Synthesis and conformational study of 3-hydroxy-4-(hydroxymethyl)-1-cyclohexanyl purines and pyrimidines

Article abstract of DOI:10.1021/jo962204x

The cyclohexane nucleosides with a 1,4-relationship between nucleoside base and hydroxymethyl moiety were synthesized using a conjugated addition reaction of the nucleobases to ethyl 1,3-cyclohexadiene-1-carboxylate and hydroboration of the cyclohexenyl precursor. The lack of antiviral activity of the compounds was correlated with the conformation of these nucleosides as deduced from NMR and X-ray analysis.

Full text of DOI:10.1021/jo962204x

J . Org. Chem. 1997, 62, 2861-2871
2861
Syn th esis a n d Con for m a tion a l Stu d y of
3-Hyd r oxy-4-(Hyd r oxym eth yl)-1-Cycloh exa n yl P u r in es a n d
P yr im id in es
Yuris Maurinsh,† J an Schraml,† Hans De Winter,† Norbert Blaton,‡ Oswald Peeters,‡
Eveline Lescrinier,† J ef Rozenski,† Arthur Van Aerschot,† Erik De Clercq,† Roger Busson,† and
Piet Herdewijn*,†
Rega Institute for Medical Research and Faculty of Pharmacy, Katholieke Universiteit Leuven,
B-3000 Leuven, Belgium
Received November 26, 1996X
The cyclohexane nucleosides with a 1,4-relationship between nucleoside base and hydroxymethyl
moiety were synthesized using a conjugated addition reaction of the nucleobases to ethyl
1,3-cyclohexadiene-1-carboxylate and hydroboration of the cyclohexenyl precursor. The lack of
antiviral activity of the compounds was correlated with the conformation of these nucleosides as
deduced from NMR and X-ray analysis.
In tr od u ction
to this problem are possible. In our hands, a Pd(0)-
catalyzed alkylation of heterocyclic bases by allylic ep-
oxide afforded low yield.7 Better results were obtained
using a Mitsunobu-type condensation of nucleoside bases
with an unsaturated alcohol. The allylic alcohol has
higher reactivity in nucleophilic substitution reactions,
and the saturated compound could be obtained after
catalytic hydrogenation.7 Another possibility is to intro-
duce the base moiety by a Michael-type addition which
likewise works efficiently.4 This method was used here
to synthesize the carbocyclic analogues of anhydrohexitol
nucleosides. Hydroboration of the resulting cyclohexenyl
derivatives was investigated to obtain the desired trans-
relationship between the 3′-hydroxyl group and the 4′-
hydroxymethyl functionality in a reaction which is not
obvious in the presence of reactive heterocycles like
pyrimidines and purines. NMR and X-ray analysis
demonstrated an opposite conformation between anhy-
drohexitol nucleosides and their carbocyclic congeners,
which may explain their difference in biological activity.
Carbocyclic nucleosides are analogues of natural nu-
cleosides where the ring oxygen is replaced by a meth-
ylene group. Main efforts in this field were made to
obtain cyclopentane derivatives of the natural furanose
nucleosides.1 The interest in the chemistry of cyclohex-
ane and cyclohexene counterparts has increased
recently.2-10 One of the reasons is the significant anti-
viral activity reported for 1,5-anhydrohexitol nucleo-
sides,11,12 such as 1,5-anhydro-2,3-dideoxy-2-(5-ethyluracil-
1-yl)-D-arabino-hexitol. Therefore, we started synthesis
of carbocyclic nucleosides with a six-membered carbohy-
drate mimic,7-9 represented here by 3-hydroxy-4-(hy-
droxymethyl)-1-cyclohexyl purines and pyrimidines, and
we tried to correlate structure with biological activity.
Nucleophilic substitution in a cyclohexane ring is more
difficult than in a cyclopentane ring because of steric
hindrance, and this hampers introduction of nucleoside
bases on the six-membered ring structure. This was
experienced during the synthesis of 4,4-bis(hydroxy-
methyl) cyclohexane nucleosides9 and during introduction
of nucleoside bases in saturated six-membered car-
bocycles using Mitsunobu conditions.7 Several solutions
Resu lts a n d Discu ssion
Syn th esis. Two main strategies were used for the
synthesis of cyclohexyl nucleosides. The first method was
based on a gradual build-up of the purine heterocycle
starting from aminocyclohexanols.8,13-16 The alternative
way consisted in the reaction of purines or pyrimidines
with cyclohexyl6 or cyclohexenyl3,4,9 epoxides, Mitsunobu-
type condensation of the heterocycle with cyclohexyl
alcohols,7 or Michael-type addition of the nucleoside base
on cyclohexadienyl derivatives.2,4 The latter method was
chosen as the most appropriate for the synthesis of the
cyclohexyl nucleosides, as the presence of a double bond
in the reaction product allowed us to further introduce
the 3′-secondary alcohol function.
† Rega Institute for Medical Research.
‡ Faculty of Pharmacy.
X Abstract published in Advance ACS Abstracts, April 1, 1997.
(1) Borthwick, A. D.; Biggadike, K. Tetrahedron 1992, 48, 571-623.
(2) Halazy, S.; Kenny, M.; Dulworth, J .; Eggenspiller, A. Nucleosides
Nucleotides 1992, 11, 1595-1606.
(3) Ramesh, K.; Wolfe, M. S.; Lee, Y.; Vander Velde, D. J . Org. Chem.
1992, 57, 5861-5868.
(4) Arango, J . H.; Geer, A.; Rodriguez, J .; Young, P. E.; Scheiner, P.
Nucleosides Nucleotides 1993, 12, 773-784.
(5) Konkel, M. J .; Vince, R. Nucleosides Nucleotides 1995, 14, 2061-
2077.
(6) Calvani, F.; Macchia, M.; Rossello, A.; Gismondo, M. R.; Drago,
L.; Fassina, M. C.; Cisternino, M.; Dominiano, P. Bioorg. Med. Chem.
Lett. 1995, 5, 2567-2572.
(7) Pe´rez-Pe´rez, M. J .; Rozenski, J .; Busson, R.; Herdewijn, P. J .
Org. Chem. 1995, 60, 1531-1537.
(8) Katagiri, N.; Ito, Y.; Shiraishi, T.; Maruyama, T.; Sato, Y.;
Kaneko, C. Nucleosides Nucleotides 1996, 15, 631-647.
(9) Mikhailov, S. N.; Blaton, N.; Rozenski, J .; Balzarini, J .; De
Clercq, E; Herdewijn,P. Nucleosides Nucleotides 1996, 15, 867-878.
(10) Rosenquist, A.; Kvarnstro¨m, I.; Classon, B.; Samuelsson, B. J .
Org. Chem. 1996, 61, 6282-6288.
(11) Verheggen, I.; Van Aerschot, A.; Toppet, S.; Snoeck, R.; J anssen,
G.; Balzarini, J .; De Clercq, E.; Herdewijn, P. J . Med. Chem. 1993, 36,
2033-2040.
(12) Verheggen, I.; Van Aerschot, A.; Van Meervelt, L.; Rozenski,
J .; Wiebe, L.; Snoeck, R.; Andrei, G.; Balzarini, J .; Claes, P.; De Clercq,
E.; Herdewijn, P. J . Med. Chem. 1995, 38, 826-835.
Initially ethyl 1,3-cyclohexadienecarboxylate (1)17
(Scheme 1) was reacted with adenine 2a , 2-amino-6-
(13) (a) Schaeffer, H. J .; Weimar, R. D., J r. J . Am. Chem. Soc. 1959,
81, 197-201. (b) Schaeffer, H. J .; Weimar, R. D., J r. J . Org. Chem.
1960, 25, 774-776.
(14) Schaeffer, H. J .; Kaistha, R. K.; Chakraborti, S. K. J . Pharm.
Sci. 1964, 53, 1371-1374.
(15) Schaeffer, H. J .; Godse, D. D.; Liu, G. J . Pharm. Sci. 1964, 53,
1510-1515.
(16) Schaeffer, H. J .; Vince, R. J . Med. Chem. 1968, 11, 15-20.
S0022-3263(96)02204-9 CCC: $14.00 © 1997 American Chemical Society

2862 J . Org. Chem., Vol. 62, No. 9, 1997
Maurinsh et al.
Sch em e 1a
DIBAL in dichloromethane (Scheme 2). This procedure
afforded 5 in 75% yield from 4. To avoid possible side
reactions during hydroboration,18 the primary hydroxyl
function of 5 was first protected with a trityl group to
obtain 6. Hydroboration of 6 using BH3-THF followed
by a hydrogen peroxide basic workup gave a separable
mixture of 7 (32%) and 8a (28%). To obtain an analytical
sample of the 1′,3′-cis isomer, 8a had to be first acetylated
giving 8b, which after chromatographic purification was
converted to 10 by deprotection. Deprotection of 7
with 80% aqueous acetic acid yielded the desired
(1RS,3SR,4RS)-9-[4-(hydroxymethyl)-3-hydroxycyclohexyl]-
adenine (9) as an enantiomeric mixture. The same
sequence of reactions was used for the guanine derivative
3c (Scheme 2). Monomethoxytritylation of 3c yielded 11.
Following reduction with DIBAL, 12 was obtained in 87%
yield. Protection of the 4′-hydroxymethyl group as in 6
led to 13, which was hydroborated with the BH3-THF
complex, followed by treatment with H2O2. The only
product which could be isolated in 40% yield was com-
pound 14. Deprotection of 14 with 80% aqueous acetic
acid afforded the guanine derivative (()-15.
As pyrimidine bases are more sensitive to addition
reactions, the reaction conditions to obtain hydroxylated
cyclohexyl pyrimidines have to be carefully controlled.
With the thymine base, the reaction time had to be
reduced to 1 h as compared to 7 h for the purine
congeners. With the uracil and cytosine derivatives the
reaction was conducted at lower temperature (-10 °C to
5 °C) for a total time of 6 h. While separation of the two
1-[4-(hydroxymethyl)-3-hydroxycyclohexyl]thymine iso-
mers 18 (34%) and 19 (21%) was possible, this was not
the case for the uracil and N4-monomethoxytrityl cytosine
derivatives. The inseparable mixtures 24/25 and 30/31
were first treated with 80% acetic acid, and separation
of both diastereoisomers was conducted at the level of
the deprotected target compounds. All other reactions
with pyrimidine bases went as smoothly as the reactions
with the purine nucleosides.
Alternatively, 26 was acetylated with Ac2O, treated
with 1H-1,2,4-triazole/POCl3,19 followed by displacement
of the 4-triazolyl substituent with 25% ammonia in 1,4-
dioxane. Final deprotection using 25% NH4OH-MeOH-
1,4-dioxane gave (1RS,3SR,4RS)-1-[4-(hydroxymethyl)-
3-hydroxycyclohexyl]cytosine (32).
