Benzo[b]thiophene derivatives. XXIII. Derivatives of 5,6‐dihydroxy‐3‐benzo[b] thienylacetic acid

Abstract

A series of 5,6‐disubstituted benzo[b]thiophenes have been synthesized for biological evaluation. These include analogs of tryptamine, melatonin and harmaline types, having hydroxy, methoxy, methoxymethyloxy, or isopropylidenedioxy groups at both the 5‐ and 6‐ positions. In order to synthesize these, the appropriate mercaptoguaiacols were prepared, and condensed with chloroacetoacetic esters to the 4‐arylthioacetoacetic esters. Cyclization of these ketones was best accomplished when the free phenolic groups were masked by methoxymethyl groups. The benzo[b] thienylacetic esters were then converted to corresponding amides, reduced to tryptamine analogs, acetylated to melatonin analogs, and cyclized to harmaline analogs. N‐Acetyltryptamine and 1‐methylmelatonin were also synthesized for comparison. Preliminary bioassay results on the melatonin analogs, which showed activity, are reported.