Improvements in the Manufacture or Preparation of Dichloroxypurine."
Year: 1897

page_text: Date of Application, 13th Feb., 1897
Complete Specification Left, 10th Nov., 1897-Accepted, 11th Dec., 1897
66
PROVISIONAL SPECIFICATION.
Improvements in the Manufacture or Preparation of
Dichloroxypurine."
I JAMES YATE JOHNSON of 47 Lincolns Inn Fields in the County of London
Gentleman do hereby declare the nature of this Invention (which has been
communicated to me from abroad by the firm of C. F. Boehringer and Soehne of Waldhof
near Mannheim in the Empire of Germany) to be as follows:-
Purine derivatives and chlorinated methylpurines have been hitherto obtained
from various methylated uric acids and xanthines (theobromine, caffeine) by the
action of phosphorus pentachloride in the presence of phosphorus oxychloride as a
solvent (Ber d. d. chem: Gesellschaft, 17, 330 & 28, 2480). Attempts made to
arrive at unmethylated purines by withdrawing oxygen from uric acid through the
agency of phosphorus pentachloride, have been hitherto unsuccessful (Ber d. d. chem
Ges 17, 329).
My foreign correspondents have now achieved this object by the action of
phosphorus oxychloride on the dry salts of uric acid such as the acid potassium,
sodium ammonium, magnesium, calcium and barium salts of uric acid. In this way,
dichloroxypurine of the composition CH,NOCl2, is obtained; the course of the
action is represented by the following equation:-
Dichloroxypurine is a dibasic acid and decomposes carbonates on boiling.
Its chief point of difference from uric acid is its stability against the action of
oxidising agents such for example as strong nitric acid. It also gives rise to a stable
silver salt when treated with an ammonical solution of silver.
It dissolves with great difficulty in water. From alcohol (in which it dissolves
sparingly) the substance separates in very small needles, which decompose above
300° Centigrade.
Methylation converts dichloroxypurine into dichloroxydimethylpurine, which has
been already prepared by Emil Fischer and has the following constitution (Ber. d. d.
chem Ges. 17. 1787):—

page_text: The following example will illustrate the manner of carrying out the Invention.
1 part by weight of dry acid potassium urate is carefully mixed with 1.2 parts by
weight of phosphorus oxychloride and heated in closed vessels for 6 hours at
160° centigrade. The excess of oxychloride is removed by distillation and the
residual mass is washed with water.
The product still contains unaltered uric acid, which is easily removed by treatment
with nitric acid.
By precipitating the ammonium salt from aqueous or alcoholic solution, pure
dichloroxypurine is obtained
JOHNSONS & WILLCOX
47 Lincolns Inn Fields London W.C. Agents.
"
Improvements in the Manufacture or Preparation of
Dichloroxypurine."
I, JAMES YATE JOHNSON; of 47 Lincolns Inn Fields, in the County of London,
Gentleman, do hereby declare the nature of this invention (which has been com-
municated to me from abroad by the firm of C. F. Boehringer and Soehne; of
Waldhof, near Mannheim in the Empire of Germany) and in what manner the same
is to be performed to be particularly described and ascertained in and by the following
statement:-
Purine derivatives and chlorinated methylpurines have been hitherto obtained from
various methylated uric acids and xanthines (theobromine, caffeine) by the action of
phosphorus pentachloride in the presence of phosphorus oxychloride as a solvent
(Berichte der deutschen cheinischen Gesellschaft, 17. 330 and 28, 2480). Attempts
to arrive at unmethylated purines by withdrawing oxygen from uric acid through the
agency of phosphorus pentachloride, have been hitherto unsuccessful (Berichte der
deutschen chemischen Gesellschaft 17, 329).
My foreign correspondents have now achieved this object by the action of phosphorus
oxychloride on the dry salts of uric acid-such as the acid potassium, sodium,
ainmonium, magnesium, calcium and barium salts-or on the free uric acid. In
this way, dichloroxypurine of the composition C₂H₂NOCI, is obtained, the course
of the action is represented by the following equation
Dichloroxypurine is a dibasic acid and decomposes carbonates on boiling.
Its chief point of difference from uric acid is its stability against the action of
oxydising agents such for example as strong nitric acid. It also gives rise to a stable
silver salt when treated with an ammonical solution of silver. It dissolves with great

page_text: difficulty in water. From alcohol (in which it dissolves sparingly) the substance
separates in very small needles, which decompose above 300° centigrade.
Methylation converts dichloroxypurine into dichloroxy-dimethylpurine, which has
been already prepared by Emil Fischer and has the following constitution (Berichte
5 der deutschen chemischen Gesellschaft 17, 1787):
1 part by weight of acid urate of potassium in a dry state is carefully mixed
with 1.2 parts by weight of phosphorus oxychloride and heated in closed vessels for
6 hours at 160° centigrade. The excess of oxychloride is removed by distillation and
the residual mass is washed with water.
The product still contains unaltered uric acid, which is easily removed by treatment
with nitric acid. By precipitating the ammonium salt from aqueous or alcoholic
solution, pure dichloroxypurine is obtained.
One part by weight of uric acid and five parts by weight of phosphorus-oxychloride
are heated in a digester to from 170° to 175° centigrade, and maintained at this
temperature for from 24 to 30 hours, the mass being constantly agitated.
After the lapse of this time the uric acid is completely dissolved. The resulting
liquor which has a brownish colour is evaporated to complete dryness in vacuo to
remove the phosphorus-oxychloride. The amorphous residue is dissolved in alcohol
(preferably pure).
The dichloroxypurine separates out of the clear alcoholic solution in the form of coarse
yellow crystalline grains after boiling and concentrating for a half hour. To
completely purify the same it is warmed or heated for a short time with nitric acid
of the specific gravity 1.41. It is thus obtained colourless.
The yield is from 45 to 50 per cent. of the uric acid employed or thereabouts.

page_text: this inven-
Having now particularly described and ascertained the nature of
tion and in what manner the same is to be performed, I declare that what I
claim is :-
1. The manufacture, or preparation, of dichloroxypurine by treating a dry salt of
uric acid with oxychloride of phosphorus.
2. The preparation of dichloroxypurine by treating the free uric acid with
oxychloride of phosphorus.
JOHNSONS & WILLCOX
47 Lincoln's Inn Fields, London, W.C., Agents.