3,4,6-Tri-O-acetyl-2-(N-acetylacetamido )-1,2-dideoxy-o-Iyxohex- 1-enopyranose, an Acetamido-n-galactal Derivative, and the Mechanism of its Formation from 2-Acetamido-2-deoxy-D-galactose

Abstract

The structure of an unsaturated amino sugar derivative, formed in low yield when 2-acetamido-2-deoxy-o-galactose _is treated with boiling isopropenyl acetate containing a trace of p-toluenesulfonic acid, and formulated as 1,4,6-tri-0-acetyl-2-(N-acetylacetamido)- 2,3-dideoxy-o-threo-hex-2-enopyranose(II) in an earlier publication, has been re-examined. Through a series of steps, including catalytic hydrogenation, the substance has been converted into a compound with an NMR spectrum which shows it to be 3,4,6-tri- 0-acetyl-2-(N -acetylbenzamido )-1,5-anhydro-2-deoxy-o-tali tol (X). This fact, together with a re-examination of its NMR spectrum, show the unsaturated compound to be 3,4,6-tri-0-acetyl-2-(N·· -acetylacetamido)-1,2-dideoxy-o-lyxo-hex-l-enopyranose (III), a derivative of 2-acetamido-o-galactal (VI). The yield of III from 2-acetamido-2-deoxy-o-galactose has been substantially improved through isolation of . 2-acetamido-1,3,4 , 6-tetra-0-acetyl-2-deoxy-~- o-galactopyranose (XIII) as an intermediate and III has been obtained in crystalline form. Evidence for the mechanism of its formation is presented