Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
1t)'~6~364
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This invention relates to intermediates for
synthesising substituted purine compounds in particular
9-(2-hydroxyethoxymethyl) derivatives of the purine~ 2-
amino-adenine and guanine, and the preparation of such
intermediates.
This application is a division of Canadian Patent
Application, Serial No. 285,592, filed August 26, 1977.
. 3-(2-Hydroxyethoxymethyl)derivatives of purines
have antiviral activity against various classes of D~A and
RNA viruses bot~ ln vitro and in vivo experiments. In
particular these compounds are active as antiviral agents
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against adenovirus, such as adenovirus 5 and rhinovirus.
hey are especially active as an antiviral agent against
vaccinia and herpes viruses, including simplex, zoster
; and:varicella in mammals, which viruses cause such diseases
as~herpetic keratitls in rabbit~ and herpetic encephalitis
in mice.
Examples:of 9-~2_hydroxyethoxymethyl)derivatives
of:purines~showing~particularly:good antiviral activity
20 ~ are~9-~2-hydroxyethoxymethyl~guanine and 2-amino-9-(.2-
hydroxyethoxymethyl~ adenlne.: .
A~:number~;of methods:of synthesis are known for
9-t2-hydroxyathoxymoth;yl~) derivatives of purine, for
exampl`e~:they~may be~prepared by :the removal of a protective
group~from~tha~2~position on tha side chain. Alter-
f~ natiYe}y they~can~be~:formed by the~conversion of the 2
and/or 6 ~ubstituant on the purine ring into a different
substituant~(sae~Canadian Patent 1,062,257,.Howard J~
Schaefar, i~s~uad Saptamber 11, 1979).
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It has now been found that certain 9-(2-hydroxy-
ethoxymethyl) derivatives of purines can be prepared by a
new and advantageous synthetic route. In particular it has
been found that compoundsof formula (I):
R
N ~
H2~ N N
I
H2~cH2.OH
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: wherein R is amino or hydroxy can be prepared in a process
:~ ~ which comprises hydrolysing, in the presence of a base, a
compound of formula (II~: ~
: .
1~ ~
X~ ~R2 N~ ~ 2
CH 0.CH CH -o-~-X .
2 2 2
whereiA~RI~is~bydroxy or -~R~.Cl~.XI, and Xl and x2 are the
same~ or dlferent and each represents an alkyl or phenyl
group,~and;~R i9 hydrogen or -CXl provided that when R
is~l;hydroxy,:R2 is hydrogen.
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When xl and x are alkyl groups they preferably
have 1 to 4 carbon atoms, most preferably they are the same
and each represent a methyl group.
The base used in the hydrolysis may be an
aqueous or alcoholic primary or secondary aliphatic amine,
an alkoxide in alcohol, or an aqueous or alcoholic hydroxide,
for example, sodium alkoxide or hydroxide, the preferred
base being an aqueous primary aliphatic amine, for example,
aqueous methylamine. Depending on the base used, the
hydrolysis can be carried out at a temperature from room
temperature up to that of a steam bath. In general the
lower the reaction temperature, the longer the reaction
time but the fewer the side reactions.
An intermediate of formula lII), in which R is
-NR2CXl, and R2 is -CXl, may be completely hydrolysed in
O O
one step using, for example, aqueous methylamine. Alter-
natively, and more preferably, the intermediate of
formula (II) is deacylated in 2-steps, in the first step -
a single -C-Xl group is removed from the 2 and 6-positions
11
on the purine ring by mild hydrolysis at room temperature
using, for example, butylamine in a lower alcohol.
The second step of the hydrolysis, to remove the
remaining -C-Xl groups, is carried out using a stronger
O
base such as aqueous methylamine.
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The intermedlates of formula (II) are novel, and
the present invention is particularly concerned with such
intermediate compounds of formula (II) as defined above.
