Organic syntheses: Modular divergent formation of anti-malarial natural products
Osborne-Benthaus, Kymberlee Alana
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Callophycus serratus, a Fijian red macro alga, is the source of an interesting family of macrolides which have been elusive to the synthetic community. Sesquiterpene bromophycolides P, Q U, and related callophycolide A have highly conserved structural motifs which can be accessed through similar transformations therefore allowing for the application of a modular strategy. Formation of the modules features an expansion of electrophilic π-cyclizations with bromodiethylsulfonium bromopentachloroantimonate(V) (BDSB), and stereoselective Sharpless epoxidation and dihydroxylation conditions. Connection of the modules entail optimization of a magnesate assisted aryl-allyl coupling and a sulfone stabilized anion epoxide ring opening. The strategies explored can be applied to access a family of approximately 30 molecules. The development of a synthetic strategy is desirable due to notable anti-bacterial (MRSA and VREF), anti-malarial properties, and low natural abundance. Herein, I report results for the progress towards the total synthesis of bromophycolides P, Q, U, and callophycolide A utilizing a modular strategy.