نتایج جستجو برای: racemization

تعداد نتایج: 821  

Journal: :Journal of the American Chemical Society 2006

Journal: :Journal of biological physics 2014
Arash Tirandaz Farhad Taher Ghahramani Afshin Shafiee

We explore the interplay between tunneling process and chiral interactions in the discrimination of chiral states for an ensemble of molecules in a biological environment. Each molecule is described by an asymmetric double-well potential and the environment is modeled as a bath of harmonic oscillators. We carefully analyze different time-scales appearing in the resulting master equation at both...

Journal: :Chemical & pharmaceutical bulletin 2001
T Yanagi K Kikuchi H Takeuchi T Ishikaw T Nishimura T Kamijo I Yamamoto

We describe the practical synthetic route for (2S)-7-methoxy-1,2,3,4-tetrahydro-2-naphthylamine 1(2S)-2-amino-7-methoxytetraline; (S)-AMT]. (2R)-2-(3-Methoxybenzyl)succinic acid [(R)-1] was obtained by the optical resolution of 2-(3-methoxybenzyl)succinic acid (1) as the salt of (1R,2S)-2-(benzylamino)cyclohexylmethanol (7), and (R)-1 was converted to the optically active (2S)-7-methoxy-1,2,3,4...

Journal: :Agricultural and Biological Chemistry 1966

Journal: :Acta Chemica Scandinavica 1967

2000
Barbara A. Cohen Christopher F. Chyba

Meteorites may have contributed amino acids to the prebiotic Earth, affecting the global ratio of right-handed to left-handed (D/ L) molecules. We calculate D/ L ratios for seven biological, α-hydrogen, protein amino acids over a variety of plausible parent body thermal histories, based on meteorite evidence and asteroid modeling. We show that amino acids in meteorites do not necessarily underg...

Journal: :Chemical communications 2010
Vanessa Kar-Yan Lo Cong-Ying Zhou Man-Kin Wong Chi-Ming Che

Silver(I) salts mediated stereospecific transformation of optically active propargylamines to axially chiral allenes with excellent enantioselectivities (17 examples with 96-99% ee; one substrate with 91% ee) without subsequent racemization.

Journal: :Organic letters 2007
Ayman El-Faham Fernando Albericio

A novel proton acceptor coupling reagent shows superiority to those described previously. The oxygen in the carbocation moiety confers more solubility to the reagent. Furthermore, it enhances coupling yields and decreases racemization, allowing the use of 1 equiv of base.

Journal: :Chemistry & biodiversity 2010
Mendel Friedman

Exposure of food proteins to certain processing conditions induces two major chemical changes: racemization of all L-amino acids (LAAs) to D-amino acids (DAAs) and concurrent formation of cross-linked amino acids such as lysinoalanine (LAL). The diet contains both processing-induced and naturally-formed DAA. The latter include those found in microorganisms, plants, and marine invertebrates. Rac...

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