Synthesis of amino-substituted hexo- and heptopyranoses from D-galactose.

After condensation of D-galactose with two equivalents of acetone, the last free hydroxy group was transformed into an acylated amino group by Swern oxidation, oxime formation, LiAlH4 reduction and acylation. The intermediate aldehyde was homologated with the Wittig reagent, (methoxymethyl)triphenylphosphonium chloride, to afford, after careful hydrolysis, a homologous heptodialdo-1,5-pyranose. Condensation of the aldehyde with hydroxylamine and subsequent LiAlH4 reduction provided a bis-O,O-isopropylidene-protected 7-amino-6,7-dideoxygalactoheptopyranose, which was acylated with various carboxylic acid derivatives. The isopropylidene protective groups were cleaved by careful hydrolysis or alcoholysis to yield 6-acylamino-6-deoxy-galactopyranoses and 7-acylamino-6,7-dideoxy-galactohepto-pyranoses.