Con for m a tion a l An a lysis. The configurations of the
synthesized diastereoisomeric pairs of cyclohexyl nucleo-
sides 9/10, 20/21, 26/27, 32/33, and guanine derivative
15 were confirmed by NMR spectroscopy. The data are
a
(a) DBU‚DMF/∆; (b) CF3COOH/H2O; (c) BSA/Py; (d) MMTrCl/
Py; (e) BSA/DMF.
chloropurine 2b, thymine 2c, uracil 2d , or cytosine 2e
following an earlier described method using methyl 1,3-
cyclohexadienecarboxylate.4 The Michael-type addition
of 2a or 2b on 1 in DMF in the presence of 0.25 equiv of
DBU proceeded smoothly at 75 °C giving as the sole
product compound 3a (85%) or 3b (74%). Compound 3b
was converted into the guanine derivative 3c by treat-
ment with TFA/H2O.7 Likewise, the thymine derivative
3d could be obtained following this procedure. However,
the uracil and cytosine bases gave only traces of the
desired products, but higher yields could be obtained
under modified conditions. Reaction of ethyl 1,3-cyclo-
hexadienecarboxylate with an excess of uracil at 50 °C
and 2.0 equiv of DBU yielded 3e in 28%. For the
synthesis of the cytosine analogue, the nucleoside base
was first protected with a monomethoxytrityl group (83%
yield) via a transient silylation procedure (BSA, pyridine).
N4-Monomethoxytritylated cytosine was used in the
Michael-type reaction (30% yield) using 6 molar excess
of 1 in the presence of DBU after silylation with BSA in
DMF.
given for each compound in Experimental Section.
A
detailed NMR conformational study was carried out on
the pairs 9/10 and 20/21 in D2O at 33 °C. A standard
numbering system is used here for carbon atoms as
exemplified for the cyclohexyl rings of 9 and 10 in Figure
1.
All 13C NMR lines and all multiplets in 1H NMR
spectra were consistently assigned by a combination of
(13C-1H) heteronuclear correlation (GHSQC20) and double-
quantum filtered COSY21 (GMQFCOPS22) experiments.
Attempts to prepare the hydroxymethylene derivative
by reduction of the ester function of 9-[4-(ethoxycarbonyl)-
3-cyclohexenyl]adenine (3a ) using LiAlH4 were unsuc-
cessful due to the poor solubility of the reaction product
in organic solvents and, hence, purification problems.
Therefore we preferred to increase the lipophilicity of the
compound by introducing a monomethoxytrityl protecting
group and investigated the reduction reaction with
(18) Koga, M.; Schneller, S. J . Org. Chem. 1993, 58, 6471-6473.
(19) Divaker, K. J .; Reese, C. B. J . Chem. Soc., Perkin Trans. 1 1982,
1171-1176; Larsen, E.; Abdeel Alem, A. A. H.; Pedersen, E. B. J .
Heterocycl. Chem. 1995, 32, 1645-1646.
(20) Willker, W.; Leibfritz, D.; Kerssebaum, R.; Bermel, W. Magn.
Reson. Chem. 1993, 31, 287-292.
(21) Piantini, U.; Sorensen, O. W.; Ernst, R. R. J . Am. Chem. Soc.
1982, 104, 6800-6801.
(17) (a) J ablonski, C. R.; Sorensen, T. S. Can. J . Chem. 1974, 52,
2085-2096. (b) Hu¨nig, S.; Kahanek, H. Ber. 1957, 90, 238-245. (c)
Grob, C. A.; Ohta, M.; Renk, E.; Weiss, A. Helv. Chim. Acta 1958, 41,
1191-1197.

Synthesis and Conformation of Cyclohexane Nucleosides
Sch em e 2a
J . Org. Chem., Vol. 62, No. 9, 1997 2863
a
(a) Ac2O, pyridine; (b) 80% aqueous HOAc; (c) NH3 (25%), dioxane, MeOH.
Sch em e 3a
a
(a) 80% aqueous HOAc; (b) Ac2O, pyridine, CH2Cl2; (c) 1H-1,2,4-triazole, POCl3, TEA, pyridine, CH3CN; (d) NH3 (25%), dioxane; (e)
NH3 (25%), dioxane, MeOH.
1
an extensive accidental degeneracy of H NMR spectra,
full spectral analysis was not possible in the cases of
compounds 9 and 20 (for a comparison see Figure 2). In
these spectra the chemical shifts of protons 4′, 5′A, 5′B,
6′A, and 6′B are so close that even 13C satellites seen in
the GHSQC spectra do not exhibit sufficient structure
to permit analysis. In the case of 9 it was, however,
possible to extract the conformationally significant cou-
pling between protons 3′ and 4′ from the 1D spectrum
measured with multisite selective decoupling23 of the
protons 2′A and 2′B (see Experimental Section). In the
case of 20 even such an approach was not possible
because of almost complete overlap of signals due to
protons 2′ and proton 4′; hence, only the upper limit of
this coupling is listed as follows from the bandwidth of
the multiplet.
F igu r e 1. Structure of diastereoisomers 9 and 10 (only the
1′R-isomer is shown).
Proton chemical shifts and coupling constants were
verified by spectral simulation of 1D spectra and iterative
fitting in the case of strong coupling.
The results are summarized in Tables 1 and 2. The
values of one-bond 13C-1H coupling constants (Table 2)
show little variation and, consequently, are of no diag-
nostic value regarding molecular conformation. Due to
Coupling constants in the cyclohexyl parts of 10 and
21 are essentially the same; hence, the conformational
(22) Davis, A. L.; Laue, E. D.; Keeler, J .; Moskau, D.; Lohman, J . J .
Magn. Reson. 1991, 94, 637-644.
(23) Kupce, E.; Freeman, R. J . Magn. Reson. A 1993, 102, 364-
369.

2864 J . Org. Chem., Vol. 62, No. 9, 1997
Maurinsh et al.
Ta ble 1. 1H NMR Ch em ica l Sh ifts (δ) a n d Cou p lin g Con sta n ts (J ) in Cycloh exyl P a r ts of Dia ster eom er ic P a ir s 9/10 a n d
20/21a
9
10
20
21
J M-21
J M-20
J M-19
J M-24
proton
1′
coupling
δ
J
δ
J
δ
J
δ
J
-
4.681
4.398
4.651
4.332
1′-2′A
1′-2′B
1′-6′A
1′-6′B
-
2′A-2′B
2′A-3′
-
4.7
10.2
12.3
3.6
13.3
3.6
4.9
12.3
3.6
12.3
3.6
13.2b
c
c
c
c
2′A
2′B
2.032
2.185
1.885
2.390
1.817
1.877
1.624
2.109
-13.8
4.8
-11.6
10.9
-13.2
-11.3
10.6
3.4b
2′B-3′
2′B-6′B
-
3.3
4.2
2.9
2.9
4.4
c
c
1.9b
3′
4′
4.047
1.86d
3.651
1.586
4.138
1.881
3.558
1.470
3′-4′
4.8
11.0
<5
10.7
-
4′-CH2OA
4′-CH2OB
4′-5′A
4′-5′B
-
5′A-5′B
5′A-6′A
5′-6′B
-
5′B-6′A
5′B-6′B
-
6′A-6′B
-
7.2b
6.7b
c
6.5
4.0
13.3
3.6
7.2
6.7
c
6.6
4.0
13.3b
3.4b
c
c
5′A
1.60d
1.303
1.695
1.201
-14.9
-13.4
13.0
3.1
-13.7
-13.2
13.3b
3.5b
c
c
c
c
5′B
6′A
1.93d
1.91d
1.977
1.813
1.890
1.66d
1.921
1.585
c
c
3.5
3.5
c
c
3.4
3.4
c
-12.6
-11.2
c
-12.7
-11.1
6′B
CH2OA
1.91d
3.638
2.109
3.616
1.66d
3.624
1.838
3.566
-
CH2OA-CH2OB
-
-11.4
-11.4
CH2OB
3.697
3.789
3.645
3.755
a
Chemical shifts of the proton indicated in the first column are values in the δ scale relative to HDO at 4.640 ppm; estimated precision
(0.001 ppm unless otherwise noted. Coupling constants between the protons indicated in the second column are values in hertz; estimated
precision (0.2 Hz unless otherwise indicated. Protons are labeled by the number of the carbon atom to which they are bonded; if two
protons are bonded to the same carbon atom the one resonating at a higher field is denoted by A and the other by B. Geminal coupling
b
d
constants are assumed to be negative. Error up to 1 Hz possible either because of overlap or strong coupling. c Not determined. Possible
error up to 0.02 ppm.
Ta ble 2. 13C NMR Ch em ica ls Sh ifts (δ) a n d On e-Bon d 13C-1H Cou p lin g Con sta n ts (J ) in Dia ster eom er ic P a ir s 9/10 a n d
20/21a
9
10
20
21
J M-21
J M-20
J M-19
J M-24
cyclohexane
carbon no.
δ
J
δ
J
δ
J
δ
J
1′
2′
3′
4′
5′
6′
CH2-O
50.78
35.05
67.68
42.35
21.64
27.50
62.38
145.3
128.4
143.9
127.7
129.8
129.2
141.8
52.97
40.39
69.90
45.50
25.45
31.23
63.55
141.7
127.4
147.6
127.4
132.4
134.0
142.8
51.35
33.16
68.03
41.05
21.36
25.65
61.97
142.1
130.0
144.7
128.9
130.5
128.1
140.6
53.53
39.22
70.04
45.42
25.41
29.79
63.51
142.8
133.4
139.7
124.2
130.2
130.6
142.8
base
2
4
5
adenine
152.48
148.98
118.91
155.81
140.72
thymine
152.66
166.91
111.26
140.01
11.79
202.1
152.60
148.93
119.03
155.97
c
202.5
-
-
152.62
166.88
111.39
139.69
11.79
-
-
-
-
-
b
-
-
-
b
-
-
6
179.1
129.3
178.3
129.1
8/CH3
a
Chemical shifts are in the δ scale; estimated precision (0.02 ppm. One-bond coupling constants are in hertz units; estimated precision
(0.5 Hz. Not determined. c Not visible in deuterium-exchanged sample.
b
conclusions for compound 10 apply to compound 21 as
well. Proton 1′ in 10 exhibits two large coupling con-
stants to two vicinal protons (2′A and 6′A). That is
possible only if all three protons assume axial positions
in a chair conformer (if one does not consider the much
less favorable boat conformations) and thus with the base
in an equatorial position. Since protons 3′ and 4′ are also
both axial according to their couplings with protons 2′A
and 3′, respectively, this fixes the configuration of the
compound as the 1′,3′-cis, 3′,4′-trans isomer as depicted
for 10 in Figure 1. These conclusions are further sup-
ported by the observed transient NOEs (DPFGNOE24).
