SYNTHESIS OF SUBSTRUCTURES OF SORAPHEN-A - FORMATION OF THE ENOLATE OF BENZYL PROPIONATE

During the preparation of substructures of the fungicidal natural product soraphen A 1, it was observed that the beta-eto ester 12 was formed as the major product upon deprotonation of benzyl propionate with LDA. Studies of the stability of the enolate 13 showed that two mechanisms operating in this example. A previously described for the decomposition of ester enolates cannot be competition between deprotonation and condensation is proposed, which is in accord with the results described here and in the literature. The use of a reactive base is shown to provide good yields of the enolate 13. In addition. temperature is shown to be another factor influencing the yield of 13.