on silica gel eluted with CHCl3/MeOH
(99:1 f 98:2, v/v, 0.5% Et3N) to give 27 (300 mg, 87%) as a white
foam: [R]20D=-26.6 (c0.34, CHCl3);1H NMR(CDCl3, 400 MHz)
δ 8.02 (s, 1 H, H-2), 7.76 (s, 1 H, H-8), 7.34-7.21 (m, 9 H, PhH),
6.95 (br, 1 H, NHDMTr), 6.80-6.76 (m, 4 H, PhH), 6.13 (br s,
1 H, OH-30), 4.24 (br s, 1 H, H-30), 2.39-2.35 (m, 1 H, H-20b),
2.27 (dd, J=14.3, 4.6 Hz, 1 H, H-40b), 2.20 (distorted dd, J=
14.4, 1.2 Hz, 1 H, H-20a), 1.95-1.88 (m, 1 H, H-50), 1.76-1.70
(m, 2 H, H-40a, H-60b), 0.95 (t, J=5.3 Hz, 1 H, H-60a); 13C
NMR (CDCl3, 100 MHz) δ 158.2, 154.2, 151.8, 148.9, 145.2,
139.8, 137.3, 130.0, 128.7, 127.8, 126.8, 121.2, 113.1, 70.6,
55.2, 45.3, 43.7, 40.3, 25.5, 25.1; FAB-MS m/z (relative inteþn-
(1R,3R,5R)-1-(Dibenzylamino)bicyclo[3.1.0]hexan-3-yl benzoate
(29): yield 89%; the spectral data were identical to those of the
enantiomeric compound 22; [R]21D=42.8 (c 1.06, CHCl3).
(1R,3R,5R)-1-Aminobicyclo[3.1.0]hexan-3-yl benzoate hydro-
chloride (30): yield 93%; the spectral data were identical to those
of the enantiomeric compound 23; [R]20D=10.9 (c 1.17, MeOH).
(10R,30R,50R)-1-(6-Chloro-9H-purin-9-yl)bicyclo[3.1.0]hexan-
3-yl benzoate (32): yield 82%; the spectral data were identical to
that of the enantiomeric compound 25; [R]20D =34.7 (c 1.21,
CHCl3).
(10R,30R,50R)-1-(6-Amino-9H-purin-9-yl)bicyclo[3.1.0]hexan-
3-ol (33): yield 95%; the spectral data were identical to those of
the enantiomeric compound 26; [R]21D=54.0 (c 0.40, MeOH).
(10R,30R,50R)-1-(6-(Bis(4-methoxyphenyl)(phenyl)methylamino)-
9H-purin-9-yl)bicyclo[3.1.0]hexan-3-ol (34): yield 88%; the spectral
data were identical to those of the enantiomeric compound 27;
[R]20D=25.4 (c 0.34, CHCl3).
sity) 534.2 (MHþ, 16.8%); HRMS (FAB) calc for (C32H32N5O3
534.2500 (MHþ), found 534.2534.
)
Diethyl ((10S,30S,50S )-1-(6-(Bis(4-methoxyphenyl)(phenyl)-
methylamino)-9H-purin-9-yl)bicyclo[3.1.0]hexan-3-yloxy)methyl-
phosphonate (28). Compound 27 (54 mg, 0.10 mmol) was dis-
solved in THF (0.5 mL) under argon and treated with 1 M
LHMDS (111 μL) at room temperature. The mixture was stirred
for 5 min and treated with diethyl [(trifluoromethanesulfonyl)-
oxy]methanephosphonate (33 mg, 0.10 mmol) dissolved in THF
(1 mL). After 25 min, the reaction was quenched with aqueous
NaHCO3 (1 mL) and diluted with CHCl3 (50 mL). The organic
phase was separated, dried (MgSO4), filtered, and evaporated in
vacuo. The residue was purified by column chromatography on
silica gel eluted with EtOAc-CHCl3-MeOH (100:0:0 f 0:99:1,
v/v, 0.5% Et3N) to give 28 (60 mg, 87%) as an oil: [R]20D=-26.7
(c 0.45, CHCl3);1H NMR(CDCl3, 400 MHz) δ 8.11 (s, 1 H, H-2),
7.78 (s, 1 H, H-8), 7.34-7.20 (m, 9 H, PhH), 6.85 (br s, 1 H,
NHDMT), 6.80-6.77 (m, 4 H, PhH), 3.84 (quintet, 1 H, J=7.4
Hz, H-30), 3.77 (s, 6 H, [(OCH3)Ph]2), 3.74-3.67 (m, 2 H,
PCH2O), 2.76 (dd, 1 H, J=12.3, 6.8 Hz, H-20a), 2.32-2.20 (m,
3 H, H-20b, H-40a, H-40b), 2.01-1.97 (m, 1 H, H-50), 1.35-1.31
Diethyl ((10R,30R,50R)-1-(6-(Bis(4-methoxyphenyl)(phenyl)-
methylamino)-9H-purin-9-yl)bicyclo[3.1.0]hexan-3-yloxy)methyl-
phosphonate (35): yield 84%; the spectral data were identical to
those of the enantiomeric compound 28; [R]20D =25.5 (c 0.30,
CHCl3).
