Two novel pyrrolo[ 2,3-b] indole alkaloids, named robustanoids A (1) and B (2), featuring an unprecedented 1,2,3,4,8b, 8c-hexahydro-2a, 4a-diazapentaleno[1,6-ab] indene moiety, were isolated from Coffea canephora beans. Their structures were determined by extensive spectroscopic analysis and electronic circular dichroism (ECD) calculation. The total synthesis of compounds 1 and 2 was successfully conducted to give a decent total yield (similar to 29%) in 8 steps, which also confirmed the structures determined by spectroscopic data. Compound 2 showed alpha-glucosidase inhibitory activity comparable to that of the positive control, acarbose.