Capsular polysaccharide of Streptococcus pneumoniae type 19F: synthesis of the repeating unit

(α‐L‐Rhamnopyranosyl)methylphosphonic Acids: Experimental Evidence of the Analogy with α‐L‐Rhamnopyranosyl Phosphate

“…The 2-hydroxy group of the known allyl rhamnopyranoside 5 [7] was protected as a pmethoxybenzyl ether, and the allyl group was then removed under standard conditions to afford rhamnopyranose 7 in 96 % yield. Reaction of 7 with the tetramethyl methylenediphosphonate anion [5] gave an α,β-unsaturated phosphonate, which spontaneously underwent an intramolecular Michael reaction to yield compound 8 in 77 % yield.…”

“…Allyl 3,4-di-O-benzyl-α-l-rhamnopyranoside (5) [7] (1.50 g, 3.90 mmol) was dissolved in dry THF (15 mL), and p-methoxybenzyl chloride (0.64 mL, 4.68 mmol) and NaH (60 % dispersion in mineral oil, 0.31 g, 7.80 mmol) were added, and the mixture was stirred at room temperature for 4 d. It was then quenched with MeOH, concentrated, and the residue dissolved in EtOAc (40 mL), and washed with water (50 mL). The aqueous layer was further extracted with EtOAc (2 × 40 mL).…”

A New Preparation of the Disaccharide β‐D‐ManNAcp‐(1 → 4)‐D‐Glc from Lactose Through a Highly Stereoselective β‐D‐Galpto β‐D‐ManNAcpTransformation

“…The structure of 1 and its anomeric composition as an about 45 : 55 a-and b-pyranose mixture were easily established on the basis of 13 C spectra. The chemical shift of the b-mannosamine carbons were, in fact, coincident for the two anomers (see Experimental) and strictly similar to those reported for other 2-acetamido-2-deoxy-b-D-mannopyranose units.…”

“…1 H NMR spectra were recorded with a Bruker AC 200 instrument at 200 MHz in the stated solvent (Me 4 Si was used as the internal standard). 13 C NMR spectra were recorded with the same spectrometer at 50 MHz. Assignments were made with the aid of DEPT and HETCOR experiments and by comparison with those of known compounds.…”

On the Influence of the C2−O2 and C3−O3 Bonds in 4,6-O-Benzylidene-Directed β-Mannopyranosylation and α-Glucopyranosylation

“…4,[6][7][8][9] This contrast in selectivity, originally seen with donors 1 and 2 ,7 on activation with trifluoromethanesulfonic anhydride in the presence of a hindered non-nucleophilic base such as 2,4,6-tri-tert-butylpyrimidine (TTBP), 10 and subsequently observed with donors 3 and 4, on activation with 1-benzenesulfinyl piperidine (BSP) and triflic anhydride, 4 is reflected in the reduced β-selectivity seen on going from the 3,4-O-carbonate protected 6-deoxymanno (rhamno) donor 5 to the corresponding gluco donor 6. 11…”