More than fifty compounds of medium sized haloether having a straight C_<15>-chained skeleton and terminal enyne or bromoallene moieties were isolated from marine origins such as red algae, Laurencia species and sea hare, Aplysia species. The presumed precursors of these haloethers, laurediols (13 and 14) have been isolated from L. nipponica. However, biosynthetic studies have not been attempted since its isolation in 1972. We wish to report herein that partially saturated laurediol mimics (15 and 16) have been cyclized by commercially available lactoperoxidase, hydrogen peroxide, and bromide ion to give bromooxolanes (17, 18, and 19) and bromohydrins. When unsaturated diol, (6S,7R,12E)-12-penta-decen-6,7-diol was subjected to the same enzymatic reaction, eight membered bromoether, octahydrodeacetyllaurencin (20) was obtained in 1% yield. These results strongly suggested that laurediols are real precursors of haloethers. Furthermore, deacetyllaurencin (2) was converted by the same enzymatic reaction into laurefucin (3) and laureoxanyne (22). This indicates that deacetyllaurefucin was also the biosynthetic key intermediate for bicyclic bromoethers. Finally, natural bromoperoxidase prepared from L. nipponica was applied to the reactions and the same results were observed with the low yield. Consequently, we could conclude that bromoperoxidase is the actual enzyme for bromo-etherification in vivo and bromo-cationic reaction causes bromine incorporation into the organic compounds in the alga.
