SYNTHESIS OF SOME 2'-C-ALKYL DERIVATIVES OF 9-(2-PHOSPHONOMETHOXYETHYL)ADENINE AND RELATED COMPOUNDS

Article abstract of DOI:10.1135/cccc19942069

To study the effect of β-substitution in 2'-alkyl derivatives of 9-(2-phosphonomethoxyethyl)adenine (Ia) on the antiviral activity or group specificity, these derivatives were synthesized. 9-(2-Hydroxyalkyl)adenines VIII were prepared by alkylation of adenine with suitably substituted oxiranes XIII or 2-hydroxyalkyl p-toluenesulfonates IV and VI.After protection of the adenine amino group by benzylation (compounds IX) or amidine formation (compounds X), the intermediates were alkylated with bis(2-propyl) p-toluenesulfonyloxymethanephosphonate (XI) in the presence of sodium hydride.After deprotection, the obtained phosphonate diesters XII were converted into phosphoniuc acids I by transsilylation and hydrolysis.This synthetic scheme was used for the preparation of ethyl (Ie), propyl (If), 2-propyl (Ig), 2-methylpropyl (Ih), cyclopropyl (Ii), cyclohexyl (Ij), benzyl (Ik) and phenyl (Il) derivatives.The 2'-trifluoromethyl derivative XXIIa was prepared analogously from 9-(2-hydroxy-3,3,3-trifluoropropyl)adenine (XXa), obtained by alkylation of adenine sodium salt with 2-hydroxy-3,3,3-trifluoropropyl bromide. 2,6-Diaminopurine derivative XXIIb was obtained analogously. 2'-Trimethylsilyl derivative XIXa was obtained by alkylation of adenine with 2-phosphonylmethoxy-3-(4-toluenesulfonyloxy)propyltrimethylsilane (XVII) followed by transsilylation and hydrolysis of diester XVIIIa. 9-(3-Phosphonomethoxybutyl)adenine (XXVIII) and 9-(2-methyl-2-phosphonomethoxypropyl)adenine (XXXV) were prepared from the corresponding hydroxy derivatives XXVIb and XXXII, respectively, by the same reaction pathway as derivatives I.

Full text of DOI:10.1135/cccc19942069

Alkyl Derivatives of 9-(2-Phosphonomethoxyethyl)adenine
2069
SYNTHESIS OF SOME 2′-C-ALKYL DERIVATIVES
OF 9-(2-PHOSPHONOMETHOXYETHYL)ADENINE
AND RELATED COMPOUNDS
Hana DVORAKOVA, Antonin HOLY and Ivan ROSENBERG
Institute of Organic Chemistry and Biochemistry,
Academy of Sciences of the Czech Republic, 166 10 Prague 6, The Czech Republic
Received February 9, 1994
Accepted May 3, 1994
To study the effect of β-substitution in 2′-alkyl derivatives of 9-(2-phosphonomethoxyethyl)adenine
(Ia) on the antiviral activity or group specificity, these derivatives were synthesized. 9-(2-Hydroxy-
alkyl)adenines VIII were prepared by alkylation of adenine with suitably substituted oxiranes XIII or
2-hydroxyalkyl p-toluenesulfonates IV and VI. After protection of the adenine amino group by ben-
zoylation (compounds IX) or amidine formation (compounds X), the intermediates were alkylated
with diisopropyl p-toluenesulfonyloxymethanephosphonate (XI) in the presence of sodium hydride.
After deprotection, the obtained phosphonate diesters XII were converted into phosphonic acids I by
transsilylation and hydrolysis. This synthetic scheme was used for the preparation of ethyl (Ie), propyl
(If), 2-propyl (Ig), 2-methylpropyl (Ih), cyclopropyl (Ii), cyclohexyl (Ij), benzyl (Ik) and phenyl (Il)
derivatives. The 2′-trifluoromethyl derivative XXIIa was prepared analogously from 9-(2-hydroxy-
3,3,3-trifluoropropyl)adenine (XXa), obtained by alkylation of adenine sodium salt with 2-hydroxy-
3,3,3-trifluoropropyl bromide. 2′-Trimethylsilyl derivative XIXa was obtained by alkylation of
adenine with 2-diisopropylphosphonomethoxy-3-(4-toluenesulfonyloxy)propyltrimethylsilane (XVII)
followed by transsilylation and hydrolysis of diester XVIIIa. 2,6-Diaminopurine derivatives XVIIId
and XXIIb were obtained analogously. 9-(3-Phosphonomethoxybutyl)adenine (XXVIII) and 9-(2-
methyl-2-phosphonomethoxypropyl)adenine (XXXV) were prepared from the corresponding hydroxy
derivatives XXVIb and XXXII, respectively, by the same reaction pathway as derivatives I.
Acyclic phosphonate analogs of nucleotides, particularly phosphonomethyl ethers of
some N-(hydroxyalkyl) derivatives of heterocyclic bases (I), attract recently much at-
tention owing to their significant antiviral effect and unusual parameters such as e.g.
unfrequent application regimen in vivo. We studied this group of compounds in detail
from the viewpoint of structure–biological activity relationships, investigating inde-
pendently the variation of all the three typical structural elements of their molecule: the
heterocyclic base, the side chain attached to it, and the phosphorus-containing moiety
(the phosphonate functionality) and its neighbourhood. We succeeded in defining the
principal characteristics of the heterocyclic base that are indispensable for the antiviral
activity in this group of compounds, as well as in specifying the relatively narrow
structural margin defining the conditions necessary for the biological effect of these
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Dvorakova, Holy, Rosenberg:
molecules1–3. This relationship reflects several partial structure-dependent steps: mem-
brane transport into the cell, transformation into the active metabolite and interaction
with the target object (enzyme or an enzyme system). We have proven that a very
specific protein can operate in the membrane transport4, the activation by phosphoryla-
tion is catalyzed by action of various nucleotide kinases depending on the character of
the base, which may or may not discriminate between the absolute configuration of the
substrate5,6, and that also the metabolism of the compounds and the targets of their
antiviral effect may be different3 (DNA polymerases, reverse transcriptases, ribonucle-
otide reductases) or yet unrecognized. Therefore, in attempts to evaluate the relation-
ships between the chemical structure and the resulting effect in a biological system, the
variety of parameters examined should be as low as possible.
Such opportunity is given by comparison of the effect of structural parameters on the
antiviral activity and its specificity in a simple series of N9-(2-phosphonomethoxyethyl)
derivatives of adenine bearing a substituent at the position 2 of the side chain, as de-
picted by the general formula I. According to the information gathered in the course of
our investigation, the unsubstituted compound of this series (PMEA, Ia) is active
against a selected group of DNA viruses (herpes viruses, vaccinia) and retroviruses
(HIV, MSV, SIV, Visna virus, hepatitis B virus etc., see refs1–3,7–9). Introduction of a
hydroxymethylene functionality into the compound of (S)-configuration ((S)-HPMPA,
Ib) results in a high, enantiospecific, and entirely group-specific effect aimed against
DNA viruses (no resistent genus has been found so far), whereas replacement of the
hydroxyl in these compounds by fluorine atom (Ic) (or by substitution of the parent
structure with the fluoromethyl functionality) leads, under preservation of enantiospeci-
ficity, to a high and group-specific antiretroviral effect, without interference with DNA
viruses5,10. Introduction of an aminomethyl or alkoxymethyl group into the said posi-
tion quenches the antiviral effect completely11,12. We have recently found6 that intro-
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Alkyl Derivatives of 9-(2-Phosphonomethoxyethyl)adenine
2071
duction of methyl group into position β of the parent structure Ia (the so-called PMP-
derivatives and related compounds with modified base) induces a group-specific anti-
retroviral effect, similar to that found for compound Ic but substantially stronger. Also
in this case, absolute enantioselectivity was observed for the adenine derivative Id: the
biological effect is connected with the same series as (S)-HPMPA or (S)-FPMPA (the
change of the designation from (S) to (R) for the PMP compounds is only formal).
The present study aims at the syntheses of alkyl derivatives of the type I bearing an
alkyl group in position β of the side chain, in other words analogs of PMP-derivatives
(Id). We synthesized systematically adenine derivatives substituted in position N9 but,
to eliminate at least in part the effect of the base, in some selected cases we extended
our studies also to 2,6-diaminopurine derivatives (in all series hitherto studied, this base
enhanced markedly the activity).
Acyclic phosphonates can be prepared by two principal methods: introduction of the
phosphonomethyl ether functionality into the molecule of N9-(2-hydroxyalkyl)adenine
or alkylation of adenine with a synthon already containing the structure of the side
chain together with the phosphonomethyl group. The latter method is of advantage if a
series of derivatives with various bases has to be synthesized10,13. We made use of both
the ways although, for practical reasons, the former was the method of choice.
The alkyl group in position β in compounds I was chosen so as to represent the
steric, the hydrophobic and the electronegative effects. The desired N9-(2-hydroxy-
alkyl)adenines were obtained by alkylation of adenine with tosylates of alkane-1,2-
diols IV and VI or oxiranes XIII (Scheme 1). Some of the diols III were commercially
available, most of them we prepared by reaction of the corresponding alkylmagnesium
halides with benzyloxyacetaldehyde and subsequent hydrogenolysis. Alkane-1,2-diols
were first converted into esters of p-toluenesulfonic acid IV under the usual conditions.
The ditosyl derivatives V, arising as side products, were separated by chromatography
on silica gel. Tosyl derivatives IV were then employed in the alkylation of adenine,
either directly or after benzoylation with benzoyl cyanide14 which afforded benzoyl
derivatives VI. The alkylation of adenine with compounds VI was performed by reac-
tion with sodium salt of adenine in dimethylformamide, the unprotected tosyl deriva-
tives reacted with adenine in the presence of equimolecular amount of cesium
carbonate in the same solvent. In the reaction with the benzoylated synthons VI, chro-
matography on silica gel gave first the benzoates VII from which the 9-(2-hydroxy-
alkyl)adenines VIII were obtained by methanolysis. Alkylation of adenine with
unprotected synthon IV also gave compounds VIII which in some cases were obtained
in sufficient purity directly by crystallization of the crude product. The third method of
preparing 9-(2-hydroxyalkyl)adenines VIII consisted in alkylation of adenine with oxi-
ranes XIII in the presence of catalytic amount of cesium carbonate. This method proved
to be useful already earlier in alkylations of adenine as well as other purine and pyri-
midine bases15.
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Alkyl Derivatives of 9-(2-Phosphonomethoxyethyl)adenine
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Condensation of these compounds with the phosphoroorganic synthon XI necessarily
required a protection of the adenine amino group; this was realized by N-selective ben-
zoylation16 which afforded N-benzoyl derivatives IX isolated by chromatography and
identified by NMR spectroscopy. Alternatively, both the amino groups of compounds
VIII were protected by conversion into N-dimethylaminomethylene derivatives X with
dimethylformamide dimethyl acetal17. The thus-protected derivatives IX or X were con-
densed with tosylate XI in the presence of excess sodium hydride in dimethylform-
amide15 and the reaction mixture was then methanolyzed or ammonolyzed. The ester
functionalities of phosphonates XII were removed by reaction with bromotrimethyl-
silane and subsequent hydrolysis. The resulting phosphonic acids I were isolated by ion
exchange chromatography and their structure was confirmed by the usual spectroscopic
1
methods, including the H NMR spectra of the zwitterionic forms or their sodium salts.
β-Trimethylsilylmethyl derivatives, representing compounds with a bulky hydro-
phobic substituent, were synthesized by alkylation of the heterocyclic base with a pre-
formed phosphoroorganic synthon. Similarly as compounds II, also the starting
protected diol XIV was prepared by Grignard rection of trimethylsilylmethylmagnesium
chloride with benzyloxyacetaldehyde. Condensation of compound XIV with tosylate XI
in the presence of sodium hydride and subsequent hydrogenolysis of the intermediate
XV gave phosphonate XVI which upon tosylation under standard conditions was con-
verted into the key synthon XVII. Alkylation of adenine with this compound in the
presence of cesium carbonate afforded the expected diester XVIIIa which was con-
verted into the desired substituted phosphonate XIXa. In the attempted preparation of
the analogous derivative XIXb by alkylation of 2,6-diaminopurine the yields were low
and we therefore chose an alternative way, analogous to that used with fluoromethyl
derivative Ic (ref.10), starting from 2-amino-6-chloropurine as the alkylation substrate.
In this case the reaction with synthon XVII gave satisfactory results; interestingly, the
reaction afforded mainly the N9-isomer whereas most alkylations of this base lead to
significant amounts (up to 30%) of the N7-regioisomer. Although the thus-obtained
intermediate XVIIIb reacted smoothly with sodium azide to give the expected substitu-
tion on the base, the reaction was accompanied with partial cleavage of the ester func-
tionality. Therefore, the mixture was only deionized and converted by hydrogenolysis
into 2,6-diaminopurine derivatives which on transsilylation and hydrolysis gave the
phosphonate XIXb as the final product of this reaction sequence (Scheme 2).