Inversion of protons 2′A and 6′A yields NOE on proton
4′ as all three protons are mutually in a 1,3 diaxial
arrangement. This finding, which in fact definitely
excludes any boatlike conformation, is in agreement with
the solid state structure determined by X-ray diffraction
(24) Stott, K.; Stonehouse, J .; Keeler, J .; Hwang, T. L.; Shaka, A. J .
J . Am. Chem. Soc. 1995, 117, 4199-4200.

Synthesis and Conformation of Cyclohexane Nucleosides
J . Org. Chem., Vol. 62, No. 9, 1997 2865
F igu r e 2. Relevant parts of 500 MHz 1H NMR spectra of compound 10 (top) and 20 (bottom) in D2O at 33 °C (water presaturation
cannot be used in the measurements of 20 because of overlap with proton 1′ multiplet).
(Figure 3), and thus the molecules maintain their chair
conformation (Figure 1) in water solutions.
both the hydroxymethyl group and hydroxyl group axially
oriented and the base moiety equatorially positioned.
These data for the 1′,3′-trans isomer 9 indicate that
the conformational preference of the six-membered car-
bocyclic nucleosides is opposite to that of the anhydro-
hexitol nucleosides.11,12 By replacement of the ring
oxygen atom by a methylene group, the base moiety is
changing preferably from an axial orientation to the
equatorial orientation. Two reasons may be given for this
observation. First, the unfavorable 1,3-diaxial interac-
tion between the nucleoside base and the hydrogen atoms
in the 3′- and 5′-position when a carbocyclic nucleoside
with an axially oriented heterocycle is considered. With
an equatorially oriented heterocycle, this unfavorable
interaction is present between the 4-hydroxymethyl
function and the hydrogen atoms in position 2′ and 6′
and also between 3′-OH and H-5′ and H-1′. These latter
interactions may be less unfavorable than with the
nucleoside base. Considering the anhydrohexitol nucleo-
sides, only one sterically unfavorable 1,3-diaxial interac-
tion is present when the nucleoside base is oriented
axially. The opposite conformation is disfavored by three
undesired interactions (CH2OH group versus two hydro-
gen atoms (H1′, H3′) positioned in an axial orientation
and 4′OH versus H2′). Secondly, the C-O bond lengths
in the hexitol nucleosides are 0.1 Å shorter than the C-C
bond lengths in the cyclohexane derivatives.12,26 This
means that with an equatorially oriented base moiety,
the 1,3-diaxial interactions of the hydroxymethyl group
In compound 9 the coupling between proton 1′ and 2′B
indicates, according to the Karplus equation, the dihedral
angle between C′1-H and C′2-HB to be close to 180°, an
angle found in an axial-axial arrangement of these two
bonds in a classical chair conformation. Again this points
to an equatorially oriented base in the molecule. The
small value of the J (2′B-3′) coupling together with the
observed coupling between protons 3′ and 4′ (or its upper
limit in 20) indicates these two protons to be in equatorial
arrangements and thus leads to a 1′,3′-trans, 3′,4′-trans
structure, as shown for 9 in Figure 1. DPFGNOE spectra
show the same NOE buildup rate for protons 4′ and 2′A
when proton 3′ is selectively inverted, lending thus
support to the proposed chair conformer.
Summarizing, the values of the vicinal H,H-coupling
constants and NOE measurements lead to the conclusion
that both 9 and 10 as well as 20 and 21 are in chair
conformations with the bases (adenine and thymine) in
equatorial positions. The other ring substituents (OH
and CH2OH) are axial in 9 and 20 and equatorial in 10
and 21.
Further confirmation of this structural analysis is
evident from the 13C chemical shifts (Table 2), where for
the isomers (9 or 20) with axial substituents a typical
2-5 ppm upfield shift is observed with respect to the
isomer with no axial substituents. The same preferential
conformation of 10 and 20 was found in the solid state.
Figure 3A shows the X-ray analysis of 10 in the chair
conformation and all substituents equatorially oriented.
Figure 3B gives the solid state conformation of 20, having
(25) Pachler, K. G. R. J . Magn. Reson. 1972, 7, 442-443.
(26) Declercq, R.; Herdewijn, P.; Van Meervelt, L. Acta Crystallogr.
1996, C52, 1213-1215.

2866 J . Org. Chem., Vol. 62, No. 9, 1997
Maurinsh et al.
dimensional structure of the anhydrohexitol pyrimidine
nucleosides resembles that of C3′-endo puckered furan-
osyl nucleosides, but not of C2′-endo puckered furanoses.
In contrast, no structural similarity at all is found
between the carbocyclic pyrimidine nucleosides and
normal furanosyl nucleoside (Figure 4). The high struc-
tural similarity between anhydrohexitol nucleosides and
C3′-endo puckered furanose nucleosides, and the lack
thereof in the case of carbocyclic nucleosides, might
explain their differences in activity against human herpes
simplex virus type 1 and 2 (Table 3).
Exp er im en ta l Section
All experiments were carried out using instrumentations
and manipulations as described previously.7
NMR Exp er im en ts. The samples for NMR conformational
study were lyophilized three times from 99.98% D2O (Aldrich);
the measured solutions contained 4 mg of the compound in
0.7 mL of D2O in a 5 mm Wilmad tube. All the NMR spectra
were measured on a Varian Unity 500 spectrometer operating
1
at 499.693 MHz for H NMR and at 125.652 MHz for 13C NMR.
All the spectra were run at 33 °C, samples not spinning. 1H
NMR spectra were referenced to the line of water (internal)
at δ ) 4.64, and 13C NMR spectra were referenced to external
acetone at δ ) 30.70. Standard Varian software version vnmr
5.1 was used throughout. All experiments (including GHSQC
(edited),20 GMQFCOPS,22 and DPFGNOE24) were performed
in a 5 mm “inverse detection” probe (with typical values for
90° pulses, 7.4 µs for 1H pulses, and 14.0 µs for 13C pulses)
equipped with pulsed magnetic field z-gradient coils. Gradient
pulses were performed by Performa II PFG source (Varian),
and shaped pulses were generated by a waveform generator
(Varian) using the shapes calculated by Pandora box program.
Heteronuclear (13C-1H) correlation (in a gradient enhanced
variant, GHSQC20) and double-quantum filtered COSY21 (DQF-
F igu r e 3. (A) Compound 10. Molecular structure with atom-
labeling scheme.36 Displacement ellipsoids are plotted at the
40% probability level. H atoms are drawn as small circles of
arbitrary radii. (B) Compound 20. Molecular structure with
atom-labeling scheme.36 Displacement ellipsoids are plotted
at the 40% probability level. H atoms are drawn as small
circles of arbitrary radii. Only the part of the molecule with
the highest occupation factor is shown for clarity.
COSYPS, again in gradient enhanced version GMQFCOPS22
)
experiments were used for assignments of 13C NMR lines and
1
are more disfavored in the hexitol ring than in the
cyclohexane ring with its longer bonds. Finally, weak
interactions between the axial base and the ring oxygen
in the hexitol may not be totally excluded.
all multiplets in H NMR spectra. Proton chemical shifts and
coupling constants derived from 1D spectra and assigned
according to the DQFCOSYPS spectra were confirmed by
spectral simulation and iterative fitting to 1D spectra using
the vnmr simulation programs.
An tivir a l Activity. All compounds (3a -e, 9, 10, 15,
16, 20-22, 26, 27, 32-34) were evaluated for their
antiviral activity against herpes simplex virus-1 (HSV-
1), herpes simplex virus-2 (HSV-2), vaccinia virus, ve-
sicular stomatitis virus, Coxsackie virus B4, respiratory
syncytial virus (RSV), parainfluenza-3 virus, reovirus-1,
Sindbis virus, and Punta Toro virus and for their cyto-
toxicity in E6SM cell cultures, Hela cell cultures, and Vero
cell cultures. None of the compounds demonstrated any
toxicity, and all compounds were completely inactive,
with the exception of 3a [minimal inhibitory concentra-
tion (MIC) against HSV-1: 10 µg/mL, against thymidine
kinase deficient (TK-) HSV-1: 20 µg/mL, against vaccinia
virus: 20 µg/mL] and 15 (MIC against HSV-1: 7 µg/mL
and against TK- HSV-1: 20 µg/mL).
In order to extract a reliable value of the coupling constant
between protons 3′ and 4′ in compound 9 selective multisite
1
decoupled H NMR spectra had to be recorded.23 The splitting
(4.1 Hz in 9) observed in these spectra in the multiplet of
proton 3′ is the residual splitting corresponding to the residual
coupling constant J ′ with proton 4′. To get the true value of
the coupling constant we took advantage of the residual
couplings observed in the spectra of CH2O protons which are
also coupled to proton 4′. Since the decoupling field employed
(γB2 in Hz units) was much larger than the difference between
the true (J ) and the residual coupling constant (J ′) we could
use Pachler’s approximation25 J ) J ′[(1 + a2)/a2]1/2, where a )
∆ν/γB2. The decoupling offset (∆ν in Hz) and the decoupling
field are the constants for the given experiment and the
coupling partner (proton 4′) concerned, hence all the couplings
to proton 4′ are reduced by the same factor. This yields true
value J (3′,4′) ) 4.6 Hz in 9.
(()-9-[4-(Eth oxycar bon yl)-3-cycloh exen yl]aden in e (3a).
A mixture of adenine 2a (5.95 g, 44.0 mmol), ethyl 1,3-
cyclohexadiene-1-carboxylate (1) (20.09 g, 132.0 mmol), DBU
(1.65 mL, 11.0 mmol), and DMF (40 mL) was stirred at 75 °C
for 48 h. After addition of AcOH (0.7 mL) and removal of
volatile materials in vacuo, the residue was treated with
MeOH (30 mL), and the resulting white crystals were filtered
off, affording 10.8 g (85%) of 3a : mp 212-213 °C. LSIMS
(THGLY) 288 [M + H]+, 136 [B + 2H]+. UV λmax (MeOH) )
262 nm (ꢀ 14900). 1H NMR (CDCl3) δ 1.34 (3H), 2.10-3.0 (6H),
4.27 (2H), 4.81(1H), 5.89 (2H), 7.05 (1H), 7.87 (1H), 8.37 (1H).
13C NMR (CDCl3) δ 14.3, 23.4, 27.9, 31.9, 50.0, 60.7, 120.0,
130.7, 135.5, 138.4, 149.9, 152.9, 155.6, 166.5. Anal. Calcd
for C14H17N5O2: C, 58.52; H, 5.96; N, 24.37. Found: C, 58.48;
H, 5.96; N, 24.37.
