Identification of 3‐deoxy‐manno‐2‐octulosonic acid, 3‐deoxy‐5‐O‐methyl‐manno‐2‐octulosonic acid and 3‐deoxy‐lyxo‐2‐heptulosaric acid in the cell wall (theca) of the green alga Tetraselmis striata Butcher (Prasinophyceae)

The main constituent of the cell wall complex carbohydrate of the scaly green alga Tetraselmis striata Butcher is shown to be 3‐deoxy‐manno‐2‐octulosonic acid (42%). In addition two other 2‐keto‐sugar acids are present, namely, 3‐deoxy‐5‐O‐methyl‐manno‐2‐octulosonic acid (7%), the first methylated derivative of 3‐deoxy‐manno‐2‐octulosonic acid found in nature, and 3‐deoxy‐lyxo‐2‐heptulosaric acid (11%). The characterization of the three 2‐keto‐sugar acids has been carried out on the corresponding methyl ester methyl glycosides using GLC‐MS and 500‐MHz 1H‐NMR spectroscopy, and on the corresponding reduced alditol acetates using GLC‐MS. Other monosaccharides occurring in the cell wall are d‐galacturonic acid (14%), d‐galactose (4%), d‐gulose (2%), d‐glucose (1%) and l‐arabinose (1%).