The outstanding properties of fluoromethyl derivative Ic (ref.5) prompted us to in-
clude also the trifluoromethyl group in the studied series of alkyl derivatives of the
parent structure Ia. The trifluoromethyl group may manifest itself as an analog of the
carboxyl functionality or of the methyl group (e.g. cytostatic and antiviral 2′-deoxy-5′-
trifluoromethyluridine behaves as a thymidine analog). Also in this case we tried to
prepare adenine as well as 2,6-diaminopurine (XXIII) derivatives (Scheme 3). The key
alkylation reagent was 1-bromo-3,3,3-trifluoro-2-propanol prepared by reduction of
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Dvorakova, Holy, Rosenberg:
SCHEME 2
Collect. Czech. Chem. Commun. (Vol. 59) (1994)

Alkyl Derivatives of 9-(2-Phosphonomethoxyethyl)adenine
2075
bromotrifluoroacetone18. This halogeno derivative smoothly alkylated sodium salt of
adenine or 2,6-diaminopurine to give 9-(2-hydroxy-3,3,3-trifluoromethyl) derivatives
XX. The adenine derivative was selectively N-benzoylated to compound XXI which was
then condensed with tosyl derivative XI. The crude product was subjected to methan-
olysis and transsilylation of the ester functionalities to yield the desired β-trifluoro-
methyl derivative XXIIa. In the case of compound XXb, instead of N-benzoylation, we
protected the amino groups with N-dimethylaminomethylene groups that are easier re-
movable than the N-benzoyl functionalities. Upon condensation of the thus-obtained
compound XXIII with tosyl derivative XI, ammonolysis and transsilylation, we isolated
the β-trifluoromethyl derivative XXIIb by ion exchange chromatography.
SCHEME 3
We also prepared several other compounds relevant to the present study: first of all
the linear homolog of the PMP-derivative Id in which the typical grouping of the PMP-
series is one CH2 group shifted farther from the heterocyclic nucleus (Scheme 4). Its
synthesis started from butane-1,3-diol which was first tosylated on the primary hy-
droxyl and the remaining hydroxyl functionality in the formed ester XXIV was pro-
tected by benzoylation. Alkylation of sodium salt of adenine with the obtained synthon
XXV afforded 4′-O-benzoyl derivative XXVIa which on methanolysis gave 9-(3-
hydroxybutyl)adenine (XXVIb). Compound XXVIb was converted into the N-benzoyl
derivative XXVII used finally in condensation with synthon XI in the presence of so-
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Dvorakova, Holy, Rosenberg:
dium hydride. The further reaction sequence involved standard operations: methan-
olysis, transsilylation, hydrolysis and finally isolation of the phosphonate XXVIII by
ion-exchange chromatography.
SCHEME 4
Related to compound XXVIII is the β,β-dimethyl derivative XXXV which was syn-
thesized by a very similar method, simpler in that it started from a symmetrical 2,2-di-
methylpropane-1,3-diol. Monotosylation to compound XXIX, its subsequent protection
by benzoylation to compound XXX, alkylation of sodium salt of adenine with this deri-
vative, isolation of the O-benzoylated intermediate XXXI and further analogous steps
depicted in Scheme 5 finally afforded compound XXXV. Its identity, as well as the
identity of most of the described compounds (intermediates and the final phosphonic
acids) has been verified by physicochemical methods, particularly by the NMR spec-
troscopy.
Detailed results of biological studies will be reported elsewhere. Preliminary anti-
viral assays19,20 afforded negative results. It seems thus that for retention of the antiviral
activity the character (bulk) of the β-alkyl group in the side chain is extraordinarily
strictly defined: the methyl group can be replaced by a hydroxymethyl or fluoromethyl
group but no more by ethyl or even cyclopropyl group. Also, the characteristic group-
ing of the PMP-derivatives Id cannot be transferred by one carbon unit farther away
Collect. Czech. Chem. Commun. (Vol. 59) (1994)

Alkyl Derivatives of 9-(2-Phosphonomethoxyethyl)adenine
2077
from the base. Equally striking is the complete inactivity of β-trifluoromethyl deriva-
tive XXII. Of course, the reason for all these negative responses may be primarily con-
nected with the transport of these compounds through the cell membrane.
SCHEME 5
EXPERIMENTAL
Unless stated otherwise, solutions were evaporated at 40 °C/2 kPa and compounds were dried at 13 Pa
over phosphorus pentoxide. Melting points were determined on a Kofler block and are uncorrected.
Thin-layer chromatography was performed on Silufol UV254 sheets in the solvent systems: S1 benzene,
S2 benzene–ethyl acetate (97 : 3), S3 benzene–ethyl acetate (95 : 5), S4 benzene–ethyl acetate (9 : 1),
S5 toluene–ethyl acetate (1 : 1), S6 chloroform–methanol (97 : 3), S7 chloroform–methanol (9 : 1) S8
chloroform–methanol (4 : 1), S9 chloroform–ethanol (7 : 3). Preparative thin-layer chromatography
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Dvorakova, Holy, Rosenberg:
was carried out on 40 × 17 × 0.4 cm plates of silica gel containing a UV indicator (Kavalier, Votice,
The Czech Republic). Paper chromatography was performed on a paper Whatman No. 1 in system
S10 2-propanol–concentrated aqueous ammonia–water (7 : 1 : 2), paper electrophoresis on a paper
Whatman No. 3 MM at 40 V/cm for 1 h in 0.05 M triethylammonium hydrogen carbonate pH 7.5.
The electrophoretical mobilities are referenced to uridine 3′-phosphate. Reversed-phase liquid chro-
matography was carried out on Separon SGX columns (150 × 3.3 mm) in 0.05 M triethylammonium
hydrogen carbonate pH 7.5, containing acetonitrile: H1 4%, H2 5%, H3 6%, H4 8%, H5 10%, H6
1
12%. H NMR spectra were measured on a spectrometer Varian UNITY-200 (at 200 MHz) or Varian
UNITY-500 (at 500 MHz) in hexadeuteriodimethyl sulfoxide with tetramethylsilane as internal standard.
The free phosphonic acids were measured in deuterium oxide containing sodium deuteroxide with
sodium 3-(trimethylsilyl)-1-propanesulfonate (DSS) as internal standard. UV absorption spectra were
measured on a Beckmann DU-65 spectrometer; the wavelengths of extrema are given in nm. Mass
spectra were taken on a ZAB-EQ spectrometer (VG Analytical) using EI (electron energy 70 eV) and
FAB (ionization by Xe, accelerating voltage 8 kV) techniques.
Starting Compounds and Reagents
2-Bromopropane and 1-bromo-2-methylpropane were prepared by reaction of the corresponding alco-
hols with phosphorus tribromide and were distilled immediately before use. Vinylcyclohexane,
styrene oxide, trifluoroacetone, 2,2-dimethyl-1,3-propanediol, chloromethyltrimethylsilane and
allylbenzene were purchased from Aldrich, cyclopropyl bromide, butane-1,2-diol and pentane-1,2-
diol from Janssen. Adenine was a Fluka product, 2,6-diaminopurine was obtained from Tokyo Kasei
(Japan) and 2-amino-6-chloropurine from Mack (Germany).
Deionization of Mixtures on Dowex 50
A solution of the mixture was applied onto a column of Dowex 50 X 8 (H+ form) and the column
was washed with water until the acid reaction disappeared and the UV absorption (254 nm) of the
eluate dropped to the original value. The column was then washed with 2.5% aqueous ammonia and
the UV-absorbing eluate was collected and evaporated in vacuo.
9-(2-Phosphonomethoxybutyl)adenine (Ie)
A mixture of compound IXe (1.56 g, 5 mmol) and tosyl derivative XI (2.1 g, 6 mmol) was codistilled
with dimethylformamide (2 × 25 ml) at 40 °C/13 Pa. The residue was dissolved in dimethylform-
amide (25 ml), cooled to 0 °C and 60% sodium hydride dispersion (0.60 g, 15 mmol) was added. The
mixture was then stirred at room temperature for 4 days (according to TLC in S7 the reaction was
quantitative). Upon addition of methanol (50 ml) the mixture was set aside at room temperature over-
night, neutralized with Dowex 50 X 8 (H+ form) and made alkaline with triethylamine. The mixture
was filtered, the ion exchanger washed with methanol (100 ml) and the filtrate evaporated to dryness
in vacuo. The residue was deionized on a column of Dowex 50 X 8 (H+ form); elution with 20%
aqueous methanol and then with dilute (1 : 10) ammonia. The UV-absorbing fraction of the ammonia
eluate was taken down in vacuo and the residue dried in vacuo overnight. Acetonitrile (25 ml) and
bromotrimethylsilane (2.5 ml) were added and the solution was set aside at room temperature over-
night under exclusion of moisture. After evaporation in vacuo, the residue was mixed with water (50 ml),
made alkaline with ammonia and allowed to stand at room temperature for 1 h. The solvent was
again evaporated, the residue was deionized on a column of Dowex 50 X 8 (H+ form, 100 ml) (vide
supra) and the material obtained from UV-absorbing fractions of the ammonia eluate was chromato-
graphed on a column of Dowex 1 X 2 (acetate form, 100 ml) in a linear gradient of acetic acid (0 – 0.5
Collect. Czech. Chem. Commun. (Vol. 59) (1994)

Alkyl Derivatives of 9-(2-Phosphonomethoxyethyl)adenine
2079
mol/l, à 1 l). The product was eluted with 0.3 – 0.4 M acetic acid. The main UV-absorbing part of
the product was evaporated in vacuo and the residue was codistilled (3 × 50 ml) with water. Crystal-
lization from 70% aqueous ethanol with addition of ether afforded 0.90 g (56.5%) of compound Ie,
m.p. 252 °C, RF 0.35 (S10), EUp = 0.80, HPLC (H3): k = 2.84. For C10H16N5O4P . H2O (319.3)
calculated: 37.60% C, 5.68% H, 21.94% N, 9.72% P; found: 37.86% C, 5.71% H, 22.22% N, 9.87% P.
1H NMR spectrum: 8.30 s, 1 H (H-2); 8.10 s, 1 H (H-8); 4.39 dd, 1 H, J(1a′,2′) = 4.2, J(gem) = 14.6
(H-1a′); 4.27 dd, 1 H, J(1b′,2′) = 5.6, J(gem) = 14.6 (H-1b′); 3.73 m, 1 H, ΣJ = 22.0 (H-2′); 1.44 m,
2 H (H-3′); 3.58 dd, 1 H, J(P,CH) = 9.5, J(gem) = 12.2 (P-CHa); 3.50 dd, 1 H, J(P,CH) = 9.3,
J(gem) = 12.2 (P-CHb); 0.96 t, 3 H, J(4′,3′) = 6.5 (CH3).
9-(2-Phosphonomethoxypentyl)adenine (If)
A mixture of compound IXf (1.62 g, 5 mmol) and tosylate XI (2.1 g, 6 mmol) was codistilled with
dimethylformamide (2 × 25 ml) at 40 °C/13 Pa. The residue was dissolved in dimethylformamide
(30 ml), cooled to 0 °C and 60% sodium hydride dispersion (0.60 g, 15 mmol) was added. The mix-
ture was then stirred at room temperature for 4 days. Upon addition of methanol (50 ml) the mixture
was set aside at room temperature overnight, neutralized with Dowex 50 X 8 (H+ form) and made
alkaline with triethylamine. The mixture was filtered, the ion exchanger washed with methanol
(100 ml) and the filtrate evaporated to dryness in vacuo. The residue was deionized on a column of
Dowex 50 X 8 (H+ form), elution with 20% aqueous methanol, and then with dilute (1 : 10) am-
monia. The UV-absorbing fraction of the ammonia eluate was taken down in vacuo and the residue
dried in vacuo overnight. Acetonitrile (40 ml) and bromotrimethylsilane (4 ml) were added and the
solution was set aside at room temperature overnight under exclusion of moisture. After evaporation
in vacuo, the residue was mixed with water (50 ml), made alkaline with ammonia and allowed to
stand at room temperature for 1 h. The solvent was again evaporated in vacuo, the residue was
deionized on a column of Dowex 50 X 8 (H+ form, 150 ml) (vide supra) and the material obtained
from UV-absorbing fractions of the ammonia eluate was chromatographed on a column of Dowex 1
X 2 (acetate form, 100 ml) in a linear gradient of acetic acid (0 – 0.5 mol/l, à 1 l). The product was
eluted with 0.2 – 0.3 M acetic acid. The main UV-absorbing part of the product was evaporated in
vacuo and the residue was codistilled (3 × 50 ml) with water. Crystallization from ethanol with ad-
dition of ether afforded 0.80 g (48%) of compound If, m.p. 269 °C, RF 0.42 (S10), EUp = 0.80, HPLC
(H3): k = 3.69. For C11H18N5O4P.H2O (333.3) calculated: 39.63% C, 6.05% H, 21.02% N, 9.31% P;
1
found: 39.95% C, 5.74% H, 20.68% N, 9.09% P. H NMR spectrum: 8.35 s, 1 H (H-2); 8.18 s, 1 H
(H-8); 4.43 dd, 1 H, J(1a′,2′) = 4.0, J(gem) = 14.8, (H-1a′); 4.30 dd, 1 H, J(1b′,2′) = 5.0, J(gem) =
14.8 (H-1b′); 3.81 brpent, 1 H, ΣJ = 20.1 (H-2′); 1.28 – 1.44 m, 4 H (H-3′ and H-4′); 3.58 dd, 1 H,
J(P,CH) = 9.3, J(gem) = 12.2 (P-CHa); 3.52 dd, 1 H, J(P,CH) = 9.3, J(gem) = 12.2 (P-CHb); 0.85 brt, 3 H,
J(5′,4′) = 7.1 (CH3).