Con clu sion s
The differences in the antiviral activity between the
anhydrohexitol nucleosides and their carbocyclic conge-
ners are presented in Table 3. It is clear that nearly all
activity disappears when the oxygen atom is replaced by
a methylene function. This loss in antiviral activity also
parallels a change in conformation. The structure of the
anhydrohexitol nucleosides with their axially positioned
base moiety resembles the structure of a furanose
nucleoside in its 2′exo/3′endo conformation, which is not
the case with the carbocyclic analogue. This is shown
in Figure 4. This figure indeed shows that the three-

Synthesis and Conformation of Cyclohexane Nucleosides
J . Org. Chem., Vol. 62, No. 9, 1997 2867
F igu r e 4. Comparison between the three-dimensional conformations of the six-membered sugar ring nucleosides (anhydrohexitol
and carbocyclic) versus a normal nucleoside with its sugar moiety modeled in the two most common puckering conformations
(C2′-endo and C3′-endo). All non-H atoms of the nucleobases were used in the fitting procedure. Figure produced with a locally
modified version of Molscript.37
(()-2-Am in o-6-ch lor o-9-[4-(et h oxyca r b on yl)-3-cyclo-
h exen yl]p u r in e (3b). Compound 3b was obtained from
2-amino-6-chloropurine (2b) and 1 as described for the syn-
thesis of 3a . The crude product was purified by column
chromatography (CH2Cl2-MeOH, 98:2) and crystallized from
MeOH-Et2O, affording 74% 3b: mp 159-160 °C. LSIMS
(THGLY) 322 [M + H]+, 170 [B + 2H]+. UV λmax (MeOH) )
249 nm (ꢀ 5300), 311 nm (ꢀ 8100). 1H NMR (CDCl3) δ 1.25
(3H), 2.00-2.90 (6H), 4.15 (2H), 4.52 (1H), 6.92 (3H), 8.19 (1H).
13C NMR (CDCl3) δ 14.6, 23.9, 27.3, 31.0, 50.2, 60.8, 124.1,
130.0, 135.3, 142.1, 150.0, 154.1, 159.9, 166.5. Anal. Calcd
for C14H16N5O2Cl: C, 52.26; H, 5.01; N, 21.77. Found: C,
52.28; H, 5.06; N, 21.72.
(()-9-[4-(Eth oxycar bon yl)-3-cycloh exen yl]gu an in e (3c).
A solution of 3b (1.0 g, 3.10 mmol) in CF3COOH-H2O (1:1,
15 mL) was stirred at rt for 48 h. The solvents were
evaporated, and the residue was reevaporated from H2O (30
mL × 3). The residue was treated with MeOH-NH4OH (10:
1, 15 mL) and evaporated. The solid was purified by column
chromatography (CH2Cl2-MeOH, 4:1) to give 0.8 g (85%) of
3c: mp >300 °C. LSIMS (THGLY) 607 [2M + H]+, 304 [M +
1
H]+, 152 [B + 2H]+. UV λmax (MeOH) ) 256 nm (ꢀ 14000). H
NMR (DMSO-d6) δ 1.24 (3H), 1.9-2.9 (6H), 4.14 (2H), 4.41
(1H), 6.42 (2H), 6.90 (1H), 7.74 (1H), 10.55 (1H). 13C NMR
(DMSO-d6) δ 14.26, 23.7, 27.4, 31.2, 49.1, 60.2, 116.9, 129.6,
135.6, 136.9, 150.9, 153.4, 156.9, 166.0. Anal. Calcd for
C14H17N5O3‚0.25H2O: C, 54.63; H, 5.73; N, 22.75. Found: C,
54.66; H, 5.72; N, 22.49.
(()-1-[4-(Eth oxycar bon yl)-3-cycloh exen yl]th ym in e (3d).
Compound 3d was prepared from thymine 2c and 1 as
described for synthesis of 3a in 67% yield: mp 233-234 °C.
LSIMS (THGLY) 557 [2M + H]+, 279 [M + H]+, 127 [B + 2H]+.
UV λmax (MeOH) ) 272 nm (ꢀ 10300). 1H NMR (CDCl3) δ 1.33
(3H), 1.85-2.10 (5H), 2.22-2.78 (4H), 4.24 (2H), 4.75 (1H), 6.97
(1H), 7.03 (1H), 9.14 (1H). 13C NMR (CDCl3) δ 12.6, 14.2, 24.2,
27.0, 30.7, 50.6, 60.7, 111.2, 130.5, 135.8, 136.1, 150.9, 163.6,

2868 J . Org. Chem., Vol. 62, No. 9, 1997
Maurinsh et al.
Ta ble 3. Activity a ga in st Her p es Sim p lex Vir u s of An h yd r oh exitol Nu cleosid es a n d Th eir Ca r bocyclic Con gen er sa
[m in im a l in h ibitor y con cen tr a tion (µg/m L) or con cen tr a tion r equ ir ed to r ed u ce vir u s-in d u ced cytop a th icity by 50%]
166.4. Anal. Calcd for C14H18N2O4: C, 60.42; H, 6.52; N,
10.07. Found: C, 60.23; H, 6.50; N, 10.12.
128.5, 128.9, 129.9, 130.3, 135.9, 136.3, 140.9, 144.2, 155.8,
158.6, 164.8, 166.4. Anal. Calcd for C33H33N3O4‚0.5H2O: C,
72.77; H, 6.29; N, 7.72. Found: C, 73.06; H, 6.14; N, 8.00.
(()-N6-(Mon om et h oxyt r it yl)-9-[4-(et h oxyca r b on yl)-3-
cycloh exen yl]a d en in e (4). A mixture of 3a (5.75 g, 20.0
mmol) and MMTrCl (9.27 g, 30.0 mmol) in pyridine (100 mL)
was stirred at 60 °C for 3 h. Another portion of MMTrCl (3.09
g, 10.0 mmol) was added, and the solution was heated at 60
°C overnight. The reaction was quenched with MeOH (10 mL)
and evaporated. The residue was dissolved in CH2Cl2 (300
mL) and treated with a saturated NaHCO3 solution (50 mL).
The organic layer was dried over MgSO4, evaporated, and
coevaporated with toluene. The residue was purified by
column chromatography (hexane to hexane-EtOAc, 1:3) to
afford 9.30 g (83%) of 4 as a foam: LSIMS (THGLY + NaOAc)
560 [M + H]+, 273 [MMTr] +, 136 [B + 2H]+. UV λmax (MeOH)
) 276 nm (ꢀ 23400). 1H NMR (CDCl3) δ 1.34 (3H), 2.15-2.95
(6H), 3.82 (3H), 4.27 (2H), 4.77 (1H), 6.83 (2H), 6.99 (1H), 7.05
(1H), 7.20-7.45 (12H), 7.80 (1H), 8.10 (1H). 13C NMR (CDCl3)
δ 14.3, 23.4, 27.9, 31.9, 50.0, 55.2, 60.7, 71.0, 113.1, 121.2,
126.8, 127.9, 128.9, 130.2, 130.6, 135.6, 137.2, 137.6, 145.2,
148.7, 152.1, 154.2, 158.3, 166.5. Anal. Calcd for
C34H33N5O3‚0.25H2O: C, 72.39; H, 5.98; N, 12.41. Found: C,
72.39; H, 6.03; N, 12.38.
(()-N6-(Mon om et h oxyt r it yl)-9-[4-(h yd r oxym et h yl)-3-
cycloh exen yl]a d en in e (5). To a solution of 4 (6.2 g, 11.0
mmol) in CH2Cl2 (100 mL) under N2 at 0 °C was added DIBAL
(1.0 M solution in hexane, 44 mL, 44.0 mmol) in 20 min, and
the reaction mixture was stirred 20 min longer. Excess of
DIBAL was destroyed by slow addition of MeOH (20 mL) at 0
°C. The resulting suspension was adsorbed on silica gel (30
mL) and put on top of a silica gel column. Elution with CH2-
Cl2-MeOH 95:5 afforded after crystallization (AcOEt-hexane)
4.3 g (75%) of 5: mp 119-121 °C. LSIMS (THGLY + NaOAc)
540 [M + Na]+, 518 [M + H]+, 273 [MMTr]+. UV λmax (MeOH)
) 277 nm (ꢀ 23500). 1H NMR (CDCl3) δ 2.1-2.8 (7H), 3.82
(3H), 4.09 (2H), 4.79 (1H), 5.80 (1H), 6.83 (2H), 7.05 (1H),
7.20-7.45 (12H), 7.84 (1H), 8.10 (1H). 13C NMR (CDCl3) δ
24.4, 28.2, 31.2, 50.5, 55.2, 66.4, 71.0, 113.1, 119.3, 121.0, 126.8,
127.8, 128.9, 130.2, 137.3, 137.9, 138.0, 145.2, 148.7, 152.0,
154.1, 158.3. Anal. Calcd for C32H31N5O2‚0.5H2O: C, 72.98;
H, 6.12; N, 13.30. Found: C, 72.77; H, 6.20; N, 12.93.
(()-N6-(Mon om et h oxyt r it yl)-9-[4-(t r it yloxym et h yl)-3-
cycloh exen yl]a d en in e (6). A mixture of 5 (2.06 g, 4.0 mmol)
and trityl chloride (TrCl) (1.12 g, 6.0 mmol) in pyridine (30
mL) was stirred at 70 °C for 3 h. After workup of the reaction
mixture as described for 4, crude compound 6 was purified by
column chromatography (hexane-EtOAc, 4:1 to 1:1) affording
2.57 g (85%) as a foam: LSIMS (THGLY + NaOAc) 760 [M +
H]+, 273 [MMTr]+, 243 [Tr]+, 136 [B + 2H]+. UV λmax (MeOH)
) 276 nm (ꢀ 25700). 1H NMR (CDCl3) δ 2.0-2.8 (6H), 2.53
(2H), 3.08 (3H), 4.76 (1H), 5.90 (1H), 6.80 (2H), 6.92 (1H),
(()-1-[4-(Eth oxyca r bon yl)-3-cycloh exen yl]u r a cil (3e).
A mixture of uracil 2d (17.93 g, 160.0 mmol), 1 (12.18 g, 80.0
mmol), DBU (20.9 mL, 160.0 mmol), and DMF (80 mL) was
stirred at 50 °C for 24 h. After addition of AcOH (8 mL), the
volatiles were removed in vacuo, and the residue was sus-
pended in CH2Cl2. Unreacted 2d was filtered off, and the
solution was washed with H2O. The organic phase was dried
with MgSO4, evaporated, and purified by column chromatog-
raphy (CH2Cl2-MeOH, 95:5) to give, after crystallization (CH2-
Cl2-Et2O), 6.0 g (28%) of 3c: mp 158-159 °C. LSIMS
(THGLY) 529 [2M + H]+, 265 [M + H]+. UV λmax (MeOH) )
267 nm (ꢀ 11300). 1H NMR (CDCl3) δ 1.31 (3H), 1.8-2.8 (6H),
4.23 (2H), 4.76 (1H), 5.78 (1H), 6.95 (1H), 7.21 (1H), 7.79 (1H).
