α-Fluoro-substituted thalidomide analogues

Thalidomide, (1), has made a remarkable comeback from its days of a sedative with teratogenic properties due to its ability to selectively inhibit TNF-α, a key pro-inflammatory cytokine and its clinical benefit in the treatment of cancer. Thalidomide contains one chiral center and is known to be chirally unstable under in vitro and in vivo conditions. It has been hypothesized that different biological properties are associated with each isomer. Thus, chirally stable analogues of thalidomide, α-fluorothalidomide, (3) and α-fluoro-4-aminothalidomide (4) were prepared by electrophilic fluorination. Analogue 3 was found to be cytotoxic and did not inhibit TNF-α production in LPS stimulated hPBMC below toxic concentrations. On the other hand, 4 was non-cytotoxic at the tested concentrations and was found to be 830-fold more potent than thalidomide as TNF-α inhibitor.