A linear correlation was established between aspartic acid racemization ratio from cave bear dentine collagen and absolute dating. The high correlation coefficient obtained allowed age calculation through amino acid racemization. Aspartic acid and glutamic acid racemization kinetics have also been explored in dentine from a North American black bear (Ursus americanus Pallas). Three sample sets ...

The ratios of d- versus l-amino acids can be used to infer the sources and composition of sedimentary organic matter. Such inferences, however, rely on knowing the rates at which amino acids in sedimentary organic matter racemize abiotically between the d- and the l-forms. Based on a heating experiment, we report kinetic parameters for racemization of aspartic acid, glutamic acid, serine, and a...

In recent years many efforts have been made aiming to define the conditions of the reaction of substitution which lead to inversion of configuration (Walden inversion). The investigations in this direction of Polanyi et al.,’ of Olson,2 of Hughes, Ingold, et aL3 are most outstanding. Polanyi et al. and Olson came to the conclusion that all reactions of substitution by a negative group or ion ar...

Production of optically pure products can be based on simple unselective synthesis of racemic mixtures combined with a subsequent separation of the enantiomers. However, this approach suffers from a 50% yield limitation which can be overcome by racemization of the undesired enantiomer and recycling. Application of biocatalyst for the racemization steps offers an attractive option for high-yield...

Despite the importance of enantiopure chiral sulfoxides, few methods exist that allow for their deracemization. Here, we show that an enantiopure sulfoxide can be produced from the corresponding racemate using Viedma ripening involving rearrangement-induced racemization. The suitable candidate for Viedma ripening was identified from a library of 24 chiral sulfoxides through X-ray structure dete...

In a previous investigation du Vigneaud and Sealock (1) have reported that the sodium salt of acetyl-l-tryptophane in aqueous solution at 35-40” is completely racemized by acetic anhydride within a few hours. The ease of racemization and particularly the mild conditions under which the reaction occurred seemed to us to offer an excellent method for racemizing amino acids if the reaction should ...

In proteins and peptides, d-aspartic acid (d-Asp) and d-β-Asp residues can be spontaneously formed via racemization of the succinimide intermediate formed from l-Asp and l-asparagine (l-Asn) residues. These biologically uncommon amino acid residues are known to have relevance to aging and pathologies. Although nonenzymatic, the succinimide racemization will not occur without a catalyst at room ...

a method is described by which it is possible to determine the high barrier to ring inversion and hindered rotation by neat racemization of optically active compounds when the racemization is caused by ring inversion or hindered rotation. the method is based preparation of sufficiently pure enantiomers, mainly by chromatography on swollen microcrystalline triacetylcellulose (tac). by this techn...