Molecular and crystal structure of methyl hepta-O-acetyl-α-laminarabioside

✍ Scribed by Masaki Ikegami; Keiichi Noguchi; Kenji Okuyama; Shinichi Kitamura; Kenichi Takeo; Shigeru Ohno

• Publisher: Elsevier Science
• Year: 1994
• Tongue: English
• Weight: 637 KB
• Volume: 253
• Category: Article
• ISSN: 0008-6215
• DOI: 10.1016/0008-6215(94)80053-7

✦ Synopsis

The molecular and crystal structure of methyl 2,3,4,6,2',4',6'-hepta-O-acetyla-laminarabioside (methyl a-laminarabioside heptaacetate) was determined by the X-ray diffraction method. The cry@ belongs to the monoclinic system, space group P2,, a = 13.179(3), b = 22.832(3), c = 5.555(2) A, p = 95.91(3)", Dobsd = 1.32 g/cm', D&'.+, = 1.308 g/cm3, Z = 2. The structure was obtained by the direct method and refined by the full-matrix least-squares procedure to R = 0.061 for 2097 observed reflections with IF, I 2 2&F,). The difference Fourier synthesis showed all the hydrogen atoms except those of the methyl moieties. The linkage conformation angles, 4=8(0-5-C-l-O-l-C-3') and 4 = @CC-l-0-l-C-3'-C-2'), are -85.5 and -111.9", respectively. These are similar to those of other B-(l--,3)-linked acetylated disaccharide compounds. The acetate substituent at C-6 of the reducing residue was in the gg conformation, while the gt conformation was observed in the nonreducing residue. The conformational analysis using the bond lengths and angles obtained revealed that the energy map for Q and JI angles was independent of the orientation of the C-6 acetate. In the crystal structure o-glucopyranose rings are amassed along the c axis and parallel to the ab-plane. These molecules interact with their surrounding molecules only by van der Waals forces.