A CONCISE, ENANTIOSELECTIVE SYNTHESIS OF (-)-HONGCONIN AND (-HONGCONIN())

Optically pure enone 9c, available in three steps from known 6-deoxy D -galactal derivative 7b, reacts with cyanophthalide 6 to directly affo rd the natural product (-)-hongconin (1), a compound from traditional Chinese medicine recently shown to exhibit antianginal activity. The e nantiomer of 1 and its (+)-cis-diastereomer were also synthesized in a parallel fashion from the L-sugar counterpart. The use of C-glycoside Michael accepters, as opposed to their O-glycoside counterparts, repr esents a potentially useful simplification of phthalide annulation met hodology in synthesizing numerous other such optically pure isochroman quinoids, since it obviates the inconvenience of additional steps late in the synthetic scheme associated with reductive manipulation of a r emaining acetal moiety into the desired pyran ring substituent.