In this paper, we describe the stereospecific synthesis and functional properties of C 2- and C 1-symmetric pyrene-fused [5]­helicene molecules 1 and 2 connected via hexagonal and heptagonal rings, respectively. Both molecules showed high configurational stability and distinct functional properties, which were attributed to the fusing mode of [5]­helicene with the pyrene and molecular symmetry. The estimated Gibbs activation energy for enantiomerization of 2 is one of the highest reported values for any π-conjugated molecules incorporating [5]­helicene moiety.

S-fimbriated Escherichia coli strains cause sepsis and meningitis in newborns and are known to recognize the carbohydrate sequence sialyl-(α2-3)-galactoside. We show that adhesion of cloned S-fimbriated E. coli to human epithelial cells is inhibited Fab independently by sialyloligosaccharides on secretory immunoglobulin A (s-IgA). This indicates an anti-infective function of s-IgA (Fc), particularly in early human milk.

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