13C NMR (CDCl3) δ 14.2, 23.9, 26.9, 30.7, 50.8, 60.7, 102.7,
130.6, 135.7, 140.4, 151.0, 163.3, 166.3. Anal. Calcd for
C13H16N2O4: C, 59.08; H, 6.10; N, 10.60. Found: C, 59.00; H,
6.15; N, 10.71.
(()-N4-(Mon om eth oxytr ityl)cytosin e (2f). Cytosine 2e
(2.22 g, 20.0 mmol) and N,O-bis(trimethylsilyl)acetamide
(BSA) (12.36 mL, 50.0 mmol) in pyridine (50 mL) was stirred
at rt for 2 h. Monomethoxytrityl chloride (MMTrCl) (9.26 g,
30.0 mmol) and DMAP (30 mg) were added to the solution.
After 16 h the reaction mixture was diluted with CH2Cl2 and
washed twice with a saturated NaHCO3 solution. The organic
layer was dried over MgSO4, evaporated, and coevaporated
with toluene. The residue was dissolved in CH2Cl2 (50 mL)
and added with stirring to Me2CO-Et2O (1:1, 400 mL). The
deposited crystals of 2f were filtered off, washed with cold CH2-
Cl2 (30 mL), and dried to give 6.39 g (83%) of 2f: mp 255-258
°C. LSIMS (THGLY + NaOAc) 428 [M - H + 2Na]+, 406 [M
+ Na]+, 273 [MMTr]+. UV λmax (MeOH) ) 273 nm (ꢀ 12000).
1H NMR (DMSO-d6) δ 3.74 (3H), 6.08 (1H), 6.83 (3H), 7.1-
7.35 (12H), 8.25 (1H), 10.23 (1H). 13C NMR (DMSO-d6) δ 56.4,
69.6, 94.7, 112.7, 126.1, 127.3, 128.4, 129.8, 136.8, 140.9, 144.8,
155.5, 157.6, 164.3. Anal. Calcd for C24H21N3O2: C, 75.18;
H, 5.52; N, 10.96. Found: C, 75.28; H, 5.55; N, 11.00.
(()-N4-(Mon om et h oxyt r it yl)-1-[4-(et h oxyca r b on yl)-3-
cycloh exen yl]cytosin e (3f). A mixture of BSA (1.97 mL, 8.0
mmol) and 2f (1.53 g, 4.0 mmol) in DMF (20 mL) was stirred
at rt for 30 min. To the resulting solution were added 1 (3.64
g, 24.0 mmol) and DBU (0.15 mL, 1.0 mmol), and the reaction
mixture was stirred at 75 °C for 48 h. After addition of AcOH
(0.1 mL) and evaporation, the residue was purified by column
chromatography, eluting with CH2Cl2 (300 mL) and CH2Cl2-
MeOH 98:2 (500 mL), to give 0.64 g (30%) of 3f as a foam:
LSIMS (THGLY + NaOAc) 558 [M + Na]+, 273 [MMTr]+. UV
λmax (MeOH) ) 286 nm (ꢀ 15000). 1H NMR (CDCl3) δ 1.28
(3H), 1.65-2.85 (6H), 3.80 (3H), 4.19 (2H), 4.85 (1H), 5.04 (1H),
6.75-6.95 (5H), 7.10-7.40 (12H). 13C NMR (CDCl3) δ 14.2,
23.8, 26.9, 31.2, 51.2, 55.2, 60.5, 70.3, 94.6, 113.5, 127.4, 128.3,

Synthesis and Conformation of Cyclohexane Nucleosides
J . Org. Chem., Vol. 62, No. 9, 1997 2869
7.20-7.45 (27H), 7.82 (1H), 8.10 (1H). 13C NMR (CDCl3) δ
25.0, 28.2, 31.3, 50.5, 55.2, 67.0, 70.9, 86.6, 113.1, 119.1, 120.9,
126.8, 126.9, 127.8, 128.6, 128.8, 130.2, 135.7, 137.2, 137.9,
144.0, 145.2, 148.7, 152.0, 154.1, 158.2. Anal. Calcd for
C51H45N5O2‚0.5H2O: C, 79.66; H, 6.03; N, 9.11. Found: C,
79.77; H, 6.19; N, 8.73.
(()-N2-(Mon om et h oxyt r it yl)-9-[4-(et h oxyca r b on yl)-3-
cycloh exen yl]gu a n in e (11). Compound 11 was obtained by
reaction of 3c with MMTrCl as described for 4. Chromato-
graphic purification (EtOAc-hexane, 1:1 to 4:1) afforded 11
in 80% yield as a foam: LSIMS (THGLY + NaOAc) 620 [M -
H + 2Na]+, 598 [M + Na]+, 273 [MMTr]+. UV λmax (MeOH) )
262 nm (ꢀ 14300). 1H NMR (CDCl3) δ 1.36 (3H), 1.64 (2H),
2.22 (4H), 3.76 (3H), 3.79 (1H), 4.26 (2H), 6.70 (3H), 7.00-
7.40 (13H), 8.03 (1H), 11.8 (1H). 13C NMR (CDCl3) δ 14.3, 23.6,
26.9, 30.6, 50.6, 55.1, 60.6, 70.4, 112.8, 118.0, 126.4, 127.5,
127.9, 128.1, 128.9, 129.8, 130.3, 135.5, 136.2, 137.1, 145.0,
152.2, 158.1, 159.3, 166.7. Anal. Calcd for C34H33N5-
O4‚0.25H2O: C, 70.39; H, 5.78; N, 12.07. Found: C, 70.61; H,
5.84; N, 11.67.
(1RS,3SR,4RS)-9-[4-(Hyd r oxym eth yl)-3-h yd r oxycyclo-
h exyl]a d en in e (9) a n d (1RS,3RS,4SR)-9-[4-(H yd r oxy-
m eth yl)-3-h yd r oxycycloh exyl]a d en in e (10). To a stirred
solution of 6 (3.04 g, 4.0 mmol) in THF (50 mL) under N2 was
added BH3-THF (1 M solution in THF, 18.0 mL) at 0 °C. After
being stirred at rt for 7 h, the solution was diluted with H2O
(20 mL) and EtOH (20 mL), made basic with a 3 M aqueous
NaOH solution (30 mL), and 35% H2O2 (35 mL) was slowly
added. The mixture was stirred at 45 °C for 20 h. To the
solution was added saturated aqueous Na2SO3 (35 mL). The
mixture was extracted with CH2Cl2 (100 mL × 3), dried over
MgSO4, and evaporated. The residue was chromatographed
(CH2Cl2-EtOAc, 4:1 to 1:1) to obtain 1.0 g (32%) of 7 and 0.87
g (28%) of 8a as foams. For 7: LSIMS (THGLY + NaOAc)
822 [M - H + 2Na]+, 800 [M + Na]+, 778 [M + H]+, 273
[MMTr]+, 243 [Tr]+, 136 [B + 2H]+. UV λmax (MeOH) ) 276
nm (ꢀ 24200). 1H NMR (CDCl3) δ 1.3-2.15 (7H), 3.10-3.22
(2H), 3.46 (1H), 3.78 (3H), 4.10 (1H), 4.81 (1H), 6.78 (2H), 6.93
(1H), 7.15-7.52 (27H), 7.62 (1H), 7.98 (1H). 13C NMR (CDCl3)
δ 21.9, 27.9, 35.6, 40.9, 50.0, 55.2, 64.8, 68.7, 70.9, 86.9, 113.1,
121.0, 126.5, 126.8, 127.2, 127.9, 128.6, 128.9, 129.2, 130.2,
137.2, 137.9, 143.7, 145.2, 148.6, 151.8, 154.1, 158.3. Anal.
Calcd for C51H47N5O3‚0.5H2O: C, 77.84; H, 6.15; N, 8.90.
Found: C, 77.53; H, 6.14; N, 8.71.
Compound 7 (1.0 g, 1.3 mmol) was deprotected by treatment
with 80% aqueous AcOH at 60 °C for 4 h. After removal of
AcOH by evaporation and coevaporation with toluene, the
residue was dissolved in MeOH (10 mL) and adsorbed on silica
gel, and the silica was placed on top of a silica gel column.
Elution with CH2Cl2-MeOH (95:5 to 85:15) afforded after
crystallization (MeOH-H2O) 0.23 g (68%) of 9: mp 229-230
°C. LSIMS (THGLY) 264 [M + H]+, 136 [B + 2H]+. UV λmax
(H2O) ) 263 nm (ꢀ 13300). 1H NMR (DMSO-d6) δ 1.55-2.05
(6H), 2.23 (1H), 3.56 (2H), 3.95 (1H), 4.43 (1H), 4.62 (1H), 4.71
(1H), 7.07 (2H), 8.10 (1H), 8.22 (1H). 13C NMR (DMSO-d6) δ
21.4, 27.6, 35.0, 42.3, 49.5, 61.3, 66.1, 118.9, 139.5, 149.3, 152.1,
156.1. Anal. Calcd for C12H17N5O2: C, 54.74; H, 6.51; N,
26.60. Found: C, 54.76; H, 6.58; N, 26.91.
To crude 8a (1.0 g, 1.3 mmol), dissolved and stirred at 0 °C
in pyridine (10 mL) were added Ac2O (1 mL) and DMAP (10
mg). The reaction mixture was stirred overnight at rt,
evaporated, and partitioned between CH2Cl2 and H2O. The
organic layer was washed with a saturated NaHCO3 solution
(20 mL), dried over MgSO4, and evaporated. Chromatographic
purification (hexane to hexane-Et2O, 1:3) of the residue
afforded 0.77 g (84%) of 8b as a foam: LSIMS (THGLY +
NaOAc) 842 [M + Na]+, 273 [MMTr]+, 243 [Tr]+. UV λmax
(MeOH) ) 276 nm (ꢀ 25100). 1H NMR (CDCl3) δ 1.80 (3H),
1.85-2.60 (7H), 3.15 (2H), 3.78 (3H), 4.57 (1H), 5.0 (1H), 6.78
(2H), 6.92 (1H), 7.10-7.45 (27H), 7.78 (1H), 8.08 (1H). 13C
NMR (CDCl3) δ 20.9, 26.2, 37.4, 52.6, 55.2, 62.2, 70.9, 86.2,
113.1, 121.2, 126.8, 126.9, 127.8, 127.9, 128.4, 128.7, 130.2,
137.3, 137.7, 143.9, 145.2, 148.5, 152.0, 154.2, 158.3, 170.0.
Anal. Calcd for C53H49N5O4‚0.1H2O: C, 77.46; H, 6.03; N, 8.52.
