Rational application of self-disproportionation of enantiomers via sublimation—a novel methodological dimension for enantiomeric purifications

Influence of TiO2 on prebiotic thermal synthesis of the Gly-Gln polymer

“…In principle, the synthesis of peptides involves both the use of condensation agents as catalysts or other different conditions, such as high pressure and temperature (Fouche and Rohlfing 1976;Simoneit 2004) and melting processes (Fouche and Rohlfing 1976;Fox and Harada 1960;Rohlfing and MacAlhaney 1976). The aspect of the enantiomeric purity in these syntheses, and the possible role of self-disproportion under chromatographic or sublimation conditions have been detailed to define possible scenarios for prebiotic source of enantiomerically enriched amino acids and peptides (Soloshonok 2006;Takahashi et al 2010;Ueki et al 2010).…”

Optical Purifications via Self‐Disproportionation of Enantiomers by Achiral Chromatography: Case Study of a Series of α‐CF3‐containing Secondary Alcohols

“…1 Furthermore, it is generally accepted practice that the analytical data reported in the literature for chiral compounds are measured on samples as they are obtained by asymmetric reactions without further purification to enantiomerically pure state. In this context, one of the promising areas is the self-disproportionation of enantiomers (SDE) [3][4][5][6] demonstrating that optical purification of enantiomerically enriched compounds via separation of racemate from the excess enantiomer †7 can be achieved under achiral conditions of any type of phase-transition [8][9][10][11][12][13][14][15][16][17][18][19][20] or achiral chromatography. 2 Apparently, the major reason for reporting chiral compounds of various enantiomeric purities, is the painstaking, expensive and time-consuming efforts usually associated with the purification of enantiomerically enriched samples to optically pure form.…”

“…Consequently, the development of new, inexpensive and simple enantiomeric purification methods is of critical importance and will undoubtedly find overwhelming support from all chemistry practitioners. In this context, one of the promising areas is the self-disproportionation of enantiomers (SDE) [3][4][5][6] demonstrating that optical purification of enantiomerically enriched compounds via separation of racemate from the excess enantiomer †7 can be achieved under achiral conditions of any type of phase-transition [8][9][10][11][12][13][14][15][16][17][18][19][20] or achiral chromatography. [21][22][23][24][25] In particular, the latter approach might be a method of very general application as it can be applied for crystalline as well as liquid compounds.…”

“…5,8,[26][27][28][29][30][31][32][33][34][35] Similar to the phenomenon of nonlinear effects in asymmetric catalysis, 27,28 the origin of the SDE under the conditions of achiral chromatography is the dynamic formation of homo-or heterochiral high-order species which have different chromatographic behaviour as compared with monomers or other low-order species. [3][4][5][6] Therefore, different compounds possessing different qualities of the corresponding homo-and heterochiral interactions show different magnitude of the SDE; or readiness for separation of racemate from the excess enantiomer. Obviously, compounds possessing noticeable magnitude of SDE are of great interest both for theoretical studies as well as for the development of practical applications.…”

Organocatalytic Enantioselective Nucleophilic Alkynylation of Allyl Fluorides Affording Chiral Skipped Ene‐ynes

“…An additional set of experiments was designed to investigate the effect of substituents on the ester function in allyl fluorides 5 (entries 15,16) and trialkyl-silyl group (entries 17,18). Quite interestingly,wefound that increasing steric bulk at both positions severely hindered the reaction progress.F or…”