Isolation, synthesis, and neurite outgrowth-promoting activity of illicinin A from the flowers of Illicium anisatum

Abstract Two new prenylated C 6 –C 3 compounds, illicinin A ( 1 ) and (4 S )-illicinone I ( 2 ), were isolated from the flowers of Illicium anisatum . The structures of the new compounds were elucidated by spectroscopic methods. The absolute structure of (4 S )-illicinone I was determined by comparing its CD spectrum and specific rotation with those of (4 S )-illicinone A ( 4 ). Illicinin A ( 1 ) and 4-allyl-2,6-dimethoxy-3-(3-methylbut-2-enyl)phenol ( 3 ) were found to exhibit neurite outgrowth-promoting activity at concentrations ranging from 0.1 to 10 μM in primary cultured rat cortical neurons. Illicinin A and its derivatives were synthesized for structure–activity relationship studies by employing sequential Stille reactions to introduce a prenyl and an allyl group to the benzene ring, thereby indicating that an allylphenyl moiety in the molecule of 1 is essential for its neurotrophic properties.