113597-96-9Relevant academic research and scientific papers
Induced-fit in the gas phase: Conformational effects on the enantioselectivity of chiral tetra-amide macrocycles
Gasparrini, Francesco,Pierini, Marco,Villani, Claudio,Filippi, Antonello,Speranza, Maurizio
, p. 522 - 534 (2008/10/09)
The structure, stability, and reactivity of proton-bound diastereomeric [M?H?A]+ complexes between some amino acid derivatives (A) and several chiral tetra-amide macrocycles (M) have been investigated in the gas phase by ESI-FT-ICR and ESI-ITMS-CID mass spectrometry. The displacement of the A guest from the diastereomeric [M?H?A]+ complexes by reaction with the 2-aminobutane enantiomers (B) exhibits a distinct enantioselectivity with regards to the leaving amino acid A and, to a minor extent, to the amine reactant B. The emerging selectivity picture, discussed in the light of molecular mechanics calculations, provides compelling evidence that the most stable conformers of the selected chiral tetraamide macrocycles M may acquire in the gas phase a different conformation by induced fit on complexation with some representative amino acid derivatives A. This leads to the coexistence in the gas phase of stable diastereomeric [M?H?A] + eq-eq and ax-ax structures, in proportions depending on the configuration of A and M and characterized by different stability and reactivity toward the 2-aminobutane enantiomers. The enantioselectivity of the gas-phase A-to-B displacement in the diastereomeric [M?H?A]+ complexes essentially reflects the free energy gap between the homo- and heterochiral [M?H?A]+ complexes, except when the tetra-amidic host presents an additional macrocycle generated by a decamethylene chain. In this case, the measured enantioselectivity mostly reflects the stability difference between the relevant diastereomeric transition structures.
Synthesis, Characterization, and X-ray Structure of the Ruthenium "Picnic-Basket" Porphyrins
Collman, James P.,Brauman, John I.,Fitzgerald, Jeffrey P.,Hampton, Philip D.,Naruta, Yoshinori,et al.
, p. 3477 - 3486 (2007/10/02)
The synthesis and characterization of a new class of sterically protected porphyrins, the "picnic-basket" porphyrins, are presented.These tetraarylporphyrins, which were prepared as cytochrome P-450 active-site analogues, bear a rigid superstucture on one face of the porphyrin macrocycle.The cavity defined by the appended superstructure may be readily varied in size, chirality, and functionality.In addition, the synthesis and characterization, including an X-ray structure, of several ruthenium picnic-basket porphyrin carbonyl complexes are reported.The regiochemistry of axial ligation in these ruthenium derivatives has been determined by 1H NMR spectroscopy.
