GB781735A - Synthesis of nucleoside polyphosphates - Google Patents

Abstract

A nucleoside polyphosphate is obtained by reacting a mononucleotide with phosphoric acid in the presence of a carbodi - imide and an aqueous pyridine solvent medium, said mononucleotide having more than one unsubstituted hydroxyl group in the phosphate grouping thereof. Specified carbodi-imides are those having the formula R1N = C = NR11 wherein R1 and R11 may be the same or different aliphatic (including cycloaliphatic) or aromatic groups, e.g. carbodi-imides in which R1 = R11 = cyclohexyl; R1 = R11 = p-tolyl; R1 = cyclohexyl, R11 = isopropyl; R1 = cyclohexyl, R11 = phenyl; and R1 = p-tolyl and R11 = phenyl. It is desirable to use a substantial excess of the phosphoric acid, e.g. 5 to 15 mols. of the phosphoric acid per mol. of the nucleotide starting material. When the nucleotide starting material is insoluble in pyridine the aqueous pyridine solvent should preferably contain between 5 and 30 per cent by volume of water based on the volume of the pyridine and when the nucleotide is soluble in pyridine the proportion of water should preferably be from 2 per cent to 30 per cent based on the volume of pyridine. Examples are given for the conversion of adenosine-51-monophosphate to adenosine-diphosphate and adenosine triphosphate and to mixtures of the di- and tri-phosphates, using dicyclohexyl carbodi-imide and di-p-tolyl carbodi-imide respectively as the carbodi-imide, the products being separated from the mixture by filtering to remove the disubstituted urea formed and adding Lohmann's reagent to the filtrate to precipitate the mercury salts of the adenosine mono- and poly-phosphates from which the free acids are liberated, by treating the salts in aqueous suspension with hydrogen sulphide. The polyphosphates are separated by neutralizing with sodium hydroxide followed by ion exchange chromatography and may be finally recovered in the form of their barium salts. Alternatively, the mixture of adenosine mono-, di- and tri-phosphates may be separated by adding sodium hydroxide to bring the pH of the hydrogen sulphide-freed solution of free acids obtained from the mercury salts to pH 3.8, adding barium acetate to precipitate the barium salt of the triphosphate which is removed by centrifugation, the diphosphate being precipitated from the supernatant liquid by raising its pH to 8.5. Other nucleoside polyphosphates which are stated to be obtainable by the process are the 51-di- and tri-phosphates of guanosine, cytidine, inosine, desoxyadenosine, desoxycytidine, desoxyguanosine, and thymidine.