Total Synthesis of Phenanthro‐Quinolizidine Alkaloids: (±)‐Cryptopleurine, (±)‐Boehmeriasin A, (±)‐Boehmeriasin B and (±)‐Hydroxycryptopleurine

The first synthesis of (±)‐boehmeriasin A and B and a concise synthesis of (±)‐cryptopleurine and (±)‐hydroxycryptopleurine are described. The piperidine ring of these alkaloids was constructed by the coupling of the phenanthrene ring with 2‐bromopyridine through a nucleophilic substitution reaction and subsequent reduction of the resulting pyridyl ketone. The first crystal structure of a phenanthro‐quinolizidine alkaloid is also reported. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)