Desymmetrisation of meso-epoxides

Enantioselective Niobium-mediated Carbon-Carbon Bond-forming Reactions 

---

Antilla developed a catalytic enantioselective desymmetrisation of meso-epoxides with thiols by using chiral lithium phosphate 17. A wide range of epoxides and aromatic thiols were observed with high enantioselectivities (Scheme 2.12). ... 

Scheme 2.12 Enantioselective desymmetrisation of meso-epoxides with thiols with the use of chiral lithium(i) phosphate.

Figure 21.6 Catalysts for desymmetrisation of meso-epoxides and their scope.

The starting material for the next desymmetrisation comes from an interesting reaction first described in chapter 19. The Pd-catalysed attack of AcOH on the mono-epoxide ( )-35 gives the racemic monoester 36. In order to convert this to a single enantiomer it is first made into the meso diester13 37. 

---