GB689390A - Improvements in the preparation of nucleosides - Google Patents

Abstract

Nucleosides are prepared by hydrolysing nucleic acid in aqueous solution at pH 6.5-8 in the presence of an agent capable of combining with the nascent phosphoric acid and maintaining the pH within this range during the hydrolysis; the nucleosides are then p separated and worked up as usual. The "agent" may be a metal compound sparingly soluble in water but soluble in acids, which forms an insoluble phosphate, e.g. magnesium, calcium, barium, lead or zinc hydroxide, or magnesium, calcium or barium carbonate. Thus the nucleic acid solution is boiled with 10-20 per cent excess of lead or zinc hydroxide (based on P2O5), preferably under increased pressure, filtered and left to crystallize. When using zinc hydroxide the products are zinc salts of nucleotides which are further hydrolysed by water at 140-150 DEG C. Further nucleosides are obtained from the mother-liquor after adding alcohol to precipitate the albumen; preferably methanol is used, to give an alcohol content of 70-80 per cent in the solution. The "agent" may also be an inorganic or organic buffer (e.g. sodium citrate), a water-soluble acid amide (e.g. formamide, methylformamide or dimethylformamide) or a water-soluble cyclic ether (e.g. dioxane, tetrahydrofurane). When using an amide or an ether alkali is added to bring the pH within the desired range. Examples are given of various methods of carrying out the process. Specified products are guanosine and adenosine, which may be isolated as picrate. Pyrimidine nucleosides are also obtained.