Spiropentane Mimics of Nucleosides: Analogues of 2′-Deoxyadenosine and 2′-Deoxyguanosine. Synthesis of All Stereoisomers, Isomeric Assignment, and Biological Activity

Article abstract of DOI:10.1021/jo991030r

Synthesis of spirocyclic analogues of 2′-deoxyadenosine and 2′-deoxyguanosine (12a-15a and 12b-15b) is described. Rhodium-catalyzed reaction of ethyl diazoacetate with methylenecyclopropane 19, obtained from 2-bromo-2-bromomethylcyclopropane 17 via debromination (16), reduction (18), and acetylation (19), gave a mixture of all four isomeric spiropentanes 20a-20d. Hydrolysis afforded hydroxy carboxylic acids 21a-21d. Acetylation of separated proximal + medial-syn isomers 21a + 21b and medial anti + distal isomers 21c + 21d furnished acetates 22a + 22b and 22c + 22d. Curtius rearrangement effected by diphenylphosphoryl azide in tert-butyl alcohol performed separately with mixtures 22a + 22b and 22c + 22d led to BOC-amino spiropentanes 23a + 23b and 23c + 23d. After deacetylation all isomers 24a-24d were separated and deprotected to give aminospiropentane hydrochlorides 25a-25d. Free bases were of limited stability. The heterocyclic moieties were introduced into individual isomers 25a-25d via 6-chloropurine derivatives 26a-26d or 30a-30d. Ammonolysis of 26a-26d furnished the adenine isomeric series 12a-15a, whereas guanine derivatives 12b-15b were obtained by hydrolysis of 30a-30d with formic acid. The isomeric assignments followed from IR spectra of BOC-aminospiropentanes 24a-24d and NMR spectra of 12a-15a including NOE and (H,H) COSY. The proximal and medial-syn isomers 12a and 12b were modest inhibitors of human cytomegalovirus (HCMV) and Epstein-Barr virus (EBV) in culture, whereas the medial-anti isomer 12c was a substrate for adenosine deaminase. The distal isomer 15b was an anti-EBV agent. The medial-syn phosphoralaninate 34 was an effective inhibitor of HCMV replication in vitro. It was also active against herpes simplex virus type 1 (HSV-1), varicella zoster virus (VZV), human immunodeficiency virus (HIV-1), hepatitis B virus (HBV), and EBV with a varying degree of cytotoxicity.

Full text of DOI:10.1021/jo991030r

1280
J . Org. Chem. 2000, 65, 1280-1290
Sp ir op en ta n e Mim ics of Nu cleosid es: An a logu es of
2′-Deoxya d en osin e a n d 2′-Deoxygu a n osin e. Syn th esis of All
Ster eoisom er s, Isom er ic Assign m en t, a n d Biologica l Activity
Hui-Ping Guan,† Mohamad B. Ksebati,‡ Yung-Chi Cheng,§ J ohn C. Drach, Earl R. Kern,| and
J iri Zemlicka*,†
Department of Chemistry, Experimental and Clinical Chemotherapy Program, Barbara Ann Karmanos
Cancer Institute, Wayne State University School of Medicine, 110 East Warren Avenue,
Detroit, Michigan 48201-1379, Central Instrumentation Facility, Department of Chemistry, Wayne State
University, Detroit, Michigan 48202, Department of Pharmacology, Yale University School of Medicine,
New Haven, Connecticut 06510-8066, Department of Biologic and Materials Sciences, School of Dentistry,
University of Michigan, Ann Arbor, Michigan 48019-1078, and Department of Pediatrics, The University
of Alabama at Birmingham, Birmingham, Alabama 35294
Received J une 28, 1999
Synthesis of spirocyclic analogues of 2′-deoxyadenosine and 2′-deoxyguanosine (12a -15a and 12b-
15b) is described. Rhodium-catalyzed reaction of ethyl diazoacetate with methylenecyclopropane
19, obtained from 2-bromo-2-bromomethylcyclopropane 17 via debromination (16), reduction (18),
and acetylation (19), gave a mixture of all four isomeric spiropentanes 20a -20d . Hydrolysis afforded
hydroxy carboxylic acids 21a -21d . Acetylation of separated proximal + medial-syn isomers 21a +
21b and medial anti + distal isomers 21c + 21d furnished acetates 22a + 22b and 22c + 22d .
Curtius rearrangement effected by diphenylphosphoryl azide in tert-butyl alcohol performed
separately with mixtures 22a + 22b and 22c + 22d led to BOC-amino spiropentanes 23a + 23b
and 23c + 23d . After deacetylation all isomers 24a -24d were separated and deprotected to give
aminospiropentane hydrochlorides 25a -25d . Free bases were of limited stability. The heterocyclic
moieties were introduced into individual isomers 25a -25d via 6-chloropurine derivatives 26a -
26d or 30a -30d . Ammonolysis of 26a -26d furnished the adenine isomeric series 12a -15a , whereas
guanine derivatives 12b-15b were obtained by hydrolysis of 30a -30d with formic acid. The
isomeric assignments followed from IR spectra of BOC-aminospiropentanes 24a -24d and NMR
spectra of 12a -15a including NOE and (H,H) COSY. The proximal and medial-syn isomers 12a
and 12b were modest inhibitors of human cytomegalovirus (HCMV) and Epstein-Barr virus (EBV)
in culture, whereas the medial-anti isomer 12c was a substrate for adenosine deaminase. The distal
isomer 15b was an anti-EBV agent. The medial-syn phosphoralaninate 34 was an effective inhibitor
of HCMV replication in vitro. It was also active against herpes simplex virus type 1 (HSV-1),
varicella zoster virus (VZV), human immunodeficiency virus (HIV-1), hepatitis B virus (HBV), and
EBV with a varying degree of cytotoxicity.
In tr od u ction
between the groups important for antiviral activitys
heterocyclic base and the hydroxymethyl group.
Nucleoside analogues are in the focus of current
interest as antiviral and antitumor agents.1 Structures
which include analogues having carbohydrate (furanose)
or various modifications thereof (e.g., cyclopentane and
dioxa- and oxathiacyclopentane) exhibit diverse biological
effects. The relevant examples are anti-AIDS drugs AZT
(zidovudine, 1, Chart 1) or 3TC (lamivudine, 2). Removal
of part or parts of nucleoside furanose moiety resulting
in a substantial simplification of the structure led in
many cases to new antiviral agents of significant thera-
peutic potency. Thus, acyclic nucleoside analogues acy-
clovir (3) and ganciclovir (4) are established antiherpetic
drugs. 2′,3′-Dideoxyribonucleosides (5) are potent anti-
HIV agents. The tetrahydrofuran moiety of the latter
analogues can be viewed as a relatively rigid “spacer”
Replacement of the tetrahydrofuran moiety with other
rigid groups of similar size also provided new antiviral
agents. Allene derivatives adenallene (6a ) and cytallene
(6b) are potent anti-HIV agents,2-4 and the latter also
inhibits replication of hepatitis B virus (HBV).5 More
recently, we have described a new class of nucleoside
analogues, (Z)- and (E)-methylenecyclopropanes 7 and 8.
The purine derivatives of (Z)-isomers 7 were found to
exhibit a particularly strong and broad-spectrum anti-
viral activity.6-8 By contrast, compounds with a trans-
posed heterocyclic and hydroxymethyl moiety 9 and 10
(2) Phadtare, S.; Zemlicka, J . J . Am. Chem. Soc. 1989, 111, 5925-
5931.
(3) Zemlicka, J . In ref 1, pp 73-100.
(4) Zemlicka, J . Nucleosides Nucleotides 1997, 16, 1003-1012.
(5) Zhu, Y.-L.; Pai, S. B.; Liu, S.-H.; Grove, K. L.; J ones, B. C. N.
M.; Simons, C.; Zemlicka, J .; Cheng, Y.-C. Antimicrob. Agents
Chemother. 1997, 41, 1755- 1760.
(6) Qiu, Y.-L.; Ksebati, M. B.; Ptak, R. G.; Fan, B. Y.; Breitenbach,
J . M.; Lin, J .-S.; Cheng, Y.-C.; Kern, E. R.; Drach, J . C.; Zemlicka, J .
J . Med. Chem. 1998, 41, 10-23.
(7) Qiu, Y.-L.; Ptak, R. G.; Breitenbach, J . M.; Lin, J .-S.; Cheng,
Y.-C.; Kern, E. R.; Drach, J . C.; Zemlicka, J . Antiviral Chem. Chemoth-
er. 1998, 9, 341-352.
† Wayne State University School of Medicine.
‡ Wayne State University.
§ Yale University School of Medicine.
University of Michigan.
| The University of Alabama at Birmingham.
(1) Nucleosides and Nucleotides as Antitumor and Antiviral Agents;
Chu, C. K., Baker, D. C., Eds.), Plenum Press: New York, 1993.
10.1021/jo991030r CCC: $19.00 © 2000 American Chemical Society
Published on Web 02/08/2000

Spiropentane Mimics of Nucleosides
J . Org. Chem., Vol. 65, No. 5, 2000 1281
Ch a r t 1
were devoid of antiviral effect, but the (E)-isomer 10 was
a substrate of moderate efficacy for adenosine deami-
nase.9 Interestingly, the spiro[3.3]heptane analogue of
adenosine 11 displayed some potency against human
cytomegalovirus (HCMV) in vitro, but it was resistant
to adenosine deaminase.10 For a further investigation of
structure-activity relationships in this series, spiro[2.2]-
pentanes 12-15 are considered crucial because their
structures11 are related to all aforementioned analogues
6-11. They are derived by replacement of double bonds
with a cyclopropane ring system in structures 6-10, and
also, they can be considered as ring-contracted mimics
of spiro[3,3]heptane 11.
Spiropentanes are currently not in the center of at-
tention of synthetic organic chemistry.12 Possible reasons
for this neglect may include the fact that natural products
comprising such a spirocyclic system have not been found.
Nevertheless, biologically active agents based on a spiro-
pentane structure have been reported. Thus, spiropen-
tylacetic acid is capable of inhibiting acyl-CoA dehydro-
genases.13 Very recently, it was shown that spiropentyl-
acetyl-CoA is a mechanism-based inactivator of acyl-CoA
dehydrogenases.14 Interestingly, these studies have also
indicated a biological relationship of spiropentane and
methylenecyclopropane analogues. Nevertheless, it must
be stressed that biological effects of stereochemically
more complex 1,4(5)-disubstituted spiropentanes have not
been described to the best of our knowledge.
A seminal publication of Gajewski and Burka11 out-
lined the problems of stereoisomerism of 1,4(5)-disubsti-
tuted spiropentanes and also procedures for synthesis of
these isomers. Their separation relied heavily on vapor-
phase chromatography, a method poorly suitable for
obtaining starting materials for further syntheses. Later,
a mixture of four stereoisomeric 1,2,4(5)-trisubstituted
spiropentanes was obtained by reaction of methylcyclo-
propanediphenylsulfonium ylide with chalcone, and their
1
isomeric structure was determined by H NMR spectros-
copy after derivatization with europium(III) shift re-
agent,15 but the isomers were not separated. More
recently, a 2:1 mixture of 1-bromo-4(5)-ethoxycarbonyl-
spiropentanes of an unspecified isomeric composition was
prepared16 and used in a futile attempt to alkylate
adenine. In this paper, we describe synthesis and biologi-
cal investigation of two complete isomeric sets of spiro-
pentane nucleoside analogues comprising adenine and
guanine moieties, compounds 12a -15a and 12b-15b.
(8) Qiu, Y.-L.; Hempel, A.; Camerman, N.; Camerman, A.; Geiser,
F.; Ptak, R. G.; Breitenbach, J . M.; Kira, T.; Li, L.; Gullen, E.; Cheng,
Y.-C.; Drach, J . C.; Zemlicka, J . J . Med. Chem. 1998, 41, 5257-5264.
(9) Qiu, Y.-L.; Ksebati, M. B.; Zemlicka, J . Nucleosides Nucleotides
in press.
Syn th esis
In the absence of stereoselective procedures17 for
synthesis of distinct (proximal, medial-syn, medial-anti,
(10) J ones, B. C. N. M.; Drach, J . C.; Corbett, T. H.; Kessel, D.;
Zemlicka, J . J . Org. Chem. 1995, 60, 6277-6280.
(11) For the basis of this nomenclature see: Gajewski, J . J .; Burka,
L. T. J . Org. Chem. 1970, 35, 2190-2196.
(15) Trost, B. M.; Bogdanowicz, M. J . J . Am. Chem. Soc. 1973, 95,
5307-5310.
(12) Lukin, K. A.; Zefirov, N. S. In The Chemistry of the Cyclopropyl
Group; Rappoport, Z., Ed.; J ohn Wiley & Sons: New York, 1995; Vol.
2, pp 861-885.
