Asymmetric cyclopropanation with diazoacetates induced by carbohydrate-derived chiral auxiliaries

α-Diazoacetates with carbohydrate-based chiral auxiliaries have been synthesized and screened in the asymmetric cyclopropanation of styrene in connection with the effect of the chiral Cu(I)-catalyzed reaction, showing the remarkable importance of the carbohydrate-based chiral auxiliaries on the enantioselectivities and an unexpected effect on the trans:cis ratios.