| Chirality is a common phenomenon in nature.Chiral drugs have similar physical and chemical character but some of these exhibit entirely different biological activity in human body,leading to chiral recognition is significance in the pharmaceutical chemistry.Recently,artificial receptor were synthesized continually and applied to chiral recognition widely,therein chiral molecular tweezers artificial acceptor have been concerned for their simple and easily modified structures.Isosteviol obtained by steviol acid hydrolysis is tetracyclic diterpenoid with ent-beyerane skeleton.Isosteviol is an ideal unit in building chiral molecular tweezers for its stable structure and multiple chiral centers.A series of chiral molecular tweezers containing arm like isosteviol and spacer like 1,2-cyclohexanediamine,binaphthol,open chain pniyethers and benzene have been designed and synthesised in this letter.Their structures were confirmed by IR,1H-NMR,13C-NMR,MS.The chiral recognition properties of these chiral molecular tweezers were evaluated towards D/L-phenylalanine methyl ester hydrochloride and D/L-phenylglycine methyl ester hydrochloride by UV-vis titration,including the binding constant,free energy changes and KD/KL.The results show that the molecular tweezers compounds are highly enantioselective towards D/L-amino acid methyl ester hydrochloride,host-guest forming a 1:1 type of supramolecular complexes.The molecular tweezers which is attact spacer to 16 position on isosteviol have higher enantioselectivity than attact spacer to 19 position.The assume is compounds that is attact spacer to 16 position on isosteviol may have a spatial structure and closely match with guest in the process of chiral recognition.Compound 5 show a chiral recognition ability towards D/L-phenylglycine methyl ester hydrochloride at KD/KL=0.43,Compound?R,R?-13 show a chiral recognition ability towards D/L-phenylglycine methyl ester hydrochloride at KD/KL=0.43. |
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