Chemical synthesis of the pyruvic acetal-containing trisaccharide unit of the species-specific glycopeptidolipid from Mycobacterium avium serovariant 8

l‐Rhamnosylation: The Solvent is the Solution

“…2‐Methylnaphthylprotection (Nap) of 2 afforded 3 , and subsequent acid hydrolysis of the isopropylidene protection group with trifluoroacetic acid (TFA) gave diol 4 in excellent yield. In the next step, phase‐transfer catalysis was used to selectively protect the C‐2 position with a p ‐chlorobenzyl ( p ‐BnCl) group to give 5 . The chloro substituent deactivates the aromatic ring, which makes it less prone to participate in an intramolecular Friedel–Craft‐type alkylation, which is a known side‐reaction in glycosylations involving highly reactive donors .…”

The synthesis and biological evaluation of mycobacterial p-hydroxybenzoic acid derivatives (p-HBADs)

“…1 H-NMR (400 MHz, CDCl 3 , δ): 8.01, 7.11 (2H, d, J = 8.7 Hz, Ar-H), 5.67 (1H, d, J 1,2 = 1.4 Hz, H1), 3.94 (1H, dd, J 3,2 = 3.7 Hz, J 3,4 = 9.6 Hz, H3), 3.90 (3H, s, CO 2 CH 3 ), 3.70 (1H, dd, J 2,1 = 1.4 Hz, J 2,3 = 3.7 Hz, H2), 3.67 (1H, m, H5), 3.56 (3H, s, OCH 3− ), 3.47 (1H, app t, J = 9.6 Hz, H4), 1.27 (3H, d, J 6,5 = 6.5 Hz, H6). 13 Compound 15 46 9 (1.00 g, 2.52 mmol) was dissolved in DMF (10 mL) with NaH (121 mg, 3.03 mmol) and BnBr (0.375 mL, 3.03 mmol) under N 2 . After 18 h the reaction was quenched with ca.…”

Chemical Synthesis Elucidates the Immunological Importance of a Pyruvate Modification in the Capsular Polysaccharide of Streptococcus pneumoniae Serotype 4

“…Synthesis of tetrasaccharide 2, which contains the trans-2,3-(S)-pyruvate,b egan with the removal of the 2-naphthylmethyl (Nap) protecting groups from 19 by using DDQ to obtain diol 20 (Scheme 2). Installation of the trans-2,3-pyruvate proved cumbersome since the only reported procedure for the formation of a trans-2,3-pyruvate and the many reported protocols for the formation of 4,6-pyruvates [14] lead to cleavage of the esters and acetals.T he trans-2,3-pyruvate was finally incorporated into tetrasaccharide 20 by using methyl 2, 2-bis(ethylthio) propionate [15] in the presence of DMTST as an activator to obtain 21 as am ixture of R and S isomers.T he reaction was not completely selective and the stereochemistry could not be assigned at this stage.Atwo-step removal of the esters and the permanent protecting groups gave 2 after HPLC purifi-cation. The S stereochemistry of the pyruvate in 2 was confirmed by 2D NMR spectroscopy (see the Supporting Information).…”