An improved synthesis of 3,8-dimethyl-3H-imidazo[4,5-f]quinoxalin-2-amine ("MeIQx") and its 2-14C-labelled analogue.

The highly mutagenic title compound (MeIQx) was prepared in 21% overall yield from 4-fluoro-o-phenylenediamine. The 3,7-dimethyl isomer may be obtained as a minor by-product. The 14C-label was introduced in the last step through cyclization with [14C]cyanogen bromide. An alternative synthesis of MeIQx from p-fluoroaniline avoided the separation of isomers but gave poorer yield.