STEREOCONTROLLED 2ND GENERATION SYNTHESES OF THE ABC AND FG RING-SYSTEMS OF BREVETOXIN-B

Stereocontrolled, second generation syntheses of the ABC and FG ring systems of brevetoxin B (1) are described. The two key intermediates 2 and 3, representing the ABC and FG ring frameworks, were prepared from 2-deoxy-D-ribose via short and efficient sequences. The synthesis of 2 proceeded via the epoxy alcohol cyclization precursors 6 and 7, and the Horner-Emmons cyclization precursor 5, to give the desired tricyclic system in 3.6% overall yield. The synthesis of 3 proceeded via the epoxy alcohol cyclization precursors 10 and 11 to give the desired bicyclic system in a 11.5% overall yield. Both syntheses represent improvements over the previous procedures and allow for rapid and facile entries into the ABC and FG ring systems of this complex natural product. © 1990.