this invention relates to the field of nucleic acid chemistry , more specifically to the field of compositions and processes that are nucleic acid analogs . more specifically , this invention relates to compositions that allow the sequencing of oligonucleotides by synthesis , and processes for sequencing by synthesis that exploit these compositions . most specifically , the instant invention discloses compositions of matter that are 5 ′- triphosphates of ribo - and 2 ′- deoxyribonucleosides wherein the 3 ′- oh group is replaced by a 3 ′- onhr group in the alpha configuration , wherein r is either a h or ch 3 group . also disclosed are these triphosphates where the nucleobase carries , via a linker , a reporter groups , such as a fluorescent species that can be used in single - or multi - copy dna sequencing , or a tag that can be visualized by ultramicroscopy . also disclosed are processes that use these compositions to do sequencing by synthesis .