Ribonucleoside 3′-Di- and -Triphosphates. Synthesis of Guanosne tetraphosphate (ppGpp)

A procedure has been outlined for the synthesis of ribonucleoside 3′-di- and -triphosphates. The synthetic scheme involves the conversion of a ribonucleoside 3′-monophosphate to its 2′-(5′-di)-O-(1-methoxyethyl) derivative, followed by successive treatments of the blocked ribonucleotide with 1,1′-carbonyldiimidazole and mono(tri-n-butyl ammonium) phosphate or pyrophosphate. The resulting ribonucleoside 3′-di- and -triphosphate derivatives are then deblocked by treatment with dilute aqueous acetic acid, pH 3.0. The use of this procedure is illustrated for adenosine 3′-monophosphate, which has been converted to its corresponding 3′-di- and -triphosphates in 61% overall yield. The decomposition of adenosine 3′-di- and -triphosphates to adenosine 2′-monophosphate, adenosine 3′-monophosphate, and adenosine cyclic 2′,3′-monophosphate as a function of pH at 100° has been studied as has the attempted polymerization of adenosine 3′-diphosphate with polynucleotide phosphorylase. Also prepared was guanosine 5′-diphosphate 3′-diphosphate (guanosine tetraphosphate; ppGpp), which was accessible via treatment of 2′-O-(lmethoxyethyl) guanosine 5′-monophosphate 3′-monophosphate with the phosphorimidazolidate of mono(tri-n-butyl ammonium) phosphate. The resulting blocked tetraphosphate was deblocked in dilute aqueous acetic acid to afford ppGpp in an overall yield of 18%.