Fluorination by anchimeric assistance of a diallylamino group: Application to the synthesis of some methyl aminofluoropentofuranosides

Article abstract of DOI:10.1016/0008-6215(93)84057-D

Methyl 2,3-trans-dialkylaminofluoro-α(or β)-D-pentofuranosides were prepared by fluorination wherein the dialkylamino group assists the replacement of a trans- vicinal mesylate. Whatever the location of the dialkylamino group (α or β face of the ring), the regioselectivity of fluorination depends mainly on the α or β orientation of the anomeric methoxyl group. The use of a diallylamino substituent led to methyl 3-amino-2,3-dideoxy-2-fluoro-β-D-xylofuranoside, methyl 2-amino-2,3-dideoxy-3-fluoro-α-D-arabinofuranoside, methyl 2-amino-2,3-dideoxy-3-fluoro-β-D-xylofuranoside, and methyl 3-amino-2,3-dideoxy-2-fluoro-α-D-arabinofuranoside. Attempts to obtain 2(or 3),5-difluoro analogues starting from corresponding dimesylates gave only disappointing results. Methyl 2,3-trans-dialkylaminofluoro-α(or B)-D-pentofuranosides were prepared by fluorination wherein the dialkylamino group assists the replacement of a trans-vicinal mestylate. Whatever the location of the dialkylamino group (α or B face of the ring), the regioselectivity of fluorination depends mainly on the α or B orientation of the anomeric methoxyl group. The use of a diallylamino substituent led to methyl 3-amino-2,3-dideoxy-2-fluoro-B-D-xylofuranoside, methyl 2-amino-2,3-dideoxy-3-fluoro-α-D-arabinofuranoside, methyl 2-amino-2,3-dideoxy-3-fluoro-B-D-xylofuranoside, and methyl 3-amino-2,3-dideoxy-2-fluoro-α-D-arabinofuranoside. Attempts to obtain 2(or 3), 5-difluoro analogues starting from corresponding dimesylates gave only disappointing results.