17. Herstellung von erythro-2-Hydroxybernsteinsaure-Derivaten aus Apfelsaureester

Article abstract of DOI:10.1002/hlca.19800630118

As a contribution to the much discussed diastereoselective synthesis of enantiomers of open chain compounds, >90percent erythro-selective branching of malic esters by alkylation of the doubly deprotonated derivative 2 (alkoxy-enolate) with methyl, allyl, and benzyl halides in THF at -78 deg (- 3aa, 3ba, 3bb, 3bc, Table 1) is described.A second alkylation (- 4) and addition of 2 to acetone (- 5) are also possible.Cyclization of 2 to the enantiomerically pure trans-epoxides 6 is achieved by treatment with iodine.Cuprate opening of 6b furnishes the same product 3ba obtained from the methylation of 2b, establishing the configurational assignment.