General Method for Preparation of Compounds Ig – Il
A mixture of hydroxy derivative VIIIg, VIIIh, VIIIi, VIIIj, VIIIk or VIIIl (10 mmol), dimethylform-
amide (50 ml) and N,N- dimethylformamide dimethyl acetal (10 ml, 75 mmol) was allowed to stand
at 20 °C for 24 h in a stoppered flask. After evaporation of the reaction mixture and codistillation
with dimethylformamide (3 × 50 ml), the residue was stirred with solid carbon dioxide and pyridine–
water (1 : 1, 100 ml) for 30 min. The mixture was then evaporated, codistilled with pyridine (3 × 50 ml)
and with dimethylformamide (3 × 50 ml) and the crude dimethylaminomethylene derivative X was
used without purification in the next reaction step.
Sodium hydride (1.2 g, 30 mmol, 60% dispersion) was added at −20 °C to a stirred mixture of
crude dimethylaminomethylene derivative X and bis(2-propyl) p-toluenesulfonyloxymethanephospho-
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Dvorakova, Holy, Rosenberg:
nate (XI) (4.2 g, 12 mmol). The mixture was then allowed to warm to room temperature and was
stirred under exclusion of moisture until the starting compound disappeared (24 h, TLC in S8). The
reaction mixture was neutralized with acetic acid and the condensation product was deblocked by
standing with ammonia–water–methanol (100 ml, 1 : 1 : 1) overnight. The mixture was taken down
and deionized on Dowex 50 X 8 (H+ form, 100 ml). The crude bis(2-propyl) ester XII was dried over
phosphorus pentoxide and then used directly in the deprotection step.
The material from the preceding step was dissolved in acetonitrile (80 ml), bromotrimethylsilane
(8 ml) was added and the mixture was set aside in a stoppered flask at 20 °C for 24 h. After evap-
oration, the residue was codistilled with acetonitrile (3 × 50 ml), mixed with water (50 ml) and ad-
justed to pH 8 with triethylamine. The mixture was allowed to stand for 1 h, then evaporated in
vacuo and the residue was deionized on Dowex 50 X 8 (H+ form, 100 ml). The obtained crude pro-
duct was purified by chromatography on a column of Dowex 1 X 2 (acetate form, 100 ml). The
product was eluted with a linear gradient of acetic acid (0 – 0.5 mol/l, 1 l each). Crystallization from
80% ethanol afforded the pure phosphonate.
9-(3-Methyl-2-phosphonomethoxybutyl)adenine (Ig), yield 1.51 g (48%), m.p. >250 °C, k = 2.5
(H1), EUp = 0.70. For C11H18N5O4P (315.3) calculated: 41.91% C, 5.75% H, 22.20% N, 9.83% P;
1
found: 41.77% C, 5.54% H, 22.29% N, 9.62% P. H NMR spectrum: 8.30 s and 8.11 s, 2 H (H-2,
H-8); 4.35 dd, 1 H, J(1a′,2′) = 3.2, J(gem) = 14.6 (H-1a′); 4.22 dd, 1 H, J(1b′,2′) = 7.3, J(gem) =
14.6 (H-1b′); 3.48 td, 1 H, J(2′,1a′) = 3.2, J(2′, 1b′) = 7.3, J(2′,3′) = 7.1 (H-2′); 3.54 dd and 3.32 dd,
2 H, J(P,CH) = 10.0 and 9.5, J(gem) = 12.4 (PCH2); 1.80 br oct, 1 H, ΣJ = 48 (H-3′); 1.01 d, 3 H
and 0.97 d, 3 H, J(CH3,CH) = 6.8 (CH3). UV spectrum (pH 2): λmax 260.5 nm (εmax 15 900); (pH 7):
λmax 261.0 nm (εmax 14 700); (pH 13): λmax 261.0 (εmax 13 900). Mass spectrum, m/z: 316.1 (M + H).
9-(4-Methyl-2-phosphonomethoxypentyl)adenine (Ih), yield 0.42 g (12%), m.p. 242 – 243 °C, k =
3.3 (H5), EUp = 0.71. For C12H20N5O4P . 2 H2O (365.3) calculated: 39.45% C, 7.17% H, 19.16% N,
1
8.49% P; found: 39.71% C, 6.69% H, 18.81% N, 7.76% P. H NMR spectrum: 8.38 s and 8.18 s, 2 H
(H-2, H-8); 4.46 dd, 1 H, J(1a′,2′) = 3.0, J(gem) = 14.2 (H-1a′); 4.30 dd, 1 H, J(1b′,2′) = 4.0, J(gem)
= 14.2 (H-1b′); 3.88 m, 1 H (H-2′); 3.59 d, 2 H, J(P,CH) = 10.8 (PCH2); 1.29 br pent, 1 H, J(3a′,2′)
= 8.2, J(3a′,4′) = 5.1, J(gem) = 12.0 (H-3a′); 1.11 brpent, 1 H, J(3b′,2′) = 5.9, J(3b′,4′) = 7.4, J(gem)
= 12.0, (H-3b′); 1.72 m, 1 H (H-4′); 0.85 and 0.83 2 × d, 2 × 3 H, J(CH3,CH) = 6.1 and 6.3 (CH3).
UV spectrum (pH 2): λmax 260.5 nm (εmax 14 200); (pH 7): λmax 262.5 nm (εmax 14 400); (pH 13):
λmax 262.5 (εmax 14 400). Mass spectrum, m/z: 330.2 (M + H).
9-(2-Cyclopropyl-2-phosphonomethoxyethyl)adenine (Ii), yield 1.70 g (51%), m.p. 241 – 242 °C, k
= 4.9 (H2), EUp = 0.77. For C11H16N5O4P . H2O (331.2) calculated: 39.88% C, 4.87% H, 21.13% N,
1
9.36% P; found: 39.71% C, 4.86% H, 21.11% N, 9.40% P. H NMR spectrum: 8.33 s and 8.18 s, 2 H
(H-2, H-8); 4.47 dd, 1 H, J(1a′,2′) = 4.9, J(gem) = 14.4 (H-1a′); 4.43 dd, 1 H, J(1b′,2′) = 5.4, J(gem)
= 14.4 (H-1b′); 3.09 dt, 1 H, ΣJ = 19.3 (H-2′); 3.77 dd and 3.52 dd, 2 H, J(P,CH) = 9.0 and 9.8,
J(gem) = 12.2 (PCH2); 0.62 m, 1 H and 0.56 m, 1 H and 0.42 m, 1 H and 0.27 m, 1 H and 0.12 m,
1 H (cyclopropyl). UV spectrum (pH 2): λmax 259.0 nm (εmax 13 000); (pH 7): λmax 261.0 nm (εmax 14 100);
(pH 13): λmax 261.0 (εmax 12 900). Mass spectrum, m/z: 314.1 (M + H).
9-(2-Cyclohexyl-2-phosphonomethoxyethyl)adenine (Ij), yield 0.31 g (8%), m.p. >250 °C, k = 6.3
(H6), EUp = 0.73. For C14H22N5O4P . 2 H2O (391.4) calculated: 42.96% C, 5.67% H, 17.89% N,
1
7.92% P; found: 43.37% C, 5.79% H, 17.97% N, 7.82% P. H NMR spectrum: 8.39 and 8.16 2 × s,
2 H (H-2, H-8); 4.41 dd, 1 H, J(1a′,2′) = 3.4, J(gem) = 14.6 (H-1a′); 4.29 dd, 1 H, J(1b′,2′) = 6.4,
J(gem) = 14.6 (H-1b′); 3.49 td, 1 H, J(2′,1a′) = 3.4, J(2′,1b′) = 6.4, J(2′,3′) = 6.6 (H-2′); 3.54, dd, 1 H
and 3.39 dd, 1 H, J(P,CH) = 9.5 and 9.3, J(gem) = 12.2 (PCH2); 1.59 – 1.86 m, 5 H and 1.36 m, 1 H
and 1.03 – 1.15 m, 5 H (cyclohexyl). UV spectrum (pH 2): λmax 260.0 nm (εmax 14 500); (pH 7): λmax
261.0 nm (εmax 13 400); (pH 13): λmax 261.0 (εmax 13 100). Mass spectrum, m/z: 356.1 (M + H).
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Alkyl Derivatives of 9-(2-Phosphonomethoxyethyl)adenine
2081
9-(3-Phenyl-2-phosphonomethoxypropyl)adenine (Ik), yield 0.59 g (16%), m.p. >250 °C, k = 3.1
(H6), EUp = 0.63. For C15H18N5O4P (363.3) calculated: 49.59% C, 4.99% H, 19.27% N, 8.53% P;
1
found: 49.12% C, 4.88% H, 18.99% N, 9.06% P. H NMR spectrum: 8.195 s, 1 H and 8.03 s, 1 H
(H-2, H-8); 7.15 m and 7.03 m, 5 H (arom.); 4.29 d, 2 H, J(1′,2′) = 5.4 (H-1′); 4.23 m, 1 H, ΣJ =
23.7 (H-2′); 3.02 dd, 1 H, J(3a′,2′) = 4.9, J(gem) = 14.4 (H-3a′); 2.67 dd, 1 H, J(3b′,2′) = 8.0, J(gem)
= 14.4 (H-3b′); 3.70 dd, 1 H and 3.59, dd, 1 H, J(P,CH) = 9.3 and 9.5, J(gem) = 12.2 (PCH2). UV
spectrum (pH 2): λmax 256.0 nm (εmax 11 400); (pH 7): λmax 262.0 nm (εmax 11 200); (pH 13): λmax
262.0 (εmax 11 000). Mass spectrum, m/z: 364.2 (M + H).
9-(2-Phenyl-2-phosphonomethoxyethyl)adenine (Il), yield 2.10 g (60%), m.p. >250 °C, k = 2.8
(H3), EUp = 0.77. For C14H16N5O4P (349.3) calculated: 48.14% C, 4.62% H, 20.04% N, 8.88% P;
1
found: 47.37% C, 4.62% H, 19.12% N, 8.22% P. H NMR spectrum: 8.03 s, 1 H and 7.90 s, 1 H
(H-2, H-8); 7.23 m and 7.10 m, 5 H (arom.); 4.53 dd, 1 H, J(1a′,2′) = 5.1, J(gem) = 14.2 (H-1a′);
4.48 dd, 1 H, J(1b′,2′) = 5.6, J(gem) = 14.2 (H-1b′); 4.87 brt, 1 H, J = 5.6 (H-2′); 3.46 dd, 1 H and
3.34 dd, 1 H, J(P,CH) = 9.0 and 9.8, J(gem) = 12.2 (PCH2). UV spectrum (pH 2): λmax 259.0 nm
(εmax 13 700); (pH 7): λmax 260.0 nm (εmax 14 100); (pH 13): λmax 261.0 (εmax 13 300). Mass spec-
trum, m/z: 250.0 (M + H).
Preparation of Compounds II (General Procedure)
A solution of the alkyl halogenide (0.25 mol) in ether (200 ml) was added dropwise to a stirred mix-
ture of magnesium (6.1 g, 0.25 mol), ether (150 ml) and a trace of iodine to maintain reflux. The
reaction mixture was then refluxed for one hour, benzyloxyacetaldehyde (32.3 g, 0.215 mol) in ether
(150 ml) was added within 30 min and the reflux was continued for two more hours. The mixture
was left to stand overnight, cooled with ice, and ammonium chloride (200 ml, saturated solution) was
added dropwise. After stirring for 30 min, the mixture was filtered through a layer of Celite and
extracted with ether. The aqueous layer was washed with ether (3 × 100 ml), the combined ethereal
extracts were dried over magnesium sulfate, filtered and the solvent was evaporated. The crude pro-
ducts were chromatographed on silica gel (400 g).
1-Benzyloxy-3-methylbutan-2-ol (IIg). Reaction with isopropyl bromide and subsequent chromato-
graphy in benzene–ethyl acetate (97 : 3) afforded 24.4 g (63%) of compound IIg, RF 0.26 (S3).
