Synthesis of a vinylchlorine-containing 1,3-diol from a marine cyanophyte

Using epoxy chiral building blocks readily derived from d-gluconolactone as the source of the stereogenic centers, both (6R,8R)- and (6R,8S)-isomers of (E)-1-chlorotridec-1-ene-6,8-diol were synthesized. The vinylchloro unit was installed onto the substrate carbon chain in an approximately 9:1 (E)/(Z) ratio via a condensation of CrCl2/CHCl3 with a terminal aldehyde. A tosylation protocol featuring addition of H2O was also developed for a highly polar tetraol. The synthetic products allowed for re-acquisition of the NMR spectra of better quality and revealed some delicate yet unignorable discrepancies in the 13C NMR for the natural isomer obtained by synthesis and that isolated some 30 years ago from the marine cyanophyte. The puzzling discrepancies were eventually shown to be caused by deuteration of the hydroxyl groups.

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