The synthesis of kawaïn

Abstract

Kawaïn, one of the pyronones occurring in the kawa kawa‐plant (Piper methysticum), has been synthesised. The melting point of the synthetic substance is not identical with the melting point of kawaïn given by Borsche. Probably this is due to the fact, that Borsche did not obtain kawaïn in a pure state.

DARK Classics in Chemical Neuroscience: Kava

“…Condensation of 3,4-methylenedioxycinnamaldehyde and methyl 4-bromo-3-methoxycrotonate with tetrahydrofuran (THF) generated synthetic methysticin and 7,8-dihydromethysticin . A recent modification of Reformatsky reaction to generate kavalactones involves condensing their respective aldehydes with ethyl 4-bromo-3-methoxycrotonate (Figure A). , The double Reformatsky reaction (Figure B) can also generate kavalactones via the 3-phenylpropanoic aldehyde or cinnamaldehyde reaction with ethyl bromozincacetate in THF with tetramethylethylenediamine (TMEDA) at 50 °C for 3 h …”

“…33 A recent modification of Reformatsky reaction to generate kavalactones involves condensing their respective aldehydes with ethyl 4-bromo-3-methoxycrotonate (Figure 3A). 34,35 The double Reformatsky reaction (Figure 3B) can also generate kavalactones via the 3-phenylpropanoic aldehyde or cinnamaldehyde reaction with ethyl bromozincacetate in THF with tetramethylethylenediamine (TMEDA) at 50 °C for 3 h. 36 Another method of generating various kavalactones is based on a Heck reaction of aryl iodides with the 4-methoxy-6-vinyl-5,6-dihydro-2H-pyran-2-one, prepared by aldol condensation of ethyl acetoacetate with acrolein and subsequent lactonization. 37 The reaction is performed under controlled microwave irradiation (300 W for 5.5 min) in the presence of Hunig's base in dimethylformamide (DMF) under tetrakis-(triphenylphosphine)palladium(0) catalysis (Figure 3C).…”