O-acylation process

The O-acylation process is much more rapid than the C-acylation one and, in general, the ortho-hydroxyaryl ketones are prevalent with respect to para-isomers. This is probably due to the ortho-directing effect of the OH group, which can stabilize by hydrogen bond the transition state leading to the ortho attack (Scheme 5.1) in a way resembling thecomplex-induced proximity effect (CIPE). ... 

HSQC NMR spectra of the O-deacylated lipopolysaccharide and the lipid-free PS in conjunction with chemical shift predictions made by the CASPER program allows to identify the positions of O-acylation process. The new approach was successfully implemented by Widmalm et al. in the structural elucidation of the O-antigen PS of E. coli 059. The algorithm used in this methodology was demonstrated as flowchart in Fig. 2a and the top-ranked structure of repeating unit of O-deacetylated repeating unit of the O-antigen PS of E. coli 059 in Fig. 2b. 

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