Synthesis of Some 1-Methyladenine Analogs and Their Biological Activities on Starfish Oocyte Maturation

Starfish oocytes are naturally arrested at the prophase stage of the first meiotic division and resume meiosis in response to the maturation-inducing hormone 1-methyladenine. Five analogs of 1-methyladenine including three novel ones were synthesized and tested for biological activities as 1-methyladenine agonists or antagonists in triggering reinitiation of meiosis of starfish Asterina pectinifera oocytes, as well as for competition in binding to putative 1-methyladenine receptors with respect to 1-methyladenine. 1-Ethyladenine was an effective agonist, but 1-propyladenine served as a weak antagonist to 1-methyladenine, indicating strict specificity for a relatively small N-1 substituent. Analogs in which carboxymethyl or methyl group substitutes for a hydrogen of 6-amino group still retained oocyte maturation-inducing activity, but to a much lesser degree. The results of the competitive binding assay with cortices of oocytes demonstrated that these agonists or antagonist inhibited the binding of [(3)H]1-methyladenine to receptors. 8-methylamino-1-methyladenine competed only weakly with [(3)H]1-methyladenine for the binding to cortices, although it behaved as a potent antagonist.