High alpha/beta-anomer selectivity in molecular recognition of carbohydrates by artificial receptors

[structure: see text] New effective, acyclic, pyridine-based receptors 1-3 show remarkable alpha/beta binding selectivity in the recognition of monosaccharides. They are able to participate in cooperative and bidentate hydrogen bonds with sugar hydroxyls as well as in CH-pi interactions with CH's of sugar molecules.     

Physovenines: Efficient Synthesis of (−)- and (+)-Physovenine and Synthesis of Carbarnate Analogues of (−)-Physovenine. Anticholinesterase Activity and Analgesic Properties of Optically Active Physovenines

Column chromatography of easy available (±)-physovenine ( 2 ) on cellulose triacetate afforded (?)- and (+)-physovenine ( 2a and 2b , resp.). Alkaloids 2a , b required for pharmacological testing were prepared from eserolincs ( 3a , b ) by an improved procedure. Natural (?)-physovenine ( 2a ) was equally potent in inhibiting AChE and BChE in vitro as natural physostigmine (1a), and twice as potent as the unnatural antipode 2b against AChE and 14 times as potent against BChE. Several carbamate analogs of 2a were at least as potent as the former compound in these assays. None of the compounds tested did bind to different opiate receptor or serotonine receptor preparations. Most of the compounds tested had considerable analgesic activity in the Writhing test.     

Molecular recognition of carbohydrates with acyclic pyridine-based receptors

The recognition capabilities of acyclic pyridine-based receptors toward monosaccharides were evaluated. Aminopyridine receptors based on the 2,4,6-trimethyl- or 2,4,6-triethylbenzene frame show high beta vs alpha binding selectivity in the recognition of glucopyranosides. Amidopyridine receptors, which are sterically less hindered at nitrogen, display high efficiency and an inverse selectivity. The 2-aminopyridine group has been established as a highly effective recognition group in the binding of monosaccharides. The factors influencing the binding properties of receptors 1-15, which differ in the nature and number of binding and spacer subunits used as the buildings blocks, are discussed.