Recently, a new heparin disaccharide-binding site on the convex side of cobra cardiotoxin (CTX) was identified by NMR spectroscopy and molecular modeling. To further characterize this site two heparin-like disaccharides were synthesized for binding studies with CTX, and a trisaccharide was synthesized for testing the sequence of the disaccharide binding to CTX. Thus six differentially protected monosaccharide building blocks (three L-iduronic acids and three D-glucosamines) were prepared. These include a L-iduronic acid elongation building block namely methyl 2-O-acetyl-4-O-levulinoyl-3-O-pivaloyl-alpha-L-idopyranosyluronate trichloroacetimidate for which a single-crystal X-ray structure was determined to have M-r = 576.79, a = 9.3098(11) Angstrom alpha = 90degrees, b = 10.3967(12) Angstrom beta = 90degrees, c = 28.026(3) Angstrom gamma = 90degrees, V = 2712.7(6) Angstrom(3), P2(1)2(1)2(1), Z = 4, mu = 0.71073 Angstrom, and R = 0.0378 for 7586 observed reflections. It shows that the molecular structure of the donor is in the C-1(4) conformation with significant 1,3-diaxial interactions between O-1 and O-3 as well as O-2 and O-4. The disaccharides and trisaccharide vary in the degree and position of O- and N-sulfation. The pivaloyl group was used as permanent protecting group of hydroxyl. The levulinoyl group was used as the temporary protecting group to protect the hydroxyl for elongation.