Study on the stereochemical control of dihydroxylation of vinyl epoxides and their derivatives

Double Stereodifferentiation in the Asymmetric Dihydroxylation of Optically Active Olefins

“…Starting from the suitable epoxy alcohols, prepared in enantiomerically enriched form by Sharpless AE, 17 all compounds, except 4,7,9,12, 4a, 4b, 7a, 7b, 9a, 9b, 12a, and 12b, are known and were prepared following the procedure already described. 16 All experimental data were consistent with the ones reported in the literature for the racemic compounds 16 ; the [α] D are given in Table 1.…”

“…Starting from the appropriate allylic alcohol, all substrates were prepared in their enantiomerically enriched form, using Sharpless protocol for the asymmetric epoxidation (AE) and then following the procedures already described in our recent work …”

“…Starting from the appropriate allylic alcohol, all substrates were prepared in their enantiomerically enriched form, using Sharpless protocol for the asymmetric epoxidation (AE) 17 and then following the procedures already described in our recent work. 16 For each compound the first attempt of the AD was made following the Sharpless procedure (procedure B) using commercially available ADmix-α or ADmix-β. * However, these conditions turned out to be unsuitable for the substrates of choice; therefore, several variations (e.g., solvent, ligand, etc.)…”

“…We have recently reported the results obtained from a study on the stereochemical control in the dihydroxylation of the double bond of vinyl epoxides and their derivatives (bromo derivatives, azido derivatives, and vinyl aziridines), achieved with OsO 4 alone without any chiral ligand . A significant diastereoselectivity was observed for the bromo derivatives, azido derivatives, and N‐protected vinyl aziridines, whereas vinyl epoxides and unprotected vinyl aziridines showed no diastereoselectivity.…”

Stereoselective Synthesis of (+)-Polyoxamic Acid Starting with a Chiral ­Aziridine

“…11 In addition, it has been reported that (E)-3-(aziridin-2-yl)acrylates, whose amine moieties are protected by electron-withdrawing groups, can be diastereoselectively dihydroxylated using osmium tetroxide in the absence of chiral ligands. 12 In recent efforts in our laboratory, we have shown that dihydroxylation reaction of N-(R)-1-phenylethyl-protected aziridin-Z-enoate using osmium tetroxide leads to nondiastereoselective (dr = ca. 1:1) production of a diol product but, in contrast, that the process proceeds with a high level of diastereoselectivity when the Sharpless AD-mix-β reagent combination is employed.…”