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Paper | Special issue | Vol 97, No. 1, 2018, pp.292-305
Published online, 2nd February, 2018
DOI: 10.3987/COM-18-S(T)19
Total Synthesis of Phenanthroquinolizidine Alkaloid Cryptopleurine and Phenanthroindolizidine Alkaloid Tylophorine

Yousuke Yamaoka,* Marie Taniguchi, Ken-ichi Yamada, and Kiyosei Takasu*

*Graduate School of Pharmaceutical Sciences, Kyoto University, 46-29 Yoshida-shimoadachi-machi, Sakyo-ku, Kyoto 606-8501, Japan


Total synthesis of phenanthroquinolizidine alkaloid cryptopleurine was achieved in 11 steps from commercially available 6-bromoveratraldehyde. The crucial step of phenanthrene construction is a formal [2 + 2] cycloaddition of 2-acyl-2’-vinyl-1,1'-biaryl, followed by an acid promoted ring-contraction/ring-opening sequence. The key point to complete the total synthesis of cryptopleurine is use of nosyl amide as a nucleophile for cyclization of piperidine ring. The synthesis of tylophorine was also achieved in the similar manner.