Application de la réaction de Wittig à la synthèse de dérivés de bromoénosuloses et d'esters bromoénuroniques . Note de laboratoire

Use of the Wittig reaction for the synthesis of derivatives of bromoenosuloses and bromoenuronic esters Treatment of 3‐ O ‐benzyl (or 3‐ O ‐methyl)‐1, 2‐ O ‐isopropylidene‐α‐ D ‐ xylo ‐pentodialdo‐1, 4‐furanoses ( 2 or 1 ) with acetylbromomethylidenetriphenylphosphorane ( 3 ), benzoylbromomethylidenetriphenylphosphorane ( 4 ) or bromoethoxycarbonylmethylidenetriphenylphosphorane ( 5 ) gave in good to excellent yields the expected enose ( 6‐‐11 ). In all cases but one ( 8 where some 10% of the E ‐isomer was formed) the reaction led to the exclusive formation of the Z ‐isomer whose configuration was established by NMR.