Carotenoids and Related Polyenes, Part 12

First Total Synthesis and Absolute Configuration of 3′-Deoxycapsanthin and 3,4-Didehydroxy-3′-deoxycapsanthin

Abstract

The synthesis of 3′-deoxycapsanthin (1) and 3,4-didehydroxy-3′-deoxycapsanthin (2), carotenoids of paprika, has been achieved by employing Lewis acid-promoted regio- and stereoselective rearrangement of the C₁₅-epoxy dienal 5a. The absolute stereochemistry of the newly formed C-5 chiral center of rearrangement product 6a was determined to be (R) from its alternative synthesis derived from (+)-(R)-camphonanic acid (11).