1H NMR spectrum: 7.33 brs, 5 H (arom.); 4.53 d, 1 H, J(CH,OH) = 5.0 (OH); 4.48 s, 2 H
(PhCH2O); 3.35 m, 3 H (OCH2,OCH); 1.68 septd, 1 H, J(CH,CH) = 4.4, J(CH,CH3) = 6.8 (CCH);
0.85 d and 0.82 d, 6 H, J = 6.8 (CH3).
1-Benzyloxy-4-methylpentan-2-ol (IIh). Reaction with isobutyl bromide and subsequent chromato-
graphy in chloroform afforded 35.4 g (79%) of compound IIh, RF 0.4 (S2). 1H NMR spectrum: 7.33 brs,
5 H (arom.); 4.49 dd, 1 H and 4.46 dd, 1 H, J(gem) = 12.2 (PhCH2O); 3.32 dd, 1 H, J = 6.1, J(gem)
= 9.5 (OCHa); 3.27 dd, 1 H, J = 5.1, J(gem) = 9.5 (OCHb); 3.67 m, 1 H, ΣJ = 24.2 (OCH); 1.25 dd,
1 H, J = 5.1, 8.8, J(gem) = 13.7 (CCHa); 1.20 dd, 1 H, J = 4.4, 8.6, J(gem) = 13.7 (CCHb); 1.76 m,
1 H, ΣJ = 54 (CCH); 0.88 and 0.85 2 × d, 6 H, J = 6.8, 6.6 (CH3).
1-Benzyloxy-2-cyclopropylethan-2-ol (IIi). Reaction with cyclopropyl bromide and subsequent
1
chromatography in system S2 afforded 27.0 g (70%) of compound IIi, RF 0.27 (S2). H NMR spec-
trum: 7.30 – 7.40 m, 5 H (arom.); 4.60 d, 1 H, J(CH,OH) = 4.9 (OH); 4.51 s, 2 H (PhCH2O); 3.44 dd,
1 H, J = 4.9, J(gem) = 9.8 (OCHa); 3.40 dd, 1 H, J = 6.8, J(gem) = 9.8 (OCHb); 3.14 tt, 1 H, ΣJ = 23.0
(OCH); 0.79 – 0.85 m, 1 H, 0.30 – 0.38 m, 2 H and 0.19 m, 2 H (cyclopropyl).
Preparation of 2-Hydroxyalkyl p-Toluenesulfonates IVg – IVi (General Procedure)
Compounds IIg – IIi (0.11 mol) were hydrogenated over 10% Pd/C (2.1 g) in methanol (300 ml) and
hydrochloric acid (2 ml) at room temperature for 4 h. The reaction mixture was filtered through a
Collect. Czech. Chem. Commun. (Vol. 59) (1994)

2082
Dvorakova, Holy, Rosenberg:
layer of Celite which was then washed with methanol (200 ml). The filtrate was neutralized with
pyridine, evaporated and the residue was codistilled with pyridine (3 × 50 ml). The obtained com-
pound III was used directly in the tosylation step.
A solution of p-toluenesulfonyl chloride (25.2 g, 0.13 mol) in pyridine (70 ml) was added drop-
wise at 0 °C to a stirred solution of the 1,2-diol (0.11 mol) and 4-dimethylaminopyridine (0.1 g) in
pyridine (70 ml) under exclusion of moisture. The reaction mixture was left to stand at 0 °C for
24 h and methanol (5 ml) was added. The mixture was stirred for 30 min, evaporated and partitioned
between ethyl acetate and water. The organic phase was washed successively with 1 M HCl, water,
sodium hydrogen carbonate solution, and water. The extract was dried over magnesium sulfate, fil-
tered, the solvent was evaporated and the residue was chromatographed on silica gel.
2-Hydroxy-3-methylbutyl p-toluenesulfonate (IVg) and 3-methyl-1,2-butanediyl bis(p-toluenesulfo-
nate) (Vg). The products were eluted with benzene–ethyl acetate (95 : 5 and then 90 : 10). Yield of
the monotosylate IVg was 10.3 g (36%), RF 0.26 (S2). For C12H18O4S (258.2) calculated: 55.80% C,
1
7.02% H, 12.39% S; found: 55.86% C, 6.94% H, 12.30% S. H NMR spectrum: 7.79 d and 7.48 d,
4 H, J = 8.3 (arom.); 5.0 br, 1 H (OH); 3.34 td, 1 H, ΣJ = 16.0, (H-2); 3.92 dd, 1 H, J(1a,2) = 4.1,
J(gem) = 9.8 (H-1a); 3.84 dd, 1 H, J(1b,2) = 6.3, J(gem) = 9.8 (H-1b); 2.42 s, 3 H (TsCH3); 1.59
septd, 1 H, ΣJ = 46.4 (H-3); 0.76 d, 3 H, J(CH3,CH) = 6.8 (CH3).
Ditosylate Vg was obtained in 29% yield (13.1 g), RF 0.84 (S2). For C19H24O6S2 (412.4) calcu-
lated: 55.33% C, 5.87% H, 15.52% S; found: 55.71% C, 5.86% H, 15.64% S. 1H NMR spectrum:
7.71 d and 7.46 d, 4 H, J = 8.3 (arom.); 7.69 d and 7.41 d, 4 H, J = 8.3 (arom.); 4.48 ddd, 1 H, ΣJ
= 14.6 (H-2); 4.08 dd, 1 H, J(1a,2) = 4.6, J(gem) = 11.5 (H-1a); 4.02 dd, 1 H, J(1b,2) = 3.2, J(gem)
= 11.5 (H-1b); 2.42 s, 3 H and 2.40 s, 3 H (TsCH3); 1.89 oct, 1 H, ΣJ = 47.6 (H-3); 0.73 d, 3 H and
0.72 d, 3 H, J(CH3,CH) = 6.8 (CH3).
2-Hydroxy-4-methylpentyl p-toluenesulfonate (IVh) and 4-methyl-1,2-pentanediyl bis(p-toluene-
sulfonate) (Vh). The products were eluted with chloroform–ethanol (98 : 2), yield of the monotosylate
IVh was 10.0 g (34%), RF 0.42 (S2). For C13H20O4S (272.3) calculated: 57.34% C, 7.40% H, 11.75% S;
1
found: 58.08% C, 7.54% H, 11.64% S. H NMR spectrum: 7.79 d and 7.48 d, 4 H, J = 8.3 (arom.);
4.95 brs, 1 H (OH); 3.63 brsext, 1 H, ΣJ = 23.0 (H-2); 3.84 dd, 1 H, J(1a,2) = 4.4, J(gem) = 9.8
(H-1a); 3.79 dd, 1 H, J(1b,2) = 5.9, J(gem) = 9.8 (H-1b); 2.42 s, 3 H (TsCH3); 1.19 ddd, 1 H, J(3a,2)
= 9.8, J(3a,4) = 5.4, J(gem) = 13.2, (H-3a); 1.05 ddd, 1 H, J(3b,2) = 3.9, J(3b,4) = 8.8, J(gem) =
13.2 (H-3b); 1.64 m, 1 H, ΣJ = 55.0 (H-4); 0.82 and 0.78 2 × d, 2 × 3 H, J(CH3,CH) = 6.8 (CH3).
Mass spectrum, m/z: 273 (M + H).
Ditosylate Vh was obtained in 26% yield (12.3 g), RF 0.80 (S2). For C20H26O6S2 (426.4) calcu-
lated: 56.33% C, 6.15% H, 15.01% S; found: 55.87% C, 6.08% H, 15.21% S. 1H NMR spectrum:
7.79 d and 7.68 d, 4 H, J = 8.3 (arom.); 7.48 d and 7.32 d, 4 H, J = 8.3 (arom.); 4.66 ddd, 1 H, ΣJ
= 21.0 (H-2); 4.06 dd, 1 H, J(1a,2) = 3.9, J(gem) = 11.2 (H-1a); 4.03 dd, 1 H, J(1b,2) = 3.4, J(gem)
= 11.2 (H-1b); 2.425 s, 3 H and 2.41 s, 3 H (TsCH3); 1.45 ddd, 1 H, J(3a,2) = 8.8, J(3a,4) = 5.4,
J(gem) = 13.6 (H-3a); 1.28 ddd, 1 H, J(3b,2) = 4.9, J(3b,4) = 8.3, J(gem) = 13.6 (H-3b); 1.37 m, 1 H,
ΣJ = 54.5 (H-4); 0.74 d, 3 H and 0.63 d, 3 H, J(CH3,CH) = 6.8 (CH3). Mass spectrum, m/z: 426 (M + H).
2-Cyclopropyl-2-hydroxyethyl p-toluenesulfonate (IVi). The product was eluted with benzene–
ethyl acetate (95 : 5 and then 9 : 1), yield 15.9 g (57%), RF 0.19 (S2). For C12H15O4S (255.2) calcu-
lated: 56.47% C, 5.92% H, 12.53% S; found: 56.43% C, 6.49% H, 11.72% S. 1H NMR spectrum:
7.82 d and 7.50 d, 4 H, J = 8.3 (arom.); 4.27 dd, 1 H, J(1a,2) = 4.3, J(gem) = 11.0 (H-1a); 4.20 dd,
1 H, J(1b,2) = 5.8, J(gem) = 11.0 (H-1b); 3.65 ddd, 1 H, ΣJ = 19.8 (H-2); 2.425 s, 3 H (CH3);
1.01 – 1.19 m, 1 H; 0.50 – 0.65 m, 2 H; 0.30 – 0.45 m, 2 H (cyclopropyl).
Collect. Czech. Chem. Commun. (Vol. 59) (1994)

Alkyl Derivatives of 9-(2-Phosphonomethoxyethyl)adenine
2083
2-O-Benzoyloxybutyl p-Toluenesulfonate (VIe) and 2-O-Benzoyloxypentyl p-Toluenesulfonate (VIf)
A solution of tosyl chloride (50 g, 0.26 mol) in pyridine (150 ml) was added dropwise with stirring
and ice-cooling to a solution of butane-1,2-diol (27 g, 0.3 mol) and 4-dimethylaminopyridine (1 g) in
pyridine (250 ml). The mixture was stirred in ice for 3 h and then set aside at 0 °C for 48 h. Meth-
anol (50 ml) was added and, after standing for 1 h, the mixture was diluted with ethyl acetate (1 l),
washed with water (3 × 200 ml) and the solvent was evaporated in vacuo. The residue was codistilled
with toluene (3 × 100 ml) and dried at 40 °C/13 Pa. The obtained crystalline tosylate IVe (62 g,
0.25 mol) was dissolved in dichloromethane (400 ml) and benzoyl cyanide (36 g, 0.275 mol) with
triethylamine (5 ml) were added under ice-cooling. The mixture was allowed to stand under exclu-
sion of moisture at room temperature overnight, methanol (10 ml) was added and the supernatant was
evaporated in vacuo. The residue was dissolved in ether (150 ml), the same amount of light petro-
leum was added, the solution was decanted from the deposited impurities and the solvent was evap-
orated in vacuo. Crystallization of the residue from cyclohexane afforded 42 g (48%) of compound
IVe, m.p. 63 °C, RF 0.40 (S1), 0.62 (S4). For C18H20O5S (348.4) calculated: 62.05% C, 5.79% H,
9.20% S; found: 61.89% C, 5.78% H, 9.21% S.
Similarly, pentane-1,2-diol (0.3 mol) was converted into the tosyl derivative VIf (55 g, 61%), RF
0.40 (S1). For C19H22O5S (362.4) calculated: 62.96% C, 6.12% H, 8.85% S; found: 62.88% C, 5.95% H,
9.14% S.
9-(2-Hydroxybutyl)adenine (VIIIe)
Sodium hydride (2.0 g, 50 mmol, 60% dispersion in paraffin) was added to a suspension of adenine
(6.8 g, 50 mmol) in dimethylformamide (300 ml) and the stirred mixture was heated at 80 °C. Tosyl
derivative VIe (18.0 g, 52 mmol) was added and the mixture was heated at 100 °C for 16 h under
exclusion of moisture. After evaporation of the solvent at 40 °C/13 Pa, the residue was extracted with
boiling chloroform (3 × 100 ml). The filtrate was taken down in vacuo and the residue chromato-
graphed on a column of silica gel (300 ml) in chloroform. The obtained benzoyl derivative VIIe was
dissolved in 0.1 M methanolic sodium methoxide (150 ml) and allowed to stand at room temperature
overnight under exclusion of moisture. The mixture was neutralized by addition of Dowex 50 X 8
(H+ form), made alkaline with triethylamine, filtered and the ion exchanger washed with methanol
(100 ml). The filtrate was taken down in vacuo and the dry residue was codistilled with ethanol and
crystallized from ethanol with addition of the same amount of ether. Yield 3.5 g (34%) of compound
VIIIe, m.p. 195 °C. For C9H13N5O (207.2) calculated: 52.16% C, 6.31% H, 33.80% N; found:
1
52.40% C, 6.39% H, 33.74% N. H NMR spectrum: 8.14 s, 1 H (H-2); 8.05 s, 1 H (H-8); 7.23 brs,
2 H (NH2); 5.03 d, 1 H, J(2′,OH) = 5.03 (OH); 4.15 dd, 1 H, J(1a′,2′) = 4.0, J(gem) = 13.7 (H-1a′);
4.00 dd, 1 H, J(1b′,2′) = 7.5, J(gem) = 13.7 (H-1b′); 3.74 d, 1 H, ΣJ = 28.5 (H-2′); 1.34 m, 2 H
(H-3′); 0.90 t, 3 H, J = 7.3 (CH3).
