| Abstract
| - The key chiral nonracemic 4,4-disubstituted 2-butyrolactone carboxylic acid, (S)-4, is readilyaccessible via an efficient and stereospecific dirhodium(II) tetraacetate catalyzed tertiary C−Hinsertion reaction of the diazomalonate (S)-5. The coupling of the acid (S)-4 with tryptamine producesthe amide (S)-3, which is then transformed into the aldehyde 23 and hydroxy-lactam 24. Acid-mediated Pictet−Spengler cyclization of 23 and 24 produces the tetracyclic indole lactams (1S,12bS)-25a and (1S,12bR)-25b. Compounds 25a and 25b are converted, via the lactam alcohols30a and 30b, to (−)-eburnamonine (1a) and (+)-epi-eburnamonine (1b).
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