Synthesis, properties, and identification of epimeric hepoxilins (-)-(10R)-B3 and (+)-(10S)-B3

Article abstract of DOI:10.1016/S0040-4020(01)89921-X

To characterize the individual epimers of hepoxilin B₃, a new total synthesis procedure was developed consisting of subsequent condensations of enentiomerically pure (2R,3S)-epoxy-5-undecynal with LiC≡CCH₂Cl and HC≡C(CH₂)₃COOMe, followed by Lindlar hydrogenation, and finally epimer separation. Derivatives of hepoxilin syn-(10R,11R,12S)-B₃ (free acid, methyl ester and acetate of methyl ester) are more polar on silica gel, have negative optical rotations [α]²⁵_D -60.6°, -62.6°, -25.2°, respectively, and in ¹H NMR spectra have the larger splitting of carbinolic H-10 signal (J_10,11 5.0-6.1 Hz). Corresponding values for less polar hepoxilin anti-(10S, 11R,12S)-B₃ derivatives are: [α]²⁵_D +73.5°, +61.9°, and -2.0°; J_10-11 2.95-3.3 Hz. These data suggest that an epimer of hepoxilin B₃ recently isolated by W.H.Gerwick et al. from red algae is syn-(10R,11R,12S)-B₃.