Deoxy-nitrosugars. 11th Communication. Reactions of 1-C-nitroglycosyl halides and 1-C-nitroglycosyl sulfones with dialkyl-phosphite anions: Nucleophilic attack vs. single-electron transfer

Treatment of the chloro-nitro-ribofuranose 7 with KPO(OMe)₂ gave the O-amino phosphate 8 (5 %) and the nitrile 9 (62 %). Compound 9 was also obtained by the reaction of 8 with KPO(OMe)₂, and its structure was established by X-ray analysis. Treatment of the chloro-nitro-mannofuranose 10 , the bromo-nitro-ribofuranose 14 , or the bromo-nitro-mannofuranose 16 , respectively, with the K or Na salt of HPO(OMe)₂ lead also to O-amino phosphates and nitriles. The (1-C-nitroglycosyl)phosphonate 22 was obtained (21 %) together with the nitrile 21 (51 %) from the chloro-nitro-mannofuranose 10 and KPO(OEt)₂. The reaction of the 1-C-nitroglycosyl sulfone 25 (NO₂-group endo) with KPO(OEt)₂ gave the (1-C-nitroglycosyl)phosphonate 22 (61%) and the nitrile 21 (11 %), whilst the anomeric sulfone 26 (NO₂-group exo) gave 22 (15 %) and 21 (58 %). In the presence of [18] crown-6, a mixture of the anomers 25 and 26 gave the (1-C-nitroglycosyl)phosphonate 22 in 67 % yield together with 21 (13 %). These findings are rationalized as the result of a competition between a nucleophilic attack of the dialkyl-phosphite anions on the NO₂-group leading ultimately to the nitrile 21 and a single-electron transfer reaction leading to the (1-C-nitroglycosyl)phosphonate 22 .