(16) Cheng, C.; Shimo, T.; Somekawa, K.; Kawaminami, M. Tetra-
hedron Lett. 1997, 38, 9005-9008.
(17) Previous work11 indicated that addition of diazomethane to syn-
2-ethylene-1-carbethoxycyclopropane catalyzed by CuSO4 in pentane
led to a mixture of proximal and medial-anti spiropentanes (2:1)
whereas reaction with an anti- isomer afforded medial-syn and distal
spiropentanes (2:1).
(13) Tserng, K.-Y.; J in, S.-J .; Hoppel, C. L. Biochemistry 1991, 30,
10755-10760.
(14) Li, D.; Zhou, H.-q.; Dakoji, S.; Shin, I.; Oh, E.; Liu, H.-w. J .
Am. Chem. Soc. 1998, 120, 2008-2017.

1282 J . Org. Chem., Vol. 65, No. 5, 2000
Guan et al.
Sch em e 1a
a
Conditions: (a) Zn, AcOH-Et2O. (b) LiAlH4, Et2O. (c) Ac2O, pyridine. (d) N2CHCO2Et, Rh2(OAc)4, CH2Cl2. (e) (1) NaOH, aqueous
MeOH. (2) Separation of 21a + 21b and 21c + 21d . (3) c. (f) (PhO)2P(O)N3, NEt3, tBuOH ∆. (g) (1) K2CO3, aqueous MeOH. (2) Separation
of 24a -24d . (h) HCl, MeOH. (i) (1) 4,6-Dichloro-5-nitropyrimidine, NEt3, EtOH. (2) SnCl2, CH(OEt)3. (j) NH3, MeOH, ∆.
or distal) isomers of 1,4(5)-disubstituted spiropentanes,
a “combinatorial” approach seemed advantageous. Thus,
synthesis of a mixture of common intermediates was
contemplated from which all four possible isomers 12a -
15a and 12b-15b needed for biological evaluation could
be generated. Ethyl methylenecyclopropanecarboxylate
(16), which was used previously for the synthesis of
several 1,4-disubstituted spiropentanes,11 was a conve-
nient starting material (Scheme 1). Although other
procedures for the preparation of 16 have been de-
scribed,11,18 we have conveniently used zinc-catalyzed
debromination of ethyl 2-bromo-2-bromomethylcyclopro-
pane-1-carboxylate6 (17). Compound 16, obtained in 80%
yield, was reduced with LiAlH4 to give methylenecyclo-
propylmethanol (18, 85%). The latter was converted to
acetate 19 (87.5%).
Reaction of compound 19 with ethyl diazoacetate
catalyzed19 by Rh2(OAc)4 in CH2Cl2 gave a mixture of all
four possible stereoisomeric spiropentanes 20a -20d . The
mixture was partially resolved by column chromatogra-
phy on silica gel to give less polar proximal and medial-
syn isomers 20a + 20b (46%) followed by more polar
medial-anti and distal isomers 20c + 20d (38%).
The unresolved mixture of 20a -20d was hydrolyzed
with NaOH in aqueous ethanol to give after chromato-
graphic separation proximal and medial-syn isomers 21a
+ 21b and medial-anti and distal isomers 21c + 21d in
were also transformed to a mixture of the BOC-amino
derivatives, which were partially separated by chroma-
52% and 45% yields, respectively. Acetylation of 21a +
tography to afford medial-anti and distal isomers 23c and
21b gave acetates 22a + 22b (96%), and 21c + 21d
23d in a total yield of 76%. Deacetylation then furnished
afforded 22c + 22d (97%). Thus, it was possible to resolve
compounds 24c and 24d , which were readily resolved by
the original mixture into two pairs of isomers early in
chromatography in 43% and 53% yields, respectively.
the synthetic sequence.
Removal of the BOC group from separated isomers 24a -
Isomers 22a + 22b were subjected to a Curtius
rearrangement after activation with diphenylphosphoryl
azide20 and triethylamine in tert-butyl alcohol to give the
BOC-aminospiropentanes 23a + 23b (78%). Compounds
23a + 23b were deacetylated using K2CO3 in aqueous
methanol to give, after column chromatography on silica
gel, proximal and medial-syn isomers 24a and 24b in
17% and 80% yields, respectively. Acetates 22c + 22d
24d was accomplished with HCl in methanol to give the
corresponding amine hydrochlorides 25a -25d in quan-
titative yields.
The introduction of heterocyclic bases, adenine and
guanine, into spiropentane systems of 25a -25d was
performed as follows. A new one-pot procedure led to a
considerable simplification of the current methods.21 In
the case of spiropentyladenines 12a -15a , amines 25a -
25d were first alkylated with 4,6-dichloro-5-nitropyrimi-
dine22 in the presence of triethylamine in ethanol at room
(18) Lai, M.-t.; Liu, L.-d.; Liu, H.-w. J . Am. Chem. Soc. 1991, 113,
7388-7397.
(19) Doyle, M. P.; Tamblyn, W. H.; Bagheri, V. J . Org. Chem. 1981,
46, 5094-5102.
(21) Agrofoglio, L. A.; Challand, S. R. Acyclic, Carbocyclic and
L-Nucleosides; Kluwer Academic Publishers: Dordrecht, The Nether-
lands, 1998; pp 182-183.
(20) Ninomiya, K.; Shioiri, T.; Yamada, S. Tetrahedron 1974, 30,
2151-2157.

Spiropentane Mimics of Nucleosides
J . Org. Chem., Vol. 65, No. 5, 2000 1283
Sch em e 2
Sch em e 3a
a
Conditions: (a) (1) 2-Acetamino-4,6-dichloro-5-nitropyrimidine,
NEt3, EtOH-DMF (1:1). (2) SnCl2, CH(OEt)3. (b) (1) 80% HCO2H,
∆. (2) NH3, MeOH.
temperature for 2 h. The solvents were then evaporated,
and the crude product was treated with SnCl2 and
triethyl orthoformate for 16 h. Chromatography then
furnished 6-chloropurine derivatives 26a -26d in yields
ranging from 45% to 57%. Ammonolysis with NH3 in
methanol (autoclave at 100 °C for 15 h) gave the desired
adenine analogues 12a -15a in 75-91% yield.
It is interesting to note that alkylation of 25a -25d
with 4,6-dichloro-5-aminopyrimidine, which is commonly
used in nucleoside analogue synthesis21 and requires a
higher temperature, led only to destruction of the spiro-
pentane moiety. Further investigation indicated that free
bases 25a -25d have a limited stability. Thus, the free
base of medial-syn isomer 25b was obtained in ap-
proximately 70-80% purity by TLC after treatment of
the hydrochloride with 10% KOH in aqueous methanol
and subsequent chromatography. It was completely
decomposed after standing in CDCl3 overnight. Ad-
ditional experiments performed with isomers 25a , 25c,
and 25d in 10% KOH in D2O indicated stability at room
temperature (9 h), approximately 20-30% decomposition
at 50 °C (16 h), and complete degradation at 80-90 °C
(5 h). These results are in line with a previous report
indicating a limited stability of aminospiropentane it-
self.23 In this respect, aminospiropentanes resemble
another class of strained amines, aminocubanes, which
also lack a sufficient stability.24 It is not clear whether
this behavior may reflect a partial enamine (aldimine)
character of such amines (see structures 27, 28, and 29
in Scheme 2).
F igu r e 1. IR spectra (3000-4000 cm-1 region) of stereoiso-
meric BOC derivatives 24a -24d in CCl4.
treatment with NH3/methanol to give guanine analogues
12b-15b in 75-85% yield.
NMR Sp ectr a a n d Isom er ic Assign m en t. Prelimi-
nary data revealed that the polarity of isomeric spiro-
pentanes (mobility on TLC) followed the order proximal
> medial-syn > medial-anti > distal irrespective of the
1,4(5)-substituents involved. In addition, IR spectra of
4-hydroxymethyl-1-BOC-amino derivatives 24a -24d
(0.03-0.04 M in CCl4) revealed a significant intramo-
lecular hydrogen bonding in proximal and medial-syn
isomers 24a and 24b (broad bands at 3300-3500 cm-1),
whereas these bands were absent in the medial-anti and
distal isomers 24c and 24d (Figure 1). As expected, this
absorption was especially strong in the proximal isomer
24a . Small peaks found in all these isomers at 3620-
3640 cm-1 can possibly be attributed to hydrogen bonding
of OH to the “edge” of the adjacent cyclopropane ring.11
It is worthwhile to note that O-H-O hydrogen bonding
was observed in the proximal 1,4-bis(hydroxymethyl)-
spiropentane but not in the medial isomer.11 However,
in this case the hydrogen-bonded structure 31 comprised
A similar approach was employed for synthesis of
spiropentylguanines 12b-15b. In this case, the alkyla-
tion of amines 25a -25d was performed with 2-ace-
tamino-4,6-dichloro-5-nitropyrimidine25,26 (Scheme 3). The
respective intermediates were then cyclized using the
SnCl2-triethyl orthoformate reagent as described above
to give 2-acetamino-6-chloropurines 30a -30d in yields
ranging from 41% to 58%. Hydrolysis and deacetylation
were performed using 80% formic acid followed by
(22) The use of 4,6-dichloro-5-nitropyrimidine for purine ring con-
struction by a two-step procedure was reported: Coe, D. M.; Myers,
P. L.; Parry, D. M.; Roberts, S. M.; Storer, R. J . Chem. Soc., Chem.
Commun. 1990, 151-153.
(23) Konzelman, L. M.; Conley, R. T. J . Org. Chem. 1968, 33, 3828-
3838.
(24) Eaton, P. E.; Shankar, B. K. R.; Price, G. D.; Pluth, J . J .; Gilbert,
E. E.; Alster, J .; Sandus, O. J . Org. Chem. 1984, 49, 185-186.
(25) Norbeck, D. W.; Sham, H. L.; Herrin, T.; Rosenbrook, W.;
Plattner, J . J . J . Chem. Soc., Chem. Commun. 1992, 128-129.
(26) Temple, C., J r.; Smith, B. H.; Montgomery, J . A. J . Org. Chem.
1975, 40, 3141- 3142.

1284 J . Org. Chem., Vol. 65, No. 5, 2000
Guan et al.
Ta ble 1. NOE En h a n cem en ts of th e pr oxim a l Isom er 12a
an eight-membered ring, whereas in the proximal and
medial-syn isomers 24a and 24b (structures 32 and 33)
obsd H (% NOE)
irr (δ, H)
0.90, H4′′
1.00, H4′
1.48, 1.51, H2′, H5′
2.01, H2′′
2.82, H6′
2.95, H6′′
4.01, H1′
H4′′ H4′ H2′, H5′ H2′′ H6′ H6′′ H1′ H8, H2 OH
14.7
1.7
2.3 0.7 2.5
1.3 4.2
1.4
14.5
7.5
9.3
1.1
22.8
2.8
5.2
12.1
1.7 8.7
1.9
0.8
19 0.6
19.5
2
6.2
3.6
2.6
4.35, OH
8.11, H8, H2
1.9 0.2 0.4 1.2
0.3
Ta ble 2. NOE En h a n cem en ts of th e m ed ia l-syn Isom er
13a
obsd H (% NOE)
irr (δ, H)
0.75, H4′′
1.23, H4′
1.49, H2′, H5′
1.65, H2′′
3.20, H6′
3.50, H6′′
3.86, H1′
4.60, OH
H4′′ H4′ H2′, H5′ H2′′ H6′ H6′′ H1′ H8, H2 OH
nine-membered rings are involved. Although the IR
spectra provided information for differentiation between
proximal and medial-syn isomers 24a and 24b, additional
data were necessary for confirmation and assignment of
medial-anti and distal isomers 24c and 24d . This infor-
mation has followed from the detailed NMR investigation
of one set of the final products, spiropentyladenines 12a -
15a . The cis and trans coupling constants of cyclopropane
protons, J 2′(2′′),1′ and J 4′(4′′),5′, of analogues 12a -15a and
12b-15b fall within the range of similar values found
for simple cyclopropane systems27 (J cis ) 6-10 Hz,
typically 8 Hz; J trans ) 3-6 Hz, typically 5 Hz). Assign-
ments of all protons were corroborated with the aid of
NOE (Tables 1-4), DEPT, and (H,C) and (H,H) COSY
NMR spectra. The H2 and H8 signals of analogues 12a -
15a were unresolved or very close (∆δmax < 0.02), and
they resembled similar signals in adenallene2 (6a ). In the
absence of significant chemical shift differences of the H8
protons and in view of the fact that the H6′(H6′′) signals
were magnetically nonequivalent in all four isomers, a
preliminary assignment of the isomeric structures suc-
cessfully used in case of (Z)- and (E)-methylenecyclopro-
pane analogues6 7 and 8 could not be perfomed.
