Studies toward the Large-Scale Synthesis of the HIV Proteinase Inhibitor Ro 31-8959

Ro 31-8959 (1), a potent and selective inhibitor of HIV proteinase, is currently in phase III clinical trials. Six approaches for the large-scale synthesis of this compound have been studied. All routes employ an initial disconnection to an electrophilic L-phenylalanine homologue equivalent 13 and the decahydroisoquinoline derivative 5. They differ in adopting either an epoxide, a cyclic sulfate, or an aldehyde as the electrophilic entity and develop chirality from L-phenylalanine, dimethyl D-tartrate, or a Sharpless epoxidation. The preferred route starts from N-phthaloyl-L-phenylalaninyl chloride and uses tris((trimethylsilyl)oxy)ethene to effect homologation to hydroxy ketone 30, which is elaborated in a five-step two-pot procedure to N-phthaloyl epoxide 33 and hence 1. Kilogram quantities of Ro 31-8959 have been prepared using this route