The Occurrence of D-mannose in Seaweed and the Separation of L-fucose and D-mannose.* by Richard H. F. Manske

The wide-spread occurrence of mannans and fucosans in nature makes it not improbable that some of these vegetable gums may in fact consist in part at least of fuco-mannans. In general the isolation and identification of two or more sugars from a mixture is often fraught with experimental difficulties, particularly if the material is available only in small amounts. Any simple procedure applicable to small quantities which facilitates the separate identification of sugars is certain, therefore, to find a use. The author had occasion to prepare comparatively large quantities of L-fucose by the excellent method of Clark1 from seaweed (Fucus vesiculosus, L.) gathered on the southern shores of the Baltic Sea. As will appear in the sequel, the method, however, is unfortunate when appreciable amounts of mannose are present because the fucose phenylhydrazone will be contaminated with the sparingly soluble mannose phenylhydrazone and the product regenerated from this is a mixture. Fortunately enough the first crops of sugar appear to be entirely free of mannose but the crystals isolated from the mother liquor have been shown to contain mannose in not inappreciable amounts. Furthermore, the final mother liquor which crystallized only with difiulty contained approximately 10 per cent mannose. This concentration of mannose in the mother liquors makes possible its isolation and identification by two different methods which in their practical application the author believes to be new.