Stereoselective enzymatic synthesis of cis-pellitorine, a taste active alkamide naturally occurring in tarragon

The alkamide cis-pellitorine [(2E,4Z)-N-isobutyldeca-2,4-dienamide] that occurs naturally in tarragon was prepared in yields up to 80% by lipase-catalyzed conversion of ethyl 2E,4Z-decadienoate, the so-called pear ester, and isobutylamine both with and without the use of cosolvents. Of 13 different commercial enzyme preparations tested (lipases, proteases, esterases), only the lipase type B from Candida antarctica has a suitable activity. The reaction of the different geometric isomers of ethyl 2,4-decadienoate to the appropriate pellitorines shows a remarkable selectivity: the 2E,4Z ester is converted between 1.4 and 3.9 times faster than the 2E,4E isomer, and the relative yield of cis-pellitorine compared with trans-pellitorine is 5.7 to 16.3 times higher. In contrast to the better known trans-pellitorine, which at 10 ppm is only slightly tingling and numbing, cis-pellitorine shows very interesting pungent and warming sensations after tasting trials already in low concentrations of 10 ppm. ((C) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004).