SYNTHESIS OF LAURENCIONE, A LABILE DIHYDRO-3(2H)-FURANONE DERIVATIVE FROM THE RED ALGA LAURENCIA-SPECTABILIS

The first total synthesis of laurencione, a naturally occurring dihydro-3(2H-furanone derivative isolated from the red alga Laurencia spectabilis, is described. The synthesis is comprised (1) of conversion of gamma-butyrolactone into alpha,alpha-dimethoxy-gamma-butyrolactone, (2) addition of methyllithium across the lactone carbonyl, and (3) acid hydrolysis of the acetal moiety. An alternative synthesis consists of the acid-catalyzed conversion of 3,3-dimethoxy-2-hydroxy-2-methyltetrahydrofuran into laurencione methyl ether and subsequent acid-catalyzed hydrolysis. In addition, a convenient synthesis of the coffee and caramel flavor component 2-methyl-3(2H)-furanone has been developed by acid-catalyzed rearrangement of 2-methoxy-2-methyltetrahydrofuran-3-one.