9-(2-Hydroxypentyl)adenine (VIIIf)
Sodium hydride (1.6 g, 40 mmol, 60% dispersion in paraffin) was added to a suspension of adenine
(5.4 g, 40 mmol) in dimethylformamide (250 ml) and the stirred mixture was heated at 80 °C. Tosyl
derivative VIf (16.3 g, 45 mmol) was added and the mixture was heated at 100 °C for 20 h under
exclusion of moisture. After evaporation of the solvent at 40 °C/13 Pa, the residue was extracted with
boiling chloroform (3 × 100 ml). The filtrate was taken down in vacuo and the residue chromato-
graphed on a column of silica gel (300 ml) in chloroform to give the 2-O-benzoyl derivative of com-
pound VIIf (9.0 g, 69%) as an amorphous foam. This product was debenzoylated as described for the
preparation of compound VIIIe. Yield 3.8 g (62%) of compound VIIIf, m.p. 189 °C. For C10H15N5O
Collect. Czech. Chem. Commun. (Vol. 59) (1994)

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Dvorakova, Holy, Rosenberg:
1
(221.3) calculated: 54.28% C, 6.83% H, 31.66% N; found: 54.17% C, 6.62% H, 31.86% N. H NMR
spectrum: 8.14 s, 1 H (H-2); 8.05 s, 1 H (H-8); 7.23 brs, 2 H (NH2); 4.14 dd, 1 H, J(1a′,2′) = 3.9,
J(gem) = 13.4 (H-1a′); 3.99 dd, 1 H, J(1b′,2′) = 7.8, J(gem) = 13.4 (H-1b′); 3.84 d, 1 H (H-2′);
1.23 – 1.46 m, 4 H (H-3′ and H-4′); 0.84 brt, 3 H, J = 6.8 (CH3).
General Method for Preparation of Compounds VIIIg – VIIIi
A mixture of adenine (1.35 g, 10 mmol), cesium carbonate (3.25 g, 10 mmol), tosylate IVg, IVh or
IVi (10 mmol) and dimethylformamide (25 ml) was heated at 120 °C for 16 h under stirring and
exclusion of moisture. The reaction course was followed by TLC (S8). After concentration in vacuo,
the residue was codistilled with toluene (3 × 50 ml) and chromatographed or crystallized.
9-(2-Hydroxy-3-methylbutyl)adenine (VIIIg). Isolated by chromatography on silica gel (80 g) in
chloroform. The product was eluted with chloroform–methanol (95 : 5). Yield 0.8 g (36%), RF 0.31
(S8), m.p. 183 – 184 °C. For C10H15N5O (221.2) calculated: 54.29% C, 6.83% H, 31.64% N; found:
1
53.11% C, 6.62% H, 30.87% N. H NMR spectrum: 8.14 s, 1 H (H-2); 8.06 s, 1 H (H-8); 7.21 brs,
2 H (NH2); 4.98 d, 1 H, J(OH,CH) = 5.6 (OH); 4.21 dd, 1 H, J(1a′,2′) = 3.0, J(gem) = 13.9 (H-1a′);
3.98 dd, 1 H, J(1b′,2′) = 8.5, J(gem) = 13.9 (H-1b′); 3.60 m, 1 H (H-2′); 1.59 broct, 1 H (H-3′); 0.93 d,
3 H and 0.92 d, 3 H (CH3). UV spectrum (pH 2): λmax 261.0 nm (εmax 14 600); (pH 7): λmax 261.0 nm
(εmax 14 900); (pH 13): λmax 261.0 (εmax 14 800).
9-(2-Hydroxy-4-methylpentyl)adenine (VIIIh). Isolated by crystallization from methanol; yield 0.92 g
(40%), RF 0.5 (S8), m.p. 183 – 185 °C. For C11H17N5O (235.2) calculated: 56.16% C, 7.28% H, 29.76%
1
N; found: 55.34% C, 6.94% H, 29.84% N. H NMR spectrum: 8.13 s, 1 H (H-2); 8.04 s, 1 H (H-8);
7.17 brs, 2 H (NH2); 4.97 d, 1 H, J(OH,CH) = 5.6 (OH); 4.13 dd, 1 H, J(1a′,2′) = 3.4, J(gem) = 13.2
(H-1a′); 3.97 dd, 1 H, J(1b′,2′) = 7.3, J(gem) = 13.2 (H-1b′); 3.88 m, 1 H (H-2′); 1.27 ddd, 1 H,
J(3a′,2′) = 8.3, J(3a′,4′) = 5.4, J(gem) = 13.7 (H-3a′); 1.23 ddd, 1 H, J(3b′,2′) = 4.1, J(3b′,4′) = 8.8,
J(gem) = 13.7 (H-3b′); 1.77 m, 1 H (H-4′); 0.88 d, 3 H and 0.82 d, 3 H, J(CH3,CH) = 6.8 and 6.35
(CH3).
9-(2-Cyclopropyl-2-hydroxyethyl)adenine (VIIIi). Isolated by chromatography on silica gel (100 g)
in chloroform. Elution with chloroform–ethanol (75 : 25) afforded 0.7 g (33%) of compound VIIIi,
RF 0.55 (S8), m.p. 204 – 205 °C. For C10H13N5O (219.2) calculated: 54.79% C, 5.98% H, 31.93%
N; found: 54.60% C, 5.91% H, 31.45% N. 1H NMR spectrum: 8.13 s, 1 H and 8.07 s, 1 H (H-2,
H-8); 7.21 brs, 2 H (NH2); 5.09 d, 1 H, J(OH,CH) = 5.1 (OH); 4.23 dd, 1 H, J(1a′,2′) = 4.4, J(gem)
= 13.7 (H-1a′); 4.20 dd, 1 H, J(1b′,2′) = 7.8, J(gem) = 13.7 (H-1b′); 3.29 tt, 1 H, ΣJ = 24.7 (H-2′);
0.80 qt, 1 H; 0.29 – 0.37 m, 2 H; 0.22 – 0.26 m, 1 H; 0.04 – 0.08 m, 1 H (cyclopropyl). UV spec-
trum (pH 2): λmax 259.0 nm (εmax 12 200); (pH 7): λmax 261.0 nm (εmax 12 700); (pH 13): λmax 261.0
(εmax 12 600).
General Method for Preparation of Compounds VIIIj – VIIIl by Alkylation of Adenine
with Oxiranes
A mixture of adenine (1.35 g, 10 mmol), cesium carbonate (0.25 g, (0.7 mmol), the appropriate oxi-
rane (12 mmol); (phenyloxirane 1.4 g, cyclohexyloxirane 1.5 g, benzyloxirane 1.6 g) and dimethyl-
formamide (25 ml) was heated at 120 °C for 8 h under stirring and exclusion of moisture. After the
end of the reaction (TLC in S8) the mixture was concentrated in vacuo and the residue codistilled
with toluene (3 × 50 ml).
9-(2-Cyclohexyl-2-hydroxyethyl)adenine (VIIIj) was prepared from cyclohexyloxirane (1.5 g).
Crystallization from methanol yielded 1.58 g (61%) of compound VIIIj, RF 0.54 (S8), m.p. 219 – 221 °C.
For C13H19N5O (261.3) calculated: 59.76% C, 7.33% H, 26.79% N; found: 59.56% C, 7.29% H,
1
26.43% N. H NMR spectrum: 8.13 s, 1 H (H-2); 8.06 s, 1 H (H-8); 7.18 brs, 2 H (NH2); 4.94 d, 1 H,
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Alkyl Derivatives of 9-(2-Phosphonomethoxyethyl)adenine
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J(OH,CH) = 5.9 (OH); 4.22 dd, 1 H, J(1a′,2′) = 3.4, J(gem) = 13.7 (H-1a′); 3.99 dd, 1 H, J(1b′,2′)
= 8.5, J(gem) = 13.7 (H-1b′); 3.58 m, 1 H, ΣJ = 22.8 (H-2′); 1.55 – 1.90 m, 5 H and 1.00 – 1.40 m,
6 H (cyclohexyl). UV spectrum (methanol) (pH 2): λmax 261.0 nm (εmax 14 800); (pH 7): λmax 261.5
nm (εmax 15 000); (pH 13): λmax 262.5 (εmax 15 900).
9-(2-Hydroxy-3-phenylpropyl)adenine (VIIIk) was prepared from benzyloxirane (1.6 g). Crystal-
lization from ethanol with addition of ether afforded 2.4 g (74%) of compound VIIIk, RF 0.60 (S8),
m.p. 136 – 138 °C. For C14H15N5O . H2O (287.3) calculated: 58.53% C, 5.96% H, 24.37% N; found:
1
57.90% C, 5.76% H, 23.98% N. H NMR spectrum: 8.13 s, 1 H (H-2); 8.07 s, 1 H (H-8); 7.19 brs,
2 H (NH2); 7.10 – 7.35 m, 5 H (arom.); 5.01 br, 1 H (OH); 4.21 dd, 1 H, J(1a′,2′) = 2.1, J(gem) =
12.3 (H-1a′); 4.03 dd, 1 H J(1b′,2′) = 8.0, J(gem) = 12.3 (H-1b′); 4.11 m, 1 H (H-2′); 2.78 dd, 1 H,
J(3a′,2′) = 4.3, J(gem) = 13.4 (H-3a′); 2.66 dd, 1 H, J(3b′,2′) = 6.6, J(gem) = 13.4 (H-3b′).
UV spectrum (pH 2): λmax 261.0 nm (εmax 12 600); (pH 7): λmax 262.0 nm (εmax 14 700); (pH 13):
λmax 262.0 (εmax 11 800).
9-(2-Hydroxy-2-phenylethyl)adenine (VIIIl) was prepared from phenyloxirane (1.4 g). Crystal-
lization from methanol with addition of water gave 1.78 g (70%) of compound VIIIl, RF 0.58 (S9),
m.p. 226 – 227 °C. For C13H13N5O (255.2) calculated: 61.17% C, 5.13% H, 27.43% N; found:
1
60.84% C, 5.20% H, 27.37% N. H NMR spectrum: 8.16 s, 1 H (H-2); 8.00 s, 1 H (H-8); 7.19 brs,
2 H (NH2); 7.20 – 7.40 m, 5 H (arom.); 5.81 d, 1 H, J(OH,CH) = 4.6 (OH); 5.00 dt, 1 H, ΣJ = 17.0
(H-2′); 4.31 dd, 1 H, J(1a′,2′) = 4.6, J(gem) = 13.9 (H-1a′); 4.23 dd, 1 H, J(1b′,2′) = 7.8, J(gem) =
13.9 (H-1b′). UV spectrum (pH 2): λmax 259.0 nm (εmax 12 200); (pH 7): λmax 261.0 nm (εmax 13 300);
(pH 13): λmax 262.0 (εmax 12 700).
9-(2-Hydroxybutyl)-N6-benzoyladenine (IXe)
Compound VIIIe (2.7 g, 12 mmol) was codistilled with pyridine (2 × 25 ml) in vacuo and suspended
in pyridine (60 ml). Chlorotrimethylsilane (10 ml) was added and the suspension was stirred under
exclusion of moisture at room temperature for 1 h. After addition of benzoyl chloride (8 ml), the
mixture was stirred for another hour, cooled with ice and water (12 ml), followed by concentrated
aqueous ammonia (30 ml) was added dropwise under ice-cooling. After 30 min at 0 °C the mixture
was taken down in vacuo, the residue was codistilled with water in vacuo (3 × 100 ml), mixed with
chloroform (500 ml) and filtered. The filtrate was evaporated and the residue chromatographed on a
column of silica gel (200 ml). Crystallization from ethanol (light petroleum added) afforded 2.30 g
(61.5%) of compound IXe, m.p. 169 °C, RF 0.27 (S7). For C16H17N5O2 (311.4) calculated: 61.72% C,
5.50% H, 22.50% N; found: 61.57% C, 5.36% H, 22.31% N.
9-(2-Hydroxypentyl)-N6-benzoyladenine (IXf)
The title compound was prepared from compound VIIIf (2.7 g, 12 mmol) in the same manner as
described for benzoyladenine IXe; yield 1.80 g (46%) of IXf, m.p. 205 °C, RF 0.30 (S7). For
C17H19N5O2 (325.4) calculated: 62.74% C, 5.89% H, 21.53% N; found: 62.57% C, 5.69% H, 21.34% N.
