| abstract |
Preparing (3R, 3'R)-zeaxanthin of the formula I ##STR1## starting from (4-hydroxy-2,2,6-trimethylcyclohexanone of the formula II ##STR2## via the novel intermediates (4R,6R)-1-formyl-2,2,6-trimethyl-7-oxabicyclo[2.2.1]heptane of the formula IV ##STR3## (4R,6R)-1-(3-oxo-1-butenyl)-2,2,6-trimethyl-7-oxabicyclo[2.2.1]heptane of the formula V ##STR4## (4R,6R)-1-(3-hydroxy-3-methyl-1,4-pentadienyl)-2,2,6-trimethyl-7-oxabicyclo[2.2.1]heptane of the formula VI ##STR5## [5-(4R,6R)-(4-hydroxy-2,2,6-trimethyl-1-cyclohexylidene)-3-methyl-1,3-pentadienyl]triarylphosphonium salt of the formula iso-III ##STR6## where Ar is aryl and X is one equivalent of an anion of a strong acid. The (4R,6R)-1-formyl-2,2,6-trimethyl-7-oxabicyclo[2.2.1]heptane of formula IV is obtained by reacting the ketone of the formula II with dichloromethyllithium, which can be prepared by metallation of dichloromethane with butyllithium or lithium diisopropylamide. |