20.4
2.2
1
2.5
1.9 1.2
19.5
2.2
5.4 2.8
7.3
8.5 1.4
1
21
2.3
1
3
3.5
4.8
1.0
22.5
21
-17.5
2
0.8
2.5
8.10, 8.12, H8, H2
1.2 1.3
Ta ble 3. NOE En h a n cem en ts of th e m ed ia l-a n ti Isom er
14a
obsd H (% NOE)
irr (δ, H)
0.75, H4′′
0.95, H4′
1.47, H5′
1.55, H2′
1.69, H2′′
3.67, 3.72, H6′, H6′′ 2-3
3.86, H1′
4.60, OH
8.09, 8.10, H8, H2
H4′′ H4′ H5′ H2′ H2′′ H6′, H6′′ H1′ H8, H2 OH
20
3.6
3
3
0.6 5.2
21
6.5
0.7
1.4
10.6
1
3
15.7
1
17.5
3
1
2
9.4
1
4.7
0.8
2.8
0.8
1.5
1.2
Ta ble 4. NOE En h a n cem en ts of th e d ista l Isom er 15a
obsd H (% NOE)
The NOE experiments were crucial for distinguishing
all isomers. Thus, proximal isomer 12a showed NOE
enhancement of the H8(H2) signal of 1.7% and 2%,
respectively, after irradiation of H6′ and H6′′ (Table 1).
Conversely, irradiation of H8(H2) led to 0.2% and 0.4%
enhancement of H6′ and H6′′. It is assumed that purine
bases in all isomers are in an anti-like conformation,28
with the C8 facing C5′ or C4′, and the H8 is then
responsible for this effect.29 Somewhat surprisingly, no
NOE was seen between the H6′, H6′′, or OH and H8(H2)
of 13a (Table 2), although an intramolecular hydrogen
bonding was present in the corresponding precursor,
compound 24b (Figure 1). According to expectation, in
the medial-anti and distal isomeric pair 14a and 15a only
the former exhibited an NOE enhancement of H8(H2)
after irradiation of H6′ and H6′′ (Table 3, 1%). The NOE
was also observed between protons located on the same
face of the spiropentane system, H4′′ and H8(H2) of the
medial-anti isomer 14a (5.2 and 0.8%) as well as H4′ and
H8(H2) of the distal isomer 15a (5.1 and 1%). Similar
effects were absent in compounds 12a and 13a .
irr (δ, H)
0.66, H4′′
1.10, H4′
1.54, H2′′
1.64, H2′, H5′
3.32, H6′
3.44, H6′′
3.74, H1′
4.57, OH
H4′′ H4′ H2′, H5′ H2′′ H6′ H6′′ H1′ H8, H2 OH
23 1.5 1.7
1
23
0.7
7
16
5.1
6.6
2.1
8.1 1.2 1.3 6.9
0.7
1.3
1
4.2
4.2
6
9.2
9
-24
-24
2.4
8.09, 8.10, H8, H2
1
1
1.5
The NOE between H1′ and H4′′ (0.8% and 2.5%, Table
1, H1′‚‚‚H4′′ ) 3.15 Å) was characteristic of the proximal
isomer 12a , whereas no effect was seen between the H1′
and H4′ (H1′‚‚‚H4′ ) 3.87 Å). As expected, this trend was
reversed in medial-syn isomer 13a with the observed
interaction between H1′ and H4′ (0.8% and 2.2%, Table
2, H1′‚‚‚H4′ ) 3.14 Å) and none between H1′ and H4′′ (H1′‚
‚‚H4′′ ) 3.82 Å). In medial-anti and distal isomers 14a
and 15a the only H1′ and H4′(H4′′) interaction was noted
in the former (0.6%, Tables 3 and 4). A strong NOE
enhancement found between H8 and H4′′ of the medial-
anti isomer 14a and H8 and H4′ of the distal isomer 15a
(5.2 and 5.1 Hz, respectively) is also characteristic. These
effects were absent in the proximal and medial-syn
isomers 12a and 13a . All these data established the
isomeric structures of 12a -15a and the respective pre-
cursors 24a -24d .
(27) Friebolin, H. Basic One- and Two-Dimensional NMR Spectros-
copy; VCH Publishers: New York, 1991; p 77.
(28) Saenger, W. Principles of Nucleic Acid Structure; Springer-
Verlag: New York, 1984; p 69.
(29) Difficulty in pinpointing the “right” signal (presumably H8) from
poorly resolved singlets of H8 and H2 may account for lower NOE
effects.

Spiropentane Mimics of Nucleosides
J . Org. Chem., Vol. 65, No. 5, 2000 1285
Ta ble 5. An tivir a l Activity of Sp ir op en ta n e Nu cleosid e An a logu esa
HSV-1
HCMVb
HFFc
HSV-2
Veroc,e
VZV
EBV
HIV-1
HBV
compd
BSC-1d
Veroc
HFFc,f
Daudig
CEM-SSe,h
2.2.15e
12a
13a
14a
15a
12b
13b
14b
15b
34
28/>100
>100/>100
70/>100
>50/89
>50
>50
>50
>50
>50
>50
>50
>50
31
>86.5
4.8/15(0.95)i
22/>202(0.61)i
153/202
>100
>100
>100
>100
>100
>100
>100
>100
3.5
>10
>10
>10
>10
>10
>10
>10
>10
3.1
20/>100j
>50/>100
>50/>100
>50/>100
>50/>100
>50/>100
>100/>100
>50/>100
20/27
245
>100/>100
>100/>100
>100/>100
>100/>100
>100/>100
>100/>100
0.38/100
>100/>100
>100/>100
>100/>100
>100/>100
>50/>100
>100/>100
7.0/70
242
>433
>216/>216
>199/>199
>199/>199
>199/>199
6.0/>199 (12)i
2.8/7.6
>399k
>399k
>399k
>399k
>8.5(1.4)k
9.3/>444m
control
2.9/>100l
2.0/>100m
13.5/>200m
32.3m
8.4/>222m
0.5/>10n
2.3/6o
a
Inhibition of viral replication (EC50, µM) and cytotoxicity (IC50, µM) in the host cells. The data are listed as EC50/IC50. For a description
of antiviral assays see refs 6 and 7. Towne strain. c Plaque reduction assay. Enzyme-linked immunosorbent assay (ELISA). The
b
d
cytotoxicities were determined in KB cells. e The cytotoxicities were determined in CEM cells; see HSV-1/Vero. f For cytotoxicities in HFF
g
h
cells see HCMV/HFF. Viral capsid antigen (VCA) immunofluorescence (IF) or ELISA assay. Supernatant reverse transcriptase assay.
i
j
k
Inhibition of EBV DNA synthesis. EC50/IC50 40/>404 in the AD 169 strain and 10.5/>404 in MCMV/MEF assay. Cytopathic effect
(CPE) inhibition assay. Ganciclovir. Acyclovir. Zidovudine (AZT). o Zalcitabine (ddC).
l
m
n
Long-range coupling across the spiropentane ring
system was observed in the (H,H) COSY NMR spectra
of medial-anti and distal isomers 14a and 15a , but it was
absent in proximal and medial-syn isomers 12a and 13a .
It is especially extensive in medial-anti isomer 14a ,
where all spiropentane protons with the exception of H2′′
are involved. A long-range interaction between H1′ and
H6′,6′′ was also seen. By contrast, a similar coupling takes
place only between the H1′ and H4′′ of the distal isomer
15a . It is recognized that the rigidity of a spiropentane
system offers a good opportunity for this type of coupling,
but the reasons for the observed isomer selectivity are
not entirely clear.
methylenecyclopropane analogues:6-8 little activity against
HIV-1, herpes simplex virus type 1 (HSV-1), and HSV-2
and more potency against CMV and EBV.
Inactive nucleoside analogues including allenic30,31 and
methylenecyclopropane derivatives32 can be activated by
conversion to lipophilic pronucleotides, thus bypassing
the first phosphorylation step in their mechanism of
action.33 Therefore, the medial-syn isomer 13a , which
exhibited the most potent anti-HCMV effect at noncyto-
toxic levels from all analogues investigated in the present
study, was transformed to phenyl phosphoralaninate 34.
Indeed, the activity of the latter prodrug against HCMV
(EC50 0.38 µM) was increased over 50-fold compared to
that of 13a , whereas the cytotoxicity remained low (IC50
100 µM). There was a similar increase of activity against
HBV (EC50 3.1 µM) and HIV-1 (EC50 3.5 µM). Antiviral
activity was also seen against HSV-1 (EC50 7 µM), and
cytotoxicity in T-lymphoblastoid cell line CEM and epi-
dermoid oral carcinoma KB cells was 27 and 70 µM,
respectively. Phosphoralaninate 34 was also active against
EBV with EC50 2.8 µM, albeit it was cytotoxic to unin-
fected cells with an IC50 of 7.8 µM. It was also effective
against varicella zoster virus (VZV; EC50 1.4 µM, IC50 95
µM) in a cytopathic effect inhibition assay. Compound
34 is a substrate for pig liver esterase (PLE), a current
model of intracellular esterases,30,34 which also indicates
that the mechanism of its antiviral activity may be
related to that of similar prodrugs of nucleoside ana-
logues.30,31,33 All these results indicated that (i) design of
antiviral nucleoside analogues where the 2′-deoxyribo-
furanose moiety is replaced by a spiropentane system is
possible and (ii) the biological activity of such analogues
can be increased by conversion to lipophilic phosphates
capable of generating the phosphorylated species inside
the virus-infected cells. These results are also in agree-
ment with a hypothesis that phosphorylation is indis-
pensable for the mechanism of antiviral activity of 13a .
Biologica l Activity
Among analogues 12a -15a and 12b-15b, adenine
proximal and medial-syn isomers 12a and 13a as well
as guanine distal isomer 15b exhibited antiviral activity
in several assays (Table 5). Compounds 12a and 13a were
moderately active against HCMV in human foreskin
fibroblast (HFF) culture as determined by a plaque
reduction assay (EC50 28 and 20 µM, respectively). The
medial-syn isomer 13a was also potent against murine
cytomegalovirus (MCMV; EC50 10.5 µM) in mouse em-
bryonic fibroblast (MEF) cells. Little or no cytotoxicity
was observed. The proximal isomer 12a was the most
effective against Epstein-Barr virus (EBV) in Daudi cells
with EC50 4.8 µM, but it was cytotoxic (IC50 15 µM). The
guanine distal isomer 15b was virtually equipotent (EC50
6.0 µM), but it was noncytotoxic (IC50 > 199 µM).
Compound 13a was less active (EC50 22 µM), and it was
also noncytotoxic (IC50 > 202 µM). Antiviral activity of
medial syn and proximal isomers 13a and 12a is in line
with the findings that antiviral activity of the cisoid
analogues (e.g., 7) is usually superior to that of transoid
analogues6 (e.g., 8), but the anti-EBV efficacy of the distal
isomer 15b is an exception. A different activity trend was
found in deamination of 12a -15a catalyzed by adenosine
deaminase. Only medial-anti isomer 14a was a substrate,
though with a very low reaction rate (t1/2 >120 h).
Analogues 12a , 13a , and 15a were not deaminated. In
summary, biological activity was found among all four
isomeric types, although the distances between the
heterocyclic base (adenine) and hydroxymethyl group
(N9‚‚‚C6′) vary significantly between 3.54 (12a ) and 5.01
(15a ) Å. At this point, it is difficult to rationalize the
antiviral results, but roughly, the trend follows that of
(30) Winter, H.; Maeda, Y.; Mitsuya, H.; Zemlicka, J . J . Med. Chem.
1996, 39, 3300-3306.
(31) Winter, H.; Maeda, Y.; Uchida, H.; Mitsuya, H.; Zemlicka, J .
J . Med. Chem. 1997, 40, 2191-2195.
(32) Qiu, Y.-L.; Ptak, R. G.; Breitenbach, J . M.; Lin, J .-S.; Cheng,
Y.-C.; Drach, J . C.; Kern, E. R.; Zemlicka, J . Antiviral Res. 1999, 43,
37-53.
(33) Meier, C. Synlett 1998, 233-242.
(34) McGuigan, C.; Tsang, H.-W.; Sutton, P. W.; De Clercq, E.;
Balzarini, J . Antiviral Chem. Chemother. 1998, 9, 109-115.

1286 J . Org. Chem., Vol. 65, No. 5, 2000
Guan et al.
125 (100.0); HRMS calcd for C9H12O2 (M - CH3CO2H) 152.0837,
found 152.0830. Anal. Calcd for C11H16O4: C, 62.26; H, 7.55.
Found: C, 62.03; H, 7.48.
