Linker dependence and disaccharides

The observed stability constants (Afobs) for compounds 140( =3)-145( =g) and 146(pyrene) with saccharidcs, which have the ability to form a furanose ring with a jjn-periplanar anomeric hydroxyl pair (o-glucose, melibiose, o-fructose and lactulose) are large, consistent with our understanding of the boronic acid diol interaction. Equally, the low or zero values of the observed stability constants (Afobs) for saccharides unable to form a furanose ring with a. syw-periplanar anomeric hydroxyl pair (maltose and leucrose) are also consistent with current thinking. 

The importance of this work compared to previous evaluations is that it was the first to probe the efficacy of diboronic acid units in disaccharide recognition. From previous results it was apparent that the second binding site could bind monosaccharides at their 3, 4, 5 or 6 positions. What had not 

It is clear from the data that where the secondary binding sites are blocked on saccharides i.e. on maltose, lactulose and leucrose, no increased stabiUty is derived from the introduction of a second boronic acid unit. 

Overall selectivity is retained for the monosaccharides with the abiUty to form cyclic complexes. An analogous trend is observed for disaccharides, which also have the ability to form cyclic complexes, however, the observed stabihty constants (Kobs) are weaker in these instances, a characteristic attributed to the increased steric hindrance at the secondary binding site. 

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