114524-87-7Relevant academic research and scientific papers
α-ALKYLTRYPTOPHANS
Brana, Miguel F.,Garrido, Mercedes,Rodriguez, Maria L. Lopez,Morcillo, M. Jose
, p. 2139 - 2151 (2007/10/02)
A study of three direct methods for the synthesis of α-alkyl α-amino acids has been applied to the preparation of α-alkyltryptophan esters. Reaction of Nb-benzylidene-L-tryptophan methyl esters 3 with tetrabutylammonium hydrogen sulfate and methyl or ethyl iodide (phase-transfer method) gives α-methyl and α-ethyltryptophan methyl esters 6a,b in poor yield with complete racemization. Reaction of L-tryptophan 1 with dimethylformamide dimethyl or diethyl acetal followed by treatment of 8a,b with LDA amd methyl iodide (Fitt and Gschwend method) gives rise to the formation of α,Na-dimethyl-Nb-dimethylaminomethylenetryptophan methyl or ethyl esters hydriodide 9a,b. Treatment of 9a or 9b with aqueous acid, under mild conditions, fails to hydrolyze the imine functionality. Reaction of 3 with LDA and methyl or ethyl iodide (Bey and Vevert method) followed by hydrolysis provides α-methyl and α-ethyltryptophan methyl esters 6a,b. By carrying out this procedure with isopropyl, benzyl and allyl iodide or bromide the corresponding α-alkyl esters are not obtained.