Exp er im en ta l Section
Gen er a l Meth od s. See ref 6. TLC and column chromatog-
raphy were performed as described previously.35
Da ta for com p ou n d s 20c + 20d : 1H NMR (CDCl3) δ 4.09-
3.82 (m, 4H), 2.0, 1.97 (s, 3H), 1.90 (m, 1H), 1.17 (2t, 3H), 1.58-
Eth yl Meth ylen ecyclop r op a n eca r bon a te (16). To a
solution of ethyl 2-bromo-2-bromomethylcyclopropanecarbon-
ate6 (17; 36.0 g, 0.126 mol) in ether (150 mL) and acetic acid
(20 mL) was added zinc powder (40 g, 0.63 mol) in portions
with stirring at room temperature. The stirring was continued
for 16 h. The solids were filtered off and washed with ether (3
× 30 mL). The filtrate was washed successively with 5% HCl,
water, aqueous NaHCO3, and brine and dried (Na2SO4).
Evaporation of the solvent at atmospheric pressure furnished
the crude product, which was distilled to give compound 16,
bp 60 °C, 5 Torr (12.8 g, 80%). The 1H NMR spectrum was
identical to that reported.17
1.28 (m), 1.06 (m), 0.85 (t) and 0.72 (t, ratio 2:1, total 5H); 13
C
NMR δ 173.52, 173.11, 170.92, 67.20, 67.03, 60.27, 22.71,
20.81, 19.72, 17.96, 16.70, 16.58, 14.21, 14.15, 12.52, 10.11,
10.02; EI-MS m/z 213 (M + H, 0.1), 169 (M - CH3CO, 1.2),
152 (M - CH3CO2H, 59.0), 139 (M - CO2Et, 15.9), 79 (100.0);
HRMS calcd for C9H12O2 (M - CH3CO2H) 152.0837, found
152.0832. Anal. Calcd for C11H16O4: C, 62.26; H, 7.55. Found:
C, 62.10; H, 7.51.
1-Ca r boxy-5-h yd r oxym eth ylsp ir op en ta n es 21a -21d . A
solution of 1-carbethoxy-4-acetoxymethylspiropentanes 20a -
20d (5.36 g, 25.3 mmol) in ethanol-water (4:1, 100 mL) was
added dropwise into 50% aqueous NaOH (10 mL) with stirring
and ice-cooling. The stirring was continued for 16 h at room
temperature. The volume of the mixture was reduced by
evaporation in vacuo, and the pH was adjusted to 3 with 4 M
HCl. The remaining solvent was evaporated, and the solid
residue was extracted with CH2Cl2-MeOH (10:1, 4 × 30 mL).
Evaporation of the extract gave a product which showed three
spots on TLC (CH2Cl2-MeOH, 6:1), 21a (Rf 0.65), 21b (Rf 0.62),
partly overlapped and clearly separated from 21c + 21d (Rf
0.45). Column chromatography on silica gel in CH2Cl2-MeOH
(10:1) afforded partially separated isomers 21a + 21b (1.88 g,
52.3%) and unseparated compounds 21c + 21d (1.61 g, 44.8%)
as syrups.
(Meth ylen ecyclop r op yl)m eth yl Aceta te (19). A solution
of compound 16 (30.0 g, 0.23 mol) in ether (40 mL) was added
to a stirred mixture of LiAlH4 (4.1 g, 0.12 mol) in ether (180
mL) at such a rate to maintain a gentle reflux. The resultant
mixture was refluxed for 10 h. It was then quenched carefully
with H2O (8 mL) and 20% aqueous NaOH (16 mL). The ether
phase was separated and the remaining white precipitate
extracted with ether (5 × 20 mL). The combined ether phase
was distilled using a Vigreux column to give (methylenecy-
clopropane)methanol (18), bp 50-55 °C, 5 Torr (16.9 g, 85%).
The 1H NMR spectrum was identical to that described.17 To
the solution of 18 (16.0 g, 0.2 mol) in pyridine (25 mL) was
added acetic anhydride (25 mL) dropwise with stirring, which
was continued at room temperature overnight. The reaction
was quenched with water and the product extracted with
pentane (4 × 70 mL). The combined organic phase was washed
successively with saturated CuSO4, 5% HCl, aqueous NaHCO3,
and brine and dried (Na2SO4). Pentane was removed at
atmospheric pressure using a Vigreux column, and the product
19 was distilled: bp 60-65 °C, 5 Torr (21.0 g, 87.5%); 1H NMR
(CDCl3) δ 5.45 (m, 1H) and 5.41 (m, 1H), 4.04 (dd, 1H, 3J )
Da ta for pr oxim a l-1-ca r boxy-5-h yd r oxym eth ylsp ir o-
p en ta n e (21a ): 1H NMR (D2O) δ 3.73 (dd, 1H, 3J ) 5.4 Hz, 2J
2
3
) 11.0 Hz) and 3.06 (t, 1H, J ) J ) 11.0 Hz), 1.93 (m, 1H),
1.59 (m, 1H), 1.38 (m, 2H), 0.98 (t, J ) 6.1 Hz) and 0.75 (1H,
m, 2H).
Da ta for m ed ia l-syn -1-ca r boxy-5-h yd r oxym eth ylsp ir o-
p en ta n e (21b). 1H NMR (D2O) δ 3.56 (dd, 1H, 3J ) 6.0 Hz, 2J
3
2
) 11.4 Hz) and 3.06 (dd, 1H, J ) 8.0 Hz, J ) 11.4 Hz), 1.88
2
3
6.3 Hz, J ) 11.2 Hz) and 3.86 (dd, 1H, J ) 8.1 Hz,2J ) 11.2
(dd, 1H, 3J trans ) 3.5 Hz, 3J cis ) 5.0 Hz), 1.20 (m, 3H), 1.01 (dd,
Hz), 2.04 (s, 3H), 1.77 (m, 1H), 1.34 (tt, 1H, J ) 3J ) 9.0 Hz,
2
2
3
2
3
1H, J ) 4.0 Hz, J cis ) 6.5 Hz) and 0.70 (t, 1H, J ) J trans
)
4J ) 2.2 Hz) and 0.98 (m, 1H); 13C NMR δ 171.06, 132.04,
104.78, 66.98, 20.94, 14.24, 8.67; EI-MS m/z 125 (M - H, 17.0),
111 (M - CH3, 7.3), 96 (M - CH2O, 32.0), 84 (M - COCH2,
100.0), 67 (M - CH3CO2, 59.1). Anal. Calcd for C7H10O2: C,
66.67; H, 7.94. Found: C, 66.82; H, 8.18.
4.0 Hz); 13C NMR δ 174.82, 64.06, 22.54, 19.71, 19.40, 12.44,
11.73; EI-MS m/z 143 (M + H, 1.7), 125 (M - OH, 4.1), 43
(100.0); HRMS calcd for C9H12O2 (M + H) 143.0708, found
143.0707.
Da ta for m ed ia l-a n ti- a n d d ista l-1-ca r boxy-5-h yd r oxy-
m eth ylsp ir op en ta n e (21c + 21d ): 1H NMR (D2O) δ 3.34 and
3.24 (m, 2H), 1.88 and 1.74 (2m, 1H), 1.34 (2m, 2H), 1.24 and
1.15 (2m, 2H), 0.98, 0.86, 0.70 and 0.67 (4m, 2H); 13C NMR δ
175.45, 175.06, 64.13, 64.86, 23.27, 22.87, 20.83, 20.24, 17.82,
14.16, 12.47, 9.76; EI-MS m/z 143 (M + H, 6.4), 125 (M - OH,
30.9), 107 (13.6), 97 (47.7), 79 (92.3), 39 (100.0); HRMS calcd
for C9H12O2 (M + H) 143.0708, found 143.0705.
1-Ca r b et h oxy-5-a cet oxym et h ylsp ir op en t a n es 20a -
20d . The method for preparation of dibromo derivative6 17 was
followed. Ethyl diazoacetate (90%, 10.0 mL, 85 mmol) in CH2-
Cl2 (10 mL) was added to a stirred mixture of Rh2(OAc)4 (200
mg, 0.45 mmol) and (methylenecyclopropyl)methyl acetate (19;
8.25 g, 65.4 mmol) in CH2Cl2 (20 mL) by a syringe pump over
a period of 24 h. The reaction mixture was diluted with ethyl
acetate (50 mL) and water (50 mL). The unsaturated byprod-
ucts (diethyl fumarate and maleate) were removed by a slow
addition of solid KMnO4 (8 g) with stirring. Solid NaHSO3 was
then added at 0-5 °C to remove excess KMnO4; MnO2 was
filtered off and washed with ethyl acetate (5 × 80 mL) using
a sonicator. The combined organic phase was washed with
aqueous NaHSO3 and brine and dried (Na2SO4). Evaporation
of solvent afforded the crude product as a mixture of diaste-
reoisomers 20a -20d (11.5 g, 84%). Chromatography on a silica
gel column in hexanes-ethyl acetate (30:1 f 20:1) gave the
faster moving fraction of proximal and medial-syn isomers 20a
+ 20b (6.1 g, 44%) followed by a slower moving fraction
containing the medial-anti and distal isomers 20c + 20d (5.0
g, 36%).
1-Ca r b oxy-5-a cet oxym et h ylsp ir op en t a n es 22a -22d .
Each of the mixtures of isomers 21a + 21b (1.88 g, 13.2 mmol)
and 21c + 21d (1.61 g, 11.3 mmol) was dissolved in acetic
anhydride-pyridine (1:2, 12 mL), and the solution was allowed
to stand at room temperature for 16 h. The volatile components
were evaporated, and the residue was dissolved in water (10
mL) and lyophilized. The crude product was chromatographed
on a silica gel column in CH2Cl2-MeOH-AcOH (100:2:0.3) to
give 1-carboxy-4-acetoxymethylspiropentanes 22a + 22b (2.34
g, 96%) and 22c + 22d (2.02 g, 97%), respectively, as syrups.
Da t a for p r oxim a l- a n d m ed ia l-syn -1-ca r b oxy-5-a ce-
toxym eth ylsp ir op en ta n e (22a + 22b, Ra tio 1:4): 1H NMR
(CDCl3) δ 3.98 (dd, 1H, 3J ) 7.2 Hz, 2J ) 11.5 Hz) and 3.72
(dd, 1H, 3J ) 7.0 Hz, 2J ) 11.5), 1.92 (3H, s), 1.85 (dd, 1H,
Da ta for com p ou n d s 20a + 20b: 1H NMR (CDCl3) δ 4.22-
3.63 (m, 4H), 2.0, 1.97 (2s, 3H, ratio 4:1), 1.89 (m, 1H), 1.7-
1.4 (m) and 1.2 (m), 0.98 and 0.78 (2m, ratio 1:4, total 8H);
13C NMR δ 173.06, 171.07, 170.90, 67.06, 66.15, 60.43, 60.21,
20.89, 22.34, 19.67, 19.34, 16.35, 15.59, 14.24, 14.11, 12.60,
12.53, 11.77, 10.31; EI-MS m/z 213 (M + H, 13.4), 169 (M -
CH3CO, 4.9), 153 (M - CH3CO2, 65.4), 139 (M - CO2Et, 26.7),
3
3J trans ) 4.1 Hz, J cis ) 7.5 Hz), 1.65 and 1.53 (m, 1H), 1.44 (t,
2
3
2
3
1H, J ) J trans ) 3.5 Hz) and 1.28 (dd, 1H, J ) 4.0 Hz, J cis
2
3
) 7.4 Hz, ratio 1:4), 1.12 (dd, 1H, J ) 4.8 Hz, J cis ) 8.0 Hz)
and 0.95, 0.77 (t, 1H, 2J ) 3J trans ) 4.8 Hz); 13C NMR δ 179.67,
171.24, 66.84, 66.03, 23.25, 23.02, 20.72, 19.53, 19.21, 16.37,
15.73, 15.04, 13.49, 11.66.
Da ta for m ed ia l-a n ti- a n d d ista l-1-ca r boxy-5-a cetoxy-
m eth ylsp ir op en ta n e (22c + 22d , Ra tio 1:1.2): 1H NMR
(CDCl3) δ 3.98 (m, 1H) and 3.80 (2dd, overlaped, 1H, J ) 7.4,
(35) Ben Cheikh, A.; Craine, L. E.; Recher, S. G.; Zemlicka, J . J .
Org. Chem. 1988, 53, 929-936.

Spiropentane Mimics of Nucleosides
J . Org. Chem., Vol. 65, No. 5, 2000 1287
11.0 Hz and 7.2, 10.3 Hz), 1.91 (s, 3H), 1.88 (m, 1H), 1.59-
1.29 (m), 1.09 (m) and 0.81-0.74 (2t, total 5H). 13C NMR δ
179. 93, 179.14, 171.27, 66.05, 23.62, 23.13, 20.71, 19.58, 17.85,
16.78, 16.65, 14.84, 13.30, 10.12.
rated, and the residue was extracted with ethyl acetate (4 ×
30 mL). Evaporation afforded spiropentanes 24a + 24b, which
were readily separated by TLC (hexanes-ethyl acetate, 2:1,
Rf 0.6 and 0.3, respectively). Column chromatography on silica
gel in hexanes-ethyl acetate (6:1 f 4:1) gave the proximal
isomer 24a (200 mg, 17%) and medial-syn isomer 24b (950
mg, 80%).
