Abstract A selective, irreversible inhibitor of proteasome function, lactacystin (1) is an important experimental tool in cell biology. An efficient and direct enantioselective synthesis of lactacystin proceeds via the intermediates shown below. This process allows for the first time easy access to analogues of lactacystin in which the isopropyl substituent is replaced by other lipophilic groups. PMB= p-methoxybenzyl.
![(1R,4R,5S)-1-((S)-1-hydroxy-2-methylpropyl)-2-(4-methoxybenzyl)-4-methyl-6-oxa-2-azabicyclo[3.2.0]heptane-3,7-dione Structure](https://image.chemsrc.com/caspic/081/212772-65-1.png)
