23dideoxyribose

2',3'-dideoxyribose is a five-carbon sugar (a furanose) that forms the sugar component of the nucleoside analogs known as dideoxynucleotides. It differs from the deoxyribose found in DNA by lacking hydroxyl groups at both the 2' and 3' positions, while retaining the 1' linkage to a nucleobase and the characteristic ring structure.

In nature, this sugar is not a standard component of native DNA or RNA. It is the sugar moiety of dideoxynucleoside triphosphates (ddNTPs), which are synthetic chain-terminating reagents used in Sanger DNA sequencing. When a ddNTP is incorporated into a growing DNA strand by DNA polymerase, the absence of a 3' hydroxyl prevents the formation of the next phosphodiester bond, terminating elongation and producing fragments that can be read to determine the sequence.

Stereochemistry and form: in sequencing reagents the sugar is typically the β-D-2',3'-dideoxyribose present in the nucleoside triphosphate form. The 2' and 3' positions lack hydroxyl groups, distinguishing ddNTPs from normal deoxynucleotides and driving their chain-terminating function.

Applications: ddNTPs are central to Sanger sequencing, enabling the generation of DNA fragment ladders that reveal nucleotide order. They remain a foundational concept in molecular genetics and educational demonstrations of DNA sequencing, alongside other nucleotide analogs and sequencing technologies. See also deoxyribonucleotides, dideoxynucleotides, and Sanger sequencing.