H1 NMR spectrum: 11.13 s, 1 H (NH); 8.73 s, 1 H (H-2); 8.39 s, 1 H (H-8); 8.05 m, 2 H and 7.62 m,
1 H and 7.56, m, 2 H (arom.); 5.05 d, 1 H, J(2′,OH) = 5.6 (OH); 4.28 dd, 1 H, J(1a′,2′) = 3.7, J(gem)
= 13.9, (H-1a′); 4.12 dd, 1 H, J(1b′,2′) = 8.0, J(gem) = 13.9 (H-1b′); 3.89 m, 1 H, ΣJ = 29.3 (H-2′);
1.30 – 1.50 m, 4 H (H-3′ and H-4′); 0.89 brt, 3 H, J(5′,4′) = 6.8 (CH3).
Cyclohexyloxirane (XIIIj)
An ice-cooled mixture of vinylcyclohexane (25 g, 0.227 mol), dichloromethane (115 ml), sodium hy-
drogen phosphate (91 g), water (110 ml) and peracetic acid21 (130 ml) was stirred for 2 h. The
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Dvorakova, Holy, Rosenberg:
aqueous phase was diluted with water (50 ml), the organic one was separated and stirred with satu-
rated solution of sodium hydrogen carbonate for 30 min, washed with water to neutrality and dried
over magnesium sulfate. The solvent was evaporated and the residue distilled to give 10.0 g (35%)
of compound XIIIj, b.p. 55 °C/2 kPa (reported22 b.p. 63 – 65 °C/2 kPa). Purity (GLC) 98%. The
product was used without further purification in the preparation of compound VIIIj.
Benzyloxirane (XIIIk) (see ref.23)
Allylbenzene (2.7 ml, 0.02 mol) and m-chloroperbenzoic acid (4.7 g, content 70 – 75%, i.e. 0.02 mol)
were added into cold chloroform (30 ml) and the mixture was stirred to homogeneity. After standing
in a refrigerator for 6 days, the deposited m-chlorobenzoic acid was filtered off, washed with chloro-
form and the filtrate was washed with saturated sodium hydrogen carbonate solution (2 × 50 ml) and
water (2 × 50 ml). The chloroform solution was dried over magnesium sulfate, the solvent was evap-
orated and the residue distilled to give 1.7 g (63%) of compound XIIIk, b.p. 90 – 95 °C/2 kPa (re-
ported24 b.p. 97 – 98 °C/ 2.4 kPa). The product was used without further purification in the
preparation of compound VIIIk.
3-Benzyloxy-2-hydroxypropyltrimethylsilane (XIV)
To a mixture of magnesium (1.7 g, 70.0 mmol), chloromethyltrimethylsilane (0.5 ml, 3.6 mmol) and
anhydrous tetrahydrofuran (5 ml) was added 1,2-dibromoethane (0.05 ml) at 60 °C. As soon as the
mixture began to boil spontaneously, it was rapidly cooled in an ice bath and chlorotrimethylsilane
(9.5 ml, 68.1 mmol) was added under stirring in the course of 30 min. After further 15 min of vi-
gorous stirring, a solution of 2-benzyloxyacetaldehyde (6.7 g, 40.1 mmol) in tetrahydrofuran (10 ml)
was adedd during 15 min. After stirring for 30 min at 0 °C, the reaction mixture was decomposed by
addition of saturated ammonium chloride solution (50 ml). The suspension was mixed with ether
(100 ml) and filtered through Celite which was then washed with ether (2 × 20 ml). The ethereal
layer of the filtrate was dried over magnesium sulfate, filtered and taken down. Distillation of the
residue afforded pure (GLC) product XIV (7.6 g, 80%) b.p. 120 °C/13 Pa, RF 0.40 (S5). For
C13H22O2Si (238.4) calculated: 65.49% C, 9.30% H; found: 65.05% C, 9.41% H.
3-Benzyloxy-2-diisopropylphosphonomethoxypropyltrimethylsilane (XV)
Sodium hydride (60% suspension in mineral oil, 1.1 g, 27.7 mmol) was added at −20 °C to a solution
of 3-benzyloxy-2-hydroxypropyltrimethylsilane (XIV) (6.0 g, 25.2 mmol) and synthon XI (9.3 g,
27.7 mmol) in dimethylformamide (20 ml) and the mixture was vigorously stirred at room tempera-
ture for 15 h. The homogeneous solution was concentrated and the residue was extracted with hot
toluene. Column chromatography on silica gel (100 g) in toluene–ethyl acetate (4 : 1) afforded com-
pound XV (3.3 g, 31%), RF 0.50 (S5). Mass spectrum, m/z: 417.3 (M + H). For C20H37O5PSi (416.6)
calculated: 57.67% C, 8.95% H, 7.43% P; found: 57.59% C, 9.01% H, 7.23% P.
2-Diisopropylphosphonomethoxy-3-(p-toluenesulfonyloxy)propyltrimethylsilane (XVII)
Compound XV (3.0 g, 7.2 mmol) was hydrogenated in methanol (150 ml) over 10% Pd/C (300 mg)
at 1.1 Pa and 20 °C for 2 h. The suspension was filtered through Celite, the catalyst was washed with
methanol (2 × 50 ml) and the combined filtrates were taken down. The remaining hydroxy derivative
XVI (RF 0.15 (S5)) was codistilled with pyridine, dissolved in pyridine (20 ml) and mixed with tosyl
chloride (2.0 g, 10.5 mmol). After standing at room temperature for 15 h, the mixture was decom-
posed with water (5 ml) and concentrated in vacuo. The residue was dissolved in chloroform (30 ml)
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Alkyl Derivatives of 9-(2-Phosphonomethoxyethyl)adenine
2087
and applied onto a column of silica gel (50 g). Elution with chloroform gave 3.35 g (97%) of homo-
1
geneous product XVII, RF 0.40 (S5). Mass spectrum, m/z: 481.0 (M + H). H NMR spectrum: 7.80 d, 2 H
and 7.49 d, 2 H (arom.); 4.55 2 × dsept, 2 H, J(P,OCH) = 7.8, J(CH,CH3) = 6.1 (POCH); 4.06 dd,
1 H, J = 3.0, J(gem) = 11.0 (OCHb); 3.90 dd, 1 H, J = 5.1, J(gem) = 11.0 (OCHa); 3.69 brtdd, 1 H,
ΣJ = 22.5 (OCH); 3.65 dd, 1 H, J(P,CH) = 9.5, J(gem) = 13.4 (PCHb); 3.61 dd, 1 H, J(P,CH) = 10.0,
J(gem) = 13.4 (PCHa); 2.42 s, 3 H (CH3); 1.22 d, 6 H, J = 6.1 (2 × CH3); 1.21 d, 3 H and 1.20 d, 3 H
(2 × CH3); 0.88 dd, J = 7.6, J(gem) = 14.65 (SiCHb); 0.67 dd, J = 6.8, J(gem) = 14.65 (SiCHa); 0.04 s,
9 H (Si(CH3)3.
9-(2-Phosphonomethoxy-3-trimethylsilylpropyl)adenine (XIXa)
A suspension of adenine sulfate (0.55 g, 3 mmol), cesium carbonate (2.9 g, 9 mmol) and tosyl deri-
vative XVII (1.5 g, 3 mmol) in dimethylformamide (30 ml) was heated at 120 °C for 4 h. The reac-
tion mixture was concentrated in vacuo, the residue extracted with hot chloroform and the solution
applied onto a column of silica gel (50 g). Elution with chloroform–ethanol (18 : 1) afforded diester
XVIIIa (0.9 g, 68%). Mass spectrum, m/z: 444 (M + H).
The obtained product was treated with bromotrimethylsilane as described above. The final purifi-
cation of the free phosphonate XIXa was performed by chromatography on Dowex 1 X 8 (acetate
form, 100 ml), elution with a gradient of acetic acid (0 – 1 mol/l, 2 × 1 l). After evaporation of the
acetic acid, the product was freeze-dried from the aqueous solution to give homogeneous (electro-
phoresis and HPLC) compound XIXa (0.4 g, 55 %), m.p. 276 °C. Mass spectrum, m/z: 481.0 (M + H).
1H NMR spectrum: 8.28 s, 1 H and 8.14 s, 1 H (H-2, H-8); 4.37 dd, 1 H, J = 3.4, J(gem) = 14.65
(NCHb); 4.21 dd, 1 H, J = 5.9, J(gem) = 14.65 (NCHa); 3.95 dddd, 1 H, ΣJ = 23.4 (OCH); 3.70 dd,
1 H, J(P,CH) = 9.5, J(gem) = 12.7 (PCHb); 3.55 dd, 1 H, J(P,CH) = 10.3, J(gem) = 12.7 (PCHa);
0.87 dd, 1 H, J = 7.3, J(gem) = 14.9 (SiCHb); 0.71 dd, 1 H, J = 6.6, J(gem) = 14.9 (SiCHa); 0.03 s,
9 H (3 × CH3).
9-(2-Phosphonomethoxy-3-trimethylsilylpropyl)-2,6-diaminopurine (XIXb)
A suspension of 2-amino-6-chloropurine (0.66 g, 3.9 mmol), cesium carbonate (2.6 g, 8 mmol), tosyl
derivative XVII (1.9 g, 3.9 mmol) and dimethylformamide (39 ml) was heated at 130 °C for 3 h. The
reaction mixture was worked up as described for the adenine derivative XIXa and afforded 9-(2-diiso-
propylphosphonomethoxy-3-trimethylsilylpropyl)-2-amino-6-chloropurine (XVIIIb) (1.3 g, 66%).
Mass spectrum, m/z: 496.0 (M + H). This intermediate (0.82 g, 1.7 mmol) was heated with sodium
azide (0.6 g, 8.6 mmol) in dimethylformamide (10 ml) at 120 °C for 2 h to give a mixture of 9-(2-
diisopropylphosphonomethoxy-3-trimethylsilylpropyl)- 2-amino-6-azidopurine (XVIIIc) and the corre-
sponding monoisopropyl ester. Both compounds were isolated by chromatography on C18 silica gel,
combined and hydrogenated in aqueous methanol (1 : 1, 100 ml) on 10% Pd/C (120 mg). After fil-
tering off the catalyst, its washing with aqueous methanol and evaporating the combined filtrates, the
mixture was dried and treated with bromotrimethylsilane (vide supra). The compound XIXb was iso-
lated by ion exchange chromatography as described for compound XIXa. Freeze-drying afforded 180 mg
1
(28%) of XIXb, m.p. >280 °C. Mass spectrum, m/z: 481.0 (M + H). H NMR spectrum: 8.08 s, 1 H
(H-8); 4.23 dd, 1 H, J = 3.9, J(gem) = 14.65 (NCHb); 4.10 dd, 1 H, J = 6.1, J(gem) = 14.65 (NCHa);
3.89 m, 1 H, ΣJ = 23.7 (OCH); 3.60 dd, 1 H, J(P,CH) = 9.5, J(gem) = 12.2 (PCHb); 3.43 dd, 1 H,
J(P,CH) = 10.0, J(gem) = 12.2 (PCHa); 0.97 dd, 1 H, J = 6.1, J(gem) = 14.9 (SiCHb); 0.70 dd, 1 H,
J = 7.6, J(gem) = 14.9 (SiCHb); 0.04 s, 9 H (Si(CH3)3).
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Dvorakova, Holy, Rosenberg:
9-(3,3,3-Trifluoro-2-hydroxypropyl)adenine (XXa)
Sodium hydride (60% dispersion in paraffin, 800 mg, 20 mmol) was added to a suspension of
adenine (2.7 g, 20 mmol) in dimethylformamide (140 ml). After stirring under exclusion of moisture
at 100 °C for 1 h, 1-bromo-3,3,3-trifluoropropan-2-ol (5.0 g, 25.9 mmol) was added and the obtained
solution was stirred at 80 °C for 24 h. Acetic acid (0.60 ml, 10 mmol) was added and the mixture
was taken down at 40 °C/13 Pa. The residue was dissolved in water (25 ml) and deionized on a
column of Dowex 50 X 8 (H+ form, 150 ml). After evaporation of the solvent, the residue was dis-
solved in water (20 ml) and applied onto a column of C18 silica gel (130 ml, 30 mesh). The column
was washed with water (3 ml/min, 30 ml fractions, monitoring by HPLC in H4, k = 0.51, product
2.84). The product fractions were combined, evaporated and the residue was crystallized from water
to give 1.70 g (35%) of compound XXa, m.p. 209 °C. For C8H8F3N5O (247.2) calculated: 38.87% C,
1
3.26% H, 23.06% F, 28.34% N; found: 38.57% C, 3.18% H, 22.79% F, 28.70% N. H NMR spec-
trum: 8.17 s, 1 H (H-2); 8.14 s, 1 H (H-8); 7.31 brs, 2 H (NH2); 6.78 d, 1 H, J(2′,OH) = 6.6 (OH);
4.51 m, 1 H, J(2′,F) = 21.5, ΣJ = 40.3 (H-2′); 4.45 dd, 1 H, J(1a′,2′) = 3.4, J(gem) = 14.2 (H-1a′);
4.30 dd, 1 H, J(1b′,2′) = 8.8, J(gem) = 14.2 (H-1b′).
