27025-25-8Relevant articles and documents
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.
Synthesis of ortho-carboranyl derivatives of (S)-asparagine and (S)-glutamine
Gruzdev,Levit,Olshevskaya,Krasnov
, p. 769 - 776 (2017/07/07)
(S)-Asparagine and (S)-glutamine ortho-carboranyl derivatives with free amino and carboxy groups in the α-position were synthesized. By an example of Nγ-(1,2-dicarba-closo-dodecarboran-3-yl)-(S)-glutamine it was demonstrated that the developed synthetic approach carboranyl derivatives of amino acids allowed the preparation of optically pure isomers.
Relationships between the structure of 6-allyl-6,8-diazabicyclo[3.2.2]nonane derivatives and their σ receptor affinity and cytotoxic activity
Holl, Ralph,Schepmann, Dirk,Gruenert, Renate,Bednarski, Patrick J.,Wuensch, Bernhard
body text, p. 777 - 793 (2009/08/07)
A series of bridged piperazine derivatives was prepared and the affinity toward σ1 and σ2 receptors by means of radioligand binding assays as well as the inhibition of the growth of six human tumor cell lines was investigated. All possible stereoisomers of the 2-hydroxy, 2-methoxy, 2,2-dimethoxy, 2-oxo, and 2-unsubstituted 6,8-diazabicyclo[3.2.2]nonanes were prepared in a chiral pool synthesis starting with (S)- and (R)-glutamate. A Dieckmann analogous cyclization was the key step in the synthesis of the bicyclic framework. The configuration in position 2 was established by a diastereoselective LiBH4 reduction and subsequent Mitsunobu inversion. Structure-affinity relationships demonstrate that substituents in position 2 decrease σ1 receptor affinity which might be due to unfavorable interactions with the σ1 receptor protein. Without a substituent in position 2 high σ1 affinity was obtained (23a ((+)-(1S,5S)-6-allyl-8-(4-methoxybenzyl)-6,8-diazabicyclo[3.2.2]nonane): Ki = 11 nM). Experiments with six human tumor cell lines showed a weak but selective growth inhibition of the human small cell lung cancer cell line A-427 by the methyl ethers ent-16b (IC50 = 18.9 μM), 21a (IC50 = 16.4 μM), ent-21a (IC50 = 20.4 μM), and 21b (IC50 = 27.1 μM) and the unsubstituted compounds 23a and 23b (42% inhibition at 20 μM).
