Tetrahedron Letters,Vol.25,No.23,pp 2415-2418,1984 0040-4039/84 $3.00 + .Oo Printed in Great Britain 01984 Pergamon Press Ltd. A METHOD FOR THE STEREOSPECIFIC SYNTHESIS OF CHIRAL CIS-2-ALKYLCYCLOPROPYLLITHIUM REAGENTS E. J. Corey and Thomas M. Eckrich Department of Chemistry, Harvard University, Cambridge, MA 02138 Summary: A general synthetic route to optically active cis-1,2-disubstituted cyclopropanes has been developed from the key intermediates 3 and 4. In connection with recent studies in these laboratories1r2 on the stereo- chemistry and total synthesis of the novel marine eicosanoid hybridalactone (1) we needed the chiral organolithium reagent 2. A survey of the literature failed to reveal either examples of synthesis of such chiral cis-2-alkylcyclo- propyllithium reagents or methodology suitable for stereospecific synthesis. We report herein a simple and effective solution of this general problem. The chiral lithium reagent 2 has been synthesized with the absolute configura- tion shown and has been applied successfully to a total synthesis of hybrida- lactone which allowed unambiguous assignment of the complete stereochemistry shown in 1. zyxwvutsrqponmlkjihgfedcbaZYXWVUTSRQPONMLKJIHGFEDCBA 1 z The first step in the sequence leading to cis-1,2- functionalized cyclo- propanes is the synthesis of the z-1,2- functionalized olefin 3, which is also an extremely useful precursor of more complex Z-olefins such as the 2415