Indole grignard reaction. III, Synthesis, crystal structure, and analgesic activity of (R)- and (S)-3-amino-2,3,4,9-tetrahydrothiopyrano[2,3-b]indoles

Both enantiomers of the title compounds were synthesized and the crystal structure of one of them was determined by X-ray crystallography. The indole Grignard reaction was effective for synthesizing the key intermediate of the (R)-isomers. The analgesic activities of the products were compared with those of 4-methylaminomethyl-2,3,4,9-tetrahydrothiopyrano[2,3-b]indole (1), Isoxal, and Tiaramide. The (R)-isomers were more potent than the corresponding (S)-isomers, and were more potent than Isoxal and Tiaramide, but less potent than 1.