((10R,30R,50R)-1-(6-Amino-9H-purin-9-yl)bicyclo[3.1.0]hexan-
3-yloxy)methylphosphonic acid sodium salt (ent-3): yield 70%; the
spectral data were identical to those of the enantiomeric com-
pound 3; [R]21D=43.1 (c 0.51, H2O).
Synthesis of dDiphosphates. The diphosphates 2-DP, 3-DP,
and ent-3-DP were custom-made from the corresponding phos-
phonate acids by TriLink BioTechnologies, San Diego, CA,
following the procedure of Herdewijn et al.1
((10R,20R,40S,50S )-4-(6-Amino-9H-purin-9-yl)bicyclo[3.1.0]-
hexan-2-yloxy)methylphosphonic diphosphoric anhydride lithium
salt (2-DP): >94% purity by AX-HPLC; the 1H NMR spectrum
was identical to that of 2; 31P NMR (D2O) δ -21.91, -9.64,
10.22; ESI-MS m/z 483.9 (MH-).
7668 J. Org. Chem. Vol. 75, No. 22, 2010

Saneyoshi et al.
JOCArticle
((10S,30S,50S )-1-(6-Amino-9H-purin-9-yl)bicyclo[3.1.0]hexan-
3-yloxy)methylphosphonic diphosphoric anhydride (free acid, 3-DP):
>96.8% purity by AX-HPLC; the 1H NMR spectrum was iden-
tical to that of 3; 31P NMR (D2O) δ -19.82, -4.50, 9.51; ESI-MS
m/z 491.2 (MH- þ Li), 497.2 (MH- þ Li2).
c=10.584(2) A, and β=108.523(5)°. Data were 97.8% complete
˚
˚
to 29.60° θ (approximately 0.73 A) with an average redundancy
of 4.07. (-)-26 crystallized with two molecules in the asymmetric
unit plus three molecules of solvent (water). One molecule was
disordered over two positions with a ratio of approximately
60:40, and one water molecule sits on a special position resulting
is disorder of the solvent.
((10R,30R,50R)-1-(6-Amino-9H-purin-9-yl)bicyclo[3.1.0]hexan-
3-yloxy)methylphosphonic diphosphoric anhydride (free acid, ent-
3-DP): >88.3% purity by AX-HPLC; the 1H NMR spectrum was
identical to that of 3 and ent-3; 31P NMR (D2O) δ -22.53, -4.50,
9.46; ESI-MS m/z 484.9 (MH-).
Atomic coordinates for compounds (-)-9 and (-)-26 have
been deposited with the Cambridge Crystallographic Data
Centre (deposition nos. 794726 and 794727).
X-ray Crystal Structure of (-)-9 and (-)-26. Single-crystal X-ray
diffraction data on compounds (-)-9 and (-)-26 were collected at
93 and 144 K, respectively, using MoKR radiation and a Bruker
APEX 2 CCD area detector. Crystals were prepared for data col-
lection by coating with high viscosity microscope oil (Paratone-N,
Hampton Research). The oil-coated crystal was mounted on a glass
rod and transferred immediately to the cold stream on the diffrac-
tometer. Corrections were applied for Lorentz, polarization, and
absorption effects. The structures were solved by direct methods and
refined by full-matrix least-squares on F2 values using the programs
found in the SHELXTL suite (Bruker, SHELXTL v6.10, 2000,
Bruker AXS Inc., Madison, WI). Parameters refined included
atomic coordinates and anisotropic thermal parameters for all
non-hydrogen atoms. Hydrogen atoms on carbons were included
using a riding model (coordinate shifts of C applied to H atoms)]
Copies of the data can be obtained, free of charge, on
application to CCDC, 12 Union Road, Cambridge, CB2 1EZ,
UK (fax: þ44(0)-1223-336033 or e-mail: deposit@ccdc.cam.
ac.uk).
Acknowledgment. We express their gratitude to Drs. Stephen
H. Hughes, Paul Boyer, and B. Christie Vu of the HIV Drug
Resistant Program at NCI for the biological testing. The advice
and help of Dr. Stefan G. Sarafianos of the Department of
Microbiology at the University of Missouri;Columbia is also
appreciated. This research was supported by the Intramural
Research Program of the NIH, National Cancer Institute, Center
for Cancer Research.
Supporting Information Available: 1H and 13C NMR spec-
tra of new compounds; complete crystallographic data on com-
pounds (-)-9 and (-)-26, including crystal data and structure
refinement, atomic coordinates, bond lengths and angles, aniso-
tropic displacement parameters, hydrogen coordinates and iso-
tropic displacement parameters, torsion angles, and hydrogen
bonds (Tables 1-14); corresponding X-ray data (CIF). This
material is available free of charge via the Internet at http://
pubs.acs.org.
˚
with C-H distance set at 0.96 A. The absolute configuration was set
on the basis of the known configuration of the starting material.
The crystal of (-)-9 was orthorhombic in space group P212121
with unit cell dimensions a=6.6440(5) A, b=7.6383(5) A, and c=
˚
˚
˚
21.5272(15) A. Data were 98.7% complete to 29.19° θ (approxi-
˚
mately 0.73 A) with an average redundancy of 7.02. (-)-9 crystal-
lized with a single molecule in the asymmetric unit.
The crystal of (-)-26 was monoclinic in space group C2
with unit cell dimensions a = 29.496(6) A, b = 8.2267(18) A,
˚
˚
J. Org. Chem. Vol. 75, No. 22, 2010 7669