Carotenoids and related polyenes, part 121) 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 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 acid (11). © 2010 Pharmaceutical Society of Japan.