Assembly of the peptidoglycan is crucial in maintaining viability of bacteria and in defining bacterial cell shapes, both of which are important for existence in the ecological niche that the organism occupies. Here, eight crystal structures for a member of the cell-shapedetermining class of Campylobacter jejuni, the peptidoglycan peptidase 3 (Pgp3), are reported. Characterization of the turnover chemistry of Pgp3 reveals cell wall D,D-endopeptidase and D,D-carboxypeptidase activities. Catalysis is accompanied by large conformational changes upon peptidoglycan binding, whereby a loop regulates access to the active site. Furthermore, prior hydrolysis of the crosslinked peptide stem from the saccharide backbone of the peptidoglycan on one side is a prerequisite for its recognition and turnover by Pgp3. These analyses reveal the noncanonical nature of the transformations at the core of the events that define the morphological shape for C. jejuni as an intestinal pathogen.
Enantioselective syntheses O 0031Asymmetric Protonation of Ketone Enolates Using Chiral β-Hydroxyethers: Acidity-Tuned Enantioselectivity. -Some new chiral β-hydroxyethers like (I) are prepared and used for enantioselective protonation of achiral enolates. Asymmetric induction is found to depend on the acidity of the proton source. In most cases best selectivity is observed using (Ic). The protonation of aliphatic enolates proceeds with very low selectivity. -(KIM*, B. M.; KIM, H.; KIM, W.; IM, K. Y.; PARK, J. K.; J.
Alkynes Q 0087 DBU-Promoted Facile, Chemoselective Cleavage of Acetylenic TMS Group. -It is disclosed that DBU is highly efficient even in the presence of bulkier alkyl silyl ethers or other base-sensitive groups. -(YEOM, C.-E.; KIM, M. J.; CHOI, W.; KIM*, B. M.; Synlett 2008, 4, 565-568; Dep. Chem., Coll. Nat. Sci., Seoul Natl. Univ., Seoul 151-742, S. Korea; Eng.) -Mais 28-068
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