Ribonucleoside 3'-di- and -triphosphates. Synthesis of guanosine 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-butylammonium) 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 degrees 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-(1-methoxyethyl)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%.