Use of Flash Vacuum Thermolysis in a Stereocontrolled Synthesis of Optically Active Alkyl-substituted Cyclopentenones with Fragrant Properties

The synthesis of four pairs of enantiopure antipodal substituted cyclopentenones is described. The synthetic sequences first comprise the preparation of a tricyclo[5.2.1.02,6]deca-4,8-dienone system, a subsequent kinetic enzymatic resolution of the appropriately functionalized tricyclic system, followed by a series of chemical transformations to install the desired substituents, and finally a retro Diels–Alder reaction using flash vacuum thermolysis to give the target products in high chemical and optical yields. The strategy makes effective use of the concept of transient chirality involving complete stereochemical control over reactions with the chiral tricyclic systems before thermal removal of the cyclopentadiene.