This invention claims processes that comprise the appending of nucleotides having a 3′-ONH2 moiety to the 3′-ends of oligonucleotide primers using 3′-deoxynucleoside triphosphates of 2′-deoxynucleoside derivatives that have, instead of a 3′-OH moiety, a 3′-ONH2 moiety, where the nucleotides contain non-standard nucleobases.