Synthetic studies towards gonytolide A and the parnafungins
Embargo Date
2022-03-17
OA Version
Citation
Abstract
Gonytolide A and parnafungins are homo- and hetero- dimeric tetrahydroxanthone natural products with synthetically challenging chemical structures and a diverse array of biological activities. The dissertation research herein describes the first total synthesis of (+)-gonytolide A and a concise synthesis of the parnafungin core structure.
In the synthesis of gonytolide A, a vanadium (V)-mediated oxidative coupling method was developed to dimerize the monomer gonytolide C to construct the key biaryl linkage found in gonytolide A. A halogen blocking group strategy was employed to control the regio- and diastereo- selectivity of the dimerization. A kinetic resolution of a racemic butenolide substrate using copper-catalyzed enantioselective conjugate reduction enabled the asymmetric synthesis of natural product (+)-gonytolide C and its dimer (+)-gonytolide A.
In the effort to synthesize the parnafungins, an oxidative cyclization was developed to synthesize the rare benzisoxazolidinone moiety from an aminobenzoate precursor. A radical arylation method was employed to construct the labile dihydrophenanthridine core structure under mild reaction conditions. A novel carbazole formation method involving concurrent methyl migration was also serendipitously discovered en route to the synthesis of the parnafungins.