95904-24-8Relevant articles and documents
Conformational preference in bis(porphyrin) tweezer complexes: A versatile chirality sensor for α-chiral carboxylic acids
Tanasova, Marina,Borhan, Babak
supporting information; experimental part, p. 3261 - 3269 (2012/07/01)
Metallated porphyrin tweezers have demonstrated a remarkable ability to function as reporters of absolute stereochemistry for a number of different classes of organic molecules. Flexibility in binding, however, can result in an ensemble of different Exciton Coupled Circular Dichroism (ECCD) active conformations that could lead to variable results. Linker flexibility was found to be a key determinant of binding conformation. Experimental results indicate that a balance between linker flexibility and rigidity could yield an optimum porphyrin tweezer that stabilizes a common conformation for all bound chiral guests. This leads to a more simplified approach to absolute stereochemical determination of asymmetry for small organic molecules. This was demonstrated by the use of a C3-linked zincated porphyrin tweezer that yields a common conformational preference for a variety of α-chiral carboxylic acids derivatized with a diamine carrier. Copyright
An unusual conformation of α-haloamides due to cooperative binding with zincated porphyrins
Tanasova, Marina,Yang, Qifei,Olmsted, Courtney C.,Vasileiou, Chrysoula,Li, Xiaoyong,Anyika, Mercy,Borhan, Babak
supporting information; experimental part, p. 4242 - 4253 (2011/02/25)
CD and NMR spectroscopic evidence of cooperative binding between an α-halogen atom and a carboxamide group with a zinc porphyrin leads to an unprecedented conformation for the determination of the absolute stereochemistry of α-haloamides (α-halocarboxylic acids derivatized with 1,4-phenylenediamine) through the use of exciton-coupled circular dichroism (ECCD). With the use of chiral lactams, whose rotomeric contributions are minimized, both ECCD and NMR spectroscopy demonstrate that the porphyrin favors binding to the side of the sterically more demanding halogen atom as compared to the smaller hydrogen atom. In all, the data is strongly suggestive of an unusual conformation not observed before for α-chiral amides. A mnemonic for determining the absolute stereochemistry of α-halogenated carboxylic acids is provided.
Synthesis and study of new α-haloacid ferroelectric liquid crystal derivatives. MM2 approach to the molecular structure-ferroelectric activity relationship
Sierra,Serrano,Ros,Ezcurra,Zubía
, p. 7645 - 7651 (2007/10/02)
In order to understand the structural factors that influence ferroelectric properties, three new series (F, Cl, and Br) of chiral naphthalene-ring derived compounds were synthesized, and their ferroelectric properties [spontaneous polarization (Ps) and response time (τ)] were evaluated in the pure compound. The chiral tails are α-halo acids derived from L-α-amino acids: L-α-alanine (1), L-leucine (2), L-isoleucine (3), and L-valine (4), with a fluorine, chlorine, or bromine atom in the chiral center. The highest Ps values were obtained for compounds containing a fluorine or chlorine atom in their asymmetric center and with chiral tail derived from L-isoleucine (3) (F-3, 102 nC/cm2; Cl-3, 100 nC/cm2). The steric requirements of the halogen atom and the bulky alkyl group in the asymmetric center determine the most stable conformations of these chiral tails, which have been studied by molecular mechanic empirical calculations, MM2. MM2 calculations prove to be a successful tool for understanding how the structure of the lateral chiral tail affects molecular arrangement and, as a consequence, the ferroelectric properties of the materials.
