Studies on the Chemical Constitution of Agar-agar. XXIII. Isolation of d -Xylose, 6-O-Methyl- d -galactose, 4-O-Methyl- l -galactose and O-Methylpentose

Commercial agar was subjected to complete hydrolysis with dilute sulfuric acid, and the products were carefully investigated. Besides d- and l-galactose, which have been known to exist, there were isolated small amounts of d-xylose, 6-O-methyl-d-galactose, 4-O-methyl-l-galactose, and O-methylpentose, all the sugars except the last one being obtained in crystalline forms. Among these products, 4-O-methyl-l-galactose is a new compound, so its structure has been fully investigated. As commercial agar is made from Gelidium amansii, occasionally mixed with several other species of seaweeds, the experiments were repeated for the agar prepared from G. amansii only. The same products as those from commercial agar were isolated except the O-methylpentose.