Hydrolytic dynamic kinetic resolution of racemic 3-phenyl-2-oxetanone to chiral tropic acid

Abstract

The hydrolytic dynamic kinetic resolution of racemic 3-phenyl-2-oxetanone using a chiral PTC and water-free basic anion exchange resin as the hydroxide ion donor was achieved.

De-epimerizing DyKAT of β-lactones generated by isothiourea-catalysed enantioselective [2 + 2] cycloaddition

“…As previous work has shown that β-lactones are prone to epimerisation at C(3) under basic reaction conditions, in situ reaction monitoring in CD 2 Cl 2 using 1 H NMR spectroscopic analysis demonstrated that the product β-lactone dr was invariant with time, presumably due to rapid epimerisation leading to equilibration. 24–26,28,57,58 Subsequent studies were aimed at in situ derivatisation to facilitate diastereoisomer separation and allow unambiguous determination of enantioselectivity. Interestingly, the use of benzylamine or pyrrolidine as a derivatisation agent gave an approximate 70 : 30 mixture of the corresponding diastereoisomeric β-hydroxyamides 9 and 10 (both in 99 : 1 er).…”