TOTAL SYNTHESIS OF ACETYLENIC CAROTENOIDS .3. FIRST TOTAL SYNTHESIS OF OPTICALLY-ACTIVE 9-Z-(3R,3'R)-DIATOXANTHIN AND 9-Z-(3R)-7,8-DIDEHYDROCRYPTOXANTHIN

Optically active 9-Z(3R,3'R)-diatoxanthin and 9-Z(3R)-7,8-didehydrocry ptoxanthin were synthesised in an overall yield of 9% and 11% respecti vely, with a seven step C-9+C-6+C-25=C-40 strategy. A key intermediate was the previously undescribed C-15-acetylenic aldehyde thylcyclohex- 1'-enyl)-3-methyl-2-penten-4-yn-1-al. Observed isomerisation shifts fo r the title compounds relative to the all-E isomers in H-1 NMR and C-1 3 NMR were as expected. CD properties are discussed.