5845-53-4Relevant articles and documents
Synthesis and host-guest studies of chiral N-linked peptidoresorc[4]arenes
Botta, Bruno,D'Acquarica, Ilaria,Delle Monache, Giuliano,Subissati, Deborah,Uccello-Barretta, Gloria,Mastrini, Massimo,Nazzi, Samuele,Speranza, Maurizio
, p. 9283 - 9290 (2007)
(Figure Presented) Four cone resorc[4]arene octamethyl ethers (10, 11, ent-10, and ent-11) tetrafunctionalized at the feet with valyl-leucine [LL- (6); DD- (ent-6)] and leucyl-valine [LL- (9); DD- (ent-9)] methyl esters have been synthesized. These compounds, obtained by conjugation of macrocycle tetracarboxylic acid chlorides with the appropriate terminal amino groups of the above dipeptides, are N-linked peptidoresorc[4]arenes. We found that these macrocycles (M) are capable of recognizing the homologue dipeptides as guests (G), both in solution and in the gas phase, by forming relatively stable host-guest complexes ([M·G]), resistant to chromatographic purification but not to heating. Complexation phenomena between M and G in solution were investigated by NMR methods, including NMR DOSY experiments, for the detection of translational diffusion. Heteroassociation constants of 2030 and 186 M -1 were obtained by the Foster-Fyfe method for the complexes [10·6] and [10·ent-6], respectively, the latter being comparable to the self-association constant of dipeptide itself. Conversely, the structural features of the proton-bound complexes [M·H·Gn] + (n = 1, 2), generated in the gas phase by electrospray ionization mass spectrometry (ESI-MS), were investigated by collision-induced dissociation (CID) experiments. In both cases, the four N-linked peptidoresorc[4]arenes were shown to act as synthetic receptors and to recognize the homologue dipeptide by means of hydrogen bonds.
Photochemical Deracemization at sp3-Hybridized Carbon Centers via a Reversible Hydrogen Atom Transfer
Bach, Thorsten,Breitenlechner, Stefan,Gro?kopf, Johannes,Plaza, Manuel,Seitz, Antonia,Storch, Golo
supporting information, p. 21241 - 21245 (2021/12/27)
A photochemical deracemization of 5-substituted 3-phenylimidazolidine-2,4-diones (hydantoins) is reported (27 examples, 69%-quant., 80–99% ee). The reaction is catalyzed by a chiral diarylketone which displays a two-point hydrogen bonding site. Mechanistic evidence (DFT calculations, radical clock experiments, H/D labeling) suggests the reaction to occur by selective hydrogen atom transfer (HAT). Upon hydrogen binding, one substrate enantiomer displays the hydrogen atom at the stereogenic center to the photoexcited catalyst allowing for a HAT from the substrate and eventually for its conversion into the product enantiomer. The product enantiomer is not processed by the catalyst and is thus enriched in the photostationary state.
Cocrystallization of Chiral N7,N16-bis (S-1-Phenylethyl)-1,4,10,13-Tetraoxo-7,16-Diazacyclooctadecane-7,16-Dicarboxamide with Hydrochlorides of Methyl Ethers of Leucine and Valine Enantiomers
Fonari,Pluzhnik-Gladyr,Kamalov,Kravtsov, V. Kh.
, p. 143 - 150 (2019/04/30)
An attempt to co-crystallize N7,N16-bis(S-1-phenylethyl)-1,4,10,13-tetraoxo-7,16-diazacyclooctadecane-7,16-dicarboxamide (1) with hydrochlorides of methyl ethers (HCMEs) of L- and D-valine and also L- and D-leucine results in separate crystallization of diazacrown-ether 1 (or its monohydrate 1·H2O) and HCMEs of respective α-amino acids. Crystal structures of D-leucine 1·H2O (1) and HCME (2) compounds, which were not described previously, are solved by single crystal X-ray diffraction.