Found: C, 77.08; H, 6.08; N, 8.50. Compound 8b (0.77 g, 0.94
mmol) was deprotected by the treatment with 80% HOAc at
60 °C for 4 h. After removal of AcOH by evaporation and
coevaporation with toluene, the residue was deacetylated by
treatment with a mixture of NH3 (25%)-MeOH-1,4-dioxane
(1:1:1, 30 mL) at rt overnight. Solvents were removed by
evaporation, and the solid residue was purified chromato-
graphically as described for 9, yielding after crystallization
(H2O-MeOH-Et2O) 0.14 g (56%) of 10: mp 232-233 °C.
LSIMS (THGLY) 264 [M + H]+, 136 [B + 2H]+. UV λmax (H2O)
) 263 nm (ꢀ 14000). 1H NMR (DMSO-d6) δ 1.1-2.2 (7H), 3.3
(2H), 3.69 (1H), 4.35 (1H), 4.44 (1H), 4.82 (1H), 7.20 (2H), 8.13
(1H), 8.22 (1H). 13C NMR (DMSO-d6) δ 25.9, 31.2, 41.2, 46.2,
52.1, 62.9, 69.0, 119.1, 139.1, 149.2, 152.2, 156.1. Anal. Calcd
for C12H17N5O2‚0.25H2O: C, 53.82; H, 6.49; N, 26.15. Found:
C, 53.68; H, 6.53; N, 26.14.
(()-N2-(Mon om et h oxyt r it yl)-9-[4-(h yd r oxym et h yl)-3-
cycloh exen yl]gu a n in e (12). Compound 12 was obtained by
reaction of 11 with DIBAL as described for 5. Chromato-
graphic purification (CH2Cl2-MeOH, 95:5 to 4:1) and crystal-
lization (EtOAC-hexane) afforded 87% of 12: mp 173-175
°C. LSIMS (THGLY + NaOAc) 1133 [2M - 2H + 3Na]+, 578
[M - H + 2Na]+, 556 [M + Na]+, 273 [MMTr]+. UV λmax
(MeOH) ) 262 nm (ꢀ 13700). 1H NMR (DMSO-d6) δ 1.35-2.3
(6H), 3.72 (3H), 3.80 (3H), 4.75 (1H), 5.42 (1H), 6.8-7.35 (15H),
7.60 (1H), 10.55 (1H). 13C NMR (DMSO-d6) δ 24.8, 27.1, 29.4,
51.2, 55.1, 64.5, 69.7, 113.0, 117.7, 126.6, 127.7, 128.5, 129.9,
136.4, 137.0, 137.9, 145.1, 149.4, 150.2, 156.7, 157.8. Anal.
Calcd for C32H31N5O3‚0.5H2O: C, 70.83; H, 5.94; N, 12.91.
Found: C, 70.78; H, 5.74; N, 13.02.
(()-N2-(Mon om et h oxyt r it yl)-9-[4-(t r it yloxym et h yl)-3-
cycloh exen yl]gu a n in e (13). Compound 13 was obtained
after reaction of 12 with TrCl as described for 6. Chromato-
graphic purification (EtOAc-hexane, 4:1) gave 90% of 13 as
a foam: LSIMS (THGLY + NaOAc) 820 [M - H + 2Na]+, 798
[M + Na]+, 273 [MMTr]+, 243 [Tr]+. UV λmax (MeOH) ) 261
nm (ꢀ 14200). 1H NMR (CDCl3) δ 1.6-2.35 (6H), 3.49 (2H),
3.75 (3H), 4.05 (1H), 5.75 (1H), 6.80 (2H), 7.20-7.60 (29H),
10.80 (1H). 13C NMR (CDCl3) δ 25.3, 27.3, 30.1, 51.3, 55.0,
67.1, 70.2, 86.6, 112.7, 117.9, 119.5, 126.1, 127.0, 127.3, 127.8,
128.6, 128.9, 130.1, 130.4, 135.0, 135.6, 137.2, 144.2, 145.1,
150.1, 150.6, 157.8, 159.4. Anal. Calcd for C51H45N5-
O3‚0.5H2O: C, 78.03; H, 5.91; N, 8.92. Found: C, 77.67; H,
5.82; N, 9.11.
(1RS,3SR,4RS)-N 2-(Mon om et h oxyt r it yl)-9-[4-(t r it yl-
oxym et h yl)-3-h yd r oxycycloh exyl]gu a n in e (14). Com-
pound 14 was obtained by reaction of 13 with BH3-THF as
described in the procedure for synthesis of 7. Column chro-
matography (CH2Cl2-MeOH, 97:3) afforded 14 (40%) as a
foam: LSIMS (THGLY + NaOAc) 794 [M + H]+, 273 [MMTr]+,
243 [Tr]+. UV λmax (MeOH) ) 263 nm (ꢀ 14200). 1H NMR
(CDCl3) δ 1.2-2.4 (7H), 3.10 (2H), 3.46 (1H), 3.62 (3H), 3.76
(1H), 3.98 (1H), 6.65 (2H), 7.00-7.50 (28H), 11.84 (1H). 13C
NMR (CDCl3) δ 21.9, 26.8, 36.0, 40.7, 49.3, 55.1, 65.1, 68.5,
70.4, 86.9, 112.7, 117.3, 126.6, 127.2, 127.4, 127.9, 128.6, 129.0,
130.6, 134.8, 137.0, 143.8, 144.2, 144.9, 145.1, 150.1, 150.6,
157.9, 159.4. Anal. Calcd for C51H47N5O4‚1.5H2O: C, 74.61;
H, 6.13; N, 8.53. Found: C, 74.72; H, 5.91; N, 8.75.
(1RS,3SR,4RS)-9-[4-(Hyd r oxym eth yl)-3-h yd r oxycyclo-
h exyl]gu a n in e (15). Compound 15 was obtained in 72% yield
from 14 as described in the procedure for synthesis of 9. 15:
mp 255-257 °C. LSIMS (THGLY) 280 [M + H]+, 152 [B +
2H]+. UV λmax (H2O) ) 253 nm (ꢀ 13200). 1H NMR (DMSO-
d6) δ 1.5-2.2 (7H), 3.53 (2H), 3.97 (1H), 4.54 (2H), 4.72 (1H),
6.44 (2H), 7.86 (1H), 10.53 (1H). 13C NMR (DMSO-d6) δ 21.5,
28.1, 35.1, 42.2, 48.4, 61.2, 66.1, 116.6, 135.8, 150.8, 153.4,
157.0. Anal. Calcd for C12H17N5O3‚H2O: C, 48.48; H, 6.44;
N, 23.55. Found: C, 48.13; H, 6.43; N, 23.28.
(()-1-[4-(Hydr oxym eth yl)-3-cycloh exen yl]th ym in e (16).
Compound 16 was obtained from 3d in 79% yield after reaction
with DIBAL as described for 5: mp 201-202 °C. LSIMS
(THGLY) 237 [M + H]+, 127 [B + 2H]+. UV λmax (MeOH) )
272 nm (ꢀ 8800). 1H NMR (DMSO-d6) δ 1.5-2.3 (9H), 3.80
(2H), 4.45 (1H), 4.73 (1H), 5.56 (1H), 7.60 (1H), 11.21 (1H).
13C NMR (DMSO-d6) δ 12.2, 25.6, 26.7, 29.5, 51.1, 64.5, 109.1,
118.2, 137.9, 138.3, 151.0, 163.9. Anal. Calcd for C12H16N2-
O3: C, 61.00; H, 6.83; N, 11.86. Found: C, 60.93; H, 6.93; N,
11.87.

2870 J . Org. Chem., Vol. 62, No. 9, 1997
Maurinsh et al.
(()-1-[4-(Tr ityloxym eth yl)-3-cycloh exen yl]th ym in e (17).
Compound 17 was obtained in the reaction of 16 with TrCl as
described for 6 in 56% yield as a foam: LSIMS (THGLY +
NaOAc) 501 [M + Na]+, UV λmax (MeOH) ) 271 nm (ꢀ 8600).
1H NMR (CDCl3) δ 1.8-2.55 (9H), 3.52 (2H), 4.76 (1H), 5.78
(1H), 7.05 (1H), 7.15-7.50 (15H), 8.98 (1H). 13C NMR (CDCl3)
δ 12.7, 25.8, 27.3, 30.2, 51.1, 67.1, 86.6, 110.8, 119.5, 127.0,
127.8, 128.6, 135.7, 136.6, 144.1, 151.1, 163.8. Anal. Calcd
for C31H30N2O3‚0.4H2O: C, 76.65; H, 6.39; N, 5.77. Found: C,
76.78; H, 6.38; N, 5.72.
(1RS,3SR,4RS)-1-[4-(Tr ityloxym eth yl)-3-h yd r oxycyclo-
h exyl]th ym in e (18) a n d (1RS,3RS,4SR)-1-[4-(Tr ityloxy-
m eth yl)-3-h yd r oxycycloh exyl]th ym in e (19). Compounds
18 and 19 were obtained in the reaction of 17 with BH3-THF
as described in the procedure for the synthesis of 7 and 8
(reaction time 1 h). Column chromatography (CH2Cl2-MeOH,
99:1) afforded 18 (34%) and 19 (21%) as foams. 18: LSIMS
(NBA) 497 [M + Na]+, 243 [Tr]+. UV λmax (MeOH) ) 271 nm
(ꢀ 9400). 1H NMR (CDCl3) δ 1.0-2.0 (10H), 3.18 (2H), 3.92
(1H), 4.60 (1H), 4.78 (1H), 6.98 (1H), 7.15-7.50 (15H), 11.17
(1H). 13C NMR (CDCl3) δ 12.5, 21.6, 26.1, 33.9, 38.9, 49.5, 62.9,
68.0, 86.6, 110.5, 127.0, 127.8, 128.7, 136.4, 143.9, 150.9, 163.7.
Anal. Calcd for C31H32N2O4‚1.3H2O: C, 71.60; H, 6.71; N, 5.39.
Found: C, 71.47; H, 6.52; N, 5.47. 19: LSIMS (TDG) 497 [M
+ H]+, 243 [Tr]+. UV λmax (MeOH) ) 271 nm (ꢀ 9300). 1H
NMR (CDCl3) δ 1.1-2.2 (10H), 3.10 (1H), 3.41 (1H), 3.62 (1H),
3.78 (1H), 4.47 (1H), 7.03 (1H), 7.2-7.3 (15H), 8.55 (1H). 13C
NMR (CDCl3) δ 12.6, 25.1, 30.4, 38.9, 43.5, 51.7, 67.7, 72.7,
87.6, 110.9, 127.2, 127.5, 128.0, 128.4, 136.0, 143.3, 150.6,
163.2. Anal. Calcd for C31H32N2O4‚1.4H2O: C, 71.35; H, 6.45;
N, 5.37. Found: C, 71.54; H, 6.72; N, 5.39.
