The method reported by Beemelmanns & Reissig (racemic, 2010) is another formal synthesis leading to the Rawal pentacycle (see amine 5 in the Rawal method). In this method indole 1 was converted to tetracycle 2 (together with by-product) in a single cascade reaction using samarium diiodide and HMPA. Raney nickel/ H reduction gave amine 3 and a one-pot reaction using methyl chloroformate, DMAP and TEA then MsCl, DMAP and TEA and then DBU gave Rawal precursor 4 with key hydrogen atoms in the desired anti configuration.
In an aborted route intermediate 2 was first reduced to imine 5 then converted to carbamate 6, then dehydrated to diene 7 (Burgess reagent) and finally reduced to 8 (sodium cyanoborohydride). The hydrogen atoms in 8 are in an undesired cis-relationship which contradicts the results obtained in 2002 by Bodwell/Li for the same reaction.