In another aspect of the invention there is pro-
vided a process of preparing the intermediates of formula
~II), as defined above, comprising reacting guanine, or 2-
amino adenine in which the 2 and 9, or 2, 6 and 9 positions
respectively are acylated, with a diester or, 2-oxa-1,4-
butanediol in the presence of a catalytic amount of a
strong acid.
:~ Suitable strong acids include sulphuric acid
sulphonic acids, for example, E~toluene sulphonic,
methanesulphonic, trifluoromethanesulphonic acid, sulphamic
aaid and polyphosphoric acid. .
The acyLated purine may in turn be prepared by
reactlng the~appropr~iate purine wlth an acid anhydride, for
example, acet1c a ~ dride, or other acylating agent, for
example~an~acid hal~i~e. : ~ ;. .
To~prepare~the~diester~ of~2-oxa-1,4-butanediol,
dioxolane:is~re:acted with~an~acid anhydride in the presence ..
s ~ o~ a~catalytlc amount:of a:strong acid such as one of those
acids~listed~ akove~
The~inventlon~will now be lllustrated with
re erence-~:to~the following examples: ~
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EXAMPLE 1
9-(2-Hydroxyethoxymethyl)~uanine
To a mixture of acetic anhydride (102 g),
acetic acid (15 g), and p-toluenesulfonic acid (5.0 g)
cooled to 10C, dioxolane (70 g) was added with stirring
and cooling at such a rate that the pot temperature never
exceeded 40C. The mixture was then cooled to room
temperature and toluene (300 ml) and diacetyl~uanine
(50 g) added. The reaction mixture was then heated at
reflux with stirring for 16 hours. It was then cooled
to room temperature, chloroform (50 ml) was added and
the solid product removed by filtration. The filter
cake was thoroughly washed with chloroform and dried.
The dried filter cake was added to 40/O aqueous methyl-
amine (350 ml) and the mixture was heated at reflux
with stirring for 40 minutes, cooled and filtered. The
filtrate was evaporated under reduced pressure to a
thick slurrya The slurry was cooled and filtered, and
the filter cake was washed with ethanol and dried to
give 9-(2-hydroxyethoxymethyl)guanine ~27 g, greater
than 9G% pure), m.pt. 255-257C. yield = 56%.
1~ 64
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EXAMPLE 2
9-(2-Hydroxyethoxymethyl)quanine
A mixture of diacetylguanine (50 g), 2-oxa-1,4-
butanediol diacetate (59.8 g), and p-toluene sulfonic
acid (1.2 g) in toluene (350 ml) was heated with stirring
at reflux for 16 hours. The mixture was cooled to room
temperature, filtered and the filter cake thoroughly
washed with toluene. The filter cake was dried and added
to 40YO aqueous methylamine (350 ml). The mixture was
heated at reflux with stirring for 40 minutes, cooled to
room temperature and filtered. me filtrate was
evaporated under reduced pres~ure to give a thick
slurry. Ethanol (200 ml) was added to the ~lurry which
was then cooled, filtered, washed with ethanol and dried
to give 9-(2-hydroxyethoxymethyl~)guanine (36 g, greater
than 9G%~ pure), yield = 75%.
EXAMPLE~3
:
2-Acetami:do-9-~(2-aaetyloxyethoxvmethvl)hYpoxanthine
; A mixture of~diacetylguanine (1.0 g), 2-oxa-1,4-
~butanediol diacetate (0.82 g) and E~toluenesulfonic acid
(23 mg) in mineral~oil (4 g) was~heated at 115C with
stirri~ng at~reduced~préssure overnight. The mineral oil
was~decanted off.; The residue was triturated with chloro-
form~and~;then~extr~cted~with boillng methanol. The
methanol~extract~was~concentrated to 50 ml, chilled, and
filtered.~ The filtrate was evaporated to dryness, giving
a~olid~residue (0.43~g). The solid was purified by
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9~36~
column chromatography (~ilica gel, 10 g, in chloroform,eluted with 1:1 chloroform:acetone) followed by
recrystalli~;ation from ethanol to give 2-acetamido-9-
(2-acetyloxyethoxymethyl)hypoxanthine (0.14 g), m.p.
