Preparation of Divergent Intermediates and Convergent Synthesis of Phytofluene

Practical synthetic methods of biogenetically and pharmaceutically important phytofluene were developed through 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 was reported for the first time. Phytofluene underwent facile thermal isomerization to other Z-isomers above room temperature, which was also confirmed by the C30 phytofluene homologue.