Impurity analysis of 7-ethyltriptophol using LC-SPE/cryo NMR

Polazna sirovina za sintezu etodolaca, nesteroidnog protuupalnog lijeka, je 7-etiltriptofol, 2-(7-etil-1H-indol-3-il)etanol. Ovisno o putu sinteze 7-etiltriptofola komercijalno dostupna sirovina može sadržavati velik broj onečišćenja koja uzrokuju nastajanje koprodukata prilikom sinteze etodolaca, a time otežavaju i pročišćavanje konačnog produkta. Kako bi se razvila optimalna metoda pročišćavanja etodolaca, potrebno je poznavati strukture onečišćenja polazne sirovine 7-etiltriptofola. U ovom istraživanju korištena je metodologija LC-SPE/krio NMR za određivanje onečišćenja u uzorku 7-etiltriptofola. Najbolje kromatografsko odjeljivanje sastojaka postignuto je na kolonama Waters XBridge Phenyl i C18 (150 mm x 4,6 mm; 3,5 m) uz kombinaciju izokratnog i gradijentnog eluiranja. Onečišćenja su ukoncentrirana poslijekolonskim višestrukim skladištenjem (engl. multitrapping) na HySphere Resin GP SPE-kolonama. Snimljeni su jedno- i dvodimenzijski spektri NMR (1H, COSY, 1H-13C HSQC, 1H-13C HMBC) i MS spektri na temelju kojih su određene strukture onečišćenja.7-Ethyltryptophol, 2(7-ethyl-1H-indol-3-yl)ethanol, is a key starting material in the synthesis of etodolac, a non-steroidal anti-inflammatory drug. Depending on the synthetic pathway for 7-ethyltryptophol, commercially available material comprises many different impurities which can cause formation of coproducts in the synthesis of etodolac thus complicating the purification of the final product. Therefore, to develop an optimal purification procedure of etodolac, it is important to elucidate the structures of impurities in 7-ethyltryptophol. In this study LC-SPE/cryo NMR methodology was used to identify impurities in 7-ethyltryptophol. The best chromatographic separation was achieved with Waters XBridge Phenyl and C18 columns (150 mm x 4.6 mm; 3.5 m) using a combination of gradient and isocratic elution. Mixture components were trapped on HySphere Resin GP cartridges in the SPE multitrapping mode. One and two dimensional NMR (1H, COSY, 1H-13C HSQC, 1H-13C HMBC) and MS spectra were recorded and analysed which enabled structure determination of the present impurities