Synthesis, conformation and enzymatic properties of l-(β-D-allofunuiosyl)uracil and some derivatives

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Abstract
A new route for the synthesis of 1 − (β-D-allofuranosyl)uracil (“allo-uridine”) and the corresponding 6′-deoxy-derivative (“6′-deoxy-allo-uridine”) as well as for 1 -(β-D-altrofuranosyl)uracil (“altro-uridine”) is described. NMR studies of allo-uridine revealed a preferred conformation with the base in anti-position, C-2′-endo-pucker of the sugar moiety, the 5′-0H-group above the furanose ring and the 5′-CH20H-group in a gt position with the OH-group in the plane of the furanose ring. The same conformation is found for the 5′- and 6′-phosphate, indicated by the influence of the phosphate group on the H-6 signal. Allo-uridine is phos-phorylated by the phosphotransferases from carrot and from malt sprouts only in the 6′-position. The phosphate ester is hydro-lysed by unspecific phosphatases but not by 5′-nucleotidase. A (3′+6′)-dinucleoside phosphate is formed by pancreatic ribonu-clease with 2′,3′-cyclic cytidylic acid and allo-uridine. It is split by nuclease Si, but not by snake-venom phosphodiesterase. It has no primer activity for polynucleotide phosphorylase. Allo-uridine 6′-diphosphate could not be prepared enzymatically by nucleotide kinase or by chemical methods, where 5′,6′-cyclic phosphates are formed, which are hydrolysed exclusively to 6′-monophosphates.