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# Chiral Selectivity in the Achiral Amino Acid Glycine

dataset

posted on 2019-12-12, 13:33 authored by Henri Brunner, Takashi Tsuno, Gábor BalázsA Cambridge Structural Database (CSD) search for the
zwitterion
of glycine, the only natural amino acid which does not have a chiral
center at C

_{α}, and its derivatives H_{3}N–C_{α}H_{2}–C′(O_{cis})O_{trans}(H/R/M) gave 425 hits, 420 of which are chiral because of the ψ conformation with regard to the central C′–C_{α}bond (ψ = O_{cis}C′C_{α}N ≠ 0 or 180°). Chiral ψ conformations distort the planar carboxylic group C_{α}C′(O_{cis})O_{trans}group stereoselectively to an asymmetric flat tetrahedron with four different corners, specified by (*R*_{θ})/(*S*_{θ}). Negative rotation angles ψ predominantly induce pyramidalization angles θ = O_{trans}C′C_{α}O_{cis}below −180°, resulting in a high diastereoselectivity for (*M*_{ψ},*S*_{θ})-glycine. Positive rotation angles ψ preferentially give (*P*_{ψ},*R*_{θ})-glycine. Density functional theory calculations confirm the results of the data analysis, indicating an increase of pyramidalization θ for increasing rotation angles ψ. This is corroborated by the analysis of section averages of the structural data, showing an increase of the ψ/θ selectivity in the series 1.5, 2.8, 3.5, and 6.0 for increasing rotation angles ψ. Without any chiral bias, 419 glycine derivatives crystallize in the ratio racemate/conglomerate 359:65.## History

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## Keywords

chiral centerC αsection averagesNegative rotation angles ψpyramidalization θtranPositive rotation angles ψAchiral Aminotheory calculationsM ψpyramidalization angles θdata analysisCSDchiral biasψ conformation425 hitsChiral Selectivityrotation angles ψ.P ψCambridge Structural Database419 glycine derivatives