Synthesis of (±) Wine Lactone and Its Analogues by a Diels–Alder Approach

A novel route to (±)‐wine lactone ( 1 ) by a cis ‐selective kinetically controlled intramolecular Diels–Alder (IMDA) cycloaddition of the linear triene 2 is reported. The triene precursor was synthesised by TBAF‐catalysed coupling of an acyl fluoride with an silyl enol ether. Four butadienyl but‐3‐enoates were prepared and cyclised under mild conditions to give a series of wine lactone analogues. The diastereoselectivity of the IMDA cycloadditions was determined by NMR spectroscopy and GC‐MS, whereby the formation of the natural cis ‐configured wine lactone ( 1 ) was established. The diastereomeric IMDA transition states were optimised by using density functional theory at the B3LYP/6‐31+G(d) level, and the Boltzmann populations of the electronic energies were found to correlate well with the experimentally observed diastereoselectivity.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)