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We developed a chiral symmetry breaking method for monoacylated meso diols. The X‐ray crystal structure analysis of monoacylated 1,4‐anhydroerythritols, meso cyclic diols with a cis configuration, revealed that the O‐(p‐anisoyl) derivative crystallized as a racemic conglomerate of the P212121 crystal system. It was confirmed that the substrate racemized by intramolecular transfer of the acyl group in the presence of a catalytic amount of base. Evaporating the solvent gradually from the solution or Viedma ripening to promote crystallization‐induced deracemization efficiently led to enantiomer crystals. These results provide the first successful example of asymmetric expression and amplification by deracemization of sugar derivatives without an external chemical chiral source. Furthermore, we applied this methodology to acyclic meso‐1,2‐diols. Three O‐monoacylated substrates were successfully deracemized to 99 % ee by Viedma ripening. We also developed asymmetric desymmetrization of meso‐1,2‐diols by combining acylation and crystallization‐induced deracemization. [ABSTRACT FROM AUTHOR]

Atroposelective resolution for axially chiral nicotinamides was achieved by dynamic chiral salt formation with L‐DBTA using six types of nicotinamides that could not be optically resolved by the preferential crystallization method. Kinetic studies of their racemization indicated that the chiral conformation was retained for a significant period of time. Two methods of crystallization‐induced asymmetric transformation were examined by dynamic diastereomeric salt formation: solvent evaporation from a supersaturated solution, and attrition‐enhanced asymmetric transformation. The attrition method was more effective for asymmetric amplification of diastereomeric salts of axially chiral materials. Attrition of equimolar amount of the nicotinamide salts with L‐DBTA converged to one diastereomer salts, and the corresponding enantiomers in 87–99 % ee were obtained after the chiral acid was removed. Changing the ratio of two of the nicotinamides with L‐DBTA to 1 : 2 inverted the axial chirality. [ABSTRACT FROM AUTHOR]

Attrition‐enhanced deracemization of two axially chiral nicotinamides, crystallizing as a conglomerate of a P21 crystal system, was performed. N,N‐Dialkylnicotinamides with substituents on the 2‐ and 4‐positions of the pyridine ring exhibited stable axial chirality due to rotationally restricted scaffolds for the Ar–C(=O)N bond. Crystallization of the racemic mixtures from the melt or attrition‐enhanced deracemization led to the chiral breaking of symmetry to give 95–96 % ee of enantiomorphic crystals. [ABSTRACT FROM AUTHOR]

Dynamic enantioselective crystallization enabled the chiral symmetry breaking of two spiropyrans and one spirooxazine. The three spiro compounds afforded racemic conglomerate crystals, and easily racemized in alcoholic solution without irradiation. Optically pure enantiomorphic crystals were obtained by vapor‐diffusion crystallization or attrition‐enhanced deracemization (Viedma ripening). Their absolute configurations were determined by single‐crystal X‐ray analysis and each enantiomorphic crystal was correlated with its solid‐state circular dichroism (CD) spectrum. [ABSTRACT FROM AUTHOR]

Irradiation of prochiral ( E)-aroylacrylamide with sunlight gave single-handed pyrrolinone quantitatively and with an enantiomeric excess ( ee) of over 99 % under absolutely achiral conditions. The phenomenon was explained by photoisomerization and reversible cyclization followed by dynamic crystallization involving deracemization. [ABSTRACT FROM AUTHOR]

Single-handed α-amino acid derivatives were generated from achiral precursors without an external chiral source. Conjugate addition of phenethylamine to an achiral aroyl acrylamide under homogeneous conditions gave the α-amino amides in quantitative yields, which crystallized as a conglomerate of a P21 crystal system. Dynamic preferential crystallization or attrition-enhanced deracemization resulted in the formation of enantiomorphic crystals of 99 % ee. [ABSTRACT FROM AUTHOR]

An asymmetric photoreaction by using chirality provided by dynamic chiral salt formation was demonstrated. Crystallization of racemic 2-quinolone-3-carboxamide and 2-quinolone-4-carboxamide with enantiopure L-dibenzoyltartaric acid led to deracemization and gave high diastereomeric excess values of the crystalline salts in almost quantitative yield. The axial chirality was retained for a long period of time after the salts were dissolved in cooled solvent. The frozen chirality derived from the chiral salts was effectively transferred to the products by using a typical [2+2] photocycloaddition reaction with alkenes. [ABSTRACT FROM AUTHOR]