The Reaction of Free Carbonyl Sugar Derivatives with Organometallic Reagents. I. 6-Deoxy-L-idose and Derivatives^1,2

Study of Stereoselectivity in Organometallic Additions to 1,2-O-Isopropylidene-O-R-α-D-xylopentodialdo-1,4-furanose

“…The design of addition of C-nucleophiles to aldehydes 6 could be based on models of either chelation-control: 1,2-(A) versus 1,3-(B) asymmetric induction or non-chelation-control (Felkin-Anh model C), leading to alcohols 8 (L-ido) (model A) or 7 (D-gluco) (models B, C) (Scheme 2). We have prepared 3-O-R-substituted aldehydes 6a-d from D-glucose (Scheme 3) with diverse protecting groups (R = H [6,7], Bn [6,8], TBDMS, Ms) in order to examine the effects of changes in the nature of the alkoxy group on the selectivity of the reaction. Treatment of aldehydes 6 with phenyl magnesium bromide in THF (see Table 1, Entry 1) or diethylether (Entries 2-4) gave in all cases the Lido diastereomer 8 as a major product as a result of 1,2-chelation-control.…”

Dérivés de sucres à groupement gem‐dihalogénoéthényle

“…Nous avons soumis a des dihalogCnomethylidCnations les aldehydosucres 1 [ 111 [12],2 [9],3 [13], 4[14] [~~1 ,~[~6 ] , 6 [~~1 ,~[~8 1 ,~[~6 1 ,~[~~] ,~0 [ 2 0 ] , 1 12 [20] et 13 [20]. Les difluoroenoses 14-20 on etC obtenus avec des rendements compris entre 56 et 71% par action, sur l'aldehydosucre correspondant, du difluoromethylidenetrisdimethylaminophosphorane ([IS], protocole B) selon un procede adapt6 de Naae & Burton [21].…”

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

“…Treatment of 3-0-benzyl (or 3-0-methyl)-1,2-O-isopropy~idene-u-~-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 2-isomer whose configuration was established by NMR.…”

“…Nous avons prtcedemment rapport6 la synthese et quelques usages de derives de sucres porteurs de synthons cyano-2-halog~no-2-kthknyles [2] [4], trait& par Fun des phosphoranes 3 [5], 4 [5] rapportent la synthese de membres de cette nouvelle classe de sucres modifies.…”