2-Amino-2,6-dideoxy-D-glucose (quinovosamine) is a component residue' of the O-chain polysaccharide in the lipopolysaccharide antigens' of Pseudomonas aeruginosa, Fisher immunotypes 3,4, and 5. In connection with synthesis of artificial antigens and immunoadsorbents based on oligosaccharide segments3 of the Ochains, a convenient preparative route to quinovosamine was of interest. This amino sugar has been synthesized from derivatives of 2-amino-2-deoxy-D-glucose by way of selective 6-O-monosulfonylation4~s, and subsequently obtained by several other route&'; a preparative route employed in this laboratory' was based on N-bromosuccinimide-mediated ring-opening of a 4,6-benzylidene acetal'. The objective of the present work was to improve the net yield in preparation of the title glycoside from 2-amino-2-deoxy-D-glucose. This was accomplished in two routes, one a modification of the methods based on the 4,6_benzylidene acetal, and the second, judged superior overall, on selective C-6 monobromination by the action of carbon tetrabromide-triphenylphosphine'. Concurrently, Anderson and coworkers lo have prepared the title glycoside, having physical constants in good agreement with those reported here, by a C-6 monobromination step employing Nbromosuccinimide-triphenylphosphine"; their report is published simultaneously with this one. Glycosidation of 2-acetamido-2-deoxy-D-glucose with methanol in the presence of cation-exchange resin'*" gave, in 91% yield, methyl 2-acetamido-2-deoxy-a&D-glucopyranoside (1) as a cocrystallized, 5: 1 cu,/3 mixture, [LY],, t-98", and this was treated in pyridine at 6@-65" with 2 equivalents of triphenylphosphine and 1 equivalent of carbon tetrabromide to give, in 46% yield, crystalline methyl 2acetamido-6-bromo-2,6-dideoxy-cY-D-glucopyranoside (2). Hydrogenolysis of the bromide 2 in the presence of Raney nickel gave crystalline methyl 2-acetamido-2,6dideoxy-a-D-glucopyranoside (3) in essentially quantitative yield. Recrystallized from isopropyl alcohol, compound 3 had a m.p. in agreement with the litera-*Supported, in part, by NIH Grant No. GM-20181.