J. Johan Lindberg

Structural studies of acetan, an exopolysaccharide elaborated by Acetobacter xylinum

The exopolysaccharide acetan, elaborated by Acetobacter xylinum, has been investigated. The polysaccharide and a heptasaccharide, obtained on enzymic hydrolysis, corresponding to the repeating unit were characterised by sugar and methylation analysis and by NMR spectroscopy and MS. It is concluded that the polysaccharide is composed of repeating units with the following structure. [formula: see text] The polysaccharide further contains approximately two O-acetyl groups per repeating unit, which have not been assigned, but it appears that they are on primary locations.

Distribution of substituents in O-(2-hydroxypropyl) derivatives of cyclomalto-oligosaccharides (cyclodextrins): influence of increasing substitution, of the base used in the preparation, and of macrocyclic size

Samples of O-(2-hydroxypropyl)derivatives of cyclomaltoheptaose (beta-cyclodextrin) with increasing substitution were prepared by withdrawing aliquots at different times from a reaction mixture containing cyclomaltoheptaose and an excess of (S)-propylene oxide in 0.39 M aqueous sodium hydroxide. The distributions of substituents between the different molecules and between the different alpha-D-glucopyranosyl residues in these samples were determined by mass spectrometry and methylation analysis, respectively. The solubilities of the samples and their association constants with phenolphthalein were also determined. The relative reactivities at O-2 and O-3 versus O-6, calculated using Spurlins equations, decreased with increasing degree of substitution, probably because of steric hindrance. No significant differences were observed when different strong bases were used as promoters of the hydroxypropylation of cyclomaltoheptaose. The hydroxypropylation of cyclomaltohexaose (alpha-cyclodextrin) and cyclomalto-octaose (gamma-cyclodextrin) was briefly investigated.

Structural studies of the capsular polysaccharide from streptococcus pneumoniae type 18f

The structure of the capsular polysaccharide (S5) elaborated by Streptococcus pneumoniae type 5 has been investigated by using n.m.r. spectroscopy, methylation analysis, and various specific degradations. It is concluded that the polysaccharide is composed of pentasaccharide repeating-units having the following structure: (Formula: see text) In this structure, L-PneNAc stands for 2-acetamido-2,6-dideoxy-L-talose (pneumosamine) and D-Sug for 2-acetamido-2,6-dideoxy-D-xylo-hexos-4-ulose. The latter sugar accounts for the lability of S5 towards alkali. N.m.r. spectra indicate heterogeneity in S5, most probably associated with the hexosyl-4-ulose residue.

Synthesis of some 2-O-(2-hydroxyalkyl) and 2-O-(2,3-dihydroxyalkyl) derivatives of cyclomaltoheptaose

On alkylation of cyclomaltoheptaose with oxiranes, promoted by alkali of low concentration, substitution at secondary positions, particularly at O-2, is favoured. The reaction has been used to prepare the 2-O-[(R)- and (S)-2-hydroxypropyl], 2-O-(2-hydroxy-2-methylpropyl), 2-O-[(R)- and (S)-2,3-dihydroxypropyl], and 2-O-[(R)- and (S)-2,3-dihydroxy-2-methylpropyl] derivatives. Each of these derivatives is less soluble in water than cyclomaltoheptaose, and their complexes with toluene, in contrast to that of cyclomaltoheptaose, are well soluble in water.

The structure of the capsular polysaccharide from Streptococcus pneumoniae type 7B

The capsular polysaccharide elaborated by Streptococcus pneumoniae type 7B is composed of the following heptasaccharide repeating-units. [formula: see text] The identities and modes of linkage of the constituents were established using sugar, methylation, and phosphorus analysis, together with 1D- and 2D-n.m.r. spectroscopy. The sequence was established from inter-residue n.O.e. data. The structure was corroborated by n.m.r. spectroscopy, f.a.b.-m.s., and methylation analysis of the oligosaccharides isolated after partial acid hydrolysis of the polysaccharide with aqueous 48% hydrogen fluoride. It is suggested that the structural basis for the common antigenic formula in the group 7 serotypes of S. pneumoniae is the disaccharide element alpha-D-GlcpNAc-(1----2)-alpha-L-Rhap-(1----.

Structural studies of the Shigella boydii type 5 O-antigen polysaccharide

The structure of the Shigella boydii type 5 O-antigen polysaccharide has been investigated by sugar and methylation analyses, and specific degradations. It is proposed that it is composed of hexasaccharide repeating units with the following structure. The repeating unit also contains an O-acetyl group, linked to one of the primary positions. [formula: see text]