Chemical and enzymatic synthesis of the alginate sugar nucleotide building block: GDP-d-mannuronic acid.

Chemical and enzymatic routes to the alginate sugar nucleotide feedstock GDP-D-ManA have been established. Synthetic access to partially protected and fully deprotected anomeric 1-phosphates of D-mannuronic acid enabled their evaluation in pyrophosphorylative coupling to the target nucleoside diphosphate. Only the partially protected glycosyl 1-phosphate was effective for this reaction under the conditions examined. This procedure is complemented by an enzymatic approach to the same sugar nucleotide using the GDP-D-mannose dehydrogenase from P. aeruginosa.