Synthesis of Optically Active Chrysanthemic Acid

An alternative method to resolution to provide optically active acids is their synthesis either taking advantage of chiral catalysts, chiral functional and removable groups or from chiral precursors [113]. [Pg.22]

Particularly the diazoacetic method has a certain appeal for this problem. The decomposition of the sterically hindered diazoacetic ester 74 is effective in the presence of 2,4-dimethyl-hexadien-2,5 75 involving transient unsymmetrical carbon-complexes with chiral copper complexes 76 of highly substituted schiff bases of saUcyhc aldehyde [116] affording the 1-R-trans ester 77 in high optical and chemical yield (Reaction scheme 45) [114]. [Pg.22]

Diazoisopropane 5 a adds stereoselectively to the optically active butenolid 5 b via the usual pyrazolin intermediate, from which nitrogen is extruded to give the 1-R-cis acid with a 95% yield according to Reaction scheme 6. [115,117] (See also scheme 109). [Pg.23]

Elimination of the problematic oxygen function in the I -position of the originally formed cyclopropane carboxylate 8 is accomphshed after transformation into a thiono carbonate [115, 117]. [Pg.23]

Even sugar can be transformed into 1-R-chrysanthemic acid [118] via a multistep procedure. Likewise, optically active pantolactone 78 [119] can be reduced, ketalized, mesylated and later on subjected to cyanide exchange to give 79. [Pg.23]

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