Sulfone-Mediated Syntheses of Crocetin Derivatives: Regioselectivity of Highly Functionalized Building Blocks

New C<sub>5</sub> sulfone building blocks containing a masked polar end group have been devised for the efficient synthesis of carotenoids with polar termini. Chemoselectivity or the regiochemical issue of the highly functionalized units has been carefully addressed depending on the soft or hard nature of electrophiles. These building blocks have been successfully applied to the syntheses of crocetin derivatives, crocetin dial and the novel crocetin dinitrile.