The determination of a chlorinated benzofuran pharmaceutical intermediate by HPLC-MS with on-line derivatization

An HPLC-MS method for the analysis of 2-chloromethylbenzofuran, a pharmaceu tical intermediate alkylating reagent employed in the preparation of a seco nd generation HIV protease inhibitor, N-(2(R)-hydroxy-1(S)-indanyl)-2(R)-ph enylmethyl-4(S)-hydroxy-5-(1-(4-(2-benzo[b]furanylmethyl)-2(S)-N'-9-t-butyl -carboxamido)-pipera zinyl))-pentaneamide, is described. Preliminary analys is of the protease inhibitor by HPLC-MS indicated that the quality of the d rug substance was influenced by the composition of the chloromethylbenzofur an. Direct analysis of the chloromethylbenzofuran by LC-MS using atmospheri c pressure ionization was unsuccessful, necessitating an alternative approa ch. The method described incorporated post-column derivatization of the chl oromethyl benzofuran using a modification of the drug substance process che mistry yielding a derivative amenable to MS analysis using atmospheric pres sure chemical ionization (APCI). This allowed measurement of an impurity in the chloromethylbenzofuran which was incorporated into the protease inhibi tor. (C) 2000 Elsevier Science B.V. All rights reserved.