The structure of a galactan sulfate from the red seaweed Bostrychia montagnei.

The sulfated, methylated galactan isolated from the red seaweed Bostrychia montagnei, showed an unusually narrow structural dispersion. This agaran has the defining linear backbone of alternating 3-linked beta-D-galactopyranosyl units and 4-linked alpha-L-galactopyranosyl and 3,6-anhydrogalactopyranosyl residues. The D-units have C-6 methylation, C-6 single stubs of xylopyranosyl and minor to trace amounts of (possible) C-6 linked single stubs of galactopyranosyl. These units are mainly sulfated on C-4 with lesser sulfation at C-6 and minor at C-2. The L-residues are mainly methylated on C-2 of the 3,6-anhydrogalactopyranosyl and sulfated on C-3 of the L-galactopyranosyl; minor amounts of 2,3- and 3,6-disulfated and 2-O-methyl or 2-O-glycosyl 3-sulfated L-galactopyranosyl were also found.