Second-Generation Synthesis of the Male Contraceptive YCT-529

We report a practical synthesis of the nonhormonal male contraceptive YCT-529. The method features key transformations: Grignard-mediated acetylation, the α-methylenation of a methyl ketone, and pyrrole formation via the Stetter and Paal–Knorr reaction sequence. It avoids iridium and palladium catalysts, overcoming the major limitations of an earlier synthesis. The current scalable synthesis proceeds in 6 steps from bromochromene 4 in 51% overall yield and does not require chromatographic purification.