An improved method for synthesizing structurally simplified analogs of cortistatin A (1), a novel antiangiogenic steroidal alkaloid from a marine sponge, was developed. In contrast to previous methods, step-and redox-economical synthesis was achieved using a known alpha-bromoketone as the starting material. The structure-activity relationship study revealed that the isoquinoline portion was strictly recognized by the target molecule. Surprisingly, the introduction of the acetamide moiety on the A-ring structure dramatically enhanced the selective antiproliferative activity against endothelial cells. This new method can be easily applied to gram-scale synthesis and enabled us to prepare various analogs, which were focused on the participation of the side chain and A-ring structure. (C) 2017 Elsevier Ltd. All rights reserved.