نتایج جستجو برای: chiral non racemic menthol
تعداد نتایج: 1354057 فیلتر نتایج به سال:
Chirality can have unexpected consequences including on properties other than spectroscopic. We show herein that a racemic mixture of bis-urea stereoisomers forms thermodynamically stable supramolecular polymers result in more viscous solution for the pure stereoisomer. The origin this macroscopic property was probed by characterizing structure and stability assemblies. Both non-racemic form tw...
Actually this account is the story of the genesis of an invention[1]. The inventative process is not clearly understood, but one factor that seems to be important is to have a heavy infusion of naivety. That is why so frequently it is not the experts that do the inventing, but they are the ones who, that once the lead is established, come in and exploit the area. Our work is an excellent illust...
A highly stereo- and regioselective functionalisation of chiral non-racemic aziridines is reported. By starting from a parent enantioenriched aziridine and finely tuning the reaction conditions, it is possible to address the regio- and stereoselectivity of the lithiation/electrophile trapping sequence, thereby allowing the preparation of highly enantioenriched functionalised aziridines. From ch...
In this report, we have presented the first diastereoselective addition of phenylacetylene to chiral racemic chloroketones. The addition is controlled by the reactivity of the chloroketones that allowed the stereoselective reaction to be performed at -20 °C. Chiral racemic chloroketones are used in the reaction. By carefully controlling the temperature and the reaction time we were able to isol...
The study of optically active polymers is a very active research field, and these materials have exhibited a number of interesting properties. Much of the attention in chiral polymers results from the potential of these materials for several specialized utilizations that are chiral matrices for asymmetric synthesis, chiral stationary phases for the separation of racemic mixtures, synthetic mole...
Alginate-metal complexes were prepared with divalent (Ca, Ba, Zn) and trivalent metals (Fe, Al) via congealing method in form of beads. Alginate mixed metals (Ca & Fe) complexes were also prepared by simultaneous and consecutive congealing. The studied beads were blank beads and racemic ketoprofen (KTP) loaded beads. Metal content was determined by atomic absorption spectroscopy and was 1.8% to...
Eighteen (3R) and (3R,4R)-N-phenyl-, N-phenylalkyl and N-arylsuccinimides were prepared with high enantioselectivity by biotransformation of maleimides with A. fumigatus. This environmentally friendly, clean and economical procedure was performed by the whole-cell fungal bioconversion methodology. Their corresponding eighteen racemic succinimides were prepared instead by synthetic methods. Both...
The rhodium-catalyzed regio- and enantioselective amination of racemic tertiary allylic trichloroacetimidates with a variety of aniline nucleophiles is a direct and efficient route to chiral α,α-disubstituted allylic N-arylamines. We describe the first dynamic kinetic asymmetric transformations of racemic tertiary allylic electrophiles with anilines utilizing a chiral diene-ligated rhodium cata...
It has previously been shown that the use of racemic mixtures of naturally chiral macromolecules such as protein and DNA can significantly aid the crystallogenesis process, thereby addressing one of the major bottlenecks to structure determination by X-ray crystallographic methods-that of crystal growth. Although previous studies have provided convincing evidence of the applicability of the rac...
The reversible Frank model is capable of amplifying the initial small statistical deviations from the idealized racemic composition. This temporary amplification can be interpreted as a chiral excursion in a dynamic phase space. It is well known that if the system is open to matter and energy exchange, a permanently chiral state can be reached asymptotically, while the final state is necessaril...
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