Rapid Methods for the High Yield Synthesis of Carbon-13 Enriched Intermediates of the Pentose-Phosphate Pathway

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Abstract
Methods for the synthesis of carbon-13 enriched substrates, intermediates and products of the pentose-phosphatase pathway, viz. ribose, arabinose, xylulose and ribulose 5-phosphates, sedoheptulose mono- and bisphosphates, octulose (both the ido- and altro-epimers) mono- and hisphosphates, are described. The procedure of the classical Kiliani synthesis was adopted for the preparation of the two starting compounds, [1-13C]ribose and [1-13C]arabinose 5-phosphates. Using these intial reactants and enzymic methods involving the group-transferring enzymes, transketolase, aldolase and transaldolase, a variety of specifically 13C-labelled five-, six-, seven- and eight-carbon sugar phosphates were synthesized in high yield and purity. The isolation and authenicity of each of the 13C-labelled sugars were establihed by column, paper and thin layer chromatographic methods and specific enzymic assays. The purity and positional isotopic analysis of these sugar-P''s were confirmed by 13C-NMR spectroscopy. These specifically 13C-enriched compounds are required for enzymatic, mechanistic and quantitative investigations of pentose-pathway reactions in animal, plant and tumor tissues in vitro and in vivo.