4-Methyl-17-alfa-Estradiol

4-Methyl-17α-Estradiol is a steroidal derivative featuring a methyl substitution at the C4 position of the estrane nucleus, with a 17α-hydroxyl group and a 3-hydroxyl moiety. This compound retains the core A and B rings of estradiol but exhibits a structural deviation at C4, altering its stereochemical profile. The 17α-hydroxyl functionality maintains partial estrogenic potential while the C4 methyl group introduces steric hindrance, reducing biological activity. It arises as a synthetic byproduct during estradiol methylation processes, particularly in C4-directed alkylation steps. This compound serves as a critical HPLC reference standard for quantifying C4-alkylation efficiency in estradiol API synthesis.