“…Based on synthetic tractability, the following seven analogs were thus designed: 3-chloro ( 1d ), 3-trifluoromethyl ( 1e ), 3-amino ( 1f ), 3-cyano ( 1g ), 3-carbamido ( 1h ), 3-boronic acid ( 1i ), and 3,4-dihydroxy ( 1j ). The synthesis of 1d-j was carried out by a stereoselective rhodium(I)-catalyzed addition of an arylboronic acid to protected enone 2 24 as the key step (Scheme 1). 25 Hereby, the 2,3- trans stereochemistry on the proline ring was set, and subsequent functional group transformations in accordance with earlier reported strategies ( 1d-f ; Scheme 2), ( 1g,h ; Scheme 3), ( 1i ;Scheme 4) and ( 1j ; Scheme 5), gave the free amino acids 1d-j ready for pharmacological evaluation.…”