Studies Toward Natural Products Belizeanic Acid, Cephalosporolide E and Spiruchostatin

Belizeanic acid is a metabolite isolated from Prorocentrum belizeanum and with potent inhibitory activity against protein phosphatase 1 as reported for its structural relative okadaic acid, a known tumor promoter. Its incomplete stereochemical assignment allows for the possibility of four diastereoisomers arising from stereocenters C16 and C19. This work builds on the most recent synthesis of one possible diastereomer of the natural product and strived to demonstrate a more efficient pathway to the key fragments of the acid in order to facilitate syntheses of its other three diastereomers in the near future.;The tricyclic motif of Cephalosporolide E was found intriguing and attracted the application of our recently developed double intramolecular oxa-Michael process towards its concerted synthesis. This report delivers efforts toward synthesizing the linear precursor of the target process and attempts at the cyclization strategy.;Spiruchostatin A is an interesting bicyclic depsipeptide capable of suppressing certain cancer cell lines through inhibition of the deacetylation of histone proteins. The design of its molecular construction, synthesis of its statine moiety, and the attractive use of the recently reported NHC-mediated amidation to attempt the assembly of its peptidyl core, have been described. Both the synthetic hurdles of our strategy and the countermeasures developed have been narrated. Furthermore, an endgame proposal to the synthesis of the natural product is depicted herein.