Stereoselective addition of a Wittig reagent to give a single nucleoside oxaphosphetane diastereoisomer. Synthesis of 2'(and 3')-deoxy-2'(and 3')-methyleneuridine (and cytidine) derivatives from uridine ketonucleosides

Article abstract of DOI:10.1055/s-1991-26774

Treatment of 3',5'(or 2',5')-bis-O-silyl-protected 2'(or 3')-ketouridine derivatives with methyltriphenylphosphonium bromide and sodium 2-methyl-2-butoxide in diethyl ether/benzene at 0-4 °C resulted in the slow formation of the corresponding 2'(or 3')-deoxy-2'(or 3')-methylene analogues. ¹H- and ³¹P-NMR spectra were in harmony with formation of a single oxaphosphetane diastereoisomer during early stages of the Wittig reaction. Conversions of protected deoxymethyleneuridine to deoxymethylenecytidine derivatives were effected smoothly via 4-(1,2,4-triazol-1-yl) intermediates. Deprotection with tetrabutylammonium fluoride gave 2'(or 3')-deoxy-2'(or 3')-methylneuridine and cytidine nucleosides.