Ribonucleosides are essential building blocks used throughout nature. They serve as basic constituents of RNA, and are key motifs found in a variety of cofactors and secondary messengers. In addition, nucleoside analogues are used extensively in the development of antiviral and anti-cancer agents, as well as forming the key building blocks for the development of therapeutic oligonucleotides (Figure ). A major challenge in the further development of nucleoside analogues for therapeutic applications is access to step efficient, environmentally sustainable and preferably convergent methods of synthesis. Whilst conventional chemical synthetic strategies typically require anhydrous conditions and toxic reagents to form the desired nucleosidic linkage, biocatalytic methods are performed in aqueous conditions and with superior stereoselectivity to form the desired -anomer product. Nucleoside purine (PuNP) and pyrimidine (PyNP) phosphorylases have been the most prominent enzymes to prepare ribonucleosides, enabling the preparation of purine and pyrimidine products with substrate tolerance at the 2ʹ position (Figure ). An enzymatic alternative to the use of NPs to prepare ribonucleoside analogues is to use nucleoside 2'deoxyribosyltransferases (NDTs). These enzymes catalyse the formation of nucleoside analogues via an overall nucleobase exchange much akin to NPs. However, NDTs are mechanistically distinct, forming a covalent adduct within the active site, thus controlling stereoselective nucleophilic attack of the incoming nucleobase on the  face. The mechanistic divergence of NDTs negates issues associated with the undesirable buildup of the C1ʹ phosphate intermediate associated with NPs, which is thermodynamically favoured over the formation of the desired nucleoside product. Exploration of the substrate promiscuity of the nucleoside sugar donor of various NDTs has revealed a preference for 2ʹ-deoxyribose donors over ribonucleoside analogues. Chroococcidiopsis thermalis (CtNDT) prefers 2'-deoxyribonucleosides as the corresponding sugar donor, in a process that is driven by a faster kcat relative to a ribonucleoside donor. At present, a defined substrate scope and structure analysis has not been conducted for LlNDT-2 around the nucleobase and the 2′-position of the nucleoside donor.