the reaction of chlorotetrolic ( 4-chloro-2-butynoic ) esters with adenine and cytosine derivatives , in which a new heterocycle bearing an alkylating chloromethyl side chain is fused to the purine or pyrimidine ring , was extended to poly ( a ) and poly ( c ) used as models of nucleic acids .
C0001407
adenine
C0034140
purine