Abstract
Peracid oxidation, acid treatment and subsequent Jones oxidation of (−)-pyrocine gave (−)-2, 2, 5, 5-tetramethyl-4-oxo-3-tetrahydrofurylacetic acid. Alkaline treatment of the optically active keto acid afforded the completely racemized one, and the Huang-Minlon reduction of the latter and treatment with acetyl chloride in the presence of zinc chloride gave (±)-pyrocine. By the reaction sequence it is possible to prepare racemic trans-chrysanthemic acid from the optically active one.
Abstract
Four geometrical isomers of (±)-pyrethric acid were synthesized in good yield by the Wittig reaction or by its phosphonate modification. High stereoselectivity was found in the Wittig reaction of 1-methoxycarbonylethylidenetriphenylphosphorane with (±)-caronhalfaldehydic ester.