positions (e.g., 41-44). Substrate mapping also identified tolerance for modifications at the N1position. For example, transglycosylation using 1-deaza acceptors were tolerated (45-47) as well as modifications at the C8 (48-50) and C6 positions (51). Surprisingly, a trifluoromethyl substituent in the C8 position forms nucleoside 49, where N3 is the glycosylated position instead of N9. Another unexpected observation was the low conversion in the synthesis of 8-aza nucleoside 50, which was formed with 11% conversion. Nitrogen atoms at both N3 and N7 positions were essential for acceptor recognition, as the corresponding deaza-purine analogues were not transformed to the desired nucleoside products (52-56). This is presumably due to the removal of specific interactions with the C-terminal carboxylate of Y157 and the side chain of D72 respectively. Having established the broader substrate specificity of LlNDT, we were able to scale up several syntheses of purine nucleoside analogues using our optimised reactions conditions (Figure ). In this way, nucleosides 32, 36, 42, 45 and 51 were prepared on 0.6-6.5 mmol.