Treatment of a solution of 3-deoxy-o-glycero-D-galacto-non-2-ulosonic (ICDN) in 11 N aqueous hydrochloric acid with an excess of ethanethiol gave in 52% yield the diethyl dithioacetal of the corresponding l,Clactone, which was further characterized as its peracetate. With 1,3_propanedithiol, only one thiol function reacted and the product, isolated in 18% yield as its peracetate, was a vinyl thioether of the &l-unsaturated 1,Clactone. The methyl ester methyl #Sglycopyranoside derivative of KDN could be converted to the 8,9-isopropylidene ketal 7 (69%). Conditions were found which allow selective silylation at C-4 with rert-butylchlorodimethylsilane, giving the 4-O-terf-butylsilyl derivative in 91% yield. Heating it with bis(tributyltin) oxide afforded the 1,7-lactone with inversion of the ring conformation. Lithium aluminium hydride reduction of 7 afforded the corresponding methyl non-2-ulopyranoside, which was converted to the 1,4-bis(sily1) ether. Bromination of 1,5anhydro-2-deoxy-o-arbino-hex-1-enitol in aqueous solution at 0°C with N-bromophthalimide gave a mixture of bromodeoxy hexoses from which 2-bromo-2-deoxy-D-mannose was isolated in 60% yield by crystallization. Its incubation with pyruvate in the presence of sialyl aldolase gave 5-bromo-3,5-dideoxy-o-glycero-D-ga~acto-non-2-ulosonic acid 16 in 70% yield.