The reaction of dimethyl-t-butylsiloxy-1-methoxyethene (1a) with the N-benzylnitrone (3a) produced the syn-1,3-adduct (4a) predominantly, while the reaction of dimethyl-t-butylsiloxy-1-t-butoxyethene (1b) with the N-diphenylmethylnitrone (3d) gave the anti-1,3-adduct (4h) predominantly; both adducts were readily transformed into the corresponding 3-benzoylamino-2,3-dideoxypentoses (8a,b) in fair yields