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. 2020 Feb 4;6(2):155–165. doi: 10.1021/acscentsci.9b00743

Figure 2.

Figure 2

Radiochemical syntheses of d-[11C]ala and d-[11C]ala–d-ala using a chiral, phase-transfer cinchonidinium-derived catalyst. (A) High enantiomeric excess synthesis of d-[11C]ala via asymmetric alkylation of a glycine-derived Schiff base with [11C]CH3I. The analytical HPLC data on the right shows the radioactive trace of d-[11C]ala (green) overlaid with a racemic sample of alanine (blue) with both d- and l-enantiomers present in equal concentrations. (B) An analogous procedure was used for the radiosynthesis of d-[11C]ala–d-ala at approximately 70% diastereomeric excess. The analytical HPLC data on the right show the radioactive trace of d-[11C]ala–d-ala (green) overlaid with a sample containing d-ala–d-ala and the undesired diastereomer l-ala–d-ala present in equal concentrations (blue).