Indoles. I. Syntheses of 1-Acetyltryptophan and Its Derivatives, and Their Friedel-Crafts Reaction

1-Acetyltryptophan and its derivatives were synthesized in good yields from dltryptophan. Reduced nucleophilic activity in the indole ring by 1-acetylation was examined in the reaction of 1-acetyl derivatives with o-nitrophenylsulfenyl chloride (NPS-Cl) and the Friedel-Crafts reaction of them. In the reaction with NPS-Cl, 7, 10, and 12 did not show the activity of 2-position in the indole ring, but the Friedel-Crafts reaction of 12 (chloride) afforded 15 cyclized to 2-position of the indole, different from only one example reported previously by Szmuszkovicz of the same reaction of 1-acetyl indole derivatives which cyclized to 4-position.