Synthesis of (R)-curcumene and (R)-xanthorrizol based on 1,2-Aryl migration via phenonium ion.
Solvolysis reaction of methyl (4S,5S)-4-(4'-methoxyphenyl)-5-tosyloxy-2(E)-hexenoate 5 in water-saturated MeNO(2) gave the 1,2-migration product, (4S,5S)-5-hydroxy-4-(4'-methoxyphenyl)-2-(E)-hexenoate 6 (55% yield), which was converted to methyl (R)-(4'-methylphenyl)hexanoate 11 in 25% overall yield (5 steps). Treatment of (R)-11 with MeLi gave tertiary alcohol congener 12, which was subjected to dehydration to afford (R)-(-)-curcumene 1. An introduction of hydroxyl group at meta-position of the aromatic ring in (R)-11 was achieved based on consecutive treatment [1) selective iodination, 2) conversion of aryl iodide to aryl boronate, 3) conversion of aryl boronate to phenol]. Thus obtained phenol (R)-16 was treated with MeLi to give tertiary alcohol congener 17, which was subjected to dehydration to afford (R)-(-)-xanthorrizol 2.
Ehara
Takeru
T
School of Pharmaceutical Sciences, Toho University, Funabashi, Chiba, Japan.
Tanikawa
Shin
S
Ono
Machiko
M
Akita
Hiroyuki
H
D001897:Boronic Acids / Q000138:chemical synthesis; D002412:Cations / Q000737:chemistry*; D002855:Chromatography, Thin Layer; D003474:Curcumin / Q000031:analogs & derivatives* / Q000138:chemical synthesis; D007202:Indicators and Reagents; D007454:Iodides / Q000737:chemistry; D009682:Magnetic Resonance Spectroscopy; D010636:Phenols / Q000138:chemical synthesis*; D012717:Sesquiterpenes; D012997:Solvents