202.5-204.5C.
~AMPLE 4
2-Amino-9-(2-hydroxyethoxymethyl)adenine
(a) 2-Formamido adenine (89.0 g) was placed in a
5-liter flask equipped with an air-stirrer and reflux
10 condenser (CaC12 drying tube), to which acetic anhydride
(4 1) were added. The mixture was brought to reflux
and held for 60 hours. At the end of this time, the
excess anhydride was removed by distillation at atmospheric
pressure until approximately 3.5 1. of di~tillate had
been obtained. The distillation was continued under
reduced pressure to remove most of the remaining
anhydride. The dark brown pot residue became a viscous
`~ gun~ny mass upon cooling to room temperature and was then
dis801ved in dichloromethane, filtered to remove any
20 ~ suspended 901ids,~and the solvent removed in vacuo to
give 211.0 g (~ 100%) of 2,6-bi~-(diacetylamino)-9-
acetyl purine. The assayed yield was 96.7% based upon
the nmr with the balance of the material being acetic
anhydride.
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(b) The penta-acetyl purine (174 g) was combined
with 1,4-diacetoxy-2-oxabutane (126.8 g) in a flask
equipped with an air-stirrer and drying tube. This
mi.xture was then placed in an oil bath at 130C and
stirred for a few minutes to homogenize the batch. The
acid catalyst, para toluenesulphonic acid (2.74 g), was
thèn added in one portion and heating was continued
in vacuo for 4 hours at which time nearly quantitative
conversion to products was observed. The reaction
mixture was then cooled to room temperature and stored
under dry nitrogen.
(c) The fusion product (208.5 g) was dissolved in
ethanol (5 ml/g) at room temperature and transferred to
:~: :
flask equipped with a dropping funnel, air-stirrer, and
thermometer, The n-butylamine (140.4 g) wae then added
dropwise over a 2 hour period and~the exothermic reaction
was controlled with the use of a water bath. The maximum
temperature;~which ~the reaction was allowed to reach being
only 30C. ~The product began to separate from the
20~ reaction mixture~during the cour~oe of the addition.
After~completion~of~the addition, the mixture was stirred
'at~room temperature~for 3~hours and then placed in the
cold~room~overnight.~ The product~was~removed by filtration
to~give a pasty mass~which was slurried with acetone
x~SOO~ml)~and~refiltered. Thls~was dried in vacuo
at~65~C~for 3~hour~s~and~then at room temperature overnight
~ to~give 154.2~g (91.P~) of a~light brown hard solid.
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~Q~364
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9 _
The product was purified by dissolving it in hot dimethyl-
formamide (10 ml/g) at 100-110C to give an opaque brown
solution. After cooling overnight at 5C, the product
was removed by filtration, washed with acetone (1 x 250
ml) and air dried to give 121.7 g (78.8%) of 2,~-di-
acetamido-9-(2-acetoxyethoxymethyl)purine.
(d) The 2,6-diacetamido-9-(2-acetoxyethoxymethyl)-
purine (121.7 g) was added to a stirred solution of aqueous
methylamine (608.5 ml of 4~/O solution) over a 5-minute
period. The addition was accompanied by a mild exotherm
which raiced the temperature of the mixture to 35C and
all of the solid material dissolved in a few minutes.
After stirring for 2-1/2 hours the tlc of the mixture
indicated completion of the reaction. The mixture was
;~ ~ then concentrated 1n vacuo on a water bath at 45-50C to
give a thick mass of brown crystals. This was then
slurried with acetone (545 ml, 7 ml/g) for l5 minutes to
remove N-methyl acetamide and vacuum filtered. The cake
was rinsed with acetone (1 x 200 ml) and air-dried to
give 74.7 g (96.0Yo) of crude, hydrated 2-amino-9-(2-
hydroxyethoxymethyl)adenine as light brown crystals.
ese~were dried in vacuo at 80C for 18 hours to give
69.3~g. ~89.0~ of dry product.
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