Da ta for pr oxim a l isom er 24a : IR (0.044 M solution in
CCl4) 3620, 3460 (sh) and 3360 (br, OH and NH), 2980 (Cs
H), 1710 and 1690 (CdO), 1545 (NH, amide II) cm-1; 1H NMR
pr oxim a l- a n d m ed ia l-syn -5-Acetoxym eth yl-1-(ter t-bu -
toxycar bon ylam in o)spir open tan es (23a an d 23b). Diphen-
ylphosphoryl azide (0.964 mL, 4.5 mmol) was added dropwise
with stirring into the solution of compounds 22a + 22b (550
mg, 3.0 mmol) in tert-butyl alcohol (10 mL) containing Et3N
(0.753 mL, 5.4 mmol). The resulting mixture was refluxed for
4 h. After evaporation of tert-butyl alcohol, the residue was
dissolved in ethyl acetate (100 mL). The resulting solution was
washed with aqueous NH4Cl and brine, dried (Na2SO4), and
evaporated. The crude product was chromatographed on a
silica gel column in hexanes-ethyl acetate (9:1 f 8:1) to give
a mixture of spiropentanes 23a and 23b (598 mg, 78%). Partial
separation of isomers was achieved in hexanes-ethyl acetate
(10:1), and uniform isomers 23a and 23b were used for
characterization.
3
2
(CDCl3) δ 6.33 (br s, 1H), 4.11 (dd, 1H, J ) 4.2 Hz, J ) 11.0
3
3
Hz) and 3.81 (br s, 1H), 3.09 (t, 1H, J cis ) J trans ) 8.8 Hz),
2.94 (br s, 1H), 1.56 (m 1H), 1.36 (s, 9H), 1.10 (m, 1H) and
3
2
2
3
0.87 (dd, 1H, J cis ) 8.8 Hz, J ) 4.5 Hz), 0.77 (t, 1H, J ) J
) 3.9 Hz) and 0.68 (m, 1H); 13C NMR δ 157.39, 79.13, 64.81,
28.90, 28.34, 19.14, 18.28, 15.25, 10.77; CI-MS m/z 214 (M +
H, 18.5), 180 (2.2), 158 (M + H - 2-methylpropene, 100.0);
HRMS calcd for C7H11NO3 (M + H - tBu) 157.0740, found
157.0740.
1
Da ta for pr oxim a l isom er 23a : H NMR (CDCl3) δ 5.21
Da ta for m ed ia l-syn isom er 24b: IR (0.046 M solution in
CCl4) 3620, 3450 and 3450-3400 (br, OH and NH), 2980 (Cs
3
2
(br s, 1H), 4.60 (dd, 1H, J ) 5.7 Hz, J ) 11.7 Hz) and 3.60
(dd, 1H, J ) 9.0 Hz, J ) 11.4 Hz,), 3.08 (br s, 1H), 2.07 (s,
3H), 1.66 (1H, m), 1.43 (s, 9H), 1.18 (t, 1H, J ) J trans ) 5.5
H), 1720 and 1700 (sh, CdO), 1545 (NH, amide II) cm-1; H
3
2
1
2
3
NMR (CDCl3) δ 5.48 (br s, 1H), 3.86 (br s, 1H), 3.56 (dd, 1H,
3J ) 6.0 Hz, 2J ) 10.5 Hz) and 3.30 (dd, 1H, 3J ) 7.5 Hz, 2J )
10.5 Hz), 2.84 (m, 1H), 1.36 (m, 1H), 1.32 (s, 9H), 0.95 (t, 2H,
J ) 5.7 Hz), 0.81 (t, 1H, J ) 4.2 Hz) and 0.54 (t, 1H, J ) 4.5
Hz); 13C NMR δ 156.78, 79.05, 65.38, 28.53, 28.30, 19.38, 18.99,
16.96, 11.11; CI-MS m/z 214 (M + H, 4.9), 158 (M + H -
2-methylpropene, 100.0); HRMS calcd for C7H11NO3 (M + H
- tBu) 157.0740, found 157.0741.
m ed ia l-a n ti- a n d d ista l-5-Hyd r oxym eth yl-1-(ter t-bu -
toxyca r bon yl)a m in osp ir op en ta n es (24c a n d 24d ). Hy-
drolysis of the isomeric mixture 23c + 23d (925 mg, 3.6 mmol)
was performed according to the procedure described above for
23a + 23b. Isomers 24c and 24d were resolved by TLC
(petroleum ether-ether, 1:1), Rf 0.6 and 0.52, respectively.
Column chromatography on silica gel in petroleum ether (5:1
f 4:1) gave medial-anti isomer 24c (334 mg, 43%) and distal
isomer 24d (413 mg, 53%).
Da ta for m ed ia l-a n ti isom er 24c: IR (0.034 M solution
in CCl4): 3630, 3460 (OH and NH), 2990 (CsH), 1730 (CdO),
1550 (NH, amide II) cm-1; 1H NMR (CDCl3) δ 4.91 (br s, 1H),
3.79 (br s, 2H, H6), 2.92 (br s, 1H), 2.75 (br s, 1H), 1.43 (s,
10H), 1.10 (t, 1H, J ) 5.4 Hz) and 0.99 (br s, 1H), 0.94 (m,
1H) and 0.86 (br s, 1H); 13C NMR δ 157.24, 79.74, 62.16, 28.24,
26.75, 20.16, 19.23, 12.93, 6.70; CI-MS m/z 214 (M + H, 15.1),
158 (100.0); HRMS calcd for C7H11NO3 (M + H - tBu)
157.0740, found 157.0734.
2
3
Hz) and 1.04 (dd, 1H, J ) 4.5 Hz, J cis ) 7.5 Hz), 0.86 (t, 1H,
2J ) 3J ) 4.2 Hz) and 0.80 (t, 1H, 2J ) 3J ) 4.2 Hz); 13C NMR
δ 171.32, 156.37, 79.28, 67.82, 20.98, 28.88, 28.32, 18.76, 16.10,
14.67, 11.55; CI-MS m/z 256 (M + H, 2.2), 200 (M + H -
2-methylpropene, 100.0); HRMS calcd for C9H13NO4 (M + H
- tBu) 199.0845, found 199.0840. Anal. Calcd for C13H21O4N:
C, 61.16; H, 8.29; N, 5.49. Found: C, 61.33; H, 8.30; N, 5.35.
Da ta for m ed ia l-syn isom er 23b: 1H NMR (CDCl3) δ 4.94
(br s, 1H), 3.88 (d, 2H), 2.76 (br s, 1H), 1.94 (s, 3H), 1.46 (m,
2
3
1H), 1.34 (s, 9H), 1.08 (m, 1H) and 1.00 (t, 1H, J ) J ) 4.5
2
2
Hz, H2), 0.75 (t, 1H, J ) 3J ) 4.2 Hz) and 0.66 (t, 1H, J ) 3J
) 4.2 Hz); 13C NMR δ 170.94, 156.36, 79.09, 67.64, 20.78,
28.16, 27.94, 19.88, 13.64, 11.81, 11.48; CI-MS m/z 256 (M +
H, 6.5), 200 (M + H - 2-methylpropene, 100.0); HRMS calcd
for C9H13NO4 (M + H - tBu) 199.0845, found 199.0847. Anal.
Calcd for C13H21NO4: C, 61.16; H, 8.29; N, 5.49. Found: C,
61.18; H, 8.18; N, 5.69.
m ed ia l-a n ti- a n d d ista l-5-Acetoxym eth yl-1-(ter t-bu -
toxyca r bon yl)a m in osp ir op en ta n es (23c a n d 23d ). Both
isomers were prepared as described above for spiropentanes
23a and 23b from a mixture of medial-anti and distal-1-
carboxy-4-acetoxymethylspiropentanes (22c + 22d ; 550 mg,
3.0 mmol). Chromatography in petroleum ether-ethyl acetate
(8:1 f 7:1) afforded partially separated spiropentanes 23c and
23d (586 mg, 76%). Uniform isomers 23c and 23d were used
for characterization.
Da ta for d ista l isom er 24d : IR (0.031 M solution in
CCl4): 3640, 3460 (OH and NH), 2990 (CsH), 1730 (sh), 1710
(CdO), 1545 (NH, amide II) cm-1; 1H NMR (CDCl3) δ 4.95 (br
s, 1H,), 3.44 and 3.41 (2m, 2H), 3.16 (br s, 1H), 2.78 (br s, 1H),
Da ta for m ed ia l-a n ti isom er 23c: 1H NMR (CDCl3) δ 4.85
(br s, 1H), 4.15 (br s, 1H) and 4.00 (dd, 1H, J ) 7.3 and 11.3
Hz), 2.91 (br s, 1H), 2.00 (s, 3H), 1.51 (t, 1H, J ) 6.0 Hz), 1.40
(s, 9H), 1.17 (t, 1H, J ) 6.0 Hz) and 1.00 (dd, 1H, 2J ) 4.5 Hz,
3J cis ) 7.5 Hz), 0.83 (t, 1H, J ) 4.2 Hz) and 0.78 (t, 1H, J )
4.6 Hz); 13C NMR δ 171.12, 156.31, 79.26, 67.39, 28.27, 26.94,
20.94, 20.45, 17.11, 13.56, 8.67; CI-MS m/z 256 (M + H, 44.2),
200 (100.0); HRMS calcd for C9H13NO4 (M + H - tBu)
199.0845, found 199.0848. Anal. Calcd for C13H21NO4: C,
61.16; H, 8.29; N, 5.49. Found: C, 61.03; H, 8.25; N, 5.43.
2
1.46 (br s, 1H), 1.32 (s, 9H), 1.15 (t, 1H, J ) 3J trans ) 6.0 Hz)
2
3
and 0.96 (dd, 1H, J ) 5.0 Hz, J cis ) 7.8 Hz), 0.68 (t, 1H, J )
4.2 Hz) and 0.55 (t, 1H, J ) 4.5 Hz); 13C NMR δ 156.62, 79.32,
65.00, 28.48, 28.23, 19.77, 14.06, 11.70, 8.09; CI-MS m/z 214
(M + H, 31.0), 158 (100.0); HRMS calcd for C7H11NO3 (M + H
- tBu) 157.0740, found 157.0740.
1-Am in o-5-h yd r oxym et h ylsp ir op en t a n e H yd r och lo-
r id es 25a -25d . A solution of a single isomer of BOC-
aminospiropentane 24a , 24b, 24c, or 24d (1-2 mmol) was
stirred in 2 M HCl in MeOH (10-20 mL) at room temperature
for 16 h, whereupon it was evaporated to give 1-amino-4-
hydroxymethylspiropentane hydrochloride 25a , 25b, 25c, or
25d in quantitative yield.
1
Da ta for d ista l isom er 23d : H NMR (CDCl3) δ 4.76 (br,
1H), 4.00 (dd, 1H, J ) 7.0 and 11.4 Hz) and 3.90 (dd, 1H, J )
7.3 and 11.4 Hz), 2.86 (br s, 1H, H1), 2.02 (s, 3H), 1.60 (m, 1H,
H5), 1.39 (s, 9H), 1.19 (t, 1H, 2J ) 5.0 Hz) and 1.12 (dd, 1H, 2J
3
) 4.5 Hz, J cis ) 7.9 Hz), 0.78 (t, 1H, J ) 4.2 Hz) and 0.70 (t,
1H, J ) 4.5 Hz); 13C NMR δ 171.11, 156.18, 79.41, 67.26, 28.26,
20.92, 20.00, 16.53, 11.79, 8.68; CI-MS m/z 256 (M + H, 2.9),
200 (80.0), 156 (9.3), 140 (100.0), 96 (80.4); HRMS calcd for
C9H13NO4 (M + H - tBu) 199.0845, found 199.0840. Anal.
Calcd for C13H21NO4: C, 61.16; H, 8.29; N, 5.49. Found: C,
60.93; H, 8.24; N, 5.48.
