New Synthetic Method for Dehydrotryptophan Derivatives. Synthetic Studies on Indoles and Related Compounds. XXXIV

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Dehydrotryptophans (9) having various substituents on the indole ring were synthesized by vinylation of the corresponding indole derivatives (6) with N-acetyldehydroalanine methyl ester (7a) by the use of a stoichiometric amount of palladium salt in acetic acid (stoichiometric condition). Although vinylation of 4-, 5-, and 7-bromoindoles (6b, g, l, m) with 7a occurred chemoselectively at the C_3-position to give the corresponding bromodehydrotryptophans (9b, g, l, m) under the stoichiometric condition, the palladium-catalyzed vinylation of 4-bromoindoles (6b, i) occurred at the bromine-bearing carbon at the C_4-position [0.1 eq PdCl_2(PPh_3)_2 in Et_3N-dimethylformamide]. Vinylation of 3-bromoindoles (17a, b) with 7a, or ethoxycarbonyl-(7b) or tert-butoxycarbonyldehydroalanine methyl ester (7c) also gave the dehydrotryptophan (18a-d) in good yields under catalytic conditions. One of two possible regioisomers of the vinylated products was isolated in all cases, and the geometry was determined as Z based on the coupling constant of the ester carbonyl carbon and the olefinic proton in the ^<13>C-NMR spectrum.
公益社団法人日本薬学会の論文
1994-04-15

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