Hydrochloric Acid → Alosetron

Participants

Reaction Steps

A solution of phenylmethyl 5-methyl-4-[(2,3,4,5-tetrahydro-5-methyl-1-oxo-1H-pyrido[4,3-b]indol-2-yl)methyl]-1H-imidazole-1-carboxylate (134 mg) in a mixture of absolute ethanol and 2N hydrochloric acid (2:1; 30 ml) was heated on a steam bath for 15 min. After cooling, the solution was concentrated in vacuo to ca. 20 ml and diluted with water (40 ml). The mixture was then washed with ethyl acetate (2×40 ml) and the acidic aqueous layer was basified with potassium carbonate solution. The solution was then extracted with ethyl acetate (3×50 ml) and the combined, dried organic extracts, were concentrated onto FCC silica and purified by FCC eluting with System A (150:8:1) to give a solid. This was dissolved in hot methanol and triturated with ether to give the title compound (69 mg). The 1H-n.m.r. and t.l.c. data obtained for this material were consistent with those obtained for the product of Example 20.

Provenance & Evidence