9-(3,3,3-Trifluoro-2-hydroxypropyl)-2,6-diaminopurine (XXb)
A mixture of 2,6-diaminopurine (6 g, 40 mmol) and sodium hydride (60% dispersion, 1.60 g, 40 mmol)
in dimethylformamide (250 ml) was stirred at 100 °C for 1 h. After cooling to 60 °C, 1-bromo-3,3,3-
trifluoropropan-2-ol (10 g, 52 mmol) was added and the mixture was stirred at 60 °C for 15 h under
exclusion of moisture (calcium chloride tube). The solvent was evaporated at 40 °C/13 Pa, the
residue was mixed with water (200 ml) and extracted with ether (2 × 50 ml). The aqueous phase was
deionized on a column of Dowex 50 X 8 (H+ form, 200 ml). The residue after evaporation was dis-
solved in methanol (200 ml) and adsorbed on silica gel (50 ml). This material was applied onto a
column of silica gel (200 ml) in chloroform. After washing the column with chloroform to remove
impurities, the product was eluted with chloroform–methanol (4 : 1). The product fractions were con-
centrated and the product crystallized from ethanol (ether added to turbidity). Yield 6.3 g (60%) of
compound XXb, m.p. 191 °C. For C8H9F3N9O (266.2) calculated: 36.64% C, 3.46% H, 21.74% F,
1
32.06% N; found: 36.91% C, 3.80% H, 21.70% F, 31.85% N. H NMR spectrum: 7.71 s, 1 H (H-8);
6.76 m, 3 H (NH2 + OH); 5.89 brs, 2 H (NH2); 4.46 m, 1 H (H-2′); 4.25 dd, 1 H, J(1a′,2′) = 3.2,
J(gem) = 13.9 (H-1a′); 4.11 dd, 1 H, J(1b′,2′) = 9.3, J(gem) = 13.9 (H-1b′).
9-(3,3,3-Trifluoro-2-hydroxypropyl)-N6-benzoyladenine (XXI)
Chlorotrimethylsilane (4.5 ml) was added to a suspension of compound XXa (1.24 g, 5 mmol) in
pyridine (30 ml). After stirring for 1 h, benzoyl chloride (3.5 ml) was added and the mixture was
then stirred for 2 h. The mixture was cooled with ice and water (6 ml) and concentrated aqueous
ammonia (14.5 ml) were successively added dropwise. After stirring in an ice bath for 30 min, the
solvent was evaporated at 40 °C/2 kPa and the residue was codistilled with ethanol (3 × 25 ml).
Chloroform (100 ml) was added and, after stirring for 15 min, the precipitated product was collected,
washed with chloroform (50 ml) and crystallized from 50% aqueous ethanol, yield 0.75 g (43%) of
compound XXI, m.p. 215 °C. The filtrate was taken down in vacuo, combined with the chloroform
residue and the mixture was purified by chromatography on silica gel (200 ml). Elution with chloro-
form–methanol (9 : 1) and crystallization from 50% aqueous methanol gave further 0.35 g of com-
pound XXI, the total yield being thus 63%. For C15H12F3N5O2 (351.3) calculated: 51.28% C, 3.44% H,
16.23% F, 19.94% N; found: 51.37% C, 3.55% H, 16.22% F, 19.89% N. RF 0.23 (S7). 1H NMR
spectrum: 11.20 s, 1 H (NH); 8.78 s, 1 H (H-2); 8.48 s, 1 H (H-8); 8.05 m, 2 H and 7.65 m, 1 H and
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Alkyl Derivatives of 9-(2-Phosphonomethoxyethyl)adenine
2089
7.55 m, 2 H (arom.); 6.84 d, 1 H, J = 6.8 (OH); 4.58 dd, 1 H, J(1a′,2′) = 3.2, J(gem) = 14.6 (H-1a′);
4.45 dd, 1 H, J(1b′,2′) = 8.8, J(gem) = 14.6 (H-1b′); 4.60 m, 1 H (H-2′).
9-(2-Phosphonomethoxy-3,3,3-trifluoropropyl)adenine (XXIIa)
A mixture of compound XXI (0.70 g, 2 mmol) and tosyl derivative XI (1.05 g, 3 mmol) was codis-
tilled with dimethylformamide (2 × 20 ml) at 40 °C/13 Pa. The residue was mixed with dimethyl-
formamide (15 ml) and sodium hydride (60% dispersion, 0.25 g, 6.2 mmol) was added. The mixture
was stirred at room temperature for 3 days, mixed with methanol (30 ml) and set aside at room tem-
perature overnight. The solution was neutralized by addition of Dowex 50 X 8 (H+ form), made al-
kaline with triethylamine, filtered and the ion exchanger was washed with ethanol (200 ml). The
filtrate was taken down in vacuo, dissolved in 50% aqueous methanol (25 ml) and applied onto a
column of the same ion exchanger (100 ml, in 20% methanol). After washing with 20% aqueous
methanol to drop of UV absorption, the product was eluted with 2.5% ammonia in 20% aqueous
methanol. The UV-absorbing fraction was concentrated in vacuo and the residue codistilled with
ethanol (3 × 25 ml) and dried in vacuo over phosphorus pentoxide overnight. The residue was
allowed to stand with acetonitrile (30 ml) and bromotrimethylsilane (3 ml) at room temperature over-
night. After evaporation of the solvent, water (20 ml) was added, the mixture was made alkaline with
concentrated aqueous ammonia and again evaporated in vacuo. The residue was deionized on a col-
umn of Dowex 50 X 8 (H+ form) and the ammonia UV-absorbing eluate was evaporated to dryness
in vacuo. The residue was dissolved in water (20 ml), the solution adjusted to pH 9 with ammonia
and applied onto a column of Dowex 1 X 2 (acetate form, 100 ml). After washing the column with
water to drop of UV absorption of the eluate, the product was eluted with a linear gradient of acetic
acid (water (1 l), 1 M acetic acid (1 l)). The product fraction was evaporated in vacuo, the residue
was codistilled with water ( 3 × 25 ml) and crystallized from 80% aqueous ethanol (ether added to
turbidity). Yield 0.40 g of compound XXIIIa (58.5%), m.p. 276 °C, EUp = 0.80. For C9H11F3N5O4P
(341.3) calculated: 31.67% C, 3.25% H, 16.70% F, 20.53% N, 9.10% P; found: 31.48% C, 3.08% H,
1
16.40% F, 20.62% N, 9.02% P. H NMR spectrum: 8.40 s, 1 H (H-2); 8.20 s, 1 H (H-8); 4.68 dd, 1 H,
J(1a′,2′) = 4.2, J(gem) = 15.2 (H-1a′); 4.59 dd, 1 H, J(1b′,2′) = 5.9, J(gem) = 15.2 (H-1b′); 4.42 m,
1 H, ΣJ = 29.6, J(2′,F) = 19.5 (H-2′); 3.79 dd, 1 H, J(P,CH) = 9.2, J(gem) = 11.9 (PCHa); 3.56 dd,
1 H, J(P,CH) = 9.5, J(gem) = 11.9 (PCHb). HPLC (H3): k = 2.53.
9-(2-Phosphonomethoxy-3,3,3-trifluoropropyl)-2,6-diaminopurine (XXIIb)
A mixture of compound XXb (4.0 g, 15 mmol), dimethylformamide (70 ml) and dimethylformamide
dimethyl acetal (30 ml) was stirred to homogeneity and the solution was set aside at room tempera-
ture for two days. The solvent was evaporated at 40 °C/13 Pa and the residue was mixed with 50%
pyridine (30 ml) with addition of dry ice to render the pH neutral. After 30 min the mixture was
evaporated at 40 °C/13 Pa and the residue codistilled with pyridine (3 × 20 ml) and dimethylform-
amide (2 × 20 ml) under the same conditions. The obtained compound XXIII was mixed with the
tosyl derivative XI (6.3 g, 18 mmol), the mixture was again codistilled with dimethylformamide
(2 × 20 ml) and dissolved in dimethylformamide (60 ml). Sodium hydride (60% suspension, 1.08 g,
45 mmol) was added to this solution at −10 °C and the mixture was stirred at room temperature for
2 days under exclusion of moisture. After addition of methanol (50%, 100 ml) and standing over-
night, the deposited precipitate was filtered off, the filtrate was evaporated in vacuo, dissolved in
water (100 ml), acidified by addition of Dowex 50 X 8 (H+ form) and the suspension was applied
onto a column of the same ion exchanger (150 ml). The column was washed with water to drop of
UV absorption of the eluate and the product was eluted with dilute (1 : 10) aqueous ammonia. The
main UV-absorbing fraction was evaporated in vacuo and the residue was codistilled with ethanol
Collect. Czech. Chem. Commun. (Vol. 59) (1994)

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Dvorakova, Holy, Rosenberg:
and dried in vacuo. This residue was mixed with acetonitrile (40 ml) and bromotrimethylsilane (4 ml)
and the solution was allowed to stand at room temperature overnight under exclusion of moisture.
The solvent was evaporated in vacuo, the residue was mixed with water (100 ml) and the solution
was made alkaline with aqueous ammonia. After standing at room temperature for 1 h, the mixture
was concentrated in vacuo and the residue in water (20 ml) was deionized on a column of Dowex
50 X 8 (H+ form, 150 ml). The ammonia UV-absorbing eluate was evaporated in vacuo and the
residue applied onto a column of Dowex 1 X 2 (acetate form, 150 ml). The column was washed with
water to remove salts and then with a linear gradient of acetic acid (0 – 0.3 mol/l, à 1 l). The product
was eluted at 0.2 – 0.3 mol/l. The product fraction was concentrated in vacuo, the residue was cod-
istilled with water (3 × 50 ml) and crystallized from water to give 1.80 g (33.5%) of compound
XXIIb, m.p. 208 °C, EUp = 0.67, k = 0.83 (H1). For C9H12F3N6O4P (356.3) calculated: 30.34% C,
3.40% H, 16.00% F, 23.60% N, 8.71% P; found: 30.51% C, 3.32% H, 16.10% F, 23.44% N, 9.07% P.
1H NMR spectrum: 8.03 s, 1 H (H-8); 4.31 – 4.56 m, 3 H (NCH2 + OCH); 3.77 dd, 1 H, J(P,CH) =
9.5, J(gem) = 11.9 (PCHa); 3.55 dd, 1 H, J(P,CH) = 9.5, J(gem) = 11.9 (PCHb).
3-O-Benzoyloxybutyl p-Toluenesulfonate (XXV)
The title compound was prepared from butane-1,3-diol (0.3 mol) as described for the tosyl deriva-
tives VIe and VIf (isolation by column chromatography on silica gel (200 ml) in benzene). The pro-
duct was crystallized from ether–light petroleum; yield 71 g (68%), m.p. 64 – 66 °C, RF 0.62 (S4).
For C18H20O5S (348.4) calculated: 62.05% C, 5.79% H, 9.20% S; found: 62.00% C, 5.66% H, 8.97% S.
9-(3-Hydroxybutyl)adenine (XXVIb)
A mixture of adenine (4.05 g, 30 mmol), sodium hydride (60% dispersion, 1.2 g, 30 mmol) and di-
methylformamide (200 ml) was stirred at 100 °C for 1 h. Compound XXV (11.5 g, 33 mmol) was
added and the mixture was stirred at 100 °C for 24 h. After evaporation of the solvent at 40 °C/13 Pa,
the residue was extracted with boiling chloroform (3 × 100 ml). The extract was filtered, the solvent
evaporated and the residue chromatographed on a column of silica gel (200 ml). The combined pro-
duct-containing fractions were concentrated and the residue was crystallized from ethyl acetate–light
petroleum to give 4.1 g (43%) of benzoyl derivative XXVIa, RF 0.45 (S7), m.p. 154 °C. For
C16H17N5O2 (311.4) calculated: 61.72% C, 5.50% H, 22.50% N; found: 61.53% C, 5.47% H, 22.79% N.
This product was stirred with 0.1 M methanolic sodium methoxide (150 ml) at room temperature
overnight, the mixture was neutralized by addition of Dowex 50 X 8 (H+ form), made alkaline with
triethylamine and filtered. The ion exchanger was washed with methanol (100 ml), the filtrate was
taken down in vacuo and the dry residue was crystallized from ethanol–ether. Yield 1.9 g (75%) of
compound XXVIb, m.p. 169 °C. For C9H13N5O (311.4) calculated: 52.16% C, 6.32% H, 33.80% N;
found: 51.96% C, 6.34% H, 34.07% N. 1H NMR spectrum: 8.16 s, 1 H (H-2); 8.13 s, 1 H (H-8);
7.29 brs, 2 H (NH2); 4.77 d, 1 H, J(3′,OH) = 4.9 (OH); 4.21 m, 2 H (H-1′); 3.57 m, 1 H, (H-3′);
1.68 – 1.98 m, 2 H (H-2′); 1.06 t, 3 H, J = 6.1 (CH3). After exchange: 4.25 ddd, 1 H, J(1a′,2a′) =
6.1, J(1a′,2b′) = 7.8, J(gem) = 14.0 (H-1a′); 4.17 dt, 1 H, J(1a′,2a′) = J(1b′,2b′) = 7.3, J(gem) = 13.7
(H-1b′); 3.55 d, 1 H, ΣJ = 31.2 (H-3′); 1.68 – 1.98 m, 2 H (H-2′); 1.05 t, 3 H, J = 6.1 (CH3).
