Chemistry of renieramycins. Part 9: Stereocontrolled total synthesis of (±)-renieramycin G

A 25-step stereocontrolled total synthesis of (±)-renieramycin G (1g) from readily available 2-hydroxy-3-methyl-4,5-dimethoxybenzaldehyde (3) is described. This synthesis features the concise construction of the pentacyclic framework using the stereoselective Pictet–Spengler type cyclization reaction of lactam (14) with ethyl diethoxyacetate, followed by the base-catalyzed isomerization of the C-1 stereo center.