Da ta for pr oxim a l isom er 25a : 1H NMR (D2O) δ 3.59 (dd,
3
2
3
1H, J ) 7.4 Hz, J ) 11.0 Hz) and 3.53 (dd, 1H, J ) 7.0 Hz,
2J ) 11.0 Hz), 2.94 (m, 1H), 1.68 (m, 1H), 1.24 (t, 1H, J ) 6.6
2
3
Hz) and 1.13 (m, 1H), 1.03 (dd, 1H, J ) 4.5 Hz, J ) 7.6 Hz)
and 0.83 (t, 1H, J ) 4.5 Hz); 13C NMR δ 63.75, 28.14, 19.37,
17.00, 10.94, 10.14; EI-MS m/z 114 (M - Cl, 29.6), 55 (100.0);
HRMS calcd for C6H8N (M - H - H2O - HCl) 94.0657, found
94.0654.
pr oxim a l- a n d m ed ia l-syn -5-Hyd r oxym eth yl-1-(ter t-
bu toxyca r bon yl)a m in osp ir op en ta n es (24a a n d 24b). A
mixture of isomers 23a and 23b (1.42 g, 5.57 mmol) and K2-
CO3 (845 mg, 6.13 mmol) in MeOH-H2O (5:1, 30 mL) was
stirred at room temperature for 16 h. Solvents were evapo-
1
Da ta for m ed ia l-syn isom er 25b: H NMR (D2O) δ 3.51
(dd, 1H, 3J ) 6.7 Hz, J ) 11.0 Hz), 3.38 (dd, 1H, J ) 7.2 Hz,
2
3

1288 J . Org. Chem., Vol. 65, No. 5, 2000
Guan et al.
3
3
3
2J ) 11.0 Hz), 2.83 (dd, 1H, J trans ) 3.3 Hz, J cis ) 6.6 Hz),
1.54 (m, 1H), 1.17 (t, 1H, J ) 6.4 Hz), 1.09 (m, 2H) and 0.69
(t, 1H, J ) 4.2 Hz); 13C NMR δ 64.19, 27.49, 16.91, 16.49, 10.42,
8.14; EI-MS m/z 114 (M - Cl, 4.9), 55 (100.0); HRMS calcd for
C6H8N (M - H - H2O - HCl) 94.0657, found 94.0655. Anal.
Calcd for C6H12ClNO: C, 48.16; H, 8.03; N, 9.36. Found: C,
47.93; H, 7.97; N, 9.16.
Hz) and 1.59 (1H, m), 1.00 (1H, dd, 2J ) 4.8 Hz, J cis ) 8.1
Hz) and 0.90 (1H, t, J ) 3J trans ) 4.9 Hz); 13C NMR δ 152.70,
2
151.63, 150.79, 145.55, 131.80, 62.68, 30.03, 20.51, 19.74,
12.63, 8.66; EI-MS m/z 253 (6.8) and 251 (M + H, 24.5), 252
(4.4) and 250 (M, 5.0), 235 (17.8) and 233 (M - OH, 50.3), 221
(76.0) and 219 (M - CH2OH, 100.0), 206 (18.7), 181 (25.2),
155 (97.0); HRMS calcd C11H1135ClN4O 250.0621, found
250.0624.
1
Da ta for m ed ia l-a n ti isom er 25c: H NMR (D2O) δ 3.50
(2H, dd, J ) 3.6 and 9.6 Hz), 2.98 (1H, d, J ) 4.2 Hz), 1.56 (m,
1H), 1.32 (1H, t, J ) 6.7 Hz), 1.16 (2H, m), and 0.83 (1H, t, J
) 4.2 Hz); 13C NMR δ 64.24, 26.29, 19.46, 17.27, 10.04, 8.22;
EI-MS m/z 114 (M - Cl, 14.1), 55 (100.0); HRMS calcd for
C6H12NO (M - Cl) 114.0919, found 114.0918.
Da ta for d ista l isom er 26d : yield 291 mg (57%) from 25d
(300 mg, 2.03 mmol), 4,6-dichloro-5-nitropyrimidine (472 mg,
2.43 mmol), Et3N (0.707 mL, 5.07 mmol), EtOH (16.0 mL), CH-
(OEt)3 (25 mL), and SnCl2‚H2O (2.75 g, 12.2 mmol); solvent
for chromatography CH2Cl2-MeOH (25:1 f 20:1); UV max
1
1
Da ta for d ista l isom er 25d : H NMR (D2O) δ 3.45 (2H,
(EtOH) 265, 215 nm; H NMR (CDCl3) δ 8.61 and 8.20 (2H,
3
3
3
3
m), 2.86 (1H, dd, J trans ) 2.5 Hz, J cis ) 6.7), 1.56 (m, 1H),
2s), 3.84 (1H, dd, J trans ) 3.0 Hz, J cis ) 6.9 Hz), 3.76 (1H, br
3 2
2
3
2
1.32 (1H, t, J ) J trans ) 6.5 Hz) and 1.13 (1H, dd, J ) 4.8
s), 3.66 (1H, dd, J ) 6.3 Hz, J ) 11.3 Hz) and 3.50 (1H, dd,
3J ) 7.3 Hz, 2J ) 11.3 Hz), 1.84 (1H, dt, J ) 6.3 Hz), 1.76 (1H,
t, J ) 6.4 Hz) and 1.50 (1H, dd, J ) 3.3 and 5.7 Hz), 1.26 (1H,
3
2
3
Hz, J trans ) 8.4 Hz), 1.07 (1H, dd, J ) 3.3 Hz, J cis ) 6.3 Hz)
and 0.79 (1H, t, J ) 4.8 Hz); 13C NMR δ 63.84, 27.51, 18.84,
17.03, 8.15, 7.94; EI-MS m/z 114 (M - Cl, 3.4), 55 (100.0);
HRMS calcd for C6H12NO (M - Cl) 114.0919, found 114.0916;
HRMS calcd for C6H8N (M - H - H2O - HCl) 94.0657, found
94.0659.
2
3
2
3
dd, J ) 4.8 Hz, J cis ) 8.4 Hz) and 0.76 (1H, t, J ) J trans
)
4.8 Hz); 13C NMR δ 152.78, 151.86, 150.57, 145.00, 131.24,
64.39, 31.25, 20.19, 11.32, 9.62; EI-MS 253 (3.9) and 251 (M
+ H, 13.2), 252 (3.0) and 250 (M, 4.7), 235 (13.8) and 233 (M
- OH, 43.6), 221 (67.5) and 219 (M - CH2OH, 100.0); EI-MS
calcd for C11H1135ClN4O 250.0621, found 250.0618.
6-Ch lor o-9-(5-h ydr oxym eth ylspir open t-1-yl)pu r in es 26a
- 26d . A mixture of aminospiropentane 25a , 25b, 25c, or 25d ,
4,6-dichloro-5-nitropyrimidine (1.2 molar equiv), and Et3N (2.5
molar equiv) in ethanol was stirred at room temperature for
2 h. The solvents were evaporated, and a solid residue was
stirred with an excess of triethyl orthoformate and SnCl2‚H2O
(6.0 molar equiv) at room temperature for 16 h. After evapora-
tion of solvents, water (20 mL) was added, and the pH was
adjusted to 8.0 with saturated aqueous K2CO3. The solution
was evaporated, the residue was washed with CH2Cl2-MeOH
(10:1, 5 × 30 mL), and evaporation of the solvents gave the
crude product, which was purified by column chromatography
on silica gel to furnish compound 26a , 26b, 26c, or 26d ).
Da ta for pr oxim a l isom er 26a : yield 156 mg (47%) from
25a (198 mg, 1.28 mmol), 4,6-dichloro-5-nitropyrimidine (312
mg, 1.60 mmol), Et3N (0.465 mL, 3.3 mmol), EtOH (10.0 mL),
CH(OEt)3 (15 mL), and SnCl2‚H2O (1.82 g, 8.0 mmol); solvent
for chromatography CH2Cl2-MeOH (40:1 f 30:1); UV max
9-(5-Hydr oxym eth ylspir open tyl-1-yl)aden in es 12a, 13a,
14a , a n d 15a . A mixture of 6-chloro-9-(5-hydroxymethylspiro-
pentyl-1-yl)purine 26a , 26b, 26c, or 26d in 25% NH3 in
methanol (50 mL) was heated in an autoclave at 100 °C (oil
bath) for 15 h. After cooling, the volatile components were
evaporated, and the crude product was chromatographed on
a silica gel column in CH2Cl2-methanol (100:5 f 100:10) to
give compound 12a , 13a , 14a , or 15a .
Da ta for pr oxim a l isom er 12a : yield 126 mg (80%) from
26a (172 mg, 0.69 mmol); mp 235-237 °C; UV max (EtOH)
261 (ꢀ 14 000), 209 (ꢀ 19 000) nm; 1H NMR (500 MHz, DMSO-
d6) δ 8.11 (2H, 2 overlapped s, H2 and H8), 7.19 (2H, s, NH2),
3
4.35 (1H, t, J ) 5.4 Hz, OH), 4.01 (1H, dd, J trans ) 3.5 Hz,
3J cis ) 7.5 Hz, H1′), 2.95 (1H, dt, 3J ) 5.5 Hz, 2J ) 11.0 Hz)
3
2
and 2.82 (1H, ddd, J ) 4.5 and 7.5 Hz, J ) 12.0 Hz, H6′′ and
H6′), 2.01 (1H, dd, J ) 4.0 and 5.5 Hz, H2′′), 1.49 (2H, m, H2′
(EtOH) 265, 217 nm; H NMR (CDCl3) δ 8.59 and 8.22 (2H,
and H5′), 1.00 (1H, dd, 2J ) 4.5 Hz, J cis ) 7.5 Hz, H4′), 0.89
1
3
2s), 4.07 (1H, dd, 3J trans ) 3.3 Hz, 3J cis ) 7.2 Hz), 3.52 (1H, dd,
3J ) 5.0 Hz, 2J ) 11.0 Hz) and 3.17 (1H, dd, 3J ) 7.0 Hz, 2J )
11.0 Hz), 3.37 (1H, br s), 1.79 (1H, dd, J ) 3.8 and 6.0 Hz),
1.63 (2H, m), 1.06 (2H, m); 13C NMR δ 153.00, 151.40, 150.40,
144.91, 131.63, 62.27, 32.70, 20.47, 19.79, 12.13, 10.40; EI-
MS m/z 253 (4.8) and 251 (M + H, 19.0), 252 (2.9) and 250
(M, 4.6), 235 (17.5) and 233 (M - OH, 58.2), 221 (70.5) and
219 (M - CH2OH, 100.0); HRMS calcd for C11H1135ClN4O
250.0621, found 250.0620.
(1H, d, J ) 4.0 and 4.5 Hz, H4′′); 13C NMR (125.7 MHz) δ
156.37, 152.74, 151.15, 139.53, 119.51 (purine), 62.29 (C6′),
32.07 (C1′), 20.72 (C5′), 19.96 (C3′), 11.93 (C2′), 10.70 (C4′); EI-
MS m/z 232 (M + H, 15.2), 231 (M, 9.1), 214 (M - OH, 79.6),
200 (M - CH2OH, 100.0), 135 (adenine, 53.9); HRMS calcd
for C11H13N5O 231.1120, found 231.1116. Anal. Calcd for
C
11H13N5O: C, 57.12; H, 5.67; N, 30.29. Found: C, 57.21; H,
5.77; N, 30.14.
Da ta for m ed ia l-syn isom er 13a : yield 139 mg (88%) from
26b (160 mg, 0.64 mmol); mp 188-190 °C; UV max (EtOH)
261 (ꢀ 14 700), 208 (ꢀ 20 400) nm; 1H NMR (500 MHz, DMSO-
d6) δ 8.12 (1H, s, H2), 8.11 (1H, s, H8), 7.20 (2H, s, NH2), 4.60
Da ta for m ed ia l-syn isom er 26b: yield 181 mg (56%) from
25b (190 mg, 1.28 mmol), 4,6-dichloro-5-nitropyrimidine (300
mg, 1.54 mmol), Et3N (0.446 mL, 3.2 mmol), EtOH (10.0 mL),
CH(OEt)3 (15 mL), and SnCl2‚H2O (1.75 g, 7.68 mmol); solvent
for chromatography CH2Cl2-MeOH (30:1 f 25:1); UV max
3
3
(1H, t, J ) 5.5 Hz, OH), 3.86 (1H, dd, J trans ) 3.5 Hz, J cis
)
7.0, H1′), 3.50 (1H, td, 3J ) 5.5 Hz, 2J ) 11.0 Hz) and 3.20
(1H, ddd, 3J ) 4.5 and 7.5 Hz, 2J ) 11.5 Hz, H6′′ and H6′), 1.65
(1H, dd, J ) 3.5 and 5.5 Hz, H2′′), 1.49 (2H, apparent t, J )
5.5 Hz, H2′ and H5′), 1.23 (1H, dd, 2J ) 4.5 Hz, 3J cis ) 8.0, H4′),
1
(EtOH) 265 (ꢀ 10 800), 215 (ꢀ 16 500) nm; H NMR (CDCl3) δ
3
3
8.58 and 8.41 (2H, 2s), 4.07 (1H, dd, J trans ) 3.5 Hz, J cis
)
7.0 Hz), 3.94 (1H, dd, 3J ) 5.1 Hz, 2J ) 10.2 Hz) and 3.27 (1H,
dd, J ) 9.0 Hz, J ) 10.8 Hz), 2.80 (1H, br s, OH), 1.73 (1H,
dd, J ) 3.5 and 5.6 Hz), 1.60 (1H, t, J ) 6.5 Hz) and 1.58 (3H,
0.75 (1H, t, J ) J trans ) 4.5 Hz, H4′′); 13C NMR (125.7 MHz)
δ 156.38, 152.87, 150.95, 139.93, 119.19 (purine), 64.21 (C6′),
30.86 (C1′), 20.24 (C5′), 18.77 (C3′), 11.45, 11.21 (C2′, C4′); EI-
MS m/z 232 (M + H, 14.0), 231 (M, 14.5), 214 (M - OH, 66.1),
200 (M - CH2OH, 100.0), 135 (adenine, 54.8); HRMS calcd
for C11H13N5O 231.1120, found 231.1120. Anal. Calcd for
2
3
2
3
m), 1.33 (1H, dd, J ) 4.8 Hz, J cis ) 8.4 Hz) and 0.85 (1H, t,
2J ) J trans ) 4.8 Hz); 13C NMR δ 152.50, 151.64, 150.45,
3
144.44, 131.21, 65.06, 32.13, 20.29, 18.85, 11.93, 11.52; EI-
MS m/z 253 (5.2) and 251 (M + H, 20.2), 252 (3.0) and 250
(M, 4.8), 235 (18.4) and 233 (M - OH, 42.8), 221 (64.1) and
219 (M - CH2OH, 100.0); HRMS calcd for C11H1135ClN4O
250.0621, found 250.0618.
