A general synthetic strategy has been developed for the synthesis of r
acemic 3,4-dihydro-3-methyl-1H-benzo[c]pyran-5,8-dione 25, -5,8-dihydr
oxy-1,3-dimethyl-4-oxo-1H-benzo[c]pyran 39, -1,3-dimethyl-4-hydroxy-1H
-benzo[c]pyran-5,8-dione 41 and the rel-(4S)-diastereoisomer 42.