(1RS,3SR,4RS)-1-[4-(Hyd r oxym eth yl)-3-h yd r oxycyclo-
h exyl]th ym in e (20). Compound 20 was obtained by depro-
tection of 18 with 80% aqueous HOAc as described for 9. The
yield of 20 after crystallization (MeOH-H2O-Et2O) was
72%: mp 218-220 °C. LSIMS (THGLY) 255 [M + H]+, 127
[B + 2H]+. UV λmax (H2O) ) 274 nm (ꢀ 9100). 1H NMR
(DMSO-d6) δ 1.3-1.9 (10H), 3.46 (2H), 3.98 (1H), 4.46 (1H),
4.65 (2H), 7.64 (1H), 11.13 (1H). 13C NMR (DMSO-d6) δ 12.0,
21.4, 26.1, 33.5, 41.7, 49.1, 61.0, 66.3, 108.8, 138.2, 150.9, 163.8.
Anal. Calcd for C12H18N2O4: C, 56.68; H, 7.13; N, 11.02.
Found: C, 56.56; H, 7.23; N, 10.93.
(1RS,3RS,4SR)-1-[4-(Hyd r oxym eth yl)-3-h yd r oxycyclo-
h exyl]th ym in e (21). Compound 21 was obtained after
deprotection of 19 with 80% HOAc as described for 9. The
yield of 21 after crystallization (MeOH-H2O-Et2O) was
81%: mp 234-236 °C. LSIMS (GLY) 255 [M + H]+. UV λmax
(H2O) ) 275 nm (ꢀ 9100). 1H NMR (DMSO-d6) δ 1.0 -1.9
(10H), 3.34 (2H), 3.67 (1H), 4.28 (1H), 4.42 (1H), 4.82 (1H),
7.63 (1H). 13C NMR (DMSO-d6) δ 12.2, 25.5, 29.7, 38.8, 45.9,
51.8, 62.8, 69.1, 109.0, 137.8, 150.7, 163.8. Anal. Calcd for
C12H18N2O4: C, 56.68; H, 7.13; N, 11.02. Found: C, 56.34; H,
7.24; N, 10.90.
was added BH3-THF (1 M solution in THF, 17.5 mL) at -10
°C. After being stirred at -10 °C for 2 h and at 5 °C for 4 h,
the solution was cooled to -30 °C, diluted with H2O (15 mL)
and EtOH (15 mL), and made basic with 3 M aqueous NaOH
(10 mL) after which 35% H2O2 (5 mL) was slowly added. The
mixture was stirred at -30 °C for 15 min and then saturated
aqueous Na2SO3 (5 mL) was added. The solution was ex-
tracted with CH2Cl2 (100 mL × 3), the combined extracts were
dried over MgSO4, and the solvent was evaporated. The
residue was chromatographed through a short column of silica
gel (2.5 × 10 cm, CH2Cl2-MeOH, 95:5) to give a mixture of
24 and 25 (1.8 g), which was deprotected by treatment of 80%
aqueous AcOH at 60 °C for 1 h. After removal of HOAc by
evaporation, the residue was purified by column chromatog-
raphy as described for compound 9, affording after crystal-
lization (MeOH-H2O-Et2O) 0.31 g (18%) of 26 and 0.26 g
(15%) of 27. For 26: mp 208-210 °C. LSIMS (GLY) 241 [M
+ H]+. UV λmax (H2O) ) 269 nm (ꢀ 8900). 1H NMR (DMSO-
d6) δ 1.4-1.95 (7H), 3.50 (2H), 3.98 (1H), 4.50 (1H), 4.71 (2H),
5.55 (1H), 7.80 (1H), 11.20 (1H). 13C NMR (DMSO-d6) δ 21.4,
26.1, 33.5, 41.7, 49.6, 61.1, 66.3, 101.1, 142.8, 151.1, 163.2.
Anal. Calcd for C11H16N2O4: C, 54.99; H, 6.71; N, 11.66.
Found: C, 54.88; H, 6.83; N, 11.46. For 27: mp 209-211 °C.
LSIMS (GLY) 241 [M + H]+. UV λmax (H2O) ) 269 nm (ꢀ 9300).
1H NMR (DMSO-d6) δ 1.0-1.95 (7H), 3.31 (2H), 3.62 (1H), 4.25
(1H), 4.40 (1H), 4.81 (1H), 5.55 (1H), 7.74 (1H), 11.23 (1H).
13C NMR (DMSO-d6) δ 25.5, 29.7, 40.0, 45.9, 52.2, 62.8, 69.1,
101.3, 142.2, 150.9, 163.2. Anal. Calcd for C11H16N2O4: C,
54.99; H, 6.71; N, 11.66. Found: C, 55.01; H, 6.79; N, 11.62.
(()-N4-(Mon om et h oxyt r it yl)-1-[4-(h yd r oxym et h yl)-3-
cycloh exen yl]cytosin e (28). As described for 5 compound
28 was obtained from 3f in 55% yield as a foam after reaction
with DIBAL: LSIMS (THGLY + NaOAc) 516 [M + Na]+, 273
[MMTr]+. UV λmax (MeOH) ) 286 nm (ꢀ 15800). 1H NMR
(CDCl3) δ 1.80-2.50 (6H), 2.95 (1H), 3.81 (3H), 4.00 (2H), 4.80-
(1H), 5.03 (1H), 5.65 (1H), 6.84-6.98 (4H), 7.15-7.36 (12H).
13C NMR (CDCl3) δ 25.0, 27.3, 30.5, 51.7, 55.2, 66.1, 70.4, 94.5,
113.5, 119.6, 127.4, 127.7, 128.2, 128.5, 129.9, 135.9, 137.7,
141.3, 144.2, 155.9, 158.6, 164.7. Anal. Calcd for C31H31
-
N3O3: C, 75.43; H, 6.33; N, 8.51. Found: C, 75.72; H, 6.42;
N, 8.90.
(()-N4-(Mon om et h oxyt r it yl)-1-[4-(t r it yloxym et h yl)-3-
cycloh exen yl]cytosin e (29). Compound 29 was obtained
after reaction of 28 with TrCl as described for 6 in 72% yield
as a foam: LSIMS (NBA) 735 [M + H]+, 273 [MMTr]+, 243
[Tr]+. UV λmax (MeOH) ) 286 nm (ꢀ 14300). 1H NMR (CDCl3)
δ 1.7-2.65 (6H), 3.49 (2H), 3.82 (3H), 4.90 (1H), 5.05 (1H),
5.80 (1H), 6.86-6.99 (4H), 7.20-7.55 (27H). 13C NMR (CDCl3)
δ 25.5, 27.3, 30.6, 51.6, 55.2, 67.0, 70.3, 86.6, 113.5, 119.6,
126.9, 127.4, 127.7, 128.3, 128.5, 129.9, 135.4, 136.0, 141.3,
144.1, 144.3, 156.0, 158.6, 164.7. Anal. Calcd for
C50H45N3O3‚0.5H2O: C, 80.62; H, 6.22; N, 5.64. Found: C,
80.47; H, 6.22; N, 5.51.
(()-1-[4-(Hyd r oxym eth yl)-3-cycloh exen yl]u r a cil (22).
Compound 22 was obtained from 3e in 69% yield after reaction
with DIBAL as described for 5: mp 167-168 °C. LSIMS
(THGLY) 445 [2M + H]+, 223 [M + H]+, 113 [B + 2H]+. UV
λmax (MeOH) ) 268 nm (ꢀ 8900). 1H NMR (DMSO-d6) δ 1.6-
2.35 (6H), 3.80 (2H), 4.45 (1H), 4.73 (1H), 5.56 (2H), 7.68 (1H),
11.24 (1H). 13C NMR (DMSO-d6) δ 25.4, 26.6, 29.5, 51.4, 64.5,
101.4, 118.1, 138.4, 142.3, 151.1, 163.3. Anal. Calcd for
C11H14N2O3: C, 59.45; H, 6.35; N, 12.60. Found: C, 59.25; H,
6.53; N, 12.64.
(()-1-[4-(Tr ityloxym eth yl)-3-cycloh exen yl]u r a cil (23).
Reaction of 22 with TrCl as described for 6 afforded 23 in 71%
yield as a foam: LSIMS (NPOE) 465 [M + H]+, 243 [Tr]+. UV
λmax (MeOH) ) 267 nm (ꢀ 9300). 1H NMR (CDCl3) δ 1.8-2.7
(6H), 3.56 (2H), 4.81 (1H), 5.79 (1H), 5.85 (1H), 7.2-7.55 (16H),
9.38 (1H). 13C NMR (CDCl3) δ 25.5, 27.2, 30.2, 51.3, 67.0, 86.7,
102.4, 119.2, 127.1, 127.8, 128.3, 128.6, 135.8, 140.8, 144.1,
151.0, 163.3. Anal. Calcd for C30H28N2O3‚0.5H2O: C, 76.09;
H, 6.17; N, 5.92. Found: C, 76.30; H, 6.20; N, 6.14.
(1RS,3SR,4RS)-1-[4-(Hyd r oxym eth yl)-3-h yd r oxycyclo-
h exyl]cytosin e (32) a n d (1RS,3RS,4SR)-1-[4-(Hyd r oxy-
m eth yl)-3-h yd r oxycycloh exyl]cytosin e (33). Meth od 1.
A mixture of compounds 30 and 31 was obtained after reaction
of 29 with BH3-THF as described for the synthesis of 24 and
25. Basic oxidation with H2O2 was performed at 40 °C for 2
h. The inseparable mixture of 30 and 31, after isolation by
short column chromatography (2.5 × 10 cm, CH2Cl2-MeOH,
99.5:0.5), was deprotected with 80% aqueous AcOH at 60 °C
for 3 h. Chromatographic purification as described for 9 and
crystallization (MeOH) afforded title compounds 32 (10%) and
33 (30%). For 32: mp 264-266 °C. LSIMS (NBA) 240 [M +
H]+, 112 [B + 2H]+. UV λmax (H2O) ) 275 nm (ꢀ 9500). 1H
NMR (DMSO-d6) δ 1.4-1.8 (7H), 3.46 (2H), 3.94 (1H), 4.46
(1H), 4.61 (1H), 4.74 (1H), 5.62 (1H), 6.89 (2H), 7.64 (1H). 13C
NMR (DMSO-d6) δ 21.5, 26.7, 33.9, 41.8, 49.6, 61.2, 66.4, 93.3,
142.9, 155.6, 165.1. Anal. Calcd for C11H17N3O3: C, 55.22;
H, 7.16; N, 17.56. Found: C, 55.08; H, 7.17; N, 17.76. For
33: mp 240-241 °C. LSIMS (GLY) 240 [M + H]+, 112 [B +
2H]+. UV λmax (H2O) ) 275 nm (ꢀ 9700). 1H NMR (DMSO-d6)
δ 0.95-1.9 (7H), 3.32 (2H), 3.63 (1H), 4.23-4.43 (2H), 4.76
(1H), 5.63 (1H), 6.95 (2H), 7.63 (1H). 13C NMR (DMSO-d6) δ
25.7, 30.2, 39.8, 46.0, 52.2, 62.7, 69.1, 93.5, 142.3, 155.6, 165.0.
