Patent GB-590995-A (GB)
Title: Improvement in recovery of rare sugars
IPC: C07H1/08
Filed: 1943-09-16
Abstract: Solutions of nucleotides as such, or after having been previously converted to nucleosides by the removal of the phosphoric ester linkages therefrom are treated at elevated temperature with cuprous ions in a sulphur containing acid medium to precipitate the prime nucleotides or nucleosides unsubstituted at the 7-position as insoluble cuprous salts.  The latter, on hydrolysis by boiling in dilute acid, split off the soluble pentose from the insoluble purine cuprous salts which are removed by filtration.  The filtrate is made neutral with an alkaline earth metal oxide or hydroxide and again filtered, leaving the sugar in solution from which it is recovered. The cuprous nucleotides or nucleosides may be precipitated by adding a soluble cupric salt and a sulphurous ion at a pH of 3.5-6.5 or by adding a cuprous salt or oxide and sulphuric acid at a pH of 2.0-3.5. In the examples: (1) the nucleosides from yeast nucleic acid, obtained for example by heating the latter with magnesium oxide or other alkali in dilute solution in an autoclave, and filtering, are treated while the solution is still hot with acid until neutral and then with a solution containing copper sulphate and sufficient sodium acid sulphite to give a pH of 3.5-6.5.  The precipitated copper salts, after filtering and washing are hydrolysed by boiling with sulphuric acid and the ribose solution obtained on filtration purified by the addition of barium hydroxide or lime to precipitate impurities.  The filtrate is decolourized with carbon, concentrated, extracted with alcohol and the extract left to crystallize; (2) nucleic acid, liberated from yeast cells by treatment with alkali is purified by repeatedly boiling with hydrochloric acid and filtering off protein which is deposited and is precipitated by adding 1 per cent ferric chloride solution.  The nucleic acid is then split up into its constituent nucleotides by boiling with dilute caustic soda. After filtering, the solution is neutralized with sulphuric acid and the purine nucleotides unsubstituted at the 7-position precipitated by means of copper sulphate and sodium acid sulphite or cuprous oxide and sulphuric acid.  The copper salts, on hydrolysis by boiling with sulphuric acid yield insoluble copper salts of adenylic and guanilic acid, the pentose and phosphoric acid going into solution.  To recover the pentose, the copper adenine and guanine are filtered off and the phosphoric acid and soluble copper salts removed by adding alkaline earth hydroxide and filtering.  The filtrate is then decolourized with carbon, concentrated by absorbing upon diatomaceous earth mixed with activated carbon, dried under reduced pressure and extracted with a selective solvent such as a mixture of ethyl ether and ethyl alcohol followed by crystallization from the extract.  An alternative procedure for directly producing nucleotides from yeast consists in boiling with a dilute aqueous alkali such as sodium hydroxide in conjunction with an alkaline earth compound such as lime.  On filtering off the solid impurities, a solution of nucleotides is obtained.  Other pentoses of the type found incorporated in the 9-position in nucleotides or nucleosides may be extracted in the same way, including rhamnose, xylose, arabinose and desoxyribose. Substances other than nucleic acids which may be used as starting materials are for example, thymonucleic acid, inosinic acid, inosine, xanthylic acid, xanthosine and crotonside.