Intramolecular oxyselenation of (5'S)-C-(4-phenyl-1,3-butadienyl)uridine: synthesis of octosyl nucleosides.

(5'S)-C-(4-Phenyl-1,3-butadienyl)uridine (8) was prepared from the (5'S)-C-styryl derivative 2. Intramolecular oxyselenation of 8 proceeded in a 6-endo-trig manner to yield the cyclized product 9. Compound 9, having appropriate substituents at the 5'-, 6'-, and 7'-positions, was found to serve as a key intermediate for the synthesis of octosyl nucleosides.