Stereocontrolled Total Synthesis of (+)-Paraherquamide B

The convergent stereocontrolled, asymmetric total synthesis of (+)-paraherquamide B is described. Key features of this synthesis include (1) an improved procedure to effect reduction of unprotected oxindoles to indoles; (2) a complex application of the Somei/Kametani coupling reaction; (3) a high-yielding and entirely stereocontrolled intramolecular S N 2‘ cyclization reaction that constructs the core bicyclo[2.2.2] ring system; (4) a mild Pd(II)-mediated cyclization reaction that constructs a complex tetrahydrocarbazole; and (5) the chemoselective reduction of a highly hindered tertiary lactam in the presence of an unhindered secondary lactam, utilizing precoordination of the more reactive secondary lactam to triethylaluminum.