C
11H13N5O‚0.9H2O: C, 53.39; H, 6.03; N, 28.30. Found: C,
53.16; H, 5.89; N, 28.64.
Da ta for m ed ia l-a n ti isom er 14a : yield 136 mg (75%)
from 26c (195 mg, 0.78 mmol); mp 185-187 °C; UV max
(EtOH) 261 (ꢀ 14 800), 209 (ꢀ 19 700) nm; 1H NMR (500 MHz,
DMSO-d6) δ 8.11 (1H, s, H2), 8.10 (1H, s, H8), 7.21 (2H, s, NH2),
Da ta for m ed ia l-a n ti isom er 26c: yield 203 mg (45%)
from 25c (270 mg, 1.82 mmol), 4,6-dichloro-5-nitropyrimidine
(423 mg, 2.18 mmol), Et3N (0.634 mL, 4.55 mmol), EtOH (16.0
mL), CH(OEt)3 (25 mL), and SnCl2‚H2O (2.46 g, 6.0 mmol);
solvent for chromatography CH2Cl2-MeOH (25:1 f 20:1); UV
3
4.60 (1H, t, J ) 5.0 Hz, OH), 3.86 (1H, dd, J trans ) 3.5 Hz,
3J cis ) 7.5 Hz, H1′), 3.71 (1H, td, 3J ) 5.5 Hz, 2J ) 11.0 Hz)
1
3
2
max (EtOH) 265, 217 nm; H NMR (CDCl3) δ 8.60 and 8.21
and 3.68 (1H, td, J ) 5.5 Hz, J ) 11.0 Hz, H6′′ and H6′), 1.69
3 2
(2H, 2s), 3.98 (1H, dd, 3J ) 5.0 Hz, 2J ) 11.3 Hz) and 3.90
(3H, m), 1.69 (1H, t, J ) 6.4 Hz), 1.61 (1H, dd, J ) 3.3 and 5.7
(1H, dd, J ) 3.5 and 5.0 Hz, H2′′), 1.55 (1H, t, J cis ) J ) 6.5
Hz, H2′), 1.47 (1H, m, H5′), 0.95 (1H, dd, 2J ) 4.5 Hz, J cis
3

Spiropentane Mimics of Nucleosides
J . Org. Chem., Vol. 65, No. 5, 2000 1289
) 8.0 Hz, H4′), 0.75 (1H, t, 2J ) 3J trans ) 4.5 Hz, H4′′); 13C NMR
(125.7 MHz) δ 156.41, 152.91, 151.08, 140.69, 119.28 (purine),
63.43 (C6′), 29.26 (C1′), 21.13 (C5′), 20.61 (C3′), 12.40 (C2′), 9.03
(C4′); EI-MS m/z 232 (M + H, 3.0), 231 (M, 8.2), 230 (M - H,
8.2), 214 (M - OH, 63.7), 200 (M - CH2OH, 100.0), 135
(adenine, 62.4); HRMS calcd for C11H13N5O 231.1120, found
231.1117. Anal. Calcd for C11H13N5O: C, 57.12; H, 5.67; N,
30.29. Found: C, 56.91; H, 5.68; N, 30.41.
8.98; EI-MS m/z 309 (1.1) and 307 (M, 5.8), 292 (7.0) and 290
(21.3, M - OH), 172 (25.2) and 170 (59.4, purine base - CH2d
CdO + H), 171 (46.5) and 169 (100.0, purine base - CH2d
CdO); HRMS calcd for
C
13H14N5O235Cl 307.0836, found
307.0840.
Da ta for d ista l isom er 30d : yield 278 mg (48%) from 25d
(282 mg, 1.90 mmol), 2-acetamino-4,6-dichloro-5-nitropyrimi-
dine (510 mg, 2.03 mmol), Et3N (0.532 mL, 3.80 mmol) in DMF
(16 mL), SnCl2‚H2O (2.57 g, 11.4 mmol), and CH(OEt)3 (20
mL); amorphous solid; UV max (EtOH) 289, 260, 234, 204 nm;
1H NMR (DMSO-d6) δ 10.80 (1H, s), 8.49 (1H, s), 4.55 (1H, t,
Da ta for d ista l isom er 15a : yield 240 mg (91%) from 26d
(285 mg, 1.36 mmol); mp 211-214 °C; UV max (EtOH) 261 (ꢀ
1
15 400), 209 (ꢀ 20 800) nm; H NMR (500 MHz, DMSO-d6) δ
3
8.10 (1H, s, H2), 8.09 (1H, s, H8), 7.21 (2H, s, NH2), 4.57 (1H,
J ) 5.4 Hz), 3.78 (1H, dd, J trans ) 3.0 Hz, 3J cis ) 6.8 Hz), 3.44
3
3
t, J ) 5.5 Hz, OH), 3.74 (1H, dd, J trans ) 3.0 Hz, J cis ) 7.5
Hz, H1′), 3.44 (1H, td, 3J ) 5.5 Hz, 2J ) 12.0 Hz) and 3.32
(1H, ddd, 3J ) 5.5 and 7.0 Hz, 2J ) 12.0 Hz, H6′′ and H6′), 1.64
(2H, m, H2′ and H5′), 1.54 (1H, dd, J ) 3.0 and 5.0 Hz, H2′′),
(1H, qt, J ) 5.7 Hz) and 3.28 (1H, qt, J ) 6.0 Hz), 2.20 (3H,
2
3
s), 1.66 (2H, m), 1.59 (1H, t, J ) J trans ) 4.2 Hz), 1.22 (1H,
2
3
2
3
dd, J ) 4.2 Hz, J cis ) 8.1 Hz), 0.93 (1H, t, J ) J trans ) 4.2
Hz); 13C NMR δ 169.29, 154.14, 152.45, 149.33, 146.32, 127.43,
63.66, 30.98, 25.0, 20.5, 10.8, 9.3; EI-MS m/z 309 (2.8) and 307
(9.7, M), 292 (4.5) and 290 (19.2, M - OH), 172 (22.6) and 170
(64.2, purine base - CH2dCdO + H), 171 (43.9) and 169
(100.0, purine base - CH2dCdO).
2
3
1.10 (1H, dd, J ) 4.0 Hz, J cis ) 8.0 Hz, H4′), 0.66 (1H, dd, J
) 4.0 and 4.4 Hz, H4′′); 13C NMR (125.7 MHz) δ 156.39, 152.99,
151.06, 140.62, 119.14 (purine), 63.74 (C6′), 30.53 (C1′), 20.53,
20.48 (C5′, C3′), 10.86 (C2′), 9.34 (C4′); EI-MS m/z 232 (M + H,
3.8), 231 (M, 13.0), 230 (6.0), 214 (M - OH, 67.7), 202 (22.6),
200 (M - CH2OH, 100.0), 187 (16.8), 146 (17.5), 135 (adenine,
56.3); HRMS calcd for C11H13N5O 231.1120, found 231.1112.
Anal. Calcd for C11H13N5O: C, 57.12; H, 5.67; N, 30.29.
Found: C, 56.91; H, 5.68; N, 30.41.
9-(5-Hyd r oxym eth ylsp ir op en t-1-yl)gu a n in es 12b, 13b,
14b, a n d 15b. A solution of compound 30a , 30b, 30c, or 30d
(150-300 mg, 0.5-1 mmol) in formic acid (80%, 10 mL) was
heated at 90 °C for 16 h, whereupon it was evaporated. The
solid residue was dissolved in water, and after lyophilization
the crude product was stirred in NH3/MeOH (20%, 8 mL) for
4 h at room temperature. The solvent was removed and the
product recrystallized from MeOH-H2O (15:1) to give com-
pound 12b, 13b, 14b, or 15b as a white solid.
2-Aceta m in o-6-ch lor o-9-(5-h yd r oxym eth ylsp ir op en t-1-
yl)p u r in es 30a , 30b, 30c, a n d 30d . Compounds 30a -30d
were prepared by a modification of the procedure employed
for the synthesis of 26a -26d . 2-Acetamino-4,6-dichloro-5-
nitropyrimidine in DMF at 0 °C was used in reactions with
aminospiropentanes 25a -25d . The products 30a -30d were
chromatographed in CH2Cl2-MeOH (40:1 f 20:1).
Da ta for pr oxim a l isom er 12b: yield 132 mg (77%) from
30a (210 mg, 0.68 mmol); mp 235-237 °C dec; UV max (EtOH)
257 (ꢀ 14 200), 206 (ꢀ 15 300) nm; 1H NMR (DMSO-d6) δ 10.59
(1H, s, NH), 7.65 (1H, s, H8), 6.46 (2H, s, NH2), 4.39 (1H, t, J
Da ta for pr oxim a l isom er 30a : yield 212 mg (41%) from
25a (250 mg, 1.69 mmol), 2-acetamino-4,6-dichloro-5-nitropy-
rimidine (470 mg, 1.86 mmol), Et3N (0.485 mL, 3.5 mmol) in
DMF (10.0 mL), SnCl2‚H2O (2.28 g, 10.2 mmol), and CH(OEt)3
(15 mL); mp 200-205 °C; UV max (EtOH) 289 (ꢀ 10 200), 235
3
3
) 5.0 Hz, OH), 3.78 (1H, dd, J trans ) 3.3 Hz, J cis ) 6.9 Hz,
H1′), 3.06 (1H, m) and 2.81 (1H, m, H6′′ and H6′), 1.84 (1H, t,
2J ) J trans ) 4.5 Hz, H2′′), 1.49 (1H, m, H5′), 1.39 (1H, t, J cis
3
3
2
3
) 6.4 Hz, H2′), 0.97 (1H, dd, J ) 3.9 Hz, J cis ) 6.6 Hz, H4′),
3
(ꢀ 24 800), 204 (ꢀ 17 100) nm; 1H NMR (DMSO-d6) δ 10.80 (1H,
0.82 (1H, t, 2J ) J trans ) 4.0 Hz, H4′′); 13C NMR δ 157.26,
3
s), 8.49 (1H, s), 4.16 (1H, t, J ) 4.5 Hz), 4.01 (1H, dd, J trans
)
153.85, 152.94, 135.61, 117.28 (purine), 62.37 (C6′), 31.74 (C1′),
20.58, 19.86 (C5′, C3′), 12.0, 10.6 (C2′, C4′); FAB-MS m/z 249
(M, 15.6), 248 (M + H, 100.0), 215 (M - H - CH2OH, 2.1).
Anal. Calcd for C11H13N5O2‚0.2H2O: C, 52.67; H, 5.38; N,
27.92. Found: C, 52.48; H, 5.57; N, 27.78.
3.0 Hz, J cis ) 7.2 Hz), 3.09 (1H, dd, 3J ) 4.8 Hz, 2J ) 10.0
3
Hz) and 2.92 (1H, dd, 3J ) 5.5 Hz, 2J ) 11.0), 2.20 (3H, s),
2
2.15 (1H, t, J ) 4.0 Hz), 1.50 (2H, m), 0.97 (1H, dd, J ) 4.2
Hz, 3J cis ) 7.5 Hz), 0.85 (1H, t, 2J ) 3J trans ) 4.2 Hz); 13C NMR
δ 169.21, 154.29, 152.16, 149.04, 145.59, 127.93, 62.28, 32.58,
24.99, 20.48, 20.07, 11.07, 10.74.
