*2.2. Acid–Catalyzed Cleavage of 8-(3-Octyloxiran-2-yl)Octanoic Acid* (**9**) *to 9,10-Didhydroxystearic Acid* (**10**)

The ring-opening of epoxystearic acid **9** to the corresponding *threo* diol derivative **10** (Figure 3) was promoted by diluted sulfuric acid, and the reaction conditions were adjusted to obtain quantitative conversion after 3 h at room temperature (Table S3 of Supplementary Material). The relative configuration of diol **10** was established following the *anti* mechanism of the hydrolytic opening of the oxirane ring of *cis*-epoxide **9** and was confirmed by literature data (see Materials and Methods). The acid-catalyzed hydrolysis was then performed, without isolation of the epoxide, by addition of a 2.0 M solution of H2SO4 directly to the reaction mixture of the epoxidation step, after removal of the enzyme by filtration and decomposition of peroxy species. This one-pot two-steps sequence led to the spontaneous crystallization of dihydroxystearic acid **10**, which was easily recovered from the reaction medium by filtration as a pure white solid. Satisfactory isolation yields (77%) were obtained, even when the reaction was run ata2g scale, starting from commercial 91% oleic acid.
