A process leading to the multikilogram GMP synthesis of Chk1 inhibitor GDC-0425 (1) was developed. Highlights of the synthesis include protection of the pyrrole ring of a 1,7-diazacarbazole as propyl ethyl ether, an efficient Pd catalyzed cyanation of an aryl chloride, aryl ether formation by SNAr fluoride displacement, and development of a controlled crystallization providing the API with the required polymorphic form. The process delivered high-quality GDC-0425 with low levels of impurities and residual metals in five steps and 31% overall yield.
Chromatographic analysis of trace organic impurities/degradants coeluting in the midst of active pharmaceutical ingredient can be challenging given similarities in their structures and differences in their relative levels/intensities. Conventional detection techniques such as diode array detection and mass spectrometry are often inadequate to detect/identify these residual coeluting impurities and could result in a false negative. Application of two-dimensional chromatography to address/evaluate coelution in conventional chromatography is presented. Areas of interest, usually corresponding to the main component, are transferred to secondary column/s for further separation termed as pseudocomprehensive two-dimensional liquid chromatography. Coelution, if any, in the rest of the chromatogram is monitored using conventional detectors. In this work, the use of similar and complementary phases in both dimensions is presented. The use of the same phase in both dimensions to resolve coeluting impurities (especially in the front and tail of the main component differing by orders of magnitude) is an easier alternative to finding complementary column/s, as hydrophobicity dominates reversed-phase separation. The same phase separation is practical as relative levels of impurities and main component in some transferred fractions are comparable enabling their separation. The results were confirmed using mass spectrometry. This work has significant bearing as a method assessment tool in pharmaceutical and other industries.
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