Da ta for m ed ia l-syn isom er 13b: yield 199 mg (84%) from
30b (290 mg, 0.94 mmol); mp 310-315 °C; UV max (EtOH)
256 (ꢀ 13 800), 206 (ꢀ 17 600) nm; 1H NMR (DMSO-d6) δ 10.60
(1H, s, NH), 7.65 (1H, s, H8), 6.48 (2H, s, NH2), 4.60 (1H, br,
Da ta for m ed ia l-syn isom er 30b: yield 303 mg (58%) from
25b (252 mg, 1.70 mmol), 2-acetamino-4,6-dichloro-5-nitropy-
rimidine (478 mg, 1.90 mmol), Et3N (0.475 mL, 3.40 mmol) in
DMF (10.0 mL), SnCl2‚H2O (2.30 g, 10.2 mmol), and CH(OEt)3
(15 mL); mp 233-235 °C; UV max (EtOH) 288 (ꢀ 10 500), 260
(ꢀ 7 900), 234 (ꢀ 26 400), 203 (ꢀ 18 400) nm; 1H NMR (DMSO-
d6) δ 10.80 (1H, s), 8.50 (1H, s), 4.49 (1H, t, J ) 5.5 Hz), 3.87
3
3
OH), 3.66 (1H, dd, J trans ) 3.3 Hz, J cis ) 6.9 Hz, H1′), 3.50
3
2
3
(1H, dd, J ) 6.0 Hz, J ) 11.0 Hz) and 3.20 (1H, dd, J ) 7.8
2
Hz, J ) 11.0 Hz, H6′′ and H6′), 1.48 (2H, m, H2′′ and H5′), 1.39
2
3
(1H, t, J ) 6.2 Hz, H2′), 1.16 (1H, dd, J ) 4.2 Hz, J cis ) 8.1
Hz, H4′), 0.71 (1H, t, 2J ) J trans ) 4.2 Hz, H4′′); 13C NMR δ
3
3
3
3
(1H, dd, J trans ) 3.0 Hz, J cis ) 6.9 Hz), 3.49 (1H, td, J ) 5.5
157.21, 153.95, 152.70, 136.00, 116.88 (purine), 64.19 (C6′),
30.64 (C1′), 19.98, 18.70 (C5′, C3′), 11.37 (C2′, C4′); FAB-MS m/z
249 (M, 15.5), 248 (M + H, 100.0), 217 (M + H - CH2OH,
16.8). Anal. Calcd for C11H13N5O2‚0.2H2O: C, 52.67; H, 5.38;
N, 27.92. Found: C, 52.38; H, 5.54; N, 27.83.
2
3
2
Hz, J ) 11.0 Hz) and 3.13 (1H, ddd, J ) 4.5 and 6.0 Hz, J
) 10.5 Hz), 2.20 (3H, s), 1.73 (1H, m), 1.53 (2H, m), 1.25 (1H,
2
3
2
3
dd, J ) 4.2 Hz, J cis ) 8.1 Hz), 0.76 (1H, t, J ) J trans ) 4.2
Hz); 13C NMR δ 169.76, 154.01, 152.15, 149.40, 145.97, 127.49,
64.91, 31.15, 24.88, 20.46, 18.54, 11.18, 10.98; EI-MS m/z 309
(1.1) and 307 (M, 3.9), 292 (3.0) and 290 (8.8, M - OH), 172
(8.7) and 170 (21.7, purine base - CH2dCdO + H), 171 (15.9)
and 169 (32.9, purine base - CH2dCdO), 43 (Ac, 100.0);
HRMS calcd for C13H1435ClN5O2 307.0836, found 307.0831.
Anal. Calcd for C13H14ClN5O2: C, 50.74; H, 4.59; N, 22.76.
Found: C, 50.58; H, 4.80; N, 22.69.
Da ta for m ed ia l-a n ti isom er 14b: yield 125 mg (80%)
from 30c (190 mg, 0.62 mmol); mp 292-295 °C dec; UV max
1
(EtOH) 256 (ꢀ 13 300), 206 (ꢀ 17 000) nm; H NMR (DMSO-
d6) δ 10.54 (1H, s), 7.66 (1H, s, H8), 6.35 (2H, s), 4.51 (1H, t, J
3
) 5.7 Hz, OH), 3.65 (2H, m, H1′ + H6′′) and 3.55 (1H, td, J )
2
6.5 Hz, J ) 13.0 Hz, H6′), 1.46 (3H, m, H5′, H2′ and H2′′), 0.96
3
(1H, dd, 2J ) 4.2 Hz, J cis ) 7.8 Hz, H4′), 0.71 (1H, t, 2J )
Da ta for m ed ia l-a n ti isom er 30c: yield 193 mg (50%)
from 25c (185 mg, 1.25 mmol), 2-acetamino-4,6-dichloro-5-
nitropyrimidine (330 mg, 1.31 mmol), Et3N (0.350 mL, 2.5
mmol) in DMF (10 mL), SnCl2‚H2O (1.70 g, 7.5 mmol), and
CH(OEt)3 (20 mL); mp 194-196 °C; UV max (EtOH) 289, 260,
3J trans ) 4.5 Hz, H4′′); 13C NMR δ 157.22, 153.89, 152.80, 136.90,
116.93 (purine), 63.38 (C6′), 29.03 (C1′), 21.10, 20.28 (C5′, C3′),
12.8, 9.0 (C2′, C4′); FAB-MS m/z 249 (M, 15.2), 248 (M + H,
100.0), 215 (M - H - CH2OH, 3.7). Anal. Calcd for C11H13N5O2‚
0.2H2O: C, 52.67; H, 5.38; N, 27.92. Found: C, 52.46; H, 5.56;
N, 27.98.
1
234, 204 nm; H NMR (DMSO-d6) δ 10.80 (1H, s), 8.49 (1H,
3
s), 4.47 (1H, t, J ) 5.5 Hz, OH), 3.91 (1H, dd, J trans ) 3.0 Hz,
Da ta for d ista l isom er 15b: yield 180 mg (85%) from 30d
(260 mg, 0.85 mmol); mp 305-310 °C dec; UV max (EtOH)
256 (ꢀ 13 500), 206 (ꢀ 16 100) nm; 1H NMR (DMSO-d6) δ 10.55
(1H, s, NH), 7.68 (1H, s, H8), 6.40 (2H, s, NH2), 4.52 (1H, t, J
3J cis ) 6.9 Hz), 3.72 (2H, m), 2.20 (3H, s), 1.71 (1H, dd, J ) 3.5
3
and 5.4 Hz), 1.57 (1H, dd, 2J ) 5.4 Hz, J cis ) 6.9 Hz), 1.44
(1H, m), 0.93 (2H, m); 13C NMR δ 169.04, 154.17, 152.27,
3
3
149.36, 146.72, 127.63, 63.36, 29.81, 24.81, 21.13, 20.76, 12.63,
) 5.2 Hz, OH), 3.55 (1H, dd, J trans ) 3.3 Hz, J cis ) 6.9

1290 J . Org. Chem., Vol. 65, No. 5, 2000
Guan et al.
Hz, H1′), 3.39 (1H, td, 3J ) 5.7 Hz, 2J ) 11.4 Hz) and 3.28
(1H, td, J ) 5.7 and 11.4 Hz, H6′′ and H6′), 1.54 (2H, m, H2′
Ad en osin e Dea m in a se Assa y.6 Compounds 12a -15a (0.6
mg, 2.6 µmol) and adenosine deaminase from calf intestine
(0.45 unit) were incubated in 0.05 M Na2HPO4 (pH 7.5, 0.4
mL) at room temperature with magnetic stirring. Aliquots
were periodically withdrawn and examined by TLC in CH2-
Cl2-MeOH (9:1). The spots of starting material and deami-
nation product were eluted with ethanol, and the UV spectra
3
and H5′), 1.38 (1H, t,2J ) J trans ) 4.3 Hz, H2′′), 1.11 (1H, dd,
3
2
3
3J trans ) 4.2 Hz, J cis ) 8.0 Hz, H4′), 0.65 (1H, t, J ) J trans
)
4.3 Hz, H4′′); 13C NMR δ 157.25, 153.89, 152.87, 136.84, 117.00
(purine), 63.7 (C6′), 30.33 (C1′), 20.40, 20.28 (C5′, C3′), 10.9, 9.3
(C2′, C4′); FAB-MS m/z 249 (M, 17.5), 248 (M + H, 100.0), 216
(M - CH2OH, 19.1). Anal. Calcd for C11H13N5O2‚0.2H2O: C,
52.67; H, 5.38; N, 27.92. Found: C, 52.25; H, 5.56; N, 27.58.
m ed ia l-syn -9-(5′-Hyd r oxym eth ylsp ir op en ta n -1′-yl)a d -
en in e (R,S)-4′-(m eth ylp h en ylp h osp h or yl-(P fN)-L-a la n i-
n a te (34). A suspension of medial-syn-9-(5′-hydroxymethyl-
spiropentan-1′-yl)adenine (13a; 200 mg, 0.866 mmol) in pyridine
(15 mL) was sonicated for 10 min with external ice-cooling. A
solution of phenyl chlorophosphoralaninate32 in THF (0.161
M, 21.5 mL, 3.46 mmol) was then added with stirring followed
by N-methylimidazole (6.93 mmol, 0.552 mL). The stirring was
continued at room temperature for 4 h. The solvent was
evaporated under reduced presure at 40 °C, and the residue
was purified by chromatography on a silica gel column using
CH2Cl2-CH3OH (20:1 f 10:1) to give compound 34 (198 mg,
49%) as a colorless foam: HPLC (H2O-MeCN, 4:1, broad
peak,36 retention time 7.72 min, purity 98.2%); UV max (EtOH)
261 (ꢀ 13 100), 206 (ꢀ 25 400) nm; 1H NMR (CDCl3) δ 8.22 (1H,
s) and 7.84, 7.81, 7.74 and 7.72 (1H, 4s, H8 and H2), 7.10 (2H,
m) and 7.03 (3H, m, Ph, 6.72 (2H, s, NH2), 4.74 (1H, m, NH of
Ala), 4.21 (1H, m, H1′), 3.80 (3H, H6′ and CH of Ala), 3.57 (3H,
4s, OCH3), 1.73 (1H, m, H5′), 1.50 (2H, m, H2′ and H2′′), 1.44
were taken. Only compound 14a was deaminated with t1/2
120 h.
>
P LE Assa y.31 A magnetically stirred mixture of compound
34 (0.72 mg, 1.5 µM) and PLE (200 units) was incubated at
40 °C. TLC in CH2Cl2-MeOH (9:1) and 2-propanol-NH4OH-
H2O (7:1:2) showed complete hydrolysis of 34 after 24 h.
Ack n ow led gm en t. Our thanks are due to Dr. Steve
M. Hannick, Abbott Laboratories, Abbott Park, IL, for
a synthetic procedure for 2-acetamino-6-chloro-5-nitro-
4-pyrimidinol and the Central Instrumentation Facility,
Department of Chemistry, Wayne State University (Dr.
Robin J . Hood, Director), for mass spectra. We thank
Roger G. Ptak and J ulie M. Breitenbach for some
antiviral assays. The work described herein was sup-
ported by U.S. Public Health Service Research Grants
RO1-CA32779 (J .Z.) RO1-CA44358 (Y.-C.C.) from the
National Cancer Institute, U19-AI31718, and RO1-
AI33332 (J .C.D.) and Contract NO1-AI35177 (E.R.K.)
from the National Institute of Allergy and Infectious
Diseases, National Institutes of Health, Bethesda, MD.
(1H, m) and 0.90 (2H, m, H4′ and H4′′), 1.20 (3H, m, CH3); 13
C
NMR δ 174.08 (CO), 155.83, 152.95, 152.77, 150.90, 150.68,
139.84, 129.51, 124.70, 120.65, 120.01, 119.33 (purine), 69.70,
52.27, 50.07, 30.74, 20.62, 20.22, 16.37, 11.52, 10.99; EI-MS
m/z 473 (M + H, 1.0), 472 (M, 2.8), 94 (100.0); 31P NMR 2.71,
2.70, 2.62, 2.58; HRMS calcd for C21H25N6O5P 472.1624, found
472.1632. Anal. Calcd for C21H25N6O5P: C, 53.39; H, 5.33; N,
17.79. Found: C, 53.27; H, 5.55; N, 17.55.
Su p p or tin g In for m a tion Ava ila ble: Spectroscopic data
for all new compounds. DEPT and (H,H) COSY spectra of 12a ,
13a , 14a , and 15a and (H,C) COSY spectra of 14a and 15a .
This material is available free of charge via the Internet at
http://pubs.acs.org.
(36) The product is a mixture of four diastereoisomers; see the 31P
NMR spectrum.
J O991030R