The radiolabeled non-natural amino acid 1-amino-3-cyclobutane-1-carboxylic acid (ACBC) and its analogs are candidate tumor imaging agents useful for positron emission tomography and single photon emission computed tomography due to their selective affinity for tumor cells. The present invention provides methods for stereo-selective synthesis of syn-ACBC analogs. The disclosed synthetic strategy is reliable and efficient and can be used to synthesize a gram quantity of various syn-isomers of the ACBC analogs, particularly, syn-[18F]-1-amino-3-fluorocyclobutane-1-carboxylic acid (FACBC) and syn-[123I]-1-amino-3-iodocyclobutane-1-carboxylic (IACBC) acid analogs.
