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

Abstract

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%).