A new water soluble Zn-salophen derivative as a receptor for alpha-aminoacids: unexpected chiral discrimination.
A new water soluble zinc-salophen complex with appended D-glucose moieties was synthesized and characterized. Its binding properties toward six aminoacids were investigated by UV-vis spectrophotometric titrations. Association constants showed to be unfavorably affected by increasing steric hindrance of the side chain. Quite surprisingly, different association constants were measured for the L and D enantiomers. These data suggest that aminoacids are bound via two interactions, zinc-carboxylate coordination and two hydrogen bonds between the ammonium group of the aminoacid and two oxygen atoms of one D-glucose moiety. Such conclusion is supported by the result of semiempirical (PM3) calculations. Notably, the K(L)/K(D) value of 9.6 observed for the association of phenylalanine rivals with the highest values found for the chiral recognition of aminoacids in water.
Dalla Cort
Antonella
A
Dipartimento di Chimica and IMC-CNR, Università La Sapienza, 00185 Roma, Italy. antonella.dallacort@uniromal.it
De Bernardin
Paolo
P
Schiaffino
Luca
L
D000042:Absorption; D000596:Amino Acids / Q000737:chemistry* / Q000378:metabolism; D005947:Glucose / Q000737:chemistry; D006863:Hydrogen-Ion Concentration; D008958:Models, Molecular; D008968:Molecular Conformation; D009942:Organometallic Compounds / Q000737:chemistry* / Q000378:metabolism; D012459:Salicylates / Q000737:chemistry*; D012995:Solubility; D013237:Stereoisomerism; D013379:Substrate Specificity; D013696:Temperature; D017186:Titrimetry; D014867:Water / Q000737:chemistry*; D015032:Zinc / Q000737:chemistry*
D000596:Amino Acids; D009942:Organometallic Compounds; D012459:Salicylates; D014867:Water; C090416:salophen; D005947:Glucose; D015032:Zinc