9-(3-Hydroxybutyl)-N6-benzoyladenine (XXVII)
Compound XXVIb (2.1 g, 10 mmol) was codistilled with pyridine (2 × 25 ml) and suspended in py-
ridine (60 ml). Chlorotrimethylsilane (8 ml) was added and the suspension was stirred at room tem-
perature for 1 h under exclusion of moisture. Benzoyl chloride (6 ml) was added, the mixture was
stirred for another hour and then cooled with ice and decomposed by successive addition of water
Collect. Czech. Chem. Commun. (Vol. 59) (1994)

Alkyl Derivatives of 9-(2-Phosphonomethoxyethyl)adenine
2091
(10 ml) and concentrated aqueous ammonia (25 ml). After 30 min at 0 °C, the mixture was concen-
trated in vacuo and the residue was codistilled with water in vacuo (3 × 100 ml). The residue was
stirred with chloroform (500 ml), filtered and the filtrate was evaporated. Chromatography of the
residue on a column of silica gel (200 ml) followed by crystallization from ethanol (with addition of
light petroleum to turbidity) afforded 1.68 g (54%) of compound XXVII, m.p. 169 °C, RF 0.27 (S7).
For C16H17N5O2 (311.4) calculated: 61.72% C, 5.50% H, 22.50% N; found: 61.57% C, 5.36% H,
22.31% N.
9-(3-Phosphonomethoxybutyl)adenine (XXVIII)
A mixture of compound XXVII (1.56 g, 5 mmol) and tosyl derivative XI (2.1 g, 6 mmol) was codis-
tilled with dimethylformamide (2 × 25 ml) at 40 °C/13 Pa. The residue was dissolved in dimethyl-
formamide (30 ml), cooled to 0 °C and mixed with sodium hydride (60% dispersion, 0.60 g,
15 mmol). The mixture was stirred at ambient temperature for 4 days and then mixed with methanol
(50 ml). After standing at room temperature overnight, the mixture was neutralized with Dowex
50 X 8 (H+ form), made alkaline with triethylamine, filtered and the ion exchanger was washed with
methanol (100 ml). The further workup was the same as described for compound Ie. Yield 0.60 g
(38%) of compound XXVIII, m.p. 229 °C, EUp 0.70. For C10H16N5O4P . H2O (319.3) calculated:
37.60% C, 5.68% H, 21.94% N, 9.72% P; found: 37.98% C, 6.02% H, 21.79% N, 10.06% P.
1H NMR spectrum: 8.16 s, 1 H (H-2); 8.08 s, 1 H (H-8); 4.35 dt, 1 H and 4.32 dt, 1 H, J(1′,2′) =
7.6 and 6.8, J(gem) = 14.2 (H-1′); 3.59 dd, 1 H, J(P,CH) = 9.5, J(gem) = 12.2 (PCHa); 3.50 sext 1 H,
J(3′,4′) = 6.1, J(2′,3′) = 6.5 (H-3′); 3.38 dd, 1 H, J(P,CH) = 9.8, J(gem) = 12.2 (PCHb); 2.02 brq 2 H,
J = 7.0 (H-2′); 1.19 brt, 3 H, J = 6.1(CH3).
1-O-Benzoyloxy-2,2-dimethyl-3-propyl p-Toluenesulfonate (XXX)
Tosyl chloride (45.2 g, 0.237 mol), followed by 4-dimethylaminopyridine (1 g), was added at 0 °C
to a solution of 2,2-dimethylpropane-1,3-diol (26 g, 0.25 mol) in pyridine (300 ml). The mixture was
stirred at 0 °C for 2 h and then set aside for 3 days at 0 °C. Water (20 ml) was added and, after
30 min, the mixture was diluted with ethyl acetate (1 l) and washed with water (3 × 200 ml). The
organic phase was dried, the solvent evaporated and the residue chromatographed on a column of
silica gel (300 ml) in benzene. Yield 42 g (67%) of chromatographically pure (S7) tosyl derivative
XXIX which was used directly in the next step.
The product obtained above was dissolved in dichloromethane (200 ml) and benzoyl cyanide (23 g,
0.175 mol) and triethylamine (10 ml) were added. After standing at room temperature for 30 min, the
solvent was evaporated in vacuo and the residue crystallized from ethyl acetate (with addition of
light petroleum to turbidity). Yield 38 g (65%) of compound XXX, m.p. 92 °C, RF 0.53 (S8). For
C19H22O5S (362.4) calculated: 62.97% C, 6.12% H, 8.85% S; found: 63.07% C, 6.18% H, 8.71% S.
1H NMR spectrum: 7.62 – 7.84 m, 5 H and 7.45 – 7.55 m, 2 H and 7.31 d, 2 H, J = 8.0 (arom); 3.96 s,
2 H (TsOCH2); 3.90 s, 2 H (BzOCH2); 2.23 s, 3 H (TsCH3), 0.95 s, 6 H (2 × CH3).
9-(2,2-Dimethyl-3-benzoyloxypropyl)adenine (XXXI)
Sodium hydride (60% dispersion in paraffin, 2 g, 50 mmol) was added to a suspension of adenine
(6.8 g, 50 mmol) in dimethylformamide (300 ml) and the mixture was stirred at 80 °C for 1 h under
exclusion of moisture. Compound XXX (18.1 g, 50 mmol) was added and the mixture was heated at
100 °C for 18 h. The solvent was evaporated at 40 °C/13 Pa and the residue was extracted with
boiling chloroform (3 × 100 ml). The filtered extract was taken down and the residue was crystal-
lized from methanol to give 9.0 g (55%) of compound XXXI, m.p. 161 °C. For C17H19N5O2 (325.4)
Collect. Czech. Chem. Commun. (Vol. 59) (1994)

2092
Dvorakova, Holy, Rosenberg:
1
calculated: 62.74% C, 5.89% H, 21.53% N; found: 62.55% C, 5.93% H, 21.37% N. H NMR spec-
trum: 8.12 s, 1 H (H-2); 8.06 s, 1 H (H-8); 7.89 m, 2 H and 7.64 m, 1 H and 7.51, m, 2 H (arom.);
7.22 brs, 2 H (NH2); 4.20 s, 2 H (H-1′); 4.06 s, 2 H, (H-3′); 1.03 s, 6 H (CH3).
9-(2,2-Dimethyl-3-hydroxypropyl)adenine (XXXII)
A solution of compound XXXI (8.7 g, 26.7 mmol) in 0.1 M methanolic sodium methoxide (200 ml)
was set aside at ambient temperature overnight. The mixture was neutralized with Dowex 50 X 8 (H+
form) and made alkaline with triethylamine. The ion exchanger was filtered off and washed with
methanol (200 ml), the filtrate was evaporated in vacuo and the dry residue was crystallized from
ethanol (ether added to turbidity). Yield 4.4 g (74%) of compound XXXII, m.p. 240 °C. For
C10H15N5O (221.3) calculated: 54.30% C, 6.83% H, 31.66% N; found: 54.14% C, 6.79% H, 31.30% N.
1H NMR spectrum: 8.15 s, 1 H (H-2); 8.04 s, 1 H (H-8); 7.30 brs, 2 H (NH2); 5.11 t, 1 H,
J(OH,CH2) = 5.9 (OH); 4.00 s, 2 H (H-1′); 3.08 d, 2 H, J(CH2,OH) = 5.9 (H-3′); 0.91 s, 6H (CH3).
9-(2,2-Dimethyl-3-hydroxypropyl)-N6-benzoyladenine (XXXIII)
Chlorotrimethylsilane (12 ml) was added to a suspension of compound XXXII (3.3 g, 15 mmol) in
pyridine (70 ml) and the mixture was stirred at room temperature for 1 h with exclusion of moisture.
Benzoyl chloride (9 ml) was added, stirring was continued for another hour, the mixture was cooled
with ice and decomposed by successive dropwise addition of water (15 ml) and concentrated aqueous
ammonia (30 ml). After being kept at 0 °C for 30 min, the solvent was evaporated in vacuo and the
residue codistilled with water in vacuo (3 × 100 ml). The residue was stirred with chloroform
(500 ml), the mixture was filtered and the filtrate was taken down. Chromatography of the residue on
a column of silica gel (200 ml) and crystallization from ethanol (light petroleum added to turbidity)
afforded 3.3 g (68%) of compound XXXIII, m.p. 181 °C, RF 0.36 (S7). For C17H19N5O2 (325.4) cal-
1
culated: 62.74% C, 5.89% H, 21.53% N; found: 62.52% C, 5.88% H, 21.87% N. H NMR spectrum:
11.15 brs, 1 H (NH); 8.74 s, 1 H (H-2); 8.38 s, 1 H (H-8); 8.05 m, 2 H and 7.64 m, 1 H and 7.55 m,
2 H (arom); 4.99 t, 1 H, J(OH,CH2) = 5.4 (OH); 4.16 s, 2 H (H-1′); 3.18 d, 2 H, J(CH2,OH) = 5.4
(H-3′); 0.95 s, 6 H (CH3).
9-(2,2-Dimethyl-3-phosphonomethoxypropyl)adenine (XXXV)
A mixture of compound XXXIII (1.65 g, 5 mmol) and tosyl derivative XI (2.1 g, 6 mmol) was co-
distilled with dimethylformamide (2 × 25 ml) at 40 °C/13 Pa and then dissolved in dimethylform-
amide (30 ml). Sodium hydride (60% dispersion, 0.60 g, 15 mmol) was added at 0 °C and the
mixture was stirred under exclusion of moisture at ambient temperature overnight. After addition of
methanol (100 ml) and standing at room temperature overnight, the mixture was neutralized with
Dowex 50 X 8 (H+ form) and made alkaline with triethylamine. The ion exchanger was filtered off
and washed with methanol (200 ml). The filtrate was taken down and the residue partitioned between
water (150 ml) and ether (2 × 100 ml). The aqueous phase was evaporated and the residue deionized
on a column of Dowex 50 X 8 (H+ form, 100 ml). The ammonia eluate of compound XXXIV was
evaporated, the residue dried in vacuo overnight and mixed with acetonitrile (20 ml) and bromotri-
methylsilane (2 ml). After standing overnight at room temperature, the mixture was evaporated,
mixed with water (100 ml), made alkaline with ammonia and taken down in vacuo. The residue was
again deionized under the same conditions on Dowex 50 X 8 (100 ml), the ammonia eluate was
taken down in vacuo and the residue was column-chromatographed on Sephadex A-25 (HCO−3 form,
100 ml). The column was washed with 0.02 M triethylammonium hydrogen carbonate pH 7.5 and
then by linear gradient of 0 – 0.4 mol/l (à 1 l) of the same buffer. The product fraction (0.30 mol/l)
Collect. Czech. Chem. Commun. (Vol. 59) (1994)

Alkyl Derivatives of 9-(2-Phosphonomethoxyethyl)adenine
2093
was evaporated in vacuo, the residue was codistilled with methanol in vacuo (3 × 25 ml), dissolved
in water and applied onto a column of Dowex 1 X 2 (acetate form, 25 ml). After washing the column
with water, the product was eluted with 1 M acetic acid. The solvent was evaporated in vacuo, the
residue codistilled with water (3 × 50 ml) and crystallized from 70% aqueous ethanol (ether added to
turbidity) to give 0.70 g (42%) of compound XXXV, m.p. 268 °C. For C11H16N5O5P . H2O (331.3)
calculated: 39.87% C, 5.48% H, 21.14% N, 9.37% P; found: 39.46% C, 5.71% H, 21.07% N, 9.34% P.
1H NMR spectrum: 8.12 s, 1 H (H-2); 8.06 s, 1 H (H-8); 4.10 s, 2 H (H-1′); 3.62 d, 2 H, J(P,CH) =
8.5 (PCH2); 3.24 s, 2 H (H-3′); 0.87 s, 6 H (CH3).
This work was sponsored by the American grant agency Amfar (grants No. 001465-11-GR and
001682-13-RGR) and by Grant Agency of the Czech Academy of Sciences (reg. No. 45519). The antiviral
activities were studied in the Rega Institute, Catholic University, Leuven, Belgium, by Professor E. De
Clercq, Dr J. Balzarini and Dr R. Snoeck. The authors are indebted to Dr M. Masojidkova and Dr J.
Kohoutova, both of Institute of Organic Chemistry and Biochemistry, for measurement and interpreta-
tion of the NMR and mass spectra, and to Mrs B. Novakova and Mrs M. Matejkova for the excellent
technical assistance.
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Translated by M. Tichy.
Collect. Czech. Chem. Commun. (Vol. 59) (1994)