Total synthesis of novel bioactive natural product paracaseolide A and analogues: computational evaluation of a 'proposed' biomimetic Diels-Alder reaction

A short and generally applicable synthesis of bioactive tetracyclic natural product paracaseolide A has been accomplished employing a 'proposed' biomimetic Diels-Alder reaction as the key strategic step. The Diels-Alder precursors for this purpose were readily assembled through a versatile Suzuki coupling on preformed α-halo butenolides. The mechanistic aspects of the 'putative' biomimetic Diels-Alder reaction have been probed using computational methods, which suggest that this [4+2]-cycloaddition proceeds through a step-wise process and product profile is thermodynamically governed.