Chemical Synthesis and Quantitative Estimation of 3‐Deoxy d ‐manno‐Octulosonic Acid

3‐Deoxy d‐manno‐octulosonic acid has been synthesised starting from d‐mannose via 2‐deoxy d‐manno heptose, cyanohydrine addition, and selective oxidation of the epimeric hydroxyl group of the resulting 3‐deoxy octonic acids. When treated with periodate in 0.1 N sulphuric acid solution at 0°, the deoxy octulosonic acid and other 3‐deoxy aldulosonic acids all yield one molar equivalent of β‐formyl pyruvate. Conditions are described in which β‐formyl pyruvate can be estimated by the thiobarbituric acid method; hence, when treated successively with periodate and thiobarbiturate, all 3‐deoxy aldulosonic acids have the same molar extinction coefficient [(92 ± 5)103 in dilute acid; 133 × 103 in cyclohexanone] and can be estimated by this method without the use of standards.