Synthesis and conformation of 1-(3'-C-methyl-2'-deoxy-b-D-xylofuranosyl)uracil and 9-(3'-C-methyl-2'-deoxy-b-D-xylofuranosyl)adenine; two novel sugar-methylated nucleoside analogs

The preparation and high-resolution 1H NMR conformational analysis of the two novel nucleoside analogues, 1-(3'-C-methyl-2'-deoxy-ß-D-xylofuranosyl)uracil (compound 1) and 9-(3'-C-methyl-2'-deoxy-ß-D-xylofuranosyl)adenine (compound 2), are described. Compounds 1 and 2 show a pronounced preference for the north conformation of the sugar ring. The north conformation corresponds with a sterically favoured equatorial location of the methyl group. The C4' - C5' conformation in 1 and 2 is predominantly t (trans orientation of O5' and C3'). The configuration at C3' in 1 and 2 was corroborated via a one-dimensional NOE experiment. The structure of compound 1 (originally assigned as having the C3'-methyl group on the ß-face of the furanosyl moiety) is revised on the basis of these data.