New synthetic methodology to prepare polyfunctionalized heptane building blocks with four stereocenters: synthesis of the (±)-C17–C23 subunit of Ionomycin

Abstract A new synthetic methodology for preparing polyfunctionalized heptane building blocks with up to four stereocenters has been developed. 2,4-Dimethyl-1-methoxy-8-oxabicyclo-[3.2.1]-oct-6-en-3-one has been used as precursor, which can be easily prepared by a [4+3] cycloaddition reaction between 2-methoxy-furan and the oxyallyl cation generated in situ from 2,4-dibromo-3-pentanone. The cycloadducts have an acetal functionality on C1 which allows easy opening of the oxabicyclic system, affording versatile synthons. The application of this methodology to the synthesis of the C17–C23 subunit of Ionomycin is presented.