Gas-phase enantioselectivity of chiral amido[4]resorcinarene receptors.
Diastereomeric proton-bound [1(L)HA]+ complexes between selected amino acids (A=phenylglycine (Phg), tryptophan (Trp), tyrosine methyl ester (TyrOMe), threonine (Thr), and allothreonine (AThr)) and a chiral amido[4]resorcinarene receptor (1(L)) display a significant enantioselectivity when undergoing loss of the amino acid guest A by way of the enantiomers of 2-aminobutanes (B) in the gas phase. The enantioselectivity of the B-to-A displacement is ascribed to a combination of thermodynamic and kinetic factors related to the structure and the stability of the diastereomeric [1(L)HA]+ complexes and of the reaction transition states. The results of the present and previous studies allow classification of the [1(L)HA]+ complexes in three main categories wherein: i) guest A does not present any additional functionalities besides the amino acid one (alanine (Ala), Phg, and phenylalanine (Phe)); ii) guest A presents an additional alcohol function (serine (Ser), Thr, and AThr); and iii) guest A contains several additional functionalities on its aromatic ring (tyrosine (Tyr), TyrOMe, Trp, and 3,4-dihydroxyphenylalanine (DOPA)). Each category exhibits a specific enantioselectivity depending upon the predominant [1(L)HA]+ structures and the orientation of the 2-aminobutane reactant in the relevant adducts observed. The results may contribute to the understanding of the exceptional selectivity and catalytic properties of enzyme mimics towards unsolvated biomolecules.
Botta
Bruno
B
Dipartimento degli Studi di Chimica e Tecnologia delle Sostanze Biologicamente Attive, Università La Sapienza, 00185 Roma, Italy.
Caporuscio
Fabiana
F
D'Acquarica
Ilaria
I
Delle Monache
Giuliano
G
Subissati
Deborah
D
Tafi
Andrea
A
Botta
Maurizio
M
Filippi
Antonello
A
Speranza
Maurizio
M
D000596:Amino Acids / Q000737:chemistry*; D047250:Calixarenes / Q000737:chemistry; D004295:Dihydroxyphenylalanine / Q000737:chemistry; D005740:Gases / Q000737:chemistry; D006838:Hydrocarbons / Q000737:chemistry*; D007700:Kinetics; D012118:Resorcinols / Q000737:chemistry*; D021241:Spectrometry, Mass, Electrospray Ionization; D013237:Stereoisomerism
D000596:Amino Acids; D005740:Gases; D006838:Hydrocarbons; D012118:Resorcinols; C447799:resorcin(4)arene receptor; D047250:Calixarenes; D004295:Dihydroxyphenylalanine