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Exemestane is a 3rd-generation aromatase inhibitor used to treat breast cancer in postmenopausal women, with a key synthetic step involving dehydrogenation using quinone compounds.
During the synthesis, researchers found two distinct hexacyclic by-products formed through a cycloaddition reaction, depending on the specific quinone used (p-chloranil or DDQ).
The unique structures of these by-products were identified using mass spectrometry, NMR techniques, and crystallographic analysis, revealing new insights into the synthesis process.
Article Abstract
Exemestane, a 3rd-generation aromatase inhibitor, is clinically used in the treatment of breast cancer in postmenopausal women. The key step of the industrial synthetic process, i.e., a dehydrogenation to introduce the Δ-unsaturation, is normally performed with quinones such as p-chloranil or DDQ. We observed the formation of two different hexacyclic by-products, depending on the quinone used in the oxidation step. These compounds arise from an initial [4+2] cycloaddition between the precursor 6-methylenandrost-4-ene-3,17-dione and the quinone reagent, followed by a twofold dehydrohalogenation (with p-chloranil) or dehydrogenation (with DDQ). The structures of these unprecedented hexacyclic adducts were determined by a combination of mass spectrometry, NMR techniques and crystallographic analysis.
