Carotenoids and Related Polyenes, Part 12 First Total Synthesis and Absolute Configuration of 3'-Deoxycapsanthin and 3,4-Didehydroxy-3'-deoxycapsanthin
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 C(15)-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