The kinetic isotope effect (KIE) was applied in the study of the mechanism of bromine elimination from p-methyl-erythro-a,b-dibromocinnamic acid, successively labeled at the a and b carbons. The large 14C KIE for the b-position and small KIE for the a one of side chain of p-methyl-erythro-a,b-dibromocinamic acid proves that elimination of bromine leading to the formation of (E)-p-methylcinnamic acid proceeds via the E1 mechanism.
The kinetic isotope effect (KIE) method was applied to study the mechanism of elimination of bromine from erythro-a,b-dibromocinamic acid. The large 14C KIE for both a- and b-position of side chain of erythro-a,b-dibromocinamic acid proves that elimination of bromine leading to formation of (E)-cinnamic acid proceeds via E2 mechanism.
Authors:W. Augustyniak, J. Bukowski, J. Jemielity, R. Kański, and M. Kańska
Convenient and efficient processes are described for the synthesis of L-enatiomers of phenylalanine specifically labeled with carbon-14 in 1-, 2-, and 3-positions of side chain. The method consists of the preparation of the proper isotopomers of cinnamic acid labeled with 14C and their conversion into L-phenylalanine using enzyme activity. The combined chemical and enzymatic approach allows to produce three different isotopomers of phenylalanine in pure L-optical form labeled with 14C.
Authors:J. Bukowski, J. Szul, R. Kański, and M. Kańska
Convenient and efficient route of the synthesis of [3-14C] cinnamic acid is reported. [1-14C]Benzoic acid, prepared by carbonation of Grignard reagent with [14C]carbon dioxide, was reduced to [1-14C]benzyl alcohol. In the enzymatic step this alcohol was selectively oxidised to [1-14C]benzaldehyde using enzyme YADH (Ec. 188.8.131.52) and immediately condensed with malonic acid. This combined chemical and enzymatic approach allows to obtain [3-14C]cinnamic acid with radiochemical yield higher than 50% in respect to the starting alcohol.