2-amino-2,6-dideoxy-L-mannose (L-rhamnosamine) isolated from the lipopolysaccharide of Escherichia coli 03:K2ab(L):H2.

Abstract

From the lipopolysaccharide of Escherichia coli U41/14 (serotype 03:K2ab(L):H2) an unusual amino sugar was isolated. By sequential oxidation with periodate and hypoiodite and by oxidation with periodate, followed by detection of acetaldehyde formed, the amino sugar was characterized as a 2-amino-dideoxyaldose. The hydrochloride of the amino sugar, in comparison to those of 2-amino-2,6-dideoxy-D-glucose, 2-amino-2,6-dideoxy-L-galactose, 2-amino-2,6-dideoxy-D-mannose, 2-amino-2,6-dideoxy-D-allose, and 2-amino-2,6-dideoxy-D-gluose, was studied with aid of ion exchange column chromatography. The N-acetylated amino sugar was compared with the N-acetylated reference amino sugars with regard to their relative mobilities in paper chromatography. The amino sugar alcohols and reference amino sugar alcohols were studied using paper electrophoresis in molybdate buffer. On the basis of the results obtained the unknown amino sugar was identified as 2-amino-2,6-dideoxymannose (rhamnosamine). Its optical rotation showed it to be of the L-configuration. This is the first report on the natural occurrence of L-rhamnosamine.