Abstract: This invention relates to novel processes for making (2S, 3S, 5S) oxetanone derivative lipase inhibitor compounds and intermediates therefor, which processes for producing such derivatives that are useful as lipase inhibitors are capable of being scaled to commercial quantities. Further the invention relates to processes for producing salts and for producing pharmaceutical compositions compounds comprising at least one such oxetanone derivative or salt, as well as methods for using such compounds and compositions for inhibiting lipases.