This paper is dedicated to the late Prof. Synnøve Liaaen-Jensen for her dedication
to carotenoid research.
Abstract
Practical synthetic methods for biogenetically and pharmaceutically important phytofluene
were developed through the divergent preparation of key C20 substrates from a common intermediate and convergent synthesis by Wittig and Julia–Kocienski
olefinations. Expeditious synthesis of phytofluene was also proposed based on the
Julia sulfone-mediated chain-extension and double elimination method. Stereochemical
outcomes of these olefination methods for phytofluene were compared and the Julia–Kocienski
method was the mildest and most efficient reaction condition to produce all-(E)-phytofluene. Complete 1H and 13C NMR analysis of all-(E)-phytofluene is reported for the first time. Phytofluene undergoes facile thermal
isomerization to other Z-isomers above room temperature, which was also confirmed with a C30 phytofluene homologue.
Key words
carotenoids - isomerization - olefination - phytofluene - sulfones - total synthesis
