Modifications in the nitric acid oxidation of d-mannose: X-ray crystal structure of N,N′-dimethyl d-mannaramide

•Nitric acid oxidation of d-mannose was carried out under computer control.•Isolated product was the crystalline diamide N,N′-dimethyl-d-mannaramide.•The diamide was directly converted to solid disodium d-mannarate.•The X-ray crystal structure of the diamide was determined.

Nitric acid oxidation of d-mannose was carried out under an oxygen atmosphere using a computer controlled reactor. The process represents a catalytic oxidation of d-mannose with oxygen as the terminal oxidant. The crude oxidation product was esterified with methanolic HCl and the esterified product directly converted to crystalline N,N′-dimethyl-d-mannaramide with methylamine. Treatment of the diamide in aqueous sodium hydroxide gave solid disodium d-mannarate. The X-ray crystal structure of N,N′-dimethyl-d-mannaramide was determined as a model for the repeating d-mannaramide units of stereoregular poly(alkylene-d-mannaramides). Disodium d-mannarate was prepared as a precursor of esterified d-mannaric acid for use as a reactive diacid monomer to prepare poly-d-mannaramides.

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