A MODIFIED SYSTEM OF NOMENCLATURE FOR RED ALGAL GALACTANS

A nomenclature system for red algal galactans based on their chemical structures is proposed. The terms 'agaran' and 'carrageenan' are sugge sted as the generic names for two possible diastereoisometric extreme structures of carbohydrate backbone built of alternating 3-linked beta -D-galactopyranose and 4-linked alpha-galactopyranose residues and dif fering only in the absolute configuration of the 4-linked alpha-galact ose residues (L- or D-, respectively). 'Agarose' and 'carrageenose' ar e the generic names for the corresponding backbones having 3,6-anhydro -alpha-galactopyranose (also L- and D-) as the 4-linked residue. All t he other known regular structures may then be designated as substitute d (methylated, sulfated, etc.) derivatives of agaran and agarose (agar group polysaccharides) or carrageenan and carrageenose (carrageenan g roup polysaccharides). A shortland notation system (uppercase letter c ode) is also proposed, which is especially useful for designation of h ybrid (masked repeating) polysaccharide structures or their correspond ing oligosaccharidic fragments and for interpretation of the NMR spect ra.