(2R,4R)-azetidine-2,4-dicarboxylic acid 127310-57-0 Lopac-A-244 Lopac-A-243 NCGC00015022-01 NCGC00015022-02 A244_SIGMA tADA trans-Azetidine-2,4-dicarboxylic acid 2,4-Azetidinedicarboxylic acid, trans-(+-)- AD-2,4-DC Azetidine-2,4-dicarboxylic acid trans-(+-)-2,4-Azetidinedicarboxylic acid