Fast and Efficient Synthesis of Maculalactone Derivatives via the Microwave Technique

Background: The γ-butyrolactone ring is present in many natural products that exhibit a broad spectrum of biological effects. Tribenzylbutyrolactones, known as maculalactones, are compounds isolated from cyanobacterial species that display diverse biological properties. Given the difficulty in isolating large amounts of maculalactones from natural sources, interest in synthesizing structural analogs of these compounds and extending studies on their biological properties has increased. For this purpose, we have developed a new one-step route based on a multicomponent reaction of the butyrolactone core to synthesize several maculalactone derivatives under microwave radiation as heat source. Methods: The maculalactone derivatives were synthesized by a multicomponent reaction; dimethyl 2- benzyl-3-methylenesuccinate, an alkyl or aryl bromide, and an aldehyde were used as starting materials. The crude reaction products were purified by flash column chromatography through silica gel, and the major diastereoisomers were isolated by recrystallization. Results: This microwave-assisted synthesis method afforded ten maculalactone derivatives. The microwave radiation technique reduced the reaction time and increased the product yields. These reactions presented good diastereoselectivity, and in all the reactions the major diastereoisomer showed the same relative configuration anti:anti. Conclusion: Microwave-assisted multicomponent synthesis proved to be an important strategy to produce several maculalactone derivatives in one step. This method affords good yields within short reaction times.