Stabilisation of pyrimidine nucleoside triflates by N-nitro groups

Abstract

Triflation of N 3-protected uridines ( NCOPh, NCHCHCOOMe, NNO 2) has been investigates. A stable 2′- O-triflyl derivative, that of N-nitro-3′,5′- O-(tetraisopropyldisiloxane-1,3-diyl)uridine, has been isolated for the first time; by contrast to its congeners, it does not give cyclonicleoside-like intermediates. Nucleophilic attacks on this substrate lead to 2′ß-substituted nucleosides rather than the usual 2′α epimers. 3′- O-Triflyl N-nitro derivatives behave similarly. Several novel nucleosides ( lyxo dihalo derivatives, 2′,3′-α-epoxy derivatives) are accessible by means of this approach.