(1RS,3SR,4RS)-1-[4-(Hyd r oxym eth yl)-3-h yd r oxycyclo-
h exyl]u r a cil (26) a n d (1RS,3RS,4SR)-1-[4-(H yd r oxy-
m eth yl)-3-h yd r oxycycloh exyl]u r a cil (27). To a stirred
solution of 23 (3.25 g, 7.0 mmol) in THF (50 mL) under N2

Synthesis and Conformation of Cyclohexane Nucleosides
J . Org. Chem., Vol. 62, No. 9, 1997 2871
Anal. Calcd for C11H17N3O3‚0.5H2O: C, 53.22; H, 7.31; N,
16.92. Found: C, 52.90; H, 7.33; N, 17.19.
Str u ctu r e Refin em en ts. The structures were solved using
SIR92,29 and full-matrix least-squares refinement on F2 using
SHELXL-9330 were carried out. For compound 10 the refine-
Meth od 2. To a solution of 26 (0.48 g, 2.0 mmol) in
pyridine/CH2Cl2 (1:1, 20 mL) were added Ac2O (0.12 mL) and
DMAP (10 mg) with stirring at 0 °C. The resulting solution
was stirred at rt for 4 h, poured on ice, and extracted with
CH2Cl2 (50 mL × 3). The pooled extracts were washed with a
saturated aqueous NaHCO3 and H2O, dried over MgSO4, and
the solvent evaporated. The residue was purified by column
chromatography (CH2Cl2-MeOH, 95:5) to give 0.48 g (74%)
of (1RS,3SR,4RS)-1-[4-(acetoxymethyl)-3-acetoxycyclohexyl]-
uracil (34) as a foam: LSIMS (GLY) 325 [M + H]+, 113 [B +
2H]+. UV λmax (MeOH) ) 267 nm (ꢀ 9500). 1H NMR (CDCl3)
δ 1.65-2.3 (13H), 4.17 (1H), 4.78 (1H), 5.20 (1H), 5.75 (1H),
7.25 (1H), 9.38 (1H). 13C NMR (CDCl3) δ 20.8, 21.2, 22.1, 26.0,
30.9, 35.6, 50.7, 63.3, 69.8, 102.5, 140.5, 150.7, 163.0. 170.0,
171.0. Anal. Calcd for C15H20N2O6: C, 55.55; H, 6.22; N, 8.64.
Found: C, 55.36; H, 6.40; N, 8.55.
To a solution of 1H-1,2,4-triazole (1.34 g, 20.0 mmol) and
POCl3 (0.63 mL, 6.8 mmol) in CH3CN (20 mL) was added TEA
(2.77 mL, 20.0 mmol) dropwise at 0 °C. Compound 34 (0.64
g, 2.0 mmol) in CH3CN/pyridine (1:1, 20 mL) was added, and
the reaction mixture was stirred at room temperature over-
night. After addition of H2O, the solvents were evaporated
and the resulting residue was partitioned between CH2Cl2 and
saturated NaHCO3 solution. The organic phase was dried over
MgSO4 and evaporated. The residue was dissolved in aqueous
ammonia (25%, 10 mL) and 1,4-dioxane (40 mL). After 6 h
the mixture was evaporated and the residue partitioned
between CH2Cl2 and saturated NaHCO3 solution. The organic
phase was dried over MgSO4, evaporated, and chromato-
graphed on short silica gel column (2.5 × 10 cm, CH2Cl2-
MeOH, 9:1). The residue left over after evaporation of the
desired fractions was deacetylated by treatment with NH3
(25%)-MeOH-1,4-dioxane (1:1:1, 60 mL) at room temperature
overnight. The solution was evaporated and purified by
column chromatography as described for 26 and 27 affording
0.19 g (40%) of 32, which was chromatographically and
spectroscopically indistinguishable from 32 obtained by method
1.
ment converged at R[I > 2σ(I)] ) 0.0520 with GOF on F2
)
1.092, extinction coefficient: 0.0009(2), largest diff peak and
hole: 0.204 and -0.232 e Å-3. For compound 20 the refine-
ment converged at R[I > 2σ(I)] ) 0.0408 with GOF on F2
)
1.105, extinction coefficient: 0.0017(2), largest diff peak and
hole: 0.192 and -0.200 e Å-3
.
H atoms were positioned
geometrically assuming fixed C-H, O-H, and N-H distances
of 0.96, 0.82, and 0.86 Å, respectively, and were constrained
to ride on their parent atoms. H atoms of the water molecule
were located by difference Fourier methods. PARST31 was
used for geometry calculations.
In compound 10 molecules A and B form a pseudo-cen-
trosymmetric dimer. The two independent molecules have
only slightly different conformations. The cyclohexane rings
in the two molecules A and B have a chair conformation with
puckering parameters according to Cremer and Pople:32 QT
) 0.58(1) Å, θ ) 178.3(9)° and QT ) 0.58(1) Å, θ ) 5.31(10)°,
respectively. The intermolecular hydrogen-bond network
involves solvent H2O molecules resulting in a three-dimen-
sional structure. The H2O molecule acts as a receptor for O3′-
H‚‚‚O hydrogen bonds and as a donor for O-H‚‚‚N3 and
O-H‚‚‚O7′ hydrogen bonds.
In compound 20 the cyclohexane moiety is disordered and
has the chair conformation: QT ) 0.564(8) Å, θ ) 176.8(9)°.
Intermolecular hydrogen bonds determine the stacking of the
molecules.
Mod elin g Meth od s. C2′- and C3′-endo puckered furanosyl
nucleoside structures were modeled in their idealized Arnott
geometry.33 Anhydrohexitol and carbocyclic nucleosides were
model built using MacroModel,34 and energy-minimized using
the AMBER* force field supplied with MacroModel. A distance-
dependent dielectric constant of ꢀ ) r was applied. Global
energy minimum conformations were found by rotating around
the ø and γ torsions in steps of 10°, each time minimizing the
energy while keeping the ø and γ torsion angles fixed. The
global energy minimum conformations of the anhydrohexitol
and carbocyclic nucleosides were used for structural compari-
son with both puckered forms of the furanosyl nucleosides.
X-r a y Diffr a ction Stu d ies.27 Colorless single crystals
were grown by slow evaporation from water-methanol solu-
tions. Both data collections and subsequent structure deter-
minations were performed under identical condtions unless
specified. Crystal data for compound 10: C24H38N10O6, MW
) 562.64, monoclinic, Cc, a ) 21.5520(9), b ) 10.9723(3), c )
14.8578(5) Å, â ) 128.893(3)°, V ) 2734.6(2) Å3, Dc ) 1.367 g
cm-3, Z ) 4, F(000) ) 1200, µ ) 0.839 mm-1, λ ) 1.54178 Å,
T ) 293 K, crystal size: 0.4 × 0.20 × 0.10 mm. Crystal data
for compound 20: C12H18N2O4, MW ) 254.28, monoclinic, C2/
c, a ) 18.487(2), b ) 11.3955(8), c ) 11.7345(7) Å, â ) 94.510-
(5)°, V ) 2464.4(4) Å3, Dc ) 1.371 g cm-3, Z ) 8, F(000) )
1088, µ ) 0.861 mm-1, λ ) 1.54178 Å, T ) 293 K, crystal size:
0.5 × 0.25 × 0.05 mm.
An tivir a l Activity. Antiviral activity assays with herpes
simplex virus (HSV-1 and HSV-2) were done using a meth-
odology (viruses, cells, assays) that has been previously
described.35
Ack n ow led gm en t. This work was supported by a
grant of the Katholieke Universiteit Leuven (GOA 97/
11) and of the Granting Agency of the Czech Republic
(203/96/O567). We thank M. Vandekinderen for edito-
rial help.
Da ta Collection . Crystals were mounted on a Siemens P4
four-circle diffractometer with graphite monochromator and
Cu KR radiation. Unit cell parameters were obtained from a
least-squares analysis of 35 reflections. Intensity data were
collected using the ω-2θ scan technique. Three standard
reflections monitored every 100 reflections did not reveal a
significant change in intensity. The 2θ range of measured
reflections was 4 e 58°. The index range was, -1 e h e 23,
-1 e k e 11, -16 e l e 12 for compound 10 and -1 e h e 20,
-1 e k e 12, -12 e l e 12 for compound 20. For compound
10, 2275 reflections were collected, 2017 were unique reflec-
tions (Rint ) 0.0202); for compound 20, 2071 reflections were
collected and 1663 were unique reflections (Rint ) 0.0548). In
both cases absorption corrections by the method of North28
were applied.
J O962204X
(29) Altomare, A.; Burla, M. C.; Camalli, M.; Cascarano, G.; Giaco-
vazzo, C.; Guagliardi, A.; Polidori G. SIR 92. J . Appl. Crystallogr. 1994,
27, 435-435.
(30) Sheldrick, G. M. SHELXL-93. Program for the Refinement of
Crystal Structures. Univ. of Go¨ttingen, Germany, 1993.
(31) Nardelli, M. Comput. Chem. 1983, 7, 95-98.
(32) Cremer, D.; Pople, J . A. J . Am. Chem. Soc. 1975, 97, 1354-
1361.
(33) Arnott, S.; Campbell-Smith, P. J .; Chandresekharan, R. CRC
Handbook of Biochemistry; CRC: Boca Raton, FL; Vol. 2, pp 411-
422.
(34) Mohamadi, F.; Richards, N. G. J .; Guida, W. C.; Liskamp, R.;
Lipton, M.; Caufield, C.; Hendrickson, T.; Still, W. C. J . Comput. Chem.
1990, 11, 440.
(35) De Clercq, E.; Descamps, J .; Verhelst, G.; Walker, R. T.; J ones,
A. S.; Torrence, P. F.; Shugar, D. J . Infect. Dis. 1980, 141, 563-574.
(36) Bergerhoff, G. DIAMOND. Visual Structure Information Sys-
tem, Gerhard-Domagsk-Str., 53121, Bonn, Germany, 1996.
(37) Kraulis, P. J . J . Appl. Crystallogr. 1991, 24, 946-950.
(27) The authors have deposited atomic coordinates for these
structures with the Cambridge Crystallographic Data Centre. The
coordinates can be obtained, on request, from the Director, Cambridge
Crystallographic Data Centre, 12 Union Road, Cambridge, CB2, 1EZ,
U.K.
(28) North, A. C. T.; Phillips, D. C.; Mathews, F. S. Acta Crystallogr.
1968, A24, 351-359.