Process Research and Development for an Efficient Synthesis of the HIV Protease Inhibitor BMS-232632

Abstract

Development of an efficient and scalable process for the human immunodeficiency virus (HIV) protease inhibitor BMS-232632 1-[4-(pyridin-2-yl)phenyl]-5(S)-2,5-bis{[N-(methoxycarbonyl)-l-tert-leucinyl]-amino}-4(S)-hydroxy-6-phenyl-2-azahexane, is described. The key step in the synthesis of the intermediate N-1-(tert-butyloxycarbonyl)-N-2-[4-(pyridin-2-yl)benzylidene]hydrazone (11) was the Pd-mediated coupling of boronic acid 9 with 2-bromopyridine. An efficient procedure was developed for the chemoselective reduction of hydrazone 11 to hydrazine carbamate 4. The key intermediate N-(tert-butyloxycarbonyl)-2(S)-amino-1-phenyl-3(R)-3,4-epoxy-butane (6) was prepared stereoselectively from chiral diol 10. The subsequent union of 4 and 6 followed by coupling with N-methoxycarbonyl-l-tert-leucine provided the free base BMS-232632 in high yield. Evaluation of a variety of salts and identification of bisulfate salt 19 with enhanced bioavailability are also described.