Synthesis of structural elements of the capsular polysaccharides of Streptococcus pneumoniae types 6A and 6B

Abstract

(27), which are structural elements of the capsular polysaccharides of Streptococcuspneumoniae types 6A and6A X = 3,6B X = 4}, have been synthesised. Ethyl 3-O-allyl-2,4,6-&i-0-benzyl-l-thio$-D-glucopyranoside (3) was coupled with benzyl2,4-di-0-benzyl-a-L-rhamnopyranoside (4), and subsequent deallylation (-14) and debenzylation gave 15. Condensation of 14 with ethyl 2,3,4,6-tetra-O-benzyl-I-thio-B-D-galactopyranoside (2) followed by debenzylation gave 17. Acetylation of I7 followed by removal of AcO-I, conversion into the imidate, coupling with 1,2,4,5-tetra-0-benzyl-D-ribitol (ll), deacetylation, anddebenzylation gave23. Coupling of the imidate with l-0-allyloxycarbonyL2,3,Mri-0-benzyl-Dribitol(l2) followed by deallyloxycarbonylation, deacetylation, and debenzylation yielded 27.

Chemical and Chemo-Enzymatic Syntheses of Glycans Containing Ribitol Phosphate Scaffolding of Matriglycan

“…The liberated 5-position of 14 was treated with salicylchlorophosphite in CH 3 CN-pyridine 16 to give the corresponding triethylammonium phosphonate (15) in 77% yield, which was activated with pivaloyl chloride (PivCl) in pyridine. 17 Compound (9) was then added to form a phosphonic diester (16) in 62% yield, the oxidation of which with I 2 in aq pyridine afforded 17 in 98% yield. The tertbutyldiphenylsilyl (TBDPS) group of 17 was removed with n-Bu 4 NF (TBAF, tetra-n-butylammonium fluoride) in THF for 4 days to give 18 in quantitative yield.…”

Synthesis and Reactions of Five-Membered Heterocycles Using Phase Transfer Catalyst (PTC) Techniques

“…4-(benzyloxy)-2-[(2E)-but-2-en-1-yloxy]-5-methoxytetrahydrofuran-3-ol 317 was obtained from benzylation of 2-O-methyl-5-O-crotyl-, -D-ribofuranoside 316 using benzyl bromide in aq. solution of NaOH/CH 2 Cl 2 and TBAB as a catalyst [103] (Figure 111).…”

β-1,4-Galactosyltransferase-catalyzed Synthesis of the Branched Tetrasaccharide Repeating Unit of Streptococcus pneumoniae Type 14

“…The residue was dissolved in butanol (15 mL) and 1,2-diaminoethane (3 mL), and the mixture heated under Ar for 24 h at 80 C, then co-concentrated with toluene. (10). To a solution of trisaccharide 7 (6.3 mg, 11 mmol) in 50 mM sodium cacodylate bu er pH 7.5 (600 mL) containing 5 mM MnCl 2 , bovine serum albumin (0.5 mg) and NaN 3 (0.02%), were added alkaline phosphatase (4 U), UDP-galactose (6.5 mg, 11 mmol) and b-1,4-galactosyltransferase (1 U).…”