Synthesis and antiproliferative activity evaluation of steroidal imidazo[1,2-a]pyridines

• Series of steroidal imidazo[1,2-a]pyridine hybrids were synthesized.
• Cytotoxic behavior against human breast and prostate cancer cells were tested.
• All tested compounds showed activities at μM level in breast cancer cells.
• Two conjugates showed good in vitro activity (IC50 = 3–4 μM) against MCF-7.
• Hybrid 4a exhibited remarkable effects as a selective ERα modulator.

An elegant approach to unknown steroidal imidazo[1,2-a]pyridine hybrids is disclosed. Unique derivatives of androstene and estrane series containing imidazo[1,2-a]pyridine motifs were prepared from 17-ethynyl steroids in good yields via copper-catalyzed cascade aminomethylation/cycloisomerization with imines. The synthesized compounds were screened for cytotoxicity against human breast (MCF-7, MDA-MB-231, HBL-100, MDA-MB-453) and prostate (LNCaP-LN3, PC-3, DU 145) cancer cell lines. The majority of tested compounds showed activities at μM level in breast cancer cells. The hormone-responsive breast cancer cells MCF-7 were more sensitive to novel compounds than ERα-negative cells; in particular, compounds 6a,b exhibited promising cytotoxicity against this cell line with the IC50 values in the range of 3–4 μM. Furthermore, compound 4a showed remarkable effects as a selective ERα receptor modulator.

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