SYNTHETIC STUDIES ON SPIROKETAL NATURAL-PRODUCTS .5. TOTAL SYNTHESIS OF (-TALAROMYCIN-A AND (-)-TALAROMYCIN-B())

The total synthesis of (+)-talaromycin A and (-)-talaromycin B was acc omplished by utilizing a common intermediate (3). The spiroketal (3) w as converted to the olefin (4) via thermolysis of the sulfinyl group, C1-unit elongation at the C9-position, and isomerization at the spiro center. On the other hand, 3 was isomerized to 7 at the C9-position an d then converted to the olefin (5) in a similar manner to that describ ed for (+)-talaromycin A. These intermediates (4 and 5) were transform ed into (+)-talaromycin A and (-)-talaromycin B via addition reaction of trifluoroacetic acid and oxymercuration, respectively.