Asymmetric Syntheses via Heterocyclic Intermediates, XLIV. Asymmetric Synthesis of Methyl (2R,3S)‐2‐Amino‐3‐cyclopropyl‐3‐hydroxyalkanoates via Diastereoselective Simmons‐Smith Reactions

The cyclopropanation of the bislactim ethers 3 with diiodomethanes and diethylzinc proceeds in good yields and with high diastereoselectivities, affording the cyclopropyl bislactim ethers 6. Protection of the hydroxy group and subsequenthydrolysis furnish virtually enantiomerically and diastereomerically pure methyl (2R,3S)‐2‐amino‐3‐cyclopropyl‐3‐hydroxyalkanoates 8. The bislactim ethers of type 3 are obtained by a known method diastereomerically pure, starting from the bislactim ether of